OCS Study

MMS 95-0051

ACOUSTIC EFFECTS OF OIL PRODUCTION ACTIVITIES ON BOWHEAD

AND WHITE WHALES VISIBLE DURING SPRING MIGRATION

NEAR PT. BARROW, ALASKA-1991 AND 1994 PHASES:

SOUND PROP AGA nON AND WHALE RESPONSES

TO PLAYBACKS OF ICEBREAKER NOISE

by

W.J. Richardson, C.R. Greene Jr., J.S. Hanna, ·W.R. Koski,

G.W. Miller, N.J. Patenaude and M.A. Smultea

assisted by

R. Blaylock, R. Elliott and B. Wursig

from

LGL Ltd., environmental research associates

22 Fisher St., POB 280, King City, Ont. L7B lA6, Canada

and

Greeneridge Sciences Inc.

4512 Via Huerto, Santa Barbara, CA 93110

for

U.S. Minerals Management Service, Procurement Operations

381 Elden SUMS 2500, Herndon, VA 22070-4817

LGL Report TA954

October 1995

Contract 14-12-0001-30412

This study was funded by the Alaska Outer Continental Shelf Region of the Minerals Management Service, U.S. Dept. of

the Interior, Anchorage, AK, under contract 14-12-0001-30412.

This report has been reviewed by the Minerals Management Service, U.S. Department of the Interior, and approved for

publication. The opinions, findings, conclusions, or recommendations expressed in the report are those of the authors and

do not necessarily reflect the views or policies of the Minerals Management Service. Mention of trade names or

commercial products does not constitute endorsement or recommendation for use.
'-.

ii
PROJECT ORGANIZATION

The 1991 and 1994 phases of this contract were conducted by LGL Ltd., environmental

research associates, assisted by subcontractor Greeneridge Sciences Inc. LGL organized the

project as a whole, and conducted the biological aspects of the work. M. Smultea, now of Foster

Wheeler Environmental Corp., and B. Wiirsig of the Marine Mammal Research Program, Texas

A & M University, worked with LGL on the biological components. Greeneridge was responsible

for the physical acoustics components. BBN Systems & Technologies Corp. assisted with physical acoustics modeling in 1989. The affiliations of the senior authors (in boldface) and co-authors

are as follows:

W. John Richardson, William R. Koski, Gary W. Miller, Nathalie J. Patenaude,

Robert E. Elliott

LGL Ltd., environmental research associates

22 Fisher St., POB 280, King City, Ont. L7B lA6, Canada

(905)-833-1244

Charles R. Greene, Jr., John S. Hanna, R. Blaylock

Greeneridge Sciences Inc.

4512 Via Huerto, Santa Barbara, CA 93110

(805)-967-7720

Mari A. Smultea

Foster Wheeler Environmental Corp.

10900 NE 8th Street, Bellevue, WA 98004-4405

(206)-688-3811

Bernd Wiirsig

Texas A & M University at Galveston, Marine Mammal Res. Prog.

4700 Ave. U, Bldg 303, Galveston, TX 77551-5923

(409)-740-4413

Another major contributor to the fieldwork in 1989-91 and 1994 was Kenneth Toovak Sr. of Barrow.

iii
iv
TABLE OF CONTENTS

PROJECT ORGANIZATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 111

TABLE OF CONTENTS v

EXECUTIVE SUMMARY xiii

Objectives xiii

General Objectives xiii

Specific 1991/94 Objectives xiii

Approach and Procedures xv

Sample Sizes xvi

Physical Acoustics xvi

Ambient Noise xvi

Transmission Loss Tests , xvii

Playback Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. xvii

Infrasounds ~ xviii

Bowhead Whales xix

Movements and General Behavior xix

Drilling Noise Playbacks ; xix

Icebreaker Noise Playbacks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. xx

Aircraft Disturbance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. xxii

White Whales . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. xxii

Drilling Noise Playbacks. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. xxii

Icebreaker Noise Playbacks xxiii

Aircraft Disturbance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . XXIV

ACKNOWLEDGEMENTS xxv

GLOSSARY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. xxvii

1. INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 1

1.1 Objectives and Rationale 3

General Objectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 3

Rationale for Various Study Components 3

Specific 1991 and 1994 Objectives. . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 5

1.2 Null and Alternate Hypotheses 7

1.3 Assumptions and Limitations 9

1.4 Study Area .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 14

Local Concerns 14

Specific Study Locations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 15

v
Table of Contents (continued) Page

2. METHODS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 19

2.1 Physical Acoustics Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 19

General Approach and Equipment 19

Sound Projectors and Signal Source . . . . . . . . . . . . . . . . . . . . . . .. 20

Generator 22

Sound Monitoring at Ice Camp 22

Sound Monitoring Aboard Aircraft 23

Ambient Noise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 24

Field Procedures 24

Analysis Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . .. 24

Transmission Loss 25

Field Procedures 25

Analysis Procedures , 28

Playback Experiments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 29

Infrasonic Components of Ambient Noise and Bowhead Calls. . . . . . . . . .. 29

Infrasonic Ambient Noise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 29

Infrasonic Components of Bowhead Calls .' . . . . . . .. 29

2.2 Whale Surveys and Observations 30

Aerial Reconnaissance and Surveys 30

General Approach 30

Survey Methods and Data Recording , 31

Aerial Photography of Bowheads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 32

Field Procedures 32

Analysis Procedures. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 33

Aerial Observations of Behavior 34

Observation Procedures 35

Behavioral Definitions and Criteria . . . . . . . . . . . . . . . . . . . . . . .. 36

Number of Observations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 37

Ice-based Observations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 37

2.3 Playback Experiments 39

General Playback Approach . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 39

Meaning of the Term "Control" 40

Acoustical Aspects of Playbacks 41

Playback Stimuli 41

Projector Operations 41

Acoustic Monitoring 42

Acoustic Analysis 42

Whale Movements and Behavior During Playbacks 43

Observation Procedures 43

Distances and Bearings of Whales from Ice Camp . . . . . . . . . . . . .. 44

Ice Conditions Near Playback Sites 46

Sound Levels Received by Whales During Playbacks. . . . . . . . . . . . . . . .. 46

vi
Table of Contents (continued)

3. ICE, WEATHER AND FIELD ACTIVITIES 51

3.1 Ice and Weather Conditions 51

Ice and Weather in 1989 ~. . . . .. 51

Ice and Weather in 1990 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 56

Ice and Weather in 1991 57

Ice and Weather in 1994 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 57

3.2 Summary of Field Activities. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 58

Fieldwork in 1989 and 1990 63

Fieldwork in 1991 63

Fieldwork in 1994 75

Overall Effort over Four Seasons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 78

4. PHYSICAL ACOUSTICS RESULTS 83

4.1 Ambient Noise 83

Results 83

Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 89

4.2 Infrasonic Ambient Noise. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 92

Results 93

Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 94

4.3 Transmission Loss . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 96

Summary of 1989-1994 Transmission Loss Data 96

Analysis of 1989-1994 Transmission Loss Data . . . . . . . . . . . . . . . . . . . .. 96

The Propagation Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 97

Results 98

Single-Frequency and Frequency-Averaged Data. . . . . . . . . . . . . .. 98

Scaled Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 99

Model Parameters 104

Comparison with BBN's Weston-Smith TL Model 106

Comparison of the Propagation Model and Playback Data 107

Sound Propagation on 13 May 1990 . . . . . . .. . . . . . . . . . . . . . . . . . . .. 109

Summary Discussion of Transmission Loss . . . . . . . . . . . . . . . . . . . . . .. 113

4.4 Fidelity of Playbacks to Original Icebreaker Sound. . . . . . . . . . . . . . . . . . .. 115

4.5 Do Bowhead Calls Contain Infrasonic Components? . . . . . . . . . . . . . . . . . .. 129

4.6 Generator Noise ;..................... 129

Results '. . . . . . . . . . . . . . . . . . . . . . . . .. 129

Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 133

5. BOWHEAD WHALE RESULTS: MOVEMENTS, BEHAVIOR

AND BASIC BIOLOGY. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 138

5.1 Bowhead Distribution & Movements . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 138

Bowheads in General 138

Spring 1989 138

Spring 1990 142

Spring 1991 142

Spring 1994 151

All Years 158

vii
Table of Contents (continued) Page

Mothers and Calves 158

Spring 1989 158

Spring 1990 158

Spring 1991 162

Spring 1994 162

5.2 Bowhead Photogrammetry & Photoidentification 162

Bowhead Lengths and Timing of Migration. . . . . . . . . . . . . . . . . . . . . .. 162

Bowhead Lengths, 1989 162

Bowhead Lengths, 1991 164

Bowhead Lengths, 1994 165

Bowhead Lengths, All Years. . . . . . . . . . . . . . . . . . . . . . . . . . .. 174

Photographic Resightings of Identifiable Bowheads . . . . . . . . . . . . . . . .. 176

Sample Sizes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 176

Within-Season Resightings 180

Within-Session Resightings : . . . . . .. 180

Between-Session Within-Day Resightings 184

Between-Day Resightings . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 189

All Between-Session Resightings . . . . . . . . . . . . . . . . . . . . . . . .. 191

Spring Migration of Mother-Calf Pairs vs. Other Bowheads . . . . .. 193

Between- Year Resightings , 193

5.3 Behavior of Undisturbed Bowheads , 197

Observation Effort and Circumstances 197

General Activities 199

Traveling 199

Socializing, . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 201

Feeding and Surfacing with Mud . . . . . . . . . . . . . . . . . . . . . . . .. 204

Resting ' , 205

Surfacing, Respiration and Dive Cycles 205

Traveling Whales . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 207

Traveling+Socializing 207

Socializing 210

Resting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 210

Other Behaviors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 210

Swimming Speed. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 210

Fluke-out Dives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 213

Pre-dive Flex. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 213

Turns 213

Social Behavior . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 214

Aerial Behavior . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . .. 214

Additional Behavioral Variables 214

Behavior of Subadults vs. Adults During Travel 215

Variables Correlated with Surfacing, Respiration and Dive Cycles of

Migrating Bowheads 218

Multiple Regression Methodology . . . . . . . . . . . . . . . . . . . . . . .. 218

Factors Related to Durations of Surfacings . . . . . . . . . . . . . . . . .. 223

viii
Table of Contents (continued) Page

Factors Related to Number of Blows per Surfacing . . . . . . . . . . .. 223

Factors Related to Median Blow Intervals :....... 225

Factors Related to Durations of Dives 225

Relationship Patterns 226

Sexual Activity 227

5.4 Mother and Calf Behavior 228

Migration and Lingering by Mothers and Calves 228

Headings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 228

Behavioral Observations in 1989 . . . . . . . . . . . . . . . . . . . . . . . .. 231

Behavioral Observations in 1990 . . . . . . . . . . . . . . . . . . . . . . . .. 233

Behavioral Observations in 1991 and 1994 . . . . . . . . . . . . . . . . .. 234

Photoidentification Data on Mother-Calf Movements . . . . . . . . . .. 234

Migration and Lingering-Summary 234

"Riding" Behavior 235

Surfacing, Respiration and Diving Behavior 237

Traveling Mothers and Calves. . . . . . . . . . . . . . . . . . . . . . . . . .. 239

Nursing vs. Not Nursing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 239

Riding vs. Not Riding 239

Other Behaviors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 239

Swimming Speeds 239

Fluke-out Dives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 246

Pre-dive Flexes 246

Turns 246

Social Activity 246

Aerial Behaviors 246

Additional Behavioral Variables 246

6. BOWHEAD DISTURBANCE 247

6.1 Summary of Icebreaker Playbacks. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 247

Number of Observations During Playbacks , . . . . . . . . . . . . . .. 247

17 May 1991 251

7 May 1994 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 256

9 May 1994 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 257

14 May 1994 259

16lVlay 1994 259

17 May 1994 260

20 May 1994 261

6.2 Distribution and Movements During Icebreaker Playbacks 261

Closest Estimated Points of Approach 261

Sound Exposure Levels , 263

Apparent Avoidance Reactions 271

Avoidance Within 400 m 271

Avoidance at 400-1500 m . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 275

Avoidance at >1500 m . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 275

IX
Table of Contents (continued) Page

Avoidance During Playback and Control Conditions 276

Avoidance vs. Icebreaker:Ambient Ratio 277

Effects on Feeding Whales 277

6.3 Behavior During Icebreaker Playbacks . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 279

Data Considered . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 279

Surfacing, Respiration and Diving Behavior 279

Behavior vs. Distance from Projectors .. . . . . . . . . . . . . . . . . . .. 279

Behavior vs. Received Level (RL) . . . . . . . . . . . . . . . . . . . . . . .. 283

Behavior VS. Icebreaker:Ambient Ratio (S:N) . . . . . . . . . . . . . . .. 283

Apparent Response Thresholds 286

Statistical Power and Apparent Response Thresholds . . . . . . . . . .. 290

Turns 292

Other Behavioral Variables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 295

All Behavioral Variables Combined .. . . . . . . . . . . . . . . . . . . . . . . . . .. 299

Behavior Factors vs. Distance . . . . . . . . . . . . . . . . . . . . . . . . . .. 299

Behavior Factors vs. RL and S:N . . . . . . . . . . . . . . . . . . . . . . . .. 304

Apparent Response Thresholds 304

6.4 Icebreaker Reaction Thresholds and Radius of Influence . . . . . . . . . . . . . . .. 305

Icebreaker Reaction Threshold Criteria . . . . . . . . . . . . . . . . . . . . . . . . .. 305

Icebreaker-to-Ambient Ratios 305

Received Levels of Icebreaker Sound. . . . . . . . . . . . . . . . . . . . .. 305

Tolerated Levels of Icebreaker Sound 306

Potential Radius of Influence of Actual Icebreaker 307

Variability and Uncertainty in Predicted Radius of Influence 310

Playbacks 312

Actual Icebreaker . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 312·

6.5 Icebreaker vs. Drilling Noise Results. . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 316

6.6 Evaluation of Playback Hypotheses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 319

Distribution & Movement Hypothesis/Icebreaker Playbacks 320

Behavior Hypothesis/Icebreaker Playbacks 321

Implications for Actual Icebreaking 321

6.7 Bowhead Reactions to Aircraft . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 323

Bowhead Reactions to Bell 212 Helicopter .. . . . . . . . . . . . . . . . . . . . .. 323

Methods 326

Results 326

Evaluation of Helicopter Overflight Hypotheses 331

Bowhead Reactions to Twin Otter 332

Methods 332

Direct Observations of Reactions . . . . . . . . . . . . . . . . . . . . . . . .. 332

Behavior vs. Time After Start of Circling. . . . . . . . . . . . . . . . . .. 333

Evaluation of Bowhead Reactions to Twin Otter . . . . . . . . . . . . .. 337

x
Table of Contents (continued) Page

7. WHITE WHALE RESULTS 338

7.1 Distribution & Movements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 338

Spring 1989 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 338

Spring 1990 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 341

Spring 1991 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 341

Spring 1994 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 341

All Years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 345

7.2 Icebreaker Playbacks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 345

17 May 1991 347

Ice-based Observations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 347

Noise Exposure 356

11 May 1991 360

Ice-based Observations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 360

Noise Exposure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 361

3 May 1994 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 361

Ice-based Observations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 364

Aerial Observations . . . . . .. 364

Noise Exposure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 364

Sighting Rates During Playback and Control Periods .. . . . . . . . . . . . . .. 368

Acoustic Response Thresholds. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 370

Potential Radius of Influence of Actual Icebreaker 371

7.3 Evaluation of Playback Hypotheses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 374

Continuous Karluk Drilling Sound . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 375

Variable Icebreaker Sound 375

7.4 White Whale Reactions to Aircraft 376

Reactions to Bell 212 Helicopter . . . . . . . . .. 377

Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 377

Evaluation of Helicopter Overflight Hypotheses 381

White Whale Reactions to Twin Otter 382

LITERATURE CITED , 386

APPENDICES 393

APPENDIX A: Field Activities 395

APPENDIX B: Transmission Loss Experiment Data, 1991/94 . . . . . . . . . . . . . . . . .. 408

APPENDIX C: Sonobuoy Impact Sound 426

APPENDIX D: Bowhead Distribution Maps, 1989-90 . . . . . . . . . . . . . . . . . . . . . . .. 431

APPENDIX E: Bowhead Resightings By NMML, 1989 . . . . . . . . . . . . . . . . . . . . . .. 440

xi
Table of Contents (continued) Page

APPENDIX F: Individual Playback Experiments, 1991/94 441

Playback in 1991 441

17 May 1991 Playback 441

Playbacks in 1994 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 449

7 May 1994 Playback . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 449

9 May 1994 Playback . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 467

14 May 1994 Playback 486

16 May 1994 Playback 493

17 May 1994 Playback 501

20 May 1994 Playback 513

APPENDIX G: White Whale Distribution Maps, 1989-94 . . . . . . . . . . . . . . . . . . . .. 521

APPENDIX H: SSDC Drilling Sounds in Winter 538

xu
EXECUTIVE SUMMARY

Previous studies of the reactions of bowhead whales to noise from oil industry operations

have been conducted during late summer or early autumn, in open water or at most light ice

conditions. Concern has arisen about potential effects of man-made noise in the leads through

which bowheads migrate in spring.

Objectives

General Objectives

In response to this concern, the Minerals Management Service funded the present experimental study of the effects of noise from oil production activities on bowhead and (secondarily)

white whales during their spring migrations around Alaska. The overall objectives were

1. To quantify sound transmission loss and ambient noise within nearshore leads off

northern Alaska in spring, emphasizing propagation of underwater sounds produced by

production platforms and icebreakers.

2. To quantify the short term behavioral responses of spring-migrating bowhead whales and,

if possible, white whales to sounds from production platforms and icebreakers.

3. To assist and coordinate with other studies and local resource users to maximize

collection of needed data and avoid conflict with subsistence whaling activities.

4. To analyze the data in order to test hypotheses concerning the effects of oil industry

noises on the movement patterns and behavior of bowhead and white whales.

Specific 1991/94 Objectives

The present report deals primarily with data collected in the springs of 1991 and 1994, the

third and fourth years of the project. However, many parts of the report also take account of data

collected in 1989 and 1990. In 1989-90, data were obtained on ambient noise, acoustic

transmission loss, activities of undisturbed bowhead and white whales during spring migration,

reactions of both species to playbacks of recorded continuous low-frequency sound from a drilling

operation on the Karluk grounded ice pad, and reactions of both species to aircraft overflights.

The 1989-90 results were reported in two previous LGL reports to MMS, OCS Studies MMS 90-

0017 and 91-0037 (Richardson et al. 1990a, 1991a).

The specific objectives of the 1991 and 1994 phases of this project were similar to those in

1989-90, with the main exception being that the top priority work involved playbacks of variable

icebreaker sounds to bowheads. When possible, reactions of white whales as well as bowheads

were to be determined. Because of poor weather and ice conditions in 1991, and the low number

of whales observable during playbacks in that year, few data on reactions to playbacks of

icebreaker sounds were acquired in 1991. Hence, the highest priority for subsequent fieldwork was

to continue studying reactions of bowheads to icebreaker noise playbacks. Fieldwork was not

Xlll
Executive Summary

possible in 1992 or 1993 because of concern about potential interference with the ice-based bowhead census at Barrow in 1992 and 1993. Fieldwork resumed in 1994.

Because of the possible effects of low-frequency industrial sound components on bowheads,

and the inability of a practical sound projector to reproduce those components adequately, indirect

methods of addressing the importance of low-frequency components were again identified as one

of the specific objectives in 1991/94 (see item 5, below).

The specific objectives for 1991/94 were as follows:

1

I

1. To record sounds from the SSDC caisson while it was drilling during winter conditions,

including infrasonic components, and to analyze those sounds to determine their levels,

spectral characteristics, and attenuation properties.

2. To measure ambient noise levels and characteristics in leads and cracks along the spring

migration corridor of bowhead and white whales in the western Beaufort Sea, including

infrasonic components.

3. To measure and model transmission loss of underwater sound along that part of the spring

migration corridor, based on playbacks of (a) test tones at selected frequencies, and

(b) continuous industrial sounds. Infrasonic components cannot be projected.

4. To measure the short-term behavioral responses of bowheads and (as possible) white

whales visible in open water areas along their spring migration corridor in the western

Beaufort Sea to underwater playbacks of variable icebreaker sounds. Infrasonic components cannot be projected.

5. To collect some of the data needed to assess the importance of the infrasonic components

of industrial noise. Specifically, (a) to measure ambient noise at infrasonic frequencies,

and (b) to determine whether bowhead calls contain infrasonic components (supplementing limited data from 1990). Also, based on the winter recordings of SSDC sounds

(specific objective 1), we were (c) to determine the frequencies, levels and attenuation

of the infrasonic components of drilling caisson sound.

6. To measure, on an opportunistic basis, the short-term behavioral responses of bowheads

and (as possible) white whales visible in open water areas along their spring migration

corridor in the western Beaufort Sea to actual helicopter overflights (supplementing

limited data from 1989-90).

7. To document, as opportunities allow, other aspects of the movements, behavior, basic

biology, disturbance responses and acoustic environment of bowhead and white whales

along their spring migration corridor in the western Beaufort Sea.

8. To assist and coordinate with other studies and local resource users to maximize

collection of needed data and to avoid interference with subsistence whaling and other

studies.

9. To analyze the data to test hypotheses concerning the effects of the icebreaker sounds and

helicopter overflights mentioned in (4) and (6) on (a) the movement patterns and (b) the

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Executive Summary

behavior of bowheads and white whales visible along their spring migration corridor in

the western Beaufort Sea.

Significant progress has been made toward meeting all nine objectives during the four spring

seasons. Several objectives-2, 3, 5a, 7 and 8-can be considered "achieved". Some data on the

responsiveness of spring-migrating bowheads and white whales to playbacks of steady drilling

noise and variable icebreaker noise were obtained, along with some data on responsiveness to

actual aircraft overflights (objectives 4, 6 and 9). However, better quantification of whale

responses to these activities than achieved in this study would be desirable. Similarly, objectives

1 and 5b,c were partially met, but additional data would be helpfu1.

Approach and Procedures

No oil production facilities have yet been constructed in or near the spring lead systems off

northern Alaska, so a study of the effects of such facilities on whales must be done by simulation

methods. The underwater sound playback method was used. Two types of playbacks were conducted: ~ In 1989-90, playbacks of steady low-frequency noise recorded near the Karluk drilling

operation on a grounded ice pad. ~ In 1991/94, playbacks of variable and broader-bandwidth

sound from the icebreaking supply ship Robert Lemeur recorded while it was managing ice.

The study had to be conducted such that it did not interfere, and was not perceived to

interfere, with either subsistence whaling or the spring bowhead census. Barrow is the

northeasternmost community with spring whaling, and the bowhead census is also done just north

of Barrow. After consultation with the Barrow Whaling Captains' Association, Alaska Eskimo

Whaling Commission, and North Slope Borough Dept of Wildlife Management, it was agreed that

the most suitable location for playbacks in 1989 was about 60+ km (32+ n.mi.) NE or ENE of Pt.

Barrow. In 1990-91 and 1994, it was agreed that the work could be done as close as 15 n.mi.

(28 km) beyond the northeastern most whaling camp.

The field crew consisted of two teams. (1) A helicopter-supported crew deployed one or two

underwater sound projectors from ice pans or, on some dates in 1991/94, the landfast ice edge.

They projected recorded drilling platform sound or icebreaker sound into leads. When whales

came within visible range of the projector site, the ice-based crew documented whale movements

and behavior, using a surveyor's theodolite to measure the successive bearings and distances of

whales from the projector(s). In addition, this crew measured the rate of attenuation of projected

underwater sounds with increasing distance from the projector(s). (2) A second crew, in a Twin

Otter aircraft, located whales and suitable projector sites, documented behavior of whales as they

swam toward and past the projector(s), and (in 1989, 1991 and 1994) obtained known-scale vertical photos of bowheads to identify and measure them. The aircraft crew also used naval

sonobuoys to monitor underwater sounds near whales.

Whale observations obtained by the two crews were complementary. Ice-based observers

obtained detailed data on the paths and speeds of some whales that passed within 1-11/2km (0.54-

0.8 n.mi.) of the projector, and observed whales even when there were low clouds. Aerial

observers could observe whales at any distance from the projector site, could follow them for

longer distances, and had a much better vantagepoint for viewing details of behavior. However,

aerial observations were only useful when the cloud ceiling was at least 460 m (1500 ft) above sea

xv
Executive Summary

level, as bowheads sometimes react to an observation aircraft circling at lower altitudes. Low

cloud frequently interfered with behavioral observations in 1989 and especially 1991, but did so

less commonly in 1990 or 1994. In 1994, strong winds often hindered behavioral observations

from both the ice and the aircraft.

Sample Sizes

The ice-based crew worked from the ice on 33 days from 27 April to 30 May in 1989-90,

and on 26 days from 28 April to 26 May in 1991/94. They conducted successful transmission loss

tests on eight days.in 1989-90 and five days in 1991/94. They projected industrial sounds into the

water for several hours on each of 19 days in 1989-90 (drilling noise) and 13 days in 1991/94

(icebreaker noise).

The aircraft-based crew conducted reconnaissance surveys on 46 dates from 29 April to 30

Mayin 1989-90, and on 45 dates from 27 April to 26 May in 1991/94. The aerial crew conducted

46 behavior observation sessions on 22 days in 1989-90, and 30 sessions on 15 days in 1991/94.

Behavioral observations totaled 72.4 h in 1989-90,4.1 h in 1991 (limited by prevailing low cloud),

and 36.2 h in 1991. Of these 112.7 h of systematic aerial observations over four spring seasons,

72.1 h involved presumably undisturbed bowheads (control data) and 40.6 h involved potentially

disturbed bowheads.

Bowheads were observed in waters ensonified by the projected industrial sounds on 10 days

with Karluk drilling noise in 1989-90 and on 7 days with icebreaker noise in 1991/94. Total

numbers of bowheads observed near the operating projector(s) during playbacks were -221

in 1989·90 and 93 in 1991/94. Bowheads were also observed near the ice camp under quiet "control" conditions at other times during most playback dates, and on a few additional days as well,

in 1989-90 (-204 bowheads) and 1991/94 (-229 bowheads). White whales were seen near the

operating projector(s) on five days in 1989-90 (-219 exposed to playbacks of Karluk drilling

sounds) and on three days in 1991/94 (-46 exposed to playbacks of Robert Lemeur icebreaker

sounds). In 1989-90, observation time near the ice camps totalled 74 h during drilling noise playbacks, plus 119 h of "control" observations near the ice camps. In 1991/94, observation time there

totalled 40 h during the icebreaker playbacks, plus 101 h of "control" observations.

Physical Acoustics

Ambient Noise

Ambient noise levels measured in 1991 were similar to those during 1989-90, with median

levels in the 20-1000 Hz band being 89-92 dB re 1 IlPa, just above the 87 dB level computed for

Knudsen's sea state zero extrapolated down to 20 Hz. In 1994, the corresponding measured

median level was notably higher, 97 dB. This is -2 dB less than the computed level for Knudsen's

sea state two. The 1994 measurements were made in higher average wind speeds than prevailed

in 1989-91. Wind speed has a dominant influence on underwater noise levels. Compared to the

Wenz spectrum level ranges at 32 and 1000 Hz, the 1991/94 levels during this project were about

mid-range. Compared to Chukchi shallow water measurements at those frequencies from May

1977, the 1991/94 levels were 7 dB re 1 IlPa2/Hz higher at 32 Hz and 18 dB higher at ~OOOHz.

xvi
Executive Summary

Overall, the measurements from the western Beaufort Sea in spring fit well into the range of

ambient noise measurements taken around the world.

Transmission Loss Tests

Transmission loss measurements were conducted 14 times during the four field seasons. The

best results came from 113-octave hyperbolic frequency modulated "sweeps" and from samples of

broadband Karluk drilling sounds. Tests with tones and clusters of tones gave more variable

results. Icebreaker sounds, although broadband, varied too much in level over the duration of

transmission to give consistent results. Assuming that bottom acoustic properties did not vary

significantly over the region where the transmission loss tests were conducted, a basic model for

sound transmission loss was developed. The validity of the assumption was ascertained by plotting, for each test frequency, transmission loss minus 20l0g(water depth) vs. range, normalized by

twice the depth. Agreement among tests was generally within about ±4 dB (s.e.) for frequencies

50-1000 Hz and within about ±6 dB for higher frequencies to 5000 Hz. The model is thus

frequency and depth dependent. All sources and receivers were at depth 18 m, and a frequencydependent Lloyd's Mirror component is included in the model for frequencies <50 Hz. For

example, the transmission loss at 10 Hz will be 28 dB greater than at 50 Hz due to the Lloyd's

Mirror effect.

Comparison of received levels at sonobuoys during playbacks with model predictions for

those ranges and water depths showed that the broadband measured levels generally agreed with

the predicted broadband levels within the ±4 dB spread expected. As expected, exceptions

occurred when the distance was so great that the predicted levels were less than the measured

ambient noise. Model estimates of received level in the strongest 113-octave band may be underestimated by a few decibels.

Transmission loss at the 13 May 1990 playback site was less than that expected based on the

transmission loss tests. The 13 May 1990 site was in water shallower (27 m) than that where any

transmission loss test was done. The observed results from 13 May 1990 can be accounted for if

there was subsea permafrost close to that playback site. Received levels of man-made noise from

a source in such an area would be higher than levels predicted by the propagation model developed

from the 14 transmission loss tests.

Comparison of transmission loss in the western Beaufort Sea (this project) with U.S. Navysponsored measurements in the Chukchi Sea (Greene 1981) suggests that the two areas are similar.

Playback Tests

In 1991/94, recorded underwater noise from an actual icebreaker (Robert Lemeur) operating

in heavy ice was transmitted repetitively to simulate an icebreaker operating at the playback test

sites. How did the playbacks compare with the original icebreaker?

Over the 40-6300 Hz range, the median source levels of the icebreaker playbacks on various

days were 20-44 dB lower than the median source level of the actual icebreaker. Thus, at any

distance from the source, the median level of the simulated icebreaker sound was 20-44 dB lower

xvii
Executive Summary

than would be expected if the actual icebreaker were operating there. A given received level

would be found much farther from the actual icebreaker than from the projectors.

The overall median playback source level in the frequency range 40-6300 Hz was 34 dB less

than the actual icebreaker source level (0.04% of the acoustic power). The median deviation from

a flat frequency response across the 40-6300 Hz range was ±10 dB. The differences in source

level at frequencies below 40 Hz increased with decreasing frequency to a median difference of

63 dB at 20 Hz. Considering the 113-octave bands centered at 20-6300 Hz (i.e. the 18-7100 Hz

band), 45% of the acoustic power emitted by the icebreaker was below 45 Hz. Because of the

more rapid attenuation of the lowest sound frequencies with increasing distance, the percentage

of power below 45 Hz is estimated to diminish to 18% at range 50-100 m from the icebreaker,

17% at 1000 m, and 6.5% at 10,000 m. In comparison, <1 % of the acoustic power emitted by the

projectors during icebreaker playbacks was below 45 Hz.

Because of the differences between the actual icebreaker sound and the projected sound, and

because of the variable levels at different times during playbacks, it was necessary to examine

whale behavior in relation to the sound level being received at the whales' locations. A sound

exposure model was developed to estimate received levels at whale locations, based on projected

level and spectral composition and on the transmission loss model.

Infrasounds

Characteristics of the infrasonic components of ambient noise and drilling caisson noise were

studied, along with the possibility that bowhead calls include infrasonic components. This work

was done to help assess whether oil-industry sources emit strong infrasounds, how far away these

infrasounds might be detectable, and whether bowheads are likely to hear infrasounds.

Infrasonic «20 Hz) ambient noise was measured in the 1I3-octave bands centered at 10, 12.5

and 16 Hz. Compared to median levels at higher frequencies, the levels in infrasonic bands

increased slightly with decreasing frequency in 1991 but decreased markedly with decreasing

frequency in 1994. The median and range of 10Hz spectral density levels agree well with measurements made in the deep Beaufort Sea and shallow Chukchi Sea during May 1977 (Greene

1981) and fit into the range of levels at 10 Hz reported by Wenz (1962). If bowhead calls include

infrasonic components at levels comparable to those of the known call components, the expected

high rate of attenuation in shallow water would result in masking by the observed levels of

ambient infrasonic noise at relatively short ranges. Similarly, industrial noise components at

infrasonic frequencies, unless much stronger than industrial noises at sonic frequencies, would be

masked by the infrasonic ambient noise at short ranges.

There was no evidence of infrasonic tones (at frequencies <20 Hz) in a brief recording of

noise from the SSDC drilling caisson engaged in drilling east of Barrow during winter.

If bowhead calls contain infrasonic components, bowheads probably can hear infrasounds.

Infrasonic sound coincident with bowhead calls was studied in 1990 and 1991. In 1990, of 45

calls analyzed, one showed coincidence with an infrasonic transient. In 1991, of 73 calls analyzed,

11 occurred coincidently with infrasonic transients. An array of acoustic sensors would be needed

xviii
Executive Summary

to determine if the source locations of infrasonic and sonic components are-coincident, thereby

providing stronger evidence of infrasonic calls by bowheads.

Bowhead Whales

Movements and General Behavior

Bowheads migrated northeast and east through the study area during late April and May of

1989-91 and 1994. In 1989, the migration was often through heavy pack ice conditions. In other

years, the ice was less compacted. In 1989-91, even when a broad nearshore lead extended east

along the landfast ice edge through the study area, the migration corridor 35+ km (19+ n.mi.) ENE

of Pt. Barrow was mainly along the offshore side of the lead or through the pack ice north of the

lead. However, up to 15 May in 1994, the landfast ice edge that far east of Pt. Barrow was farther

offshore than normal, and at times bowheads traveled near the landfast ice edge as far as 70 km

(38 n.mi.) east of Pt. Barrow. This allowed much of the 1994 playback work to be done from the

landfast ice edge 40-70 km east of Pt. Barrow.

Bowheads visible under undisturbed conditions in 1989-94, mainly amidst pack ice and in

the main nearshore lead, were engaged predominantly in traveling (migration), sometimes intermixed with socializing. In 1989, when ice conditions were heavy, some resting bowheads were

seen in small areas of open water amidst heavy ice. In subsequent years when heavy ice cover was

less common, a higher proportion of the whales observed were actively migrating northeast or east.

No surface feeding was seen, and apparent water-column or under-ice feeding was rare. A few

bowheads were seen surfacing with mud streaming from their bodies and (rarely) from their

mouths. Pre-dive flexes and fluke-out dives were seen less commonly in spring than in previous

summer/autumn studies. A few bouts of sexual activity were observed during early May. Most

mating apparently occurs earlier in the spring.

Bowhead calves and their mothers were seen only in the latter half of May in 1989, 1990 and

1991; only one calf was seen in 1994. In late May, mothers and calves often constituted the

majority of the bowheads present in the study area. They did not migrate as strongly or consistently eastward as did other bowheads, especially in 1989 when the ice was heavy. Direct observations and photographic resightings showed that a few mother-calf pairs traveled west for at least

a few kilometers. Some of these pairs may have been waiting for ice conditions to ameliorate

before continuing east. During travel, bowhead calves often "rode" on the backs of their mothers.

Dives by calves tended to be short. Heavy ice conditions pose a greater impediment to spring

migration of mother-calf pairs than of other bowheads.

Drilling Noise Playbacks

Results of the drilling noise playbacks in 1989-90 were described and summarized in OCS

Study MMS 91-0037. Migrating bowheads tolerated exposure to high levels of continuous drilling

noise if this was necessary to continue their migration. Bowhead migration was not blocked by

projected drilling sounds, and there was no evidence that bowheads avoided the projector by distances exceeding 1 km (0.54 n.mi.). However, local movement patterns and various aspects of the

behavior of these whales were affected by the noise exposure, sometimes at distances considerably

exceeding the closest points of approach of bowheads to the operating projector. When ice was

XIX
Executive Summary

loose, some migrating bowheads diverted their courses enough to remain a few hundred meters to

the side of the projector. Surfacing and respiration behavior, and the occurrence of turns during

surfacings, were strongly affected out to 1 km. Turns were unusually frequent out to 2 km (1.1

n.mi), and there was evidence of subtle behavioral effects at distances up to 2-4 km (1.1-2.2

n.mi.).

From a statistical viewpoint, the null hypotheses of no playback effects on migration route

and behavior were rejected. However, the demonstrated effects were localized and temporary. We

concluded that the effects of the Karluk playbacks on distribution and movements were not biologically significant, and that playback effects on behavior probably were not biologically significant

either. At distances beyond 100 m (109 yd), the projector used in 1989-90 adequately reproduced

the overall 20-1000 Hz level even though sound components below 80 Hz were underrepresented.

If bowheads are no more responsive to sound components at 20-80 Hz than to those above 80 Hz,

then the playbacks provided a reasonable test of bowhead responsiveness to components of the

actual Karluk sound above 20 Hz.

Icebreaker Noise Playbacks

Bowheads migrating in the nearshore lead often tolerated exposure to projected icebreaker

sounds at received levels up to 20 dB or more above the natural ambient noise levels at

corresponding frequencies. Bowheads are believed to be able to hear sounds of this type at levels

near ambient. Thus, most of them apparently did not react in a manner that we could detect when

they received weak icebreaker sounds.

However, some bowheads that would have come within a few hundred meters of the projectors if they had not turned apparently diverted so as to remain farther away. Diversion was

apparently common when bowheads were exposed to levels of projected icebreaker sound more

than 20 dB above the natural ambient noise level in the 1/3-octaveband of strongest icebreaker

noise. However, not all bowheads diverted at that signal-to-noise ratio (S:N), and a minority of

them apparently diverted at lower S:N.

Bowhead behavior was significantly correlated with S:N and with received level (RL) of

icebreaker sound in the 1I3-octave of strongest icebreaker sound, but not with distance from the

projectors. The lack of correlation with distance was no doubt related to the highly variable levels

of icebreaker sound at different times. Various measures of behavior were significantly different

when S:N (the icebreaker-to-ambient ratio) exceeded 20 dB or, in the case of frequency of turning

during surfacings, exceeded 10 dB. Measures of behavior that were significantly correlated with

S:N were turning, duration of surfacing, number of blows per surfacing, and two multivariate

indices of behavior. With icebreaker noise, turns during surfacings tended to be more common

and larger, durations of surfacing longer, and blows per surfacing more numerous.

In general, movements and behavior of migrating bowheads exposed to playbacks of variable

icebreaker noise were altered subtly but statistically significantly when S:N (as defined above)

exceeded 20 dB, and when RL of icebreaker sound exceeded 100 dB re 1 IlPa. Statistical power

analyses showed that the possibility of behavioral effects at lower S:N and RL values cannot be

excluded. One measure of behavior (frequency of turning) was apparently affected at S:N as low

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Executive Summary

as 10-20 dB, and another measure (duration of surfacings) was apparently affected at RL as low

as 90-100 dB re 1 IlPa (I13-octave basis).

The source level of an actual icebreaker is much higher than that of the projectors used in

this study (median difference 34 dB over the frequency range 40-6300 Hz). If bowheads react to

an actual icebreaker at S:N and RL values similar to those found during this study, they might

commonly react at distances up to 10-50 km (5.4-27 n.mi.) from the actual icebreaker, depending

on many variables. Predicted reaction distances around an actual icebreaker far exceed those

around an actual drillsite like Karluk because of (a) the high source levels of icebreakers and (b)

the better propagation of sound from an icebreaker operating in water depths 40+ m than from a

bottom-founded platform in shallower water.

This study is consistent with previous analyses that predicted highly variable reaction distances even for a single source of man-made noise. Predicted reaction distances depend on

~ temporal variations in its source level;

~ temporal and geographic variations in propagation loss between source and receiver;

~ temporal and geographic variations in ambient noise (and thus signal-to-ambient ratio);

~ variations in the response thresholds of individual whales.

Given these factors and the observed reactions to playbacks of icebreaker sound, predicted reaction

distances for bowheads around an icebreaker like Robert Lemeur vary from as little as -2 km to

as much as 95 km.

One of the main limitations of the study (during all four years) was the inability of a

practical sound projector to reproduce the low-frequency components of recorded industrial sounds

(see "Playback Tests", p. xvii). Both the Karluk rig and the icebreaker Robert Lemeur emitted

strong sounds down to -10-20 Hz, and quite likely at even lower frequencies. It is not known

whether the underrepresentation of low-frequency «45 Hz) components during icebreaker playbacks had significant effects on the responses by bowheads. Bowheads presumably can hear

sounds extending well below 45 Hz. It is suspected but not confirmed that their hearing extends

into the infrasonic range below 20 Hz.

Also, this study was not designed to test the potential reactions of whales to non-acoustic

stimuli detected via sight, olfaction, etc. At least in summer/autumn, responses of bowheads to

actual dredges and drillships seem consistent with reactions to playbacks of recorded sounds from

those same sites (Richardson et al. 1990b, Mar. Environ. Res. 29:135-160). This observation gives

us some reason for optimism that playbacks provide meaningful results.

Additional limitations of the playbacks included low sample sizes (especially for the 1991/94

icebreaker tests, see p. xvi) and the fact that responses were only evident if they could be seen or

inferred based on surface observations. The numbers of bowhead and white whales observed during both playback and control conditions were low percentages of the total Beaufort Seapopulations. These samples mayor may not have been representative of the overall populations. Also,

differences between whale activities and behavior during playback vs. "control" periods represent

the incremental reactions when playbacks are added to a background of other activities associated

with the research. Thus, the playback results may somewhat understate the differences between

truly undisturbed whales vs. those exposed to playbacks.

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Executive Summary

Nonetheless, the data allow us to conclude that exposure to a single playback of variable

icebreaker sounds can cause statistically but probably not biologically significant effects on the

movements and behavior of migrating bowheads visible in the open water of nearshore lead systems during spring migration east of Pt. Barrow. Reaction distances around an actual icebreaker

like Robert Lemeur are predicted to be much greater, commonly on the order of 10-50 km. Effects

of an actual icebreaker on migrating bowheads, especially mothers and calves, could be

biologically significant.

Aircraft Disturbance

The 1989-94 observations show that a minority of spring-migrating bowheads dive or

exhibit other short-term behavioral changes in response to a close approach by a turbine-powered

helicopter. However, other bowheads show no obvious reaction to single passes-even at altitudes

of 150 m (500 ft) or below, and lateral distances $250 m (820 ft).

We conclude that, although some bowheads exhibit short-term behavioral reactions, single

helicopter overflights at altitudes of 150 m (or below) do not appear to disrupt the distribution,

movements or behavior of bowheads visible during spring migration in pack ice or nearshore leads

in a biologically significant way. This assessment concerns potential effects of single, straight-line

overflights. Repeated passes, circling, or prolonged hovering at low altitude would be more likely

than single, straight-line overflights to cause significant disturbance effects.

Spring-migrating bowheads occasionally dive, turn or otherwise react in an obvious manner

to low-altitude overflights (altitude $182 m or $600 ft) by a Twin Otter fixed wing aircraft. A

very small percentage (-1.3%) react similarly to overflights at. altitude 460 m (1500 ft) if the

lateral distance is $300 m ($1000 ft). In spring, migrating bowheads do not react in an obvious

manner to a Twin Otter aircraft circling at altitude 460 m and radius 1-1Yz km, nor is there any

clear evidence of subtle alterations in their behavior within 15 min after circling begins as

compared with later observations.

White Whales

Sightings of white whales were more numerous than those of bowheads, and white whales

tended to be more widely scattered and slightly farther offshore than bowheads. However, their

migration corridors overlapped broadly.

Drilling Noise Playbacks

Results of the drilling noise playbacks in 1989-90 were described and summarized in OCS

Study MMS 91-0037. In brief, we observed migrating white whales close to the operating

projector on five dates. On four of these dates, at least a few white whales came within -200 m

(655 ft) of the operating projector, including a few within 50-100 m (165-330 ft). Whitewhales

migrating toward the projector appeared to travel unhesitatingly toward it until they came within

a few hundred meters. Some white whales that came that close continued past without apparent

hesitation or turning. Others reacted temporarily to the noise, or perhaps to visual cues, at

distances on the order of 200-400 m (655-1310 ft). Some white whales slowed down, milled, or

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Executive Summary

reversed course for several minutes. Then they continued past the projector, in some cases passing

within 50-100 m of it.

We saw no evidence that white whales reacted at distances greater than 200-400 m even

though projected drilling noise was measurable up to several kilometers away. This was probably

related to the poor hearing sensitivity of white whales at low frequencies where the Karluk drilling

sounds were concentrated. At distances beyond -200 m, received levels of low-frequency drilling

sounds (on a 113-octave basis) usually were less than the measured hearing sensitivity of white

whales.

The observed reactions may have been to weak artifactual components of the projected sound

at frequencies above 2-3 kHz rather than to stronger Karluk components at -63-300 Hz. Although

weak, the high-frequency components were potentially audible to white whales at somewhat

greater ranges, given the much better hearing of white whales at higher frequencies.

The maximum acoustic reaction distance of white whales near a shallow-water drillsite like

Karluk is predicted to be similar to that observed in our tests (a few hundred meters). Reaction

distances near the actual drillsite might be less than those near the projector if the observed

reactions were to the weak high-frequency system noise rather than the drilling noise per se. This

high-frequency noise would not be present near the actual drillsite. However, minimum reaction

distances near an actual drill site like Karluk probably exceed those observed near the projector

(15-50 m) because of the higher noise levels and other stimuli present within -200 m of the actual

site relative to those at corresponding distances from the projector site.

We conclude, based on a small sample size, that playbacks of sounds from drilling on a

bottom-founded ice platform like Karluk have no biologically significant effects on migration

routes and spatial distribution of white whales visible while migrating through pack ice and along

the seaward side of the nearshore lead east of Point Barrow in spring. Furthermore, we expect that

maximum reaction distances of white whales to an actual drill site like Karluk (a few hundred

meters) would be similar to those observed during the playback experiments. In drawing these

conclusions, we consider that the observed temporary hesitation and minor changes in migration

paths exhibited by some white whales within 200-400 m of the noise source were not biologically

significant. Our acceptance of the amended null hypothesis is based on a "weight of evidence"

approach; available data are not suitable for a statistical test of the hypothesis. Also, the available

data are not adequate for a test, statistical or otherwise, of the second hypothesis, concerning

effects of Karluk drilling noise on subtle aspects of the individual behavior of white whales.

Icebreaker Noise Playbacks

We observed migrating white whales close to the operating projector(s) on three dates in

1991/94. Interpretable data were collected on 17 groups of white whales observed during

playbacks on two of these dates. At least six groups appeared to alter their paths in response to

playbacks. As in the drilling noise playbacks, however, white whales approached within a few

hundreds (and sometimes tens) of meters before showing any response. At these distances

received levels at frequencies below 1000 Hz were high, but below the hearing threshold at

corresponding frequencies. However, white whales within a few hundred meters of the projectors

probably could hear, at least faintly, higher frequency components of the projected sounds, around

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Executive Summary

5000 Hz. Icebreaker sounds received by six groups of white whales that reacted were estimated

as 78-84 dB re 1 IlPa in the 1/3-octave band centered at 5000 Hz, or 8-14 dB above ambient in that

band. Corresponding levels for 11 groups showing no obvious diversion were generally similar.

If some white whales react to an actual icebreaker at RL near 80 dB re 1 IlPa or S:N near 10

dB (both in the 113-octave band near 5000 Hz), reactions would be expected to occur at distances

on the order of 10 km from an icebreaker like Robert Lemeur operating in the present study area

in spring.

Because we saw few groups of white whales near the projector(s) during icebreaker

playbacks, additional field tests would be needed before formally evaluating their effects on

movements of migrating white whales. However, small-scale diversions such as those sometimes

seen in 1991/94 are unlikely to be biologically significant. Given the much larger anticipated

radius of influence around an actual icebreaker and our small sample size, any conclusions about

the effects of icebreaker playbacks on white whales cannot be applied directly to actual icebreaker

effects.

Aircraft Disturbance

Opportunistic observations in 1989-94 showed that spring-migrating white whales appeared

more responsive to aircraft overflights than were bowheads, often responding to a close approach

by a turbine-powered helicopter. Apparent reactions were observed during 31 % of overflights.

Whales reacted by diving, veering away, or showing other changes in behavior. During

overflights, reactions occurred exclusively when the helicopter passed at ~250 m (820 ft) lateral

distance from the white whales, and at altitudes up to 460 m ASL (1500 ft). However, most white

whales showed no obvious reaction to single passes at altitudes >150 m ASL. These white whales

maintained their headings and continued respiring at the surface when the helicopter operated

nearby. Reactions were also noted among half of the 14 groups observed from the ice camp when

the helicopter was stationary on the ice with its engines running.

Operations by a Bell 212 helicopter can locally alter the movements of white whales visible

in the open water of nearshore lead systems and amidst the pack ice during spring migration near

Pt. Barrow. However, these local effects do not cause migration blockage or biologically

significant diversion from migration routes in the circumstances studied. Likewise, single overflights at lateral distances <250 m, especially at altitudes ~150 m ASL, often affect the behavior

of the white whales. There is no objective way to assess the biological significance of these

behavioral reactions, but they appear brief and probably are not of lasting significance. This

assessment concerns potential effects of single, straight-line overflights.

White whale groups were sometimes observed reacting overtly to Twin Otter overflights.

Most reactions occurred when the aircraft was at altitudes ~182 m (600 £1) and lateral distances

~250 m (820 ft). Direct overflights generated the most pronounced reactions, such as vigorous

swimming, abrupt dives, or tail thrashing. In a few cases, white whale responses involved turning

directly away from the aircraft. In other cases, white whales responded to overflights by looking

up at the aircraft. The number of white whales observed reacting overtly to Twin Otter overflights

represented a very small fraction of the total number of white whales observed from the aircraft:

24 of -760 groups.

xxiv
ACKNOWLEDGEMENTS

We thank the Barrow Whaling Captains' Association (BWCA), Alaska Eskimo Whaling Commission (AEWC), and North Slope Borough (NSB) for their agreement that this project could be

conducted near Barrow during the spring whaling season. Individuals from Barrow who provided

valuable advice or assistance at various times from 1989 to date included Thomas Albert, Charlie

Brower, Geoff Carroll, J. Craig George, Ben Nageak, Mike Philo, and Robert Suydam (NSB Dep.

Wildl. Manage.), Edward E. Hopson and Burton Rexford (AEWC and BWCA), Rosie Habeich,

Charlotte Brower and Maggie Ahmaogak (AEWC), and Eugene Brower and Edward Itta (BWCA).

We also thank the management and staff of UIC-NARL, Dano Bollman and Duane Ambuehl

(Alaska Dep. Transport.), Mike Aamodt (Arctic Enterprises), John Trent (Alaska Dep. Fish &

Game), and Richard Glen (Barrow Technical Services).

We thank the members of the project's Scientific Review Board (SRB) for their advice and

constructive criticisms. The SRB members in 1991 and/or 1994-95 were as follows:

Dr. Thomas Albert

Mr. Mark Fraker

Ms. Michelle Gilders

Dr. Roger Green

Mr. Edward Itta

Mr. Charles Malme

Mr. Allen Milne

Mr. Ron Morris

Mr. Thomas Napageak

Mr. Burton Rexford

Dr. Steven Swartz

North Slope Borough Dep. Wildl. Manage. (1989-95),

BP Exploration (Alaska) (1989-91),

BP Exploration (Alaska) (1994-95),

University of Western Ontario (1990-95),

Barrow Whaling Captains Assoc. (1994-95),

Hingham, MA (1994-95),

Sci. Rev. Board Chairman (1989-91),

Nat. Mar. Fish. Servo (1990-95),

Alaska Eskimo Whaling Commission (1989-91),

Barrow Whaling Captains' Assoc. (1989-91) and

Alaska Eskimo Whaling Commission (1994-95),

Nat. Mar. Fish. Serv. (1989-95; SRB Chairman in 1994-95).

For help in the field all four years of the study, we thank Kenneth Toovak Sr. of Barrow.

Other participants in the fieldwork were Greg Silber and Dave Schmidt in 1989, Thorn Woodley

in 1990, and Moira W. Brown in 1991. The National Oceanic & Atmospheric Administration

supplied the helicopter and some other equipment. We thank Dave Gardner of NOAA, who flew

the NOAA helicopter in all four years, assisted at various times by Carl Anderson, Debbie Barr,

Roy DeHart, Ron Helguson, Steve Pape and Julie Vance, all of NOAA. We also thank the following Twin Otter pilots: Frank Hennessey and Ron Sprang (Aklak Airways, 1989); Stan Ashland

and Leon Smith (Evergreen, 1990); Vic Walters and Brant Smith (Empire Airlines, 1991); and Bill

Steck and Don Nyberg (Leading Edge Aviation, 1994).

In 1989-91, we valued the cooperation and assistance provided by the National Marine Mammal Laboratory (NMML) photogrammetry field crew, led by David Rugh and David Withrow.

They, Robyn Angliss, and Kim Shelden, all of NMML, kindly provided unpublished data on bowheads, and exchanged bowhead photos with us. We thank Joanne Groves of ADVAL (Alaska Data

Visualization and Analysis Lab., Geophysical Inst., Univ. Alaska) for supplying satellite imagery.

xxv
Acknowledgements

William Stringer, S.A. Bowling and Carl Byers of that group also assisted in supplying satellite

imagery and/or weather data.

C.r. Malme and A. Owen of BBN Systems & Technologies Corp. assisted with propagation

modeling for the study area before and after the first (1989) season of fieldwork. P. Dysart of

SAIC kindly developed new bathymetric contours for the study area, taking account of bathymetric

data acquired recently. The theodolite data acquisition programs used in 1991 and 1994 were

supplied by Frank Cipriano and Adam Frankel. At LGL, Chris Holdsworth assisted with the 1989-

90 and 1994 data analyses, and Gordon Cameron helped in 1990-91. Kathleen Hester and Bev Griffen of LGL assisted with data entry and report production. We thank all of these individuals.

We thank the Alaska OCS Region, U.S. Minerals Management Service, for conceiving and

funding the project, and for many constructive comments. Dr. Cleve Cowles, Jerry Imm, Dr.

Jerome Montague, and Jim MacKay of MMS were instrumental in initiating the work and in overcoming obstacles. The work was conducted under Permit 670 issued by the National Marine Fisheries Service under provisions of the Marine Mammal Protection Act and Endangered Species Act.

xxvi
GLOSSARY

absorption. The process by which sound energy

is converted into heat.

acoustic impulse. Integral Over time of the

initial positive acoustic pressure pulse, measured in pascal-seconds (Pa -s); used in describing sound pulses.

acoustic intensity. Acoustic power crossing a

unit area; pressure squared divided by

acoustic impedance (pc, where p represents

the density of the medium and c the sound

speed).

acoustic power. The energy per unit time, measured in watts. The acoustic power is proportional to acoustic pressure squared.

acoustic pressure. Pressure variations around an

ambient static pressure (such as the hydrostatic pressure in water at some depth) at

acoustic frequencies. These are very small

pressures compared to the static pressure or

compared to shock or blast wave pressures.

ambient noise. Background noise; noise not of

direct interest during a measurement or

observation. Excludes sounds produced by

the measurement equipment, such as cable

flutter.

Argotec 220. A particular type of underwater

sound transducer that can project lowfrequency sounds. Used in 1994.

ASL. Above sea level.

audiogram. A graphical depiction of auditory

thresholds, showing the sound levels that are

barely detectable by an animal, in the

a15sence of significant background noise, as a

function of frequency.

auditory sensitivity. An animal's hearing sensitivity as a function of frequency.

auditory threshold. The minimum amplitude of

sound that can be perceived by an animal in

the absence of significant background noise.

Auditory threshold varies with frequency and

is inversely related to the animal's auditory

sensitivity.

xxvii

bandpass filter. A filter with high-pass and lowpass cutoff frequencies, designed to pass only

a desired band of frequencies.

bandwidth. A range of frequencies.

Bell 212. Medium-size helicopter (4500-5100 kg

gross weight) with 2-bladed main and tail

rotors producing families of tones with fundamental frequencies -11 and 55 Hz, respectively. Powered by paired turboshaft engines

(PT6T), together producing 1100 shp for

cruise and a maximum of 1800 shp. Civil

equi valent of military Twin Huey UH -1 N.

biologically significant. Likely to affect the

long-term well-being or reproductive productivity of individuals or of the population.

blow interval. The interval, in seconds, between

two successive respirations within the same

surfacing by a whale.

CEPA. Closest Estimated Point of Approach. A

term used in this study to represent the

closest known distance of a whale from the

ice camp. It is (a) the interpolated Closest

Point of Approach for whales observed both

before and after passing the ice camp; and (b)

the closest observed distance for whales seen

either approaching or moving away from the

ice camp, but not both.

CPA. Closest Point of Approach.

critical band. The frequency band within which

background noise can affect detection of a

sound signal at a particular frequency.

critical ratio. The ratio of power in a barelyaudible tone to the spectrum level of background noise at nearby frequencies.

continuous wave. A sound whose waveform

continues with time.

crosscorrelation. A measure of the similarity of

two waveforms. As a function of time displacement or delay between the two waveforms, useful for determining the travel time

difference of a signal received at two spatially separated sensors. Computed for each
value of displacement by averaging the product of the two waveforms.

cylindrical spreading. Sound spreading as cylindrical waves. The transmission loss for

cylindrical spreading is given by

10*loglO(Range/Ro),

where R, is a reference range. The received

level diminishes by 3 dB when range doubles,

and by 10 dB for a tenfold increase in range.

cylindrical wave. A sound wave with cylindrical

fronts. For a point source in shallow water,

a cylindrical wave forms at distances that are

large compared to the water depth because of

the way sound reflected from the surface and

bottom reinforces the direct wave.

decibel (dB). A logarithmically based relative

measure of sound strength. A sound pressure

P can be expressed in dB as a sound pressure

level of 20*loglO(P/Pref), where Pref is a

reference pressure (usually a standard

pressure like 1 microPascal). Note that

20*log(X) is the same as 10*log(X2), where

X2is the mean square sound pressure and is

proportional to power, intensity or energy.

DIFAR. A type of sonobuoy (AN/SSQ-53B)

with the ability to determine the direction of

arrival of a sound. Effective at 10-2400 Hz.

DSP. Digital Signal Processor. A microprocessor whose internal design is optimized for the

types of repetitive mathematical calculations

required during signal analysis.

electrical noise. Noise generated by electronic

circuits, as distinct from acoustic noise.

F-40. A particular type of U.S. Navy underwater

sound transducer that can project highfrequency sounds, e.g. 1-10 kHz. Used in

1991 with J-13.

faired cable. A cable with many ribbon- or hairlike attachments to reduce strumming in currents.

filter. An instrument or mechanism for restricting or altering the frequency range or spectral

shape of a waveform.

xxviii

Glossary

fluke-out dive. A dive in which the whale raises

its tail flukes above the surface of the water

as it dives.

frequency. The rate at which a repetitive event

occurs, measured in hertz (cycles per sec.).

GPS. Global Positioning System. A system for

determining position (latitude, longitude,

altitude) based on reception of signals from

several of the GPS satellites that orbit the

earth; horizontal accuracy 100 m or better.

hertz (Hz). A measure of frequency corresponding to a cycle per second.

high-pass filter. A filter passing only sounds

above a specified frequency, to eliminate

lower-frequency sounds.

hydrophone. A transducer for detecting underwater sound pressures; an underwater microphone.

impulse. see "acoustic impulse.

infrasound. Sound energy at frequencies too low

to be directly audible to humans; generally

taken to be sound at frequencies below 20

·Hz.

intensity. See" acoustic intensity".

J-ll; J-13. Particular types of U.S. Navy underwater sound projectors. The J-11 is a broadband projector (used in 1994 with or without

Argotec 220); the J-13 is a low-frequency

projector (used in 1991 with F-40).

Karluk. Karluk was a grounded ice platform that

was constructed in 6 m of water near Prudhoe

Bay, Alaska, during the winter of 1988-89.

The Karluk ice platform was used as a drillsite during that winter. The underwater

sounds projected during playback experiments in the 1989-90 phases of this study

were recorded 130 m from Karluk while it

was drilling during March 1989.

Lemeur. See Robert Lemeur.

level. The term "level" is usually applied to

sound amplitudes, powers, energies or intensities expressed in dB.

Lloyd's mirror effect. The diminished pressure

of a sound from an underwater source when

it is received near the water/air boundary (the
surface). The reflected sound wave is inverted (out of phase) with respect to the incident

sound wave, and their sum at the receiver

approaches zero as the receiver approaches

the surface.

low-pass filter. A filter passing sounds below a

specified frequency.

masking. The obscuring of sounds of interest by

stronger interfering sounds.

microbar (ubar). A unit of pressure previously

used as a reference pressure in dB level

measurements. A ubar is equivalent to

1 dyne/ern" and to 0.1 pascal, or 105IlPa.

noise. Sounds that are not of particular interest

during an acoustic study and that form the

background to the sound being studied.

Noise can include both natural sounds and

man-made sounds.

micropascal (IlPa). The usual reference pressure

in underwater sound level measurements.

octave band. A frequency band whose upper

limit in hertz is twice the lower limit.

one-third octave band. A frequency band whose

upper limit in hertz is 2l!3 times the lower

limit. Three V3-octave bands span an octave

band. Such bands have widths proportional

to the center frequency; the center frequency

is given by the square root of the product of

the upper and lower limit frequencies, and

the bandwidth is 23% of the center frequency. There is a standard set of V3-octave

frequency bands for sound measurements.

pascal. A unit of pressure equal to 1 newton per

square meter.

peak level. The sound level (in dB) associated

with the maximum amplitude of a sound.

point source. A hypothetical point from which

sound is radiated. The concept is useful in

describing source levels by a pressure level at

unit distance. The concept is an abstraction;

to describe a 300 m ship as a point source

stretches the imagination, but at a distance of

10 n.mi. the received sound may as well have

come from a point source radiator.

power. See "acoustic power".

Glossary

power density spectrum. The result of a frequency spectrum analysis to determine the

distribution of power in a signal vs. frequency where continuously distributed sound

(not tones) is the important signal component. Correct units of a power density spectrum are watts/Hz but the usual units in

acoustics are IlPa2/Hz, because the power is

proportional to the mean square pressure and

pressure is the commonly measured quantity.

power spectrum. The result of a frequency

spectrum analysis to determine the distribution of power in a signal vs. frequency where

tones are the important components of the

signal. Correct units of a power spectrum are

watts but the usual units in acoustics are

IlPa2, because the power is proportional to

pressure squared and pressure is the commonly measured quantity.

pre-dive flex. A distinctive concave bending of

the back occasionally exhibited by bowheads

while they are at the surface but shortly

before they are about to dive.

pressure. A physical manifestation of sound.

The dimensions of pressure are force per unit

area. The commonly used unit of acoustical

pressure is the micropascal.

projector. An underwater transducer used to

transmit sounds; an underwater loudspeaker.

propagation loss. The loss of sound power with

increasing distance from the source. Identical to transmission loss. It is usually

expressed in dB referenced to a unit distance

like 1 m. Propagation loss includes spreading, absorption and scattering losses.

proportional bandwidth filters. A set of filters

whose bandwidths are proportional to the filter center frequencies. One octave and onethird octave filters are examples of proportional bandwidth filters.

pure tone. A sinusoidal waveform, sometimes

simply called a tone. There are no harmonic

components associated with a pure tone.

reflection. The physical process by which a

traveling wave is returned from a boundary.

The angle of reflection equals the angle of

incidence.

XXIX
refraction. The physical process by which a

sound wave passing through a boundary between two media is bent. If the second medium has a higher sound speed than the first,

then the sound rays are bent away from the

perpendicular to the boundary; if the second

medium has a lower sound speed than the

first, then the sound rays are bent toward the

perpendicular. Snell's law governs refraction: c2*sin 8, = c,*sin 82, where c is the

sound speed, subscript 1 refers to the first

medium and subscript 2 refers to the second

medium, and the angles are measured from

the perpendicular to the boundary. Refraction may also occur when the physical properties of a single medium change along the

propagation path.

RL. Received Level; the level of sound reaching

a location some distance from the sound

source (cf. source level).

Robert Lemeur. An Arctic Class 3 icebreaking

supply ship whose underwater sounds,

recorded during icebreaking, were projected

during playback tests in 1991 and 1994. The

ship has 83 m length overall, 3184 tons gross

displacement, with two turbocharged diesel

engines of combined power 9600 bhp (7.2

MW). The two four-bladed controllable-pitch

propellers are in Kort nozzles.

scattering. The physical process by which sound

energy is diverted from following a regular

path as a consequence of inhomogeneities in

the medium (volume scattering) or roughness

at a boundary (boundary scattering).

signal. A sound of interest during an acoustic

study.

S:N. Signal-to-Noise ratio; the difference in

level, measured in decibels, between a signal

of interest (in this study, usually Karluk or

icebreaker sound) and the background noise

at the same location (in this study, usually

ambient noise).

sonobuoy. A sound monitoring and transmitting

device that includes a hydrophone, amplifier

and an FM radio transmitter. Sonobuoys are

designed to be dropped into the water from

an aircraft. They can also be deployed from

Glossary

the surface. Sounds in the water can be monitored from a remote location via radio

receivers.

sound. A form of energy manifested by small

pressure and/or particle velocity variations.

sound pressure. The pressure associated with a

sound wave.

sound pressure density spectrum. The description of the frequency distribution of sound

pressure in which the actual pressure at any

frequency is infinitesimal but, integration

over any non-zero frequency band results in

a non-zero quantity. The correct dimensions

of sound pressure density spectrum are pressure squared per unit frequency; a common

unit is f.lPa2/Hz. cf. power density spectrum.

sound pressure density spectrum level. The

measure, in decibels, of sound pressure

density spectrum. A common unit is dB re

1 f.lPa2/Hz.

sound pressure level (SPL). The measure, in

decibels, of sound pressure. The common

unit is dB re 1 f.lPa.

sound pressure spectrum. The description of

the frequency distribution of a sound pressure

waveform consisting of tones. The dimension is that of pressure; a common unit is the

micropascal (f.lPa).

source level. A description of the strength of an

acoustic source in terms of the acoustic pressure expected a hypothetical reference distance away from the source, typically 1 m,

assuming that the source is a point source.

Source level may be given in units of dB re

1 f.lPa-m. Source level may vary with frequency (see source spectrum level) but it may

be given for some band of frequencies.

source spectrum level. A description in decibels

of the strength of an acoustic source as a

function of frequency. The description is

meaningful for sources of tones. Source

spectrum levels are described in decibels

referred to a unit pressure at a unit distance,

such as dB re 1 f.lPa-m.

spectrum level. See "sound pressure density

spectrum level".

xxx
spherical spreading. Sound spreading as spherical waves. The transmission loss for spherical spreading is given by

20*loglQ(Range/Ro),

where R, is a reference range. The received

level diminishes by 6 dB when range doubles,

and by 20 dB for a tenfold increase in range.

spherical wave. A sound wave whose fronts are

spherically shaped. Such a wave forms in

free space without reflecting boundaries or

refraction. Typically, spherical waves are

emitted by point sources and retain their

sphericity until the influence of reflected

waves or refraction becomes noticeable.

spreading loss. The loss of acoustic pressure

with increasing distance from the source due

to the spreading wavefronts. There would be

no spreading loss with plane waves. Spreading loss is distinct from absorption and

scattering losses.

SSDC. Single Steel Drilling Caisson or SteelSided Drilling Caisson; this is a mobile

bottom-founded drilling platform constructed

from part of a supertanker.

surfacing. As defined in this study, a surfacing

by a whale is the interval from the arrival of

the whale at the surface following one long

di ve until the start of the next long dive.

Periods while the animal is just below the

surface between breaths (blow intervals) are

not counted as dives. Equivalent to the term

"surfacing sequence" used by some authors.

threshold of audibility. The level at which a

sound is just detectable. The threshold of

audibility depends on the listener and varies

with frequency.

third octave. Abbreviation for one-third or Y3

octave (see above).

time delay. A time difference between related

events, such as the time between arrivals of

a sound wave at two receivers, or the time

between sound transmission and the reception

of its reflection.

tone. A sinusoidal waveform, sometimes called

a pure tone. There are no harmonics. A tone

is distinct from waveforms consisting of

Glossary

components continuously distributed with

frequency.

transducer. A device for changing energy in

one form (say mechanical) into energy in

another form (say electrical). An acoustic

transducer might change a pressure waveform

into an electrical waveform, or vice versa.

Microphones, hydrophones, and loudspeakers

are examples of transducers.

transmission loss. The loss of sound power with

increasing distance from the source. Identical to propagation loss. It is usually

expressed in dB referenced to a unit distance

like 1 m. Transmission loss includes spreading, absorption and scattering losses.

Twin Otter (de Havilland). A relatively small

(::;5670 kg gross weight) fixed-wing utility

aircraft commonly used for offshore aerial

surveys. Two PT6A gas turbine engines

totalling - I 200 shp turn 3-bladed propellers,

producing a family of tones with fundamental

frequency about 83 Hz.

VLF Navigation (Very Low Frequency). VLFI

Omega navigation systems, based on very

long-wavelength radio transmissions, have

been widely used for aircraft navigation,

especially in remote areas where LORAN was

not usable. Accuracy variable, often deteriorating during a flight. Now being replaced

by GPS in most applications.

waterfall spectrogram. A graphical depiction of

the intensity of sound components at various

frequencies over time. Time and frequency

are shown on the X and Y axes, and intensity

is shown as a third dimension. A waterfall

graph may indicate only relative powers.

waveform. The functional form, or shape, of a

signal or noise vs. time.

wavelength. The length of a single cycle of a

periodic waveform. The wavelength A, frequency f, and speed of sound c are related by

the expression c = f*A.

xxxi
XXXll
1. INTRODUCTION!

The possible effects of underwater noise from offshore oil and gas activities have been a

significant concern to Minerals Management Services (MMS), the National Marine Fisheries

Service (NMFS), and other agencies for several years. Hence, MMS has funded studies to

document the characteristics of oil industry noises and their effects on the behavior of bowhead

and gray whales (e.g. Gales 1982; Malme et al. 1984; Richardson et al. 1985b; Miles et al. 1987;

Ljungblad et al. 1988). The oil industry has funded related monitoring studies of the reactions of

bowhead whales to oil industry operations in the Alaskan Beaufort Sea (e.g. LGL and Greeneridge

1987; Hall et al. 1994). These and other similar studies have been reviewed by Richardson and

Malme (1993) for bowheads, and by Richardson et al. (in press) for marine mammals in general.

Prior to this study, all systematic studies of disturbance to bowheads had been done in

summer or early autumn when the whales are either in open water or in loose pack ice where their

movements are relatively unrestrained by ice. There had been no work on the disturbance

reactions of bowheads migrating in leads through areas of heavy ice cover-the normal situation

in spring. Also, there had been no systematic scientific study of the suggestion by Inupiat whalers

that bowhead whales are especially sensitive to noise in the spring.

The sounds considered in the summer-autumn studies conducted in the Beaufort Sea have

been those associated with some of the major offshore exploration activities: aircraft and boat

traffic, marine seismic exploration, drillships, and offshore construction. Previous to this project,

only a very limited effort had been devoted to the reactions of bowheads to ice breaking, which is

a particularly noisy activity (e.g. Greene 1987a; Thiele 1988; reviewed in Greene and Moore in

press: 117!/). Reactions of bowheads to sounds from an oil production platform had not been

studied, in part because no production platforms exist in arctic waters deeper than a few meters.

Reactions of migrating gray whales to noise from a production platform were studied by Malme

et al. (1984), but the type of platform involved was very different from the types likely to be used

in the Arctic.

The National Marine Fisheries Service took note of the above situation in its Biological

Opinions on lease sales in the Beaufort and Chukchi seas. NMFS believed that development and

production activities in spring lead systems used by bowheads might, in certain circumstances,

jeopardize the continued existence of the Western Arctic bowhead whale population (Evans 1987;

Brennan 1988; Fox 1990). The possibility of significant disturbance in spring lead systems, when

bowheads may have few or no optional migration routes, was one of the factors about which

NMFS was concerned.

The beluga or white whale is the one other cetacean that migrates through the spring lead

systems in a manner similar to the bowhead. The sensitivity of various populations of white

whales to several types of human activities and underwater noises has been studied in summer in

Alaska, in late spring and summer in the Mackenzie Delta area, and in spring in the eastern

! By W.J. Richardson
Introduction 2

Canadian High Arctic. There has also been a playback study with captive white whales (Thomas

et al. 1990). The sensitivity of the white whales in these situations varied widely. There was great

tolerance in some situations. However, white whales exhibited strong avoidance reactions to ships

and icebreakers at very great distances during spring in the eastern high arctic (LGL and

Greeneridge 1986; Cosens and Dueck 1988; Finley et al. 1990). The responsiveness of white

whales to underwater noise during the spring migration around western and northern Alaska had

not been studied previous to this project.

Bowhead and white whales are both important to subsistence hunters in Alaska. An

assessment of the potential effects of industrial activities on subsistence hunting is beyond the

scope of this project. However, if industrial sounds affect the availability of these species to

subsistence hunters, there could be economic, social, cultural, and political implications.

To answer some of these questions, MMS funded this study. The main objectives were to

determine the short-term effects of production platform noise and icebreaker noise on the

movements and behavior of bowhead and white whales migrating through open leads and pack ice

near Pt. Barrow, Alaska, in spring. A related objective was to determine the characteristics of

sound propagation and of natural ambient noise in spring lead systems. These physical acoustic

phenomena affect the received levels and prominence of man-made noise. Reactions of whales

to helicopter overflights were also to be determined when possible.

This report describes results from 1991 and 1994, the third and fourth years of the study.

In 1989-1990, we obtained

~ considerable information on physical acoustic phenomena (ambient noise and sound

propagation) in spring lead systems,

~ considerable data on reactions of bowhead and white whales to playbacks into spring lead

systems of continuous sounds from one drilling platform-a rig on a bottom-founded ice

pad, and

~ limited data on reactions of bowhead and white whales to the Twin Otter fixed wing aircraft and the Bell 212 helicopter (Richardson et al. 1990a, 1991 a).

In 1991 and 1994, our highest priority objective was to determine the reactions of bowhead

and white whales to a second type of industrial noise, the variable noise from an icebreaker that

was actively breaking ice. There were several additional related objectives (see below).

Weather and ice conditions were generally unfavorable for this type of work near Barrow,

Alaska, during the spring of 1991. In 1991, we obtained additional information about physical

acoustic phenomena and whale movement patterns past Barrow, but results from the playback

experiments with icebreaker noise were very limited. Consequently, the Minerals Management

Service decided to continue the project for another spring season, and to cancel the requirement

for a detailed report on the 1991 data. The additional fieldwork was not possible in 1992 or 1993

because of concern about the potential for interference with bowhead censusing efforts underway

in those years. Consequently, the fourth field season was delayed until 1994.
Introduction 3

This report was planned and funded to describe results from 1991 and 1994, years 3 and 4

of the study, not as an integrated account of results from all four years of the study. Results from

1989 and 1990 were described in Richardson et al. (l990a, 1991a). However, some sections of

the present report do incorporate data from 1989-90 as well as 1991 and 1994. These include the

sections on acoustic transmission loss (§4.3), the activities of undisturbed bowheads in the study

area during spring (§5.1-5.4), the migration of white whales during spring (§7 .1), and the reactions

of both species to aircraft (§6.7 and §7.4). These comprise most of the sections for which data

were collected in comparable ways during 1989-90 and 1991/94. The top-priority acoustic

playback work in 1989-90 involved playback tests of whale reactions to steady low-frequency

drilling sounds, whereas the corresponding work in 1991 and 1994 tested reactions to more

variable and wider-bandwidth icebreaker sounds. Thus, the 1989-90 and 1991/94 playback data

cannot be combined, although the two sets of results can be compared. Sections 6.1-6.6 and 7.2

of this report present the 1991/94 icebreaker playback results, and compare them with the

previously-reported 1989-90 drilling noise playbacks.

1.1 Objectives and Rationale

General Objectives

In early 1988, MMS requested proposals for an experimental study of the effects of noise

from oil production activities on bowhead and (secondarily) white whales during their spring

migrations around Alaska. The overall objectives of the study, as defined by MMS, were

1. "To quantitatively characterize the marine acoustic environment including sound

transmission loss and ambient noise within the nearshore leads of the Alaskan Chukchi

Sea and Beaufort Sea in the spring.

2. "To quantitatively describe the transmission loss characteristics of underwater sound

produced by production platforms and icebreakers in the spring lead study area.

3. "To quantitatively document the short term behavioral response of spring migrating

bowhead and, as possible, beluga [white] whales resulting from exposure to the [above]

sources (see objective 2) of production sounds.

4. "To assist and coordinate with other MMS sponsored studies and local resource users to

maximize collection of needed data and avoid conflict with subsistence whaling activities.

5. "To analyze acquired and synthesized data to test the generalized null hypothesis."

Rationale for Various Study Components

The rationale for studying topics such as sound transmission loss; ambient noise levels, and

received sound levels near whales requires some explanation. These data are needed in order to

develop quantitative models for predicting the radii of noise detectability and noise responsiveness

around the specific types of noise sources that are tested. The basic components and

interrelationships of this model are illustrated in Figure 1.1.
1.11ntroduction: Objectives & Rationale 4

200

/' Source Level of

180

P Man-Made Noise

160

as Q..

:1 140

~

Q)

~

to 120

"0

100

Ambient Noise Level

80

60

0.001 0.01

/" Received Level of Man-Made Noise

~ vs. Distance from Source

Response Threshold of

Marine Mammal

Maximum I

Reaction I

Distance I

i-c>1

!

Maximum!

Detection I

Dist~~

0.1 1

Range (km)

10 100

FIGURE1.1. Components of a simple zone of acoustic influence model. See text for explanation.

The underwater noise received from an industrial source diminishes in level with increasing

distance from the source. The rate of transmission loss depends on water depth, bottom

conditions, ice conditions, and other factors. Hence, the slope of the received level vs. range curve

illustrated in the diagram can vary from place to place and time to time. The transmission loss

properties of a particular study area need to be studied during the season of interest to make

meaningful predictions of received noise levels as a function of range.

The level of the natural ambient noise has a major influence on the maximum distance to

which man-made noise can be detected. Man-made noise is normally detectable by an animal (or

hydrophone) if its received level exceeds the level of natural background noise at similar

frequencies. The range at which the received level of man-made noise diminishes below the

ambient noise level is, to a first approximation, the maximum radius of detectability (Fig. 1.1).

Beyond that distance, the man-made noise will be weaker than the natural background noise, and

is likely to be undetectable. Closer to the source of man-made noise, the received level of manmade noise will exceed the ambient noise level and the man-made noise is likely to be detectable.

Ambient noise levels vary naturally from day to day as a function of wind, waves, ice conditions,

calling rates by animals, and other factors. Day-to-day variations of ±10 dB or even ±20 dB are

not uncommon. A 10 or 20 dB change in the ambient level has a drastic change on the range at

which the received level of man-made noise falls below the ambient noise level, and thus on the

radius of detectability of the man-made noise. Hence, it is important to characterize the typical

ambient noise levels in the study area and season, the normal range of variation of these ambient

noise levels, and the factors affecting ambient noise levels in any particular circumstance.
Ll introduction: Objectives & Rationale 5

In most previous studies of the disturbance reactions of marine mammals, it has been found

that disturbance responses do not begin until the received level of man-made noise exceeds the

minimum detectable level by a substantial margin. This has been the case in studies of bowhead

whales, including the 1989-90 phases of this study. Thus, the received level of man-made noise

diminishes below the response threshold before it diminishes below the ambient noise level and

becomes inaudible (Fig. 1.1). To quantify the responsiveness of bowheads and white whales to

man-made noise, it is necessary to determine the response threshold level. This will not be a

constant. Whale responsiveness varies considerably. As a minimum, the average response threshold should be determined. If sample size allows, the noise levels to which various percentages of

the animals react should also be determined. The lower the response threshold, the greater the

distance at which the received level of man-made noise will diminish below that threshold.

One additional component of the zone of acoustic influence model is the source level of the

man-made noise. An increase in source level will shift the received level vs. range curve upward

by a corresponding amount. This shift will result in an increase in the distances at which the

recei ved level diminishes below the response threshold (= maximum reaction distance) and the

ambient noise level (= maximum detection distance).

In many cases the source level of the sounds emitted during a playback experiment is less

than that of the actual industrial activity being simulated, e.g. due to projector limitations. If the

source levels of the projector and the actual industrial activity are known, along with the other

components of the model (Fig. 1.1), then it is possible to estimate the maximum reaction and

detection distances around the actual industrial site based on the results collected near the

projector. This assumes that a given received level of sound from the projector causes the same

reaction as the same received level of sound from the actual industrial source. This assumption

is discussed as item (3) in §1.3, Assumptions and Limitations.

Thus, by considering the source level of man-made noise, its propagation loss, the ambient

noise level, and the response threshold of whales, a meaningful quantitative model of acoustic

influence can be developed, given various assumptions. This study aims to collect the types of

data needed to quantify, for particular situations, the conceptual model illustrated in Figure 1.1.

Section 6.4 of this report develops a preliminary model of this type for reactions of springmigrating bowheads to playbacks of icebreaker sound (Fig. 6.26, p. 314). Section 6.5 compares

it to a similar preliminary model concerning their reactions to steady drilling sound. The model

for drilling is based mainly on our 1989-90 work (Richardson et al. 1991a).

Specific 1991 and 1994 Objectives

The specific objectives of the 1989-90 and the 1991/94 phases of this project were similar,

except that a different type of industrial sound was to be used during sound playback experiments

in 1991/94. Specific objectives in 1989-90 were listed by Richardson etal, (l990a:17, 1991a:5).

As in 1989-90, physical acoustic measurements-including data on received sound levels near

whales, sound propagation loss, and ambient noise-were necessary to interpret the 1991/94

playback results. Because of concern about the effects of low-frequency industrial sound

components on bowheads, and the inability of a practical sound projector to reproduce those
1.1 Introduction: Objectives & Rationale 6

components, indirect methods of addressing the importance of low-frequency components were

again identified as objectives in 1991/94 (see specific objective 5, below). As a lower priority,

the reactions of bowhead and white whales to actual helicopter overflights again were to be determined if opportunities allowed.

The first of the specific objectives for the third and fourth years of the project involved work

during the winter, not the spring:

1. To record sounds from the SSDC caisson while it was drilling during winter conditions,

including infrasonic components, and to analyze those sounds to determine their levels,

spectral characteristics, and attenuation properties.

It had originally been thought that this effort might provide a suitable sound stimulus for use

during playbacks in years three and/or four of the study. However, it was later decided that a

recording of underwater sounds from the Canmar icebreaker Robert Lemeur while it was actively

breaking ice would be more appropriate for playbacks in 1991 and subsequently in 1994.2 The

icebreaker sounds used for the 1991/94 playbacks vary widely during the duration of the recording.

It was agreed that reactions of whales to these variable sounds, relative to their reactions to the

steady Karluk drilling platform sounds tested in the 1989-90 playbacks, would be of much interest.

Tests of the reactions of whales to icebreaker sounds had been identified by MMS as one of the

top priority objectives since the beginning of the project.

Only a few data on reactions of bowheads and white whales to icebreaker sounds were

obtained in 1991 (year 3) because of difficult weather and ice conditions. Therefore, specific

objectives for the spring work in 1994 (year 4) were essentially unchanged from those in the

spring of 1991:

2. To measure ambient noise levels and characteristics in leads and cracks along the spring

migration corridor of bowhead and white whales in the western Beaufort Sea, including

infrasonic components.

3. To measure and model transmission loss of underwater sound along that part of the spring

migration corridor, based on playbacks of (a) test tones at selected frequencies, and

(b) continuous industrial sounds. Infrasonic components cannot be projected, as

discussed on page 10, item (3).

2 Winter drilling from the icebound SSDC (Steel-Sided Drilling Caisson), which operated in the

Alaskan Beaufort Sea during the winters of 1990-91 and 1991-92, was considered a potentially suitable

source of sounds for playbacks. Drilling by the SSDC ceased early in December 1990, before the caisson

operator considered it practical for us to make the desired field measurements. Hence, this objective was

not met in 1990-91. In the absence of a suitable recording of drilling noise from an icebound caisson, it

was decided to use icebreaker sounds as the playback stimulus during the spring of 1991. The SSDC drilled

again at another site east of Barrow during the winter of 1991-92, and SSDC sounds were recorded in

January 1992. Thereafter, discussions were held with the project's Scientific Review Board, the Barrow

Whaling Captains' Association, and the Minerals Management Service to determine whether to use the

icebreaker or the SSDC sounds during the fourth spring season of playback work in 1994. It was agreed

to continue using the icebreaker sound.
1.1 Introduction: Objectives & Rationale 7

4. To measure the short-term behavioral responses of bowheads and (as possible) white

whales visible in open water areas along their spring migration corridor in the western

Beaufort Sea to underwater playbacks of variable icebreaker sounds. Infrasonic components cannot be projected.

5. To collect some of the data needed to assess the importance of the infrasonic components

of industrial noise. Specifically, (a) to measure ambient noise at infrasonic frequencies,

and (b) to determine whether bowhead calls contain infrasonic components (supplementing limited data from 1990). Also, based on the winter recordings of SSDC sounds

(specific objective 1), we were (c) to determine the frequencies, levels and attenuation

of the infrasonic components of drilling caisson sound.

6. To measure, on an opportunistic basis, the short-term behavioral responses of bowheads

and (as possible) white whales visible in open water areas along their spring migration

corridor in the western Beaufort Sea to actual helicopter overflights (supplementing

limited data from 1989-90).

7. To document, as opportunities allow, other aspects of the movements, behavior, basic

biology, disturbance responses and acoustic environment of bowhead and white whales

along their spring migration corridor in the western Beaufort Sea.

8. To assist and coordinate with other studies and local resource users to maxmuze

collection of needed data and to avoid interference with subsistence whaling and other

studies.

9. To analyze the data to test hypotheses concerning the effects of the icebreaker sounds and

helicopter overflights mentioned in (4) and (6) on (a) the movement patterns and (b) the

behavior of bowheads and white whales visible along their spring migration corridor in

the western Beaufort Sea.

Significant progress has been made toward meeting all nine objectives during the four spring

seasons. Several objectives-2, 3, Sa, 7 and 8-can be considered "achieved". Some data on the

responsiveness of spring-migrating bowheads and white whales to playbacks of steady drilling

noise and variable icebreaker noise were obtained, along with some data on responsiveness to

actual aircraft overflights (objectives 4, 6 and 9). However, better quantification of whale

responses to these activities than achieved in this study would be desirable. Similarly, objectives

1 and Sb,c were partially met, but additional data would be helpful.

1.2 Null and Alternate Hypotheses

MMS initially indicated that the primary purpose of the study was to test the following

generalized null hypothesis:

"Noises associated with offshore oil and gas production activities will not significantly

alter the migratory movements, spatial distribution, or other overt behavior of bowhead

whales during the spring migration in the eastern Chukchi and western Beaufort Seas."
1.2 Introduction: Hypotheses 8

MMS indicated that the secondary purpose of this study was to test a similar generalized null

hypothesis concerning white whales.

During the planning phase of this study, the hypotheses to be assessed were made more specific by adding more specific wording about four topics: (1) the types of oil and gas activities of

concern, (2) the criteria of whale behavior to be considered, (3) the geographic location and environmental circumstances of the tests, and (4) the fact that playback techniques were to be used to

simulate the noise from some production activities. Four null hypotheses of a more specific nature

were developed for each of the two whale species:

1. Playbacks of recorded noise from a bottom-founded platform (1989-90) or an icebreaker

working on ice (1991/94) will not (or alternatively will) significantly alter measures of

migration routes and spatial distribution of whales in the open water of nearshore lead

systems during the spring migration near Pt. Barrow, Alaska.

2. Playbacks of recorded noise from a bottom-founded platform (1989-90) or an icebreaker

working on ice (1991/94) will not (or alternatively will) significantly alter subtle aspects

of individual whale behavior in the open water of nearshore lead systems during the

spring migration near Pt. Barrow, Alaska.

3. Helicopter overflights will not (or alternatively will) significantly alter measures of

migration routes and spatial distribution of whales in the open water of nearshore lead

systems during the spring migration near Pt. Barrow, Alaska.

4. Helicopter overflights will not (or alternatively will) significantly alter subtle aspects of

individual whale behavior in the open water of nearshore lead systems during the spring

migration near Pt. Barrow, Alaska.

MMS indicated that greater emphasis should be placed on hypotheses (1) and (3) relating to effects

on migration routes and distribution, than to hypotheses (2) and (4), relating to subtle aspects of

the behavior of individual whales. However, we undertook to address hypotheses (2) and (4) as

well, at least for bowheads. Difficulties in observing some aspects of the individual behavior of

white whales from an aircraft circling at high altitude made it doubtful whether hypotheses (2) and

(4) could be assessed for white whales.

Hypotheses 1 and 2 have already been addressed with respect to the effects on bowheads of

playbacks of recorded continuous noise from a bottom-founded platform like Karluk (Richardson

et al. 1991a:226ff, 246ff). We concluded that, at least in the circumstances studied," Karluk

playbacks resulted in statistically significant small-scale changes in migration routes, spatial

distribution, and individual behavior. However, there was no evidence of migration blockage, and

we concluded that the observed effects were likely to be biologically non-significant. (By

biologically non-significant, we mean "Would be unlikely to affect the long-term well-being or

reproductive productivity of individuals or of the population. ") We have discussed elsewhere the

3 For whales visible in open water amidst the pack ice and in the seaward side of the nearshore lead

system during spring migration east of Pt. Barrow, Alaska.
1.2 Introduction: Hypotheses 9

numerous complications and limitations in applying these 1989-90 results from playback tests with

one type of industrial sound to the situation of an actual drilling platform operating in or near a

spring lead system (Richardson et al. 1991a:lOff, 261ff). One purpose of the 1991/94 tests with

a second and more variable type of industrial sound was to evaluate the generality of the 1989-90

results. Section 6.6 of this report addresses hypotheses 1 and 2 as regards reactions of springmigrating bowheads to playbacks of icebreaker noise.

Hypothesis I has also already been addressed with respect to the effects on white whales of

playbacks of the Karluk sounds (Richardson et al. 1991a:281). We concluded that, in the

circumstances studied (see footnote 2), playbacks of Karluk sounds had detectable but biologically

non-significant effects on migration routes and spatial distribution of white whales. Again, various

complications and limitations apply. Hypothesis 2, concerning effects on individual behavior,

could not be tested for Karluk drilling sounds vs. white whales. Section 7.3 of this report

addresses hypothesis 1 as regards reactions of spring-migrating white whales to playbacks of

icebreaker noise.

Hypotheses 3 and 4, relating to effects of helicopter overflights on bowheads and white

whales, were not formally tested during the 1989 or 1990 phases of the work. Relevant data were

obtained in 1989-90, but this work was given a low priority; the 1989-90 data were opportunistic.

Further relevant data of the same types were obtained in 1991 and 1994, and hypotheses 3 and 4

are evaluated in §6.7 and §7.4 of this report for bowheads and white whales, respectively.

1.3 Assumptions and Limitations

A number of assumptions had to be made in designing an experimental field study that would

address the general project objectives and the specific 1989-94 objectives. This section lists

several assumptions that may need to be made in using the results to predict the reactions of

whales to actual oil industry operations. Associated with most of these assumptions are various

limitations.

(1) The study area, located NE, ENE and E of Point Barrow, is assumed to be reasonably

representative of locations where bowheads and white whales migrating around northern Alaska

in spring might encounter oil industry activities.

Limitations: (a) The applicability of the 1989-94 results to the Chukchi Sea is not verified.

All 1989-90 data were necessarily obtained in the western Beaufort Sea. However, it is noteworthy that sound propagation conditions in the western Beaufort Sea during spring (this

study) are similar to those in the Chukchi Sea during late winter-early spring (Greene

1981)-see §4.3 (p. 115).

(b J Water depths at many 1989-94 study locations were greater than those where bottomfounded drilling and production platforms are likely to be constructed. Water depth affects

sound propagation.
1.3 Introduction: Assumptions & Limitations 10

(2) In order to draw conclusions about all whales migrating around northern Alaska in spring, it

would be necessary to assume that whales visible in leads and amidst the pack ice (i.e. those

studied here) react to underwater noise in about the same way as those that are not visible. The

accuracy of this assumption is unknown, so we restrict our discussion (and the title of the report)

to whales visible during spring migration.

Limitations: (a) Some whales migrate along the open nearshore lead, others through

extensive leads and cracks in the pack ice, and others through closed-lead or heavy pack ice

conditions. The likelihood of detecting whales differs greatly among these three habitats.

Also, once detected, the likelihood of successfully observing them for a prolonged period

differs greatly among habitats. Almost all 1989-94 data on reactions to noise were from

whales migrating through open pack ice or along an open nearshore.lead. We obtained no

data on whales migrating through closed lead conditions, and very few data on whales

traveling through heavy pack ice (but see 30 April 1989 results-Richardson et al.

1990a: 174).

(b) Even in open pack ice, some individual whales are likely to behave in ways that make

them more visible than other whales. Because observations are concentrated on the area

close to the noise source, whales that come close to the source are most likely to be seen.

This "observability bias" was a problem in 1989, when heavy ice hindered observations, and

1991, when aerial observations were not possible during playbacks, but it was less of a

problem in 1990 and 1994.

(c) Because of masking problems, acoustic monitoring and localization methods are not as

useful in a noise playback study as in a study of undisturbed whales.

(d) Relatively low numbers of whales were observable during playbacks in the area where

this study had to be conducted (§ 1.4, Study Area). Sample sizes during playbacks are shown

later in this report, in Tables 2.2, 6.1 and 6.2 (see §2.2 and §6.1).

(3) Underwater playback of recorded underwater sounds from an industrial operation is assumed

to be a useful method for evaluating the likely reactions of whales to actual industrial operations

of corresponding types.

Limitations: (a) Underwater playback techniques simulate the sounds emitted by an

industrial site, but exclude other stimuli to which whales may be sensitive, e.g. sight, smell,

effects of physical presence on water flow. This is an advantage in the sense that it allows

an assessment of the effects of noise per se, but a disadvantage in that the playback does not

simulate all aspects of the actual industrial operation.

(b) The types of sounds available for use in this study were limited. ~ It is uncertain how

closely the Karluk drilling sound and the Robert Lemeur icebreaker sound resemble sounds

that would emanate from future oil industry activities in or near spring lead systems. To

date, neither drilling nor production have been done in or near spring lead systems off northern Alaska, so it has been impossible to record or study the sounds emitted by such an operation. ~ Also, icebreaker sound is unlikely to be commonly associated with future oil
1.3 Introduction: Assumptions & Limitations 11

production activities in or near leads used by migrating whales in spring. ~ However, the

steady, low-frequency drilling sounds and the variable, broader-bandwidth icebreaker sounds

used during the playbacks represent a wide range of noise characteristics. Whales may react

in a similar way regardless of the specific type of industrial noise used for playbacks,

provided that it is continuous (Malme et al. 1984; Richardson et al. 1991b, in press).

Nonetheless, any extrapolation of the 1989-94 playback results to situations involving other

types of industrial sounds would be speculative.

(c) Sounds emitted during playbacks do not simulate the full range of sounds that an actual

industrial site would emit over time. In 1989-90, we repeatedly projected a 3-minute

segment of sounds emitted by the Karluk drillsite while it was drilling, simulating a

continuous drilling operation with no interruptions. There was no attempt to simulate the

noise from other activities that occur intermittently on a drillrig. In 1991/94, we repeatedly

projected a 14.3-min segment of sounds emitted by one icebreaker operating in a particular

type of ice conditions at one site. Icebreaker noise varies somewhat depending on the vessel

and the circumstances of operation.

(d) Sounds emitted during playbacks do not simulate the full frequency range of sound and

vibration emitted by an industrial site. ~ Procedures used in 1989-90 provided a reasonable

simulation of the components of Karluk sound within the 50 to 12,000 Hz band. Procedures

used during most playbacks in 1991/94 provided a reasonable simulation of the components

of icebreaker sound within the 40 to 6300 Hz bands, and probably up to 12,000 Hz. To the

human ear, the projected Karluk and icebreaker sounds, as received by hydrophone or sonobuoy 100 m to 1+ km from the projector(s), strongly resembled the original recordings of

Karluk and icebreaker sounds. ~ However, the playback systems used in 1989-90 and 1991/

94 underrepresented the components at frequencies below, respectively, 80 Hz and 40 Hz,

and especially the components below, respectively, 63 Hz and 32 Hz (see Richardson et al.

1991a:88 for 1989-90, and §4.4 for 1991/94). ~ White whales are not sensitive to these low

frequency components unless their levels are very high (§7.2). Hence, the inability to project

them was not a problem during playback tests on white whales. However, bowhead whales

are expected to be sensitive to these low frequency components. ~ In summer, bowheads

seem at least as sensitive to playbacks of drillship and dredge sounds as to actual drillships

and dredges (Richardson et al. 1990b), suggesting that playbacks can provide relevant data.

(e) The rate of change of received sound level with increasing distance (sound gradient) may

be steep near a playback site, potentially causing stronger reactions than with shallower gradients (Ellison and Weixel 1994a,b). When the playback source level is less than that of the

human activity being simulated, a given received sound level will occur closer to the playback site than to the actual source. The gradient usually diminishes with increasing range.

Whales approaching through a steep gradient close to a playback site would be exposed to

a more rapidly increasing sound level than would those swimming at the same speed through

an equally strong but shallower gradient farther from the actual source. Whales often seem

to be more responsive to rapidly changing sound (Richardson et al. in press). If so, a given

sound level may have more effect on traveling whales when it comes from a "weak" source

nearby (e.g. playback) as compared with a strong source farther away (e.g. icebreaker). If
1.3 Introduction: Assumptions & Limitations 12

so, the reaction threshold to the full-scale noise source would be less than that estimated by

playbacks simulating that source. Differences in the vertical position of the playback vs.

actual sources, and in their acoustic coupling into the bottom, may also affect the propagation and received level of the sound.

(4) It is assumed that the presence of the observers did not bias the results significantly. Three

potential problems existed (see below). However, the potential for bias was limited, and

comparison of playback vs. control data provided meaningful data.

Limitations: (a) Whales are known to react to aircraft overflights in some situations; many

of the 1989-90 and 1994 observations were obtained from an aircraft circling above the

whales. However, studies in summer and autumn, corroborated in this spring study (§6.7),

indicate that an observation aircraft circling over bowheads very rarely causes any overt

disturbance reaction provided that it. remains at an altitude of at least 460 m (1500 ft) at a

low power setting, and avoids passing directly over the whales (Richardson and Malme

1993). Opportunistic observations suggest that white whales also tolerate aircraft at that

height (reviewed by Richardson et al. 1991b, in press; this study, §7.4). Given this, and the

fact that we excluded behavioral observations from periods when the aircraft was below

460 m, the presence of the aircraft is not considered to be a significant problem.

(b) The projected drill site noise came from a small camp located on the edge of an ice pan.

This camp, including the ice-based personnel, may have been visible to some of the closer

whales while they were at the surface. However, reactions to visual cues would be

minimized by the small size of the ice-based operation, the limitations of vision through the

air-water interface, and the frequent presence of visual obstructions (ice floes) between the

camp and the whales. In 1991/94, personnel at the ice camp wore long, white snow-shirts

to reduce their visual conspicuousness. Also, interpretation problems arising from any nonacoustic effects that do exist can be minimized by comparing behavior of whales passing the

camp when the projector is operating vs. silent.

(c) It was necessary to use a small gasoline-powered generator at the ice camp during

playbacks. For consistency, the generator was also operated during most control periods,

whether or not it was needed as a power source. The generator emitted underwater noise,

which was detectable underwater within a few hundred meters of the campsite during control

(quiet) periods in 1989-90. There may have been some short-range responses to acoustic (or

non-acoustic) cues from the camp itself during 1989-90. However, these cannot explain the

more pronounced responses observed during projection of drilling noise than when the

projector was off. In 1991 and 1994, underwater noise from the generator was greatly

reduced through use of a suspension system (§4.6).

(5) It is assumed that disturbance of whales is evident by visual observations of their distribution

and movements near the noise source, and (for bowheads) visual observations of the details of

their individual behaviors. Previous studies have shown that bowhead and white whales often

react in visually observable ways when subjected to strong noise from actual or simulated oil

industry operations.
1.3 Introduction: Assumptions & Limitations 13

Limitations: (a) Even the most conspicuous whales are visible for only a fraction of the

time-typically less than 20% in migrating bowheads. Whales migrating past a disturbance

source are often below the water and invisible when at their closest point of approach. During periods while whales are underwater or under ice, it usually is not possible to observe

them directly. However, some aspects of their movements underwater or under ice often can

be inferred from their diving and re-surfacing positions, headings, and times. Also, migrating whales occasionally travel at sufficiently shallow depths such that aerial observers can

see them below the surface throughout part or all of a dive in open water. This was common

on some days in 1990, including the playbacks on 11, 13 and 16 May 1990.

(b) The calling rates of whales could not be compared under playback vs. control conditions.

Some other studies of whales have suggested, often based on equivocal evidence, that call

rates diminish in the presence of man-made noise. This could not be studied here because

the majority of the calls heard in the absence of projected noise would be undetectable due

to masking even if they were present during playbacks.

(c) No direct measure of physiological stress is possible during field observations of passing

whales. However, in the case of bowheads, surfacing, respiration and diving cycles were

monitored quantitatively. These variables may provide indirect and limited indications of

stress. These variables could not be observed reliably for white whales, so we had no similar

indicator for that species.

(d) No data of any type could be collected on any whales that avoided detection, e.g. by

remaining amidst heavy ice. This was not considered to be a significant problem in 1990

or 1994 (see limitation 2b, above).

(e) This study concerns the short-term reactions of migrating whales, mainly to two sources

of man-made noise. The long-term consequences with respect to the well-being of

individuals and the population are not addressed directly.

(6) To perform meaningful tests of hypotheses about disturbance effects on bowheads and belugas,

it is necessary to have adequate data. The lack of a statistically significant disturbance effect does

not prove the absence of a disturbance effect. A statistical power analysis will indicate how large

a disturbance effect might have occurred without being detectable statistically.

Limitations: Because of logistical constraints, sample sizes for most types of disturbance

observations in this study are small. Nonetheless, playbacks of both drilling and icebreaker

sound were shown to cause statistically significant effects on bowhead behavior. Thus, the

limited sample sizes and limited power are not central issues in determining whether the null

hypotheses of "no disturbance effect from playbacks" can be rejected. The limited sample

sizes and limited power are, however, an issue in evaluating the threshold distances and

threshold sound levels at which disturbance become detectable. Section 6.3 (p. 290-295)

includes analyses of the power of this study to detect whether disturbance effects from icebreaker playbacks occurred at various received sound levels and icebreaker-to-ambient ratios.
1.3 Introduction: Assumptions & Limitations 14

(7) Evaluations of potential disturbance radius often assume that ambient noise levels and propagation loss rates are average, or are equal to those at a particular date and time. Also, it is often

assumed that a given human activity is representative of other activities of the same general type,

e.g., that icebreaking by the specific icebreaker whose sounds were used in the 1991 and 1994

playbacks is representative of icebreakers in general.

Limitations: (a) There is much variability in ambient noise levels and propagation loss rates

in leads and below pack ice during spring. Therefore, a given received sound level or signalto-ambient ratio may occur at widely differing distances from a particular noise source,

depending on physical factors such as ice cover, water depth, wind speed, bottom conditions,

etc. If marine mammals begin to react at a given received sound level or a given signal-toambient ratio, reaction radii are expected to vary drastically depending on these physical

factors. This variability is added to the variability in expected reaction radii caused by

differences in the responsiveness of different animals. This topic is discussed in §6.4.

(b) There can be differences in the levels and spectral characteristics of the sounds emitted

by different human activities of a given class, e.g., different icebreakers. Robert Lemeur,

the icebreaking supply ship whose sounds were used in the 1991 and 1994 playbacks, is a

relatively low-powered icebreaker (9600 bhp or 7.2 MW).

1.4 Study Area

In choosing a study area, it was necessary to compromise between choosing (a) an area

where many whales would be encountered in situations where playbacks and observations were

practical, and (b) an area where project activities would not interfere (or be perceived to interfere)

with native subsistence whaling or other scientific studies.

Local Concerns

This study could not have been conducted if it had been opposed by local organizations such

as the North Slope Borough (NSB), the Alaska Eskimo Whaling Commission (AEWC), or the

Barrow Whaling Captains' Association (BWCA). Strong opposition would have occurred if the

proposed study site were southwest of the northeastern most of the spring whaling communities

(Barrow). Whalers would have been strongly concerned about a proposed disturbance experiment

anywhere "upstream" (south or southwest) of any whaling site. They would have been concerned

that such a study might block the passage of some whales, or interfere with the subsequent timing

or route of the whale migration past the whaling community. For the same reasons, the study area

could not have been near Barrow itself.

In addition, for almost two decades there has been a spring bowhead census near Pt. Barrow

in certain years. In 1988, a very intensive census effort was conducted, and.in 1989 a scaled-down

census effort was planned for late April and May. A minor effort was planned again for 1990 but

no work was actually conducted in 1990 or 1991. A full-scale census was attempted in 1992

(unsuccessful due to ice conditions) and again in 1993 (successful). This census at Barrow has

been very important to the local people, to U.S. regulatory agencies, and to the International
i.4 introduction: Study Area 15

Whaling Commission. The census and data analysis procedures depend on the consistent

migratory behavior of the whales. Disturbance-related changes in swimming speeds, average distance from the ice edge, or whale headings could affect the census results. Also, if background

noise levels at acoustic monitoring sites were elevated because industrial sounds were being

projected into the water nearby, the range of effective acoustic monitoring (and especially of call

localization) would be reduced. Any real or potential interference with the census was

unacceptable to a variety of local, national, and international interests.

Given these considerations, the project would not have received local acceptance if the

proposed field site were anywhere near or southwest of Barrow. Locations well to the east of Pt.

Barrow appeared to be the only locations that might be acceptable to local people and to agencies

concerned about the whale census.

Specific Study Locations

As part of the planning process for this study, Miller (1989) reviewed the available

information on ice conditions and on whale distribution in the area east and northeast of Pt.

Barrow during spring. Results of this review are summarized in Richardson et al. (1990a:2-12).

Logistically, the most advantageous location for the study area and ice camp was expected to be

along the landfast ice edge where a semi-permanent camp might be established. However, the

literature reviewed by Miller (1989) indicated that, in most years, few whales are found along the

landfast ice edge more than about 35 km east of Barrow. This was confirmed by our 1989-91

studies, although 1994 was an exception (§5.l). Farther east, most whales in most years move

offshore into the seaward side of the nearshore lead or into the pack ice beyond the nearshore lead.

Thus, during most if not all years, the best location for the sound projector would be along

the landfast ice edge within 35 km of Pt. Barrow. Given that such a site might be too close to

whaling and census areas, LGL recognized from the start of the planning process that the projector

might have to be set up on pack ice northeast of Pt. Barrow. However, the whale migration

corridor widens as the whales travel east of Pt. Barrow, reducing the numbers of whales expected

to pass close to any given site. Also, logistic support becomes more difficult with increasing

distance to the east. Dedicated helicopter support was essential for work on the pack ice.

Given the above, it was desirable to work as close to Barrow as possible without causing real

or perceived interference to whaling and to the census. The most appropriate distance east of

Barrow was determined through an acoustic modeling study (Mal me et al. 1989; included as

p.261-284 in Richardson et al. 1990a) and consultation with local Barrow organizations,

indi viduals, and scientific investigators.

In 1989, to provide convincing "safety" margins and to avoid opposition from the various

concerned groups, we selected an area about 60 km (32 n.mi.) NE or ENE of Pt. Barrow as the

approximate location for the industrial noise playback experiments. We also undertook not to fly

within 10 km of the census or whaling sites (unless these were within 10 km of Barrow's airport).

The specific locations of the main ice-based and aerial work in 1989 and subsequent years of the

study are mapped later, in §3.2 (Fig. 3.2-3.9) and §5.2 (Fig. 5.19, 5.21).
The 1989 study showed that we could conduct the work without interfering with whaling.

Therefore, in 1990 and 1991, after consultation with the BWCA, AEWC and NSB, it was agreed

that we could work closer to Barrow. In 1990, it was agreed that our projector sites would be at

least 15 n.mi. (28 km) northeast or east of the northeastern most whaling camp. At any times when

the bowhead census crew was working on the ice, we undertook to keep the projector at least 20

n.mi. (37 km) away. In addition, we again undertook not to fly within 10 km of the whaling or

census sites except as necessary to take off or land at Barrow. The reduced distance limit in 1990-

91 proved to be very helpful in providing more flexibility in choice of projector sites.

In 1991, spring whaling at Barrow ended in mid-May, and there was no ice-based whale

census. During consultations in mid-May, representatives of the BWCA, AEWC and NSB agreed

that we could work close to Barrow, where the whale migration corridor seems to be more

concentrated and consistent. Starting on 17 May 1991, we began to conduct aerial surveys west

and north of Barrow as well as in our usual study area farther to the northeast. On 17 and 18 May,

the sound projector was set up on the landfast ice closer to Pt. Barrow than we had worked before.

The sound playback results from 17 May were the most valuable playback results obtained in

1991. On other dates in mid- and late May 1991, experimental opportunities were better on the

pack ice, and we worked there rather than on the landfast ice. However, we continued to work

closer to Barrow than had been possible previously.

In 1992 and 1993, the Barrow Whaling Captains' Association requested that LGL and MMS

not undertake this study in the usual area northeast of Barrow because of the possibility that it

might interfere with the full-scale bowhead census efforts planned for those years. In the absence

of any logistically-practical alternative study area, this study was deferred from 1992 to 1993 and

then again from 1993 to 1994.

In 1994, when no census work was planned, the BWCA indicated that it had no objection to

resumption of the study in the usual area northeast of Barrow. The agreed-upon guidelines were

the same as for 1990 and 1991: projector 15 n.mi. beyond northeasternmost whaling camp; no

flying within 5 n.mi. of whaling camps.

In 1994, bowheads migrating through the area up to 15 May often traveled close tothe landfast ice edge even in areas as much as 70 km east of Pt. Barrow where, in 1989-91, they tended

to be at least a few kilometers north of the landfast ice edge. This difference was related to the

fact that, until 15 May in 1994, the landfast ice in the eastern part of the study area extended

unusually far offshore (§3.1, Ice and Weather Conditions). This situation allowed us to conduct

playback work from the landfast ice edge 40-70 km ENE of Pt. Barrow during the 7-14 May 1994

period. However, because of the precarious nature of the ice there, it was again necessary to go

to that area on a daily basis by helicopter rather than to establish a longer-term camp on the

landfast ice edge. The landfast ice in that area began to break up on 15 May 1994. Thereafter,

the main bowhead migration corridor was far enough north of the new landfast ice edge to require

that ice-based work be done from the pack ice, as in previous years.
1.5 Introduction: Decibel Scales 17

1.5 Decibel Scales

Sound levels are expressed in decibels in this report. Decibels are logarithmic units. Decibel

scales cause considerable confusion and misunderstanding among acousticians and nonacousticians alike, but serve a useful purpose. The range of sound levels perceived by human

beings extends from the molecular noise of air molecules colliding on the low side to the roar of

jet engines at close range. The ratio of sound pressures thus spanned is about 1,000,000: 1. A

linear pressure scale to portray such a range of sound pressures would be cumbersome, and sounds

at low and intermediate levels (e.g., molecular noise and typewriter noise) would seem very similar

on this scale. A logarithmic scale for pressures solves this problem.

Human beings respond to sound pressures on a logarithmic basis as well. The minimum

change in sound level perceived by humans is on the order of 1 dB. In the middle of the frequency and intensity ranges for human hearing, a sound pressure increase of 10 dB is perceived by

humans as an apparent doubling of loudness. Thus, there is more than one reason for using a

logarithmic scale.

A logarithmic scale has to be "anchored" by some reference unit of pressure. The reference

unit now used to describe underwater sounds is the micropascal. Thus, decibels on a sound pressure level scale are said to be referred to 1 micropascal, or "dB re 1 IlPa". Other reference units

are sometimes used, including 20 IlPa (=0.0002 ubar) for airborne sounds, and 1 ubar (0.1 Pa) in

much of the older underwater acoustics literature. Table 1.1 summarizes the interrelationships of

various scales for acoustic measurements, and shows the levels of some airborne and underwater

sounds on these measurement scales. More details, including information about decibel scales as

used to describe sound pressure spectral density and sound energy, are given in Greene (in press).
TABLE 1.1. Interrelationships of various scales for acoustic measurements; standard reference units are underlined"

dB re

Dynesl dB re dB re 0.0002 Typical airborne sounds Typical underwater sounds

Pascals cm2 Bars 1 flPa 1 ubar ubar and human thresholds and marine mammal thresholds

1,000,000 107

10 240 140 214

2 kg high explosive, 100 m

100,000 1,000,000 1 220 120 194 Beluga echolocation call, 1 m

10,000 100,000 .1 200 100 174 Airgun array, 100 m

Some military guns

1,000 10,000 .01 180 80 154

Sonic booms

100 1,000 .001 160 60 134 Large ship, 100 m

10 100 100fl 140 40 114 Discomfort threshold, 1 kHz Fin whale call, 100 m

500 m from jet airliner

1 10 10 fl 120 20 94

.1 1 !J! 100 !

74 15 m from auto, 55 km/h Beluga threshold, 1 kHz

Speech in noise, 1 m Ambient, SS4, Va-OB @ 1 kHzb

.01 .1 .1 fl 80 -20 54 Speech in quiet, 1 m Seal threshold, 1 kHz

.001 .01 .01 fl 60 -40 34 Ambient, SSO, Va-OB @ 1 kHz

.0001 .001 .001 fl 40 -60 14 Beluga threshold, 30 kHz

20 fl 200 fl .0002 H 26 -74 J! Open ear threshold, 1 kHz

IOfl 100fl .0001 fl 20 -80 -6 Open ear threshold, 4 kHz

!J! 10 fl .00001 fl 0 -100 -26

8 From Greene (in press); airborne portions adapted from Kryter (1985:8).

b Ambient noise in Va-octave band centered at 1 kHz under sea state 4 conditions.

00-
2.1 Methods: Physical Acoustics 19

2. METHODS4

2.1 Physical Acoustics Methods

The specific 1991 and 1994 field objectives that concerned physical acoustics, in whole or

in part, were as follows:

1. Ambient Noise: To measure ambient noise levels and characteristics in leads.and.cracks

along the spring migration corridor of bowhead and white whales in the western Beaufort

Sea, including infrasonic components.

2. Transmission Loss: To measure and model underwater sound transmission loss along the

study portion of the spring migration corridor, based on transmissions of (a) test tones

at selected frequencies between 20 Hz and 10 kHz, and (b) steady drilling platform

sounds (Karluk) and variable icebreaking sounds (Robert Lemeur).

3. Playback Experiments: To measure the short-term behavioral responses of bowheads and

6(as possible) white whales visible in open water areas along their spring migration

corridor in the western Beaufort Sea to underwater playbacks of variable icebreaking

(Robert Lemeur) sounds.

4. Infrasonic Sounds: To collect some of the data needed to assess the importance of the

infrasonic components of industrial noise. Specifically, (a) to measure ambient noise at

infrasonic frequencies (less than 20 Hz), and (b) to determine whether bowhead calls

contain infrasonic components (supplementing limited data from 1990).

An additional objective associated with the 1991 effort was to obtain and analyze recordings

of the SSDC during winter drilling operations east of Pt. Barrow (Appendix H). The sounds associated with the SSDC were considered for use during playback experiments.

This section begins with a general description of the approach and equipment used in the

acoustic work. Then there are sections describing specific methods applicable to each of the above

objectives. Emphasis is given to acoustical methods applied in 1991 and 1994, but significantlydifferent procedures used in 1989-90 are mentioned as well. Methods applied in 1989 and 1990

were described in more detail by Richardson et al. (1990a, 1991a).

General Approach and Equipment

Acoustical work in 1991 and 1994 generally followed the methods of 1989-90. The work

occurred at two types of places: (1) ice camps located along the edges of ice pans or (less often)

the landfast ice edge, and (2) aboard the project's chartered Twin Otter fixed-wing aircraft:

4 By W.J. Richardson, C.R. Greene Jr., and W.R. Koski
2.1 Methods: Physical Acoustics 20

~ The ice-based personnel were transported by helicopter to a suitable place on the ice on

a daily basis. Weather and ice conditions permitting, personnel typically remained on the

ice for 8 to 12 hours. On most days, the ice-based crew attempted to perform either a

transmission loss test or a playback experiment, as well as measuring ambient noise and

observing whales.

~ The aircraft-based crew dropped sonobuoys to measure sounds received near whales, as

well as observing and photographing whales (§2.2, Whale Surveys and Observations).

At a minimum, the ice camps were occupied by an acoustician, two field biologists, and an

Eskimo guide from Barrow. A second acoustician was present occasionally in 1991 and frequently

in 1994. The biologists observed marine mammals and operated a theodolite to measure azimuth

and depression angles to whales and seals. Distances were computed from depression angles and

the measured height of the theodolite above the sea. Ice camps were established by flights from

Barrow, AK, in a NOAA Bell 212 helicopter dedicated to support the field work.

The major types of equipment used at and near the ice camp for acoustical aspects of the

work were as follows:

~ sound projector(s) for use in both playbacks and transmission loss tests, with tape

recorder and amplifier(s) to play the recorded sounds;

~ generator to power this and other equipment;

~ hydrophone(s) deployed near the projector(s) to monitor the projected or ambient sounds,

and tape recorder to record these sounds;

~ monitor sonobuoy deployed -1 km from the ice camp to monitor sounds received at that

distance.

Also, sonobuoys were air-dropped from the project's Twin Otter aircraft to record projected and

ambient sounds received near whales. During transmission loss experiments, a hydrophone and

tape recorder were taken to various receiving stations to record the sounds received at different

distances from the sound projectors. The specific equipment varied from year to year, as

summarized in Table 2.1.

Sound Projectors and Signal Source.- To project sounds for transmission loss and playback

experiments, a davit installed in the ice about 1 m from the edge of the ice floe supported various

sound projectors and one or more monitor hydrophones lowered over the edge. The sound

projectors were at depth 18 m (60 ft) except during a transmission loss test on 30 April 1989,

when projector depth was 9 m.

In 1989 and 1990, a U.S. Navy model J-11 wideband electrodynamic acoustic transducer

served as the sound projector. The J-l1 is limited to a maximum sound pressure source level of

about 166 dB re 1 IlPa-m. It is rated as effective at 20-12,000 Hz, but its output diminishes at

frequencies below about 100 Hz, becoming negligible at frequencies below 50 Hz. The J-ll was

powered by a Bogen model MT250 amplifier rated at 250 W. The signal source in 1989-90 was

an audio cassette recorder (Table 2.1 A) with servo-controlled capstan for accurate speed control.

Playback frequency response was flat ±5 dB from 20 to 10,000 Hz. Further details are given in

Richardson et al. (l990a, 1991a).
TABLE 2.l. Equipment used for acoustic work in each year of the project.

1989 1990 1991 1994

A. Projectors and Signal Source

Projector(s) J-11 J-11 J-13 & F-40 Argotec 220 & J-11

Amplifier( s) Bogen MT250 Bogen MT250 Bogen MT250 Techron 7560 &

Techron 7550

Source tape recorder Marantz PMD-430 cas. Sony TC-D5M cas. Sony TCD-D3 DAT Sony TCD-D3 DAT

Generator Honda 2.2kW Homelite 2.2 kW Homelite 2.2 kW Kubota 5 kW

EH2500HD EH2500HD (most days)

B. Sound Monitoring on Ice

Monitor hydrophone near proj. ITC 1042 ITC 1042 ITC 1042 ITC 1042

Ambient & TL signals @ depth ITC 6050C @ 18 m ITC 6050C @ 18 m ITC 6050C @ 18 m ITC 6050C @ 18 m

Infrasonic ambient @ depth ITC 1032 @ 18 m ITC 1032 @ 18 m

Monitor sonobuoy at approx. AN/SSQ-41B @ 9 m -41B@9m -57A@18m -57A@ 18m

1 km range from camp or-57A@12m or-57A@14m (usually)

Sonobuoy receiver L-tronics LS44 Kenwood RZ-l (mod.) Kenwood RZ-l (mod.) L-tronics LS44

Tape recorders

Playback monitor @ camp * & Sony TC-D5M cas. * & Marantz PMD-430 cas. * & TEACRD-I0ITDAT * & TEAC RD-I01T DAT

Ambient @ camp Sony TC-D5M cas. TEAC RD-I0lT DAT TEAC RD-I0lT DAT TEAC RD-I0IT DAT

TL monitor @ camp * & Marantz PMD-430 cas. * & Sony TC-D5M cas. * & Sony TCD-D7 DAT

TL & Amb. @ TL receive sites Sony TC-D5M cas. TEAC RD-I0lT DAT TEAC RD-lOlT DAT TEAC RD-I0IT DAT

C. Sound Monitoring from Twin Otter

Sonobuoys AN/SSQ-57 A @ 12 m -57A @ 14 or 18 m -57A @ 14 or 18 m -57A @ 14 or 18 m

~•....

or-41B@18m or -53B@27m or -53B@27m ~

Sonobuoy '" receivers 2xRegency MX5000 2xRegency MX5000 2x Kenwood RZ-l (mod.) 3x Kenwood RZ-l (rnod.) So

<:l

(modified) (modified) & 1 ICOM RI00 (mod.) ~

Tape recorder Marantz PMD-430 cas. TEAC RD-I01T DAT TEAC RD-I0lT DAT TEAC RD-I0IT DAT "1:l

;:,-

'<'" D. Position Finding ri'

~

Ice camp Si-Tex A-310 SatNav Si-Tex A-310 SatNav Magellan OEM GPS Magellan OEM GPS ».

Bell 212 helicopter GNS-500VLF GNS-500VLF GPS & VLF GPS& VLF

t")

<:l

l::

Twin Otter aircraft GNS-500A VLF GNS-500A VLF Wulfsburg GPS/VLF 2xGPS& VLF '"..•

ri'

'"

"* An oscilloscope and voltmeter were used to monitor projector output during each year. N

-
In 1991 a U.S. Navy model J-13 electrodynamic sound projector served to project the low

frequency sounds and a model F-40 ceramic spherical transducer was used for frequencies above

about 1000 Hz. A crossover network set for 1 kHz was used to divide the sound between low and

high frequencies. Each projector was driven separately with signals from one 250-W Bogen model

MT250 power amplifier. In use, the J-13/F-40 combination was disappointing, providing source

levels on the order of 164-167 dB re 1 IlPa-m, about the same as obtained with the J-11 during

1989-90. The signal source in 1991 was a Sony TCD-D3 DAT Walkman, with frequency response

flat ±3 dB from 6 Hz to 23 kHz.

In 1994 an Argotec model 220 low frequency projector was obtained, along with two model

219 transducers for mid-range frequencies, and an F-56 for high frequencies. Separate power

amplifiers were used for each of the three frequency ranges, and frequency equalizers were used

to divide the DAT recorder output signal into three bands for driving the power amplifiers. The

model 220, having pistons at each end, required two amplifiers, although their inputs were the

same. There were thus four power amplifiers: two 1600-W Techron model 7560 amplifiers for

the Argotec 220, and two 350- W Techron model 7550 amplifiers, one for the mid- and one for the

high frequencies. The system was designed to provide sound pressure source levels up to 180 dB

at the low frequencies and to 170 dB at the higher frequencies. This frequency-related difference

in maximum potential source level was acceptable because the playback stimulus sounds were at

least 10 dB lower at the mid- and high frequencies than at the lower frequencies.

The 1994 projector system was tested at Argotec and at the Navy's Underwater Sound

Reference Detachment, Orlando, FL, before our 1994 field season. However, operational problems

with the projectors at the ice camps led to use of only one end of the model 220 for low

frequencies (up to 500 Hz) and a J-ll for frequencies from 500 Hz upward. These were powered

by two of the Techron amplifiers, one model 7560 and one model 7550. Furthermore, during three

playback days in 1994 (3, 9 and 17 May), only the J-11 was operational. Source levels varied

from day to day, and typically were comparable to those obtained in previous years (§4.4,

Playback Fidelity). The signal source in 1994 was a Sony TCD-D3 DAT Walkman.

Generator.- The sound projectors and other equipment were powered by a small gasolineengine generator (Table 2.1A). In 1989-90 the generator was placed directly on the ice. In 1991

and 1994, it was suspended by bungee cords from a frame constructed of PVC pipe. The frame

stood on the ice, but the bungee cords isolated the generator from the frame and ice. In all years,

the generator was placed about 20 m back from the ice edge where the projector was suspended.

Sound Monitoring at Ice Camp.-Whenever the projectors were deployed during any of the

four years, an International Transducer Corporation (ITC) model 1042 spherical hydrophone was

used to monitor the projected signals. This was secured to the lowering line at a measured

position 1.6-3 m above the projector face (1990-94) or was positioned 0.8 m in front of the

projector (1989). An ITC model 6050C wideband low-noise hydrophone was also lowered to

depth 18 m over the edge of the floe, usually 3-5 m from the sound projector. The hydrophone

cable was faired with 15-cm long nylon fibers to minimize cable strum. This hydrophone was used

to record ambient noise when the projectors were silent, and during projector operations in 1994

it served as a second monitor of the projected sounds.
2.1 Methods: Physical Acoustics 23

During almost all days of ice-based work, a sonobuoy was deployed -1 km from the ice

camp to serve as a far-field monitor of projected sounds (Table 2.1B). This buoy was attached to

an ice edge to minimize its drift relative to the ice camp, with the exception of 17 May 1994 when

the sonobuoy drifted freely. In 1991 and 1994, sonobuoy position at installation time was

determined by the helicopter's GPS navigation system. The buoy radio signal was received at the

ice camp with a sonobuoy receiver (Table 2.1B). When the sonobu~y and ice camp were on different ice pans, the distance from ice camp to sonobuoy was, when possible, determined periodically

through the day by theodolite readings taken from the ice camp and/or by crosscorrelation of the

sounds recorded near the projector and at the sonobuoy. This monitor sonobuoy, along with a

hydrophone at the ice camp, provided ambient noise data at times when there was no playback.

To document the sounds being projected during playbacks and transmission loss tests, a tape

recorder was used to record the signals from the ITC 1042 monitor hydrophone and, during

playbacks, the monitor sonobuoy. During playbacks in 1991 and 1994, we also recorded, on the

same recorder, the signals being fed to the projector amplifier(s) and the signals received at the

ITC 6050C hydrophone a few meters from the projector(s). Equipment and procedures varied

somewhat, depending on the year and whether a playback or a TL test was in progress (Table

2.1B). This acoustic monitoring is described further in later subsections on methods for

"Transmission Loss" and "Playback Experiments".

Sound Monitoring Aboard Aircraft.-Acoustics work from the Twin Otter was based on airdropping sonobuoys at locations near whales or where whales were likely to pass. The aircraft had

an antenna, preamplifier, two or four calibrated sonobuoy radio receivers (depending on year), and

a TEAC four-channel DAT recorder (1990-94) or a calibrated cassette recorder (1989; Table 2.1C).

The sonobuoys were mainly of two types: Sparton AN/SSQ-57 A omnidirectional, calibrated

wideband (10-20,000 Hz) sonobuoys, and AN/SSQ-53B DIFAR (DIrectional low Frequency and

Recording) 10-2400 Hz sonobuoys. Calibrations were extrapolated down to 8 Hz to permit

measuring the sound level in 1/3-octave bands centered down to 10 Hz. Hydrophone depth was

18 m for most -57A buoys (a few had been customized for 14-m or, in 1989, 12-m depth for use

in shallow areas) and 27 m for the -53B buoys.

Sonobuoy position was determined from the aircraft navigation system (GPS in 1991/94;

VLF in 1989-90; Table 2.1D) at launch and impact time, and (when the sonobuoy was visible from

the air) by fly overs at later times. Also, we sometimes flew directly from the ice camp to a

sonobuoy (or the reverse) to take GPS or VLF readings in quick succession at the two locations.

Generally, the signal from the ice camp's monitor sonobuoy located -1 km from the projector(s)

was recorded on one channel of the same recorder that was recording the signals from aircraftdeployed sonobuoys. This allowed us to use crosscorrelation methods to determine relative

distances of two sonobuoys from the projector based on differences in arrival times of projected

sounds.

The following sections describing specific acoustic tasks include more information about

specific equipment and procedures applied during those types of work.
2.1 Methods: Physical Acoustics 24

Ambient Noise

Field Procedures.-Ambient noise was recorded from the 6050C hydrophone at the ice camps

and, during transmission loss (TL) tests, at TL receiving sites. Standard practice was to record

ambient noise before and after projector operation at each ice camp. During TL tests, ambient

noise was recorded at the various receiving stations prior to transmission of the test signals.

Hydrophone depth was 18 m in all of these cases. Ambient noise was also recorded from the

monitor sonobuoy near the ice camp and from sonobuoys deployed and recorded by the aircraftbased crew. Sonobuoy frequency range was 10-2400 Hz for the AN/SSQ-53B DIFAR sonobuoys

and 10-20,000 Hz for the AN/SSQ-57 A sonobuoys. Sonobuoy hydrophones were at depths ranging

from 9 to 27 m (Table 2.1B,C). An ITC model 1032 spherical hydrophone was used in 1990 and

1991 to record infrasonic sounds.

Ambient noise was recorded on a TEAC DAT recorder in 1990-94 and a calibrated cassette

recorder in 1989 (Table 2.1B). At the ice camp, the TEAC DAT recorder was sometimes operated

as a four-channel recorder in 1990-91, and always in 1994. In 4-channel mode, the frequency

range on each channel was 0-10,000 Hz. Analyses were restricted to frequencies up to 8000 Hz

(see "Analysis", below). This 8000 Hz upper limit was reasonable because the man-made sounds

used in playbacks during 1989-94 diminished severely in level with increasing frequency, and

because bowhead calls rarely contained components approaching 8 kHz.

A major component of arctic springtime ambient noise is bearded seal calls. When

measuring ambient noise, we avoided sampling the taped data at times when there were prominent

bearded seal calls. At times such sounds had to be included; these were times for which an

ambient analysis was needed but there was no 8.5-s segment lacking bearded seal sound. At these

times the spectrum had higher than usual levels at high frequencies, anywhere from 400 Hz up.

Thus, the resulting ambient noise data represent noise levels in the quieter periods between

bearded seal calls or, when bearded seal calls were nearly continuous, at times with such calls.

When the 113-octave ambient noise data were summarized on a percentile basis, the shape of the

100th percentile (maximum) 113-octave spectrum may be influenced by the presence of a bearded

seal call. However, the 95th percentile spectrum usually does not manifest such calls.

Analysis Procedures.-Segments of ambient recordings were analyzed to characterize the

noise on each day of ice camp operation and during TL tests. Analysis methods in 1991 and 1994

were generally the same as in 1989 and 1990. Recorded sounds were analyzed with a computer

workstation that included a two-channel 12-bit analog-to-digital converter in 1989-90, and a twochannel 16-bit analog-to-digital converter and digital signal processor (DSP) in 1991/94. The

sample frequency was generally 2

14 = 16,384 samples/second, permitting useful analyses of sounds

up to 8 kHz and determination of levels in 1/3-octave bands centered up to 6300 Hz. System

calibrations (hydrophones, amplifiers, sonobuoys, sonobuoy receivers, tape recorders, A/D

converter, and processing software) permitted results to be computed in units of pressure

(micropascals) and pressure spectral density (/lPa2/Hz) at frequencies from 8 to 8000 Hz.

A standard ambient noise analysis was based on an 8.5-s segment of sound (139,264 samples). These data were processed by Fourier transforming 0.5-s blocks (8192 samples/block) to
2.1 Methods: Physical Acoustics 25

which a Blackman-Harris window had been applied, overlapping blocks by 50%, and averaging

the results from the 0.5-s blocks. The resulting spectrum elements were spaced by 2 Hz and the

effective bandwidth of each element was 3.4 Hz.

From these narrowband results, we summed the powers to determine the levels in 113-octave

bands centered at frequencies 10 to 6300 Hz. The 113-octave bands centered at 10, 12.5 and 16

Hz constituted the infrasonic components. Levels in several broader bands were also computed

from the narrowband spectra or from the 113-octave band levels. In the latter case, half of the

power in each of the relevant 1I3-octave end-bands was assumed to be within the broadband

frequency range. The resulting 113-octave and broadband levels were saved in a spreadsheet.

After the 1989 field season, the project's Scientific review Board (SRB) recommended

investigating the shorter-term variability of the ambient noise. This would show whether there

were short periods of time (briefer than the standard 8.5 s analysis interval) during which the noise

level was significantly lower than the measured average level. If so, whales might, at times, be

able to hear weak sounds from distant sources-sounds with received levels lower than the longerterm average ambient noise. The characteristics for short-term analyses were

~ Sample rate: 2048 samples/second;

~ Sample block size: 122,880 samples (1 minute);

~ Block sizes for acoustic power computations: 512 and 17,408 samples (0.25 and 8.5 s).

The work was part of the 1990 effort and the results are reported in Richardson et al. (1991a).

Transmission Loss

Field Procedures.- Transmission loss (TL) tests were completed on 13 dates over the four

years: on four dates in each of 1989, 1990 and 1991, and on one date in 1994. An additional

partial test was done in 1994. Figure 2.1 shows the projector locations and, for each of these, the

line along which the receive stations were located.

The bathymetric contours on this and subsequent maps were developed by Paul Dysart, SAle

Applied Ocean Sciences, McLean, VA, based on soundings on National Ocean Service chart

16004, the NOAA bathymetric databases, and soundings taken by us in 1989-94 at our ice camp

locations and at many TL receive sites.

During TL measurements, the sound projector system described above and in Table 2.1A

projected a sequence of sounds that had been recorded at carefully-chosen levels on a test tape:

~ discrete tones (1989-90) or combined tones (1991 and 1994),

~ 1I3-octave band tonal sweeps (1989-90) or tone clusters (1991 and 1994),

~ steady drilling sounds from Karluk (1989-90 and 1994), and

~ varying icebreaking sounds from Robert Lemeur (1991 and 1994).
'- --.....•.

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FIGURE 2.1. Projector locations during transmission loss tests and, for each test, the line along which the receive stations were located.
2.1 Methods: Physical Acoustics 27

These signals were as follows:

~ The discrete tones used in 1989-90 consisted of 10- or 20-s segments of pure tone at the

following frequencies: 50, 100, 200, 500, 1000, 2000, 5000 and 10,000 Hz.

~ The combined tones used in 1991 and 1994 were combinations of continuous wave (CW)

tones at different frequencies, phased to assure that peak levels were not too high. There

were three waveforms of this type, containing tones at (a) 20 and 40 Hz, (b) at 50, 100,

200 and 500 Hz, and (c) at 1000, 2000, 5000, and 10,000 Hz. These three waveforms

were each transmitted for 30 s.

~ The tonal sweeps used in 1989-90 were hyperbolic frequency modulation (HFM) signals

synthesized by BBN Systems & Technologies Corp. following Rihaczek (1986). Each

5-s sweep spanned 113-octave at a center frequency of 100, 200, 500, 1000, 2000 or 5000

Hz. Each sweep was projected two or four times.

~ The tone clusters used in 1991 and 1994 were clusters of narrowly-spaced tones spanning

20 Hz. There were two waveforms of this type: (a) with clusters centered at 150 and 300

Hz, and (b) with clusters centered at 500 and 1000 Hz. Each was transmitted for 30 s.

~ The sample of Karluk drilling sound used in 1989-90 and 1994 was a 35-s (or longer)

segment of the rather steady, low-frequency (mainly 50-350 Hz) drilling sound used

during playback experiments in 1989-90. It was recorded in shallow water under ice

130 m from a drillrig on an ice pad east of Prudhoe Bay on 30-31 March 1989, as

described in Richardson et al. (1990a:80).

~ The sample of icebreaker sounds used in 1991 and 1994 was a 60-s (1991) or 20-s (1994)

segment of the icebreaking sounds used during playback experiments in those years. This

sound had been recorded 460 m from the icebreaking supply ship Robert Lemeur while

it was breaking ice in water 35 m deep, as described in Greene (1987a).

At the projector site (base camp), TL test signals were played back with the DAT (1991 and

1994) or cassette (1989-90) recorders listed in Table 2.1 A. In 1990-94, another DA T or cassette

tape recorder was used to record the monitor hydrophone signal and, in 1994, the projector

amplifier input signal. These recordings provided the basis for measuring the projector source

levels. During each TL test, the sequence of test sounds was projected several times, twice during

the period of recording at each receiving station. The location of the ice camp, which was on

drifting pack ice during all but one TL test, was recorded periodically via GPS (1991 and 1994)

or a Si- Tex model A-31O satellite navigation receiver (1989-90).

During each TL test, ambient noise and the transmitted sounds were received successively

at various distances from 100 m to 18.5 km along or near a single azimuth. Receiving stations

were along the edges of ice pans or, during one TL test (18 May 1991), on the landfast ice edge

and on drifting floes in the lead. To obtain data at distances 100 m, 200 m and (rarely) 400 m

from the projectors, a sled was used to haul the equipment along the ice edge from the base camp.

Distance to these sites was determined with a Rolotape distance measuring wheel rolled along the

ice. The helicopter provided transportation to the more distant sites at nominal distances 0.5, I,

2,5,7.5 and 10 n.mi. (0.93, 1.85, 3.7, 9.3, 13.9 and 18.5 km). The 10 n.mi. station was skipped

if no projected sounds were heard at 7.5 n.mi. Positions of these sites were determined via the

helicopter's navigation system (GPS in 1991 and 1994; GNS-500 VLF in 1989-90). In 1989-90,
2.1 Methods: Physical Acoustics 28

when the less-precise VLF navigation system was used, the helicopter often flew back over the ice

camp and noted its apparent VLF position before moving to a new receiving station and noting its

VLF position. About 4 h were required to measure the received signals at -8 ranges, exclusive

of the time (4-5 h) needed to set up and remove the projection equipment.

At each receiving station, the transmitted test signals were recorded with an ITC model

6050C hydrophone suspended via faired cable at 18 m depth. Also, ambient noise was recorded

at each receiving station before and after the period with test signals. During some tests in 1989-

91, ambient noise was recorded at the closer ranges with the generator at the base camp turned off

as well as operating. This was done to determine the characteristics and range of detectability of

the generator sounds. The received sounds were tape recorded with a battery-powered portable

TEAC DAT recorder in two-channel mode (bandwidth 0-20,000 Hz) during 1990-94, and with a

calibrated cassette recorder in 1989 (Table 2.lB). Water depths at the ice camp and at most of the

more distant receiving stations were measured with an echosounder. An ITC 1032 hydrophone was

used to record infrasound at TL receive stations in 1990-91.

Analysis Procedures.-Signal analysis was generally the same as was used for ambient noise

analysis (see above). Signal segments 8.5-s long were sampled at 16,384 samples/so For each

receive station, we measured the received level of each projected signal and of the ambient noise

level. These signals were analyzed by Fourier transformation of windowed, overlapped blocks

0.5 s long (8192 samples), and the results were averaged. The spectrum resolution was 3.4 Hz on

2-Hz centers. The powers (pressures squared) in the analysis cells spanning each ll3-octave band

were summed to derive the 1I3-octave band levels for the drilling, icebreaker, and ambient sounds

received at each station. The tone levels were measured from the appropriate narrowband

frequency element, and the sweeps were analyzed by taking the appropriate 1I3-octave band level.

Results were kept separate by type of signal: tones, HFM sweeps, clusters, Karluk drilling,

and Robert Lemeur icebreaking. The variable qualities of the icebreaking sounds, even over the

relatively short period of 20 s, and the fact that the received and transmitted signals were not

recorded on the same tape recorder, made it impossible to analyze exactly the same transmitted

and received segments. Thus, the TL measurements based on the samples of variable icebreaker

sounds were less accurate than the measurements based on the steady Karluk drilling sounds and

the HFM sweeps.

Transmission loss was computed by subtracting the measured received levels from the

measured source levels. The resulting data were used directly when the signal + noise level

exceeded the ambient noise level in the corresponding frequency band by at least 10 dB. When

the signal + noise level exceeded the noise level by 3-10 dB, the combined level was corrected for

the noise to calculate the signal level alone. The TL modeling effort based on the resulting data

is described in §4.3. This effort resulted in a model that, for the conditions prevailing in our study

area in late April and May, predicts transmission loss in relation to frequency, water depth, and.

distance from source.
2.1 Methods: Physical Acoustics 29

Playback Experiments

The acoustical methods used during playback experiments are best described in conjunction

with methods for biological observations during playbacks. This material appears in §2.3.

Infrasonic Components of Ambient Noise and Bowhead Calls

Because of concerns about the possibility that bowheads are sensitive to frequencies lower

than those that can be reproduced adequately by' projectors of practical size, we wanted to obtain

information concerning the sources, transmission and reception of sounds at low frequencies,

including infrasonic frequencies «20 Hz). Of the several possible avenues of investigation, two

were practical in this study. We measured the infrasonic components ofthe natural ambient noise,

and we undertook a preliminary assessment of bowhead calls to see if they included infrasonic

components. (1) The levels of ambient noise at infrasonic frequencies are relevant to any attempt

to evaluate how far away an infrasonic component of an industrial noise might be audible above

the natural background noise at corresponding frequencies. (2) If bowhead calls contain infrasonic

components, there would be increased reason for believing that bowheads can hear those

frequencies.

Infrasonic Ambient Noise.- The standard methods for determining ambient noise also

provided data on infrasonic ambient noise. The hydrophone, preamplifier and DAT recorder used

for hydrophone-based ambient noise recordings in 1990-94 were calibrated at frequencies from 5

to 20,000 Hz; the response was suitable for recording the infrasonic sounds from 8 to 18 Hz. The

sonobuoys, radio receivers and DAT recorders used at the ice camp and on the aircraft in 1990-94

were sufficiently calibrated to be useful at infrasonic frequencies as well. Both the -57 A and -53B

sonobuoys are sensitive from 10 Hz upward. All ambient noise recordings from 1991 and 1994

that were suitable for measurements at higher frequencies were also suitable for infrasonic noise

measurements at 8-18 Hz. The 1/3-octave band levels centered at 10, 12.5 and 16 Hz were

determined along with the levels in higher-frequency bands. Those infrasonic band levels were

saved in the same spreadsheet with the higher frequency 1/3-octave band levels.

A special hydrophone (ITC model 1032 sphere) was used in 1990-91 to sense infrasonic

ambient noises and bowhead calls that might contain infrasonic sounds. The 1032 with a highimpedance preamplifier was essentially flat down to a frequency of 1 or 2 Hz.

Infrasonic Components of Bowhead Calls.- The 1990 results on the question of infrasonic

components in bowhead calls were presented in Richardson et al. (l991a:91fj). In 1991, narrowband spectral density analyses were performed on all bowhead calls received on the 6050C

hydrophone or sonobuoys and recorded on the TEAC DAT recorder during five dates: 1, 11, 18,

25 and 26 May 1991. Waterfall spectrograms were plotted .forthe frequency range 6-250 Hz to

support a search for call energy at frequencies below 20 Hz. A minority of the calls analyzed in

this way included infrasonic energy that may have been associated with the call (§4.5).
2.1 Methods: Physical Acoustics 30

Waterfall spectrum analysis was useful in determining whether, at the times when bowheads

emitted their known types of calls, there also were infrasonic components that have not previously

been recognized. The characteristics for waterfall spectrum analysis were as follows:

~ Sample rate: 1024 samples/second.

~ Fourier transform blocksize: 1024 samples (l Hz bin spacing).

~ Blackman-Harris minimum 3-term window applied (1.7 Hz bin width).

~ 87.5% overlap of transform blocks.

~ I s of data analyzed and displayed per spectrum displayed.

~ Typically, 9.45 s of data were displayed in a waterfall plot showing frequencies 5 to

250 Hz.

2.2 Whale Surveys and Observations

Aerial Reconnaissance and Surveys

General Aonroach.s--Aerial reconnaissance and surveys were necessary to meet specific

objective 4, "To measure the short-term behavioral responses of ... whales ... to underwater

playbacks of variable icebreaker sounds ... ". Aircraft-based work was also important in addressing

specific objective 7, "To document, as opportunities allow, other aspects of the movements,

behavior, basic biology, disturbance responses and acoustic environment ... ".

Aerial reconnaissance of the study area was done daily to locate whale migration corridors,

which often changed from day to day. This information was used in selecting the location where

the sound projectors were set up each day. Aerial reconnaissance was also a necessary first step

in locating and selecting the specific whales to be observed and photographed from the air.

The flight route depended upon ice conditions, and was non-systematic. On most days, the

survey route initially followed the south side of the nearshore lead along the landfast ice edge.

We generally began surveying about 15 km northeast of Pt. Barrow and flew east along the ice

edge for as much as -75 km. (We did not search that far east on days ~ when the nearshore lead

did not extend that far east, or ~ when it was apparent that the main bowhead migration corridor

was farther offshore, or ~ when weather deteriorated to the east.) If a suitable projection site was

not identified along the landfast ice edge, the north side of the lead was then surveyed. Finally,

if a suitable projection site was not found in or adjacent to the nearshore lead, or if the nearshore

lead was congested with pack ice, a series of widely-spaced transects was usually flown over the

pack ice farther offshore to determine ice conditions there, the locations and orientations of leads

and cracks, and the locations of any bowhead or white whale concentrations. When searching for

whales in the pack ice, we often followed leads and cracks that seemed likely to provide migration

routes for migrating bowheads and white whales.

