MARCH 2004

NOAA-TM-NMFS-SWFSC-358

U.S. DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

National Marine Fisheries Service

Southwest Fisheries Science Center

NOAA Technical Memorandum NMFS

James V. Carretta, Karin A. Forney, Marcia M. Muto,

Jay Barlow, Jason Baker, and Mark Lowry

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U.S. PACIFIC MARINE MAMMAL STOCK ASSESSMENTS: 2003

with contributions from

David Cantillon, Annette Henry, Jane McCrae, Don Petersen, and Joe Cordaro
ii

TABLE OF CONTENTS

Stock assessments revised in 2003 are shown in bold; all others are reprinted unrevised as they appear in the 2001/2002

Pacific Region Stock Assessment Reports (Carretta et al. 2001, 2002).

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 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50

HARBOR PORPOISE (Phocoena phocoena): Monterey Bay Stock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55

HARBOR PORPOISE (Phocoena phocoena): San Francisco-Russian River Stock . . . . . . . . . . . . . . . . . . . . . 60

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 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84

RISSO'S DOLPHIN (Grampus griseus): California/Oregon/Washington Stock . . . . . . . . . . . . . . . . . . . . . . . 89

BOTTLENOSE DOLPHIN (Tursiops truncatus): California Coastal Stock . . . . . . . . . . . . . . . . . . . . . . . . . . 93

BOTTLENOSE DOLPHIN (Tursiops truncatus): California/Oregon/Washington Offshore Stock . . . . . . . 97

STRIPED DOLPHIN (Stenella coeruleoalba): California/Oregon/Washington Stock . . . . . . . . . . . . . . . . . 101

SHORT-BEAKED COMMON DOLPHIN (Delphinus delphis): California/Oregon/Washington Stock . . 105

LONG-BEAKED COMMON DOLPHIN (Delphinus capensis): California Stock . . . . . . . . . . . . . . . . . . . . 111

NORTHERN RIGHT-WHALE DOLPHIN (Lissodelphis borealis): California/Oregon/Washington . . . . . 116

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

KILLER WHALE (Orcinus orca): Eastern North Pacific Southern Resident Stock . . . . . . . . . . . . . . . . . . . 126

SHORT-FINNED PILOT WHALE (Globicephala macrorhynchus): California/Oregon/Washington . . . . 132

BAIRD'S BEAKED WHALE (Berardius bairdii): California/Oregon/Washington Stock . . . . . . . . . . . . . . 137

MESOPLODONT BEAKED WHALES (Mesoplodon spp.): California/Oregon/Washington Stocks . . . . . 141

CUVIER'S BEAKED WHALE (Ziphius cavirostris): California/Oregon/Washington Stock . . . . . . . . . . . 145

PYGMY SPERM WHALE (Kogia breviceps): California/Oregon/Washington Stock . . . . . . . . . . . . . . . . . 149

DWARF SPERM WHALE (Kogia sima): California/Oregon/Washington Stock . . . . . . . . . . . . . . . . . . . . . 153

SPERM WHALE (Physeter macrocephalus): California/Oregon/Washington Stock . . . . . . . . . . . . . . . . . . 156

HUMPBACK WHALE (Megaptera novaeangliae): Eastern North Pacific Stock . . . . . . . . . . . . . . . . . . . . . 162

BLUE WHALE (Balaenoptera musculus): Eastern North Pacific Stock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 170

FIN WHALE (Balaenoptera physalus): California/Oregon/Washington Stock . . . . . . . . . . . . . . . . . . . . . . . 175

BRYDE'S WHALE (Balaenoptera edeni): Eastern Tropical Pacific Stock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 180
iii

SEI WHALE (Balaenoptera borealis): Eastern North Pacific Stock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 184

MINKE WHALE (Balaenoptera acutorostrata): California/Oregon/Washington Stock . . . . . . . . . . . . . . . . 188

CETACEANS - HAWAII

ROUGH-TOOTHED DOLPHIN (Steno bredanensis): Hawaiian Stock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193

RISSO'S DOLPHIN (Grampus griseus): Hawaiian Stock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 196

BOTTLENOSE DOLPHIN (Tursiops truncatus): Hawaiian Stock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 199

PANTROPICAL SPOTTED DOLPHIN (Stenella attenuata): Hawaiian Stock . . . . . . . . . . . . . . . . . . . . . . . 203

SPINNER DOLPHIN (Stenella longirostris): Hawaiian Stock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 206

STRIPED DOLPHIN (Stenella coeruleoalba): Hawaiian Stock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 210

MELON-HEADED WHALE (Peponocephala electra): Hawaiian Stock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 213

PYGMY KILLER WHALE (Feresa attenuata): Hawaiian Stock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 216

FALSE KILLER WHALE (Pseudorca crassidens): Hawaiian Stock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 218

KILLER WHALE (Orcinus orca): Hawaiian Stock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 222

SHORT-FINNED PILOT WHALE (Globicephala macrorhynchus): Hawaiian Stock . . . . . . . . . . . . . . . . . 224

BLAINVILLE'S BEAKED WHALE (Mesoplodon densirostris): Hawaiian Stock . . . . . . . . . . . . . . . . . . . . 227

CUVIER'S BEAKED WHALE (Ziphius cavirostris): Hawaiian Stock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 230

PYGMY SPERM WHALE (Kogia breviceps): Hawaiian Stock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 233

DWARF SPERM WHALE (Kogia sima): Hawaiian Stock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 235

SPERM WHALE (Physeter macrocephalus): Hawaiian Stock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 237

BLUE WHALE (Balaenoptera musculus): Hawaiian Stock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 241

FIN WHALE (Balaenoptera physalus): Hawaiian Stock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 244

BRYDE'S WHALE (Balaenoptera edeni): Hawaiian Stock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 246

APPENDICES

APPENDIX 1: Description of U.S. Commercial Fisheries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 248

APPENDIX 2: Cetacean Survey Effort . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 276

APPENDIX 3: Summary of 2003 U.S. Pacific Marine Mammal Stock Assessment Reports . . . . . . . . . . . . . . . . 279

APPENDIX 4: Chronology of U. S. Pacific Stock Assessment Reports, 1995-2003 . . . . . . . . . . . . . . . . . . . . . . . 283

APPENDIX 5: U.S. Fish and Wildlife Service California & Washington sea otter stock assessments . . . . . . . . . 287
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 42 Pacific marine mammal stocks under NMFS

jurisdiction. Information on the remaining 14 Pacific region stocks is reprinted without revision and also appears in the

2001 and 2002 reports (Carretta et al. 2001, 2002). Stock Assessments for Alaskan marine mammals are published by

the National Marine Mammal Laboratory (NMML) in a separate report. 

The 42 revised stock assessments in this report include stocks studied by the Southwest Fisheries Science Center

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

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

southern resident killer whale, Washington inland waters harbor seal, Oregon/Washington coast harbor seal, Washington

inland waters harbor porpoise, Oregon/Washington coast harbor porpoise, and San Miguel Island northern fur seal.

Honolulu laboratory staff prepared the report on the Hawaiian monk seal. SWFSC, La Jolla Laboratory staff prepared

stock assessments for the remaining 35 stocks. 

New abundance estimates are available for 26 stock assessments prepared by the Southwest Fisheries Science

Center. The report for the California/Oregon/Washington stock of pygmy sperm whale (Kogia sima), which had been

eliminated in 2000 due to the rarity of sighting or stranding records along the U.S. west coast, has been reinstated in this

volume because of recent strandings in southern California. 

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.

Any omissions or errors are the sole responsibility of the authors. 

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

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

or comments which would improve future stock assessment reports.

References:

Carretta, J.V., M.M. Muto, J. Barlow, and J. Baker. 2002. U.S. Pacific Marine Mammal Stock Assessments: 2002.

U.S. Department of Commerce, NOAA Technical Memorandum NMFS-SWFSC-346. 286p.

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. Department of Commerce, NOAA Technical Memorandum NMFS-SWFSC-317.

280p.

Cover photograph: Northern elephant seals at San Miguel Island, California. Photographed by Mark S. Lowry.
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125 120 115 110 105 100

West Longitude

20

25

30

35

40

45

North 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.

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.

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.

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
2

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).

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%.

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 slight

decrease (thick line) and net production averages 12.5%. Maximum net productivity rates cannot be estimated from

available data.
3

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 humanrelated 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 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
4

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 centershowed 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 stranding

databases shows the following non-fishery related mortality: boat collision (three mortalities), entrainment in power
5

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

80 82 84 86 88 90 92 94 96 98 00

YEAR

NET PRODUCTION RATE

NET PRODUCTION = Population Growth + Human related mortalities

United States

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.

plants (21 mortalities), and shootings

(54 mortalities and three injuries).

Stranding records are a gross underestimate 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 minimum

number in 2001 was 78. 

 Several Pacific Northwest

treaty Indian tribes have promulgated

tribal regulations allowing tribal members 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 central California coast have recently been linked to the algal-produced

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

of such harmful algal blooms.

STATUS OF STOCK

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

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

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

They are not considered a "strategic" stock under the MMPA because total human-caused mortality ( 1,483 fisheryrelated 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.

REFERENCES

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

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

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

15:405-425.

Barlow, 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. 

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

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

Galveston TX, November 11-15, 1993.

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.

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.
6

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.

Julian, F. And M. Beeson. 1998. Estimates for marine mammal, turtle, and seabird mortality for two California gillnet
7

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.
8

Figure 1. Stock boundaries for the California and

Oregon/Washington coastal stocks of harbor seals.

Dashed line represents the U.S. EEZ.

Revised 12/15/2003

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. 

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 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
9

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 5. Harbor seal haulout counts in California during May/June (Hanan

1996; R.Read, CDFG unpubl. data; NMFS unpubl. data from 2002 survey). 

(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, in prep.)

and Hanan’s revised correction factor, the harbor seal population in California is estimated to number 27,863. 

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

(s.e.=0.007) which gives an annualized growth rate estimate of 3.5%. The current rate of net production is greater than

this observed growth rate because fishery mortality takes a fraction of the net production. Annual gillnet mortality may

have been as high as 5-10% of the California harbor seal population in the mid-1980s; a kill this large would have

depressed population growth rates appreciably. Net productivity was therefore calculated for 1980-1994 as the realized

rate of population growth (increase in seal counts from year i to year i+1, divided by the seal count in year i) plus the

human-caused mortality rate (fishery mortality in year i divided by population size in year i). Between 1983 and 1994,
10

-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

Figure 3. Net production rates and regression line estimated

from haulout counts and fishery mortality.

the net productivity rate for the California stock

averaged 9.2% (Fig. 3). A regression shows a

decrease in net production rates, but the decline is not

statistically significant. Maximum net productivity

rates cannot be estimated because measurements

were not made when the stock size was very small.

POTENTIAL BIOLOGICAL REMOVAL

The potential biological removal (PBR)

level for this stock is calculated as the minimum

population size (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.

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). 

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
11

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

unmonitored

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

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

(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.
12

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 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.
13

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 EastWest 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.

Lowry, M.S. and J.V. Carretta. In prep. Pacific harbor seal Phoca vitulina richardsi, census in California during MayJuly 2002. U.S. Department of Commerce, NOAA Technical Memorandum NMFS-SWFSC-xxx.

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

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

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

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

Admin. Rep. LJ-83-13C. Southwest Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271,

La Jolla, CA 92038. 233 pp.

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

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

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

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

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

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

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

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

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

Oregon.
14

WA Inland stock

OR/WA

Coastal

stock

CA stock

Figure 1. Approximate distribution of harbor

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

Stock boundaries separating the three stocks are

shown.

Revised 12/15/2003

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 nonmigratory, 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). This report considers only the 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.

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).
15

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. 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,
16

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. Thus, the mean
17

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 ESAlisted 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.
18

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 (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.

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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:

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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.

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

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

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

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

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

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observer programs: minutes and recommendations from a workshop held in Galveston, Texas, November 10-11,

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

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
19

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.

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. NMFSAFSC-138. 145 pp.

Pitcher, K. W., and D. G. Calkins. 1979. Biology of the harbor seal (Phoca vitulina richardsi) in the Gulf of Alaska.
20

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

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

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

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

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

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

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

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

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

Whisler, G. Columbia River Management, Oregon Department of Fish and Wildlife, 2021 Marine Drive, Room 103,

Astoria, OR 97103.
21

WA Inland stock

OR/WA

Coastal

stock

CA stock

Figure 1. Approximate distribution of harbor

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

Stock boundaries separating the three stocks are

shown.

Revised 12/15/2003

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 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.
22

0

2000

4000

6000

8000

10000

12000

14000

1975 1980 1985 1990 1995 2000

Year

Total count

Figure 2. Generalized logistic population growth curve for the

Washington Inland Waters stock of harbor seals, 1978-1999

(Jeffries et al. 2003).

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 statefinanced 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).

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).

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 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
23

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 non-

 treaty 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 strand

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 non-treaty

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

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

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

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

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 Fuca (areas 4B, 5, and 6C)

were also monitored in 1994 (NWIFC 1995). No harbor seal mortalities were reported in the observer programs covering
24

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

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

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

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

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

per set, which 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 nontreaty 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 self-reported fishery data

cover the entire fishery (including treaty and non-treaty components). There were fisher self-reports 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 selfreports. 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 struck by
25

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
26

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

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

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

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

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 non-treaty

salmon gill net fishery: Puget Sound and Hood Canal Washington. Unpubl. report. Washington Dept. Fish

and Wildlife, Olympia, WA. 39 pp. Available at WDFW, 600 Capitol Way N, Olympia, WA 98501.

