NOAA Technical Memorandum NMFS This TM Series is used for documentation and timely communication of 

 preliminary results, interim reports, or special purpose information. The TMs 

have not received complete formal review, editorial control, or detailed editing.

 

 

 

 MAY 2005 

U.S. PACIFIC MARINE MAMMAL STOCK ASSESSMENTS: 2005 

James V. Carretta1

, Karin A. Forney1, Marcia M. Muto2, 

Jay Barlow1

, Jason Baker3, Brad Hanson2, and Mark S. Lowry1 

with contributions from 

Dale Sweetnam, Don Petersen, and Joe Cordaro 

1

Southwest Fisheries Science Center, NMFS/NOAA 

La Jolla Laboratory 

8604 La Jolla Shores Drive 

La Jolla, CA 92037-1508 

2

National Marine Mammal Laboratory, NMFS/NOAA 

7600 Sand Point Way, N.E. 

Seattle, WA 98115 

3

Pacific Islands Fisheries Science Center, NMFS/NOAA 

2570 Dole Street 

Honolulu, HI 96822 

NOAA-TM-NMFS-SWFSC-375 

U.S. Department of Commerce 

Carlos M. Gutierrez, Secretary 

National Oceanic and Atmospheric Administration 

VADM Conrad C. Lautenbacher, Jr., Undersecretary for Oceans and Atmosphere 

National Marine Fisheries Service 

William T. Hogarth, Assistant Administrator for Fisheries 
The National Oceanic and Atmospheric Administration (NOAA), organized in 1970, has evolved 

into an agency which establishes national policies and manages and conserves our oceanic, 

coastal, and atmospheric resources. An organizational element within NOAA, the Office of 

Fisheries is responsible for fisheries policy and the direction of the National Marine Fisheries 

Service (NMFS). 

In addition to its formal publications, the NMFS uses the NOAA Technical Memorandum series 

to issue informal scientific and technical publications when complete formal review and editorial 

processing are not appropriate or feasible. Documents within this series, however, reflect sound 

professional work and may be referenced in the formal scientific and technical literature. 
ii

TABLE OF CONTENTS

Stock assessment reports and appendices revised in 2004 are highlighted; all others are reprinted as they appear in 

the 2003 Pacific Region Stock Assessment Reports (Carretta et al. 2003). 

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 Coast Stock....................................................14 

HARBOR SEAL (Phoca vitulina richardsi): Washington Inland Waters Stock .......................................................21 

NORTHERN ELEPHANT SEAL (Mirounga angustirostris): California Breeding Stock........................................27

GUADALUPE FUR SEAL (Arctocephalus townsendi) .............................................................................................32 

NORTHERN FUR SEAL (Callorhinus ursinus): San Miguel Island Stock ...............................................................36 

HAWAIIAN MONK SEAL (Monachus schauinslandi).............................................................................................41 

CETACEANS - U.S. WEST COAST

HARBOR PORPOISE (Phocoena phocoena): Morro Bay Stock ...............................................................................49 

HARBOR PORPOISE (Phocoena phocoena): Monterey Bay Stock..........................................................................54 

HARBOR PORPOISE (Phocoena phocoena): San Francisco-Russian River Stock...................................................59

HARBOR PORPOISE (Phocoena phocoena): Northern California/Southern Oregon Stock.....................................64

HARBOR PORPOISE (Phocoena phocoena): Oregon/Washington Coast Stock .....................................................68 

HARBOR PORPOISE (Phocoena phocoena): Washington Inland Waters Stock .....................................................73

DALL'S PORPOISE (Phocoenoides dalli): California/Oregon/Washington Stock ...................................................80 

PACIFIC WHITE-SIDED DOLPHIN (Lagenorhynchus obliquidens): 

 California/Oregon/Washington, Northern and Southern Stocks ...................................................................85 

RISSO'S DOLPHIN (Grampus griseus): California/Oregon/Washington Stock .......................................................90 

BOTTLENOSE DOLPHIN (Tursiops truncatus): California Coastal Stock .............................................................94 

BOTTLENOSE DOLPHIN (Tursiops truncatus): California/Oregon/Washington Offshore Stock..........................98 

STRIPED DOLPHIN (Stenella coeruleoalba): California/Oregon/Washington Stock............................................102 

SHORT-BEAKED COMMON DOLPHIN (Delphinus delphis): California/Oregon/Washington Stock................106 

LONG-BEAKED COMMON DOLPHIN (Delphinus capensis): California Stock.................................................112 

NORTHERN RIGHT-WHALE DOLPHIN (Lissodelphis borealis): California/Oregon/Washington ....................117 

KILLER WHALE (Orcinus orca): Eastern North Pacific Offshore Stock ...............................................................122

KILLER WHALE (Orcinus orca): Eastern North Pacific Southern Resident Stock ................................................127

SHORT-FINNED PILOT WHALE (Globicephala macrorhynchus): California/Oregon/Washington ..................133 

BAIRD'S BEAKED WHALE (Berardius bairdii): California/Oregon/Washington Stock .....................................138 

MESOPLODONT BEAKED WHALES (Mesoplodon spp.): California/Oregon/Washington Stocks ....................142 

CUVIER'S BEAKED WHALE (Ziphius cavirostris): California/Oregon/Washington Stock.................................147 

PYGMY SPERM WHALE (Kogia breviceps): California/Oregon/Washington Stock ...........................................151 

DWARF SPERM WHALE (Kogia sima): California/Oregon/Washington Stock....................................................155 

SPERM WHALE (Physeter macrocephalus): California/Oregon/Washington Stock .............................................158

HUMPBACK WHALE (Megaptera novaeangliae): Eastern North Pacific Stock ...................................................164 

BLUE WHALE (Balaenoptera musculus): Eastern North Pacific Stock..................................................................171 

FIN WHALE (Balaenoptera physalus): California/Oregon/Washington Stock.......................................................176

BRYDE'S WHALE (Balaenoptera edeni): Eastern Tropical Pacific Stock.............................................................181

SEI WHALE (Balaenoptera borealis): Eastern North Pacific Stock .......................................................................185 

MINKE WHALE (Balaenoptera acutorostrata): California/Oregon/Washington Stock ........................................189 
iii

CETACEANS - HAWAII

ROUGH-TOOTHED DOLPHIN (Steno bredanensis): Hawaiian Stock ..................................................................194 

RISSO'S DOLPHIN (Grampus griseus): Hawaiian Stock ........................................................................................197 

BOTTLENOSE DOLPHIN (Tursiops truncatus): Hawaiian Stock ..........................................................................201 

PANTROPICAL SPOTTED DOLPHIN (Stenella attenuata): Hawaiian Stock .......................................................205 

SPINNER DOLPHIN (Stenella longirostris): Hawaiian Stock.................................................................................210 

STRIPED DOLPHIN (Stenella coeruleoalba): Hawaiian Stock...............................................................................214 

FRASER’S DOLPHIN (Lagenodelphis hosei): Hawaiian Stock (new stock)...........................................................217 

MELON-HEADED WHALE (Peponocephala electra): Hawaiian Stock ................................................................219 

PYGMY KILLER WHALE (Feresa attenuata): Hawaiian Stock ............................................................................222 

FALSE KILLER WHALE (Pseudorca crassidens): Hawaiian Stock.......................................................................225 

KILLER WHALE (Orcinus orca): Hawaiian Stock .................................................................................................230 

SHORT-FINNED PILOT WHALE (Globicephala macrorhynchus): Hawaiian Stock ...........................................233 

BLAINVILLE'S BEAKED WHALE (Mesoplodon densirostris): Hawaiian Stock.................................................238 

CUVIER'S BEAKED WHALE (Ziphius cavirostris): Hawaiian Stock....................................................................242 

LONGMAN’S BEAKED WHALE (Indopacetus pacificus): Hawaiian Stock (new stock) .....................................245 

PYGMY SPERM WHALE (Kogia breviceps): Hawaiian Stock ..............................................................................248 

DWARF SPERM WHALE (Kogia sima): Hawaiian Stock ......................................................................................251 

SPERM WHALE (Physeter macrocephalus): Hawaiian Stock.................................................................................254 

BLUE WHALE (Balaenoptera musculus): Western North Pacific Stock.................................................................259 

FIN WHALE (Balaenoptera physalus): Hawaiian Stock..........................................................................................263 

BRYDE'S WHALE (Balaenoptera edeni): Hawaiian Stock .....................................................................................266 

SEI WHALE (Balaenoptera borealis): Hawaiian Stock (new stock)........................................................................269 

MINKE WHALE (Balaenoptera acutorostrata): Hawaiian Stock (new stock)........................................................272 

APPENDICES

APPENDIX 1: Description of U.S. Commercial Fisheries .......................................................................................275 

APPENDIX 2: Cetacean Survey Effort.....................................................................................................................302 

APPENDIX 3: Summary of 2004 U.S. Pacific Marine Mammal Stock Assessment Reports...................................306 

APPENDIX 4: Chronology of U. S. Pacific Stock Assessment Reports, 1995-2003................................................310 

APPENDIX 5: U.S. Fish and Wildlife Service California & Washington sea otter stock assessments ....................312
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 30 Pacific marine 

mammal stocks under NMFS jurisdiction, including four new stocks from Hawaiian waters (Barlow 2003): Sei 

whale (Balaenoptera borealis), minke whale (Balaenoptera acutorostrata), Fraser’s dolphin (Lagenodelphis hosei), 

and Longman’s beaked whale (Indopacetus pacificus). Information on the remaining 31 Pacific region stocks is 

reprinted without revision in this report and also appears in the 2003 reports (Carretta et al. 2003). Stock 

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

separate report. 

 The 30 revised stock assessments in this report include stocks studied by the Southwest Fisheries Science 

Center (SWFSC, La Jolla, California), the Pacific Islands Fisheries Science Center (PIFSC, Honolulu, Hawaii), and 

the National Marine Mammal Laboratory (NMML, Seattle, Washington). New abundance estimates are available 

for 27 stock assessments prepared by the Southwest Fisheries Science Center. Staff of the Alaska Fisheries Science 

Center prepared the report on the Eastern North Pacific Southern Resident killer whale. Pacific Islands Fisheries 

Science Center staff prepared the report on the Hawaiian monk seal. Southwest Fisheries Science Center staff 

prepared stock assessments for the remaining 28 stocks. 

 New information on U.S. commercial fisheries that may interact with marine mammals is presented in 

Appendix 1. We thank Dale Sweetnam, California Department of Fish and Game, for providing an updated 

description of the market squid purse seine fishery. 

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

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

unpublished data, especially Robin Baird, who provided valuable information on Hawaiian cetaceans. We also 

thank The Marine Mammal Commission, The Center for Biological Diversity, and The Ocean Conservancy for their 

comments and suggestions. 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. Background information and 

guidelines for preparing stock assessment reports are reviewed in Wade and Angliss (1997). The authors solicit any 

new information or comments which would improve future stock assessment reports. 

Cover photograph: Killer whale in Prince William Sound, Alaska, 18 July 2004. Photographed by Cornelia 

Oedekoven during the SWFSC SPLASH cruise. 

References:

Barlow, J. 2003. Cetacean abundance in Hawaiian waters during summer/fall of 2002. Southwest Fisheries 

Science Center Administrative Report LJ-03-13. Available from U.S. National Marine Fisheries Service, 

Southwest Fisheries Science Center, 8604 La Jolla Shores Drive, La Jolla, CA 92037. 20p. 

Carretta, J.V., K.A. Forney, M.M. Muto, J. Barlow, J. Baker, and M. Lowry. 2003. U.S. Pacific Marine Mammal 

Stock Assessments: 2003. U.S. Department of Commerce, NOAA Technical Memorandum NMFSSWFSC-358. 291p. 

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. NOAA Technical Memorandum NMFS-OPR-12. 

Available from Office of Protected Resources, National Marine Fisheries Service, Silver Spring, MD. 93p. 
Revised 12/15/2003 

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. 

125 120 115 110 105 100

West Longitude

20

25

30

35

40

45

N orth Latitude

Pacific Ocean

Western Baja California Stock

United States 

 Stock

Gulf of California

 Stock

MEXICO

UNITED STATES

OREGON

CALIFORNIA

WASHINGTON

Figure 1. Geographic range of California 

sea lions showing stock boundaries and 

locations of major rookeries. The United 

States stock ranges north into Canadian

waters. 

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

pup count in 2001 (49,078) was adjusted for an estimated 15% pre-census mortality (Boveng 1988; Lowry et al.

1992), giving an estimated 56,440 live births in the population. The fraction of newborn pups in the population (

23.1% to 23.8%) 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 

(5.4% to 6.1% yr-1, respectively, see below). Multiplying the number of pups born by the inverse of these fractions

(4.32 to 4.20) results in population estimates ranging from 244,000 to 237,000 (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 2001 breeding season. The minimum population size of the U.S. 

stock is 138,881(NMFS unpubl. data). It includes all California sea lions counted during the July 2001 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.

1
Current Population Trend

Records of pup counts from 1975

to 2001 (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 2001 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 5.4% between 1975 and 2001. When pup counts for El Niño years (1983, 1992, 1993, 

and 1998) are removed from the 1975-2001 time series, the count of pups increased at an annual rate of 6.1%. 

10

15

20

25

30

35

40

45

50

PUP COUNT INDEX

Thousands

1975 1980 1985 1990 1995 2000 2005

YEAR

CALIFORNIA SEA LION PUPS

United States

COUNTS

COUNTS AND ESTIMATES

Figure 2. U.S. pup count index for California sea lions (1975-

2001).

The 1975-2001 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 three to five years). 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 1980-2001 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, 2,757, 1,905, 3,522, 2,039, 948, 834, 1,166, 1,558, 1,587, 

1,560, 1,672 and 1,373 for 1980 to 2001, 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).

Between 1980 and 2001 the net production rate averaged 15.1% (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, 1993, and 1998) and El Niño recovery years (1994 and 1999) are removed, the regression line shows a 

2
slight decrease (thick line) and net production averages 12.5%. 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 

(138,881) 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 8,333 sea lions 

per year. 

ANNUAL HUMAN-CAUSED MORTALITY

Historical Depletion 

Records of historic exploitation of California sea lions include harvest for food by native Californians in 

the Channel Islands 4,000-5,000 years ago (Stewart et al. 1993) and for oil and hides in the mid 1800s (Scammon 

1874). More recent exploitation of sea lions for pet food, target practice, bounty, trimmings, hides, reduction of 

fishery depredation, and sport are reviewed in Helling (1984), Cass (1985), Seagers et al. (1985), and Howorth 

(1993). Lowry et al. (1992) stated that there were few historical records to document the effects of such exploitation 

on sea lion abundance. 

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, 1997-2001 (Julian 1997; Cameron and Forney 

1999, 2000; Carretta 2001, 2002). 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 2003). 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. 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. Mortality estimates from the drift gillnet fishery are based on 1997-

2001 observer data (~20% observer coverage). Estimates of mortality for the halibut/angel shark set gillnet fishery 

in southern California are based on 1991-94 kill rates and current levels of fishing effort, except for the Monterey 

portion of the fishery, which was observed in 1999 and 2000 (Table 1). Mortalities from these and other fisheries 

result in an average estimate of 1,476 (CV = 0.03) California sea lions taken annually (Table 1). 

 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 and 

Oregon/Washington Marine Mammal Stranding Network databases maintained by the National Marine Fisheries 

Service contain records of human-related fishery mortalities of stranded California sea lions. These records show 

that at least five additional mortalities and nine injuries occurred in 2001 as a result of fishing net entanglement and 

two additional mortalities and six injuries from hook and line fisheries. 

 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 

3
fisheries. Previous efforts to convert the Mexican swordfish driftnet fishery to a longline fishery have resulted in a 

mixed fishery, with 20 vessels alternately using longlines or driftnets, 23 using driftnets only, 22 using longlines 

only, and seven with unknown gear type (Berdegué 2002). 

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

fisheries that might take this species ( Cameron and Forney 1999, 2000; Carretta 2001; 2002, M. Perez per. comm, 

Appendix 1). Mean annual takes are based on 1997-2001 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

1997 

1998 

1999 

2000

2001

observer 

23.0% 

20.0% 

20.0% 

22.9%

20.4%

36 

23 

6 

13

2

201(0.34) 

114 (0.23) 

30 (0.36) 

50 (0.43) 

9 (0.69)

81 (0.19)

CA set gillnet fishery for 

halibut and angel shark

1997 

1998 

1999 

2000

2001

extrapolated 

estimate 

0% 

0% 

4% 

1.8% 

0%

- 

- 

13 

28

0

1,206 (0.06)1

1,228 (0.07)1

1,360 (0.07)1

1,346 (0.07)1

1,194 (0.07)1

1,267 (0.03)1

WA, OR, CA domestic 

groundfish trawl fishery 

(At-sea processing Pacific 

whiting fishery only)

1997 

1998 

1999 

2000

2001

observer 

65.7% 

77.3% 

68.6% 

80.6%

96.2%

0 

1 

1 

0

0

0 

1 (0.48) 

3 (0.55) 

0 

0 

0.8 (0.43)

WA, OR salmon net pen 

fishery

1997 

1998 

1999 

2000

2001

MMAP 

n/a

9 

12 

n/a

9 

12 

n/a

11

Canada: BC salmon pen 

fishery

1997 

1998 

1999 

2000

2001

MMAP

52 

88 

134 

217

88

52 

88 

134 

217

88

116

Minimum total annual takes 1,476 (0.03)

1

 The California set gillnets were not observed after 1994; mortality was extrapolated from effort estimates and previous entanglement rates, 

except for Monterey Bay, where 20-25% of the fishery was observed in 1999 and 2000. Changes in the distribution of effort in this fishery add 

considerable uncertainty to these estimates and associated CVs are likely to be underestimated. 

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. Data from a marine mammal rehabilitation center showed that 87% of 87 rescued California sea lions 

were entangled in 4-4.5 inch square-mesh monofilament gillnet (Howorth 1994). 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; 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, Goldstein et al. 1999). A summary of records 

for 2001 from the California Marine Mammal Stranding Network (CMMSN) and the Oregon and Washington 

4
stranding databases shows the

following non-fishery related 

mortality: boat collision (three 

mortalities), entrainment in power 

plants (21 mortalities), and

shootings (54 mortalities and three

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, five 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 m

Several Pacific Northwest t

NET PRODUCTION = Population Growth + Human related mortalities

United States

2.0

1.5

1.0

0.5

0.0

-0.5

-1.0

80 82 84 86 88 90 92 94 96 98 00

YEAR

inimum number in 2001 was 78. 

reaty Indian tribes have promulgated tribal regulations allowing tribal

ember

ntral California coast have recently been linked to the algaloduce

TATUS OF STOCK

992) concluded that there was no evidence of a density dependent signal in counts of

aliforn

EFERENCES

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

Barlow, on. 2003. Field experiments show that acoustic pingers reduce marine mammal bycatch

Barocchi tions among live stranded 

Berdegu esca deportiva y especies en peligro de

Figure 3. Net production 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.

m s to exercise treaty rights for subsistence harvest of sea lions. Current estimates of annual take are zero to 

two animals per year. 

Sea lion mortalities in 1998 along the ce

pr d neurotoxin domoic acid (Scholin et al. 2000). Future mortalities may be expected to occur, due to the

periodic nature of such harmful algal blooms. 

S

Lowry et al. (1

C ia 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 (1,483 fishery-related mortalities plus 78 from other sources) is less than the PBR (8,333). 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 5.4% to 6.1% per year.

R

Barlow, J., R. W.

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. 

J. and G. A. Camer

in the California drift gillnet fishery. Marine Mammal Science 19(2):265-283. 

, M., L. E. Morgan, and K. D. Hanni. 1993. Frequency of fishery interac

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

Marine Mammals, Galveston TX, November 11-15, 1993. 

é, J. 2002. Depredación de las especies pelágicas reservadas a la p

extinción con uso indiscriminado de artes de pesca no selectivas (palangres, FAD's, trampas para peces y 

redes de agallar fijas y a la deriva) por la flota palangrera Mexicana. Fundación para la conservación de los 

picudos. A.C. Mazatlán, Sinaloa, 21 de septiembre. 

5
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 1998 

(unpublished). 14 pp. 

Cameron, G.A. and K.A. Forney. 2000. Preliminary estimates of cetacean mortality in California/Oregon Gillnet 

Fisheries for 1999. Report SC/52/O24 presented to the Scientific Committee of the International Whaling 

Commission, June 2000 (unpublished). 12p. [Available from Southwest Fisheries Science Center, National 

Marine Fisheries Service, 8604 La Jolla Shores Drive, La Jolla, CA 92037, USA.] 

Carretta, J.V. 2001. Preliminary estimates of cetacean mortality in California gillnet fisheries for 2000. Report 

SC/53/SM9 presented to the Scientific Committee of the International Whaling Commission, June 2001 

(unpublished). 21p. [Available from Southwest Fisheries Science Center, National Marine Fisheries 

Service, 8604 La Jolla Shores Drive, La Jolla, CA 92037, USA.]. 

Carretta, J.V. 2002. Preliminary estimates of cetacean mortality in California gillnet fisheries for 2001. Report 

SC/54/SM12 presented to the Scientific Committee of the International Whaling Commission, April 2002 

(unpublished). 22p. [Available from Southwest Fisheries Science Center, National Marine Fisheries 

Service, 8604 La Jolla Shores Drive, La Jolla, CA 92037, USA.]. 

Cass, V.L. 1985. Exploitation of California sea lions, Zalophus californianus, prior to 1972. Marine Fisheries 

Review 47:36-38. 

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. 

Goldstein, T., S. P. Johnson, A. V. Phillips, K. D. Hanni, D. A. Fauquier, and F. M. D. Gulland. 1999. Aquatic 

Mammals 25:43-51. 

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. 

Helling, H.E. 1984. A follow-up report on available data for California and Stellar sea lion (Zalophus 

californianus), Eumetopias jubata) exploitation prior to 1950. Administrative Report LJ-84-45C. National 

Marine Fisheries Service, Southwest Fisheries Center, La Jolla, CA 92037. 10pp. 

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. 

Howorth, P.C. 1993. Commercial collection of pinnipeds in the California Channel Islands, 1877-1981. In:

Hochberg, F. G. (editor), Third California Islands Symposium: Recent Advances in Research in the 

California Islands. Santa Barbara, CA, Santa Barbara Museum of Natural History. pp. 

Howorth, P. C. 1994. Entanglement of marine mammals in synthetic debris. In W. L. Halvorson and G. J. Maender 

(editors), The Fourth California Islands Symposium: Update on the status of resources, p. 111-121. 

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. 

6
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. 

Scammon, C.M. 1874. The marine mammals of the north-western coast of North America, described and 

illustrated: Together with an account of the American whale fishery. John H. Carmany and Company, San 

Francisco, CA. 319p. 

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. 

Seagers, D.J., D.P. DeMaster, and R.L. DeLong. 1985. A survey of historic rookery sites for California and 

northern sea lions in the Southern California Bight. Administrative Report LJ-85-13, National Marine 

Fisheries Service, Southwest Fisheries Center, 8604 La Jolla Shores Dr., La Jolla, CA. 

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. 

Stewart, B.S., P.K.Yochem, R.L. DeLong, and G.A. Antonelis. 1993. Trends in Abundance and Status of Pinnipeds 

on the Southern California Channel Islands. In: Hochberg, F. G. (editor), Third California Islands 

Symposium: Recent Advances in Research in the California Islands. Santa Barbara, CA, Santa Barbara 

Museum of Natural History. pp 501_516. 

7
Revised 12/15/2003 

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 three 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. An unknown number of harbor seals also occur along the west coast

of Baja California, at least as far south as Isla Asuncion, which is about 100 miles south of Punta Eugenia.

Animals along Baja California are not considered to be a part of the California stock because it is not 

known if there is any demographically significant movement of harbor seals between California and

Mexico and there is no international agreement for joint management of harbor seals. 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. 

W132 W129 W126 W123 W120 W117

N30

N34

N38

N42

N46

WASHINGTON

OREGON

CALIFORNIA

OR/WA

COASTAL

STOCK

 CA

STOCK

PACIFIC

 OCEAN

Figure 1. Stock boundaries for the California 

and Oregon/Washington coastal stocks of

harbor seals. Dashed line represents the U.S. 

EEZ.

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 (May 

8
to July)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 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-hour 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 (21,433 in May-July 2002; Lowry and 

Carretta 2003) and Hanan’s revised correction factor, the harbor seal population in California is estimated

to number 27,863. 

0

5000

10000

15000

20000

25000 Number Seals Counted

1955 1965 1975 1985 1995 2005

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; 

NMFS unpubl. data from 2002 survey).

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 

25,720. 

Current Population Trend

Counts of harbor seals in California showed a rapid increase from approximately 1972 (when the

MMPA was first passed) to 1990 (Fig. 2). Net production rates appeared to be decreasing from 1982 to

1994 (Fig. 3). Since 1990 there has been no net population growth along the mainland or on the Channel

Islands. Although earlier analyses were equivocal (Hanan 1996) and there has been no formal

determination that the California stock has reached OSP (Optimal Sustainable Population level as defined 

by the MMPA), the decrease in population growth rate has occurred at the same time as a decrease in 

human-caused mortality and may indicate that the population has reached its environmental carrying

capacity. Population growth has also slowed or stopped for the harbor seal stock on the outer coasts of

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 (when annual counts were 

available) by linear regression of the natural logarithm of total count versus year. The slope of this

regression line was 0.035 (SE = 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 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 

9
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 year i). 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. 

-0.2

-0.1

0

0.1

0.2

0.3

0.4

Net Production Rate

1982 1984 1986 1988 1990 1992 1994

Year

Harbor Seal Net Production in CA

POTENTIAL BIOLOGICAL 

REMOVAL

The potential biological removal

(PBR) level for this stock is calculated as 

the minimum population size (25,720)

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 or for a 

stock at OSP, Wade and Angliss 1997),

resulting in a PBR of 1,543. 

Figure 3. Net production rates and regression line 

estimated from haulout counts and fishery mortality.

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

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 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 (1997-

2001). Rough estimates for 1997-2001 have been made by extrapolation of prior kill rates using recent 

effort estimates and observations in the Monterey portion of the fishery from 1999 and 2000 (Table 1).

Observations from the Monterey Bay portion of the fishery included 57 and 24 harbor seals taken in 1999

and 2000, respectively. Stranding data reported to the California Marine Mammal Stranding Network in

1997-2000 include harbor seal deaths and injuries caused by hook-and-line fisheries (nine deaths, four

injuries) and gillnet fisheries (three deaths, three injuries). The locations and timing of harbor seal

strandings attributed to gillnet fisheries suggest that the halibut/angel shark or white seabass set gillnet

fishery are responsible for the interactions (see Appendix 1 for fishery descriptions). 

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 1997-2000: (1) boat collision (12 mortalities, two injuries), (2) entrainment in power plants (20 

mortalities), and (3) shootings (five mortalities), and (4) all-terrain vehicle (ATV) collision (one injury). 

10
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 estimated for recent years, but extrapolations from past years indicate that fishing mortality (433 

per year) is less than the calculated PBR for this stock (1,543), 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 

stabilizing at what may be their carrying capacity 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 three 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). 

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; Carretta 2001; 2002). n/a indicates that data are not available. 

Mean annual takes are based on 1997-2001 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

1997-

2001

observer 

data

20-23% 

0 0,0,0,0,0 01

CA angel shark/halibut 

and other species large 

mesh (>3.5") set gillnet 

fishery

1997 

1998 

1999 

2000 

2001

extrapolated 

estimate 

observer 

data 

extrapolated

0.0% 

0.0% 

4.0% 3

1.7%3

0.0%3

- 

- 

57 

24 

-

349 (0.08)1

392 (0.10)1

662 (0.10)1

415 (0.08)1

329 (0.09)1

429 (0.04)1

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

1997 

1998 

1999 

2000 

2001 

1997-

2001

observer data

unmonito ed r

hauls

65.7% 

77.3% 

68.6% 

80.6%

96.2%

0 

0 

0 

2 

0 

1

0 

0 

0 

3 (0.21) 

0 

1

0.6 (0.21) 

0.2 (n/a)

CA squid purse seine 

fishery

1997-

2001 logbook data

Warden obs 

2-3 

trips/month 0

Avg. Annual 

take = 0 n/a

11
Fishery Name Year(s) Data Type

Percent 

Observer 

Coverage

Observed 

Mortality

Estimated 

Mortality (CV in 

parentheses)

Mean 

Annual Takes 

(CV in parentheses)

(unknown net and hook 

fisheries)

1997-

2000 stranding data 12 3

Total annual takes 433 (0.04)

1

The CA set gillnets were not observed after 1994, except for Monterey Bay, where the fishery was observed in 1999 and 2000. 

Mortality in other regions was extrapolated from current (1997-2001) effort estimates and 1990-94 entanglement rates, thus the CV of 

the mortality estimate for this fishery is likely to be underestimated by an unknown amount. There was no observer coverage in this 

fishery in 2001.

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, 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. 

Carretta, J.V. 2001. Preliminary estimates of cetacean mortality in California gillnet fisheries for 2000. 

Report SC/53/SM9 presented to the Scientific Committee of the International Whaling 

Commission, June 2001 (unpublished). 21p. [Available from Southwest Fisheries Science Center, 

National Marine Fisheries Service, 8604 La Jolla Shores Dr., La Jolla, CA 92037, USA.] 

Carretta, J.V. 2002. Preliminary estimates of cetacean mortality in California gillnet fisheries for 2001. 

Report SC/54/SM12 presented to the Scientific Committee of the International Whaling 

Commission, April 2002 (unpublished). 22p. [Available from Southwest Fisheries Science 

Center, National Marine Fisheries Service, 8604 La Jolla Shores Dr., La Jolla, CA 92037, 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 

12
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. 

Lowry, M.S. and J.V. Carretta. 2003. Pacific harbor seal Phoca vitulina richardsi, census in California 

during May-July 2002. U.S. Department of Commerce, NOAA Technical Memorandum NMFSSWFSC-353, 47 pp. 

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 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. 

13
Revised 12/15/2003

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 haulout sites

(Pitcher and Calkins 1979, Pitcher and McAllister 1981). 

. 1996). This report considers only the 

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 three separate 

harbor seal stocks along the west coast of the continental U.S. 

(Boveng 1988): 1) inland waters of Washington State (including

Hood Canal, Puget Sound, and the 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

waters possess unique haplotypes not found in seals from the 

coasts of Washington, Oregon, and California (Lamont et al

Oregon/Washington Coast stock. Harbor seal stocks that occur in the inland and coastal waters of Alaska are

discussed separately in the Stock Assessment Reports for the Alaska Region. 

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. 

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 1999 pupping season. Total numbers of hauled-out seals (including pups) were counted 

during these surveys. In 1999, the mean count of harbor seals occurring along the Washington coast was 10,430

(CV=0.14) animals (Jeffries et al. 2003). In 1999, the mean count of harbor seals occurring along the Oregon coast 

and in the Columbia River was 5,735 (CV=0.14) animals (Brown 1997; ODFW, unpubl. data). Combining these 

counts results in 16,165 (CV=0.10) harbor seals in the Oregon/Washington Coast stock.

Radio-tagging studies conducted at six locations (three Washington inland waters sites and three Oregon

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

seals in 1992. Haulout 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 et al. 2001). Using this correction factor results in a population estimate of 24,732 (16,165 x

1.53; CV=0.12) for the Oregon/Washington Coast stock of harbor seals in 1999 (Jeffries et al. 2003; ODFW,

unpubl. data). 

14
Minimum Population Estimate

 The log-normal 20th percentile of the 1999 population estimate for this stock is 22,380 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 state-financed bounty programs. 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 bounty hunters and a state-hired seal hunter (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 passage of the Marine Mammal Protection Act (MMPA) in 1972, 

harbor seal counts for this stock have increased from 6,389 in 1977 to 16,165 in 1999 (Jeffries et al. 2003; 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). 

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

 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 by 1983, the 

observed rates of increase may underestimate the maximum net productivity rate (RMAX). When a logistic model 

was fit to the Washington portion of the 1975-1999 abundance data, the resulting estimate of RMAX was 18.5% (95% 

CI = 12.9-26.8%) (Jeffries et al. 2003). This value of RMAX is higher than the default pinniped population growth 

rate value of 12%; however, since it applies to only a portion of the stock, the actual rate for the entire stock is 

uncertain. Therefore, until additional data for the entire stock 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 (22,380) 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 1,343 harbor seals 

per year. 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Fisheries Information

 NMFS observers monitored the northern Washington marine set gillnet fishery in 1997, 1998, and 2000. 

There was no observer coverage in 1999 or 2001; the total fishing effort was four and 46 net days, respectively, in 

those years and occurred only in inland waters (Gearin et al. 1994, 2000; P. Gearin, unpubl. data). For the entire 

fishery (coastal + inland waters), observer coverage ranged from approximately 40 to 98% during observed years. 

Fishing effort is conducted within the range of both stocks of harbor seals (Oregon/Washington Coast and 

Washington Inland Waters stocks) occurring in Washington State waters. 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 Washington Inland 

Waters 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 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 et al. 2001). 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 1997 and 2000. No fishing effort occurred in the coastal 

portion of the fishery in 1998, 1999, or 2001. The mean estimated mortality for this fishery in 1997-2001 is 3.2 

(CV=0.79) harbor seals per year from this stock. 

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

during 1997-2001 (Perez 2003). The only harbor seal mortalities occurred in 1997 and 2000. The mortality in 1997 

occurred during an unmonitored haul and therefore was not used to estimate mortality for the entire fishery that year. 

15
However, observer coverage (based on observed tons) was 66% in 1997, observers monitored 100% of the vessels 

during the fishery, and the reported mortality is thought to be the only harbor seal mortality in the fishery that year. 

In 1997-2001, the mean estimated mortality in this fishery is 0.8 (CV=1.0) harbor seals per year (from monitored 

hauls), plus 0.2 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 1997-2001 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 in coastal waters: 

areas 4 and 4A)

97 

98 

99 

00

01

obs data

100% 

no fishery 

no fishery 

100% 

no fishery

13 

0 

0 

3

0

13 

0 

0 

3

0

3.2 (0.79)

WA/OR/CA groundfish trawl 

(Pacific whiting component) 

97 

98 

99 

00 

01 

97

obs data 

unmonitored 

hauls

65.7% 

77.3% 

68.6% 

80.6%

96.2%

0 

0 

0 

2 

0 

1

0 

0 

0 

4

0

0.8 (1.0) 

0.2 (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

WA Willapa Bay drift gillnet 90-93 self 

reports n/a 0, 0, 6, 8 n/a

≥3.5 (n/a)

see text

Unknown west coast fisheries 97-01 strand data n/a 0, 0, 1, 0, 0 ≥0.2 (n/a)

Minimum total annual takes ≥14.6 (0.4)

 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 Oregon Department of 

Fish and Wildlife (ODFW) conducted test fisheries in the lower Columbia River in 2000-2002 to evaluate the use of 

small-mesh (31⁄2"-6") tangle (tooth) nets in commercial, spring chinook fisheries to effectively harvest target stocks, 

while allowing the live release of non-target stocks and species (G. Whisler, pers. comm.). An experimental 

commercial permit fishery and a full-fleet commercial demonstration fishery were also conducted in 2001 and 2002, 

respectively, to test the small-mesh gear. Data on marine mammal interactions (predation, entanglement), recorded 

by observers during the permit and demonstration fisheries, have not yet been summarized; however, no marine 

mammal mortalities or serious injuries were reported to NMFS by vessel operators. The test fishery in the lower 

Columbia River is expected to continue in 2003. 

 The Washington Grays Harbor salmon drift gillnet fishery was also monitored in 1991-1993 (Herczeg et 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 one harbor seal mortality incidental to the 

fishery, resulting in an extrapolated estimated total kill of 10 seals (CV=1.0). In 1993, observers recorded one 

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. 

16
Thus, the mean estimated mortality for this fishery in 1991-1993 is 6.7 (CV=0.50) harbor seals per year (Table 1). 

No observer data are available for this fishery after 1993, however, harbor seal takes are unlikely to have increased 

since the fishery was last observed, due to reductions in the number of participating vessels and available fishing 

time (see details in Appendix 1). Fishing effort and catch have declined throughout all salmon fisheries in the 

region due to management efforts to recover ESA-listed salmonids. 

 Combining the estimates from the northern Washington marine set gillnet (3.2), WA/OR/CA groundfish 

trawl (0.8 from monitored hauls + 0.2 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 10.9 harbor seals per year 

from this stock. 

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

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). Harbor seal takes are unlikely to have increased 

since the fishery was last observed in 1993, due to reductions in the number of participating vessels and available 

fishing time (see details in Appendix 1). Fishing effort and catch have declined throughout all salmon fisheries in 

the region due to management efforts to recover ESA-listed salmonids. 

 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 1997 and 2001, 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. Logbook data are available for part of 1989-1994, after which 

incidental mortality reporting requirements were modified. Under the new system, logbooks are no longer required; 

instead, fishers provide self-reports. Data for the 1994-1995 phase-in period is fragmentary. After 1995, the level 

of reporting dropped dramatically, such that the records are considered incomplete and estimates of mortality based 

on them represent minimums (see Appendix 7 in Angliss et al. 2001 for details). 

 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. One fishery-related stranding was reported in 1999 (B. 

Norberg, pers. comm.) and, since it could not be attributed to a particular fishery, it is listed in Table 1 as occurring 

in an unknown west coast fishery. Fishery-related strandings during 1997-2001 resulted in an estimated annual 

mortality of 0.2 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). 

Other Mortality

 According to Northwest Marine Mammal Stranding Network records, maintained by the NMFS Northwest 

Region, a total of eight human-caused harbor seal mortalities or serious injuries were reported from non-fisheries 

sources in 1997-2001. Seven animals were shot (one each in 1997, 1999, and 2000 and two each in 1998 and 2001) 

and one animal was struck by an off-road-vehicle (in 1997), resulting in an estimated mortality of 1.6 harbor seals 

per year 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).

Subsistence Harvests by Northwest Treaty Indian Tribes

 Several Pacific Northwest treaty Indian tribes have promulgated tribal regulations allowing tribal members 

to exercise treaty rights for subsistence harvest of harbor seals. There have been only a few reported takes of harbor 

seals from directed tribal subsistence hunts. It is possible that very few seals have been taken in directed hunts 

because tribal fishers use seals caught incidentally to fishing operations, in the northern Washington marine set 

gillnet fishery, for their subsistence needs before undertaking a ceremonial or subsistence hunt. From 

communications with the tribes, the NMFS Northwest Regional Office (J. Scordino, pers. comm.) believes that 5-10 

harbor seals from this stock may be taken annually in directed subsistence harvests. 

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 

17
mortality and serious injury (14.6 + 1.6 + 5-10 = 21.2-26.2) is not known to exceed the PBR (1,343). 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 (14.6: based on observer data (10.9) and self-reported fisheries 

information (3.5) or stranding data (0.2) where observer data were not available or failed to detect harbor seal 

mortality) appears to be less than 10% of the calculated PBR (134) and, therefore, appears 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

Angliss, R. P., D. P. DeMaster, and A. L. Lopez. 2001. Alaska marine mammal stock assessments, 2001. U.S. 

Dep. Commer., NOAA Tech. Memo. NMFS-AFSC-124. 203 pp. 

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. 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 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. 

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. 

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. 

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. 

18
Huber, H. R., S. J. Jeffries, R. F. Brown, R. L. DeLong, and G. VanBlaricom. 2001. Correcting aerial survey 

counts of harbor seals (Phoca vitulina richardsi) in Washington and Oregon. Mar. Mammal. Sci. 

17(2):276-293. 

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 

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

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

Jeffries, S., H. Huber, J. Calambokidis, and J. Laake. 2003. Trends and status of harbor seals in Washington State: 

1978-1999. J. Wildl. Manage. 67(1):208-219. 

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. 

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

Norberg, B. National Marine Fisheries Service, Northwest Region, 7600 Sand Point Way NE, Seattle, WA 98115. 

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. 

Perez, M. 2003. Compilation of marine mammal incidental take data from the domestic and joint venture 

groundfish fisheries in the U.S. EEZ of the North Pacific, 1989-2001. U.S. Dep. Commer., NOAA Tech. 

Memo. NMFS-AFSC-138. 145 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. 

19
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-OPR12. 93 pp. 

Whisler, G. Columbia River Management, Oregon Department of Fish and Wildlife, 2021 Marine Drive, Room 

103, Astoria, OR 97103. 

20
Revised 12/15/2003

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 haulout 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 three separate 

harbor seal stocks along the west coast of the continental U.S. 

(Boveng 1988): 1) inland waters of Washington State

(including Hood Canal, Puget Sound, and the 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 waters possess unique haplotypes not found

in seals from the coasts of Washington, Oregon, and California 

(Lamont et al. 1996). In this report only the Washington Inland 

Waters stock is addressed. Harbor seal stocks that occur in the inland and coastal waters of Alaska are reported 

separately in the Stock Assessment Reports for the

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. 

Alaska Region. 

POPULATION SIZE

Aerial surveys of harbor seals in Washington were conducted during the pupping season in 1999, during

which time the total number of hauled-out seals (including pups) were counted. In 1999, the mean count of harbor

seals occurring in Washington’s inland waters was 9,550 (CV=0.14) animals (Jeffries et al. 2003). 

Radio-tagging studies conducted at six locations (three Washington inland waters sites and three 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 et al. 2001). Using this correction factor results in a population estimate of 14,612 (9,550 x 1.53; CV=0.15) 

for the Washington Inland Waters stock of harbor seals (Jeffries et al. 2003). 

Minimum Population Estimate

The log-normal 20th percentile of the 1999 population estimate for this stock is 12,844 harbor seals. 

21
Current Population Trend

Historical levels of harbor seal 

abundance in Washington are unknown.

The population apparently decreased

during the 1940s and 1950s due to a 

state-financed bounty program.

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 passage of the Marine

Mammal Protection Act (MMPA) in 

1972, harbor seal numbers in

Washington have increased (Jeffries

1985). 

0

2000

4000

6000

8000

10000

12000

14000

1975 1980 1985 1990 1995 2000

Year

Total count

Between 1983 and 1996, the 

annual rate of increase for this stock was 

6% (Jeffries et al. 1997). The peak count

occurred in 1996 and, based on a fitted 

generalized logistic model (Fig. 2), the

population is thought to be stable (Jeffries

et al. 2003). 

Figure 2. Generalized logistic population growth curve for the

Washington Inland Waters stock of harbor seals, 1978-1999 

(Jeffries et al. 2003).

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 by 1991, the observed rate of increase may 

underestimate the maximum net productivity rate (RMAX). When a logistic model was fit to the 1978-1999 

abundance data, the resulting estimate of RMAX was 12.6% (95% CI = 9.4-18.7%) (Jeffries et al. 2003). This value 

of RMAX is very close to the default pinniped maximum theoretical net productivity rate of 12% (RMAX), therefore, 

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 

(12,844) times one-half the default maximum net growth rate for pinnipeds (1⁄2 of 12%) times a recovery factor of 

1.0 (for stocks within OSP, Wade and Angliss 1997), resulting in a PBR of 771 harbor seals per year. 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Fisheries Information

NMFS observers monitored the northern Washington marine set gillnet fishery in 1997, 1998, and 2000;

there was no observer coverage in 1999 or 2001 (Gearin et al. 1994, 2000; P. Gearin, unpubl. data). For the entire 

fishery (coastal + inland waters), observer coverage ranged from approximately 40 to 98% during observed years.

Fishing effort is conducted within the range of both stocks of harbor seals (Oregon/Washington Coast and 

Washington Inland Waters stocks) occurring in Washington State waters. 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 Washington Inland 

Waters 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 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 et al. 2001). Accordingly, Table 1 includes data only from that portion of the northern Washington marine

set gillnet fishery occurring within the range of the Washington Inland Waters stock (those waters east of Cape

Flattery), where observer coverage ranged from 40 to 80% between 1997 and 2001 and fishing effort ranged from 4-

46 net days per year (1 net day equals a 100-fathom length net 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

22
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 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 (Washington 

Inland Waters 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 1997-2001 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 in inland waters: 

areas 4B and 5)

97 

98 

99 

00 

01 

97-01

obs data 

selfreports

80% 

40% 

0% 

58% 

0% 

0 

0 

n/a 

0 

n/a 

0, 0, 0, 0, 2

0 

0 

n/a 

0 

n/a 

01

≥0.4 (n/a)

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 nontreaty sockeye salmon gillnet 

(areas 7 and 7A)

94 obs data 7% 1 15 15 (1.0)

WA salmon net pens 97-01 self 

reports n/a 10, 5, 0, 0, 0 n/a ≥3 (n/a)

Unknown Puget Sound fishery 97-01 stran d

data n/a 1, 1, 0, 2, 2 n/a ≥1.2 (n/a)

Minimum total annual takes ≥29.6 (1.0)

1

1997-98 and 2000 mortality estimates are included in the average.

 

 In 1994, NMFS, in conjunction with WDFW conducted an observer program during the Puget Sound nontreaty 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 mortalities for the entire fishery. The Puget Sound treaty chum salmon gillnet fishery in Hood 

Canal (areas 12, 12B, and 12C) and the Puget Sound treaty sockeye/chum gillnet fishery in the Strait of Juan de 

23
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 

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). 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 was 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 fishery (0.4), the Puget Sound 

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

sockeye salmon gillnet fishery in areas 7 and 7A (15) results in an estimated minimum annual mortality rate in 

observed fisheries of 25.4 harbor seals from this stock. It should be noted that the 1994 observer programs did not 

sample all segments of the 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, 25.4 is an 

underestimate of the harbor seal mortality due to the entire fishery. The percentage of the overall Washington Puget 

Sound Region salmon set/drift gillnet fishery effort that was observed in 1994 was not quantified. 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.). Harbor seal takes in the Washington Puget Sound Region 

salmon drift gillnet fishery are unlikely to have increased since the fishery was last observed in 1994, due to 

reductions in the number of participating vessels and available fishing time (see details in Appendix 1). Fishing 

effort and catch have declined throughout all salmon fisheries in the region due to management efforts to recover 

ESA-listed salmonids. 

 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 2001, there were no fisher self-reports of harbor seal mortalities from the 

Washington Puget Sound Region salmon set/drift gillnet fishery. Unlike the 1994 observer program data, the selfreported fishery data cover the entire fishery (including treaty and non-treaty components). There were fisher selfreports of 15 harbor seal mortalities due to entanglement in Washington salmon net pens in 1997-2001, 10 in 1997 

and five in 1998 (Table 1), resulting in an estimated annual mortality of three harbor seals from 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. Logbook data are available for part of 1989-

1994, after which incidental mortality reporting requirements were modified. Under the new system, logbooks are 

no longer required; instead, fishers provide self-reports. Data for the 1994-1995 phase-in period is fragmentary. 

After 1995, the level of reporting dropped dramatically, such that the records are considered incomplete and 

estimates of mortality based on them represent minimums (see Appendix 7 in Angliss et al. 2001 for details). 

 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 1997 to 2001, small numbers of 

fishery-related strandings of harbor seals have occurred in most years (B. Norberg, pers. comm.). 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 1997-2001 resulted in an estimated annual mortality of 1.2 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 29.6 harbor seals per year, 

based on observer program data (25.4), fisher self-reports (3), and stranding data (1.2). 

Other Mortality

 According to Northwest Marine Mammal Stranding Network records, maintained by the NMFS Northwest 

Region, a total of 18 human-caused harbor seal mortalities or serious injuries were reported from non-fisheries 

sources in 1997-2001. Fifteen animals were shot (seven, two, one, three and two each year, respectively), two were 

24
struck by ships (one each in 1999 and 2001), and one was found with neck injuries in 1999, resulting in an estimated 

mortality of 3.6 harbor seals per year from this stock. This estimate is considered 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 Pacific Northwest treaty Indian tribes have promulgated tribal regulations allowing tribal members 

to exercise treaty rights for subsistence harvest of harbor seals. There have been only a few reported takes of harbor 

seals from directed tribal subsistence hunts. It is possible that very few seals have been taken in directed hunts 

because tribal fishers use seals caught incidentally to fishing operations, in the northern Washington marine set 

gillnet and Washington Puget Sound Region treaty salmon gillnet fisheries, for their subsistence needs before 

undertaking a ceremonial or subsistence hunt. From communications with the tribes, the NMFS Northwest Regional 

Office (J. Scordino, pers. comm.) believes that 0-5 harbor seals from this stock may be taken annually in directed 

subsistence harvests. 

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 (29.6 + 3.6 + 0-5 = 33.2-38.2) is not known to exceed the PBR (771). Therefore, the 

Washington Inland Waters stock of harbor seals is not classified as a “strategic” stock. At present, the minimum 

estimated fishery mortality and serious injury for this stock (29.6) appears to be less than 10% of the calculated PBR 

(77) and, therefore, appears to be insignificant and approaching zero mortality and serious injury rate. The stock is 

within its Optimum Sustainable Population (OSP) level (Jeffries et al. 2003). 

REFERENCES

Angliss, R. P., D. P. DeMaster, and A. L. Lopez. 2001. Alaska marine mammal stock assessments, 2001. U.S. 

Dep. Commer., NOAA Tech. Memo. NMFS-AFSC-124. 203 pp. 

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. 

25
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. 

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. 

Huber, H. R., S. J. Jeffries, R. F. Brown, R. L. DeLong, and G. VanBlaricom. 2001. Correcting aerial survey 

counts of harbor seals (Phoca vitulina richardsi) in Washington and Oregon. Mar. Mammal. Sci. 

17(2):276-293. 

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. 

Jeffries, S., H. Huber, J. Calambokidis, and J. Laake. 2003. Trends and status of harbor seals in Washington State: 

1978-1999. J. Wildl. Manage. 67(1):208-219. 

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. 48 pp. 

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

Norberg, B. National Marine Fisheries Service, Northwest Region, 7600 Sand Point Way NE, Seattle, WA 98115. 

Northwest Indian Fisheries Commission (NWIFC). 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) and U.S. Fish and Wildlife Service. 

Unpubl. report. 41 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 nontreaty 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-OPR12. 93 pp. 

26
Revised 10/31/2002

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 45o

N (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

asons.

tion is considered here to be a separate stock.

se

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 popula

W130 W125 W120 W115 W110 W105 W100

Longitude

N15

N20

N25

N30

N35

N40

N45

Latitude

WASHINGTON

OREGON

CALIFORNIA

MEXICO

UNITED STATES

PACIFIC OCEAN

CALIFORNIA BREEDING

 STOCK

 Isla

Cedros

Isla Guadalupe

Isla Benito

 Del Este

SE Farallon Is.

Ano Nuevo

Channel

 Islands

Figure 1. Stock boundary and major rookery

areas for northern elephant seals in the U.S. and 

Mexico.

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 28,845 pups born in California in 2001 (Fig. 2) and this 3.5 multiplier, the California stock 

was approximately 101,000 in 2001. 

Minimum Population Estimate

The minimum population size for northern elephant seals can be estimated very conservatively as

60,547, which is equal to twice the observed pup count (to account for the pups and their mothers) plus

2,317 males and 17 juveniles counted at the Channel Island sites in 2001 (Mark Lowry, NMFS unpubl. 

data) and 523 males counted at Año Nuevo sites in 1996 (Le Boeuf 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. 

27
Current Population Trend

Based on trends in pupcounts, northern elephant seal colonies were continuing to grow in

California through 2001 (Figure 2), but appear to be stable or slowly decreasing in Mexico (Stewart et al.

1994). 

Figure 2. Estimated number of northern elephant seal births in California 1958-2001. Multiple 

independent estimates are presented for the Channel Islands 1988-91. Estimates are from Stewart et al. 

(1994), Lowry et al. (1996), and unpublished data from Sarah Allen, Dan Crocker, Brian Hatfield, Ron 

Jameson, Bernie Le Boeuf, Mark Lowry, Pat Morris, Guy Oliver, and William Sydeman.

0 

5000 

10000 

15000 

20000 

25000 

30000 

# BIRTHS

1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 

Year

 N. Elephant Seal Births in CA

TOTAL

Channel

Islands

Central CA

 

CURRENT AND 

MAXIMUM NET 

PRODUCTIVITY RATE

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

-0.05 

0 

0.05 

0.1 

0.15 

Growth + Human Caused Mortality Rates

1978 1980 1982 1984 1986 1988 1990 1992 1994 1996 1998 2000 

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 1980-87 is assumed

to be 300, the average of 1988-90 values (Perkins et al. 1994). 

28
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 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 (60,547) 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 2,513.

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; Cameron and 

Forney 1999, 2000; Carretta 2001; Perez, in prep.; NMFS unpubl. data). n/a indicates information is not 

available. Mean annual takes are based on 1996-2000 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

1996 

1997 

1998 

1999

2000

observer 

data 

12.4% 

22.8% 

20.2% 

20.0%

25.1%

4 

8 

4 

1

6

37 (0.55) 

45 (0.33) 

20 (0.44) 

10 (0.61)

26 (0.41)

25 (0.21) 1

CA angel shark/halibut 

and other species large 

mesh (>3.5") set gillnet 

fishery

1996 

1997 

1998 

1999

2000

observer 

data 

extrapo-lated 

estimate

0.0% 

0.0% 

0.0% 

23.1% 3

26.9% 3

- 

- 

- 

10 †

4 †

46 (0.23) 2 

60 (0.24) 2 

70 (0.26) 2

76 (0.19) 2

48 (0.23) 2

60 (0.10)

WA, OR, CA groundfish 

trawl 1998

observer 

data 77% 1 1 (n/a) 1 (n/a) 

WA Willapa Bay drift 

gillnet fishery (salmon) 1991

personal 

communication n/a 2 2 n/a

Chehalis River salmon 

setnet fishery

1993 personal 

communication

n/a 4 4 n/a

Total annual takes > 86 (0.14)

1

 Only 1997-2000 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 in 1995-98, and observations in 1999-2000 only included Monterey Bay; mortality for 

unobserved areas and times was extrapolated from effort estimates and 1991-94 entanglement rates. †

 Observer coverage and observed mortality in 1999-2000 only includes the portion of the fishery in Monterey Bay. 

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. The set gillnet fishery 

in Monterey was observed again in 1999-2000 after a lapse of four years. Entanglement rates of northern 

elephant seals were similar to extrapolated rates in the previous three years; therefore, mortality estimates 

for the five most recent years were averaged to give the mean annual take for that fishery. Current 

mortality could not be estimated for a few fisheries that have taken small numbers of elephant seals in the 

past; therefore, the overall mortality is likely to be slightly greater than 86 per year. Stranding data reported 

to the California Marine Mammal Stranding Network in 1996-2000 include elephant seal injuries caused by 

hook-and-line fisheries (two injuries) and gillnet fisheries (one injury). 

 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 

29
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 speciesspecific information is not available for the Mexican fisheries. There are currently efforts underway to 

convert the Mexican swordfish driftnet fishery to a longline fishery (David Holts, NMFS, SWFSC, 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 1996-2000: (1) boat collision (2 mortalities, 1 injury), (2) automobile collision (5 mortalities), 

(3) shootings (three mortalities) and (4) entanglement in marine debris (1 injury). 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 (2,513), they would not be considered a "strategic" stock under the 

MMPA. The average rate of incidental fishery mortality for this stock over the last five years (86) 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. 

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 (unpublished). 12 pp. 

Carretta, J.V. 2001. Preliminary estimates of cetacean mortality in California gillnet fisheries for 2000. 

Paper SC/53/SM9 presented to the International Whaling Commission (unpublished). 21 pp. 

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. 

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. 1997. Cetacean mortality in California gillnet fisheries: preliminary estimates for 1996. Paper 

SC/49/SM02 presented to the International Whaling Commission (unpublished). 13pp. 

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. 

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. NOAA Technical Memorandum 

NMFS-OPR-12 available from Office of Protected Resources, National Marine Fisheries Service, 

Silver Springs, MD. 93pp. 

31
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 specie’s continued existence 

(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 HernadezCamacho 1999). The population is considered to

be a single stock because all are recent descendants 

from one breeding colony at Isla Guadalupe,

Mexico. 

W130 W125 W120 W115 W110 W105 W100

Longitude

N15

N20

N25

N30

N35

N40

N45

Latitude

WASHINGTON

OREGON

CALIFORNIA

MEXICO

UNITED STATES

PACIFIC OCEAN

Isla Guadalupe

Isla Benito

 Del Este

 Islas

Revillagigedos

Figure 1. Geographic range of the Guadalupe fur 

seal, showing location of two rookeries at Isla

Guadalupe and Isla Benito Del Este.

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. Subsampling 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

32
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).

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.

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. 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 91 Guadalupe fur

seals per year. The vast majority of this PBR would apply towards incidental mortality in Mexico. 

HUMAN-CAUSED MORTALITYAND 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 human-caused 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 

33
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.

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

01

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 

02

02

02

02

02

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. 

34
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 

 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
Revised 12/15/2003

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 

(June-November). 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 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. 

San Miguel Island

Pribilof

Islands

Figure 1. Approximate distribution of northern fur

seals in the eastern North Pacific (shaded area). 

The following information was considered in classifying stock structure based on the Dizon et al. (1992) 

phylogeographic approach: 1) Distributional data: continuous geographic distribution during feeding, geographic

separation during the breeding season, and high natal site fidelity (DeLong 1982); 2) Population response data:

substantial differences in population dynamics between the 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, two year olds, 

three year olds, and animals at least four 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

commercial harvest of juvenile males was terminated in 1984. 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 events in 1982-

1983 and 1997-1998 (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, and by

2002 the total pup count was 1,946 (S. Melin, unpubl. data). Based on the 2002 count and the expansion factor, the

36
most recent population estimate of the San Miguel Island stock is 7,784 (1,946 x 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 coefficient of variation (CV), 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 2002 (to account for the pups and their

mothers) plus the maximum

number of adult and sub-adult

males counted for the 2002 

season, which results in an NMIN

of 4,190 ((1,946 x 2) + 298).

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). 

0

500

1000

1500

2000

2500

3000

1972197419761978198019821984198619881990199219941996199820002002

Year

Number of live pups

Figure 2. Northern fur seal live pup counts on San Miguel Island, 1972-

2002. 

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 1,946 in 2002 (S. Melin, unpubl. data), recovery from the 1998 decline has been

slowed by the adult female mortality which occurred in addition to the high pup mortality in 1997 and 1998 (Melin 

and DeLong 2000; S. Melin, unpubl. data).

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 

37
growth 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 (4,190) 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 180 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 is listed in Table 1. There were no observer reports of northern fur seal mortalities in any 

observed fishery along the west coast of the continental U.S. during the period from 1997-2001 (Table 1; Cameron 

and Forney 1999, 2000; Carretta 2001, 2002; Perez 2003). 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 1997 and 2001, there were two fisher self-reports of northern fur seal mortalities in the 

Washington/Oregon/California groundfish trawl (Pacific whiting) fishery, resulting in an annual estimated mortality 

of 0.4 fur seals from 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. Logbook data are 

available for part of 1989-1994, after which incidental mortality reporting requirements were modified. Under the 

new system, logbooks are no longer required; instead, fishers provide self-reports. Data for the 1994-1995 phase-in 

period is fragmentary. After 1995, the level of reporting dropped dramatically, such that the records are considered 

incomplete and estimates of mortality based on them represent minimums (see Appendix 7 in Angliss et al. 2001 for 

details). 

 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. One fishery-related stranding was reported in 2001 (J. 

Cordaro, pers. comm.) and, since it could not be attributed to a particular fishery, it is listed in Table 1 as occurring 

in an unknown west coast fishery. Fishery-related strandings during 1997-2001 resulted in an estimated annual 

mortality of 0.2 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). 

Other Mortality

 According to California Marine Mammal Stranding Network records, maintained by the NMFS Southwest 

Region, one human-caused northern fur seal mortality (due to a head injury) was reported from a non-fisheries 

source in 1999, resulting in an estimated annual mortality of 0.2 northern fur seals in 1997-2001. 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 (0.6 + 0.2 = 0.8) does not exceed the PBR 

(180). 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 (0.6) is not known to exceed 10% of the calculated 

PBR (18) and, therefore, appears to be insignificant and approaching zero mortality and serious injury rate. The 

stock decreased 79.6% from 1997 to 1998, began to recover in 1999, and is currently at 63.4% of the 1997 level. 

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. 

