OCS Study

MMS 2002-012

BOWHEAD WHALE FEEDING IN THE

EASTERN ALASKAN BEAUFORT SEA:

UPDATE OF SCIENTIFIC AND

TRADITIONAL INFORMATION

by

for

MMS Contract 1435-01-97-CT-30842

LGL Report TA2196-7

October 2002

Volume 1 of 2
Suggested Format for Citations:

Richardson, W.J. and D.H. Thomson (eds.). 2002. Bowhead whale feeding in the eastern Alaskan Beaufort

Sea: update of scientific and traditional information. OCS Study MMS 2002-012; LGL Rep. TA2196-7.

Rep. from LGL Ltd., King City, Ont., for U.S. Minerals Manage. Serv., Anchorage, AK, and Herndon, VA.

Vol. 1, xliv + 420 p; Vol. 2, 277 p.

Individual chapters can also be cited, e.g. as follows:

Galginaitis, M.S. and W.R. Koski. 2002. Kaktovikmiut whaling: historical harvest and local knowledge of whale

feeding behavior. p. 2-1 to 2-30 In: W.J. Richardson and D.H. Thomson (eds.), Bowhead whale feeding

in the eastern Alaskan Beaufort Sea: update of scientific and traditional information, vol. 1. OCS Study

MMS 2002-012; LGL Rep. TA2196-7. Rep. from LGL Ltd., King City, Ont., for U.S. Minerals Manage.

Serv., Anchorage, AK, and Herndon, VA.

Disclaimer:

This report has been reviewed by the MMS and approved for publication. The opinions, findings, conclusions, or

recommendations expressed in this report are those of the authors, and do not necessarily reflect the views or

policies of the MMS. Mention of trade names or commercial products does not constitute endorsement or recommendation for use. This report has been technically reviewed according to contractual specifications; however, it is

exempt from further review by the MMS Technical Publications Unit.
OCS Study

MMS 2002-012

BOWHEAD WHALE FEEDING IN THE

EASTERN ALASKAN BEAUFORT SEA:

UPDATE OF SCIENTIFIC AND

TRADITIONAL INFORMATION

Edited by

W. John Richardson and Denis H. Thomson

LGL Limited, environmental research associates

22 Fisher Street, POB 280, King City, Ont. L7B 1A6, Canada

and

LGL Ecological Research Associates Inc.

1410 Cavitt St. Bryan TX 77801

for

Department of the Interior

Minerals Management Service

Alaska OCS Region, 949 East 36th Ave., Anchorage, AK 99508-4302

Procurement Operations Branch, 381 Elden Street, Herndon, VA 20170-4817

MMS Contract 1435-01-97-CT-30842

LGL Report TA2196-7

October 2002

Volume 1 of 2 
ii
Table of Contents

iii

TABLE OF CONTENTS

VOLUME 1

ACRONYMS......................................................................................................................................... xiii

EXECUTIVE SUMMARY.....................................................................................................................xv

Introduction and Approach ..........................................................................................................xv

Kaktovikmiut Whaling: Harvest Data and Local Knowledge .................................................. xix

Zooplankton: Acoustic vs. Net Biomass................................................................................... xxi

Zooplankton: Species Composition, Biomass and Distribution .............................................. xxii

Zooplankton: Characteristics of Bowhead Feeding Areas...................................................... xxiv

Bowheads: Distribution and Abundance................................................................................. xxvi

Bowheads: Habitat Use by Size Class .................................................................................. xxviii

Bowheads: Rates of Movement and Residence Times ......................................................... xxviii

Bowheads: Activities and Behavior..........................................................................................xxx

Bowheads: Surfacing, Respiration and Dive Cycles vs. Whale Activity ............................... xxxi

Bowheads: Surfacing, Respiration and Dive Cycles vs. Age ................................................ xxxii

Bowheads: Correction Factors for Aerial Surveys ............................................................... xxxiii

Bowhead Distribution, Numbers & Activities: Conclusions ................................................ xxxiv

Diet & Regional Feeding: Introduction ..................................................................................xxxv

Diet & Regional Feeding: Stomach Contents.........................................................................xxxv

Diet & Regional Feeding: Fatty Acids.................................................................................. xxxvi

Diet & Regional Feeding: Stable Isotopes........................................................................... xxxvii

Diet and Regional Feeding: Conclusions............................................................................ xxxviii

Energetics of Bowhead Whales ........................................................................................... xxxviii

Integration and Conclusions ....................................................................................................... xli

1. INTRODUCTION, by W.J. Richardson & D.H. Thomson ............................................................. 1-1

The Bowhead Whale.................................................................................................................. 1-1

Background to this Project......................................................................................................... 1-3

Objectives of the Study.............................................................................................................. 1-4

Study Area and Periods.............................................................................................................. 1-5

Why Concentrate on the Eastern Alaskan Beaufort Sea? ..................................................... 1-5

Specific Study Area Boundaries ........................................................................................... 1-7

Study Periods ........................................................................................................................ 1-7

Project and Report Title ........................................................................................................ 1-9

Questions to be Addressed......................................................................................................... 1-9

Study Components................................................................................................................... 1-11

Present Study Components ................................................................................................. 1-11

Other Potential Study Components..................................................................................... 1-13

Integration........................................................................................................................... 1-14

Local Coordination .................................................................................................................. 1-14

Scientific Review Board .......................................................................................................... 1-17

Scientific Research Permits ..................................................................................................... 1-17

Report Organization................................................................................................................. 1-17

Acknowledgements.................................................................................................................. 1-18

Literature Cited ........................................................................................................................ 1-19

2. KAKTOVIKMIUT WHALING: HISTORICAL HARVEST AND LOCAL KNOWLEDGE 

OF WHALE FEEDING BEHAVIOR, by M.S. Galginaitis & W.R. Koski................................2-1

Introduction................................................................................................................................ 2-1
Table of Contents

iv

Kaktovik―A Brief Description [history, population, economy, infrastructure] ....................... 2-1

Historical Kaktovikmiut Whaling.............................................................................................. 2-4

Historical Subsistence Whaling East of Barrow ................................................................... 2-4

Contemporary Kaktovikmiut Whaling.................................................................................. 2-6

Recent Bowhead Harvest at Kaktovik .................................................................................. 2-8

Local and Traditional Knowledge of Whale Feeding Near Kaktovik ..................................... 2-14

Concept and Use of “Local and Traditional Knowledge”................................................... 2-14

Chronology of Local Coordination and LTK Activities ..................................................... 2-16

Whale Workshop in Kaktovik (Jan. 1998).......................................................................... 2-16

Limited Interviews (16–20 Jan. 1998) ................................................................................ 2-17

Local Boat Effort ................................................................................................................ 2-23

Existing Documented Local and Traditional Knowledge................................................... 2-24

Summary.................................................................................................................................. 2-25

Acknowledgements.................................................................................................................. 2-27

Literature Cited ........................................................................................................................ 2-27

SPECIES COMPOSITION AND BIOMASS OF ZOOPLANKTON IN

RELATION TO BOWHEAD WHALE FEEDING IN THE EASTERN

ALASKAN BEAUFORT SEA............................................................................................3-1

3. INTRODUCTION TO THE ZOOPLANKTON COMPONENTS OF THE STUDY,

by D.H. Thomson & W.B. Griffiths........................................................................................... 3-1

Acknowledgements.................................................................................................................... 3-4

Literature Cited .......................................................................................................................... 3-4

4. RELATIONSHIPS BETWEEN ACOUSTIC BIOMASS AND NET BIOMASS OF

ZOOPLANKTON IN THE EASTERN ALASKAN BEAUFORT SEA, by W.B. Griffiths...... 4-1

Introduction................................................................................................................................ 4-1

Methods ..................................................................................................................................... 4-3

Data Sources ......................................................................................................................... 4-3

Hydroacoustic Sampling of Zooplankton ............................................................................. 4-3

Net Sampling Methods.......................................................................................................... 4-5

Laboratory Analyses of Zooplankton ................................................................................... 4-6

Data Processing and Analysis............................................................................................... 4-6

Results........................................................................................................................................ 4-7

Discussion................................................................................................................................ 4-11

Net Sampling Biases ........................................................................................................... 4-11

Physical Biases.................................................................................................................... 4-12

Biological Biases................................................................................................................. 4-13

Summary.................................................................................................................................. 4-14

Literature Cited ........................................................................................................................ 4-15

5. SPECIES COMPOSITION, BIOMASS, AND LOCAL DISTRIBUTION OF ZOOPLANKTON

RELATIVE TO WATER MASSES IN THE EASTERN ALASKAN BEAUFORT SEA,

by W.B. Griffiths & D.H. Thomson ................................................................................................. 5-1

Introduction................................................................................................................................ 5-1

Methods ..................................................................................................................................... 5-2

Temperature and Salinity Measurements.............................................................................. 5-2

Net Sampling of Zooplankton............................................................................................... 5-4

Hydroacoustic Sampling of Zooplankton ............................................................................. 5-5

Sample Analysis.................................................................................................................... 5-6

Results........................................................................................................................................ 5-6
Table of Contents

v

Physical Oceanography......................................................................................................... 5-6

Vertical and Horizontal Species Composition and Biomass Distribution of Zooplankton. 5-10

Echosounder Surveys of Zooplankton Biomass ................................................................. 5-20

Discussion................................................................................................................................ 5-33

Physical Oceanographic Features ....................................................................................... 5-33

Zooplankton Biomass and Composition ............................................................................. 5-33

Echosounder Surveys.......................................................................................................... 5-37

Summary.................................................................................................................................. 5-38

Introduction and Objectives................................................................................................ 5-38

Methods............................................................................................................................... 5-38

Results................................................................................................................................. 5-38

Literature Cited ........................................................................................................................ 5-40

Appendices 5.1 to 5.29............................................................................................................. 5-43

6. ZOOPLANKTON AND WATER MASSES AT BOWHEAD WHALE FEEDING

LOCATIONS IN THE EASTERN BEAUFORT SEA, by W.B. Griffiths et al. ........................ 6-1

Introduction................................................................................................................................ 6-1

Methods ..................................................................................................................................... 6-2

Temperature and Salinity Measurements.............................................................................. 6-2

Zooplankton Sampling.......................................................................................................... 6-5

Hydroacoustic Sampling....................................................................................................... 6-5

Analyses of Zooplankton ...................................................................................................... 6-6

Results........................................................................................................................................ 6-6

Zooplankton Near Bowhead Whales in the Eastern Alaskan Beaufort Sea.......................... 6-6

Zooplankton Near Bowhead Whales in the Canadian Beaufort Sea................................... 6-13

Physical Oceanography....................................................................................................... 6-20

Discussion................................................................................................................................ 6-22

Local and Traditional Knowledge of Bowhead Feeding .................................................... 6-22

Zooplankton Biomass Available to Whales........................................................................ 6-22

Characteristics of Feeding Areas ........................................................................................ 6-26

Prey in Whale Stomachs vs. Zooplankton Sampled Near Feeding Whales........................ 6-29

Summary.................................................................................................................................. 6-30

Introduction and Objectives................................................................................................ 6-30

Methods............................................................................................................................... 6-30

Results................................................................................................................................. 6-30

Acknowledgements.................................................................................................................. 6-31

Literature Cited ........................................................................................................................ 6-32

Appendices 6.1 to 6.5 .............................................................................................................. 6-35

7. ZOOPLANKTON: SUMMARY AND CONCLUSIONS, by W.B. Griffiths & D.H. Thomson. 7-1

Acoustic vs. Net Biomass .......................................................................................................... 7-1

Species Composition, Biomass, and Distribution...................................................................... 7-2

Characteristics of Bowhead Feeding Areas ............................................................................... 7-3

Recommended Research............................................................................................................ 7-4

BOWHEAD WHALE DISTRIBUTION, NUMBERS AND ACTIVITIES.............8-1

8. INTRODUCTION TO BOWHEAD WHALE COMPONENTS OF STUDY,

by W.J. Richardson & W.R. Koski .................................................................................................. 8-1

Literature Cited .......................................................................................................................... 8-5
Table of Contents

vi

9. DISTRIBUTION AND NUMBERS OF BOWHEAD WHALES IN THE EASTERN ALASKAN

BEAUFORT SEA DURING LATE SUMMER AND AUTUMN, 1979–2000,

by G.W. Miller et al. ......................................................................................................................... 9-1

Introduction................................................................................................................................ 9-1

Methods ..................................................................................................................................... 9-2

Data Sources ......................................................................................................................... 9-3

Aerial Survey Methods ......................................................................................................... 9-5

Data Analyses ....................................................................................................................... 9-7

Results...................................................................................................................................... 9-10

Survey Coverage and Effort................................................................................................ 9-10

Geographic Variation.......................................................................................................... 9-10

Seasonal Variation .............................................................................................................. 9-10

Feeding Whales................................................................................................................... 9-20

Annual Variation................................................................................................................. 9-20

Estimated Numbers of Bowheads Present .......................................................................... 9-22

Discussion................................................................................................................................ 9-29

Local and Traditional Knowledge of Bowhead Occurrence............................................... 9-29

Tendency for more Sightings in Recent Years ................................................................... 9-29

Summary.................................................................................................................................. 9-32

Acknowledgements.................................................................................................................. 9-34

Literature Cited ........................................................................................................................ 9-34

Appendices 9.1 to 9.2 .............................................................................................................. 9-38

10. HABITAT USE BY DIFFERENT SIZE CLASSES OF BOWHEAD WHALES IN THE

EASTERN ALASKAN BEAUFORT SEA DURING LATE SUMMER AND AUTUMN,

by W.R. Koski & G.W. Miller....................................................................................................... 10-1

Introduction.............................................................................................................................. 10-1

Methods ................................................................................................................................... 10-2

Data Sources ....................................................................................................................... 10-2

Photogrammetry.................................................................................................................. 10-4

Geographic and Temporal Categories................................................................................. 10-5

Results...................................................................................................................................... 10-5

Overall Length–Frequency Distribution ............................................................................. 10-5

Year-to-Year Variation ....................................................................................................... 10-5

Variation by Region............................................................................................................ 10-9

Variation by Water Depth................................................................................................... 10-9

Temporal Variation............................................................................................................. 10-9

Discussion.............................................................................................................................. 10-13

Summary................................................................................................................................ 10-19

Acknowledgements................................................................................................................ 10-19

Literature Cited ...................................................................................................................... 10-20

11. RATES OF MOVEMENT AND RESIDENCE TIMES OF BOWHEAD WHALES

IN THE BEAUFORT SEA AND AMUNDSEN GULF DURING SUMMER AND

AUTUMN, by W.R. Koski et al. ................................................................................................. 11-1

Introduction.............................................................................................................................. 11-1

Methods ................................................................................................................................... 11-2

Photogrammetry.................................................................................................................. 11-2

Behavioral Observation Procedures.................................................................................... 11-4

Computing Rates of Movement .......................................................................................... 11-5

Estimating Residence Times............................................................................................... 11-5

Results...................................................................................................................................... 11-8
Table of Contents

vii

1. Photos: Intervals Between Resightings.......................................................................... 11-8

2. Photos: Intervals Between Resightings + Travel ........................................................ 11-11

3. Photos: Stop-over Duration, Best Fit .......................................................................... 11-12

4. Photos: Stop-over Duration, Constant Survival.......................................................... 11-13

5. Photos: Within-day Speeds ......................................................................................... 11-13

6. Behavior: Overall Speeds............................................................................................ 11-15

7. Behavior: Activity Speeds .......................................................................................... 11-16

8. Aerial Survey Densities ............................................................................................... 11-17

9. Aerial Survey Whale-Days .......................................................................................... 11-18

10.Telemetry ..................................................................................................................... 11-18

Residence Time................................................................................................................. 11-19

Discussion.............................................................................................................................. 11-19

Local and Traditional Knowledge of Residence Times.................................................... 11-19

Year-to-Year Differences in Use of the Study Area ......................................................... 11-19

Intervals Between Resightings.......................................................................................... 11-22

Stop-over Duration............................................................................................................ 11-23

Photogrammetry: Within-day Speeds .............................................................................. 11-23

Behavior Speeds................................................................................................................ 11-24

Aerial Surveys................................................................................................................... 11-25

Telemetry Data.................................................................................................................. 11-25

Best Estimates of Residence Times .................................................................................. 11-25

Summary................................................................................................................................ 11-26

Acknowledgements................................................................................................................ 11-28

Literature Cited ...................................................................................................................... 11-28

Appendices 11.1 to 11.7......................................................................................................... 11-31

12. ACTIVITIES AND BEHAVIOR OF BOWHEAD WHALES IN THE EASTERN ALASKAN

BEAUFORT SEA DURING LATE SUMMER AND AUTUMN, by B. Würsig et al. ........... 12-1

Introduction.............................................................................................................................. 12-1

Methods ................................................................................................................................... 12-3

Data Sources ....................................................................................................................... 12-3

Aerial Observations............................................................................................................. 12-3

Data Analyses ..................................................................................................................... 12-5

Results...................................................................................................................................... 12-6

Feeding Activities―Descriptions ....................................................................................... 12-6

Feeding Activities―Occurrence......................................................................................... 12-9

Travel ................................................................................................................................ 12-12

Social Activities ................................................................................................................ 12-14

Mother–Calf Associations................................................................................................. 12-15

Orientations....................................................................................................................... 12-15

Time Budget Summary ..................................................................................................... 12-16

Discussion.............................................................................................................................. 12-18

Local and Traditional Knowledge of Bowhead Activities................................................ 12-18

Possible Human Influences............................................................................................... 12-20

General Activities ............................................................................................................. 12-21

Feeding.............................................................................................................................. 12-21

Traveling........................................................................................................................... 12-23

Socializing......................................................................................................................... 12-24

Mothers and Calves........................................................................................................... 12-24

Orientations....................................................................................................................... 12-25

Time Budgets .................................................................................................................... 12-25
Table of Contents

viii

Summary................................................................................................................................ 12-26

Acknowledgements................................................................................................................ 12-28

Literature Cited ...................................................................................................................... 12-28

Appendices 12.1 to 12.2......................................................................................................... 12-32

13. SURFACING, RESPIRATION AND DIVE CYCLES OF BOWHEAD WHALES

IN THE EASTERN ALASKAN BEAUFORT SEA DURING LATE SUMMER AND

AUTUMN AS RELATED TO WHALE ACTIVITY, by T.A. Thomas et al. ........................ 13-1

Introduction.............................................................................................................................. 13-1

Methods ................................................................................................................................... 13-2

Data Sources ....................................................................................................................... 13-2

Field Procedures.................................................................................................................. 13-2

Categories of Behavior........................................................................................................ 13-3

Analysis Procedures............................................................................................................ 13-3

Results...................................................................................................................................... 13-5

Feeding Whales................................................................................................................... 13-5

Traveling Whales ................................................................................................................ 13-6

Socializing Whales............................................................................................................ 13-10

Factors Related to Surfacing, Respiration and Dive Cycles ............................................. 13-11

Discussion.............................................................................................................................. 13-14

Feeding Whales................................................................................................................. 13-14

Traveling Whales .............................................................................................................. 13-18

Socializing Whales............................................................................................................ 13-18

Summary................................................................................................................................ 13-19

Acknowledgements................................................................................................................ 13-20

Literature Cited ...................................................................................................................... 13-20

Appendix 13.1 ....................................................................................................................... 13-22

14. SURFACING, RESPIRATION AND DIVE CYCLES OF BOWHEAD WHALES IN THE

BEAUFORT SEA: CALVES, SUBADULTS AND ADULTS, by T.A. Thomas et al. ........... 14-1

Introduction.............................................................................................................................. 14-1

Methods ................................................................................................................................... 14-2

Data Sources ....................................................................................................................... 14-2

Field Procedures.................................................................................................................. 14-2

Activity Categories ............................................................................................................. 14-4

Analysis Procedures............................................................................................................ 14-4

Results...................................................................................................................................... 14-4

Status Differences ............................................................................................................... 14-4

Seasonal Differences........................................................................................................... 14-7

Yearly Differences .............................................................................................................. 14-9

Nursing vs. Not Nursing ................................................................................................... 14-10

Discussion.............................................................................................................................. 14-12

Variability in SRD Cycles as Related to Age ................................................................... 14-12

Variability among Seasons................................................................................................ 14-12

Nursing vs. Not Nursing ................................................................................................... 14-13

Summary................................................................................................................................ 14-13

Acknowledgements................................................................................................................ 14-14

Literature Cited ...................................................................................................................... 14-14

Appendices 14.1 to 14.4......................................................................................................... 14-16

15. CORRECTION FACTORS TO CALCULATE BOWHEAD WHALE NUMBERS

FROM AERIAL SURVEYS OF THE BEAUFORT SEA, by T.A. Thomas et al. .................. 15-1

Introduction.............................................................................................................................. 15-1
Table of Contents

ix

Methods ................................................................................................................................... 15-3

Data Sources ....................................................................................................................... 15-3

Field Procedures.................................................................................................................. 15-3

Analysis Methods................................................................................................................ 15-5

Results...................................................................................................................................... 15-7

Lateral Distance Factor f(0) ................................................................................................ 15-7

Availability Bias Factor ga(0) ........................................................................................... 15-13

Detectability Bias Factor gd(0).......................................................................................... 15-13

Discussion.............................................................................................................................. 15-20

Lateral Distance Factor f(0) .............................................................................................. 15-20

Availability Bias Factor ga(0) ........................................................................................... 15-22

Detectability Bias Factor gd(0).......................................................................................... 15-23

Summary................................................................................................................................ 15-24

Acknowledgements................................................................................................................ 15-25

Literature Cited ...................................................................................................................... 15-26

16. BOWHEAD WHALE DISTRIBUTION, NUMBERS AND ACTIVITIES: SUMMARY AND

CONCLUSIONS, by W.R. Koski & W.J. Richardson................................................................ 16-1

Distribution and Abundance .................................................................................................... 16-2

Habitat Use by Size Class........................................................................................................ 16-4

Rates of Movement and Residence Times............................................................................... 16-5

Activities and Behavior............................................................................................................ 16-6

Surfacing, Respiration and Dive Cycles vs. Whale Activity ................................................... 16-7

Surfacing, Respiration and Dive Cycles vs. Whale Age.......................................................... 16-8

Correction Factors for Aerial Surveys ..................................................................................... 16-9

Disturbance to Feeding Bowhead Whales ............................................................................. 16-10

Conclusions............................................................................................................................ 16-11

Recommended Research........................................................................................................ 16-12

Acknowledgements................................................................................................................ 16-14

Literature Cited ...................................................................................................................... 16-14

VOLUME 2

DIET AND REGIONAL OCCURRENCE OF FEEDING ....................................17-1

17. INTRODUCTION TO DIET AND REGIONAL OCCURRENCE OF FEEDING

COMPONENTS OF STUDY, by W.J. Richardson .................................................................... 17-1

Stomach Contents .................................................................................................................... 17-1

Fatty Acids............................................................................................................................... 17-2

Stable Isotopes ......................................................................................................................... 17-3

Other Evidence on Diet and Regional Feeding........................................................................ 17-4

Literature Cited ........................................................................................................................ 17-5

18. STOMACH CONTENTS OF BOWHEAD WHALES HARVESTED IN THE ALASKAN

BEAUFORT SEA, by L.F. Lowry & G. Sheffield ...................................................................... 18-1

Introduction.............................................................................................................................. 18-1

Methods ................................................................................................................................... 18-2

Field Records and Feeding Status....................................................................................... 18-2

Collection and Analyses of Stomach Contents Samples..................................................... 18-3

Results...................................................................................................................................... 18-4

Data and Specimen Collection............................................................................................ 18-4
Table of Contents

x

Bowhead Feeding, Kaktovik Fall........................................................................................ 18-4

Bowhead Feeding, Cross Island Fall................................................................................... 18-7

Bowhead Feeding, Barrow Fall .......................................................................................... 18-7

Bowhead Feeding, Barrow Spring ...................................................................................... 18-9

Comparisons of Bowhead Diet Between Sexes, Sizes, Regions, and Seasons................... 18-9

Discussion.............................................................................................................................. 18-13

Acknowledgements................................................................................................................ 18-17

Summary................................................................................................................................ 18-17

Literature Cited ...................................................................................................................... 18-18

Appendices 18.1 to 18.6......................................................................................................... 18-20

19. FATTY ACIDS IN BOWHEAD WHALES AND POTENTIAL PREY FROM THE

ALASKAN BEAUFORT SEA, by S.J. Iverson et al. ................................................................ 19-1

Introduction.............................................................................................................................. 19-1

Methods ................................................................................................................................... 19-2

Analysis of Fatty Acids in Bowhead Blubber and Prey...................................................... 19-2

Statistical Analysis of Bowhead Blubber Fatty Acids ........................................................ 19-3

Preliminary Modeling of Bowhead Diets .......................................................................... 19-5

Results and Discussion ............................................................................................................ 19-5

Summary................................................................................................................................ 19-22

Acknowledgements................................................................................................................ 19-22

Literature Cited ...................................................................................................................... 19-22

20. REGIONAL AND SEASONAL FEEDING BY BOWHEAD WHALES AS INDICATED BY

STABLE ISOTOPE RATIOS, by S.H. Lee & D.M. Schell........................................................ 20-1

Introduction.............................................................................................................................. 20-1

Methods ................................................................................................................................... 20-4

Use of δ13C in Baleen to Assess Feeding............................................................................ 20-6

Correction for Changing δ13C and δ15N in the Bering and Chukchi Seas Biota ................. 20-9

Results...................................................................................................................................... 20-9

Zooplankton Isotope Ratios in the Eastern Beaufort Sea.................................................... 20-9

Seasonal Isotope Ratios in Muscle.................................................................................... 20-10

Isotope Ratio Patterns of Subadult vs. Adult Whales ....................................................... 20-13

Discussion.............................................................................................................................. 20-13

Estimation of Feeding Activity Using Same-Year Data ................................................... 20-15

Bowhead Whale Feeding Scenario ................................................................................... 20-18

Nitrogen Isotope Data ....................................................................................................... 20-19

Feeding by Subadult vs. Adult Bowheads ........................................................................ 20-20

Summary................................................................................................................................ 20-21

Acknowledgements................................................................................................................ 20-22

Literature Cited ...................................................................................................................... 20-22

APPENDIX 20.1. VARIANCE OF BOWHEAD FEEDING FRACTION..., by T.L. McDonald......... 20-25

21. DIET AND REGIONAL OCCURRENCE OF FEEDING: SUMMARY AND 

CONCLUSIONS, by D.H. Thomson & W.J. Richardson .......................................................... 21-1

Stomach Contents of Bowhead Whales................................................................................... 21-1

Fatty Acids in Bowhead Whales and Potential Prey................................................................ 21-2

Regional and Seasonal Feeding as Indicated by Stable Isotope Ratios ................................... 21-3

Conclusions.............................................................................................................................. 21-4

Recommended Research.......................................................................................................... 21-7

22. ENERGETICS OF BOWHEAD WHALES, by D.H. Thomson .............................................. 22-1

Introduction.............................................................................................................................. 22-1

Size and Other Physical Attributes of Bowhead Whales......................................................... 22-1
Table of Contents

xi

Length and Weight.............................................................................................................. 22-2

Quantity of Blubber ............................................................................................................ 22-3

Surface Area........................................................................................................................ 22-7

Growth and Reproduction................................................................................................... 22-7

Weight Gain During Summer/Loss During Fall–Winter .................................................... 22-9

Theoretical Energetic Requirements...................................................................................... 22-11

Time Budgets .................................................................................................................... 22-11

Respiration Method........................................................................................................... 22-13

Basal Metabolic Rate ........................................................................................................ 22-18

Standard Metabolism ........................................................................................................ 22-18

Energetic Cost of Swimming ............................................................................................ 22-19

Feeding Rates in Nature......................................................................................................... 22-21

Feeding Mechanism and Mouth Opening......................................................................... 22-21

Habits and Nutritive Value of Potential Food Species and Their Relationship to

Bowhead Energetics.......................................................................................................... 22-24

Assimilation Efficiency..................................................................................................... 22-26

Time Spent Feeding .......................................................................................................... 22-26

Feeding Rate ..................................................................................................................... 22-27

Comparison of Estimates for Bowheads and Other Whales .................................................. 22-28

Food Requirements of Different Segments of the Population ............................................... 22-29

Summary and Conclusions .................................................................................................... 22-32

Acknowledgements................................................................................................................ 22-35

Literature Cited ...................................................................................................................... 22-35

23. INTEGRATION AND CONCLUSIONS, by D.H. Thomson et al. ......................................... 23-1

Introduction.............................................................................................................................. 23-1

Study Area and Period ........................................................................................................ 23-1

Questions............................................................................................................................. 23-3

Background......................................................................................................................... 23-4

Bowhead Feeding Areas Across the Arctic ............................................................................. 23-6

Distributional and Behavioral Observations ....................................................................... 23-7

Seasonal Time Budgets....................................................................................................... 23-9

Stomach Contents ............................................................................................................... 23-9

Weight Loss in Winter/Gain in Summer............................................................................. 23-9

Potential Prey Consumption in Summer and Autumn ...................................................... 23-10

An Interpretation of the Isotope Data................................................................................ 23-11

Percentage of Diet from Eastern and Central Beaufort Sea.............................................. 23-11

Amount of Time that Bowheads Spend in the Study Area .................................................... 23-13

Population as a Whole....................................................................................................... 23-13

Individual Bowheads......................................................................................................... 23-15

Summary re Residence Times........................................................................................... 23-15

Feeding in the Study Area...................................................................................................... 23-15

Numbers of Whales that Feed........................................................................................... 23-17

Food Availability to Feeding Whales ............................................................................... 23-18

Food Consumed in the Study Area by the Population and by Individual Whales................. 23-19

Use of the Area by Feeding Whales.................................................................................. 23-20

Amount of Food Consumed in the Study Area................................................................. 23-21

Food Consumed in Study Area vs. Overall Annual Diet .................................................. 23-23

Uncertainties and Potential Errors in the Estimate ........................................................... 23-23

Summary of Food Consumed ........................................................................................... 23-24

Individual Bowhead Requirements................................................................................... 23-25
Table of Contents

xii

Recommended Research........................................................................................................ 23-26

Zooplankton ...................................................................................................................... 23-26

Bowhead Distribution, Numbers and Activities ............................................................... 23-27

Bowhead Diet and Regional Feeding................................................................................ 23-28

Bowhead Energetics and Other......................................................................................... 23-28

Summary................................................................................................................................ 23-29

Acknowledgements................................................................................................................ 23-33

Literature Cited ...................................................................................................................... 23-33

APPENDIX 23.1 SENSITIVITY ANALYSIS FOR ESTIMATED AVERAGE DAYS SPENT BY

BOWHEAD WHALES IN THE FLAXMAN ISL. TO HERSCHEL ISL. AREA, by B.F.J. Manly....... 23-37

Calculation of the Statistic of Interest.................................................................................... 23-37

Assessing the Variances of Estimates.................................................................................... 23-38

Results.................................................................................................................................... 23-40

References.............................................................................................................................. 23-40

APPENDIX 23.2 SENSITIVITY ANALYSIS FOR ESTIMATED PROPORTION OF FOOD TAKEN

BY BOWHEAD WHALES IN THE EASTERN ALASKAN BEAUFORT SEA, by B.F.J. Manly ......... 23-43

Calculation of the Statistic of Interest.................................................................................... 23-43

Daily Feeding Rates............................................................................................................... 23-44

Assessing the Variances of Estimates.................................................................................... 23-46

Results.................................................................................................................................... 23-50

References.............................................................................................................................. 23-51

ANNEX A. Final Report of the Scientific Review Board (SRB), with LGL Responses ............... A-1

ANNEX B. Kaktovik Interview Transcripts .....................................................................................B-1

Introduction................................................................................................................................B-2

Thomas Agiak............................................................................................................................B-3

Bert Akootchook and George Kaleak ......................................................................................B-14

Daniel and Lillian Akootchook................................................................................................B-27

Isaac Akootchook ....................................................................................................................B-37

Charles Brower ........................................................................................................................B-47

Joe Kaleak................................................................................................................................B-54
Acronyms

xiii

ACRONYMS AND ABBREVIATIONS

~ Approximately

a.d. Angular deviation

ADF&G Alaska Department of Fish and Game

AEWC Alaska Eskimo Whaling Commission

AIC Akaike’s Information Criterion (chapters 11, 15)

ANWR Arctic National Wildlife Refuge

ASA American Standards Organization (as related to film speed ― see ISO)

a.s.l. Above sea level

ASW Arctic Surface Water

AVHRR Advanced very high-resolution radiometer (an instrument on a satellite)

BAR-1 Komakuk Distant Early Warning (DEW) station

BCB Bering–Chukchi–Beaufort (stock of bowhead whales)

Bf Beaufort state―a measure of wave height (cf. SS)

BIA Bureau of Indian Affairs (chapter 2)

BLM Bureau of Land Management

BMR Basal Metabolic Rate (chapter 22)

BOS Behavioral observation session

B.P. Before Present (chapter 2)

BWASP Bowhead Whale Aerial Survey Project (MMS)

CART Classification and Regression Tree Analysis (chapter 19)

CI Confidence interval

CTD Conductivity (salinity), temperature and depth.

dB Decibels, intensity relative to the minimum target strength

DEW Distant Early Warning

DWM Department of Wildlife Management (NSB)

EIS Environmental Impact Statement

f(0) Correction factor for declining detectability of animals with increasing distance from the

survey track line

FLIR Forward Looking Infrared

ga(0) Correction factor to account for the probability of detecting diving animals during aerial

censuses (availability bias)

gd(0) Correction factor to account for animals at the surface along the track line but not recorded

(detectability or perception bias)

GC Gas chromatograph (chapter 19)

GPS Global Positioning System

IHLC [Commission on] Inupiat History Language and Culture (chapter 2)

ISO International Standards Organization (as related to film speed ― see ASA)

IWC International Whaling Commission

KWCA Kaktovik Whaling Captains’ Association
Acronyms

xiv

LTK Local and Traditional Knowledge (chapter 2)

LTS Least Trimmed Squares — a robust regression method (chapter 4)

MMPA Marine Mammal Protection Act

MMS Minerals Management Service

MT Metric Tonne; equals 1000 kg or 2203 pounds

NEPA National Environmental Policy Act

NMFS National Marine Fisheries Service

NOSC Naval Ocean Systems Center

NSB North Slope Borough

OPR Office of Protected Resources (NMFS)

PDB Pee Dee Belemnite, a standard for stable isotope work (chapter 20)

ppt Parts per thousand; same as ‰

psu Practical salinity unit, approximately = parts per thousand

QFASA Quantitative Fatty Acid Signature Analysis (chapter 19)

r, R Simple (r) and multiple (R) Correlation coefficient

r

2

, R2 Percent of variance explained

SAC Science Advisory Committee (NSB)

s.d. Standard deviation

s.e. Standard error

SODA Stop Over Duration Analysis (chapter 11)

SRB Scientific Review Board

SRD Surfacing, respiration and dive (chapters 13, 14)

SS Sea State―a measure of wave height, differing slightly from the Bf scale

Sv (dB) Volume back scattering strength of a target as recorded by an echosounder (chapter 3)

SWEPI Shell Western Exploration and Production, Inc.

TEK Traditional Ecological Knowledge (chapter 2, etc.)

USGS U.S. Geological Survey

UAF University of Alaska Fairbanks

UHF Ultra High Frequency

VHF Very High Frequency

VLF Very Low Frequency (a type of navigation system formerly used)

δ13C A measure of carbon isotope ratio

δ18O A measure of oxygen isotope ratio

‰ Parts per thousand (ppt)
Executive Summary

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EXECUTIVE SUMMARY

Introduction and Approach

The purpose of the project, as defined by the Minerals Management Service, was to compile and

integrate existing traditional and scientific knowledge about the importance of the eastern Alaskan Beaufort Sea for feeding by bowhead whales; to build consensus on the need for and approach to fieldwork to

augment this knowledge; to conduct the field studies and to analyze the results; to integrate them with

existing traditional and scientific knowledge; and to report on and publish the results.

The activities of bowhead whales throughout the year need to be considered when assessing the

importance of feeding in the eastern Alaskan Beaufort Sea during late summer and autumn. Bowhead

whales are known to feed in the Canadian Beaufort Sea in summer/early fall, and during westward migration across the Alaskan Beaufort Sea during late summer and fall (Fig. S.1). At least some of the bowheads also feed in the southwest Chukchi Sea in mid- to late fall. Bowhead activities in the Bering Sea

during winter have not been studied. There is some feeding, probably quite limited, during spring migration around western Alaska. Although behavioral observations and stomach contents provide some data

on feeding intensity during spring, summer, and fall, such data are lacking for late fall in the Chukchi Sea,

and from winter. It is unclear, from the available data of those types, what fraction of the annual feeding

occurs in any one part of the annual range.

FIGURE S.1. Schematic depiction of the seasonal migration of the Bering–Chukchi–Beaufort stock of

bowhead whales, and locations mentioned in text. The “eastern Alaskan Beaufort Sea” is shaded.
Executive Summary

xvi

FIGURE S.2. Map of the primary study area in the eastern Alaskan Beaufort Sea. Some data collection

efforts and analyses extended farther to the west, north, and east.

The specific area of concern in this project is the eastern part of the Alaskan Beaufort Sea (Fig.

S.2). The community of Kaktovik is located along the coast within that area. Subsistence whaling for

bowhead whales is of high importance to the people of Kaktovik. Bowhead whales occur in the Kaktovik

area in late summer and autumn. Bowheads are hunted as they feed in and travel through the Kaktovik

area at that time of year.

This report is an integrated account of traditional knowledge, previous scientific knowledge, and

results from recent scientific studies concerning the use of the study area for feeding by bowhead whales.

The new data collected during this study, mainly during September of 1998, 1999 and 2000, have been

supplemented with data collected earlier in and adjacent to the study area. In particular, this project is an

extension of a bowhead feeding study conducted in the same area during 1985 and 1986. The present

study is intended to provide additional data from more years, and to do so in collaboration with subsistence hunters and other local stakeholders. Where appropriate and possible, methods applied during the

new three-year study were consistent with methods used during the 1985–86 study. Thus, there are now

consistent data from five years, supplemented by additional data (e.g., aerial surveys) from other years,

with which to address the main objectives and hypotheses. Although the main fieldwork during the feeding studies in 1985–86 and 1998–2000 was during September, the project also incorporated aerial survey

results and local knowledge concerning bowhead use of the study area earlier and later in summer and

autumn.

Objectives of the Study.—The objectives of this study, as defined by MMS and revised based on

the advice of the project’s Scientific Review Board (SRB), are as follows. References to “Year 1” refer to
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xvii

mid-1997 through mid-1998. Years 2, 3 and 4 included the September 1998, 1999 and 2000 field

seasons, respectively:

1. Use existing data (traditional and scientific) to assess when and how feeding bowheads can be

recognized and distinguished from those engaged in social/milling and other behaviors (Year 1),

and distinguish those activities whenever possible during field studies (Years 2–4).

2. Mutually develop hypotheses that scientists and subsistence whale hunters concur can be successfully tested to determine and quantify the relative importance of the eastern Alaskan Beaufort Sea

as a feeding area for bowhead whales (Year 1).

3. Design (Year 1) and conduct (Years 2–4) research appropriate for testing the above hypotheses

and for quantifying potential feeding by bowhead whales in the same area.

4. Analyze previous and updated scientific information, summarize pertinent knowledge of area

subsistence whale hunters, and, where possible, test the above hypotheses and quantify bowhead

area feeding for previous years (Years 1 and 2–4).

5. Use historical satellite and aerial survey data to search for links between spatial or temporal

patterns in bowhead feeding vs. ambient oceanographic conditions (Year 1). If links are evident,

use all available data to characterize those links (Year 4).

6. Summarize (Year 1) and update (Year 4) available information, including traditional knowledge,

on the effects of acoustic and visual disturbance to bowhead whales (or other planktivorous

whales) engaged in apparent feeding behavior. This is considered to be a secondary objective.

7. Use the above information to determine and quantify the relative importance of the eastern

Alaskan Beaufort Sea as a seasonal feeding habitat for bowhead whales (Year 4).

Questions to be Answered.—Questions were developed to address the study objectives and the study

design was based on these questions. These questions were worded as “hypotheses” at some stages in the

project. However, a consensus developed late in the project that they should be considered to be research

questions that were addressed by the project rather than formal hypotheses to be tested:

Question (1). In an average year, how important is the eastern Alaskan Beaufort Sea for

bowhead whales; what percentage of the population’s annual energetic requirements is

derived from the area?

Question (1) was the key question for the project. It was addressed by considering many different types

of data acquired or assembled during the project, integrated by means of an energetic model (Chapter 22

and below).

Question (2). How much of its annual food requirements does the Bering–Chukchi–Beaufort

(BCB) population of bowhead whales derive in the eastern and central Beaufort Sea? At

least 10 percent?

Question (2) concerns the eastern and central Beaufort Sea as a whole, not just the eastern Alaskan Beaufort Sea. This question was addressed by examining the isotopic composition of bowhead tissue in spring

and fall, and of prey tissue through the range of the bowhead whale.

Question (3a). Of the bowheads that travel through the eastern Alaskan Beaufort Sea, how

long does an average whale spend there? At least 7 days?
Executive Summary

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Question (3b). Of the individual bowheads that travel through the eastern Alaskan Beaufort

Sea, how long do some individuals spend there? At least 7 days?

These two related questions were addressed through analysis of aerial photogrammetric data documenting

the residence times of individually-recognizable bowhead whales. The question has been split into two

because there are questions about the importance of the study area both to individual whales that linger in

the area and to the population as a whole.

Question (4). What percentage of the bowheads that pass through the eastern Alaskan

Beaufort Sea feed there? At least 10 percent?

Question (5). What percentage of the geographic area within the study area is suitable as

feeding habitat in different years? Is at least 1 % of the study area suitable in some years?

Question (6). During migration through the eastern Alaskan Beaufort Sea, how often are

bowheads observed to feed while they are traveling? Is feeding while traveling evident more

than 10 % of the time while traveling?

Question (4) was answered using stomach content data from the Kaktovik harvest, supplemented with

behavioral observations of whales. Question (5) was answered using boat-based observations of the

quantities and types of zooplankton at locations where bowheads feed, and the spatial extent of plankton

concentrations. Question (6) was answered using aerial observations of the behavior of the whales.

The answers to these questions, as derived by the project, are summarized in the last section of this

Executive Summary (below).

Approach.—In general, the project plan called for us to determine if the study area is important to

feeding bowhead whales in the following way:

• determine if numbers of animals remain in the study area for an extended period of time,

• determine what proportion of these animals are feeding,

• describe the zooplankton and hydrography near feeding whales,

• attempt to locate and characterize whale feeding habitat,

• determine what the whales are eating through examination of stomach contents and fatty acid

analysis, and compare stomach fullness and contents between Kaktovik and Barrow,

• determine how much feeding occurs in the eastern and central Beaufort Sea through isotopic

studies, and

• estimate the annual energetic requirement of the population (based on an updated energetics

model), and estimate what proportion of this is acquired in the study area.

These tasks have all been done, with the exception that the fatty acid study was limited to a pilot project.

The results of the stable isotope study remain difficult to reconcile with those of other study components.

However, one feeding scenario that could be consistent with all the data has been identified. This scenario is summarized in the last section of this Executive Summary.

Local Coordination.—Local cooperation and participation was considered critical to the success of

the study. Including the July 1998 Scientific Review Board (SRB) meeting, we met with representatives

of the Kaktovik Whaling Captains Association (KWCA), Alaska Eskimo Whaling Commission (AEWC),

and North Slope Borough (NSB) on six occasions during Year 1. The purposes were to seek traditional

knowledge and advice on project design, and to coordinate fieldwork with the bowhead hunt. We again

met with the KWCA, AEWC and NSB during the June 1999 SRB meeting. One or more project

participants also met with some of the whaling captains and other Kaktovik residents in Kaktovik during
Executive Summary

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June and early September 1999, and August 2000, to further coordinate our planned fieldwork with

whaling activities during those years. One key objective of all these meetings was to develop and refine a

field plan that whalers would accept as non-interfering and likely to be effective in assessing the importance of the area to feeding by individual bowheads and the population.

 Key items discussed at the meetings and incorporated into the Project Plan were as follows: (1)

Kaktovik residents were to be directly involved with the project through participation in the boat-based

field sampling in September of 1998–2000, conduct of boat-based reconnaissance surveys during August

1998–2000, and participation on the Scientific Review Board. (2) Aircraft-based field work was permitted east of Kaktovik during the whaling season, provided that the aircraft did not fly over whaling operations and that a radio communications protocol was established for coordination. (3) Boat-based work

would not be conducted east of or near Kaktovik until after whalers landed their second whale. In 2000,

because whalers landed their third whale early in the season (8 Sept.), boat-based work was not conducted

until after the third whale was landed. (4) An LGL representative would attend the pre-whaling-season

meeting of the Kaktovik Whaling Captains' Association during each year of fieldwork (see preceding

paragraph). (5) LGL’s aerial survey crew would be based in Kaktovik during the 1998–2000 field

seasons, facilitating local coordination. (6) Subcontractor ADF&G would station a biologist in Kaktovik

during the 1998–2000 whaling seasons (as they had done in 1997) to collect stomach content and bowhead tissue samples from bowheads landed at Kaktovik.

After the draft final report on this project was completed, AEWC, KWCA and NSB representatives

participated in a final Scientific Review Board meeting (January 2002) where the results were discussed.

Immediately thereafter, a one-day workshop was held in Kaktovik to present the results to Kaktovik

residents and to seek input on the interpretation. Discussion at the January 2002 SRB meeting and Kaktovik workshop has been taken into account in the final report. The SRB comments on the draft report are

included in Annex A of the report, along with responses by the project team. The report has been considerably revised since January 2002 to allow for the comments and to make other improvements.

Kaktovikmiut Whaling: Harvest Data and Local Knowledge

The desire to characterize the degree to which the eastern part of the Alaskan Beaufort Sea is used

by bowhead whales for feeding arises from a number of concerns. The importance of subsistence whaling for the Kaktovikmiut (“people of Kaktovik”) ranks high among these. Chapter 2 by M.S. Galginaitis

and W.R. Koski, summarized here, provides a brief description of the community of Kaktovik and Kaktovikmiut subsistence whaling, summarizes the Kaktovikmiut whale harvest, describes local coordination

efforts undertaken as part of this project, and summarizes Local and Traditional Knowledge (LTK)

pertinent to whale feeding behavior.

Kaktovik is a small community located on Barter Island in the extreme northeast of Alaska (Fig. S.1,

S.2), within the boundaries of the Arctic National Wildlife Refuge (ANWR). The 2000 U.S. Census

enumerated 293 people, most of whom (247, or 84 percent) are Native. Household economies rely upon

both wage labor and subsistence activities as vital components of an integrated system. The major employers are the North Slope Borough, the City of Kaktovik, and the village Native (ANCSA) corporation. There

are also a few private sector jobs and businesses separate from the Native corporations, but most

employment is related to government or Native Corporations. Subsistence activities, and especially activities surrounding the bowhead whale hunt, are central to the structural organization and cultural identity of

Kaktovik residents.
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Definitive information on the antiquity of whaling on the North Slope east of Barrow does not

really exist, but available information is consistent with whaling activity at least in the late Thule period

(beginning about 900 years ago). Informants maintain that whaling took place at Barter Island in aboriginal times. It is also not altogether clear when subsistence whaling ceased at Barter Island (prior to 1964),

or why whaling was suspended in the mid-Beaufort area in general. Whaling at Kaktovik resumed in

1964 and has taken place during most subsequent late summer/autumn seasons, with a high degree of success, especially since 1989. After the formation of the Alaska Eskimo Whaling Commission (AEWC) in

1977, Kaktovik received a formal quota. One to three bowheads were landed during most years in the

1980s, and two to four bowheads during most years in the 1990s and beyond.

The bowhead hunt normally begins the day after Labor Day and 83% of harvested whales have been

taken in September. In recent years, whales have been taken earlier in the season than in earlier years. The

core whaling area extends from the Hulahula River in the west to Tapkaurak Point in the east and offshore

as far as 32 km (20 mi). Most whales have been taken within 30 km of the village and the mean distance of

harvest locations from Kaktovik has not changed from the 1970s to present. Whaling captains select small

whales over large whales and there has been a significant decrease in the average size of whales harvested

from the 1970s to the present. The size of whales harvested does not increase with date although other data

show that smaller whales become less common in the area as the season progresses. This confirms that

whalers are selective in their harvest. Male and female bowheads are harvested in very similar numbers, but

females make up a significantly higher proportion of whales harvested early in the season and males make

up a significantly higher proportion of whales harvested late in the season.

Bowhead whales are of great cultural importance to the Inupiat and are a major source of food, and

Inupiat know a great deal about whales. However, one elder noted that it is difficult to transmit local

knowledge and understanding verbally if others lack the personal experience that underlies it. This study

required much cooperation and direct participation from local residents in the study design and field

work. All concerned wanted to ensure that Inupiat knowledge of bowhead whales would be integrated

into the planning of the project and the interpretation of its findings. Local participation also insured that

the study did not interfere with the hunt for bowhead whales. Assembly of LTK of bowheads, and

coordination of project and local activities, were two closely intertwined tasks.

Numerous local coordination efforts were built into the project in order to encourage local participation, to respond to local desires for project modification, and to incorporate local knowledge into

research design and interpretation of results. These efforts included meetings and interviews in Kaktovik

in 1997–98 before the first major field season, and additional meetings in Kaktovik before subsequent

field seasons. A final workshop in Kaktovik was conducted on 31 January 2002 to discuss the project

findings and to provide input for use in the final report. In addition, there was local Kaktovik representation (as well as AEWC and NSB representation) on a Scientific Review Board that provided technical

advice on project plans and results. As a result of recommendations by Kaktovik residents, a local boat

and crew, in conjunction with the LTK researcher, searched for bowheads present in late August and early

September, earlier than the main field season. While in Kaktovik for that effort, the LTK researcher

served many project liaison functions. No specific LTK research was conducted during the part of

September when Kaktovik residents were actively whaling. However, a local resident was employed to

work as a member of the boat-based zooplankton sampling crew during the September 1998–2000 field

seasons. Also, another project biologist worked closely with the whalers during September 1997–2000,

obtaining measurements and samples of stomach contents and whale tissue from the harvested whales.

Furthermore, the project’s survey aircraft was based in Kaktovik during September 1998–2000 (and

1985–86), affording opportunities for coordination between project biologists and local people.
Executive Summary

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Kaktovik residents are very knowledgeable about the times and locations near Kaktovik where

bowheads are present (including small vs. large bowheads), the places where bowheads tend to linger, and

other information relevant to whaling. However, relatively little specific LTK is available about whale

feeding behavior near Kaktovik. “Whale feeding behavior” is a discrete category of definable behaviors

to a scientist, but is for the most part beside the point for an Inupiat subsistence whaler. Nonetheless, two

feeding areas in the general area are recognized: (1) the Demarcation Point/Icy Reef area in the southeast

corner of the study area, and (2) waters near Arey Island just west of Kaktovik. Some local residents

mentioned that they often see whale food in the water, and know that whales tend to occur in those places.

Local residents emphasized that some bowheads occur in the area in August and even July, before the

start of the main westward migration, and that the project should consider these times as well as later in

the season. However, they noted that bowheads are more common in Canadian waters than near

Kaktovik in July–August. The main hunting period for bowheads is in September, but they are present

near Kaktovik as late as mid-October in some years. LTK research activities during this project, although

limited, were closely related to the broader local coordination efforts, and served to structure the local

participation aspects of the research in fruitful ways.

Zooplankton: Acoustic vs. Net Biomass

There was a need for a method to estimate zooplankton biomass from echosounder data acquired

along transects and at whale feeding locations in the eastern Alaskan Beaufort Sea. As described in

Chapter 4 by W.B. Griffiths, this was done by comparing zooplankton biomass collected in horizontal

bongo-net tows with concurrent echosounder measurements of acoustic backscatter at corresponding

depths. Paired data of these types were collected during late summer/early autumn in five years: 1985–

86, and 1998–2000. Linear regression techniques (robust LTS regression in 1998–2000) were used to

develop equations that could predict zooplankton biomass from acoustic backscatter when only the latter

is measured. In all five years, there was a positive and statistically significant (P < 0.05 or better)

correlation between net biomass and acoustic backscatter. Predictive equations were developed for data

collected in 1985, 1986, 1999, and 2000. In 1998, the relationship between backscatter and zooplankton

biomass was too weak to be of use. The equations are used in Chapters 5 and 6 to convert acoustic

backscatter along transects and at whale feeding stations into estimates of relative zooplankton biomass, and

from this to define the nature and extent of suitable bowhead feeding habitat in the study area. The resultant

echosounder-based data are useful primarily in comparing relative amounts of zooplankton at different

locations, depths, and years.

Numerous sources of error can confound the relationship between acoustic backscatter data and

zooplankton biomass measured with nets. A strong relationship between backscatter and net biomass is

difficult to obtain because the acoustic data may contain echoes from other biotic as well as abiotic sources.

Sources of variability include such things as the presence of fish larvae or other large swift animals that are

not captured by the net, the shape and orientation of zooplankters, sediment plumes, and density discontinuities in the water. Some of these biases (e.g., backscatter from fish and density discontinuities) can be

partially or completely removed. Other biases cannot be eliminated. These reduce the strength of correlation between acoustic backscatter and zooplankton biomass in concurrent net samples, and thus the

accuracy with which biomass can be estimated from backscatter data. More expensive and technologically

advanced zooplankton samplers, and more sophisticated acoustic systems, were not practical in this study.

Also, other studies have shown that these approaches do not guarantee better or more consistent results.

Despite the limitations and biases, the method provided useful data concerning the locations and

depths of high-density zooplankton patches, and the relative amounts of zooplankton at different locations,
Executive Summary

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depths, and times within and among the four years when useful data were available. This approach was an

important technique in assessing the characteristics and quality of feeding habitat available to bowhead

whales in the eastern Alaskan Beaufort Sea during those four years.

Zooplankton: Species Composition, Biomass and Distribution

Introduction and Objectives.—Chapter 5, by W.B. Griffiths and D.H. Thomson, describes the first

comprehensive study on late summer zooplankton biomass in the eastern Alaskan Beaufort Sea from

shore to the 200 m depth contour. The primary objective was to gather data on the taxonomic composition, biomass, patchiness, and variability of the zooplankton available to feeding bowhead whales in that

area during late summer and early autumn. Consequently, emphasis was placed on species and taxa that

were major contributors to overall zooplankton biomass. The study was based on coordinated net sampling and quantitative echosounder surveys conducted over 7- to 16-day periods during early-mid or midlate September of five years. It describes the vertical and horizontal distribution, composition, and patchiness of zooplankton biomass in relation to water mass characteristics.

Methods.—In all 5 years (1985–86; 1998–2000) sampling was conducted from a 13-m vessel

during September. Zooplankton and CTD data were collected at stations along transects perpendicular to

shore between central Camden Bay and Demarcation Bay, extending seaward to ~200 m depth (1985–86)

or 50 m depth (1998–2000). Quantitative echosounder data were collected along the same transects. All

data were used to describe the nature and variability of the zooplankton community, and its relationships

to water masses in the study area.

Three types of bongo tows were used to collect zooplankton samples each year: surface tows,

oblique tows, and horizontal tows at depth. A flow meter was placed in the center of one frame. The

echosounder was used to help select depths for horizontal tows, to ensure sampling within and outside

layers of concentrated zooplankton. Actual tow depth was measured directly.

Hydroacoustic sampling to estimate zooplankton distribution (horizontal and vertical) and relative

biomass along transects was conducted in all 5 years using single- (1998) or dual-frequency (other years)

echosounders. Relative biomass was determined for each 2 min (~240 m) horizontal segment by 1– or 2–

m depth interval for all transects.

CTD profiles were measured at stations along each transect each year. Near-surface temperature

(and, in 1985–86, salinity) were recorded continually during transits between sampling.

Results.—In all five years of the study, at least two water masses were deemed to be present: (1) a

Shallow Cold Saline water mass, usually without sharp discontinuities in the vertical distribution of temperature and salinity (i.e., without pycnoclines). These waters were typically relatively cold and saline

from surface to bottom. (2) A Mackenzie-Influenced more-offshore water mass with Mackenzieinfluenced water at the surface, overlying water that was generally colder and more saline than that of the

nearshore water mass. In 1985, 1986 and 1998, warm fresh Mackenzie plume water was transported into

the study area; in 1999 and 2000 it was absent. The distribution of water masses did not appear to have a

strong effect on the distribution of major zooplankton taxa. However, the highest biomass of zooplankton

occurred in the presence of strong pycnoclines, in the colder and more saline bottom waters.

The annual average zooplankton biomasses collected in Shallow Cold Saline waters varied over

the five years of study: 189–409 mg/m3

 for the water column as a whole, 18–205 mg/m3 for surface

waters, and 236–516 mg/m3

 for horizontal tows at depth. In all years, zooplankton biomasses in surface

waters were lower than in samples taken at depth. Typically, zooplankton biomasses were higher in the
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cold saline bottom layer than in the fresher warm surface water. In 1985–86, the maximum biomass in

individual horizontal tows at depth was 900–2000 mg/m3

, considerably higher than the 500–1000 mg/m3

recorded in 1998–2000. Overall, zooplankton biomasses were higher in 1986 than in 1985, 1998, 1999

and 2000. The lowest biomass levels were recorded in 1999, while those in 1985, 1998 and 2000 were

intermediate.

The high zooplankton biomasses in 1985–86 were due to the much higher biomasses of copepods,

particularly Limnocalanus macrurus. In 1998–2000, Calanus glacialis and C. hyperboreus were the

dominant species among all taxa. Predatory cnidarians, ctenophores and chaetognaths were abundant in

the study area in 1998–2000 and not in 1985–86. These predators may have contributed to the lower

biomass of copepods in 1998–2000.

In the water column as a whole, within the Shallow Cold Saline zone, five major zooplankton taxa

were collected in all five years. These were copepods, gelatinous zooplankton (i.e., ctenophores + cnidarians), chaetognaths, mysids, and fish. Copepods were the dominant taxon in all years, especially in

1985 and 1986. Gelatinous zooplankton and chaetognaths, considered together, were major contributors

(>10 mg/m3

) to zooplankton biomass in every year, and in 1998–2000 their biomass approached that of

copepods. Euphausiids were collected in all years except 1986 and were major contributors to the zooplankton biomass in 1985 and 2000, while decapods were major contributors only in 1986.

In all five years, the copepods Calanus hyperboreus and C. glacialis were major contributors to the

copepod biomass. In 1985 and 1986, biomass of the copepod Limnocalanus macrurus was higher than

that of any other species, but it was not found in the nearshore zone at all in 1998 and 1999 and only in

small quantities in 2000.

The low biomass in the surface waters was composed of copepods, gelatinous zooplankton and, to

a lesser extent, chaetognaths. Below the surface, the composition of the zooplankton collected in horizontal tows was similar to that in the water column as a whole

The Mackenzie-Influenced more-offshore water mass was present in the study area during 1985,

1986 and 1998, but not in 1999 and 2000. The annual average zooplankton biomasses in this water mass

were 170 to 223 mg/m3

 for the water column as a whole, and 4 to 25 mg/m3 for surface waters. Each of

these averages was lower than the corresponding value in Shallow Cold Saline zone. The warm

freshened water layer above the pycnocline contained a very low biomass of zooplankton (annual

averages 46–115 mg/m3

) compared to the cold saline water below (394–659 mg/m3). Copepods and

gelatinous zooplankton, with lesser contributions from amphipods, euphausiids, chaetognaths, pteropods

and fish, accounted for most of the biomass. In all three years, copepods were the dominant taxon,

particularly in 1985 and 1986. Overall, C. glacialis and C. hyperboreus were the major contributors to

the total copepod biomass in the Mackenzie-Influenced waters in all three years. Limnocalanus

macrurus, the dominant copepod in Shallow Cold Saline waters in 1985–86, was also a major contributor

to biomass in Mackenzie-Influenced waters in 1985 but not in 1986. It was not found in this water mass

in 1998.

The Outer Shelf Arctic water mass was only sampled in 1985 and 1986 when transects extended

out to the 200 m contour (vs. 50 m in 1998–2000). Zooplankton biomass in this zone was, on average,

less than that in nearshore and inner shelf waters. In both years, Calanus hyperboreus and C. glacialis

contributed most of the copepod biomass.

Average biomasses of zooplankton collected in summer and early autumn in the eastern Alaskan

and Canadian Beaufort Seas are similar. Zooplankton biomass collected by oblique (1985–2000) or
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vertical (1980) tows in the top 50 m of the water column have ranged from ~150 to 600 mg/m3 with an

overall average for all 218 of these tows of ~260 mg/m3

. Under some circumstances, biomass in layers of

concentrated zooplankton, as measured with horizontal bongo tows, can equal or exceed 1000 or 2000

mg/m3

.

Echosounder surveys in 1985 and 1986 showed that only a small fraction of the water along the

transects contained a high (>500 mg/m3) biomass of zooplankton, although there were patches where the

estimated biomass apparently exceeded 3000 mg/m3

 in 1985 and 3500 mg/m3 in 1986. In 1999, zooplankton patches were more extensive than in 1985–86 but the estimated biomass levels were lower with

the densest patches containing only an estimated maximum of 800–1000 mg/m3

. In 2000, there was a

pattern of increasing zooplankton biomass from east to west, with highest values from Barter Island to

eastern Camden Bay. In 2000, there were also many more patches where estimated biomass exceeded

700 or 1000 mg/m3

 along the western three transects than along the three eastern transects.

Zooplankton: Characteristics of Bowhead Feeding Areas

Introduction and Objectives.—Bowhead whales winter in the Bering Sea and annually migrate to

summering areas in the Beaufort Sea (Fig. S.1). If bowheads, like other mysticete whales, feed mainly

during summer, a primary reason for the annual migration would be to reach preferred summer feeding

areas. This would imply that summering areas are sufficiently rich in food to justify migrating several

thousand kilometers (round-trip) to feed. This component of the study, described in Chapter 6 by W.B.

Griffiths, D.H. Thomson and M.S.W. Bradstreet, had three main objectives: (1) to describe the characteristics of bowhead feeding areas in the eastern Alaskan and Canadian Beaufort Seas, with emphasis on the

zooplankton and water masses; (2) to determine whether bowhead whales feed in areas where zooplankton is concentrated; and (3) to determine the quantity and kinds of zooplankton associated with feeding

bowheads.

Methods.—In the Eastern Alaskan Beaufort Sea, zooplankton was sampled during September of

1986, 1998 and 1999 at 21 stations where bowhead whales were either observed feeding or where whales

had been observed feeding the previous day. Sampling near feeding bowheads was not possible in 1985

and 2000. For each feeding station sampled, a control station about 8 to 10 km from the feeding station

was also sampled. Zooplankton near feeding bowheads was sampled at 16 additional stations in the

Canadian Beaufort Sea during August and early September of 1980–81, 1985–86, and 1988. The eastern

Alaskan and Canadian data are presented separately, but are also considered together to provide a broader

view of bowhead feeding in the eastern Beaufort Sea. Vertical profiles of temperature and salinity were

obtained at all but one systematic sampling station.

At most stations, oblique and horizontal zooplankton tows were made using a standard bongo

frame fitted with two 0.5 mm mesh, 0.61 m diameter, plankton nets, and a flow meter. At most stations,

at least one horizontal tow was targeted to a specific depth where an echosounder showed an apparent

zooplankton concentration. The limited 1980 and 1988 sampling in Canadian waters employed vertical

tows, and in 1986 the horizontal tows in Alaskan waters used an opening-and-closing bongo system.

Animals from all oblique tows were identified to species, and those from horizontal tows to major taxa.

Sorted animals were wet-weighed, and wet-weight biomass/m3

 was calculated using flow-meter data on

volume filtered.

In the Alaskan Beaufort Sea, quantitative echosounder surveys were conducted between whale

feeding and control stations during 1986, 1999 and 2000, and along other transects during all five field

seasons. Regression equations were developed to relate zooplankton biomass in horizontal net tows to
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measured acoustic backscatter, and then used to estimate biomass where only echosounder data were

available. In the Canadian Beaufort, the echosounder used in 1981, 1985 and 1986 identified depths with

high (and low) apparent biomasses of zooplankton, but did not provide quantitative data on biomass.

Results.—Bowhead whales feed in areas with a higher than average concentrations of zooplankton.

A high biomass of zooplankton was found in areas where feeding bowheads were observed from the

sampling boat in the eastern Alaskan and Canadian Beaufort Sea. Mean wet-weight biomass in the water

column near actively feeding whales was 529 mg/m3

, a value considerably higher than the mean biomass

in the water column elsewhere in the eastern Alaskan and Canadian parts of the Beaufort Sea (230

mg/m3

). Mean biomass in the horizontal tows with maximum biomass at 17 stations where whales were

observed within 1 km of the boat and the echosounder was functioning was 1841 ± s.d. 1226 mg/m3

. The

distribution of biomass values at places with feeding bowheads indicates that the feeding threshold for

bowheads may be a wet biomass of ~800 mg/m3

.

A high biomass of zooplankton near feeding whales in nearshore waters was usually associated

with the presence of strong temperature and salinity gradients (pycnocline) in the water column. In these

cases, concentrations of zooplankton are found in the cold saline water that underlies the warmer

freshened layer. These conditions are found at varying locations in the Canadian Beaufort Sea regardless

of wind direction, but occur in shallow waters of the eastern Alaskan Beaufort Sea mainly under east

wind conditions. The eastern Alaskan Beaufort Sea appears to be more important to feeding whales in

years when oceanographic conditions that cause zooplankton to concentrate in nearshore waters off the

Yukon coast extend west into Alaska.

The small copepod Limnocalanus macrurus dominated the zooplankton biomass near feeding bowheads in nearshore waters along the Yukon coast and into northeast Alaska when cold saline water was

overlain by warm Mackenzie water. Farther offshore, the large copepods Calanus hyperboreus and

C. glacialis dominated. Stomach contents of whales landed at Kaktovik show that bowheads sometimes

feed on dense swarms of euphausiids. However, euphausiids are rarely the dominant zooplankters around

bowheads feeding in the present study areas. Other taxa that occasionally are dominant near feeding

whales are gelatinous cnidarians and ctenophores, chaetognaths, and mysids.

We did not find places with feeding whales where euphausiids were dominant, but this has been

reported previously from the Camden Bay area, and euphausiids are the dominant components of the prey

in the stomachs of a minority of the bowheads landed at Kaktovik (see below and Chapter 18). Euphausiids are known to show avoidance reactions to sampling nets. As a result euphausiids are probably

somewhat under-represented in our net samples. However, where euphausiids are abundant, as they are at

times in the western Beaufort Sea, they are prominent in net samples. In general, euphausiids are

apparently less important as prey for bowhead whales in the eastern Alaskan Beaufort Sea than farther

west near Point Barrow.

Most whales observed in the areas sampled were subadults. Adult bowheads tend to feed in deeper

water, where large copepods predominate. By early autumn, most large copepods have descended to their

overwintering depths (>100 m).

Water masses in the areas sampled are defined by the presence or absence of the plume of freshened and warmer water influenced by Mackenzie River outflow. Wind conditions have rapid effects on

the Mackenzie plume, so oceanographic conditions can change rapidly. These changes influence the biomass and composition of the zooplankton community in the eastern Beaufort Sea, and especially the

portion that is in Alaska.
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Bowheads: Distribution and Abundance

Previous studies plus observations by local people have shown that some bowhead whales may

spend at least part of the summer feeding period off the north coast of Alaska. Many others summer in

Canadian waters but continue to feed as they begin to travel west through the Alaskan Beaufort Sea

during September and October. Bowhead use of the Alaskan Beaufort Sea during late summer and

autumn has been documented since 1979 by systematic aerial surveys, mainly conducted or sponsored by

BLM and MMS. The surveys have gathered much information that can be used to evaluate bowhead use

of the eastern Alaskan Beaufort Sea during August–October, including relative utilization according to

year, season, and region within the study area.

Chapter 9, by G.W. Miller and others, describes the seasonal distribution and numbers of bowheads

observed in the eastern Alaskan Beaufort Sea and adjacent Canadian waters during August–October of

1979–2000, based on existing and new aerial survey data from the 139°–146°W region, south of 71°10'N.

(This “Flaxman Isl.–to–Herschel Isl.” area is a larger area than outlined in Figure S.2.) The 21 years of data

considered here (no data were available from 1980) include (1) annual aerial surveys by MMS, (2) some of

the aerial surveys conducted during industry-sponsored monitoring programs (1986 and 1993), and (3) surveys that we conducted specifically to assess the importance of the eastern Alaskan Beaufort Sea to bowheads in 1985–86 and 1998–2000. The combined dataset includes more data from the central Beaufort Sea

than have been analyzed by previous authors; it involves 155,000 km of systematic aerial surveys within the

“Flaxman–to–Herschel” study area. For periods where sufficient aerial survey data are available, we have

estimated the numbers of bowheads present in the part of the study area inshore of the 200 m contour off

Alaska (“Flaxman–to–border”). These estimates are based on line transect techniques, including correction

factors for whales missed by aerial surveyors (see Chapter 15 for derivation of correction factors).

The “Flaxman–to–Herschel” area was divided into four E–W regions, and four water-depth strata

―a total of 16 analysis zones. For seasonal analyses, the data were categorized into six half-month (15–

or 16–day periods) from 1 Aug. to 31 Oct.

When standardized for survey effort, the overall average abundance index during systematic aerial

surveys under acceptable sighting conditions (Aug.–Oct. combined) was 0.77 bowheads seen/100 km.

Bowhead abundance differed significantly among the four depth strata, with highest average abundance

recorded in the Shelf Break stratum (40–200 m deep), followed by the Middle Shelf stratum (20–40 m)

and Nearshore stratum (<20 m); average abundance was lowest in the Continental Slope stratum (>200 m

deep). Differences in bowhead abundance among the four E–W regions were marginally significant, with

bowhead abundance highest in the east and declining with increasing longitude.

Local residents occasionally see bowheads in the study area during July and August; they see peak

numbers in September, and some bowheads during October.

Aerial surveys showed that bowhead abundance and distribution varied significantly by half-month

period during August–October of 1979–2000. Moderate numbers of bowheads were present during early

August, especially in offshore waters (>200 m deep) of the three easternmost regions of the study area.

Bowhead abundance was somewhat lower during the second half of August, and there was a slight

shoreward shift in the distribution of bowheads from early to late August.

 During the first half of September the relative abundance of bowheads in the study area increased.

Also, their distribution shifted inshore and expanded westward to span the full width of the study area,

coincident with increased migration into and through the study area. Peak bowhead abundance was
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recorded during the second half of September, when bowheads were most abundant in the Shelf Break

and Middle Shelf strata (20–200 m deep).

Bowhead relative abundance in the study area was lower during early October, and the highest densities were again shoreward of the 200 m contour. By late October, the relative abundance of bowheads

was very low.

The percentage of the bowhead sightings recorded as “traveling” was similar (86–100%) over the

six half-month periods. For traveling whales, the headings were significantly non-uniform (and predominantly westward or northwestward) in all half-month periods except for late August. However, the variation in headings was larger up to 15 Sept. than thereafter.

Few bowheads were identified as feeding during systematic aerial surveys. The low apparent numbers of feeding bowheads reflect, in large part, the difficulty of recognizing feeding activity in the brief

glimpses of whales that typically occur during systematic aerial surveys. Areas where feeding was seen

most commonly included Nearshore waters close to Komakuk (Yukon); Nearshore, Middle Shelf and

Shelf Break waters off Demarcation Bay; and Middle Shelf and Shelf Break waters off Camden Bay.

During the 1979–2000 period, the relative abundance of bowheads recorded during aerial surveys

has varied markedly from year to year. Eight years had abundance indices higher than the overall average

of 0.77 bowheads seen/100 km. The highest indices were recorded in 1995 (3.23 /100 km), 1999 (3.32

/100 km) and 1990 (4.05 /100 km). Seven of the eight years with above-average bowhead abundance

were in the 1990s and most (9 of 13) of the years with below-average bowhead abundance occurred prior

to 1990. The average of the annual abundance indices was 0.36 bowheads seen/100 km during the 1979–

89 period vs. 1.60 bowheads/100 km for 1990–2000. The increase since 1989 was larger than can be

accounted for by the previously-reported rate of increase of this population (3.2% per year).

The numbers of bowheads present in the restricted “Flaxman–to–border” area were estimated

whenever survey coverage allowed, considering waters inshore of the 200 m contour. This area was

similar to that outlined in Figure S.2, but extended 20 n.mi. (37 km) farther west, to longitude 146oW.

These line-transect estimates were based on 81 surveys or combinations of surveys flown during 1– or 2–

day periods during 1979–2000, and include allowance for missed whales. The estimates ranged from 0

(during many surveys) to a maximum of 4505 bowheads (based on 765 km of survey coverage on 13

Sept. 1999).

Within most half-month periods, the estimated numbers of bowheads present were highly variable.

All six half-month periods included some surveys for which no bowheads were estimated to be present.

However, the average estimated numbers of bowheads present in the restricted study area during the six

half-month periods followed the same pattern as the abundance indices described above for the overall

study area: moderate in August, high in September and early October (peaking during late September),

and almost none during the second half of October.

We compared the estimated numbers of bowheads present in the restricted “Flaxman–to–border”

area during 1979–89 vs. 1990–2000, considering only the September and early October periods when

peak numbers of bowheads were present. The estimates from the 1990–2000 period were, on average,

significantly higher than those from 1979–89 even after de-trending to remove the assumed annual 3.2%

population increase over the 22-year study period. Thus, the increased sighting rates in the 1990–2000

period are apparently attributable in part to an increase in the relative utilization of the present study area

as compared with other areas.
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Bowheads: Habitat Use by Size Class

Chapter 10, by W.R. Koski and G.W. Miller, examines year, location, water depth, and date effects

on the size and status of bowhead whales occurring in and near the eastern Alaskan Beaufort Sea (water

depths ≤200 m) during late summer and early autumn. It assesses the population structure of bowhead

whales found in this area and evaluates whether there was habitat or seasonal segregation by whales of

different sizes (ages) and status (subadult and adult), including mothers and calves. This information is

relevant in evaluating the importance of the study area to the different components of the bowhead whale

population, and is a factor in subsequent energetic calculations.

We used the calibrated vertical photography technique developed by LGL to obtain vertical photographs of 901 different whales during mid-August to early October of 1982–86 and 1998–2000 in the area

between Flaxman and Herschel islands (longitudes 146° to 139°W). Whale images were measured directly from the film and the measured image sizes were converted to whale lengths by accounting for systematic biases introduced by the cameras and the radar altimeter.

Subadults, adults and calves made up 64.7, 29.2 and 6.2%, respectively, of the bowheads photographed in the “Flaxman–to–Herschel” area over all years of this study. We found proportionally more

subadults and fewer adults within that area than are estimated to be in the overall population. Some, but

not all, of this difference was a result of the fact that most of our effort was in the peak whale migration

period, with little effort during the initial 20% and final 29% of the bowhead migration through our study

area. The presence of a relatively high proportion of subadults in our length–frequency distribution even

after allowance for the seasonal bias in sampling suggests that the parts of the eastern Alaskan Beaufort

Sea ≤200 m deep are relatively more important for subadult bowheads than for adults.

There was significant variation in length–frequency distributions of whales among years, geographic

subdivisions of the study area, water depth categories, and time periods. This variation was due to variable use

of the study area by each age class in different years, differences in the water depths preferred by different age

classes, and different migration timing by each age class. Small subadult whales (<10 m long) are the

dominant group in shallow (<20 m) nearshore habitats, with progressively fewer small subadult whales and

more adults as water depth increases. Small subadults start to arrive in the study area during late August,

numbers peak in early September, and they have passed through the study area by early October. Large

subadults start to arrive in late August but are scarce until September; moderate numbers are still present in

early October. Mothers and calves start to arrive in early September and are common in the study area until

early October. Other adults arrive mainly in late September and are common in early October.

In the mid-1980s, large numbers of subadult bowheads tended to occur in shallow nearshore areas

in the eastern part of the study area from the Kongakut River Delta to Herschel Island, and they lingered

in that area for days to a few weeks. Few whales were seen in that nearshore area during 1998–2000, and

those that were seen there did not appear to linger.

Bowheads: Rates of Movement and Residence Times

To determine the importance of the eastern Alaskan Beaufort Sea to bowhead whales, we need to

know how long whales remain in the area. This is one key factor in estimating how much food bowheads

consume while there. We also need to know how fast they travel while feeding to estimate how much

water they might filter. Chapter 11, by W.R. Koski and others, documents short-term rates of movement

of bowhead whales and estimates average residence times in waters from Flaxman Island (146oW) to
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Herschel Island (139°W). Probable residence times in the smaller “Flaxman–to–border” area are discussed in Chapter 23, and are estimated to be about 76% of those in the larger “Flaxman–to–Herschel” area.

We estimated rates of movement from within-day sightings of photographed bowhead whales in the

“Flaxman–to–Herschel” portion of the Beaufort Sea and compared them to similar data collected during

the 1980s off the Yukon east of Herschel Island (Yukon East) and in Amundsen Gulf.

Over periods of 15 min to a few hours, bowheads gradually moved away from the location where

they were initially photographed, but as the interval between the initial sighting and resighting increased,

speeds declined. This suggested that some movements were local, in part associated with feeding.

Within-day speeds were not significantly different between the “Flaxman–to–Herschel” zone and the

more easterly Canadian zones. Within the “Flaxman–to–Herschel” zone there was a significant

difference in speeds among years. The difference appeared to be due to slower speeds by feeding adults

photographed in 1999 than by primarily subadult whales photographed in other years.

The primary activities recorded for bowheads during late summer and autumn were feeding and

traveling. Based on the successive locations of bowheads observed during prolonged behavioral observation sessions, the average rate of movement of bowheads in the “Flaxman–to–Herschel” zone was

about 1.54 km/h for feeding whales vs. 4.50 km/h for traveling whales. The mean alongshore component

of the net speed, measured along the 288°–108° (True) axis, was 0.71 km/h eastward for feeding whales

and 3.67 km/h westward for traveling whales.

We attempted to estimate residence times of bowhead whales in the “Flaxman–to–Herschel” area

using four general types of data: photoidentification data, behavioral observations, aerial survey results,

and telemetry data. Photoidentification data from the 1980s were also used to estimate residence times in

the Yukon East and Amundsen Gulf zones. (1) Photographic resightings were used to determine withinday rates of movement and intervals between resightings for the “Flaxman–to–Herschel” zone and for the

Yukon East and Amundsen Gulf zones in all years with sufficient data. Net speeds from within-day

photographic resightings were the basis for one estimate of residence times of whales in each zone.

Resighting intervals indicated minimum residence times for the specific whales resighted. A computer

program (SODA, “stop-over duration analysis”) was used to derive an unbiased estimate of residence

time in each zone based on data on photographic effort as well as resightings. (2) Behavioral observations of bowhead whales were used to determine short-term rates of movement of whales, and net

westward speeds of whales engaged in different activities, in the “Flaxman–to–Herschel” zone during late

summer and autumn of 1985–86 and 1998–2000. (3) Aerial survey data were used to estimate residence

times in that area based on relative densities during aerial surveys and based on numbers of whales

estimated to be present during aerial surveys. (4) Data on whale locations obtained during telemetry

studies in three years were used to estimate residence times of whales in the “Flaxman–to–Herschel”

zone.

Annual residence time estimates for the “Flaxman–to–Herschel” zone were extremely variable

among years and among different methods of analysis applied to the same year. We attribute the latter

variability to biases in the different methods that interacted with year-to-year variability in sampling

effort, whale distribution, and whale activities. For example, most behavioral data and some photographs

collected in 1985 were from feeding whales off the Yukon coast (“border–to–Herschel Isl.”); activities

and speeds of those whales were not representative of whales in Alaskan waters in 1985. In general, estimates based on behavior data, and to a lesser extent photogrammetry data, were positively biased.
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We identified six calculation methods based on photoidentification, behavioral observation, aerial

survey, and telemetry data that provided residence time estimates most representative of actual residence

times. However, even with these six methods, a few of the residence time estimates were recognizably

biased. The annual residence time estimates for the “Flaxman–to–Herschel” area during 1985–86, 1988,

1989, 1992, and 1998–2000 based on these six methods varied from 2.1 to 8.3 d and averaged 5.1 d. A

sensitivity analysis (in Appendix 23.1) indicated that the 95% confidence limit for the 5.1-d estimate of

mean residence time was 4.2 to 6.1 d.

Residence times varied dramatically among years because of different levels of use of the

“Flaxman–to–Herschel” zone for feeding during late summer and autumn. In 1985 and 1986, the eastern

part of the area was used for feeding by subadult bowheads during late summer. In 1998, subadult whales

briefly stopped to feed in central and western parts of the study area during their migration through the

study area. In 1999, adult whales stopped to feed for extended periods in eastern and central parts of the

study area. During 2000, most whales migrated through the study area without stopping.

The mean interval for between-day photographic resightings was 4.35 days in the “Flaxman–to–

Herschel” zone and 5.91 days in Canadian zones east of there, and estimates for both areas were highly

variable among years. A tendency for residence times in the “Flaxman–to–Herschel” zone to be shorter

than those in the more easterly Canadian areas became more evident when the SODA model was used to

estimate total residence times, including allowance for time present before the first and after the last

sighting, and for whales photographed only once. SODA showed that the mean residence times for the

Canadian zones were considerably longer (12.6 d) than the mean resighting intervals (5.9 d), whereas the

mean residence times for the “Flaxman–to–Herschel” zone were either lower than (1985) or similar to

(1986, 1999) the mean resighting intervals. The shorter residence times in the latter zone compared to the

Yukon East and Amundsen Gulf zones are consistent with distributional and behavioral data in suggesting that bowhead whales spent less time feeding in the “Flaxman–to–Herschel” area than in adjacent

Canadian zones in most years. Furthermore, residence time estimates for eastern Alaska would be further

reduced if data from Canadian waters west of Herschel Island (the Komakuk area) were excluded from

the “Flaxman–to–Herschel” zone.

Bowheads: Activities and Behavior

Chapter 12, by Dr. B. Würsig and others, describes the general activities of bowhead whales while

they are off northeastern Alaska, and in adjacent Canadian waters, during late summer and early autumn

(feeding, traveling, socializing, and combinations thereof). It also documents the specific behaviors

associated with these activities, and determines the proportion of time engaged in each activity (time

budget). During September of 1985, 1986, 1998, 1999, and 2000 (and early October in 1986), systematic

behavioral observations were obtained from twin-engine aircraft circling at an altitude of 460 m (occasionally 610 m) a.s.l., with a minimum of three observers describing and videotaping behavioral events.

We obtained data on the activities and behaviors of whales during 84 Behavioral Observation Sessions

totaling 91.9 h of observations under presumably undisturbed conditions. Of these, 69 sessions were off

northeast Alaska (Flaxman Island to border), and 15 were in Canadian waters from the Alaska-Yukon

border to Herschel Island. We compared our data for this “Flaxman–to–Herschel” area in September/early October to previously reported data on activities, behaviors, and time budgets during spring and

during summer, and demonstrated seasonal differences. For the late summer/early autumn period, the

time-budgets also differed among years.
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Feeding was the most common activity of bowhead whales in and near the eastern Alaskan Beaufort Sea in September/early October during 1985, 1986, 1998, and 1999; but not in 2000. Over the five

seasons, bowheads engaged in feeding for ~47% of the total time (9% in 2000; 38–66% in other years).

Overall, ~34% of the time was spent feeding in the water column, 8% on near-surface (“skim-”) feeding,

and 4% on near-bottom feeding. Almost all observed feeding in water >20 m deep was water-column

feeding; surface and bottom feeding were proportionally more common in areas ≤20 m deep, but there too

water-column feeding was the most common activity. Mothers and first-year calves were rarely sighted

in waters ≤20 m deep, and the most common activity of mothers was feeding in the water column in areas

>20 m deep. Most whales fed singly. Bottom feeders were usually widely spaced, but water-column and

skim feeders generally were more aggregated, typically with 4+ whales within 1 km of each other. We

did not see skim feeding in echelon formation during late summer–early autumn, although it has been

reported previously in the Alaskan Beaufort Sea. The estimated proportion of time devoted to feeding

during September/early October (47%) was intermediate between values during spring migration east of

Point Barrow, Alaska (1%), and on the summer range in the Canadian Beaufort Sea (71%).

Traveling was the second-most common activity, accounting for 31% of time overall; but 74% in

2000. Travel tended to be in areas 20–49 m deep and in groups of one to two whales. Whales spent more

time traveling during the latter half of September than in early September. Traveling whales were oriented mainly westward. Bowheads commonly interspersed feeding and socializing with travel during the

latter half of September. The estimated proportion of time devoted to traveling (31%) was also intermediate between that during spring migration (81%) and that on the summer range (9%).

Socializing accounted for 18% of the time during September/early October, and other activities

(aside from feeding, travel or socializing) accounted for 4%. Socializing tended to consist of low-level

behaviors such as nudges and other touches, with the exception of apparent sexual aggregations of up to

seven whales per aggregation on two days in September 1998. First-year calves stayed close to their

mothers, showed little surface-active behavior, and were not observed to play. No lone calves were seen,

indicating that calves had not been weaned.

Although feeding was the most common activity of bowhead whales in and near the eastern Alaskan Beaufort Sea during September/early October, there was much intra- and inter-season variability in

the amount and type of feeding, other activities, and specific behaviors, and in the locations (within the

study area) where these activities occurred. These variable results are generally consistent with the

apparent variability in prey availability in the study area, as documented in other parts of this study.

However, bowheads observed in 1999 spent a high proportion of their time feeding, and exhibited

relatively long residence times, even though average zooplankton abundance (at least inshore of the 50 m

contour) was relatively low that year. Overall, the importance of the study area for late-summer feeding

by bowhead whales varies considerably from year to year, and is difficult to predict for any one late

summer–early autumn season.

Bowheads: Surfacing, Respiration and Dive Cycles vs. Whale Activity

Data on surfacing, respiration and dive (SRD) cycles of bowhead whales during late summer and

early autumn were needed to derive correction factors for whales missed during aerial surveys, and as a

basis for analyses of bowhead energetics. As described in Chapter 13 by T.A. Thomas and others, bowheads were observed systematically during September and early October of 1985–86 and 1998–2000 in

the Eastern Alaskan Beaufort Sea and adjacent Canadian waters (Flaxman Island to Herschel Island).

Bowhead behavior was observed from an aircraft circling at an altitude of ≥457 m (≥1500 ft), high
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enough to avoid significant aircraft disturbance. Data collected near other human activities were excluded. We documented the durations of surfacings and dives, number of blows (respirations) per surfacing, and intervals between successive blows. These four variables were defined as in our recent studies of

bowhead behavior in other seasons and regions. We first summarized the SRD variables for various

categories of whale activity, year, and (for feeding whales) water depth. The main bowhead activities distinguished here are feeding, traveling, and socializing. Then we used multiple regression to assess the

joint effects of these and other temporal, environmental, and whale-behavior variables on the four measures of SRD cycles.

Whales engaged in feeding showed a noticeable increase in the number of blows per surfacing and

the durations of surfacings and dives across years. Some of this variability may be attributable to the

water depth in which the whales were feeding. In the 1980s most of the observed surfacing–dive cycles

occurred in shallow (≤20 m) water, whereas in the 1990s more of observations came from deeper water.

An average SRD cycle by an undisturbed bowhead feeding in shallow (≤20 m) water, calves excluded,

consisted of a 1.10 min surfacing with 4.9 blows spaced 13.1 s apart, followed by a 5.84 min dive. A

corresponding average SRD cycle in water >20 m deep (average 45 m) consisted of a 1.77 min surfacing

with 8.5 blows spaced 13.1 s apart, followed by a 16.09 min dive. Whale status and distance from shore

had a strong effect on the SRD cycles of bowheads feeding in and near the Eastern Alaskan Beaufort Sea.

During feeding, surfacings and dives were longer, with more blows per surfacing and longer intervals

between blows, with increasing distance from shore, and for older, larger whales as compared with

subadults.

Traveling bowheads (including those feeding while traveling) tended to have surfacing and dive

cycles similar to those of bowheads feeding in water >20 m deep. Some of this similarity may be attributable to the habitat that the whales are occupying, as traveling whales tended to be in water >20 m deep.

An average SRD cycle by a traveling bowhead (including bowheads that were feeding as they traveled)

consisted of a 1.65 min surfacing with 6.4 blows spaced 15.76 s apart, followed by a 13.66 min dive.

Whale status and group size had a strong influence on the SRD cycles of bowheads traveling in and near

the Eastern Alaskan Beaufort Sea. The standard measures of these cycles were higher for mothers and for

increased group sizes, and were shorter for subadults.

Socializing whales and whales feeding in shallow water tended to have similar breathing characteristics. Some of this similarity may be attributable to the habitat (shallow water) that the whales were

occupying. An average SRD cycle by a socializing bowhead (including bowheads that intermixed socializing with other activities) consisted of a 1.29 min surfacing with 6.0 blows spaced 12.67 s apart, followed by a 5.54 min dive.

Bowheads: Surfacing, Respiration and Dive Cycles vs. Age

Data on age- and size-dependence of surfacing, respiration and dive (SRD) cycles of bowhead

whales were needed as a basis for analyses of bowhead energetics. This type of information is also

relevant in deriving correction factors for whales missed during aerial surveys, especially when there is

geographic and seasonal variation in the ages and sizes of bowheads present. Chapter 14, by T.A.

Thomas and others, provides this information based on several studies, including the present study.

Bowheads in the Alaskan and Canadian Beaufort Sea were observed systematically at various

times in 1980–2000 during spring, summer, and fall. During each of six studies, bowhead behavior was

observed from an aircraft circling at an altitude of ≥457 m (≥1500 ft), high enough to avoid significant

aircraft disturbance. Data collected in the presence of other human activities were excluded. We docu-
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mented the durations of surfacings and dives, number of blows (respirations) per surfacing, and intervals

between successive blows. These four variables were defined as in our recent studies of bowhead

behavior in various seasons and regions. We summarized the SRD variables by whale status (calf,

subadult, adult other then mother, mother), various categories of whale activity (traveling, feeding, and

socializing), season (spring, summer, fall), year, and nursing vs. not nursing.

Subadult whales had lower median blow intervals than adults and mothers; this was evident for

bowheads engaged in all three whale activities studied (traveling, feeding, and socializing). Subadults

also had lower dive durations during traveling, and marginally lower surface times during feeding, as

compared with adults and mothers. Mothers and other adults had similar SRD cycles, with the exception

that, during feeding, other adults had lower median blow intervals than mothers.

Subadults engaged in traveling showed no spring–fall differences in any of the SRD variables.

Adult whales, in contrast, showed differences in all four variables. Mothers and calves engaged in traveling showed seasonal variability in SRD cycles. For both mothers and calves, there was a noticeable

increase in the number of blows per surfacing, surface times, and dive times from spring to fall.

During travel, nursing dives by calves were much shorter than their other dives in both spring and

fall. Occurrence of nursing also affected SRD cycles of traveling mothers. When nursing, traveling

mothers tended to have long surfacings with long blow intervals. Dive durations by traveling mothers

also tended to average slightly longer when nursing.

Bowheads: Correction Factors for Aerial Surveys

Aerial surveys have been used to estimate the number of bowheads present in the eastern Alaskan

Beaufort Sea at various times during late summer and autumn for the present study. However, meaningful estimates of numbers present can only be made if the raw aerial survey data are adjusted using

appropriate correction factors for missed whales. Not all whales present close to an aerial survey trackline are detected by the aerial surveyors, and raw aerial survey results underestimate the densities and

numbers of whales present. (1) Sightability is often reduced directly below the aircraft and, beyond some

“optimum” lateral distance, diminishes with increasing lateral distance. (2) Some whales are below the

surface and undetectable as the aircraft passes; this is “availability bias”. (3) Not all whales at the surface

at the optimum lateral distance are detected; this is “detectability bias”, sometimes called “perception

bias”. In theory, three correction factors, designated f(0), ga(0), and gd(0), can be computed to compensate in large part for these three biases. Chapter 15, by T.A. Thomas and others, estimated these three

correction factors for aerial surveys of bowhead whales, and investigated their variability.

Lateral Distance from Trackline and f (0).—Aerial survey data were used to determine the effect

of lateral distance on sightability, and the influences of aircraft type, survey altitude, wave height, and ice

cover. Eight aerial-survey studies in the Alaskan and Canadian Beaufort Sea during 1979–2000 provided

data on distances of bowhead sightings from the trackline. Altitude and aircraft type affected the size of

the zone directly below an aircraft where sightability was reduced. The higher the altitude, the wider the

zone. Twin Otter aircraft had a narrower zone of reduced sightability below the aircraft than did Twin

Commanders; a TurboGoose was intermediate. Wave height (expressed as Beaufort sea state, Bf) and ice

cover each affected the rate at which sightability diminished with increasing distance from the trackline.

Also, the effect of Bf state depended on aircraft type. With increasing Bf conditions and ice cover, the

relative number of sightings at the longer lateral distances diminished. As a result, the lateral distance

where sighting probability diminished to 15% of that at the optimum distance declined with increasing Bf

state and ice cover, and f(0) values also changed.
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Availability Bias Factor ga(0).—This factor estimates the proportion of whales at the surface and

potentially visible to aerial surveyors as the aircraft passes overhead. We determined this factor for

whales in the “Flaxman Isl.–to–Herschel Isl.” area during September–October based on three studies of

bowhead behavior in that area during 1985–86 and 1998–2000. This correction factor varied

substantially with whale activities. The probability was lowest for traveling whales, slightly higher for

feeding whales, and notably higher for whales engaged in socializing: ga(0) = 0.125, 0.153, and 0.234,

respectively. Our overall estimate of ga(0) for an average bowhead in the eastern Alaskan Beaufort Sea

during late summer and autumn is 0.144. These factors are slightly higher than the corresponding proportions of time the whales spend at the surface, as the factors assume that any whale near the trackline

will be sighted if it surfaces during an (approx.) 21.6-s period while that area is in view.

Detectability Bias Factor gd (0).—This factor estimates the proportion of whales at the surface near

the trackline that are detected by observers. We estimated gd(0) based on the double independent observer method, as applied during three aerial survey projects in the Canadian (1981) and Alaskan (1985–86,

1998–2000) Beaufort Sea. This method applies an analysis of the capture–recapture type to sightings by

two surveyors observing independently from the same side of the aircraft, considering sightings within a

400-m strip of where detectability is optimal. Our estimates of gd (0) for bowheads are 0.59 ± s.e. 0.160

for a single observer, and 0.84 for two observers on the same side of the aircraft. Detectability was lower

in a 600-m strip just beyond the inner 400-m strip (gd = 0.42 ± 0.129 for one observer). Other aerial

survey evidence indicates that this factor very likely is affected by sea state.

The correction factors developed here are used elsewhere (Chapter 9) to convert raw aerial survey

data into estimates of the actual numbers of bowheads present in the eastern Alaskan Beaufort Sea on

various occasions.

Bowhead Distribution, Numbers & Activities: Conclusions

There were substantial differences in the numbers, distribution, size classes, residence times, activity budgets, and specific behaviors of bowhead whales in and near the eastern Alaskan Beaufort Sea

during late summer and early autumn of the five years with feeding studies. As summarized in Chapter

16 by W.R. Koski and W.J. Richardson, bowhead use of that area during August–October is highly

variable. Systematic aerial survey data from 1979–2000 suggest that the five years when the feeding

studies were conducted included years with low, moderate and high use by bowheads and thus may be

reasonably representative of the range of possible usage patterns. However, usage in any future year

probably will differ in at least minor ways from that in any of our five years of study.

Most bowhead whales of the Bering–Chukchi–Beaufort stock migrate through the eastern Alaskan

Beaufort Sea each year during late summer or early autumn en route to autumn feeding areas farther west

and wintering areas in the Bering Sea. Behavioral observations (and also the stomach contents of

bowheads harvested at Kaktovik―Chapter 18) show that feeding is a common activity while these whales

are in the eastern Alaskan Beaufort Sea. Over the five years studied, the two most common activities of

bowheads, at least during daytime when aerial observations were possible, were feeding (47%) and

traveling (31%). The proportions of time engaged in these two activities during late summer and early

autumn were intermediate between those observed during spring, when bowheads spend most of their

time traveling and little time feeding, and during summer, when bowheads spend most of their time feeding and little time traveling. However, the estimated proportions of time spent feeding during late summer and autumn ranged from 9% to 66% in different years. The inter-annual differences in numbers esti-
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mated to have been present probably were related to how long whales stopped to feed in the study area,

and thus to residence times.

The abundance and locations of zooplankton concentrations had a strong influence on bowhead

feeding locations (Chapter 6), and very likely also influenced residence times in the study area. We found

that different size classes of bowhead whales had different habitat preferences and different timing of

migration through the study area. Small subadult whales preferred Nearshore waters. As water depth

increased, small subadults became less common and the proportion of large subadults and adults increased. When prey was locally abundant in Nearshore and Middle Shelf waters, as in 1985 and 1986, some

subadult whales lingered in the study area to feed, and many larger whales (which tended to be found in

deeper water) traveled through the study area without stopping to feed. When prey biomass was higher in

Shelf Break waters (40–200 m) than closer to shore, as in 1999, large subadult and adult whales lingered

to feed there, and most small subadult whales traveled through without stopping. When prey was sparse

in the eastern part of the study area, as in 2000, most if not all whales traveled through that area without

stopping. Over all years of this study, subadult whales seemed to make more use of the study area than

adults, but there was year-to-year variation in the use by different age classes. Possible reasons for these

year-to-year differences in utilization are discussed further in Chapter 23, “Integration”.

Diet and Regional Feeding: Introduction

This component of the study sought to determine (1) what types of prey bowhead whales of the

Bering–Chukchi–Beaufort (BCB) stock eat, and (2) what parts of their seasonal range provide the predominant part of this food. The principal and most direct method for determining what bowheads eat was

analysis of the stomach contents of bowheads harvested by Inupiat whalers (Chapter 18). The project

also included a pilot study of the fatty acid composition of bowhead blubber in relation to the fatty acid

composition of potential zooplankton prey (Chapter 19). It was hoped that this approach might, when

further developed, provide a method for assessing food consumption over a longer period (and larger

geographic area) than can be assessed from stomach contents. To assess the proportion of the food consumed in different parts of the seasonal range, the carbon and nitrogen isotope ratios in bowhead tissues

were compared with those in the prey from the eastern Beaufort Sea vs. the Bering–Chukchi area (Chapter 20). Several of the earlier chapters also provide information directly or indirectly relevant to “Diet and

Regional Occurrence of Feeding”.

Diet & Regional Feeding: Stomach Contents

This component of the study, by L.F. Lowry and G. Sheffield of Alaska Department of Fish &

Game (Chapter 18), documents bowhead whale feeding in the Alaskan Beaufort Sea based on stomach

contents of whales harvested by Alaska Natives. They examined field records and archived data from

previous studies of bowhead stomach contents, and analyzed similar samples from 85 additional bowhead

whales harvested during 1986–2000 near Kaktovik, Barrow, and Cross Island. All available data from

bowheads harvested near those locations were used to characterize and compare diet by harvest location

and season (i.e., Kaktovik fall; Barrow fall; Barrow spring), and by whale size and sex.

Thirty-two bowheads harvested near Kaktovik during fall 1979–2000 have been examined for evidence of feeding. Of 29 whales whose feeding status could be classified as “feeding” or “not feeding”, at

least 83% had been feeding prior to death. Copepods, most commonly Calanus hyperboreus and C.

glacialis, were the most important prey; copepods occurred in all 21 stomachs with food and were the

dominant prey by volume in 62% of the samples. Euphausiids, mainly Thysanoessa raschii, were also an
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important food item. Estimated volume of stomach contents was as much as 150 liters, and in 7 of 18

cases was greater than 20 liters.

Four of five bowheads harvested near Cross Island during 1987–2000 were recorded as having

been feeding. Copepods were the main prey in the three stomach contents samples examined.

Stomachs of 106 bowheads harvested in fall near Barrow during 1976–2000 were examined. Of

the 103 “non-calf” whales that could be classified as “feeding” or “not feeding”, at least 75% had been

feeding prior to death. Euphausiids were the most important prey; they occurred in 94% of the stomachs

with food and were the dominant prey by volume in 88%. Estimated volumes of stomach contents were

as much as 189 liters, and in many cases were recorded as ≥100 liters or “full”.

Stomachs of 100 bowheads harvested in spring near Barrow during 1969–2000 were examined. Of

the 90 whales that could be classified as “feeding” or “not feeding”, at least 33% had been feeding prior

to death. Euphausiids occurred in 93% of the samples and were the dominant prey in 61%. Copepods

were also an important diet item, especially in samples collected before the 1990s. Estimated volumes of

stomach contents were smaller than for whales taken in fall, and never exceeded 60 liters.

There was no significant difference in the proportion of bowheads that had been feeding in the fall

near Kaktovik and Barrow. However, there was a significant difference in composition of the fall diet at

these locations. Copepods occurred more often and were more frequently the dominant prey by volume

in whales from Kaktovik. Euphausiids occurred more often and were more frequently the dominant prey

by volume in whales from Barrow.

At Barrow, the frequency of feeding in harvested bowheads was significantly greater in the fall

than in the spring. Copepods occurred significantly more often in whales harvested near Barrow in the

spring than in the fall.

Male and female bowheads ate essentially the same food items. The data suggest the possibility of

a slight difference in the prey eaten by small (<13 m) and larger (≥13 m) whales. There was no difference

in the frequency of feeding of small versus large whales.

Preliminary estimates of the overall bowhead diet composition by location/season were as follows:

Kaktovik fall, 61–62% copepod, 22–24% euphausiid, 15–17% other prey; Barrow fall, 5% copepod, 84–

88% euphausiid, 7–11% other prey; and Barrow spring, 27–28% copepod, 61–63% euphausiid, and 10–

11% other prey.

Lowry and Sheffield conclude that coastal waters of the Alaskan Beaufort Sea should be considered as part of the bowheads’ normal summer–fall feeding range. During spring, feeding by bowheads

near Barrow is more common than previously thought, but the frequency and apparent intensity of feeding is less in spring than in the fall.

Diet & Regional Feeding: Fatty Acids

Fatty acids, the dominant constituent of lipids, are often deposited in animal tissue with minimal

modification from those in the diet. Lipids in the marine food web are exceptionally complex and

diverse. Dr. S.J. Iverson et al. (Chapter 19) undertook a pilot study to assess whether analysis of fatty

acid signatures in bowheads and their potential prey (zooplankton) would be a useful tool for better

understanding the foraging ecology and diets of bowheads in Alaskan waters. They identified and measured the fatty acids in samples of blubber from 28 bowheads harvested at Kaktovik (fall) and Barrow
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(spring and fall); 33 samples of mixed zooplankton from the eastern Alaskan Beaufort Sea; and 32

samples of zooplankton that had been sorted into seven major prey groups (copepods, euphausiids, etc.).

This preliminary study indicates that fatty acid signature analysis could be a very useful tool in

better understanding the foraging ecology and diets of bowheads in Alaskan waters. The inferences that

can be made now are limited because of small sample sizes of whales and potential prey, and lack of data

on fatty acid profiles in individual species of prey. However, there are indications that fatty acid analyses

may show differences in diets of whales of different sexes and size classes; such differences have not

been clearly detectable from stomach contents analyses. Iverson et al. analyzed samples of mixed zooplankton from two years, and the fatty acids of the zooplankton are consistent with them being bowhead

diet items. Additionally, although there are very limited data on fatty acid patterns in potential prey, preliminary results from a QFASA (Quantitative Fatty Acid Signature Analysis) model indicate that fatty

acid patterns of the inner blubber, presumably indicative of recent diet, are consistent with general diet

data obtained from stomach contents analyses. The high fat content of these prey, especially copepods,

also suggests high dietary intakes of fat. With further and more extensive sampling and analysis, the taxonomic composition of bowhead prey could likely be better assessed using the quantitative tools now

being developed. Fatty acid signatures are expected to represent the integrated diet over weeks or possibly months, and thus over larger geographic areas, than are the stomach contents of harvested whales.

Diet & Regional Feeding: Stable Isotopes

This part of the work (Chapter 20) was done by Sang Heon Lee and Dr. D.M. Schell of University

of Alaska Fairbanks, with assistance from Dr. Trent McDonald of WEST Inc. δ13C and δ15N ratios in

muscle and baleen from harvested bowhead whales were used to estimate the relative amounts of food

acquired from the eastern Beaufort Sea (summer and early autumn range) versus the Bering and Chukchi

seas―the two regions previously proposed as major feeding grounds. This analysis was based on the fact

that isotope ratios in the zooplankton prey of bowheads are different in the two regions. Isotope ratios in

prey are reflected in the predators. When isotope ratios differ regionally, this provides a basis for

determining the main area(s) where the predators feed.

Samples obtained from whales harvested in autumn of 1997–99 and spring of 1986–88 were

compared. Both δ13C and δ15N values in the whales have decreased in recent years in response to a long

term decreasing trend in isotope ratios in the Bering–Chukchi food chain. The whale samples collected

~10 yr apart were normalized to allow direct comparison.

For all whales, the δ13C values in muscle sampled in fall were not significantly different from the

muscle sampled in spring. Muscle δ13C during both seasons closely matched the isotope ratios of zooplankton from Bering and Chukchi water, indicating that most of the annual food requirement of adults

and subadults is met from that portion of their range. Isotope data from baleen showed, however, different feeding strategies by adult and subadult whales. Subadults acquired sufficient food in the eastern

Beaufort Sea to alter the carbon isotope ratios in baleen deposited there relative to baleen representing

feeding in Bering and Chukchi water. Baleen plates from subadults showed a wider range in isotope

ratios than those from adults, suggesting active feeding by subadults over all parts of their range. A simple approximation based upon observed seasonal shifts in muscle isotope ratios indicates that between 10

and 26 percent of the muscle carbon is replaced over the summer, depending on the method of

calculation. A sensitivity analysis that allowed for variability in each factor involved in the calculation

indicated that the true percentage probably did not exceed 23 %. Limited data on blubber indicates an

even smaller percentage. Although these specific estimates are subject to a variety of assumptions, the
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isotopic evidence indicates that only a minority of the feeding by either subadults or (especially) adults is

in the eastern Beaufort Sea.

Diet and Regional Feeding: Conclusions

At least at first glance, there seems to be an inconsistency between isotopic evidence (Chapter 20)

and other evidence concerning the importance of feeding in the eastern Beaufort Sea. The isotope record

in bowhead muscle, blubber, and baleen seems to indicate that bowheads (especially adults) feed mainly

on prey from the Bering and/or Chukchi Seas. However, behavioral, aerial-survey, and stomach-content

data, as well as certain energetics data (see below), show that bowheads also feed widely across the

eastern and central Beaufort Sea in summer and fall.

Behavioral and stomach content data do not directly show how much food is consumed in the

eastern Beaufort Sea as compared with the Bering/Chukchi system. One could hypothesize that bowhead

feeding in the Beaufort Sea might be frequent, as shown by behavioral and stomach-content data, but not

very efficient. Behavioral and stomach content results might be reconcilable with isotopic data if prey

availability to bowheads were notably better in Chukchi and/or Bering water than in the eastern Beaufort

Sea. This hypothesis would be consistent with the known high productivity of the Bering Sea and of

water from the Bering Sea that is transported north into the Chukchi. That possibility is discussed further

under “Integration and Conclusions”, below. However, if feeding in the Beaufort Sea were not important

to bowhead whales, it is difficult to understand why bowheads would spend so much time feeding there,

and why they would adapt their movements and local distribution to prey concentrations. Indeed, it is

difficult to understand why bowheads would migrate from the Bering–Chukchi area to the Beaufort Sea if

feeding in the Beaufort Sea were unimportant.

Energetics of Bowhead Whales

An estimate of the importance of the eastern Alaskan Beaufort Sea to feeding bowheads requires that

their daily and annual food requirements be estimated and then used to determine what proportion of their

annual requirements could be obtained in the study area. Chapter 22, by D.H. Thomson, first describes the

size, growth and reproduction of bowhead whales and the related physical attributes needed for the estimation

of energetic requirements. This is followed by several approaches to the estimation of the metabolic rate of

bowheads. These are compared to estimates of the amount of food consumed by bowhead whales as

determined through observations of behavior, swimming speed, and amount of food found near feeding

whales. The only specific data on the amount of food near feeding whales come from the Canadian and

eastern Alaskan Beaufort Sea. There are numerous other data gaps where it has been necessary to make

assumptions. Identification of these data gaps is useful in showing topics on which additional research would

be desirable.

The sizes of bowhead whales and their blubber content can be estimated using known-scale vertical

aerial photographs. The results are in agreement with blubber content as estimated from old whaling

records and weights of a few whales harvested at Barrow. Baleen length was estimated as a function of

whale length using data from whales harvested at Kaktovik and from data in old whaling records.

Important relationships needed for energetic calculations are summarized below, where “a” and “b” are

the coefficients for an equation of the form y = a × (body length in meters)b

, r is the correlation coefficient, and P denotes the significance level of the correlation:
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Parameter/ units a a b r P

Whale Weight MTb 0.047 2.58 0.98 < 0.001

Blubber Weight MT 0.052 2.19 0.95 < 0.001

Total surface area m2 0.54 1.85 0.99 < 0.001

Surface area of fluke m2 0.012 1.94 0.92 < 0.001

Weight of metabolic core MT 0.03 2.53 0.97 < 0.001

Surface area of metabolic core m2 0.49 1.70 0.97 < 0.001

a Equation form: y = a x body length (m)b

. b 1 MT (metric tonne) = 1000 kg.

Theoretical energetic requirements were calculated for a 12.5 m whale that weighs 31 MT, taking

account of the available data on whale physiology and bowhead dimensions, seasonal activities,

swimming speeds, and surfacing–respiration–dive cycles. The energetic requirements of bowhead

whales, as estimated using the respiration method, are higher than estimates based on calculated power

output or hydrodynamic considerations plus the standard metabolism approach, which is based on heat

loss.

The theoretical energy requirements of bowheads appear to be quite low and are in keeping with

the adaptations that bowheads possess for living in a cold environment where food is relatively scarce

compared to some other marine waters. These adaptations include

• A very slow maturation rate where males mature when 12 to 13 m long at an age of ~25

years, and females at a length of 13 to 13.5 m when ~27 years old.

• Very slow growth rates: after weaning, subadults initially show little growth and an average

subadult gains only about 0.8 to 1MT/yr; adults gain 0.2–0.9 MT/yr.

• The highest blubber content on a percentage basis of any species of whale.

• The longest baleen of any species of whale.

• A long reproductive cycle which spreads the energetic cost of reproduction over about four

years.

Potential feeding rates in nature were computed from the area of the mouth opening, speed while

swimming, and quantity of food available to bowheads in the eastern and central Beaufort Sea. The

mouth opening computed from width of the mouth at ~1/3 the distance between the tip of the rostrum and

the rear corner of the mouth, as a function of body length, was estimated as

 Mouth Opening (m2

) = –2.15 + 0.312 × Length (m); r = 0.93, P < 0.001

Because the lower lip holds the baleen in place when the mouth is open, bowheads could feed with their

mouths open very wide. The relationship between whale length in m and maximum mouth opening in m2

was best described as

 Maximum mouth opening (m2

) = –2.03 + 0.342 Length (m); r = 0.94, P < 0.001

Bowheads feed on zooplankters that have a high lipid content. The small size of the bowhead stomach

and observations of bowhead feces are consistent with a hypothesis that bowheads extract only the lipids from

their prey, at least when feeding in areas with much zooplankton. Zooplankton concentrations near feeding

subadult bowheads in the Canadian and eastern Alaskan Beaufort Sea average 1.8 g/m3

 on a wet weight basis,

based on echosounder-guided net sampling. This corresponds to an energetic value of about 2069 J/g wet
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weight considering only the lipid content of the prey. Observations of behavior indicate that bowheads may

feed an equivalent of ninety-three 24-hour-days per year. This estimate has wide uncertainty given the lack of

specific time-budget data for the western Chukchi Sea and Bering Strait in fall (where we assume intensive

feeding) or the central Bering Sea in winter (where we assume no feeding). Assuming 93 days of feeding per

year and a swimming speed of 2.5 km/h while feeding, a 12.5 m whale feeding at locations with average prey

biomass of 1.8 g/m3

 could consume 1.4 × 105 kJ/d, averaged over the year and adjusted for annual differences

in lipid content. For comparison, the calculated value assuming a swimming speed while feeding of 5 km/h

and prey density 4 g/m3

 was 6.0 × 105 kJ/d,

 Several different methods have been used to compute the energetic requirements of an average

12.5-m bowhead whale weighing 31 MT:

kJ/d x 105

Standard metabolism 2.8

Standard metabolism + swimming 3.4

Basal metabolic rate 5.8

Basal metabolic rate of core only 4.1

Power output + BMR 6.6

Cost of swimming +BMR 6.437

Core BMR + Cost of swimming 4.7

Respiration 6.4

Feeding in nature (2.5 km/h, 1.8 g plankton/m3 1.4

Feeding in nature (5 km/h, 4 g zooplankton/m3 6.0

Growth/Food Storage for Winter 1.4

Estimated basal metabolism is higher than standard metabolism computed through consideration of

heat loss. However, estimated basal metabolism for the core weight (excluding blubber) is about the

same as standard metabolism. The metabolic rate of bowhead whales may be quite low for their size.

The evidence tends to support a low estimate based on BMR calculated from the core weight not

including blubber, plus some small but unknown amount for maintenance of the blubber layer. The cost

of locomotion derived through consideration of power output and cost of swimming were also computed,

and added to standard and basal metabolism.

About 1.4 × 105

 kJ/d needs to be added to the above estimates to account for growth and food

storage, and ~1.8 × 105

 kJ/d need to be added to adult female requirements for the cost of reproduction

averaged over a 4-year reproductive cycle. When these amounts are added to the two theoretical estimates, the difference between those estimates and the lower “feeding in nature” estimate becomes even

greater.

One major uncertainty affecting the energetic analysis is the unknown amount of feeding in the

Chukchi Sea and Bering Strait in fall, and the Bering Sea in winter. Isotopic results suggest that most

feeding by both subadult and (especially) adult bowheads occurs outside the Canadian and eastern

Alaskan Beaufort Sea. However, feeding is commonly observed in those areas, most whales harvested at

Kaktovik have food in their stomachs, and subadult bowheads harvested in fall are heavier and have a

higher lipid content in their blubber than do spring harvested animals. Measurements of length and girth

from known-scale aerial photographs confirm some loss of girth (and thus weight) in winter. Available
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data indicate that the net loss of weight from the time bowheads leave the Beaufort in fall until they return

in spring may be on the order of 2.5 to 3.6 MT for an 11 m subadult and a 14.5 m adult. Actual weight

loss in winter is probably greater, assuming there is further weight gain in the Chukchi Sea and Bering

Strait in late autumn before the (presumed) period of winter fasting and weight loss begins.

Sampling of food available at places where bowheads were observed feeding has only been conducted near subadults feeding in summer and early fall. These data came from feeding sites in the Canadian and eastern Alaskan Beaufort Sea. The average prey availability at the depth of maximum prey

biomass at these sites was measured as 1.8 g/m3

 on a wet weight basis. Estimated prey consumption by

subadults feeding in such locations is only about half that required by even the lower of the estimates of

theoretical energetic requirements if average food availability in other feeding locations is similar.

Subadults and adults would need to feed in higher concentrations of zooplankton. The quantity of prey

available at specific locations where adult bowheads feed is unknown. Given our assumptions about the

number of days of feeding in various seasons, subadults and adult males would, over the course of the

year, need to feed on average concentrations of 4 g/m3

 at an average speed of 5 km/h to meet energetic

requirements. A swimming speed of 5 km/h while feeding, and zooplankton concentrations of 4 g/m3

near feeding whales, are at the upper ends of the observed ranges of values in the Beaufort Sea, and above

the average observed values for that area.

The estimate of energetic requirements derived through consideration of respiration is at the high

end of the range of estimates derived here. It is based on weights of only 5 lungs and assumptions about

the undocumented relationship (for bowheads) between weight of lungs and their volume. Tidal volume

and oxygen consumption of bowheads are unknown, as are breathing rates in winter.

The estimate derived through consideration of heat loss and cost of motion is an intermediate

estimate relative to other methods. This intermediate estimate may represent the best available estimate

of the energetic requirements of bowhead whales. It is consistent with adaptation to a cold environment

with relatively low food availability, and with the morphology and physiology of the animal.

Integration and Conclusions

The purpose of the project, as stated at the outset, was to compile and integrate existing traditional

and scientific knowledge about the importance of the eastern Alaskan Beaufort Sea for feeding by bowhead whales; to build consensus on the need for and approach to fieldwork to augment this knowledge; to

conduct the field studies and to analyze the results; to integrate them with existing traditional and

scientific knowledge; and to report on and publish the results. Chapters 1–22, and the foregoing

summaries of those chapters, describe the variety of studies included in the project, efforts to coordinate

the work with local residents, and incorporation local knowledge of bowhead whales into the project.

Chapter 23, by D.H. Thomson, W.R. Koski and W.J. Richardson, with assistance by B.F.J. Manly, draws

the various lines of evidence together in order to address several key questions regarding the importance

of the study area for feeding by bowhead whales. Those questions were stated in the introduction of this

Executive Summary. In these final analyses, the study area is considered to extend from Flaxman Island

to the Alaska/Canada border (a distance of ~205 km), and from the shore to the 200 m depth contour.

This is the area outlined in Figure S.2 plus a westward extension by 20 n.mi. (37 km) to Flaxman Island.

A comparison of carbon isotope ratios in bowhead muscle and baleen with those in the main food

organisms suggests that bowhead whales consume only a minority of their food in the eastern and central

Beaufort Sea, including Canadian as well as eastern Alaskan waters:
Executive Summary

xlii

• Based on stable-isotope evidence, bowhead whales likely consume only 10 to 26 % of their

food in the eastern and central Beaufort Sea. Subadult bowheads appear to derive >10 % of

annual food requirements there, although the 95 % confidence interval extends below 10 %.

It is also probable that adults gain >10 % of their food in that area, but for adults the isotope

evidence considered in isolation would support an answer of <10 %.

The isotope results are surprising in relation to several other types of evidence that show considerable feeding by bowheads in the eastern and central Beaufort Sea during summer and early autumn:

• Behavioral observations show that bowheads spend much of their time feeding while in those areas.

• Zooplankton sampling near bowheads feeding in those areas shows that whales concentrate their feeding

at locations with much higher than average biomasses of zooplankton. • Stomach contents of bowheads

harvested during late summer and autumn at three locations in the Alaskan Beaufort Sea (including Kaktovik, within the eastern Alaskan Beaufort) show that most bowheads, both subadult and adult, had been

feeding shortly prior to death. • Length–girth relationships show that subadult bowheads, and possibly

adults, gain weight while in the Beaufort Sea in summer, and lose weight while elsewhere. • Lipid content of blubber, at least of subadults, is higher when they leave the Beaufort in fall than when they return

in spring. Although some of this evidence is preliminary and based on small sample sizes, the evidence

suggests the importance of feeding in the Beaufort Sea during summer and early autumn.

A feeding scenario that might be consistent with all these data is as follows: Feeding occurs commonly in the Beaufort Sea in summer and early autumn, and bowheads gain energy stores while feeding

there. However, zooplankton availability is not as high in the Beaufort Sea during summer as in the

Chukchi and northern Bering seas during autumn. Also, feeding in the western Beaufort in autumn may

effectively be on Chukchi prey advected to that area. Thus, bowheads might acquire more energy from

Bering/Chukchi prey in autumn than from eastern and central Beaufort prey in summer/early autumn.

Given this, plus an assumed low turnover rate of body components, the overall body composition of bowheads may be dominated by components from the Bering/Chukchi system even at the end of the summer

when leaving the Beaufort. Energy gained in the Beaufort and Chukchi seas during summer and fall is

presumably used during winter when food availability is low, resulting in reduced girth and energy stores

when returning to the Beaufort Sea in spring than when leaving in autumn.

Several aspects of this scenario are speculative. Also, as noted above, it remains unclear why bowheads would migrate to the Beaufort Sea and feed there so frequently during summer and early fall if

bowheads obtain little of their annual diet in that region. These uncertainties point toward topics warranting further research.

Although various types of evidence (with the exception of isotope ratios) indicate that the eastern

Beaufort Sea as a whole, including the Canadian Beaufort, is important to bowhead whales for feeding,

the eastern Alaskan Beaufort Sea is only a small fraction of that area. It was of interest to know how

much time an average whale, and some individual whales, spend in the specific eastern Alaskan Beaufort

Sea. Was there evidence of average or individual residence times of at least 7 days? Analysis of several

types of data resulted in the following conclusions:

• An average bowhead spends ~3.8 days in the area from Flaxman Island to the Alaska/

Canada border during the late summer/autumn period, or ~1.4 d longer than expected for a

whale that swims steadily across that area. Averages in various years ranged from ~2.5 to

6.3 d. Although the average was <7 d in all years studied, it might exceed 7 days in a small

minority of the years, based on the calculated upper 95 % confidence bounds.
Executive Summary

xliii

• Of the individual bowheads that travel through the eastern Alaskan Beaufort Sea, some

spend at least 7 days between the Alaska/Canada border and Flaxman Island during late

summer and autumn.

What percentage of the geographic area within the eastern Alaskan study area is suitable as feeding

habitat? At least 1 % in some years? At whale feeding locations in the Canadian and eastern Alaskan

Beaufort Sea, zooplankton biomass at the depth of maximum biomass, where bowheads presumably fed,

averaged 1.8 g/m3

 and was usually ≥800 mg/m3. The latter was assumed to be the minimum biomass that

was sufficient for economical feeding by bowheads.

• The percentage of the study area suitable as feeding habitat, i.e., with ≥800 mg/m3

 zooplankton at some depth, averaged 25 % over four years with effective echosounder sampling,

and varied from 7 % to 43 % in individual years.

Two additional questions of interest concerned the proportion of bowheads that feed while in the

eastern Alaskan Beaufort Sea, and the frequency with which they feed while actively traveling:

• Based on stomach content data, supplemented by behavioral evidence, far more than 10 %

of the bowheads that pass through the eastern Alaskan Beaufort Sea during late summer and

autumn feed there. Of the whales harvested at Kaktovik, 83 % had food in their stomachs,

and 39 % had ≥20 L of stomach contents.

• Bowheads fed for an average of 47 % of their time in the eastern Alaskan Beaufort Sea

during late summer and autumn. A substantial minority of the feeding occurred during

travel. Among traveling whales, feeding as well as travel was occurring during a substantial

percentage of the time, on the order of 43 %. 

A key objective for this study was to estimate what percentage of the bowhead population’s annual

energetic requirements might be derived from the study area. The estimated number of whale-days in the

study area during August–October averaged ~16,953 /yr across the five study years, but varied widely

from year to year. Whale-days estimates were based on aerial survey data adjusted to allow for whales

missed by the surveyors. Based on the whale-days estimates, and the fact that bowheads in the study area

were observed to feed for 47 % of the time (9 to 67 % in different years), we estimated the number of

effective feeding-days in the study area each year. Given this, the bowhead energetics model developed

in the preceding chapter, and various assumptions, it was possible to estimate the fraction of the population’s annual dietary requirements that might be derived from the eastern Alaskan study area:

• In an average year, the population of bowhead whales derives an estimated 2.4 % of annual

energetic requirements in the eastern Alaskan Beaufort Sea. In 1 of 5 years of study, the

population may have derived 7.5 % or more of annual energetic requirements from the area.

Utilization of the study area varies widely in time and space depending on zooplankton

availability and other factors.

In 4 of 5 study years, the bowhead population was estimated to consume <2 % of its annual requirements

within the eastern Alaskan Beaufort Sea during late summer and autumn. A sensitivity analysis by Dr. B.F.J.

Manly indicated that, in those four years, the upper bound of the 95 % confidence interval was below 5 %.

However in 1999, when the best estimate was 7.5 %, the upper bound was 16.5 %. We suspect that the whaledays figure for 1999 was overestimated, and that the 16.5 % upper bound is unrealistically high. However,

consumption in the study area during a high-utilization year might exceed 5 % of annual population require-
Executive Summary

xliv

ments. Given some of the approximations that were made, these estimates are more likely to be over- than

underestimates. It is implausible that the population would consume more than a few percent of its annual

food requirements in the study area in an average year.

A related analysis showed that an individual whale would need to spend 10 days in the eastern

Alaskan Beaufort Sea in order to consume 5 % of annual food requirements. A small (but uncertain)

fraction of the individuals spend 10 days there in late summer/autumn. Few if any individuals spend 20

days in the area, which would be required to obtain 10 % of their individual annual food requirements

there.

Overall, the results show that the eastern Alaskan Beaufort Sea is used for feeding to widely varying

degrees depending on the year and on the individual bowhead. It is not surprising that the average

contribution to the annual diet is apparently rather small: Most individual bowheads remain in that area for

only a rather short period in late summer/fall, averaging ~4 days. That is too little time to allow an average

bowhead to consume more than a small fraction of its annual dietary intake. Also, the eastern Alaskan study

area is rather small in comparison to the overall area in the Beaufort and Chukchi seas where bowheads are

known to feed. It would be unreasonable to expect that a high percentage of the annual diet would be

acquired during a short stay in one small area. However, it was beyond the scope of this study to assess the

importance (for feeding) of the present study area as compared to other similar-sized areas.

Bowhead whales are of great cultural importance to the Inupiat and are a major source of food.

Thus, any area used by bowheads, especially when it is also a hunting area, is considered important by the

local residents. No matter what percentage of the annual food requirement is derived from the eastern

Alaskan Beaufort Sea, local residents will continue to view their hunting grounds as an important area for

bowhead whales.

This study has devoted much effort to the integration of existing and new scientific knowledge with

local and traditional knowledge. It has provided many new data concerning bowhead feeding ecology

and related aspects of bowhead biology, especially in the eastern Alaskan Beaufort Sea. However, there

are still numerous approximations, assumptions, data gaps, and variations of opinion regarding interpretation of data. This is inevitable in dealing with such a complex topic, especially in an environment

where field studies must cope with severe logistical difficulties. The authors do not claim that the project

has resolved all uncertainty about the importance of the eastern Alaskan Beaufort Sea for feeding by

bowhead whales—only that much progress has been made, and that the range of uncertainty has been

narrowed. One of the major outcomes of the project is to better identify the major questions that remain

to be answered. A list of potential research topics is included in the “Integration and Conclusions”

chapter of the final report.
The Department of the Interior Mission

As the Nation's principal conservation agency, the Department of the Interior has responsibility for

most of our nationally owned public lands and natural resources. This includes fostering sound use

of our land and water resources; protecting our fish, wildlife, and biological diversity; preserving the

environmental and cultural values of our national parks and historical places; and providing for the

enjoyment of life through outdoor recreation. The Department assesses our energy and mineral

resources and works to ensure that their development is in the best interests of all our people by

encouraging stewardship and citizen participation in their care. The Department also has a major

responsibility for American Indian reservation communities and for people who live in island

territories under U.S. administration.

The Minerals Management Service Mission

As a bureau of the Department of the Interior, the Minerals Management Service's (MMS) primary

responsibilities are to manage the mineral resources located on the Nation's Outer Continental Shelf

(OCS), collect revenue from the Federal OCS and onshore Federal and Indian lands, and distribute

those revenues.

Moreover, in working to meet its responsibilities, the Offshore Minerals Management Program

administers the OCS competitive leasing program and oversees the safe and environmentally sound

exploration and production of our Nation's offshore natural gas, oil and other mineral resources. The

MMS Royalty Management Program meets its responsibilities by ensuring the efficient, timely and

accurate collection and disbursement of revenue from mineral leasing and production due to Indian

tribes and allottees, States and the U.S. Treasury.

The MMS strives to fulfill its responsibilities through the general guiding principles of (1) being

responsive to the public's concerns and interests by maintaining a dialogue with all potentially

affected parties and (2) carrying out its programs with an emphasis on working to enhance the

quality of life for all Americans by lending MMS assistance and expertise to economic development

and environmental protection.
1. INTRODUCTION

W. John Richardson and Denis H. Thomson 1

The Bowhead Whale

The bowhead whale, Balaena mysticetus, is a large arctic-dwelling baleen whale in the right whale

family (Balaenidae). Bowheads, like other right whales, are rotund, slow-swimming whales with long

and fine baleen, well adapted for filtering small prey from large volumes of water. This introductory

section provides some basic information on the species. References are generally excluded, as most of

this information is common knowledge, and summarized in the standard monograph on The Bowhead

Whale (Burns et al. [eds.] 1993).

The distribution of the bowhead whale is limited to arctic and subarctic regions, rarely very far from ice.

Historically there were five populations of bowhead whales distributed around the arctic. All were subject to

commercial whaling before and/or during the 19th century. All five populations were greatly reduced by this

whaling, and only one of the five stocks has recovered to a substantial degree. That is the Bering–Chukchi–

Beaufort (BCB) population, which winters in the Bering Sea and travels north and east around Alaska to the

Beaufort Sea in summer (Fig. 1.1). As of 1993, the BCB stock was estimated to contain about 8200 animals

and to be increasing at about 3.2% per year. That would suggest a population of somewhat over 10,000

whales by 2000. The next census was in 2001, and preliminary results from 2001 confirm that the current

BCB population is indeed near 10,000 whales and continuing to increase (George et al. 2002).

Alaskan natives conduct subsistence hunts for BCB bowheads every year. Communities in western

Alaska, northeast as far as Barrow, hunt bowheads during the spring migration. Three communities along

the coast of the Alaskan Beaufort Sea – Kaktovik, Nuiqsut, and Barrow – hunt bowheads during their

westward migration in late summer and autumn. In recent years, the maximum allowable harvest has

been about 67 bowheads struck or 56 landed per year; actual landings are generally somewhat less. The

harvests have been well below the sustainable yield of the population, as confirmed by the upward trend

in population size. The quota is assigned by the International Whaling Commission (IWC), and managed

by the Alaska Eskimo Whaling Commission and National Marine Fisheries Service. A Special Meeting

of the IWC in October 2002 provided for up to 280 bowheads to be landed in the period 2003–2006. The

bowhead harvest is of great significance, both cultural and nutritional, to the communities that participate.

The importance of bowheads to Alaskan natives has been a dominant factor in elevating concerns about

the potential impacts on bowheads of industrial activities and other factors.

The BCB bowhead whales winter in the pack ice of the northern Bering Sea, and migrate northward into the Chukchi Sea in early spring. Most of the population travels northeastward through leads in

the pack ice until they reach Point Barrow, and then travel east into the Beaufort Sea. The spring

migration past Barrow is predominantly from mid-April through early June, with the subadults tending to

pass first, then adults, and finally mothers with newborn calves. From the Barrow area, many bowheads

 

1

 LGL Ltd., environmental research associates, 22 Fisher St., POB 280, King City, Ont. L7B 1A6.

Phone: 905-833-1244; e-mail: wjr@lgl.com, dthomson@lgl.com
1-2 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

FIGURE 1.1. Seasonal migration of the Bering–Chukchi–Beaufort stock of bowhead whales, and locations

mentioned in text. The “eastern Alaskan Beaufort Sea” is shaded.

travel east through cracks and leads in the pack ice until they reach more extensive lead systems in the

Canadian Beaufort Sea. Little is known of their activities there until mid-summer, when the ice has usually

receded and bowheads are commonly seen feeding in open waters of the southeastern Beaufort Sea and

western Amundsen Gulf. In August and early September of some years, large numbers of bowheads

(mainly subadults) feed in shallow waters along the north coast of the Yukon. (The adults tend to be farther

offshore and east at this time.) Most summer feeding is apparently in the water column. However, bowheads are sometimes seen bringing mud to the surface, indicative of feeding near the bottom, and sometimes

they are seen swimming at the surface with mouths open. In addition to feeding, summering bowheads are

commonly seen to rest, socialize, or travel. They sometimes exhibit “aerial behaviors” (breaching, flipper or

fluke slapping), and they occasionally play with inanimate objects such as logs.

Although most bowheads apparently move into the Canadian part of the Beaufort Sea in summer,

some may not. Local residents in northern Alaska report occasional sightings of bowheads in July and

August, and aerial surveys in August have found bowheads far offshore in the eastern part of the Alaskan

Beaufort Sea. Also, by late August or early September, the whales that concentrate in late summer (in

some years) along the Yukon coast often start to move into eastern Alaskan waters. Those whales are

often seen feeding in the same ways as they feed in the Canadian Beaufort Sea. Most of the bowheads

harvested in the annual subsistence hunt at Kaktovik, in the eastern Alaskan Beaufort Sea, have prey in

their stomachs – predominantly copepods and to a lesser extent euphausiids and other organisms. The

bulk of the westward migration from Canada into the eastern Alaskan Beaufort Sea occurs from late

August until mid October.
§1. Introduction 1-3

The speed of westward travel across the Alaskan Beaufort Sea is quite variable, with some

individuals traveling west rather steadily (as indicated by telemetry) but others lingering, in many cases to

feed. Bowheads have often been seen to feed while traveling west, but at other times they linger in

feeding aggregations, at times including tens or even hundreds of whales. In addition to the eastern

Alaskan Beaufort Sea near and east of Kaktovik, concentrations of bowheads feed in waters east of

Barrow in some years. Bowheads harvested at Barrow in fall frequently have much food in their

stomachs, predominantly euphausiids.

From the Barrow area, many bowheads travel southwestward across the northern Chukchi Sea to

the northeast coast of Russia, where feeding aggregations have sometimes been seen in autumn. There is

relatively little direct information about the nature and amount of feeding along the Russian coast.

Eventually these whales turn southeastward and travel through the Bering Strait toward the wintering

grounds. Almost nothing is known about the activities of bowheads in winter. However, a previous

study of carbon isotope ratios in bowhead prey and bowhead tissues suggested that much of the annual

food intake is obtained from Chukchi or Bering Sea waters, where most BCB bowheads occur from late

autumn until spring. The same study suggested that only a minority of their food comes from the eastern

and central Beaufort Sea, including the eastern Alaskan Beaufort. This was surprising given the frequent

observations of feeding in the Beaufort Sea, the common occurrence of food in stomachs of bowheads

harvested in the Alaskan Beaufort in fall, and the fact that other baleen whales feed mainly in summer.

Bowheads are notable for their slow growth rates and long lifetimes. Calves are born in spring after a

gestation period of just over one year. They remain with their mothers through the summer and autumn but

most are weaned by the following spring. After weaning, their growth becomes very slow for the first few

years of independent life. Bowheads do not become sexually mature for many years – much later than other

baleen whales. After reaching sexual maturity, bowhead females appear to have calving intervals of 3–4 years.

Recent evidence suggests that some bowheads may live to very great ages – well beyond 100 years.

Background to this Project

The purpose of the present project, as defined by the Minerals Management Service, was to

compile and integrate existing traditional and scientific knowledge about the importance of the eastern

Alaskan Beaufort Sea for feeding by bowhead whales; to build consensus on the need for and approach to

fieldwork to augment this knowledge; to conduct the field studies and to analyze the results; to integrate

them with existing traditional and scientific knowledge; and to report on and publish the results.

This feeding study was considered necessary by MMS to support environmental risk assessments,

environmental impact statements (EISs), and other pre- and post-leasing decision documents for potential

gas and oil leasing in the Beaufort Sea planning area.

Chapters 2 through 23 of this report are an integrated account of traditional knowledge, previous

scientific knowledge, and results from recent scientific studies concerning the use of the eastern Alaskan

Beaufort Sea for feeding by bowhead whales. The new data collected during this study, mainly during

September of 1998, 1999 and 2000, have been supplemented with data collected earlier in and adjacent to

the study area. This increases the power of analyses and provides a better basis for assessing among-year

variation in the various aspects of bowhead feeding ecology.

This project is an extension of a bowhead feeding study conducted in the same area during 1985

and 1986 (Richardson [ed.] 1987). The present MMS-sponsored study is intended to provide additional

data from more years, and to do so in collaboration with subsistence hunters and other local stakeholders.

The 1985–86 study concluded that the eastern Alaskan Beaufort Sea did not, in those years, provide more
1-4 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

than a small proportion of the food consumed by the Bering–Chukchi–Beaufort stock of bowheads,

although the area may be important to some individual bowheads. That conclusion was controversial.

The main concerns were the short duration of the previous study (two field seasons, one of which was

limited by ice cover), questions about sampling designs, and difficulties in estimating food availability

and consumption. Two years is too short a period in which to fully characterize use of an area by bowhead whales. Environmental conditions, and the distribution and activities of bowheads, are all known to

vary widely from year to year.

The current project is similar in scope and purpose to the previous study, but includes changes and

refinements to deal with concerns about the earlier study raised by the North Slope Borough’s Science

Advisory Committee (SAC) in 1987. The Project Plan (Thomson and Richardson 1999) was designed to

take account (insofar as possible) of the main concerns about the 1985–86 work. Major differences

between this study and the one done in 1985–86 are as follows:

• closer coordination with the Kaktovik Whaling Captains’ Association (KWCA), North Slope

Borough (NSB), Alaska Eskimo Whaling Commission (AEWC), National Marine Fisheries

Service (NMFS), and industry to involve stakeholders in the project and its planning,

• use of a Scientific Review Board (SRB) including both independent scientists and representatives of the aforementioned stakeholder groups to review project plans and draft reports,

• extended use of stable isotope analyses, taking account of developments since 1985–86,

• a pilot study to investigate the potential usefulness of promising new methods of fatty acid

analysis to help characterize prey types,

• use of 14 more years of bowhead distribution data, mainly based on aerial surveys conducted

annually by MMS (total of 21 years now available),

• addition of 3 more years of specific feeding studies in the eastern Alaskan Beaufort Sea (total of

5 years now available), and

• most importantly, greatly increased efforts on local coordination, with the objective of ensuring

that key stakeholders support the need for the project, its objectives, its methods, and the

interpretation of its results.

Where appropriate and possible, methods applied during the new three-year study were consistent

with methods used during the 1985–86 study. Thus, there are now consistent data from five years, supplemented by additional data (e.g., aerial surveys) from other years, with which to address the main

objectives and hypotheses.

Objectives of the Study

The objectives of this study are listed below. References to “Year 1” refer to mid-1997 through

mid-1998. Year 2 began in mid-1998 and included the September 1998 field season. Year 3 began in

mid-1999 and included the September 1999 field season. Year 4 began in mid-2000 and included the

final field season in September 2000.

1. Use existing data (traditional and scientific) to assess when and how feeding bowheads can be

recognized and distinguished from those engaged in social/milling and other behaviors

(Year 1), and distinguish those activities whenever possible during field studies (Years 2–4).

2. Mutually develop hypotheses that scientists and subsistence whale hunters concur can be successfully tested to determine and quantify the relative importance of the eastern Alaskan Beaufort Sea as a feeding area for bowhead whales (Year 1).
§1. Introduction 1-5

3. Design (Year 1) and conduct (Years 2–4) research appropriate for testing the above hypotheses

and for quantifying potential feeding by bowhead whales in the same area.

4. Analyze previous and updated scientific information, summarize pertinent knowledge of area

subsistence whale hunters, and, where possible, test the above hypotheses and quantify bowhead area feeding for previous years (Years 1 and 2–4).

5. Use historical satellite and aerial survey data to search for links between spatial or temporal

patterns in bowhead feeding vs. ambient oceanographic conditions (Year 1). If links are evident, use all available data to characterize those links (Year 4).

6. Summarize (Year 1) and update (Year 4) available information, including traditional knowledge, on the effects of acoustic and visual disturbance to bowhead whales (or other planktivorous whales) engaged in apparent feeding behavior. This is considered to be a secondary

objective.

7. Use the above information to determine and quantify the relative importance of the eastern

Alaskan Beaufort Sea as a seasonal feeding habitat for bowhead whales (Year 4).

Also, although the limited available pre-1998 and 1998–2000 satellite data on sea-surface

conditions were acquired, these data were not used in any detailed way. All other objectives listed above

were addressed in detail.

Study Area and Periods

Why Concentrate on the Eastern Alaskan Beaufort Sea?

The eastern part of the Alaskan Beaufort Sea has been known for many years as an area where

bowhead whales commonly feed during late summer and early autumn. By the early-mid 1980s, it was

recognized that, in some years, considerable numbers of feeding bowheads occur in that area, especially

in September (e.g., Johnson 1984). By that time it was also known that there is zooplankton – mainly

copepods and euphausiids – in the stomachs of most bowheads harvested in autumn near Kaktovik (e.g.,

Lowry and Burns 1980; Lowry and Frost 1984). It was recognized that some feeding occurs farther west

during autumn, especially in the area just east of Barrow, but feeding frequency seemed to decrease as

bowheads moved west through the Alaskan Beaufort during autumn (Ljungblad et al. 1986). Whether

there really is such a decrease is uncertain, as specific studies of feeding have not been done in the central

and western parts of the Alaskan Beaufort Sea. In fact, feeding frequency may be as high or higher just

east of Barrow than in more easterly parts of the Alaskan Beaufort (Treacy in prep.). Most bowheads harvested at Barrow in fall have been feeding shortly before death (Lowry 1993; see also Chapter 18 of this

report). However, during the early-mid 1980s the eastern part of the Alaskan Beaufort Sea was judged to

be of special significance to bowheads. Now-available data confirm that it is, at the least, one of the parts

of the Alaskan Beaufort where feeding is common in late summer and early autumn.

Given the concern in the mid-1980s about the importance of the eastern Alaskan Beaufort Sea as a

feeding area, MMS sponsored an intensive study of bowhead feeding in that area during 1985–86 (Richardson [ed.] 1987). That study concentrated on the area from eastern Camden Bay (144°W, just west of

Kaktovik) to the Alaska–Canada border, and from the shore to the 200 m depth contour roughly 50–65

km offshore (Fig. 1.2). However, some attention was also given (via aerial surveys) to deeper waters

north of the 200 m contour.
1-6 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

FIGURE 1.2. The eastern Alaskan Beaufort Sea and adjacent waters, showing the areas identified as the

primary study areas for the 1985–86 and 1998–2000 feeding studies.

The 1985–86 study concluded that, in those years, the eastern Alaskan Beaufort Sea did not provide a very high proportion of the annual energy requirements of the bowhead population, although food

from that area may have been important to some individual bowheads that fed there longer than did the

average whale. That conclusion was controversial. Among other concerns, the Science Advisory Committee of the North Slope Borough concluded that the 1985–86 study did not cover a sufficient number of

years to justify any general conclusion about the importance of the area. This conclusion, and subsequent

expressions of concern about the adequacy of the 1985–86 study, was one of the main reasons why MMS

decided to sponsor a follow-up study in the same general region, with amendments in study procedures to

address the concerns about the 1985–86 study.

It is well known that much feeding by bowheads occurs elsewhere, both farther east in the Canadian Beaufort Sea during summer (e.g., Würsig et al. 1985, 1989; Bradstreet et al. 1987), and farther

west in the Alaskan Beaufort Sea and the Chukchi Sea during autumn (e.g., Lowry 1993; Landino et al.

1994; Moore et al. 1995). There is also a limited amount of feeding along the spring migration route

(Carroll et al. 1987; Lowry 1993; Richardson et al. 1995). Evidence from stable isotopes suggests that

feeding is, in fact, predominantly in Bering and Chukchi waters (Schell and Saupe 1993). The eastern

Alaskan Beaufort Sea constitutes only a small percentage of the total range of the BCB bowheads, and

likewise only a small percentage of the part of that range where feeding is known to occur (Fig. 1.1). The

MMS-sponsored feeding study in 1985–86 concentrated on the eastern Alaskan part of the Beaufort Sea

because, of the feeding areas under MMS jurisdiction (waters off Alaska), the eastern Alaskan part of the

Beaufort Sea was of particular concern in the mid-1980s. The study area for the current 1998–2000 study

was similar because of continued interest in that area, and because of a desire to resolve questions that

had been raised about the results of the initial 1985–86 study.
§1. Introduction 1-7

Specific Study Area Boundaries

As noted above, the study area for the 1985–86 project extended from eastern Camden Bay, just

west of Kaktovik (144°W), to the Alaska–Canada border (141°W at the coast), and from the coast

offshore to the 200 m contour (intensive effort) and beyond (aerial surveys only). During the planning

process for the present study, we reviewed the available information available from a wider area, from

Flaxman Island near the western edge of Camden Bay (146°W) to Herschel Island some 75 km into

Canadian waters (139°W). Based on that review, advice from Kaktovik whalers (see Chapter 2), and

advice from the project’s Scientific Review Board (SRB), it was decided to extend the primary study area

westward by 1° of longitude (37 km) as compared with the western edge of the 1985–86 study area. This

placed the new western boundary near the middle of Camden Bay (145°; Fig. 1.2). Also, with SRB

concurrence, it was decided to further de-emphasize efforts in deep offshore areas in order to concentrate

available resources in the shallower areas of particular concern to Kaktovik hunters and (potentially) the

oil industry. During the 1998–2000 study, boat-based zooplankton sampling was limited to areas seaward

to the 50 m contour (vs. 200 m in 1985–86). However, our standard aerial survey coverage in 1998–2000

extended to the 200 m contour, and in those years less intensive aerial survey coverage was obtained

farther offshore by ourselves and as part of the broad-scale aerial survey program conducted by MMS

(Treacy 2000, 2002).

Although the official study areas for the 1985–86 and 1998–2000 projects were as defined above,

relevant data of various types were obtained from adjacent areas to the west, north, and east. For

example, the aerial surveys conducted or sponsored by MMS each year since 1979 have extended slightly

east and far west of the official study areas for the 1985–86 and 1998–2000 feeding studies. Behavioral

observations of bowheads, and aerial photogrammetric data on bowheads, have also been obtained from

areas farther east and west during certain years. Other bowhead feeding studies, especially in Canadian

waters (e.g., Bradstreet et al. 1987), provide data that are relevant in interpreting the data from the specific

“eastern Alaskan” study area. The overall approach in this study was to make use of relevant data from

other projects when appropriate, thereby expanding the available data and strengthening the conclusions

that can be drawn. Thus, in some chapters of this report, we include data from areas bordering the official

study area. For each chapter or analysis, we have described the area in which data were collected or

assembled. This inclusive approach causes some complications in deriving averages and estimates specific to the official study area, as described in various chapters. However, within limits, the advantages of

larger sample size and broader perspective outweigh the disadvantages.

Study Periods

Years.—The specific MMS-sponsored studies of bowhead feeding in the eastern Alaskan Beaufort

Sea were in 1985–86 and 1998–2000, for a total of five late summer/early autumn seasons. However,

bowhead utilization of that area was documented in at least a general way during other years in the 1979–

2000 period. MMS conducted or sponsored systematic aerial surveys including the eastern Alaskan

Beaufort Sea in all of those years aside from 1980. In addition to the broad-scale MMS aerial surveys and

the additional surveys conducted in 1985–86 and 1998–2000 as part of the feeding studies, other industrysponsored or Canadian-based aerial surveys covered parts of the eastern-Alaskan study area in certain

years. Aerial surveys in years other than 1986–86 and 1998–2000 were used to obtain an extended (in

time) perspective on utilization of the study area. Comparison of aerial survey data from the five feedingstudy years vs. other years provides information as to how representative the feeding-study years were.

Chapter 9 of this report summarizes the aerial survey data from 1979 to 2000.
1-8 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

Whalers and other local residents also provided information about certain whale activities in the

eastern Alaskan study area during some years aside from the five feeding-study years. Most of the

Kaktovik residents who provided us with Local and Traditional Knowledge (LTK) have lived and hunted

in the study area for several decades, and are very familiar with year to year variability in use of the area

by bowhead whales. The information that they provided is summarized in Chapter 2 and in Annex B (in

volume 2). As with the aerial survey information, LTK provided an additional basis for judging whether

the detailed results from the five feeding-study years were representative.

Samples of bowhead stomach contents from whales harvested at Kaktovik were available not only

from the feeding-study years (except 1985, when no bowheads were taken at Kaktovik) but also from

1997 and various other years (see Chapter 18). Only a very small number of samples of bowhead

stomach contents can be obtained at Kaktovik each year given the low number of animals harvested there

per year (maximum of 3 in most recent years, not all of which contain prey when landed). However, the

samples from other years broaden the perspective.

Study Dates.—Boat-based fieldwork was conducted for about 2 weeks during early-to-mid or midto-late September of 1985–86 and 1998–2000. Aircraft-based fieldwork specifically for the feeding study

occurred for 3–4 weeks during September in each of those years. These main field periods occurred

during the time of peak occurrence of bowheads in the study area. However, these periods began after

bowheads first arrived in the area (especially in 1998–2000), and ended well before the end of the

bowhead migration. Indeed, it is possible that some bowhead whales are in the general area throughout

the summer, given the occasional sightings of bowheads in the area during July (see Chapter 2). However, the scarcity of summer (as compared with fall) sightings indicates that bowheads are present in

summer only sporadically and/or in low numbers, at least in the nearshore areas that are of most concern.

The limited duration of the main field periods during the five years of the feeding studies was a

result of several factors:

• limited resources that precluded intensive operations throughout the whale migration season;

• a desire (during the 1998–2000 study) to sample in three additional years rather than concentrate

a fixed amount of effort into two longer field seasons;

• an agreement with the Kaktovik hunters, during each of 1998–2000, to avoid boat-based sampling east of Kaktovik until after two bowheads had been harvested; and

• a serious risk that ice would interfere with boat operations, including safe return of the boat to

Prudhoe Bay, if sampling continued into October. The 1985 field season was, in fact, curtailed

early because of an incursion of pack ice that threatened to trap the sampling vessel.

To help interpret the results of the September sampling, we took advantage of several supplementary sources of data that provided information about whale use of the study area during a larger

fraction of the migration period. These additional sources of information included

• MMS and other aerial survey data (1979 to 2000), typically extending from about 1 September

until early or mid October, and occasionally late October; from 1979 to 1986, aerial survey data

were also available from the present study area during much of August (see Chapter 9);

• local knowledge, as assembled through meetings and discussions with individual residents of

Kaktovik (see Chapter 2 and Annex B); and

• boat-based reconnaissance surveys near Kaktovik during late August (mainly of 2000), as suggested by Kaktovik residents (see Chapter 2).
§1. Introduction 1-9

We acknowledge that the intensive feeding study work did not extend through the full period while

bowhead whales are present in the eastern Alaskan Beaufort Sea. However, it did occur during the time

of peak utilization of that area by bowhead whales, as documented by aerial surveys. It would be

interesting to have specific information about food availability and whale feeding during the early and

late parts of the late summer/autumn season. However, we believe that the various sources of data, in

combination, provide a reasonable basis for assessing the overall importance of the study area for feeding

by bowhead whales.

Project and Report Title

The title of the present final report is the title that was assigned to the 1998–2000 feeding study by

MMS in the “Request for Proposals” (April 1997) and in the contract:

“Bowhead whale feeding in the eastern Alaskan Beaufort Sea: Update of Scientific and

Traditional Information”

The Scientific Review Board suggested, at its January 2002 meeting, that the final report be given a title

including more specific details concerning the study area and study period. However, the areas and

periods of study depended on the type of data being collected. Any attempt to be more precise leads to a

long and cumbersome title. These matters are discussed further in Annex A (in volume 2). We decided

to retain the original project title as the report title; it accurately represents the overall study scope, and

maintains continuity with titles used earlier in the project.

Questions to be Addressed

Questions to be addressed by the study were developed around the study objectives. The study

design was, in turn, based in large part on these questions.

A set of general hypotheses was developed during Year 1 and included in the Project Plan (Thomson and Richardson 1998). An updated set of seven hypotheses was subsequently developed that included specific cutpoints such as numbers of days whales might spend in the study area and percent of time

they might spend feeding. In selecting cutpoints, we took the view that small differences in food intake

may have major consequences for individuals and populations. Insufficient food intake might cause

reproductive failure and retardation of the age at maturity, among other effects. Thus, some of the cutpoints that we used in the revised hypotheses were relatively low values. These hypotheses were not

conventional “null” and “alternate” hypotheses. Following review of the draft final report by the project’s

Scientific Review Board (see Annex A), it was agreed by all concerned that these hypotheses should be

re-phrased as research questions that were addressed by the project.

Question (1)

The overall question addressed during this study is as follows:

In an average year, how important is the eastern Alaskan Beaufort Sea for bowhead whales;

what percentage of the population’s annual energetic requirements is derived from the area?

This overall question is addressed by considering many different types of data acquired or assembled

during the project (see Chapters 2 – 22), integrated by means of an energetic model (Chapter 22). Here, as

in the more specific questions listed below, the project aims to estimate an actual value rather than simply

determine whether the value is above or below some specified cutpoint. However, for Questions 2 – 6, the

cutpoints included in the (former) hypotheses have been retained. We consider these cutpoints to represent

levels of feeding activity that, if exceeded, would indicate substantial feeding in the area.
1-10 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

Question (2)

How much of its annual food requirements does the Bering–Chukchi–Beaufort (BCB) population

of bowhead whales derive in the eastern and central Beaufort Sea? At least 10 percent?

This question is to be addressed by examining isotopic composition of bowhead tissue in spring

and fall, and of prey tissue through the range of the bowhead whale. Presently-available stable isotope

techniques cannot discriminate food acquired in the Canadian vs. the eastern Alaskan Beaufort Sea. As

written, this is an important and potentially answerable question if there is consensus about the

applicability of the stable isotope method to this question. If it is established that bowheads derive little

of their annual food requirements from the larger area (eastern and central Beaufort Sea), as previous

isotope data suggest (Schell and Saupe 1993), then the smaller “eastern Alaskan Beaufort Sea” would

necessarily provide an even smaller proportion of the population’s annual energetic requirements. However, before the isotopic method could be accepted as resolving this matter one way or the other, the

applicability of this method needed further consideration. Results of earlier isotopic studies (and of some

of the additional isotopic work described in Chapter 20) are surprising in light of several other types of

evidence documenting frequent feeding in the eastern and central Beaufort Sea during summer and early

autumn. Also, a related isotope-based study (Hoekstra et al. 2002) has provided some data that differ

from those of the present study. These data need to be compared and reconciled. This topic is addressed

in Chapters 20–23.

Question (3a)

Of the bowheads that travel through the eastern Alaskan Beaufort Sea, how long does an

average whale spend there? At least 7 days?

Question (3b)

Of the individual bowheads that travel through the eastern Alaskan Beaufort Sea, how long

do some individuals spend there? At least 7 days?

These two related questions can be answered based on evidence concerning residence times,

including aerial photogrammetric data documenting residence times of individually-recognizable bowhead

whales, previously-reported telemetry data, etc. The question has been split into two because there are

distinct questions about the importance of the study area to certain individual whales vs. the population as a

whole. The 7-day cutpoint is substantially less than the duration of each field season. Several sources of

data such as behavioral observations and stomach contents show that most if not all whales that travel

through the eastern Alaskan Beaufort Sea feed there to at least a limited extent. Thus, total residence times

in the area can be assumed to be closely related to the importance of the area for feeding.

Question (4)

What percentage of the bowheads that pass through the eastern Alaskan Beaufort Sea feed

there? At least 10 percent?

This question addresses the proportion of the whales passing through the area that feed. This can

be answered with two independent types of data: stomach content data from the Kaktovik harvest, and

behavioral observations.

Question (5)

What percentage of the geographic area within the study area is suitable as feeding habitat

in different years? Is at least 1% of the study area suitable in some years?

This question can be answered through boat-based observations of the quantities and types of zooplankton present at locations where bowheads feed, the spatial extent of such plankton concentrations,
§1. Introduction 1-11

and the stomach contents of bowheads harvested near Kaktovik. Dense concentrations of zooplankton

tend to occupy only a small proportion of the available space in the world’s oceans. One percent of the

study area would represent a large amount of feeding habitat and a large quantity of potential food.

Question (6)

During migration through the eastern Alaskan Beaufort Sea, how often are bowheads

observed to feed while they are traveling? Is feeding while traveling evident more than 10%

of the time while traveling?

This question can be addressed based on aerial observations of the activities of whales in the study

area during late summer and fall, taking account of such indications of feeding such as surface feeding,

defecation, and surfacing with mud streaming from the mouth. One concern in addressing this question is

the reliability with which water column feeding can be recognized, especially during travel. Failure to

detect much feeding while traveling would not necessarily lead to a conclusion that feeding while traveling is rare. However, if traveling whales are seen to feed more than 10% of the time, we could conclude

that feeding while traveling is fairly common. This question is important to the overall objectives of the

study. If a large proportion of the population feeds while actively migrating through the area, then a large

amount of food would be consumed.

In general, the project plan calls for us to determine if the study area is important to feeding bowhead whales in the following way:

• determine if numbers of animals remain in the study area for an extended period of time,

• determine what proportion of these animals are feeding,

• describe the zooplankton and hydrography near feeding whales,

• attempt to locate and characterize whale feeding habitat,

• determine what the whales are eating through examination of stomach contents and fatty acid

analysis, and compare stomach fullness and contents between Kaktovik and Barrow,

• determine how much feeding occurs in the eastern and central Beaufort Sea through isotopic

studies, and

• estimate the annual energetic requirement of the population (based on an updated energetics

model), and estimate what proportion of this is acquired in the study area.

These tasks have all been done, with the exceptions that the fatty acid study was limited to a pilot project, and

the results of the stable isotope study remain difficult to reconcile with those of other study components.

Study Components

Present Study Components

The project included

• retrospective studies and compilation of local and traditional knowledge about bowhead whales

in and near the study area; this work was conducted primarily in Year 1 (1997–98) but was later

updated for inclusion in this final report;

• boat-based sampling of prey (zooplankton) via net-sampling and echosounder methods during

1998–2000, plus use of comparable data collected during 1985–86;

• aircraft-based surveys, behavioral observations, and photogrammetry/photoidentification of

bowheads during 1998–2000, plus use of comparable data collected during 1985–86, other

aerial survey results from 1979–2000, and behavioral and photographic data from various years;

• collection and analysis of bowhead stomach contents in 1997–2000, plus analysis of additional
1-12 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

archived samples from earlier years, to document diet directly;

• stable-isotope and fatty acid analyses of tissue samples from bowheads and potential prey to

document trophic relationships (fatty acid work was limited to a pilot study);

• data analysis;

• integration; and

• preparation of reports and publications.

Retrospective Studies.―The retrospective analyses conducted during Year 1 (1997–98) included

several different studies, the results of which were reported in a draft report to MMS and the project’s

Scientific Review Board during July 1998. The final reports of each of these retrospective studies were

submitted in September 1999 as part of Richardson and Thomson (eds., 1999). Most of that material has

been incorporated into relevant chapters of the present report, most notably

• Chapter 2, local and traditional knowledge,

• Chapters 5 and 6, zooplankton and water masses in the study area, both generally and at specific

bowhead feeding locations,

• Chapter 9, bowhead distribution and abundance from aerial surveys,

• Chapter 18, bowhead stomach contents, and

• Chapter 20, regional feeding as evident from stable isotopes.

In addition, most of the other major chapters of this report, specifically Chapters 4, 10–15, and 22, also

incorporate data from studies conducted previous to 1998, even though the Year 1 work did not specifically include retrospective analyses of those topics.

Project Plans.―A Project Plan for the work in years 2–4 was prepared in 1998 based on the results of

the retrospective and traditional knowledge studies. A draft of that plan was presented to the SRB in July 1998

for its evaluation and comments. The final Project Plan, dated 31 August 1998, was prepared taking those

comments into account (Thomson and Richardson 1998). Studies conducted during year 2 (1998–99) were

based on this plan. A Project Plan for years 3 and 4 (1999–2001), dated 21 May 1999, was presented at the

June 1999 SRB meeting. This project plan was revised to account for comments and suggestions made by the

SRB and was submitted in final form in August 1999 (Thomson and Richardson 1999).

Project Reports.―A final report on the retrospective studies and on fieldwork during September

1998 (years 1 and 2 of the study) was distributed in September of 1999 (Richardson and Thomson 1999).

The data collected during the second season of intensive fieldwork (September 1999) were presented in

an interim report circulated in July 2000. No further substantive changes to the study plan were recommended or implemented based on the data presented then. The present final report includes the first presentation of data from the third season of intensive fieldwork (September 2000) plus all relevant data from

earlier years. Much additional analysis of data from years previous to 1998 has also been done for the

present final report. The present report supersedes all previous project reports. The organization of the

present report is described later in this Introductory chapter.

Project Participants.―The prime contractor for this project (and for the related 1985–86 feeding

study) was LGL Ecological Research Associates Inc. and its affiliate LGL Ltd., environmental research

associates. LGL was responsible for the boat-based studies of zooplankton (Chapters 3–7), the aircraftbased studies of bowheads (Chapters 8–16), the energetics and integration tasks (Chapters 22–23), and

management aspects of the project. Several personnel from BioSonics Inc. assisted LGL with collection
§1. Introduction 1-13

and analysis of echosounder data on zooplankton. Consultant Dr. Bernd Würsig of Texas A & M University at Galveston worked with LGL on aircraft-based studies of bowheads.

Several chapters of this report have been contributed by others. Consultant Michael Galginaitis of

Applied Sociocultural Research, Anchorage, was responsible for working with Kaktovik residents to

compile local and traditional knowledge (LTK; Chapter 2); he also undertook or assisted with various

local coordination tasks. Stomach contents of bowheads landed at Kaktovik and elsewhere were determined by the Alaska Department of Fish and Game (ADF&G), principally Lloyd Lowry and Gay Sheffield (Chapter 18). The pilot study on fatty acids was done by Dr. Sara Iverson, Dalhousie University, in

collaboration with ADF&G (Chapter 19). The stable isotopes study was done by Dr. Don Schell and

Sang Heon Lee, University of Alaska Fairbanks (Chapter 20). Sensitivity analyses for some key calculations have been done by Drs. Bryan Manly and Trent McDonald of WEST Inc. (Chapters 20, 23).

Many others assisted in numerous ways, as acknowledged near the end of this chapter and (more

specifically) near the ends of many of the subsequent chapters.

Other Potential Study Components

An up-to-date model concerning the energetics of bowhead whales was needed for this project. A

previous energetics model, developed during the 1985–86 bowhead feeding study, was available (Thomson 1987). Also, J.C. George of the North Slope Borough Department of Wildlife Management has been

conducting research in this area. We deferred updating our model until the last year of the project in

order to take account of the latest available information. This updating has now been done in collaboration with J.C. George. The updated model is described in Chapter 22 of this report.

No analysis of satellite images was done. Borstad Associates, who conducted the retrospective

analysis of satellite imagery, obtained and archived AVHRR satellite images during late summer and

early autumn of 1998–2000 to ensure that they would be available if needed, but performed no processing

of the images.

Fatty acid analysis of bowhead tissue and prey might be able to provide information on what kinds

of animals are eaten. If so, this type of analysis would provide data on diet over a longer time scale (and

thus over a larger area) than can be obtained from sampling of stomach contents. Samples of bowhead

tissue and zooplankton suitable for fatty acid analysis were collected in 1998–2000 but were not initially

analyzed. A pilot study was done and the results are reported in Chapter 19. Although the results show

promise for helping to elucidate bowhead trophic relationships, this pilot study was not carried sufficiently far to provide much information relevant to the overall objectives of the present project.

MMS originally requested that the present study include some acoustic components. This work

would have been peripheral to the main objectives of the project. In the interest of devoting limited

resources to key tasks, the SRB indicated that acoustic modeling work, if deemed important, should be

funded separately. No acoustic work was done as part of this project.

There was also some discussion of incorporating radio- or satellite-tagging into this project. All

concerned have recognized the potential value of this. However, funding for a tagging component was

not available. The SRB noted (most recently in 1999) that tagging should only be incorporated if it could

be separately funded. No radio- or satellite-linked tags were deployed during the present project. When

reviewing the draft of this report, the SRB again commented on the potential value of a separate radio- or

satellite-tagging study (see Annex A in volume 2).
1-14 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

Integration

Integration across disciplines has occurred to some extent throughout all phases of the project, and

is a central feature of the present final report. Each study component was designed so as to provide the

data needed by other study components. The cross-disciplinary data needs were taken into account during

planning, fieldwork, analysis, and reporting.

A primary requirement was to ensure that, by the latter stages of the project, we would have all the

data necessary to test key questions and to assess the importance of the study area for feeding by bowhead

whales. This integrated assessment requires the following:

• description of zooplankton distributions in terms of physical habitat,

• description of whale distributions in terms of the biophysical attributes of the study area, such as

depth, water mass characteristics, and zooplankton distributions,

• description of bowhead feeding areas in terms of zooplankton, water mass characteristics, and

presence of feeding and non-feeding bowhead whales,

• estimates of theoretical energetic requirements of bowheads, and a comparison with zooplankton biomasses near feeding bowheads,

• estimates of the amount of feeding in the Beaufort sea vs. other areas, and the contributions of

various prey taxa to the bowhead diet,

• an estimate of the percentage of the study area with suitable feeding habitat for bowheads,

• estimates of numbers and residence times of bowheads in the study area,

• an estimate of the percentage of time that bowheads in the study area spend feeding, and

• an estimate of the relative importance of the study area for individual whales that feed there for

extended periods.

A stated objective of this integration was to set bounds on the overall energetic importance of the

study area to the population as a whole, as estimated from calculated feeding rates and estimated whaledays of feeding within the study area.

Data bearing on these topics are included in various chapters of this report. Figure 1.3 shows many

of the main connections among the various project components. Each box in Figure 1.3 represents one of

the main chapters of the present report. Some additional connections are excluded in order to avoid

further complicating the Figure. The overall integration is done in Chapter 23.

Local Coordination

From the earliest phases of planning, local cooperation and participation were considered critical to

the success of the study. Including the July 1998 SRB meeting, we met with representatives of the

Kaktovik Whaling Captains Association (KWCA), Alaska Eskimo Whaling Commission (AEWC), and

North Slope Borough (NSB) on six occasions during Year 1 to seek traditional knowledge and advice on

project design, and to coordinate fieldwork with the bowhead hunt. These meetings were in Kaktovik

during December 1997 and January 1998, Barrow in May, Kaktovik in July, Anchorage in July (SRB),

and Kaktovik in August 1998. We again met with the KWCA, AEWC and NSB during the June 1999

SRB meeting. One or more project participants also met with some whaling captains and other Kaktovik

residents in Kaktovik during June and early September 1999, and August 2000, to further coordinate

planned fieldwork with whaling activities during those years. One key objective of all these meetings

was to develop and refine a field plan that whalers would accept as non-interfering and likely to be

effective in assessing the importance of the area to feeding by individual bowheads and the population.
FIGURE 1.3. Major linkages among feeding study tasks and report chapters.

4. Zooplankton: Acoustic vs. Net BiomassConvert Acoustic Biomassto Zooplankton Biomass

Quantity and Distribution ofZooplankton in the StudyArea, Energetic Value of Food

6. Zooplankton: Characteristics Bowhead Feeding Areas 

Amount and Kinds ofZooplankton Near Feeding Whales

13. Bowheads: Surfacing, Respiration & Dive Cycles vs. Activity 

Percent of Time Visible atthe Surface & Blow Rates

11. Bowheads: Rates of Movement and Residence Times

How Long WhalesRemain in Study Areaand How Quickly they Pass Through

12. Bowheads: Activities and Behavior 

Percent of Time SpentFeeding, Migrating and Socializing

10. Bowheads: Habitat Use by Size Class

Spatial and TemporalDistribution by Size/Age

9. Bowheads: Distribution and Abundance 15.Bowheads: Correction

 Factors

Correction Factors Need to Convert Density Indices to Numbers of Whales

5. Zooplankton: Species Composition, Biomass and Distribution

14. Bowheads: Surfacing, Respiration & Dive Cycles vs. Age 

Percent of Time Visible atthe Surface & Blow Rates 18. Diet and Regional Feeding:

Stomach Contents

Kinds of Foods Eaten byBowheads and Amount of Feeding in Various Areas

20. Diet and Regional Feeding:Stable Isotopes

Proportion of Food Obtained inEach of Two Broad GeographicalAreas

22. Energetics of Bowhead Whales

Amount of Food Consumedby Subadults, and AdultsThrough Consideration of Basal Metabolism, HeatLoss, Respiration andFood Consumed in nature

23. Integration

Number of Whale Days inArea by Migrating and Lingering WhalesNumber of Whales that Land Time Spent LingeringAmount of Food ConsumPopulationAmount of Food Consumthe Study AreaAmount of Food ConsumOther AreasImportance of the Study Ato Bowhead Whales

2. Kaktovikmiut Whaling: Harvest Data & Local Knowledge
1-16 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

Key items discussed at the meetings and incorporated into the Project Plan were as follows: (1)

Kaktovik residents were to be directly involved with the project through participation in the boat-based

field sampling in September of 1998–2000, conduct of boat-based reconnaissance surveys during August

1998–2000, and participation on the Scientific Review Board. (2) Aircraft-based field work was permitted east of Kaktovik during the whaling season, provided that the aircraft did not fly over whaling operations and that a radio communications protocol was established for coordination. (3) Boat-based work

would not be conducted east of or near Kaktovik until after whalers landed their second whale. In 2000,

because whalers landed their third whale early in the season (8 Sept.), boat-based work was not conducted

until after the third whale was landed. (4) An LGL representative would attend the pre-whaling-season

meeting of the Kaktovik Whaling Captains' Association during each year of fieldwork (see preceding

paragraph). (5) LGL’s aerial survey crew would be based in Kaktovik during the 1998–2000 field seasons, facilitating local coordination. (6) Subcontractor ADF&G would station a biologist in Kaktovik

during the 1998–2000 whaling seasons (as they had done in 1997) to collect stomach content and bowhead tissue samples from bowheads landed at Kaktovik.

As noted in (1), above, direct participation of Kaktovik residents in the project included three main

components:

• A Kaktovik resident (Mr. Leonard Solomon) was employed to work aboard the zooplankton sampling vessel during September of 1998, 1999, and 2000. He served as a full member of the zooplankton sampling team, helped in spotting whales, and provided another line of communication

with the local community.

• The Kaktovik hunters recommended that a “local boat” survey be initiated during August to

determine whether the vanguard of the migrating bowheads reaches the area before aerial surveys

commence in September. This was to be a cooperative effort involving locally-based boats operated by knowledgeable hunters, plus a biologist or subsistence specialist from the project team.

Arrangements were made to conduct local-boat surveys during late August of 1998–2000, earlier

in the season than any aerial surveys planned for those years. The “local boat” surveys were

attempted by the project’s sociocultural specialist, Mr. Michael S. Galginaitis, with the cooperation of several Kaktovik residents and boat-owners. Results are described in Chapter 2. These

boat surveys were most successful in 2000.

• From the start of the project, the project’s Scientific Review Board has included a representative

of the Kaktovik Whaling Captains’ Association (KWCA), Mr. Joseph Kaleak. Mr. Kaleak was

President of the KWCA during the early stages of the project, and is Kaktovik’s senior representative on the AEWC (Alaska Eskimo Whaling Commission). The SRB also includes representatives from the AEWC and the North Slope Borough Department of Wildlife Management

(NSB–DWM).

In order to present the results of the project to Kaktovik residents and to seek input on their

interpretation, a one-day workshop in Kaktovik held 31 January 2002. Representatives of the AEWC and

NSB also attended, along with the chair of the project’s SRB. Representatives of the project team

presented the key results and our interpretation of those results. Representatives of the SRB attending the

workshop were able to convey the SRB’s views regarding the results and their interpretation. We sought

feedback from workshop participants on all aspects of the project. This has been taken into account when

revising the draft final report to produce the present final report. As requested at the 31 January 2002

workshop, we plan that project representatives will return to Kaktovik in late 2002 to describe how the

SRB and local comments were taken into account in the final report.
§1. Introduction 1-17

Scientific Review Board

The purpose of the SRB was to evaluate all aspects of the study, with a view to improving study

design and interpretation, and to help build consensus among stakeholders. The SRB included representatives of key stakeholders as well as independent scientists. The SRB included a representative from

each of the KWCA, AEWC, NSB–DWM, oil industry (2 representatives), NMFS, and three knowledgeable independent scientists. MMS asked that the SRB meet in Anchorage three times during the project

to review draft plans for the coming field season and/or the draft report for the previous year.

The first SRB meeting was held in Anchorage on 20–21 July 1998. That meeting discussed a draft

Project Plan that had been circulated before the meeting, and made recommendations regarding project

plans and priorities.

The second SRB meeting was held in Anchorage on 3–4 June 1999. The SRB reviewed the draft

report on the fieldwork conducted in 1998, and the proposed plan for work in August–September 1999.

During the June 1999 SRB meeting it was agreed that no SRB meeting would be held in 2000, but that

the report on results from the 1999 field season would be circulated to SRB members for comment prior

to the 2000 field season. (That report was provided to the SRB in July 2000.)

A third and final meeting of the SRB was held in Anchorage on 28–29 January 2002. The purpose

was to review the draft final report circulated before that meeting, and to make recommendations that

should be taken into account while the report is being finalized. We expected that the SRB would also

make other comments and recommendations concerning the overall outcome of the project. The report

compiled by the SRB based on their January 2002 meeting is included as Annex A near the back of the

present report (in volume 2), along with responses by project participants to some SRB comments.

 Scientific Research Permits

A Scientific Research Permit under the provisions of the Marine Mammal Protection Act (MMPA)

and Endangered Species Act was obtained from NMFS for the 1998 and subsequent field seasons. We

requested that the permit cover the project activities near Kaktovik during 1998 through 2000, and permit

number 481–1463 was issued on that basis. In 1999, a permit modification was received to authorize

collection of stomach contents and tissue samples from bowheads landed at other Alaskan communities,

as well as extension of aircraft operations near bowheads to the Prudhoe Bay area, where a test of a Forward Looking Infrared device was planned and conducted.

We also applied for and received permits to extend some of the work into Canadian waters between

the Alaska–Yukon border and Herschel Island (~40 n.mi. to the east, Fig. 1.2) if this proved to be advantageous. These permits were issued by Fisheries and Oceans Canada and by the Environmental Impact

Screening Committee of the Inuvialuit Joint Secretariat. The latter permit was initially issued for 1998

and was renewed for 1999–2000. The Fisheries and Oceans Canada permit was issued for the 1998

season and was renewed for each of the 1999 and 2000 field seasons.

Report Organization

This final report is divided into several major sections and numerous smaller chapters. The sections concern whaling and local knowledge of bowheads at Kaktovik (Chapter 2), zooplankton (Chapters

3–7), bowhead distribution, numbers and activities (Chapters 8–16), diet and regional feeding dependencies (Chapters 17–21), energetics of bowheads (Chapter 22), and integration (Chapter 23). The three

multi-chapter sections each contain short introductory and concluding chapters.
1-18 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

The major chapters are designed to be more-or-less self-contained, with their own introduction,

methods, results, discussion, and summary subsections. Where necessary, detailed data are included as

Appendices at the end of the chapter in question. Most major chapters have been written in a format that

will facilitate the completion of scientific papers based on the corresponding topics; the MMS contract for

this project encouraged this approach. Thus, some material (particularly Methods) is mentioned in more

than one chapter, although with different emphasis in different chapters. This approach has the advantage

that the chapters are largely self-contained, and most are reasonably compact. Many chapters are expected to be suitable for submission to journals with only minor modification (e.g., deletion of Appendices).

The various short introductory and concluding chapters are not intended to become journal papers, but are

included here to tie together the chapters on various specific topics.

Acknowledgements

We thank the Kaktovik whaling captains, whaling crew members, and other Kaktovik residents

who participated in the several meetings and discussions that were part of the project planning process.

We appreciate their willingness to work out a way in which fieldwork could be conducted during the

autumn whaling seasons. Joe Kaleak, whaling captain and AEWC Commissioner for Kaktovik, has been

especially helpful in all aspects of this process. Charles Brower, President of the KWCA during the latter

part of the project, has also been very helpful in coordinating meetings and during the field seasons.

Leonard Solomon of Kaktovik provided able and enthusiastic assistance with the boat-based sampling in

1998 and 1999. Many Kaktovik residents provided information about whale use of the area, and several

participated in the “local boat” surveys (see Chapter 2).

We also thank Maggie Ahmaogak of the AEWC, Fred Kanayurak of the Barrow Whaling Captains’ Association, and Thomas Napageak of the AEWC and Nuiqsut, for participating in meetings and

providing various types of assistance.

Craig George, Dr. Todd O’Hara, and Dr. Tom Albert of the North Slope Borough Dept. of Wildlife

Management also participated in meetings and gave much valuable advice and assistance, including provision of stomach content and baleen samples from bowheads harvested at Barrow. Mark Major of

ARCO and Phillips Petroleum kindly arranged to obtain stomach contents samples from some bowheads

harvested at Cross Island in 1999 and 2000.

We are grateful to the members of the project’s Scientific Review Board (or their alternates) for

reviewing project plans, participating in meetings, and preparing constructive comments. SRB members

or alternates were Dr. Steven L. Swartz (Chair), Mrs. Maggie Ahmaogak or Mr. Thomas Napageak

(AEWC), Mr. Craig George or Dr. Todd O’Hara (NSB–DWM), Dr. Ray Jakubczak (BP Exploration

Alaska), Mr. Joe Kaleak (KWCA), Dr. Robert Kenney (University of Rhode Island), Mr. Mark Major

(ARCO Alaska and Phillips Petroleum), Mr. Brad Smith (NMFS–Anchorage), and Dr. Judy Zeh (University of Washington).

LGL thanks the various subcontractors and consultants for their participation. Subcontractors and

consultants have included Alaska Dept of Fish & Game, BioSonics Inc., Borstad Associates, SAIC

Maritime Services, University of Alaska Fairbanks, Western EcoSystems Technology (WEST) Inc., and

consultants Michael Galginaitis of Applied Sociocultural Research and Dr. Bernd Würsig of Texas

A & M University at Galveston. We also thank Oceanic Research Services (Bill Kopplin) and Commander Northwest for providing excellent boat and aircraft service, respectively. Nell Stallard (Applied

Technical Services) analyzed the zooplankton samples from 1998–2000 and 1985–86.
§1. Introduction 1-19

At LGL, Kathleen Hester and Anne Wright (King City) and Lynnette Cox, Shelly Schwenn, and

Bill Wilson (Anchorage) have had significant roles in producing reports, organizing meetings, and other

related administrative matters.

We thank the Minerals Management Service for initiating and supporting this project, and for their

willingness to be flexible as schedules and plans have evolved. Steve Treacy (COTR) and Dr. Cleve

Cowles of the MMS Alaska OCS Region, Anchorage, and Contracting Officer Jane Carlson, Herndon,

VA, have been very supportive. We also acknowledge Steve Treacy and Don Hansen of MMS for their

efforts in collecting aerial survey data each autumn since 1987. They kindly provided those data to us for

use here, along with related data collected in 1979–86 for MMS by Don Ljungblad, Sue Moore, Janet

Clarke et al. of Naval Ocean Systems Center and SAIC.

Additional acknowledgements pertaining to specific aspects of the project are included at the ends

of subsequent chapters of this report.

Literature Cited

Bradstreet, M.S.W., D.H. Thomson and D.B. Fissel. 1987. Zooplankton and bowhead whale feeding in the Canadian Beaufort Sea, 1986. Chapter 1 (204 p.) In: Bowhead whale food availability characteristics in the southern Beaufort Sea: 1985 and 1986. Environ. Stud. 50. Indian & North. Affairs Canada, Ottawa, Ont. 359 p.

Burns, J.J., J.J. Montague and C.J. Cowles (eds.). 1993. The bowhead whale. Spec. Publ. 2. Soc. Mar. Mammal.,

Lawrence, KS. 787 p.

Carroll, G.M., J.C. George, L.F. Lowry and K.O. Coyle. 1987. Bowhead whale (Balaena mysticetus) feeding near

Point Barrow, Alaska, during the 1985 spring migration. Arctic 40(2):105-110.

George, J.C., J. Zeh, R. Suydam and C. Clark. 2002. Population size of the Bering-Chukchi-Beaufort Seas stock of

bowhead whales, Balaena mysticetus, based on the 2001 census off Point Barrow, Alaska. SC/54/BRG5.

Intern. Whal. Comm., Cambridge, U.K.

Hoekstra, P.F., L.A. Dehn, J.C. George, K.R. Solomon, D.C.G. Muir and T.M. O'Hara. 2002. Trophic ecology of

bowhead whales (Balaena mysticetus) compared with that of other arctic marine biota as interpreted from

carbon-, nitrogen-, and sulphur-isotope signatures. Can. J. Zool. 80(2):223-231.

Johnson, S.R. 1984. Birds and marine mammals. Chapter 2 In: J.C. Truett (ed.), Environmental characterization

and biological use of lagoons in the eastern Beaufort Sea. Rep. from LGL Ecol. Res. Assoc., Bryan, TX, for

U.S. Dep. Commer., NOAA, OCSEAP Final Rep. 24: 129-579. NTIS PB85-212603.

Landino, S.W., S.D. Treacy, S.A. Zerwick and J.B. Dunlap. 1994. A large aggregation of bowhead whales (Balaena mysticetus) feeding near Point Barrow, Alaska, in late October 1992. Arctic 47(3):232-235.

Ljungblad, D.K., S.E. Moore and J.T. Clarke. 1986. Assessment of bowhead whale (Balaena mysticetus) feeding

patterns in the Alaskan Beaufort and northeastern Chukchi seas via aerial surveys, fall 1979-84. Rep. Int.

Whal. Comm. 36:265-272.

Lowry, L.F. 1993. Foods and feeding ecology. p. 201-238 In: J.J. Burns, J.J. Montague and C.J. Cowles (eds.),

The bowhead whale. Spec. Publ. 2. Soc. Mar. Mammal., Lawrence, KS. 787 p.

Lowry, L.F. and J.J. Burns. 1980. Foods utilized by bowhead whales near Barter Island, Alaska, autumn 1979.

Mar. Fish. Rev. 42(9-10):88-91.

Lowry, L.F. and K.J. Frost. 1984. Foods and feeding of bowhead whales in western and northern Alaska. Sci. Rep.

Whales Res. Inst. 35:1-16.

Moore, S.E., J.C. George, K.O. Coyle and T.J. Weingartner. 1995. Bowhead whales along the Chukotka coast in

autumn. Arctic 48(2):155-160.
1-20 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

 Richardson, W.J. (ed.) 1987. Importance of the eastern Alaskan Beaufort Sea to feeding bowhead whales, 1985-

86. OCS Study MMS 87-0037. Rep. from LGL Ecol. Res. Assoc. Inc., Bryan, TX, for U.S. Minerals

Manage. Serv., Reston, VA. 547 p. NTIS PB88-150271.

Richardson, W.J. and D.H. Thomson (eds.). 1999. Bowhead whale feeding in the Eastern Alaskan Beaufort Sea:

Update of scientific and traditional information. Retrospective and 1998 results. LGL Rep. TA2196-2. Rep.

from LGL Ltd., King City, Ont., and LGL Ecol. Res. Assoc., Bryan, TX, for Minerals Manage. Serv., Herndon, VA. 366 p.

Richardson, W.J., C.R. Greene Jr., J.S. Hanna, W.R. Koski, G.W. Miller, N.J. Patenaude and M.A. Smultea. 1995.

Acoustic effects of oil production activities on bowhead and white whales visible during spring migration

near Pt. Barrow, Alaska—1991 and 1994 phases. OCS Study MMS 95-0051; LGL Rep. TA954. Rep. from

LGL Ltd., King City, Ont., for U.S. Minerals Manage. Serv., Herndon, VA. 539 p. NTIS PB98-107667.

Schell, D.M. and S.M. Saupe. 1993. Feeding and growth as indicated by stable isotopes. p. 491-509 In: J.J. Burns,

J.J. Montague and C.J. Cowles (eds.), The bowhead whale. Spec. Publ. 2. Soc. Mar. Mammal., Lawrence,

KS. 787 p.

Thomson, D.H. 1987. Energetics of bowheads. p. 417-448 In: W.J. Richardson (ed.), Importance of the eastern

Alaskan Beaufort Sea to feeding bowhead whales, 1985-86. OCS Study MMS 87-0037. Rep. from LGL

Ecol. Res. Assoc. Inc., Bryan, TX, for U.S. Minerals Manage. Serv., Reston, VA. 547 p. NTIS PB88-

150271.

Thomson, D.H. and W.J. Richardson. 1998. Bowhead whale feeding in the eastern Alaskan Beaufort Sea: Update

of scientific and traditional information/Project Plan. Rep. from LGL Ltd., King City, Ont., and LGL Ecol.

Res. Assoc., Bryan, TX, for Minerals Manage. Serv., Herndon, VA. 66 p.

Thomson, D.H. and W.J. Richardson. 1999. Bowhead whale feeding in the eastern Alaskan Beaufort Sea: Update

of scientific and traditional information/Study Plan―Year 3. Rep. from LGL Ltd., King City, Ont., and LGL

Ecol. Res. Assoc., Bryan, TX, for Minerals Manage. Serv., Herndon, VA. 70 p.

Treacy, S.D. 2000. Aerial surveys of endangered whales in the Beaufort Sea, fall 1998-1999. OCS Study MMS

2000-066. U.S. Minerals Manage. Serv., Anchorage, AK. 135 p.

Treacy, S.D. 2002. Aerial surveys of endangered whales in the Beaufort Sea, fall 2000. OCS Study MMS 2002-

014. U.S. Minerals Manage. Serv., Anchorage, AK. 111 p.

Treacy, S.D. in prep. Aerial surveys of endangered whales in the Beaufort Sea, fall 2001. OCS Study MMS 2002-

061. U.S. Minerals Manage. Serv., Anchorage, AK.

Würsig, B., E.M. Dorsey, M.A. Fraker, R.S. Payne and W.J. Richardson. 1985. Behavior of bowhead whales,

Balaena mysticetus, summering in the Beaufort Sea: a description. Fish. Bull. 83(3):357-377.

Würsig, B., E.M. Dorsey, W.J. Richardson and R.S. Wells. 1989. Feeding, aerial and play behaviour of the bowhead whale, Balaena mysticetus, summering in the Beaufort Sea. Aquat. Mamm. 15(1):27-37.
2. KAKTOVIKMIUT WHALING: HISTORICAL HARVEST AND

LOCAL KNOWLEDGE OF WHALE FEEDING BEHAVIOR

Michael S. Galginaitis1 and William R. Koski2

Introduction

The desire to characterize the degree to which the eastern part of the Alaskan Beaufort Sea is used

by bowhead whales for feeding arises from a number of concerns. Subsistence whaling is of high importance to the Kaktovikmiut, the “people of Kaktovik” (Kaktovikmiut and Francis n.d.). This chapter

describes the community of Kaktovik and Kaktovikmiut subsistence whaling, summarizes the historic and

recent subsistence whale harvests of the Kaktovikmiut, and presents local and traditional knowledge

pertinent to whale feeding behavior near Kaktovik. None of these topics is treated exhaustively, but they

are presented in the detail appropriate to the main objective of the project: understanding the importance

of the eastern Alaskan part of the Beaufort Sea for feeding by bowhead whales. For present purposes, the

eastern Alaskan Beaufort Sea is taken to extend from the middle of Camden Bay to the Canadian border

(Fig. 2.1; see also Fig. 1.2 in Chapter 1 for a specific study area map). The complete transcripts of several

interviews with Kaktovik residents are included as Annex B of this report (in Volume 2).

Kaktovik―A Brief Description [history, population, economy, infrastructure]

Kaktovik, also referred to as Barter Island, is a small community located on Barter Island in the

extreme northeast of Alaska, within the boundaries of the Arctic National Wildlife Refuge (ANWR) (Fig.

2.1). The 2000 U.S. Census enumerated 293 people, most of whom (247, or 84 percent) are Native.

Household economies rely upon both wage labor (and other income sources) and subsistence activities as

vital components of an integrated system. The major employers are the North Slope Borough, the City of

Kaktovik, and the village Native corporation. There are also a few private sector jobs and businesses

separate from the Native corporations. These include retail stores, a hotel, and air carrier services. However, most employment is related to government or Native Corporations (IAI 1990a).

Subsistence activities in Kaktovik make use of a unique set of resources. Because of Kaktovik’s

location, hunters have access to terrestrial, riparian, and marine resources, and make substantial use of all

three. Fish caught both in rivers and in the ocean are important resources. Caribou are the most important terrestrial subsistence resource, but sheep, muskox, and grizzly bears are also taken. Of the marine

mammals, the bowhead whale is the primary subsistence resource, but seals and polar bears are also taken

(Jacobson and Wentworth 1982; IAI 1990b). Subsistence activities, and especially activities surrounding

the bowhead whale hunt, are central to the structural organization and cultural identity of Kaktovik residents.

 

1

 Applied Sociocultural Research, 608 West 4th Ave, Suite 31, POB 101352, Anchorage, AK 99510-1352.

Phone: 907-272-6811; e-mail: msgalginaitis@gci.net

2

 LGL Ltd., environ. res. assoc., 22 Fisher St., POB 280, King City, Ont. L7B 1A6. Phone: 905-833-

1244; e-mail: bkoski@lgl.com
2-2 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

FIGURE 2.1. Kaktovik and vicinity showing place names mentioned in the text. Place names are according to USGS Geographic Names Information System (http://geonames.usgs.gov)
§2. Kaktovikmiut Whaling: Harvest Data & Local Knowledge 2-3

Before contact with Euroamericans, the site of the present community of Kaktovik was not a

permanent Inupiat settlement, but had a long history as the location for seasonal gatherings for trading.

Along with the surrounding area and most of the adjoining coastline, it was also used for seasonal

subsistence activities of the highly mobile Inupiat people (Nielson 1977:1; Kisautaq 1981:161–173). One

account of how the site came to be called “Kaktovik” (or “Qaaktugvik”) also serves as an explanation for

why it was not the site for a permanent village. The story relates how the Qagmaliks from the east

(Canada) came to trade and decided to live in the area. They later abandoned the area after someone had

killed the only son of a couple living in the area. The couple found their son’s body while seining, and so

the place acquired its name from that activity and became “A-Seining-Place” and those “... living in the

wrong way had caused it to have no more people” (Kisautaq 1981:167–168; Libbey 1983:2).

In 1923, the Gordon family moved their store to Barter Island from Demarcation Point, where they

had lived since 1917. (Prior to that time Tom Gordon had worked with Charles Brower in Barrow and

other North Slope locations.) Apparently this move was made because Tom Gordon’s wife had relatives

who had taken up residence on Barter Island because of its location in relation to fishing spots and the

mountains (Kaveolook 1977; Jacobson and Wentworth 1982:3). The nascent settlement also was a more

viable location for the trading post, which in turn increased the desirability of Barter Island as a place for

families to live. People still lived on the land and traveled extensively, but Kaktovik had become more of

a central service center than before (Jacobson and Wentworth 1982:3–4; Libbey 1983:15).

Later in the 1920s, reindeer were brought into the Barter Island area under the sponsorship of the

BIA (Bureau of Indian Affairs). It is reported that reindeer herding combined with hunting kept people

out on the land for most of the time, although their residential focus was Barter Island. Reindeer herding

was a family business, with each family having a defined herding area. Taakpaq, a famous whaling captain from Barrow (but sometimes referred to as a Kaktovik whaling captain), herded in the area between

Beechey Point and Brownlow Point. Richmond Ologak herded from Brownlow Point east to the Sadlerochit River, while the Akootchooks and Tiglooks herded between the Sadlerochit and Jago Rivers.

Gallegher Arey and Mickey Gordon herded from the Jago River to Demarcation Bay (Libbey 1983:15).

Reindeer herding in the Kaktovik area ended in the late 1930s or early 1940s (by 1937 according to

Kaktovik elder Isaac Akootchook, pers. comm., Jan. 2002). A number of reasons are commonly cited.

However, an assessment of the relative importance of the various factors in the Kaktovik area is hardly

possible as almost all studies of Alaskan reindeer have focused on the Seward Peninsula and seldom

mention North Slope operations. The interested reader is referred to Andrews (1939), Grosvenor (1902),

Jackson (1904), Koughan (1931), Miller (1935), Olson (1969), Stern (1980) and Ray (1983).

Trapping also supported a dispersed population, and trappers tended to focus on a supply center

where furs could be traded for consumer goods of various sorts. In addition to the trading post on Barter

Island run by Tom Gordon, other trading posts were operated by Jack Smith at Beechey Point, Henry

Chamberlain at Brownlow Point, John Olson at Imaignauraq, Old Man Store at Demarcation Bay, and

others as well (Fig. 2.1). These trading posts tended to change locations (and proprietors) depending on

the productivity of the trapping territory surrounding them. The decline of the fur market in the mid1930s caused many of these trading posts to close, and other traders died (Tom Gordon died in 1938,

John Olson in 1942) or simply moved elsewhere. The result was that, by the 1930s and 1940s, there were

few trading posts left and people once again dispersed—some to Canada (the Mackenzie River area,

where a trading post remained open), Barrow, or other places. A core population remained in the area,

maintaining a mobile subsistence lifestyle (Libbey 1983:16–18).
2-4 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

In the mid-1940s the U.S. Coast and Geodetic Survey began mapping the Beaufort seacoast, with

their main base camp on Tigvariak Island, 137 km (85 mi) west of Kaktovik. Several relatives of presentday Kaktovik residents worked on this project and spent time at Tigvariak Island. In 1947, the Air Force

began construction of the airstrip and hangar facility at Kaktovik, forcing the relocation of some Kaktovik

residents and disturbing a significant prehistoric village site. In 1951, the entire area around Kaktovik

was designated a military reserve, and again some Kaktovik residents had to relocate (Nielson 1977;

Jacobson and Wentworth 1982). A Distant Early Warning (DEW) station was constructed there in

1952/3, as a prototype/test facility for the other proposed stations of the DEW-line system (Denfeld

1994:190–192). A BIA school was opened in Kaktovik in 1951. The combination of the school and the

availability of local wage employment supported a population influx. The population stabilized at ~140

people, and remained at about this level until the late 1970s. Then the establishment of the NSB (North

Slope Borough) in 1972 resulted in more local employment opportunities, and an increased and improved

housing supply (Jacobson and Wentworth 1982:5).

The period of time since the establishment of the NSB has been one of increased economic stability

in Kaktovik, in terms of wage employment, and a modification of the schedule of subsistence activities to

accommodate steady wage employment. This is not a static system, however, and there is uncertainty

whether an equilibrium has been reached or whether wage labor as a scheduling force will remain as

important as it is at present. There are currently (2001) few active subsistence specialists in Kaktovik

who do not also work for wages. That is, few people support themselves solely by hunting and by trading

the game they procure for other goods that they cannot harvest. Most hunters participate directly in the

wage economy, and some wage laborers do little or no hunting.

Historical Kaktovikmiut Whaling

Historical Subsistence Whaling East of Barrow

Definitive information on the antiquity of whaling in the regions of the Alaskan North Slope east of

Barrow does not really exist, although evidence for such activity at least in the late Thule period (starting

about 900 years Before Present) is generally accepted. Informants maintain that whaling took place at

Barter Island in aboriginal times (Kisautaq 1981:170–173). Hall (1987) and Hall and Associates (n.d.)

could possibly provide more site specific information in this regard, but access to those sources is restricted. Hall’s more accessible publications do not suggest that whaling occurred there in aboriginal times.

No fully documented and dated excavation at Barter Island itself has taken place, but prehistoric features

with whale bone suggest a whaling tradition (Jacobson and Wentworth 1982). It is likely that the prehistoric sites excavated by Diamond Jenness in 1914 have either eroded away or were destroyed when the

airstrip was built (Wescott et al. 2000), although it is possible that remnants remain (Yarborough 2001).

In a summary publication, Hall (1981:48) states that the available archaeological evidence from

other sites along the Alaskan north coast east of Barrow provides only the most meager cultural history:

“Essentially, there is no unequivocal evidence of occupation in the area previous to 4,000

years ago, precious little data on the nature of human adaptation in Arctic Small Tool

tradition times, and only enough information from the more recent sites to broadly outline

a picture of human occupation in the past 600 years [the late prehistoric].”

For the late prehistoric period, ~1350 to present, there are only three well documented archaeological sites east of Barrow, all within or near the Colville Delta 250 km (155 mi) west of Kaktovik:

(1) Nigalik is a specialized activity site in the Colville River Delta. The lack of systematic archaeological
§2. Kaktovikmiut Whaling: Harvest Data & Local Knowledge 2-5

testing at this site has resulted in an inability to establish prehistoric roots for the Native seasonal trade

fair at Nigalik. Little has been recovered at this site that would address the subsistence behavior of the

people using the site. (2) Thetis Island, just northeast of the Colville Delta, has prehistoric remains dated

to A.D. 1350–1500. There is evidence of whaling activity, but both the nature of the tools and faunal

remains found there support a subsistence pattern oriented primarily toward caribou (50 percent) and seal

(25%), with the remainder representing birds, foxes, whales, and various small animals (25%, in that

order). Thus, whales must have been an infrequent catch, given their large size relative to the other

resources being harvested. (3) Pingok Island, near Thetis Isl., has prehistoric remains dated to A.D.

1550–1700. Land subsistence activities are well represented in this archaeological assemblage as well,

but seals and whales are also common. The bearded seal and walrus are not well represented, but overall

it appears that whaling was a significant activity at Pingok Island during this period. A site at Herschel

Island, in the Canadian Beaufort, dates to the late Thule period, about 900 years B.P. (Stanford 1976).

However, the interpretation of this information in terms of cultural history is far from clear (Hall

1981:4–49, 71–73). Sites on Barter Island and Arey Island display whale bone, but have not been dated

with any precision. Arey Island is named for Ned Arey, a commercial whaler, and the Inupiat name,

Naalagiagvik, means “Where you go to listen for whales” (Libbey 1983:46–48). Arey Island is often

mentioned by Kaktovik residents as a location where whales feed and linger. Diamond Jenness excavated

these sites in 1914, but never published the results (Jenness 1914). Jenness did write some non-analytical

accounts of this work (Jenness 1957, 1991), but for the most part these describe day-to-day activities

rather than scientific findings. Edwin Hall performed an analysis of the artifacts and field notes from the

Jeness excavations and concluded “... most of the features were built and utilized between 550 and 400

years ago, although a few of the recovered artifacts dated to a much earlier period and others indicated

use of the sites up through the historic period. ... The types of artifacts found suggest a subsistence quest

that emphasized land hunting as much or more than marine hunting. Whaling was practiced by at least

some of the families that occupied the sites, though when in the occupational sequence is not known.

Fishing also played a role in the subsistence efforts of some families” (Hall 1987:258-259).

Time was not available to review the commercial (Yankee) whaler literature for information relevant to Kaktovik whaling. Commercial whaling ships first appeared at Barter Island in 1886, and reached

the Mackenzie Delta whaling grounds in 1888. By 1894, fifteen ships were spending the winter at Herschel Island, attracting native hunters to supply them from as far away as Point Hope (Bockstoce 1986;

Wilson 1991). How much time these ships spent in the eastern Alaskan Beaufort sea is not clear, but

ships logs and accounts may contain observations of whale behavior in that area from that time.

Cross Island has been reported by Inupiat informants to have been the site of whaling activities for

hundreds of years, and so could date back at least to the late prehistoric period. It is known that Taaqpak,

a whaling captain who Spencer (1959:154) places in Barrow, whaled from Cross Island from the 1920s to

1940 or so (Carnahan 1979:25–31). Taaqpak was one of several Inupiat who bought boats from Euroamerican whalers or traders in the 1920s, and a history of such transactions, especially as they affected

Inupiat whaling, would be very informative. Such a history has not been written, however, and would

likely require extensive research with no guarantee of ultimate success. The Commission on Inupiat History, Language, and Culture (in Barrow) has some tape-recorded oral history possibly relating to Taaqpak

and Cross Island, but this information either has not as yet been translated or was unavailable for other

reasons. In any event, Taaqpak also had a reindeer herd in the area and many of the men on his whaling

crew worked for him, and some of those with reindeer herds to the east of him also whaled with him.
2-6 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

It is not known if Taaqpak ever lived in Kaktovik or had that community as his center of orientation, but many of those who served on his crew did. Many of the people now whaling in Kaktovik

received their training while whaling in the Cross Island area with Taaqpak (or with someone who had

learned from such a person). Thus, although whaling in the immediate Kaktovik area is not documented

prior to 1964, Kaktovik people certainly have a long and continuous history and tradition of whaling

(Jacobson and Wentworth 1982:52–53), directly related to that of Barrow and the mid-Beaufort Sea area.

It is not altogether clear why whaling was suspended in the mid-Beaufort area west of Kaktovik,

but primary factors were probably economic and demographic dynamics (which were also important for

the community history of Kaktovik). The decline of the reindeer industry may have prompted most of the

people who had been in the general mid-Beaufort Sea area to relocate to Barrow or Kaktovik. The midBeaufort Sea and Colville River areas were experiencing depopulation at this time. Schools and wage

labor jobs were serving to attract people off the land and into central communities.

Contemporary Kaktovikmiut Whaling

Whaling resumed at Kaktovik in 1964 (Kaleak 1996), and since then has been a central focus of

life in Kaktovik. The immediate reasons for the resumption of whaling in 1964 are not clear, but the

community had been growing, whales had been observed regularly, and some residents had experience

from whaling elsewhere. Information for some years soon after 1964 is not complete, but whaling has

taken place out of Kaktovik during most years since then, with a high degree of success―especially since

1989 (Braund et al. 1988: Appendix 1, page 14; see also next section). After the formation of the Alaska

Eskimo Whaling Commission (AEWC) in 1977, Kaktovik received a formal quota. One to three bowheads were landed during most years in the 1980s, and two to four bowheads during most years in the

1990s. Braund and Moorehead (1995) briefly describe the institutional development of the current subsistence whaling management system. Huntington (1992) provides a similar background and treatment

within the broader context of federal, state, and cooperative management programs.

People from Kaktovik hunt whales only in the fall, as the spring migration of bowheads past Kaktovik occurs far offshore beyond the landfast ice zone. The autumn whaling season starts no sooner than

late August, though most commonly near Labor Day in early September, and ends later in September or

sometimes October. At Kaktovik, whaling is done from powerboats. These boats can vary widely in

characteristics, from an 18 foot open Lund skiff to a 24 or 25 foot cabin-cruiser type vessel. As speed is a

much desired characteristic, motor size has tended to increase through time. Depending on the year, there

are up to 11 whaling crews in Kaktovik. With a minimum of four or five men to a crew, most adult men

are involved with whaling. Most other people in the village are involved in some support or processing

capability. Whaling is truly a community-wide activity.

Whaling crews use the village as their home base, leaving from the village and returning to it every

day. As described by one informant, a crew leaves Kaktovik, cruises in search of whales, and then ties up

to a piece of ice. Eventually a number of boats will congregate and the crews will set out their provisions,

eat, and socialize while a few of their number watch for whales. There are some years when there is little

or no ice, but even when there is ice the boats spend much time cruising the water and searching for

whales. Coordination between boats may be more difficult at these times, although CB and marine VHF

radios plus GPS units have made this easier in recent years.

When whales are spotted, the boats are arranged to intercept them in such a way that at least one

should have a good shot. There is some competition to be the first to strike a whale, as this increases the

prestige of that captain and his crew, but the process as described is mainly cooperative. Once a whale is
§2. Kaktovikmiut Whaling: Harvest Data & Local Knowledge 2-7

struck, all crews in the area go to help procure the whale, haul it back to Kaktovik, and process it. In

recent years, heavy equipment has been used to haul the whales onto the beach for butchering, as well as

to shift the whale during the process of butchering. The heavy equipment is also used for transporting the

butchered muktuk and meat (which is placed directly into the equipment’s buckets) and for the ultimate

removal of the whale carcass. A similar method has been adopted for the butchering of fall-harvested

whales in Barrow, and is one of a series of adaptations that make the butchering of a large and heavy

animal on a gravel beach easier, faster, and more efficient than more “traditional” methods.

The “core” whaling area for Kaktovik is from the Okpilak and Hulahula Rivers in the west to

Tapkaurak Point in the east. The core whaling area extends out as far as 20 miles (32 km) from the coast,

although crews usually stay within 12 miles or so of shore. Nearly all whales harvested since 1964 have

been struck within this “core” area and there is an explicit effort to stay within this range. Available

information on the locations where bowheads were struck is shown in the next section.

Towing a whale is hard work and relatively slow, especially if there is a wind or rough seas to contend

with. The farther away from Kaktovik a whale is killed, the longer the tow will be, and the greater the chance

that at least part of the meat will spoil. The extreme limits of the “Kaktovik whaling area”―the middle of

Camden Bay in the west and just north of the Kogotpak River in the east―are as far as Kaktovik whalers can

conceive of trying to tow a whale back to Kaktovik. As previously stated, most whales are taken within the

smaller “core” area, and within that area most of the whales are in fact struck close to the village.

Crews could function with as few as three people in the boat, but most crews have four or five, and

some claim as many as eight. Not all days are equally good for whaling, and there are periods when

crews do not go out because of wind, waves, or large amounts of sea ice. Because of the quota system

that has applied since 1978, the season is over once the allocated number of strikes is used. Kaktovik

currently has a quota of three strikes or kills, but is often in a position to request additional strikes since it

is common for spring whaling communities not to use their entire quota. However, since 1997 the

Kaktovik hunters have not requested that unused strikes from other communities be transferred to

Kaktovik. The prevailing local opinion is that three whales are adequate to meet Kaktovik’s needs.

Kaktovik has what is essentially an intercommunity agreement with Anaktuvuk Pass under which

Kaktovik muktuk and whale meat is sent to Anaktuvuk Pass and caribou is sent from Anaktuvuk Pass to

Kaktovik. This is not trade in the strict sense, as in years when Kaktovik does not harvest a whale they

still receive caribou from Anaktuvuk Pass, and may indeed receive more caribou in those years than in

years when they do harvest a whale because of the greater nutritional need. Most of the food thus

exchanged is redistributed at public functions and feasts, primarily at major holidays such as Thanksgiving, Christmas, Easter, and the Fourth of July.

Whaling is a cooperative activity and as such the Kaktovik whaling area is open to all who wish to

participate in the hunt, as long as each person belongs to a crew whose captain is a member of the

Kaktovik Whaling Captains Association (KWCA). The AEWC administers the hunt, and has slowly

assumed a greater role than merely ensuring that the quota is not exceeded. However, in most matters

related to the local hunt, the AEWC will defer to the KWCA. The AEWC is very concerned with safety

during the hunt and the qualifications of the crews that participate. To these ends the AEWC registers all

whaling captains and collects information on crew members. This serves, to a degree, as a restricting

mechanism on who can organize a whaling crew. Almost anyone who wants to participate in whaling can

find a role on an existing crew, but the AEWC process serves to deter the formation of new and inexperienced whaling crews by prospective whaling captains who may be resource-rich but experience-poor.
2-8 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

In terms of use of the whaling area, there are no restrictions. In fact, in 1979 when conditions in

the area where Nuiqsut crews normally whale made whaling there impossible, the Nuiqsut crews whaled

with the Kaktovik crews.

The division of a whale harvested at Kaktovik is essentially similar to that in other villages (Daniel

and Lillian Akootchook, interview). The captain of the first crew to strike the whale receives credit for

taking that whale, and receives a large share of the whale. He is expected to redistribute a good deal of

this, and does so, so that most whales taken are in fact treated as community property.

Recent Bowhead Harvest at Kaktovik

Numbers Taken by Year.―Recent bowhead harvests at Kaktovik commenced in 1964 when two

whales were harvested. National Marine Fisheries Service (NMFS) records of harvests in 1964–72 are

incomplete and do not list any whales harvested at Kaktovik from 1965–72 (Marquette 1977). However,

a map in Oil/Whalers Working Group (1986) indicates that single whales were harvested there in 1968

and 1969. It is unlikely that many additional whales were harvested during this period because Kaktovik

residents would remember an event as rare as a bowhead harvest from that period.

There was no quota on the number of bowheads that could be harvested before 1978, but rapid

increases in bowhead harvest levels throughout Alaska in the mid-1970s caused concern that harvest

levels were not sustainable. The International Whaling Commission (IWC) decided to impose quotas on

the number of bowheads that could be taken by Alaskan native hunters starting in 1978. The IWC quota

is administered and monitored by the AEWC. From 1978 to 1991, no more than two bowhead strikes or

kills were allocated per year to Kaktovik. From 1992 to 2001, Kaktovik has been allocated three strikes

or kills per year. In most years when Kaktovik reached its quota, the KWCA could have applied for additional strikes because some strikes were not used by spring whaling villages. The most recent year when

a 4th strike was transferred to Kaktovik was 2001 (and before that, 1997). During 1998–2000, additional

strikes were available but KWCA decided not to request additional strikes because village requirements were

met by the three whales landed in each of those years.

Since 1973, data on bowhead harvests have been collected by NMFS and the NSB, including

information on numbers of whales landed, dates when whales were landed, the sizes and gender of those

whales. Figure 2.2 summarizes harvests at Kaktovik from 1973 to 2000. From 1973 to 1988, one to two

whales were generally harvested, reflecting the village quota. In 1979 and 1981, whaling crews from

Nuiqsut joined the Kaktovik whalers and the higher catches of five and three, respectively, in those years

reflect the quotas from both villages. From 1989 to 2000, generally 2–4 whales were harvested.

Timing of the Harvest.―Each year the KWCA decides, at a meeting shortly before the start of the

whaling season, the date at which the hunt will begin (weather permitting). In recent years, the bowhead

hunt at Kaktovik has normally begun Labor Day weekend. The scheduled starting dates for the 1997 to

2001 hunts were 3, 4, 11, 2, and 2 September. (The starting date of the 1999 hunt was delayed by a local

emergency―a fatal boating accident.) However, the hunt has started earlier in some years (e.g., by 22

Aug. in 1992). In most years, few bowhead whales are present near Kaktovik until the beginning of the

westward migration of whales from the main summering areas east of Kaktovik (see Chapter 9). Also,

some hunters state that the hunt is now delayed until early September because the tendency for warmer

weather in August means that whale meat is more likely to deteriorate before completion of butchering if

whales are taken in August. Thus, the start of the hunt is usually timed to coincide with the early part of

the main westward migration in early September. The whales accessible then tend to consist primarily of

the small subadult whales that are preferred by hunters (Chapter 10).
§2. Kaktovikmiut Whaling: Harvest Data & Local Knowledge 2-9

0

2

4

6

73 75 77 79 81 83 85 87 89 91 93 95 97 99

Year

Number of Whales

FIGURE 2.2. Numbers of bowhead whales landed at Kaktovik each year, 1973–2000. Main sources:

Marquette 1977; Braham 1987; Withrow et al. 1991; J.C. George, pers. comm.; G. Sheffield, pers. comm.

The dates when whales landed at Kaktovik during 1976 to 2000 were struck are shown in Figure

2.3, organized by year (panel A) and 10-day period (panel B). (The date is unknown for 1 of the 61

whales landed in these years.) The majority (83%) of the whales landed during this period have been

struck during September. Thirty-two percent of the whales were struck in each of the 1–10 and 11–20

September periods, 20% were struck 21–30 September, 10% were struck 1–10 October, and 3% were

struck in each of 22–31 August and 11–20 October (Fig. 2.3B).

In recent years, the typical harvest dates have become earlier even though the quota and the number

of whales taken have increased. The trend for an earlier harvest is significant (r = –0.46, df = 58, P =

0.00022). This change appears to have resulted from an increase in the efficiency of the Kaktovik hunters

in harvesting whales. Another contributing factor may be that the size of this bowhead population is

increasing. As a result, whales presumably are now more numerous near Kaktovik early in the hunting

season than they were during the 1970s and 1980s. Changes in whale utilization of the general Kaktovik

area (see Chapter 9) may also be involved. Average sighting rates during aerial surveys increased markedly in the 1990s relative to the 1980s (Chapter 9).

Harvest Locations.―Since 1973, all bowheads harvested by residents of Kaktovik for which the

harvest locations have been reported were struck within 43 km (27 mi) of the village. Most of these

whales were struck within 30 km or 19 mi (Fig. 2.4). As mentioned above, the core area where whalers

search for whales is from the Okpilak and Hulahula Rivers in the west to Tapkaurak Point in the east and

offshore as far as 32 km (20 miles) (Fig. 2.1). Although a few of the most distant harvest locations were

during the 1970s (Fig. 2.4), the mean distance of reported harvest locations from Kaktovik was not

significantly different among the 1970s (17.0 km, n = 16), 1980s (17.9 km, n = 14) and 1990–2000 (15.2

km, n = 21) (Kruskal–Wallis χ

2

 = 0.96, df = 2, P = 0.62). It should be noted that the locations where 10

bowheads were struck are not known to us, and some reported locations, especially for years before GPS

units were widely used, are approximate.

Sizes of Harvested Bowheads.―The Kaktovik whalers attempt to harvest small whales because

they are easier to handle and are considered to be better to eat. Thus, the sizes of the harvested whales are

partly an indication of the sizes of the whales near Kaktovik at the dates in question, but are also strongly

influenced by hunter selectivity. The frequency distribution for the lengths of whales landed at Kaktovik
2-10 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

FIGURE 2.3. Dates when bowheads were struck at Kaktovik (A) by year and (B) by 10-day period,

1973-2000. The square symbol near the upper left side of panel A represents a young-of-the-year calf

(approx. 5 months old). Main sources same as Fig. 2.2.

day of year = 1498.1 - 0.6234year

r = -0.46 A.

12 Aug

19 Aug

26 Aug

2 Sep

9 Sep

16 Sep

23 Sep

30 Sep

7 Oct

14 Oct

21 Oct

1971 1976 1981 1986 1991 1996 2001

Year

Date

B.

0

4

8

12

16

20

22-31 Aug 1-10 Sep 11-20 Sep 21-30 Sep 1-10 Oct 11-20 Oct

Date

Number of Whales

is shown in Figure 2.5B. The reported lengths in this and subsequent Figures have been reduced by 8.2%

to account for the stretching that occurs when the whale is dragged onto land (see Thomson, Chapter 22).

The overall size range (adjusted) of the whales landed at Kaktovik is similar to that of the living whales

whose lengths have been measured in the Arey Island to Humphrey Point area during September (Fig.

2.5B vs. 2.5A). Whales as long as 16.1 m (17.4 m before adjustment for stretching) have been landed at

Kaktovik (Fig. 2.5B)―approximately the same length as the longest whale (16.2 m) measured

photogrammetrically near Kaktovik (see Koski and Miller, Chapter 10).
§2. Kaktovikmiut Whaling: Harvest Data & Local Knowledge 2-11

FIGURE 2.4. Locations where bowhead whales were reported to have been harvested by residents of

Kaktovik, 1976–2000. Not shown are two whales taken ~170 km west of Kaktovik in 1937 and 1940.

Major Sources: Oil/Whalers Working Group (1986), Kaleak (1996), G. Sheffield, pers. comm., J.C.

George, pers. comm.

However, small whales constitute a higher percentage of the landed whales than of the whales

photographed in the area. Of the bowheads harvested by Kaktovik whalers, 23.6% were longer than 13 m

(after allowance for stretching), and therefore were considered to be adults (Koski et al. 1993). This

compares to 43.4% adults in the overall bowhead population, if calves are excluded (Angliss et al. 1995),

and 50% adults among whales photographed near Kaktovik (calves excluded, Koski and Miller, Chapter

10). The proportion of adults was significantly lower among the harvested whales than among the population as a whole (χ

2

 = 8.80, df = 1, P = 0.0030) or among the whales that were photographed near

Kaktovik (χ

2

 = 14.98, df = 1, P = 0.00011). These data confirm that the bowheads landed by Kaktovik

whalers tend to be smaller than those in the population as a whole.

The autumn bowhead migration is partially segregated according to size, with the smaller whales

tending to occur earlier in the autumn (Koski and Miller, Chapter 10). However, there was no significant

correlation between date and the size of a whale harvested (r = –0.064, df = 53, P = 0.64; Fig. 2.6). This

indicates that whalers were able to select small whales throughout the whaling season even though the

small whales become proportionally scarcer as the season progresses.
2-12 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

Length (m)

Number of Whales

    

A. Photogrammetry near Kaktovik

n =173

0

10

20

30

 <6.0

6.0-6.5

6.5-7.0

7.0-7.5

7.5-8.0

8 - 8.5

8.5-9.0

9.0-9.5

9.5-10.0

10.0-10.5

10.5-11.0

11.0-11.5

11.5-12.0

12.0-12.5

12.5-13.0

13.0-13.5

13.5-14.0

14.0-14.5

14.5-15.0

15.0-15.5

15.5-16.0

16.0-16.5

16.5-17.0

17.0-17.5

 Others

Mothers

Calves

B. Harvested near Kaktovik

n =56

0

5

10

<6

6.0-6.5

6.5-7.0

7.0-7.5

7.5-8.0

8.0-8.5

8.5-9.0

9.0-9.5

9.5-10.0

10.0-10.5

10.5-11.0

11.0-11.5

11.5-12.0

12.0-12.5

12.5-13.0

13.0-13.5

13.5-14.0

14.0-14.5

14.5-15.0

15.0-15.5

15.5-16.0

16.0-16.5

16.5-17.0

17.0-17.5

Others

Calves

FIGURE 2.5. Length frequency distributions of bowheads (A) photographed near Kaktovik 1982–2000

(from Koski and Miller, Chapter 10) and (B) harvested near Kaktovik 1976–2000 (same sources as Fig.

2.2). In (B), lengths have been adjusted downward by 8.2% to account for stretching (see text).

Figure 2.7 shows the lengths of the harvested whales by the year harvested. There has been a

significant decline in the average size of whales harvested over the 1976–2000 period (r = –0.33, df = 53, P =

0.014). This suggests that the whalers have become more selective about the sizes of whales that they have

harvested in recent years. This increased selectivity has probably been possible through some combination of

two factors: increased availability of whales associated with the bowhead population increase, and increased

efficiency of the hunters in capturing whales (allowing them to be selective while still filling their quota).

Sex of Harvested Bowheads.―The sex of 55 bowhead whales harvested at Kaktovik has been

recorded. Twenty-eight were males and 27 were females, which is not significantly different than the

50% males and 50% females that would be expected (χ

2

 = 0.0012, df = 1, P = 0.91). However, during the

first half of the harvest (22 Aug.–13 Sept.), 67% of the harvested whales were female, and during the last

half of the harvest (14 Sept.–11 Oct.), only 32% were female (Fig. 2.6, 2.8). This difference is significant

(χ

2

 = 6.55, df = 1, P = 0.010). From 1990 to the present females have been more common among the

harvested whales (18 females and 13 males), but before 1990 more males than females were harvested

(15 males and 8 females). This difference is marginally significant (χ

2

 = 2.87, df = 1, P = 0.090) and is

due to small females commonly being caught early in the season since 1990 (Fig. 2.6, 2.7).
§2. Kaktovikmiut Whaling: Harvest Data & Local Knowledge 2-13

whale length = 14.27 - 0.0136day-of-year

r = -0.064

6

9

12

15

18

17 Aug 27 Aug 6 Sep 16 Sep 26 Sep 6 Oct 16 Oct

Date

Whale Length (m)

Females

Males

Unknown

FIGURE 2.6. Whale length vs. date for bowheads harvested at Kaktovik, 1976–2000; females and males are

distinguished. A 6.2-m calf harvested on 2 October 1977 is excluded. Whale lengths are adjusted downward to allow for stretching (see text).

whale length = 225.3 - 0.108year

r = -0.33

6

9

12

15

18

1975 1980 1985 1990 1995 2000

Year

Whale Length (m)

Females

Males

Unknown

FIGURE 2.7. Whale length vs. year for bowheads harvested at Kaktovik, 1976–2000; females and males

are distinguished. A 6.2-m calf harvested in 1977 is excluded. Whale lengths are adjusted downward to

allow for stretching (see text).
2-14 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

0

2

4

6

22 Aug 29 Aug 5 Sep 12 Sep 19 Sep 26 Sep 3 Oct 10 Oct

Date

Number of Whales

Females

Males

FIGURE 2.8. Sex of whales vs. date for bowheads harvested at Kaktovik, 1976-2000.

Local and Traditional Knowledge of Whale Feeding Near Kaktovik

Bowhead whales are of great cultural importance to the Inupiat and are a major source of food.

Inupiat know a great deal about bowhead whales. This study required much cooperation with and direct

participation from local residents in the study design and field work, for two major reasons: (1) A major

objective of the project was to integrate Inupiat knowledge of bowhead whales into the planning of the

project, the fieldwork, and the interpretation of the findings. The project devoted significant effort, both

during the planning phase and during fieldwork, to the compilation of local and traditional knowledge

concerning use of the Kaktovik area by feeding whales. Resources to document broader aspects of local

and traditional knowledge related to whales and whaling were not available, given the need to concentrate

on work directly bearing on use of the area by feeding whales. (2) Local coordination and participation

also insured that the study did not interfere with the hunt for bowhead whales and, to the fullest extent

possible, respected Inupiat cultural sensitivities. Several types of liaison functions were built into the

project plan to meet these requirements.

Concept and Use of “Local and Traditional Knowledge”

Defining what is meant by “local and traditional knowledge” (LTK) or “traditional ecological

knowledge” (TEK) is not a simple process, and summarizing such knowledge is even more difficult

(Kinsella 1999). There have been many attempts to define TEK and its place in research and in the

assessment of the effects of development or management projects (see, for example, Bielawski 1992;

Freeman 1992; Hobson 1992; Johnson 1992; Sallenave 1994; Government of Canada 1996; Carter 1997;

Huntington and Fernandez-Gimenez 1999). This is not the place to reprise this discussion, from which no

complete consensus has as yet emerged, nor is it likely to emerge soon. Rather, we have extracted certain

themes from this literature that are most pertinent in a pragmatic way for this project.

The label “traditional” often seems to serve as a barrier to the integration of such knowledge with

“Western scientific” knowledge. “Tradition” is often interpreted as unchanging and of the past, and

“science” with the investigation of the present in order to support some change in knowledge or thought.

In fact, both “traditional” and “scientific” knowledge are evolving and changing systems of thought,

based on life experiences organized in certain ways. The scientific method is an explicit set of rules for
§2. Kaktovikmiut Whaling: Harvest Data & Local Knowledge 2-15

organizing and drawing conclusions from experience. Traditional knowledge does not have such an

explicit method of evaluating information and drawing general conclusions, and thus in many specific

cases is quite situationally or contextually bounded, with no obvious way to broaden its application.

Thus, local and traditional knowledge is sometimes dismissed as “anecdotal” when in fact it is merely

over-specific for the purposes at hand, and the underlying generalizations (or the methods to arrive at

such generalizations) have not been perceived.

In the present project, we have used several approaches in attempts to compile LTK by Kaktovik

residents concerning whale feeding in the Kaktovik area. We first conducted a literature review of selected published and unpublished sources. Then, during January 1998, we consulted local Kaktovik residents

through a 11⁄2-day whale workshop held in Kaktovik. During that meeting, LTK was compiled and local

participants helped modify the research design to address local concerns and to incorporate local

knowledge. In addition, we interviewed a limited number of whaling captains and other experienced

whalers during the first year of the project. Complete transcripts of the interviews that were rccorded are

included as Annex B in Volume 2 of this report.

Prior to each year’s main field season (1998, 1999 and 2000), one team member spent two to three

weeks in Kaktovik during mid-late August, meeting with local residents, coordinating logistics, and (with

local residents) attempting to conduct a “local boat” survey to detect any early-arriving bowhead whales

in the Kaktovik area. The local boat survey included both a visual search and use of hydrophones to

listen for calling bowhead whales. This component of the research had been suggested by local participants at the Whale Workshop in January 1998. It was hoped that it would document some of the whales

that might occur in the area prior to the start of whaling and of the project’s more intensive aerial- and

boat-based fieldwork in September. Also, the “local boat” survey provided an additional opportunity to

collect LTK related to whale feeding behavior. Furthermore, during September of 1997–2000, a project

participant from Alaska Dept of Fish & Game worked closely with the whalers to collect biological data

and samples of the stomach contents from bowheads harvested at Kaktovik. Other opportunities for

exchanges between local residents and project scientists are described in the next subsection. These

included the project’s three Scientific Review Board meetings, annual meetings in Kaktovik before the

whaling season, employment of a local resident on the project boat, basing of the project aircraft at

Kaktovik, and an additional workshop in Kaktovik in January 2002 to discuss the draft of this report.

Overall, although Kaktovik residents are very knowledgeable about bowhead whales generally,

rather little LTK related specifically to whale feeding behavior was found, as summarized below. There

are probably several reasons for this. One is that whale feeding behavior, in and of itself, is not of central

interest to Inupiat whalers. LTK tends to emphasize the types of observations most salient for the success

of whatever activity one is engaged in (or for safety or survival in general). Thus, many people remarked

that they were concerned with where whales could be found, and when, but not with what they were

doing there. Also, LTK is embedded in life experience and, as such, those components of it most pertinent to a specific topic such as whale feeding behavior can be difficult to isolate from this larger context.

This is especially true if the research effort must take place within a short period of time. Long-term,

nondirective research is more likely to be successful in compiling LTK on any specific topic than is shortterm and more “direct” research―although directed research will also compile much information on other

specific (and general) topics as well.

The following sections summarize the local contact activities conducted for this project, and

include a summary of LTK related to whale feeding in the Kaktovik area.
2-16 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

Chronology of Local Coordination and LTK Activities

After initial contacts with the North Slope Borough, the Alaska Eskimo Whaling Commission, and

the Kaktovik Whaling Captains Association during the late summer and autumn of 1997, a meeting to

introduce the project to Kaktovik whaling captains was held in Kaktovik in December 1997. This was

followed by a 11⁄2-day workshop in Kaktovik in January 1998, at which a rough draft of possible study

options was discussed with the Kaktovik whaling captains and representatives of the AEWC, NSB, federal government agencies, and the oil industry. Local advice was obtained about the timing of the study,

its feasibility and compatibility with bowhead hunting activities, and options for improving the research.

The formal workshop agenda included time for public statements by local residents concerning LTK of

bowhead whales. There was also time for two-way discussions about bowheads between local residents

and project scientists who had studied bowhead whales near Kaktovik and elsewhere in previous years. A

number of informal and private discussions with whaling captains and other knowledgeable Kaktovik

residents were conducted in the days following the workshop to further develop the traditional knowledge

information base. A limited number of interviews with whaling captains and other experienced whalers

were recorded and transcribed, or otherwise documented when recording was not possible.

The feedback received at the workshop and at a subsequent meeting on 30 May 1998 was taken

into account in the Project Plan that was completed in draft during early July 1998. During July, that

draft plan was further discussed at meetings with local residents in Kaktovik and with the project’s

Scientific Review Board (SRB) in Anchorage. The SRB includes representatives of the Kaktovik whaling captains (Mr. Joe Kaleak), the AEWC (Mr. Thomas Napageak or Mrs. Maggie Ahmaogak), and the

North Slope Borough (Dr. Todd O’Hara or Mr. Craig George) as well as NMFS, industry, and

independent scientists. The SRB, with local representation, also met in June 1999 to review the results of

the first (1998) field season and plans for subsequent field seasons. The SRB did not meet after the

second (1999) field season, but reviewed the 1999 results individually. The SRB met a final time during

January 2002 to review results of the overall project as described in this draft final report.

Project scientists participated in several Kaktovik Whaling Captains Association meetings, including meetings in July and August 1998, June and August 1999, and early September 2000. The meetings

in August–September, in particular, provided an opportunity for final coordination of research plans with

whaling plans, for local comments, and for possible research modifications. Also, during September of

1998, 1999 and 2000, a Kaktovik resident was employed aboard the boat that was used for systematic

studies of food available to bowheads near Kaktovik (see Chapters 3–7). This provided another avenue

for interchange between the project and the community. As noted earlier, a project representative was in

Kaktovik in late August of 1998–2000 for the local boat survey, and another worked closely with the

whalers in September 1997–2000 to collect biological data and samples of the stomach contents from

bowheads harvested at Kaktovik (see Chapter 18). Finally, the project’s aerial survey crew was based at

Kaktovik for their work during the 1998–2000 whaling seasons (see Chapters 8–16), providing further

opportunities for communication.

A meeting to present and discuss the results of the study was conducted in Kaktovik on 31 January

2002, shortly after the final SRB meeting. The discussion at those two meetings has been taken into

account in the final version of this report.

Whale Workshop in Kaktovik (Jan. 1998)

The workshop extended for two days (15–16 Jan. 1998), and primarily addressed specific aspects

of the research design that those present believed could potentially affect the behavior of whales (and
§2. Kaktovikmiut Whaling: Harvest Data & Local Knowledge 2-17

Kaktovikmiut whaling success) during the course of the research. While these discussions reflected local

and traditional knowledge and beliefs derived from life experience (for instance, how noise sources affect

whales), little in the way of observations related to whale feeding was presented. Rather, the local

attendees were concerned with understanding the proposed research program, and then suggesting modifications to the planned research design and schedule to minimize possible effects on subsistence whaling

(noise, timing of the research). There were also concerns that the research, as designed, could base its

conclusions on information that was too limited. An extensive discussion on the appropriate geographical

boundaries of the study area was one example. Another example was the concern that not all years are

the same, and if there were a year when whale feeding could not be documented, because of ice or other

conditions, that this could skew the results. These concerns revealed a great depth of local knowledge

about whale behavior in the Kaktovik area, although not specifically related to feeding behavior.

At the beginning of the second day of the workshop, one Elder briefly summarized the depth and

orientation of local knowledge, and contrasted it with the approach proposed by the Whale Feeding Study

methodology:

“Since I started to know about the whales is―beautiful. My knowledge can see that, because this

area, Kaktovik all the way to Demarcation-Icy Reef―since I find out about it, my parents and my

uncles already know about that. They don’t have any history. They never talk about much about

it. When you was a little boy and your grandpa or your grandparents and your uncle tell you―

beautiful. They never write it onto paper, but you have it, it’s all the time in your mind, in your

knowledge. That’s what we have.” (Isaac Akootchook, 16 Jan. 1998)

This describes an expertise derived from a lifetime of experience, as well as the transmission of such

experience from one generation to the next. Such transmission is not written, and in many cases is not

even verbal, but is the guidance provided by the older generation while hunting or engaged in other

shared activities. Subsistence―obtaining food and the other requirements for a good life―was the

unifying theme. Knowledge is inside a person’s head, and is used for the pragmatic purpose of making a

living.

The Elder mentioned that what he and others said in meetings such as this often had little apparent

effect; it is difficult to transmit this knowledge and understanding verbally if others lack the personal

experience that underlies it. He also stated that he knew the study was necessary, since it would provide a

potential way for outsiders to understand about whales in the area. The study also provided the opportunity for local residents and outside scientists to work cooperatively together to better investigate and

communicate how whales were using the Kaktovik area, to their potential common benefit.

The workshop concluded with the Kaktovik Whaling Captains Association giving permission for

the research to proceed, with some modifications in the research design as initially proposed. Foremost

was the condition that, during the first main field season (1998), the project’s boat-based work would not

begin until Kaktovik whalers had landed two bowheads. Some conditions were also placed on the aerial

survey component of the project. A local boat component was added to the project to increase local

participation, and potentially expand the temporal and geographic range of observations for the project.

Lastly, to the extent possible, local and traditional knowledge would be incorporated into the project

documents and fully acknowledged.

Limited Interviews (16–20 Jan. 1998)

Individual discussions were held with several Kaktovik whaling captains and other residents

during and shortly after the workshop summarized in the preceding subsection. These discussions were
2-18 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

held to seek additional information about utilization of the study area by bowheads, and particularly by

feeding bowheads. Kaktovik residents know much about the occurrence of bowheads in their area, but

they usually cannot determine whether the whales that they see are feeding as opposed to migrating or

engaged in some other activity. Nonetheless, much local information on whale occurrence and behavior

exists and can be elicited.

The following summaries are not intended as complete records of the interviews conducted following the workshop in Kaktovik. Rather, they indicate the type of information that was discussed and some

of the content. Content has been confined for the most part to local and traditional knowledge concerning

whale behavior and Kaktovik whaling. Unless noted, the interviews were recorded on tape cassettes. In

most cases, the quality of the recording is fair to poor, in part due to the sites of the interviews. With one

exception, the interviews were conducted in Kaktovik on 16–19 January 1998 by Steven MacLean, a

biologist (and Inupiat) employed by LGL Alaska, and by Michael Galginaitis of Applied Sociocultural

Research (Anchorage). Herman Aishanna was contacted by phone in Barrow on 20 January 1998.

Copies of original tapes and draft transcripts were sent to each person interviewed, for their review. The

detailed transcripts are included, largely un-edited, as Annex B to the present report (see Volume 2).

MMS will distribute copies of these tapes and transcripts to the appropriate repositories (AEWC, IHLC,

KWCA). The order in which the interviews appear below is the order in which they were conducted.

George Kaleak and Bert Akootchook (Steerer, Harpooner).—Both interviewees stated several

times that they cannot say anything about whale feeding behavior, as whalers are not looking for such

behavior when they are out whaling. They sometimes see krill in the water, but not always when they see

whales, nor is krill always present when they see whales. The amount of krill they observe varies by year,

and they related that they did not see much krill in 1997, although they saw many whales.

They stated that whales “hang around” the Kaktovik area in September, although they do not know

why. Whales could be feeding, but whalers are not looking for that behavior, and search for whales by

looking for “blows”. Whales can be seen in the area as late as October, but do not seem to linger in the

area at that time.

During the summer, on their trips to Canada, the interviewees commonly encounter many whales.

In July, bowheads are mainly on the Canadian side, especially in the Herschel Island to Shingle Point

region. However, they also reported that people hunting caribou in July near Camden Bay see whales in

that area. In the past, they have whaled as early as August, but found that the weather was too warm at

that time and the meat spoiled too easily.

Daniel and Lillian Akootchook (retired Whaling Captain and spouse).—This conversation took

place at the interviewees’ home in Kaktovik. The Akootchooks shared many stories of their experiences

in Kaktovik, both whaling and more generally. Little of this related directly to the question of whale

feeding in the Kaktovik area. The stories are not really suited to summation, but speak to the centrality of

whaling and subsistence to Inupiat life in general, and in the lives of the Akootchooks in particular. They

did not generalize broadly, but did explain that whales seem to listen to what people say, and respond to

what they do. Not only are whales very sensitive to the noises people make but, according to the interviewees, whales are also very concerned with the propriety of peoples’ actions and their relations with

each other. That is, whales allow themselves to be taken by those who respect them and behave properly.

The Akootchooks’ stories thus indicate that whaling is very much about the Inupiat relationship with the

whale and each other.

Isaac Akootchook (Whaling Captain, Lay Preacher).—Isaac Akootchook (IA) started with the

observation that, before the Kaktovik residents started (or restarted) whaling in 1964, they saw many
§2. Kaktovikmiut Whaling: Harvest Data & Local Knowledge 2-19

whales right off Arey Island, Bernard Spit, and Jago Spit. His parents told him that the whales were feeding in those areas. He does not know from his own observation, as he cannot tell when a whale is feeding. He asked, “Who can say what a whale is doing underwater?” Many other people told the researchers

essentially the same thing—they cannot tell if a whale is feeding.

IA said that, when out boating, you see little things in the water wherever you travel. He related

that he often looks to see what is in the water. What they see is not only whale food—ringed seals and

ugrook (bearded seals) need food as well. People go seal and ugrook hunting in the spring, and (sometimes) see whales while doing that. The hunters do not bother the whales at this time. IA also used to

just go out boating in the fall, just to look around, and used these trips to spot whales. IA said that the

whales were communicating with one another, and that the “leader whales” of the migration should be

left alone. Otherwise the main body of whales may deflect further offshore. The whale leaders establish

the “trail” for the whale migrations. Once the leaders go by, the main pack will follow this trail. IA said

it is like the caribou of Anaktuvuk Pass.

When asked whether whales travel in groups IA said that some years there are lots of whales, and

then relatively few, and then lots again. Some whales can be early. In July, it is not uncommon to see

single whales, but the hunters do not know if these are migrating from the east. The migration noticeably

starts in August and lasts through October. IA said that there are more whales now in October than there

used to be. “[In 1997 we] went out in a boat in October [when there was quite a bit of open water] and

there were lots of whales—seemed to be smaller ones.” Ice does not really affect the numbers of whales

that go by or the migration, but does affect the hunt. Hunters need to find open water. When they see a

whale, they need to be able to get to it, but find it difficult to do so in heavy ice years. Hence, their

success rate under those conditions is low. IA reported that Kaktovik residents like to hunt other things in

October, and ice cover tends to increase in October, so they try to finish whaling in September. Hunters

tend to go south into the mountains to hunt caribou (or sheep) in October. They also hunt caribou in July,

but more in coastal locations.

IA said that the best spots for whaling are the areas near Jago Entrance (between Bernard Spit and

Jago Spit) and Kuvritovik Entrance (between Barter Island and Arey Island). Some whalers go west a

little way and check Arey Island first, while some check off Jago Spit first. Tapkaurak Entrance also is a

place that people check and find whales. The important waters for Kaktovik whalers are Camden Bay to

Tapkaurak Entrance. When hunting whales, some boats are closer to shore and others are farther out,

with spacing of maybe a mile between “adjacent” boats. Most of the time the whale to be hunted is seen

by one of the middle boats. Sometimes they spot the whale in the morning, near Kaktovik; bring it in and

cut it up in the afternoon; and are done by evening [and then they do it again for the rest of the quota].

They generally look for a 25 to 30 footer, as these small whales are tender and relatively easy to handle.

Sometimes they do take bigger whales, as it can be difficult to be sure of the size of a whale when

hunting. Some years they finish the season early.

One year off Jago Spit there were no whales. There was lots of open water, but they could not see

whales for some reason. IA reported that the old people say

“Don’t talk about whales before you go out, don’t say you are going to get one, whales hear you

and will react to what you say, and will stay away.... The year before, there had been lots of ice

and whales had been hard to see. No whales taken, maybe one. The next year, the ice was gone

but they still did not get any whales. People had been talking before they went out, said that maybe

they would get a whale this year. People were talking, so they did not get any whales.”
2-20 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

IA concluded that “... you can never know about the whale, who will get one, if anyone will. Have to ask

God. Animals are all here to use the earth. People are just sitting here, make plans and then break it.”

During a later meeting (31 Jan. 2002), IA mentioned that in his younger days, before the DEW

facilities were built, many whalebones were evident at Barter Island, including bones inside the lagoon

behind the spit. These bones are buried now. IA believes that the Kaktovik area is an important feeding

area for bowheads.

Thomas Agiak (Whaling Captain).—Thomas Agiak (TA) said that in early August whales can be

found offshore from West Barter Island, in Kuvritovik Entrance. His brother goes to the Camden Bay

area in July and August and sees whales (but generally only a few). Kaktovik whalers catch them off

Bernard Spit in September. TA reported that, as late as conditions allow boating, maybe the second week

of October, whales can be observed in the area―but that he is not really sure what the “ending” date for

the whale migration is. When people go out to hunt caribou in October on Arey Island they see small

whales (Kuvritovik Entrance).

TA indicated that in August, you can see all sizes of whales in the Kaktovik area, sometimes

including some big ones, and that you can tell the difference in size by a difference in the size of the

blows. Smaller whales tend to be closer to shore. TA stated that big whales will also go by early (around

1 Sept.) with smaller whales. Whalers stay away from those pairs of whales, big with small, as often it is

a mother and a young one. By the end of September the larger whales, 43 to 46 footers, are present.

In his experience of travel by boat to Canada or hunting during [early] August, TA seldom has seen

whales between Kaktovik’s usual hunting area and Herschel Island. East of Herschel Island he has seen

many whales during this period. On his way back to Kaktovik [presumably during late August] he

reports seeing many whales in both areas. Regardless of other comments, he said that the migration can

sometimes be early, or late.

When whales are very close to shore they are easy to spot and whalers can follow them by the

“brown bubbles” they stir up from the bottom. In the shallow water, the whales disturb the bottom as

they swim. However, TA also said that when whales are that close to shore (and in shallow water) that

they “spook” quite easily and thus are more difficult to catch.

TA said that for the last 10 years Kaktovik whalers have not had to look beyond a limited

geographical area east to west, up to 20 miles out into the ocean. When there was seismic activity in the

area, he reported that Kaktovik whalers had to go farther out to sea in order to find whales—but they

never struck whales out there because it was too far from Kaktovik. TA reported that when the oil

companies were doing seismic work off Jago, Kaktovik whalers had to go quite a ways to find whales.

He said that noise affects whales quite a lot. One year they saw many whales but they were easily

spooked. When the whalers turned towards them they spooked and disappeared—the whalers could not

get near the whales. The year when seismic work was being done, there was also a good amount of ice.