After a location for the sound projectors had been selected, additional surveys were usually

conducted as far as -20 km west and southwest of the projector site. At the point when it became

apparent that further reconnaissance surveys were unnecessary in meeting that day's objectives,

the aerial crew
2.2 Methods: Whale Studies 31

~ began to conduct systematic aerial observations of whale behavior if bowheads were

found and if clouds either were absent or were above 460 m Above Sea Level (1500 ft

ASL); or

~ began to photograph bowheads if bowheads were present but low cloud prevented

behavioral observations from 460 m ASL; or

~ returned to Barrow if no bowheads could be found or if the weather was too marginal for

productive or safe flying.

In 1989-91, insofar as possible, we ,avoided flying low (at <460 m) over the main nearshore

lead during midday. At midday, a National Marine Mammal Laboratory (NMML) crew was usually flying low over the leads within the study area, searching for bowheads to photograph. In 1994,

the NMML crew was not present so low-level flights were possible at any time.

We avoided flying within 5 n.mi. (9 km) of active whaling camps except when this was

unavoidable because of the presence of camps within 5 n.mi. of the approach to Barrow's airport.

In 1991, whaling at Barrow ended in mid May. From 17 May onward, we conducted reconnaissance surveys along the landfast ice edge and nearshore lead west and northwest of Barrow as well

as in the usual study area farther northeast of Pt. Barrow. In 1994, whaling continued until the

end of the our field season, and surveys were restricted to the normal study area east and northeast

of Pt. Barrow.

Survey Methods and Data Recording.-We conducted aerial surveys from 28 April through

26 May 1991 and from 27 April through 25 May 1994 in a DHC-6-300 Twin Otter aircraft. (Table

3.2, on p. 62, summarizes aerial efforts in all four years of the project.) In addition to the standard

belly fuel tanks, the aircraft had wingtip tanks (1991 only) and an additional tank in the cabin;

total aircraft endurance under our typical operating conditions was 9+ or 8+ hours in 1991 and

1994, respectively. Other special equipment included marine VHF radios, VLF/GPS navigation

system, radar altimeter with digital display, invertors for 120 V/60 Hz AC power, three bubble

windows (right center, left center, left rear), intercom system with voice activated microphones,

and ventral camera port.

In 1991, the aircraft was equipped with a Wulfsburg combined VLF/GPS navigation system

that operated in GPS mode normally and reverted to the less-precise GNS- VLF mode during the

small percentage of the time when GPS was unusable. (The GPS satellite constellation was not

yet complete during the 1991 work.) When GPS became usable again after a period of VLF navigation, the GPS automatically updated the VLF system to correct for accumulated errors. When

the GPS was usable, position readouts were usually accurate within 0.2 n.mi., based on the readout

upon return to a known location at Barrow. As usual, position errors as large as 1 km were

common when operating in VLF mode. A microcomputer interfaced to the VLF/GPS system and

the radar altimeter automatically recorded aircraft position and altitude at intervals of 10 s or less.

In 1994, the aircraft was equipped with two independent GPS systems in addition to a VLF

system. One GPS was part of the aircraft navigation equipment. The second GPS system, a

Trimble Pathfinder, was part of a GeoLink data acquisition and mapping system that provided a
2.2 Methods: Whale Studies 32

real-time map display on a portable computer (Dell 25 MHz 386/387), and stored GPS positions

at I-s intervals.

There were a total of 30 offshore flights on 23 different dates from 28 April to 26 May during 1991 (Table 3.2, p. 62). On five of these days, the single flight was terminated within 0.3-1.0

hours because of poor weather offshore. The remaining 25 flights ranged from 1.6 to 5.2 h in

duration. Longer flights were not warranted during 1991 because of the low clouds that almost

always prevented observations from altitude 460 m. Total flight time during the 30 offshore

flights was 75.4 h, of which 55.8 h was spent on reconnaissanceIn 1994, there were 35 flights on 22 dates from 27 April to 25 May. Poor visibility or high

winds prevented any useful work during flights conducted on the afternoons of 2 and 18 May. The

remaining 33 flights ranged from 1.0 to 7.3 h in duration. Total flight time during the 35 offshore

flights was 119.0 h, of which 66.0 h was spent on reconnaissance.

Flight and observation procedures were consistent with those during the 1989-90 phases of

this project. During reconnaissance work, the aircraft was flown at -185-200 km/h groundspeed

and, when possible, at 460 m ASL. When the cloud ceiling was lower than 460 m, as it almost

always was in 1991 and frequently was in 1994, the maximum possible altitude below the cloud

layer was maintained.

Four observers were present during almost all surveys in 1990-94 (three in 1989). During

surveys, one observer (right front) was in the co-pilot's seat, two were at bubble windows on the

left and right sides of the aircraft two seats behind the pilot's seat, and the fourth was at a rear-left

bubble window. When a whale was sighted, the obServer(s) notified other members of the crew

via the intercom. Most bowheads were circled at least briefly to obtain information on the activity

of the whale and to determine whether additional whales were present nearby. White whales were

usually not circled, but large groups were sometimes circled to obtain more accurate counts and

heading information. For each whale sighting, we recorded on paper and/or a tape recorder the

time, location, species, number, general activity, orientation, and percent ice cover. Ice conditions

were recorded throughout the survey, particularly whenever a change in ice type or percent cover

occurred. Aircraft position and altitude were recorded manually from the GPS or VLF system

whenever sightings were made and whenever the aircraft changed course. Position and altitude

were also logged automatically throughout each flight, as noted earlier.

All sightings of bowheads and white whales from all years of the project (1989-90 as well

as 1991 and 1994) have been transcribed into a standard numerical format, computerized, and

mapped in this report.

Aerial Photography of Bowheads

Field Procedures.-Aerial photography of bowheads was one of the lower priorities during

this project. However, it was often possible at times when higher priority work was prevented by

the low clouds that prevailed during the spring of 1991 and that occurred commonly during other

years. Vertical photos of bowheads were obtained in 1991 during 11 flights on 10 dates ranging
2.2 Methods: Whale Studies 33

from 29 April through 26 May, and in 1994 during 12 flights on 10 dates ranging from 30 April

to 25 May. Similar work was done during the 1989 phase of this project, when vertical photos

were obtained during 9 flights on 8 days (Richardson et al. 1990a). Vertical photography was not

possible in 1990.

We used the calibrated vertical photography technique developed by LGL and described by

Davis et al. (1983) and Koski et al. (1992). The resulting photos provided data on the individual

identities and sizes of many of the whales photographed. These data are relevant to specific

objective 7 concerning the movements, behavior and basic biology of bowheads (p. 7). The data

are also at least indirectly relevant in certain aspects of the evaluation of playback effects (specific

objective 4).

Field procedures were as described by Davis et al. (1983), Richardson et al. (1990a:60fj), and

Koski et al. (1992). Briefly, the aircraft, flying at an airspeed of -160 km/h and-cloud ceiling

permitting-an altitude of -137 m (450 ft), passed directly over bowheads. Because of the

prevailing low clouds in 1991, some 1991 photographs were taken from lower altitudes. Photographs were taken through the aircraft's ventral camera port with one of two hand-held Pentax

medium-format cameras (6x7 em film size), each with a 105 mmj2.4lens, pointed directly downward. Ektachrome 200 and Fujichrome 400 color positive film were used. Aircraft altitude was

recorded from the radar altimeter at the moment the camera shutter fired. In 1989 and 1994, radar

altitude was manually recorded by the observers in the rear of the aircraft from a digital display

and, independently, in the front of the aircraft from an analog display on the instrument panel.

In 1991, the radar altitude was recorded both manually and via the computerized data logger.

On one date in each year, a calibration target of known dimensions was spread out on a flat

surface (airport runway in 1989; lagoon ice in 1991 and 1994) and photographed with each of the

two cameras from the same altitudes used to photograph whales. Both whale and calibration

photographs were most commonly taken from -137 m, but in 1991 a few photographs were taken

from altitudes as low as -76 m.

When behavioral observations of whales were possible either from the aircraft or by icebased observers, low-altitude photographic work was avoided until the behavioral observations

were completed. In 1989 and 1991, we also did not purposefully photograph bowheads at locations where the NMFS/NMML crew had photographed bowheads on the same date. We supplied

NMML with copies of our 1989, 1991 and 1994 photos of identifiable bowheads, and they reciprocated with copies of their relevant 1989 and 1991 photos (NMML did not conduct photography

in 1994).

Analysis Procedures.- The procedures used to identify individual whales and to determine

their sizes are summarized by Richardson et al. (1990a:62-63); Koski et al. (1992), and Rugh et

al. (1992a).

Measurements of the 1991 LGL calibration target as photographed from -76 m ASL were

more variable than those from higher altitudes. Hence, we considered whale lengths determined

from photographs taken at <91 m «300 ft) to be approximate. Such lengths are included in
2.2 Methods: Whale Studies 34

histograms when no "better" measurement was available for the whale in question. However, these

approximate lengths will be excluded from analyses that require precise length measurements, e.g.

analyses of growth rate.

All LGL and NMML whale images obtained were classified as Grade A (recognizable

between years if compared to a photo of similar or better quality), Grade B (recognizable on a

different day within the same season if compared to a photo of similar or better quality), or Grade

C (not recognizable). The reader is referred to Davis et al. (1983) for a more detailed description

of grading of photos for reidentification purposes.

To check for whales photographed more than once within a given year, each LGL image

from 1989 was compared to all others acquired by LGL in 1989, and to all images acquired by

NMML in 1989 after 11 May. For 1991, each LGL and NMML Grade A and B whale image was

compared with all other Grade A and B images acquired within 7 days of that image. The

procedure used in 1994 was the same as that in 1991, except that in 1994 there were no NMML

photos. The procedure used in 1991 and 1994 assumes that no whale would linger in the Barrow

area for more than 7 days during spring migration.

To identify between-year resightings, we also compared all LGL and NMML Grade A images

from 1989, 1991 and 1994 with the complete 1981-94 LGL and 1984-91 NMML collection of

Grade A photos. (NMML's 1992 photos were not considered.) In these inter-year comparisons,

the new Grade A whale images were compared with images in the same file and in "adjacent" files.

The adjacent files are those containing whale images with similar characteristics (Rugh et al.

1992a).

Aerial Observations of Behavior

Our standard procedures for aerial observations offocal groups of bowheads (e.g. Richardson

et al. 1991a:27fj) were applied whenever observations were possible from an altitude of 460 m.

Previous studies have indicated that bowheads observed from an aircraft circling at 460 m ASL

and at reduced power (-165 kmlh) are usually not disturbed by the aircraft (Richardson et al.

1985a,b, 1991; Richardson and Malme 1993). Results from the present study verified this (§6.7).

In 1991, the prevailing low cloud usually prevented useful behavioral observations from the

aircraft. We obtained only 4.1 h of systematic behavioral observations; these came from 7

observation sessions on 5 dates (29 April, 4,6,20 and 25 May). In 1991, we were never able to

obtain aerial observations of bowheads near the operating sound projectors. The few times when

the aircraft crew could observe from 460 m ASL near the ice camp were times ~ when no bowheads were present, or ~ when the sound projection equipment was still being set up, or ~ when

dangerous ice conditions or encroaching fog forced termination of ice camp and/or aircraft

operations before useful data could be obtained.

In 1994, we were able to observe the behavior of bowheads or (rarely) white whales from

the Twin Otter circling at 460 m ASL for a total of 36.2 hours during 23 observation sessions on

ten different days (Table 3.2, p. 62). Twelve of these sessions on four days (7, 9, 16 and 17 May)
2.2 Methods: Whale Studies 35

were done near the ice camp either during a playback of icebreaker sounds or during the preceding

or following control period; five of these 12 sessions were at times while icebreaker sounds were

being projected. Numerous bowheads were observed during most playback sessions (see Table 3.8,

p.80-81). However, the high sea states encountered commonly during 1994 resulted in discontinuous and fragmentary observations on most days. When the sea state is high, it is often impossible

to detect bowheads when they first surface. This prevents determination of the duration of surfacing, number of blows per surfacing, amount of turning during surfacing, and other variables that

require observation of the complete surfacing. Also, with high sea states it is frequently impossible to be sure whether any surfacings have been missed, or to see the distinctive markings that

show whether a given whale is the same one observed during a previous surfacing. These problems were unusually common during the 1994 behavioral observation work.

Observation Procedures.- Throughout each observation session, two full-time observers plus

(in 1990-94) one part-time observer 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. The two full-time observers were seated in the

co-pilot's seat and the seat two rows behind it. The part-time observer occupied a seat 2-3 rows

behind the primary observers. During each surface/dive sequence by bowheads, they described

the same behavioral attributes as recorded in our previous studies of bowhead behavior and

disturbance reactions (e.g., Wiirsig et al. 1984,1985,1989; Richardson et al. 1985a, 1986, 1990b,

1991a, 1995; Koski and Johnson 1987; Dorsey et al. 1989). These data included times when each

focal whale surfaced, blew and dove; its headings and turns; occurrence of pre-dive flexes, flukeout dives and aerial activities (breaches, tail and flipper slaps, etc.); and occurrence of numerous

other behaviors as listed in §5.3, Behavior of Undisturbed Bowheads.

Another observer, also on the right side during behavioral observations, operated a highresolution 8-mm video camera whenever whales were at the surface. In 1991, this was usually a

Sony CCD-V99 with 11-88 mm zoom lens, x1.4 teleconverter, and monochrome viewfinder. In

1994, we usually used a Sony CCD- TR500 with 5.4 to 54 mm lens, x2 teleconverter (on some

days), and color LCD viewfinder. Videotaping was through a side window at the rear of the aircraft. In 1991/94, the standard plexiglass window there had been replaced by flat glass. The video

camera was usually operated with manual focusing and with high shutter speed (e.g. 1/1000 s) to

provide sharp images when viewed in stop-frame mode. Automatic exposure was used when

practical, but manual exposure adjustment was necessary when there was much ice within the field

of view. The date and time (to the second, synchronized with observers' digital watches) were

recorded on each video frame to facilitate analyses. The audio signal recorded on the videotape

was taken from the aircraft intercom, and thus included the behavioral, positional, and other data

dictated by all personnel on the aircraft. While the focal whale or group of whales was at the

surface, the video camera was normally kept tightly framed on those whales. After they dove, a

wide-angle view of the area was normally recorded to assist in determining whale position relative

to ice features and the ice camp.

Behavioral data were transcribed from audiotape between flights or, in some cases, 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
2.2 Methods: Whale Studies 36

Richardson and Finley 1989:25-28 for details). These records were hand checked and then typed

into an IBM-compatible microcomputer for computerized validation and analysis. Statistical

analyses of the resulting behavioral data were done with the BMDP program system (BMDP/

Dynamic, release 7.0 for MS-DOS computers-Dixon 1992).

Behavioral Definitions and Criteria.-Most definitions and criteria were the same as in our

previous related studies (e.g. Dorsey et al. 1989; Richardson et al. 1995). In particular, a surfacing

is again defined as the interval from the first arrival of a whale at the surface after a long ("sounding") dive to the time when the whale descends below the surface for the next long dive. A surfacing usually includes several blows, and is equivalent to a "surfacing sequence" as defined by some

other authors. Some studies define the surface time as the interval from the first blow to the last

blow of a surfacing sequence. In contrast, we define it as the interval from first arrival of the

whale at the surface to the final submergence of the sequence. Bowheads are often visible at the

surface for a few seconds after the last blow, and occasionally for a few seconds before the first

blow. Therefore, surface times defined on the basis of the first and last blows presumably would

average a few seconds shorter than those obtained with our procedure.

There were two changes in procedures in this study (1989-94) relative to our previous

projects concerning bowhead behavior in summer and autumn:

~ Occasions when the whales's blowholes rose above the surface in the pattern usually

associated with a blow, but no blow was seen, were recorded as "presumed blows". Such

cases seemed to be more common in spring than in summer or autumn. These cases were

treated as actual blows when determining blow intervals and number of blows per

surfacing. Ice-based observers noted that these whales were in fact blowing; the invisible

blows were audible.

~ The primary measure of blow interval in this study is the "median blow interval for a

surfacing". In some previous summer/autumn analyses we used mean, not median, blow

intervals. The median is less affected by occasional extreme values, or by missed blows.

There can be some doubt as to whether certain brief « 1 min) sub mergences should be counted as dives or as intervals between two blows within a surfacing sequence. The procedure for

handling these cases is important because it has major effects on variables such as duration of

surfacing and number of blows per surfacing. One approach is to use "log survivorship analysis"

(Fagen and Young 1978) to identify a specific time interval to be used to separate long blow intervals from short dives. We did not use that approach, as no one simple arithmetic criterion is

appropriate. Certain blow intervals, e.g. by some whales resting at the surface, are quite long but

nonetheless clearly blow intervals and not dives. Conversely, certain dives, e.g. when bowheads

are being actively pursued, are quite short but nonetheless clearly dives and not blow intervals.

Thus, the longest blow intervals are longer than the shortest dives and no single "duration" criterion is appropriate for all cases.

When viewed from an aircraft, the behavior of bowheads at the start of a sounding dive is

usually distinct from that at the start of a submergence between blows. When sounding, a bowhead usually arches its back as it submerges, the flukes are sometimes raised, and the whale typic-
2.2 Methods: Whale Studies 37

ally appears to be diving deeper and/or more steeply. However, bowheads occasionally surface

again within '12-1 min after such an apparent sounding dive. In this study, we classified these short

sub mergences as dives if one or more of the usual indicators of a dive were seen: an arch, flukeout, or steep submergence. If the whale sank out of sight without any of these indicators of a dive,

and surfaced again within 1 min, the submergence was classified as a blow interval within a

surfacing sequence. Shallow dives during which whales swam close enough to the surface to be

visible from above were counted as dives only if they were >1 min in length (>'12min for calves).

Number of Observations.-In this report; when analyzing the behavior of undisturbed bowheads (§5.3, §5.4), we combined results from 1991 and 1994 with those from the 1989-90 phase

of the project. Observation procedures in 1989-90 were very similar to those described above for

1991 and 1994 (see Richardson et al. 1990a, 1991a for details). Results from all four years are

directly comparable. Over the four years of the study, the numbers of bowhead surfacings and

dives for which we have at least partial behavioral data are shown in Table 2.2.

TABLE 2.2. Number of bowhead surfacings and dives for which behavioral data (complete or

partial) were obtained via the aerial observation technique.

1989 1990 1991 1994 Total

Surfacings

Presumably undisturbed whales 258 558 57 496 1369

Potentially disturbed whales"

Drilling noise playbacks 128 261 389

Icebreaker noise playbacks 0 149 149

<30 min after playback 0 27 0 26 53

Aircraft at <460 m ASL 58 2 0 0 60

Other or combination 39 12 0 26 77

Total, undisturbed + disturbed 483 860 57 697 2097

Dives

Presumably undisturbed whales 157 377 40 325 899

Potentially disturbed whales"

Drilling noise playbacks 105 136 241

Icebreaker noise playbacks 0 83 83

<30 min after playback 0 15 0 20 35

Aircraft at <460 m ASL 35 2 0 1 38

Other or combination 36 4 0 22 62

Total, undisturbed + disturbed 333 534 40 451 1358

a Includes observations during 30-min or (for aircraft) 15-min post-disturbance periods.

Ice-based Observations

Ice-based observations of bowheads and white whales were obtained to help meet specific

objectives 4, 6 and 7 (p. 7). A watch for whales was maintained by 1-4 people (most often 2 or
2.2 Methods: Whale Studies 38

3) starting within a few minutes of arrival on the ice and continuing until about Yz h before

departure. At least one person watched throughout this period, but the number of additional

people who were watching for whales tended to be lower early and late in each day's observation

period, when equipment was being set up or packed, than during the middle hours. When no

whales were present, ringed and bearded seals were observed opportunistically, or the day's plan

was changed to conduct a transmission loss test.

Field procedures in 1991 and 1994, primarily involving use of a surveyor's theodolite to

observe and locate whales, were very similar to those during 1990 (see Richardson et al.

1991a:29fj). In 1991, we used a Lietz/Sokkisha model DT5 digital theodolite with 10 second precision. In 1994, we used a Lietz/Sokkisha model DT5A with 5 second precision. The height of

the theodolite was determined each day by taking a gravity-referenced reading from a vertical

stadia rod at the projector location. Theodolite readings in degrees, minutes and seconds were

referenced to magnetic north and to gravity. Ice ridges on which the theodolite was placed ranged

in height from 2.8 to 6.0 m ASL, but were less stable than desired. To control for errors caused

by movement of the theodolite base, the horizontal and vertical zeroes were checked every 15-30

min and after tracking episodes, and were reset if off by > 1 minute of arc in 1991 or >40 seconds

of arc in 1994.

One difference from 1989-90 was that, on most dates, the digital theodolite was interfaced

by way of an RS-232 serial interface to a Hewlett Packard 71B "palmtop" computer (1991) or a

Tandy 102 "laptop" computer (1994). This allowed direct logging of bearings and depression

angles in relation to time. The program also permitted entry of notes about whale behavior and

identification. Distances were computed using an iterative equation that included correction for

curvature of the earth." Data were stored on diskette and, for backup, printed in real time via a

portable ink jet printer. A heating pad designed for a car battery and powered by the generator

at the ice camp kept the computer batteries and ink jet printer warm enough to work on the ice.

This data logging system allowed for automated and hence quicker collection of theodolite

readings, resulting in more detailed tracks of successive animal positions.

Because of the low vantage point from the ice, ice-based observers could not see whales

unless they were within Yz-2 km, depending on ice conditions, visibility, and perch height. Also,

because of the near-horizontal observation angle, whales could not be seen when slightly below

the surface, and many aspects of behavior were difficult to observe. The most valuable data

obtained from the ice-based observations were data, on the closest point of approach (CPA) of

whales to the ice camp, and on the paths of the whales passing close to the camp. For whales

passing within about 1 km, ice-based observers aided by the theodolite could obtain more precise

data on whale CPAs and tracks than could aerial observers. Also, ice-based observers maintained

a continuous watch on the area near the ice camp throughout each playback and its associated preand post-playback control periods. During much of this time, aerial observations were not possible

5 The computer program that acquired and processed the theodolite data in 1991 was prepared by

F. Cipriano, Dept of Ecology and Evolutionary Biology, University of Arizona. A similar program prepared

by A. Frankel, Dept of Oceanography, University of Hawaii, was used in 1994.
2.2 Methods: Whale Studies 39

near the ice camp because the aerial crew was observing other whales farther away, or was away

refueling, or was unable to observe because of low clouds. Thus, the ice-based and aerial

observations were complementary to one another.

During each day of ice-based work, ice conditions near the ice camp were documented by

taking theodolite readings of ice edges and other prominent ice features visible from camp. These

readings were taken about once per hour, and/or immediately after whales were observed. The

theodolite-to-projectors distance was also measured each day using a Rolotape measuring wheel.

During 1991 and 1994 all personnel at the ice camp wore long white snow-shirts over their

parkas to minimize their visual conspicuousness.

2.3 Playback Experiments

General Playback Approach

The general approach was very similar to that in preceding years of this project, as described

by Richardson et al. (1991a:30jj). Icebreaker sounds were projected from a mobile ice-based camp

established on the landfast or pack ice each day when weather or ice conditions were suitable. The

reactions of whales to these sounds were determined by systematic observations of whales

approaching, passing, and moving away from the ice camp. Such observations were obtained both

when the projectors were operating ("playbacks") and when they were silent ("control"). These

types of observations were obtained by observers at the ice camp and, when the cloud ceiling

exceeded 460 m, by observers in an observation aircraft, as described in §2.2.

Playback experiments had higher priority than any other project task during all four years

of fieldwork. This was particularly so on days when whales were observed migrating through the

study area and when weather conditions were suitable for behavioral observations of whales from

the circling fixed-wing aircraft. On these occasions, personnel at the ice camp projected sounds,

and personnel on the ice and in the aircraft observed whale behavior. On many days, the cloud

was too low for aerial observations from 460 m altitude, but horizontal visibility was good. If

whales were migrating in the area on these "low-cloud" days, playback experiments were usually

attempted, with all observations then being from the ice camp. In either case, the Twin Otter

aircraft generally departed Barrow first, conducted a survey for whales and ice conditions, and

selected a possible site for the ice camp before the helicopter arrived.

Cloud permitting, the Twin Otter crew then conducted "control" observations of the behavior

of undisturbed whales within a few kilometers of the ice camp while the ice-based crew set up the

projection equipment and, simultaneously, began ice-based control observations of whales.

Weather permitting, both aerial and ice-based observations of whales continued during the subsequent playback period and during a following post-playback "control" period. Often weather

conditions changed during the day. Sometimes this forced cancelation of aerial observations but

allowed continuation of ice-based work. Occasionally clouds were too low for aerial observation

during the pre-playback control period early in the day, but aerial observations became possible

later, during and after the playback period.
2.3 Methods: Playback Experiments 40

Playbacks were done with the equipment listed in Table 2.1A (p. 21). The time required to

set up the equipment at an ice camp was 1-2 h in 1989-90, 2-3 h in 1991, and 3-4 h in 1994.

These are the approximate intervals from first arrival on the ice until everything was ready to

project underwater sound. Setup time became longer after 1990 because of the increasingly heavy

and elaborate sound projector systems and associated electronics in 1991 and especially 1994.

Control observations were collected during the setup process but, especially in 1991 and 1994,

conditions on the ice sometimes became untenable before the equipment was ready for a playback

or shortly after the playback began.

Meaning of the Term "Control"

Insofar as possible, we obtained control observations near the ice camp under conditions that

differed from those during playbacks only by the emission of sound from the projectors. This is

the usual definition of "control". This approach is appropriate for determining whether playbacks

per se had any discernible effects. However, concern has been expressed that this approach might

underestimate the actual effects of playbacks if whales observed under control conditions were

already somewhat disturbed.

Some whales that approached the ice camp during control conditions probably could hear

man-made sounds associated with operation of the generator, intermittent helicopter operations,

and the circling Twin Otter observation aircraft. We attempted to minimize exposure of whales

to noise from these sources, but it was not possible to eliminate all exposure. Section 4.6

describes the generator noise, and §6.7 and §7.4 describe reactions of spring-migrating bowhead

and white whales to aircraft. The few cases of bowheads and belugas reacting to helicopter

operations near the ice camp are excluded from our "control" datasets. There was little indication

of reactions to our other activities during control periods. However, we cannot exclude the

possibility that these activities had subtle effects on some whales observed near the ice camp

during control periods.

Strictly speaking, therefore, the differences between whale activities and behavior during

playback vs. control periods represent the incremental reactions to playbacks when playbacks are

added to a background of other human activities associated with the research. If the whales

observed under control conditions were somewhat disturbed, then the differences in whale

activities between control and playback conditions might understate the differences between

activities of truly undisturbed whales vs. those exposed to playbacks. However, almost all

bowhead and white whales observed during control conditions during this study behaved in a

manner indistinguishable from that seen, during this and other studies, by ice- or shore-based

personnel observing in the absence of any known disturbance. Of the few exceptions, most involved helicopter disturbance, and these cases have been excluded. Therefore, we believe that the

playback vs. control comparisons in this study provide a good indication of the differences in

whale activities that would occur between playback conditions and otherwise-similar situations

with no human activities.
2.3 Methods: Playback Experiments 41

Acoustical Aspects of Playbacks

Playback Stimuli.-During 1989 and 1990, the steady underwater sounds of drilling on an

ice pad, as recorded at the Karluk site, were projected as the playback stimulus. The collection

and characteristics of these sounds were described in Richardson et al. (1990a, p. 44 and 80ff).

During 1991 and 1994, the varying sounds of an icebreaker operating in heavy ice were used,

as recommended by project personnel and agreed by the Minerals Management Service and the

project's Scientific Review Board. In contrast to the steady , low-frequency drilling sound used

in the 1989-90 tests, icebreaker sound has significant energy at frequencies up to a few kilohertz,

and the source level is quite variable over time. After data on whale reactions to the drilling

sound were collected in 1989-90, it was considered important to test the reactions to a more

variable sound with broader frequency composition.

The icebreaking sounds used for playback stimulus were recorded on 2 September 1986 from

a drifting boat 0.25 n.mi. (460 m) from the icebreaking supply ship Robert Lemeur operating in

heavy ice near the Corona drillsite -40 km north of Camden Bay (Greene 1987a). This ship is an

Arctic Class 3 icebreaker of 83 m length overall and 3184 tons gross displacement. It has two

turbocharged diesel engines of combined power 9600 bhp (7.2 MW). The two four-bladed

controllable-pitch propellers are in Kort nozzles. Sounds were recorded continuously for over 14

minutes. The characteristics of these received icebreaker sounds were reported by Greene (1987a)

and are further summarized in §4.4 of this report (p. 115ff).

Prior to the field season, the taped icebreaker sounds were played back several times to

record a 2-h DAT tape of icebreaking sounds, which was itself copied to provide a second 2-h

DAT tape. The end time of the 14-min segment was selected such that the levels at the start and

end of the segment were closely matched. Thus, there was no sharp change in the sound at 14-min

intervals when the segment began to repeat. During playback experiments on the ice, the two

tapes were played sequentially, replacing the played-out tape with the alternate quickly to minimize the break in transmission (about 30 s), and then rewinding the first tape while the second one

played.

Projector Operations.-Playbacks were done with the equipment listed in Table 2.1A and described in §2.1 under "General Approach and Equipment". Briefly, during 1991 and 1994, a Sony

DAT recorder was used to play back the icebreaker sounds. This resulted in accurate speed and

frequency reproduction for the playbacks. These sounds were projected into the water by a

J-13/F-40 system (1991) or an Argotec 220/J-11 system (1994) suspended at a depth of 18 m. In

1991, we used a 250-W amplifier powered by a 2.2 kW gasoline generator. In 1994, we used a

1600- W amplifier to drive the Argotec 220, only one side of which was operational, and a 350- W

amplifier to drive the J-11; these were powered by a 5 kW gasoline generator. In 1991 and 1994,

the generators were suspended from a frame via bun gee cords to minimize transmission of generator noise and vibration into the water. In both years, the projectors were turned on at a time

when no whales were known to be within Y2 km of the ice camp, as required by Scientific Research

Permit 670/Modification 2, issued by the National Marine Fisheries Service. At the start of most

playbacks, the sound level was increased gradually over 1-5 minutes ("ramped up").
2.3 Methods: Playback Experiments 42

In 1991 and 1994, icebreaker playbacks were done for a total of -40 h distributed over 13 d.

This included 7 d when bowheads were seen near the ice camp during the playback, and 3 d when

white whales were seen there during the playback (see Table 6.1 in §6.1).

Playback operations in 1989-90 were described by Richardson et al. (1990a,1991a). Drilling

sounds were projected for prolonged periods on 19 d, including 10 d when bowheads were seen

near the ice camp during the playback, and 6 d when white whales were seen there during the playback (Table 6.2 in §6.1). Equipment used for playbacks in 1989-90 is summarized in Table 2.1.

Acoustic Monitoring.-During all playback experiments in 1994, a four-channel TEAC DAT

recorder was operated continuously to record the following signals: (1) the tape player output

signal (the signal being amplified for projection); (2) an ITC 1042 monitor hydrophone within 3 m

of the projectors; (3) an ITC 6050C hydrophone about 3-5 m from the projectors; and (4) when

available, a sonobuoy installed manually about 1 km from the projector site. Date and time were

recorded continuously and automatically, and periodic voice announcements by the operator were

recorded on a special fifth memo channel. Amplifier and tape recorder gain settings were noted,

along with the exact times of any changes. In 1991, procedures were similar, except that usually

only the monitor hydrophone and sonobuoy signals were recorded on the DAT recorder, and these

recordings were intermittent during the playback. In 1989-90, the signal from the ITC 1042

monitor hydrophone and the monitor sonobuoy -1 km away were recorded intermittently on a calibrated audio cassette recorder (Table 2.1B).

When the cloud ceiling was high enough to allow the aerial observation crew to observe from

460 m ASL, personnel on the aircraft dropped sonobuoys (AN/SSQ-57A or AN/SSQ-53B DIFAR)

near bowheads to monitor and record the sounds received near the whales. This was done in 1989-

90 and 1994. In 1991 the prevailing low cloud made it impractical to conduct aircraft operations

near the projector site during playback experiments. The procedures followed when using both

manually-deployed and air-dropped sonobuoys are described in §2.1. Because the positions of

many buoys relative to the ice camp changed over time, especially when the ice camp was on

landfast ice, sonobuoy data were used to determine received levels of projected sounds only when

the distance from the ice camp was known through one or more of the following procedures:

~ the buoy had just been deployed at a known distance, or

~ the buoy's location relative to the camp was more-or-less fixed by ice and was

determined when it was first deployed, or

~ the buoy's location was variable but known and periodically measurable from the ice

camp by theodolite or from the observation aircraft by direct overflight and GPS readout,

or

~ the buoy's location was variable but measurable by crosscorrelating the sounds received

near the projector and at the sonobuoy.

Acoustic Analysis.-In all years, the taped acoustic data, along with notations about gain

settings and associated calibration data, allowed us to measure the source level of the projected

sounds on an overall and a 1I3-octave basis. These source level analyses were done after each

field season for various representative times during each playback test.
2.3 Methods: Playback Experiments 43

To determine the source level of the projected sounds at a given time, an 8.5-s segment of

the sound recorded from the ITC 1042 monitor hydrophone was sampled at 16,384 samplesls and

analyzed by Fourier transforming windowed, overlapped blocks of 8192 samples, followed by

averaging of the various Y2-S blocks and application of calibration data. This was the same process

that was applied in analyzing ambient noise, signals received during transmission loss tests, and

signals received at sonobuoys. From the resulting narrowband spectrum, we determined the levels

received at the monitor hydrophone in 1I3-octave bands from 10 to 6300 Hz, and in various broad

bands. These data were converted to source levels based on the measured distance of the monitor

hydrophone from the projectors; assuming spherical spreading over this distance. Because the

icebreaker sounds were variable, repeating after 14 minutes, it was important to determine the time

of each source level measurement within the 14.3-min sequence. For each source level measurement, the offset time from the start of the sequence was determined by crosscorrelating the sample

segment against the entire 859-s sequence length.

Levels of icebreaker sound received at sonobuoys that had been deployed near the ice camp

manually or from the aircraft were determined in a similar manner, taking account of the strongly

sloped frequency response of sonobuoys.

The crosscorrelation method could be used to determine the distance between the projector

and any hydrophone, including a sonobuoy, when sounds at the two sites were recorded on the

same tape recorder. By crosscorrelating the projector input signal or the monitor hydrophone

signal with the signal from the monitor sonobuoy, the delay time between the two signals could

be determined to an accuracy of about 5 ms. Distance was determined by multiplying the time

delay by the speed of sound (about 1435 mls near the surface under our field conditions). Crosscorrelation was also used occasionally to determine the difference in distances of two sonobuoys

from the projector based on differences in arrival times of projected sounds.

Ambient noise levels just before and after the playback period were determined from

hydrophone and sonobuoy signals recorded at the ice camp and from sonobuoy signals recorded

aboard the project aircraft, as described in §2.1, Physical Acoustics Methods. These data were

later used to estimate the signal-to-noise ratio at locations of observed whales, i.e. the difference

(in decibels) between the levels of the icebreaker signal and the ambient noise in a corresponding

band (§6.1-6.3).

Whale Movements and Behavior During Playbacks

Observation Procedures.- To maximize the power of the observations in assessing the

hypotheses, we planned to use whales approaching the sound projectors as their own controls

insofar as possible. Our intent was to compare the movement patterns and behavior of the same

whales when they were at various distances from the projectors. This approach reduces the

complications caused by differences in the natural activities of different individual whales. We'

planned to begin observing the movements and behavior of whales when they were far enough
2.3 Methods: Playback Experiments 44

from the projector system that they could not hear it or, at the least, were not likely to react to it."

This required aerial observations, as ice-based observers stationed near the projectors would be

unable to see whales more than Yz-2 km away, depending on ice conditions and visibility. We then

intended to observe whale movements and behavior as they approached and passed the projectors.

This would involve both aerial and ice-based observations.

Specific procedures for aerial and ice-based observations of whale movements and behavior

are described in §2.2. Near the ice camp, the same ice-based and aerial observation procedures

were used during playback and non-playback periods. Also, the aerial observation procedures used

for whale observations in the absence of an ice camp were the same as those near the ice camp,

with the exception that bearings and distances of whales from the ice camp were not relevant in

the latter case.

Because the ice camp and projector system had to be reestablished on the ice each day, the

projectors often began operating while whales were already under observation from the aircraft.

To minimize observer expectancy biases, during 1991/94 we prevented the two primary behavioral

observers in the aircraft from knowing whether the sound projector was operating. A third parttime observer on the aircraft was, unavoidably, often aware of projector status because she was

monitoring the signals received by sonobuoys, which detected the projected sound when it was

present. The fourth biologist on the aircraft (project director) was in radio communication with

the acoustician on the ice, and was aware of projector status. The 3rd and 4th observers did not

discuss projector status on the aircraft intercom, and behavioral data were transcribed from

audiotape and videotape onto dataforms without knowledge of projector status.

The ice-based observers, because of their proximity to the projector site and their involvement in its deployment and retrieval, occasionally were aware of projector status (on or off).

However, most of their data were theodolite readouts, which do not involve subjective judgments.

Thus, observer expectancy bias would not be a problem in these data. Furthermore, the ice-based

biologists often were unaware of projector status. The generator was operated during both playback and control periods. During control periods as well as playbacks, the tape recorder used to

play back the icebreaker (1991/94) or drilling (1989-90) sounds was operated, and those sounds

were played over a monitor speaker in the tent at the ice camp. With this procedure, only the

acoustician at the camp knew whether sounds were being projected into the water.

Distances and Bearings of Whales from Ice Camp.-When whales were seen by observers

at the ice camp, the distances and bearings were determined using a theodolite (§2.2). This was

done whether or not the projectors were operating at the time.

When aerial observations were obtained within 10 km of the ice camp, bearings and distances

of whales from the camp were determined for each surfacing. Again, this was done whether or

not man-made sounds were being projected from the ice camp. (As described above, the primary

6 Previous studies of bowheads and other baleen whales have shown that they generally show no

discernible reaction to steady sounds that are weak but presumably detectable (Richardson and Malme 1993;

Richardson et al. in press).
2.3 Methods: Playback Experiments 45

aerial observers did not know when sounds were being projected.) Several types of data were used

to determine whale position relative to the ice camp; not all of these were relevant or available at

anyone time. Types of data used included the following:

~ Whale-to-projector bearings were estimated by eye to the nearest 10° by reference to the aircraft's

gyrocompass and, on some occasions in 1994, real-time GPS readouts of aircraft-to-camp bearing.

These estimates were usually accurate within 10°, and should always be accurate within 20°.

~ The distance from the whale to the projector was estimated visually during most whale surfacings.

When distance between two points could be determined by some independent means, we compared

our visual estimates with the independent determination. For distances of 0.5 to 5 km, visual

estimates were usually within 25% of the correct value. In most cases, one or more of the

following types of data were available to replace or refine the visual estimate.

~ Whales within Y2-2 km of the ice camp were often under observation from the ice camp as well

as the aircraft. When accurate theodolite data on bearing and distance from the ice camp were

available, these data were used in preference to visual estimates by aerial observers.

~ In all years, aerial observers frequently dictated onto audiotape the position of the aircraft

according to the aircraft's GPS (1991/94) or VLF (1989-90) navigation system as we reached a

consistent point on the observation circle (e.g., north of the whale position). Although the focal

whale(s) usually were -1 km from this location, the offset from aircraft to whale was similar from

one surfacing to the next, as we attempted to fly circles of consistent radius.

~ In 1994, the aircraft's GPS position was logged by computer about once per second. A program

was written to compute the centroid positions of successive observation circles and, from those

plus ice camp position, the distance and bearing from ice camp to centroid. The focal whales

were usually near the centroid.

~ When the focal whale(s) were not at the center of the observation circle, whale position relative

to the center was often dictated onto audiotape (e.g., "whale is about 400 m north of the center").

~ Whale position relative to any nearby distinctive ice features was usually dictated onto audiotape

and/or visible on videotape. Locations of ice features relative to the ice camp were determined

by vertical photography from high altitude on days when cloud ceiling permitted (see below).

~ Whale positions were estimated by eye relative to locations of other whales and locations of the

same whale during preceding surfacing(s).

~ The aircraft was occasionally (1991/94) or often (1989-90) flown from the location where whales

hadjust dived to the ice camp. By flying directly over these two positions within a short interval,

even the less-accurate VLF navigation system used on the aircraft in 1989-90 provided accurate

(±0.3 km) data on the whale-to-projector distance and bearing.

~ The absolute location of the ice camp was determined using the GPS (1991/94) or VLF (1989-90)

navigation systems on the Twin Otter and helicopter, and a separate GPS (1991/94) or Si-Tex

model A-310 SatNav receiver (1989-90) at the ice camp. When the ice camp was on pack ice,

its position often changed substantially during an experiment due to wind- and current-induced

drift of the ice. To account for this, all whale sightings and movements were plotted relative to

the sound projector location at the sighting time.

By considering all of these types of data, positions of most whales relative to the ice camp

were determined within ±20% distance and ±20° bearing. In the few cases where the uncertainty

appeared to be greater, the distance and/or bearing were recorded as unknown. A high proportion

of the distance and bearing records are accurate within ±20% and ±20°, and we believe that many

are accurate within ±10% and ±10°. Also, relative distances and bearings of the same whale during successive surfacings were determined with greater accuracy than were the absolute distances
2.3 Methods: Playback Experiments 46

and bearings. Distance uncertainties of ±10% and ±20% translate into received level uncertainties

of only 1 or 2 dB, respectively, if spherical spreading is occurring, and less with cylindrical

spreading. Even a 40% error in a distance estimate, which would be rare, translates into no more

than a 4 dB error in estimated received level.

Ice Conditions Near Playback Sites

On playback days when clouds were absent or high, we obtained vertical photographs of the

area near the ice camp in order to "map" the ice in the area. Whale locations were often identified,

in part, relative to ice features described or videotaped by the aerial observers. Thus, vertical

photos of the ice were extremely valuable in mapping positions and movements of whales relative

to the ice camp.

In 1994, once or twice during each day with coordinated aerial and ice-based work, the

project aircraft climbed to an altitude as high as 9000 ft or 2750 m (cloud ceiling permitting). A

sequence of vertical photographs was taken through the aircraft's ventral camera port using a 35-

mm camera with 17-mm very wide angle lens and/or a video camera with wide angle lens. One

photo-mosaic prepared from these vertical photos appears as Plate 6.1 on p. 258. In addition,

oblique photos of the ice and leads were sometimes taken with a Polaroid camera; these provided

prints onto which notes could be made immediately. In 1991, ice photos were not available at playback sites because low clouds prevented aircraft operations near the ice camp.

During each day of ice-based work, ice conditions near the ice camp were documented by

taking theodolite readings for ice edges and other prominent ice features visible from the camp.

From these theodolite readings, distances were later calculated.

Sound Levels Received by Whales During Playbacks

Unlike the steady drillrig sounds from Karluk, the icebreaker sounds played back in 1991 and

1994 varied considerably with time, corresponding to the phases of heavy icebreaking: ramming

ahead, stopping but maintaining full-ahead power, and backing down. Accordingly, the received

signal levels near the actual icebreaker and near our projectors varied with time as well as with

distance from the projector. Figure 2.2 shows the distribution of 1/3-octave received levels as

recorded at distance 460 m from the actual icebreaker at the Corona site. These levels represent

the range of recorded levels provided to the projector amplifiers during the playback experiments

reported here.

The effective source levels for the actual icebreaker were estimated by using the acoustic

transmission loss model developed in the present project for the western Beaufort Sea (see §4.3,

Transmission Loss, p. 96fj), the Water depth at the icebreaker recording site (35 m), and the

measured received levels near the Corona site off Camden Bay. We estimated the source level in

various broad bands (e.g., 20-1000 Hz; 20-5000 Hz) and in each 113-octave band from 20 to 6300

Hz. The underlying assumption for this derivation is that the bottom properties at the Corona

drillsite are similar to those in the present study area.
Icebreaking Noise

1'l:I14 Minutes on 02 Sep 86

150 r-------------'------------------------======1

130

-III

Q.

::L 120

~

CI) ..

m

'C

-

~

110

.J

i

>

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90

140

,

,

,

,

...._--...

,

,

,

,

'-•..•..•.•.•..

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,

,

,

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,

,

,

,

,

,

,

,

,

'"

,

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-,

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,

,

•.._--.

------100%

--95%

--+-50%

--5%

------ 0%

70

0 III co 0 III ~ 0 0 (') 0 0 III 0 0 0 III 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 •.. N

•.. ('II ('II •.. ~ III co co 0 ('II co 0 III •.. 0 0 (') 0 0 III 0 0 0 III 0 0 0 0 0 0

•.. (')

•.. •.. •.. ('II ('II (') ~ III co co 0 ('II co 0 LO e- 0 0 (') 0 0 0 •.. •.. •.. ('II ('II (') ~ LO co •..

~

LO

0 0 ('II ('II ('II

1/3 Octave Band Center Frequency (Hz)

..._-----_ ...,

'....

•....._--..

,

,

,

,

"'----..'-',

'.._--.•.---

80

FIGURE 2.2. The distribution of received levels from the icebreaker Robert Lemeur operating at range 460 m, by 1I3-octave band center

frequency. This distribution was computed from the 14+ minute recording of Greene (1987a:48fj).
2.3 Methods: Playback Experiments 48

Figure 4.25 in §4.4 shows the resulting estimates of 113-octave effective source levels during

the 14-min recording. Figure 4.26 shows the time-variability of the resulting estimated source

levels in four bands in relation to changes in ship activity. The results shown in these Figures are

important in the discussion of playback fidelity (§4.4).

To interpret our observations of whale behavior, it was necessary to estimate the sound levels

to which the observed whales were exposed. Whales under observation at a given distance from

the projectors at various times in 1991 and 1994 were subjected to widely varying sound levels

because of

~ moment-to-moment variability in received levels of the original icebreaker sound at the

recording site 460 m from the icebreaker,

~ day-to-day variability in projector capabilities, and

~ site-to-site variability in sound propagation conditions at different projector locations.

Thus, sound levels received at any specified distance on a given date and time had to be estimated

on a statistical basis. We chose to estimate the minimum, median and maximum levels expected

for each band within the 64-s period preceding the observation time, and the minimum, median

and maximum plus 5th and 95th percentiles expected for each band during the entire 14-min

segment of recorded icebreaker sound. Because the 14-minute segment was repeated over and over

during prolonged playbacks, the distribution of sound levels at a given distance from the projectors

would be the same for one 14-min period as for the next if the projection equipment was not

adjusted in the meantime and if the playback did not start or stop within the 14-min period.

Some sonobuoy measurements were available for directly measuring the received levels at

specific sites, times and distances from the projector. However, given the variability in the

sounds, it was usually essential to rely on a complex source level/transmission loss database and

prediction program (which we call the "sound exposure model") to estimate the received level

statistics for a given projector location, time, and projector-to-whale distance.

The basic elements of the resulting sound exposure model are as follows:

a. Measurements of the 113-octave spectrum of the recorded icebreaker sounds at 8-s

intervals throughout the 14+ minute sequence used in the playbacks. This database

consists of a series of 109 113-octave spectra, each of which represents the average signal

characteristics over an 8.5-s interval. This series characterizes the playback levels vs.

time. Although not calibrated absolutely, the series spectra are comparable to one

another. Given calibrated acoustic pressure source levels for one spectrum in the series

(see [c], below), all other series spectra can be adjusted to be calibrated source spectra,

thereby characterizing the source levels of the projected icebreaking sounds for any time

during the playback until the playback conditions changed.

b. A histogram arrangement of the 109 series spectral elements in "a" above, where the

levels for each frequency band are ordered and the corresponding minimum, 5th, 50th,

95th percentiles, and maximum values are identified. Once calibrated for a given
2.3 Methods: Playback Experiments 49

playback condition, these values characterize the distribution of playback levels during

any I4-min interval until the playback conditions changed.

c. A database of measured projector source levels from selected times during every

icebreaker playback experiment when whales were observed, keyed by date, time, and

offset time from the beginning of the 14+ minute icebreaking sequence. As a minimum,

a new source level measurement was taken whenever there was a change in amplifier

setting or other playback conditions. Each of the several measured source level spectra

in the database for each day was calculated from an 8.5-s segment of recorded sound, and

the offset time of each such segment relative to the start of the 14-min icebreaker

sequence was determined (see p. 43 in "Acoustic Analysis"). Knowing the offset time,

one can match the source levels with specific elements in the 109 series analyses. Thus,

each source level measurement can be used to calibrate all 109 members of the series

database. In other words, having measured the projected source level 'in one 8.5-s

segment of the playback, and knowing when during the 14-min sequence this segment

occurred, one can determine the projected source level during any 8.5-s segment until the

playback conditions changed. The water depth associated with each source level

measurement, for use in the transmission loss model, is also stored in this database.

d. A depth-dependent transmission loss model with parameters for the II3-octave bands

centered at 20-6300 Hz. This model was developed based on the transmission loss data

collected during all four years of the present project, as described in §4.3, Transmission

Loss. This TL model is specific to the present study area northeast and east of Pt.

Barrow under spring (late April and May) conditions.

To use the sound exposure model to estimate the levels of projected icebreaker sound that

will reach a given distance from a particular playback site, the user has only to specify one of the

playback dates, a time during that playback, and the distance. The program follows a sequence

of steps:

1. It searches the source level database ("c" above) to find the closest measurement time

preceding the specified time of interest.

2. From the offset time associated with the source level measurement in "1", the program

selects the two series spectra in "a" that bracket that time. Interpolating between the two,

the program computes a 113-octave spectrum corresponding to the exact time of the

source level measurement.

3. The program calculates the differences between the measured source level spectrum and

the interpolated series spectrum. These differences may be added to any series spectrum,

and to the histogram spectra, to derive corresponding calibrated source level spectra.

4. The program selects the eight consecutive spectra from "a" that characterize the 64-s

period up to the time of interest specified in "1" above.

5. From these eight spectra, the program calculates the minimum, median and maximum

levels in each 113-octave spectral band for the 64-s period up to the time of interest.
2.3 Methods: Playback Experiments 50

6. Applying the differences from "3" to the minimum, median and maximum values in "5",

the program calculates the range of source levels for each 1/3 octave band for the 64-s

period immediately preceding the specified time of interest.

7. Applying the differences from "3" to the 14-min minimum, 5%, 50%, 95% and maximum

113-octave band levels in "b" above, the program calculates the calibrated source level

distribution, by 1/3-octave band, for the full 14-min playback cycle and for all following

times, including the specified time of interest, up to the time of some change in projector

operation.

8. The program applies the transmission loss model mentioned in "d" to the source levels

computed in "6" and "7" above to obtain the expected ranges of received levels at the

specified distance for both the 64-s period preceding the time of interest and the entire

14-minute playback duration.

9. The program also calculates the expected received broadband levels for the 20-1000 Hz,

20-2000 Hz, and 20-5000 Hz bands.

The 1/3 octave band spectra from "8" and the broadband received levels from "9" constitute the

output of the sound exposure model program. If the specified time of interest occurred within 64 s

after some change in projector operation, such as turning it on or adjusting the transmitted power,

the 64-s results are reported as "discontinuity". Similarly, if the specified time of interest occurred

sooner than 14 min after a change in projector operation, the 14-minute results are reported as

"discontinuity" .

To validate the sound exposure model, we used it to estimate the expected received levels

of projected icebreaker sounds at times and distances where sonobuoy measurements of actual

received levels were obtained during 1991 and 1994. The sonobuoy measurements were not used

in developing either the transmission loss model or the sound exposure model. Thus, the sonobuoy

measurements provided an independent source of data useful in checking the models. Results of

this comparison are described in §4.3 (Fig. 4.21, 4.22). As described there, the sound exposure

model provides reasonable estimates of actual received levels.

The sound exposure model has been implemented as a series of 14 interlinked spreadsheets

in a MicroSoft Excel version 5 notebook. It can be used either to process single date/time/distance

requests entered from the keyboard or, in batch mode, to process a file containing any number of

such requests, saving the results to output files for subsequent use in other analyses. The latter

capability was used to estimate the received sound levels at times and distances when whales were

observed. The resulting estimates of received sound level were subsequently used in analyses of

whale movements and behavior relative to received sound levels and relative to the ratio of

icebreaker sound to ambient noise (§6.1-6.3).
3.11ce and Weather Conditions 51

3. ICE, WEATHER AND FIELD ACTIVITIES7

3.1 Ice and Weather Conditions

Ice conditions in 1991 and 1994 were generally similar to the typical conditions described

by Marko and Fraker (1981) and Richardson et al. (1990a:28fj). A nearshore lead along the landfast ice edge extended from the Chukchi Sea, around Point Barrow, and ENE into our study area

during most of each field season. However, within the more easterly part of the study area, the

1andfast ice extended farther offshore in 1994 than in 1991 (Plate 3.2 vs. 3.1). In both 1991 and

1994, the offshore pack ice and the 1andfast ice at the floe edge were thinner than normal. Therefore, on several days we could not find suitable and safe sites for the projector system even though

extensive areas of open water were found along the migration corridor being used by whales.

In 1991, low cloud prevented aerial observations from altitude 460 m ASL on most days.

In 1994, low cloud was less common and fog was unusually infrequent, but stronger-than-normal

winds made aerial observations difficult during most days with ceilings >460 m.

Because this report takes account of some acoustic and biological data from 1989-90 as well

as 1991 and 1994, weather and ice conditions encountered during all four field seasons are briefly

described and compared below. More details concerning conditions in 1989 and 1990 are given

in Richardson et al. (1990a, 1991a).

Ice and Weather in 1989

Very heavy sea ice conditions prevailed in the Barrow area from late April through mid-tolate May 1989. When the study was initiated in late April, the overall ice cover was 98 to >99%

and no major leads were present. The few open water areas consisted of small holes among pans

plus narrow cracks and leads that tended to be oriented NW to SE. From 7 to 11 May slightly

colder temperatures (Fig. 3.1A) and calm winds resulted in freezing of virtually all open water in

the study area. On 12 May moderate NNE winds shifted the offshore pack ice, forming several

minor leads oriented SW to NE. The overall ice cover decreased to 95% on that date, and ranged

from 85-95% until 20 May, when a "nearshore" lead 1-6 km wide formed along the landfast ice

edge, extending well east of Barrow. This lead, shown in Richardson et al. (1990a:Plate 2),

remained open for the remainder of the 1989 study period.

Ice conditions during much of the 1989 season were worse than normal for conducting

bowhead whale studies, and at times when ice conditions were better, the weather usually was not

good. The weather was clear in late April and early May in 1989, but little open water was present

so whales could not be studied effectively. Unusually cold weather from 5 to 8 May 1989 froze

existing open water areas and consolidated the offshore pack ice, making observations even more

difficult. From 10 to 26 May 1989, low ceilings, snow and fog prevented aerial observations from

7 By G.W. Miller, W.R. Koski and W.J. Richardson, with R. Elliott and N. Patenaude
3.11ce and Weather Conditions 52

-I

I

o

••

o,50 100nmi

I I

o,50 100mi

I I

o,

50

I

100

,

km

I

,-

PLATE 3.1. NOAA satellite imagery of the Beaufort Sea, 4 May 1991, showing a well-developed

nearshore lead and extensive offshore pack ice.
3.11ce and Weather Conditions 53

J PLATE3.2. NOAA satellite imagery of the Beaufort Sea, 16 May 1994, showing the recently-

! formed nearshore lead and offshore pack ice conditions, including the much wider former

nearshore lead. Note the formation of cracks in the landfast ice east of Pt. Barrow.
3.1 lee and Weather Conditions 54

501....-~---------------------,

40

A. /'-. •••••_J * *

..............._ _ ~ ;:····7··_ ..······

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r> ""'_,1' -- 1989 High, Low . , '" '\ I

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r•.., ,/ '_,,I " --- 1990 High, Low

, v \ I

•. ,. ----_. Normal High Low l..••••••••• y ••.L •.'), ••••• ,-:::......J ••••••••.••.•.•..••.•..••.....•.•..••.•.•.•.•.•.•.•.•.•.•.•....•.••.•......•..•..••.•.•..••.•.•.•.•.•.•.•.•.•.•..••••. _ •.•.•..••.••. _ •..•.•..•.•.•.•.•.••.•..•.•...•.•.•. ~•.•.•.•...•.••.••. _ •.•.

, I, I '-" R rd H" h L '-', l :l ------ eco Ig, ow

" Ii

"

10 20 30 10 20 30

April May

FIGURE3.1. Daily Barrow weather in April and May of 1989-91 and 1994. Normal and record high and

low temperatures are based on data from 1961-90. Asterisks indicate temperatures that set (1989-90) or

exceeded (1991, 1994) those record temperatures.
i:L

-e 1 ~

1tl

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0

a.

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C• ,~••••• _./~\ '" I

...........................................•.................•...••...•..•.......... __•.......•.......•....•••.•••....••.•.•.•••••• ;.:•..•..•: ...•..7'......•.•...••••,,!...\l.••

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3.1 lee and Weather Conditions 55

5,1h--------------------------,

.:z,: ,....,:::=:~:=::=~~ .....'

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.,.- _ ,.,.' ,•••_",J

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............................................... ;:..:.,.,...,............................................................................•.............................

,"\ I ,I H' h L

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.•..;:-.••;/.....•....••••...•.• .,..........•••••••......•.•..••.••....•. 7.:.7.:.7.~•.•!':J.9.~~!.tij£I.~!..I::9.'!Y. ..•..•

, -----. RecordHigh, Low

10 20 30 10 20 30

5u'T--------------------------,

D. ,"<,.:»: /..,.

....................................................... ~.........................................................•.........;: ·;:···..·7··············"r "··

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r, A : \ /\/ ••, :\ I \ l " '-I

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, I •

•• I I • Normal High Low

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, I, I •••••, R rd H' Lo

'-, I \ I -----. eco Igh w \,' ,,' t

"

20 10 20 30

April May

FIGURE 3.1. (continued).
3.11ce and Weather Conditions 56

altitude 460 m ASL mostof the time. Observing conditions were ideal on 27-30 May 1989, but

most bowheads had already migrated past Barrow by that time.

Ice and Weather in 1990

Ice conditions in 1990 were more similar to those in typical years. When the study was

started in late April, there was a narrow nearshore lead along the landfast ice edge ENE of Barrow.

Little open water was present amidst the offshore pack ice north and NE of Barrow. The lead

started to widen at Barrow on 7 May, and was several kilometers wide by 10 May. This major

lead extended across much of our study area. The pack ice north of the lead was generally heavy,

but there were localized corridors of less-dense pack ice, especially in the first few kilometers

north of the main nearshore lead.

The main nearshore lead and pack ice farther offshore, shown for 19 May 1990 in Plates 1

and 2 of Richardson et al. (1991a), remained more or less unchanged until 20 May when strong

winds moved the ice. The lead near Barrow widened but the lead became choked with ice -40 km

ENE of Barrow. During the final few days of the 1990 study, strong winds altered the lead and

pack ice conditions almost daily. The lead along the landfast ice edge was reduced to 1 km wide

by 25 May, and secondary leads developed in the offshore pack ice north of Barrow.

Weather conditions near Barrow during the spring of 1990 were much more amenable to

aerial observations of whale behavior than they had been in 1989. During the last few days of

April and the first six days of May, temperatures were near normal (Fig. 3.1B). However, during

the remainder of May temperatures were consistently above normal, and record high temperatures

were recorded or equaled on several days (Fig. 3.1B). The overall average temperature at Barrow

in May 1990 was 7 F

O

above normal (Table 3.1). Although fog was common, especially in the

mornings, ceilings often were high enough to permit aerial observations of behavior from the

desired 460 m ASL altitude.

TABLE3.1. Weather conditions recorded at Barrow, Alaska, during April and May 1989-91 and

1994 in comparison to long-term average conditions from Brower et al. (1977).

Average Wind Average Sky Cover Average Temperature

Speed (mph) (tenths) (degrees F)

Year April May April May April May

1989a 12.8 10.3 7.1 7.7 6.0 17.4

1990a 12.5 14.0 6.1 8.3 7.5 26.5

199P 11.5 13.6 6.8 9.4 3.3 28.0

1994a 10.6 15.9 6.7 7.8 -0.1 18.6

1948-1974 11.5 11.6 -2.2 19.4

Average

a Data from National Climatic Data Center, Asheville, NC.
3.1 lee and Weather Conditions 57

Ice and Weather in 1991

When the 1991 field season began in late April, ice conditions near Barrow were more open

than during typical years. A wide nearshore lead was present along the landfast ice from

southwest to northeast of Barrow (Plate 3.1). The ice within this lead was primarily newly-frozen

ice with a few large pans of old ice. This broad lead extended far to the east. The ice cover was

in particular contrast with that in 1989, when there was nearly total ice cover, largely by thick

multi-year ice.

A period of strong easterly winds on 6-10 May forced pack ice against the landfast ice,

ground many of the ice pans into brash ice, and closed the lead Nand NE of Barrow. When the

wind subsided, a wide lead remained west and southwest of Barrow, but the lead was closed to the

north and northeast. However, irregular openings were present along the landfast ice edge in that

area. The prevalence of brash, small pans, and generally thin, unstable ice, and the small sizes of

open water areas near the landfast ice edge, made it difficult to locate safe and suitable locations

for the projector system. On several occasions, we began setting up the equipment along the edge

of a pan bordering open water but, before projection could begin, loose ice moved toward the

equipment and forced its retrieval from the water.

During mid-to-late May 1991, a narrow discontinuous lead was present along the landfast

ice edge north and northeast of Barrow. The lead consisted of a series of small to large openings

in the pack ice along the landfast ice edge. West and northwest of Barrow the lead remained open

and was several kilometers wide. The ice along the northern margin of the lead was primarily

unstable new ice.

Temperatures during the 1991 field season tended to be well above normal (Fig. 3.1C; Table

3.1). Low cloud was more frequent than normal. Although the cloud ceiling was high enough to

allow low-altitude VFR flights on most days, days with clear skies or high clouds were very

infrequent. This greatly curtailed our ability to obtain systematic aerial observations of whale

movements and behavior from an altitude of 460 m. In 1991, it was rarely possible to climb that

high without losing sight of the sea; on most occasions the cloud ceiling was at or below 305 m

(1000 ft). The average sky cover at Barrow (in tenths) was 9.4 for May 1991; this was the highest

monthly average sky cover recorded during April or May of any of the four years of this study

(Table 3.1).

Ice and Weather in 1994

Only small areas of open water were present in our study area during late April and early

May, 1994. Ice, primarily first-year ice, covered from 97 to 99% of the sea, and the only areas

that could be used by migrating whales consisted of small open areas between pans of ice, cracks,

and narrow discontinuous leads. These areas were often covered with thin layers of new ice.

By 3 May, the pack ice in the study area began to loosen and by 4 May there was a major

(in places 2-3 km wide) continuous lead along the landfast ice edge extending east to 75 km east

of Pt. Barrow. The landfast ice edge continued ENE across the entire study area rather than
3.1 lee and Weather Conditions 58

curving to the ESE in the more easterly areas. The lead along this ice edge remained open until

10 May, when the effects of several days of strong east winds pushed pack ice against the landfast

ice (Plate 3.3). For the next few days, the nearshore lead along the landfast ice edge was variously

open or choked with pack ice.

By the evening of 15 May, the outer 2.5 km of the landfast ice broke free along a 75 km

extent, forming an inner lead along the new landfast ice edge and an outer lead along the former

landfast ice edge (now drifting; Plates 3.2, 3.4. Ice conditions changed from day to day for the

remainder of the study period (through 25 May) as winds (frequently in the moderate to strong

range) and currents shifted the pack ice (Plate 3.5).

Temperatures during the 1994 field season fluctuated from above normal in late April and

early May to below normal in mid-May, and back to above normal around 20 May (Fig. 3.1D).

The proportion of days with clear skies or ceilings suitable for VFR aviation was similar to 1989

and 1990 and was much higher than in 1991. However, on many days in 1994, thin ice, high

winds, and the resulting shifting of pack ice made it difficult to find stable pack ice on which to

establish ice camps. On most days when aerial observations were possible near an ice camp, high

sea states associated with the high winds made it difficult to observe whale behavior. The average

wind speed at Barrow during May 1994 was 15.9 miles per hour; this was the highest average wind

speed recorded during the four years of the study (Table 3.1) and was well above the May average

for 1948-74 (Table 3.1; Brower et al. 1977).

3.2 Summary of Field Activities

This report deals primarily with results from fieldwork in 1991 and 1994. The first priority

of this fieldwork was to study the effects of playbacks of icebreaker noise on the distribution,

movements and behavior of bowhead whales and (as possible) white whales during their spring

migration near Barrow. An important component of this assessment was to obtain data on

distribution, movements and behavior of presumably undisturbed whales for comparison with the

experimental data. Data on ambient noise and sound propagation in the study area were also

needed for interpretation of playback results. Data on ambient noise, sound propagation, whale

movements and whale behavior during all four years of study are relevant as a basis for

interpreting the 1991 and 1994 playback results. Therefore, several types of data from 1989-90

are integrated into this report.

We present here a summary of project activities during 1989 and 1990, and then a more

detailed account of the previously-unreported activities during 1991 and 1994. More detailed

information about the activities in 1989 and 1990 is given by Richardson et al. (1990a:67ff, 1991a:

34ff). Table 3.2 summarizes the amount of effort of various types in the four years of the study.

Table A-I in Appendix A summarizes the observation effort near the ice camp, and the number

of whales seen there, under control, playback and other conditions on each date with ice-based

work during all four years of study.
3.1 lee and Weather Conditions 59

PLAT13 3.3. NOAA satellite imagery of the study area, 11 May 1994, showing the ice-choked

nearshore lead and offshore pack ice conditions."

~------ ----------------------------------- ---------
3.1 lee and Weather Conditions 60

PLATE3.4. NOAA satellite imagery of the study area, 16 May 1994, showing the recently-formed

nearshore lead and offshore pack ice conditions, including the much wider former nearshore lead.

Note the formation of cracks in the landfast ice east of Pt. Barrow.
3.1 lee and Weather Conditions 61

~_-_~_----_~_---"

.-

PLATE 3.5. NOAA satellite imagery ofthe study area, 20 May 1994, showing the nearshore lead

and offshore pack ice conditions.
3.2 Summary of Field Activities 62

TABLE 3.2. Summary of observation effort of various types during each year of the study.

1989 1990 1991 1994 Total

A. Ice-Based Work

First date

Last date

Total Days

Projector(s)

29 Apr

30 May

17

J-ll

Playback Days-Total

With bowheads during plbk u

With white whales ,,"

11

4

5

4

64.9

43.3

13.2

Transmission Loss Tests

Obs. hours - Control

" - Playback

" - Other

B. Aerial Work

First date

Last date

# days with flights

#" ">1 h

1 May

30 May

24

24

28

28

88.4

57.8

25.6

5.0

10

17

12.3

13.3

# flights offshore

# ">1 h

Flight hours offshore - Total

" - recon.

" - behav. obs.

" - photog.

Behav. obs. - days

- sessions

" - undisturbed hours

" - other hours

Photo Sessions

# Days

# Sessions

# Flights

8

10

9

C. Combined Ice-based and Aerial

Observation near Ice-Camps h

Hours - Control

- Playback

- Other

Bowheads - Control

- Playback

- Other

White Whales - Control

- Playback

- Other

65.4

43.3

15.0

16

21

16

132

170

19

27 Apr

26 May

16

J-ll

8

6

1

4

45.8

30.7

4.8

29 Apr

26 May

22

20

37

34

98.8

52.0

46.8

o

12

29

31.6

15.2

53.3

30.7

4.8

188

200

43

277

49

42

28 Apr

26 May

13

J-13 +

F-40

6

1

2

4

35.4

12.7

13.4

28 Apr

26 May

23

18

30

25

75.4

55.8

4.1

15.5

5

7

4.1

o

o

o

o

35.4

12.7

13.4

18

9

7

165

14

70

28 Apr

25 May

13

A220+

J-ll

7

6

1

1.5

59.3

27.2

14.1

27 Apr

25 May

22

21

35

33

119.0

66.0

36.2

16.8

10

23

24.1

12.1

10

13

11

10

15

12

27 Apr

30 May

59

32

17

9

13.5

205.4

113.9

45.5

27 Apr

30 May

91

83

130

120

381.6

231.6

112.7

37.3

37

76

72.1

40.6

28

38

32

219.3

113.9

47.5

433

314

123

600

265

137

"Counting whales seen near camp by aerial as well as ice-based observers.

h From Appendix A, Table A-I.

65.2

27.2

14.3

211

84

57

26

32

6
3.2 Summary of Field Activities 63

Fieldwork in 1989 and 1990

The 1989 study provided only a limited amount of playback data, but provided considerable

baseline information on ambient noise, sound propagation, whale movement patterns, and whale

behavior. In 1989 the ice-based crew was able to work on the ice on 17 days (Table 3.3, Fig. 3.2).

They completed transmission loss experiments on four days, and obtained ambient noise data on

most days when they were on the ice. They projected continuous drilling noise into the water on

11 days, but bowheads were seen near the ice camp on only four of these days: on 1 d by the ice

crew only, 1 d by the aircraft crew only, and 2 d by both crews (Table 3.3). White whales were

seen near the operating projector on five days: 2 d by the ice crew only, 1 d by the aircraft crew

only, and 2 d by both crews. Behavior of bowheads was observed from the circling Twin Otter

aircraft during 17 observation sessions on 10 days (Table 3.3, Fig. 3.3). Aerial observations of

the behavior of bowheads exposed to drilling noise playbacks were obtained on three days. Vertical photography of bowheads was done on 8 days.

The 1990 field study was highly successful, largely because of the large numbers of

bowheads that passed the sound projector during control and experimental periods on a few of the

days. The ice-based crew was able to work on the ice on 16 days (Table 3.4, Fig. 3.4). Transmission loss experiments were completed on four days, and ambient noise data were collected on

most days. Bowheads were seen from the ice on eight days (Table 3.4). Continuous drilling noise

was projected into the water on eight days and bowheads were seen from the ice while sounds were

being projected on six of these days. Aerial observations of bowhead behavior were done on 29

occasions during 12 days (Table 3.4, Fig. 3.5). Aerial observations were conducted near the

projector site during both control and playback periods on five playback days. Data on behavior

of undisturbed bowheads were obtained on seven additional days at locations near the ice camp

(2 days) or elsewhere (5 days). No vertical photography of bowheads was possible in 1990.

Fieldwork in 1991

The 1991 field study provided data on ambient noise, sound propagation, and whale

movement patterns in the study area, but obtained few data on whale reactions to icebreaker sound

or on behavior of undisturbed whales. The ice-based crew was able to work on the ice on 13 days,

and icebreaker noise was projected into the water, at least briefly, on six of these days (Table 3.5).

Bowheads were seen from the ice camp on eight days, but on only one day were they seen while

icebreaker sounds were projected (Table 3.5). Deteriorating ice conditions forced premature

termination of ice-based operations on some days. Because of prevailing low cloud, the aerial

crew was not able to obtain behavioral observations near the ice camp on any day in 1991, and

obtained brief observations elsewhere on only five days. In general, persistently low ceilings and

unstable ice conditions limited the useful work that could be done in 1991. However, vertical

photography of bowheads, which can be done under low cloud, was possible on 10 days, and the

planned number of transmission loss tests (4) were also completed. The one successful playback

test with bowheads in 1991 was done on the first day when it was possible to set up the projector

system on the landfast ice edge close to Pt. Barrow. All previous playbacks in 1989-91 had been

from pack ice farther east or northeast.
3.2 Summary of FieldActivities 64

TABLE 3.3. Daily activities by the aerial and ice-based crews in 1989". See Richardson et al.

(1990a:68ff) for more details.

Date

Aerial Crew

Aerial Behav. Near Camp Other Photo- Control

Survey Control Playback Behavior graphy

Ice-based Crew

Playback TL Test

29 April

30 April

1 May

2 May

3 May

5 May

6 May

7 May

8 May

9 May

12 May

13 May

14 May

15 May

16 May

17 May

18 May

19 May

20 May

21 May

23 May

24 May

25 May

27 May

28 May

29 May

30 May

0"

W

BW

W

BW

BW

W

W

BW

BW

BW

BW

W

BW

BW

o

W

BW

BW

BW

BW

BW

BW

o

Obs.

0"

o

B B

o

o

o

o

o

o

o

BW

o

BW

o

BW

o

W

o

o

B

B

o

o

a 0 indicates that no whales were seen, B indicates that bowheads were seen, and W indicates that white whales were seen;

blanks mean "no work of this type on this date".

h Incomplete transmission loss test.

e During this session whales were subjected to potential aircraft disturbance.

d A helicopter overflight experiment was conducted on this date.

c Measurements of underwater noise from helicopter and Twin Otter overflights were obtained.

f White whales were seen near the ice camp during the survey but were not observed systematically.

o

Be

BW B

B

BW W

B

o

B

W

BW BW

Be

B B

B

BW

B

B

B

B

o

o

Oc

W

B

[W] f
3.2 Summary of Field Activities 65

156 155

._._._._._----_.,.

,

\

\

"

,

.,<;

'89 Playbacks

o No Bhd. Present

l8l: Bhd. While Quiet

e Bhd. Our. Plbk. -'-

"-, '89 Trans. Loss Tests

o No Bhd. Present

J8{ Bhd. While Quiet

il Bhd. Our. Plbk.

'89 Control Obs. From Ice

/::,. No Bhd. Present

X Bhd. Present

72

o

9M

""Qo..

---------------:1: .",

---0. 3M +

14M

~+

18l

16M

r

r

............

•_-0'29M .

/ --.D2M':

23M 6M D29A:

O._---,li07M 0 025M 1130·..\ ....

/::"17M / 21M 0 0 0

.i->:: 26M 27M 27M

/~.......• -------_ .

/+

---_...•.....

+

---

,-- ,----------' -; .. -'

....•, .•......- •...._-- •._.r" "'...

Landlas! Ice Edge·· .. '-<!o ",-

-"'"

'-.." -.

+

"<, .....

o 5 lOnmi

o lOmi

...............

....... -+. 10 m.· 71

5

+

o 5 10 km

72

7130

157 154

FIGURE 3.2. Locations where ice-based crews projected drilling sounds, conducted transmission loss tests,

and made control observations, 29 April to 29 May 1989. X and solid symbols represent days when

bowheads were observed. Locations on the pack ice are approximate because of ice drift during the

course of each day's work.

156 155
,

,

,

,

\

'-,...•.•..

.......,.•.•.•

\

I 1''''••••----- "<,\

, ,

•••••••••••••••• ,,1 \ -,

-------'\\

,

,

,

-,

"

----' 07M(B4)

__--./".--;-- ~M(B8) eli 14M(B7) /".- ••--------------1:: "

,

(' 6M(B3A) 29M(B17B)@29M(B16)/(lj';3M(B9)""-"""-'60

,/ 6M(B3B)0 0 14M(B6) 29M(~:7.A'''-: 11I---

6M(B3C) 0 O.28M(B15) "

./-- 3M(B2) @ @~3M(Bl0) : ., .... '

"

./"--//" :"-~)"''' ..""(,.,

,,' / ••----------.----03M(B1 27M(B13)@ 027M(B121,:

7130//_--./. + __ ___---./ + ... ,.

..... ,....... .'._"._-.-

..................

..•.••...•.•- '

..... _--_ ..•

3.2 Summary of Field Activities 66

157 156 155

-'--_._.- ..•.•..<,

,

\

\

\,

•..... , <,

'89 Beh. Obs. Sites

o Presumably Undisturbed

Undisturbed +

<) Potentially Disturbed

e Potentially Disturbed

72 + + "

'<,•.... ,

I

i

\

"

"

\

\

-,

"-"'."-~o

o~

+

+

<. >

Landlast Ice Edge··,._

'~O

~"

.......

-. .............

...... +

".

.......... ....." m- "

o 5 lOnni

o 5 lOmi

+

o 5 10 km

157 156 155

72

7130

FIGURE 3.3. Locations where behavior of bowhead whales was observed by the aerial crew, 3-29 May

1989. Annotations represent the date in May (M) and, in parentheses, the behavioral observation session

number (B 1-B 17). On other dates, behavioral observations were prevented by low clouds that precluded

observations from altitude 460 m ASL.
3.2 Summary of Field Activities 67

TABLE 3.4. Daily activities by the aerial and ice-based crews in 1990°. See Richardson et al.

(1991a: 35ff) for more details.

Aerial Crew Ice-based Crew

Aerial Behav. Near Camp Other Photo- Control

Date Survey Control Playback Behavior graphy Obs. Playback TL Test

27 April 0

29 April BO B B

30 April 0 0 [0] b

1 May 0 0 0

2 May W 0 0

3 May 0

4 May 0 0 0

5 May B B 0 0

6 May 0

9 May B B B B

10 May BW BW B BW B

11 May BW Be B BW B

12 May BW B

13 May BW B B B B

16 May BW B B B B

17 May BW

19 May BW BW

21 May BW BW B BW BW

22 May 0

23 May B B

24 May BW B 0 0

25 May BW B 0 0

26 May BW

a 0 indicates that no whales were seen, B indicates that bowheads were seen, and W indicates that white whales were seen;

blanks mean "no work of this type on this date".

b Incomplete transmission loss test.

eHelicopter overflight experiment on this date.
3.2 Summary of Field Activities 68

157 156 155

_.-.-._--- <.

\

\

\

"

,

.••....•....•.•.

'90 Playbacks

0 No Bhd. Present

~ Bhd. While Quiet

e Bhd. Our. Plbk.

'90 Trans. Loss Tests

0 No Bhd. Present

J:8l Bhd. While Quiet

Ii Bhd. Our. Plbk.

'90 Control Obs. From Ice

~ No Bhd. Present

X Bhd. Present

72 72

+

+

'~Qo..

+ // .>: -------_ ••__.~ __.,. 111

A .> ....<, '>"

D1M 4MlB21M I.llM -roM'--- D24M

21M~~~_Ji!il X D 2M

• ••• --. 25M 19M

,." X29A

//+ 6.27A···· DSOA 7'130 + +

.1SM ········ .. 1I16M

......... -.._-" ..'..... ,.._- •..-..__ .• ......

....~ .

..... --.

.......

o 5 1lnmi

o

==--

1lmi

.................. ····-+.·· 10 m.······ 7'1

5

+

o 5 1l km

157 156 155

FIGURE 3.4. Locations where ice-based crews projected drilling sounds, conducted transmission loss tests,

and made control observations, 27 April to 25 May 1990. X and solid symbols represent days when

bowheads were observed. Locations on the pack ice are approximate because of ice drift during the

course of each day's work.
7130

3.2 Summary of Field Activities 69

157 156 155

72

._-.-.__ ._._ ...•..

'.,

"'i

\...<; 25M(B29)

<; 0

(j~(B26)

.,.•...\ \

i ~ -r--c- ...J

o 25M(B28) l '\

o 25M(B27) i ;: ',_._/ ./

72

'90 Beh. Obs. Sites

o Presumably Undisturbed

Undisturbed +

() Potentially Disturbed

e Potentially Disturbed

+

+

,.....--------.._-..*

¢23M(B24) "-",

, •• J \.

",,," .... "

.' . "'60

.: 1"/)--_

21M(B23) 5M(B3) //

23M(B25) ~21M(B22) / 10M(B9)••/

e 21M(B21A)::::::;0 e <b'10M(B7)

21M(B21B),/ .----1OM(B8)

21M(B2_l~t:---!.•.•~!B.1a,() 010M(B6)

/llM(Bll)O 0 ...O ..·······CD29A(B2

Oi~·9M(B4) llM(Bl~)\12M(B14)'29.a!lB~ ) +

l1M(B.. . •. ' '. l6M(B20)

~

. 13M(B15)··•....•. O~ 16M(B19)

13M(B16) .. '.

13M(B17) l6M(B18)•

7130

+

+

,.'

".-,i

•...•..•..•..•.• _- -..... ->.

..... _--_ ...

----_.--

- "".'

"~

~ 0",. .....

~

.......

+ ............... +

" .

................ Landfas! Ice Edge o 5 lOnm

o 5 10m

+

o 5 10km '"..+. ....10 m.······· 71

157 155

FIGURE 3.5. Locations where behavior of bowhead whales was observed by the aerial crew, 29 April-25

May 1990. Annotations represent the date in April (A) or May (M) and, in parentheses, the behavioral

observation session number (BI-B29). On other dates, behavioral observations were prevented by low

clouds that precluded observations from altitude 460 m ASL.
3.2 Summary of Field Activities 70

TABLE 3.5. Daily activities by the aerial and ice-based crews in 1991'. See Appendix A, Table A-2,

for more details.

Aerial Crew Ice-based Crew

Aerial Behav. Near Camp Other Photo- Control

Date Survey Control Playback Behavior graphy Obs. Playback TL Test

28 April W' B

29 April B B B

1 May BW B 0 0

2 May 0

3 May BW B

4 May BW BW

5 May BW W 0

6 May BW B 0

7 May B

8 May BW B

10 May BW B

11 May BW B BW W

12 May BW

13 May 0

16 May BW

17 May BW B BW BW

18 May BW B B 0 0

20 May BW B 0

21 May W

22 May BW B 0 Ob

23 May BW 0 0

25 May BW B B B

C

0

26 May BW B B 0

'0 indicates that no whales were seen, B indicates that bowheads were seen, and W indicates that white whales were seen;

blanks mean "no work of this type on this date".

b One bowhead was seen shortly after a distorted playback ended and before an undistorted playback started.

C One bowhead was seen as the helicopter landed. None were seen during presumably undisturbed conditions.
3.2 Summary of Field Activities 71

Ice-based work was possible on 13 days in the period 28 April through 26 May 1991. The

13 locations are mapped in Figure 3.6. Bowheads were seen by the ice-based crew on 8 of these

days (Table 3.5):

1. During 4 of 13 days, only "control" observations were obtained; the projectors did not

operate (Table 3.5; no playback and no TL test). On three of these days deterioratirig ice

and/or weather conditions forced the crew off the ice before the playback could begin (3,

6 and 20 May). On one day equipment problems prevented a playback (28 April).

Bowheads were seen from the ice during two of these 4 "control" days (28 April, 3 May).

White whales were not seen from the ice on "control" days.

2. During 6 of 13 days, icebreaker sounds were projected for prolonged periods (Table 3.5).

Bowheads were seen from the ice during four of these six days (11, 17, 18, and 22 May).

On the 11th and 18th, bowheads were seen only during the periods of "control" observations before and after icebreaker sounds were projected. On 22 May, a bowhead was seen

shortly after distorted icebreaker sounds ended. Bowheads were seen during the actual

playback period only on 17 May. White whales were seen from the ice on 3 of 6 days

with playbacks (5, 11 and 17 May). They were seen during the actual playback period

on 11 and 17 May, and during the control periods on 5, 11 and 17 May.

3. During 4 of the 13 days, transmission loss tests were conducted. (On one of these 4

days~18 May-s-there also was a prolonged playback.) Bowheads were seen within 5 km

of the projector site on three of these 4 days, always while the projectors were silent.

However, on one occasion (25 May) the observation was only 11 min after test sounds

were projected. White whales were not seen during TL tests.

The aircraft crew conducted 30 flights on 23 different days from 28 April to 26 May 1991.

However, on five of these days, poor weather (low ceiling, poor visibility, or high winds)

prevented any useful work. The remaining 25 flights ranged from 1.6 to 5.2 hours in duration.

Although the aircraft used in 1991 had an endurance of about 9 hours, longer flights were not

warranted during 1991 because of the low clouds that almost always prevented observations from

altitude 460 m (1500 ft). The ceiling was below 460 m during 18 of the 25 "effective" flights.

Total flight time during the 30 offshore flights was 75.4 h.

On five days when it was possible to see the surface from an altitude of 460 m, the aerial

crew conducted 7 behavior observation sessions totaling 4.1 h (Fig. 3.7; Table 3.6). Although this

work was our top priority, the prevailing low cloud rarely allowed it. Furthermore, of the 7 flights

when we could observe from 460 m, the winds were too strong for effective observations during

two flights. Bowheads were very scarce (only 1 seen per flight) during two additional flights.

Thus, only three of the 1991 flights provided a reasonable prospect for obtaining many behavioral

observations. All behavioral observations in 1991 involved presumably undisturbed whales. The

aircraft crew did not obtain observations of whales subjected to icebreaker noise because, during

our opportunities to project icebreaker noises to whales (Table 3.5), cloud ceilings were too low

to permit aerial observations near the projectors (Appendix A, Table A-2).
3.2 Summary of Field Activities 72

157 156 155

-'-'---_.-."

,

""'

"

".•••..••..........

'91 Playbacks

0 No Bhd. Present

~ Bhd. While Quiet

e Bhd. Our. Plbk.

'91 Trans. Loss Tests

0 No Bhd. Present

~ Bhd. While Quiet

il Bhd. Our. Plbk .

'91 Control Obs. From Ice

f:::" No Bhd. Present

X Bhd. Present

,

,

,

,

\

-,

" .

.,." ..\

, +: ..,.....-----"<, "

..,/~ \

...•.._..... '..

".

<,

72

+

05M _ .•...----.._- .....

""

',,..... '"- :t

'.""',

,..........•

,//"" "'60 ",. ••

.-

DIM ./'.--'

l8l11M •••• _---------.

26M"-- 66M .X····..

18,~,l+ X 28A .•...• ' 3M ~" .

23M /'-' 17M ••.••

_0' Landfasl Ice Edge

...•....,.. .

•••••••.•_-_ •••••.r ••••••••- ••••<, , ••••••••••••

+ +

'-' ..

+

. -<0 1tI•

............

...............

+

......

o 5 10nni

o 10 ••.• .......

.........

..... 10 m.···· .. 71

5

+

o 5 10km ".-+..

157 156 155

FIGURE 3.6. Locations where ice-based crews projected icebreaker sounds, conducted transmission loss

tests, and made control observations, 28 April to 26 May 1991. X and solid symbols represent days when

bowheads were observed: Locations on the pack ice are approximate because of ice drift during the

course of each day's work.

L

72

7130
3.2 Summary of Field Activities 73

156 155

.-..... -'-_'_'_'_".,

"'

"'-,

<;

'91 Beh. Obs. Sites

o Presumably Undisturbed

Undisturbed +

() Potentially Disturbed

e Potentially Disturbed

-'- <,-,._\ r

i ~ .,..- -----'

i

I

i

i

\

72

+ '."\

,

.i

./

/.,.

+

+ / •.••---------------l:

o 0 25M/S;) ---',

\ 06M(B5),

4M(B3) /", .'.. -.

.: -'60 It>--_

°20M(B6) /'

// »»: .>

...--'---"

~9A'(82)----"6;;;~4)

;' 0 0 .:

-,' + q.29A(B11·.. +", + +

.> '"Landfasi "Ic:e" Edge <.........::

-. ..........~.

+

.........

o 5 10nmi

o 5 IOmi

.........

········ ..·..·-+.·· 10 m 71 +

o 5 lOkm

157 154 156 155

72

7130

FIGURE 3.7. Locations where behavior of bowhead whales was observed by the aerial crew, 29 April-25

May 1991. Annotations represent the date in April (A) or May (M) and, in parentheses, the behavioral

observation session number (B1-B7). On other dates, behavioral observations were prevented by low

clouds that precluded observations from altitude 460 m ASL.

l

-

3.2 Summary of Field Activities 75

More details about the field activities during 1991 and the ice and weather conditions that

affected the fieldwork are given in Appendix A, Table A-2. Numbers of bowheads and white

whales sighted near the ice camp each day by the ice-based and aircraft-based crews are

summarized in Appendix A, Table A-I.

Because the top-priority behavioral observations were rarely possible, a higher-than-expected

proportion of the aerial effort was devoted to vertical photography of bowheads in 1991. A total

of 15.5 flight hours were spent on aerial photography during 11 different flights on 10 different

days (Table 3.5).

In summary, because of the difficult weather and ice conditions in 1991, we were able to

project industrial sounds on fewer occasions in 1991 (6 days) than in 1989 (11 days), 1990 (8

days) or 1994 (7 days). The prevailing low clouds in 1991 had a particularly severe effect on

aerial observations of whale behavior: we were able to observe bowheads during only 7 sessions

in 1991, as compared to 17,29 and 23 sessions in 1989, 1990 and 1994, respectively. The low

clouds totally prevented systematic aerial observations of bowheads near the operating projectors

in 1991. Because of the extensive areas of new ice and brash ice in the study area during 1991,

there were far fewer suitable locations for the sound projectors in 1991 than in any other year of

the study. Also, on several occasions in 1991, drifting ice encroached on the projector site after

it was established, forcing curtailment of ice-based work.

Fieldwork in 1994

The 1994 field study was partly successful, but success was limited by stronger-than-normal

winds (Table 3.1), the usual frequency of low ceilings, and sometimes-unstable ice conditions.

Large numbers of bowheads were seen migrating along or near the landfast ice edge where

additional playback trials could have been conducted with better weather and ice conditions. In

1994, more than 300 bowheads were observed briefly as they passed the ice camp, but-largely

due to high sea states-a high proportion of the sightings involved brief observations of single

surfacings or partial surfacings. In contrast, during 1990, we obtained lengthy sequences of data'

for many whales as they approached and passed the projector.

In 1994, ice-based work was possible on 13 days (Table 3.7). Two transmission loss tests

were done, one of which was incomplete. Four transmission loss tests had been planned but, given

the higher priority assigned to icebreaker noise playback tests, all field days when playbacks were

possible were devoted to playbacks. Icebreaker noise was projected into the water for extended

periods on seven days. Bowheads were observed by the ice-based observers during six playbacks,

and the aircraft-based observers also observed bowheads during four of those playbacks (Table

3.7) .. Control observations of bowheads were obtained from the ice on 7 days, and by aerial

observations near the ice camp on four of those seven days plus three additional days. Overall,

aerial observations were obtained on 23 occasions during 10 days. Vertical photography of

bowheads was done on 10 days, and vertical video imagery was obtained on one additional day.

The 13 locations where ice-based work was done in 1994 are mapped in Figure 3.8.

Bowheads were seen by the ice-based crew on 9 of these days (Table 3.7):

i

-
3.2 Summary of Field Activities 76

TABLE 3.7. Daily activities by the aerial and ice-based crews in 1994". See Appendix A, Table A-3,

for more details.

Aerial Crew Ice-based Crew

Aerial Behav. Near Camp Other Photo- Control

Date Survey Control Playback Behavior graphy Obs. Playback TL Test

27 April BW"

28 April 0 0

30 April BW B

2 May W 0

3 May BW BW B W

4 May BW B

b

5 May BW B

7 May BW B B B B B B

8 May BW B B

9 May BW B B B B B

10 May BW B B

11 May B B B B

14 May BW B B B

15 May BW B

16 May BW B B 0 B

17 May BW B B 0 B

18 May B

19 May BW

20 May BW B B B B

22 May BW BW W W

24 May W

25 May BW B W Oc

a 0 indicates that no whales were seen, B indicates that bowheads were seen, and W indicates that white whales were seen;

blanks mean "no work of this type on this date".

b Only video images were obtained.

C Incomplete transmission loss test.
7130

3.2 Summary of Field Activities 77

·························..., '0 m.······· 71

155 154

Playbacks

No Bhd. Present

Bhd. While Quiet

Bhd. Our. Plbk .

Trans. Loss Tests

No Bhd. Present 72

Bhd. While Quiet

Bhd. Our. Plbk.

Control Obs. From Ice

No Bhd. Present

Bhd. Present

72

-'--'-'--.......\ '94

\\. a

-. ~

,.............e

..... -.- '94

o

Jg

Iii

'94

6

X

'"C••••·~9O"

/ ..._---------* ", '91 ..••.

_-/----. r:: ""'60

j"" ~--

_O~2M

,,--_ .

025M @ 16M _-----/

:-·-·----x~~;----~7M 9M '. , Landr~SI Ice }Edge, ~~tore 15 May

________// +., ;;-.:~:.>~. ·~·~.~~..·~:!'~::~ce E~9;;.. ..' +

••-- ,. __ - - - - - c. ", . aller lS··M!ly

•.- ••••_-'-" .' .. -'.... --.. . . . . )<8M) ' ....

,....•..--.._---_ .

.....-.._-_ .

+ +

628A

+

~ ....."...

............. +

0 5 10nm

0 5 10m

+

0 5 10 km

A

157 156

7130

155

FIGURE 3.8. Locations where ice-based crews projected icebreaker sounds, conducted transmission loss

tests, and made control observations, 28 April to 25 May 1994. X and solid symbols represent days when

bowheads were observed. Locations on the pack ice are approximate because of ice drift during the

course of each day's work.
3.2 Summary of Field Activities 78

1. During 4 of 13 days, only control observations were obtained. On two "control" days (28

April and 2 May), tones were projected for brief periods and no whales were seen from

the ice. On the other two "control" days, bowheads (but no white whales) were seen from

the ice: On 8 May, high winds in the morning delayed ice-based operations, and it was

not practical to being playback operations late in the day. On 11 Maya large ice pan

collided with the pan supporting the camp, forcing the crew to abort operations before

the playback could begin.

2. During 7 of 13 days, icebreaker sounds were projected for prolonged periods (Table 3.7).

(On four of these days, 3, 7, 14 and 16 May there were also periods when calibration

tones were projected.). Bowheads were seen from the ice on all seven of these days:

during both control and playback periods on 7, 9, 14 and 20 May; during the control

period on 3 May; and during the playback period on 16 and 17 May. White whales were

seen from the ice on only 1 day with playbacks (3 May). They were seen only during the

playback period on that day.

3. During 2 of 13 days (22 and 25 May), transmission loss tests were conducted. No

bowheads were seen by the ice-based crew on these days. White whales were seen both

before and during the TL test on 22 May. On 25 May white whales were seen 20 min

prior to an incomplete TL test.

The aerial crew conducted a total of 35 flights on 22 different days from 25 April to 25 May

1994 (Table 3.7; Appendix A, Table A-3). Poor visibility or high winds prevented any useful

work during brief flights on the afternoon of 2 May, and on 18 May. The remaining 33 flights

ranged from 1.0 to 7.3 h in duration. Total flight time during the 35 offshore flights was 119.0 h,

with 66.0 h of this being reconnaissance surveys.

The aerial crew conducted behavioral observations on 23 occasions during 10 days (Fig. 3.9;

Table 3.8). These observations totaled 36.2 h: 24.1 h under presumably undisturbed conditions

and 12.1 h under potentially disturbed conditions, mainly icebreaker noise playbacks.

Vertical photography of bowheads occupied 16.8 flight hours during 12 flights on 10 different days in 1994, excluding a flight and day when only vertical video images were obtained (Table

3.7). As in 1989 and 1991, most vertical photography was done when low clouds prevented aerial

observations of bowhead behavior.

Overall Effort over Four Seasons

Table 3.2 summarizes the amount of field effort for the four spring seasons, individually and

combined.

Ice-based work was done on a total of 59 days ranging from 27 April to 30 May.

Transmission loss tests were completed on 13 days. Underwater playbacks of man-made noise

were done on 32 days. Bowhead whales were observed by the ice-based and/or aerial observers

during the playback periods on 17 days-lO days during 1989-90 while Karluk drilling noise was

being projected, and 7 days during 1991 and 1994 while Robert Lemeur icebreaker noise was being
3.2 Summary of Field Activities 79

157 156 155

._--.----.

'.\

"'\

"

".

,...•............

<; "............ <»

". G

<, "\

) "I..o------~---------..J

i· -,·

i \

i ./

\ -c,_ ...••.••.... ./

'94 Beh. Obs. Sites

o Presumably Undisturbed

Undisturbed +

Potentially Disturbed

Potentially Disturbed

72

+ "

-,

\

i

"'

"'

"'

"'

"'", -,

''''''"i!oo

/"""---------------t: -. '"

/',,.'----' I" '-, "'-'60 11J--_

22M(823).00 22M(822)

_.>: ~

16M(815) 10M/~)

~ 161!l4B-141-·--~'(D 07M(84) 17M(817) "

11M(P~--4" ~ 9M(87) 0 !Bm.4(8~')

3M(~) 0 (f 'F ,? 7~(I36 7M(86)" 17M(820) 0017M(~1.6'

/ + / I I ' ..J... '. 17M(818)",

./ /.., i l 20,~!B-21). " Landtaat Ice Edge" --

••-----.- 11~81 '-,. - _.- " .• ' ' ,,

,/' .! 10M(88) 8fter 15 'M8Y.__,

,,/ 15M(812)

,,,....

/ ...•....._--....__ ....,.•..•.

............. __ •......

03M(81)

+ +

()3M(B2)

7130 + +

~"""

o 5

o 5 .....

······· .. ·.. -e.. 10 m.· ·· 71 +

o 5

157

FIGURE 3.9. Locations where behavior of bowhead whales was observed by the aerial crew, 3-25 May

1994. Annotations represent the date in May (M) and, in parentheses, the behavioral observation session

number (B1-B23). On other date'), behavioral observations were prevented by low clouds that precluded

observations from altitude 460 m ASL.

72

7130
TABLE 3,8. Summary of behavioral observation sessions, aerial crew, 1994,

% Ice

No. Bowheads

Behav. Predom. Predom. Water

Date Obs. Obs. General Orient. Speed of Size Depth Sea In In

1994 Sess. Location Period Circle Area Activity °T Travel Classes Disturbance (m) State Circle Area

3 May 71°53' 10:03- 2 Travel 030-060 Slow Subadult None 300 80 90

155°04' 11:05 + unknown

2 71°37' 11:22- Aerial Various Medium- Unknown Hel. til 11:38; none 140 70 95

156°16' 13:46 slow 11:38-12:21; sonobuoy

12:21-12:46; tones

12:32-13:09; postdisturbance til 13:39

3 71°31' 17:50 4 8 Travel 060-080 Medium 2 Adults, subadult None 20 3 60 95

155°57' 18:48 + unknown

7 May 4 71°34' 09:20- 4 10 Travel 060-080 Slow- 3 Adults, subadult None 37 2 60 95

155°05' 10:38 medium + unknown

5 71°32' 11:03- 9 15+ Travel 050-070 Slow- 2 Adults, 2 subadults None 37 3 50 90

155°15' 13:09 medium + unknown

6 71°32' 16:14 3 15+ Travel 060 Slow- 2 Adults, subadult Icebreaker playback 33 3 20 90

155°21' 17:41 medium + unknown throughout

9 May 7 71°33' 15:11- 7 35+ TraveUsome 030-080 Slow 3 Adults, 2 subadults Icebreaker playback til 37 3-6 30 90

155°15' 19:54 social, ace. mother, yearling, 17:30, post-playback

feeding calf + unknown til 18:00

10 May 8 71°32' 11:36- 2 9 TraveU 030-070 Slow Adult, 2 subadults None 22 3 50 85

155°40' 12:34 ace. social + unknown

~

9 71°34' 13:34 3 6 TraveU 040-070' Slow Adult, 2 subadults None to 13:53; then 27 2 80 85 N

155°11' 14:49 some feed! + unknown helicopter overflight e;"

Ii:

occ. rest s

:i

l:l

11 May 10 71°32' 08:56- 6 15+ SociaU 050-090 Slow- Unknown None 20 4 60 85 ~

155°50' 10:14 travel medium

~

":1

11 71°31' 10:46- 3 8+ Travell 050-080 Slow- 2 Adults, 2 subadults None 20 4 60 85 (i;'

155°51' 13:21 ace. social medium + unknown -~

)..

15 May 12 71°32' 20:08- 2 5 Travell ~

080' Slow Adult, subadult None 22 3 2 80

... ~.

155°42' 20:41 rest + unknown 5:

'"'"

Continued", 00

0
TABLE 3.8. Concluded.

% Ice

No. Bowheads

Behav. Predom. Predom. Water

Date Obs. Obs. General Orient. Speed of Size Depth Sea In In

1994 Sess. Location Period Circle Area Activity °T Travel Classes Disturbance (m) State Circle Area

IS May 13 71°36' 20:54- 3 7 Travel 060-070 Slow- Adult, subadult None 37 4 2 SO

154°26' 21:41 medium + unknown

16 May 14 71°33' 12: 17- 5 10+ Travel! 040-100 Slow- 2 Adults None to 12:50; then tones 24 20 SO

155°40' 14:21 occ. social medium + unknown to 12:59; then post-playback

to 13:02; then icebreaker

playback 3:02-end

IS 71°34' 14:31- 3 5 Travel! 040-090 Slow 1 Adult + Icebreaker playback ISS 60 SO

155°46' 16:22 social unknown throughout

17 May 16 71 °32' 09:41- 5 S+ Travel 060 Slow- Unknown None 40 5 20 SO

154°33' 10:40 medium

17 71 °33' 10:5S- 4 S+ Travel!occ. 030-070 Slow- Subadult None to 1l:3S, then 40 3-5 20-70 SO

154°30' 12:44 rest, feeding medium + unknown helicopter overflight

and social

IS 71 °32' 13:10- 2 6+ Travel 040-060 Medium Adult, subadult Icebreaker playback 40 4-6 5 SO

154°37' 15:05 yearling + unknown throughout

19 71 °33' 17:10- 2 7 Travel 050-070 Slow- Unknown Post-playback 17: 10- 37 6-7 30 SO

154°29' IS:12 medium 17:32

17 May 20 71°33' IS:37- 2 5 Travel 040-070 Slow Mother, yearling None 43 4 70 SO

154°43' 19:32 2 subadults

+ unknown

~

tv

20 May 21 71°32' 09:43- 4 9 Travel! 060 Slow 2 Adults, subadult None 40 2 2 SO v,

155°32' 12:1S occ. social. + unknown l:: :I:I

22 May 22 71°3S' 09:46- 2 Travel 090 Slow Unknown None 52 2 2 75

c::.

~ 154°55' 10:40

~

23 71°3S' 10:47- O· 4 Travel 060 Slow Unknown None 55 3 2 75 ~

i\'

154°59' 11:33 i:l:

~

~..•

• Predominant orientation for traveling whales only. ~:

• Observation session 23 was devoted to behavioral observations of white whales. =:.

"'

Co

00

-
3.2 Summary of Field Activities 82

projected. White whales were observed during the playback periods on 9 days-6 days with

drilling noise and 3 days with icebreaker noise.

Aircraft-based work was done on 91 days ranging from 27 April to 30 May (Table 3.2).

There were a total of 130 offshore flights totaling 381.6 hours. Of these hours,

~ 231.6 h were spent on reconnaissance or ferrying.

~ 112.7 h of behavioral observation were distributed over 76 observation sessions on 37

days. This effort included 72.1 h when the whales were presumably undisturbed, i.e.

aircraft at ~460 m ASL and no other known sources of potential disturbance. The

remaining 40.6 h of behavioral observations from the aircraft involved whales that were

potentially disturbed, usually by playbacks of drilling or icebreaker noise.

~ 37.3 h were spent on vertical photography of bowheads. This effort included 38 photo

sessions on 28 different days in 1989, 1991 and 1994.

Observations near the ice camp, including both ice-based and/or aerial observations, totaled

380.7 hours: 219.3 h during "control" conditions, 113.9 h during playbacks (74.0 h with drilling

noise in 1989-90 and 39.9 h with icebreaker noise in 1991/94), and 47.5 h under other potentially

disturbed situations (including the first half hour after playbacks ended).

The number of different bowhead and white whales observed near the ice camp during these

periods cannot be determined precisely, as it was not always certain whether a given whale had

been seen previously. Our best estimates of the number of different whales observed within

several kilometers of the ice camp under control, playback and other conditions were, respectively,

433, 314 and 123 bowheads, and 600,265 and 137 white whales (Appendix A:Table A-I). Of the

whales seen during playback periods, the breakdown between drilling noise playbacks (1989-90)

and icebreaker playbacks (1991/94) was 221 vs. 93 for bowheads, and 219 vs. 46 for white whales

(Table 3.2).

\
4.1 Physical Acoustics: Ambient Noise 83

4. PHYSICAL ACOUSTICS RESUL TS8

The results of the physical acoustics effort are presented in six subsections: ambient noise,

infrasonic ambient noise, transmission loss, fidelity of playback experiments, bowhead call infrasonic components, and generator noise. The results of the winter recording effort at the SSDC are

contained in Appendix H.

4.1 Ambient Noise

The ambient noise component of the study responds to specific objective 2, "To measure

ambient noise levels and characteristics in leads and cracks along the spring migration corridor of

bowhead and white whales in the western Beaufort Sea, including infrasonic components" (p. 6).

Ambient noise is an important factor in determining the distances at which whales can detect, may

react to, and may show a strong avoidance of, sources of industrial noise.

Methods used to study ambient noise are described in §2.1 (p. 19ff). Ambient noise analyses

from 1989 and 1990 indicated that there was not much difference in the spread of noise levels

measured with sonobuoys compared with ITC model 6050C hydrophones deployed from the ice.

However, the presentation of 1991 and 1994 ambient noise measurements continues to distinguish

between the two types of sensors. Two kinds of sonobuoys were used: AN/SSQ-57 A wideband

buoys effective up to 20 kHz and AN/SSQ-53B DIFAR (DIrectional low Frequency Analysis and

Recording) sonobuoys with an upper limiting frequency of 2400 Hz. These -53B sonobuoys could

not provide measurements in the highest 1I3-octave bands that we examined-2500, 3150,4000,

5000 and 6300 Hz. Thus, there are not as many measurements at these higher frequencies, and

there are not as many measurements for the 20-5000 Hz band as there are in the lower bands. No

DIFAR sonobuoys were used for ambient noise measurements in 1991.

Results

Table 4.1 presents the statistical distribution of ambient noise during 1991 for the 1I3-octave

bands from 10 to 6300 Hz, plus various broader bands. Tables 4.2 and 4.3 present the corresponding ambient noise data for 1994 and for the combined years 1991194. The 1991 sonobuoy and

hydrophone medians are about the same (Table 4.1A vs. B). The 1994 sonobuoy levels are notably

higher than the hydrophone levels at all frequencies up to 4 kHz, probably because the sonobuoys

were launched into substantially higher sea states and wind speeds.

Figure 4.1 presents the distribution of 113-octave band levels from 10 to 6300 Hz, and levels

in broader bands, for the 54 analyses computed for the spring 1991 season. In this and similar

figures, bearded seals are responsible for occasional high levels at frequencies >400 Hz, and these

elevate the 95th percentile and maximum curves at frequencies >400 Hz. Figure 4.2 presents the

57 analyses for 1994 in the same format, and Figure 4.3 presents the 111 analyses for both years.

Higher levels of ambient noise were measured in 1994. The explanation is that more of the field

work was done in high wind and sea state conditions in 1994 than in 1991 or earlier years.

8 By C.R. Greene Jr. and J.S. Hanna, with R. Blaylock
TABLE 4.1. Ambient noise statistics from the t 991 measurements, by II3-octave band and wideband levels, in dB re I ~Pa. (A) 47

hydrophone measurements; (B) 7 sonobuoy measurements; and (C) 54 combined sensor measurements.

IA. Spring 1991 Ambient Noise

47 Hydrophone Samples

100% 95% 50% 5% 0%

10111. 99.9 94.9 79.5 69.0 68.9

12.5111. 95.0 91.4 76.1 69.5 68.8

16111. 91.3 88.4 76.5 69.7 68.1

20111. 87.0 86.0 75.0 69.0 69.0

25111. 86.0 85.0 75.0 69.0 67.0

31.5 Ill. 87.0 84.0 76.0 69.0 66.0

40111. 88.0 83.0 76.0 69.0 65.0

50111. 88.0 84.0 76.0 66.0 65.0

63111. 88.0 83.0 76.0 67.0 62.0

80111. 89.0 84.0 76.0 68.0 60.0

100 Hz 87.0 84.0 76.0 68.0 59.0

125 liz 90.0 86.0 77.0 68.0 59.0

160 liz 89.0 87.0 77.0 69.0 60.0

200111. 88.0 84.0 76.0 69.0 61.0

250 liz 87.0 85.0 76.0 67.0 64.0

315 liz 87.0 86.0 79.0 69.0 67.0

400111. 96.0 89.0 81.0 69.0 64.0

500111. 98.0 91.0 81.0 66.0 63.0

630111. 99.0 88.0 80.0 64.0 61.0

800111. 99.0 90.0 81.0 65.0 61.0

1000111. 104.0 89.0 76.0 64.0 60.0

1250111. 101.0 98.0 74.0 62.0 60.0

1600 liz 98.0 95.0 74.0 61.0 59.0

2000111. 96.0 89.0 73.0 60.0 56.0

2500111. 91.0 90.0 71.0 60.0 58.0

3150 liz 89.0 89.0 70.0 60.0 55.0

4000117. 88.0 85.0 67.0 56.0 53.0

5000 liz 89.0 83.0 66.0 56.0 53.0

6300 liz 88.0 83.0 65.0 57.0 53.0

20-1000 liz 102.5 100.8 92.5 84.1 80.3

20-2000111. 106.1 103.1 92.6 84.2 80.9

20-5000 liz 106.2 103.2 92.6 84.2 81.5

B. Spring 1991 Ambient Noise

7 Sonobuoy Samples

100% 95% 50% 5% 0%

10111. 98.3 98.3 78.6 69.7 69.7

12.5111. 93.7 93.7 RO.4 70.2 70.2

16111. 89.4 89.4 81.1 68.3 68.3

20111. 86.0 86.0 77.0 60.0 60.0

25111. 85.0 85.0 75.0 64.0 64.0

31.5 111. 84.0 84.0 74.0 68.0 68.0

40111. 84.0 84.0 75.0 70.0 70.0

50 liz 83.0 83.0 74.0 71.0 71.0

6HIz 83.0 83.0 74.0 70.0 70.0

80 liz 81.0 81.0 74.0 69.0 69.0

100Hz 80.0 80.0 73.0 70.0 70.0

125 Hz 80.0 80.0 72.0 69.0 69.0

160 liz 81.0 81.0 73.0 69.0 69.0

200 liz 83.0 83.0 74.0 70.0 70.0

250111. 90.0 90.0 75.0 68.0 68.0

315111. 89.0 89.0 75.0 70.0 70.0

400111. 92.0 92.0 78.0 66.0 66.0

500 liz 91.0 91.0 75.0 65.0 65.0

630111. 90.0 90.0 74.0 68.0 68.0

800111. 87.0 87.0 73.0 69.0 69.0

1000111. 84.0 84.0 75.0 65.0 65.0

1250111. 78.0 78.0 74.0 65.0 65.0

1600111. 87.0 87.0 71.0 67.0 67.0

2000 liz 85.0 85.0 69.0 64.0 64.0

2500 Hz 76.0 76.0 69.0 64.0 64.0

3150111. 72.0 72.0 68.0 64.0 64.0

4000 liz 71.0 71.0 68.0 64.0 64.0

5000111. 71.0 71.0 67.0 63.0 63.0

6300111. 72.0 72.0 67.0 64.0 64.0

20-1000 liz 97.2 97.2 92.8 82.7 82.7

20-2000111. 97.7 97.7 92.9 83.0 83.0

20-5000 liz 97.9 97.9 93.0 83.2 83.2

C. Spring 1991 Ambient Noise

47 Hydrophone Samples

7 Sonobuoy Samples

100% 95% 50% 5% 0%

10111. 99.9 95.7 78.6 69.1 68.9

12.5 117 95.0 92.5 76.1 69.6 68.8

16 liz 91.3 89.1 76.5 68.9 68.1

20111. 87.0 86.0 75.0 69.0 60.0

25 liz 86.0 85.0 75.0 69.0 64.0

31.5 111. 87.0 84.0 76.0 69.0 66.0

40111. 88.0 83.0 76.0 69.0 65.0

50Hz 88.0 83.0 75.0 68.0 65.0

63 liz 88.0 83.0 76.0 69.0 62.0

80111. 89.0 83.0 75.0 68.0 60.0

100111. 87.0 82.0 75.0 68.0 59.0

125 liz 90.0 84.0 76.0 68.0 59.0

160 Hz 89.0 86.0 76.0 69.0 60.0

200111. 88.0 84.0 74.0 69.0 61.0

250111. 90.0 85.0 76.0 68.0 64.0

315111. 89.0 87.0 78.0 69.0 67.0

400111. 96.0 89.0 81.0 69.0 64.0

500 Hz 98.0 91.0 80.0 66.0 63.0

630111. 99.0 90.0 78.0 67.0 61.0

800 liz 99.0 88.0 77.0 67.0 61.0

1000 liz 104.0 88.0 75.0 65.0 60.0

1250 Hz 101.0 97.0 74.0 62.0 60.0

1600 Hz 98.0 94.0 72.0 61.0 59.0

2000 Hz 96.0 89.0 72.0 60.0 56.0

2500 liz 91.0 88.0 71.0 61.0 58.0

3150111. 89.0 87.0 69.0 61.0 55.0

4000111. 88.0 83.0 67.0 58.0 53.0

5000111. 89.0 83.0 66.0 57.0 53.0

6300111. 88.0 82.0 65.0 57.0 53.0

20-1000111. 102.5 100.2 92.5 83.3 80.3

20-2000 liz 106.1 101.7 92.6 83.8 80.9

20-5000111. 106.2 102.4 92.6 84.2 81.5
TABLE 4.2. Ambient noise statistics from the t994 measurements, by tl3-octave band and wideband levels, in dB re I fJPa. (A) 36

hydrophone measurements; (B) 21 sonobuoy measurements; and (C) 57 combined sensor measurements.

A. Spring 1994 Ambient Noise

36 Hydrophone Samples

100% 95% 50% 5% 0%

10 liz 92.0 89.3 69.4 64.8 63.7

12.5 liz 87.3 80.2 69.5 62.2 61.7

16 liz 88.8 87.1 72.8 65.3 64.0

20 liz 93.2 87.7 74.0 66.4 64.3

25 liz 96.6 87.8 78.0 67.6 66.8

31.5 liz 98.2 87.9 80.0 69.2 68.6

40 liz 96.6 85.5 79.0 69.6 67.2

50 liz 99.5 87.9 80.9 70.7 69.2

63 liz 100.5 90.0 80.0 72.3 70.1

80 liz 95.0 87.0 81.0 71.1 69.6

100 liz 93.6 91.0 81.2 70.8 69.4

125 Hz 91.7 88.4 82.7 71.1 69.9

160 liz 91.2 87.3 81.8 73.4 69.9

200 liz 90.6 89.5 81.0 72.1 67.5

250 liz 91.1 87.5 80.4 72.7 66.3

315 liz 95.0 88.7 80.7 73.7 72.1

400 liz 98.0 90.1 81.2 74.0 72.4

500 liz 93.0 88.0 81.8 74.8 71.4

630 liz 98.4 89.0 82.0 75.8 69.1

800 liz 102.3 91.0 82.2 75.6 70.2

1000 liz 102.0 91.0 82.0 75.5 66.2

1250 liz 100.2 88.5 81.5 74.2 65.3

1600 Hz 91.1 88.3 80.8 73.0 64.9

2000 liz 90.2 87.4 80.2 71.5 65.1

2500 liz 86.8 86.5 79.5 71.7 65.1

3150 liz 86.2 85.6 78.3 70.3 64.8

4000 liz 85.1 83.9 77.3 70.1 64.8

5000 liz 84.3 83.1 76.4 68.2 64.2

6300 liz 83.5 82.4 76.1 68.1 64.6

20-1000 liz 109.0 103.8 94.4 85.2 82.6

20-2000 liz 109.2 104.1 94.7 86.7 82.8

20-5000 liz 109.3 104.2 94.9 88.0 83.1

B. Spring 1994 Ambient Noise

21 Sonobuoy Samples

100% 95% 50% 5% 0%

10 liz 108.4 105.5 88.2 75.3 70.1

12.5 liz 99.3 98.9 88.0 71.1 64.5

16 liz 100.0 99.8 88.3 75.0 66.0

20 IIr. 102.7 102.0 94.0 74.2 64.1

25 liz 105.9 105.2 94.7 74.7 65.0

31.5 liz 105.4 103.8 93.0 76.4 63.2

40 liz 102.6 101.0 91.0 74.0 63.0

50Hz 101.9 99.7 90.0 72.5 68.4

63 liz 100.2 99.1 90.0 70.2 67.9

80Hz 101.1 100.8 91.0 70.9 68.1

100 liz 10Q.4 98.0 89.0 69.2 65.8

125I1z 100.1 96.9 90.0 71.1 67.5

160 liz 100.3 97.7 91.0 75.4 71.2

200 liz 101.1 100.2 91.0 75.2 67.0

250 Hz 99.7 99.0 92.0 70.7 70.1

315 liz 101.3 99.5 93.0 73.9 67.9

400Hz 100.7 98.8 93.4 74.7 67.2

500 liz 102.8 101.1 93.0 73.4 70.3

630Hz 99.7 99.3 93.0 73.0 72.8

800 liz 100.6 99.2 92.0 73.0 71.8

1000 liz 100.0 96.2 91.0 70.9 70.1

1250 liz 97.6 92.5 90.0 68.1 67.5

1600 liz 92.9 92.3 88.0 68.4 63.6

2000 Hz 94.1 90.0 86.0 65.0 63.0

2500 liz 92.3 92.3 83.3 63.6 63.6

3150 liz 90.3 90.3 80.9 62.8 62.8

4000 Hz 89.7 89.7 76.6 59.8 59.8

5000 liz 87.5 87.5 74.6 58.3 58.3

6300 liz 85.9 85.9 75.7 58.1 58.1

20-1000 Hz 112.9 111.1 106.2 87.9 85.9

20-2000 liz 113.0 111.2 107.2 88.2 . 86.0

20-5000 liz 111.0 111.0 98.9 86.1 86.1

C. Spring 1994 Ambient Noise

36 Hydrophone Samples

21 Sonobuoy Samples

100% 95% 50% 5% 0%

10 liz 108.4 102.9 72.1 64.8 63.7

12.5 liz 99.3 92.0 73.8 62.5 61.7

16 liz 100.0 96.4 78.0 65.7 64.0

20 liz 102.7 101.0 82.0 66.4 64.1

25 liz 105.9 102.4 83.0 67.6 65.0

31.5 liz 105.4 101.0 81.5 69.2 63.2

40 liz 102.6 100.3 81.0 69.6 63.0

50 liz 101.9 99.0 82.0 70.7 68.4

63Hz 100.5 99.0 83.0 71.8 67.9

80 liz 101.1 97.3 82.7 70.9 68.1

100 Hz 100.4 95.0 82.0 70.4 65.8

125 liz 100.1 94.5 84.0 71.1 67.5

160 liz 100.3 94.9 83.0 73.4 69.9

200 liz 101.1 95.2 84.0 72.1 67.0

250 liz 99.7 97.7 82.3 72.4 66.3

315 liz 101.3 98.2 84.4 73.7 67.9

400 liz 100.7 98.0 85.6 74.0 67.2

500 liz 102.8 97.6 85.6 73.5 70.3

630 liz 99.7 98.4 84.0 73.0 69.1

800 liz 102.3 99.2 85.5 73.0 70.2

1000 liz 102.0 96.2 82.8 70.9 66.2

1250 liz 100.2 92.3 82.2 68.3 65.3

1600 liz 92.9 90.9 81.5 68.4 63.6

2000 liz 94.1 89.6 81.0 66.0 63.0

2500 liz 92.3 88.3 79.5 65.5 63.6

3150 liz 90.3 88.3 78.3 65.7 62.8

4000 liz 89.7 85.9 76.6 65.1 59.8

5000 liz 87.5 84.3 75.9 64.7 58.3

6300 liz 85.9 83.5 75.7 65.3 58.1

20-1000 liz 112.9 110.1 96.8 85.9 82.6

20-2000 liz 113.0 110.3 97.4 86.7 82.8

20-5000 liz 111.0 107.7 94.9 86.1 83.1

00

Vl
4.1 Physical Acoustics: Ambient Noise 86

Spring 1991 Ambient Noise

47 Hydrophone Samples

7 Sonobuoy Samples

120,....-----------------------------------,

.................•..

.........

...... ......

······100%

--95%

_50%

--5%

•.....0%

110

~

!

! 90

!

I 80

l

J 70r-=-:o:-=:-----_- --_- _

'----......

'" ....

.......

60

....

" '

'. -: -, .: '"

'" ..-

......

.........

080

8 0 g

..• '" '"

Third Octave Band came, Frequency (Hz)

FIGURE 4.1. The distribution of ambient noise levels for the 1991 field season vs. 1/3-octave band

center frequency; levels in three broad bands are also shown at right. There were 47 samples from

ice-based hydrophone recordings and seven samples from sonobuoys.

Spring 1994 Ambient Noise

36 Hydrophone Samples

21 Sonobuoy Samples

120

110i

...-.

l

100

:>.

!

III

~ 90

'i

=

...•

I

80

I

". 70 :I

80

..·..·100%

--95"/•

_50%

--5%

.-. .....

", .. .

.........

. .

"

......

50

~

II) ~ 0 OIl It! 0 0

l3 s S! ~

0 0 0 II) 0

8 ~

0 0 0

8

0

~

0 0 0 0

~

0

!

~ '" '" ..• OIl

'"

0

'"

;;; 0 0

S! OIl

~

II) 0

~ ;;; 0 g- - '" '" ..• OIl

'"

l:! ~ ;;; 0 .,

'" ...• '" '" •• ,;

'" '" '" Third Octave Band came, Frequency (Hz)

FIGURE 4.2. The distribution of ambient noise levels for the 1994 field season vs. 113-octave band

center frequency; levels in three broad bands are also shown at right, There were 42 samples from

ice-based hydrophone recordings and 21 samples from sonobuoys.
4.1 Physical Acoustics: Ambient Noise 87

Spring 1991 & 1994 Ambient Noise

83 Hydrophone Samples

28 Sonobuoy Samples

120 r--~-------------------------------,

110

............

'.

,'.

• •• ···100%

--95"1•

--+-50-1.

--5%

•• •••• 0%

.............

...... "

........................................ ..... '[100

~'"

!

ID

:!!. 90

]

I

i 80

~

:I! 70

.

".

... - .

........

,," ....

.....

-,

. .

60

o 0 0 0

~ 8 8 c

'" ..• '" :a

Third OCtave Band c.me, Frequency (Hz)

.....

FIGURE 4.3, The distribution of ambient noise levels for the combined 1991 and 1994 field

seasons vs. 1/3-octave band center frequency; levels in three broad bands are also shown at right.

There were 89 samples from ice-based hydrophone recordings and 28 samples from sonobuoys.

Median Ambient Noise Levels

1991 & 1994

120.0 ...----------------------------------,

110.0

-0- 28 Sonobuoys Only

-0-111 Hydrophones & Sonobuoys

{ 100.0 -x- 83 Hydrophones Only

!

ID

:!!. 90.0 ..

...~

I

i

80.0

~

il

... 70.0'

:Ii

60.0

FIGURE 4.4. Median 1I3-octave band spectra for sonobuoys, hydrophones, and the two types of

sensors combined, 1991194.
TABLE 4.3. Ambient noise statistics from the combined 1991/94 measurements, by II3-octave band and wideband levels, in dB re I IlPa.

(A) 83 hydrophone measurements; (B) 28 sonobuoy measurements; and (C) III combined sensor measurements.

A. Spring 1991 & 1994 Ambient Noise

83 Hydrophone Samples

100% 95% 50% 5% 0%

10 lIz 99.9 94.1 73.9 65.3 63.7

12.5 liz 95.0 89.8 74.2 62.5 61.7

16 lIz 91.3 87.3 75.5 66.6 64.0

20 liz 93.2 87.0 75.0 67.0 64.3

25 liz 96.6 86.4 76.0 67.7 66.8

31.5 liz 98.2 87.0 17.0 69.0 66.0

40 liz 96.6 85.5 17.0 69.0 65.0

50 liz 99.5 87.9 17.2 69.0 65.0

63 lIz 100.5 87.9 17.0 69.0 62.0

80 liz 95.0 87.0 17.0 69.0 60.0

100 liz 93.6 87.0 17.0 69.0 59.0

125 liz 91.7 88.0 78.0 68.0 59.0

160 lIz 91.2 87.3 78.0 69.0 60.0

200 lIz 90.6 88.0 17.8 69.0 61.0

250 liz 91.1 87.0 78.0 69.0 64.0

315 liz 95.0 87.0 79.4 69.0 67.0

400 liz 98.0 90.0 81.0 69.0 64.0

500 liz 98.0 90.0 81.7 68.0 63.0

630 liz 99.0 89.0 81.6 67.0 61.0

800 liz 102.3 91.0 81.6 67.0 61.0

1000 liz 104.0 91.0 81.0 65.0 60.0

1250 liz 101.0 97.0 80.0 63.0 60.0

1600 liz 98.0 93.0 79.0 61.0 59.0

2000 liz 96.0 89.0 78.0 61.0 56.0

2500 liz 91.0 88.0 17.2 63.0 58.0

3150 lIz 89.0 87.0 17.0 62.0 55.0

4000 liz 88.0 85.0 75.0 58.0 53.0

5000 liz 89.0 83.1 74.0 58.0 53.0

6300 liz 88.0 83.0 74.0 57.0 53.0

20-1000 liz 109.0 101.8 92.5 84.4 80.3

20-2000 liz 109.2 104.1 93.4 84.6 80.9

20-5000 liz 109.3 104.1 93.5 84.8 81.5

B. Spring 1991 & 1994 Ambient Noise

28 Sonobuoy Samples

100% 95% 50% 5% 0%

10 liz 108.4 105.5 88.2 70.1 69.7

12.5 liz 99.3 98.9 84.7 70.2 64.5

16 liz 100.0 99.8 85.6 68.3 66.0

20 liz 102.7 102.0 86.0 61.0 60.0

25 liz 105.9 105.2 85.0 65.0 M.O

31.5 liz 105.4 103.8 86.6 68.0 63.2

40 liz 102.6 101.0 84.0 70.0 63.0

50Hz 101.9 99.7 83.8 71.0 68.4

63 lIz 100.2 99.1 83.9 70.0 67.9

80 liz 101.1 100.8 85.4 69.0 68.1

100Hz 100.4 98.0 84.5 69.2 65.8

125 lIz 100.1 96.9 84.5 69.0 67.5

160 liz 100.3 97.7 86.3 70.0 69.0

200 lIz 101.1 100.2 86.6 70.0 67.0

250 liz 99.7. 99.0 90.0 70.1 68.0

315 liz 101.3 99:5 92.0 70.0 67.9

400 lIz 100.7 98.8 93.0 67.2 66.0

500 liz 102.8 101.1 92.0 68.0 65.0

630 Hz 99.7 99.3 91.0 68.0 68.0

800 liz 100.6 99.2 87.7 71.0 69.0

1000 liz 100.0 96.2 86.7 69.0 65.0

1250 Hz 97.6 92.5 83.0 67.5 65.0

1600 lIz 92.9 92.3 86.5 67.0 63.6

2000 lIz 94.1 90.0 84.8 64.0 63.0

2500 lIz 92.3 90.5 75.0 64.0 63.6

3150 liz 90.3 90.1 72.0 64.0 62.8

4000 liz 89.7 86.7 71.0 64.0 59.8

5000 liz 87.5 85.0 70.4 63.0 58.3

6300 liz 85.9 84.6 69.8 64.0 58.1

20-1000 lIz 112.9 111.1 104.5 83.3 82.7

20-2000 liz 113.0 111.2 104.8 83.8 83.0

20-5000 lIz 111.0 107.7 94.0 84.2 83.2

C. Spring 1991 & 1994 Ambient Noise

83 Hydrophone Samples

28 Sonobuoy Samples

100% 95% 50% 50/. 0%

10 liz 108.4 99.1 75.8 65.4 63.7

12.5 liz 99.3 93.7 75.5 63.1 61.7

16Hz 100.0 93.5 76.6 66.6 64.0

20 lIz 102.7 98.4 17.0 66.4 60.0

25 liz 105.9 97.8 78.0 67.6 64.0

31.5 Hz 105.4 98.5 78.0 69.0 63.2

40 liz 102.6 96.6 78.0 69.4 63.0

50 liz 101.9 96.7 78.2 69.2 65.0

63 Hz 100.5 96.9 78.0 70.0 62.0

80 liz 101.1 96.0 17.0 69.0 60.0

100 liz 100.4 94.0 78.0 69.0 59.0

125 liz 100.1 94.0 78.0 69.0 59.0

160 liz 100.3 93.0 79.0 69.0 60.0

200 Hz 101.1 93.0 79.0 69.0 61.0

250 liz 99.7 94.0 79.0 69.0 64.0

315 liz 101.3 95.2 80.5 70.0 67.0

400 Hz 100.7 96.0 82.0 69.0 64.0

500 liz 102.8 95.8 82.0 68.0 63.0

630 liz 99.7 95.2 82.0 68.0 61.0

800 liz 102.3 96.6 82.0 68.0 61.0

1000 Hz 104.0 95.0 81.0 66.0 60.0

1250 Hz 101.0 92.5 80.1 64.0 60.0

1600 liz 98.0 92.3 79.0 63.0 59.0

2000 liz 96.0 89.0 78.0 62.0 56.0

2500 lIz 92.3 88.3 76.8 63.0 58.0

3150 Hz 90.3 88.3 76.8 62.8 55.0

4000 liz 89.7 85.0 74.7 59.8 53.0

5000 liz 89.0 83.7 73.5 58.0 53.0

6300 liz 88.0 83.4 73.7 58.0 53.0

20-1000 lIz 112.9 109.4 93.7 84.4 80.3

20-2000 liz 113.0 109.6 95.1 84.6 80.9

20-5000 liz 111.0 106.2 93.5 84.2 81.5

00

00
4.1 Physical Acoustics: Ambient Noise 89

Figure 4.4 displays the median l/3-octave band spectra for the two combined years by sensor

type, showing graphically the higher levels for the sonobuoys. The drop in the broadband level

for the 20-5000 Hz band, compared to the 20-1000 Hz band, occurs because the DIFAR buoys do

not sense sounds at frequencies above 2400 Hz.

Figure 4.5 presents the 20-1000 Hz band levels for each 1991 measurement plotted against

the measurement times. The ice camp hydrophone and sonobuoy measurements are differentiated

by plotted symbol. Figure 4.6 presents the 20-1000 Hz band levels for each 1994 measurement

plotted against the measurement times. Sonobuoy measurement levels on 3 May 94 were 7-17 dB

higher than measurement levels with the hydrophone, and sonobuoy levels on 16 and 17 May were

also higher than the hydrophone levels. The highest levels recorded for 1994 were obtained from

sonobuoys on 3, 11 and 17 May. The 6050C hydrophone cable was faired to prevent strumming,

although there may still have been noise from water flow around the sensor. Each sonobuoy

hydrophone was suspended by a spring, mass and damper system to decouple surface motion from

the sensor, and there should not have been cable strumming.

Discussion

Major environmental influences on ambient noise in the Beaufort Sea during spring include

wind and waves, biologics, thermal ice cracking, and ice deformation (ice floe collisions, pressure

ridge formation). The effects of wind and waves are well-studied. Biologic noise sources include

seals, especially bearded seals, whose calls glissade across frequencies from several kilohertz down

to about 400 Hz, and the bowhead and beluga whales. During this project, animal sounds were

deliberately excluded from ambient noise analyses if possible. A close animal could raise the

sound levels above ambient noise levels expected from storms. Thermal ice cracking is a minor

source of sound, especially after the diurnal temperature cycling moderates when the sun no longer

sets (after 10 May in Barrow). Ice floe collisions and pressure ridge formation are transient but

on-going events occurring at unknown and varying distances from the measurement point and

contributing varying amounts of sound.

Short-term variability in ambient noise levels was studied and reported for the 1990 field

season (Richardson et al. 1991 :55f.l)· The study compared noise levels for 33 recordings, each

averaged over one minute, 8.5-s periods, and 0.25-s periods. The result was that shorter averaging

often yielded lower noise levels. The implication was that animals with suitably responsive hearing often would be expected to hear weak sound signals during brief periods when the ambient

noise was lower than average even if the average ambient noise level over a longer period was

high enough to mask the signal. There were 33 different I-min periods analyzed, or 231 8.5-s

periods. Figure 16C in Richardson et al. (1991 :61) graphs the difference between the 8.5-s average noise level and the corresponding median 0.25-s average noise level (the median of

8.5/(0.25)=34 separate 0.25-s averages; there were 231 such medians). Almost all differences were

positive, and the largest difference was 18 dB. From the Figure, it appears that about half the 231

differences exceeded 2 dB. This 2 dB figure is used in a later discussion of icebreaker signal-tonoise ratios vs. distance (Figure 6.25 in §6.4).
"iU

'5. 110

~

CO

~ 100

N

::I:

o

o

o.•..

~ 90

~

~ 80

o

z

C

.9l

~ 70

-c

4.1 Physical Acoustics: Ambient Noise 90

120,..-------------------------..,.

o

o

o

'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-._._._.,.-

I!I 0

•

o

8 10

I , e 0

o t • 0 0

·············•···· ..·····~c·..···..········· ·······..·· .., .

o

8

o Hydrophone

e Sonobuoy

- - - Sea Slate 6

-. -. Sea State 2

••••• -Sea State 0

60 -i-rrTTTTTtrrTTTn+r-rrrTTTT-rrnTT'rhTTTn""""'m-rrfnTrn-rtrrrTTTT'/-rn"T'TTT'ie,.,.,.,.,,.,..frm-rrr+rrr-TTTTtrrTTTn+r-rrrTTT+rrrr=t

27 29 01 03 05 07 09 11 13 15 17 19 21 23 25 27

DayinAprillMay 1991

FIGURE 4.5. Ambient noise level, 20-1000 Hz band, vs. recording date and time in 1991.

"iU

'5. 110

~

co

~ 100

N

::I:

o

o

o.•..

6 90

C\l

a:;

>

Ql

-l

Ql

rn 80

'0

Z

CQl

:c 70 E

-c

120,..---------------------------,

a

e

----------------------------------~--------------- e e 8

e

o

._._._._._._._o_._._._._.~._~_._._._._._._._._._._._._._._._._._._

0' 0 e. 0

o 0

o

o o o

................................................................................•............

~ ,

e 0

o

o

o Hydrophone

e Sonobuoy

- - - Sea Slate 6

_. -. Sea State 2

••••• -Sea State 0

60 ~,...,.,f,..,..,..,.,..-.+rrT'TTTTi-rrn"T'ITi-r'l'TTn'"'"""T'TTT'i.,.,..,...,,.,..frrTTTT"rh-rr,...,....f'!"M'TTTTf-r,'!"M'TT+rrn.,..m,"TTTT'l.,-trr."TT'l"I"l"TTTT'l-n+

27 29 01 03 05 07 09 11 13 15 17 19 21 23 25 27

DayinAprillMay 1994

FIGURE 4.6. Ambient noise level, 20-1000 Hz band, vs. recording date and time in 1994.
4.1 Physical Acoustics: Ambient Noise 91

A key concern about the 1994 ambient noise data arises from the higher levels observed from

the sonobuoys than from the ice camp hydrophone. Furthermore, one questions whether there

might have been a bias of some kind in the DIFAR sonobuoy measurements. No DIFAR

sonobuoys were used in 1991 and the sonobuoy and hydrophone data were comparable for that

year.

However, associating the type of sonobuoy with each plotted value in Figure 4.6 reveals that

DIFAR buoys were used on 3, 9 and 17 May, while -57A sonobuoys were used on 11, 15, 16 and

20 May. The highest levels, which were observed on 3, 11 and 17 May, came from both types of

sonobuoys. The moderate levels observed on 9 May came from a DIFAR buoy and were

comparable to the hydrophone levels recorded on that date. Also, the somewhat higher levels

observed on 15 May came from a -57A sonobuoy. Thus, there does not appear to be a bias toward

higher levels from DIFAR sonobuoys.

An alternative explanation for the high sonobuoy levels is that, in 1994, the sonobuoys were

deployed into open water under high sea state conditions. Even when the wind speed was high,

the ice camp hydrophone was generally deployed on the lee side of a large ice floe, assuring sea

state zero from the area covered by ice and a lower-than-open-water sea state extending away from

the floe because of low fetch (the distance the wind has blown over water to create waves).

A simple comparison of ambient noise over the four years of the project field work is

possible with the ranges of the 20-1000 Hz broadband levels observed each year (Fig. 4.7). The

first three years were roughly comparable, neglecting the extraordinarily low level observed on

2 May 1990. The 1994 levels were higher, corresponding to the higher wind and sea state conditions under which much of the 1994 work was done (§3.1, p. 51).

During 1980-84 summer (August) studies in the Canadian Beaufort Sea, the median ambient

noise level was 99 dB re 1 IlPa in the 20-1000 Hz band (Greene 1985). This was 10 dB higher

than the corresponding median level in spring 1989, 7 dB higher than in 1990 and 1991, but only

2 dB higher than the median level in 1994. These levels are close to the 100 dB level expected

for sea state two based on the Knudsen curves extended to low frequencies (Fig. 4.7). Miles et

al. (1987) reported ambient noise statistics for six sites in the Alaskan Beaufort Sea measured for

brief periods in late summer and early fall (September and October); their levels also corresponded

to nominal sea state two value.

Measurements were made during late September 1984 near Seal Island, Alaskan Beaufort Sea

(water depth 13 m), while a drillrig on this artificial gravel island was in standby mode (Davis et

al. 1985). The median level in the 20-1000 Hz band was close to 93 dB, or 2 dB below the level

expected for sea state one and close to the median level for this project in spring 1990 and 1991.

Another comparison is possible with ambient noise data collected from one drifting buoy in

the Chukchi Sea (shallow water) and from one in the deep Beaufort Sea during May 1977 (Greene

1981). Acoustic pressure spectral density data were measured every three hours at three frequencies: 10, 32 and 1000 Hz. The 5th, 50th and 95th percentiles of the acoustic pressure spectral

densities were obtained at those three frequencies. The percentile values for those same 1/3-octave
4.1 Physical Acoustics: Ambient Noise 92

120

110

100

ctS a.

:::L. 90

,.-

Q)

"- 80

CD"'0

70

60

50

...................................................................................... SS6

.................................................................................. SS2

.................................................................................. SSO

1989 1990 1991

Project Year

1994

FIGURE4.7. Minimum, median and maximum ambient noise levels, 20-1000 Hz band, during the

four project years. Circled-X symbols mark median levels. Levels for three sea states are

extrapolated Knudsen et al. (1948) spectra.

bands from the present project, 1991/94, were adjusted to compute spectral densities. All these

data are graphed in Figure 4.8 for comparison. Wenz's limits (maxima and minima) for the three

frequencies are also plotted; they show that the project and buoy data fall within the expected

range at those frequencies. The wider range of levels from the present project may possibly be

explained by the confluence in the project operating area of the generally northeasterly coastal

current from the Chukchi Sea with the generally north-northwestward clockwise Beaufort Gyre,

leading at times to extraordinary ice deformation and noise.

4.2 Infrasonic Ambient Noise

The infrasonic ambient noise component of the study responds to project objective 5, "To

collect some of the data needed to assess the importance of the infrasonic components of industrial

noise. Specifically, (a) to measure ambient noise at infrasonic frequencies ... " (§ 1.1, p. 7). Such

noise would be important in determining the detection radius if infrasonic industrial noises are

detectable by bowheads, or if bowhead calls include infrasonic components that are detectable by

other bowheads.
4.2 Physical Acoustics: Infrasonic Ambient Noise 93

120

110

100

90

N

::I: C\r- 80

ca C.

:l. 70 0ra>~

rn 60

"0

50

40

30

20

@ Chukchi Shallow

1:1 Beaufort Deep

== Project 91-94

.... Wenz Extrema

1I

I

I

I

10 Hz 32 Hz 1000 Hz

FIGURE4.8. Comparison of 5th, 50th and 95th percentile ambient noise spectral density levels at

10, 32 and 1000 Hz, based on two data buoys operating in the Chukchi and Beaufort Seas during

May 1977 and on the present project (1991194 phases). The upper and lower limits from Wenz

(1962) for those frequencies are also shown.

Results

Figures 4.1-4.3, the percentile distributions for the 1991194 ambient noise data, include the

levels for the 1I3-octave bands centered at 10, 12.5 and 16 Hz. The pattern of levels in these three

bands relative to levels at higher frequencies differs for the two years. In 1991, the low and

median levels at infrasonic frequencies appear to be extensions of the higher frequency levels, but

the 95th percentile and maximum levels increase with decreasing frequency below 20 Hz (Fig.

4.1). In 1994, the low and median levels decrease with decreasing frequency (Fig. 4.2). For the

two years combined (Fig. 4.3), the median levels follow the trend established at frequencies up

to 400 Hz of decreasing slightly with decreasing frequency.

As seen in Table 4.1C and 4.2C, the median level for the 10 Hz 113-octave band was 79 dB

re 1 flPa in 1991 and 72 dB re 1 flPa in 1994, or 7 dB lower. At 20 Hz, however, the
4.2 Physical Acoustics: Infrasonic Ambient Noise 94

corresponding levels are 75 and 82 dB, or 7 dB higher in 1994. Generally, the 1994 median levels

are higher than the 1991 median levels, except at infrasonic frequencies.

In separate presentations, the sums of the ambient noise mean square pressures in the 10,

12.5 and 16 Hz 113-octave bands are graphed against time for 1991 (Fig. 4.9) and for 1994 (Fig.

4.10). These bands span the frequency range 8.9 to 18 Hz. Although the highest levels were

measured from sonobuoys on 3, 9 and 16 May 1994, there were high levels in the hydrophone

measurements on 18 and 25 May 1991.

Discussion

D'Spain et al. (1991) studied infrasonic energy at frequencies 0.5-20 Hz. They used

neutrally buoyant Swallow floats at great depths (e.g., 2960 and 5700 m) in deep water west of

California, where there is shipping. At 10 Hz, they show the range of spectral density levels off

California to be 75-80 dB re 1 IlPa2/Hz, compared with median levels in this project of 71 dB for

1990, 75 dB for 1991, and 68 dB for 1994. Thus, the spring Beaufort Sea measurement results

at 10 Hz are comparable to or slightly lower than the results from deep water off California.

What is the likely effect of infrasonic noise on reception of infrasonic bowhead calls, if these

exist? Analyses to date suggest the possibility that bowhead calls may sometimes include infrasonic components (§4.5, p. 129). For discussion purposes, let us assume that the levels of any

infrasonic components of bowhead calls are similar to the levels of sonic components-that is, the

distribution of call energy is approximately flat with frequency, including infrasonic frequencies.

Keeping in mind the typically-high transmission loss for infrasonic sounds in shallow water, the

infrasonic components of bowhead calls, which are strongly attenuated by propagation losses, are

more likely to be masked by ambient noise than are the higher frequency components of bowhead

calls, which are less strongly attenuated during propagation. This assessment assumes that ambient

noise levels are similar at infrasonic and sonic frequencies, and that-as in other mammalsreceived sound signals are masked primarily by ambient noise at frequencies similar to those of

the signals. It should be noted that this conclusion would not necessarily be true in the deep-water

portions of the range of bowhead, where infrasonic sounds might not be attenuated any more

rapidly with increasing range than are higher-frequency sounds.

Infrasonic ambient noise also has the potential to mask infrasonic components of industrial

noise, when these exist. Icebreakers, other large ships, and some bottom-founded oil-industry

platforms are known to emit strong infrasounds (reviewed in Greene and Moore in press). The

relatively high levels of ambient noise at infrasonic frequencies will limit the radius around a

source of infrasonic sounds within which those sounds will be detectable above the ambient level.

In shallow water, which for infrasonic frequencies is water less than 150-300 m deep, infrasonic

components of industrial sound will normally be attenuated rapidly by poor sound propagation.

However, the infrasonic components will be detectable out to some distance determined by factors

affecting the rate of propagation loss (e.g., sound frequency, water depth, bottom materials) and

by the ambient noise level. The radius around the source of infrasound within which those sounds

would be above the ambient level, and presumably detectable to an animal with infrasonic hearing

capability, would need to be assessed on a site-specific basis, taking account of the local sound
4.2 Physical Acoustics: Infrasonic Ambient Noise 95

Ambient Noise, Sum of 10,12.5,and 16 Hz Third Octave Bands

I0 HydrophoneI

Ic Sonobuoy I

0

0

0

c

~ 0

0

0

c

o ,

0

•

0

0

8 0

0 0

0 t.

FIGURE 4.9. Infrasonic ambient noise levels, 8.9-18 Hz band, vs. recording date and time in 1991.

120

110

-C'll c..

::1.

.•..100

l!!

CD:EO) 90 >Q) ..J 0

"C c

t:

C'll 0

CD 80 • •

«i 0

0 c

~

0 8 c

c

70

120

110

C? c..

::1.

.•..100

Q) "-

CD:EO) 90 >Q) ..J

"C

t:

C'll

CD 80

~

70

60 +r....TTTT"rr,..,.,.TT"ri-rT'T"T'T.,..,f,-rT'T"T'T.,.r,.,.rT'T"T'T-!-n-rT'T'T"T"i.,..,.,..,.n-r-r..,..,.,..,..,.,-f,-,r"T'TT'T.,.r,.,.rT'T"T'T-!-n-rT'T'T"T"i""""",n-r-r..,..,.,..,.ntn.,..,.,..,.r+rn.,.,...,.,f

27 29 01 03 05 07 09 13 15 23 25 27

FIGURE 4.10. Infrasonic ambient noise levels, 8.9-18 Hz band, vs. recording date and time in

1994.

11 17 19 21

Day in AprillMay 1991

Ambient Noise, Sum of 10,12.5,and 16 Hz Third Octave Bands

c

I~HydroPhone!:

cSonobuoy

c

c

c

lil

0

0 c c

0

c

0

0

0

•

C

C

0

t 0

c 0 0

0

0 0

0

0 0

s

t

0

c

o

o

, , 60 +rn"T'TTTf,.,.,.'T'TTThTTTT"I-n-nrTTT'/"T'TTTTTTl-TTTT"T'TT'hrTT"M.,-,+."T'TTT-rrh-TTT'T"rrt-rrT'T"T"1...-/-T'1"T'TTT-rtrrTMT..m-l'TTT'l-h-n-'T'TTTf-rr,-,..,..,..,.f .,.