38
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 1997-2001 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

97 

98 

99 

00

01

obs data

23.0% 

20.0% 

20.0% 

22.9%

20.4%

0 

0 

0 

0

0

0 

0 

0 

0

0

0

CA angel shark/halibut set 

gillnet

97 

98 

99 

00

01

obs data 

0% 

0% 

4% 

1.8% 

0%

0 

0 

0 

0

0

01

01

01

01

01

0

WA/OR/CA groundfish trawl 

(Pacific whiting component)

97 

98 

99 

00

01

obs data

65.7% 

77.3% 

68.6% 

80.6%

96.2%

0 

0 

0 

0

0

0 

0 

0 

0

0

0

WA/OR/CA groundfish trawl 

(Pacific whiting component) 97-01 self reports n/a 2, 0, 0, 0, 0 n/a ≥0.4 (n/a)

Unknown west coast fishery 97-01 strand data n/a 0, 0, 0, 0, 1 n/a ≥0.2 (n/a)

Minimum total annual takes ≥0.6 (n/a)

1

 The California set gillnets were not observed after 1994; mortality was extrapolated from effort estimates and previous entanglement rates, 

except for Monterey Bay, where the fishery was observed in 1999 and 2000.

REFERENCES

Angliss, R. P., D. P. DeMaster, and A. L. Lopez. 2001. Alaska marine mammal stock assessments, 2001. U.S. 

Dep. Commer., NOAA Tech. Memo. NMFS-AFSC-124. 203 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, June 2000 

(unpublished). 12 pp. 

Carretta, J. V. 2001. Preliminary estimates of cetacean mortality in California gillnet fisheries for 2000. Paper 

SC/53/SM9 presented to the International Whaling Commission, June 2001 (unpublished). 21 pp. 

Carretta, J. V. 2002. Preliminary estimates of cetacean mortality in California gillnet fisheries for 2001. Paper 

SC/54/SM12 presented to the International Whaling Commission, April 2002 (unpublished). 22 pp. 

Cordaro, J. National Marine Fisheries Service, Southwest Region, 501 West Ocean Blvd., Long Beach, CA 90802. 

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. 

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. 

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. 

39
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. 

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. 

Perez, M. 2003. Compilation of marine mammal incidental take data from the domestic and joint venture 

groundfish fisheries in the U.S. EEZ of the North Pacific, 1989-2001. U.S. Dep. Commer., NOAA Tech. 

Memo. NMFS-AFSC-138. 145 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-OPR12. 93 pp. 

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

40
Revised 03/15/2005

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 and Lisianski Islands, Pearl and Hermes Reef, and 

Midway and Kure Atoll. Small numbers also occur at Necker, Nihoa, and the Main Hawaiian Islands (MHI), 

primarily at Niihau. Genetic variation among NWHI monk seals is extremely low and may reflect both a long-term 

history at low population levels and more recent human influences (Kretzmann et al. 1997, 2001). On average, 10-

15% of the seals migrate among the NWHI subpopulations (Johnson and Kridler 1983; Harting 2002). Thus, the 

NWHI subpopulations are not demographically isolated, though the different island subpopulations have exhibited 

considerable independence. For example, abundance at French Frigate Shoals grew rapidly from the 1950s-1980s, 

while other subpopulations declined rapidly. Genetic comparisons between NWHI and MHI seals has not been 

conducted, but observed interchange of individuals among the regions is extremely rare, suggesting these may be 

more appropriately designated as separate stocks. Further evaluation of a separate MHI stock will be pursued 

following additional population assessment and studies of movements of monk seals in the MHI. In the mean time, 

while research and recovery activities may focus on the problems of single island/atoll subpopulations, the species is 

managed as a single stock. 

POPULATION SIZE

 The best estimate of the total population size is 1,304. This estimate is the sum of counts at the six 

Northwest Hawaiian Islands subpopulations, an extrapolation of counts at Necker and Nihoa Islands, and counts at 

the Main Hawaiian Islands. Abundance of the main reproductive subpopulations is best estimated using the number 

of seals identified at each site. Individual seals are identified by flipper-tags and applied bleach-marks, and 

distinctive natural features such as scars and 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 2002, identification efforts were conducted during two- to six-month studies at all main reproductive sites. 

A total of 1,156 seals (including 196 pups) were observed at the main reproductive subpopulations in 2002 (Johanos 

and Baker, in press). The estimated probability that known-aged seals are identified during a given field season 

average over 90% at French Frigate Shoals, Laysan Island, Midway Atoll and Kure atoll; approximately 85% at 

Lisianski Island, and approximately 80% at Pearl and Hermes Reef (Harting 2002). These probabilities likely 

represent the potential extent of negative bias in enumerating the subpopulations. 

 Monk seals also occur at Necker and Nihoa Islands, where counts are conducted from zero to 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 between 1998-2002 were 16.4 (± 6.4) at Necker Island 

and 15.4 (± 7.3) at Nihoa Island (Johanos and Ragen 1999; Johanos and Baker 2000, 2001, 2002, in press). The 

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 during 1997-2001) are 48.3 (±18.5 ) 

at Necker Island and 47.3 (± 21.1) at Nihoa Island. 

 A 2001 aerial survey determined a minimum abundance of 52 seals in the MHI and remains the most recent 

available estimate (Baker and Johanos 2003). Seals in the MHI include those naturally occurring and any animals 

remaining from 21 seals released around the islands in 1994. 

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., 1,156 seals). Minimum population sizes for Necker and Nihoa Islands (based on 

the formula provided by Wade and Angliss (1997) are 35 and 33, respectively. The minimum abundance estimate 

for the main Hawaiian Islands based upon the 2001 aerial survey is 52 seals. The minimum population size for the 

entire stock (species) is the sum of these estimates, or 1,276 seals. 

41
Current Population Trend

The total of mean non-pup beach counts at the six main reproductive NWHI subpopulations in 2002 is 

approximately 60% lower than in 1958. Counts declined from 1985 to 1993, then became rather stable. As a result, 

a log-linear trend through the entire time series results in lack of fit. To remedy this, a broken-line regression is 

fitted (two regression lines joined at a break point), with the break point chosen to minimize the sum of squares error 

(B. Venables, s-news website, http://www.biostat.wustl.edu/mailinglists/s_news/200004/msg00212.html). This 

method estimates that the total counts declined 4.2% yr

-1 until 1993, then declined at 1.1% yr-1 thereafter (Fig. 1). 

The broken line regression fit significantly better than a single regression line (p = 0.03). Thus, current population

trend is best estimated as minus 1.1% yr

-1 (95% CI = -2.4% to 0.2% yr-1). 

CURRENT AND MAXIMUM NET 

PRODUCTIVITY RATES

Assuming mean beach counts are a reliable

index of total abundance, the current net productivity 

rate for this species is -0.011 yr-1 (see above). 

Trends in abundance vary considerably among the

six main subpopulations. For example, the decline 

since the mid-1980's (Fig. 1) was largely due to a 

severe decline at French Frigate Shoals, where nonpup beach counts decreased by 7% from 1989-2002.

Populations at Laysan and Lisianski Islands have 

remained relatively stable since approximately 1990, 

though the former has tended to increase slightly

while the latter has decreased slowly. 

Until recently, the three westernmost

subpopulations, Kure, Midway and Pearl and 

Hermes Reef, exhibited substantial growth. The 

subpopulation at Kure Atoll grew at an average rate

of 5% yr

-1 from 1983 to 2000 (loglinear regression of

beach counts; R2

 = 0.85, p<0.001), due largely to decreased human disturbance and introduced females. However,

since 2000, counts at Kure have declined coinciding with very low survival of the 2000-2001 cohorts from weaning

to age 1 yr (15% and 18%, respectively). The subpopulation at Pearl and Hermes Reef increased after the mid1970s. The average growth rate from 1983-2000 was 6%yr-1 (loglinear regression of beach counts; R2

 = 0.84, 

P<0.001), and prior to 1999, growth rates of up to 7%yr-1 were observed. This is the highest estimate of the 

maximum net productivity rate (Rmax) observed for this species. Growth of this subpopulation has slowed recently 

and early survival has declined. Recovery of the small subpopulation at Midway Atoll appears to have slowed or

stopped, also accompanied by relatively poor juvenile survival. These demographic trends at the western end of the 

NWHI do not bode well for recovery, especially if recent low juvenile survival rates become chronic. While the

MHI monk seal population may be on the rise (Baker and Johanos 2003), this remains unconfirmed and abundance

appears to be too low to strongly influence current total stock trends. 

300

350

400

450

500

550

600

Mean number of non-pups

1985 1987 1989 1991 1993 1995 1997 1999 2001

Year

Figure 1. Mean beach counts of Hawaiian monk seals 

at the six main NWHI subpopulations, 1985-2002.

POTENTIAL BIOLOGICAL REMOVAL

Potential biological removal (PBR) is designed to allow stocks to recover to, or remain above, the

maximum net productivity level (MNPL) (Wade 1998). An underlying assumption in the application of the PBR

equation is that marine mammal stocks exhibit certain dynamics. Specifically, it is assumed that a reduced stock will 

naturally grow toward OSP, and that some surplus growth can be removed while still allowing recovery. The 

Hawaiian monk seal population is far below historical levels and has declined 1.1% yr

-1 on average for the past 

decade. Thus, for unknown reasons, the stock’s dynamics do not conform to the underlying model for calculating 

PBR. The prescribed PBR calculation for this stock would be the minimum population size (1,276) times one half

the maximum net growth rate (1⁄2 of 7%) times a recovery factor of 0.1 (for an endangered species, Wade and

Angliss 1997), which yields 4.5 monk seals per year. However, given the stock’s current status and trend, the 

intended standard for determining PBR, i.e., recovery to MNPL, will not be achieved in the foreseeable future if a 

take of 4.5 seals a year is realized. Meanwhile, it also appears unlikely that some non-zero level of removal below 

4.5 animals could explain the lack of recovery of this stock. Given this unique set of circumstances, PBR for the

Hawaiian monk seal is undetermined. 

 

42
HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

 Human-related mortality has caused two major declines of the Hawaiian monk seal (Ragen 1999). In the 

1800s, this species was decimated by sealers, crews of wrecked vessels, and guano and feather hunters (Dill and 

Bryan 1912; Wetmore 1925; Bailey 1952; Clapp and Woodward 1972). Following a period of at least partial 

recovery in the first half of the 20th century (Rice 1960), most subpopulations again declined. This second decline 

has not been fully explained, but trends at several sites appear to have been determined by human disturbance from 

military or U.S. Coast Guard activities (Ragen 1999; Kenyon 1972; Gerrodette and Gilmartin 1990). 

Fishery Information

 Fishery interactions with monk seals include: operations/gear conflict, seal consumption of discarded fish, 

and competition for prey. Entanglement of monk seals in fishing gear, which is believed to originate outside the 

Hawaiian archipelago, is described in a separate section below. Since 1976, known fishery-related monk seal deaths 

have included the following (NMFS unpubl. data): one seal drowned in a nearshore gillnet off Kauai (1976), another 

seal died from entanglement in the bridle rope of lobster trap near Necker Island (1986), another died from 

entanglement in an illegally set gill net off Oahu (1994), and one ingested a fish hook and likely drowned off Kauai 

(1995). A total of 26 seals have been observed with embedded fish hooks during 1982- 2002. The hooks were not 

always recovered and it was not possible to attribute each hooking event to a specific fishery. Among hooks that 

could be identified, sources included state-managed nearshore fisheries (esp. for Caranx sp. in the main Hawaiian 

Islands), federal and state bottomfish and federal longline fisheries (NMFS unpubl. data). A recent Biological 

Opinion summarized hookings and entanglements (NMFS 2002). 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 have potential to interact with Hawaiian monk seals. The NWHI lobster fishery was closed 

in 2000 due to uncertainty in the estimates of biomass, and the fishery remains closed to date. Neither incidental 

mortality nor serious injury were observed by NMFS observers of the lobster fishery through 2001, though one 

mortality was documented in 1986. The potential for indirect interaction due to competition for prey is being 

investigated (see Habitat Issues below). 

 The NWHI bottomfish fishery has been reported to interact 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 95 - 201 metric tons per year from 1989-2002 (Kawamoto 1995; Kawamoto, pers. comm.). 

The number of vessels rose from 19 in 1984 to 28 in 1987, and then varied from 9 to 17 in 1988 through 2002 

(Kawamoto 1995; Kawamoto, 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). NMFS has prepared 

an Environmental Impact Statement and prepared a Section 7 Biological Opinion on the Fishery Management Plan 

for the bottomfish fishery, and concluded that the operation of this fishery is not likely to jeopardize the continued 

existence of the Hawaiian monk seal nor would it likely destroy or adversely modify the monk seal’s critical habitat 

(NMFS 2002). The fishery 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 from logbooks. Fishers, however, are required to report all incidental mortality and 

injury within 48 hours of their return to port (pursuant to MMPA section 118(e)); no such mortality or injury has 

been reported since 1994 when the MMPA was amended to include section 118. 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 observer reports of seals 

taking bottomfish and bait off fishing lines, and observer reports of seals attracted to discarded bottomfish bycatch. 

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 prey items recovered from scats and spews were identified only to the 

level of family; Goodman-Lowe 1998, Parrish et al. 2000). Fatty acid signature analysis is incomplete regarding the 

importance of commercial bottomfish in the monk seal diet, but this methodology continues to be pursued. 

 In the past, interactions between the pelagic longline fishery and monk seals were documented. This 

fishery targets swordfish and tunas, primarily, and does not compete with Hawaiian monk seals for prey. In October 

1991, in response to 13 unusual seal wounds thought to have resulted from interactions with this fishery, NMFS 

established a permanent Protected Species Zone extending 50 nautical miles around the NWHI and the corridors 

between the islands. Subsequent shore-based observations of seals have found no further evidence of interactions 

with the longline fishery. Until 2000, interactions with protected species were assessed using Federal logbooks and 

43
observers (4-5% coverage) Since 2001, the observer program has maintained observer coverage levels for the 

Hawaii-based longline fleet above 20%. However, since 1991, there have been no observed or reported interactions 

of this fishery with monk seals. 

 There have also been interactions between nearshore fisheries and monk seals in both the NWHI and the 

MHI. At least three seals were hooked at Kure Atoll before the U.S. Coast Guard vacated the atoll in 1993. In the 

main Hawaiian Islands (MHI), one seal was found dead in a nearshore (non-recreational) gillnet in 1994 and a 

second seal was found dead with a hook lodged in its esophagus. A total of 16 seals have been observed with 

embedded hooks in the MHI during 1989-2002. Several incidents, including the dead hooked seal mentioned above, 

involved hooks used to catch ulua (jacks, Caranx spp.). Interactions in the MHI appear to be on the rise, as half the 

observed hookings have occurred since 2000, and a seal was also entangled in an actively fished nearshore gillnet 

off Oahu in 2002 (NMFS unpubl. data). 

 Interest in the harvest of precious coral in the NWHI represents a potential for future interactions with 

monk seals. However, some seals forage at patches of precious gold corals occurring over 500m in depth (Parrish et 

al., 2002). 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 data on impacts of such 

harvests become available. 

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 Data type

Range of 

observer 

coverage

Total 

observed 

mort.

Estimated 

mort. (in 

given years)

Mean 

annual 

mort.

NWHI lobster 1991-2000 0-12 Observer 

Log book 0-100% 0 n/a n/a

NWHI 

Bottomfish 1991-2002 9-17 n/a n/a n/a n/a n/a

Pelagic longline 1991-2002 100-141 Observer 

Log book

 

 3-28% 0 n/a n/a

Recreational 1991-1995 n/a n/a n/a 2† n/a n/a

† Data collected incidentally. 

 

Fishery Mortality Rate

 Data are unavailable to fully assess interaction with specific fisheries in Hawaii, thus one cannot conclude 

that the total fishery mortality and serious injury for this stock is less than 10% of the calculated PBR. Therefore, 

total fishery mortality and serious injury cannot be considered to be insignificant and approaching a rate of zero. 

Monk seals also continue to die from entanglement in North Pacific fishing gear and other debris (likely originating 

from various countries), and NMFS along with partner agencies, is pursuing a program to mitigate this source of 

mortality (see below). 

 Direct fishery interactions with monk seals remains to be thoroughly evaluated and the information above 

represents only observed 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. 

Entanglement in Marine Debris

 Hawaiian monk seals become entangled in fisheries and other marine debris at rates higher than reported 

for other pinnipeds (Henderson 2001). A total of 222 cases of seals entangled in fishing gear or other debris have 

been observed through 2002 (Henderson 2001; NMFS, unpubl. data), including seven documented mortalities 

resulting from entanglement in fisheries debris (Henderson 1990, 2001; NMFS, unpubl. data). The fishing gear 

fouling the reefs and beaches of the NWHI and entangling monk seals only rarely includes types used in Hawaiian 

fisheries. For example, trawl net and monofilament gillnet accounted for approximately 35% and 34% of the debris 

removed from reefs in the NWHI by weight, and trawl net alone accounted for 88% of the debris by frequency 

(Donohue et al. 2001). Yet there are no commercial trawl fisheries in Hawaii. 

 The NMFS and partner agencies continue to pursue an ambitious effort to mitigate impacts of marine 

44
debris on monk seals as well as turtles, coral reefs and other wildlife. Marine debris is removed from beaches and 

entangled seals during annual population assessment activities at the main reproductive sites. During 1996-2002 

debris survey and removal efforts, over 360,000 kg of derelict net and other debris were removed from the coral reef 

habitat in the NWHI (Donohue et al. 2000, Donohue et al. 2001; Donohue, pers. comm). 

Other Mortality

 Since 1982, 23 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 (Baker and Johanos, 2002). 

 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. 

 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 may impede recovery include single and multiple male aggression 

(mobbing), shark predation, 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. The resulting increase in 

female mortality appears to have been a major impediment to recovery at Laysan and Lisianski Islands. Since 1982, 

at least 67 seals have died or disappeared after suffering multiple male aggression at Laysan Island. 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 adult sex ratios, with males outnumbering females. In 1994, 

22 adult males were removed from Laysan Island, and only three seals are thought to have died from mobbing at this 

site since their removal (1995-2002). 

 In addition, 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 that killed 

pups in 1997 were translocated to Johnston Atoll, 870 km to the southwest. Subsequently, mounting injury to pups 

have decreased. 

 Shark-related injury and mortality incidents 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 recent 

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). It is believed that as many as 25 pups of a 

total 92 born at French Frigate Shoals in 1999 were killed by sharks. After 1999, losses of pups to shark predation 

have been fewer, but this source of mortality remains a serious concern. Various mitigation efforts have been 

undertaken by NMFS in cooperation with the USFWS, which manages French Frigate Shoals as part of the 

Hawaiian Islands National Wildlife Refuge. 

 Disease effects on monk seal demographic trends is uncertain. In 2001, an Unusual Mortality Event was 

declared following the deaths of four yearling monk seals in the course of nine days at Laysan Island. At least 11 

deaths occurred in the NWHI, but many more are suspected due to unusually low survival of juveniles at most 

subpopulations. Health screening of both healthy and unhealthy seals was conducted, and necropsies were 

performed on six seals. No evidence of infectious disease or toxicosis was found which would link the mortalities. 

However, all the necropsied animals were emaciated. Notably, while fewer dead seals were observed in 2002, 

overall yearling survival rates (2001 cohort) were comparable to those observed during the Unusual Mortality Event. 

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 has not recovered from past declines. Therefore, the Hawaiian monk 

seal is characterized as a strategic stock. 

Habitat Issues

 Vessel groundings pose a continuing threat to monk seals and their habitat, through potential physical 

damage to reefs, oil spills, and release of debris into habitats. Two relatively recent groundings include the Paradise 

Queen II, a lobster fishing vessel, at Kure Atoll in 1998, and the 77 ft longliner Swordman I at Pearl and Hermes 

Reef in 2000. 

45
 Available data indicate that the substantial decline at French Frigate Shoals was related to lack of available 

prey and subsequent emaciation and starvation. Two leading hypotheses to explain the lack of prey are 1) the local 

population reached its carrying capacity in the 1970s and 1980s, diminishing its own food supply, and 2) carrying 

capacity was simultaneously reduced by changes in oceanographic conditions and a subsequent decline in 

productivity (Polovina et al. 1994; Craig and Ragen 1999). Similarly, recently observed poor juvenile survival rates 

suggest that prey availability may be limiting recovery of other NWHI subpopulations. 

 Goodman-Lowe (1998) provided information on prey selection using hard parts in scats and spewings. 

Information on at-sea movement and diving is available for seals at all six main subpopulations in the NWHI using 

satellite telemetry (Stewart 2004a,b; Stewart and Yochem 2004 a,b,c). Preliminary studies to describe the foraging 

habitat of monk seals in the MHI are underway in 2004. 

 Currently, human activities in the NWHI are limited and, consequently, human disturbance, which 

impacted monk seals in the past (Ragen 1999), is relatively rare. 

 Tern Island is the site of a 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 raised concerns about the potential release of toxic wastes into the ocean. The 

Fish and Wildlife Service is scheduled to begin a project to repair and stabilize the seawall and shoreline of Tern 

Island in 2004. 

 There are indications that monk seal abundance is increasing in the main Hawaiian Islands (Baker and 

Johanos 2003). Further, the excellent condition of pups weaned on these islands suggests that there may be ample 

prey resources available. If the monk seal population does expand in the MHI, it may bode well for the species’ 

recovery and long-term persistence. In contrast, there are many challenges that may limit the potential for growth in 

this region. The human population in the MHI is approximately 1.2 million compared to less than 100 in the NWHI, 

so that the potential impact of disturbance in the MHI is great. Potential for disease transfer from domesticated 

animals to naive monk seals in the main islands, which could, in turn, transmit disease to the core population in the 

NWHI is also a concern. As noted above, the hooking of monk seals by fishermen in the MHI is another source of 

injury and mortality. Finally, vessel traffic around the populated islands carries the potential for collision with seals 

and impacts from oil spills. Thus, issues surrounding the presence of monk seals in the main Hawaiian Islands will 

likely become an increasing focus for management and recovery of this species. 

REFERENCES

Bailey, A. M. 1952. The Hawaiian monk seal. Museum Pictorial, Denver Museum of Natural History 7:1-32. 

Baker, J. D. and T. C. Johanos. 2003. Abundance of Hawaiian monk seals in the main Hawaiian Islands. Biological 

Conservation 116:103-110. 

Baker, J. D. and T. C. Johanos. 2002. Effects of research handling on the endangered Hawaiian monk seal. Mar. 

Mammal Sci. 18:500-512. 

Clapp, R. B., and P. W. Woodward. 1972. The natural history of Kure Atoll, Northwestern Hawaiian Islands, Atoll 

Res. Bull. 164:303-304. 

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. 

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. 

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. 2001. Derelict fishing gear in the Northwestern 

Hawaiian Islands: diving surveys and debris removal in 1999 confirm threat to coral reef ecosystems. 

Marine Pollution Bulletin 42(12):1301_1312. 

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. 

46
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. 

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. 

Harting, A.L. 2002. Stochastic simulation model for the Hawaiian monk seal. PhD thesis, Montana State University, 

328 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. 

Johanos, T. C. and J. D. Baker (editors). 2000. The Hawaiian monk seal in the Northwestern Hawaiian Islands, 

1998. U.S. Dep. Commer., NOAA Tech. Memo. NOAA-TM-NMFS-SWFSC-292, 125 p. 

Johanos, T. C. and J. D. Baker (editors). 2001. The Hawaiian monk seal in the Northwestern Hawaiian Islands, 

1999. U.S. Dep. Commer., NOAA Tech. Memo. NOAA-TM-NMFS-SWFSC-310, 130 p. 

Johanos, T. C. and J. D. Baker (editors). 2002. The Hawaiian monk seal in the Northwestern Hawaiian Islands, 

2000. U.S. Dep. Commer., NOAA Tech. Memo. NOAA-TM-NMFS-SWFSC-340, 100 p. 

Johanos, T. C. and J. D. Baker (editors). In press. The Hawaiian monk seal in the Northwestern Hawaiian Islands, 

2001. U.S. Dep. Commer., NOAA Tech. Memo. NOAA-TM-NMFS-SWFSC-XXX, XXX p. 

Johanos, T. C. and J. D. Baker (editors). In press. The Hawaiian monk seal in the Northwestern Hawaiian Islands, 

2002. U.S. Dep. Commer., NOAA Tech. Memo. NOAA-TM-NMFS-SWFSC-XXX, XXX p. 

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. 

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. 

Kretzmann, M. B., N. J. Gemmell, and A. Meyer. 2001. Microsatellite analysis of population structure in the 

endangered Hawaiian monk seal. Conserv. Biol. 15(2):457-466. 

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. 

National Marine Fisheries Service. 2002. Biological Opinion for the Management of the Bottomfish and Seamount 

Groundfish Fisheries in the Western Pacific Region According to the Fishery Management Plan for the 

Bottomfish and Seamount Groundfish Fisheries of the Western Pacific Region. 

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. 

Parrish, F.A., K Abernathy, G.J. Marshall, and B.M. Buhleier. 2002. Hawaiian monk seals (Monachus 

schauinslandi) foraging in deepwater coral beds. Mar. Mamm. Science 18:244-258. 

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. 

Pooley, S. G., and K. E. . 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. 

Ragen, T.J. 1999. Human activities affecting the population trends of the Hawaiian monk seal. Pages 183-194 in

J.A. Musick, ed. Life in the slow lane: Ecology and conservation of long-lived marine animals. American 

Fisheries Society Symposium 23, American Fisheries Society, Bethesda, MD. 

Rice, D. W. 1960. Population dynamics of the Hawaiian monk seal. J. Mammal. 41:376-385. 

Stewart, B. S. 2004a. Geographic patterns of foraging dispersion of Hawaiian monk seals (Monachus 

47
schauinslandi) at the Northwestern Hawaiian Islands. Pacific Islands Fisheries Science Center Admin. Rep. 

H-04-05C. 

Stewart, B. S. 2004b. Foraging ecology of Hawaiian monk seals (Monachus schauinslandi) at Pearl and Hermes 

Reef, Northwestern Hawaiian Islands: 1997-1998. Pacific Islands Fisheries Science Center Admin. Rep. H04-03C. 

Stewart, B. S., and P. K. Yochem. 2004a. Dispersion and foraging of Hawaiian monk seals (Monachus 

schauinslandi) near Lisianski and Midway Islands: 2000-2001. Pacific Islands Fisheries Science Center 

Admin. Rep. H_04_04C. 

Stewart, B. S., and P. K. Yochem. 2004b. Use of marine habitats by Hawaiian monk seals (Monachus 

schauinslandi) from Laysan Island: Satellite-linked monitoring in 2001-2002. Pacific Islands Fisheries 

Science Center Admin. Rep. H_04_02C. 

Stewart, B. S., and P. K. Yochem. 2004c. Use of marine habitats by Hawaiian monk seals (Monachus schauinslandi) 

from Kure Atoll: Satellite-linked monitoring in 2001-2002. Pacific Islands Fisheries Science Center 

Admin. Rep. H_04_01C. 

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-OPR12. 93 pp. 

Wade, P. R. 1998. Calculating limits to the allowable human-caused mortality of cetaceans and pinnipeds. Marine 

Mammal Science 14:1-37. 

Wetmore, A. 1925. Bird life among lava rock and coral sand. The Natl. Geograp. Mag. 48:77-108. 

48
Revised 03/15/2005 

HARBOR PORPOISE (Phocoena phocoena): Morro Bay 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 is small-scale subdivision within the U.S. portion of this range (Chivers et al., 2002). 

W128.0 W126.0 W124.0 W122.0 W120.0 W118.0

N34.0

N36.0

N38.0

N40.

N42.

N44.

0

0

0

Oregon

California Northern California/

Southern Oregon

San FranciscoRussian River

Monterey

 Bay

Morro Bay

Cape Blanco

Monterey Bay

Cape Mendocino

Point Conception

Point Arena

Morro Bay

Oregon/Washington

 coast

Russian River

Figure 1. Stock boundaries and distributional range

of harbor porpoise along the California/southern

Oregon coast. Shaded area represents harbor 

porpoise habitat (0-200 m) along the U.S. west

coast. 

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. Based on

recent genetic findings (Chivers et al., 2002), California coast stocks were re-evaluated, and significant

genetic differences were found among 4 identified sampling sites. Revised stock boundaries are presented

here based on these genetic data and density discontinuities identified from aerial surveys, resulting in six

California/Oregon/Washington stocks where previously there had been four (Carretta et al. 2001a). The 

stock boundaries for animals that occur in California/southern Oregon waters are shown in Figure 1. For

the 2004 Marine Mammal Protection Act (MMPA) Stock Assessment Reports, other Pacific coast harbor

porpoise stocks include: 1) a Monterey Bay stock, 2) a San Francisco-Russian River stock, 3) a northern

California/southern Oregon stock, 4) an Oregon/Washington coast stock, 5) an Inland Washington stock,

49
6) a Southeast Alaska stock, 7) a Gulf of Alaska stock, and 8) a Bering Sea stock. Stock assessment reports

for Monterey Bay, San Francisco-Russian River, northern California/southern Oregon, Oregon/Washington

coast, and Inland Washington waters harbor porpoise appear in this volume. The three Alaska harbor

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

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 systematic ship survey of

depth strata out to 90 m in northern California showed that porpoise abundance declined significantly in

waters deeper than 60 m (Carretta et al. 2001b). 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). In 1999 and 2002, aerial surveys extended farther offshore (to the 200m 

depth contour or a minimum of 10 nmi from shore in the region of the Morro Bay stock) to provide a more 

complete abundance estimate. Based on 1999 and 2002 aerial surveys under good survey conditions

(Beaufort #2, cloud cover #25%) the estimate of abundance for this stock is 1,656 animals (CV = 0.39) 

(Carretta and Forney 2004 ).

 

Minimum Population Estimate

The minimum population estimate for the Morro Bay harbor porpoise stock is taken as the lower

20th percentile of the log-normal distribution of the abundance estimated from the 1999-2002 aerial

surveys, or 1,206 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. 

There has been an increasing trend in porpoise abundance in the Morro Bay stock since 1988, which is

statistically significant (p < 0.002), Figure 2. More detailed studies of encounter rate patterns in relation to

satellite-derived sea surface temperature are planned to shed light on potential oceanography-related

movement patterns of harbor porpoise in this region. 

Morro Bay

0

1000

2000

3000

4000

5000

198819891990199119921993199419951996199719981999200020012002

Year

Porpoise Abundance

Figure 2. Aerial survey estimates of abundance for the Morro Bay 

stock of harbor porpoise, 1988-2002. Error bars represent lower 

and upper 95% confidence intervals. Solid line represents a linear 

regression on the natural logarithm of abundance over time. The 

slope of this regression is statistically significant (p < 0.002). 

50
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 Morro Bay harbor porpoise, we use the default 

maximum net productivity rate (RMAX) of 4% for cetaceans (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 (1,206) times one half the default maximum net growth rate for cetaceans (1⁄2 of 4%) times

a recovery factor of 0.4 (for a stock of unknown status with a mortality rate CV $ 0.80; Wade and Angliss 

1997), resulting in a PBR of 10. 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Fishery Information

 The set gillnet fishery for halibut and angel shark has operated in the vicinity of Morro Bay, and 

fishing effort there peaked in 2001. A ban on set gillnets inshore of 60 fathoms from Point Arguello to 

Point Reyes, California, has been in place since September 2002. California Department of Fish and Game 

(CDFG) estimated fishing effort for 1998-2002 in this fishery is 139, 121, 284, 391, and 21 days 

respectively. Mortality rates of harbor porpoise in the set gillnet fishery in this region are available only 

from 43 trips observed between 1990-94 (Julian and Beeson 1998), in which one harbor porpoise was 

killed. This represents a kill rate of 0.023 porpoise/day fished (bootstrap CV = 0.97). Projected mortality 

levels based on this kill rate and effort levels for 1998-2002 are summarized in Table 1. It should be noted 

that this kill rate includes sets made in less than 30 fathoms of water, where the potential to entangle 

porpoise is higher. The white seabass set gillnet fishery also has operated in the vicinity of Morro Bay, 

and this fishery has been documented to take harbor porpoise in the past (Norris and Prescott 1961). Effort 

in the white seabass fishery in the vicinity of Morro Bay for the last five years (1998-2002) has been 26, 7, 

61, 132, and 32 fishing days respectively. Because of the aforementioned depth restrictions for gillnets in 

this region, it is expected that harbor porpoise interactions with the white seabass set gillnet fishery would 

be near zero. 

Table 1. Summary of available information on incidental mortality and injury of harbor porpoise (Morro 

Bay stock) in commercial fisheries that might take this species (Cameron and Forney 2000, Carretta 2001, 

Forney et al., 2001; Carretta 2002, Carretta and Chivers 2003). Mean annual takes are based on 1998-

2002 data unless noted otherwise. 

Fishery Name Year(s) Data Type 

Percent 

Observer 

Coverage

Observed 

Mortality Kill/Day 

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

1998 

1999 

2000 

2001 

2002 

1990-94 

observer data

Fishery closed 

permanently 

in waters < 60 

fathoms 

0% 

0% 

0% 

0% 

- 

- 

- 

- 

- 

0.0231

3 (0.97) 

3 (0.97) 

7 (0.97) 

9 (0.97) 

0.5 (n/a) 

 4.5 (0.97)2

Minimum total annual takes 4.5 (0.97)2

1

Mortality rate is based on 1 observed mortality from 43 observed trips in this region between 1990-94. 2

Mean annual takes are based on 1998-2002 effort data and 1990-94 kill rates.

51
Both of the above central California gillnet fisheries were restricted by a series of emergency 

closures beginning in September 2000, because of concern over mortality of Common Murres and a decline 

in the southern sea otter population. During the emergency closure, fishing was allowed in waters deeper 

than 30 fathoms between Yankee Point (Monterey County) and Pt. Sal (Santa Barbara County) until April 

2002, and fishing effort initially increased within the range of the Morro Bay harbor porpoise stock. A ban 

on the use of gill and trammel nets in all ocean waters 60 fathoms or less between Point Reyes (Marin 

County) and Point Arguello (Santa Barbara County) became effective on September 4, 2002. The ban is 

expected to virtually eliminate bycatch of Morro Bay harbor porpoise in these two gillnet fisheries, because 

this species is primarily found in waters shallower than 60 fathoms. 

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 backprojection. They calculate that the central California population (including Morro Bay, Monterey Bay, and 

San Francisco-Russian River stocks) 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 central California harbor porpoise populations relative to their Optimum Sustainable Population (OSP) 

levels must be treated as unknown. 

 Based on the last 5 years of fishing effort (1998-2002), mean annual takes are 4.5 porpoise per 

year, which is less than the PBR of 10 animals, resulting in a “non-strategic” classification. A set gillnet 

closure inside of 60 fathoms was finalized in September 2002, effectively eliminating set gillnets from 

most harbor porpoise habitat in the region of this stock. This is expected to reduce fishery mortality of 

Morro Bay harbor porpoise to near zero. Although in recent years the average fishery mortality exceeded 

10% of the PBR and, therefore, cannot be considered to be insignificant and approaching zero mortality 

and injury rate, it is likely that this goal will be met following the 2002 gillnet closure. 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. 

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. 

Carretta, J.V. 2001. Preliminary estimates of cetacean mortality in California gillnet fisheries for 2000. 

Paper SC/53/SM9 presented to the International Whaling Commission (unpublished). 21pp. 

Carretta, J.V., J. Barlow, K.A. Forney, M.M. Muto, and J. Baker. 2001a. U.S. Pacific Marine Mammal 

Stock Assessments: 2001. U.S. Dep. Commer. NOAA Technical Memorandum NMFS-SWFSC317. 280pp. 

Carretta, J.V., B.L. Taylor, and S.J. Chivers. 2001b. Abundance and depth distribution of harbor porpoise 

(Phocoena phocoena) in northern California determined from a 1995 ship survey. U.S. Fishery 

Bulletin 99:29-39. 

Carretta, J.V. 2002. Preliminary estimates of cetacean mortality in California gillnet fisheries for 2001. 

Paper SC/54/SM12 presented to the International Whaling Commission (unpublished). 22pp. 

Carretta, J.V. 2003. Preliminary estimates of harbor porpoise abundance in California from 1997 and 1999 

aerial surveys. Southwest Fisheries Science Center Administrative Report LJ-03-04. 12 p. 

52
Carretta, J.V. and S.J. Chivers. 2003. Preliminary estimates of marine mammal mortality and biological 

sampling of cetaceans in California gillnet fisheries for 2002. Paper SC/55/SM3 presented to the 

International Whaling Commission (unpublished). 21pp. 

Carretta, J.V. and K.A. Forney. 2004. Preliminary estimates of harbor porpoise abundance in California 

from 1999 and 2002 aerial surveys. SWFSC Administrative Report LJ-04-01, available from 

Southwest Fisheries Science Center, 8604 La Jolla Shores Drive, La Jolla, CA, USA. 13pp. 

Chivers, S.J., A.E. Dizon, P.J. Gearin, and K.M. Robertson. 2002. Small-scale population structure of 

eastern North Pacific harbour porpoises, (Phocoena phocoena), indicated by molecular genetic 

analyses. Journal of Cetacean Research and Management 4(2):111-122. 

Forney, K.A., D.A. Hanan, and J. Barlow. 1991. Detecting trends in harbor porpoise abundance from 

aerial surveys using analysis of covariance. U.S. Fishery Bulletin 89:367-377. 

Forney, K. A. 1999a. The abundance of California harbor porpoise estimated from 1993-97 aerial linetransect 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 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 of mammal, turtle, and bird mortality for two California gillnet 

fisheries: 1990-1995. U.S. Fishery Bulletin 96:271-284. 

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. 

Norris, K.S. and J.H. Prescott. 1961. Observations on Pacific cetaceans of Californian and Mexican 

waters. Univ. Calif. Publ. Zool. 63(4):291-402. 

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.

53
Revised 03/15/2005 

HARBOR PORPOISE (Phocoena phocoena): Monterey Bay 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

is small-scale subdivision within the U.S. portion of this range (Chivers et al., 2002). 

W128.0 W126.0 W124.0 W122.0 W120.0 W118.0

N34.0

N36.0

N38.0

N40.

N42.

N44.

0

0

0

Oregon

California Northern California/

Southern Oregon

San FranciscoRussian River

Monterey

 Bay

Morro Bay

Cape Blanco

Monterey Bay

Cape Mendocino

Point Conception

Point Arena

Morro Bay

Oregon/Washington

 coast

Russian River

Figure 1. Stock boundaries and distributional

range of harbor porpoise along the 

California/southern Oregon coast. Shaded are

represents harbor porpoise habitat (0-200 m)

along the U.S. west coast.

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. Based on

recent genetic findings (Chivers, et al. 2002), California coast stocks were re-evaluated, and significant

genetic differences were found among 4 identified sampling sites. Revised stock boundaries are presented

here based on these genetic data and density discontinuities identified from aerial surveys, resulting in six

California/Oregon/Washington stocks where previously there had been four (Carretta et al. 2001a). The 

stock boundaries for animals that occur in California/southern Oregon waters are shown in Figure 1. For

the 2003 Marine Mammal Protection Act (MMPA) Stock Assessment Reports, other Pacific coast harbor

porpoise stocks include: 1) a Morro Bay stock, 2) a San Francisco-Russian River stock, 3) a northern

California/southern Oregon stock, 4) an Oregon/Washington coast stock, 5) a Washington Inland waters

54
stock, 6) a Southeast Alaska stock, 7) a Gulf of Alaska stock, and 8) a Bering Sea stock. Stock assessment

reports for Morro Bay, San Francisco-Russian River, northern California/southern Oregon,

Oregon/Washington coast, and Inland Washington waters harbor porpoise appear in this volume. The three

Alaska harbor porpoise stocks are reported separately in the Stock Assessment Reports for the Alaska 

Region. 

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 systematic ship survey of

depth strata out to 90 m in northern California showed that porpoise abundance declined significantly in

waters deeper than 60 m (Carretta et al. 2001b). 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). In 1999 and 2002, aerial surveys extended farther offshore (to the 200m 

depth contour or a minimum of 15 nmi from shore in the region of the Monterey Bay stock) to provide a

more complete abundance estimate. Based on 1999 and 2002 aerial surveys under good survey conditions

(Beaufort #2, cloud cover #25%) the estimate of abundance for this stock is 1,613 animals (CV = 0.42) 

(Carretta and Forney 2004).

 

Minimum Population Estimate

The minimum population estimate for the Monterey Bay harbor porpoise stock is taken as the

lower 20th percentile of the log-normal distribution of the abundance estimated from the 1999-2002 aerial

surveys, or 1,149 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. A linear regression of of the natural logarithm

of abundance over time for the Monterey Bay stock is not statistically significant (p=0.64, Figure 2). More 

detailed studies of encounter rate patterns in relation to satellite-derived sea surface temperature during 

Monterey Bay

0

1000

2000

3000

4000

5000

6000

198819891990199119921993199419951996199719981999200020012002

Year

Porpoise Abundance

Figure 2. Aerial survey estimates of abundance for the Monterey 

Bay stock of harbor porpoise, 1988-2002. Error bars represent

lower and upper 95% confidence intervals. Solid line represents a 

linear regression of the natural logarithm of abundance over time. 

The slope of this regression is not statistically significant (p = 0.64).

55
1993-99 are planned to shed light on potential oceanography-related movement patterns of harbor porpoise 

in this region. 

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 Monterey Bay harbor porpoise, we use the default 

maximum net productivity rate (RMAX) of 4% for cetaceans (Wade and Angliss 1997). 

POTENTIAL BIOLOGICAL REMOVAL

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

population size (1,149) times one half the default maximum net growth rate for cetaceans (1⁄2 of 4%) times

a recovery factor of 0.45 (or a stock of unknown status with a mortality rate CV $0.60 and # 0.80 ; Wade 

and Angliss 1997), resulting in a PBR of 10. 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Fishery Information

 The incidental capture of Monterey Bay harbor porpoise is largely limited to the halibut angel 

shark set gillnet fishery. Detailed information on this fishery is provided in Appendix 1. A summary of 

estimated fishery mortality and injury for this stock of harbor porpoise for 1998-2002 is given in Table 1. 

Mortality estimates for 1998 are based on total estimated fishing effort and prior-year entanglement rate 

data (Julian and Beeson 1998), because no observer program was in place that year. Mortality estimates for 

1999-2001 are based on a National Marine Fisheries Service monitoring program in Monterey Bay 

(Cameron and Forney 2000, Carretta 2001; Carretta 2002, Carretta and Chivers 2003). 

 

Table 1. Summary of available on incidental mortality and injury of harbor porpoise (central CA stock 

1997-98; Monterey Bay stock 1999-2002) in commercial fisheries that might take this species (Cameron 

and Forney 2000, Carretta 2001, Carretta 2002, Forney et al., 2001). Mean annual takes are based on 

2001-2002 data because of fishery restrictions implemented in late 2000. n/a indicates that data are not 

available. 

Fishery Name Year(s) Data Type

Percent 

Observer 

Coverage

Observed

Mortality Kill/Day

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

1998 

1999 

2000 

2001 

2002

1990-94 

observer data

observer 

data 

2000 observer 

data 

Fishery closed 

permanently

0% 

23.0% 

27.0% 

0% 

0%

- 

- 

282

7 

- 

-

- 

- 

0.17 

0.10 

0.10 

0.10

57 (0.19) 

133 (0.23)2

26 (0.50) 

3 (0.77) 

16 (0.77)

 9.5 (0.66)1

Minimum total annual takes 9.5 (0.66)1

1

Only 2001-2002 mortality estimates are included in the average because the fishery was largely closed under emergency regulations 

in September 2000. The closure was made permanent in September 2002. 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). 

56
All central California nearshore gill and trammel net fisheries were restricted by a series of 

emergency closures beginning in September 2000, because of concern over mortality of Common Murres 

and a decline in the southern sea otter population. During the emergency closures, fishing was prohibited 

in waters less than 60 fathoms in the region of the Monterey Bay harbor porpoise stock. There were an 

estimated 156 days of set gillnet fishing effort in Monterey Bay in 2002 following a brief lapse in the 

closure prior to a ban on set gillnets in this region on September 4, 2002. The ban is expected to virtually 

eliminate bycatch of Monterey Bay harbor porpoise in these gillnet fisheries, because this species is 

primarily found in waters shallower than 60 fathoms. Although mortality estimates for the most recent 

five years (1998-2002) are presented in Table 1, average annual takes in the setnet fishery are estimated 

using 2001-2002 data, because the fishery was largely closed under emergency regulations after September 

2000. The closure was made permanent in September 2002. An annual average of 9.5 harbor porpoise 

(CV= 0.66) were killed in this fishery in Monterey Bay from 2001-2002. 

 Twelve fishery-related stranding mortalities of harbor porpoise were documented within the range 

of the Monterey Bay harbor porpoise stock between 1998 and 2002: 1998(1); 1999(2); 2000 (2); 2001 (2) 

and 2002 (5). The five strandings in 2002 occurred during March and April, prior to a September ban on 

gillnets inshore of 60 fathoms in this region. These mortalities probably originated from the halibut set 

gillnet fishery in Monterey Bay, and are thus accounted for in the mortality estimates for this fishery. 

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 backprojection. 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 annual mortality for 2001, after implementation of the emergency closure for central 

California gillnet fisheries, was 9.5 harbor porpoise, which is less than the calculated PBR (10) for 

Monterey Bay harbor porpoise; therefore, the Monterey Bay harbor porpoise population is not considered 

“strategic” under the MMPA. A permanent set gillnet closure inside of 60 fathoms was implemented in 

September 2002, effectively eliminating set gillnets from most harbor porpoise habitat in the region of this 

stock. This is expected to virtually eliminate gillnet mortality of Monterey Bay harbor porpoise. Although 

in recent years the average fishery mortality exceeded the PBR and, therefore, cannot be considered to be 

insignificant and approaching zero mortality and injury rate, it is likely that this goal will be met following 

the 2002 permanent gillnet closure. 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. 

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. 

Carretta, J.V. 2001. Preliminary estimates of cetacean mortality in California gillnet fisheries for 2000. 

Paper SC/53/SM9 presented to the International Whaling Commission (unpublished). 21 pp. 

Carretta, J.V. 2002. Preliminary estimates of cetacean mortality in California gillnet fisheries for 2001. 

Paper SC/54/SM12 presented to the International WhalingCommission(unpublished). 22pp. 

57
Carretta, J.V. and S.J. Chivers. 2003. Preliminary estimates of marine mammal mortality and biological 

sampling of cetaceans in California gillnet fisheries for 2002. Paper SC/55/SM3 presented to the 

International Whaling Commission (unpublished). 21pp. 

Carretta, J.V., Barlow, J., K.A. Forney, M.M. Muto, and J. Baker. 2001a. U.S. Pacific Marine Mammal 

Stock Assessments: 2001. U.S. Dep. Commer. NOAA Technical Memorandum NMFS-SWFSC317. 280pp. 

Carretta, J.V., B.L. Taylor, and S.J. Chivers. 2001b. Abundance and depth distribution of harbor porpoise 

(Phocoena phocoena) in northern California determined from a 1995 ship survey. U.S. Fishery 

Bulletin 99:29-39. 

Carretta, J.V. 2003. Preliminary estimates of harbor porpoise abundance in California from 1997 and 1999 

aerial surveys. Southwest Fisheries Science Center Administrative Report LJ-03-04. 12 p. 

Carretta, J.V. and K.A. Forney. 2004. Preliminary estimates of harbor porpoise abundance in California 

from 1999 and 2002 aerial surveys. SWFSC Administrative Report LJ-04-01, available from 

Southwest Fisheries Science Center, 8604 La Jolla Shores Drive, La Jolla, CA, USA. 13pp. 

Chivers, S.J., A.E. Dizon, P.J. Gearin, and K.M. Robertson. 2002. Small-scale population structure of 

eastern North Pacific harbour porpoises, (Phocoena phocoena), indicated by molecular genetic 

analyses. Journal of Cetacean Research and Management 4(2):111-122. 

Forney, K. A. 1999a. The abundance of California harbor porpoise estimated from 1993-97 aerial linetransect 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 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
Revised 03/15/2005 

HARBOR PORPOISE (Phocoena phocoena): 

San Francisco-Russian River 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 is small-scale

subdivision within the U.S. portion of this range (Chivers et al., 2002). 

W128.0 W126.0 W124.0 W122.0 W120.0 W118.0

N34.0

N36.0

N38.0

N40.0

N42.0

N44.0

Oregon

California Northern California/

Southern Oregon

San FranciscoRussian River

Monterey

 Bay

Morro Bay

Cape Blanco

Monterey Bay

Cape Mendocino

Point Conception

Point Arena

Morro Bay

Oregon/Washington

 coast

Russian River

Figure 1. Stock boundaries and distributional

range of harbor porpoise along the California and 

southern Oregon coast. Shaded area represents

harbor porpoise habitat (0-200 m) along the U.S.

west coast.

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. Based on

recent genetic findings (Chivers et al., 2002), California coast stocks were re-evaluated, and significant

genetic differrences were found among 4 identified sampling sites. Revised stock boundaries are presented

here based on these genetic data and density discontinuities identified from aerial surveys, resulting in six

California/Oregon/Washington stocks where previously there had been four (Carretta et al. 2001a). The 

stock boundaries for animals that occur in California/southern Oregon waters are shown in Figure 1. For

the 2002 Marine Mammal Protection Act (MMPA) Stock Assessment Reports, other Pacific coast harbor

59
porpoise stocks include: 1) a Morro Bay stock, 2) a Monterey Bay stock, 3) a northern California/southern

Oregon stock, 4) an Oregon/Washington coast stock, 5) an Inland Washington stock, 6) a Southeast Alaska

stock, 7) a Gulf of Alaska stock, and 8) a Bering Sea stock. Stock assessment reports for Morro Bay,

Monterey Bay, northern California/southern Oregon, Oregon/Washington coast, and Inland Washington

waters harbor porpoise appear in this volume. The three Alaska harbor porpoise stocks are reported 

separately in the Stock Assessment Reports for the Alaska Region. 

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 systematic ship survey of

depth strata out to 90 m in northern California showed that porpoise abundance declined significantly in

waters deeper than 60 m (Carretta et al. 2001b). 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). In 1999 and 2002, aerial surveys extended farther offshore (to the 200m 

depth contour or a minimum of 15 nmi from shore in the region of the San Francisco-Russian River stock)

to provide a more complete abundance estimate. Although two harbor porpoise sightings were 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 abundance estimate for this stock. Based on 1999-2002 aerial surveys

under good survey conditions (Beaufort #2, cloud cover #25%) the estimate of abundance for this stock is

8,521 animals (CV = 0.38) (Carretta and Forney 2004).

 

Minimum Population Estimate

The minimum population estimate for the San Francisco-Russian River harbor porpoise stock is

taken as the lower 20th percentile of the log-normal distribution of the abundance estimated from 1999-

2002 aerial surveys, or 6,254 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

Figure 2. Aerial survey estimates of abundance for the San 

Fr o-Russian River stock of harbor porpoise, 1988-2002. 

Er o rs represent lower and upper 95% confidence intervals. 

So e represents a linear regression of the natural logarithm of

a n ce over time. The slope of this regression is not

statistically significant (p = 0.24). 

ancisc

r r ba

lid lin

bu dan

San Francisco - Russian River

0

5000

10000

15000

20000

25000

198819891990199119921993199419951996199719981999200020012002

Year

Porpoise Abundance

Figure 2. Aerial survey estimates of abundance for the San 

Francisco-Russian River stock of harbor porpoise, 1988-2002. 

Error bars represent lower and upper 95% confidence intervals.

Solid line represents a linear regression of the natural logarithm 

over time. The slope of this regression line is not statistically

significant (p=0.24). 

60
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. Abundance of the San Francisco - Russian 

River harbor porpoise stock appeared to be stable or declining between 1988-1991 and has steadily 

increased since 1993. The slope of the linear regression on the natural logarithm of abundance over time is 

not statistically significant (p = 0.24, Figure 2). More detailed studies of encounter rate patterns in relation 

to satellite-derived sea surface temperature are planned to shed light on potential oceanography-related 

movement patterns of harbor porpoise in this region. 

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, we use the 

default maximum net productivity rate (RMAX) of 4% for cetaceans (Wade and Angliss 1997). 

POTENTIAL BIOLOGICAL REMOVAL

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

population size (6,254) times one half the default maximum net growth rate for cetaceans (1⁄2 of 4%) times

a recovery factor of 0.5 (for a species of unknown status; Wade and Angliss 1997), resulting in a PBR of 

63. 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Fishery Information

 The incidental capture of harbor porpoise in California has largely been limited to set gillnet 

fisheries in Monterey Bay and to a lesser extent, Morro Bay. Coastal setnets are not allowed north of 

Bodega Head (to protect salmon resources there). However, two harbor porpoise strandings near Bodega 

Head in 1998, one inside San Francisco Bay in 1998, and one near Montara, San Mateo County in 2001 

were attributed to fishery-related mortality, but the responsible fishery is unknown. Although the stranding 

locations fall within the range of the San Francisco-Russian River harbor porpoise stock and this is 

probably the source stock for the mortalities, it is possible that some of these animals were taken from the 

northern California/southern Oregon stock and subsequently drifted southward to the stranding location. A 

ban on set gillnets inshore of 60 fathoms from Point Reyes south to Point Arguello, California has been in 

place since September 2002. 

Table 1. Summary of available information on incidental mortality and injury of harbor porpoise (San 

Francisco-Russian River stock) in commercial fisheries that might take this species. Mean annual takes are 

based on 1998-2002 data unless noted otherwise. n/a indicates that data are not available. 

Fishery Name Year(s) Data 

Type

Percent 

Observer 

Coverage

Observed 

Mortality

Kill/Day Estimated 

Mortality (CV in 

parentheses)

Mean Annual 

Takes (CV in 

parentheses)

Unknown 

fishery 1998-2002

stranding n/a 3 (in 1998) 

1 in 2001

n/a

$0.8 (n/a)

Minimum total annual takes

$0.8 (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. Barlow and Hanan (1995) calculate 

the status of harbor porpoise relative to historic carrying capacity (K) using a technique called backprojection. They calculate that the central California population (including Morro Bay, Monterey Bay, and 

61
San Francisco-Russian River stocks) 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 central California harbor porpoise populations relative to their Optimum Sustainable Population (OSP) 

levels must be treated as unknown. There are no known habitat issues that are of particular concern for this 

stock. Because the known human-caused mortality or serious injury (0.8 harbor porpoise per year) is less 

than the PBR (63), 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. 

Carretta, J.V., J. Barlow, K.A. Forney, M.M. Muto, and J. Baker. 2001a. U.S. Pacific Marine Mammal 

Stock Assessments: 2001. U.S. Dep. Commer. NOAA Technical Memorandum, NOAA-TMNMFS-SWFSC-317. 280 p. 

Carretta, J.V., B.L. Taylor, and S.J. Chivers. 2001b. Abundance and depth distribution of harbor porpoise 

(Phocoena phocoena) in northern California determined from a 1995 ship survey. U.S. Fishery 

Bulletin 99:29-39. 

Carretta, J.V. 2003. Preliminary estimates of harbor porpoise abundance in California from 1997 and 1999 

aerial surveys. Southwest Fisheries Science Center Administrative Report LJ-03-04. 12 p. 

Carretta, J.V. and K.A. Forney. 2004. Preliminary estimates of harbor porpoise abundance in California 

from 1999 and 2002 aerial surveys. SWFSC Administrative Report LJ-04-01, available from 

Southwest Fisheries Science Center, 8604 La Jolla Shores Drive, La Jolla, CA, USA. 13pp. 

Chivers, S.J., A.E. Dizon, P.J. Gearin, and K.M. Robertson. 2002. Small-scale population structure of 

eastern North Pacific harbour porpoises, (Phocoena phocoena), indicated by molecular genetic 

analyses. Journal of Cetacean Research and Management 4(2):111-122. 

Forney, K. A. 1999a. The abundance of California harbor porpoise estimated from 1993-97 aerial linetransect 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 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. 

62
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. 

63
Revised 10/31/2002 

HARBOR PORPOISE (Phocoena phocoena): 

Northern California/Southern Oregon 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 is small-scale subdivision within the U.S. portion of this range

Chivers et al., in press). 

W128.0 W126.0 W124.0 W122.0 W120.0 W118.0

N34.0

N36.0

N38.0

N40.

N42.

N44.

0

0

0

Oregon

California Northern California/

Southern Oregon

San FranciscoRussian River

Monterey

 Bay

Morro Bay

Cape Blanco

Monterey Bay

Cape Mendocino

Point Conception

Point Arena

Morro Bay

Oregon/Washington

 coast

Russian River

Figure 1. Stock boundaries and distributional

range of harbor porpoise along the 

California/southern Oregon coast. Shaded area

represents harbor porpoise habitat (0-200 m)

along the U.S. west coast.

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. Based on

recent genetic findings (Chivers et al., in press), California coast stocks were re-evaluated and significant 

genetic differences were found among four identified sampling sites. Revised stock boundaries are 

presented here based on these genetic data and density discontinuities identified from aerial surveys, 

resulting in six west coast stocks where previously there had been four (Carretta et al. 2001a). These new

stock boundaries are shown in Figure 1. For the 2002 Marine Mammal Protection Act (MMPA) Stock 

64
Assessment Reports, other Pacific coast harbor porpoise stocks include: 1) a Morro Bay stock, 2) a

Monterey Bay stock, 3) a San Francisco-Russian River stock, 4) an Oregon/Washington coast stock, 5) an

Inland Washington stock, 6) a Southeast Alaska stock, 7) a Gulf of Alaska stock, and 8) a Bering Sea 

stock. The stock assessment reports for Morro Bay, Monterey Bay, and San Francisco-Russian River,

harbor porpoise appear in this volume. The three Alaska harbor porpoise stocks are reported separately in

the Stock Assessment Reports for the Alaska Region. 

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 systematic ship survey of

depth strata out to 90 m in northern California showed that porpoise abundance declined significantly in

waters deeper than 60 m (Carretta et al. 2001b). 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 1997-99 aerial survey data including data from both

inshore and offshore areas, an updated estimate of abundance for the northern California/southern Oregon 

harbor porpoise stock is 17,763 harbor porpoise (CV=0.39). Approximately 1,572 (CV=0.86) porpoise 

were estimated in the northern California offshore stratum (SWFSC, unpublished data); 11,135 (CV= 0.38) 

in the northern California inshore stratum (SWFSC, unpublished data); 4,808 (CV = 0.49) from southern

Oregon Area VI (Laake et al. 1998), and 250 (CV = 1.09) animals from southern Oregon Area VIF (Laake 

et al. 1998). 

Minimum Population Estimate

The minimum population

estimate for harbor porpoise in

northern California/southern

Oregon is taken as the lower 20th

percentile of the log-normal

distribution of the abundance

estimated from 1997-99 aerial

surveys in northern California and

1997 aerial surveys in southern 

Oregon, or 12,940 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

mines

nds i

Forney (1999b) exa

tre n 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). 

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 central 

California (Pt. Conception to Russian River) harbor porpoise, 

1986-99, adjusted for sea state and cloud cover (following 

methods of Forney 1995). The trend shown includes the range of

three California stocks (Morro Bay, Monterey Bay, and SanFrancisco-Russian River. 

65
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, we use the 

default maximum net productivity rate (RMAX) of 4% for cetaceans (Wade and Angliss 1997). 

POTENTIAL BIOLOGICAL REMOVAL

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

population size (12,940) 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 259. 

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 for the Klamath River tribal salmon 

gillnet fishery in 1995 (NMFS, Southwest Region, unpublished data). There have been no observed harbor 

porpoise mortalities or fishery-related strandings in the Klamath River tribal salmon gillnet fishery for the 

most recent five-year period (1996-2000) (pers. comm., Kathleen Williamson, Yurok tribe biologist). 

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

1996-

2000 Observation n/a 0 $0 $0

Minimum total annual takes

$0

 

STATUS OF STOCK

 Harbor porpoise in northern California/southern Oregon 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 harbor porpoise per year) is less than the PBR (259), 

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. 

66
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. 

Carretta, J.V. J. Barlow, K.A. Forney, M.M. Muto, and J. Baker. 2001a. U.S. Pacific Marine Mammal 

Stock Assessments: 2001. U.S. Dep. Commer. NOAA Technical Memorandum, NOAA-TMNMFS-SWFSC-317. 280p. 

Carretta, J.V., B.L. Taylor, and S.J. Chivers. 2001b. Abundance and depth distribution of harbor porpoise 

(Phocoena phocoena) in northern California determined from a 1995 ship survey. U.S. Fishery 

Bulletin 99:29-39. 

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 linetransect 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 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. 

Laake, J., J. Calambokidis, S. Osmek. 1998. Survey report for the 1997 aerial surveys for harbor porpoise 

and other marine mammals of Oregon, Washington, and British Columbia outside waters. Alaska 

Fisheries Science Center Processed Report 98-10. pp. 77-97. 

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. 

67
Revised 12/15/2003 

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 waters 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. 