Pierce, D. J., M. Alexandersdottir, S. J. Jeffries, P. Erstad, W. Beattie, and A. Chapman. 1996. Interactions of marbled

murrelets and marine mammals with the 1994 Puget Sound sockeye gill net fishery. Final Report, Washington

Dept. Fish and Wildlife, Olympia, WA. 21 pp.

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

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

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

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

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

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

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

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

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

April 3-5, 1996, Seattle, Washington. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-12. 93 pp.
27

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.

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 seasons.

Populations of northern elephant seals in the U.S. and

Mexico were all originally derived from a few tens or a few

hundreds of individuals surviving in Mexico after being nearly

hunted to extinction (Stewart et al. 1994). Given the very

recent derivation of most rookeries, no genetic differentiation

would be expected. Although movement and genetic

exchange continues between rookeries, most elephant seals

return to their natal rookeries when they start breeding (Huber

et al. 1991). The California breeding population is now

demographically isolated from the Baja California population.

No international agreements exist for the joint management of

this species by the U.S. and Mexico. The California breeding

population is considered here to be a separate stock.

POPULATION SIZE

A complete population count of elephant seals is not possible because all age classes are not ashore at the same

time. Elephant seal population size is typically estimated by counting the number of pups produced and multiplying by

the inverse of the expected ratio of pups to total animals (McCann 1985). Stewart et al. (1994) used McCann's multiplier

of 4.5 to extrapolate from 28,164 pups to a population estimate of 127,000 elephant seals in the U.S. and Mexico in 1991.

The multiplier of 4.5 was based on a non-growing population. Boveng (1988) and Barlow et al.(1993) argue that a

multiplier of 3.5 is more appropriate for a rapidly growing population such as the California stock of elephant seals.

Based on the estimated 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.

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).
28

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

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. 

-0.05 

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 1980-1987 is assumed to be

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

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

Although growth

rates as high as 16% per year

have been documented for

elephant seal rookeries in the

U.S. from 1959 to 1981

(Cooper and Stewart 1983),

much of this growth was

supported by immigration

from Mexico. The highest

growth rate measured for the

whole U.S./Mexico

population was 8.3% between

1965 and 1977 (Cooper and

Stewart 1983). A continuous

growth rate of 8.3% is

consistent with an increase

from approximately 100

animals in 1900 to the current

population size. The

"maximum estimated net

productivity rate" as defined

in the Marine Mammal

Protection Act (MMPA)

would therefore be 8.3%. In
29

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

extrapolated

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

communica

tion

n/a 2 2 n/a

Chehalis River salmon

setnet fishery 1993

personal

communica

tion

n/a 4 4 n/a

Total annual takes

> 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).
30

Although all of the mortalities in Table 1 occurred in U.S. waters, some may be of seals from Mexico's breeding

population that are migrating through U.S. waters. Similar drift gillnet fisheries for swordfish and sharks exist along

the entire Pacific coast of Baja California, Mexico and probably take northern elephant seal. Quantitative data are

available only for the Mexican swordfish drift gillnet fishery, which has increased from two vessels in 1986 to 29 vessels

in 1992 (Sosa-Nishizaki et al. 1993). The total number of sets in this fishery in 1992 can be estimated from data provided

by these authors to be approximately 2,700, with an observed rate of marine mammal bycatch of 0.13 animals per set

(10 marine mammals in 77 observed sets; Sosa-Nishizaki et al. 1993). This overall mortality rate is similar to that

observed in California driftnet fisheries during 1990-95 (0.14 marine mammals per set), but species-specific information

is not available for the Mexican fisheries. There are currently efforts underway to convert the Mexican swordfish driftnet

fishery to a longline fishery (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.

Julian, F. 1997. Cetacean mortality in California gillnet fisheries: preliminary estimates for 1996. Paper SC/49/SM02
31

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.
32

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.

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 (MaravillaChavez and Lowry 1999) and a pup was born at San Miguel

Island, California (Melin and DeLong 1999). Individuals

have stranded or been sighted as far north as Blind Beach,

California (38o

 26' 10" N, 123o 07' 20" W); inside the Gulf of

California and as far south as Zihuatanejo, Mexico (17o

 39' N,

101o

 34'W; Hanni et al. 1997 and Aurioles-Gamboa and

Hernadez-Camacho 1999). The population is considered to be

a single stock because all are recent descendants from one

breeding colony at Isla Guadalupe, Mexico. 

POPULATION SIZE

The size of the population prior to the commercial

harvests of the 19th century is not known, but estimates range

from 20,000 to 100,000 animals (Wedgeforth 1928, Hubbs 1956, Fleischer 1987). The population was estimated by

Gallo (1994) to be about 7,408 animals in 1993. The population estimate was derived by multiplying the number of pups

(counted and estimated) by a factor of 4.0.

Minimum Population Estimate

All the individuals of the population cannot be counted because all age and sex classes are never ashore at the

same time and some individuals that are on land are not visible during the census. Sub-sampling portions of the rookery

indicate that only 47-55% of the seals present (i.e., hauled out) are counted during the census (Gallo 1994). The 1993

count of all age classes plus the estimate of missed animals was 6,443 (Gallo 1994). The minimum size of the population

in Mexico can be estimated as the actual count of 3,028 hauled out seals [The actual count data were not reported by

Gallo (1994); this number is derived by multiplying the estimated number hauled out by 47%, the minimum estimate

of the percent counted]. In the United States, a few Guadalupe fur seals are known to inhabit California sea lion

rookeries in the Channel Islands (Stewart et al. 1987). 

Current Population Trend

Counts of Guadalupe fur seals have been made sporadically since 1954. Records of Guadalupe fur seal counts

through 1984 were compiled by Seagars (1984), Fleischer (1987), and Gallo (1994). The count for 1988 was taken from

Torres et al. (1990). A few of these counts were made during the breeding season, but the majority were made at other

times of the year (Figure 1). Also, the counts that are documented in the literature generally provide only the total of

all Guadalupe fur seals counted (i.e., the counts are not separated by age/sex class). The counts that were made during

the breeding season, when the maximum number of animals are present at the rookery, were used to examine population

growth (Gallo 1994). The natural logarithm of the counts was regressed against year to calculate the growth rate of the

population. These data indicate that the population of Guadalupe fur seals is increasing exponentially at an average

annual growth rate of 13.7% (Gallo 1994; Figure 2).
33

0 

1000 

2000 

3000 

4000 

5000 

6000 

7000 

COUNTS

50 55 60 65 70 75 80 85 90 95

YEAR

Non-breeding season Breeding season Pop. growth curve

GUADALUPE FUR SEAL COUNTS

Guadalupe Island, Mexico

Figure 2. Counts of Guadalupe fur seals at Guadalupe Island,

Mexico, and the estimated population growth curve derived

from counts made during the breeding season.

CURRENT AND MAXIMUM NET

PRODUCTIVITY RATES

The maximum net productivity rate can

be assumed to be equal to the annual growth rate

observed over the last 30 years (13.7%) because

the population was at a very low level and should

have been growing at nearly its maximum rate.

POTENTIAL BIOLOGICAL REMOVAL

The potential biological removal (PBR)

for this stock is calculated as the minimum

population size (3,028) times one half the default

maximum net growth rate for pinnipeds (1⁄2 of

12%) times a recovery factor of 0.5 (for a

threatened species, Wade and Angliss 1997),

resulting in a PBR of 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.

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
Fishery Name Year(s) Data Type

Percent Observer

Coverage

Observed

Mortality

Estimated

Mortality (CV in

parentheses)

Mean

Annual Takes

(CV in parentheses)

34

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.

Other mortality

Juvenile female Guadalupe fur seals have stranded in central and northern California with net abrasions around the neck,

fish hooks and monofilament line, and polyfilament string (Hanni et al. 1997). 

STATUS OF STOCK

The state of California lists the Guadalupe fur seal as a fully protected mammal in the Fish and Game Code of

California (Chap. 8, sec. 4700, d), and it is listed also as a threatened species in the Fish and Game Commission

California Code of Regulations (Title 14, sec. 670.5, b, 6, H). The Endangered Species Act lists it as a threatened

species, which automatically qualifies this as a "depleted" and "strategic" stock under the Marine Mammal Protection

Act. There is insufficient information to determine whether the fishery mortality in Mexico exceeds the PBR for this

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

therefore, can be considered to be insignificant and approaching zero mortality and serious injury rate. The population

is growing at approximately 13.7% per year.

REFERENCES

Aurioles-Gamboa, D. and C. J. Hernadez-Camacho. 1999. Notes on the southernmost records of Guadalupe fur seal,

Arctocephalus townsendi, in Mexico. Mar. Mamm. Sci. 15:581-583.

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

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

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

15:405-425.

Cameron, G., and K. A. Forney. 1999. Estimates of cetacean mortality in the California gillnet fisheries for 1997 and

1998. Paper SC/51/O4 presented to the International Whaling Commission, May 1999 (unpublished). 14 pp.

Fleischer, L. A. 1987. Guadalupe fur seal, Arctocephalus townsendi. In J. P. Croxall and R. L. Gentry (eds.). Status,

biology, and ecology of fur seals. Proceedings of an international symposium and workshop. Cambridge,

England, 23-27 April 1984. p. 43-48. U.S. Dept. of Commerce, NOAA, NMFS, NOAA Tech. Rept. NMFS 51.

Gallo, J. P. 1994. Factors affecting the population status of Guadalupe fur seal, Arctocephalus townsendi (Merriam,

1897), at Isla de Guadalupe, Baja California, Mexico. Ph.D. Thesis, University of California, Santa Cruz, 199

p.

Hanni, K. D., D. J. Long, R. E. Jones, P. Pyle, and L. E. Morgan. 1997. Sightings and strandings of Guadalupe fur seals

in central and northern California, 1988-1995. J. of Mamm. 78:684-690.

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

Hubbs. C. L. 1956. The Guadalupe fur seal still lives! Zoonooz, S. D. Zool. Soc. 29(12):6-9.

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

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

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

fisheries: 1990-95. Fish. Bull. 96:271-284.

Maravilla-Chavez, M. O. and M. S Lowry. 1999 Incipient breeding colony of Guadalupe fur seals at Isla Benito del
35

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.
36

San Miguel Island

Pribilof

Islands

Figure 1. Approximate distribution of northern fur seals

in the eastern North Pacific (shaded area).

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 (JuneNovember). After their respective times ashore, seals of

both genders spend the next 7-8 months at sea (Roppel

1984). Adult females and pups from the Pribilof Islands migrate through the Aleutian Islands into the North Pacific

Ocean, often to Oregon and California offshore waters. Many pups may remain at sea for 22 months before returning

to their rookery of birth. Adult males from the Pribilof Islands generally migrate only as far south as the Gulf of Alaska

(Kajimura 1984). There is considerable interchange of individuals between rookeries.

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

phylogeographic approach: 1) Distributional data: 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 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.
37

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.

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).

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 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.
38

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. 
39

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
40

phylogeographic approach. Conserv. Biol. 6:24-36.

Fiscus, C. F. 1983. Fur seals and island. In: Background papers submitted by the United States to the 26th annual

meeting of the Standing Scientific Committee of the North Pacific Fur Seal Commission, Washington, D.C.,

March 28-April 5, 1983. Available at National Marine Mammal Laboratory, 7600 Sand Point Way NE, Seattle,

WA 98115.

Gerrodette, T., D. Goodman, and J. Barlow. 1985. Confidence limits for population projections when vital rates vary

randomly. Fish. Bull. 83(3):207-217.

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. NMFSAFSC-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-OPR-12. 93 pp.

York, A. E. National Marine Mammal Laboratory, AFSC, NMFS, 7600 Sand Point Way NE, Seattle, WA 98115.
41

Revised 12/15/2003

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, primarily at Niihau. Genetic

variation in Hawaiian 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., 2001). The tendency for genetic drift may have been relatively large,

due to the small size of different island/atoll subpopulations. However, 10-15% of these seals migrate among the

subpopulations (Johnson and Kridler 1983; National Marine Fisheries Service [NMFS] unpubl. data) and, to some

degree, this movement should counter the development of separate genetic stocks. Genetic variation among the different

island populations is low (Kretzmann et al., 1997; 2001).

Demographically, 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.

Variability in past population trends may be partially explained by changes in levels of human disturbance (Gerrodette

and Gilmartin 1990; Ragen 1999). Current demographic variability among the subpopulations probably reflects a

combination of age structure effects resulting from different recent histories and variable environmental conditions.

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 1,409. This estimate is the sum of counts at the six main

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 2001, identification

efforts were conducted during two- to six -month studies at all main reproductive sites. A total of 1,257 seals (including

178 pups) were observed at the main reproductive subpopulations in 2001 (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 1997-2001 were 15.4 (± 6.8) at Necker Island and 18.0

(± 9.2) 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 45.7 (± 19.8) at Necker Island and

54.3 (± 26.5) at Nihoa Island. 

A 2001 aerial survey determined a minimum abundance of 52 seals in the main Hawaiian Islands (Baker and

Johanos, submitted). Seals in the main Hawaiian Islands 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., 1,257 seals). Minimum population sizes for Necker and Nihoa Islands (based on the formula

provided by Wade and Angliss (1997)) are 32 and 37 , 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 1,378 seals.
42

300

350

400

450

500

550

600

Mean number of non-pups

1985 1987 1989 1991 1993 1995 1997 1999 2001

Year

Figure 17. Mean beach counts of Hawaiian monk seals (non-pups) at the six main

NWHI subpopulations, 1985-2001.

