U. S. Pacific 

Marine Mammal Stock Assessments: 2001

by

James V. Carretta, Jay Barlow, Karin A. Forney, 

Marcia M. Muto, and Jason Baker

with contributions from

Grant Cameron, Charles Stinchcomb, and Robert Read

U. S. Department of Commerce

National Oceanic and Atmospheric Administration

National Marine Fisheries Service

Southwest Fisheries Science Center

NOAA Technical Memorandum NOAA-TM-NMFS-SWFSC-317
ii

TABLE OF CONTENTS

(Stock assessments revised in 2001 are shown in bold, all others are reprinted unrevised as they appear in the 2000

Stock Assessment Reports (Forney et al. 2000).

PINNIPEDS

CALIFORNIA SEA LION (Zalophus californianus californianus): U.S. Stock ........................... 1

HARBOR SEAL (Phoca vitulina richardsi): California Stock ...................................... 8

HARBOR SEAL (Phoca vitulina richardsi): Oregon & Washington Coastal Waters Stock ................. 14

HARBOR SEAL (Phoca vitulina richardsi): Washington Inland Waters Stock .......................... 20

NORTHERN ELEPHANT SEAL (Mirounga angustirostris): California Breeding Stock .................. 26

GUADALUPE FUR SEAL (Arctocephalus townsendi) ............................................. 31

NORTHERN FUR SEAL (Callorhinus ursinus): San Miguel Island Stock .............................. 35

HAWAIIAN MONK SEAL (Monachus schauinslandi) ........................................... 40

CETACEANS - U.S. WEST COAST

HARBOR PORPOISE (Phocoena phocoena): Central California Stock ............................ 49

HARBOR PORPOISE (Phocoena phocoena): Northern California Stock ........................... 54

HARBOR PORPOISE (Phocoena phocoena): Oregon/Washington Coast Stock ......................... 58

HARBOR PORPOISE (Phocoena phocoena): Washington Inland Waters Stock ......................... 63

DALL'S PORPOISE (Phocoenoides dalli): California/Oregon/Washington Stock ........................ 70

PACIFIC WHITE-SIDED DOLPHIN (Lagenorhynchus obliquidens): 

California/Oregon/Washington, Northern and Southern Stocks ................................ 74

RISSO'S DOLPHIN (Grampus griseus): California/Oregon/Washington Stock .......................... 79

BOTTLENOSE DOLPHIN (Tursiops truncatus): California Coastal Stock ......................... 83

BOTTLENOSE DOLPHIN (Tursiops truncatus): California/Oregon/Washington Offshore Stock ........... 87

STRIPED DOLPHIN (Stenella coeruleoalba): California/Oregon/Washington Stock ..................... 91

SHORT-BEAKED COMMON DOLPHIN (Delphinus delphis): California/Oregon/Washington Stock ....... 95

LONG-BEAKED COMMON DOLPHIN (Delphinus capensis): California Stock ....................... 100

NORTHERN RIGHT-WHALE DOLPHIN (Lissodelphis borealis): California/Oregon/Washington Stock ... 105

KILLER WHALE (Orcinus orca): Eastern North Pacific Transient Stock .............................. 109

KILLER WHALE (Orcinus orca): Eastern North Pacific Offshore Stock .............................. 116

KILLER WHALE (Orcinus orca): Eastern North Pacific Southern Resident Stock .................. 121

SHORT-FINNED PILOT WHALE (Globicephala macrorhynchus): California/Oregon/Washington Stock ... 127

BAIRD'S BEAKED WHALE (Berardius bairdii): California/Oregon/Washington Stock ................. 131

MESOPLODONT BEAKED WHALES (Mesoplodon spp.): California/Oregon/Washington Stocks ........ 134

CUVIER'S BEAKED WHALE (Ziphius cavirostris): California/Oregon/Washington Stock ............... 138

PYGMY SPERM WHALE (Kogia breviceps): California/Oregon/Washington Stock .................... 141

SPERM WHALE (Physeter macrocephalus): California/Oregon/Washington Stock ................. 144

HUMPBACK WHALE (Megaptera novaeangliae): Eastern North Pacific Stock ..................... 149

BLUE WHALE (Balaenoptera musculus): Eastern North Pacific Stock ............................... 156

FIN WHALE (Balaenoptera physalus): California/Oregon/Washington Stock ...................... 161

BRYDE'S WHALE (Balaenoptera edeni): Eastern Tropical Pacific Stock ............................. 166

SEI WHALE (Balaenoptera borealis): Eastern North Pacific Stock .................................. 170

MINKE WHALE (Balaenoptera acutorostrata): California/Oregon/Washington Stock .................. 174
iii

CETACEANS - HAWAII

ROUGH-TOOTHED DOLPHIN (Steno bredanensis): Hawaiian Stock ............................... 178

RISSO'S DOLPHIN (Grampus griseus): Hawaiian Stock .......................................... 181

BOTTLENOSE DOLPHIN (Tursiops truncatus): Hawaiian Stock ................................... 184

PANTROPICAL SPOTTED DOLPHIN (Stenella attenuata): Hawaiian Stock .......................... 188

SPINNER DOLPHIN (Stenella longirostris): Hawaiian Stock ....................................... 191

STRIPED DOLPHIN (Stenella coeruleoalba): Hawaiian Stock ...................................... 194

MELON-HEADED WHALE (Peponocephala electra): Hawaiian Stock .............................. 197

PYGMY KILLER WHALE (Feresa attenuata): Hawaiian Stock .................................... 200

FALSE KILLER WHALE (Pseudorca crassidens): Hawaiian Stock ............................... 202

KILLER WHALE (Orcinus orca): Hawaiian Stock ............................................... 205

SHORT-FINNED PILOT WHALE (Globicephala macrorhynchus): Hawaiian Stock .................... 208

BLAINVILLE'S BEAKED WHALE (Mesoplodon densirostris): Hawaiian Stock ....................... 211

CUVIER'S BEAKED WHALE (Ziphius cavirostris): Hawaiian Stock ................................ 214

PYGMY SPERM WHALE (Kogia breviceps): Hawaiian Stock ..................................... 217

DWARF SPERM WHALE (Kogia sima): Hawaiian Stock ......................................... 219

SPERM WHALE (Physeter macrocephalus): Hawaiian Stock ....................................... 221

BLUE WHALE (Balaenoptera musculus): Hawaiian Stock ......................................... 225

FIN WHALE (Balaenoptera physalus): Hawaiian Stock ........................................... 228

BRYDE'S WHALE (Balaenoptera edeni): Hawaiian Stock ......................................... 230

APPENDICES

APPENDIX 1: Description of U.S. Commercial Fisheries .......................................... 232

APPENDIX 2: Cetacean Survey Effort ......................................................... 262

APPENDIX 3: Summary of 2001 U.S. Pacific Marine Mammal Stock Assessment Reports ................ 268

APPENDIX 4: Chronology of U. S. Pacific Stock Assessment Reports, 1995-2001 ...................... 272

APPENDIX 5: U.S. Fish and Wildlife Service California & Washington sea otter stock assessments ........ 276
iv

PREFACE

Under the 1994 amendments to the Marine Mammal Protection Act (MMPA), the National Marine Fisheries

Service (NMFS) and the U.S. Fish and Wildlife Service (USFWS) are required to publish Stock Assessment Reports

for all stocks of marine mammals within U.S. waters, to review new information every year for strategic stocks and

every three years for non-strategic stocks, and to update the stock assessment reports when significant new information

becomes available. This report presents revised stock assessments for 10 Pacific marine mammal stocks under NMFS

jurisdiction. Information on the remaining 45 stocks is reprinted from the 2000 report without revision. Stock

Assessments for Alaskan marine mammals are published by the National Marine Mammal Laboratory (NMML) in a

separate report. 

The 10 revised stock assessments in this report include stocks studied by the Southwest Fisheries Science

Center (SWFSC, La Jolla, California and Honolulu, Hawaii laboratories) and the National Marine Mammal Laboratory

(NMML, Seattle, Washington). Staff of the National Marine Mammal Laboratory prepared the report on the Eastern

North Pacific Southern Resident killer whale. Honolulu laboratory staff prepared the report on the Hawaiian monk seal.

SWFSC, La Jolla Laboratory staff prepared stock assessments for the remaining 8 stocks. A summary table of the

revised stock assessment reports is provided in Appendix 3. Information on the commercial fisheries that interact with

these stocks is provided in Appendix 1.

New estimates of abundance are available for 9 stocks: California harbor seal (Channel Islands only), Hawaiian

monk seal, northern and central California stocks of harbor porpoise, California coastal bottlenose dolphin, eastern

North Pacific southern resident killer whale, eastern North Pacific humpback whale, and the

California/Oregon/Washington sperm whale stock. New information on changes in the Hawaiian longline fishery is

presented in the Hawaii false killer whale report. The stock of humpback whale previously referred to as the

‘California/Oregon/Washington - Mexico stock’ has been renamed the ‘eastern North Pacific’ stock, reflecting increased

knowledge of their range and movements.

Earlier versions of these stock assessment reports were reviewed by members of the Pacific and Alaska

Scientific Review Groups; we thank them for their helpful comments. The authors also wish to thank those who

provided unpublished data. Any omissions or errors are the sole responsibility of the authors. 

This is a working document and individual stock assessment reports will be updated as new information

becomes available and as changes to marine mammal stocks and fisheries occur. The authors solicit any new information

or comments which would improve future stock assessment reports.

References:

Forney, K.A., J. Barlow, M.M. Muto, M. Lowry, J. Baker, G. Cameron, J. Mobley, C. Stinchcomb, and J.V. Carretta.

2000. U.S. Pacific Marine Mammal Stock Assessments: 2000. U.S. Department of Commerce, NOAA

Technical Memorandum NMFS-SWFSC-300. 276p.
1

Figure 1. Geographic range of California sea

lions showing stock boundaries and locations of

major rookeries.

Revised 12/15/2000

CALIFORNIA SEA LION (Zalophus californianus californianus): U.S. Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

The California sea lion Zalophus californianus includes

three subspecies: Z. c. wollebaeki (on the Galapagos Islands), Z.

c. japonicus (in Japan, but now thought to be extinct), and Z. c.

californianus (found from southern Mexico to southwestern

Canada; herein referred to as the California sea lion). The

breeding areas of the California sea lion are on islands located in

southern California, western Baja California, and the Gulf of

California (Figure 1). These three geographic regions are used to

separate this subspecies into three stocks: (1) the United States

stock begins at the U.S./Mexico border and extends northward

into Canada; (2) the Western Baja California stock extends from

the U.S./Mexico border to the southern tip of the Baja California

Peninsula; and (3) the Gulf of California stock which includes the

Gulf of California from the southern tip of the Baja California

peninsula and across to the mainland and extends to southern

Mexico (Lowry et al. 1992). Some movement has been

documented between these geographic stocks, but rookeries in the

United States are widely separated from the major rookeries of

western Baja California, Mexico. Males from western Baja

California rookeries may spend most of the year in the United

States. Genetic differences have been found between the U.S.

stock and the Gulf of California stock (Maldonado et al. 1995).

There are no international agreements for joint management of

California sea lions between the U.S., Mexico, and Canada.

POPULATION SIZE

The entire population cannot be counted because all age

and sex classes are never ashore at the same time. In lieu of counting all sea lions, pups are counted during the breeding

season (because this is the only age class that is ashore in its entirety), and the number of births is estimated from the

pup count. The size of the population is then estimated from the number of births and the proportion of pups in the

population.

Censuses are conducted in July after all pups have been born. To estimate the number of pups born, the pup

count in 1999 (42,388) was adjusted for an estimated 15% pre-census mortality (Boveng 1988; Lowry et al. 1992),

giving an estimated 48,746 live births in the population. The fraction of newborn pups in the population (22.8% to

23.9%) was estimated from a life table derived for the northern fur seal (Callorhinus ursinus) (Boveng 1988, Lowry

et al. 1992) which was modified to account for the growth rate of this California sea lion population (5.0% to 6.2% yr-1,

respectively, see below). Multiplying the number of pups born by the inverse of these fractions (4.39 to 4.19) results

in population estimates ranging from 214,000 to 204,000 (respectively).

Minimum Population Estimate

The minimum population size was determined from counts of all age and sex classes that were ashore at all

the major rookeries and haulout sites during the 1999 breeding season. The minimum population size of the U.S. stock

is 109,854 (NMFS unpubl. data). It includes all California sea lions counted during the July 1999 census at the four

rookeries in southern California and at the haulout sites located between Point Conception and the Oregon/California

border. An additional unknown number of California sea lions are at sea or hauled out at locations that were not

censused.
2

10 

15 

20 

25 

30 

35 

40 

45 

PUP COUNT INDEX

Thousands

1975 1980 1985 1990 1995 2000 

YEAR

CALIFORNIA SEA LION PUPS

United States

COUNTS

COUNTS AND ESTIMATES

Figure 2. U.S pup count index for California sea lions

(1975-99).

Current Population Trend

Records of pup counts from 1975 to 1999

(Figure 2) were compiled from the literature, NMFS

reports, unpublished NMFS data, and Lowry 1999 (the

literature up to 1992 is listed in Lowry et al. 1992).

Pup counts from 1975 through 1999 were examined for

four rookeries in southern California and for haulouts

in central and northern California. Log-linear

interpolation between adjacent counts was used to

estimate counts for rookeries when they were not

censused in a given year: (1) 1980 at Santa Barbara Is.;

(2) 1978-1980 at San Clemente Is.; (3) 1978, 1979,

1988, and 1989 at San Nicolas Is. The mean was used

when more than one count was available for a given

rookery. Also, an index was used for San Miguel

Island because some years lacked data for certain areas.

Three major declines in the number of pups counted

occurred during El Niño events in 1983, 1992-93, and

1998 (Figure 2). A regression of the natural logarithm

of the pup counts against year indicates that the counts

of pups increased at an annual rate of 5.0% between

1975 and 1999. The counts of pups between the 1976,

1983, and 1992 El Niño events increased at 8.8%

annually (from 1976 to 1982) and at 10.2% annually (from 1983 to 1991). Since 1983, the counts of pups has

increased at 6.2% annually. 

The 1975-99 time series of pup counts shows the effect of three El Niño events on the sea lion population.

Pup production decreased by 35 percent in 1983, 27 percent in1992, and 64 percent in 1998. After the 1992-93 and

1997-98 El Niños, pup production rebounded by 52 percent and 185 percent, respectively, but there was no rebound

after the 1983-84 El Niño (Figure 2). Unlike the 1992-93 and 1997-98 El Niños, the 1983-84 El Niño affected adult

female survivorship (DeLong et al 1991) which prevented the rebound in pup production after the event was over

because there were fewer adult females available in the population to produce a pup (it took five years for pup

production to return to the 1982 level). Other characteristics of El Niños are higher pup and juvenile mortality rates

(DeLong et al 1991, NMFS unpubl. data) which affect future recruitment into the adult population for the affected

cohorts. The long term effects of the 1992-93 event, which resulted in fewer females being recruited into the adult

population, is manifested in lower net productivity rates for 1997 and 1999 (relative to 1997; Figure 2) because fewer

females reached reproductive age (females reach reproductive age at 3 to 5 years). Therefore, the effects of the 1992-93

and 1997-98 El Niños will result in lower net productivity rates for several years due to a drop in adult female

recruitment. The drop in net production shows the long-term effect of El Niños and does not signal that the population

has reached carrying capacity. The severity, timing, length, and frequency of future El Niños will govern the growth

rate of the sea lion population in the future.

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

The rate of net production is greater than the observed growth rate because human related mortalities take a

fraction of the net production. Net productivity was, therefore, calculated for 1980-1999 as the realized rate of

population growth (increase in pup counts from year I to year I+1, divided by pup count in year I) plus human related

mortalities (fishery and non-fishery mortalities in year I divided by population size in year I). For California sea lions,

the total mortalities estimated from NMFS, California Dept. of Fish and Game, Columbia River Area observer programs,

and reports from stranding programs and from salmon net pen fisheries were 1,967, 1,967, 1,967, 4,344, 2,476, 2,364,

4,417, 2,847, 3,753, 2,315, 2,753, 1,901, 3,520, 2,039, 946, 827, 1,107, 1,502, 1,435, 1,348 for 1980 to 1998,

respectively (Miller et al. 1983; Hanan et al. 1988; Hanan and Diamond 1989; Brown and Jeffries 1993; Barlow et al.

1994, Julian 1997, Julian and Beeson 1998, Cameron and Forney 1999, NMFS unpubl. data). Fishery mortality for

1999 (1,261) was estimated as the mean of 1996-1998.
3

-0.8 

-0.6 

-0.4 

-0.2 

0 

0.2 

0.4 

0.6 

0.8 

1 

1.2 

1.4 

1.6 

1.8 

2 

NET PRODUCTION RATE

80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99

YEAR

NET PRODUCTION = Growth + Human related mortalities

United States

Figure 3. Net productivity rates and regression lines

estimated from pup counts with corrections for incidental

human related mortalities. Thick line excludes El Niño years

and El Niño recovery years (i.e., triangles); thin line includes

all years.

Between 1980 and 1999 the net productivity rate averaged 16.1% (Figure 3). A regression (thin line) shows

a slight increase in net production rates, but the regression is strongly influenced by the El Niño years (1983, 1992, and

1998) and the high net production rate during El Niño recovery years (1994 and 1999). When El Niño years (1983,

1992, and 1998) and El Niño recovery years (1994 and 1999) are removed, the regression line shows a slight decrease

(thick line) and net production averages 13.2%. Maximum net productivity rates cannot be estimated from available

data.

POTENTIAL BIOLOGICAL REMOVAL

The potential biological removal (PBR) level

for this stock is calculated as the minimum population

size (109,854) times one half the default maximum net

growth rate for pinnipeds (1⁄2 of 12%) times a recovery

factor of 1.0 (for a stock of unknown status that is

growing, Wade and Angliss 1997); resulting in a PBR

of 6,591 sea lions per year.

ANNUAL HUMAN-CAUSED MORTALITY

Fisheries Information

California sea lions are killed incidentally in

set and drift gillnet fisheries (Hanan et al. 1993;

Barlow et al. 1994; Julian 1997; Julian and Beeson,

1998, Cameron and Forney 1999; Table 1). Detailed

information on these fisheries is provided in Appendix

1. Mortality estimates for the California the set and

drift gillnet fisheries are included in Table 1 for the five

most recent years of monitoring, 1994-98 (Julian and

Beeson 1998; Julian 1997; Cameron and Forney 1999).

A controlled experiment during 1996-97 demonstrated

that the use of acoustic warning devices (pingers)

reduced sea lion entanglement rates considerably within

the drift gillnet fishery (Barlow and Cameron 1999).

However, entanglement rates increased again during the

1997 El Niño and continued during 1998. The reasons for the increase in entanglement rates are unknown. However,

it has been suggested that sea lions may have foraged further offshore in response to limited food supplies near

rookeries, which would provide opportunity for increased interactions with the drift gillnet fishery (Barlow and Cameron

1999). Because of interannual variability in entanglement rates, additional years of data will be required to fully

evaluate the effectiveness of pingers for reducing mortality of this particular species. Because of the changes in this

fishery after implementation of the Take Reduction Plan, mean annual takes in Table 1 are based only on 1997-98 data.

This results in an average estimate of 158 (CV = 0.23) California sea lions taken annually.

 Logbook and observer data, and fisher reports, indicate that mortality of California sea lions occurs, or has

occurred in the past, also in the following fisheries: (1) California, Oregon, and Washington salmon troll fisheries; (2)

Oregon and Washington non-salmon troll fisheries; (3) California herring purse seine fishery; (4) California anchovy,

mackerel, and tuna purse seine fishery; (5) California squid purse seine fishery, (6) Washington, Oregon, California and

British Columbia, Canada salmon net pen fishery, (7) Washington, Oregon, California groundfish trawl fishery, and

(8) Washington, Oregon and California commercial passenger fishing vessel fishery (NMFS 1995, M. Perez pers.

comm, and P. Olesiuk pers. comm.). The OR Columbia River gillnet fishery has been reduced to such levels that

California sea lion mortality, if any, is negligible (J. Scordino, per. comm.). The California Marine Mammal Stranding

Network database maintained by the National Marine Fisheries Service, Southwest Region contains records of humanrelated fishery mortalities of stranded California sea lions. These records show that at least 17 additional mortalities

and 17 injuries occurred in 1998 as a result of fishing net entanglement and 24 additional mortalities and 31 injuries

from hook and line fisheries.

Drift gillnet fisheries for swordfish and sharks exist along the entire Pacific coast of Baja California, Mexico
4

and may take animals from the U.S. stock. Quantitative data are available only for the Mexican swordfish drift gillnet

fishery, which uses vessels, gear, and operational procedures similar to those in the U.S. drift gillnet fishery, although

nets may be up to 4.5 km long (Holts and Sosa-Nishizaki 1998). The fleet has increased from two vessels in 1986 to

31 vessels in 1993. (Holts and Sosa-Nishizaki 1998). The total number of sets in this fishery in 1992 can be estimated

from data provided by these authors to be approximately 2,700, with an observed rate of marine mammal bycatch of

0.13 animals per set (10 marine mammals in 77 observed sets; Sosa-Nishizaki et al. 1993). This overall mortality rate

is similar to that observed in California driftnet fisheries during 1990-95 (0.14 marine mammals per set; Julian and

Beeson 1998), but species-specific information is not available for the Mexican fisheries. There are currently efforts

underway to convert the Mexican swordfish driftnet fishery to a longline fishery (D. Holts, pers. comm.). 

Table 1. Summary of available information on the mortality and serious injury of California sea lions in commercial

fisheries that might take this species (Julian 1997, Julian and Beeson 1998, Cameron and Forney 1999, M. Perez per.

comm, Appendix 1). Mean annual takes are based on 1994-98 data unless noted otherwise. 

Fishery Name Year(s) Data Type

Percent Observer

Coverage

Observed

Mortality

Estimated

Mortality (CV in

parentheses)

Mean

Annual Takes

(CV in parentheses)

CA driftnet fishery

for sharks and

swordfish

1994

1995

1996

1997

1998

observer

17.9%

15.6%

12.4%

23.0%

20.0%

5

4

4

36

23

28 (0.40)

26 (0.45)

36 (0.55)

201(0.34)

114 (0.23)

158 (0.23)1

CA set gillnet fishery

for halibut and angel

shark

1994

1995

1996

1997

1998

observer

estimate

extrapolated

estimate

7.7%

0%

0%

0%

0%

109

-

-

-

-

 905 (0.15)

 724 (0.08) 1

999 (0.06) 1

1,206 (0.06) 1

1,228 (0.07) 1

1,012 (0.04)2

WA, OR, CA

domestic groundfish

trawl fishery (At-sea

processing Pacific

whiting fishery only)

1994

1995

1996

1997

1998

observer

53.8%

56.2%

65.2%

65.7%

77.3%

1

0

0

0

1

2(0.68)

0

0

0

1(0.48)

1(0.48)

WA, OR salmon net

pen fishery 1996

1997

1998

logbook

4

9

9

4

9

9

7(0.39)

Canada: BC salmon

pen fishery 1994

1995

1996

reports

13

23

54 30(0.71)

Minimum total annual takes 1,208 (0.05)

1

 Only 1997-98 mortality estimates are included in the average because of gear modifications implemented within the fishery as part of a 1997 Take

Reduction Plan. Gear modifications included the use of net extenders and acoustic warning devices (pingers).

2

 The CA set gillnets were not observed after 1994; mortality was extrapolated from effort estimates and previous entanglement rates. Changes in

the distribution of effort in this fishery add considerable uncertainty to these estimates.

Other Mortality

California sea lions that were injured by entanglement in gillnet and other man-made debris have been observed

at rookeries and haulouts (Stewart and Yochem 1987, Oliver 1991). The proportion of those entangled ranged from

0.08% to 0.35% of those present on land, with the majority (52%) entangled with monofilament gillnet material. A
5

marine mammal rehabilitation center found that 87% of 87 rescued California sea lions were entangled in 4 to 4.5 inch

square-mesh monofilament gillnet ( Howorth 1995). Of California sea lions entangled in gillnets, 0.8% in set gillnets

and 5.4% in drift gillnets were observed to be released alive from the net by fishers during 1991-95 (Julian and Beeson

1998). Clearly, some are escaping from gillnets after being caught by them; however, the rate of escape from gillnets,

as well as the mortality rate of these injured animals, is unknown. 

Live strandings and dead beach-cast California sea lions have also been observed with gunshot wounds in

California (Lowry and Folk 1987, Deiter 1991, Barocchi et al. 1993). A summary of records for 1998 from the

California Marine Mammal Stranding Network (CMMSN) and the Oregon and Washington stranding databases shows

the following non-fishery related mortality: boat collision ( 3 mortalities), entrainment in power plants (30 mortalities),

and shootings (70 mortalities and 8 injuries). Stranding records are a gross under-estimate of injury and mortality.

However, CMMSN stranding records indicate a higher mortality rate as a result of shootings and hook and line

entanglements during the1997-98 El Niño period (115 shootings, 26 hook and line entanglements) than during the 1995-

96 non-El Niño period (61 shootings, 5 hook and line entanglements). There are currently no estimates of the total

number of California sea lions being killed or injured by guns, boat collisions, entrainment in power plants, marine

debris, or gaffs, but the minimum number in 1998 was 144. 

Several Northwest Indian tribes have developed, or are in the process of developing, regulations for ceremonial

and subsistence harvests of California sea lions and for the incidental take of marine mammals during tribal fisheries.

The tribes have agreed to cooperate with NMFS in gathering and submitting data on takes of marine mammals.

Sea lion mortalities in 1998 along the central California coast have recently been linked to the algal-produced

neurotoxin domoic acid (Scholin et al. 2000). Future mortalities may be expected to occur, owing to the periodic nature

of such harmful algal blooms.

STATUS OF STOCK

Lowry et al. (1992) concluded that there was no evidence of a density dependent signal in counts of California

sea lions between 1983 and 1990, and that it was not possible to determine the status of this stock relative to OSP. 

They are not listed as "endangered" or "threatened" under the Endangered Species Act or as "depleted" under the

MMPA. They are not considered a "strategic" stock under the MMPA because total human-caused mortality (1208

fishery-related mortalities plus 144 from other sources) is less than the PBR (6,591). The total fishery mortality and

serious injury rate for this stock is not less than 10% of the calculated PBR and, therefore, cannot be considered to be

insignificant and approaching a zero mortality and serious injury rate. The population has been growing recently at

6.2% per year, and the fishery mortality is increasing.

REFERENCES

Barlow, J., R. W. Baird, J. E. Heyning, K. Wynne, A. M. Manville II, L. F. Lowry, D. Hanan, J. Sease, and V. N.

Burkanov. 1994. A review of cetacean and pinniped mortality in coastal fisheries along the west coast of the

USA and Canada and the east coast of the Russian Federation. Rept. Int. Whaling Comm., Special Issue

15:405-425.

Barlow, Jay, and G. A. Cameron. 1999. Field experiments show that acoustic pingers reduce marine mammal bycatch

in the California drift gillnet fishery. Paper SC/51/SM2 presented to International Whaling Commission, May

1998 (unpublished). 20 pp.

Barocchi, M., L. E. Morgan, and K. D. Hanni. 1993. Frequency of fishery interactions among live stranded pinnipeds

in central and northern California. (abstract). Tenth Biennial Conference on the Biology of Marine Mammals,

Galveston TX, November 11-15, 1993.

Boveng, P. 1988. Status of the California sea lion population on the U.S. west coast. Admin. Rep. LJ-88-07.

Southwest Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA 92038.

26 pp.

Brown, R. F. and S. J. Jeffries. 1993. Preliminary report on estimated marine mammal mortality in Columbia River

fall and winter salmon gillnet fisheries, 1991-1992. Columbia River Area Marine Mammal Observer Program,

53 Portway St., Astoria, OR. 13 pp.

Cameron, G. A. and K. A. Forney. 1999. Preliminary estimate of cetacean mortality in the California gillnet fisheries

for 1997 and 1998. Paper SC/51/04 presented to International Whaling Commission, May 1999 (unpublished).

14 pp.
6

Deiter, R. L. 1991. Recovery and necropsy of marine mammal carcasses in and near the Point Reyes national Seashore,

May 1982-March 1987. In J. E. Reynolds III and D. K. Odell (editors), Marine mammal strandings in the

United States, Proceedings of the second marine mammal stranding workshop, Miami, Florida, December 3-5-

1987. p. 123-141. NOAA Technical Rept. NMFS 98.

DeLong, R. L., G. A. Antonelis, C. W. Oliver, B. S. Stewart, M. S. Lowry, and P. K. Yochem. 1991. Effects of the

1982-1983 El Niño on several population parameters and diet of California sea lions on the California Channel

Islands. In F. Trillmich and K. A. Ono (editors), Pinnipeds and El Niño: Responses to environmental stress.

p. 166-172. Springer-Verlag, Berlin Heidelberg New York.

Hanan, D. A., and S. L. Diamond. 1989. Estimates of sea lion, harbor seal, and harbor porpoise mortalities in California

set net fisheries for the 1986-87 fishing year. Final Report. Cooperative agreement No. NA-86-ABH-00018.

NOAA/NMFS SWR, January 1989. 10 pp.

Hanan, D. A., D. B. Holts, and A. L. Coan, Jr. 1993. The California drift gill net fishery for sharks and swordfish,

1981-82 through 1990-91. Calif. Dept. Fish and Game Fish. Bull. No. 175. 95 p.

Hanan, D. A., J. P. Scholl, and S. L. Diamond. 1988. Estimates of sea lion and harbor seal mortalities in California set

net fisheries for 1983, 1984, and 1985. Final Report. Cooperative agreement No. NA-86-ABH-00018.

NOAA/NMFS SWR October 1988. 10 pp.

Holts, D. and O. Sosa-Nishizaki. 1998. Swordfish, Xiphias gladius, fisheries of the eastern North Pacific Ocean. In:

I. Barrett, O. Sosa-Nishizaki and N. Bartoo (eds.). Biology and fisheries of swordfish, Xiphias gladius. Papers

from the International Symposium on Pacific Swordfish, Ensenada Mexico, 11-14 December 1994. U.S. Dep.

Commer., NOAA Tech. Rep. NMFS 142, 276 pp.

Holts, D. Southwest Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA 92038.

Howorth, P. C. 1995. Entanglement of marine mammals in synthetic debris. NMFS/SWFSC contract report

40JGNF100597.

Julian, F. 1997. Cetacean mortality in California gill net fisheries: Preliminary estimates for 1996. Paper SC/49/SM02

presented to the International Whaling Commission, September 1997 (unpublished). 13 pp.

Julian, F. And M. Beeson. 1998. Estimates for marine mammal, turtle, and seabird mortality for two California gillnet

fisheries: 1990-1995. Fish. Bull. 96:271-284.

Lowry, M. S. 1999. Counts of California sea lion (Zalophus californianus) pups from aerial color photographs and

from the ground: a comparison of two methods. Marine Mammal Science 15:143-158.

Lowry, M. S. and R. L. Folk. 1987. Feeding habits of California sea lions from stranded carcasses collected at San

Diego County and Santa Catalina Island, California. Admin. Rep. LJ-87-15. Southwest Fisheries Science

Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA 92038. 33 pp.

Lowry, M. S., P. Boveng, R. J. DeLong, C. W. Oliver, B. S. Stewart, H. DeAnda, and J. Barlow. 1992. Status of the

California sea lion (Zalophus californianus californianus) population in 1992. Admin. Rep. LJ-92-32.

Southwest Fisheries Science Center, National Marine Fisheries Service, La Jolla, CA 92038. 34 pp.

Maldonado, J. E., F. O. Davila, B. S. Stewart, E. Greffen, and R. K Wayne. 1995. Intraspecific genetic differentiation

in California sea lions (Zalophus californianus) from southern California and the Gulf of California. Mar.

Mamm. Sci. 11(1):46-58.

Miller, D. J., M. J. Herder, and J. P. Scholl. 1983. California marine mammal-fishery interaction study, 1979-1981.

Administrative Rept. LJ-83-13C. Southwest Fisheries Science Center, National Marine Fisheries Service, P.O.

Box 271, La Jolla, CA. 233 p.

NMFS. 1995. Environmental assessment of proposed regulations to govern interactions between marine mammals and

commercial fishing operations, under Section 118 of the Marine Mammal Protection Act. Department of

Commerce, National Oceanic and Atmospheric Administration, National Marine Fisheries Service, Office of

Protected Resources, June 1995. 139 pp. + 4 Appendices.

Oliver, C. W. 1991. 1988-1991 field studies on pinnipeds at San Clemente Island. Admin. Rep. LJ-91-27. Southwest

Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA 92038. 33 pp.

Scholin, C. A., Gulland, F., Doucette, G. J., Benson, S., Busman, M., Chavez, F. P., Cordaro, J., DeLong, R., De

Vogelaere, A., Harvey, J., Haulena, M., Lefebvre, K., Lipscomb, T., Loscutoff, S., Lowenstine, L. J., Marin

III, R., Miller, P. E., McLellan, W. A., Moeller, P. D. R., Powell, C. L., Rowles, T., Silvagni, P., Silver, M.,

Spraker, T., Trainer, V., and Van Dolah, F. M. 2000. Mortality of sea lions along the central California coast

linked to a toxic diatom bloom. Nature, 403:80-84.
7

Stewart, B. S. and P. K. Yochem. 1987. Entanglement of pinnipeds in synthetic debris and fishing net and line

fragments at San Nicolas and San Miguel Islands, California, 1978-1986. Marine Pollution Bulletin 18:336-

339.
8

Figure 1. Stock boundaries for the California and

Oregon/Washington coastal stocks of harbor seals.

Dashed line represents the U.S. EEZ.

Revised 12/31/2001

HARBOR SEAL (Phoca vitulina richardsi): California Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

Harbor seals (Phoca vitulina) are widely distributed in

the North Atlantic and North Pacific. Two subspecies exist in the

Pacific: P. v. stejnegeri in the western North Pacific, near Japan,

and P. v. richardsi in the eastern North Pacific. The latter

subspecies inhabits near-shore coastal and estuarine areas from

Baja California, Mexico, to the Pribilof Islands in Alaska. These

seals do not make extensive pelagic migrations, but do travel 300-

500 km on occasion to find food or suitable breeding areas

(Herder 1986; D. Hanan unpublished data). In California,

approximately 400-500 harbor seal haulout sites are widely

distributed along the mainland and on offshore islands, including

intertidal sandbars, rocky shores and beaches (Hanan 1996). 

Within the subspecies P. v. richardsi, abundant evidence

of geographic structure comes from differences in mitochondrial

DNA (Huber et al. 1994; Burg 1996; Lamont et al. 1996), mean

pupping dates (Temte 1986), pollutant loads (Calambokidis et al.

1985), pelage coloration (Kelly 1981) and movement patterns

(Jeffries 1985; Brown 1988). LaMont (1996) identified four

discrete subpopulation differences in mtDNA between harbor

seals from Washington (two locations), Oregon, and California.

Another mtDNA study (Burg 1996) supported the existence of

three separate groups of harbor seals between Vancouver Island

and southeastern Alaska. Although we know that geographic

structure exists along an almost continuous distribution of harbor

seals from California to Alaska, stock boundaries are difficult to

draw because any rigid line is (to a greater or lesser extent)

arbitrary from a biological perspective. Nonetheless, failure to

recognize geographic structure by defining management stocks can lead to depletion of local populations. Previous

assessments of the status of harbor seals have recognized 3 stocks along the west coast of the continental U.S.: 1)

California, 2) Oregon and Washington outer coast waters, and 3) inland waters of Washington. Although the need for

stock boundaries for management is real and is supported by biological information, the exact placement of a boundary

between California and Oregon was largely a political/jurisdictional convenience. A small number of harbor seals also

occur along the west coast of Baja California, but they are not considered to be a part of the California stock because

no international agreements exist for the joint management of this species by the U.S. and Mexico. Lacking any new

information on which to base a revised boundary, the harbor seals of California will be again treated as a separate stock

in this report (Fig. 1). Other Marine Mammal Protection Act (MMPA) stock assessment reports cover the five other

stocks that are recognized along the U.S. west coast: Oregon/Washington outer coastal waters, Washington inland

waters, and three stocks in Alaska coastal and inland waters. 

POPULATION SIZE

A complete count of all harbor seals in California is impossible because some are always away from the haulout

sites. A complete pup count (as is done for other pinnipeds in California) is also not possible because harbor seals are

precocious, with pups entering the water almost immediately after birth. Population size is estimated by counting the

number of seals ashore during the peak haul-out period (the May/June molt) and by multiplying this count by the inverse

of the estimated fraction of seals on land. Boveng (1988) reviewed studies estimating the proportion of seals hauled

out to those in the water and suggested that a correction factor for harbor seals is likely to be between 1.4 and 2.0.

Huber (1995) estimated a mean correction factor of 1.53 (CV=0.065) for harbor seals in Oregon and Washington during

the peak pupping season. Hanan (1996) estimated that 83.3% (CV=0.17) of harbor seals haul out at some time during
9

0 

5,000 

10,000 

15,000 

20,000 

25,000 

Number Seals Counted

1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 

Year

Harbor Seals: CA Haulout Counts

TOTAL

Mainland

Channel Islands

Figure 2. Harbor seal haulout counts in California during

May/June (Hanan 1996; R. Read, CDFG unpubl. data).

Figure 3. Net production rates and regression line estimated

from haulout counts and fishery mortality.

the day during the May/June molt, and he

estimated a correction factor of 1.20 based on

those data. Neither correction factor is directly

applicable to an aerial photographic count in

California: the 1.53 factor was measured at the

wrong time of year (when fewer seals are hauled

out) and in a different area and the 1.20 factor

was based on the fraction of seals hauled out

over an entire 24 hr day (correction factors for

aerial counts should be based on the fraction of

seals hauled out at the time of the survey).

Hanan (pers. comm.) revised his haul-out

correction factor to 1.3 by using only those seals

hauled out between 0800 and 1700 which better

corresponds to the timing of his surveys. Based

on the most recent harbor seal counts (23,302 in

May/June 1995, Hanan 1996) and Hanan’s

revised correction factor, the harbor seal

population in California is estimated to number

30,293. A harbor seal count in California was

attempted in 1999, but was not successful due to

bad weather and camera failure (Hanan, pers.

comm.). An aerial survey in May/June 2000 was successful in obtaining a new haul-out estimate for the Channel Islands

in southern California (Fig. 2), but weather and other factors precluded a complete survey of the entire state.

Minimum Population Estimate

Because of the way it was calculated (based on the fraction of seals hauled out at any time during a 24 hr day),

Hanan’s (1996) correction factor of 1.2 can be viewed as a minimum estimate of the fraction hauled out at a given

instant. A population size estimated using this correction factor provides a reasonable assurance that the true population

is greater than or equal to that number, and thus fulfills the requirement of a minimum population estimate. The

minimum size of the California harbor seal population is therefore 27,962. 

Current Population Trend

Harbor seal counts have continued to

increase except during El Niño events (eg. 1992-93)

(Fig. 2). The net production appears, however, to

be slowing in California (Fig. 3) and in Oregon and

Washington (see separate Stock Assessment

Report).

CURRENT AND MAXIMUM NET

PRODUCTIVITY RATES

A realized rate of increase was calculated

for the 1982-1995 period by linear regression of the

natural logarithm of total count versus year. The

slope this regression line was 0.035 (s.e.=0.007)

which gives an annualized growth rate estimate of

3.5%. The current rate of net production is greater

than this observed growth rate because fishery

mortality takes a fraction of the net production.

Annual gillnet mortality may have been as high as

5-10% of the California harbor seal population in
10

the mid-1980s; a kill this large would have depressed population growth rates appreciably. Net productivity was

therefore calculated for 1980-1994 as the realized rate of population growth (increase in seal counts from year i to year

i+1, divided by the seal count in year i) plus the human-caused mortality rate (fishery mortality in year i divided by

population size in yeari). Between 1983 and 1994, the net productivity rate for the California stock averaged 9.2% (Fig.

3). A regression shows a decrease in net production rates, but the decline is not statistically significant. Maximum net

productivity rates cannot be estimated because measurements were not made when the stock size was very small.

POTENTIAL BIOLOGICAL REMOVAL

The potential biological removal (PBR) level for this stock is calculated as the minimum population size

(27,962) times one half the default maximum net productivity rate for pinnipeds (1⁄2 of 12%) times a recovery factor of

1.0 (for a stock of unknown status that is growing, Wade and Angliss 1997), resulting in a PBR of 1,678.

Table 1. Summary of available information on the mortality and serious injury of harbor seals (California stock) in

commercial fisheries that might take this species (NMFS 1995; Julian 1997; Julian and Beeson 1998; Cameron and

Forney 1999; 2000). n/a indicates that data are not available. Mean annual takes are based on 1994-98 data unless

noted otherwise.

Fishery Name Year(s) Data Type

Percent

Observer

Coverage

Observed

Mortality

Estimated

Mortality (CV in

parentheses)

Mean

Annual Takes

(CV in parentheses)

CA/OR thresher

shark/swordfish drift

gillnet fishery

1995-99 observer

data

12-23% 0 0,0,0,0,0 0

1

CA angel shark/halibut and

other species large mesh

(>3.5") set gillnet fishery

1995

1996

1997

1998

1999

extrapo-lated

estimate

observer

data

0.0%

0.0%

0.0%

0.0%

4.0% 3

-

-

-

-

57

228 (0.13)2

296 (0.08)2

349 (0.08)2

392 (0.10)2

662 (0.10)3

662

CA, OR, and WA salmon

troll fishery

1990-92 logbook data

-

Avg. Annual

 take = 7.33 n/a

CA herring purse seine

fishery

1990-92 logbook data

-

Avg. Annual

 take = 0 n/a

CA anchovy, mackerel, and

tuna purse seine fishery

1990-92 logbook data

-

Avg. Annual

 take = 0.67 n/a

WA, OR, CA groundfish

trawl

1991-95 observer

data

54-73% 0 0,0,0,0,0 0

CA squid purse seine

fishery

1990-92 logbook data

-

Avg. Annual

 take = 0 n/a

(unknown net and hook

fisheries)

1995-98 stranding

data

17 4

Total annual takes 666

1 Only 1997-98 mortality estimates are included in the average because of gear modifications implemented within the

fishery as part of a 1997 Take Reduction Plan. Gear modifications included the use of net extenders and acoustic

warning devices (pingers).

2The CA set gillnets were not observed from 1995-98; mortality was extrapolated from effort estimates and previous

entanglement rates.

3Set gillnet observer coverage in 1999 was limited to Monterey Bay fishing effort only. Mortality in other areas was

extrapolated from 1999 effort estimates and 1991-94 entanglement rates. 

HUMAN-CAUSED MORTALITY

Historical Takes

Prior to state and federal protection and especially during the nineteenth century, harbor seals along the west

coast of North America were greatly reduced by commercial hunting (Bonnot 1928, 1951; Bartholomew and Boolootian

1960). Only a few hundred individuals survived in a few isolated areas along the California coast (Bonnot 1928). In
11

the last half of this century, the population has increased dramatically.

Fishery Information

A summary of known fishery mortality and injury for this stock of harbor seals is given in Table 1. More

detailed information on these fisheries is provided in Appendix 1. Because the vast majority of harbor seal mortality

in California fisheries occurs in the set gillnet fishery, because that fishery has undergone dramatic reductions and

redistributions of effort, and because the entire fishery has not been observed since 1994, average annual mortality

cannot be accurately estimated for the recent years (1995-1999). Rough estimates for 1995-1999 have been made by

extrapolation of prior kill rates using recent effort estimates (Table 1). Preliminary gillnet observations from April to

September 1999 included 47 harbor seals in 24.6% of the sets for a rough extrapolated estimate of 191 mortalities in

this half-year period. Stranding data reported to the California Marine Mammal Stranding Network in 1995-98 include

harbor seal deaths and injuries caused by hook-and-line fisheries (17 deaths, 4 injuries) and gillnet fisheries (1 death,

2 injuries). 

Other Mortality

The California Marine Mammal Stranding database maintained by the National Marine Fisheries Service,

Southwest Region, contains the following records of human-related harbor seal mortalities and injuries in 1995-99: (1)

boat collision (11 mortalities, 2 injuries), (2) entrainment in power plants (24 mortalities), and (3) shootings (11

mortalities).

STATUS OF STOCK

A review of harbor seal dynamics through 1991 concluded that their status relative to OSP could not be

determined with certainty (Hanan 1996). They are not listed as "endangered" or "threatened" under the Endangered

Species Act nor as "depleted" under the MMPA. Total fishing mortality cannot be accurately estimate for recent years,

but extrapolations from past years and preliminary data for 1999 indicate that fishing mortality is less than the calculated

PBR for this stock (1,678), and thus they would not be considered a "strategic" stock under the MMPA. The average

rate of incidental fishery mortality for this stock is likely to be greater than 10% of the calculated PBR; therefore, fishery

mortality cannot be considered insignificant and approaching zero mortality and serious injury rate. The population

appears to be growing and the fishery mortality is declining. There are no known habitat issues that are of particular

concern for this stock. Two unexplained harbor seal mortality events occurred in Point Reyes National Park involving

at least 90 seals in 1997 and 16 seals in 2000. Necropsy of 3 seals in 2000 showed severe pneumonia; tests for

morbillivirus were negative, but attempts are being made to identify another virus isolated from one of the three (F.

Gulland, pers. comm.). All west-coast harbor seals that have been tested for morbilliviruses were found to be

seronegative, indicating that this disease is not endemic in the population and that this population is extremely

susceptible to an epidemic of this disease (Ham-Lammé et al. 1999). 

REFERENCES

Barlow, J., R. W. Baird, J. E. Heyning, K. Wynne, A. M. Manville, II, L. F. Lowry, D. Hanan, J. Sease, and V. N.

Burkanov. 1994. A review of cetacean and pinniped mortality in coastal fisheries along the west coast of the

U.S. and Canada and the east coast of the Russian Federation. Rep. Int. Whal. Commn, Special Issue 15:405-

425.

Bartholomew, G. A., R. A. Boolootian. 1960. Numbers and population structure of the pinnipeds on the California

Channel Islands. J. Mammal. 41:366-375.

Bonnot, P. 1928. Report on the seals and sea lions of California. Fish Bulletin Number 14. California Division of Fish

and Game.

Bonnot, P. 1951. The sea lions, seals and sea otter of the California coast. California Fish and Game 37(4):371-389.

Boveng, P. 1988. Status of the Pacific harbor seal population on the U.S. west coast. Admin. Rep. LJ-88-06. Southwest

Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA 92038. 43 pp.

Brown, R. F. 1988. Assessment of pinniped populations in Oregon. Processed Report 88-05, National Marine Fisheries

Service, Northwest and Alaska Fisheries Center, Seattle, Washington.

Burg, T. M. 1996. Genetic analysis of eastern Pacific harbor seals (Phoca vitulina richardsi) from British Columbia

and parts of Alaska using mitochondrial DNA and microsatellites. Masters Thesis, Univ. of British Columbia,
12

Vancouver, British Columbia. 77pp.

Calambokidis, J., S. M. Speich, J. Peard, G. H. Steiger, and J. C. Cubbage. 1985. Biology of Puget Sound marine

mammals and marine birds: population health and evidence of pollution effects. U.S. Dep. Commer., NOAA

Tech. Memo. NOS-OMA-18. 159 pp.

Cameron, G. A. and K. A. Forney. 1999. Preliminary estimates of cetacean mortality in the California gillnet fisheries

for 1997 and 1998. Paper SC/51/O4 presented to the International Whaling Commission, May 1999

(unpublished). 14 pp.

Cameron, G.A. and K.A. Forney. 2000. Preliminary Estimates of Cetacean Mortality in California/Oregon Gillnet

Fisheries for 1999. Paper SC/52/O24 presented to the International Whaling Commission, 2000 (unpublished).

12 pp. Available from NMFS, Southwest Fisheries Science Center, P.O. Box 271, La Jolla, California, 92038,

USA.

Forney, K.A., J. Barlow, M.M. Muto, M. Lowry, J. Baker, G. Cameron, J. Mobley, C. Stinchcomb, and J.V. Carretta.

2000. U.S. Pacific Marine Mammal Stock Assessments: 2000. U.S. Department of Commerce, NOAA

Technical Memorandum NMFS-SWFSC-300. 276p.

Ham-Lammé, K. D., D. P. King, B. C. Taylor, C. House, D. A. Jessup, S. Jeffries, P. K Yochem, F. M. D. Gulland, D.

A. Ferrick, and J. L. Stott. 1999. The application of immuno-assays for serological detection of morbillivirus

exposure in free ranging harbor seals (Phoca vitulina) and sea otters (Enhydra lutris) from the western coast

of the United States. Mar. Mamm. Sci. 15(2):601-608.

Hanan, D. A. 1993. Status of the Pacific harbor seal population on the coast of California in 1992. Final Report to

the National Marine Fisheries Service, Southwest Region. 27pp.

Hanan, D. A. 1996. Dynamics of Abundance and Distribution for Pacific Harbor Seal, Phoca vitulina richardsi, on

the Coast of California. Ph.D. Dissertation, University of California, Los Angeles. 158pp.

Hanan, D. A., and S. L. Diamond. 1989. Estimates of sea lion, harbor seal, and harbor porpoise mortalities in California

set net fisheries for the 1986-87 fishing year. Final Report. Cooperative agreement No. NA-86-ABH-00018.

NOAA/NMFS SWR, January 1989. 10 pages.

Hanan, D. A., D. B. Holts, and A. L. Coan, Jr. 1993. The California drift gill net fishery for sharks and swordfish,

1981-82 through 1990-91. Calif. Dept. Fish and Game Fish. Bull. No. 175. 95pp.

Hanan, D. A., J. P. Scholl, and S. L. Diamond. 1988. Estimates of sea lion and harbor seal mortalities in California set

net fisheries for 1983, 1984, and 1985. Final Report. Cooperative agreement No. NA-86-ABH-00018.

NOAA/NMFS SWR October 1988. 10 pages.

Herder, M. J. 1986. Seasonal movements and hauling site fidelity of harbor seals, Phoca vitulina richardsi, tagged at

the Russian River, California. MS Thesis. Humbolt State Univ. 52 pages.

Huber, H. 1995. The abundance of harbor seals (Phoca vitulina richardsi) in Washington, 1991-1993. MS Thesis,

Univ. of Washington, Seattle, Washington. 56 pp.

Huber, H., S. Jeffries, R. Brown, and R. DeLong. 1994. Harbor seal stock assessment in Washington and Oregon

1993. Annual report to the MMPA Assessment Program, Office of Protected Resources, NMFS, NOAA, 1335

East-West Highway, Silver Spring, MD 20910.

Jeffries, S. J. 1985. Occurrence and distribution patterns of marine mammals in the Columbia River and adjacent

coastal waters of northern Oregon and Washington. In: Marine Mammals and Adjacent Waters, 1980-1982.

Processed Report 85-04, National Marine Fisheries Service, Northwest and Alaska Fisheries Center, Seattle,

Washington.

Julian, F. And M. Beeson. 1998. Estimates for marine mammal, turtle, and seabird mortality for two California gillnet

fisheries: 1990-1995. Fish. Bull. 96:271-284.

Kelly, B. P. 1981. Pelage polymorphism in Pacific harbor seals. Can. J. Zool. 59:1212-1219.

Lamont, M. M., J. T. Vida, J. T. Harvey, S. Jeffries, R. Brown, H. H. Huber, R. DeLong, and W. K. Thomas. 1996.

Genetic substructure of the Pacific harbor seal (Phoca vitulina richardsi) off Washington, Oregon, and

California. Mar. Mamm. Sci. 12(3):402-413.

Miller, D. J., M. J. Herder, and J. P. Scholl. 1983. California marine mammal-fishery interaction study, 1979-1981.

Admin. Rep. LJ-83-13C. Southwest Fisheries Science Center, National Marine Fisheries Service, P.O. Box

271, La Jolla, CA 92038. 233 pp.

NMFS. 1995. Environmental assessment of proposed regulations to govern interactions between marine mammals and

commercial fishing operations, under Section 118 of the Marine Mammal Protection Act. Department of
13

Commerce, National Oceanic and Atmospheric Administration, National Marine Fisheries Service, Office of

Protected Resources, June 1995. 139 p. + 4 Appendices.

Perkins, P., J. Barlow, and M. Beeson. 1994. Report on pinniped and cetacean mortality in California gillnet fisheries:

1988-90. Admin. Rep. LJ-94-11. Southwest Fisheries Science Center, National Marine Fisheries Service, P.

O. Box 271, La Jolla, California, 92038. 16 pp.

Temte, J. L. 1986. Photoperiod and the timing of pupping in the Pacific harbor seal (Phoca vitulina richardsi) with

notes on reproduction in northern fur seals and Dall’s porpoises. Masters Thesis, Oregon State Univ.,

Corvallis, Oregon.
14

WA Inland stock

OR/WA

Coastal

stock

CA stock

Figure 1. Approximate distribution of harbor

seals in the U.S. Pacific Northwest (shaded area).

Stock boundaries separating the three stocks are

shown.

Revised 12/15/2000

HARBOR SEAL (Phoca vitulina richardsi):

Oregon/Washington Coast Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

Harbor seals inhabit coastal and estuarine waters off Baja

California, north along the western coasts of the continental U.S.,

British Columbia, and Southeast Alaska, west through the Gulf of

Alaska and Aleutian Islands, and in the Bering Sea north to Cape

Newenham and the Pribilof Islands. They haul out on rocks,

reefs, beaches, and drifting glacial ice, and feed in marine,

estuarine, and occasionally fresh waters. Harbor seals generally

are non-migratory, with local movements associated with such

factors as tides, weather, season, food availability, and

reproduction (Scheffer and Slipp 1944; Fisher 1952; Bigg 1969,

1981). Harbor seals do not make extensive pelagic migrations

though some long distance movement of tagged animals in Alaska

(174 km) and along the U.S. west coast (up to 550 km) have been

recorded (Pitcher and McAllister 1981, Brown and Mate 1983,

Herder 1986). Harbor seals have also displayed strong fidelity for

haul out sites (Pitcher and Calkins 1979, Pitcher and McAllister

1981).

For management purposes, differences in mean pupping

date (Temte 1986), movement patterns (Jeffries 1985, Brown

1988), pollutant loads (Calambokidis et al. 1985) and fishery

interactions have led to the recognition of 3 separate harbor seal

stocks along the west coast of the continental U.S. (Boveng 1988):

1) inland waters of Washington State (including the Hood Canal,

Puget Sound, and Strait of Juan de Fuca out to Cape Flattery), 2)

outer coast of Oregon and Washington, and 3) California (see Fig.

1). Recent genetic analyses provide additional support for this

stock structure (Huber et al. 1994, Burg 1996, Lamont et al.

1996). Samples from Washington, Oregon, and California

demonstrate a high level of genetic diversity and indicate that the

harbor seals of inland Washington possess unique haplotypes not found in seals from the coasts of Washington, Oregon,

and California (Lamont et al. 1996). This report considers only the Oregon/Washington Coast stock. Three harbor seal

stocks are also recognized in the inland and coastal waters of Alaska, including the Southeast Alaska, Gulf of Alaska,

and Bering Sea stocks. The three Alaska harbor seal stocks are reported separately in the Stock Assessment Reports

for the Alaska Region.

POPULATION SIZE

Aerial surveys of harbor seals in Oregon and Washington were conducted by personnel from the National

Marine Mammal Laboratory (NMML) and the Oregon and Washington Departments of Fish and Wildlife (ODFW and

WDFW) during the 1997 pupping season. Total numbers of hauled-out seals (including pups) were counted during

these surveys. In 1997, the mean count of harbor seals occurring along the Washington coast was 11,864 (CV=0.028)

animals (WDFW, unpubl. data; NMML, unpubl. data). In 1997, the mean count of harbor seals occurring along the

Oregon coast and in the Columbia River was 5,247 (CV=0.042) animals (ODFW, unpubl. data; Brown 1997).

Combining these counts results in 17,111 (CV=0.023) harbor seals in the Oregon/Washington Coast stock.

Radio-tagging studies conducted at 6 locations (3 Washington inland waters sites and 3 Oregon and

Washington coastal sites) collected information on haulout pattern from 63 harbor seals in 1991 and 61 harbor seals

in 1992. Data from coastal and inland sites were not significantly different and were thus pooled, resulting in a

correction factor of 1.53 (CV=0.065) to account for animals in the water which are missed during the aerial surveys
15

(Huber 1995). Using this correction factor results in a population estimate of 26,180 (17,111 x 1.53; CV=0.069) for

the Oregon/Washington Coast stock of harbor seals in 1997 (WDFW, unpubl. data; NMML, unpubl. data; ODFW,

unpubl. data).

Minimum Population Estimate

The log-normal 20th percentile of the 1997 population estimate for this stock is 24,705 harbor seals.

Current Population Trend

Historical levels of harbor seal abundance in Oregon and Washington are unknown. The population apparently

decreased during the 1940s and 1950s due to bounty hunting. Approximately 17,133 harbor seals were killed in

Washington by bounty hunters between 1943 and 1960 (Newby 1973). More than 3,800 harbor seals were killed in

Oregon between 1925 and 1972 by a state-hired seal hunter, as well as bounty hunters (Pearson 1968). The population

remained relatively low during the 1960s, but since the termination of the harbor seal bounty program and with the

protection provided by the Marine Mammal Protection Act (MMPA) harbor seal counts for this stock have increased

from 6,389 in 1977 to 17,111 in 1997 (WDFW, unpubl. data; NMML, unpubl. data; ODFW, unpubl. data).

Between 1983 and 1996, the annual rate of increase for this stock was 4%, with the peak count of 18,667 seals

occurring in 1992. From 1991 to 1996, however, this stock declined 1.6% (t=3.25; p=0.083) annually (Jeffries et al.

1997), which may indicate that this population has exceeded equilibrium levels. Analyzing only the Oregon data

(average annual rate of increase was 0.3% from 1988-96) indicates that the Oregon segment of the stock may be

approaching equilibrium (Brown 1997). It is possible that the lower total counts for the population as a whole may have

resulted from changes in haulout behavior. Increased disturbance, reduced food availability necessitating longer

foraging periods, or other unknown reasons may have caused a larger number of seals to be in the water during the

surveys (Jeffries et al. 1997).

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

From 1978 to 1993, counts of harbor seals throughout Washington State increased at an annual rate of 7.68%

(Huber 1995). The Oregon/Washington Coast harbor seal stock increased at an annual rate of 7% from 1983 to 1992

and at 4% from 1983 to 1996 (Jeffries et al. 1997). Because the population was not at a very low level, the observed

rates of increase will underestimate the maximum net productivity (RMAX). Therefore, until additional data become

available, the pinniped default maximum theoretical net productivity rate (RMAX) of 12% will be employed for this harbor

seal stock (Wade and Angliss 1997).

POTENTIAL BIOLOGICAL REMOVAL

The potential biological removal (PBR) level for this stock is calculated as the minimum population estimate

(24,705) times one-half the default maximum net growth rate for pinnipeds (1⁄2 of 12%) times a recovery factor of 1.0

(for stocks thought to be within OSP, Wade and Angliss 1997), resulting in a PBR of 1,482 harbor seals per year.

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Fisheries Information

NMFS observers monitored the northern Washington marine set gillnet fishery during 1993-1998 (Gearin et

al. 1994, 2000; P. Gearin, unpubl. data); 1994 observer data recently became available and will be included in a future

stock assessment report. For the entire fishery (coastal + inland waters), observer coverage ranged from approximately

40 to 98% during those years. Fishing effort is conducted within the range of both stocks of harbor seals

(Oregon/Washington Coast and Inland Washington stocks) occurring in Washington State waters. Some of the animals

taken in the inland waters portion of the fishery (see the Inland Washington stock assessment report for details) may

have been animals from the coastal stock. Similarly, some of the animals taken in the coastal portion of the fishery may

have been from the inland stock. For the purposes of this stock assessment report, the animals taken in the inland

portion of the fishery are assumed to have belonged to the Inland Washington stock and the animals taken in the coastal

portion of the fishery are assumed to have belonged to the Oregon/Washington Coast stock. However, as noted, some

movement of animals between Washington’s coastal and inland waters is likely, although data from tagging studies have

not shown movement of harbor seals between the two locations (Huber 1995). Accordingly, Table 1 includes data only

from that portion of the northern Washington marine set gillnet fishery occurring within the range of the
16

Oregon/Washington Coast stock (those waters south and west of Cape Flattery), where observer coverage was 100%

in 1995-1997. No fishing effort occurred in the coastal portion of the fishery in 1993 or 1998. Data from 1993 to 1998

are included in Table 1, although the mean estimated annual mortality is calculated using only the most recent 5 years

for which data are available. The mean estimated mortality for this fishery is 5 (CV=0.52) harbor seals per year from

this stock.

The WA/OR/CA groundfish trawl fishery (Pacific whiting component) was monitored for incidental take

during 1994-1998. The only harbor seal mortalities occurred in 1996 and 1997, years in which observer coverage (based

on observed tons) was 65 and 66%, respectively. Both mortalities occurred during unmonitored hauls and therefore

were not used to estimate mortality for the entire fishery in those years. However, observers monitored 100% of the

vessels during the fishery and the reported mortalities are thought to be the only harbor seal mortalities in that fishery.

The mean estimated mortality from 1994 to 1998 for monitored hauls in this fishery is zero harbor seals per year from

this stock, plus 0.4 animals per year from unmonitored haul data.

Table 1. Summary of available information on the incidental mortality and injury of harbor seals (Oregon/Washington

Coast stock) in commercial and tribal fisheries that might take this species and calculation of the mean annual mortality

rate; n/a indicates that data are not available. All entanglements resulted in the death of the animal. Mean annual takes

are based on 1994-98 data unless otherwise noted.

Fishery name Years Data type

Percent

observer

coverage

Observed

mortality

Estimated

mortality

Mean annual

takes (CV in

parentheses)

Northern WA marine set gillnet

(tribal fishery: coastal waters)

93

94

95

96

97

98

obs data no fishery

n/a

100% 

100%

100% 

no fishery

0

n/a

3

9

13

0

0

n/a

3

9

13

0

5 (0.52)1

WA/OR/CA groundfish trawl

(Pacific whiting component)

94

95

96

97

98

96

97

obs data

unmonitored

hauls

53.8%

56.2%

65.2%

65.7%

77.3%

0

0

0

0

0

1

1

0

0

0

0

0

0

0.4 (n/a)

WA Grays Harbor salmon drift

gillnet

91-93 obs data 4-5% 0, 1, 1 0, 10, 10 6.7 (0.50)

WA Willapa Bay drift gillnet 91-93 obs data 1-3% 0, 0, 0 0, 0, 0 0

Reported

mortalities

WA Willapa Bay drift gillnet 90-98 self

reports

n/a 0, 0, 6, 8,

n/a, n/a, n/a,

n/a, n/a

n/a ≥ 3.5 (n/a)

see text

Minimum total annual takes ≥ 15.6 (0.36)

1

1993 and 1995-98 mortality estimates are included in the average.

The Washington and Oregon Lower Columbia River drift gillnet fishery was monitored during the entire year

in 1991-1993 (Brown and Jeffries 1993, Matteson et al. 1993c, Matteson and Langton 1994a). Harbor seal mortalities,

incidental to the fishery, were observed only in the winter season and were extrapolated to estimate total harbor seal

mortality. However, the structure of the fishery has changed substantially since the 1991-1992 fishing seasons, and this

level of take no longer applies to the current fishery (see Appendix 1).

The Washington Grays Harbor salmon drift gillnet fishery was also monitored from 1991-1993 (Herczeg et
17

al. 1992a; Matteson and Molinaar 1992; Matteson et al. 1993a; Matteson and Langton 1994b, 1994c). During the 3-year

period, 98, 307 and 241 sets were monitored, representing approximately 4-5% observer coverage in each year. No

mortalities were recorded in 1991. In 1992 observers recorded 1 harbor seal mortality incidental to the fishery, resulting

in an extrapolated estimated total kill of 10 seals (CV=1.0). In 1993 observers recorded 1 harbor seal mortality

incidental to the fishery, though a total kill was not extrapolated. Similar observer coverage in 1992 and 1993 (4.2%

and 4.4%, respectively) suggests that 10 is also a reasonable estimate of the total kill in 1993. Thus, the mean estimated

mortality for this fishery from 1991-1993 is 6.7 (CV=0.50) harbor seals per year (Table 1). No observer data are

available for this fishery after 1993. 

Combining the estimates from the northern Washington marine set gillnet (5), WA/OR/CA groundfish trawl

(0 from monitored hauls + 0.4 from unmonitored haul data), and Washington Grays Harbor salmon drift gillnet (6.7)

fisheries results in an estimated mean mortality rate in observed fisheries of 12.1 harbor seals per year from this stock.

The Washington Willapa Bay drift gillnet fishery was also monitored at low levels of observer coverage from

1991-1993 (Herczeg et al. 1992a, 1992b; Matteson and Molinaar 1992; Matteson et al. 1993b; Matteson and Langton

1994c, 1994d). In those years, 752, 576, and 452 sets were observed representing approximately 2.5%, 1.4% and 3.1%

observer coverage, respectively. No harbor seal mortalities were reported by observers. However, because mortalities

were self-reported by fishers in 1992 and 1993, the low level of observer coverage failed to document harbor seal

mortalities which had apparently occurred. Due to the low level of observer coverage for this fishery, the self-reported

fishery mortalities have been included in Table 1 and represent a minimum mortality estimate resulting from that fishery

(3.5 harbor seals per year). 

An additional source of information on the number of harbor seals killed or injured incidental to commercial

fishery operations is the self-reported fisheries information required of vessel operators by the MMPA. During the

period between 1994 and 1998, there were no fisher self-reports of any harbor seal mortalities. However, because

logbook records (fisher self-reports required during 1990-94) are most likely negatively biased (Credle et al. 1994), these

are considered to be minimum estimates. Self-reported fisheries data are incomplete for 1994, not available for 1995,

and considered unreliable after 1995 (see Appendix 4 of Hill and DeMaster 1998).

Other Mortality

Strandings of harbor seals resulting from collisions with boats, from gunshot injuries, or entanglement in line

unrelated to fisheries are another source of mortality data. During the 5-year period from 1994 to 1998, human-related

mortalities or serious injuries occurred in 1994 (4), 1997 (2) and 1998 (2), resulting in an estimated annual mortality

of 1.6 harbor seals (rounded to 2) from this stock during 1994 to 1998. This estimate is considered a minimum because

not all stranded animals are found, reported, or examined for cause of death (via necropsy by trained personnel).

Subsistence Harvests by Northwest Treaty Indian Tribes

Several Northwest Indian tribes have developed, or are in the process of developing, regulations for ceremonial

and subsistence harvests of harbor seals and for the incidental take of marine mammals during tribal fisheries. The

tribes have agreed to cooperate with NMFS in gathering and submitting data on takes of marine mammals.

STATUS OF STOCK

Harbor seals are not considered as “depleted” under the MMPA or listed as “threatened “ or “endangered”

under the Endangered Species Act. Based on currently available data, the level of human-caused mortality and serious

injury (16 + 2 = 18) does not exceed the PBR (1,482). Therefore, the Oregon/Washington Coast stock of harbor seals

is not classified as a strategic stock. The minimum total fishery mortality and serious injury for this stock (16; based

on observer data (12) and self-reported fisheries information (4) where observer data were not available or failed to

detect harbor seal mortality) is also less than 10% of the calculated PBR (148) and, therefore, can be considered to be

insignificant and approaching zero mortality and serious injury rate. The stock size increased until 1992, but has

declined in recent years. At this time it is not possible to assess the status of this stock relative to its Optimum

Sustainable Population (OSP) level.

REFERENCES

Bigg, M. A. 1969. The harbour seal in British Columbia. Fish. Res. Bd. Can. Bull. 172. 33 pp.

Bigg, M. A. 1981. Harbour seal, Phoca vitulina, Linnaeus, 1758 and Phoca largha, Pallas, 1811. Pp. 1-27, In:
18

Ridgway, S. H., and R. J. Harrison (eds.), Handbook of Marine Mammals. Vol. 2: Seals. Academic Press,

New York.

Boveng, P. 1988. Status of the Pacific harbor seal population on the U.S. west coast. Admin. Rept. LJ-88-06.

Southwest Fisheries Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA. 43 pp.

Brown, R. F. 1988. Assessment of pinniped populations in Oregon. Processed Report 88-05, National Marine

Fisheries Service, Northwest and Alaska Fisheries Center, Seattle, WA.

Brown, R. F. 1997. Abundance of Pacific harbor seals (Phoca vitulina richardsi) in Oregon: 1977-1996. Oregon

Dept. Fish and Wildlife, Wildlife Diversity Program, Tech. Report No. 97-6-04. 12 pp.

Brown, R. F., and B. R. Mate. 1983. Abundance, movements, and feeding habits of the harbor seal, Phoca vitulina,

at Netarts and Tillamook Bays, Oregon. Fish. Bull. 81:291-301.

Brown, R. F., and S. J. Jeffries. 1993. Preliminary report on estimated marine mammal mortality in Columbia River

fall and winter salmon gillnet fisheries, 1991-1992. Unpubl. report. Columbia River Area Gillnet Fishery

Observer Program, 13 pp. Available at Oregon Dept. Fish and Wildlife, Newport, OR 97365.

Burg, T. M. 1996. Genetic analysis of eastern Pacific harbor seals (Phoca vitulina richardsi) from British Columbia

and parts of Alaska using mitochondrial DNA and microsatellites. MS Thesis, Univ. of British Columbia,

Vancouver, BC. 77 pp.

Calambokidis, J., S. Speich, J. Peard, G. Steiger, D. M. Fry, J. Lowenstine, and J. Cubbage. 1985. Biology of Puget

Sound marine mammals and marine birds: population health and evidence of pollution effects. U.S. Dep.

Commer., NOAA Tech. Memo. NOS-OMA-18. 159 pp.

Credle, V. R., D. P. DeMaster, M. M. Merklein, M. B. Hanson, W. A. Karp, and S. M. Fitzgerald (eds.). 1994. NMFS

observer programs: minutes and recommendations from a workshop held in Galveston, Texas, November 10-

11, 1993. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-94-1. 96 pp.

Fisher, H. D. 1952. The status of the harbour seal in British Columbia, with particular reference to the Skeena River.

Fish. Res. Bd. Can. Bull. 93. 58 pp.

Gearin, P. J. National Marine Mammal Laboratory, AFSC, NMFS, 7600 Sand Point Way NE, Seattle, WA 98115.

Gearin, P. J., S. R. Melin, R. L. DeLong, H. Kajimura, and M. A. Johnson. 1994. Harbor porpoise interactions with

a chinook salmon set-net fishery in Washington State. Rep. Int. Whal. Commn. Special Issue 15:427-438.

Gearin, P. J., M. E. Gosho, J. L. Laake, L. Cooke, R. L. DeLong, and K. M. Hughes. 2000. Experimental testing of

acoustic alarms (pingers) to reduce bycatch of harbour porpoise, Phocoena phocoena, in the state of

Washington. J. Cetacean Res. Manage. 2(1):1-9.

Herczeg, K. M., A. A. Abajian , and V. M. C. Molinaar. 1992a. Summary report on the 1991 summer dip-in salmon

gillnet fisheries in Willapa Bay and Grays Harbor. Unpubl. report. Pacific States Marine Fisheries

Commission, Astoria, OR. 10 pp. Available at PSMFC, 45 SE 82nd Ave., Ste. 100, Gladstone, OR 97027.

Herczeg, K. M., V. M. C. Molinaar, and A. A. Abajian. 1992b. Summary report on the 1991 fall Willapa Bay salmon

gillnet fishery. Unpubl. report. Pacific States Marine Fisheries Commission, Astoria, OR. 10 pp. Available

at PSMFC, 45 SE 82nd Ave., Ste. 100, Gladstone, OR 97027.

Herder, M. J. 1986. Seasonal movements and hauling site fidelity of harbor seals, Phoca vitulina richardsi, tagged at

the Russian River, California. MS Thesis, Humbolt State Univ., Humbolt, California. 52 pp.

Hill, P. S, and D. P. DeMaster. 1998. Alaska marine mammal stock assessments, 1998. U.S. Dep. Commer., NOAA

Tech. Memo. NMFS-AFSC-97. 166 pp.

Huber, H. 1995. The abundance of harbor seals (Phoca vitulina richardsi) in Washington, 1991-1993. MS Thesis,

Univ. of Washington, Seattle, WA. 56 pp.

Huber, H., S. Jeffries, R. Brown, and R. DeLong. 1994. Harbor seal, Phoca vitulina richardsi, stock assessment in

Washington and Oregon, 1993. 1993 Annual Report to the MMPA Assessment Program, Office of Protected

Resources, NMFS, NOAA, 1335 East-West Highway, Silver Spring, MD 20910. Available at National Marine

Mammal Laboratory, 7600 Sand Point Way NE, Seattle, WA 98115.

Jeffries, S. J. 1985. Occurrence and distribution patterns of marine mammals in the Columbia River and adjacent

coastal waters of northern Oregon and Washington. In: Marine mammals and adjacent waters, 1980-1982.

Processed Report 85-04, National Marine Fisheries Service, Northwest and Alaska Fisheries Center, Seattle,

WA.

Jeffries, S. J., R. F. Brown, H. R. Huber, and R. L. DeLong. 1997. Assessment of harbor seals in Washington and

Oregon, 1996. Pp. 83-94, In: Hill, P. S., and D. P. DeMaster (eds.), MMPA and ESA Implementation
19

Program, 1996. AFSC Processed Report 97-10. 255 pp. Available at National Marine Mammal Laboratory,

7600 Sand Point Way NE, Seattle, WA 98115.

Lamont, M. M., J. T. Vida, J. T. Harvey, S. Jeffries, R. Brown, H. H. Huber, R. DeLong, and W. K. Thomas. 1996.

Genetic substructure of the Pacific harbor seal (Phoca vitulina richardsi) off Washington, Oregon, and

California. Mar. Mammal Sci. 12(3):402-413.

Matteson, K. M., and J. A. Langton. 1994a. Summary report on the 1993 fall Columbia River salmon gillnet fishery.

Unpubl. report. Pacific States Marine Fisheries Commission, Astoria, OR. 19 pp. Available at PSMFC, 45

SE 82nd Ave., Ste. 100, Gladstone, OR 97027.

Matteson, K. M., and J. A. Langton. 1994b. Summary report on the 1993 fall Grays Harbor salmon gillnet fishery.

Unpubl. report. Pacific States Marine Fisheries Commission, Astoria, OR. 18 pp. Available at PSMFC, 45

SE 82nd Ave., Ste. 100, Gladstone, OR 97027.

Matteson, K. M., and J. A. Langton. 1994c. Summary report on the 1993 summer dip-in salmon gillnet fisheries in

Willapa Bay and Grays Harbor. Unpubl. report. Pacific States Marine Fisheries Commission, Astoria, OR.

22 pp. Available at PSMFC, 45 SE 82nd Ave., Ste. 100, Gladstone, OR 97027.

Matteson, K. M., and J. A. Langton. 1994d. Summary report on the 1993 fall Willapa Bay salmon gillnet fishery.

Unpubl. report. Pacific States Marine Fisheries Commission, Astoria, OR. 18 pp. Available at PSMFC, 45

SE 82nd Ave., Ste. 100, Gladstone, OR 97027.

Matteson, K. M., and V. M. C. Molinaar. 1992. Summary report on the 1992 summer dip-in salmon gillnet fisheries

in Willapa Bay and Grays Harbor. Unpubl. report. Pacific States Marine Fisheries Commission, Astoria, OR.

13 pp. Available at PSMFC, 45 SE 82nd Ave., Ste. 100, Gladstone, OR 97027.

Matteson, K. M., W. B. Barnett, and J. A. Langton. 1993a. Summary report on the 1992 fall Grays Harbor salmon

gillnet fishery. Unpubl. report. Pacific States Marine Fisheries Commission, Astoria, OR. 17 pp. Available

at PSMFC, 45 SE 82nd Ave., Ste. 100, Gladstone, OR 97027.

Matteson, K. M., W. B. Barnett, and J. A. Langton. 1993b. Summary report on the 1992 fall Willapa Bay salmon

gillnet fishery. Unpubl. report. Pacific States Marine Fisheries Commission, Astoria, OR. 17 pp. Available

at PSMFC, 45 SE 82nd Ave., Ste. 100, Gladstone, OR 97027.

Matteson, K. M., J. A. Langton, and R. L. Hadley. 1993c. Summary report on the 1993 winter Columbia River salmon

gillnet fishery. Unpubl. report. Pacific States Marine Fisheries Commission, Astoria, OR. 29 pp. Available

at PSMFC, 45 SE 82nd Ave., Ste. 100, Gladstone, OR 97027.

National Marine Mammal Laboratory, AFSC, NMFS, 7600 Sand Point Way NE, Seattle, WA 98115.

Newby, T. C. 1973. Changes in Washington State harbor seal population, 1942-1972. Murrelet 54:5-6.

Oregon Department of Fish and Wildlife, Marine Science Dr., Bldg. 3, Newport, OR 97365.

Pearson, J. P. 1968. The abundance and distribution of harbor seals and Steller sea lions in Oregon. MS Thesis,

Oregon State Univ., Corvallis, OR. 23 pp.

Pitcher, K. W., and D. G. Calkins. 1979. Biology of the harbor seal (Phoca vitulina richardsi) in the Gulf of Alaska.

U.S. Dep. Commer., NOAA, OCSEAP Final Rep. 19(1983):231-310.

Pitcher, K. W., and D. C. McAllister. 1981. Movements and haul out behavior of radio-tagged harbor seals, Phoca

vitulina. Can. Field Nat. 95:292-297.

Scheffer, V. B., and J. W. Slipp. 1944. The harbor seal in Washington State. Amer. Midl. Nat. 32:373-416.

Temte, J. L. 1986. Photoperiod and the timing of pupping in the Pacific harbor seal (Phoca vitulina richardsi) with

notes on reproduction in northern fur seals and Dall's porpoises. MS Thesis, Oregon State Univ. Corvallis,

OR.

Wade, P. R., and R. Angliss. 1997. Guidelines for assessing marine mammal stocks: report of the GAMMS workshop

April 3-5, 1996, Seattle, Washington. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-12. 93 pp.

Washington Department of Fish and Wildlife, Marine Mammal Investigations, 7801 Phillips Rd. SW, Tacoma, WA

98498.
20

WA Inland stock

OR/WA

Coastal

stock

CA stock

Figure 1. Approximate distribution of harbor

seals in the U.S. Pacific Northwest (shaded area).

Stock boundaries separating the three stocks are

shown.

Revised 12/15/2000

HARBOR SEAL (Phoca vitulina richardsi): 

Washington Inland Waters Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

Harbor seals inhabit coastal and estuarine waters off

Baja California, north along the western coasts of the continental

U.S., British Columbia, and Southeast Alaska, west through the

Gulf of Alaska and Aleutian Islands, and in the Bering Sea north

to Cape Newenham and the Pribilof Islands. They haul out on

rocks, reefs, beaches, and drifting glacial ice, and feed in marine,

estuarine, and occasionally fresh waters. Harbor seals generally

are non-migratory, with local movements associated with such

factors as tides, weather, season, food availability, and

reproduction (Scheffer and Slipp 1944; Fisher 1952; Bigg 1969,

1981). Harbor seals do not make extensive pelagic migrations

though some long distance movement of tagged animals in Alaska

(174 km) and along the U.S. west coast (up to 550 km) have been

recorded (Pitcher and McAllister 1981, Brown and Mate 1983,

Herder 1986). Harbor seals have also displayed strong fidelity for

haul out sites (Pitcher and Calkins 1979, Pitcher and McAllister

1981).

For management purposes, differences in mean pupping

date (Temte 1986), movement patterns (Jeffries 1985, Brown

1988), pollutant loads (Calambokidis et al. 1985) and fishery

interactions have led to the recognition of 3 separate harbor seal

stocks along the west coast of the continental U.S. (Boveng

1988): 1) inland waters of Washington State (including the Hood

Canal, Puget Sound, and Strait of Juan de Fuca out to Cape

Flattery), 2) outer coast of Oregon and Washington, and 3)

California (see Fig. 1). Recent genetic analyses provide

additional support for this stock structure (Huber et al. 1994, Burg

1996, Lamont et al. 1996). Samples from Washington, Oregon,

and California demonstrate a high level of genetic diversity and

indicate that the harbor seals of inland Washington possess

unique haplotypes not found in seals from the coasts of Washington, Oregon, and California (Lamont et al. 1996). This

report considers only the Inland Washington stock. Three harbor seal stocks are also recognized in the inland and

coastal waters of Alaska, including the Southeast Alaska, Gulf of Alaska, and Bering Sea stocks. The three Alaska

harbor seal stocks are reported separately in the Stock Assessment Reports for the Alaska Region.

POPULATION SIZE

Aerial surveys of harbor seals in Washington were conducted during the pupping season in 1997, during which

time the total number of hauled-out seals (including pups) were counted. In 1997 the mean count of harbor seals

occurring in Washington’s inland waters was 10,494 (CV=0.017) animals (WDFW, unpubl. data; NMML, unpubl.

data). 

Radio-tagging studies conducted at 6 locations (3 Washington inland waters sites and 3 Oregon and

Washington coastal sites) collected information on haulout patterns from 63 harbor seals in 1991 and 61 harbor seals

in 1992. Data from coastal and inland sites were not significantly different and were thus pooled, resulting in a

correction factor of 1.53 (CV=0.065) to account for animals in the water which are missed during the aerial surveys

(Huber 1995). Using this correction factor results in a population estimate of 16,056 (10,494 x 1.53; CV=0.067) for

the Inland Washington stock of harbor seals (WDFW, unpubl. data; NMML, unpubl. data).
21

Minimum Population Estimate

The log-normal 20th percentile of the 1997 population estimate for this stock is 15,174 harbor seals.

Current Population Trend

Historical levels of harbor seal abundance in Washington are unknown. The population apparently decreased

during the 1940s and 1950s due to bounty hunting. Approximately 17,133 harbor seals were killed in Washington by

bounty hunters between 1943 and 1960 (Newby 1973). The population remained relatively low during the 1970s, but

since the termination of the harbor seal bounty program in 1960 and with the protection provided by the Marine

Mammal Protection Act (MMPA), harbor seal numbers in Washington have increased (Jeffries 1985).

Between 1983 and 1996, the annual rate of increase for this stock was 6%. From 1991 to 1996, this stock

increased 10% (t=5.28; p=0.034) annually, with the peak count occurring in 1996. The higher rate of increase in recent

years may be due to emigration of harbor seals from the Canadian waters of the Strait of Georgia to the San Juan Islands

(Jeffries et al. 1997).

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

From 1991 to 1996, counts of harbor seals in Washington State have increased at an annual rate of 10%

(Jeffries et al. 1997). Because the population was not at a very low level, the observed rate of increase will

underestimate the maximum net productivity (RMAX). Therefore, until additional data become available, the pinniped

default maximum theoretical net productivity rate (RMAX) of 12% will be employed for this harbor seal stock (Wade and

Angliss 1997).

POTENTIAL BIOLOGICAL REMOVAL

The potential biological removal (PBR) level for this stock is calculated as the minimum population size

(15,174) times one-half the default maximum net growth rate for pinnipeds (1⁄2 of 12%) times a recovery factor of 1.0

(for stocks of unknown status that are increasing in size, Wade and Angliss 1997), resulting in a PBR of 910 harbor

seals per year. 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Fisheries Information

NMFS observers monitored the northern Washington marine set gillnet fishery during 1993-1998 (Gearin et

al. 1994, 2000; P. Gearin, unpubl. data); 1994 observer data recently became available and will be included in a future

stock assessment report. For the entire fishery (coastal + inland waters), observer coverage ranged from approximately

40 to 98% during those years. Fishing effort is conducted within the range of both stocks of harbor seals

(Oregon/Washington Coast and Inland Washington stocks) occurring in Washington State waters. Some of the animals

taken in the inland waters portion of the fishery may have been animals from the coastal stock. Similarly, some of the

animals taken in the coastal portion of the fishery (see the Oregon/Washington Coast stock assessment report for details)

may have been from the inland stock. For the purposes of this stock assessment report, the animals taken in the inland

portion of the fishery are assumed to have belonged to the Inland Washington stock and the animals taken in the coastal

portion of the fishery are assumed to have belonged to the Oregon/Washington Coast stock. However, as noted, some

movement of animals between Washington’s coastal and inland waters is likely, although data from tagging studies have

not shown movement of harbor seals between the two locations (Huber 1995). Accordingly, Table 1 includes data only

from that portion of the northern Washington marine set gillnet fishery occurring within the range of the Inland

Washington stock (those waters east of Cape Flattery), where observer coverage ranged from 6 to 80% between 1993

and 1998. Data from 1993-1998 are included in Table 1, although the mean estimated annual mortality is calculated

using the most recent 5 years of available data. Little effort occurred in the inland portion of the fishery in 1995, 1997,

and 1998. No harbor seal mortalities were observed or reported in this fishery from 1995 to 1998. The mean estimated

mortality for this fishery is 4 (CV=1.0) harbor seals per year from this stock.

In 1993 as a pilot for future observer programs, NMFS in conjunction with the Washington Department of Fish

and Wildlife (WDFW) monitored all non-treaty components of the Washington Puget Sound Region salmon gillnet

fishery (Pierce et al. 1994). Observer coverage was 1.3% overall, ranging from 0.9% to 7.3% for the various

components of the fishery. Two harbor seal mortalities were reported (Table 1). Pierce et al. (1994) cautioned against

extrapolating these mortalities to the entire Puget Sound fishery due to the low observer coverage and potential biases
22

inherent in the data. The area 7/7A sockeye landings represented the majority of the non-treaty salmon landings in 1993,

approximately 67%. Results of this pilot study were used to design the 1994 observer programs discussed below. 

Table 1. Summary of available information on the incidental mortality and injury of harbor seals (Inland Washington

stock) in commercial and tribal fisheries that might take this species and calculation of the mean annual mortality rate;

n/a indicates that data are not available. All entanglements resulted in the death of the animal. Mean annual takes are

based on 1994-98 data unless noted otherwise.

Fishery name Years

Data

type

Percent

observer

coverage

Observed

mortality

Estimated

mortality

Mean annual

takes (CV in

parentheses)

Northern WA marine set gillnet

(tribal fishery: inland waters)

93

94

95

96

97

98

obs data 61%

n/a

24%

6%

80%

40%

12

n/a

0

0

0

0

20

n/a

0

0

0

0

4.0 (1.0)1

WA Puget Sound Region salmon

set/drift gillnet (observer

programs listed below covered

segments of this fishery):

- - - - - -

 Puget Sound non-treaty salmon

 gillnet (all areas and species)

93 obs data 1.3% 2 n/a see text

 Puget Sound non-treaty chum

 salmon gillnet (areas 10/11 and

 12/12B)

94 obs data 11% 1 10 10 (n/a)

 Puget Sound treaty chum

 salmon gillnet (areas 12, 12B,

 and 12C)

94 obs data 2.2% 0 0 0

 Puget Sound treaty chum and

 sockeye salmon gillnet (areas

 4B, 5, and 6C)

94 obs data 7.5% 0 0 0

 Puget Sound treaty and non-

 treaty sockeye salmon gillnet

 (areas 7 and 7A)

94 obs data 7% 1 15 15 (1.0)

Reported

mortalities

WA Puget Sound Region salmon

set/drift gillnet

94-98 self

reports

n/a n/a, n/a, n/a, n/a,

n/a

n/a see text

WA salmon net pens 97-98 self

reports

n/a 10, 5 n/a ≥ 7.5 (n/a)

unknown Puget Sound fishery 94-98 strand

data

n/a 3, 0, 2, 1, 1 n/a ≥ 1.4 (n/a)

Minimum total annual takes ≥ 37.9 (0.82)

1

1993 and 1995-98 mortality estimates are included in the average.

In 1994, NMFS in conjunction with WDFW conducted an observer program during the Puget Sound non-treaty

chum salmon gillnet fishery (areas 10/11 and 12/12B). A total of 230 sets were observed during 54 boat trips,

representing approximately 11% observer coverage of the 500 fishing boat trips comprising the total effort in this fishery

as estimated from fish ticket landings (Erstad et al. 1996). One harbor seal was taken in the fishery, resulting in an

entanglement rate of 0.02 harbor seals per trip (0.004 harbor seals per set), which extrapolated to approximately 10
23

mortalities for the entire fishery. The Puget Sound treaty chum salmon gillnet fishery in Hood Canal (areas 12, 12B,

and 12C) and Puget Sound treaty sockeye/chum gillnet fishery in the Strait of Juan de Fuca (areas 4B, 5, and 6C) were

also monitored in 1994 (NWIFC 1995). No harbor seal mortalities were reported in the observer programs covering

these treaty salmon gillnet fisheries, where observer coverage was estimated at 2.2% (based on % of total catch

observed) and approximately 7.5% (based on % of observed trips to total landings), respectively.

Also in 1994, NMFS in conjunction with WDFW and the Tribes monitored the Puget Sound treaty and nontreaty sockeye salmon gillnet fishery (areas 7 and 7A). During this fishery observers monitored 2,205 sets, representing

approximately 7% of the estimated number of sets in the fishery (Pierce et al. 1996). There was one observed harbor

seal mortality (two others were entangled and released unharmed), resulting in a mortality rate of 0.00045 harbor seals

per set, which extrapolated to 15 mortalities (CV=1.0) for the entire fishery. In 1996, Washington Sea Grant Program

conducted a test fishery in the non-treaty sockeye salmon gillnet fishery (area 7) to compare entanglement rates of

seabirds and marine mammals and catch rates of salmon using three experimental gears and a control (monofilament

mesh net). The experimental nets incorporated highly visible mesh in the upper quarter (50 mesh gear) or upper eighth

(20 mesh gear) of the net or had low-frequency sound emitters attached to the corkline (Melvin et al. 1997). In 642 sets

during 17 vessel trips, there were two harbor seal mortalities (one other was released alive with no apparent injuries).

Combining the estimates from the northern Washington marine set gillnet (4), Puget Sound non-treaty chum

salmon gillnet in areas 10/11 and 12/12B (10), and Puget Sound treaty and non-treaty sockeye salmon gillnet in areas

7 and 7A (15) fisheries results in an estimated minimum annual mortality rate in observed fisheries of 29 harbor seals

per year from this stock. It should be noted that the 1994 observer programs did not sample all segments of the entire

Washington Puget Sound Region salmon set/drift gillnet fishery, and further, the extrapolations of total kill did not

include effort for the unobserved segments of this fishery. Therefore, 29 is an underestimate of the harbor seal mortality

due to the entire fishery. It is not possible to quantify what percentage of the Washington Puget Sound Region salmon

set/drift gillnet fishery was actually observed in 1994. However, the areas having the highest salmon catches and in

which a majority of the vessels operated in 1994 were covered by the 1994 observer programs (J. Scordino, pers.

comm.).

An additional source of information on the number of harbor seals killed or injured incidental to commercial

fishery operations is the self-reported fisheries information required of vessel operators by the MMPA. Fisher selfreports from 1994-1998 for the Washington Puget Sound Region salmon set and drift gillnet fishery are shown in Table

1. Unlike the 1994 observer program data, the self-reported fishery data cover the entire fishery (including treaty and

non-treaty components) and have thus been included in the table. There were fisher self-reports of 15 harbor seal

mortalities due to entanglement in Washington salmon net pens, 10 in 1997 and 5 in 1998 (Table 1), resulting in an

annual mortality of 7.5 harbor seals from this stock in those two years. However, because logbook records (fisher selfreports required during 1990-94) are most likely negatively biased (Credle et al. 1994), these are considered to be

minimum estimates. Self-reported fisheries data are incomplete for 1994, not available for 1995, and considered

unreliable after 1995 (see Appendix 4 in Hill and DeMaster 1998). 

Strandings of harbor seals entangled in fishing gear or with injuries caused by interactions with gear are a final

source of fishery-related mortality information. During the period from 1994 to 1998, small numbers of fishery-related

strandings of harbor seals have occurred in most years. As the strandings could not be attributed to a particular fishery,

they have been included in Table 1 as occurring in an unknown Puget Sound fishery. Fishery-related strandings during

1994-1998 result in an estimated annual mortality of 1.4 harbor seals from this stock. This estimate is considered a

minimum because not all stranded animals are found, reported, or examined for cause of death (via necropsy by trained

personnel).

The minimum estimated fishery mortality and serious injury for this stock is 37.9 (rounded to 38) harbor seals

per year, based on observer program data (29), fisher self-reports (7.5), and stranding data (1.4). However, a reliable

estimate of the total mortality rate incidental to commercial fisheries is currently unavailable due to the absence of

observer placements in segments of the Washington Puget Sound Region salmon set and drift gillnet fishery.

Other Mortality

Strandings of harbor seals resulting from collisions with boats, from gunshot injuries, or entanglement in line

unrelated to fisheries are another source of mortality data. During the 5-year period from 1994 to 1998, human-related

mortalities occurred each year, with reports of 7, 1, 8, 7, and 2 animals for those years, respectively. These mortalities

resulted in an estimated annual mortality of 5 harbor seals from this stock during 1994-1998. This estimate is considered
24

a minimum because not all stranded animals are found, reported, or cause of death determined (via necropsy by trained

personnel).

Subsistence Harvests by Northwest Treaty Indian Tribes

Several Northwest Indian tribes have developed, or are in the process of developing, regulations for ceremonial

and subsistence harvests of harbor seals and for the incidental take of marine mammals during tribal fisheries. The

tribes have agreed to cooperate with NMFS in gathering and submitting data on takes of marine mammals.

STATUS OF STOCK

Harbor seals are not considered to be “depleted” under the MMPA or listed as “threatened “ or “endangered”

under the Endangered Species Act. Based on currently available data, the level of human-caused mortality and serious

injury (38 + 5 = 43) does not exceed the PBR (910). Therefore, the Inland Washington stock of harbor seals is not

classified as a strategic stock. At present, the minimum estimated fishery mortality and serious injury for this stock (38)

is less that 10% of the calculated PBR (91) and, therefore, can be considered to be insignificant and approaching zero

mortality and serious injury rate. The stock size has increased in recent years, although at this time it is not possible to

assess the status of the stock relative to its Optimum Sustainable Population (OSP) level.

REFERENCES

Bigg, M. A. 1969. The harbour seal in British Columbia. Fish. Res. Bd. Can. Bull. 172. 33 pp.

Bigg, M. A. 1981. Harbour seal, Phoca vitulina, Linnaeus, 1758 and Phoca largha, Pallas, 1811. Pp. 1-27, In:

Ridgway, S. H., and R. J. Harrison (eds.), Handbook of Marine Mammals. Vol. 2: Seals. Academic Press,

New York.

Boveng, P. 1988. Status of the Pacific harbor seal population on the U.S. west coast. Admin. Rep. LJ-88-06.

Southwest Fisheries Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA. 43 pp.

Brown, R. F. 1988. Assessment of pinniped populations in Oregon. Processed Report 88-05, NMFS, Northwest and

Alaska Fisheries Science Center, Seattle, WA.

Brown, R. F., and B. R. Mate. 1983. Abundance, movements, and feeding habits of the harbor seal, Phoca vitulina,

at Netarts and Tillamook Bays, Oregon. Fish. Bull. 81:291-301.

Burg, T. M. 1996. Genetic analysis of eastern Pacific harbor seals (Phoca vitulina richardsi) from British Columbia

and parts of Alaska using mitochondrial DNA and microsatellites. MS Thesis, Univ. of British Columbia,

Vancouver, BC. 77 pp.

Calambokidis, J., S. Speich, J. Peard, G. Steiger, D. M. Fry, J. Lowenstine, and J. Cubbage. 1985. Biology of Puget

Sound marine mammals and marine birds: population health and evidence of pollution effects. U.S. Dep.

Commer., NOAA Tech. Memo. NOS-OMA-18. 159 pp.

Credle, V. R., D. P. DeMaster, M. M. Merklein, M. B. Hanson, W. A. Karp, and S. M. Fitzgerald (eds.). 1994. NMFS

observer programs: minutes and recommendations from a workshop held in Galveston, Texas, November 10-

11, 1993. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-94-1. 96 pp.

Erstad, P., S. J. Jeffries, and D. J. Pierce. 1996. 1994 Report for the Puget Sound fishery observer program in

management areas 10/11 & 12/12B: nontreaty chum gill net fishery. Final Report, Washington Dept. Fish and

Wildlife, Olympia, WA. 14 pp.

Fisher, H. D. 1952. The status of the harbour seal in British Columbia, with particular reference to the Skeena River.

Fish. Res. Bd. Can. Bull. 93. 58 pp.

Gearin, P. J. National Marine Mammal Laboratory, AFSC, NMFS, 7600 Sand Point Way NE, Seattle, WA 98115.

Gearin, P. J., S. R. Melin, R. L. DeLong, H. Kajimura, and M. A. Johnson. 1994. Harbor porpoise interactions with

a chinook salmon set-net fishery in Washington State. Rep. Int. Whal. Commn. Special Issue 15:427-438.

Gearin, P. J., M. E. Gosho, J. L. Laake, L. Cooke, R. L. DeLong, and K. M. Hughes. 2000. Experimental testing of

acoustic alarms (pingers) to reduce bycatch of harbour porpoise, Phocoena phocoena, in the state of

Washington. J. Cetacean Res. Manage. 2(1):1-9.

Herder, M. J. 1986. Seasonal movements and hauling site fidelity of harbor seals, Phoca vitulina richardsi, tagged at

the Russian River, California. MS Thesis, Humbolt State Univ., Humbolt, CA. 52 pp.

Hill, P. S, and D. P. DeMaster. 1998. Alaska marine mammal stock assessments, 1998. U.S. Dep. Commer., NOAA

Tech. Memo. NMFS-AFSC-97. 166 pp.
25

Huber, H. 1995. The abundance of harbor seals (Phoca vitulina richardsi) in Washington, 1991-1993. MS Thesis,

Univ. of Washington, Seattle, WA. 56 pp.

Huber, H., S. Jeffries, R. Brown, and R. DeLong. 1994. Harbor seal, Phoca vitulina richardsi, stock assessment in

Washington and Oregon, 1993. 1993 Annual Report to the MMPA Assessment Program, Office of Protected

Resources, NMFS, NOAA, 1335 East-West Highway, Silver Spring, MD 20910. Available at National Marine

Mammal Laboratory, 7600 Sand Point Way NE, Seattle, WA 98115.

Jeffries, S. J. 1985. Occurrence and distribution patterns of marine mammals in the Columbia River and adjacent

coastal waters of northern Oregon and Washington. In: Marine mammals and their interactions with fisheries

of the Columbia River and adjacent waters, 1980-1982. Processed Report 85-04, NMFS, Northwest and

Alaska Fisheries Center, Seattle, WA.

Jeffries, S. J., R. F. Brown, H. R. Huber, and R. L. DeLong. 1997. Assessment of harbor seals in Washington and

Oregon, 1996. Pp. 83-94, In: Hill, P. S., and D. P. DeMaster (eds.), MMPA and ESA Implementation

Program, 1996. AFSC Processed Report 97-10. 255 pp. Available at National Marine Mammal Laboratory,

7600 Sand Point Way NE, Seattle, WA 98115.

Lamont, M. M., J. T. Vida, J. T. Harvey, S. Jeffries, R. Brown, H. H. Huber, R. DeLong, and W. K. Thomas. 1996.

Genetic substructure of the Pacific harbor seal (Phoca vitulina richardsi) off Washington, Oregon, and

California. Mar. Mammal Sci. 12(3):402-413.

Melvin, E. F., L. L. Conquest, and J. K. Parrish. 1997. Seabird bycatch reduction: new tools for Puget Sound drift

gillnet salmon fisheries. 1996 Sockeye and 1995 Chum Salmon Test Fisheries Final Report. Washington Sea

Grant Program, Seattle, WA. 48pp.

Newby, T. C. 1973. Changes in Washington State harbor seal population, 1942-1972. Murrelet 54:5-6.

National Marine Mammal Laboratory, AFSC, NMFS, 7600 Sand Point Way NE, Seattle, WA 98115.

Northwest Indian Fisheries Commission. 1995. Monitoring of marbled murrelet and marine mammal interactions with

1994 tribal gillnet fisheries in northern Puget Sound, Hood Canal, and the Strait of Juan de Fuca. Final Report

to NMFS Contract No. 52ABNF400087. Unpubl. report. Northwest Indian Fisheries Commission. 43 pp.

Available at NWIFC, 6730 Martin Way E, Olympia, WA 98516.

Pierce, D. J., W. P. Ritchie, and R. Kreuziger. 1994. Preliminary findings of seabird interactions with the non-treaty

salmon gill net fishery: Puget Sound and Hood Canal Washington. Unpubl. report. Washington Dept. Fish

and Wildlife, Olympia, WA. 39 pp. Available at WDFW, 600 Capitol Way N, Olympia, WA 98501.

Pierce, D. J., M. Alexandersdottir, S. J. Jeffries, P. Erstad, W. Beattie, and A. Chapman. 1996. Interactions of marbled

murrelets and marine mammals with the 1994 Puget Sound sockeye gill net fishery. Final Report, Washington

Dept. Fish and Wildlife, Olympia, WA. 21 pp.

Pitcher, K. W., and D. G. Calkins. 1979. Biology of the harbor seal (Phoca vitulina richardsi) in the Gulf of Alaska.

U.S. Dep. Commer., NOAA, OCSEAP Final Rep. 19(1983):231-310.

Pitcher, K. W., and D. C. McAllister. 1981. Movements and haul out behavior of radio-tagged harbor seals, Phoca

vitulina. Can. Field Nat. 95:292-297.

Scheffer, V. B., and J. W. Slipp. 1944. The harbor seal in Washington State. Amer. Midl. Nat. 32:373-416.

Scordino, J. National Marine Fisheries Service, Northwest Region, 7600 Sand Point Way NE, Seattle, WA 98115.

Temte, J. L. 1986. Photoperiod and the timing of pupping in the Pacific harbor seal (Phoca vitulina richardsi) with

notes on reproduction in northern fur seals and Dall's porpoises. MS Thesis, Oregon State Univ., Corvallis,

OR.

Wade, P. R., and R. Angliss. 1997. Guidelines for assessing marine mammal stocks: report of the GAMMS workshop

April 3-5, 1996, Seattle, Washington. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-12. 93 pp.

Washington Department of Fish and Wildlife, Marine Mammal Investigations, 7801 Phillips Rd. SW, Tacoma, WA

98498.
26

Figure 1. Stock boundary and major rookery

areas for northern elephant seals in the U.S. and

Mexico.

Revised 12/15/2000

NORTHERN ELEPHANT SEAL (Mirounga angustirostris): 

California Breeding Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

Northern elephant seals breed and give birth in California

(U.S.) and Baja California (Mexico), primarily on offshore islands

(Stewart et al. 1994), from December to March (Stewart and

Huber 1993). Males feed near the eastern Aleutian Islands and in

the Gulf of Alaska, and females feed further south, south of 45oN

(Stewart and Huber 1993; Le Boeuf et al. 1993). Adults return to

land between March and August to molt, with males returning

later than females. Adults return to their feeding areas again

between their spring/summer molting and their winter breeding

seasons.

Populations of northern elephant seals in the U.S. and

Mexico were all originally derived from a few tens or a few

hundreds of individuals surviving in Mexico after being nearly

hunted to extinction (Stewart et al. 1994). Given the very recent

derivation of most rookeries, no genetic differentiation would be

expected. Although movement and genetic exchange continues

between rookeries, most elephant seals return to their natal

rookeries when they start breeding (Huber et al. 1991). The

California breeding population is now demographically isolated

from the Baja California population. No international agreements

exist for the joint management of this species by the U.S. and

Mexico. The California breeding population is considered here to

be a separate stock.

POPULATION SIZE

A complete population count of elephant seals is not possible because all age classes are not ashore at the same

time. Elephant seal population size is typically estimated by counting the number of pups produced and multiplying by

the inverse of the expected ratio of pups to total animals (McCann 1985). Stewart et al. (1994) used McCann's

multiplier of 4.5 to extrapolate from 28,164 pups to a population estimate of 127,000 elephant seals in the U.S. and

Mexico in 1991. The multiplier of 4.5 was based on a non-growing population. Boveng (1988) and Barlow et al.(1993)

argue that a multiplier of 3.5 is more appropriate for a rapidly growing population such as the California stock of

elephant seals. Based on the estimated 24,000 pups born in California in 1994-96 (Fig. 2) and this 3.5 multiplier, the

California stock was approximately 84,000 in 1996. 

Minimum Population Estimate

The minimum population size for northern elephant seals can be estimated very conservatively as 51,625, twice

the observed pup count (to account for the pups and their mothers) plus the peak number of males and juveniles counted

at the Channel Island (Lowry, pers. comm.) and Año Nuevo (Le Boeuf 1996) sites in 1996. More sophisticated methods

of estimating minimum population size could be applied if the variance of the multiplier used to estimate population

size were known.

Current Population Trend

Based on trends in pup counts, northern elephant seal colonies were continuing to grow in California through

1994 but appear to be stable or slowly decreasing in Mexico (Stewart et al. 1994). The number of pups born appears
27

0 

5000 

10000 

15000 

20000 

25000 

# BIRTHS

1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 

Year

 N. Elephant Seal Births in CA

TOTAL

Channel

Islands

Central CA

Figure 2. Estimated number of northern elephant seal births in California 1958-98. Multiple independent estimates

are presented for the Channel Islands 1988-91. Total and central California counts are not yet available for 1998.

Estimates are from Stewart et al. (1994), Lowry et al. (1996), and unpublished data from S. Allen, B. Hatfield, R.

Jameson, B. Le Boeuf, M. Lowry, and W. Sydeman.

-0.05 

0 

0.05 

0.1 

0.15 

Growth + Harvest Rates

1978 1980 1982 1984 1986 1988 1990 1992 1994 1996 

Year

N. Elephant Seal Net Production in CA

Figure 3. Net production rates for northern elephant seals in

California based on pup births and fishery mortality. Annual

mortality for 1980-1987 is assumed to be 300, the average of

1988-90 values (Perkins et al. 1994).

to be leveling off in California over the last five years (Fig. 2). More time is required to determine whether the reduction

in growth at the California rookeries is temporary

(as was observed in 1985) or whether it represents

an approach to carrying capacity. 

CURRENT AND MAXIMUM NET

PRODUCTIVITY RATES

Although growth rates as high as 16% per

year have been documented for elephant seal

rookeries in the U.S. from 1959 to 1981 (Cooper

and Stewart 1983), much of this growth was

supported by immigration from Mexico. The

highest growth rate measured for the whole

U.S./Mexico population was 8.3% between 1965

and 1977 (Cooper and Stewart 1983). A

continuous growth rate of 8.3% is consistent with

an increase from approximately 100 animals in

1900 to the current population size. The "maximum

estimated net productivity rate" as defined in the

Marine Mammal Protection Act (MMPA) would

therefore be 8.3%. In California, the net

productivity rate appears to have declined in recent

years [Figure 3; net production rate was calculated
28

as the realized rate of population growth (increase in pup abundance from year i to year i+1, divided by pup abundance

in year i) plus the harvest rate (fishery mortality in year i divided by population size in year i)].

POTENTIAL BIOLOGICAL REMOVAL

The potential biological removal (PBR) level for this stock is calculated as the minimum population size

(51,625) times one half the observed maximum net growth rate for this stock (1⁄2 of 8.3%) times a recovery factor of 1.0

(for a stock of unknown status that is increasing, Wade and Angliss 1997) resulting in a PBR of 2,142.

HUMAN-CAUSED MORTALITY

Fisheries Information

A summary of known fishery mortality and injury for this stock of northern elephant seals is given in Table

1. More detailed information on these fisheries is provided in Appendix 1. Because the set gillnet fishery has

undergone dramatic reductions and redistributions of effort and because that fishery has not been observed since 1994,

average annual mortality for that fishery cannot be accurately estimated for the recent years (1995-98). Rough estimates

for 1995-1998 have been made by extrapolation of prior kill rates using recent effort estimates (Table 1). Preliminary

set gillnet observations in Monterey Bay from April to September 1999 included 3 elephant seals in 24.6% of the sets

for a rough extrapolated estimate of 12 mortalities in this half-year period. Stranding data reported to the California

Marine Mammal Stranding Network in 1995-98 include elephant seal injuries caused by hook-and-line fisheries (2 

Table 1. Summary of available information on the mortality and serious injury of northern elephant seals (California

breeding stock) in commercial fisheries that might take this species (Julian 1997; Julian and Beeson 1998; Cameron and

Forney 1999; Perez, in prep.; NMFS unpubl. data). n/a indicates information is not available. Mean annual takes are

based on 1994-98 data unless noted otherwise.

Fishery Name Year(s) Data Type

Percent Observer

Coverage

Observed

Mortality

Estimated

Mortality (CV in

parentheses)

Mean

Annual Takes

(CV in

parentheses)

CA/OR thresher

shark/swordfish drift

gillnet fishery

1994

1995

1996

1997

1998

observer

data

17.9%

15.6%

12.4%

22.8%

20.2%

22

14

4

8

4

123 (0.23)

 90 (0.25)

37 (0.55)

45 (0.33)

20 (0.44)

33 (0.27)1

CA angel shark/halibut

and other species large

mesh (>3.5") set gillnet

fishery

1991

1992

1993

1994

1995

1996

1997

1998

observer

data

extrapolated

estimate

9.8%

12.5%

15.4%

7.7%

0.0%

0.0%

0.0%

0.0%

3

7

11

2

-

-

-

-

30 (0.55)

51 (0.35)

70 (0.27)

16 (0.66)

47 (0.29) 2

46 (0.23) 2

60 (0.24) 2

70 (0.26) 2

n/a

WA, OR, CA

groundfish trawl

1991-95 observer

data

54-73% 0 0,0,0,0,0 0

WA Willapa Bay drift

gillnet fishery (salmon) 1991

personal

communica

tion

n/a 2 2 n/a

Chehalis River salmon

setnet fishery 1993

personal

communica

tion

n/a 4 4 n/a

Total annual takes >33.0 (0.27)

1

 Only 1997-98 mortality estimates are included in the average because of gear modifications implemented within the

fishery as part of a 1997 Take Reduction Plan. Gear modifications included the use of net extenders and acoustic

warning devices (pingers). Following these changes in the fishery, entanglement rates of northern elephant seals

declined.

2

 The CA set gillnets were not observed after 1994; mortality was extrapolated from effort estimates and previous

entanglement rates.
29

injuries) and gillnet fisheries (1 injuries). The average estimated annual mortality for northern elephant seals in these

fisheries for the five most recent years of monitoring (1994-98) is likely to be substantially greater than 33 (the number

estimated for the drift gillnet fishery alone) but, based on extrapolations from previous years, is not likely to be more

than two or three times greater (ie. less than 100). 