WA Inland

Waters stock

OR/WA

Coast

stock

Northern CA/

Southern OR

stock

Cape Blanco

Figure 1. Approximate distribution of harbor

porpoise in the U.S. Pacific Northwest (shaded

area). Stock boundaries separating the stocks

are shown.

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 waters, a specific stock boundary line cannot be identified based upon biological or genetic differences.

However, harbor porpoise movements and rates of intermixing within the eastern North Pacific are restricted, and 

there has been a significant decline in harbor porpoise sightings within southern Puget Sound since the 1940s;

therefore, following a risk averse management strategy, two stocks are recognized: the Oregon/Washington Coast

stock (between Cape Blanco, OR, and Cape Flattery, WA) and the Washington Inland Waters stock (in waters east

of Cape Flattery) (see Fig. 1). Recent genetic evidence suggests that the population of eastern North Pacific harbor 

68
porpoise is more finely structured than is currently recognized (Chivers et al. 2002). 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 

recognized in California, with the stock boundary at the Russian River. Based on recent genetic findings (Chivers et 

al. 2002), California coast stocks were re-evaluated and significant genetic differences were found among four 

identified sampling sites. Revised stock boundaries based on these genetic data and density discontinuities 

identified from aerial surveys resulted in six California/Oregon/Washington stocks where previously there had been 

four (Carretta et al. 2001): 1) the Washington Inland Waters stock, 2) the Oregon/Washington Coast stock, 3) the 

Northern California/Southern Oregon stock, 4) the San Francisco-Russian River stock, 5) the Monterey Bay stock, 

and 6) the Morro Bay stock. This report considers only the Oregon/Washington Coast stock. Stock assessment 

reports for the Washington Inland Waters, Northern California/Southern Oregon, San Francisco-Russian River, 

Monterey Bay, and Morro Bay harbor porpoise stocks appear 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 11,599 (CV=0.115) harbor 

porpoise in U.S. waters north of Cape Blanco, OR (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 (north of Cape Blanco) and Washington waters is 39,586 (CV=0.384). This 

estimate represents a substantial increase over the 1991 estimate of 26,175 (Osmek et al. 1996), even though it 

excludes the area south of Cape Blanco, 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 39,586 and its associated CV(N) of 0.384, NMIN for the Oregon/Washington Coast stock of harbor porpoise is 

28,967. 

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 

(28,967) 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 290 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. 

69
 NMFS observers monitored the northern Washington marine set gillnet fishery in 1997, 1998, and 2000. 

There was no observer coverage in 1999 or 2001; the total fishing effort was 4 and 46 net days, respectively, in 

those years and occurred only in inland waters (Gearin et al. 1994, 2000; P. Gearin, unpubl. data). For the entire 

area fished (coastal + inland waters), observer coverage ranged from approximately 40 to 98% during observed 

years. Fishing effort is conducted within the range of both harbor porpoise stocks (Oregon/Washington Coast and 

Washington Inland Waters stocks) occurring in Washington State waters. 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 Washington Inland 

Waters 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, WA, and north of Cape 

Blanco, OR), where observer coverage was 100% in 1997 and 2000. No fishing effort occurred in the coastal 

portion of the fishery in 1998, 1999, or 2001. The mean estimated mortality for this fishery is 3.2 (CV=0.79) 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 1997-2001 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 in coastal waters: 

areas 4 and 4A)

97 

98 

99 

00

01

obs data

100% 

no fishery 

no fishery 

100% 

no fishery

13 

0 

0 

3

0

13 

0 

0 

3

0

3.2 (0.79)

Estimated total annual takes 3.2 (0.79)

 In 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). In 1997, 96% of the sets were equipped with acoustic alarms and 13 

mortalities were observed (Gearin et al. 2000; P. Gearin, unpubl. data). Harbor porpoise were displaced by an 

acoustic buffer around the alarmed nets, 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). However, the acoustic alarms 

did not appear to affect the target catch (chinook salmon and sturgeon) in the fishery (Gearin et al. 2000). 

 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 1997 and 2001, 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. Logbook data are available for part of 1989-1994, after which incidental 

mortality reporting requirements were modified. Under the new system, logbooks are no longer required; instead, 

fishers provide self-reports. Data for the 1994-1995 phase-in period is fragmentary. After 1995, the level of 

reporting dropped dramatically, such that the records are considered incomplete and estimates of mortality based on 

them represent minimums (see Appendix 7 in Angliss et al. 2001 for details). 

 There have been no fishery-related strandings of harbor porpoise from this stock dating back to at least 

1990 (B. Norberg, pers. comm.). 

Other Mortality

 According to Northwest Marine Mammal Stranding Network records, maintained by the NMFS Northwest 

Region, no human-caused harbor porpoise mortalities or serious injuries were reported from non-fisheries sources in 

1997-2001. 

70
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 (3.2) does not exceed the PBR (290). Therefore, the Oregon/Washington Coast stock of harbor 

porpoise is not classified as “strategic.” The total fishery mortality and serious injury for this stock (3.2: based on 

observer data) is not known to exceed 10% of the calculated PBR (29) 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

Angliss, R. P., D. P. DeMaster, and A. L. Lopez. 2001. Alaska marine mammal stock assessments, 2001. U.S. 

Dep. Commer., NOAA Tech. Memo. NMFS-AFSC-124. 203 pp. 

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. 

Carretta, J. V., J. Barlow, K. A. Forney, M. M. Muto, and J. Baker. 2001. U.S. Pacific Marine Mammal Stock 

Assessments: 2001. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-SWFSC-317. 280 pp. 

Chivers, S. J., A. E. Dizon, P. J. Gearin, and K. M. Robertson. 2002. Small-scale population structure of eastern 

North Pacific harbour porpoises (Phocoena phocoena) indicated by molecular genetic analyses. J. 

Cetacean Res. Manage. 4(2):111-122. 

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. 

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. 

71
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. 

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. 

Norberg, B. National Marine Fisheries Service, Northwest Region, 7600 Sand Point Way NE, Seattle, WA 98115. 

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 porpoise, 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-OPR12. 93 pp. 

72
Revised 12/15/2003

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 waters 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. 

WA Inland

Waters stock

OR/WA

Coast

stock

Northern CA/

Southern OR

stock

Cape Blanco

Figure 2. Approximate distribution of

harbor porpoise in the U.S. Pacific 

Northwest (shaded area). Stock boundaries

separating the stocks are shown.

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 waters, a specific stock boundary line cannot be identified based upon biological or genetic differences.

However, harbor porpoise movements and rates of intermixing within the eastern North Pacific are restricted, and 

there has been a significant decline in harbor porpoise sightings within southern Puget Sound since the 1940s;

therefore, following a risk averse management strategy, two stocks are recognized: the Oregon/Washington Coast

stock (between Cape Blanco, OR, and Cape Flattery, WA) and the Washington Inland Waters stock (in waters east

of Cape Flattery) (see Fig. 1). Recent genetic evidence suggests that the population of eastern North Pacific harbor 

73
porpoise is more finely structured than is currently recognized (Chivers et al. 2002). 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 

recognized in California, with the stock boundary at the Russian River. Based on recent genetic findings (Chivers et 

al. 2002), California coast stocks were re-evaluated and significant genetic differences were found among four 

identified sampling sites. Revised stock boundaries based on these genetic data and density discontinuities 

identified from aerial surveys resulted in six California/Oregon/Washington stocks where previously there had been 

four (Carretta et al. 2001): 1) the Washington Inland Waters stock, 2) the Oregon/Washington Coast stock, 3) the 

Northern California/Southern Oregon stock, 4) the San Francisco-Russian River stock, 5) the Monterey Bay stock, 

and 6) the Morro Bay stock. This report considers only the Washington Inland Waters stock. Stock assessment 

reports for the Oregon/Washington Coast, Northern California/Southern Oregon, San Francisco-Russian River, 

Monterey Bay, and Morro Bay harbor porpoise stocks appear 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 Washington Inland Waters 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 Washington 

Inland Waters 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 Washington Inland Waters 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 Washington Inland Waters 

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 Washington inland waters. 

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 Washington Inland Waters harbor 

porpoise stock. 

74
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.

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Fisheries Information

 NMFS observers monitored the northern Washington marine set gillnet fishery in 1997, 1998, and 2000; 

there was no observer coverage in 1999 or 2001 (Gearin et al. 1994, 2000; P. Gearin, unpubl. data). For the entire 

area fished (coastal + inland waters), observer coverage ranged from approximately 40 to 98% during observed 

years. Fishing effort is conducted within the range of both harbor porpoise stocks (Oregon/Washington Coast and 

Washington Inland Waters stocks) occurring in Washington State waters. 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 Washington Inland 

Waters 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 Washington Inland Waters stock (those waters east of Cape Flattery), where observer coverage ranged from 

40 to 80% between 1997 and 2001 and fishing effort ranged from 4-46 net days per year (1 net day equals a 100-

fathom length net set for 24 hours). There was no observer program in 1999 or 2001; the total fishing effort was 4 

and 46 net days (respectively) in those years, it occurred only in inland waters, and no harbor porpoise takes were 

reported. No mortalities were observed in the inland portion of the fishery between 1997 and 2001, thus, 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 nontreaty 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 that it 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. 

75
Table 1. Summary of incidental mortality of harbor porpoise (Washington Inland Waters 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 1997-2001 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 in inland waters: 

areas 4B and 5)

97 

98 

99 

00

01

obs data

80% 

40% 

0% 

58%

0%

0 

0 

n/a 

0 

n/a

0 

0 

n/a 

0 

n/a

01

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 nontreaty sockeye salmon gillnet 

(areas 7 and 7A)

94 obs data 7% 1 15 15 (1.0)

Unknown Puget Sound fishery 97-01 strand 

data 0, 0, 0, 1, 0 ≥0.2 (n/a)

Minimum total annual takes ≥15.2 (1.0)

1

1997-98 and 2000 mortality estimates are included in the average.

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 unobserved segments of this fishery. Therefore, 15 is an underestimate of the harbor porpoise mortality due 

to the entire fishery. Although the percentage of the overall Washington Puget Sound Region salmon set/drift 

gillnet fishery effort that was observed in 1994 was not quantified, 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.). Since the Washington Inland Waters stock of harbor 

porpoise occurs primarily in the Strait of Juan de Fuca and the San Juan Islands, it is unlikely that many harbor 

porpoise are taken in other areas of the Washington Puget Sound Region salmon gillnet fishery (i.e., Hood Canal 

and southern Puget Sound). Harbor porpoise takes in the Washington Puget Sound Region salmon drift gillnet 

fishery are unlikely to have increased since the fishery was last observed in 1994, due to reductions in the number of 

participating vessels and available fishing time (see details in Appendix 1). Fishing effort and catch have declined 

throughout all salmon fisheries in the region due to management efforts to recover ESA-listed salmonids. 

 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 2001, there were no fisher self-reports of harbor porpoise mortalities from the 

Washington Puget Sound Region salmon set/drift gillnet fishery. Unlike the 1994 observer program data, the self76
reported fisheries data cover the entire fishery. 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 of harbor porpoise mortality. Logbook data are available for part of 1989-1994, after which incidental 

mortality reporting requirements were modified. Under the new system, logbooks are no longer required; instead, 

fishers provide self-reports. Data for the 1994-1995 phase-in period is fragmentary. After 1995, the level of 

reporting dropped dramatically, such that the records are considered incomplete and estimates of mortality based on 

them represent minimums (see Appendix 7 in Angliss et al. 2001 for details). 

 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. One fishery-related stranding of a harbor porpoise occurred 

in 2000 (B. Norberg, pers. comm.). As the stranding could not be attributed to a particular fishery, it has been 

included in Table 1 as occurring in an unknown Puget Sound fishery. Fishery-related strandings during 1997-2001 

resulted in an estimated annual mortality of 0.2 harbor porpoise 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). 

 Although, commercial gillnet fisheries in Canadian waters are known to have taken harbor porpoise in the 

past (Barlow et al. 1994, Stacey et al. 1997), few data are available because the fisheries were not monitored. In 

2001, the Department of Fisheries and Oceans, Canada, conducted a federal fisheries observer program and a survey 

of license holders to estimate the incidental mortality of harbor porpoise in selected salmon fisheries in southern 

British Columbia (Hall et al. 2002). Based on the observed bycatch of porpoise (2 harbor porpoise mortalities) in 

the 2001 fishing season, the estimated mortality for southern British Columbia in 2001 was 20 porpoise per 810 boat 

days fished or a total of 80 harbor porpoise. However, it is not known how many harbor porpoise from the 

Washington Inland Waters stock are currently taken in the waters of southern British Columbia. 

 The minimum estimated fishery mortality and serious injury for this stock is 15.2 harbor porpoise per year, 

based on observer program data (15) and stranding data (0.2) in U.S. waters. 

Other Mortality

 According to Northwest Marine Mammal Stranding Network records, maintained by the NMFS Northwest 

Region, one human-caused harbor porpoise mortality was reported from non-fisheries sources in 1997-2001. An 

animal was struck by a ship in 2001, resulting in an estimated mortality of 0.2 harbor porpoise per year from this 

stock. 

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 total level of human-caused mortality and 

serious injury (15.2 + 0.2 = 15.4) is not known to exceed the PBR (20). Therefore, the Washington Inland Waters 

harbor porpoise stock is not classified as “strategic.” The minimum total fishery mortality and serious injury for this 

stock (15.2) 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. 

 This stock is not recognized as “strategic,” however, the estimated take level is close to the PBR. The 

mortality rate is based on observer data from a subset of the Washington Puget Sound Region salmon set/drift gillnet 

fishery. Evaluation of the estimated take level is complicated by a lack of knowledge about the extent to which 

harbor porpoise from U.S. waters frequent the waters of British Columbia, and are therefore subject to fisheryrelated mortality. Given that the estimated take level is from 1994, it is appropriate to consider whether the current 

take level is different. No new information is available about mortality per set, but 1) fishing effort has decreased in 

recent years and 2) preliminary analysis of data from vessel (1999, 2002) and aerial (2002) surveys indicates that 

abundance and range have not declined since 1996. 

REFERENCES

Angliss, R. P., D. P. DeMaster, and A. L. Lopez. 2001. Alaska marine mammal stock assessments, 2001. U.S. 

Dep. Commer., NOAA Tech. Memo. NMFS-AFSC-124. 203 pp. 

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. 

77
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. 

Carretta, J. V., J. Barlow, K. A. Forney, M. M. Muto, and J. Baker. 2001. U.S. Pacific Marine Mammal Stock 

Assessments: 2001. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-SWFSC-317. 280 pp. 

Chivers, S. J., A. E. Dizon, P. J. Gearin, and K. M. Robertson. 2002. Small-scale population structure of eastern 

North Pacific harbour porpoises (Phocoena phocoena) indicated by molecular genetic analyses. J. 

Cetacean Res. Manage. 4(2):111-122. 

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. 

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. 

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. 

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. 

Hall, A., G. Ellis, and A. W. Trites. 2002. Harbour porpoise interactions with the 2001 selective salmon fisheries in 

southern British Columbia and license holder reported small cetacean by-catch. Unpubl. report. Selective 

Salmon Fisheries Science Program, Fisheries and Oceans Canada. 51 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. 

78
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. 

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. 48 pp. 

Norberg, B. National Marine Fisheries Service, Northwest Region, 7600 Sand Point Way NE, Seattle, WA 98115. 

Northwest Indian Fisheries Commission (NWIFC). 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) and U.S. Fish and Wildlife Service. 

Unpubl. report. 41 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 porpoise, 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 nontreaty 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. 

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. 

Scheffer, V. B., and J. W. Slipp. 1948. The whales and dolphins of Washington State with a key to the cetaceans of 

the west coast of North America. Am. Midl. Nat. 39(2):257_337. 

Scordino, J. National Marine Fisheries Service, Northwest Region, 7600 Sand Point Way NE, Seattle, WA 98115. 

Stacey, P. J., R. W. Baird, and D. A. Duffus. 1997. A preliminary evaluation of incidental mortality of small 

cetaceans in coastal fisheries in British Columbia, Canada. Mar. Mammal Sci. 13:321-326. 

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-OPR12. 93 pp. 

79
Revised 12/15/2003

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 well-documented, 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, noncontiguous areas: 1) waters off California, Oregon

and Washington (this report), and 2) Alaskan

waters. 

W132 W129 W126 W123 W120 W117

N3

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). Two summer/fall shipboard surveys were conducted within

300 nmi of the coasts of California Oregon and Washington in 1996 (Barlow 1997) and 2001 (Barlow 

2003). 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

1996-2001 weighted average abundance estimate for California, Oregon and Washington waters based on

two ship surveys is 98,617 (CV = 0.33) Dall’s porpoise (Barlow 2003). Additional aerial surveys were 

conducted in the inland waters of Washington in 1996, resulting in Dall’s porpoise abundance estimates of

900 (CV=0.40) (Calambokidis et al. 1997). This estimate includes approximate correction factors for

animals missed due to perception and availability bias. Combining the 1996 estimate for inland

0

N34

N38

N42

N46

WASHINGTON

OREGON

CALIFORNIA

Figure 1. Dall’s porpoise sightings based on

aerial and shipboard surveys off California,

Oregon, and Washington, 1991-2001 (see 

Appendix 2 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. Key: •

= summer/autumn ship-based sightings and + = 

winter/spring aerial-based sightings. 

80
Washington waters with the 1996-2001 outer coast estimate from NMFS ship surveys yields a total 

abundance estimate of 99,517 (CV=0.33) Dall’s porpoise for the California/Oregon/Washington stock. 

Minimum Population Estimate

 The log-normal 20th percentile of the 1996-2001 weighted average abundance estimate for both 

the outer coast of California, Oregon and Washington and inland Washington waters is 75,915 Dall's 

porpoise. 

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 (75,915) 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 and a mortality rate CV>0.30 and #0.60; Wade 

and Angliss 1997), resulting in a PBR of 729 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, 1997-2001 

(Cameron and Forney 1999, 2000; Carretta 2001, 2002). 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 20031999). 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. Mean annual takes in 

Table 1 are based on 1997-2001 data. This results in an average estimate of four (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 animals from this 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. Previous efforts to 

convert the Mexican swordfish driftnet fishery to a longline fishery have resulted in a mixed-fishery, with 

20 vessels alternately using longlines or driftnets, 23 using driftnets only, 22 using longlines only, and 

seven with unknown gear type (Berdegué 2002). 

 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 1997 and 2001, with 66%-96% of the fishing effort observed, six Dall’s porpoise were 

reported killed in the at-sea processing portion of the Pacific whiting trawl fishery, and two animals were 

reported in unmonitored hauls. Based only on the systematically observed hauls, Dall’s porpoise mortality 

was estimated to be ten (CV=0.69) in 1997, three (CV= 0.40) in 1998, and one (CV = n/a) in 1999 (Perez, 

81
in prep). Combining these estimates with the two reported mortalities for 1997 and 1998 that are not 

accounted for in the estimates, the minimum average annual mortality for 1997-2001 is 3.2 (CV=0.50) 

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 

1997-2001 (7 animals) is estimated to be less than the PBR (729), 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.

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 1997-2001 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 

1997 

1998 

1999 

2000 

2001 

23.0% 

20.0% 

20.0% 

22.9% 

20.4% 

4 

0 

0 

0 

0 

20 (0.95) 

0 

0 

0 

0 

4 (0.95) 

WA/OR/CA domestic 

groundfish trawl fisheries 

(At-sea processing Pacific 

whiting fishery only). 

observer data 

1997 

1998 

1999 

2000 

2001 

65.7% 

77.3% 

68.6% 

80.6% 

96.2% 

3 

2 

1 

0 

0 

10 (0.69) 

3 (0.40) 

1 ( n/a ) 

0 

0 

2.8 (0.50) 

Minimum total annual takes 7 (0.58) 

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. 2003. Field experiments show that acoustic pingers reduce marine mammal 

bycatch in the California drift gillnet fishery. Marine Mammal Science 19(2):265-283. 

Barlow, J. 2003. Preliminary estimates of the abundance of cetaceans along the U.S. west coast: 

1991_2001. Southwest Fisheries Science Center Administrative Report LJ_03_03. Available 

from SWFSC, 8604 La Jolla Shores Dr., La Jolla CA 92037. 31p. 

Berdegué, J. 2002. Depredación de las especies pelágicas reservadas a la pesca deportiva y especies en 

peligro de extinción con uso indiscriminado de artes de pesca no selectivas (palangres, FAD's, 

trampas para peces y redes de agallar fijas y a la deriva) por la flota palangrera Mexicana. 

Fundación para la conservación de los picudos. A.C. Mazatlán, Sinaloa, 21 de septiembre. 

82
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. 

Cameron, G.A. and K.A. Forney. 2000. Preliminary estimates of cetacean mortality in California/Oregon 

Gillnet Fisheries for 1999. Report SC/52/O24 presented to the Scientific Committee of the 

International Whaling Commission, June 2000 (unpublished). 12p. [Available from Southwest 

Fisheries Science Center, National Marine Fisheries Service, 8604 La Jolla Shores Drive, La Jolla, 

CA 92037, USA.] 

Carretta, J.V. 2001. Preliminary estimates of cetacean mortality in California gillnet fisheries for 2000. 

Report SC/53/SM9 presented to the Scientific Committee of the International Whaling 

Commission, June 2001 (unpublished). 21p. [Available from Southwest Fisheries Science Center, 

National Marine Fisheries Service, 8604 La Jolla Shores Drive, La Jolla, CA 92037, USA.]. 

Carretta, J.V. 2002. Preliminary estimates of cetacean mortality in California gillnet fisheries for 2001. 

Report SC/54/SM12 presented to the Scientific Committee of the International Whaling 

Commission, April 2002 (unpublished). 22p. [Available from Southwest Fisheries Science 

Center, National Marine Fisheries Service, 8604 La Jolla Shores Drive, La Jolla, CA 92037, 

USA.]. 

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. 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. NMFSSWFSC-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. 

83
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, 1989-2001. 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. 

84
Revised 12/15/2003

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 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). 

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

33o

N, (Southern California to Alaska), and southern

specimens were obtained from about 36o

N 

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, an area of

mixing between the two forms appears to be located

off Southern California (Lux et al. 1997). 

W132 W129 W126 W123 W120 W117

N30

N34

N38

N42

N46

WASHINGTON

OREGON

CALIFORNIA

Figure 1. Pacific white-sided dolphin sightings

based on aerial and shipboard surveys off

California, Oregon, and Washington, 1991-2001 

(see Appendix 2 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. Key: 

• = summer/autumn ship-based sightings; + =

winter/spring aerial-based sightings. 

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

85
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 were based on three 

summer/autumn shipboard surveys conducted within 300 nmi of the coasts California in 1991 and 1993 

(Barlow and Gerrodette 1996) and California, Oregon, and Washington in 1996 (Barlow 1997). More 

recently, a shipboard survey within 300 nmi of the coasts of California, Oregon, and Washington was 

conducted in summer/autumn of 2001 (Barlow 2003). 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 whitesided 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 1996-2001 weighted average abundance estimate for California, 

Oregon and Washington waters based on the two most recent ship surveys is 59,274 (CV =0.50) Pacific 

white-sided dolphins (Barlow 2003). 

Minimum Population Estimate

 The log-normal 20th percentile of the 1996-2001 weighted average abundance estimate is 39,822 

Pacific white-sided 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, Barlow 2003). 

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 (39,822) 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 and #0.60; Wade 

and Angliss 1997), resulting in a PBR of 382 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, 

1997-2001 (Cameron and Forney 1999, 2000; Carretta 2001, 2002). 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 2003). 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. 

Mean annual takes in Table 1 are based on 1997-2001 data. This results in an average estimate of 5.9 (CV 

= 0.42) Pacific white-sided dolphins taken annually. 

 Drift gillnet fisheries for swordfish and sharks exist along the entire Pacific coast of Baja 

California, Mexico and may take animals from this 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 

86
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. Previous efforts to 

convert the Mexican swordfish driftnet fishery to a longline fishery have resulted in a mixed-fishery, with 

20 vessels alternately using longlines or driftnets, 23 using driftnets only, 22 using longlines only, and 

seven with unknown gear type (Berdegué 2002). 

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 1997-2001 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 

1997 

1998 

1999 

2000 

2001 

23.0% 

20.0% 

20.0% 

22.9% 

20.4% 

3 

0 

0 

2 

2 

12 (0.68) 

0 

0 

5 (1.02) 

9 (0.69) 

5.2 (0.44) 

WA/OR/CA domestic 

groundfish trawl fisheries

(At-sea processing Pacific 

whiting fishery only).

observer data 

1997 

1998 

1999 

2000 

2001 

65.7% 

77.3% 

68.6% 

80.6% 

96.2% 

0 

1 

0 

0 

0 

0 

1 (0.48) 

0 

0 

0 

0.2 (0.48) 

Minimum total annual takes 5.4 (0.42) 

 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 1997 and 2001, with 66%-96% 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 1997-2001 is 0.8 (CV=0.48) Pacific white-sided 

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 whitesided 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 

1997-2001 (5.4 animals) is estimated to be less than the PBR (382), 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 

87
10% of the calculated 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. 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. 2003. Field experiments show that acoustic pingers reduce marine mammal 

bycatch in the California drift gillnet fishery. Marine Mammal Science 19(2):265-283. 

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. 

Barlow, J. 2003. Preliminary estimates of the abundance of cetaceans along the U.S. west coast: 

1991_2001. Southwest Fisheries Science Center Administrative Report LJ_03_03. Available 

from SWFSC, 8604 La Jolla Shores Dr., La Jolla CA 92037. 31p. 

Berdegué, J. 2002. Depredación de las especies pelágicas reservadas a la pesca deportiva y especies en 

peligro de extinción con uso indiscriminado de artes de pesca no selectivas (palangres, FAD's, 

trampas para peces y redes de agallar fijas y a la deriva) por la flota palangrera Mexicana. 

Fundación para la conservación de los picudos. A.C. Mazatlán, Sinaloa, 21 de septiembre. 

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. 

Cameron, G.A. and K.A. Forney. 2000. Preliminary estimates of cetacean mortality in California/Oregon 

Gillnet Fisheries for 1999. Report SC/52/O24 presented to the Scientific Committee of the 

International Whaling Commission, June 2000 (unpublished). 12p. [Available from Southwest 

Fisheries Science Center, National Marine Fisheries Service, 8604 La Jolla Shores Drive, La Jolla, 

CA 92037, USA.] 

Carretta, J.V. 2001. Preliminary estimates of cetacean mortality in California gillnet fisheries for 2000. 

Report SC/53/SM9 presented to the Scientific Committee of the International Whaling 

Commission, June 2001 (unpublished). 21p. [Available from Southwest Fisheries Science Center, 

National Marine Fisheries Service, 8604 La Jolla Shores Drive, La Jolla, CA 92037, USA.]. 

Carretta, J.V. 2002. Preliminary estimates of cetacean mortality in California gillnet fisheries for 2001. 

Report SC/54/SM12 presented to the Scientific Committee of the International Whaling 

Commission, April 2002 (unpublished). 22p. [Available from Southwest Fisheries Science 

Center, National Marine Fisheries Service, 8604 La Jolla Shores Drive, La Jolla, CA 92037, 

USA.]. 

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. 

88
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. 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. and M. Beeson. 1998. Estimates of mammal, turtle and bird mortality for two California gillnet 

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

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, 1989-2001. 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. 

89
Revised 12/15/2003

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.

W132 W129 W126 W123 W120 W117

N30

N34

N38

N42

N46

WASHINGTON

OREGON

CALIFORNIA

POPULATION SIZE

The previous best estimates of abundance

for Risso’s dolphins were based on three summer/autumn shipboard surveys conducted within 300 nmi of

the coasts California in 1991 and 1993 (Barlow and Gerrodette 1996) and California, Oregon, and

Washington in 1996 (Barlow 1997). More recently, a shipboard survey within 300 nmi of the coasts of

California, Oregon, and Washington was conducted in summer/autumn of 2001 (Barlow, 2003). 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 1996-2001 weighted average abundance estimate for California, Oregon and

Washington waters based on the two most recent ship surveys is 16,066 (CV = 0.28) Risso’s dolphins

(Barlow 2003). 

Figure 1. Risso’s dolphin sightings based on

aerial and shipboard surveys off California,

Oregon, and Washington, 1991-2001 (see 

Appendix 2 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. Key: • = 

summer/autumn ship-based sightings; + = 

winter/spring aerial-based sightings. 

90
Minimum Population Estimate

 The log-normal 20th percentile of the 1996-2001 weighted average abundance estimate is 12,748 

Risso's dolphins. 

Current Population Trend

 The pooled abundance estimate from the most recent two surveys of California, Oregon, and 

Washington waters is 16,066 (CV = 0..28) (Barlow 2003), which is relatively unchanged from the estimate 

of 16,483 (CV = 0.28) from pooled 1991-1996 surveys (Barlow 1997). Currently, there is no evidence of 

a trend in abundance for this stock. 

 

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

 No information on current or maximum net productivity rates is available for this stock. 

POTENTIAL BIOLOGICAL REMOVAL

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

population size (12,748) 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 115 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, 1997-2001 

(Julian 1997; Cameron and Forney 1999, 2000; Carretta 2001, 2002). 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 2003). 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. Mean annual 

takes in Table 1 are based on 1997-2001 data. This results in an average estimate of 3.6 (CV = 0.63) 

Risso’s dolphins taken annually. 

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 1997-2001 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

1997 

1998 

1999 

2000

2001

23.0% 

20.0% 

20.0% 

22.9%

20.4%

3 

0 

0 

2

0

11 (0.96) 

0 

0 

7 (0. 8) 5

0

3.6 (0.63)

Minimum total annual takes 3.6 (0.63) 

 Drift gillnet fisheries for swordfish and sharks exist along the entire Pacific coast of Baja 

California, Mexico and may take animals from this 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 

91
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. Previous efforts to 

convert the Mexican swordfish driftnet fishery to a longline fishery have resulted in a mixed-fishery, with 

20 vessels alternately using longlines or driftnets, 23 using driftnets only, 22 using longlines only, and 

seven with unknown gear type (Berdegué 2002). 

 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 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). In 2002, two Risso’s dolphin stranded 

in close proximity in southern California on the same day; bullets were retrieved from one animal, the other 

showed evidence of gunshot wounds. The timing and location of the strandings suggests that the squid 

purse seine fishery may have been responsible for the mortalities. 

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. Over the last 5-year period (1997-2001), the 

average annual human-caused mortality 3.6 animals) is estimated to be less than the PBR (115), 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. 2003. Field experiments show that acoustic pingers reduce marine mammal 

bycatch in the California drift gillnet fishery. Marine Mammal Science 19(2):265-283. 

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. 

Barlow, J. 1997. Preliminary estimates of cetacean abundance off California, Oregon, and Washington 

based on a 1996 ship survey and comparisons of closing and passing modes. Administrative 

Report LJ-97-11, Southwest Fisheries Science Center, National Marine Fisheries Service, 8604 La 

Jolla Shores Drive, La Jolla, CA 92037. 25p. 

Barlow, J. 2003. Preliminary estimates of the abundance of cetaceans along the U.S. west coast: 

1991_2001. Southwest Fisheries Science Center Administrative Report LJ_03_03. Available 

from SWFSC, 8604 La Jolla Shores Dr., La Jolla CA 92037. 31p. 

Berdegué, J. 2002. Depredación de las especies pelágicas reservadas a la pesca deportiva y especies en 

peligro de extinción con uso indiscriminado de artes de pesca no selectivas (palangres, FAD's, 

trampas para peces y redes de agallar fijas y a la deriva) por la flota palangrera Mexicana. 

Fundación para la conservación de los picudos. A.C. Mazatlán, Sinaloa, 21 de septiembre. 

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 

92
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 28 - November 6, 1993. U.S. Dep. Commer., NOAA Tech. Memo. NMFSSWFSC-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. 

93
Revised 12/15/2003

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, Or

W123 W122 W121 W120 W119 W118 W117 W116

N31

N32

N33

N34

N35

N36

N37

N38

N39

N40

San Francisco

Monterey Bay

Point Conception

San Diego

Los Angeles

California

Pacific Ocean

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. 

egon and Washington offshore stock, and 3) Hawaiian stock. 

1996-98 (Dudzik 1999). Because coastal bottlenose dolphins spend an unknown amount of time in 

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. Markrecapture 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 (Dudzik 1999). The

most recent photographic mark-recapture abundance estimate is 356 (95% CI 306 - 437) for the period 

94
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

entile of the above average abundance estimate for U.S. waters based on 

e 1999

urrent Population Trend

son of mark-recapture abundance estimates for the periods 1987-89 (Nˆ = 354) 

nd 199

 MAXIMUM NET PRODUCTIVITY RATES

ates is available for California coastal 

ottleno

OTENTIAL BIOLOGICAL REMOVAL

BR) level for this stock is calculated as the minimum 

lati

 The log-normal 20th perc

th -2000 surveys is 186 coastal bottlenose dolphins. 

C

 Based on a compari

a 6-98 (Nˆ = 356), Dudzik (1999) stated that the population size had remained stable over an 11-year 

period. 

CURRENT AND

 No information on current or maximum net productivity r

b se dolphins. 

P

 The potential biological removal (P

popu on 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

sive use of coastal habitats, this bottlenose dolphin population is susceptible to 

shery-r

ble 1. Summary of available information on the incidental mortality and serious injury of bottlenose 

Fishery Name Data Type

Yea (s) Observed Mean Annual 

Fishery Information

 Due to its exclu

fi elated 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. 

 

Ta

dolphins (California Coastal Stock) in commercial fisheries that might take this species.

Percent Estimated r Observer 

Coverage Mortality Annual 

Mortality Takes

CA angel shark/ halibut and 

o ) observer 

1997 0 %

4. ther species large mesh (>3.5in 0 0 0

set gillnet fishery data

1998 

1999 

2000 

2001

0%

0 %1

1.8%1

0%

Minimum total annual takes 0 1

 The CA set gillnets were not observed during 1997-98 and in 2001; mortality was extrapolated from effort estimates and previous 

ore detailed information on the set gillnet fishery is provided in Appendix 1. From 1991-94, no 

(1991-94 ) entanglement rates. In 1999 and 2000, approximately 25% of Monterey portion of the set gillnet fishery was observed, 

representing <5% of the overall fishery. 

 

M

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 

95
waters deeper than 30 fathoms (56m) since 1991 in all areas except between Point Sal and Point Arguello. 

In 2002, a ban on set gill and trammel nets inshore of 60 fathoms from Point Reyes to Point Arguello 

became effective. 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 36 stranding records 

for 1997-2001 do not include any evidence of fishery interactions for this stock. Coastal gillnet fisheries 

exist in Mexico and probably take animals from this population, but no details are available. 

ther removals

astal bottlenose dolphins were collected during the late 1950s in the vicinity of San Diego 

orris 

TATUS OF STOCK

astal bottlenose dolphins in California relative to OSP is not known, and there is 

o evide

abitat Issues

t levels, especially DDT residues, found in Southern California coastal bottlenose 

lphins

EFERENCES

. B. Howard. 1983. Tissue residues of selected environmental contaminants in marine 

Carretta orney and J. L. Laake. 1998. The abundance of southern California coastal 

Defran, ttlenose 

Defran, f Pacific 

Dudzik, Population dynamics of the Pacific coast bottlenose dolphin (Tursiops truncatus). 

Forney, . Stinchcomb, and 

Hansen, and R.R. Reeves (eds.), 

Hansen, dies of California coastal 

Hanson, ast bottlenose 

Julian, F mortality for two California gillnet 

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

O

 Seven co

(N 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.

S

 The status of co

n nce 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. 

H

 Pollutan

do 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). 

R

Britt, J. O. and E

mammals. In: Howard, E. B. (ed.), Pathobiology of Marine Mammal Diseases. CRC Press, Boca 

Raton, Florida. 

, J. V., K. A. F

bottlenose dolphins estimated from tandem aerial surveys. Mar. Mamm. Sci. 14:655-675. 

R. H. and D. W. Weller. 1999. Occurrence, distribution, site fidelity and school size of bo

dolphins (Tursiops truncatus) off San Diego, California. Mar. Mamm. Sci. 15:366-380. 

R. H., D. W. Weller, D. L. Kelly, and M. A. Espinosa. 1999. Range characteristics o

coast bottlenose dolphins (Tursiops truncatus) in the Southern California Bight. Mar. Mamm. Sci. 

15:381-393. 

K.J. 1999. 

M.S. Thesis, San Diego State University, San Diego, California 92182. 63pp.

K.A., J. Barlow, M.M. Muto, M. Lowry, J. Baker, G. Cameron, J. Mobley, C

J.V. Carretta. 2000. U.S. Pacific Marine Mammal Stock Assessments: 2000. U.S. Department of 

Commerce, NOAA Technical Memorandum NMFS-SWFSC-300. 276p. 

 L. J. 1990. California coastal bottlenose dolphins. In: S. Leatherwood 

The Bottlenose Dolphin, p. 403-420. Academic Press, Inc., San Diego. 

 L. J. and R. H. Defran. 1990. A comparison of photo-identification stu

bottlenose dolphins. Rep. Int. Whal. Commn. Special Issue 12:101-104. 

 M.T. and R.H. Defran. 1993. The behavior and feeding ecology of the Pacific co

dolphin, Tursiops truncatus. Aquatic Mammals 19:127-142. 

. and M. Beeson. 1998. Estimates of mammal, turtle and bird

96
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 

O'Shea, 

ne pollutants in small cetaceans from the Pacific and South Atlantic Oceans, 

O’Shea, 

kshop, Keystone, Colorado, 

NMFS, S

Norris, K fornian and Mexican 

iversity of California 

Reeves, 

l. Commn. 34:497-507. 

ttlenose Dolphin (eds. S. Leatherwood 

Schafer, 

astal Water Research Project, Long 

Van Wa

 from the Pacific coast of South America. In: The Bottlenose Dolphin (eds. S. 

Walker, 

1. 

ries Science Center, 

Ward, B

fornia, 92182. 

Wells, R

R. Reeves (eds.), The Bottlenose Dolphin, p. 421-431. Academic Press, Inc., San Diego. 

. 

30:567-571. 

T. J., R. L. Brownell, Jr., D. R. Clark, W. A. Walker, M. L. Gray, and T. G. Lamont. 1980. 

Organochlori

November 1968-June 1976. Pesticides Monitoring Journal 14:35-46. 

T. J., R. R. Reeves, and A. Kirk Long (eds.). 1999. Marine Mammals and Persistent Ocean 

Contaminants: Proceedings of the Marine Mammal Commission Wor

12-15 October 1998. Marine Mammal Commission, Bethesda, MD. 150pp. 

outhwest Fisheries Science Center. P.O. Box 271, La Jolla, CA 92038-0271 

. S. and J. H. Prescott. 1961. Observation on Pacific cetaceans of Cali

waters. University of California Publications in Zoology 63:291-402. Un

Press, Berkeley and Los Angeles. 

R. R. and S. Leatherwood. 1984. Live-capture fisheries for cetaceans in USA and Canadian 

waters, 1973-1982. Rep. Int. Wha

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 Bo

and R. R. Reeves). pp. 101-128. Academic Press, 653pp. 

H. A., R. W. Gossett, C. F. Ward, and A. M. Westcott. 1984. Chlorinated hydrocarbons in marine 

mammals. Biennial Report, 1983-84, Southern California Co

Beach, California. 

erebeek, K., J. C. Reyes, A. J. Read, and J. S. McKinnon. 1990. Preliminary observations of 

bottlenose dolphins

Leatherwood and R. R. Reeves). pp. 143-154 Academic Press, 653 pp. 

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. 32:1197-121

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 Fishe

National Marine Fisheries Service, P.O. Box 271, La Jolla, CA 92038, USA. 52p. 

.G. 1999. Movement patterns and feeding ecology of the Pacific coast bottlenose dolphin 

(Tursiops truncatus). M.S. Thesis, San Diego State University, San Diego, Cali

98pp. 

. S., L. J. Hansen, A. B. Baldridge, T. P. Dohl, D. L. Kelly and R. H Defran. In: S. Leatherwood 

and R. 

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. 

97
Revised 12/15/2003

BOTTLENOSE DOLPHIN (Tursiops truncatus): 

California/Oregon/Washington Offshore 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). 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 warm-water 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. 

W132 W129 W126 W123 W120 W117

N30

N34

N38

N42

N46

WASHINGTON

OREGON

CALIFORNIA

Figure 1. Offshore bottlenose dolphin sightings 

based on shipboard surveys off California,

Oregon, and Washington, 1991-2001 (see 

Appendix 2 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. 

POPULATION SIZE

 The most recent shipboard surveys conducted within 300 nmi of the coasts of California, Oregon, 

and Washington were in 1996 (Barlow 1997) and 2001 (Barlow 2003). 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 1996-2001 ship surveys, 5,065 (CV = 

0.66) offshore bottlenose dolphins (Barlow 2003). 

Minimum Population Estimate

The log-normal 20th percentile of the 1996-2001 weighted average abundance estimate is 3,053

offshore bottlenose dolphins. 

Current Population Trend

No information on trends in abundance of offshore bottlenose dolphins is available. 

98
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 (3,053) 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 31 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, 1997-2001 

(Cameron and Forney 1999, 2000; Carretta 2001; 2002). 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 2003). 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. Mean annual takes in Table 1 are 

based on 1997-2001 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 1997-2001 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 

1997 

1998 

1999 

2000 

2001 

23.0% 

20.0% 

20.0% 

22.9% 

20.4% 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

Minimum total annual takes 0 

 

 Drift gillnet fisheries for swordfish and sharks exist along the entire Pacific coast of Baja 

California, Mexico and may take animals from this 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. Previous efforts to 

convert the Mexican swordfish driftnet fishery to a longline fishery have resulted in a mixed-fishery, with 

20 vessels alternately using longlines or driftnets, 23 using driftnets only, 22 using longlines only, and 

seven with unknown gear type (Berdegué 2002). 

 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 

99
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. 2003. Field experiments show that acoustic pingers reduce marine mammal 

bycatch in the California drift gillnet fishery. Marine Mammal Science 19(2):265-283. 

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. 

Barlow, J. 2003. Preliminary estimates of the abundance of cetaceans along the U.S. west coast: 

1991_2001. Southwest Fisheries Science Center Administrative Report LJ_03_03. Available 

from SWFSC, 8604 La Jolla Shores Dr., La Jolla CA 92037. 31p. 

Berdegué, J. 2002. Depredación de las especies pelágicas reservadas a la pesca deportiva y especies en 

peligro de extinción con uso indiscriminado de artes de pesca no selectivas (palangres, FAD's, 

trampas para peces y redes de agallar fijas y a la deriva) por la flota palangrera Mexicana. 

Fundación para la conservación de los picudos. A.C. Mazatlán, Sinaloa, 21 de septiembre. 

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. 

Cameron, G.A. and K.A. Forney. 2000. Preliminary estimates of cetacean mortality in California/Oregon 

Gillnet Fisheries for 1999. Report SC/52/O24 presented to the Scientific Committee of the 

International Whaling Commission, June 2000 (unpublished). 12p. [Available from Southwest 

Fisheries Science Center, National Marine Fisheries Service, 8604 La Jolla Shores Drive, La Jolla, 

CA 92037, USA.] 

Carretta, J.V. 2001. Preliminary estimates of cetacean mortality in California gillnet fisheries for 2000. 

Report SC/53/SM9 presented to the Scientific Committee of the International Whaling 

Commission, June 2001 (unpublished). 21p. [Available from Southwest Fisheries Science Center, 

National Marine Fisheries Service, 8604 La Jolla Shores Drive, La Jolla, CA 92037, USA.]. 

Carretta, J.V. 2002. Preliminary estimates of cetacean mortality in California gillnet fisheries for 2001. 

Report SC/54/SM12 presented to the Scientific Committee of the International Whaling 

Commission, April 2002 (unpublished). 22p. [Available from Southwest Fisheries Science 

100
Center, National Marine Fisheries Service, 8604 La Jolla Shores Drive, La Jolla, CA 92037, 

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. 

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. 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., 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. 

101
Revised 12/15/2003 

STRIPED DOLPHIN (Stenella coeruleoalba): 

California/Oregon/Washington Stock 

STOCK DEFINITION AND GEOGRAPHIC RANGE

Striped dolphins are distributed worldwide 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, non-contiguous areas: 1) waters off 

California, Oregon and Washington (this report), and

2) waters around Hawaii. 

W132 W129 W126 W123 W120 W117

N3

N3

0

N34

8

N42

N46

WASHINGTON

OREGON

CALIFORNIA

Figure 1. Striped dolphin sightings based on

aerial and shipboard surveys off California,

Oregon, and Washington, 1991-2001 (see 

Appendix 2 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. 

POPULATION SIZE

Two summer/fall shipboard surveys were conducted within 300 nmi of the coasts of California, 

Oregon and Washington in 1996 (Barlow 1997) and 2001 (Barlow 2003). 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 multiyear average abundance estimate is the most appropriate for management within U.S. waters. The 1996-

2001 weighted average abundance estimate for California, Oregon and Washington waters based on the 

above two ship surveys is 13,934 (CV = 0.53) striped dolphins (Barlow 2003). 

Minimum Population Estimate

The log-normal 20th percentile of the 1996-2001 weighted average abundance estimate is 9,165

striped dolphins. 

102
Current Population Trend

 Prior to a 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 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. Estimates of abundance from surveys conducted in 1991/93, 1996, and 2001 in California 

waters were 28,396 (CV = 0.31); 5,489 (0.48); and 22,316 (0.65) striped dolphin, respectively (Barlow 

2003). Currently, there is no evidence of a trend in abundance for this stock. 

 

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 ( 9,165) 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 92 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, 1997-2001 

(Cameron and Forney 1999, 2000, Carretta 2001; 2002). No striped dolphin were observed killed in the 

most recent five-year period. One striped dolphin was observed killed in the drift gillnet fishery in 1994. 

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 2003). 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. Mean annual takes in Table 1 are based on 1997-2001 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. Coefficients 

of variation for mortality estimates are provided in parentheses. Mean annual takes are based on 1997-

2001 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

1997 

1998 

1999 

2000

2001

23.0% 

20.0% 

20.0% 

22.9%

20.4%

0 

0 

0 

0

0

0 

0 

0 

0

0

0

Minimum total annual takes 0

 Drift gillnet fisheries for swordfish and sharks exist along the entire Pacific coast of Baja 

California, Mexico and may take animals from this 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). 

103
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. Previous efforts to 

convert the Mexican swordfish driftnet fishery to a longline fishery have resulted in a mixed-fishery, with 

20 vessels alternately using longlines or driftnets, 23 using driftnets only, 22 using longlines only, and 

seven with unknown gear type (Berdegué 2002). 

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 1997-2001 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. 2003. Field experiments show that acoustic pingers reduce marine mammal 

bycatch in the California drift gillnet fishery. Marine Mammal Science 19(2):265-283. 

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. 2003. Preliminary estimates of the abundance of cetaceans along the U.S. west coast: 

1991_2001. Southwest Fisheries Science Center Administrative Report LJ_03_03. Available 

from SWFSC, 8604 La Jolla Shores Dr., La Jolla CA 92037. 31p. 

Berdegué, J. 2002. Depredación de las especies pelágicas reservadas a la pesca deportiva y especies en 

peligro de extinción con uso indiscriminado de artes de pesca no selectivas (palangres, FAD's, 

trampas para peces y redes de agallar fijas y a la deriva) por la flota palangrera Mexicana. 

Fundación para la conservación de los picudos. A.C. Mazatlán, Sinaloa, 21 de septiembre. 

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. 

Cameron, G.A. and K.A. Forney. 2000. Preliminary estimates of cetacean mortality in California/Oregon 

Gillnet Fisheries for 1999. Report SC/52/O24 presented to the Scientific Committee of the 

International Whaling Commission, June 2000 (unpublished). 12p. [Available from Southwest 

Fisheries Science Center, National Marine Fisheries Service, 8604 La Jolla Shores Drive, La Jolla, 

CA 92037, USA.] 

Carretta, J.V. 2001. Preliminary estimates of cetacean mortality in California gillnet fisheries for 2000. 

Report SC/53/SM9 presented to the Scientific Committee of the International Whaling 

Commission, June 2001 (unpublished). 21p. [Available from Southwest Fisheries Science Center, 

National Marine Fisheries Service, 8604 La Jolla Shores Drive, La Jolla, CA 92037, USA.]. 

Carretta, J.V. 2002. Preliminary estimates of cetacean mortality in California gillnet fisheries for 2001. 

Report SC/54/SM12 presented to the Scientific Committee of the International Whaling 

Commission, April 2002 (unpublished). 22p. [Available from Southwest Fisheries Science 

Center, National Marine Fisheries Service, 8604 La Jolla Shores Drive, La Jolla, CA 92037, 

USA.]. 

104
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. NMFSSWFSC-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 seasurface 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. 

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
Revised 12/15/2003 

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 42o

N (Figure 1). 

Four strandings of common dolphins (Delphinus

sp.) have been reported in Oregon and Washington

since 1942 (B. Norberg, pers. comm.), but three of

these could not be identified to species. 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 13o

N 

(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 longbeaked 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. 

W132 W129 W126 W123 W120 W117

N30

N34

N38

N42

N46

WASHINGTON

OREGON

CALIFORNIA

Figure 1. Short-beaked common dolphin

sightings based on shipboard surveys off

California, Oregon, and Washington, 1991-2001

(see Appendix 2, for data sources and

information on timing and location of survey

effort). No Delphinus sightings have been made 

off Washington. Dashed line represents the U.S. 

EEZ, thick line indicates the outer boundary of 

all surveys combined. 

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 

106
locations, the majority of these were probably short-beaked common dolphins. More recent, speciesspecific abundance estimates are available based on two summer/fall shipboard surveys that were 

conducted within 300 nmi of the coasts of California, Oregon and Washington in 1996 (Barlow 1997) and 

2001 (Barlow 2003). 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 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 

1996-2001 weighted average abundance estimate for California, Oregon and Washington waters based on 

the two ship surveys is 449,846 (CV= 0.25) short-beaked common dolphins (Barlow 2003). 

Minimum Population Estimate

 The log-normal 20th percentile of the 1996-2001 weighted average abundance estimate is 

365,617 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 1996-2001 summer/fall surveys (Barlow 

2003) 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 short-beaked 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 shift would likely be 

reflected in an increase in short-beaked common dolphin abundance. Heyning and Perrin (1994) have 

detected changes in the proportion of short-beaked to long-beaked common dolphins stranding along the 

California coast, with 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 (365,617) 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 3,656 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 estimates for 

the California drift gillnet fishery are included for the five most recent years of monitoring, 1997-2001 

(Cameron and Forney 1999, 2000; Carretta 2001, 2002). Because of the difficulty in distinguishing shortbeaked 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 

107
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

2003 1999), but entanglement rates increased again in 1999 and 2000 (Figure 2) and have since returned to

low levels. 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. 

Mean annual takes in Table 1 are based on 1997-2001 data. This results in an average estimate of

93(CV=0.23) short-beaked common dolphins taken annually. 

Short-beaked common dolphin: kill rates

0

0.05

0.1

0.15

1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002

Year

Kill/D

a

y

No pingers Pingers

Figure 2. Kill rates of short-beaked common dolphin per day fished in the California drift gillnet

fishery for swordfish and thresher shark, 1990-2002. Kill rates include observations from pingered 

and unpingered sets. Pingers were not used from 1990-95 and were used experimentally in 1996 and 

1997. In 1996, no short-beaked common dolphin were observed killed in 146 pingered sets. For the 

period 1998-2002, over 99% of all observed sets utilized pingers. 

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. Approximately 4% and 1.8% of the entire fishery was observed in Monterey Bay in 1999

and 2000, respectively, and no common dolphin were observed taken. 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. 

Nine common dolphins (type not specified) stranded with evidence of fishery interaction (NMFS,

Southwest Region, unpublished data) between 1997-2001. 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, Mexico and may take animals from this 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. Previous efforts to

convert the Mexican swordfish driftnet fishery to a longline fishery have resulted in a mixed-fishery, with 

20 vessels alternately using longlines or driftnets, 23 using driftnets only, 22 using longlines only, and 

seven with unknown gear type (Berdegué 2002). 

108
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 and later resumed in Monterey Bay from 1999-2000. Coefficients of variation 

for mortality estimates are provided in parentheses; n/a = not available. Mean annual takes are based on 

1997-2001 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 

1997 

1998 

1999 

2000 

2001 

23.0% 

20.0% 

20.0% 

22.9% 

20.4% 

21 

9 

34 

23 

7 

105 (0.30) 

51 (0.33) 

191 (0.31) 

75 (0.32) 

26 (0.41) 

(includes prorated)

90 (0.17) 

Common dolphins, species not determined 

CA angel shark/ 

halibut and other 

species large mesh 

(>3.5in) set gillnet 

fishery

extrapolated 

estimates 

MMAP 

self-reporting 

1997-

2001 

1997 

1998 

1999 

2000 

2001 

0 - 4% 

- 

- 

- 

- 

- 

0 

0 

2 

0 

0 

0 

31

0 

2 

0 

0 

0 

$0.61

$0.4 (n/a) 

Undetermined strandings 1997-

2001 

9 common dolphins (species not determined) stranded with 

evidence of fishery interactions $1.8 (n/a) 

Minimum total annual takes 93 (0.23) 

1

The set gillnet fishery was observed from 1991-94 and then only in Monterey Bay during 1999-2000, 

where 20-25% of the local fishery was observed. Recent mortality estimates for common dolphin in this 

fishery are based on kill rates observed from 1991-94 and current levels of fishing effort. 

 

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 1997 and 2001, annual fishing 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 101 (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 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 1997-2001 (93 animals) is estimated to be less 

than the PBR (3,656), 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 

109
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. 2003. Field experiments show that acoustic pingers reduce marine mammal 

bycatch in the California drift gillnet fishery. Marine Mammal Science 19(2):265-283. 

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. 2003. Preliminary estimates of the abundance of cetaceans along the U.S. west coast: 

1991_2001. Southwest Fisheries Science Center Administrative Report LJ_03_03. Available 

from SWFSC, 8604 La Jolla Shores Dr., La Jolla CA 92037. 31p. 

Berdegué, J. 2002. Depredación de las especies pelágicas reservadas a la pesca deportiva y especies en 

peligro de extinción con uso indiscriminado de artes de pesca no selectivas (palangres, FAD's, 

trampas para peces y redes de agallar fijas y a la deriva) por la flota palangrera Mexicana. 

Fundación para la conservación de los picudos. A.C. Mazatlán, Sinaloa, 21 de septiembre. 

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. 

Cameron, G.A. and K.A. Forney. 2000. Preliminary estimates of cetacean mortality in California/Oregon 

Gillnet Fisheries for 1999. Report SC/52/O24 presented to the Scientific Committee of the 

International Whaling Commission, June 2000 (unpublished). 12p. [Available from Southwest 

Fisheries Science Center, National Marine Fisheries Service, 8604 La Jolla Shores Drive, La Jolla, 

CA 92037, USA.] 

Carretta, J.V. 2001. Preliminary estimates of cetacean mortality in California gillnet fisheries for 2000. 

Report SC/53/SM9 presented to the Scientific Committee of the International Whaling 

Commission, June 2001 (unpublished). 21p. [Available from Southwest Fisheries Science Center, 

National Marine Fisheries Service, 8604 La Jolla Shores Drive, La Jolla, CA 92037, USA.]. 

Carretta, J.V. 2002. Preliminary estimates of cetacean mortality in California gillnet fisheries for 2001. 

Report SC/54/SM12 presented to the Scientific Committee of the International Whaling 

Commission, April 2002 (unpublished). 22p. [Available from Southwest Fisheries Science 

Center, National Marine Fisheries Service, 8604 La Jolla Shores Drive, La Jolla, CA 92037, 

USA.]. 

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. 

110
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. 166pp. 

Hodder, J. Oregon Institute of Marine Biology, Charleston, OR, 97420. 

Holts, D. Southwest Fisheries Science Center, National Marine Fisheries Service, 8604 La Jolla Shores 

Drive, La Jolla, CA 92037. 

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). Report on the International Dolphin Conservation Program. Document MOP-7-04. 19 

p. 

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, NOAATM-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. 

111
Revised 12/15/2003 

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 interannually, 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), longbeaked ("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. 

W132 W129 W126 W123 W120 W117

N30

N34

N38

N42

N46

WASHINGTON

OREGON

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 short-beaked common dolphins. More recent, 

species-specific abundance estimates are available based on two summer/fall shipboard surveys that were 

conducted within 300 nmi of the coasts of California, Oregon and Washington in 1996 ( Barlow 1997) and

2001 (NMFS, unpublished data). 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 43,360 (CV=0.72) long-beaked common dolphins (Barlow 2003). 

Figure 1. Long-beaked common dolphin 

sightings based on shipboard surveys off

California, Oregon, and Washington, 1991-2001

(see Appendix 2 for data sources and

information on timing and location of survey

effort). No Delphinus sightings have been made 

off Washington. Dashed line represents the U.S. 

EEZ, thick line indicates the outer boundary of 

all surveys combined.

Minimum Population Estimate

The log-normal 20th percentile of the weighted average abundance estimate is 25,163 long-beaked 

common dolphins. 

112
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 short-beaked 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 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 

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 (25,163) 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 and #0.60; Wade 

and Angliss 1997), resulting in a PBR of 242 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 estimates for 

the California drift gillnet fishery are included for the five most recent years of monitoring, 1997-2001 

(Cameron and Forney 1999, 2000; Carretta 2001, 2002). Because of the difficulty in distinguishing shortbeaked 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 2003). 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. Mean annual takes in Table 1 are based 

on 1997-2001 data. This results in an average estimate of 11 (CV= 0.50) 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. Approximately 4% and 1.8% of the entire fishery was observed in Monterey Bay in 1999 

and 2000, respectively, and no common dolphin were observed taken. Marine Mammal Authorization 

Permit (MMAP) fisher self-reports for 1997-2001 indicate that at least two common dolphins (type not 

specified) were killed between 1997 and 2001. Although these reports are considered unreliable (see 

Appendix 4 of Hill and DeMaster 1998) they represent a minimum mortality for this fishery. 

113
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 and later resumed in Monterey Bay from 1999-

2000. Coefficients of variation for mortality estimates are provided in parentheses, when available. Mean 

annual takes are based on 1997-2001 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 

1997 

1998 

1999 

2000 

2001 

23.0% 

20.0% 

20.0% 

22.9% 

20.4% 

4 

0 

1 

1 

0 

25 (0.74) 

0 

8 (0.93) 

9 (0.76) 

0 

8.4 (0.50) 

Common dolphins, species not determined 

CA angel shark/ halibut 

and other species large 

mesh (>3.5in) set gillnet 

fishery

observer 

data 

MMAP 

selfreporting 

1997-2001 

1997 

1998 

1999 

2000 

2001 

0 - 4% 

- 

- 

- 

- 

- 

0 

0 

2 

0 

0 

0 

31

0 

$2 

0 

0 

0 

0.6 (n/a) 

$0.4 (n/a) 

Undetermined strandings 1997-2001 9 common dolphins (species not determined) stranded 

with evidence of fishery interactions $1.8 (n/a) 

Minimum total annual takes 11 (0.50) 

1

The set gillnet fishery was observed from 1991-94 and then only in Monterey Bay during 1999-2000, 

where 20-25% of the local fishery was observed. Recent mortality estimates for common dolphin in this 

fishery are based on kill rates observed from 1991-94 and current levels of fishing effort. 

Nine common dolphins (type not specified) stranded with evidence of fishery interaction (NMFS, 

Southwest Region, unpublished data) between 1997-2001. 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, Mexico and may take animals from this 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. Previous efforts to 

convert the Mexican swordfish driftnet fishery to a longline fishery have resulted in a mixed-fishery, with 

20 vessels alternately using longlines or driftnets, 23 using driftnets only, 22 using longlines only, and 

seven with unknown gear type (Berdegué 2002). 

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 1997 and 2001, annual mortality of northern common dolphins (potentially 

including both short-beaked and long-beaked common dolphins) ranged between 9 and 261 animals, with 

114
an average of 101 (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 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 1997-2001 (14 animals) is estimated to be less than the PBR (226), 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. 2003. Field experiments show that acoustic pingers reduce marine mammal 

bycatch in the California drift gillnet fishery. Marine Mammal Science 19(2):265-283. 

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. 

Barlow, J. 2003. Preliminary estimates of the abundance of cetaceans along the U.S. west coast: 

1991_2001. Southwest Fisheries Science Center Administrative Report LJ_03_03. Available 

from SWFSC, 8604 La Jolla Shores Dr., La Jolla CA 92037. 31p. 