27 29 01 03 05 07 09 11 13 15 17

Day in AprillMay 1994

19 21 23 25 27
4.2 Physical Acoustics: Infrasonic Ambient Noise 96

propagation conditions as well as the source level of the infrasonic man-made noise and the

anticipated levels of infrasonic ambient noise.

4.3 Transmission Loss

The acoustic transmission loss component of the study responds to specific objective 3, "To

measure and model transmission loss of underwater sound along ...the spring migration corridor,

based on playbacks of (a) test tones at selected frequencies, and (b) continuous industrial sounds.

Infrasonic components cannot be projected ... " (§ 1.1, p. 6). Transmission loss, or propagation loss,

generally causes the sound level from any source to diminish as distance increases. In shallow

water, transmission loss is influenced primarily by the water depth, the sound frequency, and by

bottom acoustic properties. Methods used to study transmission loss are described in §2.1.

Summary of 1989-1994 Transmission Loss Data

There were four transmission loss tests during the 1991 phase of the program and two during

the 1994 phase. The second 1994 test was aborted after data were collected at ranges 100 and

200 m because an ice floe drifted threateningly toward the projector site. The 1991/94 results are

tabulated in Appendix B, Tables B-1 to B-6. Corresponding data from 1989-90 were reported

previously, by Richardson et al. (l990a: 106ff; 1991 a:63fj). There were four successful

transmission loss tests in 1989 and four in 1990.

Figure 2.1 summarizes the .locations of the transrrussion loss tests in all four years,

superimposed on newly-derived depth contours for the area. These contours, derived by Paul

Dysart, SAIC, take account of depth soundings taken at many of the 1989-94 source and receive

stations, and at many of our other ice-camp locations, as well as previously-available soundings.

Figures B-15 to B-18 in Appendix B provide additional details regarding receive station locations.

Analysis of 1989-1994 Transmission Loss Data

The propagation data from all four years of measurements near Barrow, AK, collected as part

of this project, have been examined for consistency. The amount of ice cover varied from test to

test as well as from station to station, but the estimated coverage was always 50% or greater. The

one environmental variable that changed significantly from one measurement to the next is the

water depth; it ranged from 40 to 180 m and was sometimes not constant along a single

measurement track. In examining the data for consistency, a simple model for propagation in an

isovelocity channel was used to account for the dependence of propagation on depth. This model

allows the depth dependence to be scaled out of the data so all data for a given frequency may be

compared. A significant finding of this comparison is that there is consistency in the scaled data,

both across years of the test and across source types. This suggests, primarily, that the acoustic

bottom conditions are relatively homogeneous over the test area. Data collected with singlefrequency tones are reasonably consistent with those from broadband sources, including frequency

sweeps and recorded broadband noise from a drilling platform, especially when allowance is made

for the frequency averaging of data from the latter sources.
4.3 Physical Acoustics: Transmission Loss 97

The Propagation Model

In general, a number of environmental variables affect the propagation of sound in the ocean,

including water depth, sound speed profile, volume attenuation in the water, and losses induced

by interactions with the ocean boundaries. In shallow water, the boundary interactions are usually

the dominant influence and the important question concerns how often a propagating path interacts

with these boundaries over a given range interval. Both the sound speed profile and the water

depth have primary control over the range between interactions. In some shallow water areas, the

sound speed does not change significantly with depth, and then the depth itself becomes the

important variable. In the analysis below, a simple model for the influence of depth on

propagation is used to collapse propagation from a variety of water depths onto a single plot. This

same model is then used to make estimates of the received level at the locations of animal

sightings during playback experiments.

In a previous report (Hanna 1991) that considered the propagation data from the 1990 test

at Barrow, an analysis tool was introduced that scales the propagation data, taken in differing

depths of water, to look for consistency in their behavior. In that report, a simple ray-theory

model (Hanna 1976) for propagation in an isovelocity channel was used to motivate this approach;

the model takes the form

(1)

where I is the intensity of the field at some range R (in m) greater than the channel depth D (in m);

e'OR accounts for the volume attenuation in water (Thorp 1967); p=RI2D is the range scaled by the

channel depth, D (both in m); Io=118/D2is the intensity at p= 1; 118 is the angular aperture of

propagating paths to be included; and a and ~ are parameters related to boundary losses at the

channel bottom. Transmission loss is given by -lOlog(I).

Thorp (1967) presents an equation for the volume absorption loss term in dB/kyd. That

equation is easily converted to dB/km, appropriate to this work. However, the e'OR term in

Equation (1) is more directly applicable if written as lO'O'R', where 0' is adapted from Thorp:

0' = (0.11 *p2)/(1 + p2) + (44*p2)/(4lO0 + p2) dB/km,

with P being frequency in kHz and R'= R/I000 being range in km.

Before proceeding to the application of Equation (1), it is instructive to examine its behavior

and develop some intuition for its implications. Consider what generally is expected of propagation in a waveguide. For a point source somewhere in the waveguide, the sound should spread

spherically (1/R2, as in free space) until it encounters the boundaries. When this occurs, the sound

will reflect from these boundaries and, if they are lossless, the wavefront will eventually spread

cylindrically (1/R), at ranges large compared with the water depth. If there is some sound loss

(from scattering or absorption) when sound reflects from a boundary, the spreading will become

asymptotically exponential with range as the propagating field loses some fraction of its intensity

with every boundary interaction.
4.3 Physical Acoustics: Transmission Loss 98

To see if Equation (1) conforms to this expectation, we begin by setting 0=0, which

corresponds to negligible volume attenuation, and by setting a and ~ to zero, which corresponds

to no boundary losses. It becomes

/=~e!

D2p

where the factor l/D2accounts for the initial spherical spreading and the factor IIp accounts for

the subsequent cylindrical spreading. For a and ~ nonzero, and ~p»I, Equation (1) approaches

~e e-ap

/=--

D2 pp2

which corresponds to the intensity for a single path at the shallowest grazing angle, experiencing

its geometrical spherical spreading and suffering a loss at the boundary expressed by the exponential factor. Although ~ is related to losses at the boundary, it is useful to interpret its reciprocal

as the transition range from cylindrical back to spherical spreading as determined by the factor

I-e -pp

pp2

since for ~p«1 it behaves like cylindrical spreading and for ~p» 1 it behaves like spherical

spreading. So, the model does include all the behaviors that are expected.

As was noted in the previous analysis, this model suggests plotting data in the form

[=erJRD2/ (2)

meas

If the region were homogeneous, meaning it had one set of values for a and ~, then all data for

a particular frequency would be described by the same curve. This idea is used below to review,

for consistency, the data from all four years of the tests at Barrow.

Results

In the discussion below, three topics are covered. First, the data collected using the tones

are compared to those collected with the wideband sources. Second, the results of scaling the data

relative to water depth are presented. Third, values of the model parameters are derived by fitting

the model to the scaled data for each frequency band.

Single-Frequency and Frequency-Averaged Data.-Propagation data were collected using a

set of single-frequency tones and several broadband waveforms (p. 25!! in §2.I). A general

expectation, born out by the data, is that the measurements made with the tones show more variability than those using the broadband waveforms. To illustrate what was found to be true across

the frequency band from 50 to 1000 Hz, the data at 200 Hz are shown here as examples. Figure

4.11 is a composite plot of all the propagation data for a 200 Hz tone from the 1989, 1990, 1991,

and 1994 tests. For comparison, Figure 4.12 presents all the data for propagation, measured using

the oil-drilling sounds (Karluk), for the 113-octave band centered at 200 Hz.
4.3 Physical Acoustics: Transmission Loss 99

Since the disturbance tests were made using broadband signals (oil-drilling and icebreaker

sounds), the frequency-averaged propagation is most appropriate for interpreting those tests.

Accordingly, the conclusions below emphasize the frequency-averaged propagation, although data

from the tones are shown for comparison.

Scaled Data.-Equation (2) has been used to scale the propagation data, and the next few figures display the results of its application. The data at 200 Hz are used to illustrate the process,

and then the data from other frequencies are summarized. Figure 4.13 is the scaled version of Figure 4.11, where the assumed depths for the various tests are summarized in Table 4.4. In this and

the following figures, the curve labelled "model" is the result of finding a representative fit to the

plotted data using the model described earlier. The fit has been judged visually, rather than by

some objective measure, such as least-squares; however, an analysis of the difference between

model and data is presented below. The depth was not constant along all the tracks; for those

cases where it was not, a representative depth was chosen for the dominant portion of the track.

TABLE 4.4. Depths at TL test sites.

Test Depth (m) Test Depth (m)

1989 #2 40. 1991 #1 60

1989 #3 50 1991 #2 100

1989 #4 120 1991 #3 100

1989 #5 50 1991 #4 150

1990 #1 180 1994 #1 70

1990 #2 40 1994 #2 178

1990 #3 75

1990 #4 75

Note that some of the variability seen in Figure 4.11 is eliminated by the scaling, suggesting

that some is attributable to significant differences in the water depth, rather than just multipath

interference that can dominate the variability of single-frequency propagation.

Figure 4.14 contains the scaled data for Karluk signals corresponding to Figure 4.12; as with

the tone data, the scaling has reduced the variance somewhat. Finally, Figure 4.15 and Figure 4.16

show data from 113-octave sweeps before and after the scaling. Again, scaling reduces the variance. Also, the data from Karluk and the sweeps are gratifyingly consistent with one another, and

with the data from the tones, when allowance is made for the additional variability that is

characteristic of single-frequency data.

One-third octave propagation data were also collected using the recorded icebreaker (Robert

Lemeur) sound; however, these results are not very consistent with the Karluk or sweep data.

Figure 4.17 shows an example of the scaled icebreaker data for 200 Hz. Comparison of this figure

with Figure 4.12, Figure 4.14, and Figure 4.16 illustrates the point. The reason for this disparity
4.3 Physical Acoustics: Transmission Loss 100

20

.~

'!,~~~-

•.••••.~ •.••.•.. T~

I

.~~~ ....---

~~ .~ I~ .....•.:

"-

~ .

. _.

-,

~

C\" , ~ 'r--.

~.

'- I\~ I---

-, f"'l~ :,

"

.,

'I'. ~

~

'\

•

40

60

80

--1989 Test#2

-1989 Test#3

-,-1989 Test#4

--1989 Test#5

--1990 Test#1

--1990 Test#2

-+-1990 Test#3

-1990 Test#4

- -1991 Test#1

-,-1991 Test#2

--1991 Test#3

-,-1991 Test#4

--1994 Test#1

100

FIGURE 4.11. Transmission loss vs. distance for 200 Hz tones measured during transmission loss

experiments, 1989-94.

100

120

0.1 1 Range (Ian) 10

20

.'-~--..

~~

.-- -~ :::::: ~ -, <,

" ..~ .\10.- ~.

~ I-.. 'Il. .~

1\..••.... :::: ::::~

r' .' ••

--1989 Test #3

--1989 Test #4

-,-1989 Test #5

--1990 Test #1

--1990 Test #2

--1990 Test #3

-+-1990 Test #4

-1994 Test #1

100

FIGURE 4.12. Transmission loss vs. distance for 200 Hz 1I3-octave band levels of Karluk drilling

sounds measured during transmission loss experiments, 1989-94.

40

60

80

100

120

0.1 Range(km) 10
4.3 Physical Acoustics: Transmission Loss 101

-20 -r--~r---'-"""""""""T'"""II""T"":iT""--"T"""-,-r-r-T"..,...,-n--""""-"T"""-r--r-,...,.."T"'n

Oi----+--+---1H-+-+-++t---+--t--+-+-+-+-+-++---t--i---+-+-+-++H

ai' :E-

~ 40+----t--+~H-+++_H--_f~f'~~~!:sE''l__t--+-+---t--r-H-ffi

E

*.3

.•.

60 i----+--+---1H-+-+-++t---+--t--+-+-t-'tH"¥:+---t- ...•••• :+--+-+-+-++H

•

\

100+-__ J....----L_l......J--l- ...•....• ~-----L--'---l---l- ....•....•...•.. -'-+-- ...•.. -..l...-...•......•.....••...•. ~

1 10 R/2D 100

-1989 Test#2

-1989 Test#3

-·-1989 Test#4

--1989 Test#S

-1990 Test#1

-1990 Test#2

-+-1990 Test#3

--1990 Test#4

- -1991 Test#1

-'-1991 Test#2

---1991 Test#3

---1991 Test#4

--1994 Test#1

- -Model

1000

FIGURE4.13. Transmission loss minus 20 Iog(Depth) vs. distance scaled by twice the water depth

for 200 Hz tones measured during transmission loss experiments, 1989-94 (cf. Fig. 4.11).

:i..~

~, .-- •

...•.•::-- -;;;

.--...

....•.•.

.•••.........-..:: ~

-'

.....•.•~;""'=i ~

"\ r..:::

~

, .•..•....

<, I <,

...•

-20

o

20

,-.

...... ~

,-.

a

~ 40

E

~

'"

'"0

...:l

60

80

100

1 10 R/2D 100 1000

-1989 Test#3

--1989 Test#4

-·-1989 Test#S

--1990 Test#1

-1990 Test#2

-1990 Test#3

-+-1990 Test#4

--1994 Test#1

- -Model

FIGURE4.14. TL-20l0g(D) vs. distance scaled by twice the water depth for 200 Hz 1/3-octave

band levels of Karluk drilling sounds measured during transmission loss experiments, 1989-94 (cf.

Fig. 4.12).
4.3 Physical Acoustics: Transmission Loss 102

20

~

:~i~

,

..••..••.

r-, ••

~

.-

\~

-, ~ •

~ r:=:

~~

<'\c

--1989 Test#4

--1989 Test#5

--1990 Test#1

--1990 Test#2

-.-1990 Test#3

--1990 Test#4

40

60

80

100

120

0.1 Range (Ian) 10 100

FIGURE4.15. TL vs. distance for 200 Hz frequency-modulation sweeps measured during transmission loss tests, 1989-90.

-20

o

~ ••.......

'" • (,

<, -...

..

.~~.'!o

I

i

~

~

:::::::::. "to.

I" ...• "', -,

•

"- r20 ,.....

c:o "'0

--,.....

~

40

~N

I

•••• oS

60

-1989 test #4

-+-1989 Test#5

-1990 Test#1

-1990 Test#2

-·-1990 Test#3

--1990 Test#4

- -Model

80

100

1 10 RJ2D 100 1000

FIGURE4.16. TL-20l0g(D) vs. scaled distance for 200 Hz FM sweeps measured during transmission loss tests, 1989-90 (cf. Fig. 4.15).
o

..~~=-- • ••••1'--

<,::::::r-c

----. ...•..

r-, •....•

--1990 Test #4

---1991 Test #2

-·-1991 Test #3

--1991 Test #4

•...•..1994Test #4

4.3 Physical Acoustics: Transmission Loss 103

·20

,... 20

c:l

S,...

eco

0 40

0

N

,

:J!

j

60

80

100

1 10 RI2D 100 1000

FIGURE4.17. TL-20l0g(D) vs. scaled distance for 200 Hz 113-octave band levels of icebreaker

Robert Lemeur sounds projected during transmission loss tests, 1990-94.

is probably related to the substantial time variability of the icebreaker waveform compared with

that for the other signals. During the TL tests it was not feasible to record the transmitted and

received signals on the same recorder, which would have permitted simultaneous source level!

received level measurements. Time alignment between the projected and received signals was

difficult.

Figures B-1 through B-14 (in Appendix B) show the scaled data at 50, 100,500, 1000,2000,

and 5000 Hz for the tone, Karluk, and sweep signals. The Karluk data only extended up to about

350 Hz. The tone and sweep data covered all the frequencies shown .. The general points made

above in connection with the 200 Hz data are seen to hold across the frequency band. The

increased variability above 1000 Hz is likely caused by scattering and absorption losses at the

water-air or water-ice interfaces. These losses are not explicitly treated in the present model.

One additional propagation mechanism is important at frequencies below 50 Hz for the

projected signals. The fact that the ocean surface creates what is called a pressure-release

boundary has a profound effect on the propagation when the source, receiver, or both are within

about one wavelength of the surface. In general, each path at the source or receiver has a surfacereflected counterpart, and it can be shown (Bannister and Pedersen 1981) that the coherent addition

of these paths results in an intensity factor that is well-approximated by the following expression:
4.3 Physical Acoustics: Transmission Loss 104

where d is the depth below the surface of either the source or receiver, e is the path angle relative

to the horizontal, and X is the wavelength. This factor multiplies the intensity associated with

either of the individual paths. When the two are in phase, the argument of the sine is an odd

multiple of rcl2, and the factor is 4, which corresponds to a doubling of the single-path pressure.

Since this mechanism affects both the source and receiver, the total effect on propagation is a

product of two such factors. When the wavelength becomes large compared to the depth, the sine

may be approximated by its argument and the total factor becomes

Because this factor is inversely proportional to the 4th power of the wavelength, it is likewise

proportional to the fourth power of frequency. Consequently, the pressure field decreases with

decreasing frequency, source depth, or receiver depth. The diminution of the level resulting from

this mechanism is often referred to as the Lloyd's mirror effect. This name arises from optics

(Jenkins and White 1957:242) where an interference pattern is observed involving lightpaths from

a common source, one arriving directly and the other via one reflection from a mirrored surface.

This frequency behavior may be seen in the data from the 1994 test #1 as shown in Figure

4.18 for a range of 200 m and in Figure 4.19 for a range of 1000 m. In both figures, the data for

the tones and Karluk signals are plotted and compared with a curve that has a slope given by the

fourth power of frequency. (Note that this power law behavior of the intensity results in a straight

line when plotted against the logarithm of frequency.) In both cases, it is apparent that the

influence of this mechanism becomes important below about 50 Hz, although this frequency would

be different for other source or receiver depths. In the model or propagation being used here, this

mechanism is included by multiplying Equation (1) by the factor for frequencies below 50 Hz.

Model Parameters.-As mentioned above, the model was used to fit the scaled data as a

function of frequency. The parameters were chosen by concentrating on the frequency-averaged

data, and then checking the resulting fit against the tone data. The reason for this is that the data

from the tones extended to somewhat longer ranges, and their decay rate was significant in picking

the parameter a, which controls the asymptotic decay of the model curve. The depth-scaled form

of Equation (1) that was used here is

(3)

where

Io=L\8 if />50 Hz

=L\ 8(L)4 otherwise

50
4.3 Physical Acoustics: Transmission Loss 105

30

I

II

/

I

/

V It.

to/ •• •• to

/

/1 ••

I

/

40

60

70

10 100 1000 roeoo

Frequency (Hz)

[=:J

ToIleS e

•• Karluk

-- Asymptote

FIGURE 4.18. The Lloyd's mirror factor for the 1994 TL test #1 data at distance 200 m.

30 1/

I

/

/

/

I

/

It. .. ..

I

/

/

40

i

- so 3

60

70

10 100 1000 iooeo

Frequeucy (Hz)

• Tones

•• Karluk

-- Asymptote

FIGURE 4.19. The Lloyd's mirror factor for the 1994 TL test #1 data at distance 1000 m.
4.3 Physical Acoustics: Transmission Loss 106

and the last expression accounts for the Lloyd's mirror effect. The parameters that resulted from

fitting the data are shown in Table 4.5. The parameters at 20 Hz have been extrapolated from 50

Hz using a comparison with the limited data from the 1994 tests at this frequency, and include the

Lloyd's mirror effect described above.

TABLE4.5. Transmission loss model parameters vs. frequency.

Frequency (Hz)

Parameter 20 50 100 200 500 1000 2000 5000

~e 0.015 0.300 0.200 0.200 0.200 0.200 0.200 0.200

a 0.03 0.02 0.01 0.01 0.035 0.045 0.055 0.065

B 0.20 0.2 0.2 0.2 0.2 0.2 0.2 0.2

The comparisons offered in the preceding figures are useful visual indicators of how well the

model represents the data. These can be complemented by estimates of the standard deviation of

the differences between the data and the model for the various signal waveforms.

Figure 4.20 shows these standard deviations for the 1I3-octave bands from 50 to 5000 Hz.

The larger deviations for the tone data are a quantitative confirmation of the point made above

about the greater variability of single-frequency propagation. The similarity between deviations

for the Karluk and sweep data confirm the consistency of these two band-averaged data sets. For

the latter data sets, a deviation of about 4 dB characterizes the model-data comparison over the

band from 50 to 1000 Hz. Above 1000 Hz, the deviation grows for the reasons mentioned above

having to do with variable surface or ice scattering losses.

To work through an example of a transmission loss computation, take frequency f = 500 Hz,

water depth D = 100 m, and distance R = 10,000 m. From Table 4.5, 500 Hz, read ~e = 0.2, a =

0.035, and B = 0.2. Thus, P = R/(2*D) = 50 and 10 = ~e/D2 = 2*10-5• To obtain transmission loss

in decibels, one needs -IOlog(I), which means Equation (1) can be factored and the 10l0g0 terms

added. The volume absorption loss term is first: 0.25 dB. The Ioe-ap term is next: 3.475*10-6 or

54.59 dB. The last term is (l_e-BP)/(Bp2) = 2.0*10-3 or 27 dB. Thus, the total transmission loss for

a 500 Hz sound traveling 10 km in water 100 m deep is 81.8 dB re 1 m.

Comparison with BBN's Weston-Smith TL Model.-The model in Equation (1) is very similar to one used in earlier analyses of shallow Beaufort Sea propagation by Miles et. al. (1986,

p. 96fj) as related to marine mammal disturbance. Using the scaled range introduced above and

the notation of this report, their equation takes the form

-~R{ 1t )1/2 e -Zap

I=e l4b D2p3/2
4.3 Physical Acoustics: Transmission Loss 107

10

8

l

• Tones

• Karluk

.•.Sweeps

2

o

ooסס1 1000 100 10

FrequcDcy (Hz)

FIGURE4.20. Standard deviations between the measurements and the model predictions vs. frequency for three types of sounds.

where a and b are parameters related to the boundary losses. This model includes the initial spherical spreading region, followed by a region with geometrical spreading midway between cylindrical

and spherical combined with exponential decay. Except for the fact that the model in Equation

(1) has geometrical spreading for this latter region that transitions from cylindrical to spherical

spreading, the two models are very similar. In fact, in analysis not reported here, it was determined that nearly identical fits to the data could be achieved with either representation by suitable

selection of the model parameters. The most important points about the two models are that

(1) they both suggest scaling the data according to Equation (2), and (2) for suitable values of the

a and b parameters, the two models agree in predicting received levels at ranges long compared

to the ranges for which transmission loss experimental data are available.

Comparison of the Propagation Model and Playback Data

The sonobuoy signals received during playback tests were not used in defining the transmission loss model parameters. Thus, they can be used to verify the validity of the model.

The validation methodology was as follows. For times when the received level was measured

via sonobuoy, the sound exposure model program described in §2.3 (p. 46fj) was run to predict

received level statistics. The program incorporates the present propagation model along with a

procedure to estimate source level spectrum at any time during a playback experiment (§2.3). The
4.3 Physical Acoustics: Transmission Loss 108

resulting received level estimates for the 20-1000 Hz broad band and for the dominant 1/3-octave

band in the 64-s and the l4-min periods preceding the specified time were compared with the

measured received levels in those bands. The l4-min estimates actually describe the distribution

of levels for all time during which projection continued without interruption or variation in

playback amplifier settings.

The results are presented in graphical form in Figures 4.21 (20-1000 Hz) and 4.22 (dominant

ll3-octave band received). Prevailing ambient noise levels measured at times before and after the

playback period are included, as some of the predicted received levels are below the noise level

and would not be expected to be heard. Some of the other predicted received levels are within a

few decibels of the ambient noise level, in which cases the level measured by the sonobuoy, representing both icebreaker and ambient noise, would be expected to be slightly above the level of

icebreaker noise predicted by the model. With these exceptions, the measured received levels

should, ideally, fall in the minimum-maximum range predicted by the model for the 64-s period

adjacent to the recording time; it would be coincidental if the measured levels agreed with the

predicted medians. Allowance for the nominal 4 dB standard error in the model predictions

increases the allowable range of the difference. At worst, the measured received levels should fall

in the range of the predicted l4-min distribution of levels ± the 4 dB allowance. Table 4.6 summarizes the results of the comparison by date and time.

TABLE4.6. Summary observations comparing the model predictions with the observed received

levels at sonobuoys during icebreaker playbacks.

Date Time Remarks

17 May 91 14:18:00

14:20:00

16:17:00

16:23:00

The measured sonobuoy levels fall within the model prediction

ranges. The playback icebreaker sounds were audible.

3 May 94

9 May 94

16 May 94

17:00:00

19:14:44

The predicted received level ranges are lower than the measured ambient

noise. The sonobuoy measurements are in the range of the ambient noise

measurements, and the icebreaking sounds were not audible.

16:55:37

17:24:43

The measured sonobuoy levels are generally within the model prediction

ranges, but so are the ambient noise levels, and the icebreaking sounds were

not audible.

13:17:33

13:20:38

13:55:58

14:42:59

17:07:31

17:08:25

Discontinuities in playback transrrussion prevented predicting

received level ranges for every time, but the sonobuoy received levels are

generally within the predicted ranges available, or within 4 dB. The

ambient noise was lower, and the icebreaking sounds were audible.

17 May 94 12:50:12

12:51:06

12:53:16

The measured sonobuoy levels are generally in the range of the ambient noise

levels and above the predicted ranges, but the icebreaking sounds were

audible weakly on the sonobuoys. It appears that the predicted levels may

be lower than the levels actually received.
4.3 Physical Acoustics: Transmission Loss 109

The measured and predicted broadband levels (20-1000 Hz) are generally in good agreement,

after discounting the 3 and 17 May 1994 cases when the measured level was largely attributable

to ambient noise (Fig. 4.21). However, for the 113-octave band of strongest icebreaker sound, the

model estimates were a few decibels below the measured levels of playback sound (17 May 1991,

16 May 1994), even after discounting cases in which ambient noise probably dominated the sonobuoy measurements (3, 9 and 17 May 1994).

This validation analysis suggests that the sound exposure model provides reasonable estimates of received sound levels, provided that these estimated levels exceed ambient noise levels

prevailing in the corresponding frequency band at the time in question. Model estimates of

received levels may be more accurate in the case of broadband levels than for levels in the dominant 1I3-octave band; the latter may be underestimated by a few decibels. Before use, estimates

of received levels need to be compared with measured or estimated ambient noise levels to determine whether the received level would be detectable above the ambient.

Sound Propagation on 13 May 1990

An unusually large number of bowhead whales (-105, see Table 6.2 in §6.1) were observed

on 13 May 1990 while Karluk drilling sounds were projected at a shallow-water site (depth 27 m)

in the southeastern part of the study area (see Fig. 3.4 on p. 68). The validity of estimated

received levels at this whale location is especially important, given that important results

concerning bowhead reactions to steady drilling sounds were obtained there (Richardson et al.

1991a). Preliminary estimates of the received levels of the projected Karluk sounds vs. range were

included in that report, based on a simpler propagation model.

Here we re-evaluate the 13 May 1990 received level

estimates based on the new propagation model. The sonobuoy data for dates in 1990 were converted to propagation

loss for these comparisons, and the associated ranges and

losses are summarized in Table 4.7. Discussion of the

playback levels from which these losses are inferred may

be found in Richardson et al. (1991a).

The transmission losses from Table 4.7 are shown in

Figure 4.23 where they are compared with the model for

200 Hz propagation, using the scaling algorithm described

above. Most of the data are within a standard deviation

of the model curve, but the behavior of the data from 13

May 1990 is significantly different from the model.

These data are about 15 dB above the model curve at

scaled ranges from 30 to 40 (actual ranges 1.6 to 2.2 km),

and then increase with range much more rapidly than the

model curve. To predict such low propagation losses at

the shortest ranges, one must assume much lower boundary losses than are implicit in the model used to fit the TL

TABLE4.7. Transmission loss measured via sonobuoys during playback

experiments in May 1990.

Date

Range (km)

(dB) TL

9-May-90

1O-May-90

ll-May-90

13-May-90

13-May-90

13-May-90

13-May-90

13-May-90

16-May-90

16-May-90

21-May-90

21-May-90

0.6

1.4

3.2

3.5

1.64

2.06

2.03

5.8

0.9

4

0.4

0.9

55

51

54

59

45

46

47

73

48

70

49

62
150 20-1000 Hz .

140- t

t?130..: a..

:J..

-r-120..:

~

~110-

---

~100-

Q) ....J

"'0 90..:

c:

:J

~ 80..:

"'0

Q)

.> 70-

Q)

o

~ 60-

t

£\11

::::::~I:t·:: IT ..· £\··1·t ..··..~l t..

.................I

It .

. , .

t

..... A .

i

......... 1 -

Weak

17 May 94

12:53:16

1390 meters

-

-

-

-

00 "Ideal Icebreaker"

£\ Sonobuoy Measurement

x Model 64 Second Prediction -

® Model 14 Minute Prediction

........ Ambient Noise

Heard Heard

FIGURE 4.21. Measured 20-1000 Hz band levels at sonobuoys (triangles) vs. model predictions of received levels from actual icebreaker

and playback source: (a) Actual icebreaker if it, instead of the sound projector, were operating at the site; (b) the 14-min period of

icebreaker playback (the full cycle of the playback recording); and (c) the 64-s period of icebreaker playback just before the sonobuoy

measurement time. The nominal ambient noise level in the same frequency band for the day, measured with both ice-based hydrophones

and sonobuoys, is also plotted as a dashed line.

t t

t

50-

40 Heard Not Heard Not Heard Heard

,

17 May 91 03 May 94 09 May 95 16 May 94

14:20:00 19:14:44 17:24:43 14:42:59

730 meters 5400 meters 1070 meters 760 meters

.

16 May 94

14:42:44

3500 meters

I

16 may 94

14:42:44

3900 meters

•... •...

o
150 Dominant One-Third Octave Bands

00 "Ideal Icebreaker"

140

l

I!Sonobuoy Measurement

x Model 64 Second Prediction

C?130 ® Model 14 Minute Prediction

a.

t

........ Ambient Noise

=to t

--120

Q)

t t

•...

00110 "0

··lK.......

I!

---

~100 AI

All t

Q) I! ....J

:'::::~tr I!

"0 90 ............ ...

xt ........ It· c

:J .........1..;...

0

en 80

"0 ................

................

Q)

> 70 ................

"05 I

0

................ ................

Q)

a: 60

50

63 Hz 800 Hz 315 Hz 500 Hz 250 Hz 250 Hz 400 Hz

40 Heard Not Heard Not Heard Heard Heard Heard Weak

17 May 91 03 May 94 09 May 95 16 May 94 16 May 94 16 may 94 17 May 94,

14:20:00 19:14:44 17:24:43 14:42:59 14:42:44 14:42:44 12:53:16

730 meters 5400 meters 1070 meters 760 meters 3500 meters 3900 meters 1390 meters

FIGURE 4.22. Measured 1/3-octave band levels at sonobuoys (triangles) vs. model predictions of received levels from actual icebreaker

and playback source. The 1/3-octave band considered here was the one containing the strongest icebreaker sound. Otherwise plotted

as in Figure 4.2!.

•.... •....

•....
4.3 Physical Acoustics: Transmission Loss 112

·20

o

- lr--

-

0

:--

A

•

r---....•.....•

<,r--..

:---.

<,

<,

r-,

r-,

'\

1\

-Mood

o 9May139m

)( 1o-May70m

o n·May 130m

• 13.May27m

A 16-May41m

20

§

eOIl

0 40

C

~

~

60

80

100

1 10 100 1000

FIGURE 4.23. TL-20log(D) vs. scaled distance for 200 Hz transmission loss data, comparing

sonobuoy measurements during Karluk playbacks in May 1990 with the TL model.

30

...••..........

-.........

r-, ~

I'--

I't--

-; <, 'x.

<, -,

<, -,

"~

\

,,\

,,~

1\

--FEPE (PmDafrost)

)( 13 MayDaIa

-- Parametric Mood

40

so

60

§

~ 70

80

90

100

0.1 10

RaDge(km)

FIGURE 4.24. Transmission loss vs. distance for the 13 May 1990 playback experiment comparing

the TL model developed in this study with a finite element parabolic equation (FEPE) model

assuming "relic permafrost" (per Miles et al. 1986, 1987) to distance 2 km.
4.3 Physical Acoustics: Transmission Loss 113

test data in the preceding section. The possibility of such low boundary losses is discussed in

Miles et al. (1986, 1987). In these reports, the occurrence of relic permafrost and overconsolidated

sediments is reviewed and some nominal sound speeds are given for those materials. In particular,

sound speeds of 2000 to 4000 mls are suggested for the permafrost. To examine the acoustic

consequences of such material, a speed of 3000 mls for the bottom was used in a Finite Element

Parabolic Equation (FEPE) model that is capable of treating such large sound speed contrasts.

Although such a bottom is indeed capable of producing the low propagation losses observed in the

shortest range 13 May 1990 data, it will not predict the observed rapid increase of loss beyond a

range of about 2 km. To account for this latter behavior, it was necessary to assume that the

bottom changed from high to low speeds at about the range of the lowest propagation losses.

The results of such a model calculation are shown in Figure 4.24. This figure compares the

13 May 1990 data to an FEPE calculation that assumes a permafrost bottom at distances to 2 km,

with a transition back to a low-speed representative of shallow water unconsolidated sediments.

Also shown is the prediction by the model developed here. The FEPE calculation for the combination high- and low-speed bottoms suggests that the occurrence of a permafrost patch surrounded

by normal sediments might account for the 13 May 1990 data. This project did not collect any

data that could confirm the presence of permafrost at the 13 May 1990 site. However, the Miles

et al. reports summarize observations of such material near the water-sediment interface in similar

shallow coastal shelf regions of the North Slope.

Based on the sonobuoy measurement data actually collected at the playback experiment site

on 13 May 1990, a separate, simple empirical model for transmission loss on that date was

developed. The spreading loss slope for distances from closer than 100 m to greater than 1000 m

was cylindrical, or expressible as 10l0g(R). Extrapolating the measured loss curve backward in

range, the loss at 100 m was 32 dB re 1 m. Fitting the longer range sonobuoy data to an equation

not based on theory, the following equations were found to fit the data:

TL = 42 + 10*log(R), 0.1 < R < 1.23 km

TL = 38.7 + 46*log(R), 1.23 < R km

The standard error of the fit is 3.5 dB, which compares with the nominal 4 dB of the model

developed for most of the study area.

Summary Discussion of Transmission Loss

Propagation data from all four years (1989, 1990, 1991, 1994) of measurements nearBarrow,

Alaska, have been examined for consistency. The one environmental variable that changed significantly among measurements was the water depth; it ranged from 40 to 180 m and was sometimes

not constant along a single measurement track. In examining the data for consistency, a simple

model for propagation in an isovelocity channel was used to suggest the dependence of the propagation on this parameter. This model was used to scale the data from all four years at each frequency; this was found to reduce the residual variation among the measurements. The propagation

loss predicted by this model was then used to fit the scaled data. The associated model coeffic-
4.3 Physical Acoustics: Transmission Loss 114

ients provide the basis for predicting received levels at whale locations during the behavioral

observations.

A significant result of comparing the scaled data is their consistency, both across years of

the test and across source types. This suggests, primarily, that the acoustic bottom conditions are

relatively homogeneous over the test area. Data collected with single-frequency tones were reasonably consistent with those from broadband sources, including frequency sweeps and recorded broadband noise from a drilling platform, especially when allowance was made for frequency averaging

of data from the latter sources. The standard deviation of the differences between the model and

the propagation measurements is estimated to be -4 dB over the band from 50 to 1000 Hz for the

broadband sources. For reasons to be expected, the corresponding value for the tone data is

higher, varying from ±6 to ±8 dB over the same band. The behavioral experiments used broadband

signals for playbacks so the smaller value (±4 dB) is most relevant in their interpretation.

In comparing the predicted levels during the disturbance tests with the levels measured by

sonobuoys, it was learned that measured levels on 13 May 1990 were considerably higher at a

range of 2 km than the propagation model predicts. The discrepancy is of order 15 dB, well

outside the range of uncertainty found during propagation tests. The location of the 13 May 1990

data is also well outside the region sampled by the propagation tests and is in shallower water

(Fig. 3.4; cfFig. 2.1). The implication is that the bottom in the vicinity of these anomalous data

is much more reflective than is the bottom over the area of the propagation tests. Drawing on

work summarized by Miles et al. (1986, 1987), discussing evidence for relic permafrost and overconsolidated sediments, computations of propagation loss with the Finite Element Parabolic Equation model helped make plausible the possibility that such material is responsible for the observed

behavior. The composition of the sea floor in this region has probably been documented by seismic exploration activities on behalf of the oil and gas industry, but much of this information is

privately owned and not available. U.S. Geological Survey personnel (P. Barnes, pers. comm.)

indicated that they have no specific data for the 13 May 1990 site but agreed that the occurrence

of relic permafrost in the general area would not be surprising.

In view of the likely existence of relic permafrost in shallower regions than those in which

the transmission loss tests were conducted, the transmission loss model in Equation (1), with the

parameters in Table 4.5, may overestimate transmission loss, and hence underestimate received

levels, in regions with relic permafrost.

There are three general influences in the frequency-related behavior of transmission loss.

(1) As frequency increases, the volume absorption loss increases; transmission loss increases with

increasing frequency. (2) At the lowest frequencies, for a given source depth, the Lloyd's Mirror

effect leads to high transmission loss. As frequency increases, the transmission loss diminishes

until a frequency is reached above which the Lloyd's mirror effect is no longer apparent. For the

18-m depths of sources and receivers used during this project, 50 Hz defines the breakpoint.

(3) Bottom interaction effects are present at both low and high frequencies for the bottom

conditions present in most of our operating areas of the Beaufort Sea northeast of Barrow.

Transmission loss due to these effects diminishes with increasing frequency up to 100 Hz. Above

200 Hz the transmission loss increases with increasing frequency.
4.3 Physical Acoustics: Transmission Loss 115

Until now, this project has attempted to average transmission loss over a broad band of frequencies, specifically, 20-1000 Hz. This has been useful for steady, low-frequency, broadband

sources of drilling noise like Karluk. The model presented in this report differentiates transmission loss by 1I3-octave bands, providing a more realistic representation of actual physical sound

transmission in the Beaufort Sea near Pt. Barrow without the complexities of full wave models.

Comparison of the transmission loss model developed in this project with the model

developed by BBN Labs for other shallow regions of the Beaufort Sea indicates that the two

models are comparable.

Transmission loss measurements in the Chukchi Sea during late winter conditions (heavy ice

cover) were reported by Greene (1981). Those measurements were done in water generally 50 m

deep. Figure 12 in that report presents curves for transmission loss vs. distance. A band of values

is presented for frequencies from 75 to 500 Hz. At distance 10 km (5.4 n.mi. in Greene 1981 :Fig.

12), the band extends from 81 to 84 dB. For frequency 200 Hz, depth 50 m, and distance 10 km,

the model presented in this report predicts a loss of 88 dB, which is 4 dB higher than the higher

value reported by Greene (1981). These results from the Chukchi Sea during March were similar

to those from the western Beaufort Sea during late April and May.

4.4 Fidelity of Playbacks to Original Icebreaker Sound

How similar to the original icebreaker sound was the playback sound? To the human ear,

sounds received with hydrophones anywhere from a few meters to 1 or 2 km from the projectors

had the distinctive quality of the original icebreaker sounds. With increasing distance from the

projectors, the icebreaker sound became less dominant, and natural sounds, e.g. bearded seal calls,

became more evident. This would also occur with increasing distance from the actual icebreaker,

but the actual icebreaker sound would dominate the ambient noise out to a considerably longer

range because of its higher source level. The major differences between the playback sounds and

the actual icebreaker were (1) the overall playback source levels were weaker than the actual

icebreaker source levels (median difference 34 dB over the 40-6300 Hz frequency band), and (2)

the playback sounds were comparatively weak at frequencies below 40 Hz (median difference of

63 dB in the source level at 20 Hz). However, as is explained in this section, the importance of

the low frequencies diminishes with increasing distance because of high sound transmission loss

at frequencies below 50 Hz.

It was important to obtain quantitative measures of the similarities and differences between

the playback sounds and the actual icebreaker sounds. There are at least two levels of comparison:

(1) how like the original taped sound (as received and recorded 460 m from the icebreaker) was

the playback sound in the water (i.e., how like the lower distribution in Fig. 4.25); and (2) how

like the "free-field" source level computed for the icebreaker was the playback sound in the water

(i.e., how like the upper distribution in Figure 4.25). We have chosen to make the latter

comparison, although we are at an immediate disadvantage in that the lowest frequencies, those

below 50 Hz especially, were differentially attenuated by propagation effects at the recording site.

Nevertheless, in an ideal experiment, the low frequency recorded sounds would have been differen-
Icebreaking Noise

Al14 Minutes on 02 Sep 86

200 r--------------------------------------:=::====!

~

0..- " 160

:1.1'1I

.••0.

l!!;-150

al 41)

" .. i~140

>-

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'8 ~ 130 ..s-g

en ~ 120

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1Uo::

E 110

~

190

180

170

100

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.•-----

....-------------- --.•.--_ . ~~~----..:..:::.:===-::.:::-',

------'•.....•

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------100%

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0 10 co 0 10 ~ 0 0 l") 0 0 10 0 0 0 10 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

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T'" .•. .•. N N l") '<t 10 co .•.

~

~

0

N N

1/3 Octave Band Center Frequency (Hz)

FIGURE 4.25. Distributions of received levels (460 m range, lower set of curves) and estimated source levels (upper curves) for the

icebreaker Robert Lemeur, by tl3-octave band center frequency; levels for three broad bands are also shown at right. The five curves

show the minimum, 5th percentile, median, 95th percentile and maximum levels in each band over the t4-min period. These

distributions were computed from the t4+ minute recording of Greene (1987a:48fj).

,....

,....

0\
4.4 Physical Acoustics: Playback Fidelity 117

tially boosted to reproduce the hypothesized icebreaker source sounds. (This was not done because

the playback transducers are inherently poor at reproducing those low frequencies.)

The monitor hydrophone sensed the sound field near the projector during all experiments and

permitted computing the actual transmitted source levels for each 1I3-octave band. Knowing the

actual source levels at an instant of time, and knowing where in the 14-min playback sequence that

instant of time is (Fig. 4.26), it is possible to calculate the distribution of 113-octave band levels

corresponding to the projector settings in use. Our playback fidelity test is to compare transmitted

distributions with the source distribution in Figure 4.25.

For each day of playback experiments, a time or times were selected when whales were

observed. For each such time, the corresponding playback source level distribution was calculated

from the sound exposure level program. The median predicted source levels were subtracted from

the median standard Robert Lemeur source level distribution shown in Figure 4.25 and the results

were plotted (Fig. 4.27-4.34). As expected, the overall source levels are lower than the original

and the low frequencies differ the most.

These figures are important. Note that the differences, although graphed for distance 1 m,

apply at all ranges. At any range, the sound level difference between the actual icebreaker and

the playback sound is the same as at 1 m. This occurs because the transmission loss would be the

same for the actual icebreaker as for the playback, given that the acoustic propagation path and

frequency are the same.

These differences in median levels varied by day, and sometimes by time of day, because of

the different transducer/amplifier settings. Table 4.8 summarizes differences in level between the

actual icebreaker and the playback, by 113-octave band, over the frequency range 40-6300 Hz.

TABLE 4.8. Comparison of playback vs. actual icebreaker sound levels for the 1I3-octave bands

centered at 40-6300 Hz. The "Deviation from Flat" column applies across the 40-6300 Hz band

of frequencies.

a Low frequency components not projected on this date.
200,-------------------------------------:-----,

190

180

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FIGURE 4.26. Variability of estimated source levels for the icebreaker Robert Lemeur over the 14+ min recording time at the Corona

drillsite in 1986, considering the 20-1000 Hz band level and 1I3-octave band ·Ievels centered at 50, 500 and 2000 Hz. The original

received level data at distance 460 m came from measurements described in Greene (1987 a:44fj).

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FIGURE4.27. Radiated source levels of icebreaker sound from icebreaker Robert Lemeur (three curves at top) and the J-13/F-40

projector system used on 17 May 1991 (three curves at middle), by 1I3-octave band and for three broad bands. Curves show the 5th,

50th, and 95th percentiles for distance 1 m. The projector source level is based on measurements made at 17:41:00 but is applicable

for the periods when whales were seen on that date. The bottom curve is the difference between the two medians, and is the same at

all ranges because transmission loss would be the same for the icebreaker and the projector sounds.

20.0

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FIGURE4.28. Radiated source levels of icebreaker sound from icebreaker Robert Lemeur (top) and the Argotec 220/J-ll projector system

used on 7 May 1994 (middle). Levels increased shortly after 18:04:56. Otherwise as in Fig. 4.27.

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FIGURE 4.29. Radiated source levels of icebreaker sound from icebreaker Robert Lemeur (top) and the Argotec 22011-11 projector system

used on 7 May 1994 (middle). Projector source level is for 18:59:32, after the projector output was increased, and is applicable for later

periods on that date. Otherwise as in Fig. 4.27.

-N

-
20.0

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One-Third Octave Band Center Frequency (Hz)

FIGURE4.30. Radiated source levels of icebreaker sound from icebreaker Robert Lemeur (top) and the J-Il projector system used on

9 May 1994 (middle). Projector source level at 16:40:50 is applicable for periods when whales were seen on that date. Otherwise as

in Fig. 4.27.

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FIGURE4.31. Radiated source levels of icebreaker sound from icebreaker Robert Lemeur (top) and the Argotec 220/J-ll projector system

used on 14 May 1994 (middle). Projector source level at 17:37:49 is applicable for periods when whales were seen on that date.

Otherwise as in Fig. 4.27.

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One-Third Octave Band Center Frequency (Hz)

FIGURE4.32. Radiated source levels of icebreaker sound from icebreaker Robert Lemeur (top) and the Argotec 220/J-II projector system

used on 16 May 1994 (middle), by 1I3-octave band and for three broad bands. Projector source level at 14:25:09 is applicable for

periods when whales were seen on that date. Otherwise as in Fig. 4.27.

-N

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17 May 9414:49:59

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. M .•...•...•..N N M ~ It)m

One-Third Octave Band Center Frequency (Hz)

FIGURE4.33. Radiated source levels of icebreaker sound from icebreaker Robert Lemeur (top) and the J-II projector system used on

17 May 1994 (middle), by II3-octave band and for three broad bands. Projector source level at 14:49:59 is applicable for periods when

whales were seen on that date. The model 220 low frequency projector was inadvertently disconnected, accounting for the low levels,

especially below 500 Hz. Otherwise as in Fig. 4.27.

N

Ul-
220.0

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i~l'IFIGURE4.34. Radiated source levels of icebreaker sound from icebreaker Robert Lemeur (top) and the Argotec 220/J-II projector system 'l:I

used on 20 May 1994 (middle), by II3-octave band and for three broad bands. Projector source level at 15:39:47 is applicable for &

periods when whales were seen on that date. Otherwise as in Fig. 4.27. ~.

0.0

0 II) <0 0 II) ~ 0 0 M 0 0 II) 0 0 0 II) 0 0 0 0 0 0 0 0 0 0 0 0 0

.•.. N

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One-ThIrd Octave Band Center Frequency (Hz)

----------~~~~-
4.4 Physical Acoustics: Playback Fidelity 127

Over the 40-6300 Hz range of 1/3-octave band levels, the smallest average difference

between the medians for the actual icebreaker and the simulated icebreaker was 20 dB on 20 May

1994. On this day, and several others as well, there were times when, at high frequencies, the

maximum source level of the icebreaker sound playback slightly exceeded the median source levels

emitted by the actual icebreaker. There also were times when the median source level of the icebreaker playback exceeded the lowest source levels of the actual icebreaker sound. (Note the

levels at 2000 Hz and higher in Fig. 4.34, 20 May 1994.) However, for most frequencies at most

times, the source level of the playback sound was substantially weaker than that of the actual icebreaker. The largest average median differences were 47 dB during a period of low-power transmission on 7 May 1994, and 44 dB during a transmission when the J-13/F40 projectors were

operating on 17 May 1991.

The variability in the median difference with frequency is a measure of the departure from

a desirable "flat" amplifier/projector response. This variability resulted from equipment limitations

and non-optimum adjustments of the equalizers and amplifier gains for the various projectors. The

least variability (flattest response) is seen in Figure 4.28 (low level on 7 May 1994 at 18:04) and

Figure 4.32 (16 May 1994). On those occasions the range between the highest and lowest differences was 11 dB. In reports on the fidelity of loudspeakers in air, this result would be described

as "within ±5.5 dB of flat from 40 to 6300 Hz". Variability ranged between 16 and 27 dB (i.e.

±8 to ±13.5 dB) on the other days, as shown in the "Max-Min" column of Table 4.8, neglecting

17 May 1994 when the low frequency components were not projected.

Because the playback source level was, on average, some 20-47 dB less than the source level

of the actual icebreaker over the 40-6300 Hz band, the received level at any given distance was

correspondingly lower during playbacks than it would have been if the actual icebreaker were

operating at those sites. Another way to describe this is that a given received level of icebreaker

sound would be found much closer to the playback site than to the actual icebreaker. Some specific examples of received level vs. range for playbacks vs. the actual icebreaker are given in §6.4

and §7.3 (Fig. 6.22, 6.23, 7.16, 7.17).

Summarizing, over the frequency range 40-6300 Hz, the median playback source level was

34 dB less than the actual icebreaker source level (0.04% of the acoustic power). The median

deviation from a flat frequency response across the 40-6300 Hz range was ± 10 dB. The differences in source level at frequencies below 40 Hz increased with decreasing frequency to a median

difference of 63 dB at 20 Hz.

What is the importance of the acoustic power at low frequencies relative to the power in the

entire frequency band 20-6300 Hz? The answer depends on distance from the source, as the rate

of attenuation of sound with distance is frequency-dependent. To calculate a quantitative answer,

the 95th-percentile 1/3-octave band levels for the actual icebreaker at 20-6300 Hz were converted

to "power" (~Pa2) and summed to compute the cumulative distribution of sound power with frequency (Table 4.9). For water depth 41 m and distance 1 m (the reference distance for the icebreaker source levels), 45% of the power occurs in the 1/3-octave bands centered at 20-40 Hz, i.e.

in the 18-45 Hz band. At increasing distances, the percentage decreases: 18% at 50 and 100 m,

17% at 1000 m, 14% at 3000 m, and 6.5% at 10,000 m. Thus, because sound propagation in shal-
4.4 Physical Acoustics: Playback Fidelity 128

low water is poor at frequencies below 50 Hz, the importance of the low frequencies diminishes

with increasing distance. Given the distances from the projectors at which most bowhead whales

were observed (§6), the 50 m to 3000 m values are the most relevant ones in judging the fidelity

of the playbacks. At 50 to 3000 m range from the actual icebreaker, 18 to 14% (respectively) of

the power would be in the 18-45 Hz band. In contrast, only a negligible proportion of the acoustic

power in the playbacks «<1 %) was at 18-45 Hz.

TABLE 4.9. Cumulative distributions of the 95th-percentile sound power from the actual icebreaker

by 1/3-octave band for six distances from the source. The transmission loss effects were computed

by the model described in §4.3 (p. 96ff) for water depth 41 m, the median depth for the playback

tests conducted in 1991/94.

1/3 OB Fre- Percentage of EnergyAt or Below Each Frequencyat Six Distances

quency (Hz)

1m 50 m 100m 1000 m 3000 m 10,000 m

25 35.1 6.3 6.3 5.7 4.4 1.5

31.5 40.6 11.8 II.8 10.9 8.9 3.4

40 44.9 18.1 18.1 17.0 14.4 6.5

50 55.2 38.1 38. I 37.0 33.7 19.7

63 62.6 50.8 50.8 50.2 47.4 32.2

80 67.9 58.8 58.8 58.5 57.2 44.2

100 70.1 61.6 61.6 62.0 61.1 50.4

125 77.0 70.6 70.7 72.1 73.5 70.3

160 80.5 75.1 75.2 77.2 79.7 80.2

200 85.8 81.9 82.1 84.8 89.1 95.2

250 87.9 84.6 84.8 87.6 92.1 98.0

315 89.3 86.4 86.5 89.3 93.6 98.9

400 91.5 89.3 89.4 91.9 95.6 99.5

500 93.2 91.4 91.5 93.7 96.8 99.7

630 94.6 93.2 93.3 95.1 97.7 99.8

800 96.1 95.1 95.2 96.6 98.5 99.9

1000 97.1 96.4 96.5 97.6 99.0 100

1250 98.4 98.0 98.1 98.7 99.5 100

1600 99.0 98.8 98.8 99.2 99.7 100

2000 99.5 99.3 99.3 99.6 99.9 100

2500 99.7 99.6 99.6 99.8 99.9 100

3150 99.8 99.8 99.8 99.9 100 100

4000 99.9 99.9 99.9 99.9 100 100

5000 100 100 99.9 100 100 100

6300 100 100 100 100 100 100
4.5 Physical Acoustics: Bowhead Calls 129

4.5 Do Bowhead Calls Contain Infrasonic Components?

Data on the possibility that bowhead calls contain infrasonic components are relevant in

evaluating the significance of industrial infrasounds to bowheads (see specific objective 5, p. 7).

All bowhead calls recorded during ambient noise recordings in 1991 were analyzed for infrasonic

energy content. Waterfall spectrograms were computed for 45 samples of recorded signals. These

45 spectrograms contained -73 calls, of which 11 occurred coincidentally with infrasonic energy.

Figure 4.35 shows two spectrograms and five calls without perceptible infrasonic components.

Figure 4.36 shows two spectrograms and three (or possibly four) calls, of which at least one occurs

with infrasonic energy. Figure 4.37 shows two more spectrograms with infrasonic energy

associated with bowhead calls.

Of 45 calls recorded in the spring of 1990 and analyzed in a similar way, one call was

associated with the occurrence of infrasonic energy (Richardson et al. 1991a:91-96).

Simultaneous arrival at the hydrophone of a bowhead call and an infrasonic signal does not

prove that the infrasonic component came from the calling whale. However, it is possible that at

least some of the cases listed above did represent bowhead calls with infrasonic components. This

possibility could be tested more readily in a study employing widely-spaced hydrophones to

localize calling whales (e.g., Cummings and Holliday 1985; Clark et al. 1986; Greene 1987a). If

whale calls and infrasonic signals are received simultaneously from the same location, this would

provide much stronger evidence that some bowhead calls include infrasonic components. Use of

widely-spaced hydrophone arrays was not logistically feasible during this study.

4.6 Generator Noise

Underwater noise arising from use of a generator at the ice camp was a concern during every

field season. The generator was necessary for prolonged operation of the power amplifiers that

drove the projectors. The generator was also operated during most periods when the projectors

were silent. This was done to ensure that the presence or absence of the projected sound was the

only difference between playback and "control" periods.

Results

In 1989-90 the 2.2 kw generator operated on the snow-covered ice; it was supported by four

rubber pads. When the projector was not operating, generator noise was detected underwater at

distances as far as 400 m from camp, depending on ambient noise conditions. The noise was

manifested by tones at a nominal fundamental frequency of 60 Hz and integer multiples thereof.

(The actual fundamental frequency depended on the generator speed, but was usually within 3 Hz

of 60 Hz.) The received levels were weak compared to the projected sound levels at those

frequencies. However, in the absence of playbacks the generator tones were audible at range

100 m and sometimes at 400 m (Richardson et al. 1990a:97ff, 1991a:98fj).

In 1991, at the suggestion of A. Milne (then-Chairman of the project's Scientific Review

Board), the generator was suspended by bun gee cords from a PVC pipe frame whose four legs
N 375

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4.5 Physical Acoustics: Bowhead Calls 130

500

P02A8026.111 01 May 91 1835 Bowhead Call, 7.5 nrn i, TL Test # 1

0 I

0 2.06 4.11 6.17 8.22

Time In seconds

P13A8848.110 25 May 91 1718 Bowhead Calls, Hydrophone #617

250

o I

7.48

Tim e in seconds

I

o 11.2

I

3.74 15

FIGURE 4.35. Waterfall spectrograms of bowhead calls without perceptible infrasonic components.

(A) shows three calls; (B) shows two calls.
4

Time in seconds

FIGURE 4.36. Waterfall spectrograms of bowhead calls with possible infrasonic components.

(A) shows one call. (B) shows two calls, the second of which-at time 3-4 s-has associated

infrasonic energy. A third possible call in (B) at time 6 s has energy only at frequencies below

30 Hz; it cannot be proven that this sound is from a bowhead.

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4.5 Physical Acoustics: Bowhead Calls 131

250

P02A8300.111 01 May 91 183e Bowhead Call, 7.5 nmi, TL Test #1 [Over-loaded]

o I

2 4 5.99 7.S9

Time in seconds

P03A4947 .210 11 May 91 1804 Bowhead Call

250

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4.5 Physical Acoustics: Bowhead Calls 132

P08A0232.110 18 May 91 1519 Bowhead Call, 0.44 nmi, TLT #2

o I

4

Time in seconds

P08AI117.110 18 May 91 1528 Bowhead Call, 0.44 nrni , TLT #2

5.99

500

o I

2 4 5.99 7.99

Time in seconds

FIGURE 4.37. Waterfall spectrograms of bowhead calls with possible infrasonic components.

(A) shows three calls, at 1, 4.5 and 7 s; infrasonic energy appears at 3 and 4.5 s. (B) shows two

or three calls, at 1.5, 4.8 and possibly 8 s, with infrasonic components at 1.5-3 s.
4.6 Physical Acoustics: Generator Noise 133

stood on the ice. No part of the generator touched the ice. Background noise recordings with and

without the generator running were made at ranges 0.1-1 km during each transmission loss experiment. The generator sounds were not audible, nor was any change in the background noise audible

at any range, when the generator was started or stopped. Underwater sound spectra from depth

18 m were computed for the different ranges but no tones that could be associated with the

generator were evident. For example, Figure 4.38 shows the spectra of the noise received at range

100 m, generator on and off, during each of the four transmission loss experiments in 1991. The

peaks in the noise spectra do not occur at multiples of 60 Hz or show any other features that might

be attributable to the generator. Thus, the suspension system adopted in 1991 successfully isolated

the generator from the ice and avoided transmission of significant levels of generator sound into

the water.

In 1994, it was essential to use a larger generator-5 kw-to power the four power amplifiers

needed for the planned projector system. The 1991 PVC frame proved inadequate to support the

heavier machine. A pipe tripod was assembled from which the generator was suspended by bungee

cords. However, after the generator had run for an hour or so, the pipe legs melted down into the

ice, necessitating repositioning. Sometimes, but not often and never for very long, the generator

sagged onto the ice. Thus, there were times in 1994 when generator noise was present underwater

near the ice camp. However, the generator noise, when present, was weak and undetectable in the

presence of the playback sounds.

Figure 4.39 presents examples of background noise spectra with and without generator noise

present in 1994. These examples are taken from recordings of the "ambient noise" hydrophone

suspended below the ice camp, depth 18 m, generally within a horizontal distance of 30 m from

the generator. The recordings were made while the camp was being disassembled for return to

Barrow, just before and just after the generator was shut down. The higher levels at frequencies

above 330 Hz at 19:29 on 3 May 1994 are from a bearded seal call, not the generator (Fig. 4.39A).

In one case-at 16:03 on 7 May 1994, a prominent tone appears at 180+ Hz (Fig. 4.39B). Weaker

peaks appear at frequencies slightly higher than 240 and 300 Hz. These are from the generator.

In another case, at 19:47 on 9 May 1994, a 300 Hz tone appears in the noise spectrum, a clear

manifestation of generator noise in the background sound (Fig. 4.39C). The peaks in the 18:27

spectrum on 16 May 1994 do not fall on power frequency harmonics and are thought to be normal

variability in the ambient noise (Fig. 4.39D).

Discussion

Generator noise was not detectable during playback experiments in any of the four spring

seasons. In ambient conditions (no playback) during 1991 the generator was not detectable at

distances beyond about 100 m. In 1994, there were short periods during "control" (no playback)

conditions when faint generator noise may have been detectable at distances up to 500 m

(estimated).
N

=: ......... 0

NO

(~

ell c,

;:l •

o

~O)

Q)

l-o

c:lO

"'dec

-Q)

> .

Q)O

~l'-

"'d

Q)

> .

...•0

~CC

Q)

~

4.6 Physical Acoustics: Generator Noise 134

A. TL Test HI

-Q)

> .

Q)O ~"'d"

"'d

Q)

> .

...•0

~tn

Q)

~

0+---,-----.---.,...----,----,----.----.----1 C\l

O. 50. 100. 150. 200. 250. 400.

Frequency, Hz

300. 350.

P07A0347.114 18 May 91 1410 Generator On. 100m. TL Test 62

P07A0510.114 18 Ma 91 1412 Ambient. 100m. TL Test 2 ~-.-,......-.:...:.:.;=:=:.:.;:,-T....:::::o....::.:-=r=-:-=--=.:::.:;:::..:<.....:.=.;=-F~~.<r.:...-r-----r"-----,

~

B. TL Test H2

04----,......----r---,...-------,.----,----.-----,..------i

I.C':I

O. 50. 100. 150. 200. 250. 400.

Frequency, Hz

300. 350.

FIGURE 4.38. Paired noise spectra observed 100 m from the ice camp with generator on and off

during the four transmission loss tests in 1991. The sound projectors were silent during these

measurements.
0

0

.....

N - c. TL Test 1/3

........... -C\lo

(~

a:l Q.,

=' 0

-co

Q)

~

ceo

't:l.l'-

-Q)

>Q)O ...Jc.o

't:l

Q)

>....0

~~

Q)

c::

0

~

O. 50. 100. 150. 200. 250. 300. 350. 400.

Frequency, Hz

0

co

N

::r:: ........... D. TL Test #4

C\lo

(l'-

a:l Q.,

=' 0

-c.o

Q)

~

ceo

"'C~

-Q)

> .

Q)O ...J,,:!,

"'C

Q)

>·...0

~M

Q)

c::

0

C\l

O. 50. 100. 150. 200. 250. 300. 350. 400.

Frequency, Hz

FIGURE 4.38 (continued).

4.6 Physical Acoustics: Generator Noise 135
N

::I:

;:-

c.III 80

:I. .•..

e

m

~ 70

Gi

>

III ..J

"Cl

III

> ./\ 60 -' , - \ t> Gi

U

v

III 0::

N

::I:

;:-

c.III 80

:I. .•..

e

m

~ 70

Gi

>III ..J

"Cl

III ~

~ 60 -,/.....'

III

u

III 0::

4.6 Physical Acoustics: Generator Noise 136

100.,..------------------------------,.

90

__ POoWl9SQ.31403May0419:28 _,-.gonomoron I

- P04M05O.314 03 May041D:31 _.-. gonomorotl

A.

50

40 +, -,.-...,.......,,...,.......,.... .••....• .....,...-.--f---,--.--.--,......,.-,.-...,.......,,...,...-+-...,.......,,...,...--.-.,.......,--.-.,...-t-..-_,......,.-,.-...,.......,-....-+

o 100 200 300 400

Frequency (Hz)

100-r---------------------------------r

90

B.

50

--P06M"Ii3ll.31401M11y041G:03 _.-.gonomoron I

.----- POo<A8720.31401 May04:ZZ:34 _.-. gonomorotl

40 -f--,--.-....,.... .••.•..•-..--.- .••.•.•.-+--.--,.....,..--.-.,.......,--.-....,.... .•......•_....,.....,.-,-..-....,.....,......,.-..--j-,......,.-,.-...,.......,_-.-.,......,.-+

o 100 200

Frequency (Hz)

300 400

FIGURE 4.39. Paired noise spectra observed at "ambient noise" hydrophone 18m below the ice

camp with generator on and off on four dates in 1994. The sound projectors were silent during

these measurements. (A) 3 May; (B) 7 May.
N

:t:

;;-

a.. l'lI 80

:I.

<po

GI .. m

~ 70

'ii

>ell ..J

'C

ell

> 60 'ii

u

ell

a:::

N

:t:

;;-

a.. l'lI 80

:I.

<po

e

m

:2- 70

'ii

>ell ..J

'C

ell

>

'ii 60

u

ell

a:::

4.6 Physical Acoustics: Generator Noise 137

100

50

--PI2A6900.314119MoylWt8:47 __ ,--..'"'

.----- P12A7208.31.09Mly1M 1St.50 ArnbIiInt noiN. genef'ItOfotf

c.

90

40

o 100 200 400

Frequency (Hz)

300

100.,.....-------------------------------,.

90

D.

50

PlllA62ll5.31418 MoyIW18:%7__ • __ '"'

.----- PlllA83C5.314 18 MoyIW18:211__ •--.. 011

o 100 200 400

Frequency (Hz)

300

FIGURE 4.39 (continued). (e) 9 May 1994. (D) 16 May 1994.
5.1 Bowheads: Distribution & Movements 138

5. BOWHEAD WHALE RESULTS:

MOVEMENTS, BEHAVIOR AND BASIC BIOLOGy9

This section describes the distribution, general activities, and behavior of bowheads in the

study area. Section 5.1 describes the spring bowhead migration east of Pt. Barrow as observed

during the four years of this study. Section 5.2 describes the movements and sizes of bowheads

observed in the study area as determined by photoidentification and photogrammetric methods.

Section 5.3 describes bowhead behavior in the absence of human disturbance, excluding mothers

and calves (which are covered in section 5.4). Together, these four subsections address specific

objective 7, "To document ... the movements, behavior, basic biology ... of bowheads ..." (§ 1.1,

p. 7). These data are needed as background information for the analysis of reactions to noise

playbacks and aircraft overflights (specific objectives 4 and 6), covered in §6.

This report deals primarily with results from the 1991 and 1994 fieldwork. However, to

maximize sample sizes and provide a more comprehensive account, §5.1-5.4 summarize data from

1989 and 1990 as well as the 1991 and 1994 data. More detailed information from 1989 and 1990

can be found in Richardson et al. (l990a, 1991a).

5.1 Bowhead Distribution & Movements

The bowhead sightings during reconnaissance flights, helicopter ferry flights, and ice-based

work provided information about the timing and routes of spring bowhead migration through the

study area during the years 1989-91 and 1994. Our primary objective when conducting reconnaissance flights was to locate the main bowhead migration corridor and, within that corridor, concentrations of bowheads. We did not conduct systematic surveys, and we devoted much less effort

to areas where few or no bowheads were expected than to the more promising areas. Hence, the

relative numbers of sightings in different parts of the study area in the following bowhead

distribution maps should not be taken as a quantitative measure of densities of whales in those

areas. The information on bowhead distribution and movements in 1989 and 1990, summarized

below, is presented in more detail in Richardson et al. (1990a, 1991a).

Bowheads in General

Spring 1989.-In 1989, reconnaissance surveys were conducted from 29 April to 30 May.

Ice cover was extensive and thick during this period. No well-defined leads occurred in our study

area until 20 May, when an E-W lead started to form along the landfast ice edge within our study

area. The heavy ice conditions in 1989 resulted in an unusually wide and northerly migration

corridor (Fig. 5.1; see also Appendix D, Fig. D-1 to D-4, for distribution by lO-day periods). The

absence of well-defined leads during much of the study may also have influenced the headings of

whales. The vector mean heading of bowheads in 1989 was more northerly than in other years

(71 °True for 1989 vs. 79-93° for other years, Table 5.1). Also, the headings in 1989 were more

9 By W.J. Richardson, W.R. Koski, G.W. Miller and B. Wiirsig, with R. Elliott and N. Patenaude
5.1 Bowheads: Distribution & Movements 139

,

,

,

,

\

••.••.......

---,

..........

-',

+ '\ -: •••• _---,

, , ,

, ,

\•.•.....•......... " ',-,

------_.,\,

,

,

,

,

......;

........•.•......- -

/ + e-

-:

,....•.

...................•

.•. ,.•....'

/

//'--"---

7130 ./ + -:

157 156 --'- _.__ .__ ._.,.\

\

\

\.

<,

"

Bowhead Whales

April - May 1989

@ Twin Otter

o Ice Camp/Helicopter

@ Cow/Calf. Twin Otter

72

+

..•..........•......

.•...,._\

/L..~ ~,-- --.J

i

i

i

e \.

0'

72

+

o ~ .

air

@-

+

'.

........ Landfast Ice Edge···._

'<0 <;... 111., "'.. ..

............

o

154

........ +

............

. .

........

5 lOnmi

o lOmi .....

.................... +.

...... 10 m.······· 71

5

+

o 5 10 km

157 156

71 30

FIGURE 5.1. LGL sightings of bowhead whales, 29 April to 30 May 1989. Symbol type

distinguishes sightings by the two crews, sightings of 1-2 vs. >2 bowheads, and sightings of

mother/calf pairs vs. other bowheads. Headings toward which the whales were oriented when first

seen are also shown when available. Survey effort was not uniform across the area mapped.
TABLE 5.1. Headings (True) of bowhead groups by date, year and part of study area. Each group is counted only once.

A. By IO-Day Period B. By Year C. By Part of Study Area

True 1-10 11-20 21-31 South South North North True

Heading April May May May TOTAL 1989 1990 1991 1994 TOTAL West Central East Central East TOTAL Heading

o N 0 0 1 0 1 0 0 0 1 1 0 0 1 0 0 1 N 0

10 1 I 3 0 5 0 2 2 I 5 1 2 2 0 0 5 10

20 0 0 4 0 4 2 0 0 2 4 0 1 2 0 I 4 20

30 2 15 11 4 32 2 11 8 11 32 2 8 20 0 2 32 30

40 0 1 6 1 8 2 2 2 2 8 0 3 4 0 I 8 40

50 1 19 17 6 43 5 9 8 21 43 3 26 12 0 2 43 50

60 2 26 31 9 68 13 10 27 18 68 5 28 24 3 8 68 60

70 3 29 21 6 59 7 13 14 25 59 2 31 19 3 4 59 70

80 5 149 82 16 252 3 60 35 154 252 6 76 167 0 2 251 80

90E 6 31 42 7 86 8 14 21 43 86 4 31 4S 1 S 86 E90

100 5 16 45 3 69 6 31 8 24 69 0 24 42 1 2 69 100

110 1 3 7 3 14 2 4 7 1 14 1 7 6 0 0 14 110

120 2 15 57 3 77 3 51 14 9 77 0 12 63 2 0 77 120

130 1 0 6 1 8 0 4 1 3 8 0 0 8 0 0 8 130

140 0 3 11 0 14 I 8 1 4 14 0 1 12 0 1 14 140

150 1 1 2 0 4 0 2 1 I 4 0 2 2 0 0 4 150

160 0 0 1 I 2 1 0 1 0 2 0 1 I 0 0 2 160

170 0 2 6 2 10 0 5 2 3 10 2 2 6 0 0 10 170

ISO 8 1 0 3 6 10 2 4 4 0 10 0 3 4 1 2 10 81SO

190 1 1 1 1 4 1 0 1 2 4 0 2 2 0 0 4 190

200 0 0 1 1 2 1 0 0 1 2 0 0 2 0 0 2 200

210 0 2 1 3 6 2 2 I 1 6 1 1 3 0 1 6 210

220 1 0 0 1 2 0 0 1 1 2 1 1 0 0 0 2 220

230 0 0 0 1 1 0 0 1 0 1 1 0 0 0 0 I 230 !Jt

•...•

240 1 0 0 0 1 0 0 I 0 I 0 I 0 0 0 1 240 b:l

250 0 0 0 1 1 0 0 1 0 I 0 0 0 0 I 1 250 <:)

~

260 0 2 2 0 4 0 0 1 3 4 0 1 3 0 0 4 260 ~

•••

270 W 0 1 S 1 7 3 0 4 0 7 0 3 1 2 1 7 W 270 Q

280 0 0 0 2 2 0 0 2 0 2 0 2 0 0 0 2 280 ~

290 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 290 tl

300 0 3 0 1 4 I 1 I 1 4 0 2 2 0 0 4 300 <;;. ..

310 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 310 ::I. ~

320 0 2 2 0 4 0 1 1 2 4 0 2 2 0 0 4 320 r:

:::.

330 0 2 1 1 4 3 0 0 1 4 0 1 0 2 1 4 330 <:)

;:s

340 0 1 0 2 3 2 0 I 0 3 0 0 3 0 0 3 340 Ro

350 0 2 2 2 6 1 2 0 3 6 0 1 5 0 0 6 350 a::

Total 34 327 371 85 817 71 236 172 338 817 29 275 463 15 34 816 Total <:)

Vector ~

:J

Mean 92 77 88 85 83 71 93 81 79 83 77 78 88 71 71 83 ••• ;:s

Length 0.72 0.86 0.80 0.51 0.79 0.58 0.82 0.71 0.87 0.79 0.67 0.81 0.82 0.43 0.65 0.79 •••

Ang.Dev. 43 30 36 56 37 52 34 44 30 37 47 36 35 61 48 37 -~

0
TABLE 5.2. Headings (True) of bowhead mother-calf groups by date, year and part of study area. Each '+' symbol represents 1 group.

A. By IO-Day Period B. By Year C. By Part of Study Area

True 1-10 11-20 21-31 South South North North True

Heading April May May May TOTAL 1989 1990 1991 1994 TOTAL West Central East Central East TOTAL Heading

0 N 0 0 0 N 0

10 0 0 0 10

20 0 0 0 20

30 + 1 + I + 1 30

40 0 0 0 40

50 + ++ 3 + + + 3 + ++ 3 50

60 + + + 3 + + + 3 + ++ 3 60

70 ++ 2 ++ 2 ++ 2 70

80 + ++ 3 + + + 3 ++ + 3 80

90E + .+++ 4 ++ ++ 4 + ++ + 4 E90

100 + 1 + 1 + 1 100

110 + 1 + I + 1 110

120 + ++ 3 ++ + 3 +++ 3 120

130 0 0 0 130

140 0 0 0 140

ISO 0 0 0 150

160 + 1 + 1 + 1 160

170 0 0 0 170

180 8 + ++ 3 + + + 3 + + + 3 8180

190 0 0 0 190

200 + I + I + I 200

210 ++ 2 + + 2 + + 2 210

220 0 0 0 220

230 0 0 0 230 !-'>....

240 0 0 0 240 b:l

250 I I I 250 0

+ + + ~

260 + I + I + I 260 ~

"' 270 W 2 2 2 W 270 l:l

+ + + + + +

280 0 0 0 280 ~

290 0 0 0 290 l::l

300 + I + I + I 300 0:;' ..•

310 0 0 0 310

..•

s

320 0 0 0 320 l::

~.

330 + I + 1 + 1 330 ;:s

340 + 1 + 1 + 1 340 !Co

350 0 0 0 350

Total ~ 0 3 8 24 35 14 7 13 35 3 9 16 2 5 35 Total '<:

Vector "' :i

Mean 40 81 107 96 100 96 100 60 96 130 82 93 225 350 96 "'

;:s

Length 0.51 0.26 0040 0.35 0.40 0.25 0.31 1.00 0.35 0.63 0.64 0.38 0.71 0.07 0.35 ~

Ang.Dev. 57 70 63 65 63 70 67 0 65 50 48 64 44 78 65 •....

~•....
5.1 Bowheads: Distribution & Movements 142

variable than those in the subsequent three years of study. The angular deviation was 52° in 1989

vs. 30-44° in the other three years (Table 5.1).10

Late in the season, mothers and calves predominated among bowhead sightings. Mothers and

calves tended to be found along or just north of the pack ice edge along the north side of the

nearshore lead that separated the landfast and pack ice from 20 May onward. Their predominant

heading was easterly (vector mean 1000T), but they were oriented in other directions somewhat

more often than were other whales (angular deviation 63° vs. 52°; Table 5.2 vs. 5.1).

Spring 1990.-During 1990 there was a nearshore lead along the landfast ice edge ENE of

Barrow during most of the study period. Bowheads were seen from the first day of aerial surveys

in 1990 (29 April) until the last day (26 May). Bowheads were found on most days with surveys,

except during the 30 April-6 May period. Numerous bowheads were present on 29 April and from

-8 May to 21 May. After 21 May, numbers declined and mother-calf pairs predominated.

The main migration corridor through our study area was narrower and tended to be farther

south in 1990 than in 1989 (Fig. 5.2 vs. 5.1; see also Appendix D, Fig. D-5 to D-8). East of

156°W longitude, most of the 1990 sightings were concentrated in a west-to-east band near

71°30'N. West of 155°W many bowheads seen by us were moving east along the middle or north

side of the lead along the landfast ice edge. However, farther east, where the lead veered to the

SE, bowheads continued eastward through the pack ice, forsaking the lead. During 1990, the great

majority of bowhead headings were in the sector from NE to ESE and the vector mean heading was

almost due east (93° true, Table 5.1). In 1990 bowheads deviated from this heading considerably

less than in 1989; the angular deviation was 34° in 1990 vs. 52° in 1989 (Table 5.1).

As during 1989, mothers and calves predominated among the whales seen at the end of the

season. They were sighted either along or just north of the nearshore lead or about 50 km farther

north among 80% pack ice. Although the vector mean heading was easterly (96°T), the easterly

trend was weak, with an angular deviation of 70° (Table 5.2).

Spring 1991.-Ice conditions were loose enough to allow bowheads to travel northeast and

east across the study area throughout the 1991 field season (28 April-26 May). There was a passable migration corridor close to the landfast ice edge throughout the spring. Early in the season,

there was a wide nearshore lead extending northeast past Pt. Barrow far into the Beaufort Sea

(Plate 3.1, p. 52). Later in the season, the broad continuous lead did not extend as far to the east,

but there were-at the least-discontinuous openings near the landfast ice edge and elsewhere in

the pack ice. Many bowheads traveled northeast and then east along that corridor (Fig. 5.3).

In 1989-90, almost all bowheads seen east of about 156°W had been either near the northern

edge of the main nearshore lead or in the pack ice north of there. In contrast, in 1991 many

10 Because heading is distributed circularly rather than linearly, a simple arithmetic average often is not

a meaningful measure of central tendency. The proper measure of central tendency is the vector mean, and

the proper measures of variance are the mean vector length and the angular deviation (Batschelet 1981).

The latter is analogous to the standard deviation of a linear variable (Batschelet 1981 :276).
5.1 Bowheads: Distribution cl Movements 143

72

157 156 155

Bowhead Whales

72

April - May 1990

@ Twin Otter

o Ice Camp/Helicopter

@ Cow/Calf, Twin Otter

+

@

@

,

\,

;

." ..../

v.

<,,

i

\

"'\

\

\

-,

,

...•••.,.

<'90~.

+ +

:' + 7'130

o 5 lOnmi

o 5 10mi

........

................. +.

+ .... 10 m.······ 7'1 o 5 IOkm

157 156 155 154

FIGURE 5.2. LGL sightings of bowhead whales, 27 April to 26 May 1990. Symbol type

distinguishes sightings by the two crews, sightings of 1-2 vs. >2 bowheads, and sightings of

mother/calf pairs vs. other bowheads. Headings toward which the whales were oriented when first

seen are also shown when available. Survey effort was not uniform across the area mapped; the

most intense effort was in the nearshore lead just north of the landfast ice.
7130

5.1 Bowheads: Distribution & Movements 144

157 '156 155

,

,

,

,

--'- _.__ ._.- .

<,

"

\

\

\

-,

April - May 1991

@ Twin Otter

o Ice Camp/Helicopter

@ Cow/Calf, Twin Otter

Bowhead Whales

72 72

.....,.

'\

i

f '---.,- ~,__----.......J

i

i

i

-,

-,

\

,

i

/

/

"

'<.

\

i

\

\.

\

\

\

".

-,

..... ,.

''"''''- -<>9.'1))....

+.

$- ..., rJ

Q~ ./

+. 7'130

+.

".

~

+.

",

.......

.........

···..··+. 10 m · 7'1

0 5 10nmi

0 5 10mi

+. 0 5 10 km

A

157 156 155 154

FIGURE 5.3. LGL sightings of bowhead whales, 28 April to 26 May 1991. Symbol type

distinguishes sightings by the two crews, sightings of 1-2 vs. >2 bowheads, and sightings of

mother/calf pairs vs. other bowheads. Headings toward which the whales were oriented when first

seen are also shown when available. Survey effort was not uniform across the area mapped; the

most intense effort was in the nearshore lead just north of the landfast ice. Surveys near Barrow

in 1991 did not begin until 17 May, after whaling had ended.
5.1 Bowheads: Distribution & Movements 145

72

. .f

1991

..... .- -.

71

157 156 155 154

FIGURE 5.4. Locations where bowheads were photographed during spring photogrammetric surveys

conducted by the U.S. National Marine Mammal Laboratory in 1991 (unpubl. data, courtesy

D. Withrow and D. Rugh, NMML). Survey effort was not uniform across the area mapped; the

most intense effort was in the nearshore lead just north of the landfast ice.
5.1 Bowheads: Distribution & Movements 146

bowheads were seen along the south side of the nearshore lead and quite close to the landfast ice

edge when they were well to the east of 156° (Fig. 5.3). Other bowheads continued to the NE or

ENE after passing Pt. Barrow (similar to 1989-90), and moved well offshore into the pack ice as

they traveled east (Fig. 5.3). This pattern was also evident in the distribution of sightings during

the National Marine Mammal Lab's bowhead photography flights in 1991 (Fig. 5.4).

East of Pt. Barrow, both NMML and ourselves devoted much more effort to areas between

71°30'N and 71°40'N, the main bowhead migration corridor in 1991, than to areas farther north

or south. However, occasional surveys north of 71°40'N showed that densities of bowheads were

lower north of 71°40'N than in the main migration corridor.

We did some reconnaissance to the west and northwest of Pt. Barrow in 1991, but only after

mid-May when spring whaling ended. During the latter half of May 1991, at least a few bowheads

were present many kilometers to the northwest, far from the landfast ice. edge (Fig. 5.3). The

National Marine Mammal Lab's aerial photography crew also saw a few bowheads far to the northwest (Fig. 5.4).

Figures 5.5-5.8 show our 1991 bowhead sightings during late April and during 10-day periods in May. The area NE and east of Pt. Barrow was searched throughout the field season. The

general distribution of sightings east of Pt. Barrow did not change substantially during most of this

period. However, late in the season (21-26 May) there was a tendency for bowheads to continue

to travel ENE rather than turning to the east after they passed Point Barrow. At that time, the

nearshore lead provided an open corridor to the ENE as well as the east. This change in

distribution may have been related to the more frequent sightings of mother-calf pairs during late

May. As noted in 1989-90, mother-calf pairs tended to follow the offshore (pack ice) rather than

the nearshore (landfast ice) side of the lead.

The vector mean heading of bowheads was 81°T in 1991, intermediate between the mean 71°

and 93° mean headings in the two previous years (Table 5.1). Most bowheads or bowhead groups

headed ENE to east. The among-group variability in headings (angular deviation 44°) was slightly

greater than in 1990 but less than in 1989 when heavy ice cover influenced headings.

The numbers of bowheads seen each day are shown in Appendix A (Table A-2), along with

a measure of reconnaissance survey effort-the number of hours of reconnaissance flying each day.

Although the number of bowheads in the area varied from day to day, bowheads were detected

quite consistently in 1991. We saw bowheads during 24 of the 25 effective offshore flights (those

>1 h in duration). This is an unusually high proportion. In 1989, in contrast, bowheads were

sighted during only 15 of the 24 days with flights (>1 h of flying on all 24 days). In 1991, the

flight on 28 April was the only prolonged flight when no bowheads were seen. Indeed, bowheads

were also seen during 2 of the 5 short flights that were terminated within 1 h because of bad

weather.

As in 1989-90, mothers and calves were common toward the end of the study. Also as in

previous years, mothers and calves tended to be sighted along or north of the northern side of the

nearshore lead in areas north and NE of Pt Barrow. In contrast to previous years, in 1991 we
5.1 Bowheads: Distribution cl Movements 147

157 156 155 --'-

-'--'-'-'-""

\

\

\"

-,<,

Bowhead Whales

72

April 1991

@ Twin Otter

o Ice Camp/Helicopter

@ Cow/Calf. Twin Otter

72

+

-,

1

i

\

\

\

\

\

"

"

-,

'~oo //_----------- * "",. '11-

;-",,,,; r: - ~

.: ....••.. ;

...........

;,/''''

......••••------_ ---_ - ---;

/~.G-~ ..e ....~

+ +

+ 7'130

. .

•.. {andlast Ice Edge

................

-.

~. ~ .....

-'<0 '11_

+

....................... +

<,

.......

0 5 lOnmi

0 5 lOmi

+

0 5 10 km

A

157 156

................. .+ 10 m········ 71

155 154

FIGURE5.5. LGL sightings of bowhead whales, late April 1991. Format as in Fig. 5.3.
,

,

,

\

<.

<.

"<.-,

\

+ \, " ..- _--- ~

, ,

, ,

........,;,,1 ', .

-----)

-,

_ ..-"

,.....-..----

----_/ +

/)/ ...

--- ...,,-

....,..~

.>

,.- ..... , ....

..",.,,,,

7'130 -- +

" ..', .

,

5.1 Bowheads: Distribution & Movements 148

157 154 156 155

-._-_.-.-

<,

,

\

\

-."

Bowhead Whales

1-10 May 1991

@ Twin Otter

o Ice Camp/Helicopter

@ Cow/Calf, Twin Otter

72

<,

"\

/ L- ......- .J

i

i

i

\.

72

+ ,

"

-,

i

/

»:

-,

,

i

\

"

"

\

"

-,

,

.....•. ,.

'<?oo ",-.

+

e <Be- + .:------.,.--<------1:

• e- ,/ e- ---'"

fi¥./i!f;/ ,". ""60 ",---_

-" ..."

e -ee- ./'-----

_- ae:--G.- --------

e- ~::....- e.•.(!f-'C·~~ + 7'130

. ..» -Landfast Ice Edge

....._-

'<?o ", .

..........................

+

o 5 lOnmi

o 10mi

-- -- -----------+. ---- 10 m 7'1

5

+

o 5 10 km

157 154 156 155

FIGURE5.6. LGL sightings of bowhead whales, 1-10 May 1991. Format as in Fig. 5.3.

_________ 
,

,

,

,

-,

"", ....•..-..-~

/" + + "/''----.----------1:. __-,

.....-..•~

.,-"",(;.. ••.•.•• t 8- ,:,,///j.. .: "".,'--

_.,-",

,/.--'-----fJ-- ..-- t:l ~ ~ _.-~---~/'--' e-

" T~ ,--.@:------~-- ",,-@~ G.

71 30 ef,,- \ •••. 'e-"" '. 8. ~

(,/ + '_ ~.$,"'-G +... +

5.1 Bowheads: Distribution & Movements 149

157 156 155

.-.

-.-.__ ._.-..•.....

'.,

\

\

-.-'...•.

Bowhead Whales

72

,

,

,

,

,

\

•.....•..•.

'.

......."

\,

+ \ //'-------- <.\.,-. +

...•.•....'" ,

.•..._--,

".

<.,

i

\

\

\

"'

"'". ,

" •.•...

'<?°O

~-

11-20 May 1991

@ Twin Otter

o Ice Camp/Helicopter

@ Cow/Calf. Twin Otter

,....,.,._\

/'--.,,--------------_---.:

i

i

i

-,

72

+

7130

. - ...-_.-

""•(andtast Ice Edge

# ••••••• _~ •••••

•........__ ....•. <,..

~ -..

................

'<?o ~.

........ +

o 5 lOnmi

o 5 lOmi

..................+... 71

+ ········10 m .

o 5 10 km

157 156 155

FIGURE 5.7. LGL sightings of bowhead whales, 11-20 May 1991. Format as in Fig. 5.3.
5.1 Bowheads: Distribution & Movements 150

157 154 156 155

'-'-'--_'_'_._.,.,

\

\

-.

Bowhead Whales

72

21-26 May 1991

@ Twin Otter

o Ice Camp/Helicopter

@ COW/Calf, Twin Otter

.•.....•...•..•........•.. <.

-\

I

i '-----0-----......,----------'

i

i

i

\.

72 +

+

&-:"""

+ 7130

....

~'"

-, .

·~o 111.

............

+

0 5 lOnrni

0 5 lOrni

+

0 5 10 km

<,

... ..

................. -+. 10 m········ 71

157 156 155

FIGURE 5.8. LGL sightings of bowhead whales, 21-26 May 1991. Format as in Fig. 5.3.
5.1 Bowheads: Distribution & Movements 151

conducted some surveys near and SW of Point Barrow. Two of three mother-calf pairs sighted

there were along the landfast ice edge. Headings of mother-calf pairs sighted in 1991 again tended

to be easterly (vector mean 1000T), but with more scatter than for other whales (Table 5.2).

Spring 1994.-Ice conditions were heavy at the start (27 April) of the 1994 field season with

little open water and no well-defined leads. However, by 3 May the pack ice began to loosen and

on 4 May there was a major continuous lead along the landfast ice edge NE of Pt. Barrow. This

extensive lead remained open and generally unbroken until 10 May. Although ice and lead

conditions varied after 10 May, there usually was a large lead (although sometimes containing

pack ice) near the landfast ice edge.

Throughout the 1994 field season, the landfast ice in areas east of longitude 156° Wextended

farther offshore than in 1990 and 1991. The landfast ice edge retained a WSW ---7ENE orientation

across most of our study area until 15 May in 1994 (Fig. 3.8, p. 77). In contrast, during much of

the spring migration season in 1989-91, the landfast ice edge as viewed by a migrating whale was

W---7Ebetween 156 and 155°W, and then curved to the right, to an orientation of about WNW---7

ESE, in areas east of about 155°.

During late April and early May 1994, few bowheads were sighted in our study area on some

days. However, after the nearshore lead formed along the landfast ice edge on 3 May, moderate

to large numbers of bowheads were consistently found in our study area through 17 May. During

the two week period from 4 to 17 May, observers in the Twin Otter sighted 25-132 bowheads

during each of the 8 days when reconnaissance surveys were conducted. Smaller numbers of

bowheads were encountered during the 18-25 May period, but even then bowheads were sighted

on 5 of 6 survey days. The numbers of bowheads seen each day during aerial surveys are given

in Appendix A (Table A-3), along with the number of hours of reconnaissance flying each day as

an indication of survey effort.

Bowhead sightings are mapped in Figures 5.9-5.12 for late April and for lO-day periods in

May. The narrow corridor of bowhead sightings, especially evident for the early May period (Fig.

5.10), closely corresponds to the location of the lead along the landfast ice edge. From the

longitude of Pt. Barrow, the landfast ice edge extended on an orientation of about 800T. Thus,

whales migrating along the ice edge lead gradually moved farther north as they proceeded east.

The headings of bowheads sighted in our study area reflected their tendency to travel along the

lead bordering the landfast ice edge. The great majority of the headings were in the range NE to

ESE, with a vector mean of 79°T (Table 5.1). The angular deviation of headings in 1994 was only

30°, the smallest value of any of the four years.

In 1994 the main bowhead migration route followed the landfast ice edge to a greater degree

than in the previous three years of the study. To some extent the concentration of sightings in this

narrow corridor reflects the high proportion of the survey effort that was assigned to this area.

The rather steady and concentrated stream of whales migrating along the ice edge provided a good

opportunity for playback experiments, so most of our efforts were devoted to the nearshore lead.

However, reconnaissance surveys farther north confirmed that few bowheads were traveling outside

the narrow migration corridor depicted in Figure 5.13. The rather narrow and consistent migration
7130

FIGURE5.9. LGL sightings of bowhead whales, late April 1994. Format as in Fig. 5.3.

5.1 Bowheads; Distribution cl Movements 152

.•...-------- ..

//-- ------t -c , '"",

;_.•..•.•.~

r: -'60 ~ __

.---

//---~-- --«~~~ ......•.--_ .•.

156 155

72

7130

o 10mi

..... ,r. 10 m · 71

.-.•.........__ ._.-..•..

'.,

\

\

-,

-,.••...••..

Bowhead Whales

April 1994

@ Twin Otter

o Ice Camp/Helicopter

@ Cow/Calf, Twin Otter

72 + -;",

\

\

"

""

"

".

,

..••... ,.

'~

~ .

+ +

t

:,' Jig ~

,~ .

, '

Landlast Ice E~Jl'" -'':

+

......

~

.

.........

........

...........•

..... +

.........

. ..... ..

'v-, - .•.•

o 5 10nmi

5

+

o 5 10km

157 156 155
5.1 Bowheads: Distribution & Movements 153

157 154 156 15S

72

,

,

,

,

\

">,

..............

"'\

+, ,//--------"'\

...•....•.,.. "

<,

72

Bowhead Whales

1-10 May 1994

~ Twin Otter

o Ice Camp/Helicopter

@ Cow/Calf, Twin Otter

I

Landtasl Ice !,dge

".

<,

....... \

i '

i "---c-,--------«:------.J

i "' i ')

i i

\,---_ ..",.'/

+

,

,

,

,

,

(

-,

••••_I

"

"

"

i

\

\

\

\

\

\

".

<.

<,

·~Oo.."..

------ --- --- ---,r ", ",

.....

-'60

11>- __

+

+ 7130 + +".

------.--./.--,'.-. Er " . . ':':,

", -.•••........ _- •.." .

....... _-- .._ .

. .

~.

'" ~.

·~o "I.

+

....... <,

0 S lOnmi

0 S lOmi

+

0 5 10 km

+

A «

157 156

....................

... -+, 10 m.······ 71

154 155

FIGURE5.10. LGL sightings of bowhead whales, 1-10 May 1994. Format as in Fig. 5.3.
,

,

,

,

,

,

,

,

<,

__---""-,J

""" + ,//"'--------------,r .•.,-,

~•.•......"-' ,

, .

r •• f -: ..... ''60 .' ~ r: .' f1>..-_

/ / e Q. \~ • &- ~

,,/ ~"fr'~ e- ~·k: __ ~

.': ,.--s.- ~--e:;';;;;..~ f:;fi~~ e-

" e' e- 4£ ..-:.,~.~~ ,......: +

7130 + Q~": -e- •.... ~ '... 7130

"

,/'" »: @":::_'!$'_.,..,...:.:"'_.;;::.-,,..;;.,-.,. _,,13--,,-, ~_' . .··· 1La':ldla.s.l.lce Edge _.. '

. .:'. ",'" after 15 ·.•••~X... "._//',"..·r._.... . '

/'

"....•......-..-..- '"

.............. - '

5.1 Bowheads: Distribution & Movements 154

157 156 155

-._._._- ,.

,

\

\

-,

., .

Bowhead Whales

72

11-20 May 1994

@ Twin Otter

o Ice Camp/Helicopter

@ Cow/Calf, Twin Otter

72 +

" .

•...,

i

\

\

\

\

\

\

"

-,

,..•.•._~

Go~

+

~. "......•.

. <'0111•

0 5 lOnmi

0 5 10m;

+

0 5 10 km

A

157 156

.............

....•..... :+: 10 'm.······· 71

FIGURE5.11. LGL sightings of bowhead whales, 11-20 May 1994. Location of ice edge changed

on 15 May (cf. Fig. 5.10). Format as in Fig. 5.3.
+ + 7130

5.1 Bowheads: Distribution & Movements 155

157 156 155

154

Bowhead Whales

72 72

21·25 May 1994

@ Twin Otter

o Ice Camp/Helicopter

@Cow/Ca~. Tw~ Ot~r

v.

<.,

i

\

\

\

-,

\

"

"

"

'- .

// »> --••----------1: ."". ~,.

, ••••.••••.••. i : ••

, "'60

/........ ~--

//e-

, .

//

/" -'-- ----_.---_.-----_.,

e /J +

/./?:._..-_.~.-_.::-:_-- ....,....:------

-

---".-/''-'

•..•( .•..•....•...- ~.-

....•...•_-,

.- -

--'--.-.,.

\

\

\

'".,

-.......•.........

'"

<, ,\

ii L--,,-, -r-e- ---I

i \

i )

i /

'"._._/

+

+ +

o

~ ..-;

<, ~

0",.

+ .....

......

0 5 10nmi

0 5 lOrni

+

0 5 10 km

. ..

........

········+. 10 m.······· 71

157 156 155 154

FIGURE5.12. LGL sightings of bowhead whales, 21-25 May 1994. Format as in Fig. 5.3.
+ 7130

5.1 Bowheads: Distribution & Movements 156

157 156 155 154

7130

Bowhead Whales

72 72

""\

,

,

,

,

\

"0

000

..•....•.

.........\

,

,

+ \, //_-------oo,'\., +

.......~..' ' ..

•..•..•..•._---

---_.-._----- ...•..

'.,

"

"\-.<,

",

...•.. ....•..•.•....•.......

\

i

,. '_-.."., -t-e- --J

i \

i ')

i i

\,_._ ...•... /

April - May 1994

@ Twin Otter

o Ice Camp/Helicopter

@ Cow/Calf, Twin Otter

,

,

,

.

"

/----;-------

(/"---

/

.:

,....•...•....

..>

-:

-- + _ --

+ +

o

.:-. " ':~

...., - -

....•-.._-_ .•

" .

'~"

.................

+

o 5 10nrri

o

=-

5 10rri .....

+

o 5 10 km

..........

.......+ '0 m · 71

156 155

FIGURE 5.13. LGL sightings of bowhead whales, 27 April to 25 May 1994. Format as in Fig. 5.3.
7130

5.1 Bowheads: Distribution & Movements 157

157 156 155

Bowhead Whales

72

,

···

\

<,

--

1989. 90, 91, 94

@ Twin Otter

o Ice Camp/Helicopter

@ Cow/Calf. Twin Otter

7130

.•..•..•.•

-,,\

.

+ \ ,,/"----------'\,. +

'•...._.... ~

...-•...•

,

.

,

,

,

-'- .--.--...-~ .>.

............ ' ..

_----e----.

••

// __-'3' (¥

.----. +

72

@

@

e •

+

Ii)-

J.~

-------_/-;-~---~~/~:.~<..........

....~ .

........

.....

+

••

&: ~ •......._ ....~

'<0111 .

. +

"",,-.

0 5 lOnmi

0 5 10 •••

+

0 5 10 km

A

157 156 155

FIGURE5.14. LGL sightings of bowhead whales during late April and May of 1989-91 and 1994.

Format as in Fig. 5.3.
5.1 Bowheads: Distribution & Movements 158

corridor in May 1994 was no doubt largely a function of the consistent "nearshore" lead, sometimes continuous and sometimes interrupted by incursions of pack ice, that was present along the

landfast ice edge across the study area after 3 May. The consistent, narrow migration corridor was

apparently also related to the fact that the landfast ice edge continued on an orientation of about

800T across most of the study area for much of the 1994 field season, rather than curving to the

ESE in the more easterly region as in previous years of the study.

Only one mother-calf pair was seen during our 1994 work. These two whales were traveling

northeast along the nearshore lead on 9 May-an unusually early date for a calf to arrive in this

study area.

All Years.- The distribution of all bowheads sighted during the four years of the study is

plotted in Figure 5.14. This distribution is heavily influenced by the 1994 sighting data. More

bowheads were sighted in 1994 than in the three previous years of the study combined.

Mothers and Calves

Spring 1989.-During 1989, mothers and calves moved through the study area later than

most other bowheads. The first mother-calf pair sighted by us was seen from the ice camp on 16

May. However, mothers and calves were not common until 23 May. During the 23-29 May

period, 67% (36 of 54) of the bowheads recorded were either mothers or calves (excluding a

mother and yearling sighted on 24 May). In contrast, during the 29 April-19 May period only

3.5% (4 of 115) were mothers or calves.

Mothers and calves tended to be found along the north side of the lead that was present along

the landfast ice edge during the last third of May 1989 (Fig. 5.15). Migrating mothers and calves

tended to move along or just north of the pack ice edge. Mothers and calves engaged in other

activities (resting or local travel) were found amidst the pack ice north of the lead and in the open

water of the lead.

Spring 1990.-ln 1990, mother-calf pairs again passed the Pt. Barrow area near the end of

the spring migration period. A few migrating mother-calf pairs were present by mid-May of 1990,

but their peak migration near Barrow was from 19 May onward. Nearly all bowheads seen during

the last four days (23-26 May) of the field season were mother-calf pairs. During the 23-25 May

period, 68% (21 of 31) of the bowheads recorded were either mothers or calves. In contrast,

during the 29 April-22 May period only 2% (10 of 528) were mothers or calves. Similarly, the

NMML aerial photography crew working in the same area saw their first mother-calf pair for 1990

on 12 May. They also saw numerous mother-calf pairs from 19 May onward, mostly far offshore

(D. Withrow, pers. comm.).

The 11 mother-calf pairs observed from our aircraft in 1990 were seen in two parts of the

study area (Fig. 5.16). (1) The four pairs seen on 19-23 May were near or just north of the north

edge of the main nearshore lead crossing the study area. Most of these pairs were oriented on

northeasterly headings. (2) The seven pairs seen on 24-26 May were about 50 km farther north
...........................

......................... +. 10 m 71

5.1 Bowheads: Distribution & Movements 159

157 155

-.-.-.__ .__ .

-",

\

\

-,

-,<,

'89 Bhd. Calves

Cow/Calf

~/ '__ -e-r- ---l

//

r....·

I.,

"

"

"

.,

.)

72 +.

+.

: .

....._- ......... Landfas! Ice Edge

-. .........................

+.

....................... +.

<,

0 5 lOomi

0 5 lOrri

+. 0 5 10 km

A

157 156 155 154

FIGURE 5.15. Locations where bowhead mothers and calves were seen by LGL, 1989. Numbers

are dates in May 1989. Headings toward which the whales were oriented when first seen are also

shown when available.

72

60 ",----

7130

'<0 ",.
72

5.1 Bowheads: Distribution & Movements 160

157 156 155

'90 Bhd. Calves

'8 Cow/Calf

'10426

+

eM25C

10425'-

M25A

+

//------------ -----:1:._--",

,/---/----- ;'." ""'80 ft>--_

f8I( 104218 ,/,----.----

M21A .i->': 0 M19 »:":

-' +

+

@'M23

+ +

•..•....•...----

...•................•...

,--

,.......•......... _-..............• '..

.....-....-.•....,...

-' a.M13

......

~ .. -;

.....

....

o 5 10nni

o 5 10ni

+

o 5 10km " .. .t 10 m.' .., . 71

157 156 155

72

7130

'<0 ""

FIGURE 5.16. Locations where bowhead mother-calf pairs were seen by LGL, 1990. Numbers are

dates in May. Headings toward which the whales were oriented when first seen are also shown

when available.
5.1 Bowheads: Distribution & Movements 161

157 156 155

'91 '9"

~~

'0~

Cow/Calf

Cow/Yrllng

72 72

Bhd. Calves

+

i

..

"'"

.,.,.\

i

..

\

\

\

\

"

., ••••••••••..• ;@;

Oo~.

+

+ 7130

Land/as! Ice Edge. 1991. .

,,,.•.•..........

-....•..••_--, .•..

~ -,..

...

. .

..... +

......

"'"

o 5 10nm

......

........

.....

.. ·-+. 10 tn ·71

o 5 10m

+

o 5 10 km

157 156 155

FIGURE 5.17. Locations where bowhead mother-calf and mother-yearling pairs were seen by LGL,

1991 and 1994. Numbers are dates in April (A) or May (M). Headings toward which the whales

were oriented when first seen are also shown when available.
5.1 Bowheads: Distribution & Movements 162

in areas that were 80% or more covered by pack ice. These pairs were traveling through the pack

ice on a wide variety of headings, or not traveling.

Spring 1991.-Aside from a mother and yearling bowhead sighted on 29 April, our first

mother-calf sighting in 1991 was on 11 May, and the next mother-calf sightings were not until

17 May. Mother-calf pairs were seen regularly from 17 May until the end of our field season on

26 May. They constituted a substantial proportion of all bowhead sightings during the last few

days of the field season. Prior to 16 May in 1991, only 2 of 159 bowheads (1%) seen from the

Twin Otter were mothers or calves (mother/yearling excluded). From 16 to 20 May, 12 of 82

bowheads (15%) seen from the Twin Otter were mothers or calves. From 21 to 26 May, 20 of 64

(31 %) were mothers or calves.

Figure 5.17 shows all of our 1991 sightings of bowhead mothers accompanied by calves.

Their distribution in 1991 was generally consistent with that of other whales seen during the latter

part of the field season (Fig. 5.17 vs. 5.8). As in 1989-90, mothers and calves often headed in

directions other than northeast or east (Fig. 5.15-5.17; Table 5.2).

Spring 1994.-0nly one mother-calf pair was observed during our 1994 field season (Fig.

5.17). This pair was observed on 9 May in the nearshore lead, traveling northeast. Fieldwork

continued until 25 May 1994, well within the usual migration period for mothers and calves.

5.2 Bowhead Photogrammetry & Photo identification

There are at least two possible explanations for the very low number of mother-calf pairs

seen in 1994. (1) Mothers with calves typically arrive during the latter part of the spring

migration. In 1994, mothers with calves may have arrived in our study area after our field season

ended on 25 May. However, a reconnaissance survey far to the southwest of Pt. Barrow (to within

25 miles of Cape Lisburne) on 25 May failed to find any mothers and calves approaching Pt.

Barrow. Although the sea state was high along much of this route, 4 bowheads were seen, none

accompanied by a calf. Thus, if the main migration of mother calf-pairs was late in reaching Pt.

Barrow in 1994, it was very late: at least a week later than in 1990 and 1991, when the peak

mother-calf migration through our study area began on 19 and 17 May, respectively; and at least

a few days later than in 1989, when the peak mother-calf migration through the study area began

on 23 May. (2) The annual production of bowhead calves appears to vary markedly from year to

year (Koski et al. 1993). Perhaps 1994 was a year of very low calf production.

Data on bowhead sizes and on re-identifications of previously-photographed whales were

relevant to specific objective 7, "to document ." other aspects of the movements, behavior, basic

biology ... of bowheads" (§1.1, p. 7).

Bowhead Lengths and Timing of Migration

Bowhead Lengths. 1989.-- Vertical photographs of bowhead whales were obtained on eight

days in 1989; however, photographs taken on 28 and 29 May were resightings of a mother-calf pair

photographed on 27 May. Locations where photographs were taken are shown in Figure 5.19A,
5.2 Bowheads: Photogrammetry & Photoidentification 163

4

3 May

n=2

0

n n

4 6 8 10 12 14 16 18

4

14 and 15 May ~ 15May

n=4and1

0 n

4 6 8 10 12 14 16 18

(J) 4

Q)

18 May en

.s::: n=7

~

n nn .•...

0 0

L. 4 6 8 10 12 14 16 18

Q)

.0

E 4

::J 26 May Z n=6

?:

0

4 6 8 10 12 14 16 18

27 May

n = 14

4 6 8 10 12 14

Length (m)

16 18

FIGURE 5.18. Length-frequency distributions for bowhead whales photographed during this study,

3-27 May 1989. Calves are represented by black bars and mothers by stippled bars. Repeat

measurements are excluded within each day. A mother and calf photographed initially on 27 May

and subsequently on 28 and 29 May are not shown for the latter two dates.
5.2 Bowheads: Photogrammetry & Photoidentification 164

16

en

CD All Whales

ca 12 n =34

.c

~

.•...

0 8

'-

(l) .0

E 4

~

Z

O+----'r-I

4 6 8 10 12 14

Length (m)

16 18

FIGURE5.18. (continued) ..

later. Usable length measurements (grades 1-6 based on the scale described in Davis et al.

1986a,b) were obtained for 30 different bowheads. Approximate lengths were obtained for an additional four whales. The latter were whales that were deeply submerged or were photographed

from uncertain altitudes (i.e. aircraft altitude <91 m or changing rapidly). We assume that

bowheads <13 mlong were subadults, and that those ~13 m long were adults (Koski et al. 1993).

Few photographs were obtained during early May; thus the few length measurements obtained in 1989 represent the later stages of the bowhead migration (Fig. 5.18). In fact, over half of

the measured whales were photographed after 25 May when mothers and calves were more abundant than other whales.

Bowhead Lengths, 1991.-Vertical photographs of bowhead whales were obtained on ten

days in 1991; the locations where these photographs were taken are shown in Figure 5.19B. Most

photographs were obtained on the many days when low overcast prevented us from conducting

behavioral observations, for which a cloud ceiling above 460 m is necessary. Usable length

measurements were obtained for 71 different bowheads. Approximate lengths were obtained for

an additional 12 whales.

Following a brief behavior observation session on 29 April 1991, the mother of a motheryearling pair was photographed; she was slightly shorter than 16.0 m (Fig. 5.20).

Length measurements were obtained for 20 different whales on 1 May. Most of these whales

were small, which is typical of the early part of the migration (Nerini et al. 1987). Eighty percent

of the whales measured on this day were subadults «13 m; Fig. 5.20).

Two adult whales were photographed on 8 May and a large subadult and small adult were

photographed on 10 May. Three subadult and three adult whales including the first mother of the
5.2 Bowheads: Photogrammetry & Photoidentijication 165

season were photographed on 11 May. This was the earliest confirmed sighting of a mother-calf

pair during the 1989-91 phase of this study. The mother was 14.8 m long; the calf was not

measurable because it was below its mother.

Thirteen bowheads were measured on 17 May; they included 3 mother-calf pairs and 5 small

subadult whales. The sighting of five small subadults 7.1-8.1 m in length this late in the season

is interesting. The migration of adults, including mothers with calves, had already started. It is

possible that these 7.1-8.1 m whales were yearlings that had recently separated from their mothers.

Bowheads photographed on 18 and 22 May were primarily adults (66% and 75%, respectively). On each of these days, we photographed one mother-calf pair and one small subadultpossibly yearlings (8.1 and 7.6 m long). The only other subadults photographed on these dates

were lOA, 11.2 and 12.9 m long (Fig. 5.20).

Seventy-three percent (11 of 15) of the whales photographed on 25 and 26 May were known

mothers or calves. The remaining four whales were adults.

Bowhead Lengths, 1994.- Vertical photographs of bowhead whales for photogrammetry were

obtained on 10 days in 1994, and video images for whale identification were obtained on one

additional day (4 May). The locations where these photographs were taken are shown in Figure

5.21. Photogrammetry effort was concentrated during the 5-14 May period when generally low

ceilings prevented us from conducting behavioral observations from 460 m ASL. Usable length

measurements were obtained for 145 different bowheads in 1994. Approximate lengths were

obtained for an additional 20 whales.

Only one bowhead was detected during surveys conducted previous to 30 April but 11

bowheads were seen during a survey on that date. Six of these whales were photographed and all

were subadult bowheads (Fig. 5.22).

The size distributions of whales changed markedly from day to day during the next 10 days

(Fig. 5.22). Fourteen bowheads were measured from photographs obtained on 5 May. Almost half

(6) were adults. A 16.9 m whale photographed on this date was the largest bowhead measured by

us during the three years of this spring study.

Length measurements were obtained for 46 different bowheads on 7 May. Most whales

(80%) were subadults and 62% of the subadults were small subadults «10 m).

The size distribution of whales photographed on 8 May was much different than that on the

previous day. Seven of 15 whales that were measured were adults and six of the remaining eight

were large subadults (10-13 m).

All but one of 15 bowheads photographed on 9 May was a subadult, and the presumed adult

was a "borderline" animal 13.0 m long (Koski et al. 1993). Of the 14 subadults, nine were large

subadults and five were small subadults.
5.2 Bowheads: Photogrammetry & Photoidentification 166

157 154 156 155

'---'-'--'--'-"

'.,

\

\

-,

-,<,

'89 Photo Sessions

/

/

"...,....•.../

./

/

r ·

I.,

""

"'

"' i

/

»:

\

i

i

i

i

i

\

"'-,

""I

\

\

X 15M(P4) "'"'

"'

"'-.

""'- ...••.

~~.

72

+

X 15M(P3)

+ ,//------------------i:: -c., ",

X 29M(Pl0) //--' r: - -,

,_-- 'Yio ">---

X~8M(P9)

X27M(P~V

X 18M(P5) X/;;~;;M(P6)

/_------------------------- 3M(Pl)

!+

./

------_ ....'

_/

, ....•' .-_-0 .. __ -.-.

/.//----

..', - -

....._--_ ..

+

X 1.M(P2)

+ .:

.....

. .

~"

"....

Land/asl Ice Edge"",

'~o

It/,

.........

. +

<,

............

o 5 10nrn

o 5 10rn ......

.......

+

o 5 10km ·······-+. 10 m.······· 71

157 154

72

7130

FIGURE 5.19A. Locations where vertical photographs of bowhead whales were obtained by the

aerial crew, 3-29 May 1989. Annotations represent the date in May (M) and, in parentheses, the

photo session number (PI-PlO).

156 155
7130

5.2 Bowheads: Photogrammetry & Photoidentification 167

157 156 155

'-'-'-'-_.__">.

\

\

\

,.,...•..

'91 Photo Sessions

\

i

i

.,

.,

i

.,

\

-.,

-'"I

\

\

\

\

\.

-,

". '.'"

'~

/'--X"1M{p.:Q __-l: .'J9>....

~' .•.••.•..,

/' ""',

17M(P9) // r- _ -.

8M(P3B) X' -'60

X X iA"(;2A) ~--

llM(P5) X 2~11)

X 18M(Pl0A) X X 25M(P12) .>

8M(P3_~l--"---- ';7M(P7)

lM(p,.l!B)'----------- ~X17M~~~ X 17M(P6)

,X + 0-29A(Plf +".

•. ' 'Landflisi'lce . Edge .

72 72 +

+ +

X'l~M(P~)

. '+ 7130

/'

..... -"

,----26M(Pljl-r·/"-'

......_-_ ••....••.•.'... •.. ,.

..........

-,~0111•

~'"

~

.........

.....

.....

+

o 5

o

=-

5 lOmi

.......

+ ... +.. .....10 m.······· 71 o 5 lOkm

157 154 156 155

FIGURE 5.19B. Locations where vertical photographs of bowhead whales were obtained by the

aerial crew, 29 April to 26 May 1991. Annotations represent the date in April (A) or May (M)

and, in parentheses, the photo session number (PI-P13).
CIJ

CD

ctS 0

4 6 8 10 16 18 .c

~

-0

"-CD .c 17 May

E

4 n = 13

::J

Z

5.2 Bowheads: Photogrammetry & Photoidentification 168

4

29 April and 1 May

n=1and20

~ 29 April mo1her

~ of yearting

4

8, 10 and 11 May

n=2,2and6

• 8May

~10May

16 18

18 May

4 n=12

Length (m)

FIGURE 5.20. Length-frequency distributions for bowhead whales photographed during this study,

29 April-26 May 1991. Calves are represented by black bars and mothers by stippled bars. Repeat

measurements are excluded.
5.2 Bowheads: Photogrammetry &: Photoidentiflcation 169

22 May

4 n=12

25 May

4 n=12

"f:;

en 0

(1) 4 6 8 10 12 18

ctS .c

~

4

- 26 May 0

lo- n=3

(1) ..c

E E ::J 0

Z

4 6 8 10 12 14 16 18

8

All Whales I

n = 83

s«

It I.a

:::.. -:;E "::i;. :~t

II n n

~

,

16

12

4

o

4 6 8 10 12 14 16 18

Length (m)

FIGURE 5.20 (continued).
5.2 Bowheads: Photogrammetry & Photoidentification 170

155

'94 Photo Sessions

72 +

72

/"'-"-------------,/:.--- -,

, .

.> -,

",/" .:'" ". "'60

X 20M(~,s) 30A(P2) ~--

,,,, X:

10Ml!'.!'.l/;,4;';;;:4) X30A(P1) 9M;~'~; >(XX14M(P11)

5M,U".4ry(- X X X X 8M(P6) 14.ItllP·13.l

1~F1lJf----- X 4M(pSj. X

25M(PI6) / +X X 14M(P.~2).'. ". I1715'&e+- __

X-,/ ..._.~M(P7) . ..... ....• Lanlllasl.lce Edge"'"

.r::' . ..'afte, 15' May

,,,--,-'--' .... "' ..' --"'.

, -- - _-_ , .

......_--.._ ...•.•.

+

+ 7130

<,......

....

............•.• +

" .... <,

+

+ .

"'-"

0 5 lOnlli

0 5 10 iii

+

0 5 lOkm

A

157 156 155

········.+· 10 m.······· 71

FIGURE 5.21. Locations where vertical photographs of bowhead whales were obtained by the aerial

crew, 30 April to 25 May 1994. Annotations represent the date in April (A) or May (M) and, in

parentheses, the photo session number (PI-PI6).
CIJ

Q)

(1j 4 6 14 16 18

.c

~

-0

~

Q) 8 7 May .c

n=46 E

::J

Z

4

5.2 Bowheads: Photogrammetry & Photoidentification 171

4.,...-----------------------,

30 April

n=6

4

5 May

n= 14

n nnn n

4 6 8 10 12 14 16 18

4

n

8 May

n = 15

DPS6

~PS7

n nn

4 6 8 10 12 14 16 18

Length (rn)

FIGURE 5.22. Length-frequency distributions for bowhead whales photographed during this study,

30 April-25 May 1994. Repeat measurements are excluded.
5.2 Bowheads: Photogrammetry & Photoidentification 172

9 May

4 n= 15

4 6 8 12 14 16 18

4...-----------------------,

10 May

n=8

0

4 6 8 10 12 14 16 18

en

Q)

etS 11 May .c 4 n= 10

~

-0

~

Q)

nn n

.0

E

:J 4 6 8 10 12 14 16 18

Z

14 May

o PS11

8

~PS12

n = 43 ~PS13

l!HlE PS14

4

4 6 8 10 12 14 16

Length (rn)

FIGURE 5.22 (continued).

18
5.2 Bowheads: Photogrammetry & Photoidentification 173

4

20 and 25 May o20 May

n = 6 and 2

~25May

.0 4 6 8 10 12 14 16 18

en

Q)

CO .c

~

- 1- 0

'- I (]) All Whales .0

E

n= 165

12 :J

Z

8

4

n nnn

4 6 8 10 12 14 16 18

Length (m)

FIGURE5.22 (continued).

Large subadults predominated (11 of 18) among whales measured from photographs obtained

on 10 and 11 May. Furthermore, four of the other seven whales photographed on these dates

bordered on the to-13 m large subadult category; they were 9.5, <to.O, 13.1 and 13.2 m long.

Two very small subadults were photographed on 11 May; they were 7.3 and 7.6 m long and may

have been yearlings.

Forty-three different bowheads were measured from photographs taken on 14 May. The main

migration of adult whales appears to have started about this time; 44% of the measured whales

were adults. Most (44%) of the remaining whales were large subadults.

All of the few bowheads photographed on 20 May were subadults and all of those

photographed on 25 May were adults (Fig. 5.22).

The combined length data from 1994 (Fig. 5.22) may not be representative of the overall

length-frequency distribution of bowhead whales that migrated past Barrow in 1994 because of the

limited effort to photograph whales after 14 May. Only 28% of all measured whales were adults.
5.2 Bowheads: Photogrammetry & Photoidentification 174

This low proportion of adults would be expected given that few photographs were obtained during

the last half of the migration when adult whales normally predominate near Barrow (Withrow and

Angliss 1992, 1994). No mothers with calves were photographed in 1994; nor were any mothers

from previous years' photographed without a calf in 1994.

Bowhead Lengths, All Years.-Our data confirm observations by others that subadults

predominate among the bowheads sighted before mid-May and that adults predominate among

whales after mid-May (Fig. 5.23). Mothers and calves tend to occur during the latter stages of the

migration. The earliest mother photographed (29 April) was accompanied by a yearling. The other

early record was of a mother with a calf on 11 May 1991. Also, the latest adult photographed

without a calf was an animal that was a mother in a previous year. The data from Figure 5.23 are

summarized below by ten-day period according to whale status:

Subadults Adults"

Period Calves Small8 Large" Others Mothers

Late April 0 3 3 0 I

b

1-10 May 0 45 46 33 0

11-20 May 4 16 35 41 6

21-29 May 17 1 1 13 17

8 Small: <10 m; Large: ~1O and <13 m; Adult: ~13 m. b This mother accompanied by yearling.

Figure 5.23 contains a small group of 11 whales -7-8.1 m long that were photographed 11-22

May. By this time most small subadults have passed Barrow. Only one whale 8.1-9.3 m long was

photographed by us later than 9 May during all years of this study. Based on the combination of

size and temporal segregation, these small whales probably were yearlings that either had recently

separated from their mothers or were migrating more slowly than other subadults.

The mean length of nine mothers measured in 1989 was 14.96 m ± s.d. 0.77 m, with range

13.9-15.9 (excluding one approximate length). The mean length of 10 mothers (excluding the

mother of the yearling and one approximate length) measured during 1991 was 14.77 m ± s.d.

0.85 m, with range 13.3-15.8 m (no inter-day repeats). The mean length for mothers was not

significantly different in 1991 than in 1989 (t=0.51, P>0.50) and was similar to the mean lengths

of mothers reported in other studies (ef. Withrow and Angliss 1992; Koski et al. 1993). One of

the mothers photographed in 1991 was the smallest mother photographed to date during the spring

migration; it was 13.3 m long, slightly smaller than a 13.4 m mother photographed by NMML in

1989 (Koski et al. 1993).

The mean length of eight calves measured during 1989 was 4.62 m ± s.d. 0.32 m, with range

4.0-5.0 m (excludes two approximate lengths). The mean length of 10 calves measured during

1991 was 4.25 m ± s.d. 0.46 m, with range 3.7-5.1 m (excludes one approximate length; no interday repeats). This mean length for calves in 1991 is significantly smaller (t=3.26, P<0.002) than

the value reported for the spring seasons of 1985-90: 4.74 m ± s.d. 0.45 m, n = 88 (Koski et al.
5.2 Bowheads: Photogrammetry & Photoidentification 175

17 +

+

+

+

A

•••

+ + ~

IJ IJ

IJ m IJ El

t

+ +

+

15 +

IJ + +

+ + IJ IJ IJ 8

+ + + :f :f +

+

+ + + + I!J

:t:

=

:f: IJ IJ IJ

+ + :1= +

+ $ + IJ

+ =4= IJ

+ :j:

*

:I:

+ + IJ :t:

13 + + :j: +

+ +

t

+ + :1= + :t:

+

+

+

+ +++ :t:

:1=

+

+

+ =1=

;I; + +

+ + +

*

+ :1= +

:1= + +

*:1=

*

+

-

11 +

E :f + +

:j:

t *

:f:

- + :t: + +

.c +

:I: +

+

+ + Other .•... + :I: *

+ +

0> +

D Mother

c +

f

+ :f

Q) +

:t: .•.Previous Mother --'

9

+ +

+ i

<> Calf

-t-

$

+ + :f: +

+ :I: +

=4= :1= +

+ + + +

+ + + +

+

+ +

7

+

5 <> ~ § <> <>

•

<>

S <>

e•

3

28-Apr 03-May 08-May 13-May 18-May 23-May 28-May

Date

FIGURE 5.23. Lengths of bowheads vs. date photographed near Barrow, Alaska, during late April

and May of 1989, 1991 and 1994. Different symbols are plotted for mothers with calves (open

square), whales without calves that had been mothers with calves in previous years (closed

triangle), calves (open diamond) and others (plus sign).
5.2 Bowheads: Photogrammetry & Photoidentification 176

1993). The smallest calf that we measured during 1991 (3.7 m long) was, however, larger than

the smallest calf (3.6 m) reported by Koski et al. (1993).

During this spring study we obtained 16 pairs of length measurements for both members of

a mother-calf pair. There was a significant correlation between the length of a mother and the

length of her calf (r=0.70, df=14, P<O.OI; Fig. 5.24A). A similar correlation was found during

summer studies (Davis et al. 1983), but has not been found previously for spring data (Nerini et

al. 1987). This correlation suggests that larger whales either calve earlier, or have larger calves.

There was no strong correlation between the date a calf was photographed and its length

(r=0.23, df=16, P>0.05; Fig. 5.24B). However, the brief period of spring migration past Barrow

(mid-May to early June) in comparison to the prolonged calving period (March to July, Nerini et

al. 1984; Koski et al. 1993) may obscure any possible correlation between length at birth and date.

Fig. 5.24A shows that the minimum-sized calf was 3.8-4.2 m long regardless of the length of the

mother. This suggests that, although minimum calf size may be slightly longer for larger mothers,

the larger calves photographed with the longer mothers were probably born earlier in the season.

The length data collected during this study are consistent with previous studies in

documenting temporal segregation of bowheads during the spring migration based on their length

(Nerini et al. 1987; Withrow and Angliss 1991). Our data also hint that yearling bowheads may

tend to migrate later than other small subadults. However, this needs confirmation from a larger

data base (i.e. the NMML study) and from other years.

Photographic Resightings of Identifiable Bowheads

Many bowheads, especially the larger and older ones, have distinctive scars or other marks

that make them individually identifiable in vertical photographs. Short-term resightings of the

same known individuals during this study provided information on speed and direction of travel,

including comparative data for mothers and calves vs. other bowheads. Resightings from one year

to the next contributed to the gradually-accumulating datasets on growth rates of whales of varying

sizes (Koski et al. 1992), calving intervals of adult females (Miller et al. 1992), and the timing of

migration of the same whales in different years.

Sample Sizes.-In May 1989 LGL acquired a total of 45 potentially re-identifiable (Grade

A and B, see §2.2, p. 34) photographic images of bowheads (Table 5.3A). These images were of

20 different bowheads photographed on 14-29 May at locations mapped in Figure 5.19A.

Nine re-identifiable bowheads were photographed once, seven were photographed twice, three

were photographed three times, and one was photographed 13 times on three days (27-29 May).

Seven of these re-identifiable bowheads were accompanied by calves, including the one photographed on 27-29 May. Images of 15 of the 20 different recognizable whales were Grade A.

We also obtained Grade A and B images of 47 bowheads photographed near Barrow by

NMML on 12-31 May 1989. These NMML images were compared to each other and to all of the

1989 LGL images.
5.2 Bowheads: Photogrammetry & Photoidentification 177

6

A.

-E5

--ca

o

-o

.J::

-C>

a54 ...J

3+---""T"""--...,.-----r-----r----..,---,..----.,...----,

13 14 15

Length of Mother (m)

16 17

6

B.

-E 5

•

•

- • -

•

ca •

o • •

••

-0

.J:: •

-C> \

a54 • •

•

...J •

•

•

3+----r----.-----,---r---r---,..----,---r--..,---,----r---,

16 May 18 May 20 May 22 May

Date

24 May 26 May 28 May

FIGURE 5.24. Lengths of bowhead whale calves vs. (A) the lengths of their mothers and (B) date.
TABLE5.3A. Number of photographs of recognizable bowhead whales acquired during LGL's 1989 photo sessions.

Number of Whale Images Number of Whales Number of

Photographed 1, 2, .... ,5 Times' Whales

Potentially Number of

Photo Grades Recognizable Between-session

Session Date Printed A and B' I

b

2 3 4 5 Between Days" Resightings

PI 3 May 0 0 0

P2 14 May 6 5 0 1 1 2

P3 15 May 1 1 1 1

P4 15 May 1 1 1 1

P5 18 May 11 11 4 2 1 7

P6 26 May 7 7 2 1 1 4

P7 27 May 5 5 1 2 3

P8 27 May 6 6 0 1 0 1 2 2 (P9, PI0)

P9 28 May 5 5 0 0 0 0 1 1 2 (P8, PlO)

PIO 29 May 4 4 0 0 0 1 1 2 (P8, P9)

46 45 9 7 3 2 1 20·

a Excludes calves, which were individually recognizable primarily through their associations with their mothers.

b These figures are maxima because some repeat photographs may not have been recognized.

• This total was reduced by two to account for between-session resightings of the same whale.

--:l

00
TABLE5.3B. Number of photographs of recognizable bowhead whales acquired during LGL's 1991 photo sessions.

Number of Whale Images Number of Whales Number of

Photographed 1, 2, .... ,7 Times" Whales

Potentially Number of

Photo Grades Recognizable Between-session

Session Date Printed A and s- I

b

2 3 4 5 6 7 Between Days" Resightings

PI 29 Apr 1 1 1 1

P2 1 May 0 0 0

P2A 1 May 20 20 9 2 1 1 13

P2B 1 May 8 8 8 8

P3A 8 May 1 1 1 1

P3B 8 May 2 1 1 1

P4 10 May 8 6 6 6

P5 11 May 11 10 6 2 8

'"~

tl;l

P6 17 May 3 3 3 3

0

~;:sP7 17 May 22 12 1 1 1 3 '"I:l

P8 17 May 10 9 4 1 1 6 2 (P7) ~

P9 17 May 6 4 2 2 "tI

;:so..

PIOA 5 5 1 2

0

18 May 1

OQ

i:l

PI0B 18 May 29 22 5 2 2 1 10 :!

Pll 22 May 29 25 7 3 4 14 s

'"..

P12 25 May 38 19 8 1 1 1 11 .:l

P13 26 May 7 5 1 1 2

Ro

"tI

;:so..

0

200 151 59 16 12 1 2 89c

~;:s

S

"I:l

a Excludes calves, which were individually recognizable primarily through their associations with their mothers. g"

b These figures are maxima because some repeat photographs may not have been recognized.

;:s

•...

c This total was reduced by two to account for between-session re-identifications. -...l

IQ
5.2 Bowheads: Photogrammetry & Photoidentification 180

In late April and May 1991, LGL acquired a total of 151 Grade A and B images of adult or

sub-adult bowheads and 34 images of calves that were re-identifiable primarily only through their

associations with their mothers. Locations of the 1991 photo sessions are shown in Figure 5.19B.

Excluding the calves, 89 different bowheads were photographed from 29 April to 26 May (Table

5.3B). Images of 36 of these whales were considered likely to be recognizable if a photographic

image of similar or better quality were acquired in another year.

We also obtained 285 images of 179 re-identifiable bowheads photographed near Barrow by

NMML from 22 April to 3 June 1991. These images were compared to each other and to the 1991

LGL images. NMML images of 38 different bowheads were considered to be Grade A.

In late April and May 1994, LGL obtained 232 Grade A and B images of 204 different

bowheads (Table 5.4). Locations of the 1994 photo sessions are shown in Figure 5.21. Grade A

images of 41 bowheads were acquired. NMML did not conduct fieldwork near Barrow in the

spring of 1994.

Within-Season Resightings

Aerial photography documented the within-season movements of recognizable bowheads that

were photographed over intervals of minutes, hours or days. Three types of within-season

resightings were considered. These included short-term within-session resightings of whales

photographed by LGL, and longer-term between-session resightings of whales photographed by

LGL and/or NMML during two sessions within one day or during two sessions on different

days.":"

Within-Session Resighting§..-Of the short-term within-session resightings, only those

obtained over intervals of 2::15minutes are considered here. These intervals ranged from 15 to 68

minutes. 13

In 1989, three adult whales were involved in four within-session resightings over intervals

of 2::15minutes (Table 5.5A). Two of these whales, including one photographed on two days, were

accompanied by calves. The four resightings occurred over intervals of 18-43 min. These whales

moved at apparent speeds of 2.4-5.2 km/h (mean 3.95 km/h) and on headings ranging from 90 to

276°T (vector mean heading 98°T, angular deviation (a.d.) 58°).

11 In 1989, five of our 20 different recognizable bowheads (25%) were also photographed by NMML,

and a sixth bowhead, not photographed by us, was photographed by NMML on two different days.

12 Among the 1991 photos, there were two bowheads that were each photographed during two different

LGL photo sessions conducted 3.4 h apart on 17 May. One of these whales was also photographed by

NMML 1 h after we first photographed it. There were an additional 8 between-session resightings of

whales photographed by both LGL and NMML, and 6 between-session resightings of whales photographed

by NMML only.

13 Although bowheads were often re-photographed at intervals less than 15 min, their locations may

not be known with sufficient accuracy for meaningful heading or speed estimates.
TABLE5.4. Number of photographs of recognizable bowhead whales acquired during LGL's 1994 photo sessions.

Number of Whale Images Number of Whales Number of

Photographed 1, 2, 3 Times Whales

Potentially Number of

Photo Grades Recognizable Between-session

Session Date Printed A and B 1

8

2 3 Between Days" Resightings

PI 30 Apr 4 4 4 4

P2 30 Apr 3 3 1 1 2

P3 4 May 5 5 5 5

P4 5 May 30 16 14 1 15

P5 7 May 76 63 54 3 1 58

P6 8 May 21 19 10 3 1 14

P7 8 May 8 4 4 4

P8 9 May 23 22 18 2 20 ~

N

t:l:l

()

P9 10 May 12 7 7 7 ~;:-

PI0 11 May 17 15 11 2 13 "' ~

Pl1 14 May 26 20 18 1 19 ~

P12 14 May 9 8 8 8

"1:l

;:-

()

C)

P13 14 May 15 14 11 0 1 12 OQ

~

P14 14 May 18 17 14 0 1 15 3

3

P15 20 May 12 12 2 2 2 6 .s"'

P16 25 May 3 3 1 1 2 ~

~()

282 232 182 16 6 204 0

C)

~;:s

• These figures are maxima because some repeat photographs may not have been recognized. 'Si

~

~

:::to

()

;:s

00-

-
TABLE 5.5A. Within-session resightings (~15 minutes) of bowheads photographed by LGL in 1989, 1991 and 1994.

Net

First Photographed Resighting (s) Distance AccomMinutes Between Apparent Whale panied

Whale Between Sightings Speed Heading Length by

Year Number Date Time Latitude Longitude Time Latitude Longitude Sightings (km) (km/h) (OT) (m) Calf?

1989 8610 18 May 11:31:20 71°35.9'N 156°01.1'W 12:14:00 71°35.4·N 155°57.4'W 43 2.4 3.3 113 15.5 no

8641 27 May 11:50:30 71°33.2'N 154°24.9'W 12:17:30 71°33.2'N 154°20.9'W 27 2.3 5.2 90 15.9 yes

8647 27 May 20:28:50 71°37.2'N 155°19.4'W 20:46:30 71°37.2'N 155°18.2'W 18 0.7 2.4 90 14.9 yes

8647 28 May 12:41:10 71°39.I'N 155°03.3'W 13:04:45 71°39.2'N 155°06.6'W 24 1.9 4.9 276 14.9 yes

Mean 28.0 1.82 3.95 98

1991 9662 I May 16:40:52 71°39.5'N 154°58.4'W 17:04:04 71°40.2'N 155°01.2'W 23 2.1 5.4 308 8.3 no

9663 I May 16:40:52 71°39.5·N 154°58.4'W 17:04:04 71°40.2'N 155°0\.2'W 23 2.1 5.4 308 7.9 no

9664 1 May . 16:45:54 71°40.I'N 155°00.9'W 17:15:04 71°40.7'N 154°59.7'W 29 1.3 2.7 32 9.9 no

9667 I May 16:47:49 71°40.2'N 155°00.2'W 17:03:00 71°40.4'N 155°01.4'W IS 0.8 3.1 298 13.2 no

9711 II May 15:56:05 71°35.5'N 155°47.3'W 16:28:08 71°35.8'N 155°44.I'W 32 2.0 3.7 73 14.0 no

9717 17 May 12:44: 18 71°33.0'N 155°18.7'W 13:27:43 71°32.7'N 155°21.4'W 43 1.7 2.3 251 15.2 yes

9719 17 May 12:52:13 71°33.4'N 155°17.6'W 13:21:30 71°32.5'N 155°19.4'W 29 2.0 4.0 212 13.3 yes

4239 18 May 17:53:56 71°38.I'N 156°14.8'W 18:36:48 71°35.8'N 156°09.9'W 43 5.1 7.2 146 14.8

~

yes N

7781 18 May 18:28:58 71°35.6'N 156°06.2'W 19:02:20 71°35.4'N 156°02.4'W 33 2.3 4.1 99 14.0 no ttl

9763 18 May 18:00:26 71°37.6'N 156°13.9'W 18:17:45 71°37.6'N 156°14.0'W 17 0.1 0.2 270 8.1 0

no ~

9767 18 May 18:09:49 71°36.7'N 156°14.3'W 18:54:10 71°35.9'N 156°08.0'W 44 4.0 5.4 112 12.9 no ~<l>

9779 18 May 18:32:08 71°35.6'N 156°06.5'W 18:58:43 71°35.2'N 156°04.I'W 27 1.6 3.6 118 13.6 no l:l

~ 9800 22 May 20:49:14 71°36.0'N 155°50.7'W 21:17:54 71°36.6'N 155°46.3'W 29 2.8 5.9 67 I\.2 no

9823 . 25 May 16:23:13 71°42.2'N 154°50.3'W 17:31:29 71°44.4'N 154°52.8'W 68 4.3 3.8 340 13.7

~

yes ~

0

9841 25 May 17:42:23 71°42.0'N 154°52.0'W 18:13:10 71°43.0'N 154°49.7'W 31 2.3 4.5 36 14.7 no ()

OQ

Mean 32.4 2.30 4.09 29 i:l :i

1994 10104 7 May 18:35:34 71°35.0'N 154°43.6'W 19:43:05 71°35.I'N 154°40.4'W 68 \.9 1.7 84 9.3 no s

<l> ..•

10238 II May 13:34:35 71°30.4'N 155°58.7'W 13:56:40 71°30.6'N 155°56.4'W 22 1.4 3.8 75 12.8 no ~

10220 II May 13:50:01 71°30.5'N 155°56.6'W 14:21:00 71°30.9'N 155°52.7'W 31 2.4 4.7 72 13.2 no Roo

1350 14 May 18:13:43 71°34.4'N 155°02.6'W 18:28:50 71°34.3'N 155°01.9'W IS 0.4 1.7 103 15.4 ~ no ~

0

10322 20 May 17:30:26 71°37.2'N 155°22.5'W 18:01:55 71°37.5'N 155°18.8'W 31 2.2 4.2 76 8.0 no ()

10323 20 May 17:30:26 71°37.2'N 155Q22.5'W 18:01 :55 71°37.5'N 155°18.8'W 31 2.2 4.2 76 10.8 no ~:3

Mean 33.0 1.75 3.38 81 ..•

'5i

~I:l

::l".

0

:3

-00

tv
TABLE 5.5B. Between-session resightings of bowheads photographed by LGL and NMML, spring 1989 and 1991 (no such cases in 1994). * at right side

denotes within-day between-session resightings.

Net

First Photographed Resighting (5) Distance AccomHours Between Apparent Whale panied

Source of Whale Between Sightings Speed Heading Length by

Photos Year Number Date Time Latitude Longitude Date Time Latitude Longitude Sightings (km) (kmlh) (OT) (m) Calf?

NMML-NMML 1989 IOS7 17 May 16:22:0S 71°35.5'N 15s052.9'W 18 May IS:13:S1 71°36.7'N IS5°42.8'W 22.9 6.3 0.3 69 IS.O no

NMML·LGL 1311 17 May 16:35:32 71°3S.S'N IS5°54.7'W 18 May 11:39:30 71°34.3'N IS6°IS.8'W 19.1 12.6 0.7 2S7 16.0 yes

LGL-NMML 8617 IS May 12:00:30 71°34.6'N IS6°07.7'W IS May IS:09:08 71°36.3'N ISso46.6'W 3.1 12.7 4.1 76 14.S no •

LGL-NMML eSI6 18 May 12:00:30 71°34.6'N IS6°07.7'W 18 May IS:09:S0 71°36.S'N ISso47.0'W 3.2 12.6 4.0 74 IS.1 no

LGL-NMML 8622 26 May 00:04:IS 71°37.7'N ISso30.I'W 27 May 11:23:10 71°39.9'N ISso20.6'W 3S.3 6.9 0.2 S4 14.2 yes

LGL-NMML S647 27 May 20:2S:50 71°37.2'N ISsoI9.4'W 2S May 11:14:34 71°40.S'N ISSoOl.l'W 14.8 12.3 0.8 60 14.9 yes

-LGL 28 May 12:S0:30 71°38.9'N ISso04.7'W 1.6 3.6 2.3 21S •

-NMML 29 May 11:26:S7 71°41.1'N ISso07.8'W 22.6 4.S 0.2 336

-LGL 29 May IS:32:S0 71°42.3'N ISso08.2'W 4.1 2.2 O.S 3S4 •

NMML-LGL 1991 9667 I May 14:04:S8 71°3S.S'N ISso06.0'W I May 16:47:49 71°40.2'N ISsoOO.2'W 2.7 9.3 3.4 21 13.2 no • ~

IV

NMML·LGL 4220 1 May 14:54:20 71°35.9'N 15S004.5'W 1 May 16:SS:IS 71°40.3'N IS4°SS.9'W 2.0 9.6 4.7 32 12.9 no • b:l

<:>

NMML-LGL 9673 . 1 May 15:25:47 71°36.4'N 155°04.3'W 1 May 16:S9:00 71°39.7'N ISso03.I'W 1.6 6.1 4.0 7 IS.O no •

~

.,. ~

NMML-LGL 9304 10 May 12:33:33 71°37.4'N ISs037.6'W II May 16:38:01 71°38.6'N ISS041.3'W 28.1 3.1 0.1 316 14.8 yes

l:l

~ NMML-LGL 9710 11 May 13:0S:27 71°31.0'N ISso54.0'W II May 15:36:3S 71°3S.S'N ISs041.0'W 2.S 11.7 4.7 40 11.7 no •

"l:I

NMML-LGL 9708 II May 13:20:00 71°32.0'N 155°S3.4'W 11 May 15:26:50 71°35.4'N 15so44.5'W 2.1 S.2 3.9 40 11.7 no • ~

<:>

NMML-LGL 9704 II May 13:22:35 71°32.2'N 155°53.4'W II May 15:25:30 71°35.4'N I 55°44.7'W 2.0 7.8 3.S 41 9.4 no •

COQ

LGL-NMML 9719 17 May 13:21:30 71°32.5'N 155°19.4'W 17 May 14:21:55 71°32.4'N 155°22.3'W 1.0 1.7 1.7 264 13.3 yes •

~

::l -LGL 17 May 17:06:0S 71 °33.4'N 155°I1.5'w 2.7 3.4 1.2 57 • ::l .,.

LGL-LGL 9723 17 May 13:0S:53 71°33.2'N 155°IS.I'w 17 May 16:59:38 1Io33.I'N rss-u.rw 3.8 3.8 1.0 93 7.8 •

..•

no ~

NMML-LGL 9813 20 May 14:36:35 71°40.6'N 155°57.2'w 22 May 22:09:46 71°43.2'N 154°15.5'w 5S.6 59.3 l.l 85 13.6 yes

Roo

NMML-NMML

"l:I

10618 25 May 11:23:06 71°28.6'N 155°57.S'W 26 May 12:33:2S 71°29.3'N 155°53.3'W 2S.2 2.9 0.1 64 14.6 no ~

<:>

NMML-NMML 10620 26 May 11:53:07 71°29.I'N 155°52.3 'W 27 May 11:46:57 71°30.4'N 155°16.9'W 23.9 20.9 0.9 83 13.5 no C

NMML-NMML ~ 10622 26 May 11:57:04 71°29.5'N 155°52.3'W 27 May 12:26:07 1I030.5'N 15S024.5'W 24.S 16.4 0.7 83 12.9 no ::s

NMML·NMML 10624 26 May 12:10:53 71°29.4'N 155°43.6'W 27 May 11:39:48 71°30.I'N 15S015.7'W 23.5 16.4 0.7 85 13.8 no Si

l"\

80 13.9

l:l

NMML-NMML 10627 26 May 12:19:03 71°2S.9'N 155°4S.6'W 27 May 11:46:49 71°30.6'N 155°17.6'W 23.5 IS.5 0.8 no ::to

<:>

NMML-NMML 1063S 26 May 13:10:36 71°2S.S'N 155°46.4'W 31 May 11:58:31 71°29.I'N 155°43.7'W 118.8 1.7 0.0 71 13.9 ::s

no

-00

W
5.2 Bowheads: Photogrammetry & Photoidentification 184

In 1991, the 15 within-session resightings occurred over intervals of 15-68 min, and averaged

32.4 min (Table 5.5A). Net distances traveled were 0.1-5.1 km (mean 2.30 km) and apparent

speeds averaged 4.09 km/h (range 0.2-7.2 kmlh). Headings were extremely variable, ranging from

32 to 340°, with vector mean 29°T ± a.d. 75°.

In 1994, six within-session bowhead resightings were observed, consisting of four sub-adults

and two adults. None of the adults were accompanied by calves (Table 5.5A). These resightings

occurred over intervals averaging 33 min (range 15-68 min). The average net distance traveled

was 1.75 km (range 0.4-2.4 km) and the average apparent speed was 3.38 km/h (range 1.7-4.7

kmlh). Headings were easterly, ranging from 72 to l03°T (vector mean 81°T ± a.d. 10°).

In all years combined, excluding mother-calf pairs, other whales reidentified within sessions

(n= 18) were resighted over intervals averaging 30.2 min (range 15-68 min). Their headings

varied considerably, ranging from 32° to 308°T with a vector mean of 68° ± a.d. 55°. Net speeds

averaged 3.74 ± s.d. 1.48 km/h (range 0.20-5.87).

There were no significant correlations between whale speed vs. resighting interval (r=O.Ol1,

df=16, P>0.50), whale speed vs. whale length (r= -0.002, df=16, P>0.50), or whale speed vs. date

(r=0.063, df=16, P>0.50).

Mother-calf pairs reidentified within-sessions during the three years of study (n=7) were

resighted over intervals averaging 36.0 min (range 18-68 min). Their headings varied markedly,

ranging from 90° to 340°, with vector mean 195° ± a.d. 75°. Only 3 of 7 (43%) mother-calf headings had an easterly (1°_179°) component; four (57%) had a westerly (181 °-359°) component.