Although all of the mortalities in Table 1 occurred in U.S. waters, some may be of seals from Mexico's

breeding population that are migrating through U.S. waters. Similar drift gillnet fisheries for swordfish and sharks exist

along the entire Pacific coast of Baja California, Mexico and probably take northern elephant seal. Quantitative data

are available only for the Mexican swordfish drift gillnet fishery, which has increased from two vessels in 1986 to 29

vessels in 1992 (Sosa-Nishizaki et al. 1993). The total number of sets in this fishery in 1992 can be estimated from data

provided by these authors to be approximately 2,700, with an observed rate of marine mammal bycatch 

of 0.13 animals per set (10 marine mammals in 77 observed sets; Sosa-Nishizaki et al. 1993). This overall mortality

rate is similar to that observed in California driftnet fisheries during 1990-95 (0.14 marine mammals per set), but

species-specific information is not available for the Mexican fisheries. There are currently efforts underway to convert

the Mexican swordfish driftnet fishery to a longline fishery (D. Holts, pers. comm.). The number of set-gillnet vessels

in this part of Mexico is unknown. The take of northern elephant seals in other North Pacific fisheries that have been

monitored appears to be trivial (Barlow et al. 1993, 1994).

Other Mortality

The California Marine Mammal Stranding database maintained by the National Marine Fisheries Service,

Southwest Region, contains the following records of human-related elephant seal mortalities and injuries in 1995-98:

(1) boat collision (1 injury), (2) automobile collision (5 mortalities), and (3) shootings (3 mortalities). Protective

measures were taken to prevent future automobile collisions in the vicinity of Piedras Blancas/San Simeon (Hatfield

and Rathbun 1999).

 STATUS OF STOCK

A review of elephant seal dynamics through 1991 concluded that their status could not be determined with

certainty, but that they might be within their Optimal Sustainable Population (OSP) range (Barlow et al. 1993). They

are not listed as "endangered" or "threatened" under the Endangered Species Act nor as "depleted" under the MMPA.

Because their annual human-caused mortality is much less than the calculated PBR for this stock (2,142), they would

not be considered a "strategic" stock under the MMPA. The average rate of incidental fishery mortality for this stock

over the last 5 years also appears to be less than 10% of the calculated PBR; therefore, the total fishery mortality appears

to be insignificant and approaching a zero mortality and serious injury rate. The population is continuing to grow and

fishery mortality is relatively constant. There are no known habitat issues that are of particular concern for this stock.

REFERENCES

Barlow, J., R. W. Baird, J. E. Heyning, K. Wynne, A. M. Manville, II, L. F. Lowry, D. Hanan, J. Sease, and V. N.

Burkanov. 1994. A review of cetacean and pinniped mortality in coastal fisheries along the west coast of the

U.S. and Canada and the east coast of the Russian Federation. Rep. Int. Whal. Commn, Special Issue 15:405-

425.

Barlow, J., P. Boveng, M. S. Lowry, B. S. Stewart, B. J. Le Boeuf, W. J. Sydeman, R. J. Jameson, S. G. Allen, and C.

W. Oliver. 1993. Status of the northern elephant seal population along the U.S. west coast in 1992. Admin.

Rept. LJ-93-01. Southwest Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La

Jolla, CA. 32 pp. 

Boveng, P. 1988. Status of the northern elephant seal population on the U.S. West Coast. Admin. Rep. LJ-88-05

Southwest Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA. 35pp.

Cooper, C. F. and B. S. Stewart. 1983. Demography of northern elephant seals, 1911-1982. Science 219:969-971.

Hatfield, B. B., and G. B. Rathbun. 1999. Interactions between northern elephant seals and vehicles near Point Piedras

Blancas, California. Mar. Mamm. Sci. 15(2):598-600.

Holts, D. Southwest Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA 92038.

Huber, H. R., A. C. Rovetta, L. A. Fry, and S. Johnston. 1991. Age-specific natality of northern elephant seals at the

South Farallon Islands, California. J. Mamm. 72(3):525-534.
30

Julian, F. and M. Beeson. 1998. Estimates for marine mammal, turtle, and seabird mortality for two California gillnet

fisheries: 1990-1995. Fish. Bull. 96:271-284.

Le Boeuf, B. J. 1996. Northern elephant seals at Año Nuevo during the breeding seasons of 1992-1996. Admin. Rep.

LJ-96-12C. Southwest Fisheries Science Center, National Marine Fisheries Service, P. O. Box 271, La Jolla,

California, 92038. 8 pp. 

Le Boeuf, B. J., D. Crocker, S. Blackwell, and P. Morris. 1993. Sex differences in diving and foraging behaviour of

northern elephant seals. In: I. Boyd (ed.). Marine Mammal: Advances in Behavioural and Population

Biology. Oxford Univ. Press.

Lowry, M. S., W. L. Perryman, M. S. Lynn, R. L. Westlake, and F. Julian. 1996. Counts of northern elephant seals,

Mirounga angustirostris, from large-format aerial photographs taken at rookeries in southern California during

the breeding season. Fish. Bull. 94:176-185.

McCann, T. S. 1985. Size, status and demography of southern elephant seal (Mirounga leonina) populations. In J. K.

Ling and M. M. Bryden (eds.), Studies of Sea Mammals in South Latitudes. South Australian Museum. 132

pp.

Perez, M. A. (In prep.). Summary of marine mammal incidental catch data for domestic and joint venture groundfish

fisheries in the U.S. EEZ of the North Pacific, 1989-96.

Perkins, P., J. Barlow, and M. Beeson. 1994. Report on pinniped and cetacean mortality in California gillnet fisheries:

1988-90. Admin. Rep. LJ-94-11. Southwest Fisheries Science Center, National Marine Fisheries Service, P.

O. Box 271, La Jolla, California, 92038. 16 pp.

Sosa-Nishizaki, O., R. De la Rosa Pacheco, R. Castro Longoria, M. Grijalva Chon, and J. De la Rosa Velez. 1993.

Estudio biologico pesquero del pez (Xiphias gladius) y otras especies de picudos (marlins y pez vela). Rep.

Int. CICESE, CTECT9306.

Stewart, B. S., and H. R. Huber. 1993. Mirounga angustirostris. Mammalian Species 449:1-10.

Stewart, B. S., B. J. Le Boeuf, P. K. Yochem, H. R. Huber, R. L. DeLong, R. J. Jameson, W. Sydeman, and S. G.

Allen. 1994. History and present status of the northern elephant seal population. In: B. J. Le Boeuf and R.

M. Laws (eds.) Elephant Seals. Univ. Calif. Press, Los Angeles.
31

Figure 1. Geographic range of the Guadalupe fur

seal, showing location of two rookeries at Isla

Guadalupe and Isla Benito Del Este.

Revised 12/15/2000

GUADALUPE FUR SEAL (Arctocephalus townsendi)

STOCK DEFINITION AND GEOGRAPHIC RANGE

Commercial sealing during the 19th century reduced the

once abundant Guadalupe fur seal to near extinction in 1894

(Townsend 1931). Prior to the harvest it ranged from Monterey

Bay, California, to the Revillagigedo Islands, Mexico (Fleischer

1987, Hanni et al. 1997; Figure 1). The capture of two adult

males at Guadalupe Island in 1928 established the species' return

(Townsend 1931); however, they were not seen again until 1954

(Hubbs 1956). Guadalupe fur seals pup and breed mainly at Isla

Guadalupe, Mexico. In 1997, a second rookery was discovered at

Isla Benito del Este, Baja California (Maravilla-Chavez and

Lowry 1999) and a pup was born at San Miguel Island, California

(Melin and DeLong 1999). Individuals have stranded or been

sighted as far north as Blind Beach, California (38o 26' 10" N,

123o 07' 20" W); inside the Gulf of California and as far south as

Zihuatanejo, Mexico (17o 39' N, 101o 34'W; Hanni et al. 1997 and

Aurioles-Gamboa and Hernadez-Camacho 1999). The population

is considered to be a single stock because all are recent

descendants from one breeding colony at Isla Guadalupe, Mexico.

POPULATION SIZE

The size of the population prior to the commercial

harvests of the 19th century is not known, but estimates range

from 20,000 to 100,000 animals (Wedgeforth 1928, Hubbs 1956,

Fleischer 1987). The population was estimated by Gallo (1994)

to be about 7,408 animals in 1993. The population estimate was

derived by multiplying the number of pups (counted and

estimated) by a factor of 4.0.

Minimum Population Estimate

All the individuals of the population cannot be counted because all age and sex classes are never ashore at the

same time and some individuals that are on land are not visible during the census. Sub-sampling portions of the rookery

indicate that only 47-55% of the seals present (i.e., hauled out) are counted during the census (Gallo 1994). The 1993

count of all age classes plus the estimate of missed animals was 6,443 (Gallo 1994). The minimum size of the

population in Mexico can be estimated as the actual count of 3,028 hauled out seals [The actual count data were not

reported by Gallo (1994); this number is derived by multiplying the estimated number hauled out by 47%, the minimum

estimate of the percent counted]. In the United States, a few Guadalupe fur seals are known to inhabit California sea

lion rookeries in the Channel Islands (Stewart et al. 1987). 

Current Population Trend

Counts of Guadalupe fur seals have been made sporadically since 1954. Records of Guadalupe fur seal counts

through 1984 were compiled by Seagars (1984), Fleischer (1987), and Gallo (1994). The count for 1988 was taken from

Torres et al. (1990). A few of these counts were made during the breeding season, but the majority were made at other

times of the year (Figure 1). Also, the counts that are documented in the literature generally provide only the total of

all Guadalupe fur seals counted (i.e., the counts are not separated by age/sex class). The counts that were made during

the breeding season, when the maximum number of animals are present at the rookery, were used to examine population

growth (Gallo 1994). The natural logarithm of the counts was regressed against year to calculate the growth rate of the

population. These data indicate that the population of Guadalupe fur seals is increasing exponentially at an average

annual growth rate of 13.7% (Gallo 1994; Figure 2).
32

0 

1000 

2000 

3000 

4000 

5000 

6000 

7000 

COUNTS

50 55 60 65 70 75 80 85 90 95

YEAR

Non-breeding season Breeding season Pop. growth curve

GUADALUPE FUR SEAL COUNTS

Guadalupe Island, Mexico

Figure 2. Counts of Guadalupe fur seals at Guadalupe Island,

Mexico, and the estimated population growth curve derived from

counts made during the breeding season.

CURRENT AND MAXIMUM NET

PRODUCTIVITY RATES

The maximum net productivity rate can

be assumed to be equal to the annual growth rate

observed over the last 30 years (13.7%) because

the population was at a very low level and should

have been growing at nearly its maximum rate.

POTENTIAL BIOLOGICAL REMOVAL

The potential biological removal (PBR)

for this stock is calculated as the minimum

population size (3,028) times one half the default

maximum net growth rate for pinnipeds (1⁄2 of

12%) times a recovery factor of 0.5 (for a

threatened species, Wade and Angliss 1997),

resulting in a PBR of 104 Guadalupe fur seals

per year. The vast majority of this PBR would

apply towards incidental mortality in Mexico.

HUMAN-CAUSEDMORTALITYAND

SERIOUS INJURY

Fisheries Information

Drift and set gillnet fisheries may cause incidental mortality of Guadalupe fur seals in Mexico and the United

States. In the United States there have been no reports of mortalities or injuries for Guadalupe fur seals (Barlow et

al.1994, Julian 1997, Julian and Beeson 1998, Cameron and Forney 1999. No information is available for humancaused mortalities or injuries in Mexico. However, similar drift gillnet fisheries for swordfish and sharks exist along

the entire Pacific coast of Baja California, Mexico and may take animals from the same population. Quantitative data

are available only for the Mexican swordfish drift gillnet fishery (Sosa-Nishizaki et al. 1993). The total number of sets

in this fishery in 1992 can be estimated from data provided by these authors to be approximately 2,700, with an observed

rate of marine mammal bycatch of 0.13 animals per set (10 marine mammals in 77 observed sets; Sosa-Nishizaki et al.

1993). This overall mortality rate is similar to that observed in California driftnet fisheries during 1990-93 (0.15 marine

mammals per set), but species-specific information is not available for the Mexican fisheries. There are currently efforts

underway to convert the Mexican swordfish driftnet fishery to a longline fishery (D. Holts, pers. comm.). The number

of set gillnets used in Mexico is unknown.

Other mortality

Juvenile female Guadalupe fur seals have stranded in central and northern California with net abrasions around the

neck, fish hooks and monofilament line, and polyfilament string (Hanni et al. 1997). 

STATUS OF STOCK

The state of California lists the Guadalupe fur seal as a fully protected mammal in the Fish and Game Code

of California (Chap. 8, sec. 4700, d), and it is listed also as a threatened species in the Fish and Game Commission

California Code of Regulations (Title 14, sec. 670.5, b, 6, H). The Endangered Species Act lists it as a threatened

species, which automatically qualifies this as a "depleted" and "strategic" stock under the Marine Mammal Protection

Act. There is insufficient information to determine whether the fishery mortality in Mexico exceeds the PBR for this

stock. The total U.S. fishery mortality and serious injury for this stock is less than 10% of the calculated PBR and,

therefore, can be considered to be insignificant and approaching zero mortality and serious injury rate. The population

is growing at approximately 13.7% per year.
33

Table 1. Summary of available information on the incidental mortality and injury of Guadalupe fur seals in commercial

fisheries that might take this species (Julian 1997, Julian and Beeson 1998, Cameron and Forney 1999, M. Perez per.

comm, Appendix 1). Mean annual takes are based on 1994-98 data unless noted otherwise.

Fishery Name Year(s) Data Type

Percent Observer

Coverage

Observed

Mortality

Estimated

Mortality (CV in

parentheses)

Mean

Annual Takes

(CV in parentheses)

CA driftnet fishery

for sharks and

swordfish

1994

1995

1996

1997

1998

observer 17.9%

15.6%

12.4%

22.8%

20.2%

0

0

0

0

0

0

0

0

0

0

0

1

CA set gillnet fishery

for halibut and angel

shark

1994

1995

1996

1997

1998

observer

extrapolated

estimates

(1995-98)

7.7%

0%

0%

0%

0%

0

0

0

0

0

0

0

2

0

2

0

2

0

2

0

2

WA, OR, CA ground

fish trawl fishery (Atsea processing Pacific

whiting fishery only)

1994

1995

1996

1997

1998

observer 53.8%

56.2% 

65.2%

65.7%

77.3%

0

0

0

0

0

0

0

0

0

0

0

Minimum total annual takes 0

1

 Only 1997-98 mortality estimates are included in the average because of gear modifications implemented within the

fishery as part of a 1997 Take Reduction Plan. Gear modifications included the use of net extenders and acoustic

warning devices (pingers).

2

 The CA set gillnets were not observed after 1994; mortality was extrapolated from effort estimates and previous

entanglement rates.

REFERENCES

Aurioles-Gamboa, D. and C. J. Hernadez-Camacho. 1999. Notes on the southernmost records of Guadalupe fur seal,

Arctocephalus townsendi, in Mexico. Mar. Mamm. Sci. 15:581-583.

Barlow, J., R. W. Baird, J. E. Heyning, K. Wynne, A. M. Manville II, L. F. Lowry, D. Hanan, J. Sease, and V. N.

Burkanov. 1994. A review of cetacean and pinniped mortality in coastal fisheries along the west coast of the

USA and Canada and the east coast of the Russian Federation. Rept. Int. Whaling Comm., Special Issue

15:405-425.

Cameron, G., and K. A. Forney. 1999. Estimates of cetacean mortality in the California gillnet fisheries for 1997 and

1998. Paper SC/51/O4 presented to the International Whaling Commission, May 1999 (unpublished). 14 pp.

Fleischer, L. A. 1987. Guadalupe fur seal, Arctocephalus townsendi. In J. P. Croxall and R. L. Gentry (eds.). Status,

biology, and ecology of fur seals. Proceedings of an international symposium and workshop. Cambridge,

England, 23-27 April 1984. p. 43-48. U.S. Dept. of Commerce, NOAA, NMFS, NOAA Tech. Rept. NMFS

51.

Gallo, J. P. 1994. Factors affecting the population status of Guadalupe fur seal, Arctocephalus townsendi (Merriam,

1897), at Isla de Guadalupe, Baja California, Mexico. Ph.D. Thesis, University of California, Santa Cruz, 199

p.

Hanni, K. D., D. J. Long, R. E. Jones, P. Pyle, and L. E. Morgan. 1997. Sightings and strandings of Guadalupe fur

seals in central and northern California, 1988-1995. J. of Mamm. 78:684-690.

Holts, D. Southwest Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA 92038.

Hubbs. C. L. 1956. The Guadalupe fur seal still lives! Zoonooz, S. D. Zool. Soc. 29(12):6-9.

Julian, F. 1997. Cetacean mortality in California gill net fisheries: Preliminary estimates for 1996. Paper SC/49/SM02

presented to the International Whaling Commission, September 1997 (unpublished). 13 pp.

Julian, F. and M. Beeson. 1998. Estimates for marine mammal, turtle, and seabird mortality for two California gillnet

fisheries: 1990-95. Fish. Bull. 96:271-284.

Maravilla-Chavez, M. O. and M. S Lowry. 1999 Incipient breeding colony of Guadalupe fur seals at Isla Benito del
34

Este, Baja California, Mexico. Mar. Mamm. Sci. 15:239-241.

Melin, S. R. and R. L. DeLong. 1999. Observations of a Guadalupe fur seal (Arctocephalus townsendi) female and

pup at San Miguel Island, California. Mar. Mamm. Sci. 15:885-888.

Perkins, P., J. Barlow, and M. Beeson. 1992. Pinniped and cetacean mortality in California gillnet fisheries: 1991.

Rept. Int. Whaling Commission, Working Paper SC/44/SM14.

Seagars, D. J. 1984. The Guadalupe fur seal: a status review. National Marine Fisheries Service, Southwest Region,

Admin. Rep. SWR-84-6. 29pp.

Sosa-Nishizaki, O., R. De la Rosa Pacheco, R. Castro Longoria, M. Grijalva Chon, and J. De la Rosa Velez. 1993.

Estudio biologico pesquero del pez (Xiphias gladius) y otras especies de picudos (marlins y pez vela). Rep.

Int. CICESE, CTECT9306.

Stewart, B. S., P. K. Yochem, R. L. DeLong, and G.A. Antonelis Jr. 1987. Interactions between Guadalupe fur seals

and California sea lions ant San Nicolas and San Miguel islands, California. In J. P. Croxall and R. L. Gentry

(eds.). Status, biology, and ecology of fur seals. Proceedings of an international symposium and workshop.

Cambridge, England, 23-27 April 1984. p. 103-106. U.S. Dept. of Commerce, NOAA, NMFS, NOAA Tech.

Rept. NMFS 51.

Torres-G., A., A. Aguayo-L., and N. Valdez-T. 1990. Tamaño y distribucion de la poblacion del lobo fino de

Guadalupe, Arctocephalus townsendi (Merriam, 1897), durante el verano de 1988. [Abstracts] XV Reunion

internacional para el estudio de los mamiferos marinos, 18-20 April 1990. La Paz, B. C. S., Mexico.

Townsend, C. H. 1931. The fur seal of the California islands with new descriptive and historical matter. Zoologica

9:443-457.

Wedgeforth, H. M. 1928. The Guadalupe fur seal (Arctocephalus townsendi). Zoonooz, S. D. Zool. Soc. 3(3):4-9.
35

San Miguel Island

Pribilof

Islands

Figure 1. Approximate distribution of northern fur seals

in the eastern North Pacific (shaded area).

Revised 12/15/2000

NORTHERN FUR SEAL (Callorhinus ursinus): San Miguel Island Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

Northern fur seals occur from southern California

north to the Bering Sea and west to the Okhotsk Sea and

Honshu Island, Japan (Fig. 1). During the breeding

season, approximately 74% of the worldwide population is

found on the Pribilof Islands in the southern Bering Sea,

with the remaining animals spread throughout the North

Pacific Ocean (Lander and Kajimura 1982). Of the seals

in U.S. waters outside of the Pribilofs, approximately 1%

of the population is found on Bogoslof Island in the

southern Bering Sea and San Miguel Island off southern

California (NMFS 1993). Northern fur seals may

temporarily haul out on land at other sites in Alaska,

British Columbia, and on islets along the coast of the

continental United States, but generally outside of the

breeding season (Fiscus 1983).

Due to differing requirements during the annual

reproductive season adult males and females typically

occur ashore at different, though overlapping times. Adult

males usually occur on shore during the 4-month period

from May-August, though some may be present until

November (well after giving up their territories). Adult

females are found ashore for as long as six months (JuneNovember). After their respective times ashore, seals of

both genders spend the next 7-8 months at sea (Roppel 1984). Adult females and pups from the Pribilof Islands migrate

through the Aleutian Islands into the North Pacific Ocean, often to the Oregon and California offshore waters. Many

pups may remain at sea for 22 months before returning to their rookery of birth. Adult males from the Pribilof Islands

generally migrate only as far south as the Gulf of Alaska (Kajimura 1984). There is considerable interchange of

individuals between rookeries.

The following information was considered in classifying stock structure based on the Dizon et al. (1992)

phylogeographic approach: (1) Distributional data: geographic distribution is continuous during feeding, geographic

separation during the breeding season, high natal site fidelity (DeLong 1982); (2) Population response data: substantial

differences in population dynamics between Pribilofs and San Miguel Island (DeLong 1982, DeLong and Antonelis

1991, NMFS 1993); (3) Phenotypic data: unknown; and (4) Genotypic data: unknown. Based on this information, two

separate stocks of northern fur seals are recognized within U.S. waters: an Eastern Pacific stock and a San Miguel Island

stock. The Eastern Pacific stock is reported separately in the Stock Assessment Reports for the Alaska Region.

POPULATION SIZE

The population estimate for the San Miguel Island stock of northern fur seals is calculated as the estimated

number of pups at rookeries multiplied by an expansion factor. Based on research conducted on the Eastern Pacific

stock of northern fur seals, a life table analysis was performed to estimate the number of yearlings, 2 year olds, 3 year

olds, and animals at least 4 years old (Lander 1981). The resulting population estimate was equal to the pup count

multiplied by 4.475. The expansion factors are based on a sex and age distribution estimated after the harvest of

juvenile males was terminated. A more appropriate expansion factor for the San Miguel Island stock is 4.0, based on

the known increased immigration of recruitment-age females (DeLong 1982) and mortality and possible emigration of

adults associated with the El Niño Southern Oscillation event in 1982-1983 (R. DeLong, pers. comm.). A 1998 pup

count resulted in a total count of 627 pups, a 79.6% decrease from the 1997 count of 3,068 (Melin and DeLong 2000).

In 1999, the population began to recover with a total pup count of 1,084 (S. Melin, unpubl. data). Based on the 1999

count and the expansion factor, the most recent population estimate of the San Miguel Island stock is 4,336 (1,084 x
36

0

500

1000

1500

2000

2500

3000

72 74 76 78 80 82 84 86 88 90 92 94 97 99

Year

Number of pups

Figure 2. Northern fur seal live pup counts on San Miguel Island, 1972-1999.

Counts from 1996 were incomplete and have not been included in the figure.

4.0) northern fur seals. Currently, a CV for the expansion factor is unavailable. 

Minimum Population Estimate

The survey technique utilized for estimating the abundance of northern fur seals within the San Miguel Island

stock is a direct count, with no associated CV(N) as sites are surveyed only once. Additional estimates of the overall

population size (i.e., NBEST) and associated CV are also unavailable. Therefore NMIN for this stock can not be estimated

by calculating the log-normal 20th percentile of the population estimate. Rather, NMIN is estimated as twice the

maximum number of pups born in 1999 (to account for the pups and their mothers) plus the maximum number of adult

and sub-adult males counted for the 1999 season, which results in an NMIN of 2,336 ((1,084 x 2) + 168). This method

provides a very conservative estimate of the northern fur seal population at San Miguel Island.

Current Population Trend

The population of

northern fur seals on San Miguel

Island originated from the Pribilof

Islands population during the late

1950s or early 1960s (DeLong

1982). The colony has increased

steadily, since its discovery in

1968, except for severe declines

in 1983 and 1998 associated with

El Niño Southern Oscillation

events in 1982-1983 and 1997-

1998 (DeLong and Antonelis

1991, Melin and DeLong 2000).

El Niño events, which occur

periodically along the California

coast, impact population growth

of fur seals at San Miguel Island

and are an important regulatory

mechanism for this population

(DeLong and Antonelis 1991;

Melin and DeLong 1994, 2000;

Melin et al. 1996). 

Specifically, live pup

counts increased about 24% annually from 1972 through 1982, an increase due, in part, to immigration of females from

the Bering Sea and the western North Pacific Ocean (DeLong 1982) (Fig. 2). The 1982-1983 El Niño event resulted

in a 60.3% decline in the northern fur seal population at San Miguel Island (DeLong and Antonelis 1991). It took the

population 7 years to recover from this decline, because adult female mortality occurred in addition to pup mortality

(Melin and DeLong 1994). The 1992-1993 El Niño conditions resulted in reduced pup production in 1992, but the

population recovered in 1993 and increased in 1994 (Melin et al. 1996).

From July 1997 through May 1998, the most severe El Niño event in recorded history affected California

coastal waters (Lynn et al. 1998). In 1997, total fur seal pup production was 3,068 pups, the highest recorded since the

colony has been monitored. However, it appears that up to 87% of the pups born in 1997 died before weaning, and total

production in 1998 was only 627 pups, a decline of 79.6% from 1997 (Melin and DeLong 2000). Although total

production increased to 1,084 in 1999 (S. Melin, unpubl. data), a slow recovery from the 1998 decline is anticipated

if adult female mortality occurred in addition to the high pup mortality in 1997 and 1998 (Melin and DeLong 2000).

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

The northern fur seal population in the Pribilof Islands increased steadily during 1912-1924 after the

commercial harvest no longer included pregnant females. During this period, the rate of population growth was

approximately 8.6% (SE=1.47) per year (A. York, unpubl. data), the maximum recorded for this species. This growth
37

rate is similar and slightly higher than the 8.12% rate of increase (approximate SE=1.29) estimated by Gerrodette et al.

(1985). Given the extremely low density of the population in the early 1900s, the 8.6% rate of increase is considered

a reliable estimate of RMAX.

POTENTIAL BIOLOGICAL REMOVAL

The potential biological removal (PBR) level for this stock is calculated as the minimum population estimate

(2,336) times one-half the observed maximum net growth rate (1⁄2 of 8.6%) times a recovery factor of 1.0 (for stocks

of unknown status that are increasing in size, Wade and Angliss 1997), resulting in a PBR of 100 San Miguel Island

northern fur seals per year.

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Fisheries Information

Northern fur seals taken during the winter/spring along the west coast of the continental U.S. could be from

the Pribilofs and thus belong to the Eastern Pacific stock. However, it is the intention of NMFS to consider any takes

of northern fur seals by commercial fisheries in waters off California, Oregon, and Washington as being from the San

Miguel Island stock. Information concerning the three observed fisheries that may have interacted with northern fur

seals are listed in Table 1. There were no reported mortalities of northern fur seals in any observed fishery along the

west coast of the continental U.S. during the period from 1994-1998 (Table 1; Julian 1997, Julian and Beeson 1998,

Cameron and Forney 1999). Overall entanglement rates in the California/Oregon thresher shark/swordfish drift gillnet

fishery dropped considerably after the 1997 implementation of a Take Reduction Plan, which included skipper education

workshops and required the use of pingers and minimum 6-fathom extenders (Barlow and Cameron 1999). Because

of the changes in this fishery after implementation of the Take Reduction Plan, mean annual takes in Table 1 are based

only on 1997-1998 data. Fishing effort in the California angel shark/halibut set gillnet fishery was substantially reduced

as a result of a California voter proposition banning gillnet fishing in certain areas (Julian 1997, Julian and Beeson

1998). For this fishery, there were no observed sets after 1994. The estimated mean mortality rate in observed fisheries

is zero northern fur seals per year from this stock. 

An additional source of information on the number of northern fur seals killed or injured incidental to

commercial fishery operations is the self-reported fisheries information required of vessel operators by the MMPA.

During the period between 1994 and 1998, there were no fisher self-reports of northern fur seal mortalities from any

fisheries operating within the range of this stock. Self-reported fisheries data are incomplete for 1994, not available for

1995, and considered unreliable after 1995 (see Appendix 4 of Hill and DeMaster 1998).

Table 1. Summary of available information on the incidental mortality and injury of northern fur seals (San Miguel

Island stock) in commercial fisheries that might take this species and calculation of the mean annual mortality rate; n/a

indicates that data are not available. Mean annual takes are based on 1994-98 data unless noted otherwise.

Fishery name Years Data type

Percent

observer

coverage

Observed

mortality

Estimated

mortality

Mean annual

takes (CV in

parentheses)

CA/OR thresher shark/

swordfish drift gillnet

94

95

96

97

98

obs data 17.9%

15.6%

12.4%

23.0%

20.0%

0

0

0

0

0

0

0

0

0

0

0

1

CA angel shark/halibut set

gillnet

94

95

96

97

98

obs data

extrapolated

estimates

(1995-98)

7.7%

0%

0%

0%

0%

0

0

0

0

0

0

0

2

0

2

0

2

0

2

0

0
Fishery name Years Data type

Percent

observer

coverage

Observed

mortality

Estimated

mortality

Mean annual

takes (CV in

parentheses)

38

WA/OR/CA groundfish trawl

(Pacific whiting component)

94

95

96

97

98

obs data 53.8%

56.2%

65.2%

65.7%

77.3%

0

0

0

0

0

0

0

0

0

0

0

CA/OR thresher shark/

swordfish drift gillnet

94-98 self reports n/a n/a, n/a, n/a, n/a,

n/a

n/a -

CA angel shark/halibut set

gillnet

94-98 self reports n/a n/a, n/a, n/a, n/a,

n/a

n/a -

unknown west coast fishery 94-98 strand data n/a 0, 0, 0, 0, 0 n/a 0

Minimum total annual takes 0

1

 Only 1997-98 mortality estimates are included in the average because of gear modifications implemented within the

fishery as part of a 1997 Take Reduction Plan. Gear modifications included the use of net extenders and acoustic

warning devices (pingers).

2

 The California set gillnets were not observed after 1994; mortality was extrapolated from effort and previous

entanglement rates.

Strandings of northern fur seals entangled in fishing gear or with injuries caused by interactions with gear are

a final source of fishery-related mortality information. During 1994-1998, no northern fur seal strandings occurred. 

Fishery-related strandings during 1994-1998 resulted in an estimated annual mortality of zero animals from this stock.

This estimate is considered a minimum because not all stranded animals are found, reported, or examined for cause of

death (via necropsy by trained personnel).

STATUS OF STOCK

The San Miguel Island northern fur seal stock is not considered to be “depleted” under the MMPA or listed

as “threatened“ or “endangered” under the Endangered Species Act. Based on currently available data, the estimated

annual level of total human-caused mortality and serious injury (0) does not exceed the PBR (100). Therefore, the San

Miguel Island stock of northern fur seals is not classified as a strategic stock. The minimum total fishery mortality and

serious injury for this stock (0) is not known to exceed 10% of the calculated PBR (10) and, therefore, can be considered

to be insignificant and approaching zero mortality and serious injury rate. The stock size decreased 79.6% from 1997

to 1998 and began to recover in 1999. The status of this stock relative to its Optimum Sustainable Population (OSP)

level is unknown, unlike the Eastern Pacific northern fur seal stock which is formally listed as “depleted” under the

MMPA.

REFERENCES

Barlow, J., and G. A. Cameron. 1999. Field experiments show that acoustic pingers reduce marine mammal bycatch

in the California drift gillnet fishery. Paper SC/51/SM2 presented to the International Whaling Commission,

May 1998 (unpublished). 20 pp.

Cameron, G. A., and K. A. Forney. 1999. Preliminary estimates of cetacean mortality in the California gillnet fisheries

for 1997 and 1998. Paper SC/51/O4 presented to the International Whaling Commission, May 1999

(unpublished). 14 pp.

DeLong, R. L. National Marine Mammal Laboratory, AFSC, NMFS, 7600 Sand Point Way NE, Seattle, WA, 98115.

DeLong, R. L. 1982. Population biology of northern fur seals at San Miguel Island, California. Ph.D. Thesis, University

of California, Berkeley, California. 185 pp.

DeLong, R. L., and G. A. Antonelis. 1991. Impacts of the 1982-1983 El Niño on the northern fur seal population at

San Miguel Island, California. Pp. 75-83, In: Trillmich, F., and K. Ono (eds.), Pinnipeds and El Niño:

Responses to Environmental Stress. Springer-Verlag, New York. 293 pp.
39

Dizon, A. E., C. Lockyer, W. F. Perrin, D. P. DeMaster, and J. Sisson. 1992. Rethinking the stock concept: a

phylogeographic approach. Conserv. Biol. 6:24-36.

Fiscus, C. F. 1983. Fur seals and island. In: Background papers submitted by the United States to the 26th annual

meeting of the Standing Scientific Committee of the North Pacific Fur Seal Commission, Washington, D.C.,

March 28-April 5, 1983. Available at National Marine Mammal Laboratory, 7600 Sand Point Way NE,

Seattle, WA 98115.

Gerrodette, T., D. Goodman, and J. Barlow. 1985. Confidence limits for population projections when vital rates vary

randomly. Fish. Bull. 83(3):207-217.

Hill, P. S, and D. P. DeMaster. 1998. Alaska marine mammal stock assessments, 1998. U.S. Dep. Commer., NOAA

Tech. Memo. NMFS-AFSC-97. 166 pp.

Julian, F. 1997. Cetacean mortality in California gillnet fisheries: preliminary estimates for 1996. Paper SC/49/SM02

presented to the International Whaling Commission, September 1997 (unpublished). 13 pp.

Julian, F., and M. Beeson. 1998. Estimates of marine mammal, turtle, and seabird mortality for two California gillnet

fisheries: 1990-1995. Fish. Bull. 96:271-284.

Kajimura, H. 1984. Opportunistic feeding of the northern fur seal, Callorhinus ursinus, in the eastern North Pacific

Ocean and eastern Bering Sea. NOAA Tech. Rep. NMFS-SSRF-779. 49 pp.

Lander, R. H. 1981. A life table and biomass estimate for Alaskan fur seals. Fishery Research (Amsterdam) 1:55-70.

Lander, R. H., and H. Kajimura. 1982. Status of northern fur seals. FAO Fisheries Series 5:319-345.

Lynn, R. J., T. Baumgartner, J. Garcia, C. A. Collins, T. L. Hayward, K. D. Hyrenbach, A. W. Mantyla, T. Murphree,

A. Shankle, F. B. Schwing, K. M. Sakuma, and M. J. Tegner. 1998. The state of the California Current, 1997-

1998: transition to El Niño conditions. CalCOFI Report 39:25-49.

Melin, S. R. National Marine Mammal Laboratory, AFSC, NMFS, 7600 Sand Point Way NE, Seattle, WA 98115.

Melin, S. R., and R. L. DeLong. 1994. Population monitoring of northern fur seals on San Miguel Island, California.

Pp. 137-141,In: Sinclair, E. H. (ed.), Fur seal investigations, 1992. U.S. Dep. Commer., NOAA Tech. Memo.

NMFS-AFSC-45. 190 pp.

Melin, S. R., and R. L. DeLong. 2000. Population monitoring studies of northern fur seals at San Miguel Island,

California. Pp. 41-51, In: Robson, B. W. (ed.), Fur seal investigations, 1998. U.S. Dep. Commer., NOAA

Tech. Memo. NMFS-AFSC-113. 101 pp.

Melin, S. R., R. L. DeLong, and J. R. Thomason. 1996. Population monitoring studies of northern fur seals at San

Miguel Island, California. Pp. 87-102, In: Sinclair, E.H. (ed.), Fur seal investigations, 1994. U.S. Dep.

Commer., NOAA Tech. Memo. NMFS-AFSC-69. 144 pp.

National Marine Fisheries Service. 1993. Final Conservation Plan for the northern fur seal (Callorhinus ursinus).

Prepared by the National Marine Mammal Laboratory, Alaska Fisheries Science Center, Seattle, WA, and the

Office of Protected Resources, NMFS, Silver Spring, MD. 80 pp.

Roppel, A. Y. 1984. Management of northern fur seals on the Pribilof Islands, Alaska, 1786-1981. U.S. Dep.

Commer., NOAA Tech. Rep. NMFS-4. 32 pp.

Wade, P. R., and R. Angliss. 1997. Guidelines for assessing marine mammal stocks: report of the GAMMS workshop

April 3-5, 1996, Seattle, Washington. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-12. 93 pp.

York, A. E. National Marine Mammal Laboratory, AFSC, NMFS, 7600 Sand Point Way NE, Seattle, WA 98115.
40

Revised 12/31/2001

HAWAIIAN MONK SEAL (Monachus schauinslandi)

STOCK DEFINITION AND GEOGRAPHIC RANGE

Hawaiian monk seals are distributed throughout the Northwestern Hawaiian Islands (NWHI) in six main

reproductive subpopulations at French Frigate Shoals, Laysan Island, Lisianski Island, Pearl and Hermes Reef, Midway

Atoll, and Kure Atoll. Small subpopulations also exist at Necker Island and Nihoa Island and a few seals are distributed

throughout the main Hawaiian Islands. Studies of Hawaiian monk seals have focused on their abundance and behavior

on land during the reproductive season (spring and summer). Expanded research is underway, but currently the pelagic

distribution and behavior of monk seals cannot be fully characterized.

In the last two centuries, the species has experienced two major declines which may have severely reduced its

genetic variation. The tendency for genetic drift may have been (and continue to be) relatively large, due to the small

size of different island/atoll subpopulations. However, 10-15% of these seals migrate among the subpopulations

(Johnson and Kridler 1983; National Marine Fisheries Service [NMFS] unpubl. data) and, to some degree, this

movement should counter the development of separate genetic stocks. Genetic variation among the different island

populations is low (Kretzmann et al., 1997).

Demographically, the different island subpopulations have exhibited considerable independence. For example,

abundance at French Frigate Shoals grew rapidly during the 1950s to the 1980s, while other subpopulations declined

rapidly. However, variation in past population trends may be partially explained by changes in the level of human

disturbance (Gerrodette and Gilmartin 1990). Current demographic variability among the subpopulations probably

reflects a combination of different recent histories and varying environmental conditions. While research and recovery

activities focus on the problems of single island/atoll subpopulations, the species is managed as a single stock.

POPULATION SIZE

Abundance of the main reproductive subpopulations is best estimated using the number of seals identified at

each site. Individual seals are identified by applied flipper-tags and bleach-marks, and natural features such as scars and

distinctive pelage patterns. Flipper-tagging of weaned pups began in the early 1980s, and the majority of the seals in

the main reproductive subpopulations can be identified on the basis of those tags. In 1999, identification efforts were

conducted during two- to five-month studies at all main reproductive sites except Midway Atoll, where the study period

was 12 months. A total of 1344 seals (including 244 pups) were observed at the main reproductive subpopulations in

1999 (Johanos and Baker, 2001). Removal analyses in previous years and sighting probability calculations suggest that

90% or more of the seals were identified at each site (i.e., any negative bias should be less than 10%). 

Monk seals also occur at Necker and Nihoa Islands, where counts are only conducted once or a few times in

a single year. Abundance is estimated by correcting the mean of all beach counts accrued over the past five years. The

mean (±SD) of all counts (excluding pups) conducted during the five years ending in 1999 were 18.4 (±9.6) at Necker

Island and 20.0 (±4.9) at Nihoa Island ( NMFS unpubl. data).

 The observed relationship between mean counts and total abundance at the reproductive sites indicates that

the total abundance can be estimated by multiplying the mean count by a correction factor (±SE) of 2.89 (±0.06, NMFS

unpubl. data). Resulting estimates (plus the average number of pups known to have been born in the five years ending

in 1999) are 54.2(±27.7) at Necker Island and 61.8 (±14.2) at Nihoa Island. 

Finally, a small number of seals are distributed throughout the main Hawaiian Islands. These include an

unknown number of seals, which naturally occur in the main Hawaiian Islands. In addition, twenty-one seals were

released around these islands in 1994. All but two were subsequently resighted near their respective release sites, but

their survival to 1999 is unknown, because there is no formal resighting effort in the main Hawaiian Islands. The first

systematic survey of Hawaiian monk seals in the main Hawaiian Islands was conducted in 2000, however the data have

not been thoroughly analyzed to date. In previous Stock Assessment Reports, abundance in the main Hawaiian Islands

had been estimated at 40 seals with a coefficient of variation of 10 seals. Because the recent survey numbers are not

analyzed, this previous estimate will be used for 1999.

Minimum Population Estimate

The total number of seals identified at the main reproductive sites is the best estimate of minimum population

size at those sites (i.e., 1344 seals). Minimum population sizes for Necker and Nihoa Islands (based on the formula
41

300 

350 

400 

450 

500 

550 

600 

Mean Number of Non-Pups

1984 1986 1988 1990 1992 1994 1996 1998 2000 

Year

Figure 8. Mean beach counts of Hawaiian monk seals (non-pups)

at the main reproductive rookeries (excluding Midway Atoll),

1985-99. 

provided by Wade and Angliss (1997)) are 36 and 51, respectively. If it is assumed that the abundance estimate for seals

in the main Hawaiian Islands is, as described above, 40 ±10 seals (i.e., a coefficient of variation of 0.25), then an

estimate of the minimum population size in the main Islands is 33 seals. The minimum population size for the entire

stock (species) is the sum of these estimates, or 1464 seals.

Current Population Trend

Between 1958 and 1999, the total of mean non-pup beach counts at the main reproductive subpopulations

declined by approximately 60%. From 1985 to 1999, the average rate of decline was approximately 3% yr-1, although

the counts have been stable since 1993 (Fig. 1). Further decline is likely, due to extremely high juvenile mortality and

an inverted age structure which will result in reduced reproductive recruitment in the largest subpopulation (French

Frigate Shoals).

CURRENT AND MAXIMUM NET

PRODUCTIVITY RATES

Assuming mean beach counts are a

reliable index of total abundance, then the current

net productivity rate for this species is -0.03 yr-1

(loglinear regression of beach counts of nonpups, 1985-99; R

2

 = 0.82, P<0.001). This trend

is largely due to a severe decline at French

Frigate Shoals, where non-pup beach counts

decreased by 60% between 1989 and 1999.

Populations at Laysan and Lisianski Islands have

remained relatively stable since approximately

1990. 

Contrary to trends at the above sites, the

subpopulation at Kure Atoll has grown at ca. 5%

yr

-1 since 1983 (loglinear regression of beach

counts, 1983-99;R

2

 = 0.82, P<0.001), due largely

to decreased human disturbance and introduced

females. The subpopulation at Pearl and Hermes

Reef has grown at approximately 6% yr-1 since

1983 (loglinear regression of beach counts, 1983-

1999; R

2

 = 0.82, P<0.001). Growth of the Pearl

and Hermes population may be slowing slightly,

as previous to 1999 the growth rate averaged

7%yr-1 (Forney et al. 2000). This latter annual growth rate is the best indicator of the maximum net productivity rate

(Rmax) for this species. Finally, the small subpopulation at Midway Atoll continues to show signs of recovery.

POTENTIAL BIOLOGICAL REMOVAL

The potential biological removal (PBR) level for this stock is calculated as the minimum population size (1464)

times one half the maximum net growth rate for this stock (1⁄2 of 7%) times a recovery factor of 0.1 (for an endangered

species, Wade and Angliss 1997), which yields a PBR of 5 monk seals per year. However, while the Pearl and Hermes

Reef population for some time exhibited the net growth rate of 7% used to calculate PBR, it is clear that the population

as a whole is not currently growing (Fig. 1). Thus, the population appears unlikely to increase in the near future, even

without the potential removal of 5 animals per year.

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Human-related mortality has caused two major declines of the Hawaiian monk seal. In the 1800s, this species was

decimated by sealers, crews of wrecked vessels, and guano and feather hunters (Dill and Bryan 1912; Wetmore 1925;

Clapp and Woodward 1972). Several subpopulations may have been driven extinct; for example, no seals were seen
42

at Midway Atoll during a 14-month period in 1888-89, and only a single seal was seen during three months of

observations at Laysan Island in 1912-13 (Bailey 1952). A survey in 1958 indicated at least partial recovery of the

species in the first half of this century (Rice 1960). However, subsequent surveys revealed that all subpopulations except

French Frigate Shoals declined severely after the late 1950s (or earlier). This second decline has not been explained at

Pearl and Hermes Reef, or Lisianski and Laysan Islands. At Kure Atoll, Midway Atoll, and French Frigate Shoals,

trends appear to have been determined by the pattern of human disturbance from military or U.S. Coast Guard activities.

Such disturbance caused pregnant females to abandon prime pupping habitat and nursing females to abandon their pups

(Kenyon 1972; Gerrodette and Gilmartin 1990). The result was a decrease in pup survival, which led to poor

reproductive recruitment, low productivity, and population decline.

Since 1979, disturbance from human activities on land has been limited primarily to Kure and Midway Atolls.

The U.S. Coast Guard LORAN station at Kure Atoll was closed in 1992 and vacated in 1993. The U.S. Naval Air

Facility at Midway was closed in 1993 and, following clean-up and restoration activities, jurisdiction was transferred

in 1997 to the U.S. Fish and Wildlife Service, which manages the atoll as a National Wildlife Refuge. The refuge station

and the atoll runway are maintained cooperatively with a commercial aircraft company, which supports its Midway

operations, in part, by establishing a tourism center at the site. Strict regulations have been established to prevent further

human disturbance of the seals, but careful monitoring of human activities will be essential to ensure that the regulations

are both adequate and observed (see Habitat Issues below).

In addition to disturbance on land, disturbance at sea (e.g., direct and indirect fisheries interactions) may also

impede recovery. As described below, however, the possible types of disturbance at sea cannot yet be characterized or

quantified. 

Fishery Information

Detrimental fishery interactions with monk seals fall into four categories: operations/gear conflict,

entanglement in fisheries debris (most of which likely originate in North Pacific fisheries outside the NWHI), seal

consumption of potentially toxic discards, and competition for prey. Since 1982, a total of nine fishery-related monk

seal deaths have been recorded, including six from entanglement in fisheries debris (Henderson 1990, 2001; NMFS,

unpubl. data), one from entanglement in the bridle rope of lobster trap (1986; NMFS, unpubl. data), one from

entanglement in an illegally set gill net off the western shore of Oahu (1994; NMFS, unpubl. data), and one from

ingestion of a recreational fish hook and probable drowning off the island of Kauai (1995; NMFS, unpubl. data). In

addition, 17 other seals have been observed with embedded fish hooks, 23 seals have been observed with wounds

suspected to have resulted from interactions with fisheries, and 197 cases of seals entangled in fishing gear or other

debris have been observed through 1999 (Henderson 2001; NMFS, unpubl. data). Importantly, the majority of these

deaths and injuries have been observed incidentally during land-based research or other activities; monk seal/fisheries

interactions need to be monitored to assess the rate of fisheries-related injury or mortality for this species.

Four fisheries interact with Hawaiian monk seals. The NWHI lobster fishery began in the late 1970s, and

developed rapidly in the early 1980s (Polovina, 1993). Annual landings peaked in 1985 (1.92 million lobsters) and 1986

(1.69 million lobsters; Haight and DiNardo 1995). Thereafter, the fishery declined and was closed temporarily in 1993

due to low spawning stock biomass of spiny lobster. Since 1994, landings remained lower than in the mid- to late 1980s,

while catch of slipper lobster has increased in some areas. The number of vessels in the fishery increased from four in

1983 to 17 in 1985, then ranged from 0-12 during 1991-1999, with six vessels participating in 1999 (Dollar 1995;

DiNardo et al. 1998; Kawamoto and Pooley, 2000). Historically, both effort and landings have been concentrated at

Gardner Pinnacles, Maro Reef, Necker Island, and St. Rogatien Bank (Clarke and Todoki 1988; Polovina and Moffitt

1989). However, spatial management of the NWHI lobster fishery began in 1998 with the formation of four management

areas: Necker Island (Area 1), Maro Reef (Area 2), Gardner Pinnacles (Area 3), and all remaining banks from Nihoa

Island in the east to Kure Atoll in the west (Area 4). This approach was adopted in an effort to prevent local depletion

of lobster stocks at Necker Island, Maro Reef, and Gardner Pinnacles and to disperse fishing effort, which in recent

years had been limited to Necker Island and Maro Reef. As a result of the new management approach, 59,500 lobsters,

comprising 25% of the total catch, were taken from Area 4, which, until 1998, had not been fished since the early 1990's

(DiNardo et al.1998; Kawamoto and Pooley 2000). Summaries of catch by area, trends and available data on bycatch

are published in annual reports, the most recent being Kawamoto and Pooley (2000). A significant portion of the Area

4 catch in 1999 was taken at locations where monk seal subpopulations occur. Neither incidental mortality nor serious
43

injury have been observed by NMFS observers of the lobster fishery through 1999. As was noted, one mortality was

documented in 1986; a monk seal drowned after becoming entangled in the bridle rope of an actively fishing lobster trap

near Necker Island. The potential for indirect interaction due to competition for prey is being investigated (see Habitat

Issues below). 

NMFS closed the Northwestern Hawaiian Islands lobster fishery for the year 2000 season due to uncertainty

in the estimates of biomass. The Agency intends to keep the fishery closed in Areas 1-3 through the year 2001 and in

Area 4 through the year 2002. The Agency is preparing an Environmental Impact Statement (EIS) for the fishery and

ESA Section 7 consultation will be conducted prior to any opening the fishery. Furthermore, President Clinton’s

Executive Order (1/18/2001) creating the Northwest Hawaiian Islands coral reef ecosystem reserve also precludes much

if not all lobster fishing in the NWHI.

On 16 October 1998 the Paradise Queen II, a lobster fishing vessel, ran aground on the eastern edge of Kure

Atoll. In 1999, large portions of the hull and wheel house still remained on the reef, smaller structural pieces had

washed ashore, and a large portion of the main deck had come to rest on Green Island. Monk seals occasionally hauled

out on this deck. During an initial clean up effort soon after Paradise Queen II ran aground, accessible hazardous

material and lobster traps were removed from the marine environment. Subsequently, more traps washed up on shore

and were stacked on Green Island to await removal. Presently, all recovered traps (totaling several hundred) have been

removed from the island. It is not known whether any more lobster traps remain in the waters of Kure Atoll.

The NWHI bottomfish fishery also interacts with monk seals. This fishery occurred at low levels (< 50 t per

year) until 1977, steadily increased to 460 metric tons in 1987, then dropped to 284 metric tons in 1988, and varied from

137 - 201 metric tons per year from 1989-1999 (Kawamoto 1995; Moffitt, pers. comm.). The number of vessels rose

from 19 in 1984 to 28 in 1987, and then varied from 10 to 17 in 1988 through 1999 (Kawamoto 1995; Moffitt, pers.

comm.). Currently, the bottomfish fishery remains open, although its area of operation has been substantially restricted

by President Clinton’s Executive Order (1/18/2001). The Agency is preparing an Environmental Impact Statement and

a Section 7 Biological Opinion on the operation of the fishery. The fishery was monitored by observers from October

1990 to December 1993 (ca. 13% coverage), but is currently monitored by the State of Hawaii using logbooks.

However, the State logbook does not include information on protected species and, therefore, the nature and extent of

interactions with monk seals cannot be assessed. Nitta and Henderson (1993) evaluated observer data from 1991-92 and

reported an interaction rate of one event per 34.4 hours of fishing, but they do not provide a confidence interval for their

estimate. The authors documented one seal found with a bottomfish hook in her mouth at French Frigate Shoals,

observer reports of seals taking bottomfish and bait off fishing lines, and observer reports of seals attracted to discarded

bottomfish bycatch, which may contain ciguatoxin or other biotoxins. Injury or mortality resulting from hooking or

consumption of toxic discards cannot be determined with the available data. The ecological effects of this fishery on

monk seals (e.g., competition for prey or alteration of prey assemblages by removal of key predator fishes) are unknown.

However, published studies on monk seal prey selection based upon scat/spew analysis and seal-mounted video, rarely

revealed evidence that monk seals fed on families of bottomfish which contain commercial species (many hard parts

of scats and spews were identified only to the level of family; Goodman-Lowe 1998, Parrish et al. 2000). Fatty acid

signature analysis is inconclusive regarding the importance of commercial bottomfish in the monk seal diet, but this

methodology continues to be pursued.

A third fishery in which past interactions with monk seals were documented was the pelagic longline fishery.

This fishery targets swordfish and tunas, primarily, and does not compete with Hawaiian monk seals for prey. The

fishery began in the 1940s, and operated at a relatively low level (< 5000 t per year) until the mid-1980s. In 1987, 37

vessels participated, but by 1991, the number had grown to 141 (Ito, 1995). The number of active vessels ranged from

103-141 during 1991-99. Entry is currently limited to a maximum of 164 vessels (Ito and Machado, 1999). Total

landings ranged from 8,100-13,000 metric tons during 1991-1999 (Ito, pers. comm.). While most of the fishery has

operated outside of the NWHI Exclusive Economic Zone, the rapid expansion raised concerns about the potential for

interactions with protected species, including the monk seal. Evidence of interactions began to accumulate in 1990,

including three hooked seals (included in hookings reported above) and 13 unusual seal wounds thought to have resulted

from interactions. In response, NMFS established a permanent Protected Species Zone extending 50 nautical miles

around the NWHI and the corridors between the islands in October 1991. Subsequent shore-based observations of seals

have found no further evidence of interactions with the longline fishery after establishment of the Protected Species

Zone. At present, interactions with protected species are assessed using Federal logbooks and observers (4-5%

coverage), which may lack sufficient statistical power to estimate monk seal mortality/serious injury rates from longline
44

interactions. However, since 1991, there have been no observed or reported interactions of this fishery with monk seals.

There have also been interactions between recreational fisheries and monk seals in both the NWHI and around

the main Hawaiian Islands. At least three seals have been hooked at Kure Atoll, but such incidents should no longer

occur at this site because the atoll was vacated by the U.S. Coast Guard in 1993. In the main Hawaiian Islands, one seal

was found dead in an offshore (non-recreational) gillnet in 1994 and a second seal was found dead with a recreational

hook lodged in its esophagus. At least seven other seals have been hooked. Three of these incidents involved hooks used

to catch ulua (Caranx spp.). One hooked seal had been translocated from Laysan Island to the main Hawaiian Islands

in July 1994. The recent establishment of sport fishing at Midway clearly increases the potential for monk seals to be

harmed by hooks at that site.

Table 1. Summary of incidental mortality of Hawaiian monk seals due to commercial and recreational fisheries since

1990 and calculation of annual mortality rate. n/a indicates that sufficient data are not available.

Fishery

Name Years

Range of 

# of vessels per

year

Date type

Range

of

observer

coverage

Total

observed

mort.

Estimated

mort. (in

given

years)

Mean

annual

mort.

NWHI

lobster

91-99 0-12 Observer

Log book

0-100% 0 n/a n/a

NWHI

Bottomfish

91-99 12-17

n/a n/a n/a n/a n/a

Pelagic

longline

91-99 103-141 Observer

Log book 4-5% 0 n/a n/a

Recreational 91-95 n/a n/a n/a 2†n/a n/a

†

 Data collected incidentally.

Recent interest in the harvest of precious coral in the NWHI represents a potential for future interactions with

monk seals. The impact that removal of precious corals might have on monk seal prey resources and foraging habitat

is not known. However, recent studies of seals with satellite transmitters and surveys using manned submersibles

indicate that some monk seals forage at patches of precious gold corals occurring over 500m in depth (Parrish, pers.

comm.). Recruitment of gold coral is very slow (perhaps on the order of 100 years), so there is concern that harvesting

could have a long term impact on monk seal foraging habitat. As a result, the Western Pacific Regional Fisheries

Management Council has recommended regulations to suspend or set to zero annual quotas for gold coral harvest at

specific locations until information on impacts of such harvests on monk seal foraging habitat become available.

Fishery Mortality Rate

Because monk seals continue to die as a result of entanglement in North Pacific fishing debris (likely

originating from various countries) and data are unavailable to assess interaction with specific fisheries, one must

conclude that the total fishery mortality and serious injury for this stock is greater than 1) zero allowable take under the

Endangered Species Act and 2) 10% of the calculated PBR. Therefore, total fishery mortality and serious injury can not

be considered to be insignificant and approaching a rate of zero. 

Direct fishery interactions with this species remain to be thoroughly evaluated and, therefore, the information

above represents only the observed level of interactions. Without further study, an accurate estimate cannot be

determined. In addition, interactions may be indirect (i.e., involving competition for prey or consumption of discards

from the bottomfish fishery) and, to date, the extent or consequences of such indirect interactions remain the topic of

ongoing investigation.
45

Other Mortality

Since 1982, 22 seals died during rehabilitation efforts; additionally, two died in captivity, two died when

captured for translocation, one was euthanized (an aggressive male known to cause mortality), three died during captive

research and three died during field research.

Seals have also died after encounters with marine debris from sources other than fisheries. In 1986, a weaned

pup died at East Island, French Frigate Shoals, after becoming entangled in wire left when the U.S. Coast Guard

abandoned the island three decades earlier. In 1991, a seal died after becoming trapped behind an eroding seawall on

Tern Island, French Frigate Shoals. This seawall continues to erode and poses an ongoing threat to the safety of seals

and other wildlife.

The only documented case of illegal killing of an Hawaiian monk seal occurred when a resident of Kauai killed

an adult female in 1989.

Other sources of mortality which are (or may be) impeding the recovery of this subpopulation include single

and multiple male aggression (mobbing), shark predation, poisoning by ciguatoxin or other biotoxins, and

disease/parasitism. When multiple males attempt to mount and mate with an adult female or immature animal of either

sex, injury or death of the attacked seal often results. Since 1982, at least 67 seals have died or disappeared after

suffering multiple male aggression. The resulting increase in female mortality appears to have been a major impediment

to recovery at Laysan and Lisianski Islands. Multiple male aggression has also been documented at French Frigate

Shoals, Kure Atoll, and Necker Island. Multiple male aggression is thought to be related to an imbalance in the adult

sex ratio, with males outnumbering females. In 1994, 22 adult males were removed from Laysan Island, and only three

seals are thought to have died from multiple male aggression at this site since their removal (1995-99). Such imbalances

in the adult sex ratio are more likely to occur when populations are reduced (Starfield et al. 1995).

In addition to mobbing, aggressive attacks by single adult males have resulted in several monk seal mortalities. This

was most notable at French Frigate Shoals in 1997, where at least 8 pups died as a result of adult male aggression. Many

more pups were likely killed in the same way but the cause of their deaths could not be confirmed. Two males who had

been known to kill pups in 1997 were observed exhibiting aggressive behavior toward pups at the beginning of the 1998

pupping season. These two males were translocated to Johnston Atoll, 870 km to the southwest. Subsequently,

mounting injury to pups have decreased.

The incidence of shark-related injury and mortality may have increased in the late 1980s and early 1990s at

French Frigate Shoals, but such mortality was probably not the primary cause of the decline at this site (Ragen 1993).

However, indications are that shark predation has accounted for a significant portion of pup mortality in the last few

years. At French Frigate Shoals in 1999, 17 pups were observed injured by large sharks, and at least 3 were confirmed

to have died from shark predation (Johanos and Baker, 2001). Assigning cause of death to shark predation is

problematic, as predation events are rarely observable. However, it is believed that as many as 25 pups of a total 92 born

at French Frigate Shoals in 1999 were killed by sharks. The potential causes of high pup mortality, including shark

predation, disease, male aggression and food limitation are currently being investigated at French Frigate Shoals.

Poisoning by ciguatoxin or related toxins may have been the primary cause of the Laysan die-off in 1978, and may have

contributed to the high mortality of juvenile seals translocated to Midway Atoll in 1992 and 1993. While virtually all

wild monk seals carry parasites after they begin to forage, the role of parasitism in monk seal mortality is unknown. The

effect of disease on monk seal demographic trends is also uncertain. 

STATUS OF STOCK

In 1976, the Hawaiian monk seal was designated depleted under the Marine Mammal Protection Act of 1972

and as endangered under the Endangered Species Act of 1973. The species is assumed to be well below its optimum

sustainable population (OSP) and, since 1985, has declined approximately 3% per year. Therefore, the Hawaiian monk

seal is characterized as a strategic stock.

Habitat Issues

Available data indicate that the substantial decline at French Frigate Shoals was to some degree attributable

to lack of available prey and subsequent emaciation and starvation. The two leading hypotheses to explain the lack of

prey are 1) the local population reached its carrying capacity in the 1970s and 1980s, and essentially diminished its own

food supply, and 2) carrying capacity was simultaneously reduced by changes in oceanographic conditions and a
46

resulting decrease in productivity (Polovina et al. 1994; Craig and Ragen 2000;). Thus, this subpopulation may have

significantly exceeded its carrying capacity, leading to a catastrophic increase in juvenile mortality. In addition, available

prey also may have been reduced by competition with the NWHI lobster fishery. Monk seals forage at the four main

banks where the fishery has primarily operated: Maro Reef, Gardiner Pinnacles, St. Rogatien Bank, and Necker Island.

In 1998, the fishery expanded into areas where monk seal breeding populations are concentrated within the fishery’s

Area 4. Thus, competition for prey is under investigation. This potential for competition cannot yet be determined,

however, because it is not known if lobster is an important component of the monk seal diet. Preliminary research

indicates that lobster have identifiable fatty acid signatures, which will potentially make possible an assessment of its

importance in the monk seal diet. This promising area of research is being actively pursued.

A second important habitat issue is the management of human activities at Midway Atoll. Historically, human

activities have led to the near extinction of the resident monk seal population at Midway both in the late 1800s, and

again in the 1960s. The seal population failed to recover in the 1970s and 1980s, but is finally beginning to show some

signs of growth due to immigration from nearby sites. Management jurisdiction of Midway Atoll has been transferred

from the U.S. Navy to the Fish and Wildlife Service. The Fish and Wildlife Service maintains a refuge station at

Midway Atoll by cooperating with a commercial aircraft company that uses the runway on Sand Island (the largest

island at Midway Atoll), and support its operations, in part, by establishing an on-site eco-tourism destination. Tourist

activities include a range of land-based and marine recreational activities (e.g., scuba diving and sport fishing), as well

as harbor services to visiting vessels. As the tourism venture develops, so does a potential conflict of interest. The

economic success of the venture may depend on the nature and variety of human activities or privileges allowed at the

site. Importantly, those activities that are intended to enhance the Midway experience may be disruptive or detrimental

to the refuge and its wildlife. The issue is whether such potential conflicts can be identified and resolved in a manner

that allows for continuation of the ecotourism venture but does not impede monk seal recovery. The Fish and Wildlife

Service and NMFS are working cooperatively to ensure that human activities do not impede recovery at this site.

Another important habitat issue is the degrading seawall at Tern Island, French Frigate Shoals. Tern Island is

the site of the U.S. Fish and Wildlife refuge station, and is one of two sites in the NWHI accessible by aircraft. The

island and the runway have played a key role in efforts to study the local monk seal population, and to mitigate its severe

and ongoing decline. During World War II, the U.S. Navy enlarged the island to accommodate the runway. A sheet-pile

seawall was constructed to maintain the modified shape of the island. Degradation of the seawall is creating entrapment

hazards for seals and other wildlife, and is threatening to erode the runway. Erosion of the sea wall has also raised

concerns about the potential release of toxic wastes into the aquatic environment. The loss of the runway could lead to

the closure of the Fish and Wildlife Service station at the site and would thereby reduce on-site management of the

refuge. The loss of the runway and refuge station would also hinder research and management efforts to recover the

monk seal population.

A fourth important habitat issue involves entanglement in marine debris. Marine debris is removed from the

beaches and entangled seals during annual population assessment activities at the main reproductive sites. Efforts to

remove potentially entangling marine debris from the reefs surrounding haulout sites utilized by monk seal are ongoing.

In 1996, efforts commenced to assess and remove potentially entangling marine debris from reefs surrounding haulout

sites utilized by monk seals. Preliminary surveys suggest a very large number of nets are fouled on nearshore reefs in

the NWHI, and may pose a serious threat to seals in these areas. During 1996-1999 debris survey and removal efforts,

35,000 kg of derelict net and other debris were removed from the coral reef habitat at French Frigate Shoals, Pearl and

Hermes Reef, Lisianski Island and Midway Atoll (Donohue et al. 2000, Donohue et al. in press). 

REFERENCES

Bailey, A. M. 1952. The Hawaiian monk seal. Museum Pictorial, Denver Museum of Natural History 7:1-32.

Clapp, R. B., and P. W. Woodward. 1972. The natural history of Kure Atoll, Northwestern Hawaiian Islands, Atoll Res.

Bull. 164:303-304 

Clarke, R. P., and A. C. Todoki. 1988. Comparison of three calculations of catch rates of the lobster fishery in the

Northwestern Hawaiian Islands. Admin. Rep. H-88-6. Southwest Fisheries Science Center, National Marine

Fisheries Service, 2570 Dole St., Honolulu, HI 96822-2396. 30 pp.

Craig, M. P. and T. J. Ragen. 1999. Body size, survival, and decline of juvenile Hawaiian monk seals, Monachus

schauinslandi. .Marine Mammal Science 15(3): 786-809.
47

Dill, H. R., and W. A. Bryan. 1912. Report on an expedition to Laysan Island in 1911. U.S. Dept. of Agric. Surv. Bull.

42:1-30.

DiNardo, G. T., W. R. Haight, and J. A. Wetherall. 1998. Status of lobster stocks in the Northwestern Hawaiian

Islands, 1995-97, and outlook for 1998. Admin. Rep. H-98-05. Southwest Fisheries Science Center, National

Marine Fisheries Service, 2570 Dole St., Honolulu, HI 96822-2396. 35 pp.

Donohue, M.J., R. Brainard, M. Parke, and D. Foley. 2000. Mitigation of environmental impacts of derelict fishing

gear through debris removal and environmental monitoring. Issue paper in International Marine Debris

Conference on Derelict Fishing Gear and the Ocean Environment, 6-11 August 2000, Honolulu, Hawaii.

Hawaiian Islands Humpback Whale National Marine Sanctuary publication, 726 S Kihei Road, Kihei, HI

96753, hawaiian@nms.noaa.gov.

Donohue, M.J., R.C. Boland, C.M. Sramek, and G.A. Antonelis. In press. Derelict fishing gear in the Northwestern

Hawaiian Islands: diving surveys and debris removal in 1999 confirm threat to coral reef ecosystems. Marine

Pollution Bulletin.

Forney, K.A., J. Barlow, M.M. Muto, M. Lowry, J. Baker, G. Cameron, J. Mobley, C. Stinchcomb, and J.V. Carretta.

2000. U.S. Pacific Marine Mammal Stock Assessments: 2000. U.S. Dep. Commer. NOAA Technical

Memorandum. NMFS-SWFSC-300. 276 p.

Gerrodette, T. M., and W. G. Gilmartin. 1990. Demographic consequences of changed pupping and hauling sites of the

Hawaiian monk seal. Conserv. Biol. 4:423-430.

Haight, W. R., and G. T. DiNardo. 1995. Status of lobster stocks in the Northwestern Hawaiian Islands, 1994. Available

Honolulu Lab., Southwest Fish. Sci. Cent., Natl. Mar. Fish. Serv., NOAA, Honolulu, HI 96822-2396.

Southwest Fish. Sci. Cent. Admin. Rep. H-95-03, 17 p.

Henderson, J. R. 1990. Recent entanglements of Hawaiian monk seals in marine debris. In R. S. Shomura and M. L.

Godfrey (eds.), Proceedings of the Second International Conference on Marine Debris, April 2-7, 1989,

Honolulu, Hawaii, p. 540-553. U.S. Dep. Commer., NOAA, Tech. Memo. NMFS-SWFSC-154.

Henderson, J.R. 2001. A Pre- and Post-MARPOL Annex V Summary of Hawaiian Monk Seal Entanglements and

Marine Debris Accumulation in the Northwestern Hawaiian Islands, 1982-1998. Marine Pollution Bulletin

42:584-589.

Ito, R. Y. 1995. Annual report of the 1994 Hawaii-based longline fishery. Admin. Rep. H-95-08 Southwest Fisheries

Science Center, National Marine Fisheries Service, 2570 Dole St., Honolulu, HI 96822-2396. 36 pp.

Ito, R. Y., and W. A. E. Machado. 1999. Annual report of the Hawaii-based longline fishery in 1998. Admin. Rep.

H-99-06. Southwest Fisheries Science Center, National Marine Fisheries Service, 2570 Dole St., Honolulu,

HI 96822-2396. 62 pp.

Johanos, T. C., and J. D. Baker (editors). 2001. The Hawaiian monk seal in the northwestern Hawaiian islands, 1999.

NOAA Technical Memorandum NOAA-TM-NMFS-SWFSC-310. 130p.

Johnson, A. M., and E. Kridler. 1983. Interisland movement of Hawaiian monk seals. 'Elepaio 44(5):43-45.

Kawamoto, K. E. 1995. Northwestern Hawaiian Islands bottomfish fishery, 1994. Admin. Rep. H-95-07. Southwest

Fisheries Science Center, National Marine Fisheries Service, 2570 Dole St., Honolulu, HI 96822-2396. 26

pp.

Kawamoto, K. E., and S. G. Pooley. 2000. Annual report of the 1998 western Pacific lobster fishery. Admin. Rep. H00-02. Southwest Fisheries Science Center, National Marine Fisheries Service, 2570 Dole St., Honolulu, HI

96822-2396. 38 pp.

Kenyon, K. W. 1972. Man versus the monk seal. J. Mammal. 53(4):687-696.

Kretzmann, M. B., W. G. Gilmartin, A. Meyer, G. P. Zegers, S. R. Fain, B. F. Taylor, and D. P. Costa. 1997. Low

genetic variability in the Hawaiian monk seal. Conserv. Biol. 11(2):482-490.

Goodman-Lowe, G. D. 1998. Diet of the Hawaiian monk seal (Monachus schauinslandi) from the Northwestern

Hawaiian islands during 1991 to 1994. Marine Biology 132:535-546.

Nitta, E. T., and J. R. Henderson. 1993. A review of interactions between Hawaii's fisheries and protected species. Mar.

Fish. Rev. 55(2):83-92.

Parrish, F. A., M. P. Craig, T. J. Ragen, G. J. Marshall, and B. M. Buhleier. 2000. Identifying diurnal foraging habitat

of endangered Hawaiian monk seals using a seal-mounted video camera. Mar. Mamm. Sci. 16:392-412.
48

Polovina, J. J. 1993. The lobster and shrimp fisheries in Hawaii. Mar. Fish. Rev. 55(2):28-33.

Polovina, J. J., G. T. Mitchum, N. E. Graham, M. P. Craig, E. E. DeMartini, and E. N. Flint. 1994. Physical and

biological consequences of a climate event in the central North Pacific. Fish. Ocean. 3:15-21.

Polovina, J. J., and R. B. Moffitt. 1989. Status of lobster stocks in the Northwestern Hawaiian Islands, 1988. Admin.

Rep. H-89-3. Southwest Fisheries Science Center, National Marine Fisheries Service, 2570 Dole St.,

Honolulu, HI 96822-2396. 10 pp.

Pooley, S. G., and K. E. Kawamoto. 1998. Annual report of the 1995-97 western Pacific lobster fishery. Admin. Rep.

H-98-09. Southwest Fisheries Science Center, National Marine Fisheries Service, 2570 Dole St., Honolulu,

HI 96822-2396. 34 pp.

Ragen, T. J. 1993. Status of the Hawaiian monk seal in 1992. Admin. Rep. H-93-05. Southwest Fisheries Science

Center, National Marine Fisheries Service, 2570 Dole St., Honolulu, HI 96822-2396. 79 pp.

Rice, D. W. 1960. Population dynamics of the Hawaiian monk seal. J. Mammal. 41:376-385.

Starfield, A. M., J. D. Roth, and K. Ralls. 1995. "Mobbing" in Hawaiian monk seals (Monachus schauinslandi): The

value of simulation modeling in the absence of apparently crucial data. Conserv. Biol. 9:166-174.

Wade, P. R. and R. P. Angliss. 1997. Guidelines for Assessing Marine Mammal Stocks: Report of the GAMMS

Workshop April 3-5, 1996, Seattle, Washington. U. S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-12.

93 pp.

Wetmore, A. 1925. Bird life among lava rock and coral sand. The Natl. Geograp. Mag. 48:77-108.
49

Figure 1. Stock boundaries and distributional

range of harbor porpoise along the U.S. west coast.

Shaded area represents harbor porpoise habitat (0-

200 m) along the U.S. west coast.

Revised: 12/31/2001

HARBOR PORPOISE (Phocoena phocoena): Central California Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

In the Pacific, harbor porpoise are found in coastal and

inland waters from Point Conception, California to Alaska and

across to Kamchatka and Japan (Gaskin 1984). Harbor porpoise

appear to have more restricted movements along the western

coast of the continental U.S. than along the eastern coast.

Regional differences in pollutant residues in harbor porpoise

indicate that they do not move extensively between California,

Oregon, and Washington (Calambokidis and Barlow 1991). That

study also showed some regional differences within California

(although the sample size was small). This pattern stands as a

sharp contrast to the eastern coast of the U.S. and Canada where

harbor porpoise are believed to migrate seasonally from as far

south as the Carolinas to the Gulf of Maine and Bay of Fundy

(Polacheck et al. 1995). A phylogeographic analysis of genetic

data from northeast Pacific harbor porpoise did not show

complete concordance between DNA sequence types and

geographic location (Rosel 1992). However, an analysis of

molecular variance (AMOVA) of the same data with additional

samples found significant genetic differences for four of the six

pair-wise comparisons between the four areas investigated:

California, Washington, British Columbia, and Alaska (Rosel et

al. 1995). These results demonstrate that harbor porpoise along

the west coast of North America are not panmictic or migratory,

and movement is sufficiently restricted that genetic differences

have evolved. Recent preliminary genetic analyses of samples

ranging from Monterey Bay, California to Vancouver Island,

British Columbia indicate that there are at least nine genetically

distinct populations, including three within the present central

California stock range (S. Chivers, pers. comm.). 

In their assessment of harbor porpoise, Barlow and Hanan (1995) recommended that the animals inhabiting

central California (defined to be from Point Conception to the Russian River) be treated as a separate stock. Their

justifications for this were: 1) fishery mortality of harbor porpoise is limited to central California, 2) movement of

individual animals appears to be restricted within California, and consequently 3) fishery mortality could cause the local

depletion of harbor porpoise if central California is not managed separately. Although geographic structure exists along

an almost continuous distribution of harbor porpoise from California to Alaska, stock boundaries are difficult to draw

because any rigid line is (to a greater or lesser extent) arbitrary from a biological perspective. Nonetheless, failure to

recognize geographic structure by defining management stocks can lead to depletion of local populations. Following

the guidance of Barlow and Hanan (1995), we will consider the harbor porpoise in central California as a separate stock.

However, based on recent genetic findings (Chivers, pers. comm.), it appears likely that the central California stock will

be further subdivided into three stocks (with one division somewhere between Monterey Bay and San Francisco and

another somewhere between Monterey Bay and Morro Bay) once the ongoing analyses have been finalized and peerreviewed. Other U.S. West coast stocks are also likely to be re-evaluated at that time. For the 2000 Marine Mammal

Protection Act (MMPA) Stock Assessment Reports, other Pacific coast harbor porpoise stocks include: 1) a northern

California stock 2) an Oregon/Washington coast stock, 3) an Inland Washington stock, 4) a Southeast Alaska stock,

5) a Gulf of Alaska stock, and 6) a Bering Sea stock. Stock assessment reports for northern California and the Oregon

and Washington stocks appear in Forney et al. (2000) and are also reprinted unrevised in this volume. The three Alaska

harbor porpoise stocks are reported separately in the Stock Assessment Reports for the Alaska Region.
50

0.00 

0.10 

0.20 

0.30 

0.40 

0.50 

Relative abundance (porpoise/km)

85 87 89 91 93 95 97 99 

Year

Figure 2. Relative abundance (+/- one standard error) of central California

harbor porpoise, 1986-99, adjusted for sea state and cloud cover (following

methods of Forney 1995).

POPULATION SIZE

Previous estimates of abundance for California harbor porpoise were based on aerial surveys conducted

between the coast and the 50-fm isobath during 1988-95 (Barlow and Forney 1994, Forney 1999a). These estimates

did not include an unknown number of animals found in deeper waters. Barlow (1988) found that the vast majority of

harbor porpoise in California were within the 0-50-fm depth range; however, Green et al.(1992) found that 24% of

harbor porpoise seen during aerial surveys of Oregon and Washington were between the 100m and 200m isobaths (55

to 109 fathoms). A recent analysis of harbor porpoise trends including oceanographic data suggested that the proportion

of California harbor porpoise in deeper waters may vary between years (Forney 1999b; see Current Population Trend

below). In 1999, aerial surveys extended farther offshore (to at least the 200m depth contour) to provide a more

complete abundance estimate. Although one harbor porpoise sighting was made in offshore waters under poor

conditions (Beaufort sea state 3), only good conditions have traditionally been included in abundance analyses for this

species (Barlow and Forney 1994, Forney 1999a), and therefore no offshore sightings contributed to the updated

abundance estimate. Based on pooled 1995-99 aerial survey data, an updated estimate of abundance for the central

California harbor porpoise stock is 7,579 harbor porpoise (CV=0.38; NMFS, K. Forney, unpublished data, following

methods of Forney 1999a). Although this is higher than the previous estimate of 5,732 (CV=0.39, Forney 1999a), the

confidence intervals overlap and the difference is not statistically significant. 

Minimum Population Estimate

The minimum population estimate for harbor porpoise in central California is taken as the lower 20th percentile

of the log-normal distribution of the abundance estimated from the 1995-99 aerial surveys, or 5,563 animals.

Current Population Trend

Analyses of a 1986-95 time series of aerial surveys have been conducted to examine trends in harbor porpoise

abundance in central California (Forney, 1995; 1999b). After controlling for the effects of sea state, cloud cover, and

area on sighting rates, Forney (1995) found a negative trend in population size; however, that trend was no longer

significant when sea surface temperature (a proxy measure of oceanographic conditions) was included in an updated

non-linear trend analysis (Forney 1999b). The negative correlation between harbor porpoise sighting rates and sea

surface temperatures indicates that apparent trends could be caused by changing oceanographic conditions and

movement of animals into and out of the study area. Encounter rates for the 1997 survey, however, were very high

(Forney 1999a) despite the warmer

sea surface temperatures caused by

strong El Niño conditions. These

observations suggest that patterns of

harbor porpoise movement are not

directly related to sea surface

temperature, but rather to the more

complex distribution of potential prey

species in this area. Although

encounter rates during the 1999 aerial

survey were again higher than in past

years, the trend in relative abundance

(following methods of Forney 1995)

is not statistically significant (p=0.12,

Figure 2). More detailed studies of

encounter rate patterns in relation to

satellite-derived sea surface

temperature during 1993-99 are

planned to shed light on potential

oceanography-related movement

patterns of harbor porpoise in this

region. 
51

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

Based on what are argued to be biological limits of the species (i.e. females give birth first at age 4 and produce

one calf per year until death), the theoretical, maximum-conceivable growth rate of a closed harbor porpoise population

was estimated as 9.4% per year (Barlow and Boveng 1991). This maximum theoretical rate may not be achievable for

any real population. [Woodley and Read (1991) calculate a maximum growth rate of approximately 5% per year, but

their argument for this being a maximum (i.e. that porpoise survival rates cannot exceed those of Himalayan thar) is not

well justified.] Population growth rates have not actually been measured for any harbor porpoise population. Because

a reliable estimate of the maximum net productivity rate is not available for central California harbor porpoise, it is

recommended that the cetacean maximum theoretical net productivity rate (RMAX) of 4% (Wade and Angliss 1997) be

employed.

POTENTIAL BIOLOGICAL REMOVAL

The potential biological removal (PBR) level for this stock is calculated as the minimum population size (5,563)

 times one half the default maximum net growth rate for cetaceans (1⁄2 of 4%) times a recovery factor of 0.50 (for a

species of unknown status and a mortality rate CV ≤ 0.30; Wade and Angliss 1997), resulting in a PBR of 56.

HUMAN-CAUSED MORTALITY

Fishery Information

The incidental capture of harbor porpoise is largely limited to the halibut set gillnet fishery in central California

(coastal setnets are not allowed in northern California, and harbor porpoise do not occur in southern California).

Detailed information on this fishery is provided in Appendix 1. A summary of estimated fishery mortality and injury

for this stock of harbor porpoise is given in Table 1. The most recent mortality estimate for 1999 is based on a 1999

National Marine Fisheries Service monitoring program in Monterey Bay (Cameron and Forney 2000). Mortality

estimates for 1995-98 are based on total estimated fishing effort and prior-year entanglement rate data (Julian and

Beeson 1998), because no observer program was in place during those years. Forney et al. (2001) evaluated

uncertainties in estimating mortality for unobserved years, and presented several alternate analyses of harbor porpoise

mortality for this fishery during 1995-98. Their analysis ‘C’, which is stratified to reflect regional differences in bycatch

rates between Monterey Bay and Morro Bay and includes data from both a 1987-90 California Department of Fish and

Game observer program and a 1990-94 National Marine Fisheries Service observer program, best captures the range

of variability in entanglement rates and is most consistent with the patterns observed more recently in the 1999 observer

program. Although mortality estimates for the most recent five years (1995-99) are presented in Table 1, average

annual takes in the setnet fishery are calculated using only 1996-99 data, because fishing effort approximately doubled

after 1995, and the majority of recent effort has taken place in the southern areas of Monterey Bay, where very little

effort took place prior to 1996. The revised mortality data indicate that an average of 79 harbor porpoise (CV= 0.21)

were killed annually in this fishery in central California during the period 1996-99. Preliminary data for calendar year

2000 indicate that mortality in the halibut set gillnet fishery has dropped, most likely because fishing effort was lower

and part of the fleet began using pingers to reduce porpoise mortality in late 1999 and early 2000. 

On September 13, 2000, the California Department of Fish and Game (CDFG) issued emergency regulations

which restricted fishing in the central California halibut set gillnet fishery to waters deeper than 60 fathoms, citing

concerns over the continued mortality of common murres and decline of the southern sea otter population. The closure

area extended from Point Reyes to Yankee Point in Monterey County and from Point Arguello to Point Sal in Santa

Barbara County (the area from Yankee Point to Point Sal remained open to fishing outside of 30 fathoms). On April

13, 2001, CDFG proposed permanent year-round regulations to eliminate set gillnet fishing inshore of 60 fathoms from

Point Reyes to Point Arguello.

Two harbor porpoise mortalities were inaccurately reported in Marine Mammal Authorization Permit (MMAP)

fisher self-reports for the California drift gillnet fishery during 1996-98. Both of the mortalities occurred on an observed

fishing trip and were actually short-beaked common dolphins (NMFS, Southwest Fisheries Science Center, unpublished

data). This fishery has not previously been known to take harbor porpoise.

Three fishery-related harbor porpoise strandings were reported in central California in 1998, north of the known

set gillnet fishing areas: two near Bodega Head and one inside San Francisco Bay (NMFS, Southwest Region,

unpublished data). These mortalities were probably taken from the central California harbor porpoise stock, although

it is possible that the northern two animals were taken from the northern California stock and drifted southward to the
52

stranding location. Efforts are underway to identify possible fisheries responsible for these mortalities. Based on

experience with other fisheries (e.g. the set gillnet fishery), the proportion of incidentally killed animals that strand is

generally only a fraction of the total mortality, and therefore these unidentified fisheries are likely to have taken more

than the three observed harbor porpoise.

STATUS OF STOCK

Harbor porpoise in California are not listed as threatened or endangered under the Endangered Species Act nor

as depleted under the Marine Mammal Protection Act. Barlow and Hanan (1995) calculate the status of harbor porpoise

relative to historic carrying capacity (K) using a technique called back-projection. They calculate that the central

California population could have been reduced to between 30% and 97% of K by incidental fishing mortality, depending

on the choice of input parameters. They conclude that there is no practical way to reduce the range of this estimate.

New information does not change this conclusion, and the status of harbor porpoise relative to their Optimum

Sustainable Population (OSP) levels in central California must be treated as unknown. The average annual mortality

for 1996-99 (80 harbor porpoise) is greater than the calculated PBR (56) for central California harbor porpoise;

therefore, the central California harbor porpoise population is “strategic” under the MMPA. The average gillnet

mortality for 1996-99 (80 porpoise per year) is greater than the calculated PBR; therefore, the fishery mortality cannot

be considered insignificant and approaching zero mortality and serious injury rate. The pending closure of the set gillnet

fishery from Point Reyes to Point Arguello inside of 60 fathoms effectively will eliminate set gillnets from most harbor

porpoise habitat in central California and thus it is expected that fishery mortality for this stock will be significantly

reduced. Research activities will continue to monitor the population size and to investigate population trends. There

are no known habitat issues that are of particular concern for this stock.

Table 1. Summary of available information on incidental mortality and injury of harbor porpoise (central CA stock)

in commercial fisheries that might take this species (Cameron and Forney 2000, Forney et al., 2001; NMFS/SWFSC,

unpublished data). Mean annual takes are based on 1995-99 data unless noted otherwise. n/a indicates that data are

not available.

Fishery Name Year(s) Data Type

Percent

Observer

Coverage

Observed

Mortality

Estimated

Mortality (CV in

parentheses)

Mean Annual Takes

(CV in parentheses)

CA angel shark / halibut

and other species large

mesh (>3.5") set gillnet

fishery

1995

1996

1997

1998

1999

1987-90 

and 

1990-94

observer data

1999 observer

data

0%

0%

0%

0%

23.0%

-

-

-

-

 282

 42 (0.19)

 48 (0.19)

 80 (0.19)

57 (0.19)

133 (0.23)2

79 (0.21)1

Unknown fishery 1995-99 Strandings - 3 (in 1998) n/a ≥ 0.60 (n/a)

Minimum total annual takes 80 (0.21)

1Only 1996- 99 mortality estimates are included in the average because of changes in the distribution and amount of fishing effort after 1995 (see

text).

2

 This includes one unidentified cetacean that was almost certainly a harbor porpoise; without this animal the mortality estimate would be 128

(CV=0.23).

REFERENCES

Barlow, J. 1988. Harbor porpoise (Phocoena phocoena) abundance estimation in California, Oregon and Washington:

I. Ship surveys. Fish. Bull. 86:417-432.

Barlow, J. and P. Boveng. 1991. Modeling age-specific mortality for marine mammal populations. Mar. Mamm. Sci.

7(1):84-119.

Barlow, J. and K. A. Forney. 1994. An assessment of the 1994 status of harbor porpoise in California. U.S. Dep.

Commer., NOAA Tech. Memo. NMFS-SWFSC-205. 17pp.

Barlow, J. and D. Hanan. 1995. An assessment of the status of harbor porpoise in central California. Rept. Int.

Whal., Special Issue 16:123-140. 
53

Calambokidis, J. and J. Barlow. 1991. Chlorinated hydrocarbon concentrations and their use for describing population

discreteness in harbor porpoises from Washington, Oregon, and California. pp. 101-110 In: J. E. Reynolds III

and D. K. Odell (eds.) Marine mammal strandings in the United States. NOAA Tech. Rep. NMFS 98. 

Cameron, G. 1998. Cetacean mortality in California gill net fisheries: Preliminary estimates for 1997. Paper

SC/50/SM02 presented to the International Whaling Commission, June 1998 (unpublished). 15 pp. 

Cameron, G.A. and K.A. Forney. 2000. Preliminary Estimates of Cetacean Mortality in California/Oregon Gillnet

Fisheries for 1999. Paper SC/52/O24 presented to the International Whaling Commission, 2000 (unpublished).

12 pp. Available from NMFS, Southwest Fisheries Science Center, P.O. Box 271, La Jolla, California, 92038,

USA.

Chivers, S. Southwest Fisheries Science Center, NMFS, P.O. Box 271, La Jolla, CA 92038

Forney, K. A. 1995. A decline in the abundance of harbor porpoise, Phocoena phocoena, in nearshore waters off

California, 1986-93. Fish. Bull. 93: 741-748.

Forney, K. A. 1999a. The abundance of California harbor porpoise estimated from 1993-97 aerial line-transect

surveys. Admin. Rep. LJ-99-02. Available from Southwest Fisheries Center, National Marine Fisheries

Service, P.O. Box 271, La Jolla, CA 92038. 16pp.

Forney, K. A. 1999b. Trends in harbor porpoise abundance off central California, 1986-95: Evidence for interannual

changes in distribution? J. Cetacean Res. Manage. 1:73-80.

Forney, K. A., J. Barlow, M. M. Muto, M. Lowry, J. Baker, G. Cameron, J. Mobley, C. Stinchcomb, and J.V. Carretta.

2000. U.S. Pacific Marine Mammal Stock Assessments: 2000. U.S. Dep. Commer., NOAA Tech. Memo.

NMFS-SWFSC-300. 276 pp.

Forney, K. A., S. R. Benson, and G. A. Cameron. 2001. Central California gillnet effort and bycatch of sensitive

species, 1990-98. In: E. F. Melvin and J. K. Parrish (eds.), Seabird Bycatch: Trends, Roadblocks and

Solutions, Proceedings of an International Symposium of the Pacific Seabird Group, Semi-Ah-Moo,

Washington, February 1999. University of Alaska Sea Grant, Fairbanks, AK.

Gaskin, D. E. 1984. The harbour porpoise (Phocoena phocoena L.): regional populations, status, and information on

direct and indirect catches. Rep. int. Whal. Commn 34:569-586. 

Green, G. A., J. J. Brueggeman, R. A. Grotefendt, C. E. Bowlby, M. L. Bonnell, and K. C. Balcomb, III. 1992.

Cetacean distribution and abundance off Oregon and Washington, 1989-1990. Ch. 1 In: J. J. Brueggeman

(ed.). Oregon and Washington Marine Mammal and Seabird Surveys. Minerals Management Service Contract

Report 14-12-0001-30426 prepared for the Pacific OCS Region.

Julian, F. and M. Beeson. 1998. Estimates for marine mammal, turtle, and seabird mortality for two California gillnet

fisheries: 1990-95. Fish. Bull. 96:271-284.

Kraus, S. D. A. J. Read, A. Solow, K. Baldwin, T. Spradlin, E. Anderson and J. Williamson. 1997. Acoustic alarms

reduce porpoise mortality. Nature 388:525.

Laake, J. L., J. C. Calambokidis, S. D. Osmek, and D. J. Rugh. 1997. Probability of detecting harbor porpoise from

aerial surveys: estimating g(0). J. Wildl. Manag. 61:63-75.

NMFS, Southwest Fisheries Science Center, P.O. Box 271, La Jolla, CA 92038-0271

NMFS, Southwest Region, 501 West Ocean Blvd, Long Beach, CA 90802-4213

Polacheck, T., F. W. Wenzel, and G. Early. 1995. What do stranding data say about harbor porpoise (Phocoena

phocoena)? Rep. Int. Whal. Comm., Special Issue 16:169-179.

Rosel, P. E. 1992. Genetic population structure and systematic relationships of some small cetaceans inferred from

mitochondrial DNA sequence variation. Ph.D. Dissertation, Univ. Calif. San Diego. 191pp.

Rosel, P. E., A. E. Dizon, and M. G. Haygood. 1995. Variability of the mitochondrial control region in populations

of the harbour porpoise, Phocoena phocoena, on inter-oceanic and regional scales. Can. J. Fish. and Aquat.

Sci. 52:1210-1219.

Trippel, E. A., M. B. Strong, J. M. Terhune, and J. D. Conway. 1999. Mitigation of harbour porpoise (Phocoena

phocoena) by-catch in the gillnet fishery in the lower Bay of Fundy. Can. J. Fish. Aquat. Sci. 56:113-123.

Wade, P. R. and R. P. Angliss. 1997. Guidelines for Assessing Marine Mammal Stocks: Report of the GAMMS

Workshop April 3-5, 1996, Seattle, Washington. U. S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-12.

93 pp.

Woodley, T. H. and A. J. Read. 1991. Potential rates of increase of a harbour porpoise (Phocoena phocoena)

population subjected to incidental mortality in commercial fisheries. Can. J. Fish. Aquat. Sci. 48:2429-2435.
54

Figure 1. Stock boundaries and distributional

range of harbor porpoise along the U.S. west coast.

Shaded area represents harbor porpoise habitat (0 -

200 m) along the U.S. west coast.

Revised 12/31/2001

HARBOR PORPOISE (Phocoena phocoena): Northern California Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

In the Pacific, harbor porpoise are found in coastal and

inland waters from Point Conception, California to Alaska and

across to Kamchatka and Japan (Gaskin 1984). Harbor porpoise

appear to have more restricted movements along the western coast

of the continental U.S. than along the eastern coast. Regional

differences in pollutant residues in harbor porpoise indicate that

they do not move extensively between California, Oregon, and

Washington (Calambokidis and Barlow 1991). That study also

showed some regional differences within California (although the

sample size was small). This pattern stands as a sharp contrast to

the eastern coast of the U.S. and Canada where harbor porpoise

are believed to migrate seasonally from as far south as the

Carolinas to the Gulf of Maine and Bay of Fundy (Polacheck et

al. 1995). A phylogeographic analysis of genetic data from

northeast Pacific harbor porpoise did not show complete

concordance between DNA sequence types and geographic

location (Rosel 1992). However, an analysis of molecular

variance (AMOVA) of the same data with additional samples

found significant genetic differences for four of the six pair-wise

comparisons between the four areas investigated: California,

Washington, British Columbia, and Alaska (Rosel et al. 1995).

These results demonstrate that harbor porpoise along the west

coast of North America are not panmictic or migratory, and

movement is sufficiently restricted that genetic differences have

evolved. Recent preliminary genetic analyses of samples ranging

from Monterey Bay, California to Vancouver Island, British

Columbia indicate that there are at least nine genetically distinct

populations (S. Chivers, pers. comm.). 

In their assessment of harbor porpoise, Barlow and

Hanan (1995) recommended that the animals inhabiting central California (defined to be from Point Conception to the

Russian River) be treated as a separate stock. Their justifications for this were: 1) fishery mortality of harbor porpoise

is limited to central California, 2) movement of individual animals appears to be restricted within California, and

consequently 3) fishery mortality could cause the local depletion of harbor porpoise if central California is not managed

separately. Although geographic structure exists along an almost continuous distribution of harbor porpoise from

California to Alaska, stock boundaries are difficult to draw because any rigid line is (to a greater or lesser extent)

arbitrary from a biological perspective. Nonetheless, failure to recognize geographic structure by defining management

stocks can lead to depletion of local populations. Following the guidance of Barlow and Hanan (1995), we will consider

the harbor porpoise in northern California as a separate stock. Based on recent genetic findings (Chivers, pers.

comm.), U.S. West coast stocks are likely to be re-evaluated once ongoing analyses have been finalized and peerreviewed. For the 2000 Marine Mammal Protection Act (MMPA) Stock Assessment Reports, other Pacific coast harbor

porpoise stocks include: 1) a central California stock, 2) an Oregon/Washington coast stock, 3) an Inland Washington

stock, 4) a Southeast Alaska stock, 5) a Gulf of Alaska stock, and 6) a Bering Sea stock. The stock assessment reports

for central California harbor porpoise appears in this volume. Oregon and Washington stock assessment reports appear

in Forney et al. (2000) and are also reprinted unrevised in this volume. The three Alaska harbor porpoise stocks are

reported separately in the Stock Assessment Reports for the Alaska Region.
55

0.00 

0.20 

0.40 

0.60 

0.80 

1.00 

1.20 

Relative abundance (porpoise/km)

87 89 91 93 95 97 99 

Year

Figure 2. Relative abundance (+/- one standard error) of northern

California harbor porpoise, 1989-99, adjusted for sea state and cloud

cover (following methods of Forney 1995).

POPULATION SIZE

 Previous estimates of abundance for California harbor porpoise were based on aerial surveys conducted

between the coast and the 50-fm isobath during 1988-95 (Barlow and Forney 1994, Forney 1999a). These estimates

did not include an unknown number of animals found in deeper waters. Barlow (1988) found that the vast majority of

harbor porpoise in California were within the 0-50-fm depth range; however, Green et al. (1992) found that 24% of

harbor porpoise seen during aerial surveys of Oregon and Washington were between the 100m and 200m isobaths (55

to 109 fathoms). A recent analysis of harbor porpoise trends including oceanographic data suggests that the proportion

of California harbor porpoise in deeper waters may vary between years (Forney 1999b; see Current Population Trend

below). In 1999, aerial surveys extended farther offshore (to the 200m depth contour or 15 nmi distance, whichever

is farther) to provide a more complete abundance estimate. Based on pooled 1995-99 aerial survey data including data

from both inshore and offshore areas, an updated estimate of abundance for the northern California harbor porpoise

stock is 15,198 harbor porpoise (CV=0.39; NMFS, K. Forney, unpublished data, following methods of Forney 1999a).

Approximately 2,554 (CV=0.80) of these animals were estimated for the offshore stratum. The estimate for the inshore

stratum (12,644, CV=0.38) is similar to the previous estimate of 11,066 (CV=0.39) for 1993-97 (Forney 1999b).

Minimum Population Estimate

The minimum population estimate for harbor porpoise in northern California is taken as the lower 20th

percentile of the log-normal distribution of the abundance estimated from the 1995-99 aerial surveys, or 11,054 animals.

This estimate includes harbor porpoise within an area extending to the 200m isobath or 15 nmi, whichever is farther

from shore.

Current Population Trend

Forney (1999b) examines trends in relative harbor porpoise abundance in central and northern California based

on aerial surveys from 1989-95. No significant trends were evident over this time period for the Northern California

Stock. The 1997-99 survey results

continue to show no trend in relative

abundance (Figure 2).

CURRENT AND MAXIMUM NET

PRODUCTIVITY RATES

Based on what are argued to be

biological limits of the species (i.e. females

give birth first at age 4 and produce one

calf per year until death), the theoretical,

maximum-conceivable growth rate of a

closed harbor porpoise population was

estimated as 9.4% per year (Barlow and

Boveng 1991). This maximum theoretical

rate may not be achievable for any real

population. [Woodley and Read (1991)

calculate a maximum growth rate of

approximately 5% per year, but their

argument for this being a maximum (i.e.

that porpoise survival rates cannot exceed

those of Himalayan thar) is not well

justified.] Population growth rates have not actually been measured for any harbor porpoise population. Because a

reliable estimate of the maximum net productivity rate is not available for northern California harbor porpoise, it is

recommended that the cetacean maximum theoretical net productivity rate (RMAX) of 4% (Wade and Angliss 1997) be

employed.

POTENTIAL BIOLOGICAL REMOVAL

The potential biological removal (PBR) level for this stock is calculated as the minimum population size
56

(11,054) times one half the default maximum net growth rate for cetaceans (1⁄2 of 4%) times a recovery factor of 1.0 (for

a species within its Optimal Sustainable Population; Wade and Angliss 1997), resulting in a PBR of 221. 

HUMAN-CAUSED MORTALITY

Fishery Information

The incidental capture of harbor porpoise in California is largely limited to set gillnet fisheries in central

California. Coastal setnets are not allowed in northern California (to protect salmon resources there). However, one

harbor porpoise mortality was documented from stranding reports for the Klamath River tribal salmon gillnet fishery

in 1995 (NMFS, Southwest Region, unpublished data). Additionally, in 1998, two harbor porpoise strandings near

Bodega Head were attributed to fishery-related mortality, but the responsible fishery is unknown. Although the stranding

location falls within the range of the central California harbor porpoise stock and this is probably the source stock for

the mortalities, it is possible that these animals were taken from the northern California stock and subsequently drifted

southward to the stranding location. Efforts are underway to identify fisheries that may have been responsible.

Table 1. Summary of available information on incidental mortality and injury of harbor porpoise (northern CA stock)

in fisheries that might take this species. n/a indicates that data are not available.

Fishery Name Year(s) Data Type Percent Observer

Coverage

Observed

Mortality

Estimated Mortality

(CV in parentheses)

Mean Annual Takes

(CV in parentheses)

CA Klamath River tribal

salmon gillnet fishery 1995-99 Stranding

reports

n/a 1(1995) ≥ 1 ≥ 0.2 (n/a)

Minimum total annual takes ≥ 0.2 (n/a)

 

STATUS OF STOCK

Harbor porpoise in California are not listed as threatened or endangered under the Endangered Species Act nor

as depleted under the Marine Mammal Protection Act. There are no known habitat issues that are of particular concern

for this stock. Because of the lack of recent or historical sources of human-caused mortality, the harbor porpoise stock

in northern California has been concluded to be within their Optimum Sustainable Population (OSP) level (Barlow and

Forney 1994). Because the known human-caused mortality or serious injury (0.2 harbor porpoise per year) is less than

the PBR (221), this stock is not considered a "strategic" stock under the MMPA. Because average annual fishery

mortality is less than 10% of the PBR, the fishery mortality can be considered insignificant and approaching zero

mortality and serious injury rate.

REFERENCES

Barlow, J. 1988. Harbor porpoise (Phocoena phocoena) abundance estimation in California, Oregon and Washington:

I. Ship surveys. Fish. Bull. 86:417-432.

Barlow, J. and P. Boveng. 1991. Modeling age-specific mortality for marine mammal populations. Mar. Mamm. Sci.

7(1):84-119.

Barlow, J. and K. A. Forney. 1994. An assessment of the 1994 status of harbor porpoise in California. U.S. Dep.

Commer., NOAA Tech. Memo. NMFS-SWFSC-205. 17 pp.

Barlow, J. and D. Hanan. 1995. An assessment of the status of harbor porpoise in central California. Rept. Int.

Whal., Special Issue 16:123-140. 

Calambokidis, J. and J. Barlow. 1991. Chlorinated hydrocarbon concentrations and their use for describing population

discreteness in harbor porpoises from Washington, Oregon, and California. pp. 101-110 In: J. E. Reynolds

III and D. K. Odell (eds.) Marine mammal strandings in the United States. NOAA Tech. Rep. NMFS 98.

Chivers, S. Southwest Fisheries Science Center, NMFS, P.O. Box 271, La Jolla, CA 92038

Forney, K. A. 1999a. The abundance of California harbor porpoise estimated from 1993-97 aerial line-transect

surveys. Admin. Rep. LJ-99-02. Southwest Fisheries Center, National Marine Fisheries Service, P.O. Box

271, La Jolla, CA 92038. 16 pp.

Forney, K. A. 1999b. Trends in harbor porpoise abundance off central California, 1986-95: Evidence for interannual

changes in distribution? J. Cetacean Res. Manage. 1:73-80.

Gaskin, D. E. 1984. The harbour porpoise (Phocoena phocoena L.): regional populations, status, and information on
57

direct and indirect catches. Rep. int. Whal. Commn 34:569-586. 

Green, G. A., J. J. Brueggeman, R. A. Grotefendt, C. E. Bowlby, M. L. Bonnell, and K. C. Balcomb, III. 1992.

Cetacean distribution and abundance off Oregon and Washington, 1989-1990. Ch. 1 In: J. J. Brueggeman

(ed.). Oregon and Washington Marine Mammal and Seabird Surveys. Minerals Management Service Contract

Report 14-12-0001-30426 prepared for the Pacific OCS Region.

Laake, J. L., J. C. Calambokidis, S. D. Osmek, and D. J. Rugh. 1997. Probability of detecting harbor porpoise from

aerial surveys: estimating g(0). J. Wildl. Manag. 61:63-75.

NMFS, Southwest Fisheries Science Center, P.O. Box 271, La Jolla, CA 92038-0271

NMFS, Southwest Region, 501 West Ocean Blvd, Long Beach, CA 90802-4213

Polacheck, T., F. W. Wenzel, and G. Early. 1995. What do stranding data say about harbor porpoise (Phocoena

phocoena). Rep. Int. Whal. Comm., Special Issue 16:169-179.

Rosel, P. E. 1992. Genetic population structure and systematic relationships of some small cetaceans inferred from

mitochondrial DNA sequence variation. Ph.D. Dissertation, Univ. Calif. San Diego. 191pp.

Rosel, P. E., A. E. Dizon, and M. G. Haygood. 1995. Variability of the mitochondrial control region in populations

of the harbour porpoise, Phocoena phocoena, on inter-oceanic and regional scales. Can. J. Fish. and Aquat.

Sci. 52:1210-1219.

Wade, P. R. and R. P. Angliss. 1997. Guidelines for Assessing Marine Mammal Stocks: Report of the GAMMS

Workshop April 3-5, 1996, Seattle, Washington. U. S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-12.

93 pp.

Woodley, T. H. and A. J. Read. 1991. Potential rates of increase of a harbour porpoise (Phocoena phocoena)

population subjected to incidental mortality in commercial fisheries. Can. J. Fish. Aquat. Sci. 48:2429-2435.
58

OR/WA

Coast

stock

Inland WA stock

Northern CA stock

Figure 1. Approximate distribution of harbor porpoise in

the U.S. Pacific Northwest (shaded area). Stock

boundaries separating the stocks are shown.

Revised 12/15/2000

HARBOR PORPOISE (Phocoena phocoena): Oregon/Washington Coast Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

In the eastern North Pacific Ocean, the harbor

porpoise ranges from Point Barrow, along the Alaskan coast,

and down the west coast of North America to Point

Conception, California (Gaskin 1984). Harbor porpoise

primarily frequent coastal waters. Harbor porpoise are

known to occur year-round in the inland trans-boundary area

of Washington and British Columbia, Canada (Osborne et

al. 1988), and along the Oregon/Washington coast (Barlow

1988, Barlow et al. 1988, Green et al. 1992). Aerial survey

data from coastal Oregon and Washington, collected during

all seasons, suggests that harbor porpoise distribution varies

by depth (Green et al. 1992). Although distinct seasonal

changes in abundance along the west coast have been noted,

and attributed to possible shifts in distribution to deeper

offshore waters during late winter (Dohl et al. 1983, Barlow

1988), harbor porpoise have also been conspicuously absent

in offshore areas in late November (B. Taylor, pers. comm.)

leaving a gap in the current understanding of their

movements.

Stock discreteness in the eastern North Pacific was

analyzed using mitochondrial DNA from samples collected

along the west coast (Rosel 1992) and is summarized in

Osmek et al. (1994). Two distinct mtDNA groupings or

clades exist. One clade is present in California, Washington,

British Columbia, and Alaska (no samples were available

from Oregon), while the other is found only in California

and Washington. Although these two clades are not geographically distinct by latitude, the results may indicate a low

mixing rate for harbor porpoise along the west coast of North America. Investigation of pollutant loads in harbor

porpoise ranging from California to the Canadian border also suggests restricted harbor porpoise movements

(Calambokidis and Barlow 1991). Further genetic testing of the same data mentioned above, along with additional

samples, found significant genetic differences for four of the six pair-wise comparisons between the four areas

investigated: California, Washington, British Columbia, and Alaska (Rosel et al. 1995). These results demonstrate that

harbor porpoise along the west coast of North America are not panmictic or migratory, and that movement is sufficiently

restricted to evolve genetic differences. This is consistent with low movement suggested by genetic analysis of harbor

porpoise specimens from the North Atlantic, where numerous stocks have been delineated with clinal differences over

areas as small as the waters surrounding the British Isles.

Using the 1990-91 aerial survey data of Calambokidis et al. (1993) for water depths < 50 fathoms, Osmek et

al. (1996) found significant differences in harbor porpoise mean densities (z=5.9, p<0.01) between the waters of coastal

Oregon/Washington and inland Washington/southern British Columbia, Canada (i.e., Strait of Juan de Fuca/San Juan

Islands). Although differences in density exist between coastal Oregon/Washington and inland Washington, a specific

stock boundary line cannot be identified based upon biological or genetic differences. However, because harbor

porpoise movements and rates of intermixing within the northeast Pacific are restricted, there has been a significant

decline in harbor porpoise sightings within southern Puget Sound since the 1940s and, following a risk averse

management strategy, two stocks are recognized to occur in Oregon and Washington waters (the Oregon/Washington

Coast stock and the Inland Washington stock), with the boundary at Cape Flattery. Recent genetic evidence suggests

that the population of eastern North Pacific harbor porpoise is more finely structured than is currently recognized (S.

Chivers, pers. comm.). All relevant data (e.g., genetic samples, contaminant studies, and satellite tagging) will be

reviewed to determine whether to adjust the stock boundaries for harbor porpoise in Oregon and Washington waters.
59

In their assessment of California harbor porpoise, Barlow and Hanan (1995) recommended two stocks be

recognized in California, with the stock boundary at the Russian River. Based on the above information, four separate

harbor porpoise stocks are recognized to occur along the west coast of the continental U.S. (see Fig. 1): 1) the Inland

Washington stock, 2) the Oregon/Washington Coast stock, 3) the Northern California stock, and 4) the Central

California stock. This report considers only the Oregon/Washington Coast stock, with stock assessment reports for the

Inland Washington and both California stocks appearing in this volume. Three harbor porpoise stocks are also

recognized in the inland and coastal waters of Alaska, including the Southeast Alaska, Gulf of Alaska, and Bering Sea

stocks. The three Alaska harbor porpoise stocks are reported separately in the Stock Assessment Reports for the Alaska

Region. The harbor porpoise occurring in British Columbia have not been included in any stock assessment report from

either the Alaska Region or Pacific Northwest (Oregon/Washington).

POPULATION SIZE

In August and September 1997, an aerial survey of Oregon, Washington, and southern British Columbia coastal

waters, from shore to 200 m depth, resulted in an observed abundance of 13,036 (CV=0.11) harbor porpoise in U.S.

waters (Laake et al. 1998a). Using a correction factor of 3.42 (1/g(0); g(0)=0.292, CV=0.366) to adjust for groups

missed by aerial observers, the corrected estimate of abundance for harbor porpoise in coastal Oregon and Washington

waters is 44,644 (CV=0.38). This estimate represents a substantial increase over the 1991 estimate of 26,175 (Osmek

et al. 1996) due to: 1) the larger sampling region in the 1997 survey (out to water depths of 200 m vs. 91 m in 1991),

and 2) a different estimate of g(0) (Laake et al. 1998a).

Minimum Population Estimate

The minimum population estimate (NMIN) for this stock is calculated using Equation 1 from the PBR Guidelines

(Wade and Angliss 1997): NMIN = N/exp(0.842*[ln(1+[CV(N)]2)]1⁄2). Using the population estimate (N) of 44,644 and

its associated CV(N) of 0.38, NMIN for the Oregon/Washington Coast stock of harbor porpoise is 32,769.

Current Population Trend

There are no reliable data on population trends of harbor porpoise for coastal Oregon, Washington, or British

Columbia waters.

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

A reliable estimate of the maximum net productivity rate is currently not available for harbor porpoise.

Therefore, until additional data become available, it is recommended that the cetacean maximum theoretical net

productivity rate (RMAX) of 4% (Wade and Angliss 1997) be employed for the Oregon/Washington Coast harbor

porpoise stock.

POTENTIAL BIOLOGICAL REMOVAL

The potential biological removal (PBR) level for this stock is calculated as the minimum population size

(32,769) times one-half the default maximum net growth rate for cetaceans (1⁄2 of 4%) times a recovery factor of 0.5 (for

a stock of unknown status, Wade and Angliss 1997), resulting in a PBR of 328 harbor porpoise per year.