Current Population Trend

The total of mean non-pup beach counts at the main reproductive NWHI subpopulations in 2001 is

approximately 60% lower than in 1958. In previous Hawaiian monk seal stock assessments, current population trend was

estimated using log-linear regression of total non-pup beach counts (excluding Midway) since 1985. This method

however, had two shortcomings. First, Midway Atoll counts were excluded because there was very little field effort at

Midway prior to 1992, due to the small number of seals present at that time. By excluding Midway, comparability

throughout the time series was achieved at the expense of completeness. By now, the Midway subpopulation has grown

considerably and is an integral part of the stock that should be represented in the trend analysis. Thus, this report analyzes

current population trend using all six main subpopulations.

Counts declined from 1985 to 1993, then became rather stable. As a result, a log-linear trend through the entire

time series has resulted 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/m

ailinglists/s-news/200004/msg0

0212.html). This method

estimates that the total counts

declined 4.3% yr-1 until 1993,

then declined at 0.7% yr-1

thereafter (Fig. 1). The broken

line regression fit significantly

better than a single regression

line (p = 0.02). Thus, current

population trend is best

estimated as -0.7% yr-1 (95% CI

= -2.1% to 0.8% yr-1. For

comparison, if Midway Atoll

counts are excluded from this

analysis, results are similar (pre1993 decline of 4.5% yr-1,

subsequent decline of 1.4% yr-1),

except that the post-1993 decline

is steeper because the increasing

trend at Midway is omitted. The

low mean beach count in 2001

reflects, in part, both continued declines in counts at French Frigate Shoals and widespread low juvenile survival

associated with an Unusual Mortality Event in 2001 (see below).

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 -0.007 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

non-pup beach counts decreased by 70% from 1989 -2001. 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. 

Contrary to trends at the above sites, the subpopulation at Kure Atoll has grown at an average rate of 5% yr-1

since 1983 (loglinear regression of beach counts, 1983-2001; R2 = 0.85, P<0.001), due largely to decreased human

disturbance and introduced females. The subpopulation at Pearl and Hermes Reef has grown at approximately 6% yr-1

since 1983 (loglinear regression of beach counts, 1983-2001; R2 = 0.84, P<0.001). Growth of the Pearl and Hermes

population may be slowing slightly, as previous to 1999 the growth rate averaged 7%yr-1. This latter annual growth rate

is the best indicator of the maximum net productivity rate (Rmax) for this species. Finally, the small subpopulation at
43

Midway Atoll continues to show signs of recovery.

POTENTIAL BIOLOGICAL REMOVAL

The potential biological removal (PBR) level for this stock is calculated as the minimum population size (1,378)

times one half the maximum net growth rate for this stock (1⁄2 of 7%) times a recovery factor of 0.1 (for an endangered

species, Wade and Angliss 1997), which yields a PBR of 4.8 monk seals per year.

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; Clapp and Woodward 1972). Several subpopulations may have been driven extinct; for example, no

seals were seen at Midway Atoll during a 14-month period in 1888-89, and only a single seal was seen during three

months of observations at Laysan Island in 1912-13 (Bailey 1952). A survey in 1958 indicated at least partial recovery

of the species in the first half of this century (Rice 1960). However, subsequent surveys revealed that all subpopulations

except French Frigate Shoals declined severely after the late 1950s (or earlier). This second decline has not been

explained at Pearl and Hermes Reef, or Lisianski and Laysan Islands. At Kure Atoll, Midway Atoll, and French Frigate

Shoals, trends appear to have been determined by the pattern of human disturbance from military or U.S. Coast Guard

activities. Such disturbance is believed to have caused pregnant females to abandon prime pupping habitat and nursing

females to abandon their pups (Kenyon 1972; Gerrodette and Gilmartin 1990), resulting in decreased pup survival,

which led to poor reproductive recruitment, low productivity, and population decline.

Fishery Information

Detrimental 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 1982, fishery-related monk seal deaths

have included the following: one seal died from entanglement in the bridle rope of lobster trap (1986; NMFS, unpubl.

data), another entanglement death in an illegally set gill net off the western shore of Oahu (1994; NMFS, unpubl. data),

and one died from ingestion of a recreational fish hook and probable drowning off the island of Kauai (1995; NMFS,

unpubl. data). A total of 24 seals have been observed with embedded fish hooks during 1982-2001. 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 recreational fisheries (esp. for Caranx sp. in the main Hawaiian Islands), federal

and state bottomfish and federal longline fisheries (NMFS unpubl. data). For the purposes of a recent Biological

Opinion, hookings conservatively judged to be of commercial origin were summarized (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 may interact with Hawaiian monk seals. The NWHI lobster fishery began in the late 1970s, and

developed rapidly in the early 1980s (Polovina, 1993). Annual landings peaked in 1985 (1.92 million lobsters) and 1986

(1.69 million lobsters; Haight and DiNardo 1995). Thereafter, the fishery declined and was closed temporarily in 1993

due to low spawning stock biomass of spiny lobster. After 1994, landings remained lower than in the mid- to late 1980s,

while catch of slipper lobster increased in some areas. The number of vessels in the fishery increased from four in 1983

to 17 in 1985, then ranged from 0-12 during 1991-2000 (Dollar 1995; DiNardo et al. 1998; Kawamoto and Pooley,

2000). Historically, both effort and landings were concentrated at Gardner Pinnacles, Maro Reef, Necker Island, and St.

Rogatien Bank (Clarke and Todoki 1988; Polovina and Moffitt 1989). However, spatial management of the NWHI

lobster fishery began in 1998 in an effort to prevent local depletion of lobster stocks and to disperse fishing effort, which

in recent years had been limited to Necker Island and Maro Reef. As a result of the new management approach, lobsters

were taken from Area 4 (all banks between Nihoa Island and Kure Atoll, excepting Necker Island, Maro Reef and

Gardner Pinnacles), which, until 1998, had not been fished since the early 1990's (DiNardo et al.1998; Kawamoto and

Pooley 2000). Summaries of catch by area, trends and available data on bycatch are published in annual reports, the most

recent being Kawamoto and Pooley (2000). Neither incidental mortality nor serious injury have been observed by NMFS

observers of the lobster fishery through 2001. As was noted, one mortality was documented in 1986; a monk seal

drowned after becoming entangled in the bridle rope of an actively fishing lobster trap near Necker Island. The potential

for indirect interaction due to competition for prey is being investigated (see Habitat Issues below). 
44

NMFS closed the Northwestern Hawaiian Islands lobster fishery in 2000 due to uncertainty in the estimates

of biomass, and the fishery remains closed to date. President Clinton’s Executive Order (1/18/2001) creating the

Northwest Hawaiian Islands coral reef ecosystem reserve may preclude some lobster fishing in the NWHI, but this issue

has yet to be resolved.

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 119 - 201 metric tons per year from 1989-2001 (Kawamoto 1995; Moffitt, pers. comm.). The number of

vessels rose from 19 in 1984 to 28 in 1987, and then varied from 10 to 17 in 1988 through 2001 (Kawamoto 1995;

Moffitt, pers. comm.). Currently, the bottomfish fishery remains open, although its area of operation has been

substantially restricted by President Clinton’s Executive Order (1/18/2001). The Agency 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 was monitored by observers from October 1990 to

December 1993 (ca. 13% coverage), but is currently monitored by the State of Hawaii using logbooks. However, the

State logbook does not include information on protected species and, therefore, the nature and extent of interactions with

monk seals cannot be assessed 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. The fishery began in

the 1940s, and operated at a relatively low level (< 5000 t per year) until the mid-1980s. In 1987, 37 vessels participated,

but by 1991, the number had grown to 141 (Ito, 1995). The number of active vessels ranged from 101-141 during 1991-

2001. Entry is currently limited to a maximum of 164 vessels (Ito and Machado, 1999). Total landings ranged from

7,076-13,000 metric tons during 1991-2001 (Ito, pers. comm.). While most of the fishery has operated outside of the

NWHI Exclusive Economic Zone, evidence of interactions began to accumulate in 1990, including at least two hooked

seals (included in hookings reported above) and 13 unusual seal wounds thought to have resulted from interactions. In

response, NMFS established a permanent Protected Species Zone extending 50 nautical miles around the NWHI and the

corridors between the islands in October 1991. Subsequent shore-based observations of seals have found no further

evidence of interactions with the longline fishery after establishment of the Protected Species Zone. At present,

interactions with protected species are assessed using Federal logbooks and observers (4-5% coverage), which may lack

sufficient statistical power to estimate monk seal mortality/serious injury rates from longline interactions. However,

since 1991, there have been no observed or reported interactions of this fishery with monk seals. 

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

Hawaiian Islands. 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, one seal was found dead in an offshore (non-recreational) gillnet in 1994 and a second

seal was found dead with a recreational hook lodged in its esophagus. A total of 14 seals have been observed with

embedded hooks in the main Hawaiian Islands during 1989-2001 (NMFS unpubl. data). Several incidents involved

hooks used to catch ulua (Caranx spp.). A sport fishing charter company recently ceased operations at Midway Atoll.

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

seals. The impact that removal of precious corals might have on monk seal prey resources and foraging habitat is

unknown. However, recent studies of seals with satellite transmitters and surveys using manned submersibles indicate

that some seals forage at patches of precious gold corals occurring over 500m in depth (Parrish et al., 2002). The

recruitment rate of gold coral is unknown, but thought to be slow, raising concern that coral harvesting could have

negative long-term impacts on monk seal foraging habitat. As a result, the Western Pacific Regional Fisheries
45

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 91-01 0-12 Observer

Log book

0-100% 0 n/a n/a

NWHI

Bottomfish

91-01 11-17

n/a n/a n/a n/a n/a

Pelagic longline 91-01 101-141 Observer

Log book 4-5% 0 n/a n/a

Recreational 91-95 n/a n/a n/a 2† n/a n/a

† Data collected incidentally.

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 212 cases of seals entangled in fishing gear or other debris have been

observed through 2001 (Henderson 2001; NMFS, unpubl. data), including six documented mortalities resulting from

entanglement in fisheries debris (Henderson 1990, 2001; NMFS, unpubl. data). The types of fishing gear fouling the

reefs and beaches of the NWHI and entangling monk seals are not among types used in fisheries conducted in the NWHI.

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 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. Efforts to remove potentially

entangling marine debris from reefs surrounding monk seal haulout sites are growing. During 1996-2001 debris survey

and removal efforts, 264,726 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). Using funds dedicated to marine debris mitigation,

this effort was greatly expanded in 2001.

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
46

an adult female in 1989.

Other sources of mortality which are (or may be) impeding the recovery of this subpopulation include single

and multiple male aggression (mobbing), shark predation, 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 (1995-2001). Such imbalances in the adult sex ratio are more likely to occur when populations

are reduced (Starfield et al. 1995).

In addition to mobbing, aggressive attacks by single adult males have resulted in several monk seal mortalities.

This was most notable at French Frigate Shoals in 1997, where at least 8 pups died as a result of adult male aggression.

Many more pups were likely killed in the same way but the cause of their deaths could not be confirmed. Two males

that killed pups in 1997 were observed exhibiting aggressive behavior toward pups at the beginning of the 1998 pupping

season. Both males were translocated to Johnston Atoll, 870 km to the southwest. Subsequently, mounting injury to pups

has 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 the last few years. At

French Frigate Shoals in 1999, 17 pups were observed injured by large sharks, and at least three were confirmed to have

died from shark predation (Johanos and Baker, 2001). Assigning cause of death to shark predation is problematic, as

predation events are rarely observable. However, it is believed that as many as 25 pups of a total 92 born at French

Frigate Shoals in 1999 were killed by sharks. 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 health 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.

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. On 16 October 1998 the Paradise

Queen II, a lobster fishing vessel, ran aground on the eastern edge of Kure Atoll. In 2001, vessel fragments remained

on the reef and shoreline of Green Island. On occasion, monk seals land on wreck debris. During an initial clean up

effort, accessible hazardous material and lobster traps were removed. In subsequent years, several hundred traps washed

ashore and were removed from Green Island.

Another grounding occurred on 6 June 2000 when the 77 ft longliner Swordman I ran aground on the perimeter

reef of Pearl and Hermes Atoll. Of 81,200 gallons of fuel on board; 79,000 gallons were recovered and the remainder

spilled. An oil spill response crew evaluated the scene one week later and determined that impacts to wildlife and coral

reefs were minimal. No evidence of oiling or other impacts to Hawaiian monk seals was found. Salvage crews

subsequently cleaned the Swordman I, removed it from the reef and sank it in deep water.

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
47

simultaneously reduced by changes in oceanographic conditions and a subsequent decline in productivity (Polovina et

al. 1994; Craig and Ragen 2000).

Studies are also being conducted to identify and characterize at-sea habitat use. In 2001, 54 seals of various

ages and both sexes were fitted with satellite-linked dive recorders to track movements and dive patterns at Laysan Island

and Kure Atoll. With these most recent instrument deployments, information on at-sea movement and diving has been

collected from seals at all six main subpopulations in the NWHI. Goodman-Lowe (1998) provides information on prey

selection using hard parts in scats and spewings.