Berdegué, J. 2002. Depredación de las especies pelágicas reservadas a la pesca deportiva y especies en 

peligro de extinción con uso indiscriminado de artes de pesca no selectivas (palangres, FAD's, 

trampas para peces y redes de agallar fijas y a la deriva) por la flota palangrera Mexicana. 

Fundación para la conservación de los picudos. A.C. Mazatlán, Sinaloa, 21 de septiembre. 

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. 

Cameron, G.A. and K.A. Forney. 2000. Preliminary estimates of cetacean mortality in California/Oregon 

Gillnet Fisheries for 1999. Report SC/52/O24 presented to the Scientific Committee of the 

International Whaling Commission, June 2000 (unpublished). 12p. [Available from Southwest 

Fisheries Science Center, National Marine Fisheries Service, 8604 La Jolla Shores Drive, La Jolla, 

CA 92037, USA.] 

Carretta, J.V. 2001. Preliminary estimates of cetacean mortality in California gillnet fisheries for 2000. 

Report SC/53/SM9 presented to the Scientific Committee of the International Whaling 

Commission, June 2001 (unpublished). 21p. [Available from Southwest Fisheries Science Center, 

National Marine Fisheries Service, 8604 La Jolla Shores Drive, La Jolla, CA 92037, USA.]. 

Carretta, J.V. 2002. Preliminary estimates of cetacean mortality in California gillnet fisheries for 2001. 

Report SC/54/SM12 presented to the Scientific Committee of the International Whaling 

Commission, April 2002 (unpublished). 22p. [Available from Southwest Fisheries Science 

Center, National Marine Fisheries Service, 8604 La Jolla Shores Drive, La Jolla, CA 92037, 

USA.]. 

115
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, 8604 La Jolla Shores 

Drive, La Jolla, CA 92037. 

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). Report on the International Dolphin Conservation Program. Document MOP-7-04. 19 

p. 

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. 

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. 

116
Revised 12/15/2003 

NORTHERN RIGHT-WHALE DOLPHIN (Lissodelphis borealis): 

California/Oregon/Washington Stock 

STOCK DEFINITION AND GEOGRAPHIC 

RANGE

W132 W129 W126 W123 W120 W117

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 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; Forney

and Barlow 1998). The southern end of this

population's range is not well-documented, 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 rightwhale 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. 

N30

N34

N38

N42

N46

WASHINGTON

OREGON

CALIFORNIA

Figure 1. Northern right whale dolphin

sightings based on aerial and shipboard surveys

off California, Oregon, and Washington, 1991-

2001 (see Appendix 2 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. Key: • = summer/autumn 

ship-based sightings; + = winter/spring aerialbased sightings. 

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. Two summer/fall shipboard surveys were conducted within 300 nmi of the coasts of

California, Oregon and Washington in 1996 (Barlow 1997) and 2001 (Barlow 2003). 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 1996-2001 weighted average abundance estimate for California, 

Oregon and Washington waters based on the two ship surveys is 20,362 (CV=0.26 ) northern right-whale

dolphins (Barlow 2003). 

117
Minimum Population Estimate

 The log-normal 20th percentile of the 1996-2001 weighted average abundance estimate is 16,417 

northern right-whale dolphins. 

Current Population Trend

 Estimates of northern right whale dolphin abundance from surveys conducted in 1991/93, 1996, 

and 2001 in California waters were 9,929 (CV = 0.49); 14,593 (0.55); and 10,915 (0.41), respectively 

(Barlow 2003). Abundance estimates for all California, Oregon, and Washington waters from 1996 and 

2001 surveys were 19,619 (0.43) and 21,104 (0.30), respectively (Barlow 1993). Currently, there is no 

evidence of a trend in abundance for this stock. 

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 ( 16,417) 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 164 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, 

1997-2001 (Cameron and Forney 1999, 2000; Carretta 2001, 2002). 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 2003). 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. 

Entanglement rates for this species may be related to oceanographic conditions, as lower entanglement 

rates have been observed during warm-water periods, such as El Niño (Figure 2). Mean annual takes in 

Table 1 are based on 1997-2001 data. This results in an average estimate of 23 (CV= 0.27) northern rightwhale 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 1997-

2001 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 

1997 

1998 

1999 

2000 

2001 

23.0% 

20.0% 

20.0% 

22.9% 

20.4% 

5 

0 

3 

11 

5 

29 (0.42) 

0 

17 (0.66) 

47 (0.51) 

22 (0.54) 

23 (0.27) 

Minimum total annual takes 23 (0.27) 

 

118
Drift gillnet fisheries for swordfish and sharks exist along the entire Pacific coast of Baja

California, Mexico and may take animals from this 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. Previous efforts to 

convert the Mexican swordfish driftnet fishery to a longline fishery have resulted in a mixed-fishery, with 

20 vessels alternately using longlines or driftnets, 23 using driftnets only, 22 using longlines only, and 

seven with unknown gear type (Berdegué 2002). 

Northern right whale dolphin: kill rates

0

0.01

0.02

0.03

1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002

Year

Kill/D

a

y

No pingers Pingers

Figure 2. Kill rates of northern right whale dolphin per day fished in the California drift gillnet fishery

for swordfish and thresher shark, 1990-2002. Kill rates include observations from pingered and

unpingered sets. Pingers were not used from 1990-95 and were used experimentally in 1996 and 1997.

For the period 1998-2002, over 99% of all observed sets utilized pingers. 

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

1997-2001 (23 animals) is estimated to be less than the PBR (158), 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. 

119
Barlow, J. and G. A. Cameron. 2003. Field experiments show that acoustic pingers reduce marine mammal 

bycatch in the California drift gillnet fishery. Marine Mammal Science 19(2):265-283. 

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. 

Barlow, J. 2003. Preliminary estimates of the abundance of cetaceans along the U.S. west coast: 

1991_2001. Southwest Fisheries Science Center Administrative Report LJ_03_03. Available 

from SWFSC, 8604 La Jolla Shores Dr., La Jolla CA 92037. 31p. 

Berdegué, J. 2002. Depredación de las especies pelágicas reservadas a la pesca deportiva y especies en 

peligro de extinción con uso indiscriminado de artes de pesca no selectivas (palangres, FAD's, 

trampas para peces y redes de agallar fijas y a la deriva) por la flota palangrera Mexicana. 

Fundación para la conservación de los picudos. A.C. Mazatlán, Sinaloa, 21 de septiembre. 

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. 

Cameron, G.A. and K.A. Forney. 2000. Preliminary estimates of cetacean mortality in California/Oregon 

Gillnet Fisheries for 1999. Report SC/52/O24 presented to the Scientific Committee of the 

International Whaling Commission, June 2000 (unpublished). 12p. [Available from Southwest 

Fisheries Science Center, National Marine Fisheries Service, 8604 La Jolla Shores Drive, La Jolla, 

CA 92037, USA.] 

Carretta, J.V. 2001. Preliminary estimates of cetacean mortality in California gillnet fisheries for 2000. 

Report SC/53/SM9 presented to the Scientific Committee of the International Whaling 

Commission, June 2001 (unpublished). 21p. [Available from Southwest Fisheries Science Center, 

National Marine Fisheries Service, 8604 La Jolla Shores Drive, La Jolla, CA 92037, USA.]. 

Carretta, J.V. 2002. Preliminary estimates of cetacean mortality in California gillnet fisheries for 2001. 

Report SC/54/SM12 presented to the Scientific Committee of the International Whaling 

Commission, April 2002 (unpublished). 22p. [Available from Southwest Fisheries Science 

Center, National Marine Fisheries Service, 8604 La Jolla Shores Drive, La Jolla, CA 92037, 

USA.]. 

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 

120
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, 8604 La Jolla Shores 

Drive, La Jolla, CA 92037. 

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. 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. 

121
Revised 12/15/2003 

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 have been

noted for killer whales throughout Alaska (Braham 

and Dahlheim 1982) and in the intracoastal

waterways of British Columbia and Washington, 

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). 

W132 W129 W126 W123 W120 W117

N30

N34

N38

N42

N46

WASHINGTON

OREGON

CALIFORNIA

Figure 1. Killer whale sightings based on aerial 

and shipboard surveys off California, Oregon

and Washington, 1991- 2001 (see Appendix 2

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 

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 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 

122
Alaska Region contain assessments of the Eastern North Pacific Northern Resident and transient stocks, 

and the most recent assessment for the Hawaii Stock is included in this volume. 

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 linetransect surveys in 1996 (Barlow 1997) and 2001 (Barlow 2003), the total number of killer whales within 

300 nmi of the coasts of California, Oregon and Washington was recently estimated to be 1,340 animals 

(CV=0.31). 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 * 1,340 

= 466 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 

1996-2001 line-transect surveys as the 20th percentile of the abundance estimate, or 1,038 killer whales. 

Using the same prorating as above, a minimum of 56/161 * 1,038= 361 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 (361) 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 3.6 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, 2000; Carretta 2001, 2002), 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 

123
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. 

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 1997-2001 data unless noted otherwise. 

Fishery Name Data Type Year(s) 

Percent 

Observer 

Coverage

Observed 

Mortality

Estimated An ual n

Mortality

Mean 

Annual Takes 

(CV in 

parentheses) 

CA/OR thresher 

shark/swordfish drift 

gillnet fishery

observer 

data

1997 

1998 

1999 

2000

2001

23.0% 

20.0% 

20.0% 

22.9%

20.4%

0 

0 

0 

0

0

0 

0 

0 

0

0

0

Minimum total annual takes 0

 

Drift gillnet fisheries for swordfish and sharks exist along the entire Pacific coast of Baja 

California, Mexico and may take animals from this 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. Previous efforts to 

convert the Mexican swordfish driftnet fishery to a longline fishery have resulted in a mixed-fishery, with 

20 vessels alternately using longlines or driftnets, 23 using driftnets only, 22 using longlines only, and 

seven with unknown gear type (Berdegué 2002). 

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 genus 

Orcinus. Oecologia 89:125-132. 

124
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. 

Barlow, J. 2003. Preliminary estimates of the abundance of cetaceans along the U.S. west coast: 

1991_2001. Southwest Fisheries Science Center Administrative Report LJ_03_03. Available 

from SWFSC, 8604 La Jolla Shores Dr., La Jolla CA 92037. 31p. 

Barrett-Lennard, L. Univ. of British Columbia, 6270 University Blvd., Vancouver, BC V6T1Z4. 

Berdegué, J. 2002. Depredación de las especies pelágicas reservadas a la pesca deportiva y especies en 

peligro de extinción con uso indiscriminado de artes de pesca no selectivas (palangres, FAD's, 

trampas para peces y redes de agallar fijas y a la deriva) por la flota palangrera Mexicana. 

Fundación para la conservación de los picudos. A.C. Mazatlán, Sinaloa, 21 de septiembre. 

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. NMFS-SWFSC-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. 

Cameron, G.A. and K.A. Forney. 2000. Preliminary estimates of cetacean mortality in California/Oregon 

Gillnet Fisheries for 1999. Report SC/52/O24 presented to the Scientific Committee of the 

International Whaling Commission, June 2000 (unpublished). 12p. [Available from Southwest 

Fisheries Science Center, National Marine Fisheries Service, 8604 La Jolla Shores Drive, La Jolla, 

CA 92037, USA.] 

Carretta, J.V. 2001. Preliminary estimates of cetacean mortality in California gillnet fisheries for 2000. 

Report SC/53/SM9 presented to the Scientific Committee of the International Whaling 

Commission, June 2001 (unpublished). 21p. [Available from Southwest Fisheries Science Center, 

National Marine Fisheries Service, 8604 La Jolla Shores Drive, La Jolla, CA 92037, USA.]. 

Carretta, J.V. 2002. Preliminary estimates of cetacean mortality in California gillnet fisheries for 2001. 

Report SC/54/SM12 presented to the Scientific Committee of the International Whaling 

Commission, April 2002 (unpublished). 22p. [Available from Southwest Fisheries Science 

Center, National Marine Fisheries Service, 8604 La Jolla Shores Drive, La Jolla, CA 92037, 

USA.]. 

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 

125
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. 

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. 

126
Revised 03/15/2005

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). 

Washington

Oregon

Vancouver

Island

Queen 

Charlotte

Islands

California

British Columbia

130°W

130°W

40°N 40°N

50°N 50°N

Figure 1. Approximate April-October distribution of the 

Eastern North Pacific Southern Resident killer whale 

stock (shaded area) and range of sightings (dotted line).

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. In May 2003, these pods were sighted off the northern end of the Queen Charlotte Islands, the furthest north 

they had ever previously been documented (J. Ford, pers. comm.). 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 L1 were observed in Monterey Bay, California, in January 2000 and March 2003 (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

127
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 and Eastern North Pacific Transient stocks. 

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 79 whales in 2001 before

increasing slightly to 83 whales in 2003 (Fig. 2;

Ford et al. 2000; Center for Whale Research, 

unpubl. data). The 2001, 2002, and 2003 counts 

include a whale born in 1999 (L-98) that was listed 

as missing during the annual census in May and June 

2001 but was subsequently discovered alone in an 

inlet off the west coast of Vancouver Island (J. Ford, 

pers. comm.). As of October 2003, L-98 has 

remained separate from L pod and it remains unclear 

whether it will rejoin L pod in the future, either on

its own or through a proposed reintroduction effort. 

For now, it will be included in the current population size. However, one new calf observed in the fall of 2003 will

not be a part of the official census until seen in May/June 2004 (Center for Whale Research, unpubl. data). 

50

60

70

80

90

100

197419761978198019821984198619881990199219941996199820002002

Year

Total population

Figure 2. Population of Eastern North Pacific Southern

Resident stock of killer whales, 1974-2002 1974-2003. 

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).

Minimum Population Estimate

or this stock of killer whales is a direct count of individually identifiable animals. 

is thou

urrent Population Trend

ure fishery that existed from 1967 to 1973, it is estimated that 47 killer whales, mostly

r

URRENT AND MAXIMUM NET PRODUCTIVITY RATES

is currently unavailable for this stock of killer 

hales.

The abundance estimate f

It ght 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 83 animals. 

C

During the live-capt

immatu e, 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 

declined to 79 whales before increasing in 2002 and 2003 to a total of 83 whales (Ford et al. 2000; Center for Whale 

Research, unpubl. data). 

C

A reliable estimate of the maximum net productivity rate

w 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% may be an underestimate 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).

128
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 0.5 (for a 

depleted stock, Wade and Angliss 1997), resulting in a PBR of 0.8 whales per year. 

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 40 to 83% in the entire 

fishery (coastal + inland waters) between 1998 and 2002. There was no observer coverage in this fishery in 1999, 

2001, or 2002. However, the total fishing effort was 4, 46, and 4.5 net days (respectively) in those years, it 

occurred only in inland waters, and no killer whale takes were reported. 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 the 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. 

 Killer whale takes in the Washington Puget Sound Region salmon drift gillnet fishery are unlikely to have 

increased since the fishery was last observed in 1994, due to reductions in the number of participating vessels and 

available fishing time (see details in Appendix 1). Fishing effort and catch have declined throughout all salmon 

fisheries in the region due to management efforts to recover ESA-listed salmonids. 

 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 2002, 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. Logbook data are available for part of 1989-1994, after which incidental mortality reporting requirements 

were modified. Under the new system, logbooks are no longer required; instead, fishers provide self-reports. Data 

for the 1994-1995 phase-in period is fragmentary. After 1995, the level of reporting dropped dramatically, such that 

the records are considered incomplete and estimates of mortality based on them represent minimums (see Appendix 

7 in Angliss and Lodge 2002 for details). 

 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. 

129
Other Mortality

 According to Northwest Marine Mammal Stranding Network records, maintained by the NMFS Northwest 

Region, no human-caused killer whale mortalities or serious injuries were reported from non-fisheries sources in 

1998-2002. 

STATUS OF STOCK

 NMFS received a petition from the Center for Biological Diversity and 10 co-petitioners on 2 May 2001 

(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. NMFS determined that the petition presented substantial scientific 

information indicating that a listing may be warranted thus was required to conduct an ESA status review of the 

stock (66 FR 42499, 13 August 2001). NMFS established a Biological Review Team (BRT) for this purpose and, in 

accordance with the BRT report (Krahn et al. 2002), determined that Southern Resident killer whales are not a 

“species” under the ESA and that a listing of “threatened” or “endangered” was not warranted (67 FR 44133, 1 July 

2002). The BRT report (Krahn et al. 2002) identified potential risk factors that could influence this killer whale 

population, including: changes in prey availability, caused by fluctuations in environmental conditions (e.g., El 

Niño events); high levels of contaminants (Ross et al. 2000, Ylitalo et al. 2001); noise generated by whale-watching 

vessels; diseases and parasites; declines in stocks of salmon which are important prey; and catastrophes, such as oil 

spills and blooms of harmful algae. However, few quantitative data are available to determine which, if any, of 

these factors are likely to place the population in imminent danger of extinction. NMFS will continue to seek new 

information on the taxonomy, biology, and ecology of these whales, as well as potential threats to their continued 

existence, and will reassess their status under the ESA within 4 years (67 FR 44133, 1 July 2002). NMFS reviewed 

the status of the stock under the MMPA, determined that the stock is below its Optimum Sustainable Population 

(OSP), classified the stock as “depleted” under the MMPA, and announced its intention to prepare a Conservation 

Plan to reverse the decline and to promote recovery of the stock to OSP (68 FR 31980, 29 May 2003). 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, appears 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). However, because the Eastern North Pacific Southern Resident killer whale stock 

has been designated as “depleted” under the MMPA, it is classified as a “strategic” stock. 

 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 November 2001, COSEWIC split the original listing for resident killer whales into 

two populations. The northern resident population was designated as “threatened” and the southern resident 

population was designated as “endangered,” i.e., facing imminent extirpation or extinction (COSEWIC 2003). In 

June 2000, the Washington Department of Fish and Wildlife (WDFW) 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”). In October 2003, WDFW released a draft status review which proposes that Southern 

Resident killer whales be added to the state’s endangered species list (WDFW 2003). 

REFERENCES

Angliss, R. P., and K. L. Lodge. 2002. Alaska marine mammal stock assessments, 2002. U.S. Dep. Commer., 

NOAA Tech. Memo. NMFS-AFSC-133. 224 pp. 

Baird, R. W. 1999. Status of killer whales in Canada. Contract Report to the Committee on the Status of 

Endangered Wildlife in Canada (COSEWIC), Ottawa. 42 pp. 

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 (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. 

130
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. Special Issue 12. 

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. 

Committee on the Status of Endangered Wildlife in Canada (COSEWIC). 2003. Species Listing. Available at 

URL: http://www.cosewic.gc.ca/eng/sct0/index_e.cfm (access date - October 2003). 

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. K. Ellifrit, and J. D. Swenson. 1997. Killer whales of Southeast Alaska: a catalogue of 

photoidentified individuals. National Marine Mammal Laboratory, AFSC, NMFS, NOAA, 7600 Sand 

Point Way NE, Seattle, WA 98115. 79 pp. 

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. Pacific Biological Station, Department of Fisheries and Oceans, Nanaimo, BC V9R 5K6. 

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. 

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. 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 

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. 

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. 

Krahn, M. M., P. R. Wade, S. T. Kalinowski, M. E. Dahlheim, B. L. Taylor, M. B. Hanson, G. M. Ylitalo, R. P. 

Angliss, J. E. Stein, and R. S. Waples. 2002. Status review of Southern Resident killer whales (Orcinus 

131
orca) under the Endangered Species Act. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-NWFSC-54. 

133 pp. 

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 Nat. 104:362_371. 

Matkin, C., G. Ellis, E. Saulitis, L. Barrett-Lennard, and D. Matkin. 1999. Killer Whales of Southern Alaska. 

North Gulf Oceanic Society. 96 pp. 

Mitchell, E. D. 1975. Report on the meeting on small cetaceans, Montreal, April 1-11, 1974. J. Fish. Res. Bd. Can. 

32:914-916. 

Northwest Indian Fisheries Commission (NWIFC). 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, and U.S. Fish and Wildlife Service. 

Unpubl. report. 41 pp. Available at NWIFC, 6730 Martin Way E, Olympia, WA 98516. 

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. 

Pierce, D. J., W. P. Ritchie, and R. Kreuziger. 1994. Preliminary findings of seabird interactions with the nontreaty 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. 

Ross, P. S., G. M. Ellis, M. G. Ikonomou, L. G. Barrett-Lennard, and R. F. Addison. 2000. High PCB 

concentrations in free-ranging Pacific killer whales, Orcinus orca: effects of age, sex and dietary 

preference. Mar. Pollut. Bull. 40(6):504-515. 

Stevens, T. A., D. Duffield, E. Asper, K. Hewlett, A. Bolz, L. Gage, and G. Bossart. 1989. Preliminary findings of 

restriction fragment differences in mitochondrial DNA among killer whales (Orcinus orca). Can. J. Zool. 

67:2592-2595. 

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-OPR12. 93 pp. 

Washington Department of Fish and Wildlife (WDFW). 2003. Species of Concern. Available at URL: 

http://www.wa.gov/wdfw/wlm/diversty/soc/concern.htm (access date - October 2003). 

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. Fish. Bull. 93:355-372. 

Ylitalo, G. M., C. O. Matkin, J. Buzitis, M. M. Krahn, L. L. Jones, T. Rowles, and J. E. Stein. 2001. Influence of 

life-history parameters on organochlorine concentrations in free-ranging killer whales (Orcinus orca) from 

Prince William Sound, AK. Sci. Total Environ. 281:183-203. 

132
Revised 12/15/2003 

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. 

W132 W129 W126 W123 W120 W117

N30

N3

POPULATION SIZE

Only two groups of pilot whales (numbering

approximately 80 animals) were seen during the two most

recent ship surveys conducted off California, Oregon, and

Washington in 1996 and 2001 (Barlow 1997; Barlow 2003). 

All animals were seen during the 1996 survey. 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 1996-2001 weighted average

abundance estimate for California, Oregon and Washington waters based on the two ship surveys is 304 (CV= 1.02)

short-finned pilot whales (Barlow 2003). 

4

N38

N42

N46

WASHINGTON

OREGON

CALIFORNIA

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- 2001 

(•). See Appendix 2 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. 

Minimum Population Estimate

The log-normal 20th percentile of the 1996-2001 weighted average abundance estimate is 149 short-finned 

pilot whales. 

133
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 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 

(149) 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 1.19 

short-finned 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, 1997-2001 (Cameron and 

Forney 1999, 2000; Carretta 2001, 2002). 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 2003). 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. 

Mean annual takes in Table 1 are based on 1997- 2001 data. This results in an average estimate of 1.2 (CV=0.96) 

short-finned pilot whales taken annually. 

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

Mexico and may take animals from this 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. Previous efforts to convert the Mexican swordfish driftnet fishery to a longline fishery have resulted in a 

mixed-fishery, with 20 vessels alternately using longlines or driftnets, 23 using driftnets only, 22 using longlines 

only, and seven with unknown gear type (Berdegué 2002). 

 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). 

 

134
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 1997-2001 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

1997 

1998 

1999 

2000 

2001 

22.8 % 

20.2 % 

20.0% 

22.9% 

20.4% 

1 

0 

0 

0 

0 

6 (0.96) 

0 

0 

0 

0 

1.2 (0.96) 

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 1.2 (0.96) 

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. Short-finned pilot whales are not listed as "threatened" or "endangered" under the 

Endangered Species Act nor as "depleted" under the MMPA. The average annual human-caused mortality from 

1997-2001 is 1.2 animals., which is greater than the PBR (1.19 ), and therefore they are classified as a "strategic" 

stock under the MMPA. 

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. 2003. Field experiments show that acoustic pingers reduce marine mammal bycatch 

in the California drift gillnet fishery. Marine Mammal Science 19(2):265-283. 

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. 

Barlow, J. 2003. Preliminary estimates of the abundance of cetaceans along the U.S. west coast: 1991_2001. 

Southwest Fisheries Science Center Administrative Report LJ_03_03. Available from SWFSC, 8604 La 

Jolla Shores Dr., La Jolla CA 92037. 31p. 

Berdegué, J. 2002. Depredación de las especies pelágicas reservadas a la pesca deportiva y especies en peligro de 

extinción con uso indiscriminado de artes de pesca no selectivas (palangres, FAD's, trampas para peces y 

redes de agallar fijas y a la deriva) por la flota palangrera Mexicana. Fundación para la conservación de los 

picudos. A.C. Mazatlán, Sinaloa, 21 de septiembre. 

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. 

Cameron, G.A. and K.A. Forney. 2000. Preliminary estimates of cetacean mortality in California/Oregon Gillnet 

Fisheries for 1999. Report SC/52/O24 presented to the Scientific Committee of the International Whaling 

Commission, June 2000 (unpublished). 12p. [Available from Southwest Fisheries Science Center, National 

Marine Fisheries Service, 8604 La Jolla Shores Drive, La Jolla, CA 92037, USA.] 

135
Carretta, J.V. 2001. Preliminary estimates of cetacean mortality in California gillnet fisheries for 2000. 

Report SC/53/SM9 presented to the Scientific Committee of the International Whaling 

Commission, June 2001 (unpublished). 21p. [Available from Southwest Fisheries Science Center, 

National Marine Fisheries Service, 8604 La Jolla Shores Drive, La Jolla, CA 92037, USA.]. 

Carretta, J.V. 2002. Preliminary estimates of cetacean mortality in California gillnet fisheries for 2001. 

Report SC/54/SM12 presented to the Scientific Committee of the International Whaling 

Commission, April 2002 (unpublished). 22p. [Available from Southwest Fisheries Science 

Center, National Marine Fisheries Service, 8604 La Jolla Shores Drive, La Jolla, CA 92037, 

USA.]. 

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. NMFS-SWFSC-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 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 long-term management strategy (LTMS), August 1990 through November 1991, for the 

U.S. Environmental Protection Agency, Region IX, San Francisco, July 1992. 

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. 

136
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. 

137
Revised 12/15/2003 

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

Two summer/fall shipboard surveys were

conducted within 300 nmi of the coasts of

California, Oregon and Washington in 1996

(Barlow 1997) and 2001 (Barlow 2003), resulting in 

a combined total of 11 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 1996-2001 

weighted average abundance estimate for California, 

Oregon and Washington waters based on the above

two ship surveys is 228 (CV=0.51) 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.

W132 W129 W126 W123 W120 W117

N30

N3

N3

4

8

N42

N46

WASHINGTON

OREGON

CALIFORNIA

Figure 1. Baird’s beaked whale sightings based 

on aerial and shipboard surveys off California,

Oregon and Washington, 1991-2001 (see 

Appendix 2 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. 

 

Minimum Population Estimate

The log-normal 20th percentile of the 1996-2001 weighted average abundance estimate is 152

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. 

138
POTENTIAL BIOLOGICAL REMOVAL

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

population size (152) 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 fishery mortality; Wade and Angliss 

1997), resulting in a PBR of 1.5 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, 

1997-2001 (Julian 1997; Cameron and Forney 1999, 2000; Carretta 2001; 2002). 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 2003). 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. Mean annual takes in Table 1 are based on 1997-2001 data. This results in an average estimated 

annual mortality of zero Baird’s beaked whales. One Baird’s beaked whale was taken in the drift gillnet 

fishery in 1994. 

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 1997-2001 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

1997 

1998 

1999 

2000

2001

23.0% 

20.0% 

20.0% 

22.9%

20.4%

0 

0 

0 

0

0

0 

0 

0 

0

0

0

Minimum total annual takes 0

Drift gillnet fisheries for swordfish and sharks exist along the entire Pacific coast of Baja 

California, Mexico and may take animals from this 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. Previous efforts to 

convert the Mexican swordfish driftnet fishery to a longline fishery have resulted in a mixed-fishery, with 

20 vessels alternately using longlines or driftnets, 23 using driftnets only, 22 using longlines only, and 

seven with unknown gear type (Berdegué 2002). 

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). 

139
 Additional, unknown levels of injuries and mortalities of Baird’s beaked whales may occur as a 

result of anthropogenic noise, such as military sonars (U.S. Dept. of Commerce and Secretary of the Navy 

2001) or other commercial and scientific activities involving the use of air guns. Such injuries or 

mortalities would rarely be documented, due to the remote nature of many of these activities and the low 

probability that an injured or dead beaked whale would strand. 

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). In particular, active sonar has been implicated in the mass stranding of beaked whales in the 

Mediterranean Sea (Frantzis 1998) and more recently in the Caribbean (U.S. Dept. of Commerce and 

Secretary of the Navy 2001). 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 

1997-2001 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. 2003. Field experiments show that acoustic pingers reduce marine mammal 

bycatch in the California drift gillnet fishery. Marine Mammal Science 19(2):265-283. 

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. 

Barlow, J. 2003. Preliminary estimates of the abundance of cetaceans along the U.S. west coast: 

1991_2001. Southwest Fisheries Science Center Administrative Report LJ_03_03. Available 

from SWFSC, 8604 La Jolla Shores Dr., La Jolla CA 92037. 31p. 

Berdegué, J. 2002. Depredación de las especies pelágicas reservadas a la pesca deportiva y especies en 

peligro de extinción con uso indiscriminado de artes de pesca no selectivas (palangres, FAD's, 

trampas para peces y redes de agallar fijas y a la deriva) por la flota palangrera Mexicana. 

Fundación para la conservación de los picudos. A.C. Mazatlán, Sinaloa, 21 de septiembre. 

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. 

Cameron, G.A. and K.A. Forney. 2000. Preliminary estimates of cetacean mortality in California/Oregon 

Gillnet Fisheries for 1999. Report SC/52/O24 presented to the Scientific Committee of the 

International Whaling Commission, June 2000 (unpublished). 12p. [Available from Southwest 

Fisheries Science Center, National Marine Fisheries Service, 8604 La Jolla Shores Drive, La Jolla, 

CA 92037, USA.] 

Carretta, J.V. 2001. Preliminary estimates of cetacean mortality in California gillnet fisheries for 2000. 

Report SC/53/SM9 presented to the Scientific Committee of the International Whaling 

Commission, June 2001 (unpublished). 21p. [Available from Southwest Fisheries Science Center, 

National Marine Fisheries Service, 8604 La Jolla Shores Drive, La Jolla, CA 92037, USA.]. 

Carretta, J.V. 2002. Preliminary estimates of cetacean mortality in California gillnet fisheries for 2001. 

Report SC/54/SM12 presented to the Scientific Committee of the International Whaling 

140
Commission, April 2002 (unpublished). 22p. [Available from Southwest Fisheries Science 

Center, National Marine Fisheries Service, 8604 La Jolla Shores Drive, La Jolla, CA 92037, 

USA.]. 

Frantzis, A. 1998. Does acoustic testing strand whales? Nature 392(5):29. 

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. 

U.S. Department of Commerce and Secretary of the Navy. 2001. Joint Interim Report, Bahamas Marine 

Mammal Stranding Event of 15_16 March 2000. Available from NOAA, NMFS, Office of 

Protected Resources, Silver Spring, MD. 

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
Revised 12/15/2003 

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 six species known to

occur in this region are: Blainville's beaked whale 

(M. densirostris), Perrin’s beaked whale (M. 

perrini), Lesser beaked whale (M. peruvianus),

Stejneger's beaked whale (M. stejnegeri), Gingkotoothed 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. 

W132 W129 W126 W123 W120 W117

N30

N34

N38

N42

N46

WASHINGTON

OREGON

CALIFORNIA

Until methods of distinguishing these six 

species are developed, the management unit must

be defined to include all Mesoplodon stocks in this 

region. However, in the future, species-level 

management is desirable, and a high priority should 

be placed on finding means to obtain speciesspecific 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). Updated analyses are 

based on 1) combining data from two surveys conducted within 300 nmi of the coasts of California, Oregon

and Washington in 1996; (Barlow 1997) and 2001 (Barlow 2003), 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). Of the 12 sightings of Mesoplodon made during the 1996 and 2001 surveys, none

Figure 1. Mesoplodon beaked whale sightings

based on aerial and shipboard surveys off

California, Oregon and Washington, 1991-2001 

(see Appendix 2 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. 

142
could be identified to the species level. Thus, an updated estimate of Blainville’s beaked whale abundance 

is unavailable. An updated estimate of abundance for unidentified mesoplodont beaked whales is 

presented, based on 1996-2001 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 1996-2001 weighted average abundance estimates for 

California, Oregon and Washington waters based on the above analyses are 1,247(CV=0.92) mesoplodont 

beaked whales of unknown species.

Minimum Population Estimate

 Based on the abundance estimate of 1,247 (CV=0.92), 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 645 animals. 

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 (645) 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 6.5 mesoplodont beaked whales per year. 

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, 

1997-2001 (Cameron and Forney 1999, 2000; Carretta 2001, 2002). 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 2003). 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. Mean 

annual takes in Table 1 are based on 1997-2001 data. This results in an average estimated annual mortality 

of zero mesoplodont beaked whales. Prior to the most recent 5-year period, there were a total of eight 

mesoplodont beaked whales entangled in the drift gillnet fishery: 1990 (one animal), 1992 (four), and 1994 

(three). 

 Drift gillnet fisheries for swordfish and sharks exist along the entire Pacific coast of Baja 

California, Mexico and may take animals from this 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. Previous efforts to 

convert the Mexican swordfish driftnet fishery to a longline fishery have resulted in a mixed-fishery, with 

20 vessels alternately using longlines or driftnets, 23 using driftnets only, 22 using longlines only, and 

seven with unknown gear type (Berdegué 2002). 

 

143
Other mortality

 Additional, unknown levels of injuries and mortalities of mesoplodont beaked whales may occur 

as a result of anthropogenic noise, such as military sonars (U.S. Dept. of Commerce and Secretary of the 

Navy 2001) or other commercial and scientific activities involving the use of air guns. Such injuries or 

mortalities would rarely be documented, due to the remote nature of many of these activities and the low 

probability that an injured or dead beaked whale would strand. 

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 deep-diving cetacean species, such as mesoplodont beaked whales 

(Richardson et al. 1995). In particular, active sonar has been implicated in the mass stranding of beaked 

whales in the Mediterranean Sea (Frantzis 1998) and more recently in the Bahamas (U.S. Dept. of 

Commerce and Secretary of the Navy 2001).

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 1997-2001 

data unless noted otherwise. 

Fishery Name Data Type

Year(s) 

Percent 

Observer 

Coverage

Observed

Mortality

Estimated 

Annual 

Mortality

Mean 

Annual Takes 

(CV in 

parentheses)

Hubbs’ beaked whale, Mesoplodon carlhubbsi

observer 

data

1997 

1998 

1999 

2000

2001

23.0% 

20.0% 

20.0% 

22.9%

20.4%

0 

0 

0 

0

0

0 

0 

0 

0

0

0

Stejneger’s beaked whale, Mesoplodon stejnegeri

observer 

data

1997 

1998 

1999 

2000

2001

23.0% 

20.0% 

20.0% 

22.9%

20.4%

0 

0 

0 

0

0

0 

0 

0 

0

0

0

Unidentified beaked whale (probably Mesoplodon)

CA/OR thresher 

shark/swordfish drift gillnet 

fishery

observer 

data

1997 

1998 

1999 

2000

2001

23.0% 

20.0% 

20.0% 

22.9%

20.4%

0 

0 

0 

0

0

0 

0 

0 

0

0

0

Minimum total annual takes of Mesoplodon beaked whales 0 

None of the six 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 1997-2001 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. 

144
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. 2003. Field experiments show that acoustic pingers reduce marine mammal 

bycatch in the California drift gillnet fishery. Marine Mammal Science 19(2):265-283. 

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. 

Barlow, J. 2003. Preliminary estimates of the abundance of cetaceans along the U.S. west coast: 

1991_2001. Southwest Fisheries Science Center Administrative Report LJ_03_03. Available 

from SWFSC, 8604 La Jolla Shores Dr., La Jolla CA 92037. 31p. 

Berdegué, J. 2002. Depredación de las especies pelágicas reservadas a la pesca deportiva y especies en 

peligro de extinción con uso indiscriminado de artes de pesca no selectivas (palangres, FAD's, 

trampas para peces y redes de agallar fijas y a la deriva) por la flota palangrera Mexicana. 

Fundación para la conservación de los picudos. A.C. Mazatlán, Sinaloa, 21 de septiembre. 

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. 

Cameron, G.A. and K.A. Forney. 2000. Preliminary estimates of cetacean mortality in California/Oregon 

Gillnet Fisheries for 1999. Report SC/52/O24 presented to the Scientific Committee of the 

International Whaling Commission, June 2000 (unpublished). 12p. [Available from Southwest 

Fisheries Science Center, National Marine Fisheries Service, 8604 La Jolla Shores Drive, La Jolla, 

CA 92037, USA.] 

Carretta, J.V. 2001. Preliminary estimates of cetacean mortality in California gillnet fisheries for 2000. 

Report SC/53/SM9 presented to the Scientific Committee of the International Whaling 

Commission, June 2001 (unpublished). 21p. [Available from Southwest Fisheries Science Center, 

National Marine Fisheries Service, 8604 La Jolla Shores Drive, La Jolla, CA 92037, USA.]. 

Carretta, J.V. 2002. Preliminary estimates of cetacean mortality in California gillnet fisheries for 2001. 

Report SC/54/SM12 presented to the Scientific Committee of the International Whaling 

Commission, April 2002 (unpublished). 22p. [Available from Southwest Fisheries Science 

Center, National Marine Fisheries Service, 8604 La Jolla Shores Drive, La Jolla, CA 92037, 

USA.]. 

Frantzis, A. 1998. Does acoustic testing strand whales? Nature 392(5):29. 

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. 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. 

145
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. 

U.S. Department of Commerce and Secretary of the Navy. 2001. Joint Interim Report, Bahamas Marine 

Mammal Stranding Event of 15_16 March 2000. Available from NOAA, NMFS, Office of 

Protected Resources, Silver Spring, MD. 

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. 

146
Revised 12/15/2003 

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, non-contiguous 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 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). 

Updated analyses are based on 1) combining data from two surveys conducted within 300 nmi of the 

coasts of California, Oregon and Washington in 1996 (Barlow 1997) and 2001 (Barlow 2003), 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 1996-2001 weighted average abundance estimate for California, Oregon and Washington

waters based on the above analyses is 1,884 (CV=0.68) Cuvier’s beaked whales. 

W132 W129 W126 W123 W120 W117

N30

N34

N38

N42

N46

WASHINGTON

OREGON

CALIFORNIA

Figure 1. Cuvier’s beaked whale sightings

based on aerial and shipboard surveys off

California, Oregon and Washington, 1991-2001 

(see Appendix 2, 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.

147
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 1,121 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 (1,121) 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 11 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, 

1997-2001 (Cameron and Forney 1999, 2000; Carretta 2001, 2002). 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 2003). 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. 

Mean annual takes in Table 1 are based only on 1997-2001 data. This results in an average estimated 

annual mortality of zero Cuvier’s beaked whales. There have been no Cuvier’s beaked whales observed 

entangled in the drift gillnet fishery since 1995. Prior to the most recent 5-year period, there were a total of 

21 Cuvier’s beaked whales entangled in the drift gillnet fishery: 1992 (six animals), 1993 (three), 1994 

(six) and 1995 (six). 

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. Mean 

annual takes are based on 1997-2001 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

1997 

1998 

1999 

2000

2001

23.0% 

20.0% 

20.0% 

22.9%

20.4%

0 

0 

0 

0

0

0 

0 

0 

0

0

0

Minimum total annual takes 0

Drift gillnet fisheries for swordfish and sharks exist along the entire Pacific coast of Baja 

California, Mexico and may take animals from this 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 

148
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. Previous efforts to 

convert the Mexican swordfish driftnet fishery to a longline fishery have resulted in a mixed-fishery, with 

20 vessels alternately using longlines or driftnets, 23 using driftnets only, 22 using longlines only, and 

seven with unknown gear type (Berdegué 2002). 

Other mortality

 Additional, unknown levels of injuries and mortalities of Cuvier’s beaked whales may occur as a 

result of anthropogenic noise, such as military sonars (U.S. Dept. of Commerce and Secretary of the Navy 

2001) or other commercial and scientific activities involving the use of air guns. Such injuries or 

mortalities would rarely be documented, due to the remote nature of many of these activities and the low 

probability that an injured or dead beaked whale would strand. 

STATUS OF STOCK

 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, active sonar has been implicated in the mass stranding of beaked 

whales in the Mediterranean Sea (Frantzis 1998) and more recently in the Caribbean (U.S. Dept. of 

Commerce and Secretary of the Navy 2001). They are not listed as "threatened" or "endangered" under the 

Endangered Species Act nor as "depleted" under the MMPA. The average annual human-caused mortality 

in 1997-2001 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. 2003. Field experiments show that acoustic pingers reduce marine mammal 

bycatch in the California drift gillnet fishery. Marine Mammal Science 19(2):265-283. 

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. 

Barlow, J. 2003. Preliminary estimates of the abundance of cetaceans along the U.S. west coast: 

1991_2001. Southwest Fisheries Science Center Administrative Report LJ_03_03. Available 

from SWFSC, 8604 La Jolla Shores Dr., La Jolla CA 92037. 31p. 

Berdegué, J. 2002. Depredación de las especies pelágicas reservadas a la pesca deportiva y especies en 

peligro de extinción con uso indiscriminado de artes de pesca no selectivas (palangres, FAD's, 

trampas para peces y redes de agallar fijas y a la deriva) por la flota palangrera Mexicana. 

Fundación para la conservación de los picudos. A.C. Mazatlán, Sinaloa, 21 de septiembre. 

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. 

Cameron, G.A. and K.A. Forney. 2000. Preliminary estimates of cetacean mortality in California/Oregon 

Gillnet Fisheries for 1999. Report SC/52/O24 presented to the Scientific Committee of the 

International Whaling Commission, June 2000 (unpublished). 12p. [Available from Southwest 

Fisheries Science Center, National Marine Fisheries Service, 8604 La Jolla Shores Drive, La Jolla, 

CA 92037, USA.] 

149
Carretta, J.V. 2001. Preliminary estimates of cetacean mortality in California gillnet fisheries for 2000. 

Report SC/53/SM9 presented to the Scientific Committee of the International Whaling 

Commission, June 2001 (unpublished). 21p. [Available from Southwest Fisheries Science Center, 

National Marine Fisheries Service, 8604 La Jolla Shores Drive, La Jolla, CA 92037, USA.]. 

Carretta, J.V. 2002. Preliminary estimates of cetacean mortality in California gillnet fisheries for 2001. 

Report SC/54/SM12 presented to the Scientific Committee of the International Whaling 

Commission, April 2002 (unpublished). 22p. [Available from Southwest Fisheries Science 

Center, National Marine Fisheries Service, 8604 La Jolla Shores Drive, La Jolla, CA 92037, 

USA.]. 

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. 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. 

U.S. Department of Commerce and Secretary of the Navy. 2001. Joint Interim Report, Bahamas Marine 

Mammal Stranding Event of 15_16 March 2000. Available from NOAA, NMFS, Office of 

Protected Resources, Silver Spring, MD. 

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. 

150
Revised 12/15/2003 

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), while strandings of dwarf sperm whales (Kogia sima) 

are rare in this region. At-sea sightings in this region have 

all been either of pygmy sperm whales or unidentified Kogia

sp. 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

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. Updated analyses are based on 1)

combining data from two surveys conducted within 300 nmi

of the coasts of California, Oregon and Washington in 1996 (Barlow 1997), and 2001 (Barlow 2003), 2) estimating a 

correction factor for animals missed because they are submerged, based on dive-interval data collected for Kogia

sima 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 1996-2001 weighted average abundance estimate for California, Oregon and

Washington waters based on the above analyses is 247 (CV=1.06) pygmy sperm whales, based on two sightings that

could only be identified to the genus Kogia. Based on previous sighting surveys and historical stranding data, it is 

likely that recent ship survey sightings were of pygmy sperm whales; K. breviceps. 

W132 W129 W126 W123 W120 W117

N30

N34

N38

N42

N46

WASHINGTON

OREGON

CALIFORNIA

Figure 1. Kogia sightings based on aerial and

shipboard surveys off California, Oregon and

Washington, 1991- 2001 (see Appendix 2 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. 

151
Minimum Population Estimate

 Based on the above abundance estimate and CV, the minimum population estimate (defined as the lognormal 20th percentile of the total Kogia abundance estimate) for pygmy sperm whales in California, Oregon, and 

Washington is 119 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 

(119) 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 one pygmy sperm whale 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, 1997-2001 (Cameron and Forney 1999, 2000; 

Carretta 2001, 2002). One pygmy sperm whale was observed killed in the drift gillnet fishery in 1992 and another in 

1993. 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 2003). 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. Mean annual takes in Table 1 are based 

on 1997-2001 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 this 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. Previous efforts to convert the Mexican swordfish driftnet fishery to a longline fishery have resulted in a 

mixed-fishery, with 20 vessels alternately using longlines or driftnets, 23 using driftnets only, 22 using longlines 

only, and seven with unknown gear type (Berdegué 2002). 

Other mortality

 Additional, unknown levels of injuries and mortalities of pygmy sperm whales may occur as a result of 

anthropogenic noise, such as military sonars (U.S. Dept. of Commerce and Secretary of the Navy 2001) or other 

commercial and scientific activities involving the use of air guns. Such injuries or mortalities would rarely be 

documented, due to the remote nature of many of these activities and the low probability that an injured or dead 

pygmy sperm whale would strand. 

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). In particular, active 

152
sonar has been implicated in the mass stranding of beaked whales in the Mediterranean Sea (Frantzis 1998) and 

more recently in the Caribbean (U.S. Dept. of Commerce and Secretary of the Navy 2001). 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 1997-2001 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. 

Coefficients of variation for mortality estimates are provided in parentheses. Mean annual takes are based on 1997-

2001 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

1997 

1998 

1999 

2000

2001

23.0% 

20.0% 

20.0% 

22.9%

20.4%

0 / 0 

0 / 0 

0 / 0 

0 / 0 

0 / 0 

0 / 0 

0 / 0 

0 / 0 

0 / 0

0 / 0

0

Minimum total annual takes 0

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. 2003. Field experiments show that acoustic pingers reduce marine mammal bycatch 

in the California drift gillnet fishery. Marine Mammal Science 19(2):265-283. 

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 trackline 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. 

Barlow, J. 2003. Preliminary estimates of the abundance of cetaceans along the U.S. west coast: 1991_2001. 

Southwest Fisheries Science Center Administrative Report LJ_03_03. Available from SWFSC, 8604 La 

Jolla Shores Dr., La Jolla CA 92037. 31p. 

Berdegué, J. 2002. Depredación de las especies pelágicas reservadas a la pesca deportiva y especies en peligro de 

extinción con uso indiscriminado de artes de pesca no selectivas (palangres, FAD's, trampas para peces y 

redes de agallar fijas y a la deriva) por la flota palangrera Mexicana. Fundación para la conservación de los 

picudos. A.C. Mazatlán, Sinaloa, 21 de septiembre. 

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. 

Cameron, G.A. and K.A. Forney. 2000. Preliminary estimates of cetacean mortality in California/Oregon Gillnet 

Fisheries for 1999. Report SC/52/O24 presented to the Scientific Committee of the International Whaling 

Commission, June 2000 (unpublished). 12p. [Available from Southwest Fisheries Science Center, National 

Marine Fisheries Service, 8604 La Jolla Shores Drive, La Jolla, CA 92037, USA.] 

Carretta, J.V. 2001. Preliminary estimates of cetacean mortality in California gillnet fisheries for 2000. Report 

SC/53/SM9 presented to the Scientific Committee of the International Whaling Commission, June 2001 

153
(unpublished). 21p. [Available from Southwest Fisheries Science Center, National Marine Fisheries 

Service, 8604 La Jolla Shores Drive, La Jolla, CA 92037, USA.]. 

Carretta, J.V. 2002. Preliminary estimates of cetacean mortality in California gillnet fisheries for 2001. Report 

SC/54/SM12 presented to the Scientific Committee of the International Whaling Commission, April 2002 

(unpublished). 22p. [Available from Southwest Fisheries Science Center, National Marine Fisheries 

Service, 8604 La Jolla Shores Drive, La Jolla, CA 92037, USA.]. 

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. 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. 

U.S. Department of Commerce and Secretary of the Navy. 2001. Joint Interim Report, Bahamas Marine Mammal 

Stranding Event of 15_16 March 2000. Available from NOAA, NMFS, Office of Protected Resources, 

Silver Spring, MD. 

154
Revised 12/15/2003 

DWARF SPERM WHALE (Kogia sima): 

California/Oregon/Washington Stock 

 

STOCK DEFINITION AND GEOGRAPHIC 

RANGE

Dwarf sperm whales are distributed 

throughout deep waters and along the continental 

slopes of the North Pacific and other ocean basins

(Caldwell and Caldwell 1989; Ross 1984). This 

species was only recognized as being distinct from

the pygmy sperm whale in 1966 (Handley, 1966), 

and early records for the two species are 

confounded. Along the U.S. west coast, no at-sea 

sightings of this species have been reported;

however, this may be partially a reflection of their

pelagic distribution, small body size and cryptic

behavior. A few sightings of animals identified

only as Kogia sp. have been reported (Figure 1),

and some of these may have been dwarf sperm 

whales. At least five dwarf sperm whales stranded 

in California between 1967 and 2000 (Roest 1970;

Jones 1981; J. Heyning, pers. comm.; NMFS, 

Southwest Region, unpublished data), and one

stranding is reported for western Canada (Nagorsen

and Stewart 1983). It is unclear whether records of 

dwarf sperm whales are so rare because they are not 

regular inhabitants of this region, or merely because

of their cryptic habits and offshore distribution. 

Available data are insufficient to identify any

seasonality in the distribution of dwarf sperm 

whales, or to delineate possible stock boundaries. 

For the Marine Mammal Protection Act (MMPA)

stock assessment reports, dwarf 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. 

W132 W129 W126 W123 W120 W117

N30

N34

N38

N42

N46

WASHINGTON

OREGON

CALIFORNIA

Figure 1. Kogia sightings based on aerial and

shipboard surveys off California, Oregon and

Washington, 1991- 2001 (see Appendix 2 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. 

POPULATION SIZE

No information is available to estimate the population size of dwarf sperm whales off the U.S. 

west coast, as no sightings of this species have been documented despite numerous vessel surveys of this

region. Based on previous sighting surveys and historical stranding data, it is likely that recent ship survey

sightings were of pygmy sperm whales; K. breviceps. 

Minimum Population Estimate

No information is available to obtain a minimum population estimate for dwarf sperm whales. 

Current Population Trend

Due to the rarity of records for this species 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. 

155
POTENTIAL BIOLOGICAL REMOVAL

 Based on this stock's unknown status and growth rate, the recovery factor (Fr) is 0.5, and 1⁄2Rmax is 

the default value of 0.02. However, due to the lack of abundance estimates for this species, no potential 

biological removal (PBR) can be calculated.

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Fishery Information

 In the California drift gillnet fishery, no mortality of dwarf sperm whales or unidentified Kogia

was observed during the most recent five years of monitoring, 1997-2001 (Cameron and Forney 1999, 

2000; Carretta 2001, 2002). 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 2003). 

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 dwarf sperm whales. Mean annual takes in Table 1 are based on 1997-2001 data. This results in an 

average estimated annual mortality of zero dwarf sperm whales. 

 Similar drift gillnet fisheries for swordfish and sharks exist along the entire Pacific coast of Baja 

California, Mexico and may take animals from this population. 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 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. Previous efforts to convert the Mexican swordfish driftnet fishery to a longline fishery 

have resulted in a mixed-fishery, with 20 vessels alternately using longlines or driftnets, 23 using driftnets 

only, 22 using longlines only, and seven with unknown gear type (Berdegué 2002). 

Table 1. Summary of available information on the incidental mortality and injury of dwarf sperm whales 

and unidentified Kogia sp. (California/Oregon/Washington Stock) in commercial fisheries that might take 

this species. Coefficients of variation for mortality estimates are provided in parentheses. Mean annual 

takes are based on 1997-2001 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

1997 

1998 

1999 

2000

2001

23.0% 

20.0% 

20.0% 

22.9%

20.4%

0 / 0 

0 / 0 

0 / 0 

0 / 0 

0 / 0 

0 / 0 

0 / 0 

0 / 0 

0 / 0

0 / 0

0

Minimum total annual takes 0

STATUS OF STOCK

 The status of dwarf 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 dwarf sperm whales (Richardson et 

al. 1995). In particular, active sonar has been implicated in the mass stranding of beaked whales in the 

Mediterranean Sea (Frantzis 1998) and more recently in the Caribbean (U.S. Dept. of Commerce and 

Secretary of the Navy 2001). They are not listed as "threatened" or "endangered" under the Endangered 

156
Species Act nor as "depleted" under the MMPA. Given that this species rarely occurs off the U.S. west 

coast and current fishery mortality is zero, dwarf sperm whales off California, Oregon and Washington are 

not classified as a "strategic" stock under the MMPA. 

REFERENCES

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. 

Barlow, J. and G. A. Cameron. 2003. Field experiments show that acoustic pingers reduce marine mammal 

bycatch in the California drift gillnet fishery. Marine Mammal Science 19(2):265-283. 

Berdegué, J. 2002. Depredación de las especies pelágicas reservadas a la pesca deportiva y especies en 

peligro de extinción con uso indiscriminado de artes de pesca no selectivas (palangres, FAD's, 

trampas para peces y redes de agallar fijas y a la deriva) por la flota palangrera Mexicana. 

Fundación para la conservación de los picudos. A.C. Mazatlán, Sinaloa, 21 de septiembre. 

Cameron, G.A. and K.A. Forney. 2000. Preliminary estimates of cetacean mortality in California/Oregon 

Gillnet Fisheries for 1999. Report SC/52/O24 presented to the Scientific Committee of the 

International Whaling Commission, June 2000 (unpublished). 12p. [Available from Southwest 

Fisheries Science Center, National Marine Fisheries Service, 8604 La Jolla Shores Drive, La Jolla, 

CA 92037, USA.] 

Carretta, J.V. 2001. Preliminary estimates of cetacean mortality in California gillnet fisheries for 2000. 

Report SC/53/SM9 presented to the Scientific Committee of the International Whaling 

Commission, June 2001 (unpublished). 21p. [Available from Southwest Fisheries Science Center, 

National Marine Fisheries Service, 8604 La Jolla Shores Drive, La Jolla, CA 92037, USA.]. 

Carretta, J.V. 2002. Preliminary estimates of cetacean mortality in California gillnet fisheries for 2001. 

Report SC/54/SM12 presented to the Scientific Committee of the International Whaling 

Commission, April 2002 (unpublished). 22p. [Available from Southwest Fisheries Science 

Center, National Marine Fisheries Service, 8604 La Jolla Shores Drive, La Jolla, CA 92037, 

USA.]. 

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. 

Handley, C. O. Jr. 1966. A synopsis of the genus Kogia (pygmy sperm whales). pp. 62-69 In: K. S. Norris 

(ed.), Whales, dolphins and porpoises. University of California Press, Berkeley. 

Jones, R. E. 1981. Food habits of smaller marine mammals from northern California. Proc. California 

Acad. Sci. 42:409-433. 

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. 

Nagorsen, D. W. and G. E. Stewart. 1983. A dwarf sperm whale (Kogia simus) from the Pacific coast of 

Canada. J. Mamm. 64:505-506. 

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. 

U.S. Department of Commerce and Secretary of the Navy. 2001. Joint Interim Report, Bahamas Marine 

Mammal Stranding Event of 15_16 March 2000. Available from NOAA, NMFS, Office of 

Protected Resources, Silver Spring, MD. 

157
Revised 12/15/2003 

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 40o

N 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 40-50o

N, and ends up at 180oW north of

50o

N; 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

150o

W) 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). 

W132 W129 W126 W123 W120 W117

N30

N34

N38

N42

N46

WASHINGTON

OREGON

CALIFORNIA

Figure 1. Sperm whale sighting locations based 

on aerial and shipboard surveys off California,

Oregon, and Washington, 1991-2001. 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. 

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. 

158
POPULATION SIZE

 Barlow and Taylor (2001) estimated 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. Forney et al. (1995) estimated 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 eight years out of date. The most recent abundance estimate is based on 

summer/autumn shipboard surveys conducted within 300 nmi of the coasts of California, Oregon, and 

Washington in 1996 (Barlow 1997) and 2001 (Barlow 2003). The combined weighted estimate for the 

1996 and 2001 surveys is 1,233 (CV = 0.41) sperm whales (Barlow 2003). 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 estimated 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 and recent estimate of sperm whale abundance for this stock is therefore from 

the ship surveys conducted in 1996 and 2001 (Barlow 2003). 

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 1996-2001 summer/fall ship surveys off 

California, Oregon and Washington (Barlow 2003) or approximately 885. 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 (885) 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 

1.8. 

159
HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

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 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 1997-2001 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 2003). 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. Mean 

annual takes for this fishery (Table 1) are based on 1997-2001 data. This results in an average estimate of 

1.0 (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 (Cameron and Forney 1999; 

2000; Carretta 2001; 2002). 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 1997-2001 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 

1997 

1998 

1999 

2000 

2001 

Observer 

data 

23.0% 

20.0% 

20.0% 

22.9% 

20.4% 

0 

1 

0 

0 

0 

0 

5 (0.89) 

0 

0 

0 

1 (0.89) 

Total annual takes 1 (0.89) 

 Drift gillnet fisheries for swordfish and sharks exist along the entire Pacific coast of Baja 

California, Mexico and may take animals from this 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, 

160
1998), but species-specific information is not available for the Mexican fisheries. Previous efforts to 

convert the Mexican swordfish driftnet fishery to a longline fishery have resulted in a mixed-fishery, with 

20 vessels alternately using longlines or driftnets, 23 using driftnets only, 22 using longlines only, and 

seven with unknown gear type (Berdegué 2002). 

Ship Strikes

 No sperm whale mortalities have been attributed to ship strikes during the period 1997-2001. 

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 (1.0 per year) is less than the calculated PBR for this stock (1.8). 

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. 2003. Field experiments show that acoustic pingers reduce marine mammal 

bycatch in the California drift gillnet fishery. Marine Mammal Science 19(2):265-283. 

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. 

Barlow, J. 2003. Preliminary estimates of the abundance of cetaceans along the U.S. west coast: 

1991_2001. Southwest Fisheries Science Center Administrative Report LJ_03_03. Available 

from SWFSC, 8604 La Jolla Shores Dr., La Jolla CA 92037. 31p. 

Berdegué, J. 2002. Depredación de las especies pelágicas reservadas a la pesca deportiva y especies en 

peligro de extinción con uso indiscriminado de artes de pesca no selectivas (palangres, FAD's, 

trampas para peces y redes de agallar fijas y a la deriva) por la flota palangrera Mexicana. 

Fundación para la conservación de los picudos. A.C. Mazatlán, Sinaloa, 21 de septiembre. 

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. 

161
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 1998 (unpublished). 14 pp. 

Cameron, G.A. and K.A. Forney. 2000. Preliminary estimates of cetacean mortality in California/Oregon 

Gillnet Fisheries for 1999. Report SC/52/O24 presented to the Scientific Committee of the 

International Whaling Commission, June 2000 (unpublished). 12p. [Available from Southwest 

Fisheries Science Center, National Marine Fisheries Service, 8604 La Jolla Shores Drive, La Jolla, 

CA 92037, USA.] 

Carretta, J.V. 2001. Preliminary estimates of cetacean mortality in California gillnet fisheries for 2000. 

Report SC/53/SM9 presented to the Scientific Committee of the International Whaling 

Commission, June 2001 (unpublished). 21p. [Available from Southwest Fisheries Science Center, 

National Marine Fisheries Service, 8604 La Jolla Shores Drive, La Jolla, CA 92037, USA.]. 

Carretta, J.V. 2002. Preliminary estimates of cetacean mortality in California gillnet fisheries for 2001. 

Report SC/54/SM12 presented to the Scientific Committee of the International Whaling 

Commission, April 2002 (unpublished). 22p. [Available from Southwest Fisheries Science 

Center, National Marine Fisheries Service, 8604 La Jolla Shores Drive, La Jolla, CA 92037, 

USA.]. 

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. 

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 and Washington Marine Mammal 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. 

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. 

162
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. 

163
Revised 03/15/2005 

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. 2001, 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. 1996) - 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. 2001) - 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. 2001), but Norris et al. (1999)

speculate that they may travel to the Bering Sea or Aleutian

Islands. This stock structure represents the predominant 

migration patterns, but there is not a perfect correspondence

between the breeding and feeding areas that are paired 

above. For example, some individuals migrate from Mexico 

to the Gulf of Alaska and others migrate from Japan to

British Columbia. In general, interchange occurs (at low levels) between breeding areas, but fidelity is extremely

high among the feeding areas (Calambokidis et al. 2001). 