Among the resighted bowheads other than mothers and calves, 14 of 18 observed headings (78%)

had easterly components and only four (22%) had westerly components. However, the observed

mother-calf headings were not significantly different from those of other whales (Watson

U

2=0.118, n1=7, n2=18, P>O.lO)

Net speeds of mother-calf pairs averaged 4.26 ± s.d. 1.71 km/h (range 2.32-7.19). Net speed

showed no obvious relationship to the interval between photos (r=0.066), whale length (r=0.106),

or date (r= -0.059), but the sample size was very small (n=7). The net speeds of mother-calf pairs

averaged slightly higher than those of "other" whales but the difference was not significant

(t=0.76, df=23, P>0.2).

Considering all whales reidentified within sessions during the three years when we conducted

photography (n=25), the mean speed over periods of 15-68 min was 3.89 ± s.d. 1.48 kmlh and the

vector mean heading was 73°T ± a.d. 64°). This is similar to the mean speed of 4.0 km/h and

"normal headings" of 49-105° that were recorded by Rugh (1990).

Between-Session Within-Day Resightings.-A total of 13 same-day between-session resightings occurred over intervals of 1.0 to 4.1 h, considering the pooled LGL and NMML photographs

from the three years (cases marked "*" in Table 5.5B).
! 5.2 Bowheads: Photogrammetry & Photoidentification 185

In 1989 there were four between-session within-day resightings of three whales or mothercalf pairs (Table 5.5B, Figure 5.25). Two adult bowheads photographed together on 18 May were

still near each other when resighted 3.1 h later. These bowheads had migrated about 13 km to the

ENE at an apparent rate of 4.0 km/h. A mother-calf pair photographed on 27, 28 and 29 May was

photographed during two different sessions on each of 28 and 29 May. (This pair was also among

the whales resighted within-sessions in 1989, see above.) The between-session resighting intervals

of this pair were 1.6 and 4.1 hours. This pair moved on headings of 215 (southwest) and 354°T

(north), and traveled net distances between successive sightings of 3.6 and 2.2 km. Apparent

speeds were 2.3 and 0.5 km/h. The calf in this pair was the smallest calf (4.0 m) photographed

by us during 1989.

Overall in 1989, the four between-session within-day resightings occurred over resighting

intervals averaging 3.0 h (range 1.6-4.1 h). Headings ranged from 74° to 354°T with vector mean

60° ± a.d. 65°. Net distances traveled were 2.2-12.7 km, and averaged 7.8 km. Apparent speeds

were 0.5-4.1 km/h and averaged 2.72 km/h.

In 1991 there were nine between-session same-day resightings of bowheads.

~ Three whales photographed in the same general area on 1 May were re-photographed 6.1-

9.6 km to the NNE 1.6-2.7 h later. These whales (12.9-15.0 m in length) traveled at

apparent speeds of 3.4-4.7 km/h (Fig. 5.26, Table 5.5B).

~ Three subadult bowheads first photographed in the same general area on 11 May were

resighted 2.0-2.5 h later 7.8-11.7 km to the NE. These whales traveled at apparent speeds

of 3.8-4.7 km/h (Fig. 5.26, Table 5.5B).

~ A 7.8 m bowhead resighted after 3.8 h on 17 May had traveled 3.8 km to the east, a rate

of only about 1.0 km/h.

~ A 13.3 m mother with a 4.0 m calf traveled 1.7 km to the west over a one hour period

(1.7 km/h) on 17 May. This mother-calf pair was resighted again 2.7 h later about 3.4

km to the NE of its second location, having moved at an apparent rate of about 1.2 km/h.

Considering only the first sighting and final resighting, this pair traveled 2 km to the NE

over a 3.7 h period at an apparent rate of 0.53 km/h.

Overall in 1991, these 9 resightings occurred over intervals of 1.0-3.8 h, and averaging

2.27 h. Headings were 7°-264°T with vector mean 35°T ± a.d. 41 0. Net distances traveled

averaged 6.84 km (range 1.7-11.7 km), and apparent speeds averaged 3.16 km/h (range 1.0-4.7

km/h).

In 1994, no between-session resightings of bowheads were discovered. In part, this lack of

inter-session resightings reflects the absence of 1994 NMML photographs. For example, in 1991

only 12% (2 of 16) of the between-session resightings were LGL-LGL resightings, and one of the

whales involved in those resightings was also photographed by NMML. However, on some dates

in 1994 (e.g., 14 May, Fig. 5.21, p. 170) we cohducted several photo-sessions at different locations

in our study area and over long time intervals (up to 8.7 h on 14 May)-a situation that offered

the potential for resighting migrating bowheads.
158'20' 154' 71'4S·;=-=.-----~~------..!:!:~~-----~~~------~:..--------!~~-----..-.:~~------.::..:,71' 45' 158' ISS'40' ISS'20' ISS' 154'40' 154'20'

71"30' + + + + + +

71"30'

!-'>

N

tI:l

C)

~::r-

"

c:.

~

~C)

LEGEND s

iAd.It .'lIal SighII.,

OQi::

Adult, Reslghtlng ~

~

~

o Cow/Calf Pair. Initial Sighting

"

..• ® Cow/Calf Pair, Reslghtlng ~

Roo

0 3 4 5 n m1 '"

::rC)

s

0 1 2 3 4 5m1

~

o 1 2 3 4 5 km

::s ..•

'Si

71'IS' f')

158' ISS' 40' ISS' 20' ISS' 154'40' 154'20' 154' c:. ..•

c'

::s

FIGURE 5.25. Between-session resightings of bowhead whales photographed northeast of Barrow during May 1989. Annotations show •....

date in May and whale number in LGL's photo catalog. See Table 5.5B for details. 00

0\

29(8847)

18(1311)

_.-...~;;;;~;~~~~~: 18(1057) 28(8822)

18(8818)

28(8847)

17(1311) 27(8847)

18(8817)

17(1057)

18(8818)

18(8817)
156·20' 154· 71·45,r~'------~=-------~~!:-._---_-!!~~-----_---!~-----_---!~..!!!:._-----~::,.;:~------..:::e:,71· 45'

71"30'

\

i

156· 155·40' 155· 154·40' 154·20'

71·30'

FIGURE 5.26. Between-session resightings of bowhead whales photographed northeast of Barrow during May 1991. Annotations show

date in May and whale number in LGL's photo catalog. See Table 5.5B for details.

155·20'

_-----------:::---------® 22(88131

@-

20(8813)

11(8304)

, 10(8304)

1(4220)

~

11(8704:1(9708~(9710)

11(9704) .

11(9708)

1(9667)

17(9723)17(9719)

"_._~ 17(9723)

17(9719) ®~fl7(9719)~

_----"A"-_.,q,.27(10620)

&~~c!~~~;.;~==~~~~~!27(10827) + + +

27(10822) 27(10624)

25(10618) ,

,

,

,

'26(10620)

LEGEND

i

Adult. Initial Sighting

Adult. Reslghtlng

o Cow/Calf Pair, Initial Sighting

@Cow/Calf Pair, Reslghtlng

o 2 3 4 8nm!

o 1 2 3 4 5m1

o 1 2 3 4 5 km

155·40' 155·20' 155· 154·40' 154·20'

-00-...l
5.2 Bowheads: Photogrammetry & Photo identification 188

In 1989 and 1991 combined, excluding mother-calf pairs, other whales resighted on the same

days during different sessions (0=9) were resighted at intervals of 1.6-3.8 h (mean=2.58 h). Net

distances traveled were 3.8-12.7 km, averaging 9.09 km. Net headings were 7°-93°T with vector

mean 85°T ± a.d. 48°, and the average net speed between resightings was 3.73 ± s.d. 1.12 km/h

(Table 5.6). There were rather high correlation coefficients between whale speed and resighting

interval (r= -0.656), whale speed and whale length (r=0.618) and, to a lesser degree, whale speed

vs. date (r= -0.338). However, given the low sample size (n=7), none of these correlations was

statistically significant (P>0.05 in each case).

Two mother-calf pairs were involved in four between-session within-day resightings during

1989 and 1991. These whales were resighted at intervals of 1.0-4.1 h, averaging 2.35 h. Headings

ranged widely, from 57°-354°T, with vector mean 354°T anda large (74°) angular deviation (Table

5.6). Three of the four (75%) mother-calf resightings had headings with westerly components

(215°,264°, and 354°), as compared to zero of nine "other" whales (Fisher Exact P<0.05). Net

distances traveled were 1.7-3.6 km, averaging 2.72 km. Net speeds were 0.5-2.3 km/h, averaging

1.44 ± s.d. 0.73 km/h. The speeds of mother-calf pairs were significantly slower than those of

other whales resighted between sessions on the same day(t=3.71, df=l1, P<O.Ol).

TABLE 5.6. Net speeds and headings of mother-calf pairs and other bowheads based on photographic resightings of three types (based on data in Table 5.5).

Others Mother-Calf

Mean s.d. n Mean s.d. n

A. Net Speeds

Within-Session 3.74 1.48 (18) 4.26 1.71 (7) ns"

Between-Session

Within Day 3.73 1.12 (9) 1.44 0.73 (4) **

Between Day 0.49 0.35 (7) 0.51 0.40 (6) ns

Combined 2.31 1.86 (16) 0.88 0.70 (10) *

Vector Ang. Vector Ang.

Mean Dev. n Mean Dev. n

B. Net Headings

Within Session 68 55 (18) 195 75 (7) ns

Between-Session

Within Day 85 48 (9) 354 74 (4) *

Between Day 77 8 (7) 13 60 (6) *

Combined 60 25 (16) 356 67 (10) **

a See text for statistical tests used; ns means not significant; * means P:::;;0.05,** means P:::;;O.01.
5.2 Bowheads: Photogrammetry & Photoidentification 189

Considering all whales involved in between-session within-day resightings during the study

(n=13), the average resighting interval was 2.5 h (range 1.0-4.1 h). The vector mean heading was

NE (39°T) ± a.d. 50°. The mean net distance traveled was 7.13 km (range 1.7-12.7) and apparent

speeds ranged from 0.5 to 4.7 km/h,averaging 3.02 ± s.d. 1.48 km/h.

No significant correlations were found between whale speed vs. resighting interval (r=

-0.347, df=l1, P>0.20) or whale speed vs. whale length (r=0.069, df=l1, P>0.50). However, a

significant correlation was found between whale speed and date (r= -0.646, dfel l , P<0.02). The

correlation was negative with decreasing whale speeds as the season advanced. The correlation

probably results from the slower speeds of the mother-calf pairs that were present and resighted

only during the latter parts of the study period (17, 28, and 29 May; mean 1.44 km/h for mothers

vs. 3.73 km/h for others).

Whale headings in 1991 were more northerly and less variable than in 1989 (vector mean

heading 35° ± a.d. 41 ° in 1991 vs. 60° ± a.d. 65° in 1989). Apparent speeds were higher in 1991

than 1989 (3.16 vs. 2.72 km/h). However, sample sizes were small (n=4 in 1989 and n=9 in 1991).

Between-Day Resightings.-A total of 13 between-day within-year resightings occurred over

intervals ranging from 1.6 hours to 5 days, considering the combined LGL and NMML

photographs for the three years (cases with no "*" in Table 5.5B).

In 1989 there were five between-day resightings of four whales or mother-calf pairs. Two

bowheads photographed in the same general location and at about the same time on 17 May had

traveled in opposite directions when they were resighted on the following day (Table 5.5B, Figure

5.25). The resighting locations on 18 May were 19 km apart. One of these bowheads traveled 6.3

km ENE in 23 h (0.3 km/h, net). The other bowhead traveled 12.6 km WSW over 19 h (0.7 km/h).

The latter bowhead was accompanied by a calf on 17 May, but the calf was neither observed nor

photographed on 18 May.

Three other resightings involved mother-calf pairs. A mother-calf pair photographed early

on 26 May had traveled 7 km to the NE when resighted 35 h later on 27 May. This pair had

traveled at an apparent rate of only 0.2 km/h. Another mother-calf pair was photographed on 27,

28 and 29 May. This pair (also included among the 1989 within-session, and between-session

within-day resightings, see above) traveled about 12.3 km to the ENE between 27 and 28 May, at

an apparent rate of 0.8 km/h. Between 28 and 29 May this pair traveled about 4.5 km to the

NNW, at a net speed of 0.2 km/h. The net distances traveled between successive sightings ranged

from 2.2 to 12.3 km, and apparent speeds ranged from 0.2 to 2.3 km/h. The net distance and net

rate of movement between the original (27 May) and final sighting locations (second sighting on

29 May, Table 5.5B) of this pair were 11.5 km (to the NE) and 0.27 km/h, respectively.

These 1989 resightings occurred over intervals averaging 22.9 h (range 14.8-35.3). The

vector mean heading of these resighted whales was 300T (range 54-336", ± a.d. 58°). Net

distances traveled averaged 8.5 km (range 4.5-12.6 km), and the mean net speed was 0.43 km/h

(range 0.2-0.8 km/h).
5.2 Bowheads: Photogrammetry & Photoidentification 190

In 1991, 8 bowheads or mother-calf pairs were photographed during more than one day.

These 8 whales or pairs were resighted from 1 to 5 days after they were first photographed (Table

5.5B, Fig. 5.26):

~ A 14.8 m mother and 4.2 m calf photographed on 10 and 11 May traveled a net distance

of only 3.1 km, and this was to the NW, over a 28 h period; the apparent rate of

movement was only 0.1 km/h.

~ An unmeasured mother and calf photographed on 20 and 22 May traveled a net distance

of 59 km to the E in 56 h-an apparent rate of movement of 1.1 km/h.

~ A 14.6 m bowhead photographed on 25 and 26 May traveled a net distance of only 2.9

km over 25 h for an apparent speed of 0.1 km/h.

~ Four bowheads photographed in the same general area on 26 May were re-photographed

-24 h later 16.4-20.9 km to the east. These whales traveled at apparent speeds of 0.7-0.9

km/h.

~ Another adult (13.9 m long) traveled a net distance of only 1.7 km over a 5 d period

(0.01 km/h, 26-31 May).

The last of these whales had a net speed lower than has been documented previously in the

Barrow area during spring. Rugh (1990) resighted a bowhead over a 5-d period during spring

migration, but that individual traveled at nearly 1 km/h. The lingering of an apparently healthy

individual in our study area in the spring of 1991 was apparently unusual, especially for a bowhead

not accompanied by a calf. This case cannot be accounted for by any hypothesized "migration

blockage" as a result of the noise playback work. This whale was first photographed on the last

day of our field season, when the projector site (for transmission loss test 91-4) was 15 km to the

WNW of the whale. Thus, when first photographed this whale had already passed the last of the

projector sites that we used.

The average interval at which these whales were resighted was 40.4 h (range 23.5-118.8).

Headings were to the ENE (vector mean heading 71° ± a.d. 36°), and the average net distance

traveled was 17.4 km (range 1.7-59.3 km). The mean apparent speed was 0.5 km/h (range 0.1-1.1

km/h).

No between-day resightings of bowheads were discovered in 1994.

In 1989 and 1991 combined, excluding mother-calf pairs, other whales resighted on different

days (n=7) were resighted at an average interval of 37.5 h (range 22.9-118.8 h). Whale headings

were consistently to the ENE and E, ranging from 64-85°T with vector mean nOT and a.d. only

±8° (Table 5.6). Net distances traveled averaged 11.9 km (range 1.7-20.9 km). The average net

speed between resightings was 0.49 ± s.d. 0.35 km/h (range 0.01-0.88 km/h).

There were rather large correlation coefficients between whale speed vs. resighting interval

(r= -0.610), whale speed vs. whale length (r= -0.593) and, to a lesser degree, whale speed vs. date

(r=0.331). However, given the low sample size (n=7), none of these correlations was statistically

significant (P>O.l in each case).
5.2 Bowheads: Photogrammetry & Photoidentification 191

Between-day resightings of mothers and calves (n=6) occurred over intervals averaging

29.2 h (range 14.8-55.6 h); Headings varied widely (range 54°-336° with vector mean heading

13°T and a broad angular deviation of ±60°. Three of the six (50%) mother-calf headings had a

westerly component (257°, 316°, 336°), whereas none of the seven "other" whales had westerly

components. The headings of mother-calf pairs differed significantly from the headings of other

whales (Rank Sum U=l, N)=6, n2=7, P=0.023). The average net distance traveled was 16.4 km

(range 3.1-59.3 km) and the average net speed was 0.51 ± S.d. 0.40 km/h (range 0.1-1.1 km/h).

Speeds of between-day mother-calf resightings did not differ significantly from those of other

whales (t=O.I, dfel l , P>0.8).

There were no significant correlations in this very small sample (n=6) between whale speed

and resighting interval (r:::0.311), whale length (r= -0.184) or date (r=0.100) (P>0.5 in each case).

Considering all whales photographed on different days in the same season (n=13), the

average resighting interval was 33.7 h (range 14.8-118.8). The vector mean heading was 600T

(range 54-336°) ± a.d. 48°. The net distance traveled was 14.0 km (range 1.7-59.3 km), and the

mean net speed was 0.50 ± s.d. 0.36 km/h (range 0.01-1.07).

Correlations between whale speed and resighting interval (r= -0.317), whale length (r=

, -0.313), and date (r=0.153) were not significantly different from zero (n=13, all P>O.l).

The whale headings based on between-day resightings in 1991 were slightly more southerly

and less variable than in 1989 (vector mean heading 71o± a.d. 36° in 1991 vs. 30° ± 58° in 1989).

As was the case among between-session within-day resightings, apparent speeds were slightly

higher in 1991 than in 1989 (0.54 vs. 0.43 km/h), respectively. Sample sizes were low (n=5 in

1989 and n=8 in 1991).

All Between-Session Resightings.-As just described, between-session resightings included

resightings over brief intervals within days, and over longer intervals between days. The data

derived from the two types of between-session resightings can be summarized as follows:

Resighting Interval (mean)

Vector Mean Heading

Angular Deviation

Net Distance (mean)

Net Speed (mean)

Same-Day

2.5 h

39°T

500T

7.1 km

3.02 km/h

Between-Day

33.7 h

600T

48°T

14.0 km

0.50 km/h

The major differences between the two sets of data concern resighting intervals, net distance,

and net speed. Resighting intervals are by definition longer in the case of between-day

resightings. The differences between the net distances and speeds in the two sets of data are

related to the size of the study area. Considering the relatively small and almost totally overlapping areas within which the LGL and NMML photo sessions were confined (Fig. 5.19, 5.21,

and 5.4), resightings over the longer (between-day) intervals inevitably involved whales that were
5.2 Bowheads: Photogrammetry & Photo identification 192

traveling at low net speeds and moving relatively short distances between sightings. In the

following section the pooled same-day and between-day between-session resightings are discussed.

In 1989, the 9 between-session resightings of bowheads were resighted at a mean interval

of 14.1 ± s.d. 11.84 h (Table 5.5B). These whales traveled at a mean net speed of 1.45 ± s.d. 1.59

krn/h and on a vector mean heading of 41 °T ± a.d. 58°.

In 1991, the 17 between-session resightings occurred over an average interval of 20.21 ± s.d.

29.59 h (Table 5.5B). The average apparent speed was 1.93 km/h ± s.d. 1.7f km/h. The vector

mean heading was 53°T ± a.d. 42°.

In all years combined, excluding mother-calf pairs, other whales reidentified between sessions (n=16) were resighted over intervals averaging 17.84 ± s.d. 28.89 h. Their vector mean

heading was 600T with a.d. only 25°, and net speeds averaged 2.31 ± s.d. 1.86 km/h (Table 5.6).

Net speeds were significantly correlated with resighting interval (r = -0.614, df=14, p<0.02)

and date (r = -0.784, df=14, P<O.OOI). Thus, net speed decreased with increasingly long resighting

intervals and increasingly later dates in May. The negative correlation of net speed with resighting

interval is an inevitable result of the rather small sampling area, but it is interesting that net speed

is lower late in the season even when mothers and calves are excluded. There was no significant

correlation between whale speed and whale length (r= -0.124, df=14, P>0.50).

Mother-calf pairs reidentified between-sessions during the three years of study (n=lO) were

resighted over intervals averaging 18.50 ± s.d. 17.71 h. Their net headings were variable, with

vector mean 356°T ± a.d. 67° (Table 5.6). Of the 10 resightings of mother-calf pairs, six had

headings with westerly components, compared to zero of 16 resightings of other whales (chi2=9.33,

df=l, P<O.Ol).

Net speeds averaged 0.88 ± s.d. 0.70 km/h. Correlations between net speed and interval

between photos (r= -0.474), whale length (r= -0.327) and date (r=0.072) were not significantly

different from zero (P>O.l in each case), but the sample size was small (n=lO). The net speeds

of mother-calf pairs averaged lower than those of "other" whales (t'=2.78, df=21.7, P<0.02).14

Considering all whales reidentified between sessions during the three years when we

conducted photography (n=26), the average resighting interval was 18.09 ± s.d. 24.78 h. The

vector mean heading was 500T ± a.d. 59°. The mean speed was 1.76 ± s.d. 1.66 km/h.

The vector mean heading in 1991 was more northerly than in 1989 (53° in 1991 vs. 41 ° in

1989) and there was less variation in headings of whales resighted during 1991 photography (±

a.d. 42°in 1991 vs. ±62° in 1989).

14The t' designation refers to the modified t-test not assuming equal population standard deviations.
5.2 Bowheads: Photogrammetry & Photo identification 193

Net whale speeds were negatively correlated with the interval between resightings (r =

-0.538, df=24, P<0.005) and date (r = -0.696, df=24, P<O.OOl). There was no significant

correlation between whale speed vs. whale length (r= -0.248, df=14, P>0.20).

Spring Migration of Mother-Calf Pairs vs. Other Bowheads.-Spring migration of mothercalf pairs through our study area differs in some respects from the spring migration of other

bowheads. Mother-calf pairs tend to pass through the Barrow region late in the season, perhaps

to avoid heavy pack ice conditions (§3.1, Ice and Weather Conditions). Differences in distribution

between mother-calf pairs and other bowheads have been noted in some years (i.e., 1991).

The speeds of mother-calf pairs were slower than speeds of other whales when estimated

from between-session within-day resightings or the combined between-session dataset (same-day

and between-day; Table 5.6). Speeds of these two groups were similar when estimated from shortterm within-session resightings or from between-day resightings. The between-day speeds are

inevitably low and biased because only the slow-moving whales would be resighted.

The net headings of mother-calf pairs in all four categories appeared to differ from those of

other whales. In each category, headings of mother-calf pairs were more variable, as indicated by

a larger angular deviation (Table 5.6). A larger proportion of the mothers and calves were

traveling toward the west.

Thus, over periods of hours, as represented by the within-day between-session resightings,

mother-calf pairs traveled more slowly through our study area than did other bowheads, with more

variable headings. Although net speeds of mother-calf pairs over brief intervals (15-68 min) did

not differ significantly from those of other bowheads, they appeared to exhibit a weaker tendency

to travel in an easterly direction even during those short intervals. Mother-calf pairs apparently

traveled more circuitous routes through the study area, thereby passing more slowly through the

area.

Between- Year Resightings

All Grade A (potentially recognizable between years) bowhead images obtained during this

study have been compared to all Grade A photos obtained in previous summer and autumn photographic studies conducted in the Alaskan and Canadian Beaufort Sea by LGL, NMML and Cascadia Research Collective (CRe) icf, Koski et al. 1988), and to each other. They were also compared

to our collection of NMML' s Grade A spring photos for 1984-1991.

In 1989, 4 of the 15 "Grade A" bowheads photographed by LGL had been photographed in

earlier years by LGL or NMML (Table 5.7). All four of these resighted bowheads were adults,

14 to 16 m long:

~ One bowhead (whale No. 1311) photographed near Barrow on 17 and 18 May 1989 was.

originally photographed on 18 August 1982 near Herschel Island, N.W.T. This whale was

photographed with a calf in 1982. It was observed with a calf on 17 May 1989 but the

calf was neither observed nor photographed on 18 May (Miller et al. 1992; Rugh et al.
Table 5.7. Between-year bowhead resightings,various origins and years, to MMS study area, May 1989, 1991, and 1994.

Calf Present

First Photographed Resighting at Barrow Length in

Source Year of

of Whale Resighting First

Photos' Number Year Date Loc'n" Latitude Longitude Date Latitude Longitude (m) Sighting Resighting

LGL-(NMML-LGL) 1311 1982-89 18 Aug HI 7000S.0'N 138°2S.9'W 17,18 May 71°34.3'N IS6°1S.8'W 16.0 yes yes

NMML-LGL 8609 1985-89 2 Jun BR 71°24.I'N IS6°36.8'W IS May 71°S4.0'N IS4°28.0'W 14.0 no no

NMML-LGL 2392 1985-89 2 Jun BR 71°24.2'N IS6°36.7'W 18 May 71°3S.3'N IS6°0S.3'W 14.7 no no

NMML-LGL 2392 1986-89 22 May BR 71°28.9'N IS6.06.1'W no

NMML-(LGL-NMML) 8622 1986-89 19 May BR 71°36A'N ISso02.2'W 26,27 May 71°37.7'N ISso30.1'W 14.2 yes yes

LGL-LGL ISS2 1982-91 4 Sep HI 700

02.3'N 138°S0.9'W 26 May 71°22.6'N IS6°40.S'W 16.2 yes no

LGL-(NMML-LGL) 4220 1984-91 23 Aug FB 70021.7'N 127°03.0'W 1 May 71°40.3'N IS4°SS.9'W 12.9 no no

NMML-LGL 1880 1984-91 8 May BR 7Io33.8'N IS5°39.6'W 8 May 71°3S.8'N 155°43.2'W 13.6< no no

LGL-LGL 4239 1984-91 23 Aug OB 70040A'N 127°24.8'W 18 May 71°38.1'N 156°14.8'W 14.8 yes yes

LGL-LGL S679 1985-91 6 Sep KP 69°13.7'N 137°19.S'W I May 71°40.3'N IS4°5S.9'W 10.3 no no

NMML-NMML 2217 1985-91 23 May BR 71°34.6'N IS3°31.5'W 10 May 71°29.1'N IS6°22.0'W 14.5 no no

. LGL = Photographic studies by LGL during summer (Davis et al. 1983, 1986a,b), fall (Richardson et al. 1986,1987) and spring (this study). NMML = Spring photographic studies

by National Marine Mammal Laboratory. CRC = Summer photographic study by Cascadia Research Collective (Ford et al. 1987).

b HI = Herschel Island, Y.T., BR = Barrow Region, AK, FB = Franklin Bay, N.W.T., OB = Offshore Bathurst Peninsula, N.W.T., KP = King Point, Y.T., OK = Offshore Kaktovik,

AK, TPS = Tuktoyaktuk Peninsula Shelf, N.W.T., DS = Mackenzie Delta Shelfbreak, N.W.T., EA = Eastern Alaska, CP = Cape Parry, N.W.T., K = Komakuk, Y.T.

e Approximate length. Continued ...
Table 5.7. Concluded.

Calf Present

Date Loc'n" Latitude Longitude Date Longitude

Length in

Year of

Resighting

(m)

First Photographed Resighting at Barrow

Source

of

Photos'

Whale

Number Year Latitude

First

Sighting Resighting

NMML-NMML 2200 1985-91 22 May BR 71°30.3'N ISs026.1 'w 26 May 71°29.I'N ISs047.7'W 16.2 no no

LGL-NMML 6970 1985-91 26 Sep OK 70026.6'N 143°13.I'W 26 May 71°32.I'N ISso28.S'W 13.9 no no

CRC-LGL 7781 1986-91 31 Aug TPS 70044.6'N 1300S0.8'W 18 May 71°3S.6'N IS6°06.2'W 14.0 no no

NMML-LGL 8288 1987-91 8 May BR 71°27.9'N IS6°1O.7'W 2S May 71°39.1'N ISso03.S'W 16.0· no yes

NMML-(NMML-LGL) 9304 1989-91 31 May BR 7l036.0'N IS4°32.6'W 10 May 71°37.4'N ISs037.6'W 14.8 no yes

NMML-(NMML-LGL) 9304 1990-91 29 May BR 71°27.4'N IS6°12.6'W II May 71°38.6'N ISs041.3'W no yes

~

LGL-LGL I3SO 1982-94 23 Aug DS 70027.0'N 136°38.9'W 14 May 71°34.4'N ISso02.6'W IS.4 no no N

tl:l

()

LGL-LGL 4230 1984-94 6 Sep FB 70034.0'N 127"24.6'W 8 May 71°3S.2'N IS4°30.4'W 14.S no no ~;:so

LGL-LGL 4230 1985-94 22 Aug' FB 69°S4.8'N 126°23.8'W no

"'

l:l

LGL-LGL 6984 1985-94 29 Sep EA 70024.3'N 143°01.4'W 7 May 71°3S.6'N IS4°46.3'W IS.3 no no ~

~;:so

LGL-LGL 6962 1985-94 26 Sep EA 70028.3'N 143°16.I'W 14 May 71°30.8'N ISso42.S'W 13.1 no no ()

COQ

LGL-LGL SI49 1985-94 21 Aug CP 69°S2.9'N 123°1O.0'W 2S May 71°28.8'N IS6°14.4'W 14.4 no no ~

:!

LGL-LGL

:!

7346 1986-94 19 Sep K -69°37.0'N -139°SS.0'W S May 71°31.3'N ISs049.3'W 13.S no no

"'

..•

~

Ro

~

• LGL = Photographic studies by LGL during summer (Davis et al. 1983, 1986a,b), fall (Richardson et al. 1986, 1987) and spring (this study). NMML = Spring photographic studies

;:so

()

by National Marine Mammal Laboratory. CRC = Summer photographic study by Cascadia Research Collective (Ford et al. 1987). C

b HI = Herschel Island, Y.T., BR = Barrow Region, AK, FB = Franklin Bay, N.W.T., OB = Offshore Bathurst Peninsula, N.W.T., KP = King Point, Y.T., OK = Offshore Kaktovik, ~

~

AK, TPS = Tuktoyaktuk Peninsula Shelf, N.W.T., DS = Mackenzie Delta Shelfbreak, N.W.T., EA = Eastern Alaska, CP = Cape Parry, N.W.T., K = Komakuk, Y.T. ..•

. Si Approximate length. ~l:l

:::.

()

~

-\C

Ul

~~-----------_ .. ~-~ -----~
5.2 Bowheads: Photogrammetry & Photoidentification 196

1992b). This is the same bowhead that traveled 13 km to the W from 17 to 18 May in

1989 (Table 5.5B). Considering the presence of the calf on 17 May 1989, this whale

calved at an apparent 7-year interval. It is not known whether this whale calved during

an intervening year.

~ The three other inter-year resightings involved whales that had been photographed during

previous spring studies near Barrow in 1985-86 (Table 5.7). Two of these, photographed

on 15 and 18 May 1989, had originally been photographed on 2 June 1985. One of these

two (whale No. 2392) had also been photographed near Barrow on 22 May 1986. The

final inter-year resighting (whale No. 8622) was of a bowhead photographed with a

yearling (>7.0 m) in 1986 and a calf «5 m) in 1989. This whale was photographed on

19 May in 1986 and on 26-27 May 1989. The yearling calf was presumably a newborn

calf in the spring of 1985, indicating a 4-year calving interval.

In analyses conducted for other projects (Koski et al. 1992; Miller et al. 1992), 133 Grade

A bowheads photographed by NMML near Barrow during the spring of 1989 were compared to

all Grade A whale photos obtained in previous years. These comparisons resulted in an additional

22 between-year resightings of bowheads. These resightings are listed in Koski et al. (1992) and

are shown in more detail in Appendix E, Table E-l.

Of these 22 resightings, 15 were of whales previously photographed on their summering

grounds or during fall migration in the years 1981, 1982, 1984, 1985 or 1986. The remaining

seven 1989 inter-year resightings were of whales photographed near Barrow during spring in 1985

or 1986 (Table E-l). One of these whales (whale No. 1483) was accompanied by a calf in 1982

and 1989-an apparent 7-year calving interval. Whether this whale calved during an intervening

year is unknown. Another of these whales (No. 1617) had a calf in 1989 but not in 1982.

In 1991, eight of the 36 "Grade A" bowheads photographed by LGL had been photographed

by LGL, NMML or CRC in one or more earlier years; #9304 was previously photographed in both

1989 and 1990. In addition, there were three between-year resightings of whales photographed

only by NMML among the 38 "Grade A" whales they photographed in that year. The 12 resightings, including 2 resightings for #9304, spanned intervals of 1-9 yr (Table 5.7).

~ Six of these resighted whales were originally photographed during summer or early autumn in the Canadian Beaufort Sea in 1982, 1984, 1985, or 1986. One of these whales

(#4239) had a calf in both 1984 and 1991, a 7-year interval. Whether this whale calved

in an intervening year is unknown. Another (#1552) had a calf in 1982 but not in 1991.

~ The remaining six resightings involved whales first photographed during spring studies

near Barrow during the years 1984, 1985, 1987, or 1989. One whale (#9304) was photographed in 1989, 1990 and 1991 in the Barrow region. This whale was photographed

without a calf in 1989 and 1990, but was accompanied by a calf in 1991. Whale #8288

was photographed without a calf in 1987 but with a calf in 1991.

In 1994, six of 41 "Grade A" bowheads photographed by LGL had been photographed in

earlier years on their summering grounds in the Canadian Beaufort Sea or during fall migration

in the eastern Alaskan Beaufort Sea (Table 5.7). The intervals associated with these resightings
5.2 Bowheads: Photogrammetry & Photoidentification 197

were 8-12 years. The 12-year interval represents the longest inter-year resighting interval

recognized to date. That whale was measured as 15.3 m long in 1982 and 15.4 m long in 1994,

illustrating the very slow growth exhibited once bowheads reach adult size (Koski et al. 1992).

These between-year resightings, over the long term, provide some types of information about

bowheads that are not available by other means. It is beyond the scope of this project to analyze

these topics, as this requires consideration of the combined dataset from many projects. Recent

papers by Koski et al. (1992) and Miller et al. (1992) have used between-year resighting data,

including those from the 1989 and 1991 phases of this study, to analyze bowhead growth rates and

calving intervals. We expect that these data will also be used in future studies to obtain an

independent estimate of bowhead population size through "mark-recapture" methodology, and to

estimate longevity through analysis of scar acquisition rates.

5.3 Behavior of Undisturbed Bowheads

Observation Effort and Circumstances

We observed the behavior of bowhead whales during a total of 112.7 hours of systematic

aerial observations during the 29 April through 29 May periods. This effort was distributed over

76 behavioral observation sessions on 37 different days during the four years of spring work

(Table 5.8).

Observation periods were counted as presumably undisturbed when the observation aircraft

was at an altitude of at least 460 m (~1500 ft), no other aircraft were nearby, the underwater sound

projector was not operating, and there had been no known potential disturbance within the preceding 30 min period. Overall, there were 72.1 hours of observation of presumably undisturbed

whales, which was 64% of the total 112.7 hours of observation time (Table 5.8). The percentage

of the observations that were under presumably undisturbed conditions was lowest in 1989 (48%),

intermediate in 1990 and 1994 (68 and 67%, respectively), and highest in 1991 (100% of 4.1 h).

The circumstances of observations varied widely within and among years. However, there

were tendencies for low or high values of water depth, ice cover, and sea state in certain years.

Table 5.8 summarizes, for each year, the circumstances of (1) all behavioral observation sessions

and (2) sessions when "presumably undisturbed" whales were seen. The circumstances of individual observation sessions are summarized in Tables 3.6 (p. 74) and 3.8 (p. 80-1) for 1991 and 1994,

and in Richardson et al. (1990a:75-6, 1991:38-40) for 1989 and 1990. The following two paragraphs concern the observation sessions when "presumably undisturbed" bowheads were observed.

In 1989, there was heavy ice cover (80-95%) at most observation sites and in the study area

generally. Observations were largely in pack ice well north of the landfast ice edge. The median

water depth at observation sites was 150 m. Sea states at observation sites were usually low in

1989 because of the dampening effect of ice on wave action. The number of bowheads within the

area circled by the observation aircraft (typically a circle 2-3 km in diameter) was 1-5. However,

on 3 May, -15 whales were within 5 km of the center of the observation circle. In 1990,

observations were more commonly in shallow water (median depth 40 m), ice cover was more
TABLE 5.8. Summary of behavioral observation sessions from aircraft, 1989-1994. For each year, first line includes all observations, and second

(boldface) line includes only observations under "presumably undisturbed" conditions.

Dales With Number of Behavioral Water Depths Ice Cover in No. Bowheads

Behavioral Observation (m) Obs. Circle (%) Sea State in Obs. Circle

Year Observations Hours Sessions Days Range Med. Range Med. Range Med. Range Med.

1989 3-29 May 25.6 17 10 40 - 280 140 o - 99 85 o - 2 1 1 - 5 2

" 12.3 12 8 40 260 150 o . 99 85 o . 2 112 1 . 5 3

1990 29 Apr-25 May 46.8 29 12 18 - 475 40 o - 90 60 o - 3 1 1 - 10 3

" 31.6 25 12 18 475 40 o . 90 60 o . 3 1 1 . 8 3

1991 29 Apr-25 May 4.1 7 5 19 - 210 130 1 - 90 50 1 - 5 1 1 - 4 2

" 4.1 7 5 19 . 210 130 1 - 90 50 1 . 5 1 1 . 4 2

1994 3-22 May 36.2 23 10 20 - 300 37 2 - 80 45 1 - 6 3 o - 9 3 ~

" 24.1 20 10 20 . 300 37 2 . 80 30 1 . 6 3 o . 9 3

_c....

~C)

~::J-

"' ~

Total 29 Apr-29 May 112.7 76 37 18 - 475 42 o - 99 60 o - 6 1 1 - 10 3 ~

" 72.1 64 35 18 475 40 o . 99 60 o - 6 1 1 . 10 3 ~

!::

••i:

~

"'

l:I..

b:l

"'

::J-

~-e

0" .,

-\0

00
5.3 Bowheads: Undisturbed Behavior 199

variable and generally lighter (median 60%), and sea state at observation sites tended to be slightly

higher. Almost all 1990 data from waters ~100 m deep were obtained late in the field season (21-

25 May) and many of those data pertained to mother-calf pairs.

In 1991, low clouds prevailed and behavioral observations from 460 m altitude were possible

on only five days. Only one observation session lasted> 1 h (6 May), and only 4.1 hours of observations were obtained during the season. Ice cover at observation sites ranged from 1 to 90%, but

most were in ~35% ice cover. In 1994, weather was much clearer than in 1991, and we collected

behavioral data for 36.2 h (24.1 h "presumably undisturbed). Depth of water at observation sites

ranged from 20 to 300 m, but most observations were in 20-55 m (median 37 m). Ice cover varied

from 2 to 80% (median 30%), with most observations being collected in or near the main "nearshore" lead between the landfast ice and the pack ice. Winds tended to be strong in 1994. This,

combined with the often-extensive open water in the nearshore lead, resulted in notably higher sea

states during the 1994 work (median 3 in 1994 vs. Y2-1 in earlier years; Table 5.8).

General Acti vities

The predominant activity of most bowheads observed in spring was travel, with social interactions and presumed feeding being less common. Considering all 76 observation sessions, travel

was noted during 64 sessions (84%), social activity during 22 (29%), and presumed feeding during

eight (11 %). During most of the observation sessions with social activity or presumed feeding,

the bowheads were also traveling at least part of the time. Overt sexual activity was infrequent,

being noted during only 4 of 76 sessions (5%). The activities of mothers and calves differed

somewhat from those of other whales, so mothers and calves are treated separately in a later

section (p. 228ff). The following material concerns only the "presumably undisturbed" whales, and

excludes mothers and calves.

Traveling.- Traveling whales constituted the largest proportions of the bowheads observed

during each of the four spring seasons with observations. The predominant activity was traveling

for 624 of 954 observed surfacings (65%), and travel plus socializing for a further 205 surfacings

(21 %) (Table 5.9). Data on traveling whales seen during the undisturbed periods are important

as control data for the playbacks.

Traveling was the predominant activity regardless of date, time of day, water depth, and ice

cover (Table 5.9A-E). However, there was a tendency for the proportion of the whales that were

traveling to be lower with high percentages of ice cover:

Ice cover

% traveling

% traveling or traveling+socializing

(based on Table 5.9D).

<30%

89%

97%

~30%

50%

80%

Headings of all bowhead groups sighted during spring are summarized in Table 5.1. The

overall vector mean was 83° True, with an angular deviation of 37°. Considering only the sightings when bowheads were classified as traveling, the vector mean was again 83°T with angular

deviation reduced to 33° (n=638 groups). Most traveling groups were headed to the NE, E or ESE.
5.3 Bowheads: Undisturbed Behavior 200

TABLE 5.9. Circumstances of observations of undisturbed bowhead whales engaged in various group activities. The

table shows numbers (left) and percentages (right) of surfacings during spring migration near Barrow, AK, 1989-94,

as observed from a Twin Otter aircraft. 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.

Number of Surfacings Percentage of Surfacings

Travel Tr+Soc Social Other All Travel Tr+Soc Social Other All

A.Date

21-30 Apr 9 0 6 1 16 1.4 0.0 12 I

1.7

1-10May 198 120 44 49 411 31.7 58.5 88 65 43.1

11-20 May 394 82 0 17 493 63.1 40.0 0 23 51.7

21-31 May 23 3 0 8 34 3.7 1.5 0 11 3.6

Total n 624 205 50 75 954

B. Hour (local)

6-8 I 3 0 0 4 0.2 1.5 0 0 0.4

9-11 188 79 4 28 299 30.1 38.5 8 37 31.3

12-14 151 120 2 28 301 24.2 58.5 4 37 31.6

15-17 119 3 44 4 170 19.1 1.5 88 5 17.8

18-20 106 0 0 15 121 17.0 0.0 0 20 12.7

21-23 59 0 0 0 59 9.5 0.0 0 0 6.2

Total n 624 205 50 75 954

C. Water Depth (m)

10-19 23 0 6 9 38 3.7 0.0 12 12 4.0

20-49 527 197 32 15 771 84.5 96.1 64 20 80.8

50-99 37 0 0 5 42 5.9 0.0 0 7 4.4

1OQ-250 28 8 12 42 90 4.5 3.9 24 56 9.4

>250 9 0 0 4 13 1.4 0.0 0 5 1.4

Total n 624 205 50 75 954

D. Ice Cover(%)

None 43 0 0 2 45 6.9 0.0 0 3 4.7

1-9% 226 29 0 0 255 36.2 14.1 0 0 26.7

10-29 67 0 0 10 77 10.7 0.0 0 13 8.1

30-59 89 86 0 6 181 14.3 42.0 0 8 19.0

60-79 125 87 0 25 237 20.0 42.4 0 33 24.8

80-90 64 3 38 21 126 10.3 1.5 76 28 13.2

>90 10 0 12 11 33 1.6 0.0 24 15 3.5

Total n 624 205 50 75 954

E.IceAhead

None 420 125 16 44 605 79.7 86.8 73 70 80.0

< 100m 14 3 0 3 20 2.7 2.1 0 5 2.6

lOQ-l000m 59 10 6 9 84 11.2 6.9 27 14 11.1

> l000m 34 6 0 7 47 6.5 4.2 0 11 6.2

Total n 527 144 22 63 756
5.3 Bowheads: Undisturbed Behavior 201

Headings were also recorded at the start of each surfacing and dive during aerial observations

of behavior. Table 5.10 summarizes those results, including data for whales engaged in traveling

each year and overall (Table 5.1 OC). For traveling whales, the vector mean direction during

behavioral observation sessions was 67°T with angular deviation 31°; vector means ranged from

59° in 1994 to 81° in 1991.

Most whales traveled along leads and cracks oriented SW ~NE or W ~E, with the result that

there usually was not a large expanse of solid ice ahead of the whales as they dove. When the

crack or lead in which a whale was swimming turned slightly left (north) or right (east or

southeast), bowheads often adopted that course in order to remain within the crack or lead. However, when whales came to the eastern or northeastern end of a lead or crack, or when they

surfaced in an isolated opening in the ice, they routinely headed under the ice to the NE, ENE, E

or ESE. About 6% of the surfacings by traveling whales ended when the whale dove under ice

that appeared to be solid (without potential breathing sites) for at least 1 km in the whale's

direction of travel. An additional 10% of the surfacings ended when the whale dove beneath ice

that appeared solid for 0.1 to 1 km ahead of the whale. (These percentages, based on Table 5.9E,

consider both traveling and "traveling+socializing" whales, and exclude situations where the ice

was obviously recently refrozen and thin.)

Bowheads usually traveled singly or in small groups, but group size depends on one's

definition for a group. It was rare for there to be more than 4 bowheads within 5 body-lengths of

one another, and by this definition the most common group sizes were one (48%) and two (32%;

Table 5.llA). However, there usually were additional bowheads within about 1 km. Only about

5% of the traveling bowheads, and 3.5% of those traveling or "traveling+socializing", seemed to

be unaccompanied by other bowheads within 1 km (Table 5.11B). Thus, most if not all bowheads

were close enough to other bowheads to be in acoustic communication.

Bowheads whose general activity was classified as traveling were, in fact, traveling during

the great majority of their individual surfacings (Table 5.11). However, during small proportions

of the surfacings they socialized while traveling (6.6%), socialized without traveling (l %), rested

nearly motionless (l %), or engaged in other activities such as aerial behaviors (breaches, flipper

slaps, tail slaps). On rare occasions, traveling whales were suspected to be feeding as they

traveled (Table 5.llE and later).

Socializing.-Social activity by bowhead whales consists of a considerable variety of

behaviors, including

~ two or more whales swimming parallel and close to one another but not otherwise

interacting in any obvious way (categorized here as "passive socializing" if the whale was

within ~ body length of another bowhead);

~ two or more whales whose actions are clearly influenced by the presence of one another,

generally involving turns toward or away from one another; often including touching with

the rostrum, flippers, or other body parts; and sometimes involving rolling around the

long axis (categorized here as "active socializing");
TABLE 5.10. Headings (True) of bowheads observed during behavioral observation sessions.

Excludes mothers, calves, and potentially disturbed whales. Each surfacing and dive with a known heading is counted separately.

A. By Year (All Activities) B. By Group Activity (All Years) C. By Year, Traveling Bowheads

True Social- Trav.+ Trav.+ Tr.s-So Other True

Heading 1989 1990 1991 1994 TOTAL Rest Travel ize Soc. Feed +Feed & Unk TOTAL 1989 1990 1991 1994 TOTAL Heading

o N 2 2 1 20 25 0 6 2 13 0 1 3 25 0 2 0 4 6 N 0

10 0 3 0 8 11 0 6 0 3 0 I 1 11 0 3 0 3 6 10

20 3 0 0 22 25 0 20 3 2 0 0 0 25 0 0 0 20 20 20

30 7 28 2 81 118 1 83 2 24 0 1 7 118 4 23 2 54 83 30

40 0 19 0 46 65 0 53 0 11 0 1 0 65 0 19 0 34 53 40

50 2 31 1 113 147 0 98 1 42 0 5 1 147 0 31 0 67 98 50

60 5 93 0 192 290 0 221 3 55 3 5 3 290 3 86 0 132 221 60

70 1 92 4 77 174 0 140 0 32 0 2 0 174 1 84 2 53 140 70

80 I 43 0 45 89 0 70 0 16 0 0 3 89 0 42 0 28 70 80

90E 11 83 4 48 146 0 120 1 16 1 0 8 146 10 73 4 33 120 E90

100 3 46 2 16 67 1 39 2 24 0 0 1 67 0 27 2 10 39 100

110 2 21 0 7 30 0 18 1 7 2 1 1 30 1 14 0 3 18 110

120 10 18 4 16 48 3 25 6 7 2 0 5 48 1 14 1 9 25 120

130 0 19 0 0 19 0 16 0 3 0 0 0 19 0 16 0 0 16 130

140 1 2 0 5 8 0 4 0 3 0 0 1 8 1 1 0 2 4 140

150 3 4 0 7 14 0 6 2 2 0 1 3 14 0 2 0 4 6 150

160 2 1 0 7 10 2 6 0 1 1 0 0 10 0 0 0 6 6 160

170 0 0 0 4 4 0 4 0 0 0 0 0 4 0 0 0 4 4 170

ISO S 1 5 0 6 12 0 6 0 1 0 0 5 12 0 2 0 4 6 SISO

190 2 0 1 1 4 1 1 0 1 0 0 I 4 1 0 0 0 1 190

200 0 0 1 1 2 0 0 0 1 0 0 1 2 0 0 0 0 0 200

210 2 0 0 6 8 0 2 2 0 0 0 4 8 0 0 0 2 2 210

220 1 0 0 1 2 0 0 1 0 0 1 0 2 0 0 0 0 0 220

230 0 0 0 2 2 0 1 0 1 0 0 0 2 0 0 O· 1 1 230 ~

240 4 0 3 6 13 2 1 0 4 0 0 6 13 0 0 0 1 1 240 t..,

250 I 0 4 5 10 0 0 0 0 0 0 10 10 0 0 0 0 0 250 b:I

0

260 0 0 2 I 3 0 0 0 0 0 1 2 3 0 0 0 0 0 260 ~

270 W 1 2 0 9 12 0 0 1 3 0 1 7 12 0 0 0 0 0 W 270 ~

"' 280 2 0 0 0 2 0 0 2 0 0 0 0 2 0 0 0 0 0 280 ~

290 0 0 0 I I 0 0 0 0 0 I 0 I 0 0 0 0 0 290 ~

300 0 0 1 1 2 0 0 0 1 0 0 I 2 0 0 0 0 0 300

~ 310 0 0 0 1 I 0 0 0 0 0 0 I 1 0 0 0 0 0 310 l:I.

320 0 0 0 5 5 0 4 0 1 0 0 0 5 0 0 0 4 4 320 1:;'

i::

330 12 0 0 9 21 8 5 1 7 0 0 0 21 2 0 0 3 5 330 ti340 I 2 0 4 7 0 5 0 1 0 0 1 7 0 I 0 4 5 340

"'

l:I.

350 0 3 0 2 5 0 4 0 0 0 0 I 5 0 2 0 2 4 350 b:I

Total 80 517 30 775 1402 18 964 30 282 9 22 77 1402 24 442 11 487 964 Total "'~

Vector ~..:

Mean 72 76 113 57 66 333 67 79 62 98 48 193 66 75 74 81 59 67 c' .,

Length 0.31 0.87 0.19 0.77 0.76 0.14 0.86 0.35 0.77 0.85 0.56 0.10 0.76 0.72 0.90 0.89 0.84 0.86

Ang. Dev. 67 29 73 39 40 75 31 65 39 32 54 77 40 43 26 26 32 31 N

0

N
5.3 Bowheads: Undisturbed Behavior 203

TABLE 5.11. Frequencies of various group sizes and activities of undisturbed bowhead whales engaged in various

group activities. Mothers and calves excluded. Presentation as in Table 5.9.

Number of Surfacings Percentage of Surfacings

Travel Tr+Soc Social Other All Travel Tr+Soc Social Other All

A. Group Size (within 5 body lengths)

1 290 37 3 60 390 47.9 18.5 6 81 42.0

2 195 52 24 7 278 32.2 26.0 48 9 29.9

3 74 20 10 7 111 12.2 10.0 20 9 11.9

4 31 68 8 0 107 5.1 34.0 16 0 11.5

5 7 22 5 0 34 1.2 11.0 10 0 3.7

>5 8 1 0 0 9 1.3 0.5 0 0 1.0

Total n . 605 200 50 74 929

B. # Bowheads Within 1 km

1 29 0 0 32 61 4.6 0.0 0 43 6.4

2 81 5 0 2 88 13.0 2.4 0 3 9.2

3 197 3 12 39 251 31.6 1.5 24 52 26.3

4 120 29 6 0 155 19.2 14.1 12 0 16.2

5 47 0 32 2 81 7.5 0.0 64 3 8.5

6 52 82 0 0 134 8.3 40.0 0 0 14.0

7 74 0 0 0 74 11.9 0.0 0 0 7.8

8 24 0 0 0 24 3.8 0.0 0 0 2.5

>8 0 86 0 0 86 0.0 42.0 0 0 9.0

Total n 624 205 50 75 954

C. Whale Activity This SfclDive Sequence

Rest 8 0 0 8 16 1.3 0.0 0 11 1.7

Travel 520 100 0 13 633 83.3 48.8 0 17 66.4

Socialize 9 48 48 0 105 1.4 23.4 96 0 11.0

Feed 2 0 0 7 9 0.3 0.0 0 9 0.9

Travel-Social 41 44 0 0 85 6.6 21.5 0 0 8.9

Travel-Feed 0 0 0 7 7 0.0 0.0 0 9 0.7

Social-Feed 0 0 0 1 1 0.0 0.0 0 1 0.1

Unknown/Other 44 13 2 39 98 7.1 6.3 4 52 10.3

Total n 624 205 50 75 954

D. Group's Predominant Feeding Mode

None 624 205 50 42 921 100.0 100.0 100 61 97.2

Water-column 0 0 0 19 19 0.0 0.0 0 28 2.0

Bottom 0 0 0 8 8 0.0 0.0 0 12 0.8

Near-surface 0 0 0 0 0 0.0 0.0 0 0 0.0

Total n 624 205 50 69 948

E. Whale's Feeding Mode During ThisSfcIDive Sequence

None 573 198 43 49 863 99.3 100.0 100 77 97.8

Water-column 4 0 0 8 12 0.7 0.0 0 13 1.4

Bottom 0 0 0 7 7 0.0 0.0 0 11 0.8

Near-surface 0 0 0 0 0 0.0 0.0 0 0 0.0

Total n 577 198 43 64 882
5.3 Bowheads: Undisturbed Behavior 204

~ two or more whales engaged in sexual activities, as described by Everitt and Krogman

(1979) and Wursig et al. (1985, 1993) (also included here as "active socializing").

For certain bowheads, it was somewhat arbitrary whether they should be classified as traveling or "traveling+socializing". Traveling bowheads were classified as "traveling+socializing"

when social activity was evident during at least 1/3 of the surfacings. The circumstances in which

"traveling+socializing" was seen were generally similar to those in which simple traveling was

seen (Table 5.9). However, group sizes tended to be larger than for traveling (Table 5.11A,B).

Socializing, with or without simultaneous' travel, was evident during 45% of the surfacings by

whales classified as "traveling+socializing" (Table 5.11C).

Bowheads were classified as "socializing" when a group of whales engaged in active socializing at one location without evidence of travel during the duration of observations. Observations

of this type were less common than those of "traveling+socializing" (Table 5.9). Although socializing was certainly less common than active traveling, its relative frequency is probably understated in Table 5.9. We often chose not to observe groups of whales that were engaged in active

socializing, or to curtail observations of these groups after only a brief period. (This was done

because it is difficult to quantify their behavior and, in particular, difficult to compare that

behavior during undisturbed and potentially disturbed conditions.) Because of this, it would not

be meaningful to undertake a detailed examination of the circumstances when socializing was

observed. Some socializing groups that were not observed systematically (excluded from our

Tables) were in areas with little or no ice. However, all systematically observed cases of active

socializing were in areas with extensive ice (Table 5.9D), suggesting a possible association

between socializing and extensive ice. Group sizes for socializing whales were not especially large

(Table 5.11A,B) but it was-of course-rare for there to be no other whale within 5 body lengths.

Headings of socializing whales and "travel-i-socializing" whales observed during behavioral

observation sessions averaged 79° and 62° True, respectively. These average headings were

similar to the 67° average for traveling whales (Table 5.10B). However, the variability in

headings was much greater during socializing (angular deviation 65°) and slightly greater during

"travels-socializing" (39°) than during travel without socializing (31°).

Sexual activity was noted during only 4 of 76 observation sessions within the four spring

seasons; on 3 May and 6 May 1989; 10 May 1990; and 7 May 1994. This suggests that there may

be more sexual activity earlier than later in the season, but the sample size is too low to be

conclusive. These sexual interactions are described later (p. 227).

Feeding and Surfacing with Mud.-Feeding apparently was not common during spring migration through our study area. On rare occasions bowheads dove repeatedly at one location,

suggesting but not proving that water-column feeding was occurring. On 9 May 1994, several

bowheads, generally small individuals, lingered near the ice camp and repeatedly dove under the

edge of the landfast ice, possibly feeding (§6.1-6.2 and Appendix F). Their behavior resembled

that observed near Barrow in late May 1985 (Carroll et al. 1987), when lingering whales dove

repeatedly under the landfast ice, and when feeding was confirmed by presence of copepods and

euphausiids in the stomachs of harvested whales. Defecation, which often accompanies feeding
5.3 Bowheads: Undisturbed Behavior 205

in summer, was observed only once during this study, and that was during a bout of sexual activity

on 3 May 1989. We saw no evidence of surface feeding.

Traveling whales sometimes seemed to have mud on their bodies when they surfaced. It is

not known why or how often they contacted the bottom. On one day (16 May 1990), much mud

was seen streaming out through the baleen of a small whale during one surfacing. It and three

other whales near it had mud streaming from their bodies during one or more surfacings in water

-40 m deep. IS On another day (12 May 1990), there was evidence of brief bottom or near-bottom

feeding by three whales that had been observed for 2.7 h as they traveled east along the middle

of the main nearshore lead. Mud was observed coming from the mouths of whales during four surfacings on this date; water depth was -14 m. Another research team working in the same area also

saw some bowheads surfacing with mud on their bodies in 1989 and 1990 (Angliss et al. 1993).

Resting.-It was quite rare for the general activity of bowheads observed during spring (aside

from mothers and calves) to be classified as resting. Only 12 of 954 surfacings were in this

category; in Table 5.9 these are combined with other rare group activities in the "Other" column.

The 12 cases were on 3 and 7 May 1989, when two small groups of resting bowheads were found

in small cracks within heavy ice. In addition, a few bowheads classed as traveling rested nearly

motionless during one or more surfacings; however, these few surfacings comprised only about

1% of all surfacings by traveling bowheads (8 of 624; Table 5.11 C).

Surfacing, Respiration and Dive Cycles

We determined the durations of surfacings and dives, the number of blows per surfacing, and

the intervals between successive visible blows within a surfacing. Most definitions and criteria

were the same as in our previous related studies (e.g. Dorsey et al. 1989; Richardson et al. 1995).

In particular, a surfacing is again defined as the interval from the first arrival of a whale at the

surface after a long ("sounding") dive to the time when the whale descends below the surface for

the next long dive. A surfacing usually includes several blows, and is equivalent to a "surfacing

sequence" as defined by some other authors.

Figure 5.27 summarizes the surfacing, respiration and dive characteristics of all presumably

undisturbed whales, excluding calves and their mothers." During surfacings, we observed an

average of 5.2 blows at average intervals of 18.2 s (Fig. 5.27 A,B). An average surfacing-dive

cycle consisted of a 1.34 min surfacing and a 5.95 min dive (Fig. 5.27C,D). Short dives «2 min)

were common, with the majority of these being 1-2 min in duration (Fig. 5.27D). The longest

documented dive, involving a traveling whale seen in 1994, was 39.0 min in duration. This is the

15 These observations of mud on 16 May 1990 were 0.45-0.9 km from the ice camp during or within

20 min after the end of a drilling noise playback.

16 The surfacing, respiration and dive cycles of calves and mothers differ from those of "other

bowheads", and are summarized later (§5.4). Our data on the reactions of bowheads to playbacks of drilling

and icebreaker noise rarely involved mothers or calves, so the appropriate control data are those for "other

bowheads".
160 160

A. All Whales B. Mean 5.19

Mean 18.2 sd 3.53

sci 11.7 n 454

120 120

n 676

CJ) CJ)

0> 0>

c c

'0 '0

{g 80 :J ~

:J 80

en sn

ci d

z z

40 40

1-4 10-13 19-22 28-31 37-40 >46

Median Blow Interval (s)

160'...-----------------....,

120

~

c-

'0

~ 80 :J

so

d

z

40

c. Mean 1.34

sd 1.17

n 498

o

160'...--------------------.

120

CI)

.~

Q 80

d

z

40

0-1 6-7 12-13 18-19 24-25 >29

No. Blows/Surfacing

FIGURE5.27. Frequency distributions of surfacing, respiration and dive variables for undisturbed bowheads during the spring migration

period near Barrow, Alaska. Other criteria: calves, yearlings, and accompanying mothers are excluded; based on aerial observations

from a Twin Otter aircraft circling at altitude ~460m, 1989-94.

o

0-0.5 1.5-2 3-3.5 4.5-5 6-6.5 >7.5

Duration of Surfacing (min)

D. Mean 5.95

sd 6.26

n 319

IV

o

0\

-------------------------------------

# Short Dives:

<0.5min: 9

0.5-1min: 37

1-2m!n: 60

o 0-2 6-8 12-14 18-20 24-26 >30

Duration of Dive (min)
5.3 Bowheads: Undisturbed Behavior 207

longest dive that we have documented during any of our studies of bowheads. Four additional dive

durations (of 319 timed dives by presumably undisturbed bowheads) exceeded 30 min. In total,

three of the five dives >30 min in duration involved traveling whales and two involved resting

whales. The longest confirmed dives during our previous studies have been just over 30 min in

duration: 31.0 min in the summer of 1980-84 in the Canadian Beaufort Sea (Dorsey et al. 1989),

31.6 min in the late summer/early autumn of 1985-86 near the Alaska/Yukon border (Richardson

et al. 1987b:343), and 31.6 min in late summer in Baffin Bay (Richardson and Finley 1989:63).

Table 5.12 provides a more detailed breakdown of data on surfacing, respiration and dive

cycles for bowheads engaged in various activities, including traveling, socializing, and various

combinations of activities. Blow interval data in Table 5.12 are presented in two ways: (1) considering each individual blow interval as a unit, and (2) considering the median of all blow

intervals within a single surfacing as a unit. In method (1), the sample size is the total number

of blow intervals recorded, whereas in method (2) it is the number of surfacings during which one

or more blow intervals were recorded. The sample sizes are smaller for median blow intervals

(method 2) than for individual blow intervals (method 1). Also, standard deviations are smaller

for method 2 than for method 1. Durations of successive individual blow intervals within a

surfacing are presumably not independent. Hence, statistical comparisons of blow intervals are

based on the median blow intervals.

Even when each surfacing or dive contributes only one observation to the analysis, there is

still concern about possible lack of independence between successive surfacings or dives of a

single whale (e.g. Machlis et al. 1985; Hoekstra and Jansen 1986). Because it is frequently

impossible to determine whether a given whale has been observed previously, there is no way to

obtain a single average value of each variable for each individual animal. Hence, in analyses in

which each surfacing or dive contributes one observation, we place little emphasis on differences

that, by standard statistical methods, are only marginally significant (e.g. 0.1 > P> 0.01). Also,

we refer to these P values as "nominal P" values (Po)'

Traveling Whales.-An average surfacing-dive cycle by an undisturbed traveling bowhead

(mothers and calves excluded) consisted of a 1.35 min surfacing and a 6.63 min dive (Fig. 5.28;

Table 5.12). There was an average of 5.0 blows per surfacing. Intervals between successive blows

within a surfacing averaged 18.1 s.

The average dive duration reported here (6.63 min) may be realistic for bowheads traveling

along open leads or through loose pack ice. However, it probably underestimates the overall

average dive duration for traveling bowheads during spring migration. We were often unable to

resight identifiable bowheads when they resurfaced after long dives under areas of extensive ice,

so these long dives are underrepresented in our sample. As noted above, the longest documented

dive by an undisturbed whale during this study was a 39.0 min dive by a whale traveling under

ice on 7 May 1994. Two additional dives by traveling bowheads were slightly longer than 30 min.

Traveling+Socializing.-Bowheads that intermixed social interactions with travel had

significantly (Po<O.OOl) shorter surfacings and dives than did the bowheads that were simply

traveling (Fig. 5.28C,D). The mean number of blows per surfacing was similar to that for
TABLE 5.12. Surfacing, respiration and dive behavior of undisturbed bowhead whales engaged in various activities during the spring migration

period near Barrow, Alaska. Mothers and calves are excluded. Based on observations from a Twin Otter aircraft at altitude 460 m, 1989-1994.

Year

Group

Activity

Individual

Blow Intervals (s)

mean s.d. n

89+90 Travel

Travel-social

Social

OtherlUnknown

19.39

17.16

21.26

4864

Median

Blow Intervals (s)

Number of Blows

per Surfacing

mean s.d. n

8.90

8.85

15.13

9679

963

135

133

214

19.78

16.95

21.15

3010

7.28

8.31

13.42

3978

225

39

40

29

4.76

3.68

2.33

882

3.14

3.11

1.53

469

All 23.68 39.65 1445 20.52 14.43 333 4.93 3.43 239

Duration of

Surfacing (min)

mean s.d. n

200

19

3

17

1.37

0.85

0.53

313

1.07

0.90

0.41

207

Duration of

Dive (min)

mean s.d.

208

20

4

19

7.11

3.92

1.02

1158

5.63

2.24

0.00

1020

5.91 192

91+94 Travel 15.81 8.16 965 16.39 7.62 226 5.36 3.48 155 1.32 0.98 159 5.67 7.33 81

Travel-social 14.79 8.24 413 15.37 7.74 95 5.16 3.68 51 1.06 0.97 60 2.60 4.44 21

Social 0 0 0 0 0

OtherlUnknown 13.79 11.97 161 13.00 5.03 22 9.00 4.47 9 1.03 1.49 28 1.20 1.59 25

Travel-feed 0 0 0 0 0

Tr-soc-feed 14.08 7.90 76 13.96 5.79 13 8.40 3.65 5 2.04 1.05 3 0

Rest 0 0 0 0 0

Other/unkn. 13.54 14.74 85 11.61 3.53 9 9.75 5.85 4 0.91 1.50 25 1.20 1.59 25

All 15.32 8.68 1539 15.89 7.55 343 5.47 3.63 215 1.23 1.05 247 4.28 6.43 127

mean s.d. n

Travel-feed 17.20 7.20 30 17.31 6.35 8 6.50 2.38 4 1.43 0.64 5 1.43 0.00 1

Tr-soc-feed 0 0 0 0 0

Rest 95.64 141.34 85 53.45 62.70 10 7.60 3.65 5 4.64 2.79 5 13.70 13.19 6

Other/unkn. 17.82 6.57 99 18.18 5.64 11 10.75 5.65 8 3.23 1.53 9 10.93 3.57 4

1.45 1.26 251 7.05

163

17

1

11

Travel-feed 17.20 7.20 30 17.31 6.35 8 6.50 2.38 4 1.43 0.64 5 1.43 0.00 1

Tr-soc-feed 14.08 7.90 76 13.96 5.79 13 8.40 3.65 5 2.04 1.05 3 0

Rest 95.64 141.34 85 53.45 62.70 10 7.60 3.65 5 4.64 2.79 5 13.70 13.19 6

Other/unkn. 15.84 11.29 184 15.23 5.77 20 10.42 5.47 12 1.52 1.82 34 2.54 3.90 29

1989-94 Travel

Travel+social

Social

Other/unknown

17.60

15.38

21.26

3368

All 19.37 28.59 2984 18.17 11.69 676 5.19 3.53 454

8.72 1928

8.45 548

15.13 133

7546 375

18.08

15.83

21.15

2273

7.64

7.91

13.42

31 14

451

134

40

51

5.02

4.76

2.33

889

3.30

3.58

1.53

453

355

70

3

26

1.35

1.00

0.53

1 88

1.03

0.95

0.41

202

367

80

4

47

6.63

3.19

1.02

437

6.27

3.64

0.00

741

5.95 6.26 319

244

38

1

36

1.34 1.17 498

n

tv

o

00
100 100 B. A. Trav. Tr+So Trav Tr+So

80

Mean 18.08 15.83 80 Mean 5.02 4.76

sd 7.64 7.91 sd 3.30 3.56

n 451 134 n 355 70

60 60 OS

a

rn

CJ)

c c

'0 40 '0

~ ~

~

Travel ~

en 20 en

ci ci

z z

Travel + Social -20

-40 -40

1-4 10-13 19-22 28-31 37-40 >46 0-1 6-7 12-13 18-19 24-25 >29

Median Blow Interval (8) No. Blows/Surfacing

100 C. 100 D.

Trav. Tr+So Trav. Tr+So

80 Mean 1.35 1.00 80

Mean 6.63 3.19

sd 1.03 0.95 sd 6.27 3.64

n :!Ji1 80 n 244 36

60 60

a

.~

• 01Short ONes c

40 '0 0-.5 min 6 4 40

~

.5-1 9 8

~

0 1-2 43 10

en 20 ci 20 ci z

z

0

f- -_.- «CO

-20

-4~ -40

0-0.5 1.5-2 3-3.5 4.5-5 6-6.5 >7.5 0-2 6-8 12-14 18-20 24-26 >30'

Duration ofSurfacing (min) Duration of Dive (min)

FIGURB5.28. Frequency distributions of surfacing, respiration and dive variables for undisturbed bowheads engaged in traveling (upward

bars) or traveling+socializing (downward bars) during the spring migration period near Barrow, Alaska. Nominal significance levels

come from t-tests on log-transformed data; ns means Pn>O.Ol and *** means PnSO.OOl. Other criteria as in Fig. 5.27.
5.3 Bowheads: Undisturbed Behavior 210

traveling whales (4.8 vs. 5.0, Pn>O.l). However, the median interval between successive blows

within a surfacing was notably shorter for whales engaged in "travel+socializing" as compared

with simple traveling, averaging 15.8 vs. 18.1 s (Pn<O.OOl). Note that the nominal significance

levels quoted here are based on t-tests on log-transformed data; the log-transform eliminates or

reduces the skewness evident in Figures 5.28A-D.

Socializing.-Bowheads whose general activity was socializing without travel were observed

too infrequently to obtain meaningful sample sizes for most variables (Table 5.12). However, their

median blow intervals (Fig. 5.29) tended to be long as compared with those for

"traveling+socializing" whales, averaging 21.2 vs. 15.8 s (Pn<O.Ol).

Resting.-Resting whales were observed infrequently, and only in 1989. Although the sample size was very small, they tended to remain at the surface for unusually long periods (mean

4.64 min, n=5), and their blow intervals were usually very long. The median blow interval for the

surfacing averaged 54 s in duration (n=lO surfacings), and the individual blow intervals averaged

96 s long (n=85) (Table 5.12). Although blow intervals by resting bowheads certainly tend to be

longer than those by other bowheads, our blow-interval data for resting bowheads may be biased

upward somewhat. Some blows by resting bowheads are invisible (Carroll and Smithhisler 1980;

this study). We counted "no blow rises" as presumed blows in this study. However, resting

bowheads do not exhibit the upward rolling motion characteristic of blowing by moving whales.

Hence, invisible blows by resting whales would not always be recognizable as "presumed blows".

Other Behaviors

Many other behavioral variables, mostly of a categorical or ordinal nature, were recorded

during the systematic behavioral observations from the circling aircraft. The most noteworthy of

these are summarized in Tables 5.13 and 5.14 for the most commonly observed general activities:

traveling, travel+socializing, and socializing.

Swimming Speed.-Speed during a particular surfacing cannot be determined quantitatively

during aerial observations. However, we recorded relative speed during each surfacing on an

ordinal "none, slow, medium, fast" scale (Table 5.13A). This scale is the same as the speed scale

applied during our previous (1980-86) summer and autumn studies in the Beaufort Sea. Each of

those studies involved 1 or 2 of the same aerial observers as in this study, so the categorization

of speeds is consistent across studies.

Not surprisingly, traveling whales were usually moving at medium speed during surfacings,

as were "traveling+socializing" whales (Table 5.13A). Whales engaged in socializing without

travel had the most variable speeds during surfacings. The few resting whales were usually

classified as having no forward speed (Richardson et al. 1991a: 114).

Speeds of migrating whales were determined directly on a few occasions, mainly in 1990,

when we followed recognizable individual bowheads for several kilometers. The majority of these
FIGURE5.29. Frequency distributions of median blow intervals for undisturbed bowheads engaged

in socializing (upward bars) or various other activities listed in Table 5.12 (downward bars) during

the spring migration period near Barrow, Alaska. Nominal significance level comes from t-test

on log-transformed data; ns means Pn>O.1. Other criteria as in Fig. 5.27.

data concerned mother-calf pairs or whales exposed to noise playbacks. 17 However, on 5 May

1990 we followed one undisturbed whale for about 1 h as it swam 4.3 km eastward along a narrow

lead; the average "ground" speed (ignoring any current) was 4.4 kmlh. The speed of this whale

during each of its surfacings was recorded as medium. On 12 May 1990 we followed a group containing several recognizable whales for 2.1 h as they swam steadily eastward for 12.3 km along

the main nearshore lead, i.e. average "ground" speed 5.9 km/h." Speed during almost all surfacings within this 2.1-h period was recorded as medium. Additional data on speeds were obtained

when the various recognizable whales were photographed twice at known locations (§5.2).

17 Many whales were observed during two or more successive surfacings. Aircraft position during most

surfacings was known reasonably accurately in 1989-90 (VLF navigation system) and very accurately in

1991/94 (GPS systems). However, we usually avoided flying directly over the whales in order to minimize

the potential for aircraft disturbance. Therefore, exact whale positions during successive surfacings usually

were not determined. The cases mentioned are ones where speed can be computed to within ±0.25 km/h

based on good aircraft position data and long intervals between first and last observed surfacing.

18 These whales were also followed for an additional 0.5 h, but during that time they began to bring mud

to the surface and slowed down to about 2.6 km/h.
5.3 Bowheads: Undisturbed Behavior 212

TABLE 5.13. Frequencies of various activities among undisturbed bowhead whales engaged in various group

activities. Mothers and calves excluded. Presentation as in Table 5.9.

Number of Surfacings Pe~nmgeofSurfacings

Travel Tr+Soc Social Other All Travel Tr+Soc Social Other All

A. Speed During This Surfacing

Zero 10 0 6 17 33 1.7 0.0 23 30 4.0

Slow 131 32 7 14 184 22.5 ' 19.3 27 25 22.1

Moderate 329 100 5 10 444 56.4 60.2 19 18 53.4

Fast 3 0 I 0 4 0.5 0.0 4 0

0.5

Unknown but >0 70 22 3 7 102 12.0 13.3 12 13 12.3

Milling 0 2 1 0 3 0.0 1.2 4 0 0.4

Change 40 10 3 8 61 6.9 6.0 11.5 14.3 7.3

ToWn 583 166 26 56 831

B. Flukes Out at End of Surfacing

No 457 106 18 39 620 91.0 87.6 100 78 89.7

Yes 45 15 0 11 71 9.0 12.4 0 22 10.3

Total n 502 121 18 50 691

C. Pre-Dive Flex Before End of Surfacing

No 431 101 15 41 588 98.4 99.0 94 95 98.2

Yes 7 1 1 2 11 1.6 1.0 6 5

1.8

Total n 438 102 16 43 599

D. Turns During Surfacing

None 276 55 2 34 367 64.0 45.1 13 55 58.3

Right 56 28 4 11 99 13.0 23.0 27 18 15.7

Left 52 19 4 7 82 12.1 15.6 27 11 13.0

Multiple 47 20 5 10 82 10.9 16.4 33 16 13.0

Total n 431 122 15 62 630

E. Degrees of Turn During Surfacing

0 276 55 2 34 367 72.6 53.4 20 59 66.6

10 23 6 0 4 33 6.1 5.8 0 7 6.0

20 29 7 0 0 36 7.6 6.8 0 0 6.5

30 10 2 0 3 15 2.6 1.9 0 5 2.7

40 8 2 0 0 10 2.1 1.9 0 0 1.8

50-80 17 6 0 2 25 4.5 5.8 0.0 3.4 4.5

90+ 17 25 8 15 65 4.5 24.3 80 26 11.8

Total n 380 103 10 58 551

F. Social Activity During Surfacing

None 449 84 0 67 600 80.8 44.4 0 93 69.8

Passive 52 17 0 4 73 9.4 9.0 0 6 8.5

Active 55 88 43 1 187 9.9 46.6 100 1 21.7

Total n 556 189 43 72 860

G. Aerial Activity During SfclDive Seq.

None 440 93 31 43 607 93.6 81.6 74 61 87.2

Roll 5 9 11 0 25 1.1 7.9 26 0 3.6

Flip. slap (FS) 4 0 0 0 4 0.9 0.0 0 0 0.6

Tail slap (TS) 12 0 0 4 16 2.6 0.0 0 6 2.3

FS+TS 3 2 0 1 6 0.6 1.8 0 1 0.9

Breach 5 7 0 17 29 1.1 6.1 0 24 4.2

Breach + FS &lor TS 1 3 0 5 9 0.2 2.6 0 7 1.3

Town 470 114 42 70 696
5.3 Bowheads: Undisturbed Behavior 213

TABLE 5.14. Number of surfacing/dive sequences with specific whale behaviors among undisturbed bowhead whales engaged in

various group activities. Mothers and calves excluded. Totals exceed "Overall n" because> 1 special behavior can occur at one

time. Presentation as in Table 5.9.

Number of Surfacings Percentage of Surfacings

Travel Tr+Soc Social Other All Travel Tr+Soc Social Other All

None 121 47 3 39 210 28.1 42.0 19 61 33.7

Defecation 0 0 1 0 1 0.0 0.0 6 0 0.2

Flukes raised during surfacing 6 5 0 0 11 1.4 4.5 0 0 1.8

Lunge or surge 5 6 0 1 12 1.2 5.4 0 2 1.9

Underwater blow 5 6 5 1 17 1.2 5.4 31 2 2.7

Arch during surfacing 30 4 0 4 38 7.0 3.6 0 6 6.1

Mouth open slightly/briefly 0 I 0 0 1 0.0 0.9 0 0 0.2

Mouth open 1 0 0 0 1 0.2 0.0 0 0 0.2

Echelon formation 0 0 0 0 0 0.0 0.0 0 0 0.0

Near-surface feeding 0 0 0 0 0 0.0 0.0 0 0 0.0

Mud from mouth 0 0 0 4 4 0.0 0.0 0 6 0.6

Mud behind whale 0 0 0 0 0 0.0 0.0 0 0 0.0

Streak in water 0 0 0 0 0 0.0 0.0 0 0 0.0

Penis visible 0 3 1 0 4 0.0 2.7 6 0 0.6

Presumed sexual activity 0 18 7 0 25 0.0 16.1 44 0 4.0

Nursing (mother or calf) 0 0 0 0 0 0.0 0.0 0 0 0.0

Play with log 0 0 0 0 0 0.0 0.0 0 0 0.0

Play with other large object 0 0 0 0 0 0.0 0.0 0 0 0.0

Play with particulates 0 0 0 0 0 0.0 0.0 0 0 0.0

Motionless at surface 12 0 1 12 25 2.8 0.0 6 19 4.0

Motionlessjust below surface 0 0 0 0 0 0.0 0.0 0 0 0.0

Motionless with head down 0 0 0 0 0 0.0 0.0 0 0 0.0

Spyhop 0 0 0 0 0 0.0 0.0 0 0 0.0

Travel along ice edge 87 14 0 4 105 20.2 12.5 0 6 16.9

Emerge from extensoice (e-lkm) 21 2 0 0 23 4.9 1.8 0 0 3.7

Riding (mother or calf) 0 0 0 0 0 0.0 0.0 0 0 0.0

Accompanied by belugas 7 0 0 1 8 1.6 0.0 0 2 1.3

Visible below surface 174 19 0 0 193 40.4 17.0 0 0 31.0

Swims in tight circles 0 0 0 2 2 0.0 0.0 0 3 0.3

Overall n 431 112 16 64 623

Fluke-out Dives.-Bowheads and other whales often raise their flukes out of the water at the

end of a surfacing as they are diving. However, in the spring, only about 10% of the dives were

fluke-out dives (Table 5.13B). Similarly low values were found in 1989/90 (8%) and 1991/94

(12%). For traveling whales, the overall 1989-94 figure was 9% (45 of 502). In contrast, during

autumn migration, bowheads raised their flukes -27% of the time in the Alaskan Beaufort Sea and

-58% of the time in Baffin Bay (Richardson et al. 1995).

Pre-dive Flex.-The pre-dive flex is a concave bending of the back that sometimes occurs

10-20 s before bowheads dive. Pre-dive flexes were rare during the spring; they were seen during

only 11 of 599 surfacings when a flex, if present, would have been noted (2%, Table 5.13C). For

traveling whales, there were pre-dive flexes during only 7 of 438 surfacings (2%). In some

previous studies, pre-dive flexes have been much more common (Wiirsig et al. 1985).

Turns.-Frequency of turns during surfacings depended on whale activity (Table 5.13D):

36% for traveling whales (n=431), 55% for traveling+socializing whales (n=122), 87% for socializ-
5.3 Bowheads: Undisturbed Behavior 214

ing whales (n=15). Surfacings with >1 turn were infrequent in traveling whales (11 %) and traveling+socializing whales (16%), but more common in socializing whales (33%). Most turns by

traveling or traveling+socializing whales were :5;300(Table 5.13E). In contrast, socializing whales

usually turned by ~90° (although few of these cases were recorded systematically).

These results are consistent with previously-summarized data on variability in headings

during behavioral observation sessions. Headings were least variable during travel, somewhat

more so during trave1+socializing, and most variable during socializing (Table 5.10, p. 202).

Social Behavior.-As previously discussed, bowheads whose general activity was classed as

traveling were swimming parallel to and within ~ body length of one or more additional bowheads

("passive socializing") during about 9% of their surfacings. During an additional 10% of these

surfacings, there was some form of more active social interaction (Table 5.13F). The frequency

of active interactions was considerably higher for traveling+socializing" bowheads (47%). Whales

classified as socializing without travel exhibited active social interactions during all surfacings.

Aerial Behavior.-Aerial activities are those in which a part of the body is raised above the

surface: breaches, flipper and tail slaps, rolls, and various combinations, as described for bowheads by Wiirsig et al. (1985, 1989). Table 5.13G shows the frequencies of various aerial activities among presumably undisturbed bowheads during spring (mothers and calves excluded):

~ Breaches were seen during 38 of 696 surfacings (5.5%), usually alone but sometimes

combined with flipper or tail slaps during the same surfacing. A given whale was often

seen to breach several times in succession, with breaches often spaced -1 min apart.

~ During a roll along the longitudinal axis of the body, at least one flipper is raised above

the surface. Rolls were seen during about 4% of the surfacings (25 of 696). Rolls were

most common when whales engaged in social interactions.

~ Tail slaps or flipper slaps occurred during small percentages of the surfacings (2.3% and

0.6%, respectively). There were additional surfacings that included both flipper and tail

slaps (0.9%), or a breach plus a flipper and/or tail slap (1.3%).

It is difficult to determine the frequency of occurrence of aerial behaviors during particular

whale activities. When aerial activities occurred in extended bouts, the underlying whale activity,

e.g. traveling or socializing, was sometimes impossible to determine. The general activity of these

whales was classed as "Other". Thus, actual frequencies of various aerial activities during traveling, traveling+socializing, and socializing are probably somewhat higher than suggested by Table

5.13G, assuming that some whales in the "Other" column probably belong under traveling, etc.

Additional Behavioral Variables.-Table 5.14 summarizes the frequencies of numerous

additional behavioral variables, almost all of which occurred quite infrequently during spring near

Barrow. Table 5.14 lists all of the miscellaneous behaviors that we record whenever they are seen,

including numerous behaviors that have been noted during previous summer/autumn studies but

not (or rarely) during this spring study. The rarity or absence of certain behaviors is noteworthy,

e.g. indications of feeding such as defecation, open mouth, or swimming in echelon formation;

occurrence of play with objects in water; and occurrence of spyhopping.
5.3 Bowheads: Undisturbed Behavior 215

In contrast, two of the behaviors listed in Table 5.14 occurred rather often:

•. Travel along ice edge: Bowheads observed in this study were often swimming parallel

to and within 100 m of the edge of a field of pack ice or brash ice, or (less often) along

the edge of the landfast ice. This situation was noted during 105 of 623 surfacings

(17%), and there were undoubtedly additional similar cases that were not recorded as

such. The frequency of this behavior is related to the tendency for bowheads to adjust

their headings to match the alignments of leads and cracks when these are oriented more

or less toward the northeast or east.

•. Visible below surface: This was noticed during dive(s) preceding and/or following 193

of 623 surfacings. These cases involved traveling bowheads (174 of 431 surfacings,

40%) and traveling+socializing bowheads (19 of 112, 17%). The rather high frequency

of this type of observation indicates that spring-migrating bowhead whales often traveled

within several meters of the surface. However, the frequency of this behavior cannot be

compared across studies because of differences in observation conditions. Times when

migrating bowheads were visible below the surface were times of good lighting and low

sea state. The water northeast of Barrow during spring is clear, and sea state is often low

because waves are dampened by nearby ice. In contrast, during our summer work in the

eastern Beaufort Sea, sea states tended to be higher and the water was often very turbid.

Behavior of Subadults vs. Adults During Travel

It is sometimes possible to categorize whales observed during aerial observations as definitely subadult or definitely adult, based on size and markings. Many adults have prominent scars,

whereas subadults tend to be more nondescript (Davis et al. 1986a). We categorized the bowheads

as subadults or adults only in obvious cases. Only 36% of the records (mothers and calves excluded) were categorized in this manner. Thus, our subadult and adult categories no doubt include primarily the smaller subadults and the larger and/or older adults. We further restricted our analysis

to whales whose general activity was classified as traveling.

Surfacing, respiration and dive cycles during travel differed significantly between adults and

subadults (Fig. 5.30). A typical cycle by an adult consisted of a 6.81 min dive and a 1.46 min

surfacing containing 4.9 blows spaced 20.6 s apart. A typical cycle by a subadult was a 5.26 min

dive and a 1.35 min surfacing containing 6.2 blows spaced 14.1 s apart. Dive durations and

median blow intervals were significantly shorter in subadults (Pn<O.Ol and Pn<O.OOl, respectively).

Durations of surfacing were similar for the two groups. This, combined with the notably shorter

blow intervals in subadults, suggests that the number of blows per surfacing should be higher for

subadults. There was only a weak indication of this (Fig. 5030B).

Some other behavioral variables also differed between subadults and adults:

•. Of the surfacings when swimming speed was estimated as zero, slow, moderate or fast,

estimated speed was zero or slow during 62% of the surfacings by subadults but during

only 25% of those by adults (Table 5.15A; X

2=22.4, dfe l , Pn<O.OOl).
A.

Aduft Subad

Mean 20.56 14.12

sd 8.94 5.65

n 159 48

35

25

a Traveling whales only

c: ·0

~ 15

~ Adults

~ 5

-5

Subadults

1-4

c. Aduft SlAlad

Mean 1.48 1.35

sd 1.09 1.22

n 152 39

35

lIS

-15.f---r---r---r--.---.---..--..--..---.----..---r-r---r---r--.----1

0-0.5 1.5-2 3-3.5 4.5-5 6-6.5 >7.5

Duration of Surfacing (min)

35

25

ac:

'0

~ 15

::l

en

~ 5

B. Adutl SlAlad

Mean 4.92 6.15

sd 3.22 err

n 152 33

("l

FIGURE5.30. Frequency distributions of surfacing, respiration and dive variables for undisturbed adult bowheads (upward bars) and

subadult bowheads (downward bars) engaged in traveling during the spring migration period near Barrow, Alaska. Nominal significance

levels come from t-tests on log-transformed data; (lie) means 0.1~p0>0.05 and •••.•.means 0.0 1~p0>0.00 I. Other criteria as in Fig. 5.27.

35

25

.1 15

o

~

-5

0-1 6-7 12-13 18-19 2~25 >29

No. Blows/Surfacing

-5

• 01ShortDIves

G-.smln 0 3

.5-1 3 3

1-2 18 3

D. Mlft SttJad

Mean 6.81 5.26

sd 8.25 6.04

n 134 19

5

0-2 6-8 12-14 18-20 2~26 >30

Duration of Dive (min)

IV

-0\
5.3 Bowheads: Undisturbed Behavior 217

TABLE 5.15. Frequencies of various activities among undisturbed bowhead subadults and adults

engaged in traveling. Mothers and calves excluded. Presentation as in Table 5.9.

Number of Surfacings Percentage of Surfacings

Subadult Adult All Subadult Adult All

A. Speed During This Surfacing

Zero 3 1 4 4.9 0.5 1.6

Slow 28 40 68 45.9 21.7 27.8

Moderate 18 124 142 29.5 67.4 58.0

Fast 1 1 2 1.6 0.5 0.8

Unknown but >0 4 3 7 6.6 1.6 2.9

Milling 0 0 0 0.0 0.0 0.0

Change 7 IS 22 10.3 7.5 8.2

Total n 61 184 245

B. Flukes Out at End of Surfacing

No 50 169 219 89.3 93.9 92.8

Yes 6 11 17 10.7 6.1 7.2

Total n 56 180 236

C. Pre-Dive Flex Before End of Surfacing

No 42 167 209 93.3 98.2 97.2

Yes 3 3 6 6.7 1.8 2.8

Total n 45 170 215

D. Turns During Surfacing

None 21 117 138 50.0 69.2 65.4

Right 8 20 28 19.0 11.8 13.3

Left 9 17 26 21.4 10.1 12.3

Multiple 4 15 19 9.5 8.9 9.0

Total n 42 169 211

E. Degrees of Turn During Surfacing

0 21 117 138 56.8 74.5 71.1

10 4 15 19 10.8 9.6 9.8

20 6 9 15 16.2 5.7 7.7

30 2 2 4 5.4 1.3 2.1

40 0 1 1 0.0 0.6 0.5

50-80 1 7 8 2.6 4.3 4.0

90+ 3 6 9 8.1 3.8 4.6

Total n 37 157 194

F. Social Activity During Surfacing

None 50 144 194 82.0 77.8 78.9

Passive 6 20 26 9.8 10.8 10.6

Active 5 21 26 8.2 11.4 10.6

Total n 61 185 246

G. Aerial Activity During SfclDive Seq.

None 42 166 208 85.7 97.6 95.0

Roll 0 1 1 0.0 0.6 0.5

Flip. slap (FS) 1 1 2 2.0 0.6 0.9

Tail slap (TS) 2 2 4 4.1 1.2 1.8

FS+TS I 0 1 2.0 0.0 0.5

Breach 2 0 2 4.1 0.0 0.9

Breach + FS &JorTS I 0 I 2.0 0.0 0.5

Total n 49 170 219
5.3 Bowheads: Undisturbed Behavior 218

~ Simple left or right turns were more common in subadults than in adults (40% vs. 22%

of surfacings; X

2=6.46, df=2, Pn<0.05). Turns by ~20° were more common in subadults

than in adults (Table 5.15D,E; 32% vs. 16% of surfacings; X

2=4.27, df=l, Pn<0.05)

~ Aerial activities, although uncommon in both groups, were slightly more common in

subadults (Table 5.15G; 14% vs. 2% of surfacings; X

2=8.99, df=l, Pn<O.Ol).

Many other behaviors (listed in Table 5.14) were seen too infrequently for meaningful comparison of their frequencies in adults vs. subadults. However, a considerably higher percentage

of the subadults were traveling parallel to and within 100 m of ice edges (36% of 44 surfacings

by sub adults vs. 13% of 171 surfacings by adults). Also, during dives, subadults were rarely

visible below the surface (7%) whereas adults often were (63%). The latter result may be related

to the larger size and more conspicuous markings of adults, which assist aerial observers in maintaining visual contact with whales migrating a few meters below the water's surface.

These results show that some aspects of surfacing, respiration and dive cycles, along with

some other behavioral variables, differed significantly between sub adult and adult bowheads even

after mothers and calves were excluded from consideration. Thus, caution is necessary when comparing bowhead behavior in situations when the proportions of adults and sub adults are unknown

but potentially varying with location or time.

The situations in which these adults and subadults were observed overlapped strongly, but

with some differences (Table 5.16). There was little difference in dates or times of observation.

For both subadults and adults, most observations were in water 20-49 m deep, but the proportion

of cases in deeper water was slightly higher for subadults (Table 5.16C). There tended to be

slightly more ice near the subadults (Table 5.16D), and more of the subadults had extensive (>1

km) solid ice ahead of them as they dove (Table 5.16E). Sub adults tended to be in smaller groups

than did the adults, and were more often by themselves based on a 5 whale-length criterion (Table

5.17 A,B). The only whales considered here were those classified as traveling, so other activities

were infrequent or absent (Table 5.17C-E).

Some differences in behavior may have been related to the weak tendencies for subadults to

occur in deeper water with more ice. The trends for slower speeds and greater frequencies of

turning by subadults are consistent with heavier ice conditions. However, the tendencies for

shorter dives and markedly shorter blow intervals by subadults are not obviously related to ice.

Mean dive duration and blow interval are both even shorter for calves than for subadults (§5.4),

suggesting that these variables are related to age or size. In general, however, multivariate analysis

is needed to help understand the interrelationships of the many intercorrelated variables.

Variables Correlated with Surfacing, Respiration

and Dive Cycles of Migrating Bowheads

Multiple Regression Methodology.-We used stepwise multiple regression analysis (SMRA)

to identify factors correlated with

~ duration of surfacing,

~ number of blows per surfacing,
5.3 Bowheads: Undisturbed Behavior 219

TABLE 5.16. Circumstances of observations of undisturbed bowhead sub adults and adults

engaged in traveling. Mothers and calves are excluded. Presentation as in Table 5.9.

Number of Surfacings Percentage of Surfacings

Subadult Adult All Subadult Adult All

A. Date

21-30 Apr 0 1 1 0.0 0.5 0.4

1-10 May 20 35 55 30.8 18.5 21.7

11-20 May 44 151 195 67.7 79.9 76.8

21-31 May 1 2 3 1.5 1.1 1.2

Total n 65 189 254

B. Hour (local)

6-8 33 64 97 50.8 33.9 38.2

9-11 8 48 56 12.3 25.4 22.0

12-14 3 42 45 4.6 22.2 17.7

15-17 15 24 39 23.1 12.7 15.4

18-20 6 11 17 9.2 5.8 6.7

21-23 0 0 0 0.0 0.0 0.0

Total n 65 189 254

C. Water Depth (m)

10-19 0 1 1 0.0 0.5 0.4

20-49 54 186 240 83.1 98.4 94.5

50-99 1 0 1 1.5 0.0 0.4

100-250 4 2 6 6.2 1.1 2.4

>250 6 0 6 .9.2 0.0 2.4

Total n 65 189 254

D. Ice Cover (%)

None 3 9 12 4.6 4.8 4.7

1-9 % 18 107 125 27.7 56.6 49.2

10-29 1 2 3 1.5 1.1 1.2

30-59 8 23 31 12.3 12.2 12.2

60-79 22 38 60 33.8 20.1 23.6

80-90 13 10 23 20.0 5.3 9.1

>90 0 0 0 0.0 0.0 0.0

Total n 65 189 254

E. Ice Ahead

None 31 158 189 54.4 87.3 79.4

< 100m 4 4 8 7.0 2.2 3.4

100-1000 m 11 14 25 19.3 7.7 10.5

> 1000m 11 5 16 19.3 2.8 6.7

Total n 57 181 238
5.3 Bowheads: Undisturbed Behavior 220

TABLE 5.17. Frequencies of various group sizes and activities of undisturbed bowhead

subadults and adults engaged in traveling. Mothers and calves excluded. Presentation as

in Table 5.9.

Number of Surfacings Percentage of Surfacings

Subadult Adult All Subadult Adult All

A. Group Size (within 5 body lengths)

I 42 60 102 65.6 32.3 40.8

2 13 84 97 20.3 45.2 38.8

3 9 28 37 14.1 15.1 14.8

4 a 7 7 0.0 3.8 2.8

5 a 5 5 0.0 2.7 2.0

>5 a 2 2 0.0 1.1 0.8

Totaln 64 186 250

B. # Bowheads Within 1 km

1 3 a 3 4.6 0.0 1.2

2 16 5 21 24.6 2.6 8.3

3 20 67 87 30.8 35.4 34.3

4 21 47 68 32.3 24.9 26.8

5 2 11 13 3.1 5.8 5.1

6 a 31 31 0.0 16.4 12.2

7 3 15 18 4.6 7.9 7.1

8 a 13 13 0.0 6.9 5.1

>8 a a a 0.0 0.0 0.0

Total n 65 189 254

C. Whale Activity This SfclDive Sequence

Rest 2 1 3 3.1 0.5 1.2

Travel 50 163 213 76.9 86.2 83.9

Socialize a a a 0.0 0.0 0.0

Feed 2 a 2 3.1 0.0 0.8

Travel+Social 4 20 24 6.2 10.6 9.4

Travel-Feed a a a 0.0 0.0 0.0

Social+Feed a a a 0.0 0.0 0.0

Unknown/Other 7 5 12 10.8 2.6 4.7

Total n 65 189 254

D. Group's Predominant Feeding Mode

None 65 189 254 100.0 100.0 100.0

Water-column a a a 0.0 0.0 0.0

Bottom a a a 0.0 0.0 0.0

Near-surface a a a 0.0 0.0 0.0

Total n 65 189 254

E. Whale's Feeding Mode During This SfclDive Sequence

None 58 184 242 96.7 98.9 98.4

Water-column 2 2 4 3.3 1.1 1.6

Bottom a a a 0.0 0.0 0.0

Near-surface a a a 0.0 0.0 0.0

Total n 60 186 246
5.3 Bowheads: Undisturbed Behavior 221

~ average interval between successive blows, and

~ duration of dive

in migrating bowhead whales. These four dependent variables were each log-transformed to

reduce skewing of residuals.

The SMRA methods used 10 this analysis were generally consistent with those used in

previous studies of bowhead behavior (Dorsey et al. 1989; Richardson et al. 1995). However,

some predictor variables were new or defined differently. Also, criteria for deciding which cases

to include in the analysis were defined differently, in order to restrict the analysis to a relatively

homogeneous dataset concerning actively-migrating bowheads.

A total of 25 variables, some of which were closely interrelated, were considered as potential

predictors of surfacing, respiration and dive behavior:

~ year = 1990? = 1991? = 1994? (3 measures, each 0 for no or 1 for yes),

~ date in May (1-31) and date-squared

~ decimal hour (0-23.99, local daylight time) and hour-squared,

~ ice cover (5 measures),

~ percent ice cover within observation circle (0-100%),

~ >5% cover (1) or not (0),

~ moderate extent (0.1-1 km) of solid ice ahead as whale dives (1) or not (0),

~ large extent (>1 km) of solid ice ahead as whale dives (1) or not (0),

~ whale emerges from under ice at start of surfacing or end of dive,

~ sea state (0-6),

~ distance from shore (in kilometers, log transformed),

~ water depth (in meters, log transformed),

~ general activity travel-t-socializing (1) or travel (0),

~ current activity travel+socializing (1) or not (0),

~ current activity resting (1) or not (0),

~ group size (1-6),

~ number of bowheads within circle of -1 km radius (1-9),

~ number of bowheads within -5 km (1-30),

~ passive socializing during this surfacing (1) or not (0),

~ flukes out as whale dove (1) or not (0),

~ known to be adult (1) or not (0),

~ known to be subadult (1) or not (0)

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 1989, that year was established as the

standard year against which others were compared. Date (in days after 30 April), date", hour and

hour- were included to allow for possible non-linear temporal effects.

In these analyses, each surfacing or dive for which all requisite variables were known

constituted a case. Case selection criteria were established to include observations typical of

traveling (i.e. actively migrating) bowhead whales, the predominant category of bowheads

observed near Barrow in spring. These criteria excluded cases when the whale was actively
5.3 Bowheads: Undisturbed Behavior 222

socializing or engaged in aerial activity. Calves, their mothers, and potentially disturbed whales

were also excluded. More specifically, cases included in the analysis met the following criteria:

~ whale group classified as traveling or traveling+socializing,

~ individual whale's present activity classed as traveling, traveling+socializing, or resting,

~ no active socializing or aerial activity during the present surfacing or dive,

~ whale was not a calf, yearling, or accompanying adult (presumed mother),

~ presumably undisturbed; no known potential disturbance in previous 30 min.

Predictor variables were entered into the SMRA model one at a time in descending order of

partial correlation until no remaining variable, if included, would improve the predictability of the

dependent variable by an amount significant at the nominal P<0.05 level. After running the

analyses with BMDP2R (Release 7.0 Dynamic, Dixon 1992), we examined scatter plots of

residuals vs. all predictors to check for violations of assumptions (Draper and Smith 1981). For

each case, the residual is the difference between the actual value of the dependent variable and the

value predicted by the SMRA model. Analysis of residuals allows one to check for previously

unrecognized non-linear effects and certain violations of the equality of variance assumption.

We also analyzed the residuals to evaluate whether there was any indication of partial

correlation between the dependent variable and swimming speed or occurrence of turns, after

allowance for all the variables mentioned above. Swimming speed and occurrence of turns were

not included in the main SMRA because they were sometimes unknown, and their inclusion in the

main analysis would have reduced the sample size to an undesirable degree. (All variables

considered as potential predictors must be known for each case included in the main SMRA.)

Results of the SMRAs on the four dependent variables are summarized in Table 5.19, later.

This table summarizes both simple and partial correlations of all predictor variables with each of

the four dependent variables. Nominal significance levels are coded as

***, +++ or - - - if P~O.OOI, **, ++ or - - if O.OO1<P~O.OI,

*, + or - if 0.01<P~0.05, ns if P>0.05.

Plus or minus signs are used to indicate direction as well as significance of relationship, e.g. ---

means a negative trend with nominal P~O.OO1. Simple and partial correlation coefficients are

indicated, respectively, by "r" and "rp". The quoted "percent of variance explained" is the adjusted

percent, allowing for sample size (Dixon 1992). Trends stated to be "strong" are those with

nominal P~O.OI.

Little emphasis is given to correlations with nominal P>O.OI, given (1) the large number of

tests done, (2) the tendency, in SMRAs, for nominal P-values to overestimate the value of

individual variables as predictors (Draper and Smith 1981 :310), and (3) the frequent inclusion of

data from more than one surfacing or dive of a given whale. The number of repeated observations

of specific whales is unknown, as it was often impossible to re-identify whales from one surfacing

to another. In addition, any multivariate analysis has important limitations when applied to

uncontrolled field data with many intercorrelated predictor variables (e.g., James and McCulloch

1990). In the absence of experimental control over the environmental variables, it is usually

impossible to identify with certainty which correlations represent direct causative links and which

ones are incidental side-effects of intercorrelations among predictor variables.
Duration

of

Surfacing

Number of

Blows per

Surfacing

Median

Blow

Interval

Duration of

Preceding

Dive

Duration of

Following

Dive

5.3 Bowheads: Undisturbed Behavior 223

TABLE5.18. Simple correlations among various measures of surfacing, respiration, and dive

cycles. Correlations are shown based on both (A) original variables and (B) logarithmicallytransformed variables. We consider the durations of both the dive preceding and the dive

following the surfacing in question. Sample size ranges from 158 to 345; values of Irl>0.17 are

significant at the a=0.05 level or better.

A. ORIGINAL VALUES

Duration of Surfacing (min)

No. Blows per Surfacing

Median Blow Interval (s)

Duration of Preceding Dive (min) _

Duration of Following Dive (min)

0.867 0.284

0.318

-0.135

0.329

0.867

0.079

0.286

0.284

-0.387

0.456

0.318

B. LOG-TRANSFORMED VALUES

Duration of Surfacing

No. Blows per Surfacing

Median Blow Interval

Duration of Preceding Dive

Duration of Following Dive

0.868 0.242

0.279

-0.026

0.257

0.868

0.158

0.297

0.242

-0.392

0.450

0.279

In reviewing the following interpretations of SMRA results, one should recall that there are

intercorrelations among the various measures of surfacing, respiration, and diving cycles (Table

5.18). For example, long surfacings show a strong tendency to have many blows (r=0.867), and

weak tendencies to be preceded and followed by long dives (r=0.286, and r=0.284). Surfacings

with many blows tend to have short blow intervals (r=-0.387).

Factors Related to Durations of Surfacings.-Durations of surfacings by traveling bowheads

were not strongly correlated with anyone of the predictor variables (Table 5.19A, simple correlation column). However, after allowance for other variables, there were a few significant (Pn<O.OI)

trends. Surfacings tended to be short in 1991 and when there was some socializing intermixed

with traveling (see also Fig. 5.28C). Surfacings tended to be long in the presence of much ice,

and when the surfacing terminated with raised flukes. After allowance for other variables, there

were also weak tendencies for longer surfacings with high sea states and for adults. Overall,

however, only a small percentage (8%) of the variance in surface times could be explained by this

combination of predictor variables.

Interestingly, the variables with the strongest partial correlations to duration of surfacing

(Pn<O.OOl) were the occurrence of a change in swimming speed and the occurrence and magnitude

of turns during the surfacing. These correlations are perhaps to be expected, as the longer the

surfacing, the more the opportunity for a change in speed or a turn during the surfacing.

Factors Related to Number of Blows per Surfacing.- There were strong positive correlations

between number of blows per surfacing and ice cover. There were strong (Pn<O.Ol) simple
Duration of dive (min)

5.3 Bowheads: Undisturbed Behavior 224

C. Median blow

interval (s)"

,

r,

TABLE 5.19. Correlations between (a) four surfacing, respiration, and dive variables in traveling' bowhead whales, and (b) various

environmental and whale activity variables. Each pair of columns shows the direction and nominal significance of simple (r) and partial (r,)

correlations between a dependent variable (top) and various environmental and whale activity variables (predictors, left)." Bottom section

of table shows "partial correlations" with variables that could not be included in the overall multiple regression analyses.'

Predictor Variable

A. Duration of

surfacing (min) "

r r:

B. No. Blows!

surfacing (+1)"

r r r '

p

r r'

p

r

d

p

r

Year = 1990' +++

Year = 1991 •

Year = 1994'

Date (1=1 May)

Date squared

Hour (0-24)

Hour squared

Ice cover (%)

>5% ice cover? •

Moderate ice ahead"

Extensive ice ahead"

Emerge from under ice"

Sea state (SS 0-6)

Dist. offshore (log km)

Water depth (log m)

Gen. activo trav.s-social"

Cur. activo trav.s-social"

Cur. activ. rest e

Group size (1-6)

No. bhd within 1 km (1-9)

No. bhd within 5 km (1-30)

Passive socializing? •

Flukes out as diving? •

Adult? •

Subadult? •

ns

+

ns

ns

ns

ns

ns

ns

+

ns

ns

++

ns

ns

ns

ns

ns

ns

ns

+++

++

+++

ns

++

++

++

+++

ns

+

+

ns

ns

ns

+

+++

ns

ns

ns

++

++

ns

ns

ns

ns

ns

ns

ns

ns

+

ns

ns

++

+

+ +

ns

ns

++

+ ns

+++ ++

+++

+

ns

ns

ns

ns

ns

ns

ns

ns

ns

ns

+

ns

ns

ns

ns

ns

+

ns

ns

ns

ns

++

ns

ns

ns

ns

+++ ns

ns

ns

ns

ns

ns

ns

ns

ns

ns

ns

ns

ns

ns

ns

ns

ns

ns

ns

+

ns

+ ns

ns

Sample size r

Multiple correlation

Adjusted % variance explained

Overall significance (nominal)

367 367

0.312

8.0

***

356 356

0.353

11.0

***

418 418

0.489

22.6

***

213 213

0.378

12.7

***

227 227

0.330

9.3

***

Residuals vs. Other Variables •

Speed slow(O) vs. moder.(l)

Speed change"

Turn: 0,1 or>1

Degrees of turn (log)

n=319 ns

n=344 +++'

n=360 +++'

n=352 +++

n=310 ns

n=335 +++'

n=355 +++'

n=353 +++

n=369 ns

n=405 ns

n=351 ns

n=311 ns

n=195 ns

n=209 ns

n=213 ns

n=210 ns

n=205 ns

n=218 ns

n=215 *'

n=211 ns

, Whales included were those whose general activity was traveling or "traveling+socia1izing", and whose activity during the current surfacing or dive was

resting, traveling or "traveling+socia1izing", excluding mothers, calves, and all surfacings with active socia1izing or aerial activity.

• The four dependent variables were all log transformed to avoid skewness. Pluses indicate positive correlations; minuses indicate significant negative

relationships. Number of +, • or· symbols indicates nominal significance level: +++, - _. or·" means P,<=O.OOI; ++, •• or·· means P.<=O.OI;

and +,. or· means p.<=O.OS .

• Separate analyses were done for durations of dives preceding and following the surfacing under consideration.

, Partial correlations are shown only for variables recognized as significant (nominal P <= 0.05) by stepwise multiple regression .

• 0 = false; I = true.

r Number of surfacings or dives for which all of the listed predictor variables were known.

• Potential predictor variable excluded from multiple regression because often unknown. t-test or ANOV A results summarized here indicate whether

this predictor, if it could be in the multiple regression model, would be of significant value in accounting for otherwise-unexplained residual variance.
5.3 Bowheads: Undisturbed Behavior 225

correlations with 4 of 5 measures of ice cover. Two of these remained evident as partial

correlations after allowance for other variables (Table 5.19B).

Another noteworthy partial correlation (Pn<O.Ol) was for fewer blows per surfacing when

some socializing was occurring. This effect was not evident until effects of other variables were

taken into account (Fig. 5.28; Table 5.19B). There were also weak tendencies for more blows

during surfacings when the whales rested or when they raised their flukes as they dove.

Despite these several seemingly-significant relationships, the multiple regression model

accounted for only 11% of the variance in the number of blows per surfacing.

Number of blows per surfacing, like duration of surfacing, showed strong partial correlations

with some of the variables not included in the SMRA model: the occurrence of a change in speed

and with the occurrence and magnitude of turn(s) during the surfacing.

Factors Related to Median Blow Intervals.-Several potential predictor variables had strong

simple correlations with the median blow interval, and a smaller number had strong partial correlations (Table 5.19C). As a result, the SMRA model accounted for more of the variance in median

blow interval (22.6%) than in durations of surfacings or number of blows per surfacing.

Median blow interval tended to diminish with increasing ice cover, sea state, distance from

shore, and water depth. There were also tendencies for long blow intervals in 1990 and short blow

intervals in 1994. Many of these potential predictor variables were also intercorrelated with one

another. It is uncertain which of these interrelated predictor variable(s) were most directly related

to median blow interval. However, the most parsimonious SMRA model included terms

representing strong (Pn<O.OOI) tendencies for short blow intervals with >5% ice cover and with

increasing distance offshore.

Median blow interval tended to be short when socializing was intermixed with travel (see

also Fig. 5.28A) but long with larger group size. Interestingly, blow intervals tended to be short

when the current whale activity was resting. This trend was still significant (Pn<O.OI) after

allowance for other predictors, indicating that bowheads resting briefly during travel tended to

have shorter blow intervals than did actively traveling bowheads. In contrast, bowheads whose

general activity was resting (not travel) tended to have very long blow intervals (Table 5.12).

The previously-recognized tendency for known adults to have longer blow intervals than

known subadults (Fig. 5.30A) was still significant after allowing for other variables (Table 5.19C).

Factors Related to Durations of Dives.-Table 5.19D,E shows relationships of potential

predictor variables recorded during a surfacing with the durations of the dives preceding and

following that surfacing. The percentages of the variation in dive duration explained by these

models was low, 12.7% and 9.3% respectively.

Dive durations documented in this study tended to be long in 1990 and short in 1991 and

1994 relative to those in 1989. This probably was at least partly an artifact of year-to-year
5.3 Bowheads: Undisturbed Behavior 226

differences in our ability to relocate and reidentify whales after long dives; there mayor may not

have been real differences in average dive duration among years. Observation conditions tended

to be good in 1990, with most whales in well defined but narrow leads amidst the ice and with low

sea states; and poor in 1994, with high sea states. Recorded dive durations tended to be shorter

with high sea state.

When the whale emerged from under ice at the start of the surfacing, the duration of the dive

preceding the surfacing tended to be long (Pn<O.OOl). Not surprisingly, duration of the dive subsequent to the surfacing was not related to the "emerge from under ice" variable. However, duration of subsequent dive was weakly and negatively related to occurrence of raised flukes as the

whale dove. The tendency for longer dives by adults than sub adults (Fig. 5.30D) was only weakly

evident in this analysis, and was not evident after allowing for other variables (Table 5.19D,E).

Relationship Patterns.-The cases considered in deriving the SMRA models represent

actively migrating bowheads that were not actively socializing, feeding, or exhibiting aerial

behavior. Calves and their mothers were also excluded. The low percentages of the variance

"explainable" by the SMRA models are doubtless partly attributable to the homogeneous dataset.

Temporal Variables: The first seven lines of Table 5.19 show correlations of surfacing,

respiration and dive variables with year, date, and time of day. Some year-to-year differences

were evident, especially for blow intervals and dive durations. As noted above, at least some of

these trends probably represented observation artifacts. Correlations of surfacing, respiration and

dive variables with date and time of day were lacking or, at most, weak.

Ice: The five lines in Table 5.19 dealing with various measures of ice cover show strong

tendencies for more blows per surfacing and short blow intervals in areas with much ice. Ice

effects on duration of surfacing and dives were less evident but there was some indication of

longer surfacings and dives with much ice. The greater number of blows per surfacing when there

is much ice may represent a tendency for bowheads to prepare for long dives when there is much

ice. The shorter blow intervals with much ice are probably related to our subjective impression

that traveling bowheads often respire at briefer-than-average intervals when they surface in a small

opening in the ice. This increases the number of breaths that can be taken before the traveling

whale reaches the ice at the other side of the open water area and is forced to dive under the ice

or to interrupt its travel.

Whale Activity and Group Size: When socializing was intermixed with travel, surfacings and

to a lesser degree dives tended to be shorter, with shorter intervals between blows (Fig. 5.28; Table

5.19). After allowance for the effects of other variables, the number of blows per surfacing also

tended to be lower when there was some socializing. However, there was little evidence that

surfacing-respiration-dive cycles were affected by the occurrence of "passive socializing"

(whales swimming in parallel and within Y2 body length). Traveling bowheads that were (briefly)

resting during the surfacing in question tended to have short blow intervals relative to those of

actively traveling whales although bowheads resting for more prolonged periods had long blow

intervals. Median blow interval was the only variable related to group size.
5.3 Bowheads: Undisturbed Behavior 227

Fluke-out Dives: Raised flukes at the end of a surfacing are sometimes taken as an indication

of probable deep diving, and deep dives tend to be long. However, in spring raised flukes were

not very common (Table 5.13B), and among actively migrating bowheads there was a weak

tendency for shorter, not longer, dives with raised flukes. There were, nonetheless, tendencies for

surfacings terminated with raised flukes to be longer and perhaps to have more blows.

Subadults and Adults: Traveling adults had longer blow intervals and longer dives than did

subadults, according to univariate analysis (Fig. 5.30). After allowance for other variables, adults

again had longer blow intervals (Pn<O.OOI), along with slightly longer surfacings and dives

(Pn<0.05), than did subadults. A weak univariate tendency for fewer blows per surfacing in adults

than in subadults was not evident after allowance for other variables.

These results suggest that a typical surfacing-dive cycle by a migrating adult is longer than

that for a migrating subadult. Adults presumably would tend to travel farther per surfacing-dive

sequence, especially if adults tend to travel faster (Table 5.15A).

Sexual Activity

Distinct bouts of definite or presumed sexual activity were seen in the study area four times

during the four spring seasons: twice in 1989, once in 1990, and once in 1994. All occurred

before or on 10 May.

In 1989, on 3 May, a group of at least 4 whales socialized by rolling together, creating

whitewater, in a manner similar to that described by Everitt and Krogman (1979). This activity,

which lasted for at least 4.2 min, was the most active socializing we saw in May 1989. We

surmise that mating was occurring based on the similarity of the behavior to mating seen in

bowheads (Everitt and Krogman 1979), right whales (Payne and Dorsey 1983), and gray whales

(Norris et al. 1983). However, it was not possible to determine the sex of any individual during

this brief observation. Several other bouts of probable sexual activity were seen on 3 May. At

four times, we saw pairs of whales with ventrums touching for 5 to 67 s. In three cases, the

whales appeared to be "stuck together" with no forward motion. One whale was dorsum up near

the surface and the other ventrum up below it. In the fourth case, the two whales traveled forward

slowly while ventrum to ventrum.

On 6 May 1989, we watched for 6 min as a pair of bowheads socialized, generally at low

intensity and positioned side by side. At one point, the lower whale turned ventrum up, half-way

underneath the dorsum-up whale. We clearly saw a penis snaking toward the belly of the dorsumup animal. The two stayed in this position, with no forward motion, for -14 s, but we do not

know if copulation took place. A third whale was -120 m from the sexually-active pair, and was

not seen to interact with the pair.

On 10 May 1990, five bowheads engaged in active sexual activity and other social interactions as they traveled gradually northeast near the north (pack ice) side of the main nearshore

lead. At one time the extended penises of two males were seen at the same time as the two whales

oriented toward a third whale. That third whale was often belly-up, seemingly attempting to avoid
5.3 Bowheads: Undisturbed Behavior 228

the two males. At other times, whales were visible belly-up below the third whale. This active

sexual activity was evident for at least 40 min, and other social interactions continued thereafter.

In 1991, sexual activity was not noticed during our few brief behavioral observation sessions.

In 1994, we saw apparent sexual activity once, on 7 May. An adult female rolled belly up

(allowing sex to be ascertained), with one animal touching her side briefly and a third individual

rolling, belly up briefly, underneath the female. The apparent sexual activity lasted for only 4

min, but other social activity continued for another 1.5 hours (when we left the area), and this may

have included sexual activity as well.

Our brief views of sexual activity in early May reinforce the general impression that mating

occurs in spring, and wanes in frequency thereafter (Nerini et al. 1984; Koski et al. 1993). Since

we witnessed apparent mating during only 4 of 76 observation sessions, it is likely that most

mating was over by the time we began our spring work in late April or early May. Although the

main mating season is believed to be in spring, much mating by bowhead whales of this population

was seen in September-October 1988 in the eastern Beaufort Sea (Wiirsig et al. 1993).

5.4 Mother and Calf Behavior

Bowhead mothers and calves were seen in the study area primarily during the latter half of

May (§5.1). Systematic behavioral observations were obtained on "presumably undisturbed"

mothers and calves during several dates in mid- and late May of 1989, 1990 and 1991. Circumstances in which we obtained systematic behavioral observations of calves, mothers and other

whales are summarized in Tables 5.20 and 5.21.

Bowheads probably calve from about March to July (Nerini et al. 1984; Koski et al. 1993).

Thus, calves encountered during May vary in age from newborn to about three months. These

calves are smaller and younger than those whose behavior has been documented during previous

late summer and early autumn studies. Thus, calf behavior in spring is expected to differ from that

documented previously. There is the additional possibility that behavior in spring may vary among

mother-calf pairs depending on the size (=age) of the calf.

Migration and Lingering by Mothers and Calves

Movements of mother-calf pairs were less consistently northeastward or eastward than were

those of other bowheads. Traveling whales followed lead systems when leads were available, and

deviations in their generally NE or E courses were related to changes in orientations of leads or

cracks. Mother-calf pairs often behaved in a similar manner. However, sometimes they lingered

in one area for a prolonged period, or even moved west. We obtained three types of evidence on

this point: observations of whale headings, observations of behavior during extended behavioral

observation sessions, and re-identifications from day to day based on photoidentification.

Headings.- The headings of bowhead groups when they were first encountered are summarized in Table 5.2 for groups containing one or more mother-calf pairs and in Table 5.1 for all groups
5.4 Bowheads: Mother-Calf Behavior 229

TABLE 5.20. Circumstances of observations of undisturbed bowhead calves, mothers and others. Calves and mothers that are and

are not nursing are shown separately. Table shows numbers of surfacings during spring migration near Barrow, AK, 1989-94, as

observed from a Twin Otter aircraft. 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.

Calves Mothers Other Whales

Traveling Other Activ. Traveling Other Activ. Trav- Other

Not Nurse Not Nurse AJI Not Nurse Not Nurse AJI eling Actjx All

A. Date

21-30 Apr 0 0 0 0 0 0 0 0 0 0 9 7 16

1-10May 0 0 0 0 0 0 0 0 0 0 193 213 406

11-20 May 26 0 0 0 26 8 0 0 0 8 394 99 493

21-31 May 147 25 81 16 269 55 16 20 7 98 23 10 33

Total n 173 25 81 16 295 63 16 20 7 106 619 329 948

B. Hour (local)

6-8 0 0 0 0 0 0 0 0 0 0 I 3 4

9-11 35 8 27 4 74 24 5 8 2 39 184 110 294

12-14 3 0 46 10 59 3 0 10 4 17 151 150 301

15-17 53 12 8 2 75 11 7 2 I 21 119 51 170

18-20 71 4 0 0 75 21 3 0 0 24 105 15 120

21-23 11 1 0 0 12 4 1 0 0 5 59 0 59

Total n 173 25 81 16 295 63 16 20 7 106 619 329 948

C. Water Depth (m)

10-19 0 0 0 0 0 0 0 0 0 0 23 15 38

20-49 31 8 0 0 39 20 5 0 0 25 523 244 767

50-99 0 0 20 1 21 . 0 0 5 1 6 37 5 42

100-250 82 0 31 1 114 25 0 10 1 36 28 61 89

>250 60 17 30 14 121 18 11 5 5 39 8 4 12

Total n 173 25 81 16 295 63 16 20 7 106 619 329 948

D. Ice Cover (%)

0 22 0 0 0 22 7 0 0 0 7 43 1 44

1-9 % 30 0 0 0 30 6 0 0 0 6 226 29 255

10-29 26 0 0 0 26 8 0 0 0 8 67 10 77

30-59 31 8 0 0 39 20 5 0 0 25 85 92 177

60-79 4 0 0 0 4 4 0 0 0 4 125 112 237

80-90 60 17 81 16 174 18 11 20 7 56 63 62 125

>90 0 0 0 0 0 0 0 0 0 0 10 23 33

Total n 173 25 81 16 295 63 16 20 7 106 619 329 948

E. Ice Ahead

None 121 25 61 16 223 44 6 17 2 69 420 185 605

<100m 21 0 1 0 22 7 4 0 0 11 14 6 20

100-1000 m 14 0 6 0 20 4 3 1 0 8 59 25 84

>1000m 0 0 0 0 0 0 0 0 0 0 34 13 47

Total n 156 25 68 16 265 55 13 18 2 88 527 229 756
5.4 Bowheads: Mother-Calf Behavior 230

TABLE 5.21. Frequencies of various group sizes and activities of undisturbed bowhead calves, mothers and others.

Presentation as in Table 5.20.

Calves Mothers Other Whales

Traveling Other Actiy Traveling Other Activ. Trav- Other

Not Nurse Not Nurse All Not Nurse Not Nurse All eling Actjy All

A. Group Size (within 5 adult lengths)

I 13 0 12 0 25 0 0 0 0 0 288 100 388

2 160 25 69 16 270 63 16 20 7 106 195 82 277

3 0 0 0 0 0 0 0 0 0 0 74 37 111

4 0 0 0 0 0 0 0 0 0 0 31 76 107

5 0 0 0 0 0 0 0 0 0 0 6 27 33

>5 0 0 0 0 0 0 0 0 0 0 8 1 9

Total n 173 25 81 16 295 63 16 20 7 106 602 323 92S

B. # Bowheads Within I krn

1 0 0 0 0 0 0 0 0 0 0 29 32 61

2 142 17 81 16 256 43 II 20 7 81 77 6 83

3 0 0 0 0 0 0 0 0 0 0 197 54 251

4 31 8 0 0 39 20 5 0 0 25 120 35 155

5 0 0 0 0 0 0 0 0 0 0 47 34 81

6 0 0 0 0 0 0 0 0 0 0 52 82 134

7 0 0 0 0 0 0 0 0 0 0 73 0 73

8 0 0 0 0 0 0 0 0 0 0 24 0 24

>8 0 0 0 0 0 0 0 0 0 0 0 86 86

Total n 173 25 81 16 295 63 16 20 7 106 619 329 948

C. Whale Activity This SfclDive Sequence

Rest 0 0 20 0 20 0 0 2 I 3 8 8 16

Travel 166 4 27 1 198 61 12 6 0 79 517 113 630

Socialize 0 0 0 0 0 0 0 0 0 0 9 96 105

Feed 0 0 0 14 14 0 0 I 4 5 2 7 9

Travel-Social 0 0 0 0 0 0 0 0 0 0 41 44 85

Travel+Feed 0 17 0 0 17 0 0 0 0 0 0 7 7

Social+Feed 0 0 0 0 0 0 0 0 0 0 0 I 1

Unknown/Other 7 4 34 I 46 2 4 II 2 19 42 53 95

Total n 173 25 81 16 295 63 16 20 7 106 619 329 948

D. Group's Predominant Feeding Mode

None 173 25 60 5 263 63 16 17 3 99 619 296 915

Water-column 0 0 0 0 0 0 0 0 0 0 0 19 19

Bottom 0 0 14 10 24 0 0 1 4 5 0 8 8

Near-surface 0 0 0 0 0 0 0 0 0 0 0 0 0

Total n 173 25 74 15 1E7 63 16 18 7 104 619 323 942

E. Whale's Feeding Mode During This SfclDive Sequence

None 169 4 80 1 2S4 63 16 17 3 99 573 289 862

Water-column 0 0 0 0 0 0 0 0 0 0 4 8 12

Bottom 0 0 0 0 0 0 0 I 4 5 0 7 7

Near-surface 0 0 0 0 0 0 0 0 0 0 0 0 0

Total n 169 4 80 254 63 16 18 7 104 577 304 881
5.4 Bowheads: Mother-Calf Behavior 231

(§5.1, p. 140-1). The vector mean heading for both categories of bowhead groups was eastward.

However, the proportion of the groups headed in directions other than 50-1200T was higher for

mother-calf groups (15 of 35 or 43%) than for other groups (134 of 782 groups or 17%). This

difference is further shown by the fact that the angular deviation of the headings (method of

Batschelet 1981:276) was 65° for mother-calf groups vs. 37° for all groups. The angular deviation

of headings was larger for mother-calf groups than for all groups during each year, 10-day period,

and part of the study area with a meaningful sample size" (Table 5.2 vs. 5.1).

Headings were also recorded during systematic behavioral observation sessions, with heading

being noted at the start of each surfacing and dive. Tables 5.22 and 5.10 (p. 202) show these

heading data for mothers and for bowheads other than mother-calf pairs during "presumably undisturbed" conditions. The vector mean heading was to the NE, E or ESE for both mother-calf pairs

and other bowheads during all years. However, the angular deviation was 59° for mothers but only

40° for bowheads exclusive of mothers and calves. Considering only traveling bowheads, the

headings were more consistently eastward, but the angular deviation remained somewhat higher

for traveling mothers (44°) than for traveling bowheads exclusive of mothers and calves (31°).

Mothers engaged in "other/unknown" activities (including nursing) had highly variable headings

(angular deviation 72°). Bowheads other than mothers and calves, when classed as resting or

"other/unknown", also tended to have unusual or variable headings. However, these activities with

unusual or variable headings accounted for a higher proportion of the surfacings and dives by

mothers (26%) than of those by other bowheads (7%).

Behavioral Observations in 1989.-1n 1989, we observed the behavior of three mother-calf

pairs during periods when no known source of potential disturbance was present.

1,2. The first two pairs were observed from 9:36 to 11:45 on 27 Mayas they moved generally east

along the north edge of the lead through open water or, at most, light pack ice. Lengths of whales

(1)-(4) were, respectively, 4.8, 15.9,4.9 and 15.7 m. Calves are 4.0-4.5 m long when born, so

these calves were among the older calves seen in spring (§5.2). Both pairs moved steadily at

moderate to slow speed and followed along or just inside the southern edge of the pack ice.

Average rates of movement of whales 1 & 2 and 3 & 4 were 5.1 and 4.8 km/h, respectivelysimilar to mean short-term rates of movement recorded during previous studies of all bowheads

(5.0 km/h-Koski and Davis 1980; 5.1 km/h-Rugh 1987) and mother-calf pairs near Barrow (4.8

km/h "best duplicate" speeds without current compensation-George and Carroll 1987).

3. The third mother-calf pair was observed on 27, 28 and 29 May 1989. Their identity was confirmed by vertical photographs taken after each day's behavioral observations were completed. The

lengths of this mother and calf were 14.9 and 4.0 m. This calf, one of the smallest calves that

has been measured photogrammetrically, was probably recently-born. From their initial position

at 19:30 h on 27 May, this mother-calf pair moved 11.5 km NE over a 44.2 h period (Fig. 5.25,

p. 186). Their net rate of movement was 0.27 km/h." During the observations on 28 May this

19 Excluding two situations with extremely small sample sizes «3).

20 Rugh (1987) noted that whales that travel slowly or deviate from their migration route are more likely

to be re-photographed on a later date than are whales that migrate steadily. Steadily migrating whales

would pass through our study area in -Y2 day, and thereafter would not be present to be rephotographed.
TABLE 5.22. Headings (True) of bowhead mothers observed during behavioral observation sessions.

Excludes potentially disturbed mothers. Each surfacing and dive with a known heading is counted separately.