Whalers would turn towards whales and never see them again. TA thinks it was because of too much

noise in the area, as they had to go far to see whales. He said that when a drill rig was offshore, for 2

years they hardly saw any whales. When there is no noise—no [industrial] boat traffic—Kaktovik

whalers can usually get their whales close to Kaktovik.

Charles Brower (Whaling Captain, President of Kaktovik Whaling Captains Association).—This

interview took place at Charles Brower’s (CB) house. He considered that others would be better sources,

as he was a relatively young captain, and he advised us to seek out the more senior captains.
§2. Kaktovikmiut Whaling: Harvest Data & Local Knowledge 2-21

CB said that they try and stay away from big whales, as they prefer 30 to 40 footers. The earliest

whales seen are in late July, and one year they saw early whales in the Jago area. The regular subsistence

activity in July is to hunt for caribou. The hunters do not actually look for whales at that time, but

sometimes notice them. When Kaktovik whalers can’t see whales nearby during whaling (September),

they look off Arey Island, near the bend. Medium-size whales tend to hang around there. CB reported

that you can see smaller whales hanging around Jago Entrance in mid-August.

When he goes to Canada by boat, he starts to meet whales near BAR-1 [Komakuk]. This is in early

August. He returns to Kaktovik in time for the whaling season there. During boat travel along the coast,

they do not see as many whales between Komakuk and Herschel Island as they do east of Herschel Island.

In July they sometimes see whales locally, or near Ptarmigan Bay if they are traveling to Canada at that

time. The last whale that they see passing Kaktovik in fall tends to be seen around 8 to 12 October.

Kaktovik residents know that whales are still going by in October. Big whales are seen later in the

season; little whales are seen more often at the time when Kaktovik hunters normally whale (early

September).

Archie Brower (Whaling Captain).—This interview took place at Mr. Brower’s (AB) house in

Kaktovik. It was not tape recorded as it had the elements of a social visit as well as the official one.

There was also quite a bit of background noise. Mr. Brower shot the whale taken in 1964 that marked the

resumption of whaling in Kaktovik; he used a .50 caliber rifle. He has passed away since the time of this

interview.

Archie Brower (AB) reported that whales are most often seen off Jago Point and west of Barter

Island. He spontaneously volunteered that the whales were feeding from Barter Island all the way down

to Demarcation Point, but pointed out especially the areas off Jago spit and Tapkaurak Spit. AB said that

whales feed in those areas. At Griffin Point, near AB’s summer camp, the whales can be very close to the

shore (he said 10 to 20 feet, probably meaning water depth). AB does not know what they feed on, but

said that they are feeding in this area—mainly in late August and early September. AB said that there are

also whales off the western end of Arey Island, but he does not know if they are feeding. They do stay in

the area for a while, and again most of the whales are close to the shore. There are not many whales far

from shore. Last year (1997) the whale taken the furthest from the community was 12 or 14 miles

offshore—a two hour tow.

AB and his family made their summer camp at the east corner of Oruktalik Lagoon near Griffin

Point. They went there in July and August, to fish and hunt for caribou and brant. Other families also

have summer camps in the area, but they tend to put up tents and not stay as long as AB and his family.

In their trip to the east to Griffin Point they encounter whales already traveling to the west. These whales

are mostly close to shore in water 20 to 30 feet deep. AB said that they seem to be feeding. Some whales

feed on the top, some dive, and some even bring up mud. The whales in this area seem to stay around for

a while. They may go out further into the ocean for a while, but often come back. AB said there is little

whale feeding further out from the shore, and there are not many whales out there. AB has observed

whales in the Griffin Point area since September of 1955 and/or 1956, when he started to travel there.

Sometimes AB traveled to Canada (Herschel Island area) by boat in August. It takes a day in good

weather to get to Shingle Point, along the coast between Herschel Isl. and Inuvik. They usually see lots of

whales by the time they get to King and Shingle Point, but sometimes see only a few. The whales are not

far off the point, and are going back and forth. AB did not know if they are feeding (at King Point), and

said they are medium size whales. AB said that at Shingle Point the whales may be farther from the shore

than at King Point.
2-22 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

When whales start to return westward during August, the smaller ones tend to be first. The

migration goes into October. There is almost always some open water, which determines to a great extent

where the whales actually are. Kaktovik whalers wait for good weather to go whaling—and the more

open the water, the better the weather has to be. Winds make for rough water when there is much open

water. Good weather and open water allow quick whaling trips, AB said, as was evident in 1997—

whaling consisted of short trips separated by a week of waiting for good weather (waiting for the wind to

die down). Winds in this area are mainly from the west or east. Those from the west tend to be the

strongest ones, while those from the east are usually not too strong.

Joe Kaleak (Whaling Captain and AEWC Commissioner).—Joe Kaleak (JK) started whaling at

Kaktovik in 1972, when he settled there. He thinks that the feeding study is quite important. He started

by saying that the area between Demarcation Point and Icy Reef, and another area on the west side of

Barter Island around Arey Island, are whale feeding areas:

“Well, we don’t really pay attention [to] feeding [by] whales―when we’re out whaling, we just go

look for some whales, you know. So we don’t really pay attention [to] where the feeding areas are.

But I know they’ve got feeding area at the east side of us, between Demarcation [Point] and Icy

Reef. And I just find out not too long ago, there’s another feeding area on the west side of us ...

Arey Island.”

Later in the interview JK stated that, on his summer trips to Canada, he had observed whales feeding in

Canadian waters, near Kay Point. He summarized his observations of feeding whales by saying “... that’s

the only place, right by Demarcation and this side of Herschel. And right over by the Arey Island toward

Camden Bay.”

JK makes a trip to Canada every year. He leaves Kaktovik in mid-July, and always meets whales

east of Demarcation Point but west of Herschel Island. East of Herschel Island, Kay Point is an area

where whales congregate for feeding. Whales that he meets on the way to Canada tend to be small

whales, close to shore. On the way back from Canada in mid-late August, he sees whales on the east side

of Herschel Isl. These whales are traveling slowly. After whales reach BAR-1 [Komakuk] on the Canadian side, it takes them 1 to 1.5 more weeks to reach Barter Island. Whales stay in certain areas for several

days, but JK does not know why. He said that whales may stay in the Demarcation Point area for two

weeks or more—“maybe for a whale convention”.

JK has seen a whale in Camden Bay as early as July, and the Kaktovik hunters used to hunt small

whales near Kaktovik during August in the early years of whaling at Kaktovik. However, JK indicated

that August is too early to whale—the meat too often spoils. Whales often stay in areas around Kaktovik,

especially in the Jago Spit area. That is why so many whales are taken there. After bowheads reach the

Kaktovik area, there will sometimes be a two week “pause” in spotting whales. Whales can be hard to

spot. Big whales come near the end of the migration—up to the middle of October.

JK stated that when Kaktovik whalers go whaling they do not bother whales in the feeding areas,

e.g., Arey Island. Rather, the strategy when the water is open and weather is clear is to go north from

Barter Island 10 to 12 miles out from shore, and then cruise slowly east looking for whales. If no whales

are spotted within 3 days or so, they will start the same way but cruise west. They do not like to go

farther than the Jago Spit–Tapkaurak Entrance area to the east, or beyond Arey Island to the west, but will

go as far east as Griffin Point if they do not find whales any closer. In bad ice years, when they cannot

otherwise get out very far from the village, they will make their way to Camden Bay and go north from

there. Even when the ice is “tight” by the village, it tends to be “loose” off Camden Bay, and allows

Kaktovik hunters to get out to the lead. They then start by first cruising east, as in the normal pattern, and
§2. Kaktovikmiut Whaling: Harvest Data & Local Knowledge 2-23

often end up getting a whale off Jago or Griffin Point anyway, as they would have in a more normal ice

year. In this case they usually end up farther out in the ocean, since open water is farther out. (In later

discussions during January 2002, JK noted that in 2001 hunting extended well offshore because of ice to

the east. He also noted that bowheads tend to remain for more than 7 days when there is no ice, and less

than 7 days with ice.)

Herman Aishanna (Whaling Captain).—HA said that Kaktovik whalers know what whales eat.

They often see whales milling around on the east side of Barter Island, especially the north side of Jago

spit, Bernard Spit. Whale food is present when whales are, and whalers (at least HA) look for whale food

when out looking for whales. It is not hard to look in the water, and when there is lots of krill and

plankton there will be lots of whales. HA said that whales sometimes mill around, and he thinks this is

probably related to the supply of whale food in the area. However, whales are often sufficiently

accessible that there is no need to look around for whale food and such signs. In 1997, there was

absolutely no ice and the first time that Kaktovik whalers went out they got a whale and towed it in. They

butchered it and used all the meat with no waste. There was no ice and thus no interference with seeing

and reaching the whales. Kaktovik whalers rely on calm weather for hunting bowheads, as windy

weather results in large waves.

Still, sometimes when there is little or no ice there are also few whales. HA thinks that this is

related to the lack of whale food—whales and whale food tend to be together in the Kaktovik area.

Whalers also need to take current into account, as HA thinks that the current brings the food to the

whales. The current is always shifting, in every direction, from time to time.

Local Boat Effort

At the workshop in Kaktovik during January 1998, whaling captains proposed a local boat effort as

an added component of the research design. In their view, the local boat effort would contribute in

several ways. (1) It furnished an additional avenue for significant local participation in the research.

(2) By taking place prior to whaling and prior to the project’s primary aerial- and boat-based fieldwork, it

broadened the time period during which use of the area by bowheads could be documented (although of

course the local boat observations were not comparable to those of the formal project survey period).

(3) This effort also afforded the possibility of extending observations west of the formal survey area, into

an area that Kaktovik whalers believed could also be significant for whale feeding. (In practice, the

primary boat-based and aerial work in September also extended west of Kaktovik.) (4) It also afforded an

opportunity for a researcher (MSG) to interact with whalers in a natural situation on the water, and

perhaps gain some local information about whale feeding in an undirected way.

For both 1998 and 1999, the local boat effort was problematic due to weather. The 2000 effort was

more successful:

• In 1998, MSG was present in Kaktovik from 24 August to 9 September. The weather did not

allow small boats to go out before whaling began on 4 September, but then the weather cleared

and Kaktovik whalers successfully harvested their full quota of whales

• In 1999, a delay in the researcher reaching Kaktovik, the involvement of many local people in a

search and rescue operation once he arrived (15 Aug.), and poor weather resulted in only two

trips being made before MSG left (6 Sept.). On the second of these trips (3 Sept.), whales were

observed and recorded with a hydrophone. The whales were located in the Jago area, where

Kaktovik whalers commonly encounter them, not far from the community. Again, Kaktovik

whalers were successful in harvesting their full quota.
2-24 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

• The 2000 small boat effort was more successful. Arrangements were made with two boats (and

crews), rather than only one, to take turns. Of the 19 days when the researcher was in Kaktovik

in 2000 (14 Aug. to 1 Sept.), 10 days had conditions suitable for boating, i.e., good weather when

the researcher was prepared to go out. Seven trips were actually made. Two days were “lost”

when both local-boat crews wished to hunt for seals and/or ducks rather than look/listen for

whales. One good weather day was skipped to allow the researcher to catch up on notes. There

were equipment problems in 2000, so few good hydrophone recordings were made. Trips were

made on 16, 17, 19, 21, 24, 25, and 31 August. A single bowhead whale was observed on 25

August, but no obvious bowhead vocalizations were noted. It was thought that whales had been

heard on 31 August, but later analysis of the tape did not confirm this. Kaktovik whalers again

took their full quota of whales in 2000.

In terms of extending the scope of the observations made by the project, both in time and space, the

local boat effort had little success. Only in the third year were a significant number of trips made, and

most were within the “regular” project area. Few whales were observed, although the 1999 and 2000

efforts did confirm that at least a few whales were in the area well before the start of more intensive

feeding-study fieldwork.

However, in terms of local participation, the small boat effort succeeded admirably. During each

of the three years, the researcher stayed in the community at the home of a local couple. Overall, four

boat crews participated directly in the project, and provided information related to whales and whaling.

Although little of this information specifically related to whale feeding behavior, all boat crews had clear

ideas about where they expected that whales would most likely be found. These areas were essentially

the same for all crews, and were the same as the “core” and “expanded” whaling areas described in earlier

interviews by Kaktovik whaling experts. Much of the crew’s conversations were about subsistence

activities (location, timing, past experiences). Information on whale presence in, and migration through,

the Kaktovik area was generally consistent with that provided during the earlier interviews and during

public meetings. This could be expected, as the KWCA assisted in the recruitment of local boats for this

research component, and ensured that the researcher only went out with experienced whalers.

Existing Documented Local and Traditional Knowledge

Previous sources of documented Inupiat local and traditional knowledge provide little or no information about whale feeding behavior in the eastern Alaskan Beaufort Sea. The Commission on Inupiat

History, Language, and Culture (IHLC) has an extensive collection of unpublished tapes and transcripts,

many of which contain information on whaling. However, they are only roughly indexed, and a quick

survey did not uncover any which appeared to contain observations on whale feeding behavior. It is

possible that some tapes, especially those of Vincent Nageak (see below), may contain such information,

but this cannot be known at present. Some tapes are completely unprocessed, and others are only

minimally indexed and abstracted.

The North Slope Borough periodically conducts conferences for the sharing and distribution of

local and traditional knowledge. The tapes from these conferences are added to the IHLC collection. A

few of these conference sessions have been processed and published. The most pertinent, Kisautaq

(1981), contains much about whaling (and especially about spring whaling), but only a little about whale

feeding behavior. Vincent Nageak stated that

“Herschel Island ... it is said they [whales] no longer reach Herschel Island. Many of them have

now begun to stay to the surface at Herschel Island also. They never used to be like that since time
§2. Kaktovikmiut Whaling: Harvest Data & Local Knowledge 2-25

immemorial. They used to stop a way far east of there. It is said the ones staying close to the

surface are beginning to be farther and farther this way, they are becoming many. In the surrounding area of Herschel Island. The whales stop their traveling as soon as they reach Herschel Island.

We learn that it takes a long time for them to get any fatter. ... Once the whale begins [its

migration] it doesn’t stop anywhere along here. We learn that only when it reaches that place in

the east on the Canadian side does it then finally stay to the surface. And so nowadays, although

they say that Herschel Island has never been like this before, now it has many whales which are

staying to the surface, ones whose only concern is trying to get something to eat.” (Kisautaq

1981:294–295)

This session continues:

Ernie Frankson: “So when they start returning do they do it the same way?”

Waldo Bodfish, Sr.: “By leisurely by frequently going close to it, it is said they take their time

returning, just barely moving at all. When they are [returning] they use a gathering-together area

places which contained food, they do not worry at all.”

Vincent Nageak: “When the whales come this way from the east they don’t travel fast, they often

become fatter and their meat is even different.” (Kisautaq 1981:296) This last point is relevant to

Chapters 20 - 23, where the question of the relative amounts of feeding in the Beaufort Sea vs.

elsewhere is addressed.

A volume in process, Hopson and Panigeo (n.d.), is similarly useful because of the information it

contains on how whaling has changed from the past to 1991, but it does not address whale feeding areas.

The volume of Uiniq devoted to Kaktovik (Hess 1993) is concerned with visually documenting whaling

and other significant village activities, and so does not address whale feeding areas.

Summary

The desire to characterize the degree to which the eastern part of the Alaskan Beaufort Sea is used

by bowhead whales for feeding arises from a number of concerns. The importance of subsistence whaling for the Kaktovikmiut (“people of Kaktovik”) ranks high among these. This chapter provides a brief

description of the community of Kaktovik and Kaktovikmiut subsistence whaling, summarizes the Kaktovikmiut whale harvest during recent years, describes the local coordination efforts undertaken as part of

this project, and summarizes local and traditional knowledge (LTK) pertinent to whale feeding behavior.

Kaktovik is a small community located on Barter Island in the extreme northeast of Alaska, within

the boundaries of the Arctic National Wildlife Refuge (ANWR). The 2000 U.S. Census enumerated 293

people, most of whom (247, or 84 percent) are Native. Household economies rely upon both wage labor

and subsistence activities as vital components of an integrated system. The major employers are the North

Slope Borough, the City of Kaktovik, and the village Native (ANCSA) corporation. There are also a few

private sector jobs and businesses separate from the Native corporations, but most employment is related to

government or Native Corporations. Subsistence activities, and especially activities surrounding the

bowhead whale hunt, are central to the structural organization and cultural identity of Kaktovik residents.

Definitive information on the antiquity of whaling on the North Slope east of Barrow does not

really exist, but available information is consistent with whaling activity at least in the late Thule period

(beginning about 900 years ago). Informants maintain that whaling took place at Barter Island in aboriginal times. It is also not altogether clear when subsistence whaling ceased at Barter Island (prior to 1964),

or why whaling was suspended in the mid-Beaufort area in general. Whaling has taken place out of
2-26 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

Kaktovik during most late summer/autumn seasons since 1964, with a high degree of success, especially

since 1989. After the formation of the Alaska Eskimo Whaling Commission (AEWC) in 1977, Kaktovik

received a formal quota. One to three bowheads were landed during most years in the 1980s, and two to

four bowheads during most years in the 1990s and beyond.

The bowhead hunt normally begins the day after Labor Day and 83% of harvested whales have been

taken in September. In recent years, whales have been taken earlier in the season than in earlier years. The

core whaling area extends from the Hulahula River in the west to Tapkaurak Point in the east and offshore

as far as 32 km (20 mi). Most whales have been taken within 30 km of the village and the mean distance of

harvest locations from Kaktovik has not changed from the 1970s to present. Whaling captains select small

whales over large whales and there has been a significant decrease in the average size of whales harvested

from the 1970s to the present. The size of whales harvested does not increase with date although other data

show that smaller whales become less common in the area as the season progresses. This confirms that

whalers are selective in their harvest. Male and female bowheads are harvested in very similar numbers, but

females make up a significantly higher proportion of whales harvested early in the season and males make

up a significantly higher proportion of whales harvested late in the season.

Bowhead whales are of great cultural importance to the Inupiat and are a major source of food, and

Inupiat know a great deal about whales. However, one elder noted that it is difficult to transmit local

knowledge and understanding verbally if others lack the personal experience that underlies it. This study

required much cooperation and direct participation from local residents in the study design and field

work. All concerned wanted to ensure that Inupiat knowledge of bowhead whales would be integrated

into the planning of the project and the interpretation of its findings. Local participation also insured that

the study did not interfere with the hunt for bowhead whales. Assembly of LTK of bowheads, and

coordination of project and local activities, were two closely intertwined tasks.

Numerous local coordination efforts were built into the project in order to encourage local participation, to respond to local desires for project modification, and to incorporate local knowledge into research

design and interpretation of results. These efforts included meetings and interviews in Kaktovik in 1997–98

before the first major field season, and additional meetings in Kaktovik before subsequent field seasons. A

final workshop in Kaktovik was conducted on 31 January 2002 to discuss the project findings and to

provide input for use in the draft final report. In addition, there was local Kaktovik representation (as well

as AEWC and NSB representation) on a Scientific Review Board that provided technical advice on project

plans and results. As a result of recommendations by Kaktovik residents, a local boat and crew, in

conjunction with the LTK researcher, searched for bowheads present in late August and early September,

earlier than the main field season. While in Kaktovik for that effort, the LTK researcher served many

project liaison functions. No specific LTK research was conducted during the part of September when

Kaktovik residents were actively whaling. However, a local resident was employed to work as a member of

the boat-based zooplankton sampling crew during the September 1998–2000 field seasons. Also, another

project biologist worked closely with the whalers during September 1997–2000, obtaining measurements

and samples of stomach contents and whale tissue from the harvested whales. Furthermore, the project’s

survey aircraft was based in Kaktovik during September 1998–2000 (and 1985–86), affording opportunities

for coordination between project biologists and local people.

Kaktovik residents are very knowledgeable about the times and locations near Kaktovik where

bowheads are present (including small vs. large bowheads), the places where bowheads tend to linger, and

other information relevant to whaling. However, relatively little specific LTK is available about whale

feeding behavior near Kaktovik. “Whale feeding behavior” is a discrete category of definable behaviors
§2. Kaktovikmiut Whaling: Harvest Data & Local Knowledge 2-27

to a scientist, but is for the most part beside the point for an Inupiat subsistence whaler. Nonetheless, two

feeding areas in the general area are recognized: the Demarcation Point/Icy Reef area, and waters near

Arey Island. Some local residents mentioned that they often see whale food in the water, and know that

whales tend to occur in those places. Local residents emphasized that some bowheads occur in the area in

August and even July, before the start of the main westward migration, and that the project should

consider these times as well as later in the season. However, they noted that bowheads are more common

in Canadian waters than near Kaktovik in July–August. The main hunting period for bowheads is in September, but they are present near Kaktovik as late as mid-October in some years. LTK research activities

during this project, although limited, were closely related to the broader local coordination efforts, and

served to structure the local participation aspects of the research in fruitful ways.

Acknowledgements

There are far too many people to thank for their hospitality and assistance during the course of this

project, and a full listing would include a majority of the adults, and a number of the teenagers and

children, of Kaktovik. Special appreciation must be given to Lillian and Daniel Akootchook, who not

only shared their true home environment with the researcher during his stays in Kaktovik, but also their

ample store of experiences and knowledge. The other local boat crew members―Joshua Soplu, Joe

Akootchook, George Akootchook, Adam Linn, and Ben Linn―are thanked for sharing their knowledge

and ensuring the safety of the researcher. We also thank those whalers who agreed to be formally

interviewed―the late Archie Brower Sr., Isaac Akootchook, Daniel and Lillian Akootchook (again), Joe

Kaleak, Thomas Agiak, Herman Aishanna, Charles Brower, George Kaleak, and Bert Akootchook. Joe

Kaleak, as President of the Kaktovik Whaling Captains Association when the project started, and Charles

Brower, as President when it ended, deserve extra thanks for the additional assistance they provided in

organizing and participating in meetings. Mayor Lon Sonsolla provided information on the community

and the use of their facilities when required. We also thank whaling captains James Lampe and James

Killbear Sr. who, although not formally interviewed, assisted in other ways. Fenton Rexford was helpful

throughout the project, and Walt Audi and Merylin Traynor of the Waldo Arms were also more than

helpful. Thanks are also due to others not mentioned, in some cases because they are members of a

community that, although sometimes unsure of the research, still welcomed the researchers.

In Barrow, we were grateful for the help of Maggie Ahmaogak of the Alaska Eskimo Whaling

Commission; Fred Kanayurak who traveled to Kaktovik to help with translation during the Whale

Workshop in January 1998, Jana Harcharek and Arlene Glenn of the Commission on Inupiat History,

Language, and Culture; and Craig George and other staff members of the North Slope Borough

Department of Wildlife Management. Craig George, as well as Gay Sheffield of Alaska Dept of Fish &

Game, provided details on some of the whales harvested at Kaktovik.

Finally, we thank the Minerals Management Service, which sponsored the project, and MMS

Technical Representative Steve Treacy, for his guidance and patience throughout the project.

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§2. Kaktovikmiut Whaling: Harvest Data & Local Knowledge 2-29

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Appendices.

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Nations. Ottawa, Ont.

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787 p.

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Libbey, D. 1983. Kaktovik area cultural resource survey. North Slope Borough Planning Dep. and Nat. Park Serv.

n.p.

Marquette, W.M. 1977. The 1976 catch of bowhead whales (Balaena mysticetus) by Alaskan Eskimos, with a

review of the fishery, 1973-1976, and a biological summary of the species. Northwest & Alaska Fish. Cent.

Proces. Rep., Nat. Mar. Fish. Serv., Seattle, WA. 96 p.

Miller, M. 1935. The great trek: the story of the five-year drive of a reindeer herd through the icy wastes of Alaska

and northwestern Canada. Doubleday, Garden City, NY.

Nielson, J.M. 1977. Kaktovik, Alaska: an overview of relocations. North Slope Borough Planning Dep., Barrow,

AK.

Oil/Whalers Working Group. 1986. Cooperative programs for the Beaufort Sea. c/o Shell Western E & P Inc.,

Anchorage, AK. 79 p.

Olson, D.F. 1969. Alaska reindeer herdsmen: a study of native management in transition. Inst. Social, Econom. &

Gov. Res., Rep. 18. Univ. Alaska, College, AK.

Ray, D.J. 1983. The making of a legend: Charlie and Mary Antisarlook’s reindeer herd. In: Ethnohistory in the

arctic: the Bering Strait Eskimo. Limestone Press, Kingston, Ont.
2-30 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

Sallenave, J. 1994. Giving traditional ecological knowledge its rightful place in environmental impact assessment.

Northern Perspec. 22(1).

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1959. The North Alaska Eskimo, a study in ecology and society. U.S. Bur. Amer. Ethnol. Bull. 171. U.S.

Gov. Printing Office, Washinton, D.C.

Stanford, D.J. 1976. The Walakpa Site, Alaska. Smithsonian Inst. Press, Washington, DC.

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Northwest Alaska. Ph.D. Dissert., State Univ. New York, Binghamton, NY.

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D-8138/0119.
SPECIES COMPOSITION AND BIOMASS OF ZOOPLANKTON

IN RELATION TO BOWHEAD WHALE FEEDING

IN THE EASTERN ALASKAN BEAUFORT SEA

3. INTRODUCTION TO THE ZOOPLANKTON COMPONENTS OF THE STUDY

Denis H. Thomson1 and William B. Griffiths2

Prior to 1998, most of the available information on the zooplankton species composition and

biomass near feeding bowheads came from studies conducted between 1980 and 1988 in the eastern

Alaskan Beaufort Sea and various parts of the Canadian Beaufort Sea: along the Yukon Coast, off the

Mackenzie Delta, and off the Tuktoyaktuk Peninsula (Bradstreet and Fissel 1986; Bradstreet et al. 1987;

Griffiths et al. 1987). Copepods were the dominant zooplankters at all whale feeding stations, with

Limnocalanus macrurus dominating at nearshore stations in the eastern Alaskan Beaufort Sea and along

the Yukon Coast, and Calanus hyperboreus and C. glacialis dominating at stations off the Mackenzie

Delta and off the Tuktoyaktuk Peninsula.

The mean biomass recorded in horizontal net tows taken within layers of concentrated zooplankton

located by echosounder near feeding whales was 1639 mg/m3

 in the eastern Alaskan Beaufort Sea and

1400 mg/m3

 along the Yukon Coast in 1986. At the one feeding station at Shingle Point off the Yukon

coast in 1988, the mean biomass was 3762 mg/m3

. Comparable values are not available for the deeper

offshore areas because of the lack of echosounder data from those situations (which meant that nets could

not be guided to depths of maximum zooplankton biomass). The values from the whale feeding stations

were much higher than the mean biomass of zooplankton taken within layers of concentrated zooplankton

evident on the echosounder at stations where no bowheads were seen (324 mg/m3

).

Biomass in oblique tows, which integrate biomass over the water column, was higher at stations

sampled near bowheads than at stations without bowheads: 499 mg/m3

 (n = 15) vs. 158 mg/m3 (n = 111).

These average biomasses were based on 1985 and 1986 data from the eastern Alaskan and Canadian

Beaufort Sea (Bradstreet and Fissel 1986; Bradstreet et al. 1987; Griffiths et al. 1987).

There is a discrepancy between the species composition of zooplankton found near feeding whales

prior to 1998 and the stomach contents of whales landed at Kaktovik, Alaska (Lowry 1993; see also

Chapter 18 in this report). Euphausiids and the large copepods Calanus spp. were very much overrepresented in the stomach contents relative to plankton samples taken near feeding whales, and the small

copepod Limnocalanus macrurus was under-represented in stomach contents. Four factors may account

for much or all of this difference: (1) The easternmost site where bowhead whales are harvested and

 

1 LGL Ltd., environmental research associates, 22 Fisher St., POB 280, King City, Ont. L7B 1A6.

Phone: 905-833-1244; e-mail: dthomson@lgl.com

2 LGL Ltd., environmental research associates, 9768 Second St., Sidney, B.C. V8L 3Y8. Phone: 250-

656-0127; e-mail: bgriff@lgl.com
3-2 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

stomach contents are available for analysis is Kaktovik, ~200 km west of most stations where (prior to

1998) zooplankton was sampled by nets near feeding whales. Food eaten 200+ km east of the harvest

sites would no longer be present in the stomachs at the time of harvest. (2) Before 1998, the composition

of stomach contents at Kaktovik had been reported for only 12 whales (Lowry 1993)―possibly not a representative sample. (3) Some of the potential bowhead feeding habitats in the eastern Alaskan Beaufort

Sea had not been sampled prior to 1998. (4) Some components of the zooplankton in areas where bowheads were feeding may not have been sampled effectively.

The main difficulty in sampling zooplankton availability for bowhead feeding is that it is very

difficult to find suitable feeding habitat in the absence of whales, even using sophisticated hydroacoustic

techniques. The best predictor of a high biomass of zooplankton in concentrated layers is the presence of

feeding bowhead whales. It was recognized, at the start of the 1998–2000 study, that it would be useful to

place more emphasis on sampling the diversity of feeding habitats used by bowhead whales. A systematic survey of zooplankton throughout the study area was beyond the logistic and funding scope of the

1998–2000 study. However, sampling during 1998–2000 has expanded the number of locations and the

number of years in which food availability has been studied in the eastern part of the Alaskan Beaufort

Sea generally, and more specifically near feeding whales.

The zooplankton chapters of this report describe work done in and near the eastern Alaskan Beaufort Sea during both 1985–86 and 1998–2000. The 1985–86 phase of this study was conducted by Griffiths et al. (1987) in the eastern Alaskan Beaufort Sea and adjacent Canadian waters west of Herschel

Island. The 1985–86 portion of the study was of relatively short duration (two late summer/early autumn

seasons), and zooplankton sampling was possible near feeding bowheads during only one of those years

(1986). The second phase of the study was conducted in 1998, 1999, and 2000, with similar objectives

and methods to those of the first phase. The combined effort was designed to provide more information

on annual variability than had been available based on 1985–86 work. The additional efforts during

1998–2000 evaluated bowhead feeding and zooplankton availability during September of three years

(1998–2000). Those data, in addition to the 1985–86 data, yield five years of data on zooplankton and

bowhead feeding in the eastern Alaskan Beaufort Sea during September.

In each of the five years of study, zooplankton sampling was limited to a duration of about 2 weeks

during early-mid or mid-late September. September is the month of peak bowhead migration through the

study area (see Chapters 2, 9). However, aerial surveys and local knowledge show that bowheads are

occasionally present in July and early August, and are commonly present in late August and in October

(Chapters 2, 9). Although the zooplankton sampling encompassed the period of peak bowhead abundance

in the eastern Alaskan Beaufort Sea, it did not include the entire period when bowheads are present. Zooplankters have seasonal patterns of growth, energy accumulation, and vertical migration, and oceanographic conditions vary from August to October. Average food availability in August and October

(especially late August and early October) is expected to be generally similar, but not identical, to that

measured in September.

The five years of zooplankton data now available, in conjunction with physical oceanographic data

collected as part of the 1985–86 and 1998–2000 studies, provide a more comprehensive and defensible

determination of the availability of zooplankton to bowheads in the eastern Alaskan Beaufort Sea,

especially during September, than was possible based on studies up to 1986 (cf. Richardson [ed.] 1987).

The following four Chapters describe and compare the zooplankton community and physical oceanography of the study area during all five years of the overall study. Chapters 4–6, collectively, address the
§3. Zooplankton: Introduction 3-3

primary objectives of the zooplankton sampling program, and are expected to form the basis of three

journal publications. Those three Chapters are on the following topics:

• Chapter 4. Relationship between acoustic biomass and net biomass of zooplankton,

• Chapter 5. Species composition and biomass of zooplankton in relation to water masses in the

eastern Alaskan Beaufort Sea, and

• Chapter 6. Characteristics of areas where bowhead whales feed in the eastern Alaskan Beaufort Sea.

In Chapter 4, relationships are established that allow data recorded with echosounders during four

of the five years of the study (“acoustic biomass”) to be converted to wet weight biomass of zooplankton.

Using these relationships, acoustic biomass recorded along transects and near whale feeding stations is

shown as zooplankton biomass in Chapters 5 and 6. Chapter 5 describes the horizontal and vertical distribution, biomass, and species composition of zooplankton in the study area in relation to physical properties. In Chapter 6, results described in Chapter 5 are compared with results of zooplankton sampling,

echosounder surveys, and physical oceanographic measurements near feeding whales in an effort to

characterize bowhead whale feeding habitat. Chapter 6 also estimates the quantities of zooplankton

available to feeding whales, on a wet-weight biomass/m3

 basis. In later chapters, these data are used to

help determine the annual variability in the amount of food available to and consumed by bowhead

whales in the study area. Chapter 7 is a summary of the zooplankton components of the work.

All marine sampling during the five field seasons was conducted from a 13-m boat, the Annika

Marie. The intent was to arrive in the Barter Island (Kaktovik) area in early September, which is the

approximate start of the period of peak use of that area by bowheads. In 1998–2000, our arrival in that

area was timed to avoid the first few days of the whaling season. In those years, the Kaktovik whalers

requested that boat-based work not extend east of Kaktovik until after they had landed the second whale

from their quota of three whales per year. After the second whale was landed, we were free to sample

east of Barter Island provided that we did not interfere with ongoing whaling activities.

Our top priority in 1998–2000 was to sample zooplankton near feeding bowheads and near bowheads that were not feeding. In conjunction with this sampling, we sampled along transects to determine

the sizes of the zooplankton patches near the feeding or non-feeding bowheads. When no bowheads were

present in the study area, we sampled sites where bowheads had been observed feeding in previous

studies, in order to determine if these areas have attributes that are associated with high concentrations of

zooplankton. We also sampled at stations along routine transects oriented perpendicular to shore in order

to determine the distribution and abundance of zooplankton in the study area as a whole. Priorities in

1985–86 had been similar, but in those years the sampling along routine transects was also a high priority.

Routine transects extended farther offshore in 1985–86 (generally to the 200-m depth contour) than in

1998–2000 (to the 50-m contour). In addition, zooplankton samples were collected in certain years for

laboratory analysis of fatty acid, stable-isotope, and caloric content of selected groups and species of zooplankton. Those results are included in Chapters 19, 20, and 22, respectively.

Few bowhead whales were present in the study region during September of 1985 or 2000, and

consequently we were not able to sample near feeding bowhead whales during those years. Instead,

zooplankton sampling in those seasons was conducted along transects and in some other locations where

bowheads had been observed feeding in previous years.
3-4 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

Acknowledgements

The success of a field program depends on the contributions of many individuals. We thank the

following people for their help and assistance in carrying out the 1998–2000 zooplankton field programs:

Larry Martin of LGL Inc., Bryan TX, for assistance in collecting physical oceanographic data and

zooplankton samples; Dave Marino, Brian McFadden and Joel Hoffman of BioSonics Inc., Seattle, WA,

for collecting hydroacoustic data; and Bill Kopplin, Captain of the Annika Marie, for diligently operating

the boat. Also, we thank Leonard Solomon of Kaktovik, AK, for assistance in conducting the boat-based

sampling, his knowledge of bowheads, and his ability to spot whales, all of which aided the scientific

crew in accomplishing their goals. Acknowledgements concerning the 1985–86 fieldwork are given in

Richardson (ed., 1987). We also thank Nell Stallard (Applied Technical Services, Victoria, B.C.) for

conducting laboratory analyses of zooplankton samples from all five years. Val Moulton of LGL ran the

robust regressions described in Chapter 4. W.J. Richardson of LGL was Project Director; he edited the

zooplankton chapters. Many others assisted during the planning phase and by providing comments on the

draft report; they are acknowledged in Chapter 1.

Literature Cited

Bradstreet, M.S.W. and D.B. Fissel. 1986. Zooplankton of a bowhead whale feeding area off the Yukon Coast in

August 1985. Part 2 (155 p) In: Bowhead whale food availability characteristics in the Southern Beaufort

Sea: 1985 and 1986. Environ. Stud. 50. Indian and Northern Affairs Canada, Ottawa, Ont. 357 p.

Bradstreet, M.S.W., D.H. Thomson and D.B. Fissel. 1987. Zooplankton and bowhead whale feeding in the Canadian Beaufort Sea, 1986. Part 1 (204 p) In: Bowhead whale food availability characteristics in the Southern

Beaufort Sea: 1985 and 1986. Environ. Stud. 50. Indian and Northern Affairs Canada, Ottawa, Ont. 357 p.

Griffiths, W.B., D.H. Thomson and G.E. Johnson. 1987. Zooplankton and hydroacoustics. p. 135-256 In: W.J.

Richardson (ed.), Importance of the eastern Alaskan Beaufort Sea to feeding bowhead whales, 1985-86.

OCS Study MMS 87-0037. Rep. from LGL Ecol. Res. Assoc. Inc., Bryan, TX, for U.S. Minerals Manage.

Serv., Reston, VA. 547 p. NTIS PB88-150271.

Lowry, L.F. 1993. Foods and feeding ecology. p. 201-238 In: J.J. Burns, J.J. Montague and C.J. Cowles (eds.),

The bowhead whale. Spec. Publ. 2. Soc. Mar. Mammal., Lawrence, KS. 787 p.

Richardson, W.J. (ed.). 1987. Importance of the eastern Alaskan Beaufort Sea to feeding bowhead whales, 1985-

86. OCS Study MMS 87-0037. Rep. from LGL Ecol. Res. Assoc. Inc., Bryan, TX, for U.S. Minerals

Manage. Serv., Reston, VA. 547 p. NTIS PB88-150271.
4. RELATIONSHIPS BETWEEN ACOUSTIC BIOMASS AND NET BIOMASS OF

 ZOOPLANKTON IN THE EASTERN ALASKAN BEAUFORT SEA

William B. Griffiths1

Introduction

During late summer and autumn, bowhead whales of the Bering–Chukchi–Beaufort stock migrate

westward across the Beaufort Sea, often either stopping to feed or feeding while traveling (Lowry 1993;

Moore and Reeves 1993). The overall study of which the present work is a part was designed to determine the importance of the eastern Alaskan portion of the Beaufort Sea to feeding bowhead whales. This

required collection of information on the distribution of zooplankton biomass from eastern Camden Bay

to the Canadian border, and from nearshore waters out to the 50 m contour, during September (Fig. 4.1).

Traditionally, studies of zooplankton have relied on sampling with nets to provide information on

species composition, distribution and biomass. However, net sampling can produce only limited amounts of

data because of the time and expense of collecting and processing the samples. Consequently, these studies

provide limited information on the distribution of biomass over large areas. Bowhead whales tend to feed in

areas with a high biomass of zooplankton (Bradstreet et al. 1987; Griffiths et al. 1987). Areas with a very

high biomass of zooplankton are relatively rare. In addition, the high biomass in these areas tends to be

concentrated in layers, some of which are very thin. These areas would likely remain undetected if only net

sampling were used. Furthermore, with net-sampling alone, there is no way to know whether the locations

and depths with maximum zooplankton biomass have been sampled. These problems can, to a large degree,

be solved through the use of a quantitative echosounder in combination with net sampling.

Over the past few decades, sophisticated sonar systems have been used to find and quantitatively

sample marine fish and zooplankton (Sameoto 1976; Stanton et al. 1994a,b; Macaulay et al. 1995; Coyle

2000; Hewitt and Demer 2000; Kirsch et al. 2000). Hydroacoustic systems that include digital acquisition

and processing can be used to estimate biomass and numbers of fish, and biomass of zooplankton. These

systems measure the strength of the echo, called back scattering, that is returned from a biological (or

other) target. Generally, a strong echo returned from a target means that the target is large and/or that

there are many targets. Hydroacoustic surveys can provide continuous information on the horizontal and

vertical distributions of zooplankton biomass if the relationship between acoustic back scattering and

actual biomass of zooplankton, as estimated by net sampling at selected stations, can be established.

A strong relationship between acoustic back scattering and biomass of zooplankton as determined

by net sampling can be difficult to establish. Acoustic data may contain echoes from fish, from large fastswimming or very small zooplankters that are not captured in nets, and from sediment or water density

discontinuities (Johnson and Griffiths 1990). In addition, the intensity of the back scattering can vary

with the size and shape of the animals, their orientation relative to the sonar beam, and species

 

1

 LGL Ltd., environmental research associates, 9768 Second St., Sidney, B.C. V8L 3Y8. Phone: 250-

656-0127; e-mail: bgriff@lgl.com
4-2 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

FIGURE 4.1. Map of the study area for the zooplankton components of the 1985–86 and 1998–2000

studies of bowhead whale feeding in and near the eastern Alaskan Beaufort Sea. The solid line outlines

the area where zooplankton sampling might potentially have been done. The smaller area within which

boat-based sampling was actually conducted is also outlined.

composition (Stanton et al. 1994a; Coyle 2000). In these cases, there may be no relationship between the

back scattering from the targets and the quantity of zooplankton in the water. A further complication is

that net sampling provides only an estimate, and often a biased estimate, of the actual biomass of

zooplankton present. Complicating factors can include net avoidance by zooplankton, uncertainties in the

volume of water filtered, uncertainty in the exact depth(s) that were sampled by the net, and passage of

small zooplankters through the mesh (Hamner 1984; Wiese 1996; Wong 1996). It is important to

minimize these problems when the objective is to use the relationship between net samples and acoustic

data in order to calibrate other acoustic data collected in the absence of net sampling.

The present results are based on data collected during studies designed to determine the importance

of the eastern Beaufort Sea to feeding bowhead whales. The first part of the study was conducted in

September of 1985 and 1986, and the second in September of 1998 through 2000. In 1985 and 1986, a

120 and 200 kHz dual-frequency echosounder system was used with variable success (Griffiths et al.

1987; Johnson and Griffiths 1990). In 1998, a split-beam single-frequency 430 kHz transducer system

was used to collect digital hydroacoustic data during all zooplankton tows and along transects. In 1999

and 2000, a split-beam dual-frequency system operating at 208 and 430 kHz was used. We also used
§4. Zooplankton: Acoustic vs. Net Biomass 4-3

bongo nets of two types to collect zooplankton samples at certain stations and depths. Many modern

hydroacoustic and zooplankton sampling methods are more sophisticated and complex than the ones used

here (e.g., Wiebe et al. 1996; Coyle 2000). Other sophisticated zooplankton sampling devices, e.g., video

systems, can also be used (e.g., Davis et al. 1996). However, we required small and lightweight equipment that could be quickly deployed and retrieved from a 13-m boat in a remote area.

Methods

During all five years of the study, boat-based sampling was conducted during September from the 13-m

Annika Marie based at Prudhoe Bay, Alaska. In 1985–86, locations of zooplankton sampling stations and of

hydroacoustic transects were established using a VLF satellite navigation system, while in 1998–2000 a global

positioning system (GPS) was used. Zooplankton, hydroacoustic, and physical oceanographic sampling were

conducted at individual stations and along extended transects perpendicular to shore within the study area. The

number of stations and the number and length of transects varied among the five years (see below).

Data Sources

In all five years of the study, concurrent acoustic backscattering data, zooplankton samples, and

physical measurements were collected at stations along transects. In years when it was possible to

approach feeding whales, the same types of data were collected at whale feeding and control stations

(Table 4.1). Figures 5.1 and 6.1A in Chapters 5 and 6 show the locations of sampling stations along

routine transects and near feeding whales, respectively.

1985–1986.—Acoustic backscattering data were acquired using a dual-frequency system with 120

and 200 kHz transducers. Instrument settings for each frequency and year are listed in Table 4.2. For a

detailed description of the hydroacoustic methods in 1985–86, see Johnson and Griffiths (1990).

1998–2000.—In 1998, hydroacoustic data were collected using a split-beam single-frequency 430

kHz transducer. In 1999–2000, a split-beam dual-frequency system with 208 and 430 kHz transducers

was used. The numbers of transects and stations sampled in these three years are listed in Table 4.1. The

instrument settings for all frequencies used in the study from 1998–2000 are listed in Table 4.2.

Hydroacoustic Sampling of Zooplankton

Echosounder procedures varied among years. The equipment and procedures used in 1985–86

were described by Johnson and Griffiths (1990) and summarized in Table 4.1. Here we describe the

1998–2000 procedures.

In 1999 and 2000, the dual frequency system consisted of a Dell Inspiron 3200 Pentium-based

laptop computer, a BioSonics surface unit, transducer cables, and two BioSonics DT 6000 Split Beam

digital transducers operating at 208 and 430 kHz. The system used in 1998 was similar, but employed a

single 430 kHz transducer.

The downward-facing transducers were mounted in a BioFin sled and were towed via armored cable

from the side of the boat, away from the wake and ~1 m below the water surface. Tow speed was ~7.2 km/h

(2 m/s) during surveys between stations, and ~3.6 km/h (1 m/s) during zooplankton tows.

When triggered, the 430 and 208 kHz echosounders both transmitted sound pulses into the water.

Returning echoes were amplified and digitized within the transducers. Real-time acoustic data and positions were collected with the BioSonics Visual Acquisition Program and were stored to the computer’s

hard drive. Real-time data for both transducers were also simultaneously displayed on the computer

screen. At the end of each day, two copies of the data were made and stored on removable Iomega disks.
4-4 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

TABLE 4.1. Number of broad-scale transects, transect stations, and whale

feeding and control stations sampled during 1985–86 and 1998–2000.

No. of No. of No. of No. of

Year Transects Transect St. Feeding St. Control St.

1985 3 12 0 0

1986 4 18 6 5

1998a 4 18 10 8

1999b 4 17 5 3

2000 7 27 0 0 a

 Three whale feeding stations and 1 control station were also Transect stations.

b

 Two whale feeding stations and 1 control station were also Transect Stations.

TABLE 4.2. Echosounder parameters used during whale feeding studies in the eastern Alaskan Beaufort

Sea, 1985–86 and 1998–2000.

Parameters 120 kHz 200 kHz 120 kHz 200 kHz

Peak to peak source level (dB re 1 μPa) 217.4 225.0 217.8 224.4

Receiver sensitivity (dBV) -153.5 -123.6 -135.2 -134.0

Pulse Width (ms) - - - -

Receiver gain (dB) 18.0 -18.0 6.0 0.0

Pulses per second (pps) 1.0 1.0 1.0 1.0

Beam pattern factor 0.005 0.002 0.002 0.002

Beam width 10° 7° 10° 7°

TVG (Time varied gain) Analog Analog Analog Analog

1998

Parameters 430 kHz 430 kHz 208 kHz 430 kHz 208 kHz

Peak to peak source level (dB re 1 μPa) 219.3 219.3 222.9 219.3 222.9

Receiver sensitivity (dBV) -129.7 -129.7 -126.0 -129.7 -126.0

Pulse Width (ms) 0.5 0.5 0.4 0.5 0.4

Receiver gain (dB) - - - - -

Pulses per second (pps) 5.0 2.0 2.0 2.0 2.0

Beam pattern factor 0.001 0.001 0.001 0.001 0.001

Beam width 7° 7° 6° 7° 6°

TVG (Time varied gain) Digital Digital Digital Digital Digital

1985 1986

1999 2000
§4. Zooplankton: Acoustic vs. Net Biomass 4-5

The acoustic data were collected at a threshold level of –90 dB relative to the minimum target

strength with 40 Log R time varied gain. Signals below this threshold were not saved to the data file.

The –90 dB threshold was used to maximize the ability of the acoustic system to pick up small zooplankters that had been common in and near the study area during the first part of the study in 1985 and 1986

(Johnson and Griffiths 1990). One option would have been to save only time- and depth-integrated backscatter data. However, this would have precluded re-processing of the data with different parameters.

Post-processing of raw hydroacoustic data in 1985 and 1986 showed that re-processing was necessary.

Hence, in all five years, all the digital raw hydroacoustic data were saved.

In all five years, the echosounder transducers were towed ~1 m below the surface. Typically, wave

turbulence and air-bubbles in surface waters prevented obtaining meaningful acoustic results from the

upper 2–3 m of the water column.

Net Sampling Methods

All zooplankton tows were made using a bongo assembly towed behind the boat. The bongo frame

was fitted with two 0.5 mm mesh, 0.61 m diameter, plankton nets. A General Oceanics Inc. model 2030

flow meter was placed in the mouth of one of the nets. Standard bongo nets were used in 1985, 1998,

1999, and 2000. A Tareq opening and closing bongo assembly was used in 1986 to collect all horizontal

tows at depth. In 1985 and 1986, the depth of all horizontal tows was recorded in real time using an

Apelco Ranger model 1650 depth sounder. The transducer was attached to the bongo frame so that it

measured distance to the water surface. In 1998, 1999 and 2000, the depth of the net during the tow was

calculated using wire angle and the amount of wire out. The actual depth profile of each tow was

determined later from data recorded with a Wildlife Computers dive recorder (Model Mk7-S) attached to

the bongo frame.

 Horizontal Bongo Tows.—All horizontal tows were of five minutes duration with the start time

being the time when the net reached the desired depth. At most stations, we did from 1 to 3 horizontal

tows. Sampling depths were selected based on real-time hydroacoustic data, and ranged from ~3 to 50 m

depth. At all stations where this was feasible, separate horizontal tows were taken both within and outside

(above or below) concentrations of zooplankton apparent on the echosounder. Except in 1986, the bongo

assembly sampled during both descent to and ascent from the desired sampling depth. Letting the net free-fall

to the desired depth while the boat was moving very slowly minimized the collection of zooplankton during

descent. Slowing the speed of the boat also minimized sampling of zooplankton during ascent.

Sample Treatment.—After each tow, the entire sample from the side of the bongo net fitted with

the flow meter was preserved in 10% formalin for analyses of zooplankton biomass and numbers. Subsamples from the other net were frozen on the boat and later sent to other project participants (University

of Alaska; Alaska Department of Fish & Game) for caloric, isotopic, and fatty acid analyses.

CTD Profiles.—In both 1985 and 1986, temperature and salinity profiles were taken from the

surface to the bottom at all zooplankton sampling stations. An Applied Microsystems CTD-12 was used

(accuracy: temperature, ± 0.2 C°; conductivity, ± 2.0 mmho/cm). All data were recorded on a self-contained tape recording unit and were processed by Arctic Sciences Ltd on their PDP 11/24 computer. In

1998, 1999 and 2000, temperature and salinity profiles were taken at all stations with a digital Sea-Bird

SBE 19 conductivity, temperature, depth (CTD) recorder (accuracy: temperature, ± 0.01 C°; conductivity, ± 0.01 mmho/cm). All data were downloaded from the CTD to a computer using Sea-Bird software

and were processed using the Sea-Bird Analyzer software. In all five years, the CTD was allowed to

equilibrate at the surface for several minutes before each cast, and was then lowered and raised at ~1 m/s.
4-6 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

The recorder collected data during both descent and ascent; however, only the descent data were analyzed. The data for all five years were transferred to Microsoft Excel for analysis.

Laboratory Analyses of Zooplankton

All samples collected during the five years of this study were analyzed by the same person (Nell

Stallard). Each sample was sieved through a 163-μm mesh Nitex sieve, carefully rinsed with tap water to

remove the preservative, and then examined under a low-power binocular microscope. Only data from

horizontal zooplankton tows at depth were used in developing the linear relationships between acoustic

backscatter data vs. zooplankton biomass from net samples. Individual organisms from all horizontal

tows at depth were identified to major group (e.g., copepods, amphipods, and fish larvae, etc.), and wetweighed to the nearest mg using an Acculab electronic balance. Before weighing, each sample was

blotted dry on damp filter paper in a consistent manner.

If large numbers of individuals were present, the sample was first scanned for large or rare organisms, and small animals were then sub-sampled with a Folsom Plankton Splitter or a Hensen-Stempel

pipette. In these cases, the zooplankters in the subsample were counted, weighed to the nearest mg, and

identified to major group. The subsample data were then applied to the whole sample to estimate total

numbers and wet weight for each major group in the sample.

Data Processing and Analysis

Zooplankton Data.—Results from the laboratory analyses of zooplankton were entered into a

Microsoft Excel spreadsheet. For each sample, the flow meter reading recorded during the tow was used

to calculate the volume of water filtered. This information, in conjunction with wet weights for the

individual groups, was used to determine the total biomass in mg/m3

.

In 1986, the sampling efficiencies of the regular bongo assembly vs. the opening and closing bongo

nets were compared based on five paired double-oblique tows at a single station. This showed that the

biomasses of most major zooplankton groups, and the total biomass, were significantly higher for samples

collected with the regular bongo assembly. The mean biomass of major taxa in the standard bongo nets

was 1.23 to 5.82 times higher than that in samples taken in opening and closing bongo nets at the same

place and depth, and nearly the same time. Therefore, all 1986 biomass estimates based on horizontal

tows with opening and closing nets were scaled up using correction factors appropriate to each major

taxonomic group and to total biomass. These factors were 2.53 for copepods and 1.32 for euphausiids

(the predominant taxa), and 2.05 for total biomass.

Hydroacoustic Data.—Methods used to process the hydroacoustic data collected in 1985 and 1986

are presented in Johnson and Griffiths (1990). Briefly, in both years, acoustic volume-scattering data

were obtained by processing digitized voltages with a BioSonics digital echo integrator. In 1985, strata

were 2 m thick between 4 and 52 m depth, and 10 m thick between 52 and 102 m depth. In 1986, the

strata were 1 m thick between 3 and 55 m depth, and 5 m thick from 55 to 100 m depth. In both years,

mean squared voltage for each stratum was calculated for every two minute interval during continuous

transects and for the duration of each horizontal net tow. In 1985 and 1986, acoustic data were collected

with a threshold of –100 dB.

Methods for 1998–2000 were generally similar to those for 1985–86. In 1998, acoustic data from

the 430 kHz transducer were analyzed using BioSonics Visual Analyzer 3.1.1. In 1999 and 2000, hydroacoustic data files for the 430 and 208 kHz transducers were processed separately using BioSonics Visual
§4. Zooplankton: Acoustic vs. Net Biomass 4-7

Analyzer 4.0 (1999) or 4.0.2 (2000). The results were the intensity of acoustic return (volume back

scattering) by location and depth. In 1998–2000, acoustic data were collected with threshold –90 dB.

The acoustic data collected during each horizontal tow were processed to estimate the average

volume backscatter at tow depth during the duration of that tow. Horizontal tow depth varied somewhat

during each tow so the time-depth plot taken from the depth recorder on the net during that tow was used

to determine actual depths sampled. The volume backscattering data from all 1-m depth strata within the

depth range sampled by the net were averaged. For example, for a tow with a mean depth of 10 m, a

maximum depth of 12 m and a minimum depth of 8 m, the average volume backscattering data from the

four 1 m strata between 8 and 12 m over the distance of the tow was used.

Acoustic vs. Net Biomass.―The mean backscattering cross section (σ) of individual zooplankters

encountered during the study was not known, and the value was set to one in the analyses. To convert the

resulting “relative” estimates of zooplankton biomass to estimates of absolute biomass, separate regression analyses were performed on each year’s data. These analyses determined the relationship between

volume back scattering and net biomass (in mg/m3

), based on the concurrent horizontal zooplankton tows

and matched acoustic samples described above.

For 1998–2000, the least trimmed squares (LTS) robust regression program in S-Plus (version 6)

was used to calculate the relationship between acoustic back scattering and net biomass of zooplankton.

This method was chosen because robust regression techniques provide a better fit for a linear regression

model when the data contain outliers, as was the case here (Fig. 4.2). The LTS technique is a highly

robust method for fitting a linear regression model, and achieves this by ordering the residuals from a

least squares fit, trimming the observations that correspond to the largest residuals, and then computing a

least squares model for the remaining observations (S-Plus 2001). This resulted in 6, 4 and 5 data points

being eliminated from the 1998, 1999 and 2000 analyses, respectively. The method provides a more

robust fit then the ordinary least squares regression because it reduces the influence of outliers. For

1985–86, the regression relationships are presented as previously derived by Johnson and Griffiths

(1990), based on geometric mean regression for 1985 and least-squares multiple regression for 1986.

Application to Echosounder Surveys.―For routine transects and transects between whale feeding

and control stations, volume backscatter data for each depth stratum (1 m thick in 1998-2000) were

averaged over 2-min time periods. A 2-min period corresponded to ~240 m distance at typical tow speed.

To estimate wet-weight biomass for each depth stratum and 2-min time interval, the regression relationship described above was applied to the measured volume backscatter. The resulting biomass estimates

were the basis for much of the analysis (in later chapters) of zooplankton availability to bowhead whales.

Results

The best-fit regressions for each of the five years and for 1999–2000 combined are listed in Table

4.3 and illustrated in Figure 4.2. In all years except 1998, dual frequency systems were used to collect

acoustic data. In 1985 and 1986, 120 and 200 kHz transducers were used; in 1999 and 2000, 208 and 430

kHz transducers were employed. Only the results from the higher frequency transducer used in any given

year are presented. In all four years with dual-frequency data, the correlation between net and acoustic

data was higher for acoustic data from the higher-frequency transducer

In the 1985–86 study, some pairs of concurrent net and acoustic data were excluded from the analyses because of the presence of sharp horizontal density gradients (pycnoclines). Pycnoclines can produce a strong acoustic return in the absence of zooplankton concentrations (Johnson and Griffiths 1990).
4-8 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

TABLE 4.3. Regression equations for zooplankton net catch vs. echosounder volume back scattering for

1985–86 and 1998–2000.

Independent

Variable Coefficient Std Error t -value P value

1985 mg/m3

 vs. 200 kHza

Constant 27.9 - - <0.001

(Sv dB 200 kHz) 346.4 - - 0.011

Correlation Coefficient r = 0.810 n = 17

r

2 (% variation explained) = 0.631 df = 15

1986 Log mg/m3 vs. 200 kHza,b

Constant 11.589 1.51 7.680 <0.001

Log (Sv dB 200 kHz) 1.079 0.182 5.920 <0.001

Sta. Depth (m) -0.007 0.003 -2.19 0.033

Multiple Correlation Coefficient R = 0.660 n = 56

R 2 (% variation explained) = 0.440 df = 53

R 2 adjusted for df = 0.420

1998 Log mg/m3

 vs. 430 kHz (-90 dB-60 dB)

b

Constant 3.6487 <0.05

10 x Sv dB 430 kHz 0.015 <0.05

Correlation Coefficient r = 0.274 n = 53

r

2 (% variation explained) = 0.070 df = 51

1999 Log mg/m3

 vs. 430 kHz (-90 dB-60 dB)

b

Constant 12.112 <0.001

10 x Sv dB 430 kHz 0.126 <0.001

Correlation Coefficient r = 0.897 n = 33

r

2 (% variation explained) = 0.804 df = 31

2000 Log mg/m3

 vs. 430 kHz (-90 dB-60 dB)

b

Constant 6.625 <0.001

10 x Sv dB 430 kHz 0.057 <0.001

Correlation Coefficient r = 0.570 n = 39

r

2 (% variation explained) = 0.325 df = 37

a

 From Johnson and Griffiths (1990). b

 1986 and 1998-2000 data reprocessed to minimize contributions by fish (see text).

Net samples taken near pycnoclines found little zooplankton. In 1998, pycnoclines were not a major problem

as distinct pycnoclines were not common at shallow depths (10-25 m) when matched net and acoustic data

were collected. In deeper waters (>25 m), pycnoclines were present during 1998 but very little zooplankton

was evident in the water above them. None of the horizontal tows used in the 1998 analysis of net vs.

hydroacoustic data were taken above or in obvious pycnoclines. In 1999 and 2000 all sampling was done in

areas inside the 50 m contour, and no obvious pycnoclines were observed at any stations there.

In 1985, the best-fit equation was a linear regression between zooplankton biomass and the

acoustic backscatter data from the 200 kHz transducer (Table 4.3; Fig. 4.2A―from Johnson and Griffiths

1990). This regression was derived via the geometric mean method (Ricker 1973, 1984). It “explained”

63% of the variation in zooplankton biomass after exclusion of eight problematic data points. In 1985,

strong temperature–salinity gradients (pycnoclines) were present in the top 10 m of the water column.

When these discontinuities were present, acoustic echoes from zooplankton could not be separated from
§4. Zooplankton: Acoustic vs. Net Biomass 4-9

FIGURE 4.2. Best-fit linear relationships

between zooplankton biomass in horizontal

tows and corresponding volume backscatter

data for 1985–86 and 1998–2000. 1986 and

1998–2000 data pre-processed to minimize

contribution by fish (see text). See “Methods”

re types of regression used; in C-E, a few

outliers shown on the graphs were excluded by

the LTS robust regression method used for

those years.
4-10 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

those attributable to the pycnocline, biasing the backscatter data. To avoid this problem, eight net tows

collected from depths near pycnoclines, and the corresponding acoustic data, were excluded from the

analysis. This resulting regression relationship (Fig. 4.2A) was used to estimate zooplankton biomass

from echosounder data obtained along 1985 transects, and to investigate the vertical and horizontal patchiness of zooplankton.

In 1986, the best-fit equation was a multiple regression equation predicting zooplankton biomass

from the 200 kHz backscatter data and station depth (m). That relationship accounted for 42% of the

variation in zooplankton biomass (Table 4.3; Fig. 4.2B―from Johnson and Griffiths 1990). Some

preliminary data selection and special processing was necessary before the regression analysis was done.

Ten pairs of concurrent net and hydroacoustic data were excluded because of problems with sharp

pycnoclines, similar to those in 1985. In addition, the presence of large numbers of small fish that were

not effectively captured by the bongo nets was a serious bias in 1986. To remove them from the analysis,

the acoustic data were re-processed at a higher threshold to estimate acoustic backscatter attributable to

fish. The “fish” backscatter was then subtracted from the overall backscatter to estimate the backscatter

attributable to zooplankton (Johnson and Griffiths 1990). The volume scattering data were already in log

format and the net biomass was log transformed to stabilize the variation across the range of the two

variables. The resulting multiple regression equation (Fig. 4.2B) was used to estimate zooplankton

biomass from echosounder data obtained in 1986 along routine transects and between whale feeding and

control stations, and to investigate the vertical and horizontal patchiness of zooplankton.

In 1998, the best-fit equation was a robust LTS linear regression between net biomass and the 430

kHz back scatter, pre-processed as described below. This regression explained only 7% of the variation

in net biomass (Table 4.3; Fig. 4.2C). Although there were some strong pycnoclines in the study area in

1998, no samples were collected near any of the discontinuities and no pairs of data required deletion.

However, as in 1986, small fish, primarily Arctic cod (Boreogadus saida), produced strong acoustic

signals but were not effectively caught in the nets. Before the regression analysis was done, the acoustic

data were re-analyzed using –60 dB as a threshold in order to estimate the backscatter attributable to fish.

These values were subtracted from the overall –90 dB data to estimate backscatter attributable to zooplankton. The Sv dB (volume backscattering) values are already on a logarithmic scale. Analysis of

scatter plots of the original data and residuals indicated that the log of zooplankton net biomass (mg/m3

)

produced the best relationship between net and acoustic biomass. Although the correlation between net

and acoustic biomass was statistically significant (P < 0.05), this relationship was too weak to be useful in

estimating zooplankton biomass along the 1998 echosounder transects (r

2

 = 0.07).

In 1999, the best-fit equation was a robust LTS linear relationship between net biomass and 430

kHz back scatter (pre-processed to eliminate fish as in 1998). Pycnoclines were not observed in the study

area in 1999 and did not present a problem in the analysis. This regression explained 80% of the variation

in net biomass (Table 4.3; Fig. 4.2D). This value was sufficiently high to allow use of the 1999 regression in estimating zooplankton biomass along the echosounder transects.

In 2000, the best-fit equation was a robust LTS linear relationship between net biomass and 430

kHz back scatter (pre-processed to eliminate fish as in 1998–99). As in 1999, no pycnoclines were

observed in the study area in 2000. This regression explained 33% of the variation in net biomass (Table

4.3, Fig. 4.2E). The correlation was statistically significant (P < 0.001), and the relationship was used to

obtain approximate estimates of zooplankton biomass along the 2000 transects.
§4. Zooplankton: Acoustic vs. Net Biomass 4-11

Discussion

The absence of strong linear relationships between zooplankton net biomass and acoustic backscatter data in some years of the study is not surprising. Several types of problems can bias the results.

The sources of error include biases in estimating actual zooplankton biomass with nets, imprecise coordination of acoustic and net sampling, back scatter from organisms not sampled by the nets, and/or back

scatter by physical properties of the water. In some cases, these biases can be reduced or removed during

analysis. In other instances they cannot be eliminated, thus leaving residual variation, and sometimes bias,

in acoustic estimates of zooplankton biomass.

Net Sampling Biases

Different groups or species of zooplankton are not equally susceptible to capture in zooplankton

nets. Some zooplankters are larger and swifter than others, and some fraction of these animals are able to

avoid capture by a relatively slow moving net (Hamner 1984; Wiese 1996; Wong 1996). Consequently,

those taxa will be under-represented in the zooplankton samples. This can cause underestimation of

zooplankton biomass. Because of the patchy nature of zooplankton, this error varies with time and

location. If large swift zooplankters represent a significant portion of the zooplankton community at a

given station, the zooplankton biomass estimated with nets will substantially underestimate actual

biomass, and the relationship of these net-based estimates with acoustic back scatter (which theoretically

represents all animals) will be weak.

It is also possible, given the relatively large mesh size used (0.5 mm), that some very small

zooplankters or some of the smaller life stages of the more common zooplankters may have passed through

the net and were thus under-sampled. The biomass of these smaller organisms would then have been underrepresented in the zooplankton sample, leading to a similar problem as that described above for the larger

swift zooplankters.

To establish the relationship of net biomass to acoustic back scatter, a high degree of coordination is

required in obtaining matched samples by the two methods. A primary assumption of this technique is that

the acoustic system is recording backscatter data from the same zooplankton that is being sampled by the

zooplankton net. However, the acoustic system is in fact towed beside the boat while the zooplankton net is

towed some distance off the stern of the boat. It is assumed that the zooplankton is evenly distributed both

vertically and horizontally over these relatively short distances, but this may not always be the case. If the

zooplankton biomass sampled by the two methods is different in the horizontal plane, then a non-correctable

error would be introduced into the data.

 In 1985 and 1986, the position of the zooplankton nets in the water column was determined by

attaching an upward looking depth sounder to the bongo net frame and reading the output directly from a

deck unit in real time. In addition, in 1986, a set of opening and closing bongo nets was used in order to

collect zooplankton samples only from the desired depth and eliminate the collection of zooplankton

during both the ascent and descent of the net. Despite the assumed advantage of using the opening and

closing nets in 1986, a stronger relationship between net and acoustic data was obtained for 1985 using

the standard bongo assembly than for 1986 using the opening and closing net (r

2

 = 0.63 vs. 0.42).

Furthermore, the r

2

 = 0.42 value for 1986 was achieved only by applying a multiple regression approach

using station depth as an additional predictor variable. Part of the problem in 1986 may have been with

the opening and closing bongo net itself, which underestimated the biomass of most major zooplankton

groups in the water column compared to the standard bongo assembly (see Methods). Correction factors

derived from paired double-oblique tows with standard bongo nets vs. opening/closing bongo nets were
4-12 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

applied to all data from the opening and closing nets. However, uncertainty in estimating those correction

factors was another source of measurement error.

From 1998 to 2000, the position of the standard bongo net in the water column was determined

after the net had been retrieved based on a time–depth recorder attached to the net frame. These data

were then used to determine the depth range from which acoustic data should be selected for correlation

with the net data. Again, the results over the three years were variable, with the strongest relationship

from 1999 (r

2

 = 0.80) and the weakest from 1998 (r

2

 = 0.07). Other studies have used larger and more

expensive multiple sampling nets that simultaneously recorded sampling depth, net angle, and a variety of

physical measurements. Analyses of those net data relative to simultaneously collected echosounder data

have resulted in r

2

 values in the same range (r

2

 = 0.23 to 0.93) as those from this study (Simard and

Mackas 1989; Coyle 2000). The net sampling gear used in those studies could not have been handled

from the small research vessel available in the present study, and it is not clear that the more complex

gear, if used, would have provided better results.

It is undoubtedly important, in a study such as this, to coordinate the collection of acoustic and net

data accurately in time and space. However, this alone does not guarantee that the relationships between the

two sets of data will be strong. There are other factors that can influence the strength of the relationship.

Physical Biases

Physical discontinuities can take several forms, e.g., temperature–salinity density gradients, surface

wave turbulence, and air bubbles dispersed deep into the water column by strong wave action. In the present

study area, strong temperature–salinity gradients or pycnoclines are common oceanographic features. The

causes include ice melt and warm freshwater river run-off during the open-water season (Coachman and

Aagaard 1974; Melling et al. 1984). Pycnoclines were common in 1985 and 1986, but were much less so in

1998 and were absent in 1999 and 2000. When present, the strong acoustic echoes attributable to the

pycnocline could not be separated from those of the zooplankton, so backscattering data from those places and

water depths were biased. If CTD data are not available, it may be difficult to determine whether an area of

strong back scatter evident during a hydroacoustic survey is attributable to zooplankton or to a pycnocline. In

the present analysis, this problem was easily remedied by eliminating data collected in or near pycnoclines

since CTD data were available from all net sampling stations used in the analyses. However, CTD data were

not available from all locations along the transects where echosounder data were collected for purposes of

estimating zooplankton biomass (Chapters 5, 6). Thus, zooplankton biomass as estimated from echosounder

surveys may have been overestimated at some locations and depths where a strong pycnocline was present.

This problem was most likely to have occurred in 1985–86, when strong pycnoclines were present, and less

likely in 1998–2000 when they were infrequent or absent.

Surface wave turbulence mixes air into the surface water. The echosounder transducers were towed

one meter below the surface and the upper meter was not sampled. Severe and prolonged wave-action produces air bubbles in the upper 2–3 m of the water column. These are clearly visible in the echograms and

can easily be removed from the data. However, small air bubbles cannot be discerned on the echogram

display or in the acoustic data but can be found at greater depths (Stanton et al. 1994a; J. Dawson, BioSonics

Inc., Seattle, WA, pers. comm.). The backscatter signal from these small bubbles cannot be separated from

that of the zooplankton and, consequently, the acoustic data can be biased upwards. This source of error

would be eliminated if all sampling could be conducted during extended periods of calm weather. However,

with limited time available to collect samples, most studies (including this one) necessarily sample in marginal as well as ideal weather conditions. This source of error could not be recognized or removed during

analyses.
§4. Zooplankton: Acoustic vs. Net Biomass 4-13

There was a weak relationship between acoustic biomass and net biomass in 1998 and a stronger

one in 1999. Large amounts of sediment were evident in the water in 1998. No direct measurements of

turbidity were made in 1998, but turbidity plumes were visible near the bottom at several stations where a

video system was being tested for possible use in detecting zooplankton layers. The 430 kHz transducer

system used in 1998 was capable of detecting and recording signals from sediment plumes in the water

column (Brock Staple, BioSonics Inc., Sumas, WA, pers. comm.). In other applications, high frequency

(500 kHz) echosounders have been used to profile the concentrations and transportation of fine sediments,

5.5 to 7.4 μm in size (Shi et al. 1999). Bradstreet et al. (1987), using a Ross 200 kHz acoustic system,

reported that high turbidity levels and strong pycnoclines were factors in causing a low correlation

between acoustic and zooplankton data during a whale feeding study along the Yukon coast of the

Beaufort Sea―an area where very turbid water is common. The turbidity plumes present during the 1998

phase of the present study may at times have caused high backscattering values regardless of zooplankton

biomass present. This may partially account for the lack of a clear relationship between acoustic and net

biomass in 1998 (Fig. 4.2C). To help address this source of error in future studies conducted in shallow

seas where suspended sediments can bias the acoustic results, it would be useful to measure turbidity vs.

depth profiles as well as standard temperature–salinity profiles. This should be done as often as possible

along the echosounder transects. In this way, data collected at locations and depths with high turbidity

and/or a pycnocline could be removed from the analysis to help improve the relationship between the

acoustic signal and net biomass, and to allow more reliable estimates of biomass from acoustic data.

Alternatively, turbidity and density gradient might be used as covariates in equations predicting zooplankton biomass from acoustic back scatter.

Biological Biases

A common problem during all years of the studies was the presence of large swift organisms, such as

juvenile fish, that produced strong backscatter signals but were not effectively captured by the zooplankton

net. This caused acoustic biomass to be relatively higher than net biomass. This bias was partially

addressed by removing the back scatter from large animals. This was done by re-analyzing the acoustic data

at a higher threshold level to estimate back scatter attributable to large animals and then subtracting these

results from the lower threshold values representing all back scatter. The results were an estimate of the

acoustic back scatter from the smaller zooplankton, which were more effectively sampled by the zooplankton nets (and more representative of the prey of bowhead whales). This process does not entirely

eliminate the problem associated with fish, because fish oriented so as to produce little back scatter, or at the

edge of the beam, could produce an echo below the upper threshold value but above the lower threshold

(i.e., indistinguishable from zooplankton). This is a source of error, and could reduce the correlation

between acoustic and net biomass (Johnson and Griffiths 1990). However, during this study, application of

the dual-threshold procedure to data collected in the four years when fish were a problem improved the

correlation between net and acoustic data.

 Echosounders have been widely and successfully used to estimate the number and biomass of fish in

a school. This success has depended on the assumption that the schools are composed primarily of a single

size and species with similar scattering characteristics (Stanton et al. 1994b). The structure of zooplankton

communities, on the other hand, is more complex. Although there can be a dominant species or group, the

Beaufort Sea zooplankton community is inevitably composed of a variety of species and groups (Bradstreet

and Fissel 1986; Bradstreet et al. 1987; Griffiths et al. 1987; see also Chapter 5). The gross anatomical

shape of individual organisms can vary widely across species and sometimes within species, resulting in

great variations in the acoustic reflective or scattering properties (Stanton et al. 1994b, 1996). The orienta-
4-14 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

tion of individual zooplankters in the water column can also dramatically affect their acoustic scattering

properties (Coyle 2000).

Thus, organisms of the same size but different species, or of the same species but oriented differently

in the water column, can produce widely different backscatter properties. Because the species structure of

the zooplankton community varies both spatially and temporally, the average backscattering cross section

(σ) of the animals will vary accordingly (Stanton et al. 1994b). This potential source of error probably goes

a long way toward explaining the wide variation in percent of variance (7% to 80%) “explained” by our

regression relationships between net and acoustic data. Coyle (2000), in summarizing the results of several

studies that used linear regressions to determine the relationship between net-caught and acoustic estimates

of biomass, found that the explained variance ranged widely, from 23% to 93%. The “percent of variance

explained” values can range widely within the same season and area. Simard and Mackas (1989) used a

104 kHz transducer to detect dense scattering layers and an instrumented multiple opening and closing net

sampler to sample within these layers. They found that large euphausiids (>12 mm long) and copepods

comprised ~70% and ~25%, respectively, of the dry weight biomass in both June and August. Based on a

stepwise linear analysis, they found an r

2

 value of 0.85 for large euphausiids in June and 0.42 in August.

They found that the addition of copepod biomass as a covariate did not significantly improve the relationship in either month.

Although other types of techniques and analyses have been used to address these problems, the

results have also been mixed. Coyle (2000) used multifrequency acoustic data to estimate wet weight

biomass in concurrently collected zooplankton samples. He used canonical correlation between the seven

acoustic variables (volume backscatter at 43, 120, 200 and 420 kHz; mean σ at 43, 120, and 200 kHz) and

the wet weights of individual taxonomic groups to identify significant correlations between acoustic and

biological variables. The technique identified significant correlations of acoustic data with euphausiids and

fish larvae, but not with copepods and chaetognaths―the two main contributors to the zooplankton biomass

(as sampled by nets) in the eastern Alaskan Beaufort Sea.

Despite these limitations and biases, the concurrent acoustic and zooplankton net data collected

during 1985, 1986, 1999 and (less adequately) 2000 provided a basis for estimating, from echosounder data

alone, the relative zooplankton biomass vs. depth, location, and year. Although the technique did not

provide a “perfect” representation of zooplankton biomass, it did provide a useful measure of relative

biomass at different places, depths, and times. A major objective of the overall study was to assess the

characteristics and quality of bowhead whale feeding habitat in the eastern Alaskan Beaufort Sea. This

required zooplankton surveys that could not be conducted with adequate resolution by net-sampling alone.

The relationships developed here provide the basis for converting echosounder data into contour plots

depicting zooplankton biomass vs. depth and location along transects (see Chapters 5 and 6). These plots

show the locations of zooplankton concentrations (“patches”) within the study area in a given year, the

relative biomasses of zooplankton available to whales at different places and times, and year-to-year

differences among the years when useable data were available (see Chapters 5 and 6).3

Summary

There was a need for a method to estimate zooplankton biomass from echosounder data acquired

along transects and at whale feeding locations in the eastern Alaskan Beaufort Sea. This was done by

comparing zooplankton biomass collected in horizontal bongo-net tows with concurrent echosounder

 

3

 Acknowledgements applicable to all zooplankton chapters are included near the end of Chapter 3.
§4. Zooplankton: Acoustic vs. Net Biomass 4-15

measurements of acoustic back scatter at corresponding depths. Paired data of these types were collected

during late summer/early autumn in five years: 1985–86, and 1998–2000. Linear regression techniques

(robust LTS regression in 1998-2000) were used to develop equations that could predict zooplankton

biomass from acoustic back scatter when only the latter is measured. In all five years, there was a positive and statistically significant (P < 0.05 or better) correlation between net biomass and acoustic back

scatter. Predictive equations were developed for data collected in 1985, 1986, 1999, and 2000. In 1998,

the relationship between back scatter and zooplankton biomass was too weak to be of use. The equations

are used in Chapters 5 and 6 to convert acoustic back scattering along transects and at whale feeding stations

into estimates of relative zooplankton biomass, and from this to define the nature and extent of suitable

bowhead feeding habitat in the study area. The resultant echosounder-based data are useful primarily in

comparing relative amounts of zooplankton at different locations, depths, and years.

Numerous sources of error can confound the relationship between acoustic backscatter data and

zooplankton biomass measured with nets. A strong relationship between backscattering data and net biomass is difficult to obtain because the acoustic data may contain echoes from other biotic as well as abiotic

sources. Sources of variability include such things as the presence of fish larvae or other large swift animals

that are not captured by the net, the shape and orientation of zooplankters, sediment plumes, and density

discontinuities in the water. Some of these biases (e.g., backscatter from fish and density discontinuities)

can be partially or completely removed. Other biases cannot be eliminated. These reduce the strength of

correlation between acoustic back scatter and zooplankton biomass in concurrent net samples, and thus the

accuracy with which biomass can be estimated from backscatter data. More expensive and technologically

advanced zooplankton samplers, and more sophisticated acoustic systems, were not practical in this study.

Also, other studies have shown that these approaches do not guarantee better or more consistent results.

Despite the limitations and biases, the method provided useful data concerning the locations and

depths of high-density zooplankton patches, and the relative amounts of zooplankton at different locations,

depths, and times within and among the four years when useful data were available. This approach was an

important technique in assessing the characteristics and quality of feeding habitat available to bowhead

whales in the eastern Alaskan Beaufort Sea during those four years.

Literature Cited

Bradstreet, M.S.W. and D.B. Fissel. 1986. Zooplankton of a bowhead whale feeding area off the Yukon Coast in

August 1985. Part 2 (155 p) In: Bowhead whale food availability characteristics in the Southern Beaufort

Sea: 1985 and 1986. Environ. Stud. 50. Indian and Northern Affairs Canada, Ottawa, Ont. 357 p.

Bradstreet, M.S.W., D.H. Thomson and D.B. Fissel. 1987. Zooplankton and bowhead whale feeding in the

Canadian Beaufort Sea, 1986. Part 1 (204 p) In: Bowhead whale food availability characteristics in the

Southern Beaufort Sea: 1985 and 1986. Environ. Stud. 50. Indian and Northern Affairs Canada, Ottawa,

Ont. 357 p.

Coachman, L.K. and K. Aagaard. 1974. Physical oceanography of Arctic and sub-Arctic seas. p. 1-72 In: Y. Rosenberg-Herman (ed.), Marine geology and oceanography of the Arctic seas. Springer-Verlag, New York,

NY.

Coyle, K.O. 2000. Acoustic estimates of zooplankton biomass and distribution: application of canonical correlation

to scaling of multifrequency acoustic data. Can. J. Fish. Aquat. Sci. 57(11):2306-2318.

Davis, C.S., S.M. Gallager, M. Marra and W.K. Stewart. 1996. Rapid visualization of plankton abundance and taxonomic composition using the Video Plankton Recorder. Deep-Sea Res. II 43(7-8):1947-1970.
4-16 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

Griffiths, W.B., D.H. Thomson and G.E. Johnson. 1987. Zooplankton and hydroacoustics. p. 135-256 In: W.J.

Richardson (ed.), Importance of the eastern Alaskan Beaufort Sea to feeding bowhead whales, 1985-86.

OCS Study MMS 87-0037. Rep. from LGL Ecol. Res. Assoc. Inc., Bryan, TX, for U.S. Minerals Manage.

Serv., Reston, VA. 547 p. NTIS PB88-150271.

Hamner, W.M. 1984. Aspects of schooling in Euphausia superba. J. Crust. Biol. 4:67-74.

Hewitt, R.P. and D.A. Demer. 2000. The use of acoustic sampling to estimate the dispersion and abundance of

euphausiids, with emphasis on Antarctic krill, Euphausia superba. Fisheries Res. 47:215-229.

Johnson, G.E. and W.B. Griffiths. 1990. Hydroacoustic surveys of zooplankton biomass and distribution in the

Beaufort Sea in 1985 and 1986. Rapp. P.-v. Réun. Cons. Int. Explor. Mer 189:345-352.

Kirsch, J., G.L. Thomas and T. Cooney. 2000. Acoustic estimates of zooplankton distributions in Prince William

Sound, spring 1996. Fisheries Res. 47:245-260.

Lowry, L.F. 1993. Foods and feeding ecology. p. 201-238 In: J.J. Burns, J.J. Montague and C.J. Cowles (eds.),

The bowhead whale. Spec. Publ. 2. Soc. Mar. Mammal., Lawrence, KS. 787 p.

Macaulay, M.C., K.F. Wishner and K.L. Daly. 1995. Acoustic scattering from zooplankton and micronekton in

relation to a whale feeding site near Georges Bank and Cape Cod. Cont. Shelf Res. 15(4/5):509-537.

Melling, H., R.A. Lake, D.R. Topham and D.B. Fissel. 1984. Oceanic thermal structure in the Western Canadian

Arctic. Cont. Shelf Res (3):233-258.

Moore, S.E. and R.R. Reeves. 1993. Distribution and movement. p. 313-386 In: J.J. Burns, J.J. Montague and C.J.

Cowles (eds.), The bowhead whale. Spec. Publ. 2. Soc. Mar. Mammal., Lawrence, KS. 787 p.

Ricker, W.E. 1973. Linear regressions in fisheries research. J. Fish. Res. Board Can. 30:409-434.

Ricker, W.E. 1984. Computation and uses of central trend lines. Can. J. Zool. 62(10):1897-1905.

S-Plus 2001. S-Plus 6 for Windows/Guide to Statistics, Vol. 1. Insightful Corp., Seattle, WA. 712 p.

Sameoto, D.D. 1976. Distribution of sound scattering layers caused by euphausiids and their relationship to chlorophyll a concentrations in the Gulf of St. Lawrence Estuary. J. Fish. Res. Board Can. 33(4-1):681-687.

Shi, Z., L.F. Ren and L.J. Hamilton. 1999. Acoustic profiling of fine suspension concentration in the Changjiang

Estuary. Estuaries 22(3A):648-656.

Simard, Y. and D.L. Mackas. 1989. Mesoscale aggregation of euphausiid sound scattering layers on the continental

shelf of Vancouver Island. Can. J. Fish. Aquat. Sci. 46(7):1238-1249.

Stanton, T.K., P.H. Wiebe, D. Chu and L. Goodman. 1994a. Acoustic characterization and discrimination of

marine zooplankton and turbulence. ICES J. Mar. Sci. 51:469-479.

Stanton, T.K., P.H. Wiebe, D. Chu, M.C. Benfield, L. Scanlon, L. Martin and R.L. Eastwood. 1994b. On acoustic

estimates of zooplankton biomass. ICES J. Mar. Sci. 51:505-512.

Stanton, T.K., D. Chu, P.H. Wiebe. 1996. Acoustic scattering characteristics of several zooplankton groups. ICES

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Wiebe, P.H., D.G. Mountain, T.K. Stanton, C.H. Greene, G. Lough, S. Kaartvedt, J. Dawson and N. Copley. 1996.

Acoustical study of the spatial distribution of plankton on Georges Bank and the relationship between volume

backscattering strength and the taxonomic composition of the plankton. Deep-Sea Res. II 43(7-8):1971-2001.

Wiese, K. 1996. Sensory capacities of euphausiids in the context of schooling. Mar. Freshwat. Behav. Physiol.

28(3):183-194.

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5. SPECIES COMPOSITION, BIOMASS, AND LOCAL DISTRIBUTION OF ZOOPLANKTON

RELATIVE TO WATER MASSES IN THE EASTERN ALASKAN BEAUFORT SEA

William B. Griffiths 1 and Denis H. Thomson 2

Introduction

There have been several published studies of the species composition and numerical standing crop

of zooplankton in the Beaufort Sea (Johnson 1956, 1958, 1963; Grainger 1965, 1975; Horner 1978, 1979,

1981; Horner and Murphy 1985; Shih and Laubitz 1978; Sutherland 1982). In waters of the Beaufort Sea

<100 m in depth, Grainger (1965) described two major groups of zooplankton based on horizontal and

vertical distribution patterns and physical characteristics of the water. One group, characteristic of the

upper 100 m of Arctic Surface Water (ASW), is tolerant of temperatures of –1° to ~5–10°C and salinities

of 12 to 34 practical salinity units (psu). This group includes the hydrozoans Aglantha digitale and Aeginopsis laurentii, the ctenophore Beroe cucumis, and several species of copepods including Calanus hyperboreus, C. glacialis, Pseudocalanus minutus, Metridia longa, and Oithona similis. A second group is

characteristic of shallow nearshore brackish waters along the coastlines of the Beaufort and Chukchi seas

and includes the hydrozoans Euphysa flammea, Halitholus cirratus, and Sarsia princeps, the ctenophore

Obelia spp., and the copepods Limnocalanus macrurus, Acartia clausi, Eurytemora herdmani, and Derjuginia tolli. During the open water season these nearshore brackish waters have relatively high temperatures

of 1 to 12°C and low salinities of 8 to 25 psu (Grainger 1965; Shih et al. 1971). These and most other

studies in the Beaufort Sea have presented results as numbers of individuals, not biomass.

Zooplankton is typically concentrated in patches or layers that can vary widely in both horizontal

extent and thickness. The occurrence of these patches can be affected by temperature and salinity, food

availability, and light intensity (Mackas et al. 1985). At times, the plume of warm, brackish, turbid water

associated with the Mackenzie River outflow can be advected into the eastern Alaskan Beaufort Sea by

the wind. The presence, in the same area, of water masses with different properties in the vertical and/or

horizontal dimension can influence the distribution and abundance of zooplankton (Simard et al. 1986;

Castel and Veiga 1990).

This chapter presents the results of 5-year study of the distribution and biomass of zooplankton in

continental shelf waters of the eastern Alaskan Beaufort Sea (central Camden Bay to the Canada/Alaska

border) during September. In September, some bowhead whales are still present on their summer range

in the Canadian Beaufort Sea, but others are migrating westward across the Alaskan Beaufort Sea, frequently stopping to feed or feeding while traveling (see Chapters 9, 12). The study was based on coordinated net sampling and quantitative echosounder surveys. It and similar summer studies in the Canadian

Beaufort Sea (Bradstreet and Fissel 1986; Bradstreet et al. 1987) were components of broader studies of

the feeding ecology of the planktivorous bowhead whale. These projects in the Canadian and eastern

 

1

 LGL Ltd., environmental research associates, 9768 Second St., Sidney, B.C. V8L 3Y8. Phone: 250-

656-0127; e-mail: bgriff@lgl.com

2

 LGL Ltd., environmental research associates, 22 Fisher St., POB 280, King City, Ont. L7B 1A6.

Phone: 905-833-1244. E-mail: dthomson@lgl.com
5-2 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

Alaskan parts of the Beaufort Sea were the first comprehensive studies on late summer biomass of

zooplankton in these areas.

The primary purpose of the present study was to gather data on the taxonomic composition, biomass, patchiness, and variability of the zooplankton available to feeding bowhead whales in the eastern

Alaskan Beaufort Sea. This study emphasized only those species and taxa that were major contributors to

the overall zooplankton biomass. We describe their vertical and horizontal distribution and patchiness in

relation to water masses in the eastern Alaskan Beaufort Sea. Chapter 6 (by Griffiths et al.) compares

average zooplankton biomass and species composition as documented here with those found near feeding

bowheads.

Methods

In all five years of the study (1985–86; 1998–2000), sampling was conducted from a 13-m vessel,

Annika Marie, during September. Zooplankton and physical oceanographic sampling were conducted at

stations along transects perpendicular to shore from central Camden Bay to Demarcation Bay near the

Alaska/Canada border (Fig. 5.1). In 1998, 1999 and 2000, transects were ~25 km in length and sampled

areas from near the shore seaward to the 50 m depth contour. In 1985 and 1986, transects were ~45 km in

length and sampled areas seaward to the 100–200 m contour. In 1985–86, locations of sampling stations

and of hydroacoustic transects were established using a VLF satellite navigation system, whereas in

1998–2000 a global positioning system (GPS) was used. Hydroacoustic and surface-temperature data

were also collected continuously along those transects. At selected stations along the transects, zooplankton tows and vertical profiles of temperature and salinity were taken (Table 5.1). The resulting data were

used to describe the nature of the zooplankton community and to investigate its relationships to the

physical oceanographic characteristics in the study area. Unless otherwise noted, the methods described

below were used in all five years.

Temperature and Salinity Measurements

CTD Profiles.—In 1985 and 1986, temperature and salinity profiles were taken from the surface to

bottom at all zooplankton sampling stations. An Applied Microsystems CTD-12 (accuracy: temperature,

± 0.2 C°; conductivity, ± 2.0 mmho/cm) was used. All data were recorded on a self-contained tape

recording unit and were processed by Arctic Sciences Ltd on their PDP 11/24 computer. In 1998–2000,

the temperature and salinity profiles were taken at all stations with a digital Sea-Bird SBE 19 conductivity, temperature, depth (CTD) recorder (accuracy: temperature, ± 0.01 C°; conductivity, ± 0.01

mmho/cm). All data were downloaded from the CTD to a computer using Sea-Bird software and were

processed using the Sea-Bird Analyzer software. In all five years, the CTD was allowed to equilibrate at

the surface for several minutes before each cast, and was then lowered and raised at ~1 m/s. The recorder

collected data during both descent and ascent; however, only the descent data were analyzed. Data for all

five years were transferred to Microsoft Excel for analysis.

Continuous Surface Measurements.—In 1985 and 1986, near-surface temperature and salinity

were recorded every 15 min during transits between sampling stations. The data were collected using a

Hydrolab System 4000 CTD meter in 1985, and a Hydrolab TC-2 (TCOSL) meter in 1986 (accuracy for

both meters: temperature ± 0.2 C°; conductivity, ± 2.0 mmho/cm). In 1998–2000, a continuous record of

near-surface temperatures was made during transits between stations. Temperatures were recorded every

15 s using an Onset Computer Corp. HOBO data recorder that had a remote uncovered thermistor (accuracy: ± 0.5 C°). The thermistor probe was attached to a piece of pipe and positioned ~0.5 m below the

surface to ensure that it did not come out of the water when the boat was under way.
§5. Zooplankton: Species Composition, Biomass & Distribution 5-3

FIGURE 5.1. Locations of transects and zooplankton stations sampled in the eastern Alaskan Beaufort

Sea during September of (A) 1985–86, (B) 1998–99, and (C) 2000.

B

70N

70.5N

Camden Bay

144W

0

Arey

Island

B

Kaktovik

(Barter Island)

Jago

Lagoon

20 40 km

B




Beaufort 

Lagoon

142W

Kongakut

Delta

B

B

Demarcation

Bay

Continental

Slope

Shelf

Break

B

1985

A T1

1986

T2

T3

T4

3

12

11

8

1

2

1

2

4

6

7

9

10

13

1

2

3

4

5

1

2

5

1

2

3

4

5

3

4

5

B

70N

70.5N

Camden Bay

144W

0

Arey

Island

B

Kaktovik

(Barter Island)

Jago

Lagoon

20 40 km

B




Beaufort 

Lagoon

142W

Kongakut

Delta

B

B

Demarcation

Bay

Continental

Slope

Shelf

Break

B

T3

T5

1998 T1

T2

T1 T4

T.4

1999 T.1

T.3 T.2

T.1

B

31

30 27

14

15

16

23

24

25

26

12

11

19

7

6

17

18

16

22

14 20

21

13

15 19

11

9

8

7

6

6

17

18

20

23

24

0

0

0

10

12
5-4 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

FIGURE 5.1. Concluded.

TABLE 5.1. Number of transects, zooplankton stations and tows, and CTD samples collected in the eastern Alaskan Beaufort Sea during September 1985–86 and 1998–2000. Details are provided in Appendices 5.1 to 5.5 at the end of this chapter.

No. of No. of No. of No. of No. of 

Sampling No. of Plankton Oblique Horizontal Surface CTD

Year Date Transects Stations Tows Tows Tows Samples

1985 4-18 Sept 3 8 8 19 3 12

1986 4-19 Sept 4 11 11 24 6 17

1998 11-22 Sept 5 19 18 31 13 18

1999 16-22 Sept 4 17 17 27 17 17

2000 9-20 Sept 8a 30 30 55 30 30 a

 Two of eight 2000 transects were short transects that duplicated the shoreward ends of two of the other six transects.

Net Sampling of Zooplankton

All oblique and surface tows, and most horizontal tows, were made with a bongo assembly of paired 0.5-mm mesh, 0.61-m diameter, plankton nets. A General Oceanics Inc. model 2030 flow meter was

placed in the center of one frame. In 1986, a Tareq opening and closing bongo assembly was used to take

all horizontal tows at depth.

B

70N

70.5N

Camden Bay

144W

0

Arey

Island

B

Kaktovik

(Barter Island)

Jago

Lagoon

20 40 km

B




142W

Kongakut

Delta

B

B

Demarcation

Bay

Continental

Slope

Shelf

Break

B

Beaufort 

Lagoon

T-8

T-7

27

2000

20

21

22

23

T-1

T-6

6

T-2

T-3

T-4

C

29

30

28

3

19

16

17

5

8

12

25

24

1

2 4

6

7

9

10

11

13

14

15
§5. Zooplankton: Species Composition, Biomass & Distribution 5-5

Horizontal Tows at Depth.―At most stations, we did from 1 to 3 horizontal tows. In 1985 and

1986, the depth of each horizontal tow was recorded in real time using an upward-looking depth sounder

transducer. In 1998–2000, approximate net depth during horizontal tows was calculated in real-time

using wire angle and wire out, and the actual depth was recorded with a Wildlife Computers dive recorder

(Model Mk7-S) attached to the bongo frame. The latter provided more accurate after-the-fact data on tow

depth, which was important in matching net samples with echosounder data from the corresponding

depths. In all years, sampling depths were selected based on real-time echosounder data, and ranged

from ~3 to 110 m depth in 1985–86 and 3 to 50 m in 1998–2000. At all stations where this was feasible,

separate horizontal tows were taken both within and outside zooplankton layers that were apparent on the

echosounder. Except in 1986, the bongo assembly sampled during both descent to and ascent from the

desired sampling depth. Letting the net free-fall to the desired depth while the boat was moving very

slowly minimized the collection of zooplankton during descent. Slowing the speed of the boat minimized

sampling of zooplankton during ascent. Each horizontal tow was five minutes in duration, with the start

time being the time when the net reached the desired depth, and tow speed was ~1 m/s. The opening and

closing bongo net used for horizontal tows in Alaska during 1986 underestimated biomass, as shown by

matched tows with that net and a standard bongo net. Therefore, results from 1986 horizontal tows with

the opening and closing net were corrected, i.e., scaled up, as described in Chapter 4.

Horizontal Surface Tows.―The bongo assembly was also used to take a near-surface tow at each

station, at ~1 m depth. Tow speed was again ~1 m/s for 5 min.

Oblique Tows.―Oblique tows were made at ~1 m/s and sampled the water column during two sequential descent–ascent cycles. The maximum depth sampled at each station was determined with real-time

hydroacoustic data to ensure that all zooplankton concentrations were included. In 1985–86, the net was

dropped to near the bottom in shallow water, and to a maximum of 100-m in deep water. All oblique tows

during 1998–2000, when most transects did not extend seaward of the 50-m contour, were to depths <50 m.

Additional sampling details are provided in Chapter 4. Station locations are listed in Appendices

5.1 to 5.5 (at the end of this chapter).

 Sample Treatment.—After each tow, the entire sample from one of the bongo nets was preserved

in 10% formalin for analyses of zooplankton biomass and numbers. Sub-samples from the other net were

frozen on the boat and later sent to University of Alaska and Alaska Department of Fish & Game for

analyses of caloric, isotopic, and fatty acid content.

Hydroacoustic Sampling of Zooplankton

Hydroacoustic sampling to estimate the distribution and relative biomass of zooplankton along

transects was conducted in all 5 years. Equipment and procedures were described by Johnson and

Griffiths (1990) and in Chapter 4.

A single frequency (1998) or dual frequency (other years) Biosonics echosounder was used. The

downward-facing transducers were mounted in a BioFin sled and were towed via armored cable from the

side of the boat, away from the wake and ~1 m below the water surface. Typically, wave turbulence and

air-bubbles in surface waters prevented obtaining meaningful acoustic results from the upper 2–3 m of the

water column. Tow speed was ~7.2 km/h (2 m/s) during surveys between stations, and ~3.6 km/h (1 m/s)

during zooplankton tows.

Hydroacoustic and position data were collected in real-time and all data were stored for later analysis.

Post-processing of raw hydroacoustic data in 1985 and 1986 showed that reprocessing was necessary (Johnson

and Griffiths 1990). Hence, in all five years, all raw hydroacoustic data were saved in digital form.
5-6 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

Regression equations were developed to relate zooplankton biomass as determined from horizontal

net tows to matched data on measured acoustic back scatter (Johnson and Griffiths 1990; Griffiths,

Chapter 4). These equations were then used to estimate zooplankton biomass at other places and depths

where echosounder but no net-tow data were available. Chapter 4 describes regression equations applicable to our 200 kHz echosounder data from the Alaskan Beaufort Sea in 1985–86, and to our 430 kHz

echosounder data in 1999–2000. For 1998, the correlation between matched net-tow and echosounder

(430 kHz) data was too weak to allow confident use of other 1998 echosounder data in estimating zooplankton biomass (Chapter 4). Along each transect, zooplankton biomass was integrated for each 2-m

(1985–86) or 1-m (1999–2000) depth interval within each 2-min (~240 m) horizontal interval.

Sample Analysis

Zooplankton.—All samples collected in the five years were analyzed by the same person (Nell

Stallard). Each sample was sieved through a 163-μm mesh Nitex sieve, carefully rinsed with tap water to

remove the preservative, and then examined under a low-power binocular microscope. Individual organisms from all oblique tows, and from selected horizontal and surface tows, were identified to species

where possible, counted, and wet-weighed by species to the nearest mg using an Acculab electronic

balance. Other samples were counted and weighed at the major taxonomic group level.

If large numbers of individuals were present, the sample was first scanned for large or rare organisms,

which were processed for the sample as a whole. Small animals were then sub-sampled with a Folsom

Plankton Splitter or a Hensen–Stempel pipette. The flowmeter reading was used to calculate the volume of

water filtered and used to determine the biomass in mg/m3

. Additional details are provided in Chapter 4.

Hydroacoustic Data.—The raw hydroacoustic data collected along transects consisted of volume

backscattering. Because the mean backscattering cross section (σ) of individual zooplankters encountered

during the study was not known, regression analyses were used to determined the relationship between

volume back scatter and net biomass (in mg/m3

). Regression equations derived from each year were applied

to the corresponding integrated volume backscattering data collected along transects to derive an estimate of

relative zooplankton biomass. In some cases, large returns from fish larvae that had air bladders obfuscated

returns from zooplankton. Because the raw data were preserved, they could be reanalyzed to remove these

large returns (see Johnson and Griffiths 1990 and Chapter 4). Especially in 1985 and 1986, strong

pycnoclines produced large backscattering values in the absence of correspondingly large biomasses

zooplankton in the nets. Returns from these pycnoclines, as evident from CTD profiles taken at the stations,

were excluded from the data. There was only a weak relationship between volume backscatter and

zooplankton biomass in 1998 (Chapter 4), so the 1998 echosounder data were not considered further.

Relative biomass for each 2-min period by 1- or 2-m depth interval was entered into MapInfo

Professional with the Vertical Mapper add-on to produce biomass contour plots for each transect.

Results

Physical Oceanography

Temperature–salinity characteristics of stations sampled during 1985–86 and 1998–2000, and the

surface temperatures along transects between those stations, are shown in Appendices 5.6–5.10 and 5.11–

5.12. Analysis of these data indicated that two water masses were present during all years of the study:

(1) A Shallow Cold Saline water mass at station depths 10 m to as much as 50 m. (2) A generally moreoffshore water mass strongly influenced by the Mackenzie River at station depths from as little as 25 m to

50 m (Fig. 5.2; Table 5.2). (3) Also, in 1985–86, an outer shelf water mass characterized by Arctic
§5. Zooplankton: Species Composition, Biomass & Distribution 5-7

FIGURE 5.2. General locations of water masses in the study area in 1985, 1986 and 1998. In 1999 and

2000, the Shallow Cold Saline water mass covered the entire study area.
5-8 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

FIGURE 5.2. Concluded

Surface Water (ASW) was also sampled. Transects in those years extended to the 200-m contour,

whereas in 1998–2000 they extended only to the 50-m contour and offshore waters were not sampled.

Shallow Cold Saline Water Mass.—The main characteristics of this water mass were the absence

of a strong influence of Mackenzie River water and, usually, the absence of sharp discontinuities in the

vertical distribution of temperature and salinity (pycnoclines). The relatively cold temperatures and high

salinities were fairly uniform from surface to bottom (Table 5.2). This water mass typically occurred in

shallow depths during 1985, 1986 and 1998. In 1986 and 1998 it extend out to depths of 28 to 34 m but

in 1985 it was found only very close to shore in water depths of 10 and 15 m (Fig. 5.2; Table 5.2). In

1999 and 2000, this water mass occupied all of the areas sampled out to water depths of 50 m. In 1998

and 1999, and at most stations in 2000, temperatures and salinities in this water mass were fairly uniform

from surface to bottom (Table 5.2).

In some cases, pycnoclines were found in this water mass: In 1986, there were strong pycnolines at

most stations. In 1998, there were some weak to moderate pycnoclines along the three most easterly

transects (Appendices 5.7, 5.8). In 2000, there was some evidence of weak pycnoclines at the deeper

offshore stations and at all stations along the two most easterly transects (Appendix 5.10). In 2000, there

was also some evidence of a weak Mackenzie River influence near the surface at six stations, as surface

salinities there were lower than those in shallower nearshore water. This Mackenzie influence was more

pronounced in the east where surface temperatures were warmer than those in the west by ~1 to 1.5°C and

salinities lower by 2 psu (Appendix 5.10).

In 1986, surface temperatures were ~2°C higher and salinities ~2 psu lower than those recorded during

the other 4 years. The presence of this relatively warm fresh surface layer caused pycnoclines in the nearshore

zone. Strong pycnoclines were not present during 1985, 1998, 1999, or 2000. Bottom water at 1986 stations

classified as being in the Shallow Cold Saline water mass was warmer and fresher than that in the more-offshore water mass strongly influenced by the Mackenzie River (Table 5.2).
§5. Zooplankton: Species Composition, Biomass & Distribution 5-9

TABLE 5.2. General physical characteristics of the Shallow Cold Saline and Mackenzie-Influenced water

masses in September of 1985–86 and 1998–2000. Details are provided in Appendices 5.6 to 5.10.

Year Shallow Cold Saline

1985 2 Stations, depth 13 to 14 m 6 Stations, depth 25 to 45 m

No pycnocline Strong pycnoclines Temperature Salinity

Temperature and salinity uniform Above 0.5 to 1.2 28 to 29 psu

surface to bottom Below <-1.0 °C >31 psu

Temperature 0.1 to 0.2 °C

Salinity 31 psu

1986 8 Stations, depth 10 to 34 m 3 Stations, depth 41 to 47 m

Strong pycnocline Strong pycnoclines Temperature Salinity

Surface temperatures 0.0 to 5 °C Above 2.2 to 3.3 °C 25 to 27 psu

Surface salinities 24 to 27 psu Below <-1.0 °C >31 psu

Bottom temeperatures -0.35 to 0.7°C

Bottom Salinities 29 to 31 psu

1998 11 Stations, depth 10 to 28 m 8 Stations, depth 27 to 40 m

No strong pycnoclines Strong pycnoclines Temperature Salinity

Surface Temperatures: <0.1 to 4.1°C Above 3.5 to 6.4 °C 28 to 31 psu

Surface Salinities: 27.7 to 32 psu Below <-1.0 to 0.8 °C 31.6 to 32.7 psu

Bottom Temperatures: -0.9 to 1.6 °C

Bottom Salinities: 31.3 to 32.4 psu

1999 17 Stations, depth 10 to 45 m No stations showed strong pycnoclines in 1999

No strong pycnoclines

Surface Temperatures: 0.5 to 3.1 °C

Surface Salinities: 26.9 to 31.5 psu

Bottom Temperatures: -1.1 to 1.8 °C

Bottom Salinities: 31.0 to 32.1 psu

2000 30 Transect Stations, depth 10 to 50 m No stations showed strong pycnoclines in 2000

No strong pycnoclines

Surface Temperatures: -1.0 to 1.0 °C

Surface Salinities: 25.6 to 31.0 psu

Bottom Temperatures: -1.6 to -0.2 °C

Bottom Salinities: 30.5 to 32.3 psu

Mackenzie-Influenced

Surface temperature patterns varied among years. In 1986, surface temperatures were considerably

higher (3.4 to 4.5°C) than at the two 1985 stations (0.4 to 0.2°C). In 1998, the surface temperatures along

transects increased from ~1°C nearshore to over 6°C offshore (Appendix 5.10). In 1999, surface temperatures did not show this pattern and, overall, were lower across the entire study area (1.5–3.5°C). In

2000, surface temperatures were uniformly cold across the study area, usually <0.0°C and only rarely

approaching 1.0°C (Appendix 5.11). Overall, the surface waters of the entire study area were colder in

2000 than during any of the other four years of the study.

Mackenzie-Influenced More-Offshore Water Mass.—This water mass was characterized by the

presence of a strong Mackenzie River influence at the surface, overlying water that was generally colder

and more saline. There were sharp discontinuities between the relatively warm, freshened water near the

surface and the cold saline water below. These sharp pycnoclines were characteristic of this water mass

(Table 5.2). When the two water masses were present, the Mackenzie-Influenced water mass was generally found offshore of the Shallow Cold Saline water mass at station depths of 25+ m.

Some stations sampled in 1985, 1986, and 1998 were located in this water mass, but it was absent from

the areas sampled in 1999 and 2000 (Fig. 5.2; Table 5.2). Attributes of the surface water varied from year to
5-10 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

year. In 1998, the surface water temperatures were much warmer and the salinities were generally higher than

those recorded in 1985 and 1986. The bottom water was cold and saline in all three years (Table 5.2).

Outer Shelf Arctic Water Mass.—The Outer Shelf Arctic water mass was characterized by Arctic

Surface Water (temperatures <1.5°C and salinity >31 psu) overlaid by a thick (5–7 m) surface layer of

Mackenzie Bay water with temperatures of 1.5 to 2.5°C and salinities of 23 to 26 psu. The ASW was

typically colder and more saline than either of the two water-masses described above.

A few stations sampled in 1985 and 1986, when transects extended to the 200 m contour or beyond,

were located in the Outer Shelf water mass (Fig. 5.2; Appendices 5.6, 5.7). The influence of Mackenzie

River water was stronger in 1985 than in 1986.

The geographical extent and depth ranges of the water masses described above varied within and among

the five years. This was particularly true for the surface waters. As shown below, the among-year variations

in these water masses appear not to have had a strong effect on the distribution of major taxa comprising the

zooplankton community. This is probably a reflection of their tolerance of a wide range of temperatures and

salinities (–1° to ~5–10°C; 20 to 30 psu). However, there were major among-year differences in the species

composition and biomass of the zooplankton, particularly copepods, in relation to water masses.

Vertical and Horizontal Species Composition and Biomass Distribution of Zooplankton

The following paragraphs describe the distribution and biomass of zooplankton in relation to water

masses (1) in the water column as a whole, (2) near the surface, (3) in all horizontal tows at depth, and (4)

distinguishing horizontal tows above and below pycnoclines, when present. The species composition of

the zooplankton is described for the Shallow Cold Saline water mass and the more-offshore MackenzieInfluenced water mass (for additional details, see Appendices 5.13–5.29).

Shallow Cold Saline Water Mass.—This water mass was present within the area sampled during

all five years of the study.

Biomass: The annual average wet-weight biomasses collected in Shallow Cold Saline waters over

the five years of study ranged from 189 to 409 mg/m3

 for the water column as a whole, from 18 to 205

mg/m3

 for surface waters, and from 236 to 516 mg/m3 for the horizontal tows at depth (Table 5.3). The

average biomass in the water column as a whole, as sampled by oblique bongo tows, was lowest in 2000

(189 mg/m3

) and substantially higher in the other four years (268–409 mg/m3; Table 5.3). The average

zooplankton biomass in surface water was much lower in 1999 and 2000 (18 and 25 mg/m3

) than in any

of the other three years (70–205 mg/m3

; Table 5.3). In all years, the mean zooplankton biomasses in

surface waters were lower than in samples taken at depth, although the difference was not large in 1998.

In all years, we conducted horizontal tows at depth both within and outside what appeared to be layers

of zooplankton evident on the echosounder. In 1998, however, because of the weak correlation between

acoustic vs. net data (see Chapter 4), we were not able to confirm that the layers where some horizontal tows

were taken actually represented concentrations of zooplankton. For example, strong acoustic backscatter

was associated with both high and low zooplankton biomass (e.g., –70.63 dB with 785 mg/m3

 and –70.01

dB with 112 mg/m3

). Conversely, weak acoustic signals were also associated with a wide range of biomasses (e.g., –85.51 dB with 438 mg/m3

 and –85.56 dB with 194 mg/m3). Consequently, to compare the

results among the five years, we calculated the average zooplankton biomass in all horizontal tows at depth

taken for each year, whether or not they were specifically taken within a layer evident on the echosounder.

The average biomass of 516 mg/m3

 in horizontal tows at depth in the nearshore zone was highest in 1986

and lowest in 2000 (Table 5.3). The maximum biomass in individual tows was 1000 and 2200 mg/m3 in

1985–86, considerably higher than the 500–1000 mg/m3

 maxima recorded in 1998–2000.
TABLE 5.3. Comparison of mean total zooplankton biomass (mg/m3) collected by various types of tows on transects 

Beaufort Sea, September 1985–86 and 1998–2000.

Water 1985 1986 1998 1999 Mass mg/m3 s.d. n mg/m3 s.d. n mg/m3 s.d. n mg/m3 

Water Column as a Whole

Shallow Cold Salinea 409 110 2 296 389 8 268 151 11 383 

Mackenzie-Influencedb 189 84 6 170 128 3 223 131 7 - Outer Shelf Arctic 133 55 4 46 22 8 - - - - 

Surface Waters

Shallow Cold Salinec 87 61 2 70 73 3 205 180 8 18 

Mackenzie-Influencedd 4g - 1 13 19 3 25 30 5 - 

Outer Shelf Arctic -h - - 43 71 7 - - - - 

Horizontal Tows at Depth

Shallow Cold Salinee 398 79 3 516 755 18 353 191 14 390 

Mackenzie-Influencedf Above Pycnocline 46 22 5 109 74 2 115 121 6 - 

Below Pycnocline 440 335 11 659 510 4 394 252 11 - 

Outer Shelf Arctic Above Pycnocline 14 4 2 91 21 2 - - - - 

Below Pycnocline 153 78 6 312 339 5 - - - - 

a Data plotted in Figure 5.3.b Data plotted in Figure 5.7.c Data plotted in Figure 5.5.d Data plotted in Figure 5.7.e Data plotted in Figure 5.6.f Data plotted in Figure 5.8.g 1985 data based on single sample.h No surface tows in 1985 because of heavy ice conditions.
5-12 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

Composition of Zooplankton: Major taxa were defined as those that contributed more than 10

mg/m3

 to total biomass in at least one year. In the water column as a whole, within the Shallow Cold

Saline zone, five major zooplankton taxa were collected in one or more of the five years. These were

copepods, gelatinous zooplankton (i.e., ctenophores + cnidarians), chaetognaths, mysids, and fish larvae

(Fig. 5.3A–E). Copepods were the dominant taxon in all years, and were especially dominant in 1985 and

1986. Gelatinous zooplankton and chaetognaths, considered together, were major contributors to zooplankton biomass in every year, and in 1998 to 2000 their biomass approached that of copepods (Fig.

5.3C,E). Other groups were major contributors in some years but not others. Euphausiids were collected

in oblique tows in all years except 1986 and were major contributors to the zooplankton biomass in 1985

and 2000; decapods were major contributors only in 1986 (Fig. 5.3A–E).

FIGURE 5.3. Mean biomasses (mg/m3) of major zooplankton taxa in the Shallow Cold Saline water mass

as evident from oblique tows through the water column in the eastern Alaskan Beaufort Sea, September

1985–86 and 1998–2000.

A. 1985 Water Column

0

100

200

300

400

500

Ctenophores

Cnidarians

Copepods

Amphipods

Euphausiids

Mysids

Chaetognaths

Pteropds

Fish

Other

Biomass (mg/m3

)

N = 2

Total = 409 mg/m N = 2 3

Total = 409 mg/m 3

B. 1986 Water Column

0

100

200

300

400

500

Ctenophores

Cnidarians

Copepods

Amphipods

Euphausiids

Mysids

Decapods

Chaetognaths

Pteropods

Fish

Other

Biomass (mg/m3

)

N = 8

Total = 296 mg/m N = 8 3

Total = 296 mg/m 3

C. 1998 Water Column

0

100

200

300

400

500

Ctenophores

Hydrozoans

Copepods

Amphipods

Euphausiids

Mysids

Decapods

Chaetognaths

Larvaceans

Fish

Other

Biomass (mg/m3

)

N = 11

Total = 268 mg/m3

N = 11

Total = 268 mg/m 3

E. 2000 Water Column

0

100

200

300

400

500

Ctenophores

Cnidarians

Copepods

Amphipods

Euphausiids

Mysids

Decapods

Chaetognaths

Larvaceans

Fish

Other

Biomss (mg/m3

)

N = 30

Total = 189 mg/m N = 30 3

Total = 189 mg/m 3

D. 1999 Water Column

0

100

200

300

400

500

Ctenophores

Cnidarians

Copepods

Amphipods

Euphausiids

Mysids

Decapods

Chaetognaths

Larvacea

Fish

Other

Biomass (mg/m3

)

N = 17

Total = 383 mg/m 3
§5. Zooplankton: Species Composition, Biomass & Distribution 5-13

In all five years, only a small number of species accounted for most of the biomass of each of the

major taxa. The copepods Calanus hyperboreus and C. glacialis were each major contributors (>10

mg/m3

) to the copepod biomass in all years (Fig. 5.4A–E). In 1985 and 1986, the biomass of

Limnocalanus macrurus was higher than that of any other species in samples taken in Shallow Cold

Saline waters, but this species was not found in these waters at all in 1998 and 1999, and only in small

quantities in 2000 (Fig. 5.4A–E). The copepod Pseudocalanus minutus was the dominant copepod at a

single shallow-water station on Transect T-3 in 1999. Derjuginia tolli was a major contributor to the

copepod biomass only in 1985.

Similarly, few species accounted for most or all of the biomass of other major zooplankton taxa in

the Shallow Cold Saline zone in any of the five years. These were the chaetognath Sagitta elegans; the

cnidarians Aglantha digitale, Halitholus cirratus, and Cyanea capillata; the ctenophore Mertensia ovum;

the mysid Mysis litoralis; the euphausiid Thysanoessa raschii; the amphipod Parathemisto libellula; and

larvae of the arctic cod Boreogadus saida (Fig. 5.4A–E). The species composition of these major taxa of

zooplankton was quite similar among years, with the exception of minor differences for gelatinous zooplankton (Fig 5.4A–E).

The low biomass in the surface waters was composed of copepods, gelatinous zooplankton and, to a

lesser extent, chaetognaths (Fig 5.5A–E). Below the surface, the composition of the zooplankton collected in horizontal tows was similar to that in the water column as a whole (Fig. 5.6A–E; cf. Fig. 5.3A–E).

Mackenzie-Influenced More-Offshore Zone.—This water mass was present in the area sampled

during 1985, 1986 and 1998, but not in 1999 and 2000.

Biomass: The annual average wet-weight biomasses collected in this zone during 1985, 1986 and

1998 ranged from 170 to 223 mg/m3

 for the water column as a whole, and from 4 to 25 mg/m3 for surface

waters (Table 5.3). For each year, each of these averages was lower than the corresponding value in the

Shallow Cold Saline zone. Average biomass in the water column was slightly higher in 1998 (223

mg/m3

) than in either 1985 or 1986 (189 and 170 mg/m3, respectively; Table 5.3). In all three years, the

warm freshened water layer above the pycnocline contained a very low biomass of zooplankton (mean 46

to 115 mg/m3

) compared to the cold saline water below (mean 394 to 659 mg/m3; Table 5.3).

Composition of Zooplankton: In the Mackenzie-Influenced more-offshore zone, zooplankton taxa

that accounted for most of the biomass varied among years in the water column as a whole (Fig. 5.7A–C)

and in surface tows (Fig. 5.7D–F). In the water column as a whole, copepods and gelatinous zooplankton, with lesser contributions from amphipods, euphausiids, chaetognaths, pteropods, and fish, accounted

for most of the biomass (Fig. 5.7A–C). In all three years, copepods were the dominant taxon, particularly

in 1985 and 1986. In 1998, the biomass of gelatinous zooplankton and chaetognaths (combined) almost

equaled that of copepods (Fig. 5.7A–C). In surface tows, copepods were major contributors in all years,

while gelatinous zooplankton, decapods, larvaceans, chaetognaths and fish were major contributors in

some years but not others (Fig. 5.7D–F).

Above the pycnocline, copepods were (by a small margin) the dominant taxon in 1985 and 1998,

but pteropods and gelatinous zooplankton dominated in 1986 (Fig. 5.8A–C). Below the pycnocline,

copepods accounted for more of the biomass than any other group during all three years, although in 1998

the biomasses of gelatinous zooplankton and chaetognaths (combined) exceeded copepod biomass (Fig.

5.8D–F). No horizontal tows were taken near the bottom, so any zooplankton concentrated there may be

underrepresented.
5-14 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

FIGURE 5.4. Mean biomasses (mg/m3) of major zooplankton species in the Shallow Cold Saline water

mass, water column as a whole, in the eastern Alaskan Beaufort Sea, September 1985–86 and 1998–

2000.

A. 1985

0

50

100

150

200

Calanus 

hyperboreas

Limnocalanus 

macrurus

Halitholus 

cirratus

Aglantha 

digitale

Sagitta 

elegans

Thysanoessa 

raschii

Boreogadus 

saida

Biomass (mg/m3

)

n = 2

Total = 409 mg/m3

n = 2

Total = 409 mg/m 3

B. 1986

0

50

100

150

200

Calanus 

hyperboreas

Calanus 

glacialis

Limnocalanus 

macrurus

Derjuginia 

tolli

Halitholus 

cirratus

Cyanea capillata

Aglantha 

digitale

Mertensia 

ovum

Sagitta 

elegans

Mysis 

litoralis

Thysanoessa 

raschii

Parathemisto 

libellula

Boreogadus 

saida

Biomass (mg/m3

)

n = 8

Total = 296 mg/m3

n = 8

Total = 296 mg/m3

C. 1998

0

50

100

150

200

Calanus 

hyperboreas

Calanus 

glacialis

Limnocalanus 

macrurus

Derjuginia 

tolli

Halitholus 

cirratus

Cyanea capillata

Aglantha 

digitale

Mertensia 

ovum

Sagitta 

elegans

Mysis 

litoralis

Thysanoessa 

raschii

Parathemisto 

libellula

Boreogadus 

saida

Biomass (mg/m3

)

n = 11

Total = 268 mg/m3

n = 11

Total = 268 mg/m3

D. 1999

0

50

100

150

200

Calanus 

hyperboreas

Calanus 

glacialis

Limnocalanus 

macrurus

Derjuginia 

tolli

Halitholus 

cirratus

Cyanea capillata

Aglantha 

digitale

Mertensia 

ovum

Sagitta 

elegans

Mysis 

litoralis

Thysanoessa 

raschii

Parathemisto 

libellula

Boreogadus 

saida

Biomass (mg/m3

)

n = 17

Total = 383 mg/m3

n = 17

Total = 383 mg/m3

E. 2000

0

50

100

150

200

Calanus

hyperboreus

Calanus

glacialis

Limnocalanus

macrurus

Derjuginia 

tolli

Halitholus 

cirratus

Cyanea 

capillata

Aglantha 

digitale

Mertensia 

ovum

Sagitta 

elegans

Mysis 

litoralis

Thysanoessa

raschii

Parathemisto 

libellula

Boreogadus 

saida

Biomass (mg/m3

)

n = 30

Total = 189 mg/m3

n = 30

Total = 189 mg/m3
§5. Zooplankton: Species Composition, Biomass & Distribution 5-15

FIGURE 5.5. Mean biomasses (mg/m3) of major zooplankton taxa in surface waters of the Shallow Cold

Saline water mass, eastern Alaskan Beaufort Sea, September 1985–86 and 1998–2000.

A. 1985 Surface Tows

0

100

200

300

400

500

Ctenophores

Cnidarians

Copepods

Amphipods

Euphausiids

Mysids

Chaetognaths

Pteropds

Fish

Other

Biomass (mg/m3

)

N = 2

Total = 87 mg/m3

N = 2

Total = 87 mg/m3

B. 1986 Surface Tows

0

100

200

300

400

500

Ctenophores

Cnidarians

Copepods

Amphipods

Euphausiids

Mysids

Decapods

Chaetognaths

Pteropods

Fish

Other

Biomass (mg/m3

)

N = 3

Total = 70 mg/m3 N = 3

Total = 70 mg/m3

C. 1998 Surface Tows

0

100

200

300

400

500

Ctenophores

Hydrozoans

Copepods

Amphipods

Euphausiids

Mysids

Decapods

Chaetognaths

Larvaceans

Fish

Other

Biomass (mg/m3

)

N = 8

Total = 205 mg/m3

N = 8

Total = 205 mg/m3

E. 2000 Surface Tows

0

100

200

300

400

500

Ctenophores

Cnidarians

Copepods

Amphipods

Euphausiids

Mysids

Decapods

Chaetognaths

Larvaceans

Fish

Other

Biomass (mg/m3

)

N = 30

Total = 25 mg/m3

N = 30

Total = 25 mg/m3

D. 1999 Surface Tows

0

100

200

300

400

500

Ctenophores

Cnidarians

Copepods

Amphipods

Euphausiids

Mysids

Decapods

Chaetognaths

Larvacea

Fish

Other

Biomass (mg/m3

)

N = 17

Total = 18 mg/m3

N = 17

Total = 18 mg/m3
5-16 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

FIGURE 5.6. Mean biomasses (mg/m3) of major zooplankton taxa in the Shallow Cold Saline water mass

as evident from horizontal tows at depth, eastern Alaskan Beaufort Sea, September 1985–86 and

1998–2000.

A. 1985 Horizontal Tows at Depth

0

100

200

300

400

500

Ctenophores

Cnidarians

Copepods

Amphipods

Euphausiids

Mysids

Chaetognaths

Pteropds

Fish

Other

Biomass (mg/m3

)

N = 3

Total = 397 mg/m3

N = 3

Total = 397 mg/m3

B. 1986 Horizontal Tows at Depth

0

100

200

300

400

500

Ctenophores

Cnidarians

Copepods

Amphipods

Euphausiids

Mysids

Decapods

Chaetognaths

Pteropods

Fish

Other

Biomass (mg/m3

)

N = 18

Total = 516 mg/m N = 18 3

Total = 516 mg/m3

C. 1998 Horizontal Tows at Depth

0

100

200

300

400

500

Ctenophores

Hydrozoans

Copepods

Amphipods

Euphausiids

Mysids

Decapods

Chaetognaths

Larvaceans

Fish

Other

Biomass (mg/m3

)

N = 14

Total = 353 mg/m 3

N = 14

Total = 353 mg/m3

E. 2000 Horizontal Tows at Depth

0

100

200

300

400

500

Ctenophores

Cnidarians

Copepods

Amphipods

Euphausiids

Mysids

Decapods

Chaetognaths

Larvaceans

Fish

Other

Biomass (mg/m3

)

N = 55

Total = 236 mg/m 3

N = 55

Total = 236 mg/m3

D. 1999 Horizontal Tows at Depth

0

100

200

300

400

500

Ctenophores

Cnidarians

Copepods

Amphipods

Euphausiids

Mysids

Decapods

Chaetognaths

Larvacea

Fish

Other

Biomass (mg/m3

)

N = 27

Total = 390 mg/m3
§5. Zooplankton: Species Composition, Biomass & Distribution 5-17

FIGURE 5.7. Mean biomasses (mg/m3) of major zooplankton taxa from the Mackenzie-Influenced water

mass as evident from oblique tows (left) and horizontal surface tows (right), eastern Alaskan Beaufort

Sea, September 1985, 1986 and 1998. Note the different scales on the vertical axes for water column

and surface tows.

Water Column Surface Tows

A. 1985

0

20

40

60

80

100

120

140

160

Ctenophores

Cnidarians

Copepods

Amphipods

Euphausiids

Mysids

Chaetognaths

Pteropds

Fish

Other

Biomass (mg/m3

)

N = 6

Total = 189 mg/m3

N = 6

Total = 189 mg/m3

B. 1986

0

20

40

60

80

100

120

140

160

Ctenophores

Cnidarians

Copepods

Amphipods

Euphausiids

Mysids

Decapods

Chaetognaths

Pteropods

Fish

Other

Biomass (mg/m3

)

N = 3

Total = 170 mg/m3

N = 3

Total = 170 mg/m3

D. 1985

0

5

10

15

20

Ctenophores

Cnidarians

Copepods

Amphipods

Euphausiids

Mysids

Chaetognaths

Pteropds

Fish

Other

Biomass (mg/m3

)

N = 1

Total = 4 mg/m3

N = 1

Total = 4 mg/m3

E. 1986

0

5

10

15

20

Ctenophores

Cnidarians

Copepods

Amphipods

Euphausiids

Mysids

Decapods

Chaetognaths

Pteropods

Fish

Other

Biomass (mg/m3)

N = 3

Total = 13 mg/m3 N = 3

Total = 13 mg/m3

F. 1998

0

5

10

15

20

Ctenophores

Cnidarians

Copepods

Amphipods

Euphausiids

Mysid/

Decapods

Chaetognaths

Larvacea

Fish

Other

Biomass (mg/m3)

N = 5

Total = 25 

mg/m3

N = 5

Total = 25 mg/m3

C. 1998

0

20

40

60

80

100

120

140

160

Ctenophores

Cnidarians

Copepods

Amphipods

Euphausiids

Mysids

Decapods

Chaetognaths

Larvacea

Fish

Other

Biomass (mg/m3

)

N = 7

Total = 223 

mg/m3

N = 7

Total = 223 mg/m3
5-18 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

FIGURE 5.8. Mean biomasses (mg/m3) of major zooplankton taxa in the Mackenzie-Influenced water

mass as evident from horizontal tows above (left) and below (right) pycnoclines in the eastern Alaskan

Beaufort Sea, September 1985, 1986 and 1998. Note the different scales on the vertical axes for tows

above and below pycnoclines.
§5. Zooplankton: Species Composition, Biomass & Distribution 5-19

In the Mackenzie-Influenced more-offshore water mass, as was the case in the Shallow Cold Saline

zone, only a few species accounted for most zooplankton biomass in the water column as a whole (Fig.

5.9A–C). Calanus hyperboreus and C. glacialis were major contributors to the copepod biomass in all

three years, with C. glacialis being the dominant contributor in 1986 and 1998, and C. hyperboreus in

1985 (Fig. 5.9A–C). Limnocalanus macrurus, the dominant copepod in the Shallow Cold Saline zone in

1985 and 1986, was a major contributor to the zooplankton biomass in Mackenzie-Influenced waters in

1985, a minor contributor in 1986, and was not found in 1998.

Other dominant species were the chaetognath Sagitta elegans; the cnidarians Aglantha digitale and

Cyanea capillata; the amphipod Parathemisto libellula; and arctic cod larvae Boreogadus saida (Fig. 5.9

A–C). Except for some minor differences in gelatinous zooplankton, the species composition of these major

taxa of zooplankton was similar in all three years when this water mass was sampled (Fig. 5.9A–C).

FIGURE 5.9. Mean biomasses (mg/m3) of major zooplankton species in the Mackenzie-Influenced water

mass, water column as a whole, eastern Alaskan Beaufort Sea, September 1985, 1986 and 1998.

A. 1985

0

50

100

150

200

Calanus 

hyperboreas

Calanus 

glacialis

Limnocalanus 

macrurus

Derjuginia 

tolli

Halitholus 

cirratus

Cyanea capillata

Aglantha 

digitale

Mertensia 

ovum

Sagitta 

elegans

Mysis 

litoralis

Thysanoessa 

raschii

Parathemisto 

libellula

Boreogadus 

saida

Biomass (mg/m3

)

n = 6

Total = 189 mg/m3

n = 6

Total = 189 mg/m 3

B. 1986

0

50

100

150

200

Calanus 

hyperboreas

Calanus 

glacialis

Limnocalanus 

macrurus

Derjuginia 

tolli

Halitholus 

cirratus

Cyanea capillata

Aglantha 

digitale

Mertensia 

ovum

Sagitta 

elegans

Mysis 

litoralis

Thysanoessa 

raschii

Parathemisto 

libellula

Boreogadus 

saida

Biomass (mg/m3

)

n = 3

Total = 170 mg/m3

n = 3

Total = 170 mg/m3

C. 1998

0

50

100

150

200

Calanus

hyperboreus

Calanusglacialis

Limnocalanus

macrurus

Derjuginia 

tolli

Halitholus 

cirratus

Cyanea capillata

Aglantha 

digitale

Mertensia 

ovum

Sagitta 

elegans

Mysis 

litoralis

Thysanoessa

raschii

Parathemisto 

libellula

Boreogadus 

saida

Biomass (mg/m3

)

n = 7

Total = 223 mg/m3

n = 7

Total = 223 mg/m3
5-20 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

Overall, C. glacialis and C. hyperboreus were the major contributors to the total copepod biomass

in this water mass in all three years. Limnocalanus macrurus, the dominant copepod in Shallow Cold

Saline waters in 1985–86, was also a major contributor to biomass in more-offshore MackenzieInfluenced waters in 1985 but not in 1986. It was not found in this water mass in 1998.

Outer Shelf Arctic Zone.—This water mass was only sampled in 1985 and 1986 when transects

extended out to the 200-m contour (vs. 50 m in 1998–2000). Zooplankton biomass in the Outer Shelf Arctic

zone was, on average, less than that in either of the other two water masses (Table 5.3). This was true for

the water column as a whole and for horizontal tows, particularly those taken below the pycnocline.

In the water column as a whole, gelatinous zooplankton was the predominant group in the Outer

Shelf water mass during 1986, but they contributed only 16 mg/m3

. In 1985, copepods were the dominant

taxon, followed by gelatinous zooplankton. Dominant species were the copepods Calanus hyperboreus

and C. glacialis, the chaetognath Sagitta elegans, the hydrozoan Aglantha digitale, and the ctenophore

Mertensia ovum. The predatory copepod Euchaeta glacialis was a major contributor to biomass only in

1985 (Griffiths et al. 1987).

In surface waters within this zone, total zooplankton biomass was very low in 1986. Biomass

above the pycnocline in 1986 was low, but twice that in surface waters (91 vs. 43 mg/m3

; Table 5.3).

Below the pycnocline in Arctic Surface Water, copepods, gelatinous zooplankton, and chaetognaths

accounted for most of the biomass in both 1985 and 1986. In both years, total biomasses were much

higher below the pycnocline than above it (Table 5.3). In both years, Calanus hyperboreus and C.

glacialis contributed most of the copepod biomass. No horizontal tows were taken near the bottom, so

any zooplankton concentrated there may be underrepresented.

Echosounder Surveys of Zooplankton Biomass

The volume backscatter data collected along the transects in 1985–86 and 1999–2000 were converted to estimates of total biomass using the regression relationships calculated from horizontal tows at

depth and corresponding backscatter data (Chapter 4). The results were used to describe (1) the vertical

distribution of zooplankton biomass at individual stations, (2) the average biomass of zooplankton along

transects, and (3) the patchiness of zooplankton along transects. Similar data are not available for 1998

when the relationship between acoustic back scatter and zooplankton biomass was weak and unusable for

predictive purposes.

Horizontal and Vertical Distribution.―The vertical distributions of zooplankton biomass differed

among the four years. In 1985–86 there were 1–3 layers of zooplankton in the upper 45 m, each 5 to 8 m

thick, at individual stations (Fig. 5.10, 5.11). In 1999, there was usually only a single layer of

zooplankton, 5–25 m thick, that extended from depth 10 m to near the bottom (Fig. 5.12). The year 2000

was different from all other years in that there was a marked spatial difference in zooplankton distribution

(Fig. 5.13). Few layers were evident on the three eastern transects, and there were 1–3 layers on the

western transects.

1985–1986: In these years, one to three layers of zooplankton were found at individual stations

(Fig. 5.10, 5.11). Throughout the study area, most of these zooplankton layers were 5 to 8 m thick and (in

deeper parts of the study area) most were in the upper 45 m of the water column. At some stations in

<30 m water depth, patches of high biomass occurred throughout most of the water column, extending all

the way to the bottom. In 1985, the estimated biomasses within layers were typically 300 to >1000

mg/m3

, while between the dense layers the values were 100–300 mg/m3. In 1986, estimated biomasses

within layers were 250–1500 mg/m3

, while between layers they were 150–350 mg/m3 (Fig. 5.10, 5.11).
§5. Zooplankton: Species Composition, Biomass & Distribution 5-21

FIGURE 5.10. Vertical distribution of zooplankton biomass estimated with the 200 kHz echosounder at

stations along transects in the eastern Alaskan Beaufort Sea, September 1985. See Figure 5.1A for

station locations.
5-22 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

FIGURE 5.11. Vertical distribution of zooplankton biomass estimated with the 200 kHz echosounder at

stations along transects in the eastern Alaskan Beaufort Sea, September 1986. Transects arranged from

west to east; see Figure 5.1A for station locations.
§5. Zooplankton: Species Composition, Biomass & Distribution 5-23

FIGURE 5.12. Vertical distribution of zooplankton biomass estimated with the 430 kHz echosounder at

stations along transects in the eastern Alaskan Beaufort Sea, September 1999. Transects arranged from

west to east; see Figure 5.1B for station locations.

A Transect 4: Off Arey Island B Transect 3: Off Barter Island C Transect 2: Off Jago Lagoon D Transect 1: Off Beaufort Lagoon

Station 22

0

5

10

15

20

0 250 500 750 1000

Estimated Biomass (mg/m3)

Depth (m)

Station 21

0

5

10

15

20

25

Depth (m)

Station 20

0

10

20

30

40

50

Depth (m)

Station 19

0

10

20

30

40

50

Depth (m)

Station 18

0 250 500 750 1000

Estimated Biomass (mg/m3)

Station 17

Station 16

Station 15

Station 14

0

10

20

30

40

50

Depth (m)

Staton 13

0 250 500 750 1000

Estimated Biomass (mg/m3)

Station 12

Station 11

Station 10

Station 9

0 250 500 750 1000

Estimated Biomass (mg/m3)

Station 8

Station 7

Station 6
A Transect 8: Camden Bay B Transect 7: Off Arey Island C Transect 6: Off Barter Island D Transect 2: Off Jago Lagoon E Transect 3: Off Beaufort Lagoon 

Station 28

05

1015

0 250 500 750 1000

Estimated Biomass (mg/m3

)

Depth (m)

Station 29

05

10152025

Depth (m)

Station 30

0

10203040

Depth (m)

Station 27

0 250 500 750 1000

Estimated Biomass (mg/m3

)

Station 26

Station 25

Station 24

0

1020304050

Depth (m)

Station 23

0 250 500 750 1000

Estimated Biomass (mg/m3

)

Station 22Station 21

Station 20

Station 19

0

1020304050

Depth (m)

Station 4

0 250 500 750 1000

Estimated Biomass (mg/m3

)

Station 5Station 6

Station 7

Station 8

0 250 500 750 1000

Estimated Biomass (mg/m3

)

Station 9

Station 10

Station 11

FIGURE 5.13. Vertical distribution of zooplankton biomass estimated with the 430 kHz echosounder at stations along t

Alaskan Beaufort Sea, September 2000. Transects arranged from west to east; see Figure 5.1C for station locations.
§5. Zooplankton: Species Composition, Biomass & Distribution 5-25

In 1985, average estimated biomass in the overall water column appeared to decrease with increasing water depth and distance from shore along Transect 1 but not Transect 2 (Fig. 5.14). Average

biomasses were uniform from about the mid-portion out to the end of the two transects (Fig. 5.14A,B).

Maximum estimated biomasses were near or above 1000 mg/m3

 along extended segments of both transects, and reached ~3000 to ~4000 mg/m3

 at several locations along each transect.3

Along all 1985 and subsequent-year transects, there are places where peaks in maximum zooplankton biomass occurred without noticeable increases in the mean water column biomass. This can occur

where the dense zooplankton layer that produces the high maximum value is relatively thin, usually only

1–2 m thick. When averaged with estimated zooplankton biomasses from other depths through the water

column, these maxima have little effect on the overall average.

In 1986, the average estimated zooplankton biomass along the four transects varied widely (Fig.

5.14C–F). Biomass increased with increasing depth along transect 1, decreased with increasing depth

along transect 2, and reached a maximum over the middle portion of Transect 3. High biomasses were

found at many locations along Transect 4 (Fig. 5.14F). Maximum estimated biomasses were 1500 to over

2000 mg/m3

 along Transect 1, and 1500 to >3000 mg/m3 on Transects 2, 3 and 4, with the highest values

typically persisting for only short segments of transect (Fig. 5.14C–F).

1999 and 2000: In 1999, only a single layer was evident at most stations, varying in thickness from 5

to 25 m (Fig. 5.12). In most places, the layer was found below 10 m and extended nearly to the bottom. At

some nearshore stations the concentrated layer extended throughout the water column. Estimated biomasses

within layers were typically 500–750 mg/m3

, while outside the layers biomass was ~200 mg/m3. The

average estimated biomass was more variable along Transect 1 off Beaufort Lagoon than along the three

more westerly 1999 transects (Fig. 5.15). Generally, mean biomass along Transect 1 increased with

distance from shore, reaching an estimated 400 mg/m3

 at the seaward end. Estimated peak biomasses were

500 to 750 mg/m3

 along this transect (Fig. 5.15). Along Transects 2 off Jago Lagoon and 3 off Barter

Island, a nearly continuous band of zooplankton with biomass 400–500 mg/m3

 extended from the shallow to

the offshore station (Fig. 5.12, 5.15). The average and maximum estimated biomasses were relatively

uniform over the entire length of each of these transects (Fig. 5.15). On Transect 4 off Arey Island, the

band of high-density zooplankton extended throughout much of the water column and was generally closer

to the surface than were similar patches along the other three transects (Fig. 5.12A). Several peaks of

zooplankton with densities in the 800 to >1000 mg/m3

 range were evident along this transect (Fig. 5.15A).

The year 2000 was different from the other three years in that there were large spatial differences in

zooplankton distribution. There were few layers at stations along the three easternmost transects (Fig.

5.13D–F). The estimated biomass was usually 200–300 mg/m3

 within layers and <150 mg/m3 outside

layers along the three easternmost transects (Transects 2, 3 and 4; Fig. 5.13D–F). In contrast, biomass was

typically 300–800 mg/m3

 in the one to three layers found on the western transects (Transects 6, 7 and 8; Fig.

5.13A–C). The layers with the highest biomass (600–800 mg/m3

) were only 1–3 m thick and were at depths

<15 m. Other thicker (5 to 15 m) layers contained an estimated biomass of 300–350 mg/m3

. Between the

dense layers, the biomass was 200–250 mg/m3

 (Fig. 5.13A–C). Average estimated zooplankton biomass

along the three eastern transects was 150–300 mg/m3

, with the highest average levels in shallow waters

close to shore (Fig. 5.16D–F). Maximum biomass levels showed peaks of 400–600 mg/m3

, but typically

 

3

 Note that the highest estimates, e.g., 1500+ mg/m3, are especially uncertain. They are based on applying regression equations for net biomass vs. acoustic backscatter (from Chapter 4) to backscatter values higher than those at

most stations with paired net and backscatter data, i.e., higher than most data used in deriving the regressions.
FIGURE 5.14. Average biomass in the water column (lower line), and maximum biomass of zooplankton within any 2 m 

Estimated from 200 kHz echosounder data for the top 50 m of the water column along transects in the eastern Alaskan B1985 and 1986. Note that the horizontal axes are much compressed relative to the vertical axes.
FIGURE 5.15. Average biomass in the water column (lower line), and maximum biomass of zooplankton within any 1 m 

Estimated from 430 kHz echosounder data from four transects in the eastern Alaskan Beaufort Sea, September 1999. axes are much compressed relative to the vertical axes.
FIGURE 5.16. Average biomass in the water column (lower line), and maximum biomass of zooplankton within any 1 m 

Estimated from 430 kHz echosounder data from six transects in the eastern Alaskan Beaufort Sea, September 2000. Note are much compressed relative to the vertical axes.
§5. Zooplankton: Species Composition, Biomass & Distribution 5-29

these areas were relatively small in horizontal extent. Between them biomasses were 200–300 mg/m3

(Fig. 5.16D–F). Along the western transects, average estimated zooplankton biomasses were 300–400

mg/m3, while maximum biomass showed numerous peaks with 400–1600 mg/m3 (Fig. 5.16A–C). High

maximum levels of estimated zooplankton biomass extended for much greater horizontal distances along

the western transects than along the eastern ones.

During all years, most concentrated layers of zooplankton were within 45 m of the surface, even

where water depth was over 100 m. Thus, most zooplankton concentrations would be easily accessible to

feeding bowhead whales. The echosounder did not measure zooplankton biomass in surface waters in

any year. However, net tows showed little zooplankton in surface waters in any year (with the exception

of shallow waters in 1998). When pycnoclines were present (mainly 1985 and 1986), zooplankton biomass was low above the pycnocline.

Zooplankton Patchiness.Zooplankton patchiness was determined along each of the transects surveyed in 1985–86 and 1999–2000; contour plots of estimated zooplankton biomass are shown in Figures

5.17 to 5.20.

With the exceptions of 1985 Transect T2 off Pokok Bay and 1986 Transect T1 off Barter Island,

zooplankton patches were more abundant in the nearshore and middle regions than at the seaward ends of

the transects (Fig. 5.17, 5.18). In 1985, zooplankton patches were generally smaller in both length and

depth than in 1986, and the highest biomasses were generally just below the pycnocline (6 to 10 m depth).

In contrast, during 1986 the highest biomasses were usually deeper in the water column, typically just

above the bottom, particularly in shallow nearshore waters and at mid-depths along the transects. Echosounder surveys in 1986 were consistent with net samples in showing that surface waters contained low

biomasses of zooplankton (Fig. 5.18). In both these years only a small fraction of the water along the

transects contained a high (>500 mg/m3) biomass of zooplankton, although there were patches where the

estimated biomass exceeded 1000 mg/m3 in 1985 and 3500 mg/m3 in 1986. (See preceding footnote

regarding the extrapolation involved in deriving these high estimates.)

FIGURE 5.17. Zooplankton patchiness estimated from continuous hydroacoustic sampling along 1985

Transects T1 and T2. Data recorded within and above pycnoclines are excluded. The horizontal axes

are much compressed relative to the vertical axes. See Fig. 5.1A for transect locations.

0

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< 100 mg/m3

100-300 mg/m3

300-500 mg/m 3

500-700 mg/m 3

700-1000 mg/m3

> 1000 mg/m3

T1 off Barter Island

T2 off Pokok Bay

0 1 2 Km

St1 St2 St3 St5 St4

St6 St7 St8 St9 St10
5-30 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

FIGURE 5.18. Zooplankton patchiness estimated from continuous hydroacoustic sampling along 1986

Transects T1, T2, T3 and T4. Data recorded within and above pycnoclines are excluded. The horizontal

axes are much compressed relative to the vertical axes. See Fig. 5.1A for transect locations.

In 1999, there were nearly continuous bands of zooplankton of at least 300 to 500 mg/m3 that

extended from nearshore to offshore stations along all transects except Transect T1, off Beaufort Lagoon.

In the latter area, most of the zooplankton was along the outer portion of the transect (Fig. 5.20). The

bands along all transects were relatively thick (10–20 m) and were usually at depths >25 m. The main

exception was along Transect T4, off Arey Island, where there was a band much closer to the surface.

Zooplankton biomass was low near the surface along all transects (Fig. 5.19). Although zooplankton

patches were more extensive in 1999 than in 1985–86, the estimated biomass levels were lower in 1999;

the densest patches contained an estimated maximum of 200 to 1000 mg/m3.

0

10

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30

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pth (m)

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T1 off Barter Island

T2 off Jago Lagoon

T3 off Beaufort Lagoon

T4 off Demarcation Bay

0

10

20

30

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< 100 mg/m3

100-300 mg/m3

300-500 mg/m 3

500-700 mg/m 3

700-1000 mg/m3

> 1000 mg/m3

0

10

20

30

40

50

< 100 mg/m3

100-300 mg/m3

300-500 mg/m 3

500-700 mg/m 3

700-1000 mg/m3

> 1000 mg/m3

0 1 2 Km

St1 St2 St3 St4 St5

St1 St2

St1 St2 St3 St4 St5

St1 St2 St3 St4 St5
§5. Zooplankton: Species Composition, Biomass & Distribution 5-31

FIGURE 5.19. Zooplankton patchiness estimated from continuous hydroacoustic sampling along 1999

Transects T1, T2, T3 and T4. Data recorded in top 3 m of the water are excluded. The horizontal axes

are much compressed relative to the vertical axes. See Fig. 5.1B for transect locations.

In 2000, the six transects between Demarcation Bay in the east and Camden Bay in the west show a

pattern of increasing zooplankton biomass from east to west, particularly from Barter Island to Camden

Bay (Fig. 5.20). The three most easterly transects, between Demarcation Bay and Jago Lagoon, contained

extensive patches of zooplankton, kilometers in length and 10s of meters thick, with biomasses 100 to

300 mg/m3. However, there were very few patches where estimated biomass exceeded 700 or especially

1000 mg/m3 (Fig. 5.20). In contrast, the westernmost transects from Barter Island to Camden Bay contained several patches where zooplankton biomasses exceeded 1000 mg/m3

, with the frequency and extent

of the high density patches increasing from east to west (Fig. 5.20). Patches with the maximum estimated

zooplankton biomasses tended to be in the mid-water to near-surface depths along all transects except for

Transect 8 in Camden Bay. There, patches of maximum biomass occurred both at mid-depth and near the

bottom (Fig. 5.20).

0

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0 1 2 Km

T4 off Arey Island

T3 off Barter Island

T2 off Jago island

T1 off Beaufort Lagoon

< 100 mg/m3

100-300 mg/m 3

300-500 mg/m3

500-700 mg/m3

700-1000 mg/m3

> 1000 mg/m3

St22 St21 St20 St19

St18 St17 St16 St15 St14

St13 St12 St11 St10

St9 St8 St7 St6
5-32 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

FIGURE 5.20. Zooplankton patchiness estimated from continuous hydroacoustic sampling along 2000

Transects T2, T3, T4, T6, T7 and T8. Data recorded in the top 3 m of the water are excluded. The

horizontal axes are much compressed relative to the vertical axes. See Fig. 5.1C for transect locations.

0

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30

40

50

Water D

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pth (m)

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pth (m)

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0

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< 100 mg/m3

100-300 mg/m3

300-500 mg/m 3

500-700 mg/m 3

700-1000 mg/m3

> 1000 mg/m3

T8 off Camden Bay

T7 off Arey Island

T6 off Barter island

T2 off Jago Island

T3 off Beaufort Lagoon

T4 off Demarcation Bay

0 1 2 Km

St28 St29 St30

St27 St26 St25 St24

St23 St22 St21 St20 ST19

St4 St5 St6 St7

St8 St9 St10 St11

St12 St13 St14 St15
§5. Zooplankton: Species Composition, Biomass & Distribution 5-33

Overall, the zooplankton biomasses estimated from echosounder data were higher in 1986 than in

1985, 1999, and 2000. This was true for peak biomasses along all transects and at individual stations

where estimated biomass levels reached 1600 mg/m3

. The lowest biomass levels were recorded in 1999,

while those in 1985 and 2000 were intermediate.

Discussion

Physical Oceanographic Features

Physical oceanographic properties of the study area, as in most other areas, vary considerably from

year to year, and they can also change rapidly within the same year and within a particular study area.

However, the present study area can show more variability than many other marine areas because of its

proximity to massive sources of ice and freshwater that can be advected into the study area by the wind.

Under persistent east winds, cold saline bottom water upwells into shallow water. This upwelling can

cause areas along the coast that are otherwise brackish and warm to become much colder and saltier

(Mangarella et al. 1982; Savoie and Wilson 1983, 1986). In this case, nearshore waters are mixed rather

than stratified. East winds can also transport the relatively warm and fresh Mackenzie River plume into

eastern and offshore portions of the study area (Bradstreet et al. 1987; Fissel et al. 1987). Its presence

causes strong temperature and salinity discontinuities in these waters. If a west wind occurs when there is

no Mackenzie plume water offshore, then only cold saline offshore water is moved inshore. However, if

west winds occur when the Mackenzie plume is offshore, then it will be blown onshore

Wind direction is from the northeast 35% of the time and from the northwest 23% of the time

(Fissel et al. 1987). Water masses in the Beaufort Sea can respond to changes in wind patterns in as little

as 12 h (Aagaard 1984; Niedoroda and Colonell 1990).

Two kinds of oceanographic regime were evident during the five years of this study. (1) In

September of 1985, 1986 and 1998, warm fresh Mackenzie River water was transported into the study

area (Bradstreet et al. 1987; Fissel et al. 1987; this study). (2) In 1999 and 2000, all water in the study

area (out to the 50 m contour) was characterized as Shallow Cold Saline with little or no Mackenzie

influence. The first regime was most readily characterized by the presence of strong pycnoclines and the

second by their absence.

Zooplankton Biomass and Composition

Species composition and biomass of the zooplankton did not correspond in any simple way to the

oceanographic regimes described above. The most obvious differences in the zooplankton occurred

between 1985–86 and 1998–2000. In the region as a whole, the total zooplankton biomass was higher in

1985 and especially in 1986 than in 1998, 1999 and 2000.

The higher zooplankton biomasses in 1985–86 were due to the much higher biomasses of copepods,

particularly Limnocalanus macrurus in the Shallow Cold Saline zone. Calanus glacialis and C. hyperboreus were also major contributors to the copepod biomass in all years. In 1986 and 1998, Calanus

glacialis was the dominant of the two species, while in 1985, 1999 and 2000 the dominant species was C.

hyperboreus. Predatory cnidarians, ctenophores, and chaetognaths were abundant in the study area in

1998–2000 and not in 1985–86. These predators may have contributed to the lower biomass of copepods

in 1998–2000.

Grainger (1965) described two major groups of Beaufort Sea zooplankton in waters <100 m in

depth. The species characteristic of the upper 100 m of Arctic surface waters are found both offshore and
5-34 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

inshore and are typically tolerant of a wide range of temperatures (–1° to ~5–10°C) and salinities (12 to 34

psu). Organisms in this group include the hydrozoans Aglantha digitale and Aeginopsis laurentii, the

ctenophore Beroe cucumis, and several species of copepods: Calanus hyperboreus, C. glacialis, Pseudocalanus minutus, Metridia longa, and Oithona similis. A second group is characteristic of shallow nearshore brackish waters along the coastlines of the Beaufort and Chukchi seas. It includes the hydrozoans

Euphysa flammea, Halitholus cirratus and Sarsia princeps, the ctenophore Obelia spp., and the copepods

Limnocalanus macrurus, Acartia clausi, Eurytemora herdmani, and Derjuginia tolli. These species are

typically found in waters with relatively high temperatures (1 to 12°C) and low salinities (8 to 25 psu),

characteristic of nearshore brackish waters during the open water season (Grainger 1965; Shih et al. 1971).

Overall, 77 of the 83 stations sampled in this study were in the first group, as defined by species composition, and only 6 in the second. Species characteristic of the second group were often found in cold saline

water as well as in nearshore brackish waters.

In all five years, net sampling showed zooplankton biomass to be low in surface and near-surface

waters above pycnoclines. Zooplankton biomass was always higher in the colder saline water at depth

>10 m. This was true even for the brackish-water copepod L. macrurus. Maximum abundances of this

copepod were recorded in cold saline water rather than in the estuarine water influenced by the Mackenzie River. This was true in 1985 and 1986 both in this study and in a similar study along the Yukon

coast (Bradstreet and Fissel 1986; Bradstreet et al. 1987). However, L. macrurus was only abundant in

the study region when the influence of Mackenzie River water extended along the coast of the Yukon and

into the eastern Alaskan Beaufort Sea. It may be that the brackish Mackenzie water brings this copepod

into eastern Alaskan waters but, once there, it is able to thrive in the colder and more saline water typically found in the region.

Copepods represented 80 to 90% of zooplankton biomass over deep ice-covered waters of the Arctic

Ocean, including those north of the Beaufort Sea (Hopkins 1969). In the eastern Canadian high arctic, copepods constituted 80% of the total zooplankton biomass in the upper 150 m of Lancaster Sound and northwestern Baffin Bay (Buchanan and Sekerak 1982). Calanoid copepods were the major component of the

zooplankton in the present study area and other parts of the Beaufort Sea (Grainger and Grohe 1975; Horner

1979, 1981; Griffiths and Buchanan 1982; Bradstreet and Fissel 1986; Bradstreet et al. 1987)

Average biomasses of zooplankton collected in summer and early autumn in the eastern Alaskan

and Canadian Beaufort Seas are similar. Depending on year and sampling area, mean wet-weight biomasses collected by oblique samples in the top 50 m of the water column in various areas have ranged

from ~150 to over 380 mg/m3 with an overall average for all 218 oblique and (1980 only) vertical tows

taken in these areas of ~260 mg/m3

 (Table 5.4). Under some circumstances, biomass in layers of concentrated zooplankton, as measured with horizontal bongo tows, can equal or exceed 1000 or 2000 mg/m3

.

Zooplankton biomass is considerably higher over the continental shelf of the Beaufort Sea than

over deeper offshore waters of the Arctic Ocean. In the latter area, Hopkins (1969) found an average biomass of only 5 mg/m3

 wet-weight in the upper 200 m, based on 39 tows.

Abundance of zooplankton in the southeastern Chukchi Sea is higher south of Cape Lisburne than

north of it (Wing 1974). Average summer zooplankton biomass in 145 samples taken in the southeastern

Chukchi Sea between Cape Lisburne and the Bering Strait was ~1700 mg/m3

 wet-weight (English 1966).

However, primary and secondary productivity in the Chukchi Sea may be highest in the southern and

southwestern part (Truett 1984). Bowhead whales are known to feed in that general area during autumn

(Moore et al. 1995).
TABLE 5.4. Wet-weight biomass of dominant zooplankton taxa taken in oblique tows (1985–2000) and vertical tows (1980) 

of the water column on transects in the Canadian and Alaskan Beaufort seas during summer and early autumn. The prepresented by each taxon is also shown.

mg/m3 % mg/m3 % mg/m3 % mg/m3 % mg/m3 % mg/m3 % mg/m3 % mg/m3 % mg/m3 

Copepods 125 39 181 86 121 70 99 65 140 22 126 60 168 75 130 73 119 

Limnocalanus macrurus 38 12 141 68 67 39 <1 <1 0 0 <1 <1 43 19 59 33 <1 

Calanus hyperboreus 62 19 15 7 27 16 74 48 128 21 97 46 80 36 17 10 16 Calanus glacialis 0 <1 13 6 23 13 21 14 11 2 26 12 25 11 52 29 100 

Mysids 44 14 8 4 7 4 7 4 6 1 5 2 5 2 1 1 8 Euphausiids 0 0 2 1 11 6 2 1 0 0 0 0 8 4 <1 <1 2 Cnidarians/Ctenophores 108 34 7 3 11 10 24 15 441 71 35 17 22 10 15 8 61 Chaetognaths 6 2 4 2 6 3 5 3 8 1 17 8 6 3 4 2 48 TotalStandard Deviation 273Number of TowsMax. Sample Depth (m)Station Depths (m)a Griffiths and Buchanan (1982). Note that all tows in 1980 were vertical tows.b Bradstreet and Fissel (1986).c Bradstreet et al. (1987).d This study.

Yukon Coast Mackenzie Delta Tuktoyaktuk Eastern Alaskan 

Peninsula

1980a 1985b 1986c 1986c 1980a 1986c 1985 1986 199

319 211 173 153 632 210 207 170 250 180 245 195 84 516 139 121 14

12 16 15 21 48 10 12 19 18 

10-25 10-50 9-50 9-50 10-50 8-50 7-4

7-17 12-171 14 -167 10-68 9-4

10-26 12-52 13-80 10-205
5-36 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

During May and June, when bowheads leave the Bering Sea, average biomass in the upper 100 m

can reach 1500 to 2000 mg/m3

 over large areas (Coyle et al. 1996). [All values in this paragraph are wetweights.] In spring, the greatest zooplankton biomass (1000 to 2000 mg/m3

) is found in the Gulf of

Anadyr, Norton Sound, and Bering Strait (Coyle et al. 1996). Average biomass of zooplankton in the

upper 50 to 100 m of the deep basin of the Bering Sea during spring ranges from 500 to over 1000 mg/m3

(Ikeda and Motoda 1978; Coyle et al. 1996). Biomass is lower in summer, but the distribution pattern is

similar. Summer biomass in the deep basin is about the same as that found in the Beaufort Sea in fall

(200–500 mg/m3

). Biomass is 500 to 1000 mg/m3 over the shelf and >1000 mg/m3 in the Gulf of Anadyr.

In fall when bowheads return to the Bering Sea, zooplankton biomass in the upper 100 m of the deep

basin is 300–400 mg/m3

 (Coyle et al. 1996), again about the same as that in the Beaufort Sea. Biomass

over the shelf is lower and ~100–200 mg/m3

. During winter, when bowheads are present, biomass in the

upper 200 m is ~50 mg/m3

, but is >200 mg/m3 below 200 m (Coyle et al. 1996).

It is acknowledged that all of these data on zooplankton biomass and species composition are

subject to a variety of potential limitations and biases. Many of these were discussed in Chapter 4. The

faster swimming taxa, e.g., euphausiids, are known to show a net-avoidance effect, resulting in underestimation of their biomass. Some individuals of the smallest species, or the smaller life-stages of somewhat

larger species, will pass through the mesh of standard sampling nets (here 0.5 mm), and also be undersampled. A further complication is that net tows of 5-min or similar duration produce an estimate of

average zooplankton biomass across a range of horizontal distances, and are likely to underestimate the

maximum biomass present. The latter is of particular relevance in studies of feeding by zooplankton

predators (such as bowhead whales) that feed preferentially in areas of maximum prey abundance. Also,

even a horizontal tow that is guided to the depth of a thin zooplankton “layer” by an echosounder, as in

this study, provides an average biomass estimate applicable to some (narrow) range of depths, not just to

the precise depth of maximum biomass. All of these problems result in a tendency for standard netsamples of zooplankton to underestimate the average and maximum biomasses of zooplankton present.

Nonetheless, biomass data obtained from this type of sampling do provide, at the least, minimum

estimates of zooplankton biomass, and approximate data on the proportions contributed by different

species and species-groups. Also, these types of data are quite suitable for comparing the relative zooplankton availability in different years, water masses, locations, depths, etc.

The likely under-sampling of fast-moving euphausiids is of particular concern in this study, as

bowhead whales are known to feed on euphausiids at times. Euphausiids dominate the stomach contents

of a minority (24%) of the bowhead whales harvested in late summer/early autumn at Kaktovik, within

the present study area. Euphausiids dominate in a majority (88%) of the bowheads harvested in autumn at

Barrow, farther west (Lowry 1993; Lowry and Sheffield, Chapter 18). Although euphausiids, mainly

Thysanoessa raschii, were caught in our net samples, euphausiids rarely contributed a large proportion of

the biomass. During a broad-scale zooplankton survey across the Alaskan Beaufort Sea during the

autumn of 1986, Griffiths et al. (1987) found considerably higher absolute and proportional biomasses of

euphausiids in the western Alaskan Beaufort (near Barrow) than in the eastern Alaskan Beaufort. Based

on these and other results, we conclude that euphausiids are very likely underrepresented in our net

samples but, when they are abundant, they are prominent components of the net samples. We interpret

the infrequent occurrence of substantial biomasses of euphausiids in zooplankton samples from the

eastern Alaskan (and Canadian) Beaufort Sea as a meaningful indication of their lower abundance there

than in the western Alaskan Beaufort Sea.
§5. Zooplankton: Species Composition, Biomass & Distribution 5-37

In this study, all zooplankton sampling was done during daylight hours in September. At this

latitude (70°N), there is 24-hour daylight from spring until early August, a few hours of darkness each

night in early September, and rapidly increasing hours of darkness as September and October progress. In

most areas, zooplankton tend to migrate toward the surface at night and to deeper depths by day. The

extent of diel vertical migration of zooplankton in the present study area has not been studied. It is

possible that the vertical distribution of zooplankton in this area during September is different at night

than in the daytime. However, most of our sampling (and all of that in 1998–2000) was in places where

we were able to document the zooplankton throughout almost all of the water column via a combination

of nets and echosounding. Although the measured biomass might have a different vertical distribution at

night, the overall average biomass would not be expected to differ appreciably at night.

Echosounder Surveys

This study has provided the first quantitative echosounder data on zooplankton in the Alaskan

Beaufort Sea. Much information about the vertical and horizontal distribution of zooplankton has been

obtained during September of four years. This information is complementary to the net-sampling data.

The echosounder data provide greatly increased resolution, both horizontal and vertical, as compared with

net sampling, but they depend on the net-sampling for calibration purposes, and (unlike the net-sampling)

they do not provide information about species composition.

The limitations and biases of the echosounder data were discussed in Chapter 4. Physical features

in the water column such as density gradients, turbidity, and air bubbles can produce acoustic backscatter,

and at times this is difficult to distinguish from zooplankton. Biological factors that can cause complications are the presence of fish, and variability in the sizes and orientations of the zooplankters themselves.

Some of these confounding factors have been alleviated in this study through exclusion of data from

locations and depths with known density gradients (pycnoclines) and special processing of the data to

minimize the contribution by fish (see “Methods” and Chapter 4). However, there is residual variability

in the echosounder data. Furthermore, our calibrations of the echosounder data to allow estimation of

zooplankton biomass from acoustic backscatter alone are based on net samples and echosounder data

from matched locations and depths. Difficulties in obtaining precise matching of the two types of

samples, and the inherent limitations and biases of the net-sample data (see preceding subsection), result

in imprecise calibration of the echosounder data (see Chapter 4).

Thus, the echosounder surveys provide only approximate estimates of absolute zooplankton biomass, along with extensive data on relative biomass at different places, depths, and times. A major

objective of the overall study of which this Chapter is one part was to assess the characteristics and

quality of bowhead whale feeding habitat in the eastern Alaskan Beaufort Sea. This required zooplankton

surveys that could not be conducted with adequate resolution by net-sampling alone. Our contour plots

depicting zooplankton biomass vs. depth and location along transects show locations of zooplankton

concentrations (“patches”) within the study area in a given year, the relative biomasses of zooplankton

available to whales at different places and times, and year-to-year differences. These data provide a

valuable basis for comparisons of food availability in the eastern Alaskan Beaufort Sea as a whole (this

chapter) with that at the specific locations where bowhead whales have been observed to feed (Chapter

6).4

 

4

 Acknowledgements applicable to all zooplankton chapters are included near the end of Chapter 3.
5-38 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

Summary

Introduction and Objectives

This chapter describes the first comprehensive study on late summer zooplankton biomass in the

eastern Alaskan Beaufort Sea from shore to ~200 m deep. The primary objective was to gather data on

the taxonomic composition, biomass, patchiness, and variability of the zooplankton available to feeding

bowhead whales in that area during late summer and early autumn. Consequently, emphasis was placed

on species and taxa that were major contributors to overall zooplankton biomass. The study was based on

coordinated net sampling and quantitative echosounder surveys conducted over 7- to 16-day periods during early-mid or mid-late September of five years. It describes the vertical and horizontal distribution,

composition, and patchiness of zooplankton biomass in relation to water mass characteristics.

Methods

In all 5 years (1985–86; 1998–2000) sampling was conducted from a 13-m vessel during September. Zooplankton and CTD data were collected at stations along transects perpendicular to shore between

central Camden Bay and Demarcation Bay, extending seaward to ~200 m depth (1985–86) or 50 m depth

(1998–2000). Quantitative echosounder data were collected along the same transects. All data were used

to describe the nature and variability of the zooplankton community, and its relationships to water masses

in the study area.

Three types of bongo tows were used to collect zooplankton samples each year: surface tows,

oblique tows, and horizontal tows at depth. A flow meter was placed in the center of one frame. The

echosounder was used to help select depths for horizontal tows, to ensure sampling within and outside

layers of concentrated zooplankton. Actual tow depth was measured directly.

Hydroacoustic sampling to estimate zooplankton distribution (horizontal and vertical) and relative

biomass along transects was conducted in all 5 years using single- (1998) or dual-frequency (other years)

echosounders. Relative biomass was determined for each 2 min (~240 m) horizontal segment by 1- or

2-m depth interval for all transects.

CTD profiles were measured at stations along each transect each year. Near-surface temperature

(and, in 1985–86, salinity) were recorded continually during transits between sampling.

Results

In all five years of the study, at least two water masses were deemed to be present: (1) a Shallow

Cold Saline water mass, usually without sharp discontinuities in the vertical distribution of temperature

and salinity (i.e., without pycnoclines). These waters were typically relatively cold and saline from

surface to bottom. (2) A Mackenzie-Influenced more-offshore water mass with Mackenzie-influenced

water at the surface, overlying water that was generally colder and more saline than that of the nearshore

water mass. In 1985, 1986 and 1998, warm fresh Mackenzie plume water was transported into the study

area; in 1999 and 2000 it was absent. The distribution of water masses did not appear to have a strong

effect on the distribution of major zooplankton taxa. However, the highest biomass of zooplankton

occurred in the presence of strong pycnoclines, in the colder and more saline bottom waters.

The annual average zooplankton biomasses collected in Shallow Cold Saline waters varied over

the five years of study: 189–409 mg/m3

 for the water column as a whole, 18–205 mg/m3 for surface

waters, and 236–516 mg/m3

 for horizontal tows at depth. In all years, zooplankton biomasses in surface

waters were lower than in samples taken at depth. Typically, zooplankton biomasses were higher in the
§5. Zooplankton: Species Composition, Biomass & Distribution 5-39

cold saline bottom layer than in the fresher warm surface water. In 1985–86, the maximum biomass in

individual horizontal tows at depth was 900–2000 mg/m3

, considerably higher than the 500–1000 mg/m3

recorded in 1998–2000. Overall, zooplankton biomasses were higher in 1986 than in 1985, 1998, 1999

and 2000. The lowest biomass levels were recorded in 1999, while those in 1985, 1998 and 2000 were

intermediate.

The high zooplankton biomasses in 1985–86 were due to the much higher biomasses of copepods,

particularly Limnocalanus macrurus. In 1998–2000, Calanus glacialis and C. hyperboreus were the

dominant species among all taxa. Predatory cnidarians, ctenophores and chaetognaths were abundant in

the study area in 1998–2000 and not in 1985–86. These predators may have contributed to the lower

biomass of copepods in 1998–2000.

In the water column as a whole, within the Shallow Cold Saline zone, five major zooplankton taxa

were collected in all five years. These were copepods, gelatinous zooplankton (i.e., ctenophores + cnidarians), chaetognaths, mysids, and fish. Copepods were the dominant taxon in all years, especially in

1985 and 1986. Gelatinous zooplankton and chaetognaths, considered together, were major contributors

(>10 mg/m3

) to zooplankton biomass in every year, and in 1998–2000 their biomass approached that of

copepods. Euphausiids were collected in all years except 1986 and were major contributors to the zooplankton biomass in 1985 and 2000, while decapods were major contributors only in 1986.

In all five years, the copepods Calanus hyperboreus and C. glacialis were major contributors to the

copepod biomass. In 1985 and 1986, biomass of the copepod Limnocalanus macrurus was higher than

that of any other species, but it was not found in the nearshore zone at all in 1998 and 1999 and only in

small quantities in 2000.

The low biomass in the surface waters was composed of copepods, gelatinous zooplankton and, to

a lesser extent, chaetognaths. Below the surface, the composition of the zooplankton collected in

horizontal tows was similar to that in the water column as a whole

The Mackenzie-Influenced more-offshore water mass was present in the study area during 1985,

1986 and 1998, but not in 1999 and 2000. The annual average zooplankton biomasses in this water mass

were 170 to 223 mg/m3

 for the water column as a whole, and 4 to 25 mg/m3 for surface waters. Each of

these averages was lower than the corresponding value in Shallow Cold Saline zone. The warm

freshened water layer above the pycnocline contained a very low biomass of zooplankton (annual

averages 46–115 mg/m3

) compared to the cold saline water below (394–659 mg/m3). Copepods and

gelatinous zooplankton, with lesser contributions from amphipods, euphausiids, chaetognaths, pteropods

and fish, accounted for most of the biomass. In all three years, copepods were the dominant taxon,

particularly in 1985 and 1986. Overall, C. glacialis and C. hyperboreus were the major contributors to

the total copepod biomass in the Mackenzie-Influenced waters in all three years. Limnocalanus

macrurus, the dominant copepod in Shallow Cold Saline waters in 1985–86, was also a major contributor

to biomass in Mackenzie-Influenced waters in 1985 but not in 1986. It was not found in this water mass

in 1998.

The Outer Shelf Arctic water mass was only sampled in 1985 and 1986 when transects extended

out to the 200 m contour (vs. 50 m in 1998–2000). Zooplankton biomass in this zone was, on average,

less than that in nearshore and inner shelf waters. In both years, Calanus hyperboreus and C. glacialis

contributed most of the copepod biomass.

Average biomasses of zooplankton collected in summer and early autumn in the eastern Alaskan

and Canadian Beaufort Seas are similar. Zooplankton biomass collected by oblique (1985–2000) or
5-40 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

vertical (1980) tows in the top 50 m of the water column have ranged from ~150 to 600 mg/m3 with an

overall average for all 218 of these tows of ~260 mg/m3

. Under some circumstances, biomass in layers of

concentrated zooplankton, as measured with horizontal bongo tows, can equal or exceed 1000 or 2000

mg/m3

.

Echosounder surveys in 1985 and 1986 showed that only a small fraction of the water along the

transects contained a high (>500 mg/m3) biomass of zooplankton, although there were patches where the

estimated biomass apparently exceeded 3000 mg/m3

 in 1985 and 3500 mg/m3 in 1986. In 1999, zooplankton patches were more extensive than in 1985–86 but the estimated biomass levels were lower with

the densest patches containing only an estimated maximum of 800–1000 mg/m3

. In 2000, there was a

pattern of increasing zooplankton biomass from east to west, with highest values from Barter Island to

eastern Camden Bay. In 2000, there were also many more patches where estimated biomass exceeded

700 or 1000 mg/m3

 along the western three transects than along the three eastern transects.

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Arctic engineering. Am. Soc. Mech. Engineers, New York, NY.
5-42 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

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Shih, C.T., A.J.G. Figueira and E.H. Grainger. 1971. A synopsis of Canadian marine zooplankton. Fish. Res.

Board Can. Bull. 176. 246 p.

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upwelling environment. Mar. Ecol. Progr. Ser. 32(2-3):203-215.

Sutherland, I. 1982. A collection of zooplankton from Tuktoyaktuk Harbour, Northwest Territories. Can. J. Zool.

60(3):477-480.

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Barrow Arch Environment and Possible Consequences of Planned Offshore Oil and Gas Development.

Girdwood AK, 30 Oct. – 1 Nov. 1983. U.S. Dep. Commer. Nat. Oceanic and Atmos. Admin. and U.S.

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Chukchi Sea. NOAA Tech. Rep. NMFS SSRF-679. Seattle, WA. 18 p.
§5. Zooplankton: Species Composition, Biomass & Distribution 5-43

APPENDIX 5.1. Locations of sampling stations along transects in the eastern Alaskan Beaufort Sea, 4-18

Sept 1985.

Transect Water Time

Station Date No Depth (m) ADT Latitude Longitude

1 4/9/1985 T-1 13 1000 70° 09' N 143° 37' W

2 5/9/1985 T-1 28 2024 70° 13' N 143° 29' W

3 5/9/1985 T-1 45 1947 70° 16' N 143° 25' W

4 6/9/1985 T-1 125 1208 70° 34' N 143° 07' W

5 6/9/1985 T-1 80 1749 70° 33' N 143° 06' W

6a 9/9/1985 T-2 10 1836 70° 03' N 142° 45' W

7 7/9/1985 T-2 25 1334 70° 07' N 142° 42' W

8 7/9/1985 T-2 42 1712 70° 11' N 142° 39' W

9 8/9/1985 T-2 56 1325 70° 20' N 142° 19' W

10 10/9/1985 T-2 185 1205 70° 31' N 142° 04' W

11 18/09/85 T-4 14 924 69° 42' N 141° 09' W

12 18/09/85 T-4 25 1323 69° 45' N 141° 09' W

13 18/09/85 T-4 40 1523 69° 53' N 140° 52' W

ADT = Alaska day light time.

a

 No zooplankton tows at this station due to ice conditions.

Station
5-44 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

APPENDIX 5.2. Locations of sampling stations along transects in the eastern Alaskan Beaufort Sea, 4-19

Sept 1986.

Transect Water Time

Station Date No. Depth (m) (ADT) Latitude Longitude

 T4-1 9/9/1986 T4 12 1430 69°42.3'N 141°17.2'W 

 T4-2 10/9/1986 T4 21 800 69°44.5'N 141°11.9'W 

 T4-3 10/9/1986 T4 43 1151 69°55.0'N 140°55.8'W 

 T4-4 10/9/1986 T4 53 1604 70°07.1'N 140°52.6'W 

 T4-5 11/9/1986 T4 180 1245 70°17.8'N 140°34.2'W 

 T3-1 12/9/1986 T3 13 835 69°52.2'N 142°05.0'W 

 T3-2 12/9/1986 T3 21 1030 69°53.9'N 141°58.0'W 

T3-3 13/09/86 T3 41 1000 70°03.1'N 141°49.9'W 

 T3-4 13/09/86 T3 53 1400 70°12.9'N 141°41.8'W 

 T3-5 14/09/86 T3 205 1234 70°24.3'N 141°31.9'W 

T1-1 16/09/86 T1 10 810 70°09.2'N 143°40.8'W 

T1-2 16/09/86 T1 34 1030 70°13.6'N 143°38.2'W 

 T1-3 16/09/86 T1 47 1345 70°21.3'N 143°31.5'W 

 T1-4 17/09/86 T1 54 1100 70°28.7'N 143°34.7'W 

 T1-5 17/09/86 T1 118 1410 70°33.2'N 143°34.2'W 

 T2-1 18/09/86 T2 10 855 70°04.5'N 142°53.3'W 

 T2-2 18/09/86 T2 26 1145 70°07.9'N 142°48.7'W 

T2-5 19/09/86 T2 150 1245 70°31.6'N 142°27.3'W 

ADT = Alaska daylight time.

Station
§5. Zooplankton: Species Composition, Biomass & Distribution 5-45

APPENDIX 5.3. Locations of sampling stations along transects in the eastern Alaskan Beaufort Sea, 11-22

Sept 1998.

Transect Water Time 

Station Date No. Depth (m) ADT Latitude Longitude

6 14/09/98 T-1 9 937 69° 48.50' N 141° 46.00' W

7 14/09/98 T-1 18 1031 69° 49.92' N 141° 40.04' W

10 15/09/98 T 1 20 952 69° 50.05' N 141° 40.46' W

11 15/09/98 T-1 36 1153 69° 56.52' N 141° 31.03' W

12a 15/09/98 T-1 48 1423 70° 03.34' N 141° 25.23' W

13 16/09/98 T-2 10 857 70° 10.94' N 143° 25.25' W

14 16/09/98 T-2 27 945 70° 13.50' N 143° 25.23' W

15 16/09/98 T-2 40 1330 70° 18.72' N 143° 25.81' W

16 16/09/98 T-2 46 1535 70° 23.52' N 143° 24.12' W

17 17/09/98 T-3 9.5 849 70° 07.76' N 143° 55.53' W

18 17/09/98 T-3 19 952 70° 11.03' N 144° 02.58' W

19 17/09/98 T-3 28 1219 70° 13.82' N 144° 09.00' W

20 17/09/98 T-3 38 1600 70° 21.82' N 144° 25.42' W

23 19/09/98 T-4 10 845 69° 55.07' N 142° 14.20' W

24 19/09/98 T-4 20 1107 69° 58.01' N 142° 07.37' W

25 19/09/98 T-4 30 1159 69° 59.56' N 142° 04.20' W

26 19/09/98 T-4 40 1501 70° 03.62' N 141° 56.07' W

30 22/09/98 T-5 12 926 70° 09.53' N 143° 37.75' W

31 22/09/98 T-5 19 1011 70° 11.31' N 143° 41.06' W

 ADT = Alaska daylight time.

a

 Only a CTD taken at this station.

Station
5-46 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

APPENDIX 5.4. Locations of sampling stations along transects in the eastern Alaskan Beaufort Sea, 16-22

Sept 1999.

Transect Water Time

Station Date No. Depth(m) ADT Latitude Longitude

6 18/9/99 T1 48 1047 70° 08.13' N 141° 51.98' W

7 18/9/99 T1 35 1254 70° 02.01' N 142° 05.47' W

8 18/9/99 T1 20 1537 69° 58.04' N 142° 13.13' W

9 18/9/99 T1 10 1629 69° 55.97' N 142° 18.29' W

10 19/9/99 T-2 50 1147 70° 20.22' N 143° 00.85' W

11 19/9/99 T-2 34 1339 70° 13.89' N 143° 12.65' W

12 19/9/99 T-2 20 1606 70° 11.81' N 143° 17.45' W

13 19/9/99 T-2 10 1646 70° 09.74' N 143° 20.45' W

14 20/9/99 T-3 40 1004 70° 16.12' N 143° 32.87' W

15 20/9/99 T-3 45 1200 70° 20.75' N 143° 25.70' W

16 20/9/99 T-3 35 1507 70° 14.76' N 143° 36.15' W

17 20/9/99 T-3 20 1626 70° 11.80' N 143° 39.75' W

18 21/09/99 T-3 10 921 70° 08.64' N 143° 43.27' W

19 21/09/99 T-4 40 1159 70° 20.09' N 143° 59.78' W

20 21/09/99 T-4 35 1523 70° 16.37' N 143° 58.09' W

21 21/09/99 T-4 21 1643 70° 11.58' N 143° 56.31' W

22 22/09/99 T-4 10 903 70° 07.76' N 143° 56.05' W

ADT = Alaska daylight time.

Station
§5. Zooplankton: Species Composition, Biomass & Distribution 5-47

APPENDIX 5.5. Locations of sampling stations along transects in the eastern Alaskan Beaufort Sea, 2-20

Sept 2000.

Transect Water Time

Station Date No Depth (m) ADT Latitude Longitude

1 9-Sep-00 T-1 10 1207 70° 08.65' N 143° 43.32' W

2 9-Sep-00 T-1 20 1337 70° 10.69' N 143° 40.18' W

3 9-Sep-00 T-1 35 1438 70° 14.52' N 143° 34.80' W

4 10-Sep-00 T-2 10 837 70° 09.74' N 143° 20.41' W

5 10-Sep-00 T-2 20 1005 70° 11.82" N 143° 17.15' W

6 11-Sep-00 T-2 30 1027 70° 13.67' N 143° 14.10' W

7 11-Sep-00 T-2 50 1236 70° 19.67" N 143° 02.82' W

8 12-Sep-00 T-3 10 802 69° 56.05' N 142° 17.68' W

9 12-Sep-00 T-3 20 845 69° 58.29' N 142° 12.98' W

10 12-Sep-00 T-3 30 1107 70° 00.57' N 142° 08.10' W

11 12-Sep-00 T-3 48 1317 70° 08.13' N 141° 51.87' W

12 13-Sep-00 T-4 10 810 69° 41.82' N 141° 16.99' W

13 13-Sep-00 T-4 20 853 69° 44.55' N 141° 13.24' W

14 13-Sep-00 T-4 30 1123 69° 47.80' N 141° 09.01' W

15 13-Sep-00 T-4 43 1331 69° 55.67' N 140° 58.50' W

16 16-Sep-00 T-5 10 855 70° 07.84' N 143° 56.88' W

17 16-Sep-00 T-5 20 947 70° 10.82' N 143° 56.82' W

18 16-Sep-00 T-5 27 1241 70° 12.64' N 143° 58.54' W

19 17-Sep-00 T-6 45 1026 70° 20.62' N 143° 25.37' W

20 17-Sep-00 T-6 40 1137 70° 16.10' N 143° 32.99' W

21 17-Sep-00 T-6 29 1407 70° 12.87' N 143° 37.31' W

22 17-Sep-00 T-6 20 1429 70° 11.64' N 143° 39.48' W

23 17-Sep-00 T-6 10 1634 70° 08.76' N 143° 43.20' W

24 18-Sep-00 T-7 40 911 70° 20.11' N 144° 00.39' W

25 18-Sep-00 T-7 30 1159 70° 15.87' N 143° 58.10' W

26 18-Sep-00 T-7 20 1315 70° 10.86' N 143° 56.75' W

27 18-Sep-00 T-7 10 1518 70° 07.74' N 143° 56.10' W

28 20-Sep-00 T-8 15 901 70° 04.84' N 144° 46.39' W

29 20-Sep-00 T-8 20 943 70° 07.58' N 144° 47.63' W

30 20-Sep-00 T-8 27 1230 70° 11.59' N 144° 53.22' W

ADT = Alaska daylight time.

Station
5-48 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

Salinity

APPENDIX 5.6. Temperature and salinity profiles (CTD) in the water column at stations on transects in the

eastern Alaskan Beaufort Sea, Sept 1985. See APPENDIX 5.1 and Fig. 5.1A for station locations. Transects are arranged from west to east. At the right of all profiles, salinity is the top line and temperature is

the bottom line.

Temperature
§5. Zooplankton: Species Composition, Biomass & Distribution 5-49

APPENDIX 5.7. Temperature and salinity profiles (CTD) in the water column at stations on transects in the

eastern Alaskan Beaufort Sea, Sept 1986. See APPENDIX 5.2 and Fig. 5.1A for station locations. Transects are arranged from west to east. At the right of all profiles, salinity is the top line and temperature is

the bottom line.
5-50 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

APPENDIX 5.8. Temperature and salinity profiles (CTD) in the water column at stations on transects in the

eastern Alaskan Beaufort Sea, Sept 1998. See APPENDIX 5.3 and Fig. 5.1B for station locations. Transects are arranged from west to east. At the right of all profiles, salinity is the top line and temperature is

the bottom line.
§5. Zooplankton: Species Composition, Biomass & Distribution 5-51

APPENDIX 5.9. Temperature and salinity profiles (CTD) in the water column at stations on transects in the

eastern Alaskan Beaufort Sea, Sept 1999. See APPENDIX 5.4 and Fig. 5.1B for station locations. Transects are arranged from west to east. Top line: salinity; bottom line temperature.
APPENDIX 5.10. Temperature and salinity profiles (CTD) in the water column at stations on transects in the eastern Alas

2000. See APPENDIX 5.5 and Fig. 5.1C for station locations. Transects arranged from west to east. Top line: salinity; botto
APPENDIX 5.11. Sea surface temperature (°C) recorded along two of the transects in the eastern Alaskan Beaufort Sea, Se
APPENDIX 5.12. Sea surface temperature (°C) recorded along the six transects in the eastern Alaskan Beaufort Sea, Sept 

west to east.
APPENDIX 5.13. Biomass (mg/m3) of the dominant zooplankton groups in horizontal (HB) and oblique (OB) bongo tows 

Beaufort Sea, Sept 1985.

Tow Sta.

Sta. Samp. Depth Depth Tow Cnidarians

Trans No. No. (m) (m) Type Horizontala Verticalb Copepods Ctenophores Mysids Euphausiids Amphipods Pteropods Chaetogna

TRN-1 1 2 10 13 HB 1 3 344.5 34.3 7.2 58.4 4.7 0.7 TRN-1 1 3 1 13 HB 1 1 116.8 7.3 0.0 0.2 1.9 0.1 TRN-1 2 6 14 28 HB 2 3 290.7 15.6 6.8 4.0 9.4 2.1 TRN-1 3 7 25 45 HB 2 3 932.6 72.3 0.0 14.9 23.6 15.6 1TRN-1 3 8 22 45 HB 2 3 124.1 25.5 0.0 2.1 7.3 2.4 TRN-1 3 9 8 45 HB 2 3 886.2 6.7 0.0 0.0 10.1 2.3 TRN-1 3 10 15 45 HB 2 3 145.2 20.9 0.0 0.0 4.6 4.1 TRN-1 3 11 0.5 45 HB 2 1 2.1 0.2 0.0 0.0 0.1 0.1 TRN-1 4 15 5 125 HB 3 2 7.3 1.0 0.0 0.0 1.1 0.2 TRN-1 4 16 30 125 HB 3 3 144.2 15.2 0.0 0.0 2.7 0.4 TRN-1 5 17 5 80 HB 3 2 4.9 6.9 0.0 0.0 1.2 0.6 TRN-1 5 18 55 80 HB 3 3 122.6 32.5 0.0 0.8 1.9 0.2 TRN-2 7 22 5 25 HB 2 2 45.3 12.5 0.0 0.0 3.9 1.4 TRN-2 7 23 16 25 HB 2 3 254.0 5.1 0.0 19.2 18.5 1.4 TRN-2 8 24 18 42 HB 2 3 173.2 34.8 0.0 0.1 7.9 1.5 TRN-2 8 25 12 42 HB 2 3 250.0 23.9 0.0 0.1 4.1 2.7 2TRN-2 8 26 6 42 HB 2 2 5.8 7.1 0.0 0.0 5.9 5.2 1TRN-2 9 30 19 56 HB 3 3 201.7 32.6 0.0 0.0 10.7 17.1 1TRN-2 9 31 32 56 HB 3 3 62.9 21.9 0.0 0.0 4.9 6.4 TRN-2 9 32 9 56 HB 3 2 0.2 20.6 0.0 0.0 9.5 1.5 TRN-2 10 35 90 185 HB 3 3 33.6 5.9 0.0 0.1 1.3 0.2 TRN-2 10 36 18 185 HB 3 3 99.3 22.3 0.0 0.0 2.6 1.0 1TRN-4 11 38 0.5 14 HB 1 1 14.4 22.9 0.0 0.0 0.9 1.0 TRN-4 11 39 8 14 HB 1 3 208.6 13.6 5.9 52.1 5.1 7.7 TRN-4 11 40 10.5 14 HB 1 3 262.0 18.2 86.8 15.2 3.5 14.7 TRN-4 12 43 12 25 HB 2 3 376.4 10.4 0.5 0.5 3.0 1.7 TRN-4 12 44 20 25 HB 2 3 681.6 37.3 10.1 5.4 5.0 3.7 TRN-4 12 45 5 25 HB 2 2 11.9 3.5 0.0 0.0 0.6 3.3 TRN-4 13 48 12 40 HB 2 2 2.1 6.1 0.0 0.0 8.8 10.5 TRN-4 13 49 30 40 HB 2 3 48.9 4.2 0.1 2.6 5.2 2.4 TRN-4 13 50 5 40 HB 2 2 1.7 6.5 0.0 0.0 0.4 0.0 TRN-1 1 1 10 13 OB 1 - 403.6 25.4 17.7 21.3 1.5 0.3 TRN-1 2 5 25 28 OB 2 - 153.3 1.9 0.5 0.0 2.7 0.3 TRN-1 3 12 35 45 OB 2 - 199.6 53.9 0.0 5.8 6.9 3.2 TRN-1 4 14 80 125 OB 3 - 98.4 13.4 0.0 0.0 1.8 0.2 TRN-1 5 19 50 80 OB 3 - 51.3 14.9 0.0 0.0 2.1 2.0 TRN-2 7 21 22 25 OB 2 - 134.7 22.7 0.0 6.6 4.5 2.4 TRN-2 8 27 39 42 OB 2 - 144.3 32.6 0.0 3.2 7.1 0.7 1TRN-2 9 29 50 56 OB 3 - 166.5 28.7 0.0 0.1 5.6 2.7 TRN-2 10 34 100 185 OB 3 - 94.2 14.7 0.0 0.9 1.1 0.0 TRN-4 11 37 10 14 OB 1 - 204.6 22.8 27.7 45.1 2.2 4.9 TRN-4 12 46 20 25 OB 2 - 214.5 13.6 6.0 1.5 2.7 2.1 TRN-4 13 47 35 40 OB 2 - 4.2 2.8 0.0 0.0 8.0 3.2 

a 1 = Shallow Cold Saline, 2 = Mackenzie Influenced, 3 = Outer Shelf Arcticb 1 = surface layer; 2 = tow made within pycnocline; 3 = arctic water.

Water Mass
APPENDIX 5.14. Biomass (mg/m3) of the dominant zooplankton species in horizontal (HB) and oblique (OB) bongo tows 

Beaufort Sea, Sept 1985. Chaetognaths Mysids Euphausiids P

Sta. Tow Sta. Sample Trans No. Type Depth Depth Horizontala Verticalb TRN-1 1 HB 13 1 1 3 19.80 7.50 82.90 3.00 1.40 0.00 0.20 0.00 0.20 0.00 0.20 

TRN-1 1 HB 13 10 1 1 148.40 42.70 66.40 83.60 0.00 1.80 9.60 22.90 7.20 7.20 55.80 TRN-1 2 HB 28 14 2 3 170.30 81.40 32.20 4.30 1.00 3.40 4.30 7.50 8.70 6.80 3.50 TRN-1 3 HB 45 25 2 3 689.30 223.10 2.40 0.00 17.80 2.10 33.30 35.90 15.80 0.00 5.70 TRN-1 3 HB 45 8 2 3 863.80 20.80 1.60 0.00 0.00 0.00 3.30 0.90 2.90 0.00 0.00 TRN-1 3 HB 45 22 2 3 84.70 30.90 0.50 0.00 7.90 5.40 8.70 2.30 4.20 0.00 0.40 TRN-1 3 HB 45 15 2 3 95.90 41.90 0.10 0.00 6.90 1.60 3.60 15.40 5.10 0.00 0.00 TRN-1 3 HB 45 0.5 2 1 0.40 0.80 0.70 0.00 0.10 0.00 0.20 0.00 0.00 0.00 0.00 TRN-1 4 HB 125 30 3 3 119.10 14.20 0.00 0.00 10.40 0.00 2.30 9.90 4.50 0.00 0.00 TRN-1 4 HB 125 5 3 2 0.70 6.50 0.00 0.00 0.10 0.00 0.00 0.00 1.40 0.00 0.00 TRN-1 5 HB 80 5 3 2 1.90 2.30 0.00 0.00 0.70 0.00 0.00 0.40 0.20 0.00 0.00 TRN-1 5 HB 80 55 3 3 77.30 17.40 0.00 0.00 21.20 0.00 19.80 12.20 3.80 0.00 0.20 TRN-2 7 HB 25 5 2 2 8.70 7.40 28.60 0.00 0.60 0.00 12.50 0.00 1.10 0.00 0.00 TRN-2 7 HB 25 16 2 3 182.10 55.80 3.30 0.00 12.70 0.00 1.80 2.70 8.90 0.00 14.10 TRN-2 8 HB 42 18 2 3 81.90 75.10 4.00 0.00 12.20 0.00 25.50 0.60 7.70 0.00 0.00 TRN-2 8 HB 42 6 2 2 1.80 1.50 2.50 0.00 0.00 0.80 1.90 4.00 11.20 0.00 0.00 TRN-2 8 HB 42 12 2 3 122.60 123.20 3.70 0.00 0.40 0.30 18.30 1.80 20.00 0.00 0.00 TRN-2 9 HB 56 9 3 2 0.20 0.00 0.00 0.00 0.00 0.00 11.20 0.80 0.60 0.00 0.00 TRN-2 9 HB 56 19 3 3 160.50 25.20 3.90 0.00 12.10 0.00 30.90 0.00 10.70 0.00 0.00 TRN-2 9 HB 56 32 3 3 43.70 9.10 0.80 0.00 9.20 0.00 19.90 0.00 6.20 0.00 0.00 TRN-2 10 HB 185 18 3 3 71.80 12.70 0.10 0.00 13.50 0.00 15.20 2.10 5.80 0.00 0.00 TRN-2 10 HB 185 90 3 3 18.90 9.20 0.00 0.00 5.50 0.00 4.20 1.50 3.20 0.00 0.00 TRN-4 11 HB 14 10.5 1 3 67.90 13.90 160.70 8.50 8.10 0.00 13.00 0.80 8.20 86.80 12.40 TRN-4 11 HB 14 0.5 1 1 13.10 0.50 0.70 0.00 0.00 4.90 1.90 0.00 1.20 0.00 0.00 TRN-4 11 HB 14 8 1 3 56.70 71.10 75.70 3.90 0.00 0.00 8.30 0.00 6.20 5.90 49.20 TRN-4 12 HB 25 5 2 2 5.70 2.60 0.50 2.80 0.00 0.30 0.70 0.00 0.00 0.00 0.00 TRN-4 12 HB 25 20 2 3 365.60 125.40 163.70 15.10 0.00 21.40 5.00 1.00 7.60 9.20 0.10 TRN-4 12 HB 25 12 2 3 45.60 9.70 286.20 34.20 0.00 3.10 0.00 2.20 5.40 0.50 0.50 TRN-4 13 HB 40 30 2 3 26.80 19.40 0.50 0.00 2.10 0.80 1.40 0.00 1.60 0.00 1.50 TRN-4 13 HB 40 5 2 2 1.10 0.00 1.00 1.00 0.00 0.00 0.00 1.00 0.00 0.00 0.00 TRN-4 13 HB 40 12 2 2 1.10 0.10 0.00 0.00 0.70 5.10 0.00 0.00 0.00 0.00 0.00 TRN-1 1 OB 13 10 1 - 83.40 11.80 195.30 100.00 0.00 11.90 10.40 1.20 8.80 17.70 19.80 TRN-1 2 OB 28 25 2 - 93.50 28.10 27.10 0.60 3.70 0.00 0.20 1.50 0.90 0.50 0.00 TRN-1 3 OB 45 35 2 - 134.80 54.40 0.40 0.00 9.20 7.60 30.30 15.60 6.60 0.00 2.30 TRN-1 4 OB 125 80 3 - 65.50 14.40 0.00 0.00 15.70 0.00 4.20 8.90 4.40 0.00 0.00 TRN-1 5 OB 80 50 3 - 28.30 14.60 0.10 0.00 8.20 1.10 7.70 0.10 2.10 0.00 0.00 TRN-2 7 OB 25 22 2 - 81.40 28.60 9.90 12.50 1.10 0.00 9.60 5.00 5.90 0.00 5.70 TRN-2 8 OB 42 39 2 - 102.50 40.20 0.90 0.20 0.20 0.00 18.80 13.70 11.60 0.00 1.10 TRN-2 9 OB 56 50 3 - 136.10 19.10 0.70 0.00 6.80 0.50 27.10 1.00 4.30 0.00 0.10 TRN-2 10 OB 185 100 3 - 61.00 18.80 0.00 0.00 12.80 0.00 4.50 10.20 2.10 0.00 0.10 TRN-4 11 OB 14 10 1 - 51.80 37.50 102.70 8.30 2.30 14.70 4.30 0.10 4.30 27.70 39.20 TRN-4 12 OB 25 20 2 - 87.90 17.90 94.20 9.60 0.00 8.20 2.40 0.10 2.30 0.00 0.10 TRN-4 13 OB 40 35 2 - 2.70 0.30 0.50 0.00 0.50 0.00 1.00 0.00 0.10 0.00 0.00 

a 1 = Shallow Cold Saline, 2 = Mackenzie Influenced, 3 = Outer Shelf Arcticb 1 = surface layer; 2 = tow made within pycnocline; 3 = arctic water.

Copepods Cnidarians and Ctenophores

Water Mass

Calanus 

hyperboreas

Calanus glacialis

Limnocalanus 

macrurus

Derjuginia tolli

Eucheata glacialis

Halitholus cirratus

Aglantha digitale

Mertensia ovum

Sagitta elegans

Mysis litoralis

Thysanoessa 

raschii
APPENDIX 5.15. Biomass (mg/m3) of the dominant zooplankton groups in oblique (OB) and surface (SB) bongo tows 

Beaufort Sea, Sept 1986.

Station 

Type Depth (m) Tow Type

Sta. 

No.

Samp. 

No.

Water Massa

Copepods

Cnidarians 

Ctenophores

Mysids

Euphausiids

Amphipods

Pteropods

Chaetognaths

Decapod

 TRN-1 9 OB 1 120 1 70.86 2.41 0.05 0.00 1.37 0.73 0.21 0.38  TRN-1 30 OB 2 124 1 144.16 45.54 0.00 4.85 2.63 0.19 2.16 9.74  TRN-1 40 OB 3 129 2 236.49 23.33 1.50 0.89 20.59 4.66 20.51 2.26  TRN-1 50 OB 4 133 3 4.93 4.76 0.00 0.00 6.01 2.26 1.02 0.33  TRN-1 50 OB 5 138 3 0.72 48.98 0.00 0.00 3.76 0.18 0.54 0.02  TRN-2 8 OB 1 142 1 46.00 0.69 0.00 0.00 4.53 0.11 0.11 0.00  TRN-2 22 OB 2 146 1 717.89 8.13 0.95 0.13 10.90 6.72 5.94 13.08  TRN-2 50 OB 5 150 3 1.24 21.78 0.00 0.00 7.92 0.03 2.36 0.00  TRN-2 100 OB 5 151 3 11.68 23.55 0.00 0.00 3.81 0.05 8.27 0.00  TRN-3 9 OB 1 79 1 12.88 21.04 0.00 0.00 2.09 2.99 0.03 6.99  TRN-3 18 OB 2 83 1 2.81 14.25 0.76 0.90 7.15 7.47 0.07 93.23  TRN-3 35 OB 3 87 2 48.59 12.95 0.00 1.98 22.35 2.61 0.99 3.23  TRN-3 50 OB 4 91 3 33.04 6.63 0.00 0.00 10.43 2.88 2.89 0.00  TRN-3 50 OB 5 95 3 1.36 4.38 0.00 0.00 4.27 1.34 0.15 0.30  TRN-4 10 OB 1 57 1 1001.20 3.35 14.80 0.00 0.32 0.66 0.50 0.45  TRN-4 18 OB 2 62 1 0.47 0.16 0.00 0.00 0.51 0.05 0.98 1.68  TRN-4 40 OB 3 66 2 6.92 28.10 0.00 0.78 5.82 18.37 0.88 1.44  TRN-4 50 OB 4 71 3 0.41 9.70 0.00 0.00 5.54 2.73 0.19 0.36  TRN-4 50 OB 5 75 3 18.70 13.95 0.00 0.01 1.38 1.42 28.50 0.00 

 WFb 16 OB 1 2 1 13.97 36.74 5.66 0.17 12.54 5.00 2.93 13.37 

 WF 12 OB 5 19 1 1179.07 30.59 2.09 0.31 1.85 0.58 2.73 3.35  WF 8 OB 7 27 1 777.10 6.72 53.38 0.15 4.04 0.09 0.22 0.55  WF 5 OB 9 36 1 165.83 13.49 127.43 0.00 6.26 0.24 0.13 0.00  WF 9 OB 10 39 1 35.44 43.81 4.85 0.00 2.01 3.01 0.12 6.33  WF 18 OB 12 48 1 869.90 10.61 2.17 0.00 5.80 1.04 6.94 0.71 CTL 12 OB 11 44 1 114.01 53.23 0.38 1.84 3.82 0.48 6.80 7.74 CTL 20 OB 2 7 1 40.68 2.89 0.00 0.00 0.61 0.26 0.73 2.49 CTL 22 OB 6 23 2 14.05 30.94 0.00 0.00 3.24 11.36 1.02 5.86 CTL 18 OB 8 32 2 12.83 4.96 0.00 0.00 15.39 0.96 1.33 1.72 CTL 21 OB 13 53 2 0.65 9.74 0.00 0.00 0.69 5.76 0.03 14.54 

 TRN-1 0 SB 1 119 1 49.41 2.17 0.00 0.00 2.54 0.04 0.11 0.39  TRN-1 0 SB 3 128 2 1.02 0.13 0.00 0.00 0.03 0.01 0.13 0.01  TRN-1 0 SB 5 137 3 0.37 0.12 0.00 0.00 0.09 0.03 0.05 0.07  TRN-2 0 SB 5 149 3 0.60 0.19 0.00 0.00 0.27 0.01 0.01 0.00  TRN-3 0 SB 1 78 1 1.10 2.02 0.00 0.00 0.59 0.28 0.24 0.00  TRN-3 0 SB 3 86 2 0.55 0.42 0.00 0.00 0.01 0.07 0.01 0.09  TRN-3 0 SB 5 94 3 0.04 0.00 0.00 0.00 0.14 0.01 0.01 0.01  TRN-4 0 SB 1 56 1 144.04 3.30 0.42 0.00 0.14 0.55 0.00 0.00  TRN-4 0 SB 3 65 2 1.24 13.53 0.00 0.00 2.48 0.87 1.74 14.07  TRN-4 0 SB 5 74 3 0.09 0.07 0.00 0.00 0.29 0.00 0.01 0.07 

 WF 0 SB 1 1 1 0.05 0.36 0.00 0.00 0.00 0.24 0.00 0.00  WF 0 SB 5 18 1 0.47 0.54 0.00 0.00 0.58 1.94 0.00 0.02  WF 0 SB 7 26 1 7.62 9.06 0.00 0.00 1.93 0.08 0.02 0.00  WF 0 SB 9 35 1 67.39 4.99 0.15 0.00 1.29 0.00 0.10 0.00  WF 0 SB 10 38 1 8.36 3.88 0.13 0.00 0.09 1.09 0.03 3.86  WF 0 SB 12 47 1 2.37 1.26 0.00 0.00 0.02 0.03 0.01 0.00 CTL 0 SB 11 43 1 0.41 13.72 0.00 0.00 0.05 1.76 0.00 9.42 CTL 0 SB 2 6 1 0.17 0.00 0.00 0.00 0.00 0.00 0.00 0.01 CTL 0 SB 6 22 2 0.21 1.72 0.00 0.00 0.28 6.35 0.00 0.12 CTL 0 SB 8 31 2 0.47 1.37 0.01 0.00 0.04 0.00 0.00 0.00 CTL 0 SB 13 52 2 4.33 0.03 0.00 0.00 0.00 0.06 0.00 0.01 

a 1 = Shallow Cold Saline, 2 = Mackenzie Influenced, 3 = Outer Shelf Arcticb WF = Whale feeding station, CTL = Control Station ( see Chapter 6).
5-58 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

APPENDIX 5.16. Biomass (mg/m3) of the dominant zooplankton groups in horizontal (HB) tows in the

eastern Alaskan Beaufort Sea, Sept 1986. The samples were collected with an opening and closing

bongo net and the data needed to be scaled to match corresponding data collected with a standard

bongo net assembly. (See Griffiths et al. 1987 for scaling factors). Station Type Depth (m) Tow Type Sta. No. Samp. No. Water Massa Copepods Cnidarians Ctenophores Mysids Euphausiids Pteropods

AmphipodsChaetognathsDecapodOtherFish Total

 TRN-1 10 HB 1 121 1 139.6 3.1 1.7 0.0 0.0 3.5 1.3 1.8 1.4 0.2 152.6

 TRN-1 5 HB 1 122 1 141.8 4.7 0.0 0.0 4.3 1.4 0.3 1.9 0.6 0.0 155.0

 TRN-1 10 HB 2 125 2 358.8 105.4 0.0 1.9 0.0 2.5 1.9 10.1 0.3 4.3 485.3

 TRN-1 21 HB 2 126 3 308.6 51.3 1.1 2.7 0.0 3.7 13.9 3.4 3.6 5.1 393.4

 TRN-1 5 HB 2 127 2 3.4 24.8 0.0 0.0 0.0 0.3 0.0 39.9 0.5 1.4 70.4

 TRN-1 11 HB 3 131 2 15.0 23.4 0.0 0.0 8.5 2.6 0.4 3.7 0.7 2.1 56.4

 TRN-1 27 HB 3 130 3 1298.9 29.4 0.0 7.7 13.7 30.4 23.1 2.2 3.0 9.2 1417.5

 TRN-1 19 HB 4 135 1 8.0 133.9 0.0 0.0 38.2 4.4 0.9 0.8 3.9 0.0 190.0

 TRN-1 11 HB 4 136 1 7.1 8.0 0.0 0.0 0.9 1.1 0.1 0.2 1.6 2.8 21.7

 TRN-1 15 HB 5 139 1 0.5 74.7 0.0 0.0 0.0 2.6 0.0 0.0 0.1 5.9 83.9

 TRN-1 34 HB 4 134 3 139.9 84.7 0.0 1.5 2.2 30.7 33.5 5.6 3.9 8.9 310.7

 TRN-1 47 HB 5 140 3 0.2 66.4 0.0 0.0 0.2 0.5 0.1 0.0 0.0 0.9 68.3

 TRN-2 5 HB 1 144 1 56.2 8.6 1.2 0.0 1.4 2.3 0.0 20.9 0.5 3.1 94.3

 TRN-2 6 HB 2 148 1 12.6 3.6 0.0 0.0 1.5 0.1 0.0 12.3 0.2 10.6 41.0

 TRN-2 8 HB 1 143 2 56.3 14.3 13.3 0.3 3.2 2.6 0.0 81.0 0.6 12.6 184.2

 TRN-2 15 HB 2 147 3 2095.0 17.6 10.1 2.5 3.0 3.0 8.3 7.7 0.6 1.1 2148.9

 TRN-2 10 HB 5 153 2 0.8 86.2 0.0 0.0 0.0 8.1 0.2 0.0 10.4 0.4 106.3

 TRN-2 50 HB 5 152 3 6.2 25.8 0.0 0.0 0.1 1.4 3.3 0.6 0.3 6.8 44.4

 TRN-3 6 HB 1 81 1 3.2 29.8 0.0 0.0 5.3 0.0 0.0 8.8 0.7 4.4 52.4

 TRN-3 10 HB 1 80 2 26.5 15.6 1.4 0.4 36.6 3.0 0.2 60.1 2.4 5.2 151.4

 TRN-3 18 HB 2 84 2 167.2 32.8 1.9 3.5 0.5 3.1 1.3 2.7 2.3 7.6 222.8

 TRN-3 10 HB 2 85 2 5.2 18.0 0.4 0.6 13.8 6.5 0.4 25.0 3.3 25.6 98.6

 TRN-3 26 HB 3 88 3 368.3 101.0 0.1 2.2 1.3 3.2 5.9 3.3 0.5 7.6 493.4

 TRN-3 17 HB 3 89 3 161.1 92.2 0.0 0.4 40.6 20.7 0.7 9.7 12.7 13.0 351.2

 TRN-3 26 HB 4 92 3 354.7 54.0 0.0 3.4 1.8 37.7 44.2 0.0 7.8 5.5 509.1

 TRN-3 17 HB 4 93 3 8.7 93.6 0.0 0.0 8.5 10.7 1.1 0.2 2.8 14.0 139.6

 TRN-3 27 HB 5 97 3 0.8 658.2 0.0 0.0 0.7 4.5 0.1 0.1 0.8 4.1 669.2

 TRN-3 30 HB 5 98 3 1.1 17.2 0.0 0.0 0.9 8.6 0.6 0.9 4.3 0.0 33.6

 TRN-4 4 HB 1 58 1 1943.5 28.0 9.3 0.0 1.3 0.0 0.0 23.0 0.3 1.7 2007.0

 TRN-4 10 HB 1 60 2 426.2 106.4 5.9 0.2 1.2 5.6 7.7 7.3 1.5 12.4 574.4

 TRN-4 8 HB 1 59 2 34.1 35.5 0.7 0.0 0.2 1.0 1.1 3.1 0.8 0.0 76.6

 TRN-4 10 HB 2 64 2 93.3 49.7 0.0 0.0 11.2 1.4 3.2 5.0 0.8 0.0 164.8

 TRN-4 19 HB 2 63 3 2111.3 53.2 4.2 15.3 0.6 12.2 9.2 4.7 0.5 2.5 2213.6

 TRN-4 7 HB 3 69 1 5.3 7.1 0.0 0.0 25.7 0.8 0.0 1.1 0.1 1.7 41.8

 TRN-4 14 HB 3 67 2 5.4 38.2 0.0 0.0 88.7 12.4 0.3 6.2 0.2 9.4 160.9

 TRN-4 36 HB 3 68 3 343.9 17.1 0.0 0.9 1.0 2.1 3.4 3.3 0.3 0.0 372.1

 TRN-4 12 HB 4 73 2 21.4 31.7 0.0 0.0 2.1 8.8 0.1 1.3 0.3 10.9 76.6

 TRN-4 34 HB 4 72 3 782.7 15.2 0.0 4.5 0.4 5.5 2.2 0.5 0.8 1.9 813.8

 TRN-4 51 HB 5 76 3 3.1 15.1 0.0 0.0 0.1 0.5 5.8 0.2 0.1 0.0 24.8

 TRN-4 30 HB 5 77 3 9.3 33.7 0.0 0.0 0.3 1.8 28.3 0.0 0.2 1.0 74.7
§5. Zooplankton: Species Composition, Biomass & Distribution 5-59

APPENDIX 5.16. Concluded. Station Type Depth (m) Tow Type Sta. No. Samp. No.

Water MassaCopepodsCnidariansCtenophoresMysidsEuphausiidsPteropodsAmphipodsChaetognathsDecapodOtherFishTotal

 WFb 4 HB 1 5 1 0.2 12.1 0.0 0.0 2.1 0.2 0.0 11.6 0.0 0.0 26.3

 WF 13 HB 1 3 2 20.0 21.2 0.0 0.0 2.3 7.0 2.4 18.5 0.6 1.8 73.9

 WF 10 HB 5 20 2 2920.1 63.0 2.5 0.2 0.0 1.4 2.0 7.5 2.2 23.8 3022.6

 WF 6 HB 5 21 2 1206.1 19.0 0.0 0.0 1.0 2.3 2.9 9.7 1.3 26.5 1268.8

 WF 7 HB 7 28 2 1069.8 38.6 118.83 0.0 0.2 4.7 1.0 4.7 0.0 14.2 1252.0

 WF 8 HB 7 29 2 2386.1 29.6 452.75 0.0 0.0 4.5 0.0 0.9 0.0 12.4 2886.1

 WF 11 HB 10 41 2 2926.1 62.5 63.6 6.0 0.0 5.4 7.2 29.3 1.5 17.5 3119.1

 WF 8 HB 10 42 2 3734.3 58.2 0.1 7.4 0.0 2.7 5.3 24.2 2.8 11.6 3846.7

 WF 13 HB 12 49 2 642.9 68.8 11.7 0.0 1.3 19.3 7.3 8.0 2.7 0.0 762.1

 WF 6 HB 12 50 2 598.3 4.2 8.3 0.0 1.3 1.6 1.0 0.8 0.5 2.6 618.8

 WF 15 HB 12 51 2 2075.2 13.6 30.7 0.3 0.0 13.5 2.7 0.0 0.9 0.0 2137.0

 WF 8 HB 1 4 2 2.0 36.7 0.0 0.0 10.6 8.5 0.0 12.6 1.2 3.1 74.7

 WF 7 HB 10 40 2 34.1 29.2 0.4 0.0 1.6 0.2 0.3 1.8 0.9 0.0 68.5

 WF 3 HB 7 30 2 64.5 25.4 1.1 0.0 0.0 3.0 0.0 0.0 0.8 0.0 94.9

CTL 17 HB 8 33 2 1128.1 90.5 11.6 2.8 0.8 11.9 23.7 7.7 1.4 1.4 1280.0

CTL 12 HB 11 45 2 867.3 127.3 94.8 4.8 0.0 2.5 14.7 12.6 1.2 23.9 1149.1

CTL 17 HB 13 54 2 5.9 59.0 0.0 0.0 1.5 1.2 0.7 28.3 1.2 6.6 104.6

CTL 8 HB 6 25 2 0.5 9.8 0.0 0.0 17.0 1.0 0.1 51.7 1.0 16.6 97.7

CTL 7 HB 8 34 2 16.6 49.0 0.0 0.0 10.3 7.7 0.3 14.6 2.2 10.0 110.7

CTL 6 HB 11 46 2 84.9 82.8 0.2 0.0 7.5 1.4 1.3 63.4 3.1 15.3 259.9

CTL 8 HB 13 55 2 5.0 20.0 0.0 0.0 1.9 1.7 0.1 74.2 1.1 3.4 107.5

CTL 22 HB 2 8 3 129.8 59.6 0.0 0.2 0.2 2.6 9.8 0.5 3.4 7.1 213.1

CTL 21 HB 6 24 3 14.7 28.7 0.3 0.3 8.0 7.9 3.8 19.4 1.9 7.3 92.2

CTL 10 HB 2 9 3 187.8 41.7 0.0 0.0 0.5 2.7 0.7 4.8 0.8 15.6 254.6 a

 1 = Shallow Cold Saline, 2 = Mackenzie Influenced, 3 = Outer Shelf Arctic

b WF = Whale feeding station, CTL = Control Station ( see Chapter 6).
5-60 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

APPENDIX 5.17. Biomass (mg/m3) of the dominant zooplankton species in oblique (OB) and horizontal

(HB) bongo tows and vertical (VT) tows in the eastern Alaskan Beaufort Sea, Sept 1986. Copepods Cnidarians Ctenophores Pteropods Mysids

EuphausiidsChaetognathsAmphipodsFish

TransectDepth (m)Tow TypeSta. No.Samp. No.Water MassaCalanusHyperboreusCalanus glacialisPseudocalanusminutusEuchaeta glacialisMetridia longaLimnocalanusmacrurusHalitholus cirratusAglantha digitaleStaurophoramertensiMertensia ovumSpiratella hellicinaMysis litoralisMysis litoralisThysansoessaraschiiSagitta elegansParathemistolibellulaBoreogadus saisaTotal

CTLb 0 HB 11 43 1 0.0 0.0 0.0 0.0 0.0 0.3 6.2 7.3 0.0 0.0 1.7 0.0 0.0 0.0 0.0 0.0 0.0 30.1

CTL 0 HB 2 6 1 0.1 0.0 0.0 0.0 0.0 0.1 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.3

CTL 0 HB 6 22 2 0.0 0.0 0.0 0.0 0.0 0.2 1.6 0.0 0.0 0.0 6.4 0.0 0.0 0.0 0.0 0.0 0.0 8.7

CTL 0 HB 8 31 2 0.0 0.0 0.0 0.0 0.0 0.3 0.6 0.1 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 1.9

CTL 0 HB 13 52 2 0.0 0.0 0.0 0.0 0.0 3.8 0.0 0.0 0.0 0.0 0.1 0.0 0.0 0.0 0.0 0.0 0.0 4.5

WF 0 HB 1 1 1 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.2 0.0 0.0 0.2 0.0 0.0 0.0 0.0 0.0 0.0 0.7

WF 0 HB 5 18 1 0.0 0.1 0.1 0.0 0.0 0.3 0.0 0.1 0.0 0.3 1.9 0.0 0.0 0.0 0.0 0.0 0.0 3.8

WF 0 HB 7 26 1 0.5 1.0 4.0 0.0 0.0 2.1 7.2 0.5 0.0 0.0 0.1 0.0 0.0 0.0 0.0 0.0 0.0 19.1

WF 0 HB 9 35 1 0.0 0.3 3.1 0.0 0.0 63.7 0.0 3.8 0.0 1.2 0.0 0.0 0.0 0.0 0.0 0.0 0.0 74.2

WF 0 HB 10 38 1 0.0 0.3 0.2 0.0 0.0 7.7 0.0 2.1 0.0 1.5 1.0 0.0 0.0 0.0 0.0 0.0 0.0 19.0

WF 0 HB 12 47 1 0.2 0.0 0.1 0.0 0.0 1.8 0.0 0.0 0.0 0.7 0.0 0.0 0.0 0.0 0.0 0.0 0.0 3.9

WF 13 HB 12 49 1 7.3 24.4 3.2 1.8 0.0 283.0 11.4 0.8 0.0 3.8 0.1 0.0 10.4 0.0 5.6 0.3 0.0 392.8

WF 6 HB 12 50 1 0.0 1.2 1.6 0.0 0.0 299.9 0.0 1.2 0.0 0.0 0.4 0.0 0.0 0.0 0.7 0.0 0.0 319.0

WF 15 HB 12 51 1 5.7 11.2 4.0 0.0 1.0 1018.6 0.0 0.0 0.0 4.2 0.0 0.0 22.0 0.0 1.8 0.0 0.0 1101.5

WF 16 OB 1 2 1 2.2 2.4 1.3 0.3 0.1 7.4 3.5 25.2 0.0 2.1 5.0 0.0 3.0 0.2 2.9 10.0 2.3 96.4

WF 12 OB 5 19 1 0.9 3.0 6.1 3.5 0.0 1162.1 22.8 0.0 0.0 6.9 0.6 0.0 1.5 0.3 2.7 0.0 2.1 1228.2

WF 8 OB 7 27 1 3.1 6.6 11.1 0.0 0.0 754.1 3.3 1.1 0.0 1.6 0.1 49.9 3.5 0.2 0.2 0.2 0.5 853.4

WF 5 OB 9 36 1 0.5 0.5 1.8 0.0 0.0 162.6 6.5 6.2 0.0 0.0 0.2 127.1 0.0 0.0 0.1 0.5 0.0 318.5

WF 9 OB 10 39 1 0.3 0.8 0.4 0.2 0.1 33.6 17.6 21.3 0.0 1.3 2.6 0.0 0.0 0.0 0.0 0.1 5.5 105.0

WF 18 OB 12 48 1 1.3 5.2 4.3 1.3 1.3 855.6 0.0 4.2 0.0 4.7 1.0 1.2 0.4 0.0 3.0 0.4 4.4 912.4

CTL 20 OB 2 7 1 9.2 6.1 0.8 1.2 1.0 22.3 0.0 2.4 0.0 0.2 0.3 0.0 0.0 0.0 0.1 0.4 3.0 51.8

CTL 22 OB 6 23 2 1.2 8.8 0.4 0.0 0.0 3.4 9.0 15.1 0.0 3.1 11.1 0.0 0.0 0.0 0.7 1.9 10.4 81.2

CTL 18 OB 8 32 2 1.1 1.9 0.4 1.4 0.5 7.5 0.0 2.8 0.0 0.0 1.0 0.0 0.0 0.0 1.2 14.7 0.0 40.5

CTL 12 OB 11 44 1 4.3 13.6 2.5 0.7 0.2 92.7 0.0 50.1 0.0 0.8 0.3 0.0 0.0 0.0 6.4 0.2 0.0 198.5

CTL 21 OB 13 53 2 0.0 0.0 0.0 0.0 0.0 0.6 0.0 8.5 0.0 0.8 5.6 0.0 0.0 0.0 0.0 0.4 11.5 58.7

TRN-1 9 OB T1-1 120 1 1.8 10.8 14.3 0.0 0.0 39.2 0.9 0.4 0.0 0.0 0.5 0.1 0.0 0.0 0.1 0.0 0.0 78.4

TRN-1 30 OB T1-2 124 1 23.7 118.5 1.4 0.0 0.1 0.1 6.2 2.9 0.0 34.8 0.0 0.0 0.0 4.9 1.9 0.0 11.4 223.0

TRN-1 40 OB T1-3 129 2 63.5 170.5 0.2 1.9 0.2 0.0 0.0 17.7 0.0 0.0 4.7 0.0 0.0 0.9 20.2 13.6 2.7 317.1

TRN-1 50 OB T1-4 133 3 1.0 3.5 0.1 0.1 0.0 0.0 0.0 2.9 0.0 0.9 2.3 0.0 0.0 0.0 0.0 4.5 2.2 24.7

TRN-1 50 OB T1-5 138 3 0.1 0.4 0.0 0.0 0.0 0.1 0.0 0.4 0.0 6.8 0.0 0.0 0.0 0.0 0.2 3.6 3.0 57.4

TRN-2 8 OB T2-1 142 1 0.2 39.8 3.2 1.1 0.3 0.9 0.0 0.0 0.0 0.0 0.1 0.0 0.0 0.0 0.0 0.0 0.0 55.5

TRN-2 22 OB T2-2 146 1 139.4 578.1 0.4 0.0 0.0 0.0 0.8 5.4 0.0 1.3 6.6 0.0 0.1 0.0 5.2 1.1 2.2 776.9

TRN-2 50 OB T2-5 150 3 0.0 1.2 0.0 0.0 0.0 0.0 0.0 0.0 0.0 21.4 0.0 0.0 0.0 0.0 2.3 7.6 0.0 43.9

TRN-2 100 OB T2-5 151 3 0.2 11.2 0.1 0.0 0.0 0.1 0.0 3.9 0.0 18.5 0.1 0.0 0.0 0.0 8.2 0.0 18.7 66.3

TRN-3 9 OB T3-1 79 1 0.0 0.4 0.6 0.0 0.0 11.8 11.2 7.8 0.0 0.0 2.0 0.0 0.0 0.0 0.0 0.0 0.0 50.3

TRN-3 18 OB T3-2 83 1 0.2 0.2 0.0 0.8 0.0 1.5 8.2 5.5 0.0 0.5 7.5 0.0 0.0 0.9 0.0 2.7 12.9 146.9

TRN-3 35 OB T3-3 87 2 43.1 4.6 0.5 0.0 0.2 0.2 4.8 3.5 0.0 1.0 2.6 0.0 0.0 1.4 0.5 17.6 15.8 112.7

TRN-3 50 OB T3-4 91 3 31.2 1.4 0.1 0.0 0.1 0.3 0.0 4.1 0.0 0.2 2.9 0.0 0.0 0.0 2.5 6.5 9.7 68.1

TRN-3 50 OB T3-5 95 3 0.4 0.9 0.0 0.0 0.0 0.0 0.0 3.7 0.0 0.1 1.2 0.0 0.0 0.0 0.0 3.5 1.4 18.2

TRN-4 10 OB T4-1 57 1 1.7 4.6 1.3 0.0 0.0 993.6 0.0 1.8 0.0 1.5 0.6 14.8 0.0 0.0 0.0 0.0 0.0 1035.8

TRN-4 18 OB T4-2 62 1 0.0 0.0 0.1 0.0 0.0 0.3 0.0 0.0 0.0 0.1 0.0 0.0 0.0 0.0 1.0 0.5 0.0 4.0

TRN-4 40 OB T4-3 66 2 0.5 0.2 0.0 0.0 0.0 6.2 1.3 24.6 0.0 1.2 17.6 0.0 0.0 0.8 0.0 5.0 18.2 81.2

TRN-4 50 OB T4-4 71 3 0.0 0.0 0.0 0.0 0.0 0.4 1.9 4.8 0.0 0.2 2.6 0.0 0.0 0.0 0.0 3.8 1.9 21.3

TRN-4 50 OB T4-5 75 3 3.2 14.3 0.3 0.1 0.3 0.2 0.0 6.8 0.0 6.7 1.4 0.0 0.0 0.0 28.3 1.1 0.5 65.1

C 50 VT 5 272 0.1 6.4 0.1 0.9 0.3 0.0 0.0 0.4 0.0 2.0 0.0 0.0 0.0 0.2 1.7 0.0 0.0 15.0

C 50 VT 10 239 0.2 18.9 0.2 1.7 0.4 0.0 0.0 2.8 0.0 50.1 0.0 0.0 0.0 0.0 22.5 0.0 0.0 97.2

D 50 VT 10 246 0.0 15.9 0.1 0.2 12.

9

0.0 0.0 0.1 269.1 1.8 0.0 0.0 0.0 1.6 19.7 0.0 0.0 328.2

D 50 VT 10 255 9.1 38.3 0.1 0.1 0.2 0.0 0.0 6.7 0.0 0.0 4.6 0.0 0.0 2.5 9.6 0.0 8.6 85.7

D 50 VT 12 261 6.5 51.3 0.2 0.0 0.1 0.0 0.0 2.2 0.0 1.5 0.1 0.0 0.0 0.4 6.7 0.5 0.0 164.8 a

 1 = Shallow Cold Saline, 2 = Mackenzie Influenced, 3 = Outer Shelf Arctic

b WF = Whale feeding station, CTL = Control Station ( see Chapter 6).
APPENDIX 5.18. Biomass (mg/m3) of the dominant zooplankton species in oblique (OB) and selected surface (SB) and hor

in the eastern Alaskan Beaufort Sea, Sept 1998.
APPENDIX 5.19. Biomass (mg/m3) of the dominant zooplankton groups in oblique (OB) bongo tows in the eastern Alas

1998. Transect Depth (m) Tow Type Sta. No. Samp. No. Water Massa

Cnidarians 

Ctenophores

Copepods

Amphipods

Euphausiids

Mysids

Decapods

Misc. 

Crustaceans

Misc. NonCrustaceans

Chaetognaths

CTLb 6.5 OB 2 4 1 2.35 7.58 0.67 0.00 20.54 0.72 0.00 0.05 37.78 

CTL 19.5 OB 5 13 1 101.83 228.16 0.16 0.02 0.16 0.21 0.00 0.01 87.57 CTL 12.5 OB 22 71 1 42.73 58.97 0.00 0.00 3.06 0.00 0.00 0.00 193.68 CTL 29.5 OB 29 99 1 59.57 158.88 0.28 0.01 5.87 0.07 0.00 0.00 204.03 

TRN 7.0 OB 9 26 1 71.42 0.96 0.00 0.04 0.00 0.00 0.00 0.00 3.56 TRN 10.0 OB 6 16 1 63.49 9.08 0.00 0.65 15.96 0.00 0.00 0.00 73.97 TRN 14.0 OB 10 29 1 175.78 81.20 0.00 3.99 0.00 0.36 0.00 0.01 30.76 TRN 31.0 OB 11 32 2 33.16 83.98 1.28 0.38 0.00 0.09 0.00 0.00 32.12 TRN 9.5 OB 13 35 1 49.74 52.52 0.00 0.03 0.81 0.03 0.00 0.00 33.54 TRN 24.5 OB 14 38 2 45.50 275.06 0.01 0.25 7.85 0.01 0.00 0.25 40.17 TRN 7.5 OB 17 51 1 56.18 39.12 0.00 0.08 14.02 0.20 0.04 0.00 49.00 TRN 19.5 OB 18 54 1 60.33 106.77 0.16 0.08 4.88 0.04 0.00 0.31 183.66 TRN 24.5 OB 19 57 1 109.20 387.96 2.36 0.01 1.10 0.16 0.00 4.35 101.62 TRN 37.5 OB 20 60 2 38.06 159.51 0.94 1.09 0.00 0.02 0.00 0.56 15.56 TRN 8.0 OB 23 75 1 20.64 95.27 0.00 9.29 11.10 0.00 0.04 0.00 44.48 TRN 14.5 OB 24 78 1 8.08 169.27 0.00 0.40 0.00 0.00 0.00 0.00 50.20 TRN 21.5 OB 25 82 2 258.20 149.76 0.03 0.11 0.00 0.09 0.00 0.02 19.24 TRN 33.0 OB 26 86 2 42.11 91.10 2.60 2.06 0.00 0.10 0.00 0.12 25.93 

TRN/CTL 46.0 OB 16 47 2 20.38 26.64 4.16 0.58 0.00 0.69 0.01 0.10 6.14 TRN/CTL 16.0 OB 7 19 1 28.04 42.31 0.00 2.90 1.93 0.04 0.00 0.00 18.04 TRN/CTL 8.5 OB 30 103 1 18.97 41.63 0.09 2.41 61.79 0.06 0.09 0.00 83.70 TRN/CTL 19.0 OB 31 106 1 38.34 256.49 0.00 2.59 25.24 26.01 1.49 0.28 44.98 

TRN/WF 32.5 OB 15 42 2 37.64 82.38 3.66 0.23 0.00 0.47 0.06 0.06 10.45 

WF 10.5 OB 1 3 1 13.63 113.89 7.89 0.26 0.00 0.70 0.01 0.06 7.43 WF 10.0 OB 3 6 1 56.50 534.79 0.43 0.10 0.00 1.95 0.07 1.32 83.17 WF 19.0 OB 4 9 1 53.66 287.03 0.21 1.19 0.00 0.51 0.00 0.73 125.10 WF 24.0 OB 8 22 2 190.83 105.10 0.00 4.32 0.00 0.27 0.06 0.00 25.81 WF 24.5 OB 21 66 1 18.97 233.58 0.00 0.00 6.44 0.00 0.00 0.00 63.38 WF 7.5 OB 27 90 1 42.06 31.33 11.40 0.07 69.93 0.00 0.00 0.00 52.82 WF 13.5 OB 28 94 1 70.80 23.62 0.00 0.04 74.32 0.27 0.00 0.00 101.47 WF 13.0 OB 32 110 1 83.28 55.27 0.10 6.57 15.87 0.72 0.00 0.00 77.21 WF 15.5 OB 33 115 2 16.53 68.00 0.00 7.77 24.05 0.48 0.00 0.00 107.48 

a 1 = Shallow Cold Saline, 2 = Mackenzie Influenced, 3 = Outer Shelf Arcticb WF = Whale feeding station, CTL = Control Station ( see Chapter 6).
APPENDIX 5.20. Biomass (mg/m3) of the dominant zooplankton groups in surface (SB) bongo tows in the eastern Alas

1998.

Transect

Depth 

(m)

Tow 

Type

Sta. 

No.

Samp. 

No.

Water 

Massa Cnidarians 

Ctenophores

Copepods

Amphipods

Mysids 

Euphausiids

Decapods

Misc. 

Crustaceans

Misc. NonCrustaceans

Chaetognaths

CTLb 1.2 SB 5 14 1 3.40 3.18 0.00 0.00 0.00 0.00 0.01 0.78 

CTL 1.6 SB 7 21 1 13.46 1.08 0.00 0.01 0.00 0.01 0.00 0.65 CTL 0.6 SB 22 74 1 7.64 8.53 0.00 0.00 0.00 0.00 0.00 1.32 CTL 0.9 SB 29 102 1 0.96 1.40 0.00 0.01 0.00 0.00 0.00 0.30 

TRN 0.9 SB 9 28 1 38.54 0.14 0.00 0.01 0.01 0.00 0.00 0.24 TRN 1.2 SB 6 17 1 9.70 0.10 0.00 0.00 0.00 0.00 0.00 0.37 TRN 0.9 SB 13 37 1 186.38 37.48 0.00 0.01 0.00 0.01 0.56 2.55 TRN 0.7 SB 17 53 1 27.50 17.06 0.00 9.97 0.01 0.00 0.01 52.38 TRN 0.6 SB 18 56 1 2.20 12.09 0.00 0.00 0.00 0.00 0.00 0.82 TRN 1.0 SB 19 59 1 9.64 111.20 0.00 0.00 0.00 0.00 0.00 0.03 TRN 1.0 SB 20 65 2 7.14 6.82 0.00 0.00 0.00 0.08 0.02 0.97 TRN 1.5 SB 24 81 1 0.70 272.34 0.00 0.03 0.04 0.00 0.00 1.64 TRN 1.0 SB 25 85 2 59.82 12.13 0.00 0.01 0.02 0.00 0.00 2.99 TRN 1.0 SB 26 89 2 13.58 0.67 0.00 0.03 1.27 0.00 0.00 1.23 

TRN/CTL 1.2 SB 16 50 2 0.29 0.12 0.00 0.02 1.08 0.00 0.00 0.20 TRN/CTL 1.2 SB 30 105 1 289.78 2.73 0.06 4.60 0.28 0.01 5.04 37.27 TRN/CTL 2.0 SB 31 109 1 12.82 504.27 0.00 0.57 0.60 0.00 0.00 19.31 

TRN/WF 1.3 SB 15 46 2 0.95 0.16 0.00 0.00 0.31 0.01 0.00 0.06 

WF 1.0 SB 4 11 1 4.05 3.94 0.00 0.00 0.00 0.03 0.01 0.57 WF 0.9 SB 21 70 1 0.28 4.82 0.00 0.00 0.00 0.00 0.00 0.20 WF 0.8 SB 27 93 1 1.62 2.10 0.00 0.00 0.00 0.00 0.00 0.85 WF 1.0 SB 28 98 1 5.72 1.64 0.00 0.00 0.00 0.00 0.00 0.56 WF 1.0 SB 32 114 1 32.13 3.32 0.00 0.92 0.40 0.02 0.01 11.37 WF 1.5 SB 33 118 2 5.67 93.29 0.00 0.00 0.03 0.00 0.07 2.19 

a 1 = Shallow Cold Saline, 2 = Mackenzie Influenced, 3 = Outer Shelf Arcticb WF = Whale feeding station, CTL = Control Station ( see Chapter 6).
APPENDIX 5.21. Biomass (mg/m3) of the dominant zooplankton groups in horizontal (HB) bongo tows in the eastern Alas

1998. Transect Depth (m) Tow Type Sta. No. Samp. No. Water Massa Cnidarians 

Ctenophores

Copepods

Amphipods

Mysids 

Euphausiids

Decapods

Misc. 

Crustaceans

Misc. NonCrustaceans

Chaetognaths

Larvaceans

Fish

Total

CTLb 5.6 HB 2 5 1 12.60 27.09 0.00 49.58 0.00 0.00 0.21 138.27 0.00 13.57 241.32

CTL 14.0 HB 5 15 1 32.94 216.76 0.18 0.22 0.00 0.00 0.69 116.38 0.00 0.00 367.17CTL 3.7 HB 14 41 2 23.17 40.60 0.00 0.01 0.07 0.36 0.00 9.30 2.70 0.01 76.21CTL 6.6 HB 22 73 1 38.21 112.53 0.01 0.00 0.01 0.00 1.65 288.89 0.00 0.00 441.29CTL 25.7 HB 29 100 1 124.21 54.38 0.00 31.83 0.54 0.00 0.00 509.34 0.00 6.27 726.56CTL 11.3 HB 29 101 1 25.08 99.29 2.16 0.06 0.56 0.00 0.45 49.31 0.01 0.00 176.93

TRN 5.4 HB 9 27 1 50.61 7.27 0.00 1.71 0.00 0.02 0.05 12.83 0.96 0.00 73.46TRN 8.8 HB 6 18 1 18.65 12.37 0.00 16.84 0.31 0.00 0.02 0.00 132.63 0.00 180.82TRN 16.7 HB 7 20 1 35.95 176.42 0.00 59.37 0.34 0.68 0.17 93.91 0.14 12.15 379.12TRN 12.2 HB 10 31 1 116.74 177.32 0.01 1.62 0.26 0.00 0.54 48.48 0.55 0.00 345.52TRN 17.2 HB 10 30 1 35.07 304.72 0.00 42.74 0.27 0.00 0.23 77.97 0.13 1.57 462.69TRN 25.3 HB 11 33 2 50.33 211.40 0.00 1.24 0.28 0.01 0.10 44.35 0.21 2.47 310.41TRN 12.4 HB 11 34 2 30.43 8.68 0.00 0.02 0.27 0.00 0.00 2.63 0.76 0.02 42.82TRN 7.6 HB 13 36 1 135.72 60.29 0.00 4.92 0.15 0.02 0.00 50.79 0.00 1.80 253.70TRN 21.9 HB 14 39 2 10.51 303.08 0.00 0.10 0.09 0.02 0.00 27.49 2.11 1.64 345.06TRN 13.1 HB 14 40 2 63.66 143.55 0.03 0.14 0.17 0.00 0.00 7.62 0.77 0.00 215.94TRN 8.6 HB 17 52 1 31.36 21.84 0.00 35.47 0.00 42.50 0.00 36.85 0.00 0.00 168.01TRN 13.0 HB 18 55 1 34.51 142.65 0.06 0.03 0.03 0.00 0.71 347.41 0.00 0.00 525.41TRN 14.5 HB 19 58 1 21.18 502.89 0.00 0.05 0.01 0.00 0.01 18.17 0.00 0.00 542.31TRN 28.9 HB 20 61 2 54.80 399.51 0.00 0.30 0.02 0.02 0.20 24.52 1.19 1.02 481.58TRN 18.4 HB 20 62 2 131.58 5.68 1.43 0.13 0.73 0.05 0.01 2.47 8.68 0.12 150.88TRN 30.9 HB 20 63 2 31.22 197.56 1.01 0.07 0.12 0.10 0.41 19.36 2.93 2.81 255.60TRN 6.2 HB 23 76 1 95.86 22.81 0.68 2.71 0.01 0.00 0.73 67.51 0.00 0.01 190.33TRN 11.3 HB 24 79 1 62.10 98.77 0.00 0.90 0.12 0.00 0.01 20.00 3.70 8.43 194.03TRN 8.8 HB 24 80 1 10.17 47.17 0.00 0.97 0.11 0.01 0.77 32.24 12.98 0.00 104.43TRN 21.5 HB 25 83 2 44.83 441.67 0.00 0.03 0.00 0.00 0.05 72.20 2.55 0.00 561.33TRN 17.5 HB 25 84 2 126.70 145.22 0.00 2.05 0.00 0.00 0.04 26.62 1.27 10.93 312.85TRN 31.5 HB 26 87 2 321.67 416.68 1.71 1.78 0.00 0.03 0.41 83.75 0.82 3.93 830.76TRN 22.0 HB 26 88 2 44.49 1.86 0.52 0.27 0.05 0.00 0.00 0.86 2.12 0.00 50.18

TRN/CTL 34.7 HB 16 48 2 42.44 37.96 0.54 10.05 1.69 0.60 3.69 43.97 0.94 6.00 147.87TRN/CTL 19.2 HB 16 49 2 3.69 0.39 2.07 0.07 1.02 0.16 0.03 1.45 0.20 4.09 13.17TRN/CTL 8.2 HB 30 104 1 59.39 68.91 0.23 111.15 0.14 2.78 0.06 133.96 0.00 116.04 492.65TRN/CTL 19.2 HB 31 107 1 26.54 262.17 1.45 18.96 77.87 0.00 0.01 270.39 0.00 127.90 785.29TRN/CTL 12.6 HB 31 108 1 21.60 172.84 0.00 70.49 0.22 0.00 3.90 42.10 0.49 4.47 316.12

TRN/WF 22.4 HB 15 44 2 763.82 3.24 0.01 0.03 0.15 0.07 0.00 0.74 2.65 0.00 770.71TRN/WF 13.8 HB 15 45 2 16.94 0.07 0.06 0.03 0.20 0.05 0.00 1.23 2.94 10.28 31.80TRN/WF 35.8 HB 15 43 2 17.15 359.65 1.02 0.14 0.94 0.00 1.05 41.69 3.97 0.00 425.61

WF 9.6 HB 1 2 1 42.16 210.44 0.55 0.00 0.07 0.00 0.21 38.78 0.00 2.66 294.86WF 11.4 HB 3 8 1 28.77 237.22 0.35 0.41 0.60 0.00 0.19 165.17 0.03 5.17 437.91WF 15.0 HB 3 7 1 33.50 264.65 0.84 6.65 0.65 0.02 0.17 303.89 0.11 5.20 615.71WF 13.5 HB 4 12 1 52.28 41.54 0.11 0.46 0.35 0.01 0.12 98.86 0.00 0.00 193.74WF 19.6 HB 4 10 1 72.16 239.62 1.34 1.36 0.23 0.00 1.65 138.09 0.00 5.83 460.27WF 13.5 HB 8 25 1 29.63 3.66 0.00 0.47 0.16 0.06 0.00 1.64 1.89 2.00 39.51WF 6.0 HB 8 23 1 21.46 0.73 0.01 0.06 0.26 0.28 0.01 0.75 0.43 0.00 23.99WF 23.5 HB 8 24 1 44.61 401.65 0.00 1.74 0.93 0.01 0.18 48.77 0.35 6.24 504.47WF 23.0 HB 21 67 1 56.43 143.86 0.02 4.46 0.01 1.06 1.21 177.42 0.00 4.50 388.96WF 18.8 HB 21 68 1 27.50 117.07 0.07 0.00 0.07 0.00 0.06 45.71 0.00 1.48 191.96WF 9.9 HB 21 69 1 36.31 174.09 0.00 0.43 0.11 0.00 0.19 24.17 0.00 0.21 235.50WF 12.1 HB 21 72 1 17.48 30.37 0.08 1.28 0.00 0.00 0.65 168.68 0.00 0.00 218.53WF 6.8 HB 27 91 1 40.79 34.69 0.00 86.60 0.06 0.00 0.72 77.17 0.00 27.26 267.29WF 5.2 HB 27 92 1 54.74 72.28 0.00 1.75 0.12 0.00 4.48 74.92 0.00 4.88 213.17WF 10.8 HB 28 95 1 158.41 24.94 0.00 100.14 0.00 0.02 0.00 121.34 0.00 15.88 420.73WF 8.4 HB 28 97 1 47.52 25.60 0.00 58.42 0.00 0.03 0.00 131.81 0.00 0.00 263.38WF 13.4 HB 28 96 1 16.39 20.05 1.45 26.50 0.05 0.23 0.00 37.79 0.00 10.13 112.60WF 8.8 HB 32 112 1 171.25 24.41 0.24 31.57 0.16 0.00 0.22 82.17 0.13 0.00 310.14WF 4.9 HB 32 113 1 39.84 6.49 0.78 79.44 0.22 0.01 0.01 48.09 0.00 12.41 187.29WF 14.1 HB 32 111 1 64.45 35.03 0.73 28.47 0.16 0.34 0.11 104.96 0.00 94.49 328.73WF 13.7 HB 33 116 2 38.07 37.80 0.43 72.70 0.17 0.00 2.44 195.01 0.32 39.31 386.25WF 10.5 HB 33 117 2 49.04 61.45 0.00 0.35 0.12 0.00 0.01 143.77 0.17 0.00 254.90

a 1 = Shallow Cold Saline, 2 = Mackenzie Influenced, 3 = Outer Shelf Arcticb WF = Whale feeding station, CTL = Control Station ( see Chapter 6).
APPENDIX 5.22. Biomass (mg/m3) of the dominant zooplankton species in oblique (OB) bongo tows in the eastern Alas

1999.