W132 W129 W126 W123 W120 W117

N30

N34

N38

N42

N46

WASHINGTON

OREGON

CALIFORNIA

Figure 1. Humpback whale sightings based on

shipboard surveys off California, Oregon, and 

Washington, 1991-2001. Dashed line represents 

the U.S. EEZ, thick line indicates the outer 

boundary of all surveys combined. See Appendix 

2 for data sources and information on timing and 

location of survey effort. 

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. 

 

164
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). Estimates of the abundance of the eastern Pacific stock of humpback whales were made 

by aerial survey (Dohl 1983; Forney et al. 1995) and ship surveys (Barlow 1995), but those estimates are now over 9

years old and the aerial estimates did not include correction factors for diving whales that would be missed. More

recent estimates are available from ship surveys and mark-recapture studies. Barlow (2003) estimated 1,314 

(CV=0.30) humpbacks in California, Oregon, and Washington waters based on summer/fall ship line-transect 

surveys in 1996 and 2001. Calambokidis et al. (2003 ) estimated humpback whale abundance in these feeding areas

from 1991 to 2002 using Petersen mark-recapture estimates based on photo-identification collections in adjacent

pairs of years (Figure 2). These data show a general upward trend in abundance followed by a large (but not 

statistically significant) drop in the 1999/2000 and 2000/2001 estimates. The 2001/2002 population estimate (1,034, 

CV=0.11) is higher than any previous estimates and may indicate that the apparent decline in the previous two

estimates exaggerates any real decline that might have occurred (Calambokidis et al. 2003) . In general, markrecapture 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 2001/2002 data contained 506 known individuals). The recent ship line transect estimate

from 1996-2001 surveys is less precise than 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 2001/2002 abundance estimated from mark-recapture 

methods (Calambokidis et al. 2003) or approximately 943.

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); however estimates 

declined between 1996 and 2001 (Barlow 2003). Mark-recapture population estimates increased steadily from 

1988/90 to 1997-98 at about 8% per 

year (Calambokidis et al. 1999). The 

apparent dip in the 1999/2000 and

2000/2001 estimates may indicate that 

population growth is slowing, but 

additional data are required to evaluate 

the significance of this. 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 

Figure 2. Mark-recapture estimates of the abundance of humpback 

whales feeding off California, Oregon, and Washington based on photoidentification studies (Calambokidis et al. 2003). Dotted lines indicate +/-

2 standard errors for each estimate. Straight, bold line indicates linear 

regression. 

0

500

1000

1500

2000

1990 1992 1994 1996 1998 2000 2002

165
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 was growing in the 1980s and early 

1990s (Barlow 1994; Calambokidis et al. 2003) with a best estimate of 8% growth per year (Calambokidis et al. 

1999). The current net productivity rate is unknown. 

POTENTIAL BIOLOGICAL REMOVAL

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

(943) 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 with a total population size of less than 1,500), 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 1.6 whales per year. 

 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Historic Whaling 

 The reported take of North Pacific humpback whales by commercial whalers totaled approximately 7,700 

between 1947 and 1987 (C. Allison, IWC unpubl. data). 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 

California-Washington 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 1998-2002 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 2003). Mean annual takes for this fishery (Table 1) are based on 1998-2002 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 1998-2002 , a humpback cow-calf pair was seen entangled in a net off Big Sur, 

California (1999) and another lone humpback was seen entangled in line and fishing buoys off Grover City (2000), 

but the fate of these animals is not known (J. Cordero, NMFS unpubl. data). One humpback whale was entangled 

and released alive in the swordfish/thresher shark drift gillnet fishery in November of 1999 at N33o

17' W120o 49' 

(set DN-SD-0949). 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. In 2001, a humpback whale with “pot gear” wrapped around its flukes was seen free-swimming 

8 miles offshore of Point Bonita, California (NMFS, Southwest Region, unpublished data). 

 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. Previous efforts to convert the Mexican swordfish driftnet fishery to a longline fishery have resulted in a 

mixed-fishery, with 20 vessels alternately using longlines or driftnets, 23 using driftnets only, 22 using longlines 

only, and seven with unknown gear type (Berdegué 2002). 

 

166
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 (Cameron and Forney 1999, 2000; Carretta 

2001, 2002; Carretta and Chivers 2003, ). 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 1998-2002 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 

1998 

1999 

2000 

2001 

2002 

Observer 

data 

20.0% 

20.0% 

22.9% 

20.4% 

20.0% 

0 

0 

0 

0 

0 

Mortality 

0,0,0,0,0 

Injury 

0,0,0,0,0 

Mortality 

0 

Injury 

0 

CA angel shark/halibut and 

other species large mesh 

(>3.5”) set gillnet fishery 

1990-94 

1999 

2000 

2001 

2002 

Observer 

data 

10-15% 

23.1%2 

26.9%2 

0% 

0% 

0,0,0,0,0 

02

02

01

01 

0,0,0,0,0 

02

02

01

01 

01

Unidentified fisheries 1998-2002 Stranding& 

sightings n/a 

0 

(4) 

n/a >0.8 

CA salmon troll fishery 1997 Incidental 

report 0% 

(1) n/a Injury 

>0.2 (n/a) 

 Total Annual Takes >1.0 

1

 The CA set gillnets were not observed in 1995-98, and observations in 1999-2000 only included Monterey Bay; mortality for unobserved areas 

and times was extrapolated from effort estimates and 1991-94 entanglement rates. The fishery was not observed in 2001-2002, owing to area 

closures that reduced fishing effort to negligible levels. 2

 Observer coverage and observed mortality in 1999-2000 only includes the observed portion of the fishery in Monterey Bay. Observer coverage 

throughout the entire fishery was only 4.0% and 1.8%, respectively. 

Ship Strikes 

Ship strikes were implicated in the deaths of at least two humpback whales in 1993, one in 1995, and one in 

2000 (J. Cordaro, NMFS unpubl. data). During 1998-2002, there were an additional 4-5 injuries and 2 mortalities 

of unidentified large whales attributed to ship strikes. 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 1998-2002 is at least 0.2 per year. 

Other human-caused mortality

 A humpback whale died and stranded near Moss Landing in 2000 with synthetic (possibly nylon) line 

wrapped around its flukes. The origin of this line (fishery or other anthropogenic source) is unknown. The average 

number of humpback deaths from unknown anthropogenic sources is 0.2 per year from 1998-2002. 

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 as a "depleted" and "strategic" stock under the MMPA. The estimated annual mortality 

and injury due to entanglement (0.8/yr), other anthropogenic sources (0.2/yr), plus ship strikes (0.2/yr) in California 

is less than the PBR allocation of 1.6 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 this animal was not seriously injured. The 

three humpbacks that were observed to be entangled at sea may have been seriously injured. Based on strandings 

and gillnet observations, annual humpback whale mortality and serious injury in California's drift gillnet fishery is 

167
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. 

REFERENCES

Allison, C. International Whaling Commission. The Red House, 135 Station Road, Impington, Cambridge, UK CB4 

9NP. 

Baker, C. S. 1992. Genetic variability and stock identity of humpback whales, world-wide. Final Contract Report 

to Int. Whal. Commn. 45pp. 

Baker, C. S., D. A. Gilbert, M. T. Weinrich, R. Lambertsen, J. Calambokidis, B. McArdle, G. K. Chambers, and S. 

J. O'Brien. 1993. Population characteristics of DNA fingerprints in humpback whales (Megaptera 

novaeangliae). J. Heredity 84:281-290. 

Baker, C. S., L. Medrano-Gonzalez, J. Calambokidis, A. Perry, F. Pichler, H. Rosenbaum, J. M. Straley, J. 

Urban-Ramirez, M. Yamaguchi, and O. von Ziegesar. 1998. Population structure of nuclear and 

mitochondrial DNA variation among humpback whales in the North Pacific. Mol. Ecol. 7:695-708. 

Baker, C. S., S. R. Palumbi, R. H. Lambertsen, M. T. Weinrich, J. Calambokidis, and S. J. O'Brien. 1990. Influence 

of seasonal migration on geographic distribution of mitochondrial DNA haplotypes in humpback whales. 

Nature 344(15):238-240. 

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. 2003. Preliminary estimates of the abundance of cetaceans along the U.S. west coast: 1991_2001. 

Southwest Fisheries Science Center Administrative Report LJ_03_03. Available from SWFSC, 8604 La 

Jolla Shores Dr., La Jolla CA 92037. 31p. 

Berdegué, J. 2002. Depredación de las especies pelágicas reservadas a la pesca deportiva y especies en peligro de 

extinción con uso indiscriminado de artes de pesca no selectivas (palangres, FAD's, trampas para peces y 

redes de agallar fijas y a la deriva) por la flota palangrera Mexicana. Fundación para la conservación de los 

picudos. A.C. Mazatlán, Sinaloa, 21 de septiembre. 

Barlow, J. and G. A. Cameron. 2003. Field experiments show that acoustic pingers reduce marine mammal bycatch 

in the California drift gillnet fishery. Marine Mammal Science 19(2):265-283. 

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. 

Berzin, A. A., and A. A. Rovnin. 1966. The distribution and migrations of whales in the northeastern part of the 

Pacific, Chukchi and Bering Seas. Izvestiya Tikhookeanskogo Nauchno-Issledovatel’skogo Institut 

Rybnogo Khozyaistva I Okeanografii 58:179-207. (Translated by Bureau of Commercial Fisheries, U. S. 

Fish and Wildlife Service, Seattle, 1968, pp. 103-136 In: K. I. Panin (ed.), Soviet Research on Marine 

Mammals of the Far East). 

Braham, H. W. 1991. Endangered whales: status update. A Report on the 5-year status of stocks review under the 

1978 amendments to the U.S. Endangered Species Act. NMFS Unpublished Report. 

Calambokidis, J., T. Chandler, K. Rasmussen, G. H. Steiger, L. Schlender. 1998. Humpback and blue whale 

photographic identification: Report on research in 1997. Contract Report to Southwest Fisheries Science 

Center, P.O. Box 271, La Jolla, CA 92038. 41pp. 

Calambokidis, J., T. Chandler, K. Rasmussen, G. H. Steiger, and L. Schlender. 1999. Humpback and blue whale 

photo-identification research off California, Oregon and Washington in 1998. Final Contract Report to 

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

35 pp. 

168
Calambokidis, J., T. Chandler, L. Schlender, G. H. Steiger, and A. Douglas. 2003. Research on humpback and blue 

whale off California, Oregon and Washington in 2002. Final Contract Report to Southwest Fisheries 

Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA 92038. 49 pp. 

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, P.O. Box 271, La Jolla, CA 92038. 31pp. 

Calambokidis, J., G. H. Steiger, J. R. Evenson, K. R. Flynn, K. C. Balcomb, D. E. Claridge, P. Bloedel, J. M. 

Straley, C. S. Baker, O. von Ziegesar, M. E. Dahlheim, J. M. Waite, J. D. Darling, G. Ellis, and G. A. 

Green. 1996. Interchange and isolation of humpback whales in California and other North Pacific feeding 

grounds. Mar. Mamm. Sci. 12(2):215-226. 

Calambokidis, J., G. H. Steiger, J. M. Straley, T. J. Quinn, II, L. M. Herman, S. Cerchio, D. R. Salden, M. 

Yamaguchi, F. Sato, J. Urbán R., J. Jacobsen, O. von Ziegesar, K. C. Balcomb, C. M. Gabriele, M. E. 

Dahlheim, N. Higashi, S. Uchida, J. K. B. Ford, Y. Miyamura, P. Ladrón de Guevara P., S. A. Mizroch, L. 

Schlender and K. Rasmussen. 1997. Abundance and population structure of humpback whales in the 

North Pacific Basin. Final Contract Report 50ABNF500113 to Southwest Fisheries Science Center, P.O. 

Box 271, La Jolla, CA 92038. 72p. 

Calambokidis, J., G. H. Steiger, J. M. Straley, L. M. Herman, S. Cerchio, D. R. Salden, J. Urbán-R., J. K. Jacobsen, 

O. von Ziegesar, K. C. Balcomb, C. M. Gabriele, M. E. Dahlheim, S. Uchida, G. Ellis, Y. Miyamura, P. 

Ladrón de Guevara-P., M. Yamaguchi, F. Sata, S. A. Mizroch, L. Schlender, K. Rasmussen, J. Barlow, and 

T. J. Quinn II. 2001. Movements and population structure of humpback whales in the North Pacific. Mar. 

Mamm. Sci. 17(4):769-794. 

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 

(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 

(unpublished). 12 

Carretta, J.V. 2001. Preliminary estimates of cetacean mortality in California gillnet fisheries for 2000. Paper 

SC/53/SM9 presented to the International Whaling Commission (unpublished). 21 pp. 

Carretta, J.V. 2002. Preliminary estimates of cetacean mortality in California gillnet fisheries for 2001. Report 

SC/54/SM12 presented to the Scientific Committee of the International Whaling Commission, April 2002 

(unpublished). 22p. [Available from Southwest Fisheries Science Center, National Marine Fisheries 

Service, 8604 La Jolla Shores Drive, La Jolla, CA 92037, USA.].pp. 

Carretta, J.V. and S.J. Chivers. 2003. Preliminary estimates of marine mammal mortality and biological sampling 

of cetaceans in California gillnet fisheries for 2002. Paper SC/55/SM3 presented to the International 

Whaling Commission (unpublished). 21pp. 

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. 

Cordaro, J. Southwest Region, NMFS, 501 West Ocean Blvd, Long Beach, CA 90802_4213. 

Darling, J. D. 1991. Humpback whales in Japanese waters. Ogasawara and Okinawa. Fluke identification catalog 

1987-1990. Final Contract Report, World Wildlife Fund for Nature, Japan. 22 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. 

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 and Washington Marine Mammal and Seabird Surveys. Minerals Management Service 

Contract Report 14-12-0001-30426. 

Hammond, P. S. 1986. Estimating the size of naturally marked whale populations using capture-recapture 

techniques. Rept. Int. Whal. Commn., Special Issue 8:253-282. 

Heyning, J. E., and T. D. Lewis. 1990. Fisheries interactions involving baleen whales off southern California. 

Rep. int. Whal. Commn. 40:427-431. 

169
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. 

Johnson, J. H., and A. A. Wolman. 1984. The humpback whale, Megaptera novaeangliae. Mar. Fish. Rev. 

46(4):30-37. 

Nishiwaki, M. 1966. Distribution and migration of the larger cetaceans in the North Pacific as shown by Japanese 

whaling results. Pp. 172-191 In: K. S. Norris (ed.), Whales, Dolphins and Porpoises. University of 

California Press, Berkeley, CA. Academic Press, New York. 

Norris, T. F., M. McDonald, and J. Barlow. 1999. Acoustic detections of singing humpback whales (Megaptera 

novaeangliae) in the eastern North Pacific during their northbound migration. J. Acoust. Soc. Am. 

106(1):506-514. 

Perry, A., C. S. Baker, L. M. Herman. 1990. Population characteristics of individually identified humpback 

whales in the central and eastern North Pacific: a summary and critique. Rep. Int. Whal. Commn. 

(Special Issue 12):307-317. 

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. 1978. The humpback whale in the North Pacific: distribution, exploitation, and numbers. pp. 29-44 

In: K. S. Norris and R. R. Reeves (eds.). Report on a Workshop on Problems Related to Humpback 

Whales (Megaptera novaeangliae) in Hawaii. Contr. Rept. to U. S. Marine Mammal Commn. NTIS PB280-794. 90pp. 

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. 

Steiger, G. H., J. Calambokidis, R. Sears, K. C. Balcomb, and J. C. Cubbage. 1991. Movement of humpback 

whales between California and Costa Rica. Mar. Mamm. Sci. 7:306-310. 

Tonnessen, J. N., and A. O. Johnsen. 1982. The History of Modern Whaling. Univ. Calif. Press, Berkeley and Los 

Angeles. 798pp.7:306-310. 

Urbán R., J., C. Alverez F., M. Salinas Z., J. Jacobson, K. C. Balcomb III, A. Jaramillo L., P. L. de Guevara P., and 

A. Aguayo L. 1999. Population size of humpback whale, Megaptera novaeangliae, in waters off the 

Pacific coast of Mexico. 

170
Revised 03/15/2005

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. 

W132 W129 W126 W123 W120 W117

N30

N34

N38

N42

N46

WASHINGTON

OREGON

CALIFORNIA

Figure 1. Blue whale sighting locations based on 

aerial and summer/autumn shipboard surveys off

California, Oregon, and Washington, 1991-2001

(see Appendix 2 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. 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 (2003) estimated 1,736 (CV=0.23) blue whales off California, Oregon, and 

Washington based on ship line-transect surveys in 1996 and 2002. Calambokidis et al. (2003) used photographic 

mark-recapture and estimated population sizes of 1,567 (CV=0.32) based on 2000-2002 photographs of left sides 

and 1,953 (CV=0.33) based on right sides. The average of the mark-recapture estimates (1,760 CV=0.32) is is very

close to the line-transect estimate. Mark-recapture estimates are often negatively biased by individual heterogeneity

in sighting probabilities (Hammond 1986); however, Calambokidis et al. 2003 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 line-transect and mark-recapture estimates, weighted by the inverse of their 

variances, or 1,744 (0.28). 

171
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 

1,384. 

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.

Estimates made by Calambokidis et al. 

(2003) and Barlow (2003) declined in

2000-2002 compared to previous years

(Figure 2), but sample sizes were small and this apparent decline may not be real. 

Line-transect Blue Whale Abundance

0

1000

2000

3000

4000

5000

1991-93 1996 2001

Year(s)

Abundance

Figure 2. Estimates of abundance from vessel-based line transect 

surveys conducted in California waters, 1991-2001 (Barlow 2003).

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

opulations in the Pacific (Best 1993). 

OTENTIAL BIOLOGICAL REMOVAL

R) level for this stock is calculated as the minimum population size 

,384) 

No information exists on the rate of growth of blue whale p

P

The potential biological removal (PB

(1 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 which has a minimum abundance less than 1,500), resulting in a PBR of 2.8. 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 1.4 whales per year. 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

e of North Pacific blue whales by commercial whalers totaled 9,500 between 1910 and 

965 (O

isheries Information 

ft gillnet fishery is the only fishery that is likely to take blue whales from this stock, but no

shery m

Historic Whaling

The reported tak

1 hsumi 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. 

F

The offshore dri

fi ortalities 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). Mean annual takes for this fishery 

(Table 1) are based only on 1998-2002 data. This results in an average estimate of zero blue whales taken annually.

172
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, 

exico 

able 1. Summary of available information on the incidental mortality and injury of blue whales (Eastern North 

Fishery Name Year(s) Data Type Mortality (and 

parentheses) 

an 

parentheses) 

M 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. Previous efforts to convert the Mexican swordfish driftnet fishery to a longline fishery have resulted in a 

mixed-fishery, with 20 vessels alternately using longlines or driftnets, 23 using driftnets only, 22 using longlines 

only, and seven with unknown gear type (Berdegué 2002). 

T

Pacific stock) for commercial fisheries that might take this species (Cameron and Forney 1999, 2000; Carretta 2001, 

2002; Carretta and Chivers 2003). Mean annual takes are based on 1998-2002 data unless noted otherwise. 

Percent Observed Estimated Me

Observer 

Coverage injury) 

mortality 

(CV in 

Annual 

Takes 

(CV in 

CA/OR thresher 

shark llnet 

1998 

/swordfish drift gi Observer 0 

fishery 

1999 

2000 

2001 

2002 

data 

20.0% 

20.0% 

22.9% 

20.4% 

20.0% 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

 Total Annua es l Tak 0 

hip Strikes 

rikes were implicated in the deaths of blue whales in 1980, 1986, 1987, 1993, and 2002 (J. Cordaro, 

outhwe

TATUS OF STOCK

e whales in the entire North Pacific were estimated to be at 33% (1,600 out of 4,900) of 

istoric 

EFERENCES

 Abundance of large whales in California coastal waters: a comparison of ship surveys in 1979/80 

Barlow, ce off California, Oregon, and Washington based on a 

S

Ship st

S st Region, NMFS and J. Heyning, pers. comm.). During 1998-2002, there were an additional 5 injuries and 

2 mortalities of unidentified large whales attributed to ship strikes. 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 0.2 per year for 1998-2002. 

S

 Previously, blu

h carrying capacity (Mizroch et al. 1984). The initial abundance has never been estimated separately for the 

"eastern” 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). 

R

Barlow, J. 1994. 

and in 1991. Rept. Int. Whal. Commn. 44:399-406. 

J. 1997. Preliminary estimates of cetacean abundan

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. 

173
Barlow, J. 2003. Preliminary estimates of cetacean abundance off the U.S. West Coast: 1991-2001. Administrative 

Report LJ-03-03. Available from Southwest Fisheries Science Center, National Marine Fisheries Service, 

8604 La Jolla Shores Dr., La Jolla, CA. 26 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. 2003. Preliminary estimates of the abundance of cetaceans along the U.S. west coast: 1991_2001. 

Southwest Fisheries Science Center Administrative Report LJ_03_03. Available from SWFSC, 8604 La 

Jolla Shores Dr., La Jolla CA 92037. 31p. 

Best, P. B. 1993. Increase rates in severely depleted stocks of baleen whales. ICES J. Mar. Sci. 50:169-186. 

Braham, H. W. 1991. Endangered whales: status update. A Report on the 5-year status of stocks review under the 

1978 amendments to the U.S. Endangered Species Act. NMFS Unpublished Report. 

Calambokidis, J., T. Chandler, L. Schlender, G. H. Steiger, and A. Douglas. 2003. Research on humpback and blue 

whale off California, Oregon and Washington in 2002. Final Contract Report to Southwest Fisheries 

Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA 92038. 49 pp. 

Calambokidis, J., G. H. Steiger, J. C. Cubbage, K. C. Balcomb, C. Ewald, S. Kruse, R. Wells, and R. Sears. 1990. 

Sightings and movements of blue whales off central California 1986-88 from photo-identification of 

individuals. Rept. Int. Whal. Commn., Special Issue 12:343-348. 

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 

1998 (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 

(unpublished). 12 

Carretta, J.V. 2001. Preliminary estimates of cetacean mortality in California gillnet fisheries for 2000. Paper 

SC/53/SM9 presented to the International Whaling Commission (unpublished). 21 pp. 

Carretta, J.V. 2002. Preliminary estimates of cetacean mortality in California gillnet fisheries for 2001. Report 

SC/54/SM12 presented to the Scientific Committee of the International Whaling Commission, April 2002 

(unpublished). 22p. [Available from Southwest Fisheries Science Center, National Marine Fisheries 

Service, 8604 La Jolla Shores Drive, La Jolla, CA 92037, USA.]. 

Carretta, J.V. and S.J. Chivers. 2003. Preliminary estimates of marine mammal mortality and biological sampling 

of cetaceans in California gillnet fisheries for 2002. Paper SC/55/SM3 presented to the International 

Whaling Commission (unpublished). 21pp. 

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. 

Forney, K. A. and R. L. Brownell, Jr. 1996. Preliminary report of the 1994 Aleutian Island marine mammal survey. 

Paper SC/48/O11 presented to the International Whaling Commission. 

Hammond, P. S. 1986. Estimating the size of naturally marked whale populations using capture-recapture 

techniques. Rept. Int. Whal. Commn., Special Issue 8:253-282. 

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. Rep. 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. 

174
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. 

Larkman, V. E. and R. R. Veit. 1998. Seasonality and abundance of blue whales off southern California. CalCOFI 

Rep. 39:236-239. 

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. 

Mate, B. R., B. A. Lagerquist, and J. Calambokidis. 1999. Movements of North Pacific blue whales during their 

feeding season off southern California and their southern fall migration. Mar. Mamm. Sci. 15(4):1246-

1257. 

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 blue whale, Balaenoptera musculus. Mar. Fish. Rev. 

46:15-19. 

Ohsumi, S. and S. Wada. 1972. Stock assessment of blue whales in the North Pacific. Working Paper for the 24th 

Meeting of the International Whaling Commission. 20 pp. 

Reilly, S. B. and V. G. Thayer. 1990. Blue whale (Balaenoptera musculus) distribution in the eastern tropical 

Pacific. Mar. Mamm. Sci. 6(4):265-277. 

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. 

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. 

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. 

Stafford, K. M., C. G. Fox, and D. S. Clark. 1998. Long-range acoustic detection and localization of blue whale 

calls in the northeast Pacific Ocean. J. Acoust. Soc. Am. 104(6):3616-3625. 

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. 

Tonnessen, J. N., and A. O. Johnsen. 1982. The History of Modern Whaling. Univ. Calif. Press, Berkeley and Los 

Angeles. 798 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. 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. 

175
Revised 12/15/2003 

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). W132 W129 W126 W123 W120 W117

N30

N34

N38

N42

N46

WASHINGTON

OREGON

CALIFORNIA

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.

Genetic studies of the fin whales have shown that the population in the Gulf of California is isolated from

fin whales in the rest of the eastern North Pacific and is an evolutionary unique population (Bérubé et al. 

2002). 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. 

Figure 1. Fin whale sighting locations based on 

aerial and shipboard surveys off California,

Oregon, and Washington, 1991-2001 (see 

Appendix 2 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. 

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 3,279 (CV = 0.31) fin whales were estimated to be off California, 

Oregon and Washington based on ship surveys in summer/autumn of 1996 (Barlow and Taylor 2001) and 

176
2001 (Barlow 2003). 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”. 

Minimum Population Estimate

 The minimum population estimate for fin whales is taken as the lower 20th percentile of the lognormal distribution of abundance estimated from 1996 and 2001 summer/fall ship surveys (Barlow and 

Taylor 2001; Barlow 2003) or approximately 2,541. 

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 (2,541) times one half the default maximum net growth rate for cetaceans (1⁄2 of 4%) times

a recovery factor of 0.3 (for an endangered species, with Nmin > 1,500 and CVNmin < 0.50), resulting in a 

PBR of 15. 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

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 2003). Mean 

annual takes for this fishery (Table 1) are based on 1997-2001 data. This results in an average estimate of 

1.0 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, Mexico and may take animals from this 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. Previous efforts to 

convert the Mexican swordfish driftnet fishery to a longline fishery have resulted in a mixed-fishery, with 

177
20 vessels alternately using longlines or driftnets, 23 using driftnets only, 22 using longlines only, and 

seven with unknown gear type (Berdegué 2002). 

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 (Cameron and Forney 1999, 2000; 

Carretta 2001, 2002). 

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 

1997 

1998 

1999 

2000 

2001 

Observer 

data 

23.0% 

20.0% 

20.0% 

22.9% 

20.4% 

0 

0 

1 

0 

0 

0 

0 

5 (09.4) 

0 

0 

1 (0.94) 

Total annual takes 1 (0.94) 

Ship Strikes

 Ship strikes were implicated in the deaths of one fin whale in 1997 and 2001 (J. Heyning and J. 

Cordaro, Southwest Region, NMFS, pers. comm.). During 1997-2001, there were an additional 4 injuries 

and 2 mortalities of unidentified large whales attributed to ship strikes. 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 1997-2001. 

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 (1.0/yr) and ship strikes (0.4/yr) appears to be less than the 

calculated PBR (15). Total fishery mortality is less than 10% of PBR and, therefore, may 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 (Croll et al.

2002). 

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. 2003. Field experiments show that acoustic pingers reduce marine mammal 

bycatch in the California drift gillnet fishery. Marine Mammal Science 19(2):265-283. 

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. 

178
Barlow, J. 2003. Preliminary estimates of the abundance of cetaceans along the U.S. west coast: 

1991_2001. Southwest Fisheries Science Center Administrative Report LJ_03_03. Available 

from SWFSC, 8604 La Jolla Shores Dr., La Jolla CA 92037. 31p. 

Berdegué, J. 2002. Depredación de las especies pelágicas reservadas a la pesca deportiva y especies en 

peligro de extinción con uso indiscriminado de artes de pesca no selectivas (palangres, FAD's, 

trampas para peces y redes de agallar fijas y a la deriva) por la flota palangrera Mexicana. 

Fundación para la conservación de los picudos. A.C. Mazatlán, Sinaloa, 21 de septiembre. 

Bérubé, M., J. Urban-R., A. E. Dizon, R. L. Brownell, and P. J. Palsbøll. 2002. Genetic identification of a 

small and highly isolated population of fin whales (Balaenoptera physalus) in the Sea of Cortez, 

México. Conservation Genetics 3:183-190. 

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. OregonWashington 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 for 1997 and 1998. Paper SC/51/O4 presented to the International Whaling 

Commission, May 1998 (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 1998 (unpublished). 12 pp. 

Carretta, J.V. 2001. Preliminary estimates of cetacean mortality in California gillnet fisheries for 2000. 

Report SC/53/SM9 presented to the Scientific Committee of the International Whaling 

Commission, June 2001 (unpublished). 21p. [Available from Southwest Fisheries Science Center, 

National Marine Fisheries Service, 8604 La Jolla Shores Drive, La Jolla, CA 92037, USA.]. 

Carretta, J.V. 2002. Preliminary estimates of cetacean mortality in California gillnet fisheries for 2001. 

Report SC/54/SM12 presented to the Scientific Committee of the International Whaling 

Commission, April 2002 (unpublished). 22p. [Available from Southwest Fisheries Science 

Center, National Marine Fisheries Service, 8604 La Jolla Shores Drive, La Jolla, CA 92037, 

USA.]. 

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. 

Croll, D.A., C.W. Clark, A. Acevedo, B. Tershy, S. Flores, J. Gedamke, and J. Urban. 2002. Only male 

fin whales sing loud songs. Nature 417:809 

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 and Washington Marine Mammal 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. 95p. 

179
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, 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. 

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. 

180
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 warmtemperate 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 110o

W (corresponding

approximately to the IWC's "Peruvian stock") and a

reduction west of 140o

W. 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 150o

W and including the Gulf of California and

waters off California; this report), and 2) Hawaiian

waters. 

W132 W129 W126 W123 W120 W117

N30

N34

N38

N42

N46

WASHINGTON

OREGON

CALIFORNIA

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 individuallyidentified 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). 

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.

181
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. 

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-or-Bryde'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 (and 

injury in 

parentheses) 

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 01

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 

2003). 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 this population. Quantitative data are available only for the Mexican 

182
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 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 humancaused 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. 2003. Field experiments show that acoustic pingers reduce marine mammal 

bycatch in the California drift gillnet fishery. Marine Mammal Science 19(2):265-283. 

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 and Washington Marine Mammal 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. 

183
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. 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. NMFSSWFSC-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. 

184
Revised 12/15/2003 

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 45-55o

N (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. 

W132 W129 W126 W123 W120 W117

N30

N34

N38

N42

N46

WASHINGTON

OREGON

CALIFORNIA

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 two confirmed sightings of sei whales and 5 possible sightings (identified as sei or Bryde's 

whales) were made in California, Oregon, and Washington waters during extensive ship and aerial surveys 

in 1991, 1992, 1993, 1996, and 2001 (Hill and Barlow 1992; Carretta and Forney 1993; Mangels and

Gerrodette 1994; VonSaunder and Barlow 1999; Barlow 2003). Green et al. (1992) did not report any

sightings of sei whales in aerial surveys of Oregon and Washington. The abundance estimate for

California, Oregon, and Washington waters out to 300 nmi, based on 1996 and 2001 shipboard surveys, is

56 (CV = 0.61) whales (Barlow 2003). 

Figure 1. Sei whale sighting locations based on

aerial and shipboard surveys off California,

Oregon, and Washington, 1991-2001 (see 

Appendix 2 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. 

Minimum Population Estimate

The minimum population estimate for sei whales is taken as the lower 20th percentile of the lognormal distribution of abundance estimated from 1996 and 2001 shipboard line-transect survey, or 

approximately 35. 

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, 

185
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). 

POTENTIAL BIOLOGICAL REMOVAL

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

population size (35) 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 0.1 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

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 

2003). Mean annual takes for this fishery (Table 1) are based on 1997-2001 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 (Cameron and Forney 1999, 

2000; Carretta 2001, 2002). 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 

1997-2001 Observer 

data 20-23% 0,0,0,0,0 0,0,0,0,0 0 

Total annual takes 0 

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. During 1997-2001, 

there were 4 injuries and 2 mortalities of unidentified large whales attributed to ship strikes. 

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 

186
world’s oceans has been suggested to be a habitat concern for whales, particularly for baleen whales that 

may communicate using low-frequency sound (Croll et al. 2002). 

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. 

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. 2003. Field experiments show that acoustic pingers reduce marine mammal 

bycatch in the California drift gillnet fishery. Marine Mammal Science 19(2):265-283. 

Barlow, J. 2003. Preliminary estimates of the abundance of cetaceans along the U.S. west coast: 

1991_2001. Southwest Fisheries Science Center Administrative Report LJ_03_03. Available 

from SWFSC, 8604 La Jolla Shores Dr., La Jolla CA 92037. 31p. 

Berdegué, J. 2002. Depredación de las especies pelágicas reservadas a la pesca deportiva y especies en 

peligro de extinción con uso indiscriminado de artes de pesca no selectivas (palangres, FAD's, 

trampas para peces y redes de agallar fijas y a la deriva) por la flota palangrera Mexicana. 

Fundación para la conservación de los picudos. A.C. Mazatlán, Sinaloa, 21 de septiembre. 

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 1998 (unpublished). 14 pp. 

Cameron, G.A. and K.A. Forney. 2000. Preliminary estimates of cetacean mortality in California/Oregon 

Gillnet Fisheries for 1999. Report SC/52/O24 presented to the Scientific Committee of the 

International Whaling Commission, June 2000 (unpublished). 12p. [Available from Southwest 

Fisheries Science Center, National Marine Fisheries Service, 8604 La Jolla Shores Drive, La Jolla, 

CA 92037, USA.] 

Carretta, J.V. 2001. Preliminary estimates of cetacean mortality in California gillnet fisheries for 2000. 

Report SC/53/SM9 presented to the Scientific Committee of the International Whaling 

Commission, June 2001 (unpublished). 21p. [Available from Southwest Fisheries Science Center, 

National Marine Fisheries Service, 8604 La Jolla Shores Drive, La Jolla, CA 92037, USA.]. 

Carretta, J.V. 2002. Preliminary estimates of cetacean mortality in California gillnet fisheries for 2001. 

Report SC/54/SM12 presented to the Scientific Committee of the International Whaling 

Commission, April 2002 (unpublished). 22p. [Available from Southwest Fisheries Science 

Center, National Marine Fisheries Service, 8604 La Jolla Shores Drive, La Jolla, CA 92037, 

USA.]. 

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. 

Croll, D.A., C.W. Clark, A. Acevedo, B. Tershy, S. Flores, J. Gedamke, and J. Urban. 2002. Only male 

fin whales sing loud songs. Nature 417:809 

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. 

187
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 and Washington Marine Mammal 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 - November 6, 1993. U.S. Dep. Commer. NOAA Tech. Memo. NMFSSWFSC-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. 

188
Revised 12/15/2003 

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 

180o

N, 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 yearround 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) are

considered as a separate stock. Minke whales in 

Alaskan waters are considered in a separate stock 

assessment report. 

W132 W129 W126 W123 W120 W117

N30

N34

N38

N42

N46

WASHINGTON

OREGON

CALIFORNIA

Figure 1. Minke whale sighting locations based 

on aerial and shipboard surveys off California,

Oregon, and Washington, 1991-2001 (see 

Appendix 2 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. 

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 1,015 (CV = 0.73) based on ship surveys in 1996 and 2001 off

California Oregon and Washington (Barlow 2003). 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 1996 and 2001 summer/fall ship surveys in

California, Oregon, and Washington waters (Barlow 2003) or approximately 585. 

Current Population Trend

There are no data on trends in minke whale abundance in waters of California, Oregon and/or

Washington. 

189
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 (585) 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 5.8. 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

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; Cameron and 

Forney 1999, 2000; Carretta 2001, 2002). Mean annual takes are based on 1997-2001 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 

1997 

1998 

1999 

2000 

2001 

Observer data 

23.0% 

20.0% 

20.0% 

22.9% 

20.4% 

0 

0 

1 

0 

0 

0 

0 

0 

0 

0 

0 

WA Puget Sound 

Region salmon 

drift gillnet fishery 

(areas 7 and 7A) 

1997-

2001 Self-reports 0% 0 0 n/a 

CA angel 

shark/halibut and 

other species large 

mesh (>3.5”) set 

gillnet fishery 

1997 

1998 

1999 

2000 

2001 

Extrapolated 

estimates & 

observer data 

0% 

0% 

4.0%1

1.8%1

0% 

0/0 0 n/a 

Total annual takes 0 1

In 1999/2000 approximately 25% of the Monterey Bay portion of this fishery was observed, accounting 

for less than 5% of all fishing effort. 

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 

2003). Mean annual takes for this fishery (Table 1) are based on 1997-2001 data. This results in an 

average estimate of zero minke whales taken annually. In 1999, a whale skin sample was retrieved from a 

large hole that had been punched through a drift gillnet (trip DN-SD-0941). The sample was later 

identified as a minke whale using genetic sequencing methods. Total fishery mortality for minke whales 

was not estimated for the 1980-86 California Department of Fish and Game observer program for the drift 

190
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 minke whales or 40 per year. 

 Drift gillnet fisheries for swordfish and sharks exist along the entire Pacific coast of Baja 

California, Mexico and may take animals from this 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. Previous efforts to 

convert the Mexican swordfish driftnet fishery to a longline fishery have resulted in a mixed-fishery, with 

20 vessels alternately using longlines or driftnets, 23 using driftnets only, 22 using longlines only, and 

seven with unknown gear type (Berdegué 2002). 

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 1997-2001. 

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 (5.8), 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 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. 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. 2003. Field experiments show that acoustic pingers reduce marine mammal 

bycatch in the California drift gillnet fishery. Marine Mammal Science 19(2):265-283. 

Barlow, J. 2003. Preliminary estimates of the abundance of cetaceans along the U.S. west coast: 

1991_2001. Southwest Fisheries Science Center Administrative Report LJ_03_03. Available 

from SWFSC, 8604 La Jolla Shores Dr., La Jolla CA 92037. 31p. 

Berdegué, J. 2002. Depredación de las especies pelágicas reservadas a la pesca deportiva y especies en 

peligro de extinción con uso indiscriminado de artes de pesca no selectivas (palangres, FAD's, 

trampas para peces y redes de agallar fijas y a la deriva) por la flota palangrera Mexicana. 

Fundación para la conservación de los picudos. A.C. Mazatlán, Sinaloa, 21 de septiembre. 

191
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. OregonWashington 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 for 1997 and 1998. Paper SC/51/O4 presented to the International Whaling 

Commission, May 1998 (unpublished). 14 pp. 

Cameron, G.A. and K.A. Forney. 2000. Preliminary estimates of cetacean mortality in California/Oregon 

Gillnet Fisheries for 1999. Report SC/52/O24 presented to the Scientific Committee of the 

International Whaling Commission, June 2000 (unpublished). 12p. [Available from Southwest 

Fisheries Science Center, National Marine Fisheries Service, 8604 La Jolla Shores Drive, La Jolla, 

CA 92037, USA.] 

Carretta, J.V. 2001. Preliminary estimates of cetacean mortality in California gillnet fisheries for 2000. 

Report SC/53/SM9 presented to the Scientific Committee of the International Whaling 

Commission, June 2001 (unpublished). 21p. [Available from Southwest Fisheries Science Center, 

National Marine Fisheries Service, 8604 La Jolla Shores Drive, La Jolla, CA 92037, USA.]. 

Carretta, J.V. 2002. Preliminary estimates of cetacean mortality in California gillnet fisheries for 2001. 

Report SC/54/SM12 presented to the Scientific Committee of the International Whaling 

Commission, April 2002 (unpublished). 22p. [Available from Southwest Fisheries Science 

Center, National Marine Fisheries Service, 8604 La Jolla Shores Drive, La Jolla, CA 92037, 

USA.]. 

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 and Washington Marine Mammal 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. 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. 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. 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. 

192
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. 

193
Revised 03/15/2005 

ROUGH-TOOTHED DOLPHIN (Steno bredanensis): 

Hawaiian Stock

STOCK DEFINITION AND

GEOGRAPHIC RANGE 

Rough-toothed dolphins are 

found throughout the world in tropical

and warm-temperate 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 of rough-toothed

dolphins during a 2002 shipboard survey

of waters within the U.S. Exclusive 

Economic Zone (EEZ) of the Hawaiian 

Islands are shown in Figure 1. Eight

strandings have been reported from

Maui, Oahu, and the island of Hawaii

(Nitta 1991; Maldini 2005). Nothing is 

known about stock structure for this

species in the North Pacific. 

Photographic identification studies 

around the main Hawaiian islands have

not demonstrated any inter-island

movement of this species (R.W. Baird,

pers. comm.). 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. EEZ of the Hawaiian Islands. 

W180 W175 W170 W165 W160 W155 W150

N10

N15

N20

N25

N30

N35

Figure 1. Rough-toothed dolphin sighting locations during the 2002

shipboard cetacean survey of U.S. EEZ waters surrounding the

Hawaiian Islands (Barlow 2003; see Appendix 2 for details on timing

and location of survey effort). Outer line represents approximate

boundary of survey area and U.S. EEZ.

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 calculated from the

combined survey data (Mobley et al. 2000). This study underestimated the total number of rough-toothed dolphins

within the U.S. EEZ off Hawaii, because areas around the Northwestern Hawaiian Islands (NWHI) and beyond 25 

nautical miles from the main islands were not surveyed. Furthermore, the data on which this estimate was based are 

now over 5 years old. A 2002 shipboard line-transect survey of the entire Hawaiian Islands EEZ resulted in an

abundance estimate of 19,904 (CV=0.52) rough-toothed dolphins (Barlow 2003). This is currently the best available 

abundance estimate for this stock. 

 

Minimum Population Estimate

The log-normal 20th percentile of the 2002 abundance estimate for Hawaiian Islands EEZ waters is 13,184

rough-toothed dolphins. 

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. 

194
POTENTIAL BIOLOGICAL REMOVAL

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

(13,184) times one half the default maximum net growth rate for cetaceans (1⁄2 of 4%) times a recovery factor of 0.50 

(for a stock of unknown status with no known fishery mortality or serious injury; Wade and Angliss 1997), resulting 

in a PBR of 132 rough-toothed dolphins per year. 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Fishery Information

Information on fishery-related mortality and serious injury of cetaceans in Hawaiian waters is limited, but 

the gear types used in Hawaiian fisheries are responsible for marine mammal mortality and serious injury in other 

fisheries throughout U.S. waters. Gillnets 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 or 

entangled in the Hawaii-based longline fishery between 1994 and 2002, with approximately 4-25% of all effort 

observed (Forney 2004). Rough-toothed dolphins 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. 

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 or serious injury. 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 roughtoothed dolphins is insignificant and approaching zero mortality and serious injury rate. 

REFERENCES

Barlow, J. 2003. Cetacean abundance in Hawaiian waters during summer/fall 2002. Admin. Rep. LJ-03-13. 

Southwest Fisheries Science Center, National Marine Fisheries Service, 8604 La Jolla Shores Drive, La 

Jolla, CA 92037. 

Forney, K.A. 2004. Estimates of cetacean mortality and injury in two U.S. Pacific longline fisheries, 1994_2002. 

Admin. Rep. LJ-04-07. Southwest Fisheries Science Center, National Marine Fisheries Service, 8604 La 

Jolla Shores Drive, La Jolla, CA 92037. 17 pp. 

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. 

Maldini, D., L. Mazzuca, and S. Atkinson. 2005. Odontocete stranding patterns in the Main Hawaiian Islands 

(1937-2002): How do they compare with live animal surveys? Pacific Science 59(1):55-67. 

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. 

195
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. 

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. 

MMC-77/23, 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-OPR12. 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. 

196
Revised 03/15/2005

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). Although they have

been considered rare in Hawaiian waters 

(Shallenberger (1981), six sightings

were made during a 2002 survey of the 

U.S. Exclusive Economic Zone (EEZ) of

the Hawaiian Islands (Figure 1). There 

are five stranding records from the main

islands (Nitta 1991; Maldini 2005). For 

the Marine Mammal Protection Act

(MMPA) stock assessment reports, 

Risso's dolphins within the Pacific U.S. 

EEZ are divided into two discrete, noncontiguous areas: 1) Hawaiian waters 

(this report), and 2) waters off 

California, Oregon and Washington. 

W180 W175 W170 W165 W160 W155 W150

N10

N15

N20

N25

N30

N35

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 and in the central 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). Only one sighting of a 

single Risso’s dolphin was made, and no abundance estimate was calculated. A 2002 shipboard line-transect survey

of the entire Hawaiian Islands EEZ resulted in an abundance estimate of 2,351 (CV=0.65) Risso’s dolphins (Barlow 

2003). This is currently the best available abundance estimate for this stock. 

Figure 1. Risso's dolphin sighting locations during the 2002

shipboard cetacean survey of U.S. EEZ waters surrounding the

Hawaiian Islands (Barlow 2003; see Appendix 2 for details on timing

and location of survey effort). Outer line represents approximate

boundary of survey area and U.S. EEZ.

Minimum Population Estimate

The log-normal 20th percentile of the 2002 abundance estimate is 1,426 Risso’s dolphins. 

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

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

(1,426) times one half the default maximum net growth rate for cetaceans (1⁄2 of 4%) times a recovery factor of 0.50

(for a stock of unknown status with no known fishery mortality or serious injury within the U.S. EEZ of the

Hawaiian Islands; Wade and Angliss 1997), resulting in a PBR of 14 Risso’s dolphins per year. 

HUMAN CAUSED MORTALITY AND SERIOUS INJURY

Fishery Information

Information on fishery-related mortality and serious injury of cetaceans in Hawaiian waters is limited, but 

the gear types used in Hawaiian fisheries are responsible for marine mammal mortality and serious injury in other 

197
fisheries throughout U.S. waters. Gillnets 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), and some of these interactions

involved Risso’s dolphins. Between 

1994 and 2002, seven Risso’s dolphins

were observed hooked or entangled in

the Hawaii-based longline fishery

outside of U.S. EEZ waters, with 

approximately 4-25% of all effort

observed (Table 1; Figure 2; Forney

2004). During the 905 observed trips 

with 11,014 sets, the average interaction

rate of Risso’s dolphins was one animal 

per 129 fishing trips, or one animal per 

1,573 sets. All Risso’s dolphins caught

were considered seriously injured

(Forney 2004), based on an evaluation of

the observer’s description of the

interaction and following established 

guidelines for assessing serious injury in 

marine mammals (Angliss and Demaster

1998). Average 5-yr estimates of annual

mortality and serious injury for 1998-

2002 are 8.2 (CV = 0.66) Risso’s

dolphins outside of U.S. EEZs, and none 

within the Hawaiian Islands EEZ. 

Several additional unidentified cetaceans,

which may have been Risso’s dolphins, 

were also taken in this fishery (Figure 2, 

Forney 2004) in international waters and 

U.S. EEZ waters of Palmyra Island. In 

2001, regulations in the Hawaii-based

longline fishery prohibited swordfish style fishing methods north of the equator in an effort to reduce sea turtle

mortality (NMFS 2001); however, a portion of the Hawaii-based fleet subsequently moved to California and

continued to fish in international waters of the North Pacific, in roughly the same areas as previously. No Risso’s 

dolphins were observed taken in the California-based longline fishery during 2001 and 2002, with roughly 5.5%

observer coverage (Forney 2004). Preliminary data for 2003 indicate one Risso’s dolphin was hooked and released

alive in international waters (NMFS/SWR, unpublished data). Since 2001, the Hawaii-based longline fishery has 

undergone further regulatory changes, but potential impacts of these changes on the rate of Risso’s dolphin takes are

unknown. 

Figure 2. Locations of Risso's dolphin takes (filled diamonds) and 

possible takes of this species (open diamonds) in the Hawaii-based 

longline fishery, 1994-2002. Solid lines represent the U.S. EEZs.

Set locations in this fishery are summarized in Appendix 1.

Table 1. Summary of available information on incidental mortality and serious injury of Risso’s dolphin (Hawaii 

stock) in commercial fisheries, within and outside of U.S. EEZs (Forney 2004). Mean annual takes are based on 

1998-2002 data unless otherwise indicated; n/a = not available. 

Mortality and Serious Injury 

outside of U.S. EEZ

Mortality and Serious Injury 

within Hawaiian Islands EEZ

Fishery Name Year Data Type

Percent 

Observer 

Coverage Observed Estimated 

(CV)

Mean Annual 

Takes 

(CV)

Observed Estimated 

(CV)

Mean Annual 

Takes 

(CV)

Hawaii-based 

longline fishery 

1998 

1999 

2000 

2001 

2002

observer

data

4.6% 

3.5% 

11.8% 

22.7% 

24.9%

0 

1 

1 

1 

0

0 (-) 

29 (1.0) 

8 (1.0) 

4 (1.0) 

0 (-)

8.2 (0.66)

0 

0 

0 

0 

0

0 (-) 

0 (-) 

0 (-) 

0 (-) 

0 (-)

0 (-)

198
Mortality and Serious Injury 

outside of U.S. EEZ

Mortality and Serious Injury 

within Hawaiian Islands EEZ

Fishery Name Year Data Type

Percent 

Observer 

Coverage Observed Estimated 

(CV)

Mean Annual 

Takes 

(CV)

Observed Estimated 

(CV)

Mean Annual 

Takes 

(CV)

California-based 

longline fishery

2001 

2002 

2003

observer 

data 

observer 

data

5.5% 

(2001-02) 

n/a

0 

0 

1

0 (-) 

0 (-) 

n/a

01

Minimum total annual takes within U.S. EEZ waters 0 (-)

1

Mean annual takes for the California-based longline fishery are based on 2001-2002. 

 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. The Hawaiian stock of Risso’s dolphin is not considered strategic under the 1994 amendments to the 

MMPA given the absence of reported fisheries related mortality within the U.S. EEZs. The potential effect of 

injuries sustained by Risso’s dolphins in U.S. pelagic longline fisheries 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. 

Barlow, J. 2003. Cetacean abundance in Hawaiian waters during summer/fall 2002. Admin. Rep. LJ-03-13. 

Southwest Fisheries Science Center, National Marine Fisheries Service, 8604 La Jolla Shores Drive, La 

Jolla, CA 92037. 

Forney, K.A. 2004. Estimates of cetacean mortality and injury in two U.S. Pacific longline fisheries, 1994_2002. 

Admin. Rep. LJ-04-07. Southwest Fisheries Science Center, National Marine Fisheries Service, 8604 La 

Jolla Shores Drive, La Jolla, CA 92037. 17 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. 

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. 

Maldini, D., L. Mazzuca, and S. Atkinson. 2005. Odontocete stranding patterns in the Main Hawaiian Islands 

(1937-2002): How do they compare with live animal surveys? Pacific Science 59(1):55-67. 

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. 

199
NMFS, Southwest Region, Observer Program, 501 W. Ocean Blvd, Long Beach, CA, 90802. 

NMFS 2001. Western Pacific Pelagic Fisheries Biological Opinion. Available from Pacific Islands Region, 1602 

Kapiolani Blvd, Suite 1110, Honolulu, HI 96814 (http://swr.nmfs.noaa.gov/pir). 

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-OPR12. 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 03/15/2005

BOTTLENOSE DOLPHIN (Tursiops truncatus): Hawaiian Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE 

Bottlenose dolphins are widely

distributed throughout the world in

tropical and warm-temperate 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. 

Bottlenose dolphins are 

common throughout the Hawaiian 

Islands, from the island of Hawaii to

Kure Atoll (Shallenberger 1981). 

Twelve strandings have been reported

within the main Hawaiian Islands (Nitta 

1991, Maldini 2005). Recent sighting

locations based on a 2002 shipboard

survey of waters within the U.S. 

Exclusive Economic Zone (EEZ) of the

Hawaiian Islands are shown in Figure 1.

In the Hawaiian Islands, they are found 

in shallow inshore waters and deep 

water, but relative to survey effort, occur primarily inshore of 500 m (Baird et al. 2003). Off the islands of Kauai

and Ni’ihau, they are found out to at least 900 m depth. Despite extensive survey effort in waters deeper than 1500

m around the main islands, there are no sightings of bottlenose dolphins (Baird et al. 2003). 

W180 W175 W170 W165 W160 W155 W150

N10

N20

N15

N25

N30

N35

Figure 1. Bottlenose dolphin sighting locations during the 2002

shipboard cetacean survey of U.S. EEZ waters surrounding the

Hawaiian Islands (Barlow 2003; see Appendix 2 for details on timin

and location of survey effort). Outer line represents approximate

boundary of survey area and U.S. EEZ.

Photographic identification surveys have shown that there is no movement of animals between the island 

groups of 1) Hawaii, 2) Maui, Molokai, Lanai and Kahoolawe, 3) Oahu and 4) Kauai and Niihau (Baird et al. 2003).

There is also a bimodal depth distribution in sightings off Kauai and Niihau, suggesting separate shallow and deep

water populations. 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 bottlenose dolphins in Hawaiian waters belong to a separate stock from those in the ETP. 

An analysis of genetic samples collected around the Hawaiian islands is ongoing and this analysis will provide

additional information on stock structure around the islands (NMFS, unpublished data). For the Marine Mammal

Protection Act (MMPA) stock assessment reports, bottlenose dolphins within the Pacific U.S. EEZ 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. Photographic mark-recapture studies off Maui and Lanai estimated 134 (95% C.I. 

107- 180) bottlenose dolphins inhabiting that area (Baird et al. 2002). More recently, a minimum of 219 distinct 

bottlenose dolphins were identified around all the main Hawaiian Islands (Baird et al. 2003). 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 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 Northwestern Hawaiian Islands (NWHI) and beyond 25 nautical miles from the main islands were

not surveyed. Furthermore, the data on which this estimate was based are now over 5 years old. A 2002 shipboard

201
line-transect survey of the entire Hawaiian Islands EEZ resulted in an abundance estimate of 3,263 (CV=0.60) 

bottlenose dolphins (Barlow 2003). This is currently the best available abundance estimate for this stock. 

Minimum Population Estimate

The log-normal 20th percentile of the 2002 abundance estimate is 2,046 bottlenose dolphins. 

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 

(2,046) times one half the default maximum net growth rate for cetaceans (1⁄2 of 4%) times a recovery factor of 0.50

(for a stock of unknown status with no estimated fishery mortality or serious injury within the U.S. EEZ of the 

Hawaiian Islands; Wade and Angliss 1997), resulting in a PBR of 20 bottlenose dolphins per year. 

HUMAN CAUSED MORTALITY AND SERIOUS INJURY

Fishery Information

Information on fishery-related

mortality of cetaceans in Hawaiian 

waters is limited, but the gear types used 

in Hawaiian fisheries are responsible for 

marine mammal mortality and serious 

injury in other fisheries throughout U.S. 

waters. Gillnets 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). In Hawaii, some mortality of 

bottlenose dolphins has been observed in 

inshore gillnets (including an entangled

dolphin that stranded in 1998;

NMFS/PIR, unpublished data), but no 

estimate of annual human-caused 

mortality and serious injury is available, 

because these fisheries are not observed

or monitored.

Interactions with cetaceans have 

been reported for all Hawaiian pelagic 

fisheries, and some of these interactions 

involved bottlenose dolphins (Nitta and 

Henderson 1993). Between 1994 and

2002 two bottlenose dolphins were

observed hooked or entangled in the 

Hawaii-based longline fishery outside of

U.S. EEZ waters, with approximately 4-

25% of all effort observed (Table 1;

Forney 2004). During the 905 observed trips with 11,014 sets, the average interaction rate of bottlenose dolphins

was one animal per 905 fishing trips, or one animal per 11,014 sets. Both animals caught were considered seriously

injured (Forney 2004), based on an evaluation of the observer’s description of the interaction and following

established guidelines for assessing serious injury in marine mammals (Angliss and Demaster 1998). Average 5-yr

estimates of annual mortality and serious injury for 1998-2002 are 5.8 (CV = 1.00) bottlenose dolphins outside of

U.S. EEZs, and none within U.S. EEZs. Several additional unidentified cetaceans, which may have been bottlenose

Figure 2. Locations of bottlenose dolphin takes (filled diamonds) in

the Hawaii-based longline fishery, 1994-2002. Solid lines represent 

the U.S. EEZ. Set locations in this fishery are summarized in

Appendix 1. 

202
dolphins, were also taken in this fishery (Figure 2, Forney 2004). Since 2001, the Hawaii-based longline fishery has 

undergone a series of regulatory changes, primarily to protect sea turtles (NMFS 2001). Potential impacts of these 

regulatory changes on the rate of bottlenose dolphin takes are unknown. 

Table 1. Summary of available information on incidental mortality and serious injury of bottlenose dolphins 

(Hawaii stock) in commercial and gillnet fisheries, within and outside of the U.S. EEZs (Forney 2004; NMFS/PIR 

unpublished data). Mean annual takes are based on 1998-2002 data unless otherwise indicated; n/a = not available. 

Mortality and Serious In ry ju

outside of U.S. EEZs

Mortality and Serious Injury 

within Hawaiian Islands EEZ

Fishery Name Year Data Type

Percent 

Observer 

Coverage

Observed Estimated 

(CV)

Mean Annual 

Takes 

(CV)

Observed Estimated 

(CV)

Mean Annual 

Takes 

(CV)

Hawaii-based 

longline fishery 

1998 

1999 

2000 

2001

2002

1998-2002 

observer data

4.6% 

3.5% 

11.8% 

22.7%

24.9%

0 

1 

0 

0

0

0 (-) 

29 (1.0) 

0 (-) 

0 (-)

0 (-)

5.8 (1.0)

0 

0 

0 

0

0

0 (-) 

0 (-) 

0 (-) 

0 (-)

0 (-)

0 (-)

Unidentified 

gillnet fishery 1998 strandings 1 n/a $0.2 (n/a)

Minimum total annual takes within U.S. EEZ waters $0.2 (n/a)

 

 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 Rock 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 that they so often remove fish from fishing lines. 

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. The Hawaiian stock of bottlenose dolphins is not considered strategic under the 1994 amendments to the 

MMPA, because the estimated rate of fisheries related mortality or serious injury within the Hawaiian Islands EEZ 

($0.2 animals per year) is less than the PBR (20). However, there is no systematic monitoring of gillnet fisheries 

that may take this species, and the potential effects of interactions with the Hawaii-based 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 

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.

Baird, R. W., A. M. Gorgone, and D. L. Webster. 2002. An examination of movements of bottlenose dolphins 

between islands in the Hawaiian Island Chain. Report prepared under contract # 40JGNF110270 to the 

203
Southwest Fisheries Science Center, National Marine Fisheries Service, 8604 La Jolla Shores Drive, La 

Jolla, CA 92037, USA. 10p. 

Baird, R.W., McSweeney D.J., Webster, D.L., Gorgone, A.M., and Ligon, A.D. 2003. Studies of odontocete 

population structure in Hawaiian waters: Results of a survey through the main Hawaiian Islands in May 

and June 2003. Report prepared under contract #AB133F-02-CN-0106 to the Southwest Fisheries Science 

Center, National Marine Fisheries Service, 8604 La Jolla Shores Drive, La Jolla, CA 92037, USA. 25 pp. 

Barlow, J. 2003. Cetacean abundance in Hawaiian waters during summer/fall 2002. Admin. Rep. LJ-03-13. 

Southwest Fisheries Science Center, National Marine Fisheries Service, 8604 La Jolla Shores Drive, La 

Jolla, CA 92037. 

Forney, K.A. 2004. Estimates of cetacean mortality and injury in two U.S. Pacific longline fisheries, 1994_2002. 

Admin. Rep. LJ-04-07. Southwest Fisheries Science Center, National Marine Fisheries Service, 8604 La 

Jolla Shores Drive, La Jolla, CA 92037. 17 pp. 

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. 

Maldini, D., L. Mazzuca, and S. Atkinson. 2005. Odontocete stranding patterns in the Main Hawaiian Islands 

(1937-2002): How do they compare with live animal surveys? Pacific Science 59(1):55-67. 

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. 

NMFS, Pacific Islands Region, Observer Program, 1602 Kapiolani Blvd, Suite 1110, Honolulu, HI 96814. 

NMFS 2001. Western Pacific Pelagic Fisheries Biological Opinion. Available from Pacific Islands Region, 1602 

Kapiolani Blvd, Suite 1110, Honolulu, HI 96814 (http://swr.nmfs.noaa.gov/pir). 

Perrin, W.F., G. P. Donovan and J. Barlow. 1994. Gillnets and Cetaceans. Rep. Int. Whal. Commn., Special Issue 

15, 629 pp. 

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. 

MMC-77/23, 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-OPR12. 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. 