Since 1979, human disturbance of seals in their terrestrial habitat has been limited primarily to Kure and

Midway Atolls. The U.S. Coast Guard LORAN station at Kure Atoll closed in 1992 and vacated in 1993. Historically,

human activities led to the near extinction of the resident monk seal population at Midway both in the late 1800s, and

again in the 1960s. The population failed to recover in the 1970s and 1980s, but has recently grown due to immigration

from nearby sites. The U.S. Naval Air Facility at Midway closed in 1993 and was transferred in 1997 to the U.S. Fish

and Wildlife Service, which manages the atoll as a National Wildlife Refuge. A private company which had provided

tourist activities (e.g., scuba diving and sport fishing), as well as harbor services, terminated their operations at Midway

Atoll in 2002. As a result, the level of human activity that could impact monk seals at the site has diminished. Any

future development which might increase access to the Refuge will need careful management and monitoring to prevent

further human disturbance. Disturbance at sea (e.g., direct and indirect fisheries interactions) may also impede recovery.

As described above, however, the possible types of disturbance at sea cannot yet be characterized or quantified.

 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 2003.

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

submitted). 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 Main Hawaiian Islands, 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 Main Hawaiian Islands is approximately 1.2 million compared to

less than 100 in the NWHI, so that the potential impact of disturbance in the Main Hawaiian Islands 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 Main Hawaiian Islands 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.

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Baker, J. D. and T. C. Johanos. Submitted. Recolonization of historic range by an endangered marine mammal, the

Hawaiian monk seal, in the main Hawaiian Islands.

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.

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Clarke, R. P., and A. C. Todoki. 1988. Comparison of three calculations of catch rates of the lobster fishery in the

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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.
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Haight, W. R., and G. T. DiNardo. 1995. Status of lobster stocks in the Northwestern Hawaiian Islands, 1994. Available

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Kawamoto, K. E., and S. G. Pooley. 2000. Annual report of the 1998 western Pacific lobster fishery. Admin. Rep. H-00-

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Kenyon, K. W. 1972. Man versus the monk seal. J. Mammal. 53(4):687-696.

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genetic variability in the Hawaiian monk seal. Conserv. Biol. 11(2):482-490.
49

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Hawaiian islands during 1991 to 1994. Marine Biology 132:535-546.

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

Starfield, A. M., J. D. Roth, and K. Ralls. 1995. "Mobbing" in Hawaiian monk seals (Monachus schauinslandi): The

value of simulation modeling in the absence of apparently crucial data. Conserv. Biol. 9:166-174.

Wade, P. R. and R. P. Angliss. 1997. Guidelines for Assessing Marine Mammal Stocks: Report of the GAMMS

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93 pp.

Wetmore, A. 1925. Bird life among lava rock and coral sand. The Natl. Geograp. Mag. 48:77-108.
50

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/southern Oregon

coast. Shaded area represents harbor porpoise habitat

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

Revised 12/15/2003

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 pairwise 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). 

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 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 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 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, 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
51

0.00 

0.10 

0.20 

0.30 

0.40 

0.50 

Relative abundance (porpoise/km)

85 87 89 91 93 95 97 99 

Year

Figure 2. Relative abundance (+/- one standard error) of central California (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

San Francisco-Russian River).

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, 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 aerial surveys from 1997-99 under good survey conditions (Beaufort 2, cloud cover 25%) the estimate ≤ ≤

of abundance for this stock is 932 animals (CV = 0.41) (Carretta 2003).

 

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 1997-99 aerial surveys, or 669 animals. 

Current Population Trend

Analyses of a 1986-95 time

series of aerial surveys have been

conducted to examine trends in harbor

porpoise abundance in central

California (Forney, 1995; 1999b).

After controlling for the effects of sea

state, cloud cover, and area on

sighting rates, Forney (1995) found a

negative trend in population size;

however, that trend was no longer

significant when sea surface

temperature (a proxy measure of

oceanographic conditions) was

included in an updated non-linear

trend analysis (Forney 1999b). The

negative correlation between harbor

porpoise sighting rates and sea surface

temperatures indicates that apparent

trends could be caused by changing

oceanographic conditions and

movement of animals into and out of

the study area. Encounter rates for

the 1997 survey, however, were very

high (Forney 1999a) despite the

warmer sea surface temperatures caused by strong El Niño conditions. These observations suggest that patterns of harbor

porpoise movement are not directly related to sea surface temperature, but rather to the more complex distribution of

potential prey species in this area. Although encounter rates during the 1999 aerial survey were again higher than in past

years, the trend in relative abundance (following methods of Forney 1995) is not statistically significant (p=0.12, Figure

2). More detailed studies of encounter rate patterns in relation to satellite-derived sea surface temperature during 1993-99

are planned to shed light on potential oceanography-related movement patterns of harbor porpoise in this region. 
52

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 (669)

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 7. 

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 steadily increased through 2001. California Department of Fish and Game (CDFG) estimated fishing effort for

1996-2001 as 32, 88, 139, 121, 284, and 391 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). Applying

this kill rate to the 2001 estimate of fishing effort results in a mortality estimate of 9 porpoise (0.023 * 391 days), which

exceeds PBR. Projected mortality levels based on this kill rate and effort levels for 1996-2001 are summarized in Table

1. It should be 

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;

NMFS/SWFSC, unpublished data). Mean annual takes are based on 1997-2001 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

1997

1998

1999

2000

2001

2002

1990-94

observer data

Fishery closed

permanently

in waters < 60

fathoms

0%

0%

0%

0%

0%

-

-

-

-

-

-

0.0231

2 (0.97)

3 (0.97)

3 (0.97)

7 (0.97)

9 (0.97)

 4.8 (0.97)2

Minimum total annual takes 4.8 (0.97)2

1

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

Mean annual takes are based on 1997-2001 effort data and 1990-94 kill rates.

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

probably 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 (1997-2001) has been 0, 26, 7, 61, and 132 fishing days respectively.

No estimates of harbor porpoise mortality are available for this fishery, although takes have been documented in the past.

Both of the above central California gillnet fisheries were restricted by a series of emergency closures beginning in
53

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) was implemented in April 2002

and became permanent 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.

Two harbor porpoise mortalities were inaccurately reported in Marine Mammal Authorization Permit (MMAP)

fisher self-reports for the California drift gillnet fishery during 1996-98. Both of the mortalities occurred on an observed

fishing trip and were actually short-beaked common dolphins (NMFS, Southwest Fisheries Science Center, unpublished

data). This fishery has not previously been known to take harbor porpoise.

STATUS OF STOCK

Harbor porpoise in California are not listed as threatened or endangered under the Endangered Species Act nor

as depleted under the Marine Mammal Protection Act. Barlow and Hanan (1995) calculate the status of harbor porpoise

relative to historic carrying capacity (K) using a technique called back-projection. They calculate that the central

California population (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 (1997-2001), mean annual takes are 4.8 porpoise per year, which is

less than the PBR of 7 animals, resulting in a “non-strategic” classification. A permanent set gillnet closure inside of

60 fathoms was implemented in April 2002 and 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-SWFSC-317. 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.

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.
54

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 line-transect surveys.

Admin. Rep. LJ-99-02. Southwest Fisheries Center, National Marine Fisheries Service, P.O. Box 271, La Jolla,

CA 92038. 16 pp.

Forney, K. A. 1999b. Trends in harbor porpoise abundance off central California, 1986-95: Evidence for interannual

changes in distribution? J. Cetacean Res. Manage. 1:73-80.

Gaskin, D. E. 1984. The harbour porpoise (Phocoena phocoena L.): regional populations, status, and information on

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.
55

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/southern Oregon

coast. Shaded area represents harbor porpoise habitat

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

Revised 12/15/2003

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 pairwise 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). 

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 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 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 porpoise stocks include: 1) a Morro Bay stock, 2) a San FranciscoRussian River stock, 3) a northern California/southern Oregon stock, 4) an Oregon/Washington coast stock, 5) a

Washington Inland waters 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.
56

0.00 

0.10 

0.20 

0.30 

0.40 

0.50 

Relative abundance (porpoise/km)

85 87 89 91 93 95 97 99 

Year

Figure 2. Relative abundance (+/- one standard error) of central California

harbor porpoise, 1986-99, adjusted for sea state and cloud cover (following

methods of Forney 1995). The trend shown includes the range of three

California stocks (Morro Bay, Monterey Bay, and San Francisco-Russian

River)

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, 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 aerial surveys from 1997-99 under good survey conditions (Beaufort 2, cloud cover 25%) the estimate ≤ ≤

of abundance for this stock is 1,603 animals (CV = 0.42) (Carretta 2003).

 

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 1997-99 aerial surveys, or 1,142 animals.

Current Population Trend

Analyses of a 1986-95 time

series of aerial surveys have been

conducted to examine trends in harbor

porpoise abundance in central California

(Forney, 1995; 1999b). After controlling

for the effects of sea state, cloud cover,

and area on sighting rates, Forney (1995)

found a negative trend in population

size; however, that trend was no longer

significant when sea surface temperature

(a proxy measure of oceanographic

conditions) was included in an updated

non-linear trend analysis (Forney

1999b). The negative correlation

between harbor porpoise sighting rates

and sea surface temperatures indicates

that apparent trends could be caused by

changing oceanographic conditions and

movement of animals into and out of the

study area. Encounter rates for the 1997

survey, however, were very high (Forney

1999a) despite the warmer sea surface

temperatures caused by strong El Niño

conditions. These observations suggest that patterns of harbor porpoise movement are not directly related to sea surface

temperature, but rather to the more complex distribution of potential prey species in this area. Although encounter rates

during the 1999 aerial survey were again higher than in past years, the trend in relative abundance (following methods

of Forney 1995) is not statistically significant (p=0.12, Figure 2). More detailed studies of encounter rate patterns in

relation to satellite-derived sea surface temperature during 1993-99 are planned to shed light on potential oceanographyrelated 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
57

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 (1,143)

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 11. 

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 is given in Table 1. Mortality estimates for 1997-98 are based on total estimated

fishing effort and prior-year entanglement rate data (Julian and Beeson 1998), because no observer program was in place

during those years. 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). Although mortality estimates for

the most recent five years (1997-2001) are presented in Table 1, average annual takes in the setnet fishery are estimated

using only 2001 data, because the fishery was largely closed under emergency regulations after September 2000. The

closure was made permanent in September 2002. An average of 3 harbor porpoise (CV= 0.50) were killed in this fishery

in Monterey Bay during 2001. 

Table 1. Summary of available on incidental mortality and injury of harbor porpoise (central CA stock 1997-98;

Monterey Bay stock 1999-2001) 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 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

1997

1998

1999

2000

2001

2002

1990-94

observer data

observer

data

2000 observer

data

Fishery closed

0%

0%

23.0%

27.0%

0%

-

-

 282

7

-

-

-

0.17

0.10

0.10

 80 (0.19)

57 (0.19)

133 (0.23)2

26 (0.50)

3 (0.77)

 3 (0.77)1

Minimum total annual takes 3 (0.77)1

1

Only 2001 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).

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. Following a brief lapse in the closure in late 2001, the restrictions were

reinstated in January 2002. A permanent 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) was implemented on September 4,
58

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. 

Two harbor porpoise mortalities were inaccurately reported in Marine Mammal Authorization Permit (MMAP)

fisher self-reports for the California drift gillnet fishery during 1996-98. Both of the mortalities occurred on an observed

fishing trip and were actually short-beaked common dolphins (NMFS, Southwest Fisheries Science Center, unpublished

data). This fishery has not previously been known to take harbor porpoise.

 Five fishery-related stranding mortalities of harbor porpoise were documented within the range of the Monterey

Bay harbor porpoise stock: one in 1998 near Watsonville, two in 1999 near Seaside and Pacific Grove, and two in 2000

at Año Nuevo State Reserve and near Santa Cruz. 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 back-projection. They calculate that the central

California population could have been reduced to between 30% and 97% of K by incidental fishing mortality, depending

on the choice of input parameters. They conclude that there is no practical way to reduce the range of this estimate. New

information does not change this conclusion, and the status of harbor porpoise relative to their Optimum Sustainable

Population (OSP) levels in central California must be treated as unknown. 

The annual mortality for 2001, after implementation of the emergency closure for central California gillnet

fisheries, was 3 harbor porpoise, which is less than the calculated PBR (11) 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). 21pp.

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., 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-SWFSC-317. 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. 

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
59

Research and Management 4(2):111-122.

Forney, K. A. 1999a. The abundance of California harbor porpoise estimated from 1993-97 aerial line-transect surveys.

Admin. Rep. LJ-99-02. Southwest Fisheries Center, National Marine Fisheries Service, P.O. Box 271, La Jolla,

CA 92038. 16 pp.

Forney, K. A. 1999b. Trends in harbor porpoise abundance off central California, 1986-95: Evidence for interannual

changes in distribution? J. Cetacean Res. Manage. 1:73-80.

Gaskin, D. E. 1984. The harbour porpoise (Phocoena phocoena L.): regional populations, status, and information on

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.
60

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/southern Oregon

coast. Shaded area represents harbor porpoise habitat

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

Revised 12/15/2003

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). 

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 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

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 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
61

0.00 

0.10 

0.20 

0.30 

0.40 

0.50 

Relative abundance (porpoise/km)

85 87 89 91 93 95 97 99 

Year

Figure 2. Relative abundance (+/- one standard error) of central California (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

San Francisco-Russian River).

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, 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 aerial surveys from 1997-99 under good survey conditions (Beaufort 2, cloud cover 25%) ≤ ≤

the estimate of abundance for this stock is 6,674 animals (CV = 0.39) (Carretta 2003).

 

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 the 1997-99 aerial surveys, or

4,858 animals. 