Euphausiids Mysid

Transect

Depth 

(m)

Tow 

Type

Sta. 

No.

Samp. 

No.

Water 

Massa

Aeginopsis laurentii

Aglantha digitale

Eumedusa birulai

Cyanea capillata

Mertensia ovum

Pleurobrachia pileus

Calanus glacialis

Calanus hyperboreus

Limnocalanus macrurus

Euchaeta glacialis

Metridia longa

Pseudocalanus minutus

Parathemisto abyssorum

Parathemisto libellula

Thysanoessa raschii

Mysis litoralis

CTLb 30 OB 5 19 1 0.00 5.13 0.00 18.32 6.74 13.71 4.69 134.65 0.00 2.51 0.05 0.03 0.01 0.07 4.14 0

CTL 40 OB 2 6 1 69.27 0.00 0.00 12.76 5.89 0.00 15.50 215.85 0.00 1.67 5.67 0.07 0.19 8.27 0.00 0

TRN 7 OB 9 34 1 0.00 0.53 0.00 0.00 1.74 0.00 1.21 0.00 0.01 0.00 0.03 2.65 0.00 0.00 0.00 0

TRN 7 OB 13 49 1 0.00 20.92 14.06 0.00 58.65 0.00 7.56 11.25 0.00 0.00 0.07 1.16 0.00 0.00 0.00 0

TRN 8 OB 18 67 1 0.00 41.49 0.00 0.00 0.00 0.00 6.51 8.26 0.04 0.00 0.00 81.33 0.00 1.83 0.00 63

TRN 8 OB 22 83 1 0.00 94.36 0.00 31.21 4.80 0.00 5.16 44.80 0.00 2.05 0.11 0.62 0.00 0.00 0.00 0

TRN 15 OB 8 31 1 0.00 1.88 0.00 0.00 2.35 0.00 0.51 0.40 0.00 0.00 0.00 0.07 0.00 0.00 0.00 0

TRN 17 OB 12 45 1 0.00 11.55 2.56 0.00 77.23 0.00 5.54 18.04 0.00 0.15 0.30 0.18 0.00 0.00 21.38 1

TRN 18 OB 21 79 1 0.00 28.54 0.00 0.00 253.26 0.00 16.58 317.55 0.00 0.00 1.44 0.07 0.02 4.31 0.00 0

TRN 29 OB 11 41 1 0.00 0.94 0.00 0.00 15.14 29.41 15.68 67.18 0.00 3.82 1.06 0.08 0.04 2.43 1.42 0

TRN 30 OB 7 27 1 0.00 10.42 0.43 0.00 16.13 0.85 9.14 101.08 0.00 0.93 0.00 0.24 0.00 1.14 20.09 0

TRN 30 OB 16 60 1 0.00 10.50 2.01 0.00 60.05 13.59 61.54 271.13 0.00 2.27 9.05 0.36 0.42 1.21 3.05 0

TRN 30 OB 20 74 1 0.00 60.59 0.00 0.00 58.87 0.00 58.31 603.59 0.00 0.53 19.34 0.85 0.03 0.28 0.00 0TRN 35 OB 19 70 1 0.00 120.45 2.38 0.00 8.78 0.00 22.53 65.66 0.00 8.38 1.09 0.00 0.06 2.14 0.29 0

TRN 40 OB 6 23 1 0.00 46.18 0.21 20.54 12.77 0.00 30.85 278.04 0.00 1.22 3.97 0.12 0.14 3.65 0.00 0

TRN 42 OB 10 37 1 0.00 11.54 1.25 0.00 13.28 0.00 12.55 147.90 0.00 2.56 0.00 0.02 0.13 3.33 0.00 0

TRN/CTL 18 OB 17 64 1 0.00 12.38 0.00 0.00 111.79 0.00 28.38 54.04 0.00 1.85 0.30 0.15 0.11 2.04 40.26 4

TRN/WF 32 OB 14 52 1 0.00 42.40 0.00 0.00 44.64 0.00 35.01 271.54 0.00 5.04 5.32 0.30 0.04 0.00 0.54 0TRN/WF 40 OB 15 56 1 0.00 21.32 1.74 0.00 46.00 0.00 87.58 356.47 0.00 11.48 11.56 0.26 1.80 0.46 1.10 0

WF 40 OB 1 2 1 1.09 17.66 0.20 0.00 13.82 0.00 43.60 242.72 0.00 1.31 10.32 0.14 0.22 4.31 2.11 0

WF 40 OB 3 11 1 11.10 0.00 1.56 0.00 1.53 0.00 18.69 127.52 0.00 4.27 1.10 0.03 0.03 5.78 3.67 0WF 41 OB 4 15 1 0.42 26.08 0.00 0.00 6.03 0.00 16.19 137.25 0.00 1.97 0.53 0.03 0.00 3.23 0.40 0

a 1 = Shallow Cold Saline, 2 = Mackenzie Influenced, 3 = Outer Shelf Arcticb WF = Whale feeding station, CTL = Control Station ( see Chapter 6).

Cnidarians/Ctenophores Copepods Amphipods 
APPENDIX 5.23. Biomass (mg/m3) of the dominant zooplankton groups in oblique (OB) bongo tows in the eastern Alas

1999. Transect Depth (m) Tow Type Sta. No. Samp. No. Water Massa

Ctenophores 

Cnidarians

Copepods

Amphipods

Euphausiids

Mysids

Chaetognaths

Larvacea

Fish

CTLb 30 OB 5 19 1 43.90 141.93 0.08 4.25 0.00 11.05 0.07 13.9

CTL 40 OB 2 6 1 89.78 238.76 9.37 0.00 0.00 41.38 0.69 3.9

TRN 7 OB 9 34 1 2.28 3.91 0.00 0.00 0.00 3.60 0.01 0.0TRN 7 OB 13 49 1 93.89 20.07 0.00 0.00 0.00 77.03 0.00 0.0TRN 8 OB 18 67 1 41.49 96.68 1.83 0.00 63.94 65.06 0.04 39.2TRN 8 OB 22 83 1 130.37 52.78 0.00 0.00 0.00 96.37 0.00 9.2

TRN 15 OB 8 31 1 4.23 0.98 0.00 0.00 0.00 3.34 0.01 0.0TRN 17 OB 12 45 1 91.34 24.21 0.00 21.38 1.56 200.07 0.00 27.3

TRN 18 OB 21 79 1 281.80 335.64 4.32 0.00 0.00 112.50 0.04 21.6TRN 29 OB 11 41 1 45.60 87.81 2.68 1.42 0.00 27.22 0.45 12.0TRN 30 OB 7 27 1 27.84 111.39 1.14 20.09 0.00 157.76 0.00 8.7

TRN 30 OB 16 60 1 86.14 344.36 2.21 3.05 0.00 180.81 0.90 9.5

TRN 30 OB 20 74 1 120.32 682.63 0.60 0.00 0.00 211.63 1.42 12.3TRN 35 OB 19 70 1 134.70 97.66 2.19 0.29 0.00 28.35 0.90 4.8

TRN 40 OB 6 23 1 79.70 314.20 3.79 0.00 0.00 57.22 0.99 10.1TRN 42 OB 10 37 1 26.07 163.03 3.47 0.00 0.00 15.74 1.12 3.1

TRN/CTL 18 OB 17 64 1 124.17 84.72 2.15 40.26 4.06 174.30 0.00 8.1

TRN/WF 32 OB 14 52 1 87.04 317.21 0.05 0.54 0.00 38.12 0.07 5.3TRN/WF 40 OB 15 56 1 69.06 467.34 2.26 1.10 0.00 36.66 1.80 4.5

WF 40 OB 1 2 1 32.76 298.08 6.32 2.11 0.00 82.11 0.14 13.7WF 40 OB 3 11 1 14.20 151.61 5.95 3.67 0.00 19.34 0.97 11.4WF 41 OB 4 15 1 33.03 155.97 3.43 0.40 0.00 21.32 0.79 5.6

a 1 = Shallow Cold Saline, 2 = Mackenzie Influenced, 3 = Outer Shelf Arcticb WF = Whale feeding station, CTL = Control Station ( see Chapter 6).
APPENDIX 5.24. Biomass (mg/m3) of the dominant zooplankton groups in horizontal (HB) bongo tows in the eastern Alas

1999.

Transect

Depth 

(m)

Tow 

Type

Sta. 

No.

Samp. 

No.

Water 

Massa

Ctenophores 

Cnidarians

Copepods

Amphipods

Euphausiids

Mysids

Chaetognaths

Larvacea

TRNb 31 HB 6 24 1 142.81 39.41 4.46 0.00 0.00 18.61 1.70 

TRN 41 HB 6 25 1 171.89 541.14 5.03 3.38 0.00 75.65 2.06 1TRN 17 HB 7 28 1 163.19 73.22 0.89 8.35 0.00 86.91 23.75 TRN 8 HB 7 29 1 34.84 1.16 3.43 0.00 0.00 3.19 0.02 TRN 8 HB 8 32 1 143.33 0.12 0.00 0.00 0.00 0.46 0.00 TRN 6 HB 9 35 1 0.30 0.51 1.10 0.81 0.00 1.57 0.01 TRN 26 HB 10 38 1 85.95 339.49 0.88 0.00 0.00 19.73 3.99 TRN 8 HB 10 39 1 9.79 0.55 2.20 0.00 0.00 0.49 1.63 TRN 27 HB 11 42 1 86.73 9.92 0.94 2.45 0.00 20.55 0.24 TRN 11 HB 11 43 1 64.60 2.68 1.60 0.00 0.00 3.94 1.01 TRN 11 HB 12 46 1 132.90 8.75 0.00 1.42 0.00 54.15 0.00 TRN 15 HB 12 47 1 493.77 38.14 0.78 57.26 0.00 335.13 0.00 TRN 7 HB 13 50 1 93.12 17.81 1.16 0.00 0.00 40.86 0.00 2TRN 23 HB 16 61 1 114.27 587.21 0.07 0.45 0.77 365.40 0.22 2TRN 10 HB 16 62 1 83.89 7.78 3.66 0.00 0.00 35.34 0.15 TRN 5 HB 18 68 1 103.37 66.42 0.00 0.00 25.12 248.27 0.00 1TRN 26 HB 19 71 1 317.60 149.29 0.31 1.79 0.00 92.62 0.53 TRN 10 HB 19 72 1 61.14 0.82 7.37 0.00 0.00 0.38 0.30 TRN 9 HB 20 77 1 166.45 430.93 0.18 0.00 0.00 125.32 1.62 1TRN 12 HB 21 80 1 137.85 406.25 0.02 2.46 0.00 237.40 0.00 TRN 6 HB 21 81 1 199.17 102.38 0.57 0.00 0.77 72.12 0.03 2TRN 8 HB 22 84 1 166.08 121.66 1.35 0.00 7.37 305.29 0.00 1

TRN/CTL 17 HB 17 65 1 287.44 243.68 0.29 12.73 4.07 263.99 0.00 

CTL 21 HB 2 8 1 88.04 2.70 12.81 0.00 0.00 8.04 0.53 CTL 8 HB 2 7 1 56.81 1.76 11.50 0.00 0.00 0.91 0.28 CTL 15 HB 5 20 1 32.24 69.90 0.22 0.00 0.00 29.72 0.12 CTL 6 HB 5 21 1 16.33 0.55 4.67 0.00 0.00 0.01 0.02 1

TRN/WF 31 HB 14 53 1 261.53 242.52 4.72 0.52 0.00 76.60 0.00 TRN/WF 13 HB 14 54 1 45.20 1.58 1.54 0.00 0.00 0.61 0.10 TRN/WF 24 HB 15 57 1 247.10 239.94 7.58 0.00 0.00 34.66 4.70 3TRN/WF 13 HB 15 58 1 9.68 1.25 0.35 0.00 0.00 1.27 4.83 

WF 37 HB 1 3 1 82.71 391.88 1.89 0.20 0.00 61.06 0.65 WF 19 HB 1 4 1 135.10 0.59 1.29 0.00 0.00 0.36 0.58 WF 10 HB 1 5 1 28.37 0.09 0.81 0.00 0.00 0.39 0.12 WF 19 HB 3 12 1 13.42 1.45 2.43 0.00 0.00 3.44 3.44 1WF 34 HB 3 13 1 146.49 593.92 6.24 21.31 0.00 102.96 1.59 1WF 40 HB 4 16 1 59.48 607.98 5.73 2.80 0.00 89.31 0.17 1WF 14 HB 4 17 1 3.18 0.16 5.04 0.00 0.00 0.38 0.36 

a 1 = Shallow Cold Saline, 2 = Mackenzie Influenced, 3 = Outer Shelf Arcticb WF = Whale feeding station, CTL = Control Station ( see Chapter 6).
APPENDIX 5.25 Biomass (mg/m3) of the dominant zooplankton groups in surface (SB) bongo tows in the eastern Alaskan B

Transect Depth (m) Tow Type Sta. No. Samp. No. Water Massa Ctenophores 

Cnidarians

Copepods

Amphipods

Euphausiids

Mysids

Chaetognath

s

Larvacea

TRNb 1 SB 6 22 1 0.36 0.06 0.00 0.00 0.00 0.00 0.01 

TRN 1 SB 7 26 1 0.80 0.05 0.00 0.00 0.00 0.15 0.03 TRN 1 SB 8 30 1 11.35 0.93 0.00 0.15 0.00 0.35 0.02 TRN 1 SB 9 33 1 0.46 0.25 0.00 0.00 0.00 0.45 0.01 TRN 1 SB 10 36 1 0.21 0.11 0.08 0.00 0.00 0.00 0.01 TRN 1 SB 11 40 1 9.13 1.59 0.04 0.00 0.00 0.23 0.03 TRN 1 SB 12 44 1 0.96 0.30 0.51 0.00 0.00 0.08 0.03 TRN 1 SB 13 48 1 10.37 0.20 0.31 0.00 0.00 0.51 0.00 TRN 1 SB 16 59 1 1.00 0.01 0.08 0.00 0.00 0.05 0.17 TRN 1 SB 18 66 1 88.68 18.98 0.00 0.00 0.00 10.81 0.01 TRN 1 SB 19 69 1 0.07 0.25 0.00 0.00 0.15 0.03 0.00 TRN 1 SB 20 73 1 1.89 3.27 0.00 0.00 0.00 0.02 0.03 TRN 1 SB 21 78 1 2.31 0.20 0.06 0.00 0.00 0.01 0.01 TRN 1 SB 22 82 1 72.60 3.67 1.41 0.00 0.70 23.92 0.00 

CTL 1 SB 2 7 1 15.99 0.04 0.00 0.00 0.00 0.01 0.17 CTL 1 SB 5 18 1 1.55 0.01 0.00 0.00 0.00 0.00 0.00 

TRN/CTL 1 SB 17 63 1 24.23 0.42 0.83 0.00 0.00 0.12 0.01 

TRN/WF 1 SB 14 51 1 0.01 0.65 0.00 0.00 0.00 0.08 0.01 TRN/WF 1 SB 15 55 1 0.25 0.37 0.00 0.00 0.00 0.10 0.07 

WF 1 SB 1 1 1 0.00 0.00 0.00 0.00 0.00 0.00 0.01 WF 1 SB 3 10 1 3.35 0.10 0.04 0.00 0.00 0.00 0.00 WF 1 SB 4 14 1 0.19 0.25 0.00 0.00 0.00 0.05 0.03 

a 1 = Shallow Cold Saline, 2 = Mackenzie Influenced, 3 = Outer Shelf Arcticb WF = Whale feeding station, CTL = Control Station ( see Chapter 6).
APPENDIX 5.26. Biomass (mg/m3) of the dominant zooplankton species in oblique (OB) bongo tows in the eastern Alas

2000.

Mysids 

Transect

Depth 

(m)

Tow 

Type

Sta. 

No.

Samp. 

No.

Water 

Massa

Aeginopsis laurentii

Aglantha digitale

Eumedusa birulai

Euphysa flammea

Halitholus cirratus

Sarsia princeps

Cyanea capillata

Mertensia ovum

Calanus glacialis

Calanus hyperboreus

Limnocalanus 

macrurus

Metridia longa

Parathemisto 

abyssorum

Parathemisto libellula

Thysanoessa raschii

Thysanoessa longipes

Mysis litoralis

Eukrohnia hamata

TRN-1 10 OB 1 1 1 0.07 0.66 16.13 0.00 10.50 0.00 0.00 8.92 26.65 1.51 1.26 0.02 0.00 0.00 1.49 0.00 0.00 0.16 

TRN-1 18 OB 2 4 1 0.09 3.36 0.00 0.00 19.24 0.00 8.39 46.69 31.41 7.34 0.20 0.27 0.08 0.00 0.85 0.00 0.00 0.1

TRN-1 30 OB 3 9 1 0.03 3.98 1.10 0.04 7.62 0.00 60.57 19.27 29.73 118.14 0.00 0.64 3.87 0.00 3.46 0.00 0.02 3.53 

TRN-2 8 OB 4 12 1 0.02 1.34 2.10 0.00 10.03 0.00 0.00 0.92 15.73 0.61 0.69 0.00 0.00 0.00 0.00 0.50 12.13 0.23 TRN-2 19 OB 5 15 1 0.00 1.10 0.00 0.00 0.00 8.41 0.00 16.24 44.38 4.41 0.02 0.14 0.38 0.00 9.59 0.00 1.73 0.02 

TRN-2 28 OB 6 19 1 0.43 3.29 0.00 0.00 3.43 0.17 0.00 2.50 26.48 40.62 0.09 0.64 1.63 0.11 3.32 0.00 0.00 0.57 

TRN-2 47 OB 7 23 1 0.20 17.74 0.00 0.00 4.65 0.00 0.00 15.64 26.46 52.08 0.16 7.93 3.81 0.52 3.14 0.00 0.00 20.20 

TRN-3 9 OB 8 27 1 0.25 4.45 0.00 0.00 0.00 0.00 0.00 0.90 38.62 43.52 2.10 0.03 0.56 5.29 0.00 0.00 3.19 1.60 

TRN-3 18 OB 9 30 1 0.55 8.43 2.05 0.00 0.00 0.00 0.00 0.97 32.43 25.27 0.05 0.63 0.23 1.82 0.45 0.00 0.00 0.36 

TRN-3 28 OB 10 34 1 0.04 15.73 1.70 0.00 0.00 0.00 0.00 0.00 30.49 64.35 0.05 2.00 0.64 2.36 2.05 0.00 0.00 0.97 

TRN-3 45 OB 11 38 1 0.00 13.57 0.00 0.00 0.00 0.00 0.00 25.51 19.02 45.49 0.11 9.26 1.85 0.52 0.35 0.00 0.00 5.53 

TRN-4 8 OB 12 42 1 0.03 3.90 6.75 0.00 0.00 0.00 0.00 0.00 25.60 62.54 4.65 0.17 0.29 0.00 0.00 0.00 3.81 0.12 

TRN-4 18 OB 13 45 1 0.06 33.52 0.30 0.86 0.00 0.00 0.00 7.03 33.63 152.39 0.58 1.16 1.33 1.12 2.51 0.00 0.09 1.77 

TRN-4 28 OB 14 49 1 0.28 18.32 1.74 0.38 0.00 0.35 0.00 0.39 29.69 38.53 0.03 0.79 0.75 4.69 2.17 0.00 0.00 1.27 

TRN-4 40 OB 15 53 1 1.15 15.45 0.00 0.00 0.00 0.00 1.84 3.22 20.69 40.71 0.02 4.24 0.66 0.00 0.52 0.00 0.00 2.97 

TRN-5 9 OB 16 58 1 0.15 0.00 7.01 0.03 36.94 0.00 0.00 0.53 27.00 1.38 6.60 0.00 0.00 0.00 0.00 0.00 2.41 0.2

TRN-5 18 OB 17 61 1 0.00 6.81 0.94 0.00 0.00 4.16 0.00 38.60 47.52 13.61 0.05 6.00 1.44 1.49 1.98 0.00 0.11 1.84 

TRN-5 20 OB 18 66 1 0.61 15.06 0.00 0.00 3.50 0.00 0.00 0.61 61.47 19.28 0.02 0.18 0.27 0.14 12.88 0.00 0.00 0.10 

TRN-6 40 OB 19 70 1 0.27 16.30 0.00 0.00 0.23 0.00 2.69 4.98 55.56 92.66 0.01 2.81 4.18 1.52 4.26 0.00 0.00 2.19 

TRN-6 39 OB 20 74 1 0.21 12.33 2.59 0.00 0.00 0.00 0.53 6.09 26.27 63.60 0.25 1.40 2.50 0.00 19.95 0.00 0.00 0.75 

TRN-6 26 OB 21 78 1 0.67 49.89 2.11 0.04 0.00 0.63 0.00 2.51 27.46 121.83 0.57 0.81 1.60 0.82 0.00 16.77 0.00 1.83 

TRN-6 18 OB 22 82 1 0.66 27.88 0.41 0.00 0.00 0.00 0.00 1.05 34.83 71.11 0.25 0.16 0.30 0.69 26.22 0.00 0.00 0.54 

TRN-6 8 OB 23 86 1 0.15 5.70 0.46 0.00 0.00 2.01 0.00 4.58 24.38 7.22 0.03 0.06 0.77 0.00 12.02 0.00 0.34 0.00 

TRN-7 38 OB 24 89 1 0.32 15.93 5.64 0.00 0.65 0.00 0.00 4.70 128.36 86.20 0.94 2.54 1.43 6.14 15.67 0.00 0.00 3.88 

TRN-7 26 OB 25 93 1 0.42 11.24 0.22 0.00 0.00 0.00 0.00 1.86 28.65 160.00 0.00 0.63 0.31 0.68 14.64 0.00 0.00 0.16 

TRN-7 18 OB 26 97 1 0.26 119.10 2.45 0.00 0.00 0.00 0.00 17.69 52.74 170.81 0.04 2.20 0.82 0.00 6.45 0.00 1.61 0.75 

TRN-7 10 OB 27 101 1 0.46 5.28 5.83 0.40 123.82 0.06 0.00 20.81 24.45 9.16 6.03 0.23 0.00 0.00 0.34 0.00 14.04 0.77 TRN-8 14 OB 28 104 1 1.58 7.47 0.98 7.97 0.00 0.00 0.00 2.61 105.75 53.85 0.42 0.03 1.35 5.78 17.73 0.00 0.42 0.00 TRN-8 18 OB 29 108 1 0.38 5.40 0.72 0.00 0.00 0.00 2.81 7.06 77.04 29.99 0.00 0.05 0.26 3.84 28.63 0.00 1.18 0.05 TRN-8 25 OB 30 112 1 0.65 41.56 0.09 0.03 2.36 0.00 0.24 0.70 32.38 92.29 0.06 0.38 2.37 0.00 107.62 0.00 0.00 0.66 

a 1 = Shallow Cold Saline, 2 = Mackenzie Influenced, 3 = Outer Shelf Arctic

Cnidarians/Ctenophores Copepods Amphipods Euphausiids Cha
APPENDIX 5.27. Biomass (mg/m3) of the dominant zooplankton groups in oblique (OB) bongo tows in the eastern Alas

2000. Transect Depth (m) Tow Type Sta. No. Samp. No. Water Massa Ctenophores 

Cnidarians

Copepods

Amphipods

Euphausiids

Mysids

Decapods

Chaetognath

s

Larvaceans

TRN-1 10 OB 1 1 1 36.28 31.85 0.00 1.49 0.00 0.00 0.85 0.14 0TRN-1 18 OB 2 4 1 77.89 39.35 0.08 0.85 0.00 0.12 37.92 0.33 1TRN-1 30 OB 3 9 1 92.61 149.48 3.93 3.46 0.02 0.05 34.16 0.49 0TRN-2 8 OB 4 12 1 14.41 17.07 0.04 0.50 12.13 0.33 7.12 0.00 4TRN-2 19 OB 5 15 1 25.75 49.35 0.83 9.59 1.73 0.24 24.14 0.02 0TRN-2 28 OB 6 19 1 9.82 68.66 2.14 3.32 0.00 0.52 41.14 0.08 1TRN-2 47 OB 7 23 1 54.98 89.54 4.59 3.14 0.00 0.03 30.84 0.31 0TRN-3 9 OB 8 27 1 10.83 84.31 9.18 0.00 3.19 0.11 40.39 0.14 5TRN-3 18 OB 9 30 1 16.30 58.87 2.86 0.45 0.00 0.08 12.13 0.27 0TRN-3 28 OB 10 34 1 18.22 98.59 3.00 2.05 0.00 0.06 7.09 0.13 0TRN-3 45 OB 11 38 1 39.08 77.40 2.37 0.35 0.00 0.15 7.79 0.25 0TRN-4 8 OB 12 42 1 10.67 93.14 1.37 0.00 3.81 0.38 4.60 0.06 0TRN-4 18 OB 13 45 1 41.77 189.56 2.65 2.51 0.09 1.20 50.13 0.64 0TRN-4 28 OB 14 49 1 21.47 69.38 5.60 2.17 0.00 0.72 19.75 0.14 0TRN-4 40 OB 15 53 1 25.10 66.89 0.80 0.52 0.00 0.45 12.87 0.39 0TRN-5 9 OB 16 58 1 45.13 35.36 0.26 0.00 2.41 0.00 1.79 0.03 7TRN-5 18 OB 17 61 1 50.52 67.26 3.23 1.98 0.11 2.07 84.57 0.02 1TRN-5 20 OB 18 66 1 19.78 80.94 0.58 12.88 0.00 3.44 30.94 0.03 9TRN-6 40 OB 19 70 1 24.53 151.33 5.92 4.26 0.00 0.68 29.32 0.19 0TRN-6 39 OB 20 74 1 21.76 92.35 2.69 19.95 0.00 2.49 29.48 0.07 2TRN-6 26 OB 21 78 1 55.84 150.75 3.11 16.77 0.00 2.41 45.55 0.38 9TRN-6 18 OB 22 82 1 30.02 107.73 1.14 26.22 0.00 4.82 63.16 0.13 8TRN-6 8 OB 23 86 1 12.92 31.88 1.02 12.02 0.34 0.12 33.09 0.00 5TRN-7 38 OB 24 89 1 27.25 218.75 8.06 15.67 0.00 0.67 61.10 0.27 10TRN-7 26 OB 25 93 1 13.74 190.97 1.25 14.64 0.00 4.25 46.22 0.13 4TRN-7 18 OB 26 97 1 139.50 227.55 1.05 6.45 1.61 0.31 43.01 0.18 1TRN-7 10 OB 27 101 1 156.66 40.36 0.00 0.34 14.04 0.06 7.41 0.03 0TRN-8 14 OB 28 104 1 22.16 160.21 7.57 17.73 0.42 0.21 50.74 0.00 6TRN-8 18 OB 29 108 1 16.38 107.97 4.55 28.63 1.18 1.25 37.81 0.05 1TRN-8 25 OB 30 112 1 45.62 125.12 2.80 107.62 0.00 2.55 55.96 0.25 1

a 1 = Shallow Cold Saline, 2 = Mackenzie Influenced, 3 = Outer Shelf Arctic
APPENDIX 5.28. Biomass (mg/m3) of the dominant zooplankton groups in horizontal (HB) bongo tows in the eastern Alas

2000.
APPENDIX 5.29. Biomass (mg/m3) of the dominant zooplankton groups in surface (SB) bongo tows in the eastern Alas

2000. Transect Depth (m) Tow Type Sta. No. Samp. No. Water Massa Ctenophores 

Cnidarians

Copepods

Amphipods

Euphausiids

Mysids

Chaetognath

s

Larvaceans

TRN-1 1 SB 1 2 1 9.34 5.07 0.04 0.00 0.00 0.01 0.02 TRN-1 1 SB 2 5 1 0.16 1.34 0.04 0.00 0.00 0.00 0.01 TRN-1 1 SB 3 8 1 4.62 1.74 0.52 0.00 0.00 0.17 0.02 TRN-2 1 SB 4 13 1 19.04 6.58 0.12 0.00 0.42 12.42 0.02 TRN-2 1 SB 5 16 1 3.52 2.00 0.00 0.00 0.00 0.01 0.00 TRN-2 1 SB 6 20 1 16.01 8.33 0.45 0.00 0.00 0.01 0.00 TRN-2 1 SB 7 24 1 4.64 3.65 0.85 0.00 0.00 0.23 0.00 TRN-3 1 SB 8 28 1 9.06 23.21 3.58 0.00 0.03 0.29 0.02 TRN-3 1 SB 9 31 1 0.48 0.73 0.48 0.00 0.00 0.05 0.05 TRN-3 1 SB 10 35 1 2.65 2.23 0.09 0.00 0.00 0.01 0.01 TRN-3 1 SB 11 39 1 0.11 0.94 0.04 0.00 0.00 0.02 0.01 TRN-4 1 SB 12 43 1 1.75 43.67 0.55 0.00 0.32 0.17 0.03 TRN-4 1 SB 13 46 1 2.28 39.66 0.72 0.00 0.02 0.66 0.27 TRN-4 1 SB 14 50 1 0.01 1.48 0.00 0.00 0.00 0.01 0.01 TRN-4 1 SB 15 54 1 0.89 1.06 0.06 0.00 0.00 0.00 0.00 TRN-5 1 SB 16 59 1 24.49 23.17 0.00 0.00 0.00 1.93 0.00 TRN-5 1 SB 17 62 1 9.35 26.39 0.06 0.00 0.00 4.35 0.01 TRN-5 1 SB 18 67 1 14.87 30.31 0.34 0.00 0.00 0.36 0.01 TRN-6 1 SB 19 71 1 6.43 31.04 0.16 0.00 0.00 0.01 0.04 TRN-6 1 SB 20 75 1 7.50 9.86 0.33 0.00 0.00 0.06 0.26 TRN-6 1 SB 21 79 1 2.88 4.26 0.00 0.40 0.00 0.06 0.09 TRN-6 1 SB 22 83 1 1.01 10.34 0.12 0.00 0.00 0.31 0.01 TRN-6 1 SB 23 87 1 29.66 51.17 0.21 0.24 0.00 28.35 0.00 TRN-7 1 SB 24 90 1 0.79 22.75 0.14 0.00 0.00 0.05 0.01 TRN-7 1 SB 25 94 1 1.10 9.80 0.22 0.00 0.00 0.13 0.01 TRN-7 1 SB 26 98 1 5.72 30.68 0.11 0.00 0.00 0.11 0.05 TRN-7 1 SB 27 102 1 3.65 0.89 0.00 0.00 0.00 0.05 0.00 TRN-8 1 SB 28 105 1 6.26 105.85 0.36 0.00 0.00 0.08 0.00 TRN-8 1 SB 29 109 1 0.12 4.91 0.07 0.00 0.00 0.01 0.00 TRN-8 1 SB 30 113 1 0.95 0.45 0.36 0.60 0.00 0.03 0.00 

a 1 = Shallow Cold Saline, 2 = Mackenzie Influenced, 3 = Outer Shelf Arctic
6. ZOOPLANKTON AND WATER MASSES AT BOWHEAD WHALE

FEEDING LOCATIONS IN THE EASTERN BEAUFORT SEA

William B. Griffiths1, Denis H. Thomson 2 and Michael S.W. Bradstreet 2,3

Introduction

Bowhead whales of the Bering–Chukchi–Beaufort (BCB) stock winter in the Bering Sea and annually migrate to summering areas in the Beaufort Sea and Amundsen Gulf (Moore and Reeves 1993). It

has traditionally been assumed that bowheads, like other mysticete whales, feed primarily during summer

and autumn (Lowry 1993). If so, a primary reason for the annual migration to the Beaufort Sea would be

to reach preferred feeding areas. This would imply that summering areas are rich in food, and important

to the whales that travel a round-trip distance of several thousand kilometers to feed in those areas.

Many BCB bowhead whales arrive in Canadian waters in June. At that time at least part of the

population is present in the extreme eastern Beaufort Sea and Amundsen Gulf area, having traveled from Point

Barrow, Alaska, to Banks Island through offshore waters where there are cracks and leads in the ice (Braham

et al. 1984; Moore and Reeves 1993). By early to mid August, bowheads are present in inshore waters of the

Canadian Beaufort Sea, near the Bathurst and Tuktoyaktuk Peninsulas, Mackenzie Delta, and/or Yukon coast.

In some years, many bowheads remain in those areas until well into September (Richardson et al. 1987; Moore

and Reeves 1993). Behavioral observations indicate that they spend a considerable amount of time feeding in

the Canadian Beaufort Sea (Würsig et al. 1985, 1989; Dorsey at al. 1989; see also Chapter 12).

The eastern part of the Alaskan Beaufort Sea may represent a western extension of the late-summer

feeding range for bowhead whales. The westward migration of bowhead whales along the Beaufort Sea

coast starts in August, when many bowheads in the Canadian Beaufort Sea begin to move gradually west,

and when bowheads start to appear along the Alaskan coast. Feeding whales have been observed in the

eastern Alaskan Beaufort Sea during the late summer/early autumn period in each of the five years of this

study, though with widely varying frequencies in different years (Chapters 9, 12). The overall sighting

rates of bowheads in the eastern Alaskan Beaufort Sea during late summer and early autumn were substantially higher in 1990–2000 than in the 1980s, although widely variable among years (Chapter 9).

Bowhead whales and the closely related right whales are filter feeders. Their feeding apparatus

allows them to feed while moving through the water (Pivorunas 1979). They feed on zooplankton. Copepods were the dominant food items (by volume) in 13 of 21 stomach samples from bowhead whales harvested in the eastern Alaskan Beaufort Sea in autumn, while euphausiids were dominant in 5 of 21

stomachs; mysids and amphipods occasionally were important (Lowry and Sheffield, Chapter 18). In

contrast, stomachs of bowheads harvested in autumn some 500 km farther west, near Barrow, Alaska,

were dominated by euphausiids (Chapter 18).

 

1

 LGL Ltd., environmental research associates, 9768 Second St., Sidney, B.C. V8L 3Y8. Phone: 250-

656-0127; e-mail: bgriff@lgl.com

2

 LGL Ltd., environmental research associates, 22 Fisher St., POB 280, King City, Ont. L7B 1A6.

Phone: 905-833-1244. e-mail: dthomson@lgl.com

3

 Present address of MSWB: Bird Studies Canada, P.O. Box 160, Port Rowan, Ont. N0E 1M0. Phone:

519-586-3531; e-mail: mbradstreet@bsc-eoc.org
6-2 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

The purposes of this study were (1) to describe the characteristics of bowhead feeding areas in the

eastern Alaskan Beaufort Sea, with emphasis on the zooplankton and water masses found there; (2) to

determine whether bowhead whales feed in areas where zooplankton is concentrated; and (3) to determine

the quantity and kinds of zooplankton associated with feeding bowhead whales. This study was one part

of a broader investigation of the importance of the eastern part of the Alaskan Beaufort Sea for feeding by

bowhead whales. The study included field sampling during September of five years, 1985–86 and 1998–

2000 (Table 6.1). In addition, similar studies were conducted during 1980, 1981, 1985 and 1986 farther

east in the Canadian part of the Beaufort Sea, where most BCB bowhead whales summer. In this

analysis, we use results from both of these areas to document characteristics of bowhead feeding areas.

Methods

In the Eastern Alaskan Beaufort Sea, zooplankton was sampled at 21 stations where bowhead

whales were either observed feeding or where whales had been observed feeding the previous day (Table

6.1; Fig. 6.1A; Appendix 6.1). 4

 Feeding bowheads were not encountered during zooplankton sampling

in that area in September 1985 and 2000. Zooplankton was sampled at other stations along systematic

transects during all five years (see Griffiths and Thomson, Chapter 5). Aircraft-based observers guided

the sampling boat to feeding whales seen during aerial reconnaissance, systematic aerial surveys, or

systematic aerial observations of whale behavior, as described in Chapters 9–12. On 7 occasions, whales

were still present when the boat arrived on site, in which case sampling was conducted near bowheads

observed from the boat. In other cases, the whales had departed by the time the boat arrived and sampling

was conducted at locations transmitted to the boat by aerial observers. For each feeding station sampled,

a “control” station was also sampled about 8 to 10 km from the feeding station.

In the Canadian Beaufort Sea, zooplankton near feeding bowheads was sampled at a total of 16

stations (Table 6.1; Fig. 6.1B). Sampling in late August and early September of 1980, and August 1981,

was conducted during an BLM-sponsored study of the behavior of bowhead whales. The project aircraft

directed the boat to areas where whales were observed to be feeding. In 1985 and 1986, the boat sampled

in areas where bowhead whales were seen from the boat. In addition, in 1986, samples taken along

systematic transects at places where no whales were seen from the boat were later classified as being in

(or not in) one of two large areas―diameter 40 and 100 km―where whales were often observed during

concurrent aerial surveys by Ford et al. (1987). In 1988, zooplankton was sampled opportunistically at a

single whale feeding station off Shingle Point, along the Yukon coast, during a zooplankton study.

Temperature and Salinity Measurements

Vertical profiles of temperature and salinity were obtained at all systematic sampling stations,

except for the single station off Shingle Point in 1988. In the Canadian Beaufort, we used a Hydrolab

System 8000 in 1980–81 and a System 4021 in 1985, and an Applied Microsystems CTD-12 (CTD =

Conductivity–Temperature–Depth) in 1986. The CTD-12 was also used in the Alaskan Beaufort Sea in

 

4

 In 1986, the vessel that sampled in the eastern Alaskan Beaufort Sea also sampled near bowheads feeding off the

Yukon coast west of Herschel Island on two dates (4 and 7 Sept.; Fig. 6.1A). Sampling at these two stations 50 and

5 km into Canada employed the same methods as in Alaska, not the methods used farther east in the Canadian Beaufort Sea in 1986. Subsequent references to sampling in the eastern Alaskan Beaufort during 1986 include these two

stations. However, whales were seen from the boat at only 1 of these 2 stations—the one 5 km into Canada. Thus,

analyses of zooplankton at stations where whales were seen from the boat use data from Alaskan waters plus one

station ~5 km into Canada. All sampling described as being in the Canadian Beaufort was east of Herschel Island.
TABLE 6.1. Summary of sampling effort in the Canadian and Eastern Alaskan Beaufort Sea, showing the dates of samp

kind of guidance received by the vessels. “# Stations” refers to stations near bowhead whales; many additional stations wsampled.

Year Dates # Stations Vessel (LOA)1 Positioning Aerial guidance References

Canadian Beaufort Sea (east of Herschel Isl.)

1980 14-26 Aug 1 Ungaluk (14 m), zodiac NavSat, theodolite Search and direction Griffiths and Buchanan 1982

Imperial Sarpik (21 m) radar

1981 31Jul-25 Aug 3 Sequel (12.5 m ) Radar, NavSat Search and direction Griffiths and Buchanan 19821985 23-30 Aug 4 Sequel (12.5 m ) Radar, NavSat Surveys in area Bradstreet and Fissel 19861986 28 Aug-8 Sep 7 Arctic Ivik (67 m) NavSat Surveys in area Bradstreet et al. 1987

1988 12 Sep 1 Boston whaler (7 m) Dead reckoning None LGL Limited, Unpublished Data

Eastern Alaskan Beaufort Sea (and east to Herschel Isl.)2

1985 1-20 Sep 0 Annika Marie (13 m) NavSat Search and direction Griffiths et al. 1987; Johnson an

1986 4-19 Sep 6 Annika Marie (13 m) NavSat Search and direction Griffiths et al. 1987; Johnson an

1998 11-22 Sep 10 Annika Marie (13 m) GPS Search and direction Chapter 51999 16-22 Sep 5 Annika Marie (13 m) GPS Search and direction Chapter 52000 10-21 Sep 0 Annika Marie (13 m) GPS Search and direction Chapter 5

1 Length overall2 Locations are shown in Appendix 6.1
6-4 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

FIGURE 6.1. Locations of sampling near feeding bowhead whales (A) in and near Alaskan Beaufort Sea,

and (B) in Canadian Beaufort Sea from Herschel Island eastward. Details about each station are shown

in Appendices 6.1 and 6.3.
§6. Zooplankton: Characteristics of Bowhead Feeding Areas 6-5

1985–86, and a digital Sea-Bird SBE 19 was used in 1998–2000. Methods for deploying the instruments

and for retrieving and analyzing the data are described by Griffiths (Chapter 4) and Griffiths and Thomson (Chapter 5). They also describe the accuracy of the meters.

Zooplankton Sampling

1981–86 and 1998–2000.―In 1981, 1985, and 1998–2000, oblique and horizontal zooplankton

tows were made using a standard bongo assembly towed behind the boat. In 1986, standard bongo nets

were used in the Canadian Beaufort and for oblique and surface tows in the eastern Alaskan Beaufort.

However, horizontal tows in Alaska in 1986 were taken with a Tareq opening and closing bongo assembly. In all cases, the bongo frame was fitted with two 0.5 mm mesh, 0.61 m diameter, plankton nets and a

General Oceanics Inc. model 2030 flow meter. The horizontal tows were targeted to specific depths

where an echosounder showed an apparent zooplankton concentration. We used a 200 kHz Ross Fine

Line 250-M echosounder in the Canadian Beaufort Sea in 1981, 1985 and 1986, and Biosonics 200–430

kHz units (described later) in the eastern Alaskan Beaufort Sea in 1985–86 and 1998–2000. In 1985 and

1986, the depth of each horizontal tow in both the Alaskan and Canadian studies was recorded in real

time using an upward-looking depth sounder (Apelco Ranger model 1650) attached to the bongo frame.

In 1998–2000, the depth of the net during the tow was calculated using wire angle and the amount of wire

out. The actual depth profile of each 1998–2000 tow was determined later from data recorded with a

Wildlife Computers dive recorder (Model Mk7-S) attached to the bongo frame. In 1981, net sampling

depth was determined by measuring wire angle and the amount wire out.

In 1981, 1985–86 and 1998–2000, in all areas, horizontal tows lasted five minutes from the time

the net reached the desired depth. The net was lowered and retrieved slowly while the boat was moving

slowly to minimize sampling during ascent and descent. During the 1986 horizontal sampling in the

eastern Alaskan Beaufort, the net was open only when at the target depth.

Oblique tows were made by lowering the net to a depth near the bottom, raising it, and repeating

the process a second time, while the boat was moving. In areas deeper than 100 m, oblique tows were to

a maximum depth of 100 m.

The entire sample from one of the paired bongo nets was preserved in 10% formalin for analyses of

zooplankton biomass and numbers. Sub-samples from the other net were frozen and later sent to other

researchers for analyses of caloric, isotopic, and/or fatty acid content.

1980 and 1988.―Sampling in these two years was less systematic. In 1980, vertical tows were

taken using a 60 cm diameter plankton net with 0.5 mm mesh and an Inter Ocean model 313 flowmeter.

In 1988, a 0.5-mm mesh, 0.25-m diameter zooplankton net equipped with a General Oceanics Inc. model

2030 flow meter was used. Only shallow vertical tows and shallow horizontal tows were done in 1988,

given that the whales observed at this station were feeding at the surface.

Hydroacoustic Sampling

Eastern Alaskan Study Area.―Quantitative echosounder surveys were conducted between whale

feeding and control stations during September of 1986, 1999 and 2000, and along other transects in that

area during all five field seasons. Methods are described in Johnson and Griffiths (1990), Griffiths

(Chapter 4), and Griffiths and Thomson (Chapter 5). A single frequency (1998) or dual frequency (other

years) Biosonics echosounder was used.

Regression equations were developed to relate measured acoustic back scatter to matched data on

zooplankton biomass as determined from horizontal net tows (Johnson and Griffiths 1990; Griffiths,
6-6 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

Chapter 4). These equations were then used to estimate zooplankton biomass at other places and depths

where echosounder but no net-tow data were available. Chapter 4 describes regression equations applicable to the 200 kHz echosounder data from the Alaskan Beaufort Sea in 1985–86, and to the 430 kHz

echosounder data in 1999–2000. For 1998, the correlation between matched echosounder (430 kHz) and

net-tow data was too weak to allow confident use of echosounder data in estimating zooplankton biomass

(Chapter 4). Along each transect, zooplankton biomass was integrated for each 2-m (1985–86) or 1-m

(1999–2000) depth interval within each 2-min (~240 m) horizontal interval.

Canadian Beaufort Sea.―The echosounder used in this area in 1981, 1985 and 1986 was useful in

selecting depths for horizontal tows through water with high (and low) apparent biomasses of zooplankton. However, it did not provide quantitative estimates of zooplankton biomass.

Analyses of Zooplankton

The same person analyzed all samples from both regions. Samples were sieved through 163-μm

mesh Nitex and examined under a low-power binocular microscope. Animals from all oblique tows were

identified to species, and those from horizontal tows to major taxa. After blotting on dry filter paper, the

sorted animals were wet-weighed to the nearest mg on an Acculab electronic balance.

For large samples, large or rare organisms were removed, identified and weighed, and then the

small animals were sub-sampled with a Folsom Plankton Splitter or a Hensen–Stempel pipette and treated

as above.

For each sample, the flow meter reading recorded during the tow was used to calculate the volume

of water filtered. This information, in conjunction with wet-weights for the individual species or groups,

was used to determine the wet-weight biomass in mg/m3

. The opening and closing bongo net used for

horizontal tows in Alaska during 1986 underestimated biomass, as shown by matched tows with that net

and a standard bongo net. Therefore, results from 1986 horizontal tows with the opening and closing net

were corrected, i.e., scaled up, as described in Griffiths (Chapter 4).

Wet-weight data from oblique tows were used to calculate the average biomass of zooplankton in

the water column. Data from the horizontal tows were used to calculate wet-weight biomass at particular

depths at each station.

Results

Zooplankton Near Bowhead Whales in the Eastern Alaskan Beaufort Sea

Total Biomass.―Feeding whales were not observed in the eastern Alaskan Beaufort Sea in 1985

and 2000. Table 6.2 shows zooplankton biomass data from whale feeding locations in that area during

1986, 1998 and 1999. Average biomass in oblique tows, in the horizontal tow with highest biomass, and

in all horizontal tows were all higher in areas where bowheads were actively feeding, or where they had

been observed feeding but departed prior to arrival of the boat, than at nearby control stations.

Average biomass of zooplankton in 94 oblique tows taken at other locations in the eastern Alaskan

Beaufort Sea not shown in Fig. 6.1 or Table 6.2, and where whales were not observed, was 237 mg/m3

 for

the years 1985–86 and 1998–2000 (Chapter 5). This value from sampling along systematic transects was

very similar to the average at control stations (233 mg/m3

; Table 6.2).
§6. Zooplankton: Characteristics of Bowhead Feeding Areas 6-7

TABLE 6.2. Mean wet-weight biomass (mg/m3) of zooplankton at whale feeding vs.

matched control stations in the eastern Alaskan Beaufort Sea during September of 1986,

1998 and 1999. Shown separately are data from the horizontal tow at the depth with maximum biomass, from all horizontal tows, and from oblique tows at those stations. Also

shown are results from the subset of these stations where whales were actually observed

while sampling was being conducted.

Feeding Stations Control

Mean ± s.d. n Mean ± s.d. n

Horizontal Tows – Max. Biomass

 All Feeding Stations 1986 2393 1431 5 578 586 5

1998 443 154 10 446 220 8

1999 675 149 5 355 398 3

All 989 1072 20 512 385 14

 Whales Seen While Sampling 1986 2973 701 4 659 644 4

1998 771 1 144 1

1999 661 165 2 126 13 2

All 2006 1307 7 433 536 7

All Horizontal Tows

 All Feeding Stations 1986 1375 1366 14 367 453 10

1998 302 178 25 370 236 11

1999 334 341 11 234 327 5

All 610 876 50 343 340 26

 Whales Seen While Sampling 1986 2101 1170 9 400 507 8

1998 409 370 3 78 92 2

1999 302 342 5 90 46 4

All 1273 1246 17 265 407 14

Oblique Tows

 All Feeding Stations 1986 586 476 6 86 65 5

1998 304 163 10 283 141 8

1999 381 162 5 346 116 3

All 403 298 21 233 152 16

 Whales Seen While Sampling 1986 684 460 5 95 71 4

1998 234 1 71 1

1999 332 157 2 300 119 2

All 529 416 8 150 124 7

There were two kinds of whale feeding stations: (1) those where whales were observed from the

boat during or immediately before sampling was conducted, and (2) those where aerial observers had seen

feeding whales within the previous day, but the whales had departed before the boat arrived and began

sampling. Mean biomass in oblique tows and in the horizontal tow with the highest biomass at stations

where whales were observed during sampling were significantly higher than those at paired control stations (Table 6.3). Mean biomass in the same kinds of tows taken at stations where whales were observed

from the aircraft but not the boat were similar to those taken at paired control stations. Thus, only stations

at which bowheads were observed from the boat during or just before sampling can be considered to be

representative of feeding locations.
6-8 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

TABLE 6.3. Comparison of the mean biomass of zooplankton at paired whale feeding and control stations

in the Eastern Alaskan Beaufort Sea in 1986, 1998 and 1999. Values shown are mean ± s.d. (n). In the

3 cases where two feeding stations were paired to one control, the average of the two feeding-station

biomasses was used. Data were log transformed prior to analysis with a t-test.

Mean Biomass (mg/m3

)

Feeding Station Control Station t statistic P (one-tail)

Whales observed from boat

 Oblique Tows 543 ± s.d. 417 (7) 150 ± s.d. 124 (7) 2.14 0.038

 Horizontal Tows 2006 ± s.d. 1307 (7) 433 ± s.d. 536 (7) 5.39 0.001

Whales not observed from boat

 Oblique Tows 299 ± s.d. 159 (10) 305 ± s.d. 154 (10) 0.20 0.424

 Horizontal Tows 382 ± s.d. 152 (9) 500 ± s.d. 222 (9) –1.66 0.068

Differences in zooplankton biomass among years were mainly due to the abundance of copepods.

Copepods accounted for 715 of the 775 mg/m3

 of total zooplankton biomass in oblique tows at feeding

stations where whales were observed during or just before sampling in 1986 (n = 4), but only 82 of 104

mg/m3

 in 1998 (n = 1), and 226 of 328 mg/m3 in 1999 (n = 2) (Fig. 6.2). Likewise, in the horizontal tows

at the depth of maximum biomass, copepods constituted most of the biomass in 1986 but not to the same

extent in 1998 or 1999 (Fig. 6.3).

Species Composition.―The species composition of copepods at whale feeding stations was quite

different in each of the three years (Fig. 6.4; Table 6.4; see also Appendix 6.2 and 6.3). In 1986, the small

copepod Limnocalanus macrurus was by far the dominant zooplankter at whale feeding and control stations, as it was in inshore areas generally (Chapter 5). It was not found at the few 1998 or 1999 whale

feeding or control stations (Fig. 6.4; Table 6.4), or elsewhere in the study area in 1998–99 (Chapter 5).

In 1986, the large copepods Calanus glacialis and C. hyperboreus were uncommon at feeding and

control stations (Table 6.4). In 1998 and 1999, C. glacialis and C. hyperboreus were the major contributors to the average biomass in the water column and in horizontal tows at depth at both whale feeding

and control stations (Fig. 6.4; Table 6.4; Appendix 6.2).

Predatory cnidarians, ctenophores, and chaetognaths were major contributors to zooplankton biomass at both feeding and control stations in 1998 and 1999, but not in 1986 (Table 6.4).

In surface waters, although copepods, gelatinous zooplankters, and chaetognaths were typically

present each year, no one zooplankton group was the major contributor to the biomass in surface waters in

all years.

Nature and Extent of Feeding Areas as Shown by Echosounder Surveys.―In 1986 and 1999,

echosounder surveys were conducted at and between feeding and control stations. Acoustic backscatter

data were converted to estimates of biomass. No similar estimates were possible for 1998 (see “Methods”

and Chapter 4). Results are presented for situations where whales were actually observed feeding just

before or during zooplankton sampling. In 1986, there were three such cases, all located in shallow water

off the Kongakut Delta in the eastern portion of the study area. In 1999, three feeding stations and two

control stations were located in somewhat deeper water off Beaufort Lagoon in the central portion of the

study area (Fig. 6.1A).
§6. Zooplankton: Characteristics of Bowhead Feeding Areas 6-9

FIGURE 6.2. Mean biomass (mg/m3) of major zooplankton groups in oblique tows taken at all whale feeding and control stations in the eastern Alaskan Beaufort Sea during Sept 1986, 1998 and 1999. Includes

stations where whales were seen during zooplankton sampling.

Whale Feeding Stations Control Stations

1986 Water Column

0

100

200

300

400

500

600

700

800

 Mean Biomass (mg/m3

)

n = 4

Total = 775 mg/m3

1986 Water Column 

n = 4

Total = 95 mg/m3

1998 Water Column 

0

100

200

300

400

500

600

700

800

Mean Biomass (mg/m3

)

n = 1

Total = 148 mg/m3

1998 Water Column 

n = 1

Total = 71 mg/m3

1999 Water Column 

0

100

200

300

400

500

600

700

800

Cnidarians

Ctenophores

Copepods

Amphipods

Mysids

Euphausiids

Decapods

Chaetognaths

Fish

Other

Mean Biomass (mg/m3

)

n = 2

Total = 329 mg/m3

1999 Water Column 

Cnidarians

Ctenophores

Copepods

Amphipods

Mysids

Euphausiids

Decapods

Chaetognaths

Fish

Other

n = 2

Total = 300 mg/m3
6-10 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

FIGURE 6.3. Mean biomass (mg/m3) of major zooplankton groups in layer of maximum biomass at all

whale feeding and control stations in the eastern Alaskan Beaufort Sea during Sept 1986, 1998 and

1999.

Whale Feeding Stations Control Stations

1986 Maximum Horizontal Layer

0

500

1000

1500

2000

2500

3000

Mean Biomass (mg/m3

)

n = 4

Total = 2973 mg/m3

1986 Maximum Horizontal Layer

n = 4

Total = 659 mg/m3

1998 Maximum Horizontal Layer 

0

500

1000

1500

2000

2500

3000

Mean Biomass (mg/m3

)

n = 1

Total = 771 mg/m3

1998 Maximum Horizontal Layer

n = 1

Total = 148 mg/m3

1999 Maximum Horizontal Layer 

0

500

1000

1500

2000

2500

3000

Cnidarians

Ctenophores

Copepods

Amphipods

Mysids

Euphausiids

Decapods

Chaetognaths

Fish

Other

Mean Biomass (mg/m3

)

n = 2

Total = 688 mg/m3

1999 Maximum Horizontal Layer 

Cnidarians

Ctenophores

Copepods

Amphipods

Mysids

Euphausiids

Decapods

Chaetognaths

Fish

Other

n = 2

Total = 126 mg/m3
§6. Zooplankton: Characteristics of Bowhead Feeding Areas 6-11

FIGURE 6.4. Mean biomass (mg/m3) of zooplankton species in oblique tows representing the water column as a whole at all whale feeding and control stations in the eastern Alaskan Beaufort Sea, 1986, 1998

and 1999.

Whale Feeding Stations Control Stations

1986

0

100

200

300

400

500

600

700

800

Mean Biomass (mg/m3

)

n = 4

Total = 775 mg/m 3

1986

n = 4

Total = 95 mg/m3

1998

0

100

200

300

400

500

600

700

800

Mean Biomass (mg/m3

)

n = 1

Total = 148 mg/m3

1998

n = 1

Total = 71 mg/m3

1999

0

100

200

300

400

500

600

700

800

Calanus

hyperboreus

Calanus

glacialis

Limnocalanus

macrurus

Halitholus

cirratus

Cyanea

capillata

Aglantha 

digitale

Mertensia

ovum

Sagitta

elegans

Mysis litoralis

Thysanoessa

raschii

Parathemisto

libellula

Boreogadus

saida

Mean Biomss (mg/m3

)

n = 2

Total = 329 mg/m 3

1999

Calanus

hyperboreus

Calanus

glacialis

Limnocalanus

macrurus

Halitholus

cirratus

Cyanea

capillata

Aglantha 

digitale

Mertensia

ovum

Sagitta

elegans

Mysis litoralis

Thysanoessa

raschii

Parathemisto

libellula

Boreogadus

saida

n = 2

Total = 300 mg/m 3
1986 % of 1998 % of 1999 % of 1986a % of 1998 % of 1986 % of 1998 % of 1999 % of 

Species mg/m3 Total mg/m3 Total mg/m3 Total mg/m3 Total mg/m3 Total mg/m3 Total mg/m3 Total mg/m3 Total 

Copepods Calanus glacialis 3 0.5 125 41.0 40 10.5 12 2.1 168 48.0 6 7.0 72 26.0 16 4.7 

Calanus hyperboreus 1 0.2 24 8.0 227 54.6 4 0.7 14 4.0 3 3.7 26 9.0 134 40.0 Pseudocalanus minutus 4 0.7 4 1.0 <1 <1 3 0.5 5 1.0 1 0.9 4 1.0 <1 <1 Limnocalanus macrurus 496 84.7 0 0.0 0 0.0 534 90.2 0 0.0 25 29.4 0 0.0 0 0.0 

Cnidarians/ Ctenophores Aglantha digitale 10 1.7 15 5.0 21 5.5 1 0.1 21 6.0 16 18.3 11 4.0 6 1.7 

Aeginopis laurentii 0 0.0 0 0.0 0 0.0 0 0.0 0 0.0 0 0.0 0 0.0 23 6.6 Bougainvillea principis 0 0.0 9 3.0 0 0.0 0 0.0 5 1.0 0 0.0 0 0.0 0 0.0 Cyanea capillata 0 0.0 17 6.0 0 0.0 0 0.0 1 0.0 0 0.0 0 0.0 10 3.0 Mertensia ovum 3 0.5 14 5.0 22 5.7 3 0.2 10 3.0 1 1.1 27 9.0 41 12.0 Halitholus cirratus 9 1.5 0 0.0 0 0.0 4 0.3 0 0.0 2 2.1 0 0.0 0 0.0 

Amphipods

Parathemisto libellula 2 0.3 2 1.0 3 0.8 <1 <1 0 0.0 4 4.1 1 0.2 3 0.9 

Pteropods

Spiratella helicina 2 0.3 0 0.0 0 0.0 <1 <1 0 0.0 4 4.3 0 0.0 0 0.0 

Mysids

Mysis litoralis 31 5.3 19 6.0 0 0.0 11 0.9 7 2.0 0 0.0 13 5.0 1 0.4 

Euphausiids

Thysanoessa rachii 0 0.0 2 0.7 2 0.5 <1 <1 2 0.6 0 0.0 1 0.3 14 4.2 

Chaetognaths

Sagitta elegans 2 0.3 65 22.0 32 8.4 3 0.2 97 27.0 2 2.0 84 30.0 74 21.4 Eukrohnia hamata 0 0.0 0 0.0 8 2.1 0 0.0 0 0.0 0 0.0 0 0.0 2 0.6 

Fish Larvae

Boreogadus saida 3 0.4 1 0.5 7 1.8 0 0.0 11 3.0 5 5.8 35 12.0 8 2.4 Other Species 20 3.4 7 2.3 19 4.9 32 5.2 12 3.4 17 19.9 9 3.2 14 4.0 Total Biomass 586 304 381 607 353 86 283 346 Number of tows 6 10 5 3 7 5 8 3 

a For 1986, horizontal tow data have been corrected to allow for underestimation by the opening and closing net.

TABLE 6.4. Species composition of mean zooplankton biomass (mg/m3) in oblique and horizontal tows at whale feeding a

eastern Alaskan Beaufort Sea and adjacent Yukon Coast. Samples from all horizontal tows taken in 1999, and from stations in 1986, were not identified to species (see also Appendix 6.2). 

Whale Feeding Stations Control Station

Water Column as a Whole Horizontal Tows at Depth Water Column as a Whole 
§6. Zooplankton: Characteristics of Bowhead Feeding Areas 6-13

In 1986, estimated zooplankton biomass along all three transects decreased between the whale

feeding and control stations. At all three whale feeding stations, a thick layer of zooplankton with an

estimated (“acoustic”) biomass of 500–2200 mg/m3

 extended from depth 4–8 m to the bottom (Fig. 6.5,

6.6, 6.7). At control stations there was only a thin layer with estimated biomass about 400 to 600 mg/m3

at depths 17–20 m. There was good correspondence between acoustic and net biomass at both the feeding

and control stations (Fig. 6.5–6.7). Layers of concentrated zooplankton extended at least 2–6 km from the

whale feeding stations in the direction of the control stations.

In 1999, a single layer of concentrated zooplankton, about 10 to 20 m thick, extended from depths

of 25 to 30 m most or all of the way to the bottom at both feeding and control stations (Fig. 6.8, 6.9). Net

sampling showed that zooplankton biomass within this layer was 350-700 mg/m3 (Table 6.2; Fig. 6.8,

6.9). In 1999, there was little change in zooplankton biomass, as estimated from echosounder data, along

transects between feeding and control stations. The depth-averaged horizontal distribution of biomass

was generally uniform, and biomass within the layer of maximum biomass was also fairly consistent

along the transects.

Zooplankton Near Bowhead Whales in the Canadian Beaufort Sea

In the Canadian Beaufort Sea east of Herschel Island, there were five years when sampling was

conducted where bowhead whales were observed prior to or during sampling (Fig. 6.1B; Appendix 6.3).

Such sampling occurred off the Tuktoyaktuk Peninsula and Mackenzie Delta in 1980, 1981 and 1986, and

along the Yukon coast in 1985, 1986 and, in a limited way, 1988.

In 1980, mean biomass in 24 vertical tows in a general area off the Mackenzie Delta where aerial

observers had seen whales feeding was 632 ± s.d. 491 mg/m3

. This is about the same as the biomass of

542 ± 221 mg/m3

 found in 6 oblique tows at stations where whales were observed within 1 km of the boat

in 1985 and 1986 (see below). For 1980, no comparable data were obtained from locations without bowheads. However, in 1985–86, mean biomass in 49 oblique tows at locations in the Canadian Beaufort Sea

where whales were not observed from the sampling vessel was 138 ± 116 mg/m3

. If 1980 “no whale”

values were similar to those in 1985–86, average biomass in the water column near feeding bowheads in

1980 was ~4 times higher than at stations where bowheads were not observed to be feeding.

In 1981, aerial observers saw 30 bowheads surface-feeding near the boat at a location off Richard's

Island on 18 August. The whales were feeding intensively an estimated 2–3 m below the surface, frequently in echelon formation (Würsig et al. 1985). The echosounder showed a concentration of zooplankton in a band at depths 1–4 m. Biomass in three surface tows was 216 ± s.d. 86 mg/m3

, and was predominantly Calanus hyperboreus. This was a relatively high biomass for surface waters; in 1981, biomass in

33 surface tows at 11 stations where no whales were observed did not exceed 21 mg/m3

. However, at the

18 August location, biomass was notably higher, 885 ± 268 mg/m3

 in 3 tows at 15 m depth, than in the

near-surface waters where the bowheads fed intensively. The zooplankton at 15 m depth was also predominantly Calanus hyperboreus. The maximum biomass in horizontal tows at depth at two other stations where whales were observed to be feeding either below the surface or near the bottom was 1405 ±

937 (n = 3 tows) and 807 mg/m3

 (Appendix 6.3). Average maximum biomass in horizontal tows at each

of 10 stations where no bowheads were observed was 298 ± 254 mg/m3

.

In 1985, average maximum biomass of zooplankton at four stations where whales were observed

from the boat off the Yukon Coast was 1684 ± s.d. 621 mg/m3

. The biomass in 17 horizontal tows taken

within layers of zooplankton at 10 stations where bowheads were not observed was 213 ± 232 mg/m3

.
6-14 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

FIGURE 6.5. Echosounder-based estimates of zooplankton biomass off the Kongakut Delta, Alaska, at

whale feeding station 86-5, at control station 86-6, and along Transect E between them. (A) Vertical distribution at stations, (B) depth-averaged (below) and maximum (above) biomass along transect between

stations, and (C) patchiness between stations. Based on 200 kHz echosounder data, 5 Sept 1986.

0

1 0

2 0

3 0

4 0

5 0

Water Depth (m)

0

1 0

2 0

3 0

4 0

5 0

T r ansectE

< 1 0 0 m g /m 3

1 0 0 -3 0 0 m g /m 3

3 0 0 -5 0 0 m g /m 3

5 0 0 -7 0 0 m g /m 3

7 0 0 -1 0 0 0 m g /m 3

> 1 0 0 0 m g /m 3

0 1 2 Km

St6 St5

Whale Feeding St. 5

0

5

10

15

0 400 800 1200 1600

Estimated Biomass (mg/m3)

Depth (m)

Control St. 6

0

5

10

15

20

25

30

0 400 800 1200 1600

Estimated Biomass (mg/m3)

Depth (m)

Control St. 6 to Whale feeding St. 5

0

500

1000

1500

2000

2500

3000

3500

1 3 5 7 9 11 13 15 17 19 21 23 25 27 29

Time (2 min intervals = approximately 7 km)

Estimated Biomass 

(mg/m3

)

Mean Water Column Biomass Maximum Biomass

B

C

A
§6. Zooplankton: Characteristics of Bowhead Feeding Areas 6-15

FIGURE 6.6. Echosounder-based estimates of zooplankton biomass off the Kongakut Delta, Alaska, at

whale feeding station 86-7, at control station 86-8, and along Transect F between them. Otherwise as in

Figure 6.5. Based on 200 kHz echosounder data, 6 Sept 1986.

0

1 0

2 0

3 0

4 0

5 0

Water Depth (m)

0

1 0

2 0

3 0

4 0

5 0

T r ansectF

St7 Offshore

< 1 0 0 m g /m 3

1 0 0 -3 0 0 m g /m 3

3 0 0 -5 0 0 m g /m 3

5 0 0 -7 0 0 m g /m 3

7 0 0 -1 0 0 0 m g /m 3

> 1 0 0 0 m g /m 3

0 1 2 Km

Whale Feeding St. 7

0

2

4

6

8

10

0 500 1000 1500 2000 2500

Estimated Biomass (mg/m3)

Depth (m)

Control St. 8

0

5

10

15

20

25

0 500 1000 1500 2000 2500

Estimated Biomass (mg/m3)

Depth (m)

Whale Feeding St.7 to Control St. 8

0

500

1000

1500

2000

2500

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22

Time (2 min intervals = approximately 5 km)

Estimated Biomass (mg/m3

)

Mean Water Column Biomass Maximum Biomass

B

A

C
6-16 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

FIGURE 6.7. Echosounder-based estimates of zooplankton biomass off the Kongakut Delta, Alaska, at

whale feeding station 86-12, at control station 86-13, and along Transect J between them. Otherwise as

in Figure 6.5. Based on 200 kHz echosounder data, 7 Sept 1986.

Whale Feeding St. 12

0

5

10

15

20

25

0 400 800 1200 1600

Estimated Biomass (mg/m3)

Depth (m)

Control St. 13

0

5

10

15

20

25

0 400 800 1200 1600

Estimated Biomass (mg/m3)

Depth (m)

Control St. 13 though Whale Feeding St. 12 and on into shore

0

1000

2000

3000

4000

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28

Time (2 min intervals = approximately 7 km)

Estimated Biomass 

(mg/m3

)

Mean Water Column Biomass Maximum Biomass

A

B

C

0

1 0

2 0

3 0

4 0

5 0

Water Depth (m)

0

1 0

2 0

3 0

4 0

5 0

T ransectJ

St1 3 Shore

< 1 0 0 m g /m 3

1 0 0 -3 0 0 m g /m 3

3 0 0 -5 0 0 m g /m 3

5 0 0 -7 0 0 m g /m 3

7 0 0 -1 0 0 0 m g /m 3

> 10 00 m g /m 3

0 1 2 Km
§6. Zooplankton: Characteristics of Bowhead Feeding Areas 6-17

FIGURE 6.8. Echosounder-based estimates of zooplankton biomass off Beaufort Lagoon, Alaska, at

whale feeding Station 1, at control Station 2, and along the transect between them. Otherwise as in Figure 6.5. Based on 430 kHz echosounder data, 16 Sept 1999.

Whale Feeding St. 1 Control St. 2

Whale Feeding St. 1 to Control Station 2

0

250

500

750

1000

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32

Time (2 min intervals = approximately 8 km)

Estimated Biomass (mg/m3

)

Mean Water Column Biomass Maximum Biomass

B

0

10

20

30

40

50

0 250 500 750 1000

Estimated Biomass (mg/m3)

Depth (m)

A

0

10

20

30

40

50

0 250 500 750 1000

Estimated Biomass (mg/m3)

Depth (m)

C
6-18 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

FIGURE 6.9. Echosounder-based estimates of zooplankton biomass off Beaufort Lagoon, Alaska, at

whale feeding Stations 3 and 4, control Station 5, and along the transects between them. Otherwise as in

Figure 6.5. Based on 430 kHz echosounder data, 17 Sept 1999. 

Whale Feeding St. 3 Whale Feeding St. 4 Control St. 5

Whale Feeding St. 3 to Whale Feeding St. 4

0

250

500

750

1000

1 2 3 4 5 6 7 8 9 10 11 12 13

Time (2 min intervals = approximately 3 km)

Depth (m)

Mean Water Column Biomass Maximum Biomass B

Whale Feeding St. 4 to Control St. 5

0

250

500

750

1000

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42

Time (2 min intervals = approximately 10 km)

Depth (m)

Mean Water Column Biomass Maximum Biomass

0

10

20

30

40

50

0 250 500 750 1000

Estimated Biomass (mg/m3)

Depth (m)

A

0

10

20

30

40

50

0 250 500 750 1000

Estimated Biomass (mg/m3)

Depth (m)

0

10

20

30

40

50

0 250 500 750 1000

Estimated Biomass (mg/m3)

Depth (m)

C
§6. Zooplankton: Characteristics of Bowhead Feeding Areas 6-19

Corresponding results from oblique tows were 562 ± 388 mg/m3 with whales (n = 2 tows) and 161 ± 189

mg/m3

 without whales (n = 14 tows).

In 1986, mean zooplankton biomasses in oblique tows, horizontal tows at depth, and surface tows

were all much higher at stations sampled near whales than at stations where the closest whales sighted from

the ship were >1 km away or where no whales were observed from the ship (Table 6.5). Mean biomass in

the horizontal tow with the highest biomass for that station was over 6 times greater within 1 km of whales

than at stations where no whales were seen. These samples were taken off the Tuktoyaktuk Peninsula and

off the Yukon coast (Fig. 6.1B). During sampling, the echosounder provided guidance to the depth of

maximum biomass at only two stations with whales <1 km away. Therefore, the average for horizontal

tows may underestimate the biomass available to whales in 1986. Maximum biomasses at the locations

where echosounder guidance was available were 1543 and 770 mg/m3

 (mean 1157 mg/m3).

In 1988, sampling near bowheads feeding at the surface off the Yukon coast revealed the highest

biomass of zooplankton recorded during all the sampling summarized here (Appendix 6.3). Biomass was

close to 5 g/m3

, and dominated by Limnocalanus macrurus.

There were some difference in species composition in samples taken at whale feeding stations in

the Canadian Beaufort Sea among locations and years (Table 6.6, Appendix 6.3):

• Off the Tuktoyaktuk Peninsula, the copepod Calanus hyperboreus was the dominant contributor to zooplankton biomass in samples taken at 4 of 5 stations. At the other station in that

area, the hydrozoan Aglantha digitale was the dominant contributor.

• Off Richards Island, the cnidarians Halitholus cirratus and Euphysa flammea were the dominant contributors to total zooplankton biomass at all 5 whale feeding stations in 1980. In 1981,

the copepod C. hyperboreus dominated at all three whale feeding stations. Mysids (Mysis

litoralis) were also a dominant contributor (18% of total biomass) at one 1981 station where

bowheads were observed to be bottom feeding.

• Off the Yukon coast, most of the high biomass collected in both 1985 and 1986 was attributable to the high biomass of the copepod Limnocalanus macrurus. At one 1986 station, euphausiids (Thysanoessa raschii and T. inermis) were also major contributors (20% of total biomass). 

TABLE 6.5. Mean biomass (mg/m3) of zooplankton in tows taken at stations in the Canadian Beaufort Sea

east of Herschel Isl. during 1986, distinguishing stations where whales were seen from the ship <1 km

away (4 stations) and >1 km away (2 stations), and stations where no whales were seen from the ship.a

The “no whales seen from ship” stations are categorized as being within or outside two large areas where

whales were observed from the air (Ford et al. 1987) at some time during the 11-day study (5 and 35 stations, respectively).

Whales <1 km Whales >1 km Seen from air No whales

Mean ± s.d. n Mean ± s.d. n Mean ± s.d. n Mean ± s.d. n

Surface tows 100 167 4 6 6 3 11 25 12 6 7 33

Horizontal towsb 672 489 7 53 - 1 123 89 12 101 112 28

Oblique tows 532 175 4 219 90 3 144 36 4 130 70 35

a

 Excludes feeding stations in Canadian waters west of Herschel Island (n = 2) that were sampled during the 1986

eastern Alaska study.

b

 Considering, for each station, the horizontal tow with the highest biomass; echosounder guidance to the depth of

maximum biomass was available for 2 of 4 stations <1 km from whales and for most of the other stations.
6-20 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

TABLE 6.6. Dominant zooplankton groups and species at whale feeding stations in the Canadian Beaufort

Sea by area and year.

Location Year

No. of

Feeding

Stations

Dominant

Group

No. Stns

Where

Dominant

% of Total

Biomass

Dominant

Species

% of

Total

Biomass

Copepods 4 71 to 87 Calanus hyperboreus 55 to 76 Tuktoyaktuk

Peninsula

1986 5

Cnidarians 1 39 Aglantha digitale 34

1980 5 Cnidarians 5 46 to 94 Halitholus cirratus 13 to 39

Euphysa flammea 7 to 55

Richards Island

off Mackenzie

Delta

1981 3 Copepods 3 64 to 92 Calanus hyperboreus 39 to 82

Yukon Coast 1985 4 Copepods 4 92 to 99 Limnocalanus macrurus 77 to 97

1986 2 Copepods 2 61 to 91 Limnocalanus macrurus 26 to 86

Physical Oceanography

Example CTD data collected at whale-feeding and control stations in the eastern Alaskan and Canadian Beaufort Sea are shown in Figure 6.10. (Station numbers in this Figure are as assigned in the

original reports; they appear in parentheses to the right of the corresponding station descriptions in

Appendix Table 6.3.) Appendices 6.4 and 6.5 show additional Alaskan data.

Eastern Alaskan Beaufort Sea.―Griffiths and Thomson (Chapter 5) described two water masses

(in depths <50 m) that were present in the eastern Alaskan Beaufort Sea during the five years of the study.

The two water masses were a Shallow Cold Saline water mass and a generally more offshore water mass

influenced by the Mackenzie River. The presence or absence of Mackenzie River water defined the properties of these two water masses. Its influence differed among years (Chapter 5). The main characteristic

of the Shallow Cold Saline water mass was the absence of a strong influence of Mackenzie River water

and the absence of sharp discontinuities in the vertical distribution of temperature and salinity (pycnoclines). The relatively cold temperatures and high salinities were fairly uniform from surface to bottom.

The Mackenzie-Influenced water mass, farther offshore, was characterized by the strong presence of

Mackenzie River water at the surface, overlying water that was generally colder and more saline than that

of the Shallow Cold Saline water mass.

Water mass characteristics varied among the three years when feeding whales were observed in the

study area and did not always correspond directly to the water masses described above. In 1986, all six

whale-feeding stations were in shallow water with depths of 7 to 22 m and the five control stations in

slightly deeper depths of 15 to 27 m (Fig. 6.10A,B; Appendix 6.4). The water was cooler and more saline

at the whale-feeding stations than at control stations, and was characterized by a relatively warm brackish

surface layer of varying thickness, overlaying cooler more saline water. All stations had sharp temperature and salinity discontinuities with differences in temperatures and salinities between surface and bottom water of ~4°C and about 5 to 6 psu. This water mass was similar to the generally offshore

Mackenzie-Influenced water mass described above. However, it was only present in the shallow nearshore region in the southeastern corner of the study area when feeding bowheads were observed, and

appeared to have moved in from along the nearshore area of the Yukon Coast.
§6. Zooplankton: Characteristics of Bowhead Feeding Areas 6-21

FIGURE 6.10. Examples of temperature–salinity profiles in Canadian and eastern Alaskan Beaufort Seas

in various years and circumstances. Also shown is biomass in mg/m3

 at each station based on H, horizontal tow, or O, oblique tow. In each case, temperature (left line in lower part of each plot, blue)

decreases with increasing depth; salinity (right line, red) increases or (in E) remains nearly constant.

Canadian Beaufort Sea 1986

Off Richards Island and

 Tuktoyaktuk Peninsula

1986 Stn 5; Feeding; H- 3023 mg

Eastern Alaskan Beaufort Sea

1986 Stn 6 Control; H - 98 mg

Eastern Alaskan Beaufort Sea

1999 Feeding Stn 3; H 886 mg 1999 Control Stn 5; H - 135 mg

Salinity

Off Richards Island and Tuktoyaktuk Peninsula

Salinity

10 16 22 28 34

Stn 2 H - 1543 mg

0

10

20

30

40

50

A B

D E F

C

H I

1981 Stn N 11; H - 1405 mg

Temperature

Salinity

G

Temperature Temperature Temperature

Temperature Temperature Temperature

Temperature

Salinity

Temp. Salinity
6-22 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

In 1998, the whale-feeding and control stations varied widely in depth (10 to 40 m) and were

located in both the shallow cold saline and the more offshore Mackenzie-influenced water masses described above. Seven of 10 feeding and 6 of 8 control stations were in the Shallow Cold Saline water mass,

while 3 feeding and 2 control stations were in the Mackenzie-Influenced water mass (Fig. 6.10G; Appendix 6.5). Strong pycnoclines were found at 3 of 10 whale feeding and 2 of 8 control stations in 1998 (Fig.

6.10G; Appendix 6.5). Vertical temperature and salinity discontinuities were not sharp at the other 1998

feeding stations or at most (6 of 8) 1998 control stations.

In 1999, only the Shallow Cold Saline water mass was present within the area studied; it extended

offshore to at least the 50 m contour. All 1999 whale-feeding and control stations were located in the

deeper waters (depths 40 to 48 m) of this water mass (Fig. 6.10D,E; Appendix 6.5). Temperature and

salinity discontinuities were present at 3 of 5 whale feeding stations but they were not as sharp as those

seen in 1986 and 1998. There were no temperature and salinity discontinuities at 2 of the feeding or any

of the control stations.

Canadian Beaufort Sea.―In 1985 and 1986, waters in nearshore areas along the Yukon coast

were overlain by relatively warm freshened water of Mackenzie River origin (e.g., Fig. 6.10I). Very high

biomasses of zooplankton were found in this area (Appendix 6.3). In 1986, sampling was also conducted

of the Tuktoyaktuk Peninsula where strong pycnoclines were not evident (e.g., Fig. 6.10H). Biomass of

zooplankton was low in this area.

In 1980 and 1981, there were vertical temperature and salinity discontinuities in areas sampled near

feeding bowheads (e.g., Fig. 6.10F,G). Zooplankton biomass was high in these areas (Appendix 6.3).

At all whale-feeding stations in both the Canadian and Alaskan Beaufort seas, the highest biomass

of zooplankton was taken in the cold saline water under a warm freshened layer. High biomasses of zooplankton were never taken in the warm freshened layer.

Discussion

Local and Traditional Knowledge of Bowhead Feeding

Whale hunters and other residents of Kaktovik, within the present eastern Alaskan study area,

know much about the seasonal and geographic patterns in bowhead use of that area and adjacent Canadian waters, and of the general activities of the whales (see Chapter 2 and Annex B). They also know that

the stomachs of most bowheads harvested near Kaktovik contain zooplankton, and believe that the area

near Kaktovik is important for feeding. In one case, many large shrimp-like organisms were released

from the mouth when a harvested bowhead was pulled up onto shore. A few local residents mentioned

that they sometimes see concentrations of “krill” in or on the water near bowheads, with amounts of krill

varying from year to year. Some residents commented that, when they see food concentrations and bowhead whales, these tend to be near water-mass boundaries or off river mouths. However, the majority of

the local residents report that they rarely can distinguish feeding from other activities when they see

whales at sea. This is not surprising, given the low vantage points available from small boats, ice, and

shore, and the fact that bowheads seen from a moving boat are likely to be avoiding the boat even if they

were originally feeding before the boat approached.

Zooplankton Biomass Available to Whales

Bowhead whales feed in concentrations of zooplankton in the both the eastern Alaskan and

Canadian Beaufort Sea. As expected, zooplankton biomass in both regions was higher at stations where
§6. Zooplankton: Characteristics of Bowhead Feeding Areas 6-23

bowhead whales were present than at routine sampling stations where whales were not present (Tables

6.2, 6.5). Furthermore, zooplankton biomass was higher when whales were present during sampling than

at stations where whales had been sighted from the aircraft recently, but were no longer present when the

boat began sampling (Tables 6.2, 6.3, 6.5, 6.7). The sea is a dynamic environment where conditions

change rapidly, and it appears that concentrations of zooplankton used by bowhead whales can be

ephemeral and difficult to find without direct observation of the whales.

To characterize zooplankton availability at places where bowheads choose to feed, we considered

horizontal plankton tows taken at the depth of maximum biomass at locations where bowheads were

observed feeding. There were 17 locations where such tows were guided to layers of concentrated zooplankton by an echosounder (or taken near the surface in concentrations of zooplankton) and where

bowheads were observed <1 km from the sampling boat. These locations were in the Canadian Beaufort

Sea in 1981, 1985, 1986 and 1988 (n = 10), and in the eastern Alaskan Beaufort Sea in 1986, 1998 and

1999 (n = 7). These are the stations designated “whales observed from boat” in the last column of

Appendix 6.3. Other samples were not included because there was no certainty that conditions during

sampling were similar to those occurring earlier when bowheads had been present, or were similar to

those at locations of whales visible >1 km from the boat. In addition, it was obvious that, in order to

document the maximum biomass available to whales, reliable echosounder data were needed to guide the

net to layers of zooplankton that were sometimes quite thin.

TABLE 6.7. Mean biomass in all horizontal tows, horizontal tows with highest

biomass at each station, and oblique tows, distinguishing routine stations,

stations where bowheads were observed from aircraft and/or sampling boat,

and stations where whales were observed from boat immediately before and/or

during sampling. Includes samples collected in 1980 (vertical tow only), 1981

(horizontal only), and 1985, 1986, 1998 and 1999 in Eastern Alaskan and Canadian Beaufort Sea. Routine sampling was conducted at stations along broadscale transects in the same manner as that at whale feeding stations; for

details, see Chapter 5 (for Alaska) and references listed in Table 6.1.

Biomass mg/m3

Mean ± s.d. n

All Horizontal Tows

All Stations - No Whales 242 315 313

 All Feeding Stations 589 829 68

 Whales Seen While Sampling 891 1058 35

Horizontal Tows – Maximum Biomass

All Stations - No Whales 360 380 165

 All Feeding Stations 975 1000 23

 Whales Seen While Sampling 1841 1226 17

Oblique Towsa

All Stations - No Whales 230 173 173

 All Feeding Stations 467 356 36

 Whales Seen While Sampling 529 416 8

a

 includes vertical tows made in 1980.
6-24 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

At these 17 whale-feeding stations, mean biomass in the horizontal tows and one vertical tow with

the highest biomass was 1841 ± s.d. 1226 mg/m3 (n = 17). The frequency distribution of biomass at these

stations was

mg/m3: 500-1000 1000-2000 2000-3000 3000-4000 4000-5000

No. samples: 5 5 4 2 1

The 1980 vertical tow with a biomass of 1153 mg/m3 was included because no horizontal tows were taken

at this whale-feeding station. Vertical tows would tend to underestimate the zooplankton biomass

available to whales so the 1153 mg/m3

 value can be viewed as conservative. The lowest biomass in any

of these tows was 545 mg/m3

. For 4 of 17 stations, the highest biomass measured was 771–807 mg/m3,

and for 12 of 17 stations the highest value was ≥1000 mg/m3

. Biomasses of ~800 mg/m3, as determined

by our horizontal tow method, may represent the feeding threshold for bowhead whales, i.e., the minimum biomass for economical feeding.

Although echosounders were used to guide the net to layers of zooplankton at these 17 whale feeding stations, at only 6 stations (4 from 1986 and 2 from 1999), all in the eastern Alaskan study area, were

both net zooplankton samples and acoustic estimates of zooplankton biomass available:

Kongakut

Delta

1986

Kongakut

Delta

1986

Kongakut

Delta

1986

Clarence

Lagoon

1986

Beaufort

Lagoon

1999

Beaufort

Lagoon

1999

Max. net tow biomass 3023 2887 2137 3847 545 778

Max. acoustic biomass 970 2131 1090 1365 650 774

A comparison of the maximum net tow biomass with the maximum estimate of acoustic biomass at the

corresponding stations suggests that the net did sample within the layer of highest zooplankton biomass at

each station. At 4 of 6 stations, the net detected an appreciably higher biomass than that estimated via the

echosounder for the depth of maximum biomass. This suggests that, at locations of high biomass, the

echosounder-based estimates may have tended to underestimate the actual maximum zooplankton biomass available, at least in 1986. As discussed in Chapters 4 and 5, even with guidance by an echosounder

to the depth of maximum biomass, the net sampling is also expected to underestimate the actual

maximum biomass some of the time.

Zooplankton biomass at the surface is generally lower than biomass in the water below (Chapter 5).

However, bowheads are sometimes seen swimming at or near the surface with their mouths open and with

water streaming from the corners of their mouths (Würsig et al. 1985; also Chapter 12). The very high

ratio of the surface area of the baleen to the cross-sectional area of the mouth opening (Thomson, Chapter

22) may reduce drag and enable bowheads to feed while swimming at the surface on the typically low

biomass of zooplankton in near-surface waters of the Beaufort Sea. During the unusually intensive nearsurface feeding observed off Richard's Island in the Canadian Beaufort Sea in 1981, the near-surface

zooplankton biomass was 216 ± s.d. 86 mg/m3

 (n = 3). At a whale feeding location off King Point

(Yukon) in 1988, a vertical tow near the surface contained almost 5000 mg/m3

, mainly Limnocalanus.

Several studies of the anatomically similar North Atlantic right whale (Eubalaena glacialis) have

reported data on zooplankton numbers or biomass collected at whale feeding stations (Wishner et al.

1988, 1995; Mayo and Marx 1990; Murison and Gaskin 1989; Kann and Wishner 1995; Beardsley et al.

1996; Woodley and Gaskin 1996). All of those studies have identified the copepod Calanus finmarchicus, particularly the larger copepodite IV and V stages, as the main food item for the right whales near

the eastern Canadian and northeastern U.S. coasts. Some of the studies reported their results as number of

organisms/m3

, while others reported the results as both numbers and biomass.
§6. Zooplankton: Characteristics of Bowhead Feeding Areas 6-25

In the Bay of Fundy, mean biomass of zooplankton in vertical tows in grids where right whales

were observed was 3566 ± s.e. 449 mg/m3

 (wet weight) in 1983, and 2639 ± s.e. 295 mg/m3 in 1984

(Murison and Gaskin 1989). They estimated that the right whale feeding threshold was ~170 mg/m3

 dry

weight (≈1133 mg/m3

 wet weight). In the same area, average density of zooplankton in the water column

(160 to 197 m deep) in areas where right whales were sighted from a sampling boat was 1139

organisms/m3

 (Woodley and Gaskin 1996), which may have translated to ~680 mg/m3 wet weight. [Most

were Calanus finmarchicus (97%) and most of these were 2–4 mm in length. Average biomass of single

copepods of this size in Wishner et al.’s (1995) samples was ~0.6 mg.] All of these values are averages

for the water column, and probably underestimate the amount of food available to feeding whales; as

evident in our results for bowhead feeding sites in the Beaufort Sea, densities and biomasses in layers of

concentrated zooplankton may have been much higher.

More specific estimates of the amount of food potentially available to right whales have been

reported from two occasions:

(1) In Cape Cod Bay, right whales were observed to be surface feeding in zooplankton densities of

6540 organisms/m3

 (Mayo and Marx 1990; ~3924 mg/m3 based on data in Wishner et al. 1995). Biomass

in surface tows where no whales were observed was 870 organisms/m3

 (~522 mg/m3). Surface feeding

began at a threshold value of ~1000 organisms/m3

 or ~600 mg/m3 (Mayo and Marx 1990).

(2) Beardsley et al. (1996) followed two feeding right whales and sampled zooplankton with an

echosounder and a MOCNESS plankton sampler. Highest biomass in horizontal tows was in the upper 10

to 20 m in a patch with mean biomass of 6000 mg/m3

 and a maximum biomass of 28,000 mg/m3. The

whale reversed direction and swam back into this dense patch when maximum biomass in the water

dropped to 1000 to 3000 mg/m3

. One whale was observed to be skim feeding at the surface in a zooplankton concentration of 256,000 mg/m3

!

Kann and Wishner (1995) and Wishner et al. (1995) did not find any difference in biomass in

vertically-stratified oblique tows in areas where whales were observed from the air within 24 h of

sampling vs. areas where whales were not seen. When mean biomass in the water column was compared

using a more rigorous definition of a whale feeding area (whales seen <1 km from sampling boat), biomass was significantly higher than average in one year, but not another.

The results obtained in the present study and in the right whale studies described above indicate

that an area can only be described as a feeding area when feeding whales are in the immediate vicinity.

To estimate the amount of food available to whales, sampling must be conducted close to feeding whales,

and an echosounder is needed to guide the net to the layers of maximum biomass in the water column

and/or to estimate biomass via quantitative echosounding methods.

Feeding thresholds of bowhead whales appear to be lower than those of the closely-related right

whale. Plankton production and biomass is lower in the Beaufort Sea than in temperate waters (MacDonald et al. 1987). Bowhead whales may have lower energetic requirements than those of other whales.

They grow very slowly and reach maturity later than other baleen whales, including right whales (Koski

et al. 1993; George et al. 1999). In addition to having lower requirements for growth than do other

species, the metabolic rate of bowheads may be lower than that of other species (George et al. 1999;

Thomson, Chapter 22). Bowheads have apparently adapted their energetic requirements, physical adaptations for feeding, and feeding threshold to food availability in their habitat.
6-26 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

Characteristics of Feeding Areas

Copepods were the dominant taxa at the majority of the whale feeding stations, and also at the

majority of the routine zooplankton sampling stations without whales, in both the eastern Alaskan and

Canadian Beaufort Sea. In eastern Alaskan waters, copepods dominated at 14 of 21 (67%) stations where

feeding whales were observed during sampling or on adjacent days, and at 24 of 47 (51%) routine transect

stations that were not feeding or control stations.

During the 1986 eastern Alaska study, sampling sites near feeding bowhead whales were mainly in

the Kongakut Delta area, in the extreme southeast part of the eastern Alaskan Beaufort Sea (Fig. 6.1).

This area was under the influence of warm turbid surface water, probably influenced by the Mackenzie

River, during the period when sampling was conducted. However, the biomass of copepods, especially

Limnocalanus macrurus, was highest in the cold saline bottom layer that lay under the warmer freshened

layer of Mackenzie River water. Limnocalanus accounted for most of the zooplankton biomass at these

Alaskan whale-feeding stations (Appendix 6.3). Here the difference in temperature and salinity between

surface water and the water below was ~4oC and about 5 to 6 psu.

Similar high biomasses of Limnocalanus macrurus were found in cold saline bottom water that lay

under warmer freshened surface water at whale feeding stations in the nearshore zone along the Yukon

Coast in 1985 and 1986 (Appendix 6.3). High biomasses of L. macrurus were associated with strong

temperature/salinity gradients in nearshore waters along the Yukon coast in 1985, 1986 and 1988. The

difference in temperature and salinity between surface water and the water below at whale feeding stations along the Yukon coast was up to 5 or 6oC and about 8 to 12 psu, i.e., somewhat more than in eastern

Alaska. Of the five years with sampling in the eastern Alaskan Beaufort Sea, these physical and biological oceanographic characteristics extended into Alaska only in 1986.

In some years, bowhead whales do not concentrate along the Yukon coast, west of the mouth of the

Mackenzie River, during August and early September. This was so in 1980 and 1981 (Richardson et al.

1987; Moore and Reeves 1993). There is some evidence showing that in 1980 and 1981 the Mackenzie

River plume was blown to the north and east, rather than west, by the winds (Thomson et al. 1986).

Conversely, in 1985 and 1986 the Mackenzie River plume had a strong influence on the oceanographic

regime off the Yukon Coast and feeding bowheads were commonly observed there.

In September of 1998 and 1999, feeding bowheads were not as concentrated in the eastern Alaskan

Beaufort Sea as they had been in 1986, and they were seen more often in offshore waters and/or the

western part of the eastern Alaskan study area (Chapter 12). In 1998 and 1999, warm fresh Mackenzie

water was not found in nearshore areas, L. macrurus was absent, and average zooplankton biomass at

whale feeding stations was lower than in 1986. Strong temperature/salinity gradients were not found in

nearshore waters in either 1998 or 1999.

Calanus hyperboreus and C. glacialis were the dominant copepod species at whale feeding and

control stations in the eastern Alaskan Beaufort Sea in 1998 and 1999, but their biomass was typically

lower than that of the Limnocalanus macrurus present at whale feeding stations in 1986. Predatory cnidarians, ctenophores, and chaetognaths were much more abundant at whale feeding and control stations in

1998–99 than in 1986. These animals feed on copepods and other zooplankters. The absence of L. macrurus in 1998–99 was largely responsible for the lower biomass observed at feeding stations in those

years as compared with 1986. The absence of L. macrurus was possibly attributable to the reduced temperature and salinity gradients in 1998–99 and/or the presence of numerous predators. The predatory
§6. Zooplankton: Characteristics of Bowhead Feeding Areas 6-27

species that were abundant in 1998–99 are of much lower nutritive value than are copepods (Thomson,

Chapter 22).

Calanus glacialis and (especially) C. hyperboreus were also the dominant copepod species at

whale feeding stations off Richard’s Island, N.W.T., in 1980 and 1981. Warm fresh water was found at

the surface in both years, and vertical temperature and salinity gradients were present. In 1981, the echosounder showed layers of zooplankton below the pycnocline, and maximum biomass of zooplankton in

horizontal tows was found in those layers. Whales were seen at distances >1 km from the ship, and

average biomass at these stations was not particularly high. At these stations, the difference in temperature and salinity between surface water and the water below was ~1oC and 4 to 6 psu.

Euphausiids did not dominate the zooplankton at any of our 37 zooplankton sampling sites where

whales were observed from the boat and/or from an aircraft either during sampling or on an adjacent day

(entries 1–37 in Appendix 6.3). Euphausiids did comprise 20% of the biomass at one whale-feeding site off

the Yukon coast in 1986. They were not abundant during routine sampling in the eastern Alaskan Beaufort

Sea in 1985–86 or 1998–2000. Euphausiids comprised 30% of biomass in one oblique tow in 2000, and

their biomass of 189 mg/m3

 accounted for 38% of total biomass in a horizontal tow taken at the same station

(see Appendix 5.28 following Chapter 5). Otherwise, euphausiids accounted for up to about 10 or 12% of

biomass in a few other tows. Euphausiids also were not abundant in any samples taken during routine

sampling or during sampling near bowhead whales in the Canadian Beaufort Sea in 1980, 1981, or 1985,

and were abundant at only 1 station in 1986, a whale-feeding station (station 31 in Appendix 6.3).

However, euphausiids did dominate the zooplankton at 2 of 4 bowhead feeding sites in the eastern

Alaskan Beaufort Sea sampled in 1989 by Wartzok et al. (1990). They found these feeding sites by

tracking radio-tagged whales, and sampled around whales that were observed to be feeding. Biomass in

vertical tows was 854, 1619 and 3287 mg/m3

 at three feeding sites in Camden Bay, and 730 mg/m3 at a

feeding site near Demarcation Bay. The 3287 and 730 mg/m3

 values came from locations where

euphausiids represented 85% and 50% of the biomass (see last subsection of Appendix 6.3). Copepods

and chaetognaths accounted for most of the biomass of zooplankters at the other two stations. Only

vertical tows were taken so no data were available on layering of zooplankton at these stations; biomass at

some depths was probably higher than that documented by vertical tows.

Thysanoessa inermis and T. raschii are the two species of euphausiids found in the study area and

in bowhead stomachs (Chapter 5; see also Lowry and Sheffield, Chapter 18). As in most species of

euphausiids, T. raschii is known to exhibit vertical migration, to form large concentrations, and (at times)

to swarm at the surface (Nicol 1984; Simard et al. 1986; Watkins et al. 1986). In the St. Lawrence estuary, a layer of euphausiids dominated by T. raschii and with a biomass >1000 mg/m3

 was 1 to 7 km in

width and over 100 km in length (Simard et al. 1986). In the Barents Sea, the highest biomass of T. inermis and T. raschii was found at depths of 400–500 m, and maximum biomass was over 3000 mg/m3

(Dalpadado and Skjoldal 1996). When they occur, euphausiids can form large dense concentrations.

Other taxa that occasionally were dominant components of the zooplankton at whale feeding

stations, aside from copepods and (less commonly) euphausiids and chaetognaths, were gelatinous groups

(cnidarians and ctenophores) and mysids. Gelatinous groups were the dominant taxa at whale-feeding

stations north of Tuktoyaktuk, west of Herschel Island, and off Clarence Lagoon (YT) in 1986; and east

of Barter Island in 1998. As described in Chapter 22, the energy content of the gelatinous groups is low

and it is doubtful that they would be a preferred food of whales. Mysids occasionally are found in bowhead stomachs (Chapter 18), and are known to swarm near the bottom at some locations (off the Kongakut Delta in 1986 and off Jago Spit in 1998).
6-28 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

In the shallow areas sampled close to shore, whale feeding stations contained a relatively high biomass

of zooplankton as compared with other stations, and were usually characterized by strong temperature and

salinity discontinuities caused by the presence of warm brackish Mackenzie River water over cold saline water

below. In these areas, the zooplankton is almost always concentrated below the pycnocline. Most of the

bowhead feeding is apparently below the surface (Chapter 12), and presumably at or near the depth of

maximum zooplankton biomass. In nearshore waters, the small copepod Limnocalanus macrurus is often the

dominant species. In water farther offshore, Calanus hyperboreus and C. glacialis are the dominant species.

In some cases, bowheads direct their feeding to dense concentrations of euphausiids.

Most of the bowheads that fed in the shallow-water areas sampled in the Canadian and eastern

Alaskan Beaufort Sea, as described above, were subadult whales (Koski et al. 1988; Chapter 10). Adult

bowheads tend to occur farther offshore (and east) in the Canadian Beaufort Sea during summer, and

farther offshore in the eastern Alaskan Beaufort Sea during late summer and autumn. In both areas,

bowheads in deep water (>50 m) have sometimes been observed feeding in the water column (Richardson

et al. 1995; Chapter 12). Some bowheads feeding in areas of the eastern Alaskan Beaufort Sea >20 m

deep during September have specifically been confirmed to be adults (Chapter 12).

The zooplankton available at times and locations in the Beaufort Sea where adult bowheads were

feeding has not been documented. By late summer and autumn, the large copepods Calanus hyperboreus

and C. glacialis have begun to descend to their overwintering depths, which range from 200–300 m to

over 1000 m in other regions (Hirche 1991). Copepods in deep water have large oil sacks and a high lipid

content (Hirche 1983; Head and Harris 1985). The timing of the autumn descent by copepods depends on

timing of ice breakup (Longhurst et al. 1984). The depth of the descent depends on the species, structure

of the water column, and water depth (Longhurst et al. 1984; Sameoto 1984). Subadult bowheads can

dive to depths >300 m (Krutzikowsky and Mate 2000). It can be assumed that adult bowheads can dive

to these depths and probably greater. At Isabella Bay, Baffin Island, bowhead behavior and the vertical

distribution of zooplankton biomass were indicative of feeding in waters >100 m deep (Finley et al. 1994;

Richardson et al. 1995). Zooplankton biomass in a trough where bowheads were feeding was significantly higher in waters >100 m deep than in the upper 100 m of the water column. Most of the whales at

Isabella Bay are large subadults and adults (Finley 1990).

Our net sampling and echosounder surveys were done during daylight. During September, there

are several hours of darkness each night in this area. The extent of diel vertical migration by zooplankton

in this area and season is unknown (see Chapter 5). Especially in deep areas, vertical migration of prey

could cause day–night differences in food availability. However, most areas where we sampled were

sufficiently shallow that any zooplankton concentrations present should have been detected (and accessible to bowheads) regardless of their depth. Krutzikowsky and Mate (2000) found no notable day–night

differences in depths of dives or surface–dive cycles of bowheads during September–October.

We did not sample near feeding whales in 1985 and 2000. Concentrations of feeding whales were

scarce in the eastern Alaskan study area in 1985 and especially 2000, and the sampling vessel was not

able to reach any feeding concentration in those years. The estimated number of bowhead feeding days in

the study area was very low in 2000, and also relatively low in 1985 (Table 6.8 and Chapter 23). Use of

the study area by feeding bowheads appears to be quite variable from year to year. Likewise, right whale

distribution appears to be related to the presence or absence of their preferred prey (Kenney 2001); in one

case, right whales did not appear in their usual summering area because of a scarcity of copepods. In our

study area, biomass of zooplankton was lower in 2000 than in the other four years, and very few

bowheads fed in the study area in 2000.
§6. Zooplankton: Characteristics of Bowhead Feeding Areas 6-29

TABLE 6.8. Estimated numbers of whale–days of use of the eastern-Alaskan study area

by bowheads during late summer and autumn (Chapter 9), proportion of time spent feeding (Chapter 12), and feeding days of use per year (from Chapter 23).

1985 1986 1998 1999 2000 Per Year

Number of whale–days of use 11,937 17,899 31,507 101,850 18,727 36,384

Proportion of time feeding 0.39 0.57 0.38 0.67 0.09 0.47

Feeding Days of Use 4,643 10,228 11,915 67,900 1,702 16,953

Prey in Whale Stomachs vs. Zooplankton Sampled Near Feeding Whales

Stomachs from 32 bowhead whales harvested by hunters from Kaktovik in 1979–2000 were

examined by Lowry and Sheffield (Chapter 18). Twenty-four of the 32 whales were considered to have

been feeding, and 21 of these contained a sufficient sample for analysis. Copepods and euphausiids were

the main prey items in stomachs. Copepods were present in every stomach sample, were the dominant

prey in 60% of stomachs, and were the only prey in 12 of the 21 stomachs that contained food. Euphausiids were also important as prey, and were the dominant prey in 5 whale stomachs. Other crustaceans and

fishes also were eaten, but they generally were minor components (Chapter 18).

Copepods and (to a lesser degree) euphausiids, cnidarians, ctenophores, chaetognaths and mysids

were, on a biomass basis, the dominant taxa collected near feeding whales in the Canadian and eastern

Alaskan Beaufort Sea during all years. With the exception of euphausiids, these groups were also the

dominant components of the zooplankton collected by net sampling in the eastern Alaskan Beaufort Sea

as a whole (Griffiths and Thomson, Chapter 5). Euphausiids were the predominant zooplankton collected

by nets at two stations near feeding whales (Wartzok et al. 1990), but were not major components of the

zooplankton collected by nets in either the eastern Alaskan or Canadian Beaufort Sea (Bradstreet and

Fissel 1986; Bradstreet et al. 1987; Chapter 5; Appendix 6.3). Euphausiids are fast swimmers and are

often able to detect and avoid nets (Wiebe et al. 1982; Hovekamp 1989), which suggests that zooplankton

sampling in the Beaufort Sea may have underrepresented euphausiids. However, we have collected large

quantities of euphausiids in bongo tows at locations in the Western Alaskan Beaufort Sea (Griffiths et al.

1987), and Wartzok et al. (1990) caught large biomasses of euphausiids in vertical tows with standard

nets. If euphausiids had been present in large quantities at other whale feeding stations, we believe that

they would have been caught in bongo tows more often, even if underrepresented.

The dominant prey items found in whale stomachs at Kaktovik have fairly well represented the

zooplankton present at whale feeding stations. The main differences between prey in bowhead stomachs

and zooplankton found near feeding whales is the relatively higher importance of euphausiids and lower

importance of the small copepod Limnocalanus macrurus in the stomachs relative to the net samples.

There are several potential reasons for the differences that were observed: • Not all potential feeding

habitats were sampled during this study. • Many whale-feeding stations in the eastern Alaskan Beaufort

Sea were well outside the area near Kaktovik where whales were harvested (cf. Chapter 2). • Thomson

(Chapter 22) argues that food passes through the bowhead gut very rapidly when whales are feeding, with

the result that stomach contents of whales harvested near Kaktovik most likely represented prey availability close to the harvest locations. • Stomach contents of harvested whales may be affected by differential digestion rates of different prey taxa, which are quite variable in size and composition.

These factors may account for the differences between prey collected near feeding whales and prey

found in whale stomachs. Limnocalanus macrurus is small compared to Calanus spp.; however, L.

macrurus has many spines which cause the animals to become entangled with each other and form a ball in
6-30 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

a plankton net, or presumably in a bowhead’s mouth. Thus, they may be easily eaten by bowhead whales.

In any event, during some years large numbers of feeding bowheads occur at nearshore locations where

Limnocalanus is the only abundant zooplankton taxon. This provides very strong evidence that these small

copepods are an important prey item in some years and locations.

Summary

Introduction and Objectives

Bowhead whales winter in the Bering Sea and annually migrate to summering areas in the Beaufort

Sea. If bowheads, like other mysticete whales, feed mainly during summer, a primary reason for the

annual migration would be to reach preferred summer feeding areas. This would imply that summering

areas are sufficiently rich in food to justify migrating several thousand kilometers (round-trip) to feed.

This component of the study had three main objectives: (1) to describe the characteristics of bowhead

feeding areas in the eastern Alaskan and Canadian Beaufort Seas, with emphasis on the zooplankton and

water masses; (2) to determine whether bowhead whales feed in areas where zooplankton is concentrated;

and (3) to determine the quantity and kinds of zooplankton associated with feeding bowheads.

Methods

In the Eastern Alaskan Beaufort Sea, zooplankton was sampled during September of 1986, 1998

and 1999 at 21 stations where bowhead whales were either observed feeding or where whales had been

observed feeding the previous day. Sampling near feeding bowheads was not possible in 1985 and 2000.

For each feeding station sampled, a control station about 8 to 10 km from the feeding station was also

sampled. Zooplankton near feeding bowheads was sampled at 16 additional stations in the Canadian

Beaufort Sea during August and early September of 1980–81, 1985–86, and 1988. The eastern Alaskan

and Canadian data are presented separately, but are also considered together to provide a broader view of

bowhead feeding in the eastern Beaufort Sea. Vertical profiles of temperature and salinity were obtained

at all but one systematic sampling station.

At most stations, oblique and horizontal zooplankton tows were made using a standard bongo

frame fitted with two 0.5 mm mesh, 0.61 m diameter, plankton nets, and a flow meter. At most stations,

at least one horizontal tow was targeted to a specific depth where an echosounder showed an apparent

zooplankton concentration. The limited 1980 and 1988 sampling in Canadian waters employed vertical

tows, and in 1986 the horizontal tows in Alaskan waters used an opening-and-closing bongo system.

Animals from all oblique tows were identified to species, and those from horizontal tows to major taxa.

Sorted animals were wet-weighed, and wet-weight biomass/m3

 was calculated using flow-meter data on

volume filtered.

In the Alaskan Beaufort Sea, quantitative echosounder surveys were conducted between whale

feeding and control stations during 1986, 1999 and 2000, and along other transects during all five field

seasons. Regression equations were developed to relate zooplankton biomass in horizontal net tows to

measured acoustic back scatter, and then used to estimate biomass where only echosounder data were

available. In the Canadian Beaufort, the echosounder used in 1981, 1985 and 1986 identified depths with

high (and low) apparent biomasses of zooplankton, but did not provide quantitative data on biomass.

Results

Bowhead whales feed in areas with a higher than average concentrations of zooplankton. A high

biomass of zooplankton was found in areas where feeding bowheads were observed from the sampling
§6. Zooplankton: Characteristics of Bowhead Feeding Areas 6-31

boat in the eastern Alaskan and Canadian Beaufort Sea. Mean wet-weight biomass in the water column

near actively feeding whales was 529 mg/m3

, a value considerably higher than the mean biomass in the

water column elsewhere in the eastern Alaskan and Canadian parts of the Beaufort Sea (230 mg/m3

).

Mean biomass in the horizontal tows with maximum biomass at 17 stations where whales were observed

within 1 km of the boat and the echosounder was functioning was 1841 ± s.d. 1226 mg/m3

. The

distribution of biomass values at places with feeding bowheads indicates that the feeding threshold for

bowheads may be a wet biomass of ~800 mg/m3

.

A high biomass of zooplankton near feeding whales in nearshore waters was usually associated

with the presence of strong temperature and salinity gradients (pycnocline) in the water column. In these

cases, concentrations of zooplankton are found in the cold saline water that underlies the warmer

freshened layer. These conditions are found at varying locations in the Canadian Beaufort Sea regardless

of wind direction, but occur in shallow waters of the eastern Alaskan Beaufort Sea mainly under east

wind conditions. The eastern Alaskan Beaufort Sea appears to be more important to feeding whales in

years when oceanographic conditions that cause zooplankton to concentrate in nearshore waters off the

Yukon coast extend west into Alaska.

The small copepod Limnocalanus macrurus dominated the zooplankton biomass near feeding bowheads in nearshore waters along the Yukon coast and into northeast Alaska when cold saline water was

overlain by warm Mackenzie water. Farther offshore, the large copepods Calanus hyperboreus and

C. glacialis dominated. Stomach contents of whales landed at Kaktovik show that bowheads sometimes

feed on dense swarms of euphausiids. However, euphausiids are rarely the dominant zooplankters around

bowheads feeding in the present study areas. Other taxa that occasionally are dominant near feeding

whales are gelatinous cnidarians and ctenophores, chaetognaths, and mysids.

We did not find places with feeding whales where euphausiids were dominant, but this has been

reported previously from the Camden Bay area, and euphausiids are the dominant components of the prey

in the stomachs of a minority of the bowheads landed at Kaktovik (see Chapter 18). Euphausiids are

known to show avoidance reactions to sampling nets. As a result euphausiids are probably somewhat

under-represented in our net samples. However, where euphausiids are abundant, as they are at times in

the western Beaufort Sea, they are prominent in net samples. In general, euphausiids are apparently less

important as prey for bowhead whales in the eastern Alaskan Beaufort Sea than farther west near Point

Barrow.

Most whales observed in the areas sampled were subadults. Adult bowheads tend to feed in deeper

water, where large copepods predominate. By early autumn, most large copepods have descended to their

overwintering depths (>100 m).

Water masses in the areas sampled are defined by the presence or absence of the plume of freshened and warmer water influenced by Mackenzie River outflow. Wind conditions have rapid effects on

the Mackenzie plume, so oceanographic conditions can change rapidly. These changes influence the biomass and composition of the zooplankton community in the eastern Beaufort Sea, and especially the

portion that is in Alaska.

Acknowledgements

Acknowledgements concerning the zooplankton work in Alaska are included near the end of Chapter 3. For guidance to whale locations in Alaska and Canada, we thank many LGL aerial surveyors

(1980–81, 1985–86, 1998–2000), plus J.C. Cubbage, J.K.B. Ford, L.A. Harwood, and P. Norton (1986).
6-32 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

In the Canadian Beaufort Sea, Robert Buchanan (1980–81, 1985–86) and M. Fabijan, L. Martin,

and N. Stallard (1985 and/or 1986), all of LGL, assisted with fieldwork. Robert Bocking of LGL collected the samples in 1988. For vessel and logistical support in Canada, we thank ESSO Resources Canada

Ltd. and crew of Imperial Sarpik (1980); L. Pearson, W. Bellham and D. MacWatt of Sequel (1981,

1985); Capt. B. Moulton and crew of Arctic Ivik (1986); and the Polar Continental Shelf Project, Tuktoyaktuk. As in Alaska, N. Stallard supervised the laboratory analyses of zooplankton, and G. Borstad,

D. Fissel and J. Marko helped with various aspects physical oceanography components. The studies in

Canada were funded by the U.S. Bureau of Land Management (1980–81) and Canadian Dept of Indian &

Northern Affairs, especially D. Stone and R. Hurst (1985–86).

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§6. Zooplankton: Characteristics of Bowhead Feeding Areas 6-35

APPENDIX 6.1. Locations of whale feeding and control stations in the eastern Alaskan Beaufort Sea,

September 1986, 1998 and 1999a.

Reference Whale Water Time

Station Numbera Date Feeding Depth (m) (ADT) Latitude Longitude

1986

 86-1 5 4/9/1986 Yes 17 9:20 69°35.7'N 139°31.6'Wb

 86-2 4/9/1986 Control 25 14:00 69°40.3'N 139°28.4'Wb

 86-5 1 5/9/1986 Yes 14 15:00 69°50.1'N 141°51.9'W 

 86-6 5/9/1986 Control 27 18:16 69°53.8'N 141°45.6'W 

 86-7 2 6/9/1986 Yes 11 11:03 69°48.9'N 141°47.8'W 

 86-8 6/9/1986 Control 23 13:28 69°52.6'N 141°48.3'W 

 86-9 3 6/9/1986 Yes 7 1704 69°48.6'N 141°46.8'W 

 86-10 6 7/9/1986 Yes 12 9:10 69°38.1'N 140°49.4'Wb

 86-11 7/9/1986 Control 15 11:47 69°38.7'N 140°52.4'Wb

 86-12 4 7/9/1986 Yes 22 14:51 69°49.2'N 141°35.3'W 

 86-13 7/9/1986 Control 25 16:25 69°51.1'N 141°33.8'W 

1998

1 7 11/09/98 Yes 15 14:11 70° 04.80' N 144° 46.45' W

2 11/09/98 Control 8 17:42 69° 59.74' N 144° 47.98' W

3 8 12/09/98 Yes 17 8:47 70° 07.55' N 144° 46.76' W

4 9 12/09/98 Yes 25 13:17 70° 11.57' N 144° 53.17' W

5 12/09/98 Control 22 15:22 70° 10.68' N 144° 32.06' W

7 14/09/98 Control 18 10:31 69° 49.92' N 141° 40.04' W

8 10 14/09/98 Yes 27 14:08 69° 50.18' N 141° 23.43' W

15 11 16/09/98 Yes 40 13:30 70° 18.72' N 143° 25.81' W

16 16/09/98 Control 46 15:35 70° 23.52' N 143° 24.12' W

21 12 18/09/98 Yes 27 12:54 70° 13.33' N 143° 49.68' W

22 18/09/98 Control 14.5 14:59 70° 09.67' N 143° 47.97' W

27 13 20/09/98 Yes 10 11:09 70° 10.14' N 143° 24.00' W

28 14 20/09/98 Yes 14.5 11:46 70° 10.44' N 143° 16.80' W

29 20/09/98 Control 34 15:14 70° 14.47' N 143° 09.71' W

30 22/09/98 Control 12 9:26 70° 09.53' N 143° 37.75' W

32 15 22/09/98 Yes 16 14:52 70° 09.92' N 143° 07.96' W

31 22/09/98 Control 19 10:11 70° 11.31' N 143° 41.06' W

33 16 22/09/98 Yes 19 15:08 70° 10.55' N 143° 07.77' W

1999

1 17 16/9/99 Yes 48 14:31 70° 08.58' N 141° 49.29' W

2 16/9/99 Control 46 16:06 70° 08.34' N 142° 05.04' W

3 18 17/9/99 Yes 48 11:24 70° 08.33' N 141° 52.50' W

4 19 17/9/99 Yes 48 13:14 70° 08.85' N 142° 00.59' W

5 17/9/99 Control 35 16:00 70° 03.36' N 142° 08.31' W

15 21 20/9/99 Yes 45 12:00 70° 20.75' N 143° 25.70' W

14 20 20/9/99 Yes 35 15:07 70° 16.12' N 143° 32.87' W

17 20/9/99 Control 20 16:26 70° 11.80' N 143° 39.75' W

ADT = Alaska daylight time.

a

 Corresponding to whale feeding stations in Figure 6.1 and Appendix 6.3.

Station

b

 Stations in the Canadian Beaufort Sea near Alaska that were sampled during the Alaskan project.
6-36 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

APPENDIX 6.2. Major zooplankton taxa and species collected in oblique tows at apparent feeding and

corresponding control stations 1986, 1998, 1999. Sample depth is the maximum water depth of the

oblique tow, which was near the bottom (see Appendix 6.1 for station depths).

Sample Zooplankton

Depth Biomass Copepods Comprising Other Taxa Comprising No. of Whale Sightings

Location (m) mg/m3 >1% of Biomass % >1% of Biomass % Whales

1986

A. 4 Sept 1986, West of Herschel Island

Sta. 86-1 16 96.4 Copepods 14.5 Cnidarians & Ctenophores 38.1 10 Whales feeding

(Whales) Limnocalanus macrurus 7.7 Amphipods 13.0 on Sept 3

Ref 5a Calanus hyperboreus 2.3 Mysids 5.9

 Calanus glacialis 2.5 Fish Larvae 2.9

 Pseudocalanus minutus 1.4 Chaetognaths 3.0

 Decapod larvae 13.9

Pteropods 5.2

Sta. 86-2 20 51.8 Copepods 78.5 Fish Larvae 5.9

(Control) Limnocalanus macrurus 43.1 Cnidarians & Ctenophores 5.6

Calanus hyperboreus 17.8 Decapod larvae 4.8

Calanus glacialis 11.8 Chaetognaths 1.4

Euchaeta glacialis 2.3 Amphipods 1.2

Metridia longa 1.9

B. 5 Sept 1986, Kongakut Delta

Sta. 86-5 12 1228.1 Copepods 96.0 Cnidarians & Ctenophores 2.5 Many Numerous whales seen

(Whales) Limnocalanus macrurus 95.0 from boat

Ref 1

Sta. 86-6 22 81.2 Copepods 17.3 Cnidarians & Ctenophores 38.1

(Control) Calanus glacialis 10.8 Fish larvae 15.7

Limnocalanus macrurus 4.2 Decapod larvae 7.2

Calanus hyperboreus 1.5 Amphipods 4.0

Chaetognaths 1.3

Pteropods 14.0

C. 6 Sept 1986, Kongakut Delta

Sta. 86-7 8 853.4 Copepods 91.1 Mysids 6.3 Many Numerous whales seen

(Whales) Limnocalanus macrurus 88.4 from boat

Ref 2 Pseudocalanus minutus 1.3

Sta. 86-8 23 40.5 Copepods 31.7 Amphipods 38.0

(Control) Limnocalanus macrurus 18.5 Cnidarians & Ctenophores 12.3

Calanus glacialis 4.7 Decapod larvae 4.3

Euchaeta glacialis 3.5 Chaetognaths 3.3

Calanus hyperboreus 2.7 Pteropods 2.4

D. 7 Sept 1986, Clarence Lagoon

Sta. 86-10 12 105.0 Copepods 33.8 Cnidarians & Ctenophores 41.7 8 Whales feeding

(Whales) Limnocalanus macrurus 32.0 Fish larvae 7.5 on Sept 7

Ref 6 Decapod larvae 6.0

Mysids 4.6

Pteropods 2.9

Amphipods 1.9

Sta. 86-11 12 198.5 Copepods 57.4 Cnidarians & Ctenophores 26.8

(Control) Limnocalanus macrurus 46.7 Fish larvae 3.2

Calanus glacialis 6.9 Chaetognaths 3.4

Calanus hyperboreus 2.2 Decapod larvae 3.9

Pseudocalanus minutus 1.3 Amphipods 1.9

E. 7 Sept 1986, Kongakut Delta 

Sta. 86-12 18 912.4 Copepods 95.3 Fish larvae 1.2 12 Whales feeding

(Whales) Limnocalanus macrurus 93.8 Cnidarians & Ctenophores 1.2

Ref 4

Sta. 86-13 21 58.7 Copepods 1.1 Fish larvae 33.7

(Control) Limnocalanus macrurus 1.0 Decapod larvae 24.8

Cnidarians & Ctenophores 16.6

Pteropods 9.8

Amphipods 1.2

Other 12.7
§6. Zooplankton: Characteristics of Bowhead Feeding Areas 6-37

APPENDIX 6.2. (continued)

Sample Zooplankton

Depth Biomass Copepods Comprising Other Taxa Comprising No. of Whale Sightings

Location (m) mg/m3 >1% of Biomass % >1% of Biomass % Whales

1998

A. 11 Sept. 1998, East Camden Bay

Sta. 98-1 10.5 144.0 Copepods 79.1 Cnidarians & Ctenophores 9.5 4+ Water-column

(Whales) Calanus glacialis 70.7 Amphipods 5.5 feeding

Ref 7 Calanus hyperboreus 7.4 Chaetognaths 5.2

Pseudocalanus minutus 1.0

Sta. 98-2 6.5 233.8 Copepods 3.2 Fish Larvae 70.2

(Control) Calanus glacialis 2.2 Chaetognaths 16.2

Calanus hyperboreus 0.2 Mysids 8.8

Pseudocalanus minutus 0.8

B. 12 Sept. 1998, East Camden Bay

Sta. 98-3 10.0 678.4 Copepods 78.8 Chaetognaths 12.3 10+ Seen Day

(Whales) Calanus glacialis 71.1 Cnidarians & Ctenophores 8.3 Before

Ref 8 Calanus hyperboreus 6.4

Pseudocalanus minutus 1.3

Sta. 98-4, 4 nmiles North Sta. 98-3 Copepods 61.3 Chaetognaths 26.7 3+ Water-column

(Whales) 19.6 468.4 Calanus glacialis 48.6 Cnidarians & Ctenophores 11.5 Feeding

Ref 9 Calanus hyperboreus 12.4

Pseudocalanus minutus 0.2

Sta. 98-5 19.5 418.1 Copepods 54.6 Cnidarians & Ctenophores 24.4

(Control) Calanus glacialis 36.1 Chaetognaths 20.9

Calanus hyperboreus 16.7

Pseudocalanus minutus 1.6

C. 14 Sept. 1998, Icy Reef

Sta. 98-8 24.0 331.0 Copepods 31.8 Cnidarians & Ctenophores 57.7 6+ Water-column

(Whales) Calanus glacialis 26.6 Chaetognaths 7.8 Feeding

Ref 10 Calanus hyperboreus 4.7 Euphausiids 1.3

Pseudocalanus minutus 0.3

Sta. 98-7 16.0 93.7 Copepods 45.1 Cnidarians & Ctenophores 29.9

(Control) Calanus glacialis 42.7 Chaetognaths 19.2

Calanus hyperboreus 2.0 Euphausiids 3.1

Pseudocalanus minutus 0.2 Mysids 2.1

D. 16 Sept. 1998, North of Bernard Spit Barter Island 

Sta. 98-15

(Whales?) 32.5 148.2 Copepods 55.6 Cnidarians & Ctenophores 25.4 3+ Seen from the 

Ref 11 Calanus glacialis 52.0 Chaetognaths 7.0 Boat, stayed in

Calanus hyperboreus 2.7 Fish Larvae 6.2 area during

Pseudocalanus minutus 0.7 Larvaceans 2.8 sampling

Amphipods 2.5

Sta. 98-16 46.0 71.5 Copepods 37.3 Cnidarians & Ctenophores 28.5

(Control) Calanus glacialis 30.5 Fish Larvae 17.3

Calanus hyperboreus 5.2 Chaetognaths 8.6

Pseudocalanus minutus 0.6

E. 18 Sept. 1998, East Camden Bay

Sta. 98-21 24.5 327.1 Copepods 71.4 Chaetognaths 19.4 14+ Water-column

(Whales) Calanus glacialis 47.5 Cnidarians & Ctenophores 5.8 Feeding

Ref 12 Calanus hyperboreus 20.9 Mysids 2.0

Pseudocalanus minutus 3.0 Fish Larvae 1.1

Sta. 98-22 12.5 298.4 Copepods 19.8 Chaetognaths 64.9

(Control) Calanus glacialis 4.1 Cnidarians & Ctenophores 14.3

Calanus hyperboreus 13.8 Mysids 1.0

Pseudocalanus minutus 1.6
6-38 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

APPENDIX 6.2. (continued)

Sample Zooplankton

Depth Biomass Copepods Comprising Other Taxa Comprising No. of Whale Sightings

Location (m) mg/m3 >1% of Biomass % >1% of Biomass % Whales

F. 20 Sept. 1998, Off Jago Spit

Sta. 98-27 7.5 207.6 Copepods 15.1 Mysids 33.7 4+ Water-column

(Whales) Calanus glacialis 5.5 Chaetognaths 25.4 feeding

Ref 13 Calanus hyperboreus 7.5 Cnidarians/Ctenophores 20.3

Pseudocalanus minutus 2.1

Sta. 98-28 orth of Sta. 98-27

(Whales) 13.5 270.5 Copepods 8.7 Chaetognaths 37.5 4+ Water-column

Ref 14 Calanus glacialis 4.1 Mysids 27.5 feeding

Calanus hyperboreus 3.0 Hydrozoans & Ctenophores 26.2

Pseudocalanus minutus 1.6

Sta. 98-29 29.5 429.2 Copepods 37.0 Chaetognaths 47.5

(Control) Calanus glacialis 19.5 Cnidarians/Ctenophores 13.9

Calanus hyperboreus 15.3 Mysids 1.4

Pseudocalanus minutus 2.0

G. 22 Sept. 1998, Off Barter Island

Sta. 98-32 13.0 239.0 Copepods 23.1 Cnidarians/Ctenophores 34.8 4+ Bottom

(Whales) Calanus glacialis 18.9 Chaetognaths 32.2 feeding

Ref 15 Calanus hyperboreus 1.8 Mysids 6.6

Pseudocalanus minutus 2.3 Euphausiids 2.8

Sta. 98-30 8.5 311.7 Copepods 13.4 Fish Larvae 33.0

(Control) Calanus glacialis 10.7 Chaetognaths 26.9

Calanus hyperboreus 1.0 Mysids 19.8

Pseudocalanus minutus 1.5 Cnidarians/Ctenophores 6.1

Sta. 98-33 15.5 224.5 Copepods 30.3 Chaetognaths 47.9 4+ Bottom

(Whales) Calanus glacialis 22.7 Mysids 10.7 feeding

Ref 16 Calanus hyperboreus 3.9 Cnidarians/Ctenophores 7.4

Pseudocalanus minutus 3.6 Euphausiids 3.5

Sta. 98-31 19.0 406.9 Copepods 63.0 Chaetognaths 11.1

(Control) Calanus glacialis 56.8 Cnidarians/Ctenophores 9.4

Calanus hyperboreus 4.9 Mysids 6.2

Pseudocalanus minutus 1.3 Decapods 6.4

Fish Larvae 2.7

1999

A. 16 Sept. 1999, Off Nug Lagoon 

Sta. 99-1 40.0 442.7 Copepods 67.3 Chaetognaths 18.5 18 Water-column

(Whales) Calanus glacialis 9.8 Cnidarians/Ctenophores 7.4 feeding

Ref 17 Calanus hyperboreus 54.8 Fish Larvae 3.1

Pseudocalanus minutus <1.0

Sta. 99-2 40.0 384.3 Copepods 62.1 Cnidarians/Ctenophores 24.4

(Control) Calanus glacialis 4.0 Chaetognaths 10.8

Calanus hyperboreus 56.2 Fish Larvae 3.6

Pseudocalanus minutus <1.0

B. 17 Sept. 1999, Off Nug Lagoon 

Sta. 99-3 40.0 207.4 Copepods 73.1 Chaetognaths 9.3 15 Water-column

(Whales) Calanus glacialis 9.0 Cnidarians/Ctenophores 6.8 feeding

Ref 18 Calanus hyperboreus 61.5 Fish Larvae 5.5

Pseudocalanus minutus <1.0

Sta. 99-4 41.0 221.2 Copepods 70.5 Cnidarians/Ctenophores 14.9 13 Water-column

(Whales) Calanus glacialis 7.3 Chaetognaths 9.6 feeding

Ref 19 Calanus hyperboreus 62.0 Fish Larvae 2.5

Pseudocalanus minutus <1.0

Sta. 99-5 30.0 215.4 Copepods 65.6 Cnidarians/Ctenophores 20.4

(Control) Calanus glacialis 2.2 Fish Larvae 6.5

Calanus hyperboreus 62.4 Chaetognaths 5.1

Pseudocalanus minutus >1.0
§6. Zooplankton: Characteristics of Bowhead Feeding Areas 6-39

APPENDIX 6.2. (concluded)

Sample Zooplankton

Depth Biomass Copepods Comprising Other Taxa Comprising No. of Whale Sightings

Location (m) mg/m3 >1% of Biomass % >1% of Biomass % Whales

C. 20 Sept. 1999, Off Barter Island

Sta. 99-14 40.0 449.50 Copepods 70.6 Cnidarians/Ctenophores 19.4 15 Water-column

(Whales) Calanus glacialis 7.8 Chaetognaths 8.5 feeding between

Ref 20 Calanus hyperboreus 60.4 Fish Larvae 1.2 St. 14 and 15

Pseudocalanus minutus <1.0

Sta. 99-15 45.0 582.80 Copepods 80.2 Cnidarians/Ctenophores 11.8 15 Water-column

(Whales) Calanus glacialis 15.0 Chaetognaths 8.5 feeding between

Ref 20 Calanus hyperboreus 61.2 Fish Larvae <1.0 St. 14 and 15

Pseudocalanus minutus <1.0

Sta. 99-17 18.0 438.00 Copepods 19.3 Chaetognaths 39.8

(Control) Calanus glacialis 6.5 Cnidarians/Ctenophores 28.3

Calanus hyperboreus 12.3 Euphausiids 9.2

Pseudocalanus minutus <1.0 Fish Larvae 1.9

Mysids 0.9

a

 Corresponding to whale feeding stations in Figure 6.1 and Appendix 6.3.
APPENDIX 6.3. Attributes of the 42 whale feeding stations sampled in eastern Alaskan Beaufort Sea, along Yukon co

Peninsula, 1981–99. Locations are shown on Figure 6.1 (from Griffiths and Buchanan 1982; Griffiths et al. 1987; BradBradstreet et al. 1987; Wartzok et al. 1990; and present study). Mean biomass and dominant taxa are from oblique 

biomass from horizontal bongo tows. Note: The station numbers in parentheses are the station numbers that appear in th

Water Depth of 

Depth (m) Mean Maximum Max Biomass Taxa (%) Species (%) 

Eastern Alaskan Beaufort Sea 1986

1 Off Kongakut Delta 5-Sep 86 14 1228 3023 10 Copepods (95%) Limnocalanus 

69°50.1'N 141°51.9'W (St 5) macrurus (93%) 

2 69°48.9'N 141°47.8'W (St 7) 6-Sep 86 11 853 2887 8 Copepods (91%) Limnocalanus 

macrurus (91%) 

3 69°48.6'N 141°46.8'W (St 9) 6-Sep 86 7 319 -b -b Copepods (90%) Limnocalanus 

macrurus (85%) 

4 69°49.2'N 141°35.3'W (St 12) 7-Sep 86 22 912 2137 15 Copepods (95%) Limnocalanus 

macrurus (94%) 

5 West of Herschel Is. (St 1) 4-Sep 86 17 96 75 8 Cnidarians + Aglantha 

69°35.7'N 139°31.6'W Ctenophores (38%) digitale (26%) 

6 Off Clarence Lagoon (St 10) 7-Sep 86 12 105 3847 8 Cnidarians + Limnocalanus 

69°38'N 140°49'W Ctenophores (42%) macrurus (32%) 

Eastern Alaskan Beaufort Sea 1998

7 Eastern Camden Bay (St. 1) 11-Sep 98 15 144 295 10.5 Copepods (79%) Calanus 

70° 04.80'N 144° 46.45'W glacialis (71%) 

8 Eastern Camden Bay (St. 3)

70° 07.55'N 144° 47.76'W 12-Sep 98 17 678 615 15 Copepods (79%) Calanus 

glacialis (71%) 

9 Eastern Camden Bay (St. 4)

70° 11.57'N 144° 53.17'W 12-Sep 98 25 468 460 10.6 Copepods (61%) Calanus 

glacialis (49%) 

10 Off Icy Cape (St. 8)

69° 50.18'N 141° 23.43'W 14-Sep 98 27 331 504 23.5 Cnidarians + Cyanea 

Ctenophores (58%) capillata (49%) 

11 Off Jago Spit (St. 15)

70° 18.72'N 143° 25.81'W 16-Sep 98 40 148 771 22.4 Copepods (56%) Calanus 

glacialis (52%) 

12 Eastern Camden Bay (St. 21)

70° 13.33'N 143 49.68'W 18-Sep 98 27 327 389 23 Copepods (71%) Calanus 

glacialis (48%) 

13 Off Jago Spit (St. 27)

70° 10.14'N 143° 24.00'W 20-Sep 98 10 208 267 6.8 Mysids (34%) Mysis 

litoralis (34%) 

14 Off Jago Spit (St. 28)

70° 10.44'N 143° 16.80'W 20-Sep 98 14.5 271 421 10.8 Chaetognaths (38% Sagitta 

elegans (38%) 

15 East of Barter Island (St. 32)

70° 09.92'N 143° 07.96'W 22-Sep 98 16 239 329 14.1 Cnidarians + Mertensia 

Ctenophores (35%) ovum (16%) 

Biomass (mg/m3) Dominant Taxa

Date
APPENDIX 6.3. (continued)

Water Depth of 

Depth (m) Mean Maximum Max Biomass Taxa (%) Species (%) O

16 East of Barter Island (St. 33)

70° 10.55'N 143° 07.77W 22-Sep 98 19 225 386 13.7 Chaetognaths (48%) Sagitta 4

Eastern Alaskan Beaufort Sea 1999 elegans (48%) a

17 Off Beaufort Lagoon (St. 1)

70° 08.58' N 141° 49.29' W 16-Sep 99 48 443 545 31 Copepods (67%) Calanus 

hyperboreus (55%a

18 Off Beaufort Lagoon (St. 3) 17-Sep 99 48 207 886 40 Copepods (73%) Calanus

70° 08.33' N 141° 52.50' W hyperboreus (62%

a

19 Off Beaufort Lagoon (St. 4) 17-Sep 99 48 221 778 40 Copepods (71%) Calanus

70° 08.85' N 142° 00.59' W hyperboreus (62%

a

20 East of Barter Island (St. 14) 20-Sep 99 40 450 595 31 Copepods (71%) Calanus

70° 16.12' N 143° 32.87' W hyperboreus (60%

Sa

21 East of Barter Island (St. 15) 20-Sep 99 45 583 571 24 Copepods (80%) Calanus 

70° 20.75' N 143° 25.70' W hyperboreus (61%S

f

Canadian Beaufort Sea 1980

22 Off Richard's Island 14-26 Aug 80 26 558 mean -b Hydrozoans (71%) Halitholus W

Mackenzie Delta 1017 max cirratus (25%) b

70°00'N 134°30'W Euphysa

Canadian Beaufort Sea 1981 flammea (38%)

23 Off Richards Island., 18-19 Aug 81 26 -c 885 15 Copepods (79%) Calanus 3

Mackenzie Delta hyperboreus (70%f

70°00'N 135°43'W b

216 0 Copepods (92%) Calanus

hyperboreus (69%

24 Off Richards Island., 24-Aug 81 30 -c 1405 15 Copepods (64%) Calanus W

Mackenzie Delta hyperboreus (52%b

70°08'N 134°38'W C. glacialis

552 0 Copepods (83%) Calanus

hyperboreus (82%C. glacialis

25 Off Richards Island., 25-Aug 81 11 -c 807 10 Copepods (61%) Calanus W

Mackenzie Delta Mysids (18%) hyperboreus (39%n

69°52'N 134°49'W Mysis littoralis (18%

Canadian Beaufort Sea 1985

26 Off Kay Pt., Yukon Coast (St 1 27-Aug 85 64 288 1098 8 Copepods (92%) Limnocalanus O

69°27'N 138°04'W macrurus (77%)

27 Off King Pt., Yukon Coast (St 28-Aug 85 12 -c 2142 1 Copepods (99%) Limnocalanus O

69°05'N 137°47'W macrurus (97%) s

Biomass (mg/m3) Dominant Taxa

Date
APPENDIX 6.3. (concluded)

Water Depth of 

Depth (m) Mean Maximum Max Biomass Taxa (%) Species (%) 

28 Off King Pt., Yukon Coast (St 3) 29-Aug 85 21 836 1203 9 Copepods (94%) Limnocalanus 

69°08'N 138°00'W macrurus (88%) 

29 Off Kay Pt., Yukon Coast (St 26) 29-Aug 85 25 -c 2294 8 Copepods (98%) Limnocalanus 

69°16'N 138°16'W 693 1 macrurus (84%) 

Canadian Beaufort Sea 1986

30 King Point, Yukon Coast (St 2) 5-Sep 86 14 776 1543 3 Copepods (91%) Limnocalanus 

69°05'N 137°47'W macrurus (86%) 

31 King Point, Yukon Coast (St 3) 5-Sep 86 21 455 771 14 Copepods (61%) Limnocalanus 

69°08'N 137°38'W macrurus (26%) 

Euphausiids (20%) Calanus 

hyperboreus (18%)

32 North of Tuktoyaktuk (St 60) 30-Aug 86 49 369 -a -a Copepods (85%) Calanus 

70°42'N 132°53'W hyperboreus (76%) 

33 North of Tuktoyaktuk (St 54) 30-Aug 86 38 260 -a -a Cnidarians + Aglantha 

70°29'N 131°27'W Ctenophores (39%) digitale (34%)

34 North of Tuktoyaktuk (St 55) 30-Aug 86 52 282 139 20 Copepods (70%) Calanus 

70°49'N 131°27'W hyperboreus (68%)

35 Off E. Tuk. Penin. (St 79.3) 3-Sep 86 43 116 93 33 Copepods (71%) Calanus 

70°51'N 130°46'W hyperboreus (55%)

36 Off E. Tuk. Penin. (St 79) 3-Sep 86 36 527 -a -a Copepods (87%) Calanus 

70°44'N 130°46'W hyperboreus (68%) 

Canadian Beaufort Sea 1988

37 Off Shingle Pointd 11-Sep 88 0 to 1 1732 4889 Copepods Limnocalanus 

69°00'N 137°28'W 0 to 2 736 2635 macrurus 

Other Studies in the Canadian and Alaskan Beaufort Sea (Wartzok et al. 1990)

38 Off Tuktoyaktuk Peninsula Sep 89 about 20 426 -b -b Copepods (67%) 39 Off Demarcation Bay Sep 89 about 20 730 -b -b Euphausiids (50%) Thysanoessa 

raschii (100%) 

40 Camden Bay Sep 89 about 20 1619 -b -b Copepods (97%) 41 Camden Bay Sep 89 about 20 854 -b -b Chaetognaths (58%) 42 Camden Bay Sep 89 about 20 3287 -b -b Euphausiids (85%) Thysanoessa 

raschii (100%) 

a Echosounder not functioning.b No horizontal taken at depthc No oblique tows taken.d Only numbers and calculated biomass for Limnocalanus macrurus known for this station.

Biomass (mg/m3) Dominant Taxa

Date
APPENDIX 6.4. Temperature and salinity profiles (CTD) in the water column at whale feeding and control stations in the e

Sea, Sept 1986 and 1999. See Figure 6.1A,B and Appendix 6.1 for station locations. At the right of all profiles, top line (re

line (blue) is temperature.
APPENDIX 6.5. Temperature and salinity profiles (CTD) in the water column at whale feeding and control stations in the e

Sea, Sept. 2000. See Figure 61.1C and Appendix 6.1 for station locations. At the right of all profiles, top line (red) is salintemperature.
7. ZOOPLANKTON: SUMMARY AND CONCLUSIONS

William B. Griffiths1 and Denis H. Thomson2

The main purpose of the zooplankton components of the study was to characterize, in a quantitative

way, the zooplankton available to feeding bowhead whales over the continental shelf from the Canadian

border to central Camden Bay (141° to 145°W) during late summer and early autumn. That is the season

when much of the Bering–Chukchi–Beaufort stock of bowhead whales travels west through that area,

often feeding on zooplankton either while traveling west or while lingering in certain parts of the area.

To characterize the zooplankton, we needed to document the general distribution (horizontal and vertical)

of the zooplankton biomass and species composition in the study area, and their variability from year to

year. Also required was an understanding of the distribution, biomass, and species composition of zooplankton at the specific locations and times where bowhead whales chose to feed.

We addressed these requirements via a program of boat-based sampling near feeding whales and in

the study area generally during varying date ranges in September of five years, 1985–86 and 1998–2000,

as documented in Chapters 4–6. Weather, oceanographic, and ice conditions varied among these years,

and the frequency and locations of conspicuous feeding by bowhead whales also varied. Coordinated net

sampling and quantitative echosounder surveys, both near feeding whales and along broader-scale

transects, provided the needed data (in conjunction with limited physical oceanographic sampling).

During all five seasons, aerial surveyors searched for bowheads in the same study area, observed whether

they were feeding, and guided the boat-based crew to feeding bowheads when possible.

Acoustic vs. Net Biomass

There was a need for a method to estimate zooplankton biomass from echosounder data acquired

along transects and at whale feeding locations in the eastern Alaskan Beaufort Sea. This was done by

comparing zooplankton biomass collected in horizontal bongo-net tows with concurrent echosounder

measurements of acoustic back scatter at corresponding depths. Paired data of these types were collected

during September in all five years of the study. Linear regression techniques (robust LTS regressions in

1998–2000) were used to develop equations that could predict zooplankton biomass from acoustic back

scatter when only the latter is measured. In all five years, there was a positive and statistically significant

(P < 0.05 or better) correlation between net biomass and acoustic back scatter. Predictive equations were

developed for data collected in 1985, 1986, 1999, and 2000. In all cases, the best-fit equations were

developed using the highest frequency transducer, 200 kHz in 1985–86 and 430 kHz in 1999–2000. In

1998, the relationship between back scatter and zooplankton biomass was too weak to be of use. A strong

relationship between backscattering data and net zooplankton biomass is difficult to obtain because the

acoustic data may contain echoes not only from zooplankton but also from other biotic as well as abiotic

 

1

 LGL Ltd., environmental research associates, 9768 Second St., Sidney, B.C. V8L 3Y8. Phone: 250-

656-0127; e-mail: bgriff@lgl.com

2

 LGL Ltd., environmental research associates, 22 Fisher St., POB 280, King City, Ont. L7B 1A6.

Phone: 905-833-1244. e-mail: dthomson@lgl.com
7-2 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

sources. Sources of variability include such things as fish larvae, other large swift or very small zooplankters not captured by nets, the shape and orientation of the zooplankton, sediment plumes, and

density discontinuities. (In any future related work, additional attention should be given at the planning

stage to possible ways of reducing these problems.) Despite the limitations and biases, the method

provided useful data concerning the locations and depths of high-density zooplankton patches, and the

relative amounts of zooplankton at different locations, depths, and times within and among the four years

when useful data were available. This approach was an important technique in assessing the characteristics

and quality of bowhead whale feeding habitat available in the eastern Alaskan Beaufort Sea during those

four years.

Species Composition, Biomass, and Distribution

There have been notable differences in zooplankton biomass and species composition of

zooplankton, particularly copepods, sampled in September of 1985–86 and 1998–2000. In the eastern

Alaskan study area as a whole, total zooplankton biomass appeared to be higher in 1985 and especially

1986 than in 1998–2000. Predatory cnidarians, ctenophores, and chaetognaths were much more abundant

in samples collected in 1998–2000 than in either 1985 or 1986. Predation may have contributed to the

lower total zooplankton biomass observed in 1998 through 2000. Another major difference was a change

in the dominant nearshore copepod species in the region. In 1985 and 1986, the brackish-water species

Limnocalanus macrurus was by far the dominant copepod (on a biomass basis) in nearshore waters. This

species was not found in the study area in 1998 and 1999 and was found only rarely in 2000, perhaps due

to the absence of a relatively warm, freshened surface water mass in these years. Copepods of the genus

Calanus were present in all samples from all five years, and were the dominant species in 1998–2000.

The vertical distribution of zooplankton biomass evident on the echosounders differed among the

four years with useful echosounder data. The 1985 and 1986 results were similar in that one to three

layers of zooplankton were observed at individual stations. Throughout the study area, most of these

zooplankton layers were 5 to 8 m thick, and most were in the upper 45 m of the water column. At some

of the 1985–86 shallow water stations (<25 m depth), the zooplankton layers occurred throughout most of

the water column, extending all the way to the bottom. During sampling in 1999, there was usually only

a single layer of zooplankton at each station, which varied in thickness from 5 to 25 m. Most of the layers

were found in water depths >10 m and extended to the bottom. The year 2000 was different from all

other years in that there was a marked difference in zooplankton between eastern and western stations,

i.e., from the Canadian border to Jago Lagoon vs. Barter Island to Camden Bay. In the eastern portion of

the study area, few zooplankton layers were evident at any stations, while to the west there were 1–3

dominant zooplankton layers.

In 1985 and 1986, the echosounder surveys and net samples showed that zooplankton biomass was

generally highest in the nearshore zone and tended to decrease with increasing distance from shore and

increasing depth. In 1999 and 2000, zooplankton was more evenly distributed along the transects. However, in 2000 the zooplankton biomasses were much higher in the western area (Barter Island to Camden

Bay) than farther east. Another major difference in zooplankton distribution was that the biomass of

zooplankton estimated to be in the concentrated layers was higher in 1985 and 1986 than in 1999 or (for

most locations) 2000. Maximum zooplankton biomass in layers exceeded 1200 mg/m3

 (wet weight) in

both 1985 and 1986, and 750 mg/m3

 on the three westernmost transects in 2000, but was only ~700

mg/m3

 in 1999 and 500 mg/m3 on most other 2000 transects.
§7. Zooplankton: Summary & Conclusions 7-3

In 1985 and 1986, along each transect, numerous zooplankton patches ~1 km in length and a few

meters in thickness contained densities ranging from an estimated 1400 to 2000 mg/m3

. In 1999, biomass

in similar-sized zooplankton patches did not exceed 500 mg/m3

, while in 2000 large patches of zooplankton biomass that ranged from 1000 to 1400 mg/m3

 were typically found only along the western three

transects.

Characteristics of Bowhead Feeding Areas

Zooplankton biomass near feeding whales was studied in September of 1986, 1998, and 1999. (In

September of 1985 and 2000, few if any bowheads lingered in the eastern Alaskan area to feed, and we

were not able to sample near whales feeding in that area.) Zooplankton biomass was much lower at the

whale feeding locations sampled in 1998 and 1999 than in 1986. In 1986, zooplankton biomass at whale

feeding stations averaged 586 mg/m3

 (maximum 1228 mg/m3) for the water column as a whole, and

averaged 1375 mg/m3

 (maximum 3847 mg/m3) in horizontal tows at depth. During 1986, some individual whales lingered to feed for several days, particularly in the nearshore zone in the southeastern corner

of the study area (Chapter 11). The small copepod Limnocalanus macrurus dominated there, as has often

been the case at whale feeding locations in nearshore waters along the Yukon coast. In 1998 and 1999,

zooplankton biomass at whale feeding stations was below 400 mg/m3

 (maximum 678 mg/m3) in the water

column as a whole, and below 400 mg/m3

 (maximum 886 mg/m3) in horizontal tows at depth. In 1998,

bowhead whales moved quickly through the area and did not appear to stop and feed for any length of

time (Chapter 11). In 1999, some bowhead whales stopped to feed in the study area for a few days, but

these were located in the deeper offshore waters (40 to 150 m depth; Chapter 11). Bowhead whale

feeding habitat in the eastern Alaskan Beaufort Sea appears to have been of better quality in 1986 than in

either 1998 or 1999.

Bowhead whales feed in concentrations of zooplankton in the both the eastern Alaskan and Canadian Beaufort Sea. There was no obvious difference in average zooplankton biomass in the water column

as a whole as measured in oblique tows in those two regions. Zooplankton biomass was higher at stations

where bowhead whales were present than at routine sampling stations where whales were not present.

Furthermore, zooplankton biomass was higher when whales were present during boat-based sampling

than at stations where whales had been sighted from the aircraft during the preceding day, but were no

longer present when the boat began sampling.

Horizontal plankton tows guided to layers of concentrated zooplankton by an echosounder have

been done at 17 stations where bowheads were observed <1 km from the sampling boat in the eastern

Alaskan and Canadian Beaufort seas. At these stations, mean biomass in the horizontal tows with the

highest biomass was 1841 ± s.d. 1226 mg/m3 (n = 17; includes one vertical tow). The lowest biomass in

these tows was 545 mg/m3

. For 4 of 17 stations, the highest biomass measured was 771–807 mg/m3, and

for 12 of 17 stations the highest value was ≥1000 mg/m3

. Biomasses of ~800 mg/m3, as determined by

horizontal bongo-net tows guided by echosounder, may represent the feeding threshold for bowhead

whales, i.e., the minimum biomass for economical feeding.

In 1998 and 1999, Calanus hyperboreus and C. glacialis were the dominant copepod species at

whale feeding stations in the eastern Alaskan Beaufort Sea, but their biomass was typically lower than

that of the Limnocalanus macrurus present at whale feeding stations in 1986. Predatory cnidarians,

ctenophores, and chaetognaths were much more abundant at whale feeding and control station in 1998

and 1999 than in 1986. These animals feed on copepods and other zooplankters. The absence of

L. macrurus in 1998–99 was largely responsible for the lower biomass observed at feeding stations in
7-4 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

those years as compared with 1986. The absence of L. macrurus was possibly attributable to the reduced

temperature and salinity gradients in 1998–99 and/or the presence of numerous predators. The predatory

species that were abundant in 1998–99 are of much lower nutritive value than are copepods (Thomson,

Chapter 22).

Calanus hyperboreus and C. glacialis were also the dominant copepod species at whale feeding

stations off Richard’s Island in the Canadian Beaufort Sea during 1980 and 1981. Calanus hyperboreus

was again the dominant copepod species at whale feeding stations off Richard’s Island in 1986. Whales

were seen at distances >1 km from the ship, and average biomass at these stations was not particularly

high.

Other taxa that occasionally were dominant components of the zooplankton at whale feeding

stations, aside from copepods and (less commonly) euphausiids and chaetognaths, were gelatinous groups

(cnidarians and ctenophores) and mysids. We did not find places with feeding whales where euphausiids

were dominant, but this has been reported previously by Wartzok et al., and euphausiids are the dominant

components of the prey in the stomachs of a minority of the bowheads landed at Kaktovik (Chapter 18).

Euphausiids are known to show avoidance reactions to sampling nets, and as a result euphausiids are

probably somewhat under-represented in our net samples. However, where euphausiids are abundant, as

they are at times in the western Beaufort Sea, they are prominent in net samples. In general, euphausiids

are apparently less important as prey for bowhead whales in the eastern Alaskan Beaufort Sea than farther

west near Point Barrow.

Recommended Research

The present study involved zooplankton sampling and echosounder surveys at a variety of dates

during September. September is known, from aerial surveys, to be the month of peak utilization of the

eastern Alaskan Beaufort Sea by westward-migrating bowheads. However, information from aerial

surveys and from local residents indicates that bowheads can be present in appreciable numbers from

August to October, with occasional sightings in July (Chapters 2 and 9). Zooplankton biomass and

energy content are expected to vary seasonally, and there could also be seasonal trends in relative

importance of different species or groups. More precise estimates of food availability to bowheads in the

eastern Alaskan Beaufort Sea would be possible if zooplankton sampling there could be extended to

include the full period when bowheads use the area, or at least the main period of use from mid-August to

mid-October. However, sampling in October would be complicated by deteriorating weather conditions

and the fact that ice would likely be present at this time.

The present zooplankton study was conducted in the eastern Alaskan part of the Beaufort Sea, for

reasons explained in Chapter 1. Similar studies have been done on parts of the summer feeding grounds

in the Canadian Beaufort Sea. However, there has been no similar zooplankton study at autumn feeding

locations farther west in the Alaskan Beaufort Sea, or along the northeast coast of the Chukotsk Peninsula

in the western Chukchi Sea. In the western Beaufort Sea (Barrow to Smith Bay) during autumn,

euphausiids apparently are a predominant part of the bowhead diet (Chapter 18). To understand the

relative importance of autumn feeding areas west of the present eastern-Alaskan area, studies of zooplankton availability in the more westerly areas during autumn would be useful. Insofar as possible,

zooplankton availability in these areas should be studied throughout the seasonal period when bowheads

occur in these areas, as evident from previous scientific studies and the experience of local residents.
§7. Zooplankton: Summary & Conclusions 7-5

Given the documented year-to-year variability in zooplankton within the eastern Alaskan study

area, any follow-up study of zooplankton availability in different months or in different areas should be

planned for a duration of at least 3 years if at all possible.

This study has shown that it is necessary to sample quite close to feeding bowhead whales in order

to obtain meaningful data on the food available to the whales (Chapter 6). This limits the number of

sampling opportunities, and makes it important for the zooplankton sampling team to be guided to

feeding whales by aerial surveyors who have a broader and more synoptic perspective on whale use of the

area. Any future bowhead feeding study needs to include guidance by aerial observers (or some other

means, e.g., telemetry) to locations of feeding whales. Such guidance was available during the present

5-season study, but has not always been available during previous studies.

There is partial segregation of size (and age) classes of bowheads when they are passing through

the eastern Alaskan Beaufort Sea during late summer and autumn, with larger (older) whales tending to

be farther offshore (see Chapter 10). To date, opportunities to sample near feeding bowheads in this area

have been largely limited to bowheads in nearshore and inner-shelf waters, where subadult whales

predominate. Within the eastern Alaskan Beaufort Sea, it would be desirable to obtain additional data on

food availability and associated aspects of bowhead feeding in deeper waters. In the deeper areas, a

higher proportion of the bowheads are larger, older individuals, and in those areas zooplankton may concentrate at deeper depths, especially in the later parts of the season.

A combination of net sampling and echosounder surveys has been shown to be necessary in studies

of food availability for bowhead whales. These methods have different strengths and limitations, and are

complementary. However, the correlation between results from the two methods, as applied in the

Alaskan and Canadian Beaufort Sea, has been weaker and more variable than desired. Several probable

or possible reasons for the weaker-than-desired correlation have been identified (Chapter 4). It will be

desirable, in any similar future study of zooplankton availability to bowhead whales, to develop and use

improved field and analysis methods that will provide more reliable and better-correlated net-sampling

and echosounder results. Possible improvements include expanded efforts to identify and measure

confounding factors (e.g., density gradients and turbidity) and to treat them as covariates, and use of

multi-frequency echosounder data to help deal with the problems created by different types and sizes

zooplankton. It would also be desirable to consider the suitability of improved or new types of zooplankton sampling gear that might be available (and practical) by the time a future study is being planned, e.g., opening-and-closing nets; video plankton recorder; specialized echosounder gear. It would be

useful to conduct preliminary fieldwork to develop and test any such improvement or new methods prior

to applying them during an extensive sampling effort.

Data on day–night differences, if any, in the vertical distribution of zooplankton in areas and

seasons where bowheads feed would be helpful in assessing food availability to bowheads. The extent of

diel vertical migration by zooplankton has not been documented for the Beaufort Sea during summer or

autumn. Seasonal variability in the occurrence of diel vertical migration is to be expected, given the

continuous daylight from spring to mid-summer, and increasing darkness from mid-August onward.

Foraging behavior of bowhead whales is likely to be affected by any pronounced vertical migration by

concentrations of prey.
BOWHEAD WHALE DISTRIBUTION,

NUMBERS AND ACTIVITIES

8. INTRODUCTION TO BOWHEAD WHALE COMPONENTS OF STUDY

W. John Richardson and William R. Koski1

Studies of the distribution, numbers, and activities of bowhead whales within and near the eastern

Alaskan Beaufort Sea, primarily via aircraft-based techniques, are described in Chapters 8–16 of this

report. This work was done as an integrated part of a broader study of the importance of that area to

feeding bowheads. Other major study components included compilation of local and traditional knowledge (Chapter 2), studies of zooplankton near feeding whales and in the study area generally (Chapters

3–7), studies of bowhead diet (Chapters 17–21), an energetic analysis (Chapter 22), and integration

(Chapter 23). As stated by MMS,

‘The goal of this study is, collaboratively with key stakeholders, to summarize available

scientific and traditional knowledge and to plan and implement a multi-year study of

bowhead whale feeding in the eastern Alaska Beaufort Sea (between Kaktovik and the

Canadian border, south of 71° N latitude) in order to determine its importance as a

feeding area for bowhead whales.’

The initial phase of this work was conducted during Year 1 of the project (September 1997 through

August 1998). During that time, we compiled the then-available information, both traditional and scientific, concerning the use of the study area and adjacent waters for feeding by bowhead whales and other

related topics (Appendices A through D in Richardson and Thomson 1999). We also worked with the

subsistence hunters, other stakeholders, and the project’s Scientific Review Board to define the key questions and hypotheses, and to develop a study plan for Years 2–4, which were to include fieldwork in

August–September of 1998 to 2000 (Thomson and Richardson 1998, 1999).

During Year 1 of the project (1997–98), considerable effort was spent in documenting local knowledge about use of the eastern Alaskan Beaufort Sea by bowheads, feeding and otherwise. Information

was assembled at a meeting and a workshop convened in Kaktovik, and from individual discussions with

whaling captains and other local people interested in bowhead whales. The results were summarized by

subcontractor M.S. Galginaitis and presented as Appendix D in Richardson and Thomson (1999). An

updated version of that document appears as Chapter 2 of the present report.

At the meetings and via individual discussions during the planning stage, local people described the

timing of occurrence of bowheads in the eastern Alaskan Beaufort Sea and the places where bowheads are

most often seen. One significant point was that, although the main autumn migration does not begin near

Kaktovik until early September, small numbers of bowheads occur in the area during August and occas-

 

1

 LGL Ltd., environmental research associates, 22 Fisher St., POB 280, King City, Ont. L7B 1A6.

Phone: 905-833-1244; e-mail: wjr@lgl.com, bkoski@lgl.com
8-2 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

ionally July. The hunters also noted that bowheads often are seen in Camden Bay just to the west of

Kaktovik as well as in the waters near and to the east of Kaktovik. Some local people suggested that the

study should extend west into Camden Bay, and this was done during fieldwork in 1998, 1999, and 2000.

Relatively little of the traditional information was explicitly about whale feeding behavior, as the hunters

generally do not distinguish feeding whales from other whales when they encounter them at sea. However, the information provided at the meetings and during individual discussions was helpful in formulating a study plan that (1) would focus on the key questions and (2) could be implemented without

interfering with the bowhead hunt. That information, and additional information obtained during further

discussions with local people during 1998–2000, has been summarized in Chapter 2 (see also Annex B in

Volume 2). Relevant local and traditional knowledge has been integrated with the scientific data

collected during this and previous studies in the area, e.g., in Chapters 9, 10 and 12, to provide a more

complete picture of bowhead use of the eastern Alaskan Beaufort Sea.

The original study plan called for additional field research in Years 2–4 (1998–2000) on bowhead

distribution, numbers, and activities in the study area. The data collected during the first year of intensive

fieldwork (1998) were presented in draft in May 1999. This report was reviewed at the June 1999

Scientific Review Board (SRB) meeting. The SRB made some specific recommendations about field

work and analyses to be conducted in following years. The revised study plan that considered comments

made by the SRB and MMS was distributed in August 1999 (Thomson and Richardson 1999) and the

final report on activities conducted during Years 1 and 2 was distributed in September of 1999 (Richardson and Thomson 1999). The data collected during the second year of intensive fieldwork (1999) were

presented in a draft report circulated in July 2000. No further substantive changes to the study plan were

recommended based on the data presented then, and the third season of fieldwork (2000) proceeded much

as in 1999.

The project plan (Thomson and Richardson 1998, 1999) called for the use of aerial surveys, aerial

observations of behavior, and aerial photographic methods to document the distribution, abundance,

behavior, sizes, and residence times of bowheads in the study area. More specifically, the purposes of the

aircraft-based fieldwork were to

• determine distributions and raw numbers of bowheads within the study area during late summer/early-autumn feeding periods in that area,

• determine correction factors for sightability during aerial surveys,

• use the above data to estimate whale-days of utilization of the study area,

• document the proportion of time spent feeding,

• characterize feeding behavior (near-surface/water-column/bottom), and

• determine residence times of individual bowheads.

The aerial survey crew had the additional critical task of providing the boat-based crew with information about locations of bowhead whales (especially feeding whales) on a real-time basis. This was

necessary to allow the boat-based crew to locate bowheads for the purpose of sampling the zooplankton

around feeding whales (described in Chapter 6).

Aerial work of these types was conducted during 1998, 1999 and 2000. Similar data were already

available from a closely-related project in the same region during September 1985–86 (Richardson [ed.]

1987). Thus, comparable data are available from five different years, providing a basis for dealing with
§8. Bowheads: Introduction 8-3

the year-to-year variability issue. Aircraft-based work during the previous study extended from 4 September to 3 October in 1985, and from 2 to 27 September in 1986.

The 1998, 1999 and 2000 field seasons for aircraft-based work were initially anticipated to be from

approximately 1 to 21 September. However, the Kaktovik whaling captains requested that, in 1998–2000,

boat-based work east of Kaktovik not commence until after two whales had been landed at Kaktovik.

Because of the need for coordination between aerial and boat-based work, the start of both aerial and boat

work in 1998 and 1999 was delayed until 10 September, when the 2nd whale was landed. In 2000,

Kaktovik whalers landed their third whale on 8 September, and both aircraft-based and boat-based work

started on 8 September. The aircraft and crew were based at Kaktovik for quick access to the study area

and to optimize opportunities for local liaison. In 1998, 1999 and 2000, our aerial work was limited to

about 2.5–3 weeks each year for budgetary reasons. However, MMS was able to modify their aerial

survey effort (Treacy 2000, 2002) to provide additional coverage of our study area, particularly just

before our field season started (1998, 1999 and 2000) and after our field season ended (1998). MMS provided those data to us for use in this project (see Chapters 9 and 15).

Many of the chapters of this report have been organized and written to facilitate production of scientific papers, which MMS has encouraged. Thus, some of the material (particularly Methods) is repeated in more than one chapter. For purposes of this report, one advantage of this approach is that the individual chapters are largely self-contained and reasonably compact.

Chapter 9 describes the distribution and numbers of bowheads observed in and near the eastern

Alaskan Beaufort Sea during aerial surveys conducted during the late summer and autumn of 1979–2000.

The data used here include not only those from the 1985–86 and 1998–2000 phases of the present study,

but also the results from the surveys conducted or sponsored by MMS each autumn since 1979 (and some

industry-sponsored projects as well). Raw densities of bowheads (numbers seen per 100 km of systematic surveying) are examined relative to four water-depth strata, four east–west strata, and half-month

periods from 1 August to 31 October. Year-to-year and seasonal variation in use of the study area are

examined. The numbers of bowheads present in the study area are calculated for specific days during

each year based on the aerial survey data and correction factors for whales missed during aerial surveys,

as developed in Chapter 15. Numbers of whale-days of use of the study area are calculated for the five

years of the feeding study. The results contribute to the assessment of the importance of autumn feeding

areas in the eastern Alaskan Beaufort Sea.

 Chapter 10 describes the length–frequency distribution of bowheads in and near the eastern

Alaskan Beaufort Sea relative to that of the population as a whole, and describes habitat segregation by

different age classes of the bowhead whale population. It assesses variation in the sizes of whales relative

to year, half-month intervals from 16 August to 15 October, geographic subdivisions, and water depth.

This chapter assesses habitat use by different age classes of bowhead whale, which is important in

energetics calculations (Chapter 22) and to assess the importance of the study area to the overall Bering–

Chukchi–Beaufort bowhead population (Chapter 23).

Chapter 11 describes rates of movements and residence times of bowhead whales in and near the

eastern Alaskan Beaufort Sea and compares them to those of bowheads in summering areas off the

eastern Yukon coast and in Amundsen Gulf. Both types of data, plus activity budgets from Chapter 12,

are required to estimate the proportion of the annual energy requirements of bowhead whales that are

obtained in the eastern Alaskan Beaufort Sea (Chapter 22).

Chapter 12 documents the observed activities and specific behaviors of bowhead whales in and

near the eastern Alaskan Beaufort Sea during late summer and autumn, and compares them with bowhead
8-4 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

activities during other seasons. An understanding of activities and behaviors in the area, especially feeding activity, are important in understanding bowhead use of the study area. Activity budgets presented in

this chapter are used in calculations of residence times (Chapter 11) and energy budgets (Chapter 22).

Chapter 13 discusses bowhead surfacing, respiration and dive (SRD) cycles in and near the study

area in relation to whale activity. The patterns in which whales surface, respire and dive vary with whale

activity. These patterns can be used to quantify whale activity. Data on SRD cycles are also one of the

critical components in the correction factors needed to estimate absolute numbers of whales present based

on the relative information provided by aerial surveys (Chapter 15). Data on SRD cycles are also needed

for whale energetics calculations (Chapter 22).

Data on surfacing, respiration and dive cycles by age category of bowhead whale are given in

Chapter 14. These age-specific characteristics of behavior are important in the calculations done in

Chapter 22 concerning energy requirements and potential water filtering capacity while feeding. In this

chapter, we include data on SRD cycles during spring migration around northwestern Alaska and on the

summering grounds in the Canadian Beaufort Sea as well as data from the present study area during September.

Chapter 15 derives the correction factors needed to estimate the numbers of whales present in the

study area from the results of aerial surveys (Chapter 9). The surfacing, respiration and dive cycle data

presented in Chapter 13 are used in the derivation of the factor that corrects for whales missed because

they are below the surface (“availability bias”). Auxiliary data acquired during aerial surveys in the present study area and elsewhere in the Beaufort Sea are used to develop other necessary correction factors,

and to assess their dependence on survey conditions.

Chapter 16 summarizes the data presented in Chapters 9 through 15, and comments on what is

known about the responsiveness of feeding bowheads to disturbance. Chapter 16 also outlines some

recommendations for future research on the topics covered in Chapters 9 to 15.

To determine the importance of the eastern Alaskan Beaufort Sea to the annual energetic requirements of bowhead whales we need to know (1) how many bowheads occur in the study area (Chapters 9

and 15), (2) the population structure of the bowheads using the study area (Chapter 10), (3) how long

individual whales remain in the area from Kaktovik to Demarcation Bay (Chapter 11), (4) what proportion of that time is spent feeding, and what feeding modes are used (Chapter 12), and (5) how much food

they consume while feeding. The last of these determinations is especially difficult, but data provided in

Chapters 4 through 7 (zooplankton chapters), plus 11, 13 and 14 are all relevant, along with subsequent

chapters 18, 20, and 22 on diet and energetics. That topic is addressed in Chapter 23, “Integration”.

During their meeting on 3–4 June 1999, the project’s Scientific Review Board (SRB) recommended that statistical power analyses be done before subsequent field seasons to evaluate the optimum allocation of aerial effort among the various possible aircraft-based tasks (Appendix A in Thomson and Richardson 1999). This was done in a limited way, in conjunction with SRB member Dr. J. Zeh, as part of the

planning for 1999 (Thomson and Richardson 1999). The power analyses resulted in three recommendations concerning allocation of field efforts.

First, the power analyses indicated that aerial surveys could not provide statistically rigorous estimates of bowhead numbers present in the study area throughout the autumn migration period (and hence

estimates of residence time). Therefore, it was recommended that less effort be expended on aerial

surveys in 1999 and 2000 than had been expended in 1998. The SRB requested that the MMS/BWASP
§8. Bowheads: Introduction 8-5

aerial survey crew put extra effort into obtaining survey coverage of the feeding study area to augment the

reduced survey effort by LGL.

Second, the number of independent samples available for assessing whale activity within the study

area needed to be increased to have the power to distinguish possible differences between areas and years.

Thus, the strategy for conducting behavior observations of whales was changed so that more observation

sessions of shorter duration would be conducted in 1999 and 2000. It was recommended that the field

time previously used to conduct aerial surveys be divided between additional behavior observation sessions and additional bowhead photography (see below).

Third, a method of estimating residence times of bowheads in the study area needed to be developed. Data from repeated photographic coverage of the study area appeared to have the potential to estimate

residence times but in 1998 the duration of coverage was too short. Therefore, the SRB recommended

that in 1999 and 2000 photography begin on the first day of the field program and continue to the end of

the season to maximize the period covered. It was also recommended that some of the time previously

spent conducting aerial surveys be used to conduct additional photography.

The recommendations of the SRB were implemented in 1999 and 2000. This resulted in more reliance on the MMS/BWASP surveys for information on bowhead distribution and numbers in the study

area (Chapter 9) but increased the amount of information obtained for the other components of the study

over what would have been collected if the 1998 strategy had been continued.

Literature Cited

Richardson, W.J. (ed.) 1987. Importance of the eastern Alaskan Beaufort Sea to feeding bowhead whales, 1985-

86. OCS Study MMS 87-0037. Rep. from LGL Ecol. Res. Assoc. Inc., Bryan, TX, for U.S. Minerals

Manage. Serv., Reston, VA. 547 p. NTIS PB88-150271.

Richardson, W.J. and D.H. Thomson (eds.). 1999. Bowhead whale feeding in the Eastern Alaskan Beaufort Sea:

Update of scientific and traditional information. Retrospective and 1998 results. LGL Rep. TA2196-2. Rep.

from LGL Ltd., King City, Ont., and LGL Ecol. Res. Assoc., Bryan, TX, for U.S. Minerals Manage. Serv.,

Herndon, VA. 366 p. [Superseded by present report.]

Thomson, D.H. and W.J. Richardson. 1998. Bowhead whale feeding in the eastern Alaskan Beaufort Sea: Update

of scientific and traditional information. Project Plan. Final (Aug. 1998) ed. LGL Rep. TA2196. Rep. from

LGL Ltd., King City, Ont., and LGL Ecol. Res. Assoc., Bryan, TX, for U.S. Minerals Manage. Serv.,

Herndon, VA. 66 p.

Thomson, D.H. and W.J. Richardson. 1999. Bowhead whale feeding in the eastern Alaskan Beaufort Sea: Update

of scientific and traditional information. Study Plan―Year 3. Final (Aug. 1999) ed. LGL Rep. TA2196-3.

Rep. from LGL Ltd., King City, Ont., and LGL Ecol. Res. Assoc., Bryan, TX, for U.S. Minerals Manage.

Serv., Herndon, VA. 70 p.

Treacy, S.D. 2000. Aerial surveys of endangered whales in the Beaufort Sea, fall 1998-1999. OCS Study MMS

2000-066. U.S. Minerals Manage. Serv., Anchorage, AK. 135 p.

Treacy, S.D. 2002. Aerial surveys of endangered whales in the Beaufort Sea, fall 2000. OCS Study MMS 2002-

014. U.S. Minerals Manage. Serv., Anchorage, AK. 111 p.
9. DISTRIBUTION AND NUMBERS OF BOWHEAD WHALES IN THE EASTERN

ALASKAN BEAUFORT SEA DURING LATE SUMMER AND AUTUMN, 1979–2000

Gary W. Miller, Robert E. Elliott, Tannis A. Thomas, Valerie D. Moulton, and W.R. Koski1

Introduction

From mid-June through October, many bowhead whales of the Bering–Chukchi–Beaufort (BCB)

stock inhabit the Canadian Beaufort Sea and Amundsen Gulf. Bowheads have often been observed feeding

in Canadian waters during summer (e.g., Würsig et al. 1985, 1989). That region has generally been assumed to be the primary feeding grounds of the BCB stock of bowhead whales, despite the evidence from isotopic studies that bowheads feed extensively during late autumn, winter, or both in Chukchi and Bering Sea

waters (Schell and Saupe 1993; see also Chapter 20). Although the Canadian Beaufort Sea is apparently the

primary summering grounds, some bowhead whales occur off the north coast of Alaska for at least part of

the summer (Moore and Clarke 1991; Chapter 2), and may feed while there. Residents of Kaktovik, adjacent to the eastern Alaskan Beaufort Sea, report that they occasionally see bowheads near Kaktovik as early

as July (Chapter 2 and Annex B). Bowhead sightings in the Alaskan Beaufort become more common in

August, and peak sighting rates near Kaktovik occur in September. At least some of the bowhead whales

that summer and feed in Canadian waters continue to feed as they migrate westward through the Alaskan

Beaufort Sea during September and October. This is evident from stomach contents of harvested whales

(Lowry 1993; see also Chapter 18), and from direct visual observations of feeding activities in Alaskan

waters during late summer and early autumn (Ljungblad et al. 1986a; Richardson et al. 1987; Landino et al.

1994; see also Chapters 2, 12). Those data show that feeding is common in the Alaskan Beaufort Sea

during September and October, but the overall importance of summer and autumn feeding in that area to

bowhead whales is not well understood.

Bowhead use of the eastern Alaskan Beaufort Sea study area during late summer and autumn has

been documented for many years by systematic aerial surveys, mainly conducted or sponsored by BLM

and MMS (e.g., Ljungblad et al. 1987; Moore et al. 1989; Treacy 2000, 2002). These surveys have

gathered much information about bowhead use of the study area, including information about relative

utilization according to year, season, and region within the study area. Results for all years from 1979

through 2000 have been described in a lengthy series of annual reports. Results for various combinations

of years have been summarized by Ljungblad et al. (1986b), Clarke et al. (1987), Moore et al. (1989,

2000), and Moore (2000). However, none of those papers uses the survey data collected by MMS after

1991. In addition to the 1979–2000 MMS data, additional survey data have been obtained in parts of the

eastern Alaskan Beaufort Sea during late summer and autumn of certain years during industry-sponsored

monitoring projects and during the present study of bowhead feeding ecology.

Richardson et al. (1987) found that in some years (e.g., 1985) very few bowheads occur in the eastern

Alaskan Beaufort until the main period of westward migration from Canadian waters begins in mid-

 

1

 LGL Ltd., environmental research associates, 22 Fisher St., POB 280, King City, Ont. L7B 1A6.

Phone: 905-833-1244; e-mail: gmiller@lgl.com
9-2 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

September. In other years (e.g., 1986), the western edge of the main summer feeding range extends into the

eastern Alaskan Beaufort Sea before the start of active westward autumn migration. Small numbers of

bowheads often occur in eastern Alaskan waters during August, usually well offshore. Moore et al. (1989)

described the late summer and early autumn (1 Aug.–15 Sept.) distribution of bowheads in the eastern Alaskan

Beaufort region based on surveys conducted from 1979–86. They found that bowheads consistently occurred

along the coast near the U.S./Canada border and north and northeast of Kaktovik, and that sighting rates

(number of whales seen/survey hour) during late August were less than half those calculated for early August

and early September. Bowheads were primarily in deep (>200 m) offshore waters in early August, with

relatively more bowheads occupying shallower nearshore waters in late August and early September.

Although mean headings of swimming bowheads were northwesterly throughout August, the variability was

high, and headings did not become significantly clustered about that direction until early September.

Recently published studies of bowhead distribution and habitat selection, based on BLM/MMS

data from the ten years 1982–91, found that in summer, bowheads in the eastern Alaskan Beaufort Sea

selected outer continental shelf and slope depth habitats without regard to ice conditions. In autumn

bowheads selected shallow inner-shelf waters during years with moderate and light ice cover, and deeper

continental slope habitat during years with heavy ice conditions (Moore 2000; Moore et al. 2000).

Estimates of bowhead numbers in the eastern Alaskan Beaufort Sea during various periods in late

summer and early autumn have included estimates of 0 (1983), <100 (1985), between 100 and 500 (1982,

1983, 1984, and 1986), and as many as 1200–3000 in early August 1982 (Richardson et al. 1987; Moore

and Clarke 1991). These estimates were calculated based on strip transect techniques, with adjustments

for missed whales.

This report describes the seasonal distribution and numbers of bowheads observed in the eastern

Alaskan Beaufort Sea and adjacent Canadian waters during aerial surveys conducted during the late summer and autumn of 1979–2000. The 21 years of data considered here include • all systematic aerial surveys conducted by or for MMS from 1979 to 2000 (no data were available from 1980 for our study area),

• some surveys conducted during industry-funded monitoring programs (1986, 1993), and • surveys conducted by us as part of the MMS-funded studies to assess the importance of the eastern Alaskan Beaufort

Sea to feeding bowheads (1985–86, 1998–2000). This data set includes considerably more data from the

present study area than were available to previous authors. For periods when sufficient aerial survey

coverage was obtained, we have estimated the numbers of bowheads present in the Alaskan portions of

the study area inshore of the 200 m depth contour, with allowance for the numbers of whales present but

missed by the aerial observers. A companion chapter (Chapter 15) describes the correction factors for

missed whales.

Methods

The general approach to this analysis was to examine the distribution and numbers of bowheads in

various geographic regions and depth strata based on aerial survey data collected over a 22-year period.

The study area for this analysis (139°–146°W, south of 71°10'N; see Fig. 9.1) extended slightly farther

east and west than the area considered in most other parts of the feeding study (cf. Fig. 1.2 in Chapter 1).

Although described as the “eastern Alaskan” study area, it included Canadian waters between the Alaska–

Yukon border and Herschel Island. This extended study area was divided into four E–W regions, and

four depth strata defined by the 20, 40 and 200 m contours (Fig. 9.1). Considering both the E–W regions

and depth strata, the study area was divided into 16 analysis zones. For seasonal analyses, the data were

categorized into six half-month (15- or 16-day periods) from 1 Aug. to 31 Oct.
§9. Bowheads: Distribution & Abundance 9-3

FIGURE 9.1. The study area, showing E–W regions, depth strata, and analysis zones used in analyses of

bowhead distribution in the 139°–146°W region of the Beaufort Sea, August to October of 1979–2000.

Data were assembled from numerous studies conducted from 1979 to 2000. Priority was placed on

obtaining data that were available in digital format. In addition, data from several important studies that

were not available in digital format were converted to digital format and validated. Studies that provided

few data and that were not available in digital form were not included in this analysis. Most, but not all,

of the systematic surveys conducted in the eastern Alaskan Beaufort Sea during the 22-year period from

1979 through 2000 were included in the following analyses.

We examined several specific measures of bowhead use of the study area, including the following:

• distribution,

• relative abundance among zones within seasons,

• relative abundance within zones among years, and

• estimated numbers of bowheads present in the study area.

Data Sources

The data from a large number of studies conducted in late summer/autumn were compiled. These

studies included aerial surveys flown by or on behalf of • the U.S. Minerals Management Service, and

• various industry groups including Shell Western Exploration & Production Inc. (SWEPI) and ARCO

Alaska Inc. Table 9.1 summarizes the amount of aerial survey effort by year during each study included

in this analysis.
9-4 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

TABLE 9.1. Linear kilometers of systematic transects flown in the 139°-146°W portion of

the Beaufort Sea during 1979-2000 and included in the present analysis. Excludes

survey effort during poor sighting conditions.

Range of NOSC/ LGL for COPAC

Survey MMS for MMS LGL for for

Year Dates MMS Feeding SWEPI ARCO Total

1979 02 Aug - 27 Oct 4960 4960

1980 - 0 0

1981 05 Sep - 11 Oct 1396 1396

1982 02 Aug - 13 Oct 9873 9873

1983 02 Aug - 12 Oct 7692 7692

1984 01 Aug - 10 Oct 8526 8526

1985 01 Aug - 20 Oct 13391 4119 17,509

1986 15 Aug - 17 Oct 8568 3968 8494 21,031

1987 02 Sep - 31 Oct 8182 8182

1988 03 Sep - 18 Oct 7895 7895

1989 04 Sep - 11 Oct 4412 4412

1990 02 Sep - 17 Oct 2444 2444

1991 31 Aug - 12 Oct 2360 2360

1992 31 Aug - 14 Oct 6023 6023

1993 17 Aug - 28 Oct 5490 15581 21,070

1994 31 Aug - 12 Oct 2666 2666

1995 31 Aug - 19 Oct 3158 3158

1996 02 Sep - 06 Oct 3554 3554

1997 01 Sep - 19 Oct 3497 3497

1998 31 Aug - 27 Oct 6099 2852 8951

1999 03 Sep - 26 Sep 3195 1593 4789

2000 01 Sep - 12 Oct 4413 956 5369

Total 117,793 13,488 8494 15,581 155,357

1979–2000 Autumn Aerial Surveys for or by MMS.—The most extensive and consistent source of

data concerning bowhead distribution in the study area is the series of aerial surveys conducted each year

from 1979 to 2000 for or by MMS (Bureau of Land Management prior to 1982). This MMS dataset has

been documented in a series of annual reports by Naval Oceans Systems Center (NOSC) for 1979–86

(e.g., Ljungblad et al.1987; Moore et al. 1989) and by MMS for 1987–99 (e.g., Treacy 2000). From the

combined 1979–2000 dataset, we selected sighting and survey effort records pertaining to longitudes

139°–146°W. MMS/NOSC data for that region exist for all years in the 1979–2000 period except 1980,

i.e., 21 years. During many early years, survey coverage of the study area began during the late summer

period, typically around 2 Aug. (Table 9.1). In most later years, the MMS/NOSC surveys began in late

August or early September, around the time when the autumn westward bowhead migration could be

expected to start. Survey coverage ended in mid-to-late October in most years. Within those date ranges,

the present study area typically was sampled on about 1 day within each 5–7 day period. During 1998–

2000, MMS surveyors modified their survey effort to provide somewhat increased coverage of the eastern

Alaskan Beaufort Sea study area in support of the present study.
§9. Bowheads: Distribution & Abundance 9-5

1985–86 Aerial Surveys During Feeding Study for MMS.—LGL conducted systematic aerial

surveys for MMS as part of a bowhead feeding study in the eastern Alaskan Beaufort Sea during 1985–86

(Richardson et al. 1987). The surveys were conducted weekly (approx.) from 5 to 27 Sept. in 1985 and

from 4 to 26 Sept. in 1986. We digitized the data into a format similar to that used by MMS in the above

studies.

1986 Aerial Surveys for SWEPI.—LGL conducted systematic aerial surveys from 2 Sept. to 9 Oct.

1986 on behalf of Shell Western Exploration & Production Inc. as part of a study to investigate the

responses of migrating bowhead whales to an exploratory offshore drilling operation. These surveys were

conducted near the Hammerhead and Corona drillsites in Camden Bay on a daily basis, weather permitting (Evans et al. 1987). We digitized the data into a format similar to that used by MMS.

1993 Monitoring Surveys for ARCO.—Coastal and Offshore Pacific Corp. (COPAC) conducted

systematic aerial surveys in 1993 for ARCO Alaska Inc. (Anchorage). These surveys were conducted to

study the distribution and relative abundance of bowheads and other marine mammals in relation to the

Kuvlum (2 and 3) and Wild Weasel drilling projects in the Camden Bay area (Hall et al. 1994). The

surveys were flown from 17 Aug. to 28 Oct. 1993 on a daily basis, weather permitting. Digital data were

provided by Jeremy Davies (then with the National Marine Mammal Laboratory, Seattle, WA). We converted those data into a format similar to that used by MMS.

1998–2000 LGL Aerial Surveys During Feeding Study for MMS.—Systematic aerial surveys

were conducted during September of 1998–2000 as part of the present study to assess the importance of

the eastern Alaskan Beaufort Sea to bowhead whales. Surveys were conducted every 7–10 days (approx.)

from 11 to 24 Sept. in 1998, from 12 to 26 Sept. in 1999, and on 12 Sept. 2000. Again, we digitized the

data into a format similar to that used by MMS.

Aerial Survey Methods

MMS Aerial Surveys, 1979–2000.—Overall, 21 of 28 aerial survey programs considered in this

analysis were the annual programs conducted or sponsored by MMS from 1979 to 2000. During these

years, late summer and autumn aerial surveys were flown over broad portions of the Alaskan Beaufort

Sea from 140°–157° W longitude, south of 72° N latitude. The surveys were flown in a modified Grumman Goose (1980–87) or a deHavilland Twin Otter (1979 and 1986–2000) at air speeds of 185–300 km/h

(100–160 knots). In recent years, surveys were conducted at an altitude of 457 m a.s.l. (1500 ft), but

some earlier surveys were as low as 100 m (330 ft) when cloud ceilings were low. The three observers

used inclinometers to measure the angle (relative to horizontal) to each cetacean sighting when the initial

sighting location was abeam of the aircraft. Observers and pilots were linked by a common communication system, and conversations and comments could be recorded onto audiotape (1979–82). Seating and

window arrangements varied, and are summarized in Chapter 15.

The aircraft were equipped with radar altimeters and either a VLF navigation system or, in recent

years, a Global Positioning System (GPS). Starting in 1982, an onboard computer interfaced with the

navigation system stored flight data (time and position) automatically for later analysis. Since 1983, the

on-board computer has also been linked to a radar altimeter or GPS for automatic input of altitudes.

Marine mammal sightings, environmental conditions (e.g., weather, sea state, ice cover), and start and end

points of transects and other survey segments, were entered manually into the computer. More details

concerning the survey aircraft and other equipment used during MMS/NOSC surveys are provided in the

reports summarizing each year’s data (e.g., Ljungblad et al. 1987; Treacy 2002) and in previously-cited

papers by S.E. Moore et al.
9-6 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

Daily flight patterns were derived by dividing each MMS/NOSC survey block into north–south

strips 30 minutes of longitude wide; 30’ is ~18.5 km or 10 n.mi. at this latitude. One of the minute marks

along the northern edge of each 30’ section was selected at random to designate one end of a transect.

The other transect endpoint was determined using a separate randomly generated number along the

southern edge of the same 30’ section. A straight line, representing one transect, was drawn between the

two points. The same procedure was followed for all 30’ sections of the survey block. The transect to be

flown within each 30’ section was determined separately each time that area was surveyed. The selection

of survey blocks to be flown on a given day was non-random, based on weather conditions, where survey

coverage had been obtained during recent days, etc. The MMS/NOSC study area was very large, extending west from 140oW (near the east edge of our study area) to 157oW (near Barrow). MMS/NOSC coverage in our study area typically occurred during one day within each 5–7 d (approx.) period.

Non-transect flight segments were identified as “Connect” and “Search” segments. “Connect”

segments were the east–west (or similar) flights from the end of one transect to the start of another.

“Search” segments were flights to or from the survey block where transects were flown, or non-random

flights to find whales. Sightings during “Connect” and “Search” segments are plotted (as open symbols)

on our maps, but were not used in quantitative analyses.

LGL and COPAC Systematic Surveys.—The 7 additional aerial survey programs considered here

were conducted by LGL Ltd (1985–86 and 1998–2000) and COPAC (1993).

Transects flown by LGL during the MMS-sponsored feeding studies (1985–86, 1998–2000) were

randomized and oriented roughly perpendicular to the coast and depth contours. The same set of

randomly-selected transects was flown repeatedly, typically about once per week in 1985–86 and every

7–10 days in 1998–99, but only once in 2000. In 1985–86, the 140°–144°W region was sampled by 13

continental shelf (0–200 m contour) transects and 8 continental slope (200–2000 m contour) transects

totaling 1260 km. During 1998–2000, the study area was extended west to 145°, and 4 continental shelf

and two continental slope transects in this new region were added to the transects flown in 1985–86. All

27 transects were flown in 1998, but in 1999–2000 only the 17 continental shelf transects were flown.

Surveys flown by LGL for SWEPI in 1986 and by COPAC for ARCO in 1993 consisted of repeated daily (weather permitting) surveys of N–S survey grids roughly centered on drillsites. • SWEPI surveys in 1986 included “intensive” grids (12 transects spaced 4 km apart; total 475 km) and “area” grids

(8 transects spaced 10 km apart; total 608 km when at Corona and 531 km when at Hammerhead). The

intensive grid was usually flown every day that weather permitted. If no whales were seen on that grid,

then portions of the “area” grid were flown. The surveys near the Corona drillsite (2–17 Sept. 1986) were

wholly within the present study area. However about half of the survey grid around Hammerhead (19

Sept.–9 Oct. 1986) was west of our study area. • COPAC surveys in 1993 were flown on a “proximal”

grid (6 transects spaced 12.9 km apart) and a “distant” grid (6 transects spaced 12.9 km apart and located

east of the “proximal” grid). The westernmost of the 6 proximal transects was west of our study area.

Typical daily survey coverage by COPAC within our study area was ~700 km.

The aerial survey methods used during the LGL and COPAC studies were generally similar to

those during surveys for MMS with the following exceptions. Survey altitude was usually 305 m a.s.l.

(1000 ft), but some surveys were conducted at 152 m (500 ft) when ceilings were low. Survey speed

varied from 185 to 220 km/h (100 to 120 knots). During all LGL surveys, data on whale sightings and

survey conditions were recorded onto tape recorders and later entered into computer files. Aircraft position data were dictated onto audiotape in 1985–86 (LGL) but were logged automatically during 1993

(COPAC) and 1998–2000 (LGL). Surveys in 1985–86 were flown in a Twin Otter. Surveys in 1993 and
§9. Bowheads: Distribution & Abundance 9-7

1998–2000 were flown in a Twin Commander 500 (1993 only) or 680FL (1993 and 1998–2000) pistonengined aircraft. Seating and window arrangements varied, and are summarized in Chapter 15. Details

concerning the aerial survey methods used in these studies can be found in Richardson et al. (1987),

Evans et al. (1987), and Hall et al. (1994).

Data Analyses

Mapping.—Bowhead sightings during the 1979–2000 study period are depicted on standard base

maps. These maps show the 139°–146°W (approx.) region, from the coast north to ~71°10’N.

MMS/NOSC survey coverage north of this boundary, although much reduced, extended as far north as

72°N. The industry-funded studies were more localized and did not extend north of 71°10’N. Bathymetric contours shown on maps were developed based on all publicly available point soundings. Sounding data from U.S. waters were obtained on CD-ROMs from NOAA, including Hydrographic Survey

Data, Vol. 1, vers. 3.1; and Marine Geophysical Data/Bathymetry, Magnetics, Gravity, vers. 3.2. Point

soundings and gridded bathymetry data were contoured using a triangulated irregular network (TIN) algorithm in the Vertical Mapper add-on module for MapInfo Professional.

Each sighting symbol on these maps represents a sighting of one or more individual bowhead whales.

“Non-transect” sightings are those seen during “search or connect” segments (generally before the start or

after the end of a transect). “Excluded” sightings are those seen during portions of transects with poor

sightability (Beaufort scale >4 or visibility <1 km). “Transect” sightings include all other sightings along

systematic transects, regardless of distance from the trackline.

The maps and analyses do not include all bowhead sightings from aircraft during the years of study.

The LGL studies during 1985–86 and 1998–2000 included aerial components other than systematic aerial

surveys (behavior observations, aerial photography of bowheads, reconnaissance―see Chapters 10 and 12)

that also resulted in many sightings of bowheads from aircraft. Those sightings are not plotted on these maps.

Similarly, the 1981–84 studies by NOSC for MMS included additional site-specific surveys, reconnaissance

flights, and behavioral studies conducted from a separate aircraft; those data are also excluded.

The maps (and analyses) exclude aerial survey sightings coded as “duplicates” or “repeats” of previous sightings, i.e., the same animal(s) seen by more than one observer or more than once at the same

location. Direction indicators (in degrees True) attached to the symbols indicate the headings of whales

classified as “traveling”.

Bowheads Per Unit Effort (Relative Abundance).—The maps described above provide much of

the distributional information. However, they are difficult to interpret because survey effort varied considerably within the study area, both within and among years. To account for this variability we computed bowheads per unit effort within various zones. The study area was divided into four E–W regions and

four depth strata: Nearshore (<20 m), Middle Shelf (20 m to 40 m), Shelf Break (40 m to 200 m) and

Continental Slope (>200 m). This resulted in 16 “analysis zones” (Fig. 9.1).

We used MapInfo, supplemented by specially-written MapBASIC computer code, to determine the

number of individual bowheads sighted and the number of kilometers of “transect” survey coverage

within each analysis zone during the 1979–2000 period. These analyses excluded “non-transect” and

“excluded” survey effort and sightings, as defined above. An index of bowhead abundance (individuals

seen/100 km) was determined for the various analysis zones by dividing the number of “transect” individuals seen in each area of interest by the number of kilometers of transect coverage within that area. For

any period where “transect” survey coverage within a particular region, stratum or zone was <200 km,

those data are not plotted on Figures showing numbers of individuals seen/100 km.
9-8 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

Seasonal Occurrence.—We examined the distribution and abundance of bowheads in the study

area by half-month periods from 1 Aug. to 31 Oct. in order to examine seasonal changes in these

parameters. These analyses were restricted to “transect” sightings in order to allow meaningful calculations of individuals per unit effort during different periods. Thus, zero individuals in a particular data

range means no sightings of bowheads during “transect” surveys, not necessarily that no individuals were

sighted on those dates.

Estimated Numbers of Bowheads Present.—Two general approaches have been used to estimate

densities and numbers of animals present in an area based on aerial transect surveys. “Line transect”

methodology (Buckland et al. 1993) is now the most commonly used approach for surveys of cetaceans.

It provides more precise estimates when adequate numbers of sightings are made during the survey.

However, the line transect method requires a minimum number of sightings to estimate some needed

parameters. “Strip-transect” methods (Eberhardt et al. 1979) have been used during most past surveys of

bowhead whales (e.g., Davis et al. 1982; Richardson et al. 1987; Moore and Clarke 1991), sometimes

because too few sightings were made for effective use of the line transect method.

Not all animals are seen during transect surveys. Further, the proportion of animals that are

detected is affected by altitude, air speed, glare, sea state, behavior of the target species, and nominal transect width. In theory, two parameters, f(0) and g(0), can be computed from the raw survey data and from

other observations of the species of interest to minimize most of the biases that lead to inaccurate estimates of the actual numbers of mammals present at the time of the survey. The f(0) factor accounts for

the reduced probability of detecting an animal at the surface of the water as its distance from the trackline

increases. The g(0) factor accounts for animals that are (1) on or near the trackline and at the surface but

not detected during the survey, and (2) animals that are below the surface and not visible at all. The

derivation of these parameters for the present surveys is discussed in Chapter 15, “Correction Factors to

Calculate Bowhead Whale Numbers from Aerial Surveys of the Beaufort Sea”.

We used f(0) and g(0) factors derived in Chapter 15 to calculate line transect estimates of the

numbers of bowheads present for each day (or two-day period) when sufficient survey effort was available to justify the use of this methodology (Buckland et al. 1993). The f(0) factors are specific to a given

aircraft type, and altitude, sea condition and ice-cover categories (see Table 15.2 in Chapter 15 for

details). The “DISTANCE” program (Thomas 1999, version 3.5, release 5) was used to calculate the

numerical estimates. The area considered encompassed the Camden Bay, Kaktovik, and Demarcation

zones from the shore to the 200 m depth contour (Fig. 9.1). This area included 9 of the 16 analysis zones

(3 E–W zones × 3 depth zones); we excluded the Komakuk region and the Continental Slope depth

stratum. This reduced 9-zone area corresponds (approximately) to the area where systematic zooplankton

sampling was conducted (Chapter 5), and to the primary study area for various other parts of the project.

The number of bowheads present in the 9-zone area was estimated for each day when transect

survey coverage met two minimum criteria: (1) ≥400 linear km of coverage within the 9 zones, and (2)

some survey coverage within at least 6 of the 9 analysis zones. Estimates were also derived for combined

surveys that together represented ≥400 linear km of survey coverage. These combinations were limited to

same-day surveys by different agencies (e.g., MMS/NOSC and LGL) or surveys on two consecutive days

by the same or different agencies. Consecutive days of surveys were only combined if the survey coverage on the second day was east of the coverage on the first day, thereby avoiding double sampling of

whales that may have been migrating in the typical autumn EÆW migratory direction. Most estimates

for single days or adjacent days were based on very small numbers of sightings (see Table 9.2, later).

Buckland et al. (2001, page 88) note that it is legitimate to apply line transect procedures to small samples
§9. Bowheads: Distribution & Abundance 9-9

of sightings when the f(0) and g(0) factors were derived from larger samples combined across days, as

was done here (cf. Chapter 15).

“Whale-Days”.―In order to assess the importance of the eastern Alaskan Beaufort Sea to bowhead whales during the specific years of the bowhead feeding studies (1985–86 and 1998–2000), we

estimated the numbers of whales in the 9-zone “restricted” study area on each day (7 Aug.–27 Oct.) during each year. There were 5 to 11 days in each year with sufficient survey coverage for a direct estimate

of total numbers present on the survey day (or an adjacent pair of days) using the transect methodology

described above and in Chapter 15. We estimated numbers present on other days by extrapolation based

on the 10-d moving-average density in the study area for that date, and an “expansion factor” (described

below) for that year.

Because bowhead numbers in the study area vary seasonally, with peak numbers occurring during

late September, it was not possible to average the raw numbers present on survey days and extrapolate to

days without surveys. To account for seasonal trends in abundance we computed mean densities in the

9-zone restricted study area for each day (1 Aug.–31 Oct.) based on combined transect data from 1979–

2000. To smooth the data for irregular sampling, we computed a 10-d moving average density for each

day during the 7 Aug.–27 Oct. period (see Fig. 9.12, later).

The “expansion factor” was included in order to adjust the estimate of bowhead numbers for a

given survey for the seasonal pattern in bowhead abundance depicted later in Figure 9.12. Computation

of the expansion factor resulted in a date-adjusted index of bowhead abundance for each survey. Averaging the expansion factors for selected years provided a means of comparing date-adjusted annual differences in the relative abundance of bowheads in the study area. An expansion factor for each survey date

was computed by dividing each of the daily “direct estimates” of the number of bowheads present in the

study area by the 10-d moving average density for that date. The expansion factors for each survey date

in each year were averaged to give an average expansion factor for that year. That expansion factor was

multiplied times the sum of the daily moving averages of bowhead abundance for the dates in the 7 Aug.–

27 Oct. period (54.341 in all years; see Appendix 9.1) to derive an estimate of the number of bowhead

“whale-days” of use of the restricted 9-zone study area during selected years. The calculations are

explained in more detail near the end of the “Results”, and the resulting estimates are used in Chapters 11

and 23.

Statistics.—For all statistical tests, results were considered statistically significant based on the

α = 0.05 criterion, and marginally significant for 0.10 > α > 0.05. The Friedman test was used to compare the observed sighting rates of bowheads (individuals/100 km of survey effort) in various geographic

zones or time periods. The blocking variable in each analysis was year. We conducted three analyses

that compared densities across the (1) four depth strata, (2) four E–W zones, and (3) three half-month

periods. Only years that had >200 km of survey effort in each of these situations were included in the

analyses. This resulted in the inclusion of 17, 18, and 17 years of data for tests involving the depth strata,

E–W zones, and half-month time periods, respectively.

We summarized the headings, in degrees True, of bowhead sightings in the study area and recorded

as traveling. Heading data were summarized and plotted for each of the six half-month periods. The

vector mean ± angular deviation were calculated (Batschelet 1981), and the Rayleigh test of uniformity

was used to test the null hypothesis that bowhead headings were distributed uniformly (Ha: headings were

concentrated around some particular direction). We included only “transect” sightings of “traveling”

whales seen during periods of acceptable sighting conditions (Beaufort scale ≤4 and visibility ≥1 km).
9-10 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

Results

Survey Coverage and Effort

This analysis is based on 155,000 km of “transect” aerial surveys (Table 9.1). The combined

1979–2000 effort in the 139°–146°W region is plotted by month in Figure 9.2. Available survey coverage east of 140°W was very limited south of 70°30’N and almost non-existent north of that latitude

during all months. August survey coverage elsewhere was fairly uniform (Fig. 9.2A). During September

and October, coverage was most intense between the shoreline and 70°30’N (Fig. 9.2B,C). The sparse

MMS/NOSC coverage north of 71°10’N is not mapped or considered in this study. The MMS/NOSC

transects flown during the late summers and autumns of 1979–2000 (except 1980) dominate the flightlines mapped in Figure 9.2. The transect selection procedure used by MMS/NOSC (see “Methods”)

resulted in wheatsheaf-shaped bands of heavy survey coverage alternating with narrower bands of

relatively sparse coverage.

Geographic Variation

The distribution of bowheads recorded during the systematic aerial surveys considered here is

shown in Figure 9.3. The 891 “transect” sightings of 1199 individual bowheads are the basis of most

analyses discussed below. When numbers of individuals were adjusted for survey effort, the overall

abundance for the study period was 0.77 bowheads sighted per 100 km (Fig. 9.4G). This figure, and subsequent “/100 km” values, are actual sighting rates, without allowance for whales either at or below the

surface that were missed by the observers. All ice conditions are included, and the only allowance for

sighting conditions is that survey coverage and sightings along portions of transects with Beaufort state

>4 or visibility <1 km are excluded.

Depth Strata.―Considering August–October as a whole, bowhead abundance differed significantly amongst the four depth strata when data were blocked by survey year (Friedman χ2

 = 12.85, df = 3, P =

0.005). The highest average sighting rate was in the Shelf Break zone (40–200 m) at 1.07 bowheads seen

per 100 km (Fig. 9.4G). Bowheads were moderately abundant in the Middle Shelf (0.78 /100 km) and

Nearshore (0.73 /100 km) strata. Average abundance for the combined August–October period was lower

in the Continental Slope stratum (0.30 /100 km).

E–W Strata.―Considering August–October as a whole, bowhead abundance in the four E–W regions differed by a marginally significant amount (Friedman χ2

 = 6.42, df = 3, P = 0.093). Overall, bowhead abundance was highest in the east (1.16 bowheads seen per 100 km in the Komakuk region; Fig.

9.4G) and declined with increasing longitude to 0.54 /100 km in the Camden Bay region. In the Shelf

Break stratum, bowhead abundance was highest in the Demarcation Bay region (1.50 /100 km) and lowest in the Camden Bay region (0.64 /100 km). In all other depth strata, bowhead abundance was higher in

the Komakuk and Kaktovik regions than in the Camden and Demarcation Bay regions (Fig. 9.4G).

Seasonal Variation

Overall bowhead abundance differed significantly among the 1–15 Sept., 16–30 Sept., and 1–15

Oct. periods (Friedman χ2

 = 10.32, df = 2, P = 0.006). During that 11⁄2-mo period, bowhead abundance

was highest during 16–30 Sept. (1.03 bowheads seen/100 km), slightly lower during the first half of

September (0.96 /100 km), and lowest during 1–15 Oct. (0.55 /100 km; Fig. 9.5). The paucity of surveys

in August and late October during certain years prevented their inclusion in this statistical analysis.

However, the available data from early and late in the season showed similar sighting rates in August as

in early October, and a very low sighting rate in late October (Fig. 9.5; details below).
§9. Bowheads: Distribution & Abundance 9-11

FIGURE 9.2. Aerial survey transects flown in the 139°–146°W region of the Beaufort Sea during (A) August, (B) September, and (C) October, 1979–2000. Excludes “non-transect” segments and “excluded”

segments with poor sighting conditions. See Methods for description of data sources.
9-12 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

FIGURE 9.3. Locations of bowhead sightings during aerial surveys in the 139°–146°W region of the Beaufort Sea during August–October of 1979–2000.

1–15 August.—Most of the early-August survey effort was restricted to the early survey years (1979,

1982–86). These data show that, in early August, there were numerous bowhead sightings in offshore portions

of the study area (Fig. 9.6A). When the data were standardized for survey effort, the overall abundance index

for early August was 0.57 bowheads seen/100 km (Fig. 9.4A). Considering the four depth strata, the highest

index was in the Continental Slope stratum (0.96 /100 km; Fig. 9.5A). The abundance index in the Shelf

Break stratum was substantially lower (0.37 /100 km), and no transect sightings of bowheads were recorded in

the Middle Shelf or Nearshore strata. Considering E–W regions (Figs. 9.4A, 9.5B), moderately high abundance was recorded in the Kaktovik and Komakuk regions (1.11 and 0.90 /100 km, respectively). Abundance

was moderate in the Demarcation region (0.48 /100 km) and very low in the Camden Bay region (0.06 /100

km). All sightings with known headings were recorded as “traveling”, and their headings were non-uniform

(Rayleigh test, P = 0.04), with a mean heading toward the northwest (326°T ± a.d. 66.8°; Fig. 9.7A).

16–31 August.—Most late-August survey effort was also restricted to the early years (1979, 1982–86),

although MMS autumn coverage of this area sometimes started on 31 Aug. in later years, and there was also

some late August effort in 1993 by COPAC. In late August, bowheads were widely distributed throughout the

study area (Fig. 9.6B). The overall sighting rate was relatively low at 0.38 bowheads seen/100 km (Fig.

9.4B)―lower than in early August. Within the various depth strata, the highest bowhead abundance again

occurred in the Continental Slope stratum (0.54 /100 km)(Fig. 9.5A). Bowhead abundance was moderate in the

Shelf Break stratum (0.37 /100 km) and low in the Middle Shelf and Nearshore strata (0.18 and 0.20 /100 km,

respectively). Abundance declined from east to west (Figs. 9.4B, 9.5B). This is consistent with the observations of Kaktovik residents that in August bowheads tend to be more common along the Canadian coastline than

in Alaskan waters (Chapter 2). Bowheads were most abundant in the Komakuk region (1.20 /100 km), and

moderately abundant in the Demarcation (0.43 /100 km) and Kaktovik (0.42 /100 km) regions. As in early
§9. Bowheads: Distribution & Abundance 9-13

FIGURE 9.4. Relative abundance of

bowheads in various E–W regions and

water depth strata by half-month periods

(and combined), based on “transect”

surveys in the 139°–146°W region of the

Beaufort Sea, August–October 1979–2000.

No symbol is plotted when <200 km of

“transect” surveys. Periods with poor

sightability excluded. Total “Transect”

survey effort for each half-month period

was 11,676, 19,339, 50,906, 42,253,

23,468 and 7714 km, respectively.
9-14 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

FIGURE 9.5. Relative abundance of bowheads during half-month periods by (A) water depth stratum or

(B) E–W zone, based on “transect” surveys in the 139°–146°W region of the Beaufort Sea, 1979–2000.

Otherwise as in Figure 9.4.
§9. Bowheads: Distribution & Abundance 9-15

FIGURE 9.6. Locations of bowhead sightings during aerial surveys in the 139°–146°W region of the Beaufort Sea during (A) 1–15 Aug. and (B) 16–31 Aug., 1979–2000.
9-16 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

FIGURE 9.7. Headings (degrees True) of bowhead whales classified as “traveling” during aerial surveys in

the 139°–146°W region of the Beaufort Sea by half-month period during August–October 1979–2000.

Based on “transect” surveys, excluding periods of poor sightability. Each sighting was counted once

regardless of number of whales in the group. The arrow represents mean vector and mean vector length

(plotted relative to circle radius = 1.0). Except in “D”, each triangular symbol represents one sighting.
§9. Bowheads: Distribution & Abundance 9-17

August, bowhead abundance was very low in the Camden Bay region (0.14 /100 km). For the 87% of the

sightings with known headings that were recorded as “traveling”, the headings were highly variable and not

significantly concentrated (Fig. 9.7B; a.d. = 78.6° and Rayleigh test, P = 0.89).

1–15 September.—In the first half of September, sightings of bowheads were concentrated inside the

200 m contour (Fig. 9.8A). The overall sighting rate was relatively high at 0.96 bowheads seen/100 km (Figs.

9.4C). The highest indices of abundance were in the Shelf Break stratum (1.33 /100 km), followed by the

Nearshore and Middle Shelf strata at 1.14 and 0.95 /100 km, respectively (Fig. 9.5A). In contrast to the

situation in August, the sighting rate in the Continental Slope stratum during early September was much lower

than for other depth strata, at only 0.16 /100 km. Bowheads were widely distributed across all E–W regions of

the study area (Fig. 9.8A). However, overall abundance was highest in the east (Komakuk, 1.49 /100 km) and

declined progressively with increasing longitude to 0.66 /100 km in the Camden Bay region (Figs. 9.4C, 9.5B).

During the first half of September, 86.2% of the sightings with known headings were recorded as “traveling”,

and the mean heading of those bowheads was 271°T ± a.d. 69.2° (Fig. 9.7C). These headings were significantly

non-uniform (Rayleigh test, P < 0.01), but many bowheads were oriented in directions other than westward.

16–30 September.—In the last half of September, bowhead sightings were again concentrated inside the

200 m contour (Fig. 9.8B). Overall bowhead abundance (1.03 bowheads seen/100 km) was higher than for any

other half-month period in August–October (Fig. 9.4D). Bowheads were most abundant in the Shelf Break and

Middle Shelf strata (1.45 and 1.22 /100 km, respectively), followed by the Nearshore and Continental Slope

strata at 0.73 and 0.12 /100 km, respectively (Fig 9.5A). Bowheads were distributed across all four E–W

regions of the study area (Fig. 9.8B). However, bowhead abundance declined slightly from east to west, i.e.,

from 1.49 /100 km in the Komakuk region to 0.86 /100 km in the Camden Bay region (Figs. 9.4D, 9.5B).

During the 16–30 Sept. period, 90.2% of the sightings with known headings were recorded as “traveling”, and

the mean heading of those bowheads was 279°T ± a.d. 55.0° (Fig. 9.7D). These headings were significantly

non-uniform (Rayleigh test, P < 0.01), with a stronger westward tendency than in early September.

1–15 October.—In early October, bowheads were sighted in all depth strata, but appeared to concentrate within the 200 m contour (Fig. 9.9A). Overall bowhead abundance was moderate at 0.55 bowheads/100 km (Fig. 9.4E). Bowheads were most abundant in the Shelf Break, Nearshore, and Middle

Shelf strata (0.88, 0.64, and 0.53 bowheads seen/100 km, respectively), and very scarce farther offshore in

the Continental Slope stratum (0.06 /100 km)(Fig. 9.5A). Bowheads were distributed across all four E–

W regions of the study area (Fig. 9.9A), but were most abundant in the Kaktovik region (0.99 /100 km).

Bowhead abundance was lower in the Komakuk, Camden Bay, and Demarcation regions (0.52, 0.39, and

0.30 /100 km, respectively)(Figs. 9.4E, 9.5B). During the first half of October, 88.5% of the sightings

with known headings were recorded as “traveling”, and the mean heading of those bowheads was

267°T ± a.d. 58.4° (Fig. 9.7E). These headings were significantly non-uniform (Rayleigh test, P < 0.01)

16–31 October.—Survey effort in late October (7714 km) was lower than in any other half-month

period, as by this time the area is usually ice-covered and most bowheads have migrated to the west. There

were 8 years with >200 km of survey coverage during late October. The few bowheads seen during transect

surveys (eight sightings of nine individuals) were outside the 20 m depth contour and predominantly in the

western half of the study area (Fig. 9.9B). Overall bowhead abundance (0.12 bowheads seen/100 km) was

lower than for any of the other five half-month periods considered (Fig. 9.4F). The few bowheads seen during

transect surveys were primarily in the Continental Slope and Shelf Break strata, but there were non-transect

sightings in shallower water (Fig. 9.9B). During late October, all 8 “transect” sightings were recorded as

“traveling”, and the mean heading of those bowheads was 289°T ± a.d. 24.3° (Fig. 9.7F). These headings

were non-uniform (Rayleigh test, P < 0.01), with less variation than in earlier half-month periods.
9-18 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

FIGURE 9.8. Locations of bowhead sightings during aerial surveys in the 139°–146°W region of the Beaufort Sea during (A) 1–15 Sept. and (B) 16–30 Sept., 1979–2000.
§9. Bowheads: Distribution & Abundance 9-19

FIGURE 9.9. Locations of bowhead sightings during aerial surveys in the 139°–146°W region of the Beaufort Sea during (A) 1–15 Oct. and (B) 16–31 Oct., 1979–2000.
9-20 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

Summary of Seasonal Variation.—Moderate numbers of bowheads were present during early

August, especially in offshore waters (>200 m deep) of the three easternmost regions of the study area

(Fig. 9.5). Bowhead abundance was somewhat lower during the second half of August, and there was a

slight shoreward shift in the distribution of bowheads. However, bowheads remained most abundant in

areas >40 m deep and in the three easternmost regions of the study area.

During the first half of September the relative abundance of bowheads in the study area increased.

Also, their distribution shifted inshore and expanded westward to span the full width of the study area,

coincident with increased migration into and through the study area. Peak bowhead abundance was

recorded during the second half of September, when bowheads were most abundant in the Shelf Break

and Middle Shelf strata (20–200 m deep).

Bowhead relative abundance in the study area declined in early October and, as in September,

highest densities were shoreward of the 200 m contour. By late October, the relative abundance of bowheads was very low.

The percentage of the bowhead sightings recorded as “traveling” was similar (86–100%) over the

six half-month periods. For traveling whales, headings were significantly non-uniform (and predominantly westward or northwestward) in all half-month periods except for late August. However, the variation

in the headings of “traveling” bowheads was larger in the three periods up to 15 Sept. than in the three

periods thereafter.

Feeding Whales

The locations of bowhead whales recorded as feeding when sighted during aerial surveys are mapped as large symbols, by half-month periods, in Figures 9.6, 9.8, and 9.9. Only 6 of 891 “transect” sightings (0.7%) in the study area, and 11 of 1199 individual bowheads (0.9%), were categorized as feeding.

These low numbers contrast with other evidence that (at least in September) bowheads in this area spend

a substantial part of their time feeding (see Chapters 12, 18). This contrast shows the difficulty of recognizing feeding behavior in the brief glimpses of whales that typically occur during systematic aerial

surveys. About 83% of the feeding in the study area is well below the surface, and extended observations

are usually needed to obtain indirect evidence of feeding below the surface (Chapter 12).

Within the 139°–146°W area, the aerial survey crews obtained additional “non-transect” sightings

of feeding bowheads. Considering all feeding whales (large symbols) mapped in Figures 9.6 and 9.8–9.9,

it is evident that Canadian waters in the nearshore Komakuk region have been an important feeding area

in August and early September. Bowheads were recorded feeding there in 1984, 1985, and 1986. In

eastern Alaskan waters, feeding bowheads were seen in the southeast part of the Demarcation region

during September of 1979–82, 1986, and 1999. In the Camden Bay region, feeding whales were observed

during September and early October in Middle Shelf and Shelf Break waters. These sightings occurred

during 1981–82 and 1998. There were also a few sightings of feeding bowheads in nearshore Kaktovik

waters during September 1980. Aerial surveyors obtained no records of feeding bowheads west of

Komakuk in August, and none in waters beyond the 200 m depth contour at any time. However, as noted

above, it difficult to recognize feeding activity during systematic aerial surveys, especially when whales

are feeding well below the surface. Data of other types show that feeding occurs commonly within the

eastern Alaska area, at least during some years (see Chapters 2, 6, 12, 18).

Annual Variation

Bowhead abundance in the study area has varied markedly from year to year (Fig. 9.10). There

were eight years when observed abundance was higher than the overall average of 0.77 bowheads
§9. Bowheads: Distribution & Abundance 9-21

FIGURE 9.10. Annual variation in relative abundance of bowheads in (A) all water-depth strata combined,

and (B) – (E) five specific water-depth strata, based on “transect” surveys in the 139°–146°W region of

the Beaufort Sea, August–October of 1979–2000. No symbol is plotted when <200 km of “transect”

surveys.
9-22 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

seen/100 km: 19822, 1990, 1993–95, and 1997–99 (Fig. 9.10A). The highest indices of abundance were

recorded in 1995 (3.23 /100 km), 1999 (3.32 /100 km) and 1990 (4.05 /100 km). These indices were 4 to

5 times higher than the overall 1979–2000 average. During the 13 years with below-average indices,

abundance ranged from 0.09 (1988) to 0.68 (1991) bowheads seen/100 km (Appendix 9.2). Seven of the

eight years with above-average bowhead abundance were in the 1990s and most (9 of 13) years with

below-average abundance occurred prior to 1990. The average of the annual abundance indices during

the 1979–89 period is 0.36 /100 km vs. 1.60 /100 km for the 1990–2000 period. Thus, there appears to

have been a marked increase in average bowhead abundance in the study area since 1989 3

.

The increase after 1989 was most pronounced in the Shelf Break stratum (40–200 m deep), usually

followed by the Middle Shelf stratum. Especially high abundance was recorded in these strata in 1990,

1995, and 1999 (Fig. 9.10C,D). However, in the Nearshore stratum, bowhead abundance was highest in

1997 (5.63 /100 km). Bowhead abundance was low in the Continental Slope stratum during almost all

survey years (mean = 0.30 /100 km), with the exception of 1982 (1.82 /100 km).

On an E–W basis, observed increases in bowhead abundance since 1989 were most pronounced in

the Kaktovik and Demarcation Bay regions (Fig. 9.11C, D). The years of post-1989 peak abundance in

those two regions (and to a lesser extent the Camden Bay region) coincide. The pattern in the Komakuk

region appears quite different, with peaks in bowhead abundance observed in 1991, 1994 and 1998, and

no strong tendency for abundance to be higher in 1990–2000 than earlier.

Estimated Numbers of Bowheads Present

The numbers of bowheads present in the study area at various times were estimated for a “restricted study area” consisting of the Camden Bay, Kaktovik, and Demarcation regions from the shore to the

200 m depth contour (Fig. 9.1). The estimates were based on 81 surveys or combinations of surveys,

each of which was flown on one day or two consecutive days during the 1979–2000 period (Table 9.2).

These estimates are based on line-transect methodology with allowance for low detectability of whales

close to the trackline, the decrease in detectability with increasing lateral distance, missed whales at the

surface, and missed whales below the surface (see Methods and Chapter 15). The estimated numbers of

bowheads within the “restricted study area” ranged from 0 (during many surveys) to a maximum of 4505

bowheads (based on 765 km of survey coverage on 13 Sept. 1999). The standard errors associated with

the single-survey estimates were typically about as large as the estimates themselves.

Seasonal Patterns in Bowhead Numbers.—A plot of the 10-day moving average of bowhead

abundance within the restricted study area indicates that, on average, the period of peak bowhead abundance occurs during September and the first half of October (Fig. 9.12). Within most half-month periods

the estimated numbers of bowheads present were highly variable. All six seasonal periods included

 

2

Bowhead abundance in 1982, especially in the Demarcation region, may have been higher than indicated on Figures 9.10 and 9.11. Johnson (1984) found very high numbers of bowheads (128 individuals seen) on 22 Sept. 1982

in a portion of his nearshore study area between 141°W (international border) and 143°45'W (near Kaktovik). This

corresponds to 33.8 bowheads seen/100 km (69 bowheads in 204 km of systematic transect flown). Johnson sampled the area from the shore to 20 n.mi. offshore (40–60 m depth). This area was not sampled during the 17 Sept.–

5 Oct. 1982 period by any of the studies included in the present analysis.

3

 It was suggested by the Scientific Review Board (see Annex A) that we should also compare the data for 1979–90

vs. 1991–2000 to assess the sensitivity of the results to the specific choice of “cutpoint”. The mean indices of abundance would then be 0.696 whales/100 km (n = 11) vs. 1.353 whales/100 km (n = 10).
§9. Bowheads: Distribution & Abundance 9-23

FIGURE 9.11. Annual variation in relative abundance of bowheads in (A) all regions of the study area, and

(B) – (E) four specific longitudinal zones, based on “transect” surveys in the 139°–146°W region of the

Beaufort Sea, August–October of 1979–2000. No symbol is plotted when <200 km of “transect” surveys.
9-24 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

TABLE 9.2. Estimated numbers of bowhead whales in a restricted portion of the eastern Alaskan Beaufort

Sea study area, based on August - October surveys by MMS, LGLa

 and COPAC. Considers the Camden

Bay, Kaktovik and Demarcation regions shoreward of the 200 m depth contour. Based on line transect

methods, including allowance for f(0), ga(0), and gd(0) correction factors (see Chapter 15).

Half- Ref. To

Month Survey

Period Est. S.E.c Est. S.E.c Detailsd

1 1982 MMS 06 Aug 585 0 0

1984 MMS 02 Aug 405 0 0

1-15 1984 MMS 14 Aug 407 0 0

Aug 1985 MMS 08 Aug 411 1 1.33 1.52 191 219 18

Maxe 191

Ave (n =4) 47.8

2 1982 MMS 28 Aug 408 0 0

1984 MMS 29 Aug 541 2 3.86 4.31 556 621 19

16-31 1985 MMS 18/19 Aug 439 0 0

Aug 1986 MMS 16 Aug 405 0 0

1986 MMS 20 Aug 559 0 0

1986 MMS 24 Aug 532 0 0

1986 MMS 28 Aug 497 0 0

1993 COPAC 18 Aug 471 0 0

1994 MMS 31 Aug 480 8 9.13 8.33 1317 1201 7

1995 MMS 31 Aug - 1 Sep 475 0 0

Maxe 1317

Ave (n =10) 187.3

3 1982 MMS 15 Sep 496 2 2.20 2.27 317 327 18

1983 MMS 03 Sep 408 0 0

1-15 1983 MMS 07 Sep 483 0 0

Sep 1985 LGL 06 Sep 410 0 0

1985 LGL 13 Sep 689 1 0.79 1.14 115 165 7

1986 MMS 03 Sep 495 1 1.10 1.31 159 189 18

1986 LGL 04 Sep 495 6 6.80 7.19 981 1037 7

1986 MMS 11 Sep 530 2 2.06 2.05 297 296 18

1986 LGL 11 Sep 703 4 3.12 2.95 450 425 7

1987 MMS 11 Sep 402 4 5.45 5.36 786 773 7

1988 MMS 14/15 Sep 573 0 0

1993 COPAC 01 Sep 600 4 3.91 3.55 565 512 16

1993 COPAC 08 Sep 759 5 3.87 4.16 558 601 16

1993 COPAC 10 Sep 471 1 1.25 1.36 180 197 16

1993 COPAC 12 Sep 1166 0 0

1993 COPAC 15 Sep 556 4 4.22 4.24 609 611 16

1994 MMS 01/02 Sep 405 5 6.77 6.22 977 897 7

1996 MMS 10 Sep 416 1 3.06 3.84 441 554 8

1998 LGL 11 Sep 558 3 3.16 2.91 455 419 16

1999 MMS 07 Sep 588 12 11.19 9.62 1615 1388 7

1999 MMS 11 Sep 478 14 16.04 13.26 2314 1912 7

1999 MMS+LGL 12 Sep 429 2 2.55 4.70 368 678 7

1999 LGL 13 Sep 765 41 31.23 25.67 4505 3702 10

Study Date

Effort 

(km)

Bhds/ 100 kmc No. Bhdsc

Bhds 

seen on

Transb Year

... continued
§9. Bowheads: Distribution & Abundance 9-25

TABLE 9.2. (continued)

Half- Ref. To

Month Survey

Period Est. S.E.c Est. S.E.c Detailsd

2000 MMS 1-Sep 569 2 2.22 2.22 320 321 9

2000 MMS 3-Sep 508 4 4.31 4.09 622 590 7

2000 LGL 12-Sep 934 2 1.25 1.32 180 190 10

Maxe 4505

Ave (n =26) 646.7

4 1979 MMS 18/19-Sept 478 1 1.15 2.99 165 432 7

1985 LGL 18-Sep 768 3 2.14 2.12 309 306 7

15-30 1985 MMS 18-Sep 502 0 0

Sep 1985 LGL 25-Sep 737 1 1.72 2.37 249 342 8

1985 MMS+LGL 26/27-Sept 432 1 1.27 1.33 183 191 7

1986 SWEPI+LGL 20-Sep 482 3 3.41 3.29 492 475 7

1986 LGL 22-Sep 767 11 7.86 7.10 1133 1024 7

1986 SWEPI+MMS 25-Sep 533 4 4.11 3.83 593 552 7

1987 MMS 29/30-Sept 629 2 2.01 1.97 289 285 9

1988 MMS 17/18-Sept 581 1 2.19 2.62 316 378 8

1988 MMS 24-Sep 410 0 0

1993 COPAC 16-Sep 438 2 2.68 2.66 387 384 16

1993 COPAC 19-Sep 1200 17 8.26 8.62 1191 1243 10

1993 COPAC 20-Sep 597 11 10.74 9.58 1550 1383 10

1993 MMS 24-Sep 451 2 2.43 2.57 351 371 7

1993 COPAC 29/30-Sept 728 3 2.42 2.45 349 353 16

1996 MMS 28/29-Sept 519 0 0

1997 MMS 26-Sep 427 0 0

1997 MMS 28-Sep 421 3 3.91 3.84 564 555 7

1998 LGL 17-Sep 1018 19 10.96 9.46 1580 1364 16

1998 MMS 18-Sep 578 15 16.36 13.68 2360 1973 9

1999 MMS 16/17-Sept 521 4 4.21 4.04 607 583 7

1999 LGL 26-Sep 481 22 26.65 22.97 3845 3313 10

2000 MMS 20-Sep 465 0 0

Maxe 3845

Ave (n =24) 688.0

5 1981 MMS 11-Oct 645 2 4.97 5.97 717 861 17

1985 MMS 13/14-Oct 462 0 0

1-15 1989 MMS 5-Oct 405 0 0

Oct 1992 MMS 4-Oct 434 0 0

1993 COPAC 02/03-Oct 569 7 7.16 6.82 1033 983 10

1993 COPAC 5-Oct 626 2 1.88 2.38 271 344 16

1993 MMS 7-Oct 401 3 4.09 4.63 591 668 7

1993 MMS 8-Oct 521 7 7.36 10.92 1062 1575 7

1993 COPAC 08 Oct 630 19 17.58 16.46 2536 2374 10

1993 MMS 13 Oct 406 1 1.35 1.92 195 277 7

1998 MMS 08/09 Oct 586 3 3.23 3.10 466 447 9

2000 MMS 10 Oct 426 1 2.98 4.26 430 613 8

Maxe 2536

Ave (n =24) 608.4

No. Bhdsc Bhds/ 100 kmc

Bhds 

seen on

Transb Year Study Date

Effort 

(km)

... continued
9-26 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

TABLE 9.2. (concluded)

Half- Ref. To

Month Survey

Period Est, S.E.c Est. S.E.c Detailsd

6 1985 MMS 19/20-Oct 444 0 0

1993 MMS 16-Oct 420 0 0

16-31 1993 COPAC 27-Oct 556 0 0

Oct 1998 MMS 22-Oct 456 0 0

1998 MMS 26/27-Oct 471 0 0

Maxe 0

Ave (n =5) 0

a

Includes surveys listed as LGL and SWEPI.

e

Minimum estimate was zero for each 1/2 month period.

Bhds 

seen on

Transb Year Study Date

Effort 

(km)

d

Numbers refer to ID numbers in Table 15.2 (in Chapter 15). Table 15.2 indicates the specific aircraft type, as well

as ranges of altitude, sea conditions (Bf), ice cover and f (0) values associated with a given survey or combination of

surveys for which bowhead numbers were estimated.

Bhds/ 100 kmc No. Bhdsc

b

Excludes sightings between trackline and inner truncation distance (159 - 600 m, depending on aircraft altitude &

type); also excludes sightings beyond outer truncation distance (900 - 3000 m, depending on aircraft altitude, sea

conditions and ice cover). c

Calculated by the DISTANCE program including use of f(0), g a (0) and g d (0) correction factors to allow for whales

missed by observers.

some surveys when no bowheads were estimated to be present (Table 9.2). Based on the average

estimated numbers of bowheads during each of the six seasonal periods, peak numbers of bowheads

occurred in the restricted study area during late September, with an average of 688 bowheads present (n =

24 surveys or combinations of surveys, Table 9.2). Substantial average numbers were also estimated for

early September (647 bowheads, n = 26) and early October (608 bowheads, n = 12). Much lower

averages were calculated for August, with an estimated 47.8 bowheads present within the restricted study

area during the first half of August (n = 4 surveys), and 187.3 bowheads present during the second half (n

= 10). No bowheads were estimated to be present during the second half of October (n = 5). These

estimates are based on sightings within a defined range of lateral distances along systematic transects.

During some surveys, no bowheads were seen in these restrictive conditions, resulting in a “zero”

estimate, but one or more bowheads were known to be present based on other sightings not meeting the

criteria for inclusion in the line-transect estimation process.

If we consider only the 1990–2000 period, the average estimated numbers of bowheads present in

the restricted study area were as follows: 439 during late August (n = 3 surveys), 914 during early

September (n = 15), 983 during late September (n = 13), 732 during early October (n = 9), and 0 during

late October (n = 4). No data were available for early August during 1990–2000.

Annual Patterns in Estimated Bowhead Numbers.—As noted earlier, there appears to have been

an increase in bowhead abundance in the eastern Alaskan Beaufort Sea study area in recent years, based

on observed trends in indices of abundance during the 1979–2000 period. The estimated numbers of

bowheads present on the specific occasions listed in Table 9.2 provide another opportunity to examine

this issue. Although the sample sizes are small in most seasons, these values include allowance for some

of the factors affecting bowhead sightability (Chapter 15). We compared the estimated numbers of bowheads present at various times during 1979–89 vs. 1990–2000, restricting the analysis to the 1 Sept.–

15 Oct. periods when peak numbers of bowheads were estimated to be in the restricted study area. The
§9. Bowheads: Distribution & Abundance 9-27

FIGURE 9.12. Plot of daily 10-day moving average of bowhead abundance (individuals seen/100 km) in

the restricted eastern Alaskan Beaufort Sea study area, 7 Aug.–27 Oct., 1979-2000, based on data from

Appendix 9.1. Restricted study area excludes Komakuk region and Continental Slope depth stratum.

September and early October estimates for 1990–2000 (n = 37) were significantly higher than those for

1979–89 (n = 25, t = –3.24, df = 46, two-tailed P = 0.002). None of the estimates in Table 9.2 are from

1990, so the results would be unchanged if 1979–1990 were compared with 1991–2000.

Estimates of Numbers of Bowhead "Whale-days".—Estimates of the numbers of “whale-days” of use

of the restricted study area were calculated for the five years of the MMS feeding studies (1985–86, 1998–

2000) as briefly described in the Methods. These calculations use daily 10-day moving averages of bowhead

abundance (Fig. 9.12, Appendix 9.1) and the estimated numbers of bowheads present on certain days within

those years (from Table 9.2). As an example of how the numbers are calculated, we consider the 1985

calculations shown in Table 9.3 in greater detail. There were 10 survey dates (or combined dates) during 1985

with sufficient survey coverage to generate estimates of bowhead numbers. These survey results are listed in

Table 9.2 and the whale-days calculations are summarized in Table 9.3. Estimated numbers of bowheads

ranged from 0 (five surveys) to 309 (18 Sept.). Each estimate of whale numbers was converted to a dateadjusted index of bowhead abundance by dividing the estimate by the 10-day moving average of bowhead

abundance (from Appendix 9.1 and depicted in Fig. 9.12) for that date. Moving average values ranged from

0.128 (8 Aug.) to 1.662 (18 Sept.) for estimates >0 bowheads. For 1985 the date-adjusted indices of bowhead

abundance ranged from 0 to 1496.4 and averaged 219.7 (Table 9.3). The latter number represents the dateadjusted index of bowhead abundance for the restricted study area in 1985. This average was multiplied times

the sum (54.341) of all daily 10-day moving average indices of bowhead abundance during the 7 Aug. – 27

Oct. period. The resulting figure (11,937) represents the estimated number of bowhead “whale-days” in the

restricted study area during the 7 Aug. – 27 Oct. period in 1985. 
9-28 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

TABLE 9.3. Estimated average bowhead “whale days” in the restricted eastern Alaskan Beaufort Sea

study area, 7 Aug.–27 Oct., 1985-86 and 1998-2000.

A. B. A. x B.

Est. Density Date- Sum of 

Half- Survey No. Index Adjusted Daily 

Month Survey Effort Bhds (10-Day Index of M.A. Bhd Total

Period Study Date (km) Presenta M.A.)b Abundance Densitiesa Whale-Days

1985 1 MMS 08 Aug 411 191 0.128 1496.4

 " 2 MMS 18/19 Aug 439 0 0.0

 " 3 LGL 06 Sep 410 0 0.0

 " 3 LGL 13 Sep 689 115 1.384 83.1

 " 4 LGL 18 Sep 768 309 1.662 185.9

 " 4 MMS 18 Sep 502 0 0.0

 " 4 LGL 25 Sep 737 249 1.012 246.0

 " 4 MMS+LGL 26/27 Sep 432 183 0.988 185.3

 " 5 MMS 13/14 Oct 462 0 0.0

 " 6 MMS 19/20 Oct 444 0 0.0

 Mean No. Bhds 219.7 54.341 11,937

1986 2 MMS 16 Aug 405 0 0.0

 " 2 MMS 20 Aug 559 0 0.0

 " 2 MMS 24 Aug 532 0 0.0

 " 2 MMS 28 Aug 497 0 0.0

 " 3 MMS 03 Sep 495 159 0.998 159.4

 " 3 LGL 04 Sep 495 981 1.008 973.1

 " 3 MMS 11 Sep 530 297 1.135 261.7

 " 3 LGL 11 Sep 703 450 1.135 396.6

 " 4 SWEPI+LGL 20 Sep 482 492 1.510 325.8

 " 4 LGL 22 Sep 767 1133 1.231 920.8

 " 4 SWEPI+MMS 25 Sep 533 593 1.012 585.8

 Mean No. Bhds 329.4 54.341 17,899

1998 3 LGL 11 Sep 558 455 1.135 401.0

 " 4 LGL 17 Sep 1018 1580 1.485 1064.3

 " 4 MMS 18 Sep 578 2360 1.662 1419.6

 " 5 MMS 08/09 Oct 586 466 0.785 593.6

 " 6 MMS 22 Oct 456 0 0.0

 " 6 MMS 26/27 Oct 471 0 0.0

 Mean No. Bhds 579.8 54.341 31,507

1999 3 MMS 07 Sep 588 1615 1.126 1433.7

 " 3 MMS 11 Sep 478 2314 1.135 2039.3

 " 3 MMS+LGL 12 Sep 429 368 1.366 269.5

 " 3 LGL 13 Sep 765 4505 1.384 3255.6

 " 4 MMS 16/17 Sep 521 607 1.485 408.9

 " 4 LGL 26 Sep 481 3845 1.002 3838.6

 Mean No. Bhds 1874.3 54.341 101,850

2000 3 MMS 01 Sep 569 320 0.906 353.4

 " 3 MMS 03 Sep 508 622 0.998 623.5

 " 3 LGL 12 Sep 934 180 1.366 131.8

 " 4 MMS 20 Sep 465 0 0.0

 " 5 MMS 10 Oct 426 430 0.700 614.4

 Mean No. Bhds 310.4 344.6 54.341 18,727

a

Line transect estimate, corrected for missed whales (from Table 9.2).

b

From Appendix 9.2.—10-d moving average (for this date) of raw "individuals seen/100 km".
§9. Bowheads: Distribution & Abundance 9-29

The results are shown in Table 9.3. The estimated numbers of whale-days within the restricted

study area during the 7 Aug.–27 Oct. period for the five years ranged from a low of 11,937 whale days in

1985, to a high of 101,850 whale days in 1999. During 4 of 5 years, the estimates were in the range

11,937 to 31,507.

Discussion

Local and Traditional Knowledge of Bowhead Occurrence

Whale hunters and other residents of Kaktovik, within the present eastern Alaskan study area,

know much about the seasonal and geographic patterns in bowhead use of that area and adjacent Canadian waters (see Chapter 2 and Annex B). Kaktovik residents occasionally see bowheads in eastern Alaskan

waters as early as July, and sightings become more common in August. However, when Kaktovik residents

travel along the Yukon coast in July and August, they see more bowheads there than in eastern Alaskan

waters. Sightings near Kaktovik are most common in September, the primary hunting season for bowheads

passing Kaktovik. Some bowheads remain in the area well into October. Bowheads are often seen close to

shore near Kaktovik. Some residents noted that bowheads may linger in specific areas for several days and

that bowheads often tend to feed near water-mass boundaries or off river mouths. Waters near Icy Reef

and Arey Island (see Fig. 2.1) are places where local residents have seen bowheads lingering.

Tendency for more Sightings in Recent Years

The observed variability in annual bowhead abundance seems very high considering that most of

the bowhead population apparently migrates through the study area each year in late summer and autumn.

A number of factors may account for this variability:

1. variability in weather and sighting conditions.

2. variability in survey aircraft, observers and methods over the 22 year period considered.

3. bowheads often migrate in “pulses”, separated by periods of reduced abundance; depending on

survey timing relative to pulses, numbers seen could vary considerably.

4. surveys in different years have started and ended on varying dates and often have not spanned the

full autumn migration period of bowheads.

5. migrating whales may be less detectable than feeding or socializing whales (see Chapters 13, 15).

6. the bowhead population has increased substantially over the study period.

The effects of the 1st, 2nd and 5th factors on annual average sighting conditions could, in theory, be

corrected to some extent based on the detectability factors derived in Chapter 15. We have not attempted

to apply such correction factors to all of the survey coverage used in calculating bowheads/100 km. (The

factors from Chapter 15 were applied for the specific dates when there was sufficient survey coverage to

allow an estimate of whale numbers in the area—see Table 9.2.)

The effects of the 4th and 6th factors, i.e., annual study period and bowhead population trend, on

annual average sighting rates can also be corrected to some extent, as described below.

Our analysis of seasonal variation indicated that, on average, peak bowhead abundance in the study

area, as measured by “bowheads seen/100 km”, occurs during the first and second half of September (Fig.

9.5). Survey coverage in September was more consistent and extensive than that in August and October.