204
Revised 03/15/2005

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 from a 2002 shipboard survey

of waters within the U.S. Exclusive 

Economic Zone (EEZ) of the Hawaiian 

Islands are shown in Figure 1 (Barlow

2003). Twelve strandings of this species 

have been documented in Hawaii (Nitta

1991, Maldini 2005). 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. 

W180 W175 W170 W165 W160 W155 W150

N10

N15

N20

N25

N30

N35

Figure 1. Pantropical spotted dolphin sighting locations during the

2002 shipboard survey of U.S. EEZ waters surrounding the Hawaiian 

Islands (Barlow 2003; see Appendix 2 for details on timing and 

location of survey effort). Outer line represents approximate

boundary of survey area and U.S. EEZ. 

Fishery interactions with pantropical spotted dolphins demonstrate that this species also occurs in U.S. EEZ 

waters around Palmyra Island (Figure 2), but it is not known whether these animals are part of the Hawaiian stock or 

a separate stock of pantropical spotted dolphins. Based on patterns of movement and population structure observed

in other island-associated cetaceans (Norris and Dohl 1980; Norris et al.1994; Baird et al. 2001, 2003; S. Chivers,

pers. comm.), the animals around Palmyra Island may represent a separate stock. Efforts are currently underway to

obtain additional tissue samples of pantropical spotted dolphins for further studies of population structure in the

North Pacific Ocean. There are at least 113 genetic samples available from Hawaiian waters for stock structure

analyses (R.W. Baird, pers. comm.). 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. EEZ of the Hawaiian 

Islands. Spotted dolphins involved in eastern tropical Pacific tuna purse-seine fisheries are managed separately

under the MMPA. Information on pantropical spotted dolphins around Palmyra Island will provisionally be

included with this stock assessment report, recognizing that separate stock status may be warranted for these animals 

in the future. Estimates of abundance, potential biological removals, and status determinations will be presented 

separately for U.S. EEZ waters of the Hawaiian Islands and Palmyra Island. 

 

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 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 Northwestern

205
Hawaiian Islands (NWHI) and beyond 25 nautical miles from the main islands were not surveyed. Furthermore, the 

data on which this estimate was based are now over 5 years old. A 2002 shipboard line-transect survey of the entire 

Hawaiian Islands EEZ resulted in an abundance estimate of 10,260 (CV=0.41) pantropical spotted dolphins (Barlow 

2003). This is currently the best available abundance estimate for pantropical spotted dolphins within the Hawaiian 

Islands EEZ. 

 No abundance estimates are currently available for pantropical spotted dolphins in U.S. EEZ waters of 

Palmyra Island; however, density estimates for pantropical spotted dolphins in other Pacific regions can provide a 

range of likely abundance estimates in this unsurveyed region. Published estimates of pantropical spotted dolphins 

(animals per km2) in the Pacific are: 0.0046 (CV=0.41) for the U.S. EEZ of the Hawaiian Islands (Barlow 2003); 

0.0407 (CV=0.45) for nearshore waters surrounding the main Hawaiian Islands (Mobley et al. 2000), 0.0678 

(CV=0.15) and 0.1064 (CV=0.09) for the eastern tropical Pacific Ocean (Wade and Gerrodette 1993; Ferguson and 

Barlow 2003), and 0.0731 (CV=0.33) for the eastern tropical Pacific Ocean west of 120°W and north of 5°N 

(Ferguson and Barlow 2003). Applying the lowest and highest of these density estimates to U.S. EEZ waters 

surrounding Palmyra Island (area size = 347,216 km2) yields a range of plausible abundance estimates of 1,590 - 

36,928 pantropical spotted dolphins. 

Minimum Population Estimate

 The log-normal 20th percentile of the 2002 abundance estimate for the Hawaiian Islands EEZ (Barlow 

2003) is 7,362 pantropical spotted dolphins. No minimum population estimate is currently available for waters 

surrounding Palmyra Island, but the pantropical spotted dolphin density estimates from other Pacific regions 

(Barlow 2003, Mobley et al. 2000, Wade and Gerrodette 1993, Ferguson and Barlow 2003; see above) can provide a 

range of likely values. The lognormal 20th percentiles of plausible abundance estimates for the Palmyra Island 

EEZ, based on the densities observed elsewhere, range from 1,141 - 34,238 pantropical spotted dolphins. 

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 the Hawaiian pantropical spotted dolphin stock is 

calculated as the minimum population size (7,362) 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 within 

the U.S. EEZ of the Hawaiian Islands; Wade and Angliss 1997), resulting in a PBR of 59 pantropical spotted 

dolphins per year. No separate PBR can presently be calculated for pantropical spotted dolphins within the Palmyra 

Island EEZ, but based on the range of plausible minimum abundance estimates (1,141 - 34,238), a recovery factor of 

0.40 (for a species of unknown status with a fishery mortality and serious injury rate CV > 0.80 within the Palmyra 

Islands EEZ; Wade and Angliss 1997), and the default growth rate (1⁄2 of 4%), the PBR would likely fall between 9.1 

and 274 pantropical spotted dolphins per year. 

 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Fishery Information 

Information on fishery-related mortality of cetaceans in Hawaiian waters is limited, but the gear types used in 

Hawaiian fisheries are responsible for marine mammal mortality and serious injury in other fisheries throughout 

U.S. waters. Gillnets 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). Between 1994 and 2002 one 

pantropical spotted dolphin was observed entangled and killed in the Hawaii-based longline fishery within U.S. EEZ 

waters, with approximately 4-25% of all effort observed (Table 1; Forney 2004). During the 905 observed trips with 

11,014 sets, the average take rate of pantropical spotted dolphins was one animal per 905 fishing trips, or one 

animal per 11,014 sets. Average 5-yr estimates of annual mortality and serious injury for pantropical spotted 

dolphins during 1998-2002 are zero outside of the U.S. EEZs, and 0.8 (CV=1.0) within the U.S. EEZ of Palmyra 

Island. No pantropical spotted dolphins were observed taken within the Hawaiian Islands EEZ during 1998-2002. 

One unidentified cetacean, which may have been a pantropical spotted dolphin, was also taken in this fishery within 

the EEZ of Palmyra Island (Figure 2, Forney 2004). Since 2001, the Hawaii-based longline fishery has undergone a 

206
series of regulatory changes, primarily to

protect sea turtles (NMFS 2001). 

Potential impacts of these regulatory

changes on the rate of pantropical spotted 

dolphin takes 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 

pantropical spotted dolphins are involved. 

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. The

Hawaiian stock of pantropical spotted dolphins is not considered strategic under the 1994 amendments to the

MMPA, because the estimated rate of fisheries related mortality or serious injury within the Palmyra Island EEZ 

(0.8 animals per year) is less than the range of likely PBRs (9.1 – 274) for this region. 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. 

Figure 2. Locations of observed pantropical spotted dolphin take 

(filled diamond) and a possible take (open diamond) in the Hawaiian 

longline fishery, 1994-2002. Solid lines represent the U.S. EEZ. Set 

locations in this fishery are summarized in Appendix 1.

Table 1. Summary of available information on incidental mortality and serious injury of pantropical spotted

dolphins (Hawaiian stock) in commercial fisheries, within and outside of the U.S. EEZs (Forney 2004). Mean

annual takes are based on 1998-2002 data unless otherwise indicated. 

Observed and estimated mortality and serious injury of pantropical spotted dolphins, by EEZ

region

Outside of U.S. EEZs Hawaiian Islands EEZ Palmyra Island EEZ Fishery 

Name Year Data Type

Percent 

Observer 

Coverage

Obs.

Estimated 

(CV)

Mean 

Annual 

Takes 

(CV)

Obs.

Estimated 

(CV)

Mean 

Annual 

Takes 

(CV)

Obs. Estimated 

(CV)

Mean 

Annual 

Takes 

(CV)

Hawaiibased 

longline 

fishery 

1998 

1999 

2000 

2001

2002

observer

data

4.6% 

3.5% 

11.8% 

22.7%

24.9%

0 

0 

0 

0

0

0 

0 

0 

0

0

0 (-) 

0 (-) 

0 (-) 

0 (-)

0 (-)

0 

0 

0 

0

0

0 (-) 

0 (-) 

0 (-) 

0 (-)

0 (-)

0 (-)

0 

0 

0 

1

0

0 (-) 

0 (-) 

0 (-) 

4 (1.0)

0 (-)

0.8 (1.0)

Minimum total annual takes within U.S. EEZ waters 0.8 (1.0)

207
REFERENCES

Baird, R. W., Ligon, A. D., Hooker, S. K., and A. M. Gorgone. 2001. Subsurface and nighttime behaviour of 

pantropical spotted dolphins in Hawai’i. Can. J. Zool. 79:988-996. 

Baird, R.W., McSweeney D.J., Webster, D.L., Gorgone, A.M., and Ligon, A.D. 2003. Studies of odontocete 

population structure in Hawaiian waters: Results of a survey through the main Hawaiian Islands in May 

and June 2003. Report prepared under contract #AB133F-02-CN-0106 to the Southwest Fisheries Science 

Center, National Marine Fisheries Service, 8604 La Jolla Shores Drive, La Jolla, CA 92037, USA. 25 pp. 

Barlow, J. 2003. Cetacean abundance in Hawaiian waters during summer/fall 2002. Admin. Rep. LJ-03-13. 

Southwest Fisheries Science Center, National Marine Fisheries Service, 8604 La Jolla Shores Drive, La 

Jolla, CA 92037. 

Chivers, S. NMFS, Southwest Fisheries Science Center, 8604 La Jolla Shores Drive, La Jolla, CA 92037. 

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. 

Ferguson, M. C. and J. Barlow. 2003. Addendum: Spatial distribution and density of cetaceans in the eastern 

tropical Pacific Ocean based on summer/fall research vessel surveys in 1986-96. Administrative Report LJ01-04 (addendum), Southwest Fisheries Science Center, National Marine Fisheries Service, 8604 La Jolla 

Shores Drive, La Jolla, CA 92037. 

Forney, K.A. 2004. Estimates of cetacean mortality and injury in two U.S. Pacific longline fisheries, 1994_2002. 

Admin. Rep. LJ-04-07. Southwest Fisheries Science Center, National Marine Fisheries Service, 8604 La 

Jolla Shores Drive, La Jolla, CA 92037. 17 pp. 

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. 

Maldini, D., L. Mazzuca, and S. Atkinson. 2005. Odontocete stranding patterns in the Main Hawaiian Islands 

(1937-2002): How do they compare with live animal surveys? Pacific Science 59(1):55-67. 

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. 

NMFS 2001. Western Pacific Pelagic Fisheries Biological Opinion. Available from Pacific Islands Region, 1602 

Kapiolani Blvd, Suite 1110, Honolulu, HI 96814 (http://swr.nmfs.noaa.gov/pir). 

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. 

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. 

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-OPR12. 93 pp. 

208
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. 

209
Revised 03/15/2005

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), and

26 strandings have been reported

(Maldini 2005). Recent sighting

locations from a 2002 shipboard survey

of waters within the U.S. Exclusive

Economic Zone (EEZ) of the main

Hawaiian Islands (Barlow 2003) 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). Currently, it is not known

whether spinner dolphins regularly move 

between islands or island groups, or 

whether separate populations may exist. 

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. EEZ of the

Hawaiian Islands. Spinner dolphins involved in eastern tropical Pacific tuna purse-seine fisheries are managed 

separately under the MMPA. 

W180 W175 W170 W165 W160 W155 W150

N10

N15

N20

N25

N30

N35

Figure 1. Spinner dolphin sighting locations during the 2002

shipboard cetacean survey of U.S. EEZ waters surrounding the

Hawaiian Islands (Barlow 2003; see Appendix 2 for details on timing

and location of survey effort). Outer line indicates approximate

boundary of survey area and U.S. EEZ.

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) photo-identified 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 calculated from

the combined survey data (Mobley et al. 2000). This study underestimated the total number of spinner dolphins

within the U.S. EEZ off Hawaii, because areas around the Northwestern Hawaiian Islands (NWHI) and beyond 25 

nautical miles from the main islands were not surveyed. Furthermore, the data on which this estimate was based are 

now over 5 years old. A 2002 shipboard line-transect survey of the entire Hawaiian Islands EEZ resulted in an

abundance estimate of 2,805 (CV=0.66) spinner dolphins (Barlow 2003). This is currently the best available 

abundance estimate for this stock, but it may be negatively biased because relatively little survey effort occurred in 

nearshore areas where these dolphins are abundant. Nearshore aerial surveys are currently being conducted for this

species. 

Minimum Population Estimate

The log-normal 20th percentile of the 2002 abundance estimate is 1,690 spinner dolphins. 

210
Current Population Trend

No data on current population trend are available. 

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 

(1,690) 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 or serious injury within the U.S. EEZ of the

Hawaiian Islands; Wade and Angliss 1997), resulting in a PBR of 17 spinner dolphins per year. 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Fishery Information

Information on fishery-related

mortality of cetaceans in Hawaiian

waters is limited, but the gear types used 

in Hawaiian fisheries are responsible for 

marine mammal mortality and serious

injury in other fisheries throughout U.S. 

waters. Gillnets 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). In

Hawaii, some entanglements of spinner

dolphins have been observed (Nitta and 

Henderson 1993; NMFS/PIR,

unpublished data), but no estimate of

annual human-caused mortality and

serious injury is available, because the

nearshore gillnet fisheries are not

observed or monitored. 

Interactions with cetaceans have 

been reported for all Hawaiian pelagic 

fisheries (Nitta and Henderson 1993).

Between 1994 and 2002, two spinner 

dolphins were observed hooked or

entangled in the Hawaii-based longline 

fishery, with approximately 4-25% of all

effort observed (Forney 2004). During 

the 905 observed trips with 11,014 sets,

the average interaction rate of spinner 

dolphins was one animal per 453 fishing

trips, or one animal per 5,507 sets. Neither of the animals caught was considered seriously injured (Forney 2004),

based on an evaluation of the observer’s description of the interaction and following established guidelines for

assessing serious injury in marine mammals (Angliss and Demaster 1998). The average 5-yr estimate of annual 

mortality and serious injury within the Hawaiian Islands EEZ during 1998-2002 is zero spinner dolphins. One 

additional unidentified cetacean, which may have been a spinner dolphin, was taken in this fishery within the U.S. 

EEZ surrounding Palmyra Island (Figure 2, Forney 2004). Since 2001, the Hawaii-based longline fishery has 

undergone a series of regulatory changes, primarily to protect sea turtles (NMFS 2001). Potential impacts of these 

regulatory changes on the rate of spinner dolphin takes are unknown. 

Figure 2. Locations of observed spinner dolphin takes (filled

diamonds) and possible takes of this species (open diamond) in the 

Hawaii-based longline fishery, 1994-2002. Solid lines represent the 

U.S. EEZ. Set locations in this fishery are summarized in Appendix 

1. 

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).

211
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. 

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-withdolphin 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 of spinner dolphins is not considered a strategic stock under the 1994 

amendments to the MMPA, because the estimated rate of mortality and serious injury within the Hawaiian Islands 

EEZ is zero. However, there is no systematic monitoring of gillnet fisheries that may take this species. 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. 

Barlow, J. 2003. Cetacean abundance in Hawaiian waters during summer/fall 2002. Admin. Rep. LJ-03-13. 

Southwest Fisheries Science Center, National Marine Fisheries Service, 8604 La Jolla Shores Drive, La 

Jolla, CA 92038. 

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. 

Forney, K.A. 2004. Estimates of cetacean mortality and injury in two U.S. Pacific longline fisheries, 1994_2002. 

Admin. Rep. LJ-04-07. Southwest Fisheries Science Center, National Marine Fisheries Service, 8604 La 

Jolla Shores Drive, La Jolla, CA 92037. 17 pp. 

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. 

Maldini, D., L. Mazzuca, and S. Atkinson. 2005. Odontocete stranding patterns in the Main Hawaiian Islands 

(1937-2002): How do they compare with live animal surveys? Pacific Science 59(1):55-67. 

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. 

NMFS, Pacific Islands Region, Observer Program, 1602 Kapiolani Blvd, Suite 1110, Honolulu, HI 96814. 

NMFS 2001. Western Pacific Pelagic Fisheries Biological Opinion. Available from Pacific Islands Region, 1602 

Kapiolani Blvd, Suite 1110, Honolulu, HI 96814 (http://swr.nmfs.noaa.gov/pir). 

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. 

212
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-OPR12. 93 pp. 

213
Revised 03/15//2005

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. 

1994b). They have been documented in

the Hawaiian Islands from 20 strandings

(Nitta 1991, Maldini 2005), although 

sightings have historically been 

infrequent (Shallenberger 1981, Mobley

et al. 2000). A comprehensive shipboard

survey of the Hawaiian Exclusive

Economic Zone (EEZ), resulted in 15

sightings of striped dolphins (Figure 1;

Barlow 2003). 

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. 

EEZ are divided into two discrete, noncontiguous 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.

W180 W175 W170 W165 W160 W155 W150

N10

N15

N20

N25

N30

N35

Figure 1. Striped dolphin sighting locations during the 2002

shipboard survey of U.S. EEZ waters surrounding the Hawaiian 

Islands (Barlow 2003; see Appendix 2 for details on timing and

location of survey effort). Outer line represents approximate

boundary of survey area and U.S. EEZ. 

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 calculated from the combined survey data (Mobley et al. 2000). This study underestimated the total number of

striped dolphins within the U.S. EEZ off Hawaii, because areas around the Northwestern Hawaiian Islands (NWHI) 

and beyond 25 nautical miles from the main islands were not surveyed. Furthermore, the data on which this estimate

was based are now over 5 years old. A 2002 shipboard line-transect survey of the entire Hawaiian Islands EEZ 

resulted in an abundance estimate of 10,385 (CV=0.48) striped dolphins (Barlow 2003). This is currently the best 

available abundance estimate for this stock. 

Minimum Population Estimate

The log-normal 20th percentile of the 2002 abundance estimate is 7,078 striped dolphins. 

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. 

214
POTENTIAL BIOLOGICAL REMOVAL

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

(7,078) 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 

71 striped dolphins per year. 

 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Fishery Information

Information on fishery-related mortality and serious injury of cetaceans in Hawaiian waters is limited, but 

the gear types used in Hawaiian fisheries are responsible for marine mammal mortality and serious injury in other 

fisheries throughout U.S. waters. Gillnets 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 striped dolphins have been documented. None were observed hooked or entangled in 

the Hawaii-based longline fishery between 1994 and 2002, with approximately 4-25% of all effort observed (Forney 

2004). 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. The Hawaiian stock of striped dolphins is not 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

Barlow, J. 2003. Cetacean abundance in Hawaiian waters during summer/fall 2002. Admin. Rep. LJ-03-13. 

Southwest Fisheries Science Center, National Marine Fisheries Service, 8604 La Jolla Shores Drive, La 

Jolla, CA 92037. 

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. 

Forney, K.A. 2004. Estimates of cetacean mortality and injury in two U.S. Pacific longline fisheries, 1994_2002. 

Admin. Rep. LJ-04-07. Southwest Fisheries Science Center, National Marine Fisheries Service, 8604 La 

Jolla Shores Drive, La Jolla, CA 92037. 17 pp. 

Kishiro, T. and T. Kasuya. 1993. Review of Japanese dolphin drive fisheries and their status. Rep. Int. Whal. 

Commn. 43:439-452. 

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. 

Maldini, D., L. Mazzuca, and S. Atkinson. 2005. Odontocete stranding patterns in the Main Hawaiian Islands 

(1937-2002): How do they compare with live animal surveys? Pacific Science 59(1):55-67. 

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. 

215
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., C. E. Wilson, and F. I. Archer, II. 1994b. 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. 

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-OPR12. 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. 

216
Revised 03/15/2005 

FRASER'S DOLPHIN (Lagenodelphis hosei): 

Hawaiian Stock 

STOCK DEFINITION AND GEOGRAPHIC RANGE

Fraser’s dolphins are distributed

worldwide in tropical waters (Perrin et al. 

1994b). They have only recently been

documented within the U.S. Exclusive

Economic Zone (EEZ) of the Hawaiian 

Islands, during a 2002 cetacean survey 

(Barlow 2003, Figure 1). No strandings

of Fraser’s dolphins have been 

documented in the Hawaiian Islands

(Nitta 1991; Maldini 2005). 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. EEZ of the

Hawaiian Islands. 

POPULATION SIZE

Population estimates for Fraser’s 

dolphins have 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 

and in the central North Pacific. No 

sightings of this species were made

during twelve aerial surveys, conducted as part of the Marine Mammal Research Program of the Acoustic 

Thermometry of Ocean Climate (ATOC) study, within about 25 nmi of the main Hawaiian Islands in 1993, 1995

and 1998 (Mobley et al. 2000). A 2002 shipboard line-transect survey of the entire Hawaiian Islands EEZ resulted in

an abundance estimate of 16,836 (CV=1.11) Fraser’s dolphins (Barlow 2003). This is currently the best available 

abundance estimate for this stock. 

W180 W175 W170 W165 W160 W155 W150

N10

N15

N20

N30

N35

N25

Figure 1. Fraser’s dolphin sighting locations during the 2002 

shipboard cetacean survey of U.S. waters surrounding the Hawaiian 

Islands (Barlow 2003; see Appendix 2 for details on timing and

location of survey effort). Outer line indicates approximate boundary

of survey area and U.S. EEZ.

Minimum Population Estimate

The log-normal 20th percentile of the 2002 abundance estimate is 7,917 Fraser’s dolphins. 

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 the Hawaiian stock of Fraser’s 

dolphin. 

POTENTIAL BIOLOGICAL REMOVAL

The potential biological removal (PBR) level for this stock of Fraser’s dolphin is calculated as the

minimum population size (7,917) times one half the default maximum net growth rate for cetaceans (1⁄2 of 4%) times

a recovery factor of 0.50 (for a stock of unknown status with no known fishery mortality or serious injury within the 

Hawaiian Islands EEZ; Wade and Angliss 1997), resulting in a PBR of 79 Fraser’s dolphins per year. 

217
HUMAN CAUSED MORTALITY AND SERIOUS INJURY 

Fishery Information

 Information on fishery-related mortality and serious injury of cetaceans in Hawaiian waters is limited, but 

the gear types used in Hawaiian fisheries are responsible for marine mammal mortality and serious injury in other 

fisheries throughout U.S. waters. Gillnets 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 none of these 

interactions are known to have involved Fraser’s dolphins. None were observed hooked or entangled in the Hawaiibased longline fishery between 1994 and 2002, with approximately 4-25% of all effort observed (Forney 2004). 

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 Fraser’s dolphins are involved. 

STATUS OF STOCK 

 The status of Fraser'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. The Hawaiian stock of Fraser’s dolphins is not considered strategic under the 1994 amendments to the 

MMPA, because there has been no reported fisheries related mortality or serious injury within the U.S. EEZ of the 

Hawaiian Islands. Insufficient information is available to determine whether the total fishery mortality and serious 

injury for Fraser’s dolphins is insignificant and approaching zero mortality and serious injury rate. 

REFERENCES

Barlow, J. 2003. Cetacean abundance in Hawaiian waters during summer/fall 2002. Admin. Rep. LJ-03-13. 

Southwest Fisheries Science Center, National Marine Fisheries Service, 8604 La Jolla Shores Drive, La 

Jolla, CA 92037. 

Forney, K.A. 2004. Estimates of cetacean mortality and injury in two U.S. Pacific longline fisheries, 1994_2002. 

Admin. Rep. LJ-04-07. Southwest Fisheries Science Center, National Marine Fisheries Service, 8604 La 

Jolla Shores Drive, La Jolla, CA 92037. 17 pp. 

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. 

Maldini, D., L. Mazzuca, and S. Atkinson. 2005. Odontocete stranding patterns in the Main Hawaiian Islands 

(1937-2002): How do they compare with live animal surveys? Pacific Science 59(1):55-67. 

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. 1994a. Gillnets and Cetaceans. Rep. Int. Whal. Commn., Special Issue 

15, 629 pp. 

Perrin, W.F., S. Leatherwood and A. Collet. 1994b. Fraser’s dolphin Lagenodelphis hosei (Fraser 1956). Pages 

225-240 In: S. H. Ridgway and R. Harrison (eds) Handbook of Marine Mammals, Vol. 5: The first book of 

dolphins. Academic Press, London. 416 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. Dept. Commer., NOAA Tech. Memo. NMFS-OPR12. 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. 

218
Revised 03/15/2005

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). A 

comprehensive shipboard survey of the

Hawaiian Exclusive Economic Zone

(EEZ), resulted in only one sighting of

melon-headed whales (Figure 1; Barlow

2003). Inter-island movements from

Kauai to Hawaii have been documented 

and genetic samples from at least 82

animals are available for future stock

structure analyses (R.W. Baird, pers. 

comm.). Little is known about this 

species elsewhere in its range, and most knowledge about its biology comes from mass strandings (Perryman et al.

1994). Fourteen strandings are known from Hawaii (Nishiwaki and Norris 1966; Shallenberger 1981; Nitta 1991;

Maldini 2005). 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. EEZ of the Hawaiian Islands. 

W180 W175 W170 W165 W160 W155 W150

N10

N15

N20

N25

N30

N35

Figure 1. Melon-headed whale sighting location during the 2002

shipboard survey of U.S. EEZ waters surrounding the Hawaiian 

Islands (Barlow 2003; see Appendix 2 for details on timing and

location of survey effort). Outer line represents approximate

boundary of survey area and U.S. EEZ. 

POPULATION SIZE

An abundance 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

calculated from the combined survey data (Mobley et al. 2000). This study underestimated the total number of

melon-headed whales within the U.S. EEZ off Hawaii, because areas around the Northwestern Hawaiian Islands

(NWHI) and beyond 25 nautical miles from the main islands were not surveyed. Furthermore, the data on which 

this estimate was based are now over 5 years old. A 2002 shipboard line-transect survey of the entire Hawaiian 

Islands EEZ resulted in an abundance estimate of 2,947 (CV=1.11) melon-headed whales (Barlow 2003). This is

currently the best available abundance estimate for this stock. 

Minimum Population Estimate

The log-normal 20th percentile of the 2002 abundance estimate is 1,386 melon-headed whales. 

urrent Population Trend

n current population trend. 

C

No data are available o

219
CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

OTENTIAL BIOLOGICAL REMOVAL

R) level for this stock is calculated as the minimum population size 

 No data are available on current or maximum net productivity rate. 

P

 The potential biological removal (PB

(1 imes ,386) t 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 14 

melon-headed whales per year. 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY 

Fishery Information

 Information on fishery-related mortality and serious injury of cetaceans in Hawaiian waters is limited, but 

th types used in Hawaiian fisheries are responsible for marine mammal mortality and serious injury in other e gear

fisheries throughout U.S. waters. Gillnets 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 ut no interactions with melon-headed whales have ), b been documented. None were observed hooked in the 

Hawaii-based longline fishery between 1994 and 2002, with approximately 4-25% of all effort observed (Forney 

2004). 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. 

STATUS OF STOCK

melon-headed whales in Hawaiian waters relative to OSP is unknown, and there are 

suffici

 The status of 

in ent 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. The Hawaiian stock of melon-headed whales is not considered strategic under the 1994 

amendments to the MMPA given the absence of reported fisheries related mortality or serious injury. 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 

Barlow, J. 2003. Cetacean abundance in Hawaiian waters during summer/fall 2002. Admin. Rep. LJ-03-13. 

Southwest Fisheries Science Center, National Marine Fisheries Service, 8604 La Jolla Shores Drive, La 

Jolla, CA 92037. 

Forney, K.A. 2004. Estimates of cetacean mortality and injury in two U.S. Pacific longline fisheries, 1994-2002. 

Admin. Rep. LJ-04-07. Southwest Fisheries Science Center, National Marine Fisheries Service, 8604 La 

Jolla Shores Drive, La Jolla, CA 92037. 17 pp. 

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. 

Maldini, D., L. Mazzuca, and S. Atkinson. 2005. Odontocete stranding patterns in the Main Hawaiian Islands 

(1937-2002): How do they compare with live animal surveys? Pacific Science 59(1):55-67. 

Mobley, J. R. , Jr, S. S. Spitz, K. A. Forney, R. A. Grotefendt, and P. H. Forestall. 2000. Distribution and 

Nishiwa 6. A new genus, Peponocephala, for the odontocete cetacean species Electra 

Nitta, E. for Hawaii: an overview. In: J.E. Reynolds III, D.K. Odell 

Nitta, E. . 

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. 

ki, M. and K. S. Norris. 196

electra. Sci. Rep. Whales Res. Inst. 20:95-100. 

1991. The marine mammal stranding network 

(eds.), Marine Mammal Strandings in the United States, pp.56-62. NOAA Tech. Rep. NMFS 98, 157 pp. 

 and J. R. Henderson. 1993. A review of interactions between Hawaii's fisheries and protected species

Mar. Fish. Rev. 55(2):83-92. 

220
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. 

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-OPR12. 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.

221
Revised 03/15/2005

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). 

Three sightings of pygmy killer whales 

were made during a 2002 shipboard

survey of U.S. Exclusive Economic

Zone (EEZ) waters surrounding the Hawaiian Islands (Figure 1; Barlow 2003). Six strandings have been

documented from Maui and the island of Hawaii (Nitta 1991, Maldini 2005). 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. EEZ of the Hawaiian Islands. 

W180 W175 W170 W165 W160 W155 W150

N10

N15

N20

N25

N30

N35

Figure 1. Pygmy killer whale sighting locations during the 2002

shipboard survey of U.S. EEZ waters surrounding the Hawaiian 

Islands (Barlow 2003; see Appendix 2 for details on timing and

location of survey effort). Outer line represents approximate

boundary of survey area and U.S. EEZ. 

POPULATION SIZE

A population estimate has been made for this species 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 (Mobley et al. 2000), but there were no sightings of pygmy killer whales. A 2002

shipboard line-transect survey of the entire Hawaiian Islands EEZ resulted in an abundance estimate of 817 

(CV=1.12) pygmy killer whales (Barlow 2003). This is currently the best available abundance estimate for this 

stock. 

Minimum Population Estimate

The log-normal 20th percentile of the 2002 abundance estimate is 382 pygmy killer whales. 

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. 

222
POTENTIAL BIOLOGICAL REMOVAL

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

(382) times one half the default maximum net growth rate for cetaceans (1⁄2 of 4%) times a recovery factor of 0.50 

(for a stock of unknown status with no known fishery mortality or serious injury within the Hawaiian Islands EEZ; 

Wade and Angliss 1997), resulting in a PBR of 3.8 pygmy killer whales per year. 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Fishery Information

Information on fishery-related mortality and serious injury of cetaceans in Hawaiian waters is limited, but 

the gear types used in Hawaiian fisheries are responsible for marine mammal mortality and serious injury in other 

fisheries throughout U.S. waters. Gillnets 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 or 

entangled in the Hawaii-based longline fishery between 1994 and 2002, with approximately 4-25% of all effort 

observed (Forney 2004). 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 pygmy killer whales 

are involved. 

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. The Hawaiian stock of pygmy killer whales is not considered strategic under the 1994 

amendments to the MMPA given the absence of reported fisheries related mortality or serious injury. 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 

Barlow, J. 2003. Cetacean abundance in Hawaiian waters during summer/fall 2002. Admin. Rep. LJ-03-13. 

Southwest Fisheries Science Center, National Marine Fisheries Service, 8604 La Jolla Shores Drive, La 

Jolla, CA 92037. 

Forney, K.A. 2004. Estimates of cetacean mortality and injury in two U.S. Pacific longline fisheries, 1994-2002. 

Admin. Rep. LJ-04-07. Southwest Fisheries Science Center, National Marine Fisheries Service, 8604 La 

Jolla Shores Drive, La Jolla, CA 92037. 17 pp. 

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. 

Maldini, D., L. Mazzuca, and S. Atkinson. 2005. Odontocete stranding patterns in the Main Hawaiian Islands 

(1937-2002): How do they compare with live animal surveys? Pacific Science 59(1):55-67. 

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, T., K. Pryor and K. S. Norris. 1965. Observations on a pygmy killer whale (Feresa attenuata Gray) from 

Hawaii. J. Mamm. 46:450-461. 

223
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. 

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-OPR12. 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. 

224
Revised 03/15/2005 

FALSE KILLER WHALE (Pseudorca crassidens): 

Hawaiian Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

False killer whales are found

worldwide mainly in tropical and warmtemperate waters (Stacey et al. 1994). In 

the North Pacific, this species is well 

known from southern Japan, Hawaii, and 

the eastern tropical Pacific. Most

knowledge about this species comes

from outside Hawaiian waters (Stacey et 

al. 1994). There are six stranding records

from Hawaiian waters (Nitta 1991;

Maldini 2005). Two sightings of false

killer whales were made during a 2002 

shipboard survey of waters within the

U.S. Exclusive Economic Zone (EEZ) of

the Hawaiian Islands (Figure 1; Barlow 

2003). 

Genetic analyses of tissue 

samples collected near the main

Hawaiian Islands indicate that Hawaiian 

false killer whales are reproductively

isolated from false killer whales found in

the eastern tropical Pacific Ocean (S. 

Chivers, NMFS/SWFSC, unpublished 

data); however, the offshore range of

this Hawaiian population is unknown.

Fishery interactions with false killer whales demonstrate that this species also occurs in U.S. EEZ waters around 

Palmyra Island (Figure 2), but it is not known whether these animals are part of the Hawaiian stock or whether they

represent a separate stock of false killer whales. Based on patterns of movement and population structure observed

in other island-associated cetaceans (Norris and Dohl 1980; Norris et al.1994; Baird et al. 2001, 2003; S. Chivers,

pers. comm.), the animals around Palmyra Island may represent a separate stock. Unconfirmed sightings of false 

killer whales have also been reported near Johnston Atoll and require further investigation (NMFS/PIR, unpublished

data). Efforts are currently underway to obtain additional tissue samples of false killer whales for further studies of 

population structure in the North Pacific Ocean. For the Marine Mammal Protection Act (MMPA) stock assessment 

reports, there is currently a single Pacific management stock including animals found within the U.S. EEZ of the

Hawaiian Islands. Information on false killer whales around Palmyra Island will provisionally be included with this 

stock assessment report, recognizing that separate stock status may be warranted for these animals in the future. 

Estimates of abundance, potential biological removals, and status determinations will be presented separately for 

U.S. EEZ waters of the Hawaiian Islands and Palmyra Island. 

W180 W175 W170 W165 W160 W155 W150

N10

N15

N20

N25

N30

N35

Figure 1. False killer whale sighting locations during the 2002 

shipboard survey of U.S. EEZ waters surrounding the Hawaiian 

Islands (Barlow 2003; see Appendix 2 for details on timing and

location of survey effort). Outer line represents approximate

boundary of survey area and U.S. EEZ.

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 evidence suggests that false killer whales around

Hawaii form a distinct population (S. Chivers, NMFS/SWFSC, unpublished data). 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 calculated from the combined survey data (Mobley et al. 2000). This 

study underestimated the total number of false killer whales within the U.S. EEZ off Hawaii, because areas around

the Northwestern Hawaiian Islands (NWHI) and beyond 25 nautical miles from the main islands were not surveyed 

and estimates were uncorrected for the proportion of diving animals missed from the survey aircraft. Furthermore,

the data on which this estimate was based are now over 5 years old. A 2002 shipboard line-transect survey of the 

225
entire Hawaiian Islands EEZ resulted in an abundance estimate of 268 (CV=1.08) false killer whales (Barlow 2003). 

This is the best available abundance estimate for false killer whales within the Hawaiian Islands EEZ. 

 No abundance estimates are currently available for false killer whales in U.S. EEZ waters of Palmyra 

Island; however, density estimates for false killer whales in other Pacific regions can provide a range of likely 

abundance estimates in this unsurveyed region. Published estimates of false killer whale density (animals per km2) 

in the Pacific are: 0.0001 (CV=1.08) for the U.S. EEZ of the Hawaiian Islands (Barlow 2003); 0.0017 (CV=0.47) for 

nearshore waters surrounding the main Hawaiian Islands (Mobley et al. 2000), 0.0021 (CV=0.64) and 0.0016 

(CV=0.31) for the eastern tropical Pacific Ocean (Wade and Gerrodette 1993; Ferguson and Barlow 2003), and 

0.0033 (CV=0.56) for the eastern tropical Pacific Ocean west of 120°W and north of 5°N (Ferguson and Barlow 

2003). Applying the lowest and highest of these density estimates to U.S. EEZ waters surrounding Palmyra Island 

(area size = 347,216 km2) yields a range of plausible abundance estimates of 42 - 1,160 false killer whales. 

Minimum Population Estimate

 The log-normal 20th percentile of the 2002 abundance estimate for the Hawaiian Islands EEZ (Barlow 

2003) is 128 false killer whales. No minimum population estimate is currently available for waters surrounding 

Palmyra Island, but the false killer whale density estimates from other Pacific regions (Barlow 2003, Mobley et al. 

2000, Wade and Gerrodette 1993, Ferguson and Barlow 2003; see above) can provide a range of likely values. The 

lognormal 20th percentiles of plausible abundance estimates for the Palmyra Island EEZ, based on the densities 

observed elsewhere, range from 20 - 746 false killer whales. 

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 the Hawaiian false killer whale stock is calculated as the 

minimum population size (128 ) 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 Hawaiian Islands EEZ mortality and serious injury 

rate CV > 0.80; Wade and Angliss 1997), resulting in a PBR of 1.0 false killer whales per year. No separate PBR 

can presently be calculated for false killer whales within the Palmyra Island EEZ, but based on the range of 

plausible minimum abundance estimates (20 - 746), a recovery factor of 0.45 (for a species of unknown status with a 

fishery mortality and serious injury rate CV between 0.60 and 0.80 within the Palmyra Island EEZ; Wade and 

Angliss 1997), and the default growth rate (1⁄2 of 4%), the PBR would likely fall between 0.2 and 6.7 false killer 

whales per year. 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY 

Fishery Information 

Information on fishery-related mortality of cetaceans in Hawaiian waters is limited, but the gear types used 

in Hawaiian fisheries are responsible for marine mammal mortality and serious injury in other fisheries throughout 

U.S. waters. Gillnets 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). In Hawaii, no mortality of false 

killer whales has been observed in inshore gillnets, but these fisheries are not observed or monitored.

Interactions with cetaceans have been reported for all Hawaiian pelagic fisheries, and false killer whales 

have been identified in fishermen's logs and NMFS observer records as taking catches from pelagic longlines (Nitta 

and Henderson 1993, NMFS/PIR unpublished data). 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.). 

226
Between 1994 and 2002, ten 

false killer whales were observed hooked 

in the Hawaii-based longline fishery with 

approximately 4-25% of all effort

observed (Table 1; Forney 2004). Seven

additional unidentified cetaceans, which 

may have been false killer whales, were 

also taken in this fishery (Figure 2,

Forney 2004). During the 905 observed 

trips with 11,014 sets, the average 

interaction rate of false killer whales was 

one animal per 91 fishing trips, or one

animal per 1,101 sets. All false killer 

whales caught were considered seriously

injured (Forney 2004), based on an

evaluation of the observer’s description

of the interaction and following 

established guidelines for assessing 

serious injury in marine mammals

(Angliss and DeMaster 1998). Average 

5-yr estimates of annual mortality and 

serious injury for 1998-2002 are 4.8 (CV

= 0.49) false killer whales outside of

U.S. EEZs, 4.4 (CV = 1.00) within the 

Hawaiian Islands EEZ, and 2.4 (CV = 

0.61) within the EEZ of Palmyra Island 

(Table 1). Total estimated annual

mortality and serious injury for all U.S.

EEZs combined averaged 6.8 (CV=0.60)

between 1998 and 2002. Since 2001, the Hawaii-based longline fishery has undergone a series of regulatory

changes, primarily to protect sea turtles (NMFS 2001). Potential impacts of these regulatory changes on the rate of 

false killer whale interactions are unknown. 

Figure 2. Locations of observed false killer whale takes (filled

diamonds) and possible takes of this species (open diamonds) in the

Hawaii-based longline fishery, 1994-2002. Solid lines represent the 

U.S. EEZ. Set locations in this fishery are summarized in Appendix 

1.

Table 1. Summary of available information on incidental mortality and serious injury of false killer whales 

(Hawaiian stock) in commercial fisheries, within and outside of U.S. EEZs (Forney 2004). Mean annual takes are 

based on 1998-2002 data unless otherwise indicated. 

Observed and estimated mortality and serious injury of false killer whales, by EEZ region

Outside of U.S. EEZs Hawaiian Islands EEZ Palmyra Island EEZ Fishery 

Name Year Data 

Type

Percent 

Observer 

Coverage

Obs.

Estimated 

(CV)

Mean 

Annual 

Takes 

(CV)

Obs.

Estimated 

(CV)

Mean 

Annual 

Takes 

(CV)

Obs. Estimated 

(CV)

Mean 

Annual 

Takes 

(CV)

Hawaiibased 

longline 

fishery 

1998 

1999 

2000 

2001

2002

observer

data

4.6% 

3.5% 

11.8% 

22.7%

24.9%

0 

0 

1 

1

3

0 (-) 

0 (-) 

8 (1.00)

4 (1.00)

12 (0.58)

4.8 (0.49)

1 

0 

0 

0

0

22 (1.00)

0 (-) 

0 (-) 

0 (-)

0 (-)

4.4 

(1.00)

0 

0 

0 

1

2

0 (-) 

0 (-) 

0 (-) 

4 (1.00)

8 (0.71)

2.4 

(0.61)

Minimum total annual takes within U.S. EEZ waters 6.8 (0.60)

 

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 that 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. 

227
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 mortality and serious injury to false killer whales within the Hawaiian Islands EEZ in 

the Hawaii-based longline fishery (4.4 animals per year) exceeds the PBR (1.0), this stock is considered a strategic 

stock under the 1994 amendments to the MMPA. The total fishery mortality and serious injury for Hawaiian false 

killer whales cannot be considered to be insignificant and approaching zero, because it exceeds the PBR. Although 

no estimates of abundance or PBR are currently available for false killer whales around Palmyra Island, the average 

rate of mortality and serious injury within the Palmyra Island EEZ (2.4 animals per year) falls within the range of 

likely PBRs (0.2 to 6.7) for this region. 

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. 

Baird, R. W., Ligon, A. D., Hooker, S. K., and A. M. Gorgone. 2001. Subsurface and nighttime behaviour of 

pantropical spotted dolphins in Hawai’i. Can. J. Zool. 79:988-996. 

Baird, R.W., McSweeney D.J., Webster, D.L., Gorgone, A.M., and Ligon, A.D. 2003. Studies of odontocete 

population structure in Hawaiian waters: Results of a survey through the main Hawaiian Islands in May 

and June 2003. Report prepared under contract #AB133F-02-CN-0106 to the Southwest Fisheries Science 

Center, National Marine Fisheries Service, 8604 La Jolla Shores Drive, La Jolla, CA 92037, USA. 10p. 

Barlow, J. 2003. Cetacean abundance in Hawaiian waters during summer/fall 2002. Admin. Rep. LJ-03-13. 

Southwest Fisheries Science Center, National Marine Fisheries Service, 8604 La Jolla Shores Drive, La 

Jolla, CA 92037. 

Chivers, S. NMFS, Southwest Fisheries Science Center, 8604 La Jolla Shores Drive, La Jolla, CA 92037. 

Ferguson, M. C. and J. Barlow. 2003. Addendum: Spatial distribution and density of cetaceans in the eastern 

tropical Pacific Ocean based on summer/fall research vessel surveys in 1986-96. Administrative Report LJ01-04 (addendum), Southwest Fisheries Science Center, National Marine Fisheries Service, 8604 La Jolla 

Shores Drive, La Jolla, CA 92037. 

Forney, K.A. 2004. Estimates of cetacean mortality and injury in two U.S. Pacific longline fisheries, 1994-2002. 

Admin. Rep. LJ-04-07. Southwest Fisheries Science Center, National Marine Fisheries Service, 8604 La 

Jolla Shores Drive, La Jolla, CA 92037. 17 pp. 

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. 

Maldini, D., L. Mazzuca, and S. Atkinson. 2005. Odontocete stranding patterns in the Main Hawaiian Islands 

(1937-2002): How do they compare with live animal surveys? Pacific Science 59(1):55-67. 

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. 

NMFS, Pacific Islands Region, Observer Program, 1602 Kapiolani Blvd, Suite 1110, Honolulu, HI 96814. 

NMFS, Southwest Fisheries Science Center, 8604 La Jolla Shores Drive, La Jolla, CA 92027. 

NMFS Western Pacific Pelagic Fisheries Biological Opinion 2001. Available from Pacific Islands Region, 1602 

Kapiolani Blvd, Suite 1110, Honolulu, HI 96814 (http://swr.nmfs.noaa.gov/pir). 

Norris, K. S., B. Würsig, R. S. Wells, and M. Würsig. 1994. The Hawaiian Spinner Dolphin. University of 

California Press, 408 pp. 

228
Norris, K. S. and T. P. Dohl. 1980. Behavior of the Hawaiian spinner dolphin, Stenella longirostris. Fish. Bull.

77:821-849. 

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. 

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-OPR12. 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.

229
Revised 03/15/2005

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 considered rare in Hawaiian 

waters. No killer whales were seen 

during 1993-98 aerial surveys within 

about 25 nmi of the main Hawaiian

Islands, but one sighting was reported

during subsequent surveys (Mobley et al.

2000, 2001). Two sightings of killer

whales were made during a 2002

shipboard survey of waters within the 

U.S. Exclusive Economic Zone (EEZ) of

the Hawaiian Islands (Figure 1; Barlow 

2003). One stranding from the island of

Hawaii was reported in 1950 (Richards 

1952) and another in 2004 (R.W. Baird,

pers. comm.). 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. Baird et al. (2003) report a sighting of this species off the island of Hawaii in 2003, and also note analyses 

of genetic results from one sample collected, indicating a haplotype similar to the Gulf of Alaska “transient” killer 

whales. 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). Stock Assessment Reports for the Eastern North 

Pacific Northern Resident stock and the Eastern North Pacific Transient stocks can be found in the Alaska Region

stock assessment reports; all other killer whale stock assessments are included in the Pacific Region stock

assessments. 

W180 W175 W170 W165 W160 W155 W150

N10

N15

N20

N25

N30

N35

Figure 1. Killer whale sighting locations during the 2002 shipboard

survey of U.S. EEZ waters surrounding the Hawaiian Islands 

(Barlow 2003; see Appendix 2 for details on timing and location of 

survey effort). Outer line represents approximate boundary of survey

area and U.S. EEZ. 

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). 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), but 

no sightings of killer whales were made. A 2002 shipboard line-transect survey of the entire Hawaiian Islands EEZ 

resulted in an abundance estimate of 430 (CV=0.72) killer whales (Barlow 2003). This is currently the best

available abundance estimate for this stock. 

Minimum Population Estimate

 The log-normal 20th percentile of the 2002 abundance estimate is 250 killer whales. 

230
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

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

(250) times one half the default maximum net growth rate for cetaceans (1⁄2 of 4%) times a recovery factor of 0.50 

(for a stock of unknown status with no known fishery mortality or serious injury within the Hawaiian Islands EEZ; 

Wade and Angliss 1997), resulting in a PBR of 2.5 killer whales per year. 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Fishery Information

 Information on fishery-related mortality and serious injury of cetaceans in Hawaiian waters is limited, but 

the gear types used in Hawaiian fisheries are responsible for marine mammal mortality and serious injury in other 

fisheries throughout U.S. waters. Gillnets 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 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 or entangled in the Hawaii-based 

longline fishery between 1994 and 2002, with approximately 4-25% of all effort observed (Forney 2004). 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 that 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. The Hawaiian stock of killer whales is not considered strategic under the 1994 amendments to the MMPA 

given the absence of reported fisheries related mortality or serious injury. 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 

Baird, R.W., D.J. McSweeney, D.L. Webster, A.M. Gorgone and A.D. Ligon. 2003. Studies of odontocete 

population structure in Hawaiian waters: results of a survey through the main Hawaiian Islands in May and 

June 2003. Report prepared under Contract No. AB133F-02-CN-0106 from the National Oceanic and 

Atmospheric Administration, Western Administrative Support Center, 7600 Sand Point Way N.E., Seattle, 

WA 98115 USA.

Barlow, J. 2003. Cetacean abundance in Hawaiian waters during summer/fall 2002. Admin. Rep. LJ-03-13. 

Southwest Fisheries Science Center, National Marine Fisheries Service, 8604 La Jolla Shores Drive, La 

Jolla, CA 92037. 

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. 

231
Forney, K.A. 2004. Estimates of cetacean mortality and injury in two U.S. Pacific longline fisheries, 1994-2002. 

Admin. Rep. LJ-04-07. Southwest Fisheries Science Center, National Marine Fisheries Service, 8604 La 

Jolla Shores Drive, La Jolla, CA 92037. 17 pp. 

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-00-14C. Southwest Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La 

Jolla, CA 92038. 26 pp. 

Mobley, J. R. , L. Mazzuca, A. S. Craig, M. W. Newcomer, and S. S. Spitz. 2001. Killer whales (Orcinus orca) 

sighted West of Ni'ihau, Hawai'i. Pacific Science 55:301_303. 

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. 

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-OPR12. 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. 

232
Revised 03/15/2005

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 also present

around the Northwestern Hawaiian 

Islands (Shallenberger 1981; Barlow

2003). During a 2002 shipboard survey 

of waters within the U.S. Exclusive 

Economic Zone (EEZ) of the Hawaiian 

Islands, 25 sightings of short-finned pilot 

whales were made (Figure 1; Barlow

2003). Fourteen strandings of shortfinned pilot whales have been

documented from the main Hawaiian

Islands, including five mass strandings

(Tomich 1986; Nitta 1991; Maldini

2005). Stock structure of short-finned 

pilot whales has not been adequately 

studied in the North Pacific, except in

Japanese waters, where 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

morphologically to the Japanese "southern form." 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). Additional

photo-identification work around the Hawaiian Islands is being done to examine whale movements between islands

(R.W. Baird, pers. comm.). 

W180 W175 W170 W165 W160 W155 W150

N10

N15

N20

N25

N30

N35

Figure 1. Short-finned pilot whale sighting locations during the 2002 

shipboard survey of U.S. EEZ waters surrounding the Hawaiian 

Islands (Barlow 2003; see Appendix 2 for details on timing and

location of survey effort). Outer line represents approximate boundary 

of survey area and U.S. EEZ. 

Genetic analyses of tissue samples collected near the main Hawaiian Islands indicate that Hawaiian shortfinned pilot whales are reproductively isolated from short-finned pilot whales found in the eastern Pacific Ocean (S. 

Chivers, NMFS/SWFSC, unpublished data); however, the offshore range of this Hawaiian population is unknown.

Fishery interactions with short-finned pilot whales demonstrate that this species also occurs in U.S. EEZ waters of

Palmyra Island (Figure 2), but it is not known whether these animals are part of the Hawaiian stock or whether they

represent a separate stock of short-finned pilot whales. Based on patterns of movement and population structure

observed in other island-associated cetaceans (Norris and Dohl 1980; Norris et al.1994; Baird et al. 2001, 2003; S. 

Chivers, pers. comm.), it is possible that the animals around Palmyra Island are a separate stock. Efforts are

currently underway to obtain additional samples of short-finned pilot whales for further studies of population

structure in the North Pacific Ocean. For the Marine Mammal Protection Act (MMPA) stock assessment reports, 

short-finned pilot whales within the Pacific U.S. EEZ are divided into two discrete, non-contiguous areas: 1) 

Hawaiian waters (this report), and 2) waters off California, Oregon and Washington. Information on short-finned 

pilot whales around Palmyra Island will provisionally be included with this stock assessment report, recognizing that

separate stock status may be warranted for these animals in the future. Estimates of abundance, potential biological

removals, and status determinations will be presented separately for U.S. waters of the Hawaiian Islands and 

Palmyra Island. 

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 

233
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 calculated from the combined survey data (Mobley et al. 2000). This study 

underestimated the total number of short-finned pilot whales within the U.S. EEZ off Hawaii, because areas around 

the Northwestern Hawaiian Islands (NWHI) and beyond 25 nautical miles from the main islands were not surveyed. 

Furthermore, the data on which this estimate was based are now over 5 years old. A 2002 shipboard line-transect 

survey of the entire Hawaiian Islands EEZ resulted in an abundance estimate of 8,846 (CV=0.49) short-finned pilot 

whales (Barlow 2003). This is currently the best available abundance estimate for short-finned pilot whales within 

the Hawaiian Islands EEZ. 

No abundance estimates are currently available for short-finned pilot whales in U.S. EEZ waters of 

Palmyra Island; however, density estimates for short-finned pilot whales in other Pacific regions can provide a range 

of likely abundance estimates in this unsurveyed region. Published estimates of short-finned pilot whale density 

(animals per km2) in the Pacific are: 0.0036 (CV=0.49) for the U.S. EEZ of the Hawaiian Islands (Barlow 2003); 

0.0237 (CV=0.32) for nearshore waters surrounding the main Hawaiian Islands (Mobley et al. 2000), 0.0084 

(CV=0.14) and 0.0040 (CV=0.23) for the eastern tropical Pacific Ocean (Wade and Gerrodette 1993; Ferguson and 

Barlow 2003), and 0.0025 (CV=0.29) for the eastern tropical Pacific Ocean west of 120°W and north of 5°N 

(Ferguson and Barlow 2003). Applying the lowest and highest of these density estimates to U.S. EEZ waters 

surrounding Palmyra Island (area size = 347,216 km2) yields a range of plausible abundance estimates of 877 - 

8,229 short-finned pilot whales.

 

Minimum Population Estimate

 The log-normal 20th percentile of the 2002 abundance estimate for the Hawaiian Islands EEZ (Barlow 

2004) is 5,986 short-finned pilot whales. No minimum population estimate is currently available for waters 

surrounding Palmyra Island, but the short-finned pilot whale density estimates from other Pacific regions (Barlow 

2003, Mobley et al. 2000, Wade and Gerrodette 1993, Ferguson and Barlow 2003; see above) can provide a range of 

likely values. The lognormal 20th percentiles of plausible abundance estimates for the Palmyra Island EEZ, based on 

the densities observed elsewhere, range from 690 - 6,327 short-finned pilot whales. 

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 the Hawaiian short-finned pilot whale stock is calculated 

as the minimum population size ( 5,986) 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 no known fishery mortality and serious 

injury within the U.S. EEZ of the Hawaiian Islands; Wade and Angliss 1997), resulting in a PBR of 60 short-finned 

pilot whales per year. No separate PBR can presently be calculated for Palmyra Island waters, but based on the 

range of plausible minimum abundance estimates (690 - 6,327), a recovery factor of 0.40 (for a species of unknown 

status with a fishery mortality and serious injury rate CV >0.80 within the Palmyra Islands EEZ; Wade and Angliss 

1997), and the default growth rate (1⁄2 of 4%), the PBR would likely fall between 5.5 and 51 short-finned pilot 

whales per year. 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Fishery Information 

Information on fishery-related mortality of cetaceans in Hawaiian waters is limited, but the gear types used 

in Hawaiian fisheries are responsible for marine mammal mortality and serious injury in other fisheries throughout 

U.S. waters. Gillnets 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). Between 1994 and 2002, five shortfinned pilot whales were observed hooked in the Hawaii-based longline fishery with approximately 4-25% of all 

effort observed (Table 1; Forney 2004). During the 905 observed trips with 11,014 sets, the average interaction rate 

of short-finned pilot whales was one animal per 181 fishing trips, or one animal per 2,203 sets. Two of the animals 

234
caught were dead upon gear retrieval, and two additional animals were considered seriously injured (Forney 2004),

based on an evaluation of the observer’s description of the interaction and following established guidelines for

assessing serious injury in marine mammals (Angliss and DeMaster 1998). Average 5-yr estimates of annual

mortality and serious injury for 1998-2002 are 4.2 (CV = 0.78) short-finned pilot whales outside of the U.S. EEZs, 

and 0.8 (CV = 1.00) within the U.S. EEZ 

of Palmyra Island (Table 1). No shortfinned pilot whales were observed taken

within the Hawaiian Islands EEZ during

1998-2002. Six additional unidentified

cetaceans, which may have been shortfinned pilot whales, were also taken in

this fishery. Two of these unidentified 

cetaceans were within the EEZ of 

Palmyra Island, and four were in 

international waters (Figure 2, Forney

2004). Since 2001, the Hawaii-based 

longline fishery has undergone a series of

regulatory changes, primarily to protect

sea turtles (NMFS 2001). Potential 

impacts of these regulatory changes on 

the rate of short-finned pilot whale

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 short-finned pilot whales are 

involved. 

Figure 2. Locations of observed short-finned pilot whale takes 

(filled diamonds) and possible takes of this species (open diamonds) 

in the Hawaii-based longline fishery, 1994-2002. Solid lines 

represent the U.S. EEZ. Set locations in this fishery are summarized 

in Appendix 1. 

Table 1. Summary of available information on incidental mortality and serious injury of short-finned pilot whales 

(Hawaiian stock) in commercial fisheries, within and outside of the U.S. EEZs (Forney 2004). Mean annual takes

are based on 1998-2002 data unless otherwise indicated. 

Observed and estimated mortality and serious injury of short-finned pilot whales, by EEZ region

Outside of U.S. EEZs Hawaiian Islands EEZ Palmyra Island EEZ

Fishery 

Name Year Data Type

Percent 

Observer 

Coverage

Obs.

Estimated 

(CV)

Mean 

Annual 

Takes 

(CV)

Obs.

Estimated 

(CV)

Mean 

Annual 

Takes 

(CV)

Obs. Estimated 

(CV)

Mean 

Annual 

Takes 

(CV)

Hawaiibased 

longline 

fishery 

1998 

1999 

2000 

2001

2002

observer

data

4.6% 

3.5% 

11.8% 

22.7%

24.9%

0 

0 

2 

1

0

0 (-) 

0 (-) 

17 (0.71)

4 (1.00)

0 (-)

4.2 (0.78)

0 

0 

0 

0

0

0 (-) 

0 (-) 

0 (-) 

0 (-)

0 (-)

0 (-)

0 

0 

0 

1

0

0 (-) 

0 (-) 

0 (-) 

4 (1.00)

0 (-)

0.8 

(1.00)

Minimum total annual takes within U.S. EEZ waters 0.8 (1.00)

 

 

235
Ship Strikes 

Short-finned pilot whales with propeller scars have been seen around the Hawaiian islands (R.W. Baird, 

pers. comm.). It is unknown if any of these injuries were serious or resulted in mortalities. 

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. The Hawaiian stock of short-finned pilot whales is not considered strategic under the 1994 

amendments to the MMPA, because the estimated rate of mortality and serious injury within the Hawaiian Islands 

EEZ is zero. However, there is no systematic monitoring of gillnet fisheries that may take this species, and the 

potential effect of mortality in the Hawaii-based fishery in international waters is not known. Although no estimates 

of abundance or PBR are currently available for short-finned pilot whales around Palmyra Island, the average rate of 

mortality and serious injury within the Palmyra Island EEZ (0.8 animals per year) falls below the range of likely 

PBRs (5.5 - 51) for this region. Insufficient information is available to determine whether the total fishery mortality 

and serious injury for short-finned pilot whales 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.

Baird, R. W., Ligon, A. D., Hooker, S. K., and A. M. Gorgone. 2001. Subsurface and nighttime behaviour of 

pantropical spotted dolphins in Hawai’i. Can. J. Zool. 79:988-996. 

Baird, R.W., McSweeney D.J., Webster, D.L., Gorgone, A.M., and Ligon, A.D. 2003. Studies of odontocete 

population structure in Hawaiian waters: Results of a survey through the main Hawaiian Islands in May 

and June 2003. Report prepared under contract #AB133F-02-CN-0106 to the Southwest Fisheries Science 

Center, National Marine Fisheries Service, 8604 La Jolla Shores Drive, La Jolla, CA 92037, USA. 10p. 

Barlow, J. 2003. Cetacean abundance in Hawaiian waters during summer/fall 2002. Admin. Rep. LJ-03-13. 

Southwest Fisheries Science Center, National Marine Fisheries Service, 8604 La Jolla Shores Drive, La 

Jolla, CA 92037. 

Chivers, S. NMFS, Southwest Fisheries Science Center, 8604 La Jolla Shores Drive, La Jolla, CA 92037. 

Ferguson, M. C. and J. Barlow. 2003. Addendum: Spatial distribution and density of cetaceans in the eastern 

tropical Pacific Ocean based on summer/fall research vessel surveys in 1986-96. Administrative Report LJ01-04 (addendum), Southwest Fisheries Science Center, National Marine Fisheries Service, 8604 La Jolla 

Shores Drive, La Jolla, CA 92037. 