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Fisheries Information

Within the EEZ boundaries of coastal Oregon and Washington, human-caused (fishery) mortalities of harbor

porpoise are presently known to occur only in the northern Washington marine set gillnet fishery. During 1992-1993

the WA/OR Lower Columbia River, WA Grays Harbor, and WA Willapa Bay drift gillnet fisheries were monitored at

observer coverages of approximately 4% and 2%, respectively. There were no observed harbor porpoise mortalities

in these fisheries.

NMFS observers monitored the northern Washington marine set gillnet fishery during 1993-1998 (Gearin et

al. 1994, 2000; P. Gearin, unpubl. data); 1994 observer data recently became available and will be included in a future

stock assessment report. For the entire area fished (coastal + inland waters), observer coverage ranged from

approximately 40 to 98% during those years. Fishing effort is conducted within the range of both harbor porpoise stocks

(Oregon/Washington Coast and Inland Washington stocks) occurring in Washington State waters. Some of the animals
60

taken in the inland waters portion of the fishery (see the Inland Washington stock assessment report for details) may

have been animals from the coastal stock. Similarly, some of the animals taken in the coastal portion of the fishery may

have been from the inland stock. For the purposes of this stock assessment report, the animals taken in the inland

portion of the fishery are assumed to have belonged to the Inland Washington stock and the animals taken in the coastal

portion of the fishery are assumed to have belonged to the Oregon/Washington Coast stock. Some movement of harbor

porpoise between Washington’s coastal and inland waters is likely, but it is currently not possible to quantify the extent

of such movements. Accordingly, Table 1 includes data only from that portion of the northern Washington marine set

gillnet fishery occurring within the range of the Oregon/Washington Coast stock (those waters south and west of Cape

Flattery), where observer coverage was 100% in 1995-1997. No fishing effort occurred in the coastal portion of the

fishery in 1993 or 1998. Data from 1993 to 1998 are included in Table 1, although the mean estimated annual mortality

is calculated using the most recent 5 years of available data. The mean estimated mortality for this fishery is 12.4

(CV=0.46) harbor porpoise per year from this stock.

Table 1. Summary of incidental mortality of harbor porpoise (Oregon/Washington Coast stock) in commercial and

tribal fisheries and calculation of the mean annual mortality rate; n/a indicates that data are not available. Mean annual

takes are based on 1994-98 data unless noted otherwise.

Fishery name Years

Data

type

Percent

observer

coverage

Observed 

mortality

Estimated

mortality

 Mean annual

 takes (CV in

parentheses)

Northern WA marine set gillnet

(tribal fishery: coastal waters)

93

94

95

96

97

98

obs data no fishery

n/a

100%

100%

100%

no fishery

0

n/a

20

29

13

0

0

n/a

20

29

13

0

12.4 (0.46)1

Estimated total annual takes 12.4 (0.46)

1

1993 and 1995-98 mortality estimates are included in the average.

The 1995-1997 data for the northern Washington marine set gillnet fishery were collected as part of an

experiment, conducted in cooperation with the Makah Tribe, designed to explore the merits of using acoustic alarms

to reduce bycatch of harbor porpoise in salmon gillnets. Results in 1995-1996 indicated that the nets equipped with

acoustic alarms had significantly lower entanglement rates, as only 2 of the 49 mortalities occurred in alarmed nets

(Gearin et al. 1996, 2000; Laake et al. 1997). Harbor porpoise were displaced by an acoustic buffer around the net, but

it is unclear whether the porpoise were repelled by the alarms or whether it was their prey that were repelled (Kraus et

al. 1997, Laake et al. 1998b). Because this fishery is likely to have acoustic devices on all nets in the future, the mean

mortality estimated from non-alarmed nets may not be applicable. In 1997, 13 mortalities were observed (100%

observer coverage) in this fishery and 96% of the sets were equipped with acoustic alarms (Gearin et al. 2000; P. Gearin,

unpubl. data).

An additional source of information on the number of harbor porpoise killed or injured incidental to

commercial fishery operations is the self-reported fisheries information required of vessel operators by the MMPA.

During the period between 1994 and 1998, there were no fisher self-reports of harbor porpoise mortalities from any

fisheries operating within the range of the Oregon/Washington Coast stock. However, because logbook records (fisher

self-reports required during 1990-94) are most likely negatively biased (Credle et al. 1994), these are considered to be

minimum estimates. Self-reported fisheries data are incomplete for 1994, not available for 1995, and considered

unreliable after 1995 (see Appendix 4 in Hill and DeMaster 1998). 

There have been no fishery-related strandings of harbor porpoise from this stock dating back to at least 1990.

STATUS OF STOCK

Harbor porpoise are not listed as “depleted” under the MMPA or listed as “threatened “ or “endangered” under

the Endangered Species Act. Based on the currently available data, the level of human-caused mortality and serious

injury (12) does not exceed the PBR (328). Therefore, the Oregon/Washington Coast stock of harbor porpoise is not

classified as strategic. The total fishery mortality and serious injury for this stock (12; based on observer data) is not
61

known to exceed 10% of the calculated PBR (33) and, therefore, can be considered to be insignificant and approaching

zero mortality and serious injury rate. The status of this stock relative to its Optimum Sustainable Population (OSP)

level and population trends is unknown.

REFERENCES

Barlow, J. 1988. Harbor porpoise,Phocoena phocoena, abundance estimation for California, Oregon, and Washington:

I. Ship surveys. Fish. Bull. 86:417-432.

Barlow, J., and D. Hanan. 1995. An assessment of the status of harbor porpoise in central California. Rep. Int. Whal.

Commn. Special Issue 16:123-140.

Barlow, J., C. W. Oliver, T. D. Jackson, and B. L. Taylor. 1988. Harbor porpoise, Phocoena phocoena, abundance

estimation for California, Oregon, and Washington: II. Aerial Surveys. Fish. Bull. 86:433-444.

Calambokidis, J., and J. Barlow. 1991. Chlorinated hydrocarbon concentrations and their use for describing population

discreteness in harbor porpoises from Washington, Oregon, and California. Reynolds, J. E., III, and D. K.

Odell (eds.), Proceedings of the second marine mammal stranding workshop: 3-5 December 1987, Miami,

Florida. NMFS, NOAA Tech. Rep. NMFS 98:101-110.

Calambokidis, J., J. C. Cubbage, J. R. Evenson, S. D. Osmek, J. L. Laake, P. J. Gearin, B. J. Turnock, S. J. Jeffries, and

R. F. Brown. 1993. Abundance estimates of harbor porpoise in Washington and Oregon waters. Final Report

by Cascadia Research, Olympia, WA, to National Marine Mammal Laboratory, AFSC, NMFS, Seattle, WA.

55 pp.

Chivers, S. Southwest Fisheries Science Center, NMFS, P.O. Box 271, La Jolla, CA 92038.

Credle, V. R., D. P. DeMaster, M. M. Merklein, M. B. Hanson, W. A. Karp, and S. M. Fitzgerald (eds.). 1994. NMFS

observer programs: minutes and recommendations from a workshop held in Galveston, Texas, November 10-

11, 1993. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-94-1. 96 pp.

Dohl, T. P., R. C. Guess, M. L. Duman, and R. C. Helm. 1983. Cetaceans of central and northern California, 1980-

1983: status, abundance, and distribution. OCS Study MMS 84-0045. Pacific OCS Region Minerals

Management Service, 1340 Sixth Street, Los Angeles, CA 90014. 284 pp.

Gaskin, D. E. 1984. The harbour porpoise Phocoena phocoena (L.): regional populations, status, and information on

direct and indirect catches. Rep. Int. Whal. Commn. 34:569-586.

Gearin, P. J. National Marine Mammal Laboratory, AFSC, NMFS, 7600 Sand Point Way NE, Seattle, WA 98115.

Gearin, P. J., S. R. Melin, R. L. DeLong, H. Kajimura, and M. A. Johnson. 1994. Harbor porpoise interactions with

a chinook salmon set-net fishery in Washington State. Rep. Int. Whal. Commn. Special Issue 15:427-438.

Gearin, P. J., M. E. Gosho, L. Cooke, R. DeLong, and J. Laake. 1996. Acoustic alarm experiment in the 1995 northern

Washington marine setnet fishery: methods to reduce by-catch of harbor porpoise. Paper SC/48/SM10

presented to the International Whaling Commission, June 1996 (unpublished). 15 pp.

Gearin, P. J., M. E. Gosho, J. L. Laake, L. Cooke, R. L. DeLong, and K. M. Hughes. 2000. Experimental testing of

acoustic alarms (pingers) to reduce bycatch of harbour porpoise, Phocoena phocoena, in the state of

Washington. J. Cetacean Res. Manage. 2(1):1-9.

Green, G. A., J. J. Brueggeman, R. A. Grotefendt, C. E. Bowlby, M. L. Bonnel, and K. C. Balcomb. 1992. Cetacean

distribution and abundance off Oregon and Washington, 1989-1990. Ch. 1, In: Brueggeman, J. J. (ed.),

Oregon and Washington marine mammal and seabird surveys. Final Rep. OCS Study MMS 91-0093.

Hill, P. S., and D. P. DeMaster. 1998. Alaska marine mammal stock assessments, 1998. U.S. Dep. Commer., NOAA

Tech. Memo. NMFS-AFSC-97. 166 pp.

Kraus, S. D., A. J. Read, A. Solow, K. Baldwin, T. Spradlin, E. Anderson, and J. Williamson. 1997. Acoustic alarms

reduce porpoise mortality. Nature 388:525.

Laake, J. L., P. J. Gearin, M. E. Gosho, and R. L. DeLong. 1997. Evaluation of effectiveness of pingers to reduce

incidental entanglement of harbor porpoise in a set gillnet fishery. Pp. 75-81, In: Hill, P. S., and D. P.

DeMaster (eds.), MMPA and ESA Implementation Program, 1996. AFSC Processed Report 97-10. 255 pp.

Available at National Marine Mammal Laboratory, 7600 Sand Point Way NE, Seattle, WA 98115.

Laake, J., J. Calambokidis, and S. Osmek. 1998a. Survey report for the 1997 aerial surveys for harbor porpoise and

other marine mammals of Oregon, Washington and British Columbia outside waters. Pp. 77-97, In: Hill, P.

S., and D. P. DeMaster (eds.), MMPA and ESA Implementation Program, 1997. AFSC Processed Report 98-

10. 246 pp. Available at National Marine Mammal Laboratory, 7600 Sand Point Way NE, Seattle, WA 98115.
62

Laake, J. L., D. J. Rugh, and L. S. Baraff. 1998b. Observations of harbor porpoise in the vicinity of acoustic alarms

on a set gillnet. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-AFSC-84. 40 pp.

Osborne, R., J. Calambokidis, and E. M. Dorsey. 1988. A Guide to Marine Mammals of Greater Puget Sound. Island

Publishers, Anacortes, WA. 191 pp.

Osmek, S. D., P. E. Rosel, A. E. Dizon, and R. L. DeLong. 1994. Harbor porpoise, Phocoena phocoena, population

assessment in Oregon and Washington, 1993. 1993 Annual Report to the MMPA Assessment Program, Office

of Protected Resources, NMFS, NOAA, 1335 East-West Highway, Silver Spring, MD 20910. 14 pp.

Available at National Marine Mammal Laboratory, 7600 Sand Point Way NE, Seattle, WA 98115.

Osmek, S., J. Calambokidis, J. Laake, P. Gearin, R. DeLong, J. Scordino, S. Jeffries, and R. Brown. 1996. Assessment

of the status of harbor porpoises, Phocoena phocoena, in Oregon and Washington waters. U.S. Dep. Commer.,

NOAA Tech. Memo. NMFS-AFSC-76. 46 pp.

Rosel, P. E. 1992. Genetic population structure and systematic relationships of some small cetaceans inferred from

mitochondrial DNA sequence variation. Ph.D. Thesis, Univ. Calif. San Diego, La Jolla, CA. 191 pp.

Rosel, P. E., A. E. Dizon, and M. G. Haygood. 1995. Variability of the mitochondrial control region in populations

of the harbour porpoise, Phocoena phocoena, on inter-oceanic and regional scales. Can. J. Fish. and Aquat.

Sci. 52:1210-1219.

Taylor, B. L. Southwest Fisheries Science Center, NMFS, P.O. Box 271, La Jolla, CA 92038.

Wade, P. R., and R. Angliss. 1997. Guidelines for assessing marine mammal stocks: report of the GAMMS workshop

April 3-5, 1996, Seattle, Washington. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-12. 93 pp.
63

OR/WA

Coast

stock

Inland WA stock

Northern CA stock

Figure 1. Approximate distribution of harbor porpoise

in the U.S. Pacific Northwest (shaded area). Stock

boundaries separating the stocks are shown.

Revised 12/15/2000

HARBOR PORPOISE (Phocoena phocoena): Washington Inland Waters Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

In the eastern North Pacific Ocean, the harbor

porpoise ranges from Point Barrow, along the Alaskan

coast, and down the west coast of North America to Point

Conception, California (Gaskin 1984). Harbor porpoise

primarily frequent coastal waters. Harbor porpoise are

known to occur year-round in the inland trans-boundary

area of Washington and British Columbia, Canada (Osborne

et al. 1988), and along the Oregon/Washington coast

(Barlow 1988, Barlow et al. 1988, Green et al. 1992).

Aerial survey data from coastal Oregon and Washington,

collected during all seasons, suggests that harbor porpoise

distribution varies by depth (Green et al. 1992). Although

distinct seasonal changes in abundance along the west coast

have been noted, and attributed to possible shifts in

distribution to deeper offshore waters during late winter

(Dohl et al. 1983, Barlow 1988), harbor porpoise have also

been conspicuously absent in offshore areas in late

November (B. Taylor, pers. comm.) leaving a gap in the

current understanding of their movements.

Stock discreteness in the eastern North Pacific was

analyzed using mitochondrial DNA from samples collected

along the west coast (Rosel 1992) and is summarized in

Osmek et al. (1994). Two distinct mtDNA groupings or

clades exist. One clade is present in California,

Washington, British Columbia, and Alaska (no samples were available from Oregon), while the other is found only in

California and Washington. Although these two clades are not geographically distinct by latitude, the results may

indicate a low mixing rate for harbor porpoise along the west coast of North America. Investigation of pollutant loads

in harbor porpoise ranging from California to the Canadian border also suggests restricted harbor porpoise movements

(Calambokidis and Barlow 1991). Further genetic testing of the same data mentioned above, along with additional

samples, found significant genetic differences for four of the six pair-wise comparisons between the four areas

investigated: California, Washington, British Columbia, and Alaska (Rosel et al. 1995). These results demonstrate that

harbor porpoise along the west coast of North America are not panmictic or migratory, and that movement is sufficiently

restricted to evolve genetic differences. This is consistent with low movement suggested by genetic analysis of harbor

porpoise specimens from the North Atlantic, where numerous stocks have been delineated with clinal differences over

areas as small as the waters surrounding the British Isles.

Using the 1990-1991 aerial survey data of Calambokidis et al. (1993) for water depths < 50 fathoms, Osmek

et al. (1996) found significant differences in harbor porpoise mean densities (z=5.9, p<0.01) between the waters of

coastal Oregon/Washington and inland Washington/southern British Columbia, Canada (i.e., Strait of Juan de Fuca/San

Juan Islands). Although differences in density exist between coastal Oregon/Washington and inland Washington, a

specific stock boundary line cannot be identified based upon biological or genetic differences. However, because harbor

porpoise movements and rates of intermixing within the northeast Pacific are restricted, there has been a significant

decline in harbor porpoise sightings within southern Puget Sound since the 1940s and, following a risk averse

management strategy, two stocks are recognized to occur in Oregon and Washington waters (the Oregon/Washington

Coast stock and the Inland Washington stock), with the boundary at Cape Flattery. Recent genetic evidence suggests

that the population of eastern North Pacific harbor porpoise is more finely structured than is currently recognized (S.

Chivers, pers. comm.). All relevant data (e.g., genetic samples, contaminant studies, and satellite tagging) will be

reviewed to determine whether to adjust the stock boundaries for harbor porpoise in Oregon and Washington waters.

In their assessment of California harbor porpoise, Barlow and Hanan (1995) recommended two stocks be
64

recognized in California, with the stock boundary at the Russian River. Based on the above information, four separate

harbor porpoise stocks are recognized to occur along the west coast of the continental U.S. (see Fig. 1): 1) the Inland

Washington stock, 2) the Oregon/Washington Coast stock, 3) the Northern California stock, and 4) the Central

California stock. This report considers only the Inland Washington stock, with stock assessment reports for the

Oregon/Washington Coast and both California stocks appearing in this volume. Three harbor porpoise stocks are also

recognized in the inland and coastal waters of Alaska, including the Southeast Alaska, Gulf of Alaska, and Bering Sea

stocks. The three Alaska harbor porpoise stocks are reported separately in the Stock Assessment Reports for the Alaska

Region. The harbor porpoise occurring in British Columbia have not been included in any stock assessment report from

either the Alaska Region or Pacific Northwest (Oregon/Washington).

POPULATION SIZE

Aerial surveys of the inside waters of Washington and southern British Columbia were conducted during

August of 1996 (Calambokidis et al. 1997). These aerial surveys included the Strait of Juan de Fuca, San Juan Islands,

Gulf Islands, and Strait of Georgia, which includes waters inhabited by harbor porpoise from British Columbia, as well

as the Inland Washington stock. A total of 2,117 km of survey effort was completed within U.S. waters, resulting in

an uncorrected abundance of 1,025 (CV=0.151) harbor porpoise in the inside waters of Washington (Calambokidis et

al. 1997, Laake et al. 1997a). When corrected for availability and perception bias, using a correction factor of 3.42

(1/g(0); g(0)=0.292, CV=0.366), the estimated abundance for the Inland Washington stock of harbor porpoise is 3,509

(CV=0.396) animals (Laake et al. 1997a, 1997b).

Minimum Population Estimate

The minimum population estimate (NMIN) for this stock is calculated using Equation 1 from the PBR Guidelines

(Wade and Angliss 1997): NMIN = N/exp(0.842*[ln(1+[CV(N)]2)]1⁄2). Using the population estimate (N) of 3,509 and

its associated CV(N) of 0.396, NMIN for the Inland Washington stock of harbor porpoise is 2,545.

Current Population Trend

There are no reliable data on long-term population trends of harbor porpoise for most waters of Oregon,

Washington, or British Columbia. For comparability to the 1996 survey, a re-analysis of the 1991 aerial survey data

was conducted (Calambokidis et al. 1997). The abundance of harbor porpoise in the Inland Washington stock in 1996

was not significantly different than in 1991 (Laake et al. 1997a). 

A different situation exists in southern Puget Sound where harbor porpoises are now rarely observed, a sharp

contrast to 1942 when they were considered common in those waters (Scheffer and Slipp 1948). Although quantitative

data for this area are lacking, marine mammal survey effort (Everitt et al. 1980), stranding records since the early 1970s

(Osmek et al. 1995), and the results of harbor porpoise surveys of 1991 (Calambokidis et al. 1992) and 1994 (Osmek

et al. 1995) indicate that harbor porpoise abundance has declined in southern Puget Sound. In 1994 a total of 769 km

of vessel survey effort and 492 km of aerial survey effort conducted during favorable sighting conditions produced no

sightings of harbor porpoise in southern Puget Sound. Reasons for the apparent decline are unknown, but it may be

related to fishery interactions, pollutants, vessel traffic, or other activities that may affect harbor porpoise occurrence

and distribution in this area (Osmek et al. 1995). Research to identify trends in harbor porpoise abundance is also

needed for the other areas within inland Washington.

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

A reliable estimate of the maximum net productivity rate is not currently available for harbor porpoise. Hence,

until additional data become available, it is recommended that the cetacean maximum theoretical net productivity rate

(RMAX) of 4% (Wade and Angliss 1997) be employed for the Inland Washington harbor porpoise stock.

POTENTIAL BIOLOGICAL REMOVAL

The potential biological removal (PBR) level for this stock is calculated as the minimum population size (2,545)

times one-half the default maximum net growth rate for cetaceans (1⁄2 of 4%) times a recovery factor of 0.40 (for a stock

of unknown status with a mortality rate CV ≥ 0.80, Wade and Angliss 1997), resulting in a PBR of 20 harbor porpoise

per year.
65

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Fisheries Information

NMFS observers monitored the northern Washington marine set gillnet fishery during 1993-1998 (Gearin et

al. 1994, 2000; P. Gearin, unpubl. data); 1994 observer data recently became available and will be included in a future

stock assessment report. For the entire area fished (coastal + inland waters), observer coverage ranged from

approximately 40 to 98% during those years. Fishing effort is conducted within the range of both harbor porpoise stocks

(Oregon/Washington Coast and Inland Washington stocks) occurring in Washington State waters. Some of the animals

taken in the inland waters portion of the fishery may have been animals from the coastal stock. Similarly, some of the

animals taken in the coastal portion of the fishery (see the Oregon/Washington Coast stock assessment report for details)

may have been from the inland stock. For the purposes of this stock assessment report, the animals taken in the inland

portion of the fishery are assumed to have belonged to the Inland Washington stock and the animals taken in the coastal

portion of the fishery are assumed to have belonged to the Oregon/Washington Coast stock. Some movement of harbor

porpoise between Washington’s coastal and inland waters is likely, but it is currently not possible to quantify the extent

of such movements. Accordingly, Table 1 includes data only from that portion of the northern Washington marine set

gillnet fishery occurring within the range of the Inland Washington stock (those waters east of Cape Flattery), where

observer coverage ranged from 6 to 80% between 1993 and 1998. Data from 1993-1998 are included in Table 1,

although the mean estimated annual mortality is calculated using the most recent 5 years of available data. No

mortalities were observed in the inland portion of the fishery between 1993 and 1998. Little effort occurred in the

inland portion of the fishery in 1995, 1997, or 1998. The mean estimated mortality for this fishery is zero harbor

porpoise per year from this stock.

In 1993, as a pilot for future observer programs, NMFS in conjunction with the Washington Department of

Fish and Wildlife (WDFW) monitored all non-treaty components of the Washington Puget Sound Region salmon gillnet

fishery (Pierce et al. 1994). Observer coverage was 1.3% overall, ranging from 0.9% to 7.3% for the various

components of the fishery. No harbor porpoise mortalities were reported (Table 1). Pierce et al. (1994) cautioned

against extrapolating these mortalities to the entire Puget Sound fishery due to the low observer coverage and potential

biases inherent in the data. The area 7/7A sockeye landings represented the majority of the non-treaty salmon landings

in 1993, approximately 67%. Results of this pilot study were used to design the 1994 observer programs discussed

below. 

In 1994, NMFS in conjunction with WDFW conducted an observer program during the Puget Sound non-treaty

chum salmon gillnet fishery (areas 10/11 and 12/12B). A total of 230 sets were observed during 54 boat trips,

representing approximately 11% observer coverage of the 500 fishing boat trips comprising the total effort in this fishery

as estimated from fish ticket landings (Erstad et al. 1996). No harbor porpoise were reported within 100 m of observed

gillnets. The Puget Sound treaty chum salmon gillnet fishery in Hood Canal (areas 12, 12B, and 12C) and Puget Sound

treaty sockeye/chum gillnet fishery in the Strait of Juan de Fuca (areas 4B, 5, and 6C) were also monitored in 1994

(NWIFC 1995). No harbor porpoise mortalities were reported in the observer programs covering these treaty salmon

gillnet fisheries, where observer coverage was estimated at 2.2% (based on % of total catch observed) and approximately

7.5% (based on % of observed trips to total landings), respectively. 

Also in 1994, NMFS in conjunction with WDFW and the Tribes conducted an observer program to examine

seabird and marine mammal interactions with the Puget Sound treaty and non-treaty sockeye salmon gillnet fishery

(areas 7 and 7A). During this fishery, observers monitored 2,205 sets, representing approximately 7% of the estimated

33,086 sets occurring in the fishery (Pierce et al. 1996). There was one observed harbor porpoise mortality (one other

was entangled and released alive with no indication the animal was injured), resulting in a mortality rate of 0.00045

harbor porpoise per set, which extrapolates to 15 mortalities (CV=1.0) for the entire fishery. In 1996, Washington Sea

Grant Program conducted a test fishery in the non-treaty sockeye salmon gillnet fishery (area 7) to compare

entanglement rates of seabirds and marine mammals and catch rates of salmon using three experimental gears and a

control (monofilament mesh net). The experimental nets incorporated highly visible mesh in the upper quarter (50 mesh

gear) or upper eighth (20 mesh gear) of the net or had low-frequency sound emitters attached to the corkline (Melvin

et al. 1997). In 642 sets during 17 vessel trips, 2 harbor porpoise were killed in the 50 mesh gear. 

Combining the estimates from the 1994 observer programs (15) with the northern Washington marine set gillnet

fishery (0) results in an estimated mean mortality rate in observed fisheries of 15 harbor porpoise per year from this

stock. It should be noted that the 1994 observer programs did not sample all segments of the entire Washington Puget

Sound Region salmon set/drift gillnet fishery, and further, the extrapolation of total kill did not include effort for the
66

unobserved segments of this fishery. Therefore, 15 is an underestimate of the harbor porpoise mortality due to the entire

fishery. Though it is not possible to quantify what percentage of the Washington Puget Sound Region salmon set/drift

gillnet fishery was actually observed in 1994, the observer programs covered those segments of the fishery which had

the highest salmon catches, the majority of vessel participation, and the highest likelihood of interaction with harbor

porpoise (J. Scordino, pers. comm.). Accordingly, the estimated harbor porpoise mortality (15) appears to be only a

slight underestimate for the fishery. See Appendix 1 for additional information regarding the Washington Puget Sound

Region salmon set/drift gillnet fishery.

Table 1. Summary of incidental mortality of harbor porpoise (Inland Washington stock) due to commercial and tribal

fisheries and calculation of the mean annual mortality rate; n/a indicates that data are not available. Mean annual takes

are based on 1994-98 data unless noted otherwise.

Fishery name Years

Data

type

Percent

observer

coverage

Observed 

mortality

Estimated

mortality

Mean annual

takes (CV in

parentheses) 

Northern WA marine set gillnet

(tribal fishery: inland waters)

93

94

95

96

97

98

obs data 61%

n/a

24%

6%

80%

40%

0

n/a

0

0

0

0

0

n/a

0

0

0

0

0

1

WA Puget Sound Region salmon

set/drift gillnet (observer

programs listed below covered

segments of this fishery):

- - - - - -

 Puget Sound non-treaty salmon

 gillnet (all areas and species)

93 obs data 1.3% 0 0 see text

 Puget Sound non-treaty chum

 salmon gillnet (areas 10/11 and

 12/12B)

94 obs data 11% 0 0 0

 Puget Sound treaty chum

 salmon gillnet (areas 12, 12B,

 and 12C)

94 obs data 2.2% 0 0 0

 Puget Sound treaty chum and

 sockeye salmon gillnet (areas

 4B, 5, and 6C)

94 obs data 7.5% 0 0 0

 Puget Sound treaty and non-

 treaty sockeye salmon gillnet

 (areas 7 and 7A)

94 obs data 7% 1 15 15 (1.0)

Reported

mortalities

WA Puget Sound Region salmon

set/drift gillnet

94-98 self

reports

n/a n/a, n/a, n/a, n/a,

n/a

n/a see text

Minimum total annual takes ≥ 15 (1.0)

1

1993 and 1995-98 mortality estimates are included in the average.

An additional source of information on the number of harbor porpoise killed or injured incidental to

commercial fishery operations is the self-reported fisheries information required of vessel operators by the MMPA.

During the period between 1994 and 1998, there were no fishery self-reports of any harbor porpoise mortalities from

the Washington Puget Sound Region salmon set and drift gillnet fishery (Table 1). Unlike the 1994 observer program

data, the self-reported fisheries data cover the entire fishery. However, because logbook records (fisher self-reports
67

required during 1990-94) are most likely negatively biased (Credle et al. 1994), these are considered to be minimum

estimates of harbor porpoise mortality. Self-reported fisheries data are incomplete for 1994, not available for 1995, and

considered unreliable after 1995 (see Appendix 4 of Hill and DeMaster 1998).

Strandings of harbor porpoise wrapped in fishing gear or with injuries caused by interactions with gear are a

final source of fishery-related mortality information. No fishery-related strandings of harbor porpoise occurred during

1994-1998.

There are few data concerning the mortality of marine mammals incidental to commercial gillnet fisheries in

Canadian waters, which have not been monitored but are known to have taken harbor porpoise in the past (Barlow et

al. 1994, Stacey et al. 1997). As a result, the number of harbor porpoise from this stock currently taken in the waters

of southern British Columbia is not known. 

STATUS OF STOCK

Harbor porpoise are not listed as “depleted” under the MMPA or listed as “threatened “ or “endangered” under

the Endangered Species Act. Based on currently available data, the level of human-caused mortality and serious injury

(15) is not known to exceed the PBR (20). Therefore, the Inland Washington harbor porpoise stock is not classified

as strategic. The minimum total fishery mortality and serious injury for this stock (15) exceeds 10% of the calculated

PBR (2.0) and, therefore, cannot be considered to be insignificant and approaching zero mortality and serious injury

rate. The status of this stock relative to its Optimum Sustainable Population (OSP) level and population trends is

unknown, although harbor porpoise sightings in southern Puget Sound have declined since the 1940s.

Although this stock is not recognized as strategic at this time, there is cause for concern due to the following

issues: 1) the estimated take level is close to exceeding the PBR, 2) the extent to which harbor porpoise from U.S. waters

frequent the waters of British Columbia, and are therefore subject to fishery-related mortality, is unknown, and 3) the

mortality rate is based on observer data from a subset of the Washington Puget Sound Region salmon set and gillnet

fishery.

REFERENCES

Barlow, J. 1988. Harbor porpoise,Phocoena phocoena, abundance estimation for California, Oregon, and Washington:

I. Ship surveys. Fish. Bull. 86:417-432.

Barlow, J., and D. Hanan. 1995. An assessment of the status of harbor porpoise in central California. Rep. Int. Whal.

Commn. Special Issue 16:123-140.

Barlow, J., C. W. Oliver, T. D. Jackson, and B. L. Taylor. 1988. Harbor porpoise, Phocoena phocoena, abundance

estimation for California, Oregon, and Washington: II. Aerial surveys. Fish. Bull. 86:433-444.

Barlow , J., R. W. Baird, J. E. Heyning, K. Wynne, A. M. Manville, II, L. F. Lowry, D. Hanan, J. Sease, and V. N.

Burkanov. 1994. A review of cetacean and pinniped mortality in coastal fisheries along the west coast of the

USA and Canada and the east coast of the Russian Federation. Rep. Int. Whal. Commn. Special Issue 15:405-

425.

Calambokidis, J., and J. Barlow. 1991. Chlorinated hydrocarbon concentrations and their use for describing population

discreteness in harbor porpoises from Washington, Oregon, and California. In: Reynolds, J. E., III, and D. K.

Odell (eds.), Proceedings of the second marine mammal stranding workshop: 3-5 December 1987, Miami,

Florida. NMFS, NOAA Tech. Rep. NMFS 98:101-110.

Calambokidis, J., J. R. Evenson, J. C. Cubbage, P. J. Gearin, and S. D. Osmek. 1992. Harbor porpoise distribution

and abundance off Oregon and Washington from aerial surveys in 1991. Final Report by Cascadia Research,

Olympia, WA, to National Marine Mammal Laboratory, AFSC, NMFS, Seattle, WA. 44 pp.

Calambokidis, J., J. C. Cubbage, J. R. Evenson, S. D. Osmek, J. L. Laake, P. J. Gearin, B. J. Turnock, S. J. Jeffries, and

R. F. Brown. 1993. Abundance estimates of harbor porpoise in Washington and Oregon waters. Final Report

by Cascadia Research, Olympia, WA, to National Marine Mammal Laboratory, AFSC, NMFS, Seattle, WA.

55 pp.

Calambokidis, J., S. D. Osmek, and J. L. Laake. 1997. Aerial surveys for marine mammals in Washington and British

Columbia inside waters. Final Report by Cascadia Research, Olympia, WA, to National Marine Mammal

Laboratory, AFSC, NMFS, Seattle, WA. 96 pp.

Chivers, S. Southwest Fisheries Science Center, NMFS, P.O. Box 271, La Jolla, CA 92038.

Credle, V. R., D. P. DeMaster, M. M. Merklein, M. B. Hanson, W. A. Karp, and S. M. Fitzgerald (eds.). 1994. NMFS
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observer programs: minutes and recommendations from a workshop held in Galveston, Texas, November 10-

11, 1993. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-94-1. 96 pp.

Dohl, T. P., R. C. Guess, M. L. Duman, and R. C. Helm. 1983. Cetaceans of central and northern California, 1980-

1983: status, abundance, and distribution. OCS Study MMS 84-0045. Pacific OCS Region Minerals

Management Service, 1340 Sixth Street, Los Angeles, CA 90014. 284 pp.

Erstad, P., S. J. Jeffries, and D. J. Pierce. 1996. 1994 Report for the Puget Sound fishery observer program in

management areas 10/11 & 12/12B: nontreaty chum gill net fishery. Final Report, Washington Dept. Fish and

Wildlife, Olympia, WA. 14 pp.

Everitt, R. D., C. H. Fiscus, and R. L. DeLong. 1980. Northern Puget Sound marine mammals. U.S. Dep. Commer.,

EPA-6000/7-80-139. 134 pp.

Gaskin, D. E. 1984. The harbour porpoise Phocoena phocoena (L.): regional populations, status, and information on

direct and indirect catches. Rep. Int. Whal. Commn. 34:569-586.

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Gearin, P. J., S. R. Melin, R. L. DeLong, H. Kajimura, and M. A. Johnson. 1994. Harbor porpoise interactions with

a chinook salmon set-net fishery in Washington State. Rep. Int. Whal. Commn. Special Issue 15:427-438.

Gearin, P. J., M. E. Gosho, J. L. Laake, L. Cooke, R. L. DeLong, and K. M. Hughes. 2000. Experimental testing of

acoustic alarms (pingers) to reduce bycatch of harbour porpoise, Phocoena phocoena, in the state of

Washington. J. Cetacean Res. Manage. 2(1):1-9.

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distribution and abundance off Oregon and Washington, 1989-1990. Ch. 1, In: Brueggeman, J. J. (ed.),

Oregon and Washington Marine Mammal and Seabird Surveys. Final Rep. OCS Study MMS 91-0093.

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Tech. Memo. NMFS-AFSC-97. 166 pp.

Laake, J. L., R. L. DeLong, J. Calambokidis, and S. Osmek. 1997a. Abundance and distribution of marine mammals

in Washington and British Columbia inside waters, 1996. Pp. 67-73, In: MMPA and ESA Implementation

Program, 1996. AFSC Processed Report 97-10. 255 pp. Available at National Marine Mammal Laboratory,

7600 Sand Point Way NE, Seattle, WA 98115.

Laake, J. L., J. Calambokidis, S. D. Osmek, and D. J. Rugh. 1997b. Probability of detecting harbor porpoise from

aerial surveys: estimating g(0). J. Wildl. Manage. 61(1):63-75.

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gillnet salmon fisheries. 1996 Sockeye and 1995 Chum Salmon Test Fisheries Final Report. Washington Sea

Grant Program, Seattle, WA. 48pp.

Northwest Indian Fisheries Commission. 1995. Monitoring of marbled murrelet and marine mammal interactions with

1994 tribal gillnet fisheries in northern Puget Sound, Hood Canal, and the Strait of Juan de Fuca. Final Report

to NMFS Contract No. 52ABNF400087. Unpubl. report. Northwest Indian Fisheries Commission. 43 pp.

Available at NWIFC, 6730 Martin Way E, Olympia, WA 98516.

Osborne, R., J. Calambokidis, and E. M. Dorsey. 1988. A Guide to Marine Mammals of Greater Puget Sound. Island

Publishers, Anacortes, WA. 191 pp.

Osmek, S., P. Rosel, A. Dizon, and R. DeLong. 1994. Harbor porpoise, Phocoena phocoena, population assessment

in Oregon and Washington, 1993. 1993 Annual Report to the MMPA Assessment Program, Office of

Protected Resources, NMFS, NOAA, 1335 East-West Highway, Silver Spring, MD 20910. 14 pp. Available

at National Marine Mammal Laboratory, 7600 Sand Point Way NE, Seattle, WA 98115.

Osmek, S. D., M. B. Hanson, J. L. Laake, S. J. Jeffries, and R. L. DeLong. 1995. Harbor porpoise Phocoena

phocoena population assessment studies for Oregon and Washington in 1994. 1994 Annual Report to the

MMPA Assessment Program, Office of Protected Resources, NMFS, NOAA, 1335 East-West Highway, Silver

Spring, MD 20910. 32 pp. Available at National Marine Mammal Laboratory, 7600 Sand Point Way NE,

Seattle, WA 98115.

Osmek, S., J. Calambokidis, J. Laake, P. Gearin, R. DeLong, J. Scordino, S. Jeffries, and R. Brown. 1996. Assessment

of the status of harbor porpoises, Phocoena phocoena, in Oregon and Washington waters. U.S. Dep. Commer.,

NOAA Tech. Memo. NMFS-AFSC-76. 46 pp.

Pierce, D. J., W. P. Ritchie, and R. Kreuziger. 1994. Preliminary findings of seabird interactions with the non-treaty

salmon gill net fishery: Puget Sound and Hood Canal Washington. Unpubl. report. Washington Dept. Fish
69

and Wildlife, Olympia, WA. 39 pp. Available at WDFW, 600 Capitol Way N, Olympia, WA, 98501.

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murrelets and marine mammals with the 1994 Puget Sound sockeye gill net fishery. Final Report, Washington

Dept. Fish and Wildlife, Olympia, WA. 21 pp.

Rosel, P. E. 1992. Genetic population structure and systematic relationships of some small cetaceans inferred from

mitochondrial DNA sequence variation. Ph.D. Thesis, Univ. Calif. San Diego, La Jolla, CA. 191 pp.

Rosel, P. E., A. E. Dizon, and M. G. Haygood. 1995. Variability of the mitochondrial control region in populations

of the harbour porpoise, Phocoena phocoena, on inter-oceanic and regional scales. Can. J. Fish. Aquat. Sci.

52:1210-1219.

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in coastal fisheries in British Columbia, Canada. Mar. Mammal Sci. 13:321-326. 

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Wade, P. R., and R. Angliss. 1997. Guidelines for assessing marine mammal stocks: report of the GAMMS workshop

April 3-5, 1996, Seattle, Washington. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-12. 93 pp.
70

Figure 1. Dall’s porpoise sightings based on aerial

and shipboard surveys off California, Oregon and

Washington, 1991-96 (see Appendix 2, Figures 1-

5, for data sources and information on timing and

location of survey effort). Dashed line represents

the U.S. EEZ, thick line indicates the outer

boundary of all surveys combined.

Revised 12/15/2000

DALL'S PORPOISE (Phocoenoides dalli): California/Oregon/Washington Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

Dall's porpoise are endemic to temperate waters of the

North Pacific Ocean. Off the U.S. west coast, they are commonly

seen in shelf, slope and offshore waters (Figure 1; Morejohn

1979). Sighting patterns from aerial and shipboard surveys

conducted in California, Oregon and Washington at different

times (Green et al. 1992, 1993; Mangels and Gerrodette 1994;

Barlow 1995; Forney et al. 1995) suggest that north-south

movement between these states occurs as oceanographic

conditions change, both on seasonal and inter-annual time scales.

The southern end of this population's range is not welldocumented, but they are commonly seen off Southern California

in winter, and during cold-water periods they probably range into

Mexican waters off northern Baja California. The stock structure

of eastern North Pacific Dall's porpoise is not known, but based

on patterns of stock differentiation in the western North Pacific,

where they have been more intensively studied, it is expected that

separate stocks will emerge when data become available (Perrin

and Brownell 1994). Although Dall's porpoise are not restricted

to U.S. territorial waters, there are no cooperative management

agreements with Mexico or Canada for fisheries which may take

this species (e.g. gillnet fisheries). For the Marine Mammal

Protection Act (MMPA) stock assessment reports, Dall's

porpoises within the Pacific U.S. Exclusive Economic Zone are

divided into two discrete, non-contiguous areas: 1) waters off

California, Oregon and Washington (this report), and 2) Alaskan

waters. 

POPULATION SIZE

Shipboard surveys are expected to be more reliable for

this species than aerial surveys because of the large, unknown

fraction of diving animals missed from the air (Forney 1994). Three summer/fall shipboard surveys were conducted

within 300 nmi of the coasts of California in 1991 and 1993 (Barlow and Gerrodette 1996) and California, Oregon and

Washington in 1996 (Barlow 1997). The distribution of Dall’s porpoise throughout this region is highly variable

between years and appears to be affected by oceanographic conditions (Forney 1997; Forney and Barlow 1998).

Because animals may spend time outside the U.S. Exclusive Economic Zone as oceanographic conditions change, a

multi-year average abundance estimate is the most appropriate for management within U.S. waters. The 1991-96

weighted average abundance estimate for California, Oregon and Washington waters based on the three ship surveys

is 116,016 (CV = 0.45) Dall’s porpoise (Barlow 1997). Additional aerial surveys were conducted in the inland waters

of Washington in 1991 and 1996, resulting in Dall’s porpoise abundance estimates of 2,747 (CV=0.48) in 1991, and

900 (CV=0.40) in 1996 (Calambokidis et al. 1997), with a weighted average estimate of 1,509 (CV=0.46). Both

estimates include approximate correction factors for animals missed due to perception and availability bias. Combining

the average estimate for inland Washington waters with the 1991-96 outer coast estimate of Barlow (1997) yields a total

abundance estimate of 117,545 (CV=0.45) Dall’s porpoise for the California/Oregon/Washington stock.

 

Minimum Population Estimate

The log-normal 20th percentile of the 1991-96 weighted average abundance estimate for both the outer coast

of California, Oregon and Washington and inland Washington waters is 81,866 Dall's porpoise.
71

Current Population Trend

No information is available regarding trends in abundance of Dall's porpoise in California, Oregon and

Washington. Their distribution and abundance in this region varies considerably at both seasonal and interannual time

scales as oceanographic conditions vary (Forney 1997; Forney and Barlow 1998).

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

No information on current or maximum net productivity rates is available for Dall's porpoise off the U.S. west

coast.

POTENTIAL BIOLOGICAL REMOVAL

The potential biological removal (PBR) level for this stock is calculated as the minimum population size

(81,866) times one half the default maximum net growth rate for cetaceans (1⁄2 of 4%) times a recovery factor of 0.45

(for a species of unknown status and a mortality rate CV>0.60 and ≤ 0.80; Wade and Angliss 1997), resulting in a PBR

of 737 Dall’s porpoise per year. 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Fishery Information

A summary of recent fishery mortality and injury for this stock of Dall’s porpoise is given in Table 1. More

detailed information on these fisheries is provided in Appendix 1. Mortality estimates for the California drift gillnet

fishery are included for the five most recent years of monitoring, 1994-98 (Julian and Beeson 1998; Julian 1997;

Cameron and Forney 1999). After the 1997 implementation of a Take Reduction Plan, which included skipper

education workshops and required the use of pingers and minimum 6-fathom extenders, overall cetacean entanglement

rates in the drift gillnet fishery dropped considerably (Barlow and Cameron 1999). However, because of interannual

variability in entanglement rates and the relative rarity of Dall’s porpoise entanglements, additional years of data will

be required to fully evaluate the effectiveness of pingers for reducing mortality of this particular species. Because of

the changes in this fishery after implementation of the Take Reduction Plan, mean annual takes in Table 1 are based only

on 1997-98 data. This results in an average estimate of 10 (CV = 0.95) Dall’s porpoise taken annually.

Drift gillnet fisheries for swordfish and sharks exist along the entire Pacific coast of Baja California, Mexico

and may take some Dall's porpoise from the same population during cold-water periods. Quantitative data are available

only for the Mexican swordfish drift gillnet fishery, which uses vessels, gear, and operational procedures similar to those

in the U.S. drift gillnet fishery, although nets may be up to 4.5 km long (Holts and Sosa-Nishizaki 1998). The fleet

increased from two vessels in 1986 to 31 vessels in 1993 (Holts and Sosa-Nishizaki 1998). The total number of sets in

this fishery in 1992 can be estimated to be approximately 2700, with an observed rate of marine mammal bycatch of

0.13 animals per set (10 marine mammals in 77 observed sets; Sosa-Nishizaki et al. 1993). This overall mortality rate

is similar to that observed in California driftnet fisheries during 1990-95 (0.14 marine mammals per set; Julian and

Beeson, 1998), but species-specific information is not available for the Mexican fisheries. There are currently efforts

underway to convert the Mexican swordfish driftnet fishery to a longline fishery (D. Holts, pers. comm.). 

Low levels of mortality for Dall’s porpoise have also been documented in the California/Oregon/Washington

domestic groundfish trawl fisheries (Perez and Loughlin 1991; Perez, in prep). Between 1994 and 1998, with 54%-77%

of the fishing effort observed, five Dall’s porpoise were reported killed in the at-sea processing portion of the Pacific

whiting trawl fishery, and five animals were reported in unmonitored hauls.. Based only on the systematically observed

hauls, Dall’s porpoise mortality was estimated to be five (CV=0.44) in 1997 and three (CV=0.33) in 1998 (Perez, in

prep). Combining these estimates with the three reported mortalities for 1994 and 1996 that are not accounted for in

the estimates, the minimum average annual mortality for 1994-98 is 2.0 (CV=0.23) Dall’s porpoise per year. 

STATUS OF STOCK

The status of Dall's porpoise in California, Oregon and Washington relative to OSP is not known, and there

are insufficient data to evaluate potential trends in abundance. No habitat issues are known to be of concern for this

species. They are not listed as "threatened" or "endangered" under the Endangered Species Act nor as "depleted" under

the MMPA. Including driftnet mortality only for years after implementation of the Take Reduction Plan (1997-98),

the average annual human-caused mortality in 1994-98 (12 animals) is estimated to be less than the PBR (737), and

therefore they are not classified as a "strategic" stock under the MMPA. The total fishery mortality and serious injury
72

for this stock is less than 10% of the calculated PBR and, therefore, can be considered to be insignificant and

approaching zero mortality and serious injury rate.

Table 1. Summary of available information on the incidental mortality and injury of Dall's porpoise (California/

Oregon/Washington Stock) in commercial fisheries that might take this species. All observed entanglements of Dall's

porpoise resulted in the death of the animal. Coefficients of variation for mortality estimates are provided in

parentheses; n/a = not available. Mean annual takes are based on 1994-98 data unless noted otherwise.

Fishery Name Data Type Year(s)

Percent

Observer

Coverage

Observed

Mortality

Estimated Annual

Mortality

Mean Annual

Takes (CV in

parentheses)

CA/OR thresher

shark/swordfish drift

gillnet fishery

observer

data 1994

1995

1996

1997

1998

17.9%

15.6%

12.4%

23.0%

20.0%

2

1

2

4

0

11 (0.64)

 6 (0.92)

24 (0.68)

20 (0.95)

0 10 (0.95)1

WA/OR/CA domestic

groundfish trawl fisheries

(At-sea processing Pacific

whiting fishery only).

observer data

unmonitored

hauls

1994

1995

1996

1997

1998

1994

1996

1997

53.8%

56.2%

65.2%

65.7%

77.3%

0

0

0

3

2

2

1

2

0

0

0

5 (0.44)

3 (0.33)

1.6 (0.23)

0.6 (n/a)

Minimum total annual takes 12 (CV=0.79)

1 Only 1997-98 mortality estimates are included in the average because overall cetacean entanglement rates dropped considerably after a Take

Reduction Plan was implemented in 1997.

REFERENCES

Barlow, J. 1995. The abundance of cetaceans in California waters. Part I: Ship surveys in summer and fall of 1991.

Fish. Bull. 93:1-14.

Barlow, J. 1997. Preliminary estimates of cetacean abundance off California, Oregon and Washington based on a 1996

ship survey and comparisons of passing and closing modes. Admin. Rep. LJ-97-11. Southwest Fisheries

Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA 92038. 25p.

Barlow, J. and T. Gerrodette. 1996. Abundance of cetaceans in California waters based on 1991 and 1993 ship

surveys. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-SWFSC-233. 15 pp. 

Barlow, J. and G. A. Cameron. 1999. Field experiments show that acoustic pingers reduce marine mammal bycatch in

the California drift gillnet fishery. Paper SC/51/SM2 presented to the International Whaling Commission, May

1998. 20 pp.

Calambokidis, J., S. Osmek, and J. L. Laake. 1997. Aerial surveys for marine mammals in Washington and British

Columbia inside waters. Final Contract Report for Contract 52ABNF-6-00092, available from Cascadia

Research Collective, Waterstreet Building 218 1⁄2 West Forth Avenue, Olympia, Washington 98501.

Cameron, G., and K. A. Forney. 1999. Estimates of cetacean mortality in the California gillnet fisheries for 1997 and

1998. Paper SC/51/O4 presented to the International Whaling Commission, May 1999 (unpublished). 14 pp.

Forney, K. A. 1994. Recent information on the status of odontocetes in Californian waters. U.S. Dep. Commer.,

NOAA Tech. Memo. NMFS-SWFSC-202. 87 pp.

Forney, K. A. 1997. Patterns of variability and environmental models of relative abundance for California cetaceans.

Ph.D. dissertation, Scripps Institution of Oceanography, University of California, San Diego.

Forney, K. A. and J. Barlow. 1998. Seasonal patterns in the abundance and distribution of California cetaceans, 1991-

92. Mar. Mamm. Sci. 14:460-489.

Forney, K. A., J. Barlow and J. V. Carretta. 1995. The abundance of cetaceans in California waters. Part II: Aerial
73

surveys in winter and spring of 1991 and 1992. Fish. Bull. 93:15-26.

Green, G., J. J. Brueggeman, R. A. Grotefendt, C. E. Bowlby, M. L. Bonnell, and K. C. Balcomb, III. 1992. Cetacean

distribution and abundance off Oregon and Washington. Ch. 1. In: Oregon and Washington Marine Mammal

and Seabird Surveys. OCS Study 91-0093. Final Report prepared for Pacific OCS Region, Minerals

Management Service, U.S. Department of the Interior, Los Angeles, California. 

Green, G., R. A. Grotefendt, M. A. Smultea, C. E. Bowlby, and R. A. Rowlett. 1993. Delphinid aerial surveys in

Oregon and Washington waters. Final Report prepared for NMFS, National Marine Mammal Laboratory, 7600

Sand Point Way, NE, Seattle, Washington, 98115, Contract #50ABNF200058.

Holts, D. Southwest Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA 92038.

Holts, D. and O. Sosa-Nishizaki. 1998. Swordfish, Xiphias gladius, fisheries of the eastern North Pacific Ocean. In:

I. Barrett, O. Sosa-Nishizaki and N. Bartoo (eds.). Biology and fisheries of swordfish, Xiphias gladius. Papers

from the International Symposium on Pacific Swordfish, Ensenada Mexico, 11-14 December 1994. U.S. Dep.

Commer., NOAA Tech. Rep. NMFS 142, 276 pp.

Julian, F. 1997. Cetacean mortality in California gill net fisheries: Preliminary estimates for 1996. Paper SC/49/SM02

presented to the International Whaling Commission, September 1997 (unpublished). 13 pp.

Julian, F. and M. Beeson. 1998. Estimates of mammal, turtle and bird mortality for two California gillnet fisheries:

1990-1995. Fish. Bull. 96:271-284.

Mangels, K. F. and Gerrodette, T. 1994. Report of cetacean sightings during a marine mammal survey in the eastern

Pacific Ocean and Gulf of California aboard the NOAA ships McARTHUR and DAVID STARR JORDAN July

28 - November 6, 1993. U.S. Dep. Commer. NOAA Tech. Memo. NMFS-SWFSC-211. 88 pp.

Morejohn, G. V. 1979. The natural history of Dall's porpoise in the North Pacific Ocean. In: Winn, H. E. and B.

L. Olla (eds.), Behavior of Marine Mammals, p. 45-83. Plenum Press, New York - London.

Perez, M. A. and T. R. Loughlin. 1991. Incidental catch of marine mammals by foreign and joint venture trawl vessels

in the U.S. EEZ of the North Pacific, 1973-88. U.S. Dep. Commer. NOAA Tech. Rep. 104. 57 p.

Perez, M. A. (in prep). Summary of marine mammal incidental catch data for domestic and joint venture groundfish

fisheries in the U.S. EEZ of the North Pacific, 1989-98. U.S. Dep. Commer. NOAA Tech. Memo.

Perrin, W. F. and R. L. Brownell, Jr. 1994. A brief review of stock identity in small marine cetaceans in relation to

assessment of driftnet mortality in the North Pacific. Rep. Int. Whal. Commn. Special Issue 15:393-401.

Sosa-Nishizaki, O., R. De la Rosa Pacheco, R. Castro Longoria, M. Grijalva Chon, and J. De la Rosa Velez. 1993.

Estudio biologico pesquero del pez (Xiphias gladius) y otras especies de picudos (marlins y pez vela). Rep.

Int. CICESE, CTECT9306.

Wade, P. R. and R. P. Angliss. 1997. Guidelines for Assessing Marine Mammal Stocks: Report of the GAMMS

Workshop April 3-5, 1996, Seattle, Washington. U. S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-12.

93 pp.
74

Figure 1. Pacific white-sided dolphin sightings

based on aerial and shipboard surveys off

California, Oregon and Washington, 1991-96 (see

Appendix 2, Figures 1-5, for data sources and

information on timing and location of survey

effort). Dashed line represents the U.S. EEZ,

thick line indicates the outer boundary of all

surveys combined.

Revised 12/15/2000

PACIFIC WHITE-SIDED DOLPHIN (Lagenorhynchus obliquidens):

California/Oregon/Washington, Northern and Southern Stocks

STOCK DEFINITION AND GEOGRAPHIC RANGE

Pacific white-sided dolphins are endemic to temperate

waters of the North Pacific Ocean, and are common both on the

high seas and along the continental margins. Off the U.S. west

coast, Pacific white-sided dolphins have been seen primarily in

shelf and slope waters (Figure 1). Sighting patterns from recent

aerial and shipboard surveys conducted in California, Oregon and

Washington at different times of the year (Green et al. 1992;

1993; Barlow 1995; Forney et al. 1995) suggest seasonal northsouth movements, with animals found primarily off California

during the colder water months and shifting northward into

Oregon and Washington as water temperatures increase in late

spring and summer (Green et al. 1992; Forney 1994). 

Stock structure throughout the North Pacific is poorly

understood, but based on morphological evidence, two forms are

known to occur off the California coast (Walker et al. 1986;

Chivers et al. 1993). Specimens belonging to the northern form

were collected from north of about 33oN, (Southern California to

Alaska), and southern specimens were obtained from about 36oN

southward along the coasts of California and Baja California.

Samples of both forms have been collected in the Southern

California Bight, but it is unclear whether this indicates sympatry

in this region or whether they may occur there at different times

(seasonally or interannually). Recent genetic analyses have

confirmed the distinctness of animals found off Baja California

from animals occurring in U.S. waters north of Point Conception,

California and in the high seas of the North Pacific (Lux et al.

1997). Based on these genetic data, a boundary or area of mixing

between the two forms appears to be located off Southern

California (Lux et al. 1997).

Although there is clear evidence that two forms of

Pacific white-sided dolphins occur along the U.S. west coast, there are no known differences in color pattern, and it is

not currently possible to distinguish animals without genetic or morphometric analyses. Geographic stock boundaries

appear dynamic and are poorly understood, and therefore cannot be used to differentiate the two forms. Until means

of differentiating the two forms for abundance and mortality estimation are developed, these two stocks must be

managed as a single unit; however, this is an undesirable management situation. Furthermore, Pacific white-sided

dolphins are not restricted to U.S. territorial waters, but cooperative management agreements with Mexico exist only

for the tuna purse seine fishery and not for other fisheries which may take this species (e.g. gillnet fisheries). Additional

means of differentiating the two types must be found, and cooperative management with Mexico is particularly

important for this species, given the apparently dynamic nature of geographical stock boundaries. Until these goals are

accomplished, the management stock includes animals of both forms. For the Marine Mammal Protection Act (MMPA)

stock assessment reports, Pacific white-sided dolphins within the Pacific U.S. Exclusive Economic Zone are divided

into two discrete, non-contiguous areas: 1) waters off California, Oregon and Washington (this report), and 2) Alaskan

waters.

POPULATION SIZE

The previous best estimates of abundance for Pacific white-sided dolphins (Barlow et al. 1997) were based
75

on winter/spring 1991-92 aerial surveys (Forney et al. 1995) off California, which were presumed to include Pacific

white-sided dolphins that are found off Oregon and Washington during summer and fall. Three summer/fall shipboard

surveys were conducted within 300 nmi of the coasts of California in 1991 and 1993 (Barlow and Gerrodette 1996) and

California, Oregon and Washington in 1996 (Barlow 1997). The distribution of Pacific white-sided dolphins throughout

this region is highly variable, apparently in response to oceanographic changes on both seasonal and interannual time

scales (Forney and Barlow 1998). As oceanographic conditions vary, Pacific white-sided dolphins may spend time

outside the U.S. Exclusive Economic Zone, and therefore a multi-year average abundance estimate including California,

Oregon and Washington is the most appropriate for management within U.S. waters. The 1991-96 weighted average

abundance estimate for California, Oregon and Washington waters based on the three ship surveys is 25,825 (CV =

0.49) Pacific white-sided dolphins (Barlow 1997).

Minimum Population Estimate

The log-normal 20th percentile of the 1991-96 weighted average abundance estimate is 17,475 Pacific whitesided dolphins.

Current Population Trend

No long-term trends in the abundance of Pacific white-sided dolphins in California, Oregon and Washington

are suggested based on historical and recent surveys (Dohl et al. 1980; 1983; Green et al. 1992; 1993; Barlow 1995;

Forney et al. 1995;).

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

No information on current or maximum net productivity rates is available for Pacific white-sided dolphins off

the U.S. west coast.

POTENTIAL BIOLOGICAL REMOVAL

The potential biological removal (PBR) level for this stock is calculated as the minimum population size

(17,475) times one half the default maximum net growth rate for cetaceans (1⁄2 of 4%) times a recovery factor of 0.45

(for a species of unknown status with a mortality rate CV ≥ 0.60 and ≤ 0.80; Wade and Angliss 1997), resulting in a

PBR of 157 Pacific white-sided dolphins per year. 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Fishery Information

A summary of recent fishery mortality and injury for this stock of Pacific white-sided dolphin is shown in Table

1. More detailed information on these fisheries is provided in Appendix 1. Mortality estimates for the California drift

gillnet fishery are included for the five most recent years of monitoring, 1994-98 (Julian and Beeson 1998; Julian 1997;

Cameron and Forney 1999). After the 1997 implementation of a Take Reduction Plan, which included skipper

education workshops and required the use of pingers and minimum 6-fathom extenders, overall cetacean entanglement

rates in the drift gillnet fishery dropped considerably (Barlow and Cameron 1999). However, because of interannual

variability in entanglement rates and the relative rarity of Pacific white-sided dolphin entanglements, additional years

of data will be required to fully evaluate the effectiveness of pingers for reducing mortality of this particular species.

Because of the changes in this fishery after implementation of the Take Reduction Plan, mean annual takes in Table 1

are based only on 1997-98 data. This results in an average estimate of 6.0 (CV = 0.68) Pacific white-sided dolphins

taken annually. 

Drift gillnet fisheries for swordfish and sharks exist along the entire Pacific coast of Baja California, Mexico

and probably take the southern form of this species. Quantitative data are available only for the Mexican swordfish drift

gillnet fishery, which uses vessels, gear, and operational procedures similar to those in the U.S. drift gillnet fishery,

although nets may be up to 4.5 km long (Holts and Sosa-Nishizaki, 1998). The fleet increased from two vessels in 1986

to 31 vessels in 1993 (Holts and Sosa-Nishizaki 1998). The total number of sets in this fishery in 1992 can be estimated

from data provided by these authors to be approximately 2700, with an observed rate of marine mammal bycatch of 0.13

animals per set (10 marine mammals in 77 observed sets; Sosa-Nishizaki et al. 1993). This overall mortality rate is

similar to that observed in California driftnet fisheries during 1990-95 (0.14 marine mammals per set; Julian and

Beeson,1998), but species-specific information is not available for the Mexican fisheries. There are currently efforts
76

underway to convert the Mexican swordfish driftnet fishery to a longline fishery (D. Holts, pers. comm.). 

Table 1. Summary of available information on the incidental mortality and injury of Pacific white-sided dolphins

(California/ Oregon/Washington Stock) in commercial fisheries that might take this species. All observed entanglements

of Pacific white-sided dolphins resulted in the death of the animal. Coefficients of variation for mortality estimates are

provided in parentheses; n/a = not available. Mean annual takes are based on 1994-98 data unless noted otherwise.

Fishery Name Data Type Year(s)

Percent

Observer

Coverage

Observed

Mortality

Estimated Annual

Mortality

Mean Annual

Takes (CV in

parentheses)

CA/OR thresher

shark/swordfish drift

gillnet fishery

observer data 

1994

1995

1996

1997

1998

17.9% 

15.6% 

12.4% 

23.0% 

20.0% 

3

1

3

3

0

17 (0.67)

 6 (0.92)

25 (0.96)

12 (0.68)

0

6.0 (0.68)1

WA/OR/CA domestic

groundfish trawl fisheries

(At-sea processing Pacific

whiting fishery only).

observer data

other records

1994

1995

1996

1997

1998

1996

53.8%

56.2%

65.2%

65.7%

77.3%

0

0

 0 

0

1

3

0

0

0

0

1 (0.48)

≥ 3

0.2 (0.48)

0.6 (n/a)

Minimum total annual takes 6.8 (0.60) 

1 Only 1997-98 mortality estimates are included in the average because overall cetacean entanglement rates dropped considerably after a Take

Reduction Plan was implemented in 1997.

Low levels of mortality for Pacific white-sided dolphins have also been documented in the California/Oregon/

Washington domestic groundfish trawl fisheries (Perez and Loughlin 1991; Perez, in prep;). Between 1994 and 1998,

with 54%-77% of the fishing effort observed, one Pacific white-sided dolphin was reported killed in the at-sea

processing portion of the Pacific whiting trawl fishery, and three additional animals were reported in unmonitored hauls.

Based only on the systematically observed hauls, mortality was estimated to be one Pacific white-sided dolphin

(CV=0.48, Perez, in prep) in 1998. Combining this estimate with the three additional reported mortalities for 1996 that

are not accounted for in the estimate, the minimum average annual mortality for 1994-98 is 0.8 (CV=0.48) Pacific whitesided dolphins.

Other removals

Additional removals of Pacific white-sided dolphins from the wild have occurred in live-capture fisheries off

California. Brownell et al. (1999) estimate a minimum total live capture of 128 Pacific white-sided dolphins between

the late 1950s and 1993. The most recent capture was in November 1993, when three animals were taken for public

display (Forney 1994). No MMPA permits are currently active for live-captures of Pacific white-sided dolphins.

STATUS OF STOCK

The status of Pacific white-sided dolphins in California, Oregon and Washington relative to OSP is not known,

and there is no indication of a trend in abundance for this stock. No habitat issues are known to be of concern for this

species. They are not listed as "threatened" or "endangered" under the Endangered Species Act nor as "depleted" under

the MMPA. Including driftnet mortality only for years after implementation of the Take Reduction Plan (1997-98), the

average annual human-caused mortality in 1994-98 (6.8 animals) is estimated to be less than the PBR (157), and

therefore they are not classified as a "strategic" stock under the MMPA. The total fishery mortality and serious injury

for this stock is less than 10% of the calculated PBR and, therefore, can be considered to be insignificant and

approaching zero mortality and serious injury rate. 
77

REFERENCES

Barlow, J. 1995. The abundance of cetaceans in California waters. Part I: Ship surveys in summer and fall of 1991.

Fish. Bull. 93:1-14.

Barlow, J. 1997. Preliminary estimates of cetacean abundance off California, Oregon and Washington based on a 1996

ship survey and comparisons of passing and closing modes. Admin. Rep. LJ-97-11, Southwest Fisheries

Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA 92038. 25p.

Barlow, J. and G. A. Cameron. 1999. Field experiments show that acoustic pingers reduce marine mammal bycatch in

the California drift gillnet fishery. Paper SC/51/SM2 presented to the International Whaling Commission, May

1998 (unpublished). 20 pp.

Barlow, J. and T. Gerrodette. 1996. Abundance of cetaceans in California waters based on 1991 and 1993 ship

surveys. NOAA Tech. Memo. NMFS-SWFSC-233. 15 pp. 

Barlow, J., K. A. Forney, P. S. Hill, R. L. Brownell, Jr., J. V. Carretta, D. P. DeMaster, F. Julian, M. S. Lowry, T.

Ragen, and R. R. Reeves. 1997. U.S. Pacific Marine Mammal Stock Assessments: 1996. U.S. Dep. Commer.,

NOAA Tech. Memo. NMFS-SWFSC-248. 223 pp.

Brownell, R. L., Jr., W. A. Walker and K. A. Forney. 1999. Pacific white-sided dolphin, Lagenorhynchus obliquidens

Gill, 1865. Pages 57-84 In: Ridgway, S. H. and R. Harrison (eds.), Handbook of Marine Mammals, Vol. 6.

Academic Press, San Diego.

Cameron, G., and K. A. Forney. 1999. Estimates of cetacean mortality in the California gillnet fisheries for 1997 and

1998. Paper SC/51/O4 presented to the International Whaling Commission, May 1999 (unpublished). 14 pp.

Chivers, S. J., K. M. Peltier, W. T. Norman, P. A. Akin, and J. Heyning. 1993. Population structure of cetaceans in

California coastal waters. Paper SOCCS9 presented at the Status of California Cetacean Stocks Workshop,

held in La Jolla, California, March 31-April 2, 1993. 49p.

Dohl, T. P., R. C. Guess, M. L. Duman, and R. C. Helm. 1983. Cetaceans of central and northern California, 1980-

1983: Status, abundance and distribution. OCS Study MMS 84-0045. Minerals Management Service Contract

# 14-12-0001-29090. 284p.

Dohl, T. P., K. S. Norris, R. C. Guess, J. D. Bryant, and M. W. Honig. 1980. Summary of marine mammal and seabird

surveys of the Southern California Bight area, 1975-1978. Part II. Cetacea of the Southern California Bight.

Final Report to the Bureau of Land Management, NTIS Rep. No. PB81248189. 414p.

Forney, K. A. 1994. Recent information on the status of odontocetes in Californian waters. U.S. Dep. Commer.,

NOAA Tech. Memo. NMFS-SWFSC-202. 87 pp. 

Forney, K. A. 1997. Patterns of variability and environmental models of relative abundance for California cetaceans.

Ph.D. dissertation, Scripps Institution of Oceanography, University of California, San Diego.

Forney, K. A. and J. Barlow. 1998. Seasonal patterns in the abundance and distribution of California cetaceans, 1991-

92. Mar. Mamm. Sci. 14:460-489.

Forney, K. A., J. Barlow and J. V. Carretta. 1995. The abundance of cetaceans in California waters. Part II: Aerial

surveys in winter and spring of 1991 and 1992. Fish. Bull. 93:15-26.

Green, G., J. J. Brueggeman, R. A. Grotefendt, C. E. Bowlby, M. L. Bonnell, and K. C. Balcomb, III. 1992. Cetacean

distribution and abundance off Oregon and Washington. Ch. 1. In: Oregon and Washington Marine Mammal

and Seabird Surveys. OCS Study 91-0093. Final Report prepared for Pacific OCS Region, Minerals

Management Service, U.S. Department of the Interior, Los Angeles, California. 

Green, G., R. A. Grotefendt, M. A. Smultea, C. E. Bowlby, and R. A. Rowlett. 1993. Delphinid aerial surveys in

Oregon and Washington waters. Final Report prepared for NMFS, National Marine Mammal Laboratory, 7600

Sand Point Way, NE, Seattle, Washington, 98115, Contract #50ABNF200058.

Holts, D. Southwest Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA 92038.

Holts, D. and O. Sosa-Nishizaki. 1998. Swordfish, Xiphias gladius, fisheries of the eastern North Pacific Ocean. In:

I. Barrett, O. Sosa-Nishizaki and N. Bartoo (eds.). Biology and fisheries of swordfish, Xiphias gladius. Papers

from the International Symposium on Pacific Swordfish, Ensenada Mexico, 11-14 December 1994. U.S. Dep.

Commer., NOAA Tech. Rep. NMFS 142. 276 pp.

Julian, F. 1997. Cetacean mortality in California gill net fisheries: Preliminary estimates for 1996. Paper SC/49/SM02

presented to the International Whaling Commission, September 1997 (unpublished). 13 pp.

Julian, F. and M. Beeson. 1998. Estimates of mammal, turtle and bird mortality for two California gillnet fisheries:

1990-1995. Fish. Bull. 96:271-284.
78

Lux, C. A., A. S. Costa, and A. E. Dizon. 1997. Mitochondrial DNA population structure of the Pacific white-sided

dolphin. Rep. Int. Whaling. Commn. 47:645-652.

Perez, M. A. and T. R. Loughlin. 1991. Incidental catch of marine mammals by foreign and joint venture trawl vessels

in the U.S. EEZ of the North Pacific, 1973-88. NOAA Tech. Rep. NMFS 104. 57 pp.

Perez, M. A. (in prep). Summary of marine mammal incidental catch data for domestic and joint venture groundfish

fisheries in the U.S. EEZ of the North Pacific, 1989-98. NOAA Tech. Memo.

Sosa-Nishizaki, O., R. De la Rosa Pacheco, R. Castro Longoria, M. Grijalva Chon, and J. De la Rosa Velez. 1993.

Estudio biologico pesquero del pez (Xiphias gladius) y otras especies de picudos (marlins y pez vela). Rep.

Int. CICESE, CTECT9306.

Wade, P. R. and R. P. Angliss. 1997. Guidelines for Assessing Marine Mammal Stocks: Report of the GAMMS

Workshop April 3-5, 1996, Seattle, Washington. U. S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-12.

93 pp.

Walker, W. A., S. Leatherwood, K. R. Goodrich, W. F. Perrin and R. K. Stroud. 1986. Geographical variation and

biology of the Pacific white-sided dolphin, Lagenorhynchus obliquidens, in the north-eastern Pacific. In:

Bryden, M. M. and R. Harrison (eds.), Research on Dolphins, p. 441-465. Clarendon Press, Oxford.
79

Figure 1. Risso’s dolphin sightings based on

aerial and shipboard surveys off California, Oregon

and Washington, 1991-96 (see Appendix 2,

Figures 1-5, for data sources and information on

timing and location of survey effort). Dashed line

represents the U.S. EEZ, thick line indicates the

outer boundary of all surveys combined.

Revised 12/15/2000

RISSO'S DOLPHIN (Grampus griseus):California/Oregon/Washington Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

Risso's dolphins are distributed world-wide in tropical

and warm-temperate waters. Off the U.S. West coast, Risso's

dolphins are commonly seen on the shelf in the Southern

California Bight and in slope and offshore waters of California,

Oregon and Washington. Based on sighting patterns from recent

aerial and shipboard surveys conducted in these three states

during different seasons (Figure 1), animals found off California

during the colder water months are thought to shift northward

into Oregon and Washington as water temperatures increase in

late spring and summer (Green et al. 1992). The southern end of

this population's range is not well-documented, but on a recent

joint U.S./Mexican ship survey, Risso's dolphins were sighted

off northern Baja California, and a conspicuous 500 nmi gap

was present between these animals and Risso's dolphins sighted

south of Baja California and in the Gulf of California (Mangels

and Gerrodette 1994). Thus this population appears distinct

from animals found in the eastern tropical Pacific and the Gulf

of California. Although Risso's dolphins are not restricted to

U.S. waters, cooperative management agreements with Mexico

exist only for the tuna purse seine fishery and not for other

fisheries which may take this species (e.g. gillnet fisheries). For

the Marine Mammal Protection Act (MMPA) stock assessment

reports, Risso's dolphins within the Pacific U.S. Exclusive

Economic Zone are divided into two discrete, non-contiguous

areas: 1) waters off California, Oregon and Washington (this

report), and 2) Hawaiian waters.

POPULATION SIZE

 The previous best estimates of abundance for Risso’s

dolphins (Barlow et al. 1997) were based on winter/spring 1991-

92 aerial surveys (Forney et al. 1995) off California, which were presumed to include Risso’s dolphins that are found

off Oregon and Washington during summer and fall. Three summer/fall shipboard surveys were conducted within 300

nmi of the coasts of California in 1991 and 1993 (Barlow and Gerrodette 1996) and California, Oregon and Washington

in 1996 (Barlow 1997). The distribution of Risso’s dolphins throughout this region is highly variable, apparently in

response to oceanographic changes on both seasonal and interannual time scales (Forney and Barlow 1998). As

oceanographic conditions vary, Risso’s dolphins may spend time outside the U.S. Exclusive Economic Zone, and

therefore a multi-year average abundance estimate is the most appropriate for management within U.S. waters. The

1991-96 weighted average abundance estimate for California, Oregon and Washington waters based on the three ship

surveys is 16,483 (CV = 0.28) Risso’s dolphins (Barlow 1997).

Minimum Population Estimate

The log-normal 20th percentile of the 1991-96 weighted average abundance estimate is 13,079 Risso's dolphins.

Current Population Trend

Although sighting records of Risso's dolphins appear to have increased during the last two decades in some

areas off the U.S. West coast (Green et al. 1992; 1993; Shane 1994), sampling effort has also increased, and there are

no statistical estimates of historical abundance on which to base a quantitative comparison. Thus, it is possible that

Risso's dolphin abundance off the U.S. West coast has increased, but no definitive statement regarding trends in
80

abundance of Risso's dolphins off California, Oregon and Washington can be made.

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

No information on current or maximum net productivity rates is available for Risso's dolphins in California,

Oregon and Washington.

POTENTIAL BIOLOGICAL REMOVAL

The potential biological removal (PBR) level for this stock is calculated as the minimum population size

(13,079) times one half the default maximum net growth rate for cetaceans (1⁄2 of 4%) times a recovery factor of 0.40

(for a species of unknown status with a mortality rate CV≥ 0.80; Wade and Angliss 1997), resulting in a PBR of 105

Risso’s dolphins per year. 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Fishery Information

A summary of recent fishery mortality and injury for this stock of Risso’s dolphin is shown in Table 1. More

detailed information on these fisheries is provided in Appendix 1. Mortality estimates for the California drift gillnet

fishery are included for the five most recent years of monitoring, 1994-98 (Julian and Beeson 1998; Julian 1997;

Cameron and Forney 1999). After the 1997 implementation of a Take Reduction Plan, which included skipper

education workshops and required the use of pingers and minimum 6-fathom extenders, overall cetacean entanglement

rates in the drift gillnet fishery dropped considerably (Barlow and Cameron 1999). However, because of interannual

variability in entanglement rates and the relative rarity of Risso’s dolphin entanglements, additional years of data will

be required to fully evaluate the effectiveness of pingers for reducing mortality of this particular species. Because of

the changes in this fishery after implementation of the Take Reduction Plan, mean annual takes in Table 1 are based only

on 1997-98 data. This results in an average estimate of 5.5 (CV = 0.96) Risso’s dolphins taken annually.

Drift gillnet fisheries for swordfish and sharks exist along the entire Pacific coast of Baja California, Mexico

and probably take animals from the same population. Quantitative data are available only for the Mexican swordfish

drift gillnet fishery, which uses vessels, gear, and operational procedures similar to those in the U.S. drift gillnet fishery,

although nets may be up to 4.5 km long (Holts and Sosa-Nishizaki 1998). The fleet increased from two vessels in 1986

to 31 vessels in 1993 (Holts and Sosa-Nishizaki 1998). The total number of sets in this fishery in 1992 can be estimated

from data provided by these authors to be approximately 2700, with an observed rate of marine mammal bycatch of 0.13

animals per set (10 marine mammals in 77 observed sets; Sosa-Nishizaki et al., 1993). This overall mortality rate is

similar to that observed in California driftnet fisheries during 1990-95 (0.14 marine mammals per set; Julian and Beeson,

1998), but species-specific information is not available for the Mexican fisheries. There are currently efforts underway

to convert the Mexican swordfish driftnet fishery to a longline fishery (D. Holts, pers. comm.). 

Table 1. Summary of available information on the incidental mortality and injury of Risso's dolphin (California/

Oregon/Washington Stock) in commercial fisheries that might take this species. All observed entanglements of Risso's

dolphins resulted in the death of the animal. Coefficients of variation for mortality estimates are provided in parentheses;

n/a = not available. Mean annual takes are based on 1994-98 data unless noted otherwise.

Fishery Name Data Type Year(s)

Percent

Observer

Coverage

Observed

Mortality

Estimated

Annual

Mortality 

Mean Annual Takes

(CV in parentheses)

CA/OR thresher

shark/swordfish drift gillnet

fishery

observer

data 

1994

1995

1996

1997

1998

17.9% 

15.6% 

12.4% 

23.0% 

20.0% 

1

6

0

3

0

6 (0.91)

39 (0.57)

0

11 (0.96)

0

5.5 (0.96) 1

Minimum total annual takes 5.5 (0.96) 

 1 Only 1997-98 mortality estimates are included in the average because overall cetacean entanglement rates dropped considerably after a Take

Reduction Plan was implemented in 1997.

Additional mortality of unknown extent has been documented for Risso's dolphins in the squid purse seine

fishery off Southern California (Heyning et al. 1994). This mortality probably represented animals killed intentionally
81

to protect catch or gear, rather than incidental mortality, and such intentional takes are now illegal under the 1994

Amendment to the MMPA. This fishery has expanded markedly since 1992 (California Department of Fish and Game,

unpubl. data). No recent Risso’s dolphin mortality has been reported for this fishery, but it is currently not monitored.

STATUS OF STOCK

The status of Risso's dolphins off California, Oregon and Washington relative to OSP is not known, and there

are insufficient data to evaluate potential trends in abundance. No habitat issues are known to be of concern for this

species. They are not listed as "threatened" or "endangered" under the Endangered Species Act nor as "depleted" under

the MMPA. Including driftnet mortality only for years after implementation of the Take Reduction Plan (1997-98), the

average annual human-caused mortality in 1994-98 (5.5 animals) is estimated to be less than the PBR (105), and

therefore they are not classified as a "strategic" stock under the MMPA. The total fishery mortality and serious injury

for this stock is less than 10% of the calculated PBR and, therefore, can be considered to be insignificant and

approaching zero mortality and serious injury rate. 

REFERENCES

Barlow, J. 1997. Preliminary estimates of cetacean abundance off California, Oregon and Washington based on a 1996

ship survey and comparisons of passing and closing modes. Admin. Rep. LJ-97-11, Southwest Fisheries

Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA 92038. 25p.

Barlow, J. and G. A. Cameron. 1999. Field experiments show that acoustic pingers reduce marine mammal bycatch in

the California drift gillnet fishery. Paper SC/51/SM2 presented to the International Whaling Commission, May

1998 (unpublished). 20 pp.

Barlow, J., K. A. Forney, P. S. Hill, R. L. Brownell, Jr., J. V. Carretta, D. P. DeMaster, F. Julian, M. S. Lowry, T.

Ragen, and R. R. Reeves. 1997. U.S. Pacific Marine Mammal Stock Assessments: 1996. U.S. Dep. Commer.,

NOAA Tech. Memo. NMFS-SWFSC-248. 223p.

Barlow, J. and T. Gerrodette. 1996. Abundance of cetaceans in California waters based on 1991 and 1993 ship

surveys. NOAA Tech. Memo. NMFS-SWFSC-233. 15 pp.

Cameron, G., and K. A. Forney. 1999. Estimates of cetacean mortality in the California gillnet fisheries for 1997 and

1998. Paper SC/51/O4 presented to the International Whaling Commission, May 1999 (unpublished). 14 pp.

Forney, K. A. and J. Barlow. 1998. Seasonal patterns in the abundance and distribution of California cetaceans, 1991-

92. Mar. Mamm. Sci. 14:460-489.

Forney, K. A., J. Barlow and J. V. Carretta. 1995. The abundance of cetaceans in California waters. Part II: Aerial

surveys in winter and spring of 1991 and 1992. Fish. Bull. 93:15-26.

Green, G., J. J. Brueggeman, R. A. Grotefendt, C. E. Bowlby, M. L. Bonnell, and K. C. Balcomb, III. 1992. Cetacean

distribution and abundance off Oregon and Washington. Ch. 1. In: Oregon and Washington Marine Mammal

and Seabird Surveys. OCS Study 91-0093. Final Report prepared for Pacific OCS Region, Minerals

Management Service, U.S. Department of the Interior, Los Angeles, California. 

Green, G., R. A. Grotefendt, M. A. Smultea, C. E. Bowlby, and R. A. Rowlett. 1993. Delphinid aerial surveys in

Oregon and Washington waters. Final Report prepared for NMFS, National Marine Mammal Laboratory, 7600

Sand Point Way, NE, Seattle, Washington, 98115, Contract #50ABNF200058.

Heyning, J. E., T. D. Lewis and C. D. Woodhouse. 1994. A note on odontocete mortality from fishing gear

entanglements off Southern California. Rep. Int. Whal. Commn. Special Issue 15:439-442.

Holts, D. Southwest Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA 92038.

Holts, D. and O. Sosa-Nishizaki. 1998. Swordfish, Xiphias gladius, fisheries of the eastern North Pacific Ocean. In:

I. Barrett, O. Sosa-Nishizaki and N. Bartoo (eds.). Biology and fisheries of swordfish, Xiphias gladius. Papers

from the International Symposium on Pacific Swordfish, Ensenada Mexico, 11-14 December 1994. U.S. Dep.

Commer., NOAA Tech. Rep. NMFS 142, 276 p.

Julian, F. 1997. Cetacean mortality in California gill net fisheries: Preliminary estimates for 1996. Paper SC/49/SM02

presented to the International Whaling Commission, September 1997 (unpublished). 13 pp.

Julian, F. and M. Beeson. 1998. Estimates of mammal, turtle and bird mortality for two California gillnet fisheries:

1990-1995. Fish. Bull. 96:271-284.

Mangels, K. F. and Gerrodette, T. 1994. Report of cetacean sightings during a marine mammal survey in the eastern

Pacific Ocean and Gulf of California aboard the NOAA ships McARTHUR and DAVID STARR JORDAN July
82

28 - November 6, 1993. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-SWFSC-211. 88 pp.

Shane, S. 1994. Occurrence and habitat use of marine mammals at Santa Catalina Island, California from 1983-91.

Bull. Southern California Acad. Sci. 93:13-29.

Sosa-Nishizaki, O., R. De la Rosa Pacheco, R. Castro Longoria, M. Grijalva Chon, and J. De la Rosa Velez. 1993.

Estudio biologico pesquero del pez (Xiphias gladius) y otras especies de picudos (marlins y pez vela). Rep.

Int. CICESE, CTECT9306.

Wade, P. R. and R. P. Angliss. 1997. Guidelines for Assessing Marine Mammal Stocks: Report of the GAMMS

Workshop April 3-5, 1996, Seattle, Washington. U. S. Dep. Commerce, NOAA Tech. Memo. NMFS-OPR-12.

93 pp.
83

Figure 1. Approximate range (in bold) of California coastal

bottlenose dolphins based on aerial surveys along the coast of

California from 1990-2000. This population of bottlenose

dolphins is found within about 1 km of shore.

Revised 12/31/2001

BOTTLENOSE DOLPHIN (Tursiops truncatus): California Coastal Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

Bottlenose dolphins are distributed worldwide in tropical and warm-temperate waters. In

many regions, including California, separate coastal

and offshore populations are known (Walker 1981;

Ross and Cockcroft 1990; Van Waerebeek et al.

1990). California coastal bottlenose dolphins are

found within about one kilometer of shore (Figure

1; Hansen, 1990; Carretta et al. 1998; Defran and

Weller 1999) primarily from Point Conception

south into Mexican waters, at least as far south as

Ensenada. In southern California, animals are

found within 500 m of the shoreline 99% of the

time and within 250 m 90% of the time (Hanson

and Defran 1993). Oceanographic events appear to

influence the distribution of animals along the

coasts of California and Baja California, Mexico, as

indicated by a change in residency patterns along

Southern California and a northward range

extension into central California after the 1982-83

El Niño (Hansen and Defran 1990; Wells et al.

1990). Since the 1982-83 El Niño, which increased

water temperatures off California, they have been

consistently sighted in central California as far

north as San Francisco. Photo-identification

studies have documented north-south movements of

coastal bottlenose dolphins (Hansen 1990; Defran

et al. 1999), and monthly counts based on surveys

between the U.S./Mexican border and Point

Conception are variable (Carretta et al. 1998),

indicating that animals are probably moving into

and out of this area. Although coastal bottlenose

dolphins are not restricted to U.S. waters,

cooperative management agreements with Mexico

exist only for the tuna purse seine fishery and not

for other fisheries which may take this species (e.g. gillnet fisheries). Therefore, the management stock includes only

animals found within U.S. waters. For the Marine Mammal Protection Act (MMPA) stock assessment reports,

bottlenose dolphins within the Pacific U.S. Exclusive Economic Zone are divided into three stocks: 1) California coastal

stock (this report), 2) California, Oregon and Washington offshore stock, and 3) Hawaiian stock.

POPULATION SIZE

Photo-identification studies along the coasts of southern California and northern Mexico identified 404 unique

individuals in this population between 1981 and 1989 based on dorsal fin characteristics, with an estimated 35% of

animals lacking identifiable characters at any particular time (Defran and Weller 1999). This cannot be considered a

minimum population estimate, however, because an unknown number of animals died during this period and rates of

acquisition of dorsal fin characters are not known. Mark-recapture estimates based on photo-identification studies in

1985-89 range from 234 (95% CI 205-263) to 285 (95% CI 265-306) animals for the entire California-Mexico

population (Defran and Weller 1999). A recent re-analysis of mark-recapture estimates from the 1980s resulted in

revised abundance estimates of 289 (95% CI 230-298) for the period 1984-86 and 354 (95% CI 330-390) for 1987-89
84

(Dudzik 1999). The most recent photographic mark-recapture abundance estimate is 356 (95% CI 306 - 437) for the

period 1996-98 (Dudzik 1999). Because coastal bottlenose dolphins spend an unknown amount of time in Mexican

waters, where they are subject to mortality in Mexican fisheries, an average abundance estimate for California only is

the most appropriate for U.S. management of this stock. Tandem aerial surveys were conducted in 1990-94 and 1999-

2000 to estimate the abundance of coastal bottlenose dolphins throughout the southern and central California portion

of their range and to correct for the fraction of animals missed by a single observer team. (Carretta et al. 1998, NMFS,

SWFSC, unpublished data). Aerial survey correction factors have been improved using recent information on California

coastal bottlenose dolphin swim speeds (Ward 1999). Using the same methods as Carretta et al. (1998), the weighted

average abundance estimate for the 1999-2000 surveys is 206 (CV=0.12) coastal bottlenose dolphins (NMFS, SWFSC,

unpublished data). This presently is the best estimate of the average number of coastal bottlenose dolphins in U.S.

waters.

Minimum Population Estimate

The log-normal 20th percentile of the above average abundance estimate for U.S. waters based on the 1999-

2000 surveys is 186 coastal bottlenose dolphins.

Current Population Trend

 Based on a comparison of mark-recapture abundance estimates for the periods 1987-89 (Nˆ = 354) and 1996-98

(Nˆ = 356), Dudzik (1999) stated that the population size had remained stable over an 11-year period.

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

No information on current or maximum net productivity rates is available for California coastal bottlenose

dolphins.

POTENTIAL BIOLOGICAL REMOVAL

The potential biological removal (PBR) level for this stock is calculated as the minimum population size (186)

times one half the default maximum net growth rate for cetaceans (1⁄2 of 4%) times a recovery factor of 0.50 (for a

species of unknown status with no known fishery mortality; Wade and Angliss 1997), resulting in a PBR of 1.9 coastal

bottlenose dolphins per year. 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Fishery Information

Due to its exclusive use of coastal habitats, this bottlenose dolphin population is susceptible to fishery-related

mortality in coastal set net fisheries. A summary of information on fishery mortality and injury for this stock of

bottlenose dolphin is shown in Table 1. More detailed information on the set gillnet fishery is provided in Appendix

1. From 1991-94, no bottlenose dolphins were observed taken in this fishery with 10-15% observer coverage (Julian

and Beeson 1998). The observer program was discontinued at the end of 1994, when coastal set gillnet fishing was

banned within 3 nmi of the southern California coast. In central California, gillnets have been restricted to waters

deeper than 30 fathoms (56m) since 1991 in all areas except between Point Sal and Point Arguello. In 2001, gillnets

were banned inshore of 60 fathoms from Point Reyes to Point Arguello by the California Department of Fish and Game.

Because of these closures, the potential for mortality of coastal bottlenose dolphins in the California set gillnet fishery

has been greatly reduced. Fisher self-report data and stranding records for 1994-98 do not include any records of

fishery interactions for this stock. Coastal gillnet fisheries exist in Mexico and probably take animals from this

population, but no details are available. 
85

Table 1. Summary of available information on the incidental mortality and serious injury of bottlenose dolphins

(California Coastal Stock) in commercial fisheries that might take this species.

Fishery Name Data Type Year(s)

Percent

Observer

Coverage

Observed

Mortality

Estimated

Annual

Mortality

Mean Annual

Takes

CA angel shark/ halibut and other

species large mesh (>3.5in) set

gillnet fishery

observer

data 1995-981

19992

0.0 %

4.0 %

0 0 0

Minimum total annual takes 0

1The CA set gillnets were not observed from 1995-98; mortality was extrapolated from effort estimates and previous entanglement rates.

2Set gillnet observer coverage in 1999 was limited to Monterey Bay fishing effort only.

Other removals

Seven coastal bottlenose dolphins were collected during the late 1950s in the vicinity of San Diego (Norris and

Prescott 1961). Twenty-seven additional bottlenose dolphins were captured off California between 1966 and 1982

(Walker 1975; Reeves and Leatherwood 1984), but based on the locations of capture activities, these animals probably

were offshore bottlenose dolphins (Walker 1975). No additional captures of coastal bottlenose dolphins have been

documented since 1982, and no live-capture permits are currently active for this species.

STATUS OF STOCK

The status of coastal bottlenose dolphins in California relative to OSP is not known, and there is no evidence

of a trend in abundance. They are not listed as "threatened" or "endangered" under the Endangered Species Act nor as

"depleted" under the MMPA. Because no recent fishery takes have been documented, coastal bottlenose dolphins are

not classified as a "strategic" stock under the MMPA, and the total fishery mortality and serious injury for this stock can

be considered to be insignificant and approaching zero.

Habitat Issues

Pollutant levels, especially DDT residues, found in Southern California coastal bottlenose dolphins have been

found to be among the highest of any cetacean examined (O'Shea et al. 1980; Schafer et al. 1984). Although the effects

of pollutants on cetaceans are not well understood, they may affect reproduction or make the animals more prone to other

mortality factors (Britt and Howard 1983; O’Shea et al. 1999). This population of bottlenose dolphins may also be

vulnerable to the effects of morbillivirus outbreaks, which were implicated in the 1987-88 mass mortality of bottlenose

dolphins on the U.S. Atlantic coast (Lipscomb et al. 1994).

REFERENCES

Britt, J. O. and E. B. Howard. 1983. Tissue residues of selected environmental contaminants in marine mammals. In:

Howard, E. B. (ed.), Pathobiology of Marine Mammal Diseases. CRC Press, Boca Raton, Florida.

Carretta, J. V., K. A. Forney and J. L. Laake. 1998. The abundance of southern California coastal bottlenose dolphins

estimated from tandem aerial surveys. Mar. Mamm. Sci. 14:655-675.

Defran, R. H. and D. W. Weller. 1999. Occurrence, distribution, site fidelity and school size of bottlenose dolphins

(Tursiops truncatus) off San Diego, California. Mar. Mamm. Sci. 15:366-380.

Defran, R. H., D. W. Weller, D. L. Kelly, and M. A. Espinosa. 1999. Range characteristics of Pacific coast bottlenose

dolphins (Tursiops truncatus) in the Southern California Bight. Mar. Mamm. Sci. 15:381-393.

Dudzik, K.J. 1999. Population dynamics of the Pacific coast bottlenose dolphin (Tursiops truncatus). M.S. Thesis, San

Diego State University, San Diego, California 92182. 63pp.

Forney, K.A., J. Barlow, M.M. Muto, M. Lowry, J. Baker, G. Cameron, J. Mobley, C. Stinchcomb, and J.V. Carretta. 2000. U.S. Pacific Marine

Mammal Stock Assessments: 2000. U.S. Department of Commerce, NOAA Technical Memorandum NMFS-SWFSC-300. 276p.

Hansen, L. J. 1990. California coastal bottlenose dolphins. In: S. Leatherwood and R.R. Reeves (eds.), The Bottlenose

Dolphin, p. 403-420. Academic Press, Inc., San Diego.

Hansen, L. J. and R. H. Defran. 1990. A comparison of photo-identification studies of California coastal bottlenose

dolphins. Rep. Int. Whal. Commn. Special Issue 12:101-104.

Hanson, M.T. and R.H. Defran. 1993. The behavior and feeding ecology of the Pacific coast bottlenose dolphin,

Tursiops truncatus. Aquatic Mammals 19:127-142.
86

Julian, F. and M. Beeson. 1998. Estimates of mammal, turtle and bird mortality for two California gillnet fisheries:

1990-1995. Fish. Bull. 96:271-284.

Lipscomb, T. P., F. Y. Schulman, D. Moffett, and S. Kennedy. 1994. Morbilliviral disease in Atlantic bottlenose

dolphins (Tursiops truncatus) from the 1987-88 epizootic. Journal of Wildlife Diseases 30:567-571.

O'Shea, T. J., R. L. Brownell, Jr., D. R. Clark, W. A. Walker, M. L. Gray, and T. G. Lamont. 1980. Organochlorine

pollutants in small cetaceans from the Pacific and South Atlantic Oceans, November 1968-June 1976.

Pesticides Monitoring Journal 14:35-46.

O’Shea, T. J., R. R. Reeves, and A. Kirk Long (eds.). 1999. Marine Mammals and Persistent Ocean Contaminants:

Proceedings of the Marine Mammal Commission Workshop, Keystone, Colorado, 12-15 October 1998. Marine

Mammal Commission, Bethesda, MD. 150pp.

NMFS, Southwest Fisheries Science Center. P.O. Box 271, La Jolla, CA 92038-0271

Norris, K. S. and J. H. Prescott. 1961. Observation on Pacific cetaceans of Californian and Mexican waters. University

of California Publications in Zoology 63:291-402. University of California Press, Berkeley and Los Angeles.

Reeves, R. R. and S. Leatherwood. 1984. Live-capture fisheries for cetaceans in USA and Canadian waters, 1973-1982.

Rep. Int. Whal. Commn. 34:497-507.

Ross, G. J. B. and V. G. Cockcroft. 1990. Comments on Australian bottlenose dolphins and the taxonomic status of

Tursiops aduncus (Ehrenberg, 1832). In: The Bottlenose Dolphin (eds. S. Leatherwood and R. R. Reeves). pp.

101-128. Academic Press, 653pp. 

Schafer, H. A., R. W. Gossett, C. F. Ward, and A. M. Westcott. 1984. Chlorinated hydrocarbons in marine mammals.

Biennial Report, 1983-84, Southern California Coastal Water Research Project, Long Beach, California.

Van Waerebeek, K., J. C. Reyes, A. J. Read, and J. S. McKinnon. 1990. Preliminary observations of bottlenose

dolphins from the Pacific coast of South America. In: The Bottlenose Dolphin (eds. S. Leatherwood and R. R.

Reeves). pp. 143-154 Academic Press, 653 pp. 

Walker, W. A. 1975. Review of the live-capture fishery for smaller cetaceans taken in Southern California waters for

public display, 1966-77. J. Fish. Res. Board. Can. 32:1197-1211.

Walker, W. A. 1981. Geographical variation in morphology and biology of bottlenose dolphins (Tursiops) in the

eastern North Pacific. Admin. Rep. LJ-81-03C. Southwest Fisheries Science Center, National Marine Fisheries

Service, P.O. Box 271, La Jolla, CA 92038, USA. 52p.

Ward, B.G. 1999. Movement patterns and feeding ecology of the Pacific coast bottlenose dolphin (Tursiops truncatus).

M.S. Thesis, San Diego State University, San Diego, California, 92182. 98pp.

Wells, R. S., L. J. Hansen, A. B. Baldridge, T. P. Dohl, D. L. Kelly and R. H Defran. In: S. Leatherwood and R. R.

Reeves (eds.), The Bottlenose Dolphin, p. 421-431. Academic Press, Inc., San Diego.

Wade, P. R. and R. P. Angliss. 1997. Guidelines for Assessing Marine Mammal Stocks: Report of the GAMMS

Workshop April 3-5, 1996, Seattle, Washington. U. S. Dep. Commerce, NOAA Tech. Memo. NMFS-OPR-12.

93 pp.
87

Figure 1. Offshore bottlenose dolphin sightings

based on aerial and shipboard surveys off

California, Oregon and Washington, 1991-96 (see

Appendix 2, Figures 1-5, for data sources and

information on timing and location of survey

effort). All sightings were made at distances

greater than a few kilometers from the mainland

California coast. Dashed line represents the U.S.

EEZ, thick line indicates the outer boundary of all

surveys combined.

Revised 12/15/2000

BOTTLENOSE DOLPHIN (Tursiops truncatus):

California/Oregon/Washington Offshore Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

Bottlenose dolphins are distributed world-wide in

tropical and warm-temperate waters. In many regions,

including California, separate coastal and offshore populations

are known (Walker 1981; Ross and Cockcroft 1990; Van

Waerebeek et al. 1990). On surveys conducted off California,

offshore bottlenose dolphins have been found at distances greater

than a few kilometers from the mainland and throughout the

Southern California Bight. They have also been documented in

offshore waters as far north as about 41oN (Figure 1), and they

may range into Oregon and Washington waters during warmwater periods. Sighting records off California and Baja

California (Lee 1993; Mangels and Gerrodette 1994) suggest that

offshore bottlenose dolphins have a continuous distribution in

these two regions. Based on aerial surveys conducted during

winter/spring 1991-92 (Forney et al. 1995) and shipboard surveys

conducted in summer/fall 1991 (Barlow 1995), no seasonality in

distribution is apparent (Forney and Barlow 1998). Offshore

bottlenose dolphins are not restricted to U.S. waters, but

cooperative management agreements with Mexico exist only for

the tuna purse seine fishery and not for other fisheries which may

take this species (e.g. gillnet fisheries). Therefore, the

management stock includes only animals found within U.S.

waters. For the Marine Mammal Protection Act (MMPA) stock

assessment reports, bottlenose dolphins within the Pacific U.S.

Exclusive Economic Zone are divided into three stocks: 1)

California coastal stock, 2) California, Oregon and Washington

offshore stock (this report), and 3) Hawaiian stock.

POPULATION SIZE

 The previous best estimates of abundance for offshore

bottlenose dolphins (Barlow et al. 1997) were based on a

weighted average for winter/spring 1991-92 aerial surveys

(Forney et al. 1995), and summer/fall ship surveys in 1991 and

1993 (Barlow and Gerrodette 1996) along the coast of California. An additional summer/fall shipboard surveys was

conducted within 300 nmi of the coasts of California, Oregon and Washington in 1996 (Barlow 1997). Because the

distribution of bottlenose dolphins appears to vary interannually and they may spend time outside the U.S. Exclusive

Economic Zone, a multi-year average abundance estimate is the most appropriate for management within U.S. waters.

The most comprehensive multi-year average abundance is the weighted average abundance estimate for California,

Oregon and Washington waters based on the 1991-96 ship surveys, 956 (CV = 0.14) offshore bottlenose dolphins

(Barlow 1997).

Minimum Population Estimate

The log-normal 20th percentile of the 1991-96 weighted average abundance estimate is 850 offshore bottlenose

dolphins.
88

Current Population Trend

No information on trends in abundance of offshore bottlenose dolphins is available.

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

No information on current or maximum net productivity rates is available for this population of offshore

bottlenose dolphins.

POTENTIAL BIOLOGICAL REMOVAL

 The potential biological removal (PBR) level for this stock is calculated as the minimum population size (850)

times one half the default maximum net growth rate for cetaceans (1⁄2 of 4%) times a recovery factor of 0.50 (for a

species of unknown status with no known fishery mortality; Wade and Angliss 1997), resulting in a PBR of 8.5 offshore

bottlenose dolphins per year. 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Fishery Information

A summary of known fishery mortality and injury for this stock of bottlenose dolphin is shown in Table 1.

More detailed information on these fisheries is provided in Appendix 1. Mortality estimates for the California drift

gillnet fishery are included for the five most recent years of monitoring, 1994-98 (Julian and Beeson 1998; Julian 1997;

Cameron and Forney 1999). After the 1997 implementation of a Take Reduction Plan, which included skipper

education workshops and required the use of pingers and minimum 6-fathom extenders, overall cetacean entanglement

rates in the drift gillnet fishery dropped considerably (Barlow and Cameron 1999). However, because of interannual

variability in entanglement rates and the rarity of bottlenose dolphin entanglements, additional years of data will be

required to fully evaluate the effectiveness of pingers for reducing mortality of this particular species. Because of the

changes in this fishery after implementation of the Take Reduction Plan, mean annual takes in Table 1 are based only

on 1997-98 data. This results in an average estimate of zero offshore bottlenose dolphins taken annually.

Table 1. Summary of available information on the incidental mortality and injury of bottlenose dolphins (California/

Oregon/Washington Offshore Stock) in commercial fisheries that might take this species. Mean annual takes are based

on 1994-98 data unless noted otherwise.

Fishery Name Data Type Year(s)

Percent

Observer

Coverage

Observed

Mortality

Estimated Annual

Mortality 

Mean

Annual Takes

(CV in

parentheses)

CA/OR thresher

shark/swordfish drift

gillnet fishery

observer

data 

1994

1995

1996

1997

1998

17.9% 

15.6% 

12.4% 

23.0% 

20.0% 

0

0

0

0

0

0

0

0

0

0

0

 1

Minimum total annual takes 0

1 Only 1997-98 mortality estimates are included in the average because overall cetacean entanglement rates dropped considerably after a Take

Reduction Plan was implemented in 1997.

 Drift gillnet fisheries for swordfish and sharks exist along the entire Pacific coast of Baja California, Mexico

and may take animals from the same population. Quantitative data are available only for the Mexican swordfish drift

gillnet fishery, which uses vessels, gear, and operational procedures similar to those in the U.S. drift gillnet fishery,

although nets may be up to 4.5 km long (Holts and Sosa-Nishizaki 1998). The fleet increased from two vessels in 1986

to 31 vessels in 1993 (Holts and Sosa-Nishizaki 1998). The total number of sets in this fishery in 1992 can be estimated

from data provided by these authors to be approximately 2700, with an observed rate of marine mammal bycatch of 0.13

animals per set (10 marine mammals in 77 observed sets; Sosa-Nishizaki et al. 1993). This overall mortality rate is

similar to that observed in California driftnet fisheries during 1990-95 (0.14 marine mammals per set; Julian and Beeson,

1998), but species-specific information is not available for the Mexican fisheries. There are currently efforts underway

to convert the Mexican swordfish driftnet fishery to a longline fishery (D. Holts, pers. comm.). 
89

Offshore bottlenose dolphins are often associated with Risso's dolphins and pilot whales, for which mortality

has been documented in the squid purse seine fishery off Southern California (Heyning et al. 1994). Based on this

association, offshore bottlenose dolphins may also have experienced some mortality in this fishery. However these

would probably represent animals killed intentionally to protect catch or gear, rather than incidental kills, and such

intentional takes are now illegal under the 1994 Amendment to the MMPA.

 

Other removals

Twenty-seven bottlenose dolphins were captured off California between 1966 and 1982 (Walker 1975; Reeves

and Leatherwood 1984). Based on the locations of capture activities, these animals probably were offshore bottlenose

dolphins (Walker 1975). No additional captures of bottlenose dolphins off California have been documented since

1982, and no MMPA live-capture permits are currently active for this species.

STATUS OF STOCK

The status of offshore bottlenose dolphins in California relative to OSP is not known, and there are insufficient

data to evaluate trends in abundance. No habitat issues are known to be of concern for this species. They are not listed

as "threatened" or "endangered" under the Endangered Species Act nor as "depleted" under the MMPA. Because no

recent fishery takes have been documented, offshore bottlenose dolphins are not classified as a "strategic" stock under

the MMPA, and the total fishery mortality and serious injury for this stock can be considered to be insignificant and

approaching zero.

REFERENCES

Barlow, J. 1995. The abundance of cetaceans in California waters. Part I: Ship surveys in summer and fall of 1991.

Fish. Bull. 93:1-14.

Barlow, J. 1997. Preliminary estimates of cetacean abundance off California, Oregon and Washington based on a 1996

ship survey and comparisons of passing and closing modes. Admin. Rep. LJ-97-11, Southwest Fisheries

Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA 92038. 25p.

Barlow, J. and G. A. Cameron. 1999. Field experiments show that acoustic pingers reduce marine mammal bycatch in

the California drift gillnet fishery. Paper SC/51/SM2 presented to the International Whaling Commission, May

1998 (unpublished). 20 pp.

Barlow, J., K. A. Forney, P. S. Hill, R. L. Brownell, Jr., J. V. Carretta, D. P. DeMaster, F. Julian, M. S. Lowry, T.

Ragen, and R. R. Reeves. 1997. U.S. Pacific Marine Mammal Stock Assessments: 1996. U.S. Dep. Commer.,

NOAA Tech. Memo. NMFS-SWFSC-248. 223p.

Barlow, J. and T. Gerrodette. 1996. Abundance of cetaceans in California waters based on 1991 and 1993 ship

surveys. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-SWFSC-233. 15 pp. 

Cameron, G., and K. A. Forney. 1999. Estimates of cetacean mortality in the California gillnet fisheries for 1997 and

1998. Paper SC/51/O4 presented to the International Whaling Commission, May 1999 (unpublished). 14 pp.

Forney, K. A. and J. Barlow. 1998. Seasonal patterns in the abundance and distribution of California cetaceans, 1991-

92. Mar. Mamm. Sci. 14:460-489.

Forney, K. A., J. Barlow and J. V. Carretta. 1995. The abundance of cetaceans in California waters. Part II: Aerial

surveys in winter and spring of 1991 and 1992. Fish. Bull. 93:15-26.

Heyning, J. E., T. D. Lewis and C. D. Woodhouse. 1994. A note on odontocete mortality from fishing gear

entanglements off Southern California. Rep. Int. Whal. Commn. Special Issue 15:439-442.

Holts, D. Southwest Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA 92038.

Holts, D. and O. Sosa-Nishizaki. 1998. Swordfish, Xiphias gladius, fisheries of the eastern North Pacific Ocean. In:

I. Barrett, O. Sosa-Nishizaki and N. Bartoo (eds.). Biology and fisheries of swordfish, Xiphias gladius. Papers

from the International Symposium on Pacific Swordfish, Ensenada Mexico, 11-14 December 1994. U.S. Dep.

Commer., NOAA Tech. Rep. NMFS 142, 276 p.

Julian, F. 1997. Cetacean mortality in California gill net fisheries: Preliminary estimates for 1996. Paper SC/49/SM02

presented to the International Whaling Commission, September 1997 (unpublished). 13 pp.

Julian, F. and M. Beeson. 1998. Estimates of mammal, turtle and bird mortality for two California gillnet fisheries:

1990-1995. Fish. Bull. 96:271-284.

Lee, T. 1993. Summary of cetacean survey data collected between the years of 1974 and 1985. U.S. Dep. Commer.,
90

NOAA Tech. Memo. NMFS-SWFSC-181. 184 pp.

Mangels, K. F. and Gerrodette, T. 1994. Report of cetacean sightings during a marine mammal survey in the eastern

Pacific Ocean and Gulf of California aboard the NOAA ships McARTHUR and DAVID STARR JORDAN July

28 - November 6, 1993. NOAA Tech. Memo. NMFS, NMFS-SWFSC-211. 88 pp.

Reeves, R. R. and S. Leatherwood. 1984. Live-capture fisheries for cetaceans in USA and Canadian waters, 1973-1982.

Rep. Int. Whal. Commn 34:497-507.

Ross, G. J. B. and V. G. Cockcroft. 1990. Comments on Australian bottlenose dolphins and the taxonomic status of

Tursiops aduncus (Ehrenberg, 1832). In: The Bottlenose Dolphin (eds. S. Leatherwood and R. R. Reeves).

pp. 101-128. Academic Press, 653pp. 

Sosa-Nishizaki, O., R. De la Rosa Pacheco, R. Castro Longoria, M. Grijalva Chon, and J. De la Rosa Velez. 1993.

Estudio biologico pesquero del pez (Xiphias gladius) y otras especies de picudos (marlins y pez vela). Rep.

Int. CICESE, CTECT9306.

Van Waerebeek, K., J. C. Reyes, A. J. Read, and J. S. McKinnon. 1990. Preliminary observations of bottlenose

dolphins from the Pacific coast of South America. In: The Bottlenose Dolphin (eds. S. Leatherwood and R.

R. Reeves). pp. 143-154 Academic Press, 653 pp. 

Walker, W. A. 1975. Review of the live-capture fishery for smaller cetaceans taken in Southern California waters for

public display, 1966-77. J. Fish. Res. Board. Can. 32:1197-1211.

Walker, W. A. 1981. Geographical variation in morphology and biology of bottlenose dolphins (Tursiops) in the

eastern North Pacific. Admin. Rep. LJ-81-03C. Southwest Fisheries Science Center, National Marine

Fisheries Service, La Jolla, CA 92038. 52p.

Wade, P. R. and R. P. Angliss. 1997. Guidelines for Assessing Marine Mammal Stocks: Report of the GAMMS

Workshop April 3-5, 1996, Seattle, Washington. U. S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-12.

93 pp.
91

Figure 1. Striped dolphin sightings based on

aerial and shipboard surveys off California, Oregon

and Washington, 1991-96 (see Appendix 2,

Figures 1-5, for data sources and information on

timing and location of survey effort). Dashed line

represents the U.S. EEZ, thick line indicates the

outer boundary of all surveys combined.

Revised 12/15/2000

STRIPED DOLPHIN (Stenella coeruleoalba):

California/Oregon/Washington Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

Striped dolphins are distributed world-wide in tropical

and warm-temperate pelagic waters. On recent shipboard

surveys extending about 300 nmi offshore of California, they

were sighted within about 100-300 nmi from the coast (Figure

1). No sightings have been reported for Oregon and

Washington waters, but striped dolphins have stranded in both

states (Oregon Department of Fish and Wildlife, unpublished

data; Washington Department of Fish and Wildlife,

unpublished data). Striped dolphins are also commonly found

in the central North Pacific, but sampling between this region

and California has been insufficient to determine whether the

distribution is continuous. Based on sighting records off

California and Mexico, striped dolphins appear to have a

continuous distribution in offshore waters of these two regions

(Perrin et al. 1985; Mangels and Gerrodette 1994). No

information on possible seasonality in distribution is available,

because the California surveys which extended 300 nmi

offshore were conducted only during the summer/fall period.