If we re-examine annual abundance, restricting the analysis to the September period, then there are 21
9-30 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

years in the 1979–2000 study period with a combined September survey coverage of 93,159 km. Excluding 1981 (with only 37 km of survey coverage), there were 20 years with September survey coverage

ranging from 1270 to 16,406 km. Among these years “bowheads seen /100 km” ranged from low values

of 0.10 (1979), 0.11 (1988) and 0.13 (1985) to high values of 3.32 (1999), 3.55 (1995) and 4.70 /100 km

(1990). Thus, the ratio of the highest observed September abundance index (4.70 /100 km) to the lowest

(0.10) was 47 : 1, which is not substantially different from the comparable ratio considering the full

August–October period (4.05 : 0.09, or 45 : 1). Thus, restricting the analysis to September did not

appreciably lessen the observed annual variability. It is possible that there is sufficient year to year

variability in the timing of bowhead migration that comparing the same seasonal period (in this case the

month of September) in each year does not adequately capture the period of peak bowhead abundance in

all years.

The BCB stock of bowhead whales was estimated, as of 1993, to contain ~8200 animals with a

95% confidence interval of 7200–9400 individuals (Zeh et al. 1996; Raftery and Zeh 1998; Ferrero et al.

2000). This estimate is lower than the population of 10,400–23,000 bowhead whales estimated to be

present before commercial whaling (Woodby and Botkin 1993). About a decade ago, the population was

believed to be increasing at a rate of ~3.2% per year (Punt and Butterworth 1999) despite annual Alaskan

subsistence harvests of 14 to 74 bowheads from 1973 to 1996 (Suydam et al. 1995). If a 3.2% rate of

increase had been in effect throughout the 1979–2000 study period, and the BCB bowhead population in

1993 was 8200 animals, then the population may have increased from 5276 individuals in 1979 to 10,223

in 2000. This near doubling of the population over the study period would explain part of the observed

increase in estimated bowhead abundance from the 1979–89 period to the 1990–2000 period.

We re-tested the early (1979–89) vs. late (1990–2000) estimates of bowhead numbers for the

restricted study area (Flaxman Island to Canadian border, shore to 200 m contour) during September–

early October after “adjusting” for the assumed 3.2% annual increase in population over the study period.

The adjustment factor, ×1.032(1993–Year), standardized each year's overall bowhead population relative to

that estimated for 1993 (8200), assuming that the population had increased at a 3.2% annual rate. The

adjustment factors ranged from 1.554 in 1979 to 0.802 in 2000 (Appendix 9.2). After adjusting for the

assumed 3.2% annual increase in overall population size, the September and early October population

estimates from the later period (n = 37) were still significantly higher than those in the early period (n =

25, t = –2.48, df = 54, two-tailed P = 0.016). Thus, the observed increase in bowhead abundance in the

1990s is greater than expected based on the assumed annual increase in the size of the bowhead

population passing through the study area. As noted in “Results”, there were no relevant data for 1990, so

the above calculation would be unaffected if 1979–90 were compared with 1991–2000. 

The fact that bowhead abundance in the study area has increased over the 22-year study period at a

rate higher than the assumed rate of increase in the bowhead population presumably represents some

change in the distribution and movements of the whales. Some possible changes that might account for

the observed trend to increased numbers of bowheads in the restricted study area include • a higher proportion of bowheads migrating through the study area in September and early October in recent years as

compared to earlier years, • a higher proportion of bowheads migrating through the restricted study area

(vs. farther north) in recent years as compared to earlier years, • the western edge of the summer feeding

range expanding west from Canada into the eastern Alaskan Beaufort Sea, • or a greater tendency on the

part of bowheads to linger in the restricted study area before beginning rapid migration (possibly related

to climatic change).
§9. Bowheads: Distribution & Abundance 9-31

The increase in bowhead numbers during the 1990s was documented for the September–early

October period. This increase might be related to changes in the timing of the main migration period

through the restricted study area, i.e., perhaps a higher proportion of bowheads migrated through the

restricted study area during September and early October during recent years (1990–2000) than in earlier

years (1979–89). There were few August data from the later (1990–2000) period for comparison with

earlier years, and the late October sample of estimated numbers was very small, especially for the early

period (1979–89, n = 1). Thus, it is not possible to determine from the data we examined whether there

have been changes in the timing of the main migration period over the 1979–2000 period.

This study was limited to the region south of 71o10'N. Thus, we have no information about the

numbers of bowheads that may have migrated west through waters north of the study area. Radio

tracking of bowheads indicates that at least some autumn migrating bowheads travel in waters north of the

continental shelf (Wartzok 1990; Mate et al. 2000). In general, aerial surveys show that densities far

offshore are low. Moore et al. (1989) found relatively low bowhead abundance in the area north of our

study area (MMS blocks 8 and 9, 71°10'N–72°N). During the first half of September 1979–86, they

found 0.26 bowheads /survey hour in MMS blocks 8 and 9 (5 bowheads in 19.4 hours of surveys), vs.

1.74 bowheads/survey hour (338 bowheads in 194.3 hours of surveys) in blocks 4–7, which closely

correspond to our study area. Thus, relative bowhead densities in our study area in early September were

~6.75 times higher than in the region north of our study area. However, the region north of our study area

is large and even low densities of bowheads might represent substantial numbers of individuals. Survey

coverage north of our study area has been sparse, and there are no published data indicating whether or

not bowhead abundance in that region has changed over the years during the autumn migration period.

The increased numbers of bowheads observed in the restricted study area during the 1990s may

indicate that the area has increasingly been used as a feeding area by bowheads. This may reflect in part a

westward expansion of the late summer/early autumn feeding range as the BCB bowhead stock has

increased in size. Alternatively, the expansion of the feeding range could reflect improved feeding conditions (i.e., prey availability) in those waters in the 1990s. Increased prey availability is presumably related to oceanographic processes (e.g., currents, upwellings, eddies, and frontal features) that concentrate

zooplankton into dense patches that can be selectively fed upon by bowhead whales. Bowhead distribution has been associated with high prey concentrations between the boundary of the Mackenzie River

plume and colder marine waters (Thomson et al. 1986; Chapter 6). The zooplankton sampling conducted

as part of the present study in 1985–86 and 1998–2000 (see Chapter 5) was not designed to quantify

trends (if any) in overall zooplankton availability in the study area. However, extensive net and echosounder sampling was done in each of those years, and no obvious trend in zooplankton availability was

evident.

Moore (2000) and Treacy (2002) found that bowhead distribution in the Alaskan Beaufort Sea

during late summer and autumn varied with ice conditions. In years of light and moderate ice, the highest

densities of bowheads tended to occur in nearshore waters, where dense patches of plankton are sometimes found (see Chapter 5). In heavy ice years, bowheads tend to occur in outer shelf and slope waters.

However, Treacy (2002) noted that this trend was less evident east of Kaktovik (and near Barrow) than in

the intervening area. Wind regimes and the resulting surface currents are primary determinants of not

only autumn ice conditions, but also the locations of major oceanographic features such as the Mackenzie

River plume. Moore (2000) speculated that the northwesterly winds that typically result in heavy ice

conditions near shore may also result in conditions that are not conducive to the concentration of prey

organisms in nearshore waters. If so, bowheads may not linger in nearshore waters during heavy ice

years due to a lack of foraging opportunities.
9-32 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

The last decade has been notable for light ice conditions in the Alaskan Beaufort. For example,

8 of the 10 years in the 1990–99 period were classed as light ice years, as compared with 6 of 11 years

during 1979–89 (Treacy 2000). The 1990s included years (1990, 1993, 1995, 1997 and 1998) with

extremely light summer ice coverage relative to that during the 1978–98 period as a whole (Serreze et al.

1995; Maslanik et al. 1996, 1999). Ice conditions in 1997 ranked 7th lightest of 45 years from 1953 to

1997, and 1998 ranked 3rd lightest for the 47 years 1953–99 (Treacy 2000). This tendency to light ice

conditions in recent years may have been associated with unusually good feeding opportunities for bowheads and unusually high bowhead abundance within our study area.

Unusually light ice conditions in the 1990s may have been related to wind patterns affected, in

recent years, by large scale processes such as the Arctic Oscillation. This is a pressure oscillation that,

when in a “positive” phase (to which it shifted in 1989), tends to reduce pressure over the North Pole,

pump more warm air into the Arctic, and open leads in the Arctic Ocean ice (Maslanik et al. 1996; Kerr

1999).

Given the long lifespans of bowhead whales (George et al. 1999), individual bowheads may experience numerous natural long-term cycles of weather patterns, pressure oscillations, and ice conditions during

their lives. The observed light ice conditions in recent years may be part of a natural oscillation that has

resulted in temporary increased feeding opportunities in the eastern Alaskan Beaufort Sea. Alternatively,

these conditions could be related to anthropogenic factors (e.g., greenhouse warming) that may be part of a

continuing trend. Interpretation of the paleoclimate record indicates that, in the arctic, the 20th century was

the warmest century of the past 400 years (Serreze et al. 2000). Some climate models project continued

decreases in sea ice thickness and extent throughout the present century (Vinnikov et al. 1999). This could

result in a markedly different ice–ocean–atmosphere regime in the Arctic (Johannessen et al. 1999). Such

changes might further alter the importance of the eastern Alaskan Beaufort Sea to bowhead whales.

Although there are several possible reasons for the increased utilization of the eastern Alaskan

Beaufort Sea during some recent years, the actual reasons remain a matter of speculation. The gradually

increasing population size is no doubt one factor, but this alone is not sufficient to account for the

observed increase. A substantial part of the increase must represent a change in the distribution and/or

movements of some or all BCB bowhead whales during late summer and early autumn. These changes

might represent a westward expansion of the summer feeding range, perhaps associated with the increased population size, or with climatic fluctuations and trends, or (most likely) with a combination of several

such factors.

Summary

Previous studies plus observations by local people have shown that some bowhead whales may

spend at least part of the summer feeding period off the north coast of Alaska. Many others summer in

Canadian waters but continue to feed as they begin to travel west through the Alaskan Beaufort Sea

during September and October. Bowhead use of the Alaskan Beaufort Sea during late summer and

autumn has been documented since 1979 by systematic aerial surveys, mainly conducted or sponsored by

BLM and MMS. The surveys have gathered much information that can be used to evaluate bowhead use

of the eastern Alaskan Beaufort Sea during August–October, including relative utilization according to

year, season, and region within the study area.

This study describes the seasonal distribution and numbers of bowheads observed in the eastern

Alaskan Beaufort Sea and adjacent Canadian waters during August–October of 1979–2000, based on existing and new aerial survey data from the 139°–146°W region, south of 71°10'N. The 21 years of data
§9. Bowheads: Distribution & Abundance 9-33

considered here (no data were available from 1980) include (1) annual aerial surveys by MMS, (2) some of the

aerial surveys conducted during industry-sponsored monitoring programs (1986 and 1993), and (3) surveys

that we conducted specifically to assess the importance of the eastern Alaskan Beaufort Sea to bowheads in

1985–86 and 1998–2000. The combined dataset includes more data from the eastern Alaskan Beaufort Sea

than have been analyzed by previous authors; it involves 155,000 km of systematic aerial surveys within the

“Flaxman Isl.-to-Herschel Isl.” study area. For periods where sufficient aerial survey data are available, we

have estimated the numbers of bowheads present in the part of the study area inshore of the 200 m contour off

Alaska (“Flaxman-to-border”). These estimates are based on line transect techniques, including correction

factors for whales missed by the aerial surveyors (see Chapter 15 for derivation of correction factors).

The “Flaxman-to-Herschel” study area was divided into four E–W regions, and four water-depth

strata―a total of 16 analysis zones. For seasonal analyses, the data were categorized into six half-month

(15- or 16-day periods) from 1 Aug. to 31 Oct.

When standardized for survey effort, the overall average abundance index during systematic aerial

surveys under acceptable sighting conditions (Aug.–Oct. combined) was 0.77 bowheads seen/100 km.

Bowhead abundance differed significantly among the four depth strata, with highest average abundance

recorded in the Shelf Break stratum (40–200 m deep), followed by the Middle Shelf stratum (20–40 m)

and Nearshore stratum (<20 m); average abundance was lowest in the Continental Slope stratum (>200 m

deep). Differences in bowhead abundance among the four E–W regions were marginally significant, with

bowhead abundance highest in the east and declining with increasing longitude.

Local residents occasionally see bowheads in the study area during July and August; they see peak

numbers in September, and some bowheads during October.

Aerial surveys showed that bowhead abundance and distribution varied significantly by half-month

period during August–October of 1979–2000. Moderate numbers of bowheads were present during early

August, especially in offshore waters (>200 m deep) of the three easternmost regions of the study area.

Bowhead abundance was somewhat lower during the second half of August, and there was a slight

shoreward shift in the distribution of bowheads from early to late August.

 During the first half of September the relative abundance of bowheads in the study area increased.

Also, their distribution shifted inshore and expanded westward to span the full width of the study area,

coincident with increased migration into and through the study area. Peak bowhead abundance was

recorded during the second half of September, when bowheads were most abundant in the Shelf Break

and Middle Shelf strata (20–200 m deep).

Bowhead relative abundance in the study area was lower during early October, and the highest densities were again shoreward of the 200 m contour. By late October, the relative abundance of bowheads

was very low.

The percentage of the bowhead sightings recorded as “traveling” was similar (86–100%) over the

six half-month periods. For traveling whales, the headings were significantly non-uniform (and predominantly westward or northwestward) in all half-month periods except for late August. However, the variation in headings was larger up to 15 Sept. than thereafter.

Few bowheads were identified as feeding during systematic aerial surveys. The low apparent numbers of feeding bowheads reflect, in large part, the difficulty of recognizing feeding activity in the brief

glimpses of whales that typically occur during systematic aerial surveys. Areas where feeding was seen

most commonly included Nearshore waters close to Komakuk (Yukon); Nearshore, Middle Shelf and

Shelf Break waters off Demarcation Bay; and Middle Shelf and Shelf Break waters off Camden Bay.
9-34 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

During the 1979–2000 period, the relative abundance of bowheads recorded during aerial surveys

has varied markedly from year to year. Eight years had abundance indices higher than the overall average

of 0.77 bowheads seen/100 km. The highest indices were recorded in 1995 (3.23 /100 km), 1999 (3.32

/100 km) and 1990 (4.05 /100 km). Seven of the eight years with above-average bowhead abundance

were in the 1990s and most (9 of 13) of the years with below-average bowhead abundance occurred prior

to 1990. The average of the annual abundance indices was 0.36 bowheads seen/100 km during the 1979–

89 period vs. 1.60 bowheads/100 km for the 1990–2000 period. The increase since 1989 was larger than

can be accounted for by the previously-reported rate of increase of this population (3.2% per year).

The numbers of bowheads present in the “Flaxman-to-border” area were estimated whenever

survey coverage allowed, considering waters inshore of the 200 m contour (i.e., 3 of 4 E–W zones, and 3

of 4 depth strata). These line-transect estimates were based on 81 surveys or combinations of surveys

flown during 1- or 2-day periods during 1979–2000, and include allowance for missed whales. The

estimates ranged from 0 (during many surveys) to a maximum of 4505 bowheads (based on 765 km of

survey coverage on 13 Sept. 1999).

Within most half-month periods, the estimated numbers of bowheads present were highly variable.

All six half-month periods included some surveys for which no bowheads were estimated to be present.

However, the average estimated numbers of bowheads present in the restricted study area during the six

half-month periods followed the same pattern as the abundance indices described above for the overall

study area: moderate in August, high in September and early October (peaking during late September),

and almost none during the second half of October.

We compared the estimated numbers of bowheads present in the “Flaxman-to-border” area during

1979–89 vs. 1990–2000, considering only the September and early October periods when peak numbers

of bowheads were present. The estimates from the 1990–2000 period were, on average, significantly

higher than those from 1979–89 even after de-trending to remove the assumed annual 3.2% population

increase over the 22-year study period. Thus, the increased sighting rates in the 1990–2000 period are

apparently attributable in part to an increase in the relative utilization of the present study area as

compared with other areas.

Acknowledgements

We thank the many pilots, aerial surveyors, and project sponsors whose efforts contributed to this

study. In particular, we thank Don Ljungblad (NOSC), Sue Moore and Janet Clarke (SAIC), and Steve

Treacy and Don Hansen (MMS), for their long-term efforts in conducting the MMS/NOSC aerial surveys.

Most of the surveys were conducted or sponsored by MMS. However, some surveys considered here

were done by LGL for Shell Western Exploration & Production (SWEPI) in 1986, and by COPAC for

ARCO Alaska in 1993. We thank Steve Treacy and Janet Clarke for providing the MMS/NOSC dataset,

and Jeremy Davies (NOAA) for access to the ARCO/COPAC data from 1993. LGL’s 1985–86 and

1998–2000 aerial surveys for MMS and SWEPI were conducted under Scientific Research Permits 517,

518 and 481-1464 issued by the National Marine Fisheries Service. Many other Acknowledgements

relevant to the project as a whole are included in Chapter 1.

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Treacy, S.D. 2000. Aerial surveys of endangered whales in the Beaufort Sea, fall 1998-1999. OCS Study MMS

2000-066. U.S. Minerals Manage. Serv., Anchorage, AK. 135 p.
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Treacy, S.D. 2002. Aerial surveys of endangered whales in the Beaufort Sea, fall 2000. OCS Study MMS 2002-

014. U.S. Minerals Manage. Serv., Anchorage, AK. 111 p.

Vinnikov, K.Y., A. Robock, R.J. Stouffer, J.E. Walsh, C.L. Parkinson, D.J. Cavalieri, J.F.B. Mitchell, D. Garrett and

V.F. Zakharov. 1999. Global warming and Northern Hemisphere sea ice extent. Science 286(5446):1934-

1937.

Wartzok, D. 1990. Industry-sponsored bowhead whale monitoring and research in the U.S. and Canadian Beaufort

Sea. p. 33-40 In: Alaska OCS Region Third Information Transfer Meeting Conf. Proc. OCS Study MMS

90-0041. U.S. Minerals Manage. Serv., Anchorage, AK. 233 p.

Woodby, D.A. and D.B. Botkin. 1993. Stock sizes prior to commercial whaling. p. 387-407 In: J.J. Burns, J.J.

Montague and C.J. Cowles (eds.), The bowhead whale. Spec. Publ. 2. Soc. Mar. Mammal., Lawrence, KS.

787 p.

Würsig, B., E.M. Dorsey, M.A. Fraker, R.S. Payne and W.J. Richardson. 1985. Behavior of bowhead whales,

Balaena mysticetus, summering in the Beaufort Sea: a description. Fish. Bull. 83(3):357-377.

Würsig, B., E.M. Dorsey, W.J. Richardson and R.S. Wells. 1989. Feeding, aerial and play behaviour of the bowhead whale, Balaena mysticetus, summering in the Beaufort Sea. Aquat. Mamm. 15(1):27-37.

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increase. Rep. Int. Whal. Comm. 46:670.
9-38 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

 August September October

No. of Km of No. Bhds 10-Day No. of Km of No. Bhds 10-Day No. of Km of No. Bhds 10-Day

Bhds Survey Seen/ Moving Bhds Survey Seen/ Moving Bhds Survey Seen/ Moving

Day Seen Coverage 100 km Average Day Seen Coverage 100 km Average Day Seen Coverage 100 km Average

1 0 8.7 0.000 - 1 15 2419.4 0.620 0.906 1 5 758.7 0.659 0.847

2 0 1065.5 0.000 - 2 24 1187.0 2.022 0.953 2 9 873.5 1.030 0.612

3 0 2.7 0.000 - 3 25 2988.3 0.837 0.998 3 15 1232.7 1.217 0.653

4 - - - - 4 31 1942.7 1.596 1.008 4 7 934.6 0.749 0.924

5 0 425.7 0.000 - 5 29 2127.0 1.363 1.007 5 7 1804.9 0.388 0.985

6 0 912.7 0.000 - 6 20 1668.7 1.199 1.018 6 4 898.5 0.445 0.944

7 1 481.4 0.208 0.131 7 28 3039.4 0.921 1.126 7 9 1344.1 0.670 0.897

8 1 638.1 0.157 0.128 8 19 2273.7 0.836 1.013 8 46 1752.4 2.625 0.824

9 1 414.5 0.241 0.159 9 13 1952.4 0.666 1.204 9 5 724.5 0.690 0.746

10 1 179.6 0.557 0.209 10 19 2307.2 0.824 1.134 10 9 1964.8 0.458 0.700

11 2 445.2 0.449 0.252 11 53 3684.4 1.439 1.135 11 2 1064.8 0.188 0.739

12 0 135.2 0.000 0.239 12 31 4477.4 0.692 1.366 12 0 906.8 0.000 0.740

13 0 137.2 0.000 0.198 13 79 3279.9 2.409 1.384 13 1 676.3 0.148 0.724

14 3 546.3 0.549 0.257 14 2 1023.7 0.195 1.420 14 0 722.0 0.000 0.265

15 1 74.6 1.340 0.248 15 32 2379.6 1.345 1.482 15 0 227.2 0.000 0.206

16 0 1133.1 0.000 0.239 16 83 1872.0 4.434 1.485 16 1 485.0 0.206 0.138

17 0 843.9 0.000 0.251 17 45 3921.9 1.147 1.485 17 0 312.6 0.000 0.125

18 5 1152.2 0.434 0.244 18 31 2434.7 1.273 1.662 18 2 477.1 0.419 0.133

19 0 195.9 0.000 0.219 19 34 2221.1 1.531 1.472 19 0 447.8 0.000 0.128

20 3 1194.5 0.251 0.200 20 19 2255.7 0.842 1.510 20 2 489.9 0.408 0.141

21 3 565.0 0.531 0.183 21 10 788.7 1.268 1.456 21 0 49.3 0.000 0.145

22 - - - 0.195 22 34 2018.5 1.684 1.231 22 0 636.9 0.000 0.099

23 0 306.0 0.000 0.206 23 0 784.7 0.000 1.196 23 0 62.8 0.000 0.098

24 0 839.5 0.000 0.202 24 36 2780.5 1.295 1.135 24 - - - 0.074

25 2 712.7 0.281 0.178 25 9 1598.2 0.563 1.012 25 0 351.4 0.000 0.051

26 0 156.6 0.000 0.202 26 51 3057.0 1.668 1.002 26 0 132.9 0.000 0.079

27 0 335.9 0.000 0.275 27 1 874.0 0.114 0.974 27 0 1062.8 0.000 0.028

28 0 976.3 0.000 0.351 28 10 1590.4 0.629 0.885 28 0 375.4 0.000 -

29 3 882.9 0.340 0.560 29 12 2231.7 0.538 0.954 29 0 313.3 0.000 -

30 3 944.4 0.318 0.667 30 5 1048.3 0.477 0.873 30 1 332.0 0.301 -

31 9 1545.5 0.582 0.822 31 0 219.8 0.000 -

Total 38 17251.8 0.220 6.815 800 66227.9 1.208 35.483 125 21634.9 0.578 12.044

APPENDIX 9.1. Daily 10-day moving average of bowhead abundance (individuals seen/100 km) in the restricted

eastern Alaskan Beaufort Sea study area, 7 August-27 October, 1979-2000. Restricted study area excludes

Komakuk region and Continental Slope depth stratum. No surveys were flown on 4 August, 22 August, or 24

October.
Entire Study Area Restricted Study Area

Adjust. 

No. of Km of No. Adjust. No. No. of Km of No. Adjus

"Transect" Transect Bhds Est. Factor Bhds "Transect" Transect Bhds Est. Facto

Bhds Survey Seen/ Pop. for Seen/ Bhds Survey Seen/ Pop. fo

Year Seen Coverage 100 km Sizea Pop incr. 100 km Seen Coverage 100 km Size Pop inc

1979 11 4960.0 0.22 5276 1.554 0.34 10 4757.7 0.21 5276 1.554 1980 - - - 5445 1.506 - - - - 5445 1.506 1981 5 1396.2 0.36 5619 1.459 0.52 5 973.7 0.51 5619 1.459 1982 118 9873.1 1.20 5799 1.414 1.69 24 5407.6 0.44 5799 1.414 1983 31 7692.2 0.40 5984 1.370 0.55 5 3343.1 0.15 5984 1.370 1984 29 8525.8 0.34 6176 1.328 0.45 20 4014.6 0.50 6176 1.328 1985 21 17509.2 0.12 6373 1.287 0.15 12 9544.4 0.13 6373 1.287 1986 83 21031.1 0.39 6577 1.247 0.49 59 15584.5 0.38 6577 1.247 1987 27 8181.8 0.33 6788 1.208 0.40 21 5529.2 0.38 6788 1.208 1988 7 7894.7 0.09 7005 1.171 0.10 6 4825.7 0.12 7005 1.171 1989 7 4411.7 0.16 7229 1.134 0.18 4 2995.1 0.13 7229 1.134 1990 99 2444.2 4.05 7461 1.099 4.45 95 2172.8 4.37 7461 1.099 1991 16 2359.8 0.68 7699 1.065 0.72 13 1495.1 0.87 7699 1.065 1992 16 6023.0 0.27 7946 1.032 0.27 14 3773.1 0.37 7946 1.032 1993 204 21070.2 0.97 8200 1.000 0.97 200 16969.0 1.18 8200 1.000 1994 45 2666.1 1.69 8462 0.969 1.64 36 2083.4 1.73 8462 0.969 1995 102 3157.8 3.23 8733 0.939 3.03 96 2035.9 4.72 8733 0.939 1996 5 3554.4 0.14 9013 0.910 0.13 5 2374.3 0.21 9013 0.910 1997 35 3496.9 1.00 9301 0.882 0.88 32 2644.3 1.21 9301 0.882 1998 147 8950.8 1.64 9599 0.854 1.40 120 6530.2 1.84 9599 0.854 1999 159 4788.5 3.32 9906 0.828 2.75 155 3924.2 3.95 9906 0.828 2000 32 5369.2 0.60 10223 0.802 0.48 31 4136.7 0.75 10223 0.802 

Grand Total 1199 155356.6 963 105114.7

APPENDIX 9.2. Annual indices of bowhead abundance (individuals seen/100 km) in the eastern Alaskan Beaufort Sea, 1 August

Restricted study area excludes Komakuk region and Continental Slope depth stratum. Adjusted indices have been standardized bowheads in 1993. "Base years" (last column) were used in calculations in Chapter 11 (Rates of Movement and Residence Time
10. HABITAT USE BY DIFFERENT SIZE CLASSES OF BOWHEAD WHALES

IN THE EASTERN ALASKAN BEAUFORT SEA

DURING LATE SUMMER AND AUTUMN

William R. Koski and Gary W. Miller 1

Introduction

Habitat segregation of different size classes of bowhead whales in the BeringñChukchiñBeaufort

(BCB) population has been documented in summering areas in the Canadian Beaufort Sea and Amundsen

Gulf (Cubbage and Calambokidis 1987; Koski et al. 1988). Those studies, and observations by Kaktovik

residents (Chapter 2 and Annex B), indicate that small subadult whales tend to occupy shallow nearshore

areas along the Yukon coast. Large subadults tend to be found farther off the Yukon coast and north of

the Mackenzie Delta and Tuktoyaktuk Peninsula. Adults tend to be found even farther east. Large adult

whales comprise most of the bowheads found in Amundsen Gulf. Data from the eastern Alaskan Beaufort Sea in the 1980s suggested that, during late summer and early autumn, subadults also tended to occur

close to shore in that area, with larger whales being seen more commonly farther offshore (Koski et al.

1988).

Temporal, as well as spatial, segregation by age class has been seen in parts of the BCB bowhead

range. Whalers from Kaktovik have suggested that, in late summer, small bowheads arrive in nearshore

waters of the eastern Alaskan Beaufort Sea earlier in the season than larger whales but that all sizes of

whales are seen near Kaktovik over the autumn season (Chapter 2). However, the harvest data from

Kaktovik do not show any seasonal trend in the proportion of small whales harvested, presumably

because whalers always attempt to harvest small whales (Chapter 2). Temporal segregation also occurs

during spring migration past Barrow (Zeh et al. 1993; Angliss et al. 1995). A large proportion of the

whales passing Barrow early in the spring migration period are small subadult whales and a large proportion passing near the end of the period are large adult whales. Females accompanied by recently-born

calves are among the last whales to pass Barrow in spring (Koski et al. MS).

Temporal and spatial segregation of the BCB stock of bowhead whales by age and habitat has not

been examined in detail for areas other than Barrow in spring and Canadian waters in summer. However,

for the Baffin Bay and Hudson Bay stocks, there is also evidence that, in summer, different components

of the stocks concentrate in different parts of their overall ranges (Finley 1990, 2001).

The eastern Alaskan Beaufort Sea may, in some years, be an important feeding area for bowhead

whales during late summer and autumn. At this time of year bowheads commence their westward migration to overwintering areas (Moore and Reeves 1993; Mate et al. 2000), at times either stopping to feed or

feeding while traveling (Chapter 12). During 1998ñ2000, we used photogrammetric methods consistent

with those applied in the 1980s to collect additional data on utilization of the eastern Alaskan Beaufort

Sea by different categories of bowhead whales. This chapter examines bowhead size data collected

during late August through early October of 1982 to 2000 in relation to year, location within the study

 

1

 LGL Ltd., environmental research associates, 22 Fisher St., POB 280, King City, Ont. L7B 1A6.

Phone: 905-833-1244; e-mail: bkoski@lgl.com, gmiller@lgl.com
10-2 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

area, water depth, and date. It assesses the population structure of bowhead whales found in this area and

evaluates whether there was habitat and/or seasonal segregation by whales of different sizes (ages) and of

different status (subadults vs. mother/calf pairs vs. other adults). This information is relevant in evaluating the importance of the study area to the different components of the bowhead whale population, and is

factored into subsequent energetic calculations (Chapters 22, 23).

Methods

The study area considered here, as in Chapters 9 and 11-13, consists of the eastern Alaskan

Beaufort Sea and adjacent Canadian waters, from Flaxman Island almost to Herschel Island (longitudes

146° to 139°W; Fig. 10.1). Hereafter, this study area is referred to as the eastern Alaskan Beaufort Sea,

although it includes some adjacent Canadian waters. Almost all of the available data came from areas

≤200 m deep.

Data Sources

Length measurements used here were obtained during numerous behavioral and photogrammetry

studies conducted in the study area shown in Figure 10.1 during late August to early October from 1982

to 2000. Table 10.1 lists, for each study, the effort, funding agency, and number of whales measured.

The largest proportion of the data presented here came from studies funded by the U.S. Minerals Management Service (MMS) in 1985, 1986, and 1998ñ2000.

TABLE 10.1. Sources of bowhead whale length measurements for this study. Additional effort and photos

outside the present study area during some listed studies are not included.

Date

Range Study

Year of Photos Sponsor Source of Data

1982 3 3 11 16 Aug - 4 Sept National Marine Fisheries Service Davis et al. (1983)

1984 4 4 34 17 Aug - 14 Sept Indian & Northern Affairs Canada Davis et al. (1986a)

1985 8 10 123 a 11-29 Sept U.S. Minerals Manage. Service Richardson (1987)

1985 2 4 60 a 28 Aug - 8 Sept Sohio Alaska Petroleum et al. Davis et al. (1986b)

1985 1 1 2 19 Sept Shell Western Explor. & Prod. Inc. Johnson et al. (1986)

1986 11 13 173 b 3-27 Sept U.S. Minerals Manage. Service Richardson (1987)

1986 10 12 41 b 5 Sept - 3 Oct Shell Western Explor. & Prod. Inc. Koski & Johnson (1987)

1998 8 18 111 14-22 Sept U.S. Minerals Manage. Service This study

1999 12 31 329 10-29 Sept U.S. Minerals Manage. Service This study

2000 6 9 27 13-21 Sept U.S. Minerals Manage. Service This study 

Total 65 105 901 a,b 16 Aug - 3 Oct

a

b Five whales were photographed during both 1986 studies so only 209 different whales were measured in 1986.

Flights Sessions Whales

Five whales were photographed during two 1985 studies so only 180 different whales were measured in 1985.

Number of

Days with Photo Measured
§10. Bowheads: Habitat Use by Size Class 10-3

FIGURE 10.1. Locations where each individual photographic whale image was taken to obtain length data,

1982–86 and 1998–2000. Each different whale is shown only once for each year, E–W geographic

region, depth stratum, and half-month time period, at the location where it was first photographed.
10-4 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

Photogrammetry

We used the calibrated vertical photography technique developed by LGL and described by Koski

et al. (1992). Briefly, the aircraft flew at an airspeed of ~160 km/h and (cloud ceiling permitting) an

altitude of ~137 m (450 ft), and passed directly over bowheads. Photographs were taken through the

aircraft's ventral camera port with one of two hand-held Pentax medium-format cameras (6×7 cm film

size), each with a 105 mm f2.4 lens, pointed directly downward. Shutter speed was 1/500th or, when

possible, 1/1000th second. We used Ektachrome 200 or 400, or Fujichrome Provia 400, which are color

positive films, or occasionally (in 1985) Ilford XP1 black and white negative film pushed to ISO (ASA)

1600. Aircraft altitude was read manually from the radar altimeterís analog display and/or from a digital

readout at the moment the camera shutter fired. The altitude was recorded manually on data sheets.

Calibration targets of known dimensions were deployed 1ñ3 times each season and photographed with

each of the cameras used during that season. These photos were taken from the same altitudes as were

flown during whale photography sessions. Both whale and calibration photographs were most commonly

taken from 120ñ140 m a.s.l. Whale images and calibration targets were measured using a stereo

microscope and stage micrometer as described by Koski et al. (1992). The measured image sizes were

converted to whale lengths by accounting for systematic biases introduced by the cameras (focal plane

shutter distortion or inaccurate nominal lens length) and by inaccurate output from the radar altimeter.

The resulting length measurements varied in reliability depending on the circumstances during photography, the position of the whale relative to the water surface, and the quality of the whale image. Length

data categorized as ìaccurateî (grades 1ñ6 of Koski et al. 1992) are generally accurate to within a few 10s

of centimeters. Length data categorized as ìapproximateî are obtained by estimating whale length from

measurements of fluke width or snout-to-blowhole distance, or from photos taken when the aircraft altitude was changing rapidly; ìapproximateî lengths are generally accurate to within ~1 m. ìAccurateî and

ìapproximateî length data are used here when we describe size distributions of whales within the study

area. Only ìaccurateî lengths (i.e., grades 1ñ6 of Koski et al. 1992) are used in describing life history

information.

All images with potential to be reidentified were printed and compared with one another to check

for whales photographed more than once within each field season. These procedures are summarized by

Rugh et al. (1992, 1998). When a whale was photographed more than once in a given year and season

(considering summer and early autumn as a single season), all ìaccurateî length measurements were

averaged to obtain a ìbest lengthî. Only a single measurement is presented for each whale for each

period or for each geographic area where it was photographed, regardless of the number of times that

whale was photographed. The sample sizes are different for the various analyses because some whales

were photographed on two or three days during a year and those whale lengths are included once in each

category where they occurred. For example, a whale photographed in the Komakuk block on one day and

the Camden block later in the same year would be included once in the lengthñfrequency distributions for

both Komakuk and Camden but only once in the lengthñfrequency distribution for that year.

During late summer and early autumn, whales less than ~7 m long are generally calves less than 1

year old. Some calves may be as long as 7.5 m by September. Whales over 13 m long are considered to

be mature adults (Nerini et al. 1984; Koski et al. 1992, 1993) although some females with calves are as

small as 12.2ñ13 m, and some females longer than 13.5 m are not mature (Nerini et al. 1984; Koski et al.

1993). Animals <13 m long are referred to as subadults in this paper unless they were closely

accompanied by a calf. Subadults are further broken down into small (<10 m) and large (≥10 m)

subadults. ìOthersî are all whales excluding mothers and calves.
§10. Bowheads: Habitat Use by Size Class 10-5

Geographic and Temporal Categories

Lengthñfrequency distributions of whales are presented below for four eastñwest subdivisions of

the study area (Fig. 10.1). Lengthñfrequency distributions are also presented by water depth category:

nearshore (depth <20 m), middle shelf (20ñ40 m), shelf break (40ñ200 m), and continental slope

(>200 m).

Lengthñfrequency distributions of bowhead whales in the study area are examined for each year

when photographs were obtained during 1982ñ2000, and for half-month periods (all years combined)

from mid-August to mid-October. For each of these periods and/or locations, lengthñfrequency distributions were condensed to numbers of whales in each of five status categories: calves, small subadults,

large subadults, adults excluding mothers, and mothers. Chi-square goodness of fit tests were used to test

for differences among periods and/or locations in the proportions of whales in the five categories.

Results

Overall Length–Frequency Distribution

A total of 901 length measurements of different bowhead whales were obtained in the eastern

Alaskan Beaufort Sea in 1982ñ2000 (Fig. 10.2). An additional 33 photographs of these 901 whales were

obtained on 1ñ2 additional dates during the same year.

Most if not all bowheads that summer in the Canadian Beaufort Sea and Amundsen Gulf migrate

west through the eastern Alaskan Beaufort Sea at a wide range of distances from shore during their migration from Canadian summering areas to overwintering areas in the Bering Sea (Moore and Reeves 1993).

If all segments of this bowhead population make equal use of the study area, the whales photographed

there during our study should reflect the lengthñfrequency distribution of the population. Of the whales

we photographed, 6.2% were calves, 64.7% subadults, and 29.1% adults. In contrast, the overall population was estimated to include 5.2% calves, 53.7% subadults, and 41.1% adults during 1985ñ92, based on

1898 whales photographed during the spring migration past Point Barrow and corrections to the lengthñ

frequency distribution for periods without photographic effort (Angliss et al. 1995). Proportionally more

subadults and fewer adults were photographed in the eastern Alaskan Beaufort Sea than reported by

Angliss et al. (1995) (χ2

 = 31.61, df = 2, P = 1.37×10-7). The proportion of bowheads photographed in the

study area that were calves was not significantly different than in the results of Angliss et al. (1995) (χ2

 =

0.93, P = 0.335).

Year-to-Year Variation

The proportions of whales of different status were significantly different among years whether

mothers and calves were included (χ2

 = 171.1, df = 24, P = 3.67×10-24) or excluded (χ2 = 135.3, df = 12,

P = 5.26×10-23) from the analysis (Fig. 10.3). Much of this year-to-year difference was due to the

considerable variation in the size distribution and proportion of subadult whales that were photographed

in the study area among years. 1984 and 1998 had the highest proportions of small subadult whales, 1986

had equal numbers of small and large subadults, and 1985 and 1999 had more large subadults than small

subadults (Table 10.2).

In all years except 1999, subadult whales predominated among the whales measured (Fig. 10.3).

Excluding mothers and calves, subadults made up 76ñ100% of the measured whales in the study area

during 1982ñ98 and 2000; in 1999, subadults made up only 52% (Table 10.2).
10-6 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

FIGURE 10.2. Overall length–frequency distribution of bowhead whales photographed in the study area,

1982–2000. Within-day and between-day repeats are excluded.

TABLE 10.2. Percentages of whales by size class within the study area, 1982–2000.

All whales

Calves 18.2 2.9 2.2 10.5 2.7 6.4 11.1 6.2

All subadults excl. calves 63.6 94.1 83.3 66.5 81.1 45.3 59.3 64.7

 Small 27.3 76.5 35.6 34.0 45.9 17.9 33.3 31.4

 Large 36.4 17.6 47.8 32.5 35.1 27.4 25.9 33.3

All adults 18.2 2.9 14.4 23.0 16.2 48.3 29.6 29.1

 Non-mother adults 0.0 0.0 12.2 15.8 13.5 41.3 18.5 23.4

 Mothers 18.2 2.9 2.2 7.2 2.7 7.0 11.1 5.7

Number measured 11 34 180 209 111 329 27 901

Excluding mothers and calves

All subadults 100.0 100.0 87.2 80.8 85.7 52.3 76.2 73.4

 Small 42.9 81.3 37.2 41.3 48.6 20.7 42.9 35.6

 Large 57.1 18.8 50.0 39.5 37.1 31.6 33.3 37.8

Adults 0.0 0.0 12.8 19.2 14.3 47.7 23.8 26.6

Number measured 7 32 172 172 105 285 21 794

 Year 1982 1984 1985 1986 1998 1999 2000 Total
§10. Bowheads: Habitat Use by Size Class 10-7

FIGURE 10.3. Length–frequency distributions of bowhead whales photographed in the study area each

year, 1982–2000. Within-day and between-day repeats are excluded.
10-8 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

FIGURE 10.3. Concluded.
§10. Bowheads: Habitat Use by Size Class 10-9

There was considerable variation in the percentages of measured whales that were mothers and

calves (excluding 1982, χ2

 = 17.45, df = 5, P = 0.0037). Calves made up 10.5, 6.4 and 11.1% of whales

in 1986, 1999 and 2000, but only 2.2–2.9% in 1984, 1985 and 1998. The 1982 sample was too small (n =

11) to provide a meaningful percent calves value.

Variation by Region

The proportions of calves, small subadults, large subadults, adults excluding mothers, and mothers

were significantly different among the four geographic subdivisions of the study area (χ2

 = 99.97, df = 12,

P = 5.7×10-16). Most (81%) of the whales in the eastern part of the study area (Komakuk block) were

subadults (Fig. 10.4A). Subadults also predominated in the Demarcation and Camden blocks (57 and

58%, respectively); 33–35% of whales there were adults. Equal numbers of adults and subadults were

photographed in the Kaktovik block.

Differences in the proportions of mothers and “others” in the four survey blocks were only marginally significant (χ2

 = 7.33, df = 3, P = 0.062). There were somewhat more mothers in the Camden and

Demarcation blocks (10.6% and 8.1%) than in the other blocks (4.2–4.4%).

Variation by Water Depth

There was a significant change in the status of bowheads with increasing water depth categories (χ2 =

237.57, df = 12, P = 5.3×10-44). Small subadults made up 57%, 41%, and 15% of whales in water depths

<20 m, 20–40 m, and 40–200 m, respectively (Table 10.3). In contrast, adults excluding mothers made up 2%,

14%, and 38%, respectively, of whales in the same depth categories (Table 10.3; Fig. 10.5). The small sample

of whales photographed in waters >200 m deep was 7% small subadults and 33% adults (excluding mothers).

The proportional occurrence of mothers (calves excluded) differed significantly among depth strata

(χ2

 = 18.03, df = 3, P = 0.00043), primarily because mothers with calves tended to avoid waters <20 m

deep (Fig. 10.5; Table 10.3). The proportions of mothers (calves excluded) were not significantly different among the three strata >20 m deep (χ2

 = 2.06, df = 2, P = 0.357).

The categories of bowheads seen in each geographic subdivision of the study area are summarized by

water depth category in Table 10.3. The same trends that were seen in the overall length–frequency distribution

were present within each geographic area (Fig. 10.6). The proportional occurrence of whales of different status

was not significantly different between the Komakuk and Demarcation blocks for water depths <20 m (χ2

 = 2.67,

df = 4, P = 0.614), nor among the four geographic areas for water depths 20–40 m (χ2

 = 15.75, df = 12, P =

0.203). (Areas and depth strata with <25 whales have been excluded from statistical tests because of small

expected values.) However, for water depths 40–200 m, there were significant differences in whale status

(mothers and calves excluded) among the Komakuk, Demarcation and Kaktovik areas (χ2

 = 27.94, df = 4, P =

1.28×10-5). This difference was due to a more pronounced shift in size distributions from small to large bowheads with increasing water depth in the Kaktovik block than in the Komakuk block (Fig. 10.6).

Temporal Variation

There was a significant change in the status of bowhead whales within the eastern Alaskan Beaufort

Sea over the mid-August to mid-October period when bowhead whales are common in that area (χ2

 = 94.37,

df = 12, P = 7.00×10-15). During 16–31 August, 93% of measured whales were subadults (small subadults +

large subadults). The percentage of subadults declined to 73%, 56% and 35% during 1–15 September, 16–30

September and 1–15 October, respectively (Fig. 10.7). Corresponding increases in the percentages of adults

(including mothers) were observed during the four time periods (4, 20, 38, and 48%, respectively).
10-10 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

FIGURE 10.4. Length–frequency distributions of bowhead whales photographed in various areas, 1982–

2000: (A) Komakuk, (B) Demarcation, (C) Kaktovik and (D) Camden Bay. Repeats are included once in

each area during each year; otherwise, within-day and between-day repeats are excluded.
§10. Bowheads: Habitat Use by Size Class 10-11

TABLE 10.3. Numbers and percentages (in parentheses) of whales of various size classes by water depth

category and geographic subdivision in the eastern Alaskan Beaufort Sea, 1982–2000. Whales

photographed more than once in a given water depth category and geographic subdivision in a given year

are counted only once.

Area

Water Depth

Category Calves Mothers Others Total 

Komakuk

<20 m 3 (2) 102 (55) 77 (41) 1 (1) 4 (2) 5 (3) 187

20-40 m 2 (4) 27 (52) 18 (35) 1 (2) 4 (8) 5 (10) 52

40-200 m 13 (18) 15 (21) 19 (26) 10 (14) 15 (21) 25 (35) 72

>200 m 1 (3) 2 (7) 15 (50) 2 (7) 10 (33) 12 (40) 30

Demarcation

<20 m 1 (3) 21 (57) 14 (38) 1 (3) 0 (0) 1 (3) 37

20-40 m 1 (3) 13 (43) 11 (37) 1 (3) 4 (13) 5 (17) 30

40-200 m 21 (9) 45 (19) 73 (30) 21 (9) 81 (34) 102 (42) 241

>200 m 0 0 0 0 0 0 0

Kaktovik

<20 m 0 (0) 15 (88) 2 (12) 0 (0) 0 (0) 0 (0) 17

20-40 m 0 (0) 13 (45) 12 (41) 1 (3) 3 (10) 4 (14) 29

40-200 m 7 (6) 7 (6) 34 (27) 6 (5) 73 (57) 79 (62) 127

>200 m 0 0 0 0 0 0 0

Camden

<20 m 0 0 0 0 0 0 0

20-40 m 7 (9) 24 (31) 24 (31) 7 (9) 15 (19) 22 (29) 77

40-200 m 2 (12) 1 (6) 5 (29) 2 (12) 7 (41) 9 (53) 17

>200 m 0 0 0 0 0 0 0

All Areas

<20 m 4 (2) 137 (57) 93 (39) 2 (1) 4 (2) 6 (3) 240

20-40 m 10 (5) 77 (41) 65 (35) 10 (5) 26 (14) 36 (19) 188

40-200 m 42 (9) 68 (15) 131 (29) 37 (8) 172 (38) 209 (46) 450

>200 m 1 (3) 2 (7) 15 (50) 2 (7) 10 (33) 12 (40) 30

Small Large

Subadults Subadults Adults (>13 m) Overal

(<10 m) (10-13 m) Total

There was also a significant seasonal difference in the proportions of mothers vs. others photographed

during late summer and early autumn (χ2

 = 10.20, df = 3, P = 0.017). Mothers formed 1.4%, 6.6%, 5.6%, and

17.4%, respectively, of the whales photographed in the four half-month periods from late August to early

October. However, the number of whales measured in October was small (4 mothers and 15 others).

The significant increase in the sizes (status) of whales as the season progressed was attributable to two

factors: a tendency for the whales in shelf-break waters (40–200 m deep) to be larger late in the season, and a

tendency for the whales to be farther offshore (where larger whales predominated) late in the season (Table

10.4, Fig. 10.8). In water 40–200 m deep, the proportions of whales of different status differed significantly

between early and late September (χ2

 = 25.03, df = 4, P = 0.000050). At those depths, the proportion of adults
10-12 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

FIGURE 10.5. Length–frequency distributions of bowhead whales photographed in various depths of

water, 1982–2000. Within-day and between-day repeats are excluded.
§10. Bowheads: Habitat Use by Size Class 10-13

FIGURE 10.6. Proportions of whales of various size classes by water depth category and geographic

subdivision in the eastern Alaskan Beaufort Sea, 1982–86 and 1998–2000. Large pie-charts have >25

different measured whales; small charts have 15–25 whales. No charts are shown for areas with <15

whales.

increased progressively from late August to late September. In contrast, in water depths <20 m, the proportions of whales of different sizes did not differ significantly with date over the late August–late September

period (χ2

 = 4.60, df = 6, P = 0.80). Similarly, in water 20–40 m deep, the proportions were not much different

between early and late September (χ2

 = 6.54, df = 4, P = 0.162). The seasonal trend in shelf-break waters,

combined with a seasonal increase in the proportion of the bowheads photographed in those waters, were the

main components of the overall seasonal increase in the sizes of the whales.

Discussion

When Kaktovik residents traveling to and from Canada encounter bowheads near the Yukon coast

in July and August, these animals tend to be small individuals (Chapter 2 and Annex B). Kaktovik

residents also report that the sizes of the bowheads seen in the Kaktovik area tend to vary over the course

of the late summer and autumn. Small whales tend to predominate early in the season, when whaling

starts. Larger whales tend to occur later in the season. This, combined with the hunters’ selectivity for

small whales (Chapter 2), means that most whales harvested at Kaktovik are small to moderate in size.

However, exceptions do occur, and there is overlap in the dates when small and large whales are present

near Kaktovik.
10-14 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

FIGURE 10.7. Length–frequency distributions of bowhead whales photographed during half-month

periods, 1982–2000. Within-day and between-day repeats are excluded.
§10. Bowheads: Habitat Use by Size Class 10-15

TABLE 10.4. Numbers and percentages (in parentheses) of whales of various size classes by water depth

category during each half-month period in the eastern Alaskan Beaufort Sea, 1982–2000. Whales photographed more than once in a given water depth during each time period in a given year are counted only once.

Date Interval

Water Depth Overall

Category Total

16-31 August

<20 m 1 (2) 28 (62) 14 (31) 1 (2) 1 (2) 2 (4) 45

20-40 m 0 (0) 5 (56) 4 (44) 0 (0) 0 (0) 0 (0) 9

40-200 m 1 (6) 7 (41) 8 (47) 0 (0) 1 (6) 1 (6) 17

>200 m 0 (0) 1 (100) 0 (0) 0 (0) 0 (0) 0 (0) 1

1-15 September

<20 m 1 (1) 63 (58) 43 (39) 1 (1) 1 (1) 2 (2) 109

20-40 m 1 (2) 24 (48) 21 (42) 0 (0) 4 (8) 4 (8) 50

40-200 m 18 (12) 33 (22) 46 (30) 18 (12) 37 (24) 55 (36) 152

>200 m 1 (14) 1 (14) 3 (43) 2 (29) 0 (0) 2 (29) 7

16-30 September

<20 m 2 (2) 46 (53) 37 (43) 0 (0) 2 (2) 2 (2) 87

20-40 m 5 (4) 48 (41) 37 (32) 6 (5) 20 (17) 26 (22) 116

40-200 m 24 (9) 28 (10) 72 (26) 22 (8) 129 (47) 151 (55) 275

>200 m 0 (0) 0 (0) 12 (55) 0 (0) 10 (45) 10 (45) 22

1-15 October

<20 m 0 (0) 0 (0) 0 (0) 0 (0) 0 (0) 0 (0) 0

20-40 m 4 (31) 0 (0) 3 (23) 4 (31) 2 (15) 6 (46) 13

40-200 m 0 (0) 0 (0) 5 (50) 0 (0) 5 (50) 5 (50) 10

>200 m 0 (0) 0 (0) 0 (0) 0 (0) 0 (0) 0 (0) 0

Calves (<10 m) (10-13 m) Total Mothers Others 

Adults (>13 m)

Small Large

Subadults Subadults

Moore and DeMaster (1998), Moore (2000) and Moore et al. (2000) examined the overall habitat use

of bowheads, gray whales (Eschrichtius robustus) and white whales (Delphinapterus leucas) during late

summer and early autumn in the Alaskan Beaufort Sea and Chukchi seas. Their analyses were based on the

systematic aerial surveys conducted by or for MMS in 1982–91 (Moore et al. 1989; Treacy 1992). Moore

and DeMaster (1998) found that bowheads selected offshore waters (mean water depth 900 m) during July

and August, and nearshore and shelfbreak waters (mean water depth 109 m) during September and October.

Further analyses by Moore (2000) and Moore et al. (2000) found that bowheads selected nearshore waters

during light and moderate ice conditions and slope waters during heavy ice conditions.

Chapter 9 examines bowhead habitat use in a smaller area―our study area vs. the entire Alaskan

Beaufort and Chukchi seas―but over a longer time period (1979–2000 vs. 1982–91). Besides using data

from 11 additional years of MMS surveys, Chapter 9 also uses survey data from this study and some

industry-funded studies not used by Moore (2000) and Moore et al. (2000). Averaged over August–

October, highest densities of whales were recorded in the shelf break area (depths 40–200 m) and lowest

densities were recorded over the continental slope (>200 m). However, in August the highest densities

were over the continental slope. Chapter 9 also documents that the highest densities of bowheads were

recorded during the second half of September and, when averaged over the season, in the Komakuk zone.

Average densities of whales gradually declined from east (Komakuk zone) to west (Camden Bay zone).
10-16 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

FIGURE 10.8. Proportions of whales of various size classes by water depth category during each half-month

period in the eastern Alaskan Beaufort Sea, 1982–86 and 1998–2000. Large pie-charts have >25 different

measured whales; small charts have 15–25 whales. No charts are shown for situations with <15 whales.

However, the above studies did not have information on the sizes of whales seen during their surveys. The apparent seasonal change in habitat use may have resulted, in part, from differences in the

movement patterns of different components of the population. Additional insight into bowhead whale use

of the Alaskan Beaufort Sea can be obtained by integrating our findings on age and seasonal segregation

with those of Moore (2000), Moore et al. (2000), and Chapter 9 on overall seasonal distribution.

Most of the BCB bowhead whale population is believed to migrate west through the eastern Alaskan

Beaufort Sea during its migration from summering areas in the Canadian Beaufort Sea and Amundsen Gulf to

overwintering areas in the Bering Sea (Moore and Reeves 1993). Bowheads feed within the present study area

during this migration, but the amount of feeding varies from year to year (Chapter 12). Our data indicate that,

in all years, subadult bowheads move primarily through shallow nearshore waters and adults move primarily

through deeper waters during late summer and autumn. This size segregation has also been noted by subsistence whalers at Kaktovik (Chapter 2). The apparent preference for shallow nearshore waters during years

with light and moderate ice conditions may reflect the prolonged use of these nearshore waters by subadult

whales for feeding rather than a shift in distribution from offshore to nearshore waters. No ice was present in

our study area during the study periods in 1986 and 1998–2000, but even in those years most adult whales

moved west through deeper waters (i.e., they were not photographed in shallow waters where primarily

subadults were photographed).

There was a significant difference between the length–frequency distribution of the whales found in

our study area in late summer and fall as compared with that for bowheads migrating into the Beaufort Sea

in spring (cf. Angliss et al. 1995). Our sample is biased because our photographic surveys did not include
§10. Bowheads: Habitat Use by Size Class 10-17

all of the late summerñearly autumn migration period. Although residents of Kaktovik have noted that in

some years bowheads are seen near Kaktovik as early as July and as late as late October (Chapter 2), most

bowheads pass Kaktovik from late August to mid-October. We acquired some data on dates ranging from

16 August to 3 October. However, during the primary years of this study (1985ñ2000), the average dates

when our photographic work began and ended were 8 and 27 September (Table 10.1). Data on the timing of

the bowhead migration in our study area indicate that, in an average year, 20% of the migration has entered

our study area during the period from 26 August through 7 September, and 29% of the migration enters the

study area after 27 September. Fourteen percent of our photographs were obtained before 8 September and

10% were obtained after 27 September (Table 10.5A). If we correct our photographic sample to account for

the under-sampling during the early and late periods, the percent subadults declines to 61.3% from 64.7%

and the percent adults increases to 32.6% from 29.2% (Table 10.5B). Thus, the corrected percentage that

were adults (32.6%) is still much lower than the 41.1% adults in the spring data of Angliss et al. (1995).

 A major factor affecting the distribution of bowheads during late summer and early autumn is food

(Bradstreet and Fissel 1987; Bradstreet et al. 1987; Chapter 6). Bowheads concentrate and linger in areas

where food is abundant (Moore et al. 1995; Chapters 6 and 11). Feeding was the most frequently observed activity of bowheads in the eastern Alaskan Beaufort Sea during September of most years (Chapter

12), and at least 75% of the bowheads harvested there have food in their stomachs (Chapter 18). Thus,

the overall higher proportion of subadults among the measured whales suggests that the eastern Alaskan

Beaufort Sea was more important as a feeding area for subadult bowheads than adults during the years of

our study. However, the deeper waters of the eastern Alaskan Beaufort Sea are important as an autumn

migration corridor for adult whales in all years, and are important feeding areas in some years. For

example, in 1999 adult bowheads spent an estimated 66% of their time in the study area feeding in waters

>20 m deep (Chapter 12). Stomach-content data from bowheads harvested at Kaktovik show that most

adults as well as most subadults had been feeding in the area (Chapter 18).

There was substantial year-to-year variation in the proportions of adult, large subadult, and small subadult bowheads in the eastern Alaska Beaufort Sea. This indicates that different segments of the population

lingered in the area for different periods in different years. In some years, most notably 2000, few bowheads of

any size category were photographed despite considerable effort to obtain photographs. This and other evidence

indicates that no segment of the population lingered in the study area in September 2000 (Chapter 11).

There was considerable among-year variation in the geographic locations where bowheads were

seen and photographed. This was probably related to the local abundance of bowhead prey and the differing locations of water mass boundaries that affect zooplankton (Chapters 5, 6). Similar among-year variation in bowhead distribution has been documented in summering areas in the Canadian Beaufort Sea

(Richardson et al. 1987; Moore and Reeves 1993).

Systematic aerial surveys suggest that bowheads have made greater use of the present study area in the

1990s than in the 1980s (Chapter 9). Whether there has been a corresponding change in utilization of different

parts of the study area by different categories of bowhead whales is uncertain, given the few years with intensive

photographic work and the large among-year variation within each decade. However, in the mid-1980s,

subadult bowheads frequently concentrated in shallow nearshore waters somewhere in the eastern part of our

study area from the Kongakut River Delta to Herschel Island, and lingered in those areas for periods of days to a

few weeks (Chapter 11). High concentrations of zooplankton, especially the small copepod Limnocalanus,

were often found in nearshore waters during those years (Chapter 5, 6). In contrast, few bowheads were

recorded there in 1998ñ2000 and those that were recorded there did not appear to linger (Chapter 11).

Limnocalanus was absent or scarce in nearshore waters of the study area in 1998ñ2000 (Chapters 5, 6).
10-18 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

TABLE 10.5. Numbers and percentages of whales of various size classes (A) photographed during three

time periods during this study, and (B) corrected for seasonal bias in sampling effort based on aerial

survey data from Chapter 9 (Appendix 9.1). In (B), italicized values are numbers expected if effort early

and late in the season had been comparable to that in the 8–27 Sept. period.

Percentage

of Whales

A: Photographed

Before 8 Sept. 4 67 46 4 2 6 123 13.6

8-27 Sept. 46 211 227 41 167 208 692 76.7

After 27 Sept. 6 5 27 6 43 49 87 9.6

Total 56 283 300 51 212 263 902 a

% of whales 6.2 31.4 33.3 5.7 23.5 29.2 100.0

B: Corrected for Sampling Effort

Before 8 Sept. 9 148 101 9 4 13 271 20.0

8-27 Sept. 46 211 227 41 167 208 692 51.0

After 27 Sept. 27 23 122 27 194 222 393 29.0

Total 82 381 451 77 366 443 1357

% of whales 6.0 28.1 33.2 5.7 27.0 32.6 100.0

a One whale was photographed during both the "8-27 Sept." and "after 27 Sept." periods. 

Small Large Adults All

Calves Subadults Subadults Mothers Others Total Whales

Large numbers of subadult bowheads have been recorded in shallow nearshore waters along the

Yukon Coast and off the Tuktoyaktuk Peninsula during summer and early autumn in some years (Davis et

al. 1986b; Moore and Reeves 1993:332). Subadults are probably attracted to these areas by abundant

food resources (Bradstreet and Fissel 1987; Bradstreet et al. 1987; Chapter 6). Subadult bowheads may

concentrate in shallow nearshore areas because they are not physiologically well adapted to feeding in

deep offshore waters. Their dive durations tend to be shorter than those of adult whales (Richardson et al.

1995; Chapters 13, 14). In deep water, subadults may not be able to spend enough time at depths where

food organisms are abundant to feed efficiently. The shorter baleen of subadults, and consequent effects

on feeding efficiency, may be a factor as well.

There was segregation among age classes in the timing of migration into and through the study

area. Small subadult whales arrived in the study area, especially the nearshore zone, in late August and

early September (Table 10.4). They were still present during late September, but were scarce or perhaps

absent from the study area by early October. Large subadults and mothers with calves became common

in early September, and other adults arrived mainly in late September and early October. The tendency

for progressively larger whales to move through the area progressively later in the autumn season is

similar to the pattern of the spring migration (Zeh et al. 1993; Angliss et al. 1995). However, the pattern

for mothers and calves is different in spring and autumn. During spring, mothers and calves are the last

segment of the population to pass Barrow (Angliss et al. 1995; Koski et al. MS). In contrast, during late

summer and autumn, mothers and calves started to arrive in the eastern Alaskan Beaufort Sea rather early

in the migration period (early September), when subadult whales were the predominant animals present.

Mothers and calves were also among the last whales present in the study area during October.

Although mothers and calves tended to avoid shallow nearshore areas, they were more evenly dispersed in the remainder of the study area than were other age groups. Proportions of mothers and calves
§10. Bowheads: Habitat Use by Size Class 10-19

were generally similar among the four geographic blocks and water depths >20 m although the

proportions of subadults and adults varied markedly among those same areas.

Summary

This chapter examines year, location, water depth, and date effects on the size and status of bowhead whales occurring in and near the eastern Alaskan Beaufort Sea (depths ≤200 m) during late summer

and early autumn. It assesses the population structure of bowhead whales found in this area and evaluates

whether there was habitat or seasonal segregation by whales of different sizes (ages) and status (subadult

and adult), including mothers and calves. This information is relevant in evaluating the importance of the

study area to the different components of the bowhead whale population, and is a factor in subsequent

energetic calculations.

We used the calibrated vertical photography technique developed by LGL to obtain vertical photographs of 901 different whales during mid-August to early October of 1982ñ86 and 1998ñ2000 in the area

between Flaxman and Herschel islands (longitudes 146° to 139°W). Whale images were measured directly from the film and the measured image sizes were converted to whale lengths by accounting for systematic biases introduced by the cameras and the radar altimeter.

Subadults, adults and calves made up 64.7, 29.2 and 6.2%, respectively, of the bowheads photographed in the ìFlaxman Isl.-to-Herschel-Isl.î area over all years of this study. We found proportionally

more subadults and fewer adults within that area than are estimated to be in the overall population. Some,

but not all, of this difference was a result of the fact that most of our effort was in the peak whale migration period, with little effort during the initial 20% and final 29% of the bowhead migration through our

study area. The presence of a relatively high proportion of subadults in our lengthñfrequency distribution

even after allowance for the seasonal bias in sampling suggests that the parts of the eastern Alaskan Beaufort Sea ≤200 m deep are relatively more important for subadult bowheads than for adults.

There was significant variation in lengthñfrequency distributions of whales among years, geographic

subdivisions of the study area, water depth categories, and time periods. This variation was due to variable use

of the study area by each age class in different years, differences in the water depths preferred by different age

classes, and different migration timing by each age class. Small subadult whales (<10 m long) are the

dominant group in shallow (<20 m) nearshore habitats, with progressively fewer small subadult whales and

more adults as water depth increases. Small subadults start to arrive in the study area during late August,

numbers peak in early September, and they have passed through the study area by early October. Large

subadults start to arrive in late August but are scarce until September; moderate numbers are still present in

early October. Mothers and calves start to arrive in early September and are common in the study area until

early October. Other adults arrive mainly in late September and are common in early October.

In the mid-1980s, large numbers of subadult bowheads tended to occur in shallow nearshore areas

in the eastern part of the study area from the Kongakut River Delta to Herschel Island, and they lingered

in that area for days to a few weeks. Few whales were seen in that nearshore area during 1998ñ2000, and

those that were seen there did not appear to linger.

Acknowledgements

We thank the numerous LGL personnel, aircraft charter companies, and pilots who assisted in

collecting the photogrammetry data over the years. The U.S. Minerals Management Service, Alaska OCS

Region, sponsored the 1998ñ2000 work, the majority of the 1985ñ86 work, and this analysis. Other

studies in the 1980s, as listed in Table 10.1, were sponsored by Shell Western Exploration & Production
10-20 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

Inc., the U.S. National Marine Mammal Laboratory (Seattle, WA), the Canadian Department of Indian

Affairs & Northern Development, and a consortium organized by Sohio Alaska Petroleum Co. (now BP).

Projects in Alaska were conducted under the provisions of Scientific Research Permits 517, 518 and 481ñ

1464 issued by the National Marine Fisheries Service. Many other Acknowledgements relevant to the

project as a whole are included in Chapter 1.

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Richardson, W.J., C.R. Greene Jr., J.S. Hanna, W.R. Koski, G.W. Miller, N.J. Patenaude and M.A. Smultea, with

R. Blaylock, R. Elliott and B. W ̧rsig. 1995. Acoustic effects of oil production activities on bowhead and

white whales visible during spring migration near Pt. Barrow, Alaska―1991 and 1994 phases. OCS Study

MMS 95-0051; LGL Rep. TA954. Rep. from LGL Ltd., King City, Ont., for U.S. Minerals Manage. Serv.,

Herndon, VA. 539 p. NTIS PB98-107667.

Rugh, D.J., H.W. Braham and G.W. Miller. 1992. Methods for photographic identification of bowhead whales,

Balaena mysticetus. Can. J. Zool. 70(3):617-624.

Rugh, D.J., J.E. Zeh, W.R. Koski, L.S. Baraff, G.W. Miller and K.E.W. Shelden. 1998. An improved system for

scoring photo quality and whale identifiability in aerial photographs of bowhead whales. Rep. Int. Whal.

Comm. 48:501-512.

Treacy, S.D. 1992. Aerial surveys of endangered whales in the Beaufort Sea, fall 1991. OCS Study MMS 92-0017.

U.S. Minerals Manage. Serv., Anchorage, AK. 93 p. NTIS PB93-193811.

Zeh, J.E., C.W. Clark, J.C. George, D. Withrow, G.M. Carroll and W.R. Koski. 1993. Current population size and

dynamics. p. 409-489 In: J.J. Burns, J.J. Montague and C.J. Cowles (eds.), The bowhead whale. Spec.

Publ. 2. Soc. Mar. Mammal., Lawrence, KS. 787 p.
11. RATES OF MOVEMENT AND RESIDENCE TIMES OF BOWHEAD WHALES

IN THE BEAUFORT SEA AND AMUNDSEN GULF

DURING SUMMER AND AUTUMN

William R. Koski, Tannis A. Thomas, Gary W. Miller,

Robert E. Elliott, Rolph A. Davis, and W. John Richardson 1

Introduction

Bowhead whales travel long distances between wintering areas in the Bering Sea and summering areas

in the Beaufort Sea and Amundsen Gulf (Braham et al. 1984; Moore and Reeves 1993). Baleen whales are

generally understood to undertake annual migrations to take advantage of abundant food resources on the

summering grounds. In the case of the bowhead whale, behavioral observations and stomach contents of

harvested animals suggest that considerable feeding occurs in the eastern and central Beaufort Sea during

summer and early autumn of at least some years (Würsig et al. 1985, 1989; Lowry 1993; Chapters 12, 18).

Measurements taken from bowheads harvested and photographed during April–May and September–October

indicate that they gain weight during June–September and lose weight during October–April, suggesting that

summer feeding areas are important to bowheads (J.C. George, NSB-DWM, pers. comm.; Chapter 22).

However, isotopic evidence suggests that bowheads obtain a major part of their annual food requirements

outside the Beaufort Sea (Schell and Saupe 1993; Chapter 20). Regardless of the relative importance of

different feeding areas, during summer and early autumn bowheads are expected to spend more time in areas

where food resources are more abundant. Therefore, one method of assessing the relative importance to

bowheads of different areas within the summering range is to compare the amount of time that individual

bowheads spend in different parts of the summer range (residence times).

The eastern Alaskan Beaufort Sea borders on important summer feeding areas offshore of the

Mackenzie Delta and Yukon coast (Bradstreet et al. 1987; Chapter 6). However, significant numbers of

bowhead whales normally are not encountered over the continental shelf in Alaska until the onset of the

main fall migration period, which begins in late August or early September (Moore and Reeves 1993;

Chapter 9). Nevertheless, the Alaskan Beaufort Sea from Kaktovik to Demarcation Bay has been identified as a potentially important feeding area of bowhead whales, primarily during September. This is based

on stomach contents of bowheads harvested at Kaktovik (Lowry and Frost 1984; Lowry 1993; Chapter

18) and frequent sightings of feeding bowheads (Ljungblad et al. 1986; Richardson 1987; Chapter 12).

To determine the importance of the eastern Alaskan Beaufort Sea to the annual energetic requirements of bowhead whales, we need to know (1) how long whales remain in that area, (2) what proportion

of that time is spent feeding, and ultimately (3) how much food they consume while there. In this chapter

we estimate residence times in the eastern Alaskan Beaufort Sea and adjacent Canadian waters, and compare them to residence times at locations farther east in the Canadian Beaufort Sea and Amundsen Gulf.

We also provide information on short-term rates of movement; those data contribute to our estimates of

 

1

 LGL Ltd., environmental research associates, 22 Fisher St., POB 280, King City, Ont. L7B 1A6.

Phone: 905-833-1244; email: bkoski@lgl.com
11-2 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

residence times, and are used in later chapters to help estimate how much food bowheads may consume

while in the study area. [Rates of movement are important in determining how much water bowheads

might filter in a given amount of time given data on the proportion of their time spend feeding (Chapter

12), and on prey availability (Chapters 5, 6).]

Our primary study area is the central Beaufort Sea from Flaxman Island and western Camden Bay

to Herschel Island (146°W to 139°W; Fig. 11.1), hereafter referred to as the “eastern Alaskan” Beaufort

Sea (although it includes some Canadian waters). This study area was the same as that used in Chapters 9

(“extensive” study area), 10, and 12-13. For comparative purposes, we also estimate residence times and

rates of movement in two other areas farther east: “Yukon East”, extending from Herschel Island to the

Yukon/ Northwest Territories border; and Amundsen Gulf at the eastern end of the Beaufort Sea.

The estimates of residence times are based on data obtained via (1) aerial photography in all three

areas during 1982–2000, (2) aerial observations of bowhead whale behavior in the “eastern Alaskan”

(Flaxman-to-Herschel) area during 1985–2000, (3) aerial surveys in that area during 1979–2000, and (4)

telemetry data collected by Wartzok et al. (1989, 1990) in 1988 and 1989, and Mate et al. (2000) in 1992.

First, we present data on the intervals between medium-term (between-day) photographic resightings as

an indication of minimum residence times. A second method examines the putative rates of movement

for whales resighted over periods of hours based on within-day photographic or visual resightings. Low

and high rates of movement would be indicative of, respectively, relatively stationary vs. mobile animals.

Thirdly, we use indices of abundance from aerial surveys to estimate variability in residence times from

year to year. Finally, we use position data obtained during telemetry studies to estimate the amount of

time that tagged whales spent in our study area.

Many of the estimates of residence time that are presented are based on small sample sizes and/or

are biased. Nevertheless, complementary results from different techniques, when taken together, provide

useful information on minimum residence times for some individual whales, on year-to-year differences

in the use of a specific part of the Beaufort Sea, and on relative use of different parts of the eastern Beaufort Sea and Amundsen Gulf during a given year.

Methods

The data for this study were obtained during a large number of studies of bowhead whale behavior

and life history conducted in the Beaufort Sea and Amundsen Gulf in 1982–2000. Table 11.1 lists the

photogrammetry studies and numbers of whale images that contributed to the analyses presented here.

The “eastern Alaska” (i.e., Flaxman-to-Herschel) studies funded by U.S. Minerals Management Service

and (in 1986) SWEPI, designated in boldface in Table 11.1, also included behavioral observations that

provided data on speeds of movement. The circumstances of the behavioral studies, and their data collection procedures, are described in detail in Chapters 12 and 13. Figure 11.1 shows the geographic areas

included. The geographic areas selected for analysis had intensive coverage and/or large numbers of

bowheads photographed during at least one year in the 1982–2000 period.

Photogrammetry

We used the calibrated vertical photography technique developed by LGL and described by Koski

et al. (1992). This method was used in all three parts of the Beaufort Sea. Briefly, the aircraft flew at an

airspeed of ~160 km/h and (cloud ceiling permitting) an altitude of ~137 m (450 ft), and passed directly

over bowheads. Photographs were taken through the aircraft's ventral camera port with one of two handheld Pentax medium-format cameras (6×7 cm film size), each with a 105 mm f2.4 lens, pointed directly
§11. Bowheads: Rates of Movement & Residence Times 11-3

FIGURE 11.1. Areas where aerial photographs were obtained during 1982–2000 to estimate speeds of

movement and residence times of bowhead whales. Table 11.1 shows years with coverage in each area.

downward. Shutter speed was 1/500th or, when possible, 1/1000th second. We used primarily Ektachrome

200 or 400 ISO (ASA) or Fujichrome 400 ISO color positive film, or occasionally (in 1985) Ilford XP1

black and white negative film pushed to ISO 1600.

All images with potential to be reidentified were printed and compared with one another to check for

whales photographed more than once within each field season. These procedures are summarized by Rugh et

al. (1992, 1998). To be considered for inter-year comparisons and analyses, “photo quality” has to be 2– or

better and “identifiability” has to be M– or better for one of the zones on the whale (Rugh et al. 1998). (See

Appendix 11.1 for inter-year re-identifications found to date among whales photographed in the study area

during 1998–2000.) For the purposes of the within-year comparisons conducted here, whales with distinctive

temporary markings but otherwise no permanent markings (i.e., identifiability = U) were upgraded to M–.

Whale images were measured directly from the film using a stereo microscope and stage micrometer as described by Koski et al. (1992) and in Chapter 10. The measured image sizes were converted to

whale lengths by accounting for systematic biases introduced by the cameras (focal plane shutter distortion or inaccurate nominal lens length) and by inaccurate output from the radar altimeter. The resulting

length measurements varied in reliability depending on the circumstances during photography, the

position of the whale relative to the water surface, and the quality of the whale image. The “accurate”

length measurements are generally accurate to within a few 10s of centimeters and the poorest quality

measurements (excluding those from oblique photographs) are generally accurate to within ~1 m (Koski

et al. 1992). All qualities of length measurements except those from oblique photographs were used to
11-4 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

TABLE 11.1. Sources of bowhead whale photographs for this study. Studies in bold typeface provided

behavior data as well.

Year Zone Source of Data/Sponsor

1982 Yukon East 354 25 9 Davis et al. (1983)/NMFS

1984 Amundsen Gulf 138 15 (21)a 3 (4) Davis et al. (1986a)/DIAND

1984 Amundsen Gulf 16 1 1 NMML (unpubl. data)/NMFS

1984 Yukon East 492 29 (31) 12 (13) Davis et al. (1986a)/DIAND

1984 Yukon East 43 3 Davis et al. (1986a)

1984 Yukon East 17 4 2 NMML (unpubl. data)/NMFS

1985 Amundsen Gulf 115 41 11 Davis et al. (1986b)/SOHIO

1985 Amundsen Gulf 2 1 1 Ford et al. (1987)/COGLA

1985 Yukon East 553 32 12 (14) Davis et al. (1986b)/SOHIO

1985 Yukon East 39 7 3 Duval (1986)/COGLA

1985 Eastern Alaska 54 12 (33) 2 (10) Davis et al. (1986b)/SOHIO

1985 Eastern Alaska 2 1 1 Johnson et al. (1986)/SWEPI

1985 Eastern Alaska 121 19 8 Richardson (1987)/MMS

1986 Eastern Alaska 216 25 (31) 12 (19) Richardson (1987)/MMS

1986 Eastern Alaska 51 29 9 Koski & Johnson (1987)/SWEPI

1998 Eastern Alaska 141 9 8 This study/MMS

1999 Eastern Alaska 397 21 11 This study/MMS

2000 Eastern Alaska 33 9 6 This study/MMS

Total 2784

a

Parentheses indicate the span if all studies from that year for that area are considered.

COGLA = Canadian Oil and Gas Lands Administration

DIAND = Canada Department of Indian Affairs and Northern Development

MMS = U.S. Minerals Management Service

NMFS = U.S. National Marine Fisheries Service

SOHIO = Standard Alaska Production Company (now BP Exploration, Alaska, Inc) and others

SWEPI = Shell Western Exploration & Production, Inc.

Span of

Study

(d)a

b

Parentheses indicate total days with photos in a given year considering all listed studies.

Potentially Days

Reidentifiable With

Whales Photosb

classify whale status. The categories were calf, subadult, adult, and mother. During late summer and

early autumn, whales less than about 7 m long are generally calves less than 1 year old. Some calves may

be as long as 7.5 m by September. Whales over 13 m long are considered to be mature adults (Nerini et

al. 1984; Koski et al. 1992, 1993) although some females with calves are as small as 12.2–13 m, and

some females longer than 13.5 m are not mature (Nerini et al. 1984; Koski et al. 1993). Animals <13 m

long are here referred to as subadults unless they were calves or mothers accompanied by a calf.

 Behavioral Observation Procedures

We used the aerial observation procedures of Würsig et al. (1985) and Richardson et al. (1985,

1995a) to observe the behavior of undisturbed bowheads in the “eastern Alaska” area. Throughout each

observation session, two or three full-time observers on the right side of the aircraft dictated standardized

behavioral observations and whale position data via the intercom into a single audio recorder and also into
§11. Bowheads: Rates of Movement & Residence Times 11-5

the audio channel of a video recorder. A third or fourth part-time observer on the right side operated a video

camera whenever whales were at the surface. During each surface/dive sequence by bowheads, observers

described the same behavioral attributes as recorded in our previous studies of bowhead behavior (e.g.,

Würsig et al. 1984, 1985, 1989; Dorsey et al. 1989; Richardson et al. 1995a). Aircraft altitude was almost

always ≥460 m, which is high enough to avoid significant aircraft disturbance (Richardson et al. 1985,

1995c; Patenaude et al. 2002). Airspeed during circling was about 160–185 km/h (86–100 kt).

Computing Rates of Movement

BOS.—During behavioral observation sessions (BOSs) in 1985–86, dye markers were dropped

from the plane and used as reference points for visual estimates of successive whale positions and, hence,

the distances that whales moved between surfacings.

During observation sessions in 1998–2000, a portable computer with data logging software

(WINGPS), plugged into the aircraft’s Global Positioning System (GPS), automatically recorded time and

aircraft position (latitude and longitude) at 1-s intervals. Using the output from this system, we estimated

the positions of whales during the behavioral observation sessions. We used the aircraft’s successive

GPS positions to estimate the location about which the aircraft was circling, which was usually close to

the whale position. These times and positions could then be used to estimate the rates of movement of

whales that were resighted within and between observation sessions.

Photoidentification.—Many bowheads, particularly the larger and older ones, have distinctive

scars or other markings, such as sloughing skin, that make them individually identifiable in vertical

photographs (Rugh et al. 1992, 1998). Photographs taken more than 15 min apart were used to document

the short-term movements of recognizable individual whales of measured sizes. The time and position

were recorded at the exact time when each photograph was taken, and were used to estimate the rate of

movement between photographs. When multiple photographs were obtained for an individual whale on a

given date, only the first and last photographs were used. Aircraft positions were obtained via Very Low

Frequency (VLF) navigation systems in 1985–86 and GPS in 1998–2000. Although the absolute accuracy of the VLF systems was often no better than ~1 km, relative positions over short intervals were

usually determined within a few hundred meters.

Estimating Residence Times

We used data from several different sources to estimate residence times of whales and then compared the results. The data sources included resighting intervals, within-day rates of movement obtained

from photogrammetry, speeds estimated during behavioral observation sessions, aerial survey data, and

telemetry data. For the “eastern Alaska” zone, ten different estimates of residence time were obtained

using combinations of data from the various sources. For the “Yukon East” and Amundsen Gulf zones,

three estimates based on photogrammetry were obtained.

Some of our estimates of residence times in the “eastern Alaska” zone distinguish between bowheads that were migrating ( = traveling) vs. feeding vs. lingering. Lingering included socializing, resting,

and other activities. Some of our estimates of residence times in the “eastern Alaska” zone involved use

of the estimated “net westward speed”. This is the vector component of speed measured parallel to the

coast, which is oriented from ~108° True to 288° True in the “eastern Alaskan” zone. The net westward

speed ignores the offshore–onshore (NNE–SSW) component of movement. Net westward speeds of

traveling whales were assumed to be 3.67 km/h based on the mean speed of traveling whales as documented during BOSs in the “eastern Alaskan” Beaufort Sea during all years of this study (see Results and

Appendix 11.7B). Net westward speeds of feeding whales were assumed to be –0.71 km/h (i.e., eastward
11-6 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

at 0.71 km/h), and net westward speeds of lingering whales were assumed to be 0.55 km/h based on the

same data source. Net westward speeds were not calculated for whales in the two Canadian zones.

The following subsections describe the ten estimates of residence time derived for the “eastern

Alaska” zone. Of these, estimate #1 (resighting intervals), #3 (SODA, best-fit), and #4 (SODA, constant

survival) were also calculated for the Yukon East and Amundsen Gulf zones.

1. Photogrammetry: Intervals Between Resightings.—The interval between the first and last

sighting of an individually-identifiable whale in a given zone in one year provides a minimum estimate of

its residence time there. We included only between-day resightings. This estimate is negatively biased

for individual whales because it does not include an estimate of the time the whale was present before it

was first photographed, or the time it was there after being photographed the last time. We attempted to

account for this bias in the next three estimates, described below. Despite the negative bias in estimating

residence times of individual whales, this method could overestimate average residence time for the population as a whole. Whales that move rapidly through the study area are less likely to be resighted than

those that linger, and hence are less likely to contribute to the overall mean estimate of residence time.

2. Photogrammetry: Intervals Between Resightings + Travel.—Data from resightings as described above were used to estimate the time that bowheads lingered in the study area and the distance across

the study area that they traveled while lingering. The minimum time taken to travel from the eastern

boundary of the study area to the “lingering area”, and from there to the western boundary of the study

area, were estimated by subtracting the net westward distance traveled while lingering from the width of

the “eastern Alaska” study area (270 km) and assuming that whales traveled at a net westward speed of

3.67 km/h (migration speed). A net eastward movement would result in a negative net westward movement and an overall movement in the study area >270 km. The time lingering (interval between resightings) was added to the travel time to estimate the overall residence time in the zone.

3. Photogrammetry: Stop-over Duration, Best Fit.—The above two methods of estimating residence time do not make use of all available information from photographs taken each year. In particular,

they do not consider failure to resight a whale when photographs are taken subsequent to the initial sighting. We used the SODA (Stop Over Duration Analysis) model in conjunction with MARK to obtain

unbiased estimates of residence time in our study areas (Schaub et al. 2001). SODA is a computer model

that estimates the period of residence before and after each encounter of an animal using information on

recapture history and sampling effort. The two estimates of time in the study zone (before and after each

capture) are added together to obtain an unbiased estimate of residence time. If photographic effort is

distributed across the full width of the study zone, then this method provides a direct estimate of the average time in the zone, not just the residence time at a specific feeding location.

Stop-over durations (“time in zone”) were calculated using the procedure of Schaub et al. (2001)

with modifications given in Reboulet et al. (2001). First, two types of capture–recapture data were

entered into a matrix: the intervals between sampling events, and the intervals between resightings of

whales. Then, MARK (White and Burnham 1999; Cooch and White 2001) was used to fit several survival and recruitment models to our data, producing a summary matrix that ranked several different models

according to Akaike’s Information Criterion (AIC). The “best-fit” model was chosen based on the AIC.

SODA, using the “best-fit” model, then produced estimates of average time in the study zone before and

after each encounter. These estimates were added together to estimate residence time in the zone. The

variance of the residence time estimate was computed using SODA, which uses a boot-strapping

procedure to resample the capture–recapture history.
§11. Bowheads: Rates of Movement & Residence Times 11-7

4. Photogrammetry: Stop-over Duration, Constant Survival.—The procedure described above in

#3 was repeated assuming constant survival and recruitment rather than using the “best-fit” model as

determined by MARK. The “best-fit” model is recommended in situations where survival or recruitment

may vary among sampling intervals. We ran the more “conventional” constant survival and recruitment

model for comparison, but the assumptions of constant survival and recruitment are probably not valid for

our study area.

5. Photogrammetry: Within-day Speeds.—Speeds from within-day photographic resightings >15

min apart were used to estimate the mean net westward speed of bowheads moving through our study

area each year. The distance across the study area (270 km) was divided by the mean within-day net

westward speed (km/h) in each year to estimate the mean residence time (in hours) for that year. The

calculations of net speed for each pair of sightings/resightings assumed that whales migrated westward

through the study area on a heading of 288° (Chapter 9), and that only the westward (positive) or eastward (negative) component of movements contributed to net movements. Unlike methods 1 and 2,

which are based on whales that linger in the study area, this estimate of residence time is based on data

for all age and sex classes. However, it is still biased because whales that moved slowly were more likely

to be resighted than those that moved rapidly and because all age and sex classes do not appear to be

photographed in proportion to their abundances in the population. This bias results from their different

habitat preferences within the study area and from the concentration of our photographic effort during the

peak of the bowhead migration season―see Chapter 10.

6. Behavior: Overall Speeds.—Whales observed during BOSs also provided data on speeds of

movement within the study area. The distance across the study area was divided by the mean net westward overall speed from BOSs. This estimate suffers from the same biases as the #5 estimate, particularly the tendency to oversample feeding whales and to undersample rapidly-migrating whales that are

difficult to follow. A further limitation of this method is that the number of different whales contributing

to speed estimates is lower for the BOS data than for the within-day photogrammetry data.

7. Behavior: Activity Speeds.—Information on the activities of bowheads during each year of the

study (see Chapter 12) and on the speeds of whales during those activities permitted another calculation

of residence time. For each year, we calculated a weighted mean net westward speed based on observed

speeds of traveling, feeding, and lingering whales, and on observed proportions of time engaged in those

activities each year (see Table 11.5, later). The proportion of time traveling, as observed during BOSs

within a given year (Chapter 12: Table 12.2), was multiplied by 3.67 km/h, the mean net westward speed

of traveling whales in all years as determined from BOSs (Appendix 11.7B). The proportion of time

feeding was multiplied by –0.71 km/h, the mean net westward (actually 0.71 km/h eastward) speed of

feeding whales in all years as determined from BOSs. The proportion of time lingering (socializing, resting, unknown etc.) in a given year was multiplied by 0.55 km/h, the mean speed during these activities in

all years (Appendix 11.7B). These three numbers were added to compute a mean speed through the study

area for each year. This mean speed was divided into the distance across the study area to compute the

average residence time each year.

8. Aerial Survey: Densities.—Density indices for bowhead whales in the “eastern Alaska” study

area during each late summer and autumn season from 1979 to 2000 have been determined based on

systematic aerial surveys (Chapter 9; Appendix 9.2). The observed densities for each year are assumed to

vary according to the residence time of whales in the study area. It is assumed that, in the three years

with the lowest observed densities (1985, 1988, and 1989, hereafter called the “base years”), whales

moved across the 270-km-wide study area without stopping. At a net westward speed of 3.67 km/h, this
11-8 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

would require 3.1 days. In other years, it is assumed that the mean residence time in that year was

proportional to the densities estimated to have been present (Corr. No. Bhds Seen/100 km column in

Appendix 9.2). For example, if the density in a given year was twice the mean density in the three base

years, the mean residence time is estimated to be twice that of the base years or 6.2 days. The density

data from years before 2000 in Appendix 9.2 have been increased by 3.2% per year to standardize densities for assumed annual increases in population size. This was necessary because the bowhead population increased at an estimated annual rate of 3.2% per year from the late 1970s until at least 1993 (Punt

and Butterworth 1999). Preliminary bowhead census results from 2001 indicate that the population has

continued to increase at about the same rate (George et al. 2002). Without this adjustment, a 3.2% annual

increase in densities would result in a similar increase in apparent residence times even if residence times

were constant across years.

9. Aerial Survey: Whale-Days.—An estimate of average residence time can be calculated by

dividing the number of whale-days of use of our study area by the number of whales that passed through

the study area during each season. Chapter 9 (Table 9.3) estimates the number of whale-days of use by

bowhead whales considering the area between the coastline and the 200 m contour from the U.S./Canada

border to Camden Bay during 1985–86 and 1998–2000.

Because our “Eastern Alaska” zone includes a larger area, extending from ~Herschel Island to

Camden Bay, we multiplied the number of whale-days from Chapter 9 by 1.316 to allow for the increased

width of our study vs. the “restricted” study area used in Chapter 9. The revised total number of whale-days

was divided by the estimated population size in that year, adjusted downward to exclude the estimated

proportion of the whales that migrate west through deep waters north of the study area. This proportion was

estimated as 0.186 based on relative densities given in Moore and Reeves (1993:334) for 1979 to 1989. The

population size was estimated to have been 8200 in 1993 and to have increased at an annual rate of 3.2% per

year during 1979–93 (Punt and Butterworth 1999) and, by extrapolation, during 1993–2000.

10. Telemetry Data.—Telemetry data provide a more continuous record of bowhead locations, and

hence use of an area, than photographs or aerial observations of behavior. Three studies have tracked

bowheads through the “eastern Alaskan Beaufort Sea” (Wartzok et al. 1989, 1990; Mate et al. 2000). We

estimated the time that each whale spent in our study area based on tracks for each whale shown in the

published paper (Mate et al. 2000) or technical reports (Wartzok et al. 1989. 1990). Constant travel was

assumed between the last sighting of each whale before they entered our “eastern Alaskan Beaufort Sea”

study area and the first sighting in the study area, and between the last sighting in and the first sighting

west of our study area.

Results

1. Photos: Intervals Between Resightings

The interval between first sighting and last resighting of an individual whale provides a minimum

estimate of the residence time of that whale in the area. Table 11.2 summarizes these intervals for the whales

resighted in the Amundsen Gulf, Yukon East, and “Eastern Alaska” (i.e., Flaxman-to-Herschel) zones during

years with sufficient photographic effort such that at least a few resightings were expected. There was considerable variation in the mean interval between resightings both among years and between zones. This measure

will underestimate residence time for whales that were resighted, as there is no allowance for time spent in the

zone before the first and after the last sighting. However, these results take no account of whales that were

sighted only once, and thus may overestimate the average residence time for all whales that enter the zone.
TABLE 11.2. Within-year resighting intervals of bowhead whales from photographs taken in different geographic areas i

Amundsen Gulf, late summer to early autumn 1982-2000. Photographs were not taken on each day in each area; therefor

not have equal probability of being recorded even if individual whales remained in the survey area. Only the first and last s

each year is included.

 Zone Unique Whales

Year Photographed 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 2

 Amundsen Gulf

1984 154 21 -b - - - 1 0 - - 1 - - - - 2 0 - - - - 0 

1985 117 41 4 1 4 3 1 1 0 - - 0 0 0 0 0 0 0 0 0 1 0 All years 

Average of means for 1984 & 1985 

 Yukon East

1982 354 25 1 9 0 1 0 1 0 0 - - 0 1 0 - 0 0 1 1 1 0 1984 509 31 1 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1985 592 32 6 0 3 0 0 0 4 2 0 0 0 3 0 0 1 0 0 0 1 1 All years 

Average of means for 1982-1985 

Mean of all resightings in Canadian waters 

Average of means for each Canadian area in each year 

 "Eastern Alaska" c

1985 177 33 0 1 2 0 1 0 0 0 0 0 2 0 0 1 0 1 - 0 - - 1986 267 31 4 3 0 1 0 0 0 0 2 0 0 0 0 1 0 0 0 0 0 0 1998 141 9 1 0 0 0 0 0 - 0 Xd X X X X X X X X X X X 

1999 397 21 2 1 1 2 1 2 0 0 1 0 0 0 0 0 0 0 0 0 0 0 2000 33 9 0 0 0 0 0 0 0 0 X X XXXX X X X XXXAll years 

Average of means for "Eastern Alaska" in each year 

a Span includes both the first and last days with photographs in the area. Maximum resighting interval is one day less than the spanb "-" indicates that resighting intervals of this length could not have been obtained because of the sampling intervals.

c Includes Yukon west of Herschel Island (Fig. 11.1).

d "X" indicates that resighting intervals of this length would have been beyond the span of the study. 

Span of Number of Resightings at Interval 1-21 days

Study (d)a
11-10 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

In the “Eastern Alaska” zone, yearly mean resighting intervals ranged from 1.00 days in 1998 (but

based on only one resighting) to 8.13 ± s.d. 5.51 days in 1985 (n = 8) and averaged 4.35 days over the

four years with photographic resightings (Table 11.2). The mean of all individual resighting intervals

from all years was 5.10 ± 4.46 days (n = 30). The lack of resightings in 2000 was a strong indication of

rapid movements through the study area because the effort to find whales to photograph in “Eastern

Alaska” was greater in 2000 than in any earlier year. In 1998, the lack of additional resightings beyond

the one reported was also indicative of rapid movements through the area. Some whales stopped briefly

near Kaktovik in 1998; we consistently encountered whales feeding there, but they did not appear to

linger there for more than hours before resuming their westward migration. We resighted only one whale

photographed near Kaktovik in 1998, despite repeated photographic coverage of the area. The resighted

whale traveled west at an average speed of 2.55 km/h over a 24.4 h period (Appendix 11.2).

In 1985, 1986 and 1999, unlike 1998 and 2000, whales seemed to be present in the same locations

from day to day and were apparently feeding there. During those years, the mean intervals between

resightings were 4.10 to 8.13 days and net speeds during those intervals were low (Appendix 11.2). In

1985, sightings and resightings were in shallow nearshore waters near Komakuk (Fig. 11.2). In 1986,

sightings were generally slightly farther offshore and extended from 15 km east to 15 km west of Demarcation Bay. In 1999, all sightings and resightings were in shelf waters ~50–70 m deep from northeast of

Demarcation Bay to northeast of Kaktovik (Fig. 11.2).

FIGURE 11.2. Locations of between-day resightings of bowhead whales in the “Eastern Alaska” area,

based on aerial photographs obtained during 1985–86 and 1998–2000. Arrows indicate sequence of

photographs. No resightings were obtained in 2000. Sightings of mothers and calves are indicated by

circles around symbols.
§11. Bowheads: Rates of Movement & Residence Times 11-11

The mean interval between resightings was longer in the two Canadian zones than in “Eastern Alaska”

(6.03 vs. 5.10 d, n = 57 vs. 30). The resighting intervals varied among the Canadian and “Eastern Alaska”

zones in the same years, and among years in each zone (Table 11.2). These mean values understate the

differences between the Canadian and “Eastern Alaska” zones because only one resighting interval contributed

to the mean value for “Eastern Alaska” during 1998 and none contributed during 2000; both 1998 and 2000

were years when residence times in “eastern Alaska” were short. The average of the yearly mean resighting

intervals is a slightly better measure; it showed a slightly greater disparity between the two Canadian zones

(5.91 d) as compared with the “Eastern Alaska” zone (4.35 d). However, even the latter measure does not

allow for the lack of resightings and associated low residence time in Eastern Alaska in 2000. Thus, the mean

value for “Eastern Alaska” is positively biased compared to values for Canadian waters.

In 1984, the mean interval between resightings was shorter in the Yukon East zone (2.00 d) than in the

Amundsen zone (10.50 d), whereas in 1985 the opposite was true (7.10 d vs. 4.00 d). Resighting intervals in

both Canadian zones varied considerably among years (Table 11.2). In 1984, there was frequent photographic

coverage in the Yukon zone so the low resighting rate for that year indicates rapid movements out of the zone.

Also, there were many chances for resightings >6 days in the Amundsen zone in 1985, but only one resighting

was made at >6 days. This suggests that whales did not remain in the Amundsen zone for as long in 1985 as in

1984, when there was much less photographic coverage but three resightings at >6 days.

2. Photos: Intervals Between Resightings + Travel

Whales that were resighted in the “Eastern Alaska” zone traveled mean distances of 210–274 km,

depending on year (Table 11.3), from the eastern edge of the zone to their first photographic sighting

location and from their last photographic sighting location to the western edge of the zone. Assuming a

net westward traveling speed of 3.67 km/h over those distances, they were in the “Eastern Alaska” zone

for 2.38–3.12 d in addition to the time that they spent lingering between resightings (Table 11.3). Thus

the estimated mean residence times for whales that were resighted in the zone, including an allowance for

travel, were 11.24, 7.12, 3.38, 6.90 and 3.07 days for 1985, 1986, 1998, 1999 and 2000 (Table 11.3).

TABLE 11.3. Calculations of yearly mean residence time in "Eastern Alaska" from mean intervals between

resightings + traveling time. Negative distances indicate movements eastward.

Alongshore A: Mean B: Assumed C: D: Time Time in

Distance Interval Speed Distance (d) Study Area

Year (km) (d) a (km/h) (km) b C/(24h/d X B) = A + D

1985 -4.38 8.13 3.67 274.38 3.12 11.24 

1986 11.38 4.18 3.67 258.62 2.94 7.12

1998 59.98 1.00 3.67 210.02 2.38 3.38

1999 23.69 4.10 3.67 246.31 2.80 6.90

2000 --- --- 3.67 270.00 3.07 3.07

a

 From Table 11.2.

b

 From width of "Eastern Alaska" zone (270 km) minus alongshore distance between sightings.

Between Sightings Before & After Sightings
11-12 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

3. Photos: Stop-over Duration, Best Fit

For the “eastern Alaskan” Beaufort Sea, estimates of time in the study area based on the best-fit

SODA models were similar to the mean resighting intervals (Table 11.4). In contrast, for the Amundsen

Gulf and Yukon East zones, most SODA estimates were substantially higher than mean resighting intervals (but with wide uncertainties). The average of the four yearly estimates of residence time from SODA

for the two Canadian zones is 12.58 days, which is more than twice as long as the corresponding estimate

(5.91 d) from resighting intervals (Table 11.4).

In the “eastern Alaskan” Beaufort Sea, the estimated periods in the zone based on the “best-fit”

SODA models were 5.3, 3.8 and 4.4 days in 1985, 1986 and 1999, respectively. The average of the three

yearly estimates was 4.50 days. The corresponding mean resighting intervals were 8.1, 4.2 and 4.1 days

and the average of the three yearly estimates was 4.35 days (Table 11.4). Thus, for two of three years

with sufficient data for the SODA procedure, the estimated mean time in the zone was less than the mean

resighting interval. This reflects the fact that the mean resighting intervals apply primarily to whales that

lingered in the study area for long enough to be resighted, whereas the SODA procedure uses all photographs and photographic effort to estimate mean residence times that may be shorter than the intervals

between resightings in the zone.

TABLE 11.4. Comparison of mean sighting interval and estimated time in the study area. Mean sighting

interval is from Table 11.2. Time in the study area was computed from SODA (Schaub et al. 2001) using

two models: (A) the best fit model for survival and recruitment based on AIC, and (B) the model assuming constant survival and recruitment. Note that resighting intervals and time in the study area are

estimates of somewhat different parameters (see text).

Zone (B) Constant Survival

Year Mean s.d. n Mean s.d. Mean s.d.

 Amundsen Gulf

1984 10.5 4.36 4 -a - --

1985 4.0 4.42 15 7.2 9.09 16.0 7.73

Average of means 7.25 2 7.2 16.0

 Yukon East

1982 5.9 6.55 16 23.1 19.00 20.0 11.67 

1984 2.0 1.41 2 3.4 5.11 4.1 2.59

1985 7.1 5.99 21 16.6 56.98 27.9 6.00

Average of means 5.01 3 14.37 17.33

 5.91 5 12.58 17.00

 "Eastern Alaska"

1985 8.1 5.51 8 5.3 4.90 19.5 6.43

1986 4.2 4.45 11 3.8 3.73 9.0 3.42

1998 1.0 - 1 - - - -

1999 4.1 2.51 10 4.4 2.61 13.4 4.30

2000 - - - - - -

Average of means 4.35 4 4.50 13.97

(A) Best Fit

Stop-over Duration

Average of means for all 

Canadian areas in each 

year

a '-' indicates that the model could not generate reliable estimates due to too few recaptures or resampling events.

Resighting

Interval (d)
§11. Bowheads: Rates of Movement & Residence Times 11-13

4. Photos: Stop-over Duration, Constant Survival

We also computed the mean (± s.d.) time in the zone assuming constant survival, recruitment, and

catchability, for comparison with the best-fit models (Table. 11.4). In most cases, the constant survival,

recruitment, and catchability model produced estimates of residence times that were considerably higher

than either the estimates derived from the best-fit models or the mean intervals between resightings

(Table 11.4). However, the assumptions of constant survival, recruitment, and catchability were probably

violated during our photographic surveys.

5. Photos: Within-day Speeds

The distances and times between same-day photographic resightings were determined for 52 bowheads in the Amundsen Gulf zone, 125 bowheads in the Yukon East zone, and 136 bowheads in the

“Eastern Alaska” zone (Appendix 11.4A, 11.5). As expected, the distances between sightings tended to

increase as the time between sightings increased (Fig. 11.3), indicating that (on average) whales gradually

moved away from the location where they were initially photographed. However, the apparent or net

speeds declined as the interval between sightings increased (Fig. 11.4). Several factors, some artifactual

and some resulting from bowhead behavior, may contribute to this trend (see Discussion).

Overall swimming speeds as determined from within-day repeated photographs were 2.84 ± s.d. 1.94

km/h in the “Eastern Alaska” zone and 2.78 ± 1.79 km/h in the combined Yukon East and Amundsen Gulf

zones. These speeds did not differ significantly (t = 0.28, 2-tailed P = 0.78, df = 294). Appendices 11.4A and

11.5 show n values and other related details. In addition, the net westward speed of movement relative to the

expected migratory direction (288° True) was calculated for whales in the “eastern Alaskan” Beaufort Sea in

order to estimate residence times. The mean net westward speed from photographs was 0.32 km/h (Appendix

11.4B), indicating that much of the 2.84 km/h mean speed noted above was in directions other than westward.

Within the “Eastern Alaska” zone, the overall mean speeds of subadults and adults (mothers excluded)

were not significantly different (2.84 vs. 2.52 km/h; t = –0.86, 2-tailed P = 0.39, df = 103). However, in all

years except 1999, the mean speed of adults was faster than that of subadults (Appendix 11.4A). Overall mean

speeds of mothers were significantly faster than other adults (3.83 vs. 2.52 km/h; t = –2.31, 2-tailed P = 0.024,

df = 58) but much of that movement by mothers was not in a westerly direction. When the direction of movement relative to the migration corridor was considered, the difference was marginally significant (t = 1.98, P =

0.053, df = 58), and net speeds of mothers had a net easterly component whereas other adults had a net

westerly component (–0.61 vs. 0.97 km/h, relative to a heading of 288° W; Appendix 11.4B).

Speeds in the “Eastern Alaskan” zone varied among years, with low speeds in 1999 when direction

was ignored. Speeds of all whales combined (calves excluded) were significantly different among 1985

(mean = 3.57 km/h), 1986 (3.54 km/h), 1998 (2.27 km/h), and 1999 (1.73 km/h) (Kruskal-Wallis χ2

 =

25.16, df = 3, P = 0.000014). The results were quite different when the net westward component of speed

was considered. Net westward speeds were –0.89 (i.e., 0.89 km/h eastward), 0.17, 1.92, and 0.67 for the

same four years, respectively (Appendix 11.4B). These values were also significantly different (KruskalWallis χ2

 = 20.67, df = 3, P = 0.00012).

There was some evidence of year-to-year differences in mean speeds of subadults and adults, direction

ignored. The mean speeds for subadults were marginally different among 1985, 1986 and 1998 (3.51, 2.78

and 2.00 km/h, respectively; Kruskal-Wallis χ2

 = 7.663, df = 3, P = 0.0535); the sample size in 1999 was low.

Sample sizes for adults (mothers excluded) were too small in most years for statistical comparison of years.

However, the mean speed of adults in 1999 (1.41 km/h, n = 22) was the lowest value detected for any age class
11-14 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

FIGURE 11.3. Net distance traveled vs. time between sightings for within-day resightings of whales from

photographs, eastern Alaskan and Canadian Beaufort seas and Amundsen Gulf, 1982-2000. Resightings

<15 min apart are excluded.

FIGURE 11.4. Net speed vs. time between sightings for within-day resightings of whales from photographs, eastern Alaskan and Canadian Beaufort seas and Amundsen Gulf, 1982-2000. Resightings <15

min apart are excluded.
§11. Bowheads: Rates of Movement & Residence Times 11-15

in any year with n > 5 resightings. In comparison, the mean speed for adults in the “Eastern Alaska” zone in

all other years combined was 3.63 km/h (n = 22). Corresponding yearly values of net westward speed for

subadults and adults are given in Appendix 11.4B; year-to-year patterns differed from those for overall speed.

In the combined Canadian zones, the overall mean speeds of subadults and adults (excluding mothers) were not significantly different (2.88 vs. 2.65 km/h; t = –0.791, 2-tailed P = 0.430, df = 168). In the

Yukon East zone, there were marginal among-year differences in net speeds of all whales (calves excluded) during 1982, 1984 and 1985 (Kruskal-Wallis, χ2

 = 5.01, df = 2, P = 0.082). However, there were no

significant differences among net speeds of subadults for the same three years (Kruskal-Wallis, χ2

 = 0.17,

df = 2, P = 0.92).

The vector mean headings of whales resighted (calves excluded) in the “Eastern Alaska” zone was

328° T (± a.d. 72°); corresponding values for the combined Canadian zones were 25°T ± 78°. The high

angular deviations (calculated according to Batschelet 1981) indicate that the headings were highly

variable. In the “Eastern Alaska” zone, mean headings in 1985 and 1986, when subadult whales were

lingering and feeding in this zone, were eastward: 94° ± a.d. 63° in 1985, and 50° ± 75° in 1986. In contrast, mean headings in 1998 and 1999 were predominantly westward and the angular deviations were

somewhat lower (295°± a.d. 31° and 310° ± 52°― see Appendix 11.4A). This indicates that whales

photographed in “Eastern Alaska” were deviating from a generally westward course less frequently in

1998 and 1999 than in 1985 and 1986.

When the mean net westward speeds from photographic resightings (Appendix 11.4B) were divided into the distance across the study area (270 km), the estimates of residence times for the “Eastern

Alaska” zone based on the mean within-day speeds for each year were indeterminate, 66, 5.7, 16.8 and 51

days for 1985, 1986, 1998, 1999 and 2000, respectively. The 1985 value is indeterminate (but presumably relatively high) because the mean of the net westward speeds that year was negative. The 2000

value (51 d) is based on only five within-day resightings and should be discounted given the strong

evidence of other types that bowheads did not linger in the eastern Alaska area during 2000. The Discussion evaluates potential biases in these results.

6. Behavior: Overall Speeds

Swimming speeds of whales were determined on a few occasions during behavioral observation

sessions in the “Eastern Alaska” zone when we identified recognizable bowheads during their surfacedive sequences. We refer to “net distance” and “net speed” because these calculations assume straightline travel while the whale was out of sight below the surface. Actual distance and speed were undoubtedly higher during some dives. Over all years and activities, the mean net speed of whales (calves

excluded) during BOSs was 3.20 ± s.d. 1.88 km/h in the “Eastern Alaska” zone (Appendix 11.6A). The

speeds were significantly different among years (Kruskal-Wallis, χ2

 = 40.72, df = 4, P = 3.1×10–8) with

the slowest speeds recorded in 1985 (1.24 km/h) and 1999 (2.09 km/h), and notably higher speeds in

1986, 1998 and 2000 (3.96, 3.97 and 3.57 km/h, respectively; see Appendix 11.6A for details).

The net westward component of swimming speed, as documented during BOSs, was also calculated for use in estimating residence times in the “Eastern Alaska” zone. The net westward speeds were

notably slower than the net speeds (means 1.99 vs. 3.20 km/h). Similar to the result for net speed, the net

westward speeds were significantly different among years (Kruskal-Wallis, χ2

 =9.73, df = 3, P =0.021;

1985 excluded). The slowest mean speeds were in 1985, 1998 and 1999 (0.26, 1.53 and 1.20 km/h), with

higher means in 1986 and 2000 (2.54 and 2.91 km/h, respectively; Fig.11.5, see Appendix 11.6B for

details).
11-16 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

1985 1986 1998 1999 2000

Year

n =37

n =27

n =20 n =37

n =4

-2

0

2

4

6

8

1985

Net Speed (km/h)

FIGURE 11.5. Net speed in a nominal westward migratory direction (288° True) during dives of all

undisturbed bowhead whales (calves excluded) during behavior observation sessions in the "Eastern

Alaska" zone, 1985, 1986 and 1998-2000. Horizontal bars represent mean speed and vertical bars show

± 1 s.d. n is the number of different dives measured; the numbers of different whales that provided data

for each year were approximately 4, 10, 12, 16, and 11, respectively. See Appendix 11.6B for details.

Mean residence times in the “Eastern Alaska” zone each year were estimated by dividing the yearly

means of the net westward components of speed into the distance across the study area (270 km). The

resulting estimated residence times are 43, 4.4, 7.4, 9.4 and 3.9 days for 1985, 1986, 1998, 1999 and

2000, respectively. Potential biases are evaluated in the Discussion. However, it is important to note that

observations in Canadian waters west of Herschel Island are included, especially for 1985 when 10 of 18

speed estimates came from Canadian waters (see Chapter 12, Fig. 12.1). Also, these estimates would be

biased if there were disproportionate sampling of whales that were feeding vs. traveling (see below).

7. Behavior: Activity Speeds

We also examined net speeds of whales according to their activity. Results are shown in Appendices 11.7A, showing overall speeds, and 11.7B, showing westward alongshore components of speed.

Figure 11.6 summarizes the latter results.

Feed Travel Travel+Feed O ther

Activity

n =13

n =64 n =18

n =30

-4

-2

0

2

4

6

8

Feed

Net Speed (km/h)

FIGURE 11.6. Net speed in a nominal westward migratory direction (288°

 True) during dives of all

undisturbed bowhead whales (calves excluded) involved in different activities in the "Eastern Alaska"

zone, 1985, 1986 and 1998-2000. Horizontal bars represent mean speed and vertical bars show ± 1 s.d.

n is the number of different dives measured; the number of different whales that provided data for each

activity were approximately 17, 21, 8 and 8, respectively. See Appendix 11.7B for details.
§11. Bowheads: Rates of Movement & Residence Times 11-17

For feeding bowheads (calves excluded), the average net speed during a dive was 1.54 ± s.d. 1.21

km/h, while traveling an average net distance of 0.31 ± 0.19 km (Appendix 11.7A). We also looked at

rates of movement for feeding bowheads of different age classes, although sample sizes for these subcategories were small. Subadults had higher net swimming speeds (2.45 ± 1.53 km/h) than adults aside from

mothers (1.18 ± 0.51 km/h). As above, we refer to “net distance” and “net speed” because these calculations assume straight-line travel while the whale was out of sight below the surface. We also calculated

the westward alongshore component (288° True) of the net speeds for use in residence time calculations.

The mean westward component for feeding non-calves was –0.71 ± 1.55 km/h (Fig 11.6). This indicates

that, on average, whales moved gradually eastward from their initial positions while feeding.

Speeds of traveling whales were determined on a few occasions when we followed recognizable bowheads during their surface–dive sequences. For traveling bowheads, the average net speed during a dive was

4.50 ± s.d 1.22 km/h, while traveling an average net distance of 0.99 ± 0.76 km. Sample sizes for specific age

classes are again small, but mean speeds of traveling whales were similar for adults and subadults (4.55 vs.

4.42 km/h). The westward component of the speed of traveling whales (calves excluded) was 3.67 ± 1.74

km/h (Fig. 11.6). Results for traveling adults and subadults were similar (4.04 vs. 4.16 km/h).

Swimming speeds of whales categorized as traveling plus feeding (combined) were intermediate

between (and more variable than) those for traveling or feeding whales. The average net speed during a

dive was 3.31 ± s.d. 1.55 km/h, while traveling a net distance of 0.81 ± 0.49 km. The westward component of the speed of traveling plus feeding whales was 1.57 ± 2.32 km/h (Fig. 11.6).

Swimming speeds of small numbers of whales engaged in other activities besides feeding and

traveling were combined into a fourth activity called other/unknown. This included whales that were

categorized as engaged in social+feed, travel+social+feed, resting, aerial activities, and unknown activities. Sample sizes were too low to treat these activities separately. The average net speed during a dive

by a bowhead engaged in other/unknown activities was 1.54 ± 1.37 km/h, while traveling an average net

distance of 0.31 ± 0.30 km. The westward component of the speed was 0.55 ± 0.86 km/h (Fig. 11.6).

The derivation of estimated mean residence times for the “Eastern Alaska” zone based on the westward component of the activity speeds and the proportion of time engaged in various activities is shown,

for each year, in Table 11.5. Residence time estimates are 11.0, 19.9, 13.7, 24.2 and 4.1 days for 1985,

1986, 1998, 1999 and 2000, respectively. The activity budgets likely underestimate the amount of time

traveling in most years (see Discussion). Thus, with the possible exception of 2000 (when there was little

“lingering”), these values probably overestimate the actual residence times.

8. Aerial Survey Densities

The mean of the relative densities during the “base years” (1985, 1988 and 1989) for the entire

study area was 0.146 bowheads/100 km, corrected for changes in population size over the 1979-2000

period (see Methods and Appendix 9.2 in Chapter 9). The residence time for 1985 was calculated by

dividing the relative density for that year (0.154 bowheads/100 km) by the base year and multiplying that

value by 3.1 days. The resulting value (3.28 days) was the estimated average residence time of a whale in

the “Eastern Alaska” zone in 1985. Other residence times estimates based on the aerial survey densities

are 10.5, 2.20, 3.82, 5.82, 29.8, 58.4 and 10.2 days for 1986, 1988, 1989, 1992, 1998, 1999 and 2000,

respectively. The 1988 value (2.20 days) is implausibly low given how much time it would require for

whales to swim directly across the 270-km-wide study area without stopping (3.1 d at 3.67 km/h), and the

1999 value (58.4 d) is implausibly high.
11-18 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

TABLE 11.5. Calculation of residence time using activity speeds (vector mean westward) and activity

budgets. Vector mean speeds from Appendix 11.7B; activity budgets from Chapter 12: Table 12.2.

A: B: A: B: A: B: F: Mean G: Mean Residence

Mean Proport'n Mean Proport'n Mean Proport'n Speed 1 Speed H: Time

Speed 1 of All C: Speed 1 of All D: Speed 1 of All E: (km/h) (km/d) Distance (d)

Year (km/h) Activities =AXB (km/h) Activities =AXB (km/h) Activities =AXB =C+D+E =FX24 h Traveled =H/G

1985 -0.71 0.39 -0.28 3.67 0.31 1.14 0.55 0.30 0.16 1.02 24.59 270 10.98

1986 -0.71 0.58 -0.41 3.67 0.24 0.88 0.55 0.18 0.10 0.57 13.60 270 19.86

1998 -0.71 0.38 -0.27 3.67 0.24 0.88 0.55 0.38 0.21 0.82 19.64 270 13.74

1999 -0.71 0.66 -0.47 3.67 0.24 0.88 0.55 0.10 0.05 0.47 11.18 270 24.16

2000 -0.71 0.09 -0.06 3.67 0.74 2.72 0.55 0.17 0.09 2.74 65.88 270 4.10

1

Mean speeds are the mean vector components of speed toward 288o True. A negative speed indicates a component of speed

toward 108o

 True.

Feeding Traveling Other Activities All Activities

9. Aerial Survey Whale-Days

The average residence time of a bowhead in the “Eastern Alaska” zone in 1985 based on whaledays was calculated in the following way: (1) The number of whale-days (11,934, from Chapter 9: Table

9.3) was multiplied by 1.316 to adjust for the larger size of our study area (adjusted whale days = 15,705).

(2) The estimated population size in 1985 (6373, Appendix 9.2) was multiplied by 0.814 (the estimated

proportion of the population passing south of the 200 m contour) to estimate the number of whales that

passed through the study area in that year (whales passing = 5188). (3) The adjusted whale days were

divided by the number of whales that passed through the study area to estimate the average residence time

of a whale in the study areas in 1985 (15,705 whale-days/5188 whales = 3.03 d). Corresponding

estimates for 1986, 1988, 1998, 1999 and 2000 are 4.40, 0.84, 5.31, 16.62 and 2.96 days, respectively.

The 1988 value (0.84 days) is very unrealistic given how much time it would require for whales to swim

directly across the 270-km-wide study area.

10. Telemetry

Telemetry data provide a more continuous record of bowhead locations and hence use of an area

than photographs or aerial observations of behavior. Three telemetry studies have collected information

on bowhead movements in or through the “eastern Alaskan” Beaufort Sea.

• Wartzok et al. (1989) tracked a 12-m whale to the eastern border of the “Eastern Alaska” zone on

24 Sept. 1988 and relocated it at Barrow, about 640 km to the west, on 2 Oct. Assuming a

constant speed, the whale would have been in the “Eastern Alaska” zone for about 3.4 days.

• Wartzok et al. (1990) tracked four subadult whales (9.5–12.5 m) through our study area during

21–29 Sept. 1989; the estimated residence times of these whales based on locations taken 1–5

days apart were 4, 2.5, 7, and 4 days.

• Mate et al. (2000) deployed satellite-linked transmitters on 12 bowhead whales in the Canadian

Beaufort Sea during early September 1992. Five of these whales were tracked in the “Eastern Alaska”

zone. Three bowheads were tracked entering the zone, presumably to feed, for 2.3, 5.5 and 4.5 d

(excluding short periods when whales moved east of the study area). Their tags stopped transmitting

before their westward migration through the area, and possibly before other incursions into our study

area to feed. Allowing for a minimum transit time of 2.5 d through the study area, their minimum
§11. Bowheads: Rates of Movement & Residence Times 11-19

residence times in the “Eastern Alaska” zone during the fall period were 4.8, 8.0 and 7.0 days. Two

other whales were tracked until they moved west of the study area. The residence times for those

whales were 6.0 and 12.3 d (allowing for a 15 h excursion outside the study area on 3–4 Sept.).

The mean residence times in 1988, 1989 and 1992 were 3.40, 4.38 and 6.45 d, respectively, and the

mean residence time of the three years with telemetry data was 4.74 d.

Residence Time

The straight-line distance across the “Eastern Alaska” zone, i.e., from Herschel Island to western

Camden Bay/Flaxman Isl., is 270 km when measured near the 40-m contour. A steadily migrating

bowhead would pass through the study area in 3.1 days if it traveled at a mean speed of 3.67 km/h, which

is the mean westward-component speed observed for traveling whales (Fig. 11.6). Thus, the residence

time of a typical bowhead whale that swam across the “Eastern Alaska” zone (Herschel Isl. to Camden

Bay/Flaxman Isl.) without stopping, either to feed or for other reasons, would be 3.1 d. The corresponding time in the area from the Alaska/Yukon border to the west side of Camden Bay would be 2.4 d. We

have one record of a mother and calf sighted near both the eastern and western boundaries of the “Eastern

Alaska” (Flaxman-to-Herschel) zone. That pair of whales took 3.9 days to travel from 51 km west of the

eastern boundary to 2 km east of the western boundary, i.e., across 80% of the “Eastern Alaska” zone. At

that rate, it would have taken them 4.9 days to cross that zone if they traveled at a steady speed.

Telemetry data have shown similar transit times by some other individual bowheads (see above).

Table 11.6 summarizes the residence time calculations based on the various photogrammetric,

behavioral, aerial survey, and telemetry methods described above. The residence times computed from

the different data sources were highly variable, indicating that the different data and/or methods are biased in varying ways. The expected biases are summarized in the right column of Table 11.6, and discussed

further below. In general, for the five years of the feeding study per se, the lowest residence times were

estimated for 1998 and 2000, and the highest residence times were for 1985 and 1999.

Discussion

Local and Traditional Knowledge of Residence Times

Whale hunters and other residents of Kaktovik, within the eastern Alaskan study area, have noted

certain areas and times when bowhead whales linger, either to feed or for other reasons (see Chapter 2

and Annex B). Kaktovik residents sometimes see bowheads in a given area for 1–2 weeks or more. One

such area is between Icy Reef and Demarcation Bay. Canadian waters along the Yukon coast east of Herschel Island are another area where bowheads (small individuals) apparently linger for extended periods,

sometimes more than two weeks. However, it is uncertain from the hunters’ observations whether the

same individual whales remain for that long, as individual whales are not recognized. One hunter

indicated that bowheads tend to remain longer when the water is open than when ice is present.

Year-to-Year Differences in Use of the Study Area

Estimates of residence times are potentially biased by the activities of whales as they enter and

move through our study area. There are year-to-year differences in the frequencies of different activities,

and in the cohorts of the population that are engaged in particular activities. Many of the data that are

used to estimate residence times may depend on whale activities, so we summarize year-to-year differences in whale use of the study area that might cause biases in our residence time estimates for each year.
TABLE 11.6. Summary of estimates of mean residence times (days) of bowhead whales in the "Eastern Alaska" zone (Flax

by year, 1985-2000. From various sources of information about resighting intervals of photographed whales, rates of movand relative abundance. Estimates considered to be unbiased are in boldface; unreliable estimates are in italics. Seevaluation of reliability.

1985 1986 1988 1989 1992 1998 1999 2000 Mean Sample Size

1. Photos: Intervals Between Resightings 8.13 4.18 - - - 1.00 4.10 - 4.35 small poten

2. Photos: Intervals Between Resightings + Trave 11.24 7.12 - - - 3.38 6.90 3.07 6.34 small poten

3. Photos: Stop-over Duration, Best Fit 5.30 3.81 - - - - 4.36 - 4.49 small-mod unbi4. Photos: Stop-over Duration, Constant Survival 19.50 9.04 - - - - 13.40 - 14.0 small-mod unrel

5. Photos: Within-day Speeds undet. 66.20 - - - 5.86 16.80 51.10 33.9 high + and 

6. Behavior: Overall Speeds 43.30 4.42 - - - 7.35 9.38 3.87 6.26 high unrel

7. Behavior: Activity Speeds 11.00 19.90 - - - 13.70 24.20 4.10 14.6 moderate posit

8. Aerial Survey: Densities 3.28 10.50 2.20 3.82 5.82 29.80 58.40 10.20 17.2 moderate unrel9. Aerial Survey: Whale Days 3.03 4.40 0.84 5.31 16.62 2.96 5.53 small-mod unbi10. Telemetry Data 3.40 4.38 6.45 4.74 small unbiMean of reliable approaches (1, 2, 3, 6, 9 & 10) 6.92 4.79 2.12 4.38 6.45 4.26 8.27 3.30 5.06

Year

Relia
§11. Bowheads: Rates of Movement & Residence Times 11-21

Canadian Zones.—Past studies have documented size segregation of bowheads in their summering

areas in the Canadian Beaufort Sea (Cubbage et. al. 1987; Koski et al. 1988). Further, based on frequency

of between-day sightings, Koski et al. (1988) concluded that small bowheads lingered off the Yukon coast

in 1982 and 1985, but they entered and left the same area in 1984. This change in behavior is reflected in

our estimates of resighting intervals for those years (Table 11.2). Between-year differences in use of the

Yukon East zone are even more pronounced when residence times are estimated via SODA based on the

best-fit models (Table 11.4). Those new estimates very likely provide the best available information on

residence times of the many bowheads (mainly subadults) that occurred in the Yukon East zone in the

specific years of study. However, the distribution and numbers of bowheads in this zone are highly variable from summer to summer. In some years (e.g., 1980, 1981) very few bowheads occur close to the

Yukon coast, whereas in other years large numbers concentrate along the coast southeast of Herschel

Island (Richardson et al. 1987; Moore and Reeves 1993). Residence times of the few bowheads that

occurred along the Yukon coast in 1980 and 1981 are unknown, but residence times during years with

high numbers are very unlikely to be representative for years with low densities.

“Eastern Alaska” Zone.—All cohorts of the Bering–Chukchi–Beaufort bowhead whale population

that summer in Canadian waters pass through the “eastern Alaskan” Beaufort Sea (Flaxman Isl to Herschel Isl.) during their migration toward wintering areas in the Bering Sea (Moore and Reeves 1993;

Chapter 10). However, changes in their activities and speeds as they pass through the area could result in

biases in estimates of speeds and residence times. In 1985, small bowheads lingered in the SE part of the

“Eastern Alaska” zone (Fig. 11.2) and few bowheads of any cohort were seen in the rest of the area. Most

behavior observations (Chapters 12–14) and photographic resightings in the “Eastern Alaska” zone in

1985 came from the SE part of that zone, and involved primarily small subadult whales (Appendix 11.4;

Chapter 10). Thus, estimates of activities, speeds, and resighting intervals for 1985 are not representative

of those in the central and western parts of the “Eastern Alaska” zone or of larger whales in the eastern

part of the zone. The biases in the data have resulted in underestimates of average speed and overestimates of average residence time for the overall bowhead population that passed through the area in 1985.

In 1986, whale use of the “Eastern Alaska” zone as a whole (Flaxman-to-Herschel) was similar to

that in 1985, but whale distribution within the zone differed somewhat. We were able to conduct

photogrammetry and behavior observations over a larger part of the zone in 1986 (see Fig. 10.1 and 12.1

in Chapters 10, 12). Primarily small whales lingered in the zone, as in 1985, but they concentrated in

areas slightly farther west than in 1985 (west rather than east of the U.S.–Canada border; Fig. 11.2).

Estimates of residence time for 1986 from SODA and from within-day speeds, as derived from both BOS

data and photogrammetry, are less biased than in 1985 because they include data from throughout the

study area. Nonetheless, they are still biased because of the preponderance of data from small whales,

which lingered in the southeastern part of the study area.

In 1998, whales (primarily subadults, Chapter 10) were seen consistently near Kaktovik. Despite

repeated photographic coverage of the area near and west of Kaktovik (Fig. 10.1, Chapter 10) only one

between-day photographic resighting was made (Fig. 11.2; Appendix 11.2). This indicates that whales

stopped in the Kaktovik area only briefly. Estimates of speeds from within-day resightings from both

photogrammetry and behavioral observations are negatively biased because rapidly moving whales are

under-represented. Hence, average residence times based on those data are overestimated.

In 1999, adult whales stopped to feed in the middle shelf waters of the “Eastern Alaska” zone for

extended periods (Fig 11.2; Appendix 12.2; Chapter 10) and the mean speed of adults was lower (1.41

km/h) than in other years combined (3.63 km/h) (Appendix 11.4A). Subadults appeared to move through
11-22 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

the study area faster than adults; there were few between-day resightings of subadults (Appendix 11.2).

Therefore, overall speeds from behavior and photogrammetry were underestimates of speeds for the entire

population, and mean residence time was correspondingly overestimated.

In 2000, all whales moved through the “Eastern Alaska” zone rapidly and few whales were seen at

any time during the study. There were no between-day resightings despite much effort (Appendix 11.2).

Mean residence times estimated from within-day speeds obtained during BOSs were likely near the actual

residence times because very little back and forth movement appeared to have occurred. Speeds from

photogrammetry sessions are seriously biased because sample size was small and 40% of measured

movements came from a single session with feeding and socializing whales.

Intervals Between Resightings

The mean interval for between-day photographic resightings in the “Eastern Alaska” zone averaged

4.35 d over four of the five years of our study and yearly mean intervals were highly variable among

years (range 1.0–8.1 d; Table 11.2). The comparable statistic for two summering areas in the Canadian

Beaufort Sea and Amundsen Gulf was 5.91 d and was also highly variable (range 2.00–10.5 d). These

results suggested that bowheads tend to be more sedentary in the Yukon East and Amundsen Gulf zones

than in the “Eastern Alaska” zone, although the difference in the averages is not large. The average

interval between sightings would be smaller for the “Eastern Alaska” zone if a value for 2000 had been

obtained and included in the mean. During 2000, rates of movement were so rapid that no whales were

resighted.

The mean interval between resightings tends to underestimate residence times for those whales that

do linger in the area because it does not include any allowance for time spent in the study area before the

initial sighting and after the last sighting. This bias can be considerable and may result in estimates of

residence times that are less than 50% of the actual value (see Schaub et al. 2001). On the other hand, if a

high proportion of the animals move through the study area rapidly, the mean interval may overestimate

the mean residence time for the population as a whole because residence times shorter than the sampling

intervals are not represented in the data. Mate et al. (2000) found that bowheads are highly mobile during

the late summer and early autumn, and sometimes move considerable distances within a 24-h period.

Three of eight whale tracks reported by Mate et al. (2000) included brief movements from our “Eastern

Alaska” zone to the Yukon East zone and then back to “Eastern Alaska” during periods when they were

mostly present in the “Eastern Alaska” zone. Photogrammetry studies have also documented movements

between zones, varying in frequency among years. In some years whales remained along the Yukon coast

for prolonged periods, and in other years they rapidly passed through the same area (Koski et al. 1988).

Thus, intervals between sightings may underestimate residence time during years when whales linger in

the study area but overestimate when movements through the area are rapid. Between-year comparisons

of residence times using intervals between resightings may not be reliable.

Intervals between resightings as high as 16, 19 and 20 d were recorded in the “Eastern Alaska",

Amundsen, and Yukon East zones, respectively, indicating that some whales remained in each zone for

prolonged periods in some years. It is not known how long these specific whales were present before and

after the first and last sightings, nor whether they temporarily moved out of the zone in question at any

time between the first and last sightings.

Allowance for traveling time before the first and after the last photograph of an individual whale

within the study area (estimate #2 in Table 11.6) results in a less biased estimate of residence time for that

individual whale. This estimate is still negatively biased for the individuals that are resighted because it
§11. Bowheads: Rates of Movement & Residence Times 11-23

makes no allowance for presence before or after the documented residence period, and it assumes rapid

movements to and from the lingering area. As noted above, it is not known how this estimate might relate

to the population as a whole.

Stop-over Duration

The SODA procedure provides a robust estimate of mean residence time. The models use the available data on sampling effort and recapture history to make unbiased estimates of the time that the whale

was present in the study area before it was photographed (immigration) and the time that it remained in

the study area after it was photographed (emigration). The models are able to estimate residence time by

summing these two values even when recapture probability is low, time present in the study area is low,

and information is not available from other sources to estimate immigration and emigration (Schaub et al.

2001).

The mean residence time estimated using SODA was based on all cohorts of the population that

were photographed, not just the cohorts that were resighted. The overall photographic samples may still

be biased samples of the whales that passed through the study area because we did not obtain photographic coverage during the early and especially the late parts of the migration period (see Chapter 10).

However, the overall photographic samples are less biased than the resighting data. In some years, primarily one cohort of the population was resighted during the sampling period (i.e., subadults during

1985). Other cohorts that passed through the study area too rapidly to be resighted were nonetheless sampled photographically and those data are used by SODA.

In 1982 and 1985, estimates of residence time in the Yukon zone from SODA were much longer

(23.1 and 16.6 d, respectively) than the mean interval between sightings (5.9 and 7.3 d, respectively).

When most of the population moved through the study area without stopping, but part of the population

lingered (e.g., in the “Eastern Alaska” zone in 1985), SODA took account of the low overall resighting

rate. For “Eastern Alaska” in 1985, the resulting mean residence time estimate from SODA (5.3 d) for

the whole population was lower than the mean interval between resightings for those individuals that lingered in the area long enough to be resighted (8.1 d).

Residence time estimates from SODA suggest that bowhead whales remained in Canadian zones on

average almost three times as long as they remained in the “Eastern Alaska” zone (12.6 d vs. 4.5 d (Table

11.4)). This difference was probably related to the activities of whales when they were present in those

zones. While in Canadian waters, bowheads spent an average of 71% of their time feeding and 9%

traveling. While in the “Eastern Alaskan” Beaufort Sea, bowheads spent an average of 47% of their time

feeding and 31% traveling (Chapter 12: Fig. 12.9).

Photogrammetry: Within-day Speeds

Over short time periods bowheads gradually moved away from the locations where they were initially photographed but over time their net speeds declined. This suggests that some of the movements

were local movements probably associated with feeding. Short-term reactions to the photogrammetry

aircraft may also be involved (Patenaude et al. 2002). Overall within-day speeds were not significantly

different between “Eastern Alaska” (2.84 km/h) and the Canadian zones (2.78 km/h). These overall

average speeds from both areas were slower than speeds of migrating whales (4.50 km/h), consistent with

behavioral and stomach content evidence that feeding forms a significant part of the activities of whales

in “Eastern Alaska” (Chapters 12, 18) and with behavioral observations of feeding in the Canadian zones

(Würsig et al. 1984, 1985, 1989).
11-24 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

Within the “Eastern Alaska” zone, speeds were significantly different among years (excluding

2000 when there were too few data). This difference appears to be mainly attributable to the slow movements of adults in 1999 (mean 1.41 km/h)―slower than adults in other years combined (3.63 km/h), and

slower than subadults in that year (2.78 km/h) and all earlier years (3.51, 2.78 and 2.00 km/h in 1985,

1986 and 1998, respectively (Appendix 11.4A). This suggests that feeding by the adult whales that

predominated in 1999 was more localized than feeding by subadults that predominated in some other

years. Similar differences were not found in the Canadian zones where no strong differences existed

among years or between adults and subadults.

The net westward component of speed was also highly variable among years and some of the data

were clearly biased. In 1985, the net westward speed was –0.89 km/h indicating that the net movement of

the sampled whales was more to the east than to the west―not a credible result for the population and

season as a whole. In 1986, the net westward speed was so slow (0.17 km/h) that the sampled whales

would have taken 66 days (on average) to pass through the study area.

Residence time estimates based on within-day speeds from photogrammetry are biased and can

either over- or underestimate rates of movement. Some of the potential biases are as follows:

• The activities of the whales that are photographed may not be representative of activities of

whales that are not photographed. In particular, migrating whales are more difficult to detect

(and hence photograph) than feeding or socializing whales because they are submerged a greater

proportion of the time (Chapters 13, 14).

• Some movements may be back-and-forth movements, in which the net distance westward and the

net westward speed over a short period of time could overestimate the total distance and net

westward speed that would be traveled by those whales over a longer period of time.

• As time passes and average distances increase, the whales that travel fastest tend to move out of

the area where photographs are taken, causing progressively more serious underestimation of

average speeds.

Behavior Speeds

Swimming speeds determined from BOSs in the “Eastern Alaska” zone were significantly different

among years. These differences were attributable to the different activities and age classes of whales that

lingered there in different years. The primary activity recorded for bowheads in the “eastern Alaskan”

Beaufort Sea during late summer and autumn of 1985–86 and 1998–2000 was feeding. The average net

speed of feeding whales determined from BOSs was 1.54 ± s.d. 1.21 km/h, which is considerably slower

than speeds of traveling whales (4.50 ± 1.22 km/h). The net westward speed of feeding whales was –0.71

km/h, indicating a net movement eastward while they were feeding. These slower net speeds by feeding

whales indicate that they remained longer in the study area than they would have if they were simply

migrating through it. Based on very small sample sizes, the net speeds of subadult feeding whales were

faster (2.45 km/h) than those of adult feeding whales (1.18 km/h), consistent with other evidence (Chapters 10, 13) that the two age classes had different feeding strategies in the study area. The observed rates

of movement of traveling whales in the “eastern Alaskan” Beaufort Sea in autumn (4.50 ± s.d. 1.22 km/h)

are similar to those recorded during spring migration at Barrow where traveling was the predominant

activity (4.0 km/h, Rugh 1990; 3.89 ± 1.48 km/h, Richardson et al. 1995b).

Speeds estimated from BOSs overestimate rates of movement over longer periods of time for

whales that are lingering in the study area (primarily feeding whales). However, because individual
§11. Bowheads: Rates of Movement & Residence Times 11-25

whales were followed, activity speeds are less likely to seriously underestimate speeds of rapidly migrating whales than are the other methods. Thus, residence times calculated using activity speeds have the

potential to be less biased than those based on resightings from photogrammetry. The activities of whales

can vary from year to year (Chapter 12) and the biases associated with the yearly estimates of the activity

budgets have not been quantified. Our estimates of residence time based on activity budgets and activity

speeds are higher than our estimates of residence time based on the seemingly-robust SODA best-fit

method. This suggests that activity budgets in Chapter 12 may underestimate the proportion of time spent

traveling in most or all years of our study.

Aerial Surveys

The two estimates of residence time based on aerial survey data vary considerably even though

they are based on the same raw data. The estimates based on raw density indices are highly variable and

do not parallel those from SODA or, indeed, any of the other procedures (Table 11.6). The raw density

indices are a tabulation of total sightings divided by total effort in each year without consideration of

when or where the surveys were conducted. Surveys conducted during August or late October would

generally contribute few sightings and would tend to reduce the mean density index for a given year.

Similarly, surveys of offshore areas or failure to conduct surveys during the mid-September period (near

the peak of the migration) would tend to lower the density index for that year; whereas, a large amount of

coverage during mid-September would likely result in a high density index for that year.

The residence time estimates based on estimates of whale-days in the study area include corrections to raw sighting data to account for date of survey, geographic effort, aircraft type, sea state, ice, and

aircraft altitude (Chapters 9, 15). The resulting estimates of residence time are generally comparable to

those from the SODA best-fit procedure.

The aerial survey estimates are not strictly comparable to the other estimates in that they include

data collected before and after the behavioral and photogrammetry studies, i.e., earlier and later in the

“autumn” migration period. Thus the aerial survey estimates, particularly those based on whale-days, are

more representative of the entire late summer to early autumn period than are the other methods.

Telemetry Data

The telemetry data provide more continuous records of the presence or absence of bowheads in our

study area than the other methods, but the times between locations are often a day or more. Thus the

times that whales entered or left the study area were estimated and the estimates of time in the study area

are not precise. Furthermore, during the telemetry studies summarized here, all of the tagged whales were

subadult whales, so they do not provide information on adult whales or mothers and calves. Finally,

behavior observations were not conducted during the years of the telemetry studies so we can only infer

the activities of whales based on their movement patterns. Even so, the telemetry data are generally consistent with the most reliable estimates from other years in suggesting a mean residence time in the

present study area of ~4.7 days.

Best Estimates of Residence Times

Estimates of bowhead whale residence time in the “Eastern Alaska” (Flaxman-to-Herschel) zone as

estimated from various sources of data varied from 0.8 for1988 aerial survey whale-days to 58.4 days for

1999 aerial survey densities. Considering the six most reliable approaches, annual estimates varied from

0.8 to 16.6 d, and averaged 5.1 d (Table 11.6). A steadily traveling whale would require 3.1 d to travel

across the “Eastern Alaska” zone (Herschel Isl. to Flaxman Isl.) or 2.4 d to travel from the Alaska/Yukon
11-26 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

border to Flaxman Isl., based on the 3.67 km/h net westward speed documented for traveling bowheads.

The various methods that were used have differing biases, as discussed above, and some procedures are

clearly more reliable than others (Table 11.6).

The “best estimates” of residence time appear to be those based on intervals between photographic

resightings (with and without allowance for travel time), on “stop-over duration analysis” (SODA) using

the “best-fit” models, on behavior overall speeds, on aerial survey estimates of whale-days in the study

area, and on telemetry data. Estimates of residence time based on speeds determined from behavioral

observations and photogrammetry are highly variable. The variability probably arises from different

activities of the whales during different years or in different parts of our study area, compounded by

difficulties in obtaining unbiased estimates of the proportion of the whales engaged in these activities

over the study area as a whole in each year (Chapter 12).

Summary

To determine the importance of the eastern Alaskan Beaufort Sea to bowhead whales, we need to

know how long whales remain in the area. This is one key factor in estimating how much food bowheads

consume while there. We also need to know how fast they travel while feeding to estimate how much

water they might filter. This chapter documents short-term rates of movement of bowhead whales and

estimates average residence times in the eastern Alaskan Beaufort Sea and adjacent Yukon waters, i.e.,

from Flaxman Isl. (146°W) to Herschel Isl. (139°W).

We estimated rates of movement from within-day sightings of photographed bowhead whales in the

“Flaxman-to-Herschel” portion of the Beaufort Sea and compared them to similar data collected during

the 1980s off the Yukon east of Herschel Island (Yukon East) and in Amundsen Gulf.

Over periods of 15 min to a few hours, bowheads gradually moved away from the location where

they were initially photographed, but as the interval between the initial sighting and resighting increased,

speeds declined. This suggested that some movements were local, in part associated with feeding.

Within-day speeds were not significantly different between the “Flaxman-to-Herschel” zone and the more

easterly Canadian zones. Within the “Flaxman-to-Herschel” zone there was a significant difference in

speeds among years. The difference appeared to be due to slower speeds by feeding adults photographed

in 1999 than by primarily subadult whales photographed in other years.

The primary activities recorded for bowheads during late summer and autumn were feeding and

traveling. Based on the successive locations of bowheads observed during prolonged behavioral observation sessions, the average rate of movement of bowheads in the “Flaxman-to-Herschel” zone was about

1.54 km/h for feeding whales vs. 4.50 km/h for traveling whales. The mean alongshore component of the

net speed, measured along the 288°–108° (True) axis, was 0.71 km/h eastward for feeding whales and

3.67 km/h westward for traveling whales.

We also attempted to estimate residence times of bowhead whales in the “Flaxman-to-Herschel”

area using four general types of data: photoidentification data, behavioral observations, aerial survey

results, and telemetry data. Photoidentification data from the 1980s were also used to estimate residence

times in the Yukon East and Amundsen Gulf zones. (1) Photographic resightings were used to determine

within-day rates of movement and intervals between resightings for the “Flaxman-to-Herschel” zone and

for the Yukon East and Amundsen Gulf zones in all years with sufficient data. Net speeds from withinday photographic resightings were the basis for one estimate of residence times of whales in each zone.

Resighting intervals indicated minimum residence times for the specific whales resighted. A computer
§11. Bowheads: Rates of Movement & Residence Times 11-27

program (SODA, “stop-over duration analysis”) was used to derive an unbiased estimate of residence

time in each zone based on data on photographic effort as well as resightings. (2) Behavioral observations of bowhead whales were used to determine short-term rates of movement of whales, and net

westward speeds of whales engaged in different activities, in the “Flaxman-to-Herschel” zone during late

summer and autumn of 1985–86 and 1998–2000. (3) Aerial survey data were used to estimate residence

times in that area based on relative densities during aerial surveys and based on numbers of whales estimated to be present during aerial surveys. (4) Data on whale locations obtained during telemetry studies

in three years were used to estimate residence times of whales in the “Flaxman-to-Herschel” zone.

Annual residence time estimates for the “Flaxman-to-Herschel” zone were extremely variable

among years and among different methods of analysis applied to the same year. We attribute the latter

variability to biases in the different methods that interacted with year-to-year variability in sampling

effort, whale distribution, and whale activities. For example, most behavioral data and some photographs

collected in 1985 were from feeding whales off the Yukon coast (“border-to-Herschel Isl.”); activities and

speeds of those whales were not representative of whales in Alaskan waters in 1985. In general, estimates

based on behavior data, and to a lesser extent photogrammetry data, were positively biased.

We identified six calculation methods based on photoidentification, behavioral observation, aerial

survey, and telemetry data that provided residence time estimates most representative of actual residence

times. However, even with these six methods, a few of the residence time estimates were recognizably

biased. The annual residence time estimates for the “Flaxman-to-Herschel” area during 1985–86, 1988,

1989, 1992, and 1998–2000 based on these six methods varied from 2.1 to 8.3 d and averaged 5.1 d. A

sensitivity analysis (in Appendix 23.1) indicated that the 95% confidence limit for the 5.1-d estimate of the

mean residence time was 4.2 to 6.1 d.

Residence times varied dramatically among years because of different levels of use of the

“Flaxman-to-Herschel” zone for feeding during late summer and autumn. In 1985 and 1986, the eastern

part of the area was used for feeding by subadult bowheads during late summer. In 1998, subadult whales

briefly stopped to feed in central and western parts of the study area during their migration through the

study area. In 1999, adult whales stopped to feed for extended periods in eastern and central parts of the

study area. During 2000, most whales migrated through the study area without stopping.

The mean interval for between-day photographic resightings was 4.35 days in the “Flaxman-toHerschel” zone and 5.91 days in Canadian zones east of there. Estimates for both areas were highly

variable among years. A tendency for residence times in the “Flaxman-to-Herschel” zone to be shorter

than those in more easterly Canadian areas became more evident when the SODA model was used to estimate total residence times, allowing for time present before the first and after the last sighting, and for

whales photographed only once. SODA showed that mean residence times for the Canadian zones were

considerably longer (12.6 d) than mean resighting intervals (5.9 d), whereas mean residence times for the

“Flaxman-to-Herschel” zone were lower than (1985) or similar to (1986, 1999) the mean resighting intervals. The shorter residence times in the latter zone compared to the Yukon East and Amundsen Gulf

zones are consistent with distributional and behavioral data in suggesting that bowhead whales spent less

time feeding in the “Flaxman-to-Herschel” area than in adjacent Canadian zones in most years.

Furthermore, residence time estimates for eastern Alaska would be further reduced if data from Canadian

waters west of Herschel Island (the Komakuk area) were excluded from the “Flaxman-to-Herschel” zone.
11-28 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

 Acknowledgements

We thank the numerous LGL personnel, aircraft charter companies, and pilots who assisted in collecting

the photogrammetry and behavioral data over the years. We thank Dr. M. Schaub for assistance in deriving the

stop-over estimates using SODA and MARK. We thank the U.S. Minerals Management Service for sponsoring

much of the fieldwork plus the present analysis. We also thank the Canadian Oil & Gas Lands Administration,

Canadian Department of Indian Affairs & Northern Development (now Indian & Northern Affairs Canada),

U.S. National Marine Fisheries Service, Standard Alaska Production Company (now BP Exploration, Alaska,

Inc.), and Shell Western Exploration & Production Inc., all of which also sponsored studies that contributed

important data (Table 11.1). LGL projects in Alaska were conducted under the provisions of Scientific

Research Permits 517, 518 and 481-1464 issued by the National Marine Fisheries Service. LGL projects in

Canada were authorized under permits issued by the Canadian Department of Fisheries and Oceans. Many

other Acknowledgements relevant to the project as a whole are included in Chapter 1.

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Würsig, B., E.M. Dorsey, W.J. Richardson and R.S. Wells. 1989. Feeding, aerial and play behaviour of the bowhead whale, Balaena mysticetus, summering in the Beaufort Sea. Aquat. Mamm. 15(1):27-37.
APPENDIX 11.1. Between-year resightings, various origins and years, to MMS study area and vicinity, 1998 and 19991.

Where First Photographed ResightingResighted/

Source of Whale 

Oiginal Photo1 Year No. Date Loc'n2 Lat. Long. Date Lat. Long.

Offshore Demarcation

NMFS3 1989-99 7728 28 Apr BR 71 32.7 155 16 30 Sep 70 14.9 141 27 522

Nearshore Kaktovik

DIAND 1984-98 4298 24 Aug KP 69 20.9 138 28 19 Sep 70 12.1 144 11 239 

MMS Spr. 1994-98 10104 7 May BR 71 35.1 154 40 15 Sep 70 11.2 143 53 422 

Offshore Camden Bay

SOHIO 1985-98 6106 14 Sep KP 69 08.6 138 02 20 Sep 70 13.8 145 08 299 

MMS4 1985-98 4586 22 Sep OK 70 11.9 139 51 20 Sep 70 13.8 145 08 199

SOHIO 1985-98 6007 13,14 Sep KP 69 10.4 138 06 20 Sep 70 12.9 144 55 287 

MMS 1986-98 7394 26 Sep OK 70 07.1 140 40 20 Sep 70 13.7 145 08 169 

NMFS 1986-98 8132 4 May BR 71 32.3 155 29 20 Sep 70 14.3 145 09 402 

3 Same whale photographed in 1986 by Cascadia Research Collective (Tuktoyaktuk Peninsula Shelf) on 31 August (Ford et al. 1987).4 Same whale photographed in 1984 (DIAND Study, in Franklin Bay, N.W.T.) on 31 August, and in 1985 on 6 September (SOHIO, KP).1 NMFS = Spring studies near Barrow, AK, by National Marine Fisheries Service. DIAND = 1984 summer study by LGL for C

Department of Indian Affairs and Northern Development (Davis et al. 1986a). MMS Spr. = 1994 spring study near Barrow, AK, by MMS (Richardson et al. 1995b). SOHIO = 1985 study by LGL for Standard Alaska Production Co. and others (Davis et al. 1986b). MM

86 Feeding studies by LGL for MMS (Richardson 1987).2 BR = Barrow, AK; OE = Offshore Komakuk; KP = King Point, Yukon Territory; NK = Nearshore Kaktovik; OC = Offshore Camden Bay

(km) 

Net Dist.

Between 

Sightings 
11-32 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

APPENDIX 11.2A. Rates and directions of movement determined from between-day resightings of

bowhead whales in the "eastern Alaskan" Beaufort Sea (including Yukon west of Herschel Isl.), late

summer and autumn 1985-2000.

Angular

n Min Max Mean s.d. Min Max Mean s.d. Min Max Mean s.d. Mean Dev.

Calves 0 - - - - - - - - - - - - - - 

Subadults 7 50.6 385.1 184.98 136.10 2.6 66.2 17.41 22.60 0 0.2 0.09 0.07 109 59.9

Adults 1 260.6 260.6 260.62 - 1.5 1.5 1.54 - 0 0 0.01 - 233 - 

Mothers 0 - - - - - - - - - - - - - - 

All non-calves 8 50.6 385.1 194.44 128.81 1.5 66.2 15.42 21.67 0 0.2 0.08 0.07 126 65.6

Calves 1 93.9 93.9 93.88 - 213.5 213.5 213.52 - 2.3 2.3 2.27 - 281 - 

Subadults 10 23.8 332.1 98.10 107.33 1.2 31.8 10.80 9.22 0.0 0.3 0.14 0.09 118 58.7

Adults 0 - - - - - - - - - - - - - - 

Mothers 1 93.9 93.9 93.88 - 213.5 213.5 213.52 - 2.3 2.3 2.27 - 281 - 

All non-calves 11 23.8 332.1 97.72 101.83 1.2 213.5 29.23 61.75 0 2.3 0.33 0.65 123 65.5

Subadults 1 24.4 24.4 24.40 - 62.1 62.1 62.10 - 2.6 2.6 2.55 - 273 - 

Calves 0 - - - - - - - - - - - - - - 

Subadults 2 46.6 93.0 69.78 32.78 11.9 12.5 12.22 0.41 0.1 0.3 0.20 0.09 224 18.9

Adults 6 22.7 216.0 90.69 72.06 6.7 57.6 31.80 19.94 0.2 0.6 0.39 0.14 313 55.6

Mothers 2 143.4 143.5 143.43 0.08 33.4 53.5 43.45 14.25 0.2 0.4 0.30 0.10 254 13.8

All non-calves 10 22.7 216.0 97.06 60.62 6.7 57.6 30.21 18.87 0.1 0.6 0.33 0.14 273 54.2

All 0 - - - - - - - - - - - - - - 

1985-2000 

Calves 1 93.9 93.9 93.88 - 213.5 213.5 213.52 - 2.3 2.3 2.27 - 281 - 

Subadults 20 23.8 385.1 121.99 117.96 1.2 66.2 15.87 18.16 0.0 2.6 0.25 0.55 133 66.1

Adults 7 22.7 260.6 114.96 91.94 1.5 57.6 27.47 21.50 0.0 0.6 0.33 0.19 296 57.4

Mothers 3 93.9 143.5 126.92 28.61 33.4 213.5 100.14 98.71 0.2 2.3 0.96 1.14 263 16.8

All non-calves 30 22.7 385.1 120.84 104.57 1.2 213.5 27.01 40.28 0.0 2.6 0.34 0.58 198 76.0

Time Between

Resightings (h)

Net Distance

Traveled (km)

Net Direction

of Movement

(Degrees True)

Apparent

Speed (km/h)

2000

1985

1986

1998

1999
§11. Bowheads: Rates of Movement & Residence Times 11-33

APPENDIX 11.2B. Net rates of movement in nominal westward migratory direction (288o True) determined

from between-day resightings of bowhead whales in the "eastern Alaskan" Beaufort Sea (including Yukon

west of Herschel Isl.), late summer and autumn 1985-2000.

 Angular

n Min Max Mean s.d. Min Max Mean s.d. Min Max Mean s.d. Mean Dev.

Calves 0 - - - - - - - - - - - - - - 

Subadults 7 50.6 385.1 184.98 136.10 -22.6 11.6 -5.13 10.10 0.0 0.0 -0.04 0.06 109 59.9

Adults 1 260.6 260.6 260.62 - 0.9 0.9 0.88 - 0.0 0.0 0.00 - 233 - 

Mothers 0 - - - - - - - - - - - - - - 

All non-calves 8 50.6 385.1 194.44 128.81 -22.6 11.6 -4.38 9.59 -0.1 0.0 -0.04 0.05 126 65.6

Calves 1 93.9 93.9 93.88 - 211.7 211.7 211.70 - 2.3 2.3 2.25 - 281 - 

Subadults 10 23.8 332.1 98.10 107.33 -30.9 5.0 -8.65 10.25 -0.3 0.2 -0.14 0.23 118 58.7

Adults 0 - - - - - - - - - - - - - - 

Mothers 1 93.9 93.9 93.88 - 211.7 211.7 211.70 - 2.3 2.3 2.25 - 281 - 

All non-calves 11 23.8 332.1 97.72 101.83 -30.9 211.7 11.38 67.14 -0.3 2.3 0.08 0.75 123 65.5

Subadults 1 24.4 24.4 24.40 - 60.0 60.0 59.98 - 2.5 2.5 2.46 - 273 - 

Calves 0 - - - - - - - - - - - - - - 

Subadults 2 46.6 93.0 69.78 32.78 1.6 8.5 5.06 4.86 0.0 0.2 0.10 0.12 224 18.9

Adults 6 22.7 216.0 90.69 72.06 -6.6 57.6 25.71 25.03 -0.3 0.6 0.20 0.33 313 55.6

Mothers 2 143.4 143.5 143.43 0.08 22.3 50.2 36.26 19.07 0.2 0.4 0.25 0.14 254 13.8

All non-calves 10 22.7 216.0 97.06 60.62 -6.6 57.6 23.70 22.60 -0.3 0.6 0.19 0.26 273 54.2

All 0 - - - - - - - - - - - - - - 

Calves 1 93.9 93.9 93.88 - 211.7 211.7 211.70 - 2.3 2.3 2.25 - 281 - 

Subadults 20 23.8 385.1 121.99 117.96 -30.9 60.0 -2.61 17.81 -0.3 2.5 0.08 0.57 133 66.1

Adults 7 22.7 260.6 114.96 91.94 22.3 211.7 22.16 24.70 0.2 2.3 0.92 1.16 296 57.4

Mothers 3 93.9 143.5 126.92 28.61 -6.7 57.6 94.74 102.24 -0.3 0.6 0.17 0.31 263 16.8

All non-calves 30 22.7 385.1 120.84 104.57 -30.9 211.7 12.90 43.98 -0.3 2.5 0.18 0.63 198 76.0

Time Between

Resightings (h)

Net Distance

Traveled (km)

Apparent

Net Direction

of Movement

Speed (km/h) (Degrees True)

2000

1985-2000 

1985

1986

1998

1999
11-34 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

APPENDIX 11.3. Rates and directions of movement determined from between-day resightings of bowhead

whales in the Canadian Beaufort Sea (east of Herschel Isl.) and Amundsen Gulf, late summer and

autumn 1982-1985.

 Angular

n Min Max Mean s.d. Min Max Mean s.d. Min Max Mean s.d. Mean Dev.

Calves 0 - - - - - - - - - - - - - - 

Subadults 0 - - - - - - - - - - - - - - 

Adults 4 116.6 339.2 249.20 106.02 2.7 79.3 28.44 34.47 0.0 0.2 0.09 0.09 266 66.9

Mothers 0 - - - - - - - - - - - - - - 

 All Non-Calves 4 116.6 339.2 249.20 106.02 2.7 79.3 28.44 34.47 0.0 0.2 0.09 0.09 266 66.9

Calves 0 - - - - - - - - - - - - - - 

Subadults 3 48.9 94.3 71.32 22.74 4.8 47.3 21.15 22.88 0.1 0.5 0.27 0.22 257 67.6

Adults 12 21.2 454.6 101.61 118.67 1.9 86.4 17.60 23.71 0.0 0.5 0.20 0.14 306 65.2

Mothers 0 - - - - - - - - - - - - - - 

 All Non-Calves 15 21.2 454.6 95.55 106.29 1.9 86.4 18.31 22.77 0.0 0.5 0.21 0.15 298 66.6

Calves 0 - - - - - - - - - - - - - - 

Subadults 11 41.5 455.8 183.27 159.53 4.6 150.3 53.19 59.52 0.0 1.3 0.37 0.45 137 61.0

Adults 5 22.2 46.0 39.53 9.81 1.7 19.0 8.01 6.68 0.0 0.4 0.22 0.17 139 40.5

Mothers 2 43.7 415.3 229.48 262.79 11.3 13.5 12.40 1.55 0.0 0.3 0.17 0.20 61 77.0

 All Non-Calves 18 22.2 455.8 148.48 155.25 1.7 150.3 36.11 50.81 0.0 1.3 0.31 0.37 137 58.7

Calves 0 - - - - - - - - - - - - - - 

Subadults 2 20.1 74.5 47.30 38.41 23.6 55.7 39.67 22.72 0.3 2.8 1.54 1.73 232 74.5

Adults 0 - - - - - - - - - - - - - - 

Mothers 0 - - - - - - - - - - - - - - 

 All Non-Calves 2 20.1 74.5 47.30 38.41 23.6 55.7 39.67 22.72 0.3 2.8 1.54 1.73 232 74.5

Calves 0 - - - - - - - - - - - - - - 

Subadults 31 19.8 481.6 169.65 139.76 2.2 71.6 23.70 14.86 0.0 2.3 0.34 0.47 89 61.8

Adults 3 20.7 189.0 125.81 91.65 26.8 53.9 39.89 13.59 0.1 1.9 0.78 0.96 250 60.4

Mothers 0 - - - - - - - - - - - - - - 

 All Non-Calves 34 19.8 481.6 165.78 135.74 2.2 71.6 25.13 15.29 0.0 2.3 0.38 0.52 91 65.6

Calves 0 - - - - - - - - - - - - - - 

Subadults 47 19.8 481.6 161.35 139.93 2.2 150.3 31.12 33.34 0.0 2.8 0.40 0.56 103 66.3

Adults 24 20.7 454.6 116.30 115.87 1.7 86.4 20.20 23.36 0.0 1.9 0.26 0.37 256 74.8

Mothers 2 43.7 415.3 229.48 262.79 11.3 13.5 12.40 1.55 0.0 0.3 0.17 0.20 61 77.0

 All Non-Calves 73 19.8 481.6 148.41 135.62 1.7 150.3 27.01 30.28 0.0 2.8 0.35 0.50 110 73.7

Net Direction

of Movement

(Degrees True)

 1984 Amundsen Gulf

 1985 Amundsen Gulf

 1985 Yukon

 1982-1985 

 1982 Yukon

 1984 Yukon

Apparent

Speed (km/h)

Time Between

Resightings (h)

Net Distance

Traveled (km)
§11. Bowheads: Rates of Movement & Residence Times 11-35

APPENDIX 11.4A. Rates and directions of movement determined from within-day resightings (>15 min) of

bowhead whales in the "eastern Alaskan" Beaufort Sea (including Yukon west of Herschel Isl.), late

summer and autumn 1984-2000.

 Angular

n Min Max Mean s.d. Min Max Mean s.d. Min Max Mean s.d. Mean Dev.

Subadults 1 38.7 38.7 38.67 - 3.2 3.2 3.22 - 5.0 5.0 4.99 - 41 -

Calves 2 27.8 45.8 27.83 12.72 1.0 2.1 1.56 0.77 2.2 2.8 2.47 0.41 164 77

Subadults 22 23.0 264.6 44.47 50.52 0.6 9.2 2.23 1.74 1.3 7.2 3.51 1.67 72 63

Adults 7 24.9 56.1 37.99 11.59 0.8 3.6 2.29 0.93 0.9 5.2 3.84 1.46 141 73

Mothers 1 28.5 28.5 28.50 - 1.4 1.4 1.35 - 2.8 2.8 2.85 - 106 -

30 23.0 264.6 42.42 43.48 0.6 9.2 2.22 1.55 0.9 7.2 3.57 1.58 94 63

Calves 7 16.9 54.5 31.48 12.61 0.9 3.7 2.23 1.33 1.1 7.3 4.42 2.14 119 75

Subadults 19 15.0 87.2 34.00 17.32 0.3 4.8 1.58 1.35 0.5 6.1 2.78 1.67 50 73

Adults 7 25.2 98.8 52.63 28.03 0.3 4.3 2.86 1.46 0.2 7.2 4.10 2.59 343 72

Mothers 7 17.6 35.9 26.06 7.33 0.7 3.9 2.46 1.32 2.4 7.9 5.41 2.15 120 75

34 a 15.0 98.8 35.79 20.14 0.3 4.8 1.99 1.44 0.2 7.9 3.54 2.22 50 75

Calves 2 32.3 36.1 34.19 2.68 1.5 1.5 1.50 0.07 2.4 2.9 2.65 0.32 302 18

Subadults 12 16.8 72.2 44.70 22.12 0.2 1.9 1.21 0.62 0.4 6.5 2.00 1.72 289 36

Adults 7 17.6 68.9 44.25 20.27 0.1 2.9 1.80 0.95 0.3 6.1 2.69 1.82 301 25

Mothers 2 28.6 52.2 40.40 16.71 1.1 2.1 1.64 0.69 2.4 2.4 2.43 0.03 306 4

21 16.8 72.2 44.14 20.20 0.1 2.9 1.45 0.77 0.3 6.5 2.27 1.65 295 31

Calves 1 19.6 19.6 19.55 - 1.0 1.0 0.98 - 3.0 3.0 3.00 - 341 -

Subadults 5 16.1 37.7 27.93 9.96 0.2 2.4 1.17 1.05 0.8 7.7 2.78 3.00 303 24

Adults 22 15.2 59.1 31.87 13.49 0.1 1.8 0.79 0.56 0.4 3.5 1.41 0.76 298 48

Mothers 4 15.1 34.0 23.35 8.11 0.2 1.8 0.88 0.71 0.5 3.2 2.17 1.23 293 14

31 15.1 59.1 30.13 12.50 0.1 2.4 0.86 0.66 0.4 7.7 1.73 1.43 310 52

Calves 2 16.4 48.9 32.68 22.97 1.3 2.0 1.65 0.55 2.5 4.6 3.56 1.49 66 79

Subadults 2 50.5 293.5 171.98 171.85 0.2 1.0 0.59 0.55 0.2 0.2 0.22 0.02 180 77

Adults 1 22.6 22.6 22.63 - 2.1 2.1 2.08 - 5.5 5.5 5.51 - 309 -

Mothers 2 27.1 48.9 38.01 15.43 2.0 2.1 2.06 0.02 2.5 4.6 3.55 1.47 64 79

All Non-Calves 5 22.6 293.5 88.52 115.27 0.2 2.1 1.48 0.86 0.2 5.5 2.61 2.44 169 74

Calves 14 16.4 54.5 31.95 11.97 0.9 3.7 1.86 1.03 1.1 7.3 3.67 1.74 69 75

Subadults 61 15.0 293.5 43.98 46.60 0.2 9.2 1.71 1.42 0.2 7.7 2.84 1.89 13 73

Adults 44 15.2 98.8 37.90 18.45 0.1 4.3 1.55 1.17 0.2 7.2 2.52 1.87 299 61

Mothers 16 15.1 52.2 28.82 10.48 0.2 3.9 1.84 1.13 0.5 7.9 3.83 2.13 56 75

All Non-Calves 122 a 15.0 293.5 39.61 35.22 0.1 9.2 1.65 1.29 0.2 7.9 2.84 1.94 328 72

a Includes one whale that was not measured and whose status could not be determined.

Apparent

Speed (km/h)

Net Direction

of Movement

(Degrees True)

All Non-Calves

2000

Time Between

Resightings (min)

1984-2000 

1984

Net Distance

Traveled (km)

1999

1985

1986

1998

All Non-Calves

All Non-Calves

All Non-Calves
11-36 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

APPENDIX 11.4B. Net rates of movement in nominal westward migratory direction (288o True) determined

from within-day resightings (>15 min) of bowhead whales in the "eastern Alaskan" Beaufort Sea

(including Yukon west of Herschel Isl.), late summer and autumn 1984-2000.

Time Between

Resightings (min)

Angular

n Min Max Mean s.d. Min Max Mean s.d. Min Max Mean s.d. Mean Dev.

Subadults 1 38.7 38.7 38.67 - -1.3 -1.3 -1.28 - -2.0 -2.0 -1.99 - 41 -

Calves 2 27.8 45.8 27.83 12.72 -0.9 1.6 0.38 1.79 -1.9 2.2 0.12 2.88 164 77

Subadults 22 23.0 264.6 44.47 50.52 -9.1 3.9 -0.73 2.58 -4.6 7.0 -0.58 3.41 72 63

Adults 7 24.9 56.1 37.99 11.59 -3.1 2.1 -1.21 1.68 -4.6 5.0 -1.60 3.12 141 73

Mothers 1 28.5 28.5 28.50 - -1.4 -1.4 -1.35 - -2.8 -2.8 -2.85 - 106 -

 All Non-Calves 30 23.0 264.6 42.42 43.48 -9.1 3.9 -0.86 2.33 -4.6 7.0 -0.89 3.28 94 63

Calves 7 16.9 54.5 31.48 12.61 -3.7 3.7 -0.82 2.42 -6.5 7.3 -1.39 4.51 119 75

Subadults 19 15.0 87.2 34.00 17.32 -3.5 2.5 -0.03 1.31 -3.7 3.5 0.14 1.92 50 73

Adults 7 25.2 98.8 52.63 28.03 -3.0 2.6 0.55 2.09 -1.8 5.2 1.87 2.89 343 72

Mothers 7 17.6 35.9 26.06 7.33 -3.7 3.7 -0.77 2.46 -6.5 7.3 -1.56 4.63 120 75

 All Non-Calves 34 a 15.0 98.8 35.79 20.14 -3.7 3.7 -0.05 1.74 -6.5 7.3 0.17 2.95 50 75

Calves 2 32.3 36.1 34.19 2.68 1.2 1.5 1.39 0.22 2.1 2.9 2.46 0.58 302 18

Subadults 12 16.8 72.2 44.70 22.12 -0.9 1.8 0.89 0.77 -1.3 6.4 1.55 1.91 289 36

Adults 7 17.6 68.9 44.25 20.27 0.1 2.7 1.61 0.94 0.3 6.1 2.42 1.88 301 25

Mothers 2 28.6 52.2 40.40 16.71 1.1 2.1 1.57 0.71 2.2 2.4 2.31 0.11 306 4

 All Non-Calves 21 16.8 72.2 44.14 20.20 -0.9 2.7 1.20 0.87 -1.3 6.4 1.92 1.81 295 31

Calves 1 19.6 19.6 19.55 - 0.6 0.6 0.59 - 1.8 1.8 1.80 - 341 -

Subadults 5 16.1 37.7 27.93 9.96 -1.1 0.5 0.04 0.69 -3.6 0.9 -0.29 1.91 303 24

Adults 22 15.2 59.1 31.87 13.49 -0.7 1.7 0.57 0.70 -1.8 3.4 0.86 1.14 298 48

Mothers 4 15.1 34.0 23.35 8.11 -0.5 1.7 0.49 0.91 -1.9 3.0 0.83 2.09 293 14

 All Non-Calves 31 15.1 59.1 30.13 12.50 -1.1 1.7 0.48 0.72 -3.6 3.4 0.67 1.42 310 52

Calves 2 16.4 48.9 32.68 22.97 -1.2 0.4 -0.38 1.17 -4.4 0.6 -1.92 3.50 66 79

Subadults 2 50.5 293.5 171.98 171.85 -0.1 0.0 -0.05 0.10 -0.1 0.0 -0.07 0.10 180 77

Adults 1 22.6 22.6 22.63 - 1.9 1.9 1.94 - 5.2 5.2 5.15 - 309 -

Mothers 2 27.1 48.9 38.01 15.43 -2.0 0.4 -0.78 1.74 -4.4 0.6 -1.95 3.53 64 79

 All Non-Calves 5 16.4 293.5 88.52 115.27 -2.0 1.9 0.06 1.42 -4.4 5.2 0.22 3.41 169 74

Calves 14 16.4 54.5 31.95 11.97 -3.7 3.7 -0.17 1.94 -6.5 7.3 -0.47 3.68 69 75

Subadults 61 15.0 293.5 43.98 46.60 -9.1 3.9 -0.12 1.83 -4.6 7.0 0.08 2.60 13 73

Adults 44 15.2 98.8 37.90 18.45 -3.1 2.7 0.48 1.45 -4.6 6.1 0.97 2.37 299 61

Mothers 16 15.1 52.2 28.82 10.48 -3.7 3.7 -0.20 1.91 -6.5 7.3 -0.61 3.60 56 75

 All Non-Calves 122 a 15.0 293.5 39.61 35.22 -9.1 3.9 0.09 1.72 -6.5 7.3 0.32 2.70 328 72

a Includes one whale that was not measured and whose status could not be determined.

Net Direction

of Movement

2000

1984-2000 

Traveled (km) Speed (km/h) (Degrees True)

Net Distance Apparent

1999

1984

1985

1986

1998
§11. Bowheads: Rates of Movement & Residence Times 11-37

APPENDIX 11.5. Rates and directions of movement determined from within-day resightings (>15 min) of

bowhead whales in the Canadian Beaufort Sea (east of Herschel Isl.) and Amundsen Gulf, late summer

and autumn 1982-1985.

 Angular

n Min Max Mean s.d. Min Max Mean s.d. Min Max Mean s.d. Mean Dev.

Calves 2 25.4 33.8 29.60 5.99 1.0 1.8 1.40 0.60 1.7 4.3 3.03 1.83 337 72

Subadults 3 30.7 33.3 32.29 1.41 1.1 2.3 1.56 0.62 2.0 4.4 2.93 1.31 6 24

Adults 9 33.5 49.9 37.78 5.30 0.4 3.7 1.52 1.02 0.8 4.4 2.36 1.35 281 52

Mothers 0 - - - - - - - - - - - - - - 

12 30.7 49.9 36.41 5.19 0.4 3.7 1.53 0.91 0.8 4.4 2.50 1.30 308 56

Calves 0 - - - - - - - - - - - - - - 

Subadults 10 18.7 54.8 28.97 10.12 0.6 2.1 1.38 0.58 1 5.3 3.14 1.57 16 72

Adults 28 19.5 85.9 35.71 15.77 0.4 3.9 1.76 1.04 0.9 7.1 3.09 1.86 84 60

Mothers 0 - - - - - - - - - - - - - - 

38 18.7 85.9 33.94 14.68 0.4 3.9 1.66 0.95 0.9 7.1 3.11 1.77 75 65

Calves 0 - - - - - - - - - - - - - - 

Subadults 9 18.9 126.5 65.85 34.87 0.8 3.9 2.57 1.18 0.8 5.1 2.77 1.58 118 68

Adults 14 24.1 193.9 80.17 54.39 0.4 9.0 2.00 2.18 0.3 3.6 1.74 1.15 99 51

Mothers 2 88.3 137.1 112.70 34.53 0.6 1.5 1.07 0.62 0.4 0.7 0.55 0.16 132 6

25 18.9 193.9 77.62 47.07 0.4 9.0 2.13 1.80 0.3 5.1 2.02 1.41 108 57

Calves 1 32.4 32.4 32.42 - 1.0 1.0 0.96 - 1.8 1.8 1.78 - 235 - 

Subadults 30 15.8 110.4 36.26 19.01 0.2 4.1 1.55 0.83 0.5 6.8 3.03 1.95 280 72

Adults 1 77.0 77.0 76.97 - 3.8 3.8 3.80 - 3.0 3.0 2.96 - 22 - 

Mothers 1 32.4 32.4 32.42 1.0 1.0 0.96 - 1.8 1.8 1.78 - 235 - 

32 15.8 110.4 37.41 19.77 0.2 4.1 1.55 0.83 0.5 6.8 2.99 1.90 283 72

Calves 0 - - - - - - - - - - - - - - 

Subadults 65 16.0 321.2 71.63 61.85 0.4 8.2 2.48 1.85 0.4 8.8 2.79 1.91 305 75

Adults 1 31.2 3.1 31.17 - 2.7 2.7 2.65 - 5.1 5.1 5.11 - 295 - 

Mothers 0 - - - - - - - - - - - - - - 

67 a 15.5 321.2 70.19 61.48 0.4 8.2 2.45 1.83 0.4 8.8 2.83 1.91 310 74

Calves 3 25.4 33.8 30.54 4.53 1.0 1.8 1.25 0.50 1.7 4.3 2.61 1.48 256 66

Subadults 117 15.8 321.2 57.46 51.12 0.2 8.2 2.13 1.55 0.4 8.8 2.88 1.84 313 76

Adults 53 19.5 193.9 48.50 35.67 0.4 9.0 1.84 1.42 0.3 7.1 2.65 1.69 81 68

Mothers 3 32.4 137.1 85.94 52.39 0.6 1.5 1.04 0.45 0.4 1.8 0.96 0.72 160 46

174 a 15.5 321.2 59.98 47.00 0.2 9.0 2.02 1.51 0.3 8.8 2.78 1.79 25 78

a Includes one whale that was not measured and whose status could not be determined.

Apparent

Speed (km/h)

Net Direction

of Movement

(Degrees True)

Net Distance

Traveled (km)

 1982-1985 

 1982 Yukon East

 1984 Amundsen Gulf

 1985 Amundsen Gulf

All Non-Calves

All Non-Calves

All Non-Calves

All Non-Calves

All Non-Calves

All Non-Calves

Time Between

Resightings (min)

 1984 Yukon East

 1985 Yukon East
11-38 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

APPENDIX 11.6A. Net speeds during surface-dive sequences of undisturbed whales in the "eastern

Alaskan" Beaufort Sea in each of the five study years (1985, 1986, 1998, 1999, 2000). Numbers in

parentheses indicate the number of individual whales observed. Based on observations from a twin

engine aircraft at altitude ≥460 m.

Year

Status mean s.d. n mean s.d. n mean s.d. n mean s.d. n

Calves 1.03 0.20 4(2) 0.25 0.00 4(2) 15.04 2.89 4(2) 1.64 1.42 4(2)

Subadults 1.36 0.64 3(2) 0.33 0.14 3(2) 16.82 8.54 3(2) 1.88 0.07 2(1)

Adults 0.86 0.50 4(2) 0.35 0.25 4(2) 24.27 4.77 4(2) 2.44 0.31 3(2)

Mothers 0.82 0.50 5(3) 0.20 0.11 5(3) 12.40 6.43 5(3) 2.20 1.01 5(3)

Unknown 1.77 1.14 6(5) 0.27 0.26 6(5) 21.17 17.28 3(2) 0.66 0.46 2(2)

1.24 0.85 18(12) 0.28 0.20 18(12) 18.20 9.73 15(9) 1.95 0.90 12(8)

Calves 2.86 1.89 5(3) 0.45 0.36 5(3) 8.79 3.88 3(2) 0.18 0.13 3(2)

Subadults 1.90 0.17 2(2) 0.15 0.15 2(2) 8.92 0.00 1(1) 1.17 0.00 1(1)

Adults 4.21 1.59 8(3) 1.23 0.51 8(3) 18.43 4.74 8(3) 2.62 1.10 7(2)

Mothers 2.87 1.43 3(2) 0.57 0.40 3(2) 12.20 6.95 3(2) 1.58 1.14 3(2)

Unknown 4.28 2.30 17(6) 1.35 1.23 17(6) 18.64 9.42 14(4) 1.51 0.22 13(5)

3.96 2.04 30(13) 1.16 1.02 30(13) 17.46 7.98 26(10) 1.83 0.85 24(10)

Calves 4.06 1.02 17(4) 0.62 0.18 17(4) 8.36 3.66 8(4) 1.67 1.18 12(4)

Subadults 3.31 1.49 11(4) 0.64 0.52 11(4) 10.27 7.10 8(3) 1.38 0.39 9(4)

Adults 4.95 0.69 5(2) 0.95 0.40 5(2) 11.23 3.67 5(2) 1.76 0.27 5(2)

Mothers 4.05 1.02 19(4) 0.81 0.30 19(4) 13.11 4.64 11(4) 2.77 0.63 16(4)

Unknown 4.27 1.40 2(2) 0.81 0.56 2(2) 7.58 0.00 1(1) 1.65 0.00 1(1)

3.97 1.23 37(12) 0.78 0.40 37(12) 11.60 5.32 25(10) 2.17 0.82 31(11)

Calves 1.73 1.79 4(3) 0.20 0.21 4(3) 7.32 0.00 1(1) 0.68 0.05 2(2)

Subadults 0.86 1.22 2(2) 0.28 0.39 2(2) 1.90 0.00 1(1) 0.33 0.00 1(1)

Adults 1.43 0.72 7(4) 0.35 0.24 7(4) 13.96 2.81 7(4) 2.11 0.89 7(4)

Mothers 1.83 0.57 2(1) 0.33 0.28 2(1) 21.37 0.00 1(1) 1.45 0.03 2(1)

Unknown 2.57 2.19 16(9) 0.65 0.53 16(9) 15.88 2.16 13(7) 2.42 0.43 12(6)

2.09 1.83 27(16) 0.52 0.46 27(16) 14.88 3.98 22(13) 2.14 0.76 22(12)

Calves 3.12 0.73 7(2) 0.38 0.17 7(2) 6.37 3.77 7(2) 1.01 0.58 6(2)

Subadults 4.59 0.68 14(4) 0.41 0.34 14(4) 5.07 5.16 14(4) 0.59 0.52 13(4)

Adults 3.38 1.93 11(3) 0.64 0.43 11(3) 9.12 4.64 11(3) 1.20 0.63 11(3)

Mothers 2.43 1.53 9(2) 0.51 0.65 9(2) 8.73 9.58 9(2) 1.45 0.97 9(2)

Unknown 2.93 2.17 3(2) 1.35 0.99 3(2) 26.54 1.81 3(2) 1.34 0.31 3(2)

3.57 1.66 37(11) 0.58 0.55 37(11) 8.90 8.24 37(11) 1.05 0.75 36(11)

ALL Non-Calves 3.20 1.88 149 0.70 0.66 149 13.39 8.04 125 1.76 0.92 125

a

Net Speed During Net Distance Duration of Duration of

Dive (km/h) Traveled (km) Dive (min) a Surfacing (min) a

1985

1986

1998

1999

2000

Durations of dives and surfacings listed here are those for the subsample where net speed was determined. See Chapters

13 and 14 for data from all whales observed.

All Non-Calves

All Non-Calves

All Non-Calves

All Non-Calves

All Non-Calves
§11. Bowheads: Rates of Movement & Residence Times 11-39

APPENDIX 11.6B. Net speeds in nominal westward migratory direction (288o T) during surface-dive sequences of undisturbed whales in the "eastern Alaskan" Beaufort Sea in each of the five study years

(1985, 1986, 1998, 1999, 2000). Numbers in parentheses indicate the number of individual whales

observed. Based on observations from a twin engine aircraft at altitude ≥460 m.

Year

Status mean s.d. n mean s.d. n mean s.d. n mean s.d. n

Calves -0.80 - 1(1) -0.24 - 1(1) 15.04 2.89 4(2) 1.64 1.42 4(2)

Subadults 1.89 - 1(1) 0.23 - 1(1) 16.82 8.54 3(2) 1.88 0.07 2(1)

Adults - - 0(0) 0.35 0.25 0(0) 24.27 4.77 4(2) 2.44 0.31 3(2)

Mothers -0.42 0.59 2(2) -0.12 0.18 2(2) 12.40 6.43 5(3) 2.20 1.01 5(3)

Unknown 1.77 - 1(1) 0.27 0.26 1(1) 21.17 17.28 3(2) 0.66 0.46 2(2)

0.26 1.16 4(4) 0.00 0.20 4(4) 18.20 9.73 15(9) 1.95 0.90 12(8)

Calves -2.11 - 1(1) -0.42 - 1(1) 8.79 3.88 3(2) 0.18 0.13 3(2)

Subadults -0.49 2.03 2(2) -0.11 0.18 2(2) 8.92 0.00 1(1) 1.17 0.00 1(1)

Adults 4.17 1.59 8(3) 1.22 0.51 8(3) 18.43 4.74 8(3) 2.62 1.10 7(2)

Mothers -1.55 - 1(1) -0.48 - 1(1) 12.20 6.95 3(2) 1.58 1.14 3(2)

Unknown 2.23 2.70 9(4) 0.62 0.71 9(4) 18.64 9.42 14(4) 1.51 0.22 13(5)

2.54 2.69 20(10) 0.73 0.75 20(10) 17.46 7.98 26(10) 1.83 0.85 24(10)

Calves 2.40 2.19 17(4) 0.35 0.33 17(4) 8.36 3.66 8(4) 1.67 1.18 12(4)

Subadults -0.83 2.76 11(4) -0.03 0.58 11(4) 10.27 7.10 8(3) 1.38 0.39 9(4)

Adults 3.38 1.25 5(2) 0.66 0.41 5(2) 11.23 3.67 5(2) 1.76 0.27 5(2)

Mothers 2.23 2.36 19(4) 0.42 0.51 19(4) 13.11 4.64 11(4) 2.77 0.63 16(4)

Unknown 3.22 2.81 2(2) 0.68 0.74 2(2) 7.58 0.00 1(1) 1.65 0.00 1(1)

1.53 2.81 37(12) 0.34 0.57 37(12) 11.60 5.32 25(10) 2.17 0.82 31(11)

Calves 0.70 0.93 3(2) 0.06 0.05 3(2) 7.32 0.00 1(1) 0.68 0.05 2(2)

Subadults 0.53 0.75 2(2) 0.17 0.24 2(2) 1.90 0.00 1(1) 0.33 0.00 1(1)

Adults -0.43 1.16 7(4) -0.09 0.28 7(4) 13.96 2.81 7(4) 2.11 0.89 7(4)

Mothers 0.90 1.21 2(1) 0.06 0.06 2(1) 21.37 0.00 1(1) 1.45 0.03 2(1)

Unknown 2.03 2.20 16(9) 0.50 0.54 16(9) 15.88 2.16 13(7) 2.42 0.43 12(6)

1.20 2.09 27(16) 0.29 0.51 27(16) 14.88 3.98 22(13) 2.14 0.76 22(12)

Calves 1.06 2.78 7(2) 0.03 0.35 7(2) 6.37 3.77 7(2) 1.01 0.58 6(2)

Subadults 4.32 0.87 14(4) 0.39 0.34 14(4) 5.07 5.16 14(4) 0.59 0.52 13(4)

Adults 3.11 1.79 11(3) 0.60 0.41 11(3) 9.12 4.64 11(3) 1.20 0.63 11(3)

Mothers 0.52 2.32 9(2) -0.10 0.56 9(2) 8.73 9.58 9(2) 1.45 0.97 9(2)

Unknown 2.77 2.29 3(2) 1.27 1.05 3(2) 26.54 1.81 3(2) 1.34 0.31 3(2)

2.91 2.21 37(11) 0.40 0.60 37(11) 8.90 8.24 37(11) 1.05 0.75 36(11)

ALL Non-Calves 1.99 2.52 125 0.40 0.60 125 13.39 8.04 125 1.76 0.92 125

a Durations of dives and surfacings listed here are those for the subsample where net speed was determined. See Chapters

13 and 14 for data from all whales observed.

1985

1986

1998

1999

 All Non-Calves

 All Non-Calves

 All Non-Calves

 All Non-Calves

 All Non-Calves

2000

Duration of

Dive (km/h) Traveled (km) Dive (min) a Surfacing (min) a

Net Speed During Net Distance Duration of
11-40 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

APPENDIX 11.7A. Net speeds during surface-dive sequences of undisturbed whales engaged in various

activities in the "eastern Alaskan" Beaufort Sea (including Yukon west of Herschel Isl.) during September

(1985-86, 1998-2000). Numbers in parentheses indicate the number of individual whales observed.

Based on observations from a twin engine aircraft at altitude ≥460 m.

Whale Activity

Status mean s.d. n mean s.d. n mean s.d. n mean s.d. n

Feed

Calves 1.22 0.82 6(3) 0.29 0.19 6(3) 10.93 1.58 2(2) 0.91 0.93 3(3)

Subadults 2.45 1.53 13(7) 0.39 0.22 13(7) 11.24 6.13 9(4) 1.51 0.41 10(5)

Adults 1.18 0.51 9(5) 0.32 0.16 9(5) 16.12 4.98 9(5) 1.90 0.24 8(4)

Mothers 1.23 0.32 4(2) 0.31 0.13 4(2) 15.15 3.20 4(2) 1.81 0.63 4(2)

Unknown 0.87 0.71 11(6) 0.20 0.17 11(6) 17.19 2.37 6(3) 1.96 0.50 8(5)

 All Non-Calves 1.54 1.21 37(20) 0.31 0.19 37(20) 14.64 5.17 28(14) 1.77 0.45 30(16)

Travel

Calves 3.93 1.02 21(6) 0.58 0.19 21(6) 7.81 3.54 13(6) 1.40 1.10 16(6)

Subadults 4.42 0.93 15(5) 0.40 0.33 15(5) 5.22 5.00 15(5) 0.59 0.52 13(4)

Adults 4.55 1.03 20(6) 1.02 0.45 20(6) 13.14 4.90 20(6) 1.80 0.98 20(6)

Mothers 4.00 0.92 17(4) 0.82 0.44 17(4) 12.41 7.80 10(4) 2.43 0.96 14(4)

Unknown 4.94 1.64 20(8) 1.53 1.06 20(8) 18.99 9.12 17(5) 1.68 0.55 15(5)

 All Non-Calves 4.50 1.22 72(23) 0.99 0.76 72(23) 12.71 8.30 62(20) 1.66 1.00 62(19)

Travel+Feed

Calves 1.45 1.10 2(1) 0.15 0.02 2(1) - - - - - -

Subadults 3.03 2.03 4(2) 0.90 0.86 4(2) 11.63 13.72 3(2) 0.88 0.47 3(2)

Adults - - - - - - - - - - - -

Mothers 3.28 1.36 9(3) 0.70 0.36 9(3) 15.56 5.08 7(3) 2.29 0.78 9(3)

Unknown 3.53 1.76 6(4) 0.92 0.43 6(4) 15.31 0.44 5(3) 2.55 0.35 4(2)

 All Non-Calves 3.31 1.55 19(9) 0.81 0.49 19(9) 14.69 6.37 15(8) 2.09 0.87 16(7)

Other/Unknown

Calves 2.79 1.84 6(4) 0.31 0.34 6(4) 7.93 6.29 5(3) 1.32 1.51 5(3)

Subadults - - - - - - - - - - - -

Adults 1.25 1.44 6(3) 0.38 0.383 6(3) 15.15 11.86 6(3) 2.25 1.36 5(3)

Mothers 1.60 1.64 8(4) 0.23 0.33 8(4) 6.14 6.24 8(4) 1.78 1.30 8(4)

Unknown 1.73 1.13 7(6) 0.35 0.202 7(6) 19.27 12.71 6(5) 1.14 0.62 4(4)

 All Non-Calves 1.54 1.37 21(13) 0.31 0.30 21(13) 12.78 11.29 20(12) 1.77 1.20 17(11)

ALL Non-Calves 3.20 1.88 149 0.70 0.66 149 13.39 8.04 125 1.76 0.92 125

a Durations of dives and surfacings listed here are those for the subsample where net speed was determined. See Chapters

13 and 14 for data from all whales observed.

Dive (km/h) Traveled (km) Dive (min) a Surfacing (min) a

Net Speed During Net Distance Duration of Duration of
§11. Bowheads: Rates of Movement & Residence Times 11-41

APPENDIX 11.7B. Net speeds in a nominal westward migratory direction (288o T) during surface-dive

sequences of undisturbed whales engaged in various activities in the "eastern Alaskan" Beaufort Sea

(including Yukon west of Herschel Isl.) during September (1985-86, 1998-2000). Numbers in

parentheses indicate the number of individual whales observed. Based on observations from a twin

engine aircraft at altitude ≥460 m.

Whale Activity

Status mean s.d. n mean s.d. n mean s.d. n mean s.d. n

Feed

Calves -0.96 1.18 4(3) -0.18 0.22 4(3) 10.93 1.58 2(2) 0.91 0.93 3(3)

Subadults -1.47 2.06 11(6) -0.20 0.31 11(6) 11.24 6.13 9(4) 1.51 0.41 10(5)

Adults -0.36 1.25 7(4) -0.05 0.35 7(4) 16.12 4.98 9(5) 1.90 0.24 8(4)

Mothers -1.55 - 1(1) -0.48 - 1(1) 15.15 3.20 4(2) 1.81 0.63 4(2)

Unknown -0.10 0.74 11(6) -0.02 0.16 11(6) 17.19 2.37 6(3) 1.96 0.50 8(5)

-0.71 1.55 30(17) -0.11 0.28 30(17) 14.64 5.17 28(14) 1.77 0.45 30(16)

Travel

Calves 2.28 2.42 20(6) 0.31 0.37 20(6) 7.81 3.54 13(6) 1.40 1.10 16(6)

Subadults 4.16 1.05 15(5) 0.38 0.33 15(5) 5.22 5.00 15(5) 0.59 0.52 13(4)

Adults 4.04 1.13 20(6) 0.93 0.48 20(6) 13.14 4.90 20(6) 1.80 0.98 20(6)

Mothers 1.10 2.66 17(4) 0.11 0.75 17(4) 12.41 7.80 10(4) 2.43 0.96 14(4)

Unknown 4.14 1.65 12(6) 4.14 1.65 12(6) 18.99 9.12 17(5) 1.68 0.55 15(5)

3.67 1.74 64(21) 0.71 0.59 64(21) 12.71 8.30 62(20) 1.66 1.00 62(19)

Travel+Feed

Calves 1.06 0.99 2(1) 0.09 0.01 2(1) - - - - - -

Subadults 1.78 1.86 4(2) 0.49 0.63 4(2) 11.63 13.72 3(2) 0.88 0.47 3(2)

Adults - - - - - - - - - - - -

Mothers 0.48 2.47 9(3) 0.05 0.47 9(3) 15.56 5.08 7(3) 2.29 0.78 9(3)

Unknown 3.35 1.14 5(3) 0.86 0.31 5(3) 15.31 0.44 5(3) 2.55 0.35 4(2)

1.57 2.32 18(8) 0.37 0.57 18(8) 14.69 6.37 15(8) 2.09 0.87 16(7)

Other/Unknown

Calves 1.18 1.81 3(2) 0.02 0.22 3(2) 7.93 6.29 5(3) 1.32 1.508 5(3)

Subadults - - - - - - - - - - - -

Adults 0.76 1.08 4(2) 0.18 0.23 4(2) 15.15 11.86 6(3) 2.25 1.36 5(3)

Mothers 0.35 0.92 6(3) 0.00 0.14 6(3) 6.14 6.24 8(4) 1.78 1.30 8(4)

Unknown 0.67 0.55 3(3) 0.13 0.06 3(3) 19.27 12.71 6(5) 1.14 0.62 4(4)

0.55 0.86 13(8) 0.09 0.17 13(8) 12.78 11.29 20(12) 1.77 1.20 17(11)

ALL Non-Calves 1.99 2.521 125 0.40 0.60 125 13.39 8.04 125 1.76 0.92 125

a

Net Speed During Net Distance Duration of Duration of

Dive (km/h) Traveled (km) Dive (min) a Surfacing (min) a

Durations of dives and surfacings listed here are those for the subsample where net speed was determined. See Chapters

13 and 14 for data from all whales observed.

All Non-Calves

All Non-Calves

All Non-Calves

All Non-Calves
12. ACTIVITIES AND BEHAVIOR OF BOWHEAD WHALES IN THE EASTERN

ALASKAN BEAUFORT SEA DURING LATE SUMMER AND AUTUMN

Bernd W ̧rsig1, William R. Koski2, Tannis A. Thomas2, and W. John Richardson2

Introduction

Bowhead whales (Balaena mysticetus) of the BeringñChukchiñBeaufort (BCB) stock migrate into

the Beaufort Sea and Amundsen Gulf in spring; reside there from May or June to August, September or

even October, depending on the individual; and migrate back to the west in late AugustñOctober (Moore

and Reeves 1993). The eastward spring migration tends to be through leads well offshore from the

Alaskan North Slope (Braham et al. 1980; Moore and Reeves 1993). However, much of the late summerñ

autumn migration is through waters <200 m deep closer to shore (Mate et al. 2000; Moore 2000; Moore et

al. 2000; Treacy 2000, 2002; see also Chapter 9). Summer activities include feeding, socializing, traveling within the summer range, resting, and various aerial behaviors (W ̧rsig et al. 1985, 1989). During the

westward migration in late summerñautumn, bowhead whales continue to engage in a variety of activities

including not only active travel, but also feeding, socializing, resting, etc. During this westward migration, numerous bowheads travel close to the Inupiat village of Kaktovik, the easternmost Alaskan village

on the North Slope. The majority of the bowheads harvested by Kaktovik hunters have food in their

stomachs, indicative of recent feeding; copepods are the predominant food items in this area, with lesser

proportions of euphausiids, amphipods, and mysids (Lowry 1993; see also Chapter 18).

The activities and behavior of bowhead whales of the BCB stock have received considerable attention in the past 20 years (summaries in W ̧rsig and Clark 1993; Richardson et al. 1995a). These studies

of bowhead behavior have concentrated on the summering grounds in the Canadian Beaufort Sea, and

spring migration around Alaska. Here we provide corresponding details on the activities of bowheads in

and near the eastern Alaskan Beaufort Sea during the late summerñearly autumn period (mainly

September), including the specific behaviors of whales engaged in the main activities. This information

was needed as one part of a broader assessment of the importance of the eastern Alaskan Beaufort Sea to

bowhead whales. This account is based on systematic behavioral studies during September of five

years―1985, 1986, 1998, 1999, and 2000. The study area consisted of the eastern Alaskan Beaufort Sea

and adjacent Canadian waters east to Herschel Island (Fig. 12.1).

In this chapter we distinguish between activities and behaviors. Activities are combinations of

behaviors that have a common purpose or function such as feeding, traveling, resting, or socializing.

Some specific behaviors are most commonly seen during one particular activity, e.g., mouth opening is

most often associated with feeding. Other behaviors such as surfacing, diving, and turning are seen during most or all activities. However, the durations or frequencies of these behaviors often change depending on the activity of the whale.

 

1

 Texas A&M University at Galveston, Marine Mammal Research Program, 4700 Ave. U., Bldg 303,

Galveston, TX 77551-5923. Phone: 409-740-4413; e-mail: wursigb@tamug.tamu.edu

2

 LGL Ltd., environmental research associates, 22 Fisher St., POB 280, King City, Ont. L7B 1A6.

Phone: 905-833-1244; e-mail: bkoski@lgl.com
12-2 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

FIGURE 12.1. Locations in and near the eastern Alaskan Beaufort Sea where activities and behavior of

bowhead whales were observed systematically during late summer and autumn, by year (1985–86,

1998–2000). Behavioral observation sessions (BOSs) including one or more mother–calf pairs are

circled. Based on observations from a twin-engine aircraft circling at altitude ≥460 m; excludes periods

with other types of potential disturbance.

Bowhead whales, like other cetaceans, spend far less than 50% of their time in view of observers at

or above the waterís surface (Richardson et al. 1995a). In most studies of cetacean behavior, it has not

been possible to apply radio tags or other instruments. Instead, we attempt to ascertain their general

activities and associated specific behaviors from the relatively short glimpses afforded to us while whales

surface to breathe or are engaged in other surface behaviors. This means that sub-surface activities, such

as presumed water column or bottom feeding, or calves nursing from their mothers, can only be surmised

from what the animals do while they are at or near the surface, and from changes in location from one

surfacing to the next. Nevertheless, we believe that our glimpses of activities at or near the surface provide generally good indications of major activities while whales are below the surface and out of sight. In

this chapter we describe these activities and associated behaviors as they occur in and near the eastern

Alaskan Beaufort Sea in September. Many of the activities and behaviors in this area and season are

similar to those previously described for summer (W ̧rsig et al. 1985, 1989; W ̧rsig and Clark 1993;

Richardson et al. 1995a). In these cases, our descriptions are brief. However, the frequencies of

occurrence of various activities and behaviors in the present study area, mainly in September, differ from

those previously reported from the Canadian summer range, mainly in August. Some of these differences

may be important in assessing the importance of the present study area to bowhead whales.

The major objectives of this chapter are (1) to describe the general activities of bowhead whales

while they are off northeastern Alaska in late summer and early autumn, (2) to document the specific

behaviors associated with these activities, and (3) to determine the proportion of time engaged in each

activity (time budget). We compare our data to previously reported data on activities, behaviors, and time

budgets during spring and summer, and also demonstrate variability among years. Companion chapters
§12. Bowheads: Activities and Behavior 12-3

provide related details on seasonal distribution and numbers in the study area; habitat preferences; rates of

movement and residence times; surfacing, respiration and dive cycles; food availability; and diet. The

concluding chapters use all of these types of data, along with an energetic model, to assess the importance

of the present study areas for feeding by bowhead whales. An ultimate goal, not to be realized here, is to

know enough about bowhead whale behavior and ecology through the year to predict feeding and social

needs for different phases of their annual migratory cycle.

Methods

Behavioral observations were carried out from a circling DHC-6-300 Twin Otter aircraft in 1985ñ

86 and a Twin Commander 680FL aircraft in 1998ñ2000.

Data Sources

Behavior of undisturbed whales was observed systematically during five years, almost exclusively

in the month of September, with the exception of 2 days in early October 1986. The data were obtained

during MMS-sponsored studies of bowhead feeding ecology in 1985ñ86 (Richardson et al. 1987b) and

1998ñ2000 (present study), and during a separate 1986 study sponsored by Shell Western Exploration &

Production (SWEPI; Koski and Johnson 1987).

A total of 84 Behavioral Observation Sessions (BOSs) were conducted while the aircraft circled

above presumably-undisturbed whales (Fig. 12.1). In 1985ñ86, BOSs lasted from tens of minutes to

3.5 h, plus one 1986 BOS that was 6.7 h long (Appendix 12.1AñC). In 1998ñ2000, BOSs tended to be

1 h or less in duration (Appendix 12.1DñF). The main reason for shorter BOSs in later years was to

increase sample size for time-budget estimates. With the shorter BOSs, we could still determine general

whale activities, obtain more BOSs per season, leave sufficient time for photogrammetry after most BOSs

(see Chapter 10), and have less variable BOS durations. The larger number of shorter and similar-length

BOSs was an advantage for statistical analysis, providing a larger number of independent samples with

less pseudoreplication. Total duration of the 84 BOSs of undisturbed whales was 91.9 h, during which

we obtained 234 observations of surfacings by mothers and calves, and 1206 records of surfacings by

other whales (Table 12.1). Appendix 12.1 lists the individual BOSs and summarizes their locations, the

numbers of whales observed, and general whale activities. Of the 84 ìundisturbedî BOSs, 69 were within

the eastern Alaskan Beaufort Sea proper, and 15 were in Canadian waters (Fig. 12.1; Appendix 12.1A-F).

Aerial Observations

We used the aerial observation procedures of W ̧rsig et al. (1985), Richardson et al. (1985, 1995a),

and Thomas et al. (Chapter 13) to describe activities and behaviors of bowhead whales. Three to four

observers (rarely, 5) in either a Twin Otter (1985ñ86) or Twin Commander (1998ñ2000) circled above

whales at altitude 460 m or occasionally 610 m above sea level (a.s.l.)―high enough to avoid significant

aircraft disturbance (Richardson et al. 1985; Patenaude et al. 2002). Airspeed during circling, often with

some ìflaps engagedî to slow the aircraft, was usually <100 knots (185 km/h). We attempted to remain

at a radius of 1ñ2 km from whales that we were observing. Aircraft navigation was primarily via a Very

Low Frequency (VLF) system in 1985ñ86 and Global Positioning System (GPS) in 1998ñ2000.

Throughout each observation session, two or three full-time observers on the right side of the aircraft dictated standardized behavioral observations and whale position data via the intercom into a single

audio recorder and also into the audio channel of a video recorder. Another person on the right side operated a video camera whenever whales were at the surface. In the 1985ñ86 studies, a fourth (and, rarely,
12-4 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

TABLE 12.1. Summary of number of behavioral observation sessions (BOSs), whales, and observations

of surfacings for various group activities during 1985-86 and 1998-2000. Data for mothers and calves are

shown separately from “others”. Excludes potentially disturbed whales.

Activities

Rest 1 1 3 0 0 0

Travel 17 122 2 6 25

Social 8 80 93 0 0 0

Feed 29 315 424 11 29 49

Travel+Social 5 60 89 2 6 25

Travel+Feed 10 124 142 5 10 92

Social+Feed 9 227 248 3 4 27

Travel+Social+Feed 1 8 16 1 4 9

Play 1 2 6 0 0 0

Aerial 2 4 43 0 0 0

Unknown 5 17 20 2 7 7

All activities 1206 26 (25*) 66 234

* There were 84 different undisturbed BOSs. Some BOSs have more than one activity. Numbers in

parentheses indicate the number of different BOSs.

** Some whales may not have been recognized when resighted, so "numbers of whales" likely

overestimate the number of different whales.

Whales Surfacings

48**

 88 (84*) 886**

BOSs Whales Surfacings BOSs

Number of

Others Mothers/Calves

fifth) observer helped with keeping track of whales and other ancillary tasks. The two primary observers

were seated in the co-pilotís seat and the seat behind it. The observer in the co-pilotís seat augmented

observations with hand-held 9×35 or 10×42 binoculars as needed. The part-time observer(s) were seated

behind the primary observers. During each surface/dive sequence by bowheads, observers described the

same behavioral attributes as recorded in our previous studies of bowhead behavior (e.g., W ̧rsig et al.

1984, 1985; Dorsey et al. 1989; Richardson et al. 1995a,b). These data included times when each focal

whale surfaced, blew and dove; its headings and turns; occurrence of pre-dive flexes, fluke-out dives and

aerial activities (breaches, tail and flipper slaps, etc.); and occurrence of several other behaviors as

described in the ìResultsî section. From details of individual and group behaviors, observers classified

the general activity of the focal whale(s) as feeding, traveling, socializing, aerial, play, other, or some

combination, distinguished as in previous related studies (e.g., Richardson et al. 1995a).

Special methods were needed to maintain station over whales during prolonged dives. During

1985ñ86, we dropped sandwich bags with fluorescein dye from the aircraft. The resulting dye mark on

the waterís surface was visible for 20 to 60 min, depending on wind/sea state. During observation sessions in 1998ñ2000, a portable computer with data logging software (WINGPS), connected to the aircraftís GPS, automatically recorded time and aircraft position (latitude and longitude) at 1-s intervals.

Using the output from this system, we were able to keep station above whales, and to estimate positions

of whales during the behavioral observation sessions. Frequently, we used the aircraftís successive GPS

positions to estimate the location about which the aircraft was circling, which was usually close to the
§12. Bowheads: Activities and Behavior 12-5

whale position. These times and positions could then be used to estimate the speeds of travel for whales

that were resighted within observation sessions (see Chapter 11).

Adult and subadult whales were distinguished by one of two methods. (1) For some BOSs, mainly

during the 1986 SWEPI and 1998ñ2000 studies, the photogrammetric method of Koski et al. (1992) was

applied immediately after the BOS ended. This provided specific length information for some of the

individual whales that had been recognized (from natural markings) during the preceding BOS. Whales

≥13.0 m in length were classified as adults; those <13.0 m long were classified as subadults or calves.

(2) In other cases, the behavioral observers classified some whales as obviously small or large; these were

counted as subadults or adults, with intermediate-sized or unclassified individuals being excluded from

both categories.

Data Analyses

Behavioral data were transcribed from audiotapes between flights and after the field seasons. The

videotape was then examined for details not noted during the real-time behavioral dictation. Video

recordings were especially useful for seeing missed blows and other details in 1998ñ2000, when we used

digital video tape with much higher resolution than the standard 8 mm system used in 1985ñ86. The

combined data were coded numerically as in our previous work (see Richardson and Finley 1989:25ñ28

for details). These records were hand-checked and then entered into a microcomputer (Apple II+ for most

1985ñ86 data; MS-Windows for 1998ñ2000) for computerized validation and analysis. The validation

program, as developed during prior LGL/MMS projects, was applied each year to check for impossible or

implausible combinations of variables; and necessary corrections were made. The 1985ñ86 data were

later re-formatted for consistency with the 1998ñ2000 data.

Data from the first 20 min of each undisturbed BOS were used to compute time budgets. Only the

first 20 min were considered because the lengths of BOSs were highly variable within and among years.

During 1985, 1986 and 1998, the observers often continued observations for 1ñ3 h (or more) if the whales

were feeding or traveling, but otherwise terminated observations of a given group of whales after 20ñ30

min. During 1999 and 2000, BOSs were terminated after 20ñ60 min as described above.

The proportion of time that whales spent engaged in each activity was determined for each BOS

based on the group activity or activities recorded during the first 20 min of observations. Eleven different

group activities were recognized in the three studies (Table 12.1). We excluded the unknown category

from analyses because unknown activities included some or all of the known activities. Inclusion of

ìunknownî as an 11th category would have negatively biased estimates of the percentage of time engaged

in the 10 known activities. For most BOSs, only one group activity was recorded during the first 20 min

of the BOS, in which case the percentage of time engaged in that activity during that BOS was 100%. If

there was more than one group activity during the first 20 min of a BOS, then the percentage of the BOS

assigned to each group activity was determined from the number of surfacings with each group activity

during the 20ñmin period. In this calculation, each surfacing was weighted by the mean duration of all

surfaceñdive sequences by whales engaged in that activity during the year in question. If group activities

are a → j, the proportion of time spent engaged in activity ëaí is

 (# surfacings (a)) (mean surface ñ dive duration (a))

 

 Σ [(# surfacings (a→j)) (surface ñ dive sequence (a→j))]

for each behavioral observation session.
12-6 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

To combine results from a number of BOSs, the percentage of each BOS assigned to a given activity (e.g., feeding) was added to corresponding percentages from other BOSs and divided by the number of

BOSs. This provided an estimate of the overall percentage of time engaged in a given activity for a situation of interest, e.g., year, water depth category, or whale status (subadult, adult, mother).

The 10 different group activities (after excluding unknown) were then combined into four general

group activities (feed, travel, social, and other). Group activities involving two activities ìAî and ìBî,

e.g., ìtravel+feedî, were assumed to be 50% ìAî and 50% ìBî. ìTravel+social+feedî was assumed to be

33% travel, 33% socializing, and 33% feeding. This method may slightly under- or overestimate the

occurrence of a particular activity during any one BOS. However, on average we believe it to be a fair

representation when multiple behaviors occur at the same time (see Discussion).

Detailed data on surfacing, respiration, and dive cycles during these observation sessions are presented in relation to whale activity in Chapter 13, and in relation to whale age in Chapter 14.

Results

Feeding Activities―Descriptions

Near-Surface Feeding.óDuring late summer and early autumn (mainly September), bowheads in

and near the eastern Alaskan Beaufort Sea spent an estimated 8% of their time feeding near the surface

(Table 12.2F). Near-surface feeding was seen during 4 of 5 years, the exception being 2000 when little

feeding of any type was seen (Table 12.2). Whales feeding at or near the surface were generally recognized readily, because their mouths were open as they traveled forward slowly or at medium speed, with

no or only slight white-water along their flanks. From our aerial view, the baleen plates often appeared as

a dark shadow between the rostrum and the outline of the submerged lower jaw. The baleen sometimes

was not visible, but the open mouth resulted in a higher-than-normal raised rostrum that made the head

look particularly thin above or at the surface. The lower jaw, if visible, appeared (from our high viewing

angle) to be extended forward and laterally relative to the upper jaw, well beyond its normal closedmouth position. From a surface vessel, the raised rostrum would be visible, and the back would not.

This behavior is also called skim feeding, as the whales effectively ìskimî copepods, euphausiids

or other zooplankton from the water near the surface. Skim feeding whales most often swam dorsum up.

However, W ̧rsig et al. (1985) observed that skim-feeding can also occur with whales ventrum up (ìupside-downî―not seen during this autumn study); or on their sides. This ìlateral skim feedingî results in

the tail traveling back and forth with one fluke tip generally at or above the surface. These surface fluke

swishes remind one of the top part of the caudal appendage of a surface-traveling shark. We suspect that

lateral skim feeding occurs when the prey are concentrated particularly close to the surface, in which case

upright whales could not propel themselves without the upstroke of the fluke being stopped by the surface. Whales skim feeding on their sides show much of one baleen rack, left or right, and present a

particularly impressive view with mouth agape up to an angle of ~60o

 (W ̧rsig et al. 1985).

Whales at times skim feed along or very close to a current interface line, where currents meet or

where upwelling (or, potentially, downwelling) occurs. There is often a visible ìslickî of organic

material associated with such lines, and we assume that prey may be particularly rich in these microhabitats. In one typical case of skim feeding along a line of surface debris, we observed two small subadult bowheads skim feeding on their sides 3 km N of Kaktovik on 19 Sept. 1998. We watched the

whales for 45 min as they traveled back and forth along the shoreward side of an interface between

muddy brackish inshore water and clearer offshore water. When we left the area at the end of our BOS,

the whale(s) were still skim feeding.
§12. Bowheads: Activities and Behavior 12-7

TABLE 12.2. Percentages of time spent engaged in various activities, subdivided by water depth, during

September-October of 1985-86 and 1998-2000. Shallow water is ≤20 m; deep water is >20 m. n is

number of behavior observation sessions (BOSs) having whales of each status in each depth category.

Based on first 20 min of 80 undisturbed BOSs; observations from a twin-engine aircraft at altitude

≥460 m. "Unknown" includes all whales of unknown status; “All Whales” include unknown whales, calves

excluded. Unknown activities are excluded.

Shallow Deep Shallow Deep Shallow Deep Shallow Deep Shallow Deep All Depths

A. 1985

Feed 32 16 50 0 25 14 0 40 25 14 39

col 0 13 33 0 8 11 0 31 8 11 20

sfc 32 3 17 0 16 3 0 9 16 3 19

Travel 0 5 33 0 25 6 0 19 25 6 31

Social 32 16 17 0 16 14 0 40 16 14 30

Other 0 0 0 0 0 0 0 0 0 0 0

22 20 42 02 42 6

B. 1986

Feed 42 0 58 16 45 13 0 74 45 13 58

col 29 0 29 16 31 13 0 74 31 13 44

bot 6 0 15 0 7 0 0 0 7 0 7

sfc 7 0 14 0 7 0 0 0 7 0 7

Travel 0 22 0 8 0 24 0 9 0 24 24

Social 11 13 12 6 7 8 0 14 7 8 15

Other 0 12 0 0 0 4 0 0 0 4 4

6 4 7 3 11 7 0 4 11 10 21

C. 1998

Feed 29 25 0 23 17 17 0 50 19 19 38

col 15 25 0 23 0 11 0 6 5 15 20

bot 14 0 0 0 6 0 0 0 6 0 6

sfc 0 0 0 0 11 6 0 44 8 4 12

Travel 0 15 0 35 0 23 0 50 0 24 24

Social 21 8 13 27 17 17 0 0 15 15 30

Other 0 0 0 0 0 9 0 0 0 8 8

4 5 2 7 6 12 0 4 7 14 21

D. 1999

Feed 0 72 0 66 0 68 0 85 0 66 66

col 0 68 0 63 0 64 0 79 0 62 62

sfc 0 4 0 3 0 4 0 6 0 4 4

Travel 0 27 0 25 0 23 0 14 0 24 24

Social 0 0 0 8 0 10 0 0 0 10 10

Other 0 0 0 0 0 0 0 0 0 0 0

0 12 0 11 0 20 0 8 0 21 22 21

E. 2000

Feed 0 0 0 0 7 7 0 0 5 5 9

bot 0 0 0 0 7 7 0 0 5 5 9

Travel 23 77 0 0 0 59 0 66 9 65 74

Social 0 0 0 0 7 7 0 34 5 5 9

Other 0 0 0 0 0 11 0 0 0 7 7

1 4 0 0 1 6 0 2 2 9 11

F. All

Feed 19 27 23 34 23 27 0 55 21 25 47

col 10 26 13 34 12 25 0 42 12 22 34

bot 5 0 5 0 3 1 0 0 3 1 4

sfc 4 1 5 0 7 2 0 13 6 2 8

Travel 5 30 2 21 2 24 0 30 4 27 31

Social 10 6 9 12 9 11 0 12 9 10 18

Other 0 3 0 0 0 3 0 0 0 4 4

13 27 11 21 22 47 0 20 24 56 80

n

n

n

n

n

n

Subadult Adult Unknown Mother All Whales but Calves
12-8 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

Surface skim feeding, alone or in combination with other types of feeding, was generally conducted by animals acting alone or with one other animal nearby; however, there usually were additional

animals within 1 km (see Table 12.3C,D, later). The animals were oriented in variable directions, and

seemed to pay no or little attention to each other as they criss-crossed the area. Echelon skim feeding,

when whales swim side-by-side in staggered formation with mouths open, has been described from August in the Canadian Beaufort Sea (W ̧rsig et al. 1985) and reported from Alaskan waters in fall (Ljungblad et al. 1986; Landino et al. 1994) but was not seen during this study. Echelon feeding is apparently

uncommon in the present study area, consistent with the fact that zooplankton biomass was usually low in

surface waters (Chapter 5, 6).

Near-Bottom Feeding.óBowheads spent an estimated 4% of their time near-bottom or bottom

feeding during late summer and autumn; this activity was seen in 3 of 5 years of this study (Table 12.2F).

Near-bottom feeding was assumed when whales came to the surface with mud on parts of their bodies or

with mud streaming behind them. This mud was usually on the back or rostrum (indicating that the

whales may have been moving along the bottom upside down), on the flanks, or streaming from the

mouth. Whale orientations usually changed from one surfacing to the next, and the whales tended to stay

within the same area throughout a BOS. Surfacings with mud on the body did not necessarily indicate

that the whales had been feeding at or near the bottom; some of these whales may have been engaged in

another activity. Nevertheless, we believe that the presence of mud streaming from the body or especially

the mouth was generally indicative of bottom or near-bottom feeding. Conversely, at times we may have

failed to recognize near-bottom feeding when it occurred if mud was not evident. Near-bottom feeding

could occur without mud being evident during surfacings, especially if the bottom was not mud.

At times, mud streamed from the anterior corners of the mouth in spurts or plumes (ìmudplumingî), as whales alternately opened and closed the mouth at the surface. These whales apparently

had fed at the bottom, perhaps in a manner similar to that of gray whales (Eschrichtius robustus) feeding

on epibenthic crustaceans swarming just above the bottom (Kim and Oliver 1989). The mouth action at

the surface may be to winnow the prey from pebbles or other inedible food, to work it toward the throat,

or simply to clean the mouth and baleen of mud.

Water-Column Feeding.óBowhead whales were assumed to be feeding in the water column

during 34% of our observation time during late summer and autumn (Table 12.2F). We scored bowhead

whales as feeding in the water column when they exhibited most or all of the following: (a) stayed in

generally the same area throughout a BOS, (b) were oriented in variable directions upon first surfacing,

(c) remained stationary or moved slowly while at the surface between dives, and (d) generally dove steeply, often with flukes out. Feeding in the water column could not be observed directly, as we could not see

open mouths or other ìevidenceî of feeding while whales were more than a few meters below the surface.

It was thus the least reliably determined, yet overall the most common, form of feeding in and near the

eastern Alaskan Beaufort Sea in September/early October. Presumed water-column feeding was estimated as ~4x as common as near-surface feeding and ~8x as common as bottom feeding. It included feeding

at all depths except the surface or bottom. Zooplankton often were concentrated in thin layers at midwater depths (see Chapters 5, 6), and water-column feeding was presumably concentrated at those depths.

During or after 44% of the sessions with apparent water-column feeding, whales were seen or

photographed with mouths open while they were stationary or moving only slowly at the surface. In

these cases, the whales were not feeding at the surface. We surmise that, after trapping prey in the mouth

while water-column feeding, whales at the surface with mouths open were working prey toward the throat

in order to swallow the prey. The action may be similar to that which generates ìmud-plumingî when
§12. Bowheads: Activities and Behavior 12-9

feeding gray whales come to the surface (Nerini 1984). BOSs with mouths open are marked in Appendix

12.1. Apparent water-column feeding was at times accompanied by defecations at the surface, but such

occurrences were too sporadic for defecation to be used as a reliable indicator of feeding. Nonetheless,

defecations indicate recent feeding.

Although neither bottom feeding nor water-column feeding have been observed directly in bowheads, we are confident that most cases labeled as such were identified correctly. We generally do not

include a qualifier such as ìsurmisedî, ìsuspectedî, or ìapparentî when describing any particular case of

near-bottom or water-column feeding, but the qualifier should be assumed.

Feeding Activities―Occurrence

Overall, feeding was the most common activity of bowheads in and near the eastern Alaskan

Beaufort Sea during late summer and autumn. Whales spent an estimated 47% of their time feeding in

comparison to 31% traveling, 18% socializing, and 4% engaged in other activities (Fig. 12.2, Table 12.2).

Feeding was the dominant activity in 4 of 5 years of the study. It occurred an estimated 38 to 66% of the

time in 1985ñ86 and 1998ñ99, but only 9% of the time in 2000 (Fig. 12.2).

Water depth affected the allocation of time to different activities. Feeding accounted for 62% of

the activities in shallow water (≤20 m) but only 38% in deeper water (Fig. 12.3). Conversely, traveling

accounted for only 12% of the activities in shallow areas but 41% in deeper water. For both subadults

and adults, ~1/3rd of our observations were of whales in shallow areas (Table 12.2). While there, both

subadults and adults spent most of their time feeding: 56% for subadults and 68% for adults (Fig. 12.3).

When in deep waters (>20 m), subadults spent slightly more time traveling than feeding (45% vs. 41%),

whereas adults spent more time feeding than traveling (51% vs. 31%; Fig. 12.3).

Feeding strategies varied somewhat among years, but water-column feeding was overall the predominant activity recorded during late summer and autumn (34% of all activities, Table 12.2; 74% of

feeding activities; Fig. 12.4). It was the most common type of feeding in 4 of 5 years, with the exception

being 2000―the year with little feeding (Table 12.2). Surface skim feeding was also seen in all years but

2000; it accounted for 8% of the time and 17% of the feeding time (Table 12.2; Fig. 12.4). Bottom feeding was the least common of the three recognized types of feeding (Fig. 12.4), and was not noted in 1985

or 1999 (Table 12.2). However, in 2000, the infrequent feeding that did occur was all bottom feeding.

Over all years, feeding modes were more diverse for whales feeding in shallow (≤20 m) water than for

those feeding in deeper (>20 m) water. In deeper water, almost all recognized feeding by bowheads was

recorded as water-column feeding (Fig. 12.4). In contrast, in shallow areas, water-column feeding accounted

for only slightly more than half of the feeding time; near-surface and near-bottom feeding each accounted for

~2/7th and 1/7th, respectively, of the feeding in shallow areas (Fig 12.4). Mothers and their calves were found

in the deeper areas, and the only feeding mode observed for mothers was water-column feeding.

The type of feeding activity and water depths where feeding occurred varied among years and with

age class. Both adults and subadults fed mainly in shallow waters in 1985 and 1986. In contrast, both

age classes were seen feeding only in deeper (>20 m) waters in 1999 (Table 12.2; Fig. 12.5). In 1998,

adults were only seen to feed in the deeper waters but subadults fed about equally in deep and shallow

waters. Feeding in deep water occurred in all years but was relatively rare, except in 1999 when it was

common. Feeding in deep water was predominantly feeding in the water column.

Mothers (adults accompanied by first-year calves) were rarely seen in waters ≤20 m deep during

BOSs in any of the five years (Fig. 12.1, 12.4) and also were rarely seen there during other types of obser-
12-10 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

FIGURE 12.2. Percentage of time when bowheads engaged in various activities while in or near the eastern Alaskan Beaufort Sea during late summer and autumn, by year (1985–86, 1998–2000). Based on the

first 20 min of 80 undisturbed BOSs, as described in “Methods”. Includes all bowhead whales except

calves. See Table 12.2 for more details.

FIGURE 12.3. Percentage of time when bowheads of different status engaged in various activities while in

shallow water (≤20 m) and deeper water (>20 m). Based on the first 20 minutes of 80 undisturbed BOSs,

as described in “Methods”. “All” includes unknown status whales but excludes calves. Adapted from

Table 12.2, with percentages recalculated separately by water depth.
§12. Bowheads: Activities and Behavior 12-11

FIGURE 12.4. Percentage of feeding time when bowheads of different status engaged in three types of

feeding in two water depths. Shallow water is ≤20 m; deep water is >20 m. Based on the first 20 minutes

of 80 undisturbed BOSs, as described in “Methods”. “All” includes unknown status whales but excludes

calves. Adapted from Table 12.2, with percentages recalculated to consider only feeding.

FIGURE 12.5. Locations where feeding was (and was not) seen in and near the eastern Alaskan Beaufort

Sea during late summer and autumn, by year (1985–86, 1998–2000). BOSs that included feeding

(circles) or combinations of activities that included feeding (squares) are distinguished. Based on observations of bowhead whales from a twin-engine aircraft circling at altitude ≥460 m; excludes periods with

other types of potential disturbance.
12-12 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

vations (Chapter 10). Overall, mothers with calves were classified as feeding 55% of the time. For mothers, water-column feeding accounted for 42% of the total observation time, and 76% of the feeding time.

The latter figure for mothers is consistent with corresponding values for subadults and for adults without

calves (Fig. 12.4). Mothers with calves fed near the surface 13% of the time, i.e., 24% of the feeding time

(Fig. 12.4). Mothers were never scored as bottom feeding (Table 12.2; Fig. 12.4).

For whales other than motherñcalf pairs (ìothersî), water column and surface feeding were observed

about equally in the first and latter half of September; however, in the first half of September surface feeding was observed in combination with water column and water column+bottom feeding, whereas in the

second half of September it was seen alone and in combination with water-column feeding (Table 12.3A).

Bottom feeding occurred in both parts of the month, as evident from the combined data for whales engaged

in bottom feeding and water-column+bottom feeding. Feeding by ìothersî was more often interspersed

with traveling and socializing in the second half of the month even though feeding alone and social+feed

each were observed about equally during the first and second halves of September (Table 12.3A).

Most of the observed feeding was recorded in areas with water depths <50 m, with surface and

bottom feeding being noted mainly in water 10ñ19 m deep (Table 12.3B). Travel+feed and social+feed

by ìothersî were found most often in 20ñ49 m depths. However, in large part because of inter-year variability, it is not possible to predict preferred depth categories for specific feeding activities by bowhead

whales in this study area.

Group size for feeding whales was usually one whale: 82% of feeding whales and 60ñ69% of

whales engaged in feeding+other activities were singletons. One exception was whales classified as

surface feeding (only), with 57% of these in groups of two (Table 12.3C). Bottom feeders were usually

found to be widely spaced, with no more than 2 or 3 whales within 1 km. However, when bottom, surface and water-column feeding were all occurring, >6 whales were present 52% of the time (Table

12.3D). Surface and water-column feeders (and combinations of the two) tended to be aggregated, typically with 4+ whales within 1 km. This same tendency for larger aggregations was true for combinations

of travel+feed, social+feed, and travel+social+feed (Table 12.3D, right hand columns).

Appendix 12.2 provides similar information about observations of mothers and calves in relation to

date, water depth and group size. Feeding by mothers was observed in both early and late September, but

combined travel+feed occurred mainly in the latter half of September. Feeding and combined travel+feed

occurred mainly in water depth 20ñ49 m. The group size was usually two (i.e., calf but no other whale

within 5 whale-lengths of mother), typically with 2ñ6 whales within a 1 km radius (Appendix 12.2).

During some BOSs with whales feeding in the water column, at the bottom, or a combination of these,

we had the strong impression that there was partial synchrony in surfacings and dives. Typically, several

whales were at the surface simultaneously within our circle of observation, followed by a long―at times over

10 minutes―period when most or all whales were below the surface. However, our variable-duration (but

often short) observation sessions did not provide data suitable for quantitative analysis of synchrony. Nonetheless, we strongly suspect that bowheads feeding (and traveling) in the present study area sometimes coordinated their surfacing/dive cycles, including some cases when the whales were >1 km from each other.

Travel

Traveling was the second most common activity of bowheads during late summer and early autumn in and near the eastern Alaskan Beaufort Sea (Fig. 12.2). These bowheads spent an estimated 31%

of their time traveling. They were seen traveling during all five years of this study (Fig. 12.2; Table

12.2).
§12. Bowheads: Activities and Behavior 12-13

TABLE 12.3. Circumstances of observations of undisturbed bowhead whales engaged in various group

activities. The table shows number of surfacings and numbers of whales observed during SeptemberOctober 1985-86 and 1998-2000, as observed from an aircraft at altitude ≥460m. Mothers and calves are

excluded. Because a given whale is counted more than once if more than one surfacing is observed,

some data are not independent and statistical analysis is not justified. Also, we tended not to observe

actively socializing groups for prolonged periods, and this affects the percentages of whales engaged in

various activities. "Total n" varies because not all variables could be determined for each surfacing.

Travel+ Travel+ Social+ All

All col bot sfc col+bot col+sfc all three Travel Feed Social Social Feed three

 A. Date

1-15 Sept 231 126 0 0 35 7 63 4 15 0 54 127 0

16-31 Sept 192 119 17 21 0 35 0 103 127 89 39 121 16

1-15 Oct 0 0 0 0 0 0 0 15 0 0 0 0 0

Total n 423 245 17 21 35 42 63 122 142 89 93 248 16

# Whales 314 200 7 19 17 33 38 47 124 60 80 226 8

 B. Water Depth (m)

1-9 97 26 0 1 35 35 0 0 0 0 0 46 0

10-19 162 64 17 18 0 0 63 15 9 0 52 74 0

20-49 136 127 0 2 0 7 0 99 91 76 39 122 0

50-99 16 16 0 0 0 0 0 8 40 0 0 0 16

100-250 0 0 0 0 0 0 0 0 2 13 0 6 0

Total n 411 233 17 21 35 42 63 122 142 89 91 248 16

# Whales 302 188 7 19 17 33 38 47 124 60 78 226 8

 C. Group Size (within 5 body lengths)

1 334 181 17 6 29 38 63 95 85 30 6 158 11

2 52 34 0 12 5 1 0 24 42 29 18 55 5

3 19 16 0 3 0 0 0 3 4 13 35 19 0

4 3 0 0 0 0 3 0 0 11 13 28 15 0

7 0 0 00 0 0 0 0 0 4 6 1 0

Total n 408 231 17 21 34 42 63 122 142 89 93 248 16

# Whales 299 186 7 19 16 33 38 47 124 60 80 226 8

 D. # Bowheads within 1 km

1 5 4 0 1 0 0 0 54 0 0 0 0 0

2 48 31 17 0 0 0 0 40 10 10 18 0 0

3 51 8 0 0 35 0 8 3 7 7 20 6 0

4 77 35 0 20 0 0 22 14 56 0 49 15 0

5 12 12 0 0 0 0 0 6 54 15 0 54 0

6 54 47 0 0 0 7 0 5 15 0 0 0 16

>6 144 76 0 0 0 35 33 0 0 57 6 113 0

Total n 391 213 17 21 35 42 63 122 142 89 93 188 16

# Whales 291 177 7 19 17 33 38 47 124 60 80 170 8

Number of Surfacings

Feed
12-14 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

Traveling whales tended to move in one direction, with only slight variations in heading (±10ñ15°)

from one surfacing to the next. They moved at medium to fast speed (~3 to 6 km/h) while at the surface,

generally with some white water (a ìwakeî) streaming off their sides. Mean speeds during dives, as

determined from positions and times of successive surfacings, indicated that traveling bowheads maintained a similar speed below the surface (mean speed 4.5 ± s.d. 1.22 km/h, Chapter 11). In late summer

and autumn, travel was almost always in a generally westward direction (see ìOrientationî subsection,

below). Traveling whales were usually found in a relatively straight line of several animals, one more or

less behind the other, separated by distances ranging from several body lengths to several kilometers.

They thus traveled along an invisible ìroadî, and we gained the impression that they were communicating

with each other to do so, presumably by sound (see Discussion).

We scored whales as ìtravel+feedî when they showed one or more of the behavioral characteristics

described for feeding, such as coming up with mud, defecating, or fluking out; but when they also covered substantial distances in a consistent direction either while at the surface or during their dives. ìTravel+feedî whales usually surfaced very slowly, moved forward while blowing, and kept their general

travel orientation. Headings of a given whale during successive surfacings tended to be similar, and

changes in orientations at the surface were slight. Subsequent positions tended to progress gradually

westward rather than back and forth through a given area. Headings of ìtravel+feedî whales averaged

westward, but with more variability than those of whales scored as ìtravelingî without feeding (see

ìOrientationî subsection, later).

In all years except 2000, travel behavior occurred somewhat less than did feeding, with 31, 24, 24,

and 24% of time spent traveling in 1985, 1986, 1998, and 1999, respectively (Fig. 12.2, Table 12.2). In

2000, however, most of the few whales seen in the study area traveled through without lingering. Travel

accounted for 74% of the total activity budget of whales in 2000.

For ìothersî, traveling―either alone or in combination with feeding or socializing―was seen more

often in the latter half of September than the first (Table 12.3A). Observations in October were very

limited but all involved traveling. Traveling per se tended to be seen mainly in 20ñ49 m depth, with one

or two whales per group, and one or two whales within 1 km. When traveling occurred in combination

with other activities (especially socializing), group sizes tended to be slightly larger but were still

commonly one or two; the number of whales within 1 km tended to increase to 4+ (Table 12.3B,C,D).

Traveling motherñcalf pairs showed similar depths, group sizes, and ìwhales within 1 kmî values as for

ìotherî whales that were traveling (Appendix 12.2).

Social Activities

Socializing was the third most common activity of bowheads during late summer and early autumn

in and near the eastern Alaskan Beaufort Sea (Fig. 12.2). Bowheads spent an estimated 18% of their time

there in social activities, and were seen socializing during all years of this study (Table 12.2; Fig. 12.2).

We termed activities ìsocialî when whales interacted by pushing, nudging, or slapping each other

with flippers or tail. We did not categorize whales as ìsocialî when they were merely swimming or

resting side-by-side. Active social interactions run the gamut from subtle (at times perhaps greeting)

displays to apparently violent, aggressive, or sexual behaviors. During this study we saw the same types

of social activities that have been seen during summer in the Canadian Beaufort Sea, as described by

W ̧rsig et al. (1985, 1993).

Social activities tended to occur with lower frequency than either feeding or traveling when all

years were combined, although social and travel activities occurred about equally in 1985 and ìsocialî
§12. Bowheads: Activities and Behavior 12-15

was more common than ìtravelî in 1998 (Table 12.2; Fig. 12.2). A low level of socializing, with whales

subtly nudging each other, was quite common during travel, and socializing while feeding was even more

common (Table 12.3). The combined ìsocial+feedî category most often involved whales that were

apparently feeding in the water column or surface feeding (Appendix 12.1).

Social activity by itself was more common in the first half of September than during the second

half (12 % vs. 5 % of surfacings during each period, respectively; Table 12.3A). However, social activity

in combination with travel or travel+feed was seen only in the latter half of the month. (Travel in general

became commoner in late September―see previous subsection and Table 12.3A). Overall, socializing

was recorded for similar percentages of surfacings in early and late September (41% vs. 36%, respectively). Whales categorized as social-only and social+feed tended to occur in water depths 10ñ49 m;

social+travel was seen mainly in 20ñ49 m, but also (15%) in 100ñ250 m (Table 12.3B).

Vigorous socializing that included apparent sexual activity was observed and filmed on 19 and 20

Sept. 1998. On 19 Sept., low cloud prevented observations from altitude 1500 ft a.s.l. On 20 Sept., two

separate surface-active groups were observed systematically (Appendix 12.1D). In the 20 Sept. cases, up

to seven whales at a time interacted vigorously, creating much whitewater and making it impossible to

sort out who was doing what. Extended penises were seen on several occasions , strongly indicating but

not proving that mating was taking place. Most animals appeared to be males and the activity appeared to

be centered about a single, larger, presumed female. Photogrammetry at the end of each BOS showed

that the whales were 10.6 to 13.9 m long (Fig. 12.6). Of the 18 different measured whales, 16 were

11.9 m or longer, but only 8 of 18 exceeded 13.0 m―the length at which an average female bowhead is

assumed to become sexually mature (Koski et al. 1993). The length at which male bowheads become

sexually mature is poorly documented, but is believed to be near 12 m (Koski et al. 1993). The groups

remained sexually active during the low-altitude photogrammetry sessions.

MotherñCalf Associations

Probable mothers and their calves were seen during all five years of study, almost always in water

>20 m deep (Fig. 12.1). When all years are combined, the proportions of time that mothers engaged in

various general activities were similar to the proportions for ìothersî (Fig. 12.3; Table 12.2).

Apparent nursing, as indicated by repeated dives toward the teat area of the mother, was observed

during 35% of the mothersí surfacings (17 of 49; Appendix 12.2). Nursing was probably more common

than this, as we probably did not notice it as often as it occurred. Calves did not appear to play with

objects or around mother. We also saw no breaches by either mothers or calves during BOSs, and only 2

cases of tail-slapping by calves. In general, we gained the impression that―during September―calves

stay close to their mothers and are not highly active, at least during the years and area of this study. We

did not see or photograph any calf that appeared to be independent of its mother (i.e., weaned). Although

calves stayed close to their mothers during September, we did not see them riding on the backs of

mothers, which is common for neonate calves during spring (W ̧rsig et al. 1999).

Orientations

The headings of whales engaged in each recognized activity are of special interest in this study as

consistent westward orientation during late summer and autumn can be presumed to indicate migration;

absence of consistent westward orientation presumably indicates that activities other than migration were

dominant. Whales engaged in feeding or simultaneous socializing and feeding were not oriented consistently westward, or in any other specific direction (Fig. 12.7A,B). However, for feeding whales, a test for
12-16 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

FIGURE 12.6. Length-frequency distributions of bowheads engaged in sexual activity, 20 Sept. 1998, as

determined by aerial photogrammetry.

bimodal orientation (Batschelet 1981) indicated that headings were more commonly toward the NE-ENE

and SW-WSW than in other directions (Fig. 12.7A). As expected, traveling bowheads were oriented

consistently westward (Fig. 12.7C). Whales engaged in active socializing, travel+feed, and travel+social

all showed significant westward orientation, although with more apparent variance than for traveling

whales (Fig. 12.7D–F vs. C).

Mothers and calves showed significant orientation toward the southwest when classified as travel+feed, and a tendency (non-significant) to orient in directions other than west when feeding only (Fig.

12.8). Mothers and calves engaged in travel+feed exhibited a higher proportion of south and southeast

headings than evident for “other” whales involved in travel (cf. Fig. 12.7).

Time Budget Summary

Over the five years of our study, feeding was the most common activity of bowhead whales in and

near the eastern Alaskan Beaufort Sea during late summer and autumn (mainly September). Over all

years, bowheads spent 47% of their time feeding, 31% traveling, 18% socializing, and 4% engaged in

other activities (Fig. 12.2; Table 12.2). Other activities included resting, play, and aerial activities such as

breaching, tail slapping, and flipper slapping. Times when activities were recorded as unknown have

been omitted when calculating these percentages.

The relative frequencies of the three major activities within the present study area and season differed

significantly among years (χ

2 = 16.91, df = 6, P = 0.0096). This analysis was based on the number of BOSs

classified as including each activity each year, with 1985 excluded because of too few BOSs (Table 12.4A).

In four of the five years, feeding was the most common activity observed. In two of these years (1985 and

1998), traveling and socializing were only slightly less common than feeding (Fig. 12.2). However, in 1986

and 1999, feeding was the predominant activity (58 and 66%, respectively), traveling was secondary (24 and

24%), and socializing was of tertiary importance (15 and 10%). In the fifth year (2000), travel was the

major activity (74%) and both feeding and socializing were infrequent (each 9%).
§12. Bowheads: Activities and Behavior 12-17

FIGURE 12.7. Headings (True) of bowheads engaged in various activities in or near the eastern Alaskan

Beaufort Sea during late summer and autumn of 1985–86 and 1998–2000. Excludes mothers, calves,

and potentially disturbed whales. Each surfacing with a known heading is counted separately in the

circular plots and in calculating the vector mean and its length (plotted relative to radius). Numbers in

parentheses are the maximum numbers of different whales observed; however, some resightings would

not have been recognized as such so these numbers are overestimates. Significance levels are based

on Rayleigh tests using the smaller (parenthetical) “n” values. *** means P ≤ 0.001; ns means P > 0.1.

270o

West

360o

North

270o

West

360o

North

90o

East

90o

East

90o

East

180o

South

180o

South

270o

West

(A) Feeding

 =2 sightings

 =425(281)

 ***

n

(B) Social+Feed

 =2 sightings

 =239(221)

 ns

n

(C) Travel

 =2 sightings

 =182(48)

 ***

n

(D) Travel+Feed

 =1 sightings

 =149(121)

 ***

n

(E) Social

 =1 sightings

 =58(45)

 ***

n

(F) Travel+Social

 =2 sightings

 =93(54)

 ***

n
12-18 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

FIGURE 12.8. Headings (True) of bowhead mothers and calves engaged in various activities in and near

the eastern Alaskan Beaufort sea during late summer and autumn of 1985-86 and 1998-2000. Otherwise

as in Figure 12.7.

The time budgets of whales did not appear to differ markedly among whales of different status, i.e.,

mothers vs. other adults vs. subadults. (Calves were excluded from this and most other analyses in this

chapter.) The proportions of BOSs during which feeding, traveling, and socializing were observed did

not differ significantly among mothers, other adults, and subadults (Table 12.4B; χ

2 = 1.91, df = 4, P =

0.75). Feeding was observed 46–57% of the time, traveling 23–35%, and socializing 12–21% of the time

regardless of whale status (based on Table 12.2, all water depths combined). However, the frequencies of

activities varied with water depth. Mothers were not seen in water depths of 20 m or less during BOSs,

and traveling by adults and subadults occurred primarily in water deeper than 20 m (Fig. 12.3).

Comparable time budget information has not previously been reported for bowheads observed during spring or summer. We calculated the percentages of time engaged in feeding, traveling, and socializing during the 4-year spring study of Richardson et al. (1995b) and the 5-year summer study of Würsig

 et al. (1985, 1989). We used the same procedures as used in this Chapter for late summer and early

autumn. In particular, we again considered only the first 20 min of each BOS in order to minimize biases

associated with preferential observation of whales engaged in some specific activities, and excluded

potentially disturbed whales. The proportions of time engaged in the three major activities were quite

different during late summer/early autumn (this study) than during either spring or summer (Fig. 12.9).

During the present study, feeding was less common (and traveling more common) than observed during

summer in the Canadian Beaufort Sea. However, feeding was much more common (and traveling much

less common) during this study than during spring migration east of Point Barrow, Alaska.

Discussion

Local and Traditional Knowledge of Bowhead Activities

Whale hunters and other residents of Kaktovik, within the eastern Alaskan study area, know much

about the seasonal and geographic patterns in bowhead use of that area and of adjacent Canadian waters

(see Chapter 2 and Annex B). They report that autumn bowhead migration through the present study area

tends to be pulsed rather than steady. Local knowledge of the activities and behavior the bowheads is less

360o

North

270o

West

360o

North

90o

East

180o

South

(A) Feeding

 =1 sightings

 =58(29)

 ns

n

(B) Travel+Feed

 =2 sightings

 =169(11)

 ***

n

180o

South
§12. Bowheads: Activities and Behavior 12-19

TABLE 12.4. Number of bowhead observation sessions (BOSs) with bowhead whales

engaged in feeding, traveling and socializing in and near the eastern Alaskan Beaufort

Sea during late summer and autumn (A) by year and (B) according to whale status,

1985, 1986, 1998, 1999 and 2000. When a BOS included more than one general

activity either simultaneously or in series, a fraction of that BOS was assigned to each

activity as described in the "Methods". Other activities not included in the tabulation.