Current Population Trend

Analyses of a 1986-95 time series of aerial surveys have been conducted to examine trends in harbor porpoise

abundance in central California

(Forney, 1995; 1999b). After

controlling for the effects of sea state,

cloud cover, and area on sighting

rates, Forney (1995) found a negative

trend in population size; however,

that trend was no longer significant

when sea surface temperature (a

proxy measure of oceanographic

conditions) was included in an

updated non-linear trend analysis

(Forney 1999b). The negative

correlation between harbor porpoise

sighting rates and sea surface

temperatures indicates that apparent

trends could be caused by changing

oceanographic conditions and

movement of animals into and out of

the study area. Encounter rates for

the 1997 survey, however, were very

high (Forney 1999a) despite the

warmer sea surface temperatures

caused by strong El Niño conditions.

These observations suggest that

patterns of harbor porpoise movement

are not directly related to sea surface

temperature, but rather to the more complex distribution of potential prey species in this area. Although encounter rates
62

during the 1999 aerial survey were again higher than in past years, the trend in relative abundance (following methods

of Forney 1995) is not statistically significant (p=0.12, Figure 2). More detailed studies of encounter rate patterns in

relation to satellite-derived sea surface temperature during 1993-99 are planned to shed light on potential oceanographyrelated 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 (4,858)

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 49. 

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.

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 1997-2000 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 1997-2001 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 back-projection. 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. 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 (49), this stock is not considered a "strategic" stock under the MMPA. Because average annual fishery mortality
63

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-TM-NMFS-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.

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 line-transect surveys.

Admin. Rep. LJ-99-02. Southwest Fisheries Center, National Marine Fisheries Service, P.O. Box 271, La Jolla,

CA 92038. 16 pp.

Forney, K. A. 1999b. Trends in harbor porpoise abundance off central California, 1986-95: Evidence for interannual

changes in distribution? J. Cetacean Res. Manage. 1:73-80.

Gaskin, D. E. 1984. The harbour porpoise (Phocoena phocoena L.): regional populations, status, and information on

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.
64

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/southern Oregon

coast. Shaded area represents harbor porpoise habitat

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

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 pairwise 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). 

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 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
65

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) or northern California

(Russian River to CA/OR border) harbor porpoise, 1989-99, adjusted for sea

state and cloud cover (following methods of Forney 1995).

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

Forney (1999b) examines

trends in relative harbor porpoise

abundance in central and northern

California based on aerial surveys

from 1989-95. No significant trends

were evident over this time period for

the Northern California Stock. The

1997-99 survey results continue to

show no trend in relative abundance

(Figure 2).

CURRENT AND MAXIMUM

NET PRODUCTIVITY RATES

Based on what are argued to

be biological limits of the species (i.e.

females give birth first at age 4 and

produce one calf per year until death),

the theoretical, maximumconceivable 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)
66

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.

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-TM-NMFS-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
67

and D. K. Odell (eds.) Marine mammal strandings in the United States. NOAA Tech. Rep. NMFS 98.

Chivers, S. Southwest Fisheries Science Center, NMFS, P.O. Box 271, La Jolla, CA 92038

Forney, K. A. 1999a. The abundance of California harbor porpoise estimated from 1993-97 aerial line-transect surveys.

Admin. Rep. LJ-99-02. Southwest Fisheries Center, National Marine Fisheries Service, P.O. Box 271, La Jolla,

CA 92038. 16 pp.

Forney, K. A. 1999b. Trends in harbor porpoise abundance off central California, 1986-95: Evidence for interannual

changes in distribution? J. Cetacean Res. Manage. 1:73-80.

Gaskin, D. E. 1984. The harbour porpoise (Phocoena phocoena L.): regional populations, status, and information on

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.
68

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.

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.

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 porpoise is more finely structured than is

currently recognized (Chivers et al. 2002). All relevant data (e.g., genetic samples, contaminant studies, and satellite
69

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
70

these fisheries.

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 selfreports 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 selfreports. 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
71

Region, no human-caused harbor porpoise mortalities or serious injuries were reported from non-fisheries sources in

1997-2001.

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
72

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.

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-OPR-12. 93 pp.
73

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.

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.

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 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
74

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.
75

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 non-treaty

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

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

as estimated from fish ticket landings (Erstad et al. 1996). No harbor porpoise were reported within 100 m of observed

gillnets. The Puget Sound treaty chum salmon gillnet fishery in Hood Canal (areas 12, 12B, and 12C) and Puget Sound

treaty sockeye/chum gillnet fishery in the Strait of Juan de Fuca (areas 4B, 5, and 6C) were also monitored in 1994

(NWIFC 1995). No harbor porpoise mortalities were reported in the observer programs covering these treaty salmon

gillnet fisheries, where observer coverage was estimated at 2.2% (based on % of total catch observed) and approximately

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

Also in 1994, NMFS in conjunction with WDFW and the Tribes conducted an observer program to examine

seabird and marine mammal interactions with the Puget Sound treaty and non-treaty sockeye salmon gillnet fishery (areas

7 and 7A). During this fishery, observers monitored 2,205 sets, representing approximately 7% of the estimated 33,086

sets occurring in the fishery (Pierce et al. 1996). There was one observed harbor porpoise mortality (one other was

entangled and released alive with no indication 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.
76

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 non-

 treaty 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
77

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 self-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 fishery-related 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:
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I. Ship surveys. Fish. Bull. 86:417-432.

Barlow, J., and D. Hanan. 1995. An assessment of the status of harbor porpoise in central California. Rep. Int. Whal.

Commn. Special Issue 16:123-140.

Barlow, J., C. W. Oliver, T. D. Jackson, and B. L. Taylor. 1988. Harbor porpoise, Phocoena phocoena, abundance

estimation for California, Oregon, and Washington: II. Aerial surveys. Fish. Bull. 86:433-444.

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

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

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

425.

Calambokidis, J., and J. Barlow. 1991. Chlorinated hydrocarbon concentrations and their use for describing population

discreteness in harbor porpoises from Washington, Oregon, and California. In: Reynolds, J. E., III, and D. K.

Odell (eds.), Proceedings of the second marine mammal stranding workshop: 3-5 December 1987, Miami,

Florida. NMFS, NOAA Tech. Rep. NMFS 98:101-110.

Calambokidis, J., J. R. Evenson, J. C. Cubbage, P. J. Gearin, and S. D. Osmek. 1992. Harbor porpoise distribution and

abundance off Oregon and Washington from aerial surveys in 1991. Final Report by Cascadia Research,

Olympia, WA, to National Marine Mammal Laboratory, AFSC, NMFS, Seattle, WA. 44 pp.

Calambokidis, J., J. C. Cubbage, J. R. Evenson, S. D. Osmek, J. L. Laake, P. J. Gearin, B. J. Turnock, S. J. Jeffries, and

R. F. Brown. 1993. Abundance estimates of harbor porpoise in Washington and Oregon waters. Final Report

by Cascadia Research, Olympia, WA, to National Marine Mammal Laboratory, AFSC, NMFS, Seattle, WA.

55 pp.

Calambokidis, J., S. D. Osmek, and J. L. Laake. 1997. Aerial surveys for marine mammals in Washington and British

Columbia inside waters. Final Report by Cascadia Research, Olympia, WA, to National Marine Mammal

Laboratory, AFSC, NMFS, Seattle, WA. 96 pp.

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.
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Laake, J. L., R. L. DeLong, J. Calambokidis, and S. Osmek. 1997a. Abundance and distribution of marine mammals

in Washington and British Columbia inside waters, 1996. Pp. 67-73, In: MMPA and ESA Implementation

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

7600 Sand Point Way NE, Seattle, WA 98115.

Laake, J. L., J. Calambokidis, S. D. Osmek, and D. J. Rugh. 1997b. Probability of detecting harbor porpoise from aerial

surveys: estimating g(0). J. Wildl. Manage. 61(1):63-75.

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 non-treaty

salmon gill net fishery: Puget Sound and Hood Canal Washington. Unpubl. report. Washington Dept. Fish

and Wildlife, Olympia, WA. 39 pp. Available at WDFW, 600 Capitol Way N, Olympia, WA, 98501.

Pierce, D. J., M. Alexandersdottir, S. J. Jeffries, P. Erstad, W. Beattie, and A. Chapman. 1996. Interactions of marbled

murrelets and marine mammals with the 1994 Puget Sound sockeye gill net fishery. Final Report, Washington

Dept. Fish and Wildlife, Olympia, WA. 21 pp.

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-OPR-12. 93 pp.
80

W132 W129 W126 W123 W120 W117

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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. ! = summer/autumn ship-based sightings;

+ = winter/spring aerial-based sightings.

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 interannual 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. 

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 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.
81

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, 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
82

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)

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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. ! = summer/autumn ship-based sightings;

+ = winter/spring aerial-based sightings.

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).

Although there is clear evidence that two forms of

Pacific white-sided dolphins occur along the U.S. west coast,

there are no known differences in color pattern, and it is not

currently possible to distinguish animals without genetic or

morphometric analyses. Geographic stock boundaries appear dynamic and are poorly understood, and therefore cannot

be used to differentiate the two forms. Until means of differentiating the two forms for abundance and mortality

estimation are developed, these two stocks must be managed as a single unit; however, this is an undesirable management

situation. Furthermore, Pacific white-sided dolphins are not restricted to U.S. territorial waters, but cooperative

management agreements with Mexico exist only for the tuna purse seine fishery and not for other fisheries which may

take this species (e.g. gillnet fisheries). Additional means of differentiating the two types must be found, and cooperative

management with Mexico is particularly important for this species, given the apparently dynamic nature of geographical

stock boundaries. Until these goals are accomplished, the management stock includes animals of both forms. For the

Marine Mammal Protection Act (MMPA) stock assessment reports, Pacific white-sided dolphins within the Pacific U.S.

Exclusive Economic Zone are divided into two discrete, non-contiguous areas: 1) waters off California, Oregon and

Washington (this report), and 2) Alaskan waters.
85

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 white-sided dolphins may spend time outside the U.S. Exclusive Economic Zone, and therefore

a multi-year average abundance estimate including California, Oregon and Washington is the most appropriate for

management within U.S. waters. The 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 whitesided dolphins.

Current Population Trend

No long-term trends in the abundance of Pacific white-sided dolphins in California, Oregon and Washington

are suggested based on historical and recent surveys (Dohl et al. 1980; 1983; Green et al. 1992; 1993; Barlow 1995;

Forney et al. 1995, 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 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
86

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 white-sided dolphins between

the late 1950s and 1993. The most recent capture was in November 1993, when three animals were taken for public

display (Forney 1994). No MMPA permits are currently active for live-captures of Pacific white-sided dolphins.

STATUS OF STOCK

The status of Pacific white-sided dolphins in California, Oregon and Washington relative to OSP is not known,

and there is no indication of a trend in abundance for this stock. No habitat issues are known to be of concern for this

species. They are not listed as "threatened" or "endangered" under the Endangered Species Act nor as "depleted" under

the MMPA. Including driftnet mortality only for years after implementation of the Take Reduction Plan (1997-98), the

average annual human-caused mortality in 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 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.
87

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. 

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
88

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

W132 W129 W126 W123 W120 W117

N30

N34

N38

N42

N46

WASHINGTON

OREGON

CALIFORNIA

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. ! = summer/autumn ship-based sightings;

+ = winter/spring aerial-based sightings.

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.

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).

Minimum Population Estimate

The log-normal 20th percentile of the 1996-2001 weighted average abundance estimate is 12,748 Risso's

dolphins.
90

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 (0.58)

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 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).
91

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 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
92

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. NMFS-SWFSC-211. 88 pp.

Shane, S. 1994. Occurrence and habitat use of marine mammals at Santa Catalina Island, California from 1983-91.

Bull. Southern California Acad. Sci. 93:13-29.

Sosa-Nishizaki, O., R. De la Rosa Pacheco, R. Castro Longoria, M. Grijalva Chon, and J. De la Rosa Velez. 1993.

Estudio biologico pesquero del pez (Xiphias gladius) y otras especies de picudos (marlins y pez vela). Rep.

Int. CICESE, CTECT9306.

Wade, P. R. and R. P. Angliss. 1997. Guidelines for Assessing Marine Mammal Stocks: Report of the GAMMS

Workshop April 3-5, 1996, Seattle, Washington. U. S. Dep. Commerce, NOAA Tech. Memo. NMFS-OPR-12.

93 pp.
93

Figure 1. Approximate range (in bold) of California coastal

bottlenose dolphins based on aerial surveys along the coast of

California from 1990-2000. This population of bottlenose

dolphins is found within about 1 km of shore.

Revised 12/15/2003

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, Oregon and Washington offshore stock, and 3) Hawaiian stock.

POPULATION SIZE

Photo-identification studies along the coasts of southern California and northern Mexico identified 404 unique

individuals in this population between 1981 and 1989 based on dorsal fin characteristics, with an estimated 35% of

animals lacking identifiable characters at any particular time (Defran and Weller 1999). This cannot be considered a

minimum population estimate, however, because an unknown number of animals died during this period and rates of

acquisition of dorsal fin characters are not known. Mark-recapture estimates based on photo-identification studies in

1985-89 range from 234 (95% CI 205-263) to 285 (95% CI 265-306) animals for the entire California-Mexico population

(Defran and Weller 1999). A recent re-analysis of mark-recapture estimates from the 1980s resulted in revised

abundance estimates of 289 (95% CI 230-298) for the period 1984-86 and 354 (95% CI 330-390) for 1987-89 (Dudzik

1999). The most recent photographic mark-recapture abundance estimate is 356 (95% CI 306 - 437) for the period 1996-
94

98 (Dudzik 1999). Because coastal bottlenose dolphins spend an unknown amount of time in Mexican waters, where

they are subject to mortality in Mexican fisheries, an average abundance estimate for California only is the most

appropriate for U.S. management of this stock. Tandem aerial surveys were conducted in 1990-94 and 1999-2000 to

estimate the abundance of coastal bottlenose dolphins throughout the southern and central California portion of their

range and to correct for the fraction of animals missed by a single observer team. (Carretta et al. 1998, NMFS, SWFSC,

unpublished data). Aerial survey correction factors have been improved using recent information on California coastal

bottlenose dolphin swim speeds (Ward 1999). Using the same methods as Carretta et al. (1998), the weighted average

abundance estimate for the 1999-2000 surveys is 206 (CV=0.12) coastal bottlenose dolphins (NMFS, SWFSC,

unpublished data). This presently is the best estimate of the average number of coastal bottlenose dolphins in U.S. waters.