A. By Year, All Bowhead Mothers B. By Group Activ., All Mothers C. By Year, Traveling Bowhead Mothers

True Other True

Heading 1989 1990 1991 1994 TOTAL Rest Travel & Unk TOTAL 1989 1990 1991 1994 TOTAL Heading

o N 6 3 0 0 9 1 6 2 9 4 2 0 0 6 N 0

10 1 2 0 0 3 0 1 2 3 0 1 0 0 1 10

20 2 0 0 0 2 0 2 0 2 2 0 0 0 2 20

30 8 3 0 0 11 0 10 1 11 8 2 0 0 10 30

40 4 9 0 0 13 0 8 5 13 2 6 0 0 8 40

50 0 6 0 0 6 0 6 0 6 0 6 0 0 6 50

60 0 8 3 0 11 0 11 0 11 0 8 3 0 11 60

70 4 6 8 0 18 0 18 0 18 4 6 8 0 18 70

80 2 2 0 0 4 0 4 0 4 2 2 0 0 4 80

90E 3 6 4 0 13 0 13 0 13 3 6 4 0 13 E90

100 2 1 0 0 3 0 3 0 3 2 1 0 0 3 100

110 5 13 0 0 18 0 17 1 18 4 13 0 0 17 110

120 6 1 0 0 7 0 5 2 7 4 1 0 0 5 120

130 7 7 0 0 14 0 11 3 14 7 4 0 0 11 130

140 8 1 0 0 9 0 9 0 9 8 1 0 0 9 140

150 0 0 0 0 0 0 0 0 0 0 0 0 0 0 150

160 1 2 0 0 3 0 2 1 3 0 2 0 0 2 160

170 0 0 0 0 0 0 0 0 0 0 0 0 0 0 170

180 8 2 0 0 0 2 0 0 2 2 0 0 0 0 0 8180

190 0 1 0 0 1 0 0 1 1 0 0 0 0 0 190

200 2 1 0 0 3 0 3 0 3 2 1 0 0 3 200

210 1 0 0 0 1 0 0 1 1 0 0 0 0 0 210

220 0 0 0 0 0 0 0 0 0 0 0 0 0 0 220

230 0 0 0 0 0 0 0 0 0 0 0 0 0 0 230 ~

240 6 0 0 0 6 0 0 6 6 0 0 0 0 0 240 ~

250 2 0 0 0 2 0 0 2 2 0 0 0 0 0 250 b:l

()

260 2 2 0 0 4 2 0 2 4 0 0 0 0 0 260 ~

270 W 2 0 0 0 2 0 0 2 2 0 0 0 0 0 W 270 ;:-

" 280 2 0 0 0 2 0 0 2 2 0 0 0 0 0 280 l:l

290 0 0 0 0 0 0 0 0 0 0 0 0 0 0 290 ~

300 4 2 0 0 6 2 2 2 6 2 0 0 0 2 300

~ 310 1 0 0 0 1 0 0 1 1 0 0 0 0 0 310 So

320 1 0 0 0 1 0 0 1 1 0 0 0 0 0 320

"

330 0 4 0 0 4 0 2 2 4 0 2 0 0 2 330 ';'

~ 340 0 0 0 0 0 0 0 0 0 0 0 0 0 0 340 .:;;

350 0 0 0 0 0 0 0 0 0 0 0 0 0 0 350 b:l

Total 84 80 15 0 179 5 133 41 179 54 64 15 0 133 Total "

;:-

Vector l:l

~

Mean 93 73 73 78 294 81 277 78 89 78 73 81 5'

.,

Length 0.24 0.62 0.98 0.46 0.81 0.71 0.21 0.46 0.59 0.76 0.98 0.71

Ang. Dev. 71 50 11 59 35 44 72 59 52 40 11 44 IV

v.>

IV

~~~~~. -- ------- --~~----
5.4 Bowheads: Mother-Calf Behavior 233

pair meandered generally southwestward. On 29 May they were several kilometers NNW of the

location where they last seen on 28 May (Fig. 5.25).

In only one other case did we obtain direct behavioral observations of bowheads moving generally west in 1989, also involving a mother-calf pair. That observation was during a drilling

noise playback, and the westward movement may have been attributable to disturbance.

The back and forth movements of the mother and calf on 28 and 29 May 1989 (Fig. 5.25)

may have been related to the overall heavy ice cover east of their locations. We presume that a

small calf cannot travel as far under ice as can a larger whale, and that a small calf may be unable

to surface through some new ice or brash ice that poses no obstacle to a larger whale. On both

28 and 29 May, the mother-calf pair was in an open water area among large ice pans and brash ice.

Similar open water areas were absent east and northeast of their locations.

Behavioral Observations in 1990.-ln 1990, the behavior of five presumably undisturbed

mother-calf pairs was observed systematically for a total of 9.3 h during five different aerial

observation sessions on 23-25 May. (Several other pairs were seen briefly.) Of the five pairs

studied, two were actively migrating throughout the observations, one pair changed behavior from

milling in one area to active migration, and the other two pairs were not actively migrating:

1. An actively migrating mother and calf were observed under undisturbed conditions for 0.9 h on

23 May ("23" in Fig. 5.16). They traveled steadily ENE at medium speed in the largely open

water of the main nearshore lead, but within a few hundred meters of the pack ice edge forming

its north side. During most dives, the mother remained faintly visible below the surface, and the

calf "rode" on her back (see below for discussion of riding).

2. An actively migrating mother and calf were observed for 3.5 h on 24 May. They traveled east

through moderately heavy pack ice, averaging 80% cover, far offshore NNE of Pt. Barrow ("24"

in Fig. 5.16, p. 160). Their observed speeds were slow to medium, with a net speed of 1.5 km/h

based on the initial and final positions. The actual average speed was somewhat greater because

the route through the ice was circuitous. Speeds and headings were more variable than those of

the mother-calf pair seen in open water. The headings varied in such a way that the whales did

not have to travel more than a few hundred meters under continuous ice. The mother and calf

sometimes surfaced synchronously, but the calf often surfaced by itself at intermediate times. The

calf swam actively; it was not seen to "ride" the mother.

3. On 25 Maya mother and calf were found milling in small openings amidst heavy pack ice (90%

cover) far offshore NE of Pt. Barrow. The mother may have been feeding during her dives. She

may also have been searching, in some unknown manner, for a route through the pack ice. The

calf spent more time at the surface. It breached several times, and sometimes nursed when the

mother was at the surface. About 1 h after we found the whales in that area, they began traveling.

They initially moved NNE and NE, skirting through cracks and other openings along the west side

of a very large ice pan (several kilometers in diameter) that obstructed the direct eastward route.

Upon reaching the north end of the large pan, the whales turned north along a major lead through

the pack ice. They passed only about 100 m to the side of another mother-calf pair migrating in

the opposite direction. Neither pair changed course or hesitated when passing the other pair.

Only one brief episode of riding was visible. The overall average speed after active migration
5.4 Bowheads: Mother-Calf Behavior 234

began was 4.7 km/h (6.8 km in 1.44 h). The average speed while moving through heavy pack ice

was slightly less than that in the open lead (4.2 vs. 5.4 km/h).

4. Another mother and calf seen on 25 May were not actively migrating during 1.9 h of observation

in an open area within heavy pack ice well offshore. The calf spent more time at the surface than

did the mother, which was suspected to be feeding below the surface. Activities at the surface

included rest, slow travel, nursing, and tailslaps by the calf.

5. Another mother-calf pair seen in the same area on 25 May were resting almost totally motionless

during 0.5 h of observation.

Behavioral Observations in 1991 and 1994.-In 1991, the first mother-calf sighting was on

11 May, and the next mother-calf sightings were not until 17 May. Mother-calf pairs were seen

regularly from 17 May until the end of our field season on 26 May. They constituted a substantial

proportion of all bowhead sightings during the last few days of the field season. Prior to 16 May

in 1991, only 2 of 159 bowheads seen from the Twin Otter were mothers or calves (mother/yearling excluded). From 16 to 20 May, 12 of 82 bowheads seen from the Twin Otter were mothers

or calves. From 21 to 26 May, 20 of 64 were mothers or calves. The concentration of mother-calf

sightings late in the spring was also evident in 1989 and 1990.

In 1991, there was only one >0.1 h behavior observation session of a mother-calf pair. During that session, for 0.7 h on 20 May, mother and calf moved at medium speed toward the NE.

In 1994, there was only one sighting of a mother-calf group from the air, on 9 May. The pair

was observed only briefly, traveling at medium speed to the northeast. These whales were observed within ~ h after an icebreaker noise playback, about 1.3-1.5 km WNW of the ice camp.

Photoidentification Data on Mother-Calf Movements.-Additional information about movements of mothers and calves obtained through repeated photography of recognizable individual

mothers appears in §5.2. In summary, the speeds of mother-calf pairs were slower than speeds of

other whales when estimated from between-session within-day resightings or the all betweensession data (Table 5.6, p. 188). Speeds of these two groups were similar when estimated from

short-term within-session resightings or from between-day resightings. The between-day speeds

are biased because only the slow-moving whales would be resighted.

The net headings of mother-calf pairs in all four categories appeared to differ from those of

other whales. In each category, headings of mother-calf pairs were more variable, as indicated by

a larger angular deviation (Table 5.6). A larger proportion of the mothers and calves were traveling west.

Migration and Lingering-Summary.-During spring migration east of Barrow, bowhead

mothers with newly-born calves travel on the same generally eastward migration route as other

bowheads. They travel past Barrow late in the spring migration period, starting in mid-May.

Their headings are more variable than are those of other bowheads, and their routes are more

circuitous. Mothers and calves-of-the-year seem less inclined to travel through heavy ice conditions than are other whales. They follow routes that provide frequent openings in which the calves
5.4 Bowheads: Mother-Calf Behavior 235

can surfacing to breathe. Where the route is obstructed by ice, the calf occasionally surfaces and

dives repeatedly in one place while the mother undertakes a long dive, possibly searching for a

suitable route through the ice. When ice conditions to the NE and E are severe, these pairs often

linger in areas of open water, as evident from our observations in 1989 and 1990. In one 1989

case, a pair lingered in one general area for at least three days.

"Riding" Behavior

I

During travel, calves alternated among (1) swimming beside the mother, usually just behind

the broadest portion of the back and in front of the tail; (2) angling toward the teat area of the

mother in apparent short nursing bouts, with each bout lasting less than 10 s; and (3) "riding" on

the back of the mother while both mother and calf were submerged. Prior to this study, this last

form of locomotion had not been described in detail for bowhead whales, but was mentioned by

Carroll and Smithhisler (1980). The calf appears to be dragged along by the hydrodynamic forces

created by the motion of the larger animal.

During riding, the calf appears to lie on the back of the mother, pointed in the same direction

as mother, with rostrum slightly behind the midback of mother and in an area where the mother's

back curves down toward the tail. From the air, we could not determine the exact spacing of

mother and calf. The calf may not actually be touching the mother's back at all times, but may

be sucked along by a Bernoulli effect of reduced (therefore attractive) pressure between two bodies

that are almost but not quite touching (Kelly 1959). Carroll and Smithhisler (1980) suggested that

a very small calf may grasp the mother with its flippers. We have no evidence of this. Dolphin

young ride beside the backs of adults in what has been termed echelon-swimming (Kelly 1959;

Norris and Prescott 1961). At times, dolphin calves are pulled along by the motions of the adults,

without any fluke beats of their own (Norris and Dohl 1980; Irvine et al. 1981). However, it is

more common for this behavior to supplement rather than totally replace swimming motions by.

the calf.

Bowhead calves beat their tails very little (and perhaps at times not at all) while in riding

position. Riding by bowhead calves appears to function at least as efficiently as echelon

swimming by dolphins.

Bowhead calves probably also receive some hydrodynamic advantage when not in "riding"

position but very close to the side of or underneath the adult whale, behind the mid-back and just

in front of the adult's tail. This advantage may continue when the calf is nursing underneath the

mother during travel, although mothers and calves usually travel at slow speed when nursing. We

here define riding to include only cases when the calf is on the adult's back. These cases are

unequivocal and are observable from the air when the animals swim within several meters of the

surface. Other positions, most likely the echelon position described by Kelly (1959) and by Norris

and Prescott (1961) for dolphins, may provide at least a partial "ride" for the bowhead calf as well.

Because the calf is on top of the mother while riding, the mother has to be submerged well

below the surface. Hence, riding can only be seen in clear water. Several times we observed lone

calves apparently moving along effortlessly on their own. After several seconds or even minutes
5.4 Bowheads: Mother-Calf Behavior 236

of observation from the aircraft, we saw the partially-obscured outline of the adult farther below

the surface. The presence of the mother below the calf would not have been evident from the low

vantage points available to ice-based observers. Riding may also occur with both animals well

below the surface; we would not be able to detect these cases even from an observation aircraft.

Riding is disrupted when the calf sinks below the mother to nurse, and when either calf or

mother surfaces to breathe. When the adult surfaces, the calf moves to either left or right of the

adult's midback (and usually blows at about that time). When the calf surfaces to breathe, it may

stay just above the adult's midback, in near-riding position, or it may briefly move to' the side of

the adult. In either case, calves that ride during travel consistently move back into riding position

after breathing, indicating that riding is of importance for young calves during migration.

We saw most incidents of riding in 1989; riding was observed from 24 to 29 May, when

mothers and their calves were migrating through the area. The first calf we saw, on 23 May, was

not riding (Table 5.23). Riding observed on 27-29 May was mainly by a single mother-calf pair

seen on three consecutive days. In 1990, we saw approximately as many calves (from 21-25 May)

as in 1989, but witnessed riding for only one mother-calf pair, on 23 May. In 1991, we observed

only one mother-calf pair in our focal animal circle (20 May), and briefly observed two other pairs

outside of our circle (25 May). We witnessed no riding. In 1994, we saw only one mother-calf

pair during the season (9 May), and the calf was riding.

In summary, we observed riding behavior involving five mother-calf pairs, out of -17

mother-calf pairs whose behavior was observed during focal observations (29%). Because of the

variable but often short « 1 h) durations of focal observations, some pairs not observed to ride may

have engaged in this behavior at other times.

We compared calculated calf-to-adult size ratios for mother-calf pairs that were and were not

observed in riding formation. The data came either from calibrated vertical photos obtained directly after the behavioral observations or, for pairs not photographed vertically, from videotape

obtained from a side window during behavioral observation sessions (see §2.2, Methods). The

length ratio was 0.283 ± s.d. 0.0131 (n = 3) for pairs seen riding (Table 5.23), and 0.312 ± s.d.

0.0072 (n = 5) for pairs not seen riding. All three "riders" had calves <0.3 the length of the

mother whereas all five apparent "non-riders" had calves >0.3 the length of the mother. Given the

absence of any overlap between the two groups, this difference is statistically significant despite

the small sample size (Mann-Whitney U=O, P=0.04).

Riding is probably important to the calf only during the first few months of life. We have

not observed riding in the Canadian Beaufort Sea in late summer or the Alaskan Beaufort in

autumn. During late summer, the combination of the calf's increased size, its muscular

development, and the absence of active migration make riding unnecessary.

Although calves may make direct contact with the mother during riding, it appears that they

are at times merely close, likely being pulled along by the larger animal's slipstream as are

dolphins and some fishes in interspecies associations. In bowheads, riding probably gives pronounced hydrodynamic and energetic advantages to migrating newborn. It probably is especially
5.4 Bowheads: Mother-Calf Behavior 237

TABLE5.23. Occurrence of "riding" in relation to calf length, from observations during systematic

behavioral observations of mother-calf pairs.

Date BOS Duration of Potential Proportion of Length (m) a Length Ratio b

Year in May No. Observ. (h) Disturbance Time Riding Calf, Mother Calf/Mother

1989 23 10 0.6 playback 0

24 11 1.2 aircraft 50 0.287

27 12 2.1 0 4.8, 15.9 0.302

27 12 2.0 0 4.9, 15.8 0.310

27 14 0.9 c 10-20 4.0, 14.9 c 0.268 c

27 13 2.0 playback &

sonobuoy 30

28 15 0.7 c 40 4.0, 14.9 c 0.268 c

29 16-17 2.0 c 40 4.0, 14.9 c 0.268 c

1990 21 21 0.05 0

21 21 0.05 0

23 25 1.0 60 0.293

24 26 3.4 0 0.322

25 27 1.9 0 0.315

25 27 0.4 0

25 29 2.4 0 0.312

1991 20 6 0.7 0

25 7 0.1 0

25 7 0.1 0

1994 9 7 0.2 post-plbk 50

a Measured photogrammetrically.

b From photogrammetric data when available; otherwise from measurements from video screen.

C Same mother-calf pair.

important during spring migration when the calves are young and when mother-calf pairs

sometimes need to travel under dense ice. As noted below, the maximum observed durations of

dives by migrating calves «14 min in this study) are much briefer than maxima for older whales.

Thus, open water areas suitable for breathing may often be spaced too far apart to allow passage

by small calves swimming unassisted, but close enough to allow passage by older whales, and

possibly by a mother-calf pair in riding formation. Riding may be more important to bowheads

than to other baleen whales, as other species rarely inhabit areas with near-100% ice cover.

Surfacing, Respiration and Diving Behavior

Table 5.24A summarizes the surfacing, respiration and diving (SRD) cycles of all mothers

and calves that were observed under "presumably undisturbed" conditions. Durations of surfacings

tended to be shorter for calves than for mothers. However, blow intervals were also markedly

shorter for calves than for mothers. As a result, the total number of blows per surfacing was

similar for the two categories of whales despite the shorter surfacings by calves. Dives tended to

be much shorter for calves than for their mothers (Table 5.24A).
TABLE 5.24. Surfacing, respiration and dive behavior of undisturbed mothers and calves as compared with other bowhead whales during spring

migration near Barrow, Alaska. Based on observations from a Twin Otter aircraft at altitude 460 m, 1989-1994.

Category of Individual Median Number of Blows Duration of Duration of

Undisturbed Blow Intervals (s) Blow Intervals (s) per Surfacing Surfacing (min) Dive (min)

Bowhead Whales mean s.d. n mean s.d. n mean s.d. n mean s.d. n mean s.d. n

A. All Group Activities

Calves Not nursing 13.27 9.22 843 12.65 5.50 201 4.41 3.71 204 0.84 0.99 220 2.29 2.04 215

Nursing 12.96 6.69 108 12.84 5.79 29 3.67 2.41 36 0.79 1.08 38 0.77 0.88 40

All 13.23 8.97 951 12.67 5.52 230 4.30 3.55 240 0.83 1.00 258 2.05 1.99 255

Mothers Not nursing 19.43 7.77 234 20.82 7.74 62 4.31 2.82 61 1.23 0.89 65 7.53 5.83 63

Nursing 26.01 20.46 91 28.79 17.58 21 5.00 2.21 19 2.20 1.15 20 13.70 6.15 13

All 21.27 12.98 325 22.84 11.49 83 4.47 2.69 80 1.46 1.04 85 8.58 6.30 76

All Other Bowheads 19.37 28.59 2984 18.17 11.69 676 5.19 3.53 454 1.34 1.17 498 5.95 6.26 319

B. Traveling Only

Calves Not nursing 12.64 7.18 493 If.34 5.45 143 4.50 3.36 138 0.82 0.78 148 2.50 2.26 143

Nursing 13.88 6.61 54 14.59 6.78 16 3.57 2.41 23 0.63 0.57 23 0.91 1.08 25

All 12.76 7.13 547 12.57 5.61 159 4.37 3.25 161 0.79 0.76 171 2.26 2.20 168

Mothers Not nursing 18.47 6.46 142 20.20 8.09 48 4.93 2.82 42 1.33 0.84 46 8.15 6.22 46

Nursing 24.23 20.28 58 26.17 16.38 15 4.92 2.47 13 2.13 1.34 14 11.27 5.78 9

All 20.14 12.42 200 21.62 10.81 63 4.93 2.72 55 1.52 1.02 60 8.66 6.21 55

Others All 17.60 8.72 1928 18.08 7.64 451 5.02 3.30 355 1.35 1.03 367 6.63 6.27 244 VI

Subadults 14.41 9.38 237 14.12 5.65 48 6.15 3.77 33 1.35 1.22 39 5.26 6.04 19 ~

Adults 19.41 8.48 738 20.56 8.94 159 4.92 3.22 152 1.46 1.09 152 6.81 6.25 134 ~Q

~::rC. Riding vs. Not Riding Mothers and Calves (Traveling and Not Nursing) "'

I:l

Calves Not riding 12.86 7.48 481 12.72 5.73 115 4.59 3.46 108 0.87 0.79 118 2.84 2.44 112 ~

Riding 11.51 5.32 95 10.77 3.77 28 4.17 2.98 30 0.65 0.72 30 1.28 0.44 31

Mothers Not Riding 18.26 6.50 171 20.02 8.52 41 5.03 3.00 35 1.36 0.89 39 8.60 6.95 35 ~

Riding 20.00 6.04 24 21.21 5.20 7 4.43 1.72 7 1.19 0.46 7 6.72 2.59 11 s

"' ":'

~.:;;

~

"'

::rI:l

'C

~.

..,

tv

W

00
5.4 Bowheads: Mother-Calf Behavior 239

Traveling Mothers and Calves.-Mother-calf pairs were traveling during the majority of the

observation time, and traveling was the one whale activity that was common enough to warrant

detailed analysis (Fig. 5.31). Most traveling whales were actively migrating, but some may have

been traveling for some other reason.

The SRD cycles of traveling mothers (Fig. 5.31) were similar to those of other traveling

"non-calves" (cf. Fig. 5.28) and especially other traveling adults (Fig. 5.30). Data for these groups

are all summarized in Table 5.24B. In contrast, the traveling calves had significantly shorter blow

intervals, surface durations, and dive durations than did their mothers (Fig. 5.31). Numbers of

blows per surfacing were similar for traveling calves and mothers (4.37 vs. 4.93, Fig. 5.31B).

Again, this reflected the fact that calves had shorter surfacings than did mothers, but also had

shorter intervals between successive blows. Calves and mothers respired about the same number

of times per surfacing even though surfacing-dive cycles were much shorter for calves. The sum

of the average surface and the average dive duration was 3.05 min for calves but 10.18 min for

mothers. Thus, the blow rate-average number of blows per minute, including dive as well as

surface time-was much higher for calves (1.43) than for their mothers (0.48).

Nursing vs. Not Nursing.-Mother-calfpairs often engage in nursing, and nursing affects surfacing-dive cycles of both calf and mother. Table 5.24A shows data for nursing vs. non-nursing

calves and mothers when all activities are considered. For traveling calves, all dives tend to be

short, but nursing dives were slhorter than other dives, averaging 0.91 vs. 2.50 min in duration

(Fig. 5.32D). Other SRD variables were similar for traveling calves that were and were not nursing (Fig. 5.32). Presence or absence of nursing also affected the SRD cycles of traveling mothers

(Fig. 5.33). 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.

Riding vs. Not Riding.-We compiled all surfacing, respiration and dive values for traveling

mothers and calves classified as riding vs. not riding (Fig. 5.34; Table 5.24C). There were no

pronounced differences in surfacing or respiration data for calves that were and were not riding

(Fig. 5.34A-C). Durations of dives tended to be shorter for calves that were riding (Fig. 5.34D).

Other Behaviors

The same categorical variables that were recorded for whales other than mothers and calves

were also recorded for mothers and calves. Tables 5.25 and 5.26 show many of the data, categorized according to whether the whales were traveling or not, and whether the mother and calf were

nursing or not. For comparison, data for all whales other than mothers and calves are also shown.

Swimming Speeds.-Speeds of traveling mothers and calves were most commonly categorized as medium, but a substantial minority of the mothers and calves were categorized as moving

slowly, especially when their general activity was not traveling (Table 5.25A). These estimates

of swimming speeds were based on partly-subjective judgments by the aerial observers.

More specific data on speeds of several presumably undisturbed mother/calf pairs were

determined in 1989-90 based on successive readouts from the aircraft's VLF navigation system.
A.

20 Mothers

Traveling whales only

Moth. CaN

Mean 21.62 12.57

sd 10.81 5.61

n 63 159 -40

Calves

1-4 10-13 19-22 28-31 37-40 >46

Median Blow Interval (5)

20 C.

~

·6 -20

.@

~

0-40

z Moth. CaN

Mean 1.52 0.79

sd 1.02 0.76

-60 n eo 171

-80 0-0.5 1.5-2 3-3.5 4.5-5 6-6.5

Duration of Surfacing (min)

>7.5

FIGURE5.31. Frequency distributions of surfacing, respiration and dive variables for undisturbed bowhead mothers (upward bars) and

calves (downward bars) engaged in traveling during the spring migration period near Barrow, Alaska. Nominal significance levels come

from t-tests on log-transformed data. Based on aerial observations from a Twin Otter aircraft circling at altitude ~460 m, 1989-94.

B.

20

~

c

'0.@

::J

en -20

o

z Moth. CaN

Mean 4.93 4.37

sd 2.72 325

n 55 181

lIS

-40

0-1 &7 12-13 18-19 2~25 >29

No. Blows/Surfacing

20 D.

m -20

5

o

Z-40

Moth. CaN

Mean 8.66 2.26

sci 8.21 220

n 55 168

-60 " of Shott Dives

o-.Sllln 0 12

.5-1 8 45

1-2 2 52

109

0-2 -80 &8 12-14 18-20 2~26

Duration of Dive (min)

>30

tv

~

o
50 A.

NotN Nurse

50 B.

NotN Nurse

Mean 12.34 14.59 Mean 4.50 3.51

40 sd 5.45 6.18 40 sd 3.38 2.41

n 143 16 n 138 23

OS OS

CJ) 30 Tmveling calves 0)

CJ)

0) 30

c c

'0 '0 {g 20 Not

{g

::J ::J 20

en

Nursing

en

0 0

z 10 z 10

100 C. 100

NotN Nurse D. NolN Nurse

Mean 0.82 0.63 Mean 2.50 0.91

80 sd 0.18 0.51 80 sd 2.26 108

n 148 23 n 143 25

OS

CJ)

0) 60 • of Short DIves

c

'0 m 0-.5 min 1 11

{g .~ .5-1 35 10

::J C 40 1-2 50 2

en 0

0

Z

z 20

FIGURE5.32. Frequency distributions of surfacing, respiration and dive variables for undisturbed bowhead calves that were not nursing

(upward bars) vs. nursing (downward bars) while traveling during the spring migration period near Barrow, Alaska. Otherwise as in

Fig. 5.31.

10-13 19-22 28-31 37-40

Median Blow Interval (8)

-20+----.--.--~.,.........,....--..--..---.--r--.--~,...-,c--r--..----4

0-0.5 1.5-2 3-3.5 4.5-5 6-6.5

Duration of Surfacing (min)

>7.5

0-1 6-7 12-13 18-19 24-25

No. Blows/Surfacing

>29

23

0-2 -20 6-8 12-14 18-20 24-26

Duration of Dive (min)

>30
25

NotN Nurse D. NotN Nurse

Mean 1.33 2.13 Mean 8.15 11.27

sd 0.84 1.34 sd 8.22 5.78

n 46 14 n 48 9

15 " 01Short Dives C/) 0-.5min 0 0

.~ .5-1 0 0

0 1·2 2 0

0

z

5

25 A.

NotN Nurse

Mean 20.20 26.17

sd 8.09 16.38

n 48 15

Not

Nursing

Traveling mothers

Nursing

1-4 10-13 19-22 28-31 37-40 >46

Median Blow Interval (5)

25 C.

0-0.5 1.5-2 3-3.5 4.5-5 6-6.5 >7.5

Duration of Surfacing (min)

25 B.

NotN Nurse

Mean 4.93 4.92

sd 2.82 2.47

n 42 13

os

FIGURE 5.33. Frequency distributions of surfacing, respiration and dive variables for undisturbed bowhead mothers that were not nursing

(upward bars) vs. nursing (downward bars) while traveling during the spring migration period near Barrow, Alaska. Otherwise as in

Fig. 5.31.

6-7 12-13 18-19 24-25 >29

No. Blows/Surfacing

0-1

0-2 6-8 12-14 18-20 24-26 >30

Duration of Dive (min)
20 A. 20 B.

10 Riding 10

rn ~=

rn

en v ~ en

c: c:

"0 .~

tU Not Riding '§ -10 '§ -10

en en

0 0

z -20 Ride Not Z -20 Ride Nol

Mean 10.77 12.72 Mean 4.17 4.59

sd 3.77 5.73 lid 2.98 3.46

-30 n 28 115 -30 n 30 108

(*) lIS

Traveling calves only

-40 -40

1-4 10-13 19-22 28-31 37-40 >46 0-1 6-7 12-13 18-19 24-25 >29

Median Blow Interval (8) No. Blows/Surfacing

30 C. 30 D.

20 20

10 10

rn

en

.~ m .fg -10 .~ -10 Ride Nol C

::J o -20

Mean 1.28 2.84

en -20 sd 0.44 2.44

0

Z n 31 112

Z -30 Ride Not -30 Mean 0.65 0.87

-40 lid 0.72 0.79 -40 II 01 Short Dives

n 30 118 0-.5 mln 0 1

-50 lIS -50 .5-1 8 27

1-2 21 29

-60

0-0.5 1.5-2 3-3.5 4.5-5 6-6.5 >7.5 0-2 6-8 12-14 18-20 24-26 >30

Duration of Surfacing (min) Duration of Dive (min)

FIGURE 5.34. Frequency distributions of surfacing, respiration and dive variables for undisturbed bowhead calves that were riding

(upward bars) vs. not riding (downward bars) while traveling during the spring migration period near Barrow, Alaska. Nursing calves

excluded. Otherwise as in Fig. 5.31.
5.4 Bowheads: Mother-Calf Behavior 244

TABLE 5.25. Frequencies of various activities among undisturbed bowhead calves. mothers and others.

Presentation as in Table 5.20.

Calves Mothers Other Whales

Trayeling Other Actiy Traveling Other Actjy Trav- Other

Not Nurse Not Nurse All Not Nurse Not Nurse All eling Activ. All

A. Speed During This Surfacing

Zero I I 3 2 7 0 2 I I 4 10 22 32

Slow 26 7 33 4 70 15 0 7 4 26 129 53 182

Moderate 99 5 4 0 108 34 2 0 0 36 329 ll5 444

Fast 0 0 0 0 0 0 0 0 0 0 3 I 4

Unknown but >0 24 6 14 8 52 4 I 2 0 7 69 32 101

Milling 0 0 0 0 0 0 0 0 0 0 0 3 3

Change 16 3 4 I 24 5 9 3 2 19 40 21 61

Total n 166 22 58 15 261 58 14 13 7 92 580 247 827

B. Flukes Out at End of Surfacing

No 158 25 71 16 270 53 16 20 6 95 457 163 620

Yes 5 0 9 0 14 I 0 0 0 1 45 26 71

Total n 163 25 80 16 284 54 16 20 6 96 502 189 691

C. Pre-Dive Flex Before End of Surfacing

No . 152 23 75 16 266 51 13 20 6 90 431 157 588

Yes 0 0 0 0 0 0 2 0 0 2 7 4 11

Total n 152 23 75 16 266 51 15 20 6 92 438 161 599

D. Turns During Surfacing

None 122 20 55 12 209 39 13 12 4 68 276 90 366

Right 14 1 4 I 20 4 I 2 I 8 56 43 99

Left 12 0 5 I 18 6 I 5 I 13 52 30 82

Multiple 4 2 9 I 16 0 0 I I 2 47 35 82

Total n 152 23 73 15 263 49 15 20 7 91 431 198 629

E. Degrees of Tum During Surfacing

0 122 20 55 12 209 39 13 12 4 68 276 90 366

10 4 I I I 7 I I I I 4 23 10 33

20 7 0 2 0 9 4 0 0 0 4 29 7 36

30 4 0 0 0 4 3 0 I 0 4 10 5 15

40 I 0 I 0 2 0 I 0 0 1 8 2 10

50-80 3 0 4 0 7 0 0 2 I 3 17 8 25

90+ 3 0 9 2 14 0 0 2 I 3 17 48 65

Total n 144 21 72 15 252 47 15 18 7 87 380 170 550

F. Social Activity During Surfacing

None 172 25 80 16 293 63 16 20 7 106 447 150 597

Passive 0 0 0 0 0 0 0 0 ·0 0 52 21 73

Active 0 0 0 0 0 0 0 0 0 0 54 132 186

Total n 172 25 80 16 293 63 16 20 7 106 553 303 856

G. Aerial Activity During SfclDive Seq.

None 161 24 68 15 268 56 16 20 6 98 440 166 606

Roll 0 0 0 0 0 0 0 0 0 0 5 20 25

Flip. slap (FS) 0 0 0 0 0 0 0 0 0 0 4 0 4

Tail slap (TS) 3 0 4 0 7 0 0 0 0 0 12 4 16

FS+TS 0 0 2 0 2 0 0 0 0 0 3 3 6

Breach 0 0 3 1 4 0 0 0 0 0 5 24 29

Breach + FS &lor TS 0 0 I 0 1 0 0 0 0 0 I 8 9

Total n 164 24 78 16 282 56 ·16 20 6 98 470 225 695
We considered only those pairs whose positions were determined over a period of at least 1 h. We

excluded cases when the navigation data were suspect.

5.4 Bowheads: Mother-Calf Behavior 245

TABLE 5.26. Number of surfacing/dive sequences with specific whale behaviors among undisturbed bowhead calves, mothers and

others. Totals exceed "Overall n" because> 1 special behavior can occur at one time. Presentation as in Table 5.20.

Calves Mothers Other Whales

Trayeling OtberActjy Trayeling Other Actjv Trav- Other

Not Nurse Not Nurse All Not Nurse Not Nurse All eling Activ. All

None 60 0 39 0 99 19 0 9 0 28 121 89 210

Defecation 0 0 0 0 0 0 0 0 0 0 0 I 1

Flukes raised during surfacing 0 0 0 1 1 0 0 0 0 0 6 5 11

Lunge or surge 0 0 0 0 0 0 0 0 0 0 5 7 12

Underwater blow 0 0 I 0 1 0 0 0 0 0 5 12 17

Arch during surfacing I 0 0 0 1 2 I I I 5 30 8 38

Mouth open slightlylbriefly 0 0 0 0 0 0 0 0 0 0 0 I 1

Mouth open 0 0 0 0 0 0 0 0 0 0 I 0 1

Echelon formation 0 0 0 0 0 0 0 0 0 0 0 0 0

Near-surface feeding 0 0 0 0 0 0 0 0 0 0 0 0 0

Mud from mouth 0 0 0 0 0 0 0 0 0 0 0 4 4

Mud behind whale 0 0 0 0 0 0 0 0 0 0 0 0 0

Streak in water 0 0 0 0 0 0 0 0 0 0 0 0 0

Penis visible 0 0 0 0 0 0 0 0 0 0 0 4 4

Presumed sexual activity 0 0 0 0 0 0 0 0 0 0 0 25 25

Nursing (mother or calf) 0 25 0 16 41 0 16 0 7 23 0 0 0

Play with log 0 0 0 0 0 0 0 0 0 0 0 0 0

Play with other large object 0 0 0 0 0 0 0 0 0 0 0 0 0

Play with particulates 0 0 0 0 0 0 0 0 0 0 0 0 0

Motionless at surface 0 I 2 3 6 0 2 I 2 5 12 13 25

Motionless just below surface 0 0 0 0 0 0 0 0 0 0 0 0 0

Motionless with head down 0 0 0 0 0 0 0 0 0 0 0 0 0

Spyhop 0 0 0 0 0 0 0 0 0 0 0 0 0

Travel along ice edge 23 7 4 4 38 7 0 0 I 8 87 18 105

Emerge from extenso ice (>Ikm) 0 0 0 0 0 0 0 0 0 0 21 2 23

Riding (mother or calf) 30 0 10 0 40 7 0 0 I 8 0 0 0

Accompanied by belugas 0 0 0 0 0 0 0 0 0 0 7 I 8

Visible below surface 71 8 30 I 110 25 5 II 0 41 174 19 193

Swims in tight circles 0 0 0 0 0 0 0 0 0 0 0 2 2

Overall n 150 25 75 16 266 49 16 20 7 92 431 192 623

The two mother/calf pairs observed in 1989 during steady eastward migration in largely open

water were traveling at speeds of 5.1 and 4.8 kmlh, averaged over about 2 h. These whales were

judged to be traveling at medium speed during most surfacings. The net motion of the third pair

seen in 1989-the pair that lingered in the area for at least 2 days-was only 12 km NE over a

44.2 h period. The fourth pair moved 12.6 km WSW in 19.1 h.

In 1990, one mother/calf pair migrating steadily through heavy pack ice had a net speed of

only 1.5 km/h, partly but not entirely due to its circuitous route through the ice. Another pair

averaged 4.7 kmlh, part of the time in moderately heavy pack ice. More details about the movements of these pairs are given in the descriptions of cases 2 and 3 on p. 233.
5.4 Bowheads: Mother-Calf Behavior 246

Fluke-out Dives.-Fluke-out dives were rarer for mothers (l of 96 dives, 1%) than for other

non-calves (71 of 691 dives, 10%, Table 5.25B). This difference is significant (chi2=7.57, df=1,

P<0.05). Calves raised their flukes above the water during 14 of 284 dives (5%; Table 5.25B).

Pre-dive Flexes.-Flexes were rarely exhibited by mothers or other non-calf bowheads

observed during the springs of 1989-90. Flexes were noted during only 2 of 92 surfacings (2%)

by mothers and during 6 of 599 surfacings (l %) by other non-calves (Table 5.25C). No calf was

ever seen to exhibit a pre-dive flex in spring (0 of 266 surfacings).

Turns.-Among traveling whales, turns were less frequent in the cases of mothers and calves

(19% of surfacings) than for other non-calves that were traveling (36%). Among whales engaged

in other activities, sample sizes were small for mothers and calves, but again turns were Jess

common than for other whales (Table 5.25D).

Social Activity.-Mothers and calves were not observed to socialize with whales other than

the other member of the mother or calf pair. In contrast, other whales often interacted with other

whales (Table 5.25F).

Aerial Behaviors.-Aerial behaviors, including breaches, tail slaps, and flipper slaps or rolls,

were not seen in the case of mothers observed in spring. Other non-calves occasionally exhibited

these behaviors, and a few breaches, tail slaps and flipper slaps were seen in the case of calves

(Table 5.25G).

Additional Behavioral Variables.-Of the many other behaviors that are noted when seen,

only a few were seen commonly in calves or their mothers (Table 5.26). These included nursing,

riding, traveling parallel to and within 100 m of an ice edge, and visible below surface during

dives, Nursing and riding were, more-or-Iess inevitably, seen only in mothers and calves.

Traveling along ice edges and traveling close enough to the surface during dives to be visible from

above were also common in other whales.
6. Bowhead Disturbance 247

6. BOWHEAD DISTURBANCE21

The highest priority objective during the 1991 and 1994 phases of this project was to test the

reactions of bowhead whales to underwater playbacks of recorded icebreaker sound. The aim was

to determine whether, and in what circumstances, these variable sounds would affect the distribution, movements, and behavior of spring-migrating bowheads and, as possible, white whales. This

top-priority task was identified as specific objective 4 in §1.1 (p. 7):

"To measure the short-term behavioral responses of bowheads and (as possible) white whales

visible in open water areas along their spring migration corridor in the western Beaufort Sea

to underwater playbacks of variable icebreaker sounds. Infrasonic components cannot be

projected. "

This work was a follow-on to earlier playback tests of bowhead and white whale reactions to the

steadier, continuous sounds from drilling on a grounded ice pad (Richardson et al. 1990a, 1991a).

Sections 6.1-6.6 of this report present and discuss the results of the 1991/94 tests of bowhead

reactions to playbacks of variable icebreaker sounds. However, the discussion in §6.5 (Icebreaker

vs. Drilling Noise Results) and §6.6 (Evaluation of Playback Hypotheses) mentions the results of

the earlier drilling noise playbacks as well.

A lower-priority objective in all four years of this project was to measure, on an

opportunistic basis, the short-term behavioral responses of bowheads and (as possible) white

whales to actual helicopter overflights (specific objective 6 from §1.1). A Bell 212 helicopter was

used for logistic support of the ice-based work during all four years of the project, and this

afforded opportunities to observe reactions of whales to this type of helicopter. When possible,

we also attempted to determine the reactions of the two whale species to the Twin Otter fixed-wing

observation aircraft that was used during all four years of this project. Section 6.7 describes the

results concerning reactions of bowheads to the two types of aircraft, based on the data from all

four years of this project.

6.1 Summary of Icebreaker Playbacks

Number of Observations During Playbacks

In 1991, there were only a few observations of bowhead whales near the operating sound

projectors, all on 17 May (Table 3.5 on p. 70; Table 6.1A; see also Table A-I in Appendix A ).

Icebreaker sounds were projected into the' lead for prolonged periods on a total of 6 days in 1991:

~ During three playback days, no bowheads were seen near the projectors.

~ Of the three playback days when bowheads were seen,

~ Two were days when bowheads were seen by the ice-based crew only during

"control" periods, while the projectors were not operating (11 and 18 May 1991).

21 By W.J. Richardson, W.R. Koski and N.J. Patenaude, with c.R. Greene Jr., G.W. Miller, M.A. Smultea, and

B. Wiirsig.
TABLE 6.1. Observation effort and numbers of bowhead and white whales seen near ice camps during control periods and playback periods, 1991 and

1994. Only dates when icebreaker noise was projected are included. Whales seen during more than one period are counted once in each period. Numbers

presented are the numbers of different whales estimated to have been present and are often less than the number of sightings in maps and tables in this report.

Aerial Observations Ice-based Observations Combined Observations

Control Playback Control Playback Control Playback

Effort No. No. Effort No. No. Effort No. No. Effort No. No. Effort No. No. Effort No. No.

Date (h) Bhds WWs (h) Bhds WWs (h) Bhds WWs (h) Bhds WWs (h) Bhds WWs (h) Bhds WWs

A: Days with Whales during Playback

11 May 1991 0.0 a 0 0 0.0 • 0 0 3.6 6 23 l.Ob 0 6 3.6 6 23 1.0 0 6

17 May 1991 0.0' 0 0 0.0' 0 0 4.1 2 96 5.3 9 8 4.1 2 96 5.3 9 8

3 May 1994 0.0< 0 0 0.0< 0 0 5.6 1 0 4.1 0 32 5.6 1 0 4.1 0 32

7 May 1994 2.1 15 0 1.5 • 15 0 7.0 36 0 3.9 8 0 7.0 47 0 3.9 18 0 !JI •...

9 May 1994 1.9 24 0 2.2 27 0 6.4 22 0 3.0 25 0 6.4 42 0 3.0 32 0 ttl

<:)

14 May 1994 0.0' 0 0 0.0· 0 0 6.4 17 0 3.2 3 0 6.4 17 0 3.2 3 0 ~no

16 May 1994 0.5 7 0 3.2 9 0 4.2 0 0 4.2 4 0 4.2 7 0 4.2 13 0

1:0

l:l.

17 May 1994 4.3 27 0 1.9 6 0 1.5 0 0 4.2 1 0 4.4 27 0 4.2 7 0

t:I

l:;'

20 May 1994 2.6 9 0 0.0' 0 0 5.2 6 0 4.6 11 0 5.5 9 0 4.6 11 0

r:g.

::s

l'\

Total 11.4 82 0 8.8 57 0 44.0 90 119 33.5 61 46 47.2 158 119 33.5 93 46 ~

~.

s:

EI

~

B: Other days with whales ~

Total 0 0 0 0 0 0 4.0 0 46 2.4 0 0 4.0 0 46 2.4 0 0

~

;:;-

no

I::Jo

C: Days without Whales ~1:0 rt

Total 0 0 0 0 0 0 5.0 0 0 4.0 0 0 5.0 0 0 4.0 0 0

..

"tl

~

a Low cloud prevented or curtailed aerial observations.

I::Jo

1:0

l'\

b Deteriorating ice conditions curtailed ice-based work. ~

c No bowheads were seen approaching the ice camp during surveys west and SW of it, so observations were conducted away from the camp. N

.J::-

00
6.1 Bowhead Disturbance: Summary of Icebreaker Playbacks 249

~ Bowheads were seen during the playback itself on one day, 17 May 1991. On

that date, the ice-based crew observed 9 bowheads (or possibly 10) that migrated

within 1.3 km of the projectors while they were broadcasting icebreaker sounds.

In 1994, there were considerably more observations of bowhead whales near the operating

sound projectors than in 1991 (Table 3.7 on p. 76; Table 6.1A). Icebreaker sounds were projected

into the lead for prolonged periods on a total of 7 days in 1994:

~ During one playback day (3 May), no bowheads were seen near the projectors during the

playback period; however, white whales were seen (Table 3.7).

~ Of the six playback days in 1994 when bowheads were seen during the playback period,

~ Two were days when the bowheads were seen by the ice-based crew only during

playback periods, while the projectors were operating (16 and 17 May 1994). On

17 May high winds resulted in observers missing many whales that were passing

and resulted in incomplete data for many whales that were seen. On both of these

days the aerial crew was able to follow bowheads during both control and playback

periods, but substantial changes in ice conditions throughout the day make

comparisons between control and playback periods problematic.

~ 14 May was a day when the ice-based crew observed bowheads during both

playback and control periods, but the aerial crew was not able to circle near the ice

camp at any time during the day because ceilings were <460 m.

~ 20 May was a day when the ice-based crew saw bowheads during both playback

and control periods; the aerial crew was able to circle near the ice camp during the

control but not the playback period; ceilings were <460 m during the latter period.

~ 7 May was a day when the ice-based crew observed bowheads during both

playback and control periods; the aerial crew was also able to circle near the ice

camp during both periods, but scattered or broken clouds below the aircraft during

the playback, along with high winds, resulted in incomplete data for most sightings.

~ 9 May was a day when both the aerial and ice-based crews were able to observe

whales during the control and playback periods. On this day, poor observing

conditions (primarily due to high sea states) reduced the quality and quantity of

data that were collected.

Over the two-season period when icebreaker playbacks were attempted, an estimated 93 bowheads (80 groups) were seen near the ice camp when the projectors were transmitting icebreaker

sounds into the water, and -158 bowheads (116 groups) were seen near there during quiet periods

(Table 6.1A). During 1989-90 playbacks of Karluk drilling noise, -221 bowheads were observed

near the ice camp during playbacks, and -187 there during quiet control periods (Table 6.2A).

Although substantial numbers of bowheads were seen near the ice camp during control and

playback periods in 1994, environmental conditions were unfavorable during most experiments.

Low cloud and high winds often interfered, as just summarized. As a result, the quality and

quantity of behavioral and movement data were often poor. On these days, we often were able to

obtain only partial data on whale behavior during surfacings, and we usually could not see the

markings that make many bowheads individually recognizable. Thus, we rarely could follow
TABLE 6.2. Observation effort and numbers of bowhead and white whales seen near ice camps during control periods and playback periods, 1989 and 1990.

Only dates when Karluk noise was projected are included. Whales seen during more than one period are counted once in each period. Numbers presented

are the numbers of different whales estimated to have been present and are often less than the number of sightings in maps and tables in this report.

Aerial Observations Ice-based Observations Combined Observations

Control Playback Control Playback Control Playback

Effort No. No. Effort No. No. Effort No. No. Effort No. No. Effort No. No. Effort No. No.

Date (h) Bhds WWs (h) Bhds WWs (h) Bhds WWs (h) Bhds WWs (h) Bhds WWs (h) Bhds WWs

A: Days with Whales during Playback

14 May 1989 0.5 1 100 2.8 6 100 2.7 0 7 8.6 5 19 2.7 1 100 8.6 10 100

19 May 1989 0.0· 0 0 0.0· 0 0 4.3 0 0 4.3 4 2 4.3 0 0 4.3 4 2

23 May 1989 0.8 • 1 1 0.7 • 5 50 3.9 2 3 5.1 2 4 3.9 3 4 5.1 5 54

27 May 1989 3.1 10 0

1.8 2 0 8.7 0 0 2.7 0 14 9.2 10 0 2.7 2 14 ?' •...

9 May 1990 0.0· 0 0 0.0· 0 0 2.2 2 0 5.0 22 0 2.2 2 0 5.0 22 0

tl;l

<:l

~

10 May 1990 1.7 21 35 3.6 25 30 2.0 4 7 5.3 22 0 2.3 23 35 5.3 40 30 ::-

"'

l:l

11 May 1990 3.5 15 0 1.0 3 0 6.0 13 6 1.6 1 0 6.0 28 6 1.6 4 0

l:l.

tl

13 May 1990 0.7 6 0 4.1 26 0 3.4 37 0 4.7 93 0 3.4 40 0 4.7 105 0

t;.

i:

16 May 1990 2.2 27 0 1.4 12 0 1.3 36 0 3.7 21 0 2.7 63 0 3.7 25 0 ~l:l

21 May 1990 2.3 17 200 2.7 4 3 3.0 1 49 4.1 1 16 3.9 17 220 4.1 4 19

;s

l')

~

~r::

Total 14.8 98 336 18.1 83 183 37.5 95 72 45.1 171 55 40.6 187 365 45.1 221 219 SI

SI

l:l

~

~

B: Other Days with Whales <\"

"' 13"

Total 1.7 1 0 0.0 0 0 17.0 2 22 14.2 0 0 18.1 3 22 14.2 0 0 ~l:l

•••• "'

.,

C: Days without Whales "tI

~

Total 0.0 0 0 0.0 0 0 18.5 0 0 14.7 0 0 18.5 0 0 14.7 0 0

13"

l:l

l')

l:"

• Low Cloud prevented or curtailed aerial observations. N

VI

0
6.1 Bowhead Disturbance: Summary of Icebreaker Playbacks 251

known individuals from one surfacing to the next, which meant that we obtained few data on the

dive durations of bowheads, or on their "tracks" as they passed the ice camp. (A "track" is the

route followed by an animal, as shown by the sequence of animal positions during two or more

surfacings.) For these reasons, the number of whales seen during an experiment was not always

a good measure of the success of that experiment; few useful data were obtained from some whales

that were observed only briefly.

The following subsections give brief summaries of the observations on the seven days

(17 May 1991 and 7, 9, 14, 16,17 and 20 May 1994) when bowheads were observed near the

operating projectors during icebreaker playbacks, and therefore were exposed to simulated

icebreaker sounds. The observation effort from the aircraft and ice camp, and the numbers of

bowheads seen during control and playback periods on each of the seven days, are summarized in

Table 6.1. Table 6.3 shows the projector systems used, the median source levels of projected

sounds, and the average ambient noise levels for each of these seven days. Finally, the estimated

maximum received levels near whales on each date are summarized in Table 6.4. The levels in

Table 6.4 do not always refer to the closest observed whales, as whales passing when the source

level was near its peak sometimes received stronger icebreaker noise than did other whales passing

closer to the projector at times when the source level was lower.

More detailed descriptions of observations, environmental conditions, and sound levels

received by whales on each of the days described in the following daily summaries are given in

Appendix F. Figures 6.1-6.3 are included here as examples of bowhead "track maps" and sound

exposure summaries for specific playback days. Appendix F includes more diagrams of these

types, dealing with all days when bowheads were exposed to playbacks. Results from all days are

summarized in §6.2 concerning playback effects on distribution and movements, and in §6.3

concerning playback effects on behavior.

Levels of icebreaker sound received by every observed bowhead at its Closest Estimated

Point of Approach (CEPA) were estimated via the sound exposure model described in §2.3 (p.

46ft>. This model produces many different measures of sound exposure. Those quoted in this

section are the estimated received levels in the 20-5000 Hz band ("broadband") or in the 113-

octave band with highest received level ("dominant 1I3-octave band). We considered 113-octave

bands centered at 20 through 6300 Hz. For both the 20-5000 Hz band and the dominant 113-

octave, we refer to both the median or the maximum level in the 64-s period preceding the

observation in question. These four estimates of received level are often abbreviated as RLBB,med'

RLBB,max, RL1I3,med' and RL1I3.maxWhen . the average ambient noise level in the corresponding band,

as measured before and/or after the playback, is subtracted from one of these received levels, the

result is the estimated icebreaker-signal to ambient-noise ratio, S:NBB.med' S:NBB,max' S:N 1I3,med' and

S:N1I3,max' .

17 May 1991

On 17 May 1991, the projectors were set up along the edge of the landfast ice several

kilometers northeast of Point Barrow (Fig. 3.6 on p. 72; Fig. 6.1). Spring whaling at Barrow had

ended by this date, allowing work closer to Barrow than at previous times in 1989-91. All
TABLE6.3. Projector configuration, source levels of icebreaker sounds (dB re 1 fJPa-m), and ambient noise levels (dB re 1 fJPa) during

projection experiments when bowheads were seen. Quoted source levels are medians over the 14-min cycle of icebreaker sound. On most

days the median source level was adjusted one or more times during the playback; the values presented here are from the times when most

whales were seen.

Median Source Ambient Noise Levels

20-5000 Hz Dom. 113-0ct. Band 20-5000 Hz In Dom.

Date Time Projector System Band Level Level Freq. (Hz) Band 1/3-0ct.

17 May 1991 12:42 - 16:49 J-13 + F-40 161 155 80 99 76

17 May 1991 16:50 - 18:01 J-13 + F-40 149 144 80 99 76

7 May 1994 16:07 - 18:08 J-11 + one side Argotec 220 146 139 80 95 82

7 May 1994 18:09 - 20:01 J-ll + one side Argotec 220 166 159 80 95 82

9 May 1994 14:22 - 15:02 J-11 162 157 500 100 86

9 May 1994 15:03 - 16:20 J-11 153 146 315&400 100 87&86

9 May 1994 16:26 - 17:30 J-11 156 149 200 100 85

14 May 1994 15:50 - 19:00 J-11 + one side Argotec 220 157 151 80 98 79

16 May 1994 13:03 - 17:13 J-11 + one side Argotec 220 166 158 80 89 75

17 May 1994 12:48 - 17:02 J-11 160 154 400 98-107 a 90-93"

20 May 1994 12:38 - 17:16 J-ll + one side Argotec 220 170 163 80 86 68

a The ambient noise gradually increased throughout the day from the lower level before playback to the higher level after playback.

N

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6.1 Bowhead Disturbance: Summary of Icebreaker Playbacks 253

TABLE6.4. Maximum estimated received levels (dB re 1 ~a) and maximum estimated icebreaker:

ambient ratios (dB) of sounds near bowhead whales each day when the projector was broadcasting

icebreaker sounds. Medians and maxima are based on estimated sound levels in 8 intervals of 8.5-s

duration within the 64 s preceding the closest estimated point of approach. Only traveling whales

are considered, except in the italicized 9 May 1994 line.

Strongest Sound Levels near Whales Ambient Highest lcebreaker:Ambient

20-5000 Hz Strongest 1I3-0ct. Noise 20-5000 Hz 1I3-0ct.

Date Med. Max. Freq. Med. Max. (20-5000 Hz) Med. Max. Med. Max.

17 May 1991 111 115 160 104 106 99 12 16 25 28

7 May 1994 116 119 80 110 113 95 21 24 29 32

9 May 1994 115c 118 c 200 108c

111c100 15c18c23c26c

b

9 May 1994 132 135 160 126 129 100 32 35 41 44

14 May 1994 107 109 80 101 103 98 9 11 22 24

16 May 1994 114 119 80 108 110 89 24 30 34 36

17 May 1994 119 123 500 112 117 99 20 24 22 26

20 May 1994 1323.C 138c

80 12Sc

131c

86 46" SOc S7c

63c

• Boldface type indicates that this whale modified its track in apparent response to the icebreaker noise.

b Data from feeding whales observed on 9 May 1994 are in italics. None of the feeding whales appeared to react

to the icebreaker sounds.

c These levels may be slight underestimates of levels that would be received below the surface.

observations of whales near the projector site on 17 May 1991 were obtained by the ice-based crew

because the cloud ceilings were too low for the aerial crew aboard the Twin Otter to observe

bowhead behavior from an altitude of 460 m. The main nearshore lead adjacent to the landfast

ice edge was several kilometers wide and largely ice-free (Fig. 6.1). The crew was on the landfast

ice edge from 10:46 through 20:59. Icebreaker sounds were projected into the lead from 12:42

through 18:01. The median broadband (20-5000 Hz) source level, measured over the full 14-min

duration of the icebreaker playback cycle, was 161 dB re 1 ~Pa-m from 12:42 to 16:49; after that

time the source level was reduced by -12 dB until the end of the session at 18:01. Because of

variation in the source level associated with the icebreaking activities within the 14-min period

of the tape, the source and received levels at certain times were as much as 4-15 dB higher or

lower than the median levels in corresponding 1I3-octave bands (Fig. 6.2). Even with the reduced

source level after 16:49, median levels of icebreaker sounds in the 113-octave band centered at 63

Hz were estimated to have exceeded ambient levels beyond 3 km from the projectors (Fig. 6.3),

and therefore were presumably audible to bowheads 3 km or more away from the projectors.

No bowheads were sighted from the ice during the period of pre-playback control observations. Five or six single bowheads plus two pairs were seen traveling east past the ice camp during

or immediately after the icebreaker playback, i.e, a total of 9 or 10 whales in 7 or 8 groups. There
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6.1 Bowhead Disturbance: Summary of Icebreaker Playbacks 254

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FIGURE6.1. Ice-based theodolite observations of bowhead whales that passed the ice camp along the

landfast ice NE ofPt. Barrow, 17 May 1991, while the projectors were broadcasting icebreaker sounds

from 12:42 to 18:01. The whale seen at 18:04, 3 min after the end of the playback, is shown because it

was exposed to icebreaker noise as it approached. Dashed lines represent presumed paths of whales while

they were below the surface. Double lines indicate the closest estimated point of approach (CEPA) for

selected whales. CEPA "A" and CEPA "B" approximate actual closest points of approach (CPA), but

CEPA "C" likely underestimates the actual CPA.

were two additional "control" sightings of single bowheads well after the playback had ended (see

Appendix F for details),

The closest estimated points of approach (CEPA) by the whales for which we have reliable

measurements or estimates were -450 to 1300 m (n=4 sightings). Calculation of CEPA assumed

that a whale sighted both as it approached and as it receded from the projector traveled in a

straight line between consecutive sightings. The shortest distance between the assumed path and

the projector was the CEPA (e.g., CEPA "A" in Fig. 6.1). For whales that were seen only as they
6.1 Bowhead Disturbance: Summary of Icebreaker Playbacks 255

17 May 1991,17:30

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FIGURE6.2. Third-octave levels of projected icebreaker noise vs. distance from projectors and ambient

noise, 17 May 1991, time 17:16-17:30: variability over 14 min at ranges 1 m and 1.0 km (median, 5th

and 95th percentiles). Plus signs show average ambient noise level after playback.

Explanatory notes: (1) Source levels are in dB re 1 fJPa-m, and ambient and received levels are

in dB re 1 fJPa. (2) Because of projector limitations, components of the icebreaker sounds at low

frequencies are underrepresented in the projector output relative to components at higher frequencies. (3)

The tape of icebreaker sounds is repeated every 14 min. As illustrated by the 5th and 95th percentiles,

the actual source or received level at any particular time can be substantially different than the median

level, depending on the precise location along the 14-min loop that is being projected or received. (4)

Source and ambient levels were measured; received levels at 1.0 km were estimated via an empiricallyvalidated propagation model, as described in section 2.3. (5) Received levels within a few meters ofthe

surface will be lower than estimated here.

approached or only as they receded from the projector, the CEPA was the closest observed distance

from the projector (CEPAs "B" and "C" in Fig. 6.1). We did not assume that the whales continued

on a straight line from their last observed heading because some approaching whales may have

diverted after they were sighted, and some receding whales may have diverted before they were

sighted. Thus CEPA for a whale that was seen only as it approached or receded likely

overestimates the actual closest point of approach, and therefore underestimates the maximum

sound levels received by that whale. A fifth whale seen on 17 May 1991 appears to have passed

-300 from the operating projectors; it was linked after an 18-min dive, although distinctive
6.1 Bowhead Disturbance: Summary of Icebreaker Playbacks 256

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17 May 1991,17:30

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FIGURE6.3. Third-octave levels of projected icebreaker noise vs. distance from projectors and ambient

noise, 17 May 1991, time 17:16-17:30: median levels at range 1m (squares) and 30 m-3.0 km. Plus

signs show average ambient noise level after playback.

Explanatory notes: See notes to Fig. 6.2. Figure 6.3 shows median received levels at more ranges,

but does not show 5th and 95th percentiles. Estimated received levels at 0.03 and 0.1 km assume

spherical spreading; model of §2.3 was used to derive estimates for 0.3 to 3 km.

markings that would confirm the link were not seen (Fig. 6.1).

At their CEPAs, six of eight groups observed on 17 May 1991 were exposed to icebreaker

sounds 22-28 dB above the ambient noise level (S:NI/3,m3J.)' No overt reactions to the sounds were

observed by the ice-based crew. Additional details are given in Appendix F.

7 May 1994

On 7 May 1994, the ice camp was set up along the landfast ice edge about 45 km ENE of

Pt. Barrow (Fig 3.8, p. 77). Tones and later icebreaker sounds were projected into the nearshore

lead adjacent to the landfast ice. Before the playback of tones and icebreaker sounds, large

numbers of bowhead whales were sighted traveling NE at medium speed through the middle and

southern third of the lead. Sighting rates were lower when tones were projected into the lead from

14:14 to 16:03, but the distribution and behavior of most whales seen then were similar to those

during the preceding control period.
6.1 Bowhead Disturbance: Summary of 1cebreaker Playbacks 257

Bowheads continued to travel past the ice camp during the period of icebreaker playback

from 16:07 to 20:01, but sighting rates were lower and some whales apparently diverted away from

the landfast ice edge where the sound projectors were located. No bowheads were seen from the

ice camp during the first 80 min of icebreaker projections and only a few whales were seen, all

in the central and offshore sides of the lead, during the following 2Y2 hours of icebreaker playback.

The broadband source levels were -20 dB higher during the final 1.9 h of the playback than during

the initial 2.0 h (Table 6.3). Aerial observations west of the projectors sighted large numbers of

bowheads heading toward the projectors; few of them were later seen by ice-based observers.·

These whales apparently moved past the ice camp through the offshore side of the lead.

Some whales seemed to alter their paths at distances where icebreaker sounds in the strongest

1/3-octave bands were similar to the ambient noise levels in those bands and thus (presumably)

barely detectable. The whale seen closest (362 m) to the -operating projectors appeared to be

detouring to the north to avoid a closer approach. It was seen during the first half of the projection experiment when source levels were low. This whale was exposed to an estimated S:NlI3,max

of 18 dB when it started to detour (maximum estimated icebreaker:ambient ratio in the 113-octave

band centered at 50 Hz). However, not all bowheads diverted. One bowhead was seen that had

apparently passed well within 500 m of the projectors on a normal northeasterly heading, tolerating

S:NII3,max well over 20 dB. Thus it appears that, on 7 May 1994, some whales altered their tracks

to avoid the projectors by >1 km, but a few approached within a few hundred meters where they

were exposed to RLBB,max as high as 119 dB re 1 flPa and S:NII3,max as high as 32 dB.

9 May 1994

On 9 May 1994, the ice camp was set up along the landfast ice edge about 2.5 km northeast

of the 7 May location (Plate 6.1), and 3.9 h of pre-playback control observations were obtained

from the ice. During this period 10 presumably undisturbed bowheads were sighted. Then

icebreaker sounds were projected into the lead adjacent to the landfast ice for 3 h, during which

32 bowheads were observed from the ice and aircraft. There was a further 3-h period of

observations after the playback ended, during which -43 bowheads were seen from the ice and

aircraft. Interpretation of the distribution and heading data was complicated by lingering whales

that were probably feeding under the landfast ice near the ice camp.

During all periods, bowheads traveled predominantly NE or ENE along the lead. A few

whales sighted from the ice camp and aircraft may have altered their headings to avoid closer

approaches to the projector (see Table 6.5, p. 274), but other whales that appeared to be feeding

headed generally south toward the landfast ice and projector. Two bowheads seen 940 m WSW

of the operating projector at 17:26 appeared to temporarily modify their path at that time and

distance in response to the icebreaker playback. They resumed traveling toward the ice camp a

few minutes after the projector was turned off at 17:30. Another group reversed course WSW

away from the projector; that group may have been feeding. Some of the whales sighted WSW

to N of the ice camp during the playback had northerly rather than NEerly headings, suggesting

that they may have been altering their tracks to avoid closer approach to the projector. However,

during the post-playback period, bowheads did not resume traveling along the landfast ice near the

ice camp; after the playback more bowheads traveled along the pack-ice edge forming the north
Edge of Mosaic ,

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PLATE 6.1. Mosaic of the lead configuration along the landfast ice edge NE of Barrow, 9 May 1994, photographed from 2835 m ASL

at 20: 10. The star shows the location of the ice camp on 9 May. The triangle shows the location of the ice camp on 7 and 8 May. This

series of photographs was taken shortly after completion of the aerial observation session shown in Figure F-23 (in Appendix F). !'oJ

UI

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6.1 Bowhead Disturbance: Summary of 1cebreaker Playbacks 259

(far) side of the nearshore lead than along the landfast ice, in contrast to the situation before and

during the playback.

On 9 May 1994, traveling whales at their CEPA were exposed to RLBBmaxas high as 118 dB

re 1 /lPa, RL1I3,maxas high as 111 dB re 1 /lPa, S:NBB,maxas high as 18 dB, and S:N1I3,maxas high as

26 dB. The group sighted 940 m from the projector at 17:26 appears to have modified its path at

RLBB,max=107dB re 1 /lPa, RLI/3,max=101 dB re 1 /lPa, S:NBB,max=7dB, and S:N1I3,max=16dB.

There were no clear differences in the distribution or behavior of presumably-feeding

bowheads during the control versus playback periods. Bowheads that were apparently feeding near

the projector while it was silent continued to do so, sometimes within a few tens of meters of the

projector, while icebreaker sounds were transmitted. The strongest levels received by feeding

whales exceeded 130 dB re 1 /lPa (RLBBmax);the highest icebreaker:ambient ratio was >40 dB

(S:N 1I3,max)'These whales appear to have tolerated levels 15-20 dB higher than did the closest

traveling whales on this date. For more information concerning these whales, see Appendix F.

14 May 1994

On 14 May 1994, the ice camp was set up on the landfast ice edge 70 km ENE of Pt. Barrow

(Fig. 3.8, p. 77) along a 3-4 km wide nearshore lead. All observations were from the ice because

low ceilings prevented behavioral observations from the aircraft. A total of 17 bowheads (13

groups) were observed during 4.3 h of pre-playback observation while the projectors were silent.

Nine of these groups were seen relatively close «500 m) to the silent projectors. The closest

CEPA relative to the ice camp was -50 m, during the pre-playback control period.

During playbacks of tones (for 1.6 h) and icebreaker sounds (for 3.2 h), five and three

groups, respectively, were sighted. They were all >500 m from the projectors; the closest sighting

was 509 m away during the icebreaker playback. Three other groups sighted <30 min after the

playback ended were also >500 m from the projectors. Thus the distribution of whales relative

to the ice edge appears to have changed during the day. The closest whale observed during the

icebreaker playback was exposed to an estimated S:N1I3,maxof 17 dB. One whale seen farther from

the projectors at a time of higher source level was exposed to S:NI/3,max=24 dB. During the preplayback control period, many of the whales seen were socializing and perhaps feeding, but during

and after playbacks only traveling whales were observed.

16 May 1994

The ice camp was set up about 35 km NE of Pt. Barrow (Fig. 3.8, p. 77) on the north side

of a large elongated ice pan along a secondary (offshore) lead oriented ENE-WSW -8 km north

of the landfast ice edge. The ice camp was present from 09:56 to 19:00, and icebreaker sounds

were projected from 13 :03 to 17: 13. On this date the median broadband (20-5000 Hz) source level

of icebreaker sounds was -166 dB re 1 /lPa-m (relatively high) and the average broadband (20-

5000 Hz) ambient noise level was 89 dB re 1 /lPa (relatively low; Table 6.3).
6.1 Bowhead Disturbance: Summary of Icebreaker Playbacks 260

Only -4 bowheads (3 groups or singletons) moved by within view of the ice camp. All sightings there occurred while the projectors were broadcasting icebreaker sounds. The closest

observed approach was to 570 m. The other two CEPAs were at 840 m and 775 m. These whales

were exposed to strong icebreaker sounds (up to S:N1/3,max=29-36 dB) but no obvious reaction was

noted.

During one aerial observation session, bowheads were followed from 4.8 km SW of camp

at 12:17 to 5.9 km SE of camp at 14:21. After the icebreaker playback started at 13:03, these

whales diverted SE from the offshore lead through a narrow crack into the inner lead. They passed

2.0-2.3 km SSW of the operating projectors and continued east along the south side of the pan

along whose north edge the ice camp was located. At CEPA, RLBB.medand RLBB,maxwere -105 and

109 dB re 1 JlPa, and S:N1/3,medand S:N1/3,maxwere 22 and 27 dB. It is possible that the whales

diverted SE to avoid closer approach to the projectors broadcasting tones and then icebreaker

sounds. However, given the rapidly-changing ice configuration at the time (see Appendix F), this

"diversion" may have been related to ice conditions instead of (or in combination with) the manmade noise.

A second aerial observation session was conducted 9 km SW of the operating projectors: at

the SW extent of the outer lead, from 14:31 to 16:22. Five bowheads were observed socializing

or traveling slowly eastward. During this session, one whale turned from a NE to a SE heading

when 9.2 km from the projectors and traveled SE. At that time and distance, S:NII3.medand

S:N1/3,maxwere at least 14 and 16 dB. The unusually high icebreaker:ambient ratio for a range of

9.2 km was related to the high source level and low ambientnoise on this date (see Appendix F,

Fig. F-34). Again, it is uncertain whether the SEward diversion was related to the icebreaker

sounds, to changing ice conditions, or both (Appendix F).

17 May 1994

On 17 May 1994, 35+ bowheads were observed as they passed within 3 km of a projector

set up in the pack ice at the east end of the main nearshore lead, some 70 km ENE of Pt. Barrow

(Fig. 3.8, p. 77). High sea states hindered both ice-based and aerial observations, and caused high

ambient noise levels. Also, the source level of the projected sounds was low, and the lowfrequency components were largely missing, because only the J-11 projector was operating on this

date. Throughout the day bowheads approached the projector from the WSW through a major lead.

Most appeared to continue NE along a secondary lead extending NEward south of the projector.

Only one bowhead was seen by the ice-based observers. It was seen 210 m north of the operating

projector and would have been exposed to estimated RLBB,medand RLBB,maxof 119 and 123 dB re

1 JlPa before it surfaced. At this location and time, the icebreaker:ambient ratio in the strongest

1/3-octave band (near 400 Hz) was up to -26 dB (S:NII3,max)'

There were five aerial observation sessions. During the first two sessions (projector silent),

whales traveled NE along a path that came as close as 600-800 m south of the projector, along the

southern (distant) side of the secondary narrow lead. During the third session, when icebreaker

sounds were being projected, some whales continued to follow that path. However, the secondary

lead had by then widened to 1.8 km and icebreaker sounds were barely detectable, if detectable
6.1 Bowhead Disturbance: Summary of Icebreaker Playbacks 261

at all, at 1.8 km distance (S:NI/3,max-4 dB). Two whales, a suspected mother/yearling pair,

approached to 2400 m from the operating projector and then appeared to reverse course to the SW.

However, it is doubtful that they could have detected icebreaker sounds at that distance, except

for very briefly and weakly, because the estimated S:NI/3,med and S:NI/3,maxwere -4 and +2 dB.

20 May 1994

On 20 May 1994, the projectors were set up on the NW side of a large pan that blocked the

nearshore lead 40 km ENE of Pt. Barrow (Fig. 3.8, p. 77). During control observations from both

the circling aircraft and the ice camp, bowheads were observed as they approached the projectors

from the west and WSW. They arrived at the large ice pan near and south of the projectors, turned

northward, and followed the edge of the pan north and east. Six of eight groups of bowheads came

within 400 m of the ice camp during the control period.

On this date the icebreaker sounds were projected at a high source level, and the ambient

noise level was low. Only ice-based observations were obtained during the playback due to

formation of low cloud. Bowheads continued to approach the projectors from the west and WSW.

However, the patterns of movement of most of the whales when they came within several hundred

meters of the ice camp were different during the playback than during the preceding control

period. During the playback, they seemed to divert both to the north and south of the projectors.

Only one whale approached the projectors closely during playback (1 of 11 groups were seen

within 400 m); it turned sharply away from the projectors when 58 m from them. (A whale that

surfaced at the same location during the control period dove toward the ice camp.) The whale that

approached closely during the playback voluntarily approached even though S:N1I3,maxwas near 60

dB. At the observed CPAs of other whales that came within 500-1000 m, S:NI/3,maxvalues were

-40-50 dB. The proportion of whales that diverted, and the actual distances when diversions

began, are unknown because of the limited viewing area from the ice and because low cloud

prevented aerial observations during this playback.

6.2 Distribution and Movements During Icebreaker Playbacks

The first of the main null hypotheses to be tested, as described in §1.2 (p. 7-9), is that

Playbacks of recorded noise from a bottom-founded platform (1989-90) or an icebreaker

working on ice (1991/94) will not (or alternatively will) significantly alter measures of

migration routes and spatial distribution of whales in the open water of nearshore lead

systems during the spring migration near Pt. Barrow, Alaska.

This section concerns reactions to icebreaker noise, based on the data given in Appendix F and

summarized in §6.1. Distributional effects of the 1989-90 playbacks of noise from drilling on an

ice pad (Karluk) are described in Richardson et al. (1990a:196ff, 1991a:148ff + 218ff).

Closest Estimated Points of Approach

The best method of determining whether whales were altering their paths to reduce their

exposure to icebreaker sounds would have been to compare the tracks of individual whales moving
6.2 Bowhead Disturbance: Icebreaker Playbacks & Distribution 262

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FIGURE6.4. Closest estimated points of approach (CEPAs) of traveling bowheads sighted within 3 km

of the ice camps during all days with playbacks of icebreaker sounds, 1991 and 1994. The different

symbol types indicate whether the observation was made by ice-based observers, aerial observers, or both.

Days included in the graphs are 17 May 1991 and 7, 9, 14, 16, 17, and 20 May 1994. CEPA is the

closest observed point to the projector for a whale seen only approaching or receding from the projector;

CEPA is the closest interpolated position to the projector for a whale followed as it approached, passed

and receded from the projector. See Appendix F for maps of whale tracks and tables including

corresponding estimates of CEPAs; this Figure summarizes the CEPAs given in those Appendix Tables.

past the ice camp during periods of silence ("control" periods) with the tracks of whales moving

past the same location during periods with playbacks of icebreaker sounds at known source levels

("experimental" periods). Any consistent changes in distribution or in tracks (i.e., diversions) that

were observed during experimental periods but not control periods could then have been attributed

to avoidance of the sound source. Because of unfavorable environmental conditions, we were

seldom able to follow whales as they approached and passed the projectors in 1991/94 as we had

done in 1990 (cf Richardson et al. 1991a). On most days in 1991 and 1994, weather conditions

either prevented observations from the Twin Otter circling at 460 m ASL, or made resighting of

whales difficult from both the Twin Otter and ice camp because of high sea states.

In the absence of many data on tracks of whales, we examined the distribution of sightings

(i.e., closest estimated point of approach to the source, or CEPA) during control and experimental

periods in order to assess changes in distribution (Fig. 6.4). However, comparisons based solely

on sighting distribution, as opposed to tracks, require substantially larger numbers of sightings to
6.2 Bowhead Disturbance: Icebreaker Playbacks & Distribution 263

on sighting distribution, as opposed to tracks, require substantially larger numbers of sightings to

demonstrate a change. This is especially so in the present case, where many CEPA distances were

overestimates, by unknown amounts, of actual CPA distances (see caption of Fig. 6.4 and examples

on p. 254). Figure 6.4 shows the CEPAs of traveling whales sighted during 1991 and 1994 during

periods of control observation and during different types of disturbance. Only days when icebreaker sounds were projected in the presence of bowheads are included in the control data, and

only bowheads that approached within 3 km of the ice camp are plotted. As evident from this

figure, ice-based observers saw few bowheads> 1.4 km from the ice camp. Thus, sightings from

the ice-based observers can only be used to monitor small-scale changes in distribution. Based

on Figure 6.4, it appears that there was a reduction in sightings of traveling bowheads within

400 m of the projectors when they were transmitting icebreaker sounds as compared with control

conditions. It cannot be determined from these data if there was a reduction in sightings beyond

this distance.

The effects of the playbacks of icebreaker noise on the distribution of traveling bowheads

would be better analyzed by comparing the CEPA data from the control and playback periods of

each individual experiment (day) than from the combined data in Figure 6.4. Some of the complications associated with differing ice conditions on different days might then be separated from

distributional changes caused by icebreaker playbacks. In addition, because the source levels of

icebreaker sounds varied among (and within) days, the effects may have been different on different

days. However, sample sizes were not adequate for meaningful within-day comparisons on most

days (Fig. 6.5). The two days with sufficient numbers of bowheads were 7 and 9 May 1994 (Fig.

6.5). On 7 May, there appears to have been a reduction in sightings within 400 m of the ice camp

during the playback period in comparison to the control period. On 9 May, the difference in distribution between the control and playback periods is not as clear. However, sightings within 500 m

of the ice camp were less frequent during the playback period. The 9 May experiment was complicated by the presence of feeding whales near the ice camp before and during the playback; this is

discussed below (see "Effects on Feeding Whales", p. 277). Although feeding whales are excluded

from Figures 6.4 through 6.11, the paths of the closest traveling whales seen on 9 May could have

been influenced by feeding whales, and may include data from whales that were feeding earlier

in the day.

Sound Exposure Levels

The variability of icebreaker sounds, and the problems associated with reproducing icebreaker sounds, complicated interpretation of the effects of this playback stimulus on bowhead distribution, movements, and behavior. The reactions by bowheads to icebreaker sounds are likely to be

related, in part, to the sound levels that are received by the whales. There has been considerable

discussion about the appropriate sound level measurements that best reflect the animals' ability

to detect, and propensity to react to, acoustic disturbances (Richardson et al. 1990b, in press:336-

8). Of the eight estimates of received level (RL) and icebreaker-to-ambient ratio (S:N) mentioned

earlier (§6.1, p. 251), some of the most consistent relationships between bowhead behavior and

estimated RL or S:N were found when we considered the maximum RL or S:N in the 113-octave

band of strongest icebreaker sound during the 64-s period preceding the whale observation

(RLII3,max or S:NII3,max; §6.3).
6.2 Bowhead Disturbance: Icebreaker Playbacks & Distribution 264

3....--------------------------------,

-E.x::

-Q)

o

c: 2

«S

1;)

o

"0

~

Q)

C/) .0

o

1ii

Q)

C/)

a

U

X

lee-based

181

Both

o

Aerial

o

o 00

o

o

x

x

X

X

X

X

o

xx

X

X

X

o-l----.-----.------,r----=-r.---..,-----r---,-----=:r:--____l

o

o

o

o

o

CIJ

CIIJ

o

o

X

oX

xSex

~

o

o

o

X

o

CD

o

X

181

181

Control Icebreaker

Playback

9 May 1994

X

X

X

X

X

X

X

X

X

181

181 X

Control Icebreaker

Playback

20 May 1994

3:-.-----------------1388---------------,

Control Icebreaker

Playback

17 May 1991

-E.x::-~

c: 2

«S

1;)

zs

"0

~

Q)

C/) .0

o

1;)

Q)

C/)

a

U

X

lee-based

181

Both

o

Aerial

X

X

X

X

X

X

7 May 1994

cD

o

o

00

000

o

o

o

o

o

o

o'4---~--.__-~--~--_r_--,.---._-__,--__T--_T_-____l

Control Icebreaker

Playback

14 May 1994

o

o

c:P

B

X

X

Icebreaker

Playback

16 May 1994

Control Icebreaker

Playback

17 May 1994

FIGURE6.5. Closest estimated points of approach (CEPAs) of traveling bowheads sighted within

3 km of the ice camps during control and playback periods on each individual day with playbacks

of icebreaker sounds, 1991 and 1994. See Figure 6.1 for explanatory notes.
6,2 Bowhead Disturbance: Icebreaker Playbacks & Distribution 265

Whatever acoustic measure is used, whale distribution and behavior need to be related to the

sound exposure level, not distance. Icebreaker sounds, unlike many other sounds that have been

projected to marine mammals, are highly variable in source level. Bowheads 500 m from the projectors at one time may be subjected to higher sound levels than the same (or different) whales

would receive when 250 m from the projectors at another time. Distance is not a good criterion

for assessing reaction thresholds when sounds are variable.

The problem of assessing distribution relative to the levels of sounds received by the whales

has been exacerbated by problems encountered while attempting to project icebreaker sounds into

the lead. The average source level differed from day to day and at different times within some

playback days (Table 6.3; see also Fig. 4.27-4.34 on p. 119fj). These variations in average source

level added to the natural moment-to-moment variability of the recorded icebreaker sounds, and

caused even greater variability in the received levels of sound at any given distance. Day-to-day

variations in source level further confounded attempts to compare bowhead distribution during

control and playback periods, and further emphasized the need to relate distribution (and behavior)

during icebreaker playbacks to sound exposure level rather than distance.

Figure 6.6 shows the estimated median and maximum broadband levels of icebreaker sounds

received near whales when they were at or near their CEPA to the projectors. This figure includes

only whales seen within 3 km of the projectors. Figure 6.6 also shows the average ambient noise

levels measured on each playback date. Ambient noise was usually measured just before and just

after each playback.

~ On a broadband basis, most whales observed within 3 km of the operating projectors were

exposed to icebreaker sound at levels of 85 to 120 dB re 1 IlPa (RLBB,medand RLBB.max)'

~ For most whales, received levels at CEPA locations ranged from 10 dB below to 30 dB

above the broadband ambient noise level. For several whales observed within 3 km of

the operating projectors on 17 May 1991 and 7, 9 and 17 May 1994, the broadband icebreaker sounds (RLBB,medand RLBB,max)were weaker than the average ambient levels.

Even so, because of variation in ambient levels and in sound propagation, some of these

whales probably were, at times, exposed to icebreaker sounds slightly exceeding broadband ambient levels.

~ On 20 May 1994, all whales seen within 3 km of the projectors were estimated to have

been exposed to high broadband levels of icebreaker sound, even in the cases of whales

seen 1-2 km away (Fig. 6.5 vs. 6.6). The source level was high and the ambient noise

level was low on 20 May 1994 (see Appendix F). For one whale observed approaching

and passing 58 m from the projectors, RLBB,medand RLBB,maxwell below the surface were

at least 132 and 138 db re 1 IlPa. These were the highest estimated RL values for any

traveling bowhead observed during icebreaker playbacks. (For this whale, and a traveling

whale 60 m from the projector at 16:31 on 9 May, the sound exposure model may have

underestimated RL and S:N at times when the whales were well below the surface.)

Levels of icebreaker sound in certain 1I3-octave bands may exceed the ambient noise level

in -those respective bands even when the overall broadband level of icebreaker sound is at or below

the overall broadband level of ambient noise. This can be seen by comparing Figures 6.6 and 6.7.
6.2 Bowhead Disturbance: Icebreaker Playbacks & Distribution 266

A. Median t-rnln RL, 20-5000 Hz

140

+

m 130

a..

::l.. +

TO" 120 4:

CD + ~

+ m ++ ++ + +

"0 + +++

- 110 + :t +

~ + 0

~+ Ctl

+ :t+

..a -1-++ +

4: ~

~ 100 Ambient '+

++ +

a.. + +

CJ) +++ ++

c

90 -+

'L: + -+.r ::J

"0 ++

...J

+ c:: 80 +

Whales >3km away not plotted

7

17 May 7 May 9 May 14 May 16 May 17 May 20 May

·1991 1994 1994 1994 1994 1994 1994

B. Maximum 1-min RL, 20-5000 Hz

140

+

-

130

a.. Ctl +

::I..

TO" + ++

120 CD~

+ + +

+t" t+

rn + +

-tt--q.

"0 +

- 110 + 7-+-t-

~ 4+- ++ ++

0 4+ +

Ctl ..a ++ -f-~+ -t +

~ 100 Ambient + + oFt ++

a.. + +

CJ) +

c + ++

'L: ::J ++

"0 ++

...J

c::

Whales >3km away not plotted

7

17 May 7 May 9 May 14 May 16 May 17 May 20 May

1991 1994 1994 1994 1994 1994 1994

FIGURE 6.6. Estimated broadband received levels of icebreaker sounds near traveling bowheads

at their CEPA distances during playback experiments, 1991 and 1994. RLBB,medand RLBB,maxwere

estimated by the sound exposure model described in section 2.3. The distances used to estimate

the RLs are shown in Figures 6.1 and 6.2. Because many CEPA distances are overestimated, many

RL values are underestimated.
6.2 Bowhead Disturbance: Icebreaker Playbacks & Distribution 267

A. Median 1-min RL, Dam. 1/3-0ct.

130

+

-

120 + <0 a..

:J.. ++

,... +

CD 110 ~ ~ •... ""!t" +

~ III + +

'0 + + ~

- 100 -Q '+

~ ++ +

-H0 if.

~

#+-f::J-+ <0 .c ++ +

~ 90 + +

a.. + -qT ++

+

C> +

++

c:

"-=: 80 Ambient ++ ::J

'0

...J +

a: 7

Whales >3km away not plotted

17 May 7 May 9 May 14 May 16 May 17 May 20 May

1991 1994 1994 1994 1994 1994 1994

B. Maximum 1-min RL, Dam. 1/3-0ct.

130

131

120 +

-<0 a.. + ++ :J..

,... ++

++ +

110 +

e

+ + ++++

+ + +

III +

+

-t+:+- '0 -tp:-+.+

- 100 +++ ++'+

~ +

:+ + +

0 ++ +!+ <0 + .c + + + ++

~ ++ +

a.. + +

C> +

+

c: +t- .-=: ::J ~ '0

...J

a: 7

Whales >3km away not plotted

60

17 May 7 May 9 May 14 May 16 May 17 May 20 May

1991 1994 1994 1994 1994 1994 1994

FIGURE6.7. Estimated received levels of icebreaker sounds in the dominant 1/3 octave near traveling bowheads at their CEPA distances during playback experiments, 1991 and 1994. RLI/3,med and

RL1I3,max were estimated by the sound exposure model described in section 2.3, The distances used

to estimate the RLs are shown in Figures 6.1 and 6.2. Because many CEPA distances are overestimated, many RL values are underestimated.
6.2 Bowhead Disturbance: Icebreaker Playbacks & Distribution 268

A. Median 1-min S:N Ratio, 20-5000 Hz

50

EI3

40

+

-

:j: CD

•...... "0 30

EI3

~ 83EEH0

m

+ +

.c 20 +

:j:

~ ~

+

a.. +EH ~

0> + EI3

C 10 + +

'L: +E13

.•..

:J

~+

+

"0 -+-,1+-

'+' --+-+-

Z 0

++ iJj + +

+

-tea+- +

+ ++

+EI3

-10 ++

+

+ Whales >3km away not plotted

-20

17 May 7 May 9 May 14 May 16 May 17 May 20 May

1991 1994 1994 1994 1994 1994 1994

B. Maximum 1-min S:N Ratio, 20-5000 Hz

50

51.r

40 +

++

-CD EI3

"0 30 +

~+

•......

~ +

m

0 + + +

.c ++ 20 EI3E13

~ I+- EI3

a.. +

0> + +

'L:

c 10

.....p-+ +83 +

~~

:J

"0 +

Z

.•.. ~

0 +.I±I

en + +

+E13

+ ++

+

·10 ++

.t

Whales >3km away not plotted

-20 . . . .

17 May 7 May 9 May 14 May 16 May 17 May 20 May

1.991 1994 1994 1994 1994 19.94 1994

FIGURE6.8. Estimated broadbandicebreaker-to-ambient ratios (S:NBB,medand S:NBB,max) near traveling bowheads at their CEPA distances during playbacks, 1991 and 1994, Ambient noise levels,

measured for periods before and/or after icebreaker sounds were projected, were subtracted from

estimated received levels shown in Figure 6.6 to get S:N. Squares show cases where tracks may

have been diverted by icebreaker noise. Qualifications as in Fig. 6.6.

"
6.2 Bowhead Disturbance: Icebreaker Playbacks & Distribution 269

vv

A. Med. 1-min S:N Ratio, Dam. 1/3 Oct.

co

~ 40

~

o

m

.0 30

~

a..

g> 20

.;::

:J

U

Z 10

iJj

50

+

EI3

+

+

+E8

EI3 + +

-10+-----.---...,-----,,----.-----,.----,---..-----1 I

Whales >3km away not plotted

+

~-+:'+

T

+

17 May

1991

7 May

1994

+

EI3

+

+

6O'....-------------------------~H---~

co

~ 40

~

~

.0 30

~

a..

g> 20

.;::

:J

U

Z 10

iJj

9 May 14 May 16 May 17 May 20 May

1994 1994 1994 1994 1994

B. Max. 1-min S: N Ratio, Dom. 1/3 Oct.

Whales >3km away not plotted

50

++

+

+

+

+

+

++

+

+

+

+

-10I-l----.-----,.---....-----..------..,.----r----..-----l I . I I

FIGURE6.9. Estimated icebreaker-to-ambient ratios in the dominant 1/3 octave (S:NII3•med and

S:NII3•max) near traveling bowheads at their estimated CEPA distances during playbacks, 1991 and

1994. Ambient noise levels, measured for periods before and/or after icebreaker sounds were projected, were subtracted from estimated received levels shown in Figure 6.8 to get S:N. Squares

show cases where tracks may have been diverted by icebreaker noise. Qualifications as in Fig. 6.8.

17 May

1991

7 May

1994

9 May 14 May 16 May 17 May 20 May

1994 1994 1994 1994 1994
6.2 Bowhead Disturbance: Icebreaker Playbacks & Distribution 270

The icebreaker-to-ambient ratio in the ll3-octave band of strongest icebreaker sound ("dominant

ll3-octave") is usually higher than the broadband icebreaker-to-ambient level (Fig. 6.8 vs. 6.9).

Levels in ll3-octave bands are relevant because the typical effective filter bandwidth of mammalian hearing systems is roughly ll3-octave (Richardson et al. in press:226fj). This means that it

is the background noise within a bandwidth of -l/3-octave that determines the animal's ability to

hear a sound, and determines its signal-to-ambient ratio.

Some bowheads were exposed to icebreaker sounds whose RL1/3in the "dominant" l/3-octave

band exceeded the ambient noise level in that band even though the RLBB did not exceed

broadband ambient levels (Fig. 6.7 vs. 6.6). If the natural variability in ambient noise is

considered, almost all (if not all) bowheads that passed within 3 km of the operating projectors

were exposed, at least intermittently, to icebreaker sounds exceeding the ambient noise level in

one or more ll3-octave bands. Also, many CEPAs are overestimated, so many RLs are

underestimated. At least some whales whose estimated RLI/3 values were below ambient may have

approached closer to the projectors than CEPA and, therefore, may have been exposed to received

levels that exceeded ambient levels.

Figure 6.10 shows that traveling bowheads were exposed to a wide range of received levels

of icebreaker sounds at their CEPA distances from the operating projectors regardless of the type

of sound measurement used. Figure 6.11 shows the frequency distribution of icebreaker-toambient ratios for the same whales at the same times and locations. Different measures of S:N

lead to different conclusions about noise exposure. The S:NBB,medmeasure in Figure 6.11A suggests that over half of the bowheads were exposed to sounds that were either below ambient or

exceeded ambient levels by <10 dB. In comparison, the S:NI/3,maxmeasure shown in Figure 6.11D

indicates that almost all whales observed within 3 km of the operating projectors were exposed to

icebreaker sound whose level in the strongest l/3-octave exceeded the ambient level in that band,

at least briefly (S:N1/3 max>OdB). If allowance is made for the natural variability in ambient noise,

"

probably all whales seen <3 km from the operating projectors were exposed to S:N>O dB for at

least brief periods. Almost half (29 of 63) of the whales observed within 3 km of the projectors

were exposed to moderately strong (S:NI/3,max>20dB) icebreaker sounds, at least briefly, when they

were near their CEPAs.

Most of these bowheads swam into the ensonified area around the projectors while the projectors were operating; bowheads were rarely under observation within 3 km of the ice camp when

playbacks began. Therefore, it appears that many bowheads exhibited some tolerance of variable

icebreaker sounds. Nonetheless, some diversion and avoidance were observed, so this tolerance

of icebreaker sounds is limited.

It would be interesting to compare the RL and S:N data for various subsets of the bowheads

observed during playbacks, including

~ bowheads whose true CPA distances were determined, as opposed to those for which the

closest observed distance was probably an overestimate of CPA;

~ bowheads for which the received icebreaker sounds at the CEPA time were higher vs.

lower than they had been in preceding minutes;
6.2 Bowhead Disturbance: Icebreaker Playbacks & Distribution 271

~ bowheads observed by aerial vs. ice-based observers (or both); and

~ bowheads that did vs. did not show evidence of diversion or avoidance.

Unforturiately, the sample sizes were too small to justify a multi-way subdivision of the data by

all of these criteria, or to allow a meaningful multivariate analysis. However, the following

subsections do discuss cases of apparent diversion and avoidance. Figures 6.8-6.11 distinguish

the bowheads with possible diversion (I±Isymbols in Fig. 6.8-6.9; shaded bars in Fig. 6.10-6.11)

vs. other bowheads (+ symbols or open bars).

Apparent Avoidance Reactions

Some bowheads were observed within a few hundred meters of the operating projectors, with

no obvious diversion or avoidance. Other bowheads seemed to alter course at similar or greater

distances in order to avoid close approach to the projectors. These observations provide some

information about situations where reactions were and were not evident.

From the available data we cannot quantify the proportion of bowheads exhibiting overt

diversion or avoidance when they approached within various distances, or within various RL or

S:N contours. Unfavorable weather conditions during most playback days in 1991/94 prevented

us from documenting tracks of most whales as they approached and passed the projectors. As a

result, cases of diversion were difficult to identify, and the frequency of diversion was probably

greater than recognized. Another limitation of not obtaining continuous tracks of whales is that

CPA distances for many whales both during control and experimental periods were overestimated.

Without knowing the track of a whale, we can only determine the closest observed point of

approach, which will often exceed the actual CPA. Where complete tracks are obtained, CPA

distances can be estimated by inferring paths taken by whales while they are below the surface.

Figures 6.4 and 6.5 suggest that some migrating whales changed their paths to remain more

than -400 m from the operating projectors. However, distance is not a very useful measure, given

the variability in sounds received by whales at any given distance. In addition, the variability in

received levels may obscure displacements at longer distances. There may have been changes in

the paths of some whales passing at distances >400 m-changes that are not evident amongst the

tracks of other whales seen at those distances during quieter periods.

Additional information on distances at which avoidance reactions occurred comes from the

behavior of whales seen close to the operating projector. Table 6.5 summarizes observations of

whales that appeared to have modified their behavior or tracks in the presence of icebreaker

sounds. It is not certain that all of these modified behaviors or tracks resulted from exposure to

icebreaker sounds; however, they represent behaviors and track characteristics that were not often

exhibited by migrating whales in the absence of exposure to icebreaker noise playbacks.

Avoidance Within 400 m.-Not surprisingly, some of the whales seen within 400 m of the

operating projectors showed apparent diversion (Table 6.5). At least one whale "voluntarily"

approached the projectors when S:N1I3,max was near 60 dB before apparently reacting by turning

sharply away (see 20 May 1994 section of Table 6.5 and Appendix F).
A: Mad. BB Ree. Level

301~------------------'''';''---'

70-80

c. Med. 1/3-Oct. Ree. Level

B: Max. BB Ree. Level

30

~

Reaction lfi

1il2O

~

'0

...

il

§ 10

Z

3O,-r-----------------------,

lfi

1il2O

s

'0

.2l

§ 10

Z

70-80 80-90 90-100 100-110110-120120-130130-140

RL near Whales (dB)

70-80

D: Max. 1/3-0ct. Ree. Level 3O-r-----------------------,

lfi

1il2O

~

'0

~ 10

Z

7Q-80 80-90 90-100 100-110110-120120-130130-140

RL near Whales (dB)

FIGURE6.10. Frequency distributions of estimated received levels of icebreaker sounds near traveling bowhead whales at their CEPA

distances from the operating projectors, 1991 and 1994. (A) RLBB,med' (B) RLBB,max, (C) RL1I3,med' and (D) RL1/3,max' Only whales sighted

within 3 km of the ice camp are plotted. Many CEPA distances are overestimated; therefore, many received levels are underestimated.

Bowheads that were and were not observed to modify their tracks near the ice camp are distinguished (shaded vs. open parts of bars);

see text for cautionary notes. .
A: Mad. BB S:N Ratio

301~---------------------''''

l3

iii 20

s

'5

~

§ 10

Z

-20-10-1M 0-1010-2020-3030-4040-505CHlO60-70

S:N near Whales (dB)

c Mad. 1/3-Oct. S:N Ratio

3O~---------------------...,

B: Max. BB S:N Ratio

301~----------------------''

l3

iii 20

~

'5

~

§ 10

Z

-20-10-1M 0-1010-2020-3030-4040-505CHlO60-70

S:N near Whales (dB)

D: Max. 1/3-Oct. S:N Ratio

301~---------------------''''

l3 l3

iii 20 iii 20 .c

~ ~

'5 '5

~

•..

§ 10 ~ 10

Z Z

-20-10-1M 0-1010-2020-3030-4040-505CHlO60-70

S:N near Whales (dB)

FIGURE6.11. Frequency distributions of icebreaker-to-ambient ratios near traveling bowhead whales at their CEPA distances from the

operating projectors, 1991 and 1994. (A) S:NBB,med' (B) S:NBB,max' (C) S:N1I3,med' and (D) S:N1I3,max. Otherwise as in Fig. 6.10. .'

-20-10-1M 0-1010-2020-3030-4040-505CHlO60-70

S:N near Whales (dB)
6.2 Bowhead Disturbance: Icebreaker Playbacks & Distribution 274

TABLE 6.5. Summary of sightings of traveling bowhead whales that appeared to modify their tracks near

the operating projectors during 1994.

Distance (m) Noise a

Date Reaction Observed RL S:N Nature of Track

7 May 362 362 to 706 96 13 W of projectors swimming N. Large wake and long blow

intervals. Turned ENE when 700 m away.

7 May 3OOO? 3000 to 3300 78b -4b Several groups seen heading north along lead west of ice

camp. Earlier whales were not seen traveling north.

9 May 206 206 to 260 111 26 NW of projector turned to N from NE and headed N

9 May 430 430 to 420 111 25 W of projector heading N, turned to NE.

9 May 940 940 to 500 101 16 W of projector heading N, turned E, turned S, then

projector turned otT; turned ENE and approached camp

to 500 m, then dove.

9 May <660 660 to 1400 >101 >16 NNE of projector heading NE toward N side of lead,

turned to E when arrived at ice edge and dove under small

pan.

9 May 500 1600 to 500 103 18 Dove NNE under brash ice when open water available to

ENE.

9 May <2000 2000 >93 >8 NW of and heading NW away from projector, turned N

and dove toward brash and pans on N side of lead.

16 May -2500 -3150 to +5900 102 27 3 groups heading ENE toward projectors turned SSE

through narrow crack between 2 large pans and passed S

of projectors 2 kID.

16 May 9200 9900 to 9200 then 91 16 Turned from NE heading to SE and resurfaced SE of that

turned SE to 9400 location, then traveled E.

then E to 8200

17 May -2200 5900 to 2400 93 1 Adult and yearling appear to have reversed course, but

(97)b (6t were not seen again. Last seen traveling south.

20 May 58 115 to 58 131c

63c

Turned sharply to NNW away from projectors.

20 May >600 600 to 1225 <108 <38 NNW of projectors traveled NE; earlier whales traveled E.

20 May >725 725 <112 <44 SW of projectors traveled SE; earlier whales traveled E.

20 May <1275 1275 >109 >41 NNW of projectors traveled NE; earlier whales traveled E.

20 May <3250 3250 to 3750 >100 >30 Same as above.

a Sound levels are maximum levels in the dominant 1/3-octave band during the previous I-min period (RLI13•

1lUIX and S:NI13,max).

b These are the highest levels during the previous 14 minutes for the same distance.

c These levels may be slight underestimates of levels that would be received below the surface.
6.2 Bowhead Disturbance: Icebreaker Playbacks & Distribution 275

Avoidance at 400-1500 m.- There is evidence that several whales altered their tracks when

400-1500 m from the operating projectors.

~ On 9 May 1994, a combination of observations by the aerial and ice-based observers

documented a bowhead modifying its track when it was 940 m from the operating

projector. The whale followed an irregular course while the projector was operating, but

when icebreaker sounds stopped the whale turned and swam toward the silent projector

(Table 6.5; Fig. F-18, F-19 in Appendix F). It then dove toward the projector, surfaced

500 m from it, and finally dove toward the silent projector. It was not resighted.

~ On 20 May 1994, several whales apparently changed course when >600 m from the projector. Aerial observations could not be conducted at that time because of low cloud, so

the diversions could not be confirmed nor could their initial distances be determined.

The following tabulation summarizes the eight sound measures in the seven cases when bowheads were observed to alter course 400-1500 m from the projectors:

Sound Measure (dB)

Date Distance

9 May 430 In

9 May 940 In

9 May <660 In

9 May 500 In

20 May >600 In

20 May >725 In

20 May <1275 In

RLBB,med RLBB,max RL1/3,med RL1/3,max S: NBB,med S: NBB,max

112 116 106 111 12 16

105 107 99 101 5 7

>102 >107 >96 >101 >2 >7

107 110 100 103 7 10

<112 <116 <105 <108 <26 <29

<114 <118 <110 <112 <28 <32

>112 >115 >108 >109 >26 >29

S : Nl13,med

21

14

>11

15

<35

<42

>40

S : N1/3,max

25

16

>16

18

<38

<44

>41

Avoidance at > 1500 m.-A voidance at distances more than -1 Yz km from the operating projectors usually was evident only from aerial observations. The ice-based observers usually cannot

see bowheads more than -1 Yz km from the ice camp. When sea states are high, they cannot reliably detect whales beyond 1 km, or possibly closer on windy days such as 17 May 1994. Without

aerial observations, it is impossible to determine whether some bowheads that are more than

1Yz km away change course to divert around the projector site. Because low ceilings prevented

the Twin Otter crew from watching whales near the ice camp on all or parts of several days in

1991 and 1994, and because we were rarely able to follow individual whales for prolonged periods,

our ability to identify larger scale avoidance was limited in 1991/94.

On 16 May 1994, we followed three small groups of whales that changed course as they

approached within -2.5 km of the projectors, appearing to divert around them. However, the local

and rapidly changing pattern of ice pans could have accounted for the paths taken, as described

in Appendix F. On the same date we observed a whale that was heading toward the projectors

change its path from a NE heading toa SE heading when it was 9.2 km from the projectors. This

whale then traveled E and passed 8.2 km south of the projectors. Again, the distribution of ice

could have caused the change in path (Appendix F). Sound levels reaching these whales are

summarized in the text table below. Because the source level was strong and ambient noise was

weak on 16 May 1994, the RL and S:N values of icebreaker sounds at these distant locations were

similar to those where small-scale avoidance reactions were seen on other days.

There was evidence of diversion at ranges> 1Yz km on other days as well. On 20 May 1994,

observers at the ice camp recorded a bowhead traveling NE when it was 3250 m NNE of the pro-
6.2 Bowhead Disturbance: Icebreaker Playbacks & Distribution 276

jectors. Based on its heading the whale may have diverted when >2 km from the projectors. On

9 May 1994, the aerial observers sighted a bowhead -2 km NW of the projector heading NW, away

from the projector. This whale turned and dove northward into the brash ice along the north side

of the lead. This whale may have approached closer to the operating projector than 2 km, but it

appears to have moved at least 2 km from the operating projector before returning to a normal

NNE heading. On 7 May 1994, some whales may have diverted offshore into a narrow Nf-7S lead

that was -3 km west of the projector. If these whales did divert, we do not know how close they

approached the projectors before they diverted. Estimated sound levels near these whales when

they were sighted are presented in the table below, but the levels that were received near the

whales when they diverted cannot be estimated because the distance where the diversion was

initiated is unknown.

Date Distance

7 May <3000 In

9 May <2000 In

16 May 2500 In

16 May 9200 In

17 May -2200 In

20 May <3250 In

Sound Measure (dB)

RLBB,med RLBB,max RLl/3,med

>81 >86 >74

>93 >99 >86

105 108 100

93 99 89

94 99 86

>102 >107 >97

RLl/3,max S:NBB,med S:NBB,max S:Nl13,med

>78 >-14 >-9 >-8

>93 >-6 >-1 >2

102 16 19 25

91 3 9 14

92 -7 -2 -5

>100 >16 >21 >27

S: Nl/3,max

>-4

>8

27

16

1

>30

In summary, there were two occasions, both on 16 May 1994, when we reliably determined

the distances where bowheads showed apparent diversion> 1Y2 km from the projectors. The values

of S:N1I3.maxfor these cases were 16 and 27 dB. The occurrence of a course change under these

conditions was confirmed, but whether these course changes were caused by icebreaker noise or

changing ice configuration is uncertain. In another case, a whale that had probably passed its CPA

was exposed to S:N1I3,max=30dB at the time it was seen.

These values of S:N 1/3,maxassociated with possible avoidance> 1Y2 km from the projectors are

consistent with S:N values where some whales closer to the projectors at other times apparently

showed avoidance reactions to icebreaker sounds. However, the proportion of whales> 1Y2 km

from the projectors that showed avoidance reactions when subjected to these levels of icebreaker

noise is unknown, as few bowheads could be followed for long enough in 1991/94 to document

such diversion. Many other whales did not appear to avoid the projectors when exposed to similar

or higher levels of sound.

Avoidance During Playback and Control Conditions.- Table 6.5 summarizes RL1I3,maxand

S:N1I3,maxfor all diverting whales. Figures 6.8 and 6.9 show levels received by the "apparently

diverting" whales listed in Table 6.5 (l±l symbols) and by the whales showing no evidence of a

change in course (+ symbols). Overall, Table 6.5 lists 18 cases in which bowhead whales (singles

or groups) exhibited apparent avoidance reactions to the projectors during icebreaker playbacks.

In contrast, during control conditions near the ice camp in 1991/94, a possible avoidance reaction

was noticed on only one occasion: On 7 May 1994, three bowheads heading ENE directly toward

the ice camp turned ESE and dove under the landfast ice when they were -300 m WSW of the ice

camp (see Fig. F-6 and Table F-2 in Appendix F, time 11 :58). The higher number of bowhead

groups showing apparent avoidance reactions during playback conditions (18 of 80) than during

control conditions (1 of 116) was highly significant (chi2=22.9, df=l, P<O.OOI).
6.2 Bowhead Disturbance: Icebreaker Playbacks & Distribution 277

Avoidance vs. Icebreaker:Ambient Ratio.-A substantial proportion (9 of 29 or 31 %) of the

traveling bowheads showed signs of avoidance upon (or before) exposure to S:NII3•max levels above

20 dB (I±I symbols in Fig. 6.9B; shaded bars in Fig. 6.11D). However, 14% (4 of 28) of the traveling bowheads exposed to S:NII3•max levels of 0-20 dB also showed indications of avoidance. Two

additional cases are not included on Figure 6.9 because they were at >3 km distance (S:NII3,max -4

dB and 16 dB; Table 6.5). These observations suggest that a typical traveling bowhead might

begin to divert when the icebreaker-to-ambient ratio (S:NII3•max) is somewhere around 20 dB, with

some individuals diverting at considerably lower S:N, and some not diverting even at considerably

higher S:N. However, this interpretation of the 1991/94 data must be treated very cautiously

because of the small sample size (Table 6.5), high variability, and known observation biases:

1. CEPA distances were often overestimated, so S:N at CEPA was often underestimated.

2. Frequency of diversion was probably underestimated in 1991/94 because ice-based

observers saw only the closer whales, and neither ice-based nor (in 1991/94) aerial

observers could follow many whales for long enough to document their tracks past the

Ice camp.

The reaction threshold would tend to be underestimated as a result of difficulty (1) and

overestimated as a result of difficulty (2).

Figures 6.lOA-D and 6.11A-C show corresponding results for the other seven RL and S:N

measures. Inspection of these diagrams shows that, for all sound measures, bowheads that diverted

tended to be exposed to somewhat higher RL or S:N levels than were the bowheads not noticed

to divert. However, this tendency was weak, with much overlap in sound levels at which bowheads did and did not react. The problems and cautionary notes mentioned in the preceding

paragraph apply to all of these measures of RL and S:N.

Effects on Feeding Whales

The projection experiment on 9 May 1994 provided information on the reactions of lingering

whales, possibly engaged in feeding, to playbacks of icebreaker sounds. On this date several

whales appeared to be feeding beneath the landfast ice edge in the area <300 m from the ice camp

before the playback experiment started. In previous analyses, we have considered only traveling

whales because our sample size of traveling whales is substantially larger than for any other

behavioral category during spring migration. However, the special case of the apparently-feeding

bowheads observed on 9 May 1994 warrants individual presentation. There are difficulties in

interpreting these data because it was often not possible to identify individual whales. To the

degree possible, individual whales have been counted only once, but it is almost certain that

several sightings were unrecognized repeat sightings. Thus the number of different feeding whales

present was no doubt considerably less than implied by the raw counts.

On 9 May 1994, feeding whales were seen closer to the operating projector than were

traveling whales, and they voluntarily subjected themselves to higher levels of icebreaker sounds

than did traveling whales (Fig. 6.12). One or two small bowheads (the identity of the whale(s)

could not be confirmed in most cases) dove -8 times within 150 m of the operating J-ll projector,

in one case diving below the surface only 17 m from the projector at a time when its source level
6.2 Bowhead Disturbance: Icebreaker Playbacks & Distribution 278

Traveling vs. Feeding Whales, 9 May

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Max. 20-5000 Hz Max. 1/3-0ct. Distance

FIGURE 6.12. Estimated icebreaker-to-ambient ratios near traveling vs. feeding bowheads at their CEPA

distances, 9 May 1994, considering bowheads seen within 3 krn ofthe ice camp (S:NBB,max and S:N1I3.max).

Many CEPA distances are overestimated, so many S:N values are underestimated. Also shown on the

right side are the CEPA distances for which the S:N ratios are computed.

was 153 dB re 1 J!Pa-m. The estimated RLBB.max at 17 m was 132 dB re 1 J!Pa, and S:NII3.med and

S:NI13.max were 36 and 38 dB. The whale dove partially toward the projector, so its actual CPA

when below the surface may have been slightly less than 17 m. This same whale (identity confirmed from photographs) was seen <20 m from the projector 83 min later, 13 min after the

projector was turned off. It was probably seen on several additional occasions between these

times, but its identity was not always confirmed. Another bowhead sighting, at distances as close

as 24 m from the operating projector, occurred at a time with higher source level than during the

17 m case. Hence, RL and S:N were higher than for the 17 m case despite the slightly greater

distance: during the 24 m sighting, RLBB.med and RLBB.max at 24 m were 132 and 135 dB re 1 J!Pa,

RLII3.med and RLI13.max were 126 and 129 dB, and S:NI/3.med and S:NI/3.max were 41 and 44 dB.

. Appendix F provides additional details for all feeding whales seen on 9 May 1994.

In general, these lingering bowheads appeared to tolerate signal-to-noise ratios as much as

15-20 dB higher than did traveling whales observed migrating toward the northeast on this date.

On this date there was no obvious avoidance of the projector by feeding whales, except possibly

at extremely close ranges «15 m).
6.3 Bowhead Disturbance: Icebreaker Playbacks & Behavior 279

6.3 Behavior During Icebreaker Playbacks

The second null hypothesis to be tested during this study, from §1.2 (p. 7-9), is that

Playbacks of recorded noise from a bottom-founded platform (1989-90) or an icebreaker

working on ice (1991/94) will not (or alternatively will) significantly alter subtle aspects

of individual whale behavior in the open water of nearshore lead systems during the

spring migration near Pt. Barrow, Alaska.

The present section concerns the reactions to icebreaker noise. Reactions to the 1989-90 playbacks

of noise from a drilling operation on an ice pad (Karluk) were described in Richardson et al.

(1991 a: 163ff and 228fj).

Data Considered

Data considered here came from systematic aerial observations of bowhead behavior during

the icebreaker playbacks in 1994. One icebreaker playback to bowheads was done in 1991, but

aerial observations were not possible then because of low cloud. Overall, we obtained partial or

"complete" behavioral data for 149 surfacings and 83 dives during icebreaker playbacks, and for

an additional 26 surfacings and 20 dives during the period 0-30 min after the ends of icebreaker

playbacks (Table 2.2, p. 37). These data were obtained on 7, 9,16 and 17 May 1994 (Table 6.1,

p. 248). Aerial observations of presumably undisturbed bowheads were obtained during preand/or post-playback control periods on these four dates, and also during the pre-playback period

on 20 May 1994 (Table 6.1). These behavioral observations tended to be less complete than usual,

largely because of the prevailing high winds and high sea states in 1994. Because of the high sea

state, we often sighted whales some time after they surfaced rather than as they surfaced. In these

cases, we could not characterize the variables that depend on observation of the full surfacing

(e.g., duration of surfacing, number of blows per surfacing, degrees of turn during surfacing).

Analyses in this section consider only whales whose group activity was classified as "traveling" or "traveling plus socializing". Individual surfacings and dives were excluded if there was

active socializing or aerial behavior (a breach, flipper or tail slap, or roll). Mothers and calves

were also excluded. These criteria restricted the analysis to a relatively homogeneous category

of whales, representing the migrating animals. These selection criteria retained most of the

observations, but excluded special cases where behavior would be expected to be "unusual" even

in the absence of any type of disturbance (cf. §5.3, 5.4). These restrictions were similar to those

adopted in the corresponding analyses of Karluk data (Richardson et al. 1990a).

Surfacing, Respiration and Diving Behavior

Behavior vs. Distance from Projectors.- There was no strong correlation between any of the

standard four measures of surfacing/respiration/dive cycles and distance from the operating sound

projector during icebreaker playbacks (Table 6.6A; Fig. 6.13). There also was no strong

correlation of any such variable with distance under control conditions, i.e. when the ice camp was

present within 10 km but there was no known source of potential disturbance at the observation

time or within the previous 30 min (Table 6.6A; Fig. 6.14). There was a weak negative correlation
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6.3 Bowhead Disturbance: Icebreaker Playbacks & Behavior 280

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FIGURE 6.13. Surfacing, respiration and dive behavior in relation to distance from projectors

during 1994 playbacks of icebreaker sounds. Aerial observations only; only traveling bowheads

included; mothers, calves, and surfacings with active socializing or aerial behavior excluded.

Numerals in graphs depict number of cases at each location.
.. .. .. ..• .. .... .. ......•........•........•........•........

6.3 Bowhead Disturbance: Icebreaker Playbacks & Behavior 281

Control Data vs. Range

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FIGURE6.14. Surfacing, respiration and dive behavior in relation to distance from silent projectors

during 1994 control periods (ice camp present within 10 km but projectors off). Case selection

criteria as in Fig. 6.13. Numerals and letters (A,B, ...) in graphs depict numbers of cases at each

location (A=IO, B=II, ...).
TABLE 6.6. Correlation of surfacing, respiration and dive behavior of traveling bowheads vs. (A) distance from projector, (B) estimated

received sound level, and (C) estimated received signal to ambient-noise ratio during (A,B,C) icebreaker playbacks and (A only) associated

control conditions, 1994. Acoustical variables (B) and (C) are measured during the 64 s preceding the behavioral observation. Mothers,

calves, and surfacings with active socializing or aerial behavior are excluded. Aerial observations only. Po is nominal 2-tailed significance

level of the correlation coefficient. See associated scatter diagrams corresponding to boldface sections.

Behavioral A. vs. Distance (log km) Acoustical Variable B. vs, RL (dB re 1 ,..Pa) C. vs, S:N (dB)

Variable Condition r n Po (Measured Over 64 s) r n Po r n Po

Median Playback 0.215 69 (+) 20-5000 Hz median 0.008 68 ns 0.055 68 ns

Blow Control 0.001 158 os maximum -0.024 68 ns 0.029 68 TIS

Interval Dom. 113-0ct. median 0.022 68 ns 0.061 68 ns

maximum 0.003 68 ns 0.046 68 ns

# Blows Playback -0.179 51 ns 20-5000 Hz median 0.278 50 (+) 0.268 50 (+)

per Sur- Control 0.039 117 maximum 0.279 50 0.271 50 (+) ?'

ns + w

facing Dom. 113-0ct. median 0.284 50 + 0.281 50 +

t:l:I

()

maximum 0.280 50 + 0.282 50 +

~

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Duration Playback 0.004 49 os 20-5000 Hz median 0.265 48 (+) 0.318 48 + t::l

of Sur- Control 0.005 119 os maximum 0.280 48 (+) 0.332 48 +

0;'

i:

facing Dom. 113-0ct. median 0.270 48 (+) 0.329 48 +

;;.

l:l

maximum 0.304 48 + 0.356 48 +

;:s

t1

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Duration Playback -0.001 23 os 20-5000 Hz median 0.122 22 ns 0.100 22 ns

;:;-

"'

0-

of Dive Control -0.297 49 maximum 0.124 22 ns 0.104 22 ns ~

Dom. 113-0ct. median 0.114 22 0.060 22 l:l

ns ns r:-

maximum 0.104 22 0.057 22

.,

ns os "1:l

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Degrees Playback -0.079 57 20-5000 Hz median 0.374 56 0.423 t1

os ++ 56 +++ ~

of Tum Control 0.150 128 (+) maximum 0.365 56 ++ 0.419 56 +++ Roo

(log) Dom. 113-0ct. median 0.387 56 ++ 0.443 56 +++

t:l:I

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IV
6.3 Bowhead Disturbance: Icebreaker Playbacks & Behavior 283

(Pn<0.05) between duration of dive and distance from camp under control conditions. There was

no hint of any similar distance effect during playbacks. (The "P," designation, following the

notation used in §5.3-5.4, refers to a nominal probability level, recognizing that some whales

contributed more than one dive or surfacing to these analyses.)

The absence of obvious relationships between distance from projector and any of the four

surfacing, respiration and dive cycles during playbacks is not necessarily surprising, given the

highly variable sounds being emitted from the projectors, along with differences in propagation

loss rates at sites with different water depths (§4.3). The received level of icebreaker sound at any

given distance varied greatly depending on date (=location) and time. Some aerial observations

of behavior during playbacks, although within 10 km of the ice camp, were at distances and times

where the received sound level was below the ambient noise level, and probably undetectable to

bowheads.

Behavior vs. Received Level (RL).-In contrast, two of the four measures of surfacing/

respiration/dive cycles were significantly correlated with some estimates of the received level (RL)

of icebreaker sound at the whales' locations (Table 6.6B). We used the model described in §2.3

and §4.3 to estimate RL at the locations and times of each whale observation. This model takes

account of the water depth, distance of the whale from the projectors, and the source level and

spectral properties of the projected icebreaker sound during the 64-s period immediately preceding

the time of the observation. We use the same four RL estimates as described in §6.1 (p. 251):

RLBB,med'RLBB,max'RLII3,med' and RLII3,max'

With increasing RL, duration of surfacing and number of blows per surfacing each showed

a weak tendency to increase. Depending on the specific estimate of RL used, correlation coefficients ranged from 0.278 to 0.284 for number of blows and 0.265 to 0.304 for duration of surfacing

(0.1>Pn>0.01 in each case). Figure 6.15 shows scatter diagrams corresponding to the boldfaced.

correlation coefficients in Table 6.6B, depicting relationships to RLII3,max' This estimate of RL

tended to show some of the highest correlation coefficients with various measures of behavior

(Table 6.6B,C). Even so, relationships of estimated RL to duration of surfacing and number of

blows per surfacing were all weak, as evident from the extensive scatter of data points in Figure

6.15B,C, the rather low correlation coefficients, and the associated low levels of nominal statistical

significance.

There was no evidence of any significant correlation between RL and either median blow

interval or duration of dive (Table 6.6B, Fig. 6.15A,D).

Behavior vs. Icebreaker:Ambient Ratio (S:N).-The duration of surfacing and the number

of blows per surfacing also showed weak but significant positive correlations with some measures

of the icebreaker-signal to ambient-noise ratio (Table 6.6C, Fig. 6.16B,C). The stronger the RL

of icebreaker sound relative to the prevailing natural background noise level, the longer the surfacings and the more blows per surfacing. Although the correlations were again weak, duration of

surfacing showed slightly stronger correlations with all measures of S:N than with corresponding

RLs (Table 6.6C vs. B).

r
6.3 Bowhead Disturbance: Icebreaker Playbacks & Behavior 284

Playback Data vs. Received Level in Strongest 1/3-0ctave Band

.. •. .. •. .• .. .. .. .. .. .. .. .. .. .. .. •. .. .. •. .. .• .. .. •. •. ..

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c

o

y ~

~

::J

- 0 10

II

I I

I

.y

II

y

II

II 1 •

11

o o.

............•.............•.............•.............•.............•....... .• ............•...............•...............•................•...........

70. 90. 110 90. 110

80. 100 80. '00

Ree. Lev. Ree. Lev. (dB re 1 ~Pa) (dB re 1 J.lPa)

FIGURE 6.15. Surfacing, respiration and dive behavior in relation to estimated received level of

icebreaker sound (RLI/3•

m3J

.) at bowhead locations during 1994 playbacks. Case selection criteria

as in Fig. 6.13.
6.3 Bowhead Disturbance: Icebreaker Playbacks & Behavior 285

Playback Data VS. Icebreaker:Ambient Ratio in Strongest 1/3-0ctave Band

60 A. 24 B.

r •• 0.282 +

n •• 50

a a •••••••••••••••••••••••••••••••••••••••••••••••••

............•.............•............•............

r •• 0.046 ns

n '" 68

-til

-

iii 40

>•..

CD

:5

~

o

iii

:; 20

'C

CD Y

:E

1

121 2

1 1 12 I

11 13

22

2 2

I

1

1

1 I

I 12

12512 2

I 1311

1

1

o.

.. .. .. .. .• .. .. .. .. .. .. .. .. ... .. .. .. .. .. ... .. •. .. .. .• ... .• ..

.• ..........•.............•............•.............•.............•......

-10 10 30 -10 10 30

o. 20 o. 20

S:N (dB) S:N (dB)

.• •. .. .. .• .. ... .. .. .. .. .. ... .. .. .. •. .. ..• .. .. .. .• .. •. .. •. .• .• .• .. .•. .. .• .. .. .... •. ............•..............

6

c. 40 D.

r •• 0.356 +

n •• 48

r •• 0.057 ns

n •• 22

c

I

CI 4

c:

U

as

-:;

en

'0

c: 2 ..2

Cii •..

::J

o

1

1 12

- f 30

CD

>

-

is

- - 20 0

1 I

c: ..2

1 1 . Cii 1 1

112 Y

•.. 11 ::J

21 1 - 0 10 2 Y

11 Y

1 II I

1 1

12 II 1 -

- 1 2

211 o. 1

y

o 111 I

............ . . . . . "

-10 10 30

•.•.•...••.....•..• + ....•.•.•.•...•.••.....•...•.•......•.•..... + .

-10 10 30

o.

S:N (dB)

20 o. 20

S:N (dB)

FIGURE6.16. Surfacing, respiration and dive behavior in relation to estimated icebreaker-toambient noise ratio (S:NII3•max) at bowhead locations during 1994 playbacks. Case selection criteria

as in Fig. 6.13.
6.3 Bowhead Disturbance: Icebreaker Playbacks & Behavior 286

In these analyses, the icebreaker-signal to ambient-noise "ratio" (S:N) was determined from

the same four measures of RL mentioned above. From these RL estimates, we subtracted the

average ambient noise level in the corresponding frequency band. Ambient levels for a given

playback day were determined by averaging several measurements of ambient noise taken shortly

before and after that playbackf'. The measured ambient noise in the 20-5000 Hz band was

subtracted from the estimated RL in this band, and measured ambient noise in the 113-octave with

the strongest icebreaker noise was subtracted from the RL of icebreaker noise in that band.

Apparent Response Thresholds.- The correlation analyses indicate that duration of surfacing

and number of blows per surfacing tended to increase with increasing RL and icebreaker-signal

to ambient-noise (S:N) ratio. It is important to determine the RL and S:N values that elicited

behavioral effects. It is not possible to do this objectively from scatter diagrams like Figures

6.15B,C and 6.16B,C. Figure 6.17 shows the same data on durations of surfacings and number

of blows per surfacing, summarized by lO-dB categories of RLl/3,max or S:N1I3,max' Also included

in Figure 6.17 are the data for" control" conditions: aerial observations of presumably-undisturbed

bowheads within 10 km of the ice camp. Page 40 in §2.3 describes "Control" conditions, which

included exposure to some noise and other stimuli associated with observational efforts.

For consistency with previous work on behavior relative to playbacks of Karluk drilling

sounds, Figure 6.17 shows the data categorized by distance-from-projector as well as RL1I3,max and

S:N1I3,max' However, no obvious relationship to distance was expected, given the aforementioned

lack of significant correlation between distance and either duration of surfacing or number of

blows per surfacing.

Analysis Procedures: Analysis of variance and orthogonal contrasts were used to help

identify RL and S:N categories in which behavioral effects were evident (Table 6.7 A,B). This was

done for th"e BB,med' "" BB,max " an d"" 1I3,med measures 0 f RL an.,d S'N as we 11 as for th"e 1/3.max "

measure depicted in Figure 6.17. The ANOV As and orthogonal contrasts were done in two ways:

(A) including only the playback data, categorized by RL or S:N, and (B) including the control data

as an additional "treatment".

In Table 6.7 A, the orthogonal contrasts were set up first to compare behavior under the two

lowest-level RL or S:N categories,

RL 90-100 dB vs. RL s 90 dB, or alternatively S:NO-lO dB vs. S:N s 0 dB;

If behavior in these categories is not significantly different, then it is useful to compare behavior

of whales exposed to that combined range of RL or S:N values with behavior of those in the next

higher category,

~ RL 100-110 dB vs. RL s 100 dB, or S:N 10-20 dB vs. S:N s 10 dB;

22 For 17 May 1994, when wind speed and ambient noise level increased notably during the experiment,

ambient noise levels were estimated separately for each hour based on linear interpolation between the average values before the playback and the average values after the playback. This was done for the overall

20-5000 Hz band and for each 1I3-octave band from 20 Hz to 6300 kHz.
6.3 Bowhead Disturbance: Icebreaker Playbacks & Behavior 287

Similarly, if behavior in those RL or S:N categories does not differ significantly, then it is

appropriate to continue to the next contrast,

~ RL> 110 dB vs. RL ~ 110 dB, or S:N > 20 dB vs. S:N s 20 dB.

A parallel procedure was used to compare behavior in distance categories >4 km, 2-4 km, 1-2 km,

and ~1 km, for consistency with the previous Karluk analyses. Contrasts with higher categories

of RL or S:N, or with closer distance categories, were not possible because of low (or nil) sample

size. In some cases, one of the aforementioned RL, S:N or distance categories and the associated

contrast had to be skipped because of low sample size.

Table 6.7B shows the results when control data were included as a treatment. In this case,

the first contrast looked for a difference between control conditions and the lowest RL or S:N

category (or the longest distance category), and then proceeded to compare behavior with successively higher RL or S:N categories vs. the combined control and lower-noise categories, e.g.

~ RL ~ 90 dB vs. Control, or S:N ~ 0 dB vs.. Control;

~ RL 90-100 dB vs. RL ~90 dB plus Control, or S:N 0-10 dB vs. S:N s 0 dB plus Control;

~ RL 100-110 dB vs. RL ~100 dB + Control, or S:N 10-20 dB vs. S:N ~ 10 dB + Control;

~ RL >110 dB vs. RL ~110 dB + Control, or S:N > 20 dB vs. S:N ~ 20 dB + Control.

The significance levels shown in Figure 6.17 refer to these analyses, as applied using the RL1I3•max

and S:N1I3,max acoustic measures.

The "control" data include observations near the ice camp during control periods on some

days when no or few aerial observations were obtainable during icebreaker playbacks. Even when

both playback and control data were obtained on a given day, relative numbers of playback and

control observations varied from day to day. These departures from a strictly balanced design may

account for some differences in behavior between whales observed in "control" periods and whales

observed with the lowest categories of RL or S:N conditions (e.g. Table 6.7B,C, bottom half).

Distance: Consistent with the correlation results, ANOV A and orthogonal contrasts provided

no indication that duration of surfacing or number of blows per surfacing were related to distance

from the sound projectors during icebreaker playbacks (Fig. 6.17 A,D; Table 6.7A).

Received Level (RL): The received level of icebreaker sound at which effects on surfacing

and respiration cycles became evident depended on

~ the behavioral measure being considered (duration of surfacing vs. number of blows per

surfacing),

~ the acoustical measure being used (broadband vs. 113-octave; median vs. maximum level).

Encouragingly, the results were similar for the two methods of analysis: comparing RL categories

during playbacks and comparing RL categories during playbacks with control data (Table 6.7B,

top vs. bottom).

There was some evidence (Pn<0.05) of an effect on duration of surfacing at RL1I3,max values

as low as 90-100 dB re 1 IlPa (Fig. 6.17E, Table 6.7B). There was evidence of an effect on
ANOVA: ns

A. # Blows/Surfacing vs. Distance

21

6.3 Bowhead Disturbance: Icebreaker Playbacks & Behavior 288

21-r----------------..,

18

C>

c

U

15

-!

::> 12 20

~

i

~ 9- 9

iD

,

ci e- ..

z

3

0

<=1 1-2 2-4 >4 Control

Distance from Projector (km)

ns

B. # Blows/Surfacing vs. Rae. Level

14

117

21,.----,--------------...,

~ 15

~

JJ 12-

1o 9

iD

ci 6

Z

18

17

19 ~

M Jt 3

Contrel <=90 9()-100 >100

Max. 1/3-00 Received Level (dB re 1 JlPa)

C. # Blows/Surfacing vs. S : N

21,.----------------...,

19

C>

-= 15-

:;J

t

re. 12

~ 9-

iD

ci 6

Z

3

117

ns

17

16

Ol.f---~'---_+_-- --..._- ---l

Contrel <=0 G-10 1G-2O >20

Max. 1/3-0Ct. RL : Ambient Ratio (dB)

D. Duration of Surfacing vs. Dislance

4

ANOVA: ns 20 119

20

3

~

8

..

1

<=1 1-2 2-4 >4 Control

Distance from Projector (km)

E. Duration of Surfacing vs. Rae. Level

*

4 119 19

13

3

~ 16

1

* * ns

0

Control <=90 90-100 >100

Max. 1/3-00 Received Level (dB re 1 JlPa)

F. Duration of Surfacing vs. S : N

4

( *)

119 17

15

3

..

2

14

1

..

(.J ns *

Control <=0 G-10 1G-2O >20

Max. 1/3-0Ct. RL : Ambient Ratio (dB)

FIGURE6.17. Surfacing and respiration behavior for various categories of distance from projectors, estimated received level, and estimated icebreaker-to-ambient ratio during 1994 playbacks

of icebreaker sound. Also shown are control observations obtained within 10 km of the ice camp

when the projectors were silent. The mean, range, ±1 s.d. (open rectangle) and ±95% confidence

interval (hatched rectangle) are shown. Significance levels near bottoms of panels depict orthogonal contrasts for the category immediately right of each symbol vs. the combination of all categories to the left (see also boldface sections of Table 6.7, and associated text). Same data as in

parts B,C of previous four graphs. Case selection criteria as in Fig. 6.13.
TABLE 6.7. ANOVA and related analyses of surfacing, respiration and dive behavior of traveling bowheads vs. (A) distance from projector,

(B) estimated received sound level, and (C) estimated received signal to ambient-noise ratio during icebreaker playbacks. Lower half includes

control data as an additional treatment level. ANOVAs test for differences among distance, received level, or S:N categories. See text for

details concerning the orthogonal contrasts. Cases highlighted in boldface are shown in Figure 6.17.

A. vs. Distance (log km)' B. vs. RL (dB re IIlPa) C. vs. S:N (dB)

Sound Measure Sound Measure

Behavioral 20-5000 Hz Dom.1I3 20-5000 Hz Dom.1I3

Variable Comparison p. Comparison Med. Max. Med. Max. Comparison Med. Max. Med. Max.

Excluding Control Data

# Blows Correl. n=51 ns Correl. n=50 (+) + + + Correl. n=50 (+) (+) + +

per Sur- ANOVA df=2,47 ns ANOVA + + ns ns ANOVA + ns (+) +

facing 2-4 >4km >90·100 <=90 dB >0-10 <=0 dB

h

vs. ns vs. ns ns ns ns vs. ns ns

<=1 vs. >2 ns >100' vs. <=100 ++ ns ns (+) >10 vs. <=10 ++ ns

>110 vs. <=110 ++ >10-20 vs. <=0 dB ns ns

>20 vs. <=20· + ++

Duration Correl. n=49 ns Correl. n=48 (+) (+) (+) + Correl. n=48 + + + + ?-

of Sur- ANOVA df=2,45 ANOVA (+) ns' (+)' ANOVA (+) (*)' (+) (+)

l..,

ns ns t:l:l

b

facing 2-4 vs. >4km ns >90-100 vs. <=90 dB ns (+) ns . + >0-10 vs. <=0 dB (+) ++ ()

~

<=1 vs. >2 ns >100' vs. <=100 + ns ns ns >10 vs. <=10 (+) ns ;:so

>110 vs. <=110 (+) >10-20 vs. <=0 (+) ns "

Q

Cl.

>20 vs. <=20· + (+) t:l

;:;.

Including Control Data

i;

~

# Blows ANOVA df=3,163 ns ANOVA + + ns ns ANOVA (+) ns (+) +

Q

;:s

per Sur- >4km vs. Control ns <=90 dB vs Control ns ns ns ns <=0 dB vs. Control ns ns ns ns

l'\

b ~

facing 2-4 vs. >4km+C ns >90-100 vs. <=90+C ns ns ns ns >0-10 vs. <=O+C ns ns 1r <=1 vs. >2+C ns >100' vs. <=100+C ++ ns ns (+) >10 vs. <=IO+C ++ ns ~

>110 vs. <=IIO+C ++ >10-20 vs. <=O+C ns ns ~

<=20+C·

l:l

>20 vs. ++ ++ ~

"

...

Duration ANOVA df=3,163 ns ANOVA ns ns' ns *' ANOVA * ns' * (*)

of Sur- >4km vs. Control ns <=90 dB vs Control ns ns ns <=0 dB vs. Control (.) ?~

facing 2-4 >4km+C >90-100 <=90+C >0-10 <=O+C

l:l

vs, ns vs. ns ns ns + vs. ns ++ l'\

<=1 vs, >2+C ns >100' vs. <=loo+C + ns ns ns >10 vs. <=IO+C + ns

~

>110 <=IIO+C >10-20 <=O+C

Roo

vs. + vs. ns ns t:l:l

>20 vs. <=20+C· + +

"

;:so

Q

-.::

• Too few cases at 1-2 km to consider. c For 20-5000 HzlMaximum, includes> 100 to 110 dB cases only .

g'

...

b Too few cases at 0-10 dB S:N to consider. • Excluding >0 to 10 dB category with few data. N

, Variances unequal; ANOVA based on Brown-Forsythe test. 00

\0
6.3 Bowhead Disturbance: Icebreaker Playbacks & Behavior 290

duration of surfacing (Pn<0.05) and especially number of blows per surfacing (Pn<O.OI) at RLBB,med

values as low as 100-110 dB, and at RLBB,maxvalues as low as 110-120 dB (Table 6.7B).

Icebreaker:Ambient Ratio (S:N): Results were again similar for the two methods of analysis. Botli duration of surfacing and number of blows per surfacing became significantly higher

at S:NII3,max values above 20 dB, i.e. when the noise level in the ll3-octave band of strongest

icebreaker noise exceeded the ambient noise level in that band by at least 20 dB (Fig. 6.l7C,F;

Table 6.7C). The same 20 dB threshold seemed to apply for the S:NII3,med acoustic measure.

Thresholds based on broadband sound levels appeared to be lower: about 10 dB above ambient

for S:NBB,med'and possibly as low as 0 dB above ambient for S:NBB,max(Table 6.7C).

Statistical Power and Apparent Response Thresholds.-Statistical power is a measure of the

ability of an analysis to reject the null hypothesis when it is false, i.e. to obtain a statistically

significant effect when an effect does exist. Power increases with increasing sample size and with

decreasing within-group variability. With low sample size or high variability, and especially when

both occur together, the analysis will have little ability to reject the null hypothesis even if it is

false. When an analysis provides no evidence of a statistically significant effect, it is important

to evaluate its power. The objective is to determine whether, with the available sample size and

the observed within-group variability, there was a reasonable chance of detecting, as statistically

significant, a disturbance effect deemed to be biologically meaningful. If not, it is not justifiable

to conclude that there is "no effect"; instead, one must conclude that the analysis is inconclusive.

Duration of surfacing and number of blows per surfacing were significantly related to the

received level (RL) and S:N ratio of icebreaker sound (see above). Because the null hypothesis

of no icebreaker noise effect on behavior must be rejected, the power of these analyses to reject

the null hypothesis is not an issue. However, the orthogonal contrasts suggest that effects on these

behavioral variables were detectable only above certain RL or S:N values. The power of these

contrasts to detect effects at lower RL or S:N values, if such effects occurred, is an issue in

determining reaction thresholds.

Number of Blows per Surfacing: The number of blows per surfacing was significantly

(P<O.Ol) higher with S:NII3,max >20 dB than with lower S:N1I3,max values (Fig. 6.17C; Table 6.7C).

However, no such difference was found when results with S:NII3,max 10-20 dB were compared with

those at S:NII3,max ~O dB (P>O.l). This was true whether or not the "control" data were included

in the "~O db" category (Table 6.7C). Did this contrast have a reasonable prospect for detecting

a difference if, in fact, there was such a difference? Power analysis indicated that a difference of

the size observed (means of 4.06 vs. 5.10 blows/surfacing) was too small to be detected with

reasonable power (actual power = 0.242). A difference of at least 2.3 blows/surfacing would be

required in order to have a reasonable (80%) chance of demonstrating a significant (a=0.05)

difference between the S:N1I3,max 10-20 dB vs. <0 dB (including control) situations.f A typical

23 Power and minimum detectable difference were calculated by the "two means" procedure in BMDP

SOLO Power Analysis (Hintze 1991 :65ff). Variances were treated as unequal and estimated from the data.

The test was two-sided. For S:Nl/3,max10-20 dB, mean 4.062 ± s.d. 2.909, n=16; for S:N < 0 dB (including

control), mean 5.097 ± s.d. 3.447, n=134.
6.3 Bowhead Disturbance: Icebreaker Playbacks & Behavior 291

surfacing by a spring-migrating bowhead includes 5.0 blows (Fig. 5.28, p. 209), so a ±2.3 blows/

surfacing change would represent a change of -46%. Thus, in the S:NII3,max10-20 dB situation,

a rather large change in "number of blows/surfacing" would have been necessary in order to detect

a significant effect on this variable."

~ -23% with approaching boat within 4 km (Richardson et al. 1985b:117; Richardson and

Malme 1993:669),

~ -31% and -60% with operating seismic vessels within 5-10 and <5 km, respectively

(Ljungblad et al. 1988:188, recalculated by Richardson and Malme 1993:672),

~ -55% at ranges ::S;1km vs. >4 km during drilling noise playback on 13 May 1990 (Richardson et al. 1991a: 171), and

~ +47% with icebreaker noise playbacks at S:NII3,max>20 dB vs. "::S;OdB + Control" (this

study, Fig, 6.17C).

The following percentage changes in "number of blows/surfacing" have been observed in

cases of severe disturbance to bowheads:

Thus, in cases of severe disturbance to bowheads, "number of blows/surfacing" sometimes (but not

always) changes by more than the 46% that we might reasonably have been able to detect in the

S:NII3,max10-20 dB category, If severe disturbance had occurred with S:NII3,max10-20 dB, it might

or might not have been evident through statistical analysis of this behavioral variable, given the

available sample sizes and the observed variability in number of blows per surfacing.

Duration of Surfacing: This variable was significantly different with S:NII3,max>20 dB than

at ::S;20dB, but not with S:NlI3max 10-20 dB vs. ::S;OdB. In the latter case, mean duration of

surfacing was very similar in the 10-20 dB vs ::S;OdB (including control) situations: 1.244 vs.

1.200 min." As one would expect, the power to detect a difference of only 0.044 min as significant was very low (power 0,052 with a=0.05). A 0.89 minute change in mean duration of surfacing would be required in order to have an 80% chance of demonstrating a significant effect. A

typical surfacing by a spring-migrating bowhead is -1.35 min in duration, so a ±0.89 min change

would be a change of 66%. This is a large change-larger than the changes in duration of

surfacing observed during cases of severe disturbance to bowheads:

~ -29% with approaching boat within 4 km,

~ -27% and -55% with operating seismic vessels within 5-10 and <5 km, respectively,

~ -51 % at range ::S;1km vs. >4 km during drilling noise playback on 13 May 1990, and

~ +35% with icebreaker noise playbacks at S:N1I3,max>20dB vs. "::S;OdB + Control" (Fig.

5.17F).

24 A similar analysis based on the RLI/3.max measure of received level indicated that, with that acoustical

measure, power was only 0.050 given the very similar mean numbers of blows/surfacing in the two conditions: for RLI/3.max 90-100, mean 5.059 blows/surfacing ± s.d. 3.325, n=17; for RL:::; 90 dB (including control), mean 5.066 ± s.d. 3.433, n=136. A difference of at least 2.52 blows/surfacing would be required to

achieve power 0.800 (a.=0.05).

25 For S:NI/3,max 10-20 dB, mean 1.244 min ± s.d. 1.210, n=17; for S:N:::; 0 dB (including control), mean

1.200 ± s.d. 0.787, n=133.
6.3 Bowhead Disturbance: Icebreaker Playbacks & Behavior 292

If bowheads exposed to S:N1I3.max10-20 dB had been strongly disturbed, this disturbance probably

would not have been detected by analysis of "duration of surfacing". Therefore, the lack of an

apparent effect at S:N1I3.max10-20 dB is inconclusive as to the actual existence of effects on

duration of surfacing at those S:N values.

Overall, duration of surfacing and number of blows per surfacing were different when levels

of icebreaker sound were >20 dB above ambient (S:N1I3.maxbasis) than when they were $20 dB

above ambient. Neither of these behavioral variables was significantly different at S:NI/3.max10-20

dB than at lower S:N values. However, with available sample sizes and the observed variability

in behavior, we might not have detected a significant effect (a=0.05) at S:N 10-20 dB even if the

behavioral variables were affected to the same degree as in some previously-observed cases of

strong disturbance to bowheads. Therefore, the response threshold for these two behavioral variables should be described as "$20 dB", i.e. at or possibly below 20 dB, on an S:N1I3.maxbasis.

Turns

There were strong positrve correlations between the number of degrees through which

bowheads turned during a surfacing and all measures of received level (Pn<O.Ol in each case) and

all measures of icebreaker-to-ambient ratio (Pn<O.OOl in each case). In contrast, there was no

significant correlation between "degrees of turn" and distance from the ice camp during either

icebreaker playbacks or control periods. Table 6.6A (p. 282, bottom part) shows all the correlation

coefficients, which ranged from 0.365 to 0.407 for RL and 0.419 to 0.461 for S:N. Figure 6.18

shows the data for distance, RL1/3.maxand S:N1I3.max'These are the RL and S:N variables to which

degrees of turn showed the highest correlation coefficients.

It is obvious from Figure 6.18C,D that degrees of turn tended to be higher than normal when

RL1/3,maxexceeded 100 dB re 11lPa, and when S:N1I3.maxexceeded 20 dB re 11lPa. This Figure also

suggests that degrees of turn may have been affected at lower RL and S:N values. However, an

ANOV A/orthogonal contrast approach as applied above to surfacing and respiration variables is

not applicable to "degrees of turn", which had a skewed and heteroscedastic distribution.

Figure 6.19A,B shows the same "degrees of turn" data grouped by 10 dB categories of

RL1I3,maxand S:N 1I3.max'Similarly, Figure 6.19C,D shows the occurrence of surfacings with no

turns, one simple right or left turn, or multiple turns (including at least one left and one right turn

during the same surfacing). These graphs show that the occurrence and extent of turning during

surfacings was elevated at RL1I3,maxvalues as low as 90-100 dB re 1 IlPa, and at S:N 1I3,maxvalues

as low as 10-20 dB. However, the lowest categories of RL and S:N for which the increased occurrence of turns was statistically significant were RL = 100-111 dB and S:N = 10-20 dB:

RLJ/3,max Turn During (1) (2) S:NI/3,max Turn During (1) (2)

Control 60 of 149 sfc 40% Control 60 of 149 sfc 40%

<80 dB 3 of 11 27% ns <0 dB 4 of 21 19% ns

80-90 3 of 13 23 ns ns 0-10 1 of 2

90-100 10 of 22 45 ns '

ns? 10-20 13 of 24 54 * ns!

100-111 13 of 18 72 * * 20-31 11 of 17 65 ns (*)
6.3 Bowhead Disturbance: Icebreaker Playbacks & Behavior 293

Degrees of Turn vs. Range and Sound Level Variables

.• .. .. .. .. •. .. •. .. •. .• •. •. .. .• .. .. .. .. .• .. .• •. ........ . .

1000- A. Icebreaker; vs. R

r •• -0.079 ns

o = 57 -Gl

Cii

o

fI)

Cl

g

C•..

::J I-

'0

fI)

Gl

Gl

til

Gl

Y

0

-;-

Cii

(,)

fI)

Cl 100 -

g

2

1 1

21

11

'0

fI) 10 Y

Gl

Gl ...

Cl

Gl

o

1 1 11 11 1

o 22 4445931

.•. . ..............................................................

0.04 0.4 4

0.01 0.1 1 10

Range (km, log scale)

- -

....................................

1000- C. Icebreaker; vs. RL

r = 0.407 ++

o = 56 -;-

2 Cii

(,)

fI)

Cl

g

C•..

::J

IY

-0

II fI)

Gl

Gl •..

Cl

Gl

0

-;-

Cii

o

fI)

Cl 100 -

g 1 2

I

1

1 I 1

'0

fI) 10

Gl

Gl ...

Cl

Gl

o

1 1 1 1

o 1 1143321 11422112 31

............y " " " " ............•......

70. 90. 110

80. 100

Ree. Lev. (dB re 1 ~Pa)

......•..........•..........•......... - -

.. .

1000- B. Cootrot vs. R

r co 0.150 (+)

n co 128

100 •

10

1

11 1 11

4 1

1 11 I

2 14312

I 1312 2

y

o 1 11 346A9N9AA2

......•.........•.....y ..•.........•.........•.........•..........•.........

0.04 0.4 4

0.01 0.1 10

Range (km, log scale)

•.............•.............•.............•.

1000- D. Icebreaker; vs. S:N

r = 0.461+++

o = 56

2

100 -

2

I

1

II II

y

10 III II I

o 123124112 I 34221121

Y. Y ...•......•......•......••..... - ...

-10 10 30

O. 20

S:N (dB)

FIGURE6.18. Degrees of tum during surfacings (log transformed) in relation to (A) distance from

projectors during playbacks, (B) distance from ice camp during control (quiet) periods, (C) estimated received level during playbacks (RL1I3•max), and (D) estimated icebreaker-to-ambient ratio

during playbacks (S:N1I3•max). Case selection criteria as in Fig. 6.13. Letters "A" and "N" in (B)

depict, respectively, 10 and 23 cases at those locations.
6.3 Bowhead Disturbance: Icebreaker Playbacks & Behavior 294

A. Degrees of Turn vs. RL

<80 80-90 ~100 100-111

Received Level (dB re 1 IJPa)

C. Type of Turnvs. RL

18

B. Degrees of Turn vs. S:N

<=0 0-10 10-20 20-31

RL: Ambient Ratio (dB)

D. Type of Tum vs. S:N

<=0 0-10 10-20 20-31

RL : Ambient Ratio (dB)

FIGURE6.19. Degrees and types of turns during surfacings in relation to estimated received level

(RLI/3,ma~) and estimated icebreaker-to-ambient ratio (S:NII3.max) during 1994playbacks of icebreaker sound.

Data are given in Table 6.9D,E. Case selection criteria as in Fig. 6.13.

These significance levels are based on 2x2 chf comparisons (with Yates correction) of the frequency of turns in that line vs. previous lines combined, either (1) excluding or (2) including data

collected near the ice camp under "control" conditions. These comparisons are analogous to the

orthogonal contrasts of surfacing/respiration data discussed earlier.

In evaluating the apparent reaction threshold for turns, it is important to consider the

statistical power of the contrasts marked 1,2,3 in the above tabulation. In each case, power was low:

0.21, 0.07 and 0.26, respectively." For S:N1I3,max' there were only two observations in the 0-10

dB category, so it is impossible to assess whether turning frequency was elevated there relative

26 Power calculations for these contrasts were done with the chi-square procedure in BMDP SOLO Power

Analysis (Hintze 1991:159fj), in which effect size is defined as w = V(chelN). For contrasts 1,2.3, respectively, chf

values were 1.311,0.185 and 1.723 (df=1 in each case). Effect sizes (w) were 0.169, 0.031 and 0.094, which are

all low values. Respective B values were all high, at 0.79,0.93 and 0.74. Power was correspondingly low at 0.21,

0.07 and 0.26 (power = I-B).

r
6.3 Bowhead Disturbance: Icebreaker Playbacks & Behavior 295

to S:N :s; 0 dB. Thus, we cannot reliably determine whether the turning threshold was lower than

the lowest sound values at which statistically significant effects on turning were evident (RL1/3 .max

100-111 dB re 1 ~Pa and S:NII3,max 10-20 dB).

Other Behavioral Variables

The occurrence of various other categorical behaviors has been tabulated in relation to

distance from the ice camp during playback and control periods (Table 6.8, 6.10), and in relation

to RLlI3,max and S:NII3,max (Table 6.9, 6.11).

Swimming speeds showed no obvious tendency to vary according to distance from the ice

camp under playback or control conditions (Table 6.8A). Speeds also did not seem to be related

to RL or S:N during playbacks (Table 6.9A). Bowhead surfacings with a change in speed tended

to occur in the highest RL category and the highest two S:N categories, but the frequency of

"change in speed during surfacing" was too low to rule out coincidence.

Fluke-out dives were scarce at all times in spring, and there was no obvious tendency for

the proportional frequency of fluke-out dives to vary with distance, RL or S:N (Table 6.8B, 6.9B).

Pre-dive flexes were even less common, being seen during 0 of 72 surfacings during playbacks and

only 3 of 148 surfacings during corresponding control observations (Table 6.8C).

Active socializing was sometimes seen during playbacks as well as control observations.

However, we rarely selected actively socializing groups for focal animal observations, especially

during playbacks, given their complex and "atypical" behavior. The few surfacings when active

socializing was observed during playbacks are excluded from all analyses in this section.

"Passive" socializing, which we define as two (or more) whales within Y2-whale-Iength of

one another and oriented parallel to one another, occurred during a minority of the surfacings

during both playback and control periods. There was no obvious relationship between occurrence

of passive socializing and distance from ice camp, RL, or S:N (Tables 6.8F, 6.9F).

Other behaviors that we routinely record whenever they are noticed are listed in Table 6.10

in relation to distance from ice camp, and in Table 6.11 in relation to RLlI3,max and S:N 1/3,max' if they

were ever seen during the icebreaker playbacks or associated control periods in 1994. (Table 5.14

on p. 213 lists other such behaviors observed sometime during this 1989-94 study, but not during

icebreaker playbacks or associated control periods in 1994.) Most of these behaviors were

infrequent at any time. There was a weak tendency for bowheads to emerge from under areas of

extensive (>1 km) ice unusually often when RL and S:N were high. There was also a weak

tendency for bowheads to be visible during dives more often when RL and S:N were low than

when they were high. These tendencies involved small sample sizes, and it is not known whether

they represented real biological effects.
6.3 Bowhead Disturbance: Icebreaker Playbacks & Behavior 296

TABLE 6.8. Frequencies of various activities among traveling bowhead whales at various distances from ice

camp (A) during icebreaker playbacks and (B) under control conditions. Mother, calves, and surfacings with

active socializing or aerial behavior are excluded. Units of observation are surfacings by an individual

whale, as observed from Twin Otter aircraft, spring 1994. Total n varies because not all variables could be

determined for each surfacing.

A. Distance (kin) from Operating Projector B. Distance (kin) from Silent Projector

up to >0.5 >1 >2 up to >0.5 >1 >2

0.5 to 1 t02 t04 >4 All 0.5 to 1 t02 t04 >4 All

A. Speed During This Surfacing

Zero 0 0 0 0 1 1 0 1 0 1 0 2

Slow 1 0 2 19 12 34 0 2 15 44 14 75

Moderate 2 5 2 17 21 47 4 7 17 39 28 95

Fast 0 0 0 0 0 0 0 0 0 0 0 0

Unknown but >0 0 1 0 1 3 5 1 2 4 9 3 19

Milling 0 0 0 0 0 0 0 0 0 0 0 0

Change 2 2 0 1 2 7 0 0 3 7 2 12

Total n 5 8 4 38 39 94 5 12 39 100 47 203

B. Flukes Out at End of Surfacing

No 5 5 1 24 29 64 5 9 32 82 35 163

Yes 0 2 0 5 4 11 0 2 5 10 2 19

Total n 5 7 29 33 75 5 11 37 92 37 182

C. Pre-Dive Flex Before End of Surfacing,

No 5 8 1 28 30 72 5 8 29 73 30 145

Yes 0 0 0 0 0 0 0 0 0 3 0 3

Total n 5 8 28 30 72 5 8 29 76 30 148

D. Tums During Surfacing

None 1 4 0 15 15 35 3 4 22 44 16 89

Right 1 1 1 2 9 14 0 1 2 19 5 27

Left 2 1 0 1 2 6 0 0 2 11 5 18

Multiple 1 2 0 6 1 10 0 2 3 7 3 15

Total n 5 8 24 27 65 3 7 29 81 29 149

E. Degrees of Tum During Surfacing

0 1 4 0 15 15 35 3 4 22 44 16 89

10 2 2 0 1 2 7 0 0 2 6 2 10

20 1 0 0 1 2 4 0 2 0 9 2 13

30 1 0 0 1 0 2 0 0 1 2 1 4

40 0 0 0 1 0 1 0 0 0 4 1 5

50-80 0 0 0 0 3 3 0 0 2 2 2 6

90+ 0 0 1 4 2 7 0 0 0 2 0 2

Total n 5 6 23 24 59 3 6 27 69 24 129

F. Social Activity During Surfacing

None 5 5 2 23 23 58 2 9 34 86 41 172

Passive 0 3 0 10 11 24 3 3 2 8 5 21

Active (Excl.)* 0 0 0 0 0 0 0 0 0 0 0 0

Total n 5 8 2 33 34 82 5 12 36 94 46 193

;0 Surfacings with active socializing were excluded.
6.3 Bowhead Disturbance: Icebreaker Playbacks & Behavior 297

TABLE 6.9. Frequencies of various activities among traveling bowhead whales at various (A) received

sound levels and (B) signal to ambient-noise ratios (S:N) during icebreaker playbacks. Sound levels and

S:Ns are for the dominant 1/3 octave and for the 8.5 s of highest sound level during the 64 s preceding

the start of the surfacing. Presentation as in Table 6.8.

A. Received Level (dB re 1 ppa) B. Received S:N (dB)

up to >80 >90 >100 >0 >10 >20

80 to 90 to 100 to 111 All <=0 to 10 to 20 to 31 All

A. Speed During This Surfacing

Zero 1 0 0 0 1 1 0 0 0 1

Slow 9 8 11 5 33 12 4 8 9 33

Moderate 10 16 13 8 47 21 7 13 6 47

Fast 0 0 0 0 0 0 0 0 0 0

Unknown but >0 1 1 2 1 5 1 1 3 0 5

Milling 0 0 0 0 0 0 0 0 0 0

Change 1 1 1 4 7 1 0 4 2 7

Total n 22 26 27 18 93 36 12 28 17 93

B. Flukes Out at End of Surfacing

No 11 17 21 14 63 21 5 23 14 63

Yes 3 3 2 3 11 6 0 2 3 11

Total n 14 20 23 17 74 27 5 25 17 74

C. Pre-Dive Flex Before End of Surfacing

No 11 19 23 18 71 23 5 26 17 71

Yes 0 0 0 0 0 0 0 0 0 0

Total n 11 19 23 18 71 23 5 26 17 71

D. Turns During Surfacing

None 8 10 12 5 35 17 1 11 6 35

Right 2 2 7 2 13 3 0 7 3 13

Left 1 0 2 3 6 1 0 3 2 6

Multiple 0 1 1 8 10 '0 1 3 6 10

Total n 11 13 22 18 64 21 2 24 17 64

E. Degrees of Tum During Surfacing

0 8 10 12 5 35 17 1 11 6 35

10 0 1 2 4 7 1 0 3 3 7

20 0 1 2 1 4 0 0 2 2 4

30 0 0 1 1 2 0 0 1 1 2

40 0 0 0 1 1 0 0 0 1 1

50-80 0 0 3 0 3 0 0 3 0 3

90+ 1 1 0 4 6 1 0 1 4 6

Total n 9 13 20 16 58 19 21 17 58

F. SocialActivity During Surfacing

None 14 11 19 13 57 20 6 18 13 57

Passive 4 10 5 5 24 11 1 8 4 24

Active (Excl.)· 0 0 0 0 0 0 0 0 0 0

Total n 18 21 24 18 81 31 7 26 17 81

• Surfacings with active socializing were excluded.

r
6.3 Bowhead Disturbance: Icebreaker Playbacks & Behavior 298

TABLE 6.10. Number of surfacing/dive sequences with specific whale behaviors among traveling

bowhead whales at various distances from ice camp (A) during icebreaker playbacks and (B) under

control conditions. Specific behaviors shown in Table 5.14 but excluded here were not observed

during icebreaker playback tests or associated control periods. Presentation as in Table 6.8.

A. Distance (km) from Operating Projector B. Distance (km) from Silent Projector

up to >0.5 >1 >2 up to >0.5 >1 >2

0.5 to 1 t02 t04 >4 All 0.5 to 1 t02 to 4 >4 Ali

None 3 2 1 7 10 23 2 4 12 23 14 55

Flukes raised during surfacing 0 1 0 2 0 3 0 0 2 0 0 2

Lunge or surge 0 0 0 1 2 3 0 0 3 1 0 4

Underwater blow 0 1 0 0 0 1 0 0 1 0 1 2

Arch du ring surfacing 0 0 0 3 2 5 0 0 3 0 2 5

Mouth open 0 0 0 0 0 0 0 0 1 0 0 1

Motionless at surface 0 0 0 1 1 2 0 1 0 1 0 2

Travel along ice edge 1 0 0 1 0 2 0 0 1 1 1 3

Emerge from extens, ice (>lkm) 1 0 0 13 6 20 2 3 5 32 9 51

Accompanied by belugas 0 0 0 0 0 0 0 0 0 1 0 1

Visible below surface 0 0 0 1 6 7 0 0 7 14 4 25

Overall n 5 4 25 26 61 4 8 31 71 29 143

TABLE 6.11. Number of surfacing/dive sequences with specific whale behaviors among traveling

bowhead whales at various (A) received sound levels and (B) signal to ambient-noise ratios (S:N) during

icebreaker playbacks. Sound levels and S:Ns are for the dominant 1/3 octave and for the 8.5 s of highest

sound level during the 64 s preceding from the start of the surfacing. Specific behaviors shown in Table

5.14 but excluded here were not observed during icebreaker playback tests or associated control periods.

Presentation as in Table 6.8.

A. Received Level (dB re 1 ppa) B. Received S:N (dB)

up to >80 >90 >100 >0 >10 >20

80 to 90 to 100 to 111 All <=0 to 10 to 20 to 31 All

None 4 3 9 6 22 7 1 9 5 22

Flukes raised during surfacing 0 0 2 1 3 0 0 3 0 3

Lunge or surge 2 0 1 0 3 2 1 0 0 3

Underwater blow 0 0 0 1 1 0 0 1 0 1

Arch during surfacing 0 3 2 0 5 1 1 2 1 5

Mouth open 0 0 0 0 0 0 0 0 0 0

Motionless at surface 1 0 1 0 2 1 0 0 1 2

Travel along ice edge 0 1 0 1 2 1 0 0 1 2

Emerge from extenso ice (>lkrn) 1 3 8 8 20 2 2 4 12 20

Accompanied by belugas 0 0 0 0 0 0 0 0 0 0

Visible below surface 2 5 0 0 7 6 0 1 0 7

Overall n 10 14 21 15 60 20 4 19 17 60
6.3 Bowhead Disturbance: Icebreaker Playbacks & Behavior 299

All Behavioral Variables Combined

It is often difficult to evaluate changes in behavior when, as in this study, many different

intercorrelated measures of behavior are recorded. One useful approach in such situations is the

following two-stage procedure: (1) Use factor analysis to reduce the behavioral variables to a

smaller number of uncorrelated indices of behavior. (2) Evaluate the relationships between these

few behavior indices and environmental circumstances-in this case playbacks of icebreaker noise.

This approach was applied in analyzing behavioral results from the Karluk drilling noise playbacks

(Richardson et al. 1991a:181ff, 240ff), and it is applied here to the 1994 icebreaker playback data.

We used factor analysis (BMDP4M, release 7.0,1993) to reduce 15 intercorre1ated measures

of behavior (Table 6.12) into a smaller number of uncorrelated indices or factors. The list of 15

behavioral variables used here was very similar to the list used in the 1989-90 analysis (cf.

Richardson et al. 1991a:182). Prior to factor analysis, four of the original measures of behavior

were logarithmically transformed to reduce skewness. Several other measures were adjusted,

relative to the original coding system, to ensure that their scales were at least ordinal. The

observations included in the factor analysis are described in the caption to Table 6.12. Principal

components were extracted from the correlation matrix, and the seven components whose

eigenvalues exceeded 1.0 were subjected to Varimax rotation. These 7 components accounted for

73% of the variance represented by the 15 original variables.

Relationships between the original variables and the 7 derived behavior indices are shown

in Table 6.12. Each index was strongly (Irl>O.4) related to two or three of the original variables.

The underlying behavioral attribute indexed by each factor can be identified by reference to these

heavily-weighted variables. For example, Factor 1 measures the occurrence of turns, which were

also associated with whales emerging from under extensive ice. Factor 2 is a measure of the

duration of dive and associated behavioral attributes, most notably number of blows per surfacing.

The underlying behavioral attribute indexed by Factor 3 is less clear, but there was strong

weighting on median blow interval and "visible below surface during dive". Similarly, factors 4-7

can be interpreted by reference to Table 6.12.

Table 6.13 shows the correlation coefficients between all seven behavioral indices (factors)

and distance from ice camp, estimated received sound level at whale locations (RL), and estimated

icebreaker-to-ambient ratio at whale locations (S:N). For distance (Table 6.13A), correlation

coefficients with behavior indices were calculated for the playback periods and, separately, for the

control periods. RL and S:N cannot be calculated meaningfully for control data, so only the

playback periods are considered in Table 6.13B,C. Correlation coefficients were calculated based

on all four of our usual methods for estimating RL and S:N: "BB,med", "BB,max", "1/3,med", and

"1I3,max" (see p. 251).

Behavior Factors vs. Distance.-During icebreaker playbacks, none of the seven behavioral

indices was significantly related to distance from the projectors (Pn>0.05 in each case; Table

6.13A). This is consistent with what was found based on individual behavioral variables. Curiously, one of the seven behavioral indices, Factor 1, was significantly (Pn<O.OI) correlated with

distance from ice camp under control (quiet) conditions (Fig. 6.20B). The reason for this is not
TABLE 6.12. Weighting placed on 15 behavioral variables by seven behavior factors; dominant variables are in

boldface', Based on aerial observations of 170 surfacings by traveling bowheads during undisturbed and playback

conditions, 1994. Excludes whales engaged in active socializing or aerial behavior; also excludes mothers and calves.

Factor Factor Factor Factor Factor Factor Factor

Original Variable I 2 3 4 5 6 7

No. blows / surfacing (log) 0.252 0.840 -0.343 0.036 0.057 -0.068 0.111

Duration of surfacing (log) 0.249 0.874 0.121 -0.014 0.089 0.080 0.132

Median blow interval (log) -0.019 -0.143 0.812 -0.040 0.029 0.195 0.020

Tum (1,2) or not (0) 0.929 0.154 -0.004 0.034 -0.056 0;023 0.030

Degrees of tum (log [deg.+ll) 0.939 0.146 -0.019 0.014 -0.038 0.034 0.009

Change speed (1) or not (0) 0.178 0.220 -0.008 -0.648 -0.082 0.143 -0.353

Speed nil/slow (1) or not (0) 0.110 0.128 0.165 0.810 -0.161 -0.034 -0.158 !=II

Group size 0.069 -0.148 0.062 -0.085 0.664 0.403 -0.036

I.o.l

tl:l

0.846

<:l

Passive socializing (1) or not (0) -0.095 0.152 0.014 0.022 -0.138 -0.001 ~

~

Flukes out 0.829 "' (1) or not (0) 0.016 0.057 0.009 -0.011 0.052 -0.001 ~Q.

t::7

Paralleling ice edge (1) or not (0) 0.181 0.001 -0.388 0.523

;;:.

0.158 0.322 -0.101 ..•

l::

Emerge from under ice (1) or not (0) 0.437 0.086 -0.213 0.045 0.278 -0.395 -0.214

a.

~;3

Visible below surface (1) or not (0) 0.863

...

-0.010 0.021 0.115 0.043 -0.113 -0.078 !l!

Arch in mid-surfacing (1) or not (0) -0.034 0.193 -0.064 -0.039 -0.083 0.030 0.813 ;:;-

"' ~

Motionless at surface (1) or not (0) -0.286 0.478 -0.055 -0.083 -0.224 0.003 -0.444 ~

~

r:-

.,

"tl

% of variance 'explained' by factor ~

~

Relative to all 15 original variables 19.2 11.5 9.9 9.6 8.4 7.7 7.1 ~...

rx

Relative to all 7 factors 26.2 15.6 13.5 13.1 11.5 10.5 9.7 Ro

tl:l

a The weightingplaced on each variableby a factoris proportionalto the absolutevalue of the correlationcoefficient betweenthe variable and factor. "' ~

~

Correlationcoefficientsfor variablesheavily weighted ( Ir I> 0.4) are large boldface, and those for variablesmoderatelyweighted(0.4 > Ir I>0.25) -e

Q'

are in boldface.

.,

w

0

0

----------
6.3 Bowhead Disturbance: Icebreaker Playbacks & Behavior 301

TABLE 6.13. Correlation of behavior indices (factor scores) for traveling bowheads vs. (A) distance from

projector, (B) estimated received sound level, and (C) estimated received signal to ambient-noise ratio

during (A,B,C) icebreaker playbacks and (A only) associated control conditions, 1994. Acoustical variables

(B) and (C) are measured during the 64 s preceding the behavioral observation. Mothers, calves, and

surfacings with active socializing or aerial behavior are excluded. Aerial observations only. Po is nominal

2-tailed significance level of the correlation coefficient. See Figures 6.20 and 6.21 for scatter diagrams

corresponding to boldface correlations involving Factors 1 and 3. Sample size = 36 for every case in (B)

and (C).

Behav- B. vs.RL C. Ys.S:N

ioral A. vs, Distance (log km) Acoustical Variable (dBre 1 ppa) (dB)

Factor Condition n p. (Measured Over 64 s) p. r p.

Playback -0.160 37 ns 20-5000 Hz median 0.373 + 0.392 +

Control 0.286 90 ++ maximum 0.354 + 0.380 +

Dom. 1I3-0ct. median 0.395 + 0.420 +

maximum 0.404 + 0.435 ++

2 Playback -0.116 37 ns 20-5000 Hz median 0.144 ns 0.162 ns

Control 0.078 90 ns maximum 0.142 ns 0.162 ns

Dom. 1I3-0ct. median 0.133 ns 0.166 ns

maximum 0.130 ns 0.167 ns

3 Playback 0.303 37 (+) 20-5000 Hz median -0.345 -0.271 ns

Control 0.114 90 ns maximum -0.375 -0.296 (-)

Dom. 1I3-0ct. median -0.350 -0.295 (-)

maximum -0.365 -0.314 (-)

4 Playback 0.137 37 ns 20-5000 Hz median 0.116 ns 0.244 ns

Control 0.018 90 ns maximum 0.149 ns 0.273 ns

Dom. 1I3-Oct. median 0.115 ns 0.228 ns

maximum 0.127 ns 0.238 ns

5 Playback 0.270 37 ns 20-5000 Hz median -0.246 ns -0.152 ns

Control -0.236 90 maximum -0.214 ns -0.127 ns

Dom. 1/3-0ct. median -0.267 ns -0.198 ns

maximum -0.198 ns -0.153 ns

6 Playback 0.035 37 IlS 20-5000 Hz median -0.091 ns -0.051 ns

Control -0.064 90 ns maximum -0.074 ns -0.038 ns

Dom. 1I3-0ct. median -0.095 ns -0.021 ns

maximum -0.088 ns -0.018 ns

7 Playback 0.078 37 ns 20-5000 Hz median -0.132 ns -0.123 ns

Control 0.061 90 ns maximum -0.086 ns -0.087 ns

Dom. 1I3-0ct. median -0.160 ns -0.152 ns

maximum -0.148 ns -0.146 ns
6.3 Bowhead Disturbance: Icebreaker Playbacks & Behavior 302

Factor t vs. Range and Sound Level Variables

2

A. Icebreaker; YS. R 2

r •• -0.160 ns

n •• 37 2

B. Control; YS. R

r •• 0.286 ++

n so 90

.• .• •. .•. •. •. •. .• ..• .• .• •. .• ..• .• .. •. •. •. •. .. •. .. .• .. .. .•. .. •. .. .. .. .•. .• •. •. .... •. ..........•.............

-

.

-Gl .. Yl

0

u

en 0

..

0

-o

as u,

2 --~ I

o

u

• en

Y ~

- 0

as

u... 0

II

4 1

.

1

22 I

I I

2 1 I

1 1 -

I Y

I I

1 I

1 3 21

1 1112

I

II

-2 -I

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21141 I

2 3 42234324121

2 I I I

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0.5 2 8 0.4 2.5

0.25 I 4

Range (km, log scale)

0.16

Range (km, log scale)

6.3

.. •. .. .. .. .. ..• .• .. .• .. .. ... " ........•............ ............•............•............•............

11

2

Y ~

Gl •..

0

c

. en 0

~

0

as u,

D. Icebreaker; YS. S:N

r •• 0.435 ++

n •• 36

I

2

2

C. Icebreaker; YS. RL

r •• 0.404 +

n •• 36

2

--Gl •..

o

u

en 0

1

1

I

I I 1

I 2

1

y

•..

o

oas u...

III

I I 311

11111 I

II II

2 12

2

1221 I

I

y

y

-2 -2

............•............•............•............•............•...... .• ..........•............•............•............•............•......

70. 90. 110 -10 10 30

80. 100

Ree. Lev. (dB re 1 JlPa)

20

FIGURE6.20. Factor scores for behavior index #1 in relation to (A) distance from projectors during playbacks. (B) distance from ice camp during control (quiet) periods. (C) estimated received

level during playbacks (RLlI3,max)' and (D) estimated icebreaker-to-ambient ratio during playbacks

(S:NlI3,max)' Factor 1 measures the occurrence of turns. which were also associated with whales

emerging from under extensive ice. Case selection criteria as in Fig. 6.13.
6.3 Bowhead Disturbance: Icebreaker Playbacks & Behavior 303

Factor 3 vs. Range and Sound Level Variables

...• ........ .• • .• ........ • .• ........ •

A. Icebreaker; vs. R

2

r •• 0.303 (+) 1 1

o •• 37

2

t') 1 ·

t')

•••• ••••

CD CD •.. •..

0 1

0

o

o

en 1 1 Y en

•.. 0 J 1

•..

0

1 3 1

0

-()

-1 · -o

0 CIS 1 1 11 CIS

u, II \\

u.

y I 1 1

-1 1

1

.• ............•............•............

B. Control; vs. R

r •• 0.114 ns

o •• 90

1

1 1

1 1

1 1

2

11

11 1

1 1

•

1 I I Y

1\\\ 112 I

1 213 12 2 I •

\ I 2 I I 11 21

Y 1 I I 22111

III 2 21 1 I -

I 11212 I

-I

.....•......•........•..........•..........•..........•........ .• ............•........•...........•...........•...........•.....

0.5 2 8 0.4 2.5

0.25 4

Range (km, log scale)

O. \6

Range (km, log scale)

6.3

............•............•...... .• .........•......

2

C. Icebreaker;·

vs. RL -

r = -0.365 -

n = 36

2

D. Icebreaker;:

vs. S:N

r = -0.314 (-)

o = 36

t') 1 ·

t') •

•••• •••• y

CD CD •.. •..

0 I

0

Y

()

()

(J) 1 1 -

(J) 2

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1 \ I - Q I \ II

()

CIS I I 2 CIS 11 I

U. 2 2

u, 22 y

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- 1

-1

••••••.•.••• to •••••••••••••.•.••••••••••.•.•••••••.•••.•••••••.••••••.••• .• .......•............•...........•...........•..........•...

70. 90. 110 -10 10 30

80. 100

Rae. Lav. (dB re 1 IJPa)

O.

S:N (dB)

20

FIGURE6.21. Factor scores for behavior index #3 in relation to (A) distance from projectors during playbacks, (B) distance from ice camp during control (quiet) periods, (C) estimated received

level during playbacks (RL1I3•max), and (D) estimated icebreaker-to-ambient ratio during playbacks

(S:NII3.max). Factor 3 included strong weighting on median blow interval and "visible below surface

during dive". Case selection criteria as in Fig. 6.13.
6.3 Bowhead Disturbance: Icebreaker Playbacks & Behavior 304

known, but the apparent effect was largely attributable to observations during three surfacings-the

ones at the lower left corner of Figure 6.20B.

Behavior Factors vs. RL and S:N.-Behavioral index 1 was significantly and positively

correlated with all eight measures of RL and S:N (Table 6.13B,C). As noted above, this index was

primarily a measure of the occurrence of turns and emergence from under extensive ice (Table

6.12). Figure 6.20C,D shows the relationships between factor (behavioral index) #1 and RL1/3,max

or S:N1/3,max,which were the RL and S:N variables to which factor 1 was most strongly correlated

(r=0.404 and 0.435, respectively). This positive relationship between the turning index and

icebreaker sound is consistent with previously-described relationships of other simple measures

of turning to RL or S:N.

Behavioral index 3 was weakly and negatively related to the RL and S:N variables, in most

cases at the Pn<0.05 or Pn<O.1 levels (Table 6.13B,C). Figure 6.21C,D shows the relationships

between factor #3 and RL1/3,maxor S:N1/3,max'

None of the other five behavioral indices identified by factor analysis was significantly

correlated with any of the eight measures of RL or S:N (Pn>O.1 in all cases; Table 6.13).

Apparent Response Thresholds.-Factor scores could only be calculated for bowhead

surfacings when all 15 of the variables listed in Table 6.12 were observed. The full duration of

the surfacing had to be observed in order to document all 15 variables. Because of the oftenwindy conditions in 1994, we obtained complete data for an unusually low proportion of the

surfacings. During icebreaker playbacks in 1994, there were only 36 usable surfacings when all

15 variables were documented. The 36 usable surfacings include the cases meeting our usual

selection criteria: traveling animals, excluding mothers, calves, active socializers, and those

exhibiting aerial activity.

This small multivariate dataset corroborates other evidence that certain aspects of behavior

(e.g. occurrence of turning) were related to the RL and S:N of icebreaker sound. These

relationships occurred within the ranges of RL and S:N values to which these particular bowheads

were exposed: estimated RLl/3,max78-110 dB re 1 flPa, and S:N1/3,max-10 to +30 dB (Fig. 6.20C,D,

6.21C,D). The threshold values must be at least a few decibels below the upper limits of these

ranges (i.e. at least a few decibels below RL1/3,max=ll0 dB and S:N1/3,max=30dB) to account for the

existence of non-zero correlations. However, a sample size of 36 is too small to allow a meaningful quantitative determination of the threshold sound level or S:N within these observed ranges

of RL or S:N. Full data were available for another 90 surfacings under control conditions near the

ice camps in 1994 (Fig. 6.20B, 6.21B). However, those additional data are not directly usable in

identifying threshold RL or S:N values.
6.4 Bowhead Disturbance: Icebreaker Reaction Thresholds 305

6.4 Icebreaker Reaction Thresholds and Radius of Influence

Icebreaker Reaction Threshold Criteria

Several estimates of the RL and S:N values above which bowheads showed evidence of

reactions have been given in the preceding two sections on distributional and behavioral effects

of the icebreaker sound playbacks.

Icebreaker-to-Ambient Ratios.-The strongest relationships between bowhead activities and

icebreaker sound levels were often found when we considered the maximum icebreaker-to-ambient

ratio in the 113 octave of strongest icebreaker sound (S:NII3,max)' Section 6.2, concerning

distributional effects, concluded (with qualifications) that a typical traveling bowhead might begin

to divert when the S:NII3,maxis near 20 dB, with some whales diverting at considerably lower S:N,

and some not diverting even at considerably higher S:N (Fig. 6.9). In §6.3, concerning behavioral

effects, we found statistically significant evidence that duration of surfacing and number of blows

per surfacing both tended to be higher at S:NII3,maxvalues >20 dB (Table 6.7C, Fig. 6.17C,F). The

frequency of turning during surfacings was significantly increased when S:NII3,maxwas as low as

10-20 dB. Attempts to estimate the overall threshold by using factor analysis to consider many

behavioral variables simultaneously were hampered by the small sample size after we excluded

records missing one or more variables. However, the threshold (S:NII3,maxbasis) was at least a few

decibels below 30 dB (Fig. 6.20D, 6.21D).

Overall, these analyses indicate that projected icebreaker sounds often caused alterations in

the tracks or behavior of traveling bowheads when the received level of icebreaker sounds in the

113-octave band of strongest icebreaker sounds was >20 dB above the ambient level in that band

during at least one 8.5-s period within the 64-s period preceding the observation time (i.e.,

S:N1I3.max>20 dB). Some individual whales showed no obvious reaction even when exposed to

higher S:N values, but others reacted at lower levels. Statistically-significant effects on the

frequency of turning during surfacings were evident at S:NII3,maxas low as 10 dB. The statistical

power analyses described on p. 290 and p. 294 show that we cannot exclude the possibility of

effects at somewhat lower S:N values.

We have not attempted to identify the threshold based on all other measures of S:N for all

other distributional and behavioral measures. However, duration of surfacing and number of blows

per surfacing both showed statistically significant (Pn<0.05 or better) "alterations" when S:N l13,med

exceeded 20 dB, when S:NBB,medexceeded 10 dB, and when S:NBB,maxexceeded 0-10 dB (Table

6.7C). A lower apparent threshold when playback noise is measured on a broadband than on a

"dominant 1/3-octave" basis is consistent with results from the 1989-90 Karluk playbacks

(Richardson et al. 1991a) and earlier summer playback work (Richardson et al. 1990b).

Received Levels of Icebreaker Sound.-Some measures of bowhead activities were also

related to icebreaker sound levels when the acoustic measure was the maximum received level in

the 1I3-octave band of strongest icebreaker sound (RLI13,max)' Duration of surfacing (Pn<0.05)

tended to be higher at RLII3,maxvalues 90·100 dB re 1 J.lPa than at lower RLs (Table 6.7B, Fig.
6.4 Bowhead Disturbance: Icebreaker Reaction Thresholds 306

6.17E). Other measures suggested that the threshold was somewhat higher. The number of blows

per surfacing showed a marginally significant tendency to be higher with RL1/

3 >100 dB than ,max

with lower RL values. Likewise, frequency of turning during surfacings was significantly

increased (Pn<0.05) when RLII3,max was >100 dB. Results of the factor analysis suggested that the

threshold for behavioral reactions (RLII3,max basis) was at least a few decibels below 110 dB re

1JlPa (Fig. 6.20C, 6.21C).

Overall, these analyses indicate that projected icebreaker sounds often altered behavior of

traveling bowheads when the received level of icebreaker sounds in the strongest 113-octave band

was >100 dB re 1 lJ.Pa during at least one 8.5-s period within the 64-s period preceding the observation time (i.e., RL1I3,max>100 dB re 1 JlPa). Some individual whales showed no obvious reaction

even when exposed to higher RL values, but others reacted at lower levels. Effects on the duration

of surfacing may have been evident at RLII3,maxas low as 90-100 dB. Again, power analyses showed that the possibility of behavioral effects at somewhat lower RL values cannot be excluded.

We did not attempt to identify the threshold based on all other measures of RL for all other

distributional and behavioral measures. However, duration of surfacing and number of blows per

surfacing both showed statistically significant (Pn<0.05 or better) "alterations" when RLBB,med

exceeded 100 dB re 1 lJ.Pa, and when RLBB,maxexceeded 110 dB re 1 lJ.Pa (Table 6.7B).

Tolerated Levels of Icebreaker Sound.-Bowheads are believed to be well adapted for

hearing low-frequency sounds, probably including some infrasonic sounds below 20 Hz (Ketten

1994). Most acoustic energy emitted by an icebreaker, and essentially all of that emitted by a

drilling operation like Karluk, is in the low frequency range where bowheads and other baleen

whales apparently have good hearing abilities. At these frequencies, bowhead hearing is probably

limited by the ambient noise level, not by absolute sensitivity (Richardson et al. in press:236fj).

If so, bowheads receiving low levels of icebreaker or Karluk sounds, e.g. levels 0-20 dB

above the ambient level in the 1I3-octave band of strongest industrial sounds, probably can hear

these sounds. However, the majority of bowheads did not exhibit strong, overt reactions unless

the received level in the strongest 1/3-octave band was ~20 dB above ambient. Thus, many springmigrating bowheads seem to tolerate exposure to weak but presumably detectable icebreaker or

drilling noise without exhibiting conspicuous behavioral reactions or avoidance. Tolerance of

weak man-made noise has also been observed in some previous bowhead studies in late summer

and autumn (Richardson and Malme 1993).

The upper limit of this tolerance varies widely, with some whales showing apparent reactions

at received levels well below S:NII3=20 dB, and others tolerating considerably higher received

levels. On 9 May 1994, bowheads that were apparently feeding near the ice camp lingered there,

in two cases coming within 17-24 m of the operating projector where RLBB,maxwas as high as 135

dB re 1 lJ.Pa and S:NII3,max was as high as 44 dB. On 20 May 1994, a traveling bowhead came

within 58 m of the operating projectors and was exposed to RLBB,max-138 dB re 1 lJ.Pa and

S:NII3,max near 60 dB. The latter whale apparently diverted after it had come close enough to be

exposed to those sound levels.
6.4 Bowhead Disturbance: Icebreaker Reaction Thresholds 307

Potential Radius of Influence of Actual Icebreaker

The source level of an actual icebreaker is much higher than the maximum source level that

could be emitted by our projectors (Fig. 4.27-4.34, p. I 99ff). Therefore, bowheads would be

expected to detect icebreaker sounds out to a considerably greater radius from the actual icebreaker

than from the projectors. Likewise, avoidance or other behavioral reactions are expected to extend

out to a greater radius around the actual icebreaker. The playback results can be used to predict

potential reaction distances around an actual icebreaker, given a number of assumptions (§1.3).

Figure 6.22A shows, for one part of the playback on 7 May 1994, the estimated 95th percentile received levels in various 1I3-octave bands (RLI13,95%' in dB re 1 flPa) at distances ranging from

0.03 to 30 km from the projectors. These are the levels exceeded 5% of the time during the 14-

min cycle of icebreaker sounds. This "95th percentile" measure of icebreaker sound is an appropriate one to use in comparisons with observed reaction thresholds based on the RLI13,maxand

S:NlI3max measures (maximum 8.5-s segment in a 64-s period). The 0.03 and 0.1 km spectra

assume spherical spreading; other spectra are based on the propagation model of §4.3. In the 113-

octave bands centered at 40-200 Hz, RLI13,95% is at or above the ambient level on 7 May at

distances out to 5-10 km, and thus presumably detectable to bowheads at those ranges. In the 113-

octave bands centered at 50-80 Hz, RLI13,95% is -20 dB above ambient at distances near 2 km. As

S:NII3,max=20 dB is one of the reaction thresholds mentioned above, reactions might be common

out to -2 km from the projectors.

Figure 6.22B shows estimated 95th percentile received levels at various distances if the

actual icebreaker Robert Lemeur, rather than the projectors, were in operation at the 7 May 1994

playback site. Given the average ambient noise levels that prevailed on 7 May 1994, the actual

icebreaker sounds (RLI13.95%) are predicted to equal or exceed ambient levels in the 1I3-octave

bands centered at 80-200 Hz, and thus be audible at those frequencies, at distances up to about

30 km. Likewise, the actual icebreaker sounds would be 20 dB above ambient out to about 10-15

km in certain 1/3-octave bands. Thus, given the propagation conditions and ambient noise level

encountered on 7 May 1994, reactions might be expected to be common out to a radius of -lOIS km from the actual icebreaker, as opposed to -2 km from the projectors.

Figure 6.23A,B, shows a similar analysis of the situation on 20 May 1994. Predicted

received levels of sound from the actual icebreaker were very similar to those at corresponding

ranges on 7 May (cf. Fig. 6.22B). Water depths at the two sites were similar (37 m on 7 May;

42 m on 20 May) and, as described in §4.3, water depth is the dominant variable in the acoustic

propagation model used to derive the estimated received levels. Although RL estimates for these

two sites were similar, the ambient noise level on 20 May 1994 was lower in many 1/3-octave

bands. Hence, the estimated received level of icebreaker sound exceeded the ambient level in

certain 1I3-octave bands at distances out to well beyond 30 km-farther than expected for the 7

May 1994 situation. At some frequencies, the predicted received level was ;:::20dB above ambient

at distances out to -30 km. Hence, reactions might have been common as much as -30 km from

the icebreaker if it had been operating in the area on this quiet day.
190

......... 170

CO

"0•......•

Q) 150

Q) >

...J

"0 130

c:

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t5

0I

(Y) 90

-T""

70

50

10

190

......... 170

CO

"0•......•

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"0 130

c:

ct1

CO 110

.<:5

0I

(Y) 90

-T""

70

50

10

6.4 Bowhead Disturbance: Icebreaker Reaction Thresholds 308

A. 7 May 1994 Playback, 19:00, 95%

--- SL-1 m