 A: Year

1985 2.34 1.86 1.80

1986 12.05 5.00 3.12

1998 8.00 5.00 6.33

1999 13.86 5.04 2.10

2000 1.00 8.22 1.00

 B: Whale Status

Subadult 18.40 14.00 6.40

Adult 18.24 7.36 6.72

Mother 11.00 6.00 2.40

Feeding Traveling Socializing

Number of BOSs

FIGURE 12.9. Percentage of time when bowheads engaged in various activities during spring near Point

Barrow, summer in the Canadian Beaufort Sea, and late summer/early autumn (present study). Based

on the first 20 min of 55 spring BOSs (from Richardson et al. 1995b), 90 summer BOSs (from Würsig et

al. 1985, 1989), and 80 late summer/early autumn BOSs (this study). All observations were from a twinengine aircraft circling at altitude ≥460 m; excludes periods with other types of potential disturbance.

Includes all whales except calves.
12-20 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

detailed (Chapter 2 and Annex B), as many of the bowhead sightings are from motorized boats, and bowheads seen from such a vessel are often reacting to the boat rather than engaging in their “normal” behavior. However, some residents noted that bowheads may linger in specific areas such as the Icy Reef and

Arey Island areas for as much as 1 to 2 weeks, and that bowheads often tend to feed near water-mass

boundaries or off river mouths. They note that waterbirds also tend to feed at these locations. Some

hunters report seeing concentrations of whale food (zooplankton) in the water, and there are indications

that bowheads tend to concentrate in those areas. One hunter mentioned that, in September, bowheads

sometimes go back and forth in certain areas, presumably feeding. The majority of the bowheads harvested by Kaktovik hunters have food in their stomachs, indicative of recent feeding.

Possible Human Influences

The bowhead whales in and near the eastern Alaskan Beaufort Sea during late summer–early

autumn (mainly September) were not exposed much to industrial activity when we observed them. In

1985–86, there was little industrial activity in the area east of Camden Bay where our observations were

obtained, and in 1998–2000 there was none. There was offshore drilling and seismic exploration farther

west in Camden Bay, where the second of the 1986 studies was centered. However, observations close to

specific industrial activities were excluded (see Appendix 12.1C). In contrast, the summer study in the

Canadian Beaufort Sea during 1980–84 included many observations within the zone where seismic

surveys and offshore construction and drilling were underway (Richardson et al. 1987a). In calculating

the summer time budget (Fig. 12.9), we excluded observations close to industrial activities. However,

many whales observed in the Canadian Beaufort Sea during the summers of 1980–84 would have been

exposed to industrial activities during the days and weeks preceding our observations. Also, some of

those classified as presumably undisturbed were nonetheless exposed to faint sounds from distant industrial activities while we were observing them (Richardson et al. 1985, 1986, 1990). We believe that the

summer data classified as “presumably undisturbed” and summarized in Figure 12.9 were largely unaffected by industrial activities when observed. However, during days previous to our observation sessions,

the bowheads observed in the Canadian Beaufort Sea during summer had no doubt been exposed (on

average) to more industrial activity than the whales observed in and near the eastern Alaskan Beaufort

during late summer and autumn.

In all five years of this study, the 13–m vessel used by the present project for zooplankton sampling

operated within the area where we observed bowhead behavior. The boat caused some localized disturbance to bowheads, especially when purposefully sampling near feeding whales (Chapter 6). However,

this vessel usually moved slowly, and always did so when sampling around bowheads. On one occasion

in 1986, photoidentification data showed that bowheads displaced by the sampling vessel had returned to

their original location 1–2 days later (Thomson and Richardson 1987).

The behavioral observations described here, including spring and summer data as well as late summer–early autumn data, were obtained by observers aboard twin-engined aircraft circling whales at

altitudes of 460–610 m (1500–2000 ft) and radii of 1–2 km. This observation procedure has been found

to cause little if any disturbance to bowheads (Richardson et al. 1985; Patenaude et al. 2002). However,

the whales would have been able to hear the aircraft at least faintly and intermittently. Also, they might

have been able to see it.

Aerial photogrammetry was conducted extensively during all five years of the present study. This

procedure requires the aircraft to fly at low altitude (typically ~145 m or 475 ft) directly over the whales.

The aircraft often travels back and forth above a group of whales for tens of minutes to obtain photos of

most of the whales present. This procedure causes some bowheads to dive abruptly or otherwise react,
§12. Bowheads: Activities and Behavior 12-21

although the proportion doing so is low (Patenaude et al. in 2002). Our standard procedure was to complete high-altitude behavioral observations of a given group of whales before descending to low altitude

to photograph them.

Some bowhead hunting occurred in our study area each year during September while the project

was occurring. However, in 1998–2000, most hunting near Kaktovik occurred before our study started

(see Chapter 2). In addition, none of our BOSs in any year were conducted within 10 km of active

hunting for bowheads. Most September BOSs were conducted considerably more than 10 km east of the

hunters or (for some 1986 BOSs) well to the west.

Overall, the present behavioral dataset for late summer and early autumn involves whales that were

exposed to relatively little human activity during the observations, or during preceding days. Furthermore, we have excluded data collected when there was a known potential for appreciable human disturbance. Our knowledge of potential disturbance effects may not be complete, but we are confident that

none of the data used here were collected in the presence of strong disturbance. The present behavioral

dataset for late summer and early autumn, including data in this chapter and related data on surfacing–

respiration–dive cycles, swimming speeds, and habitat use as described in other chapters, may be valuable

as baseline data for future analyses concerning effects of human presence and underwater noise.

General Activities

Our definitions of general activities (feeding, traveling, socializing, and “other”) and the specific

behaviors that make up these activities follow the descriptions used for whales and dolphins elsewhere.

Wells et al. (1999) and Mann et al. (2000) provide detailed summaries for a variety of species. Nevertheless, when constructing time budgets, complications arise because whales can engage in different

activities within short periods of time, and sometimes simultaneously. For example, our assignation of

33% to each activity when a whale was classified as “feed+social+travel” has the potential to either overestimate or underestimate any of these three general activities during any given BOS. However, we

believe that these potential biases will balance out among the activities and BOSs; and that our overall

estimates of time spend on each activity are reasonably accurate, albeit not perfect.

Our estimates of the proportion of time spent in various activities may have been biased by our

different abilities to detect whales engaged in different activities. Durations of surfacings and dives vary

according to whale status, water depth, and season (Tables 14.1, 15.6). The net affect is to slightly overestimate feeding in shallow water relative to deep water, and to overestimate socializing relative to other

activities. However, these differences are reduced whenever more than one whale is present in the area

being observed.

Feeding

Whales engaged in feeding at the surface, in the water column, and at or near the bottom, as previously described from studies during spring (Carroll et al. 1987; Richardson et al. 1995b), summer

(Würsig et al. 1985, 1989), and autumn (Landino et al. 1994). Our results are similar to those of several

other studies of bowhead whales (summarized in Würsig and Clark 1993) in indicating that whales

change areas and modes of feeding readily, presumably in response to changes in locations and densities

of prey as demonstrated in Chapter 6. Additional evidence of feeding in the study area comes from the

stomachs of the whales harvested by Kaktovik whalers during late summer and early autumn. At least

75% (24 of 32) of these stomachs contained food (Lowry 1993; Chapter 18). Most of the food in these

stomachs consisted of copepods, which would not remain in the stomachs for long. Thus, at least 75% of

the whales harvested at Kaktovik had been feeding recently.
12-22 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

The fact that bowhead whales often occurred in loose aggregations at feeding sites, especially when

surface and water-column feeding (Table 12.3D), suggests that they may coordinate their feeding by

communicating with each other by sound, as postulated by Würsig and Clark (1993). Aggregating does

not prove that the whales were actually communicating with each other to locate feeding areas. However,

we observed one instance of a bowhead rapidly approaching a group of feeding bowheads from a long

distance, suggesting that they may have been communicating acoustically: During early September 1997,

a single bowhead whale was seen swimming strongly southeast ~15 km northwest of a feeding aggregation of 20–30 bowhead whales in shallow water near Prudhoe Bay, Alaska (WRK, unpubl. data). The

whale was not followed to determine if it joined the feeding group, but the rapid speed and unusual

southeastward heading of the whale suggest that it was intentionally approaching the feeding area from a

distance ≥15 km.

Feeding bowhead whales seen in this study were generally alone or in small groups, as has been

found for other baleen whales whose feeding does not depend on close cooperation. (Cooperative feeding

in baleen whales includes some forms of lunge feeding by groups of humpback whales, e.g., Jurasz and

Jurasz (1979), and echelon feeding by bowheads―see below.). Clapham (1993, 1996) suggested that

group size is determined by the quantity of prey available in an area, and that scarcity of prey may be

most responsible for small and unstable groups of whales.

We never saw―during the five years of this study―the highly-coordinated echelon formations of

surface-feeding whales originally described for bowheads feeding in the Canadian Beaufort Sea during

summer (Würsig et al. 1985). Other workers have occasionally seen echelon-feeding in the Alaskan

Beaufort Sea during late summer and autumn (Ljungblad et al. 1986; Landino et al. 1994). It is possible,

but remains unproved, that some echelons form when bowheads feed on larger, more maneuverable, prey

such as euphausiid or mysid crustaceans, instead of calanoid copepods. However, the most impressive

case of echelon feeding observed in the Canadian Beaufort (18 Aug. 1981) was at a time and location

when copepods (Calanus hyperboreus) dominated the zooplankton biomass (Würsig et al. 1985; see also

Chapter 6). Copepods also were the predominant zooplankters in the water column during the present

study, especially where bowheads were feeding (Chapter 6).

There was substantial variability in whether whales were feeding near the surface, in the water column, or near the bottom. This changed with location, season, and year. Similar variability has been

described for summer (Würsig et al. 1985, 1989). In the eastern and central Beaufort Sea, locations

where bowheads choose to feed have higher than average biomass of zooplankton in the water column as

a whole, and a biomass of at least 800 mg/m3

 at the depth of maximum biomass (Chapter 6). Locations in

the Beaufort Sea where such concentrations of zooplankton occur vary from year to year and probably

with date, and the depth of maximum biomass varies with location (Chapter 5). Seasonal and geographic

changes in food distribution represent the norm for many marine mammals (Bowen and Siniff 1999), and

bowhead whales are no exception.

The predominant feeding mode of bowheads during summer and early autumn is water-column

feeding, but near-surface feeding sometimes occurs. It is rare for there to be dense concentrations of prey

in the top few meters of the water column of the Beaufort Sea (Chapters 5 and 6), and we are uncertain of

the importance of surface skim feeding. Euphausiids and mysids occasionally swarm at the surface in the

arctic, and were significant components of the stomach contents in a few whales harvested in the present

study area, and in most bowheads harvested farther west near Point Barrow (Chapter 18). It is possible

that some cases of surface feeding are on these types of prey aggregations. However, neither euphausiids

nor mysids were common during the aforementioned 18 August 1981 case of near-surface feeding in
§12. Bowheads: Activities and Behavior 12-23

echelon formation. Northern right whales also skim feed near the surface but spend most of their feeding

time below ~10 m depth (Watkins and Schevill 1976).

The variable occurrence of the small copepod Limnocalanus glacialis in nearshore waters appears

to be especially important to bowheads. In years and locations when Limnocalanus is abundant along the

coast of the central Beaufort Sea (Yukon and eastern Alaska), bowheads (especially subadults)

concentrate and feed in those areas (Chapters 6, 10). The occurrence of this nominally “brackish-water”

species appears to be affected by wind and oceanographic factors that affect the distribution of water from

the Mackenzie River (Chapters 5, 6).

In 2000, very little feeding was observed in the study area, and most if not all bowheads apparently

traversed the area quickly without lingering to feed. Prey availability in the present study area was lower

in 2000 than in other years of this study (Chapter 5). Nevertheless, some of the whales landed in

September 2000 by hunters at Kaktovik, as well as at Cross Island to the west and Pt. Barrow farther

west, had food in their stomachs (see Chapter 18). At least in the Kaktovik area, it is probable that some

whales were feeding as they traveled west during September 2000.

Traveling

Whales traveled westwards more consistently in late September–early October than in early September. Feeding continued to occur in the eastern Alaskan study area during late September, but combined feeding and traveling was more common then than in early September (Table 12.3). During

combined feeding and travel, bowheads moved predominantly westward (Fig. 12.7D). Westward travel

without simultaneous feeding or socializing were infrequent in early September, but became common in

late September. We assume that most of the traveling whales observed in late September were actively

migrating, given their generally westward orientation and other evidence of migration from distributional

surveys (Chapter 9), photographic re-identifications (Koski et al. 1988), acoustic tracking (Greene et al.

2001, 2002), and radio-tagging (Wartzok 1990; Mate et al. 2000).

Traveling bowheads tended to be singletons or groups of two, but other bowheads were often present within 1 km. This is consistent with previous studies in and near this area (Würsig et al. 1985;

Richardson et al. 1995a). Migratory travel in spring is usually also by single whales, again with others

present in the general area (Carroll and Smithhisler 1980; Zeh et al. 1993; Richardson et al. 1995b).

Spring migration tends to occur in pulses lasting many minutes to many hours, with dozens and sometimes hundreds of whales following a particular “corridor”, often consisting of ice leads and polynyas.

Bowheads call often during spring migration, and whales in a “pulse” are probably in acoustic contact

(Würsig and Clark 1993).

Kaktovik hunters state that autumn bowhead migration through the present study area is sometimes

pulsed (e.g., I. Akootchook in Chapter 2), and aerial surveys sometimes show large day-to-day changes in

numbers (e.g., Chapter 9). Moore et al. (1989) recorded underwater sounds near Kaktovik throughout

most of the late summer and autumn in 1986, one of our study years. They found periods of several days

with almost-continuous calling by bowheads, indicative of a prolonged pulse of whales, and periods of

several days when no calls were recorded, apparently indicative of intervals between pulses. Acoustic

monitoring near Prudhoe Bay (~200 km farther west) during September has also detected large numbers

of bowhead calls, and has shown a strongly pulsed structure to hourly call counts (Greene et al. 1999,

2001, 2002). Some of this structure is probably an artifact of changes in background sound levels, which

mask faint calls. However, acoustic data, along with the variable aerial survey results and observations of

subsistence whalers, show that autumn as well as spring migration is in pulses, and suggest that migrating

bowheads are often in acoustic contact with one another. The lesser frequency and amount of ice in
12-24 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

autumn than in spring means that, in many years, precise routes of whales are less affected by ice in

autumn.

Although whales were below the surface and out of sight most of the time when they were classified as traveling (for details, see Chapter 13), we believe that little feeding was done by whales classified

as traveling. Speeds of traveling bowheads averaged 4.50 ± s.d. 1.22 km/h (Chapter 11). Because of the

large gape of the bowhead mouth when they feed, it is unlikely that they would travel this fast if they

were feeding appreciably while traveling.

Socializing

Social behavior occurred throughout September, with mainly low levels of interactions, similar to

those seen in summer (Würsig et al. 1985). Social activity was more common during late summer and

autumn than in spring (Fig. 12.9); however, a general decrease from a high in late winter and early spring

to late spring and summer has been described before (summary by Würsig and Clark 1993).

We saw apparent surface-sexual aggregations in September, as have been described for right (Eubalaena spp., e.g., Donnelly 1967), gray (Houck 1962), and bowhead whales (Everitt and Krogman 1979)

during winter/spring. These surface-active groups are speculated to consist mainly of males aggregating

(and competing) around one or more females in estrus (Brownell and Ralls 1986). It is unknown whether

sexual behavior in summer/autumn represents actual breeding behavior. Similar seemingly “out-ofseason” sexual behavior has been observed during late summer in Davis Strait bowheads near Baffin

Island (Finley 1990) and during autumn in Bering–Chukchi–Beaufort bowheads in the eastern Canadian

Beaufort Sea (Würsig et al. 1993). In the present study, two groups involved in presumed sexual activity

were approaching or had recently attained sexual maturity, based on their measured lengths. However,

these groups did not contain large bowheads that are known to be sexually mature, which are generally

present in that area at the time when sexually activity was seen (Chapter 10). Our observations appeared

to be of male–female encounters, and so―unlike homosexual activities described by Finley (1990)―

could have reproductive functions. However, based on a gestation period of 12–14 months and the lack

of sightings of recently-born calves outside the calving period (primarily April–May but extends from

February–July), these sexual encounters in early autumn are not likely to have a reproductive function

(Koski et al. 1993; Würsig et al. 1993). Our few observations of sexual behavior in nearly- or recentlymature bowheads are consistent with speculation (see also Finley 1990; Würsig et al. 1993) that sexual

activity outside the breeding season is experimental or play in nature. Similar out-of-season sexual

behavior has been described in some other species of baleen whales, e.g., by Sauer (1963) and Fay (1963)

among gray whales off St. Lawrence Island, Bering Sea, in summer.

Mothers and Calves

Mothers socialized with other bowheads (aside from their calves) sporadically during late summer

and autumn and very rarely in spring (Richardson et al. 1995b). This seasonal difference may be related

to encounter rates of mothers and calves with other whales. The migration period of mothers and calves

overlaps more with that of “others” during autumn in the present study area than during spring in the

Point Barrow region. During spring, most mothers and calves pass Barrow 3–4 weeks after the peak of

subadult movements and 1–2 weeks after the peak of adult movement (Braham et al. 1980; Richardson et

al. 1995b). During late summer and autumn, mothers and calves start migrating in early September, part

way through the migration of small subadults, and continue to migrate throughout the remainder of the

autumn season, thus overlapping with movements by most other categories of bowheads (Chapter 10).
§12. Bowheads: Activities and Behavior 12-25

Mother-calf associations were generally similar in late summer and early autumn to those in spring

and especially summer, but calves were of course substantially larger during the present study than earlier

in the season. For related data on mothers and calves, see Koski et al. (1993) and, for spring, Würsig et

al. (1999), Richardson et al. (1995b); for summer, Würsig et al. (1985, 1989); for late summer–autumn,

Chapter 10. One notable seasonal difference is that calves did not “ride” on the backs of mothers in

August–September, whereas this is often seen in May (Würsig et al. 1999). By August, calves are probably too large to make this behavior possible, and/or too well-developed for it to be necessary. The

absence of observations of calf “play” during this study, and the very low level of surface-active behavior

by calves, represented a waning of activity from summer (cf. Würsig et al. 1985, 1989). We did not see

lone calves during late summer or autumn, indicating that weaning had not started. (In spring, summer

and autumn, calves are sometimes seen alone at the surface, but extended observations show that they are

soon joined by their mothers, whose dives tend to be longer than those of their calves―see Chapters 13

and 14). Calves are probably still learning the migration route, feeding strategies, and other life skills

from their mothers prior to weaning, which occurs sometime between the calf’s first autumn and the subsequent spring migration to the Beaufort Sea (Koski et al. 1993).

Orientations

Consistent orientation to the west is probably a good indication of migratory travel in late summer

and early autumn. The consistent westward headings of traveling whales, and the less consistent but

nonetheless significant westward tendencies during travel+feed, travel+social, and even socializing per se

(Fig. 12.7), indicated that whales were generally moving west while engaged in these activities.

Bowheads categorized as feeding (the most common activity) and social+feed during September

were not consistently oriented west. The feeding whales (mothers and calves excluded) showed significantly bimodal orientation toward northeast and southwest. This axis is perpendicular to shore in much

of the present study area (cf. Fig. 12.1), and perhaps represents onshore–offshore movements of whales

between nearshore feeding areas and the main southeast–northwest migration corridor farther offshore.

Satellite-tag and photo-identification data on tracks of bowheads in the present area show that some

whales linger in the area or “double back” to the east (Mate et al. 2000; Chapter 11). Thus, a wide variety

of orientations is to be expected for feeding whales.

Feeding mother–calf pairs were significantly oriented, but toward directions other than west (Fig.

12.8A). Reasons for this are unknown, but these animals clearly did not show much indication of westward migration. Mothers and calves engaged in travel+feed exhibited significant southwesterly orientation, different from the predominantly westward headings of “other” bowheads engaged in travel+feed

(Fig. 12.8B vs. 12.7B); we do not speculate why.

Time Budgets

Bowhead whales observed in spring just east of Point Barrow spent most of their time traveling

(Richardson et al. 1995b), and those observed in the Canadian Beaufort Sea in summer spent most of their

time feeding (Würsig et al. 1985) (Fig. 12.9). The time spent engaged in various activities in the present

study area during late summer and autumn differed from both spring and summer in that bowheads spent

substantial parts of their time both feeding and traveling (Fig. 2.9). The change in activities from spring

(near Point Barrow) to summer is not unexpected. Although feeding occurs near Point Barrow in spring,

the amounts of food found in the stomachs of bowheads harvested there during spring are usually small

(Carroll et al. 1987; Chapter 18). Assuming that the eastern Beaufort Sea is an important feeding area, it

makes sense for the animals to migrate quickly to the main summer feeding range in spring and, once

there, to feed as much as possible throughout the summer. Carbon isotope ratios in bowhead and zoo-
12-26 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

plankton tissues suggest that the summer range (eastern Beaufort Sea) is not the primary feeding area

(Schell and Saupe 1993; Chapter 20). However, this conclusion is difficult to reconcile with the high

proportion of the summer devoted to feeding (Fig. 12.9), the occurrence of prey in the stomachs of most

bowheads harvested at Kaktovik (Chapter 18), and other evidence (Chapter 22).

The activity budgets of bowheads in the present study area during late summer and autumn were

variable among years. During the westward migration toward additional feeding areas in the western

Beaufort Sea (e.g., Landino et al. 1994; Treacy in prep.; Chapter 18) and western Chukchi Sea (e.g.,

Moore et al. 1995), activities appear to change from traveling to feeding on an opportunistic basis where

food is abundant (Chapter 6). The eastern Alaskan Beaufort Sea is one area where some bowheads stop

to feed for periods of hours (1998) to days or even a few weeks (1986, 1999; Chapter 11). In other years,

such as 2000, they apparently migrate through that area without stopping, though some limited feeding

probably occurs as they travel. These variations in stopover frequency, location, and duration result in

year-to-year differences in activity budgets of bowheads in the present study area. In some years, e.g.,

1986, parts of the eastern Alaskan Beaufort Sea appear to be a westward extension of late-summer feeding areas in the western part of the Canadian Beaufort Sea (Yukon coast). However, utilization of eastern

Alaskan waters varies greatly from year to year.

The time budget derived in this study for late summer–autumn is based mainly on September data.

We have shown that the proportions of time devoted to feeding vs. migration differed in early vs. late

September. Although September is the month of peak utilization of the present study area, appreciable

numbers of bowhead whales occur there during August and early October as well, and a few are present

in late October (Chapter 9). The time budget for the overall August–October period may differ somewhat

from that described here for September.

Averaged across years, the proportional occurrence of feeding and traveling is considerably different during summer in the Canadian Beaufort vs. September in eastern Alaska. The latter area is not used

by bowheads in the same manner as is the Canadian summer range. However, the eastern Alaskan part of

the Beaufort Sea is more than a migration corridor. It is used by feeding whales to variable degrees in

different years.

It is beyond the scope of this chapter to assess the importance of the observed feeding in the eastern

Alaskan Beaufort Sea in meeting the overall energy requirements for the year, and in assuring the wellbeing of the individuals and the population (see Chapters 22 and 23). However, from an ecological

perspective, in years when “casual” or infrequent feeding occurs within this area, that feeding is unlikely

to be vital to survival and successful reproduction. When more intensive and prolonged feeding occurs

there, for several days or perhaps a few weeks, that feeding could be important to the well being and

reproductive performance of those whales. This issue is addressed further in Chapter 22, “Energetics”,

and Chapter 23, “Integration”.

Summary

Chapter 12 describes the general activities of bowhead whales while they are off northeastern

Alaska, and in adjacent Canadian waters, during late summer and early autumn (feeding, traveling,

socializing, and combinations thereof). It also documents the specific behaviors associated with these

activities, and determines the proportion of time engaged in each activity (time budget). During September of 1985, 1986, 1998, 1999, and 2000 (and early October in 1986), systematic behavioral observations

were obtained from twin-engine aircraft circling at an altitude of 460 m (occasionally 610 m) a.s.l., with a

minimum of three observers describing and videotaping behavioral events. We obtained data on the
§12. Bowheads: Activities and Behavior 12-27

activities and behaviors of whales during 84 Behavioral Observation Sessions totaling 91.9 h of observations under presumably undisturbed conditions. Of these, 69 sessions were off northeast Alaska

(Flaxman Isl. to border) and 15 were in Canadian waters from the Alaska-Yukon border to Herschel

Island. We compared our data for this “Flaxman-to-Herschel” area in September/early October to

previously reported data on activities, behaviors, and time budgets during spring and during summer, and

demonstrated seasonal differences. For the late summer/early autumn period, the time-budgets also

differed among years.

Feeding was the most common activity of bowhead whales in and near the eastern Alaskan Beaufort Sea in September/early October during 1985, 1986, 1998, and 1999; but not in 2000. Over the five

seasons, bowheads engaged in feeding for ~47% of the total time (9% in 2000; 38–66% in other years).

Overall, ~34% of the time was spent feeding in the water column, 8% on near-surface (“skim-”) feeding,

and 4% on near-bottom feeding. Almost all observed feeding in water >20 m deep was water-column

feeding; surface and bottom feeding were proportionally more common in areas ≤20 m deep, but there too

water-column feeding was the most common activity. Mothers and first-year calves were rarely sighted

in waters ≤20 m deep, and the most common activity of mothers was feeding in the water column in areas

>20 m deep. Most whales fed singly. Bottom feeders were usually widely spaced, but water-column and

skim feeders generally were more aggregated, typically with 4+ whales within 1 km of each other. We

did not see skim feeding in echelon formation during late summer–early autumn, although it has been

reported previously in the Alaskan Beaufort Sea. The estimated proportion of time devoted to feeding

during September/early October (47%) was intermediate between values during spring migration east of

Point Barrow, Alaska (1%), and on the summer range in the Canadian Beaufort Sea (71%).

Traveling was the second-most common activity, accounting for 31% of time overall; but 74% in

2000. Travel tended to be in areas 20–49 m deep and in groups of one to two whales. Whales spent more

time traveling during the latter half of September than in early September. Traveling whales were oriented mainly westward. Bowheads commonly interspersed feeding and socializing with travel during the

latter half of September. The estimated proportion of time devoted to traveling (31%) was also intermediate between that during spring migration (81%) and that on the summer range (9%).

Socializing accounted for 18% of the time during September/early October, and other activities

(aside from feeding, travel or socializing) accounted for 4%. Socializing tended to consist of low-level

behaviors such as nudges and other touches, with the exception of apparent sexual aggregations of up to

seven whales per aggregation on two days in September 1998. First-year calves stayed close to their

mothers, showed little surface-active behavior, and were not observed to play. No lone calves were seen,

indicating that calves had not been weaned.

Although feeding was the most common activity of bowhead whales in and near the eastern Alaskan Beaufort Sea during September/early October, there was much intra- and inter-season variability in

the amount and type of feeding, other activities, and specific behaviors, and in the locations (within the

study area) where these activities occurred. These variable results are generally consistent with the

apparent variability in prey availability in the study area, as documented in other parts of this study.

However, bowheads observed in 1999 spent a high proportion of their time feeding, and exhibited

relatively long residence times, even though average zooplankton abundance (at least inshore of the 50 m

contour) was relatively low that year. Overall, the importance of the study area for late-summer feeding

by bowhead whales varies considerably from year to year, and is difficult to predict for any one late

summer–early autumn season.
12-28 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

Acknowledgements

We thank the numerous LGL personnel, aircraft charter companies, and pilots who assisted in

collecting the behavioral data over the years. The U.S. Minerals Management Service, Alaska OCS

Region, sponsored the 1998–2000 work and the majority of the 1985–86 work. “Study 2” in 1986 was

sponsored by Shell Western Exploration & Production. These projects were conducted under the provisions of Scientific Research Permits 517, 518 and 481–1464 issued by the National Marine Fisheries

Service. Projects in Canadian waters were authorized under permits issued by the Canadian Department

of Fisheries and Oceans and in consultation with the Inuvialuit. Many other Acknowledgements relevant

to the project as a whole are included in Chapter 1.

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Publ. 2. Soc. Mar. Mammal., Lawrence, KS. 787 p.
12-32 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

APPENDIX 12.1a. Behavioral observation sessions, 1985. ‘Boxed’ locations are in Canadian waters.

Behav. Predominant

Date Sess. Time in in General Active Predominant of Depth

1985 # Location of Obs. Circle Area Feeding Traveling Socializing Orientation Travel (m)

12 Sept 1 69°37'N 16:28- 5-8 30-40 skim feedingb some-low random slow-medium 10

140°30'W 18:17 level

13 Sept 2a 69°37' N 16:08- 7-10 20-30 skim feedingb possibly some-low mainly west slow-medium 8

140°07' W 17:04 slow travel level

19 Sept A 3a 69°54' N 9:03- 1 3 mainly west zero-slow 20

142°00' W 12:19 water column

19 Sept B 4 69°40' N 12:31- 4 8-10 strongly nearly all medium 13

141°00' W 13:00 directed west

22 Sept 5a 70°14' N 10:44- 6-8 15-22 up to 5 random zero-slow 280

139°56' W 12:50 water column socializing

23 Sept A 6 69°37' N 11:27- 3-4 5-8 possibly mainly west slow 14

140°38' W 12:13 water column slow travel

23 Sept B 7a 70°24' N 16:40- 4-6 4-6 possibly north-west slow 40

143°45' W 18:15 water column slow travel

24 Sept 8 69°36' N 10:58- 4-6 15-25 skim feedingb some random zero-slow 15

140°13' W 11:43

26 Sept A 9a 69°52' N 10:34- 4 4-5 north-west slow 40

139°58' W 12:00 water column

26 Sept B 10 70°29' N 15:08- 4-6 13-18 some random zero-medium 42

143°23' W 16:30 water column

29 Sept 11 70°23' N 9:26- 5-6 12-15 possibly some south-west slow-medium 50

143°02' W 10:34 water column

a

 Behavioral observation session not used in analysis because it was considered disturbed. 

b

 Whales observed or photographed with mouths open and/or defecations.

Number of Whales

Obs. Speeds
§12. Bowheads: Activities and Behavior 12-33

APPENDIX 12.1b. Behavioral observation sessions, 1986. ‘Boxed’ locations are in Canadian waters.

Behav. Predominant

Date Sess. Time in in General Active Predominant of Depth

1986 # Location of Obs. Circle Area Feeding Traveling Socializing Orientation Travel (m)

3 Sept A 1 69°36'N 12:13- 10-15 random medium 8

138°54'W 13:03 water column

3 Sept B 2 69°34' N 13:15- 6-10 random 10

139°28' W 13:26 water column

5 Sept 3 69°49' N 10:45- 10-13 20 water column; random slow-medium 11

141°48' W 12:06 surface; bottomb

7 Sept 4 69°49' N 11:32- 6 12 random slow-medium 20

141°37' W 12:44 water column

8 Sept 5 69°47' N 14:38- 6-8 8 random slow-medium 19

141°24' W 16:07 water column

9 Sept 6 69°37' N 16:09- 6-8 6-8 some mostly SW, slow-medium 13

140°20' W 16:43 water columnb W & NW

10 Sept 7a 69°44' N 10:22- 8-10 10-15 some random slow-medium 15

141°21' W 11:16 water columnb

14 Sept 8 69°40' N 10:25- 40-50 water column random slow-medium 20

140°21' W 11:46 and surfaceb

15 Sept 9 69°43' N 10:01- 6-8 40-50 some-low random slow 27

140°37' W 11:46 water columnb level

16 Sept 10 69°36' N 11:26- 5-8 5-8 water column random slow-medium 5

140°33' W 12:11 and surfaceb

19 Sept 11 69°37' N 11:22- 6-8 50 water column some random slow-medium 9

139°55' W 12:36 and surfaceb

22 Sept A 12 70°02' N 16:33- 1 2 west and slow 22

142°20' W 17:08 south-west

22 Sept B 13 69°53' N 17:21- 2 2 yes yes west slow-medium 32

141°24' W 18:12

26 Sept A 14a 70°03' N 11:42- 6-8 20-30 water column south-west slow-medium 44

140°30' W 12:53 and surface north-west

26 Sept B 15a 70°09' N 15:39- 1 1 zero 43

141°52' W 16:21

26 Sept C 16 70°10' N 16:30- 5-6 5-6 random zero-slow 48

141°26' W 17:55 water column

27 Sept 17 70°02' N 12:41- 3-6 20+ possibly some west and zero-medium 45

140°27' W 13:37 slow travel north-west

a

 Behavioral observation session not used in analysis because it was considered disturbed. 

b

 Whales observed or photographed with mouths open and/or defecations.

Number of Whales

Obs. Speeds
12-34 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

APPENDIX 12.1c. Behavioral observation sessions, S-1986 (SWEPI). ‘Boxed’ location is in Canadian

waters.

Behav. Predominant

Date Sess. Time in in General Active Predominant of Depth

S-1986 # Location of Obs. Circle Area Feeding Traveling Socializing Orientation Travel (m)

4 Sept 1 69°49'N 13:55- 4 7 water column; random zero-slow 10-18

141°48'W 16:23 surface; bottomb

5 Sept 2a 69°39'N 14:35- 5 8 water column random slow-fast 10

141°51'W 15:57 and bottom

8 Sept 3 69°39'N 15:03- 3 12 water column random slow-medium 9

140°31'W 15:57 and bottomb

9 Sept 4 70°30'N 14:55- 3-5 10 random zero-slow 46

145°06'W 18:23 water column

10 Sept 5a 70°29'N 12:05- 2-3 4 south-east slow 42-55

144°23'W 14:55

11 Sept 6a 70°25'N 10:58- 3 10 random zero-medium 37-46

144°02'W 14:25 water column

17 Sept A 7a 70°09'N 11:22- 1 1 east slow 18

144°34'W 11:55 water column

17 Sept B 8a 70°09'N 16:29- 1 1 west unk 18

144°34'W 16:39 water column

19 Sept 9 70°32'N 14:03- 2 3 strongly west medium 36

146°29'W 17:05 directed

26 Sept 10 70°37'N 14:07- 1 2 strongly west medium 46

145°48'W 16:40 directed

28 Sept 11a 69°39'N 14:35-

141°51'W 15:57

3 Oct 12 70°37'N 12:01- 6 18 slow travel north-west slow 66

145°29'W 13:00

6 Oct 13 70°30'N 10:49- 1 1 strongly north-west medium 36-45

145°30'W 17:33 directed

a

 Behavioral observation session not used in analysis because it was considered disturbed. 

b

 Whales observed or photographed with mouths open.

Number of Whales

Obs. Speeds
§12. Bowheads: Activities and Behavior 12-35

APPENDIX 12.1d. Behavioral observation sessions, 1998. ‘Boxed’ locations are in Canadian waters.

Behav. Predominant

Date Sess. Time in in General Active Predominant of Depth

1998 # Location of Obs. Circle Area Feeding Traveling Socializing Orientation Travel (m)

13 Sept A 1a 69°41'N 11:46- 3 3 north-east slow 35

139°05'W 11:59 water column

13 Sept B 2 69°38' N 12:16- 4 7 some-low mainly west slow 51-100

138°26' W 13:00 water column level

15 Sept A 3 70°11' N 10:34- 4 9 up to 4 mainly west slow 16

143°34' W 11:03 socializing

15 Sept B 4 70°11' N 11:51- 4 20 up to 4 mainly west slow 18

143°47' W 13:21 water columnb socializing

15 Sept C 5 70°12' N 18:11- 2 6 possibly nearly all zero-slow 27

144°55' W 19:34 slow travel west

16 Sept A 6 70°13' N 10:30- 3 5 up to 3 nearly all slow 28

145°03' W 12:02 water columnb socializing west

16 Sept B 7 70°13' N 17:13 3 5 random slow 30

145°02' W 17:48

16 Sept C 8 70°14' N 17:54 2 2 2 whales random slow 28

144°28' W 18:43 chasing

18 Sept A 9 70°13' N 10:11 4 14 possibly nearly all zero-slow 25

144°04' W 12:37 water columnb slow travel west

18 Sept B 10 70°02' N 16:21 5 16 possibly west slow 30

142°06' W 18:44 water column slow travel

19 Sept A 11 70°14' N 10:52 2 3 breaching west slow 26

143°31' W 11:50

19 Sept B 12a 70°10' N 11:54 4 16 up to 3 random zero-medium 16

143°45' W 12:05 socializing

19 Sept C 13 70°10' N 12:15 3 6 up to 3 random slow 20

144°11' W 12:24 socializing

19 Sept D 14 70°12' N 12:27 2 3 strongly nearly all slow-medium 23

144°01' W 13:43 directed west

19 Sept E 15 70°10' N 18:55 4 4 skim feedingb some-low random slow-medium 12

143°40' W 19:40 level

20 Sept A 16 70°09' N 9:51 1 1 low-level south slow 9

143°39' W 10:01 skim feedingb

20 Sept B 17 70°11' N 10:04 14 30 some-low random zero-slow 15

143°16' W 11:45 water columnb level

20 Sept C 18 70°14' N 14:33 7 10 possibly up to 7 random zero-slow 28

145°06' W 15:34 slow travel socializing

20 Sept D 19 70°13' N 17:00 7 8 up to 7 random slow 27

144°55' W 17:12 socializing

22 Sept A 20 70°10' N 9:20 2 4 bottom random slow 14

143°07' W 10:53 feeding

22 Sept B 21 70°14' N 11:00 1 1 breaching south-west slow-medium 25

143°26' W 11:13

22 Sept C 22 70°13' N 11:36 2 2 possibly west slow-medium 27

143°56' W 11:58 slow travel

22 Sept D 23 70°14' N 11:59 3 3 possibly random slow-medium 28

143°58' W 13:08 water columnb slow travel

22 Sept E 24 70°12' N 16:11 2 4 skim feedingb possibly south to west slow 25

144°06' W 17:28 and slow travel

water column

a

 Behavioral observation session not used in analysis because it was considered disturbed. 

b

 Whales observed or photographed with mouths open.

Number of Whales

Obs. Speeds
12-36 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

APPENDIX 12.1e. Behavioral observation sessions, 1999. ‘Boxed’ locations are in Canadian waters.

Behav. Predominant

Date Sess. Time in in General Active Predominant of Depth

1999 # Location of Obs. Circle Area Feeding Traveling Socializing Orientation Travel (m)

10 Sept 1 70°18'N 13:19- 6 9 possibly some-low random slow 75

142°08'W 14:21 water columnb slow travel level

11 Sept A 2 70°18' N 11:16- 7 10 random slow 80

142°09' W 11:40 water columnb

11 Sept B 3 70°20' N 11:44- 7 10 south-east slow 125

141°58' W 12:08

11 Sept C 4 70°04' N 12:35- 5 8 south-west slow 40

140°17' W 13:41 water columnb

12 Sept A 5 70°19' N 13:36- 3 8 random zero-slow 100

142°05' W 14:37 water column

12 Sept B 6 69°57' N 15:04- 6 10 water column up to 3 west slow 48

140°14' W 15:24 and surfaceb socializing

16 Sept A 7 70°08' N 11:00- 6 13 random slow 45

141°51' W 12:05 water columnb

16 Sept B 8 69°59' N 15:59- 6 12 random zero-slow 40

141°32' W 16:30 water column

16 Sept C 9 70°04' N 17:00- 1 2 nearly all random 48

141°22' W 18:03 water column west

16 Sept D 10 70°12' N 18:16- 5 7 strongly west slow 43

142°08' W 19:16 directed

17 Sept A 11 70°08' N 9:14- 8 15 north-east zero-slow 43

141°52' W 9:50 water columnb

17 Sept B 12 70°16' N 10:15- 4 12 possibly west slow-medium 75

142°19' W 11:16 water columnb slow travel

17 Sept C 13 70°09' N 12:18- 8 13 random zero-slow 42

142°01' W 12:38 water columnb

17 Sept D 14 70°15' N 16:41- 4 6 random zero-slow 31

143°32' W 17:26 water column

17 Sept E 15 70°14' N 17:36- 4 10 possibly west zero-medium 30

144°19' W 18:26 water column slow travel

20 Sept 16 70°18' N 14:08- 4 15 some-low random zero-slow 31

143°35' W 14:39 water column level

21 Sept 17 70°18' N 10:54- 4 4 strongly west slow-medium 35

145°10' W 11:42 directed

26 Sept A 18 70°21' N 10:24- 3 3 up to 3 random zero-slow 48

143°47' W 10:54 socializing

26 Sept B 19 70°34' N 11:25- 3 4 possibly south-west slow 200

142°57' W 12:34 water column slow travel

26 Sept C 20 70°23' N 14:20- 15 50 strongly some-low west slow 130

142°13' W 14:40 directed level

29 Sept 21 70°14' N 10:36- 3 5 some-low south-west north 250

141°24' W 11:06 water columnb level

30 Sept 22 70°18' N 10:58- 2 6 possibly south-west slow 48

143°11' W 11:28 water columnb slow travel

a

 Behavioral observation session not used in analysis because it was considered disturbed. 

b

 Whales observed or photographed with mouths open.

Number of Whales

Obs. Speeds
§12. Bowheads: Activities and Behavior 12-37

APPENDIX 12.1f. Behavioral observation sessions, 2000. All locations are in Alaskan waters.

Behav. Predominant

Date Sess. Time in in General Active Predominant of Depth

2000 # Location of Obs. Circle Area Feeding Traveling Socializing Orientation Travel (m)

13 Sept A 1 70°13'N 13:43- 1 1 north slow 25

143°18'W 14:37

13 Sept B 2 70°20' N 14:53- 3 3 strongly south-west slow-medium 100

142°45' W 16:03 directed

18 Sept A 3 70°20' N 11:08- 2 8 strongly west slow-medium 40

144°03' W 12:08 directed

18 Sept B 4 70°03' N 16:29- 2 2 north-west slow 45

141°15' W 17:05

18 Sept C 5 70°03' N 17:31- 1 1 north zero 42

141°49' W 18:24

19 Sept A 6 69°53' N 10:34- 1 1 strongly west medium 40

141°22' W 11:34 directed

19 Sept B 7 69°55' N 13:13- 3 3 possibly some-low random slow-medium 27

141°52' W 13:56 slow travel level

20 Sept A 8 70°19' N 10:15- 1 1 strongly west medium 35

144°36' W 11:20 directed

20 Sept B 9 70°02' N 14:07- 1 6 strongly west slow 27

142°10' W 15:10 directed

20 Sept C 10 70°07' N 17:22- 2 3 bottom possibly west slow-medium 22

142°46' W 18:57 feeding slow travel

21 Sept 11 69°52' N 11:17- 4 5 bottom up to 4 random zero-slow 20

141°50' W 12:22 feedingb socializing

23 Sept 12 70°06' N 16:56- 1 1 strongly west medium 15

142°50' W 18:03 directed

25 Sept 13 70°06' N 10:39- 1 1 strongly west medium 22

142°42' W 11:03 directed

a

 Behavioral observation session not used in analysis because it was considered disturbed. 

b

 Whales observed or photographed with mouths open.

Number of Whales

Obs. Speeds
12-38 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

APPENDIX 12.2. Circumstances of observations of undisturbed bowhead calves, mothers and others

engaged in travelling and/or feeding (socializing excluded). Calves and mothers that are and are not

nursing are shown separately. Table shows number of surfacings and numbers of whales observed

during September-October 1985-86 and 1998-2000, as observed from an aircraft at altitude ≥460m.

Because a given whale is counted more than once if more than one surfacing is observed, some data are

not independent and statistical analysis is not justified. "Total n" varies because not all variables could be

determined for each surfacing.

Not Nurse Not Nurse Not Nurse ALL Not Nurse Not Nurse Not Nurse ALL Feed Travel ALLa

A. Date

1-15 Sept 13 2 13 3 3 0 34 8 2 8 1 1 0 20 231 4 15 250

16-31 Sept 0 0 8 8 22 45 83 0 0 5 3 10 11 29 192 103 127 422

1-15 Oct 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 15 0 15

Total n 13 2 21 11 25 45 117 8 2 13 4 11 11 49 423 122 142 687

# Whales 4 0 13 4 4 1 26 1 1 9 2 4 1 18 314 47 124 485

B. Water Depth (m)

1-9 0 0 0 0 0 0 0 0 0 0 0 0 0 0 97 0 0 97

10-19 0 0 2 0 0 0 2 0 0 0 0 0 0 0 162 15 9 186

20-49 8 1 16 11 18 45 99 5 1 11 4 7 11 39 136 99 91 326

50-99 0 0 2 0 3 0 5 0 0 1 0 1 0 2 16 8 40 64

100-250 5 1 1 0 4 0 11 3 1 1 0 3 0 8 0 0 2 0

Total n 13 2 21 11 25 45 117 8 2 13 4 11 11 49 411 122 142 675

# Whales 4 0 13 4 4 1 26 1 1 9 2 4 1 18 302 47 124 473

C. Group Size (within 5 body lengths)

1 2 0 12 0 7 0 21 0 0 2 0 0 0 2 334 95 85 514

2 8 2 7 11 18 37 83 6 2 9 4 11 10 42 52 24 42 118

3 3 0 2 0 0 8 13 2 0 2 0 0 1 5 19 3 4 26

4 0 0 0 0 0 0 0 0 0 0 0 0 0 0 3 0 11 14

7 0 0 0 0 0 0 00 0 0 0 0 0 0 0 0 0 0

Total n 13 2 21 11 25 45 117 8 2 13 4 11 11 49 408 122 142 672

# Whales 4 0 13 4 4 1 26 1 1 9 2 4 1 18 299 47 124 470

D. # Bowheads within 1 km

1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 5 54 0 59

2 8 1 0 0 8 6 23 5 1 0 0 2 3 11 48 40 10 98

3 5 1 1 0 10 4 21 3 1 1 0 6 2 13 51 3 7 61

4 0 0 2 0 4 35 41 0 0 1 0 2 6 9 77 14 56 147

5 0 0 7 3 0 0 10 0 0 5 1 0 0 6 12 6 54 72

6 0 0 5 8 3 0 16 0 0 4 3 1 0 8 54 5 15 74

>6 0 0 6 0 0 0 6 0 0 2 0 0 0 2 144 0 0 144

Total n 13 2 21 11 25 45 117 8 2 13 4 11 11 49 391 122 142 655

# Whales 4 13 4 4 1 26 1 1 9 2 4 1 18 291 47 124 462

Calf Mother Other Whalesa

Feed Travel+Feed

a

See Table 12.3 for additional breakdown for "Other Whales", including results for those engaged in socializing (excluded from ALL columns in this

table).

Travel Feed Travel+Feed Travel

Travel

+Feed
13. SURFACING, RESPIRATION AND DIVE CYCLES OF BOWHEAD WHALES

IN THE EASTERN ALASKAN BEAUFORT SEA DURING LATE SUMMER AND AUTUMN

AS RELATED TO WHALE ACTIVITY

Tannis A. Thomas 1, William R. Koski 1, W. John Richardson 1, and Bernd Würsig 2

Introduction

Feeding, traveling, and socializing are the three dominant activities of bowhead whales (Balaena

mysticetus) observed in the eastern Alaskan Beaufort Sea during the late summer and autumn. The surfacing, respiration, and dive (SRD) cycles of bowheads vary with whale activity, at least during spring

and summer―the seasons when these cycles have been studied (Würsig et al. 1984; Dorsey et al. 1989;

Richardson et al. 1995a,b, MS). These types of variation are relevant in deriving correction factors to

allow for whales missed during aerial surveys, and in analyses of whale energetics. Both of those topics

are important in this study: In estimating numbers of whales present based on aerial survey results, it is

important to know the relative time spent at vs. below the surface, and also the typical durations of

surfacings. In calculating the amount of food a bowhead can consume, the typical duration of a feeding

dive is one important factor. In addition, though not of direct relevance in this study, data on SRD cycles

are useful indicators in assessing reactions of whales to human activities (e.g., Richardson et al. 1986).

Many studies have shown that specific environmental factors and whale status can affect SRD variables of baleen whales engaged in a particular activity such as feeding or traveling. In spring and summer, SRD cycles of bowhead whales engaged in feeding or traveling can vary with age–sex category,

year, water depth, and other environmental variables (Würsig et al. 1984; Dorsey et al. 1989; Richardson

et al. 1995a,b, MS). These relationships have not previously been investigated in any detail for the late

summer–early autumn period when bowheads are present in the eastern Alaskan Beaufort Sea.

In this chapter, we use behavioral data collected in the late summer and autumn of 1985–86 and

1998–2000 to investigate the influence of whale activities and other factors on SRD cycles of bowhead

whales during that season. We first consider the main factors individually, and then use multiple regression to assess the joint effects of various factors on four measures of SRD cycles. Companion chapters

provide related data on the seasonal distribution of bowheads in the study area (Chapter 9), age segregation (Chapter 10), residence times (Chapter 11), and general activities (Chapter 12). In addition, Chapter

14 provides additional information, beyond that in this chapter, on the influence of bowhead age on SRD

cycles. Chapter 15 uses some of the present results in deriving correction factors for aerial surveys.

 

1 LGL Ltd., environmental research associates, 22 Fisher St., POB 280, King City, Ont. L7B 1A6.

Phone: 905-833-1244; e-mail: bkoski@lgl.com or wjr@lgl.com.

2 Texas A & M University at Galveston, Marine Mammal Research Program, 4700 Ave. U., Bldg 303,

Galveston, TX 77551-5923. Phone: 409-740-4413; e-mail: wursigb@tamug.tamu.edu
13-2 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

Methods

Data Sources

We combined data from three studies of bowhead behavior in the eastern Alaskan Beaufort Sea and

adjacent Canadian waters (longitudes 138°–146°W) during the periods 3 September–6 October in 1985–

86 and 10–30 September in 1998–2000 (Table 13.1). In four of five years, some behavioral observations

were obtained as much as 98 km east of the Alaska/Yukon border in the western part of the Canadian

Beaufort Sea. Locations where systematic behavioral data were obtained are mapped in Figure 12.1 and

listed in Appendices 12.1a-f (in Chapter 12). We excluded data when bowheads may have been disturbed

by an aircraft flying at <457 m (1500 ft) altitude or by industrial activities. Also excluded were all data

concerning calves, which were recognized by their size, light color, morphology, behavior, and (in almost

all cases) close association with an adult. Thus, this chapter concerns “non-calves”, including adults

associated with calves ― presumed to be “mothers”.

TABLE 13.1. Sources of data on bowhead whale surfacing, respiration and dive cycles for this study.

Behavioral observation sessions (BOS) categorized as rest, play and unknown/other were excluded

because they were not used in the analyses.a

 Also excluded are surfacings of calves.

Date Range No. BOSs by Area

Year BOS Surfacings of BOS of Beaufort Sea Source of Data

1985 6 133 12-29 Sept E. Alaskan (3); W. Canadian (3) Richardson (1987)

1986 13 310 3-27 Sept E. Alaskan (5); W. Canadian (8) Richardson (1987)

1986 7 120 4 Sept - 6 Oct E. Alaskan (6); W. Canadian (1) Koski & Johnson (1987)

1998 19 365 13-22 Sept E. Alaskan (18); W. Canadian (1) This study

1999 21 194 10-30 Sept E. Alaskan (19); W. Canadian (2) This study

2000 10 84 13-25 Sept E. Alaskan (10) This study

a

 See Figure 12.1 and Appendix 12.1a-f (in Chapter 12) for map and list of BOS locations.

Number of

Field Procedures

All aerial observations of behavior were obtained from either a Twin Otter turboprop aircraft (1985–

86) or a Twin Commander 680FL piston-engined aircraft (1998–2000). The aircraft was based at Kaktovik,

Alaska, for the duration of each season’s fieldwork except during study (2), when the aircraft was based in

Deadhorse (Prudhoe Bay). The Twin Otter aircraft (studies 1 and 2) were equipped with wingtip fuel tanks

for extended endurance, GNS 500A Very Low Frequency navigation systems, radar altimeters, inverters for

120 V/60 Hz power, bubble windows, and ventral camera ports. The Twin Commander aircraft used in

study (3) had ventral camera hatches, two photo-grade glass windows that were used for video taping and

binocular observations, bubble windows at other observation positions, extended fuel capacity, and winglets

that improve slow-speed handling. In each study, the field crew consisted of three or four biologists plus

two pilots. The co-pilot moved to a rear seat once the aircraft was at survey altitude over the sea, allowing a

biologist to move to the co-pilot’s seat until the aircraft began to return to base.

We used the aerial observation procedures of Würsig et al. (1985) and Richardson et al. (1985, 1995a,b)

to observe the behavior of bowheads. A focal group of bowheads was observed systematically while the

aircraft circled at an altitude of at least 457 m a.s.l. and at a radius of 1–2 km. With this procedure, bowheads

show very little evidence of disturbance by the aircraft (Patenaude et al. 2002). At most times while the focal

whales were at the surface, they were videotaped using a hand-held video camera (usually with tele-extender).
§13. Bowheads: Surfacing, Respiration & Dive Cycles vs. Whale Activity 13-3 

Whale activities (e.g., traveling, feeding, socializing) and specific behaviors were defined and

distinguished as in previous related studies (Richardson et al. 1995a,b, MS). We recognize only one type

of dive, often referred to by others as a “sounding” or long dive. Dive durations were recorded only when

whales were individually identified from one surfacing to the next, usually on the basis of distinctive

marks. Shallow submergences between breaths were not counted as dives or as interruptions of a surfacing. A surfacing is a period when a whale is at or just below the surface, including a full breath sequence.

We obtained four standard measures of SRD cycles: the interval between successive blows in a surfacing

(blow interval), the number of blows per surfacing, the duration of surfacing (surface time), and the

duration of dives between surfacings (dive time). When analyzing blow-interval data, we used the

median of all blow intervals within a given surfacing as a single measure of blow interval for that

surfacing.

After completing the behavioral observations of a given group of whales, we often used the aerial

photogrammetric method of Koski et al. (1992) to document their lengths and individual identities.

Whales <13 m and ≥13 m long were considered to be subadults and adults. When no photogrammetric

data were available, whales that were obviously small or large were counted as subadults and adults;

others were not classified.

Behavioral data were transcribed from audiotape between flights and after each field season. The

videotape was then examined for details not noted during the real-time behavioral dictation. The combined data were coded numerically as in our previous work (see Richardson and Finley 1989:25–28 for

details). These records were hand-checked, and then entered into an Apple II (1985–86) or MS-Windows

(1998–2000) format for computerized validation and analysis. A validation program that checks for

impossible or implausible combinations of variables, as developed during prior LGL/MMS projects, was

applied to the data and necessary corrections were made.

Categories of Behavior

Whale activities were divided into nine categories: rest, travel, socialize, feed, travel+social,

travel+feed, social+feed, travel+social+feed, play, and unknown/other. These activities are described in

Chapter 12. Rest, play and unknown/other were excluded from the analyses either because their sample

sizes were too small (1% rest and 1% play) or because the activities were heterogeneous and/or ill-defined

(unknown/other, 8%). When isolated whales engaged in repeated “aerial behavior”, including breaches,

tail and flipper slaps, and rolls around the longitudinal axis, their activity was generally classified as

“unknown/other” and thus excluded from the present analyses.

Analysis Procedures

For each whale activity, we used ANOVA to test for significant (P ≤ 0.05) year-to-year differences

in each of the four standard measures of SRD cycles. Years for which the sample size was <5 were

excluded. If there were no significant differences among years, we then used ANOVA to determine

whether whales engaged in related activities, e.g., traveling vs. traveling+feeding combined, had similar

SRD cycles. If so, these related activities were combined prior to additional comparisons with other

activities. When ANOVA showed significant differences, we used post hoc tests to determine which

particular groups were different: the Tamhane procedure when variances were unequal (Tamhane 1979),

and otherwise the Bonferroni procedure.

We used multiple regression analysis to identify environmental, temporal, and whale-related variables correlated with the four standard measures of a SRD cycle: number of blows per surfacing, duration

of surfacing, median blow interval, and duration of dive. Procedures were generally consistent with those
13-4 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

of Richardson et al. (1995a,b, MS). Data from calves and all potentially disturbed whales were excluded.

Prior to each multiple regression analysis, data on median blow intervals were logarithmically transformed to compensate for skewness. (This was not necessary for the other three dependent variables.)

Separate multiple regression analyses were done for whales engaged in three specific activities: traveling,

feeding, and socializing.

Twenty-five variables were considered as potential predictors of the four dependent variables:

YEAR: = 1986? = 1998? = 1999? = 2000? (4 measures, each 0 for no or 1 for yes; 1985 was the

standard)

DATE: date, in days after 2 September, and date-squared

TIME: decimal hour (0–24 scale, local time), and hour-squared

LOG.DEPTH: water depth (m), log transformed because of skewness

LOG.DIST: distance from shore (km), log transformed because of skewness

SEA.STATE: sea state (0–5 on Beaufort scale)

ICE.%: percent ice cover

GT.5%.ICE: 1 if greater than 5% ice cover; 0 otherwise

GRP.ACT.T+S: 1 if whale was traveling and socializing; 0 otherwise

GRP.ACT.T+F: 1 if whale was traveling and feeding; 0 otherwise

GRP.ACT.S+F: 1 if whale was socializing and feeding; 0 otherwise

SUBADULT: 1 if whale was a subadult; 0 otherwise

ADULT: 1 if whale was an adult; 0 otherwise

MOTHER: 1 if whale was a mother; 0 otherwise

No. BHD.1KM: estimated number of bowhead whales within 1 km of the focal whale, log transformed because of skewness

GRP.SIZ: estimated number of bowheads within five whale lengths of focal whale

ACT.SOCIAL: 1 if actively socializing; 0 otherwise

PASS.SOCIAL: 1 if passively socializing (“proximity”); 0 otherwise

AERIAL: 1 if aerial behavior(s) seen; 0 otherwise

FLUKE: 1 if pre-dive fluke-out; 0 otherwise

Years and many of the other variables were represented by dummy 0/1 variables (Draper and Smith

1981:241). By not including a dummy variable for 1985, that year was established as the standard year to

which others were compared. Date (in days after 2 September), date2

, hour, and hour2 were included to

allow for possible non-linear temporal effects. Water depths were estimated based on location,

bathometric charts, and NOAA bathometric datasets (as described in Chapter 9).

Predicted variables were included in the regression models if their nominal significance levels were

≤0.05. A forward and backward-stepping procedure was used (Systat Version 9, 1998). We ran each

analysis twice, once forward and once backward, and used the one that ended up with a higher multiple

correlation value. In most situations, the forward and backward procedures produced similar results.

Little emphasis is given to correlations with nominal P > 0.01 given three considerations: (1) the large

number of tests done; (2) the tendency, in stepwise multiple regression, for nominal P-values to overestimate the value of individual variables as predictor variables (Draper and Smith 1981:310); and (3) the
§13. Bowheads: Surfacing, Respiration & Dive Cycles vs. Whale Activity 13-5 

frequent inclusion of data from >1 surfacing or dive by a given whale, with the result that sample sizes

may overestimate actual degrees of freedom (Machlis et al. 1985).

For each whale activity, two multiple regression equations were calculated for each of the four

dependent variables: (1) using all surfacings or dives for which all 25 predictor variables were known,

and (2) using all surfacings or dives for which 22 predictors were known. In the latter case, the three

whale status variables (SUBADULT, ADULT, MOTHER) were excluded. Whale status was unknown

about half the time, so exclusion of these status variables resulted in a notably larger sample size, at the

expense of excluding some potentially important predictor variables.

Results

Whales engaged in feeding and travel exhibited strong year-to-year differences in surfacing, respiration and dive (SRD) cycles; for both of those whale activities, 3 of 4 SRD variables differed significantly among years. Socializing whales showed no significant year-to-year variability in SRD cycles.

Whales engaged in “travel+social” or “travel+feed” showed significant year-to-year variability only in

one variable: median blow interval (ANOVA; P < 0.001, and P = 0.015, respectively). For whales

engaged in combined “social+feed”, durations of surfacings differed among years (ANOVA, P = 0.004).

For combined “travel+social+feed” there were too few data for analysis.

Feeding Whales

In whales categorized as “feeding” (without simultaneous traveling or socializing), the overall

mean of the median blow intervals in 1986 and 1998–99 was 13.08 ± s.d. 6.34 s (n = 324; Appendix

13.1), with yearly means ranging from 12.60 to 13.90 s. (These values, and all others in this chapter,

exclude observations of potentially disturbed bowheads and of calves. Appendix 13.1 tabulates many of

the numerical values mentioned here.) Median blow interval was the one variable that did not differ

significantly among years (ANOVA, P = 0.291; Fig. 13.1A). Number of blows per surfacing averaged

5.89 ± 3.61 (n = 123), with yearly means ranging from 4.38 to 8.33. (Note: Figures 13.1-13.5 show medians, not the means quoted in text, thus accounting for apparent discrepancies.) Year to year variability

was highly significant, with values in 1986 being significantly lower than other years (Fig. 13.1B).

Duration of surfacing averaged 1.28 ± 0.74 (n = 157) min, with yearly means ranging from 1.02 to 1.68.

These surface times varied significantly from year to year, with 1986 values being significantly lower

than for other years (Fig. 13.1C). The overall mean dive duration was 8.94 ± 7.12 (n = 63) min, with

yearly means ranging from 7.37 to 14.95. Dive times varied significantly from year to year (ANOVA,

P = 0.004) with dives in 1999 being significantly longer than in other years (Fig. 13.1D).

Previous studies in the Beaufort Sea during spring and summer have shown that surfacing, respiration, and dive cycles often depend on environmental situations such as water depth (Würsig et al. 1984;

Dorsey et al. 1989; Richardson et al. 1995a,b, MS). In this study area and season, whales feeding in

water >20 m deep had significantly longer surfacings and dives, and more blows per surfacing, than

whales feeding in water ≤20 m deep (P<0.001 in each case; Fig. 13.2). An average surfacing-dive cycle

by an undisturbed whale feeding in shallow (≤20 m) water, calves excluded, consisted of a 1.10 min surfacing with 4.9 ± 3.4 blows followed by a 5.84 ± 5.62 min dive (Appendix 13.1). The median blow intervals averaged 13.1 s. In contrast, an average surfacing–dive cycle by an undisturbed whale feeding in

water deeper than 20 m, calves excluded, consisted of a 1.77 min surfacing with 8.5 blows per surfacing

followed by a 16.09 min dive. Median blow intervals averaged 13.1 s. Water depths for surfacings

categorized as shallow and deep were, respectively, 5–20 m and 28–100 m (means 12 vs. 45 m).
13-6 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

Year

Median Blow Interval (s)

Year

Duration of Surfacing (min)

Year

Duration of Dive (min)

Year

Number of Blows per Surfacing

A. C.

B. D.

5

10

15

20

25

1986 1998 1999

ns ns

132

101

91

0

2

4

6

8

10

12

14

1986 1998 1999

** ns

53

46 24

0

0.5

1.0

1.5

2.0

2.5

1986 1998 1999

** ns

77

50

30

0

5

10

15

20

25

1986 1998 1999

ns *

38

13

11

ns

***

***

**

FIGURE 13.1. Year-to-year comparison of surfacing, respiration, and dive variables for feeding bowhead

whales. Calves and potentially disturbed whales are excluded; individual years are excluded when n < 5. In

the Box plots, the bottom and top lines represent the 10th and 90th quantiles; boxes show 25th, 50th, and 75th

quantiles; numbers are sample sizes. Overall significance of among-year difference (by ANOVA) is shown

at the top of each panel. Significance of differences between adjacent pairs of categories are shown at

bottom, based on the multiple comparison procedures of Tamhane (when variances unequal, panels A, D)

or Bonferroni (when variances equal, panels B, C). Significance levels coded as *** for P ≤ 0.001; ** for

0.001 < P ≤ 0.01; * for 0.01 < P ≤ 0.05; ns for P > 0.10; and in later Figures (*) for 0.05 < P ≤ 0.1.

Appendix 13.1 lists the average percent of time at the surface for each category of whale, and the

average number of blows per minute (“blow rate”). These values are based on dividing mean duration of

surfacing or mean number of blows per surfacing (respectively) by mean duration of surfacing plus mean

duration of dive. Feeding whales were at the surface an average of 12.5% of the time, and their mean

blow rate was 0.58 blows/min.

Traveling Whales

In whales categorized as “traveling” (without simultaneous feeding or socializing), the overall

median blow interval for presumably undisturbed noncalves in 1985–86 and 1998–2000 averaged 16.27 ±

s.d. 4.78 s (n = 108) (Appendix 13.1), with yearly means ranging from 14.58 to 18.09 s. Median blow
§13. Bowheads: Surfacing, Respiration & Dive Cycles vs. Whale Activity 13-7 

5

10

15

20

25

Travel Feed

Deep

 Feed

Shallow

Social

0

2

4

6

8

10

12

14

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0

5

10

15

20

25

Number of Blows per Surfacing

Duration of Surfacing (min) Duration of Dive (min)

Median Blow Interval (s)

A. C.

B. D.

ns

*

***

Travel Feed

Deep

 Feed

Shallow

Social

Travel Feed

Deep

 Feed

Shallow

Social

Travel Feed

Deep

 Feed

Shallow

Social

***

***

***

ns

ns

ns ns

ns ns

Group Activity

Group Activity Group Activity

Group Activity

249

129

195

361

110

33

90

116

125

42

115

158

87

19

44

34

***

***

***

***

FIGURE 13.2. Comparison of surfacing, respiration, and dive variables by whale activity in 1985–86 and

1998–2000. Whale activities are traveling (including travel+feed), feeding in deep and shallow water

(>20 m and ≤20 m), and socializing (including travel+social, social+feed, travel+social+feed). Otherwise

as in Figure 13.1, except that A, C and D used Tamhane multiple comparisons, and B used Bonferroni

multiple comparisons. See Appendix 13.1 for mean ± s.d. values.

intervals did not differ significantly among years (ANOVA, P = 0.121; Fig. 13.3A). Number of blows

per surfacing averaged 6.13 ± 3.33 (n = 68), with yearly means in 1986, 1998, and 2000 ranging from

4.27 to 8.00 during the three years with n > 5. Year to year variability was significant, with values in

2000 being lower than for other years (Fig. 13.3B). Duration of surfacing averaged 1.56 ± 0.97 (n = 75)

min, with means for three years ranging from 0.96 to 2.04. Those surface times differed significantly

among years, with 2000 values being significantly lower than for other years (Fig. 13.3C). The overall

mean dive duration was 13.99 ± 8.09 (n = 66), with means for three years ranging from 9.85 to 18.13.

Those mean dive times differed significantly among years with dives being significantly longer in 1986

than in other years (Fig. 13.3D). On average, traveling bowheads were at the surface 10.0% of the time,

with a mean blow rate of 0.39 blows/min (Appendix 13.1).
13-8 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

Year

Median Blow Interval (s)

A.

5

10

15

20

25

1985 1986 1998 1999 2000

ns ns ns ns

6 39

18

11

34

Year

Number of Blows per Surfacing

0

2

4

6

8

10

12

14

 1986 1998 2000

29

8

26

ns *

Year

Duration of Surfacing (min)

C.

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

 1986 1998 2000

31

8

30

ns *

Year

Duration of Dive (min)

0

5

10

15

20

25

30

 1986 1998 2000

31

6

27

*** ns

A.

B.

C.

D.

ns

***

***

***

FIGURE 13.3. Year-to-year comparison of surfacing, respiration, and dive cycles for traveling bowhead

whales. Otherwise as in Figure 13.1, except that A and D used Tamhane multiple comparisons, and B

and C used Bonferroni multiple comparisons.

We compared the SRD cycles of traveling whales with those of whales engaged simultaneously in

travel plus other activities (travel+feed, travel+social, and travel+social+feed) to determine if some of

these groups could be combined. Median blow intervals and dive durations differed significantly among

these whale activities (Fig. 13.4A,D). Multiple comparisons showed no differences between travel and

travel+feed, but occurrence of socializing along with travel did result in altered blow intervals and dive

durations. Number of blows per surfacing did not vary significantly among the various categories of

traveling whales (P = 0.258; Fig. 13.4B), and the differences in duration of surfacing were not large (P =

0.026; Fig. 13.4C). Again, multiple comparisons showed no significant difference between travel and

travel+feed (Fig. 13.4B,C).

Thus, it was appropriate to combine SRD data for whales in the “travel” and the “travel+feed”

categories. For these whales, an average surfacing–dive cycle consisted of a 1.65 min surfacing and a

13.66 min dive. There was an average of 6.4 blows per surfacing. Median intervals between successive

blows within a surfacing averaged 15.76 s (Appendix 13.1). On average, these bowheads were at the

surface 10.8% of the time, with a mean blow rate of 0.42 blows/min (Appendix 13.1).
§13. Bowheads: Surfacing, Respiration & Dive Cycles vs. Whale Activity 13-9 

5

10

15

20

25

0

2

4

6

8

10

12

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

0

5

10

15

20

25

Number of Blows per Surfacing

Duration of Surfacing (min) Duration of Dive (min)

Median Blow Interval (s)

A. C.

B. D.

ns ( ) *** *

*** ns ns

ns ns

ns

78

108

141

19

51 68

42

55

75 50

16

66

21

Travel

+ Social

Travel Travel

+ Feed

Travel

+ Social

+ Feed

Travel

+ Social

 Travel Travel

+ Feed

Travel

+ Social

 Travel Travel

+ Feed

Travel

+ Social

 Travel Travel

+ Feed

Group Activity

Group Activity Group Activity

Group Activity

***

*** ns

*

Figure 13.4. Comparison of surfacing, respiration, and dive variables for traveling bowhead whales with

and without other activities in 1985–86 and 1998–2000. Otherwise as in Figure 13.1, except that A, C

and D used Tamhane multiple comparisons, and B used Bonferroni multiple comparisons. See Appendix

13.1 for mean ± s.d. values.

Traveling whales (travel and travel+feed combined) were then compared to whales engaged in

feeding and socializing. Traveling whales had similar surface and dive times as whales feeding in water

>20 m deep (Fig. 13.2C,D). However, traveling whales had significantly longer surface and dive times

than whales feeding in water ≤20 m deep or socializing whales (P = 0.003 for surface times of traveling

vs. socializing whales; otherwise P < 0.001; Fig. 13.2C,D). Median blow intervals of traveling whales

were significantly higher than for whales engaged in feeding or social activities (Fig. 13.2A). Number of

blows per surfacing for traveling whales differed significantly from that for whales feeding in deep or in

shallow water (P = 0.012 and P = 0.014, respectively; Fig. 13.2B).
13-10 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

Group Activity

Number of Blows per Surfacing

Group Activity

Duration of Surfacing (min)

Group Activity

Duration of Dive (min)

Group Activity

Median Blow Interval (s)

A. C.

B. D.

5

10

15

20

25

30

35

59

78

205

19

Social Travel

Social

Social

 Feed

Travel

Social

 Feed

** ns ns

Social Travel

Social

Social

 Feed

0.0

0.5

1.0

1.5

2.0

2.5

3.0

20

55 82

ns ns

ns 0

2

4

6

8

10

12

14

ns

Social Travel

Social

Social

 Feed

18

51

46

Social Travel

Social

Social

 Feed

0

5

10

15

20

7

16

9

ns ns

*** ns

ns ns

Figure 13.5. Comparison of surfacing, respiration, and dive variables for socializing bowhead whales

with and without other activities in 1985–86 and 1998–2000. Otherwise as in Figure 13.1, except that all

multiple comparisons used the Tamhane procedure for unequal variances. See Appendix 13.1 for mean

± s.d. values.

Socializing Whales

We compared SRD cycles of socializing whales with those of whales engaged simultaneously in

socializing plus other activities (social+travel, social+feed, and travel+social+ feed) to determine if some

of these activities could be combined. Median blow intervals differed significantly among these whale

activities, but multiple comparisons showed no significant difference between social and travel+social, or

between social and travel+social+feed (P = 0.590 and 0.345, respectively; Fig. 13.5A). Number of blows

per surfacing, duration of surfacing, and duration of dive did not differ significantly among these whale

activities (ANOVA, P = 0.387, 0.436, 0.142, respectively; Fig. 13.5B,C,D).
§13. Bowheads: Surfacing, Respiration & Dive Cycles vs. Whale Activity 13-11 

Thus, it seemed appropriate to combine SRD data for all activities involving social activity (i.e.,

social, travel+social, social+feed, travel+social+feed). An average surfacing–dive cycle by an undisturbed socializing bowhead, calves excluded, consisted of a 1.29 min surfacing and a 5.54 min dive. There

was an average of 6.0 blows per surfacing. Intervals between successive blows within a surfacing

averaged 12.67 s (Appendix 13.1). On average, these bowheads were at the surface 18.9% of the time,

with a mean blow rate of 0.88 blows/min (Appendix 13.1).

Socializing whales were then compared to whales engaged in traveling and feeding. Socializing

whales had similar SRD cycles as whales feeding in water ≤20 m deep (Fig. 13.2A–D). Median blow

interval for socializing whales was significantly lower than for traveling whales (P < 0.001; Fig. 13.2A).

Number of blows per surfacing was significantly lower in socializing whales than in whales feeding in

water >20 m deep (P = 0.002; Fig. 13.2B). Surface and dive times were significantly shorter for socializing whales than for traveling whales or whales feeding in deep water (P = 0.003 for surface times of

socializing vs. traveling whales; otherwise P < 0.001; Fig. 13.2C,D).

Factors Related to Surfacing, Respiration and Dive Cycles

The preceding analyses describe relationships of surfacing, respiration, and dive variables to three

whale activities and various combinations thereof, along with years and (for feeding whales) water depth.

However, some of these factors are interrelated, such as the depths where whales tended to occur in

different years, and other potentially important factors have not yet been considered. Multiple regression

analysis was used to help assess the relationships of SRD variables to various environmental, temporal,

and whale-related variables.

Feeding Whales.All four surfacing respiration and dive variables had significant simple correlations

with several predictor variables (Table 13.2, columns headed “r”). For example, all four behavior variables for

feeding whales tended to be low in 1986, as evident from the negative correlations with “1986”, and high in

1999. All four variables tended to be higher in deeper water and with greater distance from the shore. All four

variables tended to be higher when there was some traveling intermixed with feeding.

When all 25 predictor variables were considered for inclusion in multiple regression equations, all

four measures of SRD cycles tended to be correlated with whale status after allowance for other variables.

Values tended to be high for mothers and/or low for subadults (Table 13.2, columns headed “rp”). Other

predictor variables that showed strong (nominal P ≤ 0.01) partial correlations with one or more of the

SRD variables were year 2000, date, number of bowheads within 1 km, and flukes-out when diving.

When whale status was excluded from the multiple regression equation, thereby increasing sample

sizes, all four behavior variables tended to be higher with increased distance from the shore (Table 13.2,

columns headed “status excluded rp”). Since water depth and distance from the shore are strongly intercorrelated (r = 0.910 – 0.917), it can also be said that all four SRD variables tended to be higher in deeper

water, which is what we saw in Figure 13.2. The strong positive relationships of the SRD variables to

distance from shore very likely occurred because adult whales tended to occur farther offshore (Chapter

10), and adults tended to have higher values of all four SRD variables (Chapter 14). Other variables that

showed strong (nominal P ≤ 0.01) partial correlations with one or more of the SRD variables were date,

time, group activity = travel+feed, number of bowheads within 1 km, group size, and flukes-out.

Traveling Whales.All four surfacing respiration and dive variables had significant simple

correlations with several predictor variables (Table 13.3). For example, all four SRD variables for

traveling whales tended to be high in 1986 and with increasing sea states. All four variables were higher

for mothers and/or adults and lower for subadults.
Predictor variable stat. exc. stat. exc. stat. exc. 

Name Scale r r p r p r r p r p r r p r p r 

1986 0-1 - - - - - - - - - - - 

1998 0-1 + ns +++ ns 1999 0-1 ++ +++ (+) ++ 2000 0-1 (-) - - - ns ns - 1-34 +++ +++ +++ ++ ns - - - - - - ++ Date2 (1-34)2 +++ ++ - - - ns (+

Time 0-24 ++ - ns +++ - - - (+

Time2 (0-24)2 ++ + ns +++ +++ + Sea State Bf ns ns - +++ + ns Ice Cover % + ns ns ns 

0-1 ++ + + ns ns Dist. From Shore log (km) +++ +++ +++ +++ +++ +++ ++

Water Depth log (m) +++ +++ +++ ++

0-1 +++ (+) +++ + ++ +

0-1 ns ns - - - ns0-1 ns ns ns ns

Subadultb 0-1 - - - (-) Exc. ns - - Exc. - - - - Exc. - 

Adultb 0-1 ns Exc. ns Exc. ns Exc. ns Motherb 0-1 +++ ++ Exc. ns Exc. +++ +++ Exc. ns No. Bhd. Within 1 km log No. ns ns - - - - - - - -

Group Size 1-4 ns ns +++ ++ ns

0-1 ns ns - - ns ns0-1 ns ns ns ns0-1 ns ns (+) ns0-1 + + +++ +++ +++ - - - - - - - - - ns

Sample size 290 121 286 212 98 208 689 243 567 94 

Multiple correlation 0.482 0.438 0.592 0.514 0.648 0.476 

Adjusted % var. explained 21.3 17.4 30.8 24.6 40.2 21.5 Overall significance *** *** *** *** *** *** 

a Median blow intervals were log transformed to avoid skewness.b 0 = false, 1 = true.

Pre-dive Flukes-outb

Note: Pluses indicate positive and significant correlations or partial correlations; minuses indicate negative relationships: ns, P > 0.1; (+) or (-), 0.05 

P < 0.05; ++ or - - , 0.001 < P < 0.01; +++ or - - -, P < 0.001. Calves and potentially disturbed whales are excluded.

Group Activ = Trav.+Soc.+Feedb

Active Socializ.bPassive Socializ.bAerial Behav.bDate (1 = 3 Sept.)>5% Ice CoverbGroup Activ = Trav. + FeedbGroup Activ = Soc. + Feedb

surfacing (min) surfacing interval (s)a 

TABLE 13.2. Comparison of surfacing, respiration, and diving behavior of bowheads feeding in the Eastern Alaskan Be

and 1998-2000) before and after allowance for environmental, temporal, and whale-related variables. Symbols shonominal significance of correlations between a dependent variable (top) and various environmental, temporal, activit(predictors, left). For each dependent variable, the three columns summarize the simple correlations (r ) and partial co

three whale status variables are included or excluded.

Duration of No. blows per Median blow 
Predictor variable

stat. exc. stat. exc. stat. exc. 

Name Scale r r p r p r r p r p r r p r p 

1986 0-1 (+) - - - + - - - - - - (+) +

1998 0-1 ns ns ns n1999 0-1 + (+) ns n2000 0-1 - - - - - - - - - - - - - - - - - - ns 

1-34 ns ns ns n

Date2 (1-34)2 ns ns (-) n

Time 0-24 ns (+) + ns Time2 (0-24)2 ns (+) ns 

Sea State Bf + (+) + +++ +Ice Cover % + (+) ns ++ n

0-1 ++ + ns 

Dist. From Shore log (km) + + ns ++ +

Water Depth log (m) (+) (+) ns +

0-1 - - - ns - - - - - - 0-1 + (+) ns n0-1 ns ns - - - - n

Subadultb 0-1 - - - - - - Exc. - - - - - - Exc. - - - Exc. - 

Adultb 0-1 ++ Exc. +++ Exc. ns Exc. +

Motherb 0-1 ns Exc. ns Exc. +++ +++ Exc. nNo. Bhd. Within 1 km log No. ns ns - - - - Group Size 1-4 ns + ns + ns + n

0-1 ns ns - - - - - - n

0-1 ns ns ns + - 0-1 ns ns ns n0-1 ns ns - - - - - - n

Sample size 181 121 181 162 109 162 346 182 318 1Multiple correlation 0.539 0.366 0.627 0.392 0.583 0.387 

Adjusted % var. explained 27.8 11.9 37.6 13.8 31.8 13.9 Overall significance *** *** *** *** *** *** 

Aerial Behav.b

Date (1 = 3 Sept.)>5% Ice Coverb

TABLE 13.3. Comparison of surfacing, respiration, and diving behavior of bowheads traveling in the Eastern Alaskan B

and 1998-2000) before and after allowance for environmental, temporal, and whale-related variables. Symbols show the significance of correlations between a dependent variable (top) and various environmental, temporal, activity, and age left). For each dependent variable, the three columns summarize the simple correlations (r ) and partial correlations (

status variables are included or excluded.

Group Activ = Trav.+Soc.+FeedbActive Socializ.bPassive Socializ.b

Duration of No. blows per Median blow 

interval (s)a

Group Activ = Trav. + Soc.b

b 0 = false, 1 = true.

Group Activ = Trav. + Feedb

surfacing (min) surfacing

a Median blow intervals were log transformed to avoid skewness.

Pre-dive Flukes-outb

Note: Pluses indicate positive and significant correlations or partial correlations; minuses indicate negative relationships: ns, P > 0.1; (+) or (-), 0.05 < 0.05; ++ or - - , 0.001 < P < 0.01; +++ or - - -, P < 0.001. Calves and potentially disturbed whales are excluded.
13-14 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

When all 25 predictor variables were considered for inclusion in a multiple regression equation, all

four behavior variables tended to be correlated with whale status. Values tended to be high for mothers or

low for subadults (Table 13.3, columns headed “rp”). Other variables that showed strong (nominal P ≤

0.01) partial correlations with one or more of the behavior variables were year 1986 and year 2000, time,

ice cover, distance from shore, group activity = travel+social, and group activity = travel+social+feed.

When whale status was excluded from the multiple regression equation, all four behavior variables

tended to increase with increasing group size, although not very strongly (0.01 < nominal P ≤ 0.05 in each

case; Table 13.3). Other variables that showed strong (nominal P ≤ 0.01) partial correlations with one or

more of the behavior variables were years 1986 and 2000, time, sea state, distance from shore, group

activity = travel+social, number of bowheads within 1 km, active socializing, and flukes.

Socializing Whales.Median blow interval was the only SRD variable that showed strong (P ≤

0.01) simple correlations with any of the predictor variables (Table 13.4). For example, median blow

intervals of socializing whales tended to be short in 1986, and when socializing was intermixed with feeding (as evident from the negative correlations). Median blow intervals showed significant positive correlations with numerous other variables (Table 13.4).

When all 25 predictor variables were considered for inclusion in a multiple regression equation,

median blow interval tended to be longer for mothers, with high sea states, and when passive socializing

was occurring (Table 13.4, “rp” column). Duration of surfacing and number of blows per surfacing showed very little relationship to the predictor variables, with multiple correlation coefficients of 0.350 and

0.502, respectively. The sample size for “duration of dive” was too low for a meaningful multiple regression analysis of that variable.

When whale status was excluded from the multiple regression equation, median blow interval

tended to be longer with greater distance from shore, and shorter later in the season and during dives

terminating with “flukes out” (Table 13.4).

Discussion

Feeding Whales

Whales engaged in feeding showed among-year variability in SRD variables. There were noticeable increases in the number of blows per surfacing, duration of surfacings, and duration of dives across

years (Fig. 13.1). Some of this year-to-year variability may be attributable to the water depths in which

the whales were feeding. In 1986, 93% of the surface–dive cycles by feeding whales occurred in shallow

(≤20 m) water. In contrast, in 1998, 72% were in shallow water; in 1999, none were in shallow water.

Bowheads in the Beaufort Sea concentrate their feeding at places and depths where zooplankton concentrates (Chapter 6). Richardson et al. (1995a) described how differences in depths of prey concentrations

likely cause differences in SRD cycles of bowheads. When the prey is deep, whales feed most efficiently

if dives are long. This minimizes the proportion of feeding time spent in descent and ascent. If dives are

long, whales must respire more times per surfacing and are likely to remain at the surface longer. When

the present observations in the Eastern Alaskan Beaufort Sea were split into shallow (≤20 m) and deeper

(28–100 m, mean 45 m) water, we found significant increases in the duration of surfacings and dives, and

more blows per surfacing, for bowheads feeding in deeper water (Fig. 13.2).
Predictor variable 

stat. exc. stat. exc. stat. 

Name Scale r r p r p r r p r p r r p r p 

1986 0-1 ns + ns - - - 1998 0-1 (-) ns - ++ + - 1999 0-1 ns ns + 2000 0-1 (-) - (-) - - (+) 

1-34 ns (+) + ns - - 

Date2 (1-34)2 (+) (+) - ns 

Time 0-24 ns ns (+) Time2 (0-24)2 ns ns (+) 

Sea State Bf ns ns +++ +++ Ice Cover % + ns ns 

0-1 + + ns ns 

Dist. From Shore log (km) ns ns +++ +++ ++

Water Depth log (m) ns ns +++ 

0-1 ns ns ++ + 0-1 ns ns - - - 

0-1 ns ns ns 

Subadultb 0-1 ns Exc. ns Exc. - Ex

Adultb 0-1 (+) Exc. + Exc. ns ExMotherb 0-1 ns Exc. ns Exc. +++ +++ ExNo. Bhd. Within 1 km log No. (+) (+) ns Group Size 1-4 ns ns +++ 

0-1 ns ns ++ 0-1 ns ns ++ ++ 0-1 ns ns +++ 0-1 ns (+) ns - 

Sample size 158 49 138 116 41 103 361 92 31Multiple correlation 0.350 0.254 0.502 0.341 0.655 0.3

Adjusted % var. explained 10.4 5.1 23.2 8.0 40.3 13

Overall significance * * *** * *** **

a Median blow intervals were log transformed to avoid skewness.b 0 = false, 1 = true.c not enough data to run a multiple regression analysis.

Group Activ = Soc. + Feedb

Duration of No. blows per Median blow

surfacing (min) surfacing interval (s)a

Group Activ = Trav.+Soc.+FeedbDate (1 = 3 Sept.)Note: Pluses indicate positive and significant correlations or partial correlations; minuses indicate negative relationships: ns, P > 0.1; (+) or (-), 0.0

0.01 < P < 0.05; ++ or - - , 0.001 < P < 0.01; +++ or - - -, P < 0.001. Calves and potentially disturbed whales are excluded.

TABLE 13.4. Comparison of surfacing, respiration, and diving behavior of bowheads socializing in the Eastern Alas

(1985-86 and 1998-2000) before and after allowance for environmental, temporal, and whale-related variables. Sdirection and nominal significance of correlations between a dependent variable (top) and various environmental, temage variables (predictors, left). For each dependent variable, the three columns summarize the simple correlatiocorrelations (r p ) when three whale status variables are included or excluded.

Active Socializ.bPassive Socializ.bAerial Behav.bPre-dive Flukes-outb>5% Ice CoverbGroup Activ = Trav. + Soc.b
13-16 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

The multivariate analysis allowed us to examine the relative importance of several factors potentially affecting the SRD variables of bowheads feeding in the Eastern Alaskan Beaufort Sea while taking

into account the effects of other factors. Two important overall results were evident. (1) For all four

SRD variables analyzed, whale status (age) had a strong effect. As compared with subadults, the larger

and older whales (mothers and adults) tended to have longer surfacings and dives, with more blows and

longer blow intervals. (2) When whale status was excluded from the multivariate analysis, all four behavioral variables were higher with increased distance from shore. Whale status and distance from shore

were strongly intercorrelated—mothers and adults tended to occur farther offshore than subadults (see

also Chapter 10). Also, distance from shore is strongly correlated with water depth, so it can also be said

that all four SRD variables were higher in deeper water.

Multivariate analyses have important limitations when applied to uncontrolled field data with many

intercorrelated predictor variables (James and McCulloch 1990). Given these intercorrelations, it is

difficult to determine which factor(s) had a direct influence on SRD variables. However, when whale

status, distance from shore, and water depth were all considered as potential predictors, there were stronger partial correlations with whale status than with distance from shore or water depth (Table 13.2). This

suggests that whale status may have had a more direct influence.

Our results for bowhead whales feeding in water >20 m deep can be compared with those for bowheads feeding in Baffin Bay in water >50 m deep (Richardson et al. 1995a). Average dive durations during these situations were similar: 15.80 min in Baffin Bay vs. 15.73 min 3 in this study. However,

surfacing and respiration parameters had significantly higher mean values in Baffin Bay (Table 13.5).

The differences are probably related mainly to water depth. In our study, most “deep water” feeding was

in water 28–100 m deep (mean 45 m), whereas in the Baffin Bay study most of the observed feeding was

in water 100–250 m deep. This difference may account for the higher surface and respiration times seen

in the Baffin Bay study. The differences between the two areas would be even more striking if the whales

feeding in shallow (≤20 m) parts of the present study area were considered; no shallow-water feeding was

seen in the Baffin Bay study.

SRD values for bowheads in the Canadian Beaufort Sea in summer (mainly August) have been reported

by Dorsey et al. (1989), but average values for all feeding whales observed in summer were not

specifically reported. SRD data for the fraction of those bowheads that were observed feeding in waters

>50 m deep were reported by Richardson et al. (1995a). However, their analysis also included the few

September 1985–86 data from deep (>50 m) parts of the present study area, and thus are not entirely

independent of the present data. Therefore, we have redone the summer analysis to make the data directly

comparable and non-overlapping. Median blow intervals were similar for feeding whales (deep and

shallow water) in both studies (Table 13.5). Duration of surfacing was significantly lower in the Canadian Beaufort for whales feeding in deep water, but there was little difference for whales feeding in

shallow water (Table 13.5). Number of blows per surfacing and mean dive duration were significantly

lower in the Canadian Beaufort for feeding in both deep and shallow water (Table 13.5).

 

3

 Some SRD values quoted here and in Table 13.5 differ slightly from corresponding values quoted in “Results”

because “mothers” are excluded from Table 13.5. This was done in order to allow direct comparisons with other

studies where “mothers” were excluded or absent. Appendix 13.1 summarizes the SRD values for “mothers” vs.

“others” as observed during the present study.
Group Activity

Status mean s.d. n mean s.d. n mean s.d. n mean s.d. n mean s.d. n mean s.d. n mean s

Feed Deep 12.73 3.93 114 8.68 2.77 31 1.73 0.56 38 15.73 5.07 15 13.36 8.54 264 3.74 2.67 114 0.91 0.

Comp. test ns' ***' *** ***'

Feed Shallow 13.08 7.54 195 4.93 3.40 90 1.10 0.71 115 5.84 5.62 44 14.04 7.45 330 3.94 3.06 145 1.25 1.

Comp. test ns * ns' ***'

All Sociald 12.42 5.59 341 6.14 3.77 108 1.27 0.72 149 5.67 5.35 26 13.77 6.39 445 4.21 2.94 230 1.12 0.

Comp. test ***' *** (*) **'

Travel 16.03 4.91 98 6.08 3.43 62 1.52 0.99 69 13.83 8.10 61 17.10 6.01 86 6.00 3.54 76 1.49 0.

Comp. test ns' ns' ns ***'

Social 15.25 8.68 59 5.83 5.07 18 1.08 0.82 20 4.50 2.67 7 17.70 11.62 50 2.10 2.86 35 1.19 1.

Comp. test ns' ** ns' *'

Feed Deep 12.73 3.93 114 8.68 2.77 31 1.73 0.56 38 15.73 5.07 15 16.90 3.70 86 17.30 6.72 23 4.74 1.

Comp. test ***' *** ***' ns'

Travel 16.03 4.91 98 6.08 3.43 62 1.52 0.99 69 13.83 8.10 61 18.08 7.64 451 5.02 3.30 355 1.35 1.

Comp. test ***' *' ns ***'

d All Social includes whales engaged in socializing, travel+social, social+feed, and travel+social+feed.

TABLE 13.5. Comparisons of surfacing, respiration and dive variables between the current study and three other s

bowhead whales. "Feed Deep" includes all whales feeding in water > 20 m, and "Feed Shallow" includes all whales fee

Mothers and calves were excluded in all studies for these comparisons. Comparisons are based on t -tests. Where thmodified t -test assuming unequal variances was used. Asterisks show significance levels as in Figure 13.1.

Canadian Beaufort Sea, Sum

Baffin Bay, Fallb

Beaufort Sea, Spring at Bar

a Canadian Beaufort data reanalyzed to make them comparable to the current study. Only August data were used, and for feeding whales only data in 

and 100 m were used.

Blow Intervals (s) Dive (min) Blow Intervals (s)

b Baffin Bay data are from Richardson et al. (1995a).c Spring Barrow data are from Richardson et al. (1995b).

Eastern Alaskan Beaufort Sea, Fall (Current Study) Other Study

Median Number of Blows Duration of Duration of Median

per Surfacing Surfacing (min)

Number of Blows Durati

per Surfacing Surfacin
13-18 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

Traveling Whales

Whales engaged in traveling showed significant among-year variability in 3 of 4 SRD variables.

There were noticeable decreases in the number of blows per surfacing, the duration of surfacings, and the

duration of dives from year 1986 to 2000 (Fig. 13.3). Some of this variability may be attributable to the

proportion of small whales observed each year. In 1986, 8% of the documented surface–dive cycles by

traveling whales whose status was determined involved subadults; in 2000, 45% involved subadults. For

traveling (and feeding) bowheads, subadult whales have shorter surfacings and dives with fewer blows

per surfacings than adult whales (Tables 13.2, 13.3; see also Chapter 14).

Traveling whales, including those engaged in both traveling and feeding, tended to have SRD

cycles similar to those of whales feeding in water >20 m deep (Fig. 13.2). Some of this similarity may be

attributable to the habitat that the whales are occupying. Traveling whales tended to occur in deeper areas

(Chapter 12), including some of the areas used by whales feeding in deep water.

Two important overall results from the multivariate analysis were as follows: (1) For traveling

whales, like feeding whales, whale status (age) had a strong influence on all four SRD variables. As compared with other whales, subadults tended to have short surfacings and dives with few blows per surfacing. Mothers tended to have long intervals between blows. (2) When whale status was excluded from the

multivariate analysis, all four behavioral variables were higher with larger group sizes.

Traveling whales observed in our September study had surfacing and respiration parameters similar to

those of bowheads migrating along the coast of Baffin Island in autumn (Richardson et al. 1995a).

However, the mean duration of dives was significantly higher in our study than in the Baffin Bay study

(Table 13.5). SRD values for bowheads migrating near Barrow, Alaska, in spring (Richardson et al.

1995b, MS) showed significantly higher median blow intervals and significantly lower dive durations and

number of blows per surfacing than whales traveling in our study (Table 13.5). Ice cover was often heavy

(1–80%) in the Barrow study, but usually light (<10%) in our study and the Baffin Bay study. The shorter mean duration of dives documented in spring may have been, at least in part, an artifact of the ice

conditions. Heavy ice conditions often make it difficult to re-sight whales after long dives, resulting in

more serious underestimation of average dive durations when there is much ice. Consistent with this,

dive durations documented for migrating bowheads in the Alaskan Beaufort in autumn 1983 (a heavy ice

year) were significantly shorter than those in 1985–86 with little ice (Richardson et al. 1995a).

Socializing Whales

Whales engaged in socializing were compared with those exhibiting other activities that included

socializing: social+travel, social+feed, and travel+social+feed. The SRD variables of socializing whales

were similar for whales engaged in all activities involving socializing (Fig. 13.5). Socializing whales and

whales feeding in shallow water tended to have similar breathing characteristics―relatively short surfacings and dives with few blows per surfacing and short intervals between blows (Fig. 13.2). Some of this

similarity may be attributable to the habitat that the whales were occupying. Most of these activities

occurred in shallow water.

Results from the multivariate analysis were quite different from those for feeding and traveling

whales. There was little relationship between duration of surfacing or number of blows per surfacing and

the environmental, temporal, and whale-related variables considered in this study (Table 13.4). However,

there were significant simple and partial correlations between blow intervals and several predictor variables.
§13. Bowheads: Surfacing, Respiration & Dive Cycles vs. Whale Activity 13-19

Socializing whales observed in our study had significantly longer dives and more blows per

surfacing than bowheads socializing in Baffin Bay (Richardson et al. 1995a) or the Canadian Beaufort

Sea during late summer (Table 13.5). Duration of surfacing was slightly higher (P = 0.07) and median

blow interval was significantly lower in our study than in the Canadian Beaufort Sea (Table 13.5).

Reasons for these differences are uncertain, but may relate to differences in the physical circumstances of

the observations, the age/status of the animals observed, or the relative intensity and frequency of social

activity in the various regions and seasons. The Canadian Beaufort observations were in August, in a

wide variety of locations with differing water depths, distances from shore, and ages of whales. The

Baffin Bay data came from late August and early September, <4 km from shore in water ≤50 m deep, in

an area occupied mainly by subadult whales. The present data were mainly from September, >4 km from

shore and in areas occupied by whales of varying ages (see Chapter 10). The estimated number of

bowheads within 1 km was usually greater in our study and the Canadian Beaufort study than in the

Baffin Bay study, but the socializing observed in Baffin Bay was often quite boisterous.

Summary

Data on surfacing, respiration and dive (SRD) cycles of bowhead whales during late summer and

early autumn were needed to derive correction factors for whales missed during aerial surveys, and as a

basis for analyses of bowhead energetics. Bowheads were observed systematically during September and

early October of 1985–86 and 1998–2000 in the Eastern Alaskan Beaufort Sea and adjacent Canadian

waters (Flaxman Island to Herschel Island). Bowhead behavior was observed from an aircraft circling at

an altitude of ≥457 m (≥1500 ft), high enough to avoid significant aircraft disturbance. Data collected

near other human activities were excluded. We documented the durations of surfacings and dives,

number of blows (respirations) per surfacing, and intervals between successive blows. These four

variables were defined as in our recent studies of bowhead behavior in other seasons and regions. We

first summarized the SRD variables for various categories of whale activity, year, and (for feeding

whales) water depth. The main bowhead activities distinguished here are feeding, traveling, and socializing. Then we used multiple regression to assess the joint effects of these and other temporal, environmental, and whale-behavior variables on the four measures of SRD cycles.

Whales engaged in feeding showed a noticeable increase in the number of blows per surfacing and

the durations of surfacings and dives across years. Some of this variability may be attributable to the

water depth in which the whales were feeding. In the 1980s most of the observed surfacing–dive cycles

occurred in shallow (≤20 m) water, whereas in the 1990s more of observations came from deeper water.

An average SRD cycle by an undisturbed bowhead feeding in shallow (≤20 m) water, calves excluded,

consisted of a 1.10 min surfacing with 4.9 blows spaced 13.1 s apart, followed by a 5.84 min dive. A

corresponding average SRD cycle in water >20 m deep (average 45 m) consisted of a 1.77 min surfacing

with 8.5 blows spaced 13.1 s apart, followed by a 16.09 min dive. Whale status and distance from shore

had a strong effect on the SRD cycles of bowheads feeding in and near the Eastern Alaskan Beaufort Sea.

During feeding, surfacings and dives were longer, with more blows per surfacing and longer intervals

between blows, with increasing distance from shore, and for older, larger whales as compared with

subadults.

Traveling bowheads (including those feeding while traveling) tended to have surfacing and dive

cycles similar to those of bowheads feeding in water >20 m deep. Some of this similarity may be attributable to the habitat that the whales are occupying, as traveling whales tended to be in water >20 m deep.

An average SRD cycle by a traveling bowhead (including bowheads that were feeding as they traveled)

consisted of a 1.65 min surfacing with 6.4 blows spaced 15.76 s apart, followed by a 13.66 min dive.
13-20 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

Whale status and group size had a strong influence on the SRD cycles of bowheads traveling in and near

the Eastern Alaskan Beaufort Sea. The standard measures of these cycles were higher for mothers and for

increased group sizes, and were shorter for subadults.

Socializing whales and whales feeding in shallow water tended to have similar breathing characteristics. Some of this similarity may be attributable to the habitat (shallow water) that the whales were

occupying. An average SRD cycle by a socializing bowhead (including bowheads that intermixed socializing with other activities) consisted of a 1.29 min surfacing with 6.0 blows spaced 12.67 s apart, followed by a 5.54 min dive.

Acknowledgements

We thank the numerous LGL personnel, aircraft charter companies, and pilots who assisted in

collecting the behavioral data over the years. The U.S. Minerals Management Service, Alaska OCS

Region, sponsored the 1998–2000 work and the majority of the 1985–86 work. A second study in 1986

was sponsored by Shell Western Exploration and Production. These projects were conducted under the

provisions of Scientific Research Permits 517, 518 and 481–1464 issued by the National Marine Fisheries

Service to LGL Ltd. Work in Canadian waters was authorized under permits issued by the Canadian

Department of Fisheries and Oceans and in consultation with the Inuvialuit. Many other Acknowledgements relevant to the project as a whole are included in Chapter 1.

Literature Cited

Dorsey, E.M., W.J. Richardson and B. Würsig. 1989. Factors affecting surfacing, respiration, and dive behaviour

of bowhead whales, Balaena mysticetus, summering in the Beaufort Sea. Can. J. Zool. 67(7):1801-1815.

Draper, N.R. and H. Smith. 1981. Applied regression analysis, 2nd ed. John Wiley, New York, NY. 709 p.

James, F.C., and C.E. McCulloch. 1990. Multivariate analysis in ecology and systematics: panacea or Pandora’s

box? Annu. Rev. Ecol. Syst. 21:129-166.

Koski, W.R. and S.R. Johnson. 1987. Behavioral studies and aerial photogrammetry. Chapter 4 (124 p.) In: LGL

and Greeneridge, Responses of bowhead whales to an offshore drilling operation in the Alaskan Beaufort

Sea, autumn 1986. Rep. from LGL Ltd., King City, Ont., and Greeneridge Sciences Inc., Santa Barbara, CA,

for Shell Western E & P Inc., Anchorage, AK. 371 p.

Koski, W.R., R.A. Davis, G.W. Miller and D.E. Withrow. 1992. Growth rates of bowhead whales as determined

from low-level aerial photogrammetry. Rep. Int. Whal. Comm. 42:491-499

Machlis, L., P.W.D. Dodd and J.C. Fentress. 1985. The pooling fallacy: problems arising when individuals contribute more than one observation to the data set. Z. Tierpsychol. 68:201-214.

Patenaude, N.J., W.J. Richardson, M.A. Smultea, W.R. Koski, G.W. Miller, B. Würsig and C.R. Greene Jr. 2002.

Aircraft sound and disturbance to bowhead and beluga whales during spring migration in the Alaskan

Beaufort Sea. Mar. Mamm. Sci. 18(2): 309-335.

Richardson, W.J. (ed.). 1987. Importance of the eastern Alaskan Beaufort Sea to feeding bowhead whales, 1985-

86. OCS Study MMS 87-0037. Rep. from LGL Ecol. Res. Assoc. Inc., Bryan, TX, for U.S. Minerals

Manage. Serv., Reston, VA. 547 p. NTIS PB88-150271.

Richardson, W.J. and K.J. Finley. 1989. Comparison of behavior of bowhead whales of the Davis Strait and

Bering/Beaufort stocks. OCS Study MMS 88-0056, LGL Rep. TA 833-1. Rep. from LGL Ltd., King City,

Ont., for U.S. Minerals Manage. Serv., Herndon, VA. 131 p. NTIS PB89-195556.
§13. Bowheads: Surfacing, Respiration & Dive Cycles vs. Whale Activity 13-21

Richardson, W.J., M.A. Fraker, B. Würsig and R.S. Wells. 1985. Behaviour of bowhead whales Balaena

mysticetus summering in the Beaufort Sea: reactions to industrial activities. Biol. Conserv. 32(3):195-230.

Richardson, W.J., B. Würsig and C.R. Greene Jr. 1986. Reactions of bowhead whales, Balaena mysticetus, to

seismic exploration in the Canadian Beaufort Sea. J. Acoust. Soc. Am. 79(4):1117-1128.

Richardson, W.J., K.J. Finley, G.W. Miller, R.A. Davis and W.R. Koski. 1995a. Feeding, social and migration

behavior of bowhead whales, Balaena mysticetus, in Baffin Bay vs. the Beaufort Sea―regions with different

amounts of human activity. Mar. Mamm. Sci. 11(1):1-45.

Richardson, W.J., C.R. Greene Jr., J.S. Hanna, W.R. Koski, G.W. Miller, N.J. Patenaude and M.A. Smultea, with

R. Blaylock, R. Elliott and B. Würsig. 1995b. Acoustic effects of oil production activities on bowhead and

white whales visible during spring migration near Pt. Barrow, Alaska―1991 and 1994 phases. OCS Study

MMS 95-0051; LGL Rep. TA954. Rep. from LGL Ltd., King City, Ont., for U.S. Minerals Manage. Serv.,

Herndon, VA. 539 p. NTIS PB98-107667.

Richardson, W.J., W.R. Koski, G.W. Miller, N.J. Patenaude and B. Würsig. MS. Behavior and movements of

bowhead whales (Balaena mysticetus) during spring migration in the Alaskan Beaufort Sea.

Tamhane, A.C. 1979. A comparison of procedures for multiple comparisons. J. Am. Stat. Assoc. 74:471-480.

Würsig, B., and C. Clark. 1993. Behavior. p. 157-199 In: J.J. Burns, J.J. Montague and C. J. Cowles (ed.), The

bowhead whale. Spec. Public. 2. Society for Marine Mammalogy, Lawrence, KS. 787 p.

Würsig, B., E.M. Dorsey, M.A. Fraker, R.S. Payne, W.J. Richardson and R.S. Wells. 1984. Behavior of bowhead

whales, Balaena mysticetus, summering in the Beaufort Sea: surfacing, respiration, and dive characteristics.

Can. J. Zool. 62(10):1910-1921.

Würsig, B., E.M. Dorsey, M.A. Fraker, R.S. Payne and W.J. Richardson. 1985. Behavior of bowhead whales,

Balaena mysticetus, summering in the Beaufort Sea: a description. Fish. Bull. 83(3):357-377.
13-22 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

% Time Number of

Group Activity at Blows per

Status mean s.d. n mean s.d. n mean s.d. n mean s.d. n Surface Minute

Feed 13.08 6.34 324 5.89 3.61 123 1.28 0.74 157 8.94 7.12 63 12.5 0.58

Mother 15.78 2.53 15 6.00 2.83 2 2.17 0.72 4 17.46 2.59 4 11.0 0.31

Other 12.95 6.44 309 5.89 3.63 121 1.25 0.73 153 8.36 6.96 59 13.0 0.61

Feed Deep 13.08 3.91 129 8.52 2.81 33 1.77 0.58 42 16.09 4.65 19 9.9 0.48

Mother 15.78 2.53 15 6.00 2.83 2 2.17 0.72 4 17.46 2.59 4 11.0 0.31

Other 12.73 3.93 114 8.68 2.77 31 1.73 0.56 38 15.73 5.07 15 9.9 0.50

Feed Shallow 13.08 7.54 195 4.93 3.40 90 1.10 0.71 115 5.84 5.62 44 15.9 0.71

Mother - - 0 - - 0 - - 0 - - 0 - -

Other 13.08 7.54 195 4.93 3.40 90 1.10 0.71 115 5.84 5.62 44 15.9 0.71

Travel+Feed 15.37 5.88 141 6.88 3.04 42 1.78 0.79 50 12.64 6.08 21 12.3 0.48

Mother 21.24 8.19 21 7.50 2.46 10 2.40 0.88 11 13.34 6.14 11 15.3 0.48

Other 14.34 4.71 120 6.69 3.21 32 1.60 0.68 39 11.88 6.24 10 11.9 0.50

Travel 16.27 4.78 108 6.13 3.33 68 1.56 0.97 75 13.99 8.09 66 10.0 0.39

Mother 18.55 2.24 10 6.67 2.25 6 1.99 0.52 6 15.87 8.65 5 11.2 0.37

Other 16.03 4.91 98 6.08 3.43 62 1.52 0.99 69 13.83 8.10 61 9.9 0.40

Travel plus

Travel + Feed 15.76 5.43 249 6.42 3.23 110 1.65 0.91 125 13.66 7.64 87 10.8 0.42

Mother 20.37 6.92 31 7.19 2.34 16 2.26 0.78 17 14.13 6.82 16 13.8 0.44

Other 15.10 4.86 218 6.29 3.35 94 1.55 0.89 108 13.56 7.85 71 10.3 0.42

Social 15.25 8.68 59 5.83 5.07 18 1.08 0.82 20 4.50 2.67 7 19.4 1.04

Mother - - 0 - - 0 - - 0 - - 0 - -

Other 15.25 8.68 59 5.83 5.07 18 1.08 0.82 20 4.50 2.67 7 19.4 1.04

Travel+Social 13.46 3.38 78 5.76 3.40 51 1.31 0.82 55 4.04 4.40 16 24.5 1.08

Mother 18.17 4.52 7 4.43 2.70 7 1.28 1.07 7 3.50 2.28 6 26.8 0.93

Other 12.99 2.90 71 5.98 3.47 44 1.32 0.79 48 4.36 5.39 10 23.2 1.05

Social+Feed 11.63 4.96 205 6.41 3.52 46 1.31 0.70 82 9.20 7.24 9 12.5 0.61

Mother 15.78 1.11 9 - - 0 3.70 - 1 17.90 - 1 17.1 -

Other 11.44 4.98 196 6.41 3.52 46 1.28 0.65 81 8.12 6.91 8 13.7 0.68

Travel +

Social + Feed 12.63 3.70 19 7.00 - 1 2.75 - 1 4.63 3.87 2 37.3 0.95

Mother 17.23 2.91 4 7.00 - 1 2.75 - 1 1.90 - 1 59.1 1.51

Other 11.40 2.86 15 - - 0 - - 0 7.37 - 1 - -

All Social 12.67 5.57 361 6.04 3.71 116 1.29 0.76 158 5.54 5.32 34 18.9 0.88

Mother 16.91 3.08 20 4.75 2.66 8 1.71 1.28 9 5.10 5.55 8 25.2 0.70

Other 12.42 5.59 341 6.14 3.77 108 1.27 0.72 149 5.67 5.35 26 18.3 0.89

Blow Intervals (s) per Surfacing Surfacing (min) Dive (min)

APPENDIX 13.1. Surfacing, respiration and dive behavior of undisturbed bowhead whales engaged in various

activities during September and early October 1985-86 and 1998-2000. Calves are excluded. Based on

observations from an aircraft at altitude >460 

Median Number of Blows Duration of Duration of
14. SURFACING, RESPIRATION AND DIVE CYCLES OF BOWHEAD WHALES

IN THE BEAUFORT SEA: CALVES, SUBADULTS AND ADULTS

Tannis A. Thomas 1, W. John Richardson 1, William R. Koski 1, and Bernd Würsig 2

Introduction

The surfacing, respiration and dive (SRD) cycles of bowhead whales in the Beaufort Sea have been

documented in several studies, including studies of whales migrating through the Alaskan Beaufort Sea in

spring and fall, and whales summering in the Canadian Beaufort Sea. Some information about differences in SRD cycles among calves, mothers, and “other bowheads” has been published. For example, in

the case of bowheads migrating near Point Barrow, Alaska, in May, the durations of surfacings and dives,

and the median blow intervals, were all substantially (P < 0.001) longer for mothers than for calves

(Richardson et al. 1995b; Koski et al. MS). Most calves observed in May are very young, as most calving

occurs in April–May (Nerini et al. 1984; Koski et al. 1993). In summer (mainly August), when calves are

~3 mo older, mean durations of surfacings and dives were again longer for mothers than for calves

(Würsig et al. 1984). In contrast to the spring results, mean number of blows per surfacing during

summer was higher for mothers than for calves, and mean blow intervals were similar for the two groups.

The only previous study that has separated the data for subadults vs. “adults aside from mothers” was

the aforementioned study of the behavior of bowheads migrating in spring. Dive durations and median

blow intervals were significantly shorter in subadults; duration of surfacing and number of blows per

surfacing were similar for the two groups (Richardson et al. 1995b, MS). Recent results from the eastern

Alaskan Beaufort Sea during late summer and early autumn indicate that SRD cycles of subadults and adults

engaged in feeding and traveling also tend to differ in that area and season (Chapter 13). No similar analysis

of age effects has been done previously for bowheads observed in other seasons (e.g., summer).

The durations of surfacings and dives of different categories of bowhead whales, and the number of

respirations per surfacing, are important in the calculation of energy requirements and potential water filtering

capacity (Chapter 22). Also, these parameters are important in determining correction factors for whales

missed by aerial surveyors (Chapter 15). If there are significant differences among age and size classes, this

may have important effects on calculated feeding capacity, energy need, and numbers present. These probable

effects assume increased importance because of the tendency for different size classes of bowheads to occur in

different parts of the eastern Alaskan study area (Chapter 10). Furthermore, utilization of this and other

regions by different size classes of bowheads may differ among years (Chapter 10).

A limitation in previous season-specific analyses of the effects of age and whale status (e.g.,

mothers vs. other adults) on SRD cycles of bowheads has been the small sample sizes for certain age

classes, activities, and seasons. Also, during a given season, most calves are in a particular narrow age

 

1 LGL Ltd., environmental research associates, 22 Fisher St., POB 280, King City, Ont. L7B 1A6.

Phone: 905-833-1244; e-mail: wjr@lgl.com or bkoski@lgl.com.

2 Texas A & M University at Galveston, Marine Mammal Research Program, 4700 Ave. U., Bldg 303,

Galveston, TX 77551-5923. Phone: 409-740-4413; e-mail: wursigb@tamug.tamu.edu
14-2 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

range, and their SRD cycles may change rapidly with season as they mature. In this chapter, we use all

available SRD data collected during spring, summer, and autumn studies of bowheads in the Beaufort Sea

(1980–2000) for which the size category of some whales is reliably known. We compare the SRD cycles

of bowhead calves as observed in spring and late summer/fall (i.e., neonates vs. calves a few months old),

subadults, adults other than mothers, and mothers. Companion chapters provide related data on the

seasonal distribution of bowheads in the eastern Alaskan study area (Chapter 9), age segregation (Chapter

10), residence times (Chapter 11), and general activities (Chapter 12). Chapter 13 provides additional

information on the influence of whale activities and other factors on SRD cycles for bowheads occurring

in the eastern part of the Alaskan Beaufort Sea during late summer and early autumn.

Methods

Data Sources

We combined data from six studies of bowhead behavior in the Beaufort Sea during the spring, late

summer, and fall: (1) A study of bowheads engaged in feeding and socializing in the Canadian Beaufort

Sea during late July or early August to late August or early September of 1980–84 (Würsig et al. 1984;

Dorsey et al. 1989; Richardson et al. 1995a). (2) A study of bowhead whales feeding and migrating in the

Alaskan Beaufort Sea during September of 1983 (Ljungblad et al. 1984; Richardson et al. 1995a). (3) A

study of bowheads engaged in feeding, socializing, and autumn migration in the eastern Alaskan Beaufort

Sea during September and early October of 1985–86 (Richardson [ed.] 1987). (4) A study of bowhead

responses to offshore drilling in the Camden Bay area during September and early October of 1986,

including some observations of undisturbed whales distant from industrial activities (Koski and Johnson

1987). (5) A study of bowheads engaged in spring migration in the Alaskan Beaufort Sea during April

and May of 1989–94 (Richardson et al. 1995b, MS). (6) The current study of bowheads engaged in

feeding, socializing, and autumn migration during September of 1998–2000. Additional details about the

sources of data, organized by season and year, are summarized in Table 14.1. We excluded data when

bowheads may have been disturbed by an aircraft flying at <457 m (1500 ft) altitude or by actual or simulated industrial activities. Only bowheads of known status (i.e., subadult, adult other than mother, mother, or calf) were used in the analysis.

Field Procedures

Aerial observations of behavior were obtained from three types of twin-engine aircraft: • a Britten–

Norman Islander with piston engines for most of study (1), • deHavilland Twin Otters with turboprop

engines in studies (2)–(5) and on 1–12 August 1983 during study (1); and • a Twin Commander 680FL

with piston engines in study (6). All aircraft were equipped with radar altimeters. The aircraft used in

1980–94 were equipped with Very Low Frequency (VLF) navigation systems; those used in 1991–2000

were equipped with GPS. Most aircraft were equipped with extended-range fuel tanks, either in the wings

or internally, plus inverters for 120 V/60 Hz power, bubble windows, and ventral camera ports. In each

study, the field crew consisted of three or four biologists plus one or two pilots. When present, the copilot moved to a rear seat once the aircraft was at survey altitude over the sea, allowing a biologist to

move to the co-pilot’s seat until the aircraft began to return to base.

We used the aerial observation procedures of Würsig et al. (1985) and Richardson et al. (1995a,b) to

observe the behavior of bowheads. A focal group of bowheads was observed systematically while the aircraft

circled at an altitude of at least 457 m a.s.l. and at a radius of 1–2 km. With this procedure, bowheads show

little evidence of disturbance by the aircraft (Patenaude et al. 2002). At most times while the focal whales

were at the surface, they were videotaped using a hand-held video camera (usually with tele-extender).
§14. Bowheads: Surfacing, Respiration & Dive Cycles vs. Age 14-3

Date Range Area of 

Year BOS Surfacings of BOS Season Beaufort Sea Source of Data

1989 4 141 3-27 May Spring Western Alaskan Richardson et al. (1995b)

1990 20 321 29 April - 25 May Spring Western Alaskan Richardson et al. (1995b)

1991 2 37 4-20 May Spring Western Alaskan Richardson et al. (1995b)

1994 14 156 3-20 May Spring Western Alaskan Richardson et al. (1995b)

1980 8 42 3-31 Aug Summer Canadian Würsig et al. (1984), Dorsey et al. (1989)

1981 9 75 8 Aug - 7 Sept Summer Canadian Würsig et al. (1984), Dorsey et al. (1989)

1982 6 88 8-24 Aug Summer Canadian Würsig et al. (1984), Dorsey et al. (1989)

1983 4 14 7-22 Aug Summer Canadian Würsig et al. (1984), Dorsey et al. (1989)

1984 9 25 17 Aug - 2 Sept Summer Canadian Würsig et al. (1984), Dorsey et al. (1989)

1983 5 34 12-28 Sept "Fall" E. Alaskan & West. Canadian Ljungblad et al. (1984)

1985 5 25 12-29 Sept "Fall" E. Alaskan & West. Canadian Richardson (1987)

1986 10 84 5-27 Sept "Fall" E. Alaskan & West. Canadian Richardson (1987)

1986 6 64 4 Sept - 3 Oct "Fall" E. Alaskan & West. Canadian Koski & Johnson (1987)

1998 14 265 13-22 Sept "Fall" E. Alaskan & West. Canadian This study

1999 18 92 10-30 Sept "Fall" E. Alaskan & West. Canadian This study

2000 9 79 13-25 Sept "Fall" Eastern Alaskan This study

Number of

TABLE 14.1. Sources of data on bowhead whale surfacing, respiration and dive cycles for this study.

Behavioral observation sessions (BOS) categorized as rest, play and unknown/other were excluded

because they were not used in the analyses. Also excluded were bowheads of unknown status.

Whale activities (e.g., traveling, feeding, socializing) and specific behaviors were defined and distinguished as in previous related studies (Richardson et al. 1995a,b, MS). We recognize only one type of

dive, often referred to by others as a “sounding” or long dive. Dive durations were recorded only when

whales were individually identified from one surfacing to the next, usually on the basis of distinctive

marks. Shallow submergences between breaths are not counted as dives or as interruptions of a surfacing.

A surfacing is a period when a whale is at or just below the surface, including a full breath sequence. We

obtained four standard measures of SRD cycles: the interval between successive blows in a surfacing

(blow interval), the number of blows per surfacing, the duration of surfacing (surface time), and the duration of dives between surfacings (dive time). When analyzing blow-interval data, we used the median of

all blow intervals within a given surfacing as a single measure of blow interval for that surfacing.

After completing the behavioral observations of a given group of whales, we often used the aerial

photogrammetric method of Koski et al. (1992) to document their lengths and individual identities. This was

done frequently in studies (4)–(6), and occasionally during studies (1) and (3). Whales <13 m and ≥13 m long

were considered to be subadults and adults. When no photogrammetric data were available, whales that were

obviously small or large were counted as subadults and adults; others were not classified. Calves were

recognized by their size, light color, morphology, behavior, and (in almost all cases) close association with an

adult. Lone “calves” were categorized as such only when they were seen well and it was certain that they were

young-of-the-year. Mothers were recognized by their size, morphology, and close association with a calf.

Behavioral data were transcribed from audiotape between flights and after the field season. The

videotape was then examined for details not noted during the real-time behavioral dictation. The combined data were coded numerically as in our previous work (see Richardson and Finley 1989:25–28 for

details). These records were hand-checked, and then entered into an Apple II (1980–86) or MS-Windows

(1989–2000) format for computerized validation and analysis. A validation program that checks for

impossible or implausible combinations of variables, as developed during prior LGL/MMS projects, was
14-4 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

applied to the data and necessary corrections were made. The 1980–86 data were converted to the more

recent format before analysis.

Activity Categories

Whale activities were divided into ten categories: rest, travel, socialize, feed, travel+social, travel+ feed,

social+feed, travel+social+feed, play, and unknown/other. These activities are described in Chapter 12. As in

Chapter 13, seven categories were combined into three composite categories as follows: (1) Travel, including

travel and travel+feed; (2) Feed, including only feeding whales; and (3) Social, including socializing whales,

travel+social, social+feed, and travel+social+feed. Rest, play, and unknown/other were excluded from the

analyses because their sample sizes were either too small (rest and play) or because the activities were

heterogeneous and/or ill-defined (unknown/other). When isolated whales engaged in repeated “aerial

behavior”, including breaches, tail and flipper slaps, and rolls around the longitudinal axis, their activity was

generally classified as “unknown/other” and thus excluded from the present analyses.

Analysis Procedures

 For each whale activity, we used ANOVA to test for significant (P ≤ 0.05) effects of whale status

on each of the four standard measures of SRD cycles. When ANOVA showed significant differences, we

used post hoc tests to determine which whale status differed: the Tamhane procedure when variances

were unequal (Tamhane 1979), and otherwise the Bonferroni procedure. For whales categorized as

“traveling” (travel and travel+feed combined), we used ANOVA to test for significant (P ≤ 0.05) year to

year, seasonal, and nursing vs. not nursing differences in each of the four standard measures of SRD

cycles. Categories for which the sample size was <5 were excluded. Logarithmic transformations were

used on the distributions of the four SRD variables when they were right-skewed.

Results

Status Differences

In whales categorized as “traveling” (travel and travel+feed combined), the overall mean of the

median blow intervals in all years was 14.35 ± s.d. 5.00 s (n = 105) for subadults, 19.19 ± s.d. 7.87 s (n =

246) for adults other than mothers, and 19.56 ± s.d. 7.52 s (n = 84) for mothers (Table 14.2). Median

blow intervals varied significantly with whale status; values for subadults were significantly lower than

those for adults and mothers (Fig. 14.1A). Number of blows per surfacing did not differ significantly

with whale status (Table 14.2; ANOVA, P = 0.875; Fig. 14.1B). Duration of surfacing averaged 1.21 min

for subadults, 1.59 min for adults, and 1.62 min for mothers (Table 14.2). These surface times were only

marginally different (ANOVA, P = 0.089; Fig. 14.1C). The overall mean dive duration was 4.78 min for

subadults, 8.79 min for adults, and 8.83 min for mothers (Table 14.2), and varied significantly with whale

status (ANOVA, P = 0.005); dives by subadults were significantly shorter than those by adults other than

mothers or by mothers (Fig. 14.1D).

In whales categorized as “feeding” (without simultaneous traveling or socializing), the overall

mean of the median blow intervals in all years was 11.34 ± s.d. 4.86 s (n = 102) for subadults, 13.41 ±

4.89 (n = 61) for adults other than mothers, and 16.22 ± s.d. 3.67 s (n = 33) for mothers (Table 14.2).

Median blow interval was the one SRD variable that differed significantly with whale status; values for

adults were significantly lower than for mothers and higher than for subadults (Fig. 14.2A). Number of

blows per surfacing did not differ significantly with whale status (ANOVA, P = 0.101; Fig. 14.2B).

Neither did duration of surfacing or dive duration (P = 0.229 and 0.558, respectively; Fig. 14.2C,D).
§14. Bowheads: Surfacing, Respiration & Dive Cycles vs. Age 14-5

TABLE 14.2. Surfacing, respiration and dive behavior of undisturbed bowhead whales engaged in various

activities during the spring, summer, and fall. Neonates refers to calves in the spring. Traveling includes

travel alone and travel+feed. Feeding includes only whales that were only feeding. Socializing includes

whales that were social, travel+social, social+feed, and travel+social+feed. Data in each box are a subset of those in line preceding box. Based on observations from an aircraft at altitude ≥460 m. The only

lines that include any data from mothers or calves engaged in nursing are the 3 lines labeled "Nursing".

Group Activity

Status

Season mean s.d. n mean s.d. n mean s.d. n mean s.d. n

Traveling

Subadult 14.35 5.00 105 5.51 3.67 69 1.21 1.04 78 4.78 5.20 37

Spring 14.11 5.65 48 6.24 3.79 34 1.35 1.22 39 4.54 5.70 19

Summer 18.70 - 1 4.50 4.95 2 1.22 1.53 2 - - 0

Fall 14.47 4.43 56 4.82 3.46 33 1.06 0.81 37 5.04 4.76 18

Adult 19.19 7.87 246 5.51 3.33 195 1.59 1.06 200 8.79 7.46 171

Spring 20.52 8.89 161 4.92 3.23 154 1.46 1.08 154 6.69 6.19 134

Summer 16.48 1.97 4 10.00 - 1 2.65 - 1 24.38 2.19 3

Fall 16.70 4.60 81 7.70 2.75 40 1.99 0.86 45 15.72 6.49 34

Mother 19.56 7.52 84 5.75 3.30 68 1.62 1.00 74 8.83 6.40 67

Spring 19.97 8.01 50 5.16 2.96 44 1.38 0.85 48 8.23 6.27 45

Summer 18.26 5.79 16 6.31 4.46 13 2.01 1.36 15 7.60 5.95 14

Fall 19.58 7.73 18 7.45 2.50 11 2.14 0.74 11 14.41 5.69 8

Nursing 23.98 12.63 28 5.11 2.54 19 2.24 1.21 20 12.60 6.76 17

Neonate 12.42 5.50 146 4.64 3.53 140 0.85 0.83 150 2.49 2.26 144

Nursing 14.59 6.78 16 3.52 2.41 23 0.63 0.57 23 0.89 1.10 24

Calf Summer 16.51 8.23 14 3.00 2.07 16 1.17 1.43 19 3.56 3.84 17

Calf Fall 11.70 2.73 33 6.88 4.12 17 1.47 1.01 18 7.06 4.24 13

Nursing 11.94 5.31 17 2.26 3.48 39 0.20 0.35 40 0.83 1.84 42

Feeding

Subadult 11.34 4.86 102 6.72 3.21 50 1.31 0.58 57 9.24 7.25 16

Adult 13.41 4.89 61 7.00 3.04 22 1.50 0.41 28 11.70 6.31 20

Mother 16.22 3.67 33 4.00 3.16 6 1.66 1.46 9 11.09 7.27 11

Neonate 11.08 3.32 12 8.57 6.36 14 1.87 2.46 14 2.73 1.26 13

Calf Fall 14.37 6.94 18 6.60 4.39 5 1.46 1.18 6 6.56 4.42 5

Socializing

Subadult 12.21 4.80 63 4.42 2.89 24 0.95 0.56 30 6.48 5.56 13

Adult 16.98 10.02 98 6.05 3.72 42 1.38 0.88 46 4.46 4.47 17

Mother 16.37 5.22 47 4.67 3.93 30 1.62 1.35 36 7.29 6.65 26

Neonate - - 0 - - 0 - - 0 - - 0

Calf Fall 9.51 3.65 15 5.70 2.87 10 1.06 1.00 11 2.91 1.85 7

Blow Intervals (s) per Surfacing Surfacing (min) Dive (min)

Median Number of Blows Duration of Duration of
14-6 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

Subadult Adult Mother

0.0

0.5

1.0

1.5

2.0

2.5

3.0

STATUS

78

200

74

ns ns

0

5

10

15

20

STATUS

37

171

67

ns ***

Subadult Adult Mother

5

10

15

20

25

30

STATUS

105

246

84

*** ns

Subadult Adult Mother

0

2

4

6

8

10

12

STATUS

69

195 68

ns ns

Subadult Adult Mother

Number of Blows per Surfacing

Duration of Surfacing (min) Duration of Dive (min)

Median Blow Interval (s)

A. C.

B. D.

***

ns

( )

*

**

FIGURE 14.1. Whale status vs. surfacing, respiration, and dive variables for traveling bowhead whales

during all years. Potentially disturbed whales and mothers that are nursing are excluded. In the Box

plots, the bottom and top lines represent the 10th and 90th quantiles; boxes show 25th, 50th, and 75th

quantiles; numbers are sample sizes. Overall significance of whale status effect (by ANOVA) is shown at

the top of each panel. Significance of differences between adjacent pairs of categories are shown at

bottom, based on multiple comparison procedures of Tamhane (when variances unequal, panel D) or

Bonferroni (equal variances, panels A, B, C). Significance levels coded as *** for P ≤ 0.001; ** for 0.001 <

P ≤ 0.01; * for 0.01 < P ≤ 0.05; (*) for 0.05 < P ≤ 0.1; ns for P > 0.10.

In whales categorized as “socializing”, including socializing per se, travel+social, social+feed, and

travel+social+feed, the overall mean of the median blow intervals in all years was 12.21 ± s.d. 4.80 s (n = 63)

for subadults, 16.98 ± s.d. 10.02 s (n = 98) for adults, and 16.37 ± s.d. 5.22 s (n = 47) for mothers (Table 14.2;

Fig. 14.3A). Median blow interval again was the one SRD variable that differed significantly with whale

status (Fig. 14.3A). Number of blows per surfacing, duration of surfacing, and dive duration did not differ

significantly with whale status (ANOVA, P = 0.156, 0.328 and 0.302, respectively; Fig. 14.3B–D).
§14. Bowheads: Surfacing, Respiration & Dive Cycles vs. Age 14-7

5

10

15

20

25

STATUS

Median Blow Interval (s)

A.

*

Subadult Adult Mother

*

102

61

33

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

STATUS

Duration of Surfacing (min)

C.

( )

*

Subadult Adult Mother

ns

57 28

9

0

2

4

6

8

10

12

14

STATUS

Number of Blows per Surfacing

B.

Subadult Adult Mother

ns

50

22 6

ns

0

5

10

15

20

25

STATUS

Duration of Dive (min)

D.

Subadult Adult Mother

16

20

11

ns ns

*** ns

ns ns

FIGURE 14.2. Whale status vs. surfacing, respiration, and dive variables for feeding bowhead whales

during all years. Otherwise as in Figure 14.1, except that Tamhane multiple comparisons used in (C),

and Bonferroni multiple comparisons in (A, B, D).

Seasonal Differences

In subadults categorized as “traveling”, including both travel and travel+feed, the median blow

intervals were similar in spring and fall (mean 14.11 vs. 14.47 s; Table 14.2, Fig. 14.4A; P = 0.716 based

on t-test). Likewise, number of blows per surfacing, duration of surfacing, and dive duration all were

similar in spring and fall (Table 14.2; Fig. 14.4B–D; P = 0.115, 0.233, and 0.777, respectively).

In adults (other than mothers) categorized as “traveling” (travel and travel+feed), in contrast, all

four SRD variables differed significantly between spring and fall (Fig. 14.4). Median blow intervals

tended to be longer in the spring than in the fall (mean 20.52 vs. 16.70 s). The other three variables were

all higher in fall than in spring.
14-8 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

5

10

15

20

25

STATUS

Median Blow Interval (s)

A.

ns ***

Subadult Adult Mother

63

98

47

0

5

10

15

20

STATUS

Duration of Dive (min)

D.

Subadult Adult Mother

13

17

26

ns ns 0

2

4

6

8

10

12

STATUS

Number of Blows per Surfacing

B.

Subadult Adult Mother

24

42

30

ns ns

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

STATUS

Duration of Surfacing (min)

C.

Subadult Adult Mother

30

46

36

ns ns

*** ns

ns ns

FIGURE 14.3. Whale status vs. surfacing, respiration, and dive variables for socializing bowhead whales

during all years. Otherwise as in Figure 14.1, except that Tamhane multiple comparisons used in (D),

and Bonferroni multiple comparisons in (A–C).

In mothers categorized as “traveling” (travel and travel+feed), median blow intervals did not vary

significantly among spring, summer and fall (Fig. 14.5A; Table 14.2; ANOVA, P = 0.735). For number

of blows per surfacing, seasonal variability was marginally significant (Fig. 14.5B; P = 0.093). Durations

of surfacings averaged longer in summer and fall than in spring (Fig. 14.5C; P = 0.017). Durations of

dives averaged longer in fall than in spring or summer (Fig. 14.5D; P = 0.028).

In calves categorized as “traveling” (travel and travel+feed combined), median blow intervals varied significantly among seasons (Fig. 14.5A; ANOVA, P = 0.018), with values in summer being highest.

Number of blows per surfacing also differed among seasons (Fig. 14.5B; P = 0.010), but for this variable

values in fall were highest. Durations of surfacing were only marginally different among seasons (Fig.

14.5C; P = 0.061). However, mean dive duration was notably longer during fall than during spring or

summer (Fig. 14.5D; P < 0.001).
§14. Bowheads: Surfacing, Respiration & Dive Cycles vs. Age 14-9

5

10

15

20

25

30

35

Median Blow Interval (s)

A.

ns ***

Spring Fall Spring Fall

Subadult Adult

48 56

161

81

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

Duration of Surfacing (min)

C.

**

Spring Fall Spring Fall

Subadult Adult

39

37

154

45

ns

Spring Fall Spring Fall

0

2

4

6

8

10

12

Number of Blows per Surfacing

B.

Subadult Adult

34 33

154

40

ns *** 0

5

10

15

20

25

Duration of Dive (min)

D.

Spring Fall Spring Fall

Subadult Adult

19

18 134

34

ns ***

FIGURE 14.4. Seasonal comparison of surfacing, respiration, and dive variables for traveling subadult

and adult bowhead whales. Data are from spring of 1989–90 and 1994, and fall of 1983, 1986, and

1998–2000. Otherwise as in Figure 14.1, except statistical tests used were independent-sample t-tests

with Levene’s test for equality of variances.

Yearly Differences

Appendices 14.1–14.4 provide data on year-to-year differences in SRD variables of bowhead whales in

the Beaufort Sea. Subadults engaged in traveling showed some yearly variability in number of blows per

surfacing (Appendix 14.2). Adult whales engaged in traveling showed significant year-to-year variability in

all four SRD variables (Appendix 14.3). Mothers engaged in traveling showed significant differences in

surface times and number of blows per surfacing, and possibly in dive durations as well (Appendix 14.4).
14-10 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

5

10

15

20

25

30

35

Spring Summer Fall Spring Summer Fall

0

2

4

6

8

10

12

14

16

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

0

5

10

15

20

25

Calf Mother

Spring Summer Fall Spring Summer Fall

Calf Mother

Spring Summer Fall Spring Summer Fall

Calf Mother

Spring Summer Fall Spring Summer Fall

Calf Mother

Number of Blows per Surfacing

Duration of Surfacing (min) Duration of Dive (min)

Median Blow Interval (s)

A. C.

B. D.

ns ( )

*

**

*

14

146

33

150

19

18

140

16

17

144

17

13

* ns

ns ns ns

ns

50 18

48

11

44

11

45

8

16

13

15

14

ns

ns ns

ns

ns *

*, ns

**, *( )

( )

* , *

***, *

FIGURE 14.5. Seasonal comparison of surfacing, respiration, and dive variables for traveling mother and

calf bowhead whales. Data are from the spring of 1989–91 and 1994, the summer of 1982, and the fall

of 1983 and 1998–2000. Nursing mothers and calves are excluded. Otherwise as in Figure 14.1, except

that Tamhane multiple comparisons used for calves in (D), and Bonferroni multiple comparisons used for

mothers in (A)–(D).

Nursing vs. Not Nursing

In mothers categorized as traveling, the median blow intervals averaged 19.56 ± s.d. 7.52 s (n = 84)

for mothers not nursing, and 23.98 ± s.d. 12.63 s (n = 28) for mothers nursing (Table 14.2); these values

differed significantly (t-test, P = 0.015; Fig. 14.6A). Number of blows per surfacing did not differ significantly between mothers that were and were not nursing (Table 14.2 and Fig. 14.6B; P = 0.620). Durations of surfacings and dives by mothers both averaged significantly longer while nursing than while not

nursing (Table 14.2 and Fig. 14.6C,D; P = 0.021 and 0.035, respectively).
§14. Bowheads: Surfacing, Respiration & Dive Cycles vs. Age 14-11 Duration of Surfacing (min)

C.

Not Nurse Not Nurse Not Nurse

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

74

20

150

23

18

40

* *** ns

 Calf

Spring

Mom Calf

Fall

Duration of Dive (min)

D.

0

5

10

15

20

25

67

17

144

24

13

42 * *** ***

Not Nurse Not Nurse Not Nurse

 Calf

Spring

Mom Calf

Fall

Median Blow Interval (s)

A.

5

10

15

20

25

30

35

84

28

146

16

33

17

* ns ns

Not Nurse Not Nurse Not Nurse

 Calf

Spring

Mom Calf

Fall

Number of Blows per Surfacing

B.

0

2

4

6

8

10

12

14

68

19

140

23

17

39

ns ns ***

Not Nurse Not Nurse Not Nurse

 Calf

Spring

Mom Calf

Fall

FIGURE 14.6. Comparison of surfacing, respiration, and dive variables for traveling mothers and calves

during times with and without nursing. Otherwise as in Figure 14.1, except that statistical tests used

were independent-sample t-tests with Levene’s test for equality of variances.

In calves that were traveling in spring, median blow intervals were not significantly different for

calves that were and were not nursing (means 12.41 vs. 14.59 s; Table 14.2 and Fig. 14.6A; t-test, P =

0.165). Likewise, number of blows per surfacing and duration of surfacing were not significantly different with and without nursing (P = 0.139 and 0.208, respectively; Fig. 14.6B,C). Mean dive durations

averaged significantly shorter with than without nursing (0.90 vs. 2.49 min; Fig. 14.6D; P < 0.001).

In calves that were traveling in fall (as in spring), median blow intervals did not differ significantly when nursing vs. not nursing (Table 14.2 and Fig. 14.6A; t-test, P = 0.742). However, in fall,

number of blows per surfacing, duration of surfacing, and duration of dive all tended to be lower during

nursing (Fig. 14.6B–D, P < 0.001 in each case).
14-12 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

Discussion

Variability in SRD Cycles as Related to Age

Subadult whales had lower median blow intervals than adults and mothers, regardless of whale

activity, i.e., travel, feed, and social (Fig. 14.1–14.3). Subadults also had shorter dive durations during

traveling, and marginally shorter surface durations during feeding, than adults and mothers. Richardson

et al. (1995b, MS) found similar results in the subset of these same data involving traveling bowheads

observed in spring. Adult whales other than mothers had surfacing–respiration–dive cycles similar to

those of mothers, except during feeding when adults had lower median blow intervals than mothers (Fig.

14.2A).

These results show that some aspects of SRD cycles differed significantly between subadults,

adults, and mothers. Thus, caution is necessary when comparing bowhead behavior in situations when

the proportions of adults and subadults are unknown but potentially varying with location or time.

Similar caution is warranted in developing and applying correction factors for bowhead whales missed

during aerial surveys because they are below the surface as the survey aircraft passes (“availability

bias”―see Chapter 15). Age class segregation has been documented during spring migration past Barrow, Alaska (Zeh et al. 1993; Angliss et al. 1995; Richardson et al. 1995b; Koski et al. MS); on the

summering areas in the Canadian Beaufort Sea and Amundsen Gulf (Cubbage and Calambokidis 1987;

Koski et al. 1988); and in the eastern Alaskan Beaufort Sea during late summer and autumn (Chapter 10).

In the Canadian and eastern Alaskan Beaufort Sea, subadult whales tend to occupy shallow nearshore

areas and adults tend to be found farther offshore. During both spring migration past Barrow (Koski et al.

MS) and fall migration past Kaktovik (Chapters 2, 10), subadults tend to precede adults, though with

much overlap in dates. The mothers and calves tend to migrate past late in the season, especially in

spring. Segregation also occurs on the summer range of the Davis Strait–Baffin Bay stock (Finley 1990).

During travel, mean surface and dive durations and number of blows per surfacing were even

shorter for calves observed in spring and summer than for subadults (Table 14.2), suggesting that these

variables may be related to age or size. Consistent with this, values of these three variables for calves

observed in fall were higher than those for calves in spring and summer. However, the values for calves

in fall were also higher than those for subadults (Table 14.2). This indicates that other factors aside from

simply size and age are involved.

Variability among Seasons

Subadults engaged in traveling showed no spring–fall differences in any of the SRD variables (Fig.

14.4). Adult whales, in contrast, showed differences in all four variables. In fall (as compared to spring)

they had shorter median blow intervals and more blows per surfacing, longer surface times, and longer

dive times (Fig. 14.4). This seasonal variation may be related to the habitat the whales occupy. In the

spring there is more ice to navigate through than in the fall. This probably affects the SRD cycles. Also,

the dive durations recorded during spring are probably a biased sample, underestimating the actual average, because of the reduced probability (even from a circling aircraft) of resighting a bowhead once it

dives under ice pans.

Mothers and calves engaged in traveling showed seasonal variability in SRD cycles. For both

mothers and calves, there was a noticeable increase in the number of blows per surfacing, surface times,

and dive times from spring to fall (Fig. 14.5). For calves, this seasonal effect may be attributable to the

age and size difference in calves observed during spring vs. fall. Bowheads probably calve from about

March to July, but mainly in April–May (Nerini et al. 1984; Koski et al. 1993). Thus, calves encountered
§14. Bowheads: Surfacing, Respiration & Dive Cycles vs. Age 14-13

during spring (May) vary in age from newborn to about three months. Those calves are smaller and

younger than those encountered during summer and autumn periods. Mean calf lengths increase from

~4.7 m in May to 6.8 m in September (Koski et al. 1993). Thus, calf behavior in spring is expected to

differ from calf behavior in fall. The seasonal variability observed in the mothers may be attributable, at

least in part, to differences in the maternal care given to younger calves in spring vs. older calves in fall

(e.g., Würsig et al. 1999).

Nursing vs. Not Nursing

Bowhead whale calves accompany their mothers during their first spring, summer and fall, and

are not weaned until sometime in winter or perhaps early spring (Koski et al. 1993). Mother–calf pairs

often engage in nursing, and nursing affects SRD cycles of both calf and mother (Fig. 14.6). During

travel, nursing dives by calves were much shorter than their other dives in both spring and fall. In fall,

calves that were nursing also had shorter surfacings with fewer blows per surfacing than calves that were

not nursing. This was not the case for the smaller calves observed in spring. Occurrence of nursing also

affected SRD cycles of traveling mothers. When nursing, traveling mothers tended to have long surfacings with long blow intervals. Dive durations by traveling mothers also tended to average slightly longer

when nursing.

Summary

Data on age- and size-dependence of surfacing, respiration and dive (SRD) cycles of bowhead

whales were needed as a basis for analyses of bowhead energetics. This type of information is also

relevant in deriving correction factors for whales missed during aerial surveys, especially when there is

geographic and seasonal variation in the ages and sizes of bowheads present.

Bowheads in the Alaskan and Canadian Beaufort Sea were observed systematically at various

times in 1980–2000 during spring, summer, and fall. During each of six studies, bowhead behavior was

observed from an aircraft circling at an altitude of ≥457 m (≥1500 ft), high enough to avoid significant

aircraft disturbance. Data collected in the presence of other human activities were excluded. We documented the durations of surfacings and dives, number of blows (respirations) per surfacing, and intervals

between successive blows. These four variables were defined as in our recent studies of bowhead

behavior in various seasons and regions. We summarized the SRD variables by whale status (calf,

subadult, adult other then mother, mother), various categories of whale activity (traveling, feeding, and

socializing), season (spring, summer, fall), year, and nursing vs. not nursing.

Subadult whales had lower median blow intervals than adults and mothers; this was evident for

bowheads engaged in all three whale activities studied (traveling, feeding, and socializing). Subadults

also had lower dive durations during traveling, and marginally lower surface times during feeding, as

compared with adults and mothers. Mothers and other adults had similar SRD cycles, with the exception

that, during feeding, other adults had lower median blow intervals than mothers.

Subadults engaged in traveling showed no spring–fall differences in any of the SRD variables.

Adult whales, in contrast, showed differences in all four variables. Mothers and calves engaged in traveling showed seasonal variability in SRD cycles. For both mothers and calves, there was a noticeable

increase in the number of blows per surfacing, surface times, and dive times from spring to fall.

During travel, nursing dives by calves were much shorter than their other dives in both spring and

fall. Occurrence of nursing also affected SRD cycles of traveling mothers. When nursing, traveling
14-14 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

mothers tended to have long surfacings with long blow intervals. Dive durations by traveling mothers

also tended to average slightly longer when nursing.

Acknowledgements

We thank the numerous LGL personnel, aircraft charter companies, and pilots who assisted in

collecting the behavioral data over the 21 years of studies. Also, we thank D. Ljungblad of Naval Ocean

Systems Center who organized study (2). The U.S. Minerals Management Service, Alaska OCS Region,

sponsored 5 of 6 studies considered here; the exception was study (4), a 1986 study sponsored by Shell

Western Exploration & Production. The five LGL projects were conducted under provisions of Scientific

Research Permits 338 and 426 (1981–84), 517 and 518 (1985–86), 670 (1989–94), and 481-1464 (1998–

2000) issued by the National Marine Fisheries Service. Projects in Canadian waters were authorized

under permits issued by the Canadian Department of Fisheries and Oceans. Many other Acknowledgements relevant to the project as a whole are included in Chapter 1.

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Zeh, J.E., C.W. Clark, J.C. George, D. Withrow, G.M. Carroll and W.R. Koski. 1993. Current population size and

dynamics. p. 409-489 In: J.J. Burns, J.J. Montague and C.J. Cowles (eds.), The bowhead whale. Spec.

Publ. 2. Soc. Mar. Mammal., Lawrence, KS. 787 p.
14-16 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

APPENDIX 14.1. Yearly Differences in SRD Variables.

In subadults categorized as traveling, median blow intervals observed in five different years had

mean values ranging from 12.60 to 13.90 s, and did not differ significantly among years (ANOVA, P =

0.990) (Appendix 14. 2A). Mean number of blows per surfacing ranged from 2.92 to 8.57 over the same

five years, and year-to-year variability was significant (ANOVA, P = 0.003). Values in 2000 were significantly lower than in 1983 and 1994 (App. 14.2B). Mean duration of surfacing ranged from 0.63 to 1.70

min, with year-to-year differences being only marginally significant (P = 0.100; App. 14.2C). The mean

dive duration ranged from 4.07 to 8.08 min, with no significant among-year differences (P = 0.846; App.

14.2D).

In adults (other than mothers) traveling during spring, SRD cycles in years 1990 and 1994 did not

differ (App. 14.3; t-tests, P = 0.341 for median blow intervals, P = 0.376 for number of blows, P = 0.265

for duration of surfacing, and P = 0.915 for dive duration). In the fall when adults were traveling, median

blow intervals observed in five years had mean values ranging from 13.72 to 18.84 s. These values varied

significantly among years, with values in 1986 being higher than in 1998 and 1999 (App. 14.3A). Mean

number of blows per surfacing during three autumns ranged from 4.71 to 8.79, again with significant

year-to-year differences. Values in 1986 were significantly higher than in 2000 (App. 14.3B). Mean duration of surfacing ranged from 1.11 to 2.49 min over three years. These values were significantly different, with 1986 surface times being significantly higher than in 1998 and 2000 (App. 14.3C). The mean

dive duration ranged from 10.59 to 19.61 min over three years, again differing significantly among years;

values in 1986 were significantly higher than in 1998 and 2000 (App. 14.3D).

In mothers categorized as traveling, median blow intervals observed in five years had mean values

ranging from 18.39 to 26.33 s. These values did not differ significantly among years (ANOVA, P =

0.632) (App. 14.4A). Mean number of blows per surfacing ranged from 1.57 to 8.67, with significant

year-to-year differences; values in 1991 were significantly lower than all other years (App. 14.4B). Mean

duration of surfacing ranged from 0.27 to 2.58 min, and varied significantly with year; values in 1991

were significantly lower than during all other years (App. 14.4C). The mean dive duration ranged from

5.49 to 12.60 min. Overall, dive durations did not differ significantly among years (ANOVA, P = 0.167),

although the few values recorded in 1998 were significantly longer than dive durations in 1982, 1989 and

1991 (App. 14.4D).

Some of these yearly differences may be related to year-to-year variations in the locations or

seasons when whales were observed. SRD cycles of feeding whales, in particular, differ depending on

the water depth, and presumably the depth of feeding (e.g., Dorsey et al. 1989; Chapter 13). In other

species of baleen whales feeding at known depths, SRD variables are strongly correlated with depth of

dive (Würsig et al. 1986; Dolphin 1987a,b). Feeding locations and depths in the Canadian and Alaskan

Beaufort Sea have differed among years (Richardson et al. 1987; Chapters 6, 9, 12 and 23). Certain areas

were used by feeding whales in more than one year, but feeding has not been observed in any one area in

all years when it was surveyed. Although variations in ice cover and human activities may have some

influence on areas used for feeding, utilization of ice-free, undisturbed areas also differs from year to

year. Variation in locations of food concentrations is apparently one of the main reasons for year-to-year

differences in feeding locations. Traveling whales may be influenced by year-to-year differences in

feeding locations when they are traveling between feeding areas. Year-to-year (and within-year) changes

in feeding locations and depths are likely to influence SRD cycles.
§14. Bowheads: Surfacing, Respiration & Dive Cycles vs. Age 14-17

APPENDIX 14.2. Yearly comparison of surfacing, respiration, and dive variables for traveling subadult

whales during 1983, 1990, 1994, 1998, and 2000. Otherwise as in Figure 14.1, except that Bonferroni

multiple comparisons were used in all panels. Number of Blows per Surfacing

Duration of Surfacing (min) Duration of Dive (min)

Median Blow Interval (s)

A. C.

B. D.

5

10

15

20

25

1983 1990 1994 1998 2000

Year

ns ns ns ns

15

9 38

15

17

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

1983 1990 1994 1998 2000

Year

ns ns ns ns

8

8 30

10

15

0

2

4

6

8

10

12

14

1983 1990 1994 1998 2000

Year

ns ns ns ns

7

8

25

9

13

0

5

10

15

20

1990 1994 2000

Year

ns ns

5

13

14

ns **

( )

* ns
14-18 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

APPENDIX 14.3. Yearly comparison of surfacing, respiration, and dive variables for traveling adult whales

during spring of 1990 and 1994, and fall of 1983, 1986, and 1998–2000. Overall ANOVA results apply to

fall data only. Otherwise as in Figure 14.1, except that Bonferroni multiple comparisons were used in all

panels.

5

10

15

20

25

30

35

 1990 1994 1983 1986 1998 1999 2000

ns

Spring Fall

Year

*** ns ns ns

89

71

16 24

21

9

10

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

 1990 1994 1986 1998 2000

ns ** ns

Spring Fall

Year

99 55

20

11

8

0

2

4

6

8

10

12

 1990 1994 1986 1998 2000

ns ns ( ) *

Spring Fall

Year

97 57

19

9

7

0

5

10

15

20

25

30

 1990 1994 1986 1998 2000

ns ** ns

Spring Fall

Year

90

44

20

5 8

Number of Blows per Surfacing

Duration of Surfacing (min) Duration of Dive (min)

Median Blow Interval (s)

A. C.

B. D. ***

***

***

***
§14. Bowheads: Surfacing, Respiration & Dive Cycles vs. Age 14-19

APPENDIX 14.4. Yearly comparison of surfacing, respiration, and dive variables for traveling mother

whales during 1982, 1989, 1990, 1991, and 1998. Nursing mothers are excluded. Otherwise as in Figure

14.1, except that Tamhane multiple comparisons used in (D), and Bonferroni multiple comparisons were

used in (A–C).

5

10

15

20

25

30

35

40

45

1982 1989 1990 1991 1998

Year

0

2

4

6

8

10

12

14

16

1982 1989 1990 1991 1998

Year

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

5.5

1982 1989 1990 1991 1998

Year

0

5

10

15

20

25

30

1982 1989 1990 1991 1998

Year

Number of Blows per Surfacing

Duration of Surfacing (min) Duration of Dive (min)

Median Blow Interval (s)

A. C.

B. D.

ns *

***

ns ns ns

ns ns

ns ns

ns ns ns ***

***

*

14 23

23

3

12

12

16 20

7

6

13

20

20

7

6

13

20

19

6

5

ns ***

*** ns
15. CORRECTION FACTORS TO CALCULATE BOWHEAD WHALE NUMBERS

FROM AERIAL SURVEYS OF THE BEAUFORT SEA

 Tannis A. Thomas, William R. Koski, and W. John Richardson 1

Introduction

Not all of the animals present are seen during aerial surveys. Some animals may be missed

because of obstruction by parts of the aircraft structure, poor sighting conditions, and limitations of observers in seeing and recognizing the animals. During surveys of marine mammals, sightability is further

reduced because most species are below the surface and invisible for a significant fraction of the time.

Thus, the raw data from aerial surveys are, at best, indices of relative density of marine mammals at

different places and times (Eberhardt et al. 1979; Best 1982; Hiby and Hammond 1989).

The proportion of animals at the surface that are detected is not only <1.0, but also quite variable.

It is affected by aircraft altitude and ground speed, seating and window arrangements in the aircraft, glare,

wave height, ice cover, behavior of the target species, and nominal transect width. Aircraft altitude

affects the width of the strip below the aircraft where, in the absence of a bubble nose or ventral window,

downward visibility is blocked or reduced. Even when bubble windows are used by rear-seat observers,

downward visibility is reduced because observers concentrate their visual scans to the side. Sometimes a

separate observer with direct downward or forward visibility is assigned to “guard the trackline”, but then

there are complications in merging sightings from the trackline and lateral observers (Buckland et al.

1993). For lateral observers, the area below or close to the aircraft is visible for less time than the area

farther to the side (Hain et al. 1999). Visibility, as influenced by haze, fog and precipitation, has obvious

effects on the probability of detecting animals that are at the surface. Glare can reduce sightability (Scott

and Winn 1980; Holt 1987). Increasing wave height (“sea state”) also reduces the sightability of various

species (Scott and Winn 1980; Holt 1987; Gunnlaugsson et al. 1988; DeMaster et al. 2001). If aerial

surveys could all be conducted in a very standardized way under optimal weather and lighting conditions,

many of the complications would be avoided or greatly reduced. However, it is rarely possible to restrict

aerial surveys to ideal conditions, and thus the results are subject to the sources of variability mentioned

above.

The problems are compounded when data collected with different types of aircraft, or aircraft with

different seating and window arrangements, must be combined. Different aircraft give observers different

views of the water, and this could result in differences in detectability. Different aircraft also emit different sounds, which can have different effects on the behavior of the animals and thus on detectability

(Patenaude et al. 2002).

Animals below the surface and invisible are a particular issue in quantitative aerial surveys of

marine mammals. During many aerial survey projects, no allowance has been made for mammals below

the surface, other than a general acknowledgement that the calculated densities and numbers are mini-

 

1

 LGL Ltd., environmental research associates, 22 Fisher St., POB 280, King City, Ont. L7B 1A6.

Phone: 905-833-1244; e-mail: bkoski@lgl.com or wjr@lgl.com
15-2 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

mum estimates. In some cases, data on surfacing–dive cycles of the species of concern have been used to

develop a correction factor for proportion of time at the surface, with or without adjustment for the finite

time a given location is in an aerial observer’s field of view. Different species are at the surface and

potentially detectable for different proportions of the time, and within-species variability causes additional complications (Leatherwood et al. 1982; Barlow 1999). A given species, including the bowhead

whale, can be at the surface for different proportions of the time depending on the activity of the animals

or the season (Richardson et al. 1995; Chapters 13, 14). Notwithstanding the complications, some correction for animals below the surface as the aircraft passes is essential if there is a need for even approximate

absolute estimates of densities and numbers of marine mammals present.

In theory, two parameters, f(0) and g(0), can be computed from raw survey data and other observations of the species of interest to minimize most biases in estimates of actual densities and numbers of

marine mammals present at the time of the survey (Buckland et al. 1993). When applied to sightings

during line transect surveys, the f(0) factor accounts for the reduced probability of detecting an animal at

the surface of the water as its distance from the trackline increases. Factor f(0) is defined as the probability density function of detected distances from the trackline, evaluated at lateral distance zero. The g(0)

factor represents the probability of detecting an animal that is on the trackline. When known, it can be

used to correct the raw sighting data for animals that are on or near the trackline but not detected during

the survey. There are two components to the g(0) factor (Marsh and Sinclair 1989): (1) Animals that are

below the surface and not visible, sometimes called “availability bias” and designated ga(0) here; and (2)

animals at the surface but not sighted, called “perception bias” or “detectability bias” and designated gd(0)

here. Availability bias can be estimated from data on surfacing and dive cycles, such as those in Chapter

13. A common approach for estimating detectability bias is to use the “independent double observer”

method (Magnusson et al. 1978; Pollock and Kendall 1987). This involves use of two independent

observers on the same side of the aircraft and an analysis of the capture–recapture type. Based on the

number of animals seen by observer 1, observer 2, and both observers, the proportion of the animals

present at the surface that were detected can be estimated.

For bowhead whales, some information about f(0), ga(0) and gd(0) has been given in various

reports, but this was often based on small samples of data, and little of this information been formally

published. Davis et al. (1982) developed preliminary estimates of ga(0) and gd(0) for aerial surveys of

bowheads summering in the Canadian Beaufort Sea, and applied these factors to the results of striptransect surveys conducted during the summer of 1981. Moore and Clarke (1991) applied those factors to

additional strip-survey data from the Canadian and Alaskan Beaufort Sea during late summer in 1982–84.

These studies did not allow for the fall-off in sightability with increasing lateral distance other than by

limiting transect width to a 1-km strip on either side of the aircraft.

As part of a study to determine the importance of the eastern Alaskan Beaufort Sea to bowhead

whales during late summer and autumn, we needed to estimate numbers of bowheads present at various

times from 1979 to 2000 (see Chapter 9). We needed to use aerial survey data collected from different

types of survey aircraft flying at different altitudes under various sea-state and ice conditions. Therefore,

we needed to develop correction factors that would compensate insofar as possible for the anticipated

effects of those factors, as well as detectability and availability bias, on numbers of bowhead whales seen.

In this chapter, we use combined results from our studies of bowhead whales in the eastern Alaskan

Beaufort Sea during September and early October of 1985–86 and 1998–2000, plus other aerial survey

and behavioral studies of bowheads, to derive the necessary correction factors and to evaluate some of the

factors influencing them. (1) To determine how sightability of bowheads in the Beaufort Sea varies with
§15. Bowheads: Correction Factors for Aerial Surveys 15-3

lateral distance from the survey aircraft and to estimate f(0), we analyzed the lateral distances recorded

during eight different single- or multi-year aerial survey projects conducted by ourselves and others in the

Alaskan and Canadian Beaufort Sea from 1979 to 2000. We subdivided the data by aircraft type and

altitude, wave height, and ice cover to determine how f(0) is affected by those factors. The DISTANCE

program (Thomas 1999) was used to calculate f(0). (2) Detection (= perception) bias, gd(0), was estimated using data from the “independent double observer” method as applied by Davis et al. (1982) and

during the 1985–86 and 1998–2000 phases of the present study of bowhead feeding. (3) Availability

bias, ga(0), was determined from observations of the surfacing and dive cycles of bowheads in and near

the eastern Alaskan Beaufort Sea during late summer–early autumn of five years (Chapter 13). The

resulting correction factors have been applied to the raw aerial survey data from the eastern Alaskan study

area in order to estimate the densities and numbers of bowheads present at various times during August–

October (see Chapter 9, Distribution and Numbers).

Procedures for analysis of line-transect data, including compensation for availability and detection

bias, have been the subject of much recent and ongoing work (e.g., Quang and Becker 1996; Borchers et

al. 1998; Garner et al. [eds.] 1999). More elaborate approaches are being developed to take account of

some of the biases and confounding influences that are not fully dealt with in the relatively straightforward “classical” approaches applied here. The present work should be treated as a first step toward

developing an ability to estimate numbers of bowhead whales present based on aerial surveys.

Methods

Data Sources

We used data from eight studies on bowhead whales in the Beaufort Sea during the summer and

autumn (Table 15.1). • All eight studies provided sighting data from systematic aerial surveys, suitable

for calculating f(0) for various aircraft types, survey altitudes, sea states, and ice conditions. • Three of

the studies used independent double observers during at least some of the surveys, and thus provided data

suitable for calculating detectability bias, gd(0). • Observed durations of surfacings and dives during three

behavioral studies were used to calculate availability bias, ga(0). Six of the eight studies were mainly or

entirely in the Alaskan Beaufort Sea at various times during August–October (Table 15.1). Two studies

were in the Canadian Beaufort Sea during July–September.

Field Procedures

Systematic Aerial Surveys.―Three types of aircraft were used for most surveys. (1) A Twin

Commander 680FL aircraft was used for the majority of the 1993 ARCO surveys, all 1996–98 BP and

WesternGeco surveys, and the 1998–2000 feeding study. (Some 1993 ARCO surveys used a Twin

Commander 500.) There were usually 3–4 observers, with bubble windows for at least the two observers

seated behind the pilot and co-pilot. A third observer sat in the co-pilot’s seat during the 1996–98 and

1998–2000 projects; that observer had a bubble window in 1996–98. (2) The 1980–85 and some 1986–87

surveys for MMS (Ljungblad et al. 1986; Moore et al. 1989) were conducted from a TurboGoose aircraft

with two observers seated beside large flat windows behind the pilot and co-pilot. A third observer was

seated either in the co-pilot’s seat or a rear seat, both with flat windows. (3) All other systematic aerial

surveys were conducted from Twin Otter aircraft with varying seating and window arrangements. Many

surveys from Twin Otters had an observer in the co-pilot’s seat (with flat side window) plus observers

behind the cockpit on either the left side or both sides of the aircraft (usually with small or large bubble

windows). During the 1997–2000 MMS surveys, the two primary observers were behind the pilot and

co-pilot, beside large bubble windows.
15-4 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

TABLE 15.1. Sources of data used to calculate correction factors f(0), ga(0), and gd(0) for aerial surveys

of bowhead whales in the Beaufort Sea during summer and autumn.

Part of

Projects Season* Beaufort Sea f (0) g a (0) g d (0)

1979-2000 Aerial Surveys for or by MMS Autumn Alaskan X - -

 (Moore et al. 1989; Treacy 2002)

1981 Aerial Surveys for SOHIO [now BP] Summer Canadian X - X

 (Davis et al. 1982)

1985 Aerial Surveys during Reproduction Study Summer Canadian X - -

 for Standard Alaska et al. (Davis et al. 1986)

1985-86 Feeding Study for MMS Autumn E. Alaskan X X X

 (Richardson et al. 1987)

1986 Aerial Surveys & Behavior Study Autumn Alaskan X X -

 for SWEPI (Evans et al. 1987)

1993 Aerial Surveys for ARCO Autumn Alaskan X - -

 (Hall et al. 1994)

1996-98 Aerial Surveys for BP & WesternGeco Autumn Cent. Alaskan X - -

 (Miller et al. 1999)

1998-2000 Feeding Study for MMS Autumn Alaskan X X X

 (Current study)

* "Autumn" studies included work in early-mid September and in some cases August.

Data Used For Correction Factors 

Overall, all surveys used two primary observers on the left and right sides, and a third observer was

usually present on the right side. The left-side observer and at least one right-side observer had bubble

windows during most projects except for the 1980–87 surveys from a TurboGoose and a minority (22%)

of the 1981 SOHIO surveys. None of the surveys used an observer looking directly downward through a

nose bubble or ventral window. However, some coverage of the trackline was obtained during most projects by an observer in the co-pilot’s seat and/or downward observations through lateral bubble windows.

Information about survey conditions recorded during all surveys included Beaufort wind force (Bf)

or sea state, an evaluation of general visibility, and ice cover. For each bowhead sighting, the position,

time, number of whales, presence of calves, apparent whale activity, heading, estimated speed, and lateral

distance from the flight line were recorded. Lateral distances were determined using Suunto inclinometers when the whale's position was 90o to the left or right of the flight track, in conjunction with aircraft altitude determined by radar or pressure altimeter.

Survey procedures and conditions varied considerably. Survey altitudes varied from 200 ft (61 m)

to 5000 ft (1524 m), although only 0.6% of the surveys were above 2000 ft and most (74%) systematic

surveys were at 500 ft to 1500 ft (152–457 m). Ice cover varied from 0% to 99%. Beaufort wind-force

(Bf) varied from 0 (calm) to 8 (gale), though surveys usually were terminated soon when Bf exceeded 5–

6. All “sea state” values in this paper are based on the Bf scale, which differs from the “sea state” (SS)

scale that is often used (see Greene 1995:89 and Table 15.5, later). When the SS scale was used during

the original surveys, SS values were converted to Bf values for this analysis. Visibility varied from

excellent to impossible during the surveys. For this analysis, we excluded data collected when visibility

was recorded as “seriously impaired” or <1km.

Independent Double Observer Surveys.―During systematic surveys for SOHIO in 1981 (Davis et

al. 1982) and for the two feeding studies in 1985–86 and 1998–2000, there were two right-side observers

who (at least some of the time) observed independently and did not announce their sightings to other

observers. The two right-side observers were separated by a bulkhead (1981 and 1985–86 ― Twin Otter)

or visual screen (1998–2000 ― Twin Commander). This visual obstruction prevented the right-side
§15. Bowheads: Correction Factors for Aerial Surveys 15-5

observers from seeing one another. When a bowhead was seen on the right side of the aircraft during

these projects, it was not possible to circle to obtain more detailed observations because this would have

required notifying the other right-side observer that a bowhead had been seen. However, when a bowhead was seen on the left side, the sighting was announced and the aircraft circled if necessary to document whale activity or other sighting details. Left-side data were not used in double independent observer

calculations.

Behavioral Observations.―Durations of surfacings and dives by bowhead whales engaged in

feeding, traveling, socializing, and other activities were determined using the systematic aerial observation procedures of Würsig et al. (1984) and Richardson et al. (1995). We considered only the data collected in the eastern Alaskan Beaufort Sea and nearby Canadian waters during September and early October of 1985–86 and 1998–2000 (Table 15.1). Aircraft altitude was 1500 ft (457 m) during most behavioral observation sessions considered here, but occasionally 2000 ft (610 m). Procedures and data are

described in Chapter 13.

Analysis Methods

Lateral Distance Factor, f(0).―The number of bowhead sightings in various lateral distance

categories, and associated f(0) values, were determined based on the systematic aerial survey data from

eight studies (Table 15.1). This was done separately for the three different types of aircraft, and for various categories of altitude, Bf, and ice cover. • Types of aircraft: The data were first divided into those

collected from a Twin Otter, Twin Commander, and TurboGoose. • Aircraft altitude: Data were further

subdivided into three aircraft altitude categories, <900 ft, 900–1500 ft, and >1500 ft (i.e., <274, 274–457,

and >457 m). • Sea conditions (Bf) and ice cover: Sea conditions were broken down into five categories,

Bf states 0–1, 2, 3, 4, and 5–6. Ice cover was categorized as 0% and 25–99% ice cover. Sightings with

ice cover 1–24% were too infrequent for analysis.

For each subdivision of the data, the probability density function and f(0) associated with the

observed distribution of lateral distances were calculated with the program DISTANCE (Thomas 1999,

version 3.5, release 5). Models considered were half-normal (with hermite polynomial and cosine series

expansions), hazard rate (cosine and simple polynomial), and uniform (cosine and simple polynomial).

The final model was selected based on minimizing Akaike's Information Criterion (AIC; Akaike 1973).

Left truncation distances were selected so as to exclude the zone below the aircraft where sightability was

reduced; the width of this zone depended on altitude and aircraft type (see Results). f(0) was calculated

both with and without right truncation. Right truncation distances were determined based on a detection

probability of 15% relative to that at the optimum lateral distance, as recommended by Buckland et al.

(1993).

Availability Bias, ga(0).―This correction factor takes into account the effects of surfacing and dive

behavior on the probability that an animal on or near the trackline will be at the surface while the surveyors are close enough to have a chance of detecting the animal. We computed this correction factor using

behavioral data from whales engaged in various activities (traveling, feeding, socializing) in the eastern

Alaskan Beaufort Sea during late summer and autumn. We excluded data collected when bowheads may

have been disturbed by an aircraft flying at <457 m altitude, or by industrial activities. Calves were excluded because their dive profiles are quite different, and because calves are usually detected after the

observer’s attention has been attracted by sighting the mother. Calves were recognized by their size, light

color, morphology, behavior, and close association with an adult.
15-6 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

Standard Formulation: If all surfacings are of duration s, all dives are of duration u, and the duration of potential detectability as the aircraft travels past the whale location is t, the probability that a whale

will be at the surface while it can be seen is

s u

s t

s u

t

s u

s

g

+

+ = +

+

+ a (0) =

(Eberhardt 1978). Here, s/(s+u) is the probability that the whale will be at the surface when its location

first comes into visual range, and t/(s+u) is the probability that the whale will surface while its location is

in visual range.

We calculated t for Twin Commander surveys at 300 m a.s.l. based on the estimated along-transect

visual field ~1.25 km to the side of the trackline, and on a sample of actual aircraft ground speeds during

1998–99. To determine the latter, we randomly selected 16 transects (northbound and southbound) from

the 1998 survey, and 16 more from 1999. Aircraft ground speed extracted at 1-min intervals (n = 602)

was determined from GPS data logged during the flights. For each of the 602 aircraft speed values (in

km/s), we calculated t by dividing the approximate view field (1.25 km) by the speed. We then used the

mean of all t values (21.6 s) in the formula for ga(0), and its s.d. (± 1.72 s) in the associated variance

formula (below). The uncorrected estimate of the number of animals present can be divided by the

correction factor (s+t)/(s+u) to allow for animals that are undetectable because they are below the water

as the survey aircraft passes.

The variance of the above standard formulation for ga(0) was calculated using the delta method

(Taylor series expansion) because it is a function of three random variables, s, t and u (B.F.J. Manly, pers.

comm.).2

 Thus,

( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) u

s u

s t t

s u

s

s u

u t

ga var (0) var 1 var var 4

2

4 2

2





 





+

+ + 



 





+

+ 



 





+

− =

Allowance for Short Dives: The standard formula for ga(0) assumes that t ≤ u and that s and u are

constants. In fact, some dives are very short (u<t), and s and u are both highly variable (Chapter 13; see

also Richardson et al. 1995). Eberhardt (1978) expressed concern about the legitimacy of the (s+t) / (s+u)

formula under these conditions. Because (s+t) / (s+u) is an estimate of the probability that an animal will

be at the surface for at least part of “observation window” of duration t, the value cannot logically exceed

1.0. In the case of the “u < t” category of dive durations, (s+t) / (s+u) > 1.0.

Davis et al. (1982) evaluated this and developed a version of the (s+t) / (s+u) formula that allows

for some dives of short duration (u < t). They computed the probability of detection (sc+t) / (sc+uc)

separately for various categories of dive duration. Within each category c, the mean surface and dive

times were used to estimate sc and uc. Before proceeding, the probability of detection for the “u < t”

category, was reduced to 1.0 ― the maximum potential value. Then the weighted average value of (s+t) /

(s+u) was calculated. The weighting factor for each category of dive durations was the total duration of

all surfacings and dives in that category. The weighted mean value of (sc+t) / (sc+uc) for all u > t is identical regardless of the number of categories of dive durations that are chosen, and regardless of the particular choice of category boundaries. Thus, the corrected value of (s+t) / (s+u) can be obtained most simply

 

2

 We thank Dr. Bryan Manly, Western EcoSystems Technology Inc., Cheyenne, WY, for deriving this formula.
§15. Bowheads: Correction Factors for Aerial Surveys 15-7

by dividing the paired surface and dive time data into only two categories: (1) n1 pairs with u ≤ t, and (2)

n2 pairs with u > t. The corrected mean probability of detection is then

( )

2

1

2

2

1

2

2

1

2

1

2 2 2 2

2

2

n

u

n

s

t n

s

A s u n

i

i

n

i

i

n

i

i

n

i

i i

















+

















+

















= +

∑ ∑

∑

∑

= =

=

=

x

( )

∑∑( )

∑

= =

=

+

 +



 





+

= 2

1 1

1

1 1

1

1 0

0

c

n

i

ci ci

n

i

i i

a c

s u

s u x A

g

.

( )

Examples of this calculation are shown in the Results (see Table 15.3, later). If any dive times have

duration < t, then the corrected value will be less than the biased conventional (s+t) / (s+u) value based on

overall mean surface and dive times. If all u ≥ t, then the conventional and corrected values will be the

same.

Detectability Bias, gd(0).―This factor for whales at the surface but not detected was calculated from

sighting data collected when two right-side observers observed independently (Magnusson et al. 1978). This

method is mathematically equivalent to a mark–recapture analysis. Two key assumptions are as follows: (1)

There is no communication between observers, so sightings by the two individuals are independent. (2) Each

whale or group is individually recognizable to the extent that one can determine unequivocally whether each

whale or group seen by one observer was also seen by the other. Both assumptions were met in the three

studies whose data were used (Table 15.1). This calculation is based on the number of whale groups sighted

by only one observer vs. the number seen by both observers (see “Results”).

Results

Lateral Distance Factor f(0)

Altitude Effects.—The zone directly below an aircraft where sightability is reduced varies in width

depending on aircraft altitude. The higher the altitude, the wider the zone. We divided aircraft altitudes

into three categories: (1) <900 ft, (2) 900–1500 ft, and (3) >1500 ft (i.e., <274, 274–457, and >457 m).

For Twin Otter aircraft, detection probability was apparently reduced within lateral distances 150 m,

300 m, and ~600 m (respectively) on either side of the aircraft (Fig. 15.1). During calculation of f(0),

sightings within these distances of the trackline were excluded and lateral distances were measured relative to the left truncation distances thus defined.

Aircraft Type Effect.—The width of the strip directly below the aircraft where sightability is

reduced varied among aircraft types. For Twin Otter surveys at altitudes of 900–1500 ft, the left truncation point is 300 m on either side of the plane; i.e., a 600 m strip directly below the aircraft is excluded

from line-transect calculations (Fig. 15.1B). With the Twin Commander at the same altitude, reduced
15-8 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

FIGURE 15.1. Aircraft altitude vs. relative detection probability at various perpendicular distances for bowhead whale sightings from Twin Otter aircraft flying at altitudes (A) <900 ft, i.e. <274 m; (B) 900–1500 ft,

i.e. 274–457 m; and (C) >1500 ft, i.e. >457 m. n = number of sightings.

A. <900 ft.

B. 900-1500 ft.

Perpendicular Distance from Trackline (m)

Relative Detection Probability

C. >1500 ft.

0

0.4

0 600

0.6

0.8

1.0

1.4

0.2

1.2

300 900 1200 1500 1800 2100 2400

0

0.4

0 600

0.6

0.8

1.0

0.2

1.2

300 900 1200 1500 1800 2100 2400

0

0.4

0 600

0.6

0.8

1.0

0.2

1.2

300 900 1200 1500 1800 2100 2400

n = 1215

n = 489

n = 454

Relative Detection Probability Relative Detection Probability
§15. Bowheads: Correction Factors for Aerial Surveys 15-9

sightability extended to ~450 m on either side of the plane, requiring that a 900 m strip below the aircraft

be excluded (Fig. 15.2A). For the TurboGoose, detectability was marginally less at 300–450 than at 450–

600 m (Fig. 15.2B), i.e., intermediate as compared with the other two aircraft. We have set the left

truncation distance at 300 m for the TurboGoose.

Bf (“Sea State”) Effects.―Sighting data were classified into five Beaufort (Bf) categories. For

this analysis, we consider (separately) sightings from the Twin Otter and Twin Commander aircraft flying

at altitudes 900–1500 ft. These were the two aircraft type/altitude categories with sufficient sample size

for meaningful analysis. The left truncation distance (Ltrun) was set as 300 m for the Twin Otter and 450

m for the Twin Commander (as above).

Twin Otter: For Bf 0 to 1, the f(0) factor is 3.72 based on all sightings beyond Ltrun = 300 m, or

2.61 after the additional exclusion of sightings >2700 m from the trackline, i.e., >2400 m laterally

(“right”) from Ltrun (Fig. 15.3A; Table 15.2). This right truncation distance (Rtrun) is the lateral distance

where detection probability diminished to 15% of that at Ltrun. Rtrun distances quoted below are measured

relative to Ltrun.

FIGURE 15.2. Aircraft type vs. relative detection probability at various perpendicular distances for bowhead whale sightings from (A) Twin Commander and (B) TurboGoose aircraft flying at altitudes 900–1500

ft, i.e. 274–457 m. See Figure 15.1B for corresponding Twin Otter data. n = number of sightings. Relative Detection Probability

Perpendicular Distance from Trackline (m)

Relative Detection Probability

0

0.4

0 600

0.6

0.8

1.0

1.6

0.2

1.2

300 900 1200 1500 1800 2100 2400

1.4

0

0.4

0 600

0.6

0.8

1.0

1.4

0.2

1.2

300 900 1200 1500 1800 2100 2400

A. Twin Commander

B. Turbo Goose

n = 210

n = 436
15-10 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

FIGURE 15.3. Beaufort sea state (Bf) vs. relative detection probability at various perpendicular distances

from inner border of transect (Ltrun = 300 m from trackline) for bowheads observed from Twin Otter aircraft flying at altitudes 900–1500 ft (274–457 m). (A) Bf 0 and 1, (B) Bf 2, (C) Bf 3, (D) Bf 4, and (E) Bf 5

and 6. f(0)b and nb apply to all sightings beyond inner border. trun = right truncation distance (in meters)

relative to inner border, based on relative detection probability of 0.15 (dashed line). f(0)a and na apply to

sightings between inner border and trun. ƒ(0) factors are calculated from a half-normal key model with

cosine adjustment terms. Relative Detection Probability

A. = 0-1 Bf Relative Detection Probability

B. = 2 Bf

Perpendicular Distance from Inner Border (m)

0

0.2

0.4

0.6

0.8

1.2

0 400 1200 800 1600 2400 2800 3200 3600 2000 4000

1.0

0

0.2

0.4

0.6

0.8

1.2

0 400 1200 2000 4000 800 1600 2400 2800 3200 3600

1.0

f(0) = 3.56

 = 368

trun = 2100

 = 336

b

b

a

n

n

f(0) = 2.06 a

f(0) = 3.72

 = 123

trun = 2400

 = 113

b

b

a

n

n

f(0) = 2.61 a
§15. Bowheads: Correction Factors for Aerial Surveys 15-11

FIGURE 15.3. Continued. Relative Detection Probability

C. = 3 Bf Relative Detection Probability

E. = 5-6 Bf

Perpendicular Distance from Inner Border (m)

Relative Detection Probability

D. = 4 Bf

0

0.2

0.4

0.6

0.8

1.2

0 400 1200 2000 4000 800 1600 2400 2800 3200 3600

1.0

0

0.2

0.4

0.6

0.8

1.2

0 400 1200 2000 4000 800 1600 2400 2800 3200 3600

1.0

0

0.2

0.4

0.6

0.8

1.2

0 400 1200 2000 4000 800 1600 2400 2800 3200 3600

1.0

f(0) = 3.67

 = 235

trun = 2200

 = 214

b

b

a

n

n

f(0) = 2.31 a

f(0) = 3.64

 = 76

trun = 1650

 = 67

b

b

a

n

n

f(0) = 1.83 a

f(0) = 3.27

 = 190

trun = 1850

 = 166

b

b

a

n

n

f(0) = 1.76 a
15-12 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

Bf Left

Altitude Sea Trun. Track- Left No. of No. of

IDa (ft) State Ice (m) line Trun. f(0) Sightings f(0) Sightings

Twin Otter

1 900-1500 0-1 0-99% 300 2700 2400 3.72 123 2.61 113

2 900-1500 2 0-95% 300 2400 2100 3.56 368 2.06 336

3 900-1500 3 0-95% 300 2500 2200 3.67 235 2.31 214

4 900-1500 4 0-50% 300 2150 1850 3.27 190 1.76 166

5 900-1500 5-6 0-10% 300 1950 1650 3.64 76 1.83 67

6 900-1500 0-4 0% 300 2400 2100 3.35 702 2.07 631

7 900-1500 0-4 0-25% 300 2700 2400 4.11 770 2.24 707

8 900-1500 0-4 25-99% 300 1250 950 5.61 93 1.61 73

9 >1500 0-4 0-25% 600 3000 2400 4.91 299 2.58 263

Twin Commander

10 <900 0-4 0-5% 150 2550 2400 5.73 116 2.38 104

11 900-1500 0-1 0-5% 450 3250 2800 2.55 95 2.11 89

12 900-1500 2 0-5% 450 2050 1600 3.51 82 1.61 71

13 900-1500 3 0-5% 450 2150 1700 3.56 70 1.74 62

14 900-1500 4 0-5% 450 1875 1425 4.26 77 2.28 70

15 900-1500 5-6 0-5% 450 1350 900 6.88 26 1.28 26

16 900-1500 0-4 0-5% 450 2850 2400 6.34 287 2.4 265

Turbo Goose

17 <900 0-4 25-99% 150 1100 950 2.89 38 2.57 33

18 900-1500 0-4 0-25% 300 2700 2400 3.38 109 2.23 88

19 900-1500 0-4 25-99% 300 1250 950 5.48 84 1.67 64

a

ID is a reference number for cross-reference to Chapter 9.

TABLE 15.2. Truncation distance and estimated values of f(0) for combinations of aircraft type, altitude, Beaufort

sea state, and ice cover. f(0) values are given before and after right truncation. All curves were fitted with a halfnormal cosine model.

Right Trun.

(m) rel. to Before R-trun After R-trun

Figure 15.3 and Table 15.2 show the results for the Twin Otter flying at altitude 900–1500 ft with

various Bf values. The overall f(0) values derived without right truncation did not change much as Bf

increased (range 3.27–3.72). As expected, the lateral distances at which detectability had diminished to

15% of the maximum tended to decrease as Bf sea states increased, from Rtrun = 2400 m at Bf 0–1 to

1650 m at Bf 5–6 (i.e., from 2700 m to 1950 m from trackline). The f(0) values derived after allowing for

the variable Rtrun tended to diminish with increasing Bf, from 2.61 at Bf 0–1 to 1.76–1.83 at Bf 4–6.

Twin Commander: For Bf 0 to 1, the f(0) factor is 2.55 based on all sightings beyond Ltrun = 450 m, or

2.11 after excluding sightings >2800 m from Ltrun (i.e., 3250 m from the trackline; Fig. 15.4A; Table 15.2).

The overall f(0) values derived without right truncation increased progressively as Bf increased, from 2.55 at

Bf 0–1 to 6.88 at Bf 5–6. The lateral distances at which detectability had diminished to 15% of the maximum

decreased markedly as Bf sea states increased, from Rtrun = 2800 m at Bf 0–1 to just 900 m at Bf 5–6 (i.e., 3250

m to 1350 m from trackline). These results indicate that observers had much reduced ability to sight bowheads

at long lateral distances when Bf sea states increased from 0 to 6. The f(0) values derived after allowing for the

strong trend in Rtrun were variable but did not form a steady progression.
§15. Bowheads: Correction Factors for Aerial Surveys 15-13

Ice Cover Effects.—Ice cover was stratified into two categories, 0% and 25–99%, and limited to

Bf sea states 0–4. Sightings from areas with 1–24% ice cover were not used due to low sample sizes.

The analysis was based on sightings from a Twin Otter flying at altitudes 900–1500 ft, for which Ltrun was

300 m. In this situation, ice cover had a substantial effect on Rtrun and f(0) (Fig. 15.5; Table 15.2). When

all sightings beyond Ltrun were considered, f(0) increased from 3.35 with no ice to 5.61 with 25–99% ice.

The lateral distance at which detectability diminished to 15% of maximum (Rtrun) was much higher with

no ice than with 25–99% ice (2100 vs. 950 m; i.e., 2400 vs. 1250 m from trackline). After allowing for

the large difference in Rtrun, f(0) was higher with no ice than with 25–99% ice (2.07 vs. 1.61). Very similar trends were evident for the TurboGoose flying at 900–1500 ft altitude over 0–25% ice vs. 25–99% ice

(Table 15.2). These results show that observers had reduced ability to sight bowheads at long lateral

distances when substantial ice was present.

Availability Bias Factor ga(0)

Behavioral observations from three studies in the central Beaufort Sea during September–October

(Table 15.1) provided information about the durations of 440 surfacings and 182 dives by “presumably

undisturbed” bowheads, excluding calves. The data for whales engaged in a variety of activities were

examined to determine how surfacing–dive profiles, proportion of time near the surface, and the “availability” correction factor ga(0) vary with whale activity (Table 15.3). Availability factors were calculated

without and with the adjustment to allow for short dives (see Methods). Feeding is the most common

activity in the eastern Alaskan Beaufort Sea during the autumn (Chapter 12). The probability that a typical feeding whale near the trackline will be at the surface while that location is visible to an aerial surveyor is about 0.153. Traveling is the second most common activity and the corresponding probability

for traveling whales is about 0.125. The availability factor was lower for traveling whales than for any

other whale activity that we examined. Socializing whales, with ga(0) = 0.234, were about twice as likely

to be sighted as compared with traveling whales (Table 15.3).

During aerial surveys, observers frequently do not have the whales in view for sufficient time to

determine the whale activity. Therefore an overall ga(0) is needed that combines the data from all activities. The overall ga(0) value calculated with the adjustment for short dives was 0.144 (Table 15.3E).

This overall factor was used to estimate the number of whales in the eastern Alaskan study area on dates

when systematic aerial surveys were done (Chapter 9). The corresponding overall ga(0) value calculated

in the conventional manner without the adjustment for short dives (see Methods) was 0.148 ± s.e. 0.113.

Detectability Bias Factor gd(0)

Besides missing submerged bowheads, aerial surveyors fail to detect some of the bowheads that are

at the surface close to the trackline as the aircraft passes. To estimate the proportion detected, two surveyors observed independently from the right side of the aircraft during three studies (Table 15.1). Based

on the lateral distance distributions shown earlier, we considered the sightings at lateral distances 300–

700 m from a Twin Otter and 450–850 m from a Twin Commander (i.e., 0–400 m from the inner truncation distance) when survey altitude was 900–1500 ft. This is the survey band where the detection probability for whales at the surface is assumed to be near 1.0 during calculation of f(0). Beaufort states at

times when these double independent surveys were done ranged from 0 to 6 with a median of 3.

There were 32 sightings of bowheads 0–400 m from the inner boundary of the transect by rightside observers during these double independent observer surveys. Of these, 13 bowheads were seen by

both observers (B = 13), 12 by only the front observer (S1 = 12), and 7 by only the rear observer (S2 = 7).
15-14 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

FIGURE 15.4. Beaufort sea state vs. relative detection probability at various perpendicular

distances from inner border of transect (Ltrun = 450 m from trackline) for bowheads observed from Twin

Commander aircraft flying at altitudes 900–1500 ft (274–457 m). Otherwise as in Figure 15.3. Relative Detection Probability

A. = 0-1 Bf Relative Detection Probability

B. = 2 Bf

Perpendicular Distance from Inner Border (m)

0

0.2

0.4

0.6

0.8

1.4

0 400 1200 2000 4000 800 1600 2400 2800 3200 3600

1.0

0

0.2

0.4

0.6

0.8

1.2

0 400 1200 2000 4000 800 1600 2400 2800 3200 3600

1.0

1.6

1.2

f(0) = 2.55

 = 95

trun = 2800

 = 89

b

b

a

n

n

f(0) = 2.11 a

f(0) = 3.51

 = 82

trun = 1600

 = 71

b

b

a

n

n

f(0) = 1.61 a
§15. Bowheads: Correction Factors for Aerial Surveys 15-15

FIGURE 15.4. Continued Relative Detection Probability

C. = 3 Bf Relative Detection Probability

E. = 5-6 Bf

Perpendicular Distance from Inner Border (m)

Relative Detection Probability

D. = 4 Bf

0

0.2

0.4

0.6

0.8

1.4

0 400 1200 2000 4000 800 1600 2400 2800 3200 3600

1.0

0

0.2

0.4

0.6

0.8

1.4

0 400 1200 2000 4000 800 1600 2400 2800 3200 3600

1.0

0

0.2

0.4

0.6

0.8

1.2

0 400 1200 2000 4000 800 1600 2400 2800 3200 3600

1.0

f(0) = 4.26

 = 77

trun = 1425

 = 70

b

b

a

n

n

f(0) = 2.28 a

1.2

1.2

f(0) = 3.56

 = 70

trun = 1700

 = 62

b

b

a

n

n

f(0) = 1.74 a

f(0) = 6.88

 = 26

 = 26

b

b

a

n

n

trun = 900

f(0) = 1.28 a
15-16 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

FIGURE 15.5. Ice cover vs. relative detection probability at various perpendicular distances from inner

border of transect (Ltrun = 300 m from trackline) for bowheads observed from a Twin Otter aircraft flying at

altitudes 900–1500 ft (274–457 m). (A) Ice cover 0%, and (B) ice cover 25–99%. Otherwise as in Figure

15.3.

Relative Detection Probability

A. Ice = 0%

Perpendicular Distance from Inner Border (m)

Relative Detection Probability

B. Ice = 25-99%

0

0.2

0.4

0.6

0.8

1.2

0 400 1200 2000 4000 800 1600 2400 2800 3200 3600

1.0

0

0.2

0.4

0.6

0.8

1.2

0 400 1200 2000 4000 800 1600 2400 2800 3200 3600

1.0

f(0) = 5.61

 = 93

trun = 950

 = 73

b

b

a

n

n

f(0) = 1.61 a

f(0) = 3.35

 = 702

trun = 2100

 = 631

b

b

a

n

n

f(0) = 2.07 a
§15. Bowheads: Correction Factors for Aerial Surveys 15-17

Mean Mean

Sum of Sum of # Dives Surface Dive

Dive Surface and Time Time s + 21.596

Group Activity Durations Times Surfacings (s ) (u ) s + u

A. Traveling Whales

Dives <21 s - - -- - -

Dives >21 s 54,054 7027 65/75 93.7 831.6 0.125

All dives 54,054 7027 65/75 93.7 831.6 0.125

B. Feeding Whales

Dives <21 s 90 37 7/3 12.3 12.9 -

Dives >21 s 32,647 11,986 56/154 77.8 583.0 0.150

All dives 32,737 12,023 63/157 76.6 519.6 0.165

Correcteda 0.153

C. Traveling + Feeding Whales

Dives <21 s - - -- - -

Dives >21 s 15,757 5337 20/50 106.7 787.8 0.143

All dives 15,757 5337 20/50 106.7 787.8 0.143

D. Socializing Whales

Dives <21 s 34 6 2/2 3.0 17.0 -

Dives >21 s 11,258 12,240 32/156 78.5 351.8 0.233

All dives 11,292 12,246 34/158 78 332 0.242

Correcteda 0.234

E. All Activities

Dives <21 s 124 43 9/5 8.6 13.8 -

Dives >21 s 113,716 36,590 173/435 84.1 657.3 0.143

All dives 113,840 36,633 182/440 83.3 625.5 0.148

Correcteda 0.144

TABLE 15.3. Calculation of the probability that an average bowhead whale near the trackline will be at the

surface while within an aerial surveyor's field of view, g a (0). All times are in seconds. Based on

behavioral observations of presumably undisturbed whales in and near the eastern Alaskan Beaufort Sea 

during September and early October, calves excluded. See "Methods" for data sources and calculation

details.

a

 See "Methods" section re procedure for calculating corrected (s + t )/(s + u ). 
15-18 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

Based on the method of Magnusson et al. (1978), the estimated number of singles or groups present

within the 400-m strip was

( )( )

( ) 1 38.0

1

1 1 ˆ 1 2 − = +

+ + + + = BS B S B N

The actual number of singles or groups sighted by one or both observers was 32, or 84% of the estimated

N = 38 present at the surface within the narrow strip and available for detection.

Again following Magnusson et al. (1978), the probability that a single observer would detect a

bowhead or group of bowheads that is at the surface within the designated 400-m strip is as follows:

( ) 0.592 ˆ 2

2 (0) 1 2 = + + = NS S B

gd

Thus, if a single observer is present on one side of the aircraft, the uncorrected number of bowheads seen

by that observer in the narrow strip where sightability is near-optimum should be divided by 0.592 to

allow for animals present at the surface but not detected. If two observers are present on one side, their

joint uncorrected count should be divided by 0.84.

The estimated variances of Nˆ and gd(0) are required when calculating the confidence limits for the

estimated numbers of bowheads present. Magnusson et al. (1978) provided a formula for ) ˆ var(N , but

this did not allow for the fact that S1, S2, and B are random variables, not constants (D.G. Chapman, pers.

comm., 1982). The variances can be approximated using the delta method (Taylor series expansion) as

shown in Figure 15.6. Raw counts of bowheads by a single observer on one side of the aircraft can be

corrected for animals present at the surface but not seen by dividing by 0.592 ± s.e. 0.1604. The gd(0)

factor was also calculated for each study separately:

_gd(0)_ s.e.(gd(0)) Sightings

1981 Aerial Survey for SOHIO 0.731 0.2949 13

1985–86 Feeding Study 0.625 0.3574 7

1998–2000 Feeding Study 0.533 0.2425 12

All Studies 0.592 0.1604 32

These gd(0) correction factors are independent of any correction for submerged whales. As derived

here, they apply only to the strip within 0–400 m of the inner truncation distance, i.e., to the strip where

detection is near-optimum. The f(0) factors, described earlier, account for the reduced probability of

detecting a whale as its distance from the trackline increases.

When gd was re-calculated for the strip 400–1000 m from the inner truncation distance, we found

gd = 0.421 ± s.e. 0.1285 (n = 32), confirming the reduced probability of detecting a whale as its distance

from the trackline increases (Table 15.4). If a strip transect method involving a wider strip were to be

used without allowance for fall-off in detectability at longer lateral distances, then a different gd factor

based on all double-independent sightings within that wider strip-width would be required. For the dataset considered here, gd calculated for a strip 0–1000 m from the inner truncation distance was 0.505 ± s.e.

0.1018 (n = 64; Table 15.4).
§15. Bowheads: Correction Factors for Aerial Surveys 15-19

FIGURE 15.6. Calculation of variance of the gd(0) factor. We are grateful to the late Dr. D.G. Chapman,

Univ. of Washington, Seattle, and Dr. P.H. Peskun, York Univ., Toronto, who derived this method for

Davis et al. (1982).

The variance of the estimated N is approximated using the delta method (Taylor series expansion) as follows:

( ) ( ) ( ) ( ) B

B

N S

S

N S

S

N N var ˆ var ˆ var ˆ ˆ var

2

2

2

2

1

2

1 















∂

∂ + 















∂

∂ + 















∂

∂ ≅

where the partial derivatives are evaluated at the mean values approximated by S1, S2 and B (12, 7 and 13 respectively, for the

present data). Now,

( )

( ) 14

21

1

ˆ 1 2

1

= +

+ + = ∂

∂

B

S B

S

N

( )

( ) 14

26

1

ˆ 1 1

2

= +

+ + = ∂

∂

B

S B

S

N

( )( ) ( ) [ ] ( )( )

( ) 14

8

1

ˆ 1 1 1 1 1

2

1 2 1 2 = +

+ + + + + + − + + + + = ∂

∂

B

B S B S B S B S B

B

N

Assuming S1, S2 and B have approximate Poisson distributions, their variances can be assumed equal to the observed values.

Thus,

( ) ( ) ( ) ( ) 13 55.3878

14

8 7

14

26 12

14

21 ˆ var

2 2 2

 = 

 



  + 

 



  + 

 



 N =

( ) 55.3878 7.442 ˆ s.e. N = =

The variance of the detection probability gd(0) must also be calculated using the delta method because gd(0) is a function of

four random variables, S1, S2, B and N, whose means are here estimated as 12, 7, 13 and 38. Given that

N

S S B

gd ˆ 2

2 (0) 1 + 2 + =

Then we have

( ) ( ) ( ) ( ) ( ) N

N

g B

B

g S

S

g S

S

g

g d d d d

d ˆ var ˆ

ˆ (0) var ˆ (0) var ˆ (0) var ˆ (0) var ˆ (0)

2 2

2

2

2

1

2

1





 





∂

∂  + 

 





∂

∂

+ 















∂

∂

+ 















∂

∂

≅

again evaluating the partial derivatives at the estimated mean values. Thus,

76

1

ˆ 2

ˆ (0) 1

1

= = ∂

∂

S N

gd

76

1

ˆ 2

ˆ (0) 1

2

= = ∂

∂

S N

gd

38

1

ˆ

ˆ (0) 1 = = ∂

∂

B N

gd

( ) 64.18

1

ˆ 2

2

ˆ

ˆ (0)

2

1 2 = − + + = − ∂

∂

N

S S B

N

gd

Assuming that S1, S2 and B have approximate Poisson distributions, and using the previous estimate of

( ) 55.3878 ˆ var N = , then

( ) ( ) ( ) ( ) ( ) 55.3878 0.025739

64.18

1 13

38

1 7

76

1 12

76

1

var ˆ (0)

2 2 2 2

 = 

 



  + − 

 



  + 

 



  + 

 





gd =

and the corresponding standard error is 0.025739 = 0.1604
15-20 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

Parameter 0-400a 400-1000 0-1000

Sightings by

Front observer only S1 12 14 26

Rear observer only S2 7 10 17

Both observers B 13 8 21

Total sightings 32 32 64

Estimated no. groups N 38 47.6 84.1

Single-obs. detection prob. g d 0.592 0.421 0.505

s.e. g d 0.1604 0.1285 0.1018

TABLE 15.4. Double independent observer results for various lateral distances, plus calculated values

for the detectability bias factor, g d . Strip widths are measured from the left truncation distance, which

varied with aircraft type.

Strip Width (m)

a

 Results from the 0-400 m zone are assumed to estimate detection probability at the optimum lateral distance, 

i.e., g d (0). 

Discussion

Lateral Distance Factor f(0)

Line transect methods for estimating densities and numbers of animals have the advantage, over

strip transects, of allowing for differences in detection probability as a function of distance from the trackline. However, standard line transect methods assume that detectability is maximum on the trackline and

diminishes with increasing lateral distance. During many aerial survey projects, it is not possible to

observe the trackline below (or in front of) the aircraft. Even if one or more observers can see the trackline, this is at the periphery of their vision if they are also required to watch for animals to the side of the

aircraft. Consequently, in the projects considered here, as in many others, detectability was reduced close

to the trackline as compared with that at an “optimum” lateral distance (Fig. 15.1, 15.2). In this situation,

a standard approach for line transect analysis is to offset the inner edge of the survey area to the “optimum” lateral distance, and to exclude sightings within the strip of reduced detectability closer to the

trackline (e.g., Hiby et al. 1984; Dohl et al. 1986; Buckland et al. 1993). That approach was used here.

The resulting “left-truncated” distribution of lateral distances is suitable as a basis for fitting standard

line-transect models. Alternative methods retaining sightings in the reduced-sightability zone close to the

trackline have been described, e.g., Quang and Lanctot (1991), but are not widely used. In this study, the

left-truncation distance was determined for surveys at varying altitudes and from three types of aircraft.

Line transect methodology (unlike strip transect methods) can use sightings at lateral distances

large enough that detection probability is considerably reduced relative to that at the optimum lateral

distance (Buckland et al. 1993). This is important in surveys of infrequently-sighted animals, as it

provides a larger sample size than would be obtained if only the sightings near the optimum distance

could be considered, as during strip transect surveys. However, in fitting a line-transect model to the

distribution of lateral distances, model fit may be improved by excluding sightings beyond some lateral

distance where detection probability is low, e.g., 15% of that at the optimum distance (Buckland et al.

1993). In this study, we analyzed the data both without and with right truncation, for comparison.

Results were obtained separately for different aircraft types, Beaufort (Bf) sea states, and ice conditions.
§15. Bowheads: Correction Factors for Aerial Surveys 15-21

Altitude and Aircraft Type: The width of the zone below the aircraft where sightability was reduced varied depending on aircraft altitude. The width of this zone, and thus the left truncation distance,

varied directly with altitude. Most surveys of bowhead whales, especially in recent years, have been

flown between 900 and 1500 ft a.s.l. (274–457 m), and the following discussion is based on surveys at

these altitudes.

The type of aircraft affected the width of the reduced-sightability zone below the aircraft. This

zone was narrower for Twin Otters than for Twin Commanders, with the TurboGoose being intermediate.

Some of these differences may have been attributable to differences in the usual window and seating

configurations in the particular aircraft used here, rather than to any inherent differences among the

aircraft. In the Twin Commander, the seats were lower (relative to the windows) than is often the case in

Twin Otters. Even with bubble windows in the Twin Commander, observers could not comfortably look

downward (as well as sideways) during an extended aerial survey. The flat side windows in the

TurboGoose no doubt restricted downward visibility despite their large size. The presence of an observer

with forward visibility in the co-pilot’s seat during many Goose surveys counteracted this to some degree.

Sea-State (Bf): The effects of wave (Bf) conditions and ice cover were also examined to determine

how they affected the rate at which the probability of detecting a bowhead whale at the surface of the

water diminishes as its distance from the trackline increases. The right truncation distance, where sighting probability is 15% of that at the optimum lateral distance, is one measure of this effect. For both the

Twin Otter and the Twin Commander, the right truncation distance diminished from Bf state 0–1 to Bf

5–6. For the Twin Otter, Rtrun values were similar for Bf 0–3 (2100–2400), and lower for Bf 4–6 (1650–

1850 m) (Fig. 15.3). Based on this measure, surveys under Bf conditions 0 to 3 would appear to be most

useful in calculating density estimates. However, for the Twin Commander, Rtrun was high for Bf 0–1

(2800 m), notably lower for Bf 2–4 (1425–1700 m), and lower still for Bf 5–6 (900 m; Fig. 15.4).

Restricting surveys to Bf 0–1 conditions is not practical, so (at least for surveys in a Twin Commander)

there is a need for different right truncation distances and correspondingly different f(0) factors depending

on Bf conditions.

Strip-transect surveys by LGL in the Canadian and Alaskan Beaufort Sea during the 1980s demonstrated that observed densities of bowheads tended to decrease as sea-state increased (Table 15.5). For

example, as compared with surveys under Bf 0–3 conditions, the average observed density during surveys

with Bf 4–5 was reduced to 51% in the Canadian Beaufort Sea (1981 and 1983 data), and to 67% in the

Alaskan Beaufort Sea (1984–86 data). Part of this effect may be attributable to the effects of increasing

sea-state on the maximum distance at which bowheads at the surface are detectable. However, the six

studies contributing to Table 15.5 were all done from Twin Otter aircraft, and the densities were

calculated based on sightings in the strips 100–1100 or 200–1200 m from the trackline, depending on

survey altitude. Within 1 km of Ltrun, the shape of the lateral-distance function from a Twin Otter is not

strongly dependent on Bf (Fig. 15.1). Therefore, much of the sea-state effect evident in Table 15.5

probably was attributable to a reduction in detectability of bowheads close to the trackline as sea-state

increased. That effect is not fully taken into account by the calculation of different Rtrun and f(0) values

for different sea states. Ideally, different gd(0) factors should also be determined for different sea states.

However, we do not have sufficient data from double-independent observer surveys to allow this (see

below).

Ice Cover: We found that the number of sightings at increasing lateral distances diminished more

rapidly with 25–99% ice cover than with 0% ice cover (Twin Otter) or 0–25% ice cover (TurboGoose).
15-22 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

Sea Bf

Statea Statea km # #/1000 km2 km # #/1000 km2

0 0 2285 19 4.16 4320 17 1.60

1 2 7623 59 3.87 12,067 23 0.95

2 3 10,885 83 3.81 8928 29 1.62

3 4 7717 25 1.62 4858 9 0.93

4 5 4704 24 2.55 1974 3 0.76

5+ 6+ 1006 0 0 985 2 1.02

0-2 0-3 20,792 161 3.87 26,314 69 1.31

3-4 4-5 12,421 49 1.97 6832 12 0.88

a

These results were originally classified by sea state; equivalent Beaufort states (Bf) are shown. b

From 1981 data of Davis et al. (1982) and 1983 data of McLaren and Davis (1985), combined.

c

From Evans et al. (1987), summarizing four LGL studies in 1984-86.

TABLE 15.5. Effect of sea state on observed densities of bowheads during strip transect surveys

of the Beaufort Sea. Transect width 1 km on each side of aircraft, with Ltrun = 100 m or 200 m for

surveys at 500 ft (152 m) or 1000 ft (305 m) altitude, respectively.

Canadian Beaufort Sea Alaskan Beaufort Sea

Aug. - Sept. b Sept. - Oct.c

The associated Rtrun values (950 vs. 2100–2400 m) provide one measure of this. Also, for both aircraft

types, f(0) was strongly dependent on ice cover. When right-truncation was applied, f(0) decreased with

increasing ice cover. Thus, ice cover tended to reduce sightability of bowheads, especially at longer

distances from the trackline, relative to that in open-water.

Before conducting this analysis, our subjective impression was that ice can either greatly impair or

substantially increase sightability of bowheads, depending on ice type. If ice is broken up into a myriad

of small pans, it is very difficult to sight bowheads amidst all the other objects in the water. However, if

most of the sea is covered by large, featureless pans with just a few isolated areas of open water, observers can ignore large parts of the field of view and concentrate their attention on the few areas where a

bowhead could surface. In this largely-retrospective analysis, we usually could not separate these two

categories of ice from the data available to us. We expect that Rtrun and f(0) factors would differ substantially between these two types of ice if they were distinguished.

Availability Bias Factor ga(0)

Bowhead whales are below the surface and invisible to aerial surveyors the majority of the time.

The proportion of time bowheads are below the surface varies with whale. In the eastern Alaskan Beaufort Sea during late summer and early autumn, traveling whales had the lowest probability of detection

(availability bias factor), and whales engaged in socializing had the highest. Socializing whales were

twice as likely to be sighted by aerial observers than were traveling whales. Feeding is the most common

activity in the eastern Alaskan Beaufort Sea during this season (Chapter 12) and the probability of detecting feeding whales during aerial surveys is only slightly higher than that of detecting traveling whales

(Table 15.3). Detection probability for bowheads feeding in water >20 m deep was very similar to that of

traveling bowheads (Table 15.6), which were mainly in water >20 m deep.
§15. Bowheads: Correction Factors for Aerial Surveys 15-23

Water % Time at

Season and Area Depth Surfacing Dive Surface g a (0)a

Traveling Whales

Spring at Barrow, AK - 1.35 6.63 16.9 0.214

"Autumn", E Alaska - 1.52 13.83 9.9 0.122

Autumn, Baffin Bay - 1.49 9.36 13.7 0.171

Feeding Whales

Summer, Canadian Beaufort ≤20 m 1.25 2.86 30.4 0.392

Summer, Canadian Beaufort >20 m 0.91 3.83 19.2 0.268

"Autumn", E Alaska ≤20 m 1.10 5.84 15.9 0.210

"Autumn", E Alaska >20 m 1.73 15.73 9.9 0.120

Late summer, Baffin Bay >50 m 1.77 15.8 10.1 0.121

Socializing Whales

Summer, Canadian Beaufortb - 1.12 2.77 28.8 0.380

"Autumn", E Alaskab - 1.27 5.67 18.3 0.235

Late Summer, Baffin Bay - 1.19 1.64 42.0 0.548

a

 (s + t )/(s + u ), with t assumed to be 21.6 s, not corrected for dive durations <t . b

Includes socializing combined with travel, feeding, or both.

TABLE 15.6. Variation in availability correction factor g a (0)a depending on whale activity and study

area/season. Mean surfacing and dive duration are from Thomas et al. (Chapter 13), incorporating

data of Richardson et al. (1995, MS). Mothers and calves excluded; exclusion of mothers accounts for

slight differences in E Alaska values relative to Table 15.3. See Table 13.4 for ± s.d and n.

Mean Duration (min) of

Mean surfacing and dive durations, and the percentage of time at the surface, can differ substantially depending on study area and season as well as whale activity (see Chapter 13; summarized in Table

15.6). “Availability” factors derived for bowheads in one area and season may not apply directly to bowheads engaged in the same activity in another area or season. Surfacing and dive durations of bowheads

can also depend significantly on specific environmental, temporal, and whale-activity variables, as shown

in Chapter 13 for the eastern Alaskan area in late summer–early autumn, and in Richardson et al. (1995,

MS) for other areas and seasons. Therefore, estimates of “percent time at surface” and “availability”

based on pooled observations of whales at different times and places are inevitably approximations.

These “average” correction factors may be appropriate for the combined data from a variety of days of

surveying, but may not be appropriate to a given whale or to a specific day of aerial surveys.

Detectability Bias Factor gd(0)

Aerial surveyors fail to detect some of the bowheads that are at the surface as the aircraft passes.

The detectability (= perception) bias factor gd(0) estimates the proportion detected in the strip where

observation conditions are optimal (commonly referred to as “along the track line”) based on surveyors

observing independently from the same side of the aircraft. This correction factor is independent of the

correction for whales missed as a function of increasing distance from the trackline, f(0). We calculated

gd(0) for the strip within 400 m of the inner truncation distance, where f(0) is assumed to be near 1.0. For

that strip, our estimates of gd(0) for bowheads are 0.59 ± s.e. 0.16 for a single observer, and 0.84 for two

observers on the same side of the aircraft.
15-24 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

The gd values for the zones 400–1000 m (and 0–1000 m) from the inner truncation distance were

lower than gd(0) based on sightings in the 0–400 m zone (Table 15.4). The data came from surveys in

both Twin Otter (1981, 1985–86) and Twin Commander (1998–2000) aircraft. The lower detectability

factor in the 400–1000 m zone was presumably attributable mainly to the Twin Commander data. The

relative number of bowhead sightings 400–1000 m vs. 0–400 m from the inner truncation distance was

reduced at high sea states during Twin Commander surveys, but less so during Twin Otter surveys (Fig.

15.4 vs. 15.3).

The available data are insufficient to allow us to calculate separate gd(0) factors for surveys under

different Beaufort sea states (Bf), especially if also partitioned by aircraft type. Aerial survey data from

the Canadian Beaufort Sea in summer and, independently, the Alaskan Beaufort Sea in autumn, show that

average apparent densities of bowheads as observed from a Twin Otter aircraft tended to diminish with

increasing Bf (Table 15.6). This suggests that gd(0) depends on sea state. However, the relationship may

be somewhat weaker than implied by Table 15.6, as those density data are based on strip transects extending 1 km outward from the left truncation distance. Sea state may have some effect on relative detectability in the 400–1000 m vs. 0–400 m zone, even for the Twin Otter (Fig. 15.3). To whatever extent this

occurs, the lower densities recorded during Twin Otter Surveys at high sea states may be partly a result of

sea state effects on f(0) as well as on gd(0). However, the factor primarily responsible for the lower

observed densities at high sea states during Twin Otter surveys was probably a reduction in gd(0).

During the double independent observer method as used here, the two observers view essentially

the same area at the same time. This is both a strength (providing matched data) and a problem. Factors

affecting detectability by one observer also affect the other observer, and this can cause bias (Pollock and

Kendall 1987). There has been considerable recent discussion of improved procedures for analysis of

double-independent observer data, taking account of factors expected to influence sightability (e.g.,

Borchers et al. 1998; Chen 1999). In future work it may be useful to apply these approaches to the

bowhead data.

In general, estimation of bowhead abundance from aerial survey data is likely to be improved by

application of line transect models that take into account the simultaneous influences of the various

factors discussed here, and others, on detection probability. At least some of the effects of aircraft type,

aircraft altitude, lateral distance, sea state, ice cover and whale activity are already considered in a

univariate sense in this analysis. Additional factors that might be built into a multivariate line-transect

detection model for bowheads include aircraft groundspeed, bubble vs. flat windows, number of observers, whale group size, visibility, glare, and ice type. In the meantime, the correction factors developed

here provide at least a preliminary basis to estimate absolute abundance of bowhead whales in the

Beaufort Sea from aerial survey data.

Summary

Aerial surveys have been used to estimate the number of bowheads present in the eastern Alaskan

Beaufort Sea at various times during late summer and autumn for the present study. However, meaningful estimates of numbers present can only be made if the raw aerial survey data are adjusted using

appropriate correction factors for missed whales. Not all whales present close to an aerial survey trackline are detected by the aerial surveyors, and raw aerial survey results underestimate the densities and

numbers of whales present. (1) Sightability is often reduced directly below the aircraft and, beyond some

“optimum” lateral distance, diminishes with increasing lateral distance. (2) Some whales are below the

surface and undetectable as the aircraft passes; this is “availability bias”. (3) Not all whales at the surface
§15. Bowheads: Correction Factors for Aerial Surveys 15-25

at the optimum lateral distance are detected; this is “detectability bias”, sometimes called “perception

bias”. In theory, three correction factors, designated f(0), ga(0), and gd(0), can be computed to compensate in large part for these three biases. We estimated these three correction factors for aerial surveys of

bowhead whales, and investigated their variability.

Lateral Distance from Trackline and f(0): Aerial survey data were used to determine the effect of

lateral distance on sightability, and the influences of aircraft type, survey altitude, wave height, and ice

cover. Eight aerial-survey studies in the Alaskan and Canadian Beaufort Sea during 1979–2000 provided

data on distances of bowhead sightings from the trackline. Altitude and aircraft type affected the size of

the zone directly below an aircraft where sightability was reduced. The higher the altitude, the wider the

zone. Twin Otter aircraft had a narrower zone of reduced sightability below the aircraft than did Twin

Commanders; a TurboGoose was intermediate. Wave height (expressed as Beaufort sea state, Bf) and ice

cover each affected the rate at which sightability diminished with increasing distance from the trackline.

Also, the effect of Bf state depended on aircraft type. With increasing Bf conditions and ice cover, the

relative number of sightings at the longer lateral distances diminished. As a result, the lateral distance

where sighting probability diminished to 15% of that at the optimum distance declined with increasing Bf

state and ice cover, and f(0) values also changed.

Availability Bias Factor ga(0): This factor estimates the proportion of whales that are at the surface

and potentially visible to aerial surveyors as the aircraft passes overhead. We determined this factor for

whales in the eastern Alaskan Beaufort Sea and adjacent Canadian waters (Flaxman Isl. to Herschel Isl.)

during September–October based on three studies of bowhead behavior in that area during 1985–86 and

1998–2000. This correction factor varied substantially with whale activities. The probability was lowest for

traveling whales, slightly higher for feeding whales, and notably higher for whales engaged in socializing:

ga(0) = 0.125, 0.153, and 0.234, respectively. Our overall estimate of ga(0) for an average bowhead in the

eastern Alaskan Beaufort Sea during late summer and autumn is 0.144. These factors are slightly higher than

the corresponding proportions of time the whales spend at the surface, as the factors assume that any whale

near the trackline will be sighted if it surfaces during an (approx.) 21.6-s period while that area is in view.

Detectability Bias Factor gd(0): This factor estimates the proportion of whales at the surface near

the trackline that are detected by observers. We estimated gd(0) based on the double independent observer method, as applied during three aerial survey projects in the Canadian (1981) and Alaskan (1985–86,

1998–2000) Beaufort Sea. This method applies an analysis of the capture–recapture type to sightings by

two surveyors observing independently from the same side of the aircraft, considering sightings within a

400-m strip of where detectability is optimal. Our estimates of gd(0) for bowheads are 0.59 ± s.e. 0.160

for a single observer, and 0.84 for two observers on the same side of the aircraft. Detectability was lower

in a 600-m strip just beyond the inner 400-m strip (gd = 0.42 ± 0.129 for one observer). Other aerial

survey evidence indicates that this factor very likely is affected by sea state.

The correction factors developed here are used elsewhere (Chapter 9) to convert raw aerial survey

data into estimates of the actual numbers of bowheads present in the eastern Alaskan Beaufort Sea on

various occasions.

Acknowledgements

We thank the many pilots and aerial surveyors whose efforts contributed to this study. In particular, we thank Don Ljungblad (NOSC), Sue Moore and Janet Clarke (SAIC), and Steve Treacy and Don

Hansen (MMS), for their long-term efforts in conducting the MMS/NOSC aerial surveys. Rolph Davis of

LGL directed the 1981 and 1985 Canadian studies plus the 1986 SWEPI study in Alaska, and John Hall
15-26 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

of COPAC directed the 1993 study for ARCO. We also thank the sponsors of the projects that contributed data: principally MMS, SOHIO (now BP Alaska), SWEPI, ARCO, and WesternGeco (see Table

15.1). We thank Steve Treacy and Janet Clarke for providing the MMS/NOSC dataset, and Jeremy

Davies (NOAA) for access to the ARCO/COPAC data from 1993. LGL’s 1985–86 and 1998–2000 aerial

surveys for MMS and SWEPI were conducted under Scientific Research Permits 517, 518 and 481-1464

issued by the National Marine Fisheries Service. For help with certain statistical issues we thank the late

Dr. D.G. Chapman and Dr. P.H. Peskun (in 1982) and Dr. B.F.J. Manly of WEST Inc.

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McLaren, P.L. and R.A. Davis. 1985. Distribution of bowhead whales and other marine mammals in the southeast

Beaufort Sea, August - September 1983. Environ. Stud. Revolv. Funds Rep. 001. Can. Oil & Gas Lands

Admin., Ottawa, Ont. 62 p. NTIS MIC-97-06454.

Miller, G.W., R.E. Elliott, W.R. Koski, V.D. Moulton and W.J. Richardson. 1999. Whales. p. 5-1 to 5-109 In:

W.J. Richardson (ed.), Marine mammal and acoustical monitoring of Western Geophysical's open-water

seismic program in the Alaskan Beaufort Sea, 1998. LGL Rep. TA2230-3. Rep. from LGL Ltd., King City,

Ont., and Greeneridge Sciences Inc., Santa Barbara, CA, for Western Geophysical, Houston, TX, and U.S.

Nat. Mar. Fish. Serv., Anchorage, AK, and Silver Spring, MD. 390 p.

Moore, S.E. and J.T. Clarke. 1991. Estimates of bowhead whale (Balaena mysticetus) numbers in the Beaufort Sea

during late summer. Arctic 44(1):43-46.

Moore, S.E., J.T. Clarke and D.K. Ljungblad. 1989. Bowhead whale (Balaena mysticetus) spatial and temporal

distribution in the central Beaufort Sea during late summer and early fall 1979-86. Rep. Int. Whal. Comm.

39:283-290.

Patenaude, N.J., W.J. Richardson, M.A. Smultea, W.R. Koski, G.W. Miller, B. Würsig and C.R. Greene Jr. 2002.

Aircraft sound and disturbance to bowhead and beluga whales during spring migration in the Alaskan

Beaufort Sea. Mar. Mamm. Sci. 18(2):309-335.

Pollock, K.H. and W.L. Kendall. 1987. Visibility bias in aerial surveys: a review of estimation techniques.

J. Wildl. Manage. 51(2):502-510.
15-28 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

Quang, P.X. and E.F. Becker. 1996. Line transect sampling under varying conditions with application to aerial surveys. Ecology 77(4):1297-1302.

Quang, P.X. and R.B. Lanctot. 1991. A line transect model for aerial surveys. Biometrics 47(3):1089-1102.

Richardson, W.J., B. Würsig and G.W. Miller. 1987. Bowhead distribution, numbers and activities. p. 257-368 In:

W.J. Richardson (ed.), Importance of the eastern Alaskan Beaufort Sea to feeding bowhead whales, 1985-86.

OCS Study MMS 87-0037. Rep. from LGL Ecol. Res. Assoc. Inc., Bryan, TX, for U.S. Minerals Manage.

Serv., Reston, VA. 547 p. NTIS PB88-150271.

Richardson, W.J., K.J. Finley, G.W. Miller, R.A. Davis and W.R. Koski. 1995. Feeding, social and migration

behavior of bowhead whales, Balaena mysticetus, in Baffin Bay vs. the Beaufort Sea―regions with different

amounts of human activity. Mar. Mamm. Sci. 11(1):1-45.

Richardson, W.J., W.R. Koski, G.W. Miller, N.J. Patenaude and B. Würsig. MS. Behavior and movements of bowhead whales (Balaena mysticetus) during spring migration in the Alaskan Beaufort Sea. LGL Ltd., King

City. Ont.

Scott, G.P. and H.E. Winn. 1980. Comparative evaluation of aerial and shipboard sampling techniques for estimating the abundance of humpback whales (Megaptera novaeangliae). MMC-77/24. U.S. Mar. Mamm.

Comm., Washington, DC. 96 p. NTIS PB81-109852.

Thomas, L. (co-ordinator) 1999. DISTANCE version 3.5, release 5. Developed by Research Unit for Wildlife

Population Assessment, Univ. St. Andrews, U.K.

Treacy, S.D. 2002. Aerial surveys of endangered whales in the Beaufort Sea, fall 2000. OCS Study MMS 2002-

014. U.S. Minerals Manage. Serv., Anchorage, AK. 111 p.

Würsig, B., E.M. Dorsey, M.A. Fraker, R.S. Payne, W.J. Richardson and R.S. Wells. 1984. Behavior of bowhead

whales, Balaena mysticetus, summering in the Beaufort Sea: surfacing, respiration, and dive characteristics.

Can. J. Zool. 62(10):1910-1921.
16. BOWHEAD WHALE DISTRIBUTION, NUMBERS AND ACTIVITIES:

SUMMARY AND CONCLUSIONS

William R. Koski and W. John Richardson1

The project plan called for the use of aerial surveys, aerial observations of behavior, and aerial

photographic methods to document the distribution, abundance, behavior, sizes, and residence times of

bowheads in the study area. More specifically, the purposes of the aircraft-based fieldwork were to

• determine distributions and raw numbers of bowheads within the study area during late summer/early-autumn feeding periods in that area,

• determine correction factors for sightability during aerial surveys,

• use the above data to estimate whale-days of utilization of the study area,

• document the proportion of time spent feeding,

• characterize feeding behavior (near-surface/water-column/bottom), and

• determine residence times of individual bowheads.

Each of these types of data has been collected and described in Chapters 9–15. Where possible, the

variability in the various measured variables has been characterized. Much of this variability relates to

year-to-year differences in the environment and in the use of the area by bowhead whales.

The aerial survey crew had the additional critical task of providing the boat-based crew with information about locations of bowhead whales (especially feeding whales) on a real-time basis. This was

necessary to allow the boat-based crew to locate bowheads for the purpose of sampling the zooplankton

around feeding whales, as described in Chapter 6.

The distribution, numbers, and activities of bowhead whales in the eastern Alaskan Beaufort Sea

during late summer and autumn are described in Chapters 9–15. Data in these chapters come from field

studies conducted in that area during September of 1998–2000 and from a closely-related study in the

same area during 1985–86, augmented with data from other studies of bowheads in and near that area

during 1979 to 2000. The aerial surveys conducted annually since 1979 by or for MMS (e.g., Treacy

2002) were of particular value in augmenting the specific feeding-study work. However, several other

projects also provided important aerial survey and photogrammetric data in various years. As called for

in the project plan, three different study methods were used to collect most of the field data: (1) aerial

surveys, (2) behavioral observations from a circling aircraft, and (3) vertical aerial photogrammetry.

Aircraft-based field studies during the present study were conducted from 10 to 24 September in 1998, 10

to 30 September in 1999, and 8 to 25 September. Aircraft-based field studies during the comparable

1985–86 study were from 4 September to 3 October in 1985 and 2 to 27 September in 1986. The project

aircraft, a Twin Commander in 1998–2000 and a Twin Otter in 1985–86, was based at Kaktovik, AK,

throughout those five field seasons. Additional information on bowhead distribution and numbers spec-

 

1

 LGL Ltd., environmental research associates, 22 Fisher St., POB 280, King City, Ont. L7B 1A6.

Phone: 905-833-1244; e-mail: bkoski@lgl.com, wjr@lgl.com
16-2 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

ific to these five years was provided by systematic aerial surveys conducted by MMS from 1 August to 20

October in 1985, 15 August to 17 October in 1986, 31 August to 27 October in 1998, 3 to 17 September

in 1999, and 1 September to 12 October in 2000.

Bowhead whales are in the eastern Alaskan study area from August (and sometimes July) through

mid- or late October. The specific feeding-study work in 1985–86 and 1998–2000 was largely limited to

the period of peak bowhead abundance during September. However, comparable data of various types

acquired during other studies in August and October helped in addressing utilization of the study area

throughout the period when significant numbers of bowheads are in the area.

For most components of the aerial work, the study area was the area from Camden Bay in Alaska

(145o or 146oW, depending on task) to Herschel Island in the Yukon (139oW), and from the shore north to

~71o10’N, which was well beyond the continental shelf. For several of the specific analyses of bowhead

distribution and habitat utilization, the study area was divided into four E–W regions, and four waterdepth strata―a total of 16 analysis zones. From west to east, the four analysis regions were the Camden

Bay, Kaktovik, Demarcation Bay, and Komakuk regions (overall, “Flaxman Isl. to Herschel Isl.”). The

most easterly of the four analysis zones (Komakuk) consisted of Canadian waters between the Alaska–

Yukon border and Herschel Island. Data from that area have been excluded from certain analyses in

order to address bowhead utilization of the eastern Alaskan Beaufort Sea proper. For seasonal analyses,

the data were categorized into six half-month (15- or 16-day periods) from 1 August to 31 October.

The eastern part of the Alaskan Beaufort Sea is not the only part of the Alaskan Beaufort where

bowhead whales feed during late summer and autumn. Feeding has been reported occasionally in the

central Alaskan Beaufort (Flaxman Island to Colville River, 146°–151°W), and more commonly from the

western Alaskan Beaufort (Landino et al. 1994; Treacy in prep.). The stomach contents of bowheads harvested at Barrow in fall also show that feeding occurs very commonly in the western Alaskan Beaufort,

just east of Barrow, during fall (Lowry 1993; Chapter 18). The few stomach content samples from Cross

Island in the central Alaskan Beaufort (Chapter 18) are consistent with Inupiat reports that bowheads

often feed in that region as well. This project’s focus on the eastern Alaskan Beaufort Sea is a result of

specific interest in the importance of that area for feeding (see Chapter 1). We do not suggest that the

eastern Alaskan Beaufort Sea is unusually important for feeding as compared to other parts of the Alaskan

Beaufort.

Distribution and Abundance

Bowhead abundance differed significantly among the four depth strata within the “Flaxman Isl. to

Herschel Isl.” study area, with highest average abundance recorded in the Shelf Break stratum (40–200 m

deep), followed by the Middle Shelf stratum (20–40 m) and Nearshore stratum (<20 m); average abundance was lowest in the Continental Slope stratum (>200 m deep). Differences in bowhead abundance

among the four E–W regions were marginally significant, with average bowhead abundance for the

August–October period being highest in the east and declining to the west (Chapter 9). The Komakuk

zone was not sampled uniformly, and some parts of that zone, especially its Nearshore and (to a lesser

degree) Middle Shelf strata, may be more important to bowheads than demonstrated here.

Local residents occasionally see bowheads in the study area during July and August; they see peak

numbers in September, and some bowheads during October (Chapter 2).

Aerial surveys showed that bowhead abundance and distribution varied significantly by half-month

period during August–October of 1979–2000. Moderate numbers of bowheads were present during early

August, especially in the Continental Slope zone (>200 m deep) of the three easternmost regions, i.e.,
§16. Bowhead Distribution, Numbers & Activities: Summary & Conclusions 16-3

Kaktovik to Komakuk. Fewer bowheads were present during the second half of August, and there was a

slight shoreward shift in the distribution of bowheads from early to late August. This suggests that,

during late August, bowheads may have been moving from offshore Alaskan waters toward the coast, as

has been seen farther east along the Yukon coast. During the first half of September, numbers of bowheads in the “Flaxman to Herschel” study area increased. Also, their distribution shifted inshore and

expanded westward to span the full width of the study area, coincident with increased migration into and

through the study area. Peak bowhead abundance in the study area was recorded during the second half

of September, when bowheads were most abundant in the Shelf Break and Middle Shelf strata (i.e.,

depths 20–200 m). Fewer bowheads were present during early October, and the highest densities were

again shoreward of the 200 m contour. By late October, only small numbers of bowheads were present

and densities were higher in the western half of the study area.

The activities of bowheads seen during aerial surveys were categorized insofar as possible,

although this is difficult to do during the brief period while a whale is in view during a straight-line aerial

survey. The percentage of bowhead sightings during aerial surveys that were recorded as “traveling” was

similar (86–100%) over the six half-month periods. For traveling whales, the headings were significantly

non-uniform (and predominantly westward or northwestward) in all half-month periods except for late

August. However, the variation in headings was larger up to 15 September than thereafter. Behavioral

studies, summarized below, indicate that the “percent traveling” figures from aerial surveys (86–100%)

were overestimated.

Few bowheads were identified as feeding during the systematic aerial surveys. The low apparent

numbers of feeding bowheads are, in large part, an artifact of the difficulty of recognizing feeding activity

during the brief glimpses of whales that typically occur during systematic aerial surveys. (Behavioral

studies, summarized below, provided more comprehensive data on feeding.) Areas where feeding was

seen most commonly included Nearshore waters close to Komakuk (Yukon); in Nearshore, Middle Shelf

and Shelf Break waters off Demarcation Bay; and in Middle Shelf and Shelf Break waters off Camden

Bay. (During behavioral studies, feeding was also seen in Nearshore waters off Kaktovik after the whaling period. Aerial surveys generally avoided that area while Kaktovik whalers were whaling, so there

were fewer opportunities to see feeding there during aerial surveys.)

During the 1979–2000 period, the relative abundance of bowheads recorded during aerial surveys

of the “Flaxman to Herschel” area has varied markedly from year to year. Eight years had abundance

indices higher than the overall average of 0.77 bowheads seen per 100 km of surveying. The highest

indices were recorded in 1990 (4.05 /100 km), 1999 (3.32 /100 km) and 1995 (3.23 /100 km). Seven of

the eight years with above-average bowhead abundance were in the 1990s, and 9 of 13 years with belowaverage bowhead abundance occurred prior to 1990. The average of the annual abundance indices was

0.36 bowheads seen/100 km during 1979–89 vs. 1.60 /100 km for 1990–2000. The increase since 1989

was larger than can be accounted for by the previously-reported rate of increase of this population (3.2%

per year). This same trend was present in numbers of whales, corrected for biases and missed whales,

estimated to be present in the area from Demarcation Bay to Camden Bay inshore of the 200 m contour

during September and early October. The increased sighting rates since 1989 are apparently attributable

in part to an increase in the relative utilization of the present study area as compared with other areas.

The abundance indices during the years when most of our behavioral and zooplankton data were

collected were

• 0.12 and 0.39 bowheads seen/100 km in 1985 and 1986, respectively (9th and 3rd highest of 10

indices before 1990), and
16-4 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

• 1.64, 3.32, and 0.60 bowheads seen/100 km in 1998, 1999 and 2000, respectively (5th, 2nd and

9th highest of 11 indices since 1989).

Thus, based on the aerial survey data, our behavioral and zooplankton field studies were conducted during

two years of relatively high bowhead use (1986 and 1999), one year of average use (1998), and two years

of low use (1985 and 2000). Behavioral and zooplankton data were obtained during years of relatively

high and relatively low bowhead use during both the 1979–89 and 1990–2000 periods.

The numbers of bowheads present inshore of the 200 m contour in the “Flaxman-to-border” area

off Alaska (i.e., in 3 of our 4 E–W zones, and 3 of 4 depth strata) were estimated whenever survey coverage allowed. These line transect estimates included allowance for aircraft type, aircraft altitude, and

missed whales. The estimates ranged from 0 during many surveys to 4505 (± s.e. 3702) bowheads. The

4505 figure was based on 765 km of survey coverage on 13 September 1999. Within most half-month

periods, the estimated numbers of bowheads present were highly variable, but average numbers followed

the same seasonal pattern as the abundance indices described above for the overall study area.

Total numbers of whale-days of utilization of continental shelf waters (depth <200 m) in the “Flaxman to border” area have been estimated for the five principal years of study. These estimates are based

on estimated numbers of bowheads present on various days (with allowance for missed whales), and on

the seasonal pattern of whale abundance. Total whale-days for the area ranged from ~12,000 to 31,000 in

four years, but was 102,000 in 1999. The accuracy of these values is unknown, but the lower values are

surprisingly low. The estimated size of this bowhead population was ~6500 in the mid-1980s and

~10,000 in the late 1990s. A bowhead would require ~2.4 days to swim steadily from the Canadian

border to western Camden Bay (Flaxman Isl.) even if it did not stop to feed (Chapter 11). A possible

explanation for the relatively low whale-days estimates in some years is that more bowheads than now

thought may migrate west through deep (>200 m) offshore areas where aerial survey coverage is limited.

Habitat Use by Size Class

Photogrammetric methods (Koski et al. 1992) were used in Chapter 10 to investigate geographic

and seasonal patterns in the size composition of bowhead whales in and near the eastern Alaskan Beaufort

Sea (Flaxman Isl. to Herschel Isl.). Subadults, adults and calves made up 64.7, 29.2 and 6.2%, respectively, of the bowheads photographed in that area (including the Komakuk region) over all years of this

study (1982, 1984–86, 1998–2000). We found proportionally more subadults and fewer adults within that

area than are estimated to be in the overall population even after allowance for our under-sampling during

the early and late parts of the migration. The presence of a relatively high proportion of subadults suggests that the parts of the “eastern Alaskan Beaufort Sea" ≤200 m deep were relatively more important for

subadult bowheads than for adults, at least during the years of our study (Chapter 10).

There was significant variation in length–frequency distributions of whales among years, geographic subdivisions of the study area, water depth categories, and time periods. This variation was due

to variable use of the study area by each age class in different years, differences in the water depths preferred by different age classes, and different migration timing by each age class. Small subadult whales

(<10 m long) are the dominant group in shallow (<20 m) nearshore habitats, with progressively fewer

small subadult whales and more large subadults and adults as water depth increases. Small subadults start

to arrive in the study area during late August, numbers peak in early September, and they have passed

through the study area by early October. Large subadults start to arrive in late August but are scarce until

September; moderate numbers are still present in early October. Mothers and calves start to arrive in
§16. Bowhead Distribution, Numbers & Activities: Summary & Conclusions 16-5

early September and are common in the study area until early October. Other adults arrive mainly in late

September and are common in early October.

In the mid-1980s, large numbers of subadult bowheads tended to occur in shallow nearshore areas

in the eastern part of the study area from the Kongakut River Delta to Herschel Island, and they lingered

in that area for days to a few weeks. Few whales were seen in that nearshore area during 1998–2000, and

those that were seen there did not appear to linger.

Rates of Movement and Residence Times

 We estimated rates of movements from within-day sightings of photographed bowhead whales in

the “Flaxman–to–Herschel” portion of the Beaufort Sea, including the eastern Alaskan Beaufort plus the

Yukon coast west of Herschel Isl. We compared those results to similar data collected farther east during

the 1980s, off the Yukon east of Herschel Isl. (Yukon East) and in Amundsen Gulf (Chapter 11). Withinday speeds were not significantly different between the “Flaxman–to–Herschel” zone and the more easterly Canadian zones. Within the “Flaxman–to–Herschel” zone there was a significant difference in

speeds among years. The difference appeared to be due to slower speeds by feeding adults in 1999 than

by primarily subadult whales in other years.

The main activities recorded for bowheads during late summer and autumn were feeding and

traveling. Based on the successive locations of bowheads observed during prolonged behavioral observation sessions, the average rate of movement of bowheads in the “Flaxman–to–Herschel” zone was

~1.54 km/h for feeding whales vs. 4.50 km/h for traveling whales. The mean alongshore component of

the net speed, measured along the 288o–108o (True) axis, was 0.71 km/h eastward for feeding whales, and

3.67 km/h westward for traveling whales.

We also attempted to estimate residence times of bowhead whales in the “Flaxman–to–Herschel”

zone using four general types of data: photoidentification data, behavioral observations, aerial survey

results, and telemetry data. Photoidentification data from the 1980s were also used to estimate residence

times in the Yukon East and Amundsen Gulf zones. (1) Photographic resightings were used to determine

within-day rates of movement and intervals between resightings for the “Flaxman–to–Herschel” zone and

for the Yukon East and Amundsen Gulf zones in all years with sufficient data. Net speeds from withinday photographic resightings were the basis for one estimate of residence times of whales in each zone.

Resighting intervals indicated minimum residence times for the specific whales resighted. A computer

program (SODA, “stop-over duration analysis”) was used to derive an unbiased estimate of residence

time in each zone based on data on photographic effort, sightings, and resightings (Reboulet et al. 2001;

Schaub et al. 2001). (2) Behavioral observations of bowhead whales were used to determine short-term

rates of movement of whales, and net westward speeds of whales engaged in different activities, in the

“Flaxman–to–Herschel” zone during late summer and autumn of 1985–86 and 1998–2000. (3) Aerial

survey data were used to estimate residence times in that area based on relative densities during aerial

surveys and based on numbers of whales estimated to be present during aerial surveys. (4) Data on whale

locations obtained during telemetry studies in three years were used to estimate residence times of whales

in the “Flaxman–to–Herschel” zone.

Annual residence time estimates for the “Flaxman–to–Herschel” zone were extremely variable

among years and among different methods of analysis applied to the same year. We attribute the latter

variability to biases in the different methods that interacted with year-to-year variability in sampling

effort, whale distribution, and whale activities. For example, most behavioral data and some photographs

collected in 1985 were from feeding whales off the Yukon coast (“border–to–Herschel Isl.”); activities
16-6 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

and speeds of those whales were not representative of whales in Alaskan waters in 1985. In general, estimates based on behavior data, and to a lesser extent photoidentification data, were positively biased.

We identified six calculation methods based on photoidentification, behavioral observation, aerial

survey, and telemetry data that provided residence-time estimates most representative of actual residence

times. However, even with these six methods, a few of the residence time estimates were recognizably

biased. The annual residence time estimates for the “Flaxman–to–Herschel” area during 1985–86, 1988,

1989, 1992, and 1998–2000 based on these six methods varied from 2.1 to 8.3 d and averaged 5.1 d. A

sensitivity analysis (in Appendix 23.1) indicated that the 95% confidence limit for the 5.1-d estimate of

mean residence time was 4.2 to 6.1 d.

Residence times varied dramatically among years because of different levels of use of the “Flaxman–to–Herschel” zone for feeding during late summer and autumn. In 1985 and 1986, the eastern part

of the area was used for feeding by subadult bowheads during late summer. In 1998, subadult whales

briefly stopped to feed in central and western parts of the study area during their migration through the

study area. In 1999, adult whales stopped to feed for extended periods in eastern and central parts of the

study area. During 2000, most whales migrated through the study area without stopping.

The mean interval for between-day photographic resightings was 4.35 days in the “Flaxman–to–

Herschel” zone and 5.91 days in Canadian zones east of there, and estimates for both areas were highly

variable among years. The tendency for residence times in the “Flaxman–to–Herschel” zone to be shorter

than those in the Canadian areas became more evident when the SODA model was used to estimate total

residence times, including allowance for time present before the first and after the last sighting, and for

whales photographed only once. SODA showed that the mean residence time estimates for the Canadian

zones were considerably longer (12.6 d) than the mean resighting intervals (5.9 d), whereas the mean

residence times for the “Flaxman–to–Herschel” zone were either lower than (1985) or similar to (1986,

1999) the mean resighting intervals. The shorter residence times in the latter zone compared to the Yukon

East and Amundsen Gulf zones are consistent with distributional and behavioral data in suggesting that

bowhead whales spent less time feeding in the “Flaxman–to–Herschel” area than in the more easterly

Canadian zones in most years. Furthermore, residence time estimates for eastern Alaska would be further

reduced if data from Canadian waters west of Herschel Island (the Komakuk area) were excluded from

the “Flaxman–to–Herschel” zone.

Activities and Behavior

We used data obtained during our behavior observation sessions to describe and quantify the activity budgets of bowhead whales while they were in the “eastern Alaskan” Beaufort Sea, including some

data from the Komakuk zone east of the Alaska–Yukon border (Chapter 12). Of 84 observation sessions

under presumably undisturbed conditions, 69 were off northeast Alaska (Flaxman Island to border) and

15 were in Canadian waters from the Alaska/Yukon border to Herschel Island.