Although striped dolphins are not restricted to U.S. waters,

cooperative management agreements with Mexico exist only for

the tuna purse seine fishery and not for other fisheries which

may take this species (e.g. gillnet fisheries). Therefore, the

management stock includes only animals found within U.S.

waters. For the Marine Mammal Protection Act (MMPA) stock

assessment reports, striped dolphins within the Pacific U.S.

Exclusive Economic Zone are divided into two discrete, noncontiguous areas: 1) waters off California, Oregon and

Washington (this report), and 2) waters around Hawaii.

POPULATION SIZE

 Three summer/fall shipboard surveys were conducted within 300 nmi of the coasts of California in 1991 and

1993 (Barlow and Gerrodette 1996) and California, Oregon and Washington in 1996 (Barlow 1997). The abundance

of striped dolphins in this region appears to be variable between years and may be affected by oceanographic conditions,

as with other odontocete species (Forney 1997, Forney and Barlow 1998). Because animals may spend time outside

the U.S. Exclusive Economic Zone as oceanographic conditions change, a multi-year average abundance estimate is the

most appropriate for management within U.S. waters. The 1991-96 weighted average abundance estimate for California,

Oregon and Washington waters based on the above three ship surveys is 20,235 (CV = 0.14) striped dolphins (Barlow

1997).

Minimum Population Estimate

The log-normal 20th percentile of the 1991-96 weighted average abundance estimate is 17,995 striped dolphins.

Current Population Trend

Prior to the 1991 shipboard survey (Barlow 1995), striped dolphins were not thought to be common off

California (Leatherwood et al. 1982), and two surveys extending approximately 200 nmi offshore of California and Baja

California in 1979 and 1980 resulted in only one sighting of three striped dolphins (Smith et al. 1986). Thus it is
92

possible that striped dolphin abundance off California has increased over the last decade (consistent with the observed

warming trend for these waters; Roemmich 1992); however, no definitive statement can be made, because statistical

estimates of abundance were not obtained for the earlier surveys.

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

No information on current or maximum net productivity rates is available for striped dolphins off California.

POTENTIAL BIOLOGICAL REMOVAL

The potential biological removal (PBR) level for this stock is calculated as the minimum population size

(17,995) times one half the default maximum net growth rate for cetaceans (1⁄2 of 4%) times a recovery factor of 0.50

(for a species of unknown status with no known fishery mortality; Wade and Angliss 1997), resulting in a PBR of 180

striped dolphins per year. 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Fishery Information

A summary of recent fishery mortality and injury for this stock of striped dolphin is shown in Table 1. More

detailed information on these fisheries is provided in Appendix 1. Mortality estimates for the California drift gillnet

fishery are included for the five most recent years of monitoring, 1994-98 (Julian and Beeson 1998; Julian 1997;

Cameron and Forney 1999). After the 1997 implementation of a Take Reduction Plan, which included skipper education

workshops and required the use of pingers and minimum 6-fathom extenders, overall cetacean entanglement rates in

the drift gillnet fishery dropped considerably (Barlow and Cameron 1999). However, because of interannual variability

in entanglement rates and the rarity of striped dolphin entanglements, additional years of data will be required to fully

evaluate the effectiveness of pingers for reducing mortality of this particular species. Because of the changes in this

fishery after implementation of the Take Reduction Plan, mean annual takes in Table 1 are based only on 1997-98 data.

This results in an average estimate of zero striped dolphins taken annually.

Table 1. Summary of available information on the incidental mortality and injury of striped dolphins (California/

Oregon/Washington Stock) in commercial fisheries that might take this species. The single observed entanglement of

a striped dolphin resulted in the death of the animal. Coefficients of variation for mortality estimates are provided in

parentheses. Mean annual takes are based on 1994-98 data unless noted otherwise.

Fishery Name Data Type Year(s)

Percent

Observer

Coverage

Observed

Mortality

Estimated Annual

Mortality 

Mean

Annual Takes

(CV in

parentheses)

CA/OR thresher

shark/swordfish drift

gillnet fishery

observer

data 

1994

1995

1996

1997

1998

17.9% 

15.6% 

12.4% 

23.0% 

20.0%

1

0

0

0

0

 6 (0.90)

0

0

0

0

0 1

Minimum total annual takes 0

1 Only 1997-98 mortality estimates are included in the average because overall cetacean entanglement rates dropped considerably after a Take

Reduction Plan was implemented in 1997.

 Drift gillnet fisheries for swordfish and sharks exist along the entire Pacific coast of Baja California, Mexico

and may take animals from the same population. Quantitative data are available only for the Mexican swordfish drift

gillnet fishery, which uses vessels, gear, and operational procedures similar to those in the U.S. drift gillnet fishery,

although nets may be up to 4.5 km long (Holts and Sosa-Nishizaki 1998). The fleet increased from two vessels in 1986

to 31 vessels in 1993; Holts and Sosa-Nishizaki 1998). The total number of sets in this fishery in 1992 can be estimated

from data provided by these authors to be approximately 2700, with an observed rate of marine mammal bycatch of 0.13

animals per set (10 marine mammals in 77 observed sets; Sosa-Nishizaki et al. 1993). This overall mortality rate is

similar to that observed in California driftnet fisheries during 1990-95 (0.14 marine mammals per set; Julian and Beeson,

1998), but species-specific information is not available for the Mexican fisheries. There are currently efforts underway
93

to convert the Mexican swordfish driftnet fishery to a longline fishery (D. Holts, pers. comm.). 

STATUS OF STOCK

The status of striped dolphins in California relative to OSP is not known, and there are insufficient data to

evaluate potential trends in abundance. No habitat issues are known to be of concern for this species. They are not

listed as "threatened" or "endangered" under the Endangered Species Act nor as "depleted" under the MMPA. Including

driftnet information only for years after implementation of the Take Reduction Plan (1997-98), the average annual

human-caused mortality in 1994-98 is zero. Because recent mortality is zero, striped dolphins are not classified as a

"strategic" stock under the MMPA, and the total fishery mortality and serious injury for this stock can be considered

to be insignificant and approaching zero.

REFERENCES

Barlow, J. 1995. The abundance of cetaceans in California waters. Part I: Ship surveys in summer and fall of 1991.

Fish. Bull. 93:1-14.

Barlow, J. 1997. Preliminary estimates of cetacean abundance off California, Oregon and Washington based on a 1996

ship survey and comparisons of passing and closing modes. Admin. Rep. LJ-97-11. Southwest Fisheries

Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA 92038. 25p.

Barlow, J. and G. A. Cameron. 1999. Field experiments show that acoustic pingers reduce marine mammal bycatch in

the California drift gillnet fishery. Paper SC/51/SM2 presented to the International Whaling Commission, May

1998 (unpublished). 20 pp.

Barlow, J. and T. Gerrodette. 1996. Abundance of cetaceans in California waters based on 1991 and 1993 ship

surveys. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-SWFSC-233. 15 pp. 

Cameron, G., and K. A. Forney. 1999. Estimates of cetacean mortality in the California gillnet fisheries for 1997 and

1998. Paper SC/51/O4 presented to the International Whaling Commission, May 1999 (unpublished). 14 pp.

Forney, K. A. 1997. Patterns of variability and environmental models of relative abundance for California cetaceans.

Ph.D. dissertation, Scripps Institution of Oceanography, University of California, San Diego.

Forney, K. A. and J. Barlow. 1998. Seasonal patterns in the abundance and distribution of California cetaceans, 1991-

92. Mar. Mamm. Sci. 14:460-489.

Holts, D. Southwest Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA 92038.

Holts, D. and O. Sosa-Nishizaki. 1998. Swordfish, Xiphias gladius, fisheries of the eastern North Pacific Ocean. In:

I. Barrett, O. Sosa-Nishizaki and N. Bartoo (eds.). Biology and fisheries of swordfish, Xiphias gladius. Papers

from the International Symposium on Pacific Swordfish, Ensenada Mexico, 11-14 December 1994. U.S. Dep.

Commer., NOAA Tech. Rep. NMFS 142, 276 p.

Julian, F. 1997. Cetacean mortality in California gill net fisheries: Preliminary estimates for 1996. Paper SC/49/SM02

presented to the International Whaling Commission, September 1997 (unpublished). 13 pp.

Julian, F. and M. Beeson. 1998. Estimates of mammal, turtle and bird mortality for two California gillnet fisheries:

1990-1995. Fish. Bull. 96:271-284.

Leatherwood, S., R. R. Reeves, W. F. Perrin, and W. E. Evans. 1982. Whales, dolphins and porpoises of the eastern

North Pacific and adjacent Arctic waters. A guide to their identification. NOAA Tech. Rep. NMFS Circular

444, U.S. Dep. Commer., NOAA, NMFS. 245 pp.

Mangels, K. F. and Gerrodette, T. 1994. Report of cetacean sightings during a marine mammal survey in the eastern

Pacific Ocean and Gulf of California aboard the NOAA ships McARTHUR and DAVID STARR JORDAN July

28 - November 6, 1993. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-SWFSC-211. 88 pp.

Perrin, W. F., M. D. Scott, G. J. Walker and V. L. Cass. 1985. Review of geographical stocks of tropical dolphins

(Stenella spp. and Delphinus delphis) in the eastern Pacific. NOAA Tech. Rep. NMFS 28. Available from

NMFS, Southwest Fisheries Science Center, P.O. Box 271, La Jolla, California, 92038. 28p.

Roemmich, D. 1992. Ocean warming and sea level rise along the southwest U.S. coast. Science 257:373-375.

Smith, R. C., P. Dustan, D. Au, K. S. Baker, and E. A. Dunlap. 1986. Distribution of cetaceans and sea-surface

chlorophyll concentrations in the California Current. Marine Biology 91:385-402.

Sosa-Nishizaki, O., R. De la Rosa Pacheco, R. Castro Longoria, M. Grijalva Chon, and J. De la Rosa Velez. 1993.

Estudio biologico pesquero del pez (Xiphias gladius) y otras especies de picudos (marlins y pez vela). Rep.

Int. CICESE, CTECT9306.
94

Wade, P. R. and R. P. Angliss. 1997. Guidelines for Assessing Marine Mammal Stocks: Report of the GAMMS

Workshop April 3-5, 1996, Seattle, Washington. U. S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-12.

93 pp.
95

Figure 1. Short-beaked common dolphin sightings

based on shipboard surveys off California, Oregon

and Washington, 1991-96 (see Appendix 2,

Figures 3-5, for data sources and information on

timing and location of survey effort). No

Delphinus sightings have been made off Oregon

and Washington. Dashed line represents the U.S.

EEZ, thick line indicates the outer boundary of all

surveys combined.

Revised 12/15/2000

SHORT-BEAKED COMMON DOLPHIN (Delphinus delphis):

California/Oregon/Washington Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

Short-beaked common dolphins are the most abundant

cetacean off California, and are widely distributed between the

coast and at least 300 nmi distance from shore. The abundance

of this species off California has been shown to change on both

seasonal and inter-annual time scales (Dohl et al. 1986; Barlow

1995; Forney et al. 1995). Historically, they were reported

primarily south of Pt. Conception (Dohl et al. 1986), but on recent

(1991/93/96) summer/fall surveys, they were commonly sighted

as far north as 42oN (Figure 1). Four strandings of common

dolphins have been reported in Oregon and Washington since

1942 (B. Norberg, pers. comm.). Of these, three were not

identified to the species level, and one animal, which stranded in

1983, was identified as a short-beaked common dolphin (J.

Hodder, pers. comm.). Significant seasonal shifts in the

abundance and distribution of common dolphins have been

identified based on winter/spring 1991-92 and summer/fall 1991

surveys (Forney and Barlow 1998). Their distribution is

continuous southward into Mexican waters to about 13oN (Perrin

et al. 1985; Wade and Gerrodette 1993; Mangels and Gerrodette

1994), and short-beaked common dolphins off California may be

an extension of the "northern common dolphin" stock defined for

management of eastern tropical Pacific tuna fisheries (Perrin et al.

1985). However, preliminary data on variation in dorsal fin color

patterns suggest there may be multiple stocks in this region,

including at least two possible stocks in California (Farley 1995).

The less abundant long-beaked common dolphin has only recently

been recognized as a different species (Heyning and Perrin 1994;

Rosel et al. 1994), and much of the available information has not

differentiated between the two types of common dolphin.

Although short-beaked common dolphins are not restricted to

U.S. waters, cooperative management agreements with Mexico

exist only for the tuna purse seine fishery and not for other fisheries which may take this species (e.g. gillnet fisheries).

Under the Marine Mammal Protection Act (MMPA), short-beaked common dolphins involved in tuna purse seine

fisheries in international waters of the eastern tropical Pacific are managed separately, and they are not included in the

assessment reports. For the MMPA stock assessment reports, there is a single Pacific management stock including only

animals found within the U.S. Exclusive Economic Zone of California, Oregon and Washington. 

POPULATION SIZE

Aerial line transect surveys conducted in winter/spring of 1991-92 resulted only in a combined abundance

estimate of 305,694 (CV=0.34) animals for short-beaked and long-beaked common dolphins, because species-level

identification was not possible from the air (Forney et al. 1995). Based on sighting locations, the majority of these were

probably short-beaked common dolphins. A better, species-specific abundance estimate is available based on three

summer/fall shipboard surveys that were conducted within 300 nmi of the coasts of California (in 1991 and 1993;

Barlow and Gerrodette 1996) and California, Oregon and Washington (in 1996; Barlow 1997). The distribution of

short-beaked common dolphins throughout this region is highly variable, apparently in response to oceanographic

changes on both seasonal and interannual time scales (Heyning and Perrin 1994; Forney 1997; Forney and Barlow
96

1998). As oceanographic conditions vary, short-beaked common dolphins may spend time outside the U.S. Exclusive

Economic Zone, and therefore a multi-year average abundance estimate is the most appropriate for management within

U.S. waters. The 1991-96 weighted average abundance estimate for California, Oregon and Washington waters based

on the three ship surveys is 373,573 (CV=0.19) short-beaked common dolphins (Barlow 1997). 

Minimum Population Estimate

The log-normal 20th percentile of the 1991-96 weighted average abundance estimate is 318,795 short-beaked

common dolphins.

Current Population Trend

In the past, common dolphin abundance has been shown to increase off California during the warm-water

months (Dohl et al. 1986). Surveys conducted during both cold-water and warm-water conditions in 1991 and 1992

(Barlow 1995, Forney et al. 1995) resulted in overall abundance estimates (for both types of common dolphins

combined) which were considerably greater than historical estimates (Dohl et al. 1986). The recent combined abundance

estimate for the 1991-96 summer/fall surveys (Barlow 1997) is the highest and most precise to date. Environmental

models (Forney 1997) and seasonal comparisons (Forney and Barlow 1998) have shown that the abundance of shortbeaked common dolphins off California varies with seasonal and interannual changes in oceanographic conditions. An

ongoing decline in the abundance of ‘northern common dolphins’ (including both long-beaked and short-beaked

common dolphins) in the eastern tropical Pacific and along the Pacific coast of Mexico suggests a possible northward

shift in the distribution of common dolphins (IATTC 1997) during this period of gradual warming of the waters off

California (Roemmich 1992). The majority of this is likely to reflect an increase in the abundance of short-beaked

common dolphins. Heyning and Perrin (1994) have detected changes in the proportion of short-beaked to long-beaked

common dolphins stranding along the California coast, with the short-beaked common dolphin stranding more

frequently prior to the 1982-83 El Niño (which increased water temperatures off California), and the long-beaked

common dolphin more commonly observed for several years afterwards. Thus, it appears that both relative and absolute

abundances of these species off California may change with varying oceanographic conditions.

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

There are no estimates of current or maximum net productivity rates for short-beaked common dolphins.

POTENTIAL BIOLOGICAL REMOVAL

The potential biological removal (PBR) level for this stock is calculated as the minimum population size

(318,795) times one half the default maximum net growth rate for cetaceans (1⁄2 of 4%) times a recovery factor of 0.50

(for a species of unknown status with a mortality rate CV< 0.30; Wade and Angliss 1997), resulting in a PBR of 3,188

short-beaked common dolphins per year. 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Fishery Information

A summary of recent fishery mortality and injury for short-beaked common dolphins is shown in Table 1.

More detailed information on these fisheries is provided in Appendix 1. Mortality of common dolphins primarily has

been observed in California drift gillnet fisheries (Julian and Beeson 1998; Julian 1997; Cameron and Forney 1999).

Because of the difficulty in distinguishing short-beaked and long-beaked common dolphins in the field, tissue samples

have been collected for most of the animals observed killed. These tissue samples have enabled positive identification

using genetic techniques for all except two of the common dolphins killed (NMFS, unpublished data). Based on past

patterns (Barlow et al. 1997), these two animals are likely to have been a short-beaked common dolphin, and they are

included below for this species. After the 1997 implementation of a Take Reduction Plan, which included skipper

education workshops and required the use of pingers and minimum 6-fathom extenders, common dolphin entanglement

rates in the drift gillnet fishery dropped considerably (Barlow and Cameron 1999). However, because of interannual

variability in entanglement rates additional years of data will be required to fully evaluate the effectiveness of pingers

for reducing mortality of this species in the long term. Because of the changes in this fishery after implementation of

the Take Reduction Plan, mean annual takes in Table 1 are based only on 1997-98 data. This results in an average

estimate of 78 (CV=0.23) short-beaked common dolphins taken annually.
97

Table 1. Summary of available information on the incidental mortality and injury of short-beaked common dolphins

(California/Oregon/Washington Stock), in commercial fisheries that might take this species. All entanglements resulted

in the death of the animal. The observer program for the set gillnet fishery was discontinued during 1994. Coefficients

of variation for mortality estimates are provided in parentheses; n/a = not available. Mean annual takes are based on

1994-98 data unless noted otherwise. 

Fishery Name Data Type Year

Percent

Observer

Coverage

Observed 

Mortality

Estimated Annual

Mortality

Mean

Annual Takes

(CV in

parentheses)

CA/OR thresher

shark/swordfish drift

gillnet fishery observer

data

1994 

1995 

1996 

1997 

1998 

17.9% 

15.6% 

12.4% 

23.0% 

20.0% 

26

36

27

21

 9

146 (0.18)

 231 (0.29) 

319 (0.23) 

105 (0.30) 

 51 (0.33)

(includes prorated)

78 (0.23)1

CA angel shark/ halibut

and other species large

mesh (>3.5in) set gillnet

fishery

observer

data

MMAP

selfreporting

Common dolphins, species not determined

n/a

≥ 0.8 (n/a)

1994

1995-98

1995

1996

1998

7.7%

0%

- 

- 

- 

0

n/a

1

1

2

0

n/a

≥ 1

≥ 1

≥ 2

Undetermined strandings 1994-98 2 common dolphins (species not determined) stranded with

evidence of fishery interactions ≥ 0.4 (n/a)

Minimum total annual takes 79 (0.23)

1Only 1997-98 mortality estimates are included in the average because of gear modifications implemented within the fishery as part of a 1997 Take

Reduction Plan. Gear modifications included the use of net extenders and acoustic warning devices (pingers). Following these changes in the fishery,

entanglement rates of short-beaked common dolphin declined.

Additional common dolphin mortality has been reported for set gillnets in California (Julian and Beeson 1998);

however, because of a 1994 ban on gillnets in nearshore areas of Southern California, the size of this fishery decreased

by about a factor of two (see Appendix 1), and the observer program was discontinued. No observer data are available

for the set gillnet fishery after 1994, but Marine Mammal Authorization Permit (MMAP) fisher self-reports for 1994-98

indicate that at least four common dolphins (type not specified) were killed between 1995 and 1998. Although these

reports are considered unreliable (see Appendix 4 of Hill and DeMaster 1998) they represent a minimum mortality for

this fishery.

Two common dolphins (type not specified) stranded with evidence of fishery interaction (NMFS, Southwest

Region, unpublished data); one animal had a hook and line in its mouth and a slit ventrum, and the other animal had its

flukes cut off. It is not known which fisheries were responsible for these deaths.

Drift gillnet fisheries for swordfish and sharks exist along the entire Pacific coast of Baja California, probably

take short-beaked common dolphins from the same population. Quantitative data are available only for the Mexican

swordfish drift gillnet fishery, which uses vessels, gear, and operational procedures similar to those in the U.S. drift

gillnet fishery, although nets may be up to 4.5 km long (Holts and Sosa-Nishizaki 1998). The fleet increased from two

vessels in 1986 to 31 vessels in 1993 (Holts and Sosa-Nishizaki 1998). The total number of sets in this fishery in 1992

can be estimated from data provided by these authors to be approximately 2700, with an observed rate of marine

mammal bycatch of 0.13 animals per set (10 marine mammals in 77 observed sets; Sosa-Nishizaki et al. 1993). This

overall mortality rate is similar to that observed in California driftnet fisheries during 1990-95 (0.14 marine mammals

per set; Julian and Beeson, 1998), but species-specific information is not available for the Mexican fisheries. There are

currently efforts underway to convert the Mexican swordfish driftnet fishery to a longline fishery (D. Holts, pers.
98

comm.). 

Other Mortality

In the eastern tropical Pacific, 'northern common dolphins' have been incidentally killed in international tuna

purse seine fisheries since the late 1950's. Cooperative international management programs have dramatically reduced

overall dolphin mortality in these fisheries during the last decade (Joseph 1994). Between 1994 and 1998, annual

mortality of northern common dolphins (potentially including both short-beaked and long-beaked common dolphins)

ranged between 9 and 261 animals, with an average of 91 (IATTC, in prep). Although it is unclear whether these

animals are part of the same population as short-beaked common dolphins found off California, they are managed

separately under a section of the MMPA written specifically for the management of dolphins involved in eastern tropical

Pacific tuna fisheries.

STATUS OF STOCK

The status of short-beaked common dolphins in Californian waters relative to OSP is not known. The observed

increase in abundance of this species off California over the last decade probably reflects a distributional shift

(Anganuzzi et al. 1993; Barlow 1995; Forney et al. 1995; Forney and Barlow 1998), rather than an overall population

increase due to growth. No habitat issues are known to be of concern for this species. They are not listed as "threatened"

or "endangered" under the Endangered Species Act nor as "depleted" under the MMPA. Including driftnet mortality

only for years after implementation of the Take Reduction Plan (1997-98), the average annual human-caused mortality

in 1994-98 (79 animals) is estimated to be less than the PBR (3,188), and therefore they are not classified as a "strategic"

stock under the MMPA. The total estimated fishery mortality and injury for short-beaked common dolphins is less than

10% of the calculated PBR and, therefore, can be considered to be insignificant and approaching zero mortality and

serious injury rate. 

REFERENCES

Anganuzzi, A. A., S. T. Buckland, and K. L Cattanach. 1993. Relative abundance of dolphins associated with tuna in

the eastern tropical Pacific Ocean: analysis of 1991 data. Rep. Int. Whal. Commn 43:459-465.

Barlow, J. 1995. The abundance of cetaceans in California waters. Part I: Ship surveys in summer and fall of 1991.

Fish. Bull. 93:1-14.

Barlow, J. 1997. Preliminary estimates of cetacean abundance off California, Oregon and Washington based on a 1996

ship survey and comparisons of passing and closing modes. Administrative Report LJ-97-11, Southwest

Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA 92038. 25p.

Barlow, J. and G. A. Cameron. 1999. Field experiments show that acoustic pingers reduce marine mammal bycatch in

the California drift gillnet fishery. Paper SC/51/SM2 presented to the International Whaling Commission, May

1998 (unpublished). 20pp.

Barlow, J., K. A. Forney, P. S. Hill, R. L. Brownell, Jr., J. V. Carretta, D. P. DeMaster, F. Julian, M. S. Lowry, T.

Ragen, and R. R. Reeves. 1997. U.S. Pacific Marine Mammal Stock Assessments: 1996. U.S. Dep. Commer.,

NOAA Tech. Memo. NMFS-SWFSC-248. 223p.

Barlow, J. and T. Gerrodette. 1996. Abundance of cetaceans in California waters based on 1991 and 1993 ship

surveys. NOAA Technical Memorandum NMFS, NOAA-TM-NMFS-SWFSC-233. 

Dohl, T. P., M. L. Bonnell, and R. G. Ford. 1986. Distribution and abundance on common dolphin, Delphinus delphis,

in the Southern California Bight: A quantitative assessment based upon aerial transect data. Fish. Bull. 84:333-

343.

Farley, T. D. 1995. Geographic variation in dorsal fin color of short-beaked common dolphins, Delphinus delphis, in

the eastern Pacific Ocean. Administrative Report LJ-95-06, Available from National Marine Fisheries Service,

Southwest Fisheries Science Center, P.O. Box 271, La Jolla, California, 92038.

Forney, K. A. 1997. Patterns of variability and environmental models of relative abundance for California cetaceans.

Ph.D. Dissertation, Scripps Institution of Oceanography, University of California, San Diego.

Forney, K. A. and J. Barlow. 1998. Seasonal patterns in the abundance and distribution of California cetaceans, 1991-

92. Mar. Mamm. Sci. 14:460-489.

Forney, K. A., J. Barlow and J. V. Carretta. 1995. The abundance of cetaceans in California waters. Part II: Aerial

surveys in winter and spring of 1991 and 1992. Fish. Bull. 93:15-26.
99

Heyning, J. E. and W. F. Perrin. 1994. Evidence for two species of common dolphins (Genus Delphinus) from the

eastern North Pacific. Contr. Nat. Hist. Mus. L.A. County, No. 442.

Hill, P. S. and D. P. DeMaster. 1998. Alaska Marine Mammal Stock Assessments, 1998. U.S. Dep. Commer., NOAA

Tech. Memo. NMFS-AFSC-97. 166pp.

Hodder, J. Oregon Institute of Marine Biology, Charleston, OR, 97420.

Holts, D. Southwest Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA 92038.

Holts, D. and O. Sosa-Nishizaki. 1998. Swordfish, Xiphias gladius, fisheries of the eastern North Pacific Ocean. In:

I. Barrett, O. Sosa-Nishizaki and N. Bartoo (eds.). Biology and fisheries of swordfish, Xiphias gladius. Papers

from the International Symposium on Pacific Swordfish, Ensenada Mexico, 11-14 December 1994. U.S. Dep.

Commer., NOAA Tech. Rep. NMFS 142, 276 p.

IATTC. 1997. Annual Report of the Inter-American Tropical Tuna Commission, 1995, La Jolla, California.

IATTC. (in prep). Annual Report of the Inter-American Tropical Tuna Commission, 1998, La Jolla, California.

Joseph, J. 1994. The tuna-dolphin controversy in the eastern Pacific Ocean: biological, economic and political impacts.

Ocean Dev. Int. Law 25:1-30.

Julian, F. 1997. Cetacean mortality in California gill net fisheries: Preliminary estimates for 1996. Paper SC/49/SM02

presented to the International Whaling Commission, 1997 (unpublished). 13 pp.

Julian, F. and M. Beeson. 1998. Estimates of mammal, turtle and bird mortality for two California gillnet fisheries:

1990-1995. Fish. Bull. 96:271-284.

Mangels, K. F. and Gerrodette, T. 1994. Report of cetacean sightings during a marine mammal survey in the eastern

Pacific Ocean and Gulf of California aboard the NOAA ships McARTHUR and DAVID STARR JORDAN July

28 - November 6, 1993. NOAA Technical Memorandum NMFS, NOAA-TM-NMFS-SWFSC-211.

NMFS, Southwest Fisheries Science Center, P.O. Box 271, La Jolla, CA 92038-027.

NMFS, Southwest Region, 501 West Ocean Blvd, Long Beach, CA 90802-4213.

Norberg, B., NMFS, Northwest Region,.7600 Sand Point Way NE, BIN C15700,Seattle, WA 98115-0070.

Perrin, W. F., M. D. Scott, G. J. Walker and V. L. Cass. Review of geographical stocks of tropical dolphins (Stenella

spp. and Delphinus delphis) in the eastern Pacific. NOAA Technical Report NMFS 28. Available from

NMFS, Southwest Fisheries Science Center, P.O. Box 271, La Jolla, California, 92038. 28p.

Roemmich, D. 1992. Ocean warming and sea level rise along the southwest U.S. coast. Science 257:373-375.

Rosel, P. E., A. E. Dizon and J. E. Heyning. 1994. Population genetic analysis of two forms of the common dolphin

(genus Delphinus) utilizing mitochondrial DNA control region sequences. Marine Biology 119:159-167.

Sosa-Nishizaki, O., R. De la Rosa-Pacheco, R. Castro-Longoria, M. Grijalva Chon, and J. De la Rosa Velez. 1993.

Estudio biologico pesquero del pez (Xiphias gladius) y otras especies de picudos (marlins y pez vela). Rep.

Int. CICESE, CTECT9306.

Wade, P. R. and R. P. Angliss. 1997. Guidelines for Assessing Marine Mammal Stocks: Report of the GAMMS

Workshop April 3-5, 1996, Seattle, Washington. U. S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-12.

93 pp.

Wade, P. R. and T. Gerrodette. 1993. Estimates of cetacean abundance and distribution in the eastern tropical Pacific.

Rep. Int. Whal. Commn 43:477-493.
100

Figure 1. Long-beaked common dolphin sightings

based on shipboard surveys off California, Oregon

and Washington, 1991-96 (see Appendix 2,

Figures 3-5, for data sources and information on

timing and location of survey effort). No

Delphinus sightings have been made off Oregon

and Washington. Dashed line represents the U.S.

EEZ, thick line indicates the outer boundary of all

surveys combined.

Revised 12/15/2000

LONG-BEAKED COMMON DOLPHIN (Delphinus capensis):

California Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

Long-beaked common dolphins have only recently been

recognized as a distinct species (Heyning and Perrin

1994; Rosel et al. 1994). Along the U.S. west coast, their

distribution overlaps with that of the short-beaked common

dolphin, and much historical information has not distinguished

between these two species. Long-beaked common dolphins are

commonly found within about 50 nmi of the coast, from Baja

California (including the Gulf of California) northward to about

central California (Figure 1). Stranding data and sighting records

indicate that the relative abundance of this species off California

changes both seasonally and inter-annually, with highest densities

observed during warm-water events (Heyning and Perrin 1994).

Although long-beaked common dolphins are not restricted to U.S.

waters, cooperative management agreements with Mexico exist

only for the tuna purse seine fishery and not for other fisheries

which may take this species (e.g. gillnet fisheries). Under the

Marine Mammal Protection Act (MMPA), long-beaked ("Baja

neritic") common dolphins involved in eastern tropical Pacific

tuna fisheries are managed separately as part of the 'northern

common dolphin' stock (Perrin et al. 1985), and these animals are

not included in the assessment reports. For the MMPA stock

assessment reports, there is a single Pacific management stock

including only animals found within the U.S. Exclusive Economic

Zone of California.

POPULATION SIZE

Aerial line transect surveys conducted in winter and

spring of 1991 and 1992 resulted only in a combined abundance

estimate of 305,694 (CV=0.34) long-beaked and short-beaked

common dolphins, because species-level identification was not

possible from the air (Forney et al. 1995). Based on sighting

locations, the majority of these animals were probably shortbeaked common dolphins. A better, species-specific abundance

estimate is available based on three summer/fall shipboard surveys that were conducted within 300 nmi of the coasts

of California (in 1991 and 1993; Barlow and Gerrodette 1996) and California, Oregon and Washington (in 1996; Barlow

1997). The distribution and abundance of long-beaked common dolphins off California appears to be variable on

interannual and seasonal time scales (Heyning and Perrin 1994). As oceanographic conditions change, long-beaked

common dolphins may spend time in Mexican waters, and therefore a multi-year average abundance estimate is the most

appropriate for management within the U.S. waters. The 1991-96 weighted average abundance estimate for California,

Oregon and Washington waters based on the three ship surveys is 32,239 (CV=0.18) long-beaked common dolphins

(Barlow 1997). 

Minimum Population Estimate

The log-normal 20th percentile of the 1991-96 weighted average abundance estimate is 27,739 long-beaked

common dolphins.
101

Current Population Trend

Due to the historical lack of distinction between the two species of common dolphins, it is difficult to establish

trends in abundance for this species. In the past, common dolphins have been shown to increase in abundance off

California during the warm-water months (Dohl et al. 1986). Surveys conducted during both cold-water and warm-water

conditions in 1991 and 1992 (Barlow 1995, Forney et al. 1995) resulted in overall abundance estimates (for both types

of common dolphins combined) which were considerably greater than historical estimates (Dohl et al. 1986). The

combined abundance estimate for the 1991-96 summer/fall surveys (Barlow 1997) is the highest and most precise to

date. An ongoing decline in the abundance of ‘northern common dolphins’ (including both long-beaked and shortbeaked common dolphins) in the eastern tropical Pacific and along the Pacific coast of Mexico (IATTC 1997) suggests

a possible northward shift in the distribution of common dolphins during this period of gradual warming of the waters

off California (Roemmich 1992). However, it is unclear how much of this increase reflects an increase in the abundance

of the long-beaked common dolphin. Heyning and Perrin (1994) have detected changes in the proportion of shortbeaked to long-beaked common dolphins stranding along the California coast, with the short-beaked common dolphin

stranding more frequently prior to the 1982-83 El Niño (which increased water temperatures off California), and the

long-beaked common dolphin more commonly observed for several years afterwards. Thus, it appears that both relative

and absolute abundance of these species off California may change with varying oceanographic conditions.

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

There are no estimates of current or maximum net productivity rates for long-beaked common dolphins.

POTENTIAL BIOLOGICAL REMOVAL

 The potential biological removal (PBR) level for this stock is calculated as the minimum population size

(27,629) times one half the default maximum net growth rate for cetaceans (1⁄2 of 4%) times a recovery factor of 0.45

(for a species of unknown status with a mortality rate CV ≥ 0.60 and ≤ 0.80; Wade and Angliss 1997), resulting in a

PBR of 250 long-beaked common dolphins per year. 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Fishery Information

A summary of recent fishery mortality and injury for long-beaked common dolphins is shown in Table 1. More

detailed information on these fisheries is provided in Appendix 1. Mortality of common dolphins primarily has been

observed in California drift gillnet fisheries (Julian 1997; Julian and Beeson 1998; Cameron and Forney 1999). Because

of the difficulty in distinguishing short-beaked and long-beaked common dolphins in the field, tissue samples have been

collected for most of the animals observed killed. These tissue samples have enabled positive identification using genetic

techniques for all except two of the common dolphins killed (NMFS, unpublished data). Based on past patterns (Barlow

et al. 1997), these two animals are likely to have been a short-beaked common dolphin, and they have not been included

in the mortality calculations below for long-beaked common dolphins. After the 1997 implementation of a Take

Reduction Plan, which included skipper education workshops and required the use of pingers and minimum 6-fathom

extenders, common dolphin entanglement rates in the drift gillnet fishery dropped considerably (Barlow and Cameron

1999). However, because of interannual variability in entanglement rates additional years of data will be required to

fully evaluate the effectiveness of pingers for reducing mortality of this species in the long term. Because of the changes

in this fishery after implementation of the Take Reduction Plan, mean annual takes in Table 1 are based only on 1997-98

data. This results in an average estimate of 13 (CV=0.74) long-beaked common dolphins taken annually.

Additional common dolphin mortality has been reported for set gillnets in California (Julian and Beeson 1998);

however, because of a 1994 ban on gillnets in nearshore areas of Southern California, the size of this fishery decreased

by about a factor of two (see Appendix 1), and the observer program was discontinued. No observer data are available

for the set gillnet fishery after 1994, but Marine Mammal Authorization Permit (MMAP) fisher self-reports for 1994-98

indicate that at least four common dolphins (type not specified) were killed between 1995 and 1998. Although these

reports are considered unreliable (see Appendix 4 of Hill and DeMaster 1998) they represent a minimum mortality for

this fishery.

Two common dolphins (type not specified) stranded with evidence of fishery interaction (NMFS, Southwest

Region, unpublished data); one animal had a hook and line in its mouth and a slit ventrum, and the other animal had its

flukes cut off. It is not known which fisheries were responsible for these deaths.
102

Table 1. Summary of available information on the incidental mortality and injury of long-beaked common dolphins

(California Stock) and prorated unidentified common dolphins in commercial fisheries that might take this species. All

observed entanglements resulted in the death of the animal. The observer program for the set gillnet fishery was

discontinued during 1994. Coefficients of variation for mortality estimates are provided in parentheses, when available.

Mean annual takes are based on 1994-98 data unless noted otherwise. 

Fishery Name Data Type Year(s)

Percent

Observer

Coverage

Observed Estimated Annual

Mortality

Mean

Annual Takes

(CV in

parentheses)

CA/OR thresher

shark/swordfish drift

gillnet fishery

observer

data

1994

1995

1996

1997

1998

17.9% 

15.6% 

12.4% 

23.0% 

20.0% 

 1

 6

 1 

 4 

 0 

 6 (0.91) 

 39 (0.65) 

 12 (0.96) 

 25 (0.74) 

 0 

13 (0.74)1

CA angel shark/ halibut

and other species large

mesh (>3.5in) set gillnet

fishery

observer

data

MMAP

selfreporting

Common dolphins, species not determined

n/a

≥ 0.8 (n/a)

1994

1995-98

1995

1996

1998

7.7%

0%

- 

- 

- 

0

n/a

1

1

2

0

n/a

≥ 1

≥ 1

≥ 2

Undetermined strandings 1994-98 2 common dolphins (species not determined) stranded

with evidence of fishery interactions ≥ 0.4 (n/a)

Minimum total annual takes 14 (0.74)

1Only 1997-98 mortality estimates are included in the average because of gear modifications implemented within the fishery as part of a 1997 Take

Reduction Plan. Gear modifications included the use of net extenders and acoustic warning devices. Following these changes in the fishery,

entanglement rates of long-beaked common dolphin declined.

 Drift gillnet fisheries for swordfish and sharks exist along the entire Pacific coast of Baja California, Mexico

and may take long-beaked common dolphins from the same population. Quantitative data are available only for the

Mexican swordfish drift gillnet fishery, which uses vessels, gear, and operational procedures similar to those in the U.S.

drift gillnet fishery, although nets may be up to 4.5 km long (Holts and Sosa-Nishizaki 1998). The fleet increased from

two vessels in 1986 to 31 vessels in 1993 (Holts and Sosa-Nishizaki 1998). The total number of sets in this fishery in

1992 can be estimated from data provided by these authors to be approximately 2700, with an observed rate of marine

mammal bycatch of 0.13 animals per set (10 marine mammals in 77 observed sets; Sosa-Nishizaki et al. 1993). This

overall mortality rate is similar to that observed in California driftnet fisheries during 1990-95 (0.14 marine mammals

per set; Julian and Beeson, 1998), but species-specific information is not available for the Mexican fisheries. There are

currently efforts underway to convert the Mexican swordfish driftnet fishery to a longline fishery (D. Holts, pers.

comm.). 

Other Mortality

In the eastern tropical Pacific, 'northern common dolphins' have been incidentally killed in international tuna

purse seine fisheries since the late 1950's. Cooperative international management programs have dramatically reduced

overall dolphin mortality in these fisheries during the last decade (Joseph 1994). Between 1994 and 1998, annual

mortality of northern common dolphins (potentially including both short-beaked and long-beaked common dolphins)

ranged between 9 and 261 animals, with an average of 91 (IATTC, in prep). Although it is likely that the long-beaked

common dolphins included in the 'northern common dolphin' stock are part of the same population as those found off

California, they are managed separately under a section of the MMPA written specifically for the management of
103

dolphins involved in eastern tropical Pacific tuna fisheries.

STATUS OF STOCK

The status of long-beaked common dolphins in California waters relative to OSP is not known, and there are

insufficient data to evaluate potential trends in abundance of this species of common dolphin. No habitat issues are

known to be of concern for this species. They are not listed as "threatened" or "endangered" under the Endangered

Species Act nor as "depleted" under the MMPA. Including driftnet mortality only for years after implementation of the

Take Reduction Plan (1997-98), the average annual human-caused mortality in 1994-98 (14 animals) is estimated to be

less than the PBR (250), and therefore they are not classified as a "strategic" stock under the MMPA. The average total

fishery mortality and injury for long-beaked common dolphins is less than 10% of the PBR and, therefore, can be

considered to be insignificant and approaching zero mortality and serious injury rate. 

REFERENCES

Barlow, J. 1995. The abundance of cetaceans in California waters. Part I: Ship surveys in summer and fall of 1991.

Fish. Bull. 93:1-14.

Barlow, J. 1997. Preliminary estimates of cetacean abundance off California, Oregon and Washington based on a 1996

ship survey and comparisons of passing and closing modes. Administrative Report LJ-97-11, Southwest

Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA 92038. 25p.

Barlow, J. and G. A. Cameron. 1999. Field experiments show that acoustic pingers reduce marine mammal bycatch in

the California drift gillnet fishery. Paper SC/51/SM2 presented to the International Whaling Commission, May

1998 (unpublished). 20pp.

Barlow, J., K. A. Forney, P. S. Hill, R. L. Brownell, Jr., J. V. Carretta, D. P. DeMaster, F. Julian, M. S. Lowry, T.

Ragen, and R. R. Reeves. 1997. U.S. Pacific Marine Mammal Stock Assessments: 1996. U.S. Dep. Commer.,

NOAA Tech. Memo. NMFS-SWFSC-248. 223p.

Barlow, J. and T. Gerrodette. 1996. Abundance of cetaceans in California waters based on 1991 and 1993 ship

surveys. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-SWFSC-233. 

Cameron, G., and K. A. Forney. 1999. Estimates of cetacean mortality in the California gillnet fisheries for 1997 and

1998. Paper SC/51/O4 presented to the International Whaling Commission, 1999 (unpublished). 14pp.

Dohl, T. P., M. L. Bonnell, and R. G. Ford. 1986. Distribution and abundance on common dolphin, Delphinus delphis,

in the Southern California Bight: A quantitative assessment based upon aerial transect data. Fish. Bull. 84:333-

343.

Forney, K. A., J. Barlow and J. V. Carretta. 1995. The abundance of cetaceans in California waters. Part II: Aerial

surveys in winter and spring of 1991 and 1992. Fish. Bull. 93:15-26.

Heyning, J. E. and W. F. Perrin. 1994. Evidence for two species of common dolphins (Genus Delphinus) from the

eastern North Pacific. Contr. Nat. Hist. Mus. L.A. County, No. 442.

Hill, P. S. and D. P. DeMaster. 1998. Alaska Marine Mammal Stock Assessments, 1998. U.S. Dep. Commer., NOAA

Tech. Memo. NMFS-AFSC-97. 166 pp.

Holts, D. Southwest Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA 92038.

Holts, D. and O. Sosa-Nishizaki. 1998. Swordfish, Xiphias gladius, fisheries of the eastern North Pacific Ocean. In:

I. Barrett, O. Sosa-Nishizaki and N. Bartoo (eds.). Biology and fisheries of swordfish, Xiphias gladius. Papers

from the International Symposium on Pacific Swordfish, Ensenada Mexico, 11-14 December 1994. U.S. Dep.

Commer., NOAA Tech. Rep. NMFS 142, 276 pp.

IATTC. 1997. Annual Report of the Inter-American Tropical Tuna Commission, 1995, La Jolla, California.

IATTC. (in prep). Annual Report of the Inter-American Tropical Tuna Commission, 1998, La Jolla, California.

Joseph, J. 1994. The tuna-dolphin controversy in the eastern Pacific Ocean: biological, economic and political impacts.

Ocean Dev. Int. Law 25:1-30.

Julian, F. 1997. Cetacean mortality in California gill net fisheries: Preliminary estimates for 1996. Paper SC/49/SM02

presented to the International Whaling Commission, 1997 (unpublished). 13 pp.

Julian, F. and M. Beeson. 1998. Estimates of mammal, turtle and bird mortality for two California gillnet fisheries:

1990-1995. Fish. Bull. 96:271-284.

NMFS, Southwest Fisheries Science Center, P.O. Box 271, La Jolla, CA 92038-027.

NMFS, Southwest Region, 501 West Ocean Blvd, Long Beach, CA 90802-4213.
104

Perrin, W. F., M. D. Scott, G. J. Walker and V. L. Cass. Review of geographical stocks of tropical dolphins (Stenella

spp. and Delphinus delphis) in the eastern Pacific. NOAA Technical Report NMFS 28. Available from

NMFS, Southwest Fisheries Science Center, P.O. Box 271, La Jolla, California, 92038. 28p.

Roemmich, D. 1992. Ocean warming and sea level rise along the southwest U.S. coast. Science 257:373-375.

Rosel, P. E., A. E. Dizon and J. E. Heyning. 1994. Population genetic analysis of two forms of the common dolphin

(genus Delphinus) utilizing mitochondrial DNA control region sequences. Marine Biology 119:159-167.

Sosa-Nishizaki, O., R. De la Rosa-Pacheco, R. Castro-Longoria, M. Grijalva Chon, and J. De la Rosa Velez. 1993.

Estudio biologico pesquero del pez (Xiphias gladius) y otras especies de picudos (marlins y pez vela). Rep.

Int. CICESE, CTECT9306.

Wade, P. R. and R. P. Angliss. 1997. Guidelines for Assessing Marine Mammal Stocks: Report of the GAMMS

Workshop April 3-5, 1996, Seattle, Washington. U. S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-12.

93 pp.
105

Figure 1. Northern right-whale dolphin dolphin

sightings based on aerial and shipboard surveys off

California, Oregon and Washington, 1991-96 (see

Appendix 2, Figures 1-5, for data sources and

information on timing and location of survey

effort). Dashed line represents the U.S. EEZ,

thick line indicates the outer boundary of all

surveys combined.

Revised 12/15/2000

NORTHERN RIGHT-WHALE DOLPHIN (Lissodelphis borealis):

California/Oregon/Washington Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

Northern right-whale dolphins are endemic to temperate

waters of the North Pacific Ocean. Off the U.S. west coast, they

have been seen primarily in shelf and slope waters (Figure 1),

with seasonal movements into the Southern California Bight

(Leatherwood and Walker 1979; Dohl et al. 1980; 1983; NMFS,

unpublished data). Sighting patterns from recent aerial and

shipboard surveys conducted in California, Oregon and

Washington during different seasons (Green et al. 1992; 1993;

Forney et al. 1995; Barlow 1995) suggest seasonal north-south

movements, with animals found primarily off California during

the colder water months and shifting northward into Oregon and

Washington as water temperatures increase in late spring and

summer (Green et al. 1992; Forney 1994; Forney and Barlow

1998). The southern end of this population's range is not welldocumented, but during cold-water periods, they probably range

into Mexican waters off northern Baja California. Genetic

analyses have not found statistically significant differences

between northern right-whale dolphins from the U.S. West coast

and other areas of the North Pacific (Dizon et al. 1994); however,

power analyses indicate that the ability to detect stock differences

for this species is poor, given traditional statistical error levels

(Dizon et al. 1995). Although northern right-whale dolphins are

not restricted to U.S. territorial waters, there are currently no

international agreements for cooperative management. For the

Marine Mammal Protection Act (MMPA) stock assessment

reports, there is a single management stock including only

animals found within the U.S. Exclusive Economic Zone of

California, Oregon and Washington.

POPULATION SIZE

The previous best estimates of abundance for northern

right-whale dolphins (Barlow et al. 1997) were based on winter/spring 1991-92 aerial surveys (Forney et al. 1995) off

California, which were presumed to include northern right-whale dolphins that are found off Oregon and Washington

during summer and fall. Three summer/fall shipboard surveys were conducted within 300 nmi of the coasts of California

in 1991 and 1993 (Barlow and Gerrodette 1996) and California, Oregon and Washington in 1996 (Barlow 1997). The

distribution of northern right-whale dolphins throughout this region is highly variable, apparently in response to

oceanographic changes on both seasonal and interannual time scales (Forney and Barlow 1998). As oceanographic

conditions vary, northern right-whale dolphins may spend time outside the U.S. Exclusive Economic Zone, and therefore

a multi-year average abundance estimate is the most appropriate for management within U.S. waters. The 1991-96

weighted average abundance estimate for California, Oregon and Washington waters based on the three ship surveys

is 13,705 (CV=0.38) northern right-whale dolphins (Barlow 1997).

Minimum Population Estimate

The log-normal 20th percentile of the 1991-96 weighted average abundance estimate is 10,060 northern rightwhale dolphins.
106

Current Population Trend

No information is available regarding trends in abundance of northern right-whale dolphins in California,

Oregon and Washington.

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

No information on current or maximum net productivity rates is available for northern right-whale dolphins

off the U.S. west coast.

POTENTIAL BIOLOGICAL REMOVAL

 The potential biological removal (PBR) level for this stock is calculated as the minimum population size

(10,060) times one half the default maximum net growth rate for cetaceans (1⁄2 of 4%) times a recovery factor of 0.48

(for a species of unknown status with a mortality rate CV>0.30; Wade and Angliss 1997), resulting in a PBR of 97

northern right-whale dolphins per year. 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Fishery Information

A summary of recent fishery mortality and injury for this stock of northern right-whale dolphin is shown in

Table 1. More detailed information on these fisheries is provided in Appendix 1. Mortality estimates for the California

drift gillnet fishery are included for the five most recent years of monitoring, 1994-98 (Julian and Beeson 1998; Julian

1997; Cameron and Forney 1999). After the 1997 implementation of a Take Reduction Plan, which included skipper

education workshops and required the use of pingers and minimum 6-fathom extenders, overall cetacean entanglement

rates in the drift gillnet fishery dropped considerably (Barlow and Cameron 1999). However, because of interannual

variability in entanglement rates and the relative rarity of northern right-whale dolphin entanglements, additional years

of data will be required to fully evaluate the effectiveness of pingers for reducing mortality of this particular species.

Because of the changes in this fishery after implementation of the Take Reduction Plan, mean annual takes in Table 1

are based only on 1997-98 data. This results in an average estimate of 15 (CV=0.42) northern right-whale dolphins

taken annually.

Table 1. Summary of available information on the incidental mortality and injury of northern right-whale dolphins

(California/Oregon/Washington Stock) in commercial fisheries that might take this species. All observed entanglements

of northern right-whale dolphins resulted in the death of the animal. Coefficients of variation for mortality estimates

are provided in parentheses. Mean annual takes are based on 1994-98 data unless noted otherwise. 

Fishery Name Data Type Year(s)

Percent

Observer

Coverage

Observed

Mortality

Estimated Annual

Mortality

Mean

Annual Takes 

(CV in

parentheses)

CA/OR thresher

shark/swordfish drift

gillnet fishery

observer

data 

1994

1995

1996

1997

1998

17.9% 

15.6% 

12.4% 

23.0% 

20.0% 

7

9

5

5

0

39 (0.42)

58 (0.59)

27 (0.68)

29 (0.42)

0

15 (0.42)1

Minimum total annual takes 15 (0.42)

1Only 1997-98 mortality estimates are included in the average because of gear modifications implemented within the fishery as part of a 1997 Take

Reduction Plan. Gear modifications included the use of net extenders and acoustic warning devices (pingers). Following these changes within the

fishery, entanglement rates of northern right-whale dolphin declined.

Drift gillnet fisheries for swordfish and sharks exist along the entire Pacific coast of Baja California, Mexico

and may take animals from the same population during cold-water periods. Quantitative data are available only for the

Mexican swordfish drift gillnet fishery, which uses vessels, gear, and operational procedures similar to those in the U.S.

drift gillnet fishery, although nets may be up to 4.5 km long (Holts and Sosa-Nishizaki 1998). The fleet increased from

two vessels in 1986 to 31 vessels in 1993 (Holts and Sosa-Nishizaki 1998). The total number of sets in this fishery in

1992 can be estimated from data provided by these authors to be approximately 2700, with an observed rate of marine

mammal bycatch of 0.13 animals per set (10 marine mammals in 77 observed sets; Sosa-Nishizaki et al. 1993). This

overall mortality rate is similar to that observed in California driftnet fisheries during 1990-95 (0.14 marine mammals

per set; Julian and Beeson, 1998), but species-specific information is not available for the Mexican fisheries. There are

currently efforts underway to convert the Mexican swordfish driftnet fishery to a longline fishery (D. Holts, pers.

comm.). 
107

STATUS OF STOCK

The status of northern right-whale dolphins in California, Oregon and Washington relative to OSP is not

known, and there are insufficient data to evaluate trends in abundance. No habitat issues are known to be of concern

for this species. They are not listed as "threatened" or "endangered" under the Endangered Species Act nor as

"depleted" under the MMPA. Including driftnet mortality only for years after implementation of the Take Reduction

Plan (1997-98), the average annual human-caused mortality in 1994-98 (15 animals) is estimated to be less than the PBR

(97), and therefore they are not classified as a "strategic" stock under the MMPA. The total fishery mortality and serious

injury for northern right-whale dolphins is greater than 10% of the calculated PBR and, therefore, cannot be considered

to be insignificant and approaching zero mortality and serious injury rate. 

REFERENCES

Barlow, J. 1995. The abundance of cetaceans in California waters. Part I: Ship surveys in summer and fall of 1991.

Fish. Bull. 93:1-14.

Barlow, J. 1997. Preliminary estimates of cetacean abundance off California, Oregon and Washington based on a 1996

ship survey and comparisons of passing and closing modes. Administrative Report LJ-97-11, Southwest

Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA 92038. 25p.

Barlow, J. and G. A. Cameron. 1999. Field experiments show that acoustic pingers reduce marine mammal bycatch in

the California drift gillnet fishery. Paper SC/51/SM2 presented to the International Whaling Commission, May

1998 (unpublished). 20pp.

Barlow, J., K. A. Forney, P. S. Hill, R. L. Brownell, Jr., J. V. Carretta, D. P. DeMaster, F. Julian, M. S. Lowry, T.

Ragen, and R. R. Reeves. 1997. U.S. Pacific Marine Mammal Stock Assessments: 1996. U.S. Dep. Commer.,

NOAA Tech. Memo. NMFS-SWFSC-248. 223p.

Barlow, J. and T. Gerrodette. 1996. Abundance of cetaceans in California waters based on 1991 and 1993 ship

surveys. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-SWFSC-233. 

Cameron, G., and K. A. Forney. 1999. Estimates of cetacean mortality in the California gillnet fisheries for 1997 and

1998. Paper SC/51/O4 presented to the International Whaling Commission, 1999 (unpublished). 14pp.

Dizon, A., C. LeDuc, and R. LeDuc. 1994. Intraspecific structure of the northern right-whale dolphin (Lissodelphis

borealis): The power of an analysis of molecular variation for differentiating genetic stocks. CalCOFI Rep.

35:61-67.

Dizon, A. E., G. M. O'Corry-Crowe, and B. L. Taylor. (1995). Why statistical power is necessary to link analyses of

molecular variation to decisions about population structure. pp. 288-294 In:J. L. Neilsen (ed.), Evolution and

the Aquatic Ecosystem: Defining Unique Units in Population Conservation. American Fisheries Society

Symposium 17.

Dohl, T. P., R. C. Guess, M. L. Duman, and R. C. Helm. 1983. Cetaceans of central and northern California, 1980-

1983: Status, abundance and distribution. OCS Study MMS 84-0045. Minerals Management Service Contract

# 14-12-0001-29090. 284p.

Dohl, T. P., K. S. Norris, R. C. Guess, J. D. Bryant, and M. W. Honig. 1980. Summary of marine mammal and seabird

surveys of the Southern California Bight area, 1975-1978. Part II. Cetacea of the Southern California Bight.

Final Report to the Bureau of Land Management, NTIS Rep. No. PB81248189. 414p.

Forney, K. A. 1994. Recent information on the status of odontocetes in Californian waters. NOAA Technical

Memorandum NMFS, NOAA-TM-NMFS-SWFSC-202. Available from NMFS, Southwest Fisheries Science

Center, P.O. Box 271, La Jolla, California, USA.

Forney, K. A. and J. Barlow. 1998. Seasonal patterns in the abundance and distribution of California cetaceans, 1991-

92. Mar. Mamm. Sci. 14:460-489.

Forney, K. A., J. Barlow and J. V. Carretta. 1995. The abundance of cetaceans in California waters. Part II: Aerial

surveys in winter and spring of 1991 and 1992. Fish. Bull. 93:15-26.

Green, G., J. J. Brueggeman, R. A. Grotefendt, C. E. Bowlby, M. L. Bonnell, and K. C. Balcomb, III. 1992. Cetacean

distribution and abundance off Oregon and Washington. Ch. 1. In: Oregon and Washington Marine Mammal

and Seabird Surveys. OCS Study 91-0093. Final Report prepared for Pacific OCS Region, Minerals

Management Service, U.S. Department of the Interior, Los Angeles, California. 

Green, G., R. A. Grotefendt, M. A. Smultea, C. E. Bowlby, and R. A. Rowlett. 1993. Delphinid aerial surveys in
108

Oregon and Washington waters. Final Report prepared for NMFS, National Marine Mammal Laboratory, 7600

Sand Point Way, NE, Seattle, Washington, 98115, Contract #50ABNF200058.

Holts, D. Southwest Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA 92038.

Holts, D. and O. Sosa-Nishizaki. 1998. Swordfish, Xiphias gladius, fisheries of the eastern North Pacific Ocean. In:

I. Barrett, O. Sosa-Nishizaki and N. Bartoo (eds.). Biology and fisheries of swordfish, Xiphias gladius. Papers

from the International Symposium on Pacific Swordfish, Ensenada Mexico, 11-14 December 1994. U.S. Dep.

Commer., NOAA Tech. Rep. NMFS 142, 276 p.

Julian, F. 1997. Cetacean mortality in California gill net fisheries: Preliminary estimates for 1996. Paper SC/49/SM02

presented to the International Whaling Commission, 1997 (unpublished). 13 pp.

Julian, F. and M. Beeson. 1998. Estimates of mammal, turtle and bird mortality for two California gillnet fisheries:

1990-1995. Fish. Bull. 96:271-284.

Leatherwood, S. and W. A. Walker. 1979. The northern right-whale dolphin Lissodelphis borealis Peale in the eastern

North Pacific. In: Winn, H. E. and B. L. Olla (eds.), Behavior of Marine Mammals, p. 85-141. Plenum Press,

New York - London.

National Marine Fisheries Service, Southwest Fisheries Science Center. Unpublished data.

Sosa-Nishizaki, O., R. De la Rosa-Pacheco, R. Castro-Longoria, M. Grijalva Chon, and J. De la Rosa Velez. 1993.

Estudio biologico pesquero del pez (Xiphias gladius) y otras especies de picudos (marlins y pez vela). Rep.

Int. CICESE, CTECT9306.

Stick, K. C. and Hreha, L. 1989. Summary of the 1988 Washington/Oregon experimental thresher shark gill net

fishery. State of Washington, Department of Fisheries, Progress Report 275. 40p.

Wade, P. R. and R. P. Angliss. 1997. Guidelines for Assessing Marine Mammal Stocks: Report of the GAMMS

Workshop April 3-5, 1996, Seattle, Washington. U. S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-12.

93 pp.
109

Southern

Resident

stock

Figure 1. Approximate distribution of killer whales in the

eastern North Pacific (shaded area). The distribution of

the Eastern North Pacific Northern Resident and Transient

stocks are largely overlapping (see text). 

Revised 12/15/2000

KILLER WHALE (Orcinus orca): 

Eastern North Pacific Transient Stock

STOCK DEFINITION AND GEOGRAPHIC

RANGE

Killer whales have been observed in all oceans

and seas of the world (Leatherwood and Dahlheim 1978).

Although reported from tropical and offshore waters,

killer whales prefer the colder waters of both

hemispheres, with greatest abundances found within 800

km of major continents (Mitchell 1975). Along the west

coast of North America, killer whales occur along the

entire Alaskan coast (Braham and Dahlheim 1982), in

British Columbia and Washington inland waterways

(Bigg et al. 1990), and along the outer coasts of

Washington, Oregon, and California (Green et al. 1992;

Barlow 1995, 1997; Forney et al. 1995). Seasonal and

year-round occurrence has been noted for killer whales

throughout Alaska (Braham and Dahlheim 1982) and in

the intracoastal waterways of British Columbia and

Washington State, where pods have been labeled as

‘resident,’ ‘transient,’ and ‘offshore’ (Bigg et al. 1990,

Ford et al. 1994) based on aspects of morphology,

ecology, genetics, and behavior (Ford and Fisher 1982,

Baird and Stacey 1988, Baird et al. 1992, Hoelzel et al.

1998). Through examination of photographs of

recognizable individuals and pods, movements of whales

between geographical areas have been documented. For

example, whales identified in Prince William Sound have

been observed near Kodiak Island (Matkin et al. 1999) and whales identified in Southeast Alaska have been observed

in Prince William Sound, British Columbia, and Puget Sound (Leatherwood et al. 1990, Dahlheim et al. 1997).

Movements of killer whales between the waters of Southeast Alaska and central California have also been documented

(Goley and Straley 1994).

Studies on mtDNA restriction patterns provide evidence that the ‘resident’ and ‘transient’ types are genetically

distinct (Stevens et al. 1989, Hoelzel 1991, Hoelzel and Dover 1991, Hoelzel et al. 1998). Analysis of 73 samples

collected from eastern North Pacific killer whales from California to Alaska has demonstrated significant genetic

differences among ‘transient’ whales from California through Alaska, ‘resident’ whales from the inland waters of

Washington, and ‘resident’ whales ranging from British Columbia to the Aleutian Islands and Bering Sea (Hoelzel et

al. 1998).

Based on data regarding association patterns, acoustics, movements, genetic differences and potential fishery

interactions, five killer whale stocks are recognized within the Pacific U.S. EEZ: 1) the Eastern North Pacific Northern

Resident stock - occurring from British Columbia through Alaska, 2) the Eastern North Pacific Southern Resident stock

- occurring mainly within the inland waters of Washington State and southern British Columbia, but also in coastal

waters from British Columbia through California, 3) the Eastern North Pacific Transient stock - occurring from Alaska

through California (see Fig. 1), 4) the Eastern North Pacific Offshore stock - occurring from Southeast Alaska through

California, and 5) the Hawaiian stock. ‘Transient’ whales in Canadian waters are considered part of the Eastern North

Pacific Transient stock. The Stock Assessment Reports for the Alaska Region contain information concerning the

Eastern North Pacific Northern Resident stock
110

POPULATION SIZE

The Eastern North Pacific Transient stock is a trans-boundary stock, including killer whales from British

Columbia. Preliminary analysis of photographic data resulted in the following minimum counts for ‘transient’ killer

whales belonging to the Eastern North Pacific Transient stock (Note: individual whales have been matched between

geographical regions and missing animals likely to be dead have been subtracted). In British Columbia and southeastern

Alaska, 219 ‘transient’ whales have been cataloged (Ford and Ellis 1999). In the Gulf of Alaska, 21 ‘transient’ killer

whales have been identified genetically and/or acoustically (Matkin et al. 1999). The ‘transient’ group AT1, commonly

seen in Prince William Sound/Kenai Fjords, had only 11 remaining whales in 1998 (Matkin et al. 1999). Based on data

collected from all Alaska waters west of Seward (Dahlheim and Waite 1993; Dahlheim 1994, 1997), 68 whales are

considered ‘residents’ as they have been linked by association to ‘resident’ whales from Prince William Sound (G. Ellis,

pers. comm.), and the remainder are provisionally classified as 174 ‘residents’ and 53 ‘transients.’ Provisional

classifications were based primarily on morphological differences identified from the photographs. Accordingly, the

numbers of ‘residents’ and ‘transients’ in Alaska waters west of Seward are considered preliminary at this time. Off

the coast of California, 105 ‘transient’ whales have been identified (Black et al. 1997): 10 whales were matched to

photos of ‘transients’ in other catalogs and the remaining 95 were linked by association. An additional 14 whales in

southeastern Alaska (M. Dahlheim, unpubl. data) and 16 whales off the coast of California (N. Black, pers. comm.) have

been provisionally classified as ‘transient’ whales by association. Combining the counts of cataloged ‘transient’ whales

gives a minimum number of 346 (219 + 21 + 11 + 95) killer whales belonging to the Eastern North Pacific Transient

stock.

Minimum Population Estimate

The abundance estimate of killer whales is a direct count of individually identifiable animals. However, the

number of cataloged whales does not necessarily represent the number of live animals. Some animals may have died,

but whales can not be presumed dead if not resighted because long periods of time between sightings is common for

some ‘transient’ animals. On the other hand, given that researchers continue to identify new whales, the estimate of

abundance based on the number of uniquely identified individuals cataloged is likely conservative. However, the rate

of discovering new whales within Southeast Alaska and Prince William Sound is relatively low. In addition, the

abundance estimate does not include 53 whales from western Alaska, 14 whales from southeastern Alaska, and 16

whales off the coast of California that have been provisionally classified as ‘transients.’

Other estimates of the overall population size (i.e., NBEST) and associated CV(N) are not currently available.

Thus, the minimum population estimate (NMIN) for the Eastern North Pacific Transient stock of killer whales is 346

animals, which includes animals found in Canadian waters (see PBR Guidelines regarding the status of migratory transboundary stocks, Wade and Angliss 1997). Information on the percentage of time animals typically encountered in

Canadian waters spend in U.S. waters is unknown. However, as noted above, this minimum population estimate is

considered conservative. This approach is consistent with the recommendations of the Alaska Scientific Review Group

(DeMaster 1996). 

Current Population Trend

At present, reliable data on trends in population abundance for the Eastern North Pacific Transient stock of

killer whales are unavailable.

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

A reliable estimate of the maximum net productivity rate is currently unavailable for this stock of killer whales.

Studies of ‘resident’ killer whale pods in the Pacific Northwest resulted in estimated population growth rates of 2.92%

and 2.54% over the period from 1973 to 1987 (Olesiuk et al. 1990, Brault and Caswell 1993). However, a population

increases at the maximum growth rate (RMAX) only when the population is at extremely low levels; thus, the estimate

of 2.92% is not a reliable estimate of RMAX. Hence, until additional data become available, it is recommended that the

cetacean maximum theoretical net productivity rate (RMAX) of 4% be employed for this stock (Wade and Angliss 1997).

POTENTIAL BIOLOGICAL REMOVAL

The potential biological removal (PBR) level for this stock is calculated as the minimum population size (346)

times one-half the default maximum net growth rate for cetaceans (1⁄2 of 4%) times a recovery factor of 0.40 (for a
111

cetacean stock of unknown status with a mortality rate CV ≥ 0.80, Wade and Angliss 1997), resulting in a PBR of 2.8

whales per year. The proportion of time that this trans-boundary stock spends in Canadian waters cannot be determined

(G. Ellis, pers. comm.).

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Fisheries Information

Six different commercial fisheries in Alaska that could have interacted with killer whales were monitored for

incidental take by fishery observers from 1994 to 1998: Bering Sea/Aleutian Islands (BSAI) and Gulf of Alaska

groundfish trawl, longline, and pot fisheries. Of the six observed fisheries, killer whale mortalities occurred only in the

Bering Sea groundfish trawl and longline fisheries (Table 1; Perez in prep.). From 1994 to 1998, one killer whale

mortality was observed in 1997 in the Bering Sea groundfish trawl fishery. The 1995 mortality in the longline fishery

occurred during an unmonitored haul and could not be used to estimate total mortality for the fishery.

NMFS observers also monitored the California/Oregon thresher shark/swordfish drift gillnet fishery from 1994

to 1998 (Table 1; Julian 1997, Julian and Beeson 1998, Cameron and Forney 1999). The observed mortality in this

fishery, in 1995, was a transient whale as determined by genetic testing (S. Chivers, pers. comm.). Overall entanglement

rates in the California/Oregon thresher shark/swordfish drift gillnet fishery dropped considerably after the 1997

implementation of a Take Reduction Plan, which included skipper education workshops and required the use of pingers

and minimum 6-fathom extenders (Barlow and Cameron 1999). Because of the changes in this fishery after

implementation of the Take Reduction Plan, mean annual takes in Table 1 are based only on 1997-1998 data. Additional

fisheries that could interact with the Eastern North Pacific Transient stock of killer whales are listed in Appendix 1.

The mean annual mortality was 0.4 (CV=1.0) for the Bering Sea groundfish trawl fishery, 0.2 (0 from

monitored hauls + 0.2 from unmonitored haul data) for the combined Bering Sea longline fishery, and zero for the

California/Oregon thresher shark/swordfish drift gillnet fishery (1997-1998 data), resulting in a mean annual mortality

rate of 0.6 killer whales per year from observed fisheries.

An additional source of information on the number of killer whales killed or injured incidental to commercial

fishery operations is the self-reported fisheries information required of vessel operators by the MMPA. During the

period between 1994 and 1998, there were no fisher self-reports of killer whale mortalities from any Alaska fisheries

operating within the range of this stock. However, because logbook records (fisher self-reports required during 1990-

94) are most likely negatively biased (Credle et al. 1994), these are considered to be minimum estimates. Self-reported

fisheries data are incomplete for 1994, not available for 1995, and considered unreliable after 1995 (see Appendix 4

of Hill and DeMaster 1998).

The estimated minimum mortality rate incidental to recently monitored U.S. commercial fisheries is 0.6

animals per year, based on observer data (0.4 from monitored hauls + 0.2 from unmonitored hauls). As the animals

which were taken incidental to commercial fisheries in Alaska have not been identified genetically, it is not possible

to determine whether they belonged to the Eastern North Pacific Northern Resident or the Eastern North Pacific

Transient killer whale stock. Accordingly, these same mortalities can be found in the stock assessment report for the

Northern Resident stock. 

Table 1. Summary of incidental mortality of killer whales (Eastern North Pacific Transient stock) due to commercial

fisheries and calculation of the mean annual mortality rate. Mean annual takes are based on 1994-98 data unless noted

otherwise.

Fishery name Years Data type

Percent 

observer

coverage

Observed 

mortality 

Estimated

mortality

Mean annual

takes (CV in

parentheses)

Bering Sea/Aleutian Is. (BSAI)

groundfish trawl

94

95

96

97

98

obs data 65.5%

67.3%

66.2%

63.9%

67.0%

0

0

0

1

0

0

0

0

2

0

0.4 (1.0)
Fishery name Years Data type

Percent 

observer

coverage

Observed 

mortality 

Estimated

mortality

Mean annual

takes (CV in

parentheses)

112

BSAI groundfish longline

(incl. misc. finfish and

sablefish fisheries)

94

95

96

97

98

95

obs data

unmonitored

haul

27.3%

28.0%

28.7%

32.5%

36.2%

0

0

0

0

0

1

0

0

0

0

0

0

0.2

CA/OR thresher shark/

swordfish drift gillnet

94

95

96

97

98

obs data 17.9%

15.6%

12.4%

23.0%

20.0%

0

1

0

0

0

0

6

0

0

0

0

1

Estimated total annual takes 0.6 (1.0)

1

 Only 1997-98 mortality estimates are included in the average because of gear modifications implemented within the fishery as part of a 1997 Take

Reduction Plan. Gear modifications included the use of net extenders and acoustic warning devices (pingers).

Due to a lack of Canadian observer programs, there are few data concerning the mortality of marine mammals

incidental to Canadian commercial fisheries, which are analogous to U.S. fisheries that are known to interact with killer

whales. The sablefish longline fishery accounts for a large proportion of the commercial fishing/killer whale

interactions in Alaska waters. Such interactions have not been reported in Canadian waters where sablefish are taken

via a pot fishery. Since 1990, there have been no reported fishery-related strandings of killer whales in Canadian waters.

However, in 1994, one killer whale was reported to have contacted a salmon gillnet, but it did not entangle (Guenther

et al. 1995). Data regarding the level of killer whale mortality related to commercial fisheries in Canadian waters,

though thought to be small, are not readily available or reliable which results in an underestimate of the annual mortality

for this stock.

Subsistence/Native Harvest Information

There are no reports of a subsistence harvest of killer whales in Alaska or Canada.

Other Mortality

There is considerable interaction between killer whales and longline vessels in the Bering Sea (Dahlheim 1988;

Yano and Dahlheim 1995; Perez in prep.; M. Perez, unpubl. data), as well as reports of killer whales consuming the

processing waste of Bering Sea groundfish trawl fishing vessels (M. Perez, unpubl. data). However, it most likely is

the ‘resident’ stock of killer whales that is involved in such fishery interactions since these whales are known to be fish

eaters, while ‘transient’ whales have only been observed feeding on marine mammals.

The shooting of killer whales in Canadian waters has also been a concern in the past. However, in recent years

there have been no reports of shooting incidents in Canadian waters. In fact, the likelihood of shooting incidents

involving ‘transient’ killer whales is thought to be minimal since commercial fishermen are most likely to observe

‘transients’ feeding on seals or sea lions instead of interacting with their fishing gear (G. Ellis, pers. comm.).

Collisions with boats are another source of mortality. One mortality due to a ship strike occurred in 1998, when

a killer whale struck the propeller of a vessel in the Bering Sea groundfish trawl fishery, resulting in an estimated annual

mortality of 0.2 killer whales from this stock in 1994-1998.

STATUS OF STOCK

Killer whales are not listed as “depleted” under the MMPA or listed as “threatened” or “endangered” under

the Endangered Species Act. Recall that the human-caused mortality has been underestimated, primarily due to a lack

of information on Canadian fisheries, and that the minimum abundance estimate is considered conservative (because

researchers continue to encounter new whales and provisionally classified whales from western Alaska, southeastern

Alaska, and off the coast of California were not included), resulting in a conservative PBR estimate. Based on currently
113

available data, the estimated annual fishery-related mortality level (0.6) exceeds 10% of the PBR (0.28) and, therefore,

can not be considered to be insignificant and approaching zero mortality and serious injury rate. The estimated annual

level of human-caused mortality and serious injury (0.6 + 0.2 = 0.8 animals per year) is not known to exceed the PBR

(2.8). Therefore, the Eastern North Pacific Transient stock of killer whales is not classified as a strategic stock.

Population trends and status of this stock relative to its Optimum Sustainable Population (OSP) level are currently

unknown.

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Barlow, J. 1995. The abundance of cetaceans in California waters. Part I: Ship surveys in summer and fall of 1991.

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in the California drift gillnet fishery. Paper SC/51/SM2 presented to the International Whaling Commission,

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Special Issue 12.

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Black, N. A., A. Schulman-Janiger, R. L. Ternullo, and M. Guerrero-Ruiz. 1997. Killer whales of California and

western Mexico: a catalog of photo-identified individuals. U.S. Dep. Commer., NOAA Tech. Memo. NMFSSWFSC-247. 174 pp.

Braham, H. W., and M. E. Dahlheim. 1982. Killer whales in Alaska documented in the Platforms of Opportunity

Program. Rep. Int. Whal. Commn. 32:643-646.

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1454.

Cameron, G. A., and K. A. Forney. 1999. Preliminary estimates of cetacean mortality in the California gillnet fisheries

for 1997 and 1998. Paper SC/51/O4 presented to the International Whaling Commission, May 1999

(unpublished). 14 pp.

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observer programs: minutes and recommendations from a workshop held in Galveston, Texas, November 10-

11, 1993. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-94-1. 96 pp.

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Dahlheim, M. E. 1988. Killer whale (Orcinus orca) depredation on longline catches of sablefish (Anoplopoma fimbria)

in Alaskan waters. NWAFC Processed Rep. 88-14. 31 pp. Available at National Marine Mammal Laboratory,

7600 Sand Point Way NE, Seattle, WA 98115.

Dahlheim, M. E. 1994. Abundance and distribution of killer whales, Orcinus orca, in Alaska, 1993. 1993 Annual

Report to the MMPA Assessment Program, Office of Protected Resources, NMFS, NOAA, 1335 East-West

Highway, Silver Spring, MD 20910. Available at National Marine Mammal Laboratory, 7600 Sand Point Way

NE, Seattle, WA 98115. 

Dahlheim, M. E. 1997. A photographic catalogue of killer whales (Orcinus orca) from the Central Gulf of Alaska to

the southeastern Bering Sea. U.S. Dep. Commer., NOAA Tech. Rep. NMFS-131. 54 pp.

Dahlheim, M. E., and J. M. Waite. 1993. Abundance and distribution of killer whales (Orcinus orca) in Alaska in

1992. 1992 Annual Report to the MMPA Assessment Program, Office of Protected Resources, NMFS,
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NOAA, 1335 East-West Highway, Silver Spring, MD 20910. Available at National Marine Mammal

Laboratory, 7600 Sand Point Way NE, Seattle, WA 98115. 

Dahlheim, M. E., D. Ellifrit, and J. Swenson. 1997. Killer Whales of Southeast Alaska: A Catalogue of Photoidentified

Individuals. Day Moon Press, Seattle, WA. 82 pp. + appendices.

DeMaster, D. P. 1996. Minutes from the 11-13 September 1996 meeting of the Alaska Scientific Review Group,

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Laboratory, 7600 Sand Point Way NE, Seattle, WA 98115.

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and Southeastern Alaska. University of British Columbia Press, Vancouver, BC. 96 pp.

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Columbia. Rep. Int. Whal. Commn. 32:671-679.

Ford, J. K. B., G. M. Ellis, and K. C. Balcomb. 1994. Killer Whales: The Natural History and Genealogy of Orcinus

orca in British Columbia and Washington State. University of British Columbia Press, Vancouver, BC, and

University of Washington Press, Seattle. 102 pp.

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surveys in winter and spring of 1991 and 1992. Fish. Bull. 93:15-26.

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killer whales (Orcinus orca) previously identified in Glacier Bay, Alaska. Can. J. Zool. 72:1528-1530.

Green, G. A., J. J. Brueggeman, R. A. Grotefendt, C. E. Bowlby, M. L. Bonnel, and K. C. Balcomb. 1992. Cetacean

distribution and abundance off Oregon and Washington, 1989-1990. Pp. 1-100, In: Brueggeman, J. J. (ed.),

Oregon and Washington Marine Mammal and Seabird Surveys. Final Rep. OCS Study MMS 91-0093.

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fishing gear entanglements of cetaceans on the west coast of Canada in 1994. Paper SC/47/O6 presented to

the International Whaling Commission, May 1995 (unpublished). 7 pp.

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Tech. Memo. NMFS-AFSC-97. 166 pp.

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conservation. Rep. Int. Whal. Commn. Special Issue 13:225-233.

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66:191-195.

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the Eastern North Pacific, and genetic differentiation between foraging specialists. J. Heredity 89:121-128.

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presented to the International Whaling Commission, September 1997 (unpublished). 13 pp.

Julian, F., and M. Beeson. 1998. Estimates of marine mammal, turtle, and seabird mortality for two California gillnet

fisheries: 1990-1995. Fish. Bull. 96(2):271-284.

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Systems Center, Tech. Rep. 443:1-39.

Leatherwood, S., C. O. Matkin, J. D. Hall, and G. M. Ellis. 1990. Killer whales, Orcinus orca, photo-identified in

Prince William Sound, Alaska 1976 to 1987. Can. Field Nat. 104:362-371.

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Gulf Oceanic Society. 96 pp.

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32:914-916.

Olesiuk, P. F., M. A. Bigg, and G. M. Ellis. 1990. Life history and population dynamics of resident killer whales

(Orcinus orca) in the coastal waters of British Columbia and Washington State. Rep. Int. Whal. Commn.

Special Issue 12:209-242.

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Perez, M. A. In prep. Compilation of marine mammal-fisheries interaction data from the domestic and joint venture

groundfish fisheries in the U.S. EEZ of the North Pacific, 1989-99.

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67:2592-2595.

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the southeastern Bering Sea and adjacent waters. Fish. Bull. 93:355-372.
116

Figure 1. Killer whale sightings based on aerial and

shipboard surveys off California, Oregon and

Washington, 1991-96 (see Appendix 2, Figures 1-5, for

data sources and information on timing and location of

survey effort). Sightings include killer whales from all

stocks found in this region. Dashed line represents the

U.S. EEZ, thick line indicates the outer boundary of all

surveys combined.

Revised 12/15/2000

KILLER WHALE (Orcinus orca):

Eastern North Pacific Offshore Stock

STOCK DEFINITION AND GEOGRAPHIC

RANGE

Killer whales have been observed in all oceans

and seas of the world (Leatherwood and Dahlheim 1978).

Although reported from tropical and offshore waters,

killer whales prefer the colder waters of both

hemispheres, with greatest abundances found within 800

km of major continents (Mitchell 1975). Along the west

coast of North America, killer whales occur along the

entire Alaskan coast (Braham and Dahlheim 1982), in

British Columbia and Washington inland waterways

(Bigg et al. 1990), and along the outer coasts of

Washington, Oregon and California (Green et al. 1992;

Barlow 1995, 1997; Forney et al. 1995). Seasonal and

year-round occurrence has been noted for killer whales

throughout Alaska (Braham and Dahlheim 1982) and in

the intracoastal waterways of British Columbia and

Washington State, where pods have been labeled as

'resident', 'transient' and ‘offshore’ (Bigg et al. 1990, Ford

et al. 1994) based on aspects of morphology, ecology,

genetics and behavior (Ford and Fisher 1982; Baird and

Stacey 1988; Baird et al. 1992, Hoelzel et al. 1998).

Through examination of photographs of recognizable

individuals and pods, movements of whales between

geographical areas have been documented. For example,

whales identified in Prince William Sound have been

observed near Kodiak Island (Heise et al. 1991) and

whales identified in Southeast Alaska have been

observed in Prince William Sound, British Columbia, and

Puget Sound (Leatherwood et al. 1990, Dahlheim et al.

1997). Movements of killer whales between the waters

of Southeast Alaska and central California have also been

documented (Goley and Straley 1994).

Offshore killer whales have more recently also been identified off the coasts of California, Oregon, and rarely,

in Southeast Alaska (Ford et al. 1994, Black et al. 1997, Dahlheim et al. 1997). They apparently do not mix with the

transient and resident killer whale stocks found in these regions (Ford et al. 1994, Black et al. 1997). Studies indicate

the ‘offshore’ type, although distinct from the other types (‘resident’ and ‘transient’), appears to be more closely related

genetically, morphologically, behaviorally, and vocally to the ‘resident’ type killer whales (Black et al. 1997, Hoelzel

et al. 1998; J. Ford, pers. comm.; L. Barrett-Lennard, pers. comm.). Based on data regarding association patterns,

acoustics, movements, genetic differences, and potential fishery interactions, five killer whale stocks are recognized

within the Pacific U.S. EEZ 1) the Eastern North Pacific Northern Resident stock - occurring from British Columbia

through Alaska, 2) the Eastern North Pacific Southern Resident stock - occurring within the inland waters of

Washington State and southern British Columbia, 3) the Eastern North Pacific Transient stock - occurring from Alaska

through California, 4) the Eastern North Pacific Offshore stock - occurring from Southeast Alaska through California

(this report), and 5) the Hawaiian stock. ‘Offshore’ whales in Canadian waters are considered part of the Eastern North

Pacific Offshore stock. The Stock Assessment Reports for the Alaska Region contain assessments of the Eastern North

Pacific Northern Resident stock, and the most recent assessment for the Hawaii Stock is included in this volume.
117

POPULATION SIZE

Off British Columbia, approximately 200 offshore killer whales were identified between 1989 and 1993 (Ford

et al. 1994), and 20 of these individuals have also been seen off California (Black et al. 1997). Using only good quality

photographs that clearly show characteristics of the dorsal fin and saddle patch region, an additional 11 offshore killer

whales that were not previously known have been identified off the California coast, bringing the total number of known

individuals in this population to 211. This is certainly an underestimate of the total population size, because not all

animals in this population have been photographed. In the future, it may be possible estimate the total abundance of

this transboundary stock using mark-recapture analyses based on individual photographs. Based on summer/fall

shipboard line-transect surveys in 1991, 1993 and 1996 (Barlow 1997), the total number of killer whales within 300 nmi

of the coasts of California, Oregon and Washington was recently estimated to be 819 animals (CV=0.38). There is

currently no way to reliably distinguish the different stocks of killer whales from sightings at sea, but photographs of

individual animals can provide a rough estimate of the proportion of whales in each stock. A total of 161 individual

killer whales photographed off California and Oregon have been determined to belong to the transient (105 whales) and

offshore (56 whales) stocks (Black et al. 1997). Using these proportions to prorate the line transect abundance estimate

yields an estimate of 56/161 * 819 = 285 offshore killer whales along the U.S. west coast. This is expected to be a

conservative estimate of the number of offshore killer whales, because offshore whales apparently are less frequently

seen near the coast (Black et al. 1997), and therefore photographic sampling may be biased towards transient whales.

For stock assessment purposes, this combined value is currently the best available estimate of abundance for offshore

killer whales off the coasts of California, Oregon and Washington.

Minimum Population Estimate

The total number of known offshore killer whales along the U.S. West coast, Canada and Alaska is 211

animals, but it is not known what proportion of time this transboundary stock spends in U.S. waters, and therefore this

number is difficult to work with for PBR calculations. A minimum abundance estimate for all killer whales along the

coasts of California, Oregon and Washington can be estimated from the 1991-1996 line-transect surveys as the 20th

percentile of the abundance estimate, or 601 killer whales. Using the same prorating as above, a minimum of 56/161

* 601 = 209 offshore killer whales are estimated to be in U.S. waters off California, Oregon and Washington.

Current Population Trend

No information is available regarding trends in abundance of Eastern North Pacific offshore killer whales.

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

No information on current or maximum net productivity rates is available for killer whales in this region. 

POTENTIAL BIOLOGICAL REMOVAL

 The potential biological removal (PBR) level for this stock is calculated as the minimum population size (209)

times one half the default maximum net growth rate for cetaceans (1⁄2 of 4%) times a recovery factor of 0.50 (for a

species of unknown status with no known fishery mortality; Wade and Angliss 1997), resulting in a PBR of 2.1 offshore

killer whales per year. 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Fishery Information

A summary of information on fisheries that may take animals from this killer whale stock is shown in Table

1. More detailed information on these fisheries is provided in Appendix 1. In the California drift gillnet fishery, no

offshore killer whales have been observed entangled ( Julian 1997; Julian and Beeson 1998; Cameron and Forney 1999),

but one killer whale from the Eastern North Pacific Transient Stock was observed taken in 1995, and offshore killer

whales may also occasionally be entangled. Additional potential sources of killer whale mortality are set gillnets and

longlines. In California, an observer program between July 1990 and December 1994 monitored 5-15% of all sets in

the large mesh (>3.5") set gillnet fishery for halibut and angel sharks, and no killer whales were observed taken. Based

on observations for longline fisheries in other regions (i.e. Alaska; Yano and Dahlheim 1995), fishery interactions may

also occur with U.S. West coast pelagic longline fisheries, but no such interactions have been documented to date.
118

Table 1. Summary of available information on the incidental mortality and injury of killer whales (Eastern North

Pacific Offshore Stock) in commercial fisheries that might take this species. Mean annual takes are based on 1994-98

data unless noted otherwise. 

Fishery Name Data Type Year(s)

Percent

Observer

Coverage

Observed

Mortality

Estimated Annual

Mortality

Mean

Annual Takes (CV

in parentheses)

CA/OR thresher

shark/swordfish drift

gillnet fishery

observer

data 

1994

1995

1996

1997

1998

17.9% 

15.6% 

12.4% 

23.0% 

20.0% 

0

0

0

0

0

0

0

0

0

0

0

1

Minimum total annual takes 0

1

 Only 1997-98 mortality estimates are included in the average because of gear modifications implemented within the fishery as part of a 1997 Take

Reduction Plan. Gear modifications included the use of net extenders and acoustic warning devices (pingers).

Set and drift gillnet fisheries for swordfish and sharks exist along the entire Pacific coast of Baja California,

Mexico and may take animals from the same population. Quantitative data are available only for the Mexican swordfish

drift gillnet fishery, which uses vessels, gear, and operational procedures similar to those in the U.S. drift gillnet fishery,

although nets may be up to 4.5 km long (Holts and Sosa-Nishizaki 1998). The fleet increased from two vessels in 1986

to 31 vessels in 1993 (Holts and Sosa-Nishizaki 1998). The total number of sets in this fishery in 1992 can be estimated

from data provided by these authors to be approximately 2700, with an observed rate of marine mammal bycatch of 0.13

animals per set (10 marine mammals in 77 observed sets; Sosa-Nishizaki et al. 1993). This overall mortality rate is

similar to that observed in California driftnet fisheries during 1990-95 (0.14 marine mammals per set; Julian and Beeson

1998), but species-specific information is not available for the Mexican fisheries. There are currently efforts underway

to convert the Mexican swordfish driftnet fishery to a longline fishery (D. Holts, pers. comm.). 

Historical mortality

California coastal whaling operations killed five killer whales between 1962 and 1967 (Rice 1974). An

additional killer whale was taken by whalers in British Columbian waters (Hoyt 1981). It is unknown whether any of

these animals belonged to the Eastern North Pacific Offshore stock.

STATUS OF STOCK

The status of killer whales in California in relation to OSP is unknown, and there are insufficient data to

evaluate trends in abundance. No habitat issues are known to be of concern for this species. They are not listed as

"threatened" or "endangered" under the Endangered Species Act nor as "depleted" under the MMPA. There has been

no documented human-caused mortality of this stock, and therefore they are not classified as a "strategic" stock under

the MMPA. The total fishery mortality and serious injury for offshore killer whales is zero and can be considered to

be insignificant and approaching zero mortality and serious injury rate. 

REFERENCES

Baird, R. W., and P. J. Stacey. 1988. Variation in saddle patch pigmentation in populations of killer whales (Orcinus

orca) from British Columbia, Alaska, and Washington State. Can. J. Zool. 66:2582-2585.

Baird, R. W., Abrams, P. A., and L. M. Dill. 1992. Possible indirect interactions between transient and resident killer

whales: implications for the evolution of foraging specializations in the genusOrcinus. Oecologia 89:125-132.

Barlow, J. 1995. The abundance of cetaceans in California waters. Part I: Ship surveys in summer and fall of 1991.

Fish. Bull. 93:1-14.

Barlow, J. 1997. Preliminary estimates of cetacean abundance off California, Oregon and Washington based on a 1996

ship survey and comparisons of passing and closing modes. Administrative Report LJ-97-11, Southwest

Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA 92038. 25p.

Barlow, J., K. A. Forney, P. S. Hill, R. L. Brownell, Jr., J. V. Carretta, D. P. DeMaster, F. Julian, M. S. Lowry, T.

Ragen, and R. R. Reeves. 1997. U.S. Pacific marine mammal stock assessments: 1996. U.S. Dep. Commer.,

NOAA Tech. Memo. NMFS-SWFSC-248. 223 pp.
119

Barrett-Lennard, L. Univ. of British Columbia, 6270 University Blvd., Vancouver, BC V6T1Z4.

Bigg, M. A., P. F. Olesiuk, G. M. Ellis, J. K. B. Ford, and K. C. Balcomb III. 1990. Social organization and genealogy

of resident killer whales (Orcinus orca) in the coastal waters of British Columbia and Washington State. Rep.

int. Whal. Commn Special Issue 12:386-406.

Black, N. A., A. Schulman-Janiger, R. L. Ternullo, and M. Guerrero-Ruiz. 1997. Killer whales of California and

western Mexico: A Catalog of photo-identified individuals. U.S. Dep. Commer., NOAA Tech. Memo. NMFSSWFSC-247. 174p.

Braham, H. W., and M. E. Dahlheim. 1982. Killer whales in Alaska documented in the Platforms of Opportunity

Program. Rep. Int. Whal. Commn., 32:643-646.

Cameron, G., and K. A. Forney. 1999. Estimates of cetacean mortality in the California gillnet fisheries for 1997 and

1998. Paper SC/51/O4 presented to the International Whaling Commission, 1999 (unpublished). 14pp.

Dahlheim, M. E., D. Ellifrit, and J. Swenson. 1997. Killer Whales of Southeast Alaska: A Catalogue of Photoidentified

Individuals. Day Moon Press, Seattle, WA. 82 pp. + appendices.

Ford, J. K. B., Vancouver Aquarium, P.O. Box 3232, Vancouver, BC V6B 3XB, Canada.

Ford, J. K. B., G. M. Ellis, and K.C. Balcomb. 1994. Killer whales. The natural history and genealogy of Orcinus orca

in British Columbia and Washington State. UBC Press, Vancouver, Canada

Ford, J. K. B., and H. D. Fisher. 1982. Killer whale (Orcinus orca) dialects as an indicator of stocks in British

Columbia. Rep. Int. Whal. Commn 32:671-679.

Forney, K. A., J. Barlow and J. V. Carretta. 1995. The abundance of cetaceans in California waters. Part II: Aerial

surveys in winter and spring of 1991 and 1992. Fish. Bull. 93:15-26.

Goley, P. D., and J. M. Straley. 1994. Attack on gray whales (Eschrichtius robustus) in Monterey Bay, California, by

killer whales (Orcinus orca) previously identified in Glacier Bay, Alaska. Can. J. Zool. 72:1528-1530.

Green, G., J. J. Brueggeman, R. A. Grotefendt, C. E. Bowlby, M. L. Bonnell, and K. C. Balcomb, III. 1992. Cetacean

distribution and abundance off Oregon and Washington. Ch. 1. In: Oregon and Washington Marine Mammal

and Seabird Surveys. OCS Study 91-0093. Final Report prepared for Pacific OCS Region, Minerals

Management Service, U.S. Department of the Interior, Los Angeles, California. 

Heise, K., G. Ellis, and C. Matkin. 1991. A catalogue of Prince William Sound Killer Whales. North Gulf Oceanic

Society, Homer, AK. Published for the National Marine Mammal Laboratory, 7600 Sand Point Way NE,

Seattle, WA 98115.

Hoelzel, A. R., M. E. Dahlheim, and S. J. Stern. 1998. Low genetic variation among killer whales (Orcinus orca) in

the Eastern North Pacific, and genetic differentiation between foraging specialists. J. Heredity 89:121-128.

Holts, D. Southwest Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA 92038.

Holts, D. and O. Sosa-Nishizaki. 1998. Swordfish, Xiphias gladius, fisheries of the eastern North Pacific Ocean. In:

I. Barrett, O. Sosa-Nishizaki and N. Bartoo (eds.). Biology and fisheries of swordfish, Xiphias gladius. Papers

from the International Symposium on Pacific Swordfish, Ensenada Mexico, 11-14 December 1994. U.S. Dep.

Commer., NOAA Tech. Rep. NMFS 142, 276 p.

Hoyt, E. 1981. The Whale Called Killer. E. P. Dutton, New York.

Julian, F. 1997. Cetacean mortality in California gill net fisheries: Preliminary estimates for 1996. Paper SC/49/SM02

presented to the International Whaling Commission, 1997 (unpublished). 13 pp.

Julian, F. and M. Beeson. 1998. Estimates of mammal, turtle and bird mortality for two California gillnet fisheries:

1990-1995. Fishery Bulletin 96:271-284.

Leatherwood, J. S., and M. E. Dahlheim. 1978. Worldwide distribution of pilot whales and killer whales. Naval Ocean

Systems Center, Tech. Rep. 443:1-39.

Leatherwood, S., C. O. Matkin, J. D. Hall, and G. M. Ellis. 1990. Killer whales, Orcinus orca, photo-identified in

Prince William Sound, Alaska 1976 to 1987. Can. Field Naturalist 104:362-371.

Mitchell, E. D. 1975. Report on the meeting on small cetaceans, Montreal, April 1-11, 1974. J. Fish. Res. Board

Canada, 32:914-916.

Rice, D. W. 1974. Whales and whale research in eastern North Pacific. p. 170-195 In: W. E. Schevill (ed.), The Whale

Problem - A Status Report. Harvard University Press, Cambridge, MA.

Sosa-Nishizaki, O., R. De la Rosa-Pacheco, R. Castro-Longoria, M. Grijalva Chon, and J. De la Rosa Velez. 1993.

Estudio biologico pesquero del pez (Xiphias gladius) y otras especies de picudos (marlins y pez vela). Rep.

Int. CICESE, CTECT9306.
120

Yano, K. and M. E. Dahlheim. 1995. Killer whale, Orcinus orca, depredation on longline catches of bottomfish in

the southeastern Bering Sea and adjacent waters. Fishery Bulletin 93:355-372.

Wade, P. R. and R. P. Angliss. 1997. Guidelines for Assessing Marine Mammal Stocks: Report of the GAMMS

Workshop April 3-5, 1996, Seattle, Washington. U. S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-12.

93 pp.
121

Vancouver Island

British Columbia

Washington

Oregon

California

Figure 1. Approximate April-October

distribution of the Eastern North

Pacific Southern Resident killer whale

stock (shaded area) and range of

sightings (dotted line).

Revised 12/31/2001

KILLER WHALE (Orcinus orca): 

Eastern North Pacific Southern Resident Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

Killer whales have been observed in all oceans and seas of the

world (Leatherwood and Dahlheim 1978). Although reported from tropical

and offshore waters, killer whales prefer the colder waters of both

hemispheres, with greatest abundances found within 800 km of major

continents (Mitchell 1975). Along the west coast of North America, killer

whales occur along the entire Alaskan coast (Braham and Dahlheim 1982),

in British Columbia and Washington inland waterways (Bigg et al. 1990),

and along the outer coasts of Washington, Oregon, and California (Green et

al. 1992; Barlow 1995, 1997; Forney et al. 1995). Seasonal and year-round

occurrence has been noted for killer whales throughout Alaska (Braham and

Dahlheim 1982) and in the intracoastal waterways of British Columbia and

Washington State, where pods have been labeled as ‘resident,’ ‘transient,’

and ‘offshore’ (Bigg et al. 1990, Ford et al. 1994) based on aspects of

morphology, ecology, genetics, and behavior (Ford and Fisher 1982, Baird

and Stacey 1988, Baird et al. 1992, Hoelzel et al. 1998). Through

examination of photographs of recognizable individuals and pods,

movements of whales between geographical areas have been documented.

For example, whales identified in Prince William Sound have been observed

near Kodiak Island (Matkin et al. 1999) and whales identified in Southeast

Alaska have been observed in Prince William Sound, British Columbia, and

Puget Sound (Leatherwood et al. 1990, Dahlheim et al. 1997). 

Studies on mtDNA restriction patterns provide evidence that the

‘resident’ and ‘transient’ types are genetically distinct (Stevens et al. 1989,

Hoelzel 1991, Hoelzel and Dover 1991, Hoelzel et al. 1998). Analysis of 73

samples collected from eastern North Pacific killer whales from California

to Alaska has demonstrated significant genetic differences among ‘transient’

whales from California through Alaska, ‘resident’ whales from the inland

waters of Washington, and ‘resident’ whales ranging from British Columbia

to the Aleutian Islands and Bering Sea (Hoelzel et al. 1998). Most sightings

of the Eastern North Pacific Southern Resident stock of killer whales have

occurred in the summer in inland waters of Washington and southern British

Columbia. However, pods belonging to this stock have also been sighted in coastal waters off southern Vancouver

Island and Washington (Bigg et al. 1990, Ford et al. 2000). The complete winter range of this stock is uncertain. Of

the three pods comprising this stock, one (J1) is commonly sighted in inshore waters in winter, while the other two (K1

and L1) apparently spend more time offshore (Ford et al. 2000). Pods K1 and L1 are often seen entering the inland

waters of Vancouver Island from the north--through Johnstone Strait--in the spring (Ford et al. 2000), suggesting that

they may spend time along the entire outer coast of Vancouver Island during the winter. Off the Washington coast,

Southern Resident killer whales have been sighted as far south as Grays Harbor (season unknown) (Bigg et al. 1990),

and members of pods K1 and L1were observed in Monterey Bay, California, in January 2000 (N. Black, pers. comm.).

Based on data regarding association patterns, acoustics, movements, genetic differences and potential fishery

interactions, five killer whale stocks are recognized within the Pacific U.S. EEZ: 1) the Eastern North Pacific Northern

Resident stock - occurring from British Columbia through Alaska, 2) the Eastern North Pacific Southern Resident stock

- occurring mainly within the inland waters of Washington State and southern British Columbia (see Fig. 1), 3) the

Eastern North Pacific Transient stock - occurring from Alaska through California, 4) the Eastern North Pacific Offshore

stock - occurring from Southeast Alaska through California, and 5) the Hawaiian stock. The Stock Assessment Reports

for the Alaska Region contain information concerning the Eastern North Pacific Northern Resident stock. 
122

50

60

70

80

90

100

1976197819801982198419861988199019921994199619982000

Year

Total population

Figure 2. Population of Eastern North Pacific Southern Resident stock

of killer whales 1976-2000. Each year’s count includes animals first

seen and first missed; a whale is considered first missed the year after

it was last seen alive (Ford et al. 2000; Center for Whale Research,

unpubl. data).

POPULATION SIZE

The Eastern North Pacific Southern Resident stock is a trans-boundary stock including killer whales in inland

Washington and southern British Columbia waters. Photo-identification of individual whales through the years has

resulted in a substantial understanding of

this stock’s structure, behaviors, and

movements. In 1993, the three pods

comprising this stock totaled 96 killer

whales (Ford et al. 1994). The population

increased to 99 whales in 1995, then

declined to the current population of 82

whales in 2000 (Fig. 2; Ford et al. 2000;

Center for Whale Research, unpubl. data).

Minimum Population Estimate

The abundance estimate for this

stock of killer whales is a direct count of

individually identifiable animals. It is

thought that the entire population is

censused every year. This estimate

therefore serves as both a best estimate of

abundance and a minimum estimate of

abundance. Thus, the minimum population

estimate (NMIN) for the Eastern North

Pacific Southern Resident stock of killer

whales is 82 animals.

Current Population Trend

During the live-capture fishery that existed from 1967 to 1973, it is estimated that 47 killer whales, mostly

immature, were taken out of this stock (Ford et al. 1994). The first complete census of this stock occurred in 1974.

Between 1974 and 1993 the Southern Resident stock increased approximately 35%, from 71 to 96 individuals (Ford

et al. 1994). This represents a net annual growth rate of 1.8% during those years. Since 1995, the population has

declined to 82 whales (Ford et al. 2000; Center for Whale Research, unpubl. data). A Southern Resident Killer Whale

Workshop, sponsored by the AFSC’s National Marine Mammal Laboratory (NMML), the Center for Whale Research,

Six Flags Marine World Vallejo, and The Whale Museum, was held at the NMML in Seattle, WA, on 1-2 April 2000.

Workshop participants discussed possible factors influencing killer whale populations including contaminant levels

(Ross et al. 2000; G. Ylitalo, pers. comm.), whale-watching activities, and the availability of prey resources (NMML

2000).

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

A reliable estimate of the maximum net productivity rate is currently unavailable for this stock of killer whales.

Studies of ‘resident’ killer whale pods in British Columbia and Washington waters resulted in estimated population

growth rates of 2.92% and 2.54% over the period from 1973 to 1987 (Olesiuk et al. 1990, Brault and Caswell 1993).

However, a population increases at the maximum growth rate (RMAX) only when the population is at extremely low

levels; thus, the estimate of 2.92% is not considered a reliable estimate of RMAX. Hence, until additional data become

available, it is recommended that the cetacean maximum theoretical net productivity rate (RMAX) of 4% be employed for

this stock (Wade and Angliss 1997).

POTENTIAL BIOLOGICAL REMOVAL

The potential biological removal (PBR) level for this stock is calculated as the minimum population size (82)

times one-half the default maximum net growth rate for cetaceans (1⁄2 of 4%) times a recovery factor of 0.5 (for a

cetacean stock of unknown status, Wade and Angliss 1997), resulting in a PBR of 0.8 whales per year.
123

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Fisheries Information

NMFS observers have monitored the northern Washington marine set gillnet fishery since 1988 (Gearin et al.

1994, 2000; P. Gearin, unpubl. data). Observer coverage ranged from approximately 33 to 98% in the entire fishery

(coastal + inland waters) between 1994 and 1998. There was no observer coverage in this fishery in 1999, however,

the total fishing effort was only 4 net days (in inland waters) and no marine mammals were reported taken. Data from

1994 to 1999 are included in Table 1, although the mean estimated annual mortality is calculated using only the most

recent 5 years for which data are available. No killer whale mortalities have been recorded in this fishery since the

inception of the observer program.

In 1993, as a pilot for future observer programs, NMFS in conjunction with the Washington Department of

Fish and Wildlife (WDFW) monitored all non-treaty components of the Washington Puget Sound Region salmon gillnet

fishery (Pierce et al. 1994). Observer coverage was 1.3% overall, ranging from 0.9% to 7.3% for the various

components of the fishery. Encounters (whales within 10 m of a net) with killer whales were reported, but not

quantified, though no entanglements occurred.

In 1994, NMFS and WDFW conducted an observer program during the Puget Sound non-treaty chum salmon

gillnet fishery (areas 10/11 and 12/12B). A total of 230 sets were observed during 54 boat trips, representing

approximately 11% observer coverage of the 500 fishing boat trips comprising the total effort in this fishery, as

estimated from fish ticket landings (Erstad et al. 1996). No interactions with killer whales were observed during this

fishery. The Puget Sound treaty chum salmon gillnet fishery in Hood Canal (areas 12, 12B, and 12C) and Puget Sound

treaty sockeye/chum gillnet fishery in the Strait of Juan de Fuca (areas 4B, 5, and 6C) were also monitored in 1994 at

2.2% (based on % of total catch observed) and approximately 7.5% (based on % of observed trips to total landings)

observer coverage, respectively (NWIFC 1995). No interactions resulting in killer whale mortalities were reported in

either treaty salmon gillnet fishery.

Also in 1994, NMFS, WDFW, and the Tribes conducted an observer program to examine seabird and marine

mammal interactions with the Puget Sound treaty and non-treaty sockeye salmon gillnet fishery (areas 7 and 7A).

During this fishery, observers monitored 2,205 sets, representing approximately 7% of the estimated number of sets in

the fishery (Pierce et al. 1996). Killer whales were observed within 10 m of the gear during 10 observed sets (32

animals in all), though none were observed to have been entangled.

An additional source of information on the number of killer whales killed or injured incidental to commercial

fishery operations is the self-reported fisheries information required of vessel operators by the MMPA. During the

period between 1994 and 1999, there were no fisher self-reports of killer whale mortalities from any fisheries operating

within the range of this stock. However, because logbook records (fisher self-reports required during 1990-94) are most

likely negatively biased (Credle et al. 1994), these are considered to be minimum estimates. Self-reported fisheries data

are incomplete for 1994, not available for 1995, and considered unreliable after 1995 (see Appendix 4 of Hill and

DeMaster 1998).

Table 1. Summary of incidental mortality of killer whales (Eastern North Pacific Southern Resident stock) due to

commercial and tribal fisheries and calculation of the mean annual mortality rate; n/a indicates that data are not

available. Mean annual takes are based on 1995-1999 data unless noted otherwise.

Fishery name Years

Data

type

Percent

observer

coverage

Observed 

mortality

Estimated

mortality

Mean annual

takes (CV in

parentheses)

Northern WA marine set gillnet

(tribal fishery: coastal + inland

waters)

94

95

96

97

98

99

obs data

33%

87%

59%

98%

40%

0%

0

0

0

0

0

n/a

0

0

0

0

0

n/a

0

1

WA Puget Sound Region salmon

set/drift gillnet (observer

programs listed below covered

segments of this fishery):

- - - - - -
Fishery name Years

Data

type

Percent

observer

coverage

Observed 

mortality

Estimated

mortality

Mean annual

takes (CV in

parentheses)

124

 Puget Sound non-treaty salmon

 gillnet (all areas and species)

93 obs data 1.3% 0 0 0

 Puget Sound non-treaty chum

 salmon gillnet (areas 10/11 and

 12/12B)

94 obs data 11% 0 0 0

 Puget Sound treaty chum

 salmon gillnet (areas 12, 12B,

 and 12C)

94 obs data 2.2% 0 0 0

 Puget Sound treaty chum and

 sockeye salmon gillnet (areas

 4B, 5, and 6C)

94 obs data 7.5% 0 0 0

 Puget Sound treaty and non-

 treaty sockeye salmon gillnet

 (areas 7 and 7A)

94 obs data 7% 0 0 0

Minimum total annual takes 0

1

1994-98 mortality estimates are included in the average.

Due to a lack of observer programs, there are few data concerning the mortality of marine mammals incidental

to Canadian commercial fisheries. Since 1990, there have been no reported fishery-related strandings of killer whales

in Canadian waters. However, in 1994 one killer whale was reported to have contacted a salmon gillnet but did not

entangle (Guenther et al. 1995). Data regarding the level of killer whale mortality related to commercial fisheries in

Canadian waters are not available, though the mortality level is thought to be minimal.

During this decade there have been no reported takes from this stock incidental to commercial fishing

operations (D. Ellifrit, pers. comm.), no reports of interactions between killer whales and longline operations (as occurs

in Alaskan waters; see Yano and Dahlheim 1995), no reports of stranded animals with net marks, and no photographs

of individual whales carrying fishing gear. The total fishery mortality and serious injury for this stock is zero.

STATUS OF STOCK

Killer whales are not listed as “depleted” under the MMPA or listed as “threatened “ or “endangered” under

the Endangered Species Act. Based on currently available data, the total fishery mortality and serious injury for this

stock (0) is not known to exceed 10% of the calculated PBR (0.08) and, therefore, can be considered to be insignificant

and approaching zero mortality and serious injury rate. The estimated annual level of human-caused mortality and

serious injury of zero animals per year is not known to exceed the PBR (0.8). Therefore, the Eastern North Pacific

Southern Resident stock of killer whales is not classified as a strategic stock. The stock size has decreased in recent

years, although at this time it is not possible to assess the status of this stock relative to its Optimum Sustainable

Population (OSP) level.

In April 1999, Canada’s Committee on the Status of Endangered Wildlife in Canada (COSEWIC) listed

resident killer whales in British Columbia as “threatened,” i.e., likely to become “endangered” if limiting factors are

not reversed (Baird 1999). In June 2000, the Washington Department of Fish and Wildlife designated killer whales in

Washington State as a “state candidate species” (a species that the Department will review for possible listing as “state

endangered, threatened, or sensitive”). On 2 May 2001, NMFS received a petition from the Center for Biological

Diversity and 10 co-petitioners (an 11th co-petitioner was added on 16 July 2001) to list the Eastern North Pacific

Southern Resident stock of killer whales as an “endangered” or “threatened” species under the Endangered Species Act

(ESA) and to designate critical habitat for this stock under that Act. On 13 August 2001 (66 FR 42499), NMFS

determined that the petition presented substantial scientific information indicating that a listing may be warranted; thus,

NMFS is required to conduct an ESA status review of the stock and issue a report on its findings by 2 May 2002.

NMFS established a Biological Review Team for this purpose in late August 2001.
125

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orca) from British Columbia, Alaska, and Washington State. Can. J. Zool. 66 (11):2582-2585.

Baird, R. W., P. A. Abrams, and L. M. Dill. 1992. Possible indirect interactions between transient and resident killer

whales: implications for the evolution of foraging specializations in the genus Orcinus. Oecologia 89:125-132.

Barlow, J. 1995. The abundance of cetaceans in California waters. Part I: Ship surveys in summer and fall of 1991.

Fish. Bull. 93:1-14.

Barlow, J. 1997. Preliminary estimates of cetacean abundance off California, Oregon and Washington based on a 1996

ship survey and comparisons of passing and closing modes. Administrative Report LJ-97-11, Southwest

Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA 92038. 25 pp.

Bigg, M. A., P. F. Olesiuk, G. M. Ellis, J. K. B. Ford, and K. C. Balcomb III. 1990. Social organization and genealogy

of resident killer whales (Orcinus orca) in the coastal waters of British Columbia and Washington State. Pp.