~~~ •.•.•.•.•... .~---..••••.••••...........-............ ....\ _ ....•

........ ." . ...•...........•.... - .....•.,-,".. km

............... "\, ,/ ..........•.•.••...••.•.•.. - _................ -,

.....

/••....•.........•..•.•..'..... ...••'....•'....................• .; ....._...•..- .. . '. '. . .. . - " '.0.03

Rec. Lev .

-+-

Ambient

~

S:N = 20

10000

.,/ .r.:..~··~~.{(··).~)~ '" .... .\.......... ....,." ""01

.{ ~. ~" . . ' ...~. :'~..?.P~)." )()( ~'")(.~.( "'x'

~ "E. ~ ." •... , .' ,>< 03

/ '" / ~~ •....•.., '.. "" " ..

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~ .•• /........ ......IIII'·F,+ +---./),/" /'.... .... """'.. "'"

'3

•••

.•/1".. ••.•••.•.•••.•.•.•.••.•.••..••••••.••.

................30 '.

'

I ,/ ./~<,J \. 1 0 \ •..•.......•

100 1000

--- SL·1 m

B. Icebreaker at 7 May 1994 Loc'n, 95%

-l--~-.~------------I

_ .....~

••••••••••••••••• 0* ••••••••••••••••••••••••••• ,.. •••••••••••••••••••

0.03 ',' , _................•"".""" :...., . .-;::--------1

01 ' _ -.. .. .

. ..~....... - .'.................. . .

••.................. .........•........•..•..•......•.....•........•........•.........••••.•.. - - ~~~~~ ......•..••• ..........••..•..._ .

03" ~ ~ . . ...........• ~" - _ ...........••_-

1 ........•.-=.:::.. ", , ••, ••.•••••- •• <,................. ....•. - .

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/i···..I~~·····i ..·..F·

-*II~ \ ~ ..:l.IIIIII+-

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30 /

...

/

Rec. Lev .

-+-

Ambient

~

S:N = 20

I I I I

,

, "

, I I I I

10000

- ""-----'-

FIGURE 6.22. Estimated 95th percentile source and received levels of icebreaker noise, by 113

octave, (A) during playback on 7 May 1994, time 19:00, and (B) if actual icebreaker were operating at that site. Also shown is the average ambient noise level on 7 May 1994, and "20 dB above

ambient", also on a 1I3-octave basis.
190

,.-... 170

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6.4 Bowhead Disturbance: Icebreaker Reaction Thresholds 309

A. 20 May 1994 Playback, 15:40, 95%

:::~~~::::::::::::::::::::>:::::::::::::::::::=:::::::::::::::::::::::~~::~::::~::::~:::::~::::~::::~:::~~~~~~~:::::::::···~.~3

--- SL -1 m

~,' ' -... . 0.1

".,..",<....-. _••, ••••••••••••.•,••••••••••.••••..•• ~••.••••••.•.••••.•••• _ ••••.••••...•.•..•. _•.•••.••••••.••.••••• , ••••:: ~.3

Rec. Lev.

-+-

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-7<ES:N = 20

....., ~ _ _ _ ..,~-~.._ ..

10000

\.30

\

100 1000

--- SL -1 m

Rec. Lev.

-+-

Ambient

-7<ES:N = 20

km

0.03

---

B. Icebreaker at 20 May 1994 Loc'n, 95%

- -

- ~

----

, ,

10000

FIGURE 6.23. Estimated 95th percentile source and received levels of icebreaker noise, by 1/3

octave, (A) during playback on 20 May 1994, time 15:40, and (B) if actual icebreaker were operating at that site. Also shown is the average ambient noise level on 20 May 1994, and "20 dB above

ambient", also on a 1/3-octave basis.

- --

I I I I

100 1000

1/3-0ct. Center Frequency

. I , I I I I
6.4 Bowhead Disturbance: Icebreaker Reaction Thresholds 310

Figures 6.24A,B show predicted levels of icebreaker noise vs. range and frequency on the

assumption that the icebreaker (rather than our projectors) was operating at two of the deeper

playback sites-those where we worked on 17 May 1991 and 3 May 1994 (water depths 110m and

105 m, respectively). Especially at the lower frequencies, predicted received levels at given

distances were higher at the deeper sites (Fig. 6.24 vs. Fig. 6.22B and 6.23B). Predicted received

levels in certain 113-octave bands were ~20 dB above ambient at distances out to 20-30 km in

these situations. If the ambient noise level on these occasions had been as low as it was on 20

May 1994, the predicted reaction distance (S:N1I3•max>20 dB criterion) would have been -50 km.

Variability and Uncertainty in Predicted Radius of Influence

The above estimates should be taken only as general indications of the likely radius of

responsiveness for traveling bowheads exposed to noise from an icebreaker. The reaction criteria

applied here are imprecise as a result of such factors as

~ the limited sample sizes and weather problems during the playback tests;

~ inevitable differences between playbacks and actual industrial operations, including the

inability to project infrasonic noise components, the imperfect fidelity of projected sounds

at sonic frequencies, the lower source level during playbacks, the steeper RL vs. range

gradient during playbacks at the range where a given RL occurs," and the exclusion

during playbacks of non-acoustic cues associated with the actual industrial operation;

~ the fact that received levels of icebreaker noise were estimates from the sound exposure

model described in §2.3 (p. 46!/), not direct measurements; this model may tend to slightly underestimate received levels in the dominant 1/3-octave band (§4.3, p.107!/);

~ the inherent variability in responsiveness of different bowheads, and probably ofthe same

bowheads at different times or in different circumstances.

In addition to uncertainties in the reaction criteria, physical acoustic aspects vary widely

from place to place and time to time. These variations are a result of

~ variation in propagation conditions",

~ among-icebreaker differences· in emitted sounds,

27 Sound levels that elicit a response from whales might be influenced by the gradient of the sound level

with distance. A given level may have more effect if the level increases rapidly with diminishing distance

than if level increases more slowly as a migrating whale approaches [see p. 11, item (e)]. The rate of

change with distance is generally greater near a source than far away. Whales receiving a given sound level

far from a strong source like an icebreaker might show less response than if receiving the same sound level

closer to a weaker source like a playback site. Nonetheless, the expected radius of responsiveness around

an actual icebreaker would be far larger than that around a playback site. Furthermore, any tendency to

overestimate the radius of responsiveness because of this consideration may be partly or entirely offset by

the possibility that bowheads would react more strongly to actual icebreaker sound than to a playback of

icebreaker sound lacking the infrasonic and other low-frequency components.

28 Depending on water depth, vertical profiles of temperature and salinity, sea state, ice cover,

composition of the sea bottom (including subsea permafrost and compacted sediments), and variations in

these phenomena along the propagation path.
6.4 Bowhead Disturbance: Icebreaker Reaction Thresholds 311

A. Icebreaker at 17 May 1991 Loc'n, 95%

--- SL -1 m

-

- --- -- 170~=-------------------"-w:-.:;;;;;-1 ---- OJ

"0•.....•• •••• ,.- ••••••••••••••••••••••••••_1

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S:N = 20

70-t--------:=;"....:...--::e..-:.,-----""'-.-:-------_1

100.//··············

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B. Icebreaker at 3 May 1994 Loc'n, 95%

-- -

--- SL -1 m

-

-

-

Rec. Lev.

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~

S:N = 20

70+---------:;,·,:.·:.::::····:::,····..::.:· ..:.:..: .\----....:::::~---..:.:::::!:::±:::!:=:::!=:"'"l-+-=i--1

.........~ \\.•.•.

100 / .

I I I I I

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100 1000

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, ,

10000

FIGURE 6.24. Estimated 95th percentile source and received levels of icebreaker noise, by 1/3

octave, if actual icebreaker were operating at the deeper sites where playbacks were done on (A)

17 May 1991, and (B) 3 May 1994. Also shown are average ambient noise levels on those dates,

and "20 dB above ambient", by 1/3-octave.
6.4 Bowhead Disturbance: Icebreaker Reaction Thresholds 312

~ temporal variability in the source level of a given icebreaker, and

~ variation in ambient noise levels.

Given these physical variations, wide variations in S:N ratio will occur at a given distance from

the icebreaker. Likewise, there will be wide variations in the distance from the icebreaker at

which a given S:N ratio (reaction criterion) will occur.

Playbacks.-Figure 6.25 gives an indication of the very strong influence that variability in

physical acoustic phenomena can have on potential detection and reaction distances. The

descending received level vs. range curves on these graphs show, for the icebreaker playback on

17 May 1991, the maximum and minimum levels of icebreaker sound expected at various distances

during the icebreaker playback. These maximum and minimum levels show the range of values

expected during a 14-min playback cycle. In deriving these curves, 4 dB were added to the

maximum received level predicted by the sound exposure model, and 4 dB were subtracted from

the predicted minimum received level, to account for the ±4 dB uncertainty and variability in the

transmission loss estimates (§4.3). Measured ambient noise levels on 17 May 1991 are also

graphed as horizontal lines, with one alteration: before plotting, 2 dB were subtracted from the

minimum and maximum noise levels (8.5 s averaging time) to allow for short-term variability in

the ambient noise (cf. Richardson et al. 1991a:55fj). Then, distances were noted for which the

difference between the maximum icebreaker noise and the minimum ambient noise was S:N=15,

25 and 35 dB. Those distances are shown as vertical lines on the graph.

The distance from the playback source at which the received level falls below the ambient

level, and presumably becomes inaudible to a bowhead, varies greatly depending on both the ambient noise level and the icebreaker noise level. In this example, the predicted minimum RLBB falls

below the high ambient level at a distance of only about 300 m, whereas the predicted maximum

RLBB remains above the low ambient level out to a distance of almost 20 km.

Actual Icebreaker.-As illustrated in Figures 6.22A vs. Band 6.23A vs. B, detection distances for sound from the actual icebreaker would be much greater than those from the playback. The

effects of variability in propagation loss, ambient noise, and reaction thresholds evident in Figure

6.25 for playbacks would also apply, on a larger scale, to the actual icebreaker. However, if we

assume that it is the peak or near-peak levels of icebreaker sound that are most relevant to bowheads (i.e. RLlI3,max or RLl/3,950/0), the variability in received level at a given range is reduced from

that shown in Fig. 6.25. Figure 6.26 shows zone of acoustic influence models for icebreaker

Robert Lemeur operating in shallow and deep water, based on predicted 95th percentile levels of

icebreaker sound in the 1/3-octave band centered at 200 Hz (RLI/3,950/0)' This frequency is one of

those for which RL and S:N would be highest at long ranges. In Fig. 6.26, predicted received

levels are shown ±4 dB, representing the uncertainty associated with variability in propagation loss

at a given water depth (§4.3, p. 106fj). At close ranges, R < 2*(water depth), where the fitted

propagation model of §4.3 overestimates propagation loss, spherical spreading is assumed. The

received levels shown by the solid curves are the same as those shown, for 200 Hz and selected

ranges, in Fig. 6.22B (shallow site) and 6.24A (deep site). The ambient noise levels shown in Fig.

6.26 are the 1991/94 median (and 5th and 95th percentiles) in the 113-octave band near 200 Hz
17 May 91 14:20:00

20-1000 Hz Band

150

140 R • 200

SIN • 36

130

120

iii

Q.

~

... 110 u•..

lI:l

~

"ii 100

>III ...I

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0

III

a:

80

70

60

50

100

R '"1250

SIN", 25

R = 4300

SIN. 16

1000 10000 100000

Range (Meters)

FIGURE 6.25. Example of the effects of variable source level, uncertainty in propagation loss, variable ambient noise, and variation in

criterion of responsiveness (S:N 15-35 dB) on potential radius of noise influence. The source levels, propagation model, and ambient

noise are appropriate to the icebreaker playback test on 17 May 1991, time 14:20,20-1000 Hz band. See text for further explanation.

w.....

w
6.4 Bowhead Disturbance: Icebreaker Reaction Thresholds 314

200

95th %i1e Source Level

~ at Range 1 m

180

.-...

as o,

:J. 160

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Q) •...

III

"0 140

"-'"

Q5

>Q) ....J 120

"0

Q)

>

'Q)

o

100

Q) ......•.•. 95th %i1eAmbient

a:

80 Median Ambient

•••....... 5th %i1e Ambient .............

I i I l\

9 km /6 26 3~<::\.

A. Icebreaker at shallow (37 m) site,

1/3-oct. band at 200Hz

60-t--.--.-"""'T>-rnn;--r--;r-rT"TT"T'TI-,...-,.,...,..rn-r--.-.,.....,--.-r""1""rl-r-- ..•...•..•..•'r-r'l'+TTi

0.001

95th %i1e Received Level

V5. Range, t 4 dB

"'~ ..--....~ . ~ ~<.,<,..

Median Ambient + 30 dB ::::---••.••••

"1---------------- + 20dB -----+, ...:...:' -,",-,

I I·· ,

I

I ..(\ ..

i f\ \

.,---------------- + 10dB -------i--i--'-:,..\.

0.01 0.1 1

Range (km, log scale)

10 100

200....---------------------------,

.,...

~

~ 140

Q5

>

~ 120

"0

~

.~ 100.,---------------- + 20dB ------t-...:....;-"'l-.

Q) •••••••••• 95th %i1eAmbient

a:

180

C? o,

:J. 160

95th %i1e Source Level

~ at Range 1 m

B. Icebreaker at deep (110m)site,

1/3-oct. band at 200Hz

,---------- Median Ambient + 30 dB

"1-----------'------ + 10dB ------f----t--"'-A.."

80 Median Ambient

.......... 5th %i1e Ambient .

12km 50 80

60-t-----r-.--r-I"'"T'T,.,.,..-_r_"'T'"""T""T"TTmr---,-_,_.....,..TTT~___,r___r_,_rT'T.,.,.,-'--_r_"r_1_+_r_r+rl

0.001 0.01 0.1 1

Range (km, log scale)

10 100

FIGURE 6.26. Zone of acoustic influence models for icebreaker Robert Lemeur operating in water

(A) 37 m and (B) 110 m deep, based on predicted 95th percentile levels of icebreaker sound in 113-

octave band at 200 Hz (RLI/3•959r,), ±4 qB model uncertainty (§4.3). Ambient noise levels are 19911

94 median (and 5th and 95th percentiles) in the 1I3-octave band near 200 Hz (Table 4.3C, p. 88).
6.4 Bowhead Disturbance: Icebreaker Reaction Thresholds 315

(from Table 4.3C, p. 88); these values differ from the ambient noise values shown in Fig. 6.22-

6.24 for specific dates. Also shown in Fig. 6.26 are the ranges at which the nominal RLII3,95%

curve diminishes below the ambient, and the ambient + 10 dB, + 20 dB and + 30 dB levels

(S:NII3,95% = 0, 10, 20, 30 dB).

The nominal received level of icebreaker sound near 200 Hz (RLII3,95% basis) is predicted to

fall below the median ambient noise level, and thus become inaudible, at a range of -39 km at a

shallow (37 m) site, and at a range of -80 km at a deeper (110 m) site. These ranges would be

reduced to -21 km and -35 km on a day, respectively, when the ambient noise was at the 95th percentile level. There would be a further reduction to -18 km and -30 km if the ambient noise were

at the 95th percentile level and propagation loss were 1 standard error (4 dB) more than the average. Conversely, with ambient noise at the 5th percentile level, the maximum range of audibility

would be near 50 km at a shallow site and> 100 km at a deeper site. Thus, maximum detection

distance for the near-peak (95th percentile) levels of Robert Lemeur icebreaking sound would be

expected to range from a low of about 18-30 km to a maximum of 50 to >100 km, depending on

water depth, ambient noise level, and propagation conditions.

The predicted distance out to which bowheads would commonly show avoidance or other

behavioral reactions can be estimated from Fig. 6.26 in a similar way if we assume that reaction

thresholds to the actual icebreaker sound would be similar to those during our playbacks.

Reactions appear to be common among bowheads exposed to icebreaker:ambient ratios> 20 dB.

The nominal received level of icebreaker sound near 200 Hz (RLI/3,95%) is predicted to fall below

the "median ambient + 20 dB" level at a range of 16 km in shallow (37 m) water, and 28 km in

deeper (110 m) water. The ±4 dB variability in propagation loss results in some variability in

these estimates, i.e. 13-21 km in shallow water and 20-35 km in deep water. Also, day-to-day

variability in ambient noise levels causes much variation in the predicted ranges at which S:N 113,95%

= 20 dB: about 7-26 km in shallow water and 9-50 km in deep water (with 95th and 5th percentile

ambient noise and nominal propagation loss). Allowance for simultaneous variation in both

propagation loss and ambient noise would result in further expansion of the spans of predicted

S:N 113,95% reaction distances.

The playbacks showed that some bowheads receiving icebreaker sound with S:NII3,max 10 dB

or even less react, whereas other bowheads receiving S:NII3,max 30 dB or even more do not react.

Figure 6.26 shows that, with nominal propagation loss and median ambient noise, S:NII3,95% = 10

dB and 30 dB are expected to occur at 26 vs. 9 km at a shallow site, and at 50 vs. 12 km ata

deeper site. These spans of distance expand greatly if one allows, simultaneously, for variation

in propagation loss and/or ambient noise level. For example, at the shallower site, a whale

reacting at S:NII3,95% = 10 dB on a day with 5th percentile ambient noise and propagation loss 4 dB

less than average would be expected to react at ranges out to -45 km. In contrast, a whale

reacting at S:NII3,95% = 30 dB on a day with 95th percentile ambient noise and propagation loss

4 dB more than average would not be expected to react at ranges more than -1 % km. Corresponding values for the deeper site would be -95 and -2 km. Even these extreme spans of predicted

ranges may not cover every case, .as reaction thresholds (S:NI/3,max) for some bowheads appear to

have been <10 dB, and thresholds for others appear to have been >30 dB (§6.2, 6.3).
6.4 Bowhead Disturbance: Icebreaker Reaction Thresholds 316

In this study, we were not able to determine with certainty whether bowheads were more

closely attuned to received levels (RL) of icebreaker sound or to icebreaker:ambient (S:N) ratios.

The estimates in preceding paragraphs assume that S:N ratios are more relevant. Because the

received level of icebreaker noise is not affected by ambient noise, predicted ranges for a specific

RLII3,95% are much less variable than are those for a specific S:N 113,95%' Reaction thresholds of

bowheads to playbacks of icebreaker sounds were on the order of 90-100 dB re 1 IlPa on an

RLII3,max basis. Predicted ranges for RLII3,max 90 and 100 dB can be extracted from Figure 6.26.

With average propagation loss, these are -25 and 15 km at the shallower site, and -48 and 26 km

at the deeper site. Again, these spans of ranges widen if one allowed for uncertainty in

propagation loss and for the fact that some bowheads may react at RLII3,max <90 dB re 1 IlPa

whereas others may not react unless RLII3,max >100 dB.

Overall, it is apparent that expected reaction distances are highly variable, depending on the

responsiveness of a particular bowhead, water depth, propagation conditions, and probably ambient

noise. However, under typical conditions along the spring migration route of bowhead whales off

northern Alaska, reactions are expected to be common at distances up to 10-50 km from an icebreaker like Robert Lemeur, assuming that reaction thresholds derived from the playbacks can be

applied. Occasionally, reactions might occur even farther away in cases involving some combination of unusually responsive whales, deep water, better-than-average propagation, low ambient

noise, and/or a noisier icebreaker. In other cases, involving some combination of unresponsive

whales, shallow water, poorer-than-average propagation, high ambient noise, and/or a less-noisy

icebreaker, some of the bowheads within 10 km of the operating icebreaker may not react.

6.5 Icebreaker vs. Drilling Noise Results

Reaction thresholds for traveling bowheads exposed to playbacks of steady, low frequency

sounds from the Karluk drilling operation on a grounded ice pad were described in Richardson et

al. (1991a). In that report, we concluded that typical traveling bowheads showed avoidance

reactions to Karluk sounds at RLBB values near 120 dB re 1 IlPa when not confined by ice, but

tolerated levels up to -135 dB when there was no alternative route through the ice (S:NBB 26-46

dB). On a "dominant 113-octave basis", corresponding figures were RLII3 about 115 or 131 dB re

1 IlPa, and S:NII3 32 or 50 dB. In each case, the higher figure refers to levels tolerated by

bowheads with no alternative route through the ice, based on results of a playback experiment on

13 May 1990 (Richardson et al. 1991a:148fj).

Sound propagation at the 13 May 1990 playback site has been re-evaluated based on all propagation data collected during the four years of the study (§4.3). This re-evaluation suggests that

received sound levels at most distances from the 13 May site were slightly lower than estimated

in our earlier report. Figure 6.27 compares the revised (solid curve) and old (dashed curve) estimates of RL vs. range. Based on this reanalysis, the various threshold RL and S:N estimates for

bowheads confined by ice should be reduced by -1-7 dB.

Based on the revised propagation loss estimates, the avoidance threshold for bowheads

exposed to Karluk sounds was about RLBB 131 dB when confined by ice vs. 120 dB re 1 IlPa in
6.5 Bowhead Disturbance: Icebreaker vs. Drilling Noise 317

180

/source Level

at Range 1 m

........ 160

roa..

~

T"""

CD 140

'- _ 1. S:N = 45 dB

rn - 2. S:N = 42dB

"0 3. S:N = 35dB '-'"

CD 120

> 4. S:N = 25dB

CD -l

"0

CD _ 5. S:N= 12 dB 100 >

'Q) Ambient Noise o

CD Level

a: 80

60

0.001

A. 13 May 1990

Undistorted Playback

20-1000 Hz Levels

·····-·······_···~l·-·-·----_

1. Closest CPA --t:>l ! i

l

2. Typical CPA

3. Strong BJ:V. Redc.Out to -d

'~. Freefent Turns Out to I --t:::>i ,

/5. Pos~ibleBehav. React.qut to l---c>j

.. .. I

0.01 0.1

Range (km, log scale)

1

B. 13 May 1990

Undistorted Playback

Dominant 1/3 Octave

····--···········--·····-r···- ---- --.~ _.....,

, '. ----------t--t------t---"i-o.. ....'.".

1. Closest CPA ----c:>!

2. Typical CPA i

3. Strong Be . v. ReJc. Out to --t:::='l I

'4. Freef.entTums Out to !--t:>1

5. Pos,ible Behav. React.~ut to !

0.01 0.1

Range (km, log scale)

1

FIGURE6.27. Zone of acoustic influence models for Karluk drilling noise playback, 13 May 1990,

based on (A) broadband 20-1000 Hz sound levels, and (B) levels in dominant l/3-octave band,

centered near 200 Hz. Modified from Richardson et al. (l991a:Fig. 95), with revised propagation

loss estimates from §4.3 (p. 109jJ). Dashed curves are former estimates of RL vs. range.

10

10
6.5 Bowhead Disturbance: Icebreaker vs. Drilling Noise 318

open conditions. This corresponds to RL1/3 125 vs. 115 dB, S:NBB 42 vs. 26 dB, and S:N1/3 44 vs.

32 dB (for "confined by ice" vs. "open water" in each case). The "confined by ice" estimates are

the RL and S:N values at range 200 m in Figure 6.27. The "open water" estimates are unchanged

from those in Richardson et al. (l99la).

As discussed in our earlier report, reaction thresholds to Karluk sounds varied widely

depending on the criterion considered. Subtle behavioral effects were evident at RL and S:N

values lower than those quoted above for active avoidance. In the "confined by ice" conditions

on 13 May 1990, subtle behavioral effects may have been evident at S:NBB values as low as 12 dB

(RLBB 101 dB re 1IlPa), and S:N1/3 values as low as 14 dB (RL1/3 95 dB), based on the updated

sound exposure model for 13 May 1990 (Fig. 6.27). ,Nonetheless, traveling whales typically

approached to much closer distances, where they were exposed to RL and S:N values as high as

those mentioned in the preceding paragraph.

During the icebreaker playbacks in 1991/94, there were again some indications of different

response thresholds depending on the behavioral measure under consideration. For example, the

occurrence of turns during surfacings seemed to be increased at S:NI/3,max>10 dB, whereas duration

of surfacing and number of blows per surfacing were not significantly altered unless S:NI13,max

>20 dB (§6.3). However, such differences must be interpreted cautiously, given the low sample

size and the consequent limitations on the power of the statistical comparisons of observations in

different S:N or RL categories (see p. 290ff).

In general, the icebreaker playback tests showed that traveling bowheads often reacted

behaviorally or by alteration of swimming tracks at icebreaker-to-ambient ratios (S:NI/3,maxor

S:NI/3,medbasis) as low as 20-30 dB. Subtle behavioral reactions to Karluk drilling sounds were

evident at similar or slightly lower S:N levels. However, obvious avoidance of Karluk sounds

required higher S:N1/3 values, on the order of 32+ dB.

Received levels of sounds from the actual Robert Lemeur icebreaker managing ice were much

higher than those from the Karluk drilling operation at any given distance. Sonic components of

Karluk sound (>20 Hz) had diminished to 124 dB re 1 IlPa at range 0.13 km, and to ~87 dB (near

or below ambient) at 2 km (Richardson et al. 1990a:86). In contrast, broadband noise from the

actual Robert Lemeur diminished to 124 dB only at range -6 km (Greene 1987a), and would be

>87 dB out to well over 30 km. Broadband (20-1000 Hz) levels of Karluk sound received by bowheads during our 1989-90 playbacks were at least as high as those that bowheads would have

received at corresponding distances from the actual Karluk site. In contrast, icebreaker sounds

received by bowheads during our playbacks were similar in broadband level to those that would

be experienced by bowheads much farther away from an actual icebreaker. Thus, the radius of

responsiveness around an actual icebreaker would be far larger than that around an actual drillsite

like Karluk, assuming that bowheads react in a similar way to real industrial sites and playbacks.
6.6 Bowhead Disturbance: Evaluation of Playback Hypotheses 319

6.6 Evaluation of Playback Hypotheses

As discussed in §1.2, Null and Alternate Hypotheses, the two null hypotheses applicable to

playback effects on bowheads were as follows:

1. Playbacks of recorded noise from a bottom-founded platform (1989-90) or an icebreaker

working on ice (1991/94) will not (or alternatively will) significantly alter measures of

migration routes and spatial distribution of whales in the open water of nearshore lead

systems during the spring migration near Pt. Barrow, Alaska.

2. Playbacks of recorded noise from a bottom-founded platform (1989-90) or an icebreaker

working on ice (1991/94) will not (or alternatively will) significantly alter subtle aspects

of individual whale behavior in the open water of nearshore lead systems during the

spring migration near Pt. Barrow, Alaska.

During the 1989-90 work with Karluk drilling noise, we found it appropriate to narrow the

wording of hypotheses (1) and (2) as follows:

"Playbacks of recorded continuous noise from a bottom-founded platform like the Karluk

drilling operation on a grounded ice pad will not (or alternatively will) significantly

alter ... of bowhead whales visible in open water amidst the pack ice and in the seaward

side of the nearshore lead system during spring migration east of Pt. Barrow, Alaska."

Here" ... " refers to either measures of migration routes and spatial distribution (hypothesis 1) or

subtle aspects of individual behavior (hypothesis 2).

Hypotheses 1 and 2 have already been addressed with respect to the effects on bowheads of

playbacks of recorded continuous noise from a bottom-founded platform like Karluk (Richardson

et al. 1991a:226ff, 246fj). In the circumstances studied," Karluk playbacks resulted in statistically-significant small-scale changes in migration routes, spatial distribution, and individual behavior.

However, there was no evidence of migration blockage, and we concluded that the observed effects

were likely to be biologically non-significant. One purpose of the 1991/94 tests with a second and

more variable type of industrial sound was to evaluate the generality of the 1989-90 results.

In 1991/94, as in 1989-90, observations during playbacks were restricted to bowheads visible

in open water within areas east of Pt. Barrow. In 1991/94, the playback noise was variable icebreaker noise from Robert Lemeur rather than continuous drilling sound, and the observations were

on both the landfast ice side and the seaward side of nearshore lead systems, but not in the offshore pack ice. Thus, for 1991/94, hypotheses (1) and (2) should be formulated as

"Playbacks of recorded variable noise from an icebreaker like Robert Lemeur working

on ice will not (or alternatively will) significantly alter ... of bowhead whales visible in

the open water of nearshore lead systems during spring migration east ofPt. Barrow, Alaska."

29 For whales visible in open water amidst the pack ice and in the seaward side of the nearshore lead

system during spring migration east of Pt. Barrow, Alaska.
6.6 Bowhead Disturbance: Evaluation of Playback Hypotheses 320

The hypotheses, as stated above, concern reactions to playbacks of icebreaker noise rather

than to noise from the icebreaker itself. Thus, questions about the fidelity of the playback noise

to the noise from the original industrial activity are not directly involved. Also, the greater radius

of anticipated effects around an actual icebreaker is not directly dealt with by the hypothesis (but

see "Implications for Actual Icebreaking", later).

Distribution & Movement Hypothesis/Icebreaker Playbacks

The hypothesis uses the phrase, "significantly alter measures of... ", but does not define

whether "significantly" refers to statistical or biological significance.P'v" No direct statistical

test of the distribution and movement hypothesis was meaningful with the data available. However, many of the bowheads exposed to S:N 1/3.max levels above about 20 dB, and a minority of those

exposed to lower S:N levels, did show changes in their tracks indicative of diversion (see §6.2).

Also, statistical tests confirmed that there was a positive relationship between sound exposure level

and the frequency and magnitude of turns during surfacings. Therefore, on a "weight of evidence"

basis", we conclude that there were significant localized diversions of the migration routes of

many of the bowheads that came close enough to the noise source to receive maximum levels of

icebreaker sound 20+ dB above the ambient noise level in the same 1/3-octave band (S:N1I3,max

basis). However, there was no evidence of migration blockage during the 1991/94 playbacks.

The spatial scale of this localized diversion was more difficult to judge than had been the

case during the Karluk playbacks. The highly variable nature of the icebreaker sounds meant that

distance was not a good measure of response probability. Responsiveness had to be assessed in

relation to sound exposure level, either on a received level or an icebreaker-to-ambient ratio basis.

The area around a playback site within which some bowheads showed diversion of their migration

tracks, although hard to define, was localized. The migration diversion caused by a single

icebreaker playback site comparable to those in this study would not, in our view, be significant

to the bowhead population.

"Playbacks of recorded variable noise from an icebreaker like Robert Lemeur working

on ice will not (or alternatively will) significantly alter the migration routes or spatial

distribution of bowhead whales visible in open water of nearshore lead systems during

spring migration east of Pt. Barrow, Alaska."

Thus, available data allow a "weight of evidence" evaluation of a modified null hypothesis

concerning effects of playbacks of icebreaker noise on distribution and movements during spring:

30 By "biologically significant", we mean "likely to affect the long-term well-being or reproductive

productivity of individuals or of the population".

31 Another possibility, "sociocultural significance", is outside the scope of this study. If icebreaker

disturbance caused a change in the migration corridor, the accessibility of bowheads to hunters might be

reduced. This could have sociocultural significance.

32 By "weight of evidence", we mean an evaluation considering all relevant datasets and variables, some

or all of which are not amenable to specific statistical tests.
6.6 Bowhead Disturbance: Evaluation of Playback Hypotheses 321

There were detectable but inconsistent alterations in migration routes and spatial distribution.

There were also statistically significant alterations in measures of turning, which are related to

distribution and movements. Thus, we conclude that the null hypothesis should be rejected:

playbacks will cause statistically significant alterations in localized migration routes and spatial

distribution in the circumstances described in the hypothesis. However, there was no evidence

of biologically significant alterations in migration routes or spatial distribution, or of migration

blockage. Note that this assessment applies to playbacks of icebreaker noise, not to noise from

an actual icebreaker (see below).

"Playbacks of recorded variable noise from an icebreaker like Robert Lemeur working

on ice will not (or alternatively will) significantly alter subtle aspects of individual

behavior of bowhead whales visible in the open water of nearshore lead systems during

spring migration east of Pt. Barrow, Alaska."

Behavior Hypothesis/Icebreaker Playbacks

The amended "behavior" hypothesis for 1991/94, consistent with the circumstances in which

the 1991/94 data were acquired, is as follows:

The 1991/94 data show that-from a statistical viewpoint-this null hypothesis must be rejected.

There were statistically significant changes in individual behavior among the bowhead whales

exposed to the highest received levels and signal-to-noise ratios of icebreaker noise. The number

of blows per surfacing, duration of surfacing, occurrence of turning, and two multivariate indices

of behavior were significantly correlated with various measures of RL and S:N.

The biological significance of these changes in behavior is less obvious. The altered

behavior was not statistically significant until the whales had approached within a few kilometers

of the projectors, with the occurrence of effects being more closely related to received icebreaker

sound levels than to distance from the projectors. Assuming that behavior was rarely affected at

distances beyond 2 km from the projectors, and that bowheads migrate at 4 km/h or more, significantly altered behavior would usually not persist for more than 1 hour as bowheads passed a

projector site.

The data provide no objective basis for determining the biological significance of the observed changes in behavior. Our subjective judgement, based on experience in conducting behavioral

and other studies of undisturbed and disturbed bowheads, is that the observed behavioral reactions

to a single playback site emitting icebreaker (or Karluk) sound are biologically insignificant.

Again, this assessment applies to playbacks of icebreaker noise, not to noise from an actual

icebreaker (see below).

Implications for Actual Icebreaking

The specific hypotheses discussed above concern playbacks of icebreaker sounds. Of much

more importance is the likely effect of one or more actual icebreakers. If the two null hypotheses

discussed above were reworded to apply to an actual icebreaker rather than playbacks, we would
6.6 Bowhead Disturbance: Evaluation of Playback Hypotheses 322

conclude that existing playback data are sufficient to justify rejection of both null hypotheses on

statistical grounds, and probably also insofar as biological significance is concerned.

The radius of influence on distribution, movements and behavior around an actual icebreaker

would be much greater than that around a playback site, given the much stronger source level of

the noise from the icebreaker as compared with the projectors. Playbacks may also underestimate

the radius of influence because of the poor reproduction of low-frequency components of icebreaker sound during playbacks (§4.4). Response distances around an actual icebreaker would be

highly variable but, for typical traveling bowheads, detectable effects on movements and behavior are predicted to extend commonly out to radii of 10-30 km, and sometimes to 50+ km (§6.4).

This assumes that response thresholds to an actual icebreaker like Robert Lemeur, on an S:N or

RL basis, are comparable to those near the playback site. This assumption is discussed on p. 10-11

(§1.3) and on p. 115-128 (§4.4). Given that assumption, an actual icebreaker in or near the spring

lead system in the NE Chukchi Sea or western Beaufort Sea might affect bowhead whale migration

through a broad area of ice for the duration of icebreaker operations.

The predicted "typical" radius of responsiveness around an icebreaker like Robert Lemeur

is quite variable because propagation conditions and ambient noise vary with time and with. location. In addition, icebreakers vary widely in engine power and thus noise output, with Robert

Lemeur being a relatively low-powered icebreaker. Furthermore, the reaction thresholds of individual whales vary by at least ±10 dB around the "typical" threshold, with commensurate variability in predicted reaction radius.

Notwithstanding these qualifications, there is strong evidence that distribution, movements,

and behavior would be altered in a statistically significant manner within a substantial radius, at

least on the order of 10-30 km. There is also substantial reason for concern about potential biologically significant effects, given the time that it would take whales to travel through an area 20-60

km in diameter, the potential difficulties in diverting around an area of this size under heavy ice

conditions, and the unknown consequences if bowheads were unable or unwilling to pass through

or around such an ensonified area.

Of greatest concern would be any diversion or interruption of migration during the late

spring when mothers and calves are migrating. During spring, calves are very young and appear

to have much less ability than older bowheads to travel through heavy ice conditions. Their swimming abilities seem limited. This is evident from their short dives, the frequent occurrence of

"riding", and their frequent lingering in one area for prolonged periods, especially when there is

much ice in the area (§5.2, 5.4). There would be fewer situations in which the spring migration

corridor in our study area would be sufficiently confined to leave older bowheads with no alternative migration corridor around an area of icebreaking.

It is not known whether bowheads would continue to travel through a strongly-ensonified

lead if there were no alternative migration corridor through the ice. Migration blockage probably

would be confined to a smaller radius around the icebreaker than would subtler effects on

movement and behavior patterns. As observed during the Karluk playback on 13 May 1990, when

there is no alternative corridor through heavy ice, many spring-migrating bowheads will travel

r
6.6 Bowhead Disturbance: Evaluation of Playback Hypotheses 323

through a strongly-ensonified migration corridor, although their behavior is conspicuously altered

while they do so (Richardson et al. 199Ia:148). We would expect the same general phenomenon

to apply to icebreaker noise. However, the maximum levels of variable icebreaker noise that

. bowheads would tolerate might differ from the maximum levels of steady drilling noise tolerated

during the 13 May 1990 Karluk experiment.

In heavy ice conditions, two or more icebreakers often work in coordination with one another

within a given area. This would cause a higher overall sound level in the area, and an increase

in the size of the area ensonified to levels above various RL or S:N criteria. Also, icebreaker

sound would reach some locations from two or more directions. The longest-distance apparent

response of bowheads to vessels reported to date (at ~15 km) involved a mother and calf located

between two ships approaching from different directions (Koski and Johnson 1987:54fj). On a

smaller scale, a common guideline for boat-handling during whalewatching operations is that

whales should not be approached from different directions simultaneously, as this often causes

more disturbance than does a single boat. Some extrapolation is required to apply these observations to the case of two or more icebreakers operating in one area. However, it would be prudent

to assume, unless demonstrated otherwise, that two or more icebreakers operating in an area

probably would result in a significantly greater disturbance effect than one icebreaker.

We speculate that any migration blockage of migration that did occur because of icebreaking

would cease soon after the icebreaking stopped. This suggests the possibility of partially mitigating any icebreaker-induced blockage that might occur by ensuring that icebreaker operations do

not occur continuously in one area for more than some specified duration. The upper limit on the

allowable duration of continuous icebreaking would need to be evaluated, but might be chosen not

to exceed the durations for which bowheads occasionally interrupt their spring migration for "natural" reasons. The necessary duration of "gaps" in icebreaking in order to allow passage of bowheads would also need to be evaluated.

6.7 Bowhead Reactions to Aircraft

Overflights of bowheads and other baleen whales by low-flying helicopters or fixed-wing

aircraft sometimes elicit obvious disturbance reactions, generally involving abrupt dives or sharp

turns. Also, bowheads and other baleen whales exposed to aircraft and other human activities

sometimes exhibit breaches or tailslaps. Those behaviors often occur in the absence of disturbance, but at times are suspected to be stimulated by disturbance (Richardson et al. in press).

Reactions of bowheads to aircraft have been described and reviewed by Richardson et al. (1985a)

and Richardson and Malme (1993). Before this study, most of the data on reactions of bowheads

to aircraft pertained to summer and autumn.

Bowhead Reactions to Bell 212 Helicopter

Specific objective 6 in 1991 and 1994 was

To measure, on an opportunistic basis, the short-term behavioral responses of bowheads

and (as possible) white whales visible in open water areas along their spring migration
6.7 Bowhead Disturbance: Reactions to Aircraft 324

TABLE 6.14. Incidental observations of bowhead whales near the operating helicopter northeast of

. Barrow during spring in 1989-1994.

Lateral Observ.

Group Altitude Distance Reac- PlatDate Time Size (m) (m) tion? form

. Comments

A. Observed During Overflight

01105/90 18:25 1 150 0 Yes H Dove immediately in short narrow crack

10/05/90 21:05 1 100 500 No I Continued travel then dove after 4-5 blows

10/05/90 21:14 1 25 0 No IIH Continued travel at surface as helicopter circled then flew over whale and landed

11/05190 10:07 1 150 ? No H Continued travel

11105/90 10:09 3 150 500 No H Continued at surface. including tail slaps

11105/90 14:38 1 90 ? No H No observed reaction as whale traveled NE

11/05/90 18:56 2 150 0 No T Controlled overflight, whales began social interactions as helicopter approached

and continued after it departed

16/05190 13:48 2 150 800 No H Continued medium speed travel

16/05190 19:07 1 150 ? No H Behavior unknown

24105190 13:41 4 100 200 No H Continued travel, surfacing twice

01105/91 18:19 1 75 150 Yes H Whales traveling ENE dove immediately

01105191 18:20 2 60 1000 No H Continued travel ENE at surface

11105/91 10:28 1 90 ? No H No observed reaction as whale traveled E

03/05/94 11:23 1 ? 400 Yes? A Breached and tails lapped; continued aerial activity for 2.4 h after overflight.

Potentially disturbed by sonobuoy launch

03/05/94 22:09 1 250 500 No H Continued travel

07/05/94 9:27 I 100 800 No H Continued travel

07/05/94 9:30 2 90 800 No H Continued travel

07/05194 9:35 I 150 500 No H Continued travel

07/05/94 9:36 2 125 500 No H Continued travel

07/05/94 9:39 1 150 0 Yes H Dove sharply

07/05/94 9:40 1 150 50 No H Sighted below surface while diving at ice edge

08/05/94 15:53 1 75 800 No H Continued travel

08/05/94 15:54 2 75 800 No H Continued travel

09/05/94 10:14 1 100 300 No H Continued travel

09/05194 10:15 2 100 200 No H Continued travel

09/05194 20:39 1 150 1600 No H Continued travel

10/05/94 12:22 1 50 15 No H Continued travel

10/05/94 12:25 1 50 250 Yes H Dove immediately

10/05194 12:26 I 50 800 No H Travel then dove at ice edge

10/05/94 13:53 1 150 500 No H Continued medium speed travel

10/05194 18:19 I 150 500 No H Travel then dove at ice edge

11105/94 9:03 1 ? 1000 No H Continued travel

14/05/94 9:13 I 50 300 No H Behavior unknown

14/05194 9:24 I 90 800 No H Behavior unknown

14/05194 9:33 1 90 400 No H Behavior unknown

14/05/94 9:36 3 125 200 No H Continued rest at surface

14/05194 9:37 2 0-15 100 No H Remained at surface while helicopter passed twice and landed within 100m

14/05/94 9:51 3 0-15 500 Yes? H At least one whale breached but group remained at surface as helicopter passed,

turned around, then landed within 500 m of whales. Whales continued

approaching (CPA = 150 m) as helicopter stationary on ice with engines on.

Dove at ice edge -20 s after helicopter landed.

16/05/94 19:04 3 250 100 No H Helicopter passed then circled group once for -1.5 min; whales continued

medium speed travel at surface

17/05/94 9:39 1 275 700 No H Continued travel at surface

17/05/94 9:44 I 200 800 No H Remained at surface near ice edge

17/05194 9:46 2 150 0 No H Continued travel at surface

17/05194 18:31 2 300 200 No H Continued travel at surface

17/05/94 19:49 2 200 400 No H Continued travel

r
TABLE 6.14. Continued.

6.7 Bowhead Disturbance: Reactions to Aircraft 325

Date

Lateral

Group Altitude Distance

Time Size (m) (m)

Reaction?

Observ.

Platform' Comments

20/05194 9: 16

20/05194 9: 19

25/05/94 13:56

Yes?

No

No

180

90

175

1600

800

1200

H

H

H

Breached 3 times 30 s after helicopter passed

Behavior unknown

Continued travel

B. Observed Within 2 min of Landing or During Take-off

13/05190 11:56 2 60 200 No Continued travel ESE at surface as helicopter lifted off. Helicopter had been

operating in area for 13 min while deploying sonobuoy

lII05/91 14:33 0 50-100 No Continued travel E. respired at least 6 times as it traveled past helicopter that

landed 2 min earlier. paralleling the ice edge

17/05191 20:38 0 700 No Whale surfaced and continued travel E while helicopter landed. Engines were

turned off 1.2 min before it resurfaced and blew 8 times

25/05191 9:53 0 125 Yes? Whale surfaced ESE of helicopter 30 s after landing. traveled NE and blew 3

times. Engines were turned off at 09:58:30 and whale resurfaced 15 s later and

tailslapped 4 times.

07/05/94 11:06 0 240 No No apparent reaction as helicopter landed

07/05/94 11:43 0 350 Yes Dove for 1.5 min as helicopter landed. then single blow surfacing 1.5 min later

when helicopter stationary on ice with engines on

10/05/94 10:27 2 0 250 No Continued medium speed travel as helicopter landed

20/05/94 10:02 1 0 500 No Dove under ice after5-6 blows while traveling at medium speed as heli, landed

20/05/94 12:11 1 0-15 190 No Continued travel during helicopter lift off

C. Helicopter Stationary on Ice, Engines Operating, >2 min After Landing

Continued travel ESE as helicopter stationary on ice with engines on

Continued travel at surface as helicopter stationary on ice with engines on

Continued social activity as helicopter on ice with engines on for 6 min

Continued social activity as helicopter on ice with engines on for 6 min

Surfaced >2 min after helicopter landed. continued travel ENE at surface while

helicopter engines on

Surfaced NNW of helicopter 3 min after landing. continued travel ENE. blew 8

times. Helicopter engines were turned off during surfacing

Continued travel at surface. blew 4-5 times as helicopter stationary on ice with

engines on 6 min after landing

Subadult surfaced and blew once; then slipped under water without an arch as

helicopter stationary on ice with engines on

13105/90 11:40 1 0 500 No

16/05/90 13:36 2 0 450 No

16/05190 13:38 2 0 520 No

16/05190 13:41 2 0 495 No

03/05/91 11:58 2 0 300 No

03/05191 11:59 0 300 No

03/05/91 13:35 0 600 No

09/05/94 12:30 0 230 Yes

D. Repeated passes Over Mother & Calf

16/05/89 11:51 2

15-30 100 No (I)

15-30 -150 No (I)

15-30 -125 No (I)

15-30 -50 Yes? (I)

15-30 500 Yes? (I)

, I = Ice camp. H = helicopter. T = Twin Otter.

Mother & calf remained in small. refrozen lead for 2.8 h as helicopter ferried

between sonobuoy and camp for a total of 5 passes (see below)

Calf remained stationary at surface; mother not at surface

Calf remained at surface; mother not at surface

Calf remained at surface

Mother dove

Mother & calf dove. surfaced in same location <2 min later. then relocated a few

minutes later farther to side of helicopter route
6.7 Bowhead Disturbance: Reactions to Aircraft 326

corridor in the western Beaufort Sea to actual helicopter overflights (supplementing

limited data from 1989-90).

There were corresponding specific objectives during the 1989 and 1990 phases of the project. This

work was assigned a lower priority than the playback work. However, some opportunistic

observations concerning responses to the project's Bell 212 helicopter were obtained in all four

years. In addition, during 1990 there was one planned overflight of bowheads by the Bell 212

(Richardson et al. 1991a:265). Helicopter sounds were measured in 1989 (Richardson et al.

1990a:81fj). The present analysis takes account of the results from all four years of the project.

Methods.-Whenever bowheads were accessible during the springs of 1989-91 and 1994,

helicopter-supported work was devoted to noise playback experiments. Aside from the one

planned helicopter overflight in 1990, we performed no specific tests of bowhead reactions to the

helicopter. However, we kept notes on opportunistic observations of the behavior of bowheads

seen near the Bell 212 helicopter including, in most cases, the helicopter altitude and lateral

distance from the whales.

Most observations of bowhead whale reactions (or lack of reactions) to the operating

helicopter consisted of brief «3 min) opportunistic sightings made from the helicopter, the ice

camp, or the Twin Otter. Probable disturbance reactions were defined as an immediate dive,

sudden turn, aerial activity (breach, tail slap), unusually short surfacing, or unusual change in

surface behavior during the surfacing. This classification is inevitably somewhat subjective, but

is based on our experience in observing the behavior of undisturbed bowheads, and on the

characteristics of the obvious reactions to aircraft that sometimes occurred during low altitude

overflights. A digital theodolite was used to measure positions of whales in relation to the

operating helicopter when observations were made by the ice-based crew. Other estimates of

lateral distance were by visual estimate. Altitudes during overflights were in most cases obtained

from the aircraft altimeter.

Chi-square tests were used to test for differences in frequency of response in relation to

aircraft altitude and lateral distance. Cases when the helicopter took off or landed on the ice

during the observation (or landed <2 min before the observation) were included with the overflights in most analyses. Cases in which the helicopter's engines were running but the helicopter

had landed >2 min before the whale observation are treated separately.

Results.-During the four years of this study, there were 65 occasions when whale behavior

was noted at known lateral and/or vertical distances from the operating helicopter (Table 6.14).

Observations of bowheads were made

~ during single overflights (n=47; Table 6.14A),

~ within 2 min of landing or during takeoff (n=9; Table 6.14B),

~ when the helicopter was stationary on the ice with its engines operating >2 min after

landing (n=8; Table 6.14C), and

~ during multiple overflights of a mother-calf pair (ne l ; Table 6.14D),
6.7 Bowhead Disturbance: Reactions to Aircraft 327

The mother-calf pair exposed to five low-altitude passes was considered to be a special case, and

was excluded from the general analysis, leaving 47 cases of single overflights (Table 6.14A), 56

cases including landing/takeoff cases (Table 6.14A+B), and 64 cases in total (Table 6. 14A+B+C).

Frequency of Reactions: Apparent reactions to the helicopter were observed during 10

(15.6%) of these 64 occasions. Apparent reactions consisted of 5 immediate dives (including an

abbreviated surfacing), 4 instances of breaching or tailslapping, and one single-blow surfacing.

Reactions were noticed when the helicopter was stationary on the ice (l of 8 cases), within 2 min

of helicopter landing (2 of 9 cases), and during overflights (7 of 47 cases). The remaining 54

bowheads or bowhead groups (84.4%) exhibited no overt reaction to the helicopter, and generally

maintained their course and continued respiring at the surface.

Although some bowheads appeared to react to the helicopter when it was operating at altitudes up to 180 m ASL and lateral distances as far as 1600 m, most reactions occurred when the

helicopter was flying lower and closer to the whales (Fig. 6.28). Of the 8 reactions for which both

altitude and lateral distance were known during the overflight, including cases observed within 2

min after the helicopter landed, most reactions (5 of 8 or 62.5%) occurred when the helicopter was

operating at altitudes ~150 m above sea level (ASL) and at lateral distances ~250 m (Table 6.15,

Fig. 6.28, 6.29).

Helicopter Altitude: Altitude ASL during 56 helicopter overflights ranged from 0 m (when

bowhead groups were observed during helicopter takeoff or within 2 min of landing) to 300 m

(Table 6.14A,B). Altitude was not recorded on two occasions. Thus, there were 54 observations

with the helicopter at known altitudes. Immediate dives occurred during 5 of 46 overflights when

the helicopter approached at altitudes ~150 m. In a few additional cases at ~150 m (2 of 46), other

types of reactions, including breaching and tailslapping, were seen. More often, however, no

TABLE6.15. Bowhead reactions to helicopter overflights in relation to helicopter altitude and lateral

distance, 1989-1994. Each bowhead group is counted only once. Includes data from Table 6.14A,B,

involving overflights (n=47) and cases when whales where observed within 2 min of landing or

takeoff (n=9).

Helicopter Altitude (m)

Lateral ~150 >150 Unknown Total

Distance No No No No

(m) Reaction Reaction Reaction Reaction Reaction Reaction Reaction Reaction

~250 5 14 0 2 0 0 5 16

>250 2 21 1 5 1 1 4 27

Unknown 0 4 0 0 0 0 0 4

Total 7 39 1 7 1 1 9 47
-E 200 ---

Unknown ?

•

o

D

A: Overflt-No React

A:

•

Overflt-React

X

B: TO&Land-No React

A

B: TO&Land-React

X

C: On Ice-No React

f2J

C: On Ice-React

FIGURE 6.28. Reactions of bowhead whales to the operating Bell 212 helicopter in relation to helicopter altitude and lateral distance,

1989-94. Includes cases when helicopter was (A) flying, (B) taking off (TO) or had landed within preceding 2 min, and (C) was on ice

with engines running (cf Table 6.14A,B,C). "?" denotes cases where it is uncertain whether the whale was reacting to the helicopter.

300- 0

Bowhead Whales

DO

O-l---'H""'---,r-BIlI~~-r-~~---"IlE----2i~---r---r---.---~---,...-----r---r---.---~....I

o

100-

o

- 0 o

o o

o

?

•

o o

o o

o

o

o o o

o

DO

a

o

•

X

.0

o

-:] o

[]

o x? ?

•

'I I TIT TTl I I I I I I I I

200 400 600 800 1000 1200 1400 1600 Unknown

Lateral Distance (m)
ena.

:J 15

e

<!J

'0

LCD

.n 10

E

:J

Z

20

n=5

5

n=2 n=2

n=O

0

<1501<250 <1501>250 >1501<250

n= 14

n=21

Altitude /Lateral Distance Category (m)

FIGURE 6.29. Reactions of bowhead whales to the operating Bell 212 helicopter vs. helicopter altitude (S150 m vs. >150 m) and lateral

distance (S250 m vs. >250 m), 1989-94. Includes cases when helicopter was flying, taking off, or had landed within the preceding 2 min

(Table 6.14A,B).

Bowhead Whales

I!I Reaction

D No reaction

n=5

n=1

>1501>250
6.7 Bowhead Disturbance: Reactions to Aircraft 330

immediate reaction occurred when the helicopter approached at ~150 m (39 of 46 cases). Bowheads often remained at the surface without apparent reaction. The sample size for altitudes

>150 m was small. There was no indication that reactions occurred significantly more frequently

during overflights at altitudes ~150 m (7 of 46 groups, 15.2%) than at altitudes >150 m (1 of 8

groups, 12.5%). However, the latter sample size was too small for a meaningful comparison, and

the one case of a reaction to the helicopter at a known altitude >150 m involved a pass at altitude

180 m.

This altitude analysis should be regarded with caution. Observers in the helicopter are more

likely to notice apparent reactions when the helicopter is at > 150 m ASL. Whales are in view for

a longer period of time when the helicopter flies at >150 m than when it flies below 150 m,

affording better opportunities to detect reactions during flights at > 150 m. Thus, the proportion

of groups reacting when overflown at altitudes ~150 m is probably underestimated.

Helicopter Lateral Distance: Lateral distance from helicopter to whales during 56

overflights ranged from 0 m (during direct overflights) to 1600 m (Table 6.14A,B). Lateral

distance is unknown for four observations. Based on the 52 observations at known lateral

distances, reactions did not occur significantly more often when the helicopter was operating at

~250 m lateral distance from bowheads (5 of 21 groups, 23.8%) than when >250 m away (4 of 31

groups, 12.9%; chi2=1.07, df=l, P>0.05) (Table 6.15). However, only one case classified as a

potential reaction was noticed at a lateral distance >500 m. A case at lateral distance 1600 m involved a whale that breached three times 30 s after the helicopter passed. Whether the breaches

were actually caused by the helicopter is uncertain. In general, it appears that reactions were less

frequent (if they occurred at all) at lateral distances beyond 400-500 m from the low-flying

helicopter.

Helicopter Stationary on Ice: Few observations were made when the helicopter was

stationary on the ice with engines operating (n=8; Table 6.14C). The one whale at distance

~250 m apparently reacted: a subadult bowhead exhibited a brief surfacing while the helicopter

was on the ice at a lateral distance of 230 m. Ofthe seven cases at distances >250 m (spanning

300-1000 m), no reactions were noticed.

Multiple Helicopter Passes: Most observations involved bowheads that were subject to a

single helicopter overflight, or that swam past the ice camp while the stationary helicopter's

engines were running. However, in 1989 we observed a mother/calf pair exposed to four close

(~150 m lateral distance) low-altitude (15-30 m ASL) passes by a Bell 212 helicopter plus a fifth

pass at 500 m lateral distance (Table 6.14D; Richardson et al. 1990a:211). The mother was at the

surface in a newly refrozen lead during two passes, and dove on each occasion. The calf was at

the surface during all four close passes, and dove only once. In all four close cases, the low flying

helicopter flew within 200 m of the whales and once was <50 m from the mother. These bowheads

showed no obvious signs of disturbance other than the dives, which mayor may not have been

attributable to the overflights. The mother and calf remained near the path of the helicopter for

about 25 min after the mother was overflown at close range.
6.7 Bowhead Disturbance: Reactions to Aircraft 331

Evaluation of Helicopter Overflight Hypotheses.-Overall, the limited 1989-94 observations

show that a minority of spring-migrating bowheads dive or exhibit other short-term behavioral

changes in response to a close approach bya turbine-powered helicopter. However, other

bowheads show no obvious reaction to single passes-even at altitudes of ::;150 m and lateral

distances ::;250 m.

Two of the hypotheses to be evaluated during this study concerned the effects of helicopter

overflights on bowheads (§ 1.2). Those hypotheses were as follows:

~ Helicopter overflights will not (or alternatively will) significantly alter measures of

migration routes and spatial distribution of whales in the open water of nearshore lead

systems during the spring migration near Pt. Barrow, Alaska.

~ Helicopter overflights will not (or alternatively will) significantly alter subtle aspects of

individual whale behavior in the open water of nearshore lead systems during the spring

migration near Pt. Barrow, Alaska.

The evidence available is mostly opportunistic, but is sufficient to indicate that the first null

hypothesis-concerning lack of effect on migration routes and distribution-can be accepted, with

some qualifications in wording. We conclude, on a weight of evidence basis, that single

overflights by a Bell 212 helicopter do not have biologically significant effects on the migration

routes and spatial distribution of migrating bowheads visible in open water areas amidst pack ice

or in nearshore lead systems during the spring migration near Pt. Barrow, Alaska. There have

been no studies of the effects of other types of helicopters on the migration route and distribution

in spring. However, it is worth noting that the Bell 212 used in this project is one of the noisier

types of helicopters used by the offshore oil industry.

The second hypothesis concerns helicopter effects on subtle aspects of individual behavior.

Most aspects of behavior are difficult or impossible to study during brief, opportunistic observations of the types that have contributed most available data concerning spring-migrating bowheads

and helicopters. Therefore, the available data are largely opportunistic. They show that a minority

of the bowheads overflown at low altitude exhibit short-term reactions such as abrupt dives and

shortened surfacings. Thus, from one perspective, the second null hypothesis can be rejected.

However, most if not all reactions seem brief, and obvious reactions occur during only a minority

of the low-altitude straight-line overflights. Effects of single overflights, even at an altitude

::;150 m, on the behavior of spring-migrating bowheads may not be biologically significant.

This assessment concerns potential effects of single, straight-line overflights. We obtained

very few data on reactions to repeated low-altitude passes (but see Table 6.14D), and no data on

reactions to circling or prolonged hovering at low altitude. These types of helicopter flights would

be more likely than single, straight-line overflights to cause significant disturbance effects.
6.7 Bowhead Disturbance: Reactions to Aircraft 332

Bowhead Reactions to Twin Otter

Tests of bowhead responsiveness to the Twin Otter observation aircraft were not identified

as a priority during this study. However, data on reactions to the Twin Otter are of interest with

respect to specific objective 7,

"To document, as opportunities allow, other aspects of the ... disturbance responses ... of

bowheads ... ",

and in relation to possible effects of the observation aircraft on the whales.

Methods.-During all four years of the project, observers in the Twin Otter noted all cases

when bowheads showed behaviors that appeared likely to be in response to the aircraft. Aircraft

operations during the project included ~ extensive aerial reconnaissance, usually flown at altitudes

between 150 and 460 m; ~ systematic behavioral observations from the aircraft while it circled,

almost always at 460 m ASL; and ~ photographic passes directly over bowheads, generally at

-145 m ASL. Numbers of hours of flying of each of these types during each year of the study are

shown in Table 3.2. The types of behaviors considered to be possible reactions to the aircraft were

the same as during helicopter overflights (see above).

A G test was used to compare the number of apparent responses by altitude category with

the number of bowheads seen from each altitude. Lateral distances of bowheads from the aircraft

usually were noted only when a reaction was observed. Therefore, we cannot compare the lateral

distances of whales that reacted with those of all whales seen.

To test for the possibility of an initial "startle" response when an aircraft begins to circle at

altitude 460 m ASL over bowheads, we examined their surfacing, respiration and dive cycles as

observed from the aircraft in relation to the number of minutes elapsed since the start of circling.

The data used were the same as those used in the multiple regression analyses (SMRAs) of §5.3.

We considered only the traveling whales, excluding mothers, calves, actively socializing whales,

and surfacings with aerial activity. We also excluded all cases where there were playbacks or any

other known source of potential disturbance aside from the observation aircraft. We re-ran the

SMRAs of §5.3, adding the following additional variables as potential predictors:

1. minutes after start of circling,

2. minutes after start squared

3. log(minutes after start+ 1), and

4. whether (l) or not (0) >15 min after start.

Variables (2) and (3) were considered to identify any non-linear effects. Variable (4) was included

to identify any effect evident only in the first IS min of circling. We also examined the

frequencies of various categorical measures of behavior during the periods 0-15 min, 15-30 min,

30-60 min, and >60 min after the start of circling.

Direct Observations of Reactions.-During the four spring seasons, only 11 bowhead whale

groups were observed to react overtly to the Twin Otter. Eight of the 11 groups involved whales
6.7 Bowhead Disturbance: Reactions to Aircraft 333

that reacted when overflown at low altitude (120-145 m ASL) during photo sessions, including five

groups that reacted during a single photo session on 1 May 1991 (Table 6.16). The other three

groups reacted when the aircraft was at 460 m ASL and within 300 m of directly overhead.

Reactions consisted of 2 immediate dives, 1 unusual turn, and 8 brief surfacings. Two groups were

mother-calf pairs.

The 11 bowhead groups that were seen to react to the aircraft in 1989-94 represent a very

small percentage (-2.2%) of the total number of bowhead groups sighted from the Twin Otter in

those four years (n=507; Table 6.17). The eight groups of bowheads seen to react to Twin Otter

overflights at altitudes ~182 m represent only 3.7% (8/218) of the total number of groups observed

when the aircraft was at ~182 m ASL. No groups were observed to reactto the smaller number

of Twin Otter overflights (n=66) at altitudes 183-427 m. The three groups reacting to the aircraft

at altitudes >427m represented 1.3% of the total number of groups observed from those altitudes

(3/223). The "altitudinal distribution" of the groups that reacted was not significantly different

from that of the groups overflown (G=5.54, df=2, P>0.05).

The number of groups noticed to react to the low-altitude Twin Otter overflights was

undoubtedly an underestimate of the actual number of groups reacting. As described previously

for helicopter overflights, the probability of detecting a response when it occurred was lower for

the low-altitude than for the higher-altitude overflights. The probability of detecting a response

during behavioral observations from 460 m ASL was high because, at those times, the observers

were watching the behavior of a particular focal group of whales for a prolonged period.

Therefore, the tendency for more frequent reactions during low-altitude overflights was probably,

in actuality, more pronounced than demonstrated above. If so, the difference in the proportions

of whales that did and did not react probably would, if determined more accurately, be statistically

significant, as even the observed difference was almost significant at a=0.05.

Nonetheless, even after a direct low-altitude overflight, bowheads often do not dive. For

example, during one photo session when we specifically tried to maintain a watch on bowheads

that had been overflown, we noted on three occasions groups of bowheads remaining at the surface

between two overflights at ~182 m ASL. Two groups, one of which displayed mild social activity,

remained at the surface for at least 32 s after a second direct overflight. A traveling bowhead

remained at the surface for at least 27 s after a second overflight.

Lateral distance from the Twin Otter to whales that were observed to react ranged from 0 m

during direct photo overflights to 300 m during one of the 460 m ASL cases (Table 6.16). Most

reactions occurred when the Twin Otter approached within a lateral distance of ~250 m (10 of 11

groups, 91 %; Table 6.16). Eight of 11 reactions occurred during vertical photography sessions

when whales were directly overflown at altitudes ~182 m. The other three reactions occurred

when the aircraft was at 460 m altitude and lateral distance ~300 m. There was no indication of

reactions by the much larger number of whales that were circled by an aircraft at an altitude of

460 m and a radius of 1 km.

Behavior vs. Time After Start of Circling.-Comparisons of behavioral variables at various

times after the start of systematic behavioral observations from the circling aircraft (altitude 460 m
6.7 Bowhead Disturbance: Reactions to Aircraft 334

TABLE6.16. Cases in which bowhead whales appeared to react to Twin Otter observation aircraft,

spring 1989-19948•

Lateral

Group Altitude Distance

Date Size (m) (m) Comments

14 May 89 1 460 0-50 Dove hastily as aircraft flew almost directly overhead during

behavioral observation session

26 May 89 2 145 0 Mother & calf, unusually brief surfacings during photo session

1 May 91 5 groups 130 0 Several bowheads in at least 5 separate groups showed brief

of 1 to 3 surfacings and rapidly swam away or partly away from

whales aircraft during a vertical photo session

22 May 91 2 152 0 Mother & calf exhibited hasty dives during photo session

9 May 94 1 460 300 Whale abruptly turned, almost stopped, dove with high fluke

out during behavioral observation session

14 May 94 4 120 0 Socializing whales exhibited brief surfacings after repeated

overflights during a vertical photo session

16 May 94 1 460 200 Whale traveling along ice edge exhibited a single blow

surfacing during reconnaissance survey

8 No groups of bowheads were observed overtly reacting to overflights in 1990

TABLE6.17. Approximate number of bowhead groups overflown by the Twin Otter aircraft

in 1989-1994, and number observed to react to the aircraft.

Altitude Category (m)

Year ~182a 183-427 >427b

Total

1989 12 21 36 69

1990 17 1 89 107

1991 100 26 25 151

1994 89 18 73 180

Total 218 66 223 507

Reacted 8 0 3 11

• 600 ft b 1400 ft
6.7 Bowhead Disturbance: Reactions to Aircraft 335

ASL) provided no clear evidence of an initial 'startle' response, or of any other relationship

between behavior and time after the start of circling at 460 m ASL.

Stepwise multiple regression analyses (SMRAs) to identify variables significantly associated

with duration of surfacing, number of blows per surfacing, median blow interval, and duration of

dive (Table 5.19) were repeated including, as additional potential predictors, four measures of the

"time after the start of circling" (see Methods, above). There was no significant (Pn~0.05) simple

or partial correlation between any of the four measures of "time after start of circling" and any of

the four measures of surfacing, respiration and dive cycles." Perhaps most notably, none of the

four behavioral measures was significantly different in either a univariate or a multivariate sense

during the first 15 min of the observation sessions than later in the sessions.

The only hint of an effect: on any measure of surfacing-respiration-dive cycles was that

median blow intervals tended to be shorter in the first 15 min of observation sessions than in the

periods 15-30 min or 30-60 min after the start of observations. However, median blow intervals

were even shorter 60+ min after the start of observations than they were in the first 15 min (Table

6.18), and the overall difference between the ~15 min vs. >15 min periods was not significant.

We also tabulated the categorical measures of behavior for surfacings <15, 15-30,30-60 and

60+ min after the start of aerial observations. There was nothing unusual about the swimming

speeds or the frequencies of turns, fluke-out dives, or aerial behavior during the first 15 minutes

vs. later in the observation sessions. There was, however, a tendency for more turns and larger

turns during surfacings >30 min and especially >60 min after the start of observations than during

the earlier parts of observation sessions. The increased turning later in observation sessions

probably was not indicative of any aircraft effect, but rather was related to tendencies for increased

socializing and increased ice cover later in observation sessions. Those tendencies were to be

expected given the criteria that we applied when deciding which whales to observe", and also

were not likely a result of any aircraft disturbance effect.

33 This conclusion, as applied to dive durations, is based on analysis of the durations of divesjollowing

the surfacing under consideration. When "duration of preceding dive" was analyzed, dives were found to

be significantly shorter in the first 15 min of observation sessions than later in the observation sessions.

This is an artifact of the fact that any dive whose duration was determined within the first 15 min of an

observation session had to be relatively short. The existence of this correlation does not comprise evidence

of aircraft disturbance.

34 Social interactions tended to be more frequent >30 min after initiation of observation sessions, and

ice cover tended to become higher llate in observation sessions. We tended to select whales that were not

actively socializing for observation. Hence, it is to be expected that the frequency of socializing would be

low early in the observation sessions, and might increase later in the sessions as some whales transitioned

from "travel" to "travel-ssocializing" or "socializing". Also, we tended to select whales in relatively open

water for observation. Hence, it is to be expected that ice cover would tend to increase later in the observation sessions as the whales traveled away from the relatively open locations where observations were initiated. Turns by bowheads at the surface become more common, and larger in magnitude, with increased

socializing and with increased ice cover. Therefore, the increased frequency and extent of turns late in

observation sessions were to be expected on the basis of the increased socializing and ice cover late in

observation sessions.
TABLE6.18. Surfacing, respiration and dive cycles of presumably-undisturbed traveling bowheads observed from the Twin Otter

aircraft in relation to minutes after start of aerial observations. Based on observations from altitudes >427 m ASL in spring 1989-1994;

excludes mothers, calves, and surfacings with active socializing or aerial activity.

Median blow # of Blowsl Duration of Duration of

Minutes interval (s) Surfacing Surfacing (min) Dive (min)

After Start mean s.d. n mean s.d. n mean s.d. n mean s.d. n

~15 16.95 7.19 74 5.27 3.84 60 1.31 0.95 62 7.23 5.11 45

15-30 19.47 7.13 82 4.21 2.79 82 1.15 0.91 88 5.08 4.67 52

31-60 19.76 8.26 105 4.68 2.93 99 1.30 0.95 99 6.34 5.63 73

>60 16.70 6.86 127 5.42 3.41 111 1.34 0.99 112 8.13 7.04 49

F = 4.83, df = 3,384 ** F= 2.56, df = 3,266 (*) F = 0.71, df= 3,357 ns F' = 2.65, df = 3,180 (*)

Notes: F' = F-statistic not assuming equal population variances (Brown-Forsythe test); ns when Pn>O.l; (*) when O.I~Pn>O.05; ** when O.01>Pn>O.OOl.
6.7 Bowhead Disturbance: Reactions to Aircraft 337

Evaluation of Bowhead Reactions to Twin Otter.-Observations during this project confirm

that, during spring migration, bowheads occasionally show evidence of brief disturbance when a

medium-sized turbine-powered fixed-wing aircraft flies overhead, or within a few hundred meters

to the side, at low altitude. The probability of reaction apparently diminishes with both aircraft

altitude and lateral distance. However, regardless of aircraft altitude (within the range -120 m to

460 m), only a low proportion of the bowhead groups overflown in this study showed evidence

of obvious disturbance. The proportion of those overflown at low altitude (e.g., ~182 m) that

reacted to the aircraft was undoubtedly underestimated by some unknown extent in this study.

The cases with overt reactions represent a very small fraction of the total number of

bowheads exposed to Twin Otter overflights, regardless of altitude. However, most low-level

overflights were made during photo sessions, and bowheads observed from these altitudes were

in view for short intervals. Behavioral responses occurring a few seconds after the overflight

during a photo session are likely to be missed, as efforts are then being directed at finding new

whales.

The analysis of bowhead behavior observed from the Twin Otter circling at 460 m altitude

vs. time since start of the observation session provides no evidence of startle effects or other

aircraft-related effects on the behavior of the focal animals. This result corroborates our previous

conclusion (from summer and autumn studies) that an observation aircraft circling at 460 m altitude, at a low power setting, and at a radius of -1-1 Y2 km around the bowheads normally does not

have significant effects on their behavior.

During studies on the reactions of bowheads to various industrial activities, it has been

difficult to obtain quantitative data on the effects of aircraft on bowhead behavior. This difficulty

is, to a degree, a consequence of the difficulty in obtaining matched data in the presence and

absence of the aircraft. Many of the available behavioral data on bowheads have necessarily been

obtained by observations from aircraft, precluding the collection of "control" data in the absence

of the aircraft. In addition, the limited data on aircraft disturbance are partly a result of the fact

that, during this and previous disturbance studies, studies of bowhead reactions to other types of

disturbance have been a higher priority study objective.

The data limitations prevent detailed quantitative comparisons of bowhead reactions to

observation aircraft in spring vs. other seasons. However, our general impression is that reactions

of spring-migrating bowheads to the Twin Otter aircraft used in this study were consistent in type,

frequency and circumstances of occurrence with those seen in previous summer and autumn studies

(cf. Richardson et al. 1985a,b; Richardson and Malme 1993).
7.1 White Whales: Distribution & Movements 338

7. WHITE WHALE RESULTS36

Although white whales were not the primary focus of this study, the objectives included

collecting information, as opportunities allowed, (1) on their movements, behavior and basic

biology; (2) on their reactions to playbacks of icebreaker sounds; and (3) on their reactions to

helicopter overflights and other aircraft disturbances. Those topics are covered, respectively, in

§7.1, 7.2-7.3, and 7.4.

7.1 Distribution & Movements

Specific objective 7 required us to document, as opportunities allowed, the movements,

behavior and basic biology of white whales along their spring migration corridor in the western

Beaufort Sea.

The sightings during Twin Otter flights, helicopter ferry flights, and ice-based work provided

information about the timing and routes of the spring migration of white whales through the study

area in 1989-1991 and 1994. Survey effort was not systematic or uniform in different parts of the

study area. Hence, the relative n.umbers of sightings in different parts of the study area must be

interpreted cautiously. The results for 1989 and 1990, summarized below, are presented in more

detail in Richardson et al. (1990a, 1991a).

Spring 1989

In late April and May 1989, we saw more white whales than bowheads. White whale

sightings for the entire study period in 1989 are shown in Figure 7.1; sightings during late April

and during 10-dayperiods in May are shown in Appendix G, Figures G-1 to G-4. Although there

was broad overlap in bowhead and white whale distributions, the main migration route of white

whales extended farther offshore into the pack ice than did the main route of bowheads. During

the latter part of May 1989, when a broad nearshore lead developed along the edge of the landfast

ice, the two species migrated both along the lead and amidst the pack ice just north of the lead.

White whales seen in 1989 were most often traveling or resting; there was seldom any

indication of feeding and never any active socializing. Migrating whales tended to follow leads

or cracks generally ENE, but they changed headings as necessary to remain within open-water

areas. The vector mean heading of white whale groups seen in 1989 was 77°True, but headings

from 0° to 130° were common (angular deviation 55°, Table 7.1B). Several groups of white

whales were seen resting quiescent beneath the thin ice covering recently-refrozen cracks amidst

heavy pack ice. In one case, a group of -25 white whales vigorously swam back and forth

between two holes -15 m apart, apparently trying to keep the ,holes from freezing over.

36 By W.R. Koski, G.W. Miller, N.J. Patenaude, W.J. Richardson and M.A. Smultea
7.1 White Whales: Distribution & Movements 339

157 156 155

White Whales

April - May 1989

@ Twin Otter

o Ice Camp/Helicopter

72

\

\

-,

.,..•..

.,

i

\

\

\

\.

+

+

Land/ast Ice Edge···...

·~O

111 ••

.............................

.......... +

.....

o 5 'IOn"';

o 5 10mi .........

............ -+. 71

··········10 m····· . +

o 5 10 km

157 156 155

72

7130

FIGURE 7.1. LGL sightings of white whales, 30 April to 29 May 1989. Symbol type distinguishes

sightings by the two crews and sightings of 1-14 whales (small circles) vs. 15+ whales (large

circles). Headings toward which the whales were oriented when first seen are also shown. Survey

effort was not uniform across the area mapped.
TABLE 7.1. Headings (True) of white whale groups by date, year and part of study area. Each group is counted only once.

A. By 10-Day Period B. ByYear C. By Part of Study Area

True 1-10 11-20 21-31 South South North North True

Heading April May May May TOTAL 1989 1990 1991 1994 TOTAL West Central East Central East TOTAL Heading

0 N 0 12 14 1 27 11 0 13 3 27 2 8 2 6 8 26 N 0

10 0 7 9 0 16 4 0 8 4 16 0 7 1 6 3 17 10

20 0 5 5 2 12 5 0 4 3 12 0 7 1 1 3 12 20

30 0 16 20 13 49 17 4 20 8 49 3 13 10 4 19 49 30

40 0 4 6 4 14 5 1 6 2 14 2 3 6 2 1 14 40

50 1 15 10 34 60 16 8 18 18 60 4 13 27 6 10 60 50

60 0 10 21 17 48 12 0 28 8 48 7 19 8 3 10 47 60

70 3 9 18 24 54 14 1 31 8 54 13 25 11 0 5 54 70

80 2 18 41 20 81 12 22 34 13 81 6 46 24 3 2 81 80

90 E 2 21 56 24 103 32 5 49 17 103 11 45 29 5 13 103 E 90

100 0 9 24 15 48 7 8 26 7 48 2 27 11 3 4 47 100

110 0 3 9 7 19 3 2 14 0 19 2 11 6 0 0 19 110

120 0 13 20 30 63 16 12 31 4 63 3 34 15 7 4 63 120

130 0 3 10 12 25 9 7 8 1 25 1 10 7 0 7 25 130

140 0 7 5 1 13 3 1 8 1 13 1 10 1 0 1 13 140

150 0 5 11 3 19 4 0 13 2 19 0 10 6 0 3 19 150

16ll 0 6 3 1 10 3 0 5 2 10 0 6 1 0 2 9 160

170 0 6 0 10 16 3 5 8 0 16 0 4 5 3 4 16 170

180 S 0 8 4 4 16 6 1 9 0 16 1 7 0 3 5 16 S 180

190 0 3 2 1 6 0 0 4 2 6 0 4 1 0 1 6 190

200 0 0 7 1 8 3 0 4 1 8 0 2 0 2 2 6 200

210 1 6 8 5 20 8 2 9 1 20 0 9 0 3 8 20 210 :'"

220 0 1 1 2 4 0 0 4 0 4 0 0 2 1 1 4 220

•...

230 0 3 5 1 9 5 0 3 1 9 0 3 2 3 1 9 230 ~

240 0 2 5 0 7 0 0 6 1 7 0 3 3 1 0 7 240 ~.

250 0 1 1 0 2 0 0 1 1 2 0 0 0 1 1 2 250

260 1 ~ 2 1 2 6 0 2 3 1 6 0 4 2 0 0 6 260 C:l

270 W 0 2 3 0 5 0 0 5 0 5 0 2 1 1 1 5 W 270 ~

280 1 0 1 0 2 0 0 2 0 2 0 2 0 0 0 2 280 ~

290 0 1 2 1 4 1 2 1 0 4 0 2 0 1 1 4 290 t:l

0:;'

300 0 3 1 2 6 2 1 3 0 6 0 2 2 2 0 6 300 ...,

310 0 3 2 0 5 1 0 4 0 5 0 3 1 0 1 5 310 c:;.:

320 1 4 1 1 7 5 0 2 0 7 0 3 2 0 2 7 320 ~

~.

330 0 7 3 0 10 3 0 7 0 10 0 3 0 3 4 10 330 ;:s

340 0 3 2 1 6 1 0 4 1 6 0 2 1 2 1 6 340 Ro

350 0 4 2 0 6 1 0 3 2 6 0 2 0 3 1 6 350 ~c

Total 12 222 333 239 806 212 84 398 112 806 58 351 188 75 129 801 Total <:

l\

Vector s

l\

Mean 67 72 83 87 82 77 91 86 69 82 75 90 82 48 69 82 ;:s

~

Length 0.40 0.42 0.59 0.70 0.57 0.54 0.69 0.53 0.70 0.57 0.87 0.60 0.68 0.29 0.42 0.57

Ang.Dev, 63 62 52 44 53 55 45 55 44 53 29 51 46 68 62 53 w.J:;..

0
7.1 White Whales: Distribution & Movements 341

Spring 1990

White whales were seen much less regularly in 1990 than in 1989 (Fig. 7.2; see also

Appendix G, Fig. G-5 to G-8). This was in part due to changes in survey effort within the study

area. In 1990 we found many bowheads during surveys along, and just north of, the nearshore lead

adjacent to the landfast ice. Therefore, we did not spend as much survey effort in areas farther

offshore where white whales may have been more common. When seen, white whales were

migrating steadily NE and E through the pack ice or along the north side of the main nearshore

lead. The vector mean heading was almost due east (97°T). The white whales observed in 1990

deviated from their mean heading less than did those observed in 1989; the angular deviation was

45° in 1990 vs. 55° in 1989 (Table 7.1B). In 1990, unlike 1989, we did not see white whales

whose migration was blocked by heavy ice.

Spring 1991

Although priority was given to finding bowheads, sightings of white whales were more

numerous than those of bowheads (Fig. 7.3 vs. 5.3). We recorded -1995 white whales in

comparison to -307 bowheads during Twin Otter flights in 1991 (Appendix A, Table A-2).

In 1991, there was much more survey effort between 71°30'N and 71°40'N than in areas

farther north. Hence, the sighting maps undoubtedly underestimate the numbers of white whales

in the northern parts of the study area relative to the numbers in the central portion. Also, as in

other years, there was less survey effort near the eastern and western edges of the area mapped

than in the middle of the study area.

Substantial numbers of white whales were seen throughout the 1991 field season (28 April

to 26 May; Appendix G, Fig. G-9 to G-12). They were seen much more regularly in 1991 than

in 1990. In 1991, as in past years, white whales were seen in the same areas where bowheads were

seen (Fig. 7.3 vs. 5.3). However, at least during the first two weeks of our 1991 field season,

there was a tendency for the main migration route of white whales to be somewhat farther offshore

than that of bowheads (Appendix G, Fig. G-9, G-IO vs. Fig. 5.5, 5.6).

The vector mean heading of white whales observed in 1991 was almost due east (86°), but

they frequently deviated from this heading (angular deviation=55°, Table 7.1B). They were seen

heading in all possible directions, but most commonly NE, E and SE (300-1200T).

Spring 1994

In 1994, as in 1989 and 1991, more white whales were sighted than bowheads. We recorded

-1282 white whales compared to -790 bowheads during Twin Otter flights in 1994 (Appendix A,

Table A-3). As in previous years the main migration corridor of white whales appeared to be

farther offshore than that of bowheads (Fig. 7.4 vs. 5.14); however, white whales were sighted

throughout the study area. The more northerly migration corridor was apparent throughout the

study period (27 April-25 May, Appendix G, Fig. G-13 to G-16), but was most striking during the

1-10 May period (Fig. G-14 vs. 5.10).
7.1 White Whales: Distribution & Movements 342

155 154

--'-

--.--.••..."

\

\

\

\,

,

".

White Whales ,

,

,

,

\

..-,..•..•

<.

<,

•.•.... ,•.

\

+ \ /"~'-------"'"

,' ."

April • May 1990

@ Twin Otter

<; o Ice Camp/Helicopter <,

-\ t.,------,------------'

; '-,

I "

i \

" "'

i i

\. /

72 +

,

----)

".

•..-"~

+

"\

\

\

~""

e- ""<00

/ .....--_._-... "'-.

.' .-.-.-l: •• ",

@.$- /,..../ ...,

~ ~.----.

e-~------_ ••--- t.,.e:

e.: @ ",9. .... ,

.-' + ,,' @t ..

@ -: .>

~ " + ....", ...•. --

:/

,

@, .> /

"...ff.>/· ••.••••

+

<;

~ ..............

~ .... +

o 5 10 n mi

o

=-

lOmi

...........+ 10 m ·.. 71

5

+

o 5 lOkm

72

7130

157 155

FIGURE 7.2. LGL sightings of white whales, 2-26 May 1990. Symbol type distinguishes sightings

by the two crews and sightings of 1-14 whales (small circles) vs. 15+ whales (large circles).

Headings toward which the whales were oriented when first seen are also shown. Survey effort

was not uniform across the area mapped; the most intense effort was in the nearshore lead just

north of the landfast ice.
7130

7.1 White Whales: Distribution &: Movements 343

157 156 155

, -._--..••..

, White Whales

April - May 1991

@ Twin Otter

o Ice Camp/Helicopter

'-

\

72 + , 72

- /,/--------- •.

..•.•.:

",

\

\

"

"

\

"

"

"

"

-,· <00

"'-.

,

,

,

,

,

,

,

":~

+ -----t_ ..

~ ~.'.,

:.~I .-'60

: ~'-. 11>---

'"., .. ;p- :

+ 7'130

'.. :?

0",.

-'. .

.....

~ .. +

o 5 lOnmi

o

=~

5 lOmi

+

o 5 10 km ..............tn m · 71

157 156 155

FIGURE 7.3. LGL sightings of white whales, 28 April to 26 May 1991. Symbol type distinguishes

sightings by the two crews and sightings of 1-14 whales (small circles) vs. 15+ whales (large

circles). Headings toward which the whales were oriented when first seen are also shown. Survey

effort was not uniform across the area mapped; the most intense effort was in the nearshore lead

just north of the landfast ice.
7.1 White Whales: Distribution & Movements 344

157 156 155

White Whales

April • May 1994

@ Twin Otter

o Ice Camp/Helicopter

72 +

\.

,

"

<,..••

i

\

\

\

\ e

~ \,.

.•.......••..•.•.

'<00 "',.

+

: e:: +

'.,.. La~!Uast..tee Edge·····

'''after lS''MBY

...._-

.........

~ ... ~ .....

....

......

+

...................

..........

. .

o 5 10nlli

o 10lIi

······..··· +. 10 m ·..71

5

+

o 5 10 km

157 156

FIGURE 7.4. LGL sightings of white whales, 27 April to 25 May 1994. Symbol type distinguishes

sightings by the two crews and sightings of 1-14 whales (small circles) vs. 15+ whales (large

circles). Headings toward which the whales were oriented when first seen are also shown. Survey

effort was not uniform across the area mapped; the most intense effort was in the nearshore lead

just north of the landfast ice.

72

7130

'<0 ",.
7.1 White Whales: Distribution & Movements 345

The more offshore corridor was apparent from the headings of white whales sighted during

1994. The vector mean heading (69°) was the most northerly recorded during the four years of

this study, and the headings were more closely grouped around the mean direction than during

other years (angular deviation 44° vs. 45°-55° in other years, Table 7.1B).

All Years

The distribution of all white whale sightings recorded during the four years of this study is

shown in Figure 7.5. In comparison to the bowhead sightings (cf Fig. 5.14), white whale sightings

were more dispersed and had a more northerly distribution. This tendency for white whales to

migrate north of the bowhead's typical migration corridor in the spring has also been noted during

studies in previous years (Braham et al. 1984; Ljungblad et al. 1984).

The overall vector mean heading of white whales observed in the study area (82°, Table 7.1)

was similar to that of bowheads (83°, Table 5.1). However, white whale headings were less

consistently in the mean direction (angular deviation 53°, vs. 37° for bowheads). The headings

of white whales seemed to vary depending on their geographic location within the study area.

White whales in the southern part of the study area (southeast and south-central areas) tended to

head eastward (vector mean headings 82°T and 900T, Table 7.1C). On average, those in the

western part of the study area headed ENE (75°), and those in the northern areas headed NE to

ENE (48° and 69°). White whale headings tended to be toward the ENE early in the field season

(67° and 72° during late April and early May) and toward the east in mid-to-late May (83° and

87°, Table 7.1). This may have been, at least in part, an artifact of our tendency to spend more

time surveying along and near the nearshore lead, which was oriented more-or-Iess west-seast, as

it became more open in mid-to-late May. White whales traveling farther offshore may have

continued to travel ENE, but we conducted fewer surveys there late in the season.

7.2 Icebreaker Playbacks

Specific objective 4 called for, as possible, measurements of the short-term behavioral

responses of white whales visible in open water to underwater playbacks of variable icebreaker

sounds. During 1991 and 1994, this was done opportunistically when white whales were present

at sites where icebreaker playbacks to bowheads were being conducted. Reactions of white whales

to playbacks of steady drilling sounds from the Karluk drillsite were tested in 1989-90, and

described in Richardson et al. (1990a, 1991a).

In 1991, white whales were seen near the operating sound projectors on two dates: 11 and

17 May (Table 3.5). On both of these days, white whales were also seen near the projector site

under quiet "control" conditions before and after the playback period. There were four additional

dates in 1991 when icebreaker sounds were projected into the water for prolonged periods. On one

ofthese days (5 May), white whales were seen during the pre-playback quiet period, but not during

or after the playback. On the other three days, no white whales were seen during either the

playback or the control periods. All systematic observations of white whales near the ice camp

were obtained by the ice-based observers. The prevailing low cloud rarely allowed systematic

aerial observations during 1991.
7.2 White Whales: Icebreaker Playbacks 346

,

+ '

,

A

/,.------.',.'\ +

"',,/ .-,

,•......... _---,\

,

1989. 90, 91, 94

@ Twin Otter

o Ice Camp/Helicopter

72

157 156 155

)\\ -.-.- .

11 30

White Whales

72

"\ 1...- ....-- _

i \.'\.

~' -,

"

..•.

'.,

\

i

\

\

\ @

@~'e~\,.,

e- ....,

<00

ft),.

+

••.J + 7130

...•.•.. _----, "-.:. .....

" -.

~ ... +

0 5 lOnmi

0 5 10 mi

4- 0 5 10 km

A

157 156 155 154

" -tn m 11

FIGURE 7.5. LGL sightings of white whales in all years, 1989-91 and 1994. Symbol type distinguishes sightings by the two crews and sightings of 1-14 whales (small circles) vs. 15+ whales

(large circles). Headings toward which the whales were oriented when first seen are also shown.

Survey effort was not uniform across the area mapped; the most intense effort was in the nearshore

lead just north of the landfast ice.
7.2 White Whales: Icebreaker Playbacks 347

In 1994, white whales were seen near the operating projector on one day: 3 May. They were

seen near the projector while icebreaker sounds were being projected into the water but were not

seen during control periods. White whales were also seen near the ice camp on two days without

prolonged icebreaker sound playbacks: 22 and 25 May. On 22 May, white whales were seen both

before and during the projection of tones during a transmission loss (TL) test. On 25 May, white

whales were seen before tones were projected during a TL test.

17 May 1991

On 17 May 1991, the ice camp was situated NE ofPt. Barrow on the landfast ice edge, which

formed the south side of the broad nearshore lead. The lead was oriented from west to east (True)

at this location. The measured water depth was 110 m. The ice-based crew was at this site from

10:46 to 20:59, and icebreaker sounds were transmitted continuously from 12:42 to 18:01. Low

cloud and fog patches prevented systematic aerial observations of whale behavior.

Ice-based Observations.-A total of about 165 white whales in 39 groups were observed by

the ice-based crew on this day. Most groups (32) were seen prior to or >30 min after the playback

period. Of these, 23 groups were seen under quiet pre- or post-playback control conditions;

9 groups were seen while the helicopter was operating close enough to be a potential source of

disturbance. Five groups were tracked during the playback, and two more groups within 30 min

after the playback ended; there was no helicopter activity at these times (Table 7.2).

Most groups of white whales were migrating eastward along the lead (Fig. 7.6). There were

only three exceptions: two groups that oriented west, at least for brief periods, when the

helicopter was operating nearby (Fig. 7.7), and one group traveling NNW 21 min after the

playback ended (Fig. 7.8).

During the pre-playback control period, 14 groups of white whales-a total of 52

individuals-were seen when there was no helicopter disturbance (Table 7.2A). All of these

whales were traveling more or less eastward along the lead within 200 m of the landfast ice. Over

half of the groups sighted (9 of 14) were within 50 m of the landfast ice. Twelve of the 14 groups

were oriented to the east, one to the ENE, and one to the NE (Fig. 7.6A,B).

An additional 8 groups were seen during the pre-playback period while the Bell 212 helicopter was operating nearby (Table 7.2B; Fig. 7.7). These observations are taken into account in

§7.4 on helicopter disturbance.

During the playback-period, 5 groups of white whales-a total of 8 individuals-were seen.

An additional 2 single whales were seen within 30 min after the end of the playback (Table

7.2C,D; Fig; 7.8).

The first group was seen just before and during the start of the playback. Two white whales

were first sighted at 12:38:30, 2 min before the start of the playback, traveling ENE well out in

the lead (693 m NNW of the projectors). The playback began at low level while these whales were

below the surface. The sound level increased gradually until 12:43:43. Two white whales,
7.2 White Whales: Icebreaker Playbacks 348

TABLE 7.2. Summary of sightings of white whales seen passing the sound projector located on the

landfast ice edge NE of Pt. Barrow on 17 May 1991. All observations were by the ice-based observers:

CEPA

No. Observed

of Distances Distance Heading

Time WW (m)" (m) Method" (True) Notes

A. Pre-Playback Control (no helicopter)

11:00 1 -130b

-130 2 E

11:02 2 _50b

-50 2 E

11:19/22 6 -200 to +130 90-175 1 E Loose group

11:22 1 25-32 25 1 E

11:23/26 8 -46 to +355 30 1 E

11:26 2 +60 to +160 25 3 E

11:30/33 2 -55 to +130 50 1 ENE

11:31 2 22 <22 3 E

11:34/35 5 +10 'to +110 10 3 E

11:44/46 2 +135 to +215 130 3 E

11:48/53 8 -300 to +110 37 1 E

11:57/59 6 -240 to -150 150 1 E

12:07/08 2 -160 to -200 160 1 NE

12:34/35 5 -315 to -235 235 4 E

B. Pre-Playback, Helicopter Operating

10:46 2 -100b

-100 2 E Heli, landing -150 m away

10:50 1 -30b

-15 2 E Heli. on ice -65 m away

11:09 18 _80b

-80 2 E " " " -130 m away

11:11 2 -50b

-50 2 E " taking off -100 m away

11:12 20 _50b

-50 2 E < 1 min after takeoff

12:08/13 5 -30 to +170 30 1 E~NE~E Veered NE as heli. landed

12:08/18 10 -135 to +120 32 1 E~W~E Temp. reversal as heli, landed

12:14/15 1 +70 to +32 30 3 W <1 min after heli. landed

C. Icebreaker Playback

12:38/44 2 -693 to +957 -750 3 E Near CPA when plbk started

14:17/19 1 -205 to +100 95 1 E Approached and passed; dove

at CPA

Continued ...
a Observed Distances: "_" indicates that whales were approaching, generally from the SW or W;

"+" indicates that whales were moving away, generally to the NE, N or E.

CEPA Method (CEPA=Closest Estimated Point of Approach): 1 = measured by theodolite at CPA

(Closest Point of Approach); 2 = visual estimate at CPA; 3 = estimate based on theodolite

measurement(s) to nearby surfacing(s); 4 = estimate based on whale position(s) and heading(s)

during sighting(s) distant from CPA (possibly unreliable).

b Distance and position estimates before 11: 15 are visual estimates made shortly after arrival on the

ice, before the theodolite was set up.
A.

"'00.-

same

loose '-.. ~

group ~ ~ "'22

11·21

,

N

LEGEND

•• whale sighting and heading

[=:J old ice

[;] open water

FIGURE 7.6. Ice-based observations of white whales that passed the ice camp along the landfast ice NE of Pt. Barrow, 17 May 1991.

(A) Initial pre-playback control observations, 10:46-11 :28. (B) Continued pre-playback control observations, 11:28-12:42. Dashed lines

represent presumed paths of whales while they were below the surface.

~~-~~-~--------

w

VI

o
B.

"'57

\

N

LEGEND

•• whale sighting and heading

CJ old Ice

[;] open water

~ __ --l ~lqometers

l-- __ ...L-__ ...:I~qo, yards

9

9

FIGURE 7.6 (continued).
,

N

LEGEND

Whole sightings

• No disturbance

o Helicopter disturbance

• Less than 5min.

post- helicopter

[==:J old ice

[;] open wafer

FIGURE 7.7. Ice-based observations of white whales that passed the ice camp along the landfast ice NE of Pt. Barrow, 17 May 1991,

during the pre-playback period while the helicopter was operating nearby. Dashed lines represent presumed paths of whales while they

were below the surface.
LEGEND

•• whole sighting and heading

o old Ice

Q open water

14'22

,

N

le'lI~

monitor IOnobuoy

~ 730m from projector

FIGURE 7.8. Ice-based observations of white whales that passed the ice camp along the landfast ice NE of Pt. Barrow, 17 May 1991,

during icebreaker playback from 12:42 to 18:01 and 30 min thereafter. Dashed lines represent presumed paths of whales while they

were below the surface.
7.2 White Whales: Icebreaker Playbacks 354

believed to be the same group, surfaced at 12:43:09 at a location 957 m to the NE of the operating

projectors, with one whale apparently oriented N and the other ENE. These whales had apparently

passed their CPA position before the playback began, and were last seen at about the time the

projected sound reached its peak level.

At 14:17-14:22, four groups totaling seven white whales were observed while the projectors

were operating at peak power. All groups were headed consistently eastward throughout these

observations:

~ The longest track involved a lone subadult for which six positions were determined

between 14:18 and 14:22 (Fig. 7.8). When first seen, this approaching whale was about

35 m from the ice edge and 235 m west of the projectors. It moved slightly farther away

from the ice edge as it approached, and was 80 m from the ice edge and at the surface as

it passed the operating projectors and continued to the east.

~ Another eastbound white whale was seen 95 m from the projectors at 14:19; it dove out

of sight while at that CPA position.

~ Two other groups (a singleton and a group of three) surfaced briefly 210 m and 185 m

from the projectors as they approached. They were not seen again; if they did not change

course subsequently, they would have come within -120 m and -30 m of the projectors.

The number of white whales seen from the projector site was considerably lower during the

playback period than during the pre- and post-playback periods. This was true both on an absolute

basis and (especially) on a "per hour" basis:

Start End Duration

Pre-playback 10:46 12:42 1.93 h

Playback 12:42 18:01 5.32

Post-playback* 18:31 20:59 2.47

* 30-min post-playback period excluded

Groups

No. /Hr

22 11

5 1

10 4

Individuals

No. /Hr

111 58

8 Ph

44+ 18+

(2 whales in 2 groups).

Furthermore, it should be noted that at least one of the two ice-based biologists was observing at

all times during the playback period, with no other duties, whereas during parts of the pre- and

post-playback periods one or both biologists were involved in equipment setup or breakdown.

Thus, fewer white whales were seen during the playback even though there was less likelihood of

missing passing whales then than during the control periods.

Two single white whales were seen 10 and 21 min after the icebreaker playback ended. One

eastbound whale was approaching the ice camp, traveling within 30 m of the ice edge. The second

was heading in an unusual NNW direction well offshore in the lead (Fig. 7.8).

During the post-playback control period (>30 min post playback), 10 groups of white whales

totaling at least 44 individuals were observed. All groups were traveling east, ENE or NE along

the lead (Table 7.2E, Fig. 7.9). Their estimated CPA distances (assuming travel on straight lines

during dives) were -100 to 600 m from the ice camp. One of these groups was exposed to helicopter operations for a small part of the period while it was under observation.

r-- -
LEGEND

oold Ice

[;] open water

I

I

I

I

I

I

I

I

I

I

I

I

I

I

I

I

I

I

I

I

I

I

"..J

Whale slvhllnv and headlnv

•• No disturbance

0+ Helicopter disturbance

~'09

,

N

FIGURE 7.9. Ice-based observations of white whales that passed the ice camp along the landfast ice NE of Pt. Barrow, 17 May 1991,

more than 30 min after icebreaker playback ended. Dashed lines represent presumed paths of whales while they were below the surface.
7.2 White Whales: Icebreaker Playbacks 356

17 May 1991,14:20

170

70

A.

I 1 !

I

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I

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. ..... , l ..I' '..... r;:/j;t.c8i. .... ......i

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-+-

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181

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CD

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- 130 CD

~

-g 110

ra

co

'ti

o 90

I

~

~

5% & 95%SL

5%& 95% RL

50

10 100 1000

1/3-0ct. Center Frequency

10000

FIGURE7.10A. Third-octave levels of projected icebreaker noise vs. distance from projectors and

ambient noise, 17 May 1991, time 14:06-14:20: variability over 14 min at ranges 1 m and 1.0 km

(median, 5th and 95th percentiles). Plus signs show average ambient noise level after playback.

IXI symbols are white whale hearing thresholds vs. frequency.

Explanatory notes: (1) Source levels are in dB re 1 JlPa-m and ambient and received levels

are in dB re 1 JlPa. (2) Because of projector limitations, components of the icebreaker sounds at

low frequencies are underrepresented in the projector output relative to components at higher frequencies. (3) The tape of icebreaker sounds is repeated every 14 min. As illustrated by the 5th

and 95th percentiles, the actual source or received level at any particular time can be substantially

different than the median level, depending on the precise location along the 14-min loop that is

being projected or received. (4) Source and ambient levels were measured; received levels at 1.0

km were estimated via an empirically-validated propagation model, as described in section 2.3.

(5) Received levels within a few meters of the surface will be lower than estimated here.

Noise Exposure.-Icebreaker sounds were projected into the lead by the J-13/F40 projector

system from 12:42 to 18:01. The 5th, median, and 95th percentile broadband (20-5000 Hz) source

levels over the full 14-min cycle of the icebreaker sounds were 156, 161, and 167 dB re 1JlPa-m.

respectively, from 12:42 to 16:49. After that time the source level was reduced by -12 dB until

the end of the session. Figure 7.10A indicates the variability in icebreaker sounds as projected

(l-m source levels) and as received at 1 km range. Figure 7.10B shows the estimated median

received levels at several standard distances at the same time. The received levels in this Figure,

and the received levels in all similar figures, are estimated by the sound exposure model described
7.2 White Whales: Icebreaker Playbacks 357

17 May 1991, 14:20

170

70

B.

~ Ir-----.

.J~

-....

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"""

C8I V..- ------

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,.•,.•.•.. ~. C81.~ C8I ••••

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..'•••....... 300m ...•....

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Ree. Level

-+-

Amb.

C8I

WWTh'hold

--- SL·1 m

150

-OJ

"0

- 130

~

-g 110

CO

CO

ti

o 90 I

S2.•...

50

10 100 1000

1/3-0ct. Center Frequency

10000

FIGURE7.10B. Third-octave levels of projected icebreaker noise vs. distance from projectors and

ambient noise, 17 May 1991, time 14:06-14:20: median levels at range 1 m (squares) and 30 m3.0 km. Plus signs show average ambient noise level after playback. IXI symbols are white whale

hearing thresholds vs. frequency.

Explanatory notes: See notes to Fig. 7.lOA. Figure 7.10B shows median received levels

at more ranges, but does not show 5th and 95th percentiles. Estimated received levels at 0.03 and

0.1 km assume spherical spreading; model of §2.3 was used to derive estimates for 0.3 to 3 km.

in §2.3. There will be small differences between the received levels estimated by the model and

those actually received at the specific distance and time. Also, estimated received levels pertain

to animals below the surface by at least several meters; while at the surface and under visual

observation, whales are exposed to lower levels than predicted by the model, because of the

pressure release (Lloyd's mirror) effect.

Ambient noise was measured near the projectors after icebreaker playbacks stopped. The

broadband ambient noise level was 93 dB re 1 J.lPa. The level in the dominant 1/3-octave band,

which was centered at 125 Hz, was 83 dB re 1 J.lPa.

During the period 14:17-14:22,4 groups of white whales migrated eastward within 80-210 m

of the operating projectors (Table 7.2). The maximum underwater sound levels during the 64-s

period previous to each observation time were estimated for the CPA distances using the sound

exposure model. The broadband (20-5000 Hz) source levels (SLBB,maxdB re 1 J.lPa-m), and the
7.2 White Whales: Icebreaker Playbacks 358

17 May 1991,14:21

170

A. •

....-r

20- 000 SL-1 m

,

-a- BB lJlvel

150 RL- 80 m

-

-+--

co Ambient '"0'-"

130 IZI

~

0 WWTh'hold

.s

'"0

c 110

m

CO

+

ti

0 90

I

C") -T""

70

IZI IIZI

50

10 100 1000 10000

1/3-0ct. Center Frequency

FIGURE 7.11. Third-octave levels of projected icebreaker noise 1 m from the projectors (closed

squares) and near white whales (A) 80 m and (B) 95 m from the projector (median levels over 64

s), 17 May 1991, times 14:21 and 14:19. Plus signs show average ambient noise level after

playback. IX! symbols are white whale hearing thresholds vs. frequency.

Explanatory notes: (1) Source levels are in dB re 1 JlPa-m and ambient and received levels

are in dB re 1 JlPa. (2) Because of projector limitations, components of the icebreaker sounds at

low frequencies are underrepresented in the projector output relative to components at higher frequencies. (3) The tape of icebreaker sounds is repeated every 14 min. The 64 s values are

estimated by determining the location on the loop that was projected at the selected time and

summarizing the data for the preceding 64 s. (4) Source and ambient levels were measured;

received levels at 80 and 95 m were estimated via the empirically-validated propagation model of .

§4.3, incorporating spherical spreading (plus Lloyd's mirror factor) at close ranges. (5) Received

levels within a few meters of the surface will be lower than estimated here.

broadband and 113-octave received levels (RLBB,maxand RLII3,maxodB re 1 JlPa) for the four whale

groups were as follows:

CPA @ 14:19:11, SL = 164, RL @ 95 m = 124, RL near 5 kHz = 96

Approach @ 14:17:00, SL = 167, RL @ <210 m = >120, RL near 5 kHz = >90

Approach @ 14:18:17, SL = 166, RL @ <185 m >119, RL near 5 kHz = >88

CPA @ 14:21:00, SL 167, RL @ 80 m <129, RL near 5 kHz = <93

The above Table also shows the RL in the 1I3-octave band centered at 5000 Hz rather than in the

1I3-octave of strongest source level because white whale hearing is poor in the low frequencies
7.2 White Whales: Icebreaker Playbacks 359

17 May 1991, 14: 19

170

B. --- •

SL-1 m

20- 000 ~

150 BB vel RL- 95 m

-

-tIII

"0 Ambient

- 130 181

CD

>

I/tNI Th'hold

~

181 0

"0

c: 110

CO

III

13 +

0 90 I

M

-y70

181 181

50

10 100 1000 10000

1/3-0ct. Center Frequency

FIGURE7.11 (continued).

where the dominant icebreaker sound was projected. Based on white whale hearing capabilities,

background ambient noise, and the estimated received levels of icebreaker sounds at the distances

where whales were likely to be seen by ice-based observer (Fig 7.10B), white whales were most

likely to hear the higher components of the icebreaker sounds shown in Fig. 7.10, if they could

detect them at all.

Ambient noise levels at the specific times when white whales were observed could not be

determined because of masking by the projected icebreaker sounds. However, the broadband level

(20-5000 Hz) after the playback was 93 dB re 1 IlPa and the 1I3-octave level was 80 dB near 5000

Hz. If that level also occurred at the CPA times during the playback, S:NBB,max values were 26-

36 dB, and S:N1I3,max values near 5000 Hz were 8-16 dB.

Figure 7.11A shows the median broadband source and received levels during the 64-s period

previous to 14:21 when the white whale was 80 m from the operating projectors. The broadband

received levels near this whale were stronger than those near the other whales, but above -800 Hz

the median received levels were near the ambient noise level. However, maximum levels near

5000 Hz probably did exceed the ambient level. This whale was at the surface, and because of

pressure release effects near the surface, the actual received levels at the whale would-especially

at low frequencies-have been a few decibels lower than those shown above. The other three
7.2 White Whales: Icebreaker Playbacks 360

groups listed here either dove or were below the surface as they passed the projectors (Fig. 7.8).

Thus, those three groups of whales were exposed to the estimated noise levels. Figure 7.11B

shows the estimated received levels near the whale estimated to be underwater 95 m from the

projectors at 14:19. Although the estimated broadband levels were weaker than for the whale

shown in Figure 7.11A, the levels near 5000 Hz were stronger-several dB above ambient levels.

The white whale hearing system has relatively low sensitivity at the low frequencies where

the icebreaker sounds were concentrated. White whale hearing thresholds by 113-octave band are

shown on Figure 7.10 and 7.11, based on White et al. (1978), Awbrey et al. (1988), and Johnson

et al. (1989). It appears that, on 17 May 1991, white whales could only hear icebreaker sounds

if they were within -300 m during sections of the 14-min tape loop when source levels were near

median levels in the 113-octave bands centered at 4000-5000 Hz. At greater distances, median

received levels of icebreaker sounds were below the hearing threshold, below the ambient noise

level, or both, in alll/3-octave bands up to at least 6300 Hz (Fig. 7.10B). Maximum levels, being

several decibels higher than medians (Fig. 7.10A), would have been detectable out to at least 1 km.

Despite the limited radius of audibility of these playbacks to white whales, fewer whales

were observed to approach the projectors during the icebreaker playback than during adjacent

control periods. Whether this was a meaningful or a coincidental relationship cannot be

determined from a single day's observations.

11 May 1991

The ice camp was at the north end of a giant ice pan, adjacent to an irregularly-shaped lead

amidst pack ice (Fig. 7.12). The measured water depth was 195 m. Icebreaker sounds were

projected for 1 h, from 16:39 to 17:37. Unfortunately, the projector system then had to be

removed from the water to protect it from drifting ice. Observers aboard the Twin Otter aircraft

conducted an aerial reconnaissance in the area, but the cloud ceiling was too low (150-300 m) to

allow systematic aerial observations of whale behavior.

Ice-based Observations.-A total of 11 groups of white whales consisting of 38 individuals

were seen from the ice camp. Five groups were tracked during the 2.0-h pre-playback control

period, one group during the playback, and five. groups during the 2.9-h period of post-playback

observations. The helicopter was at the ice camp with its engines running while four of the groups

of white whales passed, including the one group seen during the playback period.

Figure 7.12A shows the paths of the five white whale groups observed during "control"

conditions, i.e., while the projectors were silent and there was no helicopter disturbance. All five

groups were seen before the playback, and all were traveling to the ENE in the southern part of

the lead close to the ice camp:

~ Two groups were seen at CPA distances 40 and 70 from the ice camp.

~ Three groups surfaced after they had passed the ice camp and were 200-515 m away. If

they were traveling on straight lines while underwater, they all passed the ice camp at

CPA distances ::;200 m.
7.2 White Whales: Icebreaker Playbacks 361

Figure 7.12B shows the paths of four groups of white whales seen during the playback and

post-playback periods while the helicopter's engines were operating at the ice camp, plus two more

groups that surfaced within 2 min after the engines stopped. (When the helicopter was standing

by on the ice for prolonged periods, it was considered necessary to run the engines periodically

to keep them warm.) Of the five groups seen during the post-playback period with possible

helicopter disturbance, four showed no apparent reaction to the helicopter; one group that was

heading NNE may have diverted in response to the helicopter.

The one group of white whales seen during the icebreaker noise playback was first sighted

at 16:44. This was 5 min after the playback had begun and 3 min after the projected sounds had

reached near-peak level. When first seen, the six white whales were 515 m NW of the projectors

and were headed NE (Fig. 7.1213). As the whales surfaced for the second time <1 min later, the

helicopter's engines were started. While the engines were operating, the position of the group was

measured four more times. The group traveled NNE across the lead toward the opposite edge.

They apparently turned about 30° to their left, away from the projectors and helicopter (Fig.

7.12B). The whales were last observed at 16:47, 900 m NNW of the projectors and helicopter.

Noise Exposure.-Icebreaker sounds were projected into the water using the J-13/F-40

system from 16:39 to 17:37 when encroaching ice forced the crew to retrieve the equipment from

the water. The source level of the projected icebreaker sounds was gradually ramped up from

16:41 to 16:46, but was adjusted both upward and downward from 16:46 to 16:48. The estimated

received levels at the whales' location-as they moved away from the camp-ranged from 100 to

111 dB re 1 IlPa broadband and 46 to 94 dB re 1 IlPa near 5000 Hz from 16:45 to 16:48. Before

the helicopter disturbance, RLBB,max was 110 db re 1 IlPa and the maximum 113-octave level near

5000 Hz was 73 dB re 1 IlPa or 5 dB below the average ambient level. It appears that icebreaker

sounds would not have been detectable by the white whales because of their poor hearing sensitivity at low frequencies and the negative S:N at high frequencies. However, given the

uncertainties associated with the estimates of received levels and hearing thresholds, it is possible

that the white whales were able to hear some components of the icebreaker sounds.

Therefore, the significance of the observations of the one group of white whales seen during

the 11 May playback cannot be interpreted for certain. They may have been unable to hear

icebreaker sounds. If so, the turn away from the camp was probably related to noise generated by

the helicopter idling on the ice.

3 May 1994

The ice camp was set up amidst the pack ice on the eastern edge of a narrow lead oriented

N-S. During the day, the width of the lead W of the camp narrowed from -500 to 300 m. The

lead was -400 m wide when the white whales were sighted. The crew was at the site from 09:50

to 22:02. Tones were projected into the lead from 12:33 to 13:09 and icebreaker sounds were

projected, using only the J-ll projector, from 15:12 to 19:20. The measured water depth was

105 m.
7.2 White Whales: Icebreaker Playbacks 362

~. LEGEND

l monitor sonobuoy

•• whale sighting and heading

c=J old ice

[:;:] open water

,

N

0 2!?O 500 meters

0 250 500 yards

FIGURE 7.12. Ice-based observations of white whales that passed the ice camp amidst pack ice NE

of Pt. Barrow, 11 May 1991. Icebreaker sounds were projected from 16:39 to 17:37. (A) Preplayback control observations, no helicopter disturbance. (B) Observations during and after

playback, with possible helicopter disturbance in each case.
7.1 White Whales: Icebreaker Playbacks 363

B. LEGEND

16147~

I

\

\

\

\

\

\

I

I

}

16·44

: Monitor sonobuoy

Whole sightings

o Icebreaker playback

o Helicopter disturbance

• Less than 5 min.

post- helicopter

c=J old lee

GJ open water

'9"2~

19:08

\

N

0 250 500 meters

0 250 500 yards

FIGURE 7.12 (continued). White whales, 11 May 1991, playback and post-playback, with possible

helicopter disturbance.
7.2 White Whales: Icebreaker Playbacks 364

Ice-based Observations.-About 32 white whales (-13 groups or singletons) were estimated

to have moved by the ice camp during 12.1 h of observation; all white whale sightings were made

from 15:40 to 16:31, during the icebreaker playback (Fig. 7.13). The 32 white whales included

25 adults and 7subadults. The number of different whales that passed the projector is approximate

because of uncertainties in discriminating "new" and "repeat" sightings, and because of the

likelihood that some passing whales were missed.

All white whales observed passed while icebreaker sounds were being projected into the lead.

Most groups were initially sighted generally NW or SW of the projector and headed either radially

to or away from the projector.

Five of 7 groups sighted to the NW had orientations or headings that would be expected; that

is, they generally followed the lead toward the NE (Fig. 7.13). Of the exceptional groups, one

group of two whales surfaced 185 m north of the projector and swam directly toward it from 16:31

to 16:33; this group's CPA was 20 m. The whales were at the surface as they approached from

185 to 20 m; they dove as they passed the projector at their CPA. The other group was initially

observed traveling to the NE some 345 m NW of the projector. It turned north until it reached the

NW side of the lead, and then returned to a NE heading. The CEPA of this group was -330 m

from the projector. The turn to the north and crossing of the lead to the west side could have been

in response to the icebreaker sounds, but did not represent much of a departure from the general

Nand NE travel of most other white whale groups. On balance, white whales sighted to the NW

of the projector showed no obvious avoidance.

In contrast to the above, 5 of 6 groups sighted SW of the projector were headed generally

south (135°-210°) and away from the projector. In particular, an adult/subadult pair seen 180 m

SW of the projector was heading SW away from it. The sixth group was oriented ESE as it dove

under the ice 390 m south of the projector. Based on the orientation of the lead and the headings

and tracks of the whales seen NW of the projector, the whales south and SW of the projector

would have been expected to travel north to NE past the projector. Thus there is circumstantial

evidence to suggest that the whales seen S to SW of the projector altered their paths to avoid a

closer approach to it. Their tracks indicate that they may have been closer to the projector before

they were sighted. However, the lack of any white whale sightings near the ice camp during the

pre- and post-playback control periods on 3 May 1994 makes it impossible to compare these

observations with control data from the same site and date.

Aerial Observations.-About 40 white whales were seen 7 km south of the ice camp in heavy

pack ice from 11:22 to 13:46. White whales were observed opportunistically as aerial observers

in the Twin Otter crew circled a bowhead engaged in aerial activity. A steady stream of white

whales traveled NNE past the bowhead in groups of one to 14 individuals. One white whale

moved -400 m NNW of the bowhead, hesitated, then turned toward the bowhead when it breached

at 12:01. Another white whale traveling NNE approached within 100 m SSW of the bowhead at

slow speed at 12:04.

Noise Exposure.-Icebreaker sounds were projected into the water using the J-ll projector

from 15:12 to 19:20. The 5th, median and 95th percentile broadband source levels over the
7.2 White Whales: Icebreaker Playbacks 365

. ..- .. (J .

:'1r

,

, .'

, ... 500 Yluds '

, _500 Meters ..

LEGEND

• Projector

• Theodolite oOpen Water

DOld Ice

• Ice Camp Obs., During Ice-breaker Playback

-' - Interpolated Surface Travel

- - - Presumed Underwater Path

FIGURE 7.13. Ice-based observations of white whales that passed the ice camp amidst pack ice NE

of Pt. Barrow while icebreaker sounds were being projected from 15:12 to 19:20,3 May 1994.
7.2 White Whales: Icebreaker Playbacks 366

14-min cycle of the icebreaker sounds were 144, 150 and 156 dB re 1 IlPa-m. The 113-octave band

with the strongest source level was the one centered at 200 Hz, with a median source level of 143

dB re 1 IlPa-m. Near 5000 Hz, where the white whale threshold is much lower ("better"), the 1/3-

octave source levels were 121 Hz. Figure 7.14A shows the variability in the sounds as projected

(l-m source levels) and as received at 1 km range at 16:02. Figure 7.14B shows the estimated

median received levels at several standard distances at the same time. Given the prevailing

ambient noise levels on 3 May 1994 plus the reported hearing thresholds of white whales, they

would not be expected to have heard the median-level projected sounds at distances beyond about

300 m (Fig. 7.14B). It would be the sounds near 5000 Hz that would be detectable farthest away.

Maximum levels of transmitted sound were several decibels higher than median levels (Fig.

7.14A), so maximum levels would be detectable somewhat farther away.

During the playback of icebreaker sounds, 13 groups of white whales were seen within 385 m

of the operating projectors (Table 7.3). The maximum underwater sound levels during the 64-s

periods previous to these times were estimated for the CEPA distances using the sound exposure

model. The maximum broadband (20-5000 Hz) source levels (dB re 1 IlPa-m) and the RLBB.max and

RLlI3,max levels (dB re 1 IlPa) for the 13 whale groups were as follows:

CEPA @ 15:42:06, SL 153, RL @ 385 m 102, RL near 5 kHz 76

CEPA @ 15:44:57, * SL 154, RL @ 210 m = 108, RL near 5 kHz 78

past CEPA @ 15:54:00, * SL 155, RL @ <240 m > 108, RL near 5 kHz > 80

CEPA @ 15:58:25, SL 154, RL @ 390 m = 103, RL near 5 kHz 74

past CEPA @ 15:59:49, * SL 156, RL @ <360 m > 105, RL near 5 kHz > 83

past CEPA @ 16:02:00,* SL 156, RL @ <180 m > 111, RL near 5 kHz > 79

CEPA @ 16:08:00, * SL 156, RL @ 260 m = 107, RL near 5 kHz 84

CEPA @ 16:16:55, SL 156, RL @ 410 m > 104, RL near 5 kHz > 67

CEPA @ 16:18:00, SL 152, RL @ 125 m = 109, RL near 5 kHz 83

CEPA @ 16:20:12, SL 150, RL @ 295 m = 101, RL near 5 kHz 77

CEPA @ 16:21:00, SL = 154, RL @ 230 m = 106, RL near 5 kHz 84

past CEPA @ 16:24:20,* SL 154, RL @ <330 m = 103, RL near 5 kHz 81

CEPA @ 16:33:00, SL 156, RL @ 20 m< 130, RL near 5 kHz < 115

For comparison, the average ambient levels were 93 dB for the 20-5000 Hz band, and 70 dB for

the 113-octave band centered at 5000 Hz. The latter value coincides with the hearing threshold

of white whales at 5000 Hz. The asterisks indicate whales that may have altered their paths.

All but one of these whales probably heard weak icebreaker sounds at least briefly, given

that, for all but one of these whales, S:N lI3,max at 5000 Hz >0 dB, and RLlI3,max at 5000 Hz exceeded

the absolute hearing threshold. For example, Figure 7.15 shows the situation for a whale 180 m

from the projector at 16:02. The median estimated received level in the 113-octave band around

5000 Hz was about equal to both the ambient noise and the white whale's auditory threshold, suggesting that this whale might, at times, have heard components of the projected sound near 5000

Hz. The whale seen closest to the projector was at the surface as it approached; therefore, it was

subjected to lower sound levels than estimated in the above tabulation while it was being observed.

However, it dove when at its CPA distance of 20 m, and would, at that time, have been exposed

to the estimated levels shown in the above text table. There was no significant difference between

the S:NI/3,max values at 5000 Hz near whales that appeared to modify their path (marked ,*, in

above tabulation) vs. those that did not (Mann-Whitney U=16, n=6,7, P=0.267). However, several
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7.2 White Whales: Icebreaker Playbacks 367

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FIGURE7.14. Third-octave levels of projected icebreaker noise vs. distance from projector and

ambient noise, 3 May 1994, time 15:48-16:02. (A) Variability over 14 min at ranges 1 m and 1.0

km (median, 5th and 95th percentiles). (B) Median levels at range 1 m (squares) and 30 m-3.0 km.

Plus signs show average ambient noise level before and after playback. 1&1 symbols are white

whale hearing thresholds vs. frequency. For additional explanation, see caption to Figure 7.10.
7.2 White Whales: Icebreaker Playbacks 368

TABLE7.3. Summary of sightings of white whales near the projector broadcasting icebreaker sounds

on 3 May 1994. All observations were made from the ice camp located amidst the pack ice NE of

Barrow. All CEPAs were determined from theodolite locations.

Radial Distance

Group Followed From CEPA

Time size Projector (m) (m) Nature of Track

15:40 1 +405 to +615 385 NW to N of projector heading fast NE across lead.

15:45 1 single sighting 210 SW of projector heading fast SE.

15:54 2 -240 to -450 <240 Adult & subadult SW of projector heading SSE at medium

speed.

15:58 1 -360 to -425 360 Subadult S of projector heading SSW at medium speed.

16:00 1 single sighting 390 Subadult S of projector heading ENE under ice edge at

medium speed.