Minimum Population Estimate

The log-normal 20th percentile of the above average abundance estimate for U.S. waters based on the 1999-2000

surveys is 186 coastal bottlenose dolphins.

Current Population Trend

 Based on a comparison of mark-recapture abundance estimates for the periods 1987-89 (N$ = 354) and 1996-98

(N$ = 356), Dudzik (1999) stated that the population size had remained stable over an 11-year period.

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

No information on current or maximum net productivity rates is available for California coastal bottlenose

dolphins.

POTENTIAL BIOLOGICAL REMOVAL

The potential biological removal (PBR) level for this stock is calculated as the minimum population size (186)

times one half the default maximum net growth rate for cetaceans (1⁄2 of 4%) times a recovery factor of 0.50 (for a species

of unknown status with no known fishery mortality; Wade and Angliss 1997), resulting in a PBR of 1.9 coastal

bottlenose dolphins per year. 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Fishery Information

Due to its exclusive use of coastal habitats, this bottlenose dolphin population is susceptible to fishery-related

mortality in coastal set net fisheries. A summary of information on fishery mortality and injury for this stock of

bottlenose dolphin is shown in Table 1. 

Table 1. Summary of available information on the incidental mortality and serious injury of bottlenose dolphins

(California Coastal Stock) in commercial fisheries that might take this species.

Fishery Name Data Type Year(s)

Percent

Observer

Coverage

Observed

Mortality

Estimated

Annual Mortality

Mean Annual

Takes

CA angel shark/ halibut and other

species large mesh (>3.5in) set

gillnet fishery observer

data 

1997

1998

1999

2000

2001

0 %

0%

4.0 %1

1.8%1

0%

00 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 (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. 

More detailed information on the set gillnet fishery is provided in Appendix 1. From 1991-94, no bottlenose dolphins

were observed taken in this fishery with 10-15% observer coverage (Julian and Beeson 1998). The observer program

was discontinued at the end of 1994, when coastal set gillnet fishing was banned within 3 nmi of the southern California
95

coast. In central California, gillnets have been restricted to waters deeper than 30 fathoms (56m) since 1991 in all areas

except between Point Sal and Point Arguello. In 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. 

Other removals

Seven coastal bottlenose dolphins were collected during the late 1950s in the vicinity of San Diego (Norris and

Prescott 1961). Twenty-seven additional bottlenose dolphins were captured off California between 1966 and 1982

(Walker 1975; Reeves and Leatherwood 1984), but based on the locations of capture activities, these animals probably

were offshore bottlenose dolphins (Walker 1975). No additional captures of coastal bottlenose dolphins have been

documented since 1982, and no live-capture permits are currently active for this species.

STATUS OF STOCK

The status of coastal bottlenose dolphins in California relative to OSP is not known, and there is no evidence

of a trend in abundance. They are not listed as "threatened" or "endangered" under the Endangered Species Act nor as

"depleted" under the MMPA. Because no recent fishery takes have been documented, coastal bottlenose dolphins are

not classified as a "strategic" stock under the MMPA, and the total fishery mortality and serious injury for this stock can

be considered to be insignificant and approaching zero.

Habitat Issues

Pollutant levels, especially DDT residues, found in Southern California coastal bottlenose dolphins have been

found to be among the highest of any cetacean examined (O'Shea et al. 1980; Schafer et al. 1984). Although the effects

of pollutants on cetaceans are not well understood, they may affect reproduction or make the animals more prone to other

mortality factors (Britt and Howard 1983; O’Shea et al. 1999). This population of bottlenose dolphins may also be

vulnerable to the effects of morbillivirus outbreaks, which were implicated in the 1987-88 mass mortality of bottlenose

dolphins on the U.S. Atlantic coast (Lipscomb et al. 1994).

REFERENCES

Britt, J. O. and E. B. Howard. 1983. Tissue residues of selected environmental contaminants in marine mammals. In:

Howard, E. B. (ed.), Pathobiology of Marine Mammal Diseases. CRC Press, Boca Raton, Florida.

Carretta, J. V., K. A. Forney and J. L. Laake. 1998. The abundance of southern California coastal bottlenose dolphins

estimated from tandem aerial surveys. Mar. Mamm. Sci. 14:655-675.

Defran, R. H. and D. W. Weller. 1999. Occurrence, distribution, site fidelity and school size of bottlenose dolphins

(Tursiops truncatus) off San Diego, California. Mar. Mamm. Sci. 15:366-380.

Defran, R. H., D. W. Weller, D. L. Kelly, and M. A. Espinosa. 1999. Range characteristics of Pacific coast bottlenose

dolphins (Tursiops truncatus) in the Southern California Bight. Mar. Mamm. Sci. 15:381-393.

Dudzik, K.J. 1999. Population dynamics of the Pacific coast bottlenose dolphin (Tursiops truncatus). M.S. Thesis, San

Diego State University, San Diego, California 92182. 63pp.

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

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

Technical Memorandum NMFS-SWFSC-300. 276p.

Hansen, L. J. 1990. California coastal bottlenose dolphins. In: S. Leatherwood and R.R. Reeves (eds.), The Bottlenose

Dolphin, p. 403-420. Academic Press, Inc., San Diego.

Hansen, L. J. and R. H. Defran. 1990. A comparison of photo-identification studies of California coastal bottlenose

dolphins. Rep. Int. Whal. Commn. Special Issue 12:101-104.

Hanson, M.T. and R.H. Defran. 1993. The behavior and feeding ecology of the Pacific coast bottlenose dolphin,

Tursiops truncatus. Aquatic Mammals 19:127-142.

Julian, F. and M. Beeson. 1998. Estimates of mammal, turtle and bird mortality for two California gillnet fisheries:

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

Lipscomb, T. P., F. Y. Schulman, D. Moffett, and S. Kennedy. 1994. Morbilliviral disease in Atlantic bottlenose

dolphins (Tursiops truncatus) from the 1987-88 epizootic. Journal of Wildlife Diseases 30:567-571.
96

O'Shea, T. J., R. L. Brownell, Jr., D. R. Clark, W. A. Walker, M. L. Gray, and T. G. Lamont. 1980. Organochlorine

pollutants in small cetaceans from the Pacific and South Atlantic Oceans, November 1968-June 1976.

Pesticides Monitoring Journal 14:35-46.

O’Shea, T. J., R. R. Reeves, and A. Kirk Long (eds.). 1999. Marine Mammals and Persistent Ocean Contaminants:

Proceedings of the Marine Mammal Commission Workshop, Keystone, Colorado, 12-15 October 1998. Marine

Mammal Commission, Bethesda, MD. 150pp.

NMFS, Southwest Fisheries Science Center. P.O. Box 271, La Jolla, CA 92038-0271

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

of California Publications in Zoology 63:291-402. University of California Press, Berkeley and Los Angeles.

Reeves, R. R. and S. Leatherwood. 1984. Live-capture fisheries for cetaceans in USA and Canadian waters, 1973-1982.

Rep. Int. Whal. Commn. 34:497-507.

Ross, G. J. B. and V. G. Cockcroft. 1990. Comments on Australian bottlenose dolphins and the taxonomic status of

Tursiops aduncus (Ehrenberg, 1832). In: The Bottlenose Dolphin (eds. S. Leatherwood and R. R. Reeves). pp.

101-128. Academic Press, 653pp. 

Schafer, H. A., R. W. Gossett, C. F. Ward, and A. M. Westcott. 1984. Chlorinated hydrocarbons in marine mammals.

Biennial Report, 1983-84, Southern California Coastal Water Research Project, Long Beach, California.

Van Waerebeek, K., J. C. Reyes, A. J. Read, and J. S. McKinnon. 1990. Preliminary observations of bottlenose

dolphins from the Pacific coast of South America. In: The Bottlenose Dolphin (eds. S. Leatherwood and R. R.

Reeves). pp. 143-154 Academic Press, 653 pp. 

Walker, W. A. 1975. Review of the live-capture fishery for smaller cetaceans taken in Southern California waters for

public display, 1966-77. J. Fish. Res. Board. Can. 32:1197-1211.

Walker, W. A. 1981. Geographical variation in morphology and biology of bottlenose dolphins (Tursiops) in the

eastern North Pacific. Admin. Rep. LJ-81-03C. Southwest Fisheries Science Center, National Marine Fisheries

Service, P.O. Box 271, La Jolla, CA 92038, USA. 52p.

Ward, B.G. 1999. Movement patterns and feeding ecology of the Pacific coast bottlenose dolphin (Tursiops truncatus).

M.S. Thesis, San Diego State University, San Diego, California, 92182. 98pp.

Wells, R. S., L. J. Hansen, A. B. Baldridge, T. P. Dohl, D. L. Kelly and R. H Defran. In: S. Leatherwood and R. R.

Reeves (eds.), The Bottlenose Dolphin, p. 421-431. Academic Press, Inc., San Diego.

Wade, P. R. and R. P. Angliss. 1997. Guidelines for Assessing Marine Mammal Stocks: Report of the GAMMS

Workshop April 3-5, 1996, Seattle, Washington. U. S. Dep. Commerce, NOAA Tech. Memo. NMFS-OPR-12.

93 pp.
97

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. 

Revised 12/15/2003

BOTTLENOSE DOLPHIN (Tursiops truncatus):

California/Oregon/Washington Offshore Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

Bottlenose dolphins are distributed world-wide in

tropical and warm-temperate waters. In many regions,

including California, separate coastal and offshore populations

are known (Walker 1981; Ross and Cockcroft 1990; Van

Waerebeek et al. 1990). On surveys conducted off California,

offshore bottlenose dolphins have been found at distances

greater than a few kilometers from the mainland and

throughout the Southern California Bight. They have also

been documented in offshore waters as far north as about 41o

N

(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.

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 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
99

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 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
100

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

W132 W129 W126 W123 W120 W117

N30

N34

N38

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.

Revised 12/15/2003

STRIPED DOLPHIN (Stenella coeruleoalba):

California/Oregon/Washington Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

Striped dolphins are distributed world-wide in

tropical and warm-temperate pelagic waters. On recent

shipboard surveys extending about 300 nmi offshore of

California, they were sighted within about 100-300 nmi from

the coast (Figure 1). No sightings have been reported for

Oregon and Washington waters, but striped dolphins have

stranded in both states (Oregon Department of Fish and

Wildlife, unpublished data; Washington Department of Fish

and Wildlife, unpublished data). Striped dolphins are also

commonly found in the central North Pacific, but sampling

between this region and California has been insufficient to

determine whether the distribution is continuous. Based on

sighting records off California and Mexico, striped dolphins

appear to have a continuous distribution in offshore waters of

these two regions (Perrin et al. 1985; Mangels and Gerrodette

1994). No information on possible seasonality in distribution

is available, because the California surveys which extended

300 nmi offshore were conducted only during the summer/fall

period. Although striped dolphins are not restricted to U.S.

waters, cooperative management agreements with Mexico

exist only for the tuna purse seine fishery and not for other

fisheries which may take this species (e.g. gillnet fisheries).

Therefore, the management stock includes only animals found

within U.S. waters. For the Marine Mammal Protection Act

(MMPA) stock assessment reports, striped dolphins within the

Pacific U.S. Exclusive Economic Zone are divided into two

discrete, non-contiguous areas: 1) waters off California,

Oregon and Washington (this report), and 2) waters around

Hawaii.

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 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 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.

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
102

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). 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
103

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.].

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.
104

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

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

Julian, F. and M. Beeson. 1998. Estimates of mammal, turtle and bird mortality for two California gillnet fisheries:

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

Leatherwood, S., R. R. Reeves, W. F. Perrin, and W. E. Evans. 1982. Whales, dolphins and porpoises of the eastern

North Pacific and adjacent Arctic waters. A guide to their identification. NOAA Tech. Rep. NMFS Circular

444, U.S. Dep. Commer., NOAA, NMFS. 245 pp.

Mangels, K. F. and Gerrodette, T. 1994. Report of cetacean sightings during a marine mammal survey in the eastern

Pacific Ocean and Gulf of California aboard the NOAA ships McARTHUR and DAVID STARR JORDAN July

28 - November 6, 1993. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-SWFSC-211. 88 pp.

Perrin, W. F., M. D. Scott, G. J. Walker and V. L. Cass. 1985. Review of geographical stocks of tropical dolphins

(Stenella spp. and Delphinus delphis) in the eastern Pacific. NOAA Tech. Rep. NMFS 28. Available from

NMFS, Southwest Fisheries Science Center, P.O. Box 271, La Jolla, California, 92038. 28p.

Roemmich, D. 1992. Ocean warming and sea level rise along the southwest U.S. coast. Science 257:373-375.