386-406, In: Hammond, P. S. , S. A. Mizroch, and G. P. Donovan (eds.), Individual Recognition of Cetaceans:

Use of Photo-identification and Other Techniques to Estimate Population Parameters. Rep. Int. Whal. Commn.

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Black, N. A. P.O. Box 52001, Pacific Grove, CA 93950.

Braham, H. W., and M. E. Dahlheim. 1982. Killer whales in Alaska documented in the Platforms of Opportunity

Program. Rep. Int. Whal. Commn. 32:643-646.

Brault, S., and H. Caswell. 1993. Pod-specific demography of killer whales (Orcinus orca). Ecology 74(5):1444-

1454.

Center for Whale Research, 1359 Smugglers Cove Rd., Friday Harbor, WA 98250.

Credle, V. R., D. P. DeMaster, M. M. Merklein, M. B. Hanson, W. A. Karp, and S. M. Fitzgerald (eds.). 1994. NMFS

observer programs: minutes and recommendations from a workshop held in Galveston, Texas, November 10-

11, 1993. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-94-1. 96 pp.

Dahlheim, M. E., D. Ellifrit, and J. Swenson. 1997. Killer Whales of Southeast Alaska: A Catalogue of Photoidentified

Individuals. Day Moon Press, Seattle, WA. 82 pp. + appendices.

Ellifrit, D. Center for Whale Research, 1359 Smugglers Cove Rd., Friday Harbor, WA 98250.

Erstad, P., S. J. Jeffries, and D. J. Pierce. 1996. 1994 Report for the Puget Sound fishery observer program in

management areas 10/11 & 12/12B: nontreaty chum gill net fishery. Final Report, Washington Dept. Fish and

Wildlife, Olympia, WA. 14 pp.

Ford, J. K. B., and H. D. Fisher. 1982. Killer whale (Orcinus orca) dialects as an indicator of stocks in British

Columbia. Rep. Int. Whal. Commn. 32:671-679.

Ford, J. K. B., G. M. Ellis, and K. C. Balcomb. 1994. Killer Whales: The Natural History and Genealogy of Orcinus

orca in British Columbia and Washington State. University of British Columbia Press, Vancouver, BC, and

University of Washington Press, Seattle. 102 pp.

Ford, J. K. B., G. M. Ellis, and K. C. Balcomb. 2000. Killer Whales: The Natural History and Genealogy of Orcinus

orca in British Columbia and Washington. 2nd edition. University of British Columbia Press, Vancouver,

BC, and University of Washington Press, Seattle. 104 pp.

Forney, K. A., J. Barlow, and J. V. Carretta. 1995. The abundance of cetaceans in California waters. Part II: Aerial

surveys in winter and spring of 1991 and 1992. Fish. Bull. 93:15-26.

Gearin, P. J. National Marine Mammal Laboratory, AFSC, NMFS, 7600 Sand Point Way NE, Seattle, WA 98115.

Gearin, P. J., S. R. Melin, R. L. DeLong, H. Kajimura, and M. A. Johnson. 1994. Harbor porpoise interactions with

a chinook salmon set-net fishery in Washington State. Rep. Int. Whal. Commn. Special Issue 15:427-438.

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distribution and abundance off Oregon and Washington, 1989-1990. Pp. 1-100, In: Brueggeman, J. J. (ed.),

Oregon and Washington marine mammal and seabird surveys. Final Rep. OCS Study MMS 91-0093.

Guenther, T. J., R. W. Baird, R. L. Bates, P. M. Willis, R. L. Hahn, and S. G. Wischniowski. 1995. Strandings and
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fishing gear entanglements of cetaceans on the west coast of Canada in 1994. Paper SC/47/O6 presented to

the International Whaling Commission, May 1995 (unpublished). 7 pp.

Hill, P. S., and D. P. DeMaster. 1998. Alaska marine mammal stock assessments, 1998. U.S. Dep. Commer., NOAA

Tech. Memo. NMFS-AFSC-97. 166 pp.

Hoelzel, A. R. 1991. Analysis of regional mitochondrial DNA variation in the killer whale; implications for cetacean

conservation. Rep. Int. Whal. Commn. Special Issue 13:225-233.

Hoelzel, A. R., and G. A. Dover. 1991. Genetic differentiation between sympatric killer whale populations. Heredity

66:191-195.

Hoelzel, A. R., M. E. Dahlheim, and S. J. Stern. 1998. Low genetic variation among killer whales (Orcinus orca) in

the Eastern North Pacific, and genetic differentiation between foraging specialists. J. Heredity 89:121-128.

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Prince William Sound, Alaska 1976 to 1987. Can. Field Nat. 104:362-371.

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Available at National Marine Mammal Laboratory, 7600 Sand Point Way NE, Seattle, WA 98115-6349.

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127

Figure 1. Short-finned pilot whale sightings made

during aerial and shipboard surveys conducted off

California in 1975-83 (+) and off California, Oregon

and Washington, 1991-96 (!). See Appendix 2,

Figures 1-5, for data sources and information on timing

and location of survey effort. Dashed line represents

the U.S. EEZ, thick line indicates the outer boundary of

all surveys combined. 

Revised 12/15/2000 

SHORT-FINNED PILOT WHALE (Globicephala macrorhynchus):

California/Oregon/Washington Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

Short-finned pilot whales were once commonly

seen off Southern California, with an apparently resident

population around Santa Catalina Island, as well as seasonal

migrants (Dohl et al. 1980). After a strong El Niño event in

1982-83, short-finned pilot whales virtually disappeared

from this region, and despite increased survey effort along

the entire U.S. west coast, few sightings were made from

1984-1992 (Jones and Szczepaniak 1992; Barlow 1997;

Carretta and Forney 1993; Shane 1994; Green et al. 1992,

1993). In 1993, six groups of short-finned pilot whales were

again seen off California (Carretta et al. 1995; Barlow and

Gerrodette 1996), and mortality in drift gillnets increased

(Julian and Beeson 1998) but sightings remain rare (Barlow

1997). Figure 1 summarizes the sighting history of shortfinned pilot whales off the U.S. west coast. Although the full

geographic range of the California/Oregon/Washington

population is not known, it may be continuous with animals

found off Baja California, and its individuals are

morphologically distinct from short-finned pilot whales

found farther south in the eastern tropical Pacific (Polisini

1981). Separate southern and northern forms of short-finned

pilot whales have also been documented for the western

North Pacific (Kasuya et al. 1988; Wada 1988; Miyazaki and

Amano 1994). For the Marine Mammal Protection Act

(MMPA) stock assessment reports, short-finned pilot whales

within the Pacific U.S. Exclusive Economic Zone are

divided into two discrete, non-contiguous areas: 1) waters

off California, Oregon and Washington (this report), and 2)

Hawaiian waters.

POPULATION SIZE

Three summer/fall shipboard surveys were

conducted within 300 nmi of the coasts of California (in 1991 and 1993; Barlow and Gerrodette 1996) and California,

Oregon and Washington (in 1996; Barlow 1997). The abundance of short-finned pilot whales in this region appears to

be variable and may relate to oceanographic conditions, as with other odontocete species (Forney 1997, Forney and

Barlow 1998). Because animals may spend time outside the U.S. Exclusive Economic Zone as oceanographic

conditions change, a multi-year average abundance estimate is the most appropriate for management within U.S. waters.

The 1991-96 weighted average abundance estimate for California, Oregon and Washington waters based on the above

three ship surveys is 970 (CV=0.37) short-finned pilot whales (Barlow 1997).

Minimum Population Estimate

The log-normal 20th percentile of the 1991-96 weighted average abundance estimate is 717 short-finned pilot

whales. 

Current Population Trend

Approximately nine years after the virtual disappearance of short-finned pilot whales following the 1982-83

El Niño, they appear to have returned to California waters, as indicated by an increase in sighting records as well as
128

incidental fishery mortality (Barlow and Gerrodette 1996; Carretta et al. 1995; Julian and Beeson 1998). However, this

cannot be considered a true growth in the population, because it merely reflects large-scale, long-term movements of

this species in response to changing oceanographic conditions. It is not known where the animals went after the 82-83

El Niño, nor where the recently observed animals came from. Until the range of this population and the movements of

animals in relation to environmental conditions are better documented, no inferences can be drawn regarding trends in

abundance of short-finned pilot whales off California, Oregon and Washington.

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

No information on current or maximum net productivity rates is available for short-finned pilot whales off

California, Oregon and Washington.

POTENTIAL BIOLOGICAL REMOVAL

The potential biological removal (PBR) level for this stock is calculated as the minimum population size (717)

times one half the default maximum net growth rate for cetaceans (1⁄2 of 4%) times a recovery factor of 0.40 (for a

species of unknown status with a mortality rate CV>0.80; Wade and Angliss 1997), resulting in a PBR of 5.7 shortfinned pilot whales per year. 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Fishery Information

A summary of known fishery mortality and injury for this stock of short-finned pilot whale is shown in Table

1. More detailed information on these fisheries is provided in Appendix 1. Mortality estimates for the California drift

gillnet fishery are included for the five most recent years of monitoring, 1994-98 (Julian and Beeson 1998; Julian 1997;

Cameron and Forney 1999). After the 1997 implementation of a Take Reduction Plan, which included skipper

education workshops and required the use of pingers and minimum 6-fathom extenders, overall cetacean entanglement

rates in the drift gillnet fishery dropped considerably (Barlow and Cameron 1999). However, because of interannual

variability in entanglement rates and the relative rarity of short-finned pilot whale entanglements, additional years of

data will be required to fully evaluate the effectiveness of pingers for reducing mortality of this particular species. The

observed mortality of a single short-finned pilot whale in 1997 was in a pingered net. Because of the changes in this

fishery after implementation of the Take Reduction Plan, mean annual takes in Table 1 are based only on 1997-98 data.

This results in an average estimate of 3.0 (CV=0.96) short-finned pilot whales taken annually.

Table 1. Summary of available information on the incidental mortality and injury of short-finned pilot whales

(California/ Oregon/Washington Stock) in commercial fisheries that might take this species. All observed entanglements

of pilot whales resulted in the death of the animal. Coefficients of variation for mortality estimates are provided in

parentheses; n/a = not available. Mean annual takes are based on 1994-98 data unless noted otherwise.

Fishery Name Data Type Year(s)

Percent

Observer

Coverage

Observed

Mortality

Estimated Annual

Mortality 

Mean

Annual Takes

(CV in

parentheses)

CA/OR thresher

shark/swordfish drift

gillnet fishery

observer

data 

1994

1995

1996

1997

1998

17.9 % 

15.6 %

 12.4 %

22.8 %

20.2 %

0

0

0

1

0

0

0

0

6 (0.96)

0

3.0 (0.96)1

Undetermined (probably

squid purse seine fishery)

strandings 1975-90 14 short-finned pilot whales stranded in Southern

California with evidence of fishery interactions,

probably with the squid purse seine fishery

n/a

Minimum total annual takes 3.0 (0.96)

1

 Only 1997-98 mortality estimates are included in the average because of gear modifications implemented within the fishery as part of a 1997 Take

Reduction Plan. Gear modifications included the use of net extenders and acoustic warning devices (pingers).

Drift gillnet fisheries for swordfish and sharks exist along the entire Pacific coast of Baja California, Mexico
129

and may take animals from the same population. Quantitative data are available only for the Mexican swordfish drift

gillnet fishery, which uses vessels, gear, and operational procedures similar to those in the U.S. drift gillnet fishery,

although nets may be up to 4.5 km long (Holts and Sosa-Nishizaki 1998). The fleet increased from two vessels in 1986

to 31 vessels in 1993 ( Holts and Sosa-Nishizaki 1998). The total number of sets in this fishery in 1992 can be estimated

from data provided by these authors to be approximately 2700, with an observed rate of marine mammal bycatch of 0.13

animals per set (10 marine mammals in 77 observed sets; Sosa-Nishizaki et al. 1993). This overall mortality rate is

similar to that observed in California driftnet fisheries during 1990-95 (0.14 marine mammals per set; Julian and Beeson,

in press), but species-specific information is not available for the Mexican fisheries. There are currently efforts

underway to convert the Mexican swordfish driftnet fishery to a longline fishery (D. Holts, pers. comm.). 

Historically, short-finned pilot whales were also killed in squid purse seine operations off Southern California

(Miller et al. 1983; Heyning et al. 1994). No recent mortality has been reported, presumably because short-finned pilot

whales are no longer common in the areas of squid purse seine fishing activity; however, there have been recent

anecdotal reports of pilot whales seen near squid fishing operations off Southern California during the October 1997-

April 98 fishing season. This fishery is not currently monitored, and has expanded markedly since 1992 (Vojkovich

1998).

STATUS OF STOCK

The status of short-finned pilot whales off California, Oregon and Washington in relation to OSP is unknown.

They have declined in abundance in the Southern California Bight, likely a result of a change in their distribution since

the 1982-83 El Niño, but the nature of these changes and potential habitat issues are not adequately understood. Shortfinned pilot whales are not listed as "threatened" or "endangered" under the Endangered Species Act nor as "depleted"

under the MMPA. Including driftnet mortality only for years after implementation of the Take Reduction Plan (1997-

98), the average annual human-caused mortality in 1994-98 (3.0 animals) is estimated to be less than the PBR (5.7), and

therefore they are not classified as a "strategic" stock under the MMPA. The total fishery mortality and serious injury

for short-finned pilot whales is greater than 10% of the calculated PBR and, therefore, cannot be considered to be

insignificant and approaching zero mortality and serious injury rate. 

REFERENCES

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Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA 92038. 25p.

Barlow, J. and G. A. Cameron. 1999. Field experiments show that acoustic pingers reduce marine mammal bycatch in

the California drift gillnet fishery. Paper SC/51/SM2 presented to the International Whaling Commission, May

1998 (unpublished). 20pp.

Barlow, J. and T. Gerrodette. 1996. Abundance of cetaceans in California waters based on 1991 and 1993 ship

surveys. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-SWFSC-233. 

Cameron, G., and K. A. Forney. 1999. Estimates of cetacean mortality in the California gillnet fisheries for 1997 and

1998. Paper SC/51/O4 presented to the International Whaling Commission, 1999 (unpublished). 14pp.

Carretta, J. V. and K. A. Forney. 1993. Report of the two aerial surveys for marine mammals in California coastal

waters using a NOAA DeHavilland Twin Otter aircraft, March 9-April 7, 1991, February 8-April 6, 1992.

U.S. Dep. Commer., NOAA Tech. Memo. NMFS-SWFSC-185. 77p.

Carretta, J. V., K. A. Forney. And J. Barlow 1995. Report of 1993-94 marine mammal surveys conducted within the

U.S. Navy Outer Sea Test Range off Southern California. U.S. Dep. Commer., NOAA Tech. Memo. NMFSSWFSC-217. 90p.

Dohl, T. P., K. S. Norris, R. C. Guess, J. D. Bryant, and M. W. Honig. 1980. Summary of marine mammal and seabird

surveys of the Southern California Bight area, 1975-1978. Part II. Cetacea of the Southern California Bight.

Final Report to the Bureau of Land Management, NTIS Rep. No. PB81248189. 414p.

Forney, K. A. 1997. Patterns of variability and environmental models of relative abundance for California cetaceans.

Ph.D. Dissertation, Scripps Institution of Oceanography, University of California, San Diego.

Forney, K. A. and J. Barlow. 1998. Seasonal patterns in the abundance and distribution of California cetaceans, 1991-

92. Mar. Mamm. Sci. 14:460-489.

Green, G., J. J. Brueggeman, R. A. Grotefendt, C. E. Bowlby, M. L. Bonnell, and K. C. Balcomb, III. 1992. Cetacean
130

distribution and abundance off Oregon and Washington. Ch. 1. In: Oregon and Washington Marine Mammal

and Seabird Surveys. OCS Study 91-0093. Final Report prepared for Pacific OCS Region, Minerals

Management Service, U.S. Department of the Interior, Los Angeles, California. 

Green, G., R. A. Grotefendt, M. A. Smultea, C. E. Bowlby, and R. A. Rowlett. 1993. Delphinid aerial surveys in

Oregon and Washington waters. Final Report prepared for NMFS, National Marine Mammal Laboratory, 7600

Sand Point Way, NE, Seattle, Washington, 98115, Contract #50ABNF200058.

Heyning, J. E., T. D. Lewis and C. D. Woodhouse. 1994. A note on odontocete mortality from fishing gear

entanglements off Southern California. Rep. Int. Whal. Commn. Special Issue 15:439-442.

Holts, D. Southwest Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA 92038.

Holts, D. and O. Sosa-Nishizaki. 1998. Swordfish, Xiphias gladius, fisheries of the eastern North Pacific Ocean. In:

I. Barrett, O. Sosa-Nishizaki and N. Bartoo (eds.). Biology and fisheries of swordfish, Xiphias gladius. Papers

from the International Symposium on Pacific Swordfish, Ensenada Mexico, 11-14 December 1994. U.S. Dep.

Commer., NOAA Tech. Rep. NMFS 142, 276 p.

Jones, P. A. and I. D. Szczepaniak. 1992. Report on the seabird and marine mammal censuses conducted for the longterm management strategy (LTMS), August 1990 through November 1991, for the U.S. Environmental

Protection Agency, Region IX, San Francisco, July 1992.

Julian, F. 1997. Cetacean mortality in California gill net fisheries: Preliminary estimates for 1996. Working Paper

SC/49/SM02 presented to the International Whaling Commission, September 1997, Bournemouth, UK.

Julian, F. and M. Beeson. 1998. Estimates of marine mammal, turtle, and seabird mortality for two California gillnet

fisheries: 1990-95. Fishery Bulletin 96:271-284.

Kasuya, O., T. Miyashita, and F. Kasamatsu. 1988. Segregation of two forms of short-finned pilot whales off the

Pacific coast of Japan. Sci. Rep. Whales Res. Inst. 39:77-90.

Miller, D. J., M. J. Herder and J. P Scholl. 1983. California marine mammal - fishery interaction study, 1979-1981.

Administrative Report LJ-83-13C. Available from NMFS, Southwest Fisheries Science Center, P.O. Box 271,

La Jolla, California, 92038. 233p.

Miyazaki, N. and M. Amano. 1994. Skull morphology of two forms of short-finned pilot whales off the Pacific coast

of Japan. Rep. Int. Whaling Commn. 44:499-508.

Polisini, J. M. 1981. A comparison of Globicephala macrorhyncha (Gray, 1846) with the pilot whale of the North

Pacific Ocean: An analysis of the skull of the broad-rostrum pilot whales of the genus Globicephala.

Dissertation Abstracts International Vol. 41, No. 08, February 1981, p. 2928-B.

Shane, S. 1994. Occurrence and habitat use of marine mammals at Santa Catalina Island, California from 1983-91.

Bull. Southern California Acad. Sci. 93:13-29.

Sosa-Nishizaki, O., R. De la Rosa-Pacheco, R. Castro-Longoria, M. Grijalva Chon, and J. De la Rosa Velez. 1993.

Estudio biologico pesquero del pez (Xiphias gladius) y otras especies de picudos (marlins y pez vela). Rep.

Int. CICESE, CTECT9306.

Vojkovich, M. 1998. The California fishery for market squid (Loligo opalescens). CalCOFI Rep. 39:55-60.

Wada, S. 1988. Genetic differentiation between forms of short-finned pilot whales off the Pacific coast of Japan. Sci.

Rep. Whales Res. Inst. 39:91-101.

Wade, P. R. and R. P. Angliss. 1997. Guidelines for Assessing Marine Mammal Stocks: Report of the GAMMS

Workshop April 3-5, 1996, Seattle, Washington. U. S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-12.

93 pp.
131

Figure 1. Baird’s beaked whale sightings based on

aerial and shipboard surveys off California, Oregon

and Washington, 1991-96 (see Appendix 2, Figures 1-

5, for data sources and information on timing and

location of survey effort). Dashed line represents the

U.S. EEZ, thick line indicates the outer boundary of all

surveys combined.

Revised 12/15/2000 

BAIRD'S BEAKED WHALE (Berardius bairdii):

California/Oregon/Washington Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

Baird's beaked whales are distributed throughout deep

waters and along the continental slopes of the North Pacific

Ocean (Balcomb 1989). They have been harvested and studied

in Japanese waters, but little is known about this species

elsewhere (Balcomb 1989). Along the U.S. west coast, Baird's

beaked whales have been seen primarily along the continental

slope (Figure 1) from late spring to early fall. They have been

seen less frequently and are presumed to be farther offshore

during the colder water months of November through April. For

the Marine Mammal Protection Act (MMPA) stock assessment

reports, Baird's beaked whales within the Pacific U.S. Exclusive

Economic Zone are divided into two discrete, non-contiguous

areas: 1) waters off California, Oregon and Washington (this

report), and 2) Alaskan waters.

POPULATION SIZE

Three summer/fall shipboard surveys were conducted

within 300 nmi of the coasts of California (in 1991 and 1993;

Barlow and Gerrodette 1996) and California, Oregon and

Washington (in 1996; Barlow 1997), resulting in a combined

total of 10 Baird’s beaked whale sightings. Because their

distribution varies and animals probably spend time outside the

U.S. Exclusive Economic Zone, a multi-year average abundance

estimate is the most appropriate for management within U.S.

waters. The 1991-96 weighted average abundance estimate for

California, Oregon and Washington waters based on the above

three ship surveys is 379 (CV=0.23) Baird’s beaked whales

(Barlow 1997). This abundance estimate includes correction

factors for the proportion of animals missed (g(0) = 0.90 for

groups of 1-3 animals, g(0)=1.0 for larger groups), which are similar to the estimate of g(0)=0.96 calculated more

recently (Barlow 1999) based on dive-interval studies. 

Minimum Population Estimate

 The log-normal 20th percentile of the 1991-96 weighted average abundance estimate is 313 Baird’s beaked

whales. 

Current Population Trend

Due to the rarity of sightings of this species on surveys along the U.S. West coast, no information exists

regarding trends in abundance of this population. Future studies of trends must take the apparent seasonality of the

distribution of Baird's beaked whales into account. 

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

No information on current or maximum net productivity rates is available for this species.

POTENTIAL BIOLOGICAL REMOVAL

 The potential biological removal (PBR) level for this stock is calculated as the minimum population size (313)

times one half the default maximum net growth rate for cetaceans (1⁄2 of 4%) times a recovery factor of 0.50 (for a
132

species of unknown status with no fishery mortality; Wade and Angliss 1997), resulting in a PBR of 3.1 Baird’s beaked

whales per year.

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Fishery Information

A summary of recent fishery mortality and injury for Baird’s beaked whales in this region is shown in Table

1. More detailed information on these fisheries is provided in Appendix 1. Mortality estimates for the California drift

gillnet fishery are included for the five most recent years of monitoring, 1994-98 (Julian and Beeson 1998; Julian 1997;

Cameron and Forney 1999). After the 1997 implementation of a Take Reduction Plan, which included skipper

education workshops and required the use of pingers and minimum 6-fathom extenders, overall cetacean entanglement

rates in the drift gillnet fishery dropped considerably (Barlow and Cameron 1999). However, because of interannual

variability in entanglement rates and the relative rarity of Baird’s beaked whale entanglements, additional years of data

will be required to fully evaluate the effectiveness of pingers for reducing mortality of this particular species. Because

of the changes in this fishery after implementation of the Take Reduction Plan, mean annual takes in Table 1 are based

only on 1997-98 data. This results in an average estimated annual mortality of zero Baird’s beaked whales.

Table 1. Summary of available information on the incidental mortality and injury of Baird's beaked whales (California/

Oregon/Washington Stock) in commercial fisheries that might take this species. The single observed entanglement

resulted in the death of the animal. Coefficients of variation for mortality estimates are provided in parentheses. Mean

annual takes are based on 1994-98 data unless noted otherwise.

Fishery Name Data Type Year(s)

Percent

Observer

Coverage

Observed

Mortality

Estimated Annual

Mortality 

Mean

Annual Takes (CV

in parentheses)

CA/OR thresher

shark/swordfish drift

gillnet fishery

observer

data 

1994

1995

1996

1997

1998

17.9% 

15.6% 

12.4% 

23.0% 

20.0% 

1

0

0

0

0

6 (0.90)

0

0

0

0

0

1

Minimum total annual takes 0

1

 Only 1997-98 mortality estimates are included in the average because of gear modifications implemented within the fishery as part of a 1997 Take

Reduction Plan. Gear modifications included the use of net extenders and acoustic warning devices (pingers).

 Drift gillnet fisheries for swordfish and sharks exist along the entire Pacific coast of Baja California, Mexico

and may take animals from the same population. Quantitative data are available only for the Mexican swordfish drift

gillnet fishery, which uses vessels, gear, and operational procedures similar to those in the U.S. drift gillnet fishery,

although nets may be up to 4.5 km long (Holts and Sosa-Nishizaki 1998). The fleet increased from two vessels in 1986

to 31 vessels in 1993 (Holts and Sosa-Nishizaki 1998). The total number of sets in this fishery in 1992 can be estimated

from data provided by these authors to be approximately 2700, with an observed rate of marine mammal bycatch of 0.13

animals per set (10 marine mammals in 77 observed sets; Sosa-Nishizaki et al. 1993). This overall mortality rate is

similar to that observed in California driftnet fisheries during 1990-95 (0.14 marine mammals per set; Julian and Beeson,

1998), but species-specific information is not available for the Mexican fisheries. There are currently efforts underway

to convert the Mexican swordfish driftnet fishery to a longline fishery (D. Holts, pers. comm.). 

Other mortality

California coastal whaling operations killed 15 Baird's beaked whales between 1956 and 1970, and 29

additional Baird's beaked whales were taken by whalers in British Columbian waters (Rice 1974).

STATUS OF STOCK

The status of Baird's beaked whales in California, Oregon and Washington waters relative to OSP is not known,

and there are insufficient data to evaluate trends in abundance. No habitat issues are known to be of concern for this

species, but in recent years questions have been raised regarding potential effects of human-made sounds on deep-diving

cetacean species, such as Baird’s beaked whales (Richardson et al. 1995). They are not listed as "threatened" or
133

"endangered" under the Endangered Species Act nor as "depleted" under the MMPA. Including driftnet mortality only

for years after implementation of the Take Reduction Plan (1997-98), the average annual human-caused mortality in

1994-98 is zero. Because recent mortality is zero, Baird’s beaked whales are not classified as a "strategic" stock under

the MMPA, and the total fishery mortality and serious injury for this stock can be considered to be insignificant and

approaching zero.

REFERENCES

Balcomb, K. C., III. 1989. Baird's beaked whale Berardius bairdii Stejneger, 1883: Arnoux's beaked whale Berardius

arnuxii Duvernoy, 1851. In: Ridgway, S. H. and Harrison, R. (eds.), Handbook of Marine Mammals, Vol. 4.,

p. 261-288. Academic Press Limited.

Barlow, J. 1997. Preliminary estimates of cetacean abundance off California, Oregon and Washington based on a 1996

ship survey and comparisons of passing and closing modes. Administrative Report LJ-97-11, Southwest

Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA 92038. 25p.

Barlow, J. 1999. Trackline detection probability for long-diving whales. p. 209-224 In: G. W. Garner, S. C. Amstrup,

J. L. Laake, B. F. J. Manly, L. L. McDonald, and D. G. Robertson (eds.) Marine Mammal Survey and

Assessment Methods. A. A. Balkema, Rotterdam. 287 pp.

Barlow, J. and G. A. Cameron. 1999. Field experiments show that acoustic pingers reduce marine mammal bycatch in

the California drift gillnet fishery. Paper SC/51/SM2 presented to the International Whaling Commission, May

1998 (unpublished). 20pp.

Barlow, J. and T. Gerrodette. 1996. Abundance of cetaceans in California waters based on 1991 and 1993 ship

surveys. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-SWFSC-233. 

Cameron, G., and K. A. Forney. 1999. Estimates of cetacean mortality in the California gillnet fisheries for 1997 and

1998. Paper SC/51/O4 presented to the International Whaling Commission, 1999 (unpublished). 14 pp.

Holts, D. Southwest Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA 92038.

Holts, D. and O. Sosa-Nishizaki. 1998. Swordfish, Xiphias gladius, fisheries of the eastern North Pacific Ocean. In:

I. Barrett, O. Sosa-Nishizaki and N. Bartoo (eds.). Biology and fisheries of swordfish, Xiphias gladius. Papers

from the International Symposium on Pacific Swordfish, Ensenada Mexico, 11-14 December 1994. U.S. Dep.

Commer., NOAA Tech. Rep. NMFS 142, 276 p.

Julian, F. 1997. Cetacean mortality in California gill net fisheries: Preliminary estimates for 1996. Paper SC/49/SM02

presented to the International Whaling Commission, 1997 (unpublished). 13 pp.

Julian, F. and M. Beeson. 1998. Estimates of mammal, turtle and bird mortality for two California gillnet fisheries:

1990-1995. Fish. Bull. 96:271-284.

Rice, D. W. 1974. Whales and whale research in eastern North Pacific. p. 170-195 In: W. E. Schevill (ed.), The Whale

Problem - A Status Report. Harvard University Press, Cambridge, MA.

Richardson, W. J., C. R. Greene, Jr., C. I. Malme, and D. H. Thompson. 1995. Marine Mammals and Noise.

Academic Press, San Diego. 576 p.

Sosa-Nishizaki, O., R. De la Rosa-Pacheco, R. Castro-Longoria, M. Grijalva Chon, and J. De la Rosa Velez. 1993.

Estudio biologico pesquero del pez (Xiphias gladius) y otras especies de picudos (marlins y pez vela). Rep.

Int. CICESE, CTECT9306.

Wade, P. R. and R. P. Angliss. 1997. Guidelines for Assessing Marine Mammal Stocks: Report of the GAMMS

Workshop April 3-5, 1996, Seattle, Washington. U. S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-12.

93 pp.
134

Figure 1. Mesoplodon beaked whale sightings

based on aerial and shipboard surveys off

California, Oregon and Washington, 1991-96 (see

Appendix 2, Figures 1-5, for data sources and

information on timing and location of survey

effort). Key: ! = Mesoplodon densirostris, + =

Mesoplodon spp. Dashed line represents the U.S.

EEZ, thick line indicates the outer boundary of all

surveys combined.

Revised 12/15/2000 

MESOPLODONT BEAKED WHALES (Mesoplodon spp.):

 California/Oregon/Washington Stocks

STOCK DEFINITION AND GEOGRAPHIC RANGE

Mesoplodont beaked whales are distributed throughout

deep waters and along the continental slopes of the North Pacific

Ocean. At least 5 species in this genus have been recorded off the

U.S. west coast, but due to the rarity of records and the difficulty in

identifying these animals in the field, virtually no species-specific

information is available (Mead 1989). The five species known to

occur in this region are: Blainville's beaked whale (M. densirostris),

Hector's beaked whale, (M. hectori), Stejneger's beaked whale (M.

stejnegeri), Gingko-toothed beaked whale (M. gingkodens), and

Hubbs' beaked whale (M. carlhubbsi). Insufficient sighting records

exist off the U.S. west coast (Figure 1) to determine any possible

spatial or seasonal patterns in the distribution of mesoplodont

beaked whales.

Until methods of distinguishing these five species are

developed, the management unit must be defined to include all

Mesoplodon stocks in this region. However, in the future, specieslevel management is desirable, and a high priority should be placed

on finding means to obtain species-specific abundance information.

For the Marine Mammal Protection Act (MMPA) stock assessment

reports, three Mesoplodon stocks are defined: 1) all Mesoplodon

species off California, Oregon and Washington (this report), 2) M.

stejnegeri in Alaskan waters, and 3) M. densirostris in Hawaiian

waters.

POPULATION SIZE

Although mesoplodont beaked whales have been sighted

along the U.S. west coast on several line transect surveys utilizing

both aerial and shipboard platforms, sightings have generally been

too rare to produce reliable population estimates, and species

identification has been problematic. Previous abundance estimates

have been imprecise and biased downward by an unknown amount

because of the large proportion of time mesoplodont beaked whales

spend submerged, and because the surveys on which they were based covered only California waters, and thus could

not include animals off Oregon/Washington. Furthermore, there were a large number of unidentified beaked whale

sightings, which were either Mesoplodon sp. or Cuvier's beaked whales (Ziphius cavirostris). Recent analyses (Barlow

and Gerrodette 1996, Barlow and Sexton 1996, Barlow 1997) have resulted in improved estimates of abundance by 1)

combining data from three surveys conducted within 300 nmi of the coasts of California (in 1991 and 1993; Barlow and

Gerrodette 1996) and California, Oregon and Washington (in 1996; Barlow 1997), 2) whenever possible, assigning

unidentified beaked whale sightings to Mesoplodon spp. or Ziphius cavirostris based on written descriptions, size

estimates, and ‘most probable identifications’ made by the observers at the time of the sightings, and 3) estimating a

correction factor for animals missed because they are submerged, based on dive-interval data collected for mesoplodont

whales in 1993-95 (about 26% of all trackline groups are estimated to be seen). The first species-specific abundance

estimate is now available for Blainville’s beaked whale, which was identified once during the 1993 cruise. Because their

distribution varies and animals probably spend time outside the U.S. Exclusive Economic Zone, a multi-year average

abundance estimate is the most appropriate for management within U.S. waters. The 1991-96 weighted average

abundance estimates for California, Oregon and Washington waters based on the above analyses are 3,738 (CV=0.50)

mesoplodont beaked whales of unknown species plus 360 (CV=2.0) Blainville's beaked whales (Barlow 1997, with
135

corrected CV).

Minimum Population Estimate

Based on the combined abundance estimate of 4,098 (CV=0.50), the minimum population estimate (defined

as the log-normal 20th percentile of the abundance estimate) for mesoplodont beaked whales in California, Oregon, and

Washington is 2,734 animals. This includes a species-specific minimum abundance estimate of 123 Blainville’s beaked

whales. 

Current Population Trend

Due to the rarity of sightings of these species on surveys along the U.S. West coast, no information exists

regarding possible trends in abundance.

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

No information on current or maximum net productivity rates is available for mesoplodont beaked whales.

POTENTIAL BIOLOGICAL REMOVAL

The potential biological removal (PBR) level for this stock is calculated as the minimum population size (2,734)

times one half the default maximum net growth rate for cetaceans (1⁄2 of 4%) times a recovery factor of 0.50 (for a

species of unknown status with no known recent fishery mortality; Wade and Angliss 1997), resulting in a PBR of 27

mesoplodont beaked whales per year. This includes at least 1.1 Blainville’s beaked whales.

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Fishery Information

A summary of recent fishery mortality and injury for mesoplodont beaked whales in this region is shown in

Table 1. More detailed information on these fisheries is provided in Appendix 1). Mortality estimates for the California

drift gillnet fishery are included for the five most recent years of monitoring, 1994-98 (Julian and Beeson 1998; Julian

1997; Cameron and Forney 1999). A recently completed genetic analysis of tissue samples has allowed the reliable

identification of the majority of these animals (Henshaw et al. 1997). Based on past patterns of identification (NMFS,

unpublished data), the remaining unidentified beaked whale is likely to have been a Mesoplodon sp. After the 1997

implementation of a Take Reduction Plan, which included skipper education workshops and required the use of pingers

and minimum 6-fathom extenders, overall cetacean entanglement rates in the drift gillnet fishery dropped considerably

(Barlow and Cameron 1999). However, because of interannual variability in entanglement rates and the relative rarity

of mesoplodont beaked whale entanglements, additional years of data will be required to fully evaluate the effectiveness

of pingers for reducing mortality of this group of species. Because of the changes in this fishery after implementation

of the Take Reduction Plan, mean annual takes in Table 1 are based only on 1997-98 data. This results in an average

estimated annual mortality of zero mesoplodont beaked whales.

Drift gillnet fisheries for swordfish and sharks exist along the entire Pacific coast of Baja California, and may

take animals from the same populations. Quantitative data are available only for the Mexican swordfish drift gillnet

fishery, which uses vessels, gear, and operational procedures similar to those in the U.S. drift gillnet fishery, although

nets may be up to 4.5 km long (Holts and Sosa-Nishizaki 1998). The fleet increased from two vessels in 1986 to 31

vessels in 1993 (Holts and Sosa-Nishizaki 1998). The total number of sets in this fishery in 1992 can be estimated from

data provided by these authors to be approximately 2700, with an observed rate of marine mammal bycatch of 0.13

animals per set (10 marine mammals in 77 observed sets; Sosa-Nishizaki et al. 1993). This overall mortality rate is

similar to that observed in California driftnet fisheries during 1990-95 (0.14 marine mammals per set; Julian and Beeson,

1998), but species-specific information is not available for the Mexican fisheries. There are currently efforts underway

to convert the Mexican swordfish driftnet fishery to a longline fishery (D. Holts, pers. comm.). 

STATUS OF STOCKS

The status of mesoplodont beaked whales in California, Oregon and Washington waters relative to OSP is not

known, and there are insufficient data to evaluate trends in abundance. No habitat issues are known to be of concern

for this species, but in recent years questions have been raised regarding potential effects of human-made sounds on
136

Table 1. Summary of available information on the incidental mortality and injury of Mesoplodon beaked whales

(California/Oregon/Washington Stocks) in commercial fisheries that might take these species. All observed

entanglements of Mesoplodon beaked whales resulted in the death of the animal. Coefficients of variation for mortality

estimates are provided in parentheses. Mean annual takes are based on 1994-98 data unless noted otherwise.

Fishery Name 

Data Type Year(s)

Percent

Observer

Coverage

Observed

Mortality

Estimated Annual

Mortality 

Mean

Annual Takes

(CV in parentheses)

CA/OR thresher

shark/swordfish drift

gillnet fishery

Hubbs’ beaked whale, Mesoplodon carlhubbsi

observer

data 

1994

1995

1996

1997

1998

17.9% 

15.6% 

12.4% 

23.0% 

20.0% 

2

0

0

0

0

11 (0.64)

0

0

0

0

0

1

Stejneger’s beaked whale, Mesoplodon stejnegeri

observer

data 

1994

1995

1996

1997

1998

17.9% 

15.6% 

12.4% 

23.0% 

20.0% 

1

0

0

0

0

6 (0.91)

0

0

0

0

0

1

Unidentified beaked whale (probably Mesoplodon)

observer

data 

1994

1995

1996

1997

1998

17.9% 

15.6% 

12.4% 

23.0% 

20.0% 

1

0

0

0

0

 6 (0.90)

0

0

0

0

0

1

Minimum total annual takes of Mesoplodon beaked whales 0

1

 Only 1997-98 mortality estimates are included in the average because of gear modifications implemented within the fishery as part of a 1997

Take Reduction Plan. Gear modifications included the use of net extenders and acoustic warning devices (pingers).

deep-diving cetacean species, such as mesoplodont beaked whales (Richardson et al. 1995). In particular, Low

Frequency Active Sonar (LFAS) has been implicated in the mass stranding of beaked whales in the Mediterranean Sea

(Frantzis 1998) and more recently in the Caribbean. None of the five species is listed as "threatened" or "endangered"

under the Endangered Species Act nor considered "depleted" under the MMPA. Including driftnet mortality only for

years after implementation of the Take Reduction Plan (1997-98), the average annual human-caused mortality in 1994-

98 is zero. Because recent mortality is zero, mesoplodont beaked whales are not classified as a "strategic" stock under

the MMPA, and the total fishery mortality and serious injury for this stock can be considered to be insignificant and

approaching zero. It is likely that the difficulty in identifying these animals in the field will remain a critical obstacle

to obtaining species-specific abundance estimates and stock assessments in the future. 

REFERENCES

Barlow, J. 1997. Preliminary estimates of cetacean abundance off California, Oregon, and Washington based on a

1996 ship survey and comparisons of passing and closing modes. Southwest Fisheries Science Center

Administrative Report. LJ-97-11. 25pp.

Barlow, J. 1997. Preliminary estimates of cetacean abundance off California, Oregon and Washington based on a 1996

ship survey and comparisons of passing and closing modes. Administrative Report LJ-97-11, Southwest

Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA 92038. 25p.

Barlow, J. and G. A. Cameron. 1999. Field experiments show that acoustic pingers reduce marine mammal bycatch in

the California drift gillnet fishery. Paper SC/51/SM2 presented to the International Whaling Commission, May

1998 (unpublished). 20pp.

Barlow, J. and T. Gerrodette. 1996. Abundance of cetaceans in California waters based on 1991 and 1993 ship

surveys. NOAA Technical Memorandum NMFS, NOAA-TM-NMFS-SWFSC-233. 
137

Barlow, J. and S. Sexton. 1996. The effect of diving and searching behavior on the probability of detecting track-line

groups, g0, of long-diving whales during line transect surveys. Administrative Report LJ-96-14. Available

from NMFS, Southwest Fisheries Science Center, P.O. Box 271, La Jolla, California, 92038, USA. 21 p.

Cameron, G., and K. A. Forney. 1999. Estimates of cetacean mortality in the California gillnet fisheries for 1997 and

1998. Paper SC/51/O4 presented to the International Whaling Commission, 1999 (unpublished). 14pp.

Frantzis, A. 1998. Does acoustic testing strand whales? Nature 392(5):29.

Henshaw, M. D., R. G. LeDuc, S. J. Chivers, and A. E. Dizon. 1997. Identifying beaked whales (family Ziphiidae)

using mtDNA sequences. Marine Mammal Science 13:487-495.

Holts, D. Southwest Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA 92038.

Holts, D. and O. Sosa-Nishizaki. 1998. Swordfish, Xiphias gladius, fisheries of the eastern North Pacific Ocean. In:

I. Barrett, O. Sosa-Nishizaki and N. Bartoo (eds.). Biology and fisheries of swordfish, Xiphias gladius. Papers

from the International Symposium on Pacific Swordfish, Ensenada Mexico, 11-14 December 1994. U.S. Dep.

Commer., NOAA Tech. Rep. NMFS 142, 276 p.

Julian, F. 1997. Cetacean mortality in California gill net fisheries: preliminary estimates for 1996. Int. Whal. Commn.

Working Paper SC/49/SM2. 13pp.

Julian, F. and M. Beeson. 1998. Estimates of mammal, turtle and bird mortality for two California gillnet fisheries:

1990-1995. Fishery Bulletin 96:271-284.

Mead, J. G. 1989. Beaked whales of the genus Mesoplodon. In: Ridgway, S. H. and Harrison, R. (eds.), Handbook

of Marine Mammals, Vol. 4., p. 349-430. Academic Press Limited.

National Marine Fisheries Service, Southwest Fisheries Science Center. Unpublished data.

Richardson, W. J., C. R. Greene, Jr., C. I. Malme, and D. H. Thompson. 1995. Marine Mammals and Noise.

Academic Press, San Diego. 576 p.

Sosa-Nishizaki, O., R. De la Rosa-Pacheco, R. Castro-Longoria, M. Grijalva Chon, and J. De la Rosa Velez. 1993.

Estudio biologico pesquero del pez (Xiphias gladius) y otras especies de picudos (marlins y pez vela). Rep.

Int. CICESE, CTECT9306.

Wade, P. R. and R. P. Angliss. 1997. Guidelines for Assessing Marine Mammal Stocks: Report of the GAMMS

Workshop April 3-5, 1996, Seattle, Washington. U. S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-12.

93 pp.
138

Figure 1. Cuvier’s beaked whale sightings based

on aerial and shipboard surveys off California,

Oregon and Washington, 1991-96 (see Appendix 2,

Figures 1-5, for data sources and information on

timing and location of survey effort). Dashed line

represents the U.S. EEZ, thick line indicates the

outer boundary of all surveys combined.

Revised 12/15/2000 

CUVIER'S BEAKED WHALE (Ziphius cavirostris):

California/Oregon/Washington Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

Cuvier's beaked whales are distributed widely throughout

deep waters of all oceans (Heyning 1989). Off the U.S. west coast,

this species is the most commonly encountered beaked whale

(Figure 1). No seasonal changes in distribution are apparent from

stranding records, and morphological evidence is consistent with the

existence of a single eastern North Pacific population from Alaska

to Baja California, Mexico (Mitchell 1968). However, there are

currently no international agreements for cooperative management

of this species. For the Marine Mammal Protection Act (MMPA)

stock assessment reports, Cuvier's beaked whales within the Pacific

U.S. Exclusive Economic Zone are divided into three discrete, noncontiguous areas: 1) waters off California, Oregon and Washington

(this report), 2) Alaskan waters, and 3) Hawaiian waters.

POPULATION SIZE

Although Cuvier's beaked whales have been sighted along

the U.S. west coast on several line transect surveys utilizing both

aerial and shipboard platforms, sightings have generally been too

rare to produce reliable population estimates. Previous abundance

estimates have been imprecise and biased downward by an unknown

amount because of the large proportion of time this species spends

submerged, and because the ship surveys on which they were based

covered only California waters, and thus could not observe animals

off Oregon/Washington. Furthermore, there were a large number of

unidentified beaked whale sightings, which were probably either

Mesoplodon sp. or Cuvier's beaked whales (Ziphius cavirostris).

Recent analyses (Barlow and Gerrodette 1996, Barlow and Sexton

1996) have resulted in improved estimates of abundance by 1)

combining data from three surveys conducted within 300 nmi of the

coasts of California (in 1991 and 1993; Barlow and Gerrodette 1996) and California, Oregon and Washington (in 1996;

Barlow 1997), 2) whenever possible, assigning unidentified beaked whale sightings to Mesoplodon spp. or Ziphius

cavirostris based on written descriptions, size estimates, and ‘most probable identifications’ made by the observers at

the time of the sightings, and 3) estimating a correction factor for animals missed because they are submerged, based

on dive-interval data collected for Cuvier’s beaked whales in 1993-95 (an estimated 13% of all groups are estimated

to be seen). Because animals probably spend time outside the U.S. Exclusive Economic Zone, a multi-year average

abundance estimate is the most appropriate for management within U.S. waters. The 1991-96 weighted average

abundance estimate for California, Oregon and Washington waters based on the above analyses is 5,870 (CV=0.38)

Cuvier’s beaked whales (Barlow 1997, with corrected CV).

Minimum Population Estimate

Based on the above abundance estimate and CV, the minimum population estimate (defined as the log-normal

20th percentile of the abundance estimate) for Cuvier's beaked whales in California, Oregon, and Washington is 4,309

animals.

Current Population Trend

Due to the rarity of sightings of this species on surveys along the U.S. West coast, no information exists

regarding trends in abundance of this population. 
139

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

No information on current or maximum net productivity rates is available for this species.

POTENTIAL BIOLOGICAL REMOVAL

The potential biological removal (PBR) level for this stock is calculated as the minimum population size (4,309)

times one half the default maximum net growth rate for cetaceans (1⁄2 of 4%) times a recovery factor of 0.50 (for a

species of unknown status with no known recent fishery mortality; Wade and Angliss 1997), resulting in a PBR of 43

Cuvier’s beaked whales per year. 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Fishery Information

A summary of recent fishery mortality and injury for Cuvier’s beaked whales in this region is shown in Table

1. More detailed information on these fisheries is provided in Appendix 1. Mortality estimates for the California drift

gillnet fishery are included for the five most recent years of monitoring, 1994-98 (Julian and Beeson 1998; Julian 1997;

Cameron and Forney 1999). After the 1997 implementation of a Take Reduction Plan, which included skipper education

workshops and required the use of pingers and minimum 6-fathom extenders, overall cetacean entanglement rates in

the drift gillnet fishery dropped considerably (Barlow and Cameron 1999). However, because of interannual variability

in entanglement rates and the relative rarity of Cuvier’s beaked whale entanglements, additional years of data will be

required to fully evaluate the effectiveness of pingers for reducing mortality of this particular species. Because of the

changes in this fishery after implementation of the Take Reduction Plan, mean annual takes in Table 1 are based only

on 1997-98 data. This results in an average estimated annual mortality of zero Cuvier’s beaked whales.

Table 1. Summary of available information on the incidental mortality and injury of Cuvier's beaked whales (California/

Oregon/Washington Stock) in commercial fisheries that might take this species. One Cuvier’s beaked whale was

released alive in the driftnet fishery in 1995; all other entanglements resulted in the death of the animal. Coefficients

of variation for mortality estimates are provided in parentheses. Annual mortality estimates for 1995 are shown both

including and excluding the animal released alive. Mean annual takes are based on 1994-98 data unless noted otherwise.

Fishery Name Data Type Year(s)

Percent

Observer

Coverage

Observed

Mortality +

ReleasedAlive

Estimated Annual

Mortality / Mortality +

Entanglements

Mean

Annual Takes

(CV in

parentheses)

CA/OR thresher

shark/swordfish drift

gillnet fishery

observer

data

1994

1995

1996

1997

1998

17.9% 

15.6% 

12.4% 

23.0% 

20.0% 

6

5+1

0

0

0

34 (0.36)

32 (0.40) / 39 (0.36)

0

0

0

0

1

Minimum total annual takes 0

1

 Only 1997-98 mortality estimates are included in the average because of gear modifications implemented within the fishery as part of a 1997 Take

Reduction Plan. Gear modifications included the use of net extenders and acoustic warning devices (pingers).

Drift gillnet fisheries for swordfish and sharks exist along the entire Pacific coast of Baja California, Mexico

and may take animals from the same population. Quantitative data are available only for the Mexican swordfish drift

gillnet fishery, which uses vessels, gear, and operational procedures similar to those in the U.S. drift gillnet fishery,

although nets may be up to 4.5 km long (Holts and Sosa-Nishizaki 1998). The fleet increased from two vessels in 1986

to 31 vessels in 1993 (Holts and Sosa-Nishizaki 1998). The total number of sets in this fishery in 1992 can be estimated

from data provided by these authors to be approximately 2700, with an observed rate of marine mammal bycatch of 0.13

animals per set (10 marine mammals in 77 observed sets; Sosa-Nishizaki et al. 1993). This overall mortality rate is

similar to that observed in California driftnet fisheries during 1990-95 (0.14 marine mammals per set; Julian and Beeson,

1998), but species-specific information is not available for the Mexican fisheries. There are currently efforts underway

to convert the Mexican swordfish driftnet fishery to a longline fishery (D. Holts, pers. comm.). 

STATUS OF STOCK
140

The status of Cuvier's beaked whales in California, Oregon and Washington waters relative to OSP is not

known, and there are insufficient data to evaluate trends in abundance. No habitat issues are known to be of concern

for this species, but in recent years questions have been raised regarding potential effects of human-made sounds on

deep-diving cetacean species, such as Cuvier’s beaked whales (Richardson et al. 1995). In particular, Low Frequency

Active Sonar (LFAS) has been implicated in the mass stranding of beaked whales in the Mediterranean Sea (Frantzis

1998) and more recently in the Caribbean. They are not listed as "threatened" or "endangered" under the Endangered

Species Act nor as "depleted" under the MMPA. Including driftnet mortality only for years after implementation of the

Take Reduction Plan (1997-98), the average annual human-caused mortality in 1994-98 is zero. Because recent

mortality is zero, Cuvier’s beaked whales are not classified as a "strategic" stock under the MMPA, and the total fishery

mortality and serious injury for this stock can be considered to be insignificant and approaching zero.

REFERENCES

Barlow, J. 1997. Preliminary estimates of cetacean abundance off California, Oregon and Washington based on a 1996

ship survey and comparisons of passing and closing modes. Administrative Report LJ-97-11, Southwest

Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA 92038. 25p.

Barlow, J. and G. A. Cameron. 1999. Field experiments show that acoustic pingers reduce marine mammal bycatch in

the California drift gillnet fishery. Paper SC/51/SM2 presented to the International Whaling Commission, May

1998 (unpublished). 20pp.

Barlow, J. and T. Gerrodette. 1996. Abundance of cetaceans in California waters based on 1991 and 1993 ship

surveys. NOAA Technical Memorandum NMFS, NOAA-TM-NMFS-SWFSC-233. 

Barlow, J. and S. Sexton. 1996. The effect of diving and searching behavior on the probability of detecting track-line

groups, g0, of long-diving whales during line transect surveys. Administrative Report LJ-96-14. Available

from NMFS, Southwest Fisheries Science Center, P.O. Box 271, La Jolla, California, 92038, USA. 21 p.

Cameron, G., and K. A. Forney. 1999. Estimates of cetacean mortality in the California gillnet fisheries for 1997 and

1998. Paper SC/51/O4 presented to the International Whaling Commission, 1999 (unpublished). 14pp.

Frantzis, A. 1998. Does acoustic testing strand whales? Nature 392(5):29.

Heyning, J. E. 1989. Cuvier’s beaked whale Ziphius cavirostris G. Cuvier, 1823. pp. 289-308 In: Ridgway, S. H. and

R. Harrison (eds.), Handbook of Marine Mammals, Vol. 4. Academic Press.

Holts, D. Southwest Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA 92038.

Holts, D. and O. Sosa-Nishizaki. 1998. Swordfish, Xiphias gladius, fisheries of the eastern North Pacific Ocean. In:

I. Barrett, O. Sosa-Nishizaki and N. Bartoo (eds.). Biology and fisheries of swordfish, Xiphias gladius. Papers

from the International Symposium on Pacific Swordfish, Ensenada Mexico, 11-14 December 1994. U.S. Dep.

Commer., NOAA Tech. Rep. NMFS 142, 276 p.

Julian, F. 1997. Cetacean mortality in California gill net fisheries: Preliminary estimates for 1996. Paper SC/49/SM02

presented to the International Whaling Commission, 1997 (unpublished). 13 pp.

Julian, F. and M. Beeson. 1998. Estimates of mammal, turtle and bird mortality for two California gillnet fisheries:

1990-1995. Fish. Bull. 96:271-284.

Mitchell, E. 1968. Northeast Pacific stranding distribution and seasonality of Cuvier's beaked whale, Ziphius

cavirostris. Can. J. Zool. 46:265-279.

Richardson, W. J., C. R. Greene, Jr., C. I. Malme, and D. H. Thompson. 1995. Marine Mammals and Noise.

Academic Press, San Diego. 576 p.

Sosa-Nishizaki, O., R. De la Rosa-Pacheco, R. Castro-Longoria, M. Grijalva Chon, and J. De la Rosa Velez. 1993.

Estudio biologico pesquero del pez (Xiphias gladius) y otras especies de picudos (marlins y pez vela). Rep.

Int. CICESE, CTECT9306.

Wade, P. R. and R. P. Angliss. 1997. Guidelines for Assessing Marine Mammal Stocks: Report of the GAMMS

Workshop April 3-5, 1996, Seattle, Washington. U. S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-12.

93 pp.
141

Figure 1. Kogia sightings based on aerial and

shipboard surveys off California, Oregon and

Washington, 1991-96 (see Appendix 2, Figures 1-5, for

data sources and information on timing and location of

survey effort). Key: ! = Kogia breviceps, + = Kogia

spp. Dashed line represents the U.S. EEZ, thick line

indicates the outer boundary of all surveys combined.

Revised 12/15/2000 

PYGMY SPERM WHALE (Kogia breviceps):

California/Oregon/Washington Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

Pygmy sperm whales are distributed throughout deep

waters and along the continental slopes of the North Pacific

and other ocean basins (Ross 1984; Caldwell and Caldwell

1989). Along the U.S. west coast, sightings of this species and

of animals identified only as Kogia sp. have been very rare

(Figure 1). However, this is probably a reflection of their

pelagic distribution, small body size and cryptic behavior,

rather than an indication of true rareness. Strandings of pygmy

sperm whales in this region are known from California, Oregon

and Washington (Roest 1970; Caldwell and Caldwell 1989;

NMFS, Northwest Region, unpublished data; NMFS,

Southwest Region, unpublished data). Available data are

insufficient to identify any seasonality in the distribution of

pygmy sperm whales, or to delineate possible stock boundaries.

For the Marine Mammal Protection Act (MMPA) stock

assessment reports, pygmy sperm whales within the Pacific

U.S. Exclusive Economic Zone are divided into two discrete,

non-contiguous areas: 1) waters off California, Oregon and

Washington (this report), and 2) Hawaiian waters. 

POPULATION SIZE

Although pygmy sperm whales have been sighted

along the U.S. west coast on several line transect surveys

utilizing both aerial and shipboard platforms, sightings have

generally been too rare to produce reliable population

estimates. Previous abundance estimates have been imprecise

and biased downward by an unknown amount because pygmy

sperm whales spend a large proportion of time submerged and

are very difficult to detect at the surface unless seas are calm.

Furthermore, the ship survey covered only California waters,

and thus could not observe animals off Oregon/Washington.

Recent analyses (Barlow and Gerrodette 1996, Barlow and

Sexton 1996) have resulted in improved estimates of abundance by 1) combining data from three surveys conducted

within 300 nmi of the coasts of California (in 1991 and 1993; Barlow and Gerrodette 1996) and California, Oregon and

Washington (in 1996; Barlow 1997), and 2) estimating a correction factor for animals missed because they are

submerged, based on dive-interval data collected for Kogia simus in 1993-95 (about 19% of all groups are estimated

to be seen). Because animals probably spend time outside the U.S. Exclusive Economic Zone, a multi-year average

abundance estimate is the most appropriate for management within U.S. waters. The 1991-96 weighted average

abundance estimate for California, Oregon and Washington waters based on the above analyses is 2,933 (CV=0.54)

pygmy sperm whales plus an estimated 1,813 (CV=1.53) pygmy or dwarf sperm whales, based on sightings that could

only be identified to the genusKogia (Barlow 1997, with corrected CV). Because there have been no reported sightings,

strandings, or entanglements of dwarf sperm whales along the U.S. West coast since the early 1970s, it is almost certain

that these additional Kogia were pygmy sperm whales, bringing the total abundance estimate to 4,746 (CV=0.67).

Minimum Population Estimate

Based on the above abundance estimate and CV, the minimum population estimate (defined as the log-normal

20th percentile of the total Kogia abundance estimate) for pygmy sperm whales in California, Oregon, and Washington
142

is 2,837 animals.

Current Population Trend

Due to the rarity of sightings of this species on surveys along the U.S. West coast, no information exists

regarding trends in abundance of this population. 

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

No information on current or maximum net productivity rates is available for this species.

POTENTIAL BIOLOGICAL REMOVAL

The potential biological removal (PBR) level for this stock is calculated as the minimum population size (2,837)

times one half the default maximum net growth rate for cetaceans (1⁄2 of 4%) times a recovery factor of 0.50 (for a

species of unknown status with no known recent fishery mortality; Wade and Angliss 1997), resulting in a PBR of 28

pygmy sperm whales per year.

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Fishery Information

A summary of recent fishery mortality and injury for pygmy sperm whales and unidentified Kogia, which may

have been pygmy sperm whales, is shown in Table 1. More detailed information on the drift gillnet fishery is provided

in Appendix 1. In the California drift gillnet fishery, no mortality of pygmy sperm whales or unidentified Kogia was

observed during the most recent five years of monitoring, 1994-98 (Julian 1997; Julian and Beeson 1998; Cameron and

Forney 1999). After the 1997 implementation of a Take Reduction Plan, which included skipper education workshops

and required the use of pingers and minimum 6-fathom extenders, overall cetacean entanglement rates in the drift gillnet

fishery dropped considerably (Barlow and Cameron 1999). However, because of interannual variability in entanglement

rates and the rarity of Kogia entanglements, additional years of data will be required to fully evaluate the effectiveness

of pingers for reducing mortality of pygmy sperm whales. Because of the changes in this fishery after implementation

of the Take Reduction Plan, mean annual takes in Table 1 are based only on 1997-98 data. This results in an average

estimated annual mortality of zero pygmy sperm whales.

 Drift gillnet fisheries for swordfish and sharks exist along the entire Pacific coast of Baja California, Mexico

and may take animals from the same population. Quantitative data are available only for the Mexican swordfish drift

gillnet fishery, which uses vessels, gear, and operational procedures similar to those in the U.S. drift gillnet fishery,

although nets may be up to 4.5 km long (Holts and Sosa-Nishizaki 1998). The fleet increased from two vessels in 1986

to 31 vessels in 1993 (Holts and Sosa-Nishizaki 1998). The total number of sets in this fishery in 1992 can be estimated

from data provided by these authors to be approximately 2700, with an observed rate of marine mammal bycatch of 0.13

animals per set (10 marine mammals in 77 observed sets; Sosa-Nishizaki et al. 1993). This overall mortality rate is

similar to that observed in California driftnet fisheries during 1990-95 (0.14 marine mammals per set; Julian and Beeson,

1998), but species-specific information is not available for the Mexican fisheries. There are currently efforts underway

to convert the Mexican swordfish driftnet fishery to a longline fishery (D. Holts, pers. comm.). 

STATUS OF STOCK

The status of pygmy sperm whales in California, Oregon and Washington waters relative to OSP is not known,

and there are insufficient data to evaluate potential trends in abundance. No habitat issues are known to be of concern

for this species, but in recent years questions have been raised regarding potential effects of human-made

sounds on deep-diving cetacean species, such as pygmy sperm whales (Richardson et al. 1995). They are not listed as

"threatened" or "endangered" under the Endangered Species Act nor as "depleted" under the MMPA. Including driftnet

mortality only for years after implementation of the Take Reduction Plan (1997-98), the average annual human-caused

mortality in 1994-98 is zero. Because recent mortality is zero, pygmy sperm whales are not classified as a "strategic"

stock under the MMPA, and the total fishery mortality and serious injury for this stock can be considered to be

insignificant and approaching zero.

 Table 1. Summary of available information on the incidental mortality and injury of pygmy sperm whales and

unidentified Kogia sp. (California/Oregon/Washington Stock) in commercial fisheries that might take this species.
143

Coefficients of variation for mortality estimates are provided in parentheses. Mean annual takes are based on 1994-98

data unless noted otherwise.

Fishery Name Data Type Year(s)

Percent

 Observer

Coverage

Observed

Mortality

K. breviceps

/Kogia sp.

Estimated Annual

Mortality of K.

breviceps/Kogia sp.

Mean

Annual Takes

(CV in

parentheses)

CA/OR thresher

shark/swordfish drift

gillnet fishery

observer

data 

1994

1995

1996

1997

1998

17.9% 

15.6% 

12.4% 

23.0% 

20.0% 

0 / 0

0 / 0

0 / 0

0 / 0

0 / 0

0 / 0

0 / 0

0 / 0

0 / 0

0 / 0

0

1

Minimum total annual takes 0

1

 Only 1997-98 mortality estimates are included in the average because of gear modifications implemented within the fishery as part of a 1997 Take

Reduction Plan. Gear modifications included the use of net extenders and acoustic warning devices (pingers).

REFERENCES

Barlow, J. 1997. Preliminary estimates of cetacean abundance off California, Oregon and Washington based on a 1996

ship survey and comparisons of passing and closing modes. Administrative Report LJ-97-11, Southwest

Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA 92038. 25p.

Barlow, J. and G. A. Cameron. 1999. Field experiments show that acoustic pingers reduce marine mammal bycatch in

the California drift gillnet fishery. Paper SC/51/SM2 presented to the International Whaling Commission, May

1998 (unpublished). 20pp.

Barlow, J. and T. Gerrodette. 1996. Abundance of cetaceans in California waters based on 1991 and 1993 ship

surveys. NOAA Technical Memorandum NMFS, NOAA-TM-NMFS-SWFSC-233. 

Barlow, J. and S. Sexton. 1996. The effect of diving and searching behavior on the probability of detecting track-line

groups, g0, of long-diving whales during line transect surveys. Administrative Report LJ-96-14. Available

from NMFS, Southwest Fisheries Science Center, P.O. Box 271, La Jolla, California, 92038, USA. 21 p.

Caldwell, D. K. and M. C. Caldwell. 1989. Pygmy sperm whale Kogia breviceps (de Blainville, 1838): Dwarf sperm

whale Kogia simus Owen, 1866. pp. 235-260 In: Ridgway, S. H. and R. Harrison (eds.), Handbook of Marine

Mammals, Vol. 4. Academic Press.

Cameron, G., and K. A. Forney. 1999. Estimates of cetacean mortality in the California gillnet fisheries for 1997 and

1998. Paper SC/51/O4 presented to the International Whaling Commission, 1999 (unpublished). 14 pp.

Holts, D. Southwest Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA 92038.

Holts, D. and O. Sosa-Nishizaki. 1998. Swordfish, Xiphias gladius, fisheries of the eastern North Pacific Ocean. In:

I. Barrett, O. Sosa-Nishizaki and N. Bartoo (eds.). Biology and fisheries of swordfish, Xiphias gladius. Papers

from the International Symposium on Pacific Swordfish, Ensenada Mexico, 11-14 December 1994. U.S. Dep.

Commer., NOAA Tech. Rep. NMFS 142, 276 p.

Julian, F. 1997. Cetacean mortality in California gill net fisheries: Preliminary estimates for 1996. Paper SC/49/SM02

presented to the International Whaling Commission, 1997 (unpublished). 13 pp.

Julian, F. and M. Beeson. 1998. Estimates of mammal, turtle and bird mortality for two California gillnet fisheries:

1990-1995. Fish. Bull. 96:271-284.

NMFS, Southwest Region, 501 West Ocean Blvd, Long Beach, CA 90802-4213.

Oregon Department of Fish and Game, Unpublished data.

Richardson, W. J., C. R. Greene, Jr., C. I. Malme, and D. H. Thompson. 1995. Marine Mammals and Noise.

Academic Press, San Diego. 576 p.

Roest, A. I. 1970. Kogia simus and other cetaceans from San Luis Obispo County, California. J. Mammal. 51:410-

417.

Ross, G. J. B. 1984. The smaller cetaceans of the south east coast of southern Africa. Ann. Cape Prov. Mus. Nat. Hist.

15:173-410.

Sosa-Nishizaki, O., R. De la Rosa-Pacheco, R. Castro-Longoria, M. Grijalva Chon, and J. De la Rosa Velez. 1993.

Estudio biologico pesquero del pez (Xiphias gladius) y otras especies de picudos (marlins y pez vela). Rep.

Int. CICESE, CTECT9306.
144

Figure 1. Sperm whale sighting locations based on

aerial and shipboard surveys off California, Oregon,

and Washington, 1989-96. Dashed line represents the

U.S. EEZ, thick line indicates the outer boundary of all

surveys combined. Greater effort was conducted off

California (south of 42°N) and in the inshore half of the

U.S. EEZ. See Appendix 2 for data sources and

information on timing and location of survey effort. 

Revised 12/31/2001

SPERM WHALE (Physeter macrocephalus): 

California/Oregon/Washington Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

Sperm whales are widely distributed across the

entire North Pacific and into the southern Bering Sea in

summer but the majority are thought to be south of 40oN in

winter (Rice 1974; Gosho et al. 1984; Miyashita et al. 1995).

For management, the International Whaling Commission

(IWC) had divided the North Pacific into two management

regions (Donovan 1991) defined by a zig-zag line which

starts at 150oW at the equator, is 160oW between 40-50oN,

and ends up at 180oW north of 50oN; however, the IWC has

not reviewed this stock boundary in many years (Donovan

1991). Sperm whales are found year-round in California

waters (Dohl et al. 1983; Barlow 1995; Forney et al. 1995),

but they reach peak abundance from April through mid-June

and from the end of August through mid-November (Rice

1974). They were seen in every season except winter (Dec.-

Feb.) in Washington and Oregon (Green et al. 1992). Of

176 sperm whales that were marked with Discovery tags off

southern California in winter 1962-70, only three were

recovered by whalers: one off northern California in June,

one off Washington in June, and another far off British

Columbia in April (Rice 1974). Recent summer/fall surveys

in the eastern tropical Pacific (Wade and Gerrodette 1993)

show that although sperm whales are widely distributed in

the tropics, their relative abundance tapers off markedly

westward towards the middle of the tropical Pacific (near the

IWC stock boundary at 150oW) and tapers off northward

towards the tip of Baja California. The structure of sperm

whale populations in the eastern tropical Pacific is not

known, but the only photographic matches of known

individuals from this area have been between the Galapagos

Islands and coastal waters of South America (Dufault and

Whitehead 1995), suggesting that the eastern tropical

animals constitute a distinct stock. A recent survey

designed specifically to investigate stock structure and

abundance of sperm whales in the northeastern temperate Pacific revealed no apparent hiatus in distribution between

the U.S. EEZ off California and areas farther west, out to Hawaii (Barlow and Taylor 1998). Recent analyses of genetic

relationships of animals in the eastern Pacific found that mtDNA and microsatellite DNA of animals sampled in the

California Current is significantly different from animals sampled further offshore and that genetic differences appeared

larger in an east-west direction than in a north-south direction (Mesnick et al. 1999).

For the Marine Mammal Protection Act (MMPA) stock assessment reports, sperm whales within the Pacific

U.S. EEZ are divided into three discrete, non-contiguous areas: 1) California, Oregon and Washington waters (this

report), 2) waters around Hawaii, and 3) Alaska waters. 

POPULATION SIZE

Barlow and Taylor (2001) estimate 1,407 (CV=0.39) sperm whales along the coasts of California, Oregon,

and Washington during summer/fall based on ship line transect surveys in 1993 and 1996. This most recent estimate
145

has been corrected for the systematic underestimation of sperm whale group size when groups are observed for only

a short period of time. Forney et al. (1995) estimate 892 (CV=0.99) sperm whales off California during winter/spring

based on aerial line-transect surveys in 1991-92, but this estimate does not correct for diving whales that were missed

and is now more than 8 years out of date. Green et al. (1992) report that sperm whales were the third most abundant

large whale (after gray and humpback whales) in aerial surveys off Oregon and Washington, but they did not estimate

population size for that area. A large 1982 abundance estimate for the entire eastern North Pacific (Gosho et al. 1984)

was based on a CPUE method which is no longer accepted as valid by the International Whaling Commission. Recently,

a combined visual and acoustic line-transect survey conducted in the eastern temperate North Pacific in spring 1997

resulted in estimates of 24,000 (CV=0.46) sperm whales based on visual sightings, and 39,200 (CV=0.60) based

acoustic detections and visual group size estimates (Barlow and Taylor 1998). However, it is not known whether any

or all of these animals routinely enter the U.S. EEZ. In the eastern tropical Pacific, the abundance of sperm whales has

been estimated as 22,700 (95% C.I.=14,800-34,600; Wade and Gerrodette 1993), but this area does not include areas

where sperm whales are taken by drift gillnet fisheries in the U.S. EEZ and there is no evidence of sperm whale

movements from the eastern tropical Pacific to the U.S. EEZ. Barlow and Taylor (2001) also estimate 1,640 (CV=0.33)

sperm whales off the west coast of Baja California, but again there is no evidence for interchange between these animals

and those off California, Oregon and Washington. 

Clearly, large populations of sperm whales exist in waters that are within several thousand miles west and south

of the California, Oregon, and Washington region that is covered by this report; however, there is no evidence of sperm

whale movements into this region from either the west or south and genetic data suggest that mixing to the west is

extremely unlikely. There is limited evidence of sperm whale movement from California to northern areas off British

Columbia, but there are no abundance estimates for this area. The most precise estimate of sperm whale abundance

for this stock is therefore from the ship survey estimate of Barlow and Taylor (2001).

Minimum Population Estimate

The minimum population estimate for sperm whales is taken as the lower 20th percentile of the log-normal

distribution of abundance estimated from the summer/fall ship surveys off California, Oregon and Washington (Barlow

and Taylor, 2001) or approximately 1,026. More sophisticated methods of estimating minimum population size would

be available if a correction factor (and associated variance) were available to correct the aerial survey estimates for

missed animals. 

Current Population Trend

Sperm whale abundance appears to have been rather variable off California between 1979/80 and 1996 (Barlow

1994; Barlow 1997) but does not show any obvious trends. Although the population in the eastern North Pacific is

expected to have grown since large-scale pelagic whaling stopped in 1980, the possible effects of large unreported

catches are unknown (Yablokov 1994) and the ongoing incidental ship strikes and gillnet mortality make this uncertain.

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

There are no published estimates of the growth rate for any sperm whale population (Best 1993).

POTENTIAL BIOLOGICAL REMOVAL

The potential biological removal (PBR) level for the California portion of this stock is calculated as the

minimum population size (1,026) times one half the default maximum net growth rate for cetaceans (1⁄2 of 4%) times

a recovery factor of 0.1 (the default value for an endangered species), resulting in a PBR of 2.1. 

HUMAN-CAUSED MORTALITY

Historic Whaling

Between 1800 and 1909, about 60,842 sperm whales were estimated taken in the North Pacific (Best 1976).

The reported take of North Pacific sperm whales by commercial whalers between 1947 and 1987 totaled 258,000 (C.

Allison, pers. comm.). Ohsumi (1980) lists an additional 28,198 sperm whales taken mainly in coastal whaling
146

operations from 1910 to 1946. Based on the massive under-reporting of Soviet catches, Brownell et al. (1998) estimate

that about 89,000 whales were additionally taken by the Soviet pelagic whaling fleet between 1949 and 1979. The

Japanese coastal operations apparently also under-reported catches by an unknown amount (Kasuya 1998). Thus a total

of at least 436,000 sperm whales were taken between 1800 and the end of commercial whaling for this species in 1987.

Of this grand total, an estimated 33,842 were taken by Soviet and Japanese pelagic whaling operations in the eastern

North Pacific from the longitude of Hawaii to the U.S. West coast, between 1961 and 1976 (Allen 1980, IWC statistical

Areas II and III), and 965 were reported taken in land-based U.S. West coast whaling operations between 1947 and 1971

(Ohsumi 1980). In addition, 13 sperm whales were taken by shore whaling stations in California between 1919 and

1926 (Clapham et al. 1997). There has been a prohibition on taking sperm whales in the North Pacific since 1988, but

large-scale pelagic whaling stopped earlier, in 1980.

Fishery Information 

The offshore drift gillnet fishery is the only fishery that is likely to take sperm whales from this stock. Detailed

information on this fishery is provided in Appendix 1. A 1995-99 summary of known fishery mortality and injury for

this stock of sperm whales is given in Table 1. After the 1997 implementation of a Take Reduction Plan, which included

skipper education workshops and required the use of pingers and minimum 6-fathom extenders, overall cetacean

entanglement rates in the drift gillnet fishery dropped considerably (Barlow and Cameron 1999). However, two sperm

whales have been observed taken in nets with pingers (1996 and 1998). Because sperm whale entanglement is rare and

because those nets which took sperm whales did not use the full mandated complement of pingers, it is difficult to

evaluate whether pingers have any effect on sperm whale entanglement in drift gillnets. Because of the changes in this

fishery after implementation of the Take Reduction Plan, mean annual takes for this fishery (Table 1) are based only

on 1997-99 data. is results in an average estimate of 1.7 (CV = 0.89) sperm whale mortalities per year.

Table 1. Summary of available information on the incidental mortality and injury of sperm whales (CA/OR/WA stock)

for commercial fisheries that might take this species (Julian 1997; Julian and Beeson 1998; Cameron and Forney 1999).

Injury includes any entanglement that does not result in immediate death and may include serious injury resulting in

death. The injured whale observed in 1996 was not expected to survive . n/a indicates that data are not available. Mean

annual takes are based on 1994-98 data unless noted otherwise. 

Fishery Name Year(s) Data Type Percent Observer

Coverage

Observed

Mortality

(and injury in

parentheses)

Estimated

Mortality (CV in

parentheses)

Mean Annual Takes 

(CV in parentheses)

CA/OR thresher

shark/swordfish drift gillnet

fishery

1995

1996

1997

1998

1999

observer

data

15.6%

12.4%

 23.0%

20.0%

20.0%

0

0 (1)

0

1

0

Mortality

0,0,0,5,0

 (0.89) 

Injury

0,1,0,0,0

Mortality

1.7 (0.89)1

Injury

0.0 (n/a)

Total annual takes 1.7 (0.89)

1

 Only 1997-99 mortality estimates are included in the average because of gear modifications implemented within the fishery as part of a 1997 Take

Reduction Plan. Gear modifications included the use of net extenders and acoustic warning devices (pingers).

Drift gillnet fisheries for swordfish and sharks exist along the entire Pacific coast of Baja California and may

take animals from the same population. Quantitative data are available only for the Mexican swordfish drift gillnet

fishery, which uses vessels, gear, and operational procedures similar to those in the U.S. drift gillnet fishery, although

nets may be up to 4.5 km long (Holts and Sosa-Nishizaki 1998). The fleet increased from two vessels in 1986 to 31

vessels in 1993 (Holts and Sosa-Nishizaki 1998). The total number of sets in this fishery in 1992 can be estimated from

data provided by these authors to be approximately 2,700, with an observed rate of marine mammal bycatch of 0.13

animals per set (10 marine mammals in 77 observed sets; Sosa-Nishizaki et al. 1993). This overall mortality rate is

similar to that observed in California driftnet fisheries during 1990-95 (0.14 marine mammals per set; Julian and

Beeson,1998), but species-specific information is not available for the Mexican fisheries. There are currently efforts

underway to convert the Mexican swordfish driftnet fishery to a longline fishery (D. Holts, pers. comm.). 

Ship Strikes
147

No sperm whale mortalities have been attributed to ship strikes during the period 1994-98 (J. Cordaro,

Southwest Region, NMFS, pers. comm.). 

STATUS OF STOCK

The only estimate of the status of North Pacific sperm whales in relation to carrying capacity (Gosho et al.

1984) is based on a CPUE method which is no longer accepted as valid. Sperm whales are formally listed as

"endangered" under the Endangered Species Act (ESA), and consequently the California to Washington stock is

automatically considered as a "depleted" and "strategic" stock under the MMPA. The annual rate of kill and serious

injury (1.7 per year) is less than the calculated PBR for this stock (2.1). Total fishery takes may not be approaching zero

mortality and serious injury rate. The increasing levels of anthropogenic noise in the world’s oceans has been suggested

to be a habitat concern for whales, particularly for deep-diving whales like sperm whales that feed in the oceans “sound

channel”. 

REFERENCES

Allison, C. International Whaling Commission. The Red House, 135 Station Road, Impington, Cambridge, UK CB4

9NP.

Allen, K. R. 1980. Size distribution of male sperm whales in the pelagic catches. Rep. Int. Whal. Commn. Special

Issue 2:51-56.

Barlow, J. 1994. Abundance of large whales in California coastal waters: a comparison of ship surveys in 1979/80

and in 1991. Rept. Int. Whal. Commn. 44:399-406.

Barlow, J. 1995. The abundance of cetaceans in California waters. Part I: Ship surveys in summer and fall of 1991.

Fish. Bull. 93:1-14.

Barlow, J. 1997. Preliminary estimates of cetacean abundance off California, Oregon and Washington based on a 1996

ship survey and comparisons of passing and closing modes. Administrative Report LJ-97-11, Southwest

Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA 92038. 25p.

Barlow, J., R. W. Baird, J. E. Heyning, K. Wynne, A. M. Manville, II, L. F. Lowry, D. Hanan, J. Sease, and V. N.

Burkanov. 1994. A review of cetacean and pinniped mortality in coastal fisheries along the west coast of the

U.S. and Canada and the east coast of the Russian Federation. Rep. Int. Whal. Commn, Special Issue 15:405-

425.

Barlow, J. and G. A. Cameron. 1999. Field experiments show that acoustic pingers reduce marine mammal bycatch

in the California drift gillnet fishery. Report SC/51/SM2 to the Scientific Committee of the International

Whaling Commission, May 1999. 20pp.

Barlow, J., K. A. Forney, P. S. Hill, R. L. Brownell, Jr., J. V. Carretta, D. P. DeMaster, F. Julian, M. S. Lowry, T.

Ragen, and R. R. Reeves. 1997. U.S. Pacific Marine Mammal Stock Assessments: 1996. U.S. Dep. Commer.,

NOAA Tech. Memo. NMFS-SWFSC-248. 223p.

Barlow, J. and B. L. Taylor. 1998. Preliminary abundance of sperm whales in the northeastern temperate Pacific

estimated from a combined visual and acoustic survey. Paper SC/50/CAWS20 presented to the International

Whaling Commission, June 1998 (unpublished). 

Barlow, J. and B. L. Taylor. 2001. Estimates of large whale abundance off California, Oregon, Washington, and Baja

California based on 1993 and 1996 ship surveys. Administrative Report LJ-01-03 available from Southwest

Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA 92038. 12p. 

Best, P. B. 1976. A review of world sperm whale stocks. Paper ACMRR/MM/SC/8 Rev. 1, FAO Scientific

Consultation of Marine Mammals, Bergen, Norway.

Best, P. B. 1993. Increase rates in severely depleted stocks of baleen whales. ICES J. Mar. Sci. 50:169-186.

Brownell, R. L., Jr., A. V. Yablokov and V. A. Zemmsky. 1998. USSR pelagic catches of North Pacific sperm whales,

1949-1979: Conservation implications. Paper SC/50/CAWS27 presented to the International Whaling

Commission, June 1998 (unpublished).

Cameron, G. A. and K. A. Forney. 1999. Preliminary estimates of cetacean mortality in the California gillnet fisheries

for 1997 and 1998. Paper SC/51/O4 presented to the International Whaling Commission, May 1999

(unpublished). 14 pp.

Clapham, P. J., S. Leatherwood, I. Szczepaniak, and R. L. Brownell, Jr. 1997. Catches of humpback and other whales

from shore stations at Moss Landing and Trinidad, California, 1919-1926. Marine Mammal Science
148

13(3):368-394.

Cordaro, J. Southwest Region, NMFS, 501 West Ocean Blvd, Long Beach, CA 90802-4213.

Dohl, T. P., R. C. Guess, M. L. Duman, and R. C. Helm. 1983. Cetaceans of central and northern California, 1980-83:

Status, abundance, and distribution. Final Report to the Minerals Management Service, Contract No. 14-12-

0001-29090. 284p.

Donovan, G. P. 1991. A review of IWC stock boundaries. Rept. Int. Whal. Commn., Special Issue 13:39-68.

Dufault, S. and H. Whitehead. 1995. The geographic stock structure of female and immature sperm whales in the

South Pacific. Rep. Int. Whal. Commn. 45:401-405.

Forney, K. A., J. Barlow, and J. V. Carretta. 1995. The abundance of cetaceans in California waters. Part II: Aerial

surveys in winter and spring of 1991 and 1992. Fish. Bull. 93:15-26.

Forney, K.A., J. Barlow, M.M. Muto, M. Lowry, J. Baker, G. Cameron, J. Mobley, C. Stinchcomb, and J.V. Carretta.

2000. U.S. Pacific Marine Mammal Stock Assessments: 2000. U.S. Department of Commerce, NOAA

Technical Memorandum NMFS-SWFSC-300. 276p.

Gosho, M. E., D. W. Rice, and J. M. Breiwick. 1984. The sperm whale. Mar. Fish. Rev. 46(4):54-64.

Green, G. A., J. J. Brueggeman, R. A. Grotefendt, C. E. Bowlby, M. L. Bonnell, K. C. Balcomb, III. 1992. Cetacean

distribution and abundance off Oregon and Washington, 1989-1990. Ch. 1 In: J. J. Brueggeman (ed.). Oregon

andWashingtonMarineMammal and SeabirdSurveys. Minerals Management Service Contract Report 14-12-

0001-30426.

Hanan, D. A. 1986. California Department of Fish and Game coastal marine mammal study, annual report for the

period July 1, 1983 - June 30, 1984. Admin. Rept. LJ-86-16 available from Southwest Fisheries Science

Center, P.O. Box 271, La Jolla, CA. 55pp.

Hanan, D. A., D. B. Holts, and A. L. Coan, Jr. 1993. The California drift gill net fishery for sharks and swordfish,

1981-82 through 1990-91. Calif. Dept. Fish and Game Fish. Bull. No. 175. 95pp.

Heyning, J. E., and T. D. Lewis. 1990. Fisheries interactions involving baleen whales off southern California. Rep.

int. Whal. Commn. 40:427-431.

Holts, D. and O. Sosa-Nishizaki. 1998. Swordfish, Xiphias gladius, fisheries of the eastern North Pacific Ocean. In:

I. Barrett, O. Sosa-Nishizaki and N. Bartoo (eds.). Biology and fisheries of swordfish, Xiphias gladius. Papers

from the International Symposium on Pacific Swordfish, Ensenada Mexico, 11-14 December 1994. U.S. Dep.

Commer., NOAA Tech. Rep. NMFS 142, 276 pp.

Julian, F. 1997. Cetacean mortality in California gill net fisheries: Preliminary estimates for 1996. Paper SC/49/SM02

presented to the International Whaling Commission, September 1997 (unpublished). 13 pp.

Julian, F. and M. Beeson. 1998. Estimates of marine mammal, turtle, and seabird mortality for two California gillnet

fisheries: 1990-95. Fishery Bulletin 96:271-284.

Kasuya, T. 1998. Evidence of statistical manipulations in Japanese coastal sperm whale fishery. Paper

SC/50/CAWS10 presented to the International Whaling Commission, June 1998 (unpublished).

Leatherwood, S., K. Goodrich, A. L. Kinter, and R. M. Truppo. 1982. Respiration patterns and 'sightability' of whales.

Rep. Int. Whal. Commn. 32:601-613.

Mesnick, S. L., B. L. Taylor, B. Nachenberg, A. Rosenberg, S. Peterson, J. Hyde, and A. E. Dizon. 1999. Genetic

relatedness within groups and the definition of sperm whale stock boundaries from the coastal waters off

California, Oregon and Washington. Admin. Rep. LJ-99-12. Southwest Fisheries Science Center, National

Marine Fisheries Service, P.O. Box 271, La Jolla, CA. 10 pp. 

Miyashita, T., H. Kato, and T. Kasuya (Eds.). 1995. Worldwide map of cetacean distribution based on Japanese

sighting data. Volume 1. National Research Institute of Far Seas Fisheries, Shizuoka, Japan. 140pp.

Ohsumi, S. 1980. Catches of sperm whales by modern whaling in the North Pacific. Rep. Int. Whal. Commn. Special

Issue 2: 11-18.

Rice, D. W. 1988. Sperm whale Physeter macrocephalus, Linnaeus 1758. pp. 177-233 In: S. H. Ridgway and R. J.

Harrison (eds.). Handbook of Marine Mammals, Vol. 4. Academic Press, London.

Sosa-Nishizaki, O., R. De la Rosa Pacheco, R. Castro Longoria, M. Grijalva Chon, and J. De la Rosa Velez. 1993.

Estudio biologico pesquero del pez (Xiphias gladius) y otras especies de picudos (marlins y pez vela). Rep.

Int. CICESE, CTECT9306.

Wade, P. R. and T. Gerrodette. 1993. Estimates of cetacean abundance and distribution in the eastern tropical Pacific.

Rept. Int. Whal. Commn. 43:477-493.
149

Figure 2. Humpback whale sighting locations

based on aerial and shipboard surveys off California,

Oregon, and Washington, 1989-96. Dashed line

represents the U.S. EEZ, thick line indicates the

outer boundary of all surveys combined. Greater

effort was conducted off California (south of 42°N)

and in the inshore half of the U.S. EEZ. See

Appendix 2 for data sources and information on

timing and location of survey effort. 

Revised 12/31/2001

HUMPBACK WHALE (Megaptera novaeangliae): 

Eastern North Pacific Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

Although the International Whaling Commission

(IWC) only considered one stock (Donovan 1991), there is

now good evidence for multiple populations of humpback

whales in the North Pacific (Johnson and Wolman 1984;

Baker et al. 1990). Aerial, vessel, and photo-identification

surveys, and genetic analyses indicate that within the U.S.

EEZ, there are at least three relatively separate populations

that migrate between their respective summer/fall feeding

areas and winter/spring calving and mating areas

(Calambokidis et al. 1997, Baker et al. 1998): 1)

winter/spring populations in coastal Central America and

Mexico which migrate to the coast of California to southern

British Columbia in summer/fall (Steiger et al. 1991,

Calambokidis et al. 1993) - referred to as the eastern North

Pacific stock (Figure 1); 2) winter/spring populations of the

Hawaiian Islands which migrate to northern British

Columbia/Southeast Alaska and Prince William Sound west

to Kodiak (Baker et al. 1990, Perry et al. 1990, Calambokidis

et al. 1997) - referred to as the central North Pacific stock;

and 3) winter/spring populations of Japan which, based on

Discovery Tag information, probably migrate to waters west

of the Kodiak Archipelago (the Bering Sea and Aleutian

Islands) in summer/fall (Berzin and Rovnin 1966, Nishiwaki

1966, Darling 1991) - referred to as the western North

Pacific stock. Winter/spring populations of humpback

whales also occur in Mexico’s offshore islands; the

migratory destination of these whales is not well known

(Calambokidis et al. 1993, Calambokidis et al. 1997), but

Norris et al. (1999) speculate that they may travel to the

Bering Sea or Aleutian Islands. Significant levels of genetic

differences were found between the California and Alaska

feeding groups based on analyses of mitochondrial DNA

(Baker et al. 1990) and nuclear DNA (Baker et al. 1993).

The genetic exchange rate between California and Alaska is

estimated to be less than 1 female per generation (Baker 1992). Two breeding areas (Hawaii and coastal Mexico)

showed fewer genetic differences than did the two feeding areas (Baker 1992). This is substantiated by the observed

movement of individually-identified whales between Hawaii and Mexico (Baker et al. 1990). There have been no

individual matches between 597 humpbacks photographed in California and 617 humpbacks photographed in Alaska

(Calambokidis et al. 1996). Only two of the 81 whales photographed in British Columbia have matched with a

California catalog (Calambokidis et al. 1996), indicating that the U.S./Canada border is an approximate geographic

boundary between feeding populations. 

Until further information becomes available, three management units of humpback whales (as described above)

are recognized within the U.S. EEZ of the North Pacific: the eastern North Pacific stock (this report), the central North

Pacific stock, and the western North Pacific stock. The central and western North Pacific stocks are reported separately

in the Stock Assessment Reports for the Alaska Region.
150

0 

200 

400 

600 

800 

1000 

1200 

1400 

Abundance

1991 1992 1993 1994 1995 1996 1997 1998 1999 

Year

Mark-recapture Estimates

Figure 3. Mark-recapture estimates of the abundance of humpback whales feeding off California, Oregon, and

Washington based on photo-identification studies (Calambokidis et al. 2000).

POPULATION SIZE

Based on whaling statistics, the pre-1905 population of humpback whales in the North Pacific was estimated

to be 15,000 (Rice 1978), but this population was reduced by whaling to approximately 1,200 by 1966 (Johnson and

Wolman 1984). The North Pacific total now almost certainly exceeds 6,000 humpback whales (Calambokidis et al.

1997). Dohl et al. (1983) first estimated the central California feeding population to be 338 (CV=0.29) based on aerial

surveys in August through November of 1980-83; however, this estimate does not include a correction for submerged

animals. More recently, the size of the "California" feeding stock of humpback whales has been estimated by three

independent methods. 1) Calambokidis et al. (2000) estimated the number of humpback whales in CaliforniaWashington to be 1,024 (CV=0.10) based on mark-recapture estimates comparing their 1998 and 1999 photoidentification catalogs. 2) Barlow and Taylor (2001) estimates 1,177 (CV=0.28) humpbacks in California, Oregon and

Washington waters based on ship line-transect surveys in summer/autumn of 1993 and 1996. 3) Forney et al. (1995)

estimate 319 (CV=0.41) humpback whales in California coastal waters based on aerial line-transect surveys in

winter/spring of 1991 and 1992 (not corrected for diving whales). Green et al. (1992) report that humpback whales were

the second most abundant large whale (after the gray whale) in aerial surveys off Oregon and Washington, but they did

not estimate population size. Based on photographic mark-recapture techniques, Urban et al. (1999) estimate that the

1987-92 population of humpback whales was 1,162 in coastal Mexico and 642 near the Revillagigedos Islands. 

The best estimate of abundance for the eastern North Pacific stock of humpback whales is the photographic

mark-recapture estimate of 1,024 (CV=0.10) whales along the U.S. west coast (Calambokidis et al. 2000). In general,

mark-recapture estimates are negatively biased due to heterogeneity in sighting probabilities (Hammond 1986);

however, this bias is likely to be minimal because the above mark-recapture estimate is based on data from over half

of the entire population (the 1998-99 catalog contained 594 known individuals). The photographic mark-recapture

estimates from Mexico (Urban et al. 1999) include whales from several feeding destinations and probably two different

stocks. The aerial line-transect estimates (Forney et al. 1995) are more than 8 years old and do not include corrections

for diving whales that would be missed. The ship line transect estimate (Barlow and Taylor 2001) is less precise than
151

the mark-recapture estimates and is negatively biased because it does not include some humpback whales which could

not be identified in the field and which were recorded as “unidentified large whale”. 

Minimum Population Estimate

The minimum population estimate for humpback whales in the California/Mexico stock is taken as the lower

20th percentile of the log-normal distribution of 1998-99 abundance estimated from mark-recapture methods

(Calambokidis et al. 1999) or approximately 944.

Current Population Trend

Ship surveys provide some indication that humpback whales increased in abundance in California coastal

waters between 1979/80 and 1991 (Barlow 1994) and between 1991 and 1996 (Barlow 1997). Mark-recapture

population estimates increased steadily from 1988/90 to 1997-98 at about 8% per year (Calambokidis et al. 1999) and

the estimate for 1998-99 is again higher than previous estimates (Calambokidis et al. 2000). Population estimates for

the entire North Pacific have also increased substantially from 1,200 in 1966 to 6,000-8,000 circa 1992. Although these

estimates are based on different methods and the earlier estimate is extremely uncertain, the growth rate implied by these

estimates (6-7%) is consistent with the recently observed growth rate of the eastern North Pacific stock. 

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

The proportion of calves in the California/Mexico stock from 1986 to 1994 appeared much lower than

previously measured for humpback whales in other areas (Calambokidis and Steiger 1994), but in 1995-97 a greater

proportion of calves were identified, and the 1997 reproductive rates for this population are closer to those reported for

humpback whale populations in other regions (Calambokidis et al. 1998). Despite the apparently low proportion of

calves, two independent lines of evidence indicate that this stock appears to be growing (Barlow 1994; Calambokidis

et al. 2000) with a best estimate of 8% growth per year (Calambokidis et al. 1999).

POTENTIAL BIOLOGICAL REMOVAL

The potential biological removal (PBR) level for this stock is calculated as the minimum population size (944)

times one half the estimated population growth rate for this stock of humpback whales (1⁄2 of 8%)times a recovery factor

of 0.1 (for an endangered species), resulting in a PBR of 3.8. Because this stock spends approximately half its time

outside the U.S. EEZ, the PBR allocation for U.S. waters is 1.9 whales per year.

HUMAN-CAUSED MORTALITY

Historic Whaling 

The reported take of North Pacific humpback whales by commercial whalers totaled approximately 7,700

between 1947 and 1987 (C. Allison, pers. comm.). In addition, approximately 7,300 were taken along the west coast

of North America from 1919 to 1929 (Tonnessen and Johnsen 1982). Total 1910-1965 catches from the CaliforniaWashington stock includes at least the 2,000 taken in Oregon and Washington, the 3,400 taken in California, and the

2,800 taken in Baja California (Rice 1978). Shore-based whaling apparently depleted the humpback whale stock off

California twice: once prior to 1925 (Clapham et al. 1997) and again between 1956 and 1965 (Rice 1974). There has

been a prohibition on taking humpback whales since 1966.

Fishery Information

 A 1995-99 summary of known fishery mortality and injury for this stock of humpback whales is given in

Table 1. Detailed information on these fisheries is provided in Appendix 1. After the 1997 implementation of a Take

Reduction Plan, which included skipper education workshops and required the use of pingers and minimum 6-fathom

extenders, overall cetacean entanglement rates in the drift gillnet fishery dropped considerably (Barlow and Cameron

1999). Because of the changes in this fishery after implementation of the Take Reduction Plan, mean annual takes for

this fishery (Table 1) are based only on 1997-99 data. This results in an average estimate of zero humpback whales taken

annually. Some gillnet mortality of large whales may go unobserved because whales swim away with a portion of the

net. The deaths of two humpback whales that stranded in the Southern California Bight have been attributed to

entanglement in fishing gear (Heyning and Lewis 1990), and a humpback whale was observed off Ventura, CA in 1993

with a 20 ft section of netting wrapped around and trailing behind. During the period 1995-99, a humpback cow-calf
152

pair was seen entangled in a net off Big Sur, California (1999), but the fate of these animals is not known (J. Cordero,

NMFS SW Region, pers. comm.). Other unobserved fisheries may also result in injuries or deaths of humpback whales.

In 1997, one humpback whale was snagged by a central California salmon troller, and the animal swam away with the

hook and many feet of trailing monofilament (NMFS, Southwest Region, unpublished data); this type of injury is not

likely to be serious. 

Table 1. Summary of available information on the incidental mortality and injury of humpback whales (eastern North

Pacific stock) for commercial fisheries that might take this species (Julian 1997, Julian and Beeson 1998, Cameron and

Forney 1999, 2000). Injury includes any entanglement that does not result in immediate death and may include serious

injury resulting in death. n/a indicates that data are not available. Mean annual takes are based on 1995-99 data unless

noted otherwise.

Fishery Name Year(s) Data Type

Percent Observer

Coverage

Observed

Mortality

(and Injury)

Estimated

Mortality (CV

in parentheses)

Mean Annual Takes 

(CV in parentheses)

CA/OR thresher

shark/swordfish drift gillnet

fishery

1995

1996

1997

1998

1999

observer

data

15.6%

12.4%

 23.0%

 20.0%

20.0%

0

0

0

0

0

Mortality

0,0,0,0,0

Injury

0,0,0,0,0

Mortality

0

Injury

0

1

CA angel shark/halibut and

other species large mesh

(>3.5") set gillnet fishery

1990-94 observer

data

10-15% 0,0,0,0,0 0,0,0,0,0 n/a

CA salmon troll fishery 1997 incidental

report

0% (1) n/a Injury

>0.2 (n/a)

Total annual takes >0.2

1

 Only 1997-99 mortality estimates are included in the average because of gear modifications implemented within the fishery as part of a 1997 Take

Reduction Plan. Gear modifications included the use of net extenders and acoustic warning devices (pingers).

Drift gillnet fisheries for swordfish and sharks exist along the entire Pacific coast of Baja California and may

take animals from the same population. Quantitative data are available only for the Mexican swordfish drift gillnet

fishery, which uses vessels, gear, and operational procedures similar to those in the U.S. drift gillnet fishery, although

nets may be up to 4.5 km long (Holts and Sosa-Nishizaki 1998). The fleet increased from two vessels in 1986 to 31

vessels in 1993 (Holts and Sosa-Nishizaki 1998). The total number of sets in this fishery in 1992 can be estimated from

data provided by these authors to be approximately 2,700, with an observed rate of marine mammal bycatch of 0.13

animals per set (10 marine mammals in 77 observed sets; Sosa-Nishizaki et al. 1993). This overall mortality rate is

similar to that observed in California driftnet fisheries during 1990-95 (0.14 marine mammals per set; Julian and Beeson

1998), but species-specific information is not available for the Mexican fisheries. There are currently efforts underway

to convert the Mexican swordfish driftnet fishery to a longline fishery (D. Holts, pers. comm.). 

Ship Strikes

Ship strikes were implicated in the deaths of at least two humpback whales in 1993 and one humpback whale

in 1995, and one unidentified whale, which may have been a humpback whale, was struck and injured by a small boat

in 1997 (J. Cordaro, pers. comm.). Additional mortality from ship strikes probably goes unreported because the whales

do not strand or, if they do, they do not have obvious signs of trauma. Several humpback whales have been

photographed in California with large gashes in their dorsal surface that appear to be from ship strikes (J. Calambokidis,

pers. comm.). The average number of humpback whale deaths by ship strikes for 1995-99 is at least 0.2 per year.

STATUS OF STOCK

Humpback whales in the North Pacific were estimated to have been reduced to 13% of carrying capacity (K)

by commercial whaling (Braham 1991). Clearly the North Pacific population was severely depleted. The initial

abundance has never been estimated separately for the eastern North Pacific stock, but this stock was also depleted

(probably twice) by whaling (Rice 1974; Clapham et al. 1997). Humpback whales are formally listed as "endangered"

under the Endangered Species Act (ESA), and consequently the California/Mexico stock is automatically considered
153

as a "depleted" and "strategic" stock under the MMPA. The estimated annual mortality and injury due to entanglement

(0.2/yr) plus ship strikes (0.2/yr) in California is less than the PBR allocation of 1.9 for U.S. waters. In a review of the

severity of injury to the humpback whale entangled in 1997, the Pacific Scientific Review Group determined that it this

animal was not seriously injured. Based on strandings and gillnet observations, annual humpback whale mortality and

serious injury in California's drift gillnet fishery is probably greater than 10% of the PBR; therefore, total fishery

mortality may not be approaching zero mortality and serious injury rate. The eastern North Pacific stock appears to be

increasing in abundance. The increasing levels of anthropogenic noise in the world’s oceans, such as those produced

by ATOC (Acoustic Thermometry of Ocean Climate) or LFA (Low Frequency Active) Sonar, have been suggested to

be a habitat concern for whales, particularly for baleen whales that may communicate using low-frequency sound.

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O'Brien. 1993. Population characteristics of DNA fingerprints in humpback whales (Megaptera

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and in 1991. Rept. Int. Whal. Commn. 44:399-406.

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U.S. and Canada and the east coast of the Russian Federation. Rep. Int. Whal. Commn, Special Issue 15:405-

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156

Figure 1. Blue whale sighting locations based on

aerial and shipboard surveys off California,

Oregon, and Washington, 1991-96(see Appendix

2, Figures 1-5, for data sources and information on

timing and location of surveys). Dashed line

represents the U.S. EEZ; bold line indicates the

outer boundary of all surveys combined.

Revised 12/15/2000 

BLUE WHALE (Balaenoptera musculus): Eastern North Pacific Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

The International Whaling Commission (IWC) has

formally considered only one management stock for blue whales

in the North Pacific (Donovan 1991), but now this ocean is

thought to include more than one population (Ohsumi and Wada

1972; Braham 1991), possibly as many as five (Reeves et al.

1998). This report covers one population that feeds in California

waters in summer/fall (from June to November) and migrates

south to productive areas off Mexico (Calambokidis et al. 1990)

and as far south as the Costa Rica Dome (10o N) (Mate et al.

1999; Calambokidis, pers. comm.) in winter/spring. Blue whales

are occasionally seen or heard off Oregon (McDonald et al. 1994,

Stafford et al. 1998; VonSaunder and Barlow 1999), but sightings

there are rare. Reilly and Thayer (1990) speculate that blue

whales found near the Costa Rica Dome from June to November

are likely to be part of a southern hemisphere population or an

isolated resident population; however, based on acoustic call

similarities, Stafford et al. (1999) linked these animals to the

population that feeds off California at the same time of year. Rice

(1974) hypothesized that blue whales from Baja California

migrated far offshore to fed in the eastern Aleutians or Gulf of

Alaska and returned to feed in California waters; however, he has

more recently concluded that the California population is separate

from the Gulf of Alaska population (Rice 1992). Recently, blue

whale feeding aggregations have not been found in Alaska despite

several surveys (Leatherwood et al. 1982; Stewart et al. 1987;

Forney and Brownell 1996). One other stock of North Pacific

blue whales (in Hawaiian waters) is recognized in the Marine

Mammal Protection Act (MMPA) Stock Assessment Reports.

POPULATION SIZE

The size of the feeding stock of blue whales in California

was estimated recently by both line-transect and mark-recapture

methods. Barlow (1997) estimates 1,927 (CV=0.16) blue whales off California, Oregon, and Washington based on ship

line-transect surveys in 1991-96. Calambokidis and Steiger (1994) used photographic mark-recapture and estimated

population sizes of 2,038 (CV=0.33) based on photographs of left sides and 1,997 (CV=0.42) based on right sides. The

average of the mark-recapture estimates (2,017, CV=0.38) is in surprisingly good agreement with the line-transect

estimate. Mark-recapture estimates are often negatively biased by individual heterogeneity in sighting probabilities

(Hammond 1986); however, Calambokidis and Steiger (1994) minimize such effects by selecting one sample that was

taken randomly with respect to distance from the coast. Similarly, the line-transect estimates may also be negatively

biased because some blue whales in this stock are probably along Baja California and, therefore, out of the study area

at the time of survey (Wade and Gerrodette 1993). The best estimate of blue whale abundance is the average of the linetransect and mark-recapture estimates, weighted by their variances, or 1,940 (CV=0.15).

Minimum Population Estimate

The minimum population estimate for blue whales is taken as the lower 20th percentile of the log-normal

distribution of abundance estimated from the combined mark-recapture and line-transect estimates, or approximately

1,716.
157

Current Population Trend

There is some indication that blue whales have increased in abundance in California coastal waters between

1979/80 and 1991 (regression p<0.05, Barlow 1994) and between 1991 and 1996 (not significant, Barlow 1997).

Although this may be due to an increase in the stock as a whole, it could also be the result of an increased use of

California as a feeding area. The size of the apparent increase abundance seen by Barlow (1994) is too large to be

accounted for by population growth alone. Also, Larkman and Veit (1998) did not detect any increase along consistently

surveyed tracklines in the Southern California Bight from 1987 to 1995. Although the population in the North Pacific

is expected to have grown since being given protected status in 1966, the possibility of continued unauthorized takes

after blue whales were protected (Yablokov 1994) and the existence of incidental ship strikes and gillnet mortality makes

this uncertain.

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

No information exists on the rate of growth of blue whale populations in the Pacific (Best 1993).

POTENTIAL BIOLOGICAL REMOVAL

The potential biological removal (PBR) level for this stock is calculated as the minimum population size (1,716)

times one half the default maximum net growth rate for cetaceans (1⁄2 of 4%) times a recovery factor of 0.1 (for an

endangered species), resulting in a PBR of 3.4 . Because this stock spends approximately half its time outside the U.S.

EEZ, the PBR allocation for U.S. waters is half this total, or 1.7 whales per year.

HUMAN CAUSED MORTALITY

Historic Whaling 

The reported take of North Pacific blue whales by commercial whalers totaled 9,500 between 1910 and 1965

(Ohsumi and Wada 1972). Approximately 2,000 were taken off the west coast of North America between 1919 and

1929 (Tonnessen and Johnsen 1982). Partially overlapping with this is Rice's (1992) report of at least 1,378 taken by

factory ships off California and Baja California between 1913 and 1937. Between 1947 and 1987, reported takes of

blue whales in the North Pacific were approximately 2,400. Shore-based whaling stations in central California took 3

blue whales between 1919 and 1926 (Clapham et al. 1997) and 48 blue whales between 1958 and 1965 (Rice 1974).

Blue whales in the North Pacific were given protected status by the IWC in 1966.

Fisheries Information 

The offshore drift gillnet fishery is the only fishery that is likely to take blue whales from this stock, but no

fishery mortalities or serious injuries have been observed (Table 1). Detailed information on this fishery is provided

in Appendix 1. After the 1997 implementation of a Take Reduction Plan, which included skipper education workshops

and required the use of pingers and minimum 6-fathom extenders, overall cetacean entanglement rates in the drift gillnet

fishery dropped considerably (Barlow and Cameron 1999). Because of the changes in this fishery after implementation

of the Take Reduction Plan, mean annual takes for this fishery (Table 1) are based only on 1997-98 data. This results

in an average estimate of zero blue whales taken annually. Some gillnet mortality of large whales may go unobserved

because whales swim away with a portion of the net; however, fishermen report that large rorquals (blue and fin whales)

usually swim through nets without entangling and with very little damage to the nets. 

Drift gillnet fisheries for swordfish and sharks exist along the entire Pacific coast of Baja California and may

take animals from the same population. Quantitative data are available only for the Mexican swordfish drift gillnet

fishery, which uses vessels, gear, and operational procedures similar to those in the U.S. drift gillnet fishery, although

nets may be up to 4.5 km long (Holts and Sosa-Nishizaki 1998). The fleet increased from two vessels in 1986 to 31

vessels in 1993 (Holts and Sosa-Nishizaki 1998). The total number of sets in this fishery in 1992 can be estimated from

data provided by these authors to be approximately 2,700, with an observed rate of marine mammal bycatch of 0.13

animals per set (10 marine mammals in 77 observed sets; Sosa-Nishizaki et al. 1993). This overall mortality rate is

similar to that observed in California driftnet fisheries during 1990-95 (0.14 marine mammals per set; Julian and Beeson

1998), but species-specific information is not available for the Mexican fisheries. There are currently efforts underway

to convert the Mexican swordfish driftnet fishery to a longline fishery (D. Holts, pers. comm.). 
158

Table 1. Summary of available information on the incidental mortality and injury of blue whales (Eastern North Pacific

stock) for commercial fisheries that might take this species (Julian 1997; Julian and Beeson 1998; Cameron and Forney

1999). Mean annual takes are based on 1994-98 data unless noted otherwise. 

Fishery Name Year(s) Data Type

Percent Observer

Coverage

Observed

Mortality

Estimated

Mortality (CV in

parentheses)

Mean

Annual Takes

(CV in

parentheses)

CA/OR thresher

shark/swordfish drift

gillnet fishery

 1994-98 observer

data

12-23% 0,0,0,0,0 0,0,0,0,0 0

1

Total annual takes 0

1

 Only 1997-98 mortality estimates are included in the average because of gear modifications implemented within the fishery as part of a 1997 Take

Reduction Plan. Gear modifications included the use of net extenders and acoustic warning devices (pingers).

Ship Strikes

Ship strikes were implicated in the deaths of blue whales in 1980, 1986, 1987, and 1993 (J. Cordaro, Southwest

Region, NMFS and J. Heyning, pers. comm.). Additional mortality from ship strikes probably goes unreported because

the whales do not strand or, if they do, they do not always have obvious signs of trauma. Several blue whales have been

photographed in California with large gashes in their dorsal surface that appear to be from ship strikes (J. Calambokidis,

pers. comm.). The average number of blue whale mortalities in California attributed to ship strikes was 0.0 per year for

1994-98.

STATUS OF STOCK

Previously, blue whales in the entire North Pacific were estimated to be at 33% (1,600 out of 4,900) of historic

carrying capacity (Mizroch et al. 1984). The initial abundance has never been estimated separately for the "California"

stock, but this stock was almost certainly depleted by whaling. Blue whales are formally listed as "endangered" under

the Endangered Species Act (ESA), and consequently the Eastern North Pacific stock is automatically considered as

a "depleted" and "strategic" stock under the MMPA. The annual incidental mortality from ship strikes is apparently less

than the calculated PBR for this stock. To date, no blue whale mortality has been associated with California gillnet

fisheries; therefore, total fishery mortality is approaching zero mortality and serious injury rate. The population appears

to be growing. The increasing levels of anthropogenic noise in the world’s oceans has been suggested to be a habitat

concern for blue whales (Reeves et al. 1998).

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Figure 1. Fin whale sighting locations based on

aerial and shipboard surveys off California,

Oregon, and Washington, 1991-96 (see Appendix

2, Figures 1-5 for data sources and information on

timing and location of surveys). Dashed line

represents the U.S. EEZ; bold line indicates the

outer boundary of all surveys combined.

Revised 12/15//2001

FIN WHALE (Balaenoptera physalus): 

California/Oregon/Washington Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

The International Whaling Commission (IWC)

recognized two stocks of fin whales in the North Pacific: the East

China Sea and the rest of the North Pacific (Donovan 1991).