Feeding was the most common activity of bowhead whales in and near the eastern Alaskan Beaufort Sea in September/early October during 1985, 1986, 1998, and 1999; but not in 2000. Over the five

seasons, bowheads engaged in feeding for ~47% of the total time (9% in 2000; 38–66% in other years).

Overall, ~34% of the time was spent feeding in the water column, 8% on near-surface (“skim-”) feeding,

and 4% on near-bottom feeding. Almost all observed feeding in water >20 m deep was water-column

feeding; surface and bottom feeding were proportionally more common in areas ≤20 m deep, but there too

water-column feeding was the most common activity. Mothers and first-year calves were rarely sighted

in waters ≤20 m deep, and the most common activity of mothers was feeding in the water column in areas
§16. Bowhead Distribution, Numbers & Activities: Summary & Conclusions 16-7

>20 m deep. Most whales fed singly. Bottom feeders were usually widely spaced, but water-column and

skim feeders generally were more aggregated, typically with 4+ whales within 1 km of each other. We

did not see skim feeding in echelon formation during late summer–early autumn, although it has been

reported previously in the Alaskan Beaufort Sea. The estimated proportion of time devoted to feeding

during September/early October (47%) was intermediate between values during spring migration east of

Point Barrow, Alaska (1%), and on the summer range in the Canadian Beaufort Sea (71%).

Traveling was the second-most common activity, accounting for 31% of time overall; but 74% in

2000. Travel tended to be in areas 20–49 m deep and in groups of one to two whales. Whales spent more

time traveling during the latter half of September than in early September. Traveling whales were oriented mainly westward. Bowheads commonly interspersed feeding and socializing with travel during the

latter half of September. The estimated proportion of time devoted to traveling (31%) was also intermediate between that during spring migration (81%) and that on the summer range (9%).

Socializing accounted for 18% of the time during September/early October, and other activities

(aside from feeding, travel or socializing) accounted for 4%. Socializing tended to consist of low-level

behaviors such as nudges and other touches, with the exception of apparent sexual aggregations of up to

seven whales per aggregation on two days in September 1998. First-year calves stayed close to their

mothers, showed little surface-active behavior, and were not observed to play. No lone calves were seen,

indicating that calves had not been weaned.

Although feeding was the most common activity of bowhead whales in and near the eastern Alaskan Beaufort Sea during September/early October, there was much intra- and inter-season variability in

the amount and type of feeding, other activities, and specific behaviors, and in the locations (within the

study area) where these activities occurred. These variable results are generally consistent with the

apparent variability in prey availability in the study area, as documented in other parts of this study.

However, bowheads observed in 1999 spent a high proportion of their time feeding, and exhibited

relatively long residence times, even though average zooplankton abundance (at least inshore of the 50 m

contour) was relatively low that year (Chapter 5). Overall, the importance of the study area for latesummer feeding by bowhead whales varies considerably from year to year, and is difficult to predict for

any one late summer–early autumn season.

The activity budgets summarized above do not consider the variable detectability of bowheads

engaged in different activities while we were searching for whales to observe. Based on availability

correction factors presented in Chapter 15 and summarized below, traveling whales are, on average,

available to be detected ~12.5% of the time. Feeding and socializing whales are available to be detected

~15.3 and 23.4% of the time, respectively. If group size and other factors were equal (they are not),

feeding and socializing whales would be 1.2 and 1.9 times more likely to be detected and observed than

traveling whales. Thus the activity budgets presented above may overestimate the proportion of time

engaged in feeding, and particularly in socializing, and underestimate the proportion of time spent

traveling through the study area.

Surfacing, Respiration and Dive Cycles vs. Whale Activity

Data on surfacing, respiration and dive (SRD) cycles of bowhead whales during late summer and

early autumn (Chapter 13) were needed to derive correction factors for whales missed during aerial surveys, and as a basis for analyses of bowhead energetics. Bowheads were observed systematically during

September and early October of 1985–86 and 1998–2000 in the Eastern Alaskan Beaufort Sea and adjacent Canadian waters (“Flaxman–to–Herschel” area).
16-8 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

Whales engaged in feeding showed a noticeable increase in the number of blows per surfacing and

the durations of surfacings and dives across years. Some of this variability may be attributable to the

water depth in which the whales were feeding. In the 1980s most of the observed surfacing–dive cycles

occurred in shallow (≤20 m) water, whereas in the 1990s more of observations came from deeper water,

particularly during 1999. An average SRD cycle by an undisturbed bowhead feeding in shallow (≤20 m)

water, calves excluded, consisted of a 1.10 min surfacing with 4.9 blows spaced 13.1 s apart, followed by

a 5.84 min dive. A corresponding average SRD cycle in water >20 m deep (average 45 m) consisted of a

1.77 min surfacing with 8.5 blows spaced 13.1 s apart, followed by a 16.09 min dive. Whale status and

distance from shore had a strong effect on the SRD cycles of bowheads feeding in and near the Eastern

Alaskan Beaufort Sea. During feeding, surfacings and dives were longer, with more blows per surfacing

and longer intervals between blows, with increasing distance from shore, and for older, larger whales as

compared with subadults.

Traveling bowheads (including those feeding while traveling) tended to have surfacing and dive

cycles similar to those of bowheads feeding in water >20 m deep. Some of this similarity may be attributable to the habitat that the whales are occupying, as traveling whales tended to be in water >20 m deep.

An average SRD cycle by a traveling bowhead (including bowheads that were feeding as they traveled)

consisted of a 1.65 min surfacing with 6.4 blows spaced 15.76 s apart, followed by a 13.66 min dive.

Whale status and group size had a strong influence on the SRD cycles of bowheads traveling in and near

the Eastern Alaskan Beaufort Sea. The standard measures of these cycles were higher for mothers and for

increased group sizes, and were shorter for subadults.

Socializing whales and whales feeding in shallow water tended to have similar breathing characteristics. Some of this similarity may be attributable to the habitat (shallow water) that the whales were

occupying. An average SRD cycle by a socializing bowhead (including bowheads that intermixed socializing with other activities) consisted of a 1.29 min surfacing with 6.0 blows spaced 12.67 s apart, followed by a 5.54 min dive.

Surfacing, Respiration and Dive Cycles vs. Whale Age

Data on age- and size-dependence of surfacing, respiration and dive (SRD) cycles of bowhead

whales (Chapter 14) were needed as a basis for analyses of bowhead energetics. This type of information

is also relevant in deriving correction factors for whales missed during aerial surveys, especially when

there is geographic and seasonal variation in the ages and sizes of bowheads present. For this analysis we

included behavioral data collected during spring bowhead migration around northwestern Alaska (Richardson et al. 1995b) and during summer in the Canadian Beaufort Sea (Dorsey et al. 1989; Richardson et

al. 1995a), along with data from the “eastern Alaskan” area (Flaxman Isl. to Herschel Isl.) in late summer–early autumn. All data were collected by the aerial observation method in 1980–2000.

Subadult whales had shorter median blow intervals than adults and mothers; this was evident for

bowheads engaged in all three whale activities studied (traveling, feeding, and socializing). Subadults

also had shorter dive durations during traveling, and marginally shorter surface times during feeding, as

compared with adults and mothers. Mothers and other adults had similar SRD cycles, with the exception

that, during feeding, other adults had shorter median blow intervals than mothers.

Subadults engaged in traveling showed no spring–fall differences in any of the SRD variables.

Adult whales, in contrast, showed differences in all four variables. Mothers and calves engaged in traveling showed seasonal variability in SRD cycles. For both mothers and calves, there was a noticeable

increase in the number of blows per surfacing, surface times, and dive times from spring to fall.
§16. Bowhead Distribution, Numbers & Activities: Summary & Conclusions 16-9

During travel, nursing dives by calves were much shorter than their other dives in both spring and

fall. Occurrence of nursing also affected SRD cycles of traveling mothers. When nursing, traveling

mothers tended to have long surfacings with long blow intervals and slightly longer than average dive

durations.

Correction Factors for Aerial Surveys

Aerial surveys have been used to estimate the number of bowheads present in the eastern Alaskan

Beaufort Sea at various times during late summer and autumn for the present study (Chapter 9). Meaningful estimates of numbers present can only be made if the raw aerial survey data are adjusted using

appropriate correction factors for missed whales (Chapter 15). Not all whales present close to an aerial

survey trackline are detected by the aerial surveyors, and raw aerial survey results underestimate the

densities and numbers of whales present. (1) Sightability is often reduced directly below the aircraft and,

beyond some “optimum” lateral distance, diminishes with increasing lateral distance. (2) Some whales

are below the surface and undetectable as the aircraft passes. (3) Not all whales at the surface at the

optimum lateral distance are detected. In theory, three correction factors, designated f(0), ga(0), and gd(0),

can be computed to compensate in large part for these three biases (Marsh and Sinclair 1989; Buckland et

al. 1993).

Lateral Distance from Trackline and f(0): Aerial survey data were used to determine the effect of

lateral distance on sightability, and the influences of aircraft type, survey altitude, wave height, and ice

cover. Eight aerial-survey studies in the Alaskan and Canadian Beaufort Sea during 1979–2000 provided

data on distances of bowhead sightings from the trackline. Altitude and aircraft type affected the size of

the zone directly below an aircraft where sightability was reduced. The higher the altitude, the wider the

zone. Twin Otter aircraft had a narrower zone of reduced sightability below the aircraft than did Twin

Commanders; a TurboGoose was intermediate. Wave height (expressed as Beaufort sea state, Bf) and ice

cover each affected the rate at which sightability diminished with increasing distance from the trackline.

Also, the effect of Bf state depended on aircraft type. With increasing Bf conditions and ice cover, the

relative number of sightings at the longer lateral distances diminished. As a result, the lateral distance

where sighting probability diminished to 15% of that at the optimum distance declined with increasing Bf

state and ice cover, and f(0) values also changed.

Availability Bias Factor ga(0): This factor estimates the proportion of whales at the surface and

potentially visible to aerial surveyors as the aircraft passes overhead. We determined this factor for

whales in the “Flaxman Isl.–to–Herschel Isl.” area during September–October based on three studies of

bowhead behavior in that area during 1985–86 and 1998–2000. This correction factor varied substantially with whale activities. The probability was lowest for traveling whales, slightly higher for feeding

whales, and notably higher for whales engaged in socializing: ga(0) = 0.125, 0.153, and 0.234, respectively. Our overall estimate of ga(0) for an average bowhead in the eastern Alaskan Beaufort Sea during

late summer and autumn is 0.144. These factors are slightly higher than the corresponding proportions of

time the whales spend at the surface, as the factors assume that any whale near the trackline will be

sighted if it surfaces during an (approx.) 21.6-s period while that area is in view.

Detectability Bias Factor gd(0): This factor estimates the proportion of whales at the surface near

the trackline that are detected by observers. We estimated gd(0) based on the double independent observer method, as applied during three aerial survey projects in the Canadian (1981) and Alaskan (1985–86,

1998–2000) Beaufort Sea. This method applies an analysis of the capture–recapture type to sightings by

two surveyors observing independently from the same side of the aircraft, considering sightings within a
16-10 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

400-m strip of where detectability is optimal. Our estimates of gd(0) for bowheads are 0.59 ± s.e. 0.160

for a single observer, and 0.84 for two observers on the same side of the aircraft. Detectability was lower

in a 600-m strip just beyond the inner 400-m strip (gd = 0.42 ± 0.129 for one observer). Other aerial

survey evidence indicates that this factor very likely is affected by sea state.

These correction factors were used in the “Distribution and Abundance” chapter (Chapter 9) to

convert raw aerial survey data into estimates of the actual numbers of bowheads present in the eastern

Alaskan Beaufort Sea on various occasions.

Disturbance to Feeding Bowhead Whales

The studies of bowhead feeding ecology in 1985–86 and 1998–2000 did not include any specific

effort to study the reactions of bowhead whales to disturbance or noise. That topic has been addressed in

various other studies sponsored by MMS and others, with work up to 1995 being summarized in Richardson and Malme (1993) and Richardson et al. (1995c). Subsequent reports have primarily concerned reactions of migrating bowheads exposed to various types of industrial activities during active travel in spring

or fall (Richardson et al. 1995b, 1999; Davies 1997; Miller et al. 1999; Schick and Urban 2000; Greene et

al. 2002; Patenaude et al. 2002).

The Discussion section of Chapter 12 includes a subsection on “Possible Human Influences” on

bowheads during the feeding studies in 1985–86 and 1998–2000. As discussed there, bowheads observed

in this study were not exposed to much industrial activity when we observed them. Most of our observations in 1985–86 were well east of the areas where a drillship and seismic vessels were active, and any

observations close to such activities were excluded from consideration. There was no drilling or seismic

exploration in the eastern part of the Alaskan Beaufort Sea during the summer or autumn in 1998–2000.

The boat that we used for zooplankton sampling caused some localized disturbance when it approached

feeding bowheads. On one occasion in 1986, photoidentification data showed that feeding bowheads

displaced by the sampling vessel had returned to their original location 1–2 days later (Thomson and

Richardson 1987). Aerial observations of behavior, from an aircraft circling at 460 m (1500 ft) altitude,

cause very little if any disturbance, and straight-line aerial surveys also cause little disturbance (Richardson et al. 1986; Patenaude et al. 2002). Aerial photogrammetry flights at low altitude (typically ~145 m

or 475 ft) cause some bowheads to dive abruptly or otherwise react, although the proportion doing so is

low (Patenaude et al. 2002). Some bowhead hunting occurs in our study area each year during September, with powerboats being used to approach the whales. Bowheads flee in response to approaching

boats.

Whales of various species seem less responsive to noise and disturbance when they are actively

engaged in certain activities, including feeding and mating (reviewed in Chapter 9 of Richardson et al.

1995c). A few of these observations have pertained specifically to bowhead whales. For bowheads on

the summer feeding grounds in the Canadian Beaufort Sea, our impression has been that animals involved

in feeding, socializing or mating seem less responsive to aircraft, including low-altitude photogrammetric

flights, than were bowheads not engaged in one of these activities (Richardson and Malme 1993). Photographed individuals were often found in the same areas on subsequent days (Koski et al. 1988; see also

Chapter 11), so these low-altitude overflights did not displace many (if any) bowheads from summer

feeding areas. However, feeding bowheads can be disturbed if exposed to a sufficiently strong disturbing

stimulus. Bowheads on the summer feeding grounds in the Canadian Beaufort Sea usually showed a

strong avoidance reaction when a small ship or motor vessel approached directly toward the whales at a

distance as great as 2–4 km (Richardson et al. 1985; Richardson and Malme 1993). Feeding bowheads
§16. Bowhead Distribution, Numbers & Activities: Summary & Conclusions 16-11

also ceased feeding and moved away upon exposure to a seismic vessel within a few kilometers or a playback of dredge sounds (Richardson et al. 1986, 1990). However, bowheads were seen as close as 6 km

from seismic vessels operating on the summer feeding grounds, whereas migrating bowheads in the

Alaskan Beaufort were rarely seen within 20 km of seismic vessels (Richardson et al. 1986 vs. 1999;

Miller et al. 1999).

Studies and observations of several other species of baleen whales in the presence of boats and

ships also indicate that those species tend to be less responsive to vessels when feeding. This has been

noted for North Atlantic right whales, humpback whales, and blue, fin, sei, and Bryde’s whales (see

review and references in Richardson et al. 1995c, p. 262ff ). Feeding whales of these species will react to

approaching vessels, but the reaction distance tends to be less than observed when the animals are not

engaged in feeding, socializing or mating. Brodie (1981a,b) indicated that various baleen whales continue to feed in areas with high fish abundance despite the presence of large numbers of fishing vessels in

those areas. However, he noted that many marine mammals, in order to feed, may have no alternative but

to occupy areas where they are chronically exposed to noise, and that this tolerance should not be assumed to mean that the animals are indifferent to the noise.

Similar observations have been obtained for beluga whales. Although belugas are not baleen

whales, it is interesting to note that feeding belugas also are less prone to react to aircraft and to vessels

than are belugas engaged in some other activities (Bel’kovich 1960; Kleinenberg et al. 1964; Frost et al.

1984; Blane 1990). However, Blane (like Brodie) notes that the continued use of some areas with much

boat traffic reflects the value of these areas to the whales, and should not be interpreted as meaning that

the whales were undisturbed.

In summary, it appears that bowhead whales, like other whales, may be somewhat less responsive

to various human activities when feeding than when not engaged in feeding, socializing or mating. However, feeding bowheads (and other whales) nonetheless can be disturbed and displaced if the disturbance

is sufficiently close and strong. Also, it has been suggested that feeding whales that appear to tolerate

various human activities may be stressed or otherwise affected even though they do not show a strong

avoidance response. In general, the evidence that whales tend to be somewhat tolerant of disturbance

when feeding is rather weak. There have been very few direct comparisons, with consistent methods, of

the proclivity for disturbance when whales are exposed to the same type of human activity while engaged

in feeding vs. other activities. Although whales may well, on average, show weaker disturbance reactions

while feeding, their feeding can nonetheless be interrupted and the whales can be displaced if the disturbance is sufficiently strong. Reactions to approaching ships and powerboats seem especially strong.

Conclusions

There were substantial differences in the numbers, distribution, size classes, residence times, activity budgets, and specific behaviors of bowhead whales in and near the eastern Alaskan Beaufort Sea

during late summer and early autumn of the five years with feeding studies. Bowhead use of that area

during August–October is highly variable. Systematic aerial survey data from 1979–2000 suggest that the

five years when the feeding studies were conducted included years with low, moderate and high use by

bowheads and thus may be reasonably representative of the range of possible usage patterns. However,

usage in any future year probably will differ in at least minor ways from that in any of our five years of

study.

Most bowhead whales of the Bering–Chukchi–Beaufort stock migrate through the eastern Alaskan

Beaufort Sea each year during late summer or early autumn en route to autumn feeding areas farther west
16-12 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

and wintering areas in the Bering Sea. Behavioral observations (and also the stomach contents of

bowheads harvested at Kaktovik―Chapter 18) show that feeding is a common activity while these whales

are in the eastern Alaskan Beaufort Sea. Over the five years studied, the two most common activities of

bowheads, at least during daytime when aerial observations were possible, were feeding (47%) and traveling (31%). The proportions of time engaged in these two activities during late summer and early autumn

were intermediate between those observed during spring, when bowheads spend most of their time

traveling and little time feeding, and during summer, when bowheads spend most of their time feeding

and little time traveling. However, the estimated proportions of time spent feeding during late summer

and autumn ranged from 9% to 66% in different years. The inter-annual differences in numbers estimated

to have been present probably were related to how long whales stopped to feed in the study area, and thus

to residence times.

The abundance and locations of zooplankton concentrations had a strong influence on bowhead

feeding locations (Chapter 6), and very likely also influenced residence times in the study area. We found

that different size classes of bowhead whales had different habitat preferences and different timing of

migration through the study area. Small subadult whales preferred Nearshore waters. As water depth

increased, small subadults became less common and the proportion of large subadults and adults increased. When prey was locally abundant in Nearshore and Middle Shelf waters, as in 1985 and 1986, some

subadult whales lingered in the study area to feed, and many larger whales (which tended to be found in

deeper water) traveled through the study area without stopping to feed. When prey biomass was higher in

Shelf Break waters (40–200 m) than closer to shore, as in 1999, large subadult and adult whales lingered

to feed there, and most small subadult whales traveled through without stopping. When prey was sparse

in the eastern part of the study area, as in 2000, most if not all whales traveled through that area without

stopping. Over all years of this study, subadult whales seemed to make more use of the study area than

adults, but there was year-to-year variation in the use by different age classes. Possible reasons for these

year-to-year differences in utilization are discussed further in Chapter 23, “Integration”.

Recommended Research

The present study incorporated aerial survey data from August to October, but most of the other

techniques for studying bowhead utilization of the eastern Alaskan study area were applied primarily in

September. September is known, from aerial surveys, to be the month of peak utilization of the eastern

Alaskan Beaufort Sea by westward-migrating bowheads. However, information from aerial surveys and

from local residents indicates that bowheads can be present in appreciable numbers from August to

October, with occasional sightings in July (Chapters 2 and 9). Zooplankton biomass and energy content

are expected to vary seasonally, and the tendency for active migration is also expected to increase seasonally. Thus, utilization of the area by bowheads is expected (and in many ways is already known) to vary

with date during the July–October period. More data on distribution, activities, size segregation, and

residence times of bowhead whales in the eastern Alaskan Beaufort Sea during the early and late parts of

the season, e.g., July-August and October, would be helpful in better understanding the importance of the

area to bowheads.

The present study was conducted in and near the eastern Alaskan part of the Beaufort Sea, for

reasons explained in Chapter 1. Some similar studies have been done on parts of the summer feeding

grounds in the Canadian Beaufort Sea. Aerial surveys across the full width of the Alaskan Beaufort Sea

have provided data on seasonal distribution and movements of bowheads in the central and western parts

of the Alaskan Beaufort. However, there is little information on autumn activities, size segregation, and

residence times of bowhead whales in these more westerly parts of the Alaskan Beaufort Sea, or along the
§16. Bowhead Distribution, Numbers & Activities: Summary & Conclusions 16-13

northeast coast of the Chukotsk Peninsula in the western Chukchi Sea. Available data from aerial surveys

and stomach contents indicate that feeding is common in some of these more westerly areas during

autumn, especially at various locations from western Harrison Bay to Barrow (Treacy in prep.). To

understand the relative importance of autumn feeding areas west of the present eastern-Alaskan area,

studies of bowhead activities, size segregation, and residence times in the more westerly areas during

autumn would be useful. Insofar as possible, these studies in the more westerly areas should occur

throughout the seasonal period when bowheads occur in these areas, as evident from previous scientific

studies and the experience of local residents.

Given the documented year-to-year variability in bowhead utilization of feeding areas in eastern

Alaskan waters over the 5 seasons of intensive study, any follow-up study of bowhead utilization in

different months or in different areas should be planned for a duration of at least 3 years if at all possible.

There is partial segregation of size (and age) classes of bowheads when they are passing through

the eastern Alaskan Beaufort Sea during late summer and autumn, with larger (older) whales tending to

be farther offshore (see Chapter 10). To date, observations of activities, residence times, and size segregation in feeding bowheads have been largely limited to bowheads in nearshore and inner-shelf waters,

where subadult whales predominate. Although aerial surveys have extended north into deep-water areas,

aerial survey coverage in those areas has been less intensive than in the areas closer to shore, and survey

coverage has been limited in August, when bowheads seem to prefer deep water areas. Within the eastern

Alaskan Beaufort Sea, it would be desirable to obtain additional data on bowhead utilization of deeper

waters throughout the summer and autumn. In the deeper areas, a higher proportion of the bowheads are

larger, older individuals, and in those areas zooplankton may concentrate at deeper depths, especially in

the later parts of the season.

Direct observations of bowhead activities in the eastern Beaufort Sea (and elsewhere) are limited to

daylight hours. Commencing in August, there are some hours of darkness in the Beaufort Sea region, and

the duration of darkness increases rapidly as autumn progresses. Vertical migration of zooplankton has

not been studied in this area and season. Foraging behavior of bowhead whales is likely to be affected by

any pronounced vertical migration by concentrations of prey. This and other factors could result in

differences in whale activities by day vs. night. Krutzikowsky and Mate (2000) found little evidence of

day–night differences in several behavioral variables, based on satellite telemetry methods applied to

bowheads in the Beaufort and Chukchi Seas during September (Mate et al. 2000). However, the

possibility of day–night differences in bowhead activities deserves further study, perhaps via VHF or

UHF telemetry (e.g., Croll et al. 1998) as well as expanded use of satellite telemetry.

New technology has considerable potential for providing additional data concerning bowhead

utilization of various parts of the Beaufort Sea and other areas. Additional studies utilizing satellite-linked

and VHF (or UHF) radio tags are recommended as these have the potential to provide new levels of

detail concerning distribution, movements, residence times, behavior, and disturbance responses of

bowheads. Ideally, these data would be acquired for whales tagged at different locations and seasons, and

the size/age, status, and (where possible) sex of each whale would be determined. Passive acoustic detection, localization, and (occasionally) tracking of bowheads can also provide data on seasonal distribution, movements, and disturbance responses during autumn migration (Greene et al. 2002). The latter

approach has potential applications in assessing bowhead use of specific regions within the Beaufort Sea

or elsewhere, although it is doubtful whether passive acoustic data could be related specifically to feeding

whales.
16-14 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

Acknowledgements

The U.S. Minerals Management Service, Alaska OCS Region, sponsored the 1998–2000 work, the

majority of the 1979–97 work, and this analysis. We thank the many pilots, aerial surveyors, behavior

observers, and other project personnel whose efforts contributed to the aircraft-based components of this

study as described in Chapters 8–16. MMS personnel conducted many of the systematic aerial surveys.

Other studies in the 1980s whose data are utilized here were sponsored by U.S. National Marine Mammal

Laboratory, the Canadian Department of Indian Affairs and Northern Development, Shell Western

Exploration & Production Inc., and a consortium organized by Sohio Alaska Petroleum Co. (now BP).

Aerial surveys in 1993 were sponsored by ARCO Alaska and conducted by COPAC. Steve Treacy of

MMS and Janet Clarke of SAIC provided digital copies of the 1979–2000 MMS/NOSC data set, and

Jeremy Davies of NOAA provided access to the ARCO/COPAC data from 1993.

LGL’s 1981–84, 1985–86, 1989–94, and 1998–2000 projects for MMS and 1986 project for

SWEPI, all of which provided data used here, were conducted under Scientific Research Permits 338,

426, 517, 518, 670, and 481-1464 issued by the National Marine Fisheries Service.

Additional Acknowledgements specific to the individual chapters concerning various aircraft-based

studies appear near the ends of Chapters 9–15.

We are grateful to the members of the project’s Scientific Review Board for reviewing various

draft plans and interim reports, participating in meetings about the project, and providing advice. SRB

members and alternates have consisted of Dr. Steven Swartz (chair), Maggie Ahmaogak or Thomas

Napageak (Alaska Eskimo Whaling Commission), Craig George or Dr. Todd O’Hara (North Slope

Borough Dept of Wildlife Management), Dr. Ray Jakubczak (BP Exploration (Alaska) Inc.), Joe Kaleak

(Kaktovik Whaling Captains’ Association), Dr. Bob Kenney (University of Rhode Island), Mark Major

(ARCO Alaska and Phillips Petroleum), Brad Smith (National Marine Fisheries Service), and Dr. Judy

Zeh (University of Washington),

We are especially grateful to the Kaktovik whaling captains and others in Kaktovik for their interest in this project, their willingness to discuss the topic repeatedly at various meetings, and their agreement that aircraft-based fieldwork could be conducted in their area during the whaling season.

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Richardson, W.J., B. Würsig and C.R. Greene Jr. 1986. Reactions of bowhead whales, Balaena mysticetus, to

seismic exploration in the Canadian Beaufort Sea. J. Acoust. Soc. Am. 79(4):1117-1128.

Richardson, W.J., B. Würsig and C.R. Greene Jr. 1990. Reactions of bowhead whales, Balaena mysticetus, to

drilling and dredging noise in the Canadian Beaufort Sea. Mar. Environ. Res. 29(2):135-160.

Richardson, W.J., K.J. Finley, G.W. Miller, R.A. Davis and W.R. Koski. 1995a. Feeding, social and migration

behavior of bowhead whales, Balaena mysticetus, in Baffin Bay vs. the Beaufort Sea―regions with different

amounts of human activity. Mar. Mamm. Sci. 11(1):1-45.

Richardson, W.J., C.R. Greene Jr., J.S. Hanna, W.R. Koski, G.W. Miller, N.J. Patenaude and M.A. Smultea, with R.

Blaylock, R. Elliott and B. Würsig. 1995b. Acoustic effects of oil production activities on bowhead and

white whales visible during spring migration near Pt. Barrow, Alaska―1991 and 1994 phases. OCS Study

MMS 95-0051; LGL Rep. TA954. Rep. from LGL Ltd., King City, Ont., for U.S. Minerals Manage. Serv.,

Herndon, VA. 539 p. NTIS PB98-107667.

Richardson, W.J., C.R. Greene Jr., C.I. Malme and D.H. Thomson. 1995c. Marine mammals and noise. Academic

Press, San Diego, CA. 576 p.

Richardson, W.J., G.W. Miller and C.R. Greene Jr. 1999. Displacement of migrating bowhead whales by sounds

from seismic surveys in shallow waters of the Beaufort Sea. J. Acoust. Soc. Am. 106(4, Pt. 2):2281.

Schaub, M., R. Pradel, L. Jenni and J.-D. Lebreton. 2001. Migrating birds stop over longer than usually thought: an

improved capture-recapture analysis. Ecology 82(3):852-859.

Schick, R.S. and D.L. Urban. 2000. Spatial components of bowhead whale (Balaena mysticetus) distribution in the

Alaskan Beaufort Sea. Can. J. Fish. Aquatic Sci. 57(11):2193-2200.

Thomson, D.H. and W.J. Richardson. 1987. Integration. p. 449-479 In: W.J. Richardson (ed.), Importance of the

eastern Alaskan Beaufort Sea to feeding bowhead whales, 1985-86. OCS Study MMS 87-0037. Rep. from

LGL Ecol. Res. Assoc., Bryan, TX, for U.S. Minerals Manage. Serv., Reston, VA. 547 p. NTIS PB88-

150271.

Treacy, S.D. 2002. Aerial surveys of endangered whales in the Beaufort Sea, fall 2000. OCS Study MMS 2002-

014. U.S. Minerals Manage. Serv., Anchorage, AK. 111 p.

Treacy, S.D. in prep. Aerial surveys of endangered whales in the Beaufort Sea, fall 2001. OCS Study MMS 2002-

061. U.S. Minerals Manage. Serv., Anchorage, AK.
DIET AND REGIONAL OCCURRENCE OF FEEDING

17. INTRODUCTION TO DIET AND REGIONAL OCCURRENCE OF FEEDING

COMPONENTS OF STUDY

W. John Richardson 1

This component of the study sought to determine (1) what types of prey bowhead whales of the

Bering–Chukchi–Beaufort (BCB) stock eat, and (2) what parts of their seasonal range provide the predominant part of this food. The principal and most direct method for determining what bowheads eat was

analysis of the stomach contents of bowheads harvested by Inupiat whalers (Chapter 18). The project

also included a pilot study of the fatty acid composition of bowhead blubber in relation to the fatty acid

composition of potential zooplankton prey (Chapter 19). It was hoped that this approach might, when

further developed, provide a method for assessing food consumption over a longer period (and larger

geographic area) than can be assessed from stomach contents. To assess the proportion of the food consumed in different parts of the seasonal range, the carbon and nitrogen isotope ratios in bowhead tissues

were compared with those in the prey from the eastern Beaufort Sea vs. the Bering–Chukchi area (Chapter 20).

Stomach Contents

Prior to this study, the most recent analysis of the stomach contents of BCB bowheads was the

review by Lowry (1993). At that time, relatively few samples of stomach contents were available from

bowheads harvested in the Beaufort Sea during autumn. This study has provided many additional data on

stomach contents of bowheads harvested at Kaktovik in autumn, and at Barrow in autumn and spring. It

has also provided some initial data on stomach contents of bowheads harvested at Cross Island by Nuiqsut hunters. The study of stomach contents was done by Lloyd Lowry and Gay Sheffield of the Alaska

Department of Fish and Game (ADF&G), under subcontract to LGL.

• Kaktovik: During the present study, ADF&G acquired stomach-content (and tissue) samples

from whales harvested at Kaktovik during 1997, 1998, 1999, and 2000. Gay Sheffield of

ADF&G was stationed in Kaktovik during each of those whaling seasons to collect stomach contents, tissue samples, and standard measurements as each whale was landed. The stomachcontent samples were later analyzed by ADF&G (Chapter 18). Bowhead tissue samples collected

at Kaktovik by ADF&G were provided to other researchers for purposes of the fatty-acid analysis

(Chapter 19) and the isotope analysis (Chapter 20). In addition, standard measurements of the

whales harvested at Kaktovik were provided to the North Slope Borough Department of Wildlife

 

1

 LGL Ltd., environmental research associates, 22 Fisher St., POB 280, King City, Ont. L7B 1A6.

Phone: 905-833-1244; e-mail: wjr@lgl.com
17-2 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

Management (NSB-DWM) for inclusion in their harvest database. Additional tissue samples

were provided to NSB-DWM for use in their “bowhead health” study. These samples were

collected under the provisions of Scientific Research Permits 797 (1997) and 481-1464 (1998–

2000) issued by the National Marine Fisheries Service.

• Cross Island: Additional stomach-content samples were obtained from some of the whales harvested in 1999–2000 at Cross Island by Nuiqsut whaling crews (also under permit 481-1464).

Cross Island is located in the Prudhoe Bay region, between Kaktovik and Barrow. Mark Major of

Phillips Petroleum made these collections possible.

• Barrow: J.C. George and Dr. T. O’Hara of the NSB-DWM provided many stomach samples

from bowheads harvested at Barrow in spring and autumn during this study (1997–2000). NSBDWM also made available archived but previously-unanalyzed samples from bowheads harvested

at Barrow during spring and autumn seasons prior to 1997.

ADF&G have analyzed these new or previously-unanalyzed stomach-content samples and associated

data, and have combined these results with previously reported results on stomach contents of bowheads

in the Beaufort Sea. Based on this overall database, they describe and compare the frequency of recent

feeding, and the predominant prey items in the stomachs, for bowheads harvested at different locations

and seasons. They also compare the diet data for whales of different age and gender (see Lowry and

Sheffield, Chapter 18).

Fatty Acids

The types and relative amounts of various fatty acids differ among prey organisms, and these

differences are reflected in the fatty acid composition of the animals that consume them (see Introduction

to Chapter 19 for background). Fatty acids are the largest constituent of lipids and those of carbon chain

length 14 or greater are often deposited in animal tissue with minimal modification from diet. Based on

this, in recent years fatty acid signature analysis has been developed as a new method to examine foraging

ecology in free-ranging animals (Iverson 1993).

Early in this study, in 1997–98, it was recognized that analysis and comparison of fatty-acids in

bowhead tissues and potential prey organisms had the potential to provide additional data on diet beyond

those available from stomach-contents analysis. Two subcontractors involved in related aspects of the

project (ADF&G and University of Alaska Fairbanks) both recommended that a fatty-acids study of

bowheads be included in the project. Stomach contents provide data on the types of foods eaten shortly

before death, and thus close to the harvest site(s). However, they do not show what the harvested whales

ate during previous days and weeks. This is a concern because, in the Beaufort Sea, bowhead whales are

harvested at only three locations. No stomach-content data on diet are available from the summering

grounds in the Canadian Beaufort Sea, or from many other parts of the annual range. Also, some harvested whales provide no stomach-content sample, either because that whale had not eaten shortly before

being struck, or because the stomach contents were lost before the stomach could be examined. The fatty

acid method has the potential to overcome these problems and to complement the data available from

stomach samples.

There has been no previous study of the fatty acids in bowheads, and relatively few such studies

have been done in other cetaceans. However, it was suspected that analyses of the fatty acid composition

of potential prey species (zooplankton) and bowhead blubber samples might help resolve questions concerning bowhead diet. For example, euphausiids are common in bowhead stomachs; however, field
§17. Diet & Regional Feeding: Introduction 17-3

studies generally find high concentrations of copepods near feeding bowheads. Fatty acid analysis may

help clarify the relative contributions of these two taxa to the bowhead diet, including their average contributions over much longer periods than are represented by the stomach contents of harvested whales

(weeks vs. hours). For purposes of fatty acid analysis, the availability of blubber tissue from harvested

whales is particularly advantageous, as the samples of the inner part of the blubber are considered most

suitable for such a study (Hooker et al. 2001). Inner blubber is available from harvested whales, but is

often not available in other studies where the samples must be obtained via remote biopsy methods (see

Chapter 19).

Blubber samples were collected from bowheads taken in the subsistence harvests at Kaktovik and

Barrow as part of this project. These collections were started in 1997 in anticipation that fatty-acids in

bowheads and their prey would be studied at some point during the project. Samples of zooplankton were

available from the zooplankton sampling program conducted by LGL in the eastern Alaskan Beaufort Sea

near Kaktovik during 1998–2000 (see Chapters 5, 6). However, analysis of the fatty acid content of these

samples did not start until later in the project, mainly for budgetary reasons. Budgetary provision was

made to conduct a pilot study on fatty acids in bowheads and their prey during the 3rd year of this 4-yr

project (1999–2000). Although all concerned recognized the potential of this method, the project’s

Scientific Review Board (SRB) advised that the effort on this topic be limited to no more than a pilot

study, given the need to avoid spreading limited resources thinly across too many disciplines. In practice,

a pilot study on this topic was conducted during 1999–2000, with some limited follow up into 2001.

Laboratory analysis and evaluation of fatty acid data were done by Dr. Sara Iverson at Dalhousie

University, Halifax, N.S., in conjunction with ADF&G. Results are reported by Iverson et al. in Chapter

19. The method shows promise, but during the present study it was not implemented early enough, or

with sufficient resources, to allow it to go beyond the pilot-study stage. After seeing the results of the

pilot study, the SRB recommended (in Feb. 2002) that this approach be included as a component of future

bowhead feeding studies (see Annex A).

Stable Isotopes

Preliminary analyses of the carbon-isotope composition of bowhead whales and their prey were

conducted as part of the 1985–86 feeding study (Schell et al. 1987, 1989; Saupe et al. 1989). That work

confirmed earlier indications that the 13C : 12C ratio was different in zooplankton of the eastern Beaufort

Sea as compared with the Bering and Chukchi seas. The early work suggested that bowhead tissues

consisted mainly of carbon from the Bering–Chukchi zooplankton. However, the temporal record of

feeding found along the length of the baleen provided isotopic evidence of some feeding in the eastern

Beaufort Sea. Subsequent work by Dr. Don Schell and colleagues provided further evidence consistent

with their original findings (e.g., Schell and Saupe 1993; Schell et al. 1998). Through continued analysis

of the temporal record of carbon isotope ratios along the length of bowhead baleen, Schell (2000, 2001)

also found evidence of a long-term decline in the productivity of the Bering–Chukchi system. He suggested that this might result in an increased importance of the Beaufort Sea as a food source for BCB

bowheads.

The suggestion that BCB bowheads acquire most of their annual food intake from the Bering and

Chukchi seas and not the summering grounds in the Beaufort Sea was, and is, controversial. Other baleen

whales feed primarily in summer. Feeding is the most commonly-observed activity of bowhead whales in

the Canadian Beaufort Sea from late July until early September (Würsig et al. 1985, 1989; Chapter 12).

(There are no specific observations of their activities in the Canadian Beaufort Sea from June to midJuly.) In most years, feeding is also the most common activity in the eastern Alaskan Beaufort Sea during
17-4 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

September, though somewhat less frequent there than in Canadian waters in summer (Chapter 12). Zooplankton concentrations near whales feeding in the Beaufort Sea are, on average, much denser than those

elsewhere in the Beaufort Sea, indicating that the bowheads are selecting the areas where feeding opportunities are most favorable (Chapter 6). The stomachs of bowhead whales harvested during late summer

and autumn both near Kaktovik and near Barrow (in the eastern and western Alaskan Beaufort Sea,

respectively) often contain large volumes of zooplankton prey (Lowry 1993; Chapter 18). There is also

some recent evidence that some bowheads have larger energy reserves when leaving the Beaufort Sea in

autumn than when arriving in spring (see Chapter 22).

The isotopic method cannot distinguish prey acquired in the Canadian vs. eastern Alaskan parts of

the Beaufort Sea. It is the importance of the smaller “eastern Alaskan” area that is the central issue in this

study. However, if it were conclusively demonstrated that bowheads consume little of their annual food

intake in the eastern Beaufort Sea as a whole, that would be a strong indication that the eastern Alaskan

portion of the eastern Beaufort Sea area must not contribute very much of the annual food intake. If that

determination were made, the key question that this project seeks to answer would be resolved.

Given the apparent inconsistencies in the isotope vs. other evidence concerning the amount of

feeding in the eastern Beaufort Sea, it was considered important to include an expanded stable-isotope

study as part of the present project. The results are provided in Chapter 20 by Sang Heon Lee and Dr.

Don Schell of the University of Alaska Fairbanks, who conducted this work under subcontract to LGL

during 1998–2000. Particular emphasis was placed on acquiring samples from more bowheads than

previously available, especially for autumn, and on comparing feeding strategies of adult vs. subadult

bowheads.

After the draft of this report was completed in January 2002, an independent study of stable

isotopes in bowhead whales from the Beaufort Sea was published by Hoekstra et al. (2002). That study

included data on isotope ratios in tissue subsamples from some of the same individual bowheads analyzed

by Lee and Schell for Chapter 20. There were some apparent discrepancies in the data from these two

studies, and the conclusions were somewhat different. Chapter 20 has been revised to discuss the Hoekstra et al. results. The updated version of Chapter 20 also takes account of further isotopic analyses of

samples from whales where there were apparent discrepancies in the data from the two studies. These

reanalyses confirm the accuracy of the measurements that Lee and Schell reported in their draft report.

Various reviewers of the draft of Chapter 20, including the project’s SRB, recommended that a

sensitivity analysis be performed to assess uncertainty in isotope-based estimates of the percent of their

annual food intake that BCB bowheads obtain in the eastern Beaufort Sea. Dr. Trent McDonald, a

statistician with Western EcoSystems Technology Inc. (WEST), Cheyenne, WY, worked with Dr. Schell

to complete such an analysis, and this is now included as an Appendix to Chapter 20.

Other Evidence on Diet and Regional Feeding

The three specific studies introduced above were designed to provide new information about bowhead diet in the Alaskan Beaufort Sea, and the regional/seasonal allocation of feeding by bowheads.

However, several other components of this project also provided data of direct or indirect relevance:

 Local and traditional knowledge (LTK) contributed by Kaktovik whalers and other Kaktovik

residents indicated that bowheads sometimes linger and feed at particular locations in the Kaktovik area,

and that some bowheads are in the area as early as August (Chapter 2 and Annex B). Hunters sometimes

observe concentrations of whale food in the water during summer and fall.
§17. Diet & Regional Feeding: Introduction 17-5

Zooplankton sampling near feeding whales vs. elsewhere in the study area confirmed that zooplankton distribution in the eastern Alaskan Beaufort Sea is patchy, and that bowheads are very selective

in choosing places where they linger to feed (Chapters 5, 6).

Systematic aerial surveys of the eastern Alaskan study area, over many years, have documented the

areas where bowheads tend to concentrate, including seasonal trends in the favored areas (Chapter 9).

Those surveys have also provided some fleeting glimpses of feeding behavior. Correction factors have

been developed to convert the raw aerial survey data into estimates of actual numbers of whales present in

the study area, allowing for the proportion of time the whales spend below the surface and invisible

(Chapters 13, 14) and for the whales that are at the surface but missed by aerial surveyors (Chapter 15).

Photogrammetric and photoidentification studies of bowheads in the eastern Alaskan Beaufort Sea have

provided more specific information about the locations favored by whales of different status (subadults,

mother/calf pairs, other adults), including seasonal and year-to-year variability in the concentration areas

(Chapter 10). Photographic, behavioral and radio-telemetry data have both provided information about

residence times of individual bowheads (Chapter 11). Systematic behavioral observations have documented the frequency of occurrence of feeding in the eastern Alaskan Beaufort Sea as compared with

feeding frequency on the summer range in the Canadian Beaufort and along the spring migration route

near Point Barrow (Chapter 12).

Observations of feeding by bowheads in other areas, such as the Canadian Beaufort Sea (Würsig et

al. 1985, 1989), central and western Alaskan Beaufort Sea (e.g., Ljungblad et al. 1986; Landino et al.

1994; Treacy in prep.), and off northeastern Russia (Moore et al. 1995), also provide information on

regional feeding. This needs to be considered when assessing the results of the three specific studies

described in the next three chapters. As noted in the introduction to Chapter 16, the eastern part of the

Alaskan Beaufort Sea is not the only part of the Alaskan Beaufort where bowhead whales feed during late

summer and autumn. The significance of all the results is addressed further in Chapter 22, Energetics,

and Chapter 23, Integration and Conclusions.

Literature Cited

Hoekstra, P.F., L.A. Dehn, J.C. George, K.R. Solomon, D.C.G. Muir and T.M. O'Hara. 2002. Trophic ecology of

bowhead whales (Balaena mysticetus) compared with that of other arctic marine biota as interpreted from

carbon-, nitrogen-, and sulphur-isotope signatures. Can. J. Zool. 80(2):223-231.

Hooker, S.K., S.J. Iverson, P. Ostrum and S.C. Smith. 2001. Diet of northern bottlenose whales inferred from fattyacid and stable-isotope analyses of biopsy samples. Can. J. Zool. 79(8):1442-1454.

Iverson, S.J. 1993. Milk secretion in marine mammals in relation to foraging: can milk fatty acids predict diet?

Symp. Zool. Soc. Lond. 66:263-291.

Landino, S.W., S.D. Treacy, S.A. Zerwick and J.B. Dunlap. 1994. A large aggregation of bowhead whales (Balaena mysticetus) feeding near Point Barrow, Alaska, in late October 1992. Arctic 47(3):232-235.

Ljungblad, D.K., S.E. Moore and J.T. Clarke. 1986. Assessment of bowhead whale (Balaena mysticetus) feeding

patterns in the Alaskan Beaufort and northeastern Chukchi seas via aerial surveys, fall 1979-84. Rep. Int.

Whal. Comm. 36:265-272.

Lowry, L.F. 1993. Foods and feeding ecology. p. 201-238 In: J.J. Burns, J.J. Montague and C.J. Cowles (eds.), The

bowhead whale. Spec. Publ. 2. Soc. Mar. Mammal., Lawrence, KS. 787 p.

Moore, S.E., J.C. George, K.O. Coyle and T.J. Weingartner. 1995. Bowhead whales along the Chukotka coast in

autumn. Arctic 48(2):155-160.
17-6 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

Saupe, S.M., D.M. Schell and W.B. Griffiths. 1989. Carbon-isotope ratio gradients in western arctic zooplankton.

Mar. Biol. 103(4):427-432.

Schell, D.M. 2000. Declining carrying capacity in the Bering Sea: isotopic evidence from whale baleen. Limnol.

Oceanogr. 45(2):459-462.

Schell, D.M. 2001. Carbon isotope ratio variations in Bering Sea biota: the role of anthropogenic carbon dioxide.

Limnol. Oceanogr. 46(4):999-1000.

Schell, D.M. and S.M. Saupe. 1993. Feeding and growth as indicated by stable isotopes. p. 491-509 In: J.J. Burns,

J.J. Montague and C.J. Cowles (eds.), The bowhead whale. Spec. Publ. 2. Soc. Mar. Mammal., Lawrence,

KS. 787 p.

Schell, D.M., S.M. Saupe and N. Haubenstock. 1987. Bowhead whale feeding: allocation of regional habitat

importance based on stable isotope abundances. p. 369-415 In: W.J. Richardson (ed.), Importance of the

eastern Alaskan Beaufort Sea to feeding bowhead whales, 1985-86. OCS Study MMS 87-0037. Rep. from

LGL Ecol. Res. Assoc. Inc., Bryan, TX, for U.S. Minerals Manage. Serv., Reston, VA. 547 p. NTIS PB88-

150271.

Schell, D.M., S.M. Saupe and N. Haubenstock. 1989. Bowhead whale (Balaena mysticetus) growth and feeding as

estimated by δ13C techniques. Mar. Biol. 103(4):433-444.

Treacy, S.D. in prep. Aerial surveys of endangered whales in the Beaufort Sea, fall 2001. OCS Study MMS 2002-

061. U.S. Minerals Manage. Serv., Anchorage, AK.

Würsig, B., E.M. Dorsey, M.A. Fraker, R.S. Payne and W.J. Richardson. 1985. Behavior of bowhead whales,

Balaena mysticetus, summering in the Beaufort Sea: a description. Fish. Bull. 83(3):357-377.

Würsig, B., E.M. Dorsey, W.J. Richardson and R.S. Wells. 1989. Feeding, aerial and play behaviour of the

bowhead whale, Balaena mysticetus, summering in the Beaufort Sea. Aquat. Mamm. 15(1):27-37.
18. STOMACH CONTENTS OF BOWHEAD WHALES HARVESTED

IN THE ALASKAN BEAUFORT SEA

Introduction

The bowhead (Balaena mysticetus) is the only baleen whale that spends its entire life in cold

northern waters. In Alaska, bowheads migrate in spring from their Bering Sea wintering grounds to the

Beaufort Sea. The return migration generally occurs during the late summer and fall. The whales travel

from their eastern Beaufort Sea summering grounds, westward along the coast, and into the Chukchi Sea

(Fraker and Bockstoce 1980; Moore and Reeves 1993). At least some of them travel southwest to the

northeast coast of the Chukotsk Peninsula in autumn before returning to the Bering Sea for the winter.

Examination of the stomach contents of bowhead whales harvested by Alaska Natives provides an

opportunity to study their diet. Bowheads are harvested by hunters from three communities along the Alaskan

coast of the Beaufort Sea (Fig. 18.1), and access to bowheads varies regionally (Stoker and Krupnik 1993).

Due to whale movement patterns and ice conditions, whalers from the community of Kaktovik, in the eastern

Alaskan Beaufort Sea, hunt only during the fall―mainly in September and early October (see Chapter 2).

The same is true of whalers from Nuiqsut, in the central Alaskan Beaufort Sea, who hunt from Cross Island.

However, whalers from Barrow, in the western Alaskan Beaufort Sea, have access to bowheads during both

the spring (April–June) and fall (September–October) migrations.

Since 1976, stomach contents samples from bowhead whales have been collected by personnel

from the North Slope Borough Department of Wildlife Management (NSB-DWM), the Alaska

Department of Fish and Game (ADF&G), and the National Marine Fisheries Service. Diet data from 30

bowhead whales harvested in the Alaskan Beaufort Sea from 1976 to 1988 were reported by Lowry et al.

(1978), Lowry and Burns (1980), Lowry and Frost (1984), Carroll et al. (1987), and Lowry (1993).

Planktonic crustaceans, especially copepods and euphausiids, were the most important food items found

in those studies.

As part of the MMS/LGL study “Bowhead whale feeding in the eastern Alaskan Beaufort Sea”, we

collected stomach content samples from bowheads harvested at Kaktovik during 1997–2000. We also acquired and analyzed field records and previously-unanalyzed stomach content samples from other bowheads

taken in the Beaufort Sea that were made available to us by the NSB-DWM and other sources. Our objectives were to (1) evaluate the frequency of bowhead feeding in this region by examining the field records and

stomach contents samples from harvested whales; and (2) to quantify the composition of the diet of bowheads in the Alaskan Beaufort Sea based on analysis of stomach contents from harvested whales.

 

1 Alaska Department of Fish & Game, Division of Wildlife Conservation, 1300 College Rd., Fairbanks,

AK 99701.

2 Current address: University of Alaska, School of Fisheries and Ocean Sciences, 1550 Coyote Trail,

Fairbanks, AK 99709. Phone: 907-455-6885; e-mail: llowry@eagle.ptialaska.net

Lloyd F. Lowry1,2 and Gay Sheffield 1
18-2 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

FIGURE 18.1. Map of Alaska and the Beaufort Sea showing the three coastal whaling locations in the

Beaufort Sea area: Barrow, Cross Island, and Kaktovik.

Methods

Field Records and Feeding Status

The NSB-DWM provided field records from bowheads harvested by Alaska Native whalers during

1969–2000. We classified each harvested whale as either “feeding”, “not feeding”, or “uncertain” based on

descriptive field records and laboratory data on stomach contents. If field records indicated that a substantial

amount (i.e., at least 10 items or 1 liter) of prey was present in the stomach, the whale was classified as

feeding. If field records indicated that the stomach was empty, the whale was classified as not feeding. If

field records recorded the presence of only a small amount of prey (i.e., less than 10 items or less than 1 liter),

or that food was present but no quantity was indicated, the feeding status of the whale was recorded as

uncertain. For some whales field records did not provide any information about stomach contents, but

collected samples were available for laboratory analysis. In those instances, a whale was classified as feeding

if the sample contained 10 or more identifiable prey items, not feeding if there were no identifiable prey items,

and uncertain if the sample contained fewer than 10 prey items. Items such as algae, feathers, and pebbles

were not considered to be food items. Data were grouped by harvest location and harvest season. The

proportions of feeding whales from different harvest locations and seasons were compared using chi-square

tests.
§18. Diet & Regional Feeding: Stomach Contents 18-3

Collection and Analyses of Stomach Contents Samples

An ADF&G Marine Mammal Biologist was stationed in Kaktovik to sample bowheads taken during

September 1997, 1998, 1999, and 2000. The stomach of each whale landed at Kaktovik during those years

was examined as soon as possible, usually within a few hours after the animal was brought to shore. An

estimate was made of the total stomach contents volume and a sample of contents was collected from the

forestomach, when possible. Stomach contents samples were kept frozen until examined in the laboratory.

The NSB-DWM provided us with stomach contents samples from bowheads harvested at Barrow

and Kaktovik during 1986–2000. Atlantic Richfield Company and Phillips Petroleum provided samples

from some of the whales taken at Cross Island in 1999–2000 by hunters from Nuiqsut. Those samples

were either preserved in 70% isopropyl alcohol or 10% buffered formalin, or were frozen.

In the laboratory, samples were gently rinsed in freshwater on a 1.0 mm screen with a 0.42 mm

screen layered underneath. Prey items were sorted macroscopically into major taxonomic groups, examined microscopically, and identified to the lowest taxonomic level possible. Current taxonomic nomenclature (Anonymous 1984) was used to name prey. Voucher specimens of prey items were stored in 70%

isopropyl alcohol. The water displacement volume of sorted prey items was measured to the nearest

0.1 ml. Data were entered into an electronic database (FoxPro 2.5) that also contained all previously

existing data on stomach contents of bowhead whales harvested in Alaska. Included in the database were

the location and date of harvest, sex and total length of the animal, and any available data regarding diet

including field and/or laboratory records.

For analysis of stomach contents, prey data from individual whales were grouped into major prey

types (i.e., copepod, euphausiid, etc.). Results from all bowhead stomachs that have been examined since

1976, and that included 10 or more prey items, were used in analyses. Comparisons were done for whales

harvested in fall at Kaktovik vs. fall at Barrow, for whales harvested at Barrow in spring vs. fall, for males

vs. females, and for whales <13 m vs. ≥13 m in length. The division into size categories is based on the

length at which bowheads reach sexual maturity, which is ~13 m (Koski et al. 1993).

We analyzed the bowhead whale prey data in two ways. (1) When a group of whales included at least five

animals, the frequency of occurrence of major prey types was calculated as the number of samples containing that

prey divided by the total number of samples examined. Then, the frequencies of all prey types consumed were

compared using 2 by 2 contingency tables with an experiment wise error rate of α = 0.05 using Bonferroni’s

procedure (Neter et al. 1990). All whale stomachs for which ≥10 prey items were enumerated were used in the

frequency of occurrence analysis. (2) Principal components analysis with varimax rotation (Johnson and Wichern 1982) was used to define diet indices, and multiple regression analysis was then applied to those indices to

test for possible simultaneous effects of the following covariates on diet: location, season, whale sex, whale

length, and collection year. Principal components analysis was applied to data on the rank order of prey

importance in each individual bowhead stomach, considering 16 identified prey groups (Appendix 18.1). For

each prey group, importance was defined as the ratio of the volumetric contribution of that prey type to the total

volume of the sample examined. Therefore, only specimens with quantitative data on prey composition were

used in this analysis. For each stomach used in the analysis, principal component scores after varimax rotation

(“dietary indices”) were computed for the three principal components that explained the greatest amount of

variance in the dataset. Those dietary indices were then used as the dependent variables in multiple regression

analyses to assess relationships between the covariates and diet. Type 3 sums of squares were used to compute

P-values for the significance of each covariate. Type 3 sums of squares for each covariate were computed by

including all other covariates in the model before computing that covariate’s sum of squares.
18-4 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

Results

Data and Specimen Collection

Field records were obtained from 444 bowheads harvested in the Beaufort Sea during 1969–2000,

of which 242 had their stomachs examined during butchering.

Thirteen bowheads were harvested during the 1997–2000 whaling seasons at Kaktovik, and

stomach contents samples were collected from 12 of them (Appendix 18.2). Additional samples not

described in previous papers were obtained from 73 bowheads harvested during 1986–2000 at Barrow

(69), Kaktovik (1), and Cross Island (3). Recognizable prey were found in 72 of the 85 new samples.

Bowhead Feeding, Kaktovik Fall

Information on feeding status is available from 32 bowheads taken at Kaktovik during 1979–2000

(Fig. 18.2). Twenty-four were considered to have been feeding, and five were categorized as not feeding

(Appendix 18.3). Feeding status was uncertain for the other three whales. Of the 29 whales whose

feeding status was classified, 9 were ≥13 m long; 7 of those had been feeding and 2 had not. Of the 20

whales <13 m long, 17 had been feeding and 3 not.

At least 46 species of prey occurred in whales taken at Kaktovik including the following: gastropods–1 species; chelicerata–1; copepods–10; mysids–2; cumaceans–2; isopods–2; gammarid amphipods–

16; hyperiid amphipods–4; euphausiids–2; shrimps–3; and fishes–3 (Appendix 18.1).

Stomach samples were available from 21 of the 24 bowheads classified as feeding (Appendix

18.3), and copepods occurred in all 21 of those stomach samples (Table 18.1). Amphipods (both

gammarid and hyperiid), euphausiids, and mysids all occurred in more than half the samples. Copepods

were the dominant prey by volume in 62% of the 21 samples with volumetric data, and euphausiids were

dominant in 24% (Fig. 18.3). The most commonly eaten species of copepods were Calanus hyperboreus

and C. glacialis. Limnocalanus was found in only 3 of 21 stomach contents samples (whales 86KK1,

92KK1, 00KK3), despite its abundance near whales observed feeding in nearshore areas during some

years (cf. Chapter 6). The most commonly eaten euphausiid was Thysanoessa raschii (Table 18.2)

TABLE 18.1. Percent frequency of occurrence of major prey types identified from bowhead whales harvested near Kaktovik, Cross Island, and Barrow. Includes samples with ≥10 prey items.

Prey type

Kaktovik fall

(n = 21)

Cross Island fall

(n = 3)

Barrow fall

(n = 69)

Barrow spring

(n = 30)

Copepod 100 100 20 80

Euphausiid 62 33 94 93

Gammarid amphipod 81 67 55 23

Hyperiid amphipod 67 67 28 33

Mysid 57 0 49 20

Fish 48 0 26 3

Decapod 52 67 29 7

Isopod 24 0 19 0

Cumacean 24 33 13 3
FIGURE 18.2. The feeding status of 32 bowhead whales harvested and examined in the eastern Alaskan Beaufort Sea 

1979–2000. In some of these years, the harvest included additional whales whose stomachs were not examined (see Cha
FIGURE 18.3. Percent prey by volume for 21 individual bowhead whales harvested in the eastern Alaskan Beaufort Sea 

during the fall, 1979–2000.
§18. Diet & Regional Feeding: Stomach Contents 18-7

TABLE 18.2. Number of identified occurrences of copepod and euphausiid species in stomach contents

samples from bowhead whales harvested near Kaktovik, Cross Island, and Barrow.

Prey species Kaktovik fall

(n = 21)

Cross Island fall

(n = 3)

Barrow fall

(n = 69)

Barrow spring

(n = 30)

Copepod

 Calanus cristatus -- - 2

 C. finmarchicus 1- - -

 C. glacialis 10 2 8 20

 C. hyperboreus 15 3 4 5

 Chiridius obtusifrons 1- - 2

 Derjuginia tolli 1- - -

 Euchaeta glacialis 21 1 4

 Heterorhabdus sp. 2- - -

 Limnocalanus grimaldi 3- - -

 Metridea lucens 2- - -

 M. longa 4- - 4

 Pseudocalanus sp. 4- - 1

Euphausiid

 Thysanoessa inermis 2- 7 8

 T. raschii 6 - 26 14

Bowhead Feeding, Cross Island Fall

Information on feeding status is available from five animals taken near Cross Island during 1987–

2000. Four were considered to have been feeding and one was not feeding.

At least 9 species of prey occurred in whales taken near Cross Island including the following:

copepods–3 species; cumaceans–1; gammarid amphipods–2; hyperiid amphipods–2; euphausiids–1

(Appendix 18.1).

Copepods occurred in all three stomach contents samples from Cross Island (Table 18.1). Gammarid

amphipods, hyperiid amphipods, and decapods each occurred in two of the three samples, while euphausiids

and cumaceans each occurred in one. Only one of the samples from Cross Island was in suitable condition

for sorting and volumetric analysis, and it contained >99% copepods. Calanus hyperboreus occurred in all

three Cross Island stomach samples, and C. glacialis occurred in two (Table 18.2).

Bowhead Feeding, Barrow Fall

Information on feeding status is available from 106 bowheads harvested near Barrow during the

fall, 1976–2000 (Fig. 18.4). One stomach, from a calf 7.0 m in length, contained only milk, and this

animal was not considered in analyses of feeding status. Seventy-seven were considered to have been

feeding (Appendix 18.4), and 26 were categorized as not feeding. The feeding status of two whales is

uncertain. Of the 103 whales whose feeding status was classified, 36 were ≥13 m long; 27 of those had

been feeding and 9 had not. Of the 67 whales <13 m long, 50 had been feeding and 17 not.
FIGURE 18.4. The feeding status of 106 bowhead whales harvested and examined during the fall in the western Alas

Barrow, Alaska, 1976–2000. In some of these years, the harvest included additional whales whose stomachs were not exa
§18. Diet & Regional Feeding: Stomach Contents 18-9

At least 54 species of prey occurred in whales taken near Barrow in fall including the following:

cnidarians–1 species; annelids–1; bivalves–1; copepods–5; mysids–3; cumaceans–2; isopods–1; gammarid

amphipods–21; hyperiid amphipods–1; euphausiids–2; shrimps–5; and fishes–11 (Appendix 18.1).

Euphausiids were the main prey item in stomach contents samples of bowheads harvested in fall near

Barrow, occurring in 94% of the 69 samples (Table 18.1). Copepods occurred in only 20% of the samples.

Euphausiids were the dominant prey by volume in 88% of the 64 samples with volumetric data, and

copepods were dominant in 5% (Fig. 18.5). The predominant species of euphausiid eaten was Thysanoessa

raschii, and Calanus glacialis and C. hyperboreus were the most commonly eaten copepods (Table 18.2).

Bowhead Feeding, Barrow Spring

Information on feeding status is available from 100 bowheads taken near Barrow during the spring,

1969–2000 (Fig. 18.6). One stomach, from a calf 5.3 m in length, contained only milk, and this animal

was not considered in analyses of feeding status. Thirty were considered to have been feeding (Appendix

18.5), and 60 were categorized as not feeding. The feeding status of eight whales is uncertain. Of the 90

whales of known length whose feeding status was classified, 19 were ≥13 m long; 6 of those had been

feeding and 13 had not. Of the 71 whales <13 m long, 24 had been feeding and 47 not.

At least 40 species of prey occurred in whales harvested near Barrow in spring including the

following: cnidarians–1 species; gastropods–6; bivalves–4; copepods–7; mysids–2; cumaceans–2; gammarid amphipods–8; hyperiid amphipods–4; euphausiids–2; shrimps–2; echinoderms–1; and fishes–1

(Appendix 18.1).

Euphausiids occurred in 93% of the 30 samples. Euphausiids were the dominant prey by volume in

63% of the 28 samples with volumetric data and copepods were dominant in 27% (Fig. 18.7). Copepods

were the dominant item in 6 of 11 whales taken in 1977–88 but only 1 of 17 taken in 1993–98 (Fig. 18.7).

Thysanoessa raschii was the most commonly eaten species of euphausiid, and Calanus glacialis was the

most commonly eaten copepod (Table 18.2).

Comparisons of Bowhead Diet Between Sexes, Sizes, Regions, and Seasons

There was no significant difference in the proportion of bowheads that was feeding in the fall at

Kaktovik and Barrow (χ

2 = 0.69; df = 1; P > 0.1). For whales harvested near Barrow, a larger proportion

was feeding in the fall than in the spring (χ

2 = 35.77; df = 1; P < 0.001).

There were differences in the frequency of occurrence of prey types between bowheads harvested

in fall at Kaktovik and Barrow (Table 18.1). Copepods occurred more often in whales harvested near

Kaktovik (χ

2 = 43.04; df = 1; P < 0.001), whereas euphausiids (χ2 = 10.61; df = 1, P < 0.005 and hyperiid

amphipods (χ

2 = 12.39; df = 1; P < 0.001) occurred more often in whales harvested near Barrow.

Bowheads harvested at Barrow showed seasonal differences in the frequency of occurrence of prey

types (Table 18.1), with copepods occurring significantly more often in whales harvested in the spring (χ

2

= 31.52; df = 1; P < 0.001). There were also marginally significant (0.05 < P < 0.1) differences for

isopods and decapods, which were found more frequently in whales harvested in fall. Euphausiids

occurred with similar frequency in fall and spring (χ

2 = 0.0106; df = 1; P >> 0.1).
FIGURE 18.5. Percent prey by volume for 64 individual bowhead whales harvested in the western Alaskan Beaufort Sea 

fall, 1976–2000.
FIGURE 18.6. The feeding status of 100 bowhead whales harvested and examined during the spring in the western Ala

Barrow, Alaska, 1969–2000. In some of these years, the harvest included additional whales whose stomachs were not exa
FIGURE 18.7. Percent prey by volume for 28 individual bowhead whales harvested in the western Alaskan Beaufort Sea 

spring, 1977–98.
§18. Diet & Regional Feeding: Stomach Contents 18-13

Within each major location and season (Kaktovik fall, Barrow fall, Barrow spring) there were no

significant differences in the frequency of occurrence of prey types in male and female bowheads

(Bonferonni-adjusted χ

2 tests; P > 0.1). Likewise, there were no significant differences in whales <13 m

and ≥13 m long (P > 0.05), although at Barrow in fall there were marginally (0.05 < P < 0.1) more mysids

and fish in whales <13 m long. Sample size from Cross Island was too small to test for differences in

prey occurrence by sex or size. When all samples were considered in aggregate (Table 18.3), the

frequency of occurrence of prey types was virtually identical in males and females (P > 0.1 for all tests).

There were some small differences between length classes, with copepods, mysids, fishes, and isopods

occurring more frequently in small whales, but the differences were not statistically significant (P > 0.1

for all tests).

In the principal components analysis (with varimax rotation), the three most important “dietary

indices” accounted for 48.9% of the variance in the ranked volumetric data on prey. Multiple regression

analysis was applied, in turn, to each of these three indices to determine whether that measure of diet

differed with location, season, whale length, or whale sex. All three dietary indices showed a significant

effect of season, while location was significant for one index (Table 18.4). There was no evidence for

effects of sex, length class, or year on diet (P > 0.1 in each case). The index that showed a difference for

both location and season (Factor 1) was one that strongly contrasted the ranking of copepods and euphausiids in the diet (Appendix 18.6).

Estimates of the volume of stomach contents are available for 46 bowheads harvested at Kaktovik

and Barrow (Appendices 18.3–18.5). The estimates are imprecise and often given as ranges, and therefore they are not suitable for statistical analysis. However, a summary of those observations (Table 18.5)

shows that at both Kaktovik and Barrow, fall stomachs frequently contained 20 liters or more, and sometimes had over 100 liters of contents. Estimates of contents volumes at Barrow in the spring were

generally lower, and never exceeded 60 liters.

Discussion

Using field records and laboratory results we determined that 105 bowheads taken in the Alaskan

Beaufort Sea during September–October had been feeding and 32 had not. There was no appreciable

difference in the percentage feeding among Kaktovik, Cross Island, and Barrow (Table 18.6). Our estimate of

77% overall frequency of feeding in fall bowheads is likely to be an underestimate for several reasons. For

example, of the five Kaktovik whales that were recorded as not feeding, two were not killed until 24–48 hours

after the initial bomb strike, and another was very young, classified as an ingutuk by the whalers. The three

Kaktovik whales assigned uncertain feeding status each had small amounts of prey in their stomachs. Also,

some stomach contents samples were received in such poor condition (e.g., filled with congealed blood) that

locating and identifying prey was difficult or impossible. Stomachs of whales taken in fall often contained

relatively large amounts of prey, and were often described as “full” in field records. The frequency of feeding

in bowheads taken at Barrow in spring was significantly less than at either Barrow or Kaktovik in the fall, and

estimated quantities of contents in the stomach were considerably smaller.

Prior to this study, our understanding of the diet composition of bowhead whales in the Alaskan

Beaufort Sea was based on samples collected from 30 animals (Lowry 1993). As a result of this project,

quantitative diet data based on laboratory analysis of stomach samples are now available for a total of 123

animals.
18-14 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

TABLE 18.3. Percent frequency of occurrence of major prey types identified in bowhead whales harvested

near Kaktovik, Cross Island, and Barrow, separated by sex and size.

Prey type Males

(n = 61)

Females

(n = 58)

Length<13m

(n = 83)

Length≥13m

(n = 36)

Copepod 49 50 55 36

Euphausiid 87 88 88 86

Gammarid amphipod 49 55 53 50

Hyperiid amphipod 39 33 35 39

Mysid 43 45 51 28

Fish 23 26 30 11

Decapod 28 28 27 31

Isopod 15 16 18 8

Cumacean 10 16 12 14

TABLE 18.4. P values from multiple regression analyses testing for differences in three

indices of bowhead diet according to location, season, whale sex and length class, and

year. Diet indices (“Factors”) are based on a principal components analysis (with varimax rotation) of the rank order of volumetric importance of major prey types identified in

123 bowhead whale stomachs from the Alaskan Beaufort Sea. See Appendix 18.6 for

variable weightings in each factor.

Variable Factor 1 Factor 2 Factor 3

Location <0.01 0.16 0.22

Season <0.01 <0.01 0.01

Sex 0.52 0.92 0.62

Length class 0.33 0.19 0.23

Year 0.06 0.60 0.10

% variance in diet explained

by this factor

18.0 15.4 15.5

TABLE 18.5. Estimates of volume of stomach contents in bowhead whales harvested

near Kaktovik and Barrow.

Estimated contents

volume

Kaktovik fall

(n =18)

Barrow fall

(n = 16)

Barrow spring

(n = 14)

% with ≥ 20 liters 39 56 29

% with ≥ 100 liters 11 33 0

range (liters) 2–150 1–189 1–60
§18. Diet & Regional Feeding: Stomach Contents 18-15

TABLE 18.6. Percentages of bowhead whales taken in the Alaskan Beaufort Sea that were categorized

as feeding, by location, season, and size category. Numbers in parentheses are total sample sizes.

Length <13m Length ≥13m All lengths

Kaktovik fall 85 (20) 78 (9) 83 (29)

Cross Island fall 100 (2) 67 (3) 80 (5)

Barrow fall 75 (67) 75 (36) 75 (103)

Barrow spring 34 (71) 32 (19) 33 (90)

Copepods and euphausiids were the main bowhead prey items near Kaktovik, which agrees with

previously presented results from this area (Lowry and Burns 1980; Lowry and Frost 1984; Lowry 1993).

Of the two groups, copepods were the most important as they were present in every stomach sample and

were essentially the only item in 12 of the 21 stomachs with food (Fig. 18.3). However, euphausiids were

also an important prey item and dominated the contents of five whale stomachs. Other crustaceans and

fishes also were eaten, but they generally were minor components of samples that consisted mostly of

copepods or euphausiids.

This project examined the first three stomach contents samples from bowheads taken near Cross

Island. Based on that small sample, whales in the Cross Island area were feeding mostly on copepods.

In the western Beaufort Sea near Barrow the bowhead diet during September–October was dominated by euphausiids, which made up almost the entire contents of 54 of the 64 samples we examined (Fig.

18.5). These results confirm the importance of euphausiids in the fall diet of bowheads in this region, a

conclusion that had previously been based on samples from only five stomachs (Lowry 1993). Copepods

were the predominant prey in three stomachs and mysids in four. Interestingly, the only whales with

copepods dominant were taken on the same day in 1998, and two of the four with mysids dominant were

taken in on the same day in 1997. This may be indicative of temporal/spatial patches of prey that are

being found and exploited by the whales.

Regional differences in diets of fall-harvested bowheads may be explained by regional differences

in prey availability. Copepods are known to dominate the zooplankton of the Canadian and eastern

Alaskan Beaufort Sea and euphausiids are not considered abundant there (Bradstreet and Fissel 1986;

Chapter 5 of this report). In that region, bowheads often occur at locations where copepods dominate the

biomass (Griffiths and Buchanan 1982; Chapter 6 of this report). In contrast, euphausiids have been

found in substantial quantities in the western Beaufort Sea, where copepods were less abundant (Griffiths

et al. 1987).

In bowheads taken at Barrow during April–June, 14 of 28 samples contained almost entirely euphausiids and 6 had nearly all copepods, but several contained mixtures of different crustacean groups. Copepods

occurred significantly more often in whales that fed near Barrow in spring than in fall. This difference could

be partly due to the locations where whales are taken, as spring hunting occurs in the Chukchi Sea to the west

of Point Barrow and fall whales are taken in the Beaufort Sea mostly to the north and east of the Point (J.C.

George, NSB-DWM, pers. comm.). In contrast with previous studies that found that copepods were the

dominant prey of bowheads taken during the spring migration in 1980–88 (Carroll et al. 1987; Lowry 1993),

this study suggests that euphausiids are overall the more important prey near Barrow in spring as well as

autumn. It appears that there may have been a change in the spring diet of bowheads at Barrow, with

euphausiids being more important in the 1990s than formerly (Fig. 18.7). It is unknown whether this apparent
18-16 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

change in diet near Barrow in spring is due to changes in oceanic conditions that may have altered abundance

patterns of copepods or euphausiids, differences in specific locations where whales were harvested or where

they were feeding, or some other factor.

The frequencies of occurrence of various prey types in stomachs of male and female bowheads

were nearly identical, and indications of slight age/size effects on diet were no more than marginally

significant. Lowry (1993) examined size-related differences in diet in a sample of 32 bowheads and

concluded there was a slightly greater tendency for benthic taxa to occur in whales <10.5 m long. Our

analysis of a larger sample also suggests slight differences in the diet of small (<13 m) versus larger

(≥13 m) whales. Prey groups such as mysids, fish, and isopods that occurred relatively infrequently in

larger whales were found more commonly in small whales. These differences are slight (Table 18.3) and

not statistically significant. The differences may reflect size-related differences in feeding abilities or in

feeding areas, as has been suggested for bowheads in the eastern Canadian Arctic (Finley 2001). There

was no difference in the frequency with which food was found in stomachs of small and large whales

(Table 18.6).

The samples collected and analyzed by this project, combined with previous studies, have resulted

in a relatively large set of data on bowhead whale feeding in the Alaskan Beaufort Sea. The frequency of

feeding and types of food being eaten are now well described for whales taken at Kaktovik in fall and at

Barrow during both fall and spring. It is difficult to use bowhead stomach contents data to estimate the

overall diet composition for a location/season for a number of reasons. These include variation in the

state of digestion of samples, the wide range in the volumes of collected samples, and the lack of data on

total volume of stomach contents. Nonetheless, we calculated preliminary estimates of diet composition

based on the data shown in Figures 18.3, 18.5 and 18.7 and two methods of calculation: (1) averaging the

percent volumes of contents for each prey type found in individual whales, and (2) calculating the percent

of times that a prey type was the dominant component of a stomach contents sample. The two methods

produced remarkably consistent estimates (Table 18.7).

TABLE 18.7. Estimates of bowhead whale diet in the Alaskan Beaufort Sea based on averaging the

percent composition by volume in individual stomach contents samples, and on the percent of times a

prey type was the dominant component of stomach contents samples

Kaktovik (n = 21) Barrow fall (n = 64) Barrow spring (n = 28)

mean %

volume

% times

dominant

mean %

volume

% times

dominant

Mean %

Volume

% times

dominant

copepod 61 62 5 5 28 27

euphausiid 22 24 84 88 61 63

amphipod 5 5 1 0 4 4

mysid 6 5 6 6 1 0

other 6 5 4 1 5 7

Results of this study change our previous understanding of the feeding ecology of bowhead whales

in two important ways. First, feeding near Barrow during the spring migration is not just occasional, but

rather a common event as evidenced by the fact that nearly a third of the animals sampled there had been

feeding. However, the frequency of feeding is clearly less near Barrow in spring than near either Barrow
§18. Diet & Regional Feeding: Stomach Contents 18-17

or Kaktovik in fall, and the amount of food in the stomachs tends to be lower in spring. Second, bowhead

whales feed regularly in the nearshore waters of the eastern, central, and western Alaskan Beaufort Sea

during September–October. With food found in more than three-quarters of the animals examined, this

entire region should be considered an integral part of the summer-fall feeding range of bowheads. This

idea is supported by the distribution of sightings of feeding whales made during aerial surveys. When

accumulated over many fall seasons, these have been widely distributed across the nearshore region of the

Alaskan Beaufort Sea (Ljungblad et al. 1986; Treacy in prep.; see also Figures 6.1A, 9.6–9.9, and 12.5 in

Chapters 6, 9, 12). Results of both stomach analysis and aerial observations suggest that reference to the

passage of bowheads through this region as a “westward fall migration” is misleading. At the least, it is a

very incomplete description of their activities in the region. In fact, a major activity of bowheads in the

Alaskan Beaufort Sea during fall is feeding, with whales moving west when prey are not available in sufficient numbers (Chapter 6), or when the whales choose not to feed, or when they combine feeding with

simultaneous westward travel (Chapter 12).

Acknowledgements

This study would not have been possible without the samples and harvest information provided by

Alaska Native whaling captains and crews from the communities of Kaktovik, Barrow, and Nuiqsut. We

thank the NSB-DWM, Atlantic Richfield Company, and Phillips Petroleum for providing stomach

contents samples and field records for analysis. Stomach contents samples from Barrow were available

primarily due to the foresight and perseverance of Craig George and Todd O’Hara of the NSB-DWM.

Mark Major of Phillips Petroleum was instrumental in acquiring samples from Cross Island. Ken Coyle

of the University of Alaska Institute of Marine Science identified zooplankton voucher specimens. Jay

Ver Hoef assisted with statistical analyses. Kathy Frost and Craig George provided helpful reviews of the

draft report. Funding for this study was provided by the U.S. Minerals Management Service through a

contract awarded to LGL Ecological Research Associates Inc. Specimen collection during 1997–2000

was done under NMFS Scientific Research Permits 797 and 481-1464 (Kaktovik and Cross Island) and

932-1489-90 (Barrow).

Summary

This study documents bowhead whale feeding in the Alaskan Beaufort Sea based on stomach

contents of whales harvested by Alaska Natives. We examined field records and archived data from

previous studies of bowhead stomach contents, and we analyzed similar samples from 85 additional bowhead whales harvested during 1986–2000 near Kaktovik, Barrow, and Cross Island. All available data

from bowheads harvested near those locations were used to characterize and compare diet by harvest

location and season (i.e., Kaktovik fall; Barrow fall; Barrow spring), and by whale size and sex.

Thirty-two bowheads harvested near Kaktovik during fall 1979–2000 have been examined for evidence of feeding. Of 29 whales whose feeding status could be classified as “feeding” or “not feeding”, at

least 83% had been feeding prior to death. Copepods, most commonly Calanus hyperboreus and C. glacialis, were the most important prey; copepods occurred in all 21 stomachs with food and were the

dominant prey by volume in 62% of the samples. Euphausiids, mainly Thysanoessa raschii, were also an

important food item. Estimated volume of stomach contents was as much as 150 liters, and in 7 of 18

cases was greater than 20 liters.
18-18 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

Four of five bowheads harvested near Cross Island during 1987–2000 were recorded as having

been feeding. Copepods were the main prey in the three stomach contents samples examined.

Stomachs of 106 bowheads harvested in fall near Barrow during 1976–2000 were examined. Of

the 103 “non-calf” whales that could be classified as “feeding” or “not feeding”, at least 75% had been

feeding prior to death. Euphausiids were the most important prey; they occurred in 94% of the stomachs

with food and were the dominant prey by volume in 88%. Estimated volumes of stomach contents were

as much as 189 liters, and in many cases were recorded as ≥100 liters or “full”.

Stomachs of 100 bowheads harvested in spring near Barrow during 1969–2000 were examined. Of

the 90 whales that could be classified as “feeding” or “not feeding”, at least 33% had been feeding prior

to death. Euphausiids occurred in 93% of the samples and were the dominant prey in 61%. Copepods

were also an important diet item, especially in samples collected before the 1990s. Estimated volumes of

stomach contents were smaller than for whales taken in fall, and never exceeded 60 liters.

There was no significant difference in the proportion of bowheads that had been feeding in the fall

near Kaktovik and Barrow. However, there was a significant difference in composition of the fall diet at

these locations. Copepods occurred more often and were more frequently the dominant prey by volume

in whales from Kaktovik. Euphausiids occurred more often and were more frequently the dominant prey

by volume in whales from Barrow.

At Barrow, the frequency of feeding in harvested bowheads was significantly greater in the fall

than in the spring. Copepods occurred significantly more often in whales harvested near Barrow in the

spring than in the fall.

Male and female bowheads ate essentially the same food items. The data suggest the possibility of

a slight difference in the prey eaten by small (<13 m) and larger (≥13 m) whales. There was no difference

in the frequency of feeding of small versus large whales.

Preliminary estimates of the overall bowhead diet composition by location/season were as follows:

Kaktovik fall, 61–62% copepod, 22–24% euphausiid, 15–17% other prey; Barrow fall, 5% copepod, 84–

88% euphausiid, 7–11% other prey; and Barrow spring, 27–28% copepod, 61–63% euphausiid, and 10–

11% other prey.

Coastal waters of the entire Alaskan Beaufort Sea are used for feeding by bowhead whales during

September–October, and this region should be considered as part of their normal summer–fall feeding

range. During spring, feeding by bowheads near Barrow is more common than previously thought, but

the frequency of feeding is less than in the fall.

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listing. Key to oceanographic records documentation no. 15, 4th ed. Nat. Oceanic & Atmosph. Admin.,

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Bradstreet, M.S.W. and D.B. Fissel. 1986. Zooplankton of a bowhead whale feeding area off the Yukon coast in

August 1985. Chap. 2 (155 p.) In: Northern Affairs Prog. Environ. Rep. 50. Rep. from LGL Ltd., King

City, Ont., for Can. Dep. Indian & Northern Affairs, Ottawa, Ont. 357 p.

Carroll, G.M., J.C. George, L.F. Lowry and K.O. Coyle. 1987. Bowhead whale (Balaena mysticetus) feeding near

Point Barrow, Alaska, during the 1985 migration. Arctic 40(2):105-110.
§18. Diet & Regional Feeding: Stomach Contents 18-19

Finley, K. J. 2001. Natural history and conservation of the Greenland whale, or bowhead, in the northwest

Atlantic. Arctic 54(1):55-76.

Fraker, M.A. and Bockstoce, J.R. 1980. Summer distribution of bowhead whales in the eastern Beaufort Sea.

Mar. Fish. Rev. 42(9-10):57-64.

Griffiths, W.B. and R.A. Buchanan. 1982. Characteristics of bowhead feeding areas. p. 347-455 In: W.J. Richardson (ed.), Behavior, disturbance responses and feeding of bowhead whales (Balaena mysticetus) in the

Beaufort Sea, 1980-1981. Rep. from LGL Ecol. Res. Assoc. Inc., Bryan, TX, for U.S. Bur. Land Manage.,

Washington, DC. 456 p. NTIS PB86-152170.

Griffiths, W.B., D.H. Thomson and G.E. Johnson. 1987. Zooplankton and hydroacoustics. p. 135-256 In: W. J.

Richardson (ed.), Importance of the eastern Beaufort Sea to feeding bowhead whales, 1985-86. OCS Study

MMS 87-0037. Rep. from LGL Ecol. Res. Assoc. Inc., Bryan, TX, for U.S. Minerals Manage. Serv.,

Reston, VA. 547 p. NTIS PB 88-150271.

Johnson, R.A. and D.W. Wichern. 1982. Applied multivariate statistical analyses. Prentice-Hall Inc., Englewood

Cliffs, NJ. 594 p.

Koski, W.R., R.A. Davis, G.W. Miller and D.E. Withrow. 1993. Reproduction. p. 239-274 In: J.J. Burns, J.J.

Montague and C.J. Cowles (eds.), The Bowhead Whale. Spec. Public. 2, Soc. Mar. Mammal., Lawrence,

KS. 787 p.

Ljungblad, D.K., S.E. Moore and J.T. Clarke. 1986. Assessment of bowhead whale (Balaena mysticetus) feeding

patterns in the Alaskan Beaufort and northeastern Chukchi Seas via aerial surveys, fall 1979-1984. Rep.

Intern. Whal. Comm. 36:265-272.

Lowry, L.F. 1993. Foods and feeding ecology. p. 201-238 In: J.J. Burns, J.J. Montague and C.J. Cowles (eds.),

The Bowhead Whale. Spec. Public. 2, Soc. Mar. Mammal., Lawrence, KS. 787 p.

Lowry, L.F. and J.J. Burns. 1980. Foods utilized by bowhead whales near Barter Island, Alaska, autumn 1979.

Mar. Fish. Rev. 42(9-10):88-91.

Lowry, L.F. and K.J. Frost. 1984. Foods and feeding of bowhead whales in western and northern Alaska. Sci.

Rep. Whales Res. Inst., Tokyo 35:1-16.

Lowry, L.F., K.F. Frost and J.J. Burns. 1978. Food of ringed seals and bowhead whales near Point Barrow,

Alaska. Can. Field-Nat. 91(1):67-70.

Moore, S.E. and R.R. Reeves. 1993. Distribution and movement. p. 313-368 In: J.J. Burns, J.J. Montague and C.J.

Cowles (eds.), The Bowhead Whale. Spec. Public. 2, Soc. Mar. Mammal, Lawrence, KS. 787 p.

Neter, J., W. Wasserman and M. H. Kutner. 1990. Applied linear statistical models: regression, analysis of variance, and experimental designs. Irwin, Boston, MA. 1181 p.

Stoker, S.W. and I.I. Krupnik. 1993. Subsistence whaling. p. 579-629 In: J.J. Burns, J.J. Montague and C.J.

Cowles (eds.), The Bowhead Whale. Spec. Public. 2, Soc. Mar. Mammal., Lawrence, KS. 787 p.

Treacy, S.D. in prep. Aerial surveys of endangered whales in the Beaufort Sea, fall 2001. OCS Study MMS 2002-

061. U.S. Minerals Manage. Serv., Anchorage, AK.
APPENDIX 18.1. List of prey and other items consumed by bowhead whales harvested in the Alaskan Beaufort Sea, 196

seasons where whales were harvested are indicated after each taxon (BS=Barrow/Spring, BF=Barrow/Fall, K=KakNumbers identify the 16 taxa used in the principal components analysis. 1. CNIDARIA Copepoda (cont.) Amphipoda (cont.) Amphipoda (cont.) 

Scyphozoa BS, BF Euchaetidae K Acanthostephia malmgreni BF Rozinante fragilis BF, K 

Euchaeta sp. BS, K Aceroides latipes K Weyprechtia sp. BF, K, C 

2. ANNELIDA Euchaeta glacialis BS, BF, K, C Anonyx sp. BS, BF, K, C Weyprechtia heuglini BF, K 

Polychaeta BF Heterorhabdus sp. K Anonyx nugax BS Weyprechtia pinguis BF, K 

Limnocalanus grimaldii K Ampelisca macrocephala BF 12. Hyperiid amphipods BS, BF, K 

MOLLUSCA Metridea sp. BS, K Apherusa glacialis K Hyperia sp. BS, K 

3. Gastropoda K Metridea lucens K Arrhis sp. BF Hyperia galba BS, K 

Limacina helicina BS Metridea longa BS, K Atylus carinatus BF, K Hyperia medusarum BS, K 

Margarites sp. BS Pseudocalanus sp. BS, K Boeckosimus affinis BF Hyperoche medusarum BS 

Natica sp. BS 8. Mysidacea BS, BF, K Boeckosimus krassini BF Parathemisto sp. BS 

Natica clausa BS Mysis sp. BF, K Boeckosimus litoralis K Parathemisto abyssorum BS, K, C 

Neptunea sp. BS Mysis litoralis BS, BF, K Byblis sp. BS, BF Parathemisto libellula BF, K, C 

4. Bivalvia BF Mysis occulata BF, K Erichthonius sp. BS 13. Euphausiacea BS, BF, K, C 

Astarte sp. BS Neomysis sp. BS, BF Eusirus cuspidatus BS, BF Thysanoessa sp. BS, BF, K 

Liocyma fluctuosa BS Neomysis rayii BS, BF Gammarus sp. BS, BF, K Thysanoessa inermis BS, BF, K 

Nuculana sp. BS 9. Cumacea K, C Gammarus zaddachi BF Thysanoessa raschii BS, BF, K 

Tellinidae BS Brachydiastylis resima BS Gammaracanthus sp. BF 14. Decapoda BF, K, C

Yoldia sp. BS, BF Diastylis sp. BF, K Gammaracanthus loricatus BF,K Crangonidae K 

Diastylis dalli K Harpinia sp. BS Argis sp. BS, BF 

5. CHELICERATA Diastylis galbra K Lysianassidae BF, K Eualus sp. BS, BF

Pycnogonidae K Diastylis sulcata BF Melita sp. BF Eualus gaimardi BF, K 

Leuconidae BF Melita quadrispinosa BF Heptacarpus sp. BF 

CRUSTACEA Leucon sp. BF Monoculodes sp. BF, K Hippolytidae BF 

6. Ostracoda BS Leucon nasica BS Monoculodes zervoni BF Pandalus goniurus K 

7. Copepoda BS, BF, K, C 10. Isopoda K Oedicerotidae BF Sabinea sp. BF 

Aetideidae BF Munnopsis sp. K Onissimus sp. BF, K Sabinea septemcarinata BF, K 

Calanus sp. BS, BF, K Saduria sp. BF, K Onissimus glacialis K Sclerocrangon sp. BF

Calanus cristatus BS Saduria entomon BF, K Onissimus litoralis K Sclerocrangon boreas BF

Calanus finmarchicus K Amphipoda BS, K, C Onissimus nanseni K decapod zoea BF, K, C

Calanus glacialis BS, BF, K, C 11. Gammarid amphipods BS, BF, K, C Podoceridae BF

Calanus hyperboreus BS, BF, K, C Acanthostepheia sp. BS, BF, K Pontoporeia femorata BF 15. ECHINODERMATA

Chiridius obtusifrons BS, K Acanthostepheia behringiensis BF,K Protomedeia sp. BF Ophiuroidea BS

Derjuginia tolli K Acanthostepheia incarinata K Rhacotropis sp. BS, BF, K
§18. Diet & Regional Feeding: Stomach Contents 18-21

APPENDIX 18.2. Number of bowhead whales stomach samples examined as part of this study. Figures

show the number of stomach samples containing recognizable prey, with the total number of samples

examined in parentheses. Excludes samples reported in Lowry (1993) and other previous papers.

Year Barrow Spring Barrow Fall Kaktovik Cross Island

1986 0 (1) - - -

1987 1 (1) - - -

1988 - - - -

1989 - - - -

1990 - - 1 (1) -

1991 - - - -

1992 - - - -

1993 1 (4) 6 (6) - -

1994 4 (4) - - -

1995 4 (4) 3 (5) - -

1996 3 (3) 1 (1) - -

1997 3 (3) 9 (9) 3 (4) -

1998 1 (2) 12 (12) 2 (2) -

1999 0 (1) 3 (3) 2 (3) 1 (1)

2000 - 9 (10) 1 (3) 2 (2)

Total 17 (23) 43 (46) 9 (13) 3 (3)
18-22 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

APPENDIX 18.3. Whales harvested near Kaktovik during fall, 1979–2000, and included in this analysis:

identification number, sex, total length, estimated volume of stomach contents, volume of prey in rinsed

laboratory sample, and field notes. Dashes indicate that no information is available. Animals classified

as not feeding are indicated by *. Animals with uncertain feeding status are indicated by **.

ID Sex

Total

Length (m)

Stomach

 Content (L)

Lab

sample (ml)

Field Notes

79KK1 M 12.7 44 2,406 ---

79KK2 F 10.7 18 545 ---

79KK3 M 10.3 22 400 ---

79KK4 M 10.8 18 131 ---

79KK5 M 10.8 37 358 ---

81KK1 F 17.4 18 146 ---

81KK2 M 14.0 3 19 Krill in the forestomach

81KK3 F 16.2 -- -- Stomach sample contained copepods – lost

82KK1 M 16.0 -- 99 A few liters in the stomach

83KK1 F 14.7 38-57 183 Reddish paste containing krill

84KK1 F 9.8 -- -- Several gallons of shrimp-like prey reported

86KK1 F 7.6 >30 11 Stomach completely full; feeding at capture site

86KK2 * F 17.2 -- -- ---

86KK3 M 10.4 15 197 All stomach chambers contained prey

88KK1 * F 14.9 -- -- ---

89KK3 ** M 11.8 -- Euphausiids reported but none in sample

90KK1 F 10.5 -- 782 Stomach contained food and much blood

92KK1 F 15.2 >10 730 ---

93KK2 M 8.7 -- -- Prey from forestomach sampled - lost

93KK3 M 9.7 -- 15 ---

97KK1 ** F 8.7 -- -- ---

97KK2 * M 13.2 -- -- ---

97KK3 F 8.3 13 57 Reddish fluid and prey in the forestomach

97KK4 M 14.6 2 8 Reddish oily fluid

98KK2 F 8.9 12 103 Reddish fluid and krill in the forestomach

98KK3 M 9.2 11 201 Reddish fluid and krill in the forestomach

99KK1 * F 7.7 -- -- Clear pink fluid in stomach

99KK2 M 12.9 150 801 A suspension of reddish liquid and prey

99KK3 M 8.3 136 500 Large copepods present

00KK1 * F 9.2 -- -- Digested prey reported but none in sample

00KK2 ** M 12.1 -- -- Digested prey reported but none in sample

00KK3 F 8.8 15 129 Stomach contains a thick red liquid with prey
§18. Diet & Regional Feeding: Stomach Contents 18-23

APPENDIX 18.4. Whales harvested near Barrow during fall, 1976–2000, and included in this analysis:

identification number, sex, total length, estimated volume of stomach contents, volume of prey in rinsed

laboratory sample, and field notes. Dashes indicate that no information is available. Animals classified

as not feeding are indicated by *. Animals with uncertain feeding status are indicated by **.

ID Sex

Total

Length (m)

Stomach

 Content (L)

Lab

sample (ml)

Field Notes

76B6F F 16.0 -- 18 ---

76B7F F 14.3 109 33 ---

87B6 * F 15.7 -- -- Flensers cut open; empty

87B7 * M 8.5 -- -- Stomach empty

88B9 M 14.6 -- 40 Krill mixed with blood and baleen fragments

88B10 M 15.1 -- 65 Prey items clearly recognizable

88B11 F 15.6 -- 58 Many intact euphausiids present

89B4 M 14.1 1 10 Large amount spilled on ground, probably was full

89B5 M 14.0 -- 230 Full stomach

89B6 M 13.2 -- 140 Full stomach; stomach punctured

89B7 F 14.6 -- 200 Full stomach

89B8 M 11.8 -- 24 Full stomach: 1/3 krill, 2/3 seawater

89B9 M 8.2 -- 140 Stomach filled to capacity

90B7 F 8.4 -- 8 ---

90B8 M 12.9 -- 70 Stomach quite full with prey

90B9 F 12.9 -- 750 Prey mixed with blood and plant matter

90B10 * F 13.5 -- -- Empty stomach

90B11 * F 14.0 -- -- Empty stomach

91B9 * F 7.9 -- -- Stomach filled only with seawater and blood

91B10 * F 11.2 -- -- Flensers cut open; empty

91B11 * M 12.0 -- -- Stomach empty

92B3 F 14.6 -- 76 Stomach full and distended

92B4 F 16.2 -- 500 ---

92B5 M 13.7 -- - Stomach contents with invertebrates spilled on the ground

92B6 M 14.6 10 370 ---

92B7 * F 14.2 -- -- Empty stomach

92B8 F 15.7 -- 12 Full stomach

92B10 F 14.6 -- 275 ---

92B11 * M 15.0 -- -- Stomach filled with blood

92B12 * F 12.0 -- -- No prey identified

92B15 * M 11.7 -- -- Empty stomach

92B17 F 7.5 -- 94 ---

92B18 M 8.8 -- 2 ---

92B20 F 8.5 10 140 ---

92B21 M 10.0 100 700 Full stomach

92B22 F 9.8 10 135 ---

93B18 M 9.3 -- 900 Full stomach
18-24 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

APPENDIX 18.4. Continued.

ID Sex

Total

Length (m)

Stomach

 Content (L)

Lab

sample (ml)

Field Notes

93B19 M 13.6 -- 26 Full stomach – mostly with liquid

93B20 F 15.5 -- 273 Stomach probably full but rolled under viscera

93B21 M 10.9 18-30 456 Stomach contents estimated from 2 chambers with 10% spillage

93B22 M 12.6 -- 631 ---

93B23 M 8.0 -- 3,422 ---

94B16 * F 11.5 -- -- Only water and gravel present

95B9 * M 17.4 -- -- Empty stomach

95B10 F 15.0 -- 720 ---

95B11 M 13.0 -- 390 Full of water and krill

95B12 * F 12.3 -- -- Empty stomach

95B13 * F 16.5 -- -- Empty stomach

95B14 M 13.9 -- 662 Full to distension with euphausiids

95B15 ** M 15.8 -- -- Less than 10 prey present

95B16 * F 14.1 -- -- Only water and gravel present

95B17 * F 7.5 -- -- Mixture of only blood and seawater(?)

95B18 * F 7.6 -- -- Contained only bloody water

95B19 * M 13.1 -- -- Contained only bloody water

96B6 F 12.7 -- N/A 6 liters of stomach contents collected - lost

96B7 M 12.7 -- N/A 6 liters of stomach contents collected - lost

96B8 M 12.7 -- N/A 1.5 liters of stomach contents collected - lost

96B9 F 12.1 -- N/A 1 liter of stomach contents collected – lost

96B10 M 13.4 -- N/A 6 liters of stomach contents collected - lost

96B11 F 14.3 -- N/A 4 liters of stomach contents collected - lost

96B12 F 11.4 -- -- 4 liters of stomach contents collected – lost

96B24 F 10.8 20-28 337 ---

97B11 M 13.6 -- 131 Stomach full of euphausiids

97B12 M 15.3 -- 39 Stomach rather full

97B13 M 9.4 23 1,152 Stomach full with 10% lost to spillage

97B14 F 8.6 5-10 82 Stomach about 1⁄4 full

97B15 F 8.9 -- 63 Stomach filled with mud containing euphausiids/molluscs

97B16 F 8.3 -- 21 ---

97B17 * M 10.5 -- -- No prey present, examined day after butchering

97B18 * M 10.8 -- -- No prey present, examined day after butchering

97B20 M 8.6 -- 255 Very full stomach

97B27 * M 9.5 -- -- Contained only bloody fluid

97B29 ** M 8.5 -- -- “A few” krill seen in the stomach
§18. Diet & Regional Feeding: Stomach Contents 18-25

APPENDIX 18.4. Continued.

ID Sex

Total

Length (m)

Stomach

 Content (L)

Lab

sample (ml)

Field Notes

97B30 F 8.0 -- 8 Mostly krill and bloody fluid

97B31 F 8.8 -- 5 ---

98B10 F 12.9 189 138 Stomach full to distension

98B14 M 8.2 -- 86 Copepods in reddish watery liquid

98B15 F 8.5 -- 164 Copepods in reddish watery liquid

98B16 M 9.2 -- 133 Copepods in reddish watery liquid; stomach lost to flensing

98B17 M 8.6 -- 43 Full stomach; reddish watery liquid with benthic organisms

98B18 M 11.5 -- 5 Partly full stomach

98B19 M 9.7 -- 227 Very full stomach

98B20 F 11.8 113-151 551 Stomach full to distension

98B21 M 15.1 -- 23 ---

98B22 F 8.0 113 223 Stomach very full with euphausiids

98B23 M 11.7 -- 250 Stomach distended with food

98B24 F 10.3 -- 74 Very full stomach

98B25 * F 9.7 -- -- Contained only bloody fluid

99B19 F 8.1 -- 264 Sample collected from spilled contents

99B20 F 9.0 -- 181 ---

99B22 F 9.7 -- 265 Very full stomach

99B23 M 10.9 -- 240 ---

00B6 M 14.7 -- 29 ---

00B7* M 8.7 -- -- Empty stomach

00B8 * U 8.6 -- 142 Sample consisted of thick gray mud

00B9 F 7.9 -- 5 ---

00B10 F 9.4 -- 9 ---

00B11 M 13.8 -- 6 ---

00B12 * M 10.9 -- -- Empty stomach

00B13 M 9.4 -- 481 ---

00B14 F 9.9 -- 258 Full stomach

00B15 F 8.9 -- 795 Stomach mostly full

00B16 F 10.0 >18 619 ---

00B17 M 9.5 18-26 586 ---

00B18 F 8.9 18 2,339 ---
18-26 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

APPENDIX 18.5. Whales harvested near Barrow during spring, 1969–2000, and included in this

analysis: identification number, sex, total length, estimated volume of stomach contents, volume of prey in

rinsed laboratory sample, and field notes. Dashes indicate that no information is available. Animals

classified as not feeding are indicated by *. Animals with an uncertain feeding status are indicated by **.

ID Sex

Total

Length (m)

 Stomach

 Content (L)

Lab

sample (ml) Field Notes

69B1 U U -- 50 ---

77B5 M 10.6 -- 20 Contents spilled from the stomach

79B1 * M 8.7 -- -- Stomach empty

79B2 * M 10.3 -- -- Stomach empty

79B3 * M 8.3 -- -- Stomach empty

80B1 * F 10.9 -- -- Contained dark watery fluid

80B3 M 8.5 -- 3 ---

80B5 M 10.4 1 73 ---

80B6 * M 8.5 -- -- Empty stomach

80B7 * F 10.0 -- -- Contained congealed blood

80B8 * M 8.7 -- -- Contained congealed blood

80B9 F 13.6 40 140 38 liters of water and 2 liters of euphausiids

84B1 * M 9.1 -- -- Empty stomach

84B2 * F 8.5 -- -- Contained reddish fluid, no prey present

84B3 ** M 7.5 -- -- Less than 10 prey

84B4 * F 8.3 -- -- Contained reddish fluid, no prey present

85B1 M 9.0 5-10 13 Krill in the forestomach

85B2 M 12.4 16-24 126 ---

85B3 M 9.5 5-10 53 Krill found in each stomach chamber; very fresh

86B1 M 8.2 -- -- Small amount of krill in the forestomach and fundic chamber.

86B2 M 8.7 -- -- Small amount of krill in the forestomach and fundic chamber.

86B3 * F 8.9 -- -- Dark watery fluid only

86B4 * M 8.9 -- -- Empty stomach

86B5 M 8.1 12 56 12 liters of fluid with krill in the forestomach.

86B6 F 12.3 60 75 Stomach contained about 60 liters solid krill.

86B7 * M 10.7 -- -- Empty stomach

87B1 * M 9.3 -- -- Empty stomach

87B2 * F 9.0 -- -- Empty stomach

87B3 * M 11.0 -- -- Empty stomach

87B4 * F 16.8 -- -- Empty stomach

87B5 F 15.7 -- 107 ---

88B1 F 8.9 -- 268 Prey intermixed with blood

88B2 * M 8.8 -- -- Empty stomach

88B3 F 7.8 8 -- ---

88B4 * F 9.0 -- -- Empty stomach

88B5 * M 8.9 -- -- Empty stomach

88B6 * F 8.3 -- -- Empty stomach

88B7 * F 8.2 -- -- Empty stomach
§18. Diet & Regional Feeding: Stomach Contents 18-27

APPENDIX 18.5. Continued.

ID Sex

Total

Length (m)

Stomach

 Content (L)

Lab

sample (ml) Field Notes

88B8 * F 7.5 -- -- Empty stomach

89B1 * F 9.0 -- -- No prey present

89B2 * F 14.7 -- -- Empty stomach

89B3 * F 16.9 -- -- Empty stomach

90B1 * M 8.4 -- -- Empty stomach

90B3 * M 11.7 -- -- Empty stomach

90B4 * F 14.9 -- -- Empty stomach

90B5 * F 15.9 -- -- Empty stomach

91B1 * F 7.7 -- -- Empty stomach

91B2 * F 8.6 -- -- No prey present

91B5 * F 12.6 -- -- Empty stomach

91B6 * M 11.0 -- -- Empty stomach

92B1 * F 8.5 -- -- No prey present

93B3 * M 13.3 -- -- Empty stomach

93B5 ** F 9.5 -- -- Less than 10 prey

93B9 * F 9.2 -- -- Dark green liquid only

93B14 * F 10.5 -- -- Blood only

93B15 * F 8.7 -- -- Empty stomach

93B16 F 11.0 -- 3 ---

94B1 * F 8.5 -- -- Empty stomach

94B2 M 10.2 -- 128 At least 2 stomach compartments contained prey

94B8 * M 7.8 -- -- Empty stomach

94B9 M 10.6 1 160 Stomach contained euphausiids and coelenterate

94B11 * M 8.7 -- -- Empty stomach

94B12 * M 8.3 -- -- Empty stomach

94B14 M 8.4 2-4 7 50-100 cc solid material

94B15 M 8.0 -- 25 Trace: euphausiids were noted in the pyloric chamber

95B1 M 8.4 4 86 ---

95B2 ** F 10.5 -- -- “Undescribed” contents

95B3 F 9.6 37-56 640 Contained prey

95B4 F 8.6 1 13 Prey in the stomach

95B5 ** F 11.7 -- -- Flensers cut stomach, euphausiids reported nearby

95B7 M 15.2 -- 1 Much watery fluid in stomach

95B8 * F 15.2 -- -- Blood present

96B1 * F 8.5 -- -- Empty stomach

96B2 F 7.7 -- 12 Stomach contents quite fresh

96B3 F 7.6 2 23 Maybe a couple liters of krill

96B4 * F 14.4 -- -- Empty stomach

96B5 F 14.9 -- 140 Contents collected from punctured stomach

97B1** M 10.0 -- 18 Stomach contents mostly bloody fluid
18-28 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

APPENDIX 18.5. Continued.

ID Sex

Total

Length (m)

Stomach

Content (L)

Lab

sample (ml) Field Notes

97B5 F 10.1 -- 53 ---

97B8 F 13.6 -- 105 Contents collected from stomach

97B10 F 16.7 -- 5 ---

98B1 * F 9.2 -- -- Empty stomach

98B2 M 8.5 -- 47 Stomach was half full with various benthic prey items.

98B3 * M 8.5 -- -- Empty stomach

98B4 * F 13.1 -- -- Empty stomach

98B5 * M 15.1 -- -- Clear fluid but no prey present

98B6 ** F 10.9 -- -- Less than 10 prey present

98B8 * M 13.6 -- -- Empty stomach

99B2 ** F 8.2 -- -- “A few” copepods present

99B3 * F 7.8 -- 100 Clear pinkish fluid, no prey present

99B5 * M 9.0 -- -- Empty stomach

99B8 * M 11.0 -- -- Empty stomach

99B9 * M 9.3 -- -- Empty stomach

99B10 * F 9.4 -- -- Empty stomach

99B12 * F 9.2 -- -- Empty stomach

99B14 * M 14.2 -- 250 Clear pinkish fluid, no prey present

00B1 * M 9.4 -- -- Empty stomach

00B2 ** F 14.5 -- -- Flensers cut stomach, less than 10 prey

00B3 * F 14.6 -- -- Empty stomach

APPENDIX 18.6. Variable weightings from varimax-rotated principal

components analysis of the ranked order of importance of prey taxa in

bowhead whale stomachs.

Variable Factor 1 Factor 2 Factor 3

Copepod 3.6393 -0.2684 1.1805

Euphausiid -1.8970 -0.9822 1.0755

Gamarid amphipod -0.2754 2.8063 0.3206

Hyperiid amphipod 0.4430 0.0231 1.0826

Mysid 0.2862 1.1176 -2.6272

Fish -0.0063 0.1257 -1.4615

Decapod -0.4890 1.7381 1.2454

Isopod -1.0143 -0.2333 -1.2185

Cumacean -0.2374 0.0029 -0.0279

Polychaete -0.2354 -0.6747 -0.2371

Gastropod 0.0813 -0.6261 0.2111

Bivalve -0.1415 -0.5804 0.0734

Pycnogonid 0.0211 -0.4715 0.0367

Ostracod 0.0311 -0.7021 0.1101

Scyphozoa -0.1178 -0.7675 0.0933

Ophiura -0.0880 -0.5078 0.1431
19. FATTY ACIDS IN BOWHEAD WHALES AND POTENTIAL PREY

FROM THE ALASKAN BEAUFORT SEA

Sara J. Iverson 1, Lloyd F. Lowry 2 and Gay Sheffield 2

Introduction

Bowhead whales (Balaena mysticetus) spend their life in cold northern waters, and in the western

Arctic migrate annually from over-wintering areas in the Bering Sea, along the west coast of Alaska past

Point Barrow, then eastward to summering areas in the eastern Beaufort Sea. They usually begin their

return westward migration in late summer or fall, passing the coastal village of Kaktovik and then Barrow

before entering the Chukchi Sea (Fraker and Bockstoce 1980; Moore and Reeves 1993). Although it is

known that bowheads generally feed on zooplankton (Lowry 1993), the species and areas of importance

for feeding have been unclear, as has the importance of the eastern Beaufort Sea to annual food consumption. We undertook a pilot study to assess whether analysis of fatty acid signatures in bowheads and their

potential prey would be a useful tool for better understanding the foraging ecology and diets of bowheads

in Alaskan waters. This was one part of a broader study of the feeding ecology of bowhead whales in the

Alaskan Beaufort Sea.

Fatty acids are the largest constituent of lipids and those of carbon chain length 14 or greater are

often deposited in animal tissue with minimal modification from diet. Based on this, in recent years fatty

acid signature analysis has been developed as a new method to examine foraging ecology in free-ranging

animals (Iverson 1993). Lipids in the marine food web are exceptionally complex and diverse. Owing to

various restrictions and specificities in the biosynthesis and modification of fatty acids among different

taxonomic groups, many components may be traced to a general or even specific ecological origin.

Certain “indicator” fatty acids are particularly useful in food web studies because they arise only or

mostly from the diet. In phocid seals, ingested fatty acids can be deposited directly into adipose tissue,

such that, when a seal is rapidly fattening on a high fat diet, its blubber fatty acid pattern may be nearly

identical to that of the diet (Iverson et al. 1995). Even on low fat diets when seals are not rapidly

fattening, blubber fatty acids reflect an integration of diet over a period of time (Kirsch et al. 2000).

Thus, by sampling a core of blubber from a free-ranging animal, one may obtain information about diet

that does not depend on evidence of recent feeding (i.e., stomach contents) or on prey with hard parts.

The results may also be indicative of feeding over a longer time interval and larger geographic area than

represented in stomach contents.

To date, the methods of fatty acid signature analysis have been used to identify the general trophic

level of diets and to detect major and minor shifts in diet within populations (Iverson et al. 1997a; Smith

et al. 1997). Fatty acid signatures have indicated that the fine-scale structure of the foraging distribution

of harbor seals (Phoca vitulina richardsi) could be discerned within Prince William Sound, Alaska

 

1

 Department of Biology, Dalhousie University, Halifax, N.S. B3H 4J1. Phone: 902-494-2566; e-mail:

siverson@is.dal.ca

2

 Alaska Department of Fish & Game, Fairbanks, AK Division of Wildlife Conservation, 1300 College

Rd., Fairbanks, AK 99701. Phone: 907-455-6885; e-mail: llowry@eagle.ptialaska.net
19-2 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

(Iverson et al. 1997b). This was likely attributable not only to localized feeding patterns in individual

seals, but also to specific differences in the fatty acid composition of prey species depending primarily on

their sizes but also habitats (Iverson et al. 1997b). Results from that study as well as studies on the

Scotian Shelf of eastern Canada (S. Iverson and W.D. Bowen, unpubl. data) indicate that fatty-acid

methods have the ability to accurately identify prey species by their fatty acid signatures, regardless of

potential seasonal changes. The method of fatty acid signature analysis is currently being further

developed at Dalhousie University to reconstruct the diets of free-ranging seals based on intensive

modeling efforts and captive study experiments.

Among the top marine predators, work with fatty acid signatures has progressed rapidly with seals,

polar bears and seabirds, primarily because these species return to land at frequent and/or predictable

times and thus can be captured and sampled. Cetaceans are more difficult to study because they never

move onto land and they rarely are accessible while at sea. Sampling of live cetaceans can generally only

be done using remote biopsy techniques, which sample the part of the blubber very near the skin surface.

Most cetacean blubber is highly stratified in many physical and biochemical characteristics, including

fatty acid patterns, and the outermost layer nearest the skin is relatively inactive. It is the innermost

layers (near the body core) that are most physiologically active and where fatty acids from diet are

deposited (reviewed in Hooker et al. 2001). Despite these drawbacks, it has been shown that the fatty

acid composition of zooplankton and other prey influences the fatty acid composition of blubber lipids of

large whales (e.g., Klem 1935; Ackman and Eaton 1966; Pascal and Ackman 1975). However, given the

limitations of available biopsy techniques, assessing diets of cetaceans using fatty acids is generally only

possible with dead or stranded animals, and thus work to date has been limited. To date, fatty acids have

been useful in assessing aspects of diet in belugas, Delphinapterus leucas, and northern bottlenose

whales, Hyperoodon ampullatus (Dahl et al. 2000; Hooker et al. 2001).

The aim of the present pilot study was to examine whether fatty acid signature analysis could be

applied successfully to understanding bowhead whale feeding patterns. Samples of bowhead blubber

were available from the subsistence harvest by Inupiat whalers, so the usual limitations in applying fatty

acid methods to cetaceans did not apply. Our initial question focused on assessing the degree to which

fatty acid composition is stratified in bowhead blubber, as is often the case in other cetaceans. With a

high degree of stratification, only the inner-most layer of blubber would likely provide useful information

about diet. Our second aim was to examine whether fatty acids could be used to detect differences

among individual bowhead whales depending upon location, season, sex, or size class. Third, we

examined the fatty acid patterns of mixed zooplankton samples collected in the eastern Alaskan Beaufort

Sea to assess whether patterns were similar to those observed in the whales. We could thus evaluate the

potential for using fatty acids to quantify diet composition. Finally, we analyzed fatty acids in a limited

number of samples of potential prey sorted by major taxonomic group. This allowed us to perform a

preliminary analysis of the prey composition of bowhead diets based on the fatty acid patterns in

potential prey groups and in bowhead blubber.

Methods

Analysis of Fatty Acids in Bowhead Blubber and Prey

Samples of bowhead whale blubber, mixed zooplankton samples, and prey types were provided to

Dalhousie University. Bowhead blubber samples were collected by ADF&G and North Slope Borough

biologists from the autumn subsistence harvest at Kaktovik and the spring and autumn harvests at Barrow
§19. Diet & Regional Feeding: Fatty Acids 19-3

(Table 19.1). Zooplankton samples were collected by LGL biologists in the eastern part of the Alaskan

Beaufort Sea during September of 1998–2000 (see Griffiths and Thomson, Chapter 5). Zooplankton

samples from 1998–99 were mixed (unsorted) samples, whereas those from 2000 had been sorted into

major taxonomic groups.

Bowhead whale samples consisted of full blubber cores (i.e., through the full layer of blubber from

outer skin to muscle). Samples from three whales were chosen for full analysis to evaluate the degree of

fatty acid stratification through the bowhead blubber. Those samples were divided into five equal

lengths: inner (nearest the body core), mid-inner, mid, mid-outer and outer (nearest the skin surface).

Fatty acids from each segment were extracted separately. After these initial analyses it was deemed

necessary to analyze only two layers (inner and mid) for the remaining whales.

Samples from a total of 28 whales (Table 19.1), 33 samples of mixed zooplankton, and 32 sorted

zooplankton samples, were analyzed. Lipids were extracted quantitatively using a modified Folch

method (Folch et al. 1957). Fat content in prey was expressed as an average of duplicate extractions.

For each sample, fatty acid methyl esters were prepared directly from 100 mg of the pure extracted

lipid (filtered and dried over anhydrous sodium sulfate), using 1.5 ml 8% boron trifluoride in methanol

(w/w) and 1.5 ml hexane, capped under nitrogen, and heated at 100°C for 1 hour. Fatty acid methyl

esters were extracted into hexane, concentrated, and brought up to volume (50 mg/ml) with high purity

hexane. This method of transesterification, as employed in our lab with fresh reagents, was routinely

tested and found to produce identical results to that using Hilditch reagent (0.5 N H2SO4 in methanol).

Duplicate analyses of fatty acid methyl esters were performed on samples using temperatureprogrammed gas liquid chromatography according to Iverson (1988) and Iverson et al. (1992). We used a

Perkin Elmer Autosystem II Capillary FID gas chromatograph (GC) fitted with a 30 m x 0.25 mm (inner

diameter) column coated with 50% cyanopropyl polysiloxane (0.25 μm film thickness; J&W DB-23;

Folsom, CA). This was linked to a computerized integration system (Turbochrom 4.1 software, PE

Nelson). Identifications of fatty acids and isomers were determined from the following sources: known

standard mixtures (Nu Check Prep., Elysian, MN); silver–nitrate (argentation) chromatography (Iverson

1988); and GC-mass spectrometry (Hewlett-Packard 6890 GC, 1:20 split injection, Micromass Autospec

oa-TOF mass spectrometer, operated at 1000 resolution, scanning masses 120 to 450). Individual fatty

acids are expressed as weight percent of total fatty acids after employing mass response factors relative to

18 : 0. Theoretical relative response factors were used for this purpose, with minor adjustments made

after tests with quantitative standard mixtures (Nu Check Prep., Elysian, MN). All sample

chromatograms and fatty acid identifications were individually checked and corrected, and reintegrated if

necessary. Fatty acids are designated by shorthand IUPAC nomenclature of carbon chain length: number

of double bonds and location (n-x) of the double bond nearest the terminal methyl group.

Means are presented as mean ± standard error of the mean unless otherwise indicated.

Statistical Analysis of Bowhead Blubber Fatty Acids

Bowhead fatty acid data were analyzed using methods of classification and regression trees

(CART) in S-Plus according to methods described in Iverson et al. (1997a) and Smith et al. (1997). In

overview, CART uses an algorithm which automatically selects the “best” variable to split data into two

named groups (“nodes”) that are as different as possible. The deviance of a node is then a measure of the

homogeneity of the observations that fall into each side of that node. The CART algorithm begins at
19-4 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

TABLE 19.1. Bowhead whales analyzed for fatty acid composition of blubber.

Collection Body Total core No. of layers

ID Year location Season Sex length (m) length (cm) analyzed

97B6 1997 Barrow Spring F 13.20 16.2 2

97B7 F 13.20 17.2 2

97B11 Fall M 13.62 17.8 2

97B12 M 15.28 12.3 2

97B13 M 9.40 14.9 2

97B14 F 8.58 12.3 2

97B15 F 8.86 15.9 2

97B16 F 8.30 17.5 2

97B17 M 10.46 16.4 2

97B18 M 10.77 16.7 2

97B19 F 9.29 17.8 2

97KK1 Kaktovik Fall F 8.72 13.5 2

97KK2 M 13.16 23.0 2

97KK3 F 8.31 15.4 2

97KK4 M 14.58 21.3 2

98KK1 1998 Kaktovik Fall M 10.42 16.2 2

98KK2 F 8.90 16.6 2

98KK3 M 9.24 16.8 2

99B13 1999 Barrow Spring M 14.09 21.8 2

99B14 M 14.15 25.9 2

99B15 M - 18.9 2

99B16 F 14.83 23.1 2

99B19 Fall F 8.05 16.4 5

99B20 F 9.03 19.8 5

99B24 M 8.84 22.8 5

99KK1 Kaktovik Fall F 7.70 16.1 2

99KK2 M 12.88 28.5 2

99KK3 M 8.33 16.3 2

the root node by considering all possible ways to split the data, i.e. all variables (fatty acids) and all

possible splitting points within each variable, and chooses that split which maximizes the difference at

that node. The observations (whales or prey) in that split are then sent down one of two branches. This

splitting is continued in a tree-like form and occurs until one of two stopping criteria (based on a

minimum number of observations in a node or a minimum deviance of a node relative to the root node) is

met. Tree growth (splitting) ends at a terminal node where a classification is made and the associated

misclassification rate (number of observations not correctly classified in the node) is given.
§19. Diet & Regional Feeding: Fatty Acids 19-5

Preliminary Modeling of Bowhead Diets

The use of fatty acid data to estimate diet composition requires “quantitative fatty acid signature

analysis” (QFASA). This involves the development of a statistical model that takes account of fatty acid

signatures from all possible prey species. QFASA computes, by maximum-likelihood methods, the

mixture of prey signatures (species and proportions) most likely to create a signature similar to that of the

predator. Such a statistical program must eventually incorporate information on the full range of potential

prey signatures and the variability in these signatures with factors such as size-class and geographical

location. The mathematical model must also weight the individual fatty acids as a function of their ability

to be biosynthesized by the predator. Finally, the relative weighting of prey signatures must reflect the

proximate fat content of each prey type, as species with higher fat content will contribute relatively more

to the predator’s fatty acid “signature” than species of lower fat content.

A model of this sort to estimate the diets of Hawaiian monk seals (Monachus schauinslandi) has been

under development for several years (Iverson et al., in prep.). We have used experiments on both captive seals

and captive mink (Mustela vison) to verify the working of the QFASA model and to make improvements as

necessary. The objective has been to try to estimate the composition of a predator's diet based on the

relationship of its fatty acid signature to the signatures of potential prey. The approach is to take a weighted

mixture of the fatty acid profiles of the prey types and to choose the weighting that minimizes the distance of

the weighted diet from the predator or predators under consideration, i.e., to minimize how far the predicted

diet is from the actual diet. The ultimate success of the QFASA modeling process depends upon having a

comprehensive and representative data base on fatty acid signatures in the potential prey. Although we

currently have fatty acid data from only seven categories of bowhead prey, we performed a QFASA exercise

as a preliminary test of the value of this method in evaluating the composition of the bowhead diet.

Results and Discussion

The full lists of fatty acids identified and quantified in bowhead blubber, mixed zooplankton, and

various major groups of zooplankton are presented in Tables 19.2, 19.3, and 19.4, respectively.

Zooplankton were relatively high in fat content, averaging 4.2% fat (range 1–8%) in 1998 and 9.1% fat

(range 4–13%) in 1999 (Table 19.3). This difference in fat content between years likely resulted from

differences in the species compositions of the zooplankton mixtures in the two years, and/or year-to-year

differences in fat content. Data from sorted prey indicated that copepods had the highest fat content at 9.6%,

followed by amphipods (6–8%), euphausiids (4.5%), and fish (4.9%). However, the available data are too

limited for any evaluation of variation in fat content of potential bowhead prey.

The degree of fatty-acid stratification in the blubber of three individual bowheads (Fig. 19.1) was

less than that so-far observed in any other cetacean. In fact, the stratification was quite minimal, which

suggests that most portions of the blubber will provide at least some information about diet. However,

the inner-most portion likely reflects the most recent diet, and we therefore used inner layer data only in

further analyses and presentations.

Although sample sizes of whales are limited, differences in blubber fatty acids (and thus diet) are

apparent between samples collected at Barrow in spring, Kaktovik in fall, and Barrow in fall (Fig. 19.2).

Classification and regression tree (CART) analysis confirmed this (Fig. 19.3) even though CART

generally performs poorly with small sample sizes. Fatty acid composition of bowhead blubber and the

mixed zooplankton samples also differed somewhat between years (Table 19.2, Fig. 19.2).
19-6 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

TABLE 19.2. Fatty acid composition of bowhead whale blubber, expressed as weight percent of total fatty

acids. See Table 19.1 for sample sizes.

Fatty 1997 1998 1999 

Acid inner mid inner mid inner mid

12:0 0.08 ± 0.01 0.07 ± 0.00 0.09 ± 0.02 0.06 ± 0.01 0.08 ± 0.01 0.07 ± 0.00

13:0 0.02 ± 0.00 0.01 ± 0.00 0.02 ± 0.00 0.01 ± 0.00 0.01 ± 0.00 0.01 ± 0.00

Iso14 0.02 ± 0.00 0.02 ± 0.00 0.02 ± 0.00 0.01 ± 0.00 0.01 ± 0.00 0.01 ± 0.00

14:0 4.63 ± 0.15 4.45 ± 0.08 5.16 ± 0.20 4.53 ± 0.08 4.32 ± 0.23 4.44 ± 0.13

14:1w9 0.17 ± 0.02 0.12 ± 0.01 0.18 ± 0.03 0.11 ± 0.01 0.20 ± 0.03 0.11 ± 0.01

14:1w7 0.05 ± 0.00 0.05 ± 0.00 0.05 ± 0.01 0.05 ± 0.00 0.04 ± 0.00 0.05 ± 0.00

14:1w5 0.27 ± 0.03 0.45 ± 0.04 0.21 ± 0.02 0.39 ± 0.02 0.22 ± 0.03 0.40 ± 0.05

Iso15 0.12 ± 0.00 0.11 ± 0.00 0.12 ± 0.00 0.10 ± 0.01 0.11 ± 0.01 0.10 ± 0.00

Anti15 0.04 ± 0.00 0.04 ± 0.00 0.04 ± 0.00 0.04 ± 0.00 0.03 ± 0.00 0.03 ± 0.00

15:0 0.26 ± 0.01 0.25 ± 0.01 0.26 ± 0.01 0.25 ± 0.00 0.23 ± 0.01 0.23 ± 0.01

15:1w8 0.03 ± 0.00 0.03 ± 0.00 0.03 ± 0.00 0.03 ± 0.00 0.02 ± 0.00 0.03 ± 0.00

15:1w6 0.02 ± 0.00 0.03 ± 0.00 0.02 ± 0.00 0.03 ± 0.00 0.02 ± 0.00 0.03 ± 0.00

Iso16 0.06 ± 0.00 0.05 ± 0.00 0.06 ± 0.01 0.05 ± 0.00 0.06 ± 0.01 0.05 ± 0.01

16:0 11.78 ± 0.56 10.07 ± 0.41 14.35 ± 0.54 10.98 ± 0.38 11.72 ± 0.71 10.22 ± 0.53

16:1w11 0.40 ± 0.01 0.44 ± 0.01 0.44 ± 0.04 0.44 ± 0.01 0.41 ± 0.02 0.46 ± 0.02

16:1w9 0.21 ± 0.01 0.21 ± 0.00 0.20 ± 0.02 0.23 ± 0.01 0.19 ± 0.02 0.21 ± 0.01

16:1w7 15.93 ± 0.58 18.82 ± 0.44 15.03 ± 0.67 18.86 ± 0.42 14.71 ± 0.61 17.48 ± 0.45

7Me16:0 0.23 ± 0.01 0.26 ± 0.01 0.24 ± 0.02 0.25 ± 0.01 0.21 ± 0.01 0.25 ± 0.01

16:1w5 0.02 ± 0.00 0.02 ± 0.00 0.07 ± 0.02 0.02 ± 0.00 0.02 ± 0.00 0.03 ± 0.00

16:2w6 0.07 ± 0.00 0.07 ± 0.00 0.07 ± 0.01 0.06 ± 0.00 0.07 ± 0.01 0.06 ± 0.00

Iso17 0.09 ± 0.01 0.08 ± 0.01 0.10 ± 0.01 0.09 ± 0.01 0.08 ± 0.01 0.07 ± 0.01

16:2w4 0.05 ± 0.00 0.04 ± 0.00 0.04 ± 0.00 0.04 ± 0.00 0.04 ± 0.00 0.03 ± 0.00

16:3w6 0.73 ± 0.01 0.77 ± 0.01 0.75 ± 0.04 0.78 ± 0.01 0.69 ± 0.02 0.75 ± 0.02

17:0 0.15 ± 0.01 0.12 ± 0.01 0.14 ± 0.02 0.13 ± 0.01 0.14 ± 0.02 0.12 ± 0.01

16:3w4 0.26 ± 0.03 0.21 ± 0.01 0.27 ± 0.07 0.20 ± 0.00 0.26 ± 0.04 0.23 ± 0.02

17:1 0.16 ± 0.02 0.18 ± 0.01 0.17 ± 0.02 0.20 ± 0.01 0.16 ± 0.02 0.18 ± 0.02

16:3w1 0.00 ± 0.00 0.00 ± 0.00 0.00 ± 0.00 0.00 ± 0.00 0.00 ± 0.00 0.00 ± 0.00

16:4w3 0.05 ± 0.00 0.05 ± 0.00 0.04 ± 0.00 0.04 ± 0.00 0.04 ± 0.00 0.04 ± 0.00

16:4w1 0.37 ± 0.04 0.30 ± 0.02 0.45 ± 0.15 0.30 ± 0.02 0.39 ± 0.07 0.35 ± 0.04

18:0 2.60 ± 0.14 2.06 ± 0.13 2.94 ± 0.25 2.32 ± 0.14 2.63 ± 0.17 2.17 ± 0.17

18:1w13 0.05 ± 0.01 0.05 ± 0.01 0.05 ± 0.01 0.07 ± 0.02 0.05 ± 0.02 0.07 ± 0.02

18:1w11 2.10 ± 0.20 2.54 ± 0.34 1.23 ± 0.14 1.81 ± 0.22 1.91 ± 0.15 2.37 ± 0.34

18:1w9 11.70 ± 0.80 11.89 ± 0.46 13.19 ± 1.56 13.30 ± 0.20 11.96 ± 1.19 12.42 ± 0.76

18:1w7 5.03 ± 0.29 5.39 ± 0.21 5.25 ± 0.27 5.74 ± 0.17 4.24 ± 0.29 5.05 ± 0.24

18:1w5 0.58 ± 0.02 0.61 ± 0.02 0.47 ± 0.02 0.56 ± 0.01 0.54 ± 0.02 0.58 ± 0.02

18:2d5,11 0.06 ± 0.00 0.06 ± 0.00 0.04 ± 0.00 0.05 ± 0.00 0.05 ± 0.00 0.05 ± 0.00

18:2w7 0.08 ± 0.00 0.08 ± 0.00 0.07 ± 0.00 0.08 ± 0.00 0.07 ± 0.01 0.08 ± 0.01

18:2w6 0.65 ± 0.01 0.65 ± 0.01 0.62 ± 0.01 0.62 ± 0.02 0.62 ± 0.03 0.63 ± 0.02

18:2w4 0.16 ± 0.01 0.18 ± 0.01 0.14 ± 0.01 0.17 ± 0.01 0.12 ± 0.01 0.16 ± 0.01

18:3w6 0.12 ± 0.01 0.12 ± 0.00 0.11 ± 0.00 0.13 ± 0.01 0.12 ± 0.01 0.12 ± 0.01

18:3w4 0.28 ± 0.01 0.30 ± 0.01 0.25 ± 0.01 0.31 ± 0.01 0.25 ± 0.02 0.28 ± 0.01

18:3w3 0.31 ± 0.01 0.33 ± 0.01 0.26 ± 0.02 0.30 ± 0.01 0.26 ± 0.02 0.28 ± 0.01

18:3w1 0.03 ± 0.00 0.03 ± 0.00 0.02 ± 0.01 0.04 ± 0.00 0.02 ± 0.01 0.02 ± 0.01

18:4w3 0.70 ± 0.05 0.67 ± 0.03 0.65 ± 0.11 0.60 ± 0.04 0.75 ± 0.13 0.65 ± 0.04

18:4w1 0.45 ± 0.02 0.51 ± 0.02 0.41 ± 0.06 0.54 ± 0.03 0.43 ± 0.03 0.50 ± 0.03

20:0 0.09 ± 0.01 0.07 ± 0.00 0.08 ± 0.01 0.06 ± 0.00 0.09 ± 0.01 0.07 ± 0.00

20:1w11 1.89 ± 0.11 1.93 ± 0.18 1.58 ± 0.05 1.69 ± 0.16 1.98 ± 0.16 2.01 ± 0.15

20:1w9 9.16 ± 0.95 8.75 ± 0.70 6.80 ± 0.65 7.44 ± 0.42 9.42 ± 1.27 9.04 ± 0.95

...continued
§19. Diet & Regional Feeding: Fatty Acids 19-7

TABLE 19.2 (continued).

Fatty 1997 1998 1999 

Acid inner mid inner mid inner mid

20:1w7 1.79 ± 0.19 1.56 ± 0.09 1.47 ± 0.02 1.39 ± 0.10 1.78 ± 0.23 1.51 ± 0.14

20:2w9 0.14 ± 0.01 0.11 ± 0.00 0.12 ± 0.01 0.10 ± 0.00 0.14 ± 0.01 0.12 ± 0.01

20:2w6 0.16 ± 0.01 0.16 ± 0.01 0.15 ± 0.00 0.15 ± 0.00 0.15 ± 0.01 0.15 ± 0.01

20:3w6 0.07 ± 0.00 0.07 ± 0.00 0.06 ± 0.00 0.07 ± 0.00 0.07 ± 0.00 0.07 ± 0.00

20:4w6 0.28 ± 0.01 0.27 ± 0.01 0.30 ± 0.03 0.29 ± 0.01 0.30 ± 0.03 0.27 ± 0.02

20:3w3 0.05 ± 0.01 0.06 ± 0.01 0.03 ± 0.00 0.03 ± 0.00 0.03 ± 0.00 0.04 ± 0.00

20:4w3 0.44 ± 0.02 0.48 ± 0.02 0.36 ± 0.01 0.44 ± 0.01 0.43 ± 0.02 0.44 ± 0.01

20:5w3 9.50 ± 0.39 9.94 ± 0.42 10.60 ± 0.43 10.35 ± 0.26 10.83 ± 0.87 10.44 ± 0.68

22:1w11 4.00 ± 0.41 4.75 ± 0.32 3.32 ± 1.04 4.02 ± 0.11 4.18 ± 1.02 5.08 ± 0.53

22:1w9 1.24 ± 0.16 1.08 ± 0.08 0.97 ± 0.18 0.93 ± 0.01 1.41 ± 0.27 1.21 ± 0.14

22:1w7 0.28 ± 0.03 0.26 ± 0.02 0.21 ± 0.05 0.22 ± 0.01 0.28 ± 0.06 0.27 ± 0.03

22:2w6 0.00 ± 0.00 0.00 ± 0.00 0.00 ± 0.00 0.00 ± 0.00 0.00 ± 0.00 0.00 ± 0.00

21:5w3 0.43 ± 0.02 0.35 ± 0.01 0.43 ± 0.04 0.37 ± 0.02 0.45 ± 0.02 0.36 ± 0.01

22:4w6 0.03 ± 0.00 0.03 ± 0.00 0.03 ± 0.00 0.02 ± 0.00 0.02 ± 0.00 0.02 ± 0.00

22:5w6 0.09 ± 0.01 0.07 ± 0.01 0.08 ± 0.02 0.05 ± 0.00 0.08 ± 0.01 0.06 ± 0.01

22:4w3 0.08 ± 0.02 0.09 ± 0.02 0.04 ± 0.01 0.04 ± 0.01 0.05 ± 0.00 0.06 ± 0.01

22:5w3 3.56 ± 0.10 3.05 ± 0.11 3.43 ± 0.04 3.16 ± 0.02 3.63 ± 0.17 3.08 ± 0.09

22:6w3 5.17 ± 0.17 3.93 ± 0.11 5.39 ± 0.29 4.16 ± 0.08 5.80 ± 0.41 4.00 ± 0.14

24:1w9 0.05 ± 0.01 0.05 ± 0.00 0.02 ± 0.01 0.05 ± 0.00 0.05 ± 0.01 0.05 ± 0.01

There was also evidence of differences in fatty acids and thus diet between small and large

bowheads (< or > 12 m long) and between male and female bowheads. This is illustrated using two

important dietary indicator fatty acids (Fig. 19.4, 19.5), and was also supported by CART analyses (Fig.

19.6, 19.7). In these preliminary analyses, size groups may be largely confounded with sex groups. A

larger sample size would be required to further evaluate these possible size and gender effects.

Patterns of major fatty acids of mixed zooplankton are shown in Fig. 19.8. The important issue for

this study is how fatty acids in zooplankton compare to those in bowhead blubber. If bowheads were

feeding in the Beaufort Sea, fatty acids in the blubber of whales harvested near Kaktovik and Barrow in

the late summer and fall should reflect those of prey organisms in the Beaufort Sea during summer and

fall. We had samples of both bowheads and mixed zooplankton from the late summer/fall periods of

1998 and 1999. In general, patterns of fatty acids found in the mixed zooplankton were quite similar to

those in the bowheads analyzed (Fig. 19.9). In particular, the mass percentage of dietary indicator

20:1w9 was nearly identical in whales and prey, and values in whales and prey changed in similar ways

from one year to the next. Dietary indicators whose levels are always somewhat reduced in predators

compared to their prey, such as 20:5w3 and 22:1w11, also showed consistent differences between years.

The high levels of these fatty acids in bowheads indicate that their prey must have contained even higher

levels, and the mixed zooplankton samples did show higher levels than bowhead blubber. Other patterns,

such as low 20:1w11 levels as compared to the isomer 20:1w9, are unusual in Alaska ecosystems (Iverson

et al. 1997b). This pattern is found in both bowheads and the mixed zooplankton from the Beaufort Sea

(Fig. 19.8).
19-8 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

TABLE 19.3. Fat and fatty acid composition of mixed zooplankton samples from the Eastern Alaskan

Beaufort Sea, expressed as weight percent of total fatty acids.

 1998 1999 1998 1999

 (n = 23) (n = 10) (n = 23) (n = 10)

Fat % 4.16 ± 0.42 9.07± 0.96

12:0 0.26± 0.01 0.13± 0.01 18:1w7 1.47± 0.24 1.49± 0.04

13:0 0.06± 0.00 0.02± 0.00 18:1w5 0.77± 0.04 0.57± 0.04

Iso14 0.05± 0.00 0.02± 0.00 18:2d5,11 0.01± 0.00 0.01± 0.00

14:0 6.52± 0.32 4.00± 0.18 18:2w7 0.00± 0.00 0.01± 0.00

14:1w9 0.54± 0.03 0.17± 0.02 18:2w6 0.98± 0.08 0.62± 0.01

14:1w7 0.09± 0.01 0.04± 0.00 18:2w4 0.15± 0.01 0.18± 0.00

14:1w5 0.16± 0.01 0.17± 0.00 18:3w6 0.28± 0.01 0.34± 0.01

Iso15 0.26± 0.02 0.09± 0.01 18:3w4 0.09± 0.01 0.07± 0.00

Anti15 0.09± 0.01 0.05± 0.00 18:3w3 0.57± 0.05 0.33± 0.01

15:0 0.34± 0.02 0.14± 0.01 18:3w1 0.10± 0.01 0.03± 0.00

15:1w8 0.13± 0.01 0.05± 0.00 18:4w3 3.91± 0.22 2.42± 0.05

15:1w6 0.03± 0.00 0.02± 0.00 18:4w1 0.36± 0.03 0.40± 0.01

Iso16 0.05± 0.01 0.00± 0.00 20:0 0.11± 0.01 0.03± 0.00

16:0 7.35± 0.44 4.32± 0.32 20:1w11 0.43± 0.03 0.69± 0.03

16:1w11 0.24± 0.02 0.24± 0.01 20:1w9 6.90± 0.51 9.89± 0.14

16:1w9 0.19± 0.02 0.09± 0.01 20:1w7 0.72± 0.12 1.67± 0.08

16:1w7 17.86 ± 0.30 21.19 ± 0.24 20:2w9 0.11± 0.01 0.11± 0.01

7Me16:0 0.95± 0.11 0.32± 0.03 20:2w6 0.13± 0.01 0.13± 0.00

16:1w5 0.05± 0.01 0.01± 0.00 20:3w6 0.05± 0.00 0.09± 0.01

16:2w6 0.24± 0.01 0.20± 0.01 20:4w6 0.31± 0.03 0.76± 0.09

Iso17 0.08± 0.01 0.06± 0.00 20:3w3 0.01± 0.00 0.02± 0.00

16:2w4 0.03± 0.00 0.05± 0.00 20:4w3 0.47± 0.01 0.51± 0.01

16:3w6 1.26± 0.08 1.21± 0.03 20:5w3 17.39 ± 0.51 18.34 ± 0.39

17:0 0.07± 0.01 0.03± 0.00 22:1w11 5.61± 0.36 9.15± 0.21

16:3w4 1.59± 0.10 1.25± 0.04 22:1w9 1.23± 0.16 2.25± 0.08

17:1 0.20± 0.04 0.07± 0.00 22:1w7 0.25± 0.03 0.50± 0.02

16:3w1 0.00± 0.00 0.00± 0.00 22:2w6 0.01± 0.00 0.00± 0.00

16:4w3 0.05± 0.01 0.14± 0.12 21:5w3 0.31± 0.01 0.17± 0.01

16:4w1 2.71± 0.17 2.38± 0.16 22:4w6 0.01± 0.01 0.01± 0.00

18:0 0.39± 0.06 0.28± 0.03 22:5w6 0.12± 0.01 0.09± 0.00

18:1w13 0.01± 0.00 0.03± 0.02 22:4w3 0.05± 0.00 0.08± 0.00

18:1w11 0.00± 0.00 0.02± 0.01 22:5w3 0.86± 0.04 1.29± 0.05

18:1w9 3.97± 0.39 2.48± 0.22 22:6w3 7.88± 0.40 5.45± 0.19

24:1w9 0.12± 0.01 0.16± 0.03

Patterns of major fatty acids in the major taxa of zooplankton differed substantially. The seven

general types of zooplankton contained quite different levels of many fatty acids (Fig. 19.10). In order to

investigate the similarity and differences of the various prey types, including those with very small

sample sizes, a hierarchical cluster analysis was performed on the prey means. The Kulback–Liebler

distance measure was used to determine how similar two prey types were with respect to their fatty acid

signatures. The average linkage method was used, which tends to identify spherical clusters. Hierarchical clustering methods produce dendrograms, which indicate how similar prey types may be to one

another and if there are natural groupings of types (Fig. 19.11). In general, the broad categories of

zooplankton were readily separated from one another based on their fatty acid content.
§19. Diet & Regional Feeding: Fatty Acids 19-9

TABLE 19.4. Fat and fatty acid composition of major categories of zooplankton from the Eastern Alaskan

Beaufort Sea. Fatty acid composition is expressed as weight percent of total fatty acids.

Chaetognath Copepod Euphausiid Fish Gammarid Hyperiid Mysid

amphipod amphipod

 (n = 5) (n =7) (n = 5) (n = 5) (n = 2) (n = 6) (n = 2)

Fat % 4.17 ± 0.64 9.59 ± 0.74 4.51 ± 0.54 4.92 ± 0.46 6.48 ± 1.68 7.88 ± 0.66 2.69

12:0 0.09 ± 0.02 0.26 ± 0.04 0.15 ± 0.02 0.19 ± 0.06 0.10 ± 0.06 0.16 ± 0.03 0.52 ± 0.05

13:0 0.02 ± 0.01 0.03 ± 0.01 0.18 ± 0.07 0.02 ± 0.01 0.03 ± 0.01 0.03 ± 0.00 0.05 ± 0.01

Iso14 0.02 ± 0.00 0.03 ± 0.01 0.15 ± 0.05 0.07 ± 0.04 0.02 ± 0.01 0.10 ± 0.04 0.03 ± 0.00

14:0 3.51 ± 0.39 5.54 ± 0.50 6.29 ± 0.56 4.69 ± 1.03 3.96 ± 0.20 5.76 ± 0.68 6.29 ± 0.99

14:1w9 0.21 ± 0.01 0.19 ± 0.03 0.11 ± 0.03 0.19 ± 0.03 0.07 ± 0.03 0.17 ± 0.01 0.10 ± 0.02

14:1w7 0.05 ± 0.01 0.05 ± 0.01 0.06 ± 0.01 0.05 ± 0.01 0.04 ± 0.00 0.08 ± 0.02 0.10 ± 0.01

14:1w5 0.07 ± 0.02 0.22 ± 0.03 0.36 ± 0.09 0.09 ± 0.00 0.14 ± 0.01 0.14 ± 0.01 0.16 ± 0.03

Iso15 0.19 ± 0.01 0.18 ± 0.02 0.19 ± 0.03 0.20 ± 0.04 0.12 ± 0.04 0.21 ± 0.03 0.19 ± 0.01

Anti15 0.04 ± 0.00 0.06 ± 0.01 0.04 ± 0.00 0.04 ± 0.01 0.02 ± 0.00 0.08 ± 0.01 0.04 ± 0.00

15:0 0.29 ± 0.01 0.25 ± 0.06 0.28 ± 0.02 0.33 ± 0.04 0.22 ± 0.01 0.31 ± 0.04 0.38 ± 0.04

15:1w8 0.07 ± 0.01 0.12 ± 0.02 0.03 ± 0.01 0.07 ± 0.01 0.02 ± 0.01 0.09 ± 0.01 0.05 ± 0.01

15:1w6 0.01 ± 0.00 0.03 ± 0.00 0.02 ± 0.00 0.01 ± 0.00 0.04 ± 0.01 0.02 ± 0.00 0.04 ± 0.01

Iso16 0.06 ± 0.00 0.02 ± 0.01 0.06 ± 0.02 0.06 ± 0.00 0.07 ± 0.01 0.04 ± 0.01 0.07 ± 0.02

16:0 13.99 ± 0.59 8.25 ± 1.93 20.80 ± 0.90 17.42 ± 0.99 14.44 ± 1.32 12.73 ± 1.00 14.51 ± 0.42

16:1w11 0.19 ± 0.01 0.19 ± 0.01 0.33 ± 0.03 0.25 ± 0.01 0.25 ± 0.09 0.24 ± 0.02 0.17 ± 0.01

16:1w9 0.12 ± 0.03 0.09 ± 0.01 0.73 ± 0.20 0.17 ± 0.02 0.21 ± 0.03 0.16 ± 0.02 0.33 ± 0.03

16:1w7 20.54 ± 0.80 28.68 ± 1.35 17.97 ± 0.60 17.26 ± 0.98 35.18 ± 5.75 23.26 ± 0.67 29.47 ± 2.51

7Me16:0 1.40 ± 0.15 0.47 ± 0.04 0.49 ± 0.05 0.71 ± 0.11 0.24 ± 0.01 0.44 ± 0.08 0.37 ± 0.10

16:1w5 0.02 ± 0.00 0.03 ± 0.01 0.04 ± 0.01 0.11 ± 0.03 0.01 ± 0.01 0.05 ± 0.02 0.01 ± 0.00

16:2w6 0.07 ± 0.00 0.13 ± 0.02 0.05 ± 0.01 0.07 ± 0.01 0.07 ± 0.02 0.08 ± 0.00 0.10 ± 0.02

Iso17 0.08 ± 0.01 0.03 ± 0.01 0.07 ± 0.02 0.18 ± 0.10 0.06 ± 0.03 0.09 ± 0.03 0.08 ± 0.01

16:2w4 0.03 ± 0.01 0.03 ± 0.01 0.02 ± 0.00 0.22 ± 0.03 0.02 ± 0.02 0.04 ± 0.01 0.03 ± 0.00

16:3w6 0.52 ± 0.03 1.11 ± 0.12 0.78 ± 0.08 0.49 ± 0.05 0.58 ± 0.22 0.70 ± 0.05 0.88 ± 0.02

17:0 0.11 ± 0.01 0.02 ± 0.01 0.04 ± 0.01 0.13 ± 0.01 0.05 ± 0.01 0.09 ± 0.01 0.06 ± 0.01

16:3w4 0.44 ± 0.03 0.97 ± 0.12 0.31 ± 0.06 0.35 ± 0.05 0.36 ± 0.11 0.61 ± 0.09 0.74 ± 0.02

17:1 0.10 ± 0.00 0.10 ± 0.01 0.09 ± 0.01 0.12 ± 0.01 0.10 ± 0.02 0.14 ± 0.00 0.18 ± 0.08

16:3w1 0.00 ± 0.00 0.00 ± 0.00 0.00 ± 0.00 0.00 ± 0.00 0.00 ± 0.00 0.00 ± 0.00 0.00 ± 0.00

16:4w3 0.07 ± 0.00 0.03 ± 0.01 0.05 ± 0.00 0.08 ± 0.01 0.03 ± 0.02 0.05 ± 0.01 0.03 ± 0.02

16:4w1 0.69 ± 0.05 1.96 ± 0.28 0.60 ± 0.08 0.56 ± 0.09 0.48 ± 0.15 0.97 ± 0.14 1.14 ± 0.14

18:0 0.82 ± 0.05 0.35 ± 0.09 1.05 ± 0.08 2.10 ± 0.23 0.72 ± 0.24 0.56 ± 0.07 0.72 ± 0.04

18:1w13 0.01 ± 0.01 0.00 ± 0.00 0.01 ± 0.00 0.02 ± 0.01 0.05 ± 0.02 0.05 ± 0.03 0.08 ± 0.05

18:1w11 0.00 ± 0.00 0.00 ± 0.00 0.02 ± 0.01 0.07 ± 0.03 0.84 ± 0.10 0.10 ± 0.02 0.02 ± 0.02

18:1w9 4.74 ± 0.30 2.63 ± 0.26 8.18 ± 0.84 6.74 ± 1.02 10.84 ± 2.36 9.19 ± 0.62 8.03 ± 0.86

18:1w7 3.51 ± 0.26 2.46 ± 0.91 7.33 ± 0.54 5.02 ± 0.87 2.72 ± 0.44 3.40 ± 0.05 3.70 ± 0.09

18:1w5 2.83 ± 0.22 0.70 ± 0.05 0.49 ± 0.06 1.25 ± 0.11 0.48 ± 0.10 0.85 ± 0.04 0.35 ± 0.02

18:2d5,11 0.06 ± 0.00 0.02 ± 0.01 0.03 ± 0.00 0.06 ± 0.00 0.06 ± 0.03 0.04 ± 0.01 0.03 ± 0.00

18:2w7 0.00 ± 0.00 0.00 ± 0.00 0.05 ± 0.01 0.01 ± 0.01 0.00 ± 0.00 0.01 ± 0.01 0.01 ± 0.01

18:2w6 0.78 ± 0.09 0.76 ± 0.11 0.70 ± 0.12 0.75 ± 0.05 0.65 ± 0.01 1.04 ± 0.05 0.80 ± 0.02

18:2w4 0.18 ± 0.02 0.20 ± 0.03 0.10 ± 0.00 0.18 ± 0.01 0.08 ± 0.01 0.20 ± 0.02 0.15 ± 0.01

18:3w6 0.16 ± 0.01 0.24 ± 0.03 0.14 ± 0.01 0.16 ± 0.03 1.09 ± 0.39 0.20 ± 0.02 0.36 ± 0.05

18:3w4 0.08 ± 0.01 0.06 ± 0.01 0.02 ± 0.00 0.07 ± 0.01 0.05 ± 0.01 0.11 ± 0.02 0.07 ± 0.01

18:3w3 0.66 ± 0.11 0.62 ± 0.15 0.39 ± 0.10 0.55 ± 0.05 0.31 ± 0.09 1.10 ± 0.13 0.56 ± 0.16

18:3w1 0.00 ± 0.00 0.02 ± 0.01 0.01 ± 0.00 0.05 ± 0.01 0.00 ± 0.00 0.00 ± 0.00 0.04 ± 0.03

18:4w3 1.95 ± 0.15 2.72 ± 0.62 0.77 ± 0.10 1.55 ± 0.09 0.98 ± 0.36 3.09 ± 0.45 1.86 ± 0.38

18:4w1 0.16 ± 0.01 0.34 ± 0.04 0.06 ± 0.02 0.12 ± 0.01 0.06 ± 0.02 0.25 ± 0.06 0.08 ± 0.00

...continued
19-10 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

TABLE 19.4 (continued).

Chaetognath Copepod Euphausiid Fish Gammarid Hyperiid Mysid

amphipod amphipod

 (n = 5) (n =7) (n = 5) (n = 5) (n = 2) (n = 6) (n = 2)

20:0 0.00 ± 0.00 0.01 ± 0.01 0.03 ± 0.01 0.02 ± 0.01 0.00 ± 0.00 0.02 ± 0.01 0.01 ± 0.00

20:1w11 0.16 ± 0.01 0.41 ± 0.07 0.14 ± 0.02 0.13 ± 0.02 0.83 ± 0.08 0.48 ± 0.05 0.19 ± 0.04

20:1w9 3.42 ± 0.28 6.06 ± 0.35 2.51 ± 0.95 4.26 ± 1.46 5.22 ± 0.74 4.52 ± 0.72 1.80 ± 0.06

20:1w7 0.47 ± 0.03 1.75 ± 0.25 0.64 ± 0.12 0.44 ± 0.02 1.22 ± 0.31 0.80 ± 0.13 0.46 ± 0.03

20:2w9 0.55 ± 0.07 0.10 ± 0.01 0.06 ± 0.02 0.13 ± 0.02 0.08 ± 0.02 0.11 ± 0.01 0.03 ± 0.01

20:2w6 0.08 ± 0.01 0.11 ± 0.04 0.16 ± 0.02 0.15 ± 0.03 0.08 ± 0.02 0.14 ± 0.01 0.22 ± 0.02

20:3w6 0.04 ± 0.00 0.06 ± 0.00 0.03 ± 0.00 0.05 ± 0.01 0.10 ± 0.02 0.04 ± 0.01 0.06 ± 0.01

20:4w6 0.25 ± 0.01 0.22 ± 0.02 0.31 ± 0.05 0.29 ± 0.05 0.55 ± 0.28 0.18 ± 0.02 0.72 ± 0.32

20:3w3 0.04 ± 0.01 0.10 ± 0.07 0.06 ± 0.01 0.08 ± 0.02 0.03 ± 0.01 0.13 ± 0.02 0.07 ± 0.01

20:4w3 0.52 ± 0.05 0.63 ± 0.07 0.23 ± 0.03 0.48 ± 0.06 0.23 ± 0.02 0.64 ± 0.11 0.32 ± 0.04

20:5w3 17.05 ± 0.64 15.88 ± 1.94 15.22 ± 1.60 13.59 ± 1.77 9.01 ± 1.66 13.53 ± 1.56 14.31 ± 0.51

22:1w11 2.15 ± 0.22 4.75 ± 0.26 2.66 ± 1.40 2.12 ± 1.16 2.18 ± 0.82 2.52 ± 0.60 0.81 ± 0.02

22:1w9 0.47 ± 0.03 1.49 ± 0.22 0.57 ± 0.17 0.43 ± 0.13 0.65 ± 0.28 0.74 ± 0.20 0.24 ± 0.02

22:1w7 0.30 ± 0.01 0.42 ± 0.06 0.22 ± 0.06 0.15 ± 0.04 0.17 ± 0.09 0.19 ± 0.03 0.08 ± 0.01

22:2w6 0.00 ± 0.00 0.00 ± 0.00 0.00 ± 0.00 0.00 ± 0.00 0.00 ± 0.00 0.00 ± 0.00 0.00 ± 0.00

21:5w3 0.28 ± 0.03 0.13 ± 0.01 0.19 ± 0.02 0.21 ± 0.02 0.10 ± 0.01 0.29 ± 0.05 0.22 ± 0.02

22:4w6 0.01 ± 0.01 0.02 ± 0.02 0.01 ± 0.01 0.02 ± 0.01 0.05 ± 0.03 0.01 ± 0.01 0.05 ± 0.01

22:5w6 0.10 ± 0.01 0.11 ± 0.05 0.07 ± 0.01 0.10 ± 0.01 0.04 ± 0.00 0.11 ± 0.02 0.08 ± 0.00

22:4w3 0.05 ± 0.01 0.17 ± 0.13 0.01 ± 0.01 0.06 ± 0.01 0.04 ± 0.01 0.08 ± 0.02 0.02 ± 0.01

22:5w3 0.71 ± 0.02 1.21 ± 0.12 0.40 ± 0.06 0.90 ± 0.14 0.25 ± 0.05 0.60 ± 0.07 0.41 ± 0.12

22:6w3 12.85 ± 0.57 5.61 ± 0.39 6.57 ± 1.04 12.78 ± 2.11 3.41 ± 1.43 7.60 ± 0.76 6.86 ± 0.85

24:1w9 1.55 ± 0.09 0.52 ± 0.04 0.23 ± 0.06 0.68 ± 0.09 0.03 ± 0.01 0.23 ± 0.02 0.17 ± 0.05

Although seven general categories of zooplankton represented by a total of 32 samples is a very

limited prey database, we used these data and the QFASA model to derive a preliminary estimate of

bowhead diets. This analysis took into account our current estimates of fat content in each prey type

(Table 19.4). We ran several variations of the model, including separate runs for whales harvested at

Kaktovik in late summer/fall, Barrow in fall, and Barrow in spring. In all cases the predominant prey

were estimated to be euphausiids and copepods, with also some evidence of fish in the diet (Fig. 19.12).

These preliminary results indicate that euphausiids were generally the prevalent prey. However, depending on the model variation used, copepods made up a high proportion of the diets of some individuals.

These results are generally consistent with the stomach contents data obtained by Lowry and Sheffield

(Chapter 18). For instance, the recent diet of bowhead 99K2 was estimated by QFASA to contain almost

100% copepods, and was found to have 100% copepods in its stomach when it was harvested near

Kaktovik (see Fig. 18.3 in Lowry and Sheffield, Chapter 18). Nevertheless, even if based on larger

sample sizes, we would not necessarily expect an exact match between QFASA and stomach contents

results. Diet estimates from fatty acid signatures represent an integration of diet over a longer time

interval (likely weeks or even months) and thus over larger geographic areas than are the snapshots of

diets represented in stomach contents.
§19. Diet & Regional Feeding: Fatty Acids 19-11

FIGURE 19.1. Limited stratification of fatty acids throughout the blubber of bowhead whales (n = 3).

Blubber cores were taken through the full blubber layer and divided into five equal sections extending

from the one closest to the skin (“outer”) to the one nearest the body core (“inner”).
19-12 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

FIGURE 19.2. Fatty acid patterns in inner blubber of bowhead whales (n = 28) by collection location and

season in 1997 and 1999. See Table 19.1 for sample sizes.
§19. Diet & Regional Feeding: Fatty Acids 19-13

Barrow

spring

Barrow

fall

Barrow

fall

Barrow

fall

Barrow

fall

Kaktovik

fall

Kaktovik

fall

Kaktovik

fall

Bowheads

n = 28

1/5

18:3n-4

<0.225>

11/23

8/17 0/6

3/5

0/5 3/7

4/12

16:4n-3

<0.055>

22:4n-6

<0.025>

17:0

<0.155>

FIGURE 19.3. Classification and Regression Tree (CART) analysis of inner blubber of bowhead whales

(n = 28) by collection location and season. See Table 19.1 for sample sizes. Ellipses represent intermediate nodes and rectangles represent terminal nodes; labels within an ellipse or rectangle indicate the

classification at that node as represented by the largest number of observations in that node. The fatty

acid listed at each split is the variable chosen by the algorithm to create the split, with < and > values

indicating the optimal splitting level (weight %) of that fatty acid. Fractions under each intermediate and

terminal node indicate the number of misclassifications over the total number of observations in that

node. See Smith et al. (1997) for further explanation of CART analysis.
19-14 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

FIGURE 19.4. Relative levels of dietary fatty acid 20:1w9 in inner blubber of bowhead whales (n = 28) by

sex (above) or body size class (below―cutpoint 12 m) depending on collection location, season, and

year (1997 and 1999). Data from 1998 are not shown in this graph due to small sample size (n = 3).
§19. Diet & Regional Feeding: Fatty Acids 19-15

FIGURE 19.5. Relative levels of dietary fatty acid 22:1w11 in inner blubber of bowhead whales (n = 28) by

sex (above) or body size class (below―cutpoint 12 m) depending on collection location, season, and

year (1997 and 1999). Data from 1998 are not shown this graph due to small sample size (n = 3).
19-16 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

Bowheads

(‘97 & ‘99)

n = 24

18:0

<2.46>

Large

Whales (> 12 m)

1/10

Small

Whales (< 12 m)

1/14

FIGURE 19.6. CART analysis of inner blubber of bowhead whales in 1997 and 1999 (n = 24) by whale

size group. See Fig. 19.3 for explanation of tree.

Bowheads

(‘97 & ‘99)

n = 25

20:1n-11

<1.87>

Females

1/12

Males

1/13

FIGURE 19.7. CART analysis of inner blubber of bowhead whales in 1997 and 1999 (n = 24) by whale

sex. See Fig. 19.3 for explanation of tree.
§19. Diet & Regional Feeding: Fatty Acids 19-17

FIGURE 19.8. Fatty acid patterns in mixed zooplankton samples collected in the late summer/fall of 1998

(n = 23) and 1999 (n = 10) from the Eastern Alaskan Beaufort Sea.
19-18 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

FIGURE 19.9. Fatty acid patterns in bowhead whales and mixed zooplankton samples collected in the late

summer/fall of 1998 and 1999. * denotes commonly biosynthesized fatty acids, disregarded in diet

analysis.
§19. Diet & Regional Feeding: Fatty Acids 19-19

0

2.5

5.0

7.5

10.0

12.5

15.0

17.5

20.0

22.5

c14.0 c16.0 c18.0 c18.1w 9 c18.1w 7 c18.2w 6 c18.3w 3 c18.4w 3

0

2

4

6

8

10

12

14

16

18

20

c20.1w 11 c20.1w 9 c20.4w 6 c20.4w 3 c20.5w 3 c22.1w 11 c22.1w 9 c22.5w 3 c22.6w 3

chaetognath

copepod

euphausiid

fish

gammarid amphipod

hyperiid amphipod

mysid

Mass % of Total Fatty Acids

FIGURE 19.10. Fatty acid patterns in sorted zooplankton samples collected in September 2000 from the

Eastern Alaskan Beaufort Sea. See Table 19.4 for sample sizes.
19-20 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

FIGURE 19.11. Hierarchical cluster analysis on the mean fatty acid patterns of major zooplankton groups

from the Eastern Alaskan Beaufort Sea. The KL–distance measure was used to determine how similar

two taxa were with respect to their fatty acid signatures. The average linkage method was used, which

tends to identify spherical clusters.
§19. Diet & Regional Feeding: Fatty Acids 19-21



0

20

40

60

80

100

chaetognath

copepod

euphausiid

fish

gammarid amphipod

hyperiid amphipod

 mysid

 0

20

40

60

80

100

chaetognath

copepod

euphausiid

fish

gammarid

 amphipod

hyperiid

 amphipod

mysid 

Barrow - fall

Barrow - spring

Kaktovik - fall

Barrow - fall

Barrow - spring

Kaktovik - fall

% Composition of Diet

a

b

FIGURE 19.12. Percent composition of diets of bowhead whales estimated with the limited available data

on fatty acids in bowheads and zooplankton groups, performed two ways: (A) Modeled using an average

composite for each prey species, and (B) modeled on each individual prey sample analyzed. Modeling

on individual prey as in (B) allows full assessment of individual variability within prey species, and thus

may provide better estimates of diets. In Box plots, horizontal lines are the 10th, 25th, 50th (median),

75th and 90th percentiles of the data. Values outside the 10th–90th percentile range are plotted as dots.
19-22 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

Summary

Fatty acids, the dominant constituent of lipids, are often deposited in animal tissue with minimal

modification from those in the diet. Lipids in the marine food web are exceptionally complex and

diverse. We undertook a pilot study to assess whether analysis of fatty acid signatures in bowheads and

their potential prey (zooplankton) would be a useful tool for better understanding the foraging ecology

and diets of bowheads in Alaskan waters. We identified and measured the fatty acids in samples of

blubber from 28 bowheads harvested at Kaktovik (fall) and Barrow (spring and fall); 33 samples of mixed

zooplankton from the eastern Alaskan Beaufort Sea; and 32 samples of zooplankton that had been sorted

into seven major prey groups (copepods, euphausiids, etc.).

This preliminary study indicates that fatty acid signature analysis could be a very useful tool in

better understanding the foraging ecology and diets of bowheads in Alaskan waters. We are currently

limited in the inferences we can make due to small sample sizes of whales and potential prey, and lack of

data on fatty acid profiles in individual species of prey. However, there are indications that fatty acid

analyses may show differences in diets of whales of different sexes and size classes; such differences

have not been clearly detectable from stomach contents analyses. We analyzed samples of mixed

zooplankton from two years, and the fatty acids of the zooplankton are consistent with them being

bowhead diet items. Additionally, although we have very limited data on fatty acid patterns in potential

prey, preliminary results from our QFASA (Quantitative Fatty Acid Signature Analysis) model indicate

that fatty acid patterns of the inner blubber, presumably indicative of recent diet, are consistent with

general diet data obtained from stomach contents analyses. The high fat content of these prey, especially

copepods, also suggests high dietary intakes of fat. With further and more extensive sampling and

analysis, the taxonomic composition of bowhead prey could likely be better assessed using the

quantitative tools now being developed. Fatty acid signatures are expected to represent the integrated diet

over weeks or possibly months, and thus over larger geographic areas, than are the stomach contents of

harvested whales.

Acknowledgements

 We thank the many whaling captains from Kaktovik and Barrow who made bowhead blubber

samples available for analysis. Personnel from the North Slope Borough Department of Wildlife

Management, particularly Craig George and Todd O’Hara, as well as Tami Mau from the University of

Alaska Fairbanks, were instrumental in sample collection. Bill Griffiths of LGL provided zooplankton

samples. Shelley Lang conducted laboratory analysis of specimens. Funding for this study was provided

by the U.S. Minerals Management Service through a contract awarded to LGL Ecological Research

Associates Inc. and a subcontract from LGL to ADF&G. Specimen collection was done under NMFS

Scientific Research Permits 797 and 481–1464 (Kaktovik) and 932–1489–90 (Barrow).

Literature Cited

Ackman, R.G. and C.A. Eaton. 1966. Lipids of the fin whale (Balaenoptera physalus) from North Atlantic waters.

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Sars) and their effect on whale oil composition. Can. J. Biochem. 44:1561-1566.

Dahl, T.M., C. Lydersen, K.M. Kovacs, S. Falk-Petersen, J. Sargent, I. Gertz and B. Gulliksen. 2000. Fatty acid

composition of the blubber in white whales (Delphinapterus leucas). Polar Biol. 23(6):401-409.
§19. Diet & Regional Feeding: Fatty Acids 19-23

Folch, J., M. Lees and G.H. Sloane-Stanly. 1957. A simple method for the isolation and purification of total lipids

from animal tissues. J. Bio. Chem. 226:497-509.

Fraker, M.A. and J.R. Bockstoce. 1980. Summer distribution of bowhead whales in the eastern Beaufort Sea.

Mar. Fish. Rev. 42(9-10):57-64.

Hooker, S.K., S.J. Iverson, P. Ostrum and S.C. Smith. 2001. Diet of northern bottlenose whales inferred from fattyacid and stable-isotope analyses of biopsy samples. Can. J. Zool. 79(8):1442-1454.

Iverson, S.J. 1988. Composition, intake, and gastric digestion of milk lipids in pinnipeds. Ph.D. Thesis, Univ. of

Maryland, College Park, MD.

Iverson, S.J. 1993. Milk secretion in marine mammals in relation to foraging: can milk fatty acids predict diet?

Symp. Zool. Soc. Lond. 66:263-291.

Iverson, S.J., J. Sampugna and O.T. Oftedal. 1992. Positional specificity of gastric hydrolysis of long-chain n-3

polyunsaturated fatty acids of seal milk triglycerides. Lipids 27:870-878.

Iverson, S.J., O.T. Oftedal, W.D. Bowen, D.J. Boness and J. Sampugna. 1995. Prenatal and postnatal transfer of

fatty acids from mother to pup in the hooded seal (Cystophora cristata). J. Comp. Physiol. B 165(1):1-12.

Iverson, S.J., J.P.Y. Arnould and I.L. Boyd. 1997a. Milk fatty acid signatures indicate both major and minor shifts

in the foraging ecology of lactating Antarctic fur seals. Can. J. Zool. 75(2):188-197.

Iverson S.J., K.J. Frost and L.F. Lowry. 1997b. Fatty acid signatures reveal fine scale structure of foraging distribution of harbor seals and their prey in Prince William Sound, Alaska. Mar. Ecol. Prog. Ser. 151(1-3):

255-271.

Kirsch, P.E., S.J. Iverson and W.D. Bowen. 2000. Effect of a low-fat diet on body composition and blubber fatty

acids of captive juvenile harp seals (Phoca groenlandica). Physiol. Biochem. Zool. 73(1):45-59.

Klem, A. 1935. Studies in the biochemistry of whale oils. Hvalrådets Skr. 11:49-108.

Lowry, L.F. 1993. Foods and feeding ecology. p. 201-238 In: J.J. Burns, J.J. Montague and C.J. Cowles (eds.),

The Bowhead Whale. Spec. Public. 2. Soc. Mar. Mammal., Lawrence, KS. 787 p.

Moore, S.E. and R.R. Reeves. 1993. Distribution and movement. p. 313-368 In: J.J. Burns, J.J. Montague and C.J.

Cowles (eds.), The Bowhead Whale. Spec. Public. 2. Soc. Mar. Mammal, Lawrence, KS. 787 p.

Pascal, J.C. and R.G. Ackman. 1975. Occurrence of 7-methyl-7-hexadecenoic acid, the corresponding alcohol, 7-

methyl-6-hexadecenoic acid, and 5-methyl-4-tetradecenoic acid in sperm whale oils. Lipids 10:478-482.

Smith, S J., S.J. Iverson and W.D. Bowen. 1997. Fatty acid signatures and classification trees: new tools for

investigating the foraging ecology of seals. Can. J. Fish. Aquatic Sci. 54(6):1377-1386.
20. REGIONAL AND SEASONAL FEEDING BY BOWHEAD WHALES

AS INDICATED BY STABLE ISOTOPE RATIOS

Sang Heon Lee and Donald M. Schell 1

Introduction

 The bowhead whale (Balaena mysticetus) is a large baleen whale that historically was abundant in

northern circumpolar waters. Commercial whaling over three centuries reduced the numbers in the

Atlantic Ocean to small remnants (Ross 1993). The Pacific populations were also reduced to small

fractions of their original numbers (Bockstoce and Burns 1993). The largest remaining stock is the

Bering–Chukchi–Beaufort stock, which numbered about 8200 animals in 1993, when it was increasing at

about 3.2 % per year (Ferrero et al. 2000). This population overwinters in the sea ice of the northern

Bering Sea and then moves northeastward in the spring, entering the Beaufort Sea in April–June. Much

of the population is in the eastern Beaufort Sea from June through the summer, with most individuals

departing westward in September and early October (Braham et al. 1980; Fig. 20.1). The whales return to

the Bering Sea by way of northern Alaska and (in at least some cases) northeastern Russia. Feeding has

been observed in the Canadian Beaufort Sea in summer and in both the Alaskan Beaufort Sea and near the

Russian coast of the Chukchi Sea during autumn. Over the past three decades, offshore oil exploration

and developmental activities have occurred in some parts of the summer and autumn range in the

Canadian and Alaskan Beaufort Sea (Richardson et al. 1987; USACE 1999), and waters off northeastern

Alaska may be of interest to the oil industry in future.

The feeding habitats of the whales during the summer and fall migration are generally known, but

the relative amounts of food consumed from various regions along the migration route are poorly understood. This study attempts to quantify the relative importance of the eastern Beaufort Sea (including the

eastern Alaskan Beaufort and Canadian Beaufort Seas) as a feeding habitat for the Bering–Chukchi–

Beaufort stock of bowhead whales. It also compares feeding strategies of subadult and adult whales in

the Bering, Chukchi, and Beaufort Seas.

Various methods can provide information about the feeding habitats and amounts of food consumed by populations of whales, including observations of feeding behavior, stomach contents, energy

reserves during different seasons, and stable isotopes. Each method provides a limited perspective, but

the results from different methods are often complementary. • Behavioral observations can show the

manner and location of feeding, and how much time is devoted to feeding, but yield little information as

to how much food the animal consumes in a given feeding location. Furthermore, feeding behavior may

at times be confused with other behavior, especially in pelagic marine mammals, which are especially

difficult to observe in extensively ice-covered areas (Moore and Reeves 1993). However, Würsig et al.

(1985, 1989) and Würsig and Clark (1993) have provided fairly detailed descriptions of feeding behavior

as observed in the Beaufort Sea (see also Chapter 12). • Stomach content analysis shows whether feeding

has occurred recently, what the animal has most recently eaten, and what quantity is present in the stom-

 

1

 Institute of Marine Science, University of Alaska Fairbanks, Fairbanks, AK 99775. Phone (DMS): 907-

474-7210; e-mail: ffdms1@uaf.edu
FIGURE 20.1. Bowhead whale migration routes (from Schell et al. 1989). S = summering ground; W = wintering ground; W

Sea; EBF = eastern Beaufort Sea.
§20. Diet & Regional Feeding: Stable Isotopes 20-3

ach. These estimates can be compared for whales examined in specific regions and seasons (Lowry 1993;

see Chapter 18). However, this method represents only the feeding that occurred close to the sampling

site(s) during a short interval of time prior to sampling (Hobson and Clark 1992; Hobson et al. 1996). It

is also complicated when there is significant delay between the time of the whale is killed and the time

when the stomach contents can be sampled. • Energy reserves as measured by blubber thickness or other

parameters during different seasons have provided data on seasonal feeding in other baleen whales (e.g.,

Lockyer 1981; Víkingsson 1990), and are now being applied in bowhead whales (see Chapter 22).

Stable isotope ratios provide an alternative approach that may enable the determination of important feeding habitats for migratory animals (Fry 1981; Schell 1987; Schell et al. 1989). Animals acquire a

natural isotopic tag from their diet (Fry 1981). If the stable isotope ratios in the food are sufficiently

different in specific parts of the annual range where feeding occurs, and if these differences are

transferred conservatively and predictably to the animals, the relative importance of the different feeding

areas can be determined (Schell and Saupe 1993).

Fry (1981) used stable carbon isotope analysis to trace shrimp movements by matching the δ13C

values of migrating shrimp with the δ13C values of resident shrimp living in specific habitats. Schell et al.

(1989) reported annual oscillations of δ13C and δ15N along the length of bowhead baleen plates. These

oscillations apparently resulted from annual migrations of the whales from summering grounds in the

eastern Beaufort Sea (where food sources are relatively depleted of 13C) to late autumn feeding areas and

wintering grounds in the Chukchi and Bering seas (where the food contains relatively more 13C). The

previous studies of isotopic composition of bowheads have provided new insight into their feeding habitats in a remote area (Schell and Saupe 1993). Their isotope results, combined with data on seasonal and

geographic patterns in zooplankton production, suggested that most annual feeding occurs in late summer

and fall during the return migration from the western Beaufort Sea through the Chukchi Sea and into the

Bering Sea. The large concentrations of zooplankton that mature over the summer in the northern Bering

Sea are carried northward by flow through the Bering Strait (Springer et al. 1989) into the Chukchi Sea,

and have been observed being preyed upon heavily by the returning whales (Moore et al. 1995).

Increased interest in the eastern Alaskan Arctic has led us to re-examine the feeding scenarios for

these whales in more detail. Our primary objective was to use stable isotope methods to assess the relative amounts of feeding in the eastern Beaufort Sea vs. the Bering and Chukchi Seas, including a comparison of feeding strategies by adult vs. subadult bowhead whales. Also, we were interested in comparing

feeding strategies in recent vs. earlier years. Recent evidence that the productivity of the Bering and

Chukchi seas may have declined suggested that feeding in the eastern Beaufort Sea might be more

important to bowhead whales now than in previous decades (Schell 2000, 2001). As in previous related

studies, our approach is based on the fact that samples of bowhead tissues can be obtained in northern

Alaska during the spring and autumn migrations, when bowhead whales are harvested by Inupiat hunters

(Stoker and Krupnik 1993; see also Chapter 2).

After the draft of this chapter was completed, Hoekstra et al. (2002) published data from a closelyrelated stable-isotope study of bowhead whale feeding, including measurements from some of the same

individual whales studied here. The data of Hoekstra et al. are discussed in this updated chapter.

The main topic of this overall report is feeding by bowhead whales in the eastern Alaskan Beaufort

Sea, which is a minority of the eastern Beaufort Sea. The isotopic method, as now available, does not

permit us to discriminate food acquired in the Canadian vs. eastern Alaskan Beaufort Sea (see Schell et al.

1998). Nonetheless, it is of interest to investigate what proportion of their annual food the Bering–

Chukchi–Beaufort stock of bowheads acquires in the eastern Beaufort Sea as a whole. That sets an upper
20-4 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

limit on the amount that might be obtained in the eastern Alaskan Beaufort Sea. Other chapters of this

report provide data on relative food availability (Chapters 5, 6), residence times (Chapter 11), and

proportion of time spent feeding (Chapter 12) in the Canadian vs. eastern Alaskan Beaufort Sea.

Methods

We obtained one of the longest baleen plates from 4 of the whales killed at Barrow and all 10 of the

whales landed at Kaktovik during 1997–99; 13 of 14 were killed in autumn (Table 20.1). Additional

comparative data were obtained from baleen collected in past studies during both spring (predominantly) and

autumn (Table 20.2). Plates were cleaned of adhered gum tissue at the proximal end and then scrubbed with

steel wool to remove surface layers of foreign matter such as diatoms and whale oil. Each plate was labeled

along its length with adhesive tape and marked at 1-cm intervals. From 0 cm to 100 cm from the proximal

end, samples were taken at 1-cm intervals using a flexible-shaft engraving tool. Beyond 100 cm, plates were

sampled at 2-cm intervals. These samples allowed us to determine isotopic ratios along the entire temporal

span of each plate, with particularly high temporal resolution within the most recently-grown (proximal)

baleen. As an example, the 13C data obtained from whale 97KK2 are shown in Figure 20.2.

TABLE 20.1. Bowhead whale samples collected during 1997–99. Baleen samples were obtained from the

whales for which baleen length is listed. Muscle samples were obtained from all listed whales except for

97B8, 97B11 and 97B12.

Whale Date Landed Village

Whale

 Length (m)

Baleen

Length (m) Sex Age Class

97B8 15 May 97 Barrow 13.6 2.54 F adult

97B11 11 Sept 97 Barrow 13.6 3.00 M adult

97B12 12 Sept 97 Barrow 15.3 3.12 M adult

97B14 20 Sept 97 Barrow 8.6 F subadult

97B16 20 Sept 97 Barrow 8.3 F subadult

97B18 22 Sept 97 Barrow 10.8 M subadult

97B20 26 Sept 97 Barrow 8.6 M subadult

97B21 27 Sept 97 Barrow 9.2 F subadult

97B22 27 Sept 97 Barrow 9.4 F subadult

97B23 27 Sept 97 Barrow 10.3 M subadult

97B24 28 Sept 97 Barrow 8.6 F subadult

97B25 28 Sept 97 Barrow 11.7 2.08 M subadult

97B26 29 Sept 97 Barrow 13.5 M adult

97B27 2 Oct 97 Barrow 9.5 M subadult

97B28 2 Oct 97 Barrow 8.4 M subadult

97B29 17 Oct 97 Barrow 8.5 M subadult

97B30 18 Oct 97 Barrow 8.0 F subadult

97KK1 3 Sept 97 Kaktovik 8.7 1.50 F subadult

97KK2 6 Sept 97 Kaktovik 13.2 2.50 M subadult

97KK3 11 Sept 97 Kaktovik 8.3 1.32 F subadult

97KK4 27 Sept 97 Kaktovik 14.6 3.06 M adult

98KK1 4 Sept 98 Kaktovik 10.4 1.92 M subadult

98KK2 10 Sept 98 Kaktovik 8.9 1.44 F subadult

98KK3 14 Sept 98 Kaktovik 9.2 1.70 M subadult

99KK1 11 Sept 99 Kaktovik 7.7 0.86 F subadult

99KK2 12 Sept 99 Kaktovik 12.9 2.44 M subadult

99KK3 16 Sept 99 Kaktovik 8.3 1.32 M subadult
§20. Diet & Regional Feeding: Stable Isotopes 20-5

TABLE 20.2. Bowhead whale samples collected during 1986–88 (Schell 1992). Baleen samples were

obtained from the whales for which baleen length is listed. Muscle samples were obtained from the

whales marked *.

Whale Date Landed Village

Whale

 Length (m)

Baleen

Length (m) Sex Age Class

86B1 27 Apr 86 Barrow 8.2 M subadult*

86B2 27 Apr 86 Barrow 8.7 M subadult*

86B3 3 Apr 86 Barrow 8.9 1.60 F subadult*

86B4 1 May 86 Barrow 8.9 1.30 M subadult*

86B5 4 May 86 Barrow 8.1 0.85 M subadult*

86B6 5 May 86 Barrow 12.3 F subadult*

86B7 6 May 86 Barrow 10.7 2.01 M subadult*

86KK1 10 Sept 86 Kaktovik 7.6 F subadult*

86KK2 17 Sept 86 Kaktovik 17.1 3.80 F adult*

86KK3 26 Sept 86 Kaktovik 10.4 1.85 M subadult*

86WW1 5 May 86 Wainwright 15.9 2.69 M adult*

86WW2 10 May 86 Wainwright 17.7 3.10 F adult*

87B1 1 May 87 Barrow 9.3 1.68 M subadult

87B2 2 May 87 Barrow 8.9 1.50 F subadult

87B3-A 4 May 87 Barrow 11.0 1.95 M subadult

87B4 2 May 87 Barrow 16.8 2.95 F adult

87B5 15 June 97 Barrow 15.7 3.00 F adult*

87B6 22 Oct 87 Barrow 15.7 3.15 F adult*

87B7 29 Oct 87 Barrow 8.5 M subadult*

87G2 24 Apr 87 Gambell 16.8 3.45 F adult

87N1 5 Oct 87 Nuiqsut 15.2 3.30 F adult*

87WW2 8 May 87 Wainwright 13.5 2.15 M adult

88B1 24 Apr 88 Barrow 8.9 0.98 M subadult*

88B2 25 Apr 88 Barrow 8.8 M subadult*

88B3 25 Apr 88 Barrow 7.8 F subadult*

88B4 25 Apr 88 Barrow 9.0 F subadult*

88B5 25 Apr 88 Barrow 8.9 M subadult*

88B6 2 May 88 Barrow 8.4 F subadult*

88B7 5 May 88 Barrow 8.2 F subadult*

88B8 6 May 88 Barrow 7.5 F subadult*

88B9 15 Sept 88 Barrow 14.6 2.57 M adult

88B10 17 Sept 88 Barrow 15.1 3.02 M adult

88G2 25 Apr 88 Gambell 15.3 F adult*

88KK1 24 Sept 88 Kaktovik 14.9 2.97 F adult

Muscle samples were obtained from 14 whales harvested at Barrow and 10 whales harvested at

Kaktovik during the autumns of 1997–99. These muscle samples provided data on isotope ratios resulting from relatively recent feeding. Approximately 5 g of muscle was collected from each whale by personnel from the Alaska Department of Fish & Game or the North Slope Borough Dept. of Wildlife Management. Subsamples were dried at 65°C for 2 days to constant weight. Muscle samples from 25 additional whales taken in 1986–88, mainly in spring, were used in comparisons (Table 20.2).

The finely powdered baleen and muscle were weighed into cups (0.8–1.0 mg) and the isotope ratios

analyzed using a Europa continuous-flow isotope-ratio mass spectrometer. All δ13C and δ15N isotope values are reported against, respectively, PDB and air standards as δ13C PDB (‰) or δ15Nair (‰):
20-6 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

FIGURE 20.2. Carbon isotope ratios along a baleen plate from bowhead whale 97KK2, a 13.2 m male

taken at Kaktovik, Alaska, by Herman Aishanna and his crew on 6 Sept 1997. Each oscillation is one

year of growth. The most recently formed baleen is at left. Open circles indicate feeding on Bering/

Chukchi prey and filled circles indicate a contribution of Beaufort Sea carbon.

 R sample – R standard

 δ = × 1000

 R standard

where R is the ratio 13C : 12C or 15N : 14N.

Student’s t-test was used to identify significant differences between the adult and subadult whales

for the years 1986–88 and 1997–99.

Use of δ13C in Baleen to Assess Feeding

To estimate feeding activity in regions represented by the isotope ratios along the baleen plates, the

approximate dietary composition (Table 20.3) and stable isotope values for various components of the diet

(Table 20.4) were defined for the eastern Beaufort and for the Bering+Chukchi regions. Because the average

isotope ratios of prey from these areas are quite distinct, and because these regions are the geographic extremes

of the range of this bowhead population, these two regions were used as end members. Zooplankton from the

central and western Beaufort Sea have intermediate δ13C values (Saupe et al. 1989). Although active feeding

has been observed in the western Beaufort Sea during autumn (e.g., Lowry 1993; Landino et al. 1994; Treacy

in prep.), it is probably on Chukchi Sea zooplankton that have been advected into the Beaufort Sea.

Specific data on diet composition are available only from locations where bowhead whales are

harvested and where their stomach contents have been examined. Stomach contents of bowheads harvested at Kaktovik in September provide data on diet composition in that area and season. Use of those data

to represent dietary proportions throughout the eastern Beaufort Sea in summer is subject to various

criticisms, including concerns about local and temporal variations, differential digestion, etc. However,
§20. Diet & Regional Feeding: Stable Isotopes 20-7

TABLE 20.3. Approximate composition of bowhead whale diets (from Lowry and Sheffield, Chapter 18).

Copepods Euphausiids Mysids Amphipods

Eastern Beaufort a 61 % 22 % 6 % 5 %

Bering + Chukchi b 28 % 61 % 1 % 4 %

a Based on stomach contents at Kaktovik in fall. b

 Based on stomach contents at Barrow in spring.

TABLE 20.4. Approximate average values of δ

13C and δ15N (ppt) for main prey taxa from 1985 and 1994,

calculated from Schell et al. (1998) and Schell (1992).

Copepods Euphausiids Mysids Amphipods

δ

13C δ15N δ13C δ15N δ13C δ15N δ13C δ15N

Eastern Beaufort -25.6 10.4 -23.7 9.2 -23.6 8.5 -23.9 8.2

Bering + Chukchi -22.2 10.5 -20.8 10.13

the net tow data from Saupe et al. (1989), Chapters 5 and 6 of this report, and other sources, indicate that

the zooplankton of the eastern Beaufort Sea is dominated by calanoid copepods with few euphausiids,

generally consistent with prey in the bowhead stomachs examined at Kaktovik. The reverse is true for

bowheads harvested near Barrow, where euphausiids have dominated the stomach contents in fall and, in

recent years, spring (Lowry 1993; Chapter 18). It is uncertain how representative this is of the actual

composition of the bowhead diet in the Bering–Chukchi diet region (including western Beaufort waters).

The tendency for more depleted δ13C values in copepods relative to euphausiids (difference ~1.1

‰), combined with the geographic difference in diet (more strongly dependent on copepods in the eastern

Beaufort), increases the overall isotopic gradient in the available food and in the diet across the migratory

range. If the diet were entirely euphausiids when in the Bering/Chukchi region, and entirely copepods in

the eastern Beaufort, the geographic and seasonal shift in the carbon isotope ratio in the diet would be

~4.8 ‰. With the opposite scenario of all copepods in the Bering/Chukchi and all euphausiids in the eastern Beaufort Sea, the difference would be only 1.5 ‰. Net tow data on zooplankton abundance and

stomach content data on bowhead diet at Kaktovik and Barrow both suggest that the former scenario is

much closer to reality (Saupe et al. 1989). Nevertheless, the relative abundances of prey taxa may change

substantially from year to year across the range. Large inter-year variations in taxon abundances in a

given region, as shown for the eastern Alaskan study area in Chapter 5, are also expected to be common.

Whether the whales target specific taxa preferentially, as opposed to feeding on the most abundant

available taxon, is also unknown.

The data on isotope ratios in zooplankton from different parts of the bowhead range are the result

of many years of sampling in many locations. The areas of most intense coverage include the eastern

Beaufort Sea in both nearshore and offshore waters, and the Bering Sea. The sampling coverage is shown

in Schell et al. (1998), with the exception that additional samples were taken in the eastern Alaskan Beaufort Sea during the present study (Table 20.5). The observed geographic patterns in isotope ratios have

remained consistent across the years.

Anticipated δ13C and δ15N values for the total consumed prey from each end-member region were

calculated by calculating a weighted average of the taxon δ13C values from Table 20.4, using the dietary

proportions from Table 20.3 as the weighting factors. We considered only copepods and euphausiids, the

dominant prey items (Saupe et al. 1989; Lowry 1993, Chapter 18). For the eastern Beaufort Sea,
20-8 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

TABLE 20.5. Average zooplankton isotope ratios (± standard deviation and number of samples) for the

Eastern Alaskan Beaufort Sea in 1998–99 (this study), compared with data of Schell et al. (1998) for the

eastern Beaufort Sea as a whole.

 δ

13C s.d. n δ15N s.d. n

1999

 Copepods -25.6 0.59 33 10.3 0.56 33

 Euphausiids -24.2 0.85 5 11.0 0.29 5

 Chaetognaths -23.5 0.18 4 12.3 0.75 4

1998

 Copepods -24.7 0.37 30 10.8 0.99 30

 Euphausiids -23.1 1.18 5 11.2 0.71 5

 Chaetognaths -23.2 0.32 11 12.8 0.81 11

Schell et al. (1998)

 Copepods -25.7 0.20 57 10.8 0.19 45

 Euphausiids -23.7 0.32 21 9.2 0.57 18

 Chaetognaths -23.4 0.33 5 13.5 0.60 5

δ13C = (average δ13C of copepods × prop’n of copepods in bowhead diets) + (average δ13C

of euphausiids × prop’n of euphausiids) = –25.10 ‰

δ15N = 10.08 ‰, based on a calculation parallel to the above, but for δ15N.

In the Bering and Chukchi seas,

δ13C = (average δ13C of copepods × prop’n of copepods in bowhead diets) + (average δ13C of

euphausiids × prop’n of euphausiids) = –21.24 ‰

δ15N = 10.25 ‰, based on a calculation parallel to the above, but for δ15N.

These values are the anticipated average isotopic composition of the prey consumed in each region.

The difference in δ13C between the assumed diets during summer and early autumn in the eastern Beaufort Sea as compared with late autumn and winter in Bering–Chukchi waters, including the western Beaufort, is 3.86 ‰. The eastern Beaufort Sea could not be further divided into Alaskan and Canadian sectors

due to the lack of significant differences in δ13C and δ15N values for zooplankton from the two regions

(Schell et al. 1998). Hence, the eastern Beaufort Sea end member includes both sectors. For simple

mixing models, use of δ13C is more practical than δ15N because a much larger gradient in δ13C is present

in progressing from the Bering and Chukchi seas to the eastern Beaufort region.

The δ13C values at locations 0 to 50 cm from the basal end of the baleen, representing the most

recent 2 or 3 years of baleen growth, were used to illustrate the amount of feeding in each isotopic

regime. [The baleen growth rate is 16 to 25 cm/year (Schell and Saupe 1993).] The baleen is also assumed to grow at a constant rate whether the whales are actively feeding or not. Comparison of plates from

whales taken in spring and fall showed similar growth rates during summer and winter (Schell et al.

1989). It is also assumed that baleen reflects immediate diet during periods of active feeding and average

body protein composition during periods of fasting (Best and Schell 1996). In the latter case overall

baleen isotope ratios would tend to reflect primary food sources year round and show only small seasonal

shifts if the whales moved into regions of differing prey isotope ratios where they did not acquire significant quantities of food. Many adult bowhead whales exhibit this type of isotopic trace.
§20. Diet & Regional Feeding: Stable Isotopes 20-9

The intermediate δ13C values between –18.8 and –22.0 ‰ evident in parts of the baleen are assumed to

arise when the whale moves from one isotopic regime into the other of the two end members (Bering/Chukchi

and eastern Beaufort) during migration. Shifts in isotope ratios along the baleen indicate that feeding was

occurring as the baleen was deposited, but do not give quantitative information as to the amount of food

consumed. However, the amplitude of the annual isotopic cycle provides some information. It is reasonable to

assume that large amplitudes in isotopic ratios reflect substantial feeding from each of the two regimes

whereas a small amplitude implies that most of the food was from one region. This interpretation also requires

the assumption that the zooplankton in the two regions retains the same difference in isotope ratios from year

to year. As such, the baleen isotopic data are useful only as a relative indicator of feeding activity, and when

comparing whales taken during periods with little year-to-year change in isotope ratios.

Correction for Changing δ13C and δ15N in the Bering and Chukchi Seas Biota

An additional correction is also needed in using our data on isotope ratios to assess regional

feeding. Carbon isotope ratios in parts of the baleen laid down in the Bering and Chukchi seas have

shown an overall 0.81‰ decrease over the years 1994–98 compared to 1983–87 (Schell 2000, 2001;

Fig. 20.3). For both carbon and nitrogen, there has been a pronounced decline in isotope ratios in the

baleen laid down over the past several decades, presumably representing a corresponding decline in the

isotope ratios in the prey. The average δ13C decreased by approximately 2.7 ‰ between 1965 and 1998.

The average δ15N decreased by about 1.3 ‰ between 1953 and 1998. This decline has been ascribed to a

progressive decline in primary productivity in the Bering Sea, although other mechanisms may be

contributing (see Schell 2000, 2001; also comment by Cullen et al. 2001). Considering the extensive

regions in the Bering and Chukchi seas in which the bowhead whales can feed, the consistency in isotope

ratios between whales for a given year is remarkable (Schell and Saupe 1993). The premise that the isotopic record is environmental in origin and not due to physiological responses in the whales is supported

by the close agreement in isotope ratios among multiple whales, adults and subadults, for a given year.

To compensate for this long-term trend, an additional 1.0 ‰ was added to the average δ13C values

measured in the parts of the baleen representing feeding on Bering/Chukchi zooplankton during 1997–99.

This allows direct comparisons of data from baleen laid down in the late 1990s vs. the 1980s, and comparisons with the regional zooplankton data from the 1980s (Table 20.4). For this study, it was assumed

that the carbon isotope ratios in the zooplankton of the eastern Beaufort Sea did not change between

1983–87 and 1994–98 (Table 20.5).

In many whales, the baleen deposited during summer shows only very small depressions in isotope

ratios, not representative of isotope ratios in prey from the eastern Beaufort Sea. Also, δ13C and δ15N values from summer baleen do not match between whales. Thus, it is not possible to determine if a significant shift has occurred in the isotope ratios within baleen deposited in the Beaufort Sea over past decades.

Results

Zooplankton Isotope Ratios in the Eastern Beaufort Sea

The carbon and nitrogen isotope ratios found for the major taxonomic groups of zooplankton

during 1998–99 were very similar to those reported by Schell et al. (1998) for 1985–95. Table 20.5 lists

the recently acquired carbon and nitrogen isotope ratios for copepods, euphausiids and chaetognaths, and

those from previous work. The 1998–99 data are based on a limited number of stations in the eastern

Alaskan Beaufort Sea; the earlier data include samples from the Canadian as well as eastern Alaskan
20-10 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

FIGURE 20.3. Average carbon and nitrogen isotope ratios in the portions of 39 bowhead whale baleen

plates laid down during feeding in the Bering and Chukchi seas each year over the past five decades.

Standard deviations around each point are approximately ±0.5 ppt for carbon and ±0.6 ppt for nitrogen.

Straight lines are least-squares linear fits from 1965 to 1998 for carbon and from 1952 to 1998 for nitrogen (from Schell 2000, 2001).

Beaufort Sea, in both coastal and offshore waters. Based on the new data we assumed, when calculating

food sources, that the carbon isotope ratios in the zooplankton of the Beaufort Sea during the 1990s were

similar to those reported in Schell et al. (1998).

Seasonal Isotope Ratios in Muscle

Muscle tissues of 24 whales harvested in autumn 1997–99 were analyzed. The isotope ratio data

are listed in Table 20.6, along with results reported by Schell (1992) for 19 whales harvested in spring

(and 6 in autumn) of 1986–88. No muscle samples were obtained by us in spring during 1997–99. Thus

we were constrained to using spring whale muscle data from Schell (1992) for comparison of fall vs.

spring.

δ13C in Bowhead Muscle.―Fall muscle for 1997–99 exhibited a unimodal distribution of δ13C

with a range from –22 to –19.5 ‰, centered about a mode of –20.5 to –21 ‰. By comparison, the spring

muscle for 1986–88 fell between –21 and –18.5 ‰ with a mode at –19 to –19.5 ‰ (Fig. 20.4). The

average δ13C values differed by 1.1 ‰ : –20.72 ‰ ± s.d. 0.56 ‰ for fall 1997–99 and –19.58 ‰ ± 0.47

‰for spring 1986–88 (Student’s t = 7.11, df = 41, P < 0.001).

There are two possible reasons for lower δ13C values in whales killed in fall 1997–99 than in spring

1986–88. This difference might mean the whales feed to a significant extent during summer in the

eastern Beaufort Sea. Alternatively, if most feeding is in the Bering/Chukchi area, a difference of about

1 ‰ would be expected based on the year-to-year decrease in average δ13C values in Bering/Chukchi

biota noted above (Fig. 20.3). The latter explanation is believed to be the major factor. The average

uncorrected δ13C value for the muscle from six fall-killed 1986–87 whales is –20.47 ‰ ± s.d. 1.05 ‰,
§20. Diet & Regional Feeding: Stable Isotopes 20-11

TABLE 20.6. δ

13C and δ15N values for bowhead muscle tissues from 1997–99 whales (this study) and

1986–88 whales (Schell 1992). All 1997–99 muscle tissue was collected from fall-killed whales. The

muscle samples for 1986–88 were from spring-killed animals, except for six fall-killed whales noted with

an asterisk. Muscle samples were not collected from whales 97B8, 97B11, and 97B12. Data have not

been corrected for the decreasing decadal trends in δ

13C and δ15N in the Bering/Chukchi seas (Schell

2000, 2001).

Whale

Whale

Length(m)

δ

13C

(‰)

δ

15N

(‰) Whale

Whale

Length (m)

δ

13C

(‰)

δ

15N

(‰)

97B8 13.6 NA NA 86B1 8.2 -19.43 15.24

97B11 13.6 NA NA 86B2 8.7 -20.10 14.63

97B12 15.3 NA NA 86B3 8.9 -20.56 12.64

97B14 8.6 -19.87 13.65 86B4 8.9 -19.55 15.56

97B16 8.3 -20.80 14.91 86B5 8.1 -19.10 14.42

97B18 10.8 -20.83 12.85 86B6 12.3 -19.73 13.30

97B20 8.6 -20.62 13.00 86B7 10.7 -20.11 15.56

97B21 9.2 -20.98 12.31 *86KK1 7.6 -21.45 13.91

97B22 9.4 -21.38 12.68 *86KK2 17.1 -19.12 13.86

97B23 10.3 -20.46 12.58 *86KK3 10.4 -21.38 14.97

97B24 8.6 -20.70 12.91 86WW1 15.9 -18.84 14.38

97B25 11.7 -21.37 12.97 86WW2 17.7 -19.35 13.62

97B26 13.5 -21.41 12.80 87B5 15.7 -18.94 14.23

97B27 9.5 -21.53 12.64 *87B6 15.7 -19.20 13.27

97B28 8.4 -19.99 13.78 *87B7 8.5 -20.83 13.85

97B29 8.5 -20.00 13.46 *87N1 16.8 -20.85 12.89

97B30 8.0 -21.78 14.45 88B1 8.9 -20.16 14.55

97KK1 8.7 -20.79 12.85 88B2 8.8 -19.43 14.80

97KK2 13.2 -20.42 12.94 88B3 7.8 -19.24

97KK3 8.3 -20.44 14.67 88B4 9.0 -19.28 14.54

97KK4 14.6 -20.01 13.62 88B5 8.9 -19.43 13.80

98KK1 10.4 -20.47 12.40 88B6 8.3 -19.94 14.30

98KK2 8.9 -19.80 12.84 88B7 8.2 -20.30 14.43

98KK3 9.2 -21.30 12.54 88B8 7.5 -19.52 13.97

99KK1 7.7 -20.91 13.72 88G2 15.3 -19.06 13.90

99KK2 12.9 -20.49 12.60

99KK3 8.3 -20.87 12.66

and closer to the average for fall-killed 1997–99 whales than to the average for spring killed 1986–88

whales. However, the δ13C values in all fall muscle (including 6 fall-killed 1986–88 whales) are not

significantly different from those in the spring muscle after adjustment for the 1 ‰ long-term decline

observed in Bering–Chukchi isotopic averages over the past 10 years.

δ15N in Bowhead Muscle.―Whales taken in fall 1997–99 have muscle with a mean δ15N value of

13.16 ‰ ± s.d. 0.72 ‰ (Fig. 20.5), whereas spring muscle samples for 1986–88 have an average δ15N of

14.32 ‰ ± 0.76 ‰ or an enrichment of 1.2‰. The average δ15N value for the six autumn-killed whales

from the 1986–87 (13.79 ± 0.71 ‰) was intermediate between spring whales in the ’80s and fall whales

in the ’90s. The δ15N values in fall muscle (including 6 fall-killed 1986–88 whales) are significantly different from those in the spring muscle (t-test, 2 tails, P < 0.001), although the δ15N values of the main
20-12 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

FIGURE 20.4. δ

13C values in bowhead whale muscle tissue taken in fall 1997–99 as compared to spring

1986–88. Values are as measured, not adjusted for decadal trend.

FIGURE 20.5. δ

15N values in bowhead whale muscle tissue taken in fall 1997–99 as compared to spring

1986–88. Values are as measured, not adjusted for decadal trend.
§20. Diet & Regional Feeding: Stable Isotopes 20-13

prey groups do not differ significantly between summer and winter feeding grounds. δ15N as well as δ13C

values in muscle have decreased in the past decade, apparently in response (at least in part) to long-term

decreases in isotope values in the Bering/Chukchi environment (Fig. 20.3). This may account for the

difference in δ15N of muscle shown in Figure 20.5, although the δ15N values in baleen deposited in 1986–

88 and 1997–99 did not show a significant change (Fig. 20.3).

Isotope Ratio Patterns of Subadult vs. Adult Whales

Muscle.―To assess the extent to which subadults and adults feed differently, all muscle data for

δ13C and δ15N are plotted against whale length in Figure 20.6 and 20.7. Subadults were separated by

body length (<13.5 m) from adults (≥13.5 m). The 13.5 m cutpoint is appropriate for bowhead whales

that have been stretched when towed out of the water. No significant differences were noted in δ13C or

δ15N in subadult vs. adult whale muscle.

Baleen.―Figure 20.8 shows δ13C and δ15N values for each point within parts of the baleen formed

during the most recent 2 or 3 years, distinguishing adults (n = 9 + 4, Fig. 20.8A) and subadults (n = 9 + 8,

Fig. 20.8B). Results for 1997–99 and 1986–88 are plotted separately. The range in δ13C values is greater in

subadults than in adults for both time periods (Fig. 20.8). The range of δ13C for adults is –20 to –17 ‰ for

1986–88 and –21 to –17.5 ‰ for 1997. By comparison, δ13C values of subadults range from –23 to –17.5‰

for both 1986–88 and 1997–99. δ15N values in recently-grown baleen also span a slightly wider range for

subadults than for adults (Fig. 20.8). The range of δ15N in adults is from 12.5 to 16 ‰ for both periods,

whereas the range in subadults is 12.5 to 17 ‰ for 1986–88 and 11 to 16 ‰ for 1997–99.

Discussion

Muscle tissue δ13C values provide a good overall indication of the bulk food sources that the

whales have consumed over the seasonal feeding cycle. George et al. (1988) estimated that muscle tissue

comprises approximately 19 % of the total body mass with blubber comprising the other large fraction.

The estimated δ13C values for total consumed prey are significantly different between the eastern Beaufort Sea and the Bering and Chukchi Seas (see Methods). Therefore, muscle tissue should change appreciably in δ13C between spring–summer and fall–winter seasons if whales feed to a significant extent in

each region and if the overall composition of the diets for bowhead whales, as listed in Table 20.3, are

approximately representative. However, the δ13C values in fall muscle in the late 1990s were not significantly different from those in the spring muscle from the 1980s after adjustment for the 1 ‰ long-term

decline observed in Bering/ Chukchi isotopic averages over the intervening 10 years. This indicates that

almost all food for the whales came from the Bering and Chukchi seas.

Appendix 20.1 calculates the estimated turnover in muscle carbon attributable to feeding in the

eastern Beaufort sea, based on the data from whales harvested at Barrow in spring of 1986–88 (n = 16)

and at Kaktovik in autumn of 1986 and 1997–99 (n =13). This calculation included an adjustment for the

long-term trend in Bering/Chukchi isotopic averages, and included derivation of confidence limits. The

observed zooplankton fractions in stomach contents of bowhead whales were used as weighting factors in

calculating the average δ13C values for zooplankton food from the Bering/Chukchi vs. Beaufort; they

differ by 3.86 ‰ (see Methods). This assumes a dietary composition of 61 % copepods and 22 %

euphausiids in the E. Beaufort Sea, vs. 28 % copepods and 61 % euphausiids in Bering/Chukchi waters.

As noted earlier, there are questions as to how representative these dietary data may be. However, the

similarity in taxonomic composition of stomach contents and samples from net tows (Saupe et al. 1989;

Schell et al. 1998; Chapter 5 vs. 18) gives some indication that the approximations are reasonable.
20-14 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

FIGURE 20.6. Carbon isotope ratios in whale muscle versus whale length. Whales >13.5 m in body

length were assumed to be adults (sexually mature). Data from 1997–99 have been adjusted upward to

allow for the decadal decline in average carbon isotope ratios (1 ‰).

FIGURE 20.7. Nitrogen isotope ratios in whale muscle versus whale length. Whales >13.5 m in body

length were assumed to be adults (sexually mature). Values were not adjusted for any decadal trend.
§20. Diet & Regional Feeding: Stable Isotopes 20-15

Assuming a 3.86 ‰ difference in the isotopic composition of the prey in the two regions, and the

(adjusted) seasonal difference in the muscle as documented in this study, 10 % of the muscle carbon has

turned over during the course of summer feeding, with 95% confidence interval of 0 % to 23 %.

Considering subadult whales only, the estimated turnover was 14 % with 95% confidence interval 4 % to

23 %. Considering adults only (for which the data are very limited), the estimated turnover was 5 % with

95% confidence interval 0 % to 30 % (see Appendix 20.1 for details).

The major assumption and weakness of the preceding analysis arises from the need to compare seasonal

isotope ratios in whales that were harvested approximately 10 years apart. The changing isotope ratios in

zooplankton of the Bering and Chukchi seas (and perhaps the Beaufort Sea) introduce an uncertainty in the

feeding estimates that is difficult to quantify, notwithstanding the procedures used in Appendix 20.1.

Estimation of Feeding Activity Using Same-Year Data

A recent paper by Hoekstra et al. (2002) contrasts isotope ratios of bowhead whales taken within

the same years in spring and fall. This allows a more direct approach to estimation of feeding, as evidenced by the turnover of carbon in muscle tissue. Hoekstra et al. determined that 10 whales taken in fall

at Kaktovik during 1997–99 (the years of our sampling) had an average muscle δ13C of –21.6 ‰ and that

28 whales taken in spring at Barrow during 1998–2000 averaged –19.9 ‰, for a seasonal shift of –1.72

‰ . The samples taken were lumbar muscle, which would be anticipated to show relatively rapid turnover as it is the primary locomotive muscle. If the zooplankton food end-members are assigned δ13C

values of –20.88 ‰ for the Bering/Chukchi waters and –25.49 ‰ for the Beaufort Sea (Schell et al.

1998), this implies a muscle carbon turnover of 1.7/4.6 or 37 %. Alternatively, assuming a 3.86 ‰

difference in the isotopic composition of the prey in the two regions (see above), and the 1.72 ‰ seasonal

difference in the muscle as observed by Hoekstra et al. (2002), approximately 45 % of the muscle carbon

has turned over during the course of summer feeding.

The above estimates of summer feeding, based on the data of Hoekstra et al. (2002), are much

higher than those determined by us based on either the analysis with allowance for long term trend (see

above) or additional analyses of same-year data, described here.

We found an average muscle δ13C of –20.7‰ in Kaktovik whales during the autumns of 1997–99,

or –0.8 ‰ as compared with the spring values from Barrow during similar years, as obtained by Hoekstra

et al. (2002). This translates into 17.4 % turnover of muscle carbon during summer feeding based on the

assumed 4.6 ‰ difference in the isotopic composition of zooplankton in the two regions, or 20.8 % if the

weighted value (3.86 ‰) based on stomach contents is used. Comparing our average muscle values for

Kaktovik in autumn (–20.7 ‰ ) and theirs for Barrow in autumn (–20.9 ‰), we find a small and nonsignificant depletion in the muscle δ13C of the whales while traveling westward, in contrast to their data.

Hoekstra et al. (2002) found an average increase in autumn δ13C values of 0.7 ‰ between Kaktovik and

Barrow, equivalent to a muscle turnover of 15–18 percent.

This discrepancy is critical in assessing the importance of feeding in the Eastern Beaufort Sea.

The source of this apparent discrepancy arises from differences in the results for the Kaktovik whale

muscle samples. Hoekstra et al. (2002) found an average muscle value of –21.6 ‰ in 1997–99, whereas

we obtained an average value of –20.7‰ from the same whales. We have repeated our isotopic analyses

on additional subsamples from the same Kaktovik whales, with the same results as we obtained initially.

The reason for the discrepancy between our data from Kaktovik and those of Hoekstra et al. is still

uncertain. We have analyzed the isotope ratios for muscle taken from 14 fall Barrow whales taken in
20-16 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

FIGURE 20.8A. δ

13C and δ15N values from recently-deposited baleen of adult bowhead whales. Each

point represents a sample taken 0 to 50 cm from the base of a baleen plate from an adult whale harvested in 1986–88 and 1997. Values have not been adjusted for any decadal trend.

1997 and obtained an average of –20.84 + s.d. 0.61 ‰. This matches closely the average value of –21.1 +

95 % CI 0.2 ‰ obtained by Hoekstra et al. for 21 whales harvested at Barrow in fall 1997. We also

analyzed three types of muscle from one 1997 Kaktovik whale, including lumbar muscle, and found no

significant difference among tissues. This suggests that differences in the types of muscle samples

analyzed probably were not important.

In view of the above, we applied this approach to data collected in 1986–87 by Schell (1992), and

the results are similar, but based on smaller numbers of whales. Seven whales taken in spring at Barrow

had average δ13C values of –19.6 ‰ for muscle and –24.9 ‰ for visceral fat. Three whales taken at Kaktovik in fall 1986 had average δ13C values of –20.6 ‰ for muscle and –26.3 ‰ for visceral fat. Thus, the
§20. Diet & Regional Feeding: Stable Isotopes 20-17

FIGURE 20.8B. δ

13C and δ15N values from recently-deposited baleen of subadult bowhead whales. Each

point represents a sample taken 0 to 50 cm from the base of a baleen plate from a subadult whale

harvested in1986–1988 and 1997–99. Values have not been adjusted for any decadal trend.

seasonal change was 1.0 ‰ in muscle and 1.3 ‰ in visceral fat. Again, assuming an end-member difference of 4.61 ‰ , this implies a replacement of about 22 % of muscle carbon and 28 % of visceral fat. If

the stomach content data of Lowry are used with an end-member difference of 3.86 ‰, the carbon

replaced is 26 % for muscle and 34 % for visceral fat.

In contrast to the relatively rapid turnover rates of visceral fat and muscle, the blubber lipids

showed very little change. Two whales taken at Barrow in 1986 each had blubber δ13C values of –25.8 ‰

and the three whales from Kaktovik averaged –26.0 ‰ or a change of only 0.2 ‰ over the summer. This

implies a turnover of only about 4–5 %, depending upon the choice of end-member differences. The
20-18 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

carbon isotope ratio in lipids is typically depleted by 5–6 ‰ from that in the diet, so the measured values

in blubber closely match expected values from feeding on Bering/Chukchi zooplankton. 

Our same-year estimates of changes of 17–26 percent in muscle tissue and 28–34 percent for

visceral fat are low considering that the whales had been in the 13C-depleted regime of the Eastern

Beaufort Sea for approximately four months. Muscle amino acid turnover in terrestrial mammals, as

measured using stable and radio-isotope measurements, ranges from 1.2 to 3 percent · day–1 for healthy

adult humans and dogs, leading to an expected complete replacement time of 33–80 days (Fischman et al.

1998). The low isotopic replacements observed in this study indicate that the metabolic rates of the

bowhead whale are slow or that very little food is acquired from the Beaufort Sea. The latter scenario is

supported by the very small seasonal isotopic changes observed in blubber tissue in the 1980s.

Isotope ratios in the blubber of bowhead whales landed at Barrow and Kaktovik have not been

determined during either the present study nor that of Hoekstra et al. (Paul Hoekstra, pers. comm.). This

information would be valuable in estimating the percent of total annual carbon intake derived from the

winter versus summer habitats. Blubber comprises approximately 40 % of bowhead body mass and is the

major energy store for the whales (George et al. 1988).

Bowhead Whale Feeding Scenario

To assess the contribution of food from Beaufort Sea habitats in meeting the annual energy

requirements of the Bering–Chukchi–Beaufort stock of bowheads, it is important to take account of time

and resource availability as well as direct evidence of feeding, such as stomach contents and observed

feeding behavior. The following feeding scenario is based upon several realistic assumptions concerning

food availability and mammalian metabolism:

• Bowhead whales feed seasonally in response to food abundance. Feeding is minimal during the

northeastward transit in the Arctic Ocean to summer grounds.

• Zooplankton abundance is proportional to ecosystem primary productivity.

• Zooplankton abundance peaks in the late summer–fall season.

• Zooplankton composition is weighted to euphausiids in the western region and to copepods in the

eastern Beaufort Sea.

• Isotope ratios in the whales respond to feeding in the different regimes only if sufficient food is

acquired to replace body carbon. Otherwise the whale relies on internal stores and the isotope

ratios of the muscle do not change.

This scenario assumes that the whales begin their northward migration in early spring when

zooplankton stocks are at an annual minimum and this condition persists during their passage through the

Chukchi Sea and into the Arctic Ocean. The whales arrive in the eastern Beaufort Sea after approximately 2–3 months of traveling, with minimal feeding having occurred along the migration route.

Bowheads harvested at Barrow in spring often contain some prey, but on average their stomachs contain

less food than those harvested in autumn (Chapter 18). Also feeding is much less commonly seen during

spring migration than during summer and autumn (Chapter 12). More intensive feeding commences upon

arrival on the summering grounds, and with the appearance of growing populations of large copepods and

amphipods. Nevertheless, zooplankton patch densities in the Beaufort Sea are constrained by the

relatively low primary productivity rates of that area. Primary production estimates are typically in the

range of 20–50 gC · m–2 in offshore regions of the Beaufort Sea, with the higher values in zones of

upwelling associated with offshore winds and open polynyas (Macdonald et al. 1987, 1998; Macdonald
§20. Diet & Regional Feeding: Stable Isotopes 20-19

and Carmack 1991). Zooplankton biomass and whale feeding would be anticipated to increase at the end

of summer.

Most whales begin their fall migration out of the Beaufort Sea in September, feeding intermittently

as they travel. On average, they cross into the areas where the zooplankton has higher isotope ratios (west

of Harrison Bay) in late September and early October (see Moore and Reeves 1993; also Chapter 9).

Here they feed on zooplankton advected from the Chukchi Sea associated with the Beaufort Sea undercurrent. As the fall progresses the whales move into the Chukchi Sea and across to the Chukotka

Peninsula region of Russia (Fig. 20.1), in the highly productive waters of the Anadyr current. Primary

productivity estimates for this region range from 150 gC · m–2 in the coastal waters to over 800 gC · m–2 in

the center of the Anadyr flow, or approximately 5–10 times estimates for the eastern Beaufort Sea

(Springer et al. 1996). This flow carries immense quantities of euphausiids and large oceanic copepods

and is known to be prime whale habitat. Thus the whales enter the Chukchi Sea in the fall coincident

with maximum annual food supply and are assumed to feed upon these resources. Secondary production

of zooplankton is proportional to the primary productivity, but not linear, with increasing trophic

efficiency occurring with higher primary production. Thus, the feeding opportunities for the whales

would be maximized in this region. Niebauer and Schell (1993) quote whaler observations describing the

southern Chukchi Sea as the “cow yard” where the very largest and most oil-rich bowheads were taken.

Feeding in reasonably dense concentrations of zooplankton could continue in late autumn/early winter as

the whales move into the northwest Bering Sea.

Assuming that the high zooplankton densities persist at least into the early winter, the fall migration past Point Barrow would correspond to the onset of the optimum feeding period for the whales.

Although energy-rich zooplankton tend to descend to deep depths in autumn, the Chukchi Sea is generally

shallow. This would prevent zooplankton from descending to depths below the diving range of bowheads. If feeding in the Bering/Chukchi system persists until late autumn or early winter, when growing

ice cover forces the whales into the Bering Sea, their period of autumn/early winter residence in the

Chukchi Sea, and perhaps the northwest Bering Sea, may be the period of maximum energy acquisition

and storage. The observation that the nine blubber samples from whales taken in 1986–87 all have

similar δ13C values near –25.8 ‰ supports this conclusion. As noted above, lipids are typically depleted

by 5–6 ‰ relative to diet, and this –25.8 ‰ value closely matches expected values from feeding on

Bering/Chukchi zooplankton.

Nitrogen Isotope Data

The δ15N values in fall muscle are significantly different from those in the spring muscle. The

nitrogen isotope ratio is often an indicator of nutritional status (e.g., Gannes et al. 1997), but the specific

reason for the observed difference is uncertain. One possibility is that it results from the same decadal

decline in environmental isotope ratios as noted for carbon. The spring whales were all taken in the

1980s whereas the fall whales were mainly from the late 1990s. The long-term trend noted for both

elemental isotope ratios (based on baleen deposited in the Bering/Chukchi region) is of the same

magnitude as the difference between the spring muscle from the 1980s vs. the fall muscle from the 1990s.

However, the nitrogen isotope data evident in baleen laid down in the specific years of capture in the ’80s

and ’90s are similar (Fig. 20.3). This tends to discount the possibility that a decadal-decline was the

cause of the spring–fall difference in the muscle δ15N values. A second possibility is that summer fasting

produced a shift toward higher δ15N values (Hobson et al. 1993, 1996; Best and Schell 1996). The seasonal change in δ15N is unlikely to arise from summer feeding as the carbon isotope ratios in muscle

would be expected to show a larger effect if a significant amount of food was consumed in summer.
20-20 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

Additionally, the δ15N values in the assumed main prey taxa are not significantly different between summer and winter feeding grounds, so summer feeding alone would not affect δ15N values.

Feeding by Subadult vs. Adult Bowheads

The carbon turnover calculations in Appendix 20.1 suggest that subadult bowheads may obtain

slightly more of their prey in the Beaufort Sea than do adults, but the best estimates for both groups are

low, and there is wide overlap in the 95% confidence intervals.

The average δ13C value for the muscle from six whales killed in the fall during 1986–87 is closer to

the average for fall-killed 1997–99 whales than to the average for spring killed 1986–88 whales. This

indicates that these whales may have fed in the eastern Beaufort Sea to a greater extent. Three of the

1986–87 fall whales were subadults, and subadults have often been observed feeding in the eastern

Beaufort Sea (Würsig et al. 1989; Chapter 12).

Younger whales have often been observed feeding in nearshore waters of the eastern Beaufort Sea

(Würsig et al. 1989; Chapter 12), whereas adults observed feeding in the Beaufort tend to be in deeper

water (Chapters 10, 12). It is possible that feeding patterns, as represented by isotope ratios, would be

related to age. However, δ13C values in muscle are similar in adults and subadults, suggesting no major

age-related shift in the relative importance of feeding in the eastern Beaufort Sea vs. elsewhere.

In contrast to the muscle data, δ13C values in the baleen plates do show considerable age-related

differences, indicating some variation in feeding patterns between subadult and adult (Fig. 20.8). Each

point along the plates records the isotopic value of the circulating baleen precursors at the time of baleen

formation, whereas muscle shows bulk isotopic composition of whales integrated over an extended (but

uncertain) period. Why there was an age effect on isotope ratios in baleen but not in muscle is not clear.

However, it is apparent that the feeding patterns of adults and subadults are quite different. The lack of

low δ13C values in either baleen or muscle of adult bowheads suggests that they feed intensively in the

Bering and Chukchi seas and the observed feeding in the eastern Beaufort Sea during summer and early

fall must be less intensive. In contrast, the wider range in baleen isotope ratios in subadults suggests that

they apparently feed continuously while they are migrating across regions of different isotope ratios. The

tendency of the average muscle and baleen δ13C values in both subadults and adults to match prey from

the Bering and Chukchi seas also suggests that feeding is more successful there, which may, in turn,

reflect the higher primary and secondary productivity of the Bering–Chukchi region.

In addition, recent measurements of blubber composition of bowhead whales showed lower lipid

contents in longer, and presumably older, whales in fall 1998 than those in small whales (Michael Castellini, pers. comm.). These observations are in general agreement with the lack of summer feeding activity

of adults indicated in the baleen isotopic ratios.

The consumption of different prey by adults versus subadults in summer could also account for the

different isotopic compositions. However, no major differences between the diet of small and large

whales were evident from stomach content samples collected from Kaktovik and Barrow over many years

(Chapter 18). Both adults and subadults probably feed on any species of zooplankton that is sufficiently

concentrated to provide a reasonable energy source (Bradstreet et al. 1987; Chapter 6). However, differences in the locations and water depths where subadult and adult bowheads tend to concentrate may be

associated with differences in prey. Subadult bowheads commonly feed in nearshore waters along the

Yukon and eastern Alaskan coast at locations and times when the small copepod Limnocalanus is concentrated (Chapter 6). Adult bowheads tend to feed farther offshore, in areas without Limnocalanus.
§20. Diet & Regional Feeding: Stable Isotopes 20-21

In conclusion, the utilization of feeding habitats appears to be more diverse for subadult than adult

bowheads, as indicated by the larger range in isotope ratios. The isotopic evidence indicates that the

eastern Beaufort Sea is not an important feeding habitat for adult bowhead whales, but may be more

important for subadults. However, the Bering and Chukchi regions are the predominant feeding areas for

both adults and subadults, based on isotopic values in both bulk body tissues and the baleen plates. The

specific estimates of the percent of the feeding that occurs in the eastern Beaufort Sea are subject to a

variety of assumptions. However, the strong Bering–Chukchi isotopic signature in the muscle and baleen,

as compared with the much more limited eastern Beaufort signature, indicates that only a minority of the

feeding by either subadults or (especially) adults is on prey from the eastern Beaufort region.

Although zooplankton prey samples have been collected from almost all of the range of this

population of bowhead whales, muscle samples have only been available and analyzed for selected

locations and seasons. No muscle samples from whales harvested along the Chukotsk Peninsula (southwestern Chukchi Sea) or at St. Lawrence Island (Bering Sea) have been analyzed. Also, in the absence of

regular bowhead harvests in the Canadian Beaufort Sea, muscle samples from that area have not been

available for analysis. The baleen, however, grows continuously and reflects the isotopic composition of

the food recently consumed. Additional analyses of the isotope composition of baleen could be useful.

For example, by analyzing the isotope ratios of individual amino acids in the baleen and comparing them

with the same amino acids from prey, many of the uncertainties noted above probably could be better

addressed. Similarly, the analysis of oxygen isotope ratios in baleen and prey should allow resolution of

offshore versus inshore feeding in the eastern Beaufort Sea, where the influence of the Mackenzie River

is pronounced. Isotopic signatures and compositional changes in fatty acids (see Chapter 19) may also

provide additional insight into feeding regimes.

Summary

δ13C and δ15N ratios in muscle and baleen from harvested bowhead whales were used to estimate

the relative amounts of food acquired from the eastern Beaufort Sea (summer and early autumn range)

versus the Bering and Chukchi seas ― the two regions previously proposed as major feeding grounds.

This analysis was based on the fact that isotope ratios in the zooplankton prey of bowheads are different

in the two regions. Isotope ratios in prey are reflected in the predators. When isotope ratios differ regionally, this provides a basis for determining the main area(s) where the predators feed.

Samples obtained from whales harvested in autumn of 1997–99 and spring of 1986–88 were

compared. Both δ13C and δ15N values in the whales have decreased in recent years in response to a long

term decreasing trend in isotope ratios in the Bering–Chukchi food chain. The whale samples collected

~10 yr apart were normalized to allow direct comparison.

For all whales, the δ13C values in muscle sampled in fall were not significantly different from the

muscle sampled in spring. Muscle δ13C during both seasons closely matched the isotope ratios of zooplankton from Bering and Chukchi water, indicating that most of the annual food requirement of adults

and subadults is met from that portion of their range. Isotope data from baleen showed, however, different feeding strategies by adult and subadult whales. Subadults acquired sufficient food in the eastern

Beaufort Sea to alter the carbon isotope ratios in baleen deposited there relative to baleen representing

feeding in Bering and Chukchi water. Baleen plates from subadults showed a wider range in isotope

ratios than those from adults, suggesting active feeding by subadults over all parts of their range. A simple approximation based upon observed seasonal shifts in muscle isotope ratios indicates that between 10

and 26 percent of the muscle carbon is replaced over the summer, depending on the method of
20-22 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

calculation. A sensitivity analysis that allowed for variability in each factor involved in the calculation

indicated that the true percentage probably did not exceed 23 %. Limited data on blubber indicates an

even smaller percentage. Although these specific estimates are subject to a variety of assumptions, the

isotopic evidence indicates that only a minority of the feeding by either subadults or (especially) adults is

in the eastern Beaufort Sea.

Acknowledgements

We thank the whaling captains of Barrow and Kaktovik, the Alaska Eskimo Whaling Commission,

and Todd O’Hara and Craig George of the North Slope Borough Department of Wildlife Management,

for access to baleen plates and muscle samples. Gay Sheffield of the Alaska Department of Fish & Game

undertook the recent field collections at Kaktovik. Laboratory analyses and sample preparation of previously collected samples were performed by Kimberly Vinette and Bruce Barnett. The mass spectrometry analyses were run by Norma Haubenstock and Tim Howe. This study was funded by the U.S. Minerals Management Service through MMS contract 30842 awarded to LGL Ecological Research Associates Inc. and a subcontract from LGL to the University of Alaska Fairbanks. Collection of bowhead

tissue specimens was done under NMFS Scientific Research Permits 797 and 481-1464 (Kaktovik) and

932-1489-90 (Barrow). We thank Dr. Keith Hobson and members of the project’s Scientific Review

Board for comments on the draft manuscript. Dr. Trent McDonald (WEST Inc.) provided the sensitivity

analysis and other calculations included as Appendix 20.1. Additional general acknowledgements applicable to the project as a whole can be found in Chapter 1.

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assessments, 2000. NOAA Tech. Memo. NMFS-AFSC-119. Nat. Mar. Fish. Serv., Seattle, WA. 195 p

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protein synthesis by positron emission tomography with L- [methyl-11C] methionine in adult humans. Proc.

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Gannes, L.Z., D.M. O'Brien and C. Martínez del Rio. 1997. Stable isotopes in animal ecology: assumptions, caveats, and a call for more laboratory experiments. Ecology 78(4):1271-1276.
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Balaena mysticetus, by Alaskan Eskimos. Rep. Intern. Whal. Comm. 38:389-392.

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tissues. Condor 94(1):181-188.

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fasting and nutritional stress: implications for isotopic analyses of diet. Condor 95(2):388-394.

Hobson, K.A., D.M. Schell, D. Renouf and E. Noseworthy. 1996. Stable carbon and nitrogen fractionation between

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feeding bowhead whales, 1985-86. OCS Study MMS 87-0037. Rep. from LGL Ecol. Res. Assoc. Inc.,

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§20. Diet & Regional Feeding: Stable Isotopes 20-25

APPENDIX 20.1. VARIANCE OF BOWHEAD FEEDING FRACTION BASED ON STABLE ISOTOPE ANALYSIS

Trent L. McDonald 2

The bowhead whales under study typically spend the winter months in the Bering Sea, migrate

northward through the Bering Strait in spring, travel northeast past Barrow, and then east across the

Beaufort Sea to their summering areas. Those summering areas are in the Eastern Beaufort Sea, including

waters near the Mackenzie River Delta and Banks Island. In fall, they return west and south and arrive in

the Bering Sea in early winter. Bowheads are known to feed, to varying degrees, during both the spring

and fall migrations and during summer; there are no specific data for winter. 

This migration pattern allows whalers to take bowheads near Barrow, Alaska, in spring soon after

the whales exit their winter habitat in the Bering Sea. During the return migration in early autumn,

whalers take bowheads near Kaktovik, Alaska, as they exit their summer habitat in the Eastern Beaufort

Sea. Bowheads are harvested elsewhere, and in particular at Barrow in autumn, but those data were not

considered here.

In the Chukchi and Bering seas during late fall and perhaps winter, feeding bowheads consume

zooplankton and other food with a specific ratio of carbon-13 to carbon-12 isotopes (δ13C). In summer

habitat of the Eastern Beaufort Sea, feeding bowheads consume food with a different carbon isotope ratio.

Because a gradient in δ13C exists between the Bering and Eastern Beaufort seas, it is possible to measure

δ13C in whales soon after exit from each area and, under certain assumptions, estimate the proportion of

annual food consumed in each area. δ13C ratios can be measured in a variety of whale tissues, including

baleen, blubber and muscle. Muscle tissue δ13C ratios have been used in Chapter 20 to estimate the proportion of food consumed in each area.

The question addressed in this Appendix is the uncertainty in the estimated proportion of food

consumed in the Eastern Beaufort and Chukchi Sea. Chapter 20 provides various point estimates of this

proportion based on average isotope ratios in samples of bowhead tissue and zooplankton prey tissue.

However, there is variability in each value used in the calculations, and as a result there is uncertainty in

the calculated feeding proportion. This uncertainty is estimated below based on the procedures described

in the next section.

Methods

The proportion of total annual food consumption occurring in the Eastern Beaufort Sea was

calculated as the difference in δ13C ratios in muscle samples collected at Kaktovik in fall vs. Barrow in

spring, divided by the difference in δ13C ratios of dietary components between the Eastern Beaufort and

Bering Sea. In equation form, the proportion of food consumed in the Eastern Beaufort Sea was

calculated as

EBF BER

Kak Barrow

R R

R R f −

− =

 

2

 Western EcoSystems Technology Inc., 2003 Central Ave., Cheyenne, WY 82001. Phone: 307-634-

1756; e-mail: tmcdonald@west-inc.com
20-26 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

where RKak was the average muscle δ13C ratio in whales taken at Kaktovik (fall), RBarrow was the average

muscle δ13C ratio in whales taken at Barrow (spring), REBF was the average δ13C ratio of zooplankton

collected in the Eastern Beaufort Sea, and RBER was the average δ13C ratio of zooplankton collected in the

Bering Sea. Under the assumption that the difference between RKak and RBarrow would equal the difference

between REBF and RBER if whales were feeding in the Eastern Beaufort Sea to such an extent that the

carbon in muscle turned over each season, f can be interpreted as the proportion of annual food

consumption occurring in the Eastern Beaufort Sea. This method does not require estimation of or

allowance for the metabolic fractionation of δ13C in muscle tissue of the whale.

Since 1965, δ13C ratios in the Bering/Chukchi seas have been declining (Schell 2000). Because our

muscle samples were taken at various times between the mid 1980s and late 1990s, an adjustment was

made for overall decline when estimating RBarrow and RKak. All δ13C ratios in RBarrow and RKak were adjusted to 1999 values by fitting a linear regression to the post-1965 values in Schell (2000, Table 1; see also

Fig. 20.3) and subtracting an appropriate amount based on the slope of this regression and the difference

in years between the sampling date and 1999. For example, if the regression of values in Schell (2000)

estimated a decline in δ13C ratios of –0.063 per year, a δ13C ratio measured in 1987 would be adjusted by

–0.063(1999 – 1987) = –0.756. A δ13C ratio measured in 1998 would be adjusted by –0.063(1999 –

1998) = -0.063. A δ13C ratio measured in 1999 would not be adjusted. Standard error of the decline was

estimated by the standard error of the slope of the regression. It should be noted that the year to which the

standardization is done (here 1999) has no influence on the final results concerning estimated proportion

of food consumption occurring in the Eastern Beaufort Sea.

After adjustment of individual δ13C ratios for the long-term decline, RBarrow and RKak were calculated

as simple arithmetic averages. Because there was an overall decline in δ13C ratios during the study

period, uncertainty in RBarrow and RKak was estimated by calculating yearly variances, then calculating a

weighted average of yearly variances. Weights used in the weighted average were yearly sample sizes.

This method of calculating variance removed the overall trend.

Average δ13C in bowhead whale diets (i.e., REBS and RBER) were derived from values in Table 20.4,

and diet composition values in Table 20.3, considering only the two dominant taxa, copepods and

euphausiids. For example, RBER was the weighted average of copepod and euphausiid δ13C ratios equal to

[(28%)(–22.2) + (61%)(–20.8)]/(89%) = –21.24. Similarly, REBS was calculated as [(61%)(–25.6) +

(22%)(–23.7)]/(83%) = –25.10 Standard errors were also calculated as weighted averages. Standard

errors for δ13C ratios in food components were calculated by averaging the standard errors from certain

geographic regions found in Table 1 of Schell et al. (1998):

• Standard errors for copepods and euphausiids in the Bering Sea were calculated as the average of

standard errors in the East Bering, Central Bering, and West Bering of Schell et al.

• Standard errors for copepods and euphausiids in the Beaufort Sea were calculated as the average

of standard errors in the Canadian Beaufort and East Alaskan Beaufort of Schell et al.

• Because they were not reported in Schell et al., standard errors for δ13C in mysids and amphipods

were assumed to equal the standard error of δ13C in euphausiids. The standard error of δ13C in

euphausiids was the highest observed standard error in any dietary component.

The square root of average standard errors, weighted by the square of percent composition, was taken to

estimate the standard error of REBS and RBER. For example, the standard error of δ13C in copepods of the

Bering Sea was 0.16 and that in euphausiids of the Bering Sea was 0.21 (Schell et al. 1998, Table 1). The

standard error of RBER was calculated as [(28%)2

(0.16)2 + (61%)2(0.21)2]

0.5/(89%) = 0.152.
§20. Diet & Regional Feeding: Stable Isotopes 20-27

To calculate a 95% confidence interval for f, a Monte Carlo simulation was implemented wherein

random deviates from a normal distribution with mean 0 and appropriate standard deviation were

repeatedly generated and added to the data comprising each component of f. For example, values for RBER

were generated as −21.23 + e for each iteration of the Monte Carlo simulation, where e was a normal

random deviate with mean 0 and standard deviation 0.152. Values for RKak and RBarrow were generated in

four steps: (1) Random normal deviates with mean 0 and appropriate standard deviation were added to

the underlying muscle carbon values found in Table 20.6. (2) A random value for the slope of the longterm decline in δ13C ratios was generated as –0.0629 + e, where e was a normal random variable with

mean 0 and standard deviation 0.00648. (3) Randomly-generated muscle δ13C ratios from step 1 were

corrected for long-term trend using the randomly generated slope from step 2. (4) The corrected sums

were averaged. After Monte Carlo generation of RKak, RBarrow, REBS, and RBER, f was recalculated and

stored. Generation of RKak, RBarrow, REBS, and RBER was repeated 1000 times, yielding 1000 random values

of f from its assumed distribution. The lower limit of the 95% confidence interval for f was the 0.025th

percentile of the 1000 generated values of f. The upper limit of the 95% confidence interval for f was the

0.975th percentile of the 1000 generated values of f. If the lower limit of the 95% confidence interval for f

was negative, the lower endpoint was truncated and set equal to 0.

Estimation of f was performed for adult and sub-adult whales separately. Whales greater than

13.3 m in length were defined to be adults. Whales less than 13.3 m were defined to be sub-adults. Upon

inspection of the data, it was found that samples from adults taken in the spring at Barrow were not

available. Because no spring adult samples were available, δ13C values from two adults taken at Wainwright in the spring of 1986 and one adult taken at Gambell in the spring of 1988 were used to calculate

RBarrow for the adult analysis. For completeness, sub-adult and adult data were combined and a separate

estimate of f was made for all whales. The three whales taken at Wainwright and Gambell were not

included in this “all whale” analysis, and consequently only 2 adults were added to the sub-adult analysis

for the all whale analysis.

Results

In 1986–88, a total of 16 muscle tissue samples were obtained from whales taken in the spring at

Barrow (7 in 1986, 1 in 1987, 8 in 1988). In 1986 and 1997–1999, a total of 13 muscle tissue samples

were obtained from whales taken in the fall at Kaktovik (3 in 1986, 4 in 1997, 3 in 1998, 3 in 1999). All

16 whales sampled at Barrow were sub-adults. Of the 10 whales taken at Kaktovik, 2 were adults and 11

were sub-adults.

Estimates and standard errors of REBS, RBER, RBarrow, RKak, and of the long-term trend in δ13C ratios

appear in Table 20.7. Assuming each component of f followed a normal distribution with mean and

standard error as listed in Table 20.7, the proportion of diet consumed in the Eastern Beaufort Sea by subadult bowhead whales was 13.7 % with 95 % confidence interval of 4.3 % to 23.3 %. The estimated

proportion of diet consumed in the Eastern Beaufort Sea by adults was 4.6 % with 95 % confidence

interval of 0 % to 30.0 %. Combining age classes, the estimated proportion of diet consumed in the

Eastern Beaufort Sea was 10.0 % with 95 % confidence interval of 0 % to 22.6 %.
20-28 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

TABLE 20.7: Estimates and standard errors of δ

13C

ratios used in calculation of f. Mean δ

13C values in

sub-adult and adult whale tissue have been adjusted to

1999 values based on long-term trend.

Age Class Statistic Estimate

Standard

Error n

Rkak -20.96 0.128 11 Sub-adult

RBarrow -20.43 0.109 16

Rkak -20.03 0.445 2 Adult

RBarrow -19.85 0.170 3*

Rkak -20.81 0.211 13 All

RBarrow -20.43 0.109 16

- REBS -25.10 0.151 -

- RBER -21.24 0.152 -

- Trend -0.0629 0.00648 -

*

Two whales taken at Wainwright, one taken at Gambell. These

three whales were not included in the ‘all’ whale analysis.

References

Schell, D.M. 2000. Declining carrying capacity in the Bering Sea: isotopic evidence from whale baleen. Limnol.

Oceanogr. 45(2):459-462.

Schell, D.M., B.A. Barnett and K. Vinette. 1998. Carbon and nitrogen isotope ratios in zooplankton of the Bering,

Chukchi and Beaufort Seas. Marine Ecol. Progr. Ser. 162:11-23. 
21. DIET AND REGIONAL OCCURRENCE OF FEEDING:

SUMMARY AND CONCLUSIONS

Denis H. Thomson and W. John Richardson1

This component of the study sought to determine (1) what types of prey bowhead whales of the Bering–

Chukchi–Beaufort (BCB) stock eat, and (2) what parts of their seasonal range provide the predominant part of

this food. The principal and most direct method for determining what bowheads eat was analysis of the

stomach contents of bowheads harvested by Inupiat whalers (Chapter 18). The project also included a pilot

study of the fatty acid composition of bowhead blubber in relation to the fatty acid composition of potential

zooplankton prey (Chapter 19). It was hoped that this approach might, when further developed, provide a

method for assessing food consumption over a longer period (and larger geographic area) than can be assessed

from stomach contents. To assess the proportion of the food consumed in different parts of the seasonal range,

the carbon and nitrogen isotope ratios in bowhead tissues were compared with those in the prey from the

eastern Beaufort Sea vs. the Bering–Chukchi area (Chapter 20). Several of the earlier chapters also provide

information directly or indirectly relevant to “Diet and Regional Occurrence of Feeding”.