Smith, R. C., P. Dustan, D. Au, K. S. Baker, and E. A. Dunlap. 1986. Distribution of cetaceans and sea-surface

chlorophyll concentrations in the California Current. Marine Biology 91:385-402.

Sosa-Nishizaki, O., R. De la Rosa Pacheco, R. Castro Longoria, M. Grijalva Chon, and J. De la Rosa Velez. 1993.

Estudio biologico pesquero del pez (Xiphias gladius) y otras especies de picudos (marlins y pez vela). Rep.

Int. CICESE, CTECT9306.

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

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.

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. 

POPULATION SIZE

Aerial line transect surveys conducted in winter/spring of 1991-92 resulted only in a combined abundance

estimate of 305,694 (CV=0.34) animals for short-beaked and long-beaked common dolphins, because species-level

identification was not possible from the air (Forney et al. 1995). Based on sighting locations, the majority of these were

probably short-beaked common dolphins. 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 (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
106

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 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 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 short-beaked and long-beaked common dolphins in the field,

tissue samples have been collected for most of the animals observed killed. These tissue samples have enabled positive

identification using genetic techniques for all except two of the common dolphins killed (NMFS, unpublished data).

Based on past patterns (Barlow et al. 1997), these two animals are likely to have been a short-beaked common dolphin,

and they are included below for this species. After the 1997 implementation of a Take Reduction Plan, which included

skipper education workshops and required the use of pingers and minimum 6-fathom extenders, common dolphin

entanglement rates in the drift gillnet fishery dropped considerably (Barlow and Cameron 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.
107

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/Da

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)

CA angel shark/ halibut

and other species large

mesh (>3.5in) set gillnet

fishery

extrapolated

estimates

MMAP

self-reporting

Common dolphins, species not determined

0.61 ≥

≥ 0.4 (n/a)

1997-

2001

1997

1998

1999

2000

2001

0 - 4%

- 

-

-

-

-

0

0

2

0

0

0

31

0

≥ 2

0

0

0

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)

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

calculated PBR and, therefore, can be considered to be insignificant and approaching zero mortality and serious injury
109

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.

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
110

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

Hodder, J. Oregon Institute of Marine Biology, Charleston, OR, 97420.

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

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

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

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

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

IATTC. 1997. Annual Report of the Inter-American Tropical Tuna Commission, 1995, La Jolla, California.

IATTC. (in prep). 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, NOAA-TM-NMFS-SWFSC-211.

NMFS, Southwest Fisheries Science Center, P.O. Box 271, La Jolla, CA 92038-027.

NMFS, Southwest Region, 501 West Ocean Blvd, Long Beach, CA 90802-4213.

Norberg, B., NMFS, Northwest Region,.7600 Sand Point Way NE, BIN C15700,Seattle, WA 98115-0070.

Perrin, W. F., M. D. Scott, G. J. Walker and V. L. Cass. Review of geographical stocks of tropical dolphins (Stenella

spp. and Delphinus delphis) in the eastern Pacific. NOAA Technical Report NMFS 28. Available from NMFS,

Southwest Fisheries Science Center, P.O. Box 271, La Jolla, California, 92038. 28p.

Roemmich, D. 1992. Ocean warming and sea level rise along the southwest U.S. coast. Science 257:373-375.

Rosel, P. E., A. E. Dizon and J. E. Heyning. 1994. Population genetic analysis of two forms of the common dolphin

(genus Delphinus) utilizing mitochondrial DNA control region sequences. Marine Biology 119:159-167.

Sosa-Nishizaki, O., R. De la Rosa-Pacheco, R. Castro-Longoria, M. Grijalva Chon, and J. De la Rosa Velez. 1993.

Estudio biologico pesquero del pez (Xiphias gladius) y otras especies de picudos (marlins y pez vela). Rep.

Int. CICESE, CTECT9306.

Wade, P. R. and R. P. Angliss. 1997. Guidelines for Assessing Marine Mammal Stocks: Report of the GAMMS

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

93 pp.

Wade, P. R. and T. Gerrodette. 1993. Estimates of cetacean abundance and distribution in the eastern tropical Pacific.

Rep. Int. Whal. Commn 43:477-493.
111

W132 W129 W126 W123 W120 W117

N30

N34

N38

N42

N46

WASHINGTON

OREGON

CALIFORNIA

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.

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), long-beaked ("Baja

neritic") common dolphins involved in eastern tropical Pacific

tuna fisheries are managed separately as part of the 'northern

common dolphin' stock (Perrin et al. 1985), and these animals

are not included in the assessment reports. For the MMPA

stock assessment reports, there is a single Pacific management

stock including only animals found within the U.S. Exclusive

Economic Zone of California.

POPULATION SIZE

Aerial line transect surveys conducted in winter and

spring of 1991 and 1992 resulted only in a combined

abundance estimate of 305,694 (CV=0.34) long-beaked and

short-beaked common dolphins, because species-level

identification was not possible from the air (Forney et al.

1995). Based on sighting locations, the majority of these

animals were probably 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 longbeaked 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). 

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 short-beaked and long-beaked common dolphins in the field,

tissue samples have been collected for most of the animals observed killed. These tissue samples have enabled positive

identification using genetic techniques for all except two of the common dolphins killed (NMFS, unpublished data).

Based on past patterns (Barlow et al. 1997), these two animals are likely to have been a short-beaked common dolphin,

and they have not been included in the mortality calculations below for long-beaked common dolphins. After the 1997

implementation of a Take Reduction Plan, which included skipper education workshops and required the use of pingers

and minimum 6-fathom extenders, common dolphin entanglement rates in the drift gillnet fishery dropped considerably

(Barlow and Cameron 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) longbeaked 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.

 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.
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)

CA angel shark/ halibut

and other species large

mesh (>3.5in) set gillnet

fishery

observer

data

MMAP

selfreporting

Common dolphins, species not determined

0.6 (n/a)

≥ 0.4 (n/a)

 1997-2001

1997

1998

1999

2000

2001

0 - 4%

- 

- 

- 

- 

- 

0

0

2

0

0

0

31

0

≥ 2

0

0

0

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)

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.

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 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
114

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.].

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.
115

Hill, P. S. and D. P. DeMaster. 1998. Alaska Marine Mammal Stock Assessments, 1998. U.S. Dep. Commer., NOAA

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

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

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

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

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

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

IATTC. 1997. Annual Report of the Inter-American Tropical Tuna Commission, 1995, La Jolla, California.

IATTC. (in prep). 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

W132 W129 W126 W123 W120 W117

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. != summer/autumn ship-based sightings; +

= winter/spring aerial-based sightings.

Revised 12/15/2003

NORTHERN RIGHT-WHALE DOLPHIN (Lissodelphis borealis):

California/Oregon/Washington Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

Northern right-whale dolphins are endemic to

temperate waters of the North Pacific Ocean. Off the U.S.

west coast, they have been seen primarily in shelf and slope

waters (Figure 1), with seasonal movements into the Southern

California Bight (Leatherwood and Walker 1979; Dohl et al.

1980; 1983; NMFS, unpublished data). Sighting patterns

from recent aerial and shipboard surveys conducted in

California, Oregon and Washington during different seasons

(Green et al. 1992; 1993; Forney et al. 1995; Barlow 1995)

suggest seasonal north-south movements, with animals found

primarily off California during the colder water months and

shifting northward into Oregon and Washington as water

temperatures increase in late spring and summer (Green et al.

1992; Forney 1994; Forney and Barlow 1998). The southern

end of this population's range is not 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

right-whale dolphins from the U.S. West coast and other areas

of the North Pacific (Dizon et al. 1994); however, power

analyses indicate that the ability to detect stock differences for

this species is poor, given traditional statistical error levels

(Dizon et al. 1995). Although northern right-whale dolphins

are not restricted to U.S. territorial waters, there are currently

no international agreements for cooperative management. For

the Marine Mammal Protection Act (MMPA) stock

assessment reports, there is a single management stock

including only animals found within the U.S. Exclusive

Economic Zone of California, Oregon and Washington.

POPULATION SIZE

The previous best estimates of abundance for

northern right-whale dolphins (Barlow et al. 1997) were based

on winter/spring 1991-92 aerial surveys (Forney et al. 1995)

off California, which were presumed to include northern rightwhale 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).

Minimum Population Estimate

The log-normal 20th percentile of the 1996-2001 weighted average abundance estimate is 16,417 northern rightwhale dolphins.
117

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 right-whale dolphins taken annually.

Table 1. Summary of available information on the incidental mortality and injury of northern right-whale dolphins

(California/Oregon/Washington Stock) in commercial fisheries that might take this species. All observed entanglements

of northern right-whale dolphins resulted in the death of the animal. Coefficients of variation for mortality estimates are

provided in parentheses. Mean annual takes are based on 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

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/Da

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. 

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).

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
119

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.].

Dizon, A., C. LeDuc, and R. LeDuc. 1994. Intraspecific structure of the northern right-whale dolphin (Lissodelphis

borealis): The power of an analysis of molecular variation for differentiating genetic stocks. CalCOFI Rep.

35:61-67.

Dizon, A. E., G. M. O'Corry-Crowe, and B. L. Taylor. (1995). Why statistical power is necessary to link analyses of

molecular variation to decisions about population structure. pp. 288-294 In: J. L. Neilsen (ed.), Evolution and

the Aquatic Ecosystem: Defining Unique Units in Population Conservation. American Fisheries Society

Symposium 17.

Dohl, T. P., R. C. Guess, M. L. Duman, and R. C. Helm. 1983. Cetaceans of central and northern California, 1980-

1983: Status, abundance and distribution. OCS Study MMS 84-0045. Minerals Management Service Contract

# 14-12-0001-29090. 284p.

Dohl, T. P., K. S. Norris, R. C. Guess, J. D. Bryant, and M. W. Honig. 1980. Summary of marine mammal and seabird

surveys of the Southern California Bight area, 1975-1978. Part II. Cetacea of the Southern California Bight.

Final Report to the Bureau of Land Management, NTIS Rep. No. PB81248189. 414p.

Forney, K. A. 1994. Recent information on the status of odontocetes in Californian waters. NOAA Technical

Memorandum NMFS, NOAA-TM-NMFS-SWFSC-202. Available from NMFS, Southwest Fisheries Science

Center, P.O. Box 271, La Jolla, California, USA.

Forney, K. A. and J. Barlow. 1998. Seasonal patterns in the abundance and distribution of California cetaceans, 1991-

92. Mar. Mamm. Sci. 14:460-489.

Forney, K. A., J. Barlow and J. V. Carretta. 1995. The abundance of cetaceans in California waters. Part II: Aerial

surveys in winter and spring of 1991 and 1992. Fish. Bull. 93:15-26.

Green, G., J. J. Brueggeman, R. A. Grotefendt, C. E. Bowlby, M. L. Bonnell, and K. C. Balcomb, III. 1992. Cetacean

distribution and abundance off Oregon and Washington. Ch. 1. In: Oregon and Washington Marine Mammal

and Seabird Surveys. OCS Study 91-0093. Final Report prepared for Pacific OCS Region, Minerals
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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 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

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 combined.

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).

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 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.
122

POPULATION SIZE

Off British Columbia, approximately 200 offshore killer whales were identified between 1989 and 1993 (Ford

et al. 1994), and 20 of these individuals have also been seen off California (Black et al. 1997). Using only good quality

photographs that clearly show characteristics of the dorsal fin and saddle patch region, an additional 11 offshore killer

whales that were not previously known have been identified off the California coast, bringing the total number of known

individuals in this population to 211. This is certainly an underestimate of the total population size, because not all

animals in this population have been photographed. In the future, it may be possible estimate the total abundance of this

transboundary stock using mark-recapture analyses based on individual photographs. Based on summer/fall shipboard

line-transect surveys in 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 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.
123

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 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).

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.

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.
124

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. NMFSSWFSC-247. 174p.

Braham, H. W., and M. E. Dahlheim. 1982. Killer whales in Alaska documented in the Platforms of Opportunity

Program. Rep. Int. Whal. Commn., 32:643-646.

Cameron, G., and K. A. Forney. 1999. Estimates of cetacean mortality in the California gillnet fisheries for 1997 and

1998. Paper SC/51/O4 presented to the International Whaling Commission, 1999 (unpublished). 14pp.

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 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.
125

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

Vancouver Island

British Columbia

Washington

Oregon

California

Figure 1. Approximate April-October

distribution of the Eastern North Pacific

Southern Resident killer whale stock

(shaded area) and range of sightings

(dotted line).

Revised 12/15/2003

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 have been noted for killer whales throughout Alaska (Braham

and Dahlheim 1982) and in the intracoastal waterways of British Columbia

and Washington State, where pods have been labeled as ‘resident,’

‘transient,’ and ‘offshore’ (Bigg et al. 1990, Ford et al. 1994) based on

aspects of morphology, ecology, genetics, and behavior (Ford and Fisher

1982, Baird and Stacey 1988, Baird et al. 1992, Hoelzel et al. 1998).

Through examination of photographs of recognizable individuals and pods,

movements of whales between geographical areas have been documented.

For example, whales identified in Prince William Sound have been observed

near Kodiak Island (Matkin et al. 1999) and whales identified in Southeast

Alaska have been observed in Prince William Sound, British Columbia, and

Puget Sound (Leatherwood et al. 1990, Dahlheim et al. 1997).