Mizroch et al. (1984) cites evidence for additional fin whale

subpopulations in the North Pacific. From whaling records, fin

whales that were marked in winter 1962-70 off southern

California were later taken in commercial whaling operations

between central California and the Gulf of Alaska in summer

(Mizroch et al. 1984). More recent observations show

aggregations of fin whales year-round in southern/central

California (Dohl et al. 1983; Barlow 1997; Forney et al. 1995),

year-round in the Gulf of California (Tershy et al. 1993), in

summer in Oregon (Green et al. 1992; McDonald 1994), and in

summer/autumn in the Shelikof Strait/Gulf of Alaska

(Brueggeman et al. 1990). Acoustic signals from fin whale are

detected year-round off northern California, Oregon and

Washington, with a concentration of vocal activity between

September and February (Moore et al. 1998). Fin whales appear

very scarce in the eastern tropical Pacific in summer (Wade and

Gerrodette 1993) and winter (Lee 1993).

There is still insufficient information to accurately

determine population structure, but from a conservation

perspective it may be risky to assume panmixia in the entire North

Pacific. In the North Atlantic, fin whales were locally depleted in

some feeding areas by commercial whaling (Mizroch et al. 1984),

in part because subpopulations were not recognized. This

assessment will cover the stock of fin whales which is found along

the coasts of California, Oregon, and Washington. Because fin

whale abundance appears lower in winter/spring in California

(Dohl et al. 1983; Forney et al. 1995) and in Oregon (Green et al.

1992), it is likely that the distribution of this stock extends

seasonally outside these coastal waters. Coincidentally, fin whale abundance in the Gulf of California increases

seasonally in winter and spring (Tershy et al. 1993). It is premature, however, to conclude that the Gulf whales are part

of the U.S. west coast population. The Marine Mammal Protection Act (MMPA) stock assessment reports recognize

three stocks of fin whales in the North Pacific: 1) the California/Oregon/Washington stock (this report), 2) the Hawaii

stock, and 3) the Alaska stock.

POPULATION SIZE

The initial pre-whaling population of fin whales in the North Pacific was estimated to be 42,000-45,000

(Ohsumi and Wada 1974). In 1973, the North Pacific population was estimated to have been reduced to 13,620-18,680

(Ohsumi and Wada 1974), of which 8,520-10,970 were estimated to belong to the eastern Pacific stock. A minimum

of 148 individually-identified fin whales are found in the Gulf of California (Tershy et al. 1990). Recently,1,851

(CV=0.19) fin whales were estimated to be off California, Oregon and Washington based on ship surveys in

summer/autumn of 1993 and 1996 (Barlow and Taylor 2001). This is probably a slight underestimate because it almost

certainly excludes some fin whales which could not be identified in the field and which were recorded as “unidentified

rorqual” or “unidentified large whale”. 
162

Minimum Population Estimate

The minimum population estimate for fin whales is taken as the lower 20th percentile of the log-normal

distribution of abundance estimated from summer/fall ship survey (Barlow and Taylor 2001) or approximately 1,581.

Current Population Trend

There is some indication that fin whales have increased in abundance in California coastal waters between

1979/80 and 1991 (Barlow 1994) and between 1991 and 1996 (Barlow 1997), but these trends are not significant.

Although the population in the North Pacific is expected to have grown since receiving protected status in 1976, the

possible effects of continued unauthorized take (Yablokov 1994) and incidental ship strikes and gillnet mortality make

this uncertain.

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

There are no estimates of the growth rate of fin whale populations in the North Pacific (Best 1993).

POTENTIAL BIOLOGICAL REMOVAL

The potential biological removal (PBR) level for this stock is calculated as the minimum population size (

1,581) times one half the default maximum net growth rate for cetaceans (1⁄2 of 4%) times a recovery factor of 0.1 (for

an endangered species), resulting in a PBR of 3.2.

HUMAN CAUSED MORTALITY

Historic Whaling

Approximately 46,000 fin whales were taken from the North Pacific by commercial whalers between 1947 and

1987 (C. Allison, IWC, pers. comm.), including 1,060 fin whales taken by coastal whalers in central California between

1958 and 1965 (Rice 1974). In addition, approximately 3,800 were taken off the west coast of North America between

1919 and 1929 (Tonnessen and Johnsen 1982), and 177 were taken by coastal whalers off California between 1919 and

1926 (Clapham et al. 1997). Fin whales in the North Pacific were given protected status by the IWC in 1976.

Fisheries Information

The offshore drift gillnet fishery is the only fishery that is likely to take fin whales from this stock, and one fin

whale death has been observed (Table 1). Detailed information on this fishery is provided in Appendix 1. After the

1997 implementation of a Take Reduction Plan, which included skipper education workshops and required the use of

pingers and minimum 6-fathom extenders, overall cetacean entanglement rates in the drift gillnet fishery dropped

considerably (Barlow and Cameron 1999). Because of the changes in this fishery after implementation of the Take

Reduction Plan, mean annual takes for this fishery (Table 1) are based only on 1997-99 data. This results in an average

estimate of 1.5 fin whales taken annually. Some gillnet mortality of large whales may go unobserved because whales

swim away with a portion of the net; however, fishermen report that large rorquals (blue and fin whales) usually swim

through nets without entangling and with very little damage to the nets. 

Drift gillnet fisheries for swordfish and sharks exist along the entire Pacific coast of Baja California and may

take animals from the same population. Quantitative data are available only for the Mexican swordfish drift gillnet

fishery, which uses vessels, gear, and operational procedures similar to those in the U.S. drift gillnet fishery, although

nets may be up to 4.5 km long (Holts and Sosa-Nishizaki 1998). The fleet increased from two vessels in 1986 to 31

vessels in 1993 (Holts and Sosa-Nishizaki 1998). The total number of sets in this fishery in 1992 can be estimated from

data provided by these authors to be approximately 2,700, with an observed rate of marine mammal bycatch of 0.13

animals per set (10 marine mammals in 77 observed sets; Sosa-Nishizaki et al. 1993). This overall mortality rate is

similar to that observed in California driftnet fisheries during 1990-95 (0.14 marine mammals per set; Julian and Beeson

1998), but species-specific information is not available for the Mexican fisheries. There are currently efforts underway

to convert the Mexican swordfish driftnet fishery to a longline fishery (D. Holts, pers. comm.). 
163

Table 1. Summary of available information on the incidental mortality and injury of fin whales (CA/OR/WA stock) for

commercial fisheries that might take this species (Julian 1997; Julian and Beeson 1998; Cameron and Forney 1999,

2000).

Fishery Name Year(s) Data Type

Percent Observer

Coverage

Observed

Mortality

Estimated

Mortality (CV in

parentheses)

Mean

Annual Takes

(CV in

parentheses)

CA/OR thresher

shark/swordfish drift

gillnet fishery

1995-99 observer

data

12-23% 0,0,0,0,1 0,0,0,0,4.5 1.5 1

Average annual takes 1.5

1

 Only 1997-99 mortality estimates are included in the average because of gear modifications implemented within the fishery as part of a 1997 Take

Reduction Plan. Gear modifications included the use of net extenders and acoustic warning devices (pingers).

Ship Strikes

Ship strikes were implicated in the deaths of one fin whale in 1991, one in 1996, and one in 1997 (J. Heyning

and J. Cordaro, Southwest Region, NMFS, pers. comm.). Additional mortality from ship strikes probably goes

unreported because the whales do not strand or, if they do, they do not always have obvious signs of trauma. The

average observed annual mortality due to ship strikes is 0.4 fin whales per year for the period 1995-99. 

STATUS OF STOCK

Fin whales in the entire North Pacific were estimated to be at less than 38% (16,625 out of 43,500) of historic

carrying capacity (Mizroch et al. 1984). The initial abundance has never been estimated separately for the "west coast"

stock, but this stock was also probably depleted by whaling. Fin whales are formally listed as "endangered" under the

Endangered Species Act (ESA), and consequently the California to Washington stock is automatically considered as

a "depleted" and "strategic" stock under the MMPA. The total incidental mortality due to fisheries (1.5/yr) and ship

strikes (0.4/yr) appears to be less than the calculated PBR ( 3.2). Total fishery mortality is greater than 10% of PBR

and, therefore, may not be approaching zero mortality and serious injury rate. There is some indication that the

population may be growing. The increasing levels of anthropogenic noise in the world’s oceans has been suggested to

be a habitat concern for whales, particularly for baleen whales that may communicate using low-frequency sound.

REFERENCES

Barlow, J. 1994. Abundance of large whales in California coastal waters: a comparison of ship surveys in 1979/80

and in 1991. Rept. Int. Whal. Commn. 44:399-406.

Barlow, J. 1997. Preliminary estimates of cetacean abundance off California, Oregon, and Washington based on a

1996 ship survey and comparisons of passing and closing modes. Admin. Rept. LJ-97-11 available from

Southwest Fisheries Science Center, P.O. Box 271, La Jolla, CA. 25 pp.

Barlow, J., R. W. Baird, J. E. Heyning, K. Wynne, A. M. Manville, II, L. F. Lowry, D. Hanan, J. Sease, and V. N.

Burkanov. 1994. A review of cetacean and pinniped mortality in coastal fisheries along the west coast of the

U.S. and Canada and the east coast of the Russian Federation. Rep. Int. Whal. Commn, Special Issue 15:405-

425.

Barlow, J. and G. A. Cameron. 1999. Field experiments show that acoustic pingers reduce marine mammal bycatch

in the California drift gillnet fishery. Report SC/51/SM2 to the Scientific Committee of the International

Whaling Commission, May 1999. 20pp.

Barlow, J. and B. L. Taylor. 2001. Estimates of large whale abundance off California, Oregon, Washington, and Baja

California based on 1993 and 1996 ship surveys. Administrative Report LJ-01-03 available from Southwest

Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA 92038. 12p. 

Best, P. B. 1993. Increase rates in severely depleted stocks of baleen whales. ICES J. Mar. Sci. 50:169-186.

Brueggeman, J. J., G. A. Green, K. C. Balcomb, C. E. Bowlby, R. A. Grotefendt, K. T. Briggs, M. L. Bonnell, R. G.

Ford, D. H. Varoujean, D. Heinemann, and D. G. Chapman. 1990. Oregon-Washington Marine Mammal and

Seabird Survey: Information synthesis and hypothesis formulation. U.S. Department of the Interior, OCS

Study MMS 89-0030.

Cameron, G.A. and K.A. Forney. 1999. Preliminary estimates of cetacean mortality in the California gillnet fisheries
164

for 1997 and 1998. Paper SC/51/O4 presented to the International Whaling Commission, May 1999

(unpublished). 14 pp.

Cameron, G.A. and K.A. Forney. 2000. Preliminary estimates of cetacean mortality in the California/Oregon gillnet

fisheries for 1999. Paper SC/52/O24 presented to the International Whaling Commission, June 2000

(unpublished). 12 pp.

Clapham, P. J., S. Leatherwood, I. Szczepaniak, and R. L. Brownell, Jr. 1997. Catches of humpback and other whales

from shore stations at Moss Landing and Trinidad, California, 1919-1926. Mar. Mamm. Sci. 13(3):368-394.

Dohl, T. P., R. C. Guess, M. L. Duman, and R. C. Helm. 1983. Cetaceans of central and northern California, 1980-83:

Status, abundance, and distribution. Final Report to the Minerals Management Service, Contract No. 14-12-

0001-29090. 284p.

Donovan, G. P. 1991. A review of IWC stock boundaries. Rept. Int. Whal. Commn., Special Issue 13:39-68.

Forney, K. A., J. Barlow, and J. V. Carretta. 1995. The abundance of cetaceans in California waters. Part II: Aerial

surveys in winter and spring of 1991 and 1992. Fish. Bull. 93:15-26.

Forney, K. A., J. Barlow, M. M. Muto, M. Lowry, J. Baker, G. Cameron, J. Mobley, C. Stinchcomb, and J. V. Carretta.

2000. U.S. Pacific Marine Mammal Stock Assessments: 2000. U.S. Dep. Commer. NOAA Technical

Memorandum NOAA-TM-NMFS-SWFSC-300. 276p. 

Green, G. A., J. J. Brueggeman, R. A. Grotefendt, C. E. Bowlby, M. L. Bonnell, K. C. Balcomb, III. 1992. Cetacean

distribution and abundance off Oregon and Washington, 1989-1990. Ch. 1 In: J. J. Brueggeman (ed.). Oregon

andWashingtonMarineMammal andSeabirdSurveys. Minerals Management Service Contract Report 14-12-

0001-30426.

Hanan, D. A. 1986. California Department of Fish and Game coastal marine mammal study, annual report for the

period July 1, 1983 - June 30, 1984. Admin. Rept. LJ-86-16 available from Southwest Fisheries Science

Center, P.O. Box 271, La Jolla, CA. 55pp.

Hanan, D. A., D. B. Holts, and A. L. Coan, Jr. 1993. The California drift gill net fishery for sharks and swordfish,

1981-82 through 1990-91. Calif. Dept. Fish and Game Fish. Bull. No. 175. 95p.

Heyning, J. E., and T. D. Lewis. 1990. Fisheries interactions involving baleen whales off southern California. Rep.

int. Whal. Commn. 40:427-431.

Holts, D. Southwest Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA 92038.

Holts, D. and O. Sosa-Nishizaki. 1998. Swordfish, Xiphias gladius, fisheries of the eastern North Pacific Ocean. In:

I. Barrett, O. Sosa-Nishizaki and N. Bartoo (eds.). Biology and fisheries of swordfish, Xiphias gladius. Papers

from the International Symposium on Pacific Swordfish, Ensenada Mexico, 11-14 December 1994. U.S. Dep.

Commer., NOAA Tech. Rep. NMFS 142, 276p.

Julian, F. 1997. Cetacean mortality in the California gill net fisheries: preliminary estimates for 1996. Paper

SC/49/SM2 presented to the International Whaling Commission, September 1997 (unpublished). 13pp.

Julian, F. and M. Beeson. 1998. Estimates for marine mammal, turtle, and seabird mortality for two California gillnet

fisheries: 1990-95. Fish. Bull. 96:271-284.

Lee, T. 1993. Summary of cetacean survey data collected between the years of 1974 and 1985. U.S. Dep. Commer.

NOAA Tech. Memo. NMFS-SWFSC-181. 184 pp.

McDonald, M. A., J. A. Hildebrand, and S. C. Webb. 1994. Blue and fin whales observer on a seafloor array in the

Northeast Pacific. (unpubl. ms.).

Mizroch, S. A., D. W. Rice, and J. M. Breiwick. 1984. The fin whale, Balaenoptera physalus. Mar. Fish. Rev. 46:20-

24.

Moore, S. E., K. M. Stafford, M. E. Dahlheim, C. G. Fox, H. W. Braham, J. J. Polovina, and D. E. Bain. 1998.

Seasonal variation in reception of fin whale calls at five geographic areas in the North Pacific. Mar. Mamm.

Sci. 14(3):617-627.

Ohsumi, S. and S. Wada. 1974. Status of whale stocks in the North Pacific, 1972. Rept. Int. Whal. Commn. 25:114-

126.

Rice, D. W. 1974. Whales and whale research in the eastern North Pacific. pp. 170-195 In: W. E. Schevill (ed.). The

Whale Problem: A Status Report. Harvard Press, Cambridge, MA.

Sosa-Nishizaki, O., R. De la Rosa Pacheco, R. Castro Longoria, M. Grijalva Chon, and J. De la Rosa Velez. 1993.

Estudio biologico pesquero del pez (Xiphias gladius) y otras especies de picudos (marlins y pez vela). Rep.

Int. CICESE, CTECT9306.
165

Tershy, B. R., D. Breese, and C. S. Strong. 1990. Abundance, seasonal distribution and population composition of

balaenopterid whales in the Canal de Ballenas, Gulf of California, Mexico. Rept. Int. Whal. Commn., Special

Issue 12:369-375.

Tershy, B. R., J. Urbán-R., D. Breese, L. Rojas-B., and L. T. Findley. 1993. Are fin whales resident to the Gulf of

California? Rev. Invest. Cient., Univ. Auton. de Baja California Sur. 1:69-71.

Tonnessen, J. N., and A. O. Johnsen. 1982. The History of Modern Whaling. Univ. Calif. Press, Berkeley and Los

Angeles. 798pp.

Wade, P. R. and T. Gerrodette. 1993. Estimates of cetacean abundance and distribution in the eastern tropical Pacific.

Rept. Int. Whal. Commn. 43:477-493.

Yablokov, A. V. 1994. Validity of whaling data. Nature 367:108.
166

Figure 1. Sighting locations of Bryde's whales

based on aerial and shipboard surveys off

California, Oregon, and Washington, 1991-96 (see

Appendix 2, Figures 1-5 for data sources and

information on timing and location of surveys).

Dashed line represents the U.S. EEZ; bold line

indicates the outer boundary of all surveys

combined.

Revised 12/15/2000 

BRYDE'S WHALE (Balaenoptera edeni): Eastern Tropical Pacific Stock 

STOCK DEFINITION AND GEOGRAPHIC RANGE

The International Whaling Commission (IWC) recognizes

3 stocks of Bryde's whales in the North Pacific (eastern, western,

and East China Sea), 3 stocks in the South Pacific (eastern, western

and Solomon Islands), and one cross-equatorial stock (Peruvian)

(Donovan 1991). Bryde's whales are distributed widely across the

tropical and warm-temperate Pacific (Leatherwood et al. 1982), and

there is no real justification for splitting stocks between the

northern and southern hemispheres (Donovan 1991). Recent

surveys (Lee 1993; Wade and Gerrodette 1993) have shown them

to be common and distributed throughout the eastern tropical

Pacific with a concentration around the equator east of 110oW

(corresponding approximately to the IWC's "Peruvian stock") and

a reduction west of 140oW. They are also the most common baleen

whale in the central Gulf of California (Tershy et al. 1990). Only

one was positively identified in surveys of California coastal waters

(Barlow 1997). Bryde's whales in California are likely to belong to

a larger population inhabiting at least the eastern part of the tropical

Pacific. For the Marine Mammal Protection Act (MMPA) stock

assessment reports, Bryde's whales within the Pacific U.S.

Exclusive Economic Zone are divided into two areas: 1) the eastern

tropical Pacific (east of 150oW and including the Gulf of California

and waters off California; this report), and 2) Hawaiian waters.

POPULATION SIZE

In the western North Pacific, Bryde's whale abundance in

the early 1980s was estimated independently by tag mark-recapture

and ship survey methods to be 22,000 to 24,000 (Tillman and

Mizroch 1982; Miyashita 1986). Bryde's whale abundance has

never been estimated for the entire eastern Pacific; however, a

portion of that stock in the eastern tropical Pacific was estimated

recently as 13,000 (CV=0.20; 95% C.I.=8,900-19,900) (Wade and Gerrodette 1993), and the minimum number in the

Gulf of California is 160 based on individually-identified whales (Tershy et al. 1990). Only one confirmed sighting of

Bryde's whales and five possible sightings (identified as sei or Bryde's whales) were made in California waters during

extensive ship and aerial surveys in 1991, 1992, 1993, and 1996 (Hill and Barlow 1992; Carretta and Forney 1993;

Mangels and Gerrodette 1994; VonSaunder and Barlow 1999). Green et al. (1992) did not report any sightings of

Bryde's whales in aerial surveys off Oregon and Washington. The estimated abundance of Bryde's whales in California,

Oregon, and Washington coastal waters is 12 (CV=2.0) (Barlow 1997).

Minimum Population Estimate

The minimum population estimate for Bryde's whales is taken as the lower 20th percentile of the log-normal

distribution of abundance estimated from the summer/fall ship surveys in 1986-90 (Wade and Gerrodette 1993) plus

the minimum of 160 whales counted in the Gulf of California (Tershy et al. 1990), or 11,163.

Current Population Trend

There are no data on trends in Bryde's whale abundance in the eastern tropical Pacific.
167

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

There are no estimates of the growth rate of Bryde's whale populations in the Pacific (Best 1993).

POTENTIAL BIOLOGICAL REMOVAL

The potential biological removal (PBR) level for this stock cannot be calculated because the only relevant

abundance estimate (Wade and Gerrodette 1993) is more than 8 years old. Additional data on the abundance of Bryde’s

whales in the eastern Pacific was gathered in 1998-99, but their abundance has not yet been estimated from those data.

HUMAN CAUSED MORTALITY

Historic Whaling 

The reported take of North Pacific Bryde's whales by commercial whalers totaled 15,076 in the western Pacific

from 1946-1983 (Holt 1986) and 2,873 in the eastern Pacific from 1973-81 (Cooke 1983). In addition, 2,304 sei-orBryde's whales were taken in the eastern Pacific from 1968-72 (Cooke 1983) (based on subsequent catches, most of

these were probably Bryde's whales). None were reported taken by shore-based whaling stations in central or northern

California between 1919 and 1926 (Clapham et al. 1997) or 1958 and 1965 (Rice 1974). There has been a prohibition

on taking Bryde's whales since 1988.

Table 1. Summary of available information on the incidental mortality and injury of Bryde’s whales (eastern tropical

Pacific stock) for commercial fisheries that might take this species (Julian 1997; Julian and Beeson 1998; Cameron and

Forney 1999). n/a indicates that data are not available. Mean annual takes are based on 1994-98 data unless noted

otherwise.

Fishery Name Year(s) Data Type

Percent Observer

Coverage

Observed

Mortality

Estimated

Mortality (CV in

parentheses)

Mean

Annual Takes

(CV in parentheses)

CA/OR thresher

shark/swordfish drift

gillnet fishery

 1994-98 observer

data

 12-23% 0,0,0,0,0 0,0,0,0,0 0

1

Mexico thresher

shark/swordfish drift

gillnet fishery

1991-95 observer

data

n/a n/a n/a n/a

Total annual takes 0

1

 Only 1997-98 mortality estimates are included in the average because of gear modifications implemented within the fishery as part of a 1997 Take

Reduction Plan. Gear modifications included the use of net extenders and acoustic warning devices (pingers).

Fishery Information 

The offshore drift gillnet fishery is the only fishery that is likely to take Bryde’s whales from this stock, but

no fishery mortalities or serious injuries have been observed (Table 1). Detailed information on this fishery is provided

in Appendix 1. After the 1997 implementation of a Take Reduction Plan, which included skipper education workshops

and required the use of pingers and minimum 6-fathom extenders, overall cetacean entanglement rates in the drift gillnet

fishery dropped considerably (Barlow and Cameron 1999). Because of the changes in this fishery after implementation

of the Take Reduction Plan, mean annual takes for this fishery (Table 1) are based only on 1997-98 data. This results

in an average estimate of zero Bryde’s whales taken annually. However, some gillnet mortality of large whales may go

unobserved because whales swim away with a portion of the net. 

Drift gillnet fisheries for swordfish and sharks exist along the entire Pacific coast of Baja California and may

take animals from the same population. Quantitative data are available only for the Mexican swordfish drift gillnet

fishery, which uses vessels, gear, and operational procedures similar to those in the U.S. drift gillnet fishery, although

nets may be up to 4.5 km long (Holts and Sosa-Nishizaki 1998). The fleet increased from two vessels in 1986 to 31

vessels in 1993 (Holts and Sosa-Nishizaki 1998). The total number of sets in this fishery in 1992 can be estimated from

data provided by these authors to be approximately 2,700, with an observed rate of marine mammal bycatch of 0.13

animals per set (10 marine mammals in 77 observed sets; Sosa-Nishizaki et al. 1993). This overall mortality rate is

similar to that observed in California driftnet fisheries during 1990-95 (0.14 marine mammals per set; Julian and Beeson

1998), but species-specific information is not available for the Mexican fisheries. There are currently efforts underway
168

to convert the Mexican swordfish driftnet fishery to a longline fishery (D. Holts, pers. comm.). 

Ship Strikes

Ship strikes may occasionally kill Bryde's whales as they are known to kill their larger relatives: blue and fin

whales. No ship strikes have been reported for this species in this area.

STATUS OF STOCK

Commercial whaling of Bryde's whales was largely limited to the western Pacific. Bryde's whales are not listed

as "threatened" or "endangered" under the Endangered Species Act (ESA). Bryde's whales in the eastern tropical Pacific

would not be considered a strategic stock under the MMPA. The total human-caused mortality rate is estimated to be

zero; therefore, under the MMPA, total fishery mortality is approaching zero mortality and serious injury rate. The

increasing levels of anthropogenic noise in the world’s oceans has been suggested to be a habitat concern for whales,

particularly for baleen whales that may communicate using low-frequency sound.

REFERENCES

Barlow, J. 1997. Preliminary estimates of cetacean abundance off California, Oregon, and Washington based on a

1996 ship survey and comparisons of passing and closing modes. Admin. Rept. LJ-97-11 available from

Southwest Fisheries Science Center, P.O. Box 271, La Jolla, CA. 25pp.

Barlow, J., R. W. Baird, J. E. Heyning, K. Wynne, A. M. Manville, II, L. F. Lowry, D. Hanan, J. Sease, and V. N.

Burkanov. 1994. A review of cetacean and pinniped mortality in coastal fisheries along the west coast of the

U.S. and Canada and the east coast of the Russian Federation. Rep. Int. Whal. Commn, Special Issue 15:405-

425.

Barlow, J. and G. A. Cameron. 1999. Field experiments show that acoustic pingers reduce marine mammal bycatch

in the California drift gillnet fishery. Report SC/51/SM2 to the Scientific Committee of the International

Whaling Commission, May 1999. 20pp.

Best, P. B. 1993. Increase rates in severely depleted stocks of baleen whales. ICES J. Mar. Sci. 50:169-186.

Cameron, G. A. and K. A. Forney. 1999. Preliminary estimates of cetacean mortality in the California gillnet fisheries

for 1997 and 1998. Paper SC/51/O4 presented to the International Whaling Commission, May 1999

(unpublished). 14 pp.

Carretta, J. V. and K. A. Forney. 1993. Report on two aerial surveys for marine mammals in California coastal waters

utilizing a NOAA DeHavilland Twin Otter Aircraft: March 9-April7, 1991 and February 8-April 6, 1992.

NOAA Tech. Memo. NOAA-TM-NMFS-SWFSC-185. 77pp.

Clapham, P. J., S. Leatherwood, I. Szczepaniak, and R. L. Brownell, Jr. 1997. Catches of humpback and other whales

from shore stations at Moss Landing and Trinidad, California, 1919-1926. Mar. Mamm. Sci. 13(3):368-394.

Cooke, J. G. 1983. Estimates of the stock of Bryde's whales fished off the coast of Peru. Rept. Int. Whal. Commn.

33:453-456.

Donovan, G. P. 1991. A review of IWC stock boundaries. Rept. Int. Whal. Commn., Special Issue 13:39-68.

Green, G. A., J. J. Brueggeman, R. A. Grotefendt, C. E. Bowlby, M. L. Bonnell, K. C. Balcomb, III. 1992. Cetacean

distribution and abundance off Oregon and Washington, 1989-1990. Ch. 1 In: J. J. Brueggeman (ed.). Oregon

andWashingtonMarineMammal and Seabird Surveys. Minerals Management Service Contract Report 14-12-

0001-30426.

Hanan, D. A. 1986. California Department of Fish and Game coastal marine mammal study, annual report for the

period July 1, 1983 - June 30, 1984. Admin. Rept. LJ-86-16 available from Southwest Fisheries Science

Center, P.O. Box 271, La Jolla, CA. 55pp.

Hanan, D. A., D. B. Holts, and A. L. Coan, Jr. 1993. The California drift gill net fishery for sharks and swordfish,

1981-82 through 1990-91. Calif. Dept. Fish and Game Fish. Bull. No. 175. 95pp.

Heyning, J. E., and T. D. Lewis. 1990. Fisheries interactions involving baleen whales off southern California. Rep.

int. Whal. Commn. 40:427-431.

Hill, P. S. and J. Barlow. 1992. Report of a marine mammal survey of the California coast aboard the research vessel

McARTHUR July 28-November 5, 1991. NOAA Technical Memorandum NOAA-TM-NMFS-SWFSC-169.

NTIS #PB93-109908. 103pp.

Holt, S. 1986. Aspects of the assessment and regulation of Bryde's whales in the Northwest Pacific. Rept. Int. Whal.
169

Commn. 36:257-262.

Holts, D. Southwest Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA 92038.

Holts, D. and O. Sosa-Nishizaki. 1998. Swordfish, Xiphias gladius, fisheries of the eastern North Pacific Ocean. In:

I. Barrett, O. Sosa-Nishizaki and N. Bartoo (eds.). Biology and fisheries of swordfish, Xiphias gladius. Papers

from the International Symposium on Pacific Swordfish, Ensenada Mexico, 11-14 December 1994. U.S. Dep.

Commer., NOAA Tech. Rep. NMFS 142, 276 p.

Julian, F. 1997. Cetacean mortality in the California gill net fisheries: preliminary estimates for 1996. Paper

SC/49/SM2 presented to the International Whaling Commission, September 1997 (unpublished). 13pp.

Julian, F. and M. Beeson. 1998. Estimates for marine mammal, turtle, and seabird mortality for two California gillnet

fisheries: 1990-95. Fish. Bull. 96:271-284.

Leatherwood, S., R. R. Reeves, W. F. Perrin, and W. E. Evans. 1982. Whales, dolphins, and porpoises of the eastern

North Pacific and adjacent Arctic waters: A guide to their identification. NOAA Technical Rept. NMFS

Circular 444. 245 pp.

Lee, T. 1993. Summary of cetacean survey data collected between the years of 1974 and 1985. NOAA Tech. Memo.

NOAA-TM-NMFS-SWFSC-181. 184 pp.

Mangels, K. F. and T. Gerrodette. Report of cetacean sightings during a marine mammal survey in the eastern Pacific

Ocean and the Gulf of California aboard the NOAA ships McArthur and David Starr Jordan July 28 -

November 6, 1993. U.S. Dep. Commer. NOAA Tech. Memo. NMFS-SWFSC-221. 88 pp.

Miyashita, T. 1986. Sighting estimate for the Bryde's whale stock in the western North Pacific. Rept. Int. Whal.

Commn. 36:249-252.

Rice, D. W. 1974. Whales and whale research in the eastern North Pacific. pp. 170-195 In: W. E. Schevill (ed.). The

Whale Problem: A Status Report. Harvard Press, Cambridge, MA.

Sosa-Nishizaki, O., R. De la Rosa Pacheco, R. Castro Longoria, M. Grijalva Chon, and J. De la Rosa Velez. 1993.

Estudio biologico pesquero del pez (Xiphias gladius) y otras especies de picudos (marlins y pez vela). Rep.

Int. CICESE, CTECT9306.

Tershy, B. R., D. Breese, and C. S. Strong. 1990. Abundance, seasonal distribution and population composition of

balaenopterid whales in the Canal de Ballenas, Gulf of California, Mexico. Rept. Int. Whal. Commn., Special

Issue 12:369-375.

Tillman, M. F. and S. A. Mizroch. 1982. Mark-recapture estimates of abundance for the western Northern Pacific

stock of Bryde's whales. Rept. Int. Whal. Commn. 32:335-337.

Von Saunder, A. and J. Barlow. 1999. A report of the Oregon, California and Washington Line-transect Experiment

(ORCAWALE) conducted in west coast waters during summer/fall 1996. U.S. Dep. Commer. NOAA Tech.

Memo. NMFS-SWFSC-264. 40 pp. 

Wade, P. R. and T. Gerrodette. 1993. Estimates of cetacean abundance and distribution in the eastern tropical Pacific.

Rept. Int. Whal. Commn. 43:477-493.
170

Figure 1. Sei whale sighting locations based on

aerial and shipboard surveys off California,

Oregon, and Washington, 1991-96 (see Appendix

2, Figures 1-5 for data sources and information on

timing and location of surveys). Dashed line

represents the U.S. EEZ; bold line indicates the

outer boundary of all surveys combined.

Revised 12/15/2000 

SEI WHALE (Balaenoptera borealis): Eastern North Pacific Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

The International Whaling Commission (IWC) only

considers one stock of sei whales in the North Pacific (Donovan

1991), but some evidence exists for multiple populations (Masaki

1977; Mizroch et al. 1984; Horwood 1987). Sei whales are

distributed far out to sea in temperate regions of the world and do

not appear to be associated with coastal features. Whaling effort

for this species was distributed continuously across the North

Pacific between 45-55oN (Masaki 1977). Two sei whales that

were tagged off California were later killed off Washington and

British Columbia (Rice 1974) and the movement of tagged

animals has been noted in many other regions of the North Pacific.

Sei whales are now rare in California waters (Dohl et al. 1983;

Barlow 1997; Forney et al. 1995; Mangels and Gerrodette 1994),

but were the fourth most common whale taken by California

coastal whalers in the 1950s-1960s (Rice 1974). They are

extremely rare south of California (Wade and Gerrodette 1993;

Lee 1993). Lacking additional information on sei whale

population structure, sei whales in the eastern North Pacific (east

of longitude 180o) will be considered as a separate stock.

POPULATION SIZE

Ohsumi and Wada (1974) estimate the pre-whaling

abundance of sei whales to be 58,000-62,000 in the North Pacific.

Later, Tillman (1977) used a variety of different methods to

estimate the abundance of sei whales in the North Pacific and

revised this pre-whaling estimate to 42,000. His estimates for the

year 1974 ranged from 7,260 to 12,620. All methods depend on

using the history of catches and trends in CPUE or sighting rates;

there have been no direct estimates of sei whale abundance in the

entire (or eastern) North Pacific based on sighting surveys. Only

one confirmed sighting of sei whales and 5 possible sightings (identified as sei or Bryde's whales) were made in

California waters during extensive ship and aerial surveys in 1991, 1992, 1993, and 1996 (Hill and Barlow 1992;

Carretta and Forney 1993; Mangels and Gerrodette 1994; VonSaunder and Barlow 1999). Green et al. (1992) did not

report any sightings of sei whales in aerial surveys of Oregon and Washington. There are no abundance estimates for

sei whales along the west coast of the U.S. or in the eastern North Pacific.

Minimum Population Estimate

Minimum population estimates do not exist for sei whales in the eastern North Pacific.

Current Population Trend

There are no data on trends in sei whale abundance in the eastern North Pacific waters. Although the

population in the North Pacific is expected to have grown since being given protected status in 1976, the possible effects

of continued unauthorized take (Yablokov 1994) and incidental ship strikes and gillnet mortality make this uncertain.

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

There are no estimates of the growth rate of sei whale populations in the North Pacific (Best 1993).
171

POTENTIAL BIOLOGICAL REMOVAL

No estimate exists for the minimum abundance of the eastern North Pacific stock of sei whales. Estimates for

the entire North Pacific are more than 10 years old and do not include statistical estimates of precision. Consequently,

PBR levels cannot be calculated.

HUMAN CAUSED MORTALITY

Historic Whaling

The reported take of North Pacific sei whales by commercial whalers totaled 61,500 between 1947 and 1987

(C. Allison, IWC, pers. comm.). Of these, 384 were taken by-shore-based whaling stations in central California between

1958 and 1965 (Rice 1974). An additional 26 were taken off central and northern California between 1919 and 1926

(Clapham et al. 1997). There has been an IWC prohibition on taking sei whales since 1976, and commercial whaling

in the U.S. has been prohibited since 1972. 

Fishery Information

The offshore drift gillnet fishery is the only fishery that is likely to take sei whales from this stock, but no

fishery mortalities or serious injuries have been observed (Table 1). Detailed information on this fishery is provided

in Appendix 1. After the 1997 implementation of a Take Reduction Plan, which included skipper education workshops

and required the use of pingers and minimum 6-fathom extenders, overall cetacean entanglement rates in the drift gillnet

fishery dropped considerably (Barlow and Cameron 1999). Because of the changes in this fishery after implementation

of the Take Reduction Plan, mean annual takes for this fishery (Table 1) are based only on 1997-98 data. This results

in an average estimate of zero sei whales taken annually. However, some gillnet mortality of large whales may go

unobserved because whales swim away with a portion of the net. 

Table 1. Summary of available information on the incidental mortality and injury of sei whales (eastern North Pacific

stock) for commercial fisheries that might take this species (Julian 1997; Julian and Beeson 1998; Cameron and Forney

1999). n/a indicates that data are not available. Mean annual takes are based on 1994-98 data unless noted otherwise.

Fishery Name Year(s) Data Type

Percent Observer

Coverage

Observed

Mortality

Estimated

Mortality (CV in

parentheses)

Mean

Annual Takes

(CV in parentheses)

CA/OR thresher

shark/swordfish drift

gillnet fishery

 1994-98 observer

data

 12-23% 0,0,0,0,0 0,0,0,0,0 0

1

Total annual takes 0

1

 Only 1997-98 mortality estimates are included in the average because of gear modifications implemented within the fishery as part of a 1997 Take

Reduction Plan. Gear modifications included the use of net extenders and acoustic warning devices (pingers).

Ship Strikes

Ship strikes may occasionally kill sei whales as they have been shown to kill their larger relatives: blue and fin

whales. No ship strikes have been reported for this species in this area.

STATUS OF STOCK

Previously, sei whales were estimated to have been reduced to 20% (8,600 out of 42,000) of their pre-whaling

abundance in the North Pacific (Tillman 1977). The initial abundance has never been reported separately for the eastern

North Pacific stock, but this stock was also probably depleted by whaling. Sei whales are formally listed as

"endangered" under the Endangered Species Act (ESA), and consequently the eastern North Pacific stock is

automatically considered as a "depleted" and "strategic" stock under the Marine Mammal Protection Act (MMPA).

Total estimated fishery mortality is zero and therefore is “approaching zero mortality and serious injury rate”. The

increasing levels of anthropogenic noise in the world’s oceans has been suggested to be a habitat concern for whales,

particularly for baleen whales that may communicate using low-frequency sound.

REFERENCES

Barlow, J. 1997. Preliminary estimates of cetacean abundance off California, Oregon, and Washington based on a
172

1996 ship survey and comparisons of passing and closing modes. Admin. Rept. LJ-97-11. Southwest Fisheries

Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA. 25 pp.

Barlow, J., R. W. Baird, J. E. Heyning, K. Wynne, A. M. Manville, II, L. F. Lowry, D. Hanan, J. Sease, and V. N.

Burkanov. 1994. A review of cetacean and pinniped mortality in coastal fisheries along the west coast of the

U.S. and Canada and the east coast of the Russian Federation. Rep. Int. Whal. Commn, Special Issue 15:405-

425.

Barlow, J. and G. A. Cameron. 1999. Field experiments show that acoustic pingers reduce marine mammal bycatch

in the California drift gillnet fishery. Report SC/51/SM2 to the Scientific Committee of the International

Whaling Commission, May 1999. 20pp.

Best, P. B. 1993. Increase rates in severely depleted stocks of baleen whales. ICES J. Mar. Sci. 50:169-186.

Carretta, J. V. and K. A. Forney. 1993. Report on two aerial surveys for marine mammals in California coastal waters

utilizing a NOAA DeHavilland Twin Otter Aircraft: March 9-April7, 1991 and February 8-April 6, 1992.

U.S. Dep. Commer. NOAA Tech. Memo. NMFS-SWFSC-185. 77 pp.

Cameron, G. A. and K. A. Forney. 1999. Preliminary estimates of cetacean mortality in the California gillnet fisheries

for 1997 and 1998. Paper SC/51/O4 presented to the International Whaling Commission, May 1999

(unpublished). 14 pp.

Clapham, P. J., S. Leatherwood, I. Szczepaniak, and R. L. Brownell, Jr. 1997. Catches of humpback and other whales

from shore stations at Moss Landing and Trinidad, California, 1919-1926. Mar. Mamm. Sci. 13(3):368-394.

Dohl, T. P., R. C. Guess, M. L. Duman, and R. C. Helm. 1983. Cetaceans of central and northern California, 1980-83:

Status, abundance, and distribution. Final Report to the Minerals Management Service, Contract No. 14-12-

0001-29090. 284 pp.

Donovan, G. P. 1991. A review of IWC stock boundaries. Rept. Int. Whal. Commn., Special Issue 13:39-68.

Forney, K. A., J. Barlow, and J. V. Carretta. 1995. The abundance of cetaceans in California waters. Part II: Aerial

surveys in winter and spring of 1991 and 1992. Fish. Bull. 93:15-26.

Green, G. A., J. J. Brueggeman, R. A. Grotefendt, C. E. Bowlby, M. L. Bonnell, K. C. Balcomb, III. 1992. Cetacean

distribution and abundance off Oregon and Washington, 1989-1990. Ch. 1 In: J. J. Brueggeman (ed.). Oregon

andWashingtonMarineMammal and Seabird Surveys. Minerals Management Service Contract Report 14-12-

0001-30426.

Hanan, D. A. 1986. California Department of Fish and Game coastal marine mammal study, annual report for the

period July 1, 1983 - June 30, 1984. Admin. Rept. LJ-86-16. Southwest Fisheries Science Center, National

Marine Fisheries Service, P.O. Box 271, La Jolla, CA. 55pp.

Hanan, D. A., D. B. Holts, and A. L. Coan, Jr. 1993. The California drift gill net fishery for sharks and swordfish,

1981-82 through 1990-91. Calif. Dept. Fish and Game Fish. Bull. No. 175. 95pp.

Heyning, J. E., and T. D. Lewis. 1990. Fisheries interactions involving baleen whales off southern California. Rep.

Int. Whal. Commn. 40:427-431.

Hill, P. S. and J. Barlow. 1992. Report of a marine mammal survey of the California coast aboard the research vessel

McARTHUR July 28-November 5, 1991. U.S. Dep. Commer. NOAA Tech. Memo. NMFS-SWFSC-169.

103 pp.

Holts, D. and O. Sosa-Nishizaki. 1998. Swordfish, Xiphias gladius, fisheries of the eastern North Pacific Ocean. In:

I. Barrett, O. Sosa-Nishizaki and N. Bartoo (eds.). Biology and fisheries of swordfish, Xiphias gladius. Papers

from the International Symposium on Pacific Swordfish, Ensenada Mexico, 11-14 December 1994. U.S. Dep.

Commer., NOAA Tech. Rep. NMFS 142, 276 p.

Horwood, J. 1987. The Sei Whale: Population Biology, Ecology and Management. Croom Helm, London, U.K.

375pp.

Julian, F. 1997. Cetacean mortality in the California gill net fisheries: preliminary estimates for 1996. Paper

SC/49/SM2 presented to the International Whaling Commission, September 1997 (unpublished). 13pp.

Julian, F. and M. Beeson. 1998. Estimates for marine mammal, turtle, and seabird mortality for two California gillnet

fisheries: 1990-95. Fish. Bull. 96:271-284.

Lee, T. 1993. Summary of cetacean survey data collected between the years of 1974 and 1985. U.S. Dep. Commer.

NOAA Tech. Memo. NMFS-SWFSC-181. 184 pp.

Mangels, K. F. and T. Gerrodette. Report of cetacean sightings during a marine mammal survey in the eastern Pacific

Ocean and the Gulf of California aboard the NOAA ships McArthur and David Starr Jordan July 28 -
173

November 6, 1993. U.S. Dep. Commer. NOAA Tech. Memo. NMFS-SWFSC-221. 88 pp.

Masaki, Y. 1977. The separation of the stock units of sei whales in the North Pacific. Rept. Int. Whal. Commn.,

Special Issue 1:71-77.

Mizroch, S. A., D. W. Rice, and J. M. Breiwick. 1984. The sei whale, Balaenoptera borealis. Mar. Fish. Rev. 46:25-

29.

Ohsumi, S. and S. Wada. 1974. Status of whale stocks in the North Pacific, 1972. Rept. Int. Whal. Commn. 25:114-

126.

Rice, D. W. 1974. Whales and whale research in the eastern North Pacific. pp. 170-195 In: W. E. Schevill (ed.). The

Whale Problem: A Status Report. Harvard Press, Cambridge, MA.

Tillman, M. F. 1977. Estimates of population size for the North Pacific sei whale. Rept. Int. Whal. Commn., Special

Issue 1:98-106.

Von Saunder, A. and J. Barlow. 1999. A report of the Oregon, California and Washington Line-transect Experiment

(ORCAWALE) conducted in west coast waters during summer/fall 1996. U.S. Dep. Commer. NOAA Tech.

Memo. NMFS-SWFSC-264. 40 pp. 

Wade, P. R. and T. Gerrodette. 1993. Estimates of cetacean abundance and distribution in the eastern tropical Pacific.

Rept. Int. Whal. Commn. 43:477-493.

Yablokov, A. V. 1994. Validity of whaling data. Nature 367:108.
174

Figure 2. Minke whale sighting locations based on

aerial and shipboard surveys off California, Oregon,

and Washington, 1991-96 (see Appendix 2, Figures 1-5

for data sources and information on timing and location

of surveys). Dashed line represents the U.S. EEZ;

bold line indicates the outer boundary of all surveys

combined.

Revised 12/15/2000

MINKE WHALE (Balaenoptera acutorostrata): 

California/Oregon/Washington Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

The International Whaling Commission (IWC)

recognizes 3 stocks of minke whales in the North Pacific: one

in the Sea of Japan/East China Sea, one in the rest of the

western Pacific west of 180oN, and one in the "remainder" of

the Pacific (Donovan 1991). The "remainder" stock only

reflects the lack of exploitation in the eastern Pacific and does

not imply that only one population exists in that area

(Donovan 1991). In the "remainder" area, minke whales are

relatively common in the Bering and Chukchi seas and in the

Gulf of Alaska, but are not considered abundant in any other

part of the eastern Pacific (Leatherwood et al. 1982;

Brueggeman et al. 1990). In the Pacific, minke whales are

usually seen over continental shelves (Brueggeman et al.

1990). In the extreme north, minke whales are believed to be

migratory, but in inland waters of Washington and in central

California they appear to establish home ranges (Dorsey et al.

1990). Minke whales occur year-round in California (Dohl et

al. 1983; Forney et al. 1995; Barlow 1997) and in the Gulf of

California (Tershy et al. 1990). Minke whales are present at

least in summer/fall along the Baja California peninsula

(Wade and Gerrodette 1993). Because the "resident" minke

whales from California to Washington appear behaviorally

distinct from migratory whales further north, minke whales in

coastal waters of California, Oregon, and Washington

(including Puget Sound) will be considered as a separate

stock. Minke whales in Alaskan waters are considered in a

separate stock assessment report.

POPULATION SIZE

No estimates have been made for the number of

minke whales in the entire North Pacific. The number of

minke whales is estimated as 631 (CV = 0.45) based on ship

surveys in 1991, 1993, and 1996 off California and in 1996

off Oregon and Washington (Barlow 1997). Forney et al. (1995) estimate at total of 73 (CV=0.62) in California based

on an aerial survey, but this estimate is negatively biased because it excludes diving whales. In addition, Green et al.

(1992) report 4 sightings of minke whales in aerial surveys of Oregon and Washington, but they did not estimate

population size for that area. Two minke whales were seen during 1996 aerial surveys in Washington and British

Columbia inland waters (Calambokidis et al. 1997), but no abundance estimates are available for this area.

Minimum Population Estimate

The minimum population estimate for minke whales is taken as the lower 20th percentile of the log-normal

distribution of abundance estimated from the summer/fall ship survey in California, Oregon, and Washington waters

(Barlow 1997 ) or approximately 440. More sophisticated methods of estimating minimum population size would be

available if a correction factor (and associated variance) were available to correct the aerial survey estimates for missed

animals.
175

Current Population Trend

There are no data on trends in minke whale abundance in waters of California, Oregon and/or Washington.

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

There are no estimates of the growth rate of minke whale populations in the North Pacific (Best 1993).

POTENTIAL BIOLOGICAL REMOVAL

The potential biological removal (PBR) level for this stock is calculated as the minimum population size (440)

times one half the default maximum net growth rate for cetaceans (1⁄2 of 4%) times a recovery factor of 0.5 (for a stock

of unknown status), resulting in a PBR of 4.4.

HUMAN CAUSED MORTALITY

Historic Whaling 

The estimated take of western North Pacific minke whales by commercial whalers was approximately 31,000

from 1930 to 1987 (C. Allison, IWC, pers. comm.). Minke whales were not harvested commercially in the eastern North

Pacific: none were reported taken by shore-based whaling stations in central or northern California between 1919 and

1926 (Clapham et al. 1997) or between 1958 and 1965 (Rice 1974). Reported aboriginal takes of minke whales in

Alaska totaled 7 between 1930 and 1987 (C. Allison, IWC, pers. comm.).

Table 1. Summary of available information on the incidental mortality and injury of minke whales (CA/OR/WA stock)

for commercial fisheries that might take this species (Pierce et al. 1996; Julian 1997, Julian and Beeson 1998; Cameron

and Forney 1999). Mean annual takes are based on 1994-98 data unless noted otherwise.

Fishery Name Year(s) Data Type

Percent Observer

Coverage

Observed

Mortality

Estimated

Mortality (CV in

parentheses)

Mean

Annual Takes

(CV in parentheses)

CA/OR thresher

shark/swordfish drift

gillnet fishery

1994

1995

1996

1997

1998

observer

data

17.9%

15.6%

12.4%

23.0%

20.0%

1

0

1

0

0

6 (0.91)

0

12 (0.96)

0

0

0

1

WA Puget Sound Region

salmon drift gillnet fishery

 (areas 7 and 7A)

1994 observer

data

7% 0 0 0

CA angel shark/halibut

and other species large

mesh (>3.5") set gillnet

fishery

1991-94 observer

data

10-18% 0,0,0,0 0,0,0,0 n/a 

Total annual takes 0.0

1

 Only 1997-98 mortality estimates are included in the average because of gear modifications implemented within the fishery as part of a 1997 Take

Reduction Plan. Gear modifications included the use of net extenders and acoustic warning devices (pingers).

Fishery Information

Minke whales may occasionally be caught in coastal set gillnets off California, in salmon drift gillnet in Puget

Sound, Washington, and in offshore drift gillnets off California and Oregon. A summary of known fishery mortality

and injury for this stock of minke whales is given in Table 1. Detailed information on this fishery is provided in

Appendix 1. After the 1997 implementation of a Take Reduction Plan, which included skipper education workshops

and required the use of pingers and minimum 6-fathom extenders, overall cetacean entanglement rates in the drift gillnet

fishery dropped considerably (Barlow and Cameron 1999). Because of the changes in this fishery after implementation

of the Take Reduction Plan, mean annual takes for this fishery (Table 1) are based only on 1997-98 data. This results

in an average estimate of zero minke whales taken annually. Total fishery mortality for minke whales was not estimated

for the 1980-86 California Department of Fish and Game observer program for the drift gillnet fishery, but based on

the 2 observed deaths in 1% of the total sets, the total mortality during this time may have been on the order of 200
176

minke whales or 40 per year.

Drift gillnet fisheries for swordfish and sharks exist along the entire Pacific coast of Baja California and may

take animals from the same population. Quantitative data are available only for the Mexican swordfish drift gillnet

fishery, which uses vessels, gear, and operational procedures similar to those in the U.S. drift gillnet fishery, although

nets may be up to 4.5 km long (Holts and Sosa-Nishizaki 1998). The fleet increased from two vessels in 1986 to 31

vessels in 1993 (Holts and Sosa-Nishizaki 1998). The total number of sets in this fishery in 1992 can be estimated from

data provided by these authors to be approximately 2,700, with an observed rate of marine mammal bycatch of 0.13

animals per set (10 marine mammals in 77 observed sets; Sosa-Nishizaki et al. 1993). This overall mortality rate is

similar to that observed in California driftnet fisheries during 1990-95 (0.14 marine mammals per set; Julian and Beeson

1998), but species-specific information is not available for the Mexican fisheries. There are currently efforts underway

to convert the Mexican swordfish driftnet fishery to a longline fishery (D. Holts, pers. comm.). 

Ship Strikes

Ship strikes were implicated in the death of one minke whale in 1977 (J. Heyning and J. Cordaro, pers. comm.).

The reported minke whale mortality due to ship strikes is zero for the period 1994-98. Additional mortality from ship

strikes probably goes unreported because the whales do not strand or, if they do, they do not always have obvious signs

of trauma.

STATUS OF STOCK

There were no known commercial whaling harvests of minke whales from Baja California to Washington.

Minke whales are not listed as "endangered" under the Endangered Species Act and are not considered "depleted" under

the MMPA. The greatest uncertainty in their status is whether entanglement in commercial gillnets and ship strikes

could have reduced this relatively small population. Because of this, the status of the west-coast stock should be

considered "unknown". The annual mortality due to fisheries (0.0/yr) and ship strikes (0.0/yr) is less than the calculated

PBR for this stock (4.4), so they are not considered a "strategic" stock under the MMPA. Fishery mortality is less than

10% of the PBR; therefore, total fishery mortality is approaching zero mortality and serious injury rate. There is no

information on trends in the abundance of this stock. The increasing levels of anthropogenic noise in the world’s oceans

has been suggested to be a habitat concern for whales, particularly for baleen whales that may communicate using lowfrequency sound.

REFERENCES

Barlow, J. 1997. Preliminary estimates of cetacean abundance off California, Oregon, and Washington based on a

1996 ship survey and comparisons of passing and closing modes. Admin. Rep. LJ-97-11. Southwest Fisheries

Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA 92038. 25 pp.

Barlow, J., K. A. Forney, P. S. Hill, R. L. Brownell, Jr., J. V. Carretta, D. P. DeMaster, F. Julian, M. S. Lowry, T.

Ragen, and R. R. Reeves. 1997. U.S. Pacific Marine Mammal Stock Assessments: 1996. U.S. Dep. Commer.

NOAA Tech. Memo. NMFS-SWFSC-248. 223 pp.

Barlow, J., R. W. Baird, J. E. Heyning, K. Wynne, A. M. Manville, II, L. F. Lowry, D. Hanan, J. Sease, and V. N.

Burkanov. 1994. A review of cetacean and pinniped mortality in coastal fisheries along the west coast of the

U.S. and Canada and the east coast of the Russian Federation. Rep. Int. Whal. Commn, Special Issue 15:405-

425.

Barlow, J. and G. A. Cameron. 1999. Field experiments show that acoustic pingers reduce marine mammal bycatch

in the California drift gillnet fishery. Report SC/51/SM2 to the Scientific Committee of the International

Whaling Commission, May 1999. 20pp.

Best, P. B. 1993. Increase rates in severely depleted stocks of baleen whales. ICES J. Mar. Sci. 50:169-186.

Brueggeman, J. J., G. A. Green, K. C. Balcomb, C. E. Bowlby, R. A. Grotefendt, K. T. Briggs, M. L. Bonnell, R. G.

Ford, D. H. Varoujean, D. Heinemann, and D. G. Chapman. 1990. Oregon-Washington Marine Mammal and

Seabird Survey: Information synthesis and hypothesis formulation. U.S. Department of the Interior, OCS

Study MMS 89-0030.

Calambokidis, J., S. Osmek, and J. L. Laake. 1997. Aerial surveys for marine mammals in Washington and British

Columbia inside waters. Final Contract Report to National Marine Mammal Laboratory, Seattle, WA. 

Cameron, G. A. and K. A. Forney. 1999. Preliminary estimates of cetacean mortality in the California gillnet fisheries
177

for 1997 and 1998. Paper SC/51/O4 presented to the International Whaling Commission, May 1999

(unpublished). 14 pp.

Dohl, T. P., R. C. Guess, M. L. Duman, and R. C. Helm. 1983. Cetaceans of central and northern California, 1980-83:

Status, abundance, and distribution. Final Report to the Minerals Management Service, Contract No. 14-12-

0001-29090. 284p.

Donovan, G. P. 1991. A review of IWC stock boundaries. Rept. Int. Whal. Commn., Special Issue 13:39-68.

Dorsey, E. M., S. J. Stern, A. R. Hoelzel, and J. Jacobsen. 1990. Minke whale (Balaenoptera acutorostrata) from the

west coast of North America: individual recognition and small-scale site fidelity. Rept. Int. Whal. Commn.,

Special Issue 12:357-368.

Forney, K. A., J. Barlow, and J. V. Carretta. 1995. The abundance of cetaceans in California waters. Part II: Aerial

surveys in winter and spring of 1991 and 1992. Fish. Bull. 93:15-26.

Green, G. A., J. J. Brueggeman, R. A. Grotefendt, C. E. Bowlby, M. L. Bonnell, K. C. Balcomb, III. 1992. Cetacean

distribution and abundance off Oregon and Washington, 1989-1990. Ch. 1 In: J. J. Brueggeman (ed.). Oregon

andWashingtonMarineMammal and SeabirdSurveys. Minerals Management Service Contract Report 14-12-

0001-30426.

Hanan, D. A. 1986. California Department of Fish and Game coastal marine mammal study, annual report for the

period July 1, 1983 - June 30, 1984. Admin. Rept. LJ-86-16. Southwest Fisheries Science Center, National

Marine Fisheries Service, P.O. Box 271, La Jolla, CA. 55 pp.

Hanan, D. A., D. B. Holts, and A. L. Coan, Jr. 1993. The California drift gill net fishery for sharks and swordfish,

1981-82 through 1990-91. Calif. Dept. Fish and Game Fish. Bull. No. 175. 95 pp.

Heyning, J. E., and T. D. Lewis. 1990. Fisheries interactions involving baleen whales off southern California. Rep.

Int. Whal. Commn. 40:427-431.

Holts, D. Southwest Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA 92038.

Holts, D. and O. Sosa-Nishizaki. 1998. Swordfish, Xiphias gladius, fisheries of the eastern North Pacific Ocean. In:

I. Barrett, O. Sosa-Nishizaki and N. Bartoo (eds.). Biology and fisheries of swordfish, Xiphias gladius. Papers

from the International Symposium on Pacific Swordfish, Ensenada Mexico, 11-14 December 1994. U.S. Dep.

Commer., NOAA Tech. Rep. NMFS 142, 276 p.

Julian, F. 1997. Cetacean mortality in the California gill net fisheries: preliminary estimates for 1996. Paper

SC/49/SM2 presented to the International Whaling Commission, September 1997 (unpublished). 13 pp.

Julian, F. and M. Beeson. 1998. Estimates for marine mammal, turtle, and seabird mortality for two California gillnet

fisheries: 1990-95. Fish. Bull. 96:271-284.

Leatherwood, S., R. R. Reeves, W. F. Perrin, and W. E. Evans. 1982. Whales, dolphins, and porpoises of the eastern

North Pacific and adjacent Arctic waters: A guide to their identification. NOAA Technical Rept. NMFS

Circular 444. 245pp.

Pierce, D. J., M. Alexandersdottie, S. J. Jeffries, P. Erstad, W. Beattie, and A. Chapman. 1996. Interactions of marbled

murrelets and marine mammals with the 1994 Puget Sound sockeye gill net fishery. Final Report, Wash. Dept.

Fish and Wildlife, Olympia, WA. 21pp.

Rice, D. W. 1974. Whales and whale research in the eastern North Pacific. pp. 170-195 In: W. E. Schevill (ed.). The

Whale Problem: A Status Report. Harvard Press, Cambridge, MA.

Sosa-Nishizaki, O., R. De la Rosa Pacheco, R. Castro Longoria, M. Grijalva Chon, and J. De la Rosa Velez. 1993.

Estudio biologico pesquero del pez (Xiphias gladius) y otras especies de picudos (marlins y pez vela). Rep.

Int. CICESE, CTECT9306.

Tershy, B. R., D. Breese, and C. S. Strong. 1990. Abundance, seasonal distribution and population composition of

balaenopterid whales in the Canal de Ballenas, Gulf of California, Mexico. Rept. Int. Whal. Commn., Special

Issue 12:369-375.

Von Saunder, A. and J. Barlow. 1999. A report of the Oregon, California and Washington Line-transect Experiment

(ORCAWALE) conducted in west coast waters during summer/fall 1996. U.S. Dep. Commer. NOAA Tech.

Memo. NMFS-SWFSC-264. 40 pp. 

Wade, P. R. and T. Gerrodette. 1993. Estimates of cetacean abundance and distribution in the eastern tropical Pacific.

Rept. Int. Whal. Commn. 43:477-493.
178

Figure 1. Rough-toothed dolphin sighting locations during

1993-98 aerial surveys within about 25 nmi of the main

Hawaiian Islands (see Appendix 2 for details on timing and

location of survey effort). Outer line indicates approximate

boundary of survey area.

Revised 12/15/2000

ROUGH-TOOTHED DOLPHIN (Steno bredanensis): Hawaiian Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

Rough-toothed dolphins are found

throughout the world in tropical and warmtemperate waters (Miyazaki and Perrin 1994). They

are present around all the main Hawaiian islands

(Shallenberger 1981; Tomich 1986) and have been

observed at least as far northwest as French Frigate

Shoals (Nitta and Henderson 1993). Recent sighting

locations around the main Hawaiian Islands are

shown in Figure 1. Five strandings have been

reported from Maui, Oahu, and the island of Hawaii

(Nitta 1991). Nothing is known about stock

structure for this species in the North Pacific. For

the Marine Mammal Protection Act (MMPA) stock

assessment reports, there is a single Pacific

management stock including only animals found

within the U.S. Exclusive Economic Zone of the

Hawaiian Islands.

POPULATION SIZE

A population estimate for this species has

been made in the eastern tropical Pacific (Wade and

Gerrodette 1993), but it is not known whether these

animals are part of the same population that occurs

around the Hawaiian Islands. As part of the Marine Mammal Research Program of the Acoustic Thermometry of Ocean

Climate (ATOC) study, a total of twelve aerial surveys were conducted within about 25 nmi of the main Hawaiian

Islands in 1993, 1995 and 1998. An abundance estimate of 123 (CV=0.63) rough-toothed dolphins was recently

calculated from the combined survey data (Mobley et al. 2000). This abundance underestimates the total number of

rough-toothed dolphins within the U.S. EEZ off Hawaii, because areas around the Northwest Hawaiian Islands (NWHI)

and beyond 25 nautical miles from the main islands were not surveyed.

Minimum Population Estimate

The log-normal 20th percentile of the combined 1993-98 abundance estimate is 76 rough-toothed dolphins.

As with the best abundance estimate above, this includes only areas within about 25 nmi of the main Hawaiian Islands

and is therefore an underestimate.

Current Population Trend

No data are available on current population trend.

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

No data are available on current or maximum net productivity rate.

POTENTIAL BIOLOGICAL REMOVAL

 The potential biological removal (PBR) level for this stock is calculated as the minimum population size (76)

times one half the default maximum net growth rate for cetaceans (1⁄2 of 4%) times a recovery factor of 0.50 (for a

species of unknown status with no known fishery mortality; Wade and Angliss 1997), resulting in a PBR of 0.8 roughtoothed dolphins per year. 
179

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Fishery Information

No estimate of annual human-caused mortality and serious injury is available, as no mortality of this species

has been documented in Hawaiian fisheries (Nitta and Henderson 1993). However, mortality of other cetacean species

has been observed in Hawaiian fisheries, and the gear types used in these fisheries are responsible for marine mammal

mortality and serious injury in other fisheries throughout U.S. waters. Gillnets are used in Hawaiian waters and appear

to capture marine mammals wherever they are used, and float lines from lobster traps and longlines can be expected to

occasionally entangle whales (Perrin et al. 1994). 

Interactions with cetaceans have been reported for all Hawaiian pelagic fisheries, and some of these interactions

involved rough-toothed dolphins (Nitta and Henderson 1993). None were observed hooked in the Hawaiian longline

fishery between 1994 and 1998, with approximately 4.4% of all effort (measured as the number of hooks fished)

observed (Kleiber 1999). They are known to take bait and catch from Hawaiian sport and commercial fisheries operating

near the main islands and in a portion of the northwestern islands (Shallenberger 1981; Schlais 1984; Nitta and

Henderson 1993), and they have been specifically reported to interact with the day handline fishery for tuna (palu-ahi)

and the troll fishery for billfish and tuna (Schlais 1984; Nitta and Henderson 1993). Interaction rates between dolphins

and the NWHI bottomfish fishery have been estimated based on studies conducted in 1990-1993, indicating that an

average of 2.67 dolphin interactions, most likely involving bottlenose and rough-toothed dolphins, occurred for every

1000 fish brought on board (Kobayashi and Kawamoto 1995). Fishermen claim interactions with dolphins who steal

bait and catch are increasing. It is not known whether these interactions result in serious injury or mortality of dolphins.

Other Removals

At least 22 rough-toothed dolphins were live-captured in Hawaiian waters between 1963 and 1976

(Shallenberger 1981). 

STATUS OF STOCK

The status of rough-toothed dolphins in Hawaiian waters relative to OSP is unknown, and there are insufficient

data to evaluate trends in abundance. No habitat issues are known to be of concern for this species. They are not listed

as “threatened” or “endangered” under the Endangered Species Act (1973), nor as “depleted” under the MMPA.

Although information on rough-toothed dolphins in Hawaiian waters is limited, this stock would not be considered

strategic under the 1994 amendments to the MMPA given the absence of reported fisheries related mortality. However,

there is no systematic monitoring of gillnet fisheries that may take this species, and the potential effects of interactions

with the bottomfish fishery in the NWHI are not known. Insufficient information is available to determine whether the

total fishery mortality and serious injury for rough-toothed dolphins is insignificant and approaching zero mortality and

serious injury rate.

REFERENCES

Kleiber, P. 1999. Estimates of marine mammal takes in the Hawaiian longline fishery. (Unpublished). Southwest

Fisheries Science Center, NMFS, 2570 Dole St, Honolulu, HI, 96822-2396.

Kobayashi, D. R. and K. E. Kawamoto. 1995. Evaluation of shark, dolphin, and monk seal interactions with

Northwestern Hawaiian Island bottomfishing activity: a comparison of two time periods and an estimate of

economic impacts. Fisheries Research 23: 11-22.

Miyazaki, N. and W. F. Perrin. 1994. Rough-toothed dolphin Steno bredanensis (Lesson, 1828). In: S. H. Ridgway

and R. Harrison (eds.), Handbook of Marine Mammals, Vol.5: The First Book of Dolphins, pp. 1-21.

Academic Press, 416 pp.

Mobley, J. R. , Jr, S. S. Spitz, K. A. Forney, R. A. Grotefendt, and P. H. Forestall. 2000. Distribution and abundance

of odontocete species in Hawaiian waters: preliminary results of 1993-98 aerial surveys Admin. Rep. LJ-00-

14C. Southwest Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA

92038. 26 pp.

Nitta, E. 1991. The marine mammal stranding network for Hawaii: an overview. In: J.E. Reynolds III, D.K. Odell

(eds.), Marine Mammal Strandings in the United States, pp.56-62. NOAA Tech. Rep. NMFS 98, 157 pp.

Nitta, E. and J. R. Henderson. 1993. A review of interactions between Hawaii's fisheries and protected species. Mar.

Fish. Rev. 55(2):83-92.
180

Perrin, W.F., G. P. Donovan and J. Barlow. 1994. Gillnets and Cetaceans. Rep. Int. Whal. Commn., Special Issue 15,

629 pp.

Schlais, J.F. 1984. Thieving dolphins: A growing problem in Hawaii's fisheries. Sea Front. 30(5):293-298.

Shallenberger, E.W. 1981. The status of Hawaiian cetaceans. Final report to U.S. Marine Mammal Commission. MMC77/23, 79pp.

Tomich, P. Q. 1986. Mammals in Hawaii: A Synopsis and Notational Bibliography. Bishop Museum Press, Hawaii,

375 pp.

Wade, P. R. and R. P. Angliss. 1997. Guidelines for Assessing Marine Mammal Stocks: Report of the GAMMS

Workshop April 3-5, 1996, Seattle, Washington. U. S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-12.

93 pp.

Wade, P. R. and T. Gerrodette. 1993. Estimates of cetacean abundance and distribution in the eastern tropical Pacific.

Rep. Int. Whal. Commn. 43:477-493.
181

Figure 1. Sighting location for the single Risso’s dolphin seen

during 1993-98 aerial surveys within about 25 nmi of the main

Hawaiian Islands (see Appendix 2 for details on timing and

location of survey effort). Outer line indicates approximate

boundary of survey area.

Revised 12/15/2000

RISSO'S DOLPHIN (Grampus griseus): Hawaiian Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

Risso's dolphins are found in tropical to

warm-temperate waters worldwide (Kruse et al.

1999). They appear to be rare in Hawaiian waters

(Figure 1). Of three reported sightings of this

species by Shallenberger (1981), only one was

verified. There are four stranding records from the

main islands (Nitta 1991). Balcomb (1987) referred

to a sighting of a large herd off the Kona Coast in

February 1985. For the Marine Mammal Protection

Act (MMPA) stock assessment reports, Risso's

dolphins within the Pacific U.S. Exclusive

Economic Zone are divided into two discrete, noncontiguous areas: 1) Hawaiian waters (this report),

and 2) waters off California, Oregon and

Washington.

POPULATION SIZE

Population estimates have been made off

Japan (Miyashita 1993) and in the eastern tropical

Pacific (Wade and Gerrodette 1993), but it is not

known whether these animals are part of the same

population that occurs around the Hawaiian Islands.

As part of the Marine Mammal Research Program

of the Acoustic Thermometry of Ocean Climate (ATOC) study, a total of twelve aerial surveys were conducted within

about 25 nmi of the main Hawaiian Islands in 1993, 1995 and 1998 (Mobley et al. 2000). Only one sighting of a single

Risso’s dolphin was made, and therefore no meaningful abundance estimate could be calculated. Based on the locations

of interactions with the Hawaiian longline fishery (Figure 2), it is likely that Risso’s dolphins primarily occur in pelagic

waters tens to hundreds of miles from the main Hawaiian islands and are only occasionally found nearshore. 

Minimum Population Estimate

No data are available for a minimum population estimate.

Current Population Trend

No data are available on current population trend.

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

No data are available on current or maximum net productivity rate for Hawaiian animals.

POTENTIAL BIOLOGICAL REMOVAL

No PBR can be calculated for this species at this time.

HUMAN CAUSED MORTALITY AND SERIOUS INJURY

Fishery Information

No estimate of annual human-caused mortality and serious injury is available as there are no reports of direct

or incidental takes of Risso's dolphins in Hawaiian waters. However, mortality of other cetacean species has been

observed in Hawaiian fisheries, and the gear types used in these fisheries are responsible for marine mammal mortality

and serious injury in other fisheries throughout U.S. waters. Gillnets are used in Hawaiian waters and appear to capture

marine mammals wherever they are used, and float lines from lobster traps and longlines can be expected to occasionally
182

10 N 15 N 20 N 25 N 30 N 35 N 40 N

180 W 170 W 160 W 150 W 140 W

GG GGTT

UC

UW

GM

GG GG

SL

PC

UW

PC

UW

TT T. truncatus

GG G. griseus

SL S longirostris

PC P. crassidens

GM G. macrorhynchus

UC Cetacean, unident.

UW Whale, unident.

Figure 2. Locations of observed cetacean interactions in the

Hawaiian longline fishery, 1994-98 (modified from Kleiber 1999).

Dashed line is the U.S. Exclusive Economic Zone (EEZ); GG =

Risso’s dolphin.

entangle whales (Perrin et al. 1994).

Interactions with cetaceans have been

reported for all Hawaiian pelagic fisheries (Nitta

and Henderson 1993), and some of these

interactions involved Risso’s dolphins in waters

outside the U.S. EEZ. Four Risso’s dolphins

were observed hooked in the Hawaiian longline

fishery between 1994 and 1998, with

approximately 4.4% of all effort (measured as

the number of hooks fished) observed. This

interaction rate extrapolates to a total 5-year

estimate of 90 (95% CI = 27-213) Risso’s

dolphins, or an average of 18 per year (Kleiber

1999). Three of the observed Risso’s dolphins

were reported to have been hooked in the mouth

or to have ingested the hook, and they were

released with hook and line still attached.

Following the guidelines of a 1997 Serious

Injury Workshop (Angliss and DeMaster 1998),

these three animals have been considered

seriously injured (defined under the MMPA as

likely to result in mortality). The fourth animal

was hooked in an unknown location and swam

normally, but was released with 20m of trailing

line and a light stick. Because a substantial length of line was still attached when the animal was released, this animal

is likely to have sustained serious injury. Reports for other odontocetes indicate they may also become hooked in other

parts of their body, and that they may occasionally become entangled in the fishing line. 

Interaction rates between dolphins and the NWHI bottomfish fishery have been estimated based on studies

conducted in 1990-1993, indicating that an average of 2.67 dolphin interactions, most likely involving bottlenose and

rough-toothed dolphins, occurred for every 1000 fish brought on board (Kobayashi and Kawamoto 1995). Fishermen

claim interactions with dolphins who steal bait and catch are increasing. It is not known whether these interactions result

in serious injury or mortality of dolphins, nor whether Risso’s dolphins are involved.

STATUS OF STOCK

The status of Risso's dolphins in Hawaiian waters relative to OSP is unknown, and there are insufficient data

to evaluate trends in abundance. No habitat issues are known to be of concern for this species. They are not listed as

“threatened” or “endangered” under the Endangered Species Act (1973), nor as “depleted” under the MMPA. Although

information on Risso's dolphins in Hawaiian waters is limited, this stock would not be considered strategic under the

1994 amendments to the MMPA given the absence of reported fisheries related mortality within the U.S. EEZ and the

species’ apparent offshore distribution. The potential effect of injuries sustained by Risso’s dolphins in the Hawaiian

longline fishery in international waters is not known. Insufficient information is available to determine whether the total

fishery mortality and serious injury for Risso’s dolphins is insignificant and approaching zero mortality and serious

injury rate.

REFERENCES

Angliss, R. P. and D. P. DeMaster. 1998. Differentiating Serious and Non-Serious Injury of Marine Mammals Taken

Incidental to Commercial Fishing Operations: Report of the Serious Injury Workshop 1-2 April 1997, Silver

Spring, Maryland. U. S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-13. 48 pp.

Balcomb, K. C., III. 1987. The Whales of Hawaii. Marine Mammal Fund, 99 pp.

Kruse, S. K., D. K. Caldwell, and M. C. Caldwell. 1999. Risso's dolphin Grampus griseus. Pages 183-212 In: S. H.

Ridgway and R. Harrison (eds.), Handbook of Marine Mammals, Volume 6. Academic Press, San Diego.
183

Kleiber, P. 1999. Estimates of marine mammal takes in the Hawaiian longline fishery. (Unpublished). Southwest

Fisheries Science Center, NMFS, 2570 Dole St, Honolulu, HI, 96822-2396.

Kobayashi, D. R. and K. E. Kawamoto. 1995. Evaluation of shark, dolphin, and monk seal interactions with

Northwestern Hawaiian Island bottomfishing activity: a comparison of two time periods and an estimate of

economic impacts. Fisheries Research 23: 11-22.

Miyashita, T. 1993. Abundance of dolphin stocks in the western North Pacific taken by the Japanese drive fishery.

Rep. Int. Whal. Commn. 43:417-437.

Mobley, J. R. , Jr, S. S. Spitz, K. A. Forney, R. A. Grotefendt, and P. H. Forestall. 2000. Distribution and abundance

of odontocete species in Hawaiian waters: preliminary results of 1993-98 aerial surveys Admin. Rep. LJ-00-

14C. Southwest Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA

92038. 26 pp.

Nitta, E. 1991. The marine mammal stranding network for Hawaii: an overview. In: J.E. Reynolds III, D.K. Odell

(eds.), Marine Mammal Strandings in the United States, pp.56-62. NOAA Tech. Rep. NMFS 98, 157 pp.

Nitta, E. and J. R. Henderson. 1993. A review of interactions between Hawaii's fisheries and protected species. Mar.

Fish. Rev. 55(2):83-92.

Perrin, W.F., G. P. Donovan and J. Barlow. 1994. Gillnets and Cetaceans. Rep. Int. Whal. Commn., Special Issue 15,

629 pp.

Shallenberger, E.W. 1981. The status of Hawaiian cetaceans. Final report to U.S. Marine Mammal Commission. MMC77/23, 79pp.

Wade, P. R. and T. Gerrodette. 1993. Estimates of cetacean abundance and distribution in the eastern tropical Pacific.

Rep. Int. Whal. Commn. 43:477-493.
184

Figure 1. Bottlenose dolphin sighting locations during 1993-98

aerial surveys within about 25 nmi of the main Hawaiian Islands

(see Appendix 2 for details on timing and location of survey

effort). Outer line indicates approximate boundary of survey

area.

Revised 12/15/2000

BOTTLENOSE DOLPHIN (Tursiops truncatus): Hawaiian Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

Bottlenose dolphins are widely distributed

throughout the world in tropical and warmtemperate waters. The species is primarily coastal

in much of its range, but there are populations in

some offshore deepwater areas as well. Separate

offshore and coastal forms have been identified

along continental coasts in several areas (Ross and

Cockcroft 1990; Van Waerebeek et al. 1990), and

similar onshore-offshore forms may exist in

Hawaiian waters. 

Although only three strandings have been

reported (Nitta 1991), bottlenose dolphins are

common throughout the Hawaiian Islands, from the

island of Hawaii to Kure Atoll (Shallenberger

1981). Recent sighting locations for systematic

aerial surveys within about 25nmi of the main

Hawaiian Islands in 1993-98 are shown in Figure 1.

In the Northwestern Hawaiian Islands, they are

found primarily in relatively shallow inshore waters

(Rice 1960). In the main Hawaiian Islands, they are

found in both shallow inshore waters and deep

channels between islands. 

In their analysis of sightings of bottlenose

dolphins in the eastern tropical Pacific (ETP), Scott and Chivers (1990) noted that there was a large hiatus between the

westernmost sightings and the Hawaiian Islands. These data suggest that the bottlenose dolphins in Hawaiian waters

belong to a separate stock from those in the ETP. For the Marine Mammal Protection Act (MMPA) stock assessment

reports, bottlenose dolphins within the Pacific U.S. Exclusive Economic Zone are divided into three stocks: 1) Hawaiian

stock (this report), 2) California, Oregon and Washington offshore stock, and 3) California coastal stock.

POPULATION SIZE

Population estimates have been made in Japanese waters (Miyashita 1993) and the eastern tropical Pacific

(Wade and Gerrodette 1993), but it is not known whether these animals are part of the same population that occurs

around the Hawaiian Islands. As part of the Marine Mammal Research Program of the Acoustic Thermometry of

Ocean Climate (ATOC) study, a total of twelve aerial surveys were conducted within about 25 nmi of the main Hawaiian

Islands in 1993, 1995 and 1998. An abundance estimate of 743 (CV=0.56) bottlenose dolphins was recently calculated

from the combined survey data (Mobley et al. 2000). This abundance underestimates the total number of bottlenose

dolphins within the U.S. EEZ off Hawaii, because areas around the Northwest Hawaiian Islands (NWHI) and beyond

25 nautical miles from the main islands were not surveyed.

Minimum Population Estimate

The log-normal 20th percentile of the combined 1993-98 abundance estimate is 479 bottlenose dolphins. As

with the best abundance estimate above, this includes only areas within about 25 nmi of the main Hawaiian Islands and

is therefore an underestimate. 

Current Population Trend

No data are available on current population trend.
185

10 N 15 N 20 N 25 N 30 N 35 N 40 N

180 W 170 W 160 W 150 W 140 W

GG GGTT

UC

UW

GM

GG GG

SL

PC

UW

PC

UW

TT T. truncatus

GG G. griseus

SL S longirostris

PC P. crassidens

GM G. macrorhynchus

UC Cetacean, unident.

UW Whale, unident.

Figure 2. Locations of observed cetacean interactions in the

Hawaiian longline fishery, 1994-98 (modified from Kleiber 1999).

Dashed line is the U.S. Exclusive Economic Zone (EEZ); TT =

bottlenose dolphin.

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

No data are available on current or maximum net productivity rate for this species in Hawaiian waters.

POTENTIAL BIOLOGICAL REMOVAL

The potential biological removal (PBR) level for this stock is calculated as the minimum population size (479)

times one half the default maximum net growth rate for cetaceans (1⁄2 of 4%) times a recovery factor of 0.50 (for a

species of unknown status with no estimated fishery mortality; Wade and Angliss 1997), resulting in a PBR of 4.8

bottlenose dolphins per year. 

HUMAN CAUSED MORTALITY AND SERIOUS INJURY

Fishery Information

Although some mortality of bottlenose

dolphins has been observed in inshore gillnets,

no estimate of annual human-caused mortality

and serious injury is available. The gear types

used in Hawaiian fisheries are responsible for

marine mammal mortality and serious injury in

other fisheries throughout U.S. waters. Gillnets

are used in Hawaiian waters and appear to

capture marine mammals wherever they are used,

and float lines from lobster traps and longlines

can be expected to occasionally entangle whales

(Perrin et al. 1994).

Interactions with cetaceans have been

reported for all Hawaiian pelagic fisheries, and

many of these interactions involved bottlenose

dolphins (Nitta and Henderson 1993). One

bottlenose dolphin was observed hooked in the

Hawaiian longline fishery between 1994 and

1998 in waters outside the U.S. EEZ (Figure 2),

with approximately 4.4% of all effort (measured

as the number of hooks fished) observed. This

interaction rate extrapolates to a total 5-year

estimate of 23 (95% CI = 1-108) bottlenose dolphins, or an average of 4.6 interactions per year (Kleiber 1999). The

single observed bottlenose dolphin was reported to have ingested the hook. Following the guidelines of a 1997 Serious

Injury Workshop (Angliss and DeMaster 1998), this animal has been considered seriously injured (defined under the

MMPA as likely to result in mortality). Reports for other odontocetes indicate they may also become hooked in the

mouth or other part of their body, and that they may occasionally become entangled in the fishing line.

Bottlenose dolphins are one of the species commonly reported to take bait and catch from several Hawaiian

sport and commercial fisheries (Nitta and Henderson 1993; Schlais 1984). Observations of bottlenose dolphins taking

bait or catch have also been made in the day handline fishery (palu-ahi) for tuna, the handline fishery for mackerel scad,

the troll fishery for billfish and tuna, and the inshore set gillnet fishery (Nitta and Henderson 1993). Nitta and

Henderson (1993) indicated that bottlenose dolphins remove bait and catch from handlines used to catch bottomfish off

the island of Hawaii and Kaula Island and on several banks of the Northwestern Hawaiian Islands. Fishermen claim

interactions with dolphins who steal bait and catch are increasing. Interaction rates between dolphins and the NWHI

bottomfish fishery have been estimated based on studies conducted in 1990-1993, indicating that an average of 2.67

dolphin interactions, most likely involving bottlenose and rough-toothed dolphins, occurred for every 1000 fish brought

on board (Kobayashi and Kawamoto 1995). It is not known whether these interactions result in serious injury or

mortality of dolphins. Beginning in the early 1970s the National Marine Fisheries Service received reports of fishermen

shooting at bottlenose dolphins to deter them from taking fish catches (Nitta and Henderson 1993). Nitta and Henderson

(1993) also reported that one bottlenose dolphin calf was removed from small-mesh set gillnet off Maui in 1991 and

expressed surprise that bottlenose dolphins are "rarely reported entangled or raiding set gill nets in Hawaii," considering
186

that they so often remove fish from fishing lines.

Other Removals

At least 36 bottlenose dolphins were live-captured in Hawaiian waters between 1963 and 1981 (Shallenberger

1981). The main capture area was around Oahu. One juvenile bottlenose dolphin was entangled in a mooring line and

stranded dead along the coast of Maui in 1998 (H. Bernard, pers. comm.).

STATUS OF STOCK

The status of bottlenose dolphins in Hawaiian waters relative to OSP is unknown, and there are insufficient

data to evaluate trends in abundance. No habitat issues are known to be of concern for this species. They are not listed

as “threatened” or “endangered” under the Endangered Species Act (1973), nor as “depleted” under the MMPA.

Although information on bottlenose dolphins in Hawaiian waters is limited, this stock would not be considered strategic

under the 1994 amendments to the MMPA given the absence of reported fisheries related mortality within the U.S. EEZ.

However, there is no systematic monitoring of gillnet fisheries that may take this species, and the potential effects of

interactions with the Hawaiian longline fishery in international waters or the bottomfish fishery in the NWHI are not

known. Insufficient information is available to determine whether the total fishery mortality and serious injury for

bottlenose dolphins is insignificant and approaching zero mortality and serious injury rate.

REFERENCES

Bernard, H. Hawai'i Wildlife Fund, P.O. Box 637, Paia, HI 96779.

Kleiber, P. 1999. Estimates of marine mammal takes in the Hawaiian longline fishery. (Unpublished). Southwest

Fisheries Science Center, NMFS, 2570 Dole St, Honolulu, HI, 96822-2396.

Kobayashi, D. R. and K. E. Kawamoto. 1995. Evaluation of shark, dolphin, and monk seal interactions with

Northwestern Hawaiian Island bottomfishing activity: a comparison of two time periods and an estimate of

economic impacts. Fisheries Research 23: 11-22.

Miyashita, T. 1993. Abundance of dolphin stocks in the western North Pacific taken by the Japanese drive fishery.

Rep. Int. Whal. Commn. 43:417-437.

Mobley, J. R. , Jr, S. S. Spitz, K. A. Forney, R. A. Grotefendt, and P. H. Forestall. 2000. Distribution and abundance

of odontocete species in Hawaiian waters: preliminary results of 1993-98 aerial surveys Admin. Rep. LJ-00-

14C. Southwest Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA

92038. 26 pp.

Nitta, E. 1991. The marine mammal stranding network for Hawaii: an overview. In: J.E. Reynolds III, D.K. Odell

(eds.), Marine Mammal Strandings in the United States, pp.56-62. NOAA Tech. Rep. NMFS 98, 157 pp.

Nitta, E. and J. R. Henderson. 1993. A review of interactions between Hawaii's fisheries and protected species. Mar.

Fish. Rev. 55(2):83-92.

Perrin, W.F., G. P. Donovan and J. Barlow. 1994. Gillnets and Cetaceans. Rep. Int. Whal. Commn., Special Issue 15,

629 pp.

Rice, D. W. 1960. Distribution of the bottle-nosed dolphin in the leeward Hawaiian Islands. J. Mamm. 41:407-408.

Ross, G.J.B. and V. G. Cockcroft. 1990. Comments on Australian bottlenose dolphins and the taxonomic status of

Tursiops aduncus (Ehrenberg, 1832). In: The Bottlenose Dolphin (eds. S. Leatherwood and R. Reeves). pp.

101-128. Academic Press, 653pp. 

Schlais, J.F. 1984. Thieving dolphins: A growing problem in Hawaii's fisheries. Sea Front. 30(5):293-298.

Scott, M. D. and S. J. Chivers. 1990. Distribution and herd structure of bottlenose dolphins in the eastern tropical

Pacific Ocean. In: The Bottlenose Dolphin (eds. S. Leatherwood and R. Reeves). pp. 387-402. Academic

Press, 653pp. 

Shallenberger, E.W. 1981. The status of Hawaiian cetaceans. Final report to U.S. Marine Mammal Commission. MMC77/23, 79pp.

Van Waerebeek, K., J. C. Reyes, A. J. Read, and J. S. McKinnon. 1990. Preliminary observations of bottlenose

dolphins from the Pacific coast of South America. In: The Bottlenose Dolphin (eds. S. Leatherwood and R.

Reeves). pp. 143-154. Academic Press, 653 pp. 

Wade, P. R. and R. P. Angliss. 1997. Guidelines for Assessing Marine Mammal Stocks: Report of the GAMMS

Workshop April 3-5, 1996, Seattle, Washington. U. S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-12.

93 pp.
187

Wade, P. R. and T. Gerrodette. 1993. Estimates of cetacean abundance and distribution in the eastern tropical Pacific.

Rep. Int. Whal. Commn. 43:477-493.
188

Figure 1. Pantropical spotted dolphin sighting locations during

1993-98 aerial surveys within about 25 nmi of the main

Hawaiian Islands (see Appendix 2 for details on timing and

location of survey effort). Outer line indicates approximate

boundary of survey area.

Revised 12/15/2000

PANTROPICAL SPOTTED DOLPHIN (Stenella attenuata): Hawaiian Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

Pantropical spotted dolphins are primarily

found in tropical and subtropical waters worldwide

(Perrin and Hohn 1994). Much of what is known

about the species in the North Pacific has been

learned from specimens obtained in the large

directed fishery in Japan and in the eastern tropical

Pacific (ETP) tuna purse-seine fishery (Perrin and

Hohn 1994). These dolphins are common and

abundant throughout the Hawaiian archipelago,

particularly in channels between islands, over

offshore banks (e.g. Penguin Banks), and off the lee

shores of the islands (see Shallenberger 1981).

Recent sighting locations around the main Hawaiian

Islands are shown in Figure 1. Nitta (1991) only

documented three strandings of this species in

Hawaii. Morphological differences and distribution

patterns have been used to establish that the spotted

dolphins around Hawaii belong to a stock that is

distinct from those in the ETP (Perrin 1975; Dizon

et al. 1994; Perrin et al. 1994b). Their possible

affinities with other stocks elsewhere in the Pacific

have not been investigated. For the Marine

Mammal Protection Act (MMPA) stock assessment

reports, there is a single Pacific management stock including only animals found within the U.S. Exclusive Economic

Zone of the Hawaiian Islands. Spotted dolphins involved in eastern tropical Pacific tuna purse-seine fisheries are

managed separately under the MMPA.

POPULATION SIZE

Population estimates are available for Japanese waters (Miyashita 1993) and the eastern tropical Pacific (Wade

and Gerrodette 1993). As part of the Marine Mammal Research Program of the Acoustic Thermometry of Ocean

Climate (ATOC) study, a total of twelve aerial surveys were conducted within about 25 nmi of the main Hawaiian

Islands in 1993, 1995 and 1998. An abundance estimate of 2,928 (CV=0.45) pantropical spotted dolphins was recently

calculated from the combined survey data (Mobley et al. 2000). This abundance underestimates the total number of

pantropical spotted dolphins within the U.S. EEZ off Hawaii, because areas around the Northwest Hawaiian Islands

(NWHI) and beyond 25 nautical miles from the main islands were not surveyed.

Minimum Population Estimate

The log-normal 20th percentile of the combined 1993-98 abundance estimate is 2,040 pantropical spotted

dolphins. As with the best abundance estimate above, this includes only areas within about 25 nmi of the main Hawaiian

Islands and is therefore an underestimate. 

Current Population Trend

No data are available on current population trend.

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

No data are available on current or maximum net productivity rate.
189

POTENTIAL BIOLOGICAL REMOVAL

The potential biological removal (PBR) level for this stock is calculated as the minimum population size (2,040)

times one half the default maximum net growth rate for cetaceans (1⁄2 of 4%) times a recovery factor of 0.50 (for a

species of unknown status with no known fishery mortality; Wade and Angliss 1997), resulting in a PBR of 20

pantropical spotted dolphins per year.

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Fishery Information

No estimate of annual human-caused mortality and serious injury is available as there are no reports of direct

or incidental takes of pantropical spotted dolphins in Hawaiian waters (Nitta and Henderson 1993). However, mortality

of other cetacean species has been observed in Hawaiian fisheries, and the gear types used in these fisheries are

responsible for marine mammal mortality and serious injury in other fisheries throughout U.S. waters. Gillnets are used

in Hawaiian waters and appear to capture marine mammals wherever they are used, and float lines from lobster traps

and longlines can be expected to occasionally entangle whales (Perrin et al. 1994a).

Interactions with cetaceans have been reported for all Hawaiian pelagic fisheries (Nitta and Henderson 1993),

but no interactions with pantropical spotted dolphins have been documented. None were observed hooked in the

Hawaiian longline fishery between 1994 and 1998, with approximately 4.4% of all effort (measured as the number of

hooks fished) observed (Kleiber 1999). Interaction rates between dolphins and the NWHI bottomfish fishery have been

estimated based on studies conducted in 1990-1993, indicating that an average of 2.67 dolphin interactions, most likely

involving bottlenose and rough-toothed dolphins, occurred for every 1000 fish brought on board (Kobayashi and

Kawamoto 1995). Fishermen claim interactions with dolphins who steal bait and catch are increasing. It is not known

whether these interactions result in serious injury or mortality of dolphins, nor whether pantropical spotted dolphins are

involved.

Other Removals

At least 52 pantropical spotted dolphins were live-captured in Hawaii between 1963 and 1978 (Shallenberger

1981).

STATUS OF STOCK

The status of pantropical spotted dolphins in Hawaiian waters relative to OSP is unknown, and there are

insufficient data to evaluate trends in abundance. No habitat issues are known to be of concern for this species. They

are not listed as “threatened” or “endangered” under the Endangered Species Act (1973), nor as “depleted” under the

MMPA. There has been no documented human-caused mortality of this stock, and therefore they are not classified as

a "strategic" stock under the MMPA. Insufficient information is available to determine whether the total fishery

mortality and serious injury for pantropical spotted dolphins is insignificant and approaching zero mortality and serious

injury rate. 

REFERENCES

Dizon, A. E., W. F. Perrin, and P. A. Akin. 1994. Stocks of dolphins (Stenella spp. and Delphinus delphis) in the

eastern tropical Pacific: a phylogeographic classification. NOAA Tech. Rep. NMFS 119, 20 pp.

Kleiber, P. 1999. Estimates of marine marine mammal takes in the Hawaiian longline fishery. (Unpublished).

Southwest Fisheries Science Center, NMFS, 2570 Dole St, Honolulu, HI, 96822-2396.

Kobayashi, D. R. and K. E. Kawamoto. 1995. Evaluation of shark, dolphin, and monk seal interactions with

Northwestern Hawaiian Island bottomfishing activity: a comparison of two time periods and an estimate of

economic impacts. Fisheries Research 23: 11-22.

Miyashita, T. 1993. Abundance of dolphin stocks in the western North Pacific taken by the Japanese drive fishery.

Rep. Int. Whal. Commn. 43:417-437.

Mobley, J. R. , Jr, S. S. Spitz, K. A. Forney, R. A. Grotefendt, and P. H. Forestall. 2000. Distribution and abundance

of odontocete species in Hawaiian waters: preliminary results of 1993-98 aerial surveys Admin. Rep. LJ-00-

14C. Southwest Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA

92038. 26 pp.

Nitta, E. 1991. The marine mammal stranding network for Hawaii: an overview. In: J.E. Reynolds III, D.K. Odell
190

(eds.), Marine Mammal Strandings in the United States, pp.56-62. NOAA Tech. Rep. NMFS 98, 157 pp.

Nitta, E. and J. R. Henderson. 1993. A review of interactions between Hawaii's fisheries and protected species. Mar.

Fish. Rev. 55(2):83-92.

Perrin, W. F. 1975. Variation of spotted and spinner porpoise (genus Stenella) in the eastern tropical Pacific and

Hawaii. Bull. Scripps Inst. Oceanogr. 21, 206 pp.

Perrin, W. F. and A. A. Hohn. 1994. Pantropical spotted dolphin Stenella attenuata. In: S. H. Ridgway and R.

Harrison (eds.), Handbook of Marine Mammals, Vol.5: The First Book of Dolphins, pp 71-98. Academic

Press, 416 pp.

Perrin, W.F., G. P. Donovan and J. Barlow. 1994a. Gillnets and Cetaceans. Rep. Int. Whal. Commn., Special Issue 15,

629 pp.

Perrin, W. F., G. D. Schnell, D. J. Hough, J. W. Gilpatrick, Jr., and J. V. Kashiwada. 1994b. Re-examination of

geographical variation in cranial morphology of the pantropical spotted dolphin, Stenella attenuata, in the

eastern Pacific. Fish. Bull. 92:324-346.

Shallenberger, E.W. 1981. The status of Hawaiian cetaceans. Final report to U.S. Marine Mammal Commission. MMC77/23, 79pp.

Wade, P. R. and R. P. Angliss. 1997. Guidelines for Assessing Marine Mammal Stocks: Report of the GAMMS

Workshop April 3-5, 1996, Seattle, Washington. U. S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-12.

93 pp.

Wade, P. R. and T. Gerrodette. 1993. Estimates of cetacean abundance and distribution in the eastern tropical Pacific.

Rep. Int. Whal. Commn. 43:477-493.
191

Figure 1. Spinner dolphin sighting locations during 1993-98

aerial surveys within about 25 nmi of the main Hawaiian Islands

(see Appendix 2 for details on timing and location of survey

effort). Outer line indicates approximate boundary of survey

area.

Revised 12/15/2000

SPINNER DOLPHIN (Stenella longirostris): Hawaiian Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

Spinner dolphins are found throughout the

world in tropical and warm-temperate waters

(Perrin and Gilpatrick 1994). They are common

and abundant throughout the entire Hawaiian

archipelago (Shallenberger 1981; Norris and Dohl

1980; Norris et al. 1994). Recent sighting locations

around the main Hawaiian Islands (Mobley et al.

2000) are shown in Figure 1. There is some

suggestion from an intensive study of spinner

dolphins off the Kona Coast of Hawaii that the

waters surrounding this island may have a large,

relatively stable "resident" population (Norris et al.

1994).

 Hawaiian spinner dolphins belong to a

stock that is separate from those involved in the

tuna purse-seine fishery in the eastern tropical

Pacific (Perrin 1975; Dizon et al. 1994). The

Hawaiian form is referable to the subspecies S.

longirostris longirostris, which occurs pantropically

(Perrin 1990). For the Marine Mammal Protection

Act (MMPA) stock assessment reports, there is a

single Pacific management stock including only

animals found within the U.S. Exclusive Economic

Zone of the Hawaiian Islands. Spinner dolphins involved in eastern tropical Pacific tuna purse-seine fisheries are

managed separately under the MMPA.

POPULATION SIZE

Although spinner dolphins are clearly among the most abundant cetaceans in Hawaiian waters, previously

available population estimates apply only to the west coast of Hawaii. Norris et al. (1994) photoidentified 192

individuals along the west coast of Hawaii and estimated 960 animals for this area in 1979-1980. Östman (1994)

photoidentified 677 individual spinner dolphins in the same area from 1989 to 1992. Using the same estimation

procedures as Norris et al. (1994), Östman (1994) estimated a population size of 2,334 for his study area along the Kona

coast of Hawaii. As part of the Marine Mammal Research Program of the Acoustic Thermometry of Ocean Climate

(ATOC) study, a total of twelve aerial surveys were conducted within about 25 nmi of the main Hawaiian Islands in

1993, 1995 and 1998. An abundance estimate of 3,184 (CV=0.37) spinner dolphins was recently calculated from the

combined survey data (Mobley et al. 2000). This abundance underestimates the total number of spinner dolphins within

the U.S. EEZ off Hawaii, because areas around the Northwest Hawaiian Islands (NWHI) and beyond 25 nautical miles

from the main islands were not surveyed.

Minimum Population Estimate

The log-normal 20th percentile of the combined 1993-98 abundance estimate is 2,355 spinner dolphins. As

with the best abundance estimate above, this includes only areas within about 25 nmi of the main Hawaiian Islands and

is therefore an underestimate.

Current Population Trend

No data on current population trend are available.
192

10 N 15 N 20 N 25 N 30 N 35 N 40 N

180 W 170 W 160 W 150 W 140 W

GG GGTT

UC

UW

GM

GG GG

SL

PC

UW

PC

UW

TT T. truncatus

GG G. griseus

SL S longirostris

PC P. crassidens

GM G. macrorhynchus

UC Cetacean, unident.

UW Whale, unident.

Figure 2. Locations of observed cetacean interactions in the

Hawaiian longline fishery, 1994-98 (modified from Kleiber 1999).

Dashed line is the U.S. Exclusive Economic Zone (EEZ); SL =

spinner dolphin.

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

No information on current or maximum net productivity rate is currently available for the Hawaiian stock. 

POTENTIAL BIOLOGICAL REMOVAL

The potential biological removal (PBR) level for this stock is calculated as the minimum population size (2,355)

times one half the default maximum net growth rate for cetaceans (1⁄2 of 4%) times a recovery factor of 0.50 (for a

species of unknown status with no estimated fishery mortality; Wade and Angliss 1997), resulting in a PBR of 24

spinner dolphins per year.

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Fishery Information

Although some mortality of spinner dolphins has been observed in inshore gillnets, no estimate of annual

human-caused mortality and serious injury is available. The gear types used in Hawaiian fisheries are responsible for

marine mammal mortality and serious injury in other fisheries throughout U.S. waters. Gillnets are used in Hawaiian

waters and appear to capture marine mammals wherever they are used, and float lines from lobster traps and longlines

can be expected to occasionally entangle whales (Perrin et al. 1994).

Interactions with cetaceans have been

reported for all Hawaiian pelagic fisheries, and

there are records of spinner dolphins taken in

inshore monofilament gillnets and net fragments

in Hawaiian waters (Nitta and Henderson 1993).

One spinner dolphin was observed hooked in the

Hawaiian longline fishery between 1994 and

1998 in waters outside the U.S. EEZ, with

approximately 4.4% of all effort (measured as the

number of hooks fished) observed. This

interaction rate extrapolates to a total 5-year

estimate of 23 (95% CI = 1-108) spinner

dolphins, or an average of 4.6 interactions per

year (Kleiber 1999). The single observed spinner

dolphin was reported to have been hooked in the

fluke. Following the guidelines of a 1997

Serious Injury Workshop (Angliss and DeMaster

1998), this animal would not be considered

seriously injured (defined under the MMPA as

likely to result in mortality). Reports for other

odontocetes indicate they may also become

hooked in the mouth or ingest the hook, and they

may occasionally become entangled in the fishing

line. Interaction rates between dolphins and the NWHI bottomfish fishery have been estimated based on studies

conducted in 1990-1993, indicating that an average of 2.67 dolphin interactions, most likely involving bottlenose and

rough-toothed dolphins, occurred for every 1000 fish brought on board (Kobayashi and Kawamoto 1995). Fishermen

claim interactions with dolphins who steal bait and catch are increasing. It is not known whether these interactions result

in serious injury or mortality of dolphins, nor whether spinner dolphins are involved. 

Other Removals

At least 85 spinner dolphins were live-captured in Hawaiian waters from 1962 to 1981 (Shallenberger 1981).

The main capture area was around Oahu.

STATUS OF STOCK

The status of spinner dolphins in Hawaiian waters relative to OSP is unknown, and there are insufficient data

to evaluate trends in abundance. A habitat issue of increasing concern is the potential effect of swim-with-dolphin
193

programs and other tourism activities on spinner dolphins around the main Hawaiian Islands. Spinner dolphins are not

listed as “threatened” or “endangered” under the Endangered Species Act (1973), nor as “depleted” under the MMPA.

The Hawaiian stock is not considered a strategic stock under the 1994 amendments to the MMPA, because there are

no estimates of mortality within the U.S. EEZ. However, there is no systematic monitoring of gillnet fisheries that may

take this species, and the potential effect of interactions with the Hawaiian longline fishery in international waters is

not known. Insufficient information is available to determine whether the total fishery mortality and serious injury for

spinner dolphins is insignificant and approaching zero mortality and serious injury rate.

REFERENCES

Angliss, R. P. and D. P. DeMaster. 1998. Differentiating Serious and Non-Serious Injury of Marine Mammals Taken

Incidental to Commercial Fishing Operations: Report of the Serious Injury Workshop 1-2 April 1997, Silver

Spring, Maryland. U. S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-13. 48 pp.

Dizon, A. E., W. F. Perrin, and P. A. Akin. 1994. Stocks of dolphins (Stenella spp. and Delphinus delphis) in the

eastern tropical Pacific: a phylogeographic classification. NOAA Tech. Rep. NMFS 119, 20 pp.

Kleiber, P. 1999. Estimates of marine marine mammal takes in the Hawaiian longline fishery. (Unpublished).

Southwest Fisheries Science Center, NMFS, 2570 Dole St, Honolulu, HI, 96822-2396.

Kobayashi, D. R. and K. E. Kawamoto. 1995. Evaluation of shark, dolphin, and monk seal interactions with

Northwestern Hawaiian Island bottomfishing activity: a comparison of two time periods and an estimate of

economic impacts. Fisheries Research 23: 11-22.

Mobley, J. R. , Jr, S. S. Spitz, K. A. Forney, R. A. Grotefendt, and P. H. Forestall. 2000. Distribution and abundance

of odontocete species in Hawaiian waters: preliminary results of 1993-98 aerial surveys Admin. Rep. LJ-00-

14C. Southwest Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA

92038. 26 pp.

Nitta, E. and J. R. Henderson. 1993. A review of interactions between Hawaii's fisheries and protected species. Mar.

Fish. Rev. 55(2):83-92.

Norris, K. S., B. Würsig, R. S. Wells, and M. Würsig. 1994. The Hawaiian Spinner Dolphin. University of California

Press, 408 pp.

Norris, K. S. and T. P. Dohl. 1980. Behavior of the Hawaiian spinner dolphin, Stenella longirostris. Fish. Bull.

77:821-849.

Östman, J. S. O. 1994. Social organization and social behavior of Hawaiian spinner dolphins (Stenella longirostris).

Ph.D. dissertation, University of California, Santa Cruz, 114 pp.

Perrin, W. F. 1975. Variation of spotted and spinner porpoise (genus Stenella) in the eastern tropical Pacific and

Hawaii. Bull. Scripps Inst. Oceanogr. 21, 206 pp.

Perrin, W. F. 1990. Subspecies of Stenella longirostris (Mammalia: Cetacea: Delphinidae). Proc. Biol. Soc. Wash.

103:453-463.

Perrin, W. F. and J. W. Gilpatrick, Jr. 1994. Spinner dolphin Stenella longirostris (Gray, 1828). In: S. H. Ridgway

and R. Harrison (eds.), Handbook of Marine Mammals, Vol.5: The First Book of Dolphins, pp. 99-128.

Academic Press, 416 pp.

Perrin, W.F., G. P. Donovan and J. Barlow. 1994. Gillnets and Cetaceans. Rep. Int. Whal. Commn., Special Issue 15,

629 pp.

Shallenberger, E.W. 1981. The status of Hawaiian cetaceans. Final report to U.S. Marine Mammal Commission. MMC77/23, 79pp.

Wade, P. R. and R. P. Angliss. 1997. Guidelines for Assessing Marine Mammal Stocks: Report of the GAMMS

Workshop April 3-5, 1996, Seattle, Washington. U. S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-12.

93 pp.

Wade, P. R. and T. Gerrodette. 1993. Estimates of cetacean abundance and distribution in the eastern tropical Pacific.

Rep. Int. Whal. Commn. 43:477-493.
194

Figure 1. Location of the single sighting of striped dolphins

during 1993-98 aerial surveys within about 25 nmi of the main

Hawaiian Islands (see Appendix 2 for details on timing and

location of survey effort). Outer line indicates approximate

boundary of survey area.

Revised 12/15/2000

STRIPED DOLPHIN (Stenella coeruleoalba): Hawaiian Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

Striped dolphins are found in tropical to

warm-temperate waters throughout the world (Perrin

et al. 1994). There is an incongruity between the

frequency of strandings and the infrequency of

sightings of this species in Hawaii. Nitta (1991)

found more stranding records of striped dolphins

(13) than of any other species between 1936 and

1988, yet Shallenberger (1981) was aware of only

two at-sea sightings, one near Niihau and one west

of Oahu. A single sighting was made during recent

systematic surveys within about 25 nmi of the main

Hawaiian Islands (Figure 1). The Sea Life Park

collecting crew never encountered striped dolphins

from the early 1960s through the late 1970s, during

their live-capture operations (Shallenberger 1981).

Striped dolphins have been intensively

exploited in the western North Pacific, where three

migratory stocks are provisionally recognized

(Kishiro and Kasuya 1993). In the eastern Pacific

all striped dolphins are provisionally considered to

belong to a single stock (Dizon et al. 1994). For the

Marine Mammal Protection Act (MMPA) stock

assessment reports, striped dolphins within the

Pacific U.S. Exclusive Economic Zone are divided into two discrete, non-contiguous areas: 1) waters off California,

Oregon and Washington, and 2) waters around Hawaii (this report). Striped dolphins involved in eastern tropical Pacific

tuna purse-seine fisheries are managed separately under the MMPA.

POPULATION SIZE

Population estimates are available for Japanese waters (Miyashita 1993) and the eastern tropical Pacific (Wade

and Gerrodette 1993), but it is not known whether any of these animals are part of the same population that occurs

around the Hawaiian Islands. As part of the Marine Mammal Research Program of the Acoustic Thermometry of Ocean

Climate (ATOC) study, a total of twelve aerial surveys were conducted within about 25 nmi of the main Hawaiian

Islands in 1993, 1995 and 1998. An abundance estimate of 114 (CV=1.19) striped dolphins was recently calculated

from the combined survey data (Mobley et al. 2000). This abundance underestimates the total number of striped

dolphins within the U.S. EEZ off Hawaii, because areas around the Northwest Hawaiian Islands (NWHI) and beyond

25 nautical miles from the main islands were not surveyed.

Minimum Population Estimate

No data are available for a minimum population estimate. The log-normal 20th percentile of the combined

1993-98 abundance estimate is 52 striped dolphins. As with the best abundance estimate above, this includes only areas

within about 25 nmi of the main Hawaiian Islands and is therefore an underestimate.

Current Population Trend

No data are available on current population trend.

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

No data are available on current or maximum net productivity rate.
195

POTENTIAL BIOLOGICAL REMOVAL

The potential biological removal (PBR) level for this stock is calculated as the minimum population size (52)

times one half the default maximum net growth rate for cetaceans (1⁄2 of 4%) times a recovery factor of 0.50 (for a

species of unknown status with no known fishery mortality; Wade and Angliss 1997), resulting in a PBR of 0.5 striped

dolphins per year.

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Fishery Information

No estimate of annual human-caused mortality and serious injury is available as there are no reports of direct

or incidental takes of striped dolphins in Hawaiian waters (Nitta and Henderson 1993). However, mortality of other

cetacean species has been observed in Hawaiian fisheries, and the gear types used in these fisheries are responsible for

marine mammal mortality and serious injury in other fisheries throughout U.S. waters. Gillnets are used in Hawaiian

waters and appear to capture marine mammals wherever they are used, and float lines from lobster traps and longlines

can be expected to occasionally entangle whales (Perrin et al. 1994).

Interactions with cetaceans have been reported for all Hawaiian pelagic fisheries (Nitta and Henderson 1993),

but no interactions with striped dolphins have been documented. None were observed hooked in the Hawaiian longline

fishery between 1994 and 1998, with approximately 4.4% of all effort (measured as the number of hooks fished)

observed (Kleiber 1999). Interaction rates between dolphins and the NWHI bottomfish fishery have been estimated

based on studies conducted in 1990-1993, indicating that an average of 2.67 dolphin interactions, most likely involving

bottlenose and rough-toothed dolphins, occurred for every 1000 fish brought on board (Kobayashi and Kawamoto

1995). Fishermen claim interactions with dolphins who steal bait and catch are increasing. It is not known whether

these interactions result in serious injury or mortality of dolphins, nor whether striped dolphins are involved.

STATUS OF STOCK

The status of striped dolphins in Hawaiian waters relative to OSP is unknown, and there are insufficient data

to evaluate trends in abundance. No habitat issues are known to be of concern for this species. They are not listed as

“threatened” or “endangered” under the Endangered Species Act (1973), nor as “depleted” under the MMPA. Although

information on striped dolphins in Hawaiian waters is limited, this stock would not be considered strategic under the

1994 amendments to the MMPA given the absence of reported fisheries related mortality. Insufficient information is

available to determine whether the total fishery mortality and serious injury for striped dolphins is insignificant and

approaching zero mortality and serious injury rate. 