Much of the interest in this general topic focuses on the relative importance of feeding in the

Bering–Chukchi region vs. the Beaufort Sea. The latter area includes the summering grounds of the BCB

bowheads in the Canadian Beaufort Sea as well as the Alaskan waters that are occupied mainly in late

summer and fall. The isotope composition of zooplankton in the Canadian and eastern Alaskan parts of

the Beaufort Sea is not distinguishable based on methods used to date. Thus, carbon and nitrogen in bowhead tissues cannot be ascribed specifically to food from the Canadian vs. the eastern Alaskan parts of the

Beaufort Sea. The central question that this study is designed to address concerns the importance of the

eastern Alaskan Beaufort Sea to feeding bowhead whales. Nonetheless, information about the importance

of feeding in the eastern Beaufort Sea as a whole is still relevant. If it were concluded that relatively little

of the annual food requirement was met in the overall eastern Beaufort Sea, this would mean that the

“eastern Alaskan Beaufort Sea” must contribute an even smaller portion of the annual food intake.

The following three subsections are near-verbatim copies of the summaries of Chapters 18 to 20. Those

summaries are followed by a short concluding section, primarily dealing with the evidence in Chapter 20

(Stable Isotopes) vs. various other chapters regarding the importance of feeding in the eastern Beaufort Sea.

Stomach Contents of Bowhead Whales

This component of the study, by L.F. Lowry and G. Sheffield of Alaska Department of Fish &

Game (Chapter 18), documents bowhead whale feeding in the Alaskan Beaufort Sea based on stomach

contents of whales harvested by Alaska Natives. They examined field records and archived data from

previous studies of bowhead stomach contents, and analyzed similar samples from 85 additional bowhead

whales harvested during 1986–2000 near Kaktovik, Barrow, and Cross Island. All available data from

bowheads harvested near those locations were used to characterize and compare diet by harvest location

and season (i.e., Kaktovik fall; Barrow fall; Barrow spring), and by whale size and sex.

 

1

 LGL Ltd., environmental research associates, 22 Fisher St., POB 280, King City, Ont. L7B 1A6.

Phone: 905-833-1244; e-mail: dthomson@lgl.com, wjr@lgl.com
21-2 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

Thirty-two bowheads harvested near Kaktovik during fall 1979–2000 have been examined for evidence of feeding. Of 29 whales whose feeding status could be classified as “feeding” or “not feeding”, at

least 83% had been feeding prior to death. Copepods, most commonly Calanus hyperboreus and C. glacialis, were the most important prey; copepods occurred in all 21 stomachs with food and were the dominant prey by volume in 62% of the samples. Euphausiids, mainly Thysanoessa raschii, were also an

important food item. Estimated volume of stomach contents was as much as 150 liters, and in 7 of 18

cases was greater than 20 liters.

Four of five bowheads harvested near Cross Island during 1987–2000 were recorded as having

been feeding. Copepods were the main prey in the three stomach contents samples examined.

Stomachs of 106 bowheads harvested in fall near Barrow during 1976–2000 were examined. Of

the 103 “non-calf” whales that could be classified as “feeding” or “not feeding”, at least 75% had been

feeding prior to death. Euphausiids were the most important prey; they occurred in 94% of the stomachs

with food and were the dominant prey by volume in 88%. Estimated volumes of stomach contents were

as much as 189 liters, and in many cases were recorded as ≥100 liters or “full”.

Stomachs of 100 bowheads harvested in spring near Barrow during 1969–2000 were examined. Of

the 90 whales that could be classified as “feeding” or “not feeding”, at least 33% had been feeding prior

to death. Euphausiids occurred in 93% of the samples and were the dominant prey in 61%. Copepods

were also an important diet item, especially in samples collected before the 1990s. Estimated volumes of

stomach contents were smaller than for whales taken in fall, and never exceeded 60 liters.

There was no significant difference in the proportion of bowheads that had been feeding in the fall

near Kaktovik and Barrow. However, there was a significant difference in composition of the fall diet at

these locations. Copepods occurred more often and were more frequently the dominant prey by volume

in whales from Kaktovik. Euphausiids occurred more often and were more frequently the dominant prey

by volume in whales from Barrow.

At Barrow, the frequency of feeding in harvested bowheads was significantly greater in the fall

than in the spring. Copepods occurred significantly more often in whales harvested near Barrow in the

spring than in the fall.

Male and female bowheads ate essentially the same food items. The data suggest the possibility of

a slight difference in the prey eaten by small (<13 m) and larger (≥13 m) whales. There was no difference

in the frequency of feeding of small versus large whales.

Preliminary estimates of the overall bowhead diet composition by location/season were as follows:

Kaktovik fall, 61–62% copepod, 22–24% euphausiid, 15–17% other prey; Barrow fall, 5% copepod, 84–

88% euphausiid, 7–11% other prey; and Barrow spring, 27–28% copepod, 61–63% euphausiid, and 10–

11% other prey.

Lowry and Sheffield conclude that coastal waters of the Alaskan Beaufort Sea should be considered as part of the bowheads’ normal summer–fall feeding range. During spring, feeding by bowheads

near Barrow is more common than previously thought, but the frequency and apparent intensity of feeding is less in spring than in the fall.

Fatty Acids in Bowhead Whales and Potential Prey

Fatty acids, the dominant constituent of lipids, are often deposited in animal tissue with minimal

modification from those in the diet. Lipids in the marine food web are exceptionally complex and
§21. Diet & Regional Feeding: Summary & Conclusions 21-3

diverse. Dr. S.J. Iverson et al. (Chapter 19) undertook a pilot study to assess whether analysis of fatty

acid signatures in bowheads and their potential prey (zooplankton) would be a useful tool for better

understanding the foraging ecology and diets of bowheads in Alaskan waters. They identified and

measured the fatty acids in samples of blubber from 28 bowheads harvested at Kaktovik (fall) and Barrow

(spring and fall); 33 samples of mixed zooplankton from the eastern Alaskan Beaufort Sea; and 32

samples of zooplankton that had been sorted into seven major prey groups (copepods, euphausiids, etc.).

This preliminary study indicates that fatty acid signature analysis could be a very useful tool in

better understanding the foraging ecology and diets of bowheads in Alaskan waters. The inferences that

can be made now are limited because of small sample sizes of whales and potential prey, and lack of data

on fatty acid profiles in individual species of prey. However, there are indications that fatty acid analyses

may show differences in diets of whales of different sexes and size classes; such differences have not

been clearly detectable from stomach contents analyses. Iverson et al. analyzed samples of mixed zooplankton from two years, and the fatty acids of the zooplankton are consistent with them being bowhead

diet items. Additionally, although there are very limited data on fatty acid patterns in potential prey, preliminary results from a QFASA (Quantitative Fatty Acid Signature Analysis) model indicate that fatty

acid patterns of the inner blubber, presumably indicative of recent diet, are consistent with general diet

data obtained from stomach contents analyses. The high fat content of these prey, especially copepods,

also suggests high dietary intakes of fat. With further and more extensive sampling and analysis, the taxonomic composition of bowhead prey could likely be better assessed using the quantitative tools now

being developed. Fatty acid signatures are expected to represent the integrated diet over weeks or possibly months, and thus over larger geographic areas, than are the stomach contents of harvested whales.

Regional and Seasonal Feeding as Indicated by Stable Isotope Ratios

This part of the work (Chapter 20) was done by Sang Heon Lee and Dr. D.M. Schell of University

of Alaska Fairbanks, with assistance from Dr. Trent McDonald of WEST Inc. δ13C and δ15N ratios in

muscle and baleen from harvested bowhead whales were used to estimate the relative amounts of food

acquired from the eastern Beaufort Sea (summer and early autumn range) versus the Bering and Chukchi

seas―the two regions previously proposed as major feeding grounds. This analysis was based on the fact

that isotope ratios in the zooplankton prey of bowheads are different in the two regions. Isotope ratios in

prey are reflected in the predators. When isotope ratios differ regionally, this provides a basis for

determining the main area(s) where the predators feed.

Samples obtained from whales harvested in autumn of 1997–99 and spring of 1986–88 were

compared. Both δ13C and δ15N values in the whales have decreased in recent years in response to a long

term decreasing trend in isotope ratios in the Bering–Chukchi food chain. The whale samples collected

~10 yr apart were normalized to allow direct comparison.

For all whales, the δ13C values in muscle sampled in fall were not significantly different from the

muscle sampled in spring. Muscle δ13C during both seasons closely matched the isotope ratios of zooplankton

from Bering and Chukchi water, indicating that most of the annual food requirement of adults and subadults is

met from that portion of their range. Isotope data from baleen showed, however, different feeding strategies

by adult and subadult whales. Subadults acquired sufficient food in the eastern Beaufort Sea to alter the

carbon isotope ratios in baleen deposited there relative to baleen representing feeding in Bering and Chukchi

water. Baleen plates from subadults showed a wider range in isotope ratios than those from adults, suggesting

active feeding by subadults over all parts of their range. A simple approximation based upon observed

seasonal shifts in muscle isotope ratios indicates that between 10 and 26 percent of the muscle carbon is
21-4 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

replaced over the summer, depending on the method of calculation. A sensitivity analysis that allowed for

variability in each factor involved in the calculation indicated that the true percentage probably did not exceed

23 %. Limited data on blubber indicates an even smaller percentage. Although these specific estimates are

subject to a variety of assumptions, the isotopic evidence indicates that only a minority of the feeding by either

subadults or (especially) adults is in the eastern Beaufort Sea.

Conclusions

At least at first glance, there seems to be an inconsistency between isotopic evidence (Chapter 20)

and other evidence concerning the importance of feeding in the eastern Beaufort Sea. The isotope record

in bowhead muscle, blubber, and baleen seems to indicate that bowheads (especially adults) feed mainly

on prey from the Bering and/or Chukchi Seas. However, behavioral, aerial-survey, and stomach-content

data show that bowheads also feed widely across the eastern and central Beaufort Sea in summer and fall.

There is certainly no doubt that bowhead whales feed on prey from the Bering/Chukchi system.

Bowheads are commonly observed to feed in the western Beaufort Sea in fall, and much of the prey

consumed there may have been advected northeastwards from the Bering/Chukchi system and be of the

Bering/Chukchi type. Bowheads also feed in the western Chukchi Sea (off Chukotka) in fall, in highly

productive waters moving north from the Bering Sea (Chapter 20). There have been no systematic observations of bowhead activities in the Bering Sea in late fall or winter, and the only stomach content data

from the Bering Sea concern bowheads harvested near St. Lawrence Island in spring. Most of those

whales have little or no food in their stomachs (Table 21.1). There is some feeding in the Chukchi Sea

during the spring migration. However, stomach-content data and behavioral data both indicate that

feeding in spring, at least near Barrow, is less frequent than feeding in the Beaufort and Chukchi seas in

summer or fall. Thus, available evidence indicates that bowheads may feed heavily in the Bering/Chukchi system in fall, but probably feed much less when in Bering/Chukchi waters during winter and spring.

Behavioral, aerial-survey, and stomach-content data show that bowheads also feed widely across

the eastern and central Beaufort Sea in summer and fall. Behavioral data show that bowheads spend most

of their time feeding while on the summer range and much of their time feeding during autumn (Chapter

12). Zooplankton sampling near bowhead whales in the Canadian and eastern Alaskan Beaufort Sea

during summer and early fall shows that feeding bowheads tend to occur at locations where the biomass

of zooplankton is considerably higher than average (Chapter 6). Most of the stomachs of bowheads

harvested in the Alaskan Beaufort Sea during late summer and fall contain food, which indicates that the

whales had been feeding shortly before being struck. Stomachs of both adult and subadult bowheads

harvested during autumn in the Alaskan Beaufort Sea usually contain food.

Behavioral and stomach content data do not directly show how much food is consumed in the

eastern Beaufort Sea as compared with the Bering/Chukchi system. One could hypothesize that bowhead

feeding in the Beaufort Sea might be frequent, as shown by behavioral and stomach-content data, but not

very efficient. Behavioral and stomach content results might be reconcilable with isotopic data if prey

availability to bowheads were notably better in Chukchi and/or Bering water than in the eastern Beaufort

Sea. This hypothesis would be consistent with the known high productivity of the Bering Sea and of

water from the Bering Sea that is transported north into the Chukchi (Chapter 20). However, if feeding in

the Beaufort Sea were not important to bowhead whales, it is difficult to understand why bowheads would

spend so much time feeding there, and why they would adapt their movements and local distribution to

prey concentrations. Indeed, it is difficult to understand why bowheads would migrate from the Bering–

Chukchi area to the Beaufort Sea if feeding in the Beaufort Sea were unimportant.
TABLE 21.1. Stomach content records from St. Lawrence Island, Bering Sea. A total of 79 records (not the originals

examined. Notes regarding the condition of the stomach were found for 17 animals. Data courtesy of North Slope BManagement, compiled by G. Sheffield of ADF&G.

ID Sex Location

Total

Length (m)

Est. Stomach

Vol. (L)

Harvest

Date St. Lawrence Island - Notes

78S1 M SAVOONGA 10.9 --- 16-Apr-78 Stomach almost empty; contained afew "euphausiid li80S2 F SAVOONGA 10.73 --- 20-Apr-80 Stomach full of blood and gas - Empty81S1 F SAVOONGA 16.8 --- 14-Apr-81 Examined; Empty81S2 F SAVOONGA 14.2 --- 21-Apr-81 Stomach contents collected in ethanol - Sample LOST90S1 F SAVOONGA 10.7 --- 7-Apr-90 Stomach empty90S2 F SAVOONGA 7.9 --- 9-Apr-90 Stomach empty; ingutuk90S3 F SAVOONGA 12.2 --- 10-Apr-90 Stomach empty92S2 F SAVOONGA 10.1 --- 18-Apr-92 Stomach empty94S1 F SAVOONGA 11 --- 22-Apr-94 Stomach empty

81G1 F GAMBELL 15.5 --- 14-Apr-81 Stomach contents collected in ethanol - Sample LOST82G2 F GAMBELL 8.8 20-40 30-Apr-82 Full stomach - Hazard and Lowry (1984)*82G1 M GAMBELL 7.92 --- 1-May-82 Stomach empty83G1 M GAMBELL 15.7 --- 17-Apr-83 Bile only85G1 F GAMBELL 9.3 --- 21-Apr-85 Stomach empty86G3 F GAMBELL 14 --- 11-Apr-86 Stomach empty90G1 F GAMBELL 9.14 --- 7-Apr-90 Stomach empty91G1 M GAMBELL 9.5 --- 17-Apr-91 Two gallons of fluid in stomach - described by residen

* Hazard, K.W. and L.F. Lowry. 1984. Benthic prey in a bowhead whale from the northern Bering Sea. Arctic 37(2):166-1

contents of whale 82G2 were principally gammarid amphipods and secondarily cumaceans.
21-6 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

Chapter 22 summarizes additional types of more direct evidence suggesting that feeding in the

Beaufort Sea does provide an important contribution to the annual energy intake of the BCB population of

bowhead whales. Measurements by J.C. George2

 (North Slope Borough Dept of Wildlife Management) of

bowheads harvested at Barrow in spring and fall, and measurements by LGL of bowhead images on aerial

photographs taken in spring and late summer/early fall, show that subadult bowheads (and perhaps adults as

well) gain weight in summer and loose weight in “winter” (Chapter 22). By “summer”, we mean from the

time they enter the Beaufort Sea in April–June until either photographed in August–September, or until they

pass Barrow when leaving the Beaufort in fall (girth data). By “winter”, we mean the reciprocal of the

above just-mentioned periods, i.e., while not in the eastern Beaufort Sea. In addition, data from T. Mau2

(UAF) indicate that the lipid content of blubber in subadult bowheads appears to be lower in spring than in

fall. Both of these types of evidence indicate that there is a net reduction in stored energy reserves over the

late-fall, winter and early-spring period, and an increase over summer.

If all of these types of evidence are accepted as reliable, then the one feeding scenario that could

(perhaps) be consistent with all the data is as follows: Feeding occurs commonly in the eastern Beaufort

Sea in summer and early autumn. Bowheads gain energy stores and their girth increases from feeding in

that area. However, zooplankton availability is not as high in the Beaufort Sea in summer as in the Chukchi Sea and northwest Bering Sea during autumn, given the much higher productivity of the Bering/Chukchi system. Also, feeding in the western Beaufort in autumn may effectively be on Chukchi prey advected into the western Beaufort. Thus, bowheads might acquire more energy from Chukchi (and Bering?)

prey in autumn than from eastern and central Beaufort prey in summer/early autumn. Given this, plus an

assumed low turnover rate of body components, their overall body composition may be dominated by

carbon (and other components) from the Bering/Chukchi system even at the end of the summer when

leaving the Beaufort. Energy gained in both the Beaufort and Chukchi seas during summer and fall

feeding is presumably used during winter when food availability is low, resulting in reduced girth and

energy stores when returning to the Beaufort in spring than when leaving the Beaufort in autumn.

The above scenario is unlikely to be fully or immediately accepted by proponents of either the

“traditional” view, i.e., that most feeding is in the Beaufort; or the isotope-based view, i.e., that most

feeding is on prey from the Bering/Chukchi system. Those who have documented the strong Bering/

Chukchi component in the isotope signatures of bowheads, even at the end of the summer, emphasize that

this can only be explained if relatively little feeding occurs in the eastern and central Beaufort Sea. Those

who have studied feeding behavior of bowheads in the Beaufort Sea, or the prey concentrations there, or

the prey in bowhead stomachs, or spring–fall changes in body composition, find it difficult to accept that

the summer and early-fall feeding in the Beaufort Sea contributes relatively little to the annual diet. Likewise, hunters and others who reside along the coast of the Beaufort Sea, and who have observed

bowheads in their areas over the years, are convinced that these areas are important to the bowheads for

feeding.

Although these groups of people have different perspectives on the probable importance of feeding

in the eastern Beaufort vs. the Bering–Chukchi waters, the feeding scenario described above is at least

generally consistent with all of the types of data and observations that they cite. We are not aware of any

other hypothesis that is not directly contradicted by some key type of data. Furthermore, the above scenario is helpful in identifying key data gaps that warrant further research (see next subsection).

 

2 Unpublished data of J.C. George and Tamara Mau are cited with their permission, and are not to be used or cited

elsewhere without their permission. Contact cgeorge@co.north-slope.ak.us; tmau@ims.uaf.edu
§21. Diet & Regional Feeding: Summary & Conclusions 21-7

The evidence concerning the importance of summer feeding is discussed further in Chapters 22 and

23. Those chapters also address the annual energetic requirements of bowhead whales, and how much of

those requirements might be met by feeding on the concentrations of prey observed in the eastern Beaufort Sea. That comparison suggests that bowheads may need to acquire a substantial proportion of their

annual diet elsewhere, consistent with the feeding scenario described above. However, many questions

about regional feeding dependencies remain open, given • the minimal data available about feeding in

areas other than the Canadian and eastern Alaskan Beaufort Sea, and • concerns about the accuracy of

present estimates of zooplankton biomass available to bowheads feeding on concentrated patches of prey.

Recommended Research

Additional data on the stomach contents of BCB bowhead whales, especially from areas where few

such data have been acquired previously, would be helpful in characterizing the frequency and intensity

of feeding in different locations and seasons, the types of prey consumed, and any long-term trends in

feeding activity. Areas and seasons where such data would be most valuable include the Chukotsk coast,

the northern Bering Sea in winter/early spring, and the west coast of Alaska in spring. Such sampling

must necessarily be done in a cooperative manner with local hunters. Wide-ranging collection of

stomach-content samples was beyond the scope of the present study (Chapter 18). However, to understand the importance of feeding in one region and season, it is important to have at least a basic understanding of the amount of feeding, and the types of prey, at other locations and seasons. Information

about prey types, during all seasons, is relevant in interpreting the stable-isotope composition of whale

tissues, and probably the fatty acid composition as well (see following recommendations). Because relatively few whales are harvested at most communities each year, and only a fraction of these provide

meaningful data on feeding, collection of stomach-content data and samples is a slow process requiring

long-term effort. Once collected, the stomach-content samples need to be analyzed and the results need to

be compiled, along with results from previous stomach-content samples.

While stomach-content samples are being obtained from harvested bowheads, tissue samples and

measurements needed for other relevant studies should also be obtained. For example, tissue samples

should be acquired for any fatty acid or stable-isotope studies that are underway or planned (see below).

Girth (vs. length) measurements should be obtained when possible.

Analyses of the fatty acid composition of bowhead blubber sampled at different geographic locations

and seasons, along with corresponding analyses of potential prey items, have the potential to provide a

different perspective on prey consumption by bowhead whales. Although fatty-acid techniques have not yet

been fully developed for use in trophic studies of bowheads, the pilot study conducted during the present

project (Chapter 19), plus related studies on other marine mammals, are promising. Data on the fatty acid

profiles of individual taxa of prey will be required in order to take full advantage of the technique. Results are

expected to provide a somewhat longer-term and geographically-broader perspective on feeding than can be

obtained from stomach-content samples. It may be possible to acquire blubber samples by biopsy methods

from free-ranging bowhead whales, thus providing the possibility of studying their diet in areas where there is

no native harvest of bowheads, and thus no access to stomach-content samples.

Stable-isotope data, principally concerning the ratio of 13C to 12C, have provided much information

about various aspects of the biology of bowhead whales, including growth rates, ages, and feeding ecology. Much of this information, when first acquired, was contrary to then-prevailing thinking, but has

been corroborated by other techniques and has come to be accepted. These stable-isotope data have been

of much value in elucidating life-history parameters and other aspects of bowhead biology.
21-8 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

Available data on stable isotope composition of bowhead muscle in spring and autumn are

important in assessing the amount of feeding in the eastern Beaufort Sea. However, the data obtained in

this study are somewhat confounded by the fact that the spring and autumn measurements generally did

not come from the same years (see Chapter 20). The complementary study by Hoekstra et al. (2002, Can.

J. Zool. 80:223-231) did obtain same-year spring vs. fall data, but there are apparent discrepancies in the

results of the two studies that are not presently explainable. It would be desirable to compare stable isotope composition of additional samples of bowhead muscle from spring and fall, collecting these samples

in the same years and processing them in strictly standardized ways. This could provide more definitive

information on carbon turnover in muscle during the period of residence in the Beaufort Sea.

During the present study, emphasis was placed on documenting the isotopic composition of muscle

and baleen. Although there are some data on stable isotope composition of bowhead blubber and visceral

fat in spring and fall, those data are limited. Additional data on the stable-isotope composition of the

blubber (and visceral fat) at various times of year would be useful in assessing seasonal turnover and the

importance of feeding in different parts of the annual range.

Presently-available isotope-based data on regional feeding dependencies of bowhead whales suggest that conventional thinking about the importance of summer feeding in baleen whales may not apply

directly to BCB bowheads. There are many questions about the nature and extent of feeding in some

areas outside the eastern Beaufort Sea, most notably the western Alaskan Beaufort Sea in autumn, the

southwestern Chukchi Sea in late autumn, and the Bering Sea in winter. To assess feeding activity in

those areas, a wide variety of study approaches could be valuable, including not only isotopic methods,

but also most or all of the other methods used in the present study.

• Western Alaskan Beaufort Sea in fall: A key question is whether feeding here is effectively on

Bering/Chukchi prey advected into the area. That could be determined from isotopes in prey.

Other types of data on prey availability, feeding behavior, residence times, etc., are also needed.

• Chukotsk coast of Russia: Data from this area are needed to evaluate the feeding scenario suggested above. A wide variety of study approaches would be again valuable, including collection

of data on prey abundance, isotopic and energy content of the prey, and energy gain by bowheads

during feeding in the area. Although it is not likely that many tissue samples from harvested

whales will be available from this area in late fall, any such samples would be very useful for

analyses of isotopic, fatty acid, and energy content. Bowhead girth vs. length measurements

would also be valuable, either from direct measurements of harvested whales or (perhaps more

practical) via photogrammetry. Data showing whether girth of bowheads increases appreciably

while they feed off the Chukotsk Peninsula during late fall would very relevant in assessing the

importance of that area vs. other areas for feeding.

• Northern Bering Sea in early spring: Data on stable isotope (and potentially fatty acid) composition of tissue from bowheads harvested here would allow assessment of nutritional status at the

end of the winter. Girth and other measures of energy stores would also be very useful. The

annual feeding scenario summarized in the preceding section assumes that bowheads utilize

stored energy for much of the winter. In understanding overall annual energy balance, it would

be important to have data on condition of bowheads at the end of the winter.

The “Discussion” section of Chapter 20 identifies additional types of isotope analyses that might be

helpful in understanding various finer-scale questions about the locations and timing of feeding, and the

predominant sources of nutrition for bowhead whales of the Bering–Chukchi–Beaufort stock.
22. ENERGETICS OF BOWHEAD WHALES

Denis H. Thomson 1

Introduction

An estimate of the importance of the eastern Alaskan Beaufort Sea to feeding bowheads requires

that their daily and annual food requirements be estimated and then used to determine what proportion of

their annual requirements could be obtained in the study area. Large whales cannot be kept in captivity,

so direct measurements of their energetic requirements cannot be made. Researchers have used several

different approaches to estimate energetic requirements of large whales. These include heat loss (Folkow

and Blix 1992), respiration (Blix and Folkow 1995), and comparing theoretical metabolic rates with those

extrapolated from small animals (Lavigne et al. 1986).

Thomson and Martin (1984) and Thomson (1987) estimated the theoretical energetic requirements

of gray and bowhead whales and compared these to observed feeding rates in nature. This is the approach

that is used here. This chapter updates the earlier estimates with recent information about, or relevant to,

the energetics of bowhead whales and other species.

This chapter first describes the size, growth, and reproduction of bowhead whales and the related

physical attributes needed for the estimation of energetic requirements. This is followed by a description

and discussion of several approaches to the estimation of the metabolic rate of bowheads. These are compared to estimates of the amount of food consumed by bowhead whales as determined through observations of behavior, swimming speed, and amount of food found near feeding whales. There are numerous

data gaps and there is much variability (year-to-year and otherwise) in the data. Sensitivity analysis

techniques have been used to assess the effects of this uncertainty and variability on estimates of the

dietary contribution of food from the eastern Alaskan Beaufort Sea. Results of the sensitivity analysis are

included in Chapter 23, “Integration and Conclusions”.

Size and Other Physical Attributes of Bowhead Whales

Energetic calculations require some basic information about the size and composition of the

animals, growth rates, details of the reproductive cycle, and the annual cycle of weight gain and loss, if

any.

Scoresby (1820) believed that the largest bowhead whale that he personally saw was 18.3 m in

length, and that a whale of 19.8 m in length was rarely encountered. The largest he actually measured

was 17.7 m long. As of spring 2001, the lengths of 3854 whales of the Bering–Chukchi–Beaufort (BCB)

population had been measured by calibrated photogrammetric methods applied to aerial photographs

taken by LGL and the National Marine Mammal Laboratory. Only 9 of these measured whales were

17 m or more in length. The largest was 17.7 m in length.

 

1

 LGL Ltd., environmental research associates, 22 Fisher St., POB 280, King City, Ont. L7B 1A6.

Phone: 905-833-1244. E-mail: dthomson@lgl.com
22-2 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

Length and Weight

Weights and lengths of bowheads were estimated using measurements made from known-scale aerial

photographs. Twenty six vertical photographs of 24 different whales, as photographed in August and September 1981–86 by Davis et al. (1982, 1983, 1986a,b), Richardson et al. (1987) and the present study

(Chapter 10), showed good definition of both sides of the whale as well as its length. Techniques used to

measure lengths of whales are described in Koski et al. (1992) and Chapter 10. Whales were assumed to be

circular in cross section and were divided into five truncated cones. Photographs showed that the head is

somewhat conical in shape (Fig. 22.1). It was assumed to be conical from the blowhole to the snout. The

length of each segment, its diameter at each end, and total length of the whale image were measured from

photographic prints or scanned images. These measurements were compared to total whale length (in m) as

determined photogrammetrically in order to obtain actual measurements of the “segments” in meters. As a

check on accuracy, fluke width was estimated from the prints by the same method, and compared to previous

photogrammetric measurements of the same parameter. The error in our measurements from prints as

compared to earlier photogrammetric results was 1.03 % ± s.d. 1.49 %. This imprecision is additional to

inherent uncertainty in the photographic technique, which was ~2 % (Koski et al. 1992). The lengths and

maximum girths of an additional 13 whales photographed in August and September of 1982–2000 and 27

photographed in late April and May 1986–92 were measured from photographs.

The maximum girth–length relationship as measured on photographs was compared to the maximum

girth–length relationship measured from 11 whales harvested in Kaktovik in fall 1997 through 2000 and

measured by Lowry and Sheffield (Chapter 18). Ingutuks, which are short, fat and possibly recently-weaned

whales, were not included. J.C. George (pers. comm.2

) measured lengths of whales in the water and after

being hauled up onto land and found that they stretched an average of 8.2 % in the process. The measured

lengths of the whales harvested at Kaktovik were adjusted downward to allow for this stretching. Scatter plots

of the data and fitted regression lines showed that a simple linear relationship best described these data.

Analysis of covariance showed that slopes of girth–length regression lines based on photographs

and measured whales were similar (ANCOVA F = 1.9, P = 0.17, df = 1,44), as were adjusted mean group

maximum girths (ANCOVA F = 0.073, P = 0.79, df = 1,45). Thus maximum girths and, presumably, the

other diameters measured from photographs appear to be an accurate representation of actual dimensions.

The weights of the 24 bowheads measured on photographs were estimated by summing the calculated volumes of the truncated cones. Density was assumed to be 1 kg/L, i.e., similar to water. Weights

were expressed in metric tonnes (MT), which equal 1000 kg.

Length–weight relationships of photographed whales as estimated with the volumetric method

were compared with those of five sub-adults harvested in fall (lengths 7.5–12.9 m) whose weights were

measured directly by George et al. (1990, 1992). The lengths of the five measured and weighed subadults

were adjusted for stretching. All weights were plotted against whale length and curves were fitted by

regression. Analysis of scatter plots and residuals indicated, as expected, that power curves (weight = a ×

lengthb

) best described the length–weight relationship.

 

2

 Data provided by Craig George from a work in progress are not to be cited without written permission of Craig

George, Department of Wildlife Management, North Slope Borough, Barrow, AK. cgeorge@co.north-slope.ak.us
§ 22. Energetics of Bowhead Whales 22-3

FIGURE 22.1. Photograph of a bowhead whale on its side.

The regression equations for whale length vs. actual measured weight of 5 harvested subadults and

length vs. weight as calculated by the volumetric method were not significantly different. The slopes

were similar (ANCOVA F = 0.06, P = 0.80, df 1,25) and the difference in adjusted group weight was not

significant (ANCOVA F = 0.09, P = 0.77, df = 1,26). Thus, the two datasets were merged (Fig. 22.2).

The length–weight relationship of all 29 whales in fall was best described by the equation

(1) Weight (MT) = 0.047 × Whale Length (m)2.58; r = 0.98, P < 0.001

For a given length, bowheads weigh about the same as North Pacific right whales and humpback

whales (cf. Lockyer 1976; Fig. 22.3). However, different techniques were used to estimate the length–

weight relationships of the different species, so caution is necessary in interpreting these results. For a

given length, bowheads are much heavier than fin, blue or sei whales (Fig. 22.3).

Lockyer estimated that the bone weight of North Pacific right whales is 13 % of body weight, and

that the weight of viscera is also 13 % of body weight. We assume that these values apply to bowheads.

Quantity of Blubber

The bowhead whale has the thickest blubber of any cetacean (George et al. 1999). Thus, much of

the weight of the animals, in a metabolic sense, is relatively inert. From 1997 to 2000, inclusive, standard

measurement were made by ADF&G personnel of 13 whales landed during the subsistence hunt at

Kaktovik in September (Chapter 18); measurement procedures followed those of the North Slope

Borough Dept of Wildlife Management. Blubber thickness as used here is the average of dorsal

measurement made 1 m behind the blowhole and ventral measurement between the flippers. There was a

significant linear relationship between length and blubber thickness for the 13 whales landed at Kaktovik

in 1997–2000:

(2) Blubber Thickness (m) = 0.085 + 0.014 × Whale length (m); r = 0.79; P = 0.003
22-4 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

FIGURE 22.2. Length–weight relationship of bowhead whales derived through the estimation of volumes

of photographed whales and actual weights of whales recorded by George et al. (1990, 1992). The solid

curved line is the fitted least-squares regression based on the natural logs of weight and length.

The blubber thickness for each photographed whale was estimated using the above equation and

subtracted from the overall body dimensions described above to estimate the weight of the core and head

minus the blubber. The weight of the blubber was estimated by subtracting the weight of the core plus

head minus blubber from the total weight. For the 24 photographed whales, weight of blubber in MT

estimated in this manner was related to body length in m as follows:

(3) Blubber (MT) = 0.027 × Length (m)2.403; r = 0.99, P < 0.001

Weight of blubber was also estimated from data collected by the whaling ships Cumbrian in 1823

and Arctic in 1873 as reported in Lubbock (1937):

• Data collected by Markham (1874, in Lubbock 1937) during a cruise of the Arctic in 1873 contained

measurements of maximum baleen length and yield of oil for 28 bowhead whales. Whale length was

not measured. After 1870, 1 ton of whale oil was composed of 20 hundredweight, i.e., 20 × 112

pounds or 2240 pounds (Lubbock 1937), = 1016 kg. Prior to that, 1 ton was 877.1 kg (Scoresby

1820; Lindquist 1992). Oil was converted to blubber using Scoresby’s (1820) estimate that 4 tons of

blubber yielded three tons of oil.

0

10

20

30

40

50

60

5 7 9 11 13 15

Length (m)

Weight (MT)

Volumetric Method

Actual Weights

Predicted Weight
§ 22. Energetics of Bowhead Whales 22-5

FIGURE 22.3. Length–weight relationship for bowhead whales, from equation (1), compared to relationships for other species of whale, from Lockyer (1976). The lines are fitted least-squares regressions

based on the natural logs of weight and length.

• In 1823, the Cumbrian collected data on maximum baleen length and whale length for 23 whales.

Alaska Department of Fish and Game collected similar data at Kaktovik (n = 13 whales) from 1997

to 2000, as an adjunct to the work described in Chapter 18. There were only marginal differences in

the relationship between natural log of body length (in m) and maximum baleen length (in m) for data

collected by the Cumbrian vs. ADF&G. The slopes were similar (ANCOVA F = 2.8, df 1,32, P =

0.10) and adjusted group mean baleen lengths of 2.32 m for the ADF&G data and 2.47 m for the

Cumbrian data were only marginally different (ANCOVA F = 3.5, df = 1,33, P = 0.07). The data

from these 36 whales, plus 2 measurements in Scammon (1874), were merged to estimate body length

from maximum baleen length for a greater range of whale lengths than would have been available for

any one data set:

(4) loge Whale Length (m) = 1.609 + 0.355 × Max. Baleen Length (m); r = 0.97, P < 0.001

Equation (4) was used to substitute whale length for maximum baleen length in the Arctic data (n = 28).

The relationship between whale length in m and weight of blubber in MT was best explained by the equation

(5) Blubber (MT) = 0.052 × Length (m)2.186; r = 0.95, P < 0.001

0

10

20

30

40

50

60

70

80

90

100

5 10 15 20 25

Length (m)

Weight (MT)

Bowhead

Pac.Right

Humpback

Fin

Blue

Sei

Gray
22-6 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

The slope of the length to blubber weight relationship derived from the volumetric method

(equation 3) was not significantly different from that derived using the old whaling data (equation 5) (F =

0.13, df = 1,47, P = 0.43). However, on average, whales collected by the Arctic had 0.9 MT more

blubber than those for which blubber mass was estimated by the volumetric method (adjusted group

means F = 5, df = 1,48, P = 0.3). Data collected by Scoresby (1820) on average oil yield for whales with

12 equally-spaced baleen lengths, from shortest to longest, were converted to whale length and blubber

weight as shown above. However, the slope of the whale length to blubber weight relationship derived

from the volumetric method (equation 3) was significantly different from that derived from Scoresby's

data (F = 11.7 df = 1,32, P = 0.002). For whales > 9 m in length, blubber content of whales taken by

Scoresby was lower than for whales taken by the Arctic or estimated using the volumetric method (Fig.

22.4). One reason for the higher weights found in the Arctic data is that whalers extracted oil from the

bones and other body parts. 

Blubber weights for two whales measured by George et al. (1987) are also plotted on Figure 22.4.

Those weights are similar to those derived from the data of Scoresby for whales of comparable length.

Blubber weights predicted by the volumetric method were intermediate between the other estimates. The

blubber thickness from the volumetric method appears to be a good approximation of average blubber

thickness of the core of the body.

FIGURE 22.4. Weight of blubber vs. whale length, based on old whaling records (Scoresby 1820; Lubbock

1937), the volumetric method applied to aerial photographs, and actual weights from George et al.

(1987). Curved lines are fitted least-squares regressions of natural logs of blubber weight and length.

0

5

10

15

20

25

30

5 7 9 11 13 15 17

Whale Length (m)

Blubber (MT)

Data from 'Arctic' in Lubbock (1937)

George et al. 1987

Scoresby (1820)

Predicted - Scoresby Data

Predicted -' Arctic' data

Predicted - photograph data
§ 22. Energetics of Bowhead Whales 22-7

The length–weight and length–blubber weight equations (equations 1 and 5) predict that a 9 m subadult

whale will contain ~39 % blubber by weight, and that a 13.5 m adult will contain ~37 % blubber. This is

about the same as found in the North Pacific right whale and higher than in any other species of whale

(Lockyer 1976).

Surface Area

The metabolically active surface area is the surface area of muscle (Brodie 1981). The region posterior to the blowhole was taken to be the body core. Its volume was calculated from aerial photographs,

considering the diameters of the truncated cones posterior to the blowhole minus the blubber thickness.

Surface area was calculated in a corresponding way. The truncated cones were also used to calculate total

surface area of the animal. The weight of muscle and viscera was calculated assuming a density of 1

kg/L. Analysis of scatter plots of the data and residuals showed that power curves of the form y = aXb

best fit the relationship between each of whale surface area, fluke surface area, and the weight of the

metabolically active core vs. whale length (Table 22.1).

TABLE 22.1. Relationship between whale length and whale surface area, weight of

the metabolic core, and other parameters. Curves of the form Y = a · length (m)b

were fitted by regression analysis.

Parameter/ units a b R P

Total surface area m2 0.54 1.85 0.99 < 0.001

Weight of metabolic core MT 0.03 2.53 0.97 < 0.001

Fluke area m2 0.012 1.94 0.92 < 0.001

Surface area of metabolic core m2 0.49 1.70 0.97 < 0.001

Growth and Reproduction

Growth in the first five years may be very slow and is quite variable (Schell et al. 1989; Koski et al.

1993; George et al. 1999). After this time, bowheads grow slowly (Koski et al 1993; George et al. 1999).

Based on aerial photographic measurements of lengths of females with calves, Koski et al. (1993) estimated

that most females become sexually mature at a length of 13 to 13.5 m. Koski et al. estimated that most males

mature at a length of 12–13 m. [See also O’Hara et al. (2002).] There are seasonal variations in isotopic

content of baleen plates that can be used to age young animals (Schell et al. 1989). Schell et al. (1989) and

Schell and Saupe (1993) estimated that bowheads mature at an age of 17 to 20 years. Koski et al. (1993) used

lengths of whales re-identified from aerial photographs to estimate growth rates as a function of length. They

estimated that bowhead females that matured at 13 m were in their late teens to early twenties. They estimated

that males grew more slowly and that males and females combined reached 13 m at an age of 22 to 31 years,

and most likely at the upper end of that range. Recently, aspartic acid racemization analysis of bowhead eye

globes has confirmed a very slow growth rate (George et al. 1999). They estimate that sexual maturity is

reached when bowheads are in their mid-twenties. It will be assumed that male bowheads mature at age 25

when they are 12.5 m in length and weigh 31 MT, and that females mature at age 27 when they are 13.5 m in

length and weigh 38 MT.

The growth equation presented in George et al. (1999) was combined with the length–weight

equation (1) to estimate weights and annual weight gain for whales of various ages and lengths (Table

22.2). When just mature, bowheads gain about 0.7 to 0.8 MT per year. Older animals gain much less.
22-8 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

TABLE 22.2. Estimated annual weight gain for bowhead whales of various ages

estimated from the age–length equations developed by George et al. (1999) and the

length–weight relationship shown in equation (1).

Male Female

Age

(yr)

Length

(m)

Weight

(MT)

Annual Gain

(MT)

Length (m) Weight

(MT)

Annual Gain

(MT)

3 8.9 13.1 0.9 9.4 15.3 1.0

6 9.5 15.7 0.9 10.1 18.3 1.0

9 10.1 18.3 0.9 10.8 21.4 1.0

12 10.7 21.0 0.9 11.3 24.5 1.0

15 11.2 23.5 0.8 11.9 27.5 1.0

20 11.9 27.6 0.8 12.6 32.3 0.9

25 12.5 31.4 0.7 13.3 36.7 0.9

27 12.7 32.9 0.7 13.5 38.4 0.8

35 13.5 38.1 0.6 14.3 44.5 0.7

49 14.4 45.2 0.4 15.3 52.8 0.5

50 14.4 45.6 0.4 15.3 53.3 0.5

75 15.3 53.1 0.2 16.3 62.1 0.2

The total energetic cost of gestation is equivalent to about twice the basal metabolic rate of the

foetus as predicted from Kleiber's equation (Lavigne et al. 1982). Assuming a 13.5 month gestation

period (Tarpley and Stott 1994) and a birth weight of 1000 kg for a bowhead, total metabolizable cost of

pregnancy would be about 220 x 105

 kJ. Not included is the calorific value of the foetus itself, about 136

x 105

 kJ at birth.

 Most calves are born in April, May and early June (Koski et al. 1993). At birth calves may be

about 3.6 to >4.5 m in length, with most being >4.0 m (Koski et al. 1993). A 4 m calf would weight

1 MT (George et al. 1992). An average calf that was 4.75 to 5 m in length in late May would be 6.25 to

6.5 m long in late summer (Koski et al. 1993). Yearlings may be 7 to 8.7 m in length (Koski et al. 1993).

Calves are weaned at about 12 months and a length of 6.6 to 8.2 m. An estimate of 7.2 m will be used

here. At weaning, whales are short and fat. Three of five sub-adults harvested in fall (lengths 7.5–12.9

m) whose weights were measured directly by George et al. (1990, 1992) were 2 to 3 MT heavier than

their predicted weight. At an average length at weaning of 7.2 m, the length–weight equation (1) predicts

a weight of 8 MT. If a newly weaned whale is 2 MT heavier than predicted, then it would weight 10 MT

at weaning and would have gained 9 MT during one year of lactation. Mature females may produce a

calf every 3 to 4 years (reviewed in Koski et al. 1993). For this analysis, the metabolic cost of pregnancy

and lactation is averaged over 4 years.

Assimilation efficiency for milk is about 90 % and cetacean milk contains about 18,000 kJ/kg

(4300 kcal/kg) wet weight (Lockyer 1981; Gaskin 1982). Sei and fin whale muscle has an energetic

value of about 6300 to 10,900 (mean 7950) kJ/kg wet weight (Lockyer et al. 1985). Blubber is about

80 % oil and wax with a mean energetic content of 22,190 kJ/kg wet weight (Lockyer et al. 1985).

Neonates would require 1365 x 105

 kJ for growth and 810 x 105 kJ for metabolism. This is based on their

daily basal metabolic rate in relation to their weight on that day, x1.5 to allow for the extra energy

required over and above BMR, and summed for the year. About 12 MT of milk would be required.
§ 22. Energetics of Bowhead Whales 22-9

Weight Gain During Summer/Loss During Fall–Winter

Photographic Data.—Measurements of aerial photographs of bowheads showed weight gain in

summer and net weight loss over the fall–winter. The lengths and girths were measured from photographs

taken in April, May and June during spring migration near Barrow, Alaska (27 bowheads), and in August and

September in the Beaufort Sea (37 whales). Linear equations provided the best fit to the length–girth data.

The regression equations of length vs. girth for whales photographed in spring and fall were compared with

analysis of covariance. The slopes of the regression equations were not significantly different (ANCOVA F =

0.093, df = 1,60, P < 0.8). Whales photographed in spring were significantly thinner than animals

photographed in fall (ANCOVA, F = 7.7, df = 1,61, P = 0.007; Fig. 22.5). J.C. George (pers. comm.3

) has

derived an equation relating actual measured weight of bowheads to length and girth: Weight (kg) = 38.28 ×

Girth (m)2 × length (m). The regression parameters and estimated weights of whales in spring and fall are

shown in Table 22.3. Because the equation relating length and girth to weight was based on stretched

animals, the lengths in Table 22.3 were adjusted for 8.2 % stretching. The equations predict that a 9 m whale

would gain about 2 MT over the summer, a 12.5 m whale would gain about 3 MT, and a 16 m whale would

gain about 4 MT.

5

6

7

8

9

10

11

7 9 11 13 15

Length (m)

Girth (m)

Spring

Fall

Spring Predicted

Fall Predicted

FIGURE 22.5. Maximum girth as a function of length as estimated from aerial photographs of bowhead

whales in spring (near Barrow, AK) and in late summer/early fall (Beaufort Sea). The lines are the fitted

least-squares linear regressions of girth vs. length for the two seasons.

 

3

 Data provided by Craig George from a work in progress are not to be cited without written permission of Craig

George, Department of Wildlife Management, North Slope Borough, Barrow, AK. cgeorge@co.north-slope.ak.us
22-10 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

TABLE 22.3. Regression parameters for the linear equations of the form girth (m) = a + b x length (m) for

bowhead whales photographed in spring (near Barrow, AK) and in late summer/early fall (Beaufort Sea).

Also shown are the adjusted group mean girths and the estimated weights, during spring and late

summer/early fall, of animals of four specific lengths adjusted for 8 % stretching.

Regression Parameters Weight (MT) vs. Length/Adj. Length (m)

Season a B r P Mean Girth 11/11.9 m 12.5/13.5 13.5/14.6 14.5/15.7

Spring -0.292 0.695 0.96 < 0.001 8.338 24.64 36.50 46.22 57.52

Early Fall 0.253 0.678 0.95 <0.001 8.672 27.10 39.45 49.48 61.09

Difference 0.334 2.46 2.95 3.26 3.56

Note that the August–September measurements were obtained before the period of feeding that occurs

in fall in the western Beaufort Sea and Chukchi Sea. It is suspected that this autumn feeding is in areas where

the zooplankton is abundant and energy-rich (see Chapter 20, 21, 23). Thus, there is probably additional gain

in girth and weight subsequent to the dates when the late summer/early fall photographs were taken. If so, the

reduction in girth and weight during winter must be larger than shown by the measurements in Figure 22.5.

Other Data.—J.C. George (pers. comm.4

) measured girths and lengths of whales harvested at Barrow.

He found that subadult bowheads had larger girths in fall than in spring, but he found little seasonal

difference in the girths of large adults. In contrast, the photographic data indicate that the seasonal difference

is evident in adults as well as subadults (Fig. 22.5). The discrepancy between the results obtained from

photographs and those of whales measured by George could be an artifact of stretching. Whales were

measured after being hauled up onto the ice or shore. George has shown that the animals are stretched when

this occurs. In spring, whales are hauled up onto the ice whereas in fall they are hauled up onto the beach;

there could be a difference in the amount of stretching in spring vs. fall. In any event, at least for subadults,

direct measurements of girth vs. length in spring and fall are consistent with the photographic data in

showing that the whales gain girth (and thus weight) while in the Beaufort Sea.

In addition to the seasonal change in girth, with animals being thinner in spring than in fall, there is

evidence that some lipid is lost from the blubber during winter. Lipid content in the blubber of subadults

harvested in fall was about 80 % (T. Mau, pers. comm.5

). In spring, lipid content of the inner 20 % of the

blubber in subadults was about 70 %; lipid content in the next 20 % of the blubber was less than 80 % but

not as low as 70 %. Lipid content in the outer 60 % of the blubber layer was unchanged from fall. An 11

m subadult bowhead contains about 9.8 MT of blubber. Based on the data of T. Mau quoted above,

seasonal loss of lipid would amount to about 0.3 MT. It appears that only subadults lose this percentage

of lipid over the winter (Chapter 20).

Inupiat on the North Slope have noticed these seasonal changes. Hunters have told us that

bowheads caught in spring and fall taste different. Also, Vincent Nageak stated that "When the whales

come this way from the east they don’t travel fast, they often become fatter and their meat is even

 

4

 Data provided by C. George from a work in progress are not to be cited without written permission of Craig

George, Department of Wildlife Management, North Slope Borough, Barrow, AK. cgeorge@co.north-slope.ak.us

5

 Data provided by T. Mau, from a work in progress, are not to be cited without written permission of Tamara Mau,

University of Alaska Fairbanks, Institute of Marine Science, 245 O'Neill Bldg., Fairbanks, AK 99775-7220.

tmau@ims.uaf.edu
§ 22. Energetics of Bowhead Whales 22-11

different." (Chapter 2; Kisautaq 1981:296). In fall, blubber appears to be dripping with fat and this is

different from the condition of the blubber in spring (J.C. George, pers. comm.6

).

As discussed elsewhere in this report, it is difficult to reconcile these and other data indicative of

feeding and weight gain during summer in the eastern and central Beaufort Sea with stable isotope data

indicating that bowheads derive most of their food from Bering/Chukchi water (Chapter 20).7

 However,

one scenario has been suggested (see Chapters 20, 21, 23) that could be at least generally consistent with

all data. This scenario acknowledges that bowheads feed and gain weight both in the Beaufort Sea in

summer and (more intensively) in Bering/Chukchi waters in autumn. (Feeding in the western Beaufort in

autumn may effectively be in Bering/Chukchi waters.) Under this scenario, weight gain must be assumed

to be greater in the highly productive Bering/Chukchi waters in autumn than in the less productive eastern

and central Beaufort Sea in summer/early autumn. This assumption is necessary to account for the predominantly Bering/Chukchi isotope signature in bowhead tissue, as documented by Lee and Schell

(Chapter 20; cf. Hoekstra et al. 2002). Aside from the isotope data, there are no other specific data on

weight gain in the Chukchi in autumn—a significant data gap. Under this scenario, bowheads are

assumed to subsist mainly on stored energy over winter and early spring, to the point that they are leaner

when returning to the Beaufort Sea in spring than when they moved from the Beaufort Sea into the

Chukchi Sea in fall.

Theoretical Energetic Requirements

The theoretical energetic requirements of bowhead whales were estimated based on the estimated

basal metabolism, cost of swimming, heat loss, and respiration. These estimates were compared to one

another and with an estimate of feeding rates in nature.

Time Budgets

During spring migration, bowheads socialize, rest and feed as well as migrate (Carroll and

Smithhisler 1980; Rugh and Cubbage 1980; Carroll et al. 1987; Richardson et al. 1995a). Feeding was

not common in the area northeast of Barrow during spring migration in 1989–91 and 1994; whales spent

only an estimated 1 % of their time feeding (Table 22.4), based on Richardson et al. (1995a) and Chapter

12. However, feeding was commonly seen southwest of Barrow during the 1978 and 1985 spring migrations (Carroll and Smithhisler 1980; Carroll et al. 1987). It is possible that, in spring, feeding is more

common in Chukchi waters near and southwest of Barrow than in Beaufort waters northeast of Barrow

(where the 1 % figure was obtained). Stomach content data from bowheads harvested at Barrow in spring

indicate that they feed less in spring than in fall. None of the 100 bowhead stomachs examined in spring

at Barrow were full, whereas about 27 of 106 stomachs examined at Barrow in fall may have been full

(Appendices 18.4, 18.5). About 33 % of the bowheads landed at Barrow in spring were classified as

 

6

 Data provided by C. George from a work in progress are not to be cited without written permission of Craig

George, Department of Wildlife Management, North Slope Borough, Barrow, AK. cgeorge@co.north-slope.ak.us

7

 The independent isotope data of Hoekstra et al. (2002) suggest that that feeding in the eastern and central Beaufort

Sea vs. Bering/Chukchi waters may be about equally important. However, as discussed in Chapter 20, additional

investigation is needed to resolve the reasons for differences between the data of Hoekstra et al. (2002) and those of

Lee and Schell (Chapter 20).
22-12 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

TABLE 22.4. Observed or assumed proportion of time when bowhead whales are

engaged in various activities during different seasons.

Observed or Assumed Percent of Time

Activity Springa Summerb

Fall

Beaufortb

Fall

Chukchic Winterd

Travel 75 7 31 7 7

Feed 8 73 47 73 0

Social 7 15 17 15 0

Other/Unknown 10 5 5 5 93

No. of Obs. Sessions (54) (85) (80)

a

 From field observations summarized in Chapter 12, but with % time feeding adjusted upward (from

observed 1 %) based on a speculative assessment of the frequency and quantity of food in stomachs of

hales harvested in spring off Barrow vs. fall off Kaktovik (see text).

b

 From field observations summarized in Chapter 12.

c

 Includes Bering Strait; activities in fall in the Chukchi Sea and Bering Strait area are assumed similar to

those in summer in the eastern Beaufort.

d

 No data for winter; assumed to be negligible feeding and same amount of travelling as during summer.

feeding, with an average quantity of ~14 L for the 17 whales where quantity could be estimated (Lowry

and Sheffield, Chapter 18 Appendix 18.5). In contrast, of the whales landed at Kaktovik in fall, 83 % were

classified as feeding, and average content was 34 L for the 18 whales where quantity could be estimated

(Appendix 18.3). The percent of time spent feeding in the latter area in fall was 47 % (Chapter 12). An

alternative estimate of the percentage of time spent feeding in spring was obtained by applying the percentage

of stomachs with food in spring at Barrow vs. fall at Kaktovik (33 % / 83 %) and their average contents in

spring vs. fall (14 L / 34 L) to the percent of time spent feeding in the Kaktovik area in fall (47 %, from

Chapter 12). The time spent feeding in spring estimated in this speculative manner was 8 %, as compared

with the 1 % estimate based on direct observation northeast of Barrow.

Bowhead whales summering in the Canadian Beaufort Sea were observed to be feeding 71 % of the

time, based on data of Würsig et al. (1985, 1989) and Dorsey et al. (1989) as re-examined in Chapter 12

(Table 22.4). Results of photoidentification and satellite-linked tagging studies show that there can also be

much local movement of bowheads in late summer while in the Canadian Beaufort Sea (Koski et al. 1988;

Mate et al. 2000). During summer, bowheads of the Hudson Bay stock spend about 74 % of their time

feeding (Thomas 1999), consistent with the results from BCB bowheads in the Canadian Beaufort Sea.

Fall migrants appear to spend a considerable proportion of their time feeding while in the eastern Alaskan

Beaufort Sea (Table 22.4, based on Chapter 12). Of 29 whales landed at Kaktovik in fall whose feeding status

could be classified, 83 % had been feeding shortly before being struck (Chapter 18). Migrating bowheads also

feed at least occasionally in the central Alaskan Beaufort, and sometimes feed heavily in the western Beaufort

east of Barrow. Four of five bowheads landed at Cross Island and 77 of 103 bowheads landed at Barrow in late

summer and fall had been feeding shortly before being struck (Lowry and Sheffield, Chapter 18).

There have been no systematic observations of bowhead whale behavior in winter. Chapter 20

indicates, via indirect evidence, that BCB bowheads feed mainly during autumn and/or winter while in

Bering/Chukchi waters. [Hoekstra et al. (2002) suggest, also based on isotopic data, that both the

Beaufort Sea and Bering/Chukchi Sea are important feeding grounds. Further investigation is needed to

resolve differences in some of the isotopic data.] The isotopic methods used in Chapter 20 and by

Hoekstra et al. cannot distinguish feeding in the Bering Sea from that in the Chukchi Sea. Bowhead
§ 22. Energetics of Bowhead Whales 22-13

whales appear to lose weight during winter, i.e., from the time they depart the Beaufort Sea in fall until

the time they return in spring. Thus, most food that bears a Bering/Chukchi isotopic signature probably is

consumed in the Chukchi Sea, and to some extent the western Beaufort Sea or northwest Bering Sea, in

fall. Time spent feeding in winter is assumed to be zero. It is assumed that, as in summer, wintering

bowheads spent ~7 % of their time traveling, and the remainder of their time doing unknown activities.

Primary and secondary productivity in the Chukchi Sea may be highest in the southern and southwestern part (Truett 1984). Abundance of zooplankton in the SE Chukchi Sea is higher south of Cape Lisburne

than north of it (Wing 1974). There is a very high biomass of zooplankton in the southern Chukchi Sea.

Average summer zooplankton biomass in 145 vertical zooplankton tows taken in the SE Chukchi Sea between

Cape Lisburne and the Bering Strait was about 1700 mg/m3

 (English 1966). By comparison, average biomass

in vertical tows in the eastern Alaskan and Canadian parts of the Beaufort Sea is about 230 mg/m3

(Chapter 6). Bowhead whales are known to feed in the SW Chukchi Sea during autumn (Moore et al. 1995).

In October 1993, they saw 11 bowheads feeding in a 5 m × 8 km patch of euphausiids located at depths of 25

to 30 m. The high productivity of invertebrates in the SW Chukchi Sea may be the result of advection of

organic carbon and zooplankton from the Bering Strait and Bering Sea (Springer et al. 1984). Zooplankton

biomass in the Bering Strait and coastal waters to the south and west are very high—higher than those in the

central Bering Sea (Coyle et al. 1996). Biomass may remain high there until early November, which is the

end of “biological fall” in the Bering Sea. Intensive feeding may continue into November as bowheads move

into the northern Bering.

Thus, the autumn can be divided into two periods: (1) migration across the Alaskan North Slope,

including some feeding, and (2) feeding in the Chukchi Sea and (presumably) coastal waters of the Bering

Strait area. Autumn feeding in the western Beaufort Sea, just east of Barrow, is probably of a transitional

type, in terms of both the likely zooplankton biomasses (probably higher than in eastern Beaufort but lower

than in the SW Chukchi) and the probable isotopic signature of the prey. Average residence time in the area

from Herschel Island to Flaxman Island was 5.1 d (Chapter 11). That area is 270 km in width. Net westward

speed would thus average 2.2 km/h (270 km in 122 h). Whales spend 47 % of their time feeding while in that

study area. If the whales maintain this speed, they would arrive the southern and western Chukchi Sea in

another 19.4 d. Total migration time across all of the Alaskan Beaufort Sea and part of the Chukchi Sea

would be ~24.6 d. This would leave ~52 d to feed in the zooplankton-rich southern and western Chukchi Sea,

the Bering Strait, and areas immediately to the south. It will be assumed that whales spend the same

proportion of time feeding (73 %) when in these areas as observed in the Canadian Beaufort Sea in summer.

Respiration Method

Energy requirements can be estimated by calculating oxygen consumption of the animals (Sumich

1983; Folkow and Blix 1992). Estimates of oxygen consumption are based on the observed breathing

rate for various activities, the percentage of time spent doing the activities, and estimates of the size of the

lungs, tidal volume, and oxygen utilization.

Blow Rates.—Observed blow rates, along with some assumptions and approximations, can be used

to estimate the total number of blows in a year by various categories of whales. In the southeastern Beaufort Sea in summer, mean blow rate for all non-calves (all activities combined) was 0.77 blows/min

(Table 22.5). Overall, blow rate is lower for feeding, migrating and traveling whales than for socializing

whales. Blow rates for feeding, socializing, and traveling whales for each season (from Table 22.5) were

scaled using blow rates by size category and activity based on data in Table 22.6. The blow rates based
22-14 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

TABLE 22.5. Respiration rates of undisturbed bowhead whales in various areas under various circumstances.

Blows/Surfacing At Surface (min) Minutes Diving

Location/ Activity Mean ± s.d. n Mean ± s.d. n Mean ± s.d. n

Blows/

Min Reference

Spring Migration

Barrow Area

Traveling 6.5 2.8 41 1.5 - 31 15.6 5.0 63 0.38 Carroll and Smithhisler 1980

Traveling 6.5 2.6 78 1.6 0.5 19 11.7 5.3 156 0.49 Carroll et al. 1987

Traveling 7.4 3.0 184 1.3 0.6 184 9.9 5.2 41 0.66 Zeh et al. 1993

Traveling* 5.0 3.3 355 1.4 1.0 367 6.6 6.3 244 0.63 Chapter 13

Traveling + socializing* 4.8 3.6 70 1.0 1.0 80 3.2 3.6 38 1.14 Richardson et al. 1995a

Feeding* 12.6 2.2 37 2.3 0.6 39 14.7 6.5 16 0.74 Carroll et al. 1987

Summer

Canadian Beaufort Sea

All non-calves, all

activities

4.3 3.3 626 1.2 1.1 715 4.4 6.3 333 0.77 Dorsey et al. 1989

Calves 2.6 2.5 41 1.1 1.1 51 5.0 5.4 45 0.43 Dorsey et al. 1989

Adult with calf 5.1 4.2 38 1.7 1.4 47 8.2 6.5 39 0.51 Dorsey et al. 1989

Feeding Shallow 3.9 3.1 145 1.2 1.7 185 2.9 4.4 99 0.96 Chapter 13

Feeding Deep 3.7 2.7 114 0.9 0.7 118 3.8 4.2 34 0.79 Chapter 13

Weighted Mean

Feeding*

3.8 259 1.1 303 3.1 133 0.91 From Above

All Social* 4.2 2.9 230 1.1 0.8 261 2.8 3.6 83 1.08 Chapter 13

No forward speed 5.1 2.9 75 1.4 0.7 91 6.5 7.4 37 0.65 Dorsey et al. 1989

Swimming , slow speed 5.4 3.0 100 1.2 0.7 111 5.5 6.5 45 0.80 Dorsey et al. 1989

Swimming, moderate

speed*

5.3 3.6 100 1.3 1.2 116 4.9 6.9 59 0.85 Dorsey et al. 1989

Swimming, Fast 4.7 3.9 10 1.0 0.8 10 4.9 6.1 3 0.80

8 Subadults 4.5 1.1 8 10.4 2.4 8 0.43 Krutzikowsky and Mate 2000

Foxe Basin, E. Arctic

Feeding 10.2 4.2 30 1.4 0.8 67 11.1 5.1 31 0.82 Thomas 1999

Traveling 5.1 2.5 25 1.1 0.7 40 4.1 2.7 25 0.98 Thomas 1999

Isabella Bay, E. Arctic

Feeding >50m 17.3 6.7 23 4.7 1.8 46 15.8 7.1 29 0.84 Chapter 13

Traveling 6.0 3.5 76 1.5 0.9 91 9.4 5.7 82 0.55 Chapter 13

Socializing 2.1 2.9 35 1.2 1.8 78 1.6 1.7 45 0.74 Chapter 13

Fall Migration

Alaska North Slope

Migrating 9.2 2.5 10 1.8 0.8 13 17.9 5.0 10 0.47 Ljungblad et al. 1988

Migrating 8.5 2.3 8 1.8 0.6 8 17.8 11.7 4 0.43 Ljungblad et al. 1988

Migrating 3.8 2.0 19 1.1 0.6 21 14.2 10.5 6 0.25 Ljungblad et al. 1988

Migrating 8.0 2.1 24 2.0 0.6 25 16.2 11.5 4 0.44 Ljungblad et al. 1988

Weighted Mean 7.0 61 1.6 67 16.7 24 0.38 Ljungblad et al. 1988

Traveling* 6.1 3.3 68 1.6 1.0 75 14.0 8.1 66 0.39 Chapter 13

Feeding* 5.9 3.6 123 1.3 0.7 157 8.9 7.1 63 0.58 Chapter 13

All Social* 6.1 3.8 108 1.3 0.7 149 5.7 5.3 26 0.89 Chapter 13

*means that these data were used in the computation of annual breathing rates.
§ 22. Energetics of Bowhead Whales 22-15

TABLE 22.6. Average respiration rates (blows/min) of

bowhead whales in relation to whale status and whale

activity (from Table 14.2).

Activity Subadult Adult Mother

Traveling 0.92 0.53 0.55

Feeding 0.64 0.53 0.31

Socializing 0.59 1.04 0.52

Unknowna 0.77 0.77 0.77

a Listed value for “Activity = Unknown” is the overall average for all noncalves and all activities in summer (Table 22.5; Dorsey et al. 1989).

on the largest samples (Table 22.5) were used; these data were also collected in a similar fashion. The

resulting estimates of blow rates by season, whale status, and whale activity are shown in Table 22.7. No

data on blow rates in winter were available. In the absence of other data, the results from summer were,

as a first approximation, assumed to apply to winter (Table 22.7). An example calculation follows. The

overall blow rate for traveling in spring, 0.63 blows/min (Table 22.5), was used as the traveling rate for

subadults because the blow rate for traveling was the highest of all subadult activities (Table 22.6). The

overall blow rate for feeding in spring, 0.74 blows/min (Table 22.5), was scaled to the ratio of the blow

rate of feeding vs. traveling subadults (0.64/0.92; Table 22.6) to yield a blow rate of 0.51 blows per

minute for feeding subadults in spring (Table 22.7). Similar calculations were performed for each age

category, activity type, and season shown in Table 22.7.

Blow rate estimates in Table 22.7 were applied to the time budgets in Table 22.4 to estimate annual

number of blows in a year (Table 22.8). The assumed seasonal timing for bowhead activities, for a typical

individual, is according to Moore and Reeves (1993). In assessing the assumed seasonal timing, note that the

total number of days is fixed at 365. Minor re-allocation of days from one column to another would have little

effect on overall estimated number of blows per year for a given category of whale. Total number of blows

per year is estimated to be on the order of 300,000 to 350,000 for an average bowhead whale.

TABLE 22.7. Estimated average respiration rates

(blows/min) of bowhead whales by season, whale

status, and whale activity. Derived from data in

Tables 22.5 and 22.6 as described in text.a

Spring Summer Fall Winter

Subadult

Traveling 0.63 0.85 0.39 0.85

Feeding 0.51 0.63 0.40 0.63

Socializing 0.73 0.70 0.57 0.70

Unknown 0.77 0.77 0.77 0.77

Adult

Traveling 0.32 0.43 0.20 0.43

Feeding 0.38 0.47 0.30 0.47

Socializing 1.14 1.08 0.89 1.08

Unknown 0.77 0.77 0.77 0.77

Mother

Traveling 0.63 0.85 0.39 0.85

Feeding 0.42 0.52 0.33 0.52

Socializing 1.08 1.03 0.84 1.03

Unknown 0.77 0.77 0.77 0.77

a

 No winter data are available; summer data assumed to apply.
22-16 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

TABLE 22.8. Number of times an average bowhead breathes during a year. Based on

blow rates from Table 22.7 and time budget from Table 22.4. Seasonal timing from

Moore and Reeves (1993). Fall-1 and Fall-2 refer to periods when whales are (1)

migrating across the Alaskan Beaufort and Chukchi Seas (with some feeding), and (2)

feeding in the SW Chukchi Sea and Bering Strait area, respectively.

Category of Spring Summer Fall-1 Fall-2 Winter

Whale and

Whale Activity

AprilMayJune15 Sep16 Sep9 Oct10 OctNovDecMar

DaysÆ 61 107 24 52 121 Blows/year

Subadult

Traveling 41,443 9,441 4,229 2,066 10,310

Feeding 3,654 71,148 6,436 21,892 -

Socializing 4,517 16,027 3,435 6,385 -

Unknown 6,733 5,559 1,325 2,702 124,204 341,506

Adult

Traveling 21,236 4,838 2,167 1,059 5,283

Feeding 2,701 52,596 4,758 16,184 -

Socializing 6,985 24,782 5,311 9,873 -

Unknown 6,733 5,559 1,325 2,702 124,204 298,294

Mother (nursing)

Traveling 41,443 9,441 4,229 2,066 10,310

Feeding 3,009 58,583 5,300 18,026 -

Socializing 6,654 23,606 5,059 9,405 -

Unknown 6,733 5,559 1,325 2,702 124,204 337,652

Blow rate data used here were collected in different years and with varying sampling strategies.

Calculated blow rates depend strongly on the mean dive durations, which can be biased by observational

problems. Also, some assumptions and approximations had to be applied to estimate blow rates for

certain combinations of season, whale status, and whale activity. Values for winter are speculative.

Thus, mean values in Table 22.8 are approximate. Apparent differences should be treated with caution.

Lung and Heart Size.—Henry et al. (1983) measured the dimensions of one preserved lung from each

of five bowhead whales. Volumes that we calculated from their measurements were used to estimate the total

volume of the preserved and collapsed lungs. Only three lungs were actually weighed. The collapsed

volumes and weights were as follows:

Vol (L) Weight (kg) Weight/Vol

30.5 33.2 1.09

26.5 30.0 1.13

32.0 33.8 1.06

Based on this, we assumed that collapsed lung weight (in kg) is closely approximated by 1.09 x volume (in L),

i.e., that the density of the preserved and collapsed lungs was 1.09 kg/L.

The estimated weights of bowhead lungs (as calculated from volume) are about 0.65 % of body

weight (Table 22.9) and are smaller than those found in other whales. For minke, right, sei, fin and blue

whales, lung weight is 0.65 to 0.85 % (mean 0.76 %) of body weight (Lockyer 1981; Lockyer and Waters

1986). In blue and fin whales, total lung capacity in liters is 2.5 to 2.8 % of body weight in kg (Lockyer
§ 22. Energetics of Bowhead Whales 22-17

TABLE 22.9. Lung size of five bowhead whales, based on measurements by Henry et al.

(1983).

Measured

Length (m)

Adjusted

Lengtha

(m)

Weightb

(MT)

Measured

Dimension of

Collapsed Lung

(cm)c

Estimated Weight

of Lungs (kg)d

Lung Weight

as a % of

Total Weight

10.9 10.1 18.0 12 x 72 x 42 79 (L)e 0.44 %

10.8 10 17.6 13 x 77 x 50 109 (R) 0.62 %

10 9.2 14.4 13 x 77 x 41 90 (L) 0.62 %

8.7 8 10.1 12 x 72 x 36 68 (R) 0.67 %

8.7 8 10.8 11 x 87 x 42 88 (R) 0.87 %

Mean ± s.d. 0.65 ± 0.15 %

a

 Adjusted for 8.2 % stretching.

b

 Estimated from equation (1) for adjusted length

c

 Thickness x mean length x mean width.

d

 Estimated from calculated volume assuming tissue density of 1 kg/L. e

 L = left; R = right—indicates which lung was used for the estimate.

1981) and in the smaller minke whales it is 7 % (Folkow and Blix 1992). If we assume that total lung

capacity is proportional to lung weight, then total lung volume in L is about 2.25 % body weight in kg.

This value is close to actual measured values (J.C. George pers. comm.8

). Lung volume in bowheads is

low when compared to that of other species.

The small lung size of bowhead whales may also be reflected in small heart size. Only a portion of

one heart has been weighed. Seventy-five percent of the heart of a 12.7 m whale was reported to weigh

80 kg (Jones and Tarpley 1981). The entire weight would have been roughly 107 kg. Adjusted for

stretching, this 11.7 m bowhead would weigh about 30 MT. According to Lockyer (1981), heart weight

of a whale is approximated by the equation Heart weight = 0.00588 Body weight0.984. Thus, for a 30 MT

whale, the heart is expected to weigh about 148 kg. Thus, based on the meager available evidence,

bowhead heart weight (n < 1!) is about 70 % of predicted weight, and the lungs (n = 5) are about 80 % of

the weight of those of other whales of comparable size. The relatively small heart and lung sizes indicate

a relatively low metabolic rate.

An average non-calf bowhead, which is about 12.5 m in length (Angliss et al. 1995) and weighs

about 31 MT (equation 1), would have a lung capacity of about 708 L. Tidal volume is about 60 % of

lung capacity (Blix and Folkow 1995). Average oxygen utilization, i.e., the proportion of the oxygen in

each breath that is extracted, may be about 8.7–9.6 % (Sumich 1994). However, this value, which is the

one used by Blix and Folkow (1995) for minke whales, is based on oxygen utilization of a gray whale calf

with surfacing-dive cycles of duration <1 min. Bowhead surfacing-dive cycles are >1 min in duration

(Table 22.5), so this may be a source of error in the calculations. One liter of O2 consumed corresponds

to 20.09 kJ (McNab 1988). Using data in Table 22.4 and 22.8, the average energy expended by an

average 12.5 m bowhead respiring at this rate is 6.4 x 105

 kJ/d.

 

8

 Data provided by Craig George from a work in progress are not to be cited without written permission of Craig

George, Department of Wildlife Management, North Slope Borough, Barrow, AK. cgeorge@co.north-slope.ak.us
22-18 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

Basal Metabolic Rate

The basal metabolic rate (BMR) is the metabolic rate measured at a metabolically indifferent

temperature at rest or without abnormal activity (Kleiber 1961). It can be estimated from Kleiber's formula:

(6) BMR = 70.5 W0.7325

W is weight in kg and BMR is basal metabolic rate in Kcal/d. This formula was derived from measurements of the metabolism of resting terrestrial mammals, but it also applies to marine mammals (Lavigne

et al. 1986). Based on this formula, basal metabolic rate for a 12.5 m bowhead whale is 5.8 x 105

 kJ/d.

About 36 to 39 % of the weight of a bowhead is blubber. By comparison blubber only accounts for

17 % of the body mass in minke whales, 24 to 26 % in Antarctic fin whales, and 17 to 21 % in Icelandic

fin whales (Lockyer and Waters 1986). The blubber may be largely inert from a metabolic perspective. It

is used for insulation and energy storage and the outside layers are cold. BMR for a 12.5 m whale,

excluding the weight of the blubber, would be 4.1 x 105

 kJ/d.

Standard Metabolism

This rate includes basal rate plus the cost of maintaining buoyancy and warming the air and food

(Brodie 1975, 1981). During this project, an attempt was made to use a forward-looking infrared sensor

(FLIR) to detect bowheads. (This test was made possible by ARCO Alaska and Mark Major.) The flukes

were not visible on FLIR imagery (W.R. Koski, LGL Ltd., pers. comm.), i.e., there was no observable

heat loss through them. However, George (pers. comm.9

) found that the rate of heat loss through the

flukes was higher than elsewhere on the animal; in contrast, he found no measurable heat loss through the

flippers.

Thus, heat loss through the layer of blubber on the core and flukes needs to be considered. The

heat conductivity of minke whale blubber is 0.25 W/m/°C (Kvadsheim et al. 1996), a figure that is higher

than previously believed (Folkow and Blix 1992; Ryg et al. 1993) and higher than that of seals

(Kvadsheim et al. 1997). Body core temperature of a bowhead whale is about 33 to 34°C and

temperature of the core of the flukes is about 15°C (J.C. George, pers. comm.9

). Water temperature is

-1.8oC in winter and 0 to about 5oC in summer. Heat loss (H) in Watts can be expressed as

(7) H = k · A · ∆t

 d

(Kvadsheim et al. 1996), where A is surface area (m2), d is depth of blubber, ∆t is temperature difference

between body core and water (°C), and k is thermal conductivity of blubber (0.25 W/m/°C). The blubber

around the body of a 12.5 m bowhead averages 0.266 m in thickness (eq’n 2). The blubber layer on the

flukes is about 1.5 cm in thickness and the thermal conductivity of the flukes is about 0.2 W/m/°C (J.C.

George, pers. comm.9

). Total heat loss computed in this manner would be 2.15 x 105 kJ/d.

To this must be added energy that heats expired air and ingested food. Heat loss through

respiration was computed as 0.00187 kJ/L/s from data in Folkow and Blix (1992). On average, a 12.5 m

adult bowhead breathes 817 times a day (from Table 22.8) and a 12.5 m bowhead would have a tidal

volume of 425 L. Total energy required to warm the air is about 0.4 x 105

 kJ/d. Given the amount of

 

9

 Data provided by C. George from a work in progress are not to be cited without written permission of Craig

George, Department of Wildlife Management, North Slope Borough, Barrow, AK. cgeorge@co.north-slope.ak.us
§ 22. Energetics of Bowhead Whales 22-19

food consumed, as computed below, an additional 0.3 kJ/d (approximately) would be required to warm

food. Heat loss though the tongue while feeding may be negligible because bowhead whales possess a

very effective heat exchange mechanism in the tongue, which conserves heat (J.C. George, pers.

comm.10). This mechanism is similar to one found in gray whales (Heyning and Mead 1997).

Overall, standard metabolic rate computed from these heat-loss estimates is about 2.8 x 105

 kJ/d for

a 12.5 m bowhead whale.

Bowheads are very efficient at conserving heat. Total metabolic rate computed through heat loss

calculations is very low—lower than theoretical BMR. When very active, bowheads would need a

cooling mechanism. George (pers. comm.10) has shown that bowheads may use a vascular heat exchanger

in the tongue and flippers to dump excess heat in these situations. The amount of heat lost in this manner

cannot be calculated. The cost of locomotion can be estimated and needs to be added to heat loss to

estimate total energetic requirements.

Energetic Cost of Swimming

Swimming Speeds.—Data on swimming speeds of bowheads are a useful indicator of the animal’s

level of activity. Traveling speeds of bowhead whales have been measured in several areas and are

summarized in Table 22.10. Fall and spring migrants may travel at about 4.5 to 5 km/h. However, over

long periods of time animals stop in various areas, engage in other activities and the average speed may

be about 3.7 km/h (Mate et al. 2000). When using photographic re-sightings to estimate speed, the time

interval between re-sightings is a critical factor in estimating speed (Fig. 11.4 in Chapter 11). Net swimspeeds become slower as time between sightings increases. Swim speeds estimated from sightings <1 h

apart are similar to those derived by direct observation (Table 22.10; see also Chapter 11).

Finley et al. (1986) used a shore-based theodolite to measure swimming speeds of bowheads

feeding in deep water near Baffin Island. Whales feeding at a specific location showed little horizontal

movement from one surfacing to the next. It is not known how far or fast they traveled while under

water. A whale feeding near the surface along a windrow visible at the surface traveled at 2.1 to 5.2 km/h

over the 5 h that it was tracked. Rate of movement slowed and dive duration increased where the

windrow was most prominent (Finley et al. 1986).

Mate et al. (2000) tracked the movements and swimming speeds of 8 subadult bowheads tagged

(with satellite-linked tags) in the Canadian Beaufort Sea. Whale movements were not coordinated and

whales swam at different speeds. Average speed of all whales was 3.7 km/h. These are net (minimum)

speeds, assuming straight-line travel between detection locations. There was some indication that swimming speeds while in the Canadian Beaufort Sea were similar to those of migrating whales (Mate et al.

2000). A whale that was tracked while migrating from the Canadian Beaufort Sea to Siberia averaged

5 km/h.

 

10 Data provided by C. George from a work in progress are not to be cited without written permission of Craig

George, Department of Wildlife Management, North Slope Borough, Barrow, AK. cgeorge@co.north-slope.ak.us
22-20 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

TABLE 22.10. Swimming speeds of undisturbed bowhead whales recorded in various

locations and circumstances.

Speed km/h

Location & Activity Mean ±s.d. Sample Size Method Reference

Eastern Arctic

Fall Migration 5.1 0.3 (s.e) 22 Theodolite Richardson et al. (1995b)

Fall Migration 4.7 0.5 (s.e.) 10 Theodolite & aerial Richardson et al. (1995b)

Western Arctic

Spring Migration 4.7 0.6 9 Theodolite Rugh and Cubbage (1980)

Spring Migration 4.1 1.1 18 (cow-calf pairs) Theodolite George and Carroll (1987)

Spring Migration 5.1 2.5 49 (< 1 h apart) Photo resighting Rugh (1987)

Spring Migration 2.6 2.3 14 (1 – 10 h apart) Photo resighting Rugh (1987)

Spring Migration 1.2 1.0 14 (> 10 h apart) Photo resighting Rugh (1987)

Fall Migration 5 2.0 5 Aerial Ljungblad et al. (1984)

Fall Migration 4.3 1 Group of 10 Aerial Ljungblad et al. (1984)

Fall Migration 8.5 1 Group of 10 Aerial Ljungblad et al. (1984)

Fall - Traveling 4.5 1.2 72 Behavior Chapter 11

Fall - Travel + Feed 3.3 1.6 19 Behavior Chapter 11

Fall - Feeding 1.5 1.2 37 Behavior Chapter 11

Fall Migration 2.8 1.8 294 Photo re-sighting Chapter 11

Summer/Fall Migr. 3.7 8 (9820 km, 111.1 d) Satellite tag Mate et al. (2000)

Summer 5.1 2.9 18 (at surface) Theodolite Würsig et al. (1982)

Summer 4.3 0.8 4 (below surface) Theodolite Würsig et al. (1982)

Summer 2.3 1.26 1 (at surface) Theodolite Würsig et al. (1982)

Summer 8.9 5.6 1 (calf) Theodolite Würsig et al. (1982)

The above represent the speeds of actively moving animals. At some times, bowheads (including

migrating animals) mill around and do not move very quickly, and may reverse direction and swim to

various parts of the same area (Koski et al. 1988; Zeh et al. 1993; Mate et al. 2000; Chapter 11). Two of

Mate et al.’s tagged animals that remained in the Canadian Beaufort Sea for 16 to 24 d averaged 1.1 and

2.8 k/h. However, mean speeds for five other whales in that area averaged 3.5 to 5.8 km/h

Power Output.—For Antarctic rorquals engaged in feeding and other activities at speeds of 5.5

km/h, Lockyer (1981) estimated that power output is about 0.0001 hp/lb (1.64 x 106

 ergs/s/kg). This

power output is equivalent to 14.2 kJ/d/kg of muscle. Only one-half the muscle is used at any one time

(Lockyer 1981). The average 12.5 m, 31 MT sub-adult whale contains about 15.3 MT in the metabolically active core, including 2 MT for organs and 2 MT for bones (see “Size of Bowhead Whales”

subsection). Thus, the musculature operative at any one time is about half of 11,300 kg, i.e., 5750 kg.

During this level of activity about 0.8 x 105

 kJ/d would be required just for motion .

Cost of Motion.—Although measured swimming speeds of both spring and fall migrants are about

4 to 5 km/h, blow rates are quite different (Table 22.7). Blow rates for traveling whales are about 0.6

blows/ min during spring migration and about 0.4 blows/min in fall. The cost of motion through the

water can be computed through hydrodynamic considerations. The cost of transport is

(8) P = 0.5 · ρ · Ct · Sw · V3

where P = power requirement in dyne · cm/s, ρ = density of water in g/cm3, Sw = surface area (cm2), V =

swimming speed (cm/s), and Ct = coefficient of drag (Sumich 1983).
§ 22. Energetics of Bowhead Whales 22-21

Sumich (1983) computed a coefficient of drag of 0.06 for a 15 MT gray whale migrating at about

7 km/h. The estimate of power requirement (P) was based on breathing rates and lung capacity. He

extrapolated lung volume of a young gray whale to the adult, assuming that tidal volume in liters equals

3.5 % of body weight in kg. However, in the gray whale, lung capacity as a percentage of body weight

appears to decrease with increasing size. In the gray whale foetus, total lung weight is 2.5 % of total body

weight (Blokhin 1984). Lung weight in a 31,460 kg (not including blood) female was 333 kg (Yablokov

and Bogoslovskaya 1984). Adding 6 % to the body weight for blood loss (Lockyer 1981), the lung

weight of this adult was 0.99 % of body weight. Most other species of whales also have a lung weight

~1 % of body weight, and a total lung capacity (in L) of 2.5 to 2.8 % of body weight in kg (Lockyer

1981). The volume of inspired air (tidal capacity) is about 80 % of total lung capacity. Based on the

higher figure for total lung capacity (2.8 %) and a tidal volume of 80 %, tidal volume in L = 2.2 % of

body weight in kg. Based on this 2.2 % figure and the cost of transport equation (8) given above, cost of

transport for a gray whale would be 2.85 kJ/kg/km and the drag coefficient would be 0.04.

The above calculations of cost of transport and drag coefficient for a gray whale are based on an

energy utilization figure that includes basal metabolism. The values cited in the preceding paragraph

were used in the equation to derive a cost of transport that excluded basal metabolism (P minus basal

metabolism). Excluding basal metabolism, the coefficient of drag for a gray whale is 0.02 and cost of

transport is 1.51 kJ/kg/km. This drag coefficient will be used to approximate the drag coefficient of a

bowhead. It takes into account only the power, over and above basal metabolism, required to move the

animal through the water.

For an average 12.5 m bowhead whale moving at 5 km/h (139 cm/s) and with total surface area of

58 m2

 (from Table 22.1), cost of transport, excluding basal metabolism, would be 0.63 x 1010 dyne · cm/s,

or about 0.55 x 105

 kJ/d. 

Feeding Rates in Nature

Bowhead whales feed on zooplankton. In this section, an estimate is made of potential feeding

rates in nature using the size of the mouth opening, swimming speed while feeding, time spent feeding,

and quantity of zooplankton found near feeding whales.

Feeding Mechanism and Mouth Opening

Bowheads filter zooplankton by swimming with their mouths open (Scoresby 1820; Pivorunas

1979). Similarly, North Atlantic right whales have been observed and photographed feeding near the

surface with their mouths open widely (Watkins and Schevill 1976, 1982). Although bowheads and right

whales feed in a similar manner, bowheads of a given length have longer baleen than do right whales

(Pivorunas 1979). In order to estimate potential feeding rates of bowheads, it is necessary to know the

size of the mouth opening. The mouth area of a bowhead can be calculated from the length of the baleen,

width of the head, and mouth gape.

The maximum length of baleen and whale length are available for 23 whales taken by the

Cumbrian in 1823 (Lubbock 1937), 13 whales measured be Sheffield (this study), and two measured by

Scammon (1874). These maximum baleen lengths were plotted against whale length and curves were

fitted by regression. The following equation best described this relationship:

(9) Max. Baleen Length (m) = –2.107 + 0.537 Length (m) – 0.012 Length2

; r = 0.97, P < 0.001
22-22 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

The mouth is narrow at the anterior end and becomes progressively wider toward the back. When

open, the anterior baleen plates are not in contact with the lips (Fig. 22.6). The lengths of the first 60

plates increase rapidly toward the rear, lengths of lamellae increase more slowly from lamellae 60 to 120,

and maximum lengths are found at lamellae 120 to 250 (Haldiman and Tarpley 1993). Thus, long baleen

begins one third of the distance from the forward end of the baleen rack. The baleen is attached to the

narrow upper jaw in such a way that, at the top of the mouth, there is very little space between the right

and left racks. The area of the mouth opening can be approximated as triangular. Its width at ~1/3rd the

distance between the tip of the rostrum and the rear corner of the mouth would be the width measured on

vertical photographs minus the thickness of the lips. We have assumed that the lips are the thickness of

the blubber. The width of the mouth, along with total whale length, was measured from vertical

photographs of 22 whales that were not calves. The inner width of the mouth and maximum baleen

length (from eq’n 9) were used to compute the area of the mouth opening. The relationship between

whale length and mouth opening at the 1/3rd-distance location was best described by a linear function

(Fig. 22.7):

 (10) Mouth Opening (m2) = –2.15 + 0.312 × Length (m), r = 0.93, P < 0.001

The morphology of the mouth, baleen, tongue, and lower lips of the bowhead whale are well adapted to

feeding on small copepods, larger fast-moving euphausiids, and continuous feeding as opposed to the gulping

method used by some other baleen whales (Lambertsen et al. 1989; Haldiman and Tarpley 1993). A rack of

baleen contains about 324 lamellae. The topology of the inner surface of the rack is complex. The shape of

the forward part of the rack suggests that it is specialized for seawater channeling and flow acceleration, and

the shape of its rear section increases the filtering area for concentrated prey (Lambertsen et al. 1989). The

shape of the rear portion of the rack and the tongue may create turbulence that may prevent prey buildup on

the baleen and increase efficiency (Lambertsen et al. 1989).

The outer surface of the baleen rack is convex. The lower jaw is articulated and, when feeding,

rotates outward forming a channel between the outer surface of the baleen and the lower lip (Lambertsen

et al. 1989). Thus, all of the rack can be used as a filtering surface while being held in place by the

massive lower lip. Lambertsen et al. (1989) believe that feeding is accomplished by hydrodynamic as

well as hydrostatic pressures. The baleen racks from a 7.5 m whale have a combined surface area of 3.5

m2 (Lambertsen et al. 1989). Water entering the mouth would be reduced in velocity quickly, thereby

reducing the pressure wave in front of the mouth and allowing the bowhead to capture fast moving prey

such as euphausiids (Lambertsen et al. 1989). Photographed whales that have their mouths completely

shut appear to have narrower heads than those with their mouths slightly open. The lower lips seem to

bulge out when the mouth is open and jets of water are often seen emanating from the rear corners of the

mouth.

Aerial photographs (Fig. 22.6) and observations of whales by ourselves and others (e.g., Scoresby

1820; Würsig et al. 1985) show that, at least when surface feeding, the mouth opening may be quite large.

Because the lower lip holds the baleen in place when the mouth is open, bowheads could feed with their

mouths open very wide. Therefore, we estimated the relationship between whale length and maximum

mouth opening. This was best described by a linear function (Fig. 22.7):

(11) Maximum mouth opening (m2) = –2.03 + 0.342 Length (m); r = 0.94, P < 0.001
§ 22. Energetics of Bowhead Whales 22-23

 FIGURE 22.6. Photograph of a bowhead whale on its side with mouth open.

FIGURE 22.7. Relationship between whale length and area of the mouth opening estimated from baleen

length and width of the head 1/3rd the distance from the rostrum to the rear of the mouth, and at the maximum width, as measured from aerial photographs. The lines are the fitted least-squares regressions of

mouth opening vs. whale length.

0.5

1

1.5

2

2.5

3

3.5

9 10 11 12 13 14 15

Length (m)

Mouth Opening (m 2) 

Mouth Opening (1/3)

Predicted (1/3)

Mouth Opening (max)

Predicted (max)
22-24 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

The difference in mouth opening as computed with equations (10) and (11) is 0.4 m2 for a whale

10 m long, i.e., 1 m2

 vs. 1.4 m2, and 0.5 m2 for a whale 13.5 m long. The maximum mouth opening was

used in subsequent calculations of potential filtering capacity.

Habits and Nutritive Value of Potential Food Species

and Their Relationship to Bowhead Energetics

Bowhead whales eat predominantly copepods and euphausiids (Lowry and Sheffield, Chapter 18).

Stomach contents and the species composition of zooplankton found near feeding whales (Chapter 6)

indicate that copepods are the primary prey species in the Canadian and eastern Alaskan Beaufort Sea.

Euphausiids are the primary prey near Barrow in fall and (recently) in spring as well (Chapter 18).

The caloric content of various zooplankton taxa collected in the Alaskan and Canadian Beaufort

Sea, and lipid content of zooplankton from the Canadian Beaufort, were measured in samples taken and

frozen during field work described in Chapter 5. Each species or life stage subsample was blended and

dried to constant weight at 70°C for about 18 h. Caloric content was estimated with a Parr high-pressure

oxygen bomb calorimeter. Lipids were extracted following methods of Bligh and Dyer (1959). An aliquot of extract was then dried to constant mass at 40 to 50°C, and used to estimate the percentage of the

dry weight that was lipid. Copepods and euphausiids contain much energy per gram of tissue (Table

22.11).

We hypothesize that bowhead whales obtain much of their energy intake, at least in summer and fall,

by extracting the lipid from their prey without digesting most of the remaining prey tissue. The stomach of a

9–m subadult bowhead whale can hold about 100 L of food (Haldiman and Tarpley 1993). A whale this size

weighs about 13.5 MT and its maximum mouth opening is about 1 m2

. During periods of substantial feeding,

a bowhead whale needs to process several hundred kg of food per day (see below). This is several times the

stomach volume. The lipid and caloric content of bowhead food is very high (Tables 22.11, 22.12), and

extraction of the lipid from the prey would provide a rich source of energy for bowheads. Copepods are

readily identifiable in bowhead feces. During two years of studies of bowheads in Baffin Bay, Finley (1990)

and Finley et al. (1994) report that northern fulmars (seabirds) fed on bowhead feces, and in those years the

feces had an oily quality. During other years, fulmars did not feed on the feces and the oily quality was not

present.

TABLE 22.11. Energy content of zooplankton (J/g dry weight) collected on the continental shelf in the

Canadian and eastern Alaskan Beaufort Sea in 1985 and 1986, expressed as mean ± s.d (sample size).

Canadian Beaufort Sea Alaskan Beaufort Sea

Species 23 - 30 Aug 1985 27 Aug - 8 Sept 86 September 1985 September 1986 October 1986

Copepods (all) 28,615 ± - (14) 20,996 ± 2943 (64) 29,662 ± 2337 (27) 26,323 ± 2588 (47) 19,722 ± 1468 (13)

<1.8 mm 28,591 ± 681 (11) 19,696 ± 3804 (10) 27,732 ± 2018 (10) - -

>1.8 mm 28,704 ± 447 (3) 21,234 ± 2730 (54) 30,797 ± 1699 (17) - -

Euphausiids 21,502 ± 293 (3) 21,811 ± 3779 (8) 21,611 ± 732 (3) 21,289 ± 1437 (25) 21,321 ± 1437 (25)

Mysids 22,442 ± 318 (4) 18,894 ± 3001 (16) 21,425 ± 2556 (3) - -

Amphipods 25,197 ± 414 (3) 20,599 ± 1463 (10) 26,907 ± 3682 (9) 28,382 ± 3118 (10) -

Decapods - 17,205 ± 1676 (9) 17,613 ± 1669 (3) - -

Fish larvae - 19,320 ± 1701 (20) 20,224 ± 1828 (5) 21,705 ± 235 (3) 16,637 ± 374 (5)

Pteropods - 18,726 ± 6634 (9) 18,948 ± 95 (2) - -

Chaetognaths - 18,421 ± 3085 (8) - 17,576 ± 531 (4) 17,576 ± 531 (4)

Hydrozoans 24,177 ± 523 (3) 8084 ± 1572 (14) - 20,344 ± 3101 (8) 3352 ± 911 (7)

Ctenophores - 8536 ± 2688 (8) - 8,571 ± 2875 (7) 8571 ± 2875 (7)
§ 22. Energetics of Bowhead Whales 22-25

TABLE 22.12. Energy content, lipid content, and energetic value of lipids in zooplankton collected in the

Canadian Beaufort Sea in late August 1985 and late August/early September 1986. Wet weight to dry

weight conversion was based on data shown in Table 22.13.

J/g Dry

Weight

Lipids/g

Dry Wt.

Species Mean ± s.d. n Mean % ± s.d. mg/g J/g

% Energy

in Lipids

1985

Copepods (all) 28,615 14 37.3 8.9 373 14,723 51.5 %

1986

Copepods (all) 20,996 2943 64 30.9 16.4 309 12,206 58.1 %

< 1.8 mm 19,696 3804 10 40.8 22.1 408 16,116 81.8 %

1.8 - 4 mm 21,076 2579 31 27.4 13.5 274 10,823 51.4 %

 > 4 mm 21,452 2968 23 33.0 18.0 330 13,035 60.8 %

Euphausiids 21,811 3779 8 25.0 11.3 250 9875 45.3 %

Mysids 18,894 3001 16 12.9 8.7 129 5096 27.0 %

Amphipods 20,599 1463 10 25.4 9.8 254 10,033 48.7 %

Decapods 17,205 1676 9 19.3 15.2 193 7624 44.3 %

Fish larvae 19,320 1701 20 18.3 16.5 183 7229 37.4 %

Pteropods 18,726 6634 9 9.4 7.2 94 3713 19.8 %

Chaetognaths 18,421 3085 8 18.5 11.4 185 7308 39.7 %

Hydrozoans 8,084 1572 14 6.9 5.5 69 2726 33.7 %

Ctenophores 8,536 2688 8 19.9 20.9 199 7861 92.1 %

TABLE 22.13. Dry weight as a percentage of wet weight for various species of zooplankton collected during late August and

early September 1986 in the eastern Alaskan Beaufort Sea.

Mean s.d. n

Copepods 18.3 1.1 5

Euphausiids 19.8 1.6 5

Mysids 20.1 1.2 5

Hyperiids 16.6 2.5 5

Chaetognaths 6.6 0.6 5

Hydrozoans 11.4 2.2 5

Ctenophores 9.8 1.8 5

Decapod larvae 13.4 1.3 5

Fish larvae 16.8 1.4 5

These observations, the small size of the bowhead stomach, the large quantity of food that a bowhead

needs to process, and the high lipid content in bowhead food are all consistent with a hypothesis that, when

food is abundant, bowheads process food quickly and extract only the easily extractable lipids. The chitinous

exoskeletons are indigestible by most animals. Even if chitin could be digested, it would be inefficient to

digest it when richer food is abundant in summer and fall. Digesting the muscle tissue within the exoskeleton

would also be inefficient when food is abundant. In extracting only the lipids, bowheads could assimilate 50

to 80 % of the energetic value of their summer prey efficiently and quickly. The extraction of the lipid may

occur in the bowhead fore-stomach. The fore-stomach has no digestive glands and does have muscles.

Haldiman and Tarpley (1993) speculate that it may be a churning vat for mixing ingesta with refluxed

digestive enzymes. It could be used for extracting lipid from zooplankton. This would require little effort.

For example, a layer of fat quickly develops on the surface of the water–preservative mixture when copepods
22-26 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

are placed in a jar with preservative. When bowheads are feeding in areas with limited food availability, they

might digest additional components of the prey.

Assimilation Efficiency

Approximately 75 % of the prey eaten by carnivores is assimilated (Lockyer 1981); for a grazer

(cow) about 53 % of the food is assimilated (Kleiber 1961). Lockyer (1981) derived an assimilation

efficiency of 87 % for pregnant or lactating female rorquals. This value is higher than the 77 to 79 %

estimated for males, subadults, and nonreproductive females (Lockyer 1981). These figures are clearly

an oversimplification; they leads to a lower predicted energy requirement for a pregnant than for a

nonreproductive female—an unrealistic result. Rorquals engulf large quantities of prey whereas

bowheads, which commonly feed on more thinly-distributed prey, typically eat a smaller amount of

prey at one time. In our subsequent calculations, we assume that bowheads extract only the lipids from

their prey and do so with 90 % efficiency. In summer, copepods contain 24,800 J/g dry weight and

euphausiids 21,650 J/g dry weight (average of August 1985 and Aug./Sept. 1986 data in Table 22.11).

The energy in lipids represents about 20 to 82 % of the total energy in zooplankton, depending on the

major group of zooplankton (Table 22.12). We assume here that, in summer and early fall, bowheads

eat mainly copepods (75 %) and euphausiids (20 %), with 5 % of other prey types. In summer, the

energetic value of the lipids in this mixture (excluding other components) would be about 12,396 J/g

dry weight based on the data in Table 22.12, or about 2283 J/g wet weight (wet/dry ratios from Table

22.13). The lipids represent about 502 % of total energetic content of this prey mixture. Lipid content

of arctic copepods is highest in summer and decreases over winter when they metabolize their stored

lipid (Lee 1974):

Month Feb Mar Apr May June July Aug Sept Oct Nov Dec

Lipid (μg/individual) 800 800 700 600 400 900 1700 2100 1300 1200 900

Lipid (% dry wt.) 42 44 38 37 29 52 74 66 64 62 51

Spring values would be about 36 % of those in summer. Bowheads apparently feed less intensively

in spring than in summer or early autumn (Table 22.4; Chapter 18). Measured fall values would be about

95 % of summer values or about 2165 J/g assuming a diet of 50 % euphausiids, 45 % copepods, and 5 %

other. Winter energetic values of potential prey would be about 50 % of summer values or about 1450

J/g, assuming 75 % copepods, 20 % euphausiids, and 5 % other. However, as noted earlier, we assume

that there is little feeding in winter.

Right whales, and presumably bowheads, are very efficient at filtering zooplankton. The filtering

efficiency of North Atlantic right whales depends on prey size, but they retain 95 % of the available energetic value of their prey (Mayo et al. 2001). Right whales prey mainly on Calanus finmarchicus, which

are >2 mm in length (Woodley and Gaskin 1996). Arctic zooplankters are generally larger than are

temperate species. An exception is Limnocalanus macrurus, which has commonly been found in

abundance near feeding bowheads (Chapter 6); it is <2 mm in length (Bradstreet et al. 1986). However,

this species has many spines, which cause the animals to clump together when collected by a plankton

net, and presumably by baleen. They could be easily filtered from the water by bowheads.

Time Spent Feeding

The number of days that BCB bowheads may spend feeding, by season, are estimated in Table

22.14 based on their seasonal distribution and activities, the proportion of time spent feeding (Table

22.4), and other factors. Bowheads do not feed constantly during the time they are classified as
§ 22. Energetics of Bowhead Whales 22-27

“feeding”. Whales feeding at depth need to surface to breath. Whales feeding at depths >50 m spend

about a quarter of their time at the surface (Table 22.5). Whales “skim-feeding” at or near the surface

spend more time at the surface than at depth (Table 22.5). We assume that, overall, the proportion of time

spent feeding should be reduced by 30 % to account for time spent at the surface breathing, cleaning the

baleen, and engaged in other non-feeding behaviors. (It is uncertain whether bowheads require a specific

allocation of time to clean the baleen.) Based on the available data, total time spent actively feeding may

be the equivalent of about 93 d/yr (Table 22.14).

TABLE 22.14. Number of days bowheads may spend feeding per year (calculated from Table 22.4

as described in text). Feeding days have been decreased by 30 % to account for time at the surface, cleaning food off the baleen, and engaged in other activities interspersed with feeding.

Spring:

April–

May

Summer:

June–

15 Sep

Fall-1:

North

Slopea

Fall-2:

Chukchi/

Bering

Winter:

Dec –

March

Total

Annual

Calendar days 61 107 24 52 121 365

Prop’n of time feeding 0.08 0.73 0.47 0.73 0.00

Effective days feeding 5 78 11 38 0 119

Days feeding – 30 % 3 55 8 27 0 93

a Includes time spent traveling across Chukchi Sea.

Feeding Rate

The feeding rate is a function of the mouth opening, swimming speed while feeding, quantity of

food available, and assimilation efficiency. The mouth opening can be computed from equation (11).

Griffiths et al. (Chapter 6) estimated that the average biomass of zooplankton near bowhead whales

feeding in the Canadian and eastern Alaskan Beaufort Sea was 1800 mg/m3

 (wet weight). This is the

average found by echosounder-guided horizontal tows at the depth of maximum biomass. As shown

above, a wet-weight of 1800 mg/m3

 may contain about 2069 J/g in the lipids alone, which we assume to

be assimilated with an efficiency of 90 %. The overall assimilation efficiency for zooplankton would be

quite low at about 50 %. The estimated number of feeding days per year is shown in Table 22.14. Average swimming speed while presumably feeding under water between surfacings has been estimated at

about 1.54 km/h (Koski et al., Chapter 11). However, this may be an underestimate because it does not

account for changes in swimming direction while underwater. A swimming speed of 2.5 km/h while

feeding may be more realistic. Right whales may feed at a speed of 5.5 km/h (Kenney et al. 1986).

However, right whale baleen is shorter than that of bowhead whales, and right whales tend to be smaller.

A 12.5 m bowhead whale with maximum mouth opening 2.25 m2

, from eq’n (11), traveling at 2.5

km/h while feeding, could consume 244 kg wet-weight during 24 h of continuous feeding at locations and

depths with average zooplankton biomass 1800 mg/m3

 wet weight. This estimate of plankton available to

bowhead whales at feeding locations in the eastern and central Beaufort Sea (1800 mg/m3

) may only

apply to subadult animals because sampling of prey availability was conducted only near subadults

(Chapter 6). Average annual daily food consumption was estimated as follows. The estimate of 244 kg/d

of food consumed during a day of continuous food consumption was converted to an energetic equivalent

using a seasonally-adjusted energetic content of zooplankton. This was then multiplied by the effective

number of feeding days per year less 30 %, from Table 22.14. The total annual energetic consumption

was then divided by 365 d. A 12.5 m bowhead could consume 1.4 x 105 kJ/d averaged over the year on

this basis.
22-28 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

Zooplankton biomass available to bowheads during autumn feeding near Barrow, Alaska, or in the

southwest Chukchi and Bering Strait, is expected to exceed that in the Canadian Beaufort Sea in summer

or the eastern Alaskan Beaufort in later summer/early autumn. The productivity of the Bering/Chukchi

water found in the southwest Chukchi Sea (and, to some extent, near Barrow) is considerably higher than

that of the eastern Beaufort Sea (see Chapters 20 and 23). Conversely, the limited feeding in spring may

be primarily at locations where food availability is less than 1800 mg/m3

.

Comparison of Estimates for Bowheads and Other Whales

Several different methods have been used to compute the energetic requirements of an average

12.5-m bowhead whale weighing an estimated 31 MT (Table 22.15).

TABLE 22.15. Average daily energetic requirements of a

12.5-m bowhead whale weighing 31 MT, estimated based on

several different methods. Energy requirement for growth is

shown as a separate item.

Method of Estimation kJ/d x 105

Standard metabolism 2.8

Standard metabolism + swimming 3.4

Basal metabolic rate 5.8

Basal metabolic rate of core only 4.1

Power output + BMR 6.6

Cost of swimming +BMR 6.4

Core BMR + Cost of swimming 4.7

Respiration 6.4

Feeding in nature (2.5 km/h, 1.8 g plankton/m3 1.4

Feeding in nature (5 km/h, 4 g zooplankton/m3 6.0

Growth/Food Storage for Winter 1.4

The energetic requirements of traveling as computed from power output and hydrodynamic considerations are close to one another and higher than standard metabolism plus the cost of motion. Basal

metabolism is higher than standard metabolism. However, basal metabolism for the weight minus the

blubber is about the same as standard metabolism.

Using empirical evidence, Lavigne et al. (1986) found that basal energetic requirements of marine

mammals are well described by Kleiber's equation, which was derived for terrestrial mammals. The

active metabolic rates for gray whales (food removal method), blue whales, and fin whales have been

estimated to be two to three times the basal metabolic rate (Lockyer 1981; Thomson and Martin 1984).

However, Hinga (1979) found evidence that large whales have average annual metabolic rates that are

only about 1.5 times the basal rate. Folkow and Blix (1992) estimated that the active metabolic rate of

minke whales was about 1.2 times BMR. Results from Brodie and Paasche (1985) are also consistent

with the idea that active metabolic rates of large whales are low. Brodie and Paasche found that the body

core temperatures of large whales were lower than those of other mammals, and there was a gradient of

decreasing temperature from the core to the muscle/blubber interface. They also found that body

temperature did not rise after exertion (pursuit), and they speculate that whales are hydrodynamically and

biomechanically very efficient. Thus, available data for large whales indicate that active metabolism is

about 1.5 times basal metabolism.
§ 22. Energetics of Bowhead Whales 22-29

One question that remains unanswered is “how is BMR to be calculated for a bowhead whale”?

Blubber is presumed to be essentially inert. It does not require as much energy for maintenance as do other

tissues. The bowhead has the largest blubber content of any whale on a percentage of body mass basis

(George et al. 1999). The bowhead is very well adapted for conserving heat. It grows very slowly, requires

many years to reach sexual maturity, and reproduces only once every 3 or 4 years (Miller et al. 1992; George

et al. 1999). Its heart and lungs are relatively small compared to other animals. Heart size is related to body

mass (Innes et al. 1986). However, for a specific animal size, animals with higher metabolic rates will have

larger hearts than those with low metabolic rates (Ridgway and Kohn 1995). Thus, metabolic rates of

bowhead whales may be quite low for their size. The evidence tends to support a low estimate based on BMR

calculated from the core weight not including blubber, plus a small but unknown amount for maintenance of

blubber. BMR calculated in this manner for a 12.5 m whale is 4.1 × 105

 kJ/d, similar to standard metabolism

plus cost of locomotion (3.41 × 105

 kJ/d).

This estimate is much higher than suggested by feeding rates in nature, 1.4 x 105

 kJ/d estimated using

average zooplankton concentrations near feeding whales in summer and early autumn (1800 mg/m3

, wet

weight) and an average swimming speed while feeding of 2.5 km/h. Subadults and adult males would need to

feed on average concentrations of 4000 mg/m3

 at an average speed of 5 km/h to meet energetic requirements

as calculated by the feeding rate method. Right whales feed at speeds 4.8 km/h (Mayo et al. 2001). A speed

of 5 km/h for feeding bowheads is perhaps possible, though it is at the high end of observed speeds while

feeding (Table 22.10). Zooplankton concentrations of 4 g/m3

 are at the upper end of the values found near

feeding whales in the Canadian and eastern Alaskan Beaufort Sea (Chapter 6). Sampling was conducted near

feeding bowheads or in areas where bowheads were feeding, using echosounder guidance to the depth of

maximum zooplankton biomass. However, sampling was not necessarily in the exact three-dimensional

location where bowheads were feeding. Bowheads are probably adept at finding highly concentrated food

patches within areas with a higher than average biomass of zooplankton. Average prey biomass at precise

sites of summer/early fall feeding probably exceeds 1800 mg/m3

 by some unknown amount.

Bowheads may feed, on occasion, in extremely dense patches of zooplankton that could meet a

substantial percentage of annual requirements within a short time. North Atlantic right whales occasionally do

so (Beardsley et al. 1996). Given the limited number of locations and times when we sampled near feeding

bowheads (Chapter 6), we very likely did not encounter a location with maximum biomass. Also, our

sampling probably underestimated the biomass present at certain times and places, especially when fastmoving prey such as euphausiids were dominant. Perhaps most importantly, all of our zooplankton sampling

near bowheads was in summer and early-autumn in the Canadian and eastern Alaskan Beaufort Sea. There

are no specific data on prey availability at locations where bowheads often feed just east of Barrow, or in the

southwest Chukchi Sea. Those locations are likely to have higher zooplankton abundance than the eastern

Beaufort Sea given the high productivity of the Bering/Chukchi water present in those areas. Bowheads

feeding in those more westerly areas during autumn may have access to zooplankton with average wet-weight

biomass well above the 1800 mg/m3

 found in the eastern and central Beaufort Sea.

Food Requirements of Different Segments of the Population

The energetic requirements of subadults, adult males, and adult females calculated by different

methods are shown in Table 22.16. Bowheads grow very slowly, and little energy is required for growth

and food storage (Table 22.16). Bowheads feed in summer and fall, and to a lesser degree in spring

(Chapters 12, 18, 20). Winter feeding has not been documented, and the loss of girth over the winter
22-30 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

TABLE 22.16. Theoretical energetic requirements of various categories of bowhead whales estimated

from respiration, heat loss, cost of motion, and basal metabolic rate. Estimates of the cost of growth,

reproduction, and weight loss over winter are included.

Units

Subadult

Male

Subadult

Female

Adult

Male at

Puberty

Adult

Female at

Puberty

Older

Adult

Male

Older

Adult

Female

Mean Length m 11 11 12.5 13.5 13.5 14.75

Age yr 14 10 25 27 35 41

Weight MT 22.6 22.6 31.5 38.4 38.4 48.3

Weight of Blubber MT 8.6 8.6 11.7 14.0 14.0 17.3

Blubber thickness m 0.24 0.24 0.265 0.28 0.28 0.30

Surface Area of flukes m2 2.49 2.49 3.19 3.70 3.70 4.40

Total surface area m2 46.1 46.1 58.4 67.3 67.3 79.3

Metabolically active core MT 11.1 11.1 15.4 18.7 18.7 23.4

Respiration

 Lung Volume (2.25 % kg body wt) l 509 509 708 864 864 1085

 Tidal Volume (60 % of lung volume) l 306 306 425 518 518 651

 Oxygen used (9.15 % of tidal volume) l/blow 28 28 39 47 47 60

 Energy (kJ/d x 105

) kJ x 105/d 5.3 5.3 6.4 8.0 7.8 10.1

Basal Metabolism (BMR; Kleiber 1961) kJ x 105

/d 4.6 4.6 5.8 6.7 6.7 7.9

Basal Metabolism (Body Core only) kJ x 105

/d 3.2 3.2 4.1 4.8 4.8 5.7

Standard Metabolism (heat loss)

 Through body surface (Folkow and Blix 1992) kJ x 105

/d 1.4 1.4 1.6 1.7 1.7 1.9

 Through flukes (Folkow and Blix 1992) 0.4 0.4 0.6 0.6 0.6 0.8

 Total Heat Loss 1.8 1.8 2.1 2.4 2.4 2.7

 Warming air (Folkow and Blix 1992) kJ x 105

/d 0.3 0.3 0.4 0.5 0.5 0.6

 Heat loss warming food kJ x 105

/d 0.3 0.3 0.3 0.5 0.3 0.5

Total kJ x 105

/d 2.4 2.4 2.8 3.3 3.2 3.8

Power Output

 Power Output (no BMR; Lockyer 1981) kJ x 105

/d 0.6 0.6 0.8 1.0 1.0 1.2

 Cost of swimming (no BMR; Sumich 1983) kJ x 105

/d 0.4 0.4 0.5 0.6 0.6 0.7

Standard Metabolism + Swimming kJ x 105

/d 2.8 2.8 3.4 4.0 3.8 4.6

Growth and Reproduction

 Growth (40 % lipid 60 % Muscle) MT 0.86 1.02 0.74 0.83 0.61 0.62

 Weight Loss over Winter MT 2.55 2.55 3.02 3.32 3.32 3.66

 Lipid loss over winter MT 0.29 0.29

Total MT 3.69 3.86 3.76 4.15 3.93 4.27

Total kJ x 105

/d 1.45 1.51 1.41 1.55 1.47 1.60

 Foetal growth and metabolism (/4 years) kJ x 105

/d 0.24 0.24

 Neonate growth and /4 years) kJ x 105

/d 1.55 1.55

Total Growth + Reproduction kJ x 105

/d 1.45 1.51 1.41 3.35 1.47 3.39

Basal Metabolism kJ x 105

/d 4.56 4.56 5.81 6.72 6.72 7.94

Core BMR+ Motion + Growth + Reproduction kJ x 105

/d 5.10 5.17 6.10 8.80 6.92 9.87

Respiration + Growth + Reproduction kJ x 105

/d 6.70 6.77 7.79 11.39 9.25 13.50

Std. Metabolism + Motion+Growth +Reprod. kJ x 105

/d 4.28 4.34 4.80 7.32 5.30 7.95

suggests that there must be little feeding in winter. However, the relative amounts of feeding in different

seasons and regions are controversial. Isotopic evidence in Chapter 20 suggests that feeding is predominantly in Bering/Chukchi waters, presumably mainly in fall, but with a minority of the feeding in the

eastern and central Beaufort Sea. Other evidence shows that feeding occurs very frequently in summer

and early fall in the Beaufort Sea, but does not specifically show how much food is acquired there as

compared with other areas and seasons. As shown above, bowheads lose weight over winter.

Females of reproductive age require the most energy. However, the full reproductive cycle

requires three or four years and, as a result, annual requirements for reproduction are not as large as those

of some other species of baleen whales that give birth at shorter intervals. The total cost of reproduction

is about 1.8 × 105

 kJ/d averaged over a 4-year reproductive cycle. The estimates of theoretical energetic
§ 22. Energetics of Bowhead Whales 22-31

requirements range from 4.6 to 9.25 × 105

 kJ/d for non-reproductive individuals, and from 6.7 to 13.5 ×

105

 kJ/d for females of reproductive age. Differences among the various theoretical estimates of food

requirements are not large, given all the uncertainties associated with the derivation of these estimates,

and they can essentially be considered equal.

Bowheads cannot satisfy even the low theoretical estimate of energy and food requirements by feeding

on average concentrations of zooplankton found near whales feeding in the eastern and central Beaufort Sea

(Table 22.17). The estimated average of 1.8 g/m3

 of zooplankton (wet weight) found near feeding subadults is

not enough to meet energetic requirements, given our assumptions about amount of feeding during each

season. Bowheads apparently need to feed in average concentrations of about 4 g/m3

 at a speed of 5 km/h to

meet energetic requirements (Table 22.17). Such swimming speeds and zooplankton concentrations have

occasionally been observed, but these values are near the upper limits of the observed speeds and zooplankton

concentrations, and are well above the averages observed in the eastern and central Beaufort Sea.

TABLE 22.17. Estimates of energy consumed by various categories of bowhead whales through

consideration of the size of the mouth opening, time spent feeding, and energetic value of food

compared to the theoretical estimates derived in Table 22.16.a,b,c

Units

Subadult

Male

Subadult

Female

Adult

Male at

Puberty

Adult

Female

at

Puberty

Older

Adult

Male

Older

Adult

Female

Mean Length m 11 11 12.5 13.5 13.5 14.75

Mean Weight MT 23 23 31 38 38 48

Total Theoretical Requirements

Respiration + Growth

 Average Requirements/d kJ x 105

/d 6.7 6.8 7.8 11.4 9.3 13.5

 Annual requirements/yr kJ x 105

/yr 2447 2470 2843 4157 3377 4927

 Annual food requirements kg/yr 111,435 112,483 129,467 189,313 153,782 224,349

 Average food per feeding daya kJ x 105

/d 26.40 26.65 30.67 44.85 36.43 53.15

 Average food per feeding daya kg/d 1202 1213 1397 2042 1659 2420

Standard Metabolism, Swimming, Growth

 Average Daily Requirements kJ x 105

/d 4.28 4.34 4.80 7.32 5.30 7.95

 Annual requirements KJx105

/yr 1561 1586 1751 2673 1934 2903

 Annual food requirements kg /yr 71,080 72,200 79,722 121,721 88,046 132,181

 Average food per feeding daya kJ x 105

/d 16.84 17.10 18.89 28.83 20.86 31.31

 Average food per feeding daya kg/d 767 779 860 1313 950 1421

Food Consumption Method

Mouth opening m2 1.7 1.7 2.3 2.6 2.6 3.0

Feeding distance (at 5 km/h) m/d 120,000 120,000 120,000 120,000 120,000 120,000

Volume filtered/feeding day m3

/d 209,136 209,136 270,827 311,955 311,955 363,365

Consumption per Feeding Dayb kg/d 837 837 1083 1248 1248 1453

Annual Food consumptionc

 Summer consumption (55 d) kJ x 105 1046 1046 1355 1560 1560 1818

 Fall consumption (35 d) kJ x 105 624 624 808 931 931 1084

 Spring consumption (3 d) kJ x 105 33 33 43 49 49 57

Total Annual Food Consumption kJ x 105/yr 1703 1703 2205 2540 2540 2959

Average Annual consumption/d kJ x 105

/d 4.7 4.7 6.0 7.0 7.0 8.1

a Assumes ninety-three 24-hour feeding days/year and seasonally weighted annual energetic content for zooplankton.

b

 Assumes zooplankton concentrations of 4 g/m3 and swimming speed 5 km/h while feeding.

c

 Adjusted for seasonal changes in energetic content of zooplankton.
22-32 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

This chapter has derived point estimates for many parameters. It has not attempted to assess the

uncertainty in estimates that are based on various other estimates, each of which is itself somewhat uncertain. Chapter 23 includes sensitivity analyses of some of the key calculations and estimates. The overall

purpose of the sensitivity analysis was to place confidence intervals around the estimated percent of

annual food requirements that bowheads consume in the eastern Alaskan Beaufort Sea.

Summary and Conclusions

An estimate of the importance of the eastern Alaskan Beaufort Sea to feeding bowheads requires that

their daily and annual food requirements be estimated and then used to determine what proportion of their

annual requirements could be obtained in the study area. The “energetics” chapter first describes the size,

growth and reproduction of bowhead whales and the related physical attributes needed for the estimation of

energetic requirements. This is followed by several approaches to the estimation of the metabolic rate of

bowheads. These are compared to estimates of the amount of food consumed by bowhead whales as

determined through observations of behavior, swimming speed, and amount of food found near feeding

whales. The only specific data on the amount of food near feeding whales come from the Canadian and

eastern Alaskan Beaufort Sea. There are numerous other data gaps where it has been necessary to make

assumptions. Identification of these data gaps is useful in showing topics on which additional research would

be desirable.

The sizes of bowhead whales and their blubber content can be estimated using known-scale vertical

aerial photographs. The results are in agreement with blubber content as estimated from old whaling

records and weights of a few whales harvested at Barrow. Baleen length was estimated as a function of

whale length using data from whales harvested at Kaktovik and from data in old whaling records.

Important relationships needed for energetic calculations are summarized below, where “a” and “b” are

the coefficients for an equation of the form y = a × (body length in meters)b

, r is the correlation

coefficient, and P denotes the significance level of the correlation:

Parameter/ units a a b r P

Whale Weight MTb 0.047 2.58 0.98 < 0.001

Blubber Weight MT 0.052 2.19 0.95 < 0.001

Total surface area m2 0.54 1.85 0.99 < 0.001

Surface area of fluke m2 0.012 1.94 0.92 < 0.001

Weight of metabolic core MT 0.03 2.53 0.97 < 0.001

Surface area of metabolic core m2 0.49 1.70 0.97 < 0.001

a Equation form: y = a x body length (m)b

. b 1 MT (metric tonne) = 1000 kg.

Theoretical energetic requirements were calculated for a 12.5 m whale that weighs 31 MT, taking

account of the available data on whale physiology and bowhead dimensions, seasonal activities, swimming

speeds, and surfacing–respiration–dive cycles. The energetic requirements of bowhead whales, as estimated

using the respiration method, are higher than estimates based on calculated power output or hydrodynamic

considerations plus the standard metabolism approach, which is based on heat loss.

The theoretical energy requirements of bowheads appear to be quite low and are in keeping with

the adaptations that bowheads possess for living in a cold environment where food is relatively scarce

compared to some other marine waters. These adaptations include

• A very slow maturation rate where males mature when 12 to 13 m long at an age of ~25

years, and females at a length of 13 to 13.5 m when ~27 years old.
§ 22. Energetics of Bowhead Whales 22-33

• Very slow growth rates: after weaning, subadults initially show little growth and an average

subadult gains only about 0.8 to 1MT/yr; adults gain 0.2–0.9 MT/yr.

• The highest blubber content on a percentage basis of any species of whale.

• The longest baleen of any species of whale.

• A long reproductive cycle which spreads the energetic cost of reproduction over about four

years.

Potential feeding rates in nature were computed from the area of the mouth opening, speed while

swimming, and quantity of food available to bowheads in the eastern and central Beaufort Sea. The

mouth opening computed from width of the mouth at ~1/3 the distance between the tip of the rostrum and

the rear corner of the mouth, as a function of body length, was estimated as

 Mouth Opening (m2) = –2.15 + 0.312 × Length (m); r = 0.93, P < 0.001

Because the lower lip holds the baleen in place when the mouth is open, bowheads could feed with their

mouths open very wide. The relationship between whale length in m and maximum mouth opening in m2

was best described as

 Maximum mouth opening (m2) = –2.03 + 0.342 Length (m); r = 0.94, P < 0.001

Bowheads feed on zooplankters that have a high lipid content. The small size of the bowhead stomach and observations of bowhead feces are consistent with a hypothesis that bowheads extract only the lipids

from their prey, at least when feeding in areas with much zooplankton. Zooplankton concentrations near

feeding subadult bowheads in the Canadian and eastern Alaskan Beaufort Sea average 1.8 g/m3

 on a wet

weight basis, based on echosounder-guided net sampling. This corresponds to an energetic value of about

2069 J/g wet weight considering only the lipid content of the prey. Observations of behavior indicate that

bowheads may feed an equivalent of ninety-three 24-hour-days per year. This estimate has wide uncertainty

given the lack of specific time-budget data for the western Chukchi Sea and Bering Strait in fall (where we

assume intensive feeding) or the central Bering Sea in winter (where we assume no feeding). Assuming 93

days of feeding/yr and a swimming speed of 2.5 km/h while feeding, a 12.5 m whale feeding at locations

with average prey biomass of 1.8 g/m3

 could consume 1.4 × 105 kJ/d, averaged over the year and adjusted for

annual differences in lipid content. For comparison, the calculated value assuming a swimming speed while

feeding of 5 km/h and prey density 4 g/m3

 was 6.0 × 105 kJ/d,

 Several different methods have been used to compute the energetic requirements of an average

12.5-m bowhead whale weighing 31 MT:

kJ/d x 105

Standard metabolism 2.8

Standard metabolism + swimming 3.4

Basal metabolic rate 5.8

Basal metabolic rate of core only 4.1

Power output + BMR 6.6

Cost of swimming +BMR 6.437

Core BMR + Cost of swimming 4.7

Respiration 6.4

Feeding in nature (2.5 km/h, 1.8 g plankton/m3 1.4

Feeding in nature (5 km/h, 4 g zooplankton/m3 6.0

Growth/Food Storage for Winter 1.4
22-34 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

Estimated basal metabolism is higher than standard metabolism computed through consideration of

heat loss. However, estimated basal metabolism for the core weight (excluding blubber) is about the

same as standard metabolism. The metabolic rate of bowhead whales may be quite low for their size.

The evidence tends to support a low estimate based on BMR calculated from the core weight not

including blubber, plus some small but unknown amount for maintenance of the blubber layer. The cost

of locomotion derived through consideration of power output and cost of swimming were also computed,

and added to standard and basal metabolism.

About 1.4 × 105

 kJ/d needs to be added to the above estimates to account for growth and food

storage, and ~1.8 × 105

 kJ/d need to be added to adult female requirements for the cost of reproduction

averaged over a 4-year reproductive cycle. When these amounts are added to the two theoretical estimates, the difference between those estimates and the lower “feeding in nature” estimate becomes even

greater.

One major uncertainty affecting the energetic analysis is the unknown amount of feeding in the

Chukchi Sea and Bering Strait in fall, and the Bering Sea in winter. Isotopic results suggest that most

feeding by both subadult and (especially) adult bowheads occurs outside the Canadian and eastern

Alaskan Beaufort Sea. However, feeding is commonly observed in those areas, most whales harvested at

Kaktovik have food in their stomachs, and subadult bowheads harvested in fall are heavier and have a

higher lipid content in their blubber than do spring harvested animals. Measurements of length and girth

from known-scale aerial photographs confirm some loss of girth (and thus weight) in winter. Available

data indicate that the net loss of weight from the time bowheads leave the Beaufort in fall until they return

in spring may be on the order of 2.5 to 3.6 MT for an 11 m subadult and a 14.5 m adult. Actual weight

loss in winter is probably greater, assuming there is further weight gain in the Chukchi Sea and Bering

Strait in late autumn before the (presumed) period of winter fasting and weight loss begins.

Sampling of food available at places where bowheads were observed feeding has only been conducted near subadults feeding in summer and early fall. These data came from feeding sites in the Canadian and eastern Alaskan Beaufort Sea. The average prey availability at the depth of maximum prey

biomass at these sites was measured as 1.8 g/m3

 on a wet weight basis. Estimated prey consumption by

subadults feeding in such locations is only about half that required by even the lower of the estimates of

theoretical energetic requirements if average food availability in other feeding locations is similar.

Subadults and adults would need to feed in higher concentrations of zooplankton. The quantity of prey

available at specific locations where adult bowheads feed is unknown. Given our assumptions about the

number of days of feeding in various seasons, subadults and adult males would, over the course of the

year, need to feed on average concentrations of 4 g/m3

 at an average speed of 5 km/h to meet energetic

requirements. A swimming speed of 5 km/h while feeding, and zooplankton concentrations of 4 g/m3

near feeding whales, are at the upper ends of the observed ranges of values in the Beaufort Sea, and above

the average observed values for that area.

The estimate of energetic requirements derived through consideration of respiration is at the high

end of the range of estimates derived here. It is based on weights of only 5 lungs and assumptions about

the undocumented relationship (for bowheads) between weight of lungs and their volume. Tidal volume

and oxygen consumption of bowheads are unknown, as are breathing rates in winter.

The estimate derived through consideration of heat loss and cost of motion is an intermediate

estimate relative to other methods. This intermediate estimate may represent the best available estimate
§ 22. Energetics of Bowhead Whales 22-35

of the energetic requirements of bowhead whales. It is consistent with adaptation to a cold environment

with relatively low food availability, and with the morphology and physiology of the animal.

Acknowledgements

I am grateful to J. Craig George of the North Slope Borough Dept of Wildlife Management and

Tamara Mau of University of Alaska Fairbanks for providing advance access to a variety of key unpublished data relevant to this analysis. That information is quoted here with their permission, and is not to

be used elsewhere without their approval. Numerous others at LGL and elsewhere have contributed data

and ideas to the development of the analysis described here. This analysis depends on data from most

preceding chapters, and I thank the authors of those chapters and others acknowledged in those chapters.

The project’s Scientific Review Board provided helpful comments on many aspects of this analysis.

Additional acknowledgements relevant to the project as a whole are included in Chapter 1.

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23. INTEGRATION AND CONCLUSIONS

Denis H. Thomson, William R. Koski, and W. John Richardson 1

Introduction

The purpose of the project, as defined by the Minerals Management Service, was to compile and

integrate existing traditional and scientific knowledge about the importance of the eastern Alaskan Beaufort Sea for feeding by bowhead whales; to build consensus on the need for and approach to fieldwork to

augment this knowledge; to conduct the field studies and to analyze the results; to integrate them with

existing traditional and scientific knowledge; and to report on and publish the results.

 The essential questions to be answered by the study were (1) what proportion of their annual food

requirements does the population of bowhead whales derive from the study area, and (2) how important is the

study area to individual bowhead whales that may linger in the study area. A multidisciplinary effort was

launched to answer the questions. Early in the project, as part of the planning process, interviews were

conducted with whaling captains and other knowledgeable individuals from Kaktovik to develop and

synthesize traditional knowledge of bowhead biology and use of the study area by bowhead whales. The field

studies included studies of zooplankton distribution and abundance, the nature of zooplankton near feeding

whales, the distribution and abundance of bowhead whales in the study area, their activities and specific

behaviors, and their rates of movement and residence times. In addition, the stomach contents of bowheads

harvested in the Beaufort Sea were analyzed to document the diet, and a pilot study of fatty acids in bowhead

blubber and bowhead prey was done to test the usefulness of that method in studying bowhead diet. Stable

isotopes in bowhead tissues and prey were studied to help assess what portion of the food for adult and

subadult bowheads is obtained in the eastern Beaufort Sea as a whole. Most field work for this specific project

was conducted in 1998, 1999, and 2000. Corresponding types of data collected during a similar study 1985

and 1986 were also used, thus providing data from five field seasons. In addition, data collected during 1979–

2000 during other studies in and adjacent to our study area were used as appropriate. This chapter attempts to

integrate information produced by each discipline to answer the key questions.

Study Area and Period

The study area for the 1985–86 project extended from eastern Camden Bay, just west of Kaktovik

(144°W), to the Alaska–Canada border as defined by the U.S., which intersects the coastline at 141°W (Fig.

23.1). The study area for the 1985–86 project extended from the coast offshore to the 200 m contour (intensive

effort) and beyond (aerial surveys only). Based on a data review, advice from Kaktovik whalers (see Chapter 2),

and advice from the project’s Scientific Review Board (SRB), the primary study area for the 1998–2000

fieldwork was extended west to the middle of Camden Bay (145°; Fig. 23.1). At this latitude, 1o of longitude

equals about 20 n.mi. or 37 km, so efforts extended about 37 km farther west in 1998–2000 than in 1985–86.

During the 1998–2000 study, boat-based zooplankton sampling was limited to areas from the shore to the 50 m

contour (vs. shore to 200 m contour in 1985–86). However, our standard aerial survey coverage in 1998–2000

extended to the 200 m contour. Less intensive aerial survey coverage was again obtained farther offshore by

ourselves and as part of the broad-scale aerial survey program conducted by MMS (Treacy 2000, 2002).

 

1

 LGL Ltd., environmental research associates, 22 Fisher St., POB 280, King City, Ont. L7B 1A6.

Phone: 905-833-1244. E-mail: dthomson@lgl.com
23-2 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

FIGURE 23.1. Map of the eastern Alaskan Beaufort Sea showing study area boundaries as defined for

different purposes. The heavy dotted line outlines the area to which whale-days estimates and energetic

calculations in Tables 23.8–23.11 apply. That area extends from Flaxman Isl. to the Alaska/Yukon border, and from the shore seaward to the 200 m contour.

Although our focus during fieldwork was on areas from 144oW (1988–86) or 145oW (1998–2000)

to the Alaska-Canada border, and from shore to the 200 m contour, relevant data of various types were

obtained from adjacent areas to the north, east, and west: (1) North – The one type of information

available from areas north of the 200 m contour was aerial survey information. (2) East – From the

outset, it was recognized that there could be times within our study periods when feeding bowhead whales

might be scarce or absent from the study area, but present just to the east in Canadian waters. Project

plans and permits included provision to observe bowheads and to sample their prey in Canadian waters as

far east as Herschel Island (139oW) when there were no opportunities to study feeding bowheads in the

“official” eastern-Alaskan study area. Aerial data (aerial surveys, behavioral observations, photography)

were sometimes obtained in Canadian waters, mainly in 1985–86, and zooplankton near feeding bowheads was studied there on two dates in 1986. (3) West – Aerial data, including aerial surveys, behavioral

observations and aerial photographs, were often available (mainly from other projects) as far west as

146oW (Flaxman Island), i.e., an additional 37 km farther west than the western boundary of the study

area as officially defined for 1998–2000.

Limits of data collected and used in each major part of this study, and the associated data collection

periods, are summarized in Table 23.1. The overall approach was to make use of relevant data from other

projects when appropriate, thereby expanding the available data temporally and spatially, and strengthening the conclusions that can be drawn. Analyses based on aerial data, including estimates of numbers of
§ 23. Integration & Conclusions 23-3

TABLE 23.1. Study area boundaries and timing of data collection for each type of data collected

during the bowhead feeding studies in 1985–86 and 1998–2000.

Study Area Boundaries

Types of Data West East North Sampling Dates

Zooplankton Distribution and Abundance Camden Bay Border 70°30’ 4 – 22 Sept

Zooplankton Near Feeding Whales Camden Bay Herschel Isl.a 70°20’ 4 – 22 Sept

Stomach Contents Camden Bay Pokok Bay 70°20’ 2 Sept – 11 Octb

Aerial Surveys (abundance, whale days) Flaxman Isl.c Borderd 71°10’ 1 Aug – 28 Octe

Aerial Photography Flaxman Isl. Herschel Isl. 70°30’ 16 Aug – 3 Oct

Aerial Observations of Behavior Flaxman Isl. Herschel Isl. 70°30’ 3 Sept – 6 Oct

Residence Times Flaxman Isl. Herschel Isl. 71°10’ 16 Aug – 6 Oct

a

 Only 2 whale feeding stations were east of border.

b

 Harvest dates of bowheads landed at Kaktovik in 1979–2000 whose stomachs were examined (Appendix 18.3).

c

 MMS-BWASP project provided data west to Flaxman Isl., 146oW. The feeding project per se provided aerial survey

data west to 144oW (1985–86) or 145oW (1998–2000).

d

 MMS-BWASP project provided survey data east to 140oW (37 km into Canada at coastline); the feeding project per

se provided data east to the border. Estimates of numbers of whales, and of whale-days, exclude data east of border.

e

 Date range is that for all aerial surveys, with the earliest and latest surveys being from the MMS-BWASP project.

The feeding project per se provided data from 4 to 27 Sept.

whales present, whale residence times, and behavioral analyses (see Chapters 9–14), were based on data

collected from 146oW east to Herschel Isl. (139oW). However, in analyzing the importance of the eastern

Alaskan Beaufort Sea to bowhead whales in this chapter, we have generally excluded the data obtained

east of the Alaska–Canada border. The analyses in this chapter consider the western edge of the study

area to be 146oW, i.e., near Flaxman Island (Fig. 23.1).

The selection of the study period for this project was discussed in Chapter 1. The primary field periods

for the feeding study per se were in September, during the time of peak occurrence of bowheads in the study

area. Some bowheads are in the area earlier and later in the season, and their occurrence has been documented

by aerial surveys (Chapter 9) and the observations of local residents (Chapter 2). We acknowledge that the

intensive feeding study work did not extend through the full period while bowhead whales are present in the

eastern Alaskan Beaufort Sea. However, it did occur during the time of peak utilization of that area by

bowhead whales. It would be interesting to have specific information about food availability and whale

feeding during the early and late parts of the late summer/autumn season. However, we believe that the

various sources of data, in combination, provide a reasonable basis for assessing the overall importance of the

study area for feeding in late summer and autumn. The available aerial survey data from August to October, as

well as local and traditional information, are of particular importance in understanding the general utilization

of the study area throughout the late summer and autumn period.

Questions

Questions were developed to address the study objectives and the study design was based on these

questions. These questions were worded as “hypotheses” at some stages in the project. However, a consensus

developed late in the project that they should be considered to be research questions that were addressed by the

project rather than formal hypotheses to be tested (see Chapter 1 and SRB report in Annex A).

The overall question to be addressed during this study was as follows:

Question (1). In an average year, how important is the eastern Alaskan Beaufort Sea for

bowhead whales; what percentage of the population’s annual energetic requirements is

derived from the area?
23-4 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

This overall question was addressed by considering many different types of data acquired or

assembled during the project (see Chapters 2 – 22), integrated by means of an energetic model (Chapter

22 and below). For each question, the project aimed to estimate a measure of study area utilization, rather

than simply determine whether utilization is above or below some specified threshold or cutpoint. However, for Questions 2 – 6, the cutpoints included in the (former) hypotheses were retained when the

hypotheses were reformulated as questions. We consider these cutpoints to represent levels of feeding

activity that, if exceeded, would indicate substantial feeding in the area. The following are the specific

questions:

Question (2). How much of its annual food requirements does the Bering–Chukchi–Beaufort

(BCB) population of bowhead whales derive in the eastern and central Beaufort Sea? At

least 10 percent?

Question (3a). Of the bowheads that travel through the eastern Alaskan Beaufort Sea, how

long does an average whale spend there? At least 7 days?

Question (3b). Of the individual bowheads that travel through the eastern Alaskan Beaufort

Sea, how long do some individuals spend there? At least 7 days?

Question (4). What percentage of the bowheads that pass through the eastern Alaskan

Beaufort Sea feed there? At least 10 percent?

Question (5). What percentage of the geographic area within the study area is suitable as

feeding habitat in different years? Is at least 1 % of the study area suitable in some years?

Question (6). During migration through the eastern Alaskan Beaufort Sea, how often are

bowheads observed to feed while they are traveling? Is feeding while traveling evident more

than 10 % of the time while traveling?

Background

The bowhead whale population occupying the Bering, Chukchi and Beaufort seas was estimated, as

of 1993, to contain about 8200 animals with upper and lower 95 % confidence intervals of 7200 to 9400

animals (Zeh et al. 1996; Ferrero et al. 2000). As of 1993, the population was believed to be increasing at

a rate of about 3.2 % per year (or possibly somewhat less—Punt and Butterworth 1999) despite annual

subsistence harvests of 14 to 74 bowheads from 1973 to 1996 (Suydam et al. 1995). If a 3.2 % rate of

increase has continued to the present day, the best estimate for the summer of 2000 would be about

10,223 animals. Preliminary results from the 2001 bowhead census, the first successful census since

1993, confirm that the current population is indeed near 10,000 whales and continuing to increase

(George et al. 2002). Thus, the population size in 2000 was probably lower than the pre-exploitation

population, which is estimated to have been 10,400–23,000 bowhead whales (Woodby and Botkin 1993).

The large increases in population estimates that occurred from the late 1970s to today are partly a result of

actual population growth, but are also (in substantial part) attributable to better census techniques (Zeh et

al. 1993). The bowhead population is currently listed as endangered under the Endangered Species Act

and is classified as a strategic stock by the National Marine Fisheries Service (Ferrero et al. 2000).

Bowhead whales of the Bering–Chukchi–Beaufort (BCB) stock winter in the central and western

Bering Sea and most of them summer in the Canadian Beaufort Sea and Amundsen Gulf (Moore and

Reeves 1993). Spring migration starts in late March and whales follow a prominent nearshore lead along

the eastern side of the Chukchi Sea northeastward to Point Barrow (Fig. 23.2). From there, they migrate
§ 23. Integration & Conclusions 23-5

FIGURE 23.2. Schematic depiction of the seasonal migration of the Bering–Chukchi–Beaufort stock of

bowhead whales, and locations mentioned in text. The “eastern Alaskan Beaufort Sea” is shaded.

through the Western Beaufort Sea through offshore ice leads, generally from mid-April to mid-June

(Braham et al. 1984; Moore and Reeves 1993). East of Point Barrow, the lead systems divide into numerous branches that vary from year-to-year in location and extent, but are typically located well offshore. In

the western part of the Alaskan Beaufort Sea, the route follows a corridor centered at about 71°30’N

latitude, and broadly occurring between latitudes 71°20’N and 71°45’N. Bowheads are not seen in spring

by Kaktovik residents (Chapter 2; Annex B). This report assumes that bowhead whales do not “utilize”

continental shelf portions of the eastern Alaskan Beaufort Sea during spring.

A few bowheads arrive in coastal areas of the eastern (Canadian) Beaufort Sea and Amundsen Gulf

in late May and June but most whales apparently remain in offshore waters (>200 m deep) among the

pack ice until mid-summer. Little is known about bowhead activities in early summer. In August of most

years, subadult whales move into nearshore and shelf waters (<100 m deep) along the Yukon coast and

Mackenzie Delta, and off the Tuktoyaktuk Peninsula. In some years, adults whales also move toward the

coast from offshore waters but adults normally remain in waters >40 m deep during summer.

After feeding in the Canadian Beaufort Sea and Amundsen Gulf, most bowheads begin migrating

west in late August to early October. Autumn migration into Alaskan waters is primarily during September and October and primarily through waters 15–100 m deep (Wartzok et al. 1989, 1990; Moore and

Reeves 1993; Miller et al. 1999; Mate et al. 2000; Treacy 2000). However, in some years local residents

see a few bowhead whales off Kaktovik in late July, and some bowheads occur near Kaktovik in August

(Chapters 2, 9; Annex B). In rare years, a few bowheads may occur almost as far west as Barrow during

mid-August (Moore 1992). It is not known if these early sightings represent early autumn migrants, or

whales that summered in Alaskan waters. It has been suggested that, as the BCB bowhead population has
23-6 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

recovered from commercial whaling, some bowheads may be summering in areas that they have not

occupied for many decades (i.e., the Alaskan Beaufort and Chukchi seas) and that autumn migration may

be starting earlier. Consistent with this, the Kaktovik and Nuiqsut whalers have stated that the earliestarriving bowheads reach the Kaktovik and Cross Island areas earlier in recent years than formerly

(Chapter 2; T. Napageak, pers. comm.). Most bowheads from the Beaufort Sea arrive in the northeastern

Chukchi Sea near Point Barrow in mid-September to early October (Moore and Reeves 1993). However,

some bowheads continue to migrate past Kaktovik as late as mid-October (Chapters 2, 9; Annex B).

Evidence from several sources suggests that bowheads travel generally west or southwest from

Point Barrow to the Russian coast off the Chukotsk Peninsula. Bowheads are known to feed in this area

(Moore et al. 1995) before migrating southeastward along the Chukotsk coast to the Bering Strait. The

latter migration continues through November (Moore and Reeves (1993). The peak of migration through

Bering Strait, at the southern extremity of the Chukchi Sea, is during the last 10 days of October and the

first 10 days of November. Bowheads are seen in the Bering Strait and coastal areas to the southwest

through November (Moore and Reeves 1993).

Feeding activities and associated behaviors of BCB bowhead whales have been described for

summer by Würsig et al. (1984, 1985, 1989) and Dorsey et al. (1989), and for late summer/early autumn

in Chapters 12–14 of this report. Three modes of feeding have been described: (1) During near-surface

feeding, bowheads move forward with mouths open at or just under the surface. Most often these whales

are alone but in some cases up to 14 whales have been observed feeding side-by-side in echelon formation. (2) Whales are assumed to be water-column feeding when they exhibit some or all of the following:

• dive and surface in the same general area for prolonged periods, • orient in variable directions from one

surfacing to the next, • remain stationary or move slowly at the surface between dives, and • dive steeply,

often with flukes out. (3) Whales are assumed to be bottom feeding when they come to the surface with

mud on parts of the body or with mud streaming behind them.

 Bowhead Feeding Areas Across the Arctic

Lee and Schell (Chapter 20) have analyzed carbon isotope ratios in bowhead muscle, baleen, and

fat, and in bowhead food organisms. Isotopic signatures in zooplankton from Bering and Chukchi waters,

which sometimes extend into the western Beaufort Sea, are similar and cannot be differentiated. Zooplankton from the eastern Beaufort Sea has an isotopic signature quite distinct from that in Bering/Chukchi zooplankton. Lee and Schell compared isotopic signatures in bowhead tissues vs. zooplankton. From

this comparison, they estimate that 10 to 26 % of the annual feeding activity was in the eastern and central

Beaufort Sea waters, roughly east of Prudhoe Bay (Chapter 20). The 10 to 26 % range of estimates

reflects different methods of calculation, and all of those estimates are uncertain given the assumptions,

variability in the data, etc. [One set of data, those of Hoekstra et al. (2002), suggest that the percentage

could be on the order of 37–45 %, but some of the data used to derive those percentages are inconsistent

with replicated measurements obtained by Lee and Schell from the same individual whales (Chapter 20).]

There was an indication, both from muscle and baleen, that subadult bowheads may feed somewhat more

than adults in the eastern Beaufort Sea. Evidence discussed in Chapter 20 and below suggests that the

Bering/Chukchi signature in bowhead isotope ratios is mainly derived from feeding in mid- to late fall in

the Chukchi Sea and probably also, to some extent, the western Beaufort Sea and northern Bering Sea.

The low estimates of summer feeding, as evident from the isotope data of Lee and Schell (Chapter

20), are difficult to reconcile with other data: behavioral observations showing frequent feeding in the

eastern Beaufort Sea during summer and early autumn, frequent occurrence of food in stomachs of bow-
§ 23. Integration & Conclusions 23-7

heads harvested in the Alaskan Beaufort during late summer and autumn, and increases in girth and

energy content over the summer. However, as noted in Chapters 20–22 and below, those data on summer/early fall feeding do not specifically show what fraction of the annual feeding occurs in the eastern

and central Beaufort Sea. No comparable data on feeding, girth, or energy content have been obtained

during and after the whales feed in the Chukchi Sea in mid- to late fall. Perhaps more feeding and energy

accumulation occurs there in fall than in the Beaufort Sea in summer. If so, the evidence of feeding in the

Beaufort might be reconcilable with the strong Bering/Chukchi isotope signature in bowhead tissues.

Distributional and Behavioral Observations

Direct observations of bowhead behavior show that bowheads spend most of their time (~73 %)

feeding while summering in the Canadian Beaufort Sea and Amundsen Gulf, and somewhat less time

feeding (~47 %) when in the eastern Alaskan Beaufort Sea during late summer and early autumn. There

are no quantitative data concerning bowhead activities in the Chukchi Sea during autumn, where feeding

is known to occur, or in the Bering Sea in winter, where bowhead activities are undocumented. In spring,

the percentage of time spent feeding is low, at least in the area northeast of Barrow (see Chapter 12).

Feeding in various parts of the annual range is discussed further in the paragraphs that follow.

Canadian Beaufort Sea and Amundsen Gulf.—Feeding areas and activities of bowhead whales

have been relatively well documented for late July through mid-September, but have not been studied for

June and most of July. Also, the majority of the information for late July to mid-September concerns

subadult bowheads, with the distribution of adults being less well known. Feeding ecology of bowhead

whales in the Canadian Beaufort Sea has been studied by Bradstreet et al. (1987) and others, using some

of the same techniques applied in the present eastern Alaskan study.

The area most consistently used for feeding by small subadult whales (<10 m long), during August

and September, was the waters <50 m deep along the Yukon coast from Herschel Island to Shingle Point

(Koski et al. 1988). In some years, small subadult bowheads were also found along the Yukon coast in

shallow waters west of Herschel Island (Davis et al. 1986a) and in shallow waters off the Mackenzie

Delta and Tuktoyaktuk Peninsula (Renaud and Davis 1981). Large subadult whales were found in and

adjacent to the areas used by small subadults, but they generally were found slightly farther offshore and

in slightly deeper water than small subadults. In many years, large subadult bowheads were common in

shelf waters east, northeast and north of Herschel Island where steep gradients cause upwelling.

Adult bowheads generally were found in shelf and offshore waters from 126° to 133°W during late

July to early September. Of the known feeding areas for adults, the most commonly used are in the easternmost part of the Canadian Beaufort Sea: shelf waters northwest of Cape Bathurst, and shelf and shelf

break waters east of the Bathurst Peninsula as far south as southern Franklin Bay (Harwood and Borstad

1985; Davis et al. 1983, 1986a,b; Duval 1986; Ford et al. 1987). Adult bowheads were rarely found feeding in shelf or offshore waters north or west of Tuktoyaktuk (~133°W) before late August (Koski et al.

1988). However, during their westward migration, which starts in late August and continues through

September, many adult bowheads moved through shelf waters and some interrupted migration to feed.

1982 was an exception, and moderate numbers of adult whales were seen and photographed throughout

August in shelf waters northeast of Herschel Island and near the 200 m depth contour north of Shingle

Point (Davis et al. 1983). In general, knowledge of the summer distribution of adults is incomplete, and

there may be additional areas that are important for feeding by adults in summer.

Eastern Alaskan Beaufort Sea.—Bowhead whales have been seen feeding at several locations

from the Alaska–Yukon border to Camden Bay. In 1985 and 1986, small subadult whales were seen
23-8 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

feeding in shallow nearshore waters near and west of Demarcation Bay. In 1998, small and large

subadults were feeding as they traveled in shelf waters north and west of Kaktovik. In 1999, adult and

some large subadult bowheads fed in shelf waters from north of Demarcation Bay to just east of Kaktovik. In 2000, bowheads moved through the study area rapidly and little feeding was observed. Thus the

size classes of whales feeding in the eastern Alaskan Beaufort Sea, the areas used for feeding, and the

amount of feeding all varied among years. Despite this variation in use of the study area among the five

field seasons of this study, the areas used agree with data from other sources as to the types of areas that

tend to be important for feeding bowhead whales. Use of shelf and nearshore waters near Demarcation

Bay and Icy Reef by feeding bowheads has also been documented in other years, including 1982 and

1984 (Johnson 1984; Davis et al. 1986a; see also Chapter 2). Nearshore and shelf waters near Kaktovik

and in Camden Bay, e.g., near Arey Island, have also been reported to be important to bowheads during

other years (Moore et al. 1989; Chapter 2).

Western Beaufort Sea.—Moore and Clarke (1993) and Moore and Reeves (1993) have documented that bowheads are more abundant in the area east of Point Barrow during late summer and autumn

than they are in other parts of the Alaskan Beaufort Sea, apparently including our study area. Of the bowheads harvested near Barrow in fall, 75 % were categorized as “feeding” based on the food found in their

stomachs (Chapter 18). Other studies have documented feeding near Point Barrow during autumn of

different years (Braham et al. 1984; Ljungblad et al. 1986; Landino et al. 1994; Treacy 1998, in prep.),

further suggesting that the area is used frequently by feeding bowheads. Bowhead whales occasionally

have been seen feeding in other areas in the western Beaufort Sea (Miller et al. 1998; Treacy 1998, in

prep.), and the few stomach contents samples from the Cross Island area (near Prudhoe Bay) suggest that

feeding may be common near there. However, feeding has been seen more frequently in the area just east

of Point Barrow than in parts of the Alaskan Beaufort Sea from western Harrison Bay eastward (Treacy in

prep.). There has been no specific study of bowhead feeding ecology in the area just east of Barrow.

Chukchi Sea.—The routes and timing of migration through the Chukchi Sea, the amount of feeding

that occurs there, and the nature of that feeding, are not as well documented as for the Beaufort Sea. Most

bowheads of the BCB stock arrive in the northeast Chukchi Sea in late September to mid-October (Moore and

Reeves 1993). Aerial surveys indicate that most bowheads travel west and southwest through this area,

moving toward Russia (Moore and Clarke 1992, 1993). During extensive cruises in the central and western

Chukchi Sea during late September and early October 1992–93, few bowheads were seen except off the

Chukotsk Peninsula south and southeast of Wrangel Island. Some feeding occurs there (Moore et al. 1995).

The southwest Chukchi Sea is highly productive, and it is probable that dense concentrations of zooplankton

are available to bowhead whales in that area during late autumn (Chapter 20; see also Niebauer and Schell

1993). From there, bowheads follow the Chukotsk Peninsula southeast to the Bering Strait. 

The timing of the passage through the Bering Strait in autumn is variable and not well documented.

Some bowheads arrive at the Bering Strait as early as 20-21 September (Moore et al. 1995) and others as late

as late November (Moore and Reeves 1993). Most bowheads leave the Chukchi Sea through the Bering Strait

during 21 October to 10 November (Moore and Reeves 1993). Given that most bowheads arrive in the

northeast Chukchi Sea near Point Barrow in mid-September to early October (Moore and Reeves 1993),

an average bowhead may spend about a month in the Chukchi Sea. Some may be there for considerably

longer. Thereafter bowheads are found in the Bering Strait and coastal areas to the southwest through

November (Moore and Reeves 1993). The waters of the Bering Strait and coastal areas to the southwest

contain a high biomass of zooplankton through November (Coyle et al. 1996).
§ 23. Integration & Conclusions 23-9

Seasonal Time Budgets

As noted above, direct observations of bowhead behavior show that bowheads spend an estimated

73 % of their time feeding while summering in the Canadian Beaufort Sea and Amundsen Gulf (Table 23.2;

Chapter 12). The time spent feeding decreases to about 47 % for bowheads in the eastern Alaskan Beaufort

Sea during late summer and early autumn. There are no quantitative data concerning bowhead activities in

the Chukchi Sea during autumn, where feeding is known to occur. There are no data on activities in the

productive northern Bering Sea in late fall, or in the Bering Sea in winter. In spring, the percentage of time

spent feeding has been determined in only one area, just northeast of Barrow (see Chapter 12).

For purposes of energetic and related calculations, there was a need for estimates of the amount of

time that might be spent feeding in each season, including seasons for which quantitative data are lacking.

Chapter 22 describes our basis for estimating the percent of time that might be spent feeding during late

fall in the Chukchi Sea, Bering Strait, and northwestern Bering Sea; during winter in the Bering Sea; and

during spring migration. The results are summarized in Table 23.2.

TABLE 23.2. Observed or assumed proportion of time when bowhead whales are engaged in various activities during different seasons (from Chapters 12 and 22).

Observed or Assumed Percent of Time

Activity Springa Summerb

Fall

Beaufortb

Fall

Chukchic Winterd

Travel 75 7 31 7 7

Feed 8 73 47 73 0

Social 7 15 17 15 0

Other/Unknown 10 5 5 5 93

No. of Obs. Sessions (54) (85) (80)

a

 From field observations summarized in Chapter 12, but with % time feeding adjusted upward

(from observed 1 %) based on a speculative assessment of stomach contents (see Chapter 22).

b

 From field observations summarized in Chapter 12.

c

 Includes Bering Strait and coastal NW Bering Sea as well as southwest Chukchi Sea; activities

in fall in these areas are assumed to be similar to those in summer in the eastern Beaufort.

d

 No data for winter; assumed to be negligible feeding. Travel assumed to be as in summer.

Stomach Contents

Most bowheads harvested during their autumn migration across the Alaskan Beaufort Sea, and

some of those harvested during spring migration near Barrow, have food in their stomachs (Chapter 18).

In this study, all whales recorded as having at least 10 prey items or 1 L of prey in their stomachs were

classified as feeding. There is a large difference between a stomach with that small amount of prey and

one that is full. The frequency and amount of food present are not necessarily direct measures of feeding

intensity. However, food is present in a higher proportion of the whales taken at Kaktovik and Barrow in

fall than of those taken at Barrow in spring. Also, the amount of food in the stomachs tends to be higher

in fall. Only a few stomach content data are available from Cross Island (near Prudhoe Bay), but those

few data suggest that feeding is also common there in fall.

Weight Loss in Winter/Gain in Summer

Inupiat on the North Slope have noticed that bowheads caught in spring and fall taste different, and

one hunter mentioned that they are fatter in fall (Chapter 2; Kisautaq 1981:296). Similarly, three indepen-
23-10 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

dent studies provide evidence that bowhead whales lose weight in winter and gain weight in summer/early

autumn (see Chapter 22 for details). By winter, we mean the interval between departure from the Beaufort

Sea in fall and return to the Beaufort Sea in spring: (1) J.C. George (pers. comm.2

) measured whales

harvested near Barrow and found that the girths of subadult bowheads were larger in autumn than in spring.

He determined that subadult bowheads were significantly heavier in autumn than in spring, but found little

seasonal difference in weights of large adults. George (pers. comm.2

) found no change in the thickness of

blubber between autumn and spring harvested animals. (2) Lipid content in the blubber of subadults

harvested in fall was about 80 % (T. Mau pers. comm.3

). In spring, lipid content of the inner 20 % of the

blubber in subadults was about 70 %; lipid content in the next 20 % of the blubber was 70–80 %. Lipid

content in the outer 60 % of the blubber layer was similar in spring and autumn. (3) Thomson (Chapter 22),

based on length and girth measurements from aerial photographs of bowheads, showed that bowheads gained weight during summer in the Beaufort Sea, and lost weight in winter. Thomson’s equations predict that a

bowhead whale 9 m long would gain ~2 MT over the summer. A 16–m whale would gain ~4 MT.

One probable reason for the difference between results of George vs. Thomson for adult bowheads

is that George used a constant value to account for stretching of animals (based on a sample size of 3) that

were hauled up prior to measurement. More measurements of stretching of animals hauled up onto ice

(spring) and land (fall) are needed to quantify stretching in relation to length, weight, and substrate. However, it is notable that George’s results are consistent with indications, from isotope techniques, that adults

feed less than subadults during summer in the Beaufort Sea (cf. Chapter 20).

Weight loss in winter was probably greater than apparent from the girth measurements by George

and Thomson. Their data concern the difference between the girths before or as bowheads leave the

Beaufort in autumn as compared with girths when bowheads enter the Beaufort in spring. Bowheads presumably gain additional girth and weight during late-autumn feeding in the southwest Chukchi Sea, and

possibly also in the coastal northern Bering Sea, after the time when the “fall” measurements quoted

above were taken. Thus, weight loss from the time of peak weight in late fall (in the southwest Chukchi

or northern Bering) until spring presumably exceeds that measured by George and Thomson.

Potential Prey Consumption in Summer and Autumn

Griffiths et al. (Chapter 6) found an average zooplankton biomass of 1.8 g/m3 near bowheads feeding in the Canadian Beaufort Sea and eastern Alaskan Beaufort Sea during summer and early autumn.

From this, Thomson (Chapter 22) estimated that a 12.5 m bowhead whale, traveling at 2.5 km/h while

feeding, could consume 244 kg wet-weight during 24 h of continuous feeding at locations and depths with

average zooplankton biomass 1.8 g/m3

 wet weight. This estimate of plankton available to bowhead

whales at feeding locations in the eastern and central Beaufort Sea (1.8 g/m3

) may only apply to subadult

animals because sampling of prey availability was conducted only near subadults (Chapter 6). If the estimate of 244 kg/d is multiplied by the assumed number of effective days of continuous feeding per season

(see Table 22.14), adjusted for seasonal variations in lipid content of zooplankton, and then divided by

365 d, a 12.5 m bowhead could consume an average of 1.3 x 105 kJ/d. This represents only ~30 % of

annual requirements as estimated though consideration of theoretical energetic requirements (Chapter 22).

 

2 Data provided by J.C. George from a work in progress are not to be cited without written permission of Craig

George, Department of Wildlife Management, North Slope Borough, Barrow, AK. cgeorge@co.north-slope.ak.us

3

 Data provided by T. Mau from a work in progress are not to be cited without written permission of Tamara Mau,

University of Alaska Fairbanks, Institute of Marine Science, 245 O'Neill Bldg., Fairbanks, AK 99775-7220,

tmau@ims.uaf.edu
§ 23. Integration & Conclusions 23-11

To meet estimated energetic requirements, subadults and adult males would need to feed on average concentrations of 4 g/m3

 at an average speed of 5 km/h. A speed of 5 km/h is possible, but is at the upper end

of the range of speeds observed during feeding in the eastern Beaufort Sea (Chapter 22; Table 22.10).

Zooplankton concentrations of 4 g/m3

 are also at the upper end of the concentrations found near feeding

whales in the eastern Beaufort Sea (Chapter 6).

We may have underestimated prey availability in the Beaufort Sea. Sampling was conducted near

feeding bowheads, but not necessarily in the exact locations where bowheads were feeding. Bowheads

are probably adept at finding highly concentrated food patches within areas with a higher than average

biomass of zooplankton. Right whales occasionally feed on very dense patches of zooplankton that could

supply, in a fairly short time, much of the annual energetic requirement (Beardsley et al. 1996). Bowheads may also feed in extremely dense patches of zooplankton that could meet a high percentage of

annual requirements. We probably did not sample in the densest patches of prey available in the eastern

Beaufort Sea, and we probably underestimated the biomass available in some patches where we did sample. However, underestimation of prey availability in the Beaufort cannot explain the strong Bering/

Chukchi isotope signature in bowhead tissue. That requires intensive feeding in Bering/Chukchi waters.

Perhaps bowheads feeding in the western Beaufort and southwest Chukchi/northern Bering Sea in autumn

have access to zooplankton with average biomass well above 1.8 g/m3

, thus increasing average prey availability at all feeding sites used during the year to >1.8 g/m3

 wet weight. This could account for both (1)

the thriving bowhead population despite the apparent inability to ingest sufficient food if average prey

availability were only 1.8 g/m3

, and (2) the strong Bering/Chukchi signature in bowhead tissue.

An Interpretation of the Isotope Data

If the types of evidence described above are accepted as reliable, then the one feeding scenario that

could (perhaps) be consistent with all the data is as follows: Feeding occurs commonly in the eastern

Beaufort Sea in summer and early autumn. Bowheads gain energy stores and their girth increases from

feeding in that area. However, zooplankton availability is not as high in the Beaufort Sea during summer

as in the Chukchi Sea and nearshore northern Bering Sea during autumn, given the much higher productivity of the Bering/Chukchi system. Also, feeding in the western Beaufort in autumn may effectively be

on Chukchi prey advected into the western Beaufort (Chapter 20; see also Niebauer and Schell 1993).

Thus, bowheads might acquire more energy from Bering/Chukchi prey in autumn than from eastern and

central Beaufort prey in summer/early autumn. Given this, plus an assumed low turnover rate of body

components, their overall body composition may be dominated by carbon (and other components) from

the Bering/Chukchi system even at the end of the summer when leaving the Beaufort. Energy gained in

the Beaufort and Chukchi seas during summer and fall, and possibly the northern Bering Sea during late

fall, is presumably used during winter when food availability is low. This would result in reduced girth

and energy stores when returning to the Beaufort Sea in spring than when leaving the Beaufort in autumn.

The above scenario is unlikely to be fully or immediately accepted by proponents of either the

“traditional” view, i.e., that most feeding is in the Beaufort, or the isotope-based view, i.e., that most

feeding is on prey from the Bering/Chukchi system. However, we are not aware of any other hypothesis

that is not directly contradicted by some key type of data.

Percentage of Diet from Eastern and Central Beaufort Sea

The first of the key questions identified in Chapter 1 concerned the importance of food from the

eastern Alaskan Beaufort Sea to the bowhead population. That is the central question to be addressed in
23-12 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

this study. Question (1) is addressed near the end of this chapter, after the more specific questions have

been discussed.

The second of the questions identified in Chapter 1, and repeated above, was as follows:

Question (2). How much of its annual food requirements does the Bering–Chukchi–Beaufort

(BCB) population of bowhead whales derive in the eastern and central Beaufort Sea? At

least 10 percent?

Note that this question pertains to the eastern and central Beaufort Sea as a whole, not just the eastern

Alaskan Beaufort Sea.

Chapter 20 provides various isotope-based estimates. The specific value depends on which group

of whales is being considered, assumptions about the isotopic composition of their prey, and the tissue

being considered (muscle, blubber, visceral fat). The most comprehensive data are available for muscle.

When whales sampled in spring and fall of the same years are considered, estimates of the food acquired

in the eastern Beaufort Sea range from 17 to 26 % of the annual total, with one outlying value of 37–45 %

derived from the data of Hoekstra et al. (2002). When whales sampled in both the 1980s and the 1990s

are considered, with allowance for a long-term trend in the isotope composition of prey in the Bering/

Chukchi system, the overall estimate is 10 % with a 95 % confidence interval of 0 % to 23 % (see Appendix 20.1 in Chapter 20). Based on the data from both the 1980s and the 1990s, the overall estimate for

subadults is 14 % with 95 % confidence interval of 4 % to 23 %. The corresponding estimate for adults

was 5 % with 95 % confidence interval of 0 % to 30 %. The greater uncertainty in the adult estimate is

associated with lower sample size and other limitations of the data for adults.

Thus, based on isotope evidence, it is likely that subadults derive >10 % of annual food requirements in the eastern and central Beaufort Sea, although the 95 % confidence interval extends below 10 %.

The best estimate for adults is below 10 %, but the data are very uncertain and the 95 % confidence

interval extends well above 10 %. Behavioral observations and stomach contents of whales harvested at

Kaktovik indicate that adults as well as subadults spend much of their time feeding in summer while in

the eastern and central Beaufort Sea. Adults either gain weight or at least maintain weight between the

time they enter the Beaufort Sea in spring and the time they depart in autumn (see above). If adults

derived 10 % or less of their food in the Beaufort Sea, they would lose weight over the summer, which is

not the case. Therefore, adults as well as subadults probably gain >10 % of their food in the eastern

Beaufort Sea. However, for adults, the isotope evidence alone would support an answer of <10 %. Further investigation is needed to resolve this uncertainty, and broader concerns as to whether the percentage

of food acquired in the eastern Beaufort is actually as low as these isotope data suggest. To summarize

the conclusions with respect to Question (2),

Answer (2): Based on stable-isotope evidence, bowhead whales likely consume only 10 to

26 % of their food in the eastern and central Beaufort Sea. Subadult bowheads appear to

derive >10 % of annual food requirements there, although the 95 % confidence interval

extends below 10 %. It is also probable that adults gain >10 % of their food in that area, but

for adults the isotope evidence considered in isolation would support an answer of <10 %.

Local and traditional knowledge (LTK) at Kaktovik does not specifically address the amount of

feeding in the eastern and central Beaufort Sea as a whole. However, Kaktovik residents consider that

overall region to be an important feeding area for bowhead whales. They, along with most biologists who

have studied bowheads in the eastern and central Beaufort Sea, would expect the area to provide a

substantially higher proportion of the total annual food requirements than is evident from the isotope data.
§ 23. Integration & Conclusions 23-13

Amount of Time that Bowheads Spend in the Study Area

The third question was in two parts, to address the fact that there are distinct questions about the

importance of the study area to certain individual whales vs. the population as a whole:

Question (3a). Of the bowheads that travel through the eastern Alaskan Beaufort Sea, how

long does an average whale spend there? At least 7 days?

Question (3b). Of the individual bowheads that travel through the eastern Alaskan Beaufort

Sea, how long do some individuals spend there? At least 7 days?

Data on residence times (Chapter 11) can be used to address these questions.

Population as a Whole

Many of the BCB bowhead whales pass through the eastern Alaskan study area during their

autumn migration to over-wintering areas. (A minority of the population migrates west through offshore

waters north of the study area.) Koski et al. (Chapter 11) used various methods and sources of data to

estimate the residence times of bowheads in a study area from Flaxman to Herschel islands (146oW to

139oW, Fig. 23.1). This area is about 1.32 times wider than the specific study area of relevance to MMS,

i.e., from Flaxman Island to the Alaska-Yukon border. Thus the residence times estimated in Chapter 11

and summarized in Table 23.3 should be divided by 1.32 to estimate the time spent in the area from

Flaxman Island to the border. It is acknowledged that this approach is an approximation. It assumes that

the rate of travel across the excluded area (border–to–Herschel Isl.) is similar to that across the area

relevant here (Flaxman Isl.–to–border). If there is any difference in these rates, it is probable that whales

have more tendency to linger in the “border–to–Herschel” area, which is an area where some bowheads

are known to linger during late summer of some years. Thus, average residence times in the “Flaxman–

to–border” area may be somewhat lower than estimated by the “divide by 1.32” procedure.

The “best estimates” of residence time derived in Chapter 11 for the “Flaxman–to–Herschel” area

and summarized in Table 23.3 appear to be those based on • intervals between photographic resightings,

• “stop-over duration analysis” (SODA) using best-fit models, • aerial survey estimates of whale-days in

the study area, and • telemetry. The various methods that were used have differing biases, and some procedures are clearly more reliable than others. This is discussed by Koski et al. in Chapter 11. Estimates

of residence time based on speeds as evident from behavioral observations, photogrammetry, or telemetry

are highly variable. This variability probably arises from variable activities of the whales among years or

among parts of the study area, difficulties in obtaining unbiased estimates of the proportion of the whales

engaged in these activities over the study area as a whole in each year, and (sometimes) low sample sizes

(Chapter 11). The variability is assessed in Appendix 23.1 taking account of the mean and standard error

of each estimate for each year. The procedure and results are described in Appendix 23.1, and the resulting confidence limits are listed in Table 23.3.

Considering various specific years and methods of calculation, the mean residence times for the

“Flaxman–to–Herschel” area vary from 1 day, an implausibly low value based on the interval between

photographic resightings in 1998; to 16 days, based on aerial survey whale-days in 1999. Average annual

estimates varied from 2 to 8 d, or 3 to 8 d if the aforementioned implausible value is excluded, and

averaged 5 d (Table 23.3). The corresponding annual figures for the “Flaxman–to–border” area would be

2.5 to 6.3 d (avg 4 d), based on the “divide by 1.32” method. A steadily traveling whale would take 2.4 d

to travel from the Alaska/Yukon border to Flaxman Isl., based on the 3.67 km/h net westward speed
23-14 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

TABLE 23.3. Summary of estimates of mean residence times of bowhead whales in the “Flaxman Island

to Herschel Island” area during late summer and autumn, by year (1985–2000). For approximate

estimates of average residence times in the “Flaxman Island to Alaska/Canada border” area, divide all

values by 1.32. All values except confidence limits are from Table 11.6. Estimates considered to be

unreliable are not included. See Chapter 11 for explanation, qualifications, and discussion of reliability.

Derivation of confidence limits by Dr. B.F.J. Manly (WEST Inc.) is described in Appendix 23.1.

Year

Method 1985 1986 1988 1989 1992 1998 1999 2000 All

Photos: Intervals Between Resightings 8.13 4.18 1.00 4.10 -

Photos: Intervals Between Resightings + Travel 11.24 7.12 3.38 6.90 3.07

Photos: Stop-over Duration, Best Fit 5.30 3.81 - 4.36 -

Behavior: Overall Speeds 4.42 7.35 9.38 3.87

Aerial Survey: Whale Days 3.03 4.40 0.84 5.31 16.62 2.96

Telemetry Dataa 3.40 4.38 6.45

Mean 6.92 4.79 2.12 4.38 6.45 4.26 8.27 3.30 5.06

Lower 95 % confidence limit 4.64 3.25 0.75 2.52 4.60 2.86 5.68 2.57 4.22

Upper 95% confidence limit 10.32 7.06 5.99 7.61 9.04 6.34 12.05 5.78 6.07

a Telemetry data from Wartzok et al. (1989, 1990); Mate et al. (2000)

documented for traveling bowheads by Koski et al. (Chapter 11). Thus, in years with minimum residence

times, such as 2000, it appears that most if not all whales traveled steadily across the study area without

lingering to feed or for other purposes. 

No useful telemetry data, either radio- or satellite-linked, were obtained during the present project,

but relevant telemetry data were obtained in three years by other investigators. In 1988, a radio-tagged

whale apparently traversed the study area without lingering (Wartzok et al. 1989). In 1989, Wartzok et al.

(1990) tracked four subadult whales (9.5–12.5 m in length) through our study area during the 21–29 September period. The estimated average residence time of these whales in the “Flaxman–to–Herschel” area,

based on locations at intervals of 1–5 days, was 4.4 days. This would represent an average of ~3.3 d in

the “Flaxman–to–border” area. Mate et al. (2000) deployed satellite-linked transmitters on 12 bowhead

whales in the Canadian Beaufort Sea during early September 1992. Five of these whales were tracked in

the present study area. Minimum residence times in the “Flaxman–to–Herschel” area during the late summer/autumn period was 6.45 d, or ~4.9 d in the “Flaxman–to–border” area. The mean residence times of

all the radio-tagged whales in the respective two regions were ~4.7 d and ~3.6 d, similar to the mean

residence times of 5.1 d or 3.8 d calculated from all data.

For the overall population, the mean residence time in the “Flaxman–to–Herschel” area was 5 days

(± 95 % CI 4.2 – 6.1), based on the mean of six approaches over all 8 years with data (Table 23.3). The

means for the 8 individual years ranged from 2.1 to 8.3 d with the upper 95 % confidence limit ranging

from 5.8 to 12.1 d. For the “Flaxman–to–border” area, the overall mean was ~3.8 d, with means for the

individual years ranging from 2.5 to 6.3 d, assuming that the “divide by 1.32” method is appropriate. On

this basis, the mean residence time in the “Flaxman–to–border” area did not exceed 7 days in any of the 8

years considered. The 95 % confidence bounds have not been calculated explicitly for the reduced estimates

of residence time in the “Flaxman–to–border” area. However, when divided by 1.32, the upper confidence

bound exceeded 7 d in two years: 1985 and 1999. Thus, although the estimated mean residence time in the

“Flaxman–to–border” area averaged less than 7 days in each of the 8 years considered, it is possible that it

might exceed 7 days in a small minority of the years.
§ 23. Integration & Conclusions 23-15

Individual Bowheads

Question (3b), above, dealt with the residence times of individual bowheads. As shown above, an

average BCB bowhead spends ~5.1 d in the “Flaxman–to–Herschel” area, or ~3.8 d in the “Flaxman–to–

border” area, during late summer and autumn. However, in 1999 the average whale spent 8.3 d and 6.3 d

in those areas. For the “Flaxman–to–border” area, the upper confidence bound probably exceeded 7 d in

2 of the 8 years. In addition, photographic resighting data show that some individual bowheads spent

substantially more than 7 d in the “Flaxman–to–Herschel” study area (Table 23.4). The maximum

recorded residence time in that area was 16 days, and there were 5 records of residence times ≥10 d. This

suggests that some whales were likely to spend more than 7 d in the smaller “Flaxman–to–border” area,

as one would expect with a mean of ~6.3 d in one year (1999).

Summary re Residence Times

Answer (3a): An average bowhead spends ~3.8 days in the area from Flaxman Island to the

Alaska/Canada border during the late summer/autumn period, or ~1.4 d longer than expected

for a whale that swims steadily across that area. Averages in various years ranged from ~2.5

to 6.3 d. Although the average was <7 d in all years studied, it might exceed 7 days in a

small minority of the years, based on the calculated upper 95 % confidence bounds.

Answer (3b): Of the individual bowheads that travel through the eastern Alaskan Beaufort

Sea, some spend at least 7 days between Flaxman Island and the Alaska/Canada border during late summer and autumn.

These conclusions are based on analysis of photoidentification data collected from mid-August to early

October, including much (but not all) of the late summer/autumn migration period of bowhead whales through

the central Beaufort Sea. The results have been scaled to estimate residence times in the “Flaxman–to–border”

area, but they are actually based on data collected in the larger “Flaxman–to–Herschel” zone. Some bowheads

are known to linger in the “border–to–Herschel” zone. Therefore, the estimates for the “Flaxman–to–border”

area, of primary interest in this study, are more likely to be overestimates than to be underestimates.

Observations by local residents are generally consistent with these conclusions. However, their

observations do not provide specific evidence on these questions because bowhead whales generally are

not individually recognizable to observers in a small boat or on shore. Kaktovik residents sometimes see

bowheads in a given area for 1–2 weeks or more (Chapter 2 and Annex B). One such area is between Icy

Reef and Demarcation Bay, within the southeast part of the “Flaxman-to-border” area. However, it is

uncertain from the hunters’ observations whether the same individual whales remain for that long. One

hunter indicated that bowheads tend to remain longer when the water is open than when ice is present.

Feeding in the Study Area

Two of the questions listed in Chapter 1 and repeated above concerned the frequency of feeding in

the eastern Alaskan study area:

Question (4). What percentage of the bowheads that pass through the eastern Alaskan

Beaufort Sea feed there? At least 10 percent?

Question (6). During migration through the eastern Alaskan Beaufort Sea, how often are

bowheads observed to feed while they are traveling? Is feeding while traveling evident more

than 10 % of the time while traveling?
TABLE 23.4. Within-year resighting intervals of bowhead whales in the ”Flaxman Isl. to Herschel Isl.” area of the Beauf

early autumn of 1985-2000 (from Chapter 11). Photographs were not taken on each day; therefore resighting interv

probability of being recorded even if individual whales remained in the survey area. Only the first and last sighting of eac

included. Zone Unique Whales Year Photographed 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 

 "Flaxman Isl. to Herschel Isl." b 1985 177 33 0 1 2 0 1 0 0 0 0 0 2 0 0 1 0 1 - 0 - - 

1986 267 31 4 3 0 1 0 0 0 0 2 0 0 0 0 1 0 0 0 0 0 0 1998 141 9 100000-0 Xc X X X X X X X X X X X 

1999 397 21 2 1 1 2 1 2 0 0 1 0 0 0 0 0 0 0 0 0 0 0 2000 33 9 00000000 XXXXXXXXXXXXAll years Average of means for "Eastern Alaska" in each year 

a Span includes both the first and last days with photographs in the area. Maximum resighting interval is one day less than the spab Includes Yukon west of Herschel Island (Fig. 11.1).

c "X" indicates that resighting intervals of this length would have been beyond the span of the study. 

Span of Number of Resightings at Interval 1-21 days

Study (d)a
23. Integration & Conclusions 23-17

Numbers of Whales that Feed

On average, bowhead whales spent 3.8 days in the “Flaxman-to-border” area during late summer

and autumn in the eight years listed in Table 23.3, based on the ÷1.32 factor previously discussed. On

average, these whales spent 47 % of their time feeding (Table 23.2). Estimates of “proportion of time

feeding” for each of the five years of the study are shown in Table 23.5. In 4 of 5 years, bowheads fed for

≥38 % of their time in the study area during late summer/autumn (Table 23.5). A considerable proportion

of the observed feeding was simultaneous with travel. Of 581 surfacings involving feeding, 158 (27 %)

also involved travel. Also, of 369 surfacings by traveling whales, 158 (43 %) also involved feeding (from

Table 12.3A in Chapter 12).

TABLE 23.5. Proportion of the time spent feeding during each year of the study, based on behavioral observations (Chapter 12).

1985 1986 1998 1999 2000 Overall

Proportion of time feeding 0.39 0.58 0.38 0.66 0.09 0.47

Of the 29 whales harvested at Kaktovik and characterized as either feeding or not feeding based on

stomach contents, 24 of 29 (83 %) were classified as feeding, including 7 of 9 adults and 17 of 20 subadults (Chapter 18). Of the 18 whales landed at Kaktovik for which volume of stomach contents was

noted, eight (39 %) had ≥20 L of stomach contents (Table 18.5).

Answer (4): Based on stomach content data, supplemented by behavioral evidence, far more

than 10 % of the bowheads that pass through the eastern Alaskan Beaufort Sea during late

summer and autumn feed there. Of the whales harvested at Kaktovik, 83 % had food in their

stomachs, and 39 % had ≥20 L of stomach contents.

Answer (6): Bowheads fed for an average of 47 % of their time in the eastern Alaskan

Beaufort Sea during late summer and autumn. A substantial minority of the feeding occurred during travel. Among traveling whales, feeding as well as travel was occurring during a

substantial percentage of the time, on the order of 43 %.

The answer to Question (4) is based mainly on stomach content data from whales harvested at

Kaktovik, and thus is to some extent specific to the fraction of the eastern Alaskan Beaufort Sea where

hunters from Kaktovik harvest whales. That area extends to ~40 km east, 25 km north, and 25 km west of

Kaktovik (Kaleak 1996). However, behavioral observations relevant to Questions (4) and (6) indicate

that feeding is common across the larger area from central Camden Bay to the Alaska/Canada border and

beyond (Fig. 12.5 in Chapter 12; see also Treacy in prep.). Both stomach content and behavioral data

extend from early September to early October (Table 23.1).

Our conclusion concerning Question (4) is consistent with local knowledge. Whale hunters and

other residents of Kaktovik know that the stomachs of most bowheads harvested near Kaktovik contain

zooplankton, and believe that the area near Kaktovik is important for feeding (Chapter 2; Annex B).

Local residents and hunters have no real opportunity to provide information relevant to Question (6).

Most local residents report that they rarely can distinguish feeding from other activities when they see

whales at sea. This is not surprising, given the low vantage points, and the fact that bowheads seen from

a moving boat are likely to be avoiding the boat even if they were originally feeding before the boat

approached (Richardson and Malme 1993).
23-18 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

Food Availability to Feeding Whales

Zooplankton sampling near bowheads found that average zooplankton biomass near whales was

very much higher than that in the water generally. Also, the mean zooplankton biomass in these concentrations varied from year to year. Copepods were the dominant organisms, on a biomass basis, in our

samples from the eastern Alaskan (and Canadian) Beaufort Sea. Euphausiids contributed a much lower

proportion of the biomass in the net samples, and we did not collect high biomasses of euphausiids during

our zooplankton sampling. However, euphausiids are commonly eaten by bowheads landed at Kaktovik

(Chapter 18; Chapter 2), and concentrations of euphausiids were found in Camden Bay by Wartzok et al.

(1990; Chapter 6).

Question (5) concerned the fraction of the study area that contained concentrations of zooplankton

sufficiently dense to allow economical feeding by bowhead whales:

Question (5). What percentage of the geographic area within the study area is suitable as

feeding habitat in different years? Is at least 1 % of the study area suitable in some years?

This type of question can be addressed based on the quantitative echosounder surveys conducted during

the project.

To address this question it is first necessary to determine what constitutes suitable feeding habitat.

Horizontal plankton tows guided to layers of concentrated zooplankton by an echosounder have been

made at 17 locations where bowheads were observed <1 km from the sampling boat (Chapter 6). These

locations were in the Canadian Beaufort Sea in 1981, 1985 and 1986 (n = 13), and in the eastern Alaskan

Beaufort Sea in 1986 and 1999 (n = 4). The lowest biomass in these tows was 545 mg/m3

. For 4 of 17

stations, the highest biomass measured was 771–807 mg/m3

, and for 11 of 17 stations the highest value

was ~1000 mg/m3

. Biomasses of ~800 mg/m3 may represent the feeding threshold for bowhead whales,

i.e., the minimum biomass for economical feeding. A comparison of the maximum biomass in net tows

with the maximum biomass estimate derived by echosounder at these stations suggests that the net did

sample within the layer of highest zooplankton biomass (Chapter 6). Mean biomass in the water column

at 173 stations where whales were not observed from the boat in the Canadian Beaufort Sea and Eastern

Alaskan Beaufort Sea in 1980, 1981, 1985, 1986, 1998 and 1999 was 230 ± s.d. 173 mg/m3

.

Griffiths et al. (Chapter 6) conducted echosounder surveys to determine the nature and extent of

zooplankton patches within the eastern Alaskan study area. Relationships between “acoustic biomass” as

measured by the echosounder and net biomass of zooplankton as determined by horizontal tows had been

developed by Johnson and Griffiths (1990) and Griffiths (Chapter 4). These acoustic biomass vs. net

biomass regressions were used to convert results from echosounder surveys over broad geographical areas

to estimates of zooplankton biomass present at each depth along the echosounder transects. During four

years of sampling, biomass was recorded for a total of 1860 two-minute transect segments, each spanning

a horizontal distance of ~240 m (Table 23.6). When these same 2-min segments were subdivided into 1-

or 2-m depth intervals, there were 53,399 such 2-min (~240 m) by 1- or 2-m depth intervals (Table 23.7).

Averaged over four years, 25 % of the surveyed area contained a zooplankton biomass ≥800

mg/m3

, the presumed feeding threshold for bowhead whales, at some depth below the surface (Table

23.6). During each year of sampling there were many segments that contained a biomass >800 mg/m3

(Tables 23.6 and 23.7). At least 7 % of the surveyed area had ≥800 mg/m3 at some depth during all four

years with effective echosounder surveys. The presumed 800 mg/m3

 threshold was exceeded in 2.2 % of

the total volume of water sampled (Table 23.7).
§ 23. Integration & Conclusions 23-19

TABLE 23.6. Number and percent of total 2-min (~240 m) horizontal

segments that contained zooplankton biomass ≥800 mg/m3

 in one or

more 2-m (1985–86) or 1-m (1999–2000) depth intervals. Sampling

was conducted in the Alaskan Beaufort Sea (Camden Bay to Alaska/

Canada border) with a 200 kHz echosounder in 1985–86, and a 430

kHz echosounder in 1999–2000.

2 minute (~240 m) horizontal segments

Year Number ≥800 mg /m3 Percent

2000 512 50 10 %

1999 370 25 7 %

1985 330 108 33 %

1986 648 280 43 %

Total 1860 463 25 %

TABLE 23.7. Number of sampling cells, and percent of total volume of

water sampled, that contained zooplankton biomass ≥800 mg/m3.

Sampling cells were 2-min (~240 m) in horizontal extent by 2-m (1985–

86) or 1-m (1999–2000) depth intervals. Otherwise as in Table 23.6.

2–min. x 1 or 2 m depth Intervals

Year Number ≥800 mg /m3 Percent

2000 14,167 83 0.6 %

1999 10,931 25 0.2 %

1985 5163 157 3.0 %

1986 23,138 902 3.9 %

Total 53,399 1167 2.2 %

Answer (5): The percentage of the study area suitable as feeding habitat, i.e., with ≥800

mg/m3 zooplankton at some depth, averaged 25 % over four years with effective echosounder

sampling, and varied from 7 % to 43 % in individual years.

The echosounder data used to address Question (5) came from continental shelf waters (0 to 200 m

deep in 1985–86; 0–50 m deep in 1998–2000) between central Camden Bay and the Alaska/Canada

border during the period of peak bowhead abundance in early–mid September (2–22 Sept.). The assumed

feeding threshold of ≥800 mg/m3

 is based on sampling near feeding whales both in that area and in the

Canadian Beaufort Sea, including data from mid-August to 22 September.

Question (5) can only be addressed through specialized zooplankton sampling procedures. Thus,

there is no specific local knowledge relevant to this point. However, residents of Kaktovik mentioned

that they sometimes see concentrations of “krill” in or on the water, and that amounts of krill vary from

year to year (Chapter 2; Annex B). 

 Food Consumed in the Study Area by the Population and by Individual Whales

The overall purpose of the project, as defined by the Minerals Management Service and quoted at

the start of this chapter, included a number of interrelated components: to compile and integrate existing

traditional and scientific knowledge about the importance of the eastern Alaskan Beaufort Sea for feeding

by bowhead whales; to build consensus on the need for and approach to fieldwork to augment this
23-20 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

knowledge; to conduct the field studies and to analyze the results; to integrate them with existing traditional and scientific knowledge; and to report on and publish the results. Although the overall purpose

was fairly broad, the central question to be addressed during this study has been phrased as follows:

Question (1). In an average year, how important is the eastern Alaskan Beaufort Sea for

bowhead whales; what percentage of the population’s annual energetic requirements is

derived from the area?

In this subsection, we attempt to estimate that percentage, recognizing that this percentage represents only

one of many possible descriptors of the importance of the study area to bowhead whales.

Thomson (Chapter 22) estimated the food requirements of various size/age/reproductive categories

of bowhead whales. The estimate of energy requirements derived through consideration of heat loss plus

the costs of motion, growth and reproduction will be used in the calculations in this section. Food

requirements per feeding day are computed based on the theoretical total annual food requirements

divided by the estimate of ninety-three 24–hour days of feeding per year, as calculated in Chapter 22.

(Feeding occurs on many more than 93 calendar days, but not for 24 hours on any one day.) Appendix

23.2 also describes the calculation procedure. The following analysis is mainly concerned with the

proportion of food obtained in the study area relative to other areas and so is insensitive to the estimated

rate of consumption. In estimating the proportion of total annual diet that is consumed in the eastern

Alaskan study area, we consider the area from Flaxman Island to the Alaska/Yukon border, and from the

shore to the 200 m depth contour, as outlined by the heavily-dotted line in Figure 23.1.

Based on the population census taken at Barrow in 1993 (Zeh et al. 1996), and the estimated rate of

increase of the population (Punt and Butterworth 1999), the BCB population is estimated to consist of

10,223 bowheads in 2000 (see “Background”, above). Angliss et al. (1995) estimated that 41.1 % of the

population were adults ≥13 m in length, 53.7 % were subadults, and 5.2 % were calves. It will be

assumed that the ratio of adult males to females is 1 : 1.

Use of the Area by Feeding Whales

Whale-days of use of the study area during the late summer and autumn period were estimated in

Chapter 9, separately by year (see Table 23.8). These estimates pertain to the specific area considered

here, i.e., from Flaxman Island to the Alaska/Canada border, and from the shore to the 200 m depth

contour. The estimates were based on aerial survey results analyzed by line-transect methods and

adjusted using various correction factors. These correction factors, derived in Chapter 15, allowed for

whales present but missed by aerial surveyors. Chapter 9 applies the correction factors to the aerial

survey data. In each year, there were 5 to 11 days with sufficient aerial survey coverage for a direct

estimate of total numbers present on that day or an adjacent pair of days. Numbers present on days with

no coverage were estimated based on these direct estimates and the seasonal pattern of densities (see

Chapter 9). Results were summed for the 7 August to 27 October period. Because there is considerable

variation in these data and because whale-days is one of the most critical numbers used in estimating

amount of food consumed in the study area, whale-days of use were included in the sensitivity analysis

described below and in Appendix 23.2.

Whale-days for each year were multiplied by the proportion of time spent feeding for each year

(from Chapter 12) to derive the estimated feeding-days of use for each year (Table 23.8).
§ 23. Integration & Conclusions 23-21

TABLE 23.8. Estimated numbers of whale days of use of the “Flaxman-to-border” area

(from Chapter 9), proportion of time spent feeding (from Chapter 12), and feeding days of

use per year and for all years combined. The estimates include calves. The “Proportion

of time feeding” and “Feeding-Days of Use” include time at the surface between feeding

dives, plus time engaged in other activities that were interspersed with active feeding and

not distinguished from feeding.

Fall Study area 1985 1986 1998 1999 2000 Avg./yr

Number of whale-days of use 11,937 17,899 31,507 101,850 18,727 36,384

Proportion of time feeding 0.39 0.57 0.38 0.67 0.09 0.47

Feeding-Days of Use 4,643 10,228 11,915 67,900 1,702 16,953

Amount of Food Consumed in the Study Area

In this subsection we estimate the proportion of annual energetic requirements consumed in the

study area by the Bering–Chukchi–Beaufort population of bowhead whales. The amount of food consumed in the study area was estimated separately for each year, and these estimates were compared to

annual consumption by the entire population.

Energetic and food requirements of bowheads were estimated in Chapter 22. The estimates of total

annual and daily food requirements of individuals, by size class, were based on the estimated standard

metabolism (heat loss) plus the energetic cost of swimming, weight gain (growth), and reproduction. Bowheads

do not feed continuously, so a feeding rate per unit of time spent feeding needed to be computed. Based on

behavioral observations and an assumption that bowheads do not feed in winter, bowhead whales may feed for

the equivalent of ~93 days of continuous 24-hour feeding per year (see Chapter 22). Thus, the feeding rate per

feeding-day, based on calculated annual requirements divided by 93 feeding-days, is 773 kg/d for an average

subadult, 905 kg/d for an average adult male, and 1421 kg/d for an average adult female (Table 23.9A). 

Because the population of bowheads increased during the course of the study, population size was

estimated separately for each year of the study (from Appendix 9.2 in Chapter 9). For each year, the

population was apportioned as numbers of subadults, adult males, and adult females according to Angliss

et al. (1995). Calves were not included in Table 23.9, as their energy requirements are included in those

of their mothers. Hence, the numbers of whales considered for each year add up to slightly less than

100% of the total population size.

Annual food consumption in the study area for each year of the study was estimated through

consideration of several factors: estimated whale days in the study area, their size class composition, the

percent of time spent feeding, and the average amount of food that must be consumed per day to meet annual

energetic requirements. The factors and calculations are summarized in Table 23.9B. Whale days for each

year were apportioned to subadults, adult males, and adult females according to their proportional presence in

the study area that year, as determined via aerial photogrammetric methods (Chapter 11). Calves were not

considered, so the total number of whale days per year, as shown in Table 23.9B, is lower than shown in Table

23.8. The number of whale days was multiplied by the proportion of time spent feeding for each year of the

study (Table 23.5) to obtain whale feeding days by size category. The estimate of feeding days was not

reduced to account for the time bowheads spend at the surface breathing, or (perhaps) cleaning baleen, or for

the time engaged in other activities that were not distinguished from “feeding”. Thus, feeding time is

overestimated by this procedure. Whale feeding days for each size category were multiplied by the estimated

average daily food requirement per feeding day for that size category (from Table 23.9A), and summed across

size categories to determine total food consumption in the study area.
23-22 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

TABLE 23.9. Theoretical energetic requirements of the entire BCB bowhead whale population and proportion of the total food requirements that could have been obtained in the eastern Alaskan study area

(Flaxman Isl. to Alaska/Canada border) in 1985, 1986, 1998, 1999, and 2000.

Units Subadults Adult Males

Adult

Females Total

A. Food Requirements of the Population

% of Populationa,b 54% 20.6% 20.6% 94.8%

Individual requirementsc kJ x 105/yr 1573 1934 2903

kg/yr 71,640 88,046 132,181

Food Requirements/Feeding Day/animald kJ x 105/d 16.97 20.86 31.31

kg/d 773 950 1,421

B. Food Consumed in the Study Area

1985 Number of Animals = 6373e 3,422 1,313 1,313 6,042

 Population Requirements kg /yr 245,173,741 115,590,284 173,532,615 534,296,640

 Proportion of Study-Area Population f 0.833 0.072 0.072 0.978

 Whale Feeding Days in Study Area g 3,869 335 335 4,540

 Zooplankton Consumption kg 2,990,116 318,489 476,625 3,785,230

 Percent of Annual Consumption 1.2% 0.3% 0.3% 0.7%

1986 Number of Animals = 6577e 3,532 1,355 1,355 6,235

 Population Requirements kg/yr 253,021,763 119,290,334 179,087,402 551,399,498

 Proportion of Study-Area Population f 0.665 0.115 0.115 0.895

 Whale Feeding Days in Study Area g 6,802 1,174 1,174 9,151

 Zooplankton Consumption kg 5,256,625 1,115,470 1,669,322 8,041,416

 Percent of Annual Consumption 2.1% 0.9% 0.9% 1.5%

1998 Number of Animals = 9599e 5,155 1,977 1,977 9,100

 Population Requirements kg/yr 369,280,204 174,101,857 261,374,482 804,756,543

 Proportion of Study-Area Population f 0.811 0.081 0.081 0.973

 Whale Feeding Days in Study Area g 9,660 966 966 11,593

 Zooplankton Consumption kg 7,465,305 917,491 1,373,043 9,755,840

 Percent of Annual Consumption 2.0% 0.5% 0.5% 1.2%

1999 Number of Animals = 9906e 5,320 2,041 2,041 9,391

 Population Requirements kg/yr 381,090,707 179,670,069 269,733,891 830,494,667

 Proportion of Study-Area Population f 0.453 0.242 0.242 0.936

 Whale Feeding Days in Study Area g 30,751 16,407 16,407 63,566

 Zooplankton Consumption kg 23,763,438 15,582,767 23,319,904 62,666,108

 Percent of Annual Consumption 6.2% 8.7% 8.6% 7.5%

2000 Number of Animals = 10,223e 5,490 2,106 2,106 9,691

 Population Requirements kg/yr 393,285,917 185,419,657 278,365,593 857,071,167

 Proportion of Study-Area Population f 0.593 0.148 0.148 0.889

 Whale Feeding Days in Study Area g 1,009 252 252 1,513

 Zooplankton Consumption kg 779,602 239,534 358,467 1,377,603

 Percent of Annual Consumption 0.2% 0.1% 0.1% 0.2%

1985 - 2000 Average Pop. Requirements kg/yr 328,370,466 154,814,440 232,418,797 715,603,703

 Zooplankton Consumption kg 8,051,017 3,634,750 5,439,472 17,125,239

 Percent of Annual Consumption 2.5% 2.3% 2.3% 2.4%

a

 From Angliss et al. (1995).

b

 Does not include calves whose energy is derived from lactating females. c

 From Chapter 22; standard metabolism + cost of motion + growth; assumes average adult is 14.5 m in length. d

 Assumes 93 feeding days per year and the “individual requirements” values quoted above. e

 Total bowhead population size from Appendix 9.2 (in Chapter 9); breakdown by age and status is from Angliss et al. (1995) and

total does not include calves.

f

 From Chapter 10; total does not include calves.

g

 From Table 9.3 (in Chapter 9) and Table 23.8, adjusted to exclude calves.

h

 Assumes late summer/autumn energy content of zooplankton (Chapter 22)
§ 23. Integration & Conclusions 23-23

Food Consumed in Study Area vs. Overall Annual Diet

Estimated food consumption by bowheads in the eastern Alaskan study area (Flaxman Isl. to Alaska/

Canada border) was expressed as a percentage of total annual consumption by the population. This was done

separately for each year of the study, and averaged for the five years of the study (Table 23.9B).

Based on this approach, in an average year the population of bowhead whales is estimated to consume about 2.4 % of its annual energetic requirements in the study area (Table 23.9B). In one of 5 years

(1999), the population of bowheads may have derived about 7.5% of annual energetic requirements there.

In all other years, estimated consumption in the study area was <2 %. On average, feeding in the eastern

Alaskan Beaufort Sea was apparently of similar importance to subadults and adults (Table 23.9B).

The substantially higher estimate of food consumption in the study area in 1999 than in other years

is a result of the markedly higher estimate of “whale-days in the study area” for 1999 (Table 23.9). Other

measures of utilization of the study area do not show such a large difference in use between 1999 and the

other four years of detailed study (Table 23.3). It is possible that we have overestimated whale-days in

the study area during 1999, and thus food consumption in the area in that year.

Many assumptions are involved in this analysis, and there is considerable uncertainty in many of

the estimates used in the calculations. However, the estimated mean consumption in the study area

(2.4 % of annual requirements) is quite low. Even if mean consumption were substantially underestimated for some unknown reason, it is implausible that the population would consume more than a few

percent of its annual food requirements in the study area in an average year (see below).

Uncertainties and Potential Errors in the Estimate

The estimate that an average bowhead whale consumes ~2.4 % of annual energetic requirements in

the study area is independent of the manner in which energetic requirements are calculated. If our

estimates of the relative food requirements of subadults, adult males, and adult females are approximately

correct, then the estimated percent of annual food requirements obtained in the study area is independent

of the actual feeding rate. Even if identical feeding rates were assumed for the three size/sex classes, the

final result would differ by only 0.01 % (i.e., 2.39 % vs. 2.40 %). 

The estimated percent of annual consumption that occurs in the study area is sensitive to the estimated number of whale-days in the study area, the proportion of time spent feeding, number of feeding

days per year, and size and makeup of the entire population. All factors used to estimate percent of food

consumed in the study area, including daily energetic requirements, were included in a sensitivity analysis

(Appendix 23.2). The main data used in the simulation were whale days, proportion of whales in the

study area by age class, proportion of time spent feeding, total population size, and proportional composition of the population by age and reproductive class. Standard errors of these and other variables were

computed from the original data, derived from the literature, or otherwise approximated, as described in

Appendix 23.2. Although the sensitivity analysis is complex and allows for many sources of variability,

it necessarily involves many assumptions and approximations. Nonetheless, it provides useful guidance

concerning the uncertainty in the estimated proportion of the diet obtained in the study area.

The 95 % confidence limits of the percent of food consumed in the study area are shown in Table

23.10, based on Appendix 23.2. In 4 of 5 years, the upper bound of the 95 % confidence interval was

below 5 %. If the high whale-days estimates for 1999 are correct, then consumption in the study area during

that “high-utilization” year, estimated in Table 23.9 as 7.5 % of annual population requirements, might have

been even higher if other parts of the calculation were underestimated. The upper 95 % confidence interval for
23-24 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

TABLE 23.10. Estimated proportion of the total annual food

requirement of the BCB bowhead population that could have

been obtained in the eastern Alaskan study area (Flaxman

Isl. to Alaska/Canada border) in each of the five study years,

and its 95 % confidence limits (from Appendix 23.2).

95% Confidence Limits

Year

Estimated

% of Food Lower Upper

1985 0.7 0.2 3.0

1986 1.5 0.6 3.6

1998 1.2 0.4 3.4

1999 7.5 3.4 16.5

2000 0.2 0.0 0.9

1999 is 16.5 % of total food consumed by the population, given the various assumptions and the observed

variability in data. However, we suspect that the whale-days figure for 1999 was overestimated, and that the

16.5 % upper confidence bound is unrealistically high. In any event, it is possible that consumption in the

study area during a high-utilization year might exceed 5 % of annual population requirements. All lines of

evidence indicate that utilization of the study area varies widely in space and time, depending on zooplankton availability and other factors.

This estimation process assumes that average prey availability is the same in all areas where bowhead whales feed. However, average prey availability at bowhead feeding locations is suspected to be

higher at autumn feeding sites in the western Beaufort Sea, southwest Chukchi Sea, and (perhaps)

northwest Bering Sea, than in the summer/early fall feeding areas in the eastern and central Beaufort Sea.

If so, the bowhead population probably obtains a lower percentage of its annual diet in the present study

area than calculated here, and a higher percentage in the late-autumn feeding areas farther west. The presumed lower prey availability in winter and spring do not offset the presumed higher prey availability in

late fall. Our calculations assume that bowheads spend no time feeding in winter, and little time feeding

in spring. Thus, low prey abundances in winter and spring would have little downward effect on the

proportion of annual requirements met in those seasons. In contrast, a high prey abundance in Bering/Chukchi waters in late fall would allow bowheads to acquire more of their annual diet in late fall, thus

reducing the proportion likely obtained in the present study area.

As noted earlier, the estimation process did not make any downward adjustment to the feeding time

to allow for time spent at the surface or otherwise “not feeding” during periods when whale activities

were classified as “feeding”. This is likely to result in an overestimate of food consumption. Given this

factor, plus the effects of the presumed higher prey abundance in the Bering/Chukchi system where

bowheads feed in autumn (see above), our estimates of the percent of the annual dietary requirements

acquired in the eastern Alaskan Beaufort Sea are more likely to be overestimates than underestimates.

Summary of Food Consumed

Bowhead whales do not spend enough time in the study area to consume more than a small fraction

of annual requirements. However, in the occasional year when utilization of the study area by feeding

bowhead whales is considerably higher than average, it is possible that the population may derive 5 % or

more of its annual energetic requirements from the area.
§ 23. Integration & Conclusions 23-25

Answer (1): In an average year, the population of bowhead whales derives an estimated

2.4 % of annual energetic requirements in the eastern Alaskan Beaufort Sea. In 1 of 5 years

of study, the population may have derived 7.5 % or more of annual energetic requirements

from the area. Utilization of the study area varies widely in time and space depending on

zooplankton availability and other factors.

These estimates are based on many different types of data collected at varying locations within and

near the study area in varying parts of the late summer/early autumn period, along with general analyses

of bowhead energetics. Specific sources of data, uncertainties, and potential biases are documented

throughout this report, including Appendix 23.2. In general, we believe that the resulting values are

reasonable estimates for the eastern Alaskan study area (Flaxman Island to the Alaska/Canada border;

from shore to the 200 m contour). If anything, the estimates are likely to overstate the actual proportion

of the diet acquired in this area, for reasons mentioned in the preceding subsection.

Some reviewers have noted that the eastern Alaskan Beaufort Sea is only a small proportion of the

Beaufort Sea, and an even smaller proportion of the area where BCB bowhead whales are known to feed.

Also, it is common knowledge, further documented in this study, that the study area is occupied by large

numbers of bowheads for only a relatively small part of the year. Given this, it would be very surprising

if the present study area did provide a high proportion of the population’s annual food requirements.

Based on this rationale, some reviewers have commented that it is unreasonable to judge the importance

of the eastern Alaskan Beaufort Sea based simply on the percentage of the annual food requirements that

it provides to BCB bowheads. They note that it would also be important to know how much food is

obtained in the present study area as compared with other areas of comparable size. Specific studies of

feeding in other areas were outside the scope of the present project.

Whale hunters and other residents of Kaktovik know that bowheads feed near Kaktovik because they see

food in the mouths and stomachs of the whales, and they sometimes see whales feeding on prey concentrations.

They believe that the area near Kaktovik, and the Beaufort Sea generally, is important for feeding (Chapter 2;

Annex B). Bowhead whales are of great cultural importance to the Inupiat and are a major source of food.

Thus, any area used by bowheads, especially when it is also a hunting area, is considered important. No matter

what percentage of the annual food requirement is derived from the eastern Alaskan Beaufort Sea, local

residents will continue to view their hunting grounds as an important area for bowhead whales.

Individual Bowhead Requirements

Given the energetic requirements of individual whales discussed above, an assumption that bowheads

feed (intermittently) for a total of ninety-three 24-hour days per year, and evidence that bowheads feed during

47 % of their time in the eastern Alaskan Beaufort Sea, individual whales would need to spend ~10 days in the

area in order to consume 5 % of annual food requirements (Table 23.11). They would need to spend ~20 days

in the area to consume 10 % of annual requirements. Over the five years of our study, the average whale spent

~4 days in the eastern Alaskan area from Flaxman Island to the Alaska/Canada border. If a whale spent 4 d in

the study area, it could consume about 2.5 % of annual requirements. This is close to the 2.4 % of annual

requirements computed in Table 23.9 based on a different approach starting from estimated whale-days of use

and other factors. 

For the overall population, the mean residence times in the “Flaxman–to–border” area during individual

years of study ranged from 2.5 to 6.3 d. These figures are based on the “Flaxman–to–Herschel” data in Table

23.3 divided by 1.32 to estimate averages for the “Flaxman–to–border” area. If the 1.32 factor is applied to the

95 % confidence bounds, the (adjusted) upper bound for mean residence time in the “Flaxman–to–border” area
23-26 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

TABLE 23.11. Percent of annual requirements potentially consumed in the eastern

Alaskan Beaufort Sea by individual whales that might remain in that area over the

specified periods of time. Energetic requirements are based on standard metabolism

plus the cost of transport, feeding for the equivalent of 93 days per year (24 hours per

day), and feeding for 47 % of their time in the eastern Alaskan Beaufort Sea.

Units Subadults

Adult

Males

Adult

Females

Annual Requirements kJ x 105/yr 1724 2270 3269

Daily Requirements/Feeding Day kJ x 105/d 20.77 27.35 39.38

Days in Study Area

 1 kJ x 105 0.5 % 0.5 % 0.5 %

 5 kJ x 105 2.5 % 2.5 % 2.5 %

10 kJ x 105 5.0 % 5.0 % 5.0 %

15 kJ x 105 7.5 % 7.5 % 7.5 %

20 kJ x 105 10.1 % 10.1 % 10.1 %

30 kJ x 105 15.1 % 15.1 % 15.1 %

exceeds 7 d in two years, 1985 and 1999 (7.8 and 9.1 d, respectively). Although these mean residence time

estimates do not pertain directly to individual whales, they imply that a minority of the individuals would

be present in the study area for 10+ d, especially in years when mean residence time is higher than

average. Individuals that spend 10 days in the eastern Alaskan Beaufort Sea could obtain ~5 % of their

individual annual food requirements in the study area.

A few bowhead whales have been documented to remain for at least 11–16 days in the larger

“Flaxman–to–Herschel” area (Table 23.4). Documented resighting-intervals of this type often underestimate residence times (see Chapter 11). Hence, a few whales probably remain in the “Flaxman–to–

Herschel” area for 20+ days. However, it is not known whether any remain in the smaller “Flaxman–to–

border” area (i.e., the eastern Alaskan Beaufort Sea proper) for the 20 days required to obtain ~10 % of

their individual annual food requirements. If so, the numbers of individuals that do so must be small.

Recommended Research

This study has assembled much information, including both scientific results and traditional

knowledge, concerning bowhead whale feeding, particularly in the eastern Alaskan Beaufort Sea. However, as is inevitable even after such a study, various questions about bowhead feeding dependencies

remain unanswered or only incompletely answered. This section lists the additional research that has

been recommended in Chapters 7, 16 and 21 concerning, respectively, • zooplankton; • bowhead distribution, numbers and activities; and • bowhead diet and regional feeding. Those three chapters include additional rationale and details concerning the recommendations on those topics. Also, this section includes a

fourth subsection concerning recommended research relating to additional topics discussed in Chapters 22

and 23. No specific attempt has been made to assign priority rankings to research topics, and the sequence is not intended to imply any such ranking.

Zooplankton

1. More precise estimates of food availability to bowheads in the eastern Alaskan Beaufort Sea

would be possible if zooplankton sampling there could be extended to include the full period

when bowheads use the area, or at least the main period of use from mid-August to mid-October.
§ 23. Integration & Conclusions 23-27

2. To understand the relative importance of autumn feeding areas west of the present easternAlaskan area, studies of zooplankton availability in the more westerly areas during autumn

would be useful.

3. Any follow-up study of zooplankton availability in different months or in different areas should be

planned for a duration of at least 3 years if at all possible.

4. Any future bowhead feeding study needs to include guidance by aerial observers (or some other

means, e.g., telemetry) to locations of feeding whales.

5. Within the eastern Alaskan Beaufort Sea, it would be desirable to obtain additional data on food

availability and associated aspects of bowhead feeding in deeper waters

6. It will be desirable, in any similar future study of zooplankton availability to bowhead whales, to

develop and use improved field and analysis methods that will provide more reliable and bettercorrelated net-sampling and echosounder results.

7. It would also be desirable to consider the suitability of improved or new types of zooplankton

sampling gear that might be available (and practical) by the time a future study is being planned,

e.g., opening-and-closing nets; video plankton recorder; specialized echosounder gear.

8. Data on day–night differences, if any, in the vertical distribution of zooplankton in areas and

seasons where bowheads feed would be helpful in assessing food availability to bowheads.

Bowhead Distribution, Numbers and Activities

9. More data on distribution, activities, size segregation, and residence times of bowhead whales in

the eastern Alaskan Beaufort Sea during the early and late parts of the season, e.g., July-August

and October, would be helpful in better understanding the importance of the area to bowheads.

10. To understand the relative importance of autumn feeding areas west of the present easternAlaskan area, studies of bowhead activities, size segregation, and residence times in the more

westerly areas during autumn would be useful.

11. Any follow-up study of bowhead utilization in different months or in different areas should be

planned for a duration of at least 3 years if at all possible.

12. Within the eastern Alaskan Beaufort Sea, it would be desirable to obtain additional data on bowhead utilization of deeper waters throughout the summer and autumn

13. New technology has considerable potential to provide additional data concerning bowhead utilization of various parts of the Beaufort Sea and other areas:

(a) Satellite-linked and VHF (or UHF) radio tags could provide new levels of detail concerning distribution, movements, residence times, behavior, and disturbance responses.

(b) The possibility of day–night differences in bowhead activities deserves further study, perhaps via VHF or UHF telemetry, as well as expanded use of satellite telemetry.

(c) Passive acoustic detection, localization, and (occasionally) tracking of bowheads could

also provide data on seasonal distribution, movements, and disturbance responses during

autumn migration, although it is doubtful whether passive acoustic data could be related

specifically to feeding whales.
23-28 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

Bowhead Diet and Regional Feeding

14. Additional data on the stomach contents of BCB bowhead whales, especially from areas where

few such data have been acquired previously, would be helpful in characterizing the frequency

and intensity of feeding in different locations and seasons, the types of prey consumed, and any

long-term trends in feeding activity. Areas and seasons where such data would be most valuable

include the Chukotsk coast, the northern Bering Sea in winter/early spring, and the west coast of

Alaska in spring.

15. While stomach-content samples are being obtained from harvested bowheads, tissue samples and

measurements needed for other relevant studies should also be obtained, e.g., for fatty acid and

stable-isotope studies; girth (vs. length) measurements.

16. Analyses of the fatty acid composition of bowhead blubber sampled at different geographic locations and seasons, along with corresponding analyses of potential prey items, have the potential

to provide a different perspective on prey consumption by bowhead whales.

17. It would be desirable to compare stable isotope composition of additional samples of bowhead

muscle from spring and fall, collecting these samples in the same years and processing them in

strictly standardized ways.

18. Additional data on the stable-isotope composition of the blubber (and visceral fat) at various

times of year would be useful in assessing seasonal turnover and the importance of feeding in

different parts of the annual range.

19. There are many questions about the nature and extent of feeding in some areas outside the

eastern Beaufort Sea, most notably the western Alaskan Beaufort Sea in autumn, the southwestern Chukchi Sea in late autumn, and the Bering Sea in winter. To assess feeding activity in those

areas, a wide variety of study approaches could be valuable, including not only isotopic methods,

but also most or all of the other methods used in the present study.

Bowhead Energetics and Other

The research recommendations listed above have been described in more detail in chapters 7, 16

and 21, but the following recommendations related to bowhead energetics and other topics have not been

described previously. Therefore, each of the following recommendations has a preamble outlining the

rationale.

One major uncertainty affecting the energetic analysis is the unknown amount of feeding in winter.

Isotopic results suggest that most feeding by both subadults and (especially) adults occurs outside the

Beaufort Sea (Chapter 20). However, subadult bowheads harvested leaving the Beaufort Sea in fall are

heavier and have a higher lipid content in their blubber than do subadults returning to the Beaufort Sea in

spring. Measurements of length and girth from known scale aerial photographs confirm some weight loss

in winter and some weight gain in the Beaufort Sea during summer (Chapter 22).

20. More girth measurements are needed from harvested and/or photographed animals to accurately

determine seasonal weight loss/gain by size category. Crucial to these measurements is an estimate of the amount of stretching that occurs when whales of varying sizes are hauled up on land

vs. ice. Data on girths vs. lengths of whales in late autumn, after feeding in the southwest Chukchi Sea, would be of great value.
§ 23. Integration & Conclusions 23-29

Many of the morphometric and physiological data used to compute theoretical energetic requirements of bowhead whales have been derived for other species of whales in the absence of needed data

from bowheads. The following is a list of some key parameters where presently-available data for bowhead whales are inadequate or lacking. Some of the needed data are being collected in an ongoing project

by J.C. George, NSB-DWM. Data gaps should be re-evaluated when his work is completed.

21. Data needed to estimate theoretical energetic requirements of bowhead whales include total lung

volume, tidal lung volume, temperature of expired air, thermal conductivity of blubber, heat loss

through the mouth, amount of heat dumped by the whales when they overheat, coefficient of drag,

size of mouth opening, and swimming speed while submerged and feeding.

Sampling of food available at places where bowheads were observed feeding has only been conducted

near subadult bowheads feeding in late summer and early fall. These data came from feeding sites in the Canadian and eastern Alaskan Beaufort Sea. At these sites, the average prey availability measured at the depth of

maximum prey biomass was 1.8 g/m3

 on a wet weight basis (Chapter 6). Estimated prey consumption by

subadults feeding in such locations is only about half that required by even the low estimate of theoretical

energetic requirements (Chapter 22). Bowhead whales may derive much of their energy by feeding in the

densest patches of zooplankton in the Beaufort Sea (denser than most or all of those sampled to date), and by

feeding in the Bering/Chukchi system. To better document the extent to which bowheads locate and feed in

dense patches of zooplankton, more zooplankton sampling near bowhead whales is needed, preferably with

improvements in matching precise sampling locations/depths with feeding locations/depths. In particular,

22. To obtain a comprehensive understanding of the annual feeding ecology of bowhead whales, zooplankton sampling should be attempted near adult bowheads feeding in summer in the Beaufort

Sea, and near bowheads feeding in fall in the western Beaufort and southwest Chukchi seas.

Bowhead whale distribution in the study area (and elsewhere) is closely related to the distribution

of zooplankton concentrations (Chapter 6). However, factors controlling zooplankton biomass and composition at specific locations and times are not well understood for the Beaufort Sea.

23. Physical and biological oceanographic studies designed specifically to better understand the

productivity and local distribution of zooplankton in the Beaufort Sea would be helpful in understanding the feeding ecology of bowhead whales. 

Summary

The purpose of the project, as defined by the Minerals Management Service, was to compile and integrate existing traditional and scientific knowledge about the importance of the eastern Alaskan Beaufort Sea

for feeding by bowhead whales; to build consensus on the need for and approach to fieldwork to augment this

knowledge; to conduct the field studies and to analyze the results; to integrate them with existing traditional

and scientific knowledge; and to report on and publish the results. Preceding chapters have described the

variety of studies included in the project, efforts to coordinate the work with local residents, and incorporation

of local knowledge of bowhead whales into the project. This chapter draws the various lines of evidence

together in order to address several key questions regarding the importance of the study area for feeding by

bowhead whales. In this final chapter, the study area is considered to extend from Flaxman Island to the

Alaska/Canada border (a distance of ~205 km), and from the shore to the 200 m depth contour.

The activities of bowhead whales throughout the year need to be considered when assessing the

importance of feeding in the eastern Alaskan Beaufort Sea during late summer and autumn. Bowhead

whales are known to feed in the Canadian Beaufort Sea in summer/early fall, and during westward migra-
23-30 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

tion across the Alaskan Beaufort Sea during late summer and fall. At least some of the bowheads also

feed in the southwest Chukchi Sea in mid- to late fall. Bowhead activities in the Bering Sea during winter

have not been studied. There is some feeding, probably quite limited, during spring migration around

western Alaska. Although behavioral observations and stomach contents provide some data on feeding

intensity during spring, summer, and early fall, such data are lacking for late fall in the Chukchi Sea, and

from winter. It is unclear, from the available data of those types, what fraction of the annual feeding

occurs in any one part of the annual range.

A comparison of carbon isotope ratios in bowhead muscle and baleen with those in the main food

organisms suggests that bowhead whales consume only a minority of their food in the eastern and central

Beaufort Sea, including Canadian as well as eastern Alaskan waters:

• Based on stable-isotope evidence, bowhead whales likely consume only 10 to 26 % of their

food in the eastern and central Beaufort Sea. Subadult bowheads appear to derive >10 % of

annual food requirements there, although the 95 % confidence interval extends below 10 %.

It is also probable that adults gain >10 % of their food in that area, but for adults the isotope

evidence considered in isolation would support an answer of <10 %.

The isotope results are surprising in relation to several other types of evidence that show considerable feeding by bowheads in the eastern and central Beaufort Sea during summer and early autumn:

• Behavioral observations show that bowheads spend much of their time feeding while in those areas.

• Zooplankton sampling near bowheads feeding in those areas shows that whales concentrate their feeding

at locations with much higher than average biomasses of zooplankton. • Stomach contents of bowheads

harvested during late summer and autumn at three locations in the Alaskan Beaufort Sea (including Kaktovik, within the eastern Alaskan Beaufort) show that most bowheads, both subadult and adult, had been

feeding shortly prior to death. • Length–girth relationships show that subadult bowheads, and possibly

adults, gain weight while in the Beaufort Sea in summer, and lose weight while elsewhere. • Lipid content of blubber, at least of subadults, is higher when they leave the Beaufort in fall than when they return

in spring. Although some of this evidence is preliminary and based on small sample sizes, this evidence

suggests the importance of feeding in the Beaufort Sea during summer and early autumn.

A feeding scenario that might be consistent with all these data is as follows: Feeding occurs commonly in the Beaufort Sea in summer and early autumn, and bowheads gain energy stores while feeding

there. However, zooplankton availability is not as high in the Beaufort Sea during summer as in the

Chukchi and northern Bering seas during autumn. Also, feeding in the western Beaufort in autumn may

effectively be on Chukchi prey advected to that area. Thus, bowheads might acquire more energy from

Bering/Chukchi prey in autumn than from eastern and central Beaufort prey in summer/early autumn.

Given this, plus an assumed low turnover rate of body components, the overall body composition of bowheads may be dominated by components from the Bering/Chukchi system even at the end of the summer

when leaving the Beaufort. Energy gained in the Beaufort and Chukchi seas during summer and fall is

presumably used during winter when food availability is low, resulting in reduced girth and energy stores

when returning to the Beaufort Sea in spring than when leaving in autumn. Several aspects of this

scenario are speculative, thus pointing toward topics warranting further research.

Although various types of evidence (with the exception of isotope ratios) indicate that the eastern

Beaufort Sea as a whole, including the Canadian Beaufort, is important to bowhead whales for feeding,

the eastern Alaskan Beaufort Sea is only a small fraction of that area. It was of interest to know how

much time an average whale, and some individual whales, spend in the specific eastern Alaskan Beaufort
§ 23. Integration & Conclusions 23-31

Sea. Was there evidence of average or individual residence times of at least 7 days? Analysis of several

types of data resulted in the following conclusions:

• An average bowhead spends ~3.8 days in the area from Flaxman Island to the Alaska/

Canada border during the late summer/autumn period, or ~1.4 d longer than expected for a

whale that swims steadily across that area. Averages in various years ranged from ~2.5 to

6.3 d. Although the average was <7 d in all years studied, it might exceed 7 days in a small

minority of the years, based on the calculated upper 95 % confidence bounds.

• Of the individual bowheads that travel through the eastern Alaskan Beaufort Sea, some

spend at least 7 days between the Alaska/Canada border and Flaxman Island during late

summer and autumn.

What percentage of the geographic area within the eastern Alaskan study area is suitable as feeding

habitat? At least 1 % in some years? At whale feeding locations in the Canadian and eastern Alaskan

Beaufort Sea, zooplankton biomass at the depth of maximum biomass, where bowheads presumably fed,

averaged 1.8 g/m3

 and was usually ≥800 mg/m3. The latter was assumed to be the minimum biomass that

was sufficient for economical feeding by bowheads.

• The percentage of the study area suitable as feeding habitat, i.e., with ≥800 mg/m3

 zooplankton at some depth, averaged 25 % over four years with effective echosounder sampling,

and varied from 7 % to 43 % in individual years.

Two additional questions of interest concerned the proportion of bowheads that feed while in the

eastern Alaskan Beaufort Sea, and the frequency with which they feed while actively traveling:

• Based on stomach content data, supplemented by behavioral evidence, far more than 10 %

of the bowheads that pass through the eastern Alaskan Beaufort Sea during late summer and

autumn feed there. Of the whales harvested at Kaktovik, 83 % had food in their stomachs,

and 39 % had ≥20 L of stomach contents.

• Bowheads fed for an average of 47 % of their time in the eastern Alaskan Beaufort Sea

during late summer and autumn. A substantial minority of the feeding occurred during

travel. Among traveling whales, feeding as well as travel was occurring during a substantial

percentage of the time, on the order of 43 %. 

A key objective for this study was to estimate what percentage of the bowhead population’s annual

energetic requirements might be derived from the study area. The estimated number of whale-days in the

study area during August–October averaged ~16,953 /yr across the five study years, but varied widely

from year to year. Whale-days estimates were based on aerial survey data adjusted to allow for whales

missed by the surveyors. Based on the whale-days estimates, and the fact that bowheads in the study area

were observed to feed for 47 % of the time (9 to 67 % in different years), we estimated the number of

effective feeding-days in the study area each year. Given this, the bowhead energetics model developed

in the preceding chapter, and various assumptions, it was possible to estimate the fraction of the population’s annual dietary requirements that might be derived from the eastern Alaskan study area:

• In an average year, the population of bowhead whales derives an estimated 2.4 % of annual

energetic requirements in the eastern Alaskan Beaufort Sea. In 1 of 5 years of study, the

population may have derived 7.5 % or more of annual energetic requirements from the area.
23-32 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

Utilization of the study area varies widely in time and space depending on zooplankton

availability and other factors.

In 4 of 5 study years, the bowhead population was estimated to consume <2 % of its annual requirements

within the eastern Alaskan Beaufort Sea during late summer and autumn. A sensitivity analysis by Dr.

B.F.J. Manly indicated that, in those four years, the upper bound of the 95 % confidence interval was

below 5 %. However in 1999, when the best estimate was 7.5 %, the upper bound was 16.5 %. We suspect that the whale-days figure for 1999 was overestimated, and that the 16.5 % upper bound is unrealistically high. However, consumption in the study area during a high-utilization year might exceed 5 % of

annual population requirements. Given some of the approximations that were made, these estimates are

more likely to be over- than underestimates. It is implausible that the population would consume more

than a few percent of its annual food requirements in the study area in an average year.

A related analysis showed that an individual whale would need to spend 10 days in the eastern

Alaskan Beaufort Sea in order to consume 5 % of annual food requirements. A small (but uncertain)

fraction of the individuals spend 10 days there in late summer/autumn. Few if any individuals spend 20

days in the area, which would be required to obtain 10 % of their individual annual food requirements

there.

Overall, the results show that the eastern Alaskan Beaufort Sea is used for feeding to widely

varying degrees depending on the year and on the individual bowhead. It is not surprising that the average contribution to the annual diet is apparently rather small: Most individual bowheads remain in that

area for only a rather short period in late summer/fall, averaging ~4 days. That is too little time to allow

an average bowhead to consume more than a small fraction of its annual dietary intake. Also, the eastern

Alaskan study area is rather small in comparison to the overall area in the Beaufort and Chukchi seas

where bowheads are known to feed. It would be unreasonable to expect that a high percentage of the

annual diet would be acquired during a short stay in one small area. However, it was beyond the scope of

this study to assess the importance (for feeding) of the present study area as compared to other similarsized areas.

Bowhead whales are of great cultural importance to the Inupiat and are a major source of food.

Thus, any area used by bowheads, especially when it is also a hunting area, is considered important by the

local residents. No matter what percentage of the annual food requirement is derived from the eastern

Alaskan Beaufort Sea, local residents will continue to view their hunting grounds as an important area for

bowhead whales.

This study has devoted much effort to the integration of existing and new scientific knowledge with

local and traditional knowledge. It has provided many new data concerning bowhead feeding ecology

and related aspects of bowhead biology, especially in the eastern Alaskan Beaufort Sea. However, there

are still numerous approximations, assumptions, data gaps, and variations of opinion regarding interpretation of data. This is inevitable in dealing with such a complex topic, especially in an environment

where field studies must cope with severe logistical difficulties. We do not claim that the project has

resolved all uncertainty about the importance of the eastern Alaskan Beaufort Sea for feeding by bowhead

whales—only that much progress has been made, and that the range of uncertainty has been narrowed.

One result of the project has been to better identify the major questions that remain to be answered. A list

of potential research topics is included in the “Integration and Conclusions” chapter of the final report.
§ 23. Integration & Conclusions 23-33

Acknowledgements

We are grateful to J. Craig George of the North Slope Borough Dept of Wildlife Management and

Tamara Mau of University of Alaska Fairbanks for providing advance access to key unpublished data

relevant to this analysis. That information is quoted here with their permission, and is not to be used

elsewhere without their approval. Numerous others at LGL and elsewhere have contributed data and

ideas to the development of the analysis described here. This analysis depends on data from most preceding chapters, and we thank the authors of those chapters and others acknowledged therein. We also thank

members of the project’s Scientific Review Board, and Steve Treacy of MMS, for many valuable comments on the draft of this chapter. Dr. Bryan F.J. Manly (WEST) provided the sensitivity analyses and

other calculations included as Appendices 23.1 and 23.2. Other acknowledgements relevant to the project

as a whole can be found in Chapter 1.

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of bowhead whales, Balaena mysticetus, summering in the Beaufort Sea. Can. J. Zool. 67(7):1801-1815.
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Duval, W.S. (ed.). 1986. Distribution, abundance, and age segregation of bowhead whales in the southeast Beaufort

Sea, August - September 1985. Environ. Stud. Revolv. Funds Rep. 057. Can. Oil & Gas Lands Admin.,

Ottawa, Ont. 117 p. NTIS MIC-97-06693.

Ferrero, R.C., D.P. DeMaster, P.S. Hill, M.M. Muto and A.L. Lopez. 2000. Alaska marine mammal stock assessments, 2000. NOAA Tech. Memo. NMFS-AFSC-119. Nat. Mar. Fish. Serv., Seattle, WA. 195 p. Available at www.nmfs.noaa.gov/protres/readingrm/MMSARS/2000AlaskaSARs.pdf.

Ford, J.K.B., J.C. Cubbage and P. Norton. 1987. Distribution, abundance, and age segregation of bowhead whales

in the southeast Beaufort Sea, August - September 1986. Environ. Stud. Res. Funds Rep. 089. Can. Oil &

Gas Lands Admin., Ottawa, Ont. 93 p.

George, J.C., J. Zeh, R. Suydam and C. Clark. 2002. Population size of the Bering-Chukchi-Beaufort Seas stock of

bowhead whales, Balaena mysticetus, based on the 2001 census off Point Barrow, Alaska. SC/54/BRG5.

Int. Whal. Comm., Cambridge, U.K.

Harwood, L.A. and G.A. Borstad. 1985. Bowhead whale monitoring study in the southeast Beaufort Sea, JulySeptember 1984. Environ. Stud. Revolv. Funds Rep. 009. Can. Oil & Gas Lands Admin., Ottawa, Ont.

99 p. NTIS MIC-97-06447.

Hoekstra, P.F., L.A. Dehn, J.C. George , K.R. Solomon, D.C.G. Muir and T.M. O'Hara. 2002. Trophic ecology of

bowhead whales (Balaena mysticetus) compared with that of other arctic marine biota as interpreted from

carbon-, nitrogen-, and sulphur-isotope signatures. Can. J. Zool. 80(2):223-231.

Johnson, G.E. and W.B. Griffiths. 1990. Hydroacoustic surveys of zooplankton biomass and distribution in the

Beaufort Sea in 1985 and 1986. Rapp. P.-v. Réun. Cons. Int. Explor. Mer 189:345-352.

Johnson, S.R. 1984. Birds and marine mammals. (Chap. 2) In: J.C. Truett (ed.), Environmental characterization

and biological use of lagoons in the eastern Beaufort Sea. Rep. from LGL Ecological Research Associates,

Inc., for U.S. Dep. Commer., NOAA, OCSEAP Final Rep. 24:129-579. NTIS PB85-212603.

Kaleak, J. 1996. History of whaling by Kaktovik village. p. 69-71 In: Proc. 1995 Arctic Synthesis Meeting, Anchorage, AK, Oct. 1995. OCS Study MMS 95-0065. U.S. Minerals Manage. Serv., Anchorage, AK. 206 p. +

Appendices.

Kisautaq. 1981. Okakok, Leaona (transcription and translation). Puiguitkaat: the 1998 elder’s conference. North

Slope Borough Comm. on History and Culture, Barrow, AK.

Koski, W.R., G.W. Miller and R.A. Davis. 1988. The potential effects of tanker traffic on the bowhead whale in the

Beaufort Sea. Environ. Stud. 58. Rep. from LGL Ltd., King City, Ont., for Dep. Indian Affairs & North.

Devel., Hull, Que. 150 p. NTIS MIC-90-04552.

Landino, S.W., S.D. Treacy, S.A. Zerwick and J.B. Dunlap. 1994. A large aggregation of bowhead whales (Balaena mysticetus) feeding near Point Barrow, Alaska, in late October 1992. Arctic 47(3):232-235.

Ljungblad, D.K., S.E. Moore and J.T. Clarke. 1986. Assessment of bowhead whale (Balaena mysticetus) feeding

patterns in the Alaskan Beaufort and northeastern Chukchi seas via aerial surveys, fall 1979-84. Rep. Int.

Whal. Comm. 36:265-272.

Mate, B.R., G.K. Krutzikowsky and M.H. Winsor. 2000. Satellite-monitored movements of radio-tagged bowhead

whales in the Beaufort and Chukchi seas during the late-summer feeding season and fall migration. Can. J.

Zool. 78(7):1168-1181.

Miller, G.W., R.E. Elliot, and W.J Richardson. 1998. Whales. p. 5-1 to 5-124 In: W.J. Richardson (ed.), Marine

mammal and acoustic monitoring of BP Exploration (Alaska)’s open-water seismic program in the Alaskan

Beaufort Sea, 1997. LGL Rep. TA2150-3. Rep. from LGL Ltd., King City, Ont., and Greeneridge Sciences,

Inc., Santa Barbara, CA, for BP Explor. (Alaska) Inc., Anchorage, AK, and U.S. Nat. Mar. Fish. Serv.,

Anchorage, AK and Silver Spring, MD. 318 p.
§ 23. Integration & Conclusions 23-35

Miller, G.W., R.E. Elliott, W.R. Koski, V.D. Moulton and W.J. Richardson. 1999. Whales. p. 5-1 to 5-109 In:

W.J. Richardson (ed.), Marine mammal and acoustical monitoring of Western Geophysical's open-water

seismic program in the Alaskan Beaufort Sea, 1998. LGL Rep. TA2230-3. Rep. from LGL Ltd., King City,

Ont., and Greeneridge Sciences Inc., Santa Barbara, CA, for Western Geophysical, Houston, TX, and U.S.

Nat. Mar. Fish. Serv., Anchorage, AK, and Silver Spring, MD. 390 p.

Moore, S.E. 1992. Summer records of bowhead whales in the northeastern Chukchi Sea. Arctic 45(4):398-400.

Moore, S.E. and J.T. Clarke. 1992. Distribution, abundance and behavior of endangered whales in the Alaskan

Chukchi and western Beaufort Seas, 1991: with a review 1982-91. OCS Study MMS 92-0029. Rep. from

SAIC Marit. Serv. Div., San Diego, CA, for U.S. Minerals Manage. Serv., Anchorage, AK. 237 p.

Moore, S.E. and J.T. Clarke. 1993. Bowhead whale autumn distribution and relative abundance in relation to oil

and gas lease areas in the northeastern Chukchi Sea. Polar Rec. 29(170):209-214.

Moore, S.E. and R.R. Reeves. 1993. Distribution and movement. p. 313-386 In: J.J. Burns, J.J. Montague and C.J.

Cowles (eds.), The bowhead whale. Spec. Publ. 2. Soc. Mar. Mammal., Allen Press, Lawrence, KS. 787 p.

Moore, S.E., J.T. Clarke and D.K. Ljungblad. 1989. Bowhead whale (Balaena mysticetus) spatial and temporal

distribution in the central Beaufort Sea during late summer and early fall 1979-86. Rep. Int. Whal. Comm.

39:283-290.

Moore, S.E., J.C. George, K.O. Coyle and T.J. Weingartner. 1995. Bowhead whales along the Chukotka coast in

autumn. Arctic 48(2):155-160.

Niebauer, H.J. and D.M. Schell. 1993. Physical environment of the Bering Sea population. p. 491-506 In: J.J.

Burns, J.J. Montague and C.J. Cowles (eds.), The bowhead whale. Spec. Publ. 2. Soc. Mar. Mammal., Allen

Press, Lawrence, KS. 787 p.

Punt, A.E. and D.S. Butterworth. 1999. On assessment of the Bering-Chukchi-Beaufort Seas stock of bowhead

whales (Balaena mysticetus) using a Bayesian approach. J. Cetac. Res. Manage. 1(1):53-71.

Renaud, W.E. and R.A. Davis. 1981. Aerial surveys of bowhead whales and other marine mammals off the Tuktoyaktuk Peninsula, N.W.T., August-September 1980. Report from LGL Ltd., Toronto, Ont., for Dome Petroleum

Ltd., Calgary, Alb. 55 p.

Richardson, W.J. and C.I. Malme. 1993. Man-made noise and behavioral responses. p. 631-700 In: J.J. Burns, J.J.

Montague and C.J. Cowles (eds.), The bowhead whale. Spec. Publ. 2. Soc. Mar. Mammal., Allen Press,

Lawrence, KS. 787 p.

Suydam, R.S., R.P. Angliss, J.C. George, S.R. Braund and D.P. DeMaster. 1995. Revised data on the subsistence

harvest of bowhead whales (Balaena mysticetus) by Alaska Eskimos, 1973-1993. Rep. Int. Whal. Comm.

45:335-338.

Treacy, S.D. 1998. Aerial surveys of endangered whales in the Beaufort Sea, fall 1997. OCS Study MMS 98-0059.

U.S. Minerals Manage. Serv., Anchorage, AK. 143 p.

Treacy, S.D. 2000. Aerial surveys of endangered whales in the Beaufort Sea, fall 1998-1999. OCS Study MMS

2000-066. U.S. Minerals Manage. Serv., Anchorage, AK. 135 p.

Treacy, S.D. 2002. Aerial surveys of endangered whales in the Beaufort Sea, fall 2000. OCS Study MMS 2002-

014. U.S. Minerals Manage. Serv., Anchorage, AK. 111 p.

Treacy, S.D. in prep. Aerial surveys of endangered whales in the Beaufort Sea, fall 2001. OCS Study MMS 2002-

061. U.S. Minerals Manage. Serv., Anchorage, AK.

Wartzok, D., W.A. Watkins, B. Würsig and C.I. Malme. 1989. Movements and behaviors of bowhead whales in

response to repeated exposures to noises associated with industrial activities in the Beaufort Sea. Rep. from

Purdue Univ., Fort Wayne, IN, for AMOCO Prod. Co. [Anchorage, AK]. 228 p.
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Wartzok, D., W.A. Watkins, B. Würsig, J. Guerrero and J. Schoenherr. 1990. Movements and behaviors of bowhead whales. Rep. from Purdue Univ., Fort Wayne, IN, for AMOCO Prod. Co. [Anchorage, AK]. 197 p.

Woodby, D.A. and D.B. Botkin. 1993. Stock sizes prior to commercial whaling. p. 387-407 In: J.J. Burns, J.J.

Montague and C.J. Cowles (eds.), The bowhead whale. Spec. Publ. 2. Soc. Mar. Mammal., Allen Press,

Lawrence, KS. 787 p.

Würsig, B., E.M. Dorsey, M.A. Fraker, R.S. Payne, W.J. Richardson and R.S. Wells. 1984. Behavior of bowhead

whales, Balaena mysticetus, summering in the Beaufort Sea: surfacing, respiration, and dive characteristics.

Can. J. Zool. 62(10):1910-1921.

Würsig, B., E.M. Dorsey, M.A. Fraker, R.S. Payne and W.J. Richardson. 1985. Behavior of bowhead whales,

Balaena mysticetus, summering in the Beaufort Sea: a description. Fish. Bull. 83(3):357-377.

Würsig, B., E.M. Dorsey, W.J. Richardson and R.S. Wells. 1989. Feeding, aerial and play behaviour of the bowhead whale, Balaena mysticetus, summering in the Beaufort Sea. Aquat. Mamm. 15(1):27-37.

Zeh, J.E., C.W. Clark, J.C. George, D. Withrow, G.M. Carroll and W.R. Koski. 1993. Current population size and

dynamics. p. 409-489 In: J.J. Burns, J.J. Montague and C.J. Cowles (eds.), The bowhead whale. Spec.

Publ. 2. Soc. Mar. Mammal., Allen Press, Lawrence, KS. 787 p.

Zeh, J.E., A.E. Raftery and A.A. Schaffner. 1996. Revised estimates of bowhead population size and rate of

increase. Rep. Int. Whal. Comm. 46:670.
23. Integration & Conclusions 23-37

APPENDIX 23.1

SENSITIVITY ANALYSIS FOR ESTIMATED AVERAGE DAYS SPENT BY

BOWHEAD WHALES IN THE FLAXMAN ISL. TO HERSCHEL ISL. AREA

Bryan F.J. Manly4

Calculation of the Statistic of Interest

The statistic of interest is the average number of days spent by bowhead whales in the study area.

The residence time data acquired in this study pertain to the area from Flaxman Island to Herschel Island

(146o to 139oW). That area includes Canadian waters between the Alaska/Canada border (141oW at the

coastline) and Herschel Isl. (see Fig. 23.1). Probable residence times in the smaller area from Flaxman

Isl. to the Alaska/Canada border (146o to ~141oW) are discussed in Chapter 23.

Ten possible methods have been considered for calculating the average residence time for each of

the years 1985, 1986, 1988, 1989, 1992, 1998, 1999 and 2000, although each method of calculation can

only be used for some of the years (see Koski et al., Chapter 11). Furthermore, only some of the methods

available for use in a particular year are considered to be reliable. Table 23.12 shows the estimates that

are considered to be suitable for use.

The goal for the sensitivity analysis was to calculate 95 % confidence limits for the true values of the

means that are shown in the last column of Table 23.12. This was done by assessing the sampling errors in the

estimated means for each of the methods, simulating this variation in Resampling Stats for Excel (Blank

2001), and hence generating distributions for the means, from which the variance can be estimated.

TABLE 23.12. Summary of reliable estimates of the average number of days bowhead

whales spent in the “Flaxman-to-Herschel” area.