16:02 2 -180 to -230 180 Adult & subadult SW of projector heading SSW at medium

speed.

16:06 5 +345 to +770 330 4 Adults & 1 subadult NW then NNE of projector heading

&260 NE then NNE then NE at medium speed.

16:17 1 single sighting <410 NNW of projector heading NE at unknown speed.

16:18 1 single sighting 125 Subadult NW of projector heading NE at medium speed.

16:19 8 +365 to +300 295 NW of projector heading E then ENE then dove E under ice

edge at medium speed.

16:21 6 single sighting 230 NNW of projector heading NE under ice edge at medium

speed.

16:24 1 -330 to -395 <330 Subadult SSW of projector heading SSE at medium speed.

16:31 2 +185 to +20 20 NNW then W of projector heading SSE along ice edge at

medium speed.

of the whales that appeared to divert were probably exposed to higher sound levels before they

were first sighted. Thus, the test underestimates any possible differences.

Sighting Rates During Playback and Control Periods

Meaningful results concerning reactions of white whales to playbacks of icebreaker sounds

were obtained on 17 May 1991 and 3 May 1994. On 17 May 1991, white whales were migrating

eastward close to the landfast ice edge prior to the playback. Eastward migration continued during

the playback, including at least two whales whose closest points of approach were only 80 and
7.2 White Whales: Icebreaker Playbacks 369

3 May 1994, 16:02

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squares) and near a white whale 180 m from the projector (median level over 64 s), 3 May 1994,

time 16:02. Plus signs show average ambient noise level before and after playback. IXI symbols

are white whale hearing thresholds vs. frequency. For additional explanation, see caption to Figure

7.11. Propagation model includes spherical spreading (plus Lloyd's mirror factor) a.tclose ranges.

95 m from the operating projectors. However, as described above, numbers of whales and of

whale groups passing per hour were considerably lower during the 17 May 1991 playback than

during the pre- and post-playback control periods on that date.

This difference in numbers is consistent with the possibility that some white whales avoided

passing close to the ice camp as a result of the playback. However, observations from the icebased platform on a single date cannot prove that the playback was the cause of the lower number

seen during the playback. Pods of white whales often migrate in loose associations spread out

over several kilometers. It is possible that the pre- and post-playback periods on 17 May 1991

happened to coincide with times when two such associations were passing the ice camp.

In contrast, on 3 May 1994, white whales passed the ice camp during but not before or after

the playback. Thus, there was no consistent pattern for lower sighting rates during playbacks.

To determine whether the sighting rate at ice camps differs during playbacks vs. control

periods, effective playback tests on more than two days would be necessary, preferably in
7.2 White Whales: Icebreaker Playbacks 370

conjunction with aerial observations to determine the distribution of whales over a larger area than

can be seen from the ice camp.

Acoustic Response Thresholds

The maximum levels of icebreaker sound received by the whales seen passing on 17 May

1991 were well above ambient on a broadband basis (20-5000 Hz band). However, much of the

energy in the projected icebreaker sounds was at relatively low frequencies and probably could not

be heard by the white whales (Fig. 7.10, 7.11). Nonetheless, white whales probably could hear

components of icebreaker sounds near 5000 Hz, where maximum received levels near whales were

88-96 dB (RL1I3,max)and where maximum icebreaker-to-ambient ratios near whales were 8-16 dB

(S:NI/3,max)' Sounds received at these low levels and S:N ratios would presumably be perceived

as relatively weak sounds.

On 3 May 1994, 13 groups of white whales were seen while icebreaker sounds were being

projected into the lead. Six of these groups appeared to alter their paths in response to the

playback. Received levels of icebreaker sounds were weaker than on 17 May 1991 (RLBB,max=102-

111 vs. 119-129 dB re 1 /lPa; RL1I3,max@ 5000 Hz=67-84 vs. 88-96 dB re 1 /lPa). However,

S:N1I3,maxlevels near 5000 Hz were generally similar near 11 of 13 groups sighted on 3 May 1994

(4-14 dB) as near the four groups sighted on 17 May 1991 (8-16 dB). The other two groups sighted on 3 May 1994 included one group that was not exposed to audible sounds (SN1I3,max= -3 dB)

and another group (2 whales) exposed to S:N1I3,maxnear 5000 Hz of -40+ dB when it approached

the projector and 45 dB when it dove at its CPA.

Considering all 17 groups observed on the two dates, 6 groups apparently diverted. Near

5000 Hz, diverting groups were receiving icebreaker sounds with estimated RL1I3,max levels of

about 78-84 dB re 1 J1Pa, and S:Nl/3,max values -8-14 dB. Corresponding estimated levels near

the 11 groups for which no diversion was evident were RL1I3max= 67-115 (96) dB re 1 /lPa and

S:N1I3,max= -3 to 45 (16) dB. The values in parentheses indicate the maximum levels near whales

if the group that approached to 20 m from the projector is excluded.

The sample size is very small (17 groups), but the data suggest that some white whales

responded to high-frequency components of icebreaker sounds at low received levels and low

icebreaker-to-ambient ratios. White whales presumably were reacting to these rather weak highfrequency components (e.g., S:N1I3,max-8-14 dB near 5000 Hz) of the icebreaker sound, which are

believed to have been audible to them, rather than to stronger and higher S:N components at lower

frequencies, which were probably not audible to these animals.

In summary, about one-third of the white whales sighted near the operating projectors

appeared to show small scale avoidance reactions when exposed to icebreaker sound that was

-8-14 dB above the background noise in the 113-octave band centered at 5000 Hz (RL1I3,max= 78-

84 dB re 1 /lPa). Although icebreaker sounds were much stronger at lower frequencies, the white

whale hearing threshold is such that they probably could not detect those sounds during the

playback experiments.
7.2 White Whales: Icebreaker Playbacks 371

Potential Radius of Influence of Actual Icebreaker

The median source levels of the projectors used during playbacks (SLBB.med)'typically 161

dB re 1 /-lPa-m on 17 May 1991 and 150 dB on 3 May 1994, were lower by -36 and 47 dB than

the corresponding median source level for the full-scale icebreaker (197 dB) whose recorded

sounds were projected. Of more relevance to white whales is the difference between the source

levels of the actual icebreaker and the projector(s) at high frequencies, e.g. near 5000 Hz. The top

curves in Figure 7.16A vs. B and Figure 7.17A vs. B show this difference for times on 17 May

1991 and 3 May 1994 when white whales were observed.

If, during playbacks of Robert Lemeur icebreaker sound, some white whales begin to show

diversion at a received level of -80 dB re 1 /-lPa (RL1I3,maxnear 5000 Hz) or an icebreaker:ambient

ratio of -10 dB (S:N 1I3,max)' at what distances from an actual icebreaker might diversion be evident?

Figure 7.16B shows estimated received levels of sounds from the icebreaker Robert Lemeur

at various distances if the actual vessel had been operating at the 17 May 1991 projector site. The

received level estimates are based on the 95th percentile source level estimates shown in Figure

4.25 (p. 116) and on the sound exposure model described in §2.3 (0.03 and 0.1 km spectra assume

spherical spreading). The ambient noise levels actually measured on 17 May 1991 are also shown.

If white whales often react to high frequency components of icebreaker sound at S:N1I3,maxlevels

near 10 dB, they would be expected to react out to the approximate distance where the 95th percentile level of high-frequency icebreaker noise is 10 dB above the ambient noise level, provided

that this level is above the absolute hearing threshold. Figure 7 .16B shows that the 95th percentile

received levels are expected to diminish to the "10 dB above ambient" or to the white whale

hearing threshold, whichever is greater at a given frequency, at ranges of 5-10 km in all1l3-octave

bands from 315 to 6300 Hz. At lower frequencies, the received level diminishes below the auditory threshold at closer ranges (:5;3km). Thus, the expected maximum reaction distance would be

expected to be -5-10 km if the actual icebreaker Robert Lemeur had been operating at the 17 May

1991 site under the ambient noise conditions prevailing on that date (Fig. 7.16B).

Figure 7 .17B allows a similar evaluation of the situation if Robert Lemeur had been operating

at the 3 May 1994 site under the ambient noise conditions prevailing there on that date. The 95th

percentile received levels diminish below the hearing thresholds at 315-4000 Hz at ranges 5-

10 km. Above 4000 Hz, received levels diminish below the "10 dB above ambient" curve before

they diminish below the hearing threshold, at ranges 7-10 km. Thus, the expected maximum reaction distance would again be -10 km if the actual icebreaker Robert Lemeur had been operating

at the 3 May 1994 site under ambient noise conditions prevailing on that date (Fig. 7.17B). At

range 10 km, the predicted received level equals the" 10 dB above ambient" curve and the hearing

threshold in only one 113-octave band for the 17 May 1991 case, but in at least three bands in the

3 May 1994 case (Fig. 7.16B vs. 7.17B). This difference is attributable to the lower ambient noise
7.2 White Whales: Icebreaker Playbacks 372

A. 17 May 1991 Playback, 14:20, 95%

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octave, (A) during playback on 17 May 1991, time 14:20, and (B) if actual icebreaker were operating at that site. Also shown is the average ambient noise level on 14 May 1991, and "10 dB above

ambient", also on a 113-octave basis. lXI-symbolsare white whale hearing thresholds.
7.2 White Whales: Icebreaker Playbacks 373

A. 3 May 1994 Playback, 16:02, 95%

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FIGURE 7.17. Estimated 95th percentile source and received levels of icebreaker noise, by 113

octave, (A) during playback on 3 May 1994, time 16:02, and (B) if actual icebreaker were operating at that site. Also shown is the average ambient noise level on 3 May 1994, and "10 dB above

ambient", also on a 1I3-octave basis. lXI-symbols are white whale hearing thresholds.
7.2 White Whales: Icebreaker Playbacks 374

levels at high frequencies on 3 May 1994; predicted received levels vs. range are almost identical

in the two cases."

Numerous assumptions are involved in making these estimates. These assumptions are, for

the most part, similar to those that apply in making corresponding "radius of responsiveness"

estimates for bowheads (discussed in §6.4). Wide variations in maximum reaction distances are

expected in different situations and when icebreakers with different high-frequency source levels

are used. Sometimes white whales would be expected to tolerate an icebreaker managing ice

closer than 5-10 km away, but at other times they are likely to avoid an area of radius substantially

larger than 5-10 km. The limited available data from playbacks of icebreaker noise do not allow

us to set meaningful upper and lower bounds on these predicted reaction distances.

Researchers in the Canadian High Arctic have documented reactions by white whales and

narwhals to ships and icebreakers 40 km or more away (LGL and Greeneridge 1986; Cosens and

Dueck 1988; Finley et a1. 1990). In this situation, the whales appeared to be reacting to sounds

that were barely detectable to them. High frequency components may have been the components

most readily detected by white whales at the long ranges where reactions were first noted (Cosens

and Dueck 1993). During the present study, we observed a few groups of white whales approaching and passing when projected icebreaker sounds were estimated to have been clearly audible in

the 1I3-octave band near 5000 Hz. Some whales appeared to have diverted when S:NII3,max was

slightly higher than 8-14 dB (i.e. many whales were moving away when first seen).

The High Arctic observations involved actual icebreakers underway in open water or ice.

There is considerable variation in the characteristics of sounds made by different vessels, and in

the sounds made by an actual vessel vs. a projector broadcasting recorded vessel sound. Also, it

has been suggested that the Canadian High Arctic whales are more "naive" and therefore more

likely to react at greater distances. For these reasons, it is difficult to compare the results of the

Canadian High Arctic studies with the present results. However, both studies provided evidence

consistent with the idea that higher-frequency components of vessel sounds may be the components

to which spring-migrating white whales are most likely to react.

7.3 Evaluation of Playback Hypotheses

As discussed in § 1.2, Null and Alternate Hypotheses, the one null hypothesis applicable to

playback effects on white whales was as follows:

Playbacks of recorded noise from a bottom-founded platform (1989-90) or an icebreaker

working on ice (1991194) will not (or alternatively will) significantly alter measures of

migration routes and spatial distribution of whales in the open water of nearshore lead

systems during the spring migration near Pt. Barrow, Alaska.

37 Water depth, the dominant factor in determining predicted propagation loss at a given frequency in

this study area and season (§4.3), was almost identical at the 17 May 1991 and the 3 May 1994 sites (110 m

vs. 105 m, respectively).
7.3 White Whales: Evaluation of Playback Hypotheses 375

The similar hypothesis concerning subtle aspects of individual whale behavior could not be

addressed for white whales because it was not practical to obtain detailed observations of white

whale behavior, aside from information about their swimming tracks.

Continuous Karluk Drilling Sound

During the 1989/90 playbacks with steady Karluk drilling sounds (Richardson et al. 1990a,

1991a), the wording of the above hypothesis was found to be somewhat broader than could be

addressed with the available data. We could only draw conclusions aboutthe effects of playbacks

of continuous noise from drilling on a bottom-founded ice platform like Karluk. Also, the 1989-

90 data applied to white whales migrating through pack ice and along the seaward side of the

nearshore lead east of Pt. Barrow.

With these restrictions and amendments to the wording, the 1989-90 data showed that

playbacks of sounds from drilling on a bottom-founded ice platform like Karluk have no

biologically significant effects on migration routes and spatial distribution of white whales visible

while migrating through pack ice and along the seaward side of the nearshore lead east of Point

Barrow in spring. Furthermore, Karluk sounds attenuated rapidly with distance (§6.5; see also

Richardson et al. 1990a:86). We concluded that maximum reaction distances of white whales to

an actual drillsite like Karluk (a few hundred meters) would be similar to those observed during

the playback experiments. In drawing these conclusions, we considered that the observed

temporary hesitation and minor changes in migration paths exhibited by some white whales within

200-400 m of the projector emitting Karluk noise were not biologically significant. Our

acceptance of the amended null hypothesis was based on a "weight of evidence" approach; the

available data for Karluk were not suitable for a statistical test of the hypothesis.

Variable Icebreaker Sound

In 1991/94, as in 1989-90, observations during playbacks were restricted to white whales

visible in open water within areas east of Pt. Barrow. In 1991/94, the playback noise was variable

icebreaker noise rather than continuous drilling sound, and the observations were on both the

landfast ice side of the nearshore lead (13 May 1991) and in a lead amidst pack ice (3 May 1994).

Thus, for 1991/94, the hypothesis (1) should be formulated as

"Playbacks of recorded variable noise from an icebreaker like Robert Lemeur working

on ice will not (or alternatively will) significantly alter measures of migration routes and

spatial distribution of white whales visible in the open water of lead systems during

spring migration east of Pt. Barrow, Alaska."

The hypothesis concerns reactions to playbacks of icebreaker noise rather than to noise from

the icebreaker itself. Thus, questions about the fidelity of the playback noise to the noise from

the original industrial activity are not directly involved. Also, the greater radius of anticipated

effects around an actual icebreaker is not directly dealt with by the hypothesis.
7.3 White Whales: Evaluation of Playback Hypotheses 376

Because we saw few white whales near the projector(s) when icebreaker sounds were being

projected, we would need to conduct additional field tests before this hypothesis could be

evaluated with confidence. However, white whales must approach within a few hundred meters

of the projectors in order to hear the playbacks of icebreaker sounds. Small-scale diversions

sometimes occur at closer ranges. These are unlikely to be biologically significant.

As discussed for bowheads in §6.6, any conclusions regarding the effects of icebreaker playbacks whales cannot be applied directly to the question of actual icebreaker effects, given the

much higher source level of the actual icebreaker than of the playback projectors. The radius of

responsiveness around an actual icebreaker would be expected to be much larger than that around

the playback site, probably on the order of several kilometers.

This conclusion assumes that response thresholds to an actual icebreaker like Robert Lemeur,

on an S:N or RL basis, are comparable to those near the playback site. This assumption is discussed on p. 10-11 (§1.3) and on p. 115-128 (§4.4). For white whales, the poor reproduction of the

low-frequency components of icebreaker sound during playbacks (§4.4) probably has little relevance. The hearing sensitivity of white whales is poor at those frequencies (Fig. 7.16, 7.17).

White whales probably react primarily or exclusively to higher frequency components, which were

reproduced with good fidelity during the playbacks.

The predicted radius of responsiveness around an icebreaker like Robert Lemeur would be

quite variable because propagation conditions and ambient noise vary with time and location.

Also, icebreakers vary widely in engine power and thus noise output, with Robert Lemeur being

a rather low-powered icebreaker. Furthermore, reaction thresholds of individual white whales no

doubt vary, with commensurate variability in predicted reaction radius.

7.4 White Whale Reactions to Aircraft

An assessment of the reactions of white whales to helicopter overflights was one of the

secondary objectives of this project (see specific objective 6 in §1.1). Collection of data on their

reactions to the project's Twin Otter fixed-wing aircraft was not an explicit objective, but this falls

under the provisions of specific objective 7, "To document, as opportunities allow, other aspects

of the ...disturbance responses ...white whales ... ".

Results from 1989-90 showed that reactions of white whales to turbine-powered aircraft

during the spring migration near Pt. Barrow are variable (Richardson et al. 1990a:239, 1991a:282).

Some individuals show no overt response to a Bell 212 helicopter or Twin Otter fixed-wing

aircraft flying at low level, or to a Bell 212 standing on the ice edge with engines running within

100-200 m of the whales. Other white whales look upward or dive abruptly when an aircraft

passes over at altitudes at least as high as 460 m (1500 ft). Some white whales whose paths come

within 100 m of a helicopter on the ice with its engines running may divert as much as 100 m

away from the helicopter. It is not known whether these small-scale and apparently brief reactions

are to the noise from the aircraft, visual cues, or both.
7.4 White Whales: Reactions to Aircraft 377

In this section, we summarize the reactions of white whales to the project's Bell 212

helicopter and Twin Otter fixed-wing aircraft during all four years of the project.

Reactions to Bell 212 Helicopter

Results-During 1989-91 and 1994, there were 42 occasions when behavior of white whale

groups was observed at known lateral and/or vertical distances (Table 7A). Observations of white

whale groups were made

~ during overflights (n = 20; Table 704A),

~ within 2 min of landing or during takeoff (n = 8; Table 704B), and

~ when the helicopter was stationary on the ice with its engines operating >2 min after

landing (n = 14; Table 704C).

Two cases are possible resightings and were excluded from the analysis, leaving 26 observations

during overflights or within 2 min of landing or takeoff and 40 cases in total.

Frequency of Reactions: Apparent reactions to the helicopter were observed on 15 (37.5%)

of these 40 occasions. Apparent reactions consisted of 7 immediate dives and 8 unusual headings

or changes in heading. Reactions were noticed when the helicopter was stationary on the ice (7

cases), within 2 min of helicopter landing (2 cases), and during overflights (6 cases). The

remaining 25 white whales or white whale groups exhibited no overt reaction to the helicopter and

generally maintained their course and continued respiring at the surface.

Reactions were noticed when the helicopter was at altitudes 0-460 m, and at lateral distances

0-320 m (Fig. 7.18). Of the 7 reactions for which both altitude and lateral distance were known

during overflight (including cases observed within 2 min of after the helicopter landed), most

reactions (6 of 7 groups or 85.7%) occurred when the helicopter was operating at altitudes $;150 m

ASL and at lateral distances $;250 m (Table 7.5, Fig. 7.19).

Helicopter Altitude: Altitude ASL during "overflights" ranged from 0 m (when white whale

groups were observed within 2 min of helicopter takeoff or landing) to 460 m (n=25 cases at

known altitudes; Table 704A,B). Immediate dives occurred during 4 overflights when the

helicopter approached at altitudes $;150 m. More often, however, no immediate dive occurred

when the helicopter approached at $;150 m (9 of 15 cases). In most of these cases, white whales

remained at the surface without apparent reaction. In two cases at $;150 m, other types of

reactions, including change in heading and reduced speed, were seen. Reactions occurred more

frequently during overflights at altitudes of $;150 m (6 of 15 groups, 40%) than at altitudes >150 m

(1 of 10 groups, 10%) (Table 7.5, Fig. 7.19). However, given the small sample size, the difference

is not statistically significant (chi2=1.397, df=l, P>0.05).

Helicopter Lateral Distance: Lateral distance from the helicopter to white whales during

26 "overflights" ranged from 0 m (during direct overflights) to 500 m. Significantly more reactions occurred when overflights were at $;250 m lateral distance from white whales (8 of 15

groups, 53.3%) than when 250-500 m away (0 of 11 groups), ignoring helicopter altitude (chi2=

6.155, df=l, P<0.05; Table 7.5). No white whales reacted during the 11 overflights at lateral
7.4 White Whales: Reactions to Aircraft 378

TABLE 7.4. Incidental observations of white whales near the operating helicopter northeast of Barrow during spring in 1989-1994.

Lateral Observ.

Group Altitude Distance Reac- PlatDate Time Size (m) (m) tion? form' Comments

A, Observed During Overflight

16105/89 ? 3 15-30 500 No Continued travel at surface

17/05/89 ? I 150 0 Yes Dove immediately before reaching end of lead whereas previously undisturbed groups did not dive

until they were a few meters from the ice edge

17/05/89 4 460 0 Yes Dove immediately before reaching end of lead whereas previously undisturbed groups did not dive

until they were a few meters from the ice edge

26105189 14:00 I 120 50 Yes H Dove rapidly and steeply as helicopter passed at cruise speed

10/05/90 13:48 2 ? 0 Yes I Dove during overflight

06105/91 11:16 I 60 0 Yes H Made deep venical dive

17/05/91 10:43 15-20 60 75 No I Continued traveling at surface as helicopter flew by

17/05/91 12:08 5 65-30 20Q.300 Yes I Social group changed heading away from ice edge as helicopter turned and landed, remained at surface

and continued social activity

03105194 9:46 2 425 500 No H Continued travel SSE

03/05/94 22:04 16 250 400 No H Continued travel E

03/05/94 22:05 2 250 400 No H Continued travel E

03/05/94 22:06 3 250 400 No H Continued travel E

08/05/94 21:12 I 200 400 No H Continued travel W

17/05/94 19:48 5 200 200 No H Continued travel E

22105/94 8:43 4 325 500 No H Continued travel ESE

22105/94 8:44 8 325 500 No H Milling, asynchronous headings

22105/94 8:51 5 375 500 No H Travel, generally SE with asynchronous headings

22105/94 9:00 I 30 50 No H Remained at surface oriented NE

25/05/94 8:31 I 60 300 No H Remained at surface oriented E

25/05194 8:32 10 60 300 No H Remained at surface oriented E

B. Observed Within 2 min or Landing or During Take-orr

10/05/90 14:04 2 0 200 Yes I Subadults continued travel at surface, after helicopter landed (14:04), dove as engine speed decreased

10/05/90 14:29 4 0 120 Yes I Approached quiet helicopter on ice, then milled (subadult spyhopped) as helicopter engines staned;

whales dove 20 s after helicopter lifted off ice (possible resighting)

10/05/90 14:33 4 0 45 No Approached helicopter as it lifted off ice (possible resighting)

21105/90 10:05 4 0 5Q.lOO No Travel at surface as helicopter lifted off ice

21/05/90 10:06 10 0 5Q.IOO No Travel at surface as helicopter lifted off ice

17/05/91 10:46 2 0 150 No Continued travel as helicopter landed -150 m away

17/05/91 11:11 2 0 100 No Adult-yearliog traveled past helicopter as it lifted off ice

17/05/91 12:08 10 30 100-250 Yes Initially eastbound. milled in closely-spaced group as helicopter approached. Resumed E surface travel

at reduced speed. Reversed course after helicopter landed. Whales resumed travel to NE after engines

off.

C. Helicopter Stationary on Ice, Engines Operating, >2 min Arter Landing

10/05190 14:09 4 0 ? Yes I Swam past stationary helicopter operating on ice; then began milling and dove as helicopter taxied

across ice (landed 6 min earlier)

Traveled past helicopter (landed 09:16) along far side of lOO-m wide lead. farther than undisturbed

whales

Traveled past stationary helicopter mid-way across lOO-m wide lead, farther than undisturbed whales

Traveled past helicopter along far side of lOQ.m wide lead. farther than undisturbed wbales

Milling before helicopter engines started; maintained heading tangential to helicopter after engines

turned on

Continued travel as helicopter stationary on ice with engines on

Continued travel as helicopter stationary on ice with engines on

Continued travel as helicopter stationary on ice with engines on

Surfaced -100 m away 30 s after helicopter engines turned off, then passed directly in front of ice

camp/belicopter

Surfaced 2 min after engines off with NNE heading, contrasting with ENE headings of 9 other groups

seen passing ice camp that day during engines off conditions.

Traveled -15 m off ice edge past helicopter stationary (landed 10:46) with engines on

Traveled past helicopter stationary on ice with engines on (lift-off II: I I)

Unusual travel (sub-surface, slow, to W) past helicopter stationary (landed 12:11) 30 s after engines

off.

Tracked for 15 min. headed ENE along nearshore lead, passing helicopter stationary on ice with

engines on. The ENE heading. veering away from the E-W alignment of the ice edge, attributed to

helicopter

21105/90 9:19

21105/90

21105/90

05/05191

9:19

9:20

12:02

11105/91

11105/91

11105/91

11105/91

19:00

19:00

19:00

19:07

11105/91 19:08

17/05/91

17105/91

17/05/91

10:50 I

11:09 15-18

12:14 I

17/05/91 19:58

3

7

2

2

4

3

2

2

4

3

o

o

o

o

o

o

o

o

o

o

o

o

o

95 Yes

• I = Ice camp. H = helicopter.

70

95

150

Yes

Yes

No

70

70

160

90

No

No

No

No

320 Yes

65

130

32

No

No

Yes

250 Yes
Unknown-

~.

400-

-

-E

- 300

Q)

"0::] +-' -

+:i

«

200-

-II

100-

--

0

0

White Whales

o

o

o o

-

o

o

-

:z:z _ ~~

1 . 'I

100

1

400

T ••••• I ~ I T

200 300

Lateral Distance (m)

D

A: Overflt-No React

A:

•

Overflt-React

Z

B: TO&Land-No React

•••

B: TO&Land-React

X

O: On Ice-No React

IE3

C: On Ice-React

FIGURE 7.18. Reactions of white whales to the operating Bell 212 helicopter in relation to helicopter altitude and lateral distance, 1989-

94. Includes cases when helicopter was (A) flying, (B) taking off (TO) or had landed within preceding 2 min, and (C) was on ice with

engines running (cf. Table 7AA,B,C).
9

8

7

n=6 n=6

en 6 0-

:J

0

~

(!J 5

-0

~

Q) 4 .c

E

:J

Z 3

2

1

0

<1501<250

n=8 White Whales

iii Reaction

o No reaction

n=3

n=l n=l

n=O n=O

<1501>250 >1501<250 >1501>250

Altitude/ Lateral Distance Category (m)

FIGURE 7.19. Reactions of white whales to the operating Bell 212 helicopter vs. helicopter altitude (::;;150m vs. >150 m) and lateral

distance (::;;250m vs. >250 m), 1989-94. Includes cases when helicopter was flying, taking off, or had landed within the preceding 2 min

(Table 7.4A,B).

w

00

o

------ ---- --
7.4 White Whales: Reactions to Aircraft 381

TABLE7.5. White whale reactionsto helicopteroverflightsin relationto helicopteraltitude and lateral

distance, 1989-1994. Each white whale group is counted once. Includesdata fromTable 7.4A,B,involving

overflights(n = 20) and cases when whales were observedwithin 2 min of landingor takeoff (n = 8).

HelicopterAltitude (m)

Lateral ~150 >150 Unknown Total

Distance No No No No

(m) Reaction Reaction Reaction Reaction Reaction Reaction Reaction Reaction

~250 6 6 1 1 1 0 8 7

>250 0 3 0 8 0 0 0 11

Unknown 0 0 0 0 0 0 0 0

Total 6 9 1 9 1 0 8 18

distances >250 m (Table 7.5).

Helicopter Stationary on Ice: Apparent reactions were observed on 7 of 14 occasions (50%)

when the helicopter was stationary on the ice with its engines operating. Reactions were noted

for 5 of 12 groups seen at lateral distances s;;250m. The only group observed at >250 m lateral

distance reacted, as did another group at unknown lateral distance. Overall, the seven reactions

consisted of 3 unusual headings or changes in heading, 3 apparent displacements, and 1 change

in behavior state (from travel to mill). The remaining 7 white whale groups that did not react

noticeably generally maintained their courses and continued respiring at the surface. Especially

clear cases of displacement were observed on 21 May 1990, when white whales diverted to the far

side or middle of a 100-m-wide lead while passing the helicopter (see Table 7AC).

Evaluation of Helicopter Overflight Hypotheses.-Opportunistic observations in 1989-91 and

1994 showed that spring-migrating white whales often responded to a close approach by a turbinepowered helicopter. Apparent reactions were observed during 31% of overflights. Reactions were

also noted during 50% of the occasions when the helicopter was stationary on the ice with its

engines running. Whales reacted by diving, veering away, or showing other changes in behavior.

During overflights, reactions occurred exclusively when the helicopter passed at s;;250m lateral

distance from the white whales, and at altitudes up to 460 m ASL. However, most white whales

showed no obvious reaction to single passes at altitudes >150 m ASL. These white whales maintained their headings and continued respiring at the surface when the helicopter operated nearby.

It is unknown whether these small-scale and apparently brief reactions are to the noise from

the aircraft, visual cues, or both. There have been no studies of the effects of other types of

helicopters on migrating white whales in spring. However, the Bell 212 used in this project is one

of the noisier types of helicopters used by the offshore oil industry.
7.4 White Whales: Reactions to Aircraft 382

We conclude that operations by a Bell 212 helicopter can locally alter the movements of

white whales visible in the open water of nearshore lead systems and amidst the pack ice during

spring migration near Pt. Barrow. However, these local effects do not cause migration blockage

or biologically significant diversion from migration routes in the circumstances studied. Some

white whales whose paths come within 100 m of a helicopter on the ice with its engines running

may divert as much as 100 m away from the helicopter but continue their migration. We do not

consider diversion of migration routes by 100 m to be biologically significant.

We also conclude that single overflights by a Bell 212 helicopter at lateral distances <250 m,

especially at altitudes ::::;150m ASL, often affect the behavior of white whales visible in the open

water of nearshore lead systems and amidst the pack ice during spring migration near Pt. Barrow.

Also, white whales exposed to a stationary helicopter operating its engines within a lateral distance

of 250 m often show overt behavioral reactions. Although there is no objective way to assess the

biological significance of these behavioral reactions, the reactions appear to be brief and we

suspect that they are not of lasting importance to the individual whales involved.

This assessment concerns potential effects of single, straight-line overflights. We did not

obtain data on reactions to repeated passes, circling, or prolonged hovering at low altitude. These

types of helicopter flights would be more likely than single, straight-line overflights to cause

significant disturbance effects.

White Whale Reactions to Twin Otter

During the four spring seasons, 24 white whale groups were observed to react overtly to the

Twin Otter fixed-wing aircraft at times when the lateral and/or vertical distances from the aircraft

were noted (Table 7.6). Reactions were noticed when the Twin Otter was at altitudes ranging from

60 m (3 cases) to 460 m (4 cases), and at lateral distances of 0 m to 500 m. Reactions consisted

of 10 immediate dives with tail thrash, 6 unusual turns or changes in heading (including a steep

dive), 5 occurrences of twisting to look up at the aircraft, 2 changes in behavior state (travel to

mill; increase swim speed), and 1 unrecorded. Strong reactions such as abrupt dives, vigorous

swimming, or tail thrash occurred only during direct overflights, most frequently (10 of 12 groups,

83.3%) at altitudes ::::;182m ASL (Table 7.6).

The 24 white whale groups that were seen to react to the aircraft in 1989-94 represent a very

small percentage (-3.1 %) of the total number of white whale groups sighted from the Twin Otter

in those four years (n=760; Table 7.7). The 18 groups seen to react to the Twin Otter at altitudes

::::;182m represent only 5.4% (18/336) of the total number of groups, observed when the aircraft was

at ::::;182m ASL. The two groups seen to react at aircraft altitudes 183-427 m represent only 1.4%

(2/141) of the total number of groups observed from those altitudes. The four groups observed

to react at aircraft altitudes >427 m also represent 1.4% (4/283) of observations from those

altitudes.

The number of groups of white whales noticed to react to the Twin Otter was undoubtedly

an underestimate of the actual number of groups reacting, as these reactions were only observed

on an opportunistic basis. Because of the brevity of observations when the aircraft was low, the
TABLE7.6. Cases in which white whales appeared to react to Twin Otter observation aircraft, spring 1989-1994.

Lateral

Group Altitude Distance

Date Size (m) (m) Comments

14/05/89 17:02 2 260 0 Adult and subadult rolled slightly and looked up at aircraft

24/05/89 20:13 7 200 0 Dove steeply and abruptly, while we were circling bowheads

29/05/89 ? 13 460 0 One looked up at aircraft while we were circling bowheads

21/05/90 8:47 6 460 ? Reacted to aircraft, unknown behavior while we were circling bowheads

21/05/90 9:40 1 150 300 Whale heading SSE abruptly turned and headed ENE, opposite to aircraft heading as high

power was applied to engines to begin a climb

21/05/90 11:08 7 460 0 Turned sharply away from aircraft, may have reacted to ice camp 200 m away

03/05/91 11:45 2 150 0 Whale heading W stopped and milled

17/05/91 11:18 30 80 0 One dove hastily

17/05/91 12:16 2 95 0 Violent reaction, unusually vigorous tail thrash

17/05/91 12:20 1 110 0 Dove

17/05/91 12:59 1 60 0 Tail thrash

17/05/91 13:00 1 60 0 Tail thrash

17/05/91 16:49 10 120 0 Sudden dive, tail thrash

18/05/91 10:30 1 60 0 Turned sharply away from aircraft :'-l

18/05/91 17:53 7 110 0 Dove hastily, some with unusually vigorous tail thrash

-l:l..

~

22/05/91 20:24 2 150 500 Whales traveling E, turned 90 degrees away from aircraft ~.

03/05/94 9:12 52 460 ? One whale resting in pack ice turned slowly 1800towards aircraft

~

04/05/94 14:47 1 65 0 Twisted and turned I:>

~

08/05/94 11:50 5 140 150 One whale resting turned and looked up ~

09/05/94 9:53 16 180 150 One dove hastily, surfaced, turned sharply to look up

:>:l

'"I:>

14/05/94 9:48 8 75 1-100 Swam vigorously with fast fluke action during second pass. It did not react during the ~

o'

previous pass at 90 m ASL ;:,

'"

19/05/94 17:22 3 150 0 One turned left, then right, another dove steeply 0

;t..

19/05/94 17:? 1 120 ? Looked up ~.

25/05/94 10:52 150 ? Reacted, behavior unknown

..•

4

o§, ..•

~

00

~
7.4 White Whales: Reactions to Aircraft 384

TABLE7.7. Number of white whale groups overflown by the Twin Otter aircraft

in 1989-1994, and number observed to react.

Altitude Category (m)

Year S183a

184-427 >427b

Total

1989 44 82 102 228

1990 12 5 35 54

1991 246 52 99 397

1994 34 2 47 86

Total 336 141 283 760

Reacted 18 2 4 24

a 600 ft b 1400 ft

TABLE7.8. Number of groups of white whales observed to react to Twin Otter overflights in

relation to aircraft altitude and lateral distance, 1989-1994. Each group is counted only once.

Lateral Altitude Category (m)

Distance (m) S182 183-427 >427 Unknown Total

S250 14 2 2 0 18

>250 2 0 0 0 2

Unknown 2 0 2 0 4

Total 18 2 4 0 24
7.4 White Whales: Reactions to Aircraft 385

underestimation was probably more severe for whales overflown at low altitude. Nonetheless, the

"altitudinal distribution" of the groups that reacted was significantly different from that of the

groups overflown (Table 7.7; G=9.39, df=2, P<O.OI). This confirms that there was a significantly

higher likelihood of reactions by whales overflown at low altitude (:5182 m ASL) than by whales

overflown at higher altitude.

Lateral distance from the Twin Otter to white whales that were observed to react ranged from

o m during direct overflights to 500 m (n=20 observations at known lateral distances). Most of

the observed reactions (18 of 20 groups, 90%) occurred when the Twin Otter was at lateral

distances :5250 m from white whales (Table 7.8).

Overall, 14 of 20 observed reactions (70%) occurred when the Twin Otter was at altitudes

of :5182 m and lateral distances of :5250 m from the white whales (Table 7.8). On 6 of these

occasions, reactions occurred when the Twin Otter flew directly over the groups of white whales.

In summary, white whale groups were sometimes observed reacting overtly to Twin Otter

overflights. Most reactions occurred when the aircraft was at altitudes :5182 m and lateral

distances :5250 m. Direct overflights generated the most pronounced reactions, such as vigorous

swimming, abrupt dives, or tail thrashing. In a few cases, white whales responses involved turning

directly away from the aircraft. In other cases, white whales responded to overflights by looking

up at the aircraft, a behavior not necessarily indicative of a negative effect. Overall the number

of white whales observed reacting overtly to Twin Otter overflights represented a very small

fraction of the total number of white whales observed.
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Appendices 393

APPENDICES A-H

APPENDIX A: Field Activities 395

APPENDIX B: Transmission Loss Experiment Data, 1991/94 . . . . . . . . . . . . . . . . .. 408

APPENDIX C: Sonobuoy Impact Sound 426

APPENDIX D: Bowhead Distribution Maps, 1989-90 . . . . . . . . . . . . . . . . . . . . . . .. 431

APPENDIX E: Bowhead Resightings By NMML, 1989 440

APPENDIX F: Individual Playback Experiments, 1991/94 441

Playback in 1991 441

17 May 1991 Playback 441

Playbacks in 1994 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 449

7 May 1994 Playback .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 449

9 May 1994 Playback . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 467

14 May 1994 Playback 486

16 May 1994 Playback 493

17 May 1994 Playback 501

20 May 1994 Playback 513

APPENDIX G: White Whale Distribution Maps, 1989-94 . . . . . . . . . . . . . . . . . . . .. 521

APPENDIX H: SSDC Drilling Sounds in Winter 538
Appendix A: Field Activities 395

APPENDIX A: Field Activities

Appendix A consists of three multi-page Tables:

TABLE A-I shows the observation effort and the numbers of whales (bowheads and white

whales) seen during each day when the ice-based crew was present on the ice watching for whales

during the four years of the study. Observation time and number of whales seen are separated into

"playback", "control", and "other" periods. Observation time and number of whales seen are

presented for ~ ice-based observations alone, ~ systematic behavioral observations from the

circling aircraft (when obtained near the ice camp), and ~ the combination of aerial and ice-based

observations. Whales observed during systematic aerial observations far from the ice camp

(generally >10 km away) are not included in this Table.

TABLE A-2 summarizes the daily activities, weather, and ice conditions during the 1991

phase of the study, and TABLE A-3 provides corresponding information for the 1994 phase.

Similar Tables giving this information for the 1989 and 1990 phases can be found in Richardson

et al. (1990a:68ff, 1991a:35fj).
TABLE A-I. Observation effort and numbers of bowheads and white whales seen during control periods. playback periods and other periods. 1989-91 and 1994. Only dates when the ice-based

crew were present on the ice and watched for whales are included. Whales seen during more than one period are included once in each period.'

Aerial Observations Ice-based Observations Combined Observations

Control Playback Other Control Playback Other Control Playback Other

Effort No. No. Effort No. No. Effort No. No. Effort No. No. Effort No. No. Effort No. No. Effort No. No. Effort No. No. Effort No. No.

Year Date (h) BhdsWWs (h) BhdsWWs (h) BhdsWWs (h) BhdsWWs (h) BhdsWWs (h) Bhds WWs (h) BhdsWWs (h) BhdsWWs (h) BhdsWWs

1989 29 April 0.0 0 0 0.0 0 0 0.0 0 0 3.3 0 0 0.0 0 0 0.0 0 0 3.3 0 0 0.0 0 0 0.0 0 0

30 April 0.0 0 0 0.0 0 0 0.0 0 0 2.9 0 0 0.0 0 0 4.6 3 0 2.9 0 0 0.0 0 0 4.6 3 0

2 May 0.0 0 0 0.0 0 0 0.0 0 0 2.8 0 0 0.0 0 0 0.0 0 0 2.8 0 0 0.0 0 0 0.0 0 0

3 May 0.0 0 0 0.0 0 0 0.0 0 0 3.2 0 0 3.2 0 0 0.2 0 0 3.2 0 0 3.2 0 0 0.2 0 0

6May 0.0 0 0 0.0 0 0 0.0 0 0 3.3 0 0 4.8 0 0 1.2 0 0 3.3 0 0 4.8 0 0 1.2 0 0

7 May 0.0 0 0 0.0 0 0 0.0 0 0 4.5 0 0 1.2 0 0 1.5 0 0 4.5 0 0 1.2 0 0 1.5 0 0

9 May 0.0 0 0 0.0 0 0 0.0 0 0 1.8 0 0 0.0 0 0 0.0 0 0 1.8 0 0 0.0 0 0 0.0 0 0

14 May 0.5 1 100 2.8 6 100 0.0 0 0 2.7 0 7 8.6 5 19 0.4 I 0 2.7 I 100 8.6 10 100 0.4 I 0

16May 0.0 0 0 0.0 0 0 0.0 0 0 8.3 2 13 2.0 0 0 0.5 0 0 8.3 2 13 2.0 0 0 0.5 0 0

17 May 0.0 0 0 0.0 0 0 0.0 0 0 1.0 0 6 0.0 0 0 0.9 0 18 1.0 0 6 0.0 0 0 0.9 0 18

19 May 0.0 0 0 0.0 0 0 0.0 0 0 4.3 0 0 4.3 4 2 0.7 0 0 4.3 0 0 4.3 4 2 0.7 0 0

21 May 0.0 0 0 0.0 0 0 0.9 0 0 3.8 0 7 3.3 0 0 0.5 0 0 3.8 0 7 3.3 0 0 0.5 0 0

23 May 0.8 I I 0.7 5 50 0.1 2 I 3.9 2 3 5.1 2 4 0.7 0 0 3.9 3 4 5.1 5 54 1.5 2 I

25 May 0.0 0 0 0.0 0 0 1.0 0 0 2.9 0 0 0.0 0 0 0.0 0 0 2.9 0 0 0.0 0 0 0.0 0 0

27 May 3.1 10 0 1.8 2 0 0.0 10 0 8.7 0 0 2.7 0 14 1.0 0 0 9.2 10 0 2.7 2 14 2.0 10 0

28 May 0.0 0 0 0.0 0 0 0.0 0 0 5.0 0 0 1.4 0 0 0.6 0 0 5.0 0 0 1.4 0 0 0.6 0 0

29 May 0.0 0 0 0.0 0 0 0.0 0 0 2.5 0 2 6.7 0 0 0.4 0 0 2.5 0 2 6.7 0 0 0.4 0 0

Total 4.4 12 101 5.3 13 150 2.0 12 1 64.9 4 38 43.3 11 39 13.2 4 18 65.4 16 132 43.3 21 170 15.0 16 19

1990 27 April 0.0 0 0 0.0 0 0 0.0 0 0 6.0 0 0 0.0 0 0 0.0 0 0 6.0 0 0 0.0 0 0 0.0 0 0

29 April 3.8 11 0 0.0 0 0 0.0 0 0 4.5 3 0 0.0 0 0 0.0 0 0 8.3 13 0 0.0 0 0 0.0 0 0

30 April 0.0 0 0 0.0 0 0 0.0 0 0 1.4 0 0 0.0 0 0 0.0 0 0 1.4 0 0 0.0 0 0 0.0 0 0

I May 0.0 0 0 0.0 0 0 0.0 0 0 1.7 0 0 0.0 0 0 0.0 0 0 1.7 0 0 0.0 0 0 0.0 0 0

2 May 0.0 0 0 0.0 0 0 0.0 0 0 3.1 0 0 0.0 0 0 0.0 0 0 3.1 0 0 0.0 0 0 0.0 0 0

4 May 0.0 0 0 0.0 0 0 0.0 0 0 2.5 0 0 4.1 0 0 0.5 0 0 2.5 0 0 4.1 0 0 0.5 0 0

5May 1.7 I 0 0.0 0 0 0.0 0 0 2.4 0 0 2.2 0 0 0.5 0 0 3.5 I 0 2.2 0 0 0.5 0 0

;l>.

~ 9 May 0.0 0 0 0.0 0 0 0.0 0 0 2.2 2 0 5.0 22 0 0.6 3 0 2.2 2 0 5.0 22 0 0.6 3 0 l\

10 May 1.7 21 35 3.6 25 30 0.2 5 0 2.0 4 7 5.3 22 0 0.5 5 16 2.3 23 35 5.3 40 30 0.5 10 16

~

II May 3.5 IS 0 1.0 3 0 0.7 8 0 6.0 13 6 1.6 I 0 1.0 0 0 6.0 28 6 1.6 4 0 1.0 8 0

~ 13 May 0.7 6 0 4.1 26 0 0.8 4 0 3.4 37 0 4.7 93 0 1.0 12 0 3.4 40 0 4.7 105 0 1.0 12 0

16May 2.2 27 0 1.4 12 0 0.2 I 0 1.3 36 0 3.7 21 0 0.2 6 0 2.7 63 0 3.7 25 0 0.2 6 0 ~

19May 0.0 0 0 0.0 0 0 0.0 0 0 4.2 I 16 0.0 0 0 0.0 0 0 4.2 I 16 0.0 0 0 0.0 0 0 lS:

21 May 2.3 17 200 2.7 4 3 0.5 4 3 3.0 1 49 4.1 I 16 0.5 0 23 3.9 17 220 4.1 4 19 0.5 4 26 ;l>.

<'I

24 May 0.0 0 0 0.0 0 0 0.0 0 0 1.4 0 0 0.0 0 0 0.0 0 0 1.4 0 0 0.0 0 0 0.0 0 0

::to ~

25 May 0.0 0 0 0.0 0 0 0.0 0 0 0.7 0 0 0.0 0 0 0.0 0 0 0.7 0 0 0.0 0 0 0.0 0 0 ~:

'"

Total 15.9 98 235 12.8 70 33 2.4 22 3 45.8 97 78 30.7 160 16 4.8 26 39 53.3 188 277 30.7 200 49 4.8 43 42 w

\0

'"
Aerial Observations Ice-based Observations Combined Observations

Control Playback Other Control Playback Other Control Playback Other

Effort No. No. Effort No. No. Effort No. No. Effort No. No. Effort No. No. Effort No. No. Effort No. No. Effort No. No. Effort No. No.

Year Date (h) BhdsWWs (h) BhdsWWs (h) BhdsWWs (h) BhdsWWs (h) BhdsWWs (h) BhdsWWs (h) BhdsWWs (h) BhdsWWs (h) BhdsWWs

1991 28 April 0.0 0 0 0.0 0 0 0.0 0 0 3.4 2 0 0.0 0 0 0.0 0 0 3.4 2 0 0.0 0 0 0.0 0 0

I May 0.0 0 0 0.0 0 0 0.0 0 0 2.5 0 0 0.0 0 0 2.0 0 0 2.5 0 0 0.0 0 0 2.0 0 0

3 May 0.0 0 0 0.0 0 0 0.0 0 0 1.9 5 0 0.0 0 0 0.0 4 0 1.9 5 0 0.0 0 0 0.0 4 0

5 May 0.0 0 0 0.0 0 0 0.0 0 0 4.0 0 46 2.4 0 0 1.7 0 0 4.0 0 46 2.4 0 0 1.7 0 0

6 May 0.0 0 0 0.0 0 0 0.0 0 0 2.3 0 0 0.0 0 0 0.0 0 0 2.3 0 0 0.0 0 0 0.0 0 0

II May 0.0 0 0 0.0 0 0 0.0 0 0 3.6 6 23 1.0 0 6 0.5 0 9 3.6 6 23 1.0 0 6 0.5 0 9

17 May 0.0 0 0 0.0 0 0 0.0 0

'0 4.1 2 96 5.3 9 II 0.5 I 61 4.1 2 96 5.3 9 8 0.5 I 61

18May 0.0 0 0 0.0 0 0 0.0 0 0 3.5 2 0 0.0 0 0 6.6 0 0 3.5 2 0 0.0 0 0 6.6 0 0

20 May 0.0 0 0 0.0 0 0 0.0 0 0 1.5 0 0 0.0 0 0 0.0 0 0 1.5 0 0 0.0 0 0 0.0 0 0

22 May 0.0 0 0 0.0 0 0 0.0 0 0 2.4 0 0 1.3 0 0 0.9 I 0 2.4 0 0 1.3 0 0 0.9 I 0

23 May 0.0 0 0 0.0 0 0 0.0 0 0 2.6 0 0 2.7 0 0 0.7 0 0 2.6 0 0 2.7 0 0 0.7 0 0

25 May 0.0 0 0 0.0 0 0 0.0 0 0 1.9 0 0 0.0 0 0 0.4 I 0 1.9 0 0 0.0 0 0 0.4 I 0

26 May 0.0 0 0 0.0 0 0 0.0 0 0 1.7 I 0 0.0 0 0 0.1 0 0 1.7 I 0 0.0 0 0 0.1 0 0

Total 0.0 0 0 0.0 0 0 0.0 0 0 35.4 18 165 12.7 9 14 13.4 7 70 35.4 18 165 12.7 9 14 13.4 7 70

1994 28 April 0.0 0 0 0.0 0 0 0.0 0 0 5.6 0 0 0.0 0 0 1.4 0 0 5.6 0 0 0.0 0 0 1.4 0 0

2 May 0.0 0 0 0.0 0 0 0.0 0 0 5.8 0 0 0.0 0 0 2.3 0 0 5.8 0 0 0.0 0 0 2.3 0 0

3 May 0.0 0 0 0.0 0 0 0.0 0 0 5.6 I 0 4.1 0 32 2.4 I 0 5.6 I 0 4.1 0 32 2.4 I 0

7 May 2.1 15 0 1.5 15 0 0.0 0 0 7.0 36 0 3.9 8 0 2.4 19 0 7.0 47 0 3.9 18 0 2.4 19 0

8 May 0.0 0 0 0.0 0 0 0.0 0 0 5.2 24 0 0.0 0 0 0.0 0 0 5.2 24 0 0.0 0 0 0.0 0 0

9May 1.9 24 0 2.2 27 0 0.5 15 0 6.4 22 0 3.0 25 0 0.5 11 0 6.4 42 0 3.0 32 0 0.5 21 0

IIMay 3.9 31 0 0.0 0 0 0.0 0 0 1.6 2 0 0.0 0 0 0.0 0 0 4.3 31 0 0.0 0 0 0.0 0 0

14 May 0.0 0 0 0.0 0 0 0.0 0 0 6.4 17 0 3.2 3 0 2.2 II 0 6.4 17 0 3.2 3 0 2.2 11 0

16 May 0.5 7 0 3.2 9 0 0.2 0 0 4.2 0 0 4.2 4 0 0.7 0 0 4.2 7 0 4.2 13 0 0.7 0 0

17May 4.3 27 0 1.9 6 0 0.4 I 0 1.5 0 0 4.2 I 0 0.2 0 0 4.4 27 0 4.2 7 0 0.4 I 0

20 May 2.6 9 0 0.0 0 0 0.0 0 0 5.2 6 0 4.6 11 0 0.5 4.0 0 5.5 9 0 4.6 II 0 0.5 4 0 ~

22 May 1.7 6 17 0.0 0 0 0.0 0 0 2.9 0 15 0.0 0 0 1.0 0 6 2.9 6 22 0.0 0 0 1.0 0 6 ~

25 May 0.0 0 0 0.0 0 0 0.0 0 0 '" 1.9 0 4 0.0 0 0 0.5 0 0 1.9 0 4 0.0 0 0 0.5 0 0

~

Total 17.0 119 17 8.8 57 0 1.1 16 0 59.3 108 19 27.2 52 32 14.1 46 6 65.2 211 26 27.2 84 32 14.3 57 6 ~

• Some whales may be included more than once in each period. particularly during 1994. because they may not have been identified as being seen previously during that period. However. the numbers presented here are the numbers of different ~

whales estimated to have been present and are often less than the number of sightings in maps and tables in this and previous reports. l:t

~<")

::to

'"::;:

lii'

'"

W

\0-..l
Appendix A: Field Activities 398

TABLE A-2. Summary of daily activities and weather and ice conditions. 28 April-26 May 1991.

Date

Ice-based Crew

Number of

No.

Ferry

Flights

Ice

Camp

Location Other

Overall

Ice

Conditions

Trans.

Loss Icebr.

Test Plbk. Bhd.

White

Whales

28 Apr Control obs.;

equip. checkout.

85%. Lead wide on

Chukchi side;

discontinuous to

E. Much new ice.

29 Apr

30 Apr

1 May

2 May

3 May

4 May

5 May

6 May

7 May

8 May

9 May

10 May

11 May

12 May

1 o

Equip. checkout

at Barrow.

85%

2 (2) *

o

o

2

85%

TL test #1. 3 bhd.

seen near 5 nmi TL

station.

o (3) o (5) 85%

Control. obs . Plbk

cancelled - weather

& ice deteriorating.

85%

85%

#1

o

1 9 (4) o

85%. Strong winds

move pack ice

close to fast ice.

Many isolated

openings but no

leads.

Icebreaker plbk.

No whales during

plbk.

Brief control obs.

Work aborted due

to extreme winds &

unstable ice.

85%. Strong winds

move pack ice

close to fast ice.

o

2 46 (39)

93%

93%. Wide lead W

of Barrow. intermittent to E.

Elsewhere 90% pack

ice.

93%

93%

93%. Nearshore

lead closed to E,

but corridor of

97% brash ice

remains. Many N-S

tracks in pack ice.

Icebreaker plbk. 93%

Pl o

93%

1

* Numbers in parentheses indicate additional whales observed during ferry flights or at TL receiver

stations.

o (3) o (3)

Continued ...

o

o

o

o

2 P2 7 (2) 38

o
Appendix A: Field Activities 399

TABLE A-2. Continued.

Aerial Crew

Number of

Behavior

Obser.

Survey Sess. Photogr. White

Date Weather (h) (h) (h) Bowheads Whales Other

28 Apr Low overcast, occ. 2.2 0 115

light snow.

29 Apr Scat. low cloud 1.2 0.9 0.7 5 0 Obs. of presum.

and fog. undist. behav.

30 Apr Fog. Fog, no flying.

1 May Low overcast, 2.5 1.8 49 17

good vis.

2 May Fog. 0.5 0 0 Fog; aborted flight.

3 May Low overcast, 1.7 6 57

some fog.

4 May Thin fog except 1.6 0.6 7 30 Obs. of presum.

in evening. undist. behav.

5 May Mostly clear. 5.2 2 128 No whales present

during plbk.

6 May Clear with strong 3.9 1.6 11 105 Obs. of presum.

ENE winds. undist. behav. ;

abort. due to

strong wind.

7 May Low overcast after 1.0 10 0 Too windy;

10 AM. High winds. abort flight.

8 May Low overcast, 0.8 0.8 7 0

high winds, and

poor vis.

9 May Low overcast, Poor weather,

high winds. no flying.

10 May Low overcast, 3.1 0.7 32 126

high winds.

11 May Low overcast,

windy.

3.5 1.8 28 135 Cloud too low

for aerial obs.

during icebreaker plbk.

12 May Fog. 0.8 4 56 Fog; aborted

flight.

Continued ...
26 May

1 #4

1o TL test #4. Camp

on pack ice.

90%

Continued ...

Appendix A: Field Activities 402

TABLEA-3. Summary of daily activities and weather and ice conditions, 25 April-25 May 1994.

Ice-based Crew

Number' of

No. Trans. Ice

Ferry Loss Icebr. White Camp Overall Ice

Date Flights Test Plbk. Bhd. Whales Location Other Conditions

25 April 0 Equipment testing

at Barrow.

26 April 0 Logistics preparation.

27 April 0 97%. Discontinuous lead.

28 April 4 Test 0 0 71°42' Initial on-ice set up 98%. Thin refrozen cracks,

tones 155°35' and test of projection small openings SW-NE.

system, test tones

broadcast, no whales

seen.

29 April 0 98%.

30 April 0 98%. Discontinuous lead,

ENE.

I May Aborted flight due to 98%.

poor visibility.

2 May 5 Test 0 0 (3W 71°50' TL test cancelled due 99%.

tones 155°48' to concerns about

deteriorating weather

3 May 4 Tone PI 1 (1) 32 (23) 71°39' Tones 12:33-13:09. 95%. Major N-S lead with

tones 156°19' Icebreaker playback, with minor cracks running

15:12-19:20. NE-SW.

4 May Aborted flight due to 90%. Major continuous lead

poor visibility. E of Pt. Barrow along fast

ice edge, 2-3 km wide in

places, narrowing

farther E.

5 May 0 90%. Major(2 km wide)lead

E of Pt. Barrow along fast

ice edge.

6 May 0 90%.

7 May 5 Test P2 63 (8) 0 71°32' Tones 14:14-16:03. 90%. Major lead E of Pt.

tones 155°15' Icebreaker playback Barrow along fast ice edge.

16:07-20:01 from

fast ice edge.

Continued ...
Appendix A: Field Activities 403

TABLE A-3. Continued.

Aerial Crew

Number of

Weather

Survey

(h)

Behavior

Obser.

Sess.

Date (h)

Photo gr.

(h) Bowheads

White

Whales Other

25 April Low overcast Aircraft arrives at Barrow.

26 April Low overcast,

light snow, fog

Poor visibility. No flying.

Equipment set up.

27 April Low ceiling, light snow,

fog clearing in p.m.

3.7 2 Recon. flights.

28 April Overcast 2.8 o o Non-systematic survey.

Recon. flight.

29 April Low, overcast, light snow, Poor weather, no flying.

poor visibility

30 April Low ceiling, fog 2.6 l.l 11 46

visibility gradually

improving in p.m.

I May Snow, with poor visibility Poor weather, no flying.

2 May Clear in a.m., low 3.9 0 20 2nd flight aborted due to fog.

cloud in p.m.

3 May Clear with strong NE wind 4.6 4.4 13 662 Icebreaker projection

experiment.

4 May Low ceiling, fog, poor 1.3 0.8 45 Large number of bowheads

visibility migrating E, deteriorating

weather ends photo session.

5 May Low cloud, fog, freezing 1.4 2.6 57 31 Photo session in nearshore lead.

drizzle by 12 p.m.

6 May Low cloud, intermittent Poor weather, no flying.

freezing drizzle, snow

showers and fog

7 May Clear offshore in a.m., 2.9 4.9 2.4 132 7 Icebreaker projection exp.; aerial

obs. curtailed by low cloud.

Continued ...
Appendix A:. Field Activities 404

TABLEA-3. Continued.

Ice-based Crew

Number" of

No. Trans. Ice

Ferry Loss Icebr. White Camp Overall Ice

Date Flights Test Plbk. Bhd. Whales Location Other Conditions

8 May 2 24 (3) 0 (1) 71°32' Control obs. from 90%. Major lead E of Pt.

155°15' fast ice edge. Barrow.

9 May 4 P3 57 (4) 0 71°33' Icebreaker playback 90%. Major lead E of Pt.

155°12' from fast ice edge, Barrow.

14:22-17:30.

10 May 3 3 (5) 0 Unable to find suit- 85%. Pack ice against land

able ice conditions fast ice, ice conditions

for camp due to changing rapidly.

moving pack ice, no

experiment.

11 May 3 2 (1) 0 71°32' Operations aborted 85%. Discontinuous lead

155°45' when a large ice pan along fast ice edge, pans

collided with the camp in rapid motion.

floe at the projection

site.

12 May 0 85%.

13 May 0 85%.

14 May 4 Test P4 30 (9) 0 71°35' Tones (13:24-15:45) 80%. Major lead to E of

tones 154°33' and icebreaker playback Pt. Barrow along fast ice

(15:50-19:00) from fast edge.

ice edge.

15 May 0 80%. Outer2.5 km widesheet

of fast ice has broken free,

drifting off new landfast

edge, forming inner and

outer leads.

16 May 4 Test P5 4 (3) 0 71°34' Tones (12:50-12:59) 80%.

tones 155°41' and icebreaker playback

(13:03-17:13) from

"outer" lead.

17 May 4 P6 (8) 0 (5) 71°33' Icebreaker playback 80%.

154°32' from pack ice along

main lead, 12:48-17:02.

18 May 0 80%.

19 May 0 75%. Wide lead along fast

ice, numerous cracks

farther E.

Continued ...
Appendix A: Field Activities 405

TABLE A-3. Continued.

II May Clear with moderate E winds 2.2 3.9 1.2 34 o Obs. of presum. undisl. behav.

12 May Low cloud. poor visibility, Poor weather. no flying.

intermittent snow and fog

13 May Low cloud. poor visibility Poor weather. no flying.

in snow and fog

14 May Overcast. moderate E winds. 3.9 3.4 99 42 Clouds too low for aerial

low cloud obs. during plbk.

IS May Clear with strong E winds, 3.1 1.3 54 8 Obs. of presum. undist. behav.

reduced visibility in

blowing snow

16 May Clear. with light winds 4.4 3.9 48 7 Icebreaker playback expo with

pre-plbk control.

17 May Clear in a.m.• NE winds 3.7 6.6 44 7 Icebreaker playback expo with

increasing to strong. in pre- and post-plbk control.

late p.m. High sea state hampers obs.

18 May Clear with strong E winds, 0.6 4 0 Heavy winds. aborted flight.

50 kts off shore at 1500'

19 May Low cloud. poor visibility, 1.3 5 134

freezing rain

Continued ...
Appendix A: Field Activities 406

TABLEA-3. Continued.

Ice-based Crew

Number' of

No. Trans. Ice

Ferry Loss Icebr. White Camp Overall Ice

Date Flights Test Plbk. Bhd. Whales Location Other Conditions

20 May 4 P7 20 (3) 0 71°31' Icebreaker playback 80%.

155°28' from giant ice pan on

edge of large area of

open water, 12:38-17:17.

21 May 80%.

22 May 3 T.L. #1 0 21 (IS) 71°3S' Transmission loss test 75%.

155°01' completed, I I:59-16:05

23 May 0 SO%.

24 May 0 0 Pack ice drifting SO%.

rapidly, no suitable

projector site found.

25 May 4 T.L. #2 0 (2) 4 (11) 71°34' T.L. test (10:32-11 :49) SO%.

156°15' ended early due to

encroaching ice.

a Numbers in parentheses indicate additional whales observed during ferry flights or at TL receiver stations.

b Includes one dead bowhead floating amidst pack ice. Continued ...
Appendix A: Field Activities 407
Appendix B: Transmission Loss Data 408

APPENDIX B: Transmission Loss Experiment Data, 1991/94

Tables B-1 through B-4 below give the measured losses by frequency, range and source type

for the 1991 phase. Tables B-5 and B-6 give the corresponding information for the 1994 phase.

Ranges from the base camp to the hydrophone locations are given in kilometers and the depths,

where available, are given in meters. Corresponding results from four transmission loss tests in

1989 and four more tests in 1990 are given in Richardson et al. (l990a, 1991a).

Figures B-1 to B-14 summarize the transmission loss data from all four years of the project

by frequency and type of test sound, scaling the data as described. in §4.3.

Figures B-15 to B-18 show the source and receive stations during all transmission loss tests,

superimposed on newly-refined bathymetric contours.

Figure B-19 presents four samples of sound velocity profiles computed from salinitytemperature-depth casts at 1994 ice camps. The apparent trend from two-layered on 28 April to

near-isovelocity on 22 May is coincidental. Profiles from other days and locations differed from

these profiles.

TABLEB-1. Transmission loss measurements by frequency and range for the tones during test #1

on 1 May 1991.

Range (km) ~ 0.0 0.1 0.2 2.0 2.8 4.2 9.6 13.9

Depth (m) ~ 56

Frequency (Hz)

Tones 20 45 54 60 68

40 45 57 74 58 59 81

50 47 56 57 59 61 80

100 42 53 59 63 64 72 85

200 54 48 59 75 66 74 80

500 x2 57 60 67 67 80 85

1000 38 43 55 62 83 87

2000 49 37 63 66 83 87

5000 49 57 58 66 70 92 105

10000 37 48 54 65 71 91
Appendix B: Transmission Loss Data 409

TABLEB-2. Transmission loss measurements by frequency and range for the tones and icebreaker

sounds during test #2 on 18 May 1991.

Range (km) ~ 0.0 0.1 0.2 0.8 2.1 4.1 10.0

Depth (m) ~ 110.0 113.0 110.0 98.0 84.0

Frequency (Hz)

Tones 20 50 47 59

40 45 52 50 63 75

50 46 56 54 59 72

100 46 49 57 73 78

200 39 46 71 65 69

500 41 48 69 71 68

~OOO 52 55 75 71 78

2000 41 42 59 64 66 91

5000 41 54 60 66 77

10000 44 51 60 71 84

Icebreaking 10

13

16

20

25

32

40

50 45 52 53 60

63 47 56 55 63

80 46 50 55 60

100 45 48 56

125 42 45 54 58

160 44 46 63

200 43 46 64

250 42 47 57 59

315 45 47 59

400

500

630 36

800 41

1000 50

1250 55 56 45

1600 47 57

2000 59 49

2500 42 57

3150 48 55 57

4000

5000 56 54

6300 46 49
Appendix B: Transmission Loss Data 410

TABLE B-3. Transmission loss measurements by frequency and range for the tones and icebreaker

sounds during test #3 on 25 May 1991.

Range (km) ~ 0.0 0.1 0.2 0.9 2.0 3.8 9.4 13.9

Depth (m) ~ 146.0 136.0 128.0 117.0 73.0 90.0

Frequency (Hz)

Tones 20 47 51

40 41 51 54 60

50 42 54 49 64 69 75

100 40 49 48 57 66 79 104

200 43 44 57 61 63 79 104

500 57 53 51 64 68 82 103 .

1000 42 51 56 71 75 84

2000 44 44 44 67 75 73

5000 45 51 51 71 80

10000 41 44 49 62 70

Icebreaking 10

13 43

16 36

20 39

25 46 33

32 42 46 38 52

40 40 50 38 52

50 38 52 41 54

63 38 49 44 58

80 37 48 43 57 59

100 34 47 39 56 47

125 35 46 45 54 54

160 35 44 43 53 55

200 38 44 44 52 57

250 41 44 42 54

315 38 45 40 45

400 37 49 37

500 42 51

630 50 44

800 44 50 44

1000 42 50 36

1250 40 48 40

1600 39 46 43 60

2000 40 45 44 59

2500 41 44 44 62

3150 39 50 40 60

4000 45 49 42

5000 47 50 39

6300 49 46 33
Appendix B: Transmission Loss Data 411

TABLE B-4. Transmission loss measurements by frequency and range for the tones and icebreaker

sounds during test #4 on 26 May 1991.

Range (km) -7 0.0 0.1 0.2 1.0 1.6 3.4 9.2 13.7 18.9

Depth (m) -7 151.0 158.0 166.0 163.0 184.0 110.0 96.0

Frequency (Hz)

Tones 20

40 45

50 42 57 52 62 57 71

100 38 55 58 59 73 83

200 42 50 61 68 62 76 82

500 41 54 73 61 66 81

1000 40 42 66 72 92

2000 45 44 55 61 68 79 90 99

5000 43 49 64 71 88 92

10000 38 38 51 54 76

Icebreaking 10 44

13 48

16

20

25 43

32 42

40 39

50 44 52

63 41 48 55

80 39 48 55

100 38 48

125 37 47 54 61

160 36 46

200 42 44 58 61

250 48 45 58

315 39 49 55

400 39

500 34 53 59

630 36 47 53 59

800 40 52 63

1000 35 42 48 56

1250 46 41 60 57 58

1600 42 47 57 58 64

2000 44 46 57 58 64

2500 47 50 60 61

3150 45 51

4000 48 52

5000 47 50

6300 46 48
Appendix B: Transmission Loss Data 412

TABLE B-5. Transmission loss measurements by frequency and range for the tones, Karluk and

icebreaker sounds during test #1 on 22 May 1994.

Range (km) ~ 0.0 0.1 0.2 1.0 2.0 4.5 9.9 14.7

Depth (m) ~ 65.0 63.0 69.0 89.0 79.0 53.0

Frequency (Hz)

Tones 20.0 34.3 58.2 60.9

40.0 28.2 44.5 51.0 64.1

50.0 32.5 42.3 46.4 50.7 69.0 82.0 82.8

100.0 30.6 49.2 50.1 54.6 68.0 78.9 85.6

200.0 33.1 50.8 50.2 57.1 68.0 78.6 80.2

500.0 26.8 41.0 48.0 61.6 67.6 95.5 85.6

1000.0 29.0 35.9 43.7 52.0 63.8 82.6

2000.0 38.6 36.1 48.9 57.8 64.4 88.2

5000.0 36.2 43.3 53.9 58.5 70.0

10000.0 25.7 29.8 61.9 66.9

Karluk 10.0 15.2 23.6 36.0

12.5 19.4 27.8 40.2

16.0 21.1 31.1

20.0 24.3 32.9

25.0 37.4 41.9 43.5

31.5 38.0 44.2 50.0 43.7

40.0 39.8 42.5 46.4 54.4

50.0 43.0 43.2 46.8 52.1

63.0 42.4 43.6 51.3 52.5 69.3

80.0 39.3 44.6 55.1 56.4 69.9

100.0 38.4 46.2 48.0 55.9 68.3 74.9

125.0 39.1 52.3 50.3 56.3 70.1

160.0 40.8 44.0 51.0 62.4 66.0

200.0 41.8 46.4 51.3 55.1 67.7

250.0 39.9 44.6 59.8 52.9 64.8 74.5

315.0 39.7 43.6 53.3 54.4

Icebreaking 10.0 20.3 28.1 38.8 33.3

12.5 25.6 31.3 27.9 36.4

16.0 30.9 36.9 28.2

20.0 40.3 43.9 47.6 48.3

25.0 38.1 42.3 52.3 50.4 54.8

31.5 36.5 43.8 49.5 50.7 62.9

40.0 37.8 42.7 47.1 51.6

50.0 39.0 42.0 44.8 49.8

63.0 41.9 43.0 52.1 51.4 67.3

80.0 40.1 43.4 57.3 53.7 67.4

100.0 38.7 46.3 46.7 51.5 63.4

125.0 38.0 51.8 49.5 53.7 70.4

160.0 39.3 40.8 48.5 60.8 64.2

200.0 39.9 44.3 49.5 52.3

250.0 37.3 42.9 55.4 49.4 60.9

315.0 36.8 41.7 53.9 52.3

400.0 36.9 40.5 51.6 54.3

500.0 36.6 39.5 49.1 55.7

630.0 33.8 37.4 46.8 46.8

800.0 32.2 40.9 46.7 47.9

1000.0 28.6 39.2 42.0 47.5

1250.0 27.9 30.9 44.9 47.3

1600.0 30.5 37.3 47.6 50.1

2000.0 30.8 33.8 44.9
Appendix B: Transmission Loss Data 413

TABLE B-6. Transmission loss measurements by frequency and range for

the tones, Karluk and icebreaker sounds during test #2 on 25 May 1994.

0 0.1 0.2

178

48.9

39.7 51.4

35.1 45.4

32.6 38.2

35.3 34.9

40.5 36.7

Range (km) -7

Depth (m) -7

Frequency (Hz)

Tones 20.0

40.0

50.0

100.0

200.0

500.0

1000.0

2000.0

5000.0

10000.0

Karluk 10.0

12.5

16.0

20.0

25.0

31.5

40.0

50.0

63.0

80.0

100.0

125.0

160.0

200.0

250.0

315.0

52.5

53.6

52.7

45.8

40.8

36.7

35.8

33.6

Icebreaking 10.0

12.5

16.0

20.0

25.0

31.5

40.0

50.0

63.0

80.0

100.0

125.0

160.0

200.0

250.0

315.0

400.0

500.0

630.0

800.0

1000.0

1250.0

1600.0

2000.0

44.8

41.1

39.3

38.0

38.2

36.2

53.5

53.2

51.7

45.6

39.9

36.4

33.8

31.7

37.8

41.2

42.1

41.6

39.7

37.9

37.4

33.0
Appendix B: Transmission Loss Data 414

-20

-10

0

10

iD 20

~

30 6'

0;

0 40

C5

C\J

en 50

Ul

....J 0

60

70

80

90

100

1

FIGURE B-l.

-®- 1989 Test #2

~ 1989 Test #3

-Q- 1989 Test #4

--+- 1989 Test #5

---I- 1990 Test #1

~ 1990 Test #2

---'-- 1990 Test #3

-

1990 Test #4

- 1991 Test #1

-4- 1991 Test #2

---A- 1991 Test #3

----v- 1991 Test #4

-e-- 1994 Test #1

Model

10 100 1000

R/2D

TL-20l0g(D) vs. scaled distance for the 50 Hz tones measured during transmission loss tests.

-20

-10

0

10

iD 20

~

30 6'

0;

0 40

C5

C\J

I

Ul 50

Ul

....J 0

60

70

80

90

100

1

---%-- 1989 Test #3

~ 1989 Test #4

-Q- 1989 Test #5

--+- 1990 Test #1

---I- 1990 Test #2

~ 1990 Test #3

---'-- 1990 Test #4

-

1994 Test #1

...... Model

10 100 1000

R/2D

FIGURE B-2. TL-20l0g(D) vs. scaled distance for the 50 and 63 Hz 1/3 octave band levels of Karluk drilling sounds

measured during transmission loss tests.
Appendix B: Transmission Loss Data 415

-20

-10

0

10

CO 20

~

30 0-

0;

0 40

C5

C\J

en 50

so

...J0

60

70

80

90

100

1

FIGUREB-3.

-0- 1989 Test #4

---€9- 1989 Test #5

---a-- 1990 Test #1

-.- 1990 Test #2

-+- 1990 Test #3

~ 1990 Test #4

...... Model

10 100 1000

R/2D

TL-20l0g(D) vs. scaled distance for the 50 Hz FM sweeps measured during transmission loss tests.

-20

-10

0

10

co 20

~

30 0-

0;

0 40

C5

C\J

I

rJ) 50

rJ)

...J0

60

70

80

90

100

1

FIGUREB-4.

-0- 1989 Test #2

---€9- 1989 Test #3

---a-- 1989 Test #4

-.- 1989 Test #5

-+- 1990 Test #1

~ 1990 Test #2

~ 1990 Test #3

-

1990 Test #4

- 1991 Test #1

---4- 1991 Test #2

-£.- 1991 Test #3

-V- 1991 Test #4

~ 1994 Test #1

Model

10 100 1000

R/2D

TL-20l0g(D) vs, scaled distance for the 100 Hz tones measured during transmission loss tests.
Appendix B: Transmission Loss Data 416

-20

-10

0

10

iii 20

~

30 5'

0;

0 40

C5

C\J

en 50

If)

....J 0

60

70

80

90

100

1

----@- 1989 Test #3

---@- 1989 Test #4

---G- 1989 Test #5

--+- 1990 Test #1

--+- 1990 Test #2

~ 1990 Test #3

-"'-- 1990 Test #4

-

1994 Test #1

...... Model

10 100 1000

R/2D

FIGURE B-5. TL-20log(D) vs. scaled distance for the 100 Hz 1/3 octave band levels of Karluk drilling sounds

measured during transmission loss tests.

-20

-10

0

10

iii 20

~

30 eO>

0 40

C5

C\J

en 50

If)

....J 0

60

70

80

90

100

1

FIGURE B-6.

----@- 1989 Test #4

---@- 1989 Test #5

---G- 1990 Test #1

--+- 1990 Test #2

--+- 1990 Test #3

~ 1990 Test #4

...... Model

10 100 1000

R/2D

TL-20log(D) vs. scaled distance for the 100 Hz PM sweeps measured during transmission loss tests.
-20

-10

0

10

m 20

~

30 0-

c;

0 40

C5

C\I

I

IfJ 50

IfJ

....J 0

60

70

80

90

100

1

FIGURE B-7.

Appendix B: Transmission Loss Data 417

-20

-10

0

10

m 20

~

30 0-

c;

0 40

C5

C\I

en 50

IfJ

....J 0

60

70

80

90

100

1

FIGURE B-8.

---®- 1989 Test #2

~ 1989 Test #3

---Q- 1989 Test #4

--+- 1989 Test #5

--+- 1990 Test #1

~ 1990 Test #2

--L-- 1990 Test #3

-

1990 Test #4

- 1991 Test #1

----4- 1991 Test #2

-A- 1991 Test #3

--¥- 1991 Test #4

-e- 1994 Test #1

Model

10 100 1000

R/2D

TL-20l0g(D) vs. scaled distance for the 500 Hz tones measured during transmission loss tests.

10 100

---®- 1989 Test #4

~ 1989 Test #5

---Q- 1990 Test #1

--+- 1990 Test #2

--+- 1990 Test #3

~ 1990 Test #4

...... Model

1000

R/2D

TL-20l0g(D) vs. scaled distance for the 500 Hz PM sweeps measured during transmission loss tests.
Appendix B: Transmission Loss Data 418

-20

-10

0

10

iIi' 20

:s.

30 0-

C;

0 40

C5

C\J

50 I

en

en

...J0

60

70

80

90

100

1

FIGURE B-9.

----0--- ~989 Test #2

~ 1989 Test #3

---G-- 1989 Test #4

--+- 1989 Test #5

--+- 1990 Test #1

~ 1990 Test #2

~ 1990 Test #3

-

1990 Test #4

- 1991 Test #1

---4-- 1991 Test #2

----A- 1991 Test #3

----¥- 1991 Test #4

-e-- 1994 Test #1

Model

10 100 1000

R/2D

TL-20log(D) vs. scaled distance for the 1000 Hz tones measured during transmission loss tests.

-20

-10

0

10

iIi' 20

:s.

30 0-

C;

0 40

C5

C\J

50 I

en

en

...J0

60

70

80

90

100

1

FIGURE B-1 O.

----0--- 1989 Test #4

~ 1989 Test #5

---G-- 1990 Test #1

--+- 1990 Test #2

--+- 1990 Test #3

~ 1990 Test #4

...... Model

10 100 1000

R/2D

TL-20log(D) vs. scaled distance for the 1000 Hz FM sweeps measured during transmission loss tests.
Appendix B: Transmission Loss Data 419

-20

-10

0

10

1D 20

~

30 5'

C;;

0 40

0

C\J,

en 50

en

....J 0

60

70

80

90

100

1

FIGURE B-l1.

-®- 1989 Test #2

-@- 1989 Test #3

---G- 1989 Test #4

--+- 1989 Test #5

-+-- 1990 Test #1

~ 1990 Test #2

---'-- 1990 Test #3

-

1990 Test #4

- 1991 Test #1

----4- 1991 Test #2

-A- 1991 Test #3

-¥- 1991 Test #4

-e- 1994 Test #1

Model

10 100 1000

R/2D

TL-20log(D) vs. scaled distance for the 2000 Hz tones measured during transmission loss tests.

-20

-10

0

10

1D 20

~

30 5'

C;;

0 40

0

C\J

en 50

en

....J 0

60

70

80

90

100

1

FIGURE B-12.

10 100

-®- 1989 Test #4

-@- 1989 Test #5

---G- 1990 Test #1

--+- 1990 Test #2

-+-- 1990 Test #3

~ 1990 Test #4

...... Model

1000

R/2D

TL-20l0g(D) vs. scaled distance for the 2000 Hz FM sweeps measured during transmission loss tests.
-20

-10

0

10

iii 20

::£.

30 5'

0;

0 40

C5

C\l

I

CIl 50

CIl

...J0

60

70

80

90

100

1

FIGURE B-13.

-20

-10

0

10

iii 20

::£.

30 e:

O'l

0 40

C5

C\l

en 50

CIl

...J0

60

70

80

90

100

1

FIGURE B-14.

Appendix B: Transmission Loss Data 420

-®- 1989 Test #2

~ 1989 Test #3

---G-- 1989 Test #4

--+- 1989 Test #5

---+- 1990 Test #1

~ 1990 Test #2

~ 1990 Test #3

-

1990 Test #4

- 1991 Test #1

---4- 1991 Test #2

-----£r- 1991 Test #3

~ 1991 Test #4

----e-- 1994 Test #1

Model

10 100 1000

R/2D

TL-20l0g(D) vs. scaled distance for the 5000 Hz tones measured during transmission loss tests.

10 100 1000

-®- 1989 Test #4

~ 1989 Test #5

---G-- 1990 Test #1

--+- 1990 Test #2

---+- 1990 Test #3

~ 1990 Test #4

...... Model

R/2D

TL-20l0g(D) vs, scaled distance for the 5000 Hz FM sweeps measured during transmission loss tests.
Appendix B: Transmission Loss Data 421

157 156 155

"

" ....... ----.>-,

....•........•.. <;

I

"j '89

I

-.' "\\"-'"

:. \ i

, \

I

i

i

i

i

\

\gOO

72 ....+ 72

"

:0.---- -"-"

7130

o 5 10nm

'.

•.•..•..•.

-,

".

"

...•...•.

·········.01; 10

m__

o 5 10m

+

o 5 10km m•• - 71

..........

······5 m··········

157 158 155

FIGURE B-15. Locations of four transmission loss tests in 1989. Solid symbols are the transmit

stations on 30 April and 2, 9 and 25 May 1989. Corresponding open symbols are the more

distant receive stations.
Appendix B: Transmission Loss Data 422

157 156 155 154

....

. .

'.

~ .

".

~~--.....

7130

, \ <:_~:~~?s~:~~\~:<~;:~:~:::_J '90 T'a"'·~oss~\:tsl

"'~'-\:""-'-':!''''I') '\) , \\),'::: ::."

<. \... ••••••••••••••••••••••••••••••••• ~•••••\. • ·.\i " '. ~':\ . '.>0

0

-, ' -, , '<. -, /1 :'"~--:'\.\ •••••.••••••.••••••. i ::i I)' \ • v : ..•

"'" .,.,............ // i \,i -,, \.) \ ./ \.~~~:~::~g:?>._-,.:<:;,./\"<'::::.

,'--- >' r i / " ' \":>:>,. '''00 »:

,: ,/ ..---------'., -: (~.:.: .<--.~><~.~ <. .:: [ ".. ' ";'0 .Joo "'"

J ~ ~);/ ".'" .;. \ -, ••. , -; "'80~'" ~$o 1'1>"

•• L>/ <;'/ /:~:,+:~~".::-/--~~.~~s::> ../<~;;:~~~

/ /

/

./

71 30 ..' -1;"+

s....•....~..~.. -- <.

-------..

-,

•••• "<0 I/)

\. "-

72

..............................

'"

~~ .....

.... •. .

'" -,

~ •...........

'\; ....

"

;...•..•.•....•. -v., .•.•..•••.

r.

<,

-- .

'•................

-;

------~..

o 5 10nmi

<,

'. .

..... .. .

Landtast 'tca. Edge

---·-----·- •... 15 m __

........'.······.0\; .•....... 10 m •• - 71

o 5 10 mi

+

o 5 10 km

····················5 m

157 156 155 154

FIGURE B-16. Locations of four transmission loss tests in 1990. Solid symbols are the transmit

stations on 1, 2, 24 and 25 May 1990. Corresponding open symbols are the more distant

receive stations.
Appendix B: Transmission Loss Data 423

7130

m

72 72 +

".

.. " /

"'. "

"'. "

'. \

::'/./

,

,

,

,

,

,

:-_.-.-.-

,

i

/

/

./

-/:.' 7130

................................ ~ m'"

155

FIGURE B-17. Locations of four transmission loss tests in 1991. Solid symbols are the transmit

stations on 1, 18, 25 and 26 May 1991. Corresponding open symbols are the more distant

receive stations.
Appendix B: Transmission Loss Data 424

157 156 155

72

'. +

".

o 5 lOnmi ~.'.-,

'"

-------.- •• 15 m ..

7130

o 5 lOmi

+

o 10 km ········."' ••••••••• 10 rnv-- 71

157 156 155 154

FIGURE B-18. Locations of two transmission loss tests in 1994. Solid symbols are the transmit

stations on 22 and 25 May 1994. Corresponding open symbols are the more distant receive

stations. The 25 May 1994 test was limited to short ranges.
0 0

10 10

20 20

~ -l!!

*

(J)

a;

e 30 e 30

s: .c

a. a.

(J) (J)

0 0

40 40

20 20

~

-l!!

*

(J)

a;

e 30 e 30

.c .c

a. a.

(J) (J)

0 0

40 40

60 Wa~~b~\~:2:{l~1~ Lo~~t:1~~:~r:r. 60 ~a~~b~\~?lg:~6 LOL;t:1~l:~~:

1420 1430 1440 1450 1420 1430 1440 1450

SoundVelocity(Meters/Second) SoundVelocity(Meters/Second)

FIGURE B-19. Sound velocity profiles for four days in AprillMay 1994.

50

28Apr 94 14:55:26 Lat: 71042'

60 WaterDe th: 66 m Lon: 155035'

1420 1430 1440 1450

SoundVelocity(Meters/Second)

10

50

Appendix B: Transmission Loss Data 425

50

03 Ma'{94 13:13:25 Lat 71039.47'

60 WaterDe th: 105m Lon; 156015.49'

1420 1430 1440 1450

SoundVelocity(Meters/Second)

10

50

•
Appendix C: Sonobuoy Impact Sound 426

APPENDIX C: Sonobuoy Impact Sound

Introduction

An ice camp was established on 29 May 1989, latitude 71 °41.1 'N, longitude 154°51.7'W,

water depth 90 m, to conduct a sound playback experiment. The project's Twin Otter aircraft

deployed a sonobuoy at a distance of 800 m from the ice camp. Although the ice camp was on

the edge of an ice floe, there was a reasonably ice-free path between the sonobuoy impact point

and the ice camp. The sound of the water impact was recorded from hydrophones at depths 3 and

18 m. The playback experiment was in progress, so strong sounds of the drillsite Karluk were

being projected from the J-l1 projector at depth 18 m, distance 2-3 m from the 18 m hydrophone.

The sonobuoy impact sound is of interest because, on rare occasions, bowhead whales were

seen to react when a sonobuoy was deployed in their vicinity (Richardson et al. 1990a:212).

Methodology

The sounds detected by the 3- and 18-m deep hydrophones (ITC model 6050C) were recorded

on a Sony model TCD-5M audio cassette recorder. The recordings were analyzed with

Greeneridge's PC-based analog-to-digital converter and analysis software.

The Karluk playback sounds dominate the recordings over the low frequency range up to

-500 Hz. Although the "slap" sound of the buoy impact can be heard in the presence of Karluk

sounds, the acoustic pressure peaks of the impact cannot be discerned in time series graphs of the

broadband sounds. Therefore, the recordings were high-pass filtered at 1 kHz before digitization

and analysis. The sampling frequency was 32,768 Hz.

Results

Figure C-l contains plots of times series for the impact sounds received at the 3- and 18-m

deep hydrophones. Each hydrophone received two pairs of pulses. No sound velocity profile was

measured at the measurement site, but profiles measured in the same area in late May five years

later, with similar ice conditions, were essentially isovelocity at 1435 m/s. Each pair of arrivals

consists of an upward-traveling sound followed by a surface-reflected sound. In the 3-m

hydrophone signal, the arrivals in each pair are closer than they are in the 18-m hydrophone signal,

as expected. The signals are stronger at the 18 m depth, which is accounted for by surface-release

effects.

It is informative to calculate the sound ray arrival angles for the signals at the two

hydrophones. The calculation is based on measuring the travel-time difference between the direct

and surface-reflected arrivals and assuming parallel rays (plane waves). Assuming a sound

velocity of 1435 mls and that the measured hydrophone depths were accurate, the arrival angles

(below horizontal) for the first pair of arrivals are 14° for the 3-m hydrophone and 13.3° for the
Appendix C: Sonobuoy Impact Sound 427

Sonobuoy Drop @ 14:40 on 29 May 89, 3m Hydrophone, HP=1 KHz

100

90

80

70

60

50

40

Ii) 30

~ 20

fIl 8!. 10

-Q) 0

:5 -10

~ -20 Q)

c: -30

-40

-50

-60

-70

-80

-90

-100

o 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1

Time (Seconds)

"

" "

A.

~" p"

'I 'I

Sonobuoy Drop @ 14:40 on 29 May 89, 18m Hydrophone, HP=1 KHz

100 8

90 .

80

70

60

50

40

Ii) 30

~ 20

fIl 8!. 10

- 0 +M/f>J'M,w.l\IV-I'MAIII'iAP Q) :5 -10

~ -20 Q)

c: -30

-40

-50

-60

-70

-80

-90

-1 0 0 -'h-r,.,.,..,.,"'I'TTTTTTT'1r'TTTT'I"'l'TT',.,.,..,.,TT'T"l''I"'l'TT'!"TT!''1,.,.,....,"'I'T'TT'I"'l'TT',.,.,..,.,TT'T"l''I"'l'TT'I'TT'M''I"'l'TT'l''M'TT.,..,....,..........,.,..,....,..~

o 0.01 0.02 0.03 0.04 0.·05 0.06 0.07 0.08 0.09 0.1

Time (Seconds)

FIGURE C-l. Sonobuoy impact sound as received at two hydrophones 800 m from the impact. The

sound was high-pass filtered at 1000 Hz to reject strong local interference (see text). (A) is for

depth 3 m and (B) is for depth 18 m.
Appendix C: Sonobuoy Impact Sound 428

18-m hydrophone. The corresponding angles for the second pair of arrivals are 26.1 ° for the 3-m

hydrophone and 25° for the 18-m hydrophone.

The simplest model for sound propagation is straight rays over the 800-m path, water depth

90 m, from the surface to the surface (a better approximation for the 3-m hydrophone than for the

18-m hydrophone). A direct (non-reflected) ray is not likely in isovelocity water. For the model

(Fig. C-2), a single bottom bounce ray arrives at an angle of 12.7° and a two-bottom-bounce ray,

including a surface reflection, arrives at an angle of 24.2°. The measured angles are -14° and 26°,

which are slightly larger than the predicted arrivals for the straight-line rays. Slight upward

refraction would account for the slightly larger angles.

s 800m R

90m

FIGURE C-2. Sound ray path model.

The geometric path length difference for the straight one- and two-bottom bounce rays,

surface source to surface receiver, is 57.27 m. At 1435 mis, 57.27 m corresponds to 40 ms; the

measured time difference for the 3-m hydrophone is 44 ms and for the 18-m hydrophone, 42 ms.

Small errors in sound speed, distance and water depth may account for the discrepancy.

Given the assumptions of accurate knowledge of water depth, hydrophone depths, sound

speed and range from hydrophones to sonobuoy splash, the one- and two-bottom bounce hypothesis

is plausible. A very weak signal may be seen at arrival times expected for a three-bottom bounce

ray path. Its arrival angle, assuming the straight-line model, would be 34°. Such a steep angle

ray may not be reflected well from the bottom, accounting for its weak presence in the received

signal signature.

Figure C-3 presents an expanded graph of the pressure amplitude signal in the first (single

bottom bounce, no surface reflection) arrival at the 18-m hydrophone. The acoustic impulse,

calculated for the positive portion of the received pulse, is 0.00694 Pa-s (the positive signal

duration is 0.26 ms). The peak pressure in this signal is 47 Pa, which corresponds to an acoustic

peak pressure source level of 212 dB re 1 IlPa-m assuming spherical spreading over a distance of

800 m. The acoustic impulse at distance 1 m from the source (assuming no positive pulse

spreading and simply scaling the pressure for spherical spreading) is estimated to be 5.55 Pa-s.

This is a very low value. The impulse from a 1 g TNT explosion underwater at depth 1 m, range

1 m, is calculated to be 61 Pa-s (Greene and Moore in press). Also, the rise time for the explosion

would be orders of magnitude shorter than for a sonobuoy impact.
Appendix C: Sonobuoy Impact Sound 429

100 Sonobuoy Drop@ 14:40 on 29 May 89, 18m Hydrophone, HP=1 KHz

90

80

70

60

50

40

en 30

C'Cl (,) 20

(J)

C'Cl 10 a.

-; 0

:5 -10

~ -20

Q)

0: -30

-40

-50

-60

-70

-80

-90

-100+--,.--.,.--.,...--r---r---r---,--r-------.-----.----,..---.----=I

o

I

0.00694 Pascal Seconds

0.0002 0.0004 0.0006 0.0008

Time (Seconds)

0.001 0.0012

FIGURE C-3. Pressure-time signature of the single bottom bounce ray arrival at the 18-m

hydrophone.

Figure C-4 presents waterfall spectrograms for the sonobuoy impact sound at the two

hydrophones. Recall that the signals were high-pass filtered at 1 kHz before being sampled to

reject most of the Karluk playback sounds present in the recording. The discrete Fourier transform

length for these waterfalls is 256 samples, corresponding to a frequency bin spacing of 128 Hz and

a bin width (frequency resolution) of 218 Hz. A high degree of overlap between transforms

provides a waterfall display with relatively gradual changes with time, although the lengths of the

signal pulses are very short.
Appendix C: Sonobuoy Impact Sound 430

8000

P08M0175.L16 29 May 89 14:40 Sonobuoy Drop. 3m Hydrophone, High Pass = 1000 Hz

I

6000

2000

o 'I ----,-----,-----,-----,--------,-------,-----,-----,

o

I

0.0257

I

0.0515

Time (s)

I

0.0772

I

0.103

P08M0175.R16 29 May 89 14:40 Sonobuoy Drop, IBm Hydrophone, High Pass = 1000 Hz

o 'I ----,.----,.----,.----,------,------.,.-----.,.--------,

o

1

0.0257

I

0.0515

Time (s)

I

0.0772

I

0.103

FIGURE C-4. Waterfall spectrograms for the pressure signatures at the two hydrophones. (A) is

for depth 3 m and (B) is for depth 18 m.
Appendix D: Bowhead Distribution Maps, 1989-90 431

APPENDIX D: Bowhead Distribution Maps, 1989-90

Appendix D shows all bowhead sightings during the present study by 10- or ll-day period

in the springs of 1989 and 1990 (four maps per year). Each map shows all bowheads detected by

observers in the Twin Otter aircraft (hatched symbols) and by observers in the helicopter or on the

ice (open symbols). Mother-calf pairs of bowheads are shown with double circles. Headings

toward which the whales were oriented when first seen are also shown.

Note that all search effort was non-systematic. The amount of effort varied greatly among

different parts of the mapped area within any given 10- or l l-day period. The distribution of

search effort also varied from one 10- or ll-day period to the next. The designated locations of

the landfast ice edge are approximate.

Corresponding sighting maps for the 1991 and 1994 phases of the project appear in section

5.1 of this report.
157

Appendix D: Bowhead Distribution Maps, 1989-90 432

156 155

,

,

,

,

,

,

\

" -,

...•......... ~.•

'\

+ \, /'---------'\

.•....•..••"•.. ";' \..••.

--------'\,

,

,

,

,

,

"

••••.•••• _ •• _J

/,---+

.............. "

('

.:

.--

,...,....

....... "" .... ,'

.>

1130 _/ +

(/---

12

+

.•..._-

o 5

.-.-._.__ ._._ ....•..

'.,

\

\

\-.-,

"

Bowhead Whales

April 1989

@ Twin Otter

o Ice Camp/Helicopter

@ Cow/Calf, Twin Otter

o 5 lOmi

+

o 5 lOkm

+

.......•....-,•..••..

\

i

i

i

i

i

\.

,

\.,

i

./

/.,.

12

1130

···················-+. 10 m······· 11

FIGURE D-l. LGL sightings of bowhead whales, late April 1989. Symbol type distinguishes sightings by the two crews, sightings of 1-2 vs. >2 bowheads, and sightings of mother/calf pairs vs.

other bowheads. Headings toward which the whales were oriented when first seen are also shown

when available. Survey effort was not uniform across the area mapped.

157

-.

,

\

\

\

\

"'\

"

"

" .

'<00

//--------~--------~---,.,-,, ~-

,..•....-

o /'----

.---

--- .>

//

/-------------------- ---------- ~-.--

i +

--_ .., .

+

o

+

:' )

<;.....

-,

Landfasl Ice Edge '

-<0 ~_

......

+ +

lOnmi

156 154 155
Appendix D: Bowhead Distribution Maps, 1989·90 433

157 156 155

Bowhead Whales

72

1-10 May 1989

@ Twin Otter

o Ice Camp/Helicopter

@ Cow/Calf, Twin Otter

72 +

',--, ,

\

i

\

"'\

\

\

"

"

.' .

'~oo

//-------------------1: -c., "", 111_

,,/; ••..••~ v,

60 ;/ ~-

-- --

/, »>:

-~_/

/------------------- .-~,.....,~-

;, ••..." +

,•..•..-----_ -•..

•..•..•..' .,., - '

.>:, .

.»',. - '

...._-_ •..

+ +

+

+ 7130

-,

.....

.........

.....

~

.

.....

....

.............

.......

Landtasl Ice Edge -

·~O 111•

o

154

..... +

...

- + n

···········10 m········

5

o 5 lOmi

+

o 5 10 km

157 156 155

FIGURE D-2. LGL sightings of bowhead whales, 1-10 May 1989. Symbol type distinguishes sightings by the two crews, sightings of 1-2 vs. >2 bowheads, and sightings of mother/calf pairs vs.

other bowheads. Headings toward which the whales were oriented when first seen are also shown

when available. Survey effort was not uniform across the area mapped.
,

,

,

\

'-,

<,

.•.....•.•....• \~

\

+ \ ,",.. ...-...----- "<,",

, ,

-, ~ \ -,

-------\\

,

,

_... -_J "-

...•........•.

" +

.:

,,'

.' "

/,' .:

.>

7130 .>

.:

Appendix D: Bowhead Distribution Maps, 1989-90 434

'156 155

.-.-'-'-_._._._.,\

\

\

-..,.••..

Bowhead Whales

11·20 May 1989

@ Twin Otter

o Ice Camp/Helicopter

@ Cow/Call. Twin Otter

"-

72

<.

"\/L....~ ----,,....- --.J

i

i

i

e \.

=-

72 + ,

\.,

/

./

"

"',

i

\

\

\

\

\

"

"

"

'.'<loa ",-

+

7130

e

'60 ",

----

+ +

.•...,.•........_-

...._-_ ..

-----_ .....-"

.>

..... ' .~- ....- ~- - .

.'

--,,,,,,""

Landlaet Ice Edge -

. <lo "'.

~ .............................

+

.........................

o 5 lOnmi

o 5 10m

+

o 5 lOkm ..+. ···· 10 m········ 71

157 154 156 155

FIGURE D-3. LGL sightings of bowhead whales, 11-20 May 1989. Symbol type distinguishes

sightings by the two crews, sightings of 1-2 vs. >2 bowheads, and sightings of mother/calf pairs

vs. other bowheads. Headings toward which the whales were oriented when first seen are also

shown when available. Survey effort was not uniform across the area mapped.
Appendix D: Bowhead Distribution Maps, 1989-90 435

157 154 156 155

'-.

-._._._. __ ....•.-,

"

\

\

-,

'.,..•...

Bowhead Whales

21-30 May 1989

@ Twin Otter

o Ice Camp/Helicopter

@ Cow/Calf, Twin Otter

<,

-,

/L-~~~_----, ---J

i

\

i

-,

72 72 +.

"\.,

i

./

»:

-.,

i

\

\

\

\

\

"

"

-,

"<00

_" ••'------- 11J_

------t '"". .

:" .. .

+ +

'60 ",----

e .._

+ 7130

~ .....

'"

Landlast Ice Edge '

'<0 ""

".

. .

+.

o 5 lOnmi

o

=-

lOmi

..................

+. ..... +. ···· 10 m······· 71 o

5

5 10 km

157 154 156 155

FIGURE D-4. LGL sightings of bowhead whales, 21-30 May 1989. Symbol type distinguishes

sightings by the two crews, sightings of 1-2 vs. >2 bowheads, and sightings of mother/calf pairs

vs. other bowheads. Headings toward which the whales were oriented when first seen are also

shown when available. Survey effort was not uniform across the area mapped; the most intense

effort was in the nearshore lead just north of the landfast ice.
Appendix D: Bowhead Distribution Maps. 1989-90 436

157 154 156 155

--"

-. __ ._-- -c.,

'.\

\

\

\..

•....,....

Bowhead Whales

April 1990

@ Twin Otter

o Ice Camp/Helicopter

@ Cow/Calf, Twin Otter

<,

".

'\

I

i

i

i

i

\

72 +

-,

\

i

\

\

\

\

\

".

,

'"'~oo

111_

+ +

$. @.. •.. "."

+

.,,30

....._-

o 5 10nmi

Landfasl Ice Edge

.+ ···········10 m .."

o 5 10m

+

o 5 lOkm

157 154 156 155

FIGURE D-5. LGL sightings of bowhead whales, late April 1990. Symbol type distinguishes sightings by the two crews, sightings of 1-2 vs. >2 bowheads, and sightings of mother/calf pairs vs.

other bowheads. Headings toward which the whales were oriented when first seen are also shown

when available. Survey effort was not uniform across the area mapped; the most intense effort was

in the nearshore lead just north of the landfast ice.
Appendix D: Bowhead Distribution Maps. 1989-90 437

157 156 155

Bowhead Whales

72 72

"'\

,

,

,

,

\

'-,

...•.......

.•.....•.... "

+ \ /--------"",

-,.•...............• " \-,

-------)

•..

"

-_ ..--~ /,---;-

..-...-,,,,

(".-"

t

,--

....-....

'-._._.__ ._._ ,.

,

\

\

-,

.,'•...•..•.•..

1·10 May 1990

@ Twin Otter

o Ice Camp/Helicopter

@ CowfCalf, Twin Otter

+

<,

-.

/l---c-----...,,-------!

i

i

i

\

,

\

.,

i

/

+ +

+ 7130

.•..•._- ...•.

0",.

o 5 lOnmi

o 5 lOmi

+

o 5 10 km

......., .., +. 71

··········10 m········

157 156 155

FIGURED-6. LGL sightings of bowhead whales, 1-10 May 1990. Format as in Fig. D-5.
7130

Appendix D: Bowhead Distribution Maps, 1989-90 438

157 154 156 155 '-'-

-._._.-.•••..

'.,

\

\

\

<,

"

Bowhead Whales ,

,

,

,

\

'-' -,

---.....•.,..

-\

\

+ \\ ; _---,,\

.•/ \

.....•••.•..•..•...•. \"' ..•

-------\\

,

,

,

-,

.•..•..•.....•.--_ ...-.•.-~

.•...."_ .•..•." +

/',/

,.•."."

.>:

.>

.:

// +

11-20 May 1990

~ Twin Otter

o Ice Camp/Helicopter

@ Cow/Calf, Twin Otter

72 72· + ,

\.

,

/

/

-:

+ +

7130

'--~

0,,>_

0 5 10nmi

0 5 10 mi

+

0 5 10 km

A

157 155 154

FIGURE D-7. LGL sightings of bowhead whales, 11-20 May 1990. Format as in Fig. D-5.
Appendix D: Bowhead Distribution Maps. 1989-90 439

157 156 155 154

72

,

,

,

,

,

,

--'-

+

-c

-.,

i

\

\

\

\

\

",

,

<.

'<00

111_,

72

-_.- -..•••..

"

,

\

\

'",.,..•..

Bowhead Whales

@

@

21-26 May 1990

@ Twin Otter

o Ice Camp/Helicopter

@ Cow/Calf, Twin Otter

+

+ 7130

-,

'-.--=

'co 111.

'"

.•..~ ....

. .

o 5 10nmi

'"

.... , ••••••• lee ,,,.

o 5 10mi

+

o 5 10 km "'+' ""'''',10 m""'" 71

157 156 155 154

FIGURED-8. LGL sightings of bowhead whales, 21-26 May 1990. Format as in Fig. D-5.
TABLE E-l. Details of NMML's 1989 between-year resightings of bowheads, various origins and years, to MMS study area, spring 1989.

Originally listed (with less detail) in Koski et al. (1992).

Calf Present

First Photographed Resighting at Barrow Length in

Source Year of

of Whale Resighting First >

Photos' Number Year Date Loc'n" Latitude Longitude Date Latitude Longitude (m) Sighting Resighting ~

~

t!j

LGL-NMML 4 1981-89 I Aug NCA -71°18.0'N -121°48.0'W 7 May 7Io35.6'N 156°23.I'W 15.8' no no Z

LGL-NMML 8 1981-89 I Aug NCA -71°18.0'N -121°48.0'W 2 May 71°39.2'N 155°25.TW 13.6 no no e

LGL-NMML 49 1981-89 II Sep FB 70039.2'N 127°42.3'W 29 Apr 71°36.6'N 155°36.9'W 14.1 no no ~

~

LGL-NMML 1057 1982-89 16 Aug HI 69°48.5'N 138°50SW 17,18 May 7Io36.6'N 155°17.5'W 15.0 no no t!j

LGL-NMML 1112 1982-89 16 Aug HI 69°48.5'N 138°49.I'W 27 May 71°37.0'N 155°33.3'W 15.8 no no

LGL-NMML 1131 1982-89 16 Aug HI 69°47.6'N 139°48.8'W 2 May 71°39.5'N 155°25.3'W 11.6' no no

LGL-NMML 1483 1982,89 24 Aug DS 70029.8'N 136°45.9'W 25 May 15.1 yes yes t:=

LGL-NMML 1576 1982-89 4 Sep HI 70008.5'N 139°06.2'W 21 Apr 71°30.3'N 156°01.0'W 11.8' no no 0

LGL-NMML 1617 1982-89 5 Sep IF 69°39.2'N 138°01.5'W 17 May 71°34.8'N 155°53.3'W 14.0 no yes ~

=-

LGL-NMML 1576 1984-89 2 Sep KP 69°22.5'N 138°41.8'W 21 Apr 71°30.3'N 156°01.0'W 11.8' no no

~

~

LGL-NMML 4020 1984-89 16 Aug IF 69°24.8'N 137°12.3'W 6 May 71°38.5'N 155°59.0'W 13.8 no no C.

LGL-NMML 4735 1984-89 2 Sep IN 70027o4'N 135°28.5'W 26 Apr 71 °47.5'N 154°30.I'W 13.7' no no

~

NMML-NMML 2246 1985-89 26 May BR 71°2304'N 156°39.I'W 6 May 71°38.6'N 155°58.8'W 14.1 no

~ no fIl

NMML-NMML 2247 1985-89 26 May BR 7\o23.9'N 156°38.0'W 17 May -71°35.6'N 155°53.9'W 13.3' no no •• lJCl

NMML-NMML 2428 1985-89 6,7 Jun BR 71°2504'N 156°36.TW 27 May 71°37.2'N 155°42.5'W 16.0 no no =-

».

LGL-NMML 5286 1985-89 25 Aug FB 69°38.7'N 126°11.4'W 7 May 7Io36.0'N 156°23.6'W 1304 no no -

~

•• '";:s

=

I:l..

NMML-NMML 4020 1986-89 II May BR 71°37.5'N 154°57.3'W 6 May 7\o38.5'N 155°59.0'W 13.8 no no lJCl ~.

LGL-NMML 7035 1986-89 II Sep EA 70022.7'N 143°49.0'W 23 Apr 7Io28.3'N 156°16.I'W 14.5' ·no no

fIl

~

CRC-NMML 7728 1986-89 31 Aug TPS 700

38.5'N 130045.2'W 28 Apr 7\o32.7'N 155°15.9'W 13.1 no no t:= I:tl

NMML-NMML 7946 1986-89 6 May BR 7\o3804'N 156°04.3'W 3 May 7\o35.8'N 155°21.1'W 13.3 no no t< c

NMML-NMML 8090 1986-89 14 May BR 7\o32.3'N 156°10.I'W 19 Apr 12.9 no no Z

~

NMML-NMML '" 8135 1986-89 22 May BR 71°29.7'N 155°50.9'W 21 Apr 71°3004'N 156°01.2'W 13.1 no no

s= ~

::0

s= . '" LGL - Photographic studies by LGL during summer (Davis et al. 1983, 1986a,b) and fall (Koski and Johnson 1987). NMML = Spring photographic studies by National Marine Mammal 00' '"

Laboratory. CRC = Summer photographic study by Cascadia Research Collective (Ford et al. 1987). ~ :::-

b

,. ::to

NCA = North Central Amundsen Gulf, N.W.T., BR = Barrow Region, AK, FB = Franklin Bay, N.W.T., HI = Herschel Island, Y.T., DS = Mackenzie Delta Shelfbreak, N.W.T.,IF =

;:s

Mackenzie Delta """'" "" Interface, Y.T., KP = King Point, Y.T., IN = Mackenzie Delta Industrial Area, N.W.T., FB = Franklin Bay, N.W.T., EA = Eastern Alaska, TPS = Tuktoyaktuk Peninsula '" \C

Shelf, N.W.T. 00 ~

c Approximate length. \C

~

?....

'000

'0

t

0
Appendix F: Individual Playbacks/I7 May 1991 441

APPENDIX F: Individual Playback Experiments, 1991/9438

Playback in 1991

17 May 1991 Playback

On 17 May 1991, the J-13 and F-40 projector system was set up along the edge of the landfast ice

several kilometers northeast of Point Barrow (Fig. 3.6 on p. 72). Spring whaling at Barrow had ended by

this date. As a result, it was possible to project icebreaker sound into the water closer to Barrow than had

been possible earlier in 1991 or at any time during 1989-90.

All observations of whales near the projector site on 17 May 1991 were obtained by the ice-based

crew stationed at the projector site. The landfast ice edge and the nearshore lead were oriented from west

to east (True) in this area. The measured water depth at the projectors was 110 m. The main nearshore

lead adjacent to the landfast ice edge was several kilometers wide and largely ice-free. However, a band

of pack ice was drifting in the lead west of the ice camp (Fig. F-IA). This ice blocked the ice-based

observers' view of the open nearshore lead farther west. This band of ice drifted closer to the camp as the

day progressed (Fig. F-IA). Whales traveling east in the main nearshore lead swam under this ice. The

crew was on the landfast ice edge from 10:46 through 20:59. Icebreaker sounds were projected into the

lead from 12:42 through 18:01.

The Twin Otter crew made two flights on this date for purposes of whale reconnaissance and vertical

photography, and with the hope of making behavioral observations. However, there was low cloud all day,

plus patches of fog. This prevented us from circling at 460 m altitude to observe whales near the projector

site or elsewhere. To avoid any possibility of aircraft disturbance to whales being observed by the icebased crew, the Twin Otter remained a minimum of several kilometers away from the ice camp.

Ice-based Observations.-No bowheads were sighted from the ice during the period of pre-playback

control observations. Five or six single bowheads plus two pairs were seen traveling east past the ice camp

during or immediately after the icebreaker playback, i.e. a total of 9 or 10 whales in 7 or 8 groups. There

were two additional "control" sightings of single bowheads well after the playback had ended.

Small numbers of bowheads traveled past the ice camp while icebreaker noise was projected into the

lead. The closest observed distances of these whales relative to the projectors were 540-1360 m (Table

F-IA). Some whales were apparently at or near their closest points of approach (CPA) when seen. However, others were approaching and/or moving away when seen at the surface, and were below the surface

when they passed the projectors (Fig. F-IA). The closest estimated points of approach (CEPA) of the

whales for which we have reliable measurements or estimates were -450 to 1300 m (n=4 sightings; Table

F-IA). Some or all of the other three single whales may have come closer than 450 m, but the CEPAs for

those three whales (sighting numbers 4, 5, 7 in Table F-IA) are subject to considerable uncertainty.

Sightings during or immediately after the playback were as follows (see Table F-IA and Fig. F-IA):

1. At 14:34, a group of two bowheads was sighted twice traveling east at medium speed at a location

840 m west (True) of the operating projectors, and -JA of the way across the lead. The same

group surfaced again at 14:50 when it was 1.87 km ENE of its 14:34 position and 1.24 km NE

of the projectors (Fig. F-IA). A total of 11 position fixes were obtained from 14:50 to 14:55 as

these whales traveled east at medium speed up the lead while remaining at the surface. If they

traveled on a straight line from the 14:34 to the 14:50 position, their CPA to the operating

projectors was -450 m. It is unlikely that they diverted far from the straight line, given that their

38 By W.R. Koski, N.J. Patenaude and M.A. Smultea, with R. Elliott, G.W. Miller and W.J. Richardson.
...-

./

./

./

/

I

I

I

I

I

,

vi

NI

!!21

'0'

ca>1 .g'1

:' ~I

,

I

\

I

I

I

I

I

I

I

I

I

I

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I

/

I

I

/

I

I

1

I

I

I

1

~I

01

N

0'

'l:I1

§I

21

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:,

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.go 1

:,

E,

I

I

1

,

I

I

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\

N

Ice

Pan

A.

16:30

0/

16:29

@,16:20

16:19@ ••••••,6:21

16:20

®

17:27'"

14:55

/ ...•....

/

/

/

/

,..

/

,..

/

,..

,..

,..

,..

,..// /"'~38

,.. /

,.. /

,.. f) /

,..'" / '

,.. /

,.. /

,.. /

,.. t}/

,.. ,.. .

,.. ,..

,.. /

,.. /

,..

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/ /'

,.. /

/ ,..

,.. /

/ d' t}/

,..,..rr" 18;04 '

,.. \V,..

17\ ,..// t} /;0 ~ ,.. ,..' 16:49

14:34' / /

,..

®~ /

17:20

LEGEND

monitor sonobuoy

whale sighting and heading

Landfast Ice

o old ice

Q openwoter

2!?0

250

FIGUREF-l. Ice-based theodolite observations of bowhead whales that passed the ice camp along the landfast ice NE of Pt. Barrow, 17 May 1991.

(A) Projectors broadcasting icebreaker sounds; (B) projectors silent. The projectors operated from 12:42 to 18:01; no bowheads were seen before

12:42. The whale seen at 18:04, 3 min after the end of the playback, is shown in (A) because it was exposed to icebreaker noise as it approached ..

Dashed lines represent presumed paths of whales while they were below the surface.
,,-

,,-

/

,,-

,,-

I

,,-

I

Ice

/

I

I

Pan

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1 , I , I

0 v'

I

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.., :1 '01 ~ ~I g, , ~I I

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.g, , :,

I ~,

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B.

® 18:41

·'8:4~

LEGEND

Whole sighting and heading

•• No disturbance

0+ Helicopter disturbance

c=J old ice

[;;] open water

FIGUREF-1 (continued). Post-playback "control" observations, 17 May 1991.

Landfast Ice

\N

oo

250 500 meters

250 500yards

....

'0

'0....
TABLE F-l. Summary of sightings of bowhead whales seen passing the sound projector located on the landfast ice edge NE of Pt. Barrow on

17 May 1991 when the projectors were (A) broadcasting icebreaker sound and (B) silent. All observations were by the ice-based observers.

Estimated Sound Levels Near Whales (dB re 1 IlPa)

Closest CEPA RLBB RLI/3 S:NBB S:NI/3

Sight- Observed

ing No. Distance

No. Time Bhds. (m) Distance Method' med max med max med max med max Nature of Track

A. Icebreaker Playback

I. 14:34 2 840 -450 3 111 115 104 106 12 16 23 25 Passed operating projectors underwater; seen

before and after CPA

2. 16:19 2 1100, 1100, 104 107 97 100 5 8 21 24 Seen once, at apparent CPA

1250 1250 102 106 95 99 3 7 18 23

3. 16:29 1360 1300 3 103 106 96 98 4 7 20 22 Seen once, just after apparent CPA

4. 16:49 540 <540 4 108 111 101 104 9 12 25 28 Seen once, approaching

5. 17:20/ -1000/ 300? 4 103 106 98 101 4 7 21 24 Seen while approaching and after passing; same

17:38 900 whale?

6. 17:27 1130 1100 3 91 94 85 86 -8 -5 9 10 Seen once, just after apparent CPA

7. 18:04 800 <800 4 97 100 91 92 -2 15 16 -800 m away and approaching at end of peakB. Silent Projector

level playback

8. 18:41 540 <540 4 Changed course, approaching

9. 20:30 500 -400 4 Seen after CPA

a 1 = measured by theodolite at CPA; 3 = estimate based on theodolite measurement(s) to nearby surfacing(s); 4 = estimate based on whale position(s) and heading(s) during

sighting(s) distant from CPA position (possibly unreliable).

'-\0

\0

'-
Appendix F: Individual Playbacks/17 May 1991 445

net speed between the two sighting locations was relatively high: 7.1 km/h (1.87 km in 0.262 h).

Thus, the actual CPA distance was less than 840 m, and probably not much above 450 m.

2. At 16:19-16:21, two more eastbound bowheads were seen 1100 m and 1250 m north of the

operating projectors. They were at their closest points of approach when they surfaced (Fig.

F-IA). These whales were -150 m apart and were traveling east at medium speed. We obtained

three position fixes on one and five fixes on the other.

3. At 16:29, a bowhead traveling east at medium speed was seen 1360 m north of the operating projectors. It surfaced shortly after passing its apparent CPA position, -1300 m from the projectors

(Fig. F-IA). Three position fixes were obtained during a lY2-min interval.

4. At 16:49, another single whale 150 m away from the landfast ice edge was sighted as it traveled

ENE at medium speed. It was 540 m west of the operating projectors when seen, but dove at that

position. It would have passed within 200 m of the projectors if it did not change course, but we

have no information about its actual CPA distance.

5. At 17:20, another single bowhead was seen close to the ice edge -1 km west of the operating projectors (distance estimated). It was traveling ENE toward the projectors, swimming at medium

speed. Actual CPA distance is unknown, but <1 km. A whale seen 900 m ENE of the projectors

at 17:38, traveling ENE at medium speed, might have been the same one, based on distance, bearings and times (Fig. F-IA). If so, and if it swam on a straight line, its CEPA was -300 m.

6. At 17:27, a single bowhead traveling east at medium speed was seen 1130 m NNE of the

operating projectors. It was slightly past its apparent CPA position. The CPA distance would

have been -1100 m if this whale was traveling on a straight line (Fig. F-IA).

7. At 18:04, just after the end of the icebreaker noise playback, a single bowhead heading ENE at

medium speed was seen 480 m WNW of the now-silent projectors. Assuming that it was

swimming at 5 km/h, it would have been -800 m WNW of the projectors at 18:00, when we

started to reduce the playback level, and -700 m away at 18:01:20 when the playback ended.

Thus, this whale is treated as having a CEP A distance of <800 m relative to the projectors

operating at full power.

There were two additional "control" sightings well after the end of the playback (Fig. F-IB; Table F-IB):

8. At 18:41,40 min after the playback ended, a small bowhead-probably a calf or yearling-was

first observed traveling SSE toward the landfast ice edge -580 m NW of the projectors. It

continued on this heading, toward the ice camp, until 18:43 (Fig. F-IB). It then turned to the ESE

and was traveling at medium speed when last seen 540 m NW of the silent projectors.

9. At 20:30, a bowhead traveling east at medium speed was seen 500 m NE of the ice camp. It was

sighted again at 20:38, 200 m ENE of its original position, and finally at 20:42. The helicopter

landed at the ice camp during the interval between the last two sightings.

Noise Exposure.-Icebreaker sounds were projected into the lead by the J-13/F-40 projector system

from 12:42 to 18:01. The 5th, median, and 95th percentile broadband (20-5000 Hz) source levels over the

full 14-min cycle of the icebreaker sounds were 156,161, and 167 dB re 1 ~Pa-m, respectively, from 12:42

to 16:49. After that time the source level was reduced by -12 dB until the end of the session. Considering

the dominant 1/3-octave band, the median source level was 155 dB re 1 ~Pa-m in the band centered at 80

Hz prior to 16:49, and 144 dB in the band centered at 80 Hz thereafter. Figure F-2 shows the variability

in the sounds as projected (I-m source levels) and as received at 1 km range at 17:30, during the quieter

period. The received level at 1 km in this figure, and the received levels in all similar figures, are

estimated by the sound exposure model described in §2.3. There will be small differences between the

received levels estimated by the model and those actually received at the specified distance and time. A

discussion of the differences between the model and actual measured sound levels is presented in §4.3.
Appendix F: Individual Playbacks/I 7 May 1991 446

17 May 1991,17:30

170-r----- ......• ---;-~----'"'"'T""-__;-,.__----....,...-__,____. r----..,

150+------+---t---t-----t--+---f------+--+__l

[jJ

"0

-- 130+-----:"7~-+_1r_-----:.,o:--_+~~:f__:¥:....------:>-+--_+__l

~

-g 110+---+-f----;--+--+-----+---f'o:-""7"'t---.:..,---t--.::::......+---i

m

co

tio 90-f------+--or==p"t--,;-.:=:::----t---t-__l-=~:__-__l--.::=--!--1

I

~.•...

SL-1 m

RL-1.0km

-+-

Amb.

5%,95%SL

5%,95%RL

50-t----,r'-'-'--..-+-..-r-+..,.,.;-----,--,--i--,-,-+-¥Ti----,---"-,--+-,-r-f-,...,..-l

10 100 1000

1/3-0ct. Center Frequency

, ,

10000

FIGURE F-2. Third-octave levels of projected icebreaker noise vs. distance from projectors and

ambient noise, 17 May 1991, time 17:16-17:30: variability over 14 min at ranges 1 m and 1.0 km

(median, 5th and 95th percentiles). Plus signs show average ambient noise level after playback.

Explanatory notes: (1) Source levels are dB re 1 ~Pa-m and ambient and received levels are

dB re 1 ~Pa. (2) Because of projector limitations, components of the icebreaker sounds at low frequencies are underrepresented in the projector output relative to components at higher frequencies.

(3) The tape of icebreaker sounds is repeated every 14 min. As illustrated by the 5th and 95th percentiles, the actual source or received level at any particular time can be substantially different

than the median level, depending on the precise location along the 14-min loop that is being

projected or received. (4) Source and ambient levels were measured; received levels at 1.0 km

were estimated via an empirically-validated propagation model. (5) Received levels within a few

meters of the surface will be lower than estimated here.

Ambient noise was measured at the monitor hydrophone near the projectors after icebreaker playbacks

stopped. The average broadband ambient noise level was 99 dB re 1 IlPa. The level in the dominant 113-

octave band was 91 dB re 1 IlPa in the band centered at 1600 Hz. Ambient noise in the 1I3-octave band

centered at 80 Hz was 76 dB re 1 IlPa; this band had the dominant source level of icebreaker sounds.

The projected icebreaker sounds varied in level, as shown in Figure F-2. On a 1I3-octave basis, the

strongest projected sounds on 17 May 1991 were between 50 and 250 Hz (Fig. F-2). Projected levels

diminished sharply with decreasing frequency in bands below 50 Hz, and diminished slowly with increasing

frequency in bands above 250 Hz.

Figure F-2 also summarizes the variation in the 113-octave levels received 1.0 km from the projectors.

The received levels fluctuated but, within the 50 to 80 Hz range, the medians were 9-10 dB above the
Appendix F: Individual Playbacks/I 7 May 1991 447

17 May 1991,17:30

170"'T"""----___,~-,--_;_-----_r_-_r____,~---- ....•... -___r____. ~--___,

--- SL-1 m

m

u

-

-

150+------I---+-+------+--+-+------!---I---;

130+-----=4---+---i'---,...-----+"'lIr--+--+-------+--f--l

<,•••.•.•.•••.•.••••••

""" 100m "" II~-····· .. . - _.............. ' .

/ ,•••••••I""'. 300m "', •.......-, "... ..•.,...:: ...,..,•.....

..•. .., 1 k 'P"'- -~ .

_..' ..~/r.··..· .", ....•..... _!!!:,. '::" - •. <, "", /11.' ..'......... .-," -,, -, .

~-:'~~...,....-Irt+"'::T"--""""-.:::. -, .... .. .•.....~

-r- ••••••• " •••••• -, ····,.·3···-k··m······ ••.•.• <. '-,-.l ' ,.............. ",

<, .....• <; .., .

........ "'. / t , <, ········t '.

-. '<,~:::::f-----,:::=- ~~:::

...

fi

I 100' " 1000

1/3-0ct. Center Frequency

Ree. Level

-+-

Amb.

10000

FIGUREF-3. Third-octave levels of projected icebreaker noise vs. distance from projectors and

ambient noise, 17 May 1991, time 17:16-17:30: median levels at range 1 m (squares) and 30 m3.0 km. Plus signs show average ambient noise level after playback.

Explanatory notes: See notes to Fig. F-2. Figure F-3 shows median received levels at more

ranges, but does not show 5th and 95th percentiles. Estimated received levels at 0.03 and 0.1 km

assume spherical spreading; model of §2.3 was used to derive estimates for 0.3 to 3 km.

background ambient levels in the corresponding 1I3-octave bands. At some times and frequencies, the

received level at range 1.0 km was 15 dB or more above the corresponding ambient noise level (Fig. F-2).

At frequencies below 20 Hz and above 300 Hz, the received level of icebreaker noise was always below

the ambient noise level. Figure F-3 shows the estimated median received levels at several standard

distances during the period with the lower source levels.

To estimate the maximum noise level near whales passing the sound projectors, an estimate of the

whales' closest point of approach to the projectors is required. Because whales are at the surface, and

therefore visible to observers, only a fraction of the time, the closest observed distance often overestimates

the actual closest point of approach (CPA). However, whale headings when they dive are not always a good

indication of tracks that they will take or headings when they first surface are not always a good indication

of tracks that they have followed to arrive at their position. In this study we calculated a Closest Estimated

Point of Approach or CEPA that used all information collected for a whale to estimate its closest approach

to the projectors. Calculation of the CEPA assumed that a whale sighted both as it approached and receded

from the projector traveled in a straight line between consecutive sightings. The shortest distance between

the assumed path and the projector was the CEPA (CEPA "A" in Fig. 6.1 on p. 254). For whales seen only

as they approached or only as they receded from the projector, the CEPA was the closest observed distance

from the projector (CEPAs "B" and "C" in Fig. 6.1). We did not assume a continuation of the last observed
Appendix F: Individual Playbacks/I7 May 1991 448

heading because some whales may have diverted after (if approaching) or before (if receding) they were

sighted. Thus CEP A for a whale that was seen only as it approached or receded likely overestimates the

actual closest point of approach, and therefore underestimates the maximum sound levels near that whale.

Levels of icebreaker sound received by every observed bowhead at its CEPA location were then estimated via the sound exposure model described in §2.3. This model produces many different measures of

sound exposure. Those quoted in this section are estimated received levels in the 20-5000 Hz band ("broadband") or in the 113-octave band with highest received level ("dominant 113-octave band"). For both the

20-5000 Hz band and the dominant 1I3-octave, we refer to both the median and the maximum level in the

64-s period preceding the observation in question. These four estimates of received level are often abbreviated as RLBB.med'RLBB,max,RL1/3,med'and RL1/3,max'When the average ambient noise level in the corresponding band, as measured before and after the playback, is subtracted from one of these received levels, the

result is the estimated icebreaker-signal to ambient-noise ratio, S:NBB,med'S:N;B,max' S:N1/3,med'and S:NI/3,max'

The closest CEPA of a traveling whale on 17 May 1991 was -300 m (see 17:20 sighting above). By

interpolation, this whale was near its CEPA to the projectors at -17:29:30. At that time and distance the

median broadband received level over a 64-speriod (RLBB,med)preceding CEP A was estimated as 103 dB

re 1 IlPa, and the maximum for any 8-s interval within that 64-s period (RLBB.max)was 106 dB. The

corresponding median and maximum levels in the dominant 1I3-octave band (RL1/3.medand RL1/3,max)were

98 and 101 dB re 1 IlPa in the band centered at 63 Hz. Thus for this closest whale at its closest point of

approach, the median and maximum icebreaker noise to ambient noise ratios in the dominant 113-octave

band (S:NI/3med and S:NI/3max)were 21 and 24 dB (Fig. F-4).

Because of the variability in the source level with time and because of the change in source level at

16:49, the whales seen closest to the projectors were not the ones that were exposed to the strongest sound

levels. The whale seen 540 m west of the projector at 16:49 was subjected to stronger sound levels when

it dove toward the projectors. At that time and distance, the whale would have been subjected S:NI/3.med and

S:N1/3.maxof 25 and 28 dB. Because this whale was not resighted, we cannot estimate its actual CPA, but

the whale probably approached closer than 540 m; thus it was probably exposed to stronger sound levels.

Summary.-On 17 May 1991, the projectors were set up along the edge of the landfast ice several kilometers northeast of Point Barrow. Spring whaling at Barrow had ended by this date, allowing work closer

to Barrow than at previous times in 1989-91. All observations of whales near the projector site on 17 May

1991 were obtained by the ice-based crew because the cloud ceilings were too low for the aerial crew

aboard the Twin Otter to observe bowhead behavior from an altitude of 460 m. The main nearshore lead

adjacent to the landfast ice edge was several kilometers wide and largely ice-free. The crew was on the

landfast ice edge from 10:46 through 20:59. Icebreaker sounds were projected into the lead from 12:42

through 18:01. The median broadband (20-5000 Hz) source level, measured over the full 14-min duration

of the icebreaker playback cycle, was 161 dB re 1 IlPa-m from 12:42 to 16:49; after that time the source

level was reduced by -12 dB until the end of the session. Because of variation in the source level

associated with the icebreaking activities within the 14-min period of the tape, the source and received

levels at certain times were 4-15 dB higher or lower than the median levels in corresponding 1I3-octave

bands (Fig. F-2). Even with the reduced source level after 16:49, median levels of icebreaker sounds in

the 113-octave band centered at 63 Hz were estimated to have exceeded ambient levels (Fig. F-3), and

therefore were presumably audible to bowheads 3 km or more away from the projectors.

No bowheads were sighted from the ice during the period of pre-playback control observations. Five

or six single bowheads plus two pairs were seen traveling east past the ice camp during or immediately after

the icebreaker playback, i.e. a total of 9 or 10 whales in 7 or 8 groups. There were two additional "control"

sightings of single bowheads well after the playback had ended.

The CEPAs of the whales for which we have reliable measurements or estimates were -450 to 1300 ill

(n=4 sightings). A fifth whale seen on 17 May appears to have passed -300 from the operating projectors;

it was linked after an 18-min dive, although distinctive markings that would confirm the link were not seen
Appendix F: Individual Playbacks/17 May 1991 449

17 May 1991,17:30

20-'000

BB vel

-CO

'0'-" 130

Q)

>

~

'0

c: 110

m

CO 0

ti +

0 90

I

S2

~

•

--- SL-1 m

-aRL-300m

-+-

Ambient

70+----J.f.l---l----!--t------+---j\..--iq=---~l___+_-_+__l

50+--....;....:;;=:---r--l---r-...,..-1.....-r-t-----.--.--+-.--r--+.....-r+-----.--.--+-.-..-+..,.....,.-l

10 100 1000

1/3-0ct. Center Frequency

10000

FIGURE F-4. Third-octave levels of projected icebreaker noise 1 m from the projectors (closed

squares) and near a bowhead 300 m from the projector (median level over 1 min), 17 May 1991,

time 17:30. Plus signs show average ambient noise level after playback.

Explanatory notes: (1) Source levels are dB re 1 flPa-m and ambient and received levels are

dB re 1 flPa. (2) Because of projector limitations, components of the icebreaker sounds at low

frequencies are underrepresented in the projector output relative to components at higher

frequencies. (3) The tape of icebreaker sounds is repeated every 14 min. The I-min values are

estimated by determining the location on the loop that was projected at the selected time and

summarizing the data for the preceding 1 min. (4) Source and ambient levels were measured;

received levels at 300 m were estimated via an empirically-validated propagation model. (5)

Received levels within a few meters of the surface will be lower than estimated here.

(Fig. 6.1). At their CEPAs, six of eight groups were exposed to icebreaker sounds 22-28 dB above the

ambient noise level (S:N1/3,max)'No overt reactions to the sounds were observed by the ice-based crew.

Playbacks in 1994

7 May 1994 Playback

The ice camp and projectors were set up on the edge of the landfast ice about 45 km ENE of Pt.

Barrow (Fig. 3.8, p. 77). The edge of the landfast ice was oriented NE-SW (Fig. F-5). The "nearshore"

lead along the ice edge near the camp was 0.4-1.8 km wide and was constricted on the western end by a

large ice pan and an outcropping of the landfast ice. This portion of the lead became congested with brash

ice and pans during the latter part of the day. Aerial reconnaissance from 08:43 to 09:19 determined that

a steady flow of bowhead whales were migrating NE along the main nearshore lead. Tones were projected
Appendix F: Individual Playbacks/Z May 1994 450

from 14:14 to 16:03 and icebreaker sounds were projected from 16:07 to 20:01. The 1-11 and one side of

the Argotec 220 were operational. The source levels were adjusted on several occasions but were generally

-20 dB weaker (20-5000 Hz broadband level) before than after 18:09, when the source levels were

increased. The measured water depth at the projectors was 37 m.

Ice-based Observations.-Large numbers of bowheads were migrating within view of the ice camp

«1500 m from camp) throughout the day. These whales approached from the SW and moved away to the

NW. About 63 bowheads (-45 groups or singletons) were estimated to have passed the ice camp during

the 13.3 h of observation. The number of sightings on this and later dates when numerous sightings were

made is approximate because of uncertainties in discriminating "new" and "repeat" sightings, and because

of the likelihood that some passing whales were missed. A steady stream of bowheads moved by the ice

camp from 10:40 to 15:30 (Fig. F-5 to F-7). There was a lull from 15:30 to 17:27 when no whales were

observed. Bowhead sightings were fewer and spaced at greater time intervals from 17:27 to 21 :28 when

the last bowhead was sighted (Fig. F-8, F-9). Observations ended at 23:03.

About 40 bowheads (-25 groups or singletons) were sighted during control observations (i.e., projectors silent) from 10:30 to 14: 14. Most whales sighted during this control period were traveling NE or

ENE at medium speed along the southern one-third of the lead (Fig. F-5, F-6). One bowhead showed no

apparent reaction as the helicopter landed on the ice -250 m away at 11:05. Another bowhead showed no

apparent reaction to the helicopter engines operating at a distance of - 350 m from 11:41 to 11:43. Repeated

surface activity (predominantly breaches) was exhibited by a group of 2-3 whales tracked from 13:44 to

14:05. Social and surface activity was observed among 5 groups or singletons. The closest approaches to

the projectors during the control period were <76 and 110 m as measured by theodolite (Table F-2).

From 14:14 to 16:02, while the projectors were broadcasting tones, -11 bowheads (-8 groups or

singletons) were sighted by observers at the ice camp. As during the control period, most whales traveled

NE or ENE at medium speed along the southern one-third of the lead and approached the projectors from

the west (Fig. F-7). However, a group of two bowheads deviated from a general NE heading; the presumed

path of this group was erratic from 15:04 to 15: 11. At 15: 11 they turned west almost directly away from

the projectors; at this time they were 607 m west of the projectors. Another group of two bowheads

hesitated near the ice edge before diving ESE under the landfast ice at 14:29. This sighting was the second

closest by bowheads to the projectors (108 m, measured by theodolite) during playback of tones. The

closest sighting was at range 77 m by a single bowhead at 14:25; the heading of this whale was eastward

directly toward the projectors, indicating that its CPA was closer than 77 m.

During projection of icebreaker sounds from 16:07 to 20:01, -8 singleton bowheads were sighted by

observers at the ice camp (Fig. F-8). No whales were sighted from the ice camp until 17:27, although aerial

observations (see below) indicated that some whales were approaching from the west during at least part

of this time. Most bowheads observed during the playback period traveled NE or ENE at medium speed

along the lead, as during preceding periods. However, sightings were farther from the projectors and more

evenly distributed across the lead (Fig. F-8). The closest observed approaches to the projectors were 362

and 408 m (theodolite measurements). The CEPA of 362 m involved a bowhead first observed west of the

projectors at 18:05. It was traveling fast (producing a large wake) to the north and away from the projectors. This whale also exhibited unusually long blow intervals (45 and 38 s, 3 blows). The same bowhead (presumably) was sighted again at 18:15, 700 m NW of the projectors. During the surfacing from

18:15 to 18:16 the whale turned from an initial northerly heading to the NE, apparently resuming NE movement. The projection of icebreaker sounds stopped briefly from 18:08: 15 to 18:08:46, while this whale was

underwater, and the source level of the icebreaker sounds was increased by -20 dB at 18:08:46 when transmission resumed. Thereafter, the closest approach to the projectors was 578 mat 19:00 and 664 mat 18:48.

There were few sightings of bowheads by observers at the ice camp after 20:01 when the projectors

stopped broadcasting icebreaker sounds. About four singletons were observed traveling ENE at medium

speed in the northern two-thirds of the lead. Two of these whales were sighted <30 min after the playback

ended. Observed CPAs were larger than during other periods on that date, and ranged from 763 to <1090 m
""" " ... , ....

:~:

• Projector

• Theodolite oOpen Water

1:::::::1 Brash Ice

oOld Ice

o Ice Camp, During Control Obs.

-- Interpolated Surface Travel

- - - Presumed Underwater Path

~ Whale Sighting and Heading

Q Social Group

0* Breach

Oh Helicopter Disturbance

o

11:39

o

11:47

11:09~

" 11:1t

,/ 11:10[2l~

,/ ~4~~

I

I

I 11:20

~

11:19

11:04 I h

11:05

I

I

I

I

I

I

I

I

I

11:40~

10:52~ .:

FIGURE F-5. Ice-based observations of bowhead tracks relative to the silent projectors (pre-playback) along the landfast ice NE of Pt. Barrow,

7 May 1994, times 09:42-11:57.
LEGEND

Projector

• Theodolite

D Open Water

1:«::1 Brash Ice

oOld Ice

o Ice Camp, During Control Obs.

-- Interpolated Surface Travel

- - - - Presumed Underwater Path

CJ' Whale Sighting and Heading

Q Social Group

0* Breach

Of Feeding

,-EY"

.>: 14:05

7

2:51

13:55

, 13:30

,,'* ee-

// 13:28

.. 5QO Yards·

---===---===---. 500 Meters .

FIGURE F-6. Ice-based observations of bowhead tracks relative to the silent projectors (pre-playback) along the landfast ice NE of Pt. Barrow,

7 May 1994, times 11:58-14:13.

13:10[2] __ - - --

13- --

14:01[4] ~ 0-

13:36[2)

12:21 * r:'I IJ-'--~

12:13[2)

11:59

~'

11:58[3)
il··

LEGEND

• Projector

• Theodolite

DOpen Water

1:::::::1 Brash Ice

oOld Ice

181 Ice Camp Obs., During Tones Playback

-- Interpolated Surface Travel

- - - - Presumed Underwater Path

0'" Whale Sighting and Heading

0* Breach

Ot Tail Slap

r:

15:16 I

~

14:28

15:09 If, -___~11t

\, - -e-;::24

14:2t _--~

IBI"- ~ .~5:06

-" 15:04[2]

1~

" 14:33

I

15:28

14:25 [3]

IBI-"

14:35

FIGURE F-7. Ice-based observations of bowhead tracks relative to the sound projectors broadcasting tones along the landfast ice NE of Pt. Barrow,

7 May 1994, times 14:14-16:05. Tones were projected from 14:14 to 16:02.
• Projector

• Theodolite

DOpen Water

1:::::::1 Brash Ice

oOld Ice

• Ice Camp Obs., During Ice-breaker Playback

-- Interpolated Surface Travel

- - - Presumed Underwater Path

eJ4' Whale Sighting and Heading

0* Breach ..-

17:46

18:--

18:15.

,

,

,

,

,

,

,

\

,

,

\

\

,

,

\

\

\

\

\

,

too

18:05

17:27 Actual Position

.- 200 Meters Due South

/"::12

,

I

,

,

19:11

•

,":05

,

,

,

,

,

"

,

,

,

,

,

,

,

,

,

,

,

,

,

,

,

/

,

,

,

,

,

,

18:491

18:48

:r

17:43

~

19:00

'500' Ya~ds.: ---=="..--==~--500. Meters .:

. . 0

'0

FIGURE F-8. Ice-based observations of bowhead tracks relative to the sound projectors broadcasting icebreaker sounds along the landfast ice NE

of Pt. Barrow, 7 May 1994, times 16:06-20:01.

----~.-----.-
21:25

20~

~

20:47

LEGEND

• Projector

• Theodolite

oOpen Water

r:: <: :1 Brash Ice

o Old Ice

o Ice Camp, During Control Obs.

[J Ice Camp Obs., Within 30 min. Post-playback

-- Interpolated Surface Travel

- - - - Presumed Underwater Path

0' Whale Sighting and Heading

FIGUREF-9. Ice-based observations of bowhead tracks relative to the silent projectors (after icebreaker playback) along the landfast ice NE of

Pt. Barrow, 7 May 1994, times 20:02-23:03.
TABLE F-2. Summary ofsightings of bowhead whales observed by ice-based and aerial observers, 7 May 1994.

Estimated Sound Levels Near Whales

Time

Group Followed From Distance

size Projector (m)" (m)

ing RLBB

Methodb Crew· med max Nature of Track

S:NI/3

Time med max med max med max

A: Pre-Playback Control (09:42 to 14:13)

10:40 2 +520 to +661 <520 10:39:48 1 IC NE of projector heading ENE

10:49 1 single sighting 800 10:49:00 2 IC Position and heading unknown

10:52 1 single sighting <76 10:52:21 1 IC SW of projector heading NE -20 m from ice edge

11:04 1 -310 to +476 240 11:06:11 1 IC WNW to NNE of projector heading ENE, heli, landed at

camp at 11:05 (heli. disturb.)

11:10 2 +439 to +493 <439 11:10:16 IC NE of projector heading ENE, 5 min. after heli, overflight

11:19 1 +261 to +290 <261 11:19:18 IC NNE of projector heading ENE, 14 min after heli, overflight

and 3 min before second overflight

11:25 +767 to +868 <767 11:24:54 1 IC NE of projector heading NE, breached twice

11:39 single sighting <1035 11:39:24 1 IC WSW of projector, heading unknown

11:47 single sighting <1159 11:47:20 1 IC WSW of projector, heading unknown

11:40 -409 to -282 282 11:43:10 1 IC SW to WNW of projector heading NE; heli, landed at camp at

11:41: no apparent reaction by whale

11:50 2 -416 to -346 <346 11:50:53 1 IC SW of projector heading NE then ENE along ice edge ~

11:56 1 -299 to -226 <226 11:57:13 1 IC SW of projector heading NE about 10 m from ice edge; dove ~

'" E under ice edge, 14 min. after heli, overflight

;:sl:l..

11:58 3 -667 to -303 <303 12:03:55 1 IC SW of projector heading ENE then dove ESE under ice edge ~.

12:17 1 single sighting <2000 12:17:53 2 A W of projector heading ENE along brash ice ~

12:13 2 -1200 to -1100 <1100 12:20:45 1 IC WSW of projector; heading unknown, breached ;:;-

12:24 3 single sighting <2500 12:23:51 2 A WSW of projector heading ENE l:l..

~.

12:23 5 single sighting <2400 12:24:36 2 A WSW of projector heading ENE s;

12:23 2 -617 to -583 583 12:25:05 1 IC NW of projector heading NE I::

~

12:27 1 single sighting <2500 12:27:19 2 A WSW of projector heading NE "tI

12:19 1 -1200 to + 1000 615 12:31:00 4 A W of projector heading NE ~

12:36 2 single sighting <830 12:36:13 2 A NNE of projector heading NE I)-

I:l

12:38 1 single sighting <1100 12:37:45 2 A E of projector heading NE '"••••

12:38 1 -316 to +603 306 12:38:00 1 IC NW to NNE of projector heading NE, flipper slaps ~

12:48 1 single sighting <800 12:48:15 2 A NE of projector heading NE along the ice edge

12:50 4 single sighting <250 12:50:07 2 A N of projector heading NE, social activity ~

'<

13:10 1 -177 to -178 177 13:10:11 1 IC NNW of projector heading ENE ....

13:10 2 -847 to + 159 110 13:19:38 1 IC W to NE of projector heading E

'0

'0

~

.j:;.

VI

0\
TABLE F-2. Continued.

Radial Distance CEPAa

Sight- Estimated Sound Levels Near Whales

Group Followed From Distance ing RLBB RLI13 S:NBB S:N1/3

Time size

e .

Projector (m) (m) Time Methol Crew· med max med max med max med max Nature of Track

13:23 2 -262 to +289 <262 13:22:59 1 IC NNW to NNE of projector heading NNE then ESE

13:28 1 +498 to +516 <498 13:28:23 1 IC NE of projector heading E

13:36 2 single sighting <631 13:36:15 1 IC W of projector heading ENE

13:43 1 single sighting <613 13:43:08 1 IC W of projector heading ESE

13:37 1 -395 to -390 385 13:38:00 1 IC NW of projector heading NE

13:44 3 -240 to + 1130 235 13:44:01 1 IC NW to NE of projector heading ENE. Separated at 13:48 to a

single and pair. Socialize and breach

14:01 4 -723 to -713 <713 14:02:20 1 IC W of projector, socializing & tailslap, overall heading ENE

B: Playback of Tones (14:14 - 16:02)

14:21 1 -795 to -587 <587 14:24:12 1 IC Not Available W of projector heading ENE

14:25 1 single sighting <77 14:25:15 1 IC Not Available W of projector heading E, breached

14:25 3 -371 to -108 108 14:29:29 1 IC Not Available SW of projector heading NE along ice edge; hesitated at

14:29, 108 m from projector; dove ESE under ice edge

14:28 1 -463 to -392 392 14:32:41 IC Not Available W to NW of projector heading ENE )..

14:35 1 single sighting <560 14:34:59 IC Not Available NE of projector heading ENE ~

15:04 2 -690 to -607 607 15:10:41 IC Not Available W of projector, reversed course; heading ENE "' to NNW to ::s

l:l..

ESE to W; tailslap 607 m from projector ~.

15:16 -499 to -508 <499 15:15:42 IC Not Available NW of projector heading ENE ~

15:28 +185 to +275 <185 15:27:32 IC Not Available NE of projector heading E :i'

~

C: Icebreaker Playback (16:07 - 20:01) '<:

~l::

16:52 1 single sighting <2200 16:52:26 2 A 86 89 79 80 -9 -6 -3 -2 W of projector heading ENE !:.