REFERENCES

Dizon, A. E., W. F. Perrin, and P. A. Akin. 1994. Stocks of dolphins (Stenella spp. and Delphinus delphis) in the

eastern tropical Pacific: a phylogeographic classification. NOAA Tech. Rep. NMFS 119, 20 pp.

Kishiro, T. and T. Kasuya. 1993. Review of Japanese dolphin drive fisheries and their status. Rep. Int. Whal. Commn.

43:439-452.

Kleiber, P. 1999. Estimates of marine mammal takes in the Hawaiian longline fishery. (Unpublished). Southwest

Fisheries Science Center, NMFS, 2570 Dole St, Honolulu, HI, 96822-2396.

Kobayashi, D. R. and K. E. Kawamoto. 1995. Evaluation of shark, dolphin, and monk seal interactions with

Northwestern Hawaiian Island bottomfishing activity: a comparison of two time periods and an estimate of

economic impacts. Fisheries Research 23: 11-22.

Miyashita, T. 1993. Abundance of dolphin stocks in the western North Pacific taken by the Japanese drive fishery.

Rep. Int. Whal. Commn. 43:417-437.

Mobley, J. R. , Jr, S. S. Spitz, K. A. Forney, R. A. Grotefendt, and P. H. Forestall. 2000. Distribution and abundance

of odontocete species in Hawaiian waters: preliminary results of 1993-98 aerial surveys Admin. Rep. LJ-00-

14C. Southwest Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA

92038. 26 pp.

Nitta, E. 1991. The marine mammal stranding network for Hawaii: an overview. In: J.E. Reynolds III, D.K. Odell

(eds.), Marine Mammal Strandings in the United States, pp.56-62. NOAA Tech. Rep. NMFS 98, 157 pp.

Nitta, E. and J. R. Henderson. 1993. A review of interactions between Hawaii's fisheries and protected species. Mar.

Fish. Rev. 55(2):83-92.
196

Perrin, W. F., C. E. Wilson, and F. I. Archer, II. 1994. Striped dolphin Stenella coeruleoalba (Meyen, 1833). In: S.

H. Ridgway and R. Harrison (eds.), Handbook of Marine Mammals, Vol.5: The First Book of Dolphins, pp

129-159. Academic Press, 416 pp.

Perrin, W.F., G. P. Donovan and J. Barlow. 1994. Gillnets and Cetaceans. Rep. Int. Whal. Commn., Special Issue 15,

629 pp.

Shallenberger, E.W. 1981. The status of Hawaiian cetaceans. Final report to U.S. Marine Mammal Commission. MMC77/23, 79pp.

Wade, P. R. and R. P. Angliss. 1997. Guidelines for Assessing Marine Mammal Stocks: Report of the GAMMS

Workshop April 3-5, 1996, Seattle, Washington. U. S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-12.

93 pp.

Wade, P. R. and T. Gerrodette. 1993. Estimates of cetacean abundance and distribution in the eastern tropical Pacific.

Rep. Int. Whal. Commn. 43:477-493.
197

Figure 1. Melon-headed whale sighting locations during 1993-

98 aerial surveys within about 25 nmi of the main Hawaiian

Islands (see Appendix 2 for details on timing and location of

survey effort). Outer line indicates approximate boundary of

survey area.

Revised 12/15/2000

MELON-HEADED WHALE (Peponocephala electra): Hawaiian Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

Melon-headed whales are found in tropical

and warm-temperate waters throughout the world.

The distribution of reported sightings suggests that

the oceanic habitat of this species is primarily

equatorial waters (Perryman et al. 1994). Small

numbers have been taken in the eastern tropical

Pacific, and they are occasionally killed in direct

fisheries in Japan and elsewhere in the western

Pacific. Large herds are seen regularly in Hawaiian

waters, especially off the Waianae coast of Oahu,

the north Kohala coast of Hawaii, and the leeward

coast of Lanai (Shallenberger 1981). Recent

sighting locations around the main Hawaiian Islands

(Mobley et al. 2000) are shown in Figure 1. Little

is known about this species elsewhere in its range,

and most knowledge about its biology comes from

mass strandings (Perryman et al. 1994). Ten

strandings are known from Hawaii (Nishiwaki and

Norris 1966; Shallenberger 1981; Nitta 1991). For

the Marine Mammal Protection Act (MMPA) stock

assessment reports, there is a single Pacific

management stock including only animals found

within the U.S. Exclusive Economic Zone of the

Hawaiian Islands.

POPULATION SIZE

An estimate of melon-headed whales is available for the eastern tropical Pacific (Wade and Gerrodette 1993),

but it is not known whether any of these animals are part of the same population that occurs around the Hawaiian

Islands. As part of the Marine Mammal Research Program of the Acoustic Thermometry of Ocean Climate (ATOC)

study, a total of twelve aerial surveys were conducted within about 25 nmi of the main Hawaiian Islands in 1993, 1995

and 1998. An abundance estimate of 154 (CV=0.88) melon-headed whales was recently calculated from the combined

survey data (Mobley et al. 2000). This abundance underestimates the total number of melon-headed whales within the

U.S. EEZ off Hawaii, because areas around the Northwest Hawaiian Islands (NWHI) and beyond 25 nautical miles from

the main islands were not surveyed.

Minimum Population Estimate

The log-normal 20th percentile of the combined 1993-98 abundance estimate is 81 melon-headed whales. As

with the best abundance estimate above, this includes only areas within about 25 nmi of the main Hawaiian Islands and

is therefore an underestimate.

Minimum Population Estimate

No data are available for making a minimum population estimate. 

Current Population Trend

No data are available on current population trend.

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

No data are available on current or maximum net productivity rate.
198

POTENTIAL BIOLOGICAL REMOVAL

The potential biological removal (PBR) level for this stock is calculated as the minimum population size (81)

times one half the default maximum net growth rate for cetaceans (1⁄2 of 4%) times a recovery factor of 0.50 (for a

species of unknown status with no known fishery mortality; Wade and Angliss 1997), resulting in a PBR of 0.8 melonheaded whales per year.

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Fishery Information

 Melon-headed whales are not known to be taken directly or incidentally in Hawaiian waters and no mortality

of this species has been documented in Hawaiian fisheries (Nitta and Henderson 1993). However, mortality of other

cetacean species has been observed in Hawaiian fisheries, and the gear types used in these fisheries are responsible for

marine mammal mortality and serious injury in other fisheries throughout U.S. waters. Gillnets are used in Hawaiian

waters and appear to capture marine mammals wherever they are used, and float lines from lobster traps and longlines

can be expected to occasionally entangle whales (Perrin et al. 1994).

Interactions with cetaceans have been reported for all Hawaiian pelagic fisheries (Nitta and Henderson 1993),

but no interactions with melon-headed whales have been documented. None were observed hooked in the Hawaiian

longline fishery between 1994 and 1998, with approximately 4.4% of all effort (measured as the number of hooks

fished) observed (Kleiber 1999). Interaction rates between dolphins and the NWHI bottomfish fishery have been

estimated based on studies conducted in 1990-1993, indicating that an average of 2.67 dolphin interactions, most likely

involving bottlenose and rough-toothed dolphins, occurred for every 1000 fish brought on board (Kobayashi and

Kawamoto 1995). Fishermen claim interactions with dolphins who steal bait and catch are increasing. It is not known

whether these interactions result in serious injury or mortality of dolphins, nor whether melon-headed whales are

involved.

Historical Mortality

Peale (1848) reported that 60 whales of this species were driven ashore by natives in Hilo Bay, Hawaii in 1841.

At least three melon-headed whales were live-captured for public display between 1966 and 1978 (Shallenberger 1981).

STATUS OF STOCK

The status of melon-headed whales in Hawaiian waters relative to OSP is unknown, and there are insufficient

data to evaluate trends in abundance. No habitat issues are known to be of concern for this species. They are not listed

as “threatened” or “endangered” under the Endangered Species Act (1973), nor as “depleted” under the MMPA.

Although information on melon-headed whales in Hawaiian waters is limited, this stock would not be considered

strategic under the 1994 amendments to the MMPA given the absence of reported fisheries related mortality.

Insufficient information is available to determine whether the total fishery mortality and serious injury for melon-headed

whales is insignificant and approaching zero mortality and serious injury rate. 

REFERENCES

Kleiber, P. 1999. Estimates of marine mammal takes in the Hawaiian longline fishery. (Unpublished). Southwest

Fisheries Science Center, NMFS, 2570 Dole St, Honolulu, HI, 96822-2396.

Kobayashi, D. R. and K. E. Kawamoto. 1995. Evaluation of shark, dolphin, and monk seal interactions with

Northwestern Hawaiian Island bottomfishing activity: a comparison of two time periods and an estimate of

economic impacts. Fisheries Research 23: 11-22.

Mobley, J. R. , Jr, S. S. Spitz, K. A. Forney, R. A. Grotefendt, and P. H. Forestall. 2000. Distribution and abundance

of odontocete species in Hawaiian waters: preliminary results of 1993-98 aerial surveys Admin. Rep. LJ-00-

14C. Southwest Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA

92038. 26 pp.

Nishiwaki, M. and K. S. Norris. 1966. A new genus, Peponocephala, for the odontocete cetacean species Electra

electra. Sci. Rep. Whales Res. Inst. 20:95-100.

Nitta, E. 1991. The marine mammal stranding network for Hawaii: an overview. In: J.E. Reynolds III, D.K. Odell

(eds.), Marine Mammal Strandings in the United States, pp.56-62. NOAA Tech. Rep. NMFS 98, 157 pp.

Nitta, E. and J. R. Henderson. 1993. A review of interactions between Hawaii's fisheries and protected species. Mar.
199

Fish. Rev. 55(2):83-92.

Peale, T. R. 1848. United States Exploring Expedition. During the Years 1838, 1839, 1840, 1841, 1842. Under the

Command of Charles Wilkes, U.S.N. Vol. VIII. Mammalia and Ornithology. C Sherman, Philadelphia, 338

pp.

Perrin, W.F., G. P. Donovan and J. Barlow. 1994. Gillnets and Cetaceans. Rep. Int. Whal. Commn., Special Issue 15,

629 pp.

Perryman, W. L., D. W. K. Au, S. Leatherwood, and T. A. Jefferson. 1994. Melon-headed whale Peponocephala

electra Gray, 1846. In: S. H. Ridgway and R. Harrison (eds.), Handbook of Marine Mammals, Vol.5: The First

Book of Dolphins, pp. 363-386. Academic Press, 416 pp.

Shallenberger, E.W. 1981. The status of Hawaiian cetaceans. Final report to U.S. Marine Mammal Commission. MMC77/23, 79pp.

Wade, P. R. and R. P. Angliss. 1997. Guidelines for Assessing Marine Mammal Stocks: Report of the GAMMS

Workshop April 3-5, 1996, Seattle, Washington. U. S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-12.

93 pp.

Wade, P. R. and T. Gerrodette. 1993. Estimates of cetacean abundance and distribution in the eastern tropical Pacific.

Rep. Int. Whal. Commn. 43:477-493.
200

Revised 12/15/2000

PYGMY KILLER WHALE (Feresa attenuata): Hawaiian Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

Pygmy killer whales are found in tropical and subtropical waters throughout the world (Ross and Leatherwood

1994). They are poorly known in most parts of their range. Small numbers have been taken directly and incidentally

in both the western and eastern Pacific. Most knowledge of this species is from stranded or live-captured specimens.

Pryor et al. (1965) stated that pygmy killer whales have been observed several times off the lee shore of Oahu, and that

"they seem to be regular residents of the Hawaiian area." Although all sightings up to that time had been off Oahu and

the Big Island, Shallenberger (1981) stated that this species might be found elsewhere in Hawaii, as well. No pygmy

killer whales were seen during 1993-98 aerial surveys within about 25 nmi of the main Hawaiian Islands (Mobley et

al. 2000; see Appendix 2 for detailed information on timing and location of effort), suggesting that they are uncommon

in these nearshore regions. Nitta (1991) documented five strandings from Maui and the island of Hawaii. For the

Marine Mammal Protection Act (MMPA) stock assessment reports, there is a single Pacific management stock including

only animals found within the U.S. Exclusive Economic Zone of the Hawaiian Islands. 

POPULATION SIZE

A population estimate has been made for this species in the eastern tropical Pacific (Wade and Gerrodette

1993), but no data are available to estimate population size in any other area of the North Pacific. As part of the Marine

Mammal Research Program of the Acoustic Thermometry of Ocean Climate (ATOC) study, a total of twelve aerial

surveys were conducted within about 25 nmi of the main Hawaiian Islands in 1993, 1995 and 1998 (Mobley et al. 2000).

No sightings of pygmy killer whales were made, and therefore no abundance estimate for nearshore Hawaiian waters

is presently available. It is likely that pygmy killer whales occur primarily in pelagic waters greater than 25 nmi from

the main Hawaiian islands.

Minimum Population Estimate

No data are available for a minimum population estimate.

Current Population Trend

No data are available on current population trend.

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

No data are available on current or maximum net productivity rate.

POTENTIAL BIOLOGICAL REMOVAL

No PBR can be calculated for this species at this time.

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Fishery Information

No estimate of annual human-caused mortality and serious injury is available as there are no reports of direct

or incidental takes of pygmy killer whales in Hawaiian waters. However, mortality of other cetacean species has been

observed in Hawaiian fisheries, and the gear types used in these fisheries are responsible for marine mammal mortality

and serious injury in other fisheries throughout U.S. waters. Gillnets are used in Hawaiian waters and appear to capture

marine mammals wherever they are used, and float lines from lobster traps and longlines can be expected to occasionally

entangle whales (Perrin et al. 1994).

 Interactions with cetaceans have been reported for all Hawaiian pelagic fisheries (Nitta and Henderson 1993),

but no interactions with pygmy killer whales have been documented. None were observed hooked in the Hawaiian

longline fishery between 1994 and 1998, with approximately 4.4% of all effort (measured as the number of hooks

fished) observed (Kleiber 1999). Interaction rates between dolphins and the NWHI bottomfish fishery have been

estimated based on studies conducted in 1990-1993, indicating that an average of 2.67 dolphin interactions, most likely

involving bottlenose and rough-toothed dolphins, occurred for every 1000 fish brought on board (Kobayashi and

Kawamoto 1995). Fishermen claim interactions with dolphins who steal bait and catch are increasing. It is not known
201

whether these interactions result in serious injury or mortality of dolphins, nor whether pygmy killer whales are

involved.

Other Removals

Three specimens were live-captured by Sea Life Park between 1963 and 1971 (Pryor et al. 1965; Pryor 1975;

Shallenberger 1981).

STATUS OF STOCK

The status of pygmy killer whales in Hawaiian waters relative to OSP is unknown, and there are insufficient

data to evaluate trends in abundance. No habitat issues are known to be of concern for this species. This species is not

listed as “threatened” or “endangered” under the Endangered Species Act (1973), nor as “depleted” under the MMPA.

Although information on pygmy killer whales in Hawaiian waters is limited, this stock would not be considered strategic

under the 1994 amendments to the MMPA given the absence of reported fisheries related mortality. Insufficient

information is available to determine whether the total fishery mortality and serious injury for pygmy killer whales is

insignificant and approaching zero mortality and serious injury rate.

REFERENCES

Kleiber, P. 1999. Estimates of marine mammal takes in the Hawaiian longline fishery. (Unpublished). Southwest

Fisheries Science Center, NMFS, 2570 Dole St, Honolulu, HI, 96822-2396.

Kobayashi, D. R. and K. E. Kawamoto. 1995. Evaluation of shark, dolphin, and monk seal interactions with

Northwestern Hawaiian Island bottomfishing activity: a comparison of two time periods and an estimate of

economic impacts. Fisheries Research 23: 11-22.

Mobley, J. R. , Jr, S. S. Spitz, K. A. Forney, R. A. Grotefendt, and P. H. Forestall. 2000. Distribution and abundance

of odontocete species in Hawaiian waters: preliminary results of 1993-98 aerial surveys Admin. Rep. LJ-00-

14C. Southwest Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA

92038. 26 pp.

Nitta, E. 1991. The marine mammal stranding network for Hawaii: an overview. In: J.E. Reynolds III, D.K. Odell

(eds.), Marine Mammal Strandings in the United States, pp.56-62. NOAA Tech. Rep. NMFS 98, 157 pp.

Nitta, E. and J. R. Henderson. 1993. A review of interactions between Hawaii's fisheries and protected species. Mar.

Fish. Rev. 55(2):83-92.

Perrin, W.F., G. P. Donovan and J. Barlow. 1994. Gillnets and Cetaceans. Rep. Int. Whal. Commn., Special Issue 15,

629 pp.

Pryor, K. 1975. Lads Before the Wind: Adventures in Porpoise Training. Harper and Row, New York, 278 pp.

Pryor, T., K. Pryor and K. S. Norris. 1965. Observations on a pygmy killer whale (Feresa attenuata Gray) from

Hawaii. J. Mamm. 46:450-461.

Ross, G. J. B. and S. Leatherwood. 1994. Pygmy killer whale Feresa attenuata Gray, 1874. In: S. H. Ridgway and

R. Harrison (eds.), Handbook of Marine Mammals, Vol.5: The First Book of Dolphins, pp.387-404. Academic

Press, 416 pp.

Shallenberger, E.W. 1981. The status of Hawaiian cetaceans. Final report to U.S. Marine Mammal Commission. MMC77/23, 79pp.

Wade, P. R. and T. Gerrodette. 1993. Estimates of cetacean abundance and distribution in the eastern tropical Pacific.

Rep. Int. Whal. Commn. 43:477-493.
202

Figure 1. False killer whale sighting locations during 1993-98

aerial surveys within about 25 nmi of the main Hawaiian Islands

(see Appendix 2 for details on timing and location of survey

effort). Outer line indicates approximate boundary of survey

area.

Revised 12/31/2001

FALSE KILLER WHALE (Pseudorca crassidens): Hawaiian Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

False killer whales are found worldwide

mainly in tropical and warm-temperate waters

(Stacey et al. 1994). In the North Pacific, this

species is well known from southern Japan, Hawaii,

and the eastern tropical Pacific. It occurs around all

the main Hawaiian Islands, but its presence around

the Northwestern Hawaiian Islands has not yet been

established (Nitta and Henderson 1993). Recent

sighting locations around the main Hawaiian

Islands (Mobley et al. 2000) are shown in Figure 1.

There are only 4 stranding records from Hawaiian

waters (Nitta 1991). Large numbers of false killer

whales have been taken in direct fisheries in

southern Japan, and small numbers have been taken

incidental to fishing operations in the eastern

tropical Pacific. Most knowledge about this species

comes from outside Hawaiian waters (Stacey et al.

1994). For the Marine Mammal Protection Act

(MMPA) stock assessment reports, there is a single

Pacific management stock including only animals

found within the U.S. Exclusive Economic Zone of

the Hawaiian Islands.

POPULATION SIZE

Population estimates for this species have been made from shipboard surveys in Japan (Miyashita 1993) and

the eastern tropical Pacific (Wade and Gerrodette 1993), but it is not known whether these animals are part of the same

population that occurs around the Hawaiian Islands. As part of the Marine Mammal Research Program of the Acoustic

Thermometry of Ocean Climate (ATOC) study, a total of twelve aerial surveys were conducted within about 25 nmi of

the main Hawaiian Islands in 1993, 1995 and 1998. An abundance estimate of 121 (CV=0.47) false killer whales was

recently calculated from the combined survey data (Mobley et al. 2000). This abundance underestimates the total number

of false killer whales within the U.S. EEZ off Hawaii, because areas around the Northwest Hawaiian Islands (NWHI)

and beyond 25 nautical miles from the main islands were not surveyed.

Minimum Population Estimate

The log-normal 20th percentile of the combined 1993-98 abundance estimate is 83 false killer whales. As with

the best abundance estimate above, this includes only areas within about 25 nmi of the main Hawaiian Islands and is

therefore an underestimate.

Current Population Trend

No data are available on current population trend.

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

No data are available on current or maximum net productivity rate for this species in Hawaiian waters.

POTENTIAL BIOLOGICAL REMOVAL

The potential biological removal (PBR) level for this stock is calculated as the minimum population size (83)

times one half the default maximum net growth rate for cetaceans (1⁄2 of 4%) times a recovery factor of 0.50 (for a

species of unknown status with no known fishery mortality; Wade and Angliss 1997), resulting in a PBR of 0.8 false
203

10 N 15 N 20 N 25 N 30 N 35 N 40 N

180 W 170 W 160 W 150 W 140 W

GG GGTT

UC

UW

GM

GG GG

SL

PC

UW

PC

UW

TT T. truncatus

GG G. griseus

SL S longirostris

PC P. crassidens

GM G. macrorhynchus

UC Cetacean, unident.

UW Whale, unident.

Figure 2. Locations of observed cetacean interactions in the

Hawaiian longline fishery, 1994-98 (modified from Kleiber 1999).

Dashed line is the U.S. Exclusive Economic Zone (EEZ); SL =

spinner dolphin.

killer whales per year. 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Fishery Information

Although little is known about incidental mortality of false killer whales in Hawaiian waters (Nitta and

Henderson 1993), mortality of other cetacean species has been observed in Hawaiian fisheries, and the gear types used

in these fisheries are responsible for marine mammal mortality and serious injury in other fisheries throughout U.S.

waters. Gillnets are used in Hawaiian waters and appear to capture marine mammals wherever they are used, and float

lines from lobster traps and longlines can be expected to occasionally entangle whales (Perrin et al. 1994).

Interactions with cetaceans have been reported for all Hawaiian pelagic fisheries, and false killer whales have

been identified in fishermen's logs as taking catches from pelagic longlines (Nitta and Henderson 1993). They have also

been observed feeding on mahi mahi, Coryphaena hippurus, and yellowfin tuna, Thunnus albacares, and frequently

steal large fish (up to 70 pounds) (Shallenberger 1981) from the trolling lines of both commercial and recreational

fishermen (S. Kaiser, pers. comm.).

Two false killer whales were observed

hooked in the Hawaiian longline fishery between

1994 and 1998 within the U.S. EEZ (Figure 2),

with approximately 4.4% of all effort (measured

as the number of hooks fished) observed. This

interaction rate extrapolates to a total 5-year

estimate of 45 (95% CI = 7-146) false killer

whales, or an average of 9 interactions per year

(Kleiber 1999). Both of the observed false killer

whales were reported to have been hooked in the

mouth or to have ingested the hook, and they

were released with trailing gear. There were no

longline fishery interactions with false killer

whales reported during 1999-2000. Reports for

other odontocetes indicate they may also become

hooked in other parts of their body, and that they

may occasionally become entangled in the fishing

line. Following the guidelines of a 1997 Serious

Injury Workshop (Angliss and DeMaster 1998),

the two observed false killer whales have been

considered seriously injured (defined under the

MMPA as likely to result in mortality), and, therefore,

the interaction rate of 9 animals per year

represents an estimate of mortality and serious injury for this stock. Because of concern over incidental mortality of

turtles and seabirds, the Hawaiian longline fishery is presently under a court order restricting effort and excluding

fishing effort from a large area north of the Hawaiian Islands. This court order will expire when the National Marine

Fisheries Service issues a final Environmental Impact Statement for the fishery, in early 2001. Observer coverage of

this fleet has been increased in recent months, and overall fishing effort has decreased. This decrease in effort should

reduce the likelihood of interactions with cetaceans, including false killer whales, unless the remaining effort is

concentrated in areas where interactions are more likely. The two previously documented interactions with false killer

whales were within 200 nmi of the Hawaiian Islands, but insufficient data are available to evaluate whether this is a

meaningful pattern. Further changes in the longline fishery are likely in the near future, but potential effects of these

changes on cetacean interactions are unknown. 

Interaction rates between dolphins and the NWHI bottomfish fishery have been estimated based on studies

conducted in 1990-1993, indicating that an average of 2.67 dolphin interactions, most likely involving bottlenose and

rough-toothed dolphins, occurred for every 1000 fish brought on board (Kobayashi and Kawamoto 1995). Fishermen

claim interactions with dolphins who steal bait and catch are increasing. It is not known whether these interactions result

in serious injury or mortality of dolphins, nor whether false killer whales are involved. 
204

Other Removals

Since the early 1960's, at least 12 false killer whales have been live-captured by aquaria or the Navy (Pryor

1975; Shallenberger 1981; J. Thomas pers. comm.).

STATUS OF STOCK

The status of false killer whales in Hawaiian waters relative to OSP is unknown, and there are insufficient data

to evaluate trends in abundance. No habitat issues are known to be of concern for this species. They are not listed as

“threatened” or “endangered” under the Endangered Species Act (1973), nor as “depleted” under the MMPA. Because

the rate of serious injury to false killer whales within the U.S. EEZ in the Hawaiian longline fishery (9 animals per year)

exceeds the PBR (0.8), this stock is considered a strategic stock under the 1994 amendments to the MMPA. The total

fishery mortality and serious injury cannot be considered to be insignificant and approaching zero, because it exceeds

the PBR. However, the available abundance estimate, on which PBR is based, applies only to a portion of this species’

range in Hawaiian waters, and additional studies of abundance, distribution, and fishery-related mortality and injury of

false killer whales in Hawaiian waters will be required to re-evaluate this species’ status in the future.

REFERENCES

Angliss, R. P. and D. P. DeMaster. 1998. Differentiating Serious and Non-Serious Injury of Marine Mammals Taken

Incidental to Commercial Fishing Operations: Report of the Serious Injury Workshop 1-2 April 1997, Silver

Spring, Maryland. U. S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-13. 48 pp.

Kleiber, P. 1999. Estimates of marine mammal takes in the Hawaiian longline fishery. (Unpublished). Southwest

Fisheries Science Center, NMFS, 2570 Dole St, Honolulu, HI, 96822-2396.

Kobayashi, D. R. and K. E. Kawamoto. 1995. Evaluation of shark, dolphin, and monk seal interactions with

Northwestern Hawaiian Island bottomfishing activity: a comparison of two time periods and an estimate of

economic impacts. Fisheries Research 23: 11-22.

Miyashita, T. 1993. Abundance of dolphin stocks in the western North Pacific taken by the Japanese drive fishery.

Rep. Int. Whal. Commn. 43:417-437.

Mobley, J. R. , Jr, S. S. Spitz, K. A. Forney, R. A. Grotefendt, and P. H. Forestall. 2000. Distribution and abundance

of odontocete species in Hawaiian waters: preliminary results of 1993-98 aerial surveys Admin. Rep. LJ-00-

14C. Southwest Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA

92038. 26 pp.

Nitta, E. 1991. The marine mammal stranding network for Hawaii: an overview. In: J.E. Reynolds III, D.K. Odell

(eds.), Marine Mammal Strandings in the United States, pp.56-62. NOAA Tech. Rep. NMFS 98, 157 pp.

Nitta, E. and J. R. Henderson. 1993. A review of interactions between Hawaii's fisheries and protected species. Mar.

Fish. Rev. 55(2):83-92.

Perrin, W.F., G. P. Donovan and J. Barlow. 1994. Gillnets and Cetaceans. Rep. Int. Whal. Commn., Special Issue 15,

629 pp.

Pryor, K. 1975. Lads Before the Wind: Adventures in Porpoise Training. Harper and Row, New York, 278 pp.

Shallenberger, E.W. 1981. The status of Hawaiian cetaceans. Final report to U.S. Marine Mammal Commission. MMC77/23, 79pp.

Stacey, P. J., S. Leatherwood, and R. W. Baird. 1994. Pseudorca crassidens. Mamm. Spec. 456:1-6.

Wade, P. R. and R. P. Angliss. 1997. Guidelines for Assessing Marine Mammal Stocks: Report of the GAMMS

Workshop April 3-5, 1996, Seattle, Washington. U. S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-12.

93 pp.

Wade, P. R. and T. Gerrodette. 1993. Estimates of cetacean abundance and distribution in the eastern tropical Pacific.

Rep. Int. Whal. Commn. 43:477-493.
205

Revised 12/15/2000

KILLER WHALE (Orcinus orca): Hawaiian Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

Killer whales have been observed in all oceans and seas of the world (Leatherwood and Dahlheim 1978).

Although reported from tropical and offshore waters (Heyning and Dahlheim 1988), killer whales prefer the colder

waters of both hemispheres, with greatest abundances found within 800 km of major continents (Mitchell 1975). They

are rare in Hawaiian waters. No killer whales were seen during 1993-98 aerial surveys within about 25 nmi of the main

Hawaiian Islands (Mobley et al. 2000; see Appendix 2 for detailed information on timing and location of effort),

suggesting that they are uncommon in these nearshore regions. One stranding from the island of Hawaii was reported

in 1950 (Richards 1952). Two sightings have been reported, one in January 1978 off the Waianae Coast of Oahu and

another in December 1979 near Kauai (Shallenberger 1981). Except in the northeastern Pacific where "resident",

"transient", and “offshore” stocks have been described for coastal waters of Alaska, British Columbia, and Washington

to California (Bigg 1982; Leatherwood et al. 1990, Bigg et al. 1990, Ford et al. 1994), little is known about stock

structure of killer whales in the North Pacific. For the Marine Mammal Protection Act (MMPA) stock assessment

reports, five killer whale stocks are recognized within the Pacific U.S. EEZ 1) the Eastern North Pacific Northern

Resident stock - occurring from British Columbia through Alaska, 2) the Eastern North Pacific Southern Resident stock

- occurring within the inland waters of Washington State and southern British Columbia, 3) the Eastern North Pacific

Transient stock - occurring from Alaska through California, 4) the Eastern North Pacific Offshore stock - occurring from

Southeast Alaska through California, and 5) the Hawaiian stock (this report). The Stock Assessment Reports for the

Alaska Region contains the assessment of the Eastern North Pacific Northern Resident stock; all other killer whale stock

assessments are included in this report.

POPULATION SIZE

Population sizes for killer whales in the coastal waters of British Columbia and Washington are known from

photo-identification studies (Bigg et al. 1990). The population of killer whales in the eastern tropical Pacific has been

estimated from shipboard sightings surveys (Wade and Gerrodette 1993). No data to estimate population size are

available for the central Pacific. As part of the Marine Mammal Research Program of the Acoustic Thermometry of

Ocean Climate (ATOC) study, a total of twelve aerial surveys were conducted within about 25 nmi of the main Hawaiian

Islands in 1993, 1995 and 1998 (Mobley et al. 2000). No sightings of killer whales were made, and therefore no

abundance estimate for Hawaiian waters is presently available. 

Minimum Population Estimate

No data are available to provide a minimum population estimate.

Current Population Trend

No data are available on current population trend.

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

No data are available on current and maximum net productivity rate in Hawaiian waters.

POTENTIAL BIOLOGICAL REMOVAL

No PBR can be calculated for this stock at this time.

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Fishery Information

No estimate of annual human-caused mortality and serious injury is available for killer whales in Hawaiian

waters (Nitta and Henderson 1993). However, mortality of other cetacean species has been observed in Hawaiian

fisheries, and the gear types used in these fisheries are responsible for marine mammal mortality and serious injury in

other fisheries throughout U.S. waters. Gillnets are used in Hawaiian waters and appear to capture marine mammals

wherever they are used, and float lines from lobster traps and longlines can be expected to occasionally entangle whales

(Perrin et al. 1994). 
206

Interactions with cetaceans have been reported for all Hawaiian pelagic fisheries (Nitta and Henderson 1993),

but killer whale interactions appear to be rare. In 1990, a solitary killer whale was reported to have removed the catch

from a longline in Hawaii (Dollar 1991). None were observed hooked in the Hawaiian longline fishery between 1994

and 1998, with approximately 4.4% of all effort (measured as the number of hooks fished) observed (Kleiber 1999).

Interaction rates between dolphins and the NWHI bottomfish fishery have been estimated based on studies conducted

in 1990-1993, indicating that an average of 2.67 dolphin interactions, most likely involving bottlenose and rough-toothed

dolphins, occurred for every 1000 fish brought on board (Kobayashi and Kawamoto 1995). Fishermen claim

interactions with dolphins who steal bait and catch are increasing. It is not known whether these interactions result in

serious injury or mortality of dolphins, nor whether killer whales are involved.

STATUS OF STOCK

The status of killer whales in Hawaiian waters relative to OSP is unknown, and there are insufficient data to

evaluate trends in abundance. No habitat issues are known to be of concern for this species. This species is not listed

as “threatened” or “endangered” under the Endangered Species Act (1973), nor as “depleted” under the MMPA.

Although information on killer whales in Hawaiian waters is limited, this stock would not be considered strategic under

the 1994 amendments to the MMPA given the insignificance of reported fisheries related mortality. Insufficient

information is available to determine whether the total fishery mortality and serious injury for killer whales is

insignificant and approaching zero mortality and serious injury rate.

REFERENCES

Bigg, M. A. 1982. An assessment of killer whale (Orcinus orca) stocks off Vancouver Island, British Columbia. Rep.

Int. Whal. Commn. 32:655-666.

Bigg, M. A., P. F. Olesiuk, G. M. Ellis, J. K. B. Ford, and K. C. Balcomb, III. 1990. Social organization and genealogy

of resident killer whales (Orcinus orca) in the coastal waters of British Columbia and Washington State. Rep.

Int. Whal. Commn. (Spec. Iss. 12):383-405.

Dollar, R. A. 1991. Summary of swordfish longline observations in Hawaii, July 1990-March 1991. Southwest Fish.

Cent. Admin. Rep. H-91-09, 13 pp.

Ford, J. K. B., G. M. Ellis, and K.C. Balcomb. 1994. Killer whales. The natural history and genealogy of Orcinus orca

in British Columbia and Washington State. UBC Press, Vancouver, Canada

Kleiber, P. 1999. Estimates of marine mammal takes in the Hawaiian longline fishery. (Unpublished). Southwest

Fisheries Science Center, NMFS, 2570 Dole St, Honolulu, HI, 96822-2396.

Kobayashi, D. R. and K. E. Kawamoto. 1995. Evaluation of shark, dolphin, and monk seal interactions with

Northwestern Hawaiian Island bottomfishing activity: a comparison of two time periods and an estimate of

economic impacts. Fisheries Research 23: 11-22.

Leatherwood, J. S., and M. E. Dahlheim. 1978. Worldwide distribution of pilot whales and killer whales. Naval Ocean

Systems Center, Tech. Rep. 443:1-39.

Heyning, J. E. and M. E. Dahlheim. 1988. Orcinus orca. Mamm. Spec.304:1-9.

Leatherwood, S., C. O. Matkin, J. D. Hall, and G. M. Ellis. 1990. Killer whales, Orcinus orca, photo-identified in

Prince William Sound, Alaska, 1976 through 1987. Can Field-Nat. 104:362-371.

Mitchell, E. D. 1975. Report on the meeting on small cetaceans, Montreal, April 1-11, 1974. J. Fish. Res. Board

Canada, 32:914-916.

Mobley, J. R. , Jr, S. S. Spitz, K. A. Forney, R. A. Grotefendt, and P. H. Forestall. 2000. Distribution and abundance

of odontocete species in Hawaiian waters: preliminary results of 1993-98 aerial surveys Admin. Rep. LJ-99-

XXC. Southwest Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA

92038. 26 pp.

Nitta, E. and J. R. Henderson. 1993. A review of interactions between Hawaii's fisheries and protected species. Mar.

Fish. Rev. 55(2):83-92.

Perrin, W.F., G. P. Donovan and J. Barlow. 1994. Gillnets and Cetaceans. Rep. Int. Whal. Commn., Special Issue 15,

629 pp.

Richards, L. P. 1952. Cuvier's beaked whale from Hawaii. J. Mamm. 33:255. 

Shallenberger, E.W. 1981. The status of Hawaiian cetaceans. Final report to U.S. Marine Mammal Commission. MMC77/23, 79pp.
207

Wade, P. R. and T. Gerrodette. 1993. Estimates of cetacean abundance and distribution in the eastern tropical Pacific.

Rep. Int. Whal. Commn. 43:477-493.
208

Figure 1. Short-finned pilot whale sighting locations during

1993-98 aerial surveys within about 25 nmi of the main

Hawaiian Islands (see Appendix 2 for details on timing and

location of survey effort). Outer line indicates approximate

boundary of survey area.

Revised 12/15/2000

SHORT-FINNED PILOT WHALE (Globicephala macrorhynchus): 

Hawaiian Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

Short-finned pilot whales are found in all

oceans, primarily in tropical and warm-temperate

waters. They are commonly observed around the

main Hawaiian Islands and are probably also present

around the Northwestern Hawaiian Islands

(Shallenberger 1981). Recent sighting locations

around the main Hawaiian Islands (Mobley et al.

2000) are shown in Figure 1. Several mass

strandings have been reported from the main islands

(Tomich 1986; Nitta 1991). In Japanese waters, two

stocks have been identified based on pigmentation

patterns and differences in the shape of the heads of

adult males (Kasuya et al. 1988). The pilot whales

in Hawaiian waters are similar to the Japanese

"southern form." Stock structure of short-finned

pilot whales has not been adequately studied in the

North Pacific, except in Japanese waters.

Preliminary photo-identification work with pilot

whales in Hawaii indicated a high degree of site

fidelity around the main island of Hawaii (Shane and

McSweeney 1990). For the Marine Mammal

Protection Act (MMPA) stock assessment reports,

short-finned pilot whales within the Pacific U.S.

Exclusive Economic Zone are divided into two discrete, non-contiguous areas: 1) Hawaiian waters (this report), and

2) waters off California, Oregon and Washington.

POPULATION SIZE

Estimates of short-finned pilot whale populations have been made off Japan (Miyashita 1993) and in the eastern

tropical Pacific (Wade and Gerrodette 1993), but it is not known whether any of these animals are part of the same

population that occurs around the Hawaiian Islands. As part of the Marine Mammal Research Program of the Acoustic

Thermometry of Ocean Climate (ATOC) study, a total of twelve aerial surveys were conducted within about 25 nmi of

the main Hawaiian Islands in 1993, 1995 and 1998. An abundance estimate of 1,708 (CV=0.32) short-finned pilot

whales was recently calculated from the combined survey data (Mobley et al. 2000). This abundance underestimates

the total number of short-finned pilot whales within the U.S. EEZ off Hawaii, because areas around the Northwest

Hawaiian Islands (NWHI) and beyond 25 nautical miles from the main islands were not surveyed.

Minimum Population Estimate

The log-normal 20th percentile of the combined 1993-98 abundance estimate is 1,313 short-finned pilot whales.

As with the best abundance estimate above, this includes only areas within about 25 nmi of the main Hawaiian Islands

and is therefore an underestimate.

Current Population Trend

No data are available on current population trend.

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

No data are available on current or maximum net productivity rate.
209

10 N 15 N 20 N 25 N 30 N 35 N 40 N

180 W 170 W 160 W 150 W 140 W

GG GGTT

UC

UW

GM

GG GG

SL

PC

UW

PC

UW

TT T. truncatus

GG G. griseus

SL S longirostris

PC P. crassidens

GM G. macrorhynchus

UC Cetacean, unident.

UW Whale, unident.

Figure 2. Locations of observed cetacean interactions in the

Hawaiian longline fishery, 1994-98 (modified from Kleiber 1999).

Dashed line is the U.S. Exclusive Economic Zone (EEZ); GM =

short-finned pilot whale.

POTENTIAL BIOLOGICAL REMOVAL

The potential biological removal (PBR) level for this stock is calculated as the minimum population size (1,313)

times one half the default maximum net growth rate for cetaceans (1⁄2 of 4%) times a recovery factor of 0.50 (for a

species of unknown status with a known fishery mortality within the U.S. EEZ off Hawaii; Wade and Angliss 1997),

resulting in a PBR of 13 short-finned pilot whales per year.

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Fishery Information

Mortality of cetaceans has been observed in Hawaiian fisheries, and the gear types used in these fisheries are

responsible for marine mammal mortality and serious injury in other fisheries throughout U.S. waters. Gillnets are used

in Hawaiian waters and appear to capture marine mammals wherever they are used, and float lines from lobster traps

and longlines can be expected to occasionally

entangle whales (Perrin et al. 1994). 

One short-finned pilot whale was

observed killed outside the U.S. EEZ in the

Hawaiian longline fishery between 1994 and 1998

(Figure 2), with approximately 4.4% of all effort

(measured as the number of hooks fished)

observed. This mortality rate extrapolates to a

total 5-year estimate of 23 (95% CI = 1-108)

short-finned pilot whales, or an average of 4.6

animals killed per year (Kleiber 1999). The

single observed short-finned pilot whale was

reported to have been entangled in the fishing

line. Reports for other odontocetes indicate

animals may also ingest the hook or become

hooked in the mouth or other part of their body. 

 Interactions with cetaceans have been

reported for all Hawaiian pelagic fisheries (Nitta

and Henderson 1993), but no other interactions

with short-finned pilot whales have been

documented. Interaction rates between dolphins

and the NWHI bottomfish fishery have been

estimated based on studies conducted in 1990-

1993, indicating that an average of 2.67 dolphin

interactions, most likely involving bottlenose and rough-toothed dolphins, occurred for every 1000 fish brought on board

(Kobayashi and Kawamoto 1995). Fishermen claim interactions with dolphins who steal bait and catch are increasing.

It is not known whether these interactions result in serious injury or mortality of dolphins, nor whether short-finned pilot

whales are involved. 

Other Removals

Since 1963, at least 20 short-finned pilot whales have been live-captured from Hawaiian waters by Sea Life

Park/Oceanic Foundation (Shallenberger 1981).

STATUS OF STOCK

The status of short-finned pilot whales in Hawaiian waters relative to OSP is unknown, and there are

insufficient data to evaluate trends in abundance. No habitat issues are known to be of concern for this species. They

are not listed as “threatened” or “endangered” under the Endangered Species Act (1973), nor as “depleted” under the

MMPA. Although information on short-finned pilot whales in Hawaiian waters is limited, this stock would not be

considered strategic under the 1994 amendments to the MMPA given the absence of reported fisheries related mortality

within the U.S. EEZ. However, the potential effect of mortality in the Hawaiian longline fishery in international waters

is not known. Insufficient information is available to determine whether the total fishery mortality and serious injury
210

for short-finned pilot whales is insignificant and approaching zero mortality and serious injury rate.

REFERENCES

Kasuya, T., T. Miyashita, and F. Kasamatsu. 1988. Segregation of two forms of short-finned pilot whales off the

Pacific coast of Japan. Sci. Rep. Whales Res. Inst. 39:77-90.

Kleiber, P. 1999. Estimates of marine mammal takes in the Hawaiian longline fishery. (Unpublished). Southwest

Fisheries Science Center, NMFS, 2570 Dole St, Honolulu, HI, 96822-2396.

Kobayashi, D. R. and K. E. Kawamoto. 1995. Evaluation of shark, dolphin, and monk seal interactions with

Northwestern Hawaiian Island bottomfishing activity: a comparison of two time periods and an estimate of

economic impacts. Fisheries Research 23: 11-22.

Miyashita, T. 1993. Abundance of dolphin stocks in the western North Pacific taken by the Japanese drive fishery.

Rep. Int. Whal. Commn. 43:417-437.

Mobley, J. R. , Jr, S. S. Spitz, K. A. Forney, R. A. Grotefendt, and P. H. Forestall. 2000. Distribution and abundance

of odontocete species in Hawaiian waters: preliminary results of 1993-98 aerial surveys Admin. Rep. LJ-00-

14C. Southwest Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA

92038. 26 pp.

Nitta, E. 1991. The marine mammal stranding network for Hawaii: an overview. In: J.E. Reynolds III, D.K. Odell

(eds.), Marine Mammal Strandings in the United States, pp.56-62. NOAA Tech. Rep. NMFS 98, 157 pp.

Nitta, E. and J. R. Henderson. 1993. A review of interactions between Hawaii's fisheries and protected species. Mar.

Fish. Rev. 55(2):83-92.

Perrin, W.F., G. P. Donovan and J. Barlow. 1994. Gillnets and Cetaceans. Rep. Int. Whal. Commn., Special Issue 15,

629 pp.

Shallenberger, E.W. 1981. The status of Hawaiian cetaceans. Final report to U.S. Marine Mammal Commission. MMC77/23, 79pp.

Shane, S. H. and D. McSweeney. 1990. Using photo-identification to study pilot whales social organization. Rep. Int.

Whal. Commn. (Spec. Iss. 12):259-263.

Tomich, P. Q. 1986. Mammals in Hawaii: A Synopsis and Notational Bibliography. Bishop Museum Press, Hawaii,

375 pp.

Wade, P. R. and R. P. Angliss. 1997. Guidelines for Assessing Marine Mammal Stocks: Report of the GAMMS

Workshop April 3-5, 1996, Seattle, WA. U. S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-12. 93 pp.

Wade, P. R. and T. Gerrodette. 1993. Estimates of cetacean abundance and distribution in the eastern tropical Pacific.

Rep. Int. Whal. Commn. 43:477-493.
211

Figure 1. Blainville’s beaked whale (!) and unidentified

Mesoplodon (+) sighting locations during 1993-98 aerial surveys

within about 25 nmi of the main Hawaiian Islands (see

Appendix 2 for details on timing and location of survey effort).

Outer line indicates approximate boundary of survey area.

Revised 12/15/2000

BLAINVILLE'S BEAKED WHALE (Mesoplodon densirostris): 

Hawaiian Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

Blainville's beaked whale has a

cosmopolitan distribution in tropical and temperate

waters, apparently the most extensive known

distribution of any Mesoplodon species (Mead

1989). Two strandings were reported in 1961 from

Midway Island (Galbreath 1963) and another in

1983 from Laysan Island (Nitta 1991). Sixteen

sightings were reported from the main islands by

Shallenberger (1981), who suggested that

Blainville's beaked whales were present off the

Waianae Coast of Oahu for prolonged periods

annually. Balcomb (1987) speculated that this

species is "more common in Hawaii than anywhere

else in the world." Recent sighting locations around

the main Hawaiian Islands (Mobley et al. 2000) are

shown in Figure 1. Although all identified

Mesoplodon records from Hawaiian waters are of

M. densirostris, several other species in the genus

Mesoplodon are known from the North Pacific and

may be recorded in Hawaiian waters in the future

(see Mead 1989). There is no information on stock

structure of Blainville's beaked whale. For the

Marine Mammal Protection Act (MMPA) stock

assessment reports, three Mesoplodon stocks are defined: 1) M. densirostris in Hawaiian waters (this report), 2) M.

stejnegeri in Alaskan waters, and 3) all Mesoplodon species off California, Oregon and Washington.

POPULATION SIZE

As part of the Marine Mammal Research Program of the Acoustic Thermometry of Ocean Climate (ATOC)

study, a total of twelve aerial surveys were conducted within about 25 nmi of the main Hawaiian Islands in 1993, 1995

and 1998. Seven sightings of Blainville’s beaked whales were made. An abundance estimate of 68 (CV=0.60)

Blainville’s beaked whales was recently calculated from the combined survey data (Mobley et al. 2000). This

abundance underestimates the total number of Blainville’s beaked whales within the U.S. EEZ off Hawaii, because areas

around the Northwest Hawaiian Islands (NWHI) and beyond 25 nautical miles from the main islands were not surveyed.

Furthermore, this species is known to spend a large proportion of time diving, causing additional downward bias in the

abundance estimate.

Minimum Population Estimate

The log-normal 20th percentile of the combined 1993-98 abundance estimate is 43 Blainville’s beaked whales.

As with the best abundance estimate above, this includes only areas within about 25 nmi of the main Hawaiian Islands

and does not include a large proportion of animals that were diving and therefore unavailable to be seen.

Current Population Trend

No data are available on current population trend.

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

No data are available on current or maximum net productivity rate.
212

10 N 15 N 20 N 25 N 30 N 35 N 40 N

180 W 170 W 160 W 150 W 140 W

GG GGTT

UC

UW

GM

GG GG

SL

PC

UW

PC

UW

TT T. truncatus

GG G. griseus

SL S longirostris

PC P. crassidens

GM G. macrorhynchus

UC Cetacean, unident.

UW Whale, unident.

Figure 2. Locations of observed cetacean interactions in the

Hawaiian longline fishery, 1994-98 (modified from Kleiber 1999).

Dashed line is the U.S. Exclusive Economic Zone (EEZ); UW =

unidentified whale; UC = unidentified cetacean. The two

westernmost unidentified whales may have been Blainville’s

beaked whales.

POTENTIAL BIOLOGICAL REMOVAL

The potential biological removal (PBR) level for this stock is calculated as the minimum population size (43)

times one half the default maximum net growth rate for cetaceans (1⁄2 of 4%) times a recovery factor of 0.50 (for a

species of unknown status with no known fishery mortality; Wade and Angliss 1997), resulting in a PBR of 0.4

Blainville’s beaked whales per year.

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Fishery Information

No estimate of annual human-caused mortality and serious injury is available as there are no reports of direct

or incidental takes of Blainville's beaked whales in Hawaiian waters (Nitta and Henderson 1993). However, mortality

of other cetacean species has been observed in Hawaiian fisheries, and the gear types used in these fisheries are

responsible for marine mammal mortality and serious injury in other fisheries throughout U.S. waters. Gillnets are used

in Hawaiian waters and appear to capture marine mammals wherever they are used, and float lines from lobster traps

and longlines can be expected to occasionally entangle whales (Perrin et al. 1994).

Interactions with dolphins are reported

for all pelagic fisheries, and humpback whales

have been entangled in longlines off the

Hawaiian Islands (Nitta and Henderson 1993),

but no takes of Blainville's beaked whales have

been documented. However, three unidentified

whales and one unidentified cetacean were

observed hooked in the Hawaiian longline fishery

between 1994 and 1998 (Figure 2), with

approximately 4.4% of all effort (measured as the

number of hooks fished) observed. Observer

descriptions and photographs of these

interactions indicate that at least two of the

unidentified whales may have been beaked

whales, including one within the U.S. EEZ. The

total interaction rate based on these two possible

beaked whales extrapolates to a 5-year estimate

of 45 (95% CI = 7-108), or an average of 9

interactions per year (Kleiber 1999). One of the

two possible beaked whales was hooked in the

fluke, and following the guidelines of a 1997

Serious Injury Workshop (Angliss and DeMaster

1998), this would not be considered a serious

injury (defined under the MMPA as likely to

result in mortality). The other interaction, which

took place within the U.S. EEZ, involved a possible beaked whale that was hooked but broke the line and swam away

before the location of the hook could be ascertained. Therefore, no determination can be made regarding the severity

of this second injury. Reports for other odontocetes indicate they may also become hooked in the mouth or ingest the

hook, and that they may occasionally become entangled in the fishing line. Insufficient information is available to

evaluate whether some of these unidentified whales may have been Blainville’s beaked whales.

STATUS OF STOCK

The status of Blainville's beaked whales in Hawaiian waters relative to OSP is unknown, and there are

insufficient data to evaluate trends in abundance. They are not listed as “threatened” or “endangered” under the

Endangered Species Act (1973), nor as “depleted” under the MMPA. Although information on Blainville's beaked

whales in Hawaiian waters is limited, this stock would not be considered strategic under the 1994 amendments to the

MMPA because there has been no reported fisheries related mortality within the U.S. EEZ. However, the effect of

potential interactions of unidentified beaked whales (which may have been Blainville’s beaked whales) with the
213

Hawaiian longline fishery in U.S. and international waters is not known. Insufficient information is available to

determine whether the total fishery mortality and serious injury for Blainville’s beaked whales is insignificant and

approaching zero mortality and serious injury rate. The increasing levels of anthropogenic noise in the world’s oceans

has been suggested to be a habitat concern for whales, particularly for deep-diving whales like Blainville’s beaked

whales that feed in the oceans’ “sound channel”.

REFERENCES

Angliss, R. P. and D. P. DeMaster. 1998. Differentiating Serious and Non-Serious Injury of Marine Mammals Taken

Incidental to Commercial Fishing Operations: Report of the Serious Injury Workshop 1-2 April 1997, Silver

Spring, Maryland. U. S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-13. 48 pp.

Balcomb, K. C., III. 1987. The Whales of Hawaii. Marine Mammal Fund, 99 pp.

Galbreath, E. C. 1963. Three beaked whales stranded on the Midway Islands, central Pacific Ocean. J. Mamm.

44:422-423.

Kleiber, P. 1999. Estimates of marine mammal takes in the Hawaiian longline fishery. (Unpublished). Southwest

Fisheries Science Center, NMFS, 2570 Dole St, Honolulu, HI, 96822-2396.

Mobley, J. R. , Jr, S. S. Spitz, K. A. Forney, R. A. Grotefendt, and P. H. Forestall. 2000. Distribution and abundance

of odontocete species in Hawaiian waters: preliminary results of 1993-98 aerial surveys Admin. Rep. LJ-00-

14C. Southwest Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA

92038. 26 pp.

Mead, J. G. 1989. Beaked whales of the genus Mesoplodon. In: S. H. Ridgway and R. Harrison (eds.), Handbook of

Marine Mammals, Vol. 4: The River Dolphins and Larger Toothed Whales, pp. 349-430. Academic Press, 442

pp.

Nitta, E. 1991. The marine mammal stranding network for Hawaii: an overview. In: J.E. Reynolds III, D.K. Odell

(eds.), Marine Mammal Strandings in the United States, pp.56-62. NOAA Tech. Rep. NMFS 98, 157 pp.

Nitta, E. and J. R. Henderson. 1993. A review of interactions between Hawaii's fisheries and protected species. Mar.

Fish. Rev. 55(2):83-92.

Perrin, W. F., G. P. Donovan and J. Barlow. 1994. Gillnets and Cetaceans. Rep. Int. Whal. Commn., Special Issue 15,

629 pp.

Shallenberger, E. W. 1981. The status of Hawaiian cetaceans. Final report to U.S. Marine Mammal Commission.

MMC-77/23, 79pp.

Wade, P. R. and R. P. Angliss. 1997. Guidelines for Assessing Marine Mammal Stocks: Report of the GAMMS

Workshop April 3-5, 1996, Seattle, Washington. U. S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-12.

93 pp.
214

Figure 1. Cuvier’s beaked whale sighting locations during

1993-98 aerial surveys within about 25 nmi of the main

Hawaiian Islands (see Appendix 2 for details on timing and

location of survey effort). Outer line indicates approximate

boundary of survey area.

Revised 12/15/2000

CUVIER'S BEAKED WHALE (Ziphius cavirostris): Hawaiian Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

Cuvier's beaked whales occur in all oceans

and major seas (Heyning 1989). In Hawaii,

strandings have been reported from Midway

Islands, Pearl and Hermes Reef, Oahu, and Hawaii

Islands (Shallenberger 1981; Galbreath 1963;

Richards 1952; Nitta 1991). Sightings have been

reported off Lanai and Maui (Shallenberger 1981).

Recent sighting locations around the main

Hawaiian Islands (Mobley et al. 2000) are shown in

Figure 1. Nothing is known about stock structure

for this species. For the Marine Mammal

Protection Act (MMPA) stock assessment reports,

Cuvier's beaked whales within the Pacific U.S.

Exclusive Economic Zone are divided into three

discrete, non-contiguous areas: 1) Hawaiian waters

(this report), 2) Alaskan waters, and 3) waters off

California, Oregon and Washington.

POPULATION SIZE

Wade and Gerrodette (1993) made an

estimate for Cuvier's beaked whales in the eastern

tropical Pacific, but it is not known whether any of

these animals are part of the same population that

occurs around the Hawaiian Islands. As part of the Marine Mammal Research Program of the Acoustic Thermometry

of Ocean Climate (ATOC) study, a total of twelve aerial surveys were conducted within about 25 nmi of the main

Hawaiian Islands in 1993, 1995 and 1998. Seven sightings of Cuvier’s beaked whales were made. An abundance

estimate of 43 (CV=0.51) Cuvier’s beaked whales was recently calculated from the combined survey data (Mobley et

al. 2000). This abundance underestimates the total number of Cuvier’s beaked whales within the U.S. EEZ off Hawaii,

because areas around the Northwest Hawaiian Islands (NWHI) and beyond 25 nautical miles from the main islands were

not surveyed. Furthermore, this species is known to spend a large proportion of time diving, causing additional

downward bias in the abundance estimate.

Minimum Population Estimate

The log-normal 20th percentile of the combined 1993-98 abundance estimate is 29 Cuvier’s beaked whales.

As with the best abundance estimate above, this includes only areas within about 25 nmi of the main Hawaiian Islands

and does not include a large proportion of animals that were diving and therefore unavailable to be seen.

Current Population Trend

No data are available on current population trend.

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

No data are available on current or maximum net productivity rate.

POTENTIAL BIOLOGICAL REMOVAL

The potential biological removal (PBR) level for this stock is calculated as the minimum population size (29)

times one half the default maximum net growth rate for cetaceans (1⁄2 of 4%) times a recovery factor of 0.50 (for a

species of unknown status with no known fishery mortality; Wade and Angliss 1997), resulting in a PBR of 0.3 Cuvier’s

beaked whales per year.
215

10 N 15 N 20 N 25 N 30 N 35 N 40 N

180 W 170 W 160 W 150 W 140 W

GG GGTT

UC

UW

GM

GG GG

SL

PC

UW

PC

UW

TT T. truncatus

GG G. griseus

SL S longirostris

PC P. crassidens

GM G. macrorhynchus

UC Cetacean, unident.

UW Whale, unident.

Figure 2. Locations of observed cetacean interactions in the

Hawaiian longline fishery, 1994-98 (modified from Kleiber 1999).

Dashed line is the U.S. Exclusive Economic Zone (EEZ); UW =

unidentified whale; UC = unidentified cetacean. The two

westernmost unidentified whales may have been Cuvier’s beaked

whales.

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Fishery Information

No estimate of annual human-caused mortality and serious injury is available as there are no reports of direct

or incidental takes of Cuvier's beaked whales in Hawaiian waters (Nitta and Henderson 1993). However, mortality of

other cetacean species has been observed in Hawaiian fisheries, and the gear types used in these fisheries are responsible

for marine mammal mortality and serious injury in other fisheries throughout U.S. waters. Gillnets are used in Hawaiian

waters and appear to capture marine mammals wherever they are used, and float lines from lobster traps and longlines

can be expected to occasionally entangle whales (Perrin et al. 1994).

Interactions with dolphins are reported

for all pelagic fisheries, and humpback whales

have been entangled in longlines off the Hawaiian

Islands (Nitta and Henderson 1993), but no takes

of Cuvier's beaked whales have been documented.

However, three unidentified whales and one

unidentified cetacean were observed hooked in

the Hawaiian longline fishery between 1994 and

1998 (Figure 2), with approximately 4.4% of all

effort (measured as the number of hooks fished)

observed. Observer descriptions and photographs

of these interactions indicate that at least two of

the unidentified whales may have been beaked

whales, including one within the U.S. EEZ. The

total interaction rate based on these two possible

beaked whales extrapolates to a 5-year estimate of

45 (95% CI = 7-108), or an average of 9

interactions per year (Kleiber 1999). One of the

two possible beaked whales was hooked in the

fluke, and following the guidelines of a 1997

Serious Injury Workshop (Angliss and DeMaster

1998), this would not be considered a serious

injury (defined under the MMPA as likely to

result in mortality). The other interaction, which

took place within the U.S. EEZ, involved a possible beaked whale that was hooked but broke the line and swam away

before the location of the hook could be ascertained. Therefore, no determination can be made regarding the severity

of this second injury. Reports for other odontocetes indicate they may also become hooked in the mouth or ingest the

hook, and that they may occasionally become entangled in the fishing line. Insufficient information is available to

evaluate whether some of these unidentified whales may have been Cuvier’s beaked whales.

STATUS OF STOCK

The status of Cuvier's beaked whales in Hawaiian waters relative to OSP is unknown, and there are insufficient

data to evaluate trends in abundance. They are not listed as “threatened” or “endangered” under the Endangered Species

Act (1973), nor as “depleted” under the MMPA. Although information on Cuvier's beaked whales in Hawaiian waters

is limited, this stock would not be considered strategic under the 1994 amendments to the MMPA because there has

been no reported fisheries related mortality within the U.S. EEZ. However, the effect of potential interactions of

unidentified beaked whales (which may have been Cuvier’s beaked whales) with the Hawaiian longline fishery in U.S.

and international waters is not known. Insufficient information is available to determine whether the total fishery

mortality and serious injury for Cuvier’s beaked whales is insignificant and approaching zero mortality and serious

injury rate. The increasing levels of anthropogenic noise in the world’s oceans has been suggested to be a habitat

concern for whales, particularly for deep-diving whales like Cuvier’s beaked whales that feed in the oceans’ “sound

channel”.
216

REFERENCES

Angliss, R. P. and D. P. DeMaster. 1998. Differentiating Serious and Non-Serious Injury of Marine Mammals Taken

Incidental to Commercial Fishing Operations: Report of the Serious Injury Workshop 1-2 April 1997, Silver

Spring, Maryland. U. S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-13. 48 pp.

Galbreath, E. C. 1963. Three beaked whales stranded on the Midway Islands, central Pacific Ocean. J. Mamm.

44:422-423.

Heyning, J. E. 1989. Cuvier's beaked whale Ziphius cavirostris G. Cuvier, 1823. In: S. H. Ridgway and R. Harrison

(eds.), Handbook of Marine Mammals, Vol. 4: The River Dolphins and Larger Toothed Whales, pp. 289-308.

Academic Press, 442 pp.

Kleiber, P. 1999. Estimates of marine mammal takes in the Hawaiian longline fishery. (Unpublished). Southwest

Fisheries Science Center, NMFS, 2570 Dole St, Honolulu, HI, 96822-2396.

Mobley, J. R. , Jr, S. S. Spitz, K. A. Forney, R. A. Grotefendt, and P. H. Forestall. 2000. Distribution and abundance

of odontocete species in Hawaiian waters: preliminary results of 1993-98 aerial surveys Admin. Rep. LJ-00-

14C. Southwest Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA

92038. 26 pp.

Nitta, E. 1991. The marine mammal stranding network for Hawaii: an overview. In: J.E. Reynolds III, D.K. Odell

(eds.), Marine Mammal Strandings in the United States, pp.56-62. NOAA Tech. Rep. NMFS 98, 157 pp.

Nitta, E. and J. R. Henderson. 1993. A review of interactions between Hawaii's fisheries and protected species. Mar.

Fish. Rev. 55(2):83-92.

Perrin, W.F., G. P. Donovan and J. Barlow. 1994. Gillnets and Cetaceans. Rep. Int. Whal. Commn., Special Issue 15,

629 pp.

Richards, L. P. 1952. Cuvier's beaked whale from Hawaii. J. Mamm. 33:255. 

Shallenberger, E.W. 1981. The status of Hawaiian cetaceans. Final report to U.S. Marine Mammal Commission. MMC77/23, 79pp.

Wade, P. R. and R. P. Angliss. 1997. Guidelines for Assessing Marine Mammal Stocks: Report of the GAMMS

Workshop April 3-5, 1996, Seattle, Washington. U. S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-12.

93 pp.

Wade, P. R. and T. Gerrodette. 1993. Estimates of cetacean abundance and distribution in the eastern tropical Pacific.

Rep. Int. Whal. Commn. 43:477-493.
217

Figure 1. Pygmy or dwarf sperm whale sighting locations

during 1993-98 aerial surveys within about 25 nmi of the main

Hawaiian Islands (see Appendix 2 for details on timing and

location of survey effort). Outer line indicates approximate

boundary of survey area.

Revised 12/15/2000

PYGMY SPERM WHALE (Kogia breviceps): Hawaiian Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

Pygmy sperm whales are found throughout

the world in tropical and warm-temperate waters

(Caldwell and Caldwell 1989). Between the years

1949 and 1982, at least nine strandings of this

species were reported in the Hawaiian Islands

(Tomich 1986; Nitta 1991). Shallenberger (1981)

reported three sightings off Oahu and Maui. Two

sightings of pygmy or dwarf sperm whales were

made between Hawaii and Maui during 1993-98

aerial surveys within about 25 nmi of the main

Hawaiian Islands (Figure 1; Mobley et al. 1999). A

stranded calf was held for several days at Sea Life

Park (Pryor 1975:94). Nothing is known about

stock structure for this species. For the Marine

Mammal Protection Act (MMPA) stock assessment

reports, pygmy sperm whales within the Pacific

U.S. Exclusive Economic Zone are divided into two

discrete, non-contiguous areas: 1) Hawaiian waters

(this report), and 2) waters off California, Oregon

and Washington.

POPULATION SIZE

No data are available to estimate

population size for this species in the central Pacific. As part of the Marine Mammal Research Program of the Acoustic

Thermometry of Ocean Climate (ATOC) study, a total of twelve aerial surveys were conducted within about 25 nmi of

the main Hawaiian Islands in 1993, 1995 and 1998. Two sightings of five pygmy or dwarf sperm whales were made;

however these sightings were excluded during recent abundance analyses (Mobley et al. 2000), because they were made

during poor observation conditions. Therefore, no abundance estimate is available for pygmy sperm whales within

Hawaiian waters.

Minimum Population Estimate

No data are available to provide a minimum population estimate.

Current Population Trend

No data are available on current population trend.

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

No data are available on current or maximum net productivity rate.

POTENTIAL BIOLOGICAL REMOVAL

No PBR can be calculated for this stock at this time.

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Fishery Information

No estimate of annual human-caused mortality and serious injury is available as there are no reports of direct

or incidental takes of pygmy sperm whales in Hawaiian waters (Nitta and Henderson 1993). However, mortality of other

cetacean species has been observed in Hawaiian fisheries, and the gear types used in these fisheries are responsible for

marine mammal mortality and serious injury in other fisheries throughout U.S. waters. Gillnets are used in Hawaiian
218

waters and appear to capture marine mammals wherever they are used, and float lines from lobster traps and longlines

can be expected to occasionally entangle whales (Perrin et al. 1994).

Interactions with cetaceans have been reported for all Hawaiian pelagic fisheries (Nitta and Henderson 1993),

but no interactions with pygmy sperm whales have been documented. None were observed hooked in the Hawaiian

longline fishery between 1994 and 1998, with approximately 4.4% of all effort (measured as the number of hooks

fished) observed (Kleiber 1999). 

STATUS OF STOCK

The status of pygmy sperm whales in Hawaiian waters relative to OSP is unknown, and there are insufficient

data to evaluate trends in abundance. They are not listed as “threatened” or “endangered” under the Endangered Species

Act (1973), nor as “depleted” under the MMPA. Although information on pygmy sperm whales in Hawaiian waters

is limited, this stock would not be considered strategic under the 1994 amendments to the MMPA because there has

been no reported fisheries related mortality. The total fishery mortality and serious injury for pygmy sperm whales is

zero and therefore can be considered to be insignificant and approaching zero mortality and serious injury rate. The

increasing levels of anthropogenic noise in the world’s oceans has been suggested to be a habitat concern for whales,

particularly for deep-diving whales like pygmy sperm whales that feed in the oceans’ “sound channel”.

REFERENCES

Caldwell, D. K. and M. C. Caldwell. 1989. Pygmy sperm whale Kogia breviceps (de Blainville, 1838): Dwarf sperm

whale Kogia simus Owen, 1866. In: S. H. Ridgway and R. Harrison (eds.), Handbook of Marine Mammals,

Vol. 4: The River Dolphins and Larger Toothed Whales, pp. 235-260. Academic Press, 442 pp.

Kleiber, P. 1999. Estimates of marine mammal takes in the Hawaiian longline fishery. (Unpublished). Southwest

Fisheries Science Center, 2570 Dole St, Honolulu, HI, 96822-2396.

Mobley, J. R., Jr., R. A. Grotefendt, P. H. Forestell, and A. Frankel. 1999. Results of aerial surveys of marine mammals

in the major Hawaiian Islands (1993-98): Report to the Acoustic Thermometry of Ocean Climate Marine

Mammal Research Program (ATOC MMRP) (unpublished). 39 pp.

Mobley, J. R., Jr, S. S. Spitz, K. A. Forney, R. A. Grotefendt, and P. H. Forestall. 2000. Distribution and abundance

of odontocete species in Hawaiian waters: preliminary results of 1993-98 aerial surveys Admin. Rep. LJ-00-

14C. Southwest Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA

92038. 26 pp.

Nitta, E. 1991. The marine mammal stranding network for Hawaii: an overview. In: J.E. Reynolds III, D.K. Odell

(eds.), Marine Mammal Strandings in the United States, pp.56-62. NOAA Tech. Rep. NMFS 98, 157 pp.

Nitta, E. and J. R. Henderson. 1993. A review of interactions between Hawaii's fisheries and protected species. Mar.

Fish. Rev. 55(2):83-92.

Perrin, W.F., G. P. Donovan and J. Barlow. 1994. Gillnets and Cetaceans. Rep. Int. Whal. Commn., Special Issue 15,

629 pp.

Pryor, K. 1975. Lads Before the Wind: Adventures in Porpoise Training. Harper and Row, New York, 278 pp.

Shallenberger, E.W. 1981. The status of Hawaiian cetaceans. Final report to U.S. Marine Mammal Commission. MMC77/23, 79pp.

Tomich, P. Q. 1986. Mammals in Hawaii: A Synopsis and Notational Bibliography. Bishop Museum Press, Hawaii,

375 pp.
219

Figure 1. Pygmy or dwarf sperm whale sighting locations

during 1993-98 aerial surveys within about 25 nmi of the main

Hawaiian Islands (see Appendix 2 for details on timing and

location of survey effort). Outer line indicates approximate

boundary of survey area.

Revised 12/15/2000

DWARF SPERM WHALE (Kogia sima): Hawaiian Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

Dwarf sperm whales are found throughout

the world in tropical to warm-temperate waters

(Nagorsen 1985). One sighting in an unspecified

locality, one stranding on Oahu (Tomich 1986), and

one stranding on Lanai (Nitta 1991) constitute the

only evidence that this species inhabits Hawaiian

waters (Tomich 1986). Two sightings of pygmy or

dwarf sperm whales were made between Hawaii

and Maui during 1993-98 aerial surveys within

about 25 nmi of the main Hawaiian Islands (Figure

1; Mobley et al. 1999). The difficulty of detecting

and identifying it at sea, as well as its confusion

with the pygmy sperm whale, may partially explain

the paucity of records. For the Marine Mammal

Protection Act (MMPA) stock assessment reports,

there is a single Pacific management stock of dwarf

sperm whales including only animals found within

the U.S. Exclusive Economic Zone of the Hawaiian

Islands. Rice (1998) recently argued that the

species name simus, is incorrect and should be

replaced by sima. This change is not taxonomic,

but merely reflects rules of Latin usage.

POPULATION SIZE

Wade and Gerrodette (1993) provided an estimate for the eastern tropical Pacific, but no data are available to

estimate population size for this species in the central Pacific. As part of the Marine Mammal Research Program of the

Acoustic Thermometry of Ocean Climate (ATOC) study, a total of twelve aerial surveys were conducted within about

25 nmi of the main Hawaiian Islands in 1993, 1995 and 1998. Two sightings of five pygmy or dwarf sperm whales were

made; however these sightings were excluded during recent abundance analyses (Mobley et al. 2000), because they were

made during poor observation conditions. Therefore, no abundance estimate is available for dwarf sperm whales within

Hawaiian waters.

Minimum Population Estimate

No data are available for a minimum population estimate.

Current Population Trend

No data are available on current population trend.

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

No data are available on current or maximum net productivity rate.

POTENTIAL BIOLOGICAL REMOVAL

No PBR can be calculated for this species at this time.

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Fishery Information

No estimate of annual human-caused mortality and serious injury is available as there are no reports of direct

or incidental takes of dwarf sperm whales in Hawaiian waters (Nitta and Henderson 1993). However, mortality of other
220

cetacean species has been observed in Hawaiian fisheries, and the gear types used in these fisheries are responsible for

marine mammal mortality and serious injury in other fisheries throughout U.S. waters. Gillnets are used in Hawaiian

waters and appear to capture marine mammals wherever they are used, and float lines from lobster traps and longlines

can be expected to occasionally entangle whales (Perrin et al. 1994).

Interactions with cetaceans have been reported for all Hawaiian pelagic fisheries (Nitta and Henderson 1993),

but no interactions with dwarf sperm whales have been documented. None were observed hooked in the Hawaiian

longline fishery between 1994 and 1998, with approximately 4.4% of all effort (measured as the number of hooks

fished) observed (Kleiber 1999).

STATUS OF STOCK

The status of dwarf sperm whales in Hawaiian waters relative to OSP is unknown, and there are insufficient

data to evaluate trends in abundance. They are not listed as “threatened” or “endangered” under the Endangered Species

Act (1973), nor as “depleted” under the MMPA. Although information on dwarf sperm whales in Hawaiian waters is

limited, this stock would not be considered strategic under the 1994 amendments to the MMPA because there has been

no reported fisheries related mortality. The total fishery mortality and serious injury for dwarf sperm whales is zero and

therefore can be considered to be insignificant and approaching zero mortality and serious injury rate. The increasing

levels of anthropogenic noise in the world’s oceans has been suggested to be a habitat concern for whales, particularly

for deep-diving whales like dwarf sperm whales that feed in the oceans’ “sound channel”.

REFERENCES

Kleiber, P. 1999. Estimates of marine mammal takes in the Hawaiian longline fishery. (Unpublished). Southwest

Fisheries Science Center, NMFS, 2570 Dole St, Honolulu, HI, 96822-2396.

Mobley, J. R., Jr., R. A. Grotefendt, P. H. Forestell, and A. Frankel. 1999. Results of aerial surveys of marine mammals

in the major Hawaiian Islands (1993-98): Report to the Acoustic Thermometry of Ocean Climate Marine

Mammal Research Program (ATOC MMRP) (unpublished). 39 pp.

Mobley, J. R. , Jr, S. S. Spitz, K. A. Forney, R. A. Grotefendt, and P. H. Forestall. 2000. Distribution and abundance

of odontocete species in Hawaiian waters: preliminary results of 1993-98 aerial surveys Admin. Rep. LJ-00-

14C. Southwest Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA

92038. 26 pp.

Nagorsen, D. 1985. Kogia simus. Mamm. Spec. 239:1-6.

Nitta, E. 1991. The marine mammal stranding network for Hawaii: an overview. In: J.E. Reynolds III, D.K. Odell

(eds.), Marine Mammal Strandings in the United States, pp.56-62. NOAA Tech. Rep. NMFS 98, 157 pp.

Nitta, E. and J. R. Henderson. 1993. A review of interactions between Hawaii's fisheries and protected species. Mar.

Fish. Rev. 55(2):83-92.

Perrin, W.F., G. P. Donovan and J. Barlow. 1994. Gillnets and Cetaceans. Rep. Int. Whal. Commn., Special Issue 15,

629 pp.

Rice, D.W. 1998. Marine Mammals of the World Systematics and Distribution. Special Publication Number 4 The

Society of Marine Mammalogy. Douglas Wartzok (ed.). 231 pp.

Tomich, P. Q. 1986. Mammals in Hawaii: A Synopsis and Notational Bibliography. Bishop Museum Press, Hawaii,

375 pp.

Wade, P. R. and T. Gerrodette. 1993. Estimates of cetacean abundance and distribution in the eastern tropical Pacific.

Rep. Int. Whal. Commn. 43:477-493.
221

Figure 1. Sperm whale sighting locations during 1993-98 aerial

surveys within about 25 nmi of the main Hawaiian Islands (see

Appendix 2 for details on timing and location of survey effort).

Outer line indicates approximate boundary of survey area.

Revised 12/15/2000

SPERM WHALE (Physeter macrocephalus): Hawaiian Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

Sperm whales are widely distributed

across the entire North Pacific and into the southern

Bering Sea in summer but the majority are thought

to be south of 40oN in winter (Rice 1974, 1989;

Gosho et al. 1984; Miyashita et al. 1995). For

management, the International Whaling

Commission (IWC) had divided the North Pacific

into two management regions (Donovan 1991)

defined by a zig-zag line which starts at 150oW at

the equator, is 160oW between 40-50oN, and ends

up at 180oW north of 50oN; however, the IWC has

not reviewed this stock boundary in many years

(Donovan 1991). Summer/fall surveys in the

eastern tropical Pacific (Wade and Gerrodette

1993) show that although sperm whales are widely

distributed in the tropics, their relative abundance

tapers off markedly westward towards the middle

of the tropical Pacific (near the IWC stock

boundary at 150oW) and tapers off northward

towards the tip of Baja California. The Hawaiian

Islands marked the center of a major nineteenth

century whaling ground for sperm whales (Gilmore

1959; Townsend 1935). Since 1936, at least five strandings have been reported from Oahu, Kauai (Nitta 1991) and

Kure Atoll (Woodward 1972). Sperm whales have also been sighted around several of the Northwestern Hawaiian

Islands (Rice 1960), off the main island of Hawaii (Lee 1993; Mobley et al. 1999, see Figure 1), in the Kauai Channel

and in the Alenuihaha Channel between Maui and the island of Hawaii (Shallenberger 1981). In addition, the sounds

of sperm whales have been recorded throughout the year off Oahu (Thompson and Friedl 1982).

The stock identity of sperm whales in the North Pacific has been inferred from historical catch records

(Bannister and Mitchell 1980) and from trends in CPUE and tag-recapture data (Ohsumi and Masaki 1977), but much

uncertainty remains. A 1997 survey designed specifically to investigate stock structure and abundance of sperm whales

in the northeastern temperate Pacific revealed no apparent hiatus in distribution between the U.S. EEZ off California

and areas farther west, out to Hawaii (Barlow and Taylor 1998). Very preliminary genetic analyses revealed significant

differences between sperm whales off the coast of California, Oregon and Washington and those sampled offshore to

Hawaii (Mesnick et al., unpubl. data); analyses of additional genetic samples are ongoing at the NMFS, Southwest

Fisheries Science Center. For the Marine Mammal Protection Act (MMPA) stock assessment reports, sperm whales

within the Pacific U.S. EEZ are divided into three discrete, non-contiguous areas: 1) waters around Hawaii (this report),

2) California, Oregon and Washington waters, and 3) Alaskan waters.

POPULATION SIZE

A large 1982 abundance estimate for the entire eastern North Pacific (Gosho et al. 1984) was based on a CPUE

method which is no longer accepted as valid by the International Whaling Commission. Recently, a combined visual

and acoustic line-transect survey conducted in the eastern temperate North Pacific in spring 1997 resulted in estimates

of 24,000 (CV=0.46) sperm whales based on visual sightings, and 39,200 (CV=0.60) based acoustic detections and

visual group size estimates (Barlow and Taylor 1998). In the eastern tropical Pacific, the abundance of sperm whales

has been estimated as 22,700 (95% C.I.=14,800-34,600; Wade and Gerrodette 1993). However, it is not known whether

any or all of these animals routinely enter the U.S. EEZ of Hawaii. As part of the Marine Mammal Research Program

of the Acoustic Thermometry of Ocean Climate (ATOC) study, a total of twelve aerial surveys were conducted within

about 25 nmi of the main Hawaiian Islands in 1993, 1995 and 1998. An average abundance estimate of 66 (CV=0.56)
222

sperm whales was recently calculated from the combined survey data (Mobley et al. 2000). This abundance

underestimates the total number of sperm whales within the U.S. EEZ off Hawaii, because areas around the Northwest

Hawaiian Islands (NWHI) and beyond 25 nautical miles from the main islands were not surveyed. Furthermore, this

species is known to spend a large proportion of time diving, causing additional downward bias in the abundance

estimate.

Minimum Population Estimate

The log-normal 20th percentile of the combined 1993-98 abundance estimate is 43 sperm whales. As with the

best abundance estimate above, this includes only areas within about 25 nmi of the main Hawaiian Islands and does not

include a large proportion of animals that were diving and therefore unavailable to be seen.

Current Population Trend

No data on current population trend are available.

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

No data on current or maximum net productivity rate are available.

POTENTIAL BIOLOGICAL REMOVAL

The potential biological removal (PBR) level for this stock is calculated as the minimum population size (43)

times one half the default maximum net growth rate for cetaceans (1⁄2 of 4%) times a recovery factor of 0.1 (the default

value for an endangered species), resulting in a PBR of 0.4 sperm whales per year.

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Fishery Information

No estimate of annual human-caused mortality and serious injury is available as there are no reports of recent

direct or incidental takes of sperm whales in Hawaiian waters (Nitta and Henderson 1993). However, mortality of other

cetacean species has been observed in Hawaiian fisheries, and the gear types used in these fisheries are responsible for

marine mammal mortality and serious injury in other fisheries throughout U.S. waters. Gillnets are used in Hawaiian

waters and appear to capture marine mammals wherever they are used, and float lines from lobster traps and longlines

can be expected to occasionally entangle whales (Perrin et al. 1994).

Interactions with dolphins are reported for all pelagic fisheries, and humpback whales have been entangled in

longlines off the Hawaiian Islands (Nitta and Henderson 1993), but no takes of sperm whales have been documented.

None were observed hooked in the Hawaiian longline fishery between 1994 and 1998, with approximately 4.4% of all

effort (measured as the number of hooks fished) observed (Kleiber 1999).

Historical Mortality

Between 1800 and 1909, about 60,842 sperm whales were estimated taken in the North Pacific (Best 1976).

The reported take of North Pacific sperm whales by commercial whalers between 1947 and 1987 totaled 258,000 (C.

Allison, pers. comm.). Factory ships operated as far south as 20oN (Ohsumi 1980). Ohsumi (1980) lists an additional

28,198 sperm whales taken mainly in coastal whaling operations from 1910 to 1946. Based on the massive underreporting of Soviet catches, Brownell et al. (1998) estimate that about 89,000 whales were additionally taken by the

Soviet pelagic whaling fleet between 1949 and 1979. The Japanese coastal operations apparently also under-reported

catches by an unknown amount (Kasuya 1998). Thus a total of at least 436,000 sperm whales were taken between 1800

and the end of commercial whaling for this species in 1987. Of this grand total, an estimated 33,842 were taken by

Soviet and Japanese pelagic whaling operations in the eastern North Pacific from the longitude of Hawaii to the U.S.

West coast, between 1961 and 1976 (Allen 1980, IWC statistical Areas II and III), and 965 were reported taken in landbased U.S. West coast whaling operations between 1947 and 1971 (Ohsumi 1980). In addition, 13 sperm whales were

taken by shore whaling stations in California between 1919 and 1926 (Clapham et al. 1997). There has been a

prohibition on taking sperm whales in the North Pacific since 1988, but large-scale pelagic whaling stopped earlier, in

1980. Some of the whales taken during the whaling era were certainly from a population or populations that occur within

Hawaiian waters.
223

STATUS OF STOCK

The only estimate of the status of North Pacific sperm whales in relation to carrying capacity (Gosho et al.

1984) is based on a CPUE method which is no longer accepted as valid. The status of sperm whales in Hawaiian waters

relative to OSP is unknown, and there are insufficient data to evaluate trends in abundance. Sperm whales are formally

listed as "endangered" under the Endangered Species Act (ESA), and consequently the Hawaiian stock is automatically

considered as a "depleted" and "strategic" stock under the MMPA. The total fishery mortality and serious injury for

sperm whales is zero and therefore can be considered to be insignificant and approaching zero mortality and serious

injury rate. The increasing levels of anthropogenic noise in the world’s oceans has been suggested to be a habitat

concern for whales, particularly for deep-diving whales like sperm whales that feed in the oceans’ “sound channel”.

REFERENCES

Allen, K. R. 1980. Size distribution of male sperm whales in the pelagic catches. Rep. Int. Whal. Commn. Special

Issue 2:51-56.

Allison, C. International Whaling Commission. The Red House, 135 Station Road, Impington, Cambridge, UK CB4

9NP.

Barlow, J. and B. L. Taylor. 1998. Preliminary abundance of sperm whales in the northeastern temperate Pacific

estimated from a combined visual and acoustic survey. Paper SC/50/CAWS20 presented to the International

Whaling Commission, June 1998 (unpublished). xx pp. 

Bannister, J. and E. Mitchell. 1980. North Pacific sperm whale stock identity: distributional evidence from Maury and

Townsend charts. Rep. Int. Whal. Commn. (Spec. Iss. 2):219-230.

Best, P. B. 1976. A review of world sperm whale stocks. Paper ACMRR/MM/SC/8 Rev. 1, FAO Scientific

Consultation of Marine Mammals, Bergen, Norway.

Brownell, R. L., Jr., A. V. Yablokov and V. A. Zemmsky. 1998. USSR pelagic catches of North Pacific sperm whales,

1949-1979: Conservation implications. Paper SC/50/CAWS27 presented to the International Whaling

Commission, June 1998 (unpublished).

Clapham, P. J., S. Leatherwood, I. Szczepaniak, and R. L. Brownell, Jr. 1997. Catches of humpback and other whales

from shore stations at Moss Landing and Trinidad, California, 1919-1926. Marine Mammal Science

13(3):368-394.

Donovan, G. P. 1991. A review of IWC stock boundaries. Rept. Int. Whal. Commn., Special Issue 13:39-68.

Gilmore, R. M. 1959. On the mass strandings of sperm whales. Pac. Nat. 1(9-10):3-15.

Gosho, M. E., D. W. Rice, and J. M. Breiwick. 1984. The sperm whale Physeter macrocephalus. Mar. Fish. Rev.

46(4):54-64.

Kasuya, T. 1998. Evidence of statistical manipulations in Japanese coastal sperm whale fishery. Paper

SC/50/CAWS10 presented to the International Whaling Commission, June 1998 (unpublished).

Kleiber, P. 1999. Estimates of marine mammal takes in the Hawaiian longline fishery. (Unpublished). Southwest

Fisheries Science Center, NMFS, 2570 Dole St, Honolulu, HI, 96822-2396.

Lee, T. 1993. Summary of cetacean survey data collected between the years of 1974 and 1985. NOAA Tech.Mem.

NMFS 181, 184pp.

Mesnick, S. Southwest Fisheries Science Center, NMFS, P.O. Box 271, La Jolla, California, 92038.

Miyashita, T., H. Kato, and T. Kasuya (Eds.). 1995. Worldwide map of cetacean distribution based on Japanese

sighting data. Volume 1. National Research Institute of Far Seas Fisheries, Shizuoka, Japan. 140pp.

Mobley, J. R., Jr., R. A. Grotefendt, P. H. Forestell, and A. Frankel. 1999. Results of aerial surveys of marine mammals

in the major Hawaiian Islands (1993-98): Report to the Acoustic Thermometry of Ocean Climate Marine

Mammal Research Program (ATOC MMRP) (unpublished). 39 pp.

Mobley, J. R. , Jr, S. S. Spitz, K. A. Forney, R. A. Grotefendt, and P. H. Forestall. 2000. Distribution and abundance

of odontocete species in Hawaiian waters: preliminary results of 1993-98 aerial surveys Admin. Rep. LJ-00-

14C. Southwest Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA

92038. 26 pp.

Nitta, E. 1991. The marine mammal stranding network for Hawaii: an overview. In: J.E. Reynolds III, D.K. Odell

(eds.), Marine Mammal Strandings in the United States, pp.56-62. NOAA Tech. Rep. NMFS 98, 157 pp.

Nitta, E. and J. R. Henderson. 1993. A review of interactions between Hawaii's fisheries and protected species. Mar.

Fish. Rev. 55(2):83-92.
224

Ohsumi, S. 1980. Catches of sperm whales by modern whaling in the North Pacific. Rep. Int. Whal. Commn. (Spec.

Iss. 2):11-18.

Ohsumi, S. and Y. Masaki. 1977. Stocks and trends of abundance of the sperm whale in the North Pacific. Rep. Int.

Whal. Commn. 27:167-175.

Perrin, W.F., G. P. Donovan and J. Barlow. 1994. Gillnets and Cetaceans. Rep. Int. Whal. Commn., Special Issue 15,

629 pp.

Rice, D. W. 1960. Distribution of the bottle-nosed dolphin in the leeward Hawaiian Islands. J. Mamm. 41:407-408.

Rice, D. W. 1974. Whales and whale research in the eastern North Pacific. pp. 170-195 In: W. E. Schevill (ed.). The

Whale Problem: A Status Report. Harvard Press, Cambridge, MA.

Rice, D. W. 1989. Sperm whale Physeter macrocephalus Linneaus, 1758. In: S. H. Ridgway and R. Harrison (eds.),

Handbook of Marine Mammals, Vol. 4: The River Dolphins and Larger Toothed Whales, pp. 177-233.

Academic Press, 442 pp.

Shallenberger, E.W. 1981. The status of Hawaiian cetaceans. Final report to U.S. Marine Mammal Commission. MMC77/23, 79pp.

Thompson, P. O. and W. A. Friedl. 1982. A long term study of low frequency sound from several species of whales

off Oahu, Hawaii. Cetology 45:1-19.

Townsend, C. H. 1935. The distribution of certain whales as shown by logbook records of American whaleships.

Zoologica 19:1-50.

Wade, P. R. and R. P. Angliss. 1997. Guidelines for Assessing Marine Mammal Stocks: Report of the GAMMS

Workshop April 3-5, 1996, Seattle, Washington. U. S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-12.

93 pp.

Wade, P. R. and T. Gerrodette. 1993. Estimates of cetacean abundance and distribution in the eastern tropical Pacific.

Rep. Int. Whal. Commn. 43:477-493.

Woodward, P. W. 1972. The natural history of Kure Atoll, northwestern Hawaiian Islands. Atoll Res. Bull. 164:302.
225

Revised 12/15/2000

BLUE WHALE (Balaenoptera musculus): Hawaiian Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

Blue whales are extremely rare in Hawaii. The only published sighting record is that of Berzin and Rovnin

(1966) north of the Hawaiian Islands. Additional evidence that blue whales occur in this area comes from acoustic

recordings made off Oahu and Midway Islands (Northrop et al. 1971; Thompson and Friedl 1982; McDonald and Fox

1999). Although the exact positions of the whales producing the sounds could not be determined, at least some of them

were within the U.S. Exclusive Economic Zone. The recordings made off Oahu showed bimodal peaks throughout the

year, suggesting that the animals were migrating into the area in summer and winter. 

The stock structure of blue whales in the North Pacific is uncertain (Mizroch et al. 1984; Reilly and Thayer

1990; Reeves et al. 1998). The International Whaling Commission (IWC) has formally considered only one management

stock for blue whales in the North Pacific (Donovan 1991), but now this ocean is thought to include up to five

populations (Reeves et al. 1998), with two occurring within the U.S. EEZ. One group of animals feeds in California

waters in summer/fall (from June to November) and migrates south to productive areas off Mexico and as far south as

the Costa Rica Dome (10o N) in winter/spring (Mate et al. 1999, Stafford et al. 1999). Rice (1974) hypothesized that

blue whales from Baja California migrated far offshore to fed in the eastern Aleutians or Gulf of Alaska and returned

to feed in California waters; however, he has more recently concluded that the California population is separate from

the Gulf of Alaska population (Rice 1992). Length frequency analyses (Gilpatrick et al. 1996) and photo-identification

studies (Calambokidis et al. 1995) support separate population status for blue whales feeding off California and those

feeding in Alaskan waters. Whaling catch data indicate that whales feeding along the Aleutian Islands are probably part

of a central Pacific stock (Reeves et al. 1998), which may migrate to offshore waters north of Hawaii in winter (Berzin

and Rovnin 1966). Recently, however, blue whale feeding aggregations have not been found in Alaska despite several

surveys (Leatherwood et al. 1982; Stewart et al. 1987; Forney and Brownell 1996). For management in U.S. Pacific

waters outside the continental EEZ, the Hawaiian stock includes only those whales within the EEZ of the Hawaiian

Islands. One other stock of North Pacific blue whales (off California and Mexico) is recognized in the Marine Mammal

Protection Act (MMPA) stock Assessment Reports.

POPULATION SIZE

From ship line-transect surveys, Wade and Gerrodette (1993) estimated 1,400 blue whales for the eastern

tropical Pacific. A weighted average estimate of 1,940 blue whales is available for California, Oregon and Washington,

based on 1991-96 shipboard line-transect surveys (Barlow 1997) and photographic mark-recapture estimates

(Calambokidis and Steiger 1994). No data are available to estimate population size for any other North Pacific blue

whale population, including the putative central stock that apparently summered along the Aleutians and wintered north

of Hawaii. A summer 1994 shipboard survey within the historical whaling grounds south of the Aleutian Islands yielded

no blue whale sightings (Forney and Brownell 1996), nor did a total of twelve aerial surveys conducted in 1993-98

within about 25 nmi of the main Hawaiian Islands as part of the Marine Mammal Research Program of the Acoustic

Thermometry of Ocean Climate (ATOC) study (Mobley et al. 2000).

Minimum Population Estimate

No data are available to provide a minimum population estimate.

Current Population Trend

No data are available on current population trend.

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

No data are available on current or maximum net productivity rate.

POTENTIAL BIOLOGICAL REMOVAL

No PBR can be calculated for this stock at this time.
226

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Fishery Information

No estimate of annual human-caused mortality and serious injury is available as there are no reports of recent

direct or incidental takes of blue whales in Hawaiian waters. However, mortality of other cetacean species has been

observed in Hawaiian fisheries, and the gear types used in these fisheries are responsible for marine mammal mortality

and serious injury in other fisheries throughout U.S. waters. Gillnets are used in Hawaiian waters and appear to capture

marine mammals wherever they are used, and float lines from lobster traps and longlines can be expected to occasionally

entangle whales (Perrin et al. 1994). Interactions with dolphins are reported for all pelagic fisheries, and humpback

whales have been entangled in longlines off the Hawaiian Islands, but no takes of blue whales have been documented

(Nitta and Henderson 1993). None were observed hooked or entangled in the Hawaiian longline fishery between 1994

and 1998, with approximately 4.4% of all effort (measured as the number of hooks fished) observed (Kleiber 1999).

Historical Mortality

 At least 9,500 blue whales were taken by commercial whalers throughout the North Pacific between 1910 and

1965 (Ohsumi and Wada 1972). Some proportion of this total may have been from a population or populations that

migrate seasonally into the Hawaiian EEZ. The species has been protected in the North Pacific by the IWC since 1966.

STATUS OF STOCK

The status of blue whales in Hawaiian waters relative to OSP is unknown, and there are insufficient data to

evaluate trends in abundance. Blue whales are formally listed as "endangered" under the Endangered Species Act

(ESA), and consequently the Hawaiian stock is automatically considered as a "depleted" and "strategic" stock under the

MMPA. The total fishery mortality and serious injury for blue whales is zero and therefore can be considered to be

insignificant and approaching zero mortality and serious injury rate. The increasing levels of anthropogenic noise in

the world’s oceans has been suggested to be a habitat concern for blue whales (Reeves et al. 1998).

REFERENCES

Barlow, J. 1997. Preliminary estimates of cetacean abundance off California, Oregon, and Washington based on a

1996 ship survey and comparisons of passing and closing modes. Admin. Rept. LJ-97-11. Southwest Fisheries

Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA. 25 pp.

Berzin, A. A. and A. A. Rovnin. 1966. Distribution and migration of whales in the northeastern part of the Pacific

Ocean, Bering and Chukchi Seas. Izv. Tikhookean. Nauchno-issled, Inst. Rybn. Khoz. Okeanogr. (TINRO)

58:179-207. {In Russian}. (Translated by U.S. Dep. Inter., Bur. Commer. Fish., Seattle, Washington, 1966,

pp. 103-106 In: Panin, K. I. (ed) Soviet Research on marine mammals of the Far East).

Calambokidis, J., R. Sears, G. H. Steiger, and J. Evenson. 1995. Movement and stock structure of blue whales in the

eastern North Pacific. P.19 In: Proceedings of the Eleventh Biennial Conference on the Biology of Marine

Mammals, Orlando, FL, 14-18 December 1995 (Abstract). Society for Marine Mammalogy, Lawrence, KS.

Calambokidis, J., and G. H. Steiger. 1994. Population assessment of humpback and blue whales using photoidentification from 1993 surveys off California. Final Contract Report to Southwest Fisheries Science Center,

National Marine Fisheries Service, P.O. Box 271, La Jolla, CA 92038. 31 pp.

Donovan, G. P. 1991. A review of IWC stock boundaries. Rept. Int. Whal. Commn., Special Issue 13:39-68.

Forney, K. A. and Brownell, R. L., Jr. 1996. Preliminary report of the 1994 Aleutian Island Marine Mammal Survey.

Paper SC/48/O11 presented to the International Whaling Commission, June 1996 (unpublished).

Gilpatrick, J., W. Perryman, M. Lynn, and M. A. DeAngelis. 1996. Geographic populations of blue whales

(Balaenoptera musculus) in the North Pacific Ocean investigated from whaling records and aerial

photogrammetry. Paper SC/47/NP4 presented to the International Whaling Commission, May 1995

(unpublished). 

Kleiber, P. 1999. Estimates of marine mammal takes in the Hawaiian longline fishery. (Unpublished). Southwest

Fisheries Science Center, NMFS, 2570 Dole St, Honolulu, HI, 96822-2396.

Leatherwood, S., R. R. Reeves, W. F. Perrin, and W. E. Evans. 1982. Whales, dolphins, and porpoises of the eastern

North Pacific and adjacent Arctic waters: A guide to their identification. NOAA Technical Rept. NMFS

Circular 444. 245 pp.
227

Mate, B.R., B.A. Lagerquist, and J. Calambokidis. Movements of North Pacific blue whales during the feeding season

off southern California and their southern fall migration. Mar. Mamm. Sci. 15(4):1246-1257.

Mizroch, S. A., D. W. Rice, and J. M. Breiwick. 1984. The blue whale, Balaenoptera musculus. Mar. Fish. Rev.

46(4):15-19.

Mobley, J. R. , Jr, S. S. Spitz, K. A. Forney, R. A. Grotefendt, and P. H. Forestall. 2000. Distribution and abundance

of odontocete species in Hawaiian waters: preliminary results of 1993-98 aerial surveys Admin. Rep. LJ-00-

14C. Southwest Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA

92038. 26 pp.

Nitta, E. and J. R. Henderson. 1993. A review of interactions between Hawaii's fisheries and protected species. Mar.

Fish. Rev. 55(2):83-92.

Northrop, J., W. C. Cummings, and M. F. Morrison. 1971. Underwater 20-Hz signals recorded near Midway Island.

J. Acoust. Soc. Am. 49:1909-1910.

Ohsumi, S. and S. Wada. 1972. Stock assessment of blue whales in the North Pacific. Int. Whal. Commn. Sci. Comm.

Rep., 20 pp.

Perrin, W.F., G.P. Donovan and J. Barlow. 1994. Gillnets and Cetaceans. Rep. Int. Whal. Commn., Spec. Iss. 15, 629pp.

Reeves, R. R., P. J. Clapham, R. L. Brownell, Jr., and G. K. Silber. 1998. Recovery plan for the blue whale

(Balaenoptera musculus). Office of Protected Resources, NMFS, NOAA, Silver Spring, Maryland. 30 pp.

Reilly, S. B. and V. G. Thayer. 1990. Blue whale (Balaenoptera musculus) distribution in the eastern tropical Pacific.

Mar. Mamm. Sci. 6:265-277.

Rice, D. W. 1974. Whales and whale research in the eastern North Pacific. pp. 170-195 In: W. E. Schevill (ed.). The

Whale Problem: A Status Report. Harvard Press, Cambridge, MA.

Rice, D. W. 1992. The blue whales of the southeastern North Pacific Ocean. pp. 1-3 In. Alaska Fisheries Science

Center, Quart. Rept. Oct.-Dec.

Stafford, K.M., S.L. Nieukirk, and C.G. Fox. 1999. An acoustic link between blue whales in the eastern tropical

Pacific and the northeast Pacific. Mar. Mamm. Sci. 15(4):1258-1268.

Stewart, B. S., S. A. Karl, P. K. Yochem, S. Leatherwood, and J. L. Laake. 1987. Aerial surveys for cetaceans in the

former Akutan, Alaska, whaling grounds. Arctic 40(1):33-42.

Thompson, P. O. and W. A. Friedl. 1982. A long term study of low frequency sound from several species of whales

off Oahu, Hawaii. Cetology 45:1-19.

Wade, P. R. and T. Gerrodette. 1993. Estimates of cetacean abundance and distribution in the eastern tropical Pacific.

Rep. Int. Whal. Commn. 43:477-493.
228

Revised 12/15/2000

FIN WHALE (Balaenoptera physalus): Hawaiian Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

Fin whales are found throughout all oceans and seas of the world from tropical to polar latitudes. They are rare

in Hawaiian waters. Balcomb (1987) observed 8-12 fin whales in a multispecies feeding assemblage on 20 May 1966

approx. 250 mi. south of Honolulu. Additional sightings were reported north of Oahu in May 1976 and in the Kauai

Channel in February 1979 (Shallenberger 1981). More recently, a single fin whale was observed north of Kauai in

February 1994 (Mobley et al. 1996). A single stranding has been reported on Maui (Shallenberger 1981). Thompson

and Friedl (1982; and see Northrop et al. 1968) suggested that fin whales migrate into Hawaiian waters mainly in fall

and winter, based on acoustic recordings off Oahu and Midway Islands. Although the exact positions of the whales

producing the sounds could not be determined, at least some of them were almost certainly within the U.S. Exclusive

Economic Zone. More recently, McDonald and Fox (1999) reported an average of 0.027 calling fin whales per 10002

km (grouped by 8-hr periods) based on passive acoustic recordings within about 16 km of the north shore of Oahu.

The International Whaling Commission (IWC) recognized two stocks of fin whales in the North Pacific: the

East China Sea and the rest of the North Pacific (Donovan 1991). Mizroch et al. (1984) cites evidence for additional

fin whale subpopulations in the North Pacific. There is still insufficient information to accurately determine population

structure, but from a conservation perspective it may be risky to assume panmixia in the entire North Pacific. In the

North Atlantic, fin whales were locally depleted in some feeding areas by commercial whaling (Mizroch et al. 1984),

in part because subpopulations were not recognized. The Marine Mammal Protection Act (MMPA) stock assessment

reports recognize three stocks of fin whales in the North Pacific: 1) the Hawaii stock (this report), 2) the

California/Oregon/Washington stock, and 3) the Alaska stock. 

POPULATION SIZE

No data are available to estimate population size. As part of the Marine Mammal Research Program of the

Acoustic Thermometry of Ocean Climate (ATOC) study, a total of twelve aerial surveys were conducted within about

25 nmi of the main Hawaiian Islands in 1993-98 (Mobley et al. 2000). Only one sighting of a single fin whale was made

(Mobley et al. 1996), and therefore no meaningful abundance estimate could be calculated. Using passive acoustic

detections from a hydrophone north of Oahu, MacDonald and Fox (1999) estimate an average density of 0.027 calling

fin whales per 1000 km2 within about 16 km from shore. However, the relationship between the number of whales

present and the number of calls detected is not known, and therefore this acoustic method does not provide an estimate

of absolute abundance for fin whales. 

Minimum Population Estimate

No data are available to provide a minimum population estimate.

Current Population Trend

No data are available on current population trend.

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

No data are available on current or maximum net productivity rate.

POTENTIAL BIOLOGICAL REMOVAL

No PBR can be calculated for this stock at this time.

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Fishery Information

No estimate of annual human-caused mortality and serious injury is available as there are no reports of recent

direct or incidental takes of fin whales in Hawaiian waters. However, mortality of other cetacean species has been

observed in Hawaiian fisheries, and the gear types used in these fisheries are responsible for marine mammal mortality

and serious injury in other fisheries throughout U.S. waters. Gillnets are used in Hawaiian waters and appear to capture

marine mammals wherever they are used, and float lines from lobster traps and longlines can be expected to occasionally
229

entangle whales (Perrin et al. 1994).

Interactions with dolphins are reported for all pelagic fisheries, and humpback whales have been entangled in

longlines off the Hawaiian Islands (Nitta and Henderson 1993), but no takes of fin whales have been documented. None

were observed hooked or entangled in the Hawaiian longline fishery between 1994 and 1998, with approximately 4.4%

of all effort (measured as the number of hooks fished) observed (Kleiber 1999).

Historical Mortality

Large numbers of fin whales were taken by commercial whalers throughout the North Pacific from the early

20th century until the 1970s (Tønnessen and Johnsen 1982). Approximately 46,000 fin whales were taken from the

North Pacific by commercial whalers between 1947 and 1987 (C. Allison, IWC, pers. comm.). Some of the whales

taken may have been from a population or populations that migrate seasonally into the Hawaiian EEZ. The species has

been protected in the North Pacific by the IWC since 1976.

STATUS OF STOCK

The status of fin whales in Hawaiian waters relative to OSP is unknown, and there are insufficient data to

evaluate trends in abundance. Fin whales are formally listed as "endangered" under the Endangered Species Act (ESA),

and consequently the Hawaiian stock is automatically considered as a "depleted" and "strategic" stock under the MMPA.

The total fishery mortality and serious injury for fin whales is zero and therefore can be considered to be insignificant

and approaching zero mortality and serious injury rate. The increasing levels of anthropogenic noise in the world’s

oceans has been suggested to be a habitat concern for whales.

REFERENCES

Allison, C. International Whaling Commission. The Red House, 135 Station Road, Impington, Cambridge, UK CB4

9NP.

Balcomb, K. C., III. 1987. The Whales of Hawaii. Marine Mammal Fund, 99 pp.

Donovan, G. P. 1991. A review of IWC stock boundaries. Rept. Int. Whal. Commn., Special Issue 13:39-68.

Kleiber, P. 1999. Estimates of marine mammal takes in the Hawaiian longline fishery. (Unpublished). Southwest

Fisheries Science Center, NMFS, 2570 Dole St, Honolulu, HI, 96822-2396.

McDonald, M. A., and C. G. Fox. 1999. Passive acoustic methods applied to fin whale population density estimation.

J. Acoust. Soc. Am. 105: 2643-2651.

Mizroch, S. A., D. W. Rice, and J. M. Breiwick. 1984. The fin whale, Balaenoptera physalus Mar. Fish. Rev.

46(4):20-24.

Mobley, J. R., Jr., M. Smultea, T. Norris, and D. Weller. 1996. Fin whale sighting north of Kaua’i, Hawai’i. Pacific

Science 50:230-233.

Mobley, J. R., Jr, S. S. Spitz, K. A. Forney, R. A. Grotefendt, and P. H. Forestall. 2000. Distribution and abundance

of odontocete species in Hawaiian waters: preliminary results of 1993-98 aerial surveys Admin. Rep. LJ-00-

14C. Southwest Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA

92038. 26 pp.

Nitta, E. and J. R. Henderson. 1993. A review of interactions between Hawaii's fisheries and protected species. Mar.

Fish. Rev. 55(2):83-92.

Northrop, J., W. C. Cummings, and P. O. Thompson. 1968. 20-Hz signals observed in the central Pacific. J. Acoust.

Soc. Am. 43:383-384.

Perrin, W.F., G. P. Donovan and J. Barlow. 1994. Gillnets and Cetaceans. Rep. Int. Whal. Commn., Special Issue 15,

629 pp.

Shallenberger, E.W. 1981. The status of Hawaiian cetaceans. Final report to U.S. Marine Mammal Commission. MMC77/23, 79pp.

Thompson, P. O. and W. A. Friedl. 1982. A long term study of low frequency sound from several species of whales

off Oahu, Hawaii. Cetology 45:1-19.

Tønnessen, J. N. and A. O. Johnsen. 1982. The History of Modern Whaling. Hurst, 789 pp.
230

Revised 12/15/2000

BRYDE'S WHALE (Balaenoptera edeni): Hawaiian Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

Bryde's whales occur in tropical and warm temperate waters throughout the world. Shallenberger (1981)

reported a sighting of a Bryde's whale southeast of Nihoa in April 1977 (see DeLong and Brownell 1977; Leatherwood

et al. 1982: Fig. 39c). Leatherwood et al. (1982) described the species as relatively abundant in summer and fall on the

Mellish and Miluoki banks northeast of Hawaii and around Midway Islands, but the basis for this statement was not

explained. Ohsumi and Masaki (1975) reported the tagging of "many" Bryde's whales between the Bonin and Hawaiian

Islands in the winters of 1971 and 1972 (Ohsumi 1977). With presently available evidence, there is no biological basis

for defining separate stocks of Bryde's whales in the central North Pacific. Bryde's whales also occasionally occur off

southern California (Morejohn and Rice 1973). For the MMPA stock assessment reports, Bryde's whales within the

Pacific U.S. Exclusive Economic Zone are divided into two areas: 1) Hawaiian waters (this report), and 2) the eastern

tropical Pacific (east of 150oW and including the Gulf of California and waters off California).

POPULATION SIZE

Tillman (1978) concluded from Japanese and Soviet CPUE data that the stock size in the North Pacific pelagic

whaling grounds, mostly to the west of the Hawaiian Islands, declined from approximately 22,500 in 1971 to 17,800

in 1977. An estimate of 13,000 (CV=0.202) Bryde's whales was made from vessel surveys in the eastern tropical Pacific

between 1986 and 1990 (Wade and Gerrodette 1993). The area to which this estimate applies is mainly east and

somewhat south of the Hawaiian Islands, and it is not known whether these animals are part of the same population that

occurs around the Hawaiian Islands. As part of the Marine Mammal Research Program of the Acoustic Thermometry

of Ocean Climate (ATOC) study, a total of twelve aerial surveys were conducted within about 25 nmi of the main

Hawaiian Islands in 1993, 1995 and 1998 (Mobley et al. 2000). No sightings of Bryde’s whales were made, and

therefore no abundance estimate is available for Hawaiian waters.

Minimum Population Estimate

No data are available for a minimum population estimate.

Current Population Trend

No data are available on current population trend.

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

No data are available on current or maximum net productivity rate.

POTENTIAL BIOLOGICAL REMOVAL

No PBR can be calculated for this stock at this time.

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY 

Fishery Information

No estimate of annual human-caused mortality and serious injury is available as there are no reports of recent

direct or incidental takes of Bryde's whales in Hawaiian waters. However, mortality of other cetacean species has been

observed in Hawaiian fisheries, and the gear types used in these fisheries are responsible for marine mammal mortality

and serious injury in other fisheries throughout U.S. waters. Gillnets are used in Hawaiian waters and appear to capture

marine mammals wherever they are used, and float lines from lobster traps and longlines can be expected to occasionally

entangle whales (Perrin et al. 1994). 

Interactions with dolphins are reported for all pelagic fisheries, and humpback whales have been entangled in

longlines off the Hawaiian Islands (Nitta and Henderson 1993), but no takes of Bryde's whales have been documented.

None were observed hooked or entangled in the Hawaiian longline fishery between 1994 and 1998, with approximately

4.4% of all effort (measured as the number of hooks fished) observed (Kleiber 1999).
231

Historical Mortality

Small numbers of Bryde's whales were taken near the Northwestern Hawaiian Islands by Japanese and Soviet

whaling fleets during the early 1970s (Ohsumi 1977). Pelagic whaling for Bryde's whales in the North Pacific ended

after the 1979 season (IWC 1981), and coastal whaling for this species ended in the western Pacific in 1987 (IWC

1989).

STATUS OF STOCK

The status of Bryde's whales in Hawaiian waters relative to OSP is unknown, and there are insufficient data

to evaluate trends in abundance. They are not listed as “threatened” or “endangered” under the Endangered Species Act

(1973), nor as “depleted” under the MMPA. Although information on Bryde's whales in Hawaiian waters is limited,

this stock would not be considered strategic under the 1994 amendments to the MMPA because there has been no

reported fisheries related mortality. The total fishery mortality and serious injury for Bryde’s whales is zero and

therefore can be considered to be insignificant and approaching zero mortality and serious injury rate. The increasing

levels of anthropogenic noise in the world’s oceans has been suggested to be a habitat concern for whales.