Method of Estimation*

Year 1 2 3 6 9 10 Mean

1985 8.13 11.24 5.30 3.03 6.92

1986 4.18 7.12 3.81 4.42 4.40 4.79

1988 0.84 3.40 2.12

1989 4.38 4.38

1992 6.45 6.45

1998 1.00 3.38 7.35 5.31 4.26

1999 4.10 6.90 4.36 9.38 16.62 8.27

2000 3.07 3.87 2.96 3.30

Mean 5.07

*Methods of estimation are (1) photo intervals between resightings; (2) photo intervals plus travel

time; (3) photos stop-over duration best fits; (6) behavior overall speeds; (9) whale days from aerial

surveys; and (10) telemetry resightings.

 

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1756; e-mail: bmanly@west-inc.com
23-38 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

Assessing the Variances of Estimates

Each of the methods of estimation shown in Table 23.12 is based on a different principle. These

methods therefore need to be considered one by one in terms of sampling errors. In many cases lognormal distributions are used to approximate the distributions of sample estimates because these estimates

must be positive.

Method 1: Photo Intervals Between Resightings

If an individual whale is sighted in the study area, and then resighted at a later date still in the study

area, then the times between these resightings are the minimum time that the whale remained in the study

area (ignoring the possibility that the whale went outside and then returned). The estimated residence

time for Method 1 for a year is the mean of these observations. The same observations are used with

Method 2. Hence the modeling of sampling errors must be done for Methods 1 and 2 at the same time.

Method 2: Photo Intervals Plus Travel Time

This is a simple extension of Method 1. If the east-west distance between the resightings of a

whale is d, then the whale must travel (270 - d) km west in the study area to reach the initial sighting

location, and to move from the resighting location to the western boundary of the study area (which is 270

km wide). The time required for the whale to move through the study area is therefore estimated as the

time between sightings, plus the time required to move (270 - d) km, at the assumed speed of 3.67

km/hour. Note that d will be negative if the whale moves east between the sighting and resighting.

A complication is that the time between locations of a whale (t) and the distance moved (d) can be

expected to be positively correlated, which needs to be taken into account for the modeling of sampling

errors. It was allowed for by a bootstrap resampling procedure (Manly 1997), with the following steps:

(1) The sample mean values were calculated for the years where data for t and v values are available.

There were eight (t,d) observations for 1985, eleven (t,d) observations for 1986, one (t,d) observation

for 1998, and ten (t,d) observations for 1999, giving 30 observations in total.

(2) The residuals (rt,rd) for (t,d) observations were calculated for each year, by subtracting the yearly

means from the (t,d) values, e.g., rt = t - Yearly Mean.

(3) The residuals were bootstrap resampled (i.e., resampled with replacement) to produce new residuals

(rtb,rdb) for each of the original observations. New observations for each year were then generated by

adding the bootstrap residuals to the yearly means for t and d.

(4) As the minimum possible time between a sighting and resighting is one day, any values of t less than

one were made equal to one.

(5) The Method 1 and Method 2 estimates of mean residence time in the study area were calculated.

(6) Steps (3) and (4) were repeated 10,000 times to generate the distribution of estimates for Methods 1

and 2.

Method 3: Photos Stop-Over Duration Best Fits

Method 3 uses the Schaub et al. (2001) mark-recapture method to estimate the residence time of

whales in the study region for the years 1985, 1986, and 1999. Bootstrap resampling of the capture

histories of individual whales was used to approximate the standard errors of these estimates. The

estimates (with standard errors in parentheses) are as follows: 1985, 5.30 (4.90); 1986, 3.81 (3.73); and

1999, 4.36 (2.62).
§ 23. Appendix 23.1: Sensitivity Analysis for Residence Times 23-39

To simulate sampling errors in the estimated mean residence times, the distributions of these estimates were assumed to be log-normally distributed with their means and standard deviations set equal to

the estimated values. A total of 10,000 sets of estimates from these distributions were generated simultaneously with the generation of bootstrap data for Methods 1 and 2.

Method 6: Behavior Overall Speeds

For method 6, westward speeds estimated from the observations of individual whales were used.

For each of the years 1985, 1986, 1998, 1999 and 2000, there is a sample of observed speeds, so the mean

can be estimated with a standard error. Sample sizes are 4, 20, 37, 27 and 37 for the years in order.

Because of the small sample size in 1985, the estimate was not used for this year. The estimates for the

other years (with standard errors in parentheses) are as follows: 1986, 3.06 (0.60); 1998, 1.31 (0.46);

1999, 0.85 (0.40); and 2000, 2.54 (2.21).

To model sampling errors, sample mean values for 1986, 1998, 1999 and 2000 were generated

from log-normal distributions with means and standard deviations equal to the sample means and

standard errors. The mean residence times in days were then estimated as 270/[(24)·(S)], where S is the

mean speed in km/hour. A total of 10,000 sets of estimates were generated simultaneously with the

10,000 sets of data for each of the other estimates.

Method 9: Whale Days from Aerial Surveys

Aerial surveys enable estimation of the number of whale days in the study area for each of the

years 1985, 1986, 1988, 1998, 1999 and 2000, with standard errors. These estimates (with standard errors

in parentheses) are as follows: 1985, 11,937 (9634); 1986, 17,899 (7639); 1988, 3638 (2306); 1998,

31,507 (14,920), 1999, 101,850 (38,692); and 2000, 18,727 (12,209). Log-normal distributions with

these means and standard deviations were used to approximate sampling distributions.

The mean time spent in the study area is estimated for each year by dividing by the total number of

whales in the population during the year in question. This total number of whales in year i is given by

Ni = N1993(1 + G)i - 1993, where N1993 is the number in 1993, and G is the yearly growth rate. The estimated

value of N1993 is 8200 with a standard error of 566, while the estimated growth rate is 0.0320, with

standard error 0.0093. Sampling errors in these estimates are approximated by assuming log-normal

distributions for the estimates with the estimated means and standard errors.

The residence time per whale in the study area is estimated for each year by the whale days divided

by the population size. However, two adjustments are needed with this method. First, the population

sizes are multiplied by 0.814 to give the numbers passing south of the 200 m depth line, which is the area

for which the whale days are estimated. Second, the width of the area used for estimating whale days is

76 % of the width of the study area of interest. Therefore, the residence time in the study area of interest

is estimated by multiplying the estimate from whale days by 1.316 = 1.00/0.76.

To account for sampling errors in the mean residence times from whale days, random values from

the log-normal distributions mentioned above were generated and used to produce simulated mean

residence time estimates for each of the years 1985, 1986, 1988, 1998, 1999 and 2000. This was repeated

10,000 times simultaneously with the generation of estimates from the other methods.

Method 10: Telemetry Resightings

Information is available on residence times in the study area for one whale in 1988, four whales in

1989, and five whales in 1992, based on telemetry data. Because of the small sample sizes, the pooled

within-sample standard deviation of 2.50 was used to estimate the standard errors of the yearly means.
23-40 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

The estimated mean residence times with standard errors in parentheses were then found to be as follows:

1988, 3.40 (2.50); 1989, 4.38 (1.25); and 1992, 6.45 (1.12).

Sampling errors in these estimated mean values were simulated by generating random values from

log-normal distributions with means and standard deviations equal to the observed means and standard

errors. This provided new values for 1988, 1989 and 1992. This process was repeated 10,000 times

simultaneously with the generation of estimates from the other methods.

Results

The generation of simulated data from each of the methods 10,000 times produced the equivalent

of 10,000 tables like Table 23.12. The estimates of mean values that were produced had skewed distributions, but in all except one case (year 2000) the logarithms of the estimates were approximately normally

distributed (Fig. 23.3). For the year 2000 the method of generating random sets of data meant that the

value for method 2 was always 3.07. Taking this into account, it was found that for this year the variable

loge[loge{Mean - 3.07/3}]

has an approximately normal distribution (Fig. 23.4). Based on the assumed normal distributions, confidence limits for the true values of the yearly means and the overall mean were as shown in Table 23.13.

The calculated 95 % confidence limits for the mean days of whale residence in the study area for

the various years are therefore as follows: 1985, 4.6 to 10.3 d; 1986, 3.3 to 7.1 d; 1988, 0.8 to 6.0 d;

1989, 2.5 to 7.6 d; 1992, 4.6 to 9.0 d; 1998, 2.9 to 6.3 d; 1999, 5.7 to 12.1 d; and 2000, 2.6 to 5.8 d. The

confidence interval for the mean of all years is 4.2 to 6.1 days.

References

Blank, S. 2001. Resampling stats for Excel. Available from Resampling Stats, Inc., at the web site

www.resample.com.

Manly, B.F.J. 1997. Randomization, bootstrap and Monte Carlo methods in biology, 2nd ed. Chapman & Hall,

London, U.K.

Schaub, M., R. Pradel, L. Jenni. and J.-D. Lebreton. 2001. Migrating birds stop over longer than usually thought:

an improved capture-recapture analysis. Ecology 82(3):852-859.
§ 23. Appendix 23.1: Sensitivity Analysis for Residence Times 23-41

FIGURE 23.3. Distributions of logarithms of simulated mean values for the years 1985 (Y1985), 1986

(Y1986), ..., 2000 (Y2000), and for the overall mean, with fitted normal distributions shown.
23-42 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

FIGURE 23.4. The distribution of loge[loge{Mean -

3.07/3}] for year 2000, with a fitted normal

distribution shown.

TABLE 23.13. Estimated mean days that whales spend in the “Flaxman–to–Herschel” area, with simulated standard errors, and 95 % confidence limits based on the assumption that transformed estimates are

normally distributed.

Estimated

Mean Days

Simulated

Std. Err.2

Transformed

Estimate3

Simulated

Std. Err.2

Transformed Confidence

Limits4

Confidence Limits for

Mean Days Residence5

Year Residence1 Lower Upper Lower Upper

1985 6.92 1.55 1.934 0.204 1.535 2.334 4.64 10.32

1986 4.79 1.02 1.567 0.198 1.178 1.955 3.25 7.06

1988 2.12 1.30 0.751 0.530 -0.287 1.790 0.75 5.99

1989 4.38 1.25 1.477 0.282 0.924 2.030 2.52 7.61

1992 6.45 1.12 1.864 0.172 1.527 2.201 4.60 9.04

1998 4.26 0.98 1.449 0.203 1.051 1.847 2.86 6.34

1999 8.27 1.67 2.113 0.192 1.736 2.489 5.68 12.05

2000 3.30 0.66 -0.195 0.326 -0.834 0.444 2.57 5.78

Mean 5.06 0.48 1.621 0.093 1.439 1.804 4.22 6.07

1

From Table 23.12.

2

From the 10,000 generated sets of data.

3

Using the natural logarithm transformation except for year 2000 (see main text).

4

The transformed estimate plus and minus 1.96 standard errors, assuming normal distributions. 5

The transformed limits untransformed back to days, e.g. 4.64 = Exp(1.535).
§ 23. Appendix 23.2: Sensitivity Analysis for Proportion of Diet 23-43

APPPENDIX 23.2

SENSITIVITY ANALYSIS FOR ESTIMATED PROPORTION OF FOOD TAKEN BY

BOWHEAD WHALES IN THE EASTERN ALASKAN BEAUFORT SEA

Bryan F.J. Manly5

Calculation of the Statistic of Interest

The statistic of interest is the proportion of the annual food consumption of bowhead whales that is

consumed in the eastern Alaskan Beaufort Sea (Flaxman Island to Alaska/Canada border). This has been

estimated for sub-adults, adult males, adult females, and all whales, for the years 1985, 1986, 1998, 1999

and 2000.

For the sub-adults in one year the statistic is given by

Psa = FSAsa / TAFsa,

where FSAsa is the kg of plankton consumed in the study area, and TAFsa is the total annual plankton

consumption for the sub-adults. Similarly, for adult males and adult females there are the feeding proportions

Pm = FSAm / TAFm,

and

Pf = FSAf / TAFf,

while for the entire population the feeding proportion is

Pt = (FSAsa + FSAm + FSAf)/(TAFsa +TAFm + TAFf).

To estimate the food consumed in the study area it is necessary to take into account the number of

whale-days for the year (the average number of whales in the area per day times the number of days when

they may be present), the fraction of the whale-days for the group of interest (sub-adults, adult males, or

adult females), the proportion of time spent feeding, and the feeding rate (kg per day) for the group. For

example, the food consumed by sub-adults in the study area is estimated by

FSAsa = (WD)·(PWsa) ·(PTF)·(FRsa),

where WD is the total number of whale days in the study area for the entire population, PWsa is the

proportion of the whales that are sub-adults, PTF is the proportion of time spent feeding, and FRsa is the

feeding rate in kg per day of sub-adults, whilst feeding.

 

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1756; e-mail: bmanly@west-inc.com
23-44 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

The estimation of the total annual consumption involves taking into account the population size,

the proportion of the population in the group of interest (sub-adults, adult males or adult females), and the

feeding rate necessary for this group. Thus, for example,

TAFsa = (N)·(PPsa)·(93)·(FRsa),

where N is the total population size, PPsa is the proportion of the population that are sub-adults, 93 is the

total number of feeding days in a year, and FRsa is the daily feeding rate defined above.

Daily Feeding Rates

The daily feeding rates are based on the energetics requirements of the whales, for which the components are the heat loss from the body, the heat loss from the flukes, the heat loss from warming air in

breathing, the heat loss from warming food, the energy required for motion, the energy required for

growth, and the energy required by females for reproduction. Each of these components is a function of

other variables, some of which depend upon the type of whale (sub-adult male, sub-adult female, etc.),

and some of which are assumed to be the same for all whales.

The heat loss from the body for a sub-adult male (kJ/day) is given by

HLBsam = (KB)·(SABsam)·()TB)/DBsam,

where KB is the thermal conductivity of blubber (watts/m/EC), SABsam is the surface area of the body

(m2

), )TB is the temperature difference between the body core and the water (EC), and DBsam is the depth

of the blubber (m). Similarly, the heat loss from the flukes is given by

HLFsam = (KF)·(SAFsam)· ()TF)/DF,

where KF is the thermal conductivity of the fluke blubber, SAFsam is the surface area of the flukes, )TF is

the temperature difference between the fluke core and the water, and DF is the depth of the fluke blubber.

Similar equations are available for sub-adult females, males at puberty, females at puberty, average adult

males, and average adult females, with the subscripts on variables changed to saf, mp, fp, am or af,

respectively. The variables without subscripts are the ones that are assumed to be the same for all whales.

The heat loss from breathing for a sub-adult male (kJ/day) is given by

HLBRsam = (BYsam/525600)·(LVPW)·(1000WTsam)·(TVP)·(WLM)·(86400/1000),

where BYsam is the number of blows per year, 525600 is the number of minutes in a year (365x24x60),

LVPW is the lung volume as a proportion of the total body weight, WTsam is the total weight in tonnes, so

that 1000WTsam is the total weight in kg, TVP is the tidal volume as a proportion of the total lung volume,

WLM is the watts per liter per minute, 86400 is the number of seconds in a day (60x60x24), and the

factor of 1000 is to make the units for heat loss kilojoules per day. Similar equations apply for sub-adult

females, males at puberty, etc.

The heat loss due to warming food for a sub-adult male (kj/day) is given by

HLWFsam = (AFCsam/365)·(CPG)·()DW)·(4.1868),

where AFCsam is the annual food consumption (kg), CPG is the heat in calories needed to raise one gram

by one degree Celsius, )DW is the degrees of warming required, and 4.1868 is the factor for converting

calories to joules. Similar equations apply to sub-adult females, males at puberty, etc.
§ 23. Appendix 23.2: Sensitivity Analysis for Proportion of Diet 23-45

The energy required for motion for a sub-adult male (kJ/day) is given by

EMsam = (0.5)·(CD)·(SABsam/10000)·(V3

)·(8.64x10-6),

where CD is the coefficient of drag, SABsam is the area of the body in square meters (already used above),

so that ABsam/10000 is the area in square centimeters, V is the average swimming velocity (cm/sec), and

8.64x10-6 is the factor required to convert from dynes times centimeters per second to kilojoules per day.

Similar equations apply to sub-adult females, males at puberty, etc.

The energy needed for growth for a sub-adult male (kJ/day) is given by

EGsam = (37394.4)·(WGsam + WGSsam) + (60794.6)·(LGsam),

where WGsam is the annual weight gain through normal growth, WGSsam is the extra weight gain in the

summer to compensate for the loss of weight over winter, and LGsam is the extra lipid gain per year for

sub-adult males, all measured in tonnes. The constant 37394.4 is the conversion factor from tonnes

weight per year to kilojoules of energy per day, assuming that normal weight gain is 40 % blubber and

60 % muscle. The constant 60794.6 is the conversion factor from tonnes weight to kilojoules of energy

per day for blubber. A similar equation applies for sub-adult females. For older males and females there

is no allowance of extra lipid gain.

The final component of the energetics model is the cost of reproduction (kJ/day) for adult females

at puberty and average adult females. For females at puberty this is

CRfp = CPfp + CLfp,

where CPfp is the average cost of pregnancy (kJ/day), and CLfp is the average cost of lactation (kJ/day). A

similar equation applies for average adult females.

Adding up the components described above gives the total energy requirements for a sub-adult

male in units of kilojoules per day. This is converted to kilojoules per feeding day by multiplying by

365/93 = 3.925, assuming 93 feeding days per year. It is then converted to kilograms of food per feeding

day by multiplying by 4.5524 x 10-4, based on an assumed energy content of zooplankton. The result is

that the food requirement in kilograms per feeding day for a sub-adult male is assumed to be given by

FRsam = 3.925x4.5524x10-4(HLBsam + HLFsam + HLBRsam + HLWFsam + EMsam + EGsam).

Similarly, for sub-adult females, males at puberty and average adult males the food requirements

are given by

FRsaf = 3.925x4.5524x10-4(HLBsaf + HLFsaf + HLBRsaf + HLWFsaf + EMsaf + EGsaf),

FRmp = 3.925x4.5524x10-4(HLBmp + HLFmp + HLBRmp + HLWFmp + EMmp + EGmp),

and

FRam = 3.925x4.5524x10-4(HLBam + HLFam + HLBRam + HLWFam + EMam + EGam),

respectively, while for adult females at puberty and average adult females the food requirements are

FRfp = 3.925x4.5524x10-4(HLBfp + HLFfp + HLBRfp + HLWFfp + EMfp + EGfp + CRfp),

and

FRaf = 3.925x4.5524x10-4(HLBaf + HLFaf + HLBRaf + HLWFaf + EMaf + EGaf + CRaf),
23-46 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

respectively.

For the purpose of calculating the fraction of food consumed in the study area, the average feeding

rate

FRsa = (FRsam + FRsaf)/2

is used for sub-adults. Similarly, for adult males and females the averages

FRm = (FRmp + FRam)/2,

and

FRf = (FRfp + FRaf)/2,

are used.

Assessing the Variances of Estimates

The main estimates of interest are for the proportions of the annual food requirements that are

obtained in the “Flaxman–to–border” area, for the years 1985, 1986, 1998, 1999 and 2000. The main

question for the sensitivity analysis therefore concerns the likely distribution of sampling errors for these

estimates and, in particular, the biases (if any) and the variances that are associated with these estimates.

Because the estimated feeding rates per day are based on a complicated energetics equation, the

distribution of sampling errors in these estimates was considered first. The method employed was a

Monte Carlo simulation, using Resampling Stats for Excel (Blank 2001) to do the calculations. Basically,

what was done was to consider each of the many variables that are used to calculate the estimated feeding

rates, and where possible give each variable the distribution that is expected because of how it is obtained.

For example, the heat loss from the body of whales is a function of the blubber thickness, and the

average value of this thickness is estimated from a regression of blubber thickness on whale length for a

sample of 11 whales. Because the estimated regression equation will be subject to sampling errors, so

will the estimated thickness of blubber for whales of a given length. An average adult male is considered

to have a length of 13.5 meters, which gives a mean blubber thickness of 0.254 m based on the regression

equation. To model the potential sampling error in this estimated blubber thickness, the observed blubber

thicknesses of the 11 males used in the regression are replaced by their expected values plus a normally

distributed random error with a mean of zero and a standard deviation equal to the estimated error standard deviation for the regression equation. The regression equation is then refitted, and the blubber thickness for an 13.5 meter whale is re-estimated. This then simulates the blubber thicknesses that the 11

whales might have had, with the corresponding mean thickness for a 13.5 meter whale. By repeating the

simulation many times, a distribution of blubber thicknesses is obtained.

By generating random variation in all variables where this is possible and calculating the corresponding proportions of food obtained in the study area, it is possible to estimate the sampling variance in

these estimated proportions. Confidence limits for the true proportions can also be obtained, subject to

some necessary assumptions.

Table 23.14 shows how random variation was introduced for the variables involved in the calculation of the feeding rates per day for different groups of whales. For all of these variables, it is assumed

that the sampling distributions are the same for all calendar years.
§ 23. Appendix 23.2: Sensitivity Analysis for Proportion of Diet 23-47

TABLE 23.14. Random variation assumed for variables involved in calculating feeding rates per day.

Variable Notation Nature of Random Variation

Thermal Conductivity of

blubber (w/m/EC).

KB Assumed normally distributed with a mean of 0.25 and a standard

deviation of 0.03. The same values for all whales.

Surface area of body

(m2

).

SAB Estimated from a regression of log(SAB) against log(Length) for 24

whales, using the lengths 11.0 m for subadults, 12.5 m for a male at

puberty, 13.5 m for an average male and adult female at puberty, and

14.75 m for an average adult female. Random variation simulated by

giving the 24 whales in the regression new log(SAB) values equal to

the expected values from the regression plus normally distributed

random errors with a variance equal to the estimated regression error

variance, and refitting the regression. Estimated SAB varies for different lengths of whale.

Temperature difference

between body core and

water (EC).

)TB Assumed constant at 33.5E.

Depth of blubber (m). DB Estimated from a regression of blubber thickness against length for 11

whales. Random variation introduced into the results from the regression in the same way as for SAB. Estimated DB varies for different

lengths of whale.

Thermal conductivity of

flukes (w/m/EC).

KF Assumed constant at 0.20.

Surface area of flukes

(m2).

SAF Estimated from a regression of log(SAF) against log(Length) for 21

whales. Random variation introduced into the results from the regression in the same way as for SAB. Estimated SAF varies for different

lengths of whale.

Temperature difference

between the fluke core

and water (EC).

)TF Assumed constant at 15E.

Depth of fluke blubber

(m).

DF Assumed constant at 0.015 m.

Blows per year. BY Estimated blow rates are based on sample observations, with sample

means and variances available. Sample means were assumed to be

normally distributed with means equal to the observed values and

standard errors equal to standard deviations divided by square roots of

sample sizes. A separate simulation with 10,000 randomly generated

sets of data was then used to estimate standard deviations for BY.

Random values for BY were then chosen from normal distributions,

with means (M) and standard deviations (SD) as follows: sub-adults M

= 341528, SD = 36407; adult male M = 29824, SD = 29633; adult

female M = 308141, SD = 25879.

Lung volume as a

proportion of total body

weight in kg.

LVPW Assumed normally distributed with a mean of 0.0225 and a standard

deviation of 0.0054. The same value used for all whales.

...continued
23-48 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

Total weight (tonnes). WT Estimated from a regression of log(WT) against log(Length) for 29

whales. Random variation introduced into the results from the regression in the same way as for SAB. Estimated WT varies for different

lengths of whale.

Tidal volume as proportion

of the lung volume.

TVP Assumed constant for all whales at 0.60.

Watts per liter of air per

minute.

WLM Assumed normally distributed with a mean of 1.8700 and a standard

deviation of 0.0373, the same for all whales.

Food consumed in a year

(kg).

AFC This is the food consumption per feeding day (FR) multiplied by 93,

which is the assumed feeding days per year. As FR is what is estimated from the energetics equation, it was necessary to iterate this

equation so that AFC/93 equals FR for all sizes of whale. Three

iterations were found to be sufficient for this purpose, and these

iterations were incorporated for all sets of simulated data.

Calories per gram of food

per degree of heating.

CPG Assumed equal to 1.0 for all whales and all food.

Degrees of warming

required for food (EC).

)DW Assumed constant at 33.5.

Coefficient of drag. CD Assumed constant at 0.02.

Average velocity of

movement (cm/sec).

V Assumed constant at 102.78.

Annual weight gain

through normal growth

(tonnes).

WG Estimated by assuming that the lengths of a male at ages 3, 13, 25, 35

and 45 are 8.89, 11.00, 12.50, 13.50 and 14.16 meters, respectively,

and that the lengths of a female at ages 3, 10, 27, 41 and 50 are 9.44,

11.00, 13.50, 14.75 and 15.33 meters, respectively. The corresponding weights can then be determined from the regression of log(weight)

against log(length) used for the variable WT. Hence average annual

weight gains can be calculated for sub-adult males, sub-adult females,

etc. Random variation is introduced through the regression equation

as is done for WT. Expected annual weight gains are 0.84, 0.72, 0.56,

0.96, 0.83, and 0.65 tonnes, for sub-adult males, males at puberty,

average adult males, sub-adult females, females at puberty, and average adult females, respectively.

Weight gain over the

summer (tonnes).

WGS The weight gain over the summer is calculated based on regressions of

circumference against length for whales measured in spring and fall. For a

whale of a given length L and circumference C (both in meters), it is

assumed that the weight is W = 38.29 C2

 (1.082L) kilograms. The factor of

1.082 is introduced because the regression equations are estimated on

"stretched" whales. Random variation is allowed for in the estimation of

WGS by simulating new data for the regression equations, in the same

way as described for SAB. The weight – circumference relationship is

assumed to be exact as no data are available for the fitting of this.

Cost of pregnancy

(kj/day).

CP Assumed constant at 24458.9 for females at puberty and average adult

females.

Cost of lactation (kg/day). CL Assumed constant at 155118.8 for females at puberty and average

adult females.
§ 23. Appendix 23.2: Sensitivity Analysis for Proportion of Diet 23-49

By applying the random variation described in Table 23.14 and the equations given in Section 2, it is

possible to derive distributions for the daily feeding rates of sub-adults, adult males, and adult females (FRsa,

FRm, and FRf). These daily feeding rates can be expected to be correlated because they are calculated from

related variables. For this reason, the distribution of daily feeding rates was described by generating 1000

values of the triplet (FRsa,FRm,FRf) and randomly resampling these to get simulated data for deriving the

distribution of the proportion of the yearly food requirements obtained from the study area. The distributions

used for the other variables involved in calculating these proportions are described in Table 23.15.

TABLE 23.15. The distributions assumed for other variables used in the calculation of proportions of

food consumed in the study area (Flaxman Isl. to Alaska/Canada border).

Variable Notation Nature of Random Variation

Whale days WD Standard errors are available from the program DISTANCE used to

analyze line-transect sampling data. Using these, it is possible to derive a

standard error for the estimated number of whale days. For the years

being considered this results in the following estimated whale days (Est)

and standard errors (SE): 1985, Est = 11936.8, SE = 9634.6; 1986, Est =

17898.9, SE = 7639.0; 1998, Est = 31507.4, SE = 14919.5; 1999, Est =

101849.5, SE = 38691.7; and 2000, Est = 18726.6, SE = 12208.8. To

model sampling variation, the whale day estimates were assumed to be

log-normally distributed with these means and standard deviations.

Proportion of the whales

in the study area in an

age class.

PW In each year of interest there is a sample of whales in the study area from

which the proportions of sub-adults, adult males and adult females are

estimated. To simulate sampling variation, the numbers in different age

classes are assumed to have Poisson distributions, with mean values

equal to the observed counts.

Proportion of time spent

feeding.

PTF Sample estimates of the proportion of time spent feeding are available,

with standard errors, for each of the years of interest. These estimates

are assumed to have log-normal distributions, with these means and

standard deviations.

Total population size. N An estimate of the total population size in 1993 is 8200, with a standard

error of 566. There is also an estimate of the growth rate of 3.2 % per

year, with a standard error of about 0.93 %. These two estimates were

combined to produce population estimates (Est) and standard errors (SE):

1985, Est = 6373, SE = 634; 1986, Est = 6577, SE = 613; 1998, Est =

9599, SE = 790; 1999, Est = 9906, SE = 867; and 2000, Est = 10223, SE =

953. The standard errors were determined using a Taylor series approximation. Sampling error in N was simulated by assuming that the estimate

for a year is a random value from a log-normal distribution with a mean

equal to the estimated size and a standard deviation equal to the estimated

standard error.

Proportion of the

population in a group.

PP Population samples are available for the years 1985, 1986, 1989, 1990,

1991 and 1992, from which the proportion of calves, sub-adults and adults

in the whole population can be estimated. It is assumed that these

proportions change little over time, but the sample proportions are highly

significantly different. It was therefore concluded that the yearly samples

are more like cluster samples than random samples. Based on the year to

year variation it was concluded that these samples are approximately

equivalent to a single random sample of size 230, consisting of 12 calves,

230 sub-adults, and 95 adults. Random sampling variation was therefore

simulated by drawing new samples with the numbers of calves, sub-adults

and adults being randomly selected from Poisson distributions with means

equal to 12, 230 and 95, respectively.
23-50 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

Results

Figure 23.5 shows the distributions obtained for daily feeding rates of sub-adults, adult males, and

adult females. These are the distributions that were resampled as part of the simulation of the proportions

of food consumed in the “Flaxman–to–border” study area. The correlation between the estimated feeding

rates is quite high, particularly for adult males and females. This is allowed for in the simulation of the

proportion of food consumed in the study area.

FIGURE 23.5. Variation in the estimated feeding rates (kg/day) as determined from the variation in the

components of the energetics calculation.
§ 23. Appendix 23.2: Sensitivity Analysis for Proportion of Diet 23-51

FIGURE 23.5. Continued.

The main simulation to determine the effects of sampling errors on the estimates of the percentages

of food consumed in the “Flaxman–to–border” area was run with 10,000 generated sets of data. The

distributions of estimates were clearly non-normal, but became close to normal after taking logarithms, as

shown in Figure 23.6. It was therefore concluded that it is appropriate to assume that the estimated

percentages are log-normally distributed, and to calculate 95 % confidence limits for the true population

proportions on this basis. The calculations are as follows:

95 % Confidence Limits

Estimated Natural Simulated On Logarithms On Percentages3

Year % of Food Logarithm Std Err Lower1 Upper2 Lower Upper

1985 0.71 -0.348 0.743 -1.804 1.109 0.16 3.03

1986 1.45 0.374 0.458 -0.523 1.271 0.59 3.56

1998 1.21 0.189 0.520 -0.830 1.208 0.44 3.35

1999 7.53 2.019 0.401 1.234 2.805 3.43 16.53

2000 0.16 -1.829 0.869 -3.533 -0.126 0.03 0.88

1

Estimate - 1.96(Standard Error).

2

Estimate + 1.96(Standard Error).

3

Values are Exp(Values for logarithms).

The confidence limits for the proportion of food consumed in the “Flaxman–to–border” area for the five

years are therefore as follows: 1985, 0.16 to 3.03 %; 1986, 0.59 to 3.56 %; 1998, 0.44 to 3.53 %; 1999,

3.43 to 16.53 %; and 2000, 0.03 to 0.88 %.

References

Blank, S. 2001. Resampling stats for Excel. Available from Resampling Stats, Inc., at the web site

www.resample.com.
23-52 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

FIGURE 23.6. The simulated distributions for the natural logarithms of the estimated proportions of food

consumed in the study area for years 1985 (Year85), 1986 (Year86), 1998 (Year98), 1999 (Year99) and

2000 (Year00).
§ 23. Appendix 23.2: Sensitivity Analysis for Proportion of Diet 23-53

FIGURE 23.6. Continued, for 1998 and 1999.
23-54 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

FIGURE 23.6. Continued, for 2000.
ANNEX A: FINAL REPORT OF THE SCIENTIFIC REVIEW BOARD (SRB),

WITH LGL RESPONSES

Note: The plain text that follows is a verbatim, unedited copy [except for a few corrected typos] of

the report prepared by the project’s SRB in February 2002 following its final meeting on 28-29 Jan

2002. At that meeting the SRB discussed the draft final report that had been circulated before the

meeting. Unless noted as “[now...]”, Page, Figure and Table numbers mentioned in the SRB’s

comments refer to the draft report, and are not always the same in the final report.

“Boxed italic” text appearing after some SRB statements represents a response by LGL or other

project participants. Page, Figure and Table numbers quoted in “Responses” refer to the final

report.

LGL is grateful to all SRB members for their extensive review efforts at various stages of the project,

and for valuable guidance and comments provided to the project team by SRB members collectively

and individually. We are especially grateful to Dr. Steven L. Swartz, chair of the SRB, for his lead

role at SRB meetings, in preparing this and earlier SRB reports, and for participating in a workshop

in Kaktovik on 31 January 2002.—W.J. Richardson, LGL Ltd.

The third and final meeting of the Scientific Review Board (SRB) for this study was convened in

Anchorage, Alaska on 28-29 January 2002. SRB members in attendance were: Steven L. Swartz, Ph.D.

(NMFS-SEFSC & Chair), Robert Kenney, Ph.D. (University of Rhode Island), Judy Zeh, Ph.D. (University

of Washington), Mr. Craig George (NSB-DWM), Ms. Maggie Ahmaogak (AEWC), Mr. Joe Kaleak

(KWCA), Mr. Thomas Napageak (AEWC), Mr. Mark Major (ARCO), Ray Jakubczak, Ph.D. (BP

Exploration), and Mr. Brad Smith (NMFS-Anchorage). W. John Richardson, Ph.D., Mr. William Griffiths,

Mr. William Koski, Ms. Gay Sheffield, Mr. Sang Heon Lee, and Mr. Michael Galginaitis represented the

contractor, LGL Limited (LGL). Mr. Steve Treacy represented the Minerals Management Service,

Anchorage office. Mr. George Ahmaogak, Mayor NSB also attended the meeting.

The purpose of this third and final SRB meeting was to review the findings and conclusions of the

project as presented in the draft final report for Minerals Management Service (MMS) sponsored project

“Bowhead Whale Feeding in the Eastern Alaskan Beaufort Sea: Update of Scientific and Traditional

Information, Volumes 1 and 2.” The draft final report of the bowhead whale feeding study contained a great

deal of information in 23 Chapters in two volumes which were provided to the SRB for review barely two

weeks before their meeting in Anchorage. While the SRB members were able to review most of this material

before the meeting, and it was able to get through discussions of each chapter at that meeting, there was

insufficient time to completely evaluate and analyze the contents of each chapter in detail...

Response: More specifically, the draft final report was sent to SRB members in two volumes, with

Chapters 1-16 being sent on 31 Dec 2001 and Chapters 17-23 on 21 Jan 2002, in both cases by

overnight delivery. The SRB meeting was on 28-29 Jan 2002.

The SRB acknowledged that the contractor (LGL) made a effort to produce the extensive draft report in time

for the SRB meeting, but in doing so it was clear that many of the chapters could have been more effectively

integrated and cross referenced if more time had been available. The SRB expects that a more complete

integration of the information in each chapter will be appearing in the final report of the feeding study. The
A-2 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

SRB believes that the final report would greatly benefit if the study’s findings were presented in the context

of the bowhead whales= life history, annual migratory cycle, and natural history...

Response: An introductory section on the biology of the bowhead whale has been added at the start

of Chapter 1 of the final report (pages 1-1 to 1-3). Additional discussion and integration has been

added to Chapter 23, “Integration and Conclusions”, and to some extent in some other chapters.

The SRB spent the time available on the last day of the meeting formulating views and conclusions on the

overall study approach, the findings, and conclusions, and evaluating whether those conclusions were

supported by the findings of the study. In addition to the general comments on the overall study, the SRB

provides additional comments on specific chapters it had the opportunity to concentrate on during the meeting.

The SRB=s comments and findings are as follows:

General Comments

Project Limitations

The SRB reaffirmed its view as expressed at its 1999 meeting, that “the overall project was well

founded and represented needed research to better understand the use and importance of the coastal habitat

of the eastern Alaskan Beaufort Sea as a feeding habitat by bowhead whales. The SRB noted again, however,

that the magnitude of the questions being asked far outstripped the resources and time available (two-three

weeks in each year) to fully address the issue of the importance of this region to bowhead whales.” The SRB

welcomed LGL’s decision to limit the study’s focus to key activities that were most likely to provide

substantive reliable results that add to and complement previous research efforts. However, the SRB was

disappointed that its previous recommendations to employ the use of statistical power analyses to evaluate

the potential outcome of specific study projects given the limited resources and effort available was not

followed, as this approach might have improved the outcome of the study’s individual projects in key areas...

Response: At the 1999 SRB meeting, the SRB recommended that power analyses be performed,

especially of the various aircraft-based tasks, to determine the level of effort required to obtain statistically meaningful results. After that meeting, LGL worked with SRB member Dr. Judy Zeh of the

University of Washington Dept of Statistics on this power analysis. This interaction provided useful

guidance regarding the statistical power of some individual data collection efforts in addressing

specific questions. However, it did not prove possible to conduct an overall power analysis of the type

originally envisaged by the SRB. The results of the effort to perform a power analysis were given in

two sections of the Study Plan for Year 3 (Thomson and Richardson 1999, LGL Rep. TA2196-3): the

section on “Aircraft-Based Field Work”, and in Appendix B. The results are summarized in the last

5 paragraphs of Chapter 8 in both the draft and the final report, starting on page 8-4.

Using these results, the final report should present an assessment of the overall characteristics of the study

area, appropriately qualified, as feeding habitat by bowhead whales.

Response: Chapters 5-7 of the final (and draft) report address this topic, with further discussion in

Chapter 23.

The SRB noted that the information obtained in this study re-affirmed some existing knowledge and

contributed new findings to the overall body of information on bowhead whale feeding in this region.

However, the project was constrained (1) geographically, (2) temporally, and (3) financially. Regarding (1),

only a portion of the bowhead’s feeding and migratory range around Barter Island was included as the
Annex A: Final SRB Report, with LGL Responses A-3

primary study area (see Figure 9.1 on page 9-3), while it is known that the whales utilize the entire Eastern

Alaskan Beaufort Sea during the summer and fall seasons...

Response: Intensive fieldwork extended from the center of Camden Bay (longitude 145oW) to the

Alaska-Yukon border, and from the shore to the 200 m depth contour (see Fig. 1.2). This is a

reasonable representation of the “eastern Alaskan Beaufort Sea”, and is the study area that was

agreed to by the SRB and local stakeholders early in the 1998-2000 project. Aerial surveys in fact

extended farther north, west, and east, providing additional perspective. A section on the definition

of the study area has been added to Chapter 1 of the final report (pages 1-5 to 1-7).

With regard to (2), to accommodate the Kaktovik whaling season and conform to the prevailing fall weather,

the study could only be conducted during the last 2-3 weeks of September each year, while it is clear from

the whalers’ local knowledge and from previous studies that bowhead whales are found in and pass through

the study area as early as July and as late as October each year (also noted in the 1999 SRB report)...

Response: Intensive boat-based work was conducted for 2-3 weeks, and intensive aerial work for

3-4 weeks, during each of the five years of feeding study; almost all work was indeed in September.

Dates when this work was done varied among years, providing some coverage throughout

September. Additional relevant aerial work was done in August of some years and October of most

years during other projects conducted by MMS, LGL, and others; all available aerial data (1979-

2000) are used in the analysis. These aerial results provide additional perspective on use of the area

throughout the period when many bowheads are present. A section on the study period has been

added to Chapter 1 of the final report (pages 1-7 to 1-9). Local knowledge concerning occasional

sightings of bowheads in the study area during July is now mentioned more frequently, in Chapter

9 and elsewhere.

Finally, regarding (3), while the SRB recognizes the limited funding available from the Minerals Management

Service (MMS) for this study, it notes again that oceanographic studies of productivity and prey species for

whales are necessarily expensive and extensive investigations owing to the magnitude of effort required to

obtain sufficient data to be meaningful. The SRB believes that this study can be best viewed as the beginning

of a bowhead whale prey study that provides initial information that should be built upon by future

investigations that are broader in scope.

Given these limitation the SRB recognizes the need for the report of the findings of this study to be

specific and to address the results in the context of the study’s limitations. For the example, the title of the

draft final report implies that the scope of the study was broader than it was. The SRB recommends that the

title of the final report be changed to accurately reflect what was done; something like:

ABowhead Whale Feeding in a Portion of the Eastern Alaskan Beaufort Sea Around

Barter Island During the Mid-September Migration: Update of Scientific Information

and Traditional Knowledge for this Region.@

Response: Underlining has been added above to show the additional words that the SRB suggests.

The title of the draft final report was the title that was assigned to the 1998–2000 feeding study by

MMS in the “Request for Proposals” (April 1997) and in the contract:

 “Bowhead whale feeding in the eastern Alaskan Beaufort Sea: Update of scientific and

 traditional information”

We believe this is a reasonable title for the project and the report. As noted in an earlier response,

“eastern Alaskan Beaufort Sea” is an appropriate description of the study area. Work was not limited
A-4 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

to waters near Barter Island. Also, although the most intensive work was in early-mid September

(zooplankton sampling) or early-late September (aircraft-based work), aerial survey data from August

and October were also used. Furthermore, it has been argued in the past that describing the study

period as the migration period is an oversimplification, as some bowheads interrupt their migration

to feed for extended periods.

Regarding addition of “information” and “...for this region” to the 2nd clause, the added words would

not convey additional information. The first clause already defines the region under consideration.

Any attempt to develop a title more specific than that assigned in 1997 by MMS seems to lead

inevitably to problems of these types, along with an increasingly long and cumbersome title. The

original title seems to us to be accurate and to identify the key topics, as well as being consistent with

the historical development of the project. We have retained it as the title of the final report.

Use of Local Traditional Knowledge

The SRB welcomed the inclusion of “local traditional knowledge” (LTK) in the report of the study

as it previously recommended. The SRB commented that this was an extremely valuable addition to the

report of this study, as well as a significant contribution to the documentation of the cultural tradition of

native of whaling for bowheads in the Arctic. However, it was the view of the SRB that the LTK presented

in the draft report could be more effectively utilized by more completely incorporating relevant information

into the various report chapters, as appropriate. For example, the LTK presented in the draft report indicates

that bowhead whales occur in the primary study area off Barter Island as early as “July”, however, in several

report chapters the draft final report refers to “August” as the earliest that whales move into the region. The

SRB also noted that results of interviews with Kaktovik whalers yielded “little information on whale feeding”

in the region, while discussions at the SRB meeting and at the meeting with Kaktovik whaler’s and

community members following the SRB meeting yielded additional information relevant to bowhead feeding

that should be incorporated into the final study report. In this regard, the SRB recommends that complete

summaries of LTK relevant to bowhead feeding be incorporated into all of the appropriate chapters of the

final report, and that complete transcripts of the interviews with whalers be reproduced as a separate

appendix or volume to the final report of the feeding study.

Response: Additional references to LTK (including the comments about some whales occasionally

being seen in July) have been added to several chapters, and some previously-included references

to LTK have been made more prominent. New LTK mentioned during the SRB meeting (28-29 Jan

2002) and the 31 Jan 2002 Kaktovik meeting has been added to Chapter 2. The complete transcripts

of the interviews with local residents are included in the report (volume 2) as Annex B.

Program Hypotheses

The SRB previously noted in 1999 that “the hypotheses to be addressed with this feeding study are

overly ambitious given the available time for the field work to be completed, the limitations of the level of

funding of the research...” The SRB considered whether or not sufficient data could be obtained in future

seasons to adequately address the hypotheses and concluded at that time the data likely to be obtained in 1999

and 2000 field seasons “would not be sufficient to accept or reject the hypotheses as written.” The SRB

previously recommended that a quantified basis be developed for general questions and that “the text of the

study report be revised to reflect specifically what information will be required to test a specific hypothesis

or other conclusive statement or finding” based on the results of statistical power analyses.
Annex A: Final SRB Report, with LGL Responses A-5

The SRB commends the LGL for attempting to develop quantifiable terms (e.g., < 5%, <10%, etc.),

however, the findings as presented do not indicate that they were based on statistical power analyses nor do

they lend themselves to hypotheses testing in a statistical sense. As such, the SRB notes that the hypotheses

as re-formulated by LGL represent general questions that were used to direct the various component research

activities that made up the feeding study. As such, these hypotheses are not testable in a scientific sense. As

an alternative, the SRB recommends that the final report re-phrase the existing draft hypotheses as research

questions, and present the relevant findings that address these questions at face value and not as “testable

hypotheses” in the appropriate chapters of the final report.

Response: The original general hypotheses were revised to include quantitative cutpoints based on

recommendations of the SRB’s 1999 meeting. See the earlier response regarding the attempted use

of power analysis in this process. In theory, the hypotheses formulated with cutpoints (rather than

in more conventional null/alternate format) could be tested statistically. However, as the SRB

indicates, this was in fact not done in the draft final report. As all concerned now agree that the best

approach is to present the (former) hypotheses as research questions rather than formal hypotheses,

they have been reworded as questions in Chapter 1 (pages 1-9 to 1-11) and Chapter 23.

Overall Null Hypothesis

Overall null hypothesis No. 1: the null hypothesis addresses whether or not the Eastern Alaskan

Beaufort Sea is or is not a major feeding area for Bowhead whales from which they derive very little (<5%)

or a significant (>5%) portion of their annual energetic requirements. The draft final report concludes that

the overall null hypothesis is supported by the findings of the study: that “...the eastern Alaskan Beaufort Sea

is not a major feeding area for bowhead whales; the population derives less than 5 percent of its annual

energetic requirements from the area” despite findings of previous studies that suggest whales do feed in the

primary study area and throughout the Alaskan Beaufort Sea during their summer and fall migration, and

despite the findings of this study that strongly support the suggestion that bowhead whales do utilize the

eastern Alaskan Beaufort Sea including the primary study area for feeding.

The conclusion that the primary study area does not represent a major feeding area for bowhead whales

is largely based on the findings reported in Chapter 22 on the Energetics of Bowhead Whales. In that Chapter

and in Chapter 23 the authors develop a “theoretical annual energy requirement” for bowhead whales, an

estimate of the seasonal prey intake of an individual whale, and extrapolated these to the population. Then,

from these “approximations”, an estimated residence time in the primary study area and a migration timetable,

the authors estimate that the “...average bowhead whale consumes 1.2% of annual energetic requirements

in the study area...” The SRB notes and is concerned about numerous inconsistencies and unresolved

uncertainties with the methods, information, and logic used in Chapters 22 and 23 to formulate analyses and

conclusions. The SRB suggests that, if these uncertainties are taken into account, the findings of this study

may not support the overall null hypothesis (see discussion of Chapters 22 and 23 below).

Response: The “overall null hypothesis” has been reworded as “Question 1” rather than a formal

hypothesis, as discussed earlier. The specific concerns alluded to above have been addressed in

finalizing various chapters; we are grateful for the SRB’s guidance in finding and resolving these

discrepancies. These revisions have resulted in generally-small changes in the resultant estimates

of residence times, proportional food consumption in different regions, etc. The calculations in

Chapters 22 and 23 of the final report have been updated (relative to the draft reviewed by the SRB)

to take account of the revisions in various estimates. Also, sensitivity analyses have been added to

Chapters 20 and 23 to assess how much overall uncertainty there is in some of the key results given
A-6 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

the uncertainties in the various estimates used in deriving those key results. After these changes, the

conclusion with respect to null hypothesis no. 1 (now “Question 1”) remains essentially unchanged.

The SRB further notes from the findings presented in several chapters of the draft final report (e.g.,

the Chapter 2 on LTK, Chapters 3-7 on zooplankton, Chapters 17 and 21 on diet and regional occurrence of

feeding, etc.) that the observed annual variability in distribution and abundance of the prey species and the

numbers of bowhead whales observed annually in the Eastern Alaskan Beaufort Sea and the primary study

area suggests that the degree to which this region provides prey for Bowhead whales may vary greatly from

year to year. It is clear that the distribution of bowhead whale prey is dynamic and variable in space and

time, and that bowhead whales have evolved a foraging strategy to optimize the available prey. The SRB

repeats its 1999 suggestion that the importance of the eastern Alaskan Beaufort Sea, and particularly the

primary study area off Barter Island, as a feeding area “...may be a temporal variable and on average could

represent an important portion of the bowhead whales’ feeding range with the significance of its contribution

to the Bowhead whale population’s food needs varying in any given year.”...

Response: We concur that the importance of the eastern Alaskan Beaufort Sea varies from year to

year, no doubt in large part because prey availability varies from year to year. This was discussed

in the draft report as well as the final report. However, the analyses described in Chapters 22 and

23 (after updating for the final report) continue to show that the eastern Alaskan study area rarely

if ever provides more than a small portion of the total annual energetic requirements of the BCB

bowhead population. It may be important for some individual whales that linger in the area longer

than average.

Noting that only a small portion of the Eastern Alaskan Beaufort Sea was included in this study, the SRB

believes that the information obtained in this study is insufficient to conclude that the Eastern Alaskan

Beaufort Sea or any portion thereof is any more or less important than any other portion as a feeding area for

bowhead whales.

Response: We do not agree that only a small portion of the Eastern Alaskan Beaufort Sea was

included in this study (see earlier discussion). Also, this study was not asked to determine whether

the Eastern Alaskan study area is more or less important for feeding than other similar-sized areas,

and this question is not addressed specifically in the report. It is likely that the present study area

is more important for feeding than some similar-sized areas where feeding has not been seen very

often, e.g., the central Alaskan Beaufort Sea. (However, no specific study of feeding has been done

in the latter area, and some feeding does occur there—see Chapter 18.) It is also likely that the

Eastern Alaskan study area is, on average, less important for feeding than some other areas where

larger numbers of feeding bowheads are known to concentrate for extended periods during certain

years (e.g., along the Yukon coast).

With regard to the overall null hypothesis, the SRB recommends that:

1. The final report be revised to reflect important new findings from this study including: Local Traditional

Knowledge confirmed many of the research findings concerning bowhead whales’ use of the primary study

area; analysis of stomach contents from harvested whales and observations of behavior indicate that bowhead

whales do feed in the primary study area in mid-September; more sub-adult whales utilize the near shore

portion of the primary study area than do adult whales; and the first ever direct measurement of bowhead

whale prey species in mid-September were obtained for the primary study area.
Annex A: Final SRB Report, with LGL Responses A-7

2. Given these findings, the final report be revised to describe the dynamic nature and annual and seasonal

variability of bowhead whale prey that occurs in the primary study area and other portions of the Eastern

Alaskan Beaufort Sea as revealed in the findings of this study;

Response (re points 1 and 2): The draft report covered all these topics, as does the final report. LTK

is mentioned more prominently in several chapters of the final report, and the detailed transcripts

of discussions with local residents are now included as Annex B.

3. The final report should clearly state that the findings of the various component projects within the overall

study indicate that in any given year the primary study area off Barter Island appears to have the potential

to provide at least as much food resources for bowhead whales as does any other portion of the Eastern

Alaskan Beaufort Sea, and;

4. The findings of this study, in and of themselves, cannot confirm or conclude that the eastern Alaskan

Beaufort Sea or any portion of it is any more or less important than any other portion as a feeding area for

bowhead whales in any given year.

Response (re points 3 and 4): The primary study area included the full Eastern Alaskan Beaufort

Sea (inshore of the shelf break), not just waters off Barter Island. Some parts of that study area more

commonly support concentrations of feeding whales than do other parts, but available evidence

suggests that bowheads may at times feed anywhere in the continental shelf portion of the Eastern

Alaskan study area. This study was not designed to determine whether the study area is more or less

important for feeding than other comparably-sized areas of the Beaufort Sea. However, based on

available evidence, one can identify similar-sized areas that, over a number of years, appear to be

more important and others that appear less important (see above).

5. Indicate that additional research on the seasonal occurrence and dynamics of bowhead whale prey need

to be evaluated in other areas of the Beaufort Sea visited by bowhead whales and at other times (i.e., before

and following September) in order to provide a comparative context to evaluate the importance of any single

area during any single year.

Response: We concur, and this is mentioned in the “Recommended Studies” sections that have been

added to Chapters 7 and 23 of the final report.

The SRB recommends that, to provide a context for the contents of the final study report, this report

of the SRB’s 28-29 January 2002 meeting including the SRB’s comments and recommendations on the draft

final should be included as a chapter in the final report of this bowhead whale feeding study along with

appropriate responses from LGL and MMS. Response: Done – this “Annex”.

Finally, the SRB recommends that a non-technical summary of the findings of this bowhead whale

feeding study be produced in “layman’s language” and widely distributed as a public information document.

Such a document should present the key findings of this study of the area off Barter Island in the overall

context of the bowhead whales’ natural history and annual migratory cycle, and make full use of LTK and

information collected from local people and historical documents and publications that is relevant to bowhead

whale feeding behavior and biology.
A-8 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

Individual Chapter Comments

Chapter 2. Kaktovik Whaling - Local Traditional Knowledge

The SRB applauds the incorporation of Local Traditional Knowledge (LTK) into this investigation of

bowhead whale feeding biology and behavior. The SRB believes, however, that more LTK relevant to the

issue of whale feeding could have been obtained if the questions asked during investigative interviews had

been formulated differently. It became clear to the SRB during discussions of this topic that relevant

information was often buried in descriptions of other topics or in historical accounts of events not specifically

about feeding (e.g., accounts of the hunting of whales). The SRB noted that additional sources of LTK were

available and should be more fully utilized in the preparation of this report. For example, G. Sheffield (LGL

Sub-Contractor) had acquired detailed information on bowhead whale feeding from her discussions with

whalers during the collection of stomach contents from harvested whales and related activities. Similarly,

the SRB wonders if additional LTK could be obtained from L. Soloman, the local Kaktovik participant in the

small boat surveys? Additional sources of LTK could be obtained from published accounts of life in the

Arctic by early explorers and historians (e.g., C. Brower’s book “50 years below Zero”).

Response: We now include the full transcripts of the individual discussions as Annex B (in volume

2). Also, subsequent to the final SRB meeting we have reviewed those transcripts again and have

identified a few additional points relevant to the study. References to that information, and to LTK

mentioned during meetings in Kaktovik, have been added or expanded in various locations in the

report, including Chapters 2, 6, 9, 10, 11, 12, 22 and 23. In most of these chapters, we have added

a paragraph on relevant LTK at the start of the Discussion, along with addition references to LTK

at relevant places elsewhere in the chapter. It is quite possible that additional relevant LTK might

be found through a more extensive review of published and unpublished sources than was possible

here; however, an exhaustive search for such sources was beyond the agreed scope of the study.

With regard to the data on the lengths of harvested whales in Figures 2.6 and 2.7 on page 2-13, the

SRB recommends that these data be presented by sex of the harvested whales rather than in aggregate, or

both ways to be most informative. Response: Done.

The SRB notes that the LTK that was obtained during this study could be more completely integrated

into the report of the findings and more accurately referenced. For example, the LTK indicates that bowhead

whales are seen off Barter Island from July through November, yet in other report chapters the authors refer

to “August” as being the earliest arrival data of the whales. The SRB recommends that: (1) the authors

review the existing interviews against the behaviors used to characterize bowhead feeding behavior, as well

as other feeding observations, and that any additional relevant information incorporated into the report of the

feeding study; Response: Done. (2) that rather than isolating the LTK in a single chapter, this information

should be fully integrated into all relevant chapters and their discussions; Response: Done. and (3) in

Chapter 23 summarize for each conclusion the contribution of LTK to that conclusion, be it in agreement or

disagreement with that conclusion... Response: Done. Given the relevance and cultural importance of the

LTK obtained in this study, the SRB further recommends that the complete text of the information interviews

with whalers and local Kaktovik residents be published in a separate appendix or volume to the final report

of this feeding study. Response: Done – see Annex B.
Annex A: Final SRB Report, with LGL Responses A-9

 Chapters 3-7. Zooplankton Sampling:

While the SRB commends LGL for undertaking zooplankton sampling as part of this study, it recognizes that obtaining samples and information adequate to accurately characterize bowhead whale prey

resources is a monumental task that requires a great deal of time, sampling over a wide range of the whales’

habitat, and funding that generally outstrips available resources. The vessel utilized for the zooplankton

studies was limited in its range and the number of days it could operate within the primary study area due to

the conduct of the Kaktovik fall whaling season and prevailing weather conditions. It was also noted that

zooplankton distributions change during the night, and that the vessel based sampling occurred only during

daylight hours.

Response: The Discussion of Chapter 5 (page 5-37) now addresses the lack of data on diel vertical

migration by zooplankton in the Beaufort, and this is also mentioned under “Recommended Studies”

(Chapters 7, 23). Most of our sampling (including all of that in 1998–2000) was in places where

water depth was sufficiently shallow that we were able to document zooplankton throughout almost

all of the water column. Although the measured biomass might have a different vertical distribution

at night, the overall average biomass would not be expected to differ appreciably at night.

In their presentation to the SRB, LGL acknowledged that there was generally a poor correlation

between the bongo net sampling and estimates of zooplankton density from the hydroacoustic sampling. In

response to questions from the SRB, LGL acknowledged that some small plankton may have passed through

the nets and escaped as could fast moving prey like euphausiids, but these zooplankton may account for high

biomass detection from the hydroacoustic records. These observations suggested that there was a need for

improved calibration of these methods. SRB member J. Zeh recommended that the authors should utilize

covariates to try to explain some of the variation in the biomass data. Such covariates might include, e.g.,

some measure of the importance of euphausiids in the net samples for a given year (see below).

Response: Over the five seasons, the correlation between echosounder data and net biomass ranged

from weak (1998) to strong (1999). Given the weak relationship in 1998, the 1998 echosounder data

were not used to estimate zooplankton biomass. Net avoidance and the possibility of small copepods

passing through the mesh are addressed in the Discussion sections of Chapters 4 and 6. No useful

covariates were available for re-analysis, but a robust regression method is used in the final report

as suggested by the SRB (below). We agree that further research is needed on methods for quantifying zooplankton from echosounder data. Possible approaches for future studies in the Beaufort

Sea are discussed in Chapter 4 (page 4-13) and under “Recommended Research” in Chapter 7.

Despite these difficulties, this study obtained new and significant information on the composition and

distribution of principal prey species of bowhead whales within the primary study area. These data, however, are

insufficient to support statements in the draft final report that characterize the entire eastern Alaskan Beaufort Sea

in all seasons when whales are present. The SRB recommends that the final report clearly state that such

characterizations are limited to the areas in which the zooplankton samples were obtained (i.e., the primary study

area off Barter Island) and specify the time periods during which they were obtained (i.e., mid-September).

Response: See previous responses to SRB comments on the study area and study period, and discussion of these matters that has been added to Chapter 1 (pages 1-7 to 1-9).

The SRB noted that euphausiids may escape the 0.6 m wide plankton nets utilized in this study, and

as a result may be under-represented in the samples obtained. This could bias the conclusions concerning the

prey types that bowhead whales feed on in the eastern Beaufort Sea compared to the Chukchi and Bering Sea.
A-10 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

The SRB recommends that the final report note this potential bias, and discuss the implications of this bias

on conclusions of the prey species bowhead whales exploit in the eastern Alaskan Beaufort Sea.

Response: The net-avoidance phenomenon and other known or potential biases were addressed in

the Discussion sections of Chapters 4 and 6 of the draft report, and these sections have been refined

in the final report.

The plots of zooplankton biomass provided in Figure 4.2 on page 4-9 present the “best fit” linear

relationships between zooplankton biomass in the horizontal net tows and corresponding volume backscatter

data. The SRB question why the data for 1999 and 2000 were pooled - presumably to improve the correlation

between the horizontal tow data and the corresponding echo-sounder data, when the result of pooling

diminished the correlation for 1999 presented in Table 4.3 on page 4-8. The SRB recommends that the data

be re-analyzed by not pooling independent years, and utilizing the correlations for each year independently

in their analyses. Alternatively, use of covariates with pooled data that would permit a better fit to the data

from each of the pooled years might be explored. The SRB further recommends that the final report contain

some discussion of the advantages, disadvantages, and effectiveness of both horizontal plankton tows and

echo sounding methods to assess zooplankton biomass in the Beaufort Sea.

Response: In the final report, separate regression equations for 1999 and 2000 are used throughout.

As a result, numerous changes, mostly subtle, have been made to diagrams in Chapters 4, 5 and 6.

These changes did not necessitate any notable changes in the interpretation.

The plots of average biomass in the water column and maximum biomass of zooplankton shown in

Figure 5.15 [now Fig. 5.16] on page 5-28 truncate the data for maximum biomass at 1,000 mg/m3

. The SRB

believes that these maximum values would be instructive, and it recommends that these data be re-plotted to

show the peaks of maximum biomass. The SRB also notes that there are instances where maximum

zooplankton biomass peaks occur, but are not evident in the corresponding plots of mean water column

biomass. The SRB recommends that these differences be explained in the final report, and suggests that LGL

investigate alternative analysis methods, such as “robust regression techniques” to evaluate the relationship

between horizontal net tows and corresponding echo-sounder data.

Response: Done. Graphs showing estimated biomasses >1000 mg/m3

 now show actual bestestimates, without truncation. A cautionary note about the uncertainties has been added to p. 5-25

(footnote). Apparent discrepancies between maximum and mean biomass are to be expected when

layers are only 1 or 2 m thick, as now discussed on page 5-25. A robust-regression technique is now

used to derive the net biomass vs. acoustic biomass relationships for 1998–2000, as described in the

revised Chapter 4 (page 4-7; see also Fig. 4.2).

In view of the findings of the limited zooplankton sampling conducted the primary study area, the SRB

repeats its 1999 view that “the available data suggest that prey availability may be highly variable from year

to year in the Eastern Alaskan Beaufort Sea and that in any given year the nature of this variability may result

in specific areas of the Beaufort Sea being more or less important as feeding areas. In this regard, the eastern

Alaskan Beaufort Sea may be more or less important to bowhead whales in different years. Thus, several

years of monitoring of the available prey in the eastern Alaskan Beaufort Sea will be required to assess the

overall importance of this area as a source of food for Bowhead whales...

Response: We concur that prey availability and importance of the area to bowheads are quite

variable from year to year, as now documented over five autumn migration seasons and discussed

in the draft and final reports (Chapter 5). However, those data, plus data on bowhead use of the
Annex A: Final SRB Report, with LGL Responses A-11

area (over 21 years), even with allowance for the uncertainties, provide strong evidence that that the

present study area provides no more than a small percentage of the food required by the bowhead

population – even in years of higher-than-average use by bowheads (see revised Chapter 23,

including sensitivity analyses in Appendices 23.1 and 23.2).

...compared to other areas such as the Chukchi Sea.” The SRB therefore recommends that MMS continue

to sponsor investigations on the distribution and seasonality of bowhead whale prey species throughout the

range of the species for comparison with, and to provide a context for understanding the importance of the

eastern Alaskan Beaufort Sea as a feeding habitat for bowhead whales.

Response: Many of the same types of data on food availability and bowhead feeding are available

for parts of the summer range of bowheads in the Canadian Beaufort Sea. However, few data of

these types are available for the western Alaskan Beaufort Sea, or the Chukchi Sea, or other areas

within the annual range of BCB bowheads where bowhead feeding is known or suspected to occur.

We concur that additional research on food availability and bowhead feeding ecology is desirable

in these areas. This is mentioned in the list of recommended research that has been added to

Chapters 7 and 23. However, this additional research is unlikely to result in any major change in

present understanding of the importance of the eastern Alaskan Beaufort Sea, which has already

been studied in considerable detail for the period of peak bowhead occurrence during September.

Chapter 9. Distribution and Numbers of Bowhead Whales in the Eastern Alaskan

Beaufort Sea During Late Summer and Autumn, 1979-2000.

The SRB viewed the results presented in this chapter as informative, except that the distinction

between observations from this feeding study relevant to the primary study area and information collected

from “a large number of studies conducted in late-summer and autumn” in other portions of the Beaufort Sea

was not clear, and implied that the information collected in this feeding study was actually more extensive

than it is and represented periods of time other than mid-September when the feeding study was conducted.

As a result, the reader is lead to believe that all the data presented was collected in and relevant to this primary

study area and collected during the 2-2.5 weeks in each September. ...

Response: The present study was planned from the outset to incorporate all relevant scientific data

(and traditional knowledge), not just the “new” data acquired during the specific feeding-study

fieldwork in 1998-2000 (or 1985-86 and 1998-2000). Extensive aerial survey data are available

from many additional years, and from August and October as well as September. These data

complement and extend those from the specific feeding studies, and have been used in Chapter 9 as

called for by the project plan. The temporal and geographic extent of the data used are described

in detail in the “Methods” of both the draft and final versions.

... In this regard, Figure 9.1 on page 9-3 was extremely helpful for understanding the location and extent of the

primary study area and its relation to the greater eastern Alaskan Beaufort Sea. The SRB recommends that figure

9.1 be replicated in appropriate chapters of the report to aid in understanding the distinction between the primary

study area within the Beaufort Sea. The SRB also recommends that a clear distinction be made between data

collected and directly relevant to the primary study area and data collected in other areas and at other times. In

this regard, the SRB recommends that the authors develop a data/information summary table, that presents all

the various data sources from each activity that was a component of the feeding study and the dates when those

data were collected. The table could also indicate the sources and dates of collection for data/information that was

collected from other studies but included because of its relevance to the feeding study.
A-12 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

Response: In the final report, study area maps have been added or clarified in some other chapters

(e.g., Chapter 1). The two regions analyzed in Chapter 9 (“extended” and “restricted”) are described in that Chapter. Some rewording has been done to help clarify which of these two regions is

under consideration in each subsection, Figure and Table. A Table has been added to Chapter 23

(Integration and Conclusions) to summarize the study area and dates for the data assembled on each

major topic.

In Figures 9.10-9.11, 1979-89 are compared with 1990-2000. This is a logical breakpoint given the

time span of the studies. However, for some water-depth strata and regions, 1990 is a more appropriate

breakpoint in terms of equalizing the number of years with surveys in the early and late periods. It would be

useful to examine the sensitivity of summary statistics and conclusions to defining the early period as 1979-90

and the late as 1991-2000. This also applies to the significance tests given on pp. 9-26 and 9-28 of the report.

Response: Done, as now noted on pages 9-22, 9-27, and 9-30. There was no effect on conclusions.

On pp. 9-28 and 9-30 [now p. 9-29 to 9-31] the authors present a good discussion of a number of

possible reasons for the estimated increase in whale population during the 1990s. However, some further

confounding factors should also be discussed. For example, the early period shows higher continental slope

values; this may be because it was surveyed in early August only during this period. Effects of changes in

survey timing, planes, observers, altitudes, prey availability, and other factors make interpretation of the

results difficult even though adjustments were attempted for some of these. Some of these factors,

particularly the years in which surveys were conducted in August and October, may have created biases in

the 10-d moving averages used in estimating whale-days.

Response: The Discussion section of Chapter 9 has been expanded to further address these

questions.

Additional Note: At the 28-29 Jan. 2002 meeting of the SRB, a question was raised concerning the

applicability of line transect procedures to single surveys with few or even zero sightings. This

practice is legitimate when the f(0) and g(0) factors were derived from larger samples combined

across days, as here (Buckland et al. 2001, p. 88). This is now noted at the bottom of p. 9-8.

Chapter 11. Bowheads: Rates of Movement & Residence Times:

In its 1999 report, the SRB noted that “the requirement of re-sighting of an individual whale for more

than 10 days to establish the significance of an individual whale’s residency in a feeding area is not feasible

due to the limited number of field days available to obtain photographic identification data.” and strongly

recommended “that a power analysis be conducted utilizing the results of the 1995, 1996, and 1998 field

season to re-evaluate the effort required to obtain sufficient data to assess whether whales remain in a

specific area for prolonged periods of time, and adjust the sampling design accordingly.” The SRB was

disappointed that such a power analysis was not included in the draft final report, but believed that LGL did

what they could to establish and estimate residence time for an individual whale given the photographic

identification and other information that was obtained during this study. ...

Response: See response to first paragraph of “General Comments”, above (p. A-2), regarding

power analysis; see also pages 8-4 to 8-5 in Chapter 8. In response to the SRB’s 1999 concerns

about the level of effort devoted to the residence time question (via photoidentification), we reduced

the proportion of the effort devoted to systematic aerial surveys and increased the effort devoted to

photoidentification during 1999 and 2000 as compared with 1998.
Annex A: Final SRB Report, with LGL Responses A-13

The estimates of residence time for migrating and feeding bowhead whales presented in the draft final report

appear reasonable for the mid-September time frame, and are consistent with historical information.

However, the SRB recommends that similar studies be continued in the future for other times of the year and

locations, and that these include statistical power analyses to maximize the information return on effort

expended and to improve the database for these kinds of analyses.

Response: We concur that additional data on residence times would be very valuable for the present

eastern Alaskan study area (where available data are limited in various ways), for more westerly

parts of the Alaskan Beaufort Sea, and for the western Chukchi Sea. This is mentioned in the list of

recommended research that has been added to Chapters 16 and 23.

Chapter 12. Activities and Behavior of Bowhead Whales in the Eastern Alaskan

Beaufort Sea During Late Summer and Autumn.

As with previous chapters that incorporate information obtained from other studies, the SRB

recommends that a clear distinction be made between data collected in the primary study area during the 2

to 2.5 weeks in September that the feeding study was conducted and data from other studies. In this regard,

the SRB recommends that the authors develop a data/information summary table, that presents all the various

data from each activity that was a component of the feeding study and the dates when those data were

collected. The table should also indicate the sources and dates of collection for data/information that was

collected from other studies but included because of its relevance to the feeding study.

Response: Page 12-3 now provides a more explicit statement concerning the number of Behavioral

Observation Sessions (BOSs) within eastern Alaskan waters vs. waters east of the Alaska/Canada

border. Also, BOSs in Canadian waters are now more explicitly identified (boxes) in Appendix 12.1.

Chapter 13. Surfacing, Respiration and Dive Cycles of Bowhead Whales in the Eastern

Alaskan Beaufort Sea During Late Summer and Autumn as Related to Whale Activity.

As with previous chapters that incorporate information obtained from other studies, the SRB

recommends that a clear distinction be made between data collected in the primary study area during the 2

to 2.5 weeks in September that the feeding study was conducted and data from other studies. In this regard,

the SRB recommends that the authors develop a data/information summary table, that presents all the various

data from each activity that was a component of the feeding study and the dates when those data were

collected. The table should also indicate the sources and dates of collection for data/information that was

collected from other studies but included because of its relevance to the feeding study.

Response: New Table 13.1 added on page 13-2. Table 13.1 and associated text include crossreferences to Appendix 12.1a-f and Figure 12.1, which list and map the locations of the individual

observation sessions.

The SRB notes that the term “respiration” has a specific meaning in a physiological context and

recommends that the words “breathing” or “blow rate” be substituted in the title and text of this chapter.

Response: “Respiration” is widely used as a synonym for “blow” or “breath” in the baleen whale

literature, and we have retained this usage. Blow rate has a specific meaning (blows per minute).

Information about blow rates (and percent of time at surface) has been added to Appendix 13.1.

The SRB assumes that the depth information presented in this chapter was obtained from nautical

charts (?), but this is not clear in the text.
A-14 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

Response: Sources of depth information were (and are) stated in Chapter 9 (page 9-7). A crossreference to this information is now repeated in the Methods of Chapter 13 (p. 13-4).

Additional Note: At the SRB meeting, it was also suggested that information about “blow rates”

should be added. Mean blow rates and mean % time at surface are now shown in Appendix 13.1,

and some of the key values are mentioned in the Results (p. 13-6 to 13-8, plus 13-11)

Chapter 14. Surfacing, Respiration and Dive Cycles of Bowhead Whales

in the Beaufort Sea: Calves, Subadults and Adults.

As with previous chapters that incorporate information obtained from other studies, the SRB

recommends that a clear distinction be made between data collected in the primary study area during the 2

to 2.5 weeks in September that the feeding study was conducted and data from other studies. In this regard,

the SRB recommends that the authors develop a data/information summary table, that presents all the various

data from each activity that was a component of the feeding study and the dates when those data were

collected. The table could also indicate the sources and dates of collection for data/information that was

collected from other studies but included because of its relevance to the feeding study.

Response: New Table 14.1 added at start of “Methods” (p. 14-3).

The SRB notes that the term “respiration” has a specific meaning in a physiological context and

recommends that the word “breathing” be substituted in the title and text of this chapter.

Response: No change; see response to corresponding comment on Chapter 13.

Chapter 18. Diet & Regional Feeding: Stomach Contents:

The SRB recognizes the importance of stomach contents from harvested whales as the most direct

evidence of bowhead whale feeding, and recommends that the sampling of stomach contents from harvested

whales continue and that previously collected samples also be analyzed. The SRB noted that the data in table

18.3 of estimated stomach volumes suggest “feeding bouts” in pockets of high prey density – higher prey

density than that indicated in the zooplankton sampling net tows. SRB members R. Kenny and C. George

did a “quick calculation” suggesting that for whale 99KK2 to fill its stomach in a “reasonable” amount of

time, the prey density would have to be ~ 5 gm/m3

 based on 150 L of prey in the stomach and a 2 m2 mouth

gape, suggesting that the zooplankton net sampling was biased low and did not collect a representative sample

of these dense prey pockets. This should be noted in this chapter and in the zooplankton and energetics

chapters...

Response: We acknowledge that whales may more adept at finding a high biomass than we are, and

that we may at times underestimate the biomass of prey that is present. However, as described in

Chapter 6, during 1986 we sampled near one whale where zooplankton biomass was found to be 3.8

g/m3 and near two other whales where biomass was found to be 3 g/m3. In 1988 we obtained 5 g/m3

in a vertical tow near whales in the Canadian Beaufort Sea, and in 1989 Wartzok et al. (1990) found

a biomass of euphausiids of 3 g/m3 in a vertical tow near whales in the Eastern Alaskan Beaufort

Sea. If a zooplankton biomass of 5 g/m3 was present at some depth at a sampling station where

echosounder-guided horizontal tows were taken, we would have documented a high biomass.

...The SRB further recommends that LGL and MMS work with the AEWC to obtain stomach samples from

whales harvested by the native whalers in areas to the west of Kaktovik, particularly attempt to get samples
Annex A: Final SRB Report, with LGL Responses A-15

from harvested whales that may have been feeding the Bering and Chukchi Seas in winter (e.g., off St.

Lawrence Island).

Response: Data from all available stomach-content samples acquired at more westerly locations in

the Beaufort Sea, i.e., Cross Island and Barrow, were already included in Chapter 18. ADF&G has

provided a Table of information about stomach contents of whales harvested during the spring hunts

at St. Lawrence Island; this Table has been added to Chapter 21. The desirability of further

sampling in the Bering and Chukchi Seas is noted in the list of “Recommended Research” on diet

and regional occurrence of feeding, added to Chapters 21 and 23.

Additional Note: At the SRB meeting on 28-29 Jan. 2002, there was a request to document the

relationships between individual diet items and the factor scores. This has been added as Appendix

18.6.

Chapter 19. Fatty Acids in Bowhead Whales and Potential Prey from the

Alaskan Beaufort Sea

The SRB welcomed the preliminary fatty acid analyses as a contribution of new information for the

study of bowhead whale feeding, recognizing that uncertainties remain in the methodology. The SRB

recommends that MMS sponsor future research on the application of fatty acid analyses as a component of

future bowhead whale feeding studies.

Response: LGL concurs, and this is now mentioned in the list of “Recommended Research” on diet

and regional occurrence of feeding, added to Chapters 21 and 23.

Chapter 20. Diet and Regional Feeding: Stable Isotopes

The overall conclusion of this chapter is that bowhead whales obtain the majority of their annual prey

intake in the Bering and Chukchi Seas and not in the Eastern Beaufort Sea. The SRB noted that this

conclusion is in contrast to the findings presented in other chapters of the draft final report and an

overwhelming body of evidence from other studies that suggest that bowhead whales feed continuously

during their spring, summer, and fall migrations across the Beaufort Sea, during which time they gain weight

and girth as is evident in the analysis of whales harvested by the native whalers and from aerial photography.

The SRB recognizes that the isotope analyses “...are subject to a variety of assumptions...” that are difficult

to test, but none the less, they raise concern about the accuracy of the method and conclusions given other

evidence of bowhead whale feeding in the Beaufort Sea as a whole.

Response: We agree that the results of Chapter 20 are not easy to reconcile with other data

demonstrating the frequent occurrence of feeding in the eastern Beaufort Sea. The final version of

Chapter 20 (Discussion section), and also the final version of Chapters 21-23, describe an annual

feeding scenario that might be at least generally consistent with all data. It is acknowledged that

additional data of numerous types are needed to verify (or otherwise) this possible interpretation of

the now-available data. Studies listed under “Recommended Research” in chapters 21 and 23 would

provide some of the needed data.

The SRB noted that an independent review of Chapter 20 was solicited by LGL, but this review was

not made available to the SRB at the time of its January 28-29, 2002 meeting in Anchorage. In an e-mail to

LGL (W.J. Richardson) the reviewer (K. Hobson) indicated that “At the very least, much more explanation

is required for the method of calculating the percent feeding in the eastern Beaufort”, and that there are likely

“...alternate explanations of the results provided.” The SRB was disadvantaged when reviewing this chapter
A-16 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

owing to a lack of expertise in isotopic analyses within its members. However, the SRB noted similar

concerns with the methods and analyses of the information presented in this chapter, and recommends that

the final report incorporate and address the points and uncertainties raised by the independent reviewer.

Response: The comments from Dr. K. Hobson, mentioned above, concerned an earlier draft of

Chapter 20, not the one included in the draft final report as reviewed by the SRB. Dr. Hobson

provided updated comments (in Feb. 2002) on the draft final version of this chapter, i.e. the version

that the SRB reviewed. He noted that “I found this to be a much improved draft...” However, he

again expressed concerns about the use of baleen data to estimate the proportion of the diet acquired

from the eastern Beaufort. He also recommended a sensitivity analysis to assess how strongly the

results depend on various uncertain estimates. Some other reviewers had similar comments. The

present final version of Chapter 20 has been substantially modified, and now uses data on isotope

ratios in muscle rather than baleen to estimate proportional food intake in the eastern Beaufort Sea.

Also, a sensitivity analysis has been added as Appendix 20.1, as suggested by several reviewers.

The SRB further noted that additional stomach contents from harvested whales were made available

to the authors of Chapter 20, but these were not, but should have been, analyzed and included in the

analysis...

Response: The final version of Chapter 20 takes account of the latest data (from Table 18.7 in

Chapter 18) on the proportional composition of the stomach contents of whales harvested at Kaktovik

and Barrow (see updated values in Table 20.3). Those data were not yet available at the time when

the draft version of Chapter 20 was being prepared. As to the suggestion that isotope composition

of stomach contents should have been analyzed, this would not have been helpful given the probable

contamination issues. Also, while it would be interesting to confirm the specific isotope composition

of prey consumed east of Barrow in fall, the isotope composition of the main types of zooplankton

prey has already been determined, from direct zooplankton sampling, for the general areas where

stomach content samples have been obtained.

...The SRB questioned whether the use of the long-term (decadal) correction factor was needed or appropriate

Response: For reasons discussed in both the draft and final versions of Chapter 20 (and in papers

cited therein), the decadal correction factor seems necessary. However, it is acknowledged that this

introduces uncertainty. This uncertainty is dealt with in the final version of Chapter 20 in two ways.

(a) Appendix 20.1 estimates the 95% confidence limits for the percent of the food acquired in the

eastern Beaufort, including allowance for uncertainty in the slope of the decadal correction factor.

(b) The Discussion section of Chapter 20 now discusses, in some detail, the recently published data

of Hoekstra et al. (2002, Can. J. Zool. 80: 223-231), which provide carbon isotope data from

bowhead whales harvested in spring and fall of the same years. For these data, no decadal

correction is needed. Those data were not available when the draft of Chapter 20 was prepared and

submitted.

...and it questioned the “isotopic fractionation factor” assumed for the tissues analyzed.

Response: In the final version of Chapter 20, baleen data are no longer used in a quantitative way

for estimating proportional feeding in the eastern Beaufort Sea, so the fractionation factor is no

longer relevant.

The SRB is curious why the isotope analysis results are contradictory to other study findings, and

recommends that a sensitivity analysis of the uncertainty in the calculated proportion of food that bowhead
Annex A: Final SRB Report, with LGL Responses A-17

whales might obtain in the eastern Beaufort Sea compared to other areas (e.g., western Beaufort Sea, Bering

and Chukchi Seas, etc.) be conducted to test the assumptions that are relevant to the calculations. The most

important of these include the value of the isotopic fractionation factor and the assumed diet composition

(Tables 20.3 and 20.4). The fractionation factor could have been examined (e.g. by analyzing prey in the

stomach and tissue samples from the same whale) but was not. Tables 20.3 and 20.4 should have been, but

were not, updated by analyzing samples collected during the present study. Note the discrepancy between

Table 20.3 and the summary of the results of the stomach content analyses of the present study on p. 21-2.

Response: A sensitivity analysis has been added in Appendix 20.1 of the final report. That Appendix

estimates 95% confidence limits for the proportion of the food acquired in the eastern Beaufort Sea.

The confidence limits are fairly wide, but are consistent with earlier evidence that prey from the

eastern Beaufort Sea provides only a minority of the total food for this stock of bowhead whales.

Analyses of isotopic composition of stomach contents would, if they had been done, be subject to

concerns about contamination. In any event, the fractionation factor is no longer relevant as baleen

data are no longer used quantitatively. Diet composition data in Table 20.3 have been updated as

described previously, eliminating the discrepancy relative to p. 21-2, and the updated values are now

used for the calculations.

The SRB further recommends that additional samples and data (e.g., prey samples, stomach contents,

fatty acid samples, genetic samples, measurements of girth, etc.) should be obtained from whales harvested

around St. Lawrence Island for comparison with the results reported in Chapter 20 of the draft final report,

in particular to test whether bowhead whales do feed in winter in the Bering and Chukchi seas. The SRB also

recommends that the final report clearly state that the isotopic composition of bowhead whale tissue and prey

tissue “through the range of the bowhead whale” was not tested, and that additional prey samples and

stomach contents will be required to constitute a comprehensive analysis of all bowhead feeding areas. Future

work should also consider the role of the lipid content in late summer and fall prey in building the bowheads’

blubber reserves.

Response: These recommendations for additional studies have been taken into account in formulating the list of Recommended Research on diet and regional feeding that is included in Chapters 21

and 23. As noted in the Discussion of Chapter 20, isotope composition of zooplankton prey has been

determined from most of the range of this bowhead population. However, no muscle samples are

available from several key areas (Chukotsk Peninsula, Bering Sea, Canadian Beaufort Sea), and only

a few data are available on isotope composition of blubber and fat. The importance of the autumn

peak in the lipid and energy content of zooplankton is addressed in the Discussion section of Chapter

20, and in other chapters, and is taken into account in energetic calculations in Chapters 22 and 23.

Chapter 22. Energetics of Bowhead Whales

The SRB found the overall approach to the analyses presented in this chapter appropriate, however,

it recognized that there are unquantifiable uncertainties in many of the assumptions that are used to develop

values for the various components of the energetic calculations. The SRB notes that the summary tables of

values for parameters used in the energetic calculations are “theoretical energetic requirements” and

“estimates of energy consumed” (Tables 22.14 and 22.15, respectively) [now Tables 22.16 and 22.17] and

that the use of these values in the energetic calculations introduces an unquantifiable level of uncertainty in

the analyses. Changing the values within the possible range of these parameters can significantly affect the

resulting analyses and, thus, the conclusions based on them. The SRB also noted that the conclusions

developed in this chapter have direct and significant implications for the interpretation of the overall null
A-18 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

hypothesis for the study - the significance of the primary study area as a feeding habitat for bowhead whales

- and in this regard, the SRB strongly recommends that the authors include statistical sensitivity analyses,

as appropriate, for each component of the energetic analyses that support assumptions and conclusions

relevant to bowhead whale energetics. For example, where a range of possible values is available for a

specific parameter (e.g., months/days of feeding each year, total caloric intake per whale per day or per year,

percent of time spent feeding per day or per season, number of days spend in the primary study area, etc.),

the authors should undertake calculations that include the full range of parameter values and present the range

of calculation results rather than providing the results of calculations that utilize only a single value from a

range of possible values for a given parameter.

Response: A sensitivity analysis was done, taking account of uncertainty in the factors involved in

the calculation of the percent of food that might be consumed in the study area (see Appendix 23.2).

The SRB had trouble understanding completely how estimates of “whale-days” were developed.

Because “whale-days” are fundamental to the energetic calculations and the evaluation of the overall null

hypothesis of the study, the SRB recommends that the authors provide a complete and clear description of

how this parameter was estimated and include the equation for calculating “whale-days” in the text of the

report.

Response: Clarified in revised Chapter 9 (p. 9-9, 9-27) where the whale-days are calculated.

The SRB notes that Table 22.4 “Percentage of time groups of bowhead whales in the Beaufort Sea

spent engaged in various activities during spring, summer, and fall” on page 22-11 [now p. 22-12] states that

whales feed only 1% of the time in the spring. However, the paragraph on page 22-10 states that “31% of the

bowhead whales landed at Barrow in spring had food in their stomachs....”, suggesting that whales are

beginning to feed during their spring migration across the Beaufort Sea and brings into question the feeding

percentages presented in Table 22.4. In addition, the statement that it is “assumed” that winter feeding is

equal to that in “summer” is not supported by direct observations or other evidence of winter feeding. The

SRB questions the validity of the assumption on page 22.11 third paragraph that “for energetic calculations,

we will assume that the time budget [for all behavior including feeding] in winter is similar to that shown

in Table 22.4 for summer” when the authors state, correctly, that there [are] “no systematic observations of

bowhead whale behavior in winter”, and (as previously noted) the SRB questions the findings reported in

Chapter 20 suggesting that whales feed extensively in winter.

Response: The 31% figure (representing the percentage of the stomachs containing some food) does

not provide direct information as to the percentage of time that whales spend feeding in spring.

However, the revised report does acknowledge the possibility that, during spring migration as a

whole, bowheads spend more of their time feeding than the 1% observed just northeast of Barrow.

The assumed percent of time feeding in spring has been changed from 1% to 8% for purposes of

energetic calculations, based on a speculative interpretation of the stomach contents data (see pages

22-11 and 22-12). The time budget in winter is no longer assumed similar to that in summer; we now

assume no feeding in winter (see Table 22.4). Wording in Chapter 20 (and elsewhere) has been

clarified regarding the assumed feeding in the Bering/Chukchi system; this is assumed to occur

mainly in the Chukchi Sea in fall and perhaps the Bering Strait area in late fall, not in the Bering Sea

in winter.

The SRB notes the reference to the controversial information presented in Chapter 20 (the isotope

analyses) that conflicts with the statement later in the third paragraph on page 22-11 that winter behavior in

the eastern Canadian Arctic during winter surveys was “qualitatively similar” to summer behavior in the
Annex A: Final SRB Report, with LGL Responses A-19

winter Chukchi and Beaufort Seas where no data are available. The SRB believes that such speculation

introduces great and unnecessary uncertainty into the analysis and conclusions in this chapter, and believes

such discussion go beyond the limits and extent of the data available. The SRB recommends that such

speculation not be included in this chapter, or any chapters of the report, and that the authors revise this and

other chapters to clearly state the actual data and revise the discussion to reflect actual information and not

unfounded speculation.

Response: The draft paragraph criticized above has been removed.

While Table 22.12 [now Table 22.14] indicates that whales do not feed in the spring, data from 32-

34% of the whales harvested off Barrow in spring (Table 18.6 on page 18.15) contained stomach contents

clearly indicating that some yet to be quantified feeding occurs during the spring migration. The SRB notes

that perhaps some of the most compelling evidence of significant bowhead whale feeding during spring,

summer and fall the eastern Alaskan Beaufort, including the primary study area, is presented in Figure 22.5

and Table 22.3 on page 22-9 that shows the maximum girth to length ratios of whales increases in the fall

(i.e., they are bigger in the fall compared to spring. These data are contrary to the conclusions in Chapter 20

and suggest that whale are feeding during the spring, summer and fall in the Beaufort Sea.

Response: See earlier response re percent of time spent feeding in spring. We agree that the data

in the referenced Figure and Table show conclusively that bowheads feed in summer and early fall;

this was emphasized in the draft report and again in the final report.

Further, the information presented in Table 22.12 on page 22-23 [now Table 22.14 on p. 22-27] is not

intuitive and needs better explanation. There is also an error - there are 121 days in the period from

December to March which increases the author’s estimate of feeding days from 132 to 139. The SRB

recommends that this table be revised to include the number of days for each time period and percentages

of time whales are estimated to be feeding along with the days feeding. For example:

Table 22.12 Revised

Time Period Apr-May Jun-15 Sep 15 Sep-Nov Dec-Mar Total

Number of days 61 107 76 121 365

% time feeding 1% 71% 47% 71%

Days feeding 1 76 36 86 198

Days feeding – 30% 0.7 53 25 60 139

The SRB notes that if Table 22.12 on page 22-23 [now Table 22.14 on p. 22-27] is revised to reflect

the lack of evidence for winter feeding, the estimated number of days feeding in the eastern Alaskan Beaufort

becomes 53 in summer and 25 in fall for a total number of days of 78 days compared to the 132 (139

corrected) feeding days the Authors present. This alternate estimate is better supported by the available data

and has implications for all of the calculations used to estimate the amount of feeding whales undertake in

the eastern Alaskan Beaufort and the primary study area. Given that bowhead whales do manage to obtain

sufficient amounts of prey each year, 78 feeding days could imply that whales are very good at locating rich

patches of prey - they optimize the patchy prey resources - , feed continuously on below average prey density

during migration, and that estimates of prey density obtained in this study are negatively biased and

underestimate actual prey densities, or some combination of these alternatives. The SRB recommends that

Table 22.12 [now 22.14] be revised to include information that is based on observations and data, something

like the following:
A-20 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

Alternative Table 22.12:

Time Period Apr-May Jun-15 Sep 15 Sep-Nov- Dec-Mar Total

Number of days 61 107 76 121 365

% time feeding 31% 71% 47% 0%

Days feeding 19 76 36 0 131

Days feeding – 30% 13 53 25 0 91

31% from stomach contents of whales harvested off Barrow in

spring.

Response: The format of the table (now Table 22.14) has been revised as the SRB suggests. See

previous comments regarding assumed percent of time feeding in winter and spring (the suggested

31% for spring is not appropriate). Chapters 22 and 23 now include a better explanation of the

procedure for subdividing the year and for estimating the number of days of feeding during each

season.

The SRB further recommends that the authors revise this section of Chapter 22 to include a statistical

sensitivity analysis of Table 22.12 [now 22.14] that presents the range of values for various input parameters

used to calculate feeding days, and discuss the implications of the range of these values on the following

calculations of the percent of prey/ annual energy requirement bowhead whales obtain in the eastern Alaskan

Beaufort Sea and the primary study area.

Response: Uncertainty in the parameters used in the energetic calculations has been taken into

account in the sensitivity analysis now included as Appendix 23.2. That analysis was used to

determine confidence limits on percent of the annual energy requirement that bowhead whales may

obtain in the primary study area (see Table 23.10 on p. 23-24).

The statement on page 22-26 [now p. 22-31] that “Bowheads cannot satisfy even the low theoretical

estimate of energy and food requirements by feeding on average concentrations of zooplankton found near

the feeding whales” and the fact that bowhead whales are surviving and even growing during the spring,

summer and fall suggests to the SRB that the theoretical estimate of energy and food requirements and/or

estimates of zooplankton concentrations presented in the draft report are inaccurate, and/or all of these

measurements are biased by some unknown amount.

Response: That paragraph has been revised to acknowledge that bowheads could meet their (low)

energetic requirements if average prey concentrations encountered in all feeding areas (both within

and outside the Beaufort Sea) are somewhat denser than those documented near feeding whales in

the Beaufort Sea in summer/early autumn. As now discussed in Chapters 21-23, the most parsimonious explanation of all data may be as follows: bowheads obtain a minority of their annual needs

in the eastern and central Beaufort Sea, sufficient for some increase in girth and energy reserves, but

need to feed intensively in late fall on denser zooplankton concentrations in the Bering/Chukchi

system in order to meet overall annual requirements.

SRB member C. George believed that that the energetic estimates are probably pretty close but that

the prey density estimates are either too low or more likely that the high density prey masses are missed by

the zooplankton sampling. He was more comfortable with the idea that important feeding events are

relatively rare (see previous SRB comment on whale feeding on dense prey pockets –Chapter 18). Like polar

bears finding a stranded whale, a few feeding events could make a huge contribution to their annual or even

"multi-annual" nutritional requirements. The bowheads’ unusual reproductive cycle whereby they calve
Annex A: Final SRB Report, with LGL Responses A-21

synchronously every 3-5 years could be reflecting these opportunistic feeding events. The energetic

requirements based on the “respiration method” are not based on direct measurements of lung volumes.

George strongly suggests that the respiration-based measurements be removed from the report but retain the

comments about the relatively small lung and heart size. These later observations fit with the bowheads'

modest metabolic rates. The SRB concurred with this suggestion.

Response: The respiration method (updated) has been retained in the report based on consideration

of J.C. George’s unpublished data on bowhead lung volume. Those data show that the volumes

obtained via the convoluted method used in the report were, in fact, close to the measured volumes.

SRB member R. Kenny noted that similar calculations and estimates for prey density and energetic

requirements for North Atlantic right whales have proven similarly uncertain, suggesting that “the whales are

far better at finding and gathering prey than are scientists.” The SRB concurs with this view, and recommends that the authors of Chapter 22 include in their discussion a balanced description of the potential biases

in their findings and implications for their conclusions concerning bowhead whale energetic requirements,

annual feeding, and the importance of the primary study area to bowhead feeding ecology.

Response: The discussion in Chapter 6 of problems in estimating zooplankton availability to feeding

bowheads has been expanded somewhat. This issue is also addressed in Chapters 22 and 23

(p. 22-29 and p. 23-11). The discussion of the importance of the study area in Chapter 23 has been

revised and expanded.

The SRB notes apparent discrepancies in Table 22.15 “Estimates of energy consumed...” on page 22-

26 [now Table 22-17 on p. 22-31] and Figure 22.7 the “Relationship between whale length and mouth

opening...” on page 22.19 [now p. 22-23]. For example, the size of the mouth opening of an 11-m long whale

is given as approximately 1.25-m2

 in Figure 22.7, but is indicated as 3.2 m2 in Table 22.15. Values for mouth

size for other lengths of whales also do not agree with the values in Figure 22.7. The SRB recommends that

the authors carefully cross-check other values in the table and figures and correct these as appropriate.

Response: Discrepancies have been corrected and related results in different Tables and Figures

have been further cross-checked.

The SRB notes the discussion on page 22-29 [now p. 22-34] that states, among other things, that “If

zooplankton abundance at sub-adult feeding sites in the Canadian and eastern Alaskan Beaufort Sea are

indicative of prey availability at all feeding sites used throughout the year, annual food intake would be

insufficient to meet the theoretical estimates of energy requirement given present assumptions about amount

of time spent feeding in different seasons.” Given that bowhead whales do gain weight during the spring,

summer, and early fall and given that the population is growing and reproducing, it is quite clear to the SRB

that the “assumptions” about prey availability, time spent feeding, and estimated energy requirements are

inaccurate and should be interpreted with great caution. Given the great degree of uncertainty with numerous

aspects of the information presented in this chapter, the SRB recommends that the analyses and conclusions

presented in the energetics chapter be revisited and revised by the authors taking into account the numerous

uncertainties inherent with the information utilized to develop them, and that the implications for the overall

null hypothesis of the study be revisited in light of these uncertainties

 Response: The assumptions about seasonal feeding have been revised in the final report as previously noted, but this does not change the results very much. The fact that bowheads gain weight

while in the eastern and central Beaufort Sea during summer and early fall does not prove that the

rate of weight gain in summer (if continued during other feeding periods) would be sufficient to
A-22 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

sustain the whales through periods when they do not feed. In the final report, Chapters 20-23 have

all been revised to discuss this issue in greater detail, and to suggest a feeding scenario that could

be consistent with all data. This scenario assumes that prey availability is higher in the western

Beaufort Sea, the southwest Chukchi Sea, and possibly the Bering Strait area in autumn than in the

Beaufort Sea in summer/early autumn, and that bowheads feed intensively in those areas during

autumn. Whatever its merits or failings, this scenario is useful in identifying data gaps deserving of

additional research.

The statement on page 22-15 [now p. 22-18] that “no measurable heat loss through the flippers and flukes”

[was] attributed to SRB member C. George. While true for the flippers, this is NOT what he found for the

flukes, in fact he found the opposite. George is not sure how this statement got reversed! The heat flux rate

through the flukes is higher than anywhere else on the animal - mainly because the blubber is so thin there

(1.5 cm). Thomson should use a mean core fluke temperature of roughly 15 C, a blubber thickness (flukes)

of 1.5 cm, and a thermal conductivity of ~0.2 W/mK for his heat loss calculation for the flukes. This will

boost the BMR estimate somewhat. George used three “zones” for the flukes but this is not really needed...

Response: Corrected and revised as suggested.

...He also suggest giving the energy output in Watts in a couple places in the text (and the conversion for

KJ/day to Watts somewhere in the text or footnotes).

SRB member C. George also noted on page 22-24 [now p. 22-29] that the statement that BMR [is]

consistent with standard metabolism plus the cost of locomotion (4.4 x 105

kJ/d) in Table 22.14 [now Table

22.16] cannot be verified. The SRB suggests that this section, like other chapters, require a careful proof

reading of the figures in the text with those in the tables for the final report.

Response: "Consistent" changed to "similar". Numbers checked and verified.

Chapter 23 Integration and Conclusions

The discussion of the discrepancy between estimates of significant bowhead feeding in the Bering and

Chukchi Seas compared to the Eastern Alaskan Beaufort Sea in Chapter 20 and information in other chapters

could be aided by references to information on advection of Bering-Chukchi water and its plankton into the

Beaufort in summer... 

Response: Discussion of the hydrographic regime in the Chukchi Sea has been added to Chapter

20 (p. 20-19).

...Except for the stomach contents of whales harvested off Barrow in the spring, it should also be noted that

there is almost no information on where bowheads are feeding in June and July.

Response: This was noted on p. 23-5 of the draft report (now p. 23-7).

The SRB has concerns for the basis of the conclusions presented on pages 23-13 to 23-15 [now p.

23-19 to 23-26] concerning the “energetic requirements of individual whales and the population” given the

uncertainties in the components that go into these calculations. For example, the authors state on page 23-13

(end elsewhere) that “Based on behavioral observations and an assumption (per Chapter 20) that bowheads

feed extensively in the winter, bowheads may feed for the equivalent of ~132 full days per year (see Chapter

22). Thus, the amount of food needed to meet the average requirements per feeding day was estimated by

dividing the annual requirements by 132 days.” Similarly, on page 23-15 the authors’ statement that the

“estimate of ...annual energetic requirements...is independent of the manner in which the energetic
Annex A: Final SRB Report, with LGL Responses A-23

requirements is calculated but is sensitive to the amount of time whales spend in the study area and the

proportion of time spent feeding” tells us that the duration of time spent in the feeding area is a key variable

affecting the overall hypothesis, and the SRB notes and commented previously on the uncertainty concerning

estimates of residence times presented in the draft report. As noted above, the number of feeding days could

be 78 or 91 days if that estimate is based on existing data and observations of spring, summer and fall feeding

and not on speculation of winter feeding. Similarly, the conclusions presented in Chapter 20 are suspect

given the body of evidence that indicates that bowhead whales do feed extensively in spring, summer and fall,

and this would significantly change the estimated 132 feeding days per year. In addition, the calculations

that support the estimation of the “average requirements per feeding day” and the “annual [energetic]

requirements” are developed from parameter values with possible ranges of values other than those presented

by the authors, and are therefore similarly uncertain. Given the significance of these estimated energetic

values and conclusions to the fundamental conclusions concerning the findings of the feeding study, the SRB

strongly repeats its recommendation above that the authors undertake statistically based sensitivity analyses

that examine the full range of possible values for the component parameters that are used to development

estimates of energetic requirements for bowhead whales, and that the full range of results be used when

developing conclusions based on the energetic calculations.

Response: All calculations have been redone taking account of the above comments and other

refinements, resulting in an updated estimate that, in an “average” year, the average bowhead whale

consumes ~2.4 % of annual energetic requirements in the study area (Table 23.7). This estimate is

independent of the manner in which energetic requirements are calculated if the ratios among

feeding rates of subadults, adult males, and adult females remain constant.

Sensitivity analyses were performed, as described in Appendix 23.1 for residence times, and

Appendix 23.2 for percent of diet acquired in study area. The latter estimate is most sensitive to the

estimates of whale-days in the study area, but is also affected by the uncertainty in various other

parameters, as addressed in Appendix 23.2. Even so, in 4 of 5 years, the upper limit of the calculated

95% confidence interval for percent of diet acquired in the study area was <4 %. In one year it is

possible that bowheads acquired more than 5% of their annual food requirements in the study area,

assuming that the (high) estimate of the number of “whale-days” in the study area that year was

realistic.

The SRB questions the choice of “reliable approaches” used to estimate “mean residence times”

presented in Tables 23.2 and 23.3 [now Tables 23.3 and 23.4] on page 23-9. First, dividing the residence

values presented in Table 11.6 on page 11-19 [now p. 11-20] by 1.32 assumes a linear relationship of whale

density between the primary study area and other portions of the eastern Alaskan Beaufort Sea. The SRB

finds no reason or support for this assumption. Further, the authors indicate their preference for the residence

time values calculated using the SODA program from photographic re-capture data, while no details of the

SODA program are presented, nor are reasons provided for not using only the “unbiased” estimates

developed by methods No. 3 “Photos: Stop-over Duration, Best Fit” or No. 9 “Aerial Survey: Whale Days.”

Instead, the authors employ the mean residence time estimated from methods Nos.1, 2, 3, and 9 without any

justification for pooling these data. The SRB was not entirely convinced by the arguments for dismissing the

estimates based on large sample sizes as unreliable, particularly No. 6 “Behavior: Overall Speeds.” That

method was apparently dismissed because of a single unusually large value to which observations from

outside the study area made a major contribution.

The SRB notes that the most reliable estimate of residence time comes from radio tagging telemetry

studies. The SRB recommends that the authors provide a complete explanation for their preference of the
A-24 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

method used to estimate residence times and provide confidence intervals for each method for comparison.

The SRB also recommends that MMS sponsor additional studies of whale residence times that employ

methods that are more reliable than photographic identification, such as VHF and satellite radio tagging (see

research recommendations below).

Response: • We acknowledge that the “divide by 1.32” method for obtaining residence time

estimates for the “Flaxman–to–border” area is approximate. If anything, it is likely to overestimate

residence times in that area, given the tendency of whales to linger in the “border–to–Herschel”

area. This is now noted on p. 23-13 and 23-15. • The estimates that have been considered more

reliable vs. less reliable have been revised in Chapter 11 (and Chapter 23) taking account of the

SRB’s comments. • The telemetry data are now included in the averaging process rather than being

treated separately as they were in Chapter 11 (and 23) of the draft report. It should be noted,

however, that the available telemetry data have their own limitations given the low sample sizes and

(often) wide spatial and temporal gaps between detections. • The suggested sensitivity analysis has

been done (Appendix 23.1), providing 95% confidence limits for the estimated residence times.

Given the uncertainties inherent in the data and other information used to develop the information

presented in Table 23.7 [now Table 23.9] on the “Theoretical energetic requirements for the entire BCB

whale population”, the values for “Percent of Annual Consumption” for the years 1985, 1986, 1998, 1999,

and 2000 attributed to the study area range from a low of 0.3% to a high of 5.2%. The SRB notes this range

of values (not their actual magnitudes) is consistent with the overall picture of the dynamic and annual

variation of prey availability in the eastern Alaskan Beaufort Sea and the primary study area supported by

the available data and LTK. This observation further supports the SRB’s view that the apparent variability

in space and time of the resources available to bowhead whales in the Beaufort Sea is truly characteristic of

the region, and prevents ranking any one portion of the region above or below any other in importance to

bowhead whales in any given year.

Response: The updated annual estimates range from 0.2% to 7.5%, with 95% confidence intervals

ranging from a low of 0.0% in 2000 to a high of 16.5% in 1999 (Tables 23.9, 23.10). We concur that

the project has shown wide spatial and temporal variability in zooplankton availability within the

eastern Alaskan study area, and in use of that resource by bowhead whales. This was described and

discussed in many chapters of the draft report, and again in the final report. To highlight this point,

it is now mentioned in Chapter 23 as part of the answer to “Question (1)” concerning the overall

importance of the study area (p. 23-25).

Future Research Needs and Recommendations

Radio-Tagging: The SRB recognizes the value of radio and satellite tagging to the estimation of

migration movement, rates of travel, and distribution which are fundamental to projects like this feeding

study. The SRB recommends that, rather than including a radio tagging activity in the feeding study, MMS

sponsor an independent directed bowhead whale tagging research program and that the results of this program

be integrated into the findings of the feeding studies and other relevant research on bowhead whales in the

Western Arctic.

Acoustic Monitoring: Technologies for passive acoustic monitoring have and continue to improve

since the bowhead whale feeding study was initiated. Such devices mounted on the sea floor can record

whale calls over long periods of time and can transmit their information to an aircraft or satellite, thereby

eliminating the need to recover the device. This would be an advantage in the arctic when weather and ice
Annex A: Final SRB Report, with LGL Responses A-25

conditions often hinder field research on the water. The SRB recommends that MMS look into sponsoring

programs that will use passive acoustic methods to gather information on seasonal occurrence and absence

of bowhead whales across their range, particularly during the spring and winter where information on

bowhead whale presence, distribution, and movements are poorly known.

Response: We concur that radio-tagging and passive acoustics have much potential in further

documenting the utilization of the Beaufort Sea (and other waters) for feeding and other activities

by bowheads. This is noted in the “Recommended Research” sections in Chapters 16 and 23. The

utility of satellite telemetry in autumn, and of acoustic monitoring in spring and autumn, has already

been demonstrated in the field. It should be noted, however, that telemetry of acoustic data to an

aircraft or satellite as suggested above is problematic because of the large volumes of data involved.

Before this will be practical, it will likely be necessary to develop the capability to process and

compress the acoustical data aboard the tagged whale prior to data transmission. However, other

types of acoustic localization methods have proven successful in monitoring bowhead whale

migration in spring at Barrow and in autumn in the Prudhoe Bay region.

Stomach Contents Analyses: The SRB encourages the continued collection and analysis of stomach

contents from harvested whales, particularly from areas where no such data have been collected, to provide

a broader base of the range of prey species, times, and locations at which bowhead whales feed.

Oceanographic data: The SRB notes the value and need to continue to gather oceanographic data that

would be helpful in better understanding the productivity and prey species available in the Beaufort Sea, and

while recognizing the cost of such research, encourages the MMS to undertake such studies as resources are

available.

Fatty Acid Research: The SRB recognizes the potential for fatty acid analyses to contribute new

information for the study of bowhead whale feeding, recognizing that uncertainties remain in the

methodology. The SRB recommends that MMS sponsor future research on the application of fatty acid

analyses as a component of future bowhead whale feeding studies.

Response: We concur with the preceding three SRB recommendations, and have included them in

the lists of “Recommended Research” in Chapter 21 (stomach contents; fatty acids) and Chapter 23

(all 3 topics).

Local Traditional Knowledge: Future studies of bowhead feeding seeking to incorporate LTK would

do well to have a biologist familiar with the community involved in designing questions in a way that would

be effective in eliciting LTK. It would also be beneficial to collect LTK while whaling is occurring, since

much discussion of observations related to bowhead feeding takes place then.

Response: We agree that future studies of this type should follow (or include) these practices, as did

the present study insofar as practical. The individual discussions conducted early in the present

study (Annex B) were conducted jointly by two people: a sociocultural specialist with much previous

experience in Kaktovik, and an LGL biologist who is also an Inupiat. LTK was also collected during

the local-boat surveys just before the whaling season, as described in Chapter 2. We concur that

there could be additional opportunities to collect LTK during the whaling season itself. In the

present study we purposefully avoided formalized efforts to collect LTK during the whaling season

to reduce concerns about interference in the hunt by the project. However, the ADF&G biologist

involved in sampling the harvested bowheads (Chapter 18) interacted with the whalers on an

informal basis during each hunting season from 1997 to 2000.
A-26 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

Agenda, Bowhead Feeding Study: 2002 SRB Meeting

Project: Bowhead Whale Feeding in the Eastern Alaskan Beaufort Sea: Update of Scientific and Traditional

Information: Draft Final Report

Contractor: LGL Ltd, environmental research associates, 22 Fisher St., POB 280, King City, Ont. L7B 1A6,

Canada, and LGL Ecological Research Associates, Inc., 1410 Cavitt St., Bryan, TX 77801, U.S.A.

Funding Agency: Department of the Interior, Minerals Management Service, Anchorage, AK

MMS Contract 1435-01-97-CT-30842.

Meeting Date and Location: 28-29 January 2002, Anchorage Hilton Hotel, 500 West 3rd Avenue, Anchorage, AK.

Ph. 907-272-7411; Fax 907 265-7140.

Contact: John Richardson, LGL Ltd., phone 905-833-1244, Fax 905-833-1255; e-mail: wjr@lgl.com

Attendees:

SRB Members or Alternates

Dr. Steve Swartz, NMFS SEFSC (Chair) Dr. Robert Kenney, Univ. Rhode Isl.

Dr. Judy Zeh, Univ. Washington Mr. Craig George, NSB-DWM

Ms. Maggie Ahmaogak, AEWC Mr. Joe Kaleak, KWCA

Mr. Thomas Napageak, AEWC Mr. Mark Major, Phillips Alaska Inc.

Dr. Ray Jakubczak, BP Explor. (Alaska) Inc. Mr. Brad Smith, NMFS Anchorage

Other Attendees

Mr. Steve Treacy, MMS Anchorage Mr. George Ahmaogak, Mayor NSB

LGL and subcontractors

Dr. W. John Richardson, LGL Ms. Gay Sheffield, ADF&G

Mr. William Koski, LGL Mr. Michael Galginaitis, Appl. Sociocult. Res.

Mr. William Griffiths, LGL Mr. Sang Heon Lee, UAF

Monday 28 January 2002

08:00 Coffee/tea/pastries available

08:30 Meeting begins

 - Introductions

 - Revisions to Agenda

08:40 Opening comments by

 - MMS -- Mr. Steve Treacy

 - Chair -- Dr. Steven Swartz charge to the SRB

 - LGL -- Dr. John Richardson on behalf of study team

 - Other -- Mr. George Ahmaogak, Mayor NSB

08:50 Chapter 1. Introduction -- background, objectives, hypotheses, study components, local coordination

 - Brief overview by John Richardson

 - SRB comments and discussion

09:20 Chapter 2. Kaktovikmiut Whaling

 - Brief overview by Michael Galginaitis (LTK) and Bill Koski (data from harvested whales)

 - SRB comments and discussion

09:50 Break

Zooplankton Chapters

10:00 Chapters 3. Introduction to Zooplankton Components, and 4, Acoustic vs. Net Biomass

 - Brief overview by Bill Griffiths

 - SRB comments and discussion

 10:30 Chapter 5. Zooplankton - Species Composition, Biomass & Distribution -- as above

 11:00 Chapter 6. Zooplankton - Characteristics of Bowhead Feeding Areas -- as above

 11:30 Chapter 7. Zooplankton - Summary & Conclusions -- as above
Annex A: Final SRB Report, with LGL Responses A-27

 Bowhead Whale Distribution, Numbers and Activities

11:45 Chapter 8. Introduction to Bowhead Whale Distribution, Numbers & Activities Components of Study

 - Brief overview by John Richardson

 - SRB comments and discussion

 12:00 Lunch served in the meeting room.

 13:00 Chapter 9. Bowheads: Distribution & Abundance

 - Brief overview by Bill Koski

 - SRB comments & discussion

 13:30 Chapter 10. Bowheads: Habitat Use by Size Class -- as above

 14:00 Chapter 11. Bowheads: Rates of Movement & Residence Times -- as above

 14:30 Chapter 12. Bowheads: Activities & Behavior -- as above

 15:00 Break

 15:15 Chapter 13. Bowheads: Surfacing, Respiration & Dive Cycles vs. Whale Activity

 - Brief overview by John Richardson

 - SRB comments & discussion

 15:40 Chapter 14: Bowheads: Surfacing, Respiration & Dive Cycles vs. Age -- as above

 16:00 Chapter 15: Bowheads: Correction Factors for Aerial Surveys -- as above

 16:30 Chapter 16: Bowheads: Summary & Conclusions -- as above

 17:00 General discussion; any other concerns about chapters 1-16 (Volume 1)

 17:30 Adjourn for the day

 Tuesday 29 January 2002

08:00 Coffee/tea/pastries available

08:30 Meeting begins

Diet & Regional Occurrence of Feeding

 08:30 Chapter 17. Introduction to Diet & Regional Occurrence of Feeding

 - Brief overview by John Richardson

 - SRB comments and discussion

 08:45 Chapter 18. Diet & Regional Feeding: Stomach Contents

 - Brief overview by Gay Sheffield

 - SRB comments and discussion

 09:15 Chapter 19. Diet & Regional Feeding: Fatty Acids -- Pilot Study

 - Brief overview by John Richardson

 - SRB comments and discussion

 09:35 Chapter 20. Diet & Regional Feeding: Stable Isotopes

 - Overview by Sang Heon Lee

 - SRB comments and discussion

 10:15 Break

 10:30 Chapter 21. Diet & Regional Feeding: Summary & Conclusions

 - Overview by John Richardson

- SRB comments and discussion

Energetics, Integration, Conclusions

 10:45 Chapter 22. Energetics of Bowhead Whales -- as above

 11:15 Chapter 23. Integration and Conclusions -- as above

 12:00 General discussion regarding any substantive concerns

 13:30 Lunch on your own (no pre-arrangements made)

 SRB Executive Session

14:30 SRB meets without project or MMS personnel to formulate recommendations

19:00 Adjourn
ANNEX B: KAKTOVIK INTERVIEW TRANSCRIPTS 1

by

Thomas Agiak

Bert Akootchook and George Kaleak

Daniel and Lillian Akootchook

Isaac Akootchook

Charles Brower

Joe Kaleak

compiled by

Michael S. Galginaitis

Applied Sociocultural Research 2

for

MMS Contract 1435-01-97-CT-30842

October 2002

1

 Annex B in W.J. Richardson and D.H. Thomson (eds.), Bowhead Whale Feeding in the Eastern Alaskan

Beaufort Sea: Update of scientific and traditional information. OCS Study MMS 2002-012; LGL Rep.

TA2196-7. Rep. from LGL Ltd., King City, Ont., for U.S. Minerals Manage. Serv., Herndon, VA.

2

 608 West 4th Ave., Suite 31, POB 101352, Anchorage, AK 99510-1352. Phone: 907-272-6811;

e-mail: msgalginaitis@gci.net
B-2 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

Introduction

Individual discussions were held with several Kaktovik whaling captains and other residents during

and shortly after the first project workshop, conducted in January 1998. These discussions were held to

seek additional information about utilization of the study area by bowhead whales, and particularly by

feeding bowhead whales. Kaktovik residents know a great deal about the occurrence of bowheads in their

area and their behavior, but in most cases say that they cannot determine whether the whales that they see

are feeding as opposed to migrating or engaged in some other activity. Nonetheless, much local information on whale occurrence and behavior exists and can be elicited through interviews.

A total of eight interviews were conducted for this limited effort. We restricted the number of

interviews because the project had neither the time nor resources to prepare a formal survey instrument

for formal review by the Office of Management and Budget (OMB). OMB regulations stipulate that no

more than nine interviews asking the same questions can be conducted without such review. Six of the

eight interviews were recorded on tape cassettes. With one exception, the interviews were conducted in

Kaktovik on 16–19 January 1998 by Steven MacLean, a staff biologist (and Inupiat) at LGL Alaska

(Anchorage), and by Michael Galginaitis of Applied Sociocultural Research (Anchorage). Herman

Aishanna was contacted by phone in Barrow on 20 January 1998, and hence his interview was not recorded. Archie Brower was interviewed in his home, but background noise precluded recording this session.

Transcripts of the six recorded interviews constitute the text of this Annex. Copies of original tapes and

draft transcripts were sent to each person interviewed, for their review. Copies of the tapes and draft

transcripts were also sent to the AEWC for review. One of the interviewers (MSG) made several subsequent trips to Kaktovik during which he discussed the transcripts with the people interviewed. MMS will

distribute copies of these tapes and transcripts to the appropriate repositories (AEWC, IHLC, KWCA), in

addition to their inclusion in this document.

It is important to recognize the limitations of the interviews and transcripts. The interviews were

focussed on a very narrow range of information, and were primarily intended to determine if a concise,

concrete body of Inupiut knowledge related to the feeding behavior of bowhead whales in the eastern

Beaufort Sea of Alaska could be elicited in a short period of time. Such a body of knowledge was not

documented. While the Inupiat possess a wide and deep knowledge of bowhead whale behavior, this

knowledge is embedded in a rich experiential context, and such a focussed interview methodology is illsuited to document that knowledge or to tease out a specific sub-component of it. Much more time and

effort would need to be devoted to such a task.

The transcripts are also very limited in scope. They are, for the most part, literal transcriptions of what

people actually said, with no attempt to represent the non-verbal aspects of the interviews or verbal expressions

with no meaning (“um” and so on). No attempt has been made to complete sentences or thoughts or otherwise

“clean up” what was said to us, as in many cases the meaning is embedded in the way an idea or experience is

related. Parts of transcripts are also unclear due to the poor quality of the recording. This poor quality was due

in part to the short period of time available for the interviews and the locations where many of the interviews

took place. While many of the transcripts would benefit from explanatory glosses, these have not been provided except for information directly related to whale feeding behavior, due to limited resources.

Nonetheless, even with their defects, the transcripts represent an important source of information for an

understanding of whaling in Kaktovik. A general study of whaling was not a component of this study, but

knowledge of whaling is vital for an understanding of the importance of this study for the people of Kaktovik

(and the North Slope in general). Thus, the transcripts supplement and expand the summary treatment of

whaling in Kaktovik that is provided in Chapter 2 of this report.
Annex B: Thomas Agiak, 17 Jan. 1998 B-3

Thomas Agiak

MG Basically, what we're, what we're interested in really is what you can tell us about whale behavior

in the Kaktovik area. [unclear sentence]. What you can tell us about where you see whales, you

know, if they're big ones or small ones, what time of year you see them [?], and tell us what they

are doing [unclear].

TA Well, all the, all the time I'm growing up I'd say I seen them right around this area and early.

August.

?? [faint brief comment on tape, may be background noise]

MG Early August when you see them there?

TA Yup, early August. At one time, I'm, when I was young, in my, me and my dad, we -- just right

off the shore up in there, toward the part of the one island.

MG So off of west, west part of Barter Island.

TA Early August, that's where I’ve seen them, right around in this area here. I'm, know I ah, most of

the time, anyway. On our map we hardly catch any this far. I think we got some right around

here. All of, every time we go out we catch them right off here.

MG So right off Bernard Spit?

TA [affirmative]. At one time I, right close to the surf here, a hundred yards off from the shore there,

where, I ran into some few of 'em right around, right around in there. But when they get that

close to the shore, there, they, ah, they spook pretty easy. Once you get close to them they take

off. You can follow them in that shallow water where they swim along and ... knock bubbles.

MG [affirmative]. They, do they hit bottom, or make sort of bubbles?

TA They make bubbles. They make that dirt around on theirs. They make a, right middle of brown

bubbles when they swim in the shallow waters, but you can't, ah. When you get 'em that close to

the shore then spook pretty easy. Harder to catch them. [Pause] Right over here, on the beach,

up on the lands, when I was growing up one year ...

SM Oh yeah?

TA ... we could hardly, ah, whalebones over there now. Arey Island right there. And last fall I was

walking on the beach there and I found a stone, about that big. Burton [?] Rexford said they used

that long time ago before they get any, any other kind of bombs, and that's what they usually hunt

whale with over there.

SM Harpoon tip, you said?

TA [affirmative]

MG So you think they whaled from Arey Island, or they bring whales back at least?

TA I don't know, that's ah, we see you when I come up, we see some few of 'em on this artifacts right

there, but, not as much as we do over here on that Arey Island. [Pause] [short unclear phrase].

Let's see, I find a whalebones back over here too ... not as much as we see 'em over here at Arey

Island there.

MG [? ?] Spit too.
B-4 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

TA Yeah, that sand spit.

MG When you say that you catch most of your whales here, that's September then, right?

TA Yeah, September.

MG But you first see them August, around in here?

TA Yep.

MG And you, you don't bother them when they're there?

TA No

MG Are these moving or are they just sort of, hanging around.

TA I don't know. Or, I never really ah, pay much attention to 'em when I go fishing over there, it

usually blows out there quite a few time. And my brother, when, when he go hunting over in

Camden Bay area, he been seeing some, early August or July, over that way. In middle of the,

August that's when maybe see 'em close to the Arey Island over there, feeding there pretty good

that time. Quite a few blows over that way. [Pause] We never, we catch our whales right out

here too, not, we got, most of our whales we catches just right in there. Then they catch him half

a mile out from ...

MG When, you say when they're close there are harder to catch, that's cause they spook

TA That's shallow water, yeah, shallow water. Spook easier.

MG Will they stay close to shore after they spook?

TA I don't know. I never ... when I'm hunting out there we usually come out there, and just [unclear],

that time we, spot him. Sometimes we go over that way and chances come. Just right in this

area.

MG That's Arey Island, ah, Jago Spit. And, when you're, when you're in this area looking for whales,

are the whales moving?

TA Yeah, seems to be swimming towards westly, going up. I don't know, theys, they just going each

different direction, also, they.

MG Oh, so sometimes you'll see whales going the other way?

TA Yeah. Also as they go up and down the [eastern sea a way?] they swim different directions there.

At one time, when we last, ah, struck a whale and when, I went out and looked for it, I got in the

middle of them right there -- just swam all the way around it. Just sit. It was sideways [or that

ways?]. And just sit that paper straight up and just sit there [?]. [Pause] So anyway, I think that

was the last whale we struck [that year], the last quota we had. We went out and looked for it and

couldn't find it. And I got in the middle of them whales out there, they just swam around, all the

way around my boat, they, clumps of them. [Pause]

MG Then, did you find the whale, after a while?

TA No

MG Never found it?

TA Never found it. [Pause] I don't know, some years there are more whales over there than right

down here [unclear] year or two, probably depend on the current there.
Annex B: Thomas Agiak, 17 Jan. 1998 B-5

MG Current different from year to year?

TA [faint affirmative]

MG The whales, do they stay near currents, or do they like currents?

TA I think when you see them, ah, there they feed, tends to feed more, by the currents there.

MG But the currents change year, every year?

TA Yeah, there are different currents out there. Sometimes when you see water, it goes out, and

some of 'em goes east and west, some of 'em north and south. Different patterns of water, it just,

aren't going around [?]

MG And some of the, the people at the workshop, they were talking about rivers flowing from the

land, too. Do the whales like that kind of water?

TA Not probably. I don't know. I never really studied much, um, they stay out, out here too, mainly.

Most of them are out here. We never go, in last ten years or so, we never go beyond the, down

below here over that way or, never go much beyond, down below Jago.

?? Just head straight out.

MG How far out will you go, to look for whales?

TA About 10, 15, 20 miles.

MG And the, of course the further you go out the longer it takes to bring the whale back?

TA Yeah, anyways, [?] and I scout around out there, sometimes I just barely can see the mountains on

the top of the ocean, when I scout around out there. [Pause] I haven't been out in a long, long

time, there. When they was doing seismic I had to go quite a ways out, just see the top of the

mountains here, then try to see some whales out there. I nev, we never strike any whales that,

that far out.

MG Do you, every year, do you always go out and scout before you go out and whale?

TA No, I just go, always go to here, or just go straight out of Barter Island about ten miles and, sit

around out there. You see them blow out there. That's what they did last fall, anyway. They

went, in a two or, this way a little bit thick. And first day, they was ... the first time we were out

we got it. In the morning.

MG Quick.

TA When it's clear they catch 'em, but last fall we hadda lot of fog out there and we couldn't. We go

too far out sometime we see 'em closer to the island and then we go back up and clears up

[PHONE RING] ... each time it clears up a little bit they see a whale, it [PHONE RING].

MG Yeah, people said [PHONE RING] it was very foggy last year.

TA Yeah, it was.

MG Is that [PHONE RING] ... how, how do you communicate with the other boats, can you still keep

in contact with [PHONE RING]...

TA CB

MG CB all right?
B-6 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

TA Yeah, when they want to find out [PHONE RING] where all the, each boat is [?], CB is on a, land

too [PHONE RING] ... find us pretty fast that time [PHONE RING] get on GPS, I suppose.

Before we got GPS I used to [PHONE RING] go out with compass.

MG And how do you find the whales when it's foggy?

TA It's a, sometimes when they blow, you can see a, lotta dark ... bolts coming outa clouds there,

most always. Most of the time when I'm going out in that really low fog out there, you can see

the dark marks going up ... that's whale blows. Can see it in a real low fog. Just gotta [?]. Find

'em pretty easy, like that out there. A couple of times, I think, me and my brother, spot whales

like that, when, when it's started to get a little foggy down there in the, ocean there and you can

see the dark marks going up.

MG Do you ever see what the whales are, are looking .. feeding on? Or do you see little things in the

water?

TA No, there, never. We just concentrate on going out and catching 'em.

MG Uh hum

TA Find a whale we going to be, when the captains find a whale, they ever found a boat can stick it,

we stick together over here in Kaktovik. When those captains find a whale we all go out. And

when captains start to whale that’s when we concentrate on killing it and taking it home. All the

boats get together once again when we strike a whale.

MG When you say when you go out you just stay within this area, uh, different times of the year are

there different numbers of whales here? Like early in the season, is it different then later?

TA Ah, I don’t know.

MG Or when do you first see whales? You said you saw them in August here?

TA Yeah. When we go fishing over there, snow machine ... you can see blows right off of there.

MG Uh hum. And you don’t see so many over in this area then?

TA Not as much. You see them over on this area, early in August.

MG And then later in September, are there more closer to Bernard Spit?

TA Uh huh. They’re out this way.

MG Can you tell, are, are they just, are they staying there, or are they moving to the east.

TA Sometimes when they’re ... ones I’ve seen right up in there they just go back and forth.

MG Uh hum. So in September they just seem to be staying there.

TA Uh huh

MG And how late do you see whales?

TA When you can boat out there, ah, tend to see them in October, second week of October. When I

went out, when I went out after we finish our quota one year I went out in a, Trailbusher [?] here

and I was going out, and I went out through here and I was going straight over to that point there,

and I seen three whales feeding there.
Annex B: Thomas Agiak, 17 Jan. 1998 B-7

MG Well, that’s still in, uh, October -- the same place you saw them in August then. Maybe different

whales, but the same place.

TA Yeah, the same place. You know, one year I took my daughter, daughter-in-law, down. We spot

a whale right in here [name or phrase in Inupiaq?]. Just playing around out there, and seen him

standing straight up like that. I don’t know how they do that, I don’t know whether they are just

playing around or feeding.

MG If you just ... If they were just hanging around, do you think and they’re small ones, real small

ones?

TA Yeah, real small ones.

MG When do the big whales go by?

TA Umm. I think they go by early in August. They say you see most of the whales feeding over in

this way in ...

MG And are there any big whales in September, uh

TA Oh yeah

MG So they don’t all go by at the beginning

TA Yeah, we see big whales out there too [when they are whaling], mixed in with small ones.

There’s a whole bunch of whales out there. ... First time when I become a captain, ah, first time I

was a captain back in '82, I got, I got my whale there, around here, about fifteen miles out. And it

was too big. I got fined.

MG By the whaling captains association?

TA No, by the lawyers down in Washington DC. I had to go to court in Barrow ... Alaska Eskimo

Whaling Commission. My whale was too big. It was fifty two and a half foot. I got him

September twenty seventh. My first year was lucky, back in '82.

MG Hmm.

TA That time we couldn’t catch ... no, no bigger than forty six [two or three unknown words], and no

smaller than thirty five.

MG What’s the size limit now? Do they restrict it, no restrictions?

TA No restrictions. But that first time when I ... we start studying the whales there, the Alaska

Eskimo Whaling Commission just come out, ah, once had a big construction here [?] one time,

you know, [word or two ?] Alaska.

MG Yeah, not very many back then.

TA No. I’m sure now that they’re start getting help from scientists and, ah, Dr. [Thomas] Albert and

Craig [George], they come in and [they didn’t know, there were more than, they didn’t have to go

out UNCLEAR ?]

MG What kind of whale do you look for now when you go out?

TA By-and-large its just bowhead. I have, I never see any gray whales. Only one time I’ve seen that

kind of ... come up, come up to a gray whale, and then we ... That’s the only time I’ve seen a

gray whale out there.
B-8 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

MG Do you look for a medium size whale, or a small whale?

TA Small whale.

MG How long would, how long ... if, if you had your choice, what how long a whale would you look

for?

TA Over a thirty footer

MG And most other captains, same way?

TA Yeah. I get, ah, thirty six. If we get them over thirty six, thirty, thirty six, they can catch up early

in the morning and butcher it in the afternoon, divide it up in the [evening time ?-- sound of door

closing] and get ready for the next whale.

MG Uh hmm.

TA One year they catch a whale in the morning, and they were done in ... they cut up that whale in

three hours ... and then in the evening they divided the [unclear ?]. [First full ray ?], get up, that

way divide it up before we go out to catch another one. First strike, first crew [get ?] in the fall

time. ... PAUSE ... Ah, one year, when I -- I can remember they -- that was before they get the

quota system, they catch five whales in one week. [Unclear phrases], cut 'em up.

MG Most of those were small whales, though?

TA Small, small

MG That’s still a lot of whales

TA That’s good [? Said faintly, as an aside]. Small whale, they done[?][laughs], pretty big, all right,

but they, ah, divide ‘em up they take [laughs], get a little piece

MG Um hmm. Some people tell us, you said whales were, lived here, were here in August. Some

people say whales are, you know, in the area as early as July?

TA Yeah. I think on my brother was out hunting over that way, toward Camden Bay, they, they

spotted some over that way. Feeding around over there, I don’t know what area. Last summer I

didn’t do much boating, I, I went back to work for a couple months there. Didn’t do too much

boating [around/out there ?]. End of August I quit, middle of August I quit working. And the rest

of us to go hunt caribou [UNCLEAR ?].

MG Would that be just a few whales that were you see over there?

TA I think when they were setting up that, uh, drill rig over there over by Camden Bay area, and I

said I seen some whales over there when I was setting up. About a hundred twenty-five blows

they spotted over that way, before it was started.

MG Yeah, I guess that’s what they said. We’ll have to ask him and see, if we can get records of how

many whales they saw and when they saw them there. I guess one thing we’re interested in is, if

you can tell us anything about the migration, you know, if it -- what time it occurs during, and

whether there’re more whales at one time of it than another.

TA The last three years have been, we’ve been -- I actually like to go in the middle of September, but

the last three years they’ve been coming up earlier. It depends on different years. Last year we

could have got done in first week of September if it wasn’t foggy. And all the whales, I must

start whaling the fifth till right around the middle of, almost the last, end of September. There’re
Annex B: Thomas Agiak, 17 Jan. 1998 B-9

not big, all those whales, they’re a little kind of big then. Forty eight footers. Forty seven, forty

three footer.

MG At the end?

TA End of September, there’re like that, too [unclear phrase ?].

MG So there’re bigger whales at the end, it sounds like.

TA [unclear]. The first of September you can sometimes they go by with, small whales are there with

'em. Those are the ones we don’t come close to.

MG You don’t go after those ones?

TA I don’t think so. I see a whale, a small whale right alongside of it, we don’t dare go near. Too

danger [unclear at the end -- lower voice ?].

MG You said you like to, you would like to go out middle of September?

TA I think it’s a lot cooler, but, you know, the last three years have been starting right at the first of

September.

MG And that’s something all the captains decide together, when to go out ...

TA We have a meeting, ah, before September. We set up date to, the captains can go out, after that

date they can go out. All the captains meet together down here before whaling starting, set up a

date, to tell them when you can go out. All of us have to go together, if they want to go out. No

captain goes out before that day, hah?

? Uh huh

TA I’ve traveled quite a bit over that west of that way, in August. I never see any whales over that

way, over to Herschel [Island, in the Canadian Beaufort Sea]. I’ve seen 'em, I’ve seen quite a few

of 'em when I coming home from, ah ... Running [placename unclear on tape] River or , ah,

Shingle Point over there, from ah King Point area right around there where the Canadians do their

whaling over there.

MG I guess we could look at that map if you want.

TA I don’t think you can go that far over.

MG Well, this one maybe goes that far over [sound of unrolling and moving map]

TA It doesn’t go that far over. Here.

MG First line

TA First line. All the way down here.

MG Oh. Way down there. Right at [Hersey Bay farm?]. But, but you don’t see whales in here when

you go hunting?

TA No, I never go any hunting, over there to [see or visit] my relatives over there. Visit them over

there.

MG You do go visit them?

TA Yeah. The only place I’ve seen real close to the shore is right off King Point. From King Point

out, on the ... the area here [unclear ?]
B-10 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

MG But even in here, no whales?

TA No. I never ... I’ve boated quite a few times over there, and I never see any of 'em.

MG What, what time of year would that be?

TA August, and July

MG Yeah, that’s pretty early, I would think ... though you say August there are already whales up here

TA Yeah ... that time around I travel with a boat out this way I never see any, ah. And one year, a

couple years ago, I went back across here three or four times, with a boat and with Albert [last

part unclear ?].

MG And you never see whales over here?

TA No

MG But you do right around Kaktovik?

TA Yeah

MG And maybe over here?

TA When I snow machine over there, do a lot of fishing over there in that channel over there, when

that was open. [Sound of maps to find the place referred to] When this channel was open there,

they do a lot of fishing -- my wife likes to go over there, Honda over there. Go char fishing over

there. It’s a good, pretty good size fish. And now she goes all the way over, over that way.

MG Do you need the open channel for the water going through?

TA Catch a lot of fish there. See, it’s all closed right there now, you got so much in, all the way, on

that island over there, all summer long. They, ah, fish over there in the fish creek by the end of,

end of July. July, hard to catch. They’re running, but they’re really hard to catch. [unclear word

or phrase]. PAUSE

MG Do you think, are the whales, do they like the, the current too, do you think?

TA Probably. You got rivers going off from the, along the shore over there, and, coming up, you

have a pretty strong current going through there.

MG But you don’t use the current when you are looking for whales or when you are hunting them?

TA No, no. All we do is look for blows.

MG Is this just because there are usually so many whales you don’t need to ... do that?

TA No [faintly, and then a pause]. They see ’em right out here before we once start whaling.

MG I guess some people say that, you know, there is a pattern to the migration.

TA Sometimes they come out early, sometimes they come out late. For some reason, I don’t know.

Some years you don’t see any whales ... over here. Some years you have to go look for ’em out

there. [Find the whales -- a faint inaudible word or phrase ?]

MG Some years there aren’t many whales? Hard to see, or ...?
Annex B: Thomas Agiak, 17 Jan. 1998 B-11

TA Hard to see or sometimes they just get swimming out there, they go by and the wind is blowing.

You see more whales in there [? unclear] and the wind is blowing out there. And then clear up

and they disappear [laughs].

MG So, so years when you don’t get whales, there are still whales out there, you just ... either can’t

get out or don’t see them?

TA Yeah, and that’s really been a hard time start whaling, when we don’t like to go out [?], and there

are whales out there. Especially when there’s no ice, the waves gets pretty high. [Pause]. And

[nowadays ?] I went with my brother [name ?] to the whale and my brother strike it, and went

over it. Waves, ... [Inaudible faint sentence], messed up. I seen this whale coming up. And I was

too high on the whale, you know [? tape somewhat unclear], to pass it up. That whale is right

there. Missed the whole thing [laughs].

MG You say you, you, you got your first whale in '82?

TA Yeah, first time I was a captain.

MG When, when did you start going out whaling?

TA Oh, no -- was before I was ever captain, I went out with my brother a long time ago. Early '60s,

when we came up here, there wasn’t going to hunt [?], start whaling around here.

MG In the early '60s? But you always whaled in Kaktovik?

TA When I was growing up here, you seen whales right off the [name ?] in August ... every year, you

don’t see 'em every year out here, early years. [sound very muddy]

MG I guess that’s one reason why they want to do the, the whale feeding study, because every year is

different. They want to see what they can find out about whales in the area, I guess, from year to

year. To see if the things that the whales are looking for are different from year to year

TA That current’s changing quite a bit out there during the year.

MG But it does sound like you’ve been very successful catching whales in this [?] area.

TA [unclear]. We never go beyond this point here, over here [name or phrase?]. And actually they

almost, pretty swim about, about ten miles out. [Pause] One year they caught a mile and a half out

here.

MG Real close

TA Yeah

MG Do you always take your whales to the same place?

TA Used to go straight in, one time, now we gotta use channel. Channel water goes quite a ways out.

You gotta go over this way, you gotta ... A long time ago they say they used to [kunuk ?unclear],

went through over there, [kuva ? unclear] went through there, back up.

SM Through the lagoon

TA Through the lagoon

MG Too shallow now?

TA Too shallow now.
B-12 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

MG Be a longer way to tow too, I guess.

TA While they were doing seismic out there, they had that drill site out there, we were quite a ways

out, [before they turn away, catch out there quit -- ? unclear part of statement]. And it was quite a

ways from [name ? unclear] -- twenty five to thirty miles out. And they quit doing the seismic

and that much start to go out next day, we never go further out.

MG So you think, uh, noise affects the, uh ...

TA What affects?

SM and other faint and confused voices

TA When they were doing that well over that way, too ... I wanted to cross [?] up close to a whale but

I couldn’t. I couldn’t, I couldn’t do it, get the strength, I, I just couldn’t ... get 'em, couldn’t be

catching up to 'em. [PAUSE] One year they were doing seismic and they had some ice out there,

[unclear phrase ?], turn around, never see ’em again.

MG Why do you think they spook so easy?

TA I don’t know. Too much noise out there or something. They were doing some seismic in that

area, and that could be why ... [continues to talk but becomes very faint]. Have to go quite a way

out to see any whales. And the drill rig was sitting out there a couple of, two years ago, [?] -- had

to go quite a ways out. When there is no noise, [very unclear phrase] quick, and we go out there

and get 'em pretty close. I even got a new update, ah, map last night ... [some of the guys went to

Anchorage ? unclear]. [At this point we are looking at the old map of Kaktovik whale strike

locations in the DMS break room. TA making some comments about it].

MG Ah, old map [TA comments on map too faint to make out]

TA That’s the [agvik ? Unclear]

MG Is that one that somebody struck here ...

TA Nope.

MG ... or came from somewhere else?

TA Died of natural causes. Had a big black clot on the undersides, on the end of it. About eighteen

feet, I think. Dr. Albert, he looked at almost every inch of the whale and he couldn’t find any

bomb holes or nothing ... [rest of sentence inaudible. Next sentence also not understandable ?] It

just died of natural causes. First one I’ve ever.

MG You took the muktuk and the meat? It look all right?

TA I take most of it here, but when I cut those off him, in places [hard to understand] -- some bacteria

that’s what makes him stomach ache and ... diarrhea. That’s what ... [very faint]. That Dr.

Albert, he always [very faint]. I thought we would find a bomb or a bomb hole in that one, but ...

that was it, nothing.

MG And that’s the only one that you’ve seen like this, died by itself?

TA And without a hole in the agvik too.

MG [to SM] I don’t know if you have any questions you want to ask -- things we may have missed

SM You’ve covered most of it.
Annex B: Thomas Agiak, 17 Jan. 1998 B-13

MG Things we may have missed.

SM What kinds of whales do you see closest to shore?

TA Small whales

SM Small whales closest to shore?

TA I say no. Sometimes we see a pretty good size whales over this way in August. There are some

big ones out there, early in the, um, late '60s. [Unclear phrase or sentence ?]. Quite a few of

them, I see big whales and small pairs out there in August, now [unclear word or two ?]. You can

tell the difference between the blow and the, the blows of the small ones. For the big ones only,

they blow pretty high. The small ones they blow just a little bit. I don’t know, it’s the last ??? ...

I heard it, and it sounds like it’s quite a ways out, but it was a hundred yards away. It was [?] run

over just between the house, and that guy was [?],.. Sound different

MG But that whale, that you got, after you heard it, how did you get up to it, so you could strike?

TA [Laughs]I give up. ... between the ice pack. I harpoon it. And it took a couple of days ...

[Some unclear sentences here]

MG So the next day, the next day you could find it.

TA Yeah, it was nice out there, we can ... [?] ... from the boat out there ... [?] ... go thirty miles out...

[?]

MG You say that one took several days before it could bring it in?

TA ... [?] Got too dark on us and I hadda, hadda send everybody home. Come back the next day and

pick up our buoy.

MG forty-eight foot whale, that’s a pretty good whale.

MG Can we share the information that you’ve given us?

TA [faint affirmative]

MG You know, talk to other people about it? And if you would be willing to I would like you to sign

a form that says that, you know, we can share this information with other people,

TA Yeah

MG and that way then what ... makes it easier for us to do that. If I can find where I put those now ...

You can tell I’m not always very organized ... [tape ends]
B-14 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

Bert Akootchook and George Kaleak

Tape was not started at the very beginning, as we had to ask them if we could tape. When we

came in there was also a larger group of people just socializing. We waited until the break was over and

people resumed work (or went out) before asking BA and GK if we could talk to them a bit more. Joe

Kaleak and others had suggested them as good people to talk with, and they had expressed interest at the

earlier workshop.

BA When they get them arthropods, and they just pull them up at, cause they did, and they get some

arthropods right on, right from the bottom. They make [???] waiting for the whalers.

MG So are they in the boat or on the ice when they are doing that?

BA On the ice, while we're waiting for whales, and when we're on the ice, and

SM Springtime?

BA That's in the fall time

GK That way you can, you can, you can, ah hear, or listen -- listen for the whale, cause they got a big

blow, you know, and you hear a tremendous amount of blow and then you know where to go.

[pause] Lot of times...

BA [???] about that long.

GK we look in the water also, you know, you can know when -- when you're, like, krill -- out in the

water you just look down and you can see all that.

MG Do you always see krill when you go out whaling?

GK Not always, but a lot of the times, you know, you can see it, some of them floating at the top and,

even under the water a little ways, you know, as far as you can see them -- some years there'll be

lots and you know some years like this year seem like there was some hardly any.

MG But you got lots of whales this year, you saw lots of whales.

GK Yeah, yes -- quite a few whales out there.

BA Even after they were done whaling they were still sticking around down here.

SM Hanging out near the island?

BA Right after that last whale.

GK Especially after they're struck seem like they, they know when to come out, you know. Every

time, seems like almost every time a whale is struck and we start towing all the whales start

showing.

BA Sometimes right through October too, you see them, going down to the airport, you'll see whale

blows. That's not too far.

MG Can you see them from the airstrip?

BA No -- from the land, from the road [which is elevated or higher up].

GK They don't go very far, I mean, a lot of 'em even, you know, they come real close to shore. Like,

like the one this year, one of the first whales, we wound up chasing -- we were, we -- was foggy

and we followed the trail. Because, you know, you know when the whale hits bottom and its, its
Annex B: Bert Akootchook and George Kaleak, 16 Jan. 1998 B-15

got brown murky water, you know, you know a whale trail's right there so we started following it.

Sure enough, there was a whale nearby.

BA Pretty near everybody find a whale by, just by listening. Last year best way -- its foggy most of

the time

GK Yeah. I think the three whales was pretty foggy. The last whale it was kind of snowing, a little

bit, with a little fog here and there.

MG So you found your whales by listening mostly?

GK By listening, you know

BA That was last year.

MG How do you decide where, where to listen from, where are you?

BA You find out how many miles you go and people just pretty much spread out since they had the

GPS and learn how to use them.

GK And that's pretty much how everybody finds each other is by coordinates. We give 'em the

coordinates and they know if they are drifting away or coming closer by trying to match the

numbers of the coordinates so they can get as close as possible to where they can see us -- and it

worked out pretty good this year, you know, I, this is, uh, actually the first year I had to use my

GPS and say "Man, this really works, you know." It's pretty amazing.

MG Does it make whaling easier, then, the GPS?

GK Oh yeah. The more boats around the better, you know, once we spot a whale, the more eyes, the

more eyes around the whaling area is a lot better than just with one boat.

[some pause or side discussion]

MG You said that the whales just hung around this year?

GK Oh, pretty much. I mean they were, seemed like they were sticking around.

MG Is that normal, is that what they normally do?

GK Oh yeah, I mean

BA Yeah, how many times we see them

GK They're always, they're always around

BA You'll see them right out there

MG What I mean, the way, the way I think of it the whales are coming from Canada and they go, you

know, past Barrow, but you say they hang around in this area for ...

BA Just for a while, yeah

GK Yeah, I mean, seem like its -- its to feed or something

?? Remember that one year, that down by Jago, every boat saw a whale

GK Yeah, that was awesome, when we ...

?? Every boat was chasing a big whale.
B-16 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

GK It was, it was so hard to decide which whale to go after they were so many, and, and ...

?? We got [???] whales enough [more than one person talking]

GK They're, they're not even a mile from, from shore either, you know. [pause] These guys got,

Akootchook's crew got piggy-backed by a whale, and I don't even think they realized it because

they were right, right on top of the whale and, he was right in line with it.

?? [????] flip the boat

MG Did, did, did they flip over?

?? No, no -- he just ride on top of it, [??] put back by itself [and quite a few voices]

SM I heard about that, a couple of years ago, huh?

GK Yeah, a couple years ago. I thought, the ah, whale was going to feel the boat and, and let its

flipper, you know, go wild and flip them over or something, but it didn't even, didn't even do that.

That was awesome. I was right behind them when I seen that.

MG Just sort of lift up a little and then down?

BA Real pretty much, yeah -- just lifted up and slide back ...

GK The whole boat was out of the water, yeah.

BA First time I ever done that before [laughing]. All of us was just [???] on the boat, its [???] all of

us to keep it moving. Just watching [?]

GK You don't ever begin to think about being scared out there, when, when its our livelihood and

when the people out there depend on us to bring 'em food, you know, you, we, we don't ever tend

to think about being scared cause the old folks, you know, they, they taught us, scared you know,

you probably either get hurt or get in trouble or -- so, me, myself, I don't ever think about being

scared, no matter what.

MG You think that's pretty true for all whalers?

GK Oh yes -- you always gotta listen to your Elders. They know best.

?? Pop -- you want some pop?

MG Well, I have coffee here.

?? Right around, right after I got out of school in 64 I [???], just a few of us. We didn't have a crew

that time, we just tagged along. And then we ... Vernon [?], we were just learning, help, just

learning anyway.

MG And you said that you just tagged along ...

?? Just with a boat, go out with a crew, and just the two of us -- boy, there was that, lot of muktuk

just, just the two of us -- just for tagging along and helping to pull the whale [laugh]. That was

before the season's came around.

MG Is there any, any one crew that you helped more than others, or

?? Pretty much all worked together

MG Everybody stays together then?
Annex B: Bert Akootchook and George Kaleak, 16 Jan. 1998 B-17

?? But they always tell us to have another boat, if another boat goes a different direction he always

ask for another partner to go with him, just in case something happens.

MG So boats still partner up?

GK Yeah, always travel in pairs, you know. Never, never go alone. You never know when the

wind's going to come or ... but now with the communications system [???] Prudhoe Bay [loud

noise from DMS building machinery]

...

?? there's another way we find out about a wind is [unclear] Rexford, she's an Elder, she must about,

close to eighty years old. And she would read her barometer and when the barometer moves

telling that we were going to have a strong west wind she'd call us ahead of time, just by checking

the barometer. And that's the only people we used to [???]

?? That was another way we find out when wind change.

GK Now with our VHF, you know, the communication system with Prudhoe Bay radio they, they get

the weather report every day, you know, every how many hours they get the weather report and,

we, we request for weather report and they give it to us, you know. Sometimes, its true but you

can never predict, because that's ... down there.

MG I was going to ask, is the weather report always right?

BA Sometimes they're wrong

GK Sometimes they're wrong, you know. They may say the wind, the winds going to pick up to like

25 miles an hour and it don't even come close to that -- calm

BA That's the [????] probably north side of Cross Island. Course I know one time when we were

hunting on this side, on the east side, it was [?] rough. The weather would be really calm.

GK So the weather report is not always right.

MG You said the whales often -- you can see whales in October still?

?? Yeah

GK Probably late, late, late ones that, you know, that, that pass on by, they might be the big ones, I

don't know. Probably the late comers. You know not all whales travel together. [noise revs up,

then down]

MG So you think [??] are sort of by themselves or are they, they're a bunch of them together

GK Some of them, you know, go in schools, but not all of them

BA Probably towards end of the year. Last year and a couple years ago there was a whole bunch of

them north side right down by [Inupiaq place name], some of them were even very close, right by

the beach. Lot of whales. We see a whole bunch of them there.

?? But we didn't go after them because we were looking for the whale they had struck the day

before.

?? The weather was [?], afterwards was looking for the one they already had struck.

?? The day after, two days after, we can't find it ... we decided try and find another one.
B-18 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

MG Did you find the one that you had struck?

?? Most of the time we do but when the wind is strong, and the wind is blowing strongly, with the

storm tides maybe a couple of days later with the bloat, it is all aired up, floats. That way it

would probably float, after a couple days.

GK Very rare though. I mean, most of the whales I think are landed. There's -- I know of one stinker

I remember in my lifetime that you see the whale so bloated up you know over half of it is

exposed in the water, out of the water. That's unreal. Still, we take that whale, we bring it back

and gather up all the muktuk and the baleen and, the meat's already spoiled so we can't touch that.

And we just leave the rest for the polar bears and foxes.

MG If we showed up some, some maps, some nautical maps, could you show us where currents are in

the areas where you've been?

?? Currents?

MG Currents, you know

GK Yes

MG Where the water flows most of the time or where you can predict where water's going to be

flowing?

GK Pretty hard to tell, I mean -- like, go out a little bit, it'll be flowing that way and you go out further

and it'll be going this way. I know when I go out, you know, oogruk [bearded seal] hunting, you

notice that. All of a sudden you see an ice going this way and further back over there it's going

this way like its going in a circle.

?? Sometimes you can't even see the currents in the bottom.

GK You have to be out there to, you know, experience that, for to see it -- it might be different closer

to shore, further out. You know, there's all sorts of different currents over here.

MG After you see currents in an area, and you go back, are they the same? do you learn where, where

they are?

GK No, it all depends on weather too, you know. Like, going since when the tide start coming in, you

know, we, we're, we're gonna, we're gonna get west wind, that's another way they decide that

we're going to get west wind, is by when the tide comes up. Usually when we get west wind the

tide comes in and when the east wind start coming around the tide goes down. That's one thing

I've learned being in Kaktovik, it's ah, it's the tide, and the weather change, sure enough. You

know, you got west wind. Even when it first freezes, you know its, all that ice -- it's setting.

Then all of a sudden there's water on top of the ice because the tide's coming up and pretty soon

we should have west wind and sure enough west wind comes around.

[long pause]

MG How late do you see whales -- what's the latest that you see whales?

BA October, last time we ... couldn't find one -- was a little, little hard. We were seeing whales, and

it was right out here. Lotta ice though. You had to break through, almost [?] the boat. Kinda

hard on the boat.

GK Yeah.
Annex B: Bert Akootchook and George Kaleak, 16 Jan. 1998 B-19

BA [?] they had to, they go out October, middle part of October.

MG Do you still whale sometimes in October?

GK Just so long as the water's open. There's, there's enough room to maneuver around ices, so, by

golly, we'll be out there.

MG It's harder conditions, though, I guess.

GK Yeah, it's more challenge. As to suppose that you had no ice and nothing to get in your way.

Whole different story. Going around ice and chasing whales is like playing cat and mouse.

Cause you know them, them whales know the ice is around and they're going to use it to their

advantage.

[Pause]

[To a co-worker] Open the top Norman [laugh]. You never put enough, hey!

?? Open the top?

GK Open the top. Lift it. [laughing again]

Every summer almost, you know, when we travel over toward Canada, we ... we almost always

see whale all the time.

MG What time of the year do you go usually?

GK July

MG Any particular place you see whales, or just any ... ?

GK Mainly around that Kay Point and Shingle Point area, from there ... Herschel Island. From

Herschel Island to Shingle Point I'd say mostly, but seem like they mostly hang around ah, Kay

Point area where it's real deep, near the, near the shore.

MG Can you think of any reasons they, they stay there?

GK I don't know, it might be feeding. There again, you never know, it playing. Or, or like some

Elders say, you know, they, they like congregate together or something and start playing.

MG But you don't, you don't hunt them in July.

GK No, no. That's. ah, Canadian waters where we're not allowed.

MK In the spring, do you ever see them Kaktovik?

BA No, we never see them, because ice always packed.

GK We don't, we don't have no open lead around here, in the springtime ...

MG So they're always ...

GK Maybe a crack here and there, but ...

MG So where do the whales go by in the springtime?

BOTH Probably further north.

MG Way out there.

GK Yeah
B-20 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

BA Where the Barrow current is mostly -- you know where Barrow is?

MG Yeah

GK I imagine about, 50 to 100 miles, maybe

MG And when does, when does the uh, ice open up enough, so that maybe ...

GK If it, if it ever -- sometime, I mean. There's some years where the ice hardly ever leaves.

MG So some years you may not see whales at all? Or whaling

GK [To BA] Some years, yeah?

BA Couple years that we, two, three years ago, we had very cold weather. The ice was ... around.

Stayed around here, the ice. That time we just got, they got only one. [cough in background] two

years ago?

GK I know two years ago we were the only one that brought a whale in because of ice, and cold

weather.

?? [? remark that draws a chuckle from people -- maybe about a cold foot?]

GK Besides that, you know, in .. the whole summer all that ice stuck around. It, it never went

anywhere. It might have broken up, but it, it didn't go out in the ocean.

MG Other crews went out that year though, to whale?

GK Yeah

BA Almost every crew

MG But just -- were there, were there a lot of whales?

GK Not that many, I mean, you couldn't spot them because there was so much ice. We practically,

how many, 20 miles out before we spot a whale.

BA And that's normal [I believe that is what he said, meaning that this is normal for those conditions -

- that is, during heavy or pervasive ice years].

GK And that's, um, trying to find a way to get to the, where the open water was, you know, a big pool

of water anyway. But, but near the shore it was, it was hard. We had to try to go find other

source of water.

MG Did you have to take your boat out over the ice?

GK Not over, around, maneuvering, you know. Some places was closed -- you can't get through, so

you had to try and find your way.

BA What really happened we were getting south wind from the, um, during August, and when's the

wind blowing south it probably hits, the waves hit the uh, northern ice and moves the current,

move the ice towards the land, and it, other time it freeze up, it just stuck around.

GK Yeah

BA [?] current pretty strong, I guess, depending on which way the wind is blowing. Seem like you

have something blocking one way, the waves hit it and you just get the bounce back.

MG You said last year whales were all close and this year they were all further out?
Annex B: Bert Akootchook and George Kaleak, 16 Jan. 1998 B-21

GK Oh no, close this year.

BA I know, when was it, three, three years ago, it was 50 degrees and [? ?] whole bunches -- whole

bunch of whales all over. That was, uh, 20th of September. 50 degrees, unbelievable.

GK And it was, too ... still too warm ...

BA No ice

GK Usually we try to wait for cold weather, you know, so we can preserve the meat and the muktuk

so it don't spoil, and that year you was talking about it was 50 degrees, when how many crews

landed a whale and ... you know, the muktuk and meat spoiled. Not so much as the muktuk but

the meat, you know, it just got stink because of warm weather. So we learned from our mistakes

in the past, and we, we try and wait for cooler weather so we can preserve the meat and the

muktuk. Cause that's a lot of meat wasted, you know, that's how many tons a square foot.

Depending on the size of the whale, and, most of them whales caught this year were no more than

40, with the exception of the last one.

MG Do you, do you go after a certain size of whale?

GK Yeah, we always try to go after the smaller whales. Because their, their muktuk is softer. Their

meat also. Besides 3 or 4 small whales is just right for this village -- enough for everybody, no

complaints.

?? [?] 49-footer. [?]

GK Even that they was happy with. Our catch, last year in 96, fall of 96 was the only whale landed.

They may look small in the water but as soon as you put them on ground they become big. So

you can never know the actual size of a whale. See, some of them can be so fat -- you know, we

call them fatso [Inupiaq word]. That's the one, the real ones they try to go after too, because even

those ones are real soft.

MG Even if they're big.

GK Right. This way, not length-wise, but round.

[some shop talk]

BA Yeah, last year was big, also ...

GK They call them num-num. Our Elders like uh, fat, round whales.

BA Their tails are shorter than [?] whales.

?? Their tails are shorter than ... ordinary, the bigger whales

MG If you go for the, the smaller-sized whales, are those, do they come any special time of the year?

I mean, are they the early whales, or late whales, or in the middle?

GK Well, I want to say, I mean, depends on what whales they are traveling with, I guess. Not every

small whale travels together or passes first -- you can't say that.

MG So they can be any time.

Gk So they can be any time.

BA [?] ... most of them are with their mother whales [?]
B-22 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

GK Some of them, you'll, you'll see like ... well one is that we saw one that might have been less than

20 feet that just was born, you know, probably that year. And it, and it wasn't even black, it was

grey. Darker than a beluga though. But, we never go after the one that are paired up, especially

if there is a mother and a cub, just born, because they can be very dangerous.

BA If they get one with a baby by accident, the mother would drag it out away, drag it away

GK Yeah, and lead it away from trouble, being us.

BA Holding on to it

GK Holding on to it, so ...

BA Pretty quick can't find 'em

GK ... we have no choice but to let it go even though it has a harpoon stuck in it. Because we're not

about to fight a battle with a mother whale. Just leave it in. You know, it's protective over its

young. Yeah, I remember how many years back, that's what happened, happened to us, we had to

let it go, no matter how much we wanted to go after it, the mother was there, protecting it, you

know, leading it away. And there's no way I'm, I would ever try to jeopardize my crew by going

after a whale.

[pause]

MG How far out do you normally have to go out for a whale?

BA Don't we have a map, over here?

GK We got a map in there that shows where all our catches are [meaning in the break room -- so we

went there and looked at it -- left the tape running so you can hear walking sounds and such]

BA This is an old one

GK This is 92, its been updated. last update. [Unintelligible for a bit] 96, 97. And all of these ones

here are the whales landed, or where they all died. All the numbers indicate who caught the

whale, and there's a scale to see how far they, they all were. Some of them were catched, you

know, quite a ways out there, at least 20 miles [?], some of them. Some could be at least 30

miles, number 28, Nolan Solomon.

MG Can you tell ... last year's [?], were they, they were pretty close, weren't they?

BA Oh yeah ... even all three of them probably

GK You know, almost all three of them was in this area, eh?

BA Yeah, two, about two hours pulling, in less than two hours.

GK That's for 3 to 5 miles an hour. [?] GPS will tell us how much, how fast we're traveling, what,

what time we'll get there. Some of them are even real close to shore, you know -- real close.

SM When they are close to shore are they usually the small ones, or big ones?

GK No, some of them big too. I wish they would have put, you know, the, the length of them [on the

whale harvest location map] that way could tell.

BA Right around here in July, last part of July [then too faint to hear clearly]

?? [too faint -- seems to be an Inupiaq name]
Annex B: Bert Akootchook and George Kaleak, 16 Jan. 1998 B-23

GK That's where they, ah ...

BA [Inupiaq name] Point Anderson

GK Warthog was all last year, and they, they spotted whales out there and they said to have eight of

'em just south of 'em, but they only know of one passing through. All the rest came back out in,

around. We have a drill rig over here too, one time, somewhere back here.

[phone rings, obliterates other sound on tape]

GK ... out here, and hardly any whales, cause activity was going on. Also seismic activity. And it

showed in their study, when we was in Prudhoe, that when, every time they, you know they were

using that air hammer to detect the seismic activity below it there was no whales spotted -- very

little. Then after, after they shut down the numbers were like in the hundreds, that they had

spotted. And it, and they told them that, yeah, no whales are going to go around a seismic boat or

vessel.

BA They always tell us that [?oil rigs will drill for?] twenty years.

MG How long ago was the test well -- that activity over there?

BA 85, 86, somewhere around there.

GK Somewhere around there, 'cause we have to go way, way ...

BA [can't hear, talking at same time] whales

GK ... that's one of the rare times we have to go, you know, way out, [pause], and, and you can spot a

whale. It was, it was pitiful. And we know it was due to that seismic activity going on.

MG 85. No whales in 85 [looking at map].

GK Yeah. 81, no whales in 81 [looking at map]. This might have been 87 -- they didn't know the, the

date [a point on the map with no date]. [?]

[some interchange here too faint to hear on tape]

MG Trying to see of there were certain years that you would have to go further out than usual. These

ones that are further out in [?] years.

GK You see how far Nuiqsut has to go at some years?

MG That was their first year.

GK There's ah, number 101 in 1973. They're usually hunting Cross Island. And, and that's in our

waters, I mean, that's in our neighborhood. Imagine how long it would take them ... days, weeks

[soft laugh].

[another soft interchange too soft to hear]

GK Even, even some years some years, like -- in POW-D area they have to cut a whale in the water

BA [Just a little too faint]

GK [Just a little too faint]

BA [Just a little too faint]

GK [Just a little too faint]
B-24 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

BA ... in fact, I was working at Prudhoe that time, [?], that's when I came back from Prudhoe I, got

out on a boat, and then they told me that they got a whale [and faint again]

GK That was one year when we caught two whales [may mean Kaleak boat got two whales, or maybe

Kaktovik as a whole] -- same year

BA Yeah -- [?] time we got five, 77

GK Yeah, or 78. Or five in 77, yeah, but 78 my dad, my dad caught two in one year.

BA So we may have to request for a new update [map]

GK [?]. See, a lot of these, a lot of these they, they, they guess because we didn't have GPSs in them

years

BA [?]

GK I'd say all of these are guesses, because ...

BA [Just a little too faint]

GK [Just a little too faint]

BA [something on report on harvest, including location of strike and kill]

MG You say when you go out whaling you sort of, do you have a formation. Do you ever just go out

on icebergs and, and watch the whales from there?

GK Yeah, we let them know, you know -- probably, maybe lunch time, you know. "Go to have lunch

time, on the ice, listen for whales." Only thing [?] they bother us sometimes [unclear phrase].

BA People would carry hook so they could hook what they caught.

GK Lot of Tom Cod

?? [too faint]

GK Like a [?] head, and sink it all the way down, and bring up whatever is on the [?] head.

BA Arthropod, yes, was there some kind of arthropod [then some faint sentences]. It was long way

down to the bottom.

?? [faint]

MG Do you ever see differences in the water when you are out there?

BA Sometimes its dirty, and sometimes its clear. One time I saw something [eating?] a small octopus

[? and then faint? Something about starfish in there]

GK I know there are starfish, too, cause my kids beach combing, you know, they find starfish, little

tiny crabs, here and there.

BA Before you remove the de, before you even move -- fall whaling, we used to live right around the

beach here, before they moved us here [where the new site of Kaktovik now is]. As we were

growing up we used to dig up all kinds of stuff -- there was crab, put them in the pot, cut their

legs off, and see if they will grow again [laugh] [then faint -- seems to talk of storms putting stuff

on the beaches].

END OF SIDE ONE
Annex B: Bert Akootchook and George Kaleak, 16 Jan. 1998 B-25

SIDE TWO

lost some content when turning tape over -- may not know how much

GK ... when it's windy we don't go out there. We wait for calm weather. I don't, I don't think whales

are affected by weather. I mean, there're in the water all the time anyway.

BA I remember one time they were waiting right there, it dying down [?] that if the wind don't [could

not make it out for a while] over nothing -- but this part right here, number one at the end of it,

the others had followed and stayed, had lunch. We spotted the whale, we pack up and [?].

GK We tried to go out but the waves were too big for our boat so we [?] turning back. [A further

sentence not understandable]

BA But now the other, the other boats were waiting here, and we just stayed over here ourselves,

watching polar bears. Heh heh. While we were having lunch.

GK Always strong currents in here too. In springtime, you go duck hunting. Lotta times that will be

open, and you never travel by channel, channeled areas.

BA Gotta good current right here too.

GK And over here.

MG Let's see, can we look at our maps? Maybe we can mark those on our maps.

BA This is [Inupiaq name]

GK Arey Island

BA Arey Island [as confirmation]

GK This is now connected, this is a whole thing, this, Barter Island, is now connected to Arey Island.

It never used to be.

BA But this part right here is opened up.

GK And yeah it created another channel.

BA Where that channel is it caused another strong current, too.

GK Same thing with our, this -- behind the hanger -- the channel is moving, this way. It, it's coming

out, because, you can know when the wind's coming around it gets longer and, and you know

where the shallow spot is. So, that in the future might connect with Barter Island also.

MG I guess it's always changing.

GK Oh yeah. Mother Nature does its worst [?].

[A part of the tape that does not appear to have much on it -- maybe some internal discussion, and

then a period of the tape with too much outside noise to be listenable]

GK This is using our long-time [LOUD PHONE RING][CRASHING NOISE] for, for their leaving

[?]

MG [?]

some other unintelligible conversation, and another loud noise

SM [some question on fish]
B-26 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

?? [LOUD whistle]

GK One of them first whales I get, you know they used to have, ah, whale bombs, or anything like

that. Lances, [?], like Archie Brower, he used a 50-caliber, that come out of a, a tanker. Don't

have to to shoot that caliber [?].

?? [can't make it out] a wooden boat.

[Section of unintelligible interchange here]

BA One [?] we caught that whale when it was dark, it was close to darkness. Possible to just happen

to look down in the spots of open water and we see our whale, cause it was real clear that, that

side's hurt.

GK People were going, "neat"

BA And yet if they looked down and that whale was at the bottom of the [?]

?? What the other [? loud noise]

[SHOP NOISE and conversation -- rather extended period]

GK Yeah, even some, some years, like, normal was unlikely to see a Orca whale follow the [? loud

shop noise] ship.

?? We saw a gray whale last year [rest of phrase unclear]

[unclear shop noise]

GK We say they may have think they seen a narwhal.

SM [totally unclear]

rest of tape pretty unusable, most of side not recorded
Annex B: Daniel and Lillian Akootchook, 16 Jan. 1998 B-27

Daniel and Lillian Akootchook

MG My name is -- I'm Mike Galginaitis

LA Okay, let's just talk first, okay, a little bit

[tape break while we talk about the overall project and how what they tell us will be used]

DA Vincent Nageak is the one that he taught me, even taught me how to shoot -- give me that whale

up there, hump whale [pause while we look at a whale carved from a piece of baleen]. He let me

draw a whale in the piece of paper. I told him, very first time I shot with that shooting iron [not

really sure of those words], with a shoulder gun, I thought it uh, it's heart was way over here,

somewhere around here [pointing out a location on the baleen whale model he is using -- then a

pause]. No. His heart is right [laughing] over here, front of ??? ???, so then he said that the

target is right here where the heart is, back of the eye.

LA You go out hunting, whaling [addressed to Steve MacLean]?

[talking over each other, SML says yes, tells of crew, LA says is a good tradition]

SM Yeah, I'm learning

DA Also, he's telling me to put your harpoon or anything when he's starting to going down -- he's

open his -- it's going to go right, right into the spine. One shot. Any how, he got the whale

without shooting any, anything with it, except ...

MG Just a lance?

DA Yeah

LA Harpoon

DA I got one, I got one outside, like, like the one he killed the whale with.

LA [to SML] You know my brother, Ralph Akiviak -- that's my brother -- he go on top of the, I heard

many time, my brother, Ralph Akiviak, he always go on top of the whale, and go like that

[making motion as with a lance], kill it, and jump off again [laughs]

MG Have to be quick

LA Yeah, when he was younger I guess he was really fast. Many times he just jump on it and he kill

it like that. Real fast. He, you, when you go, when you, notice when you go you gotta be really

physical fit, you know -- you can't just be slugging around, you gotta be worker. [some softer

talk here, and a pause]

DA Yeah, when the whalers ???, we got ??? ??? on the boat, every boat has CB. When you don't, um,

look at them, just look at them -- they just slowly coming back this way, in the way, from way

over in POW-D. They coming back that way, all here [looking at map?] -- just going back and

forth over here, especially over at, ah

LA Naalagiagvik

DA Naalagiagvik Arey Island

LA You probably seen the ???
B-28 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

DA You know, what's out in the front of the rivers, maybe that's what all the good eating sometimes

MG You think whales are in front of rivers mostly?

DA You harmonize on a mention about a current that go, um, just like a trail, You see, when you,

when it's nice, waters are calm, and you could see that the water is really moving, and that's a

pretty good spot. And you see lots of little birds feeding in there.

LA You could see, you could see sometime a top, you know, that, dirt like you know, and you notice

that the birds always feed on those, at the current. What do they call it in Inupiaq? [addressing

DA -- a short interchange in Inupiaq with no apparent resolution]

DA Well, ??? mention it. Some kind of a name, yes, but, um [at a loss for the name]

LA [suggests a name in Inupiaq -- not confirmed by DA]

MG Does that current, does it always stay in the same place?

LA No.

MG So that's different too

LA Once in a while ??? and seagulls always feeding on that, you know

MG So there's food in there for them

LA Something in there they eat

MG Can you find whales there too, or, sometimes

LA You just see whale anyplace

MG When you go out hunting, do you look for whales in certain places?

LA [starts to answer, but defers to DA]

DA We have about ten boats. Before we spot any whales we just separate, up by maybe five miles

LA Two by two

DA apart

LA two by two

DA From here, go that way about maybe fifteen, twenty mile that way, that way

MG So, both ways -- east, east, west

LA And they spot one, you know ...

DA [taking over from LA] You know, soon as somebody spot one, they get [makes noise like shot]

LA Yeah -- whale. Whale come up there, you know -- Oh [sentence or phrase in Inupiaq] B they say

that going [katok ? Inupiaq word?] -- boat drivers go like crazy people [everyone laughs]. You

remind me of Bob ??, Bob ?? -- you met Papadiak (?), Apachook (?)?

MG No

LA Okay, he [laughs], he finish school and he harpoon two ????? -- how old was he, about sixteen,

first time, when he harpoon, and then this year.

DA How old is Burdell?
Annex B: Daniel and Lillian Akootchook, 16 Jan. 1998 B-29

LA He's eighteen

DA Eighteen?

LA Yeah, he must be sixteen when he first harpooned a whale, his grandpa -- like this year too, end

up eighteen. Just neat kid, you know [laughs]. [Pause] So, okay -- so they feed most mainly

[Inupiaq aside or question to DA]

DA I, and that, over that way [pause] -- drag(?) over here. This is where, the further of the far we go

is up to here [location on map].

LA Is that Pokok?

DA, LA some repetition and then agreement on the name and location

LA Yeah

both Down there -- we'll go that way, and then slowly and slowly we just go, maybe not even, slow, go

way over there, back and back, ???, go that way. Sometime whaling, kind of bad weather, we

get into those sand spits. Talk and talk and watch and look [pause]

MG How long do you stay out when you go out?

LA Let's see, we [DA cuts in]

DA Soon as -- we station in the morning, when the weather, depending on the weather, soon as the

daylights come up.

LA Seven o'clock, seven I guess, seven thirty

DA And then, two hours before the daylight would give out because if we started to ? after the whale,

just for, two hours before the kick in the weather happens, the daylight down, and we had a

chance to lose the whale. Sometimes it take us quite a while to get the whale.

LA To their limit, they try to set five o'clock, you know, that way, it takes a long time to try to kill it,

cause you know, like in morning, ten o'clock, sometime they put the buoy out or [Inupiaq?] and

we follow it all day long, you know, so, so that five o'clock in the evening, and they lose, a couple

of times, ??? to that, you know, going to five o'clock they

DA But we learn, we talk, before we go out hunting, go after whaling, we get together and talk --

once ??? start talking about how it faster or how we will be doing, if we just spot a whale. We get

to one whale, even though there's a whale over here, over there -- go for ONE whale [emphasis

on the ”one” meaning that they single out one whale for all the boats to try for].

LA Yeah, one that put buoy on, you know, we go after that one with one buoy. Whales all over all

right, look good [laughing]

MG How do you pick the whale?

LA Oh, whoever, whoever first strike, first got there and then just put the buoy on, so that's where --

good job! They put buoy on, you know, that's it -- sometimes they name them [say what crew

struck the whale], sometimes they just say they put buoy on, so we just quit looking at that whale

[a whale that their boat may have been following] and go after that one [go and help with the

whale already struck by another crew].

DA The person who, who, who puts the harpoon first -- kill him [and some unintelligible/inaudible]
B-30 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

MG I can, I can imagine. I don't know ...

DA No, never can tell if the whale is cold or winded, you get sweat [laughs]

LA How long you been here?

MG Been in Kaktovik?

LA No, in North Slope

MG Well, I live in Anchorage, but I -- first time I visited the North Slope was in 1982, Nuiqsut.

Yeah, I spent -- I don't know, I've never lived full-time on the slope, but in Nuiqsut, like, I was

there 8 months. I spent about 8 months in Point Lay ...

LA It was different Nuiqsut than here, you know, you have to travel long way, long way. You been

there [directed to SM]?

SM Nuiqsut? Uh-huh [affirmative]

LA That long way, that was scary, bad enough we just jump in the boat and take off.

MG Real close here, then in Nuiqsut

LA Yes, just thankful. Boy, I don't know how they can do that, that lotta ...

MG Lot of hard work and, and the river there too, it's not even easy to get out in a boat sometimes

LA Yeah, it's shallow, huh. [Pause] So mainly was you just interested in feeding area, huh?

MG Well, feeding areas, and then since we know it's hard to tell feeding from non-feeding, just where

you see whales, and what different kinds of -- are bigger whales in different places than little

whales?

LA Um [then in Inupiaq, to DA -- translation of question, probably]

DA Inupiaq answer to her

LA The first one

DA The scout

LA The scout, they

DA Scouting, in July sometime they shows up -- before they talks to each other, by telephone or ...

LA [laughs] Yeah, they do

DA or they could talk in hundreds of miles away.

LA I notice that they see whales not too far from right here, you know, in July -- not too far, you

know, and I notice that every time they follow the first one. He made a trail, you know.

DA The very first one we see a whale, just trying to remember we isn't hunting, being taught -- don't

bother the first -- ?? ?? the caribou. Don't bother the very first caribou that goes that far. If you

do, you have a hard time -- bad luck. So the feeding area, we don't really go way up far -- the

farthest we go is up to Anderson Point sometime, right here [locates on map]. The furthest that

we ...

LA [Inupiaq]
Annex B: Daniel and Lillian Akootchook, 16 Jan. 1998 B-31

DA Anderson Point ...

LA Oh, [?] and POW-D, right there, yeah -- right there

DA yeah, up to here [pointing at map], I think. The further we go is up to HERE, Pokok. When we

don't see [pause] ... and seems to me there's a whale here feeding there nows

MG Do they stay around a while?

DA They stay around two weeks.

MG Same whale?

DA Same -- I don't know, all kinds of whales.

MG All kinds

LA I notice that just once, you know ...

DA big, small

LA big

DA big go that way, swimming that way ... before we get our opening, opening season to go out to

whale is September 1. Before that, in August, we just go down there and look at them just play

around. They just, when you pass by them, they just, if you don't go after them, you just move

along along with them. They don't seem to have [can't understand the phrase] any sound or

anything, they just -- feeding -- that way, good, going around that way, getting into it, that way.

LA I notice that, um, they kill one in August and the meat spoiled -- it spoiled, so after that they have,

they start having meetings. September 1 we go out, so the meat won't spoil -- something just

right.

DA Some time in August the water come to ????

MG Yeah, warm water

DA That -- it doesn't take long for the whale meat to spoil, if you don't butcher in the right ???.

MG Some people have told us that they see whales in July too, sometimes.

DA Yes, yes -- whale what are they, scouting area and then reporting to, whatever -- a whale is

coming. "Okay, you guys -- clear." [laugh] "Lot of food to eat!" [laughing]

MG So that's a real early whale.

LA No, they are just scouting, they just scouting -- and I don't know how, you talk to people to

Nuiqsut?

MG No, people here have told us they see whales in July sometimes.

LA Oh yeah, no -- in Nuiqsut, you know, they usually don't try to go down

MG Right, they don't go down this far at all. No, I, I have talked to them about whaling, but not about

down here. Up where they whale.

[Pause]

Is the scouting whale, is that any special kind of whale? Is it a big one or a small one or ...?
B-32 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

LA No, it's just a whale, you know.

DA Well, if nobody tried to figure out how, well we don't carry measurement ...

MG Right

DA [Laughs]. They just telling by how hard a blow, how high the noise goes up, some people knows

how many signs

LA Yeah, they know. The old people, you know, they know.

MG And whales, do they come in spurts or waves ... or pulses, like, do a lot of whales come at once?

LA Sometime they do [then some in Inupiaq]. Whole bunch of times, I remember, you know, whale

all over. Yeah, they do.

DA How many years ago did Isaac get a whale? Two years ago?

LA Yeah

DA Three years ago?

LA Two

DA Two years ago. Boy, there was a lot of whales. When they report, "Isaac got a whale" we were

all going after a whale down THAT way ... but we had to quit, quit following the other whales to

go go to, go to them, where they were going out, over the waves When we take off way over

there, whales were all over ... right along side us, everywhere.

LA And last year too, after we all got ... Eddie Rexford take movie and there was whales all over ...

long ones, big ones

MG When do, when are, when do all the whales go by? When are there no more whales?

LA I think October, you know, first part of

DA October

LA First part of

DA ????

LA I don't know [to DA]. I notice that when it ices quick, you know, I mean, you know, it start icing

and then we still see some in October but nobody dare to go down there because it kind of slush,

you know.

MG And so you can't really see anymore, so there could still be whales out there still.

LA Yeah

DA In order to be a good whaler, you got to be, ah, you know, keep together, with everybody ...

LA One mind, one spirit

DA don't talk about this other motor[?] not too good, we not doing very well, now don't talk about

what he does, but, counsel him more -- tell him. This is how you are supposed to do. Help each

other. When you, when you, when you have a happy crew, you see ????. Happy crew, that means

the whale is not going to be very far. There he goes. Also, for other captains. Head of the ship.

But, is the general, is the wife of the captain [laughs].
Annex B: Daniel and Lillian Akootchook, 16 Jan. 1998 B-33

LA They always say that, you heard that, huh?

DA Ever since I could remember, you tell that the wife of a captain is the boss of every whaling

captain, whaling crew ..

LA And me, you know, I could strike out (?) people, but dreams, I see whales, that's when I try and

shut my mouth and try to be humble.

DA And that body been told not to talk about other, other whalers or try to be brag about did you do

now -- not that kind of talk, humble. Humble, you had to be humble. Don't argue with no other

whaler or other wife of other whaler. Be just listen.

LA Ruth Nukapigak, you probably met her? [MG indicates yes] Okay. First thing, she came over for

something, you know, first thing she talked to me, she was the Elder, you know, and I listened to

her. She said, you know, when you're whaling, people, ah, when you get a whale people like to

have clean meat, you know, clean stuff. Make sure you clean your whale real good and show

them, you know, that is what she told me. I never forget that. [then speaks Inupiaq to DA].

DA And you have to have a clean cellar, where you put the whale. And some people make a story of

a whale. Talk about it, before they start coming. For that way, way over there, they meet each

other too and talk about it. "Well we're going up that way again. I remember one guy back ...

very kind, he treated us really good. We're going to visit him again."

LA "Clean house" you say. "Clean cellar, they welcome me, I feel at home" you know this whale

was talking. "I going to go to that person's camp, so that person, same person, get a whale again.

DA My sister make mistake one time, my oldest sister. Maryaq [?], he usually get whale all the time,

very first person get whale. Every year. The captain could say anything he want and tell other

guys not to

LA He could cuss at them or swear at them, but then not the woman [laugh]. Got to keep quiet and

humble.

DA But my sister say something like, you know, she don't want to get first, very first, how do you say

LA He don't want it, he don't want to be first, you know, the crew don't want to be first to get the

whale [Inupiaq to DA]

DA She don't want to be first no more. That's what she said, and not supposed to say anything about

that kind of talk. After that, they never came no whale.

LA You guys want 7-up or root beer or ...

SM I'm okay

DA We got pop. Give me hot coffee.

LA You want hot coffee?

MG Sure, I'll have a little bit.

DA I made that one for you guys, here, here's my cup and ??? over here.

SM I'll have coffee.

DA Oh, I never even open it yet. Sugar? Cream?
B-34 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

MG Thank you

DA Cream? Sugar over there.

LA Sugar?

SM No, just black

LA Just black

DA Maybe him

MG Yeah, I'm a .. I need sweet in my coffee

DA [Laughs] I use this one. [Stirs coffee] There are all kinds of stories about whalers. We been

told, I been told, to follow. When you follow them, everything fine -- no problem. [Pause] They

really say truth about whales -- they listening, they listen, and they can hear. I got ear. [DA gets

up and brings us whale ears to see]

LA It was small, but [something about size of] ear.

DA This a bomb

LA 90 and 91 I think, it was [the years he took the whales whose ear drums he is showing us]

SM 92

DA 92

MG Yeah, this one is 91

DA What year?

MG 91

LA First year, we got that one first time.

DA I did it before I retired.

LA I told, ... we were just three of us, he [Daniel] got sick, you know, he had a cold sore, all three of

us, my son-in-law, and Eddie Rexford and me, went out and here I was telling sonny, you know,

that [Inupiaq word], you know that [], you know that float, I said, this is light, I could throw it

out. You harpooned it, I could throw it out, you know. So Eddie raised him up and son-in-law, I

guess he forgot to take the pin off and he harpooned it and that thing just shook and I looked at it

and I forgot all about, I had that ball in my hand, and I forgot, I look at the whale I forgot about to

see "Turn around and throw it over" [laughs]. Soon as it over, that when I start ???? That was

fun, that was first time. And he was sick, he was listening to CB, you know. What do you do

when them, that we got a whale?

DA PRAISE THE LORD!!! [laughing]

LA And they come over trying to get buckets and stuff, and they look at him -- "Wrong, wrong

person is in house -- he supposed to be down there [in the boat] and

MG Right, and you supposed to be up here

LA And I'm supposed to be up there [in town] to get everything, pots and pans, ready ... That was

good, you know. It's, You can't explain it, the joy you get from that animal, or something. It do

something, make you humble or something, you know, just really good feeling, to feed all the
Annex B: Daniel and Lillian Akootchook, 16 Jan. 1998 B-35

people. First time, you know, to feed all the people. In fact we had that flag up there how many

years, I mean couple days, you know, we forgot to -- "You still have your flag up there, we can

still eat" she said. [laugh] That year we the only one catch a whale, you know.

MG Ah, that would be special.

DA Not very far from here, THAT way, east, northeast -- they got a whale. They got, they killed a

whale before it swallowed the ... the one that put it in his mouth. Didn't have a chance to swallow

them, and he died, and he was mouth closed, I think, all the way to the beach. And then, when

they stopped pulling it the mouth opened wide (or twice) [noise]. Chance of something coming

out, man there were some of them that were still alive.

LA What do you call those?

SM Arthropods -- little toe biters.

LA [Unclear]

DA Hundreds and hundreds and hundreds of them. They kept coming out [side of tape ends]

Side two

MG ... their mouth open and take in a lot and.

SM How big were those arthropods?

LA Big, you know ...

SM A couple of inches

LA Uh-huh, a couple inches

DA There's a little shrimp we got in the beach, about that size

SM About one inch

DA And the further you go, sometime we down, go down there 20 mile, sometime and stop, they ???

??? lot of ice, you know, and some people start hooking them little fish and then they put

something .. hard, or something, to put a big chunk of meat and let it go down to the bottom of

the ocean, so many feet, way down. Let it stay there and almost time to go and pull him up and

LOT of shrimp in there. Then, the further you go the bigger you get.

MG And, they're real good?

DA [Unintelligible]. The shrimp? I can't eat them [?] They get bigger.

LA She'll eat them, you know. I remember. She'll eat them. And I remember my dad and them.

When they get a seal they tie that seal gut, that stomach, and they cook it, and they usually put

shrimp in there. We don't do that no more -- cook with the guts, you know.

DA Everybody eat Tunik food now [laughs].

MG Do you ever go catch the shrimp like this and eat them by themselves?

LA No, uh-huh, and we know we got them flounders too, you know -- those black

SM flounder
B-36 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

DA Look like, uh [various unintelligible, maybe several people at once] ... halibut -- THAT kind.

Maybe they're down there because halibut ?? big, the deeper you go the bigger they get.

[Unintelligible sentence -- everyone laughs]. Nobody ever really look for them, you know.

LA Well

MG I, I didn't bring my papers with me today, but I guess, we have to ask, can we share what you've

told us with other people?

LA Yeah, yes [and DA signifies affirmation as well]

MG I mean, we want to be able to, you know, to share it with people in Kaktovik but also with North

Slope Borough and Minerals Management Service, too.

DA I tell you the same thing

MG Well, I think you tell us a lot more. I think you know more than a lot of other people, certainly

more than Minerals Management Service, but North Slope Borough I think will be interested

people, at the Inupiat History, Language, and Culture Center, Commission, and I'd like to make a

tape of this for them so that they can have it.

LA What little we know we'd like to share it.

MG Well, I'm glad you ...

DA I'm glad to help, along with. That's why I visit, glad to have a visitor.
Annex B: Isaac Akootchook, 17 Jan. 1998 B-37

Isaac Akootchook

IA [tape stated late] ... some of the whales,[several indistinct words], because um, if we start

whaling [indistinct phrase], here and there, sometime -- if we ever spot the whale, and we go

there sometimes he moved, he ... either way, you know. [Sentence very fast and unclear] almost

always, feeding.

MG And I guess ...

IA Our knowledge, but, ah, maybe different from the other guys, too. That=d be good

MG You say, you always go back and forth?

IA Yeah, might be over here. This Kaktovik over there? [looking at and referring to map]

MG Kaktovik=s right here.

IA Oh right here, this, a, that=s ... oh, okay.

MG Yeah, ah Barrow ...

IA Sometime they, we usually whaling here down here anyway.

Mg Uh huh

IA We not ... one time we go farther, out of town here somewhere, we never start to whale so far

MG [some sound]

IA for many many years.

[faint phrase in background]

IA If we were lucky here, we do it around here

MG I guess we have a bigger map over here, too.

IA Yeah, that=s the one

MG Is this the area you use then, or would it be a little further south?

IA No, we use this over, over here.

MG Right here, mostly?

IA Yeah, mostly. Yeah, we have been lucky, with a using down here.

SM So right on Barter Island?

IA Yeah, right on Barter Island ... and we, they have a map. And [unclear phrase], you know, and

ah, [faint, talking while referring to map on wall of the room]

MG [faint, talking while referring to map on wall of the room]

IA [faint, talking while referring to map on wall of the room]

Unknown number of interchanges

MG The whales that you get here, are they moving?

IA Yeah, sometimes they move moving in down here, yeah [unclear]. How many people you have

already now? [that is, how many whalers have we talked with?] Yes.
B-38 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

MG Talk to you?

IA Yeah

MG I guess we talked to Daniel [Akootchook] last night, and we talked to George Kaleak and I think

ah, maybe, Bert Akootchook

IA Ah, this is my son ... Bert, my son [further faint remark]. Whatever, that=s all I gotta say, and I

feel that I don=t much farther [?]

MG Have you ever seen whale feeding that you know of?

IA You know, ah, early -- early, before we, ah, got, before we whaling.

MG [affirmative noise]

IA And ah the first time we spot, ah they spot the whale, [?] round here. And we seen it down here.

They never move, you know, before we got, before we start whaling, whale, whaling

MG And so they ...

IA And that one around about maybe, what? Fifty, fifty-nine or fifty-three, whatever [referring to

years]. You know, a long long time before we got, we start whaling [whaling was resumed in

Kaktovik in 1964]. They spot the whale before that. And, ah, again, its um our parents and um

uncles who always spot the whales right on here

MG Right off the island ...?

IA Yeah, right on here and here, and, and Arey Island.

MG Here?

IA Yeah, west of Barter. Right here, at that place, yeah. That was always is, ah, telling us is, she=s,

ah, the whale feeding, I=ve, I heard that. That=s where we have [finding/fighting?] for those, ah,

people try to find out, you know, that=s why we always asking about, who always ask. We have

interview, who is our interview anyway? But, this is good, you know. Not only one person, take

it, so ...

MG Right

IA [not clear]

MG And, are there, currents in here that, that are, where you find ...

IA Yeah, current is always is, pretty clear sometimes. You know, these, ah, the current is as, not

only one, maybe always have three, a little farther out, too. When there=s [phrase?]. Just, just

like a river. And, ah, maybe you, boating on the river is just, ah, there=s shallow one is always

black, right? You have a current that=s just, and a clear one is down here. Just like that, it=s

always happening. Clear, and the one side is always red and it usually turns a lot of, muddy or

something like that, so that=s, ah, I think that=s what he=s, whale is feeding, too. They have a lot of

seagulls around here. Got the seagull always eating something, too, you know. So [?unclear?],

crap.

MG [Unclear] parallel to the coast?

IA Yeah, Uh huh, you could. Sometime they have, ah, maybe about three or four miles, five miles,

and ah sometimes they a little farther out, maybe about twelve miles. And some then these
Annex B: Isaac Akootchook, 17 Jan. 1998 B-39

coming close to um, down here. Way down here. Mostly we go that far as we always go.

Sometime we, one time we got down here, because we never start to whale much, and we moved

[word?], first we look at it back here, Arey Island. This is Arey Island, we always, very

important ...

MG [talking over IA] Arey, Arey Island is a big old spit [?]

IA ... maybe a little farther out too, but, I=m not saying that, ah, we, just when we use this, we use

this ...

MG Right

IA ... all the boat

MG Use, use as much as you need to, right?

IA Right, ah huh -- we just lucky we use about here [?place name?], every time we start whaling.

This is what, about, I don=t know how ... What, what=s this number system, I don=t know.

MG That=s supposed to be how deep it is

SM Water depth

IA Oh, how ... oh, deep it is. Oh, I see, yeah. Twenty feet, forty eight feet ...

MG Soundings are in feet

IA [statement or two too faint to hear] ... must be a current or something, I don=t know. I don=t know

about it.

MG It says, ah, territorial sea. I think that means that=s three miles.

IA Three mile=s limit.

MG Yeah.

IA That=s a [?word?] for the federal? [laughs] Federal water, whatever.

MG That means it=s state, I guess, and this is federal water here.

IA And what else is there?

MG Do you notice currents in between these islands ... or ?

IA Yeah, they haven=t, not, they never stop this current is cut, back and forth, you know, over her in

the channel, all the time. These channels, that=s where these always current ... always open in

[opening?]. But this one is this map is been here for a long time. There haven=t already ...

MG This is closed?

IA Closed. This is closed. And, this open it down here.

? That one is closed already, now.

IA And again, this is, ah, ... [?word or two] Kaktovik. It just come down the shallow water, come

down here.

[? Several voices at once -- faint and confused -- Come down the, ah, shallow water down here, ... ?]

? We seen it in the wake
B-40 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

? Just washed up down there

IA Every time we get a, ... drag the whale, we gotta go a little farther down there and come back that

ways, you know. Go around that ways.

MG So you still, you still butcher the whale over in here?

IA Yeah, ah huh, right down to here about, Right behind the village. That way=s a house down there,

used for cooking, have a coffee break, ... We usually [or “used to”] use the tent, but its [?] now,

whale camp. [Further sentence or two very faint]. Well?

MG Do you notice, does do the, how much the river flows, does that affect how many whales there

are or where they stay?

IA I don=t know the lagoon, they never go through the lagoon. No, not up here, just stay in the

ocean. Maybe, um, this is pretty shallow up here, you know, and ah ... muddy, ah ... early, early

long, long time, that, that we see a lotta bones down here. Here, and Arey Island, and ah the

people who used to whaling up here, many many years and years [?unclear words?] whaling

captain [?unclear phrase?], I don=t= know how many years [unclear again]. I remember my

brother here, Daniel, have a cabin down here, this summer, go to hunt, go to get something to eat.

He found a bones down here, whale bone.

? Eih

IA But I don=t know how long [unclear]. If you let ‘em quite a few around, still go sideways [?].

For people, ah, that have a house, along here, just like a, he talk about the Arey Island.

Same, same thing, you know.

? Yeah, this [quite unclear] down here, before they U.S. get the Navy boundary, you know [?].

Nineteen ... forties, four-forties -- it was that long. It was ... come over? Thirty, thirty-five years

ago? [faint and unclear]

IA We never know about [unclear] at that time, but is today, after I heard [this part of the tape very

faint and difficult to understand] ... Anyway, and ah, we, we got to this ah, Air Force was coming

in here 1948. That=s when we gotta leave. Both sides, hunting [?]. Some of them is still around,

right on the corner, around here [becomes faint]. Who, who=s usually picking up something --

oak[?], bones[?], stones[?], stuff like that.

MG And is this eroding any now?

IA This one?

MG Yeah

IA A little bit. And then down here he, he may go down, usually have right down here, especially

right in here, you know? Early on, early ah thirties, ah twenties. Before the twenties there was

filling over here -- usually it just here, but it started over here, this, this one over here, it=s already

here. They, they have more on the other side, maybe he started more over here to seen it in the

summer time. They=re erosion [?], and um, at some of them it, they come up, and this one is

channel. There supposed to be cut down here somewhere too, you got a channel over here

somewhere. Yeah, open here some where. Yeah, that=s why we maybe gone through further up

higher, I don=t know. PAUSE
Annex B: Isaac Akootchook, 17 Jan. 1998 B-41

IA This one? But I never go boating, there=re, there=re usually open, that over here too. But maybe

some people more in boat out here. But I usually boating up here, right over here [faint here].

[Faint sentences]

MG When do you think the last time you went, went out there in ...?

IA About a two years ago, I go with them. But I usually go with ‘em, but this, ah, too many. My

grandsons and grandkids. Friends who want to come along, you know, my brother George like to

come over and ah, you have about five people in a boat is, is enough. Sometime you don=t like to

overload the boat, stuff like that, you know. And George and them, they get him out, we=ll be

going out. But, ah, that=s why ah, we have a first-time my grandsons is, where they=ll get a,

harpoon a whale. [Next statement very faint] Yeah, we were happy about that [laughs] At that

[?word?] Yeah, that=s a, that=s the way we been [trails off, a few faint words] ... That ways Bert is

always real close because that ah he=s the harpooner. [two or three other statements too faint to

understand, may be different people speaking]. Joe, and me, myself, I still, I used to steering, the

boat. And ah, the Rexford crew, Herman Rexford, ah, whaling, we used, ah, we worked together,

Herman and, and our family, together, still. I was steering the boat all the time, after me and

Albert[?], Bert was always behind us, as I was steering the boat all the time. [Next several

sentences unclear -- too faint to really understand what was said] Some of them would stay in

the boat, too. Kept, they got harpoon and the float all the time too. As soon as they see that,

harpoon and float over sides, float up [then unclear]. Everybody learn from that old timers -- talk

about it

? [Seems to be a faint question].

IA [faint response]

MG Who decides where to look for whales?

IA Well, ah, people used to go hunting. Seal hunting, ougruk hunting in spring time, when we find

ah, for the winter. Make some seal oils, then we often hunt.

MG [Affirmative noise]

IA But this, ah, they always find it. They not really look at it, but, ah, we spot the whale. We

always [unclear word] ‘em. But it=s ah, and it is ah, people use boat out, for boating. And make

sure its, ah something in the village. I don=t know anybody who says he=s going to look around,

you know, he always ,he always [becomes faint]. Before we start whaling we always spot

whales, because we already know that whales is coming. And we always ah, are telling ‘em not

fail, scare them something=s wrong. Because if, if you [?unclear?] come early, just, just to bother

them, check, check them out ... we never know if maybe they might [unclear words -- worried

about disturbing whales]. If they have a migration [unclear], it happens, they don=t always turn

around and go back, go a little farther out. That=s what you=re supposed to, you know everybody,

ask the Elders that talk talk last night. The leaders is always is just coming toward through here,

but it=s, how much we gonna make it for us, if they haven=t already had leaders go through here,

they always go right by. They always follow that trail, just like caribou. We ah, make this ...

[cabin?] if you really want to [fill?] people, down in here. How we got a lot of caribou ...

MG Right.

IA that about [word] 19th. Then when the whales, ah comes and put ‘em ... [stops speaking]
B-42 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

MG So when they know, when the whales are coming, but is there any one, one place that you look,

when you know whales are ...

IA Not really. They always move them. But mostly ah, people always a spotted at, over here -- and

um, and ah, and down here, and down here in the Arey Island side. People always going out, if

we decide to go whaling, they goes out straight drive [?], about three miles maybe, [faint phrase].

And ah, some of the people always going up this way. [Unclear phrase ] They always is going AI

gotta go, I gotta go west for a little bit,@ you know, some of them people coming this way. And

and either way they always spot it over here, sometime they spot it, whale, down here. They are

[name -- Unaparak?], it=s always slowly going up east all the time, and there=s some people

always take that Arey Island perch before they go, go farther east. They not seen it over there,

always coming behind us, see, behind this, ah, boat [faint, maybe point?]. [Unclear phrase].

Sometime we not started over here, um uh, down here, you know, mostly, uh, started down here

too, you know, we=re whaling down here. That=s where they saw ... [name? -- karak].

[Eight seconds or so very faint and unclear on tape -- may have been looking at map to see location

-- not really sentences -- check maps]

IA This is important waters down here, all the way from here, all the way down to ... Camden Bay.

We=re lucky ah for a couple, three years and we always go whaling, not too far. But if, about a

couple years ago, we got one whale, still got one whale, because of, ah, ice. Too many ice. Ah,

too many ice, and ah, [ PHONE RINGS]

MG When there=s ice, does that affect how many whales [PHONE RINGS] , or just ...

IA Well, not really, not really. There, there, uh, uh, if they have a lotta ices around, yeah [PHONE

RINGS], that brings always problems, they don=t have a migration, ‘cause they always go out [too

faint to understand]. [PHONE RINGS] They not stopping. If there=s a lot of open lead around ...

[PHONE RINGS] that where those, that where we always sits, we gotta get them. If they hadn=t

[PHONE RINGS] cleared out a lotta ice, we gotta look for open water somewhere. [PHONE

RINGS PHONE RINGS PHONE RINGS]

MG Think, think we should answer?

IA No, I don=t think so [PHONE RINGS]. It could be [word], I don=t know.

MG No, I don=t think so.

IA don=t think so. Somebody going to be answer it, somebody always answers. [PHONE RINGS

PHONE RINGS]

MG Do you, do you ever notice what the whales are feeding on, do you ever [PHONE RINGS] see

little shrimps or anything like that ...?

IA Um, if you go down to whaling [goes/crews ?], a little fences [?] around the small one?

MG Yeah

IA And, ah, you go down to floating on the water, you see there=s a lot of right on the water. Just,

just floating. And that ways ah, the old people, and ah, telling us about the [word?], that=s the

whale, food. That=s what he is always eating on. But, we never, we never study it but we seen it -

- anywhere, anywhere you travel, there=s a real bubble like this, you know. They are in the water.

They are right on the water. All kinds a, and ah, little, to little things [faint word].
Annex B: Isaac Akootchook, 17 Jan. 1998 B-43

MG And you=ve seen them all, all the time ...?

IA Yeah ...

MG Or just sometimes ...?

IA I=m, ah mostly all the time here, sometimes in the harvesting [?] too. You haven=t seen a lot of

them around until [pause and then faint]. At, we always try to look and stop and look down,

water you know. The water=s always clear, [faint phrase]. Just, must be the wonderful, water.

MG So that you can see that in July sometimes? July, June, August -- all of them?

IA Summer. Maybe that=s why you ah, got to more inspect ‘em, you know, since summer they ah,

ah, haven=t [fast faint phrase]. AMS, you know, got a little more [faint and hard to understand]

three seconds. That=s why I=m I=m always, my mind, if I=m going down to ocean, have to look

for, you know, what I see in that water. ‘Cause it=s really important to ah [then becomes too soft

and faint]. [short unclear phrase] I, I=m always tell my family all the time,@Toova, gotta check

that water. See that [word] look like these. But ah, maybe ah, my [word?] told me, AGet

something and drag him up here.@ Then, pick him up, make sure [unclear], bring it up. See what

is [unclear -- in his stomach?]. Check that. Make sure [unclear middle] animal. See you. See

you have to have ah, have food, have ougruk and food, not only a whale, you know, but all kinds

of ... fish come out from our boat [last phrase not all that clear].

MG Do people still go hunting for seals and ougruk quite a bit?

IA Yeah, ah ... just only, quite a bit of ougruk, you know. We hunt seal once in a while, just down

[or a place name ?], here. We have, we have dogs ... we have a lot of need for the, for, for the

quota [unclear remark -- we have a lotta meat for the ___ ?]. We not usually hunt too much seal

because we not really use it. Because ah, we ... sometimes we get it for ... cook [unclear

sentences]. Food seal, they cook, [uclear continuation]. Get up [unclear]. Last fall we shot about

two or three. People out there eat them [Unclear remark].

MG When you hunt beluga, do you, do you hunt ...

IA Yeah, usually they want to, they want ... a lot of people on that hunt. [Unclear last sentence or

two]

MG I know in Point Lay they ...

IA Yeah

MG they hunt together, with, with many boats at once. Do you do that here too?

IA [Not clear on tape -- started answer during question]

MG Right

IA Just like, ah, [?], right on the ... ah, what do you call it, that place sticking out for ... hunting ...

beluga [and then too faint to hear]

MG But here do, do just people go out in single boats for beluga?

IA Just some of them always do, the people, people in boats, [?]. If they=ve started to surface call [?]

, then people would like to go hunt them. [further unclear remarks]

PAUSE
B-44 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

MG Do you know, do ... Just ... Are some whales close to the shore and others further away? I mean,

on their size or ...

IA Yeah, [on that one we do ?].And ah, those is always spot a, spotted from here. Some of them is

close to the shore, boat is down here some ... more than, a little farther out, but it=s always [?]ing

for them ... About a mile and a half, two miles [?], you know? [unclear for a bit] a little farther

out, sometimes. Mostly, as I was saying, right two or three hours [?] right on the middle.

[Some faint discussion here -- not clear]

IA And early on, a couple years we have lucky. Every time that he went out for early in the

morning, his [unclear statement and further, several sentences]. Yeah. Early in the morning, he=s

always AYou strike that one.@

MG But most of the time you go for a smaller whale?

IA That one [answer not really clear -- too faint]. Try to get the smaller.

You know, ah, early ah, 80, 87 -- I have ah, a big one we have at that time. [unclear for several

sentences]. After that, everybody AYou take the small one.@ [Laughs] Lot of people worked hard,

especially [?] family [some more that is unclear].

MG Are the big whales, are they further out, in the ocean?

IA They always go through close, some of them. Some of them are farther out, some of them.

[unclear][several sentences]

MG [?] too big?

IA Yeah, too big is a lot of work, but is good though [and then unclear]

MG What, what kind of year ... is there a time of year when you don=t see any whales at all out there?

IA One time, I have a real, really down [?] year, something [unclear]. Last year we never did get a

whale. Not only that, but they don/=t have any ah, [?] around here some years with [?], price of,

ah, water. I don=t know, whatever, you know [and following is unclear]

MG Was it, was there a lot of ice that year? Was it open water?

IA Open water, all the way.

MG Just couldn=t see any whales.

IA [unclear]. You know, in the old ... story, going to talk about the whaling, this is mine, I know

what, I know how to hunt. Don=t thinks nothing until you see him [?] doing something else.

Whale is his hearing. [unclear] That=s why you think you hear, but sometimes you have to say

something earlier, you know, because people always come to [phrase] to do something. Whale

always know about it, and you [?]. The whale and God appear is over there ....[unclear]

IA You know, ah, before that, we have a lot of ice. Before that, a lot of ice, [?], we didn=t get any

whales, because of a lot of ice and hardly see ‘em. They around all right, but, it is hard to find

them, hard to spot 'em. Next year, our ice is gone. And that year we didn=t get any. And that the

people started comment on it. AWell, maybe we=ll get a, we=re going to get a whale this year, no

ice at all.@ But, no ice means the whale is ... [?] seen that whale. Just comes down there, just see

him. [unclear] We find out [unclear]. We always say something about [?], but we can=t always,
Annex B: Isaac Akootchook, 17 Jan. 1998 B-45

you know, talking about and screw it up . You know these, you know, this, this is really

important, for the [unclear], about the whale. Whale is [inaudible]. You know, [inaudible].

MG Yeah, I think that=s, that=s why it=s important, too, for ...

IA Right, yeah

MG ... for MMS, they have to know that too...

IA That=s what I telling them, [unclear] and, um, it gotta be asked God for this, before we start to do

something, and that way/why we always [unclear]. [?] God always answer.

? May be some remark or question in here, but if so is very faint

IA 'Cause they are free, all of them, animals, use 'em, the land, use it well freely, you should follow.

Disappear, give thanks that because we not doing it without him [?]. [word?]. Sometimes we

make a plan, to do this, [unclear phrase]. Not to talk about [unclear]. [several unclear sentences]

MG I don=t know, I guess that=s really what we wanted to know ...

IA Uh hmm

MG ... was where, where whales were ...

SM [Unclear]

MG ... how, how you went about going after them. Some people say that when the whales come from

the east, the west, that sometimes they come in groups, you know, there=s groups that ...

IA Yes, they are always group. Sometime that we go whaling, you know, they probably down here,

and seeing a lot of 'em. Lot of 'em together. Nothing we ah, no. Ah, sometime we have to use

this whale, and we start to take it, the whale never stop. It always AHey, look at the whale down

here.@ AHey, Look at that down here, too.@ Blows, you know. They awful many, many of them.

Never stop. Not there, maybe later on the ... sometimes they have a slow down, after time.

About after later on he come back, they the same place. Moving [unclear phrase]. We never,

never really strike that all of 'em. That would be something just completely [very faint]. Strike

'em, the other have problems. [several unclear statements -- very faint]

MG So each whale is ... pretty much any time, must be.

IA Yeah, must be, ah. Yeah, anytime, come in ... July. In a week or two, we ... we have our, we

always spot the whale, [unclear]. [Last sentence unclear]. We ah, I don=t know, we can=t tell if

just feeding around here somewhere, just like it, see it in the waters.

MG Do you catch some of those whales, or ...

IA Migrating

MG Migrating [unclear]?

IA [Response is too faint to understand]

MG [unclear]

IA And after we get finished Prudhoe bay, a lot of guys going out with the boats [uclear finish].

AHay, look at that spouter!@ AHuh?@

MG Yah, I guess a lot of open water in [?]
B-46 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

IA [unclear]

MG So are the whales ... [?] a lot smaller than the last half week [?]

IA [response too faint]

MG Do you think maybe sometime you=ll wail till October to whale?

IA Well, that we usually that ah, we not gonna wait till October. That=s ah, the last month that we

like to go hunt [unclear]. [Further remarks too faint on tape]. And there a lotta, lotta people who

usually go hunting in July. [Some other faint remarks on tape]. After the whaling, it always

boating [unclear]. PAUSE Well, I think that=s about all ...

MG Yeah, that=s pretty good. Can, can we share the information that=s you gave with other people?

IA Sure, I like to. This time, it=s good. Maybe um, maybe after you writing together, maybe ah, I=ll

want the paper, you know.

MG Yeah, then I=ll, I=ll we=ll give it back, show you a copy so you can look and see what you said.

IA Yeah, I like that one. [unclear remark]

MG And I guess what I have here is a paper that says that we talked to you, and that you uh, you will

agree to share this, and what I=ll -- down here is that you want us to write, we=ll give you a copy

of everything so that you can see what you are saying.

IA [last remarks too faint]

MG And, and what I=ll do is I=ll ...

IA I sign it here?

MG Yeah, I=ll give you my card and that way you=ll know who I was and, I=ll put Steve=s name on here

I guess.

IA Yeah, let me have a copy if you have the time [and faint after that for a bit] ... my box is 139 [?],

Kaktovik

MG Well, it, it won=t be before we leave, but what I=ll do is next week when I get back in Anchorage

I=ll make, make copies of everything and send it back to you.

IA Good [and then faint]

MG You know, if you have any questions for us, we=d be glad to answer them.

IA [to SM] You always been to Barrow or Anchorage?

SM I live in Anchorage, and my mom [end of tape]
Annex B: Charles Brower, 17 Jan. 1998 B-47

Charles Brower

MSG Don't bother calling Hagland.

CB Yeah.

MSG But anyway, that's sort of what we'd like to talk about with you. We did bring some maps, if you

want to look at maps to show us specific areas and things like that.

CB I know places where we used to go see whales would be like around Arey Island on that one

bend.

MSG Uhm-hm (affirmative).

CB That's usually where they hang around.

MSG Any special time of year, or just all summer?

CB Well, during whaling time, that's -- when we can't see whales anywhere close by, that's usually

the first place we go to then, then we started heading eastward.

MSG And whaling time, that's the beginning of September?

CB Yeah.

MSG Is there any -- big ones, small ones, all kinds?

CB Oh, I'd say about medium size.

MSG And are they migrating then or are they hanging around?

CB They used to hang around right around that area, few days around -- around there.

MSG And other people, they've said, you know, when they -- before whaling, sometimes they go out

hunting, different parts.

CB Uhm-hm (affirmative).

MSG And they see whales in other areas. Has that been your experience too, when you go out there

you see whales

 ?

CB Once we saw some over by the Jago entrance.

MSG Uhm-hm (affirmative).

CB Just a small one over that area.

MSG And that's still pretty close to shore. What time of year was that?

CB This was like in mid-August.

MSG Uhm-hm (affirmative). So -- and other people say they go over to Canada, some by boat, some

on snowmachine, and of course, snowmachine, I guess you don't see too many whales. But by

boat -- some people say they don't see too many whales over that way, really. I don't know, have

you gone over there by boat.

CB Oh, I go over there a lot, used to go over there a lot.

MSG Uhm-hm (affirmative).
B-48 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

CB Right around that, uh, Komakuk Bay, that's where we used to start really meeting up with them.

MSG Komakuk Bay?

CB BAR-1, Komakuk Bay.

MSG BAR-1, okay. That's when you start to meet them?

CB Uhm-hm (affirmative).

MSG And are -- what time do you generally travel over to Canada, what time of year would that be?

CB We usually go -- we used to go in, like early August, try to be back before whaling time. And

some years we'd go in July, see them around Ptarmigan Bay area.

MSG And once, once you'd seen them at Komakuk Bay, do you see them all the way then into Canada,

all the rest of the way?

CB Pretty much, but there's not so many like -- between Komakuk and Herschel Island, in that area.

MSG Uhm-hm (affirmative).

CB But once you get past Herschel Island, then there's quite a bit right around that, ah, Ptarmigan

Bay area.

MSG That's not the study area, but I think that they'll be real interested to know that, and -- but you say

there are whales out here already, early August too?

CB Uhm-hm (affirmative). Yeah, my wife's from Herschel Island, born and raised over there. I go

visit over there sometimes and just watch the whales just swimming around, around Herschel

Island, kind of a bay area.

MSG So they stay around there for -- I guess those are the -- some of the summer feeding grounds,

probably.

CB Yeah.

MSG Then how late do whales go by here, by Kaktovik?

CB You mean heading back?

MSG Yeah. Right here.

CB I know it's sometime in October. One year we were catching whales, like the 8th, 10th, and 12th

of October. That's when there was not much ice.

MSG Just scared somebody, I think. {Child had peeked around the doorway, but then jerked back

behind it]

CB Hey, my baby. Archie Robert -- where are you?

MSG But you have whales as late as that?

CB Oh, yeah.

MSG Do you notice any difference where big whales go and where big -- small whales go?

CB Not -- I know they travel at different times. The little whales, usually by the time we start

whaling, usually go in too, and then a little later in the season the big ones start.
Annex B: Charles Brower, 17 Jan. 1998 B-49

MSG And before you start whaling, is there any special kind of whale that goes then?

CB I don't know [too faint].

MSG But the little ones do go beginning of September, then the -- sort of big ones at the end?

CB Yeah.

MSG People too have told us that you usually don't have to go too far to whale.

CB Always --

MSG Pretty close to --

CB -- to -- just right off -- not too far offshore. You know, two or three miles at a time.

MSG Do people ever take boat trips further to the west for other things?

CB Well, caribou hunting and all that, they usually go up to -- first, I know they go up to, like,

Brownlow Point.

MSG Uhm-hm (affirmative).

CB Some people used to go to Flaxman Island, but I don't know if they really go that way anymore.

MSG Don't they ever talk about seeing whales over that way, or pretty much just --

CB I -- I don't -- they're just mostly looking for caribou. That's all we ever hear about. That and

beluga whales.

MSG Yeah, they probably see them and they just probably won't talk about it. They do look for beluga

too?

CB Oh, yeah. I don't know if they look for them, but they'll run into them and --

MSG Uhm-hm (affirmative).

CB -- and you hear them on the CB, Abeluga's over there@.

MSG Guess we should have asked you how long you've been whaling, when you started whaling, what

sort of experience you grew up with.

CB I started the year I graduated, like 1978.

MSG Uhm-hm (affirmative).

(Background remarks - indiscernible). And then I took over my dad=s crew [too faint]

MSG And does he still give advice and --

CB Oh, yeah.

MSG -- pretty much things like that?

CB We try to take him out when he's not too busy working.

MSG Crew is how many -- five in the boat, pretty much?

CB Oh, sometimes we got a whole bunch. But we usually use one of them sea dories. I'd say we

average about eight.

MSG That's a big crew.
B-50 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

CB Uhm-hm (affirmative).

MSG And I guess everybody -- all the crews are coordinated, so -- that's a whole lot of people out there

at one time.

CB Yeah.

MSG Do you notice anything -- people tell us there are a lot of currents out there too. Do whales and

currents, do they occur together? Do whales --

CB Sometimes.

MSG -- like currents?

CB Yeah. There's one time we were out whaling, we saw -- you know, where the current is and it's

got stuff floating around?

MSG Uhm-hm (affirmative).

CB There was a whole bunch of them black seabirds sitting around there. We just thought those were

ducks, and we looked them a little closer, and there was a whale floating around with the ducks

too. And so some people started calling them whale ducks or whale birds.

SM Do you see that often, the whales hanging out where the birds are?

CB Not very much. It's once in a while you=ll se it.

MSG So sometimes you'll see the birds but no whales?

CB Uhm-hm (affirmative).

MSG And do you see the -- I don't know what -- little whale food, I guess what they call them,

copepods, all that stuff? Do you see that in the water very often?

CB Never really looked for them [and then very faint].

MSG I guess I've heard some people say they see a mass of red stuff, but not very often. But unless it's

that vivid, probably, it's not really necessary, they [faint].

CB Yeah, during whale divings, you can just looking for blows until looking in the water, by the time

you're looking at the horizon.

MSG So there really are -- there are enough whales out there, you just need to -- for the blows, you

don't have to worry about?

CB Uhm-hm (affirmative).

MSG If they=re there, you'll see them?

CB Oh, yeah.

MSG Some years you don't see many whales, though?

CB Yeah. Especially on warm weather, it's pretty hard to see the blows too. You have to look kinda

[?], keep an eye on 'em.

MSG In years when you don't get whales, why do you think that is?

CB Mostly ice conditions [faint].
Annex B: Charles Brower, 17 Jan. 1998 B-51

MSG Just too much ice, too many chunks --

CB Yeah.

SM -- what have you?

CB Sometimes we'll see them and we'll try to go after them, but then we have to try to go around ice

and all that, and just gets to be too much.

MSG Uhm-hm (affirmative). Guess they can dodge around the ice better than you can.

CB Uhm-hm (affirmative).

MSG Let's see. What else can we ask about whale behavior?

SM Do you see a -- different kind of whales closer to the shore or farther away from the shore?

Smaller whales, _______________?

CB Smaller whales usually are closer -- closer to the shore, yeah.

SM Smaller whales are closer.

MSG Do you ever see whales inside the Barrier Islands?

CB Not really, no.

MSG How about whales that bring up mud or seem to hit the bottom? I don't know if they're feeding or

doing something else, but do ever -- do they ever bring up mud?

CB I haven't really noticed that, actually. Some people talk about it, they say they've been chasing

them and see a brown spout.

MSG Uhm-hm (affirmative).

SM Some people said that whales like to -- some whales like to hang out where the rivers --

CB Uhm-hm (affirmative).

MSG -- come into the water? Do you see that?

CB That one around Jago that was -- that's right around near that river. And I think the ones at Arey

Island part, that's where -- where -- where it comes out to.

MSG Uhm-hm (affirmative).

CB So right around the Two (ph) -- Two River area.

MSG But again, that's just where you find whales, so --

CB Uhm-hm (affirmative).

MSG -- you don't know if that's because of the rivers, but that's where they --

CB Yeah.

(Background remarks - indiscernible)

MSG Have you seen whaling change at all while you -- you said you started in '78? Has it been pretty

much the same or --

CB [faint -- other voices].
B-52 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

MSG Have you seen whaling change, the way that people whale here?

CB No, it really been about the same. See, I know when they first started -- when I first started in, it

used to, sometimes they'd shoot the whale before they put the harpoon on it.

MSG Uhm-hm (affirmative).

CB They'd get away with that and start putting the harpoon and floats on before they'd start trying to

shoot the -- they cut down on the lost whales.

MSG And they'd do this for any special kind of whale?

CB Just the small ones.

MSG Okay.

CB That's what it -- try to stay away from the big ones. They try to. And some years they just have

pretty big ones.

MSG And what do you think is a small whale? What's the kind that you like?

CB I'd say about, between ... 30- to 40-footers.

MSG And that's something that the whaling captains association, they sort of say that's what people

should try to be looking for?

CB I think it's just whalers consult with this [consensus?], they just like that smaller, not so hard

muktuk.

MSG I guess we should ask if you can -- can you tell a feeding whale from a whale that's just not

feeding? Is there any way to tell?

CB I really don't know.

SM What's the earliest you've ever seen whales?

CB There was one year we saw one, like in late July.

SM Where did you see that one?

CB Right around by Jago area.

SM Was it a small one or a big one, do you know?

CB I couldn't really tell. We were, like inside the sand spit there, and could see the blow on the

outside, so --

MSG Uhm-hm (affirmative).

CB -- we never really tried to go out after it.

MSG That's unusual to see them that early?

CB Well, they see them once in a while, but not very often.

MSG I don't know; when you see one that early, does it get people excited, or is it just --

CB Well, everybody's thinking about caribou hunting and all that. They -- never mind.

MSG Has to get towards late August --

CB Uhm-hm (affirmative).
Annex B: Charles Brower, 17 Jan. 1998 B-53

MSG -- I guess. (Pause) I don't know, I guess that pretty much answers the questions we want to try to

get at, which is where whales are seen, distribution, and that. Is there anything you think we

should know about whales or whaling in Kaktovik that the study needs to be aware of that we

may not be right now?

CB No, I don't know [faint].

MSG Okay. I think that's good enough for this recording, anyway.

(End of interview)
B-54 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

Joe Kaleak

JK What -- really want me to talk anyway? What's the --

MSG Well, if you can tell us anything specific about where whales are or -- you know, everybody said

that they really couldn't tell if whales were feeding when you were out there.

JK Well, we don't really pay attention for -- on the, ah, feedings for whales, so when we're -- when

we're out whaling, we just go, ah, look for some whales, you know. So we don't really pay

attention whether -- where the feeding areas are.

MSG Uhm-hm (affirmative).

JK But I know they've got feeding area at the east side of us, right -- right by -- right around the --

between Demarcation and Icy Reef, right between there -- between there.

MSG Uhm-hm (affirmative).

JK And I just find out not too long ago, there's another feeding area on the west side of us. So, ah --

gee -- yeah, oh, did you -- did anybody mention about this map here? [indicating the NSB map of

Kaktovik whale strike locations]

MSG Yeah, the map.

Several talking at once, not understandable

JK Yeah, okay. So this is the -- no, that's the -- the other one we got, it was just about everything [an

updated version of the map which JK has received]. This is -- we got to catch up on this map

here, so we never --

UNIDENTIFIED Did -- do you know how many whales now we're behind to -- we got to put it on that

map.

JK So -- yeah. See --

MSG This one is -- this map is just around the Barter--

JK Right.

MSG -- island area.

JK Uhm-hm (affirmative). Uhm-hm (affirmative). Okay. Now, where is Barter Island -- oh, way

back over here, okay. Okay. See, let's see, what’s this here. This is Barter here. Okay.

MSG This is Arey Island here.

JK Right. Right, Arey Island right here, see. And, ah, they probably -- they probably have some

feeding -- feeding areas somewhere around this area too, sometimes. But they come up from --

from Demarcation Bay some --

? We have a bigger map out here

MSG This one has Demarcation Bay, Barter Island ...

JK [Makes affirmative sounds]. That’s, that’s where, that’s where probably feeding areas start off

from here, all the way to Icy Reef some place. Where’s that Icy Reef?

MSG Icy Reef...
Annex B: Joe Kaleak, 19 Jan. 1998 B-55

JK Icy Reef. Someplace around here, so --

SM Right here, Icy Reef.

JK Yeah, right. It's right -- right between there, there's some -- there's, its a feeding, feeding, ah,

area, right -- right around those -- right around that area.

MSG Demarcation _______________.

JK Right. Right. Icy Reef and Demarcation. Right, between there. So we don't really go check all

those feeding areas when we're going out whaling in the fall time. When we take out from Barter

Island, we go out about -- we go north, straight down about 10 miles or more --

MSG Uhm-hm (affirmative).

JK -- sometimes. When it's -- when it's really calm weather -- calm and clear and no ice, and we

always thought going out north about 10 to 12 miles out, of course, and start traveling slowly,

straight east to try to meet whales, you know. So sometimes when we are trying to meet whales

here, if we didn't see any whales for about three or four days straight, and next -- next day, next

three or four days after, when we start going out west from Barter, from Barter to the Arey Island.

So that's the only place we go for in fall whaling time. Because when you never see any whales

in,-- around this area, right around this area, anyway, for three or four days when we don't see no

whales, if it's clear, calm, no ice, and next -- next day we start heading toward the -- toward west,

going down about same -- about -- it's about same thing, eight, ten miles out west. And

sometimes we see some whales right close to the Arey Island. I think they always trying to feed

themselves right close to the -- right close to the Arey Island too.

MSG You mean Arey Island here?

JK Right, right. Right.

MSG You never go past Camden Bay, though?

JK No. We don't -- no, we don't -- we don't pass the Camden Bay. Sometimes when we have a -- a

really bad ice condition in fall time.

MSG Uhm-hm (affirmative).

JK Sometime we go down -- down straight to Camden Bay, maybe, about 10, 12 miles out

_______________.

MSG So if there's bad ice, you won't go down here?

JK Right. Sometimes when there's bad ice around here, but we may have open lead, down side of

the ice, if you can't go through going to the other open lead, you try to go west, it used to be open,

open by -- by -- goes to Camden Bay. That -- we'd go there how many -- how many times, more

than once. What, at least good, clear -- at least good, clear or calm weather, no ice, we just keep

going from here on out this way and going straight down. Sometimes we just go straight down,

about four or five miles out, we spot some whales. And we don't watch the whales, we go to at

the Griffin Point -- there's Griffin Point here, that's a fishing camp. And we go -- and we go

down. And we always find some whales around -- around this area too. So that's the only place

we're going out -- going out for hunting in fall time. It only is a problem when there's bad ice

conditions. When this is bad, we can't go out to other lead. This Camden Bay always have open,

you know.
B-56 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

SM To get to the lead?

JK Right, to -- to get to the lead. This one always too -- too tight, but this one always kind of open,

you know, loose. And we go out. And after we pass that -- and after we pass that ice, when we

go out to the open lead, we start heading toward the east again. And sometimes we spot a whale

right down side of the Griffin Point, down the ice -- down side of the ice. We did that a lot of

times. So --

MSG When you have to go out that way, do you have to go out further then?

JK Right, further -- further out, yeah. Further out. When we -- when we have a -- a solid ice on -- on

here, right close to the shore, then whales always go down side of the ice, see, north side of this

open lead.

MSG Uhm-hm (affirmative). And the easiest way for you to get out is --

JK Right.

MSG -- from Camden Bay then?

JK Right. Right. Uhm-hm (affirmative).

MSG Is it the ice that controls how far the whales are out _______________?

JK Well, it's pretty -- it's -- it's pretty hard, it's really hard to -- when is, when is too much ice, it's

really hard to say how far the whales -- on the lead. Sometimes we go down about 15, 20 miles

out, straight out, and there's another lead, and this is like -- ice. But we don't really -- they check

all those are feeding it. We -- we never go that -- we never go that far to the Demarcation

anyway, see.

MSG Right.

JK That's too far, too far out for whales.

MSG At least not for whaling. People tell us that sometimes --

JK Right.

MSG -- they travel to Canada for trips, you know, _______________.

JK Right. I go there -- I -- I -- I -- I -- I make a trip every summer. And there's Herschel here, right?

Okay.

MSG Yeah.

JK When I -- when I travel, I stay -- start out July, middle part of July. When I -- heading to Canada,

I always meet -- meet some whales right at the -- what's that come about -- far away. That's

Herschel here. This is -- what's this, Demarcation area?

MSG It's Demarcation, yeah.

JK Okay. Someplace -- someplace -- some -- some -- someplace right here, always meets -- meets

whales, going -- going west, and this side of Herschel. Right -- right around there, right -- this is

really deep, ah, ocean here, on the Canadian sides.

MSG Really, right there, right --

JK Right -- yeah, past --
Annex B: Joe Kaleak, 19 Jan. 1998 B-57

MSG -- close to shore?

JK No, past -- past -- past this one. There's a Kay Point -- there's a -- it -- got another map?

MSG No.

JK That's how far you go, okay.

MSG No, that's as far as it --

JK Yeah, there's another Kay Point way back this way a little bit, got a south point. That's where all

the whales always -- that's where they are for feeding -- feeding area between Canadian waters. I

go there every summer for 17 years now. So I always meet whales right around past Komakuk

(ph) and the either side of Komakuk, west side, right close to shore.

MSG Uhm-hm (affirmative). You meet them starting here --

JK Right.

MSG -- and then they're feeding right down there?

JK Right, uh-huh (affirmative). Right, uh-huh (affirmative). I -- I go there every summer myself,

take my family over -- family relations over there, uncles and cousins, you know -- family.

MSG Are those small whales or big whales or --

JK Yeah, small -- yeah, mostly all small -- small whales. Them -- yeah, them small whales, we

always let the first -- first whale past, the first one we let them pass, so -- we used to hunt them

first when we -- when we went out early, in August middle part sometime we go out, but it's too

early to go out in August, it’s too warm. And -- and -- and -- and we're out about 15, 20 miles out

from Barter, and we struck a whale, and we can't tow it -- we can't tow it back when it's warm, it'd

take us about 12 hours sometimes.

MSG Oh.

JK So kind of spoiled the meat, too warm. Yeah, but in fall, in early, first of September, it's nice and

cool, and when we get the whale, we save all the meat. That's where we -- we used to get out

early before. So we hold the hunting to after Labor Day or September, it's cool.

MSG When do you come back from Canada _______________?

JK About the last part of August.

MSG So in time for whaling?

JK Right, just before whaling, about two weeks' time before whaling.

MSG And on your way back, do you see whales _______________?

JK Yeah, on the -- on the way back, I always see some whales the east side of Herschel. More than

once, more than one whale; small ones too.

MSG Uhm-hm (affirmative).

JK Small whales. And when you -- when you go out through here, through this channel here,

sometimes we see some whales around -- around -- around this area too. Right around this area,

you have small whales, right around there, when you go out to this channel.

MSG But you still don't see any whales over here, or do you?
B-58 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

JK Well -- no, well, it's -- they're traveling pretty slow, you know, they're -- when somebody told us

there's some whales at POW-1, Canadian side. Take about week and a half or a week to reach

Barter Island, just because they probably always stop on the feeding area for about a week or so,

you know.

MSG Uhm-hm (affirmative).

JK So that's how that's -- I've been start -- I've been -- started whaling here in 1972, myself. I settled

down here. So I've been whaling since. And so it's really important, so that's why we sure like to

go and try to get out those, all feeding areas, so -- so the oil companies don't have to disturb the

whales out their feeding area, see.

MSG Yeah, uhm-hm (affirmative). Yeah.

JK So that's real important, so we don't want to damage anything, from the oil companies, where

their feeding areas are. So that's --

MSG The whales you run into when you go down there in July, do you think they're just sort of staying

in this area, or are they --

JK Yeah, some -- yeah, sometimes they're -- sometimes they're staying right around this pass, on --

on this side, steady or over and forth in about more than two weeks sometimes, just go back and

forth.

MSG So east of Herschel Bay they --

JK Right. East of --

MSG -- stay then?

JK -- Herschel, right.

MSG And then the --

JK Over two weeks, yeah.

MSG Then the ones that you run into here, are they --

JK Yeah.

MSG -- traveling, or what?

JK Yeah, yeah. They always traveling -- when I meet some whales here, they're always traveling

west, yeah, even on the POW-D leavings [?] right here.

MSG So as early as July it would be --

JK Right.

MSG -- they're coming this way.

JK Right. Right, right, coming that way already in early July.

MSG So there are some whales going by Barter that early?

JK Yeah. Last summer -- last summer they’re -- spot a whale the middle part of July right this side

of Camden Bay. Early July, middle part.

MSG That's pretty early.
Annex B: Joe Kaleak, 19 Jan. 1998 B-59

JK Yeah, it's pretty early, yeah. Yeah, them small ones, they were probably traveling early, you

know, so it's really hard -- it's really hard, how many whales traveling. They always trying to --

they -- one time they told us to count the whales, how many we seen each day.

MSG Uhm-hm (affirmative).

JK But we -- when we spot a whale, we -- we -- we never thought to put it down how many [?]

whales we saw when we were out dazing [?], you know. Lot of whales. Yeah. So that's really

important for the subsistence for all the hunters anyway, all the way from St. Lawrence [Island]

out to here.

MSG Right. Because it's all --

JK We -- yeah, right.

MSG -- the same whales.

JK We can't -- we can't live without -- without muktuk, ougruk, seal oil, you know, we have to have it.

MSG When, when would you say the big whales come by?

JK Well, the big -- the big whales come by on the last -- last part, you know, them with the baby -- all

of them with a baby whale, they'll come last. So they'll travel -- they'll -- sometimes they'll travel

till middle of October. One time -- one time we went out whaling. The weather was -- and the ice

was bad condition, we went out whaling till October, but it was [unclear ?]. We got to go -- we got

to track our boat on towards the Arey Island on this side. This side was already tight.

MSG Uhm-hm (affirmative).

JK We stopped, ice too tight, and we went over -- that's where that -- that's where that -- they had a

little open -- open area, you know, loose, so we did that about three or four times.

MSG Over by Arey Island?

JK Yeah.

MSG You had to drag your boat _______________?

JK Yeah, we got -- yeah, we got to -- we got to -- got -- put -- put it on the trailer and drag it all the

way to Arey Island.

MSG Oh.

JK Put it on the trailer, yeah. Yeah. So it's really tough sometimes, really hard going out, really --

ice patches, bad. But right now, we're lucky. For -- for about three or four years now, we’ve

been one hundred percent landing, lots of the weather's good, hardly any ice, calm weather. We

don't -- we don't go out when it’s getting about ten, fifteen knots wind. So we don't like to -- we

don't like to lose our quota. So we wait for the good, calm weather, clear weather. We don't like

-- don't like to loss, but we have to catch for our community. Sometimes it's tough, sometimes

[unclear ?].

MSG And last year, I guess -- people tell us that the trips were short, but they had to wait for a week for

the right weather?

JK Yeah, right. Yeah -- yeah, right. We got to wait for the good weather, see. If it's -- if it's -- if it's

windy, we don't go. But if it’s good weather, we go out. Sometimes the good weather for a
B-60 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

week, little over a week, we land all three quota, sometimes, less than a week or a little over a

week, [PHONE RINGS] eight days _______________. [last sentence too faint to understand]

MSG Do you go out first of September?

JK Yeah, right after Labor Day we go out.

SM This year Labor Day's real late, not till September 7th.

JK Well --

SM Do you still wait for Labor Day?

JK Yeah, we still -- yeah, we still could wait for Labor Day. I like -- the people like to go out their

own holidays, go out for -- for different subsistence hunt for caribou, on holiday for their own --

for their own food, for caribous here, so they always wait until after Labor Day. So on their own

holidays, they like to go out and do some caribou hunting, take their family out for a long

weekend. So we don't go out till after Labor Day. I don't know about this year, but probably

going to do the same thing. PAUSE So I'll be -- appreciate if you guys -- you guys going to do

some survey for the -- for these feeding areas. They get them all -- they get them all where

they're really at and let us know, appreciate. So that's why I want to get some report from them --

soon, I should get a re, [?].

SM Yes, [inaudible for one or two sentences ?], that's why we’ve got to get the boat out there. [Faint

statement].

JK So what we say after we get our two landed, they could go out any time they want to go, you

know, for -- to do some more survey on the whale, ah, after we get two landing or between. I

hope it's going to be a good weather like --

SM Yeah.

JK I hope it's going to be a good whaling season again this year, like last year. If it's -- if it's -- if

it's -- if it's good, they're going to have a lot of time to do some surveying, soon as we get our

quota feel free.

MSG Well, to get -- can never tell.

JK Yeah, it's never -- can't never tell, it's hard to tell. Might be -- might be bad weather, might be too

much ice. We might even not catch any whales, you mean you can try. Try to the, ah, weather,

ice conditions, [unclear word or two ?], can't tell. So it's hard.

MSG You said, you know, the areas down by Demarcation Point especially were feeding areas. Do

whales, when they go through here, do they also?

JK I -- I don't know. That's the only place -- that's the only place, right by the Demarcation and this

side of Herschel. And right over by the Arey Island toward the Camden Bay, yeah.

MSG And over here?

JK Yeah. See, they're -- they do some surveying there, don't bother us. It's going to be about 30, 40

miles west of us, but Nuiqsut still going to --

MSG Yeah.
Annex B: Joe Kaleak, 19 Jan. 1998 B-61

JK -- still fight. So that's one that's over [unclear ?]. So you gotta talk to Nuiqsut whalers. They

want -- they want to go ahead and do some surveying even in August, early, but -- it's okay with

us, but listen, you're going to -- so...

MSG Do you notice the whales, are they just traveling when they go by here, or do some of them stay

in this area?

JK Well, they always -- they always stay around right by -- where was that sheet.

MSG Barter, here.

JK Yeah, Barter, sometimes. They always -- yeah, they go -- right. They used to be -- just stick

around here too, someplace around this area, go back and forth too, in-out, in-out, all this area,

too. See, that's where -- that's where -- always mostly get some whales on almost -- just one --

one area, see. Some --

MSG Yeah.

JK -- some -- some -- some -- somewhere around like here, yeah. They always go fast [?] -- no, they

don't -- they -- they always stay there for a few days too.

MSG Do you have any guesses why whales like to stay there?

JK I don't know why, but might be -- might be -- it might be more feeding -- feeding areas may

belong there, too. But we don't know, we don't -- yeah, we don't know. They always stick

around right there too, for -- for a few days, go back and forth, in and out, you know; sometimes

go back and forth. Might be some -- might be some more feed -- feeding area around there, too.

But it's hard -- I can't -- it's hard to tell.

MSG When, when you got out and look for whales, are there -- you know, when you went out when,

like when they do on Wednesday [?], are there usually so many whales that all you need to do is

look for the blows?

JK Yeah, sometimes we got -- sometimes we got to look for blows, yeah. It's really hard. Some --

sometimes whales probably stay in one area someplace roughly -- right between Demarcation and

Icy Reef. Maybe always stay there for, for a awhile -- maybe two, two weeks, maybe more. I

don't know why. Maybe they have a convention like us, maybe too, see. Yeah.

MSG Have the whale convention.

JK Yeah, yeah. That's how they do in Barrow, so every springtime, they got to wait for other bucks

[?] coming in about -- after two weeks sometimes. Same thing right here. Same -- same thing.

Then we got to wait two weeks or less, to see any more whales. So sometimes you really --

sometimes when they're traveling, we always spots right around this area. So that's why we don't

like to pass this too much, you know, if we don't see about three or four days, we've passed it, and

we go all the way to down side of -- what they call that -- Griffin Point.

MSG Oh, yeah.

JK Yeah

JK So since I'm start whaling myself, '72, that's where we -- just about spot whales, where -- where

the -- all the whales are. It's really hard for -- to spot a whale sometimes, [Indistinct ?].

MSG Do you know the --
B-62 Bowhead Whale Feeding in the E Alaskan Beaufort Sea

JK They're -- they're not -- they're not that easy to find them, you know, you’ve got to,got to, got to

search and try to look. Sometimes you go out 5:00 -- 5:00 o'clock in the morning, soon as it gets

daylight, taking off, if it's good weather, don’t wait -- don’t wait for nobody, everybody always

with you anyway -- every,every day.

MSG But you don't use currents or anything else to help find whales?

JK No. No. Sometimes we go out for Barter Island, most of the crew go straight out.

MSG Uhm-hm (affirmative).

JK We don't find -- we don't spot any whales for about three or four days. Most the crew went west.

We would split sometimes, trying to spot some whales, where the whales are. Sometimes we

split in two groups, five on that side, five on that side; split about a quarter-mile apart, you know,

if it's good weather. If it's kind of little light, ah, foggy, stick together, not too far apart for -- for,

for each other, so we can see each other, too. It's really -- it's not really -- it's not easy to going

out for subsistence [fall ?].

MSG And even, even if you've seen whales before, while going up for caribou or something, you can't

depend that they'll be in the same places when you go out in September?

JK No, no, no. They -- they don't, no. They're moving, they've moving. They don't stay in one spot

unless they have to, for a while, you know. But when -- when we have a real pack [?] ice, all the

way from Demarcation, all the way to Barter. They always try to [?] sometimes. If there's an

open lead downside, they always stay back for a while until they get the open lead, right, [unclear

?}.

MSG And they say you can't predict that.

JK No, no. No. So far we’re lucky for our whaling season for three, four years now. [Unclear

statements in here -- low voice] We used to _______________ three, four years

_______________.

MSG Well, I think you've told us pretty much --

JK Yeah.

MSG -- what we wanted to know. I guess a lot of the questions we have are things that just are hard to

know, and that’s partly why we’re doing the study.

JK Yeah, that's the -- well, we appreciate it. We just a keep his promise to, ah, give us some report

we’ll appreciate it.

MSG Well, we'll make sure that _______________.

JK Yeah.

MSG We'll make sure he remembers what you told him.

JK Yeah.

MSG Now, can we share this information that we -- you've given to us?

JK Yeah, right.

MSG I guess what I have, what I have is a form that they like us to fill out for people we talk to, saying

that we asked -- to participate in the -- a study with us and agree to be tape recorded, let you know
Annex B: Joe Kaleak, 19 Jan. 1998 B-63

it's being funded by the Minerals Management Service, and that’s where we, for their report, but

that we're also going to supply you with information if you want it. And basically, it says you’re

willing to be tape recorded --

JK Right.

MSG -- that we can share this information with other people, and then I can write down that you want

copies of the tapes?

JK Yes. Well -- well, be -- be better, so...

SM That way you can make sure what you're saying?

JK Right. I'll appreciate it.

MSG Then I write this down and what I'll do is, when I get back to Anchorage then, I'll make a copy of

the tape and send it back to you with a copy of this.

JK Great. Okay.

MSG So that, you know, you go --

JK And -- and when they're out -- are you going to be one tape, even the other --

MSG No, just your tape. But --

JK Oh. Oh, oh, oh.

MSG -- I'll send other tapes back to the other people too.

JK Oh. Oh, okay. Okay. Good.

MSG And then, you know, all you have to do is sign this, that you have -- that we talked about this --

JK Okay.

MSG -- with you.

JK Okay.

MSG And I'll leave you another one of my cards _______________.

JK Yeah, just in case, yeah. Okay. That's it.

MSG Yeah.

JK [Unclear ?] going to have to [unclear ?] this afternoon. Okay.

MSG I sure do appreciate it.

JK Okay. Have a nice trip. Okay.

MSG Okay.

JK Yeah.

MSG And I'll probably come by and maybe just drink some coffee or something, but we don't have to

talk about anything.

JK Well, any time, any time, we'll have coffee, right. Okay.

(End of interview)