Forney, K.A. 2004. Estimates of cetacean mortality and injury in two U.S. Pacific longline fisheries, 1994_2002. 

Admin. Rep. LJ-04-07. Southwest Fisheries Science Center, National Marine Fisheries Service, 8604 La 

Jolla Shores Drive, La Jolla, CA 92037. 17 pp. 

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. 

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. 

Maldini, D., L. Mazzuca, and S. Atkinson. 2005. Odontocete stranding patterns in the Main Hawaiian Islands 

(1937-2002): How do they compare with live animal surveys? Pacific Science 59(1):55-67. 

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. 

236
NMFS, Southwest Fisheries Science Center, 8604 La Jolla Shores Drive, La Jolla, CA 92037. 

NMFS 2001. Western Pacific Pelagic Fisheries Biological Opinion. Available from Pacific Islands Region, 1602 

Kapiolani Blvd, Suite 1110, Honolulu, HI 96814 (http://swr.nmfs.noaa.gov/pir). 

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. 

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. 

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.

237
Revised 03/15/2005

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. Three 

sightings were made during a 2002 

shipboard survey of waters within the 

U.S. Exclusive Economic Zone (EEZ) of

the Hawaiian Islands (Figure 1; Barlow 

2003). While nothing is known about

stock structure, some genetic samples 

have been collected recently from

around the main Hawaiian islands, and 

there have been re-sightings of

individuals from the island of Hawaii

(R.W. Baird, pers. comm.). For the

Marine Mammal Protection Act

(MMPA) stock assessment reports, three

Mesoplodon stocks are defined within the Pacific U.S. EEZ : 1) M. densirostris in Hawaiian waters (this report), 2)

M. stejnegeri in Alaskan waters, and 3) all Mesoplodon species off California, Oregon and Washington. 

W180 W175 W170 W165 W160 W155 W150

N10

N15

N20

N25

N30

N35

Figure 1. Sighting locations of Mesoplodon densirostris (filled 

circles), Indopacetus pacificus (triangle), and unidentified 

Mesoplodon beaked whales (cross) during the 2002 shipboard 

cetacean survey of U.S. EEZ waters surrounding the Hawaiian 

Islands (Barlow 2003; see Appendix 2 for details on timing and

location of survey effort). Outer line indicates approximate boundary

of survey area and U.S. EEZ.

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 calculated from the combined survey data (Mobley et al. 2000). This study 

underestimated the total number of Blainville’s beaked whales within the U.S. EEZ off Hawaii, because areas 

around the Northwestern 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. The data on which this estimate was based are now over 5 years old. A 

2002 shipboard line-transect survey of the entire Hawaiian Islands EEZ resulted in an abundance estimate of 2,138 

(CV=0.77) Blainville’s beaked whales (Barlow 2003), including a correction factor for missed diving animals. This 

is currently the best available abundance estimate for this stock. 

Minimum Population Estimate

The log-normal 20th percentile of the 2002 abundance estimate is 1,204 Blainville’s beaked whales. . 

 

Current Population Trend

No data are available on current population trend. 

238
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 

(1,204 ) 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 Hawaiian Islands EEZ fishery mortality and serious injury rate CV>0.80; 

Wade and Angliss 1997), resulting in a PBR of 9.6 Blainville’s beaked whales per year. 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Fishery Information

Information on fishery-related

mortality of cetaceans in Hawaiian

waters is limited, but the gear types used 

in Hawaiian fisheries are responsible for 

marine mammal mortality and serious

injury in other fisheries throughout U.S. 

waters. Gillnets 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 are

reported for all pelagic fisheries (Nitta 

and Henderson 1993). Between 1994 and 

2002, one Blainville’s beaked whale was

observed hooked and killed in the

Hawaii-based longline fishery, with

approximately 4-25% of all effort

observed (Table 1; Forney 2004). Three

additional unidentified cetaceans, which

may have been Blainville’s beaked

whales, were also taken in this fishery 

(Figure 2, Forney 2004). During the 905 

observed trips with 11,014 sets, the

average interaction rate of Blainville’s 

beaked whales was one animal per 905 

fishing trips, or one animal per 11,014

sets. Average 5-yr estimates of annual

mortality and serious injury for 1998-

2002 are zero Blainville’s beaked whales outside of the U.S. EEZs, and 0.8 (CV = 1.00) within the Hawaiian Islands 

EEZ (Table 1). Since 2001, the Hawaii-based longline fishery has undergone a series of regulatory changes, 

primarily to protect sea turtles (NMFS 2001). Potential impacts of these regulatory changes on the rate of

Blainville’s beaked whale interactions are unknown. 

Figure 2. Location of the single Blainville’s beaked whale take 

(filled diamond) and possible takes of this species (open diamonds) 

in the Hawaii-based longline fishery, 1994-2002. Solid lines 

represent the U.S. EEZ. 

Other Mortality

In recent years, there has been increasing concern that loud underwater sounds, such as active sonar and 

seismic operations, may be harmful to beaked whales (Malakoff 2002). The use of active sonar from military vessels 

has been implicated in mass strandings of beaked whales in the Mediterranean Sea during 1996 (Frantzis 1998), the 

Bahamas during 2000 (U.S. Dept. of Commerce and Secretary of the Navy 2001), and the Canary Islands 2002

(Martel 2002). Similar military active sonar operations occur around the Hawaiian islands. No estimates of

potential mortality or serious injury are available for U.S. waters. 

 

239
Table 1. Summary of available information on incidental mortality and serious injury of Blainville’s beaked whales 

(Hawaiian stock) in commercial fisheries, within and outside of the Hawaiian Islands EEZ (Forney 2004). Mean 

annual takes are based on 1998-2002 data unless otherwise indicated. 

Mortality and Serious In ry ju

outside of U.S. EEZ

Mortality and Serious Injury 

within Hawaiian Islands EEZ

Fishery Name Year Data Type

Percent 

Observer 

Coverage

Observed Estimated 

(CV)

Mean Annual 

Takes 

(CV)

Observed Estimated 

(CV)

Mean Annual 

Takes 

(CV)

Hawaii-based 

longline fishery 

1998 

1999 

2000 

2001

2002

1998-2002 

observer 

data

4.6% 

3.5% 

11.8% 

22.7%

24.9%

0 

0 

0 

0

0

0 (-) 

0 (-) 

0 (-) 

0 (-)

0 (-)

0 (-)

0 

0 

0 

0

1

0 (-) 

0 (-) 

0 (-) 

0 (-) 

4 (1.00)

0.8 (1.00)

Minimum total annual takes within U.S. EEZ waters 0.8 (1.00)

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. The Hawaiian stock of Blainville’s beaked 

whales is not considered strategic under the 1994 amendments to the MMPA because the estimated rate of fisheries 

related mortality or serious injury within the Hawaiian Islands EEZ (0.8 animals per year) is less than the PBR (9.6). 

However, the effect of potential interactions of unidentified beaked whales (which may have been Blainville’s 

beaked whales) with the Hawaii-based 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 (Richardson et al. 

1995), particularly for deep-diving whales like Blainville’s beaked whales that feed in the oceans’ “sound channel”. 

REFERENCES

Balcomb, K. C., III. 1987. The Whales of Hawaii. Marine Mammal Fund, 99 pp. 

Barlow, J. 2003. Cetacean abundance in Hawaiian waters during summer/fall 2002. Admin. Rep. LJ-03-13. 

Southwest Fisheries Science Center, National Marine Fisheries Service, 8604 La Jolla Shores Drive, La 

Jolla, CA 92037. 

Forney, K.A. 2004. Estimates of cetacean mortality and injury in two U.S. Pacific longline fisheries, 1994-2002. 

Admin. Rep. LJ-04-07. Southwest Fisheries Science Center, National Marine Fisheries Service, 8604 La 

Jolla Shores Drive, La Jolla, CA 92038. 17 pp. 

Frantzis, A. 1998. Does acoustic testing strand whales? Nature 392(5):29. 

Galbreath, E. C. 1963. Three beaked whales stranded on the Midway Islands, central Pacific Ocean. J. Mamm. 

44:422-423. 

Malakoff, D. 2002. Suit ties whale deaths to research cruise. Science 298:722-723. 

Martel, V. M. 2002. Summary of the report on the atypical mass stranding of beaked whales in the Canary Islands 

in September 2002 during naval exercises. Society for the Study of the Cetaceans in the Canary 

Archipelago (SECAC). Unpublished report. 11p. 

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. 

NMFS 2001. Western Pacific Pelagic Fisheries Biological Opinion. Available from Pacific Islands Region, 1602 

Kapiolani Blvd, Suite 1110, Honolulu, HI 96814 (http://swr.nmfs.noaa.gov/pir). 

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. 

240
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. 

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. 

Shallenberger, E. W. 1981. The status of Hawaiian cetaceans. Final report to U.S. Marine Mammal Commission. 

MMC-77/23, 79pp. 

U.S. Department of Commerce and Secretary of the Navy. 2001. Joint Interim Report, Bahamas Marine Mammal 

Stranding Event of 15_16 March 2000. Available from NOAA, NMFS, Office of Protected Resources, 

Silver Spring, MD. 

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-OPR12. 93 pp. 

241
Revised 03/15/2005 

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, five strandings have

been reported from Midway Islands,

Pearl and Hermes Reef, Oahu, and 

Hawaii Islands (Shallenberger 1981;

Galbreath 1963; Richards 1952; Nitta 

1991; Maldini 2005). Sightings have

been reported off Lanai and Maui

(Shallenberger 1981) and Hawaii, 

Ni’ihau, and Kauai (Mobley 2000, Baird

et al. 2004). Four sightings were made 

during a 2002 shipboard survey of

waters within the U.S. Exclusive 

Economic Zone (EEZ) of the Hawaiian 

islands (Figure 1; Barlow 2003). While

nothing is known about stock structure, 

some genetic samples have been

collected recently from around the island 

of Hawaii, and there have been resightings of individuals from the island

of Hawaii (R.W. Baird, pers. comm.). 

For the Marine Mammal Protection Act 

(MMPA) stock assessment reports, 

Cuvier's beaked whales within the

Pacific U.S. EEZ are divided into three discrete, non-contiguous areas: 1) Hawaiian waters (this report), 2) Alaskan 

waters, and 3) waters off California, Oregon and Washington. 

W180 W175 W170 W165 W160 W155 W150

N10

N15

N20

N25

N30

N35

Figure 1. Cuvier’s beaked whale sighting locations during the 2002 

shipboard survey of U.S. EEZ waters surrounding the Hawaiian 

Islands (Barlow 2003; see Appendix 2 for details on timing and

location of survey effort). Outer line represents approximate

boundary of survey area and U.S. EEZ. 

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 calculated from the combined survey data (Mobley et al. 2000). This study

underestimated the total number of Cuvier’s beaked whales within the U.S. EEZ off Hawaii, because areas around

the Northwestern 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. The data on which this estimate was based are now over 5 years old. A 2002 shipboard

line-transect survey of the entire Hawaiian Islands EEZ resulted in an abundance estimate of 12,728 (CV=0.83) 

Cuvier’s beaked whales (Barlow 2003), including a correction factor for missed diving animals. This is currently

the best available abundance estimate for this stock. 

Minimum Population Estimate

The log-normal 20th percentile of the 2002 abundance estimate is 6,919 Cuvier’s beaked whales. 

 

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. 

242
POTENTIAL BIOLOGICAL REMOVAL

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

(6,919) 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 within the Hawaiian Islands EEZ; Wade and 

Angliss 1997), resulting in a PBR of 69 Cuvier’s beaked whales per year. 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY 

Fishery Information 

 Information on fishery-related mortality of cetaceans in Hawaiian waters is limited, but the gear types used 

in Hawaiian fisheries are responsible for marine mammal mortality and serious injury in other fisheries throughout 

U.S. waters. Gillnets 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 are reported for all pelagic fisheries (Nitta and Henderson 1993), but no takes of 

Cuvier's beaked whales have been documented. None were observed hooked or entangled in the Hawaii-based 

longline fishery between 1994 and 2002, with approximately 4-25% of all effort observed (Forney 2004). However, 

three unidentified cetaceans, which may have been Cuvier’s beaked whales, were taken in this fishery (Figure 2, 

Forney 2004). Since 2001, the Hawaii-based longline fishery has undergone a series of regulatory changes, 

primarily to protect sea turtles (NMFS 2001). Potential impacts of these regulatory changes on the rate of Cuvier’s 

beaked whale interactions are unknown. 

Other Mortality

 In recent years, there has been increasing concern that loud underwater sounds, such as active sonar and 

seismic operations, may be harmful to beaked whales (Malakoff 2002). The use of active sonar from military vessels 

has been implicated in mass strandings of beaked whales in the Mediterranean Sea during 1996 (Frantzis 1998), the 

Bahamas during 2000 (U.S. Dept. of Commerce and Secretary of the Navy 2001), and the Canary Islands 2002 

(Martel 2002). Similar military active sonar operations occur around the Hawaiian islands. No estimates of 

potential mortality or serious injury are available for U.S. waters. 

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. The Hawaiian stock of Cuvier’s beaked 

whales is not considered strategic under the 1994 amendments to the MMPA because there has been no reported 

fisheries related mortality within the Hawaiian Islands EEZ. However, the effect of potential interactions of 

unidentified beaked whales (which may have been Cuvier’s beaked whales) with the Hawaii-based 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 (Richardson et al. 1995), particularly for deep-diving whales like Cuvier’s beaked whales 

that feed in the oceans’ “sound channel”. 

REFERENCES 

Baird, R.W., D.J. McSweeney, A.D. Ligon and D.L. Webster. 2004. Tagging feasibility and diving of Cuvier's 

beaked whales (Ziphius cavirostris) and Blainville's beaked whales (Mesoplodon densirostris) in Hawai'i.

Report prepared under Order No. AB133F-03-SE-0986 to the Hawai'i Wildlife Fund, Volcano, HI, from 

the Southwest Fisheries Science Center, National Marine Fisheries Service, La Jolla, CA, 92037 USA. 

Barlow, J. 2003. Cetacean abundance in Hawaiian waters during summer/fall 2002. Admin. Rep. LJ-03-13. 

Southwest Fisheries Science Center, National Marine Fisheries Service, 8604 La Jolla Shores Drive, La 

Jolla, CA 92037. 

Forney, K.A. 2004. Estimates of cetacean mortality and injury in two U.S. Pacific longline fisheries, 1994-2002. 

Admin. Rep. LJ-04-07. Southwest Fisheries Science Center, National Marine Fisheries Service, 8604 La 

Jolla Shores Drive, La Jolla, CA 92038. 17 pp. 

Frantzis, A. 1998. Does acoustic testing strand whales? Nature 392(5):29. 

Galbreath, E. C. 1963. Three beaked whales stranded on the Midway Islands, central Pacific Ocean. J. Mamm.

44:422-423. 

243
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. 

Malakoff, D. 2002. Suit ties whale deaths to research cruise. Science 298:722-723. 

Maldini, D., L. Mazzuca, and S. Atkinson. 2005. Odontocete stranding patterns in the Main Hawaiian Islands 

(1937-2002): How do they compare with live animal surveys? Pacific Science 59(1):55-67. 

Martel, V. M. 2002. Summary of the report on the atypical mass stranding of beaked whales in the Canary Islands 

in September 2002 during naval exercises. Society for the Study of the Cetaceans in the Canary 

Archipelago (SECAC). Unpublished report. 11p. 

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. 

NMFS 2001. Western Pacific Pelagic Fisheries Biological Opinion. Available from Pacific Islands Region, 1602 

Kapiolani Blvd, Suite 1110, Honolulu, HI 96814 (http://swr.nmfs.noaa.gov/pir). 

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. 

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. 

Shallenberger, E. W. 1981. The status of Hawaiian cetaceans. Final report to U.S. Marine Mammal Commission. 

MMC-77/23, 79pp. 

U.S. Department of Commerce and Secretary of the Navy. 2001. Joint Interim Report, Bahamas Marine Mammal 

Stranding Event of 15_16 March 2000. Available from NOAA, NMFS, Office of Protected Resources, 

Silver Spring, MD. 

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-OPR12. 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. 

244
Revised 03/15/2005 

LONGMAN’S BEAKED WHALE (Indopacetus pacificus): 

Hawaiian Stock 

STOCK DEFINITION AND GEOGRAPHIC RANGE

Longman’s beaked whale is 

considered one of the rarest and least

known cetacean species (Jefferson et al. 

1993; Rice 1998; Dalebout et al 2003). 

Until recently, it was known only from 

two skulls found in Australia and 

Somalia (Longman 1926; Azzaroli 

1968). Recent genetic studies (Dalebout

et al. 2003) have revealed that sightings 

of ‘tropical bottlenose whales’ 

(Hyperoodon sp.; Pitman et al. 1999) in 

the Indopacific region were in fact 

Longman’s beaked whales, providing 

the first description of the external 

appearance of this species. Although 

originally described as Mesoplodon 

pacificus (Longman 1926), it has been 

proposed that this species is sufficiently 

unique to be placed within its own 

genus, Indopacetus (Moore 1968;

Dalebout et al. 2003). The distribution 

of Longman’s beaked whale, as

determined from stranded specimens and

sighting records of ‘tropical bottlenose

whales’, includes tropical waters from

the eastern Pacific westward through the

Indian Ocean to the eastern coast of 

Africa. No strandings of Longman’s beaked whales have been documented in Hawaiian waters, although numerous

strandings of unidentified beaked whales have been reported (Nitta 1991; Maldini 2005). One sighting of

Longman’s beaked whale was made during a 2002 survey of waters within the U.S. Exclusive Economic Zone 

(EEZ) of the Hawaiian Islands (Figure 1; Barlow 2003). For the Marine Mammal Protection Act (MMPA) stock

assessment reports, there is one Pacific stock of Longman’s beaked whales, found within waters of the Hawaiian 

Islands EEZ. 

W180 W175 W170 W165 W160 W155 W150

N10

N15

N20

N25

N30

N35

Figure 1. Sighting locations of Indopacetus pacificus (triangle), 

Mesoplodon densirostris (circle) and unidentified Mesoplodon 

beaked whales (crosses) during the 2002 shipboard cetacean survey 

of U.S. waters surrounding the Hawaiian Islands (Barlow 2003; see 

Appendix 2 for details on timing and location of survey effort).

Outer line indicates approximate boundary of survey area and U.S.

EEZ.

POPULATION SIZE

A 2002 shipboard line-transect survey of the entire Hawaiian Islands EEZ resulted in an abundance

estimate of 766 (CV=1.05) Longman’s beaked whales (Barlow 2003). This is currently the best available

abundance estimate for this stock. 

Minimum Population Estimate

The log-normal 20th percentile of the 2002 abundance estimate is 371 Longman’s beaked whales. 

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 Longman’s beaked whales. 

245
POTENTIAL BIOLOGICAL REMOVAL

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

(371) times one half the default maximum net growth rate for cetaceans (1⁄2 of 4%) times a recovery factor of 0.50 

(for a stock of unknown status with no known fishery mortality or serious injury within the Hawaiian Islands EEZ; 

Wade and Angliss 1997), resulting in a PBR of 3.7 Longman’s beaked whales per year. 

HUMAN CAUSED MORTALITY AND SERIOUS INJURY

Fishery Information

Information on fishery-related

mortality and serious injury of cetaceans

in Hawaiian waters is limited, but the 

gear types used in Hawaiian fisheries are 

responsible for marine mammal mortality

and serious injury in other fisheries

throughout U.S. waters. Gillnets 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

none of these interactions are known to

have involved Longman’s beaked

whales. None were observed hooked or

entangled in the Hawaii-based longline 

fishery between 1994 and 2002, with

approximately 4-25% of all effort

(measured as the number of sets made) 

observed by on-board observers (Forney

2004). However, there were two

interactions with unidentified whales that

may have been Longman’s beaked

whales (Figure 2). Since 2001, the

Hawaii-based longline fishery has

undergone a series of regulatory changes, 

primarily to protect sea turtles (NMFS

2001). Potential impacts of these regulatory changes on the rate of Longman’s beaked whale interactions are

unknown. 

Figure 2. Locations of observed takes of possible Longman’s

beaked whales (open diamonds) in the Hawaii-based longline fishery

1994-2002. The solid lines represent the U.S. Exclusive Economic

Zone (EEZ). 

Other Mortality

In recent years, there has been increasing concern that loud underwater sounds, such as active sonar and 

seismic operations, may be harmful to beaked whales (Malakoff 2002). The use of active sonar from military vessels 

has been implicated in mass strandings of beaked whales in the Mediterranean Sea during 1996 (Frantzis 1998), the 

Bahamas during 2000 (U.S. Dept. of Commerce and Secretary of the Navy 2001), and the Canary Islands 2002

(Martel, 2002). Similar military active sonar operations occur around the Hawaiian islands. No estimates of

potential mortality or serious injury are available for U.S. waters.

STATUS OF STOCK

The status of Longman'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. The Hawaiian stock of Longman’s beaked

whales is not considered strategic under the 1994 amendments to the MMPA, because there has been no reported

fisheries related mortality or serious injury within the Hawaiian Islands EEZ. However, the effect of potential 

interactions of unidentified beaked whales (which may have been Longman’s beaked whales) with the Hawaii-based

246
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 Longman’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 (Richardson et al. 1995), particularly for deep-diving whales like 

Longman’s beaked whales that feed in the oceans’ “sound channel”. 

REFERENCES

Azzaroli, M. L. 1968. Second specimen of Mesoplodon pacificus, the rarest living beaked whale. Monitore 

Zoologico Italiano (N.S.) 2:67-79. 

Barlow, J. 2003. Cetacean abundance in Hawaiian waters during summer/fall 2002. Admin. Rep. LJ-03-13. 

Southwest Fisheries Science Center, National Marine Fisheries Service, 8604 La Jolla Shores Drive, La 

Jolla, CA 92038. 

Dalebout, M. L., G. J. B. Ross, C. S. Baker, R. C. Anderson, P. B. Best, V. G. Cockcroft, H. L. Hinsz, V. Peddemors 

and R. L. Pitman. 2003. Appearance, distribution and genetic distinctiveness of Longman’s beaked whale, 

Indopacetus pacificus. Marine Mammal Science 19:421-461. 

Forney, K.A. 2004. Estimates of cetacean mortality and injury in two U.S. Pacific longline fisheries, 1994-2002. 

Admin. Rep. LJ-04-07. Southwest Fisheries Science Center, National Marine Fisheries Service, 8604 La 

Jolla Shores Drive, La Jolla, CA 92037. 17 pp. 

Frantzis, A. 1998. Does acoustic testing strand whales? Nature 392(5):29. 

Jefferson, T. A., S. Leatherwood, and M. A. Webber. 1993. FAO species identification guide: marine mammals of 

the world. United States Environment Programme; Food and Agriculture Organization of the United 

Nations (FAO), Rome. 320p. 

Longman, H.A. 1926. New records of Cetacea, with a list of Queensland species. Memoirs of the Queensland 

Museum 8:266-278. 

Malakoff, D. 2002. Suit ties whale deaths to research cruise. Science 298:722-723 

Maldini, D., L. Mazzuca, and S. Atkinson. 2005. Odontocete stranding patterns in the Main Hawaiian Islands 

(1937-2002): How do they compare with live animal surveys? Pacific Science 59(1):55-67. 

Martel, V. M. 2002. Summary of the report on the atypical mass stranding of beaked whales in the Canary Islands 

in September 2002 during naval exercises. Society for the Study of the Cetaceans in the Canary 

Archipelago (SECAC). Unpublished report. 11p. 

Moore J. C. 1968. Relationships among the living genera of beaked whales. Fieldiana Zoology 53:209-298. 

NMFS 2001. Western Pacific Pelagic Fisheries Biological Opinion. Available from Pacific Islands Region, 1602 

Kapiolani Blvd, Suite 1110, Honolulu, HI 96814 (http://swr.nmfs.noaa.gov/pir). 

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. 

Pitman, R. L., D. M. Palacios, P. L Brennan, K.C. III. Balcomb, and T. Miyashita. 1999. Sightings and possible 

identity of a bottlenose whale in the tropical Indo-Pacific: Indopacetus pacificus? Marine Mammal Science 

15:531-549. 

Rice, D. W. 1998. Marine Mammals of the world: systematics and distribution. Special Publication 4. The Society 

for Marine Mammalogy, Lawrence, KS, USA. 

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. 

U.S. Department of Commerce and Secretary of the Navy. 2001. Joint Interim Report, Bahamas Marine Mammal 

Stranding Event of 15_16 March 2000. Available from NOAA, NMFS, Office of Protected Resources, 

Silver Spring, MD. 

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-OPR12. 93 pp. 

247
Revised 03/15/2005 

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 2002, at least 22 strandings of

this species were reported in the

Hawaiian Islands (Tomich 1986; Nitta 

1991; Maldini 2005). A stranded calf 

was held for several days at Sea Life

Park (Pryor 1975:94). 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 (Mobley et al. 2000). 

Two sightings were made during a 2002 

shipboard survey of waters within the 

U.S. Exclusive Economic Zone (EEZ) of

the Hawaiian Islands (Figure 1; Barlow 

2003). Baird (2005) reported one

sighting off Ni’ihau and another off the

island off Hawaii (R.W. Baird, pers. 

comm.). 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. EEZ are divided into two discrete, non-contiguous areas: 1) Hawaiian waters (this report), 

and 2) waters off California, Oregon and Washington. 

W180 W175 W170 W165 W160 W155 W150

N10

N15

N20

N25

N30

N35

Figure 1. Sighting locations of pygmy sperm whales (filled circle) 

and unidentified Kogia (cross) during the 2002 shipboard cetacean 

survey of U.S. EEZ waters surrounding the Hawaiian Islands 

(Barlow 2003; see Appendix 2 for details on timing and location of

survey effort). Outer line indicates approximate boundary of survey

area and U.S. EEZ.

 

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. Two sightings of five pygmy or dwarf sperm whales were made; however, these sightings

were excluded during abundance analyses (Mobley et al. 2000), because they were made during poor observation

conditions. A 2002 shipboard line-transect survey of the entire Hawaiian Islands EEZ resulted in an abundance 

estimate of 7,251 (CV=0.77) pygmy sperm whales (Barlow 2003), including a correction factor for missed diving

animals. This is currently the best available abundance estimate for this stock. 

Minimum Population Estimate

 The log-normal 20th percentile of the 2002 abundance estimate is 4,082 pygmy sperm whales. 

 

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 

(4,082) times one half the default maximum net growth rate for cetaceans (1⁄2 of 4%) times a recovery factor of 0.50

248
(for a stock of unknown status with no known fishery mortality or serious injury within the Hawaiian Islands EEZ; 

Wade and Angliss 1997), resulting in a PBR of 41 pygmy sperm whales per year. 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Fishery Information

 Information on fishery-related mortality of cetaceans in Hawaiian waters is limited, but the gear types used 

in Hawaiian fisheries are responsible for marine mammal mortality and serious injury in other fisheries throughout 

U.S. waters. Gillnets 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 Hawaii-based longline fishery between 1994 and 

2002, with approximately 4-25% of all effort observed ( Forney 2004). 

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. The Hawaiian stock of pygmy sperm whales is 

not considered strategic under the 1994 amendments to the MMPA because there has been no reported fisheries 

related mortality or serious injury. Insufficient information is available to determine whether the total fishery 

mortality and serious injury for pygmy sperm 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 (Richardson et al. 1995), particularly for deep-diving whales like pygmy sperm whales that feed 

in the oceans’ “sound channel”. 

REFERENCES 

Baird, R.W. 2005. Sightings of dwarf (Kogia sima) and pygmy (K. breviceps) sperm whales from the main 

Hawaiian Islands. Pacific Science 59: in press.

Barlow, J. 2003. Cetacean abundance in Hawaiian waters during summer/fall 2002. Admin. Rep. LJ-03-13. 

Southwest Fisheries Science Center, National Marine Fisheries Service, 8604 La Jolla Shores Drive, La 

Jolla, CA 92037. 

Forney, K.A. 2004. Estimates of cetacean mortality and injury in two U.S. Pacific longline fisheries, 1994-2002. 

Admin. Rep. LJ-04-07. Southwest Fisheries Science Center, National Marine Fisheries Service, 8604 La 

Jolla Shores Drive, La Jolla, CA 92038. 17 pp. 

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. 

Maldini, D., L. Mazzuca, and S. Atkinson. 2005. Odontocete stranding patterns in the Main Hawaiian Islands 

(1937-2002): How do they compare with live animal surveys? Pacific Science 59(1):55-67. 

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. 

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. 

Shallenberger, E.W. 1981. The status of Hawaiian cetaceans. Final report to U.S. Marine Mammal Commission. 

MMC-77/23, 79pp. 

Tomich, P. Q. 1986. Mammals in Hawaii: A Synopsis and Notational Bibliography. Bishop Museum Press, Hawaii, 

375 pp. 

249
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-OPR12. 93 pp. 

250
Revised 03/15/2005

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). Rice (1998) recently argued that 

the species name simus, was incorrect

and should be replaced by sima to reflect

rules of Latin usage. At least four

strandings of dwarf sperm whales have

been documented in Hawaii (Tomich

1986; Nitta 1991; Maldini 2005). 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 (Mobley et al. 2000). 

Five sightings of dwarf sperm whale 

were made during a 2002 shipboard

survey of waters within the U.S. 

Exclusive Economic Zone (EEZ) of the

Hawaiian Islands (Figure 1; Barlow

2003). Baird (2005) reports that dwarf

sperm whales are the sixth most 

commonly sighted odontocete around

the main Hawaiian islands. This species’ 

small size, tendency to avoid vessels, 

deep-diving habits, combined with the

high proportion of Kogia sightings that

are not identified to species, may result in negatively biased relative abundances in this region (R.W. Baird, pers.

comm.). For the Marine Mammal Protection Act (MMPA) stock assessment reports, dwarf sperm whales within the 

Pacific U.S. EEZ are divided into two discrete, non-contiguous areas: 1) Hawaiian waters (this report), and 2) waters 

off California, Oregon and Washington. 

W180 W175 W170 W165 W160 W155 W150

N10

N15

N20

N25

N30

N35

Figure 1. Sighting locations of dwarf sperm whales (filled circle) 

and unidentified Kogia (cross) during the 2002 shipboard cetacean 

survey of U.S. waters surrounding the Hawaiian Islands (Barlow 

2003; see Appendix 2 for details on timing and location of survey

effort). Outer line indicates approximate boundary of survey area

and U.S. EEZ.

 

POPULATION SIZE

Wade and Gerrodette (1993) provided an estimate for the eastern tropical Pacific, but it is not known 

whether these animals are part of the same population that occurs in the central 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. Two 

sightings of five pygmy or dwarf sperm whales were made; however these sightings were excluded during

abundance analyses (Mobley et al. 2000), because they were made during poor observation conditions. Therefore,

no abundance was estimated from these surveys for dwarf sperm whales within Hawaiian waters. A 2002 shipboard

line-transect survey of the entire Hawaiian Islands EEZ resulted in an abundance estimate of 19,172 (CV=0.66) 

dwarf sperm whales (Barlow 2003), including a correction factor for missed diving animals. This is currently the 

best available abundance estimate for this stock. 

Minimum Population Estimate

 The log-normal 20th percentile of the 2002 abundance estimate is 11,555 dwarf sperm whales. 

 

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. 

251
POTENTIAL BIOLOGICAL REMOVAL

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

(11,555) times one half the default maximum net growth rate for cetaceans (1⁄2 of 4%) times a recovery factor of 0.50 

(for a stock of unknown status with no known fishery mortality or serious injury within the Hawaiian Islands EEZ; 

Wade and Angliss 1997), resulting in a PBR of 116 dwarf sperm whales per year. 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Fishery Information

 Information on fishery-related mortality of cetaceans in Hawaiian waters is limited, but the gear types 

used in Hawaiian fisheries are responsible for marine mammal mortality and serious injury in other fisheries 

throughout U.S. waters. Gillnets 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 Hawaii-based longline fishery 

between 1994 and 2002, with approximately 4-25% of all effort observed ( Forney 2004). 

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. The Hawaiian stock of dwarf sperm whales is not 

considered strategic under the 1994 amendments to the MMPA because there has been no reported fisheries related 

mortality or serious injury. Insufficient information is available to determine whether the total fishery mortality 

and serious injury for dwarf sperm 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 (Richardson et al. 1995), particularly for deep-diving whales like dwarf sperm whales that feed in the 

oceans’ “sound channel”. 

REFERENCES 

Baird, R.W. 2005. Sightings of dwarf (Kogia sima) and pygmy (K. breviceps) sperm whales from the main 

Hawaiian Islands. Pacific Science 59: in press.

Barlow, J. 2003. Cetacean abundance in Hawaiian waters during summer/fall 2002. Admin. Rep. LJ-03-13. 

Southwest Fisheries Science Center, National Marine Fisheries Service, 8604 La Jolla Shores Drive, La 

Jolla, CA 92037. 

Forney, K.A. 2004. Estimates of cetacean mortality and injury in two U.S. Pacific longline fisheries, 1994-2002. 

Admin. Rep. LJ-04-07. Southwest Fisheries Science Center, National Marine Fisheries Service, 8604 La 

Jolla Shores Drive, La Jolla, CA 92038. 17 pp. 

Maldini, D., L. Mazzuca, and S. Atkinson. 2005. Odontocete stranding patterns in the Main Hawaiian Islands 

(1937-2002): How do they compare with live animal surveys? Pacific Science 59(1):55-67. 

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. 

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. 

Tomich, P. Q. 1986. Mammals in Hawaii: A Synopsis and Notational Bibliography. Bishop Museum Press, Hawaii, 

375 pp.

252
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-OPR12. 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. 

253
Revised 03/15/2005 

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 40o

N 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 160o

W between 40-50oN, and 

ends up at 180o

W 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 150o

W) 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 18 strandings have been reported from Oahu, Kauai and Kure Atoll (Woodward 1972; Nitta

1991; Maldini 2005). Sperm whales have also been sighted around several of the Northwestern Hawaiian Islands 

(Rice 1960; Barlow 2003), off the main island of Hawaii (Lee 1993; Mobley et al. 2000) 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). A summer/fall 2002

shipboard survey of waters within the U.S. Exclusive Economic Zone (EEZ) of the Hawaiian Islands resulted in 43

sperm whale sightings throughout the study area (Figure 1; Barlow 2003).

W180 W175 W170 W165 W160 W155 W150

N10

N15

N20

N25

N30

N35

Figure 1. Sperm whale sighting locations during the 2002 shipboard

survey of U.S. EEZ waters surrounding the Hawaiian Islands 

(Barlow 2003; see Appendix 2 for details on timing and location of 

survey effort). Outer line represents approximate boundary of survey

area and U.S. EEZ. 

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. A spring 1997 

combined visual and acoustic line-transect survey conducted in the eastern temperate North Pacific resulted in

estimates of 24,000 (CV=0.46) sperm whales based on visual sightings, and 39,200 (CV=0.60) based on 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

254
is not known whether any or all of these animals routinely enter the U.S. EEZ of 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 average abundance estimate of 66 (CV=0.56) sperm whales was calculated from the combined survey data 

(Mobley et al. 2000). This study underestimated the total number of sperm whales within the U.S. EEZ off Hawaii, 

because areas around the Northwestern 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. The data on which this estimate was based are now over 5

years old. A 2002 shipboard line-transect survey of the entire Hawaiian Islands EEZ resulted in an abundance

estimate of 7,082 (CV=0.30) sperm whales (Barlow 2003), including a correction factor for missed diving animals.

This is currently the best available abundance estimate for this stock. 

Minimum Population Estimate

The log-normal 20th percentile of the 2002 abundance estimate is 5,531 sperm whales. 

 

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 

(5,531 ) 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; Wade and Angliss 1997), resulting in a PBR of 11 sperm whales per 

year. 

HUMAN-CAUSED MORTALITY AND 

SERIOUS INJURY

Fishery Information

Information on fishery-related

mortality of cetaceans in Hawaiian

waters is limited, but the gear types used 

in Hawaiian fisheries are responsible for 

marine mammal mortality and serious

injury in other fisheries throughout U.S. 

waters. Gillnets 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 are

reported for all pelagic fisheries, and

large whales have been entangled in

longlines off the Hawaiian Islands (Nitta 

and Henderson 1993; NMFS/PIR,

unpublished data). Between 1994 and 

2002, one sperm whale was observed 

entangled within the Hawaiian Islands 

EEZ in the Hawaii-based longline

fishery, with approximately 4-25% of all

effort observed (Table 1; Forney 2004).

During the 905 observed trips with 11,014

sets, the average interaction rate of sperm 

whales was one animal per 905 fishing 

trips, or one animal per 11,014 sets. The 

Figure 2. Location of the observed sperm whale take in the Hawaiibased longline fishery, 1998-2002 (filled diamond), and the take 

observed during an experimental longline set in 2002 (open

diamond). Solid lines represent the U.S. Exclusive Economic Zone 

(EEZ). 

255
caught animal was apparently able to free itself and was not considered seriously injured (Forney 2004), following 

established guidelines for assessing serious injury in marine mammals (Angliss and DeMaster 1998). The average 

5-yr estimate of annual mortality and serious injury within the Hawaiian Islands EEZ during 1998-2002 is zero 

sperm whales. One additional sperm whale was observed taken in an experimental set outside the U.S. EEZ, but the 

severity of its injuries could not be determined (Forney 2004). Since 2001, the Hawaii-based longline fishery has 

undergone a series of regulatory changes, primarily to protect sea turtles (NMFS 2001). Potential impacts of these 

regulatory changes on the rate of sperm whale interactions are unknown. 

 

Table 1. Summary of available information on incidental mortality and serious injury of sperm whales (Hawaiian 

stock) in commercial fisheries, within and outside of the Hawaiian Islands EEZ (Forney 2004). Mean annual takes 

are based on 1998-2002 data unless otherwise indicated; n/a = not available. 

Mortality and Serious In ry ju

outside of U.S. EEZ

Mortality and Serious Injury 

within Hawaiian Islands EEZ

Fishery Name Year(s) Data Type

Percent 

Observer 

Coverage Observed

Estimated 

(CV in 

parentheses)

Mean Annual 

Takes 

(CV in 

parentheses)

Observed

Estimated 

(CV in 

parentheses)

Mean Annual 

Takes 

(CV in 

parentheses)

Hawaii-based 

longline fishery 

1998 

1999 

2000 

2001

2002

1998-2002 

observer 

data

4.6% 

3.5% 

11.8% 

22.7%

24.9%

0 

0 

0 

0

0

0 (-) 

0 (-) 

0 (-) 

0 (-)

0 (-)

0 (-)

0 

0 

0 

0

0

0 (-) 

0 (-) 

0 (-) 

0 (-)

0 (-)

0 (-)

Experimental 

longline fishery 2002 observed 1 n/a 0.2 (n/a)

Minimum total annual takes within U.S. EEZ waters 0 (-)

 

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 20o

N (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 underreported 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. Some of the whales taken during the whaling era were certainly from a 

population or populations that occur within Hawaiian waters. 

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. Insufficient information is 

available to determine whether the total fishery mortality and serious injury for sperm whales is insignificant and 

approaching zero mortality and serious injury rate. Furthermore, the effect of interactions with the Hawaii-based 

longline fishery in U.S. and international waters is not known. The increasing levels of anthropogenic noise in the 

world’s oceans has been suggested to be a habitat concern for whales (Richardson et al. 1995), particularly for deepdiving whales like sperm whales that feed in the oceans’ “sound channel”. 

256
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. 

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. 2003. Cetacean abundance in Hawaiian waters during summer/fall 2002. Admin. Rep. LJ-03-13. 

Southwest Fisheries Science Center, National Marine Fisheries Service, 8604 La Jolla Shores Drive, La 

Jolla, CA 92037. 

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. 

Forney, K.A. 2004. Estimates of cetacean mortality and injury in two U.S. Pacific longline fisheries, 1994-2002. 

Admin. Rep. LJ-04-07. Southwest Fisheries Science Center, National Marine Fisheries Service, 8604 La 

Jolla Shores Drive, La Jolla, CA 92037. 17 pp. 

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). 

Lee, T. 1993. Summary of cetacean survey data collected between the years of 1974 and 1985. NOAA Tech.Mem. 

NMFS 181, 184pp. 

Maldini, D., L. Mazzuca, and S. Atkinson. 2005. Odontocete stranding patterns in the Main Hawaiian Islands 

(1937-2002): How do they compare with live animal surveys? Pacific Science 59(1):55-67. 

Mesnick, S. Southwest Fisheries Science Center, NMFS, 8604 La Jolla Shores Drive, La Jolla, California, 92037. 

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, 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. 

NMFS, Pacific Islands Region, 1602 Kapiolani Blvd, Suite 1110, Honolulu, HI 96814. 

NMFS 2001. Western Pacific Pelagic Fisheries Biological Opinion. Available from Pacific Islands Region, 1602 

Kapiolani Blvd, Suite 1110, Honolulu, HI 96814 (http://swr.nmfs.noaa.gov/pir). 

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. 

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. 

257
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. 

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. 

Shallenberger, E.W. 1981. The status of Hawaiian cetaceans. Final report to U.S. Marine Mammal Commission. 

MMC-77/23, 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-OPR12. 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. 

258
Revised 03/15/2005 

BLUE WHALE (Balaenoptera musculus): Western 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 up to five

populations have been proposed (Reeves

et al. 1998). 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). 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);

however, blue whale calls have been recorded there between 1995 and 2001 (Stafford et al. 2001, Stafford 2003).

Recent analyses of acoustic

Figure 1. Locations of two blue whale sightings made by observers

aboard Hawaii-based longline fishing vessels in July 1994 and 

February 1997 (NMFS/PIR unpublished data). Solid lines represent 

the U.S. Exclusive Economic Zone (EEZ). 

 data obtained throughout the North Pacific Ocean (Stafford et al. 2001; 

Stafford 2003) has revealed two distinct blue whale call types, suggesting two North Pacific stocks: eastern and 

western. The regional occurrence patterns indicate that blue whales from the eastern North Pacific stock winter off 

Mexico, central America, and as far south as 8ES (Stafford et al. 1999), and feed during summer off the U. S. West

Coast and to a lesser extent in the Gulf of Alaska, and in central North Pacific waters. This stock has previously

been documented to feed in waters off California (and occasionally as far north as British Columbia; Calambokidis 

et al. 1998) in summer/fall (from June to November) migrating south to productive areas off Mexico (Calambokidis 

et al. 1990) and as far south as the Costa Rica Dome (10o N) in winter/spring (Mate et al. 1999, Stafford et al. 1999).

Blue whales belonging to the western Pacific stock appear to feed in summer southwest of Kamchatka, south of the

Aleutians, and in the Gulf of Alaska (Stafford 2003; Watkins et al. 2000), and in winter they migrate to lower 

latitudes in the western Pacific and less frequently in the central Pacific, including Hawaii (Stafford et al. 2001). The 

only published sighting record of blue whales near Hawaii is that of Berzin and Rovnin (1966). Two sightings have

been made by observers on Hawaii-based longline vessels (Figure 1; NMFS/PIR, unpublished data). 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), which included at least some within the U.S. Exclusive 

Economic Zone (EEZ). The recordings made off Hawaii showed bimodal peaks throughout the year (Stafford et al. 

2001), with western Pacific call types heard during winter and eastern Pacific calls heard during summer. . For the 

Marine Mammal Protection Act (MMPA) stock assessment reports, there are two blue whale stocks within the 

259
Pacific U.S. EEZ: 1) the western North Pacific stock (this report), which includes whales found around the Hawaiian 

Islands during winter, 2) the eastern North Pacific stock, which feeds primarily off California.

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 1,744 blue whales is available for California, Oregon and 

Washington, based on shipboard line-transect surveys in 1996 and 2002(Barlow 2003a) and photographic markrecapture estimates (Calambokidis et al. 2003 ). 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. No blue whale sightings were made during a summer 1994 shipboard 

survey south of the Aleutian Islands (Forney and Brownell 1996), during twelve aerial surveys conducted in 1993-

98 within about 25 nmi of the main Hawaiian Islands (Mobley et al. 2000), or during a summer/fall 2002 shipboard 

surveys of the entire Hawaiian Islands EEZ (Barlow 2003b). Therefore, no estimate of abundance is available for 

the western Pacific blue whale stock. 

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 

 Information on fishery-related mortality of cetaceans in Hawaiian waters is limited, but the gear types used 

in Hawaiian fisheries are responsible for marine mammal mortality and serious injury in other fisheries throughout 

U.S. waters. Gillnets 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). Large whales have been 

entangled in longline gear off the Hawaiian Islands (Nitta and Henderson 1993, Forney 2004), but no interactions 

with blue whales were observed in the Hawaii-based longline fishery between 1994 and 2002, with approximately 4-

25% of all effort observed (Forney 2004).

 

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. Insufficient information is available to determine whether the total fishery mortality and serious injury 

for blue whales is insignificant and approaching zero mortality and serious injury rate. 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. 2003a. Preliminary estimates of cetacean abundance off the U.S. West Coast: 1991-2001. Admin. Rept. 

LJ-03-03. Southwest Fisheries Science Center, National Marine Fisheries Service, 8604 La Jolla Shores 

Drive, La Jolla, CA, 92037. 26 pp. 

260
Barlow, J. 2003b. Cetacean abundance in Hawaiian waters during summer/fall 2002. Admin. Rep. LJ-03-13. 

Southwest Fisheries Science Center, National Marine Fisheries Service, 8604 La Jolla Shores Drive, La 

Jolla, CA 92037. 

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, T. Chandler, K. Rasmussen, G.H. Steiger, and L. Schlender. 1998. Humpback and blue whale 

photographic identification: Report of research in 1997. Final report to Southwest Fisheries Science 

Center, Olympic Coast National Marine Sanctuary, University of California at Santa Cruz, and Cornell 

University. Cascadia Research, 2181⁄2 W. Fourth Ave., Olympia, WA 98501. 41pp. 

Calambokidis, J, T. Chandler, L. Schlender, G.H. Steiger, and A Douglas. 2003. Research on humpback and blue 

whale off California, Oregon and Washington in 2002. Final contract report to Southwest Fisheries Science 

Center, National Marine Fisheries Service. 8604 La Jolla Shores Drive, La Jolla, CA 92037. 49pp. 

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., G. H. Steiger, J.C. Cubbage, K.C. Balcomb, C. Ewald, S. Kruse, R. Wells, and R. Sears. 1990. 

Sightings and movement of blue whales off central California 1986-88 from photo-identification of 

individuals. Rep. Int. Whaling. Commn., Special Issue 12:343-348. 

Donovan, G. P. 1991. A review of IWC stock boundaries. Rept. Int. Whal. Commn., Special Issue 13:39-68. 

Forney, K.A. 2004. Estimates of cetacean mortality and injury in two U.S. Pacific longline fisheries, 1994-2002. 

Admin. Rep. LJ-04-07. Southwest Fisheries Science Center, National Marine Fisheries Service, 8604 La 

Jolla Shores Drive, La Jolla, CA 92037. 17 pp. 

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). 

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. 

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. 

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. 

NMFS, Pacific Islands Region, Observer Pogram, 1602 Kapiolani Blvd, Suite 1110, Honolulu, HI 96814. 

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. 

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. 

261
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. 

Stafford, K.M., S. L. Nieukirk, and G.G. Fox. 2001. Geographic and seasonal variation of blue whale calls in the 

North Pacific. J. Cetacean Res. Manage. 3(1):65-76. 

Stafford. K.M. 2003. Two types of blue whale calls recorded in the Gulf of Alaska. Mar. Mamm. Sci. 19:682-693 

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. 

Watkins, W. A., J. E. George, M. A. Daher, K. Mullin, D. L. Martin, S. H. Haga, and N. A. DiMarzio. 2000. Whale 

call data for the North Pacific November 1995 through July 1999: Occurrence of calling whales and source 

locations from SOSUS and other acoustic systems. Technical Report WHOI_00_02 available from Woods 

Hole Oceanographic Institution. 160pp. 

262
Revised 03/15/2005 

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 have been considered 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), and five sightings were made 

during a 2002 survey of waters within 

the U.S. Exclusive Economic Zone 

(EEZ) of the Hawaiian Islands (Barlow 

2003; Figure 1). 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. EEZ. 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. 

W180 W175 W170 W165 W160 W155 W150

N10

N15

N20

N25

N30

N35

Figure 1. Fin whale sighting locations during the 2002 shipboard 

survey of U.S. EEZ waters surrounding the Hawaiian Islands 

(Barlow 2003; see Appendix 2 for details on timing and location of 

survey effort). Outer line represents approximate boundary of survey

area and U.S. EEZ. 

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

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 no

abundance estimate was 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. A

2002 shipboard line-transect survey of the entire Hawaiian Islands EEZ resulted in an abundance estimate of 174

(CV=0.72) fin whales (Barlow 2003). This is currently the best available abundance estimate for this stock. 

Minimum Population Estimate

 The log-normal 20th percentile of the 2002 abundance estimate is 101 fin whales. 

263
 

Current Population Trend 

No data are available on current population trend. 

URRE

No data are available on current or maximum net productivity rate.

C NT AND MAXIMUM NET PRODUCTIVITY RATES 

POTENTIAL BIOLOGICAL REMOVAL

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

(101) 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; Wade and Angliss 1997), resulting in a PBR of 0.2 fin whales per year. 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Fishery Information 

 Information on fishery-related mortality of cetaceans in Hawaiian waters is limited, but the gear types used 

in Hawaiian fisheries are responsible for marine mammal mortality and serious injury in other fisheries throughout 

U.S. waters. Gillnets 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 are 

reported for all pelagic fisheries, and large whales have been entangled in longline gear off the Hawaiian Islands 

(Nitta and Henderson 1993, Forney 2004). Between 1994 and 2002, no interactions with fin whales were observed 

in the Hawaii-based longline fishery, with approximately 4-25% of all effort observed (Forney 2004). 

istoric

e seasonally into the Hawaiian EEZ. 

he species has been protected in the North Pacific by the IWC since 1976.

H al 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 migrat

T

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. Insufficient information is available to determine whether the total fishery mortality and serious injury 

for fin 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 (Richardson et al. 

1995). 

Allison, rnational Whaling Commission. The Red House, 135 Station Road, Impington, Cambridge, UK CB4 

REFERENCES

C. Inte

9NP. 

Balcomb, K. C., III. 1987. The Whales of Hawaii. Marine Mammal Fund, 99 pp. 

Barlow, J. 2003. Cetacean abundance in Hawaiian waters during summer/fall 2002. Admin. Rep. LJ-03-13. 

Southwest Fisheries Science Center, National Marine Fisheries Service, 8604 La Jolla Shores Drive, La 

Jolla, CA 92037. 

Donovan, G. P. 1991. A review of IWC stock boundaries. Rept. Int. Whal. Commn., Special Issue 13:39-68. 

Forney, K.A. 2004. Estimates of cetacean mortality and injury in two U.S. Pacific longline fisheries, 1994-2002. 

Admin. Rep. LJ-04-07. Southwest Fisheries Science Center, National Marine Fisheries Service, 8604 La 

Jolla Shores Drive, La Jolla, CA 92037. 17 pp. 

McDonald, M. A., and C. G. Fox. 1999. Passive acoustic methods applied to fin whale population density 

Mizroch, S. A., D. W. Rice, and J. M. Breiwick. 1984. The fin whale, Balaenoptera physalus Mar. Fish. Rev. 

Mobley, orris, and D. Weller. 1996. Fin whale sighting north of Kaua’i, Hawai’i. 

estimation. J. Acoust. Soc. Am. 105: 2643-2651. 

46(4):20-24. 

 J. R., Jr., M. Smultea, T. N

Pacific Science 50:230-233. 

264
Mobley,

species in Hawaiian waters: preliminary results of 1993-98 aerial surveys Admin. 

 Am. 43:383-384. 

 J. R., Jr, S. S. Spitz, K. A. Forney, R. A. Grotefendt, and P. H. Forestall. 2000. Distribution and 

abundance of odontocete 

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.

Perrin, W.F., G. P. Donovan and J. Barlow. 1994. Gillnets and Cetaceans. Rep. Int. Whal. Commn., Special Issue 

15, 629 pp. 

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. 

eral species of whales 

Tønness

Shallenberger, E.W. 1981. The status of Hawaiian cetaceans. Final report to U.S. Marine Mammal Commission. 

MMC-77/23, 79pp. 

Thompson, P. O. and W. A. Friedl. 1982. A long term study of low frequency sound from sev

off Oahu, Hawaii. Cetology 45:1-19. 

en, J. N. and A. O. Johnsen. 1982. The History of Modern Whaling. Hurst, 789 pp. 

Wade, P P. Angliss. 1997. Guidelines for Assessing Marine Mammal Stocks: Report of the GAMMS . R. and R. 

Workshop April 3-5, 1996, Seattle, Washington. U. S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR12. 93 pp. 

265
Revised 03/15/2005 

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). A summer/fall 2002 shipboard 

survey of waters within the U.S.

Exclusive Economic Zone (EEZ) of the

Hawaiian Islands resulted in 13 Bryde’s 

whale sightings throughout the study

area (Figure 1; Barlow 2003).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. EEZ

are divided into two areas: 1) Hawaiian waters (this report), and 2) the eastern tropical Pacific (east of 150o

W and

including the Gulf of California and waters off California).

W180 W175 W170 W165 W160 W155 W150

N10

N15

N20

N25

N30

N35

Figure 1. Bryde’s whale sighting locations during the 2002 

shipboard survey of U.S. EEZ waters surrounding the Hawaiian 

Islands (Barlow 2003; see Appendix 2 for details on timing and

location of survey effort). Outer line represents approximate

boundary of survey area and U.S. EEZ. 

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. A 2002 shipboard line-transect survey of the entire Hawaiian Islands EEZ resulted in an

abundance estimate of 493 (CV=0.34) Bryde’s whales (Barlow 2003). This is currently the best available 

abundance estimate for this stock. 

Minimum Population Estimate

 The log-normal 20th percentile of the 2002 abundance estimate is 373 Bryde’s whales. 

 

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.

266
POTENTIAL BIOLOGICAL REMOVAL

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

(373) times one half the default maximum net growth rate for cetaceans (1⁄2 of 4%) times a recovery factor of 0.50 

(for a stock of unknown status with no known fishery mortality or serious injury within the Hawaiian Islands EEZ; 

Wade and Angliss 1997), resulting in a PBR of 3.7 Bryde’s whales per year. 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY 

Fishery Information

 Information on fishery-related mortality of cetaceans in Hawaiian waters is limited, but the gear types used 

in Hawaiian fisheries are responsible for marine mammal mortality and serious injury in other fisheries throughout 

U.S. waters. Gillnets 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 are 

reported for all pelagic fisheries, and large whales have been entangled in longline gear off the Hawaiian Islands 

(Nitta and Henderson 1993, Forney 2004). Between 1994 and 2002, no interactions with Bryde’s whales were 

observed in the Hawaii-based longline fishery, with approximately 4-25% of all effort observed (Forney 2004). 

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. The Hawaiian stock of Bryde’s whale is not considered strategic 

under the 1994 amendments to the MMPA because there has been no reported fisheries related mortality or serious 

injury. Insufficient information is available to determine whether the total fishery mortality and serious injury for 

fin 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 (Richardson et al. 

1995). 

REFERENCES 

Barlow, J. 2003. Cetacean abundance in Hawaiian waters during summer/fall 2002. Admin. Rep. LJ-03-13. 

Southwest Fisheries Science Center, National Marine Fisheries Service, 8604 La Jolla Shores Drive, La 

Jolla, CA 92037. 

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. 

Forney, K.A. 2004. Estimates of cetacean mortality and injury in two U.S. Pacific longline fisheries, 1994-2002. 

Admin. Rep. LJ-04-07. Southwest Fisheries Science Center, National Marine Fisheries Service, 8604 La 

Jolla Shores Drive, La Jolla, CA 92037. 17 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. 

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. 

267
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. 

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. 

Shallenberger, E.W. 1981. The status of Hawaiian cetaceans. Final report to U.S. Marine Mammal Commission. 

MMC-77/23, 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 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-OPR12. 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. 

268
Revised 03/15/2005 

SEI WHALE (Balaenoptera borealis): Hawaiian 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. 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. Four sightings of sei whales were 

recently made during a summer/fall 2002 

shipboard survey of waters within the U.S.

Exclusive Economic Zone (EEZ) of the Hawaiian Islands (Figure 1; Barlow 2003). For the Marine Mammal

Protection Act (MMPA) stock assessment reports, sei 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. 

W180 W175 W170 W165 W160 W155 W150

N10

N15

N20

N25

N30

N35

Figure 1. Sei whale sighting locations during the 2002 shipboard 

cetacean survey of U.S. EEZ waters surrounding the Hawaiian

Islands (Barlow 2003; see Appendix 2 for details on timing and

location of survey effort). Outer line indicates approximate

boundary of survey area and U.S. EEZ. 

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 North Pacific based on sighting surveys. 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), but no sightings of sei whales were made. A 2002 shipboard line-transect survey of the entire Hawaiian 

Islands EEZ resulted in a summer/fall abundance estimate of 77 (CV=1.06) sei whales (Barlow 2003). This is

currently the best available abundance estimate for this stock, but the majority of sei whales would be expected to be

at higher latitudes in their feeding grounds at this time of year. 

Minimum Population Estimate

The log-normal 20th percentile of the 2002 abundance estimate is 37 sei whales. 

Current Population Trend

No data are available on current population trend. 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 takes 

(Yablokov 1994) make this uncertain. 

269
CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

 No data are available on current or maximum net productivity rate for sei whales. 

POTENTIAL BIOLOGICAL REMOVAL

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

(37) 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; Wade and Angliss 1997), resulting in a PBR of 0.1 sei whales per year. 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Fishery Information 

 Information on fishery-related mortality of cetaceans in Hawaiian waters is limited, but the gear types used 

in Hawaiian fisheries are responsible for marine mammal mortality and serious injury in other fisheries throughout 

U.S. waters. Gillnets 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 are 

reported for all pelagic fisheries, and large whales have been entangled in longline gear off the Hawaiian Islands 

(Nitta and Henderson 1993; Forney 2004). Between 1994 and 2002, no interactions with sei whales were observed 

in the Hawaii-based longline fishery, with approximately 4-25% of all effort observed (Forney 2004). 

Historical Whaling

 The reported take of North Pacific sei whales by commercial whalers totaled 61,500 between 1947 and 

1987 (C. Allison, IWC, pers. comm.). There has been an IWC prohibition on taking sei whales since 1976, and 

commercial whaling in the U.S. has been prohibited since 1972. 

STATUS OF STOCK 

Previously, sei whales were estimated to have been reduced to 20% (8,600 out of 42,000) of their prewhaling abundance in the North Pacific (Tillman 1977). Sei 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. Insufficient information is available to determine whether the total fishery 

mortality and serious injury for sei 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 (Richardson et al. 1995). 

REFERENCES

Allison, C. International Whaling Commission. The Red House, 135 Station Road, Impington, Cambridge, UK CB4 

9NP. 

Barlow, J. 2003. Cetacean abundance in Hawaiian waters during summer/fall 2002. Admin. Rep. LJ-03-13. 

Southwest Fisheries Science Center, National Marine Fisheries Service, 8604 La Jolla Shores Drive, La 

Jolla, CA 92038. 

Donovan, G. P. 1991. A review of IWC stock boundaries. Rept. Int. Whal. Commn., Special Issue 13:39-68. 

Forney, K.A. 2004. Estimates of cetacean mortality and injury in two U.S. Pacific longline fisheries, 1994-2002. 

Admin. Rep. LJ-04-07. Southwest Fisheries Science Center, National Marine Fisheries Service, 8604 La 

Jolla Shores Drive, La Jolla, CA 92037. 17 pp. 

Horwood, J. 1987. The Sei Whale: Population Biology, Ecology and Management. Croom Helm, London, U.K. 

375pp. 

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. 

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. 

270
Ohsumi, S. and S. Wada. 1974. Status of whale stocks in the North Pacific, 1972. Rept. Int. Whal. Commn. 

25:114-126. 

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. 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. 

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. 

Tillman, M. F. 1977. Estimates of population size for the North Pacific sei whale. Rept. Int. Whal. Commn., 

Special Issue 1:98-106. 

Yablokov, A. V. 1994. Validity of whaling data. Nature 367:108. 

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-OPR12. 93 pp. 