16:59 1 single sighting <2400 16:58:57 2 A 82 86 74 77 -13 -9 -7 -4 WSW of projector heading ENE "tI

17:01 1 single sighting <2400 17:01:11 2 A 80 86 74 78 -15 -10 -7 -3 WSW of projector heading ENE i:i"

'C

17:21 1 single sighting <2100 17:21:15 2 A 87 89 80 81 -8 -6 -4 -2 W of projector heading ENE <:)-

l:l

17:27 1 single sighting <1030 17:26:56 1 IC 89 92 82 83 -6 -3 1 2 SW of projector heading ENE

<"l •....

17:43 I -408 to -432 408 17:42:45 1 IC 101 104 94 96 6 9 16 18 NW of projector heading ENE ~

'I

17:46 1 single sighting 773 17:46:05 1 IC 95 100 88 93 0 4 8 12 NW of projector heading ENE

~

18:05 1 -362 to -706 362 18:04:56 1 IC 102 104 95 96 7 9 12 13 W then NW of projector; heading N fast away from projector 'C

at 362 m; headed ENE at next surfacing; long blow intervals

....

'0

18:48 -664 to + 1153 <664 18:48:14 IC 116 119 110 113 21 24 29 32 NNW then NNE of projector heading NE '0

~

+>-

Vl .....:I
TABLE F-2. Continued.

Radial Distance CEPAa

Sight- Estimated Sound Levels Near Whalesd

Group Followed From Distance ing RLBB RLI/3 S:NBB S:N1/3

Time size Projector (m)e (m) Time Methodb

Crewe med max med max med max med max Nature of Track

18:51 single sighting <1052 18:50:45 IC 110 116 105 111 15 21 24 29 NE of projector heading ENE along ice edge, surface active

including breach

19:00 +578 to +664 <578 18:59:32 IC 114 117 109 113 18 22 27 32 NE of projector heading ENE

19:11 -1023 to -1131 <1023 19:11:00 IC 112 116 104 109 17 21 20 26 NNW of projector heading NE

D: < 30 min After Playback (20:01 - 20:31)

20:10 1 single sighting <1081 20:10:11

20:28 1 single sighting < 834 20:27:34

IC

IC

WNW of projector heading ENE

WNW of projector heading ENE

1

1

E: Post Playback Control (> 20:31)

20:47 1 single sighting 763

21:25 1 -1080 to -1090 < 1080

IC

IC

20:47:08

21:25:02

NNW of projector heading ENE

NNW of projector heading NE

a CEPA = Closest Estimated Point of Approach. See text for description of estimation procedures.

b 1 = measured by theodolite at CPA; 2 = visual estimate at CPA; 3 = estimate based on theodolite measurement(s) to nearby surfacings; 4 = estimate based on whale position(s) and

heading(s) during sightings distant from CEPA (possibly unreliable).

e IC = ice-based crew; A = aerial crew.

d Data in italics are not included in analyses of traveling whales because this whale was engaged in aerial activities.

e "_" indicates that whales were approaching, generally from the SW or W; "+" indicates that whales were moving away, generally to the NE or E.
Appendix F: Individual Playbacksl7 May 1994 459

(measured by theodolite). However, one approaching whale sighted at 20:28 may have passed -500 m from

the projectors if it maintained its heading while underwater (Fig. F-9).

Aerial Observations.- Three behavioral observation sessions were conducted in the main nearshore

lead SW, NE and W of camp on 7 May 1994. The first session was conducted from 09:20 to 10:38 -7 km

east of the ice camp location prior to the camp being set up. About 10 bowheads were observed as they

traveled ENE at slow to medium speed. During the second session we followed 15 bowheads from 5 km

SW to 6 km NE of the ice camp. Observations extended from 11 :03 to 13:09, again with silent projectors.

Whales observed during this period (15+ individuals) were actively socializing and/or traveling NE or ENE

at slow to medium speed (Fig. F-IO, F-11). Only one group was observed passing close to the ice camp

(CEPA <250 m) at 12:50; it was a group of four socializing whales. Whales SW of camp traveled through

a constriction created by a large ice pan and generally traveled in the center of the lead. Whales observed

NE of camp were traveling along the landfast ice, maintaining the same general NE heading.

The third behavioral observation session near the camp was from 16:14 to 17:41 while icebreaker

sounds were projected into the lead at a low source level. Observations were fragmentary and intermittent

due to rapid incursion of low cloud and an uneven stream of whales. The western end of the lead became

congested with brash ice and pans and was reduced to a small lead (l00-200 x 1000 m); -15 whales were

observed traveling ENE at slow to medium speed. Several whales where observed traveling in heavy brash

ice NW of the ice camp. A few whales (3-5 individuals) were observed traveling generally north in a small

secondary lead oriented N-S about 3.2 km WNW of camp (Fig. F-12). No whales were seen in that area

or with northerly headings during earlier aerial observation sessions on this date. Icebreaker sounds

probably were not audible or barely audible at this distance and time, although some of these whales might

have detected the sounds earlier when they may have been slightly closer to the projectors (see below).

The closest observed point of approach during this aerial observation session was 2.1 km. Bowheads

were observed heading toward the projectors at that distance. Many of these whales would have passed the

ice camp between 17:00 and 18:30 at distances <I km if they had maintained their general headings and

speeds (Fig. F-12). Few, if any, of these whales were seen by the ice-based crew (cf. Fig. F-8). Thus, it

appears that on 7 May some whales were altering their tracks to avoid the projectors by >I km. Some

whales may have altered their paths at greater distances, given the observation at 16:43 of northbound

whales in the small lead through pack ice.

Noise Exposure.-Icebreaker sounds were transmitted from 16:07 to 20:01 on 7 May 1994. The J-II

and one side of the Argotec 220 were operational. From 16:07 to 18:08 the median 14-min broadband (20-

5000 Hz) source level was 146 dB re I f..lPa-m and from 18:09 to 20:01 it was 166 dB re I f..lPa-m. The

corresponding median source level in the dominant 1/3-octave band was 139 dB re I f..lPa-m in the band

centered at 80 Hz up to 18:08, and 159 dB re I f..lPa-m near 80 Hz thereafter. Figure F-13 shows the

variability in the sounds as projected (I-m source levels) and as received at I km range during the two time

periods. Figure F-14 shows the estimated median received levels at several standard distances for the two

periods with different source levels.

On 7 May at 11 :26 a 57 A sonobuoy was deployed manually 1.77 km SW of the ice camp along the

landfast ice. A 53B sonobuoy was air-dropped into the main near-shore lead 2.9 km SW of the projectors

at 16:34. Ambient noise was measured with a hydrophone at the ice camp before and after projection of

the icebreaker sounds. The average broadband (20-5000 Hz) ambient noise level was 95 dB re I f..lPa, and

the ambient noise level in the strongest II3-octave was 86 dB re I f..lPa in the band centered at 200 Hz

(pluses in Fig. F-13 to F-15). Ambient noise in the 1I3-octave band centered at 80 Hz was 82 dB re I f..lPa;

this band had the dominant source level of icebreaker sounds.

The closest observed bowhead with respect to the operating projectors on 7 May was a whale seen

362 m from the projectors at 18:05. It was moving north, away from the projectors (Fig. F-8). At this time

and horizontal distance, the median and maximum broadband received levels (RLBB,med and RLBB,max) below

the surface during the preceding 64 s were estimated to be 102 and 104 dB re I f..lPa. The median and
J

j'

1

..

..

'Q . . .500'-.: .. 1000 Yards' .:

o 500 1006 Meters'

LEGEND

• Projector

• Theodolite

r Monitor Sonobuoy

DOpen Water

1:::::::1 Brash Ice

DOld Ice

o Aerial, During Control Obs.

-- Interpolated Surface Travel

- - - - Presumed Underwater Path

~ Whale Sighting and Heading

Q Social Group

FIGUREF-I0. Aerial observations of bowhead tracks relative to the silent projectors (pre-playback) along the landfast ice NE of Pt. Barrow, 7

May 1994, times 11:03-12:39.
.........

. . . . . . . . . . .

............. . . ............. .

. •.

. . 0.' ". ' 500' .' ·100.0·Yilr.ds.·

-- ..

'0 . "500. 1000' Meters

LEGEND

• Projector

• Theodolite

DOpen Water

1:::::::1 Brash Ice

DOld Ice

o Aerial, During Control Obs.

-- Interpola1ed Surface Travel

- - - - Presumed Underwater Path

~ Whale Sighting and Heading

Q Social Group

FIGUREF-ll. Aerial observations of bowhead tracks relative to the silent projectors (pre-playback) along the landfast ice NE of Pt. Barrow, 7

May 1994, times 12:40-13:09.
. A .

(t .

-e~)...

. . . . .

. . . . .

••••

17:12 .. Q.

o

.. 5QO .. ·10QO Vardl! .

500· . 1000 Meters

LEGEND

• Projector

• Theodolite

r Monitor Sonobuoy

DOpen Water

1:<:::1 Brash Ice

o Old Ice

• Aerial Obs., During Ice-breaker Playback

-- Interpolated Surface Travel

- - - - Presumed Underwater Path

~ Whale Sighting and Heading

FIGUREF-12. Aerial observations of bowheads relative to the sound projectors broadcasting icebreaker sounds along the landfast ice NE of Pt.

Barrow, 7 May 1994, times 16:14-17 :41. Observations of each whale were brief and fragmentary due to buildup of low cloud below the aircraft.
Appendix F: Individual Playbacks/7 May 1994 463

7 May 1994,18:05

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~

Amb .

5%,95%SL

5%,95% RL

10000

SL-1 m

RL-1.0 km

~

Amb.

5%,95%SL

5%,95% RL

10000

FIGUREF-13. Third-octave levels of projected icebreaker noise vs. distance from projectors and ambient

noise, 7 May 1994: variability over 14 min at ranges 1 m and 1.0 km (median, 5th and 95th percentiles).

(A) Time 17:51-18:05. (B) Time 18:46-19:00. Plus signs show average ambient noise level before and

after playback. For additional explanation, see caption to Figure F-2.
Appendix F: Individual Playbacks/7 May 1994 464

7 May 1994, 18:05

A.

170,--------r---,--r------r---,---,.-----~-...---. r------,

~

SL-1 m

7 May 1994, 19:00

Ree. Level

-+-

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T""

'<,-,

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100 1000 10000

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-+-

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FIGURE F-14. Third-octave levels of projected icebreaker noise vs. distance from projectors and

ambient noise, 7 May 1994: median levels at range 1 m (squares) and 30 m-3.0 km. (A) Time

17:51-18:05. (B) Time 18:46-19:00. Plus signs show average ambient noise level before and after

playback. For additional explanation, see captions to Fig. F-2 and F-3.
Appendix F: Individual Playbacks/Z May 1994 465

maximum levels in the strongest 113-octave band (RLlI3.medand RLI/3.maxwere ) 95 and 96 dB re 1 IlPa in the

band centered at 160 Hz, with similar levels near 50 Hz (Fig. F-15). S:NlI3.medand S:NlI3.maxwere 12 and

13 dB. Because the ambient noise level was lower at 50 than at 160 Hz, S:N near 50 Hz was higher: 16

dB for the median level over the 64-s period, and 18 dB for the maximum. This whale was at the surface

at 18:05 and thus, at that specific time, was receiving lower sound levels than shown in Figure F-15 because

of pressure release effects near the surface. The track of the whale suggests that it must have turned

northward when it was below thesurface previous to its 18:05 surfacing, at a distance similar to or perhaps

slightly greater than its range at 18:05 (362 m). Thus, the whale apparently reacted to sound levels similar

to or slightly lower than those estimated above.

This same whale would have been subjected to sound levels that were considerably higher when the

projectors were restarted at 18:09 at a higher source level. By interpolation between its positions at 18:05

and 18: 15, the whale would have been -500 m from the projectors and underwater at 18:09 when the stronger icebreaker noises were first projected. Because of the discontinuity in the projected signal, we are not

able to estimate the received levels at that time. However, they would have been higher than the levels at

18:05; during its dive the whale may have been exposed to levels as high as those received by the whale

described below at 19:00 (578 m from the projectors). When the whale surfaced at 18:15 it was still heading generally north away from the projectors; during its surfacing at 18:15-18:16 it turned toward the east.

The closest observation of a bowhead that approached or passed the projectors while they were

projecting the strong icebreaker sounds was at 19:00. This whale was seen 578 m NE of the projectors and

heading away. It is very likely that the whale passed the projectors at a considerably closer distance while

underwater. In the 64-s period preceding the 19:00 surfacing, RLBB.medand RLBB.max578 m from the projectors were estimated to be 114 and 117 dB re 1 IlPa. RLlI3.medand RLlI3.maxwere 109 and 113 dB re 1 IlPa

in the band centered at 80 Hz. Thus, prior to surfacing, this whale that had just passed the projectors had

been exposed to S:NI/3.medand S:NI/3.maxof at least 27 and 32 dB in the strongest 1I3-octave band (Fig. F-15).

Several bowheads were seen traveling north or northeast in a thin lead more than 3 km WNW of the

projectors from 16:43 to 16:55 (Fig. F-12). None were seen moving north or amidst the pack ice before

icebreaker playbacks started. At that distance and time, the estimated RLl/3.medof icebreaker sound at the

whales' location was below the ambient noise level even in the 1I3-octave bands with strongest icebreaker

noise (Fig. F-14A). Peak levels in those bands at instants when the icebreaker sound was strongest

probably were similar to the ambient noise, and some of these whales may have been exposed to slightly

higher levels of icebreaker sound at an earlier time when they may have been slightly closer to the ice

camp. Even so, if they diverted north in response to icebreaker sound, it appears that they did so at a long

range (-3 km) and a low received noise level.

Summary.-On 7 May 1994, the ice camp was set up along the landfast ice edge about 45 km ENE

of Pt. Barrow (Fig 3.8). Tones and later icebreaker sounds were projected into the nearshore lead adjacent

to the landfast ice. Before the playback of tones and icebreaker sounds, large numbers of bowhead whales

were sighted traveling NE at medium speed through the middle and southern third of the lead. Sighting

rates were lower when tones were projected into the lead from 14:14 to 16:03, but the distribution and

behavior of most whales seen then were similar to those during the preceding control period.

Bowheads continued to travel past the ice camp during the period of icebreaker playback from 16:07

to 20:01, but sighting rates were lower and some whales apparently diverted away from the landfast ice

edge where the sound projectors were located. No bowheads were seen from the ice camp during the first

80 min of icebreaker projections and only a few whales were seen, all in the central and offshore sides of

the lead, during the following 2% hours of icebreaker playback. The broadband source levels were -20 dB

higher during the final 1.9 h of the playback than during the initial 2.0 h (Table 6.3 on p. 252). Aerial

observations west of the projectors sighted large numbers of bowheads heading toward the projectors; few

of them were later seen by ice-based observers. These whales apparently moved past the ice camp through

the offshore side of the lead.
Appendix F: Individual Playbacks/7 May 1994 466

170

--- SL·1 m

-aRL- 578 m

--+-

Ambient

7 May 1994, 18:05

170

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FIGUREF-15. Third-octave levels of projected icebreaker noise 1 m from the projectors (closed squares)

and near bowheads (A) 362 m and (B) 578 m from the projector (median level over 1 min), 7 May 1994,

times (A) 18:05 and (B) 19:00. Plus signs show average ambient noise level before and after playback.

For additional explanation, see caption to Figure F-4.
Appendix F: Individual Playbacksl7 May 1994 467

Some whales seemed to alter their paths at distances where icebreaker sounds in the strongest 113-

octave bands were similar to the ambient noise levels in those bands and thus (presumably) barely

detectable. The whale seen closest (362 m) to the operating projectors appeared to be detouring to the north

to avoid a closer approach. It was seen during the first half of the projection experiment when source levels

were low. This whale was exposed to an estimated S:N1I3,max of 18 dB when it started to detour (I13-octave

band centered at 50 Hz). However, not all bowheads diverted. One bowhead was seen that had apparently

passed well within 500 m of the projectors on a normal northeasterly heading, tolerating S:N1I3•max well over

20 dB. Thus it appears that, on 7 May 1994, some whales altered their tracks to avoid the projectors by

> 1 km, but a few approached within a few hundred meters where they were exposed to RLBB.max as high as

119 dB re 1 IlPa and S:Nl/3,max as high as 32 dB.

9 May 1994 Playback

The ice camp was set up on the northern edge of the landfast ice along a major lead oriented NE-SW.

The camp was -2.5 km NE of the location where a playback was conducted on 7 May and where ice-based

control observations were obtained on 8 May. The measured water depth at the projector was 40 m. NW

of the ice camp the lead was -2000 m wide and it narrowed to 250 m wide -2.3 km NE of the camp (Plate

6.1). Aerial reconnaissance from 08:59 to 10:39 found that many bowheads were migrating NE in the main

nearshore lead, which was ice-free within the first 3 km NE of the ice camp and discontinuous farther to

the east. After the ice-based crew arrived at the site, 3.9 h of control observations were obtained from the

ice. During this period 10 bowheads (not counting 2 bowheads potentially disturbed by the helicopter) were

sighted. Then icebreaker sounds were projected into the lead adjacent to the landfast ice for 3 h via a J-ll

projector; during that period 32 bowheads were observed from the ice and aircraft. There was a further 3-h

period of observations after the playback ended, during which -43 bowheads (excluding 1 potentially

disturbed by the helicopter) were seen from the ice and aircraft.

The ice-based crew arrived at the camp site at 10:19, started behavioral observations at 10:28, and

left the site at 20:29. Icebreaker sounds were projected into the lead from 14:22 to 17:30. During the first

40 min the source levels were -9 dB stronger (20-5000 Hz broadband) than during the remainder of the

period. The projection of icebreaker sounds was interrupted from 16: 19:57 to 16:26:00. One bowhead

surfaced 30 m from the ice camp less than 1 min before the sound playback was interrupted, swam to a

position 17 m from the projector, and dove toward it a few seconds before the sound was interrupted. A

number of whales were seen very close to the projector during the playback and post-playback periods; most

of these whales were suspected to be feeding underneath the landfast ice. Aircraft-based behavioral

observations were often fragmentary due to moderate-to-high sea states (3-6) throughout the day.

Ice-based Observations.-Many bowheads moved by within view of the ice camp. They approached

from the SW and moved to the NE. Sightings were made throughout the day but the frequency of sightings

varied during the day. During the first 3.9 h of control observations, 11 sightings (12 bowheads, including

2 singletons potentially disturbed by the helicopter) were made; during the 3 h of icebreaker playbacks, 20

sightings (26 bowheads) were made; during the first 2 h after playbacks, 16 sightings (19 bowheads,

including 1 potentially disturbed by the helicopter) were made; and during the last 1 h only two sightings

of three whales were made. In total, -60 bowheads (-49 groups or singletons) were sighted from the ice

during 10 h of observation. Most of these sightings were of traveling whales but 13 sightings (I4 whales)

were of small whales that appeared to be lingering (possibly feeding under the landfast ice) near the ice

camp. There was no direct evidence of feeding, such as mud streaming from the mouths; however, these

whales moved very slowly while at the surface, they turned frequently, they were seen diving under or

surfacing from under the landfast ice, and one of the whales that had distinctive markings was reidentified

from photographs taken at the ice camp 83 min apart. Thus, many of the sightings of whales lingering near

the ice camp and along the landfast ice edge may be resightings of a few whales that could not be linked.

A total of -12 bowheads (-11 groups or singletons) were sighted during pre-playback control observations from 10:28 to 14:21 (Fig. F-16, F-17). Most groups (9 of 11, 82%) were traveling NE or ENE at
LEGEND G Projector

• Theodolite

r Monitor Sonobuoy

oOpen Water

o Old Ice

o Ice Camp, During Control Obs,

-- Interpolated Surface Travel

- - _. Presumed Underwater Path

cr Whale Sighting and Heading

0* Breach

On Helicopter Disturbance

12:28J2f

,

,

,

....•.

·0· -

12:45 13""

11:54

~3:38

13:37

FIGURE F-16. Ice-based observations of bowhead tracks relative to the silent projector (pre-playback) along the landfast ice NE of Pt. Barrow,

9 May 1994, times 10:28-14:21
LEGEND

• Projector

• Theodolite

D Open Water

oOld Ice

o Ice Camp, During Control Obs.

-- Interpolated Surface Travel

- - - - Presumed Underwater Path

o: Whale Sighting and Heading

,-

13:52 [3-""--:- - - - - -

13:45

.. o· . 20· ·40· .60· .. 80 .. 100 Yards .

. ·0 20 .40 60 . 80 100 Meiers· .

FIGUREF-17. Ice-based observations of a subadult bowhead relative to the silent projector (pre-playback) along the landfast ice NE of Pt. Barrow,

9 May 1994, times 13:38-14:16. This subadult may have been attracted to the observers and equipment located at the ice edge.

.------- --------------- ------- ---- --- --- -------------------------------------------------- 
Appendix F: Individual Playbacks/9 May 1994 470

medium speed along the lead (Table F-3). However, one small subadult milled in front of the camp from

13:38 to 14: 16, repeatedly passing back and forth between the silent projector and the theodolite <30 m

from the ice edge (Fig. F-17). This subadult may have been attracted to the observers and equipment located at the ice edge. However, similar sized whales were observed near the camp throughout the day; their

behavior suggests that they may have been feeding under the landfast ice near the projector. The whale was

observed as close as 5 m from the surface location above the silent projector (theodolite measurement of

horizontal distance). This was the closest observed approach to the projector site throughout the day.

At 13:21 a group of two bowheads appeared to deviate briefly from a NE to a N, then NW, and then

ENE heading when -308 m west of the silent projector. A subadult bowhead apparently reacted to the helicopter engines operating on the ice -230 m away at 12:30 by abbreviating its surface duration; the whale

blew once and slipped under the water without an arch. A single bowhead breached six times from 12:08

to 12: 16 while traveling ENE 628-792 m from the projector. The closest observed approaches to the projector during the control period were 5 m (see above), <185 m, and <243 m (theodolite measurements).

From 14:22 to 17:30, while the projector was broadcasting icebreaker sounds, -26 bowheads (-20

groups or singletons) were sighted by observers at the ice camp. Two of these groups were seen during the

14:22 to 15:02 period when the projected icebreaker sounds were stronger. As during the previous control

period, many bowheads (9 groups) traveled consistently NE or ENE along the lead at medium speed as they

approached the projector from the west. However, more whales (10 of 19 groups with known headings)

had other orientations during this period as compared to the previous control period (2 of 11 groups). Most

of these "other orientations" may have involved feeding whales because most were sighted along the ice

edge and their headings were generally toward the landfast ice and angling toward the projector (Fig. F-18).

Only two traveling whales passed within 400 m of the projector but seven presumed feeding groups

were seen within that distance (see Fig. F-26, later). The closest approach by a traveling whale was by a

single bowhead followed from 324 m west of the projector to 320 m east of it from 16:31 to 16:36. It is

estimated that the whale passed -60 m from the projector during the intervening dive, and there was no

apparent change in the track of this whale as it passed the projector. However, some other traveling whales

appeared to change their tracks in reaction to the operating projector. A single whale that surfaced 206 m

NW of the projector at 16:50 turned to the north (from its previous NEward heading) as it surfaced. It

traveled north until it dove at 16:52. Two whales sighted at 14:59 at a location 420 m west of the projector

were observed heading slowly NNW away from the projector; they then turned to an ENE heading (see inset

in Fig. F-18). The most distant apparent reaction seen from the ice camp was by a group of two traveling

whales that appeared to alter their course when 940 m WSW of the projector at 17:26. They were initially

sighted traveling slowly NNE, then turned east, and then SE (Fig. F-18). After the playback ended at 17:30,

they turned and followed the landfast ice NE and were last seen 500 m WSW of the projector and heading

NE (Fig. F-19). A group of two bowheads was sighted briefly at 14:36 as they traveled slowly ENE along

the ice edge 390 m WSW of the ice camp. This group reversed course away from the projector and along

the ice edge. They may have been feeding or they may have reacted to the projection of icebreaker sounds.

Three groups of presumed feeding whales were observed <100 m from the operating projector by

personnel at the ice camp. The closest observed approaches by presumed feeding bowheads during the

playback period were 17,24,43, and 130 m from the projector (theodolite measurements of horizontal

distances). One of these whales moved SSW along and then under the ice edge away from the projector

at a distance of 43 m; however, its actual CPA may have been <43 m before it surfaced. A subadult

bowhead was sighted just before the projector was briefly turned off at 16:20; the subadult subsequently

turned from an ENE heading and dove SE under the ice edge 17 m from the operating projector. The

projector was turned off a few seconds after this whale dove. This same whale was resighted <20 m from

the projector at 17:43 (-13 min after the end of the icebreaker noise playback), and may have been sighted

several other times between these two times. The whale was reidentified from photographs taken at 16:20

and 17:43 by the ice crew; the whale had a pair of distinctive scars on its right side. The path of this whale

was not "blocked" by icebreaker sounds. It was seen a few meters east of the projector at 16:19, it was
TABLEF-3. Summary of sightings of bowhead whales observed by ice-based and aerial observers, 9 May 1994.

Radial Distance CEPA' Sight- Estimated Sound Levels Near Whales·

Group Followed From Distance ing RL•• RL'I3 S:N •• S:N'13

Time size Projector (m)' (m) Time Methodb

Crew' med max med max med max med max Nature of Track

A: Pre-Playback Control (10:28 to 14:22)

10:56 -298 to -243 <243 10:56:35 IC W of projector heading ESE, 9 min. after heli. overflight

11:54 single sighting <625 11:53:48 IC WNW of projector heading ENE

12:01 single sighting 135 12:01:27 IC NW of projector heading ENE

12:06 single sighting <793 12:06:20 IC NW of projector heading ENE

12:08 -792 to -705 628 12:13:06 IC NW to N of projector heading ENE; 6 breaches

12:18 -342 to +488 325 12:18:52 IC NW to N of projector heading NE

12:30 single sighting 285 12:30:18 IC Subadult NW of projector heading ENE. Appeared to react to heli.

idling on ice at-230 m; blew once then slipped under without arch

12:45 1 -811 to -780 <780 12:45:31 IC WNW of projector heading ENE

13:21 2 -308 to -185 <185 13:23:17 IC W of projector heading NE; turned N when 308 m from projector, then

NW,thenENE

13:37 -865 to -820 <820 13:37:37 IC W of projector heading ENE

13:38 -90 to +100 5 14:04:40 IC Subadult SW to NE of projector, heading variable. Milled near

projector 13:38-14:16; rested once at surface, feeding?

)0.

B: Icebreaker Playback (14:22-17:30) ~

'"::.

14:36 2 -390 to -390 390 14:36:07 IC 124 126 II7 120 24 26 32 35 WSW of projector heading slowly NE; reversed course when along ice

e,

~.

edge 390 m SW of projector; feeding? ~

14:59 I -430 to -420 420 15:00:10 1 IC 112 116 106 111 12 16 21 25 W of projector heading NNW then ENE ;;-

15:23 1 single sighting <420 15:22:57 1 IC 102 107 96 99 2 7 II 14 W of projector heading SE under ice edge; feeding? ~

15:45 I +495 to +540 <495 15:44:59 1 IC 102 109 95 100 2 9 10 15 NNE of projector heading ENE

~.

15:57 3 single sighting <2800 15:57:28 2 A 89 92 84 86 -11 -8 -1 1 WSW of projector heaidng ENE, social. §:

15:57 2 -472 to -442 <442 15:58:13 1 IC 102 105 95 98 2 5 8 10 W of projector heading NE

!:.

16:04 1 -370 to -251 <251 16:06:22 1 IC 108 II2 100 106 8 12 12 19 Subadult NW to W of projector heading ENE then SE; feeding? ~

is"

16:08 1 single sighting <1275 16:08:12 I IC 95 99 88 90 -5 -1 3 5 NW of projector heading ENE '<~

16:14 2 single sighting 1700 16:14:17 1 IC 88 91 83 84 -12 -9 -2 -1 WSW of projector, heading unknown; breached ~<'I

1'<-

16:19 1 -30 to +17 17 16:19:56 1 IC 128 132 121 123 28 32 36 38 Subadult W to N of projector heading ENE. Playback interrupted. Dove

~

SE under ice edge. Resighted at 17:43 W of projector heading ENE;

feeding? ~

'<:

16:28 -985 to -946 <946 16:29:25 1 ICIA 105 107 99 101 5 7 14 16 W of projector heading ENE; breached ....

16:29 -34 to -24 24 16:30:22 I IC 132 135 126 129 32 35 41 44 W of projector heading ENE, dove SE under ice edge; feeding? '0

'0

16:31 -324 to +320 60 16:33:50 3 ICIA 115 117 108 109 15 17 23 24 W of projector heading ENE then E

-I>..

.j:::..

-...J

•....
TABLE F-3. Continued.

Radial Distance CEPA' Sight- Estimated Sound Levels Near Whales d

Group Followed From Distance ing RL•• RL'13 S:N•• S:N'13

Time size Projector (m)" (m) Time Method" Crew e

med max med max med max med max Nature of Track

16:16 -2900 to +500 480 16:39:00 3 A 107 110 100 103 7 10 15 18 NW to N of projector heading NE. Dove NNE under brash with open

water to ENE

16:46 I single sighting 2000 16:46:21 2 A 93 99 86 93 -7 -1 2 8 WNW of projector heading N

16:50 I -206 to +260 206 16:50:01 1 ICJA 114 118 108 111 14 18 23 26 NW to NNW of projector heading NNE. Adult

16:49 2 single sighting <910 16:50:25 I ICJA 104 107 98 102 4 7 14 17 WNW of projector heading ENE; tailslapped

16:52 I single sighting 70 16:53:01 2 A 119 122 114 115 19 22 29 30 NE of projector, motionless, oriented ENE, turned SE, dove under ice

pan. Subadult, feeding?

16:54 2 single sighting 1500 16:53:36 2 A 98 102 93 96 -2 2 8 11 ENE of projector heading ESE, dove under ice edge. Subadults

16:59 I single sighting <730 16:59:25 2 A 107 110 101 103 7 10 16 18 NNE of projector heading ENE, aerial activity

16:59 I +730 to +804 <730 16:59:32 I IC 106 109 100 103 6 9 15 18 NE of projector heading ENE

17:03 I -58 to -43 43 17:03:52 I ICJA 124 128 116 122 24 28 31 37 W of projector heading SSW under ice edge; feeding?

17:05 2 -366 to +890 281 17:06:12 I ICJA 108 113 101 104 8 13 16 19 NW of projector heading ENE, social, aerial activity. Adult & subadult

17:06 I single sighting <1000 17:06:55 2 ~ 100 104 95 97 0 4 10 12 N of projector heading NNE

17:13 I single sighting <1500 17:12:50 2 A 101 104 96 99 I 4 11 14 NNE of projector heading E along brash ice

17:14 I single sighting <1600 17:13:36 2 A 101 103 95 96 I 3 10 11 NE of projector heading slowly ENE

17:19 I single sighting <850 17:18:40 2 A 105 108 99 102 5 8 14 17 NE of projector heading NNE, following group of 17:05 ~

17:20 I -140 to -130 130 17:21:13 I IC 114 117 108 110 14 17 23 25 SW of projector heading slowly SW under landfast ice, rest/feeding? ~

17:22 1 single sighting 825 17:22:23 2 A 103 107 97 101 3 7 12 16 NE of projector, slowly heading NNW, turned S, dove steeply under ice <\

;:s

pan. Subadult; feeding?

I:>..

~'

17:24 2 single sighting <2100 17:24:28 2 A 94 97 88 90 -6 -3 3 5 NE of projector heading ENE in brash ice ~

17:25 I single sighting <750 17:25:37 2 A 102 106 96 103 2 6 11 18 NNE of projector heading NNE ;;-

17:27 I single sighting <1400 17:26:40 2 A 99 101 93 95 -1 I 8 10 NNE of projector heading NNE along brash ice I:>..

17:29 I single sighting 1910 17:28:37 1 IC 92 96 87 90 -8 -4 2 5 WSW of projector, heading unknown; breached ~'

~ 17:26 2 -940 to -750 <750 17:30:05 2 ICJA 101 106 95 100 I 6 10 15 WSW of projector heading slowly NNE, then turned E, then SE. l:::

l:l

Playback ends. Whales then approach projector. -'"tl

i:l

C: <30 mIn After Playback (17:30-18:00) '<0-

l:l

17:33 100 to -50 17(100) 17:32:40 2 A 113 119 107 113 13 19 22 28 N to WSW of projector heading SSE, dove under ice edge. Yearling; '"~

feeding? ~

17:33 2 -750 to -500 <500 17:33:35 2 ICJA WSW of projector heading ENE along ice edge. Followed during

~ playback at 17:26 (See above) '<

17:36 +660 to + 1400 <660 17:36:19 1 ICJA 102 107 96 101 2 7 11 16 NNE of projector heading NE across lead. CEPA during playback

....

10

10 17:37 single sighting <850 17:36:44 2 A NNE of projector heading NNE ""

~-.l

N
TABLE F-3. Continued.

Radial Distance CEPA' Sight- Estimated Sound Levels Near Whales •

Group Followed From Distance ing RLa. RL'fl S:N •• S:N,"

Time size Projector (m)" (m) Time Method" Crew' med max med max med max med max Nature of Track

17:43 single sighting <20 17:43:19 IC N of projector heading slowly SE, dove SSE under ice toward projector

at 20 m. Sighted during plbk at 16: 19; subadult, feeding?

17:42 single sighting <650 17:45:23 2 A WNW of projector heading E. Adult

17:48 -290 to +279 <279 17:49:04 I IC W of projector heading ENE

17:50 +142 to +168 <142 17:51:08 I IC NE of projector heading slowly SW along landfast ice edge toward

projector; feeding?

17:52 2 single sighting <1600 17:52:28 2 A WNW of projector heading NE

17:54 I single sighting 1100 17:55:21 2 A NNW of projector heading E

17:56 I -780 to -721 <721 17:56:55 I ICIA W of projector heading ENE

17:49 2 -1500 to -1300 1300 18:00:28 2 A WNW of projector heading ENE; mother-calf -30 min post-plbk

18:00 I -295 to -244 <244 18:01:06 I ICIA W of projector heading ENE

D: Post Playback Control (>18:00)

18:03 -750 to -742 <742 18:03:45 I IC W of projector heading ENE

18:02 -120 to +110 110 18:14:24 2 A WSW of projector, dove under ice edge. Yearling; feeding?

18:20 single sighting <720 18:21:01 2 A WSW of projector, surfaced from under ice heading slowly NNE ~

18:23 single sighting <600 18:23:19 2 A WSW of projector heading SSW. dove under ice edge ~

18:27 -100 to +17 17 18:26:33 I ICIA N to SW of projector heading slowly WSW past projector; then dove '";:s

~

SSE under ice edge. Resurfaced WSW of projector heading ENE, turned li'

SE and dove under ice; feeding? ~

18:09 2 -1600 to +1500 283 18:27:00 3 ICIA WSW to NE of projector heading ENE. Adults ;;-

18:30 I +290 to +920 <290 18:29:50 I ICIA NE of projector heading ENE along ice edge. Subadult ~~.

18:47 I single sighting 278 18:47:18 I IC W of projector heading NNE s;

18:52 I single sighting <2200 18:52:00 2 A NNE of projector heading ENE ;:

I:l

18:56 I single sighting <2300 18:55:45 2 A ENE of projector heading NNE along ice edge -"'1:1

19:05 I single sighting 1039 19:05:20 I IC NE of projector, heading unknown SO

'< 19:14 2 -316 to -328 311 19:14:47 I IC NW of projector heading NE, 3 min. after helLoverflight <::rI:l

19:20 I +959 to + 1052 <959 19:20:09 I IC NE of projector heading ENE l")

~

19:24 I +741 to +822 <741 19:24:02 I IC NE of projector heading NE

~

19:25 I single sighting <1500 19:25:40 2 A W of projector heading slowly NE along brash ice

19:24 2 -1700 to -1600 <1500 19:27:11 2 A WNW of projector heading ENE along edge of brash ice ~

'<

19:31 I +1300 to +1400 <1300 19:31:30 2 A NW of projector heading NNE along brash ice, turned ESE •.....•

19:35 2 single sighting <2700 19:36:45 2 A WNW of projector heading NE in brash ice '0

'0

~ 19:39 2 single sighting <1200 19:39:00 2 A W of projector heading ENE

~

-:J

W
TABLE F-3. Continued.

Radial Distance CEPA' Sight· Estimated Sound Levels Near Whales•

Group Followed From Distance ing RLa. RL'I) S:N•• S:N'I)

Time size Projector (m)" (rn) Time Method" Crew' med max med max med max med max Nature of Track

19:39 2 +750 to +885 <750 19:39:01 I IC NNE of projector heading NE; social traveVrnill, flipperslap

19:37 I single sighting <2600 19:39:08 2 A WNW of projector heading NE in brash ice

19:40 I single sighting <1400 19:40:42 2 A NW of projector heading ENE in brash ice

19:40 1 single sighting <1400 19:40:45 2 A NW of projector heading ENE in brash ice

19:41 1 single sighting <1400 19:41:25 2 A WNW of projector heading ENE in brash ice

20:01 1 single sighting 524 20:00:54 1 IC N of projector heading ENE

, CEPA = Closest Estimated Point of Approach. See text for description of estimation procedures.

" 1= measured by theodolite at CPA; 2 = visual estimate at CPA; 3 = estimate based on theodolite measurement(s) to nearby surfacings; 4 = estimate based on whale posilion(s) and

heading(s) during sightings distant from CEPA (possibly unreliable).

, IC = ice-based crew; A = aerial crew.

• Data in italics are not included in analyses of traveling whales because these whales were socializing, feeding or engaged in aerial activities.

, "." indicates that whales were approaching, generally from the SW or W; "+" indicates that whales were moving away, generally to the NE or E.
FEEDING

• Projector

• Theodolite

oOpen Water

o Old Ice

DBrash Ice

• Ice Camp Obs., During Ice-breaker

Playback

• Aerial and Ice Camp Obs., During

Ice-breaker Playback

• Aerial Obs., During Ice-breaker

Playback

-. - Interpolated Surface Travel

- - - - Presumed Underwater Path

if Whale Sighting and Heading

0* Breach

Ot Tail Slap

Of Feeding

O! Aerial Activity

o Social Group

:;;; Track Continued .On Another Map t¥

16:49(2)

16:~~

17:26[2) ti\:28

~ 16:14(2) .*

17:29 .*

'..•.'

'0

FIGUREF-18. Ice-based observations of bowhead tracks relative to projector broadcasting icebreaker sounds along the landfast ice NE of Pt.

Barrow, 9 May 1994, times 14:22-17:30. Aerial observations are included where they concern bowheads observed from both the ice and the

aircraft.
>f.<: •••• <'j::::::>:: ..........' .

........ . .. .

<-: »»:.:-:: : : :

........

............ .

.. .

.',' .

.........

.. .

........

............ .

LEGEND

• Projector

• Theodolite

DOpen Water

oOld Ice

1::::1 Brash Ice

[J Ice Camp Obs., Within 30 min. Post-playback

4 Aerial and Ice Camp Obs., Within 30 min. Post-playback

~ Aerial Obs.• Within 30 min. Post-playback

-- Interpolated Surface Travel

- - - - Presumed Underwater Path

o: Whale Sighting and Heading

-::/ Track Continued From Previous Map

~:57

17:56

17:~~ -:

/

/

/

/

/

I

I

I

I

/

I

I

I

I

I

~~:38

17:36

. : O!,,_iIII. ':':::;::::" ••••••. iC'::;::i~~~o~~v~rdi .:

o~."';"==:"'';':;:::::::;:oio--'"''!5!o· 0-0 Meters.

FIGURE F-19. Ice-based observations of bowhead tracks relative to silent projector «30 min after icebreaker playback) along the

landfast ice NE ofPt. Barrow, 9 May 1994, times 17:31-18:01. Aerial observations are included where they concern bowheads observed

from both the ice and the aircraft.

17:48,...../

18:00~---~~-'"
:::::~:::::::: ."

..... .... .....'

..........

.. .... .....

::: .: ':::: . :::: -: :--:

.. . . . '. .'

. . .

.' '. .. .' '. . .' '.

,", . ,". . ",

.' '. . ." . .' '.

.. . .. . .

',,' ',,' ',,'

',,' . :-. .: -:

. ,", . ,",

,":d

D

"':::',':

>:'.'.-:' :-:< . ...... . . .....

18:~~d"

/

19:42[21 - - •

- 19:21 --

19:39[21 19:~5-~B'

- _--0'- 019:05

19:24 _• -- 19:20

20:01

e'

___ _

18:46_

_ - a,

.if

-a-;~:30[21 -.---/ , • ' • • ' '

_A~:16 g-' •• -.

J . 4(2) 18:30, ' , ' , ' , ' , ' , '

,--.! 18:27

,,'18:47CJ f

c::r' _/'

18:0~/

,,

,

,

,

,

,

LEGEND

• Projector

• Theodolite

DOpen Water

oOld Ice

1::::1 Brash Ice

o Ice Camp. During Control Obs.

A Aerial and Ice Camp, During Control Obs.

,0 Aerial, During Control Obs.

-- Interpolated Surface Travel

- - - Presumed Underwater Path

cr Whale Sighting and Heading

Q Social Group

,

,

,

,

,

,

. ...•. --- .

, 0,' 500 Meters,

FIGURE F-20. Ice-based observations of bowhead tracks relative to silent projector (>30 min after icebreaker playback) along the landfast ice NE

of Pt. Barrow, 9 May 1994, times 18:02-20:29. Aerial observations are included where they concern bowheads observed from both the ice and

the aircraft.
Appendix F: Individual Playbacks/9 May 1994 478

probably seen SW of the projector from 16:29 to 17:20, and it was photographed 20 m N of the projector

at 17:43 (13 min after the projector was turned off).

There were -22 bowheads (-18 groups or singletons) sighted by observers at the ice camp after the

projector stopped broadcasting icebreaker sounds. Three of these sightings may have been of one or more

feeding whale(s) near the ice camp (Fig. F-19, F-20). Their headings deviated from NE or ENE. These

three groups also had the closest observed approaches to the now-silent projector during the post-playback

period: 17, <20, and <142 m. About half of the whales (53% of 17 groups) sighted during the postplayback period were <500 m from the projector (Fig. F-19). Only one group was sighted during the last

45 min of observation from the ice camp, when aerial observers were seeing large numbers of whales

traveling along the north side of the lead, beyond the visual range of ice-based observers. It is not known

why this change in distribution across the lead occurred at this time, 2 h after the end of the playback.

Aerial Observations.-A large number of bowheads (-66) were observed by the Twin Otter crew

during 4.7 h of observation on 9 May 1994. Many of these whales may represent repeat sightings of the

same whales that could not be recognized because of rough sea conditions. Whales were observed during

the playback, post-playback, and subsequent control periods. A low cloud ceiling prevented aerial

observations during the pre-playback period.

From 15:11 to 17:30, while the projector was broadcasting icebreaker sounds, bowheads were

generally traveling NNE to ENE along the lead at slow to medium speed (Fig. F-2l). They approached the

projector from the west or WSW. Bowheads followed during the early part of the session (15:11-16:20)

included many whales engaged in social and aerial activities. Because of these behaviors, many of these

whales had headings other than the NNE heading that would be expected of migrating whales. Many of

the whales observed from the air were migrating east near the pack-ice edge along the north side of the

lead.

Aerial observers saw -27 bowheads approach within 1 km of the projector during the playback period.

The closest of these were also seen by the ice-based observers and are described above under "Ice-based

Observations". There is circumstantial evidence that a few additional whales seen from the aircraft may

have altered their headings in response to the icebreaker playbacks. One well-marked traveling whale was

initially seen heading ENE 2.9 km west of the projector at 16:16. It was resighted 500m north of the

projector along the south edge of brash ice. When it dove, it headed NNE under the brash ice although it

could have continued ENE along the lead without passing under the ice (Fig. F-2l). Another single

bowhead, seen briefly 2 km NW of the projector at 16:45, was traveling slowly directly away from the

projector. It turned slowly to the right and dove oriented north into the pack ice (Fig. F-2l). Finally, a

whale seen 660 m NE of the projector at 17:36, some 6 min after the projector stopped transmitting

icebreaker sounds, was heading NNE (Fig. F-22). The expected heading along the lead would have been

ENE. This whale would have been near its CPA to the projector when the projection stopped. It apparently

continued its NNE heading after it dove and it resurfaced along the edge of the brash ice 1.4 km NNE of

the projector. It then turned and followed the ice edge eastward (Fig. F-22).

In addition to the whale seen presumably feeding near the ice camp, aerial observers saw presumably

feeding bowheads along the ice edge ENE of the camp. One subadult whale that was 825 m NE of the ice

camp appeared to be feeding. It surfaced close to the ice edge heading NNW, turned slowly south, then

dove sharply under the landfast ice edge. Two subadults 1.5 km NE of camp were also observed diving

under the landfast ice edge heading ESE.

A group of 4-5 whales was engaged in social/sexual behavior -5.0 km WSW of camp during the

playback from 15:27 to 16:14. One whale repeatedly breached and lunged near the group. Another

bowhead 4.6 km W of the ice camp was possibly disturbed by the observation aircraft when the aircraft

passed almost directly over the whale at 16:20 (actual lateral distance unknown). Initially the bowhead was

traveling ENE; it turned sharply, almost stopped, and then dove with a final heading of WNW.
18:~

~

8:05 .r'>:

., a 18:11 ! 15:59[3]

18-20 18:00 .-

- 18:15[2] \ \ 18:18 1,*

15~.4 15:52\,.15:45

e~~-

" !W1S:49

15:22[4J ,,' 15:51 !" 1S:~,'

--. lS~

;:~

r16:22 •.•..

15:57[3]

•• ••

....- •••

0 500 1000 Yards

'0- - SOO -1000 Meters

LEGEND

CD Projector

• Theodolite

r Monitor Sonobuoy

DOpen Water

\:«::1 Brash Ice

oOld Ice

• Aerial Obs., During Ice-breaker Playback

A Aerial and Ice Camp Obs., During

Ice-breaker Playback

-- Interpolated Surface Travel

- - - - Presumed Underwater Path

~ Whale Sighting and Heading

Q Social Group

0* Breach

oi Tall Slap

Of Feeding

Oa Aircraft Disturbance

-:;::::::-Track Continued On Next Map

FIGUREF-21. Aerial observations of bowhead tracks relative to the projector broadcasting icebreaker sounds along the landfast ice NE of Pt.

Barrow,9 May 1994, times 15:11-17:30. v,

------ ----------- -----
Q "500 ." "1000 Ya.rds "

LEGEND

• Projector

• Theodolite

DOpen Water

1:::::::1 Brash Ice

oOld Ice

() Aerial Obs., Within 30 min. Post-playback

4 Aerial and Ice Camp Obs., Within 30 min. Post-playback

-- Interpolated Surface Travel

- - - - Presumed Underwater Path

0' Whale Sighting and Heading

Om Mother and Calf

.;::::- Track Continued From Previous Map

FIGURE F- 22. Aerial observations of bowhead tracks relative to the silent projector «30 min after icebreaker playback) along the landfast ice NE

of Pt. Barrow, 9 May 1994, times 17:31-18:01. Ice-based observations are included where they concern bowheads observed from both the aircraft

and the ice. aircraft. ~00

o

-----------
LEGEND

• Projector

• Theodolite

DOpen Water

1:::::::1 Brash lee

o Old Ice

o Aerial, During Control Dbs.

A Aerial and Ice Camp, During Control Obs,

-- Interpolated Surface Travel

- - - - Presumed Underwater Path

0--' Whale Sighting and Heading

Q Social Group

Of Feeding

.. . .

....

::::::::::.::::::.:~:.::.::

··m. .

. .

19:11

. . (). . . .100. . . 20() Yards

·0 .. 1M ... 200 Meters

·0 500 1000 Yilfds .

.. 0 .: . .50.0 .. . WOO. Met~rs

FIGUREF-23. Aerial observations of bowhead tracks relative to the silent projector (>30 min after icebreaker playback) along the landfast ice NE

of Pt. Barrow, 9 May 1994, times 18:02-19:54. .j:>..

00

-
Appendix F: Individual Playbacks/9 May 1994 482

A bowhead mother and calf were observed 1.5 km WNW of camp during the 30 min post-playback

period. The pair traveled at medium speed heading NE along a row of brash ice. The calf was seen 'riding'

(Fig. F-22). This was the only mother and calf observed during this study in 1994.

Approximately 3/4 of the bowheads observed during more than 30 min after the end of the playback

period (18:01 to 19:54) were traveling ENE along the north side of the lead, generally parallel to the edge

of brash ice or pack ice (Fig. F-23). Most of the other whales seen during this period traveled ENE along

the landfast ice edge, but one small whale was seen 600 m WSW from camp heading SSW away from the

ice camp at very slow speed. Seven whales (6 groups or singletons) were seen within 1 km of the silent

projector. The CEPA was 17 m (theodolite measurement, see "Ice-based Observations" above). This same

whale surfaced 100 m WSW of the ice camp 13 min later and subsequently it again dove under the ice edge.

A subadult (possible yearling) was also observed twice -110 m WSW of the ice camp. It was stationary

while at the surface, and when it dove it went under the ice edge. Like several whales seen by the ice

camp, this lingering whale may have been feeding along the landfast ice edge.

Noise Exposure.-Icebreaker sounds were projected into the lead from 14:22 to 17:30 using only the

J-11 projector. The median broadband (20-5000 Hz) source level of icebreaker sounds (RLBB,med)was

~ 162 dB re 1 /-lPa-m from 14:22 to 15:02,

~ 153 dB from 15:02-16:20, and

~ 156 dB from 16:26-17:28.

Corresponding source levels for the dominant 113-octave bands were 157 dB near 500 Hz, 146 dB near both

315 and 400 Hz, and 149 dB near 200 Hz. Figure F-24A shows, for the last of these three periods, the

variability in the sound levels as projected (l-m source levels) and as received at 1 km range. Figure F-24B

shows the estimated median received levels at several standard distances at the same time.

At 12:34 on 9 May 1994, a 57A sonobuoy was deployed manually 890 m WSW ofthe ice camp along

the edge of the landfast ice. A 53B DIFAR sonobuoy was air-dropped in the main lead 3 km WSW of the

ice camp at 16:22. Ambient noise measurements were obtained from the monitor hydrophone near the

projector and from the 57A sonobuoy. The average broadband (20-5000 Hz) ambient noise level was 100

dB re 1 /-lPa,and ambient noise levels in 1I3-octave bands were relatively uniform across a wide frequency

range (84-87 dB, pluses in Fig. F-24).

Traveling Whales: Because of the variability in the source levels of the projected icebreaker sounds

over time, the closest traveling whales to the projector were not necessarily exposed to the highest received

levels (Table F-3). The highest maximum 20-5000 Hz broadband signal (118 dB re 1 /-lPa)was estimated

for a whale that was 206 m from the projector at 16:50. The highest median broadband signal over 1 min

(at least 115 dB) was estimated for a whale that was estimated to be 60 m from the projector at 16:34, based

on interpolation of positions (Fig. F-21, F-25). A whale sighted 206 m west of the projector at 16:50 was

subjected to the highest maximum icebreaker:ambient ratio in the strongest 113-octave band (26 dB), and

the whale whose CPA was estimated as 60 m from the projector was subjected to the highest median icebreaker:ambient ratio in the strongest 1I3-octave band (Fig. F-25). Traveling whales were exposed to

substantially lower signal:noise ratios than some feeding whales, given the close CEPA distances of some

feeding whales (Fig. F-26).

Feeding Whales: The closest observed bowheads to the operating projector on this date were feeding

whales. These whales have not been included in our analyses of the CEPA distances or behavior of traveling whales, presented in sections 6.2 and 6.3. The closest of these whales to the projector was sighted 17 m

from the projector at 16:20; at that time the whale dove toward the ice edge, angling toward but to the side

of the projector. During that minute, the median and maximum broadband received levels at a horizontal

distance of 17 m from the projector were estimated as 128 and 132 dB re 1 /-lPa. The median and maximum

levels in the dominant 1I3-octave band were 121 and 123 dB in the band centered at 250 Hz. Thus, median

and maximum icebreaker:ambient ratios in the strongest 1/3-octave band were 36 and 38 dB. Another
170

150

-"0m

-- 130

~

-g 110

ca

rn

t3

o 90

I

~

or70

50

10

Appendix F: Individual Playbacks/9 May 1994 483

9 May 1994,16:41

I

-

A. SL- 1m

/;.__ •..•..••..•.•-.....•..•................ ..-...•

~ ...=:....

~

RL- 1.0km

.~

;::: -,

'"

.•...... .•........._.•.•-

--+-

••.•..........•..._ ........

.....•..........•

"/,,,, .........•

........ ,.. -. ..•....•.••..........•.••..-,.........._.•_.•.•.•~ Amb.

•.•...•. ...._.....

-..- " .

~

v- 5%, 95%SL

.........._•..•...... "\" -

<, -

"

5%, 95%RL

.•....... .-....

............ .-.......

/'00".. /~ <,

L .•.;.... /~-........ .•... -,......... ...•

~

f

.....•...... ~ .•.•/

"<,,"<, ./ / ...... ' -

"'--'" ~ -

- /" ./"/ •...•......•.,......

..•... /--:..... 1/' ......

..-</ ........ .........•..•.•.......•..................• .,.......

....

f

..••.....••..

,

f

./ .....

~. .....-

, I I I I I. I I t

100 1000 10000

9 May 1994, 16:41

170..,.-------.-_,r--.-------r--.---r-----_,r--;---, r----...,

1501----r-TI-;;:::IFII::iiiI~.-I-I---_t-il

130

~

-g 11O-+----- __I-----::;'+--+-~=:_--t----''"'':+-+-----_t--+--I

ca

m

t3o 90+-,~----¥-,..::--+:-:::-+7'_--~=f'~----"I~'t<::-----_+_--+-_l

I

~ori

B. --- SL-1 m

Ree. Level

--+-

Amb.

-

-

30m

I I

100 1000

1/3-0ct. Center Frequency

I I I 10000

FIGURE F-24. Third-octave levels of projected icebreaker noise vs. distance from projector and ambient

noise, 9 May 1994, time 16:27-16:41. (A) Variability over 14 min at ranges 1 m and 1.0 km (median,

5th and 95th percentiles). (B) Median levels at range 1 m (squares) and 30 m-3.0 km. Plus signs show

average ambient noise level before and after playback. For additional explanation, see caption to Figure

F-2 or F-3.
--- SL-1 m

-aRL- 60 m

-+-

Ambient

Appendix F: Individual Playbacks/9 May 1994 484

9 May 1994,16:34

170-r------,-----r---r------,----,.-~-----r__-~__, r__---,

~

"0

C

m

co

t5

oI

(")

-T""

130-/------+-r--t--t-------i1---+-lH------+--_t__t

110-/------+--t--t-="""""6l:----i1---+--+------+--_t_-1

..L. ..L.

I

I

I

I

70+------~-_t_-t------t--_+-_t_-----~-_t__t

I I I I I I

100 1000

1/3-0ct. Center Frequency

-

20-dooo

SS L

1 vel

•

FIGUREF-25. Third-octave levels of projected icebreaker noise 1 m from the projector (closed

squares) and near a bowhead 60 m from the projector (median level over 1 min), 9 May 1994, time

16:34. Plus signs show average ambient noise level before and after playback. For additional

explanation, see caption to Figure F-4. However, because of the short range, received levels at

60 m were estimated from source levels assuming spherical spreading.

-.. -

I

-

feeding whale sighted 24 m from the projector at 16:29, which also dove under the ice edge angling toward

the projector, was subjected to even higher noise levels before it surfaced:

• broadband: 132 dB re I ~Pa median and 135 dB maximum;

• strongest 113-octave (near 200 Hz): 126 dB median and 129 dB maximum

• icebreaker:ambient in strongest 1I3-octave band: 41 dB median and 44 dB maximum.

Several other feeding whales sighted at various distances from the projector were subjected to similar

icebreaker:ambient ratios (Table F-3, Fig. F-26).

Summary.-On 9 May 1994, the ice camp was set up along the landfast ice edge about 2.5 km

northeast of the 7 May location, and 3.9 h of pre-playback control observations were obtained from the ice.

During this period 10 presumably undisturbed bowheads were sighted. Then icebreaker sounds were

projected into the lead adjacent to the landfast ice for 3 h, during which 32 bowheads were observed from

the ice and aircraft. There was a further 3-h period of observations after the playback ended, during which

-43 bowheads were seen from the ice and aircraft. Interpretation of the distribution and heading data was

complicated by lingering whales that were probably feeding under the landfast ice near the ice camp.

I I

- 0

+

I

10000
Appendix F: Individual Playbacks/9 May 1994 485

Traveling vs. Feeding Whales, 9 May

50

+

+

+

+ +

+ +

+ +

+ +

+ ++ +

+ +

+ +

+

++

-f:+ +: +...p;--P.- +

-+'-

~

+ +

+

+ +

4- -+t-t "!+-

.p-'t-+t ++ + ~ +

...T+ ++ +++

T +

*

+

-++ + ++++ ++ +

+

+

± + ±-+:t

, , ,

3

40

-a:l

"0

-~ 30

0

as .0

~

a.. 20

C)

c

"i:: ::J

"0 10

Z

en

0

E~

-•...

2 0

'0

Q)

·0•... a..

E

o

~

Q)

o

c:

as 1;)

C5

-10 o

Travel Feed Travel Feed Travel Feed

Max. 20-5000 Hz Max. 1/3-0ct. Distance

FIGURE F-26. Estimated signal-to-noise ratios (S:N) for icebreaker sound vs. ambient noise at the

"CPA distances" of presumably feeding and traveling bowheads seen within 3 km of the ice camp

on 9 May 1994. Maximum broadband (20-5000 Hz) and maximum 1/3-octave received levels during the I-rnin period previous to the CPA were used to compute the S:N ratio for each whale.

Many CPA distances are overestimated, so S:N values are often underestimated. Also shown on

the right side of the panel are the CPA distances for which the S:N ratios are computed.

During all periods, bowheads traveled predominantly NE or ENE along the lead. A few whales

sighted from the ice camp and aircraft may have altered their headings to avoid closer approaches to the

projector (see Table 6.5 on p. 274), but other whales that appeared to be feeding headed generally south

toward the landfast ice and projector. Two bowheads seen 940 m WSW of the operating projector at 17:26

appeared to temporarily modify their path at that time and distance in response to the icebreaker playback.

They resumed traveling toward the ice camp a few minutes after the projector was turned off at 17:30. Another group reversed course WSW away from the projector; that group may have been feeding. Some

whales sighted WSW to N of the ice camp during the playback had northerly rather than NEerly headings,

suggesting that they may have been altering their tracks to avoid closer approach to the projector. However,

during the post-playback period, bowheads did not resume traveling along the landfast ice near the ice

camp; after the playback more bowheads traveled along the pack-ice edge forming the north (far) side of

the nearshore lead than along the landfast ice, in contrast to the situation before and during the playback.

On 9 May 1994, traveling whales at their CEPA were exposed to RLBB.maas• high as 118 dB re 1 IlPa,

RL1/3.maxas high as 111 dB re 1 IlPa, S:NBB.maas• high as 18 dB, and S:NII3.maxas high as 26 dB. The group

sighted 940 m from the projector at 17:26 appears to have modified its path at RLBB.max=107dB re I IlPa,

RLI/3.max=101dB re 1 IlPa, S:NBB.ma.=7dB, and S:NI/3.ma.=16dB.
Appendix F: Individual Playbacks/9 May 1994 486

There were no clear differences in the distribution or behavior of presumably-feeding bowheads

during the control versus playback periods. Bowheads that were apparently feeding near the projector while

it was silent continued to do so, sometimes within a few tens of meters of the projector, while icebreaker

sounds were transmitted. The strongest levels received by feeding whales exceeded 130 dB re 1 j.!Pa

(RLBB,max);the highest icebreaker:ambient ratio was >40 dB (S:N1/3,max)' These whales appear to have

tolerated levels 15-20 dB higher than did the closest traveling whales on this date.

14 May 1994 Playback

The ceiling on 14 May was low, preventing aerial observations of bowhead behavior. The Twin Otter

crew conducted a reconnaissance survey (from 08:55 to 10:12) to help the ice-based crew find a suitable

ice camp location where bowheads were present. The ice camp was set up 70 km ENE of Point Barrow on

the landfast ice edge along a major lead oriented E- W (Fig. 3.8, p. 77). North of the ice camp the lead was

-3-4 km wide. Small pieces of brash ice were scattered throughout the lead. The crew arrived on the ice

at 09:51 and remained there until 21:34. Very weak test-tones were projected from 13:24 to 14:08; these

were considered too weak to be disturbing. Strong tones were projected from 14:08 to 15:45. Icebreaker

sounds were projected from 15:50 to 19:00 with a brief interruption from 17:52:02 to 17:52:31. One side

of the Argotec projector plus the I-II projector were used on this date. The measured water depth at the

projectors was 40 m.

Ice-based Observations.-About 30 bowheads (-24 groups or singletons) were estimated to have

moved by within view «1800 m) of the ice camp during 11.8 h of observation. One-half of the groups

were observed before the projectors began broadcasting sounds. Few (3) groups were sighted after the

playback, and these three groups were seen ~30 min after playbacks ended.

A total of -17 bowheads (-13 groups or singletons) were observed during control observations from

09:49 to 14:08; sightings during projection of very weak tones were considered control observations. Many

of these groups were engaged in activities other than traveling, i.e., socializing and possibly feeding. As

a result, the headings of whales were variable and even the headings of traveling whales may have been

influenced by the activities of these non-traveling groups (Fig. F-27). The closest observed approach to

the silent projectors was <50 m (visual estimate, Table F-4). This group of 3 whales did not appear to react

to the helicopter as it landed at the camp -150 m away. The next closest CEPAs were <232 and 282 m.

Nine groups (64%) were observed <500 m from the projectors.

While the projectors were broadcasting strong tones from 14:08 to 15:45, -6 bowheads (5 groups or

singletons) were sighted by observers at the ice camp. All whales were headed ENE or ESE up the lead

at medium speed. Most groups (83%) were observed >1000 m from the projectors at or near their probable

CPA while tones were being projected.

From 15:50 to 19:00, while icebreaker sounds were being projected, -3 singletons were sighted by

observers at the ice camp. The two whales with known headings were traveling ENE up the lead at medium

speed. The other whale was briefly engaged in aerial activity (tail slapping at 18:35, Fig. F-28). The closest observed approach to the projectors was 509 m (theodolite measurement). The other two bowheads were

each observed once ~1900 m from the projectors (Fig. F-28).

During the post-playback period from 19:00 to 21:34, -3 single bowheads were sighted by observers

at the ice camp, all ~30 min after the playback ended. All were traveling ENE at medium speed at or near

their CEPA to the ice camp. The CEPAs were -650 m (visual estimates) by two singletons. The third

whale passed the projectors at a distance of -1760 (theodolite measurement; perch height 4.65 m).

Noise Exposure.-From 15:50 to 19:00, icebreaker sounds were projected into the lead using the I-II

and one side of the Argotec 220. There were a few brief periods when source levels were reduced by -6

dB, but for most of the period the median broadband (20-5000 Hz) source level of icebreaker sounds was

157 dB re 1j.!Pa-m, considering the full 14-min cycle of the icebreaker sound. The corresponding source

level for the dominant 1I3-octave band was 151 dB near 80 Hz. Figure F-29A indicates the variability in
LEGEND

• Projector

• Theodolite o Open Water

o Old Ice

o Ice Camp, During Control Obs.

-- Interpolated Surface Travel

- - Presumed Underwater Path

0' Whale Sighting and Heading

Q Social Group

0* Breach

Oh Helicopter Disturbance

10:32

n ~_... 10:39 r~_@ cI' 10:4S....•...... EJ

10:31(2) 10:36

......•11:0S

......... ~ .•.11:32

.......•:f§~

11:22 11:24[3)

lY

12:08[2]

GJ....

12:32

[3-'"

12:09

..

_-.==, .

. Q' ., 109 '?OQ Yarc;js , .

, ,0 " '1,00,' '~Oo Meters,

SOOYards' --='=•...••==•...•

, ,500'Meten, .

o

, , '0

FIGURE F-27. Ice-based observations of bowhead tracks relative to the silent projectors (pre-playback) along the landfast ice NE of Pt. Barrow,

14 May 1994, times 09:49 to 14:07.
LEGEND

~ •

Projector

-e e Theodolite

~

o Open Water

DOld Ice

1m Ice Camp Obs., During Tones Playback

I. Ice Camp Obs., During Ice-breaker Playback

m Ice Camp Obs., Within 30 min. Post-playback .- -- Interpolated Surface Travel

18:43 m- - - - Presumed Underwater Path

19:14 0' Whale Sighting and Heading

Ot Tall Slap

15:08[2] '------

W"

IlD14:50

e--

r

15:07

15:24

r

15:00

Ir'" .t [Y" 19:30

18:35 19:19...-

17:38

-

<. . _e

_.

0 500 Yards'

0 'SOOt,1et,ers '

FIGUREF-28. Ice-based observations of bowhead tracks relative to the sound projectors along the landfast ice NE of Pt. Barrow, 14 May 1994,

times 14:08-21:34. The projectors broadcasted tones from 14:08 to 15:45 and icebreaker sounds from 15:50 to 19:00.
TABLE F-4. Summary of sightings of bowhead whales observed by ice-based and aerial observers, 14 May 1994.

Radial Distance CEPAaSight- Estimated Sound Levels Near Whalesd

Group Followed From Distance ing RLBB RLI/3 S:NBB S:NI/3

Time size Projector (m)e (m) Time ethod Crew med max med max med max med max Nature of Track

A: Pre-Playback Control (09:51 to 14:08)

09:49 3 -150 to -50 <50 09:49:00

10:31 2 -680 to -433 433 10:36:00 1

10:46 1 -320 to -312 300 10:46:25 1

11:00 1 +350 to +398 340 11:02:02 1

11:01 1 single sighting <334 11:00:56 1

11:12 2 -290 to +510 282 11:12:21 1

11:15 1 +465 to +510 460 11:15:21

11:44 1 -636 to -631 <631 11:44:19

12:08 2 single sighting <1710 12:08:20

12:09 1 single sighting <895 12:09:05

12:24 1 -408 to -232 <232 12:25:24

12:32 single sighting <1335 12:31:34

13:51 +327 to +329 327 13:51:08

B: Playback of Tones (14:08 to 15:45)

14:50 1 single sighting 1510 14:50:00

15:00 1 single sighting < 1295 15:00:15

15:07 1 -1212 to -1210 1210 15:07:11

15:08 2 single sighting 1390 15:08:19

15:24 1 single sighting < 1250 15:24:24

C: Icebreaker Playback (15:50 to 19:00)

17:38 1 -515 to -510 509 17:37:49 1

18:35 1 single sighting 1900 18:35:00 1

18:43 1 single sighting 1950 18:43:12 2

2 IC N of projector heading SE; social. No apparent reaction to heli, -150

m S of whales, 1 whale breached, others remained at surface as heli,

turned then landed on ice at 9:50. Whales dove under ice edge -20 s

after heli. landed

NW of projector, heading variable/social mill; spyhop, feeding?

NW of projector heading NE

N to NE of projector, heading variable/slow mill

NW of projector heading ENE

N to NE of projector, slow mill with overall heading to NE. Joined

group below at -11:24, socialize and aerial

NE of projector heading NNW. Joined group above at -11 :24

NW of projector heading ENE

NW of projector heading ENE

NW of projector heading ENE

Subadult, N of projector heading ENE then SE, 13. min after heli.

overflight

NNW of projector heading ESE

N of projector heading ESE

IC

IC

IC

IC

IC

IC

IC

IC

IC

IC

IC

IC

IC

IC

IC

IC

IC

NE of projector heading ESE

NW of projector heading ENE

N of projector heading ENE

N of projector heading ENE

NW of projector heading ENE

IC

IC

IC

107 109

98 102

104 109

98 99

93 95

101 103

11

4

11

11 12 NNW of projector heading ENE

14 16 WNW of projector, heading unknown; tail slaps

22 24 NW of projector heading ENE

9

o

6
TABLE F-4. Continued.

CEPAa Estimated Sound Levels Near Whales

Group Followed From Distance ing S:NBB S:Nv3

Time size Projector (m) (m) Time ethod Crew med max med max med max med max Nature of Track

D: <30 min After Playback (19:00 to 19:30)

19:14 1 single sighting 1760 19:14:29

19:19 1 single sighting 650 19:19:00

19:30 1 single sighting 650 19:30:30

IC

IC

IC

NNW of projector heading ENE

NW of projector heading ENE

N of projector heading ENE

1

2

2

E: Post Playback Control (> 19:30 - No whales were observed)

a CEPA = Closest Estimated Point of Approach. See text for description of estimation procedures.

b 1 = measured by theodolite at CPA; 2 = visual estimate at CPA; 3 = estimate based on theodolite measurement(s) to nearby surfacings; 4 = estimate based on whale position(s) and

heading(s) during sightings distant from CEPA (possibly unreliable).

c IC = ice-based crew; A = aerial crew.

d Data in italics are not included in analyses of traveling whales because this whale was engaged in aerial activities.

e "_" indicates that whales were approaching. generally from the SW or W; "+" indicates that whales were moving away. generally to the NE or E.
150

-m

"0.....-

130

Q)

>CD ....I

"0

c 110

CO

m

t5

0 90

I

('I)

-T'""

70

Appendix F: Individual Playbacks/14 May 1994 491

14 May 1994, 17:38

,.'---'~~,... / ~-- ._.1-..--._<,_ .._ •.•.•

1

/···~1·'······1·-·-······/ _ - / ~ ~ .

,'~' .•. , .••... ,'.... ~

I I I r··. !

L I .r-, ~ I I .

~

~/II I I <. I······· I

i / i I ! -.,

/ i I I I {

• I" ,. .

, ,. 100 I '1 000 ' '" '10000

5%,95%RL

14 May 1994,17:38

SL-1m

RL-1.0km

-+-

Amb.

5%,95%SL

170.-------r-----.--.--------,---.--.-----,--..,....---, r-----,

150+------+--+-'!-------+---+--+-----+--+--I

130+-----Jll: •. -+-+1-~--_t--1-+_--=:::a~.J:_--+-_1..... ------'

! I

"Oc110+--' l---:o~~ .A··.--,--. _~: 'i-•.,.-----+--+--I

co ---"-I··t••••• rr ······'r·· I

ti 30m / -r·f-/--/r··~---·_-·-

~ 90 100m ./ ~:~!::::::L~:::~::··· :::,~

70-+--~/rO/

:: ,.'

~ / 1..1.,.

........•....•

~- +

I

300m/!.//" ········_······.t -. I'

1 krn z ! 1"'" ,

B.

100 1000

1/3-0ct. Center Frequency

--- SL-1m

Ree. Level

-+-

Amb.

10000

FIGUREF-29. Third-octave levels of projected icebreaker noise vs. distance from projectors and ambient

noise, 14 May 1994, time 17:24-17:38. (A) Variability over 14 min at ranges 1 m and 1.0 km (median,

5th and 95th percentiles). (B) Median levels at range 1 m (squares) and 30 m-3.0 krn, Plus signs show

average ambient noise level after playback. For additional explanation, see caption to Figure F-2 or F-3.
Appendix F: Individual Playbacks/14 May 1994 492

14 May 1994, 17:38

170.--------r--,---r-----,----r----r------r--......,...---.,,------,

o

--- SL-1m

-aRL-509 m

-+-

Ambient

110+------f---t---Jf-----t--+--f------t---t---l

I I

1501---I--t=1---Jii;::jll:ttHi~-_=_I__t1

130+-----;III~-__+-+_----_+-_+-+_---'-----+--__j_--t

+

100 1000

1/3-0ct. Center Frequency

10000

FIGUREF-30. Third-octave levels of projected icebreaker noise 1 m from the projectors (closed

squares) and near a bowhead 509 m from the projector (median level over 1 min), 14 May 1994,

time 17:38. Plus signs show average ambient noise level after playback. For additional

explanation, see caption to Figure F-4.

the sounds as projected (l-m source levels) and received at I km range. Figure F-29B shows the median

received levels at several standard distances at the same time.

Ambient noise was measured from the monitor hydrophone after the playback experiment. The

ambient noise level was 98 dB re 1 IlPa broadband (20-5000 Hz) and 93 dB for the strongest 113-octave

band (centered at 630 Hz). Ambient noise in the 113-octave band centered at 80 Hz was 79 dB re 1 IlPa;

this band had the dominant source level of icebreaker sounds.

The closest whale to the operating projectors on this day was sighted 509 m away at 17:38 (Fig.

F-28); the whale was traveling tangential to the projectors and dove at approximately the same distance.

In the preceding 64-s period, the median and maximum broadband received levels at that distance were

estimated as 107 and 109 dB re 1 IlPa. The median and maximum 113-octave levels were 98 and 99 dB in

the band centered at 400 Hz. Thus the median and maximum icebreaker:ambient ratios in the strongest 1/3-

octave bands were 11 and 12 dB. However, the icebreaker:ambient ratios in the band centered at 80 Hz

were 16 and 17 dB, respectively, given that the ambient noise was weaker in that 113-octave band (Fig.

F-30). The only other two whales sighted during the playback were -1900 m from the projectors at 18:35

and 18:43. The median and maximum received levels at that distance at 18:43 were 104 and 109 dB re

1 IlPa broadband and 101 and 103 dB in the 113-octave near 80 Hz, on the usual 64-s basis. The median

and maximum icebreaker:ambient ratios in the strongest 1/3-octave band were 22 and 24 dB.
Appendix F: Individual Playbacks/14 May 1994 493

Summary.-On 14 May 1994, the ice camp was set up on the landfast ice edge 70 km ENE of Pt.

Barrow (see Fig. 3.8 on p. 77) along a 3-4 km wide nearshore lead. All observations were from the ice

because low ceilings prevented behavioral observations from the aircraft. A total of 17 bowheads (13

groups) were observed during 4.3 h of pre-playback observation while the projectors were silent. Nine of

these groups were seen relatively close «500 m) to the silent projectors. The closest CEPA relative to the

ice camp was -50 m, during the pre-playback control period. During playbacks of tones (for 1.6 h) and

icebreaker sounds (for 3.2 h), five and three groups, respectively, were sighted. They were all >500 m from

the projectors; the closest sighting was 509 m away during the icebreaker playback. Three other groups

sighted <30 min after the playback ended were also >500 m from the projectors. Thus the distribution of

whales relative to the ice edge appears to have changed during the day. The closest whale observed during

the icebreaker playback was exposed to an estimated S:N l/3.rnaxof 17 dB. One whale seen farther from the

projectors at a time of higher source level was exposed to S:Nl/3,rnax= 24 dB. During the pre-playback

control period, many of the whales seen were socializing and perhaps feeding, but during and after

playbacks only traveling whales were observed.

16 May 1994 Playback

The ice camp was set up on the north side of a large elongated ice pan that had broken off the

landfast ice edge. The lead bordering the north side of the pan was a secondary (offshore) lead amidst the

pack ice. The main nearshore lead was south of the elongated pan. The ice camp was -8 km north of the

landfast ice edge. The secondary (offshore) lead was oriented ENE-WSW. The width of the secondary lead

directly north of the ice camp was -3 km. The lead contained scattered brash ice and was covered with

slush ice that froze during the day. A large pan SW of the ice camp pan rotated counterclockwise during

the day such that, in the afternoon, it extended diagonally across the inner lead south of the ice camp pan,

This rotating pan had originally been part of the ice camp pan,

Aerial reconnaissance from 08: 14 to 09:37 showed that many bowhead whales were traveling along

the offshore lead far to the east of the area described above. However, a few whales were traveling in the

offshore and nearshore leads in the described area. Given the prevailing logistic, ice and weather

conditions, it was decided to attempt a playback at the site described above. The ice-based crew was

present from 09:56 to 19:00. Tones were projected from 12:50 to 12:59 and icebreaker sounds from 13:03

to 17: 13. The projector configuration included one side of the Argotec 220 plus the J-1 I. The measured

water depth at the projectors was 149 m.

Ice-based Observations.-A total of -4 bowheads (3 groups or singletons) moved by within view of

the ice camp «1500 m) during 9. I h of observation (Table F-5). All sightings occurred while the projectors

were broadcasting icebreaker sounds. The closest observed approach to the ice camp was 570 m (theodolite

measurement; Fig. F-32). This bowhead was observed at 14:25 resting at the surface for <30 sec and

oriented NE. The other two CEPAs were at 840 and 775 m. The first of these was a pair of bowheads

sighted NW of the projectors and traveling NE along the lead at slow speed from 14:28 to 14:29. The second was a singleton that rested at the surface for at least 6 min while oriented WSW in a hole in the consolidated slush ice. The singleton reoriented to the ESE when it slipped below the surface at 15:54.

Aerial Observations.-Two aerial observation sessions were conducted on 16 May 1994. During the

first session, bowheads were followed from 4.8 km SW of camp at 12: 17 to 5.9 km SE of camp at 14:21

(Fig. F-31, F-32), Two whales were observed WSW of the ice camp traveling NE along the south side of

the offshore lead. One group of five individuals was actively socializing in the same area. One identifiable

whale was followed from 12:53 to 14: 17 while tones (12:50-12:59) and then icebreaker noise (13:03- 17: 13)

were projected into the lead (Fig. F-31, F-32). After the icebreaker playback started (13:03), this focal

group and all other whales observed from the circling Twin Otter diverted from the offshore lead through

a narrow crack in the elongated pan. This crack provided a route into the inner lead. The focal group then

passed 2.0-2.3 km SSW of the projectors along the south side of the ice camp pan, i.e. the north side of the

inner lead. The CEPA of the focal whales was during the icebreaker playback. Given the earlier sightings
LEGEND

• Projector

• Theodolite

:- Monitor Sonobuoy

DOpen Water

1:<::::1 Brash Ice

oOld Ice

o Aerial, During Control Obs.

@ Aerial Obs., During Tones Playback

• Aerial Obs., During Ice-breaker Playback

() Aerial Obs., Within 30 min. Post-playback

-- Interpolated Surface Travel

- - - - Presumed Underwater Path

~ Whale Sighting and Heading

Q Social Group

! Track Continued On Next Map

o

o

500

500

FIGUREF-31. Aerial observations of bowhead tracks relative to the sound projectors amidst the pack ice NE of Pt. Barrow, 16 May 1994, times

12:17-13:01. The projectors broadcasted tones from 12:51 to 12:59.
14:2~1!

~:48

15:54.

14:25

·13:22· .

LEGEND

" Projector

• Theodolite

l Monitor Sonobuoy

DOpen Water

1:;::::1 Brash Ice

o Old Ice

• Aerial Obs., During Ice-breaker Playback

• Ice Camp Obs., During Ice-breaker Playback

-- Interpolated Surface Travel

";.;"; ";.Presumed Underwater Path

0' Whale Sighting and Heading

,f Track Continued From Previous Map

o 1000 Yards

1000 Meters

FIGUREF-32. Aerial and ice-based observations of bowhead tracks relative to the sound projectors amidst the pack ice NE of Pt. Barrow, 16 May

1994. The projector broadcasted icebreaker sounds from 13:03 to 17: 13. Aerial observations of bowhead tracks are shown for the period 13:02-

14:21. Ice-based observations of bowhead tracks are shown for the period 13:02-17:13.

500

o 500
TABLE F-5. Summary of sightings of bowhead whales observed by ice-based and aerial observers, 16 May 1994.

Radial Distance CEPAa

Sight- Estimated Sound Levels Near Whales

Group Followed From Distance ing RLBB RL1I3 S:NBB S:N1I3max

Time size Projector (m)d (m) Time Methodb Crew c

med max med max. med max. med max Nature of Track

A: Playback of Tones (12:50 to 12:59)

12:53 2 -3300 to -3150 3150 12:58:45 2 A SW of projector heading NE along ice edge, turned ESE.

Whales resighted during playback

B: Icebreaker Playback (13:03 to 17:13)

13:13 1 -3150 to +5900 2300 13:13:14 2 A 106 109 100 102 17 20 22 24 SSW of projector heading SSE, then E along S edge of

pan with projector. 1 of 2 above whales, appears to have

diverted from initial NNE heading

13:07 2 -2420 to +4200 2000 13:14:00 4 A 105 109 98 103 16 20 22 27 2 adults SSW of projector following S edge of pan with

projector

13:19 -3150 to +5100 2250 13:18:45 2 A 105 107 98 99 15 18 24 25 S of projector heading SSE then E along S edge of pan

with projector. 1 of 2 whales initially described at 12:53,

appears to have diverted from initial NNE heading

14:25 1 single sighting 570 14:25:09 1 IC 110 115 102 107 20 26 26 30 NW of projector resting at surface oriented NE

14:28 2 -855 to-840 840 14:29:12 1 IC 108 113 101 104 19 24 27 29 NW of projector heading slowly NE

15:48 1 -805 to -775 775 15:53:40 1 IC 114 119 108 110 24 30 34 36 NW of projector resting for 6 min at surface oriented

WSW then NE in hole in consolidated slush ice

a CEP A = Closest Estimated Point of Approach. See text for description of estimation procedures.

b 1 = measured by theodolite at CPA; 2 = visual estimate at CPA; 3 = estimate based on theodolite measurement(s) to nearby surfacings; 4 = estimate based on whale position(s)

and heading(s) during sightings distant from CEPA (possibly unreliable).

C Ie = ice-based crew; A = aerial crew.

d •_. indicates that whales were approaching, generally from the SW or W; • -i-" indicates that whales were moving away, generally to the NE or E.

------------------------------------------------------------
Appendix F: Individual Playbacks/16 May 1994 497

of whales along the south side of the outer lead, it is possible that the whales diverted southward to avoid

closer approach to the projectors broadcasting tones and then icebreaker sounds. However, changes in the

ice configuration, i.e. the opening of a route into the nearshore lead, could also have contributed to or

caused the observed diversion from the outer to the inner lead.

The second aerial observation session was conducted 9 km SW of the ice camp at the SW end of the

outer lead from 14:31 to 16:22 (Fig. F-33). Five bowheads were observed actively socializing or traveling

slowly eastward. Most whales dove under the large consolidated ice pan SW of camp and moved into the

inner lead south of the ice camp pan. The projectors were broadcasting icebreaker noise throughout. The

eastward movements were not expected given the general NE movement of whales earlier in the day. Earlier in the day whales were following the NW side of the large consolidated pan toward the ice camp. During

this session one whale actually traveled SE from 15: 11 to 15:25 (Fig. F-33). However the large consolidated pan had rotated _450

counterclockwise since the morning, and the changes in the paths of the whales

may have been due to the changes in ice configuration, which now provided routes from the outer lead to

the inner lead.

Noise Exposure.-From 13:03 to 17: 13 icebreaker sounds were projected into the lead using the J-ll

and half of the Argotec 220. Source levels were adjusted up and down by 2-3 dB during the projection

period, but for most of the period the median broadband (20-5000 Hz) source level over a full 14-min cycle

of icebreaker sounds was 166 dB re 1 J.lPa-m. The corresponding source level for the dominant 1I3-octave

was 158 dB for the band centered at 80 Hz. Figure F-34A indicates the variability in the sounds as

projected (I-m source levels) and received at 1 km range. Figure F-34B shows the median received levels

at several standard distances at the same time.

A 57A sonobuoy was manually deployed 715 m WSW of the ice camp along the southern edge of the

outer lead at 11:30. The aircraft crew deployed two sonobuoys along the path of the whales followed by

the aircraft crew (Fig. F-31, F-32). The first was dropped 3.4 km WSW of the ice camp at 12:48 in the

outer lead. The second sonobuoy was dropped 3.8 km SSE of the projectors in the inner lead south of the

ice camp pan at 13:54. Ambient noise was measured by hydrophone at the ice camp before and after the

playback experiment, from the first sonobuoy before and after the experiment, and from the second

sonobuoy after the playback experiment. The average broadband (20-5000 Hz) ambient noise level was 89

dB re 1 J.lPa, and the ambient noise levels in the 113-octave bands centered at 400 and 80 Hz were 79 and

75 dB (Fig. F-34).

The closest whale to the operating projectors on this day was sighted 570 m away at 14:25 (Fig.

F-32). The whale was resting at the surface oriented NE. When it dove, it would have approached slightly

closer to the projectors. At that time and horizontal distance, the median and maximum broadband received

levels were estimated as 110 and 115 dB re 1 J.lPa in the previous 64-s period. The median and maximum

1I3-octave levels were 102 and 107 dB in the band centered at 500 Hz. Thus the median and maximum icebreaker:ambient ratios in the strongest 1I3-octave band were 26 and 30 dB (Fig. F-35).

A whale sighted 775 m from the projectors at 15:54 may have been subjected to stronger sounds. The

median and maximum broadband received levels were estimated to be 114 and 119 dB re 1 J.lPa(over 64 s),

and the median and maximum 1I3-octave levels were 108 and 110 dB near 80 Hz. The median and maximum icebreaker:ambient ratios in the strongest 1I3-octave band were 34 and 36 dB.

The CEPA of the whales followed by the aircraft-based crew was -2.0 from the projectors at 13:14

while it was broadcasting icebreaker noise. At that time and horizontal distance, the median and maximum

broadband received levels were estimated as 105 and 109 dB re 1 J.lPa (64-s basis). The median and maximum 1I3-octave levels were 98 and 103 dB in the band centered at 500 Hz. Thus the median and maximum

icebreaker:ambient ratios in the strongest 1I3-octave band were estimated to be 22 and 27 dB.

Icebreaker sounds apparently were clearly audible to bowheads seen during the second aerial observation session that was conducted -9 km southwest of the operating projectors, given the comparatively high

source level and low ambient level on this date. A bowhead that was observed at 15: 11 turned sharply from
LEGEND

• Projector

DOpen Water

f::<::1 Brash Ice

oOld Ice

• Aerial Obs., During Ice-breaker Playback

-- Interpolated Surface Travel

- - - - Presumed Underwater Path

0' Whale Sighting and Heading

Q Social Group

.Landfasf Ice Edge:

. . 0 . 1000Y~rd8'

-=~=-::;:=-==--=:::J

. .0 . . . .1000.Meters ..

500

. .509

FIGUREF-33. Aerial observations of bowhead tracks relative to the sound projectors broadcasting icebreaker sounds amidst the pack ice NE of

Pt. Barrow, 16 May 1994, times 14:31-16:22.
Appendix F: Individual Playbacks/16 May 1994 499

.... 1 ......... I J -

A.

..;;~./ ............. _.•.•.•.•.•...•.•.~r·······....-.......... -...~__....

SL-1 m

/\. .......- / ..•.-.•..•..•.

,,,.•" .....\ - .a_.....

...•.

./ ,.•,........

.................•.....................•...•.....

.....\..

~

RL-1.0km

- .'

_.......••.•.............

...•..•... -+-

........•..•..•..•.•..•....•. Amb.

<, ---_.

••• •.••••• 1 5%,95%SL

................•.

-

5%, 95%RL

r:.:::...~- I

/~ .........~

!

,........,

'j ..... .......... ....•...•.•...

<.--- v...... " ....-. ...,~................. '.'.. "

, •.....••..• /. ........ •.......

//'1'" •...............• \.. "'. ......•...•..

....•..........•. --------- <//. -"

r-,---"~.,<,

..' ..'. . .. --t-

~

. ,.- I

--1--', ""

•.............

/

..~".

'.•..••..

.....••.....••.

, . . . , . , ,

16 May, 14:25

170

150

-III

"0

- 130

~

-g 110

co

III

ti

o 90

I

~.•...

70

50

10 100 1000

170-.-------..,.----,---,...,......------,--..---r--------,--..,....--, r-----,

iii'

"0

-

B.

-!------r--t-.---t------f--+--+--------pt.:::II •..•··jI!

30m

90

70

10000

Ree. Level

-+-

Amb.

--- SL-1 m

FIGUREF-34. Third-octave levels of projected icebreaker noise vs. distance from projectors and ambient

noise, 16 May 1994, time 14:11-14:25. (A) Variability over 14 min at ranges 1 m and 1.0 Ian (median,

5th and 95th percentiles). (B) Median levels at range 1 m (squares) and 30 m-3.0 Ian. Plus signs show

average ambient noise level before and after playback. For additional explanation, see caption to Figure

F-2 or F-3.
Appendix F: Individual Playbacks//6 May 1994 500

16 May 1994, 14:25

170.....--------r---.--r------.-~-.._----_;_-_r__, ,....------.

50

10 100 1000 10000

1/3-0ct. Center Frequency

FIGUREF-35. Third-octave levels of projected icebreaker noise 1 m from the projectors (closed squares)

and near bowheads (A) 570 m and (B) 2000 m from the projector (median level over 1 min), 14 May

1994, times (A) 14:25 and (B) 13:14. Plus signs show average ambient noise level before and after

playback. For additional explanation, see caption to Figure F-4.

150

••.....

CO

"0

- 130 CD

Q) >

-J

"0

c: 110

a1

CO

1:5

0 90

I

C") -or70

100 1000

16 May 1994,13:14

170

B. ---- 20-~:

-~

,.

r- 1-. .-- BB Lbvel

,,.. --- ---

.

0

..a.

r-t-t -"'" 1Sl

= =~

"I<::l.

~

=

~

=-- ~

.r ,.,...,

~ ~

'-'

, -....1--+--,- .1-••

. , , I I I I

150

m

"0

- 130

~

-g 110

a1

CO

1:5

o 90

~or70

--- SL-1 m

-eRL- 570m

-+-

Ambient

--- SL-1 m

-eRL-2.0km

-+-

Ambient
Appendix F: Individual Playbacks/16 May 1994 501

a NE heading to a SE heading while it was 9.2 km from the projectors. At that time and horizontal distance, the median and maximum received levels (over 64 s) were estimated as 93 and 99 dB re 1 IlPa broadband, and 89 and 91 dB in the strongest 1/3-octave, centered at 80 Hz. Thus the median and maximum

signal:noise ratios in the strongest 1/3-octave band were estimated as 14 and 16 dB. The sonobuoy dropped

in the outer lead 3.4 km WSW of the camp showed received levels several decibels higher than those predicted by the model. Therefore, received levels near the whales 9.2 km southwest of the projectors may

also have been higher than those estimated above.

Summary.-The ice camp was set up about 35 km NE of Pt. Barrow (Fig. 3.8 on p. 77) on the north

side of a large elongated ice pan along a secondary (offshore) lead oriented ENE-WSW -8 km north of the

landfast ice edge. The ice camp was present from 09:56 to 19:00, and icebreaker sounds were projected

from 13:03 to 17:13. On this date the median broadband (20-5000 Hz) source level of icebreaker sounds

was -166 dB re 1 IlPa-m (relatively high) and the average broadband (20-5000 Hz) ambient noise level was

89 dB re 1 IlPa (relatively low; Table 6.3 on p. 252).

Only -4 bowheads (3 groups or singletons) moved by within view of the ice camp. All sightings

there occurred while the projectors were broadcasting icebreaker sounds. The closest observed approach

was to 570 m. The other two CEPAs were at 840 m and 775 m. These whales were exposed to strong icebreaker sounds (up to S:NII3•

rnax = 29-36 dB) but no obvious reaction was noted.

During one aerial observation session, bowheads were followed from 4.8 km SW of camp at 12: 17

to 5.9 km SE of camp at 14:21. After the icebreaker playback started at 13:03, these whales diverted SE

from the offshore lead through a narrow crack into the inner lead. They passed 2.0-2.3 km SSW of the

operating projectors and continued east along the south side of the pan along whose north edge the ice camp

was located. At CEPA, RLBB,rned and RLBB,rnax were -105 and 109 dB re 1 IlPa, and S:NII3,rned and S:NII3,rnax

were 22 and 27 dB. It is possible that the whales diverted SE to avoid closer approach to the projectors

broadcasting tones and then icebreaker sounds. However, given the rapidly-changing ice configuration at

the time, this "diversion" may have been related to ice conditions instead of (or in combination with) the

man-made noise.

A second aerial observation session was conducted 9 km SW of the operating projectors, at the SW

extent of the outer lead, from 14:31 to 16:22. Five bowheads were observed socializing or traveling slowly

eastward. During this session, one whale turned from a NE to a SE heading when 9.2 km from the projectors and traveled SE. At that time and distance, S:NI/3,rned and S:NI/3,rnax were at least 14 and 16 dB. The

unusually high icebreaker:ambient ratio for a range of 9.2 km was related to the high source level and low

ambient noise on this date (Fig. F-34). Again, it is uncertain whether the SEward diversion was related to

the icebreaker sounds, to changing ice conditions, or both.

17 May 1994 Playback

The ice camp was set up amidst pack ice on the south-west tip of an ice pan, at the eastern end of

the main nearshore lead. The ice camp pan was bordered to the north and south by secondary leads oriented

NE-SW and ENE-WSW, respectively. The width of the secondary lead south of camp increased from 200 m

to 2.5 km throughout the day as ice pans drifted apart. Aerial reconnaissance from 08:39 to 09:40 showed

that many bowhead whales were traveling along the main nearshore lead into the narrow ENE-WSW branch.

The ice-based crew conducted observations from 11:20 to 17: 15. Icebreaker sounds were projected by the

J-11 projector from 12:48 to 17:02. The measured water depth at the projector was 39 m. The playback

was interrupted briefly from 16:52:21 to 16:53:26. High sea states throughout the day (SS 3-6, depending

on proximity of ice) limited the ability of the aerial observers to resight whales. The ice-based crew left

the ice at 19:47 due to deteriorating ice and rough sea conditions.

Ice-based Observations.-Only one bowhead was sighted from camp during 5.9 h of observation. It

traveled ENE up the northern lead at 13:01 as icebreaker sounds were projected (see Fig. F-38 later). Its

closest observed position was 210 m from the projector. However, based on the whale's heading, its actual
Appendix F: Individual Playbacks//7 May 1994 502

CPA was probably slightly closer. The high sea state, combined with sun-glare when looking south toward

across the southern lead, were at least partly responsible for the lack of ice-based sightings of bowheads

in the southern lead. Bowheads continued to migrate into that lead through the day (see below).

Aerial Observations.-Five observation sessions were conducted on 17 May 1994. The first was

conducted -3.0 km SW of the silent projector from 09:41 to 10:40. Approximately eight whales were

traveling ENE at slow to medium speed along the edge of some brash ice in the main nearshore lead (Fig.

F-36, Table F-6). Whales were moving toward the southwest point of a large ice pan bordering the south

side of the secondary lead SW of camp. A non-focal group of 3-5 bowheads was actively socializing along

the south side of this point and may have attracted whales traveling along this lead. This socializing group

was 2.8 km SW of camp in a small embayment formed by ice. One whale was repeatedly observed

swimming in tight circles and is presumed to have been injured (09:55 and 10:29, Fig. F-36).

During the second observation session (also pre-playback control) the aerial crew followed -8 whales

from 3.8 km SW to 3.3 km ENE of the ice camp from 10:58 to 12:44. As during the previous session,

whales approached the ice camp from the SW, heading for the SW point of the large ice pan south of the

ice camp (Fig. F-37). They then traveled past the ice camp (CEPA distance 0.76 to 1.1 km) along the south

(far) side of the southern lead. Two subadult whales 1.1 km ESE of camp were presumed to have briefly

stopped to feed. They were motionless near the ice edge and then dove steeply ESE under the large ice pan

bordering the S edge of the lead. One of these subadults resurfaced 100 m from where it dove 3 min

earlier. Whales farther NE emerged from under the large ice pan bordering the south side of the secondary

lead and then traveled more or less parallel to the ice edge, heading NE. Whales observed during this

period passed 750 to 1000 m from the silent projector (visual estimates). There was no observable response

from whales when a helicopter flew over the observation area at 11:37:39.

The third aerial observation session was from 13:10 to 15:05 while icebreaker sounds were being

projected. The width of the secondary lead south of the camp had increased to - 1.8 km. Bowheads (-6)

appeared to have followed the same general path as had the whales observed during the previous control

period. They approached through the brash ice along the main lead SW of the ice camp, and then appeared

to have traveled along the southern (far) edge of the secondary lead south of camp. However, the route that

they followed past the projector is not known for certain. A very small whale (presumed to be a yearling)

and an adult (presumed to be its mother) appeared to reverse course and may not have followed this general

course. The mother and yearling were first observed SW of the ice camp, traveling ENE at medium speed,

at 13:35 (Fig. F-38). The pair dove under the large pan bordering the southern edge of the secondary lead

and resurfaced -100 m farther NE. They then reversed course at slow speed and dove under the ice pan

heading south at 14:44. We circled the area to the NE until 15:05 and did not resight them; they probably

continued their southward path after 14:44 but, because they were not resighted, their actual route cannot

be confirmed. The assumed CPA distance to the operating projector for this pair was 2400 m (visual

estimate). The other -4 bowheads may also have altered their paths when south of the projector. Two

whales were heading ENE along the south side of the lead (14:34 and 14:48, Fig. F-38) when we last sighted them and another was heading SE under the ice (14:51) on the south side of the lead. As mentioned

above, we circled the area east of there until 15:05 without sighting any of them. During the third

observation session, the closest bowhead CPA to the projector was 1700 m (visual estimate).

The fourth aerial observation session was conducted -4 km ESE of camp beginning 8 min after the

end of the icebreaker playback at 17:02. Thus, observations began <30 min after the playback ended, and

extended into the >30 min post-playback control period. Seven bowheads traveled at slow to medium speed

heading NE along the secondary lead south of the ice camp. The locations and headings of all of these

whales suggest that they passed the projector during the playback of icebreaker sounds, although none were

seen by the ice-based observers. Contrary to the situation during the previous session, whales did not travel

along the ice edge south of the ice camp but generally traveled in the center of the lead (Fig. F-39). The

closest bowhead sighting to the ice camp was 1600 m (visual estimate) SW and heading toward it. The

paths followed past the projector by bowheads seen from 17:35 to 18:09 is unknown.
'-'~-

&

T

G9:42

S

10:31:10:11 10'27 0·03·S·····

. '. G- 10:29 . ' ....

9:45 .... '. 10:0k' __ }---{i3~ .

0... . _-~J---o--;:, 10:1210:12[4)

e:___ ------_,,~'"Q 10.32\;1

9:46 ---?-----~------ 10:0410:35~ ~

9:55 10:23[3)

LEGEND

• Projector

• Theodolite

DOpen Water

1:::::::1 Brash Ice

o Old Ice

o Aerial, During Control Obs.

-- Interpolated Surface Travel

- - - - Presumed Underwater Path

~ Whale Sighting and Heading

Q Social Group

·0

O .:

500

'50P

FIGUREF-36. Aerial observations of bowhead tracks relative to the silent projector (pre-playback) amidst the pack ice NE of Pt. Barrow, 17 May

1994, times 09:41-10:40.
LEGEND

12:24

12:26

, _j~:21_

12:09 i 1~:31 !....

,012. 1 '/ .

1t'28 ',/ .:

/. /.,." ,,' .

.....~~..~~;.j.:~~:>/.. .

, i.;' ,

11:551 12:00f .

11:341

11:48

11:45

(to ~?:31 position)

• Projector

• Theodolite

oOpen Water

o Old Ice

o Aerial, During Control Obs.

-- Interpolated Surface Travel

::.:':.~ Presumed Underwater Path

0" Whale Sighting and Heading

Q Social Group

Of Feeding

. . O. . . .500 . 1000' Yards. .

.0 . . . '500 . . 1000 Meters'

FIGUREF-37. Aerial observations of bowhead tracks relative to the silent projector (pre-playback) amidst the pack ice NE of Pt. Barrow, 17 May

1994, times 10:58-12:44.

11:00

0"'"

10:58

0-'

d

11:05
TABLE F-6. Summary of sightings of bowhead whales observed by ice-based and aerial observers, 17 May 1994.

Radial Distances CEPAa

Sight- Estimated Sound Levels Near Whales

Group Followed From Distance ing RLo. RLI13 S:N •• S:NI13

Time size Projector (m)" (m) Time Method" Crewe med max med max med max med max Nature of Track

A: Pre-Playback Control (09:41 to 12:48)

10:12 3 single sighting <2800 10:11:42 2 A SW of projector heading NE, dove under pan

9:45 1 -5400 to -3000 <3000 10:12:22 2 A WSW of projector heading E then ENE

10:38 1 single sighting <2800 10:37:32 2 A SW of projector heading NNE, dove under ice pan

11:14 1 single sighting <2200 11:15:27 2 A SW of projector heading E

11:20 2 single sighting <2300 11:21:21 2 A SW of projector heading ENE, turned NNE to parallel ice edge

11:19 I -2600 to -2500 <2200 11:21:45 2 A SW of projector heading ENE, turned NNE to parallel ice edge

11:24 1 single sighting <2200 11:26:52 2 A SW of projector heading NE along ice edge

11:34 1 single sighting 1000 11:34:03 2 A ESE of projector, resting along ice edge on S side of lead, dove

under large pan heading SSE, feeding?

11:17 -2200 to +3300 800 11:41:00 3 A SW of projector heading ENE, dove under large pan resurfaced SE

of camp, dove under pan, resurfaced E of camp

)0-

11:47 single sighting 980 11:47:56 2 A ESE of projector, surfaced from under large ice pan heading NE ~

11:55 + 1100 to +2700 1100 11:54:42 2 A ESE of projector, motionless against ice edge, dove steeply under

III

;:s

ice edge, resurfaced ENE of projector dove under ice edge and

e,

~.

resurfaced E of projector, feeding? ~

11:56 I single sighting <755 11:56:23 2 A SSE of projector heading SSE, dove under large pan ;;;-

12:07 2 +2300 to +3200 <2300 12:07:25 2 A E of projector heading NNE along ice edge !::

-= 12:11 2 +1900 to +3300 <1900 12:11:08 2 A E of projector, surfaced from under ice pan, dove under ice pan ~

10:58 1 -3800 to +3000 <3000 12:30:34 2 A SW of projector, resighted E of projector heading ENE, dove under

l::

~

ice pan "1:1

is"

'<

B: Icebreaker Playback (12:48 to 17:02)

e-

~....

""" 13:01 1 single sighting <210 13:01:27 1 IC 119 123 112 117 19 24 22 26 NNE of projector heading ENE ~....

14:33 1 single sighting <2300 14:34:16 2 A 94 97 87 90 -8 -5 -4 -I SSW of projector heading NE along ice edge ~

13:34 2 -5900 to -2400 2400 14:43:46 2 A 94 99 86 92 -7 -2 -5 1 Adult-yearling WSW to S of projector heading ENE. Appeared to ~

reverse course, but were not seen again. Last seen traveling S. '<

....

14:47 single sighting <2200 14:50:24 2 A 96 98 90 92 -6 -3 -I 1 S of projector heading NE along ice edge on S side of lead

'0

:f

14:51 single sighting 1700 14:51:10 2 A 99 101 93 95 -3 0 2 4 SSE of projector heading NNE, turned SE, dove under ice pan

VI

0

VI
TABLE F-6. Continued.

CEPAa

Sight-

--------- -----------------

Radial Distances Estimated Sound Levels Near Whales

Group Followed From Distance ing R4.B

Time size Projector (m) (m) Time Method" Crew" med max med max med max med max Nature of Track

C: <30 min After Playback (17:02 to 17:32)

17:10 single sighting <1600 17:10:04 2 A SW of projector heading ENE

D: Post Playback Control (>17:32)

17:35 single sighting <2650 17:34:35 2 A

17:37 single sighting <3100 17:37:16 2 A

18:57 single sighting <3000 18:58:11 2 A

19:00 single sighting <2800 19:01:08 2 A

19:08 single sighting <2780 19:09:20 2 A

19:11 single sighting <2100 19:12:56 2 A

19:24 single sighting <1400 19:25:27 2 A

19:27 single sighting <1800 19:28:19 2 A

E of projector heading NE

ESE of projector heading ENE

WSW of projector heading NNE

WSW of projector heading ESE, turned to parallel ice edge

WSW of projector heading E

SW of projector heading ENE

WSW of projector heading N

SSW of projector heading NE

a CEPA = Closest Estimated Point of Approach. See text for description of estimation procedures.

b 1= measured by theodolite at CPA; 2 = visual estimate at CPA; 3 = estimate based on theodolite measurement(s) to nearby surfacings; 4 = estimate based on whale position(s) and

heading(s) during sightings distant from CEPA (possibly unreliable) .

e IC = ice-based crew; A = aerial crew.

d "_" indicates that whales were approaching, generally from the SW or W; "+" indicates that whales were moving away, generally to the NE or E.
LEGEND

12:30 sonobuoy drift

14:151iJD

o~

-

FIGUREF-38. Aerial and ice-based observations of bowhead tracks relative to the sound projector broadcasting icebreaker sounds amidst the pack

ice NE of Pt. Barrow; 17 May 1994, times 12:48-17:02. Observations were conducted from 13:10-15:05 (aerial) and 12:48-17:02 (ice-based).

••

u\1

"--~~~Q:1422

. . - - 14:11 - - - - - - -

CD Projector

• Theodolite

: Monitor Sonobuoy

o Open Water

1:::::::1 Brash Ice

o Old Ice

• Aerial Obs., During Ice-breaker Playback

• Ice Camp Obs., During Ice-breaker Playback

-- Interpolated Surface Travel

- - - - Presumed Underwater Path

0"" Whale Sighting and Heading

G. V . ---

- -----

13:47 _-- .•.••• --

.• 13:51

------;3~ 13:45 r------

13:35 r13:10

500

'·50j) , , 1000Ml;lte,rs
17:10<J'"

0

.... ···

FIGUREF-39. Aerial observations of bowhead tracks relative to the silent projector (after icebreaker playback) amidst the pack ice NE of Pt.

Barrow, 17 May 1994, times 17:10-18:12. The playback ended at 17:02.

(;{

17:35

....•.-' ..... 500 . 1000 Yards·

-

'... ••• - - t .

·500 . . 1000 Meters'

17:48c{

17:~

e:

17:46

18:09CJ'

18:040-

(;{

17:37

.------------------...,.,

LEGEND

• Projector

• Theodoll1e

DOpen Water

DOld Ice

o Aerial, Ourlng Control Obs.

() Aerial Obs., Within 30 min. Post-playback

-- Interpolated Surface Travel

- - - - Presumed Underwater Path

0' Whale Sighting and Heading

....

'0

~

VI

o

00

_________ 
LEGEND

., Projector

• Theodolite

o Open Water

1:::::::1 Brash Ice

oOld Ice

o Aerial, During Control Obs.

-- Interpolated Surface Travel

- - - - Presumed Underwater Path

0""" Whale Sighting and Heading

Q Social Group

-

5001000 Meters·

.. 500 .. 1000Yarda .:

.. -- ..

FIGUREF-40. Aerial observations of bowhead tracks relative to the silent projector (after icebreaker playback) amidst the pack ice NE of Pt.

Barrow, 17 May 1994, times 18:37-19:32.

\.
Appendix F: Individual Playbacks/I 7 May 1994 510

The fifth aerial observation period (control) was conducted near the ice camp from 18:37 to 19:32.

Approximately five whales were traveling slowly NE or ENE amidst pack ice in the main lead SW of the

ice camp (Fig. F-40). Low clouds and high sea states limited our ability to resight whales. A presumed

mother and yearling were observed 4.5 km from camp traveling parallel to a large pan and heading NE.

The closest whale sighting to camp was 1400 m away (visual estimate). Most of these whales would have

passed 0.5-1.5 km from camp if their pattern of movement remained the same after observations stopped.

Noise Exposure.-From 12:48 to 17:02 icebreaker sounds were projected into the lead using only the

J-11. It was projecting the higher-frequency components of the icebreaker sound. The Argotec 220 was

in the water to project the low-frequency components but, unknown at the time, was not operating. A

crossover network was in use to direct low-frequency energy to the Argotec 220. Therefore, icebreaker

components below -500 Hz were underrepresented, and little energy was projected below -200 Hz on this

date (Fig. F-41; cf. Fig. F-34). Source levels were adjusted during the projection period, but for most of

the period the median broadband (20-5000 Hz) source level projected by the J-11 over the 14-min

icebreaker cycle was -160 dB re 1 J.lPa"m. The corresponding median source level for the dominant 113-

octave was 154 dB for the band centered at 400 Hz. Figure F-41A shows the variability in the sounds as

projected (I-m source levels) and as received at 1 km range. Figure F-41B shows the median received

levels at several standard distances.

On 17 May 1994, a 57A so no buoy was manually deployed 1.62 km west of the ice camp at 12:30.

That sonobuoy drifted eastward, passing 50 m from the ice camp at 15:00. The distance of the drifting

so no buoy from the projector at various times was determined by cross-correlating the sounds received by

a monitor hydrophone near the projector with those received by the sonobuoy. A 57B DIFAR buoy was

air-dropped into the main lead 5.5 km SW of the ice camp at 13:16. A second DIFAR buoy was airdropped 2.7 km SSWof the ice camp at 14:21 to replace the first one, which had failed. Ambient noise

was measured from a monitor hydrophone at the ice camp and from the manually-deployed sonobuoy before

and after the icebreaker projections. Because of gradually increasing winds during the day, the ambient

noise levels increased throughout the period of playback. The average broadband (20-5000 Hz) ambient

noise level was 98 dB re 1 J.lPa before icebreaker sounds were projected and 107 dB after the end of the

playback. The latter value was higher than on any other playback day in 1991 or 1994. The ambient noise

in the 113-octave centered at 400 Hz, where the strongest icebreaker sounds occurred, varied from 90

(before) to 93 dB (after). We estimated ambient noise levels near whales during the playback period by

linear interpolation between the pre- and post-playback measurements.

The aerial observers' closest observation of a bowhead to the operating projector involved a whale

1700 m south of the projector at 14:51. The median and maximum received levels of icebreaker noise at

the whale while underwater at that distance and time were estimated as 99 and 101 dB re 1 J.lPabroadband

(64-s basis) and 93 and 95 dB in the strongest 113-octave band, centered at 400 Hz. At this time, the

ambient noise was estimated as 101 broadband and 91 in the 1I3-octave band near 400 Hz. Thus the median

and maximum icebreaker:ambient ratios were -2 and 0 dB on a broadband basis, and 2 and 4 dB in the

strongest 113-octave bands (Fig. F-42A). Given the usual variation in source levels and ambient noise

levels, the whales may have encountered slightly higher icebreaker:ambient ratios at certain times, but none

of the whales under observation by aerial observers were subjected to strong icebreaker sounds.

The whale sighted closest to the operating projector was seen 210 m north of it by observers at the

ice camp at 13:01. At that time and horizontal distance, the median and maximum broadband received

levels (over 64 s) were estimated as 119 and 123 dB re 1 J.lPa. The median and maximum levels in the

dominant 113-octave band were 112 and 117 dB in the band centered at 500 Hz. At this time, the ambient

noise level was estimated by interpolation as 99 dB broadband and 90 dB in the 1I3-octave band near 500

Hz. Thus the median and maximum icebreaker:ambient ratios were 19 and 24 dB on a broadband basis,

and 22 and 26 dB in the strongest 1I3-octave band (Fig. F-42B).

Summary.-On 17 May 1994, relatively large numbers (35+) of bowheads were observed as they

passed within 3 km of a projector set up in the pack ice at the east end of the main nearshore lead, some 
Appendix F: Individual Playbacks/17 May 1994 511

-

A. •.•.•.....•.•.•.•..•••••.. •.•.~•.•.•.•. ..,..,,.•.•..........•.•...•. _.......-.•....•....

SL-1m

..•......•...•.,...•.. --..... ...._..-

-....._.

RL-1.0km %- ....•..••...•...•... =~...... ~

: •.•. -+- ,/ •.•..•...........•. '., ...•.•.

, ••••• # , •••• <,

<, r-- Amb.- Min.

......

.......•.••..•... .•.••••••• ,Il

'

'......." --..-

~

.,

....•..' ". .-I "...•......... 5%,95%SL ;' '. "

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After~

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-, b.:.~.....•...

~

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r

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// ....../ -~ ~

~

••••••••", »» i'i--+-

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<,

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//

. . . ,

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17 May 1994, 14:50

170

150

-a:l

"0

- 130

CD

>CD ....I

"0

c 110

co a:l

1:5

0 90

I

('I)

-"""

70

50

10 100 1000

17 May 1994, 14:50

10000

170-r--------r--,---r--------.--.---,------,---...,....--, ,....----,

--- SL-1m

co

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-

B.

150-+------+--l--i-----:=_~

130+---I •...••--+--"""';;;!;;;>--------!--t--t------!__-+_-l

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-g 110+------+--!__-+-----f:...----",,...,::,t

co a:l

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oI

~

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After~=-,"-+-l--loct

90 Before -,--"t'-r"...h.::..--±~"-I--+-""t1'!'"""":s.

,; •.•.......

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~.~.? ..~ :::::::.:. ..::: :::::::J./ ~:................... "".

'............•................

70+-=:..:..:..:..~"'-O::-:+-::-~!__-+--7'----+--t--t----.:.:=._.:_1!__-+_-l

..... ....••......

1km'/

................................. ,

3 km.../"

100 1000

1/3-0ct. Center Frequency

Ree.Level

-+-

Amb.

10000

FIGUREF-41. Third-octave levels of projected icebreaker noise vs. distance from projector and ambient

noise, 17 May 1994, time 14:36-14:50. (A) Variability over 14 min at ranges 1 m and 1.0 km (median,

5th and 95th percentiles). (B) Median levels at range 1 m (squares) and 30 m-3.0 km. Plus signs show

average ambient noise levels before and after playback. For additional explanation, see caption to Figure

F-2 or F-3.
A.

Appendix F: Individual Playbacks/17 May 1994 512

17 May 1994, 14:50

170.,.-----"""""T'"----;--.----- .....•----;-.------r--"""""T'"~ r----~

• --- SL-1 m

-eRL-1.7km

-+-

Ambient

150-+------l---+--t---=...==-j_~~rl_--, __--_+~:7f~

iii"

'0

- 130-l-----_._...--!---t--.rii------!---I--+------+--...=!--;

~

-g 110-l------+--+--+------!---I--+------+----+--;

CO

CO

tio 90+--~.:.:::::±*~9:*_l_+-i~#~~==9=;~oc::;:c:-_;__--+-_i_l

~

T'""

70-+------l-~__l::I_"""'Et:f_----j_-+_-+-----~~-+___I

50

10 100 1000 10000

17 May 1994, 13:01

170 I. B. --- SL-1 m 20-qDOO

SS Level -e150 RL-210m

-

-+-

CO Ambient

'0

- 130

Q)

>

~ 0

'0

c: 110

CO

CO

+

ti

0 90

I

~

T'""

70

100 1000

1/3-0ct. Center Frequency

FIGUREF-42. Third-octave levels of projected icebreaker noise 1 m from the projector (closed squares)

and near bowheads (A) 1700 m and (B) 210 m from the projector (median level over Imin), 17 May

1994, times (A) 14:50 and (B) 13:01. Plus signs show estimated ambient noise levels for those times.

For additional explanation, see caption to Figure F-4.

10000
Appendix F: Individual Playbacksl17 May 1994 513

70 km ENE of Pt. Barrow (Fig. 3.8 on p. 77). High sea states hindered both ice-based and aerial observations, and caused high ambient noise levels. Also, the source level of the projected sounds was low, and

the low-frequency components were largely missing, because only the J-ll projector was operating on this

date. Throughout the day bowheads approached the projector from the WSW through a major lead. Most

appeared to continue NE along a secondary lead extending NEward south of the projector. Only one bowhead was seen by the ice-based observers. It was seen 210 m north of the operating projector and would

have been exposed to estimated RLBB,med and RLBB,max of 119 and 123 dB re 1 IlPa before it surfaced. At

this location and time, the icebreaker:ambient ratio in the strongest 113-octave band (near 400 Hz) was up

to -26 dB (S:N1I3,max)'

There were five aerial observation sessions. During the first two sessions (projector silent), whales

traveled NE along a path that came as close as 600-800 m south of the projector, along the southern (distant) side of the secondary narrow lead. During the third session, when icebreaker sounds were being projected, some whales continued to follow that path. However, the secondary lead had by then widened to

1.8 km and icebreaker sounds were barely detectable, if detectable at all, at 1.8 km distance (S:N1I3,max -4

dB). Two whales, a suspected mother/yearling pair, approached to 2400 m from the operating projector and

then appeared to reverse course to the SW. However, it is doubtful that they could have detected icebreaker

sounds at that distance, except for very briefly and weakly, because the estimated S:N1I3,med and S:N1I3,max

were -4 and +2 dB.

20 May 1994 Playback

The ice camp was set up on the NW edge of a very large ice pan that abutted the landfast ice edge

to the south, blocking the nearshore lead. There was extensive open water to the west (nearshore lead) and

north. Aerial reconnaissance from 08:29 to 09:42 found that various bowhead whales were traveling eastward or socializing in the large open area SW and W of the large pan. Bowheads migrating eastward in

the nearshore lead were constrained to detour north or south along the edge of this large ice pan, and any

that detoured south would soon reach the landfast ice edge. The ice camp was present from 10:00 to 20:20.

Icebreaker sounds were projected by the Argotec 220 (one side) plus J-11 from 12:38 to 17:17. The measured water depth at the projectors was 42 m. On this date, the source level of the projected sounds was

high and the ambient noise level was low.

Ice-based Observations.-About 19 bowheads (-17 groups or singletons) were estimated to have passed within 3250 m of the ice camp during 10.3 h of observation. Six sightings occurred during the preplayback control period; the remainder occurred during the playback of icebreaker sounds. No whales were

sighted during a post-playback control period from 17: 17 to 20:20.

Eight bowheads (6 groups or singletons) were sighted during pre-playback control observations from

10:00 to 12:38 (Table F-7). Most traveled NE or ENE at slow to medium speed as they approached the ice

camp from the WSW (Fig. F-43). Two whales that were near the ice camp when the ice-based crew arrived

were headed ESE or east directly under the large ice pan. One of these whales (10:02 on Fig. F-43) showed

no apparent reaction to the helicopter as it landed at the ice camp -500 m away. It is not known whether

these two bowheads diverted around the pan to the north or to the south. The closest sightings to the ice

camp during the control period were <20, <55, and <68 m from the (silent) projector site. The whale that

approached to <55 m did so even though the helicopter had landed at the ice camp 3 min earlier <100 m

from where the whale surfaced. The longest observed track was for a group of 3 whales followed for -1 h.

The group traveled slowly and socialized as it moved ENE until 11:27 when it dove under the large pan

460 m SSW of the projectors. Based on the group's heading, its CPA to the projectors was probably

-280 m. The group was resighted -20 min later traveling north -1000 m north of the ice camp.

In addition to the potential helicopter disturbances mentioned above, a subadult whale sighted at

12: 11 showed no apparent reaction to the helicopter as it lifted off from the ice camp -200 from the whale.
TABLE F-7. Summary of sightings of bowhead whales observed by ice-based and aerial observers, 20 May 1994.

Radial Distance CEPA" Sight- Estimated Sound Levels Near Whalesd

Group Followed From Distance ing RLBB RLlI3 S:NBB S:NI13

Time size Projector (m)e (m) Time Methodb

Crew" med max med max moo max med max Nature of Track

• CEPA = Closest Estimated Point of Approach. See text for description of estimation procedures.

b 1 = measured by theodolite at CPA; 2 = visual estimate at CPA; 3 = estimate based on theodolite measurement(s) to nearby surfacings; 4 = estimate based on whale position(s) and

heading(s) during sightings distant from CEPA (possibly unreliable).

c IC = ice-based crew; A = aerial crew.

d nata in italics are not included in analyses of traveling whales because this whale was engaged in aerial activities.

• "-" indicates that whales were approaching, generally from the SW or W; "+" indicates that whales were moving away. generally to the NE or E.
LEGEND

• Projector

• Theodolite

D Open Water

oOld Ice

o Aerial, During Control Obs.

o Ice Camp, During Control Obs.

6. Aerial and Ice Camp, During Control Obs.

-- Interpolated Surface Travel

.;:;?=':~Presumed Underwater Path

0"" Whale Sighting and Direction

o Social Group

0. Breach

or Tail Slap

Oh Helicopter Disturbance

01 Aerial Activity

o

I

200 400 Vards

.,

o 200 400 Meters

12:11

10:07 h

10:02 h

11:42 \.

10:39 ~42

,0 " 10:47

" 'Q

10

'14 10:31 _- .0

.' 10:22 -0- -- 10:35

9:47 9:52 9:58 ~~.~~O--------------E»--

9:44 -0- - -E>- - - - 0- - - 10:10 10:27 0---

o 500

500

\

I

I

I

\

\

I

I

I

I

\

10:54<;>

- f:i. 10:56 (2) o

FIGUREF-43. Aerial and ice-based observations of bowhead tracks relative to the silent projectors (pre-playback) amidst the pack ice NE of Pt.

Barrow, 20 May 1994, times 09:43-12:37. Aerial observations ended at 12:18.

....

'0

~

VI •....•

VI
Appendix F: Individual Playbacks/20 May 1994 516

From 12:38 to 17:17, while the projectors were broadcasting icebreaker sounds, -11 single bowheads

were sighted by observers at the ice camp (Fig. F-44, Table F-7). A lower proportion of the groups were

sighted S;500m from the projectors during the playback period (33%) than during the control period (75%).

This is evident by comparing Figures F-43 and F-44; note that the scale of Fig. F-44 is the same as that of

the inset in Fig. F-43. As during the control period, most whales (7 of 8 groups with known headings)

traveled generally eastward. However, one bowhead approached the camp along the ice edge to the SW

and then turned sharply to the NNW away from the projectors at a distance of 58 m. This was the closest

sighting to the projectors during the playback of icebreaker sounds on this date.

During the post-playback period from 17:17 to 20:20 no bowheads were sighted.

Given the consistent pattern of sightings close to the ice camp during the control period, the more

distant locations of most sightings during the playback suggest that bowheads were altering their tracks to

avoid the projectors. Except for the whale that approached to 58 m, the closest sightings to the operating

projectors were 500-600 m away. Several whales seen 500-600 m SW of the projectors during the playback

would have been expected to continue to approach the ice camp, based on observations during the control

period. However, they apparently did not do so.

Aerial Observations.-Most of the bowheads observed from the ice camp during the pre-playback period were also observed over much longer distances by observers in the circling aircraft. Whales were

followed from 5.3 km west of the ice camp at 09:43 to 8.3 km NNE of the camp at 12:18. A single bowhead 5.3 km W of the projectors traveled westward and then turned south to join a group of two socializing

bowheads. As described above, these three whales then headed ENE and dove under the large ice pan

460 m SSW of the projectors. This group resurfaced NNE of camp and continued to travel NNE along the

ice edge. The presumed CPA of their underwater track, based on general headings and locations of distant

surfacings, was 280 m. It was not possible to conduct aerial observations during the playback period

because, by then, low cloud had moved into the area.

Noise Exposure.-From 12:38 to 17:17, icebreaker sounds were projected into the lead using the J-ll

and one side of the Argotec 220. Source levels were relatively uniform during the projection period. The

median broadband (20-5000 Hz) source level of icebreaker sounds was -170 dB re I IlPa-m over the 14-min

icebreaker cycle. The corresponding source level for the dominant 1/3-octave band was 163 dB in the band

centered at 80 Hz. Figure F-45A indicates the variability in the sounds as projected (l-rn source levels)

and as received at 1 km range. Figure F-45B shows the median received levels at several standard distances

at the same time.

On 20 May 1994, a 57A sonobuoy was manually deployed along the ice edge 765 m south of the ice

camp at 12:05. Ambient noise was measured from that sonobuoy before the icebreaker projections. The

broadband (20-5000 Hz) ambient noise level was 86 dB re 1 IlPa, and the ambient noise in the 1/3-octave

band centered at 80 Hz, where the strongest icebreaker noise occurred, was 68 dB (Fig. F-45).

The closest whale to the operating projectors was seen 58 m WSW of it by observers at the ice camp

at 15:39. The whale turned to the NNW and dove away from the projectors, so it was at the surface at its

CPA. At that minute and horizontal distance, the median and maximum broadband received levels below

the surface were estimated as being at least 132 and 138 dB re 1 IlPa. The median and maximum 1/3-octave

levels were at least 125 and 131 dB in the band centered at 80 Hz. Thus the median and maximum icebreaker:ambient ratios in the strongest 1/3-octave band were at least 57 and 63 dB (Fig. F-46A). The whale

would not have been exposed to levels quite this high because received sound levels, especially for lowfrequency components, are lower near the water surface. However, in the minute before the approaching

whale surfaced 115 m from the projectors, the median and maximum 1/3-octave levels 120 m from the projectors were estimated as 125 and 128 dB re 1 IlPa, the same as or only 3 dB lower than those quoted above

for range 58 m. Thus the maximum noise level to which this whale was exposed was apparently -60 dB

above the ambient level in the strongest 1/3-octave band.
Appendix F: Individual Playbacks/20 May 1994 517

4

T

LEGEND

• Projector

• Theodolite

o Open Water

o Old Ice

• Ice Camp Obs., During Ice-breaker Playback

-- Interpolated Surface Travel

- - - Presumed Underwater Path

0' Whale Sighting and Heading

0* Breach

,

,

/

13:41

,

,

~'

13:32 13:33

a-tI,

.---____ ",13:36

13:31 - - - - - - - --.... '~13:38

13:35 ~

14:40 .* 14:20

<.

14:35

•

16:09

--

.-

16:00

,

,

,

,

15:39

o 500 Yards

FIGURE F-44. Ice-based observations of bowhead tracks relative to the projectors broadcasting icebreaker

sounds amidst the pack ice NE of Pt. Barrow, 20 May 1994, times 12:38-17:17.

o 500 Meters
Appendix F: Individual Playbacks/20 May 1994 518

20 May 1994, 15:40

170

A.

150

.•....•

m"0- 130 Q)

Q) >

..J

"0

c 110

ctl

eo

ti

0 90

I

S2.

~

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" _...............•

'.

...."'...

100

I

'. I

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-, <, I

·'·····1

r-, I

"'1--1..-+-..... .-,-, , I

I

1000

20 May 1994, 15:40

SL-1 m

RL-1.0km

-+-

Amb.

5%,95%SL

5%,95% RL

10000

170

B.

150

.•.....

m"0

- 130

Q)

>Q) ..J

"0

c: 110

ctl

m

ti

0 90

I

C')

-~

70

--- SL -1 m

Ree. Level

-+-

Amb.

"'" I

10000

FIGUREF-45. Third-octave levels of projected icebreaker noise vs. distance from projectors and ambient

noise, 20 May 1994, time 15:26-15:40. (A) Variability over 14 min at ranges 1 m and 1.0 Ian (median,

5th and 95th percentiles). (B) Median levels at range 1 m (squares) and 30 m-3.0 Ian. Plus signs show

average ambient noise level before playback. For additional explanation, see caption to Figure F-2 or F-3.

/
Appendix F: Individual Playbacks/20 May 1994 519

20 May 1994, 15:40

170.-------;--;---r------,..--.----.-----...----,--;.-, ,....---...:,

50

10 100 1000 10000

20 May 1994, 13:38

170

--- SL1 m

-e150 RL1.5 km

-+-

- Ambient CO

"0•......• 130

(j)

...J~

"0 110 0

c

as

CO

ti

0 90 I

M +

-T'""

70

150

-CO

"0•.......

130 Q5

>Q) ...J

"0

c 110

as

CO

ti

0 90

I

M

-T'""

70 .

50-t----,,....-.,...-+.,...,..-t'"T"T+-----r-..,.--t-..,.-r+TTr--.....,--.,.--t-.,....,-t-rrl

10 100 1000 10000

1/3-0ct. Center Frequency

--- SL1 m

-eRL- 58 m

-+-

o Ambient

FIGUREF-46. Third-octave levels of projected icebreaker noise 1 m from the projectors (closed

squares) and near bowheads (A) 58 m and (B) 1.5 km from the projector (median level over 1

min), 14 May 1994, times (A) 15:40 and (B) 13:38. Plus signs show average ambient noise level

before playback. For additional explanation, see caption to Figure F-4. In (A), because of the

short range, received levels at 60 m were estimated from source levels assuming spherical

spreading.
Appendix F: Individual Playbacks/20 May 1994 520

The second closest observation of a bowhead to the operating projector was a whale 500 m south of

the projectors at 15:30. The median and maximum 64-s broadband received levels of icebreaker noise at

the whale while underwater were estimated as 123 and 128 dB re 1 IJPa. The median and maximum 113-octave levels were 119 and 121 dB in the band centered at 80 Hz. Thus the median and maximum icebreaker:

ambient ratios in the strongest 113-octave bands were -51 and 53 dB.

Even the most distant whales that could be seen by the ice-based observers during the playback period

on this date were exposed to strong icebreaker signals. The median and maximum icebreaker.ambient ratios

in the strongest l/3-octave band were estimated as 39 and 40 dB at a whale observed 1485 m from the projectors at 13:38 (Fig. F-46B). This distance was near the limit of the range where whales could have been

reliably seen from the ice platform.

Summary.-On 20 May 1994, the projectors were set up on the NW side of a large pan that blocked

the nearshore lead 40 km ENE of Pt. Barrow (Fig. 3.8 on p. 77). During control observations from both

the circling aircraft and the ice camp, bowheads were observed as they approached the projectors from the

west and WSW. They arrived at the large ice pan near and south of the projectors, turned northward, and

followed the edge of the pan north and east. Six of eight groups of bowheads came within 400 m of the

ice camp during the control period.

On this date the icebreaker sounds were projected at a high source level, and the ambient noise level

was low. Only ice-based observations were obtained during the playback due to formation of low cloud.

Bowheads continued to approach the projectors from the west and WSW. However, the patterns of movement of most of the whales when they came within several hundred meters of the ice camp were different

during the playback than during the preceding control period. During the playback, they seemed to divert

both to the north and south of the projectors. Only one whale approached the projectors closely during

playback (l of 11 groups were seen within 400 m); it turned sharply away from the projectors when 58 m

from them. (A whale that surfaced at the same location during the control period dove toward the ice

camp.) The whale that approached closely during the playback voluntarily approached even though

S:N1I3.maxwas near 60 dB. At the observed CPAs of other whales that came within 500-1000 m, S:Nl/3,max

values were -40-50 dB. The proportion of whales that diverted, and the actual distances when diversions

began, are unknown because of the limited viewing area from the ice and because low cloud prevented

aerial observations during this playback.
Appendix G: White Whale Distribution Maps. 1989-94 521

APPENDIX G: White Whale Distribution Maps, 1989-94

Appendix G shows all white whale sightings during the present study by 10- or l I-day period

in the springs of 1989, 1990, 1991 and 1994 (four maps per year). Each map shows all white

whales detected by observers in the Twin Otter aircraft (hatched symbols) and by observers in the

helicopter or on the ice (open symbols). Headings toward which the whales were oriented when

first seen are also shown.

Note that all search effort was non-systematic. The amount of effort varied greatly among

different parts of the mapped area within any given 10- or ll-day period. The distribution of

search effort also varied from one 10- or l l-day period to the next. The designated locations of

the landfast ice edge are approximate.
Appendix G: White Whale Distribution Maps. 1989-94 522

157 156 155

72

.-.-._--._._ ....•..

-,

"\

\

'\.

<.<,

White Whales

72

April 1989

e Twin Otter

o Ice Camp/Helicopter

+

+

\,

-,,,-,

i

\

\

\

\

\

-.-,

""'<10

0

111_,

+

o

........ + 7130

~

.., .... "

....

<;

Landfast Ice Edge "

'<10

111

,

- "",'

-'"

.......

+

.......

o 5 lOnm

",

..............

"''''''''+' ....•....•. 10 m..···..· 71

o 5 10 mi

+

o 5 10 km

157 155 154

FIGURE G-l. LGL sightings of white whales. late April 1989. Symbol type distinguishes sightings

by the two crews and sightings of 1-14 vs. 15+ whales. Headings toward which the whales were

oriented when first seen are also shown. Survey effort was not uniform across the area mapped.

/
Appendix G: White Whale Distribution Maps. 1989-94 523

157 154 156 155

---._._._.- .•......

'\

\

\

\-,'.

"",.$ ,

'~'e .,.,.,.,.,\ L.;-------,--~-----.J

i

i

i

i

i, /i

'-.iL/··

White Whales

1-10 May 1989

~ Twin Otter

o Ice Camp/Helicopter

72 +

+

+

~. -,

Landfast Ice Edge ". ~

0111•

"---.'

- ....

'.

.........................

. +

<, ....

".

".

o 5 lOnmi

+

o ,5 10mi

o 5 lOkm

........................ +

........... 10 m 71

155 157 154 156

FIGURE G-2. LGL sightings of white whales, 1-10 May 1989. Symbol type distinguishes sightings

by the two crews and sightings of 1-14 vs. 15+ whales. Headings toward which the whales were

oriented when first seen are also shown. Survey effort was not uniform across the area mapped.

72

7130
Appendix G: White Whale Distribution Maps. 1989-94 524

157 155 154

72

--- ..

156 '-.-..._.-..._---

......<.

,

\

\

\-,••..

...........

White Whales

11-20 May 1989

@ Twin Otter

o Ice Camp/Helicopter

+

+ .......

'.

.........

Landlast Ice Edge .... :l

011)•

............

......

......

......

+

......... <,

".

".

o lOnm

===---

o

==--

5 10m

......................... + · 10 m--"--" 71

+

o 5 10 km

157 156 155

72

7130

FIGURE G-3. LGL sightings of white whales, 11-20 May 1989. Symbol type distinguishes

sightings by the two crews and sightings of 1-14 vs. 15+ whales. Headings toward which the

whales were oriented when first seen are also shown. Survey effort was not uniform across the

area mapped.
Appendix G: White Whale Distribution Maps. 1989-94 525

157 156 155

'-'-'-'_._._._._.,",

\

\

\..,.

<;

White Whales

21-30 May 1989

e Twin Otter

o Ice Camp/Helicopter

72

+

7130 +

..........

<;

,

..

.

.......

Landfast Ice Edge '-

'<011/. '----:

-.....

- ~~.'

...... +

.- ....

""" ..

. .

o 5 lOnm

o

=-

5 lOmi

........

................. +

+ · 10 m········ 71 o 5 lOkm

157 155

FIGURE G-4. LGL sightings of white whales, 21-30 May 1989. Symbol type distinguishes sightings by the two crews and sightings of 1-14 vs. 15+ whales. Headings toward which the whales

were oriented when first seen are also shown. Survey effort was not uniform across the area

mapped; the most intense effort was in the nearshore lead just north of the landfast ice.

72

7130
Appendix G: White Whale Distribution Maps. 1989-94 526

157 154 156 155 ~'-'-

-'-'-'-::"- ..•..•,.

\

\

\

"

-.'.

White Whales

April 1990

e Twin Otter

o Ice Camp/Helicopter

\

\,

-,

'.,

i

\

\.

\

\

-,"<,

<lQo

----------1::-e-.,""" 11I-

: .

. .

72

+

---

+

"

~.

"' .

'.._-.'

- ....

+

0 5 10nm

0 5 101ni

+

0 5 10 km

A

157 156 155 154

Landfasl Ice Edge

................+

L

'<lo III,

'80 III

----

..... 10 m· 71

FIGURE G-5. LGL sightings of white whales, late April 1990. Symbol type distinguishes sightings

by the two crews and sightings of 1-14 vs. 15+ whales. Headings toward which the whales were

oriented when first seen are also shown. Survey effort was not uniform across the area mapped;

the most intense effort was in the nearshore lead just north of the landfast ice.
Appendix G: White Whale Distribution Maps. 1989-94 527

157 156 155

White Whales

1·10 May 1990

e Twin Otter

o Ice Camp/Helicopter

72

71 30

//-------------- -----\:---'"

...-" "', "......... .... ...

/'_-/ ··00 IlI _

.----./--

_________ ---------e:

//..... - 0 .~.-....

.... "'/ +

+ +

o 5 IOnmi

Landfast Ice Edge

......................... + 10 m········ 71

o 5 lOmi

+

o 5 IOkm

154 157 156 155

FIGURE G-6. LGL sightings of white whales, 1-10 May 1990. Format as in Fig. G-5.

72
Appendix G: White Whale Distribution Maps, 1989-94 528

156 155

White Whales

72

11-20 May 1990

@ Twin Otter

o Ice Camp/Helicopter

72

+

+ +

+ + 7130

,,/,/"-----

-_.- ../-//-- •...,............. - --'

....•._--_ ..

<;..... -,

"~

o "t.

-'-,'

....................•

+

., .

"

o 5 IOn ••.•

+. o 5 10km

Landfasl Ice Edge

......................... +. ·· 10 m········ 71

o 5 IOmi

157 156 155 154

FIGURE G-7. LGL sightings of white whales, 11-20 May 1990. Format as in Fig. G-5.
Appendix G: White Whale Distribution Maps. 1989-94 529

157 155 154

White Whales

21-26 May 1990

~ Twin Otter

o Ice Camp/Helicopter

72

+

+

.....

~ ...................

........... -'-,.

.................

o 5 lOnmi

Landfast Ice Edge

.......................... +.

· 10 m········ 71

o 5 10mi

+

o 5 10 km

157 156 155

FIGUREG-8. LGL sightings of white whales, 21-26 May 1990. Format as in Fig. G-5.

72

7130

"<0 "J"
Appendix G: White Whale Distribution Maps, 1989-94 530

157 155 '-'--'--_.-.......•-,

"

\

\

-,

,..•..•...•...

White Whales

April 1991

@ Twin Otter

o Ice Camp/Helicopter

72

+

+

+" . + 7130

.'-,'

............................

+

....

o 5 lOnlTi

. .

o 5 10 ITi

+

o 5 10 km ......................... ,J, 10 m ····· 71

157 156 155

FIGURE G-9. LGL sightings of white whales, late April 1991. Format as in Fig. G-5.
Appendix G: White Whale Distribution Maps. 1989-94 531

157 156 155

.-•.......-.-._._._ .

.......,.

,

\

\

-,

'.'.<,

White Whales

1-10 May 1991

@ Twin Otter

o Ice Camp/Helicopter

72 \

"

<;

<.

1

i

\

\

\

\

\

-.

-.<,

<00

"'-. + ---------t

e -~'"",

.r-~-··" "So ", _

7130 +

- ....

-........................

....... -

.....

............

+

"<, ....

. .

o 5 lOnmi

o 5 lOmi '.

................

+

o 5 10 km ....+ 10 m 71

157 156 155

FIGURE0-10. LOL sightings of white whales, 1-10 May 1991. Format as in Fig. 0-5.

72

7130

'<0 ",_

/

/
Appendix G: White Whale Distribution Maps, 1989-94 532

155 '-.......-.-.-

11-20 May 1991

~ Twin Otter

o fce Camp/Helicopter

....•~,

\

\

-,

<.

<.

....,

White Whales

72

+

+ +

'80

111 _

+

-,

< >

~..•.... "....._-

-....-..._-'"

<;.. \,..

. .

o 5

o 5

........................ -+. · 10 m ·.. · 71

+

o 5

157 156 155

FIGURE0-11. LOL sightings of white whales, 11-20 May 1991. Format as in Fig. 0-5.

72

7130

'. /l

0111•
157

Appendix G: White Whale Distribution Maps. 1989-94 533

156 155

'\\

\•.

---

'--'--"-"

+ \, II/~--"---"''''''''\

, ,

..•..••••.•. ,,-',,1/ \''-

'.-..._--- •.

,

,

,

,

,

,

,

,

,

'--,

,.,.>------_.1

->:,'/ +

~(/

..//"

/'

,-/<;;;;;' ~~

/,//

/' +

;","' .....

r

7130

72

+

o 5 10nmi

o 5 10mi

+

o 5 lOkm

157

-'--'-.- _ ..•.....••..••\

\

\

\-,

-,..••.•.•..••...

White Whales

21-26 May 1991

e Twin Otter

o Ice Camp/Helicopter

+

+

..----.

.f¥

....' +" . +

_-.·Landl';.t Ice Edge

~ ....................

-'" ..... ~.

+

...................... -+. · 10 m········ 71

156 155 154

FIGURE G-12. LGL sightings of white whales, 21-26 May 1991. Format as in Fig. G-5.

72

7130

"~ 0",.
Appendix G: White Whale Distribution Maps. 1989-94 534

157 156 155

.-.-.-.-._._.-

-"'\

\

\

\..

White Whales

April 1994

@ Twin Otter

o Ice Camp/Helicopter

72 \,

-,

'-.,

i

\

"

"

"

"

-,

<,

'':00

;//-------------------t "" 111_.

"

,__//--- r- - ""80 111

----

/

.."'....

.1,/" .>: ,

...-_ •..--_ ...-.•.---_ ..

72

+

+ +

+ 7130

Landfasl Ice Edll·"

<;.... ,

-,

"~

...... 0111•

" .

.................... ,.

+

................

................ + 10 m· ·.. 71

o 5 lOnmi

o 5 10 mi

+

o ,5 10 km

157 156 155

FIGURE G-13. LGL sightings of white whales, late April 1994. Format as in Fig. G-5.
Appendix G: White Whale Distribution Maps, 1989-94 535

157 155 154

+

,

,

,

,

,

,

,

,

,

--~~e e-

~

_.__ .- ,.

,

\

\

\.,.,.,

White Whales

1-10 May 1994

~ Twin Otter

o Ice Camp/Helicopter

\.

,

"

-""l

\

\

\

\

\ @

"

.,.,., <,

'<00

111,.

72

+

'. Landfasl Ice lOdge ,:

+", +

........

.-. '<0 III,

...........

+

0 5 10nmi

0 5 10mi

+

0 5 10 km

A

157 156 155

.................

........+ 10 m ·· 71

FIGURE G-14. LGL sightings of white whales, 1-10 May 1994. Format as in Fig. G-5.

72

7130
Appendix G: White Whale Distribution Maps, 1989-94 536

157 156 155 '-.-.-.- _._.-...•...-,

"

\

\

-,..

-,<,

White Whales

11·20 May 1994

@ Twin Otter

o Ice Camp/Helicopter

72

+

+ .+

+

.•....------_ ... /" ..

/-If'

///-////---- .•..---'

-- -'

........... ....

+

..... La~sIfastJca Edge .. ··

"'aftar Is·May ....

, ,.••..._- ..

•..•._---_ .••.......

'"

"~ .

" ...~.

......................

'<0117 •

.......

+ ......

.'

" .

..........................

........

"'''''''+ " ".10 m · 71

o 5 lOnmi

o

=-

5 tOmi

+

o 5 to km

157 156 155

FIGUREG-15. LGL sightings of white whales, 11-20 May 1994. Location of ice edge changed

on 15 May (cf, Fig. G-14). Format as in Fig. G-5.

72

7130
Appendix G: White Whale Distribution Maps, 1989-94 537

157 156 155

72

7130

White Whales

21·25 May 1994

~ Twin Otter

o Ice Camp/Helicopter

+

e-;:

"...~a~sIfas-t.I~e Edge' _.,'

+

.........~ .

......~.

......

.............. +

o 5 1O·n mi

o 10mi

.......................... +

· 10 m.······ 71

5

+

o 5 10 km

157 156 155

FIGURE G-16. LGL sightings of white whales, 21-25 May 1994. Format as in Fig. G-5.

72

7130
Appendix H: SSDC Drilling Sounds in Winter 538

APPENDIX H: SSDC Drilling Sounds in Winter

Introduction

With the cooperation of ARCa Alaska, a physical acoustician went to Canadian Marine

Drilling Ltd's SSDC/MAT (a mobile arctic drilling caisson) during drilling operations about 30

miles east of Barrow, Alaska, in January 1992. The purpose of the trip was to record the drilling

sounds at different distances from the structure. It was thought that the sounds might be appropriate for use in playback experiments during spring whale migration.

Methodology

The planned approach was to use battery-powered, portable equipment (an ITC model 6050C

low-noise, wideband hydrophone, an ITC model 1032 spherical hydrophone for infrasonic sound

transduction, and a TEAC model RD-1 01 T digital audio tape recorder) for recording the drilling

sounds. An ice auger was to be used to drill through the ice at each recording site, permitting the

hydrophones to be lowered into the water for sound recordings. Analyses were based on 8.5 s

averaged Fourier transform spectra spanning frequencies from 1 to 4000 Hz.

The recordings were made on 11 January 1992. Air temperature was -21°C; wind speed measured about 12 m above the ice was 20 knots. (It was somewhat lower at the ice surface.)

Results

Recordings were made successfully at only one range, on the starboard side at distance

115 m from the drillrig position on SSDC. The tape froze in the recorder transport after operating

for 10 s, but data from this 10 s segment were usable (Fig. H-1). The 20-1000 Hz broadband level

was 111 dB re 1 IlPa, but the sound spectrum appeared to be only very low ambient noise at frequencies above 700 Hz. Prominent tones appear in the spectrum at 149 Hz 006 dB re 1 IlPa) and

at 447 Hz (92 dB re 1 IlPa). (Note: These tone levels are 5.3 dB higher than the corresponding

apparent peak levels in Figure H-1; the latter must be adjusted upward by 10 log(3.4) to allow for

the 3.4 Hz effective filter bandwidth used in deriving Fig. H-l.) There was a weak tone at 20 Hz

(97 dB re 1 IlPa) but there was no evidence of infrasonic tones (at frequencies less than 20 Hz).

The sounds had the dull quality of droning machinery.
Appendix H: SSDC Drilling Sounds in Winter 539

-N

(\j- :r: 100

etS

CL:::l.

~ 90

~

CO

-0

-- 80

CD

>CD

...J 70

-0

CD

>

'Q5

o 60 CD

a:

50 8.25 Seconds

o 500 1000

Frequency (Hz)

1500 2000

FIGURE H-l. Received signal pressure density spectrum of underwater sounds 115 m from the

drillrig on SSDC during drilling operations. The effective analysis filter bandwidth was 3.4 Hz.

/