REFERENCES

DeLong, R. L. and R. L. Brownell, Jr. 1977. Hawaiian monk seal (Monachus schauinslandi) habitat and population

survey in the northwestern (Leeward) Hawaiian Islands, April 1977. Northwest Alaska Fish Cent. Proc. Rep.,

43 pp.

International Whaling Commission. 1981. Japan. Progress report on cetacean research June 1979-May 1980. Rep. Int.

Whal. Commn. 31:195-200.

International Whaling Commission. 1989. Japan. Progress report on cetacean research June 1987 to April 1988. Rep.

Int. Whal. Commn. 39:201-204.

Kleiber, P. 1999. Estimates of marine mammal takes in the Hawaiian longline fishery. (Unpublished). Southwest

Fisheries Science Center, NMFS, 2570 Dole St, Honolulu, HI, 96822-2396.

Leatherwood, S., R. R. Reeves, W. F. Perrin, and W. E. Evans. 1982. Whales, dolphins, and porpoises of the eastern

North Pacific and adjacent arctic waters: A guide to their identification. NOAA Tech. Rep. NMFS 444, 245

pp.

Mobley, J. R. , Jr, S. S. Spitz, K. A. Forney, R. A. Grotefendt, and P. H. Forestall. 2000. Distribution and abundance

of odontocete species in Hawaiian waters: preliminary results of 1993-98 aerial surveys Admin. Rep. LJ-00-

14C. Southwest Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA

92038. 26 pp.

Morejohn, G. V. and D. W. Rice. 1973. First record of Bryde's whale (Balaenoptera edeni) off California. Cal. Fish

Game 59:313-315.

Nitta, E. and J. R. Henderson. 1993. A review of interactions between Hawaii's fisheries and protected species. Mar.

Fish. Rev. 55(2):83-92.

Ohsumi, S. 1977. Stocks and trends of abundance of the sperm whale in the North Pacific. Rep. Int. Whal. Commn.

27:167-175.

Ohsumi, S. and Y. Masaki. 1975. Japanese whale marking in the North Pacific, 1963-72. Bull. Far Seas Fish. Res.

Lab. 12:171-219.

Perrin, W.F., G. P. Donovan and J. Barlow. 1994. Gillnets and Cetaceans. Rep. Int. Whal. Commn., Special Issue 15,

629 pp.

Shallenberger, E.W. 1981. The status of Hawaiian cetaceans. Final report to U.S. Marine Mammal Commission. MMC77/23, 79pp.

Tillman, M. F. 1978. Modified Delury estimates of the North Pacific Bryde's whale stock. Rep. Int. Whal. Commn.

28:315-317.

Wade, P. R. and T. Gerrodette. 1993. Estimates of cetacean abundance and distribution in the eastern tropical Pacific.

Rep. Int. Whal. Commn. 43:477-493.
232

Revised 12/15/2000

Appendix 1. Description of U.S. Commercial Fisheries

This appendix describes commercial fisheries that are currently active in California, Oregon, Washington, and

Hawaii and that interact or may interact with marine mammals. The first three sections describe sources of marine

mammal mortality data for these fisheries. The fourth section describes the commercial fisheries for these states. A

list of all known fisheries for these states was published in the Federal Register, vol. 64, no. 36 dated 24 February 1999.

Category I fisheries are described in more detail. Category II and III fisheries are summarized to the extent possible.

Following the fishery descriptions is a table giving basic characteristics of California gillnet fisheries and a series of

figures. Figures 1-10 show approximate locations of fishing effort and marine mammal entanglements for the California

shark/swordfish drift gillnet fishery. Figures 11-17 show set locations of observed sets in 1994, observed entanglements

1990-1994 and estimated effort for 1994-1998 for the set gillnet fishery. Figures 18 and 19 show estimated and

observed effort and percent coverage for both the drift and set gillnet fisheries. 

1. Sources of Mortality/Injury Data

There are three major sources of marine mammal mortality/injury data for the active commercial fisheries in

California, Oregon, and Washington. These sources are the NMFS Observer Programs, the Marine Mammal

Authorization Program (MMAP) data, and the NMFS Marine Mammal Stranding Network (MMSN) data. Each of

these data sources has a unique objective. The National Marine Fisheries Service (NMFS) observes about 12-15% of

the annual CA swordfish drift-net effort and (as of 1999) about 20% of the annual CA halibut/angel shark set-net effort

in the NMFS Observer Program. Data from these observer programs are combined with estimates of total effort

provided by the California Department of Fish and Game (CDFG), to estimate marine mammal mortality. Data on

mammal mortality and injury are reported to the MMAP by fishers in any commercial fisheries. Marine mammal

mortality and injury is also monitored by the NMFS Marine Mammal Stranding Network. Data provided by the MMSN

is not duplicated by either the NMFS Observer Program or MMAP reporting. Human-related data from the MMSN

include occurrences of mortality due to entrainment in power station intakes, ship strikes, shooting, net fishery

entanglement (with net remaining on animal), and ingestion of hooks. 

2. Marine Mammal Reporting from Fisheries

The Marine Mammal Exemption Program (MMEP) was put into place in mid-1989 as a result of the 1988

amendments to the MMPA. It required fishers to register with NMFS and to complete annual logbooks detailing each

day’s fishing activity, including: date fished, hours fished, area fished, marine mammal species involved, injured and

killed due to gear interactions, and marine mammal species harassed, injured and killed due to deterrence from gear or

catch. If the marine mammal was deterred, the method of deterrence was required, as well as indication of its

effectiveness. Fishers were also required to report whether there were any losses of catch or gear due to marine

mammals. These logbooks were submitted to NMFS on an annual basis, as a prerequisite to renewing their registration.

Logbook data are available for part of the 1989 and 1991-1994. Logbook data received for part of 1994 and 1995 was

not entered into the MMEP logbook database in order to focus staff efforts on implementing the 1994 amendments to

the MMPA.

In 1994, the MMPA was amended again to implement a long-term regime for managing mammal interactions

with commercial fisheries (the Marine Mammal Authorization Program, or MMAP). Logbooks are no longer required -

instead vessel owners/operators in any commercial fishery (Category I, II, or III) are required to submit one-page preprinted reports for all interactions (including those that occur while an observer is onboard) resulting in an injury or

mortality to a marine mammal. The report must include owner/operator’s name and address, vessel name and ID, where

and when the interaction occurred, the fishery, species involved, and type of injury (if the animal was released alive).

These postage-paid report forms are mailed to all Category I and II fishery participants that have registered with NMFS,

and must be completed and returned to NMFS within 48 hours of returning to port for trips in which a marine mammal
Appendix 1. Fishery Descriptions

1

Pers. Comm. Robert Read California Dept. of Fish and Game.

2Read, R. B. 1999. Effort estimates of California gill net fisheries: halibut-angel shark set net, sharkswordfish drift net, white seabass-yellowtail set/drift net, for January through December 1998 and each calendar

quarter. Report submitted to NOAA Fisheries/National Marine Fisheries Service, Southwest Region in partial

fulfillment of Cooperative Agreement No. NA77FX0349. Available from Southwest Fisheries Science Center, La

Jolla, CA.

233

injury or mortality occurred. Since the inception of this system in April 1996, the number of interactions have been

grossly under-reported by drift-net fishers. In 1997, the first full year of reporting, only 54 interactions were reported

by fishers, far fewer than the number (85) reported by the observers which is based on observing only one-fifth of the

total effort (Table 1). 

3. NMFS Marine Mammal Stranding Network data

Reported strandings of cetaceans and pinnipeds in both California and Oregon/Washington have steadily increased since

1996. In California, for the years 1996 through 1998 there were 89, 101 and 120 cetacean strandings respectively and

1,449, 2,061, 3,568 pinniped strandings respectively (Table 2). California human related cetacean and pinniped

strandings of interest include 1 Pacific white-sided dolphin (‘97), 1 Peruvian beaked whale (‘98), 14 gray whales (5-

‘96,6-‘97,3-‘98), 2 fin whales (‘96,’97), 1 humpback whale (‘97) and 1 unidentified balaenopterid (‘97), 2 Steller sea

lions (‘98). In Oregon/Washington for the same years, there were 18, 20 and 43 cetacean strandings respectively and

188, 254 and 321 pinniped strandings respectively. A stranding of interest in Oregon/Washington is 1 Steller Sea Lion

in 1997. Human-related causes of mortality include: entrainment in power station intakes, shooting, net fishery

entanglement, and hook/line, set-net and trap fishery interaction.

4. Fishery Descriptions

Category I, CA/OR thresher shark/swordfish drift gillnet fishery

Number of permit holders: The number of eligible permit holders in California for 1994-1998 are 162, 185, 167, 120

and 147 respectively.1 Since 1995, 10 developmental (“unlimited”) fishery permits and a smaller number of “limited”

swordfish landing permits have been issued by the state of Oregon.

Number of active permit holders: The number of vessels actively fishing during 1995 and 1997-1998 was 130, 115 and

123 (3 from Oregon) respectively. The number of permit holders observed by NMFS from 1994-1998 were 70, 52, 51,

74 and 67 respectively.1

Total effort: Both estimated and observed effort for the drift-net fishery during the calendar years 1990 through 1998

are shown in Figure 18. In 1998 there was an estimated 3,353 effort-days, where an effort-day is defined to be one day

of effort by one vessel.2 (In this fishery, 1 effort-day is equivalent to 1 set.). There were 636 (113 trips) of observed

effort-days in 1998. 

Geographic range: Effort in this fishery ranges from the U.S./Mexico border north to waters off the state of Oregon.

For this fishery there are area-season closures (see below). Figures 1-5 show locations of observed sets and Figures

6-10 show approximate locations of observed marine mammal entanglements for each year 1994 - 1998.

Seasons: This fishery is subject to season-area restrictions. From February 1 to May 15 effort must be further than 200
Appendix 1. Fishery Descriptions

3Barlow, Jay and Grant Cameron. 1999. Field experiments show that acoustic pingers reduce marine

mammal bycatch in the California drift gillnet fishery. IWC working paper SC/51/SM2.

4

J. Spratt, California Dept. of Fish and Game (Monterey)

5

 Statutory Description of California Set Gillnet Closures

Closure One is “between a line extending 245E magnetic from the most westerly point of the west point of the

234

nautical miles (nmi) from shore; from May 16 to August 14, effort must be further than 75 nmi from shore, and from

August 15 to January 31 there is only the 3 nmi off-shore restriction for all gillnets in southern California (see angel

shark/halibut fishery below). The majority of the effort occurs from October through December. 

Gear type and fishing method: Typical gear used for this fishery is a 1000 fathom gillnet with a stretched mesh size

typically ranging from 18-22 inches (14 inch minimum). The net is set at dusk and allowed to drift during the night after

which, it is retrieved. The fishing vessel is typically attached to one end of the net. Soak duration is typically 12-14

hours depending on the length of the night. Net extender lengths of a minimum 36 ft. became mandatory for the 1997-

1998 fishing season. The use of acoustic warning devices (pingers) became mandatory 28 October 1997. 

Regulations: This fishery is managed by the California Dept. of Fish and Game and by Oregon Dept. of Fish and

Wildlife in accordance with state and federal laws.

Management type: The drift-net fishery is a limited entry fishery with seasonal closures and gear restrictions (see

above). The state of Oregon restricts landing to swordfish only. 

Comments: This fishery has had a NMFS observer program in place since July 1990. Due to bycatch of strategic stock

including short-finned pilot whale, beaked whales, sperm whale and humpback whale, a Take Reduction Team was

formed February 12, 1996. Since then, the implementation of increased extender lengths and the deployment of pingers

has substantially decreased cetacean entanglement3.

Category I, CA angel shark/halibut large mesh (>8.0 in) set gillnet fishery.

Number of permit holders: There is no specific permit category for this fishery. However, in 1996 there were an

estimated 80 permit holders. Overall, the current number of legal permit holders for gill and trammel nets, excluding

swordfish drift gillnets and herring gillnets for 1994 through 1998 are, respectively, 308, 300, 273, 219 and 2654. This

general permit category includes the fishery, “CA. large mesh (>3.5") for other species” described below.

Number of active permit holders: At least 81; the number of permit holders observed by NMFS observers during 1994

was 22. Nine vessels have been observed in Monterey Bay during 1999. The number of boats fishing 1995 through

1998 were 58, 54, 71 and 81 respectively.2

Total effort: Both estimated and observed effort for the set-net fishery during calendar year 1990-1998 are shown in

Figure 19. In 1998 there was an estimated 2,836 effort-days where an effort-day is defined to be one day of effort by

one vessel (typically 2-4 sets). During 1994, an effort-day was equivalent to 3.62 sets (s.e. = 0.16). Figures 11-15 show

estimated effort for the years 1994-1998. Beginning in 1994, a gillnet area closure was implemented. From Pt. Arguello

south to the U.S./Mexico border, gillnets are restricted to waters farther than 3 nmi offshore and more than 1 nmi from

any of the Channel Islands. Because of this closure, effort has decreased dramatically from about 7,000 days of effort

in 1991 to about 2,500 days of effort in subsequent years. Use of gillnets north of Pt. Arguello (e.g. Monterey Bay

effort) has been unaffected by this closure but is subject to other California Dept. of Fish and Game restrictions5.
Appendix 1. Fishery Descriptions

Point Reyes headlands in Marin County and the westerly extension of the California-Oregon boundary.” [CA Fish

& Game Code section 8664.8(a)].

Closure Two is in waters which are “40 fathoms or less in depth at mean lower low water between a line extending

245E magnetic from the most westerly point of the west point of the Point Reyes headlands in marine County and a

line extending 225E magnetic from Pillar Point at Half Moon Bay in San Mateo County” and “60 fathoms or less in

depth at mean lower low water between a line extending 225E magnetic from Pillar Point at Half Moon Bay in San

Mateo County to a line extending 220E magnetic from the mouth of Waddell Creek in Santa Cruz County.” [CA

Fish & Game Code section 8664.8(b)].

Closure Three is in “that portion of District 18 north of a line extending due west from Point Sal in Santa Barbara

County in waters 30 fathoms or less in depth at mean lower low water.” [CA Fish & Game Code section 8664.5(b)].

Closure Four is “in waters less than 35 fathoms between a line running 180E true from Point Fermin and a line

running 270E true from the south jetty of Newport Harbor.” [CA Fish & Game Code section 8610.2(d)(3)].

235

Geographic range: Effort in this fishery previously ranged from the U.S./Mexico border north to Monterey Bay and

was localized in more productive areas: San Ysidro, San Diego, Oceanside, Newport, San Pedro, Ventura, Santa

Barbara, Morro Bay, and Monterey Bay. Fishery effort is now predominantly in the Ventura Flats area off of Ventura,

the San Pedro area between Pt. Vicente and Santa Catalina Island and in the Monterey Bay area.

Seasons: This fishery operates year round. Effort generally increases during the summer months and declines during

the last three months of a year.

Gear type and fishing method: Typical gear used for this fishery is a 200 fathom gillnet with a stretched mesh size of

8.5 inches. The net is generally set during the day and allowed to soak for up to 2 days. Soak duration is typically 8-10,

19-24, or 44-49 hours. The depth of water ranges from 15-50 fathoms with most sets in water depths of 15-35 fathoms.

Regulations: This fishery is managed by the California Dept. of Fish and Game in accordance with state and federal

laws.

Management type: The halibut/angel shark set-net fishery is a limited entry fishery with gear restrictions and area

closures.

Comments: NMFS has re-established the (1990-1994) observer program for this fishery in Monterey Bay due to a

suspected increase in harbor porpoise mortality caused by a shift in effort from the northern to the southern section of

Monterey Bay. The most recent (11/1999) data clearly shows an increase in mortality for this species with extrapolated

take exceeding PBR. Mortalities and injuries reported to the MMAP for California set gill net fisheries are given in

Table 1. On September 13, 2000, the California Department of Fish and Game (CDFG) restricted the halibut

set gillnet fishery in central California to waters deeper than 60 fathoms, citing concerns over the continued

mortality of common murres and decline of the southern sea otter population. The closure area extends from

Point Reyes to Yankee Point in Monterey County and from Point Arguello to Point Sal in Santa Barbara

County. The area from Yankee Point to Point Sal will remain open to halibut fishing outside of 30 fathoms.

This closure is effective for 120 days and may be extended or reissued by the CDFG. The exclusion of this

fishery from inshore waters less than 60 fathoms is expected to considerably reduce the mortality of harbor

porpoise in Monterey Bay.
Appendix 1. Fishery Descriptions

6

Pers. Comm. Mary Larson, CDFG biologist.

236

Category I, CA other species, large mesh (>3.5 in) set gillnet fisheries.

Note: This fishery was previously combined with the California halibut/angel shark fishery. Because marine mammal

mortality estimates were determined specifically for that fishery, other large mesh set gillnet fisheries have been

separately described here.

Number of permit holders: There is no specific permit category for this fishery. See the fishery “CA halibut/angel

shark, large mesh (>8 in)” for the number of legal permit holders in the category gill/trammel nets.

Number of active permit holders:. The number of permit holders observed by NMFS observers during 1994 was 6.

In the gillnet fishery for white sea bass and yellowtail, the number of vessels actively fishing in 1995-1998 were 20,

23, 28 and 59, respectively.2

Total effort: Total effort for these set-net fisheries is not currently estimated but the majority of effort is due to the white

sea bass and yellowtail fishery. For this fishery, 1995-1998, there were an estimated 261, 276, 411 and 761 days of

effort. The fisheries comprising this category are further described in Table 3.

Geographic range: Effort in this fishery ranges from the U.S./Mexico border north to Monterey Bay and is localized

in more productive areas: San Ysidro, San Diego, Oceanside, Newport, San Pedro, Ventura, Santa Barbara, Morro Bay,

and Monterey Bay. As with the halibut/angel-shark set-net fishery, effort from Pt. Arguello south to the U.S./Mexico

border is restricted to waters farther than 3 nmi offshore and greater than 1 nmi from any of the Channel Islands.

Seasons: This fishery operates year round. Targeted species is typically determined by market demand on a short-term

basis.

Gear type and fishing method: Typical gear used for this fishery is a 150-200 fathom gillnet. The mesh size depends

on the target species but typical values observed are 6.0 and 6.5 inches. Typical characteristics for these fisheries are

found in Table 3. Fishing methods vary according to target species but are similar to methods used in the halibut/angel

shark fishery.

Regulations: This fishery is managed by the California Dept. of Fish and Game in accordance with state and federal

laws.

Management type: These fisheries have gear restrictions and area closures.

Comments: This fishery is not currently observed by NMFS or the state of California. Mortalities and injuries reported

to the MMAP for California set gill net fisheries are given in Table 1.

Category II, California Round Haul Fisheries.6

Note: This category includes purse seine, drum seine and lampara net fisheries for wetfish (anchovy, mackerel, and

sardine), and tuna. Choice of targeted species is primarily driven by availability and varying market demand.

Number of permit holders: Number of permit holders is estimated at 175 for the wetfish fisheries (currently, tuna does

not require a specific permit to operate other than a general commercial fishing permit). Starting January 1, 2000 under

a new Coastal Pelagic Species Fishery Management Plan (CPS-FMP), a limited entry program will be initiated for the

area south of 390 North latitude. Eligibility will require a minimal of 100 metric tons of CPS finfish be landed between
Appendix 1. Fishery Descriptions

7Descriptions of Washington and Oregon fisheries provided by the Northwest Region, NMFS.

237

January 1, 1993 through November 5, 1997. 

Number of active permit holders: For the wetfish fishery, there are an estimated 65 vessels/persons actively fishing;

for tuna, there are approximately 15 vessels/persons fishing. 

Total effort: No estimate is currently available, however, overall effort has been relatively constant for these fisheries

in recent years. 

Geographic range: These fisheries occur along the coast of California predominantly from San Pedro, including the

Channel Islands, north to San Francisco. 

Seasons: This fishery operates year round. Targeted species vary seasonally with availability and market demand.

Gear type and fishing method: Purse seine, drum seine and lampara nets utilizing standard seining techniques.

Regulations: Starting on January 1, 2000 the wetfish fishery will be managed by PFMC in accordance with a CPS/FMP

under federal laws.

Management type: The mackerel and sardine fisheries are quota fisheries, but no closure has been required by the State

of California for the past 15 years.

Comments: Beginning in 1999 the sardine population is considered fully recovered since its collapse during the middle

of the century. Typically, anchovy is targeted for bait or reduction while mackerel and sardine are destined for fresh

fish , aquaculture or canning overseas.

Category II, WA Puget Sound Region salmon drift gillnet fishery. 7 

Number of permit holders: This commercial fishery includes all inland waters south of the US-Canada border and east

of the Bonilla/Tatoosh line, at the entrance to the Strait of Juan de Fuca. Treaty Indian salmon gillnet fishing is not

included in this commercial fishery. The total number of permit holders for this commercial fishery in 1990 was 1149.

That number declined steadily to 773 total permits by 1998.

Number of active permit holders: Under the cooperative program that integrates issuance of Marine Mammal

Authorization Certificates into the existing State license process, NMFS receives data on vessels that have completed

the licensing process and are eligible to fish. These vessels are a subset of the total permits extant (773 in 1998), and

the remainder of the permits are inactive and do not participate in the fishery during a given year. The number of

"active" permits is assumed to be equal to or less than the number of permits that are eligible to fish. For 1996 the

number of active permits was 552, 633 in 1997 and 559 in 1998. The total number of permits available has been

reduced, from 1995 to present, through combined State and federal license buy-back programs and is not expected to

return to previous levels.

Total effort: Effort in the Puget Sound salmon drift gillnet fishery is regulated by systematic openings and closures

that are specific to area and target salmon species. Since 1994, the number of active vessels in the Puget Sound drift

gillnet fishery has declined. In addition, at least one major portion of the fishery, the previously observed sockeye

fishery in areas 7 and 7A, has experienced reductions in available fishing time (openings). The number of days and total

number of hours that the sockeye fishery remained open, approached the 1994 level only once (1997) in the period from
Appendix 1. Fishery Descriptions

238

1995 through 1998. In the remaining years the available sockeye fishing time was less than half of the 1994 level. 

Geographic Range: The fishery occurs in the inland marine waters south of the U.S./Canada border and east of the

Bonilla/Tatoosh line at the entrance to the Strait of Juan de Fuca. The inland waters are divided into smaller statistical

catch areas which are regulated independently.

Seasons: This fishery has multiple seasons throughout the year that vary among local areas dependent on local salmon

runs. The seasons are managed to access harvestable surplus of robust stocks of salmon while minimizing impacts on

weak stocks.

Gear type and fishing methods: Vessels operating in this fishery use a drift gillnet of single web construction, not

exceeding 300 fathoms in length. Minimum mesh size for gillnet gear varies by target species. Fishing directed at

sockeye and pink salmon are limited to gillnet gear with a 5 inch minimum mesh and a 6 inch maximum, with an

additional "bird mesh" requirement that the first 20 meshes below the corkline be constructed of 5 inch opaque white

mesh for visibility; the chinook season has a 7 inch minimum mesh; the coho season has a 5 inch minimum mesh; and

the chum season has a 6 to 6.25 inch minimum mesh. The depth of gillnets can vary depending upon the fishery and

the area fished. Normally they range from 180 to 220 meshes in depth, with 180 meshes as a common depth. It is the

intention of the fisher to keep the net off the bottom. The vessel is attached to one end of the net and drifts with the net.

The entire net is periodically retrieved onto the vessel and catch is removed. Drift times vary depending on fishing area,

tidal condition and catch.

Regulations: The fishery is a limited entry fishery with seasonal openings, area closures, and gear restrictions.

Management type: The fishery occurs in State waters and is managed by the Washington Department of Fish and

Wildlife consistent with the U.S.-Canada Pacific Salmon Commission management regimes and the ocean salmon

management objectives of the Pacific Fishery Management Council.

Comments: In 1993, observers were placed onboard vessels in a pilot program to monitor seabird and marine mammal

interactions with fishing effort for several target salmon species in a number of areas throughout the Puget Sound region.

In 1994 observer effort was concentrated in the sockeye fishery in areas 7 and 7A, where interactions with seabirds and

marine mammals were most likely to occur. Incidental takes of harbor porpoise, Dall’s porpoise and harbor seals have

been documented in the fishery. The overall take of marine mammals for the salmon drift gillnet fisheries in Puget

Sound is unlikely to have increased since the fisheries were last observed, owing to reductions in the number of

participating vessels and available fishing time.

Category II, OR swordfish surface longline fishery.

Number of permit holders: The number of Oregon Developmental Fishery Permits for fishing swordfish using a floating

longline is limited to 20. Nine (9) developmental swordfish longline permits were issued in 1995, one (1) in 1996, two

(2) in 1997, three (3) in 1998, and four (4) in 1999.

Number of active permit holders: Based on landings of swordfish with this gear type, there were no active permit

holders in this fishery during 1998 or 1999.

Total effort: In 1998, and again in 1999 there were no reported swordfish landings using longline gear.

Geographic range: This fishery occurs off the coast of Oregon. Swordfish longlines may not be fished within 25

nautical miles of the mainland.
Appendix 1. Fishery Descriptions

239

Seasons: This fishery could occur year-round, however, effort would generally terminate by late fall.

Gear type: Fishing gear consists of a buoyed mainline fitted with leaders and baited hooks. The mainline is fished near

the surface suspended from buoys (rather than anchored to the bottom as in groundfish longline fisheries). Swordfish

longlines may not exceed 1000 fathoms in length and must be attached at one end to the vessel when fishing. The gear

is typically set in the evening and retrieved in the morning.

Regulations: The fishery is a limited entry fishery with gear and bycatch restrictions.

Management type: This fishery is managed by the Oregon Department of Fish and Wildlife, Developmental Fisheries

Program.

Comments: The Developmental Fisheries Permit requires permit holders to take observers aboard if requested to do

so, however, to date no observer placements have been made. No marine mammal interactions have been documented.

Category II, OR blue shark surface longline fishery.

Number of permit holders: The number of Oregon Developmental Fishery Permits for fishing blue shark using a

floating longline is limited to 20. In 1995, six (6) of the available blue shark permits were issued, two (2) in 1996, four

(4) in 1997 and no (0) permits were issued in 1998. For 1999, there again were no (0) developmental permits were

issued for the blue shark longline fishery.

Number of active permit holders: There were no active permits in the blue shark longline fishery off Oregon during

1998 or 1999. The effort in this fishery prior to 1998 was estimated to be low based on the number of permits issued

and very limited landings. 

Total effort: Actual catch by the few developmental permit holders is unknown. Landings of blue shark by all vessels

using longline gear totaled 3,628 pounds for the period 1995 through 1998 (477 lbs - '95, 871 lbs - '96, 542 lbs - '97,

and 1,738 lbs - '98). Note that these landing totals are for all longline including blue shark landed incidental to the

groundfish sunken longline fishery.

Geographic range: This fishery occurs off the coast of Oregon. There are no area restrictions for shark longline gear.

Seasons: This fishery occurs year-round, however, effort in this fishery generally terminates by late fall.

Gear type: Fishing gear consists of a buoyed mainline fitted with leaders and baited hooks. The mainline is fished near

the surface suspended from buoys (rather than anchored to the bottom as in groundfish longline fisheries). Shark

longlines must be marked at each terminal surface end with a pole and flag, an operating light, a radar reflector, and a

buoy showing clear identification and gear owner. The gear is typically set in the evening and retrieved in the morning.

Regulations: The fishery is a limited entry fishery with gear and bycatch restrictions.

Management type: This fishery is managed by the Oregon Department of Fish and Wildlife, Developmental Fisheries

Program.

Comments: The Developmental Fisheries Permit requires permit holders to take observers aboard if requested to do

so, however, to date no observer placements have been made. No marine mammal interactions have been documented
Appendix 1. Fishery Descriptions

8

 Pers. Comm. Diana Watters, biologist at CDFG Menlo Park.

9

This fishery description was provided by Marija Vojkovich, biologist at CDFG Santa Barbara.

240

Category III, CA herring purse seine fishery.8

This fishery is composed of a roe herring fishery and a fresh herring fishery. The roe herring component has recently

undergone some changes. During the early 1990's, there were 26 permits fishing for roe herring using round hauls

(either purse seine or lampara nets). Between 1993 and 1998, all roe herring fishers converted their gear to gillnets with

stretched mesh size less than 2.5 inches (which are not known to take mammals) as part of CDFG efforts to protect

herring resources. There are presently 416 gillnet permits for the roe herring fishery in San Francisco Bay, and an

additional 45 permits along the northern California coast (Tomales Bay, Humboldt Bay, and near Crescent City). This

fishery begins in December (San Francisco Bay) or January (northern California) and ends when the quotas have been

reached, but no later than mid-March. There are 10 permits available for the fresh herring round haul fishery (purse

seine or lampara nets). This fishery is restricted to the non-spawning season, or approximately mid-March through the

end of November. Fishing may take place in open ocean areas ( e.g. Monterey Bay) or inside bays (e.g. San Francisco

Bay).

Category II, CA squid purse seine fishery.9

Number of permit holders: A permit to participate in the squid fishery was required as of April 1, 1998 and must be

renewed annually. Permits are classified as Market Squid Vessel permits which allow the vessel to light and/or catch

squid and a Light Boat Owners permit that allows lighting of squid only. In the 1999/00 permit year there were 217

Market Squid Vessel permits and 51 Light Boat Owners permits.

Number of active permit holders: The number of active permits varies by year depending on market conditions and

squid availability. During 1999/00 there were approximately 60 vessels active during some portion of the year. In the

year of greatest squid landings (1996/97) and prior to the 1997/98 El Niño, approximately 105 vessels landed more than

one ton of squid. During the 1998/99 fishing year, approximately 78 vessels landed more than one ton of squid.

Additional vessels “lighted” for squid, but there are no data to arrive at a number.

Total effort: Effort can only be documented as successful fishing days (when vessels made landings). Therefore, days

of unsuccessful effort or effort by light boats is undocumented. In the 1996/97 fishing year for vessels landing more

than one ton during that year, approximately 4,202 landings were made. In 1998/99, approximately 1,125 landings were

made. Environmental conditions have not been “normal” since 1996/97 for the squid industry and for the years since

1992/93 market demand has played a major role in fishing activity and landings. 

Geographic range: The majority of the fishing activity and catches are made in southern California. Traditionally, the

Channel Islands have been the area of greatest activity; coastal areas produce from 3%-30% of the catch. Monterey Bay

has a squid fishery which is of historical significance in California. This fishery began in the mid 1800s and has been

operational since that time. There is also some squid fishing that occurs at the northern end of the Bay off Santa Cruz.

Seasons: This fishery occurs year-round, however, effort in this fishery generally is greatest during the months of

November through March in southern California and from May through September in the Monterey area. Unusual water

conditions in 1998/99 have provided for an uncharacteristic fishery to take place in southern California during the
Appendix 1. Fishery Descriptions

241

months of April through June.

Gear type: There are several gears employed in this fishery. The majority of vessels use purse seine nets or lampara

nets. Dip or brail nets are used by a few small vessels in southern California. Lights are used by almost all vessels to

attract spawning aggregations of squid. The use of lights to attract squid has never been restricted in southern California

but in the Monterey fishery it has been allowed and disallowed several times in the past 15 years. Presently, lights are

allowed statewide. The use of lights has not been regulated thus far due to biological concerns only sociological.

Regulations: All vessels participating in the squid fishery must have a permit. The fishery north of Point Conception

is open from noon Sunday to noon Friday each week. The squid fishery in southern California is open each day of the

week, however, the Fish and Game Commission recently adopted a regulation restricting the squid fishing days to those

in effect north of Point Conception. It also adopted a mandatory logbook program for both fishing and lighting vessels.

Management type: This fishery came under more strict regulatory control by the Department of Fish and Game in

January 1998 although it is a monitored fishery in the Pacific Fishery Management Council’s newly adopted Coastal

Pelagic Species Plan. A state management plan is to be completed by April 1, 2001. Limited entry, use of lights, closed

areas, gear restrictions, and seasons are management options to be considered in the development of the management

plan.

Comments: The squid fishery operates primarily at night and uses lights. Encounters between the fishery and pilot

whales, pinnipeds, and birds have been documented. Seal bombs are used regularly. Lethal and nonlethal interaction

rates are unknown. The fishery grew rapidly from 1993/94 until 1997/98 due to increased market demands from Asian

countries especially China. That market demand has been eliminated and many vessels are left without a buyer for their

squid. Consequently, fishing effort has slowed considerably.

Category III, WA Willapa Bay salmon drift gillnet fishery.

Number of permit holders: The total number of permit holders for this fishery in 1995 and 1996 was 300 but this

number has declined in subsequent years. In 1997 there were 264 total permits and 243 in 1998.

Number of active permit holders: The number of active permit holders is assumed to be equal to or less than the number

of permits eligible to fish in a given year. The number of permits renewed and eligible to fish in 1996 was 300 but

declined to 224 in 1997 and 196 permits were renewed for 1998. The 1996-98 counts do not include permits held on

waivers for those years, but do include permits that were eligible to fish at some point during the year and subsequently

entered into a buyback program. The number of permits issued for this fishery has been reduced through a combination

of State and federal permit buyback programs. Vessels permitted to fish in the Willapa Bay are also permitted to fish

in the lower Columbia River drift gillnet fishery.

 

Total effort: Effort in this fishery is regulated through area and species openings. The fishery was observed in 1992

and 1993 when fishery opening were greater than in recent years. In 1992 and 1993 there were 42 and 19 days of open

fishing time during the summer "dip-in" fishery. The "dip-in" fishery was closed in 1994 through 1999. Available

openings have also declined in the fall chinook/coho fisheries. In 1992/93 respectively there were 44 and 78 days of

available fishing time. There were 43, 45, 22 and 16.5 available open fishing days during 1995 through 1998. 

Geographic range: This fishery includes all inland marine waters of Willapa Bay. The waters of the Bay are further

divided into smaller statistical catch areas.

Seasons: Seasonal openings coincide with local salmon run timing and fish abundance.
Appendix 1. Fishery Descriptions

242

Gear type: Fishing gear used in this fishery is a drift gillnet of single web construction, not exceeding 250 fathoms in

length, with a minimum stretched mesh size ranging upward from 5 inches depending on target salmon species. The

gear is commonly set during periods of low and high slack tides. It is the intention of the fisher to keep the net off the

bottom. The vessel is attached to one end of the net and drifts with the net. The entire net is periodically retrieved onto

the vessel and catch is removed. Drift times vary depending on fishing area, tidal condition, and catch.

Regulations: This fishery is a limited entry fishery with seasonal openings and gear restrictions.

Management type: The salmon drift gillnet fishery is managed by the Washington Department of Fish and Wildlife.

Comments: Observers were placed onboard vessels in this fishery to monitor marine mammal interactions in the early

1980s and in 1990-93. Five incidentally taken harbor seals were recovered by observers in the fishery from 1991through

1993 (3 in ‘92 and 2 in ‘93). Two incidentally taken northern elephant seals were recovered by observers from the

fishery in 1991 but no takes of this species were observed. The summer fishery (July- August) in Willapa Bay has been

closed since it was last observed in 1993 and available fishing time declined from 1996 through 1998. 

Category III, WA Grays Harbor salmon drift gillnet fishery. 

Number of permit holders: This commercial drift gillnet fishery does not include Treaty Indian salmon gillnet fishing.

The total number of permit holders for this commercial fishery in 1995 and 1996 was 117 but this number has declined

in subsequent years. In 1997 there were 101 total permits and 87 in 1998.

Number of active permit holders: The number of active permit holders is assumed to be equal to or less than the number

of permits eligible to fish in a given year. The number of permits renewed and eligible to fish in 1996 was 117 but

declined to 79 in 1997 and 59 permits were renewed for 1998. The 1996-98 counts do not include permits held on

waivers for those years but do include permits that were eligible to fish at some point during the year and subsequently

entered a buyback program. The number of permits issued for this fishery has been reduced through a combination of

State and federal permit buyback programs. Vessels permitted to fish in Grays Harbor are also permitted to fish in the

lower Columbia River salmon drift gillnet fishery.

Total effort: Effort in this fishery is regulated through area and species openings. The fishery was observed in 1992

and 1993 when fishery openings were greater than in recent years. In 1992 and 1993 there were 42 and 19 days of open

fishing time during the summer "dip-in" fishery. The "dip-in" fishery was closed in 1994 through 1999. Available

openings have also declined in the fall chinook/coho fisheries. There were 11, 17.5, 9 and 5 available open fishing days

during the 1995 through 1998 fall season. 

Geographic range: Effort in this fishery includes all marine waters of Grays Harbor. The waters are further divided

into smaller statistical catch areas.

Seasons: This fishery is subject to seasonal openings which coincide with local salmon run timing and fish abundance.

Gear type: Fishing gear used in this fishery is a drift gillnet of single web construction, not exceeding 250 fathoms in

length, with a minimum stretched mesh size ranging of 5 inches depending on target salmon species. The gear is

commonly set during periods of low and high slack tides and retrieved periodically by the tending vessel. It is the

intention of the fisher to keep the net off the bottom. The vessel is attached to one end of the net and drifts with the net.

The entire net is periodically retrieved onto the vessel and catch is removed. Drift times vary depending on fishing area,

tidal condition, and catch
Appendix 1. Fishery Descriptions

243

Regulations: The fishery is a limited entry fishery with seasonal openings and gear restrictions.

Management type: The salmon drift gillnet fishery is managed by the Washington Department of Fish and Wildlife.

Comments: Observers were placed onboard vessels in this fishery to monitor marine mammal interactions in the early

1980s and in 1990-93. Incidental take of harbor seals was observed during the fishery in 1992 and 1993. In 1992, one

harbor seal was observed entangled dead during the summer fishery and one additional seal was observed entangled

during the fall fishery but it escaped uninjured. In 1993, one harbor seal was observed entangled dead and one

additional seal was recovered by observers during the summer fishery. The summer fishery (July-August) in Grays

Harbor has been closed since it was last observed in 1993. Available fishing time in the fall chinook fisheries declined

from 1996 through 1998.

Category III, WA, OR lower Columbia River salmon drift gillnet fishery.

Number of permit holders: The total number of permit holders was 856 (344 from Oregon and 512 from Washington)

when the fishery was last observed in 1993. In 1995 through 1998 the number of permits was 747, 693, 675 and 620

respectively. The number of permits issued for this fishery by Washington has been reduced through a combination of

State and federal buy-back programs. This reduction is reflected in the overall decline in the total number of permits.

Number of active permit holders: The number of active permits is a subset of the total permits issued for the fishery.

For example, in 1995, 110 vessels (of the 747 vessels holding permits) landed fish in the mainstem fishery.

Total effort: Effort in this fishery is regulated through species related seasonal openings and gear restrictions. The

fishery was observed in 1991, 1992 and 1993 during several seasons of the year. The winter seasons (openings) for

1991 through 1993 totaled 13, 9.5, and 6 days respectively. The winter season has subsequently been reduced to

remnant levels to protect upriver ESA listed salmon stocks. In 1995 there was no winter salmon season, in 1996 the

fishery was open for 1 day. In 1997 and 1998 the season was shifted to earlier in the year and gear restrictions were

imposed to target primarily sturgeon. The fall fishery in the mainstem was also observed 1992 and 1993 as was the

Young's Bay terminal fishery in 1993, however, no marine mammal mortalities were observed during these fisheries.

The fall mainstem fishery openings varied from 1 day in 1995 to just under 19.5 days in 1997 and 6 days in 1998. The

fall Youngs Bay terminal fishery fluctuated between 60 and 70 days for the 1995 through 1998 period which was similar

to the fishery during the period observed. 

Geographic range: This fishery occurs in the main stem of the Columbia river from the mouth at the Pacific Ocean

upstream to river mile 140 near the Bonneville Dam. The lower Columbia is further subdivided into smaller statistical

catch areas which can be regulated independently.

Seasons: This fishery is subject to season and statistical area openings which are designed to coincide with run timing

of harvestable salmon runs while protecting weak salmon stocks and those listed under the Endangered Species Act.

In recent years, early spring (winter) fisheries have been sharply curtailed for the protection of listed salmon species.

In 1994, for example, the spring fishery was open for only three days with approximately 1900 fish landed. In 1995

the spring fishery was closed and in 1996 the fishery was open for one day but fishing effort was minimal owing to

severe flooding. Only 100 fish were landed during the one day in 1996.

Gear type: Typical gear used in this fishery is a gillnet of single web construction, not exceeding 250 fathoms in length,

with a minimum stretched mesh size ranging upwards from 5 inches depending on target salmon species. The gear is

commonly set during periods of low and high slack tides. It is the intention of the fisher to keep the net off the bottom.

The vessel is attached to one end of the net and drifts with the net. The entire net is periodically retrieved onto the vessel

and catch is removed. Drift times vary depending on fishing area, tidal condition, and catch
Appendix 1. Fishery Descriptions

244

Regulations: The fishery is a limited entry fishery with seasonal openings, area closures, and gear restrictions.

Management type: The lower Columbia River salmon drift gillnet fishery is managed jointly by the Washington

Department of Fish and Wildlife and the Oregon Department of Fish and Wildlife.

Comments: Observers were placed onboard vessels in this fishery to monitor marine mammal interactions in the early

1980s and in 1990-93. Incidental takes of harbor seal and California sea lion were documented, but only during the

winter seasons (which have been reduced dramatically in recent years to protect ESA listed salmon) . No mortalities

were observed during the fall fisheries. 

Category III, WA, OR salmon net pens.

Number of permit holders: There were 12 commercial salmon net pen (“grow out” ) facilities licensed in Washington

in 1998. There are no commercial salmon net pen or aquiculture facilities currently licensed in Oregon. Noncommercial salmon enhancement pens are not included in the list of commercial fisheries.

Number of active permit holders: Twelve salmon net pen facilities in Washington. 

Total effort: The 12 licensed facilities on Washington operate year-round. 

Geographic range: In Washington, net pens are found in protected waters in the Straits (Port Angeles), northern Puget

Sound (in the San Juan Island area) as well as in Puget Sound south of Admirality Inlet. There are currently no

commercial salmon pens in Oregon.

Seasons: Salmon net pens operate year-round.

Gear type: Net pens are large net impoundments suspended below a floating dock-like structure. The floating docks

are anchored to the bottom and may also support guard (predator) net systems. Multiple pens are commonly rafted

together and the entire facility is positioned in an area with adequate tidal flow to maintain water quality.

Regulations: Specific regulations unknown.

Management type: In Washington, the salmon net pen fishery is managed by the Washington Department of Natural

Resources through Aquatic Lands Permits as well as the Washington Department of Fish and Wildlife. 

Comments: Salmon net pen operations have not been monitored by NMFS for marine mammal interactions, however,

incidental takes of California sea lions and harbor seals have been reported. 

Category III, WA, OR, CA groundfish trawl. 

Approximate number of vessels/persons: In 1998, approximately 332 vessels used bottom and mid-water trawl gear

to harvest Pacific coast groundfish. This is down from 383 vessels in 1995. Groundfish trawl vessels harvest a variety

of species including Pacific whiting (hake), flatfish, sablefish, lingcod, and rockfish. This commercial fishery does not

include Treaty Indian fishing for groundfish.

All observed incidental marine mammal takes have occurred in the mid-water trawl fishery for Pacific whiting. The

annual whiting allocation is divided between vessels that harvest and process catch at sea and those that harvest and

deliver catch to shore-based processing facilities. At least one NMFS-trained observer is placed on board each at-sea
Appendix 1. Fishery Descriptions

10Descriptions of Hawaii State managed fisheries provided by William Devick, State of Hawaii,

Department of Land and Natural Resources, Division of Aquatic Resources, Honolulu Hawaii.

245

processing vessel to provide comprehensive data on total catch, including marine mammal takes. Whiting vessels that

deliver to shore-based processors are issued Exempted Fishing Permits that requires the entire catch to be delivered

unsorted to processing facilities where State technicians have the opportunity to sample. In 1998, 13% of the whiting

deliveries landed at shore-based processors were monitored. The following is a description of the commercial whiting

fishery.

Number of permit holders/active permit holders: A license limitation ("limited entry") program has been in effect in

the Pacific coast groundfish fishery since 1994. Non-tribal trawl vessels that harvest groundfish are required to possess

a limited entry permit to operate in the fishery. Any vessel with a federal limited entry trawl permit may fish for whiting,

but the number of vessels that do is smaller than the number of permits. In 1998, approximately 61 limited entry vessels,

7 catcher/processors and 50 catcher vessels delivering to shoreside and mothership processors, made commercial

landings of whiting during the regular season. In addition, 6 unpermitted mothership processors received unsorted

whiting catch.

Total effort: The whiting allocation continues to be fully utilized. From 1997 to 1999 the annual allocation was 232,000

mt/year, this is an increase over the 1996 allocation of 212,000 mt and the 1995 allocation of 178,400 mt. In 1998,

motherships vessels received 50,087 mt of whiting in 17 days, catcher/processors took 70,365 mt of whiting in 54 days

and shore-based processors received 87,862 mt of whiting over a 196 day period.

Geographic range: The fishery extends from northern California (about 40E30' N. latitude) to the U.S.-Canada border.

Pacific whiting migrate from south to north during the fishing season, so effort in the south usually occurs earlier than

in the north.

Seasons: From 1997 to 1999, season start dates have remained unchanged. The shore-based season in most of the

Eureka area (between 42O- 40O30' N latitude) began on April 1, the fishery south of 40O30' N latitude opened April 15,

and the fishery north of 42O N latitude started on June 15. In 1998, the primary season for the shore-based fleet closed

on October 13, 1998. The primary seasons for the mothership and catcher/processor sectors began May 15, north of

420 N. lat. In 1998, the mothership fishery closed on May 31, the catcher/processor fishery closed on August 7. 

Gear type: The Pacific whiting trawl fishery is conducted with mid-water trawl gear with a minimum mesh size of 3

inches throughout the net.

Regulations/Management type: This fishery is managed through federal regulations by the Pacific Fishery Management

Council under the Groundfish Fishery Management Plan.

Comments: Since 1991, incidental takes of Steller sea lions, Pacific white-sided dolphin, Dall's porpoise, California

sea lion, harbor seal, and northern elephant seal have been documented in the whiting fishery. From 1996 to 1999 , 2

Steller sea lions, 2 northern elephant seals, 2 California sea lions, 3 Pacific white-sided dolphins, and 6 Dall's porpoise

were reported by observers in the at-sea processing fleet. Between 1996 and 1999, one incidental take of a harbor seal

was documented in the shore-based fleet.

Category III, Hawaii gillnet fishery.10

Number of active permit holders: In 1997 there were 129 active commercial fishers. In 1995 there were approximately

115.
Appendix 1. Fishery Descriptions

11 Ito, Russell Y. and Walter A. Machado. 1999. Annual report of the Hawaii-based longline fishery for

1998. Administrative Report H-99-06, available from NMFS, Southwest Fisheries Science Center, La Jolla, CA

92038.

246

Total effort: In 1997 there were 2,109 trips for a total catch of 864,194 pounds with 792,210 pounds sold. This fishery

operates in nearshore and coastal pelagic regions.

Seasons: This fishery operates year-round with the exception of Juvenile big-eyed scad less than 8.5 inches which

cannot be taken from July through October.

Gear type: Gillnets of stretched mesh greater than 2 inches and stretched mesh size greater than 2.75 inches for

stationary gillnets. Stationary nets must be inspected every 2 hours and total soak time cannot exceed four hours in the

same location. Additional mesh restrictions are in place for taking the big-eyed scad.

Regulations: Gear and season restrictions (see above).

Management type: Managed by the State of Hawaii Division of Aquatic Resources.

Comments: The principle catches include reef fishes and big-eyed scad (akule) and mackerel scad (opelu). Interactions

have been documented with bottlenose dolphin and spinner dolphin.

Category III, Hawaii swordfish, tuna, billfish, mahi mahi, wahoo, and oceanic shark longline/set line fishery.11

Number of permit holders: There are 164 permits under a (1994) federal limited entry program.

Number of active permit holders: In 1998 there were 114 active fishing vessels. For the years 1991-1997 the average

number of active fishing vessels was 118 vessels, declining from the peak in 1991 of 141 vessels. 

Total effort: For the years 1994-1998, there were on average 1,120 (min=1,100,max=1,140) trips made, 11,700

(sd=609) days of fishing effort and 14.7 million (sd=1.97 million) hooks set. The number of hooks set has been steadily

increasing since 1994 and has peaked in 1998 with 17.4 million hooks set. Most of the effort occurred outside the and

the main Hawaiian Islands’ EEZ with less effort in the EEZ’s of US possessions, with the exception of Kingman Reef

and Palmyra Atoll. Fleet landings for 1998 totaled 28.6 million pounds ($46.6 million), one of the highest years on

record.

Geographic range: This fishery encompasses a huge geographic range extending North-South from 40° N to the equator

and East-West from Kure Atoll to as far as 135° W. Fishing for broadbills generally occurs north of Hawaii, (as much

as 2,000 miles from Honolulu), whereas fishing for tunas occurs around the Main Hawaiian Islands (MHI) and south

of the Hawaiian Islands. 

Seasons: This fishery operates year-round. Effort is generally lower in the third quarter of the year.

Gear type: For broadbills, typically a 16-48 km monofilament line having as many as 700-1,000 branch lines (9-18 m

long), one in five attached with a “lightstick” (to attract squid, which in turn attracts the broadbills) placed about 76 cm

above the hook (usually baited with squid) is set in the evening and retrieved early the next morning. For tunas, a 32

km long main line, set during the day, is suspended from buoys and 1,000-1,400 dropper lines are attached to the main

line each with a hook (usually baited with whole fish).
Appendix 1. Fishery Descriptions

12Kawamoto, K. and Samuel G. Pooley. 1999. Draft Annual report of the 1998 western pacific lobster

fishery.

13Kawamoto, K. 1999. Summary of the 1999 NWHI Lobster Fishing Season. NMFS Honolulu Laboratory.

247

Regulations: Effort is required to be outside of 50 nautical miles from the entire Northwestern Hawaiian islands

(NWHI) because of possible protected species (monk seal) interactions. Several 25-75 mile closed areas also exist

around the MHI to prevent gear conflicts with smaller fishing vessels.

Management type: Federal limited access program.

Comments: This Hawaii longline fishery is active year-round and targets swordfish and tuna, other species are caught

incidentally. A small number of marine mammal interactions with bottlenose dolphin and false killer whale, humpback

whale, Risso’s dolphin, and bottlenose dolphin have been documented. In 1998 interaction with one humpback whale

was reported (NMFS logbook data) by a fisher. This may have been a result of the whale getting fouled in longline gear.

No interactions with monk seals have been reported. Due to interactions with protected species, especially turtles, this

fishery has been observed since February 24, 1994 with a coverage of less than 5%.

Category III, Hawaii lobster trap fishery.

10 12 13

Note: The portion of this fishery managed by the State of Hawaii and operating in the MHI is about 1% of the size (total

pounds of lobster caught) of the federally managed fishery operating primarily in the NWHI. The description that

follows refers to the NWHI fishery unless stated otherwise.

Number of permit holders: There are 15 permit holders under a (1991) federal limited access program. 

Number of active permit holders: In 1998 and 1999 there were 5 and 6 vessels that participated respectively. In the MHI

there were 5 active fishers in 1997.

Total effort: The number of trap hauls for 1999 is not available at this time. However, the majority of the effort took

place in the 4 harvest guideline areas; Necker Bank, Gardner Pinnacles and Maro Reef, with the remaining effort spread

out over 10 unique areas. In 1998 171,000 trap hauls were made by the 5 vessels during 9 trips and in 1997 a total of

177,700 hauls were made. In the MHI 19 trips were made in 1997.

Geographic range: Lobster permits allow fishing operations in the US EEZ from 3 to 200 nmi offshore American

Samoa, Guam and Hawaii (including the EEZ areas of the NWHI and MHI). However, no vessels have operated in the

EEZ’s of American Samoa or Guam since 1983. 

Seasons: This fishery operates under a seasonal harvest guideline system opening on July 1. The season ends once the

harvest guideline is met, but no later than December 31. In 1998, the harvest guideline was divided into the 4 areas

mentioned above with total lobster catch set at (in thousands) 70, 20, 80, and 116, respectively. Area closure occurs

once an area’s harvest guideline is met. In the MHI, open season is from September through April.

Gear type: One string consists of approximately 100 Fathom-plus plastic lobster traps. About 10 such strings are pulled

and set each day. Since 1987 escape vents that allow small lobsters to escape from the trap have been mandatory. In

1996, the fishery became “retain all”, i.e. there are no size limits or prohibitions on the retention of berried female

lobsters. The entry-way of the lobster trap must be less than 6.5 inches to prevent monk seals from getting their heads

stuck in the trap. In the MHI, rigid trap materials must have a dimension greater than 1 inch by 2 inches, with the trap

not exceeding 10 feet by six feet. 
Appendix 1. Fishery Descriptions

248

Regulations: Season, gear and quota restrictions (see above) for the NWHI were formulated by the Western Pacific

Regional Fishery Management Council and implemented by NMFS. The MHI fishery is managed by the State of

Hawaii, Division of Aquatic Resources with season and gear restrictions (see above).

Management type: Limited access program with bank specific quotas and closures. In the MHI, open access.

Comments: The NWHI fishery targets the red spiny lobster and the common slipper lobster. The ridgeback slipper

lobster is also taken. Protected species of concern include monk seals (mentioned above) and turtles. There have been

no interactions with these species since 1995 but they have been seen in the vicinity of the fishing gear.

Category III, Hawaii inshore handline fishery.

 

In 1997 a total 750 fishers made 8,526 fishing trips in the main Hawaiian Islands and caught 531,449 pounds and sold

475,562 pounds for an ex-vessel landing value of $1,010,758. This fishery occurs in nearshore and coastal pelagic

regions. The principal catches include reef fishes and big-eyed scad (akule) and mackerel scad (opelu). In 1995

approximately 650 fishers were active. Interactions have been documented for bottlenose dolphin.

Category III, Hawaii deep sea bottomfish handline and jig fishery.

Note: There are two commercial bottomfish fisheries in Hawaii: a distant water Northwestern Hawaiian Islands (NWHI)

limited entry fishery under federal jurisdiction and the main Hawaiian Islands bottomfish fishery primarily under the

State of Hawaii jurisdiction.

Number of permit holders: The main Hawaiian Islands fishery is open access with close to 2,000 bottomfish vessels

registered with the State of Hawaii, whereas the NWHI is restricted to a maximum of 17 vessels. 

Number of active permit holders: In 1997 in the MHI a total of 750 fishers were active. The NWHI are divided into

the Mau Zone (closer to MHI) and the Hoomalu Zone. The Hoomalu Zone is a limited entry zone with 6 vessels

participating in 1998, 7 vessels fished the Mau Zone in the same year. Restrictions on new entry into the Mau Zone

were implemented in 1998.

Total effort: In 1998 in the MHI approximately 8,500 trips were made with a total catch of 424,000 pounds for an exvessel landing value of $1,336,000. This fishery occurs primarily in offshore banks and pinnacles. In the NWHI

332,000 pounds ($894,000) were caught in 1998, below average since 1990.

Seasons: Year round.

Gear type: This fishery is a hook-and-line fishery that takes place in deep water. In the NWHI fishery, vessels are 30

ft or greater and conduct trips of about 10 days. In the MHI the vessels are smaller than 30 ft and trips last from 1 to

3 days.

Regulations: In the MHI, the sale of snappers (opakapaka, onaga and uku) and jacks less than one pound is prohibited.

In June of 1998, Hawaii Division of Aquatic Resources (HDAR) closed 19 areas to bottomfishing and regulations

pertaining to seven species (onaga, opakapaka, ehu, kalekale, gindai, hapuupuu and lehi) were enacted.

Management type: The MHI is managed by the HDAR with catch, gear and area restrictions (see above) but no permit

limits. The NWHI is a limited access federal program. 

Comments: The deep-slope bottomfish fishery in Hawaii concentrates on species of eteline snappers, carangids, and
Appendix 1. Fishery Descriptions

249

a single species of grouper concentrated at depths of 30-150 fathoms. These fish have been fished on a subsistence basis

since ancient times and commercially for at least 90 years. NMFS is considering the possibility of re-categorizing the

NWHI bottomfish fishery from Category III to Category II due to concerns for potential interactions between bottomfish

fishing vessels and Hawaiian monk seals, although there were none observed during 26 NWHI bottomfish trips during

1990-1993, and none reported. On 12 of the 26 trips, bottlenose dolphins have been observed steeling fish from the

lines, but not hookings or entanglements occurred. Effort in this fishery increases significantly around the Christmas

season because a target species, a true snapper, is typically sought for cultural festivities.11 No data is collected for

recreational or subsistence fishermen, but their MHI catch is estimated to be about equal to the MHI commercial catch.

Category III, Hawaii tuna handline and jig fishery.

In 1997 a total of 543 fishers made 6,627 trips in the MHI and caught 2,014,656 pounds and sold 1,958,759 pounds for

an ex-vessel value of $3,788,391. This fishery occurs around offshore fish aggregating devices and mid-ocean

seamounts and pinnacles. The principal catches are small to medium sized bigeye, yellowfin and albacore tuna. There

are several types of handline methods in the Hawaiian fisheries. Baited lines with chum are used in day fishing

operations (palu-ahi), another version uses squid as bait during night operations (ika-shibi), and an operation called

“danglers” uses multiple lines with artificial lures suspended or dangled over the water. Interactions have been

documented for rough-toothed dolphin, bottlenose dolphin, and Hawaiian monk seal.
Appendix 1. Fishery Descriptions

250

Table 1. The number of animals injured (I) and killed (K) reported to the Marine Mammal Authorization

Program (MMAP) compared with data reported from the NMFS Observer Program for two California gillnet

fisheries for the years 1996-1998.

Category I, CA/OR thresher shark/swordfish drift gillnet fishery

1996 1997 1998

Species

MMAP NMFS MMAP NMFS MMAP NMFS

I K I K I K I K I K I K

Minke whale 0 1 0 1 0 0 0 0 0 0 0 0

Sperm whale 1 0 1 0 0 0 0 0 0 1 0 1

Gray Whale 0 0 0 0 0 0 0 0 0 1 0 1

Pacific white-sided dolphin 2 2 0 3 1 3 0 3 0 0 0 0

Common dolphin 19 6 0 28 1 20 1 24 1 6 0 9

Northern right-whale dolphin 0 1 0 5 0 4 0 5 0 0 0 0

Dall’s porpoise 0 1 0 2 0 0 0 4 0 0 0 0

Unidentified Small cetacean 0 4 0 0 0 0 0 0 0 0 0 0

California sea lion 0 6 0 4 4 15 2 37 0 19 0 23

Steller sea lion 0 0 0 0 0 0 0 0 0 1 0 0

Northern elephant seal 0 5 0 5 0 6 1 8 0 0 0 4

Total Occurrences Reported 22 26 1 48 6 48 4 81 1 28 0 38

Category I, CA large mesh (>3.5in) set gillnet fisheries (angel shark/halibut and other species)

1996 1997 1998

Species

MMAP NMFS MMAP NMFS MMAP NMFS

I K I K I K I K I K I K

Common dolphin 0 1 0 3 0 2

California sea lion 0 10 0 4 0 2

Harbor seal 0 2 0 0 0 0

Total Occurrences Reported 0 13 0 7 0 4 Not Observed Not Observed

Not Observed
Appendix 1. Fishery Descriptions

251

Table 2. Strandings reported to the NMFS Marine Mammal Stranding Network 1996-1998.

Species

1996 1997 1998

CA OR/WA CA OR/WA CA OR/WA

n %HR (#) n % HR (#) n %HR (#) n % HR (#) n %HR (#) n % HR (#)

Harbor Porpoise 18 16.7 (3) 0 0 (0) 26 0 (0) 3 0 (0) 37 10.8(4) 25 0 (0)

Dall’s Porpoise 2 0 (0) 8 0 (0) 4 0 (0) 10 0 (0) 2 0 (0) 2 0 (0)

Pac. White-sided Dolphin 1 0 (0) 0 0 (0) 5 20.0(1) 0 0 (0) 5 0 (0) 1 0 (0)

Risso’s Dolphin 1 0 (0) 0 0 (0) 2 0 (0) 0 0 (0) 3 0 (0) 0 0 (0)

Bottlenose Dolphin 3 0 (0) 0 0 (0) 3 0 (0) 0 0 (0) 4 0 (0) 0 0 (0)

Common Dolphin 30 0 (0) 0 0 (0) 15 6.7(1) 0 0 (0) 35 2.9(1) 0 0 (0)

Striped Dolphin 0 0(0) 0 0 (0) 1 0 (0) 1 0 (0) 2 0 (0) 0 0 (0)

N. Right Whale Dolphin 0 0 (0) 0 0 (0) 0 0 (0) 0 0 (0) 1 0 (0) 0 0 (0)

Rough-toothed Dolphin 0 0 (0) 0 0 (0) 0 0 (0) 0 0 (0) 1 0 (0) 0 0 (0)

Killer Whale 1 0 (0) 0 0 (0) 1 0 (0) 0 0 (0) 0 0 (0) 1 0 (0)

Short-finned Pilot Whale 0 0 (0) 1 0 (0) 0 0 (0) 0 0 (0) 0 0 (0) 0 0 (0)

Stejneger’s Beaked Whale 0 0 (0) 1 0 (0) 0 0 (0) 0 0 (0) 0 0 (0) 0 0 (0)

Cuvier’s Beaked Whale 1 0 (0) 0 0 (0) 2 0 (0) 0 0 (0) 2 0 (0) 1 0 (0)

Peruvian Beaked Whale 0 0(0) 0 0 (0) 0 0 (0) 0 0 (0) 1 100(1) 0 0 (0)

Unident. Beaked Whale 1 0 (0) 0 0 (0) 0 0 (0) 0 0 (0) 0 0 (0) 0 0 (0)

Pygmy Sperm Whale 2 0 (0) 1 0 (0) 0 0 (0) 0 0 (0) 6 0 (0) 0 0 (0)

Sperm Whale 0 0(0) 0 0 (0) 1 0 (0) 0 0 (0) 0 0 (0) 0 0 (0)

Gray Whale 13 38.5 (5) 4 0 (0) 10 60.0(6) 3 0 (0) 3 100(3) 4 0 (0)

Minke Whale 1 0 (0) 0 0 (0) 0 0 (0) 0 0 (0) 1 0 (0) 1 0 (0)

Blue Whale 1 0 (0) 0 0 (0) 0 0 (0) 0 0 (0) 0 0 (0) 0 0 (0)

Fin Whale 1 100 (1) 0 0 (0) 1 100(1) 1 0 (0) 1 0 (0) 0 0 (0)

Humpback Whale 1 0 (0) 0 0 (0) 3 33.3(1) 0 0 (0) 2 0 (0) 2 0 (0)

Unidentified Cetacean 2 0 (0) 0 0 (0) 3 0 (0) 0 0 (0) 0 0 (0) 0 0 (0)

Unidentified Porpoise 0 0 (0) 2 0 (0) 0 0 (0) 0 0 (0) 0 0 (0) 0 0 (0)

Unidentified Dolphin 8 0 (0) 0 0 (0) 16 0 (0) 1 0 (0) 12 0 (0) 5 0 (0)

Unidentified Whale 1 0 (0) 1 0 (0) 7 14.3(1) 1 100(1) 2 0 (0) 0 0 (0)

Unident. Balaenopterid 1 0 (0) 0 0 (0) 1 100(1) 0 0 (0) 0 0 (0) 1 0 (0)

Northern Fur Seal 12 0 (0) 0 0 (0) 50 0(0) 1 0 (0) 21 0 (0) 1 0 (0)

Guadalupe Fur Seal 2 0 (0) 0 0 (0) 2 0(0) 0 0 (0) 3 0 (0) 0 0 (0)

Steller (Nthn) Sea Lion 10 0 (0) 2 0 (0) 7 0(0) 3 33.3(1) 10 20.0(2) 7 0 (0)

California Sea Lion 724 14.6 (106) 30 23.3 (7) 1262 10.6(134) 10 30.0(3) 2576 77.3(199) 75 12.0(9)

Unidentified Sea Lion 0 0 (0) 23 4.76 (1) 0 0(0) 0 0 (0) 0 0 (0) 0 0 (0)

Harbor Seal 302 4.30 (13) 109 19.3 (21) 297 5.7(17) 127 9.4(12) 313 6.7(21) 121 5.8(7)

Northern Elephant Seal 240 2.08 (5) 2 50 (1) 241 0.4(1) 0 0 (0) 409 1.5(6) 24 0 (0)

Unidentified Seal 0 0 (0) 21 0 (0) 0 0(0) 0 0 (0) 0 0 (0) 5 0 (0)

Unidentified Pinniped 159 0 (0) 1 0 (0) 202 0(0) 113 0 (0) 236 0 (0) 88 0 (0)

Totals for Cetaceans 89 10.1 (9) 18 0 (0) 101 11.9(12) 20 5.0(1) 120 6.1(9) 43 0 (0)

Totals for Pinnipeds 1449 8.63(125) 188 16.0 (30) 2061 152 254 6.3(16) 3568 228 321 5.0(16)
Appendix 1. Fishery Descriptions

Table 3. Characteristics of Category I Gillnet Fisheries in California.

Fishery Species Mesh Size Water Depth Set Duration Deployment Miscellaneous

Category I

CA/OR Thresher

Shark/Swordfish 

drift gillnet fishery

Swordfish/

Shark

14" - 22" Ranges from 50fms to

 2500fms

Typically 8-15 hrs. Drift Net

Only

Nets 300-1000 fms;

1000fms common; Other species

caught: opah, louvar, tuna,

thresher, blue shark, mako shark.

Category I 

CA angel shark/

halibut and other

species large mesh

(>3.5in) set gillnet

fisheries

Halibut/angel shark 8.5" < 40 fms 24 hrs Set Net

Barracuda 3.5" -- < 12 hrs Drift Net April - July

Leopard Shark 7.0" - 9.0" < 50 fms -- – Fished similar to halibut. Few

boats target leopard shark.

Perch/Croaker 3.5" - 4.0" < 15 - 20 fms < 24 hrs Set Net Few boats target these species.

Rockfish 4.5" - 7.5" > 50 fms 12 - 18 hrs Set Net Net lengths 250 - 1000 fms. Soupfin

shark is a major incidental catch in

rockfish fisheries.

Soupfin Shark 6.0" - 8.5" > 30 fms 24 hrs Set Net Few boats target soupfin shark.

White Sea bass/

Yellowtail

Usually 6.5"

6.0" - 7.0"

Usually 10 - 50 fms 

or Shallow 3 - 4 fms

8 - 24 hrs. Mostly Drift Net White sea bass predominant target

species. Nets 200 - 1000 fms.

Miscellaneous Shark 6.0" - 14" < 40 fms 8 - 24 hrs Drift, some Set Net Species include thresher and swell

sharks.

Additional Notes:

1. In southern California, gillnets are generally prohibited within three miles of shore.

2. In central California, there are 30 or 40 fathom closures depending on area.

3. In northern California, set gillnets are not allowed.

252
Appendix 1. Fishery Descriptions

Longitude

Latitude

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31 N 33 N 35 N 37 N 39 N 41 N 43 N 45 N

Monterey Bay

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Pt. Dume

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OREGON

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Figure 2. Observed set locations of the drift-net fishery during

1995

Longitude

Latitude

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31 N 33 N 35 N 37 N 39 N 41 N 43 N 45 N

Monterey Bay

Morro Bay

Pt. Arguello

Pt. Dume

San Pedro

OREGON

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253
Appendix 1. Fishery Descriptions

Longitude

Latitude

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31 N 33 N 35 N 37 N 39 N 41 N 43 N 45 N

Monterey Bay

Morro Bay

Pt. Arguello

Pt. Dume

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1997.

Longitude

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Monterey Bay

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Figure 3. Observed set locations of the drift-net fishery during

1996.

254
Appendix 1. Fishery Descriptions

Longitude

Latitude

129 W 126 W 123 W 120 W 117 W

31 N 33 N 35 N 37 N 39 N 41 N 43 N 45 N

Monterey Bay

Morro Bay

Pt. Arguello

Pt. Dume

San Pedro

OREGON

CALIFORNIA

MEXICO

Figure 6. Observed locations of marine mammal

entanglements in the drift-net fishery during 1994.

Longitude

Latitude

129 W 126 W 123 W 120 W 117 W

31 N 33 N 35 N 37 N 39 N 41 N 43 N 45 N

Monterey Bay

Morro Bay

Pt. Arguello

Pt. Dume

San Pedro

OREGON

CALIFORNIA

MEXICO

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Figure 5. Observed set locations of the drift-net fishery during

1998. 

255
Appendix 1. Fishery Descriptions

Longitude

Latitude

129 W 126 W 123 W 120 W 117 W

31 N 33 N 35 N 37 N 39 N 41 N 43 N 45 N

Monterey Bay

Morro Bay

Pt. Arguello

Pt. Dume

San Pedro

OREGON

CALIFORNIA

MEXICO

Figure 8. Observed locations of marine mammal

entanglements in the drift-net fishery during 1996.

Longitude

Latitude

129 W 126 W 123 W 120 W 117 W

31 N 33 N 35 N 37 N 39 N 41 N 43 N 45 N

Monterey Bay

Morro Bay

Pt. Arguello

Pt. Dume

San Pedro

OREGON

CALIFORNIA

MEXICO

Figure 7. Observed locations of marine mammal

entanglements in the drift-net fishery during 1995.

256
Appendix 1. Fishery Descriptions

Longitude

Latitude

129 W 126 W 123 W 120 W 117 W

31 N 33 N 35 N 37 N 39 N 41 N 43 N 45 N

Monterey Bay

Morro Bay

Pt. Arguello

Pt. Dume

San Pedro

OREGON

CALIFORNIA

MEXICO

Figure 10. Observed locations of marine mammal

entanglements in the drift-net fishery during 1998.

Longitude

Latitude

129 W 126 W 123 W 120 W 117 W

31 N 33 N 35 N 37 N 39 N 41 N 43 N 45 N

Monterey Bay

Morro Bay

Pt. Arguello

Pt. Dume

San Pedro

OREGON

CALIFORNIA

MEXICO

Figure 9. Observed locations of marine mammal

entanglements in the drift-net fishery during 1997.

257
Appendix 1. Fishery Descriptions

Longitude

Latitude

123 W 122 W 121 W 120 W 119 W 118 W 117 W

32 N 33 N 34 N 35 N 36 N 37 N 38 N

Monterey Bay

Morro Bay

Pt. Arguello

Pt. Dume

San Pedro

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Figure 11. Observed set locations of the set gillnet fishery during

1994.

Longitude

Latitude

123 W 122 W 121 W 120 W 119 W 118 W 117 W

32 N 33 N 34 N 35 N 36 N 37 N 38 N

Monterey Bay

Morro Bay

Pt. Arguello

Pt. Dume

San Pedro

Figure 12. Observed marine mammal entanglements in the set

gillnet fishery, 1990-1994.

258
Appendix 1. Fishery Descriptions

Longitude

Latitude

123 W 122 W 121 W 120 W 119 W 118 W 117 W

32 N 33 N 34 N 35 N 36 N 37 N 38 N

Monterey Bay

Morro Bay

Pt. Arguello

Pt. Dume

San Pedro

57 6

117 67 8

2

8

2

3

1

2

4 4

71

3

14

3

1

3 22 450 214

15 13 1 4 128

4 16 56 59 1

1 16

17 173 124 1

2 7

7 31 4

2

1 6 2 90

24

In addition, there was:

 1 days of effort between 35.8N and 37.2N,

 45 days of effort between 35.8N and 34.0N,

 8 days of effort between 33.4N and 32.3N,

 and 21 days of effort without location

Figure 13. Set gillnet fishery estimated days of fishing effort by

CDFG block for 1994.

Longitude

Latitude

123 W 122 W 121 W 120 W 119 W 118 W 117 W

32 N 33 N 34 N 35 N 36 N 37 N 38 N

Monterey Bay

Morro Bay

Pt. Arguello

Pt. Dume

San Pedro

74 93 14

35 4 30

13

1

11

1

5

12

18

1 1

9 1 161 601 108

38 2 2 89

3 4 29 83

6 9 1

65 163 148 8

49 14 23

1 1

27 5 260

9 10

In addition, there was:

 2 days of effort between 35.8N and 34.0N,

 4 days of effort between 34.0N and 33.4N,

 4 days of effort between 33.4N and 32.3N,

 and 5 days of effort without location

Figure 14. Set gillnet fishery estimated days of fishing effort by

CDFG block for 1995.

259
Appendix 1. Fishery Descriptions

Longitude

Latitude

123 W 122 W 121 W 120 W 119 W 118 W 117 W

32 N 33 N 34 N 35 N 36 N 37 N 38 N

Monterey Bay

Morro Bay

Pt. Arguello

Pt. Dume

San Pedro

42 22 104

142 61

43

1

1 1

38

15

2

2 9

18 7 113

105 576 157

10 36 5 7 121 1

2 5 50

1 117 39

1 39 288 258 4

2 1

1 3 5 273 5

2 13 196

26

In addition, there was:

 89 days of effort between 35.8N and 37.2N

 and 22 day of effort between 35.8N and 34.0N

 3 days of effort between 34.0N and 33.4N

 1 day of effort between 33.4N and 32.3N

 7 days of effort without location

Figure 16. Set gillnet fishery estimated days of fishing effort by

CDFG block for 1997.

Longitude

Latitude

123 W 122 W 121 W 120 W 119 W 118 W 117 W

32 N 33 N 34 N 35 N 36 N 37 N 38 N

Monterey Bay

Morro Bay

Pt. Arguello

Pt. Dume

San Pedro

24 47 32

121 28

1

3

1 2

12

7

6 4

12

3 13 131 579 138

6 36 4 1 8 1 103

3 1 70 51

31 3 52 21

90 77 201 24

3 5 215 4

1

1 1 31 214

4

In addition, there was:

 48 days of effort between 35.8N and 37.2N,

 3 days of effort between 35.8N and 34.0N,

 3 days of effort between 33.4N and 32.3N,

 and 3 days of effort without location

Figure 15. Set gillnet fishery estimated days of fishing effort by

CDFG block for 1996.

260
Appendix 1. Fishery Descriptions

Longitude

Latitude

123 W 122 W 121 W 120 W 119 W 118 W 117 W

32 N 33 N 34 N 35 N 36 N 37 N 38 N

Monterey Bay

Morro Bay

Pt. Arguello

Pt. Dume

San Pedro

14 63 26 16

21 14 7 178

5

54

1

5

1 4

10

2 1 3 9 4

5 276 220 172

12 68 21 34 2 251

1 2 2 8 20 192

47 132 1

3 93 242 314

1

3 2 60 1

5 2 157 2

2 27

In addition, there was:

 49 days of effort between 35.8N and 37.2N

 and 1 day of effort between 35.8N and 34.0N.

Figure 17. Set gillnet fishery estimated days of fishing effort by

CDFG block for 1998.

2.0% 10.0%

13.0% 15.0%

8.0%

0.0% 0.0%

0.0% 0.0%

0

1000

2000

3000

4000

5000

6000

7000

8000

1990 1991 1992 1993 1994 1995 1996 1997 1998

Year

Effort (days)

Estimated

Observed

Figure 19. Estimated and observed set-net fishery days of

effort. Percent coverage is indicated above bars.

4.0% 10.0%

17.0%

13.0%

18.0%

16.0%

12.0%

23.0%

18.0%

0

1000

2000

3000

4000

5000

6000

1990 1991 1992 1993 1994 1995 1996 1997 1998

Year

Effort (days)

Estimated

Observed

Figure 18. Estimated and observed drift-net fishery days of

effort. Percent coverage is indicated above bars.

261
Revised 12/15/2000

Appendix 2. Cetacean Survey Effort

This appendix presents a summary of survey effort from which cetacean sighting locations were taken and plotted in stock assessment

reports.

Figure 1. Transect lines completed during a 1991

aerial survey of California waters. (Forney et al. 1995)

Figure 2. Transect lines completed during a 1992

aerial survey of California waters (Forney et al. 1995).

262
Figure 3. Transect lines completed during a 1991

vessel survey of California waters (Barlow 1995).

Figure 4. Transect lines completed during a 1993

vessel survey of California waters (Mangels and

Gerrodette 1994)

Appendix 2. Cetacean Survey Effort

263
Figure 5. Transect lines completed during a 1996

vessel survey of California, Oregon, and Washington

waters (Barlow 1997; Von Saunder and Barlow

1999).

Figure 6. Transect lines surveyed during 1989-97 aerial surveys of

central and northern California (Forney et al. 1991; Forney 1995).

Appendix 2. Cetacean Survey Effort

264
Monterey Bay

Point

Conception

California

San Francisco

Pacific Ocean

Los

Angeles

San Diego

Figure 7. Coastline section (in bold) surveyed

during 1990-1999 aerial surveys in southern and

central California (Carretta et al. 1998).

 

Hawaii

Maui

Oahu

Kauai

Pacific Ocean

Figure 8. Transect lines completed during 1993 aerial surveys of

the main Hawaiian islands (Mobley et al. 1999).

Appendix 2. Cetacean Survey Effort

265
Hawaii

Kauai

Oahu

Maui

Pacific Ocean

Figure 9. Transect lines completed during 1995 aerial

surveys of the main Hawaiian Islands (Mobley et al. 1999).

Pacific Ocean

Figure 10. Transect lines completed during 1998 aerial

surveys of the main Hawaiian Islands (Mobley et al. 1999).

Appendix 2. Cetacean Survey Effort

266
267

Appendix 2. Cetacean survey effort

References

Barlow, J. 1995. The abundance of cetaceans in California waters. Part I: Ship surveys in summer and fall of

1991. Fish. Bull. 93:1-14.

Barlow, J. 1997. Preliminary estimates of cetacean abundance off California, Oregon, and Washington based on a

1996 ship survey and comparisons of passing and closing modes. Admin. Rep. LJ-97-11. Southwest

Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA 92038. 25 pp.

Carretta, J.V., K.A. Forney, and J.L. Laake. 1998. Abundance of southern California coastal bottlenose dolphins

estimated from tandem aerial surveys. Mar. Mamm. Sci. 14(4):655-675.

Forney, K.A., D. Hanan, and J. Barlow. 1991. Detecting trends in harbor porpoise abundance from aerial surveys

using analysis of covariance. Fish. Bull. 89:367-377.

Forney, K.A. 1995. A decline in the abundance of harbor porpoise, Phocoena phocoena, in nearshore waters off

California, 1986-93. Fish. Bull. 93(4):741-748.

Forney, K.A., J. Barlow, and J.V. Carretta. 1995. The abundance of cetaceans in California waters. Part II: Aerial

surveys in winter and spring of 1991 and 1992. Fish. Bull. 93(4):15-26.

Mobley, J.R., R.A. Grotefendt, P.H. Forestell, and A. Frankel. 1999. Results of aerial surveys of marine mammals

in the major Hawaiian Islands (1993-98): Report to the Acoustic Thermometry of Ocean Climate Marine

Mammal Research Program (ATOC MMRP). University of Hawaii-West Oahu 96-129 Ala Ike, Pearl

City, HI 96782. 39 pp.

Mangels, K.F. and T. Gerrodette. 1994. Report of cetacean sightings during a marine mammal survey in the

eastern Pacific Ocean and the Gulf of California aboard the NOAA ships McArthur and David Starr

Jordan July 28 - November 6, 1993. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-SWFSC-221. 88

pp.

Von Saunder, A. and J. Barlow. 1999. A report of the Oregon, California, and Washington line-transect

experiment (ORCAWALE) conducted in west coast waters during summer/fall 1996. U.S. Dep. Commer.,

NOAA Tech. Memo. NMFS-SWFSC-264. 49 pp.

 
APPENDIX 3 (revised 12/31/2001) 

Stocks for which new assessment reports were written in 2001 are indicated by bold font.

SUMMARY OF 2001 PACIFIC MARINE MAMMAL STOCK ASSESSMENT REPORTS

(FOR STOCKS UNDER NMFS JURISDICTION)

268

Species Stock Area Region

NMFS

Center Nmin Rmax Fr PBR

Total

Annual

Mortality

+ Serious

Injury

Annual

Fish.

Mortality

+ Serious

Injury

Strategic

Status

California sea

lion

U.S. PAC SWC 109,854 0.12 1.0 6,591 1,352 1,208 N

Harbor Seal California PAC SWC 27,962 0.12 1.0 1,678 ≥ 714 666 N

Harbor Seal Oregon/

Washington

Coast

PAC AKC 24,705 0.12 1.0 1,482 ≥ 18 ≥ 16 N

Harbor Seal Washington

Inland Waters

PAC AKC 15,174 0.12 1.0 910 ≥ 43 ≥ 38 N

Northern

Elephant Seal

California

breeding

PAC SWC 51,625 0.083 1.0 2,142 ≥ 33 ≥ 33 N

Guadalupe Fur

Seal

Mexico to

California

PAC SWC 3,028 0.137 0.5 104 0.0 0.0 Y

Northern Fur

Seal

San Miguel

Island

PAC AKC 2,336 0.086 1.0 100 0.0 0.0 N

Monk seal Hawaii PAC SWC 1,436 0.07 0.1 5.0 n/a n/a Y

Harbor

porpoise

Central

California

PAC SWC 5,563 0.04 0.5 56 80 80 Y

Harbor

porpoise

Northern

California

PAC SWC 11,054 0.04 1.0 221 ≥ 0.2 ≥ 0.2 N

Harbor porpoise Oregon/

Washington

Coast

PAC AKC 32,769 0.04 0.5 328 12 12 N

Harbor porpoise Washington

Inland Waters 

PAC AKC 2,545 0.04 0.4 20 15 15 N

Dall’s Porpoise California/

Oregon/

Washington

PAC SWC 81,866 0.04 0.45 737 12 12 N

Pacific Whitesided DolphinCalifornia/

Oregon/

Washington

PAC SWC 17,475 0.04 0.45 157 ≥ 6.8 ≥ 6.8 N

Risso’s Dolphin California/

Oregon/

Washington

PAC SWC 13,079 0.04 0.4 105 5.5 5.5 N
APPENDIX 3 (revised 12/31/2001) 

Stocks for which new assessment reports were written in 2001 are indicated by bold font.

SUMMARY OF 2001 PACIFIC MARINE MAMMAL STOCK ASSESSMENT REPORTS

(FOR STOCKS UNDER NMFS JURISDICTION)

Species Stock Area Region

NMFS

Center Nmin Rmax Fr PBR

Total

Annual

Mortality

+ Serious

Injury

Annual

Fish.

Mortality

+ Serious

Injury

Strategic

Status

269

Bottlenose

Dolphin

California

coastal

PAC SWC 186 0.04 0.5 1.9 0 0 N

Bottlenose

Dolphin

California/

Oregon/

Washington

Offshore

PAC SWC 850 0.04 0.5 8.5 0 0 N

Striped Dolphin California/

Oregon/

Washington

PAC SWC 17,995 0.04 0.5 180 0 0 N

Common

dolphin,

 short-beaked

California/

Oregon/

Washington

PAC SWC 318,795 0.04 0.5 3,188 79 79 N

Common

dolphin,

 long-beaked

California PAC SWC 27,739 0.04 0.45 250 14 14 N

Northern rightwhale dolphinCalifornia/

Oregon/

Washington

PAC SWC 10,060 0.04 0.48 97 15 15 N

Killer whale Eastern North

Pacific

Transient

PAC AKC 376 0.04 0.45 3.4 2.6 2.4 N

Killer whale Eastern North

Pacific

Offshore

PAC SWC 209 0.04 0.5 2.1 0 0 N

Killer whale Eastern North

Pacific

Southern

Resident

PAC AKC 82 0.04 0.5 0.8 0 0 N

Short-finned 

pilot whale

California/

Oregon/

Washington

PAC SWC 717 0.04 0.4 5.7 3.0 3.0 N

Baird’s Beaked

Whale

California/

Oregon/

Washington

PAC SWC 313 0.04 0.5 2.0 0 0 N

Mesoplodont

Beaked Whales

California/

Oregon/

Washington

PAC SWC 2,734 0.04 0.5 27 0 0 N
APPENDIX 3 (revised 12/31/2001) 

Stocks for which new assessment reports were written in 2001 are indicated by bold font.

SUMMARY OF 2001 PACIFIC MARINE MAMMAL STOCK ASSESSMENT REPORTS

(FOR STOCKS UNDER NMFS JURISDICTION)

Species Stock Area Region

NMFS

Center Nmin Rmax Fr PBR

Total

Annual

Mortality

+ Serious

Injury

Annual

Fish.

Mortality

+ Serious

Injury

Strategic

Status

270

Cuvier’s Beaked

Whale

California/

Oregon/

Washington

PAC SWC 4,309 0.04 0.5 43 0 0 N

Pygmy Sperm

Whale

California/

Oregon/

Washington

PAC SWC 2,837 0.04 0.5 28 0 0 N

Sperm whale California/

Oregon/

Washington

PAC SWC 1,026 0.04 0.1 2.1 2.5 2.5 Y

Humpback

whale

Eastern North

Pacific

PAC SWC 944 0.08 0.1 1.9 1.4 1.2 Y

Blue whale Eastern North

Pacific

PAC SWC 1,716 0.04 0.1 1.7 0.0 0 Y

Fin whale California/

Oregon/

Washington

PAC SWC 1,581 0.04 0.1 3.2 0.4 0 Y

Bryde’s whale California/

Oregon/

Washington

PAC SWC 11,163 0.04 0.5 n/a 0 0 N

Sei whale California/

Oregon/

Washington

PAC SWC n/a 0.04 0.1 n/a 0 0 Y

Minke whale California/

Oregon/

Washington

PAC SWC 440 0.04 0.45 4.0 0 0 N

Rough-Toothed

Dolphin

Hawaii PAC SWC 76 0.04 0.5 0.8 n/a n/a N

Risso’s

Dolphin

Hawaii PAC SWC n/a 0.04 0.5 n/a n/a n/a N

Bottlenose

Dolphin

Hawaii PAC SWC 479 0.04 0.5 4.8 n/a n/a N

Pantropical

spotted dolphin

Hawaii PAC SWC 2,040 0.04 0.5 20 n/a n/a N

Spinner dolphin Hawaii PAC SWC 2,355 0.04 0.5 24 n/a n/a N

Striped dolphin Hawaii PAC SWC 52 0.04 0.5 0.5 n/a n/a N
APPENDIX 3 (revised 12/31/2001) 

Stocks for which new assessment reports were written in 2001 are indicated by bold font.

SUMMARY OF 2001 PACIFIC MARINE MAMMAL STOCK ASSESSMENT REPORTS

(FOR STOCKS UNDER NMFS JURISDICTION)

Species Stock Area Region

NMFS

Center Nmin Rmax Fr PBR

Total

Annual

Mortality

+ Serious

Injury

Annual

Fish.

Mortality

+ Serious

Injury

Strategic

Status

271

Melon-headed

whale

Hawaii PAC SWC 81 0.04 0.5 0.8 n/a n/a N

Pygmy killer

whale

Hawaii PAC SWC n/a 0.04 0.5 n/a n/a n/a N

False killer

whale

Hawaii PAC SWC 83 0.04 0.5 0.8 9.0 9.0 Y

Killer whale Hawaii PAC SWC n/a 0.04 0.5 n/a n/a n/a N

Pilot whale,

short-finned

Hawaii PAC SWC 1,313 0.04 0.5 13 n/a n/a N

Blainville’s

beaked whale

Hawaii PAC SWC 43 0.04 0.5 0.4 n/a n/a N

Cuvier’s

beaked whale

Hawaii PAC SWC 29 0.04 0.5 0.3 n/a n/a N

Pygmy sperm

whale

Hawaii PAC SWC n/a 0.04 0.5 n/a n/a n/a N

Dwarf sperm

whale

Hawaii PAC SWC n/a 0.04 0.5 n/a n/a n/a N

Sperm whale Hawaii PAC SWC 43 0.04 0.1 0.4 n/a n/a Y

Blue whale Hawaii PAC SWC n/a 0.04 0.1 n/a n/a n/a Y

Fin whale Hawaii PAC SWC n/a 0.04 0.1 n/a n/a n/a Y

Bryde’s whale Hawaii PAC SWC n/a 0.04 0.5 n/a n/a n/a N

n/a indicates that data are not available.
APPENDIX 4 (revised 12/31/2001)

CHRONOLOGY OF U.S. PACIFIC MARINE MAMMAL STOCK ASSESSMENT REPORTS, 1995-2001.

Key: X = Revised with new information; R = Reprinted without revision, N = New stock, E = Eliminated stock,

Shading indicates that a stock was not defined for that year.

272

U.S. PACIFIC MARINE MAMMAL STOCK 1995 1996 199811999 2000 2001

PINNIPEDS

CALIFORNIA SEA LION (Zalophus californianus californianus): 

U.S. Stock

X X X R

HARBOR SEAL (Phoca vitulina richardsi): 

California Stock

X X X X

HARBOR SEAL (Phoca vitulina richardsi): 

Oregon & Washington Coastal Waters Stock

X X X X R

HARBOR SEAL (Phoca vitulina richardsi): 

Washington Inland Waters Stock

X X X X R

NORTHERN ELEPHANT SEAL (Mirounga angustirostris): 

California Breeding Stock

X X X R

GUADALUPE FUR SEAL (Arctocephalus townsendi) X R X R

NORTHERN FUR SEAL (Callorhinus ursinus): 

San Miguel Island Stock

X X X X R

HAWAIIAN MONK SEAL 

(Monachus schauinslandi)

X X X X X

CETACEANS - U. S. WEST COAST

HARBOR PORPOISE (Phocoena phocoena): 

Central California Stock

X X X X X

HARBOR PORPOISE (Phocoena phocoena): 

Northern California Stock

X X X X X

HARBOR PORPOISE (Phocoena phocoena): 

Oregon/Washington Coast Stock

X X X X X R

HARBOR PORPOISE (Phocoena phocoena): 

Washington Inland Waters Stock

X X X X X R

DALL'S PORPOISE (Phocoenoides dalli): 

California/Oregon/Washington Stock

X X X R

PACIFIC WHITE-SIDED DOLPHIN (Lagenorhynchus

obliquidens): California/ Oregon/Washington, Northern and

Southern Stocks

X X X R

RISSO'S DOLPHIN (Grampus griseus): 

California/Oregon/Washington Stock

X X X R

BOTTLENOSE DOLPHIN (Tursiops truncatus): 

California Coastal Stock

X X X X

BOTTLENOSE DOLPHIN (Tursiops truncatus): 

California/Oregon/Washington Offshore Stock

X X X R
APPENDIX 4 (revised 12/31/2001)

CHRONOLOGY OF U.S. PACIFIC MARINE MAMMAL STOCK ASSESSMENT REPORTS, 1995-2001.

Key: X = Revised with new information; R = Reprinted without revision, N = New stock, E = Eliminated stock,

Shading indicates that a stock was not defined for that year.

U.S. PACIFIC MARINE MAMMAL STOCK 1995 1996 199811999 2000 2001

273

STRIPED DOLPHIN (Stenella coeruleoalba): 

California/Oregon/Washington Stock

X X X R

SHORT-BEAKED COMMON DOLPHIN (Delphinus delphis):

California/Oregon/Washington Stock

X X X R

LONG-BEAKED COMMON DOLPHIN (Delphinus capensis): 

California Stock

X X X R

NORTHERN RIGHT-WHALE DOLPHIN (Lissodelphis borealis):

California/Oregon/Washington Stock

X X X R

KILLER WHALE (Orcinus orca): 

California/Oregon/Washington Pacific Coast Stock

X X E E E

KILLER WHALE (Orcinus orca): 

Eastern North Pacific Southern Resident Stock

X X X X X

KILLER WHALE (Orcinus orca): 

Eastern North Pacific Transient Stock

(INCLUDED IN ALASKA

REPORTS)

X X R

KILLER WHALE (Orcinus orca): 

Eastern North Pacific Offshore Stock

N X R

SHORT-FINNED PILOT WHALE (Globicephala macrorhynchus):

California/Oregon/Washington Stock

X X X X R

BAIRD'S BEAKED WHALE (Berardius bairdii): 

California/Oregon/Washington Stock

X X X R

MESOPLODONT BEAKED WHALES (Mesoplodon spp.): 

California/Oregon/Washington Stocks

X X X X R

CUVIER'S BEAKED WHALE (Ziphius cavirostris): 

California/Oregon/Washington Stock

X X X R

PYGMY SPERM WHALE (Kogia breviceps): 

California/Oregon/Washington Stock

X X X R

DWARF SPERM WHALE (Kogia sima): 

California/Oregon/Washington Stock

X X E E

SPERM WHALE (Physeter macrocephalus): 

California/Oregon/Washington Stock

X X X X X

HUMPBACK WHALE (Megaptera novaeangliae): 

Eastern North Pacific Stock

X X X X X

BLUE WHALE (Balaenoptera musculus): 

Eastern North Pacific Stock

X X X R

FIN WHALE (Balaenoptera physalus): 

California/Oregon/Washington Stock

X X X X

BRYDE'S WHALE (Balaenoptera edeni): 

Eastern Tropical Pacific Stock

X X X R
APPENDIX 4 (revised 12/31/2001)

CHRONOLOGY OF U.S. PACIFIC MARINE MAMMAL STOCK ASSESSMENT REPORTS, 1995-2001.

Key: X = Revised with new information; R = Reprinted without revision, N = New stock, E = Eliminated stock,

Shading indicates that a stock was not defined for that year.

U.S. PACIFIC MARINE MAMMAL STOCK 1995 1996 199811999 2000 2001

274

SEI WHALE (Balaenoptera borealis): 

Eastern North Pacific Stock

X X X R

MINKE WHALE (Balaenoptera acutorostrata): 

California/Oregon/Washington Stock

X X X X R

CETACEANS - HAWAII

ROUGH-TOOTHED DOLPHIN (Steno bredanensis): 

Hawaiian Stock

X R X R

RISSO'S DOLPHIN (Grampus griseus): 

Hawaiian Stock

X R X R

BOTTLENOSE DOLPHIN (Tursiops truncatus): 

Hawaiian Stock

X R X R

PANTROPICAL SPOTTED DOLPHIN (Stenella attenuata): 

Hawaiian Stock

X R X R

SPINNER DOLPHIN (Stenella longirostris): 

Hawaiian Stock

X R X R

STRIPED DOLPHIN (Stenella coeruleoalba): 

Hawaiian Stock

X R X R

MELON-HEADED WHALE (Peponocephala electra): 

Hawaiian Stock

X R X R

PYGMY KILLER WHALE (Feresa attenuata): 

Hawaiian Stock

X R X R

FALSE KILLER WHALE (Pseudorca crassidens): 

Hawaiian Stock

X R X X

KILLER WHALE (Orcinus orca): 

Hawaiian Stock

X R X R

SHORT-FINNED PILOT WHALE (Globicephala macrorhynchus): 

Hawaiian Stock

X R X R

BLAINVILLE'S BEAKED WHALE (Mesoplodon densirostris): 

Hawaiian Stock

X R X R

CUVIER'S BEAKED WHALE (Ziphius cavirostris): 

Hawaiian Stock

X R X R

PYGMY SPERM WHALE (Kogia breviceps): 

Hawaiian Stock

X R X R

DWARF SPERM WHALE (Kogia sima): 

Hawaiian Stock

X R X R

SPERM WHALE (Physeter macrocephalus): 

Hawaiian Stock

X R X R
APPENDIX 4 (revised 12/31/2001)

CHRONOLOGY OF U.S. PACIFIC MARINE MAMMAL STOCK ASSESSMENT REPORTS, 1995-2001.

Key: X = Revised with new information; R = Reprinted without revision, N = New stock, E = Eliminated stock,

Shading indicates that a stock was not defined for that year.

U.S. PACIFIC MARINE MAMMAL STOCK 1995 1996 199811999 2000 2001

275

BLUE WHALE (Balaenoptera musculus): 

Hawaiian Stock

X R X R

FIN WHALE (Balaenoptera physalus): 

Hawaiian Stock

X R X R

BRYDE'S WHALE (Balaenoptera edeni): 

Hawaiian Stock

X R X R

APPENDIX TITLES APPENDIX NUMBERS

Summary of Pacific Stock Assessment Reports 1 3 1 2 3 3

Description of U.S. Commercial Fisheries 1 1 1

Cetacean Survey Effort 2 2 2

Review of New Information for Pacific Marine Mammal Stocks 2

Chronology of U. S. Pacific Stock Assessment Reports 1 4 4

U.S. Fish and Wildlife Service California & Washington sea otter

stock assessments

5 5

1The public comment, review and revision process has necessitated about a one year time lag between the draft revision and final publication of

Marine Mammal Stock Assessment Reports. Therefore, in 1997, the Stock Assessment Report dates were changed to ‘1998' to match the 1998

publication year of the report.
Appendix 5. The following stock assessment reports were prepared by the U.S.Fish and

Wildlife Service. NMFS includes these reports in this Technical Memorandum as a

convenience to interested readers and in response to a recommendation from regional

Scientific Review Groups.

Revised 10/4/1995

SOUTHERN SEA OTTER (Enhydra lutris nereis):

California Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

Southern sea otters breed and give birth in California year round, however the seasonality is not highly

synchronous and the birth peak may extend over several months (Siniff and Ralls 1991, Riedman et al. 1994). The

population ranges along the mainland coast from Pt. Ano Nuevo, Santa Cruz County south to Purisima Point, Santa

Barbara County; an experimental population currently exists at San Nicolas Island, Ventura County. The initial

translocation of sea otters to San Nicolas Island occurred in August 1987.

The population of southern sea otters historically ranged from northern California or Oregon to approximately

Punta Abreojos, Baja California (Wilson el al. 1991). Harvest of sea otters during the 1700's and 1800's reduced the

species throughout its range. In 1914, the total California population was estimated to be about 50 animals (California

Department of Fish and Game 1976). The estimated carrying capacity in California ranges between 13,500 and 30,000

sea otters (Marzin and DeMaster, In prep.).

POPULATION SIZE

Data on population size and distribution of the southern sea otter have been gathered for more than 50 years.

In 1982, a standardized survey technique was adopted to eliminate variation from future counts (Estes and Jameson

1988). This method involves shore-based censuses of approximately 80 percent of the population, supplemented with

aerial surveys of the remaining 20 percent. These surveys are conducted twice each year (in spring and fall). The San

Nicolas Island experimental population is surveyed approximately every two months.

Minimum Population Estimate

Based on the 1994 spring survey (actual count), the minimum southern sea otter population size of the mainland

population is 2,359 individuals. Based on the most recent survey of the San Nicolas Island experimental population,

the minimum sea otter population size is 17 individuals. Counts of sea otters at San Nicolas Island during 1994 and

1995 have ranged between 10 and 17 individuals.

Current Population Trend

Based on annual spring count totals since 1983, the southern sea otter population is continuing to increase.

The mean growth rate from 1983 through 1994 is 5.7 percent (R. Jameson, National Biological Service, pers. comm.,

Estes et al., In press) (The 1994 count represented a 5.4 percent increase over 1993). Recent counts of the San Nicolas

Island experimental population indicate a slight increase in the population; available information is inadequate to

determine trends at this time.

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

The maximum growth rate (rmax) for sea otter populations is about 20 percent (Estes 1990). Except for

California and Washington, all increasing sea otter populations for which data are available have grown at about this

rate. Since the early 1900's, the California sea otter population increased at about 4 to 5 percent a year until the mid1970's. Available information suggests that between 1976 and 1982 population growth ceased and possibly declined

by as much as 20 percent. Counts from 1983 to 1994 have increased at about 5 to 6 percent per year (Estes et al., In

press). In California, the rmax appears to be 6 percent.

276
Appendix 5.

277

ANNUAL HUMAN-CAUSED MORTALITY

Incidental drowning of sea otters in gill and trammel entangling nets has been a significant source of mortality

(Wendell et al. 1985). Mortality assessments for southern sea otters in California's commercial fisheries have been

based on direct observations. Monitoring of commercial fisheries was initiated in 1982. Extrapolations from the

number of otters observed drowned and the proportion of the set-net fishery sampled indicated that from June 1982 to

June 1984, an average of 80 sea otters drowned in gill and trammel nets each year (Wendell et al. 1985). The first of

several State restrictions of gill and trammel net fishing to protect sea otters was enacted in 1985. The most recent

restriction, California Senate Bill No. 2563, was enacted in 1990 and became effective on January 1, 1991. This bill

prohibits the use of gill and trammel nets in waters shallower than 30 fathoms between Waddell Creek in Santa Cruz

County and Point Sal in Santa Barbara County. Gill and trammel net fishing are prohibited within 30 fathoms around

San Nicolas Island, Ventura County.

Since 1988, 26 otters have been observed or otherwise known to have drowned in legally set commercial

fishing nets: 5 in 1988, 11 in 1989, 9 in 1990, and 0 in 1991 and 1992, 1 in 1993, and 0 in 1994. The net responsible

for the 1993 mortality is of unknown origin. It may have been legally or illegally set, or a piece of netting set adrift in

which the otter became entangled. In 1992, a dead sea otter was recovered by a California Department of Fish and

Game warden in a crab pot located in 30 to 60 feet of water off Point Santa Cruz, Santa Cruz County. The level of take

of southern sea otters in lobster and crab fisheries in California is unknown. Although the level of take is unknown,

it has been postulated by some to have made a significant contribution to the lack of population growth in the colony

of sea otters translocated to San Nicolas Island.

Other sources of human-caused mortality include shooting, boat strikes, capture and relocation efforts, oil spills

and possibly elevated levels of polychlorinated biphenyls (PCBs) and other toxic contaminants. 

FISHERIES INFORMATION

Fishing with set gillnets has been restricted throughout most of the range of the southern sea otter with one

exception. Set gillnets are used by approximately 6 vessels (T. Price, National Marine Fisheries Service, pers. comm.)

to catch halibut and flounder, along the coastline from Point Sal to Point Arguello, Santa Barbara County. Because this

area is remote and difficult to access, this fishery is not monitored and no data exists on the level of take of southern

sea otters. 

Lobster and crab fishing occur within the range of the southern sea otter. Available information suggests that

sea otters are accidentally caught and drowned in lobster and crab traps. 

As part of the southern sea otter recovery effort, the Fish and Wildlife Service has attempted to establish a sea

otter colony at San Nicolas Island. Public Law 99-625, which provided the legislative authority for the translocation

of sea otters from the mainland to San Nicolas Island, specified that the area surrounding the translocation zone be

designated a "management zone" from which sea otters are to be excluded by non-lethal means to prohibit range

expansion and protect fishery resources south of Point Conception.

STATUS OF STOCK

The southern sea otter was designated as a threatened species in 1977 (42 FR 2965-2968) pursuant to the

Endangered Species Act of 1973, as amended (16 U.S.C. 1531 et seq.). Because of its threatened status, the southern

sea otter also is designated as depleted under the Marine Mammal Protection Act of 1972, as amended (16 U.S.C. 1361

et seq.). Furthermore, the southern sea otter population is below its Optimum Sustainable Population level. 

If the restrictions on the use of gill and trammel nets in areas inhabited by southern sea otters were lifted, the

southern sea otter population would be designated as a "strategic stock" as defined by the Marine Mammal Protection

Act, requiring constitution of a Take Reduction Team to advise on measures that could and should be taken to ensure

that the incidental take of sea otters, by itself and in combination with other possible sources of non-natural mortality,

does not exceed the calculated potential biological removal level.

POTENTIAL BIOLOGICAL REMOVAL

The Potential Biological Removal (PBR) for the California stock is 7 animals. PBR is the product of three
Appendix 5.

278

elements: the minimum population estimate (Nmin); half the maximum net productivity rate (0.5 Rmax); and a recovery

factor (Fr). For the California sea otter stock, Nmin=2,376; Rmax= 6 percent; and Fr=0.1.

 Calculating a PBR for the southern sea otter serves no practical purpose. Incidental take of the southern sea

otter is not governed under section 118 of the Marine Mammal Protection Act.

REFERENCES

California Department of Fish and Game. 1976. A proposal for sea otter protection and research, and request for return

of management to the State of California, January 1976. 2 Vols. Unpubl. rep.

Estes, J. A. 1990. Growth and equilibrium in sea otter populations. J. Anim. Ecol. 59:358-401.

Estes, J. A. and R. J. Jameson. 1988. A double-survey estimate for sighting probability of sea otters in California. J.

Wildl. Manage. 52:70-76.

Estes, J. A., R. J. Jameson, J. L. Bodkin, and D. R. Carlson. (In Press) California sea otters. Our Living Resources

1995 - Mammals. National Biological Service.

Marzin, C. G. and D. P. DeMaster. (In prep.) Estimating the carrying capacity of sea otters (Enhydra lutris) along the

California coast. 

Riedman M. L, J. A. Estes, M. M. Staedler, A. A. Giles, and D. R. Carlson. 1994. Breeding patterns and reproductive

success of California sea otters. J. Wildl. Manage. 58:391-399.

Siniff, D. B., and K. Ralls. 1991. Reproduction, survival and tag loss in California sea otters. Marine Mammal Science

7(3):211-229.

Wendell, F. E., R. A. Hardy, and J. A. Ames. 1985. Assessment of the accidental take of sea otters, Enhydra lutris,

in gill and trammel nets. Mar. Res. Branch, Calif. Dep. Fish Game. Unpubl. rep. 30 pp.

Wilson, D. E., M. A. Bogan, R. L. Brownell, Jr., A. M. Burdin, and M. K. Maminov. 1991. Geographic variation in

sea otters, Enhydra lutris. J. Mammal. 72(1):22-36.
Appendix 5.

279

Revised 10/4/1995

 SEA OTTER (Enhydra lutris kenyoni):

Washington Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

Sea otters breed and give birth year-round (Riedman and Estes 1990). The peak pupping period for the

Washington population is not defined; however, breeding and pupping seasons peak about 2-3 months later in

Alaska than in California. The Washington population ranges from Neah Bay south to Destruction Island.

Enhydra lutris kenyoni historically ranged throughout the Aleutian Islands, originally as far north as the

Pribilof Islands and in the eastern Pacific Ocean from the Alaskan Peninsula south along the coast to Oregon

(Wilson el al. 1991). This subspecies was extirpated from most of its range during the 1700's and 1800's as the

species was exploited for its fur. In 1969 and 1970, a total of 59 sea otters captured at Amchitka Island, Alaska

were released in Washington (Jameson et al. 1982). The estimated carrying capacity in Washington has not been

determined.

For management purposes pursuant to the Marine Mammal Protection Act of 1972, the range of this stock

currently is being considered as within the boarders of the state of Washington.

POPULATION SIZE

The reintroduced population was not surveyed between 1970 and 1977. In 1977, the U.S. Fish and

Wildlife Service surveyed the coast and counted only 19 sea otters. The population was surveyed again in 1978. 

Between 1981 and 1989 the population was surveyed every other year. Since 1989, data on size and distribution of

the Washington sea otter population have been gathered annually using combined aerial and ground counts. 

Minimum Population Estimate

Based on the 1994 spring survey (actual count), the minimum population size is 360. Survey conditions

during 1994 were less than optimal and the Service believes that the population is probably slightly larger than this

count. 

Current Population Trend

Based on count totals from 1977 to the present, the Washington sea otter population is continuing to

increase. Since 1989 (when the current survey method was initiated) through 1994, the population has grown at an

average rate of 12 percent per year (R. Jameson, National Biological Service, pers. comm.).

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

 The maximum growth rate (rmax) for sea otter populations is about 20 percent. Except for California and

Washington sea otter populations, all increasing populations for which data are available have grown at about this

rate (Estes 1990). In Washington, the rmax appears to be 12 percent. 

ANNUAL HUMAN-CAUSED MORTALITY

Incidental drowning of sea otters in gill and trammel entangling nets has been a significant source of

mortality for southern sea otters (Wendell et al. 1985). In 1992, a dead sea otter was recovered by a California

Department of Fish and Game warden in a crab pot located in 30 to 60 feet of water off Point Santa Cruz. The level

of take of southern sea otters in lobster and crab fisheries in California is unknown. Reports from Alaska further

substantiate the incidental take of sea otters in traps fisheries.
Appendix 5.

280

Sea otters are susceptible to drowning in gill nets in Washington's coastal gill net fisheries, but documented

incidental takes are rare. In Washington, one sea otter was killed in a tribal chinook salmon set-net in the vicinity of

the mouth of the Ozette River on the north Washington coast. However, as the sea otter population expands,

mortality in crab pot and tribal set-net fisheries may increase.

Other sources of human-caused mortality affecting the Washington population of sea otters are not well

documented. Documented sources of human-caused mortality for the southern sea otter include shooting, boat

strikes, capture and relocation efforts, oil spills and possibly elevated levels of polychlorinated biphenyls (PCBs)

and other toxic contaminants. In Washington , an uncertain number of sea otters may have been killed in recent

years by small oil spills. 

Native Americans of the Pacific northwest have Tribal Rights to wildlife resources. These resources are

claimed by the tribes to include sea otters. Currently there is no harvest of sea otters by the Native Americans;

however, there is an interest to develop such a program.

FISHERIES INFORMATION

At present, there has been only one recorded otter-fishery interaction in Washington. Set gill nets are used

by Native Americans to catch salmon along the north coast of Washington and the Strait of Juan de Fuca. This

fishery operates out of Neah Bay. As the Washington sea otter population moves north, or if the fishery moves

south, the probability of fisheries-related incidental take will increase. 

As sea otters expand their range north or south, they will encounter several sport and commercial shellfish

fisheries (urchins, razor clams, Dungeness crabs) along the coast. Evidence from California and Alaska suggests

that incidental take of sea otter in crab traps may occur.

STATUS OF STOCK

The Washington sea otter has no formal Federal designation. It is legally designated as endangered by the

State of Washington (Washington Administrative Code 232-12-014). The Washington sea otter population is below

its Optimum Sustainable Population level. 

POTENTIAL BIOLOGICAL REMOVAL

The Potential Biological Removal (PBR) for the Washington stock is 11 animals. PBR is the product of

three elements: the minimum population estimate (Nmin); half the maximum net productivity rate (0.5 Rmax); and a

recovery factor (Fr). For the Washington sea otter stock, Nmin=360; Rmax=12 percent; and Fr=0.5.

REFERENCES

Estes, J. A. 1990. Growth and equilibrium in sea otter populations. J. Anim. Ecol. 59:358-401.

Jameson, R. J., K. W. Kenyon, A. M. Johnson, and H. M. Wight. 1982. History at status of translocated sea otter

populations in North America. Wildl. Soc. Bull. 10:100-107.

Riedman, M. L., and J. A. Estes. 1990. The sea otter (Enhydra lutris): behavior, ecology, and natural history. U.S.

Fish and Wildlife Service, Washington, D.C., Biological Report 90(14). 126 pp.

Wendell, F. E., R. A. Hardy, and J. A. Ames. 1985. Assessment of the accidental take of sea otters, Enhydra lutris,

in gill and trammel nets. Mar. Res. Branch, Calif. Dep. Fish Game. Unpubl. rep. 30 pp.

Wilson, D. E., M. A. Bogan, R. L. Brownell, Jr., A. M. Burdin, and M. K. Maminov. 1991. Geographic variation

in sea otters, Enhydra lutris. J. Mammal. 72(1):22-36.