271
Revised 03/15/2005

MINKE WHALE (Balaenoptera acutorostrata): Hawaiian 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 have only been

recently confirmed to occur seasonally

around the Hawaiian Islands (Barlow 2003, 

Rankin and Barlow, in prep), and their

migration routes or destinations are not

known. Four reliable sightings of minke 

whales were made by observers in the

Hawaii-based longline fishery during the 

months of December-March, 2000-2002

(Figure 1; NMFS/PIR unpublished data). One confirmed sighting of a minke whale was made in November 2002

during a survey of waters within the U.S. Exclusive Economic Zone (EEZ) of the Hawaiian Islands (Barlow 2003),

and additional acoustic detections of this species’ distinctive call (known as the ‘boing’) were made that could not 

be visually verified (Figure 1). There are no known stranding records of this species from the main islands (Nitta 

1991; Maldini 2005). For the Marine Mammal Protection Act (MMPA) stock assessment reports, there are three 

stocks of minke whale within the Pacific U.S. EEZ: 1) a Hawaiian stock (this report), 2) a California/Oregon/

Washington stock, and 3) an Alaskan stock.

Figure 1. Locations of minke whale sightings from longline 

observer records (diamonds; NMFS/PIR, unpublished data), and

sighting (closed circle) and acoustic detections (open circles)

made during the 2002 shipboard survey of U.S. EEZ waters 

surrounding the Hawaiian Islands (Barlow 2003; see Appendix 2 

for details on timing and location of survey effort). Solid lines 

represent the U.S. EEZ. 

POPULATION SIZE

A summer/fall 2002 shipboard line-transect survey of the entire Hawaiian Islands EEZ resulted in one ‘off 

effort’ sighting of a minke whale following the acoustic detection of a so-called ‘boing’ (Barlow 2003; Rankin and

Barlow, in prep). This sighting was not part of regular survey operations and, therefore, could not be used to

calculate an estimate of abundance (Barlow 2003). Furthermore, the majority of this survey took place during

summer and early fall, when the Hawaiian stock of minke whale would be expected to be farther north. There 

currently is no abundance estimate for this stock of minke whales, which appears to occur seasonally (about

November - March) around the Hawaiian Islands. 

272
Minimum Population Estimate

 There is no minimum population estimate for the Hawaiian stock of minke whales. 

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 minke whales. 

POTENTIAL BIOLOGICAL REMOVAL

 No PBR can be calculated for this stock at this time. 

HUMAN CAUSED MORTALITY AND SERIOUS INJURY 

Fishery Information

 Information on fishery-related mortality and serious injury of cetaceans in Hawaiian waters is limited, but 

the gear types used in Hawaiian fisheries are responsible for marine mammal mortality and serious injury in other 

fisheries throughout U.S. waters. Gillnets 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 none of these 

interactions are known to have involved minke whales. None were observed hooked or entangled in the Hawaiibased longline fishery between 1994 and 2002, with approximately 4-25% of all effort (measured as the number of 

sets made) observed by on-board observers (Forney 2004). 

STATUS OF STOCK

 The status of minke 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 minke 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 or serious injury within the Hawaiian Islands EEZ. Insufficient 

information is available to determine whether the total fishery mortality and serious injury for minke 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 (Richardson et al. 1995). 

REFERENCES

Barlow, J. 2003. Cetacean abundance in Hawaiian waters during summer/fall 2002. Admin. Rep. LJ-03-13. 

Southwest Fisheries Science Center, National Marine Fisheries Service, 8604 La Jolla Shores Drive, La 

Jolla, CA 92037. 

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. 

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. 

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. 

Forney, K.A. 2004. Estimates of cetacean mortality and injury in two U.S. Pacific longline fisheries, 1994-2002. 

Admin. Rep. LJ-04-07. Southwest Fisheries Science Center, National Marine Fisheries Service, 8604 La 

Jolla Shores Drive, La Jolla, CA 92037. 17 pp. 

Maldini, D., L. Mazzuca, and S. Atkinson. 2005. Odontocete stranding patterns in the Main Hawaiian Islands 

(1937-2002): How do they compare with live animal surveys? Pacific Science 59(1):55-67. 

NMFS, Pacific Islands Region, Observer Program, 1602 Kapiolani Blvd, Suite 1110, Honolulu, HI 96814. 

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. 

273
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., Spec. Issue 15, 

629p. 

Rankin, S. and J. Barlow. (in prep). Description of stereotyped minke whale vocalizations from the North Pacific 

Ocean. 

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. 

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Revised 03/15/2005 Appendix 1. Description of U.S. Commercial Fisheries 

 The Marine Mammal Protection Act requires NMFS to publish a list of commercial fisheries and classify 

each fishery based on whether incidental mortality and serious injury of marine mammals is frequent (Category I), 

occasional (Category II), or mortality is unlikely or unknown (Category III). This “List of Fisheries” is published 

annually in the Federal Register. 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. 68, no. 135 dated 15 July 2003. 

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. 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 (MMSN). 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, evidence of net fishery entanglement (net remaining 

on animal, net marks, severed flukes), and ingestion of hooks. 

2. Marine Mammal Reporting from Fisheries 

 In 1994, the MMPA was amended 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 pre-printed 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 injury or mortality occurred. The number of self-reported marine mammal 

interactions is considerably lower than the number reported by fishery observers, even though observer reports are 

typically based on 20% observer effort. For example, from 1998-2002, there were 115 fisher self-reports of marine 

mammal interactions in the California swordfish/thresher shark drift gillnet fishery. This compares with 201 

observed interactions over the same period, based on only 20% observer coverage. This suggests that fisher selfreports are grossly underreported. 

3. NMFS Marine Mammal Stranding Network data

In California, for the years 1998 through 2002 there were 120, 154, 152, 100, and 183 cetacean strandings 

respectively and 3568, 1066, 1857, 1482, and 2,367 pinniped strandings respectively. In Oregon/Washington from 

1998-2002, there were 43, 50, 48, 28, and 17 reported cetacean strandings and 321, 267, 235, 250, 139 pinniped 

strandings, respectively. Approximately 10% of all cetacean and 7% of all pinniped strandings showed evidence of 

human-caused mortality during this period. Human-related causes of mortality include: entrainment in power 

station intakes, shooting, net fishery entanglement, and hook/line, set-net and trap fishery interaction. A species 

summary of all cetacean and pinniped strandings for the period 1998-2002 is given in Table 2 of this Appendix. 

4. Fishery Descriptions

Category II , CA/OR thresher shark/swordfish drift gillnet fishery ($14 inch mesh)

Note: This fishery was previously classified as a Category I fishery. 

Number of permit holders: The number of eligible permit holders in California for 1998-2002 are 148, 136, 126, 

113, and 105, respectively. 

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Number of active permit holders: The number of vessels active in this fishery from 1998-2002 were 123, 96, 81, 

65, and 56, respectively. 

Total effort: Both estimated and observed effort for the drift-net fishery during the calendar years 1990 through 2002 

are shown in Figure 7. In 2002 there was an estimated 1,630 effort-days, where an effort-day is defined to be one 

day of effort by one vessel. (In this fishery, 1 effort-day is equivalent to 1 set.). There were 360 (64 trips) observed 

effort-days in 2002. 

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 Figure 6 

shows approximate locations of observed marine mammal entanglements for the period 1998-2002. 

Seasons: This fishery is subject to season-area restrictions. From February 1 to May 15 effort must be further than 

200 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. A seasonarea closure to protect leatherback sea turtles was implemented in this fishery in August 2001. The closure area 

prohibits drift gillnet fishing from August 15 through November 15, in the area bounded by straight lines from Point 

Sur, California (N36o 17') to N 34o 27' W 123o

 35', west to W129o, north to N 45o, then east to the Oregon coast. 

The Highly Migratory Species Management Team of the Pacific Fishery Management Council is considering reopening the area south of Point Sur, California in this fishery. An additional season-area closure south of Point 

Conception and east of W120 degrees longitude is effective during the months of June, July, and August during El 

Niño years to protect loggerhead turtles (Federal Register, Vol 68, No 241, 16 December 2003). 

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 entanglement. This fishery was reclassified from a Category I to a 

Category II fishery in 2003 (Federal Register, Vol. 68, No. 135, 15 July 2003). 

Category I, CA angel shark/halibut and other speciesset gillnet fishery (>3.5 inch mesh).

Note: The “CA angel shark/halibut set gillnet fishery” and “CA other species, large mesh (>3.5 in) set gillnet 

fishery” were previously listed as separate fisheries. Angel shark and halibut are typically targeted using 8.5 inch 

mesh while the remainder of the fishery targets white seabass and yellowtail using 6.5 inch mesh. In recent years, 

there has been an increasing number of 6.0-6.5 inch mesh sets fished using drifting methods; this component is now 

identified as a separate fishery (see “CA yellowtail, barracuda, white seabass, and tuna drift gillnet fishery (>3.5 

and <14 in mesh)” fishery described below). 

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Number of permit holders: There is no specific permit category for this fishery. Overall, the current number of 

legal permit holders for gill and trammel nets, excluding swordfish drift gillnets and herring gillnets for 1998 

through 2002 are, respectively, 255, 245, 232, 223, and 209. 

Number of active permit holders: For the period 1998-2001, there were 45, 66, 62, 57, and 52 active permit holders 

in this fishery. 

Total effort: Effort in the angel shark/halibut set-net fishery has historically been as high as 7,000 days in 1991, 

declined to fewer than 2,000 days following a gillnet closure within 3 nautical miles of the mainland and 1 nmi of 

the Channel Islands in 1994, and has been steady at about 3,000-4,000 days in the last five years. A summary of 

estimated fishing effort and observer coverage for the years 1990-2002 is shown in Figure 8. Effort in the white 

seabass and yellowtail portion of this fishery from 1998 to 2002 were 761, 460, 657, 551, and 733 days, 

respectively. For the first two quarters of 2003, there were 366 days fished. A portion of the effort in the white 

seabass and yellowtail fishery utilizes drifting nets (see “CA yellowtail, barracuda, white seabass, and tuna drift 

gillnet fishery (>3.5 and <14 in mesh)” fishery description below). 

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. The 

central California portion of the fishery from Point Arguello to Point Reyes has been closed since September 2002 

when a ban on gillnets inshore of 60 fathoms took effect. 

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 component of this fishery that targets white seabass and yellowtail utilizes 6.5 inch mesh. 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: An observer program for the halibut/angel shark portion of this fishery operated from 1990-94 and was 

discontinued after area closures were implemented in 1994, which prohibited gillnets within 3 nmi of the mainland 

and within 1 nmi of the Channel Islands in southern California. NMFS re-established an observer program for this 

fishery in Monterey Bay in 1999-2000 due to a suspected increase in harbor porpoise mortality in Monterey Bay. In 

1999 and 2000, fishery mortality exceeded PBR for the Monterey Bay harbor porpoise stock, and the stock is 

currently designated as strategic. In the autumn of 2000, the California Department of Fish and Game implemented 

the first in a series of emergency area closures to set gillnets within 60 fathoms along the central California coast. 

This effectively reduced fishing effort to negligible levels in 2001 and 2002 in Monterey Bay. A ban on gill and 

trammel nets inside of 60 fathoms from Point Reyes to Point Arguello became effective in September 2002. 

Category II, CA yellowtail, barracuda, white seabass, and tuna drift gillnet fishery (>3.5 and <14 in mesh) 

Note: This fishery has developed recently as an offshoot of the “CA other species, large mesh (>3.5 in) set gillnet 

fishery” (see above). Fishermen use the same gear as in the set gillnet fishery (typically 6.5 inch mesh nets, 100-

200 fathoms in length, except that they instead utilize drifting nets to target white seabass and yellowtail. Albacore 

tuna and barracuda are also targeted in this fishery. 

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Number of permit holders: There are approximately 24 active permit holders in this fishery. 

Total effort: In the first two quarters of 2003, there were 366 days fished in the white seabass - yellowtail fishery. 

Of these 366 effort days, 69 days (19%) were drift sets, 267 (73%) were set gillnets, and 30 days (8%) were 

unspecified set type. In 2002, there were a total of 733 days fished in the white seabass - yellowtail fishery. Of 

these 733 effort days, 195 days (27 %) were drift sets, 447 days (61%) were set gillnets, and 91 days (12%) were 

unspecified set type. 

Geographic range: This drift gillnet component of this fishery operates primarily south of Point Conception. 

Observed sets have been clustered around Santa Cruz Island, the east Santa Barbara Channel, and Cortez and Tanner 

Banks. Some effort has also been observed around San Clemente Island and San Nicolas Island. 

Seasons: This fishery operates year round. Targeted species is typically determined by market demand on a shortterm basis. 

Gear type and fishing method: Typical gear used for this fishery is a 150-200 fathom gillnet, which is allowed to 

drift. The mesh size depends on the target species but typical values observed are 6.0 and 6.5 inches. 

Regulations: This fishery is managed by the California Dept. of Fish and Game in accordance with state and federal 

laws. 

Management type: This fishery is a limited entry fishery with gear restrictions and area closures. 

Comments: This fishery primarily targets white seabass and yellowtail, but also targets barracuda and albacore tuna. 

For the period May 2001 through July 2003, there were 42 sets observed from 11 vessel trips. Observed mortality 

included one short-beaked common dolphin and 2 California sea lions. Also, 4 California sea lions were entangled 

and released alive during this period. 

Category II, CA swordfish longline fishery

Number of permit holders: About 20-30 vessels based in California participate in the longline fishery. 

Number of active permit holders: As of 2002, approximately 20-30 vessels participated in this fishery. 

Total Effort: An estimated 1 - 1.5 million hooks are fished annually by 20-30 California-based vessels. 

Geographic range: This fishery operates in west coast waters outside the 200 nm EEZ and unload their catch in 

California ports. 

Seasons: The fishery operates year-round. 

Gear type: Typically, vessels fish 24_72 km of mainline, rigged with 22 m gangions at approximately 60 m 

intervals. Anywhere from 800 to 1,300 hooks are deployed in a set, with large squid (Illex sp.) used for bait. 

Variously colored lightsticks are used, for fishing takes place primarily during the night, when more swordfish are 

available in surface waters. The mainline is deployed in 4_7 hours and left to drift unattached for 7_10 hours. 

Retrieval typically takes about 7_10 hours. 

Regulations: Longline vessels are prohibited from operating within the 200 nmi limit, but may unload their catch in 

California ports and are required to have a California state commercial fishing license. 

Management type: The California longline fishery is currently covered by a fishery management plan (FMP) that 

was submitted for Secretarial review in November 2003. The FMP was partially approved by NMFS on February 4, 

2004. NMFS published a final rule on March 11, 2004 which prohibits shallow longline sets of the type normally 

targeting swordfish on the high seas in the Pacific Ocean east of 150o

 W. longitude. The Pacific Fishery 

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Management Council’s Highly Migratory Species (HMS) Management Team is currently investigating scenarios 

under which swordfish may once again be targeted in this region with the adoption of gear modification measures 

(circle hooks and mackerel baits) used in the Atlantic that have been shown to significantly reduce takes of 

loggerhead and leatherback sea turtles. The HMS Management Team is also investigating options to create a 

limited-entry program for this fishery. A mandatory observer program became effective for this fishery in August 

2002. 

Comments: Many of the vessels in this fishery previously landed in Hawaii, but closures around the Hawaiian 

Islands have moved fishing effort farther east, and as a result some longline vessels now land in California. 

Preliminary catch data has been compiled for the California longline fishery from skipper logbooks, dated between 

August 1, 1995 and December 31, 1999. The logbooks do not report any whale or dolphin interactions, but do show 

interactions with California sea lions. Other documented bycatch in this fishery includes striped marlin, blue shark, 

seabirds, and sea turtles (Vojkovich and Barsky, 1998). Since 1993, the number of vessels in this fishery has 

increased, from 3 to the current estimate of 40-50. This increase in vessels initially resulted from the movement of 

vessels based in the Gulf of Mexico into southern California in the summer of 1993, and more recently from 

increased effort eastward by vessels originating in Hawaii, responding to a court injunction closing fishing areas 

around the Hawaiian islands. Approximately 40-50 longline vessels unload in California, and of these, 40 boats 

originated from Hawaii (and which also have Hawaii longline limited entry permits); these have unloaded their 

catch in California ports since December, 1999 (D. Petersen, NMFS, personal communication, April, 2000). 

Between October 2001 and November 2003, 19 trips were observed by California-based longline observers, with 

391 sets observed (<15% observer coverage). Between October 2001 and November 2003, observed cetacean 

interactions have included one injured Risso’s dolphin and one mortality of an unidentified dolphin. 

Category II, California Round Haul Fisheries. 

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 150 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 was 

initiated for the area south of 39o

 North latitude. Eligibility required a minimum of 100 metric tons of CPS finfish 

landed between 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: An estimated 70 vessels are eligible to fish under the limited entry permit requirements. 

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 

(coastal pelagic species) /FMP (fishery management plan) under federal laws. 

Management type: The mackerel and sardine fisheries are quota fisheries. Several closures for both mackerel and 

sardine have been required by NMFS in recent years (mackerel 2001, 2002; sardine 2002, subarea closure) (pers. 

comm., Dale Sweetnam, California Department of Fish and Game). 

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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.

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. In 1999, the U.S. and Canada reached an agreement that significantly 

reduced the U.S. share of sockeye salmon. In order to compensate the non-treaty U.S. fishermen for the impact of 

this reduction, a federally funded buyback program was established. By the 2001 fishing season, the number of 

available drift gillnet permits had been reduced from 675 (1999) to 216. The intent of the buyback program was to 

reduce the number of drift gillnet permits to 200 (pers. comm., David Cantillon, NMFS, Northwest Region). 

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 (725 in 

2001), 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. 

From 1997-2001, the number of active permits was 633, 559, 199, 248, and 182, respectively. 

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 1995 through 1998. In the remaining years the available sockeye fishing time was less than half 

of the 1994 level. In recent years, poor sockeye returns and market conditions have combined to reduce 

participation in the fishery beyond the reductions created originally by the federal buyback program. In 2001, drift 

gillnets fished for only one opening and 182 gear units were fished in all areas as compared to the 559 cited for 

1998. Owing to the buyback program and reduced salmon runs, it is expected that the number of active permits will 

remain low. 

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. 

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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. U.S. and Canadian Fraser River sockeye and 

pink salmon fisheries are managed by the bilateral Fraser Panel in Panel Area waters. This includes the entire U.S. 

drift gillnet fishery for Fraser sockeye and pink salmon. For U.S. fisheries, Fraser Panel Orders are given effect by 

federal regulations that consist of In-season Orders issued by the NMFS Regional Administrator of the NMFS 

Northwest Region. These regulations are filed in the Federal Register post-season. 

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. The number of permits issued for the period 1998-2002 (through May 2002) were 

3, 4, 7, 2, and 3, respectively (pers. comm., Jane McCrae, Oregon Department of Fish and Wildlife, Marine 

Resources Program). 

Number of active permit holders: Based on landings of swordfish with this gear type, there were no active permit 

holders in this fishery from 1997-2002. 

Total effort: From 1997-2002, 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. 

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 10. From 1997-2002, there were 4,0,0,4,1, and 3 permits issued for this fishery (pers. 

comm., Jane McCrae, Oregon Department of Fish and Wildlife, Marine Resources Program). 

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Number of active permit holders: There were no active permits in the blue shark longline fishery off Oregon from 

1997 through mid-2002. 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. 

Category III, CA herring purse seine fishery.1

This fishery is composed of a roe herring fishery and a fresh herring fishery. The sac-roe fishery occurs in 

California’s four largest herring spawning regions: San Francisco Bay, Tomales Bay, Humboldt Bay, and Crescent 

City Harbor. The largest spawning aggregations occur in San Francisco Bay and produces more than 90% of the 

herring catch. The four spawning areas are managed separately by the California Department of Fish and Game 

(CDFG); catch quotas are based on population estimates derived from acoustic and spawning-ground surveys. 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. The sac-roe fishery is managed through a 

limited-entry program. Since 1983, only five new permits have been issued, and the number of annual permits has 

remained at about 450. 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). 

 

1

 Pers. Comm. Diana Watters, biologist at CDFG Menlo Park. 

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Category II, CA squid purse seine fishery.2

Number of permit holders: A permit to participate in the squid fishery has been required since April 1998. There 

are two types of permits. Market squid vessel permits allow a light vessel to attract squid with lights and catch 

squid. Light boat owner permits only allow the use of attracting lights to aggregate market squid. In the 2002/2003 

season there were 184 market squid vessel permits and 40 light boat owner permits issued. Landings of two tons or 

less are considered incidental and no permit is required. 

Number of active permit holders: The number of active permits varies by year depending on market conditions and 

squid availability. During the 2002/2003 season, there were approximately 105 vessels active during some portion 

of the year. Thirty-four vessels harvested 90% of the total landings greater than two tons. The 1999/2000 season 

had the highest squid landings to date, with 132 vessels making squid landings greater than two tons. 

Total effort: Beginning in May 2000, logbooks were required for the squid fishery. Results for the 2001 calendar 

year indicate that each hour of fishing required 5.5 hours of search time by light boats. Combined searching and 

fishing effort resulted in 3.7 mt of catch per hour. In the 2002/2003 season, the fishery made 2,244 landings. This is 

a 34.0% decrease from the previous season. In addition, the average landing decreased from 28.2 mt to 19.0 mt. 

Geographic range: Since the mid-1980s, the majority of the squid fishing harvest has occurred south of Point 

Conception. However, during the 2002/2003 season, a moderate El Nino condition resulted in nearly 60% of the 

catch landed in northern California. The northern fishery harvest ranged from Morro Bay to Fort Bragg, although 

the majority of fishing occurred within a half mile of the Monterey Bay shoreline. The Monterey Bay fishery has 

been in operation since the mid-1800s and has historical significance for California. Squid catch south of Point 

Conception accounted for only 41% of the 2002/2003 landings and declined 54% from 84,024 mt in the previous 

season to 17,387 mt. 

Seasons: This fishery occurs year-round, however, effort in this fishery differs north and south of Point Conception. 

Typically, the fishery north of Point Conception operates from April through September while the southern fishery 

is most active from October through March. El Niño conditions hamper the fishery and squid landings are minimal 

during these events, while landings in the northern fishery often increase. The La Niña event in 1999 resulted in the 

southern fishery landing squid year-round. 

Gear type: There are several gears employed in this fishery. From 1997-2001, the vast majority (98%) of vessels 

uses either purse (77%) or drum (21%) seine nets. Other types of nets used include lampara, dip and brail nets 

which are used by a few vessels in southern California. Another gear type associated with the market squid fishery 

is attracting lights that are used to aggregate spawning squid. In 2000, attracting lights were regulated and each 

vessel is now restricted to no more than 30,000 watts of lights during fishing activities. Further, to reduce light 

scatter, lights must be shielded and oriented directly downward. The lighting restrictions were enacted to avoid risks 

to nesting brown pelicans and interactions with other seabird species of concern. 

Regulations: All vessels participating in the squid fishery must have a permit. Commercial squid fishing is 

prohibited between noon on Friday and noon on Sunday of each week to allow a two-day consecutive uninterrupted 

period of spawning. A mandatory logbook program for fishing and lighting vessels has been in place since May 

2000. In May 2001, a seasonal harvest guideline of 125,000 short tons for market squid was established to limit 

further expansion of the fishery. 

Management type: This fishery was largely unregulated until 1998 when it came under more strict regulatory 

control by the Department of Fish and Game. The fishery is considered a monitored fishery in the Pacific Fishery 

Management Council’s Coastal Pelagic Species Fishery Management Plan. A state fishery management plan is to 

be adopted by the Fish and Game Commission by December 2004. The plan considers seasonal and daily catch 

limitations; weekend closures, research and monitoring programs, harvest replenishment areas, live bait and 

 

2

This fishery description was provided by Dale Sweetnam, Senior Biologist at CDFG La Jolla. 

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incidental market squid catch, restricted access programs including transferability, gear restrictions, area and time 

closures to address seabird issues, and permit fees. 

 

Comments: The squid fishery operates primarily at night and targets spawning aggregations with the use of 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. During the 1980s, California’s squid fishery 

grew rapidly in fleet size and landings when international demand for squid increased due to declining squid 

fisheries in other parts of the world. In 1997, the rapid growth of fleet size was halted by a moratorium on new 

permits. Landing records were set several times during the 1990s, but have been curtailed with the establishment of 

the 125,000 short ton seasonal harvest guideline. 

 

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. The NMFS 2001 

List of Fisheries lists an estimate of 82 vessels/persons in this fishery. 

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. 

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. 

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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 NMFS 2001 List of Fisheries lists a total of 24 vessels/persons operating in 

this fishery. 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. 

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. 

 

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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. 

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 aquaculture facilities currently licensed in Oregon. 

Non-commercial 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. 

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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. The NMFS List of Fisheries for 2001 

lists 585 vessels as participating in this fishery. 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 atsea processing vessel to provide comprehensive data on total catch, including marine mammal takes. In the 

California, Oregon, and Washington range of the fishery, the number of vessels fishing ranged between 12 and 16 

(all with observers) during 1997-2001. 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 40o

 30' 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. 

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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, northern fur seal, and northern elephant seal have been documented in the whiting fishery. 

From 1997-2001, 4 California sea lions, 2 harbor seals, 2 northern elephant seals, 1 Pacific white-sided dolphin, and 

6 Dall’s porpoise were reported taken in California/Oregon/Washington regions by this fishery. 

 

Category III, Hawaii gillnet fishery.3

Number of active permit holders: In 1997 there were 129 active commercial fishers. In 1995 there were 

approximately 115. 

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. New restrictions implemented in 2002 include that nets may not: 1) be used more than once in a 

24-hour period; 2) exceed a 12 ft stretched height limit; 3) exceed a single-panel; 4) be used at night; 5) be set within 

100 ft. of another lay net; 6) be set in more than 80 ft depths; 7) be left unattended for more than 1⁄2 hour; 8) break 

coral during retrieval and nets must be 1) registered with the Division of Aquatic Resources; 2) inspected within two 

hours after being set; 2) tagged with two marker buoys while fished. In addition to these gear restrictions, noncommercial users of lay nets may not use a net longer than 500 ft, while commercial users may use nets up to 1200 

ft in length. 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. 

 

3

Descriptions of Hawaii State managed fisheries provided by William Devick, State of Hawaii, Department of Land 

and Natural Resources, Division of Aquatic Resources, Honolulu Hawaii.

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Category III, Hawaii swordfish, tuna, billfish, mahi mahi, wahoo, and oceanic shark longline/set line fishery.4

Number of permit holders: There are 164 permits under a (1994) federal limited entry program. 

Number of active permit holders: From 1998-2002 there were 115, 122, 125, 101, and 102 vessels actively 

fishing, respectively. 

Total effort: For the years 1998-2002, there were 1,181, 1,165, 1,135, 1,075, and 1,193 trips made respectively. 

The number of hooks set has steadily increased since 1997 (15.5 million) and peaked in 2002 with 27 million hooks 

set. In 2002, most effort occurred within the U.S. EEZ (approximately 15 million hooks set), while 12 million 

hooks were set outside the U.S. EEZ. At Kingman Reef and Palmyra Atoll there were 2.1 million hooks set in 2002. 

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. The fishery is closed north of the equator to swordfish-style fishing, while tunastyle fishing is permitted with certain time/area closures. 

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). 

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. This fishery currently operates under 

restrictions which prohibit swordfish style fishing methods (deepest hooks fished at depths < 100 m, use of 

lightsticks, setting at night) in an effort to reduce sea turtle mortality (NMFS Western Pacific Pelagic Fisheries 

Biological Opinion 2001). Other sea turtle bycatch reduction methods implemented include time and area closures 

for tuna style fishing methods, limited access permit restrictions, gear modification research, and skipper workshops 

aimed at reducing sea turtle interactions. Changes in this fishery have not been in place long enough to assess their 

influence on the rate of cetacean interactions. 

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. Initially, observer coverage was 

less than 5%, increased to 10% in 2000, and has exceeded 20% in 2001 and 2002. 

 

 

4

 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 and 

Honolulu Laboratory annual longline reports.

289
Revised 03/15/2005 Appendix 1. Description of U.S. Commercial Fisheries 

Category III, Hawaii lobster trap fishery.

5 6

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. 

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. 

 

 

5

Kawamoto, K. and Samuel G. Pooley. 1999. Draft Annual report of the 1998 western pacific lobster fishery.

6

Kawamoto, K. 1999. Summary of the 1999 NWHI Lobster Fishing Season. NMFS Honolulu Laboratory.

290
Revised 03/15/2005 Appendix 1. Description of U.S. Commercial Fisheries 

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 

ex-vessel 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 

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 recategorizing 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 stealing 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 midocean 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. 

291
Revised 03/15/2005 Appendix 1. Description of U.S. Commercial Fisheries 

Table 1. The number of animals injured (I) and killed (K) reported to the Marine Mammal Authorization Program (MMAP) creported from the NMFS Observer Program for two California gillnet fisheries for the years 1998-2002. 

Species I K I K I K I K I K I K I K I K Minke whale 0 0 0 0 001 0 0 000 0 0 0 0 Sperm whale 0 1 0 1 000 0 0 000 0 0 0 0 Gray whale 0 1 0 1 000 0 0 000 0 0 0 0 Humpback whale 0 0 0 0 000 0 1 000 0 0 0 0 Short-finned pilot whale 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Pacific white-sided dolphin 0 0 0 0 000 0 0 102 0 0 0 2 Common dolphin spp. 2 5 0 9 8 29 0 35 3 15 0 25 1 6 0 7 Risso's dolphin 0 0 0 0 000 0 0 203 0 0 0 0 Northern right whale dolphin 0 0 0 0 010 3 0 6 0 11 0 1 0 5 Dall's porpoise 0 0 0 0 000 0 0 000 0 0 0 0 Unidentified small cetacean 0 0 0 0 030 0 4 100 2 2 0 0 California sea lion 3 19 0 23 0 5 0 6 0 14 0 13 1 2 0 2 Steller's sea lion 0 1 0 0 010 0 0 000 0 0 0 0 Northern elephant seal 0 0 0 4 210 2 1 106 0 0 0 1 Harbor seal 0 0 0 0 000 0 0 000 0 0 0 0 Unidentified seal 0 0 0 0 000 0 0 100 0 0 0 0 Unidentified baleen whale 0 0 0 0 010 0 0 000 0 0 0 0 Unidentified toothed whale 0 0 0 0 000 0 0 000 1 0 0 0 Total Occurrences Reported 5 27 0 38 10 41 1 46 9 41 0 60 5 11 0 17 

2000

MMAP NMFS

2001

MMAP NMFS

1998

MMAP NMFS

1999

MMAP NMFS

292
Revised 03/15/2005 Appendix 1. Description of U.S. Commercial Fisheries 

Table 2. Strandings reported to the NMFS Marine Mammal Stranding Network 1998-2002. hr = human-related strandings. 

Species

CA hr OR/WA hr CA hr OR/WA hr CA hr OR/WA hr CA hr OR/WA hr 

Harbor Porpoise 37 4 25 0 31 2 7 0 20 2 6 1 12 4 15 1 Dall's Porpoise 2 0 2 0 4 0 3 0 3 0 9 1 2 1 6 0 Pac. White-sided Dolphin 5 0 1 0 4 1 1 0 3 0 0 0 6 2 0 0 Risso's Dolphin 3 0 0 0 2 4 1 0 6 0 1 0 3 0 0 0 Bottlenose Dolphin 4 0 0 0 3 0 0 0 12 0 0 0 14 0 0 0 Common Dolphin 35 1 0 0 37 0 0 0 30 1 0 0 33 4 0 0 Striped Dolphin 2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 N. Right Whale Dolphin 1 0 0 0 2 0 0 0 0 0 0 0 5 0 0 0 Rough-toothed Dolphin 1 0 0 0 2 0 0 0 0 0 0 0 0 0 0 0 Killer Whale 0 0 1 0 1 0 1 0 0 0 0 0 0 0 1 0 Short-finned Pilot Whale 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 Baird's Beaked Whale 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Stejneger's Beaked Whale 0 0 0 0 1 0 0 0 0 0 0 0 0 0 2 0 Cuvier's Beaked Whale 2 0 1 0 0 0 0 0 1 0 0 0 0 0 1 1 Peruvian Beaked Whale 1 1 0 0 0 0 0 0 0 0 0 0 1 0 0 0 Unident. Beaked Whale 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 Pygmy Sperm Whale 6 0 0 0 1 0 0 0 0 0 0 0 1 0 0 0 Dwarf Sperm Whale 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 Sperm Whale 0 0 0 0 1 0 0 0 0 0 1 0 0 0 0 0 Gray Whale 3 3 4 1 47 6 31 2 58 8 25 0 5 1 1 0 Minke Whale 1 0 1 0 1 0 0 0 0 0 0 0 1 0 0 0 Blue Whale 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Fin Whale 1 0 0 0 0 0 0 0 0 0 0 0 1 1 0 0 Sei Whale 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Humpback Whale 2 0 2 0 0 0 0 0 4 3 0 0 2 1 0 0 Unidentified Cetacean 0 0 0 0 0 0 3 0 1 0 4 1 0 0 0 0 Unidentified Porpoise 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Unidentified Dolphin 12 0 5 0 13 2 2 0 11 0 2 0 9 0 2 0 Unidentified Whale 2 0 0 0 3 1 0 0 1 0 0 0 4 4 0 0 Unident. Balaenopterid 0 0 1 0 0 0 1 0 0 0 0 0 2 0 0 0 Northern Fur Seal 21 0 1 0 7 1 3 0 3 0 6 0 2 0 1 1 Guadalupe Fur Seal 3 0 0 0 5 0 0 0 1 0 0 0 3 1 0 0 Steller (Nthn) Sea Lion 10 2 7 0 11 1 3 0 10 2 5 0 9 0 4 0 California Sea Lion 2576 199 75 9 596 52 35 3 1268 67 32 5 990 98 27 1 Unidentified Sea Lion 0 0 0 0 0 0 9 1 1 0 8 0 0 0 17 0 Harbor Seal 313 21 121 7 135 7 176 4 230 13 148 8 152 8 170 8 Northern Elephant Seal 409 6 24 0 200 1 2 0 211 3 11 0 216 4 11 0 Unidentified Seal 0 0 5 0 0 0 26 1 0 0 17 1 0 0 11 1 Unidentified Pinniped 236 0 88 0 112 0 13 0 133 0 8 0 110 0 9 0 Totals for Cetaceans 120 9 43 1 154 16 50 2 152 14 48 3 101 18 28 2 Totals for Pinnipeds 3568 228 321 16 1066 62 267 9 1857 85 235 14 1482 111 250 11 

0.100.07

1998-2002 human-related fraction (Cetaceans)

1998-2002 human-related fraction (Pinnipeds)

1998 1999 2000 2001

293
Revised 03/15/2005 Appendix 1. Description of U.S. Commercial Fisheries 

Table 3. Characteristics of Category I and Category II gillnet fisheries in California. Fishery Species Mesh Size Water Depth Set Duration Deployment Category II CA/OR thresher shark/swordfish drift gillnet fishery 

swordfish/shark 14 to 22 inches Ranges from 90 to 

4600 meters 

Typically 8 to 15 hrs 

Drift net only 

Halibut/angel shark 8.5 inch < 70 meters 24 hrs Set net Barracuda 3.5 inch < 12 hrs Drift net Leopard Shark 7.0 to 9.0 inch < 90 meters Perch/Croaker 3.5 to 4.0 inch < 40 meters < 24 hrs Set net Rockfish 4.5 to 7.5 inch > 90 meters 12 to 18 hrs Set net Soupfin shark 6.0 to 8.5 inch > 50 meters 24 hrs Set net 

Category I CA angel shark/halibut and other species set gillnet fishery (>3.5 inch mesh) 

Miscellaneous shark 6.0 to 14 inch < 70 meters 8 to 24 hrs Drift, some set ne

Category II CA Yellowtail, barracuda, white seabass, and tuna drift gillnet fishery 

White seabass, yellowtail, barracuda, white seabass, and tuna 

Typically 6.5 inch 15 to 90 meters 8 to 24 hrs Mostly drift net 

294
Revised 03/15/2005 Appendix 1. Description of U.S. Commercial Fisheries 

Figure 1 – 3. Locations of 587, 526, and 444 observed sets in the swordfish/thresher shark drift gillnet fishery in 1998, 1999, and 2000

estimated 3353, 2634, and 1936 sets were fished in 1998, 1999, and 2000, respectively. 

W129 W126 W123 W120 W117

N30N34N38N42N46

WASHINGTON

OREGON

CALIFORNIA

Figure 1

WASHINGTON WASHINGTON

N46 N46

OREGON OREGON

N42 N42

CALIFORNIA CALIFORNI

N38 N38N34 N34

Figure 2 N Figure 3 N30 30

W129 W126 W123 W120 W117 W129 W126 W123 W120 

295
Revised 03/15/2005 Appendix 1. Description of U.S. Commercial Fisheries 

Figures 4-6. Locations of 339 and 360 observed sets in the swordfish/thresher shark drift gillnet fishery in 2001 and 2002, respectivelylocations of 199 observed marine mammal entanglements resulting in injury or death over the period 1998-2002. There were approximduring this period.

W129 W126 W123 W120 W117

N30N34N38N42N46

WASHINGTON

OREGON

Figure 4

CALIFORNIA

WASHINGTON WASHIN

N46 N46

OREGON OREGON

N42 N42

CALIFORNIA CALI

N38 N38

N34 N34

N Figure 5 Figure 6 30 N30

W129 W126 W123 W120 W117 W129 W126 W123 

296
Revised 03/15/2005 Appendix 1. Description of U.S. Commercial Fisheries 

CA drift gillnet fishery for thresher

shark/swordfish

20%

16%

18%

13%

14% 10%

4%

23% 20% 22%

20%

12% 23% 18%

0

1000

2000

3000

4000

5000

6000

19901991199219931994199519961997199819992000200120022003

Year

Effort (d

ays)

Figure 7. Estimated (gray) and observed (black) days of fishing effort for 1990-2003 in the California/Oregon thresher

shark/swordfish drift gillnet fishery (≥ 14 inch mesh). Percent observer coverage for each year is shown above the bars. 

CA set gillnet fishery for halibut/angel shark

8.5-inch mesh

0% 5%

10%

13% 15%

8% 0% 0% 0% 0%

4% 2% 0% 0%

0

2000

4000

6000

8000

19901991199219931994199519961997199819992000200120022003

Year

Effort (days)

Figure 8. Estimated (gray) and observed (black) days of fishing effort for 1990-2003 in the California angel shark/halibut

set gillnet fishery (> 3.5 inch mesh). The fishery was observed only from 1990-94 and again in 1999 and 2000. Percent 

observer coverage for each year is shown above the bars. 

297
Revised 03/15/2005 Appendix 1. Description of U.S. Commercial Fisheries 

W123 W122 W121 W120 W119 W118 W117

N31N32N33N34N35N36N37N38

Monterey Bay

Pt. Arguello

Long Beach

S.D.

Morro Bay

63 26 16

178

54

5

1 4

3 9 18

172 276220

34 251 12 68 21

2 192 2

47 132

3 93 242314 4

3 60 1

2 157

2 27

Reported days of effort by CDFG block in the set gillnet fishery for halibut/angel shark in 1998. A total of 2,821 days are shown. Therewere an additional 15 effort days reported without block number from Morro Bay.

14

21 14 7

5

1

10

2 1 4

5

2

1 8 20

1

2

2

5

W123.5 W122.5 W121.5 W120.5 W119.

N31N32N33N34N35N36N37N38

1 16

290 116 11

11 1 130 7

91

44

1 31

1

1 2 7

3

5 157 2

1 76 63 5 576 

61 7 15 20 1 

3 4 

4 1 1

1

1 

1 

Monterey Bay

Morro Bay

Pt. Arguello

Reported days of effort by CDFG block halibut/angel shark in 1999. A total of 4were an additional 3 effort days reporteMonterey Bay, 8 days from Morro Bay, a

Figure 10. Reported fishing effort in days in set gillnet fishery for 1999. 

Figure 9. Reported fishing effort in days in the halibut/angel shark set gillnet fishery for 1998. 

298
Revised 03/15/2005 Appendix 1. Description of U.S. Commercial Fisheries 

W123.5 W122.5 W121.5 W120.5 W119.5 W118.5 W117.5

N31N32N33N34N35N36N37N38

46 141 608 121

45 5 2 12 261

10 2 9 4

175

2 22 511 832 2

173

218

64

Monterey Bay

Morro Bay

Pt. Arguello

Long Beach

S.D.

2 1

85 33 17

90

2

24

1 1

1

150

88

8

5

41

5

3

2 2 156

3

12 3

1

7 24

Reported days of effort by CDFG block in the set gillnet fishery forhalibut/angel shark in 2000. A total of 3,989 days are shown. Therewere an additional 2 effort days reported without block number fromMonterey Bay and 21 days from Morro Bay.

W123.5 W122.5 W121.5 W120.5 W

N31N32N33N34N35N36N37N38

3 3

24 18 2 

6 

Monterey Bay

Morro Bay

Pt. Arguello

26

272

105

166 12

Reported days of effort by CDFG halibut/angel shark in 2001. A totwere an additional 7 effort days reMorro Bay.

2

1

2 2

1

4 

Figure 12. Reported fishing effort in days set gillnet fishery for 2001. 

Figure 11. Reported fishing effort in days in the halibut/angel shark set gillnet fishery for 2000. 

299
Revised 03/15/2005 Appendix 1. Description of U.S. Commercial Fisheries 

-123 -122.5 -122 -121.5 

34.5

35

35.5

36

36.5

37

37.5

38

144

2 addit

from g

Estimated days fishing effset gillnet fishery by CDFG Monterey Bay and Morro B

9

-121 -120.5 -120 -119.5 -119 -118.5 -118 -117.5 -117

32

32.5

33

33.5

34

34.5

35

-121 -120.5 -120 -119.5 -119 -118.5 -118 -117.5 -117

32

32.5

33

33.5

34

34.5

35

160

3

70

Estimated days fishing effort in the halibut/angel shark set gillnet fishery by CDFG block for calendar year 2002. Southern California, Ventura, and Channel Islands strata are shown.

97 5 36 26 1

15

1

20

154 1

5 756 297 17

144

1

56 152 1

56 645

152

32

1

3

5

37

1 2

3

Figure 13. Reported fishing effort in days in the halibut/angel shark set gillnet fishery for 2002 (southern California). 

Figure 14. Reported fishing effort in dayfishery for 2002 (central California). 

300
Revised 03/15/2005 Appendix 1. Description of U.S. Commercial Fisheries 

Figure 15. Observed set locations in the Hawaii-based longline fishery, 1994-2002. 

301
Revised 03/15/2005 

Appendix 2. Cetacean Survey Effort 

This Appendix presents a summary of survey effort from which cetacean sighting locations were

plotted in the stock assessment reports. In Figures 1-6, the thick solid line represents the outer

boundary of all surveys and the thin dashed line represents the U.S. EEZ. 

Figure 1. Transect lines completed

during a 1991 winter/spring aerial survey

of California waters (Forney et al. 1995). 

Figure 2. Transect lines completed 

during a 1992 winter/spring aerial survey

of California waters (Forney et al. 1995). 

Figure 3. Transect lines completed 

during a 1991 summer/autumn vessel

survey of California waters (Barlow 

1995). 

Figure 4. Transect lines completed

during a 1993 summer/autumn vessel

survey of California waters (Mangels and 

Gerrodette 1994). 

Figure 5. Transect lines completed 

during a 1996 summer/autumn vessel

survey of California, Oregon, and

Washington waters (Barlow 1997; Von

Saunder and Barlow 1999). 

Figure 6. Transect lines completed 

during a 2001 summer/autumn vessel

survey of California, Oregon, and 

Washington waters (Appler et al. 2004). 

W132 W129 W126 W123 W120 W117

N30

N34

N38

N42

N46

WASHINGTON

OREGON

CALIFORNIA

W132 W129 W126 W123 W120 W117

N30

N34

N38

N42

N46

WASHINGTON

OREGON

CALIFORNIA

W132 W129 W126 W123 W120 W117

WASHINGTON

N46

OREGON

N42

CALIFORNIA

N38

N34

N30

W132 W129 W126 W123 W120 W117

N30

N34

N38

N42

N46

WASHINGTON

OREGON

CALIFORNIA

W132 W129 W126 W123 W120 W117

N30

N34

N38

N42

N46

WASHINGTON

OREGON

CALIFORNIA

W132 W129 W126 W123 W120 W117

WASHINGTON

N46

OREGON

N42

CALIFORNIA

N38

N34

N30

302
Revised 03/15/2005 

Appendix 2. Ce

N44

Figure 7. Harbor porpoise stock boundaries in California and southern Oregon. Stippled area shows approximate harbor porpoise habitat between 0-200 meters. Thick solid line represent surveytransects flown during 1989-2002 aerial surveys (Forney et al.1991; Forney 1995; Carretta and Forney 2004). Survey coveragenorth of the California/Oregon border has been completed by theNational Marine Mammal Laboratory (Laake et al. 1998).

Figure 8. Coastline section (in bold) suduring 1990-2000 coastal bottlenose dolphisurveys in southern and central California (Cet al. 1998, NMFS unpublished data).

W128.0 W126.0 W124.0 W122.0 W120.0 W118.0

.0 N4

N34.0N36.0N38.0N40.0N42.0 Oregon

Northe California rn California/Southern Oregon

San FranciscoRussian River

Monterey Bay

Morro Bay

Cape Blanco

Monterey Bay

Cape Mendocino

Point Conception

Point Arena

Morro Bay

Oregon/Washington coast

Russian River

W123 W122

0

N39

N38 San Francisco

N37

Monterey Bay California

N36

N35

Point Conception

N34 Los Angeles

Pacific Ocean

N33 San 

N32

N31

W121 W120 W119 W118 W117 

303
Revised 03/15/2005 

Appendix 2. Cetacean Survey Effort 

N3

Figure 9. Transect lines completed during a 2002 summer/autumn vessel survey of 

Hawaiian waters (Barlow et al. 2004). Thick outer survey boundary line represents the 

U.S. EEZ and the inner thick line represents a separate ‘Main Hawaiian Islands’ stratum. 

Thin lines represent completed transect lines. 

References 

Appler, J., J. Barlow, and S. Rankin, 2004. Marine mammal data collected during the Oregon, California and

Washington line-transect expedition (ORCAWALE) conducted aboard the NOAA ships McARTHUR and

DAVID STARR JORDAN, July - December 2001. NOAA Techinal Memorandum NOAA-TM-NMFSSWFSC-359. 32p. 

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. 

Barlow, J., S. Rankin, E. Zele, and J. Appler. 2004. Marine mammal data collected during the Hawaiian Islands

Cetacean and Ecosystem Assessment Survey (HICEAS) conducted aboard the NOAA ships McArthur and 

David Starr Jordan, July - December 2002. U.S. Department of Commerce, NOAA Technical

Memorandum, NMFS-SWFSC-362. 39 p. 

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(3):655-675. 

Carretta, J.V. and K.A. Forney. 2004. Preliminary estimates of harbor porpoise abundance in California from 1999

and 2002 aerial surveys. SWFSC Administrative Report LJ-04-01, available from Southwest Fisheries 

Science Center, 8604 La Jolla Shores Drive, La Jolla, CA, USA. 13pp. 

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. 

W180 W175 W170 W165 W160 W155 W150

N10

N15

N20

N25

N30

5

304
Revised 03/15/2005 

Appendix 2. Cetacean Survey Effort 

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. 

Laake, J., J. Calambokidis, S. Osmek. 1998. Survey report for the 1997 aerial surveys for harbor porpoise and other 

marine mammals of Oregon, Washington, and British Columbia outside waters. Alaska Fisheries Science 

Center Processed Report 98-10. pp. 77-97. 

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.

305
Append

Information for stocks which were revised in 2004 appears shaded. SUMMARY OF 2004 PACIFIC MARINE MAMMAL STOCK ASSESSMENT REPORTS 

Species Stock Area Region 

NMFS 

Center Nmin Rmax Fr PBR 

Total 

Annual 

Mortality + 

Serious 

Injury 

California sea lion U.S. PAC SWC 138,881 0.12 1.0 8,333 1,562 

Harbor seal California PAC SWC 25,720 0.12 1.0 1,543 ≥ 389 Harbor seal Oregon/Washington Coast PAC AKC 22,380 0.12 1.0 1,343 ≥17 Harbor seal Washington Inland Waters PAC AKC 12,844 0.12 1.0 771 ≥34 

Northern Elephant Seal California breeding PAC SWC 60,547 0.083 1.0 2,513 ≥88 

Guadalupe Fur Seal Mexico to California PAC SWC 3,028 0.12 0.5 91 0 

Northern Fur Seal San Miguel Island PAC AKC 4,190 0.086 1.0 180 0.8 

Monk Seal Hawaii PAC PIC 1,378 0.07 0.1 n/a n/a 

Harbor porpoise Morro Bay PAC SWC 1,206 0.04 0.4 10 4.5 Harbor porpoise Monterey Bay PAC SWC 1,149 0.04 0.45 10 9.5 Harbor porpoise San Francisco – Russian River PAC SWC 6,254 0.04 0.5 63 ≥ 0.8 Harbor porpoise Northern CA/Southern OR PAC SWC 12,940 0.04 1.0 259 ≥ 0 Harbor porpoise Oregon/Washington Coast PAC AKC 28,967 0.04 0.5 290 3.2 Harbor porpoise Washington Inland Waters PAC AKC 2,545 0.04 0.4 20 15.2 

Dall’s porpoise California/Oregon/Washington PAC SWC 75,915 0.04 0.48 729 7 

Pacific white-sided dolphin California/Oregon/Washington PAC SWC 39,822 0.04 0.48 382 ≥ 5.4 

Risso’s dolphin California/Oregon/Washington PAC SWC 12,748 0.04 0.4 115 3.6 

Bottlenose dolphin California Coastal PAC SWC 186 0.04 0.5 1.9 0 Bottlenose dolphin 

California/Oregon/Washington 

Offshore PAC SWC 3,053 0.04 0.5 31 0 

Striped dolphin California/Oregon/Washington PAC SWC 9,165 0.04 0.5 92 0 

306
Append

Information for stocks which were revised in 2004 appears shaded. SUMMARY OF 2004 PACIFIC MARINE MAMMAL STOCK ASSESSMENT REPORTS 

Species Stock Area Region 

NMFS 

Center Nmin Rmax Fr PBR 

Total 

Annual 

Mortality + 

Serious 

Injury 

Common dolphin, short-beaked California/Oregon/Washington PAC SWC 365,617 0.04 0.5 3,656 93 

Common dolphin, long-beaked California/Oregon/Washington PAC SWC 25,163 0.04 0.48 242 11 

Northern right whale dolphin California/Oregon/Washington PAC SWC 16,417 0.04 0.5 164 23 

Killer whale Eastern North Pacific Offshore PAC SWC 361 0.04 0.5 3.6 0 Killer whale 

Eastern North Pacific Southern 

Resident PAC AKC 83 0.04 0.5 0.8 0 

Short-finned pilot whale California/Oregon/Washington PAC SWC 149 0.04 0.4 1.2 1.0 

Baird’s beaked whale California/Oregon/Washington PAC SWC 152 0.04 0.5 1.5 0 

Mesoplodont beaked whales California/Oregon/Washington PAC SWC 645 0.04 0.5 6.5 0 

Cuvier’s beaked whale California/Oregon/Washington PAC SWC 1,121 0.04 0.5 11 0 

Pygmy Sperm whale California/Oregon/Washington PAC SWC 119 0.04 0.5 1 0 

Sperm whale California/Oregon/Washington PAC SWC 885 0.04 0.1 1.8 1.0 

Humpback whale Eastern North Pacific PAC SWC 943 0.08 0.1 1.6 ≥ 1.2 

Blue whale Eastern North Pacific PAC SWC 1,384 0.04 0.1 1.4 0.2 

Fin whale California/Oregon/Washington PAC SWC 2,541 0.04 0.1 5.1 1.4 

Bryde’s whale California/Oregon/Washington PAC SWC 11,163 0.04 0.5 n/a 0 

Sei whale Eastern North Pacific PAC SWC 35 0.04 0.1 0.1 0 

Minke whale California/Oregon/Washington PAC SWC 585 0.04 0.45 5.8 0 

Rough-toothed dolphin Hawaii PAC SWC 13,184 0.04 0.5 132 n/a 

Risso’s dolphin Hawaii PAC SWC 1,426 0.04 0.5 14 n/a 

Bottlenose dolphin Hawaii PAC SWC 2,046 0.04 0.5 20 ≥ 0.2 

307
Append

Information for stocks which were revised in 2004 appears shaded. SUMMARY OF 2004 PACIFIC MARINE MAMMAL STOCK ASSESSMENT REPORTS 

Species Stock Area Region 

NMFS 

Center Nmin Rmax Fr PBR 

Total 

Annual 

Mortality + 

Serious 

Injury 

Pantropical spotted dolphin Hawaii PAC SWC 7,362 0.04 0.5 59 ≥ 0.8 

Spinner dolphin Hawaii PAC SWC 1,690 0.04 0.5 17 0 

Striped dolphin Hawaii PAC SWC 7,078 0.04 0.5 71 n/a 

Fraser’s dolphin Hawaii PAC SWC 7,917 0.04 0.5 79 n/a 

Melon-headed whale Hawaii PAC SWC 1,386 0.04 0.5 14 n/a 

Pygmy killer whale Hawaii PAC SWC 382 0.04 0.5 3.8 n/a 

False killer whale Hawaii PAC SWC 128 0.04 0.5 1.0 6.8 

Killer whale Hawaii PAC SWC 250 0.04 0.5 2.5 n/a 

Pilot whale, short-finned Hawaii PAC SWC 5,986 0.04 0.5 60 0.8 

Blainville’s beaked whale Hawaii PAC SWC 1,204 0.04 0.5 9.6 0.8 

Indopacetus pacificus Hawaii PAC SWC 371 0.04 0.5 3.7 n/a 

Cuvier’s beaked whale Hawaii PAC SWC 6,919 0.04 0.5 69 n/a 

Pygmy sperm whale Hawaii PAC SWC 4,082 0.04 0.5 41 n/a 

Dwarf sperm whale Hawaii PAC SWC 11,555 0.04 0.5 116 n/a 

Sperm whale Hawaii PAC SWC 5,531 0.04 0.1 11 n/a 

Blue whale Hawaii PAC SWC n/a 0.04 0.1 n/a n/a 

308
Append

Information for stocks which were revised in 2004 appears shaded. SUMMARY OF 2004 PACIFIC MARINE MAMMAL STOCK ASSESSMENT REPORTS 

Species Stock Area Region 

NMFS 

Center Nmin Rmax Fr PBR 

Total 

Annual 

Mortality + 

Serious 

Injury 

Fin whale Hawaii PAC SWC 101 0.04 0.1 0.2 n/a 

Sei whale Hawaii PAC SWC 37 0.04 0.1 0.1 n/a 

Minke whale Hawaii PAC SWC n/a 0.04 0.5 n/a n/a 

Bryde’s whale Hawaii PAC SWC 373 0.04 0.5 3.7 n/a 

309
Appendix 4. Summary of U.S. Pacific Marine Mammal Stock Assessment Report Revisions.

U.S. Pacific Marine Mammal Stock Year Last Revised

Pinnipeds

California sea lion (Zalophus californianus californianus): U.S. Stock 2003 

Harbor seal (Phoca vitulina richardsi): California stock 2003 

Harbor seal (Phoca vitulina richardsi): Oregon and Washington Coastal Waters Stock 2003 

Harbor seal (Phoca vitulina richardsi): Washington Inland Waters Stock 2003 

Northern elephant seal (Mirounga angustirostris): California Breeding Stock 2003 

Guadalupe fur seal (Arctocephalus townsendi) 2000 

Northern fur seal (Callorhinus ursinus): San Miguel Island Stock 2003 

Hawaiian monk seal (Monachus schauinslandi) 2004 

Cetaceans (Eastern North Pacific & California/Oregon/Washington Stocks)

Harbor porpoise (Phocoena phocoena): Morro Bay Stock 2004 

Harbor porpoise (Phocoena phocoena): Monterey Bay Stock 2004 

Harbor porpoise (Phocoena phocoena): San Francisco-Russian River Stock 2004 

Harbor porpoise (Phocoena phocoena): Northern California/Southern Oregon Stock 2003 

Harbor porpoise (Phocoena phocoena): Oregon/Washington Coast Stock 2003 

Harbor porpoise (Phocoena phocoena): Washington Inland Waters Stock 2003 

Dall’s porpoise (Phocoenoides dalli): California/Oregon/Washington Stock 2003 

Pacific white-sided dolphin (Lagenorhynchus obliquidens): 

California/Oregon/Washington, Northern and Southern Stocks 2003 

Risso’s dolphin (Grampus griseus): California/Oregon/Washington Stock 2003 

Bottlenose dolphin (Tursiops truncatus): California Coastal Stock 2003 

Bottlenose dolphin (Tursiops truncatus): California/Oregon/Washington Offshore Stock 2003 

Striped dolphin (Stenella coeruleoalba): California/Oregon/Washington Stock 2003 

Short-beaked common dolphin (Delphinus delphis): California/Oregon/Washington Stock 2003 

Long-beaked common dolphin (Delphinus capensis): California Stock 2003 

Northern right whale dolphin (Lissodelphis borealis): California/Oregon/Washington Stock 2003 

Killer whale (Orcinus orca): Eastern North Pacific Offshore Stock 2003 

Killer whale (Orcinus orca): Eastern North Pacific Southern Resident Stock 2004 

Short-finned pilot whale (Globicephala macrorhynchus): California/Oregon/Washington 

St k

2003 

Baird’s beaked whale (Berardius bairdii): California/Oregon/Washington Stock 2003 

Mesoplodont beaked whales (Mesoplodon spp.): California/Oregon/Washington Stocks 2003 

Cuvier’s beaked whale (Ziphius cavirostris): California/Oregon/Washington Stock 2003 

Pygmy sperm whale (Kogia breviceps): California/Oregon/Washington Stock 2003 

Dwarf sperm whale (Kogia sima): California/Oregon/Washington Stock 2003 

310
Appendix 4. Summary of U.S. Pacific Marine Mammal Stock Assessment Report Revisions.

U.S. Pacific Marine Mammal Stock Year Last Revised

Sperm whale (Physeter macrocephalus): California/Oregon/Washington Stock 2003 

Humpback whale (Megaptera novaeangliae): Eastern North Pacific Stock 2004 

Blue whale (Balaenoptera musculus): Eastern North Pacific Stock 2004 

Fin whale (Balaenoptera physalus): California/Oregon/Washington Stock 2003 

Bryde’s whale (Balaenoptera edeni): Eastern Tropical Pacific Stock 2000 

Sei whale (Balaenoptera borealis): Eastern North Pacific Stock 2003 

Minke whale (Balaenoptera acutorostrata): California/Oregon/Washington Stock 2003 

Cetaceans (Hawaii Stocks)

Rough-toothed dolphin (Steno bredanensis): Hawaii Stock 2004 

Risso’s dolphin (Grampus griseus): Hawaii Stock 2004 

Bottlenose dolphin (Tursiops truncatus): Hawaii Stock 2004 

Pantropical spotted dolphin (Stenella attenuata): Hawaii Stock 2004 

Spinner dolphin (Stenella longirostris): Hawaii Stock 2004 

Striped dolphin (Stenella coeruleoalba): Hawaii Stock 2004 

Fraser’s dolphin (Lagenodelphis hosei): Hawaii Stock 2004 

Melon-headed whale (Peponocephala electra): Hawaii Stock 2004 

Pygmy killer whale (Feresa attenuata): Hawaii Stock 2004 

False killer whale (Pseudorca crassidens): Hawaii Stock 2004 

Killer whale (Orcinus orca): Hawaii Stock 2004 

Short-finned pilot whale (Globicephala macrorhynchus): Hawaii Stock 2004 

Blainville’s beaked whale (Mesoplodon densirostris): Hawaii Stock 2004 

Longman’s beaked whale (Indopacetus pacificus): Hawaii Stock 2004 

Cuvier’s beaked whale (Ziphius cavirostris): Hawaii Stock 2004 

Pygmy sperm whale (Kogia breviceps): Hawaii Stock 2004 

Dwarf sperm whale (Kogia sima): Hawaii Stock 2004 

Sperm whale (Physeter macrocephalus): Hawaii Stock 2004 

Blue whale (Balaenoptera musculus): Western North Pacific Stock 2004 

Fin whale (Balaenoptera physalus): Hawaii Stock 2004 

Sei whale (Balaenoptera borealis): Hawaii Stock 2004 

Minke whale (Balaenoptera acutorostrata): Hawaii Stock 2004 

Bryde’s whale (Balaenoptera edeni): Hawaii Stock 2004 

311
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 mid-1970'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. 

312
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 etseq.). 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 

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 

313
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. 

314
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. 

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 

315
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. 

316