Studies on mtDNA restriction patterns provide evidence that the

‘resident’ and ‘transient’ types are genetically distinct (Stevens et al. 1989,

Hoelzel 1991, Hoelzel and Dover 1991, Hoelzel et al. 1998). Analysis of 73

samples collected from eastern North Pacific killer whales from California

to Alaska has demonstrated significant genetic differences among ‘transient’

whales from California through Alaska, ‘resident’ whales from the inland

waters of Washington, and ‘resident’ whales ranging from British Columbia

to the Aleutian Islands and Bering Sea (Hoelzel et al. 1998). Most sightings

of the Eastern North Pacific Southern Resident stock of killer whales have

occurred in the summer in inland waters of Washington and southern British

Columbia. However, pods belonging to this stock have also been sighted in

coastal waters off southern Vancouver Island and Washington (Bigg et al.

1990, Ford et al. 2000). The complete winter range of this stock is uncertain. Of the three pods comprising this stock,

one (J1) is commonly sighted in inshore waters in winter, while the other two (K1 and L1) apparently spend more time

offshore (Ford et al. 2000). Pods K1 and L1 are often seen entering the inland waters of Vancouver Island from the

north–through Johnstone Strait–in the spring (Ford et al. 2000), suggesting that they may spend time along the entire

outer coast of Vancouver Island during the winter. Off the Washington coast, Southern Resident killer whales have been

sighted as far south as Grays Harbor (season unknown) (Bigg et al. 1990), and members of pods K1 and L1 were

observed in Monterey Bay, California, in January 2000 (N. Black, pers. comm.).

Based on data regarding association patterns, acoustics, movements, genetic differences and potential fishery

interactions, five killer whale stocks are recognized within the Pacific U.S. EEZ: 1) the Eastern North Pacific Northern

Resident stock - occurring from British Columbia through Alaska, 2) the Eastern North Pacific Southern Resident stock -

occurring mainly within the inland waters of Washington State and southern British Columbia (see Fig. 1), 3) the Eastern

North Pacific Transient stock - occurring from Alaska through California, 4) the Eastern North Pacific Offshore stock -

occurring from Southeast Alaska through California, and 5) the Hawaiian stock. The Stock Assessment Reports for the

Alaska Region contain information concerning the Eastern North Pacific Northern Resident and Eastern North Pacific

Transient stocks.
127

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. Each year’s count includes animals first seen and

first missed; a whale is considered first missed the year after it was last seen

alive (Ford et al. 2000; Center for Whale Research, unpubl. data).

POPULATION SIZE

The Eastern North Pacific

Southern Resident stock is a transboundary stock including killer whales in

inland Washington and southern British

Columbia waters. Photo-identification of

individual whales through the years has

resulted in a substantial understanding of

this stock’s structure, behaviors, and

movements. In 1993, the three pods

comprising this stock totaled 96 killer

whales (Ford et al. 1994). The population

increased to 99 whales in 1995, then

declined to the current population of 80

whales in 2002 (Fig. 2; Ford et al. 2000;

Center for Whale Research, unpubl. data).

The 2001 and 2002 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 December 2003, L-98

has remained separate from L pod, and it remains unclear whether it will rejoin L pod in the future. For now, it will be

included in the current population size. However, one new calf observed in the fall of 2002 will not be a part of the

official census until seen in May/June 2003 (Center for Whale Research, unpubl. data).

Minimum Population Estimate

The abundance estimate for this stock of killer whales is a direct count of individually identifiable animals. It

is thought that the entire population is censused every year. This estimate therefore serves as both a best estimate of

abundance and a minimum estimate of abundance. Thus, the minimum population estimate (NMIN) for the Eastern North

Pacific Southern Resident stock of killer whales is 80 animals.

Current Population Trend

During the live-capture fishery that existed from 1967 to 1973, it is estimated that 47 killer whales, mostly

immature, were taken out of this stock (Ford et al. 1994). The first complete census of this stock occurred in 1974.

Between 1974 and 1993 the Southern Resident stock increased approximately 35%, from 71 to 96 individuals (Ford et

al. 1994). This represents a net annual growth rate of 1.8% during those years. Since 1995, the population has declined

to 80 whales (Ford et al. 2000; Center for Whale Research, unpubl. data).

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

A reliable estimate of the maximum net productivity rate is currently unavailable for this stock of killer whales.

Studies of ‘resident’ killer whale pods in British Columbia and Washington waters resulted in estimated population

growth rates of 2.92% and 2.54% over the period from 1973 to 1987 (Olesiuk et al. 1990, Brault and Caswell 1993).

However, a population increases at the maximum growth rate (RMAX) only when the population is at extremely low

levels; thus, the estimate of 2.92% 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).

POTENTIAL BIOLOGICAL REMOVAL

The potential biological removal (PBR) level for this stock is calculated as the minimum population size (80)

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.
128

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 98% in the entire fishery

(coastal + inland waters) between 1997 and 2001. There was no observer coverage in this fishery 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 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 2001, 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 et al. 2001 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.

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 1997-

2001.
129

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 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”) (WDFW 2003).

REFERENCES

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whales: implications for the evolution of foraging specializations in the genus Orcinus. Oecologia 89:125-132.

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photoidentified individuals. National Marine Mammal Laboratory, AFSC, NMFS, NOAA, 7600 Sand Point

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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

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Ford, J. K. B., and H. D. Fisher. 1982. Killer whale (Orcinus orca) dialects as an indicator of stocks in British

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Ford, J. K. B., G. M. Ellis, and K. C. Balcomb. 2000. Killer Whales: The Natural History and Genealogy of Orcinus

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surveys in winter and spring of 1991 and 1992. Fish. Bull. 93:15-26.

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Oregon and Washington marine mammal and seabird surveys. Final Rep. OCS Study MMS 91-0093.

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fishing gear entanglements of cetaceans on the west coast of Canada in 1994. Paper SC/47/O6 presented to

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Krahn, M. M., P. R. Wade, S. T. Kalinowski, M. E. Dahlheim, B. L. Taylor, M. B. Hanson, G. M. Ylitalo, R. P. Angliss,

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132

W132 W129 W126 W123 W120 W117

N30

N34

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.

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 short-finned pilot

whales off the U.S. west coast. Although the full geographic

range of the California/Oregon/Washington population is not

known, it may be continuous with animals found off Baja

California, and its individuals are morphologically distinct

from short-finned pilot whales found farther south in the

eastern tropical Pacific (Polisini 1981). Separate southern and

northern forms of short-finned pilot whales have also been

documented for the western North Pacific (Kasuya et al. 1988;

Wada 1988; Miyazaki and Amano 1994). For the Marine

Mammal Protection Act (MMPA) stock assessment reports,

short-finned pilot whales within the Pacific U.S. Exclusive

Economic Zone are divided into two discrete, non-contiguous

areas: 1) waters off California, Oregon and Washington (this

report), and 2) Hawaiian waters.

POPULATION SIZE

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).

Minimum Population Estimate

The log-normal 20th percentile of the 1996-2001 weighted average abundance estimate is 149 short-finned pilot

whales.

Current Population Trend

Approximately nine years after the virtual disappearance of short-finned pilot whales following the 1982-83

El Niño, they appear to have returned to California waters, as indicated by an increase in sighting records as well as
133

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. Shortfinned 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.

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ship survey and comparisons of passing and closing modes. Administrative Report LJ-97-11, Southwest

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Barlow, J. and G. A. Cameron. 2003. Field experiments show that acoustic pingers reduce marine mammal bycatch in

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Berdegué, J. 2002. Depredación de las especies pelágicas reservadas a la pesca deportiva y especies en peligro de

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

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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. NMFSSWFSC-217. 90p.

Dohl, T. P., K. S. Norris, R. C. Guess, J. D. Bryant, and M. W. Honig. 1980. Summary of marine mammal and seabird

surveys of the Southern California Bight area, 1975-1978. Part II. Cetacea of the Southern California Bight.

Final Report to the Bureau of Land Management, NTIS Rep. No. PB81248189. 414p.

Forney, K. A. 1997. Patterns of variability and environmental models of relative abundance for California cetaceans.

Ph.D. Dissertation, Scripps Institution of Oceanography, University of California, San Diego.

Forney, K. A. and J. Barlow. 1998. Seasonal patterns in the abundance and distribution of California cetaceans, 1991-

92. Mar. Mamm. Sci. 14:460-489.

Green, G., J. J. Brueggeman, R. A. Grotefendt, C. E. Bowlby, M. L. Bonnell, and K. C. Balcomb, III. 1992. Cetacean

distribution and abundance off Oregon and Washington. Ch. 1. In: Oregon and Washington Marine Mammal

and Seabird Surveys. OCS Study 91-0093. Final Report prepared for Pacific OCS Region, Minerals

Management Service, U.S. Department of the Interior, Los Angeles, California. 

Green, G., R. A. Grotefendt, M. A. Smultea, C. E. Bowlby, and R. A. Rowlett. 1993. Delphinid aerial surveys in

Oregon and Washington waters. Final Report prepared for NMFS, National Marine Mammal Laboratory, 7600

Sand Point Way, NE, Seattle, Washington, 98115, Contract #50ABNF200058.

Heyning, J. E., T. D. Lewis and C. D. Woodhouse. 1994. A note on odontocete mortality from fishing gear

entanglements off Southern California. Rep. Int. Whal. Commn. Special Issue 15:439-442.

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

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

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

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

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

Jones, P. A. and I. D. Szczepaniak. 1992. Report on the seabird and marine mammal censuses conducted for the longterm management strategy (LTMS), August 1990 through November 1991, for the U.S. Environmental

Protection Agency, Region IX, San Francisco, July 1992.

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

fisheries: 1990-95. Fishery Bulletin 96:271-284.

Kasuya, O., T. Miyashita, and F. Kasamatsu. 1988. Segregation of two forms of short-finned pilot whales off the

Pacific coast of Japan. Sci. Rep. Whales Res. Inst. 39:77-90.

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

Administrative Report LJ-83-13C. Available from NMFS, Southwest Fisheries Science Center, P.O. Box 271,

La Jolla, California, 92038. 233p.

Miyazaki, N. and M. Amano. 1994. Skull morphology of two forms of short-finned pilot whales off the Pacific coast

of Japan. Rep. Int. Whaling Commn. 44:499-508.

Polisini, J. M. 1981. A comparison of Globicephala macrorhyncha (Gray, 1846) with the pilot whale of the North

Pacific Ocean: An analysis of the skull of the broad-rostrum pilot whales of the genus Globicephala.

Dissertation Abstracts International Vol. 41, No. 08, February 1981, p. 2928-B.

Shane, S. 1994. Occurrence and habitat use of marine mammals at Santa Catalina Island, California from 1983-91.

Bull. Southern California Acad. Sci. 93:13-29.

Sosa-Nishizaki, O., R. De la Rosa-Pacheco, R. Castro-Longoria, M. Grijalva Chon, and J. De la Rosa Velez. 1993.

Estudio biologico pesquero del pez (Xiphias gladius) y otras especies de picudos (marlins y pez vela). Rep.

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

93 pp.
137

W132 W129 W126 W123 W120 W117

N30

N34

N38

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.

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. 

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).

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
139

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 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. 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
140

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

W132 W129 W126 W123 W120 W117

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N34

N38

N42

N46

WASHINGTON

OREGON

CALIFORNIA

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.

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.

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 species-specific

abundance information. For the Marine Mammal Protection

Act (MMPA) stock assessment reports, three Mesoplodon

stocks are defined: 1) all Mesoplodon species off California,

Oregon and Washington (this report), 2) M. stejnegeri in

Alaskan waters, and 3) M. densirostris in Hawaiian waters.

POPULATION SIZE

Although mesoplodont beaked whales have been

sighted along the U.S. west coast on several line transect

surveys utilizing both aerial and shipboard platforms, sightings

have generally been too rare to produce reliable population

estimates, and species identification has been problematic.

Previous abundance estimates have been imprecise and biased

downward by an unknown amount because of the large

proportion of time mesoplodont beaked whales spend

submerged, and because the surveys on which they were based covered only California waters, and thus could not

include animals off Oregon/Washington. Furthermore, there were a large number of unidentified beaked whale sightings,

which were either Mesoplodon sp. or Cuvier's beaked whales (Ziphius cavirostris). 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 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 multiyear average abundance estimate is the most appropriate for management within U.S. waters. The 1996-2001 weighted
142

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 lognormal 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).

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. 
143

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)

CA/OR thresher

shark/swordfish drift

gillnet fishery

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)

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. 

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
144

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.

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.
145

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.

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.

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.
146

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 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
147

(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.]

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.
148

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.
149

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.

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. Atsea 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.

Minimum Population Estimate

Based on the above abundance estimate and CV, the minimum population estimate (defined as the log-normal

20th percentile of the total Kogia abundance estimate) for pygmy sperm whales in California, Oregon, and Washington

is 119 animals.
150

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 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
151

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 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.

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

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

8604 La Jolla Shores Drive, La Jolla, CA 92037, USA.].
152

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.
153

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.

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.

 

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.
154

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; SosaNishizaki 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 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.
155

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.
156

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 42o

N) and in the inshore half of the

U.S. EEZ. See Appendix 2 for data sources and

information on timing and location of survey effort.

Revised 12/15/2003

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 150o

W at the equator, is 160oW 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). 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).

For the Marine Mammal Protection Act (MMPA) stock assessment reports, sperm whales within the Pacific

U.S. EEZ are divided into three discrete, non-contiguous areas: 1) California, Oregon and Washington waters (this

report), 2) waters around Hawaii, and 3) Alaska waters. 

POPULATION SIZE

Barlow and Taylor (2001) 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
157

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. 

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.
158

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 largescale 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 (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,

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
159

"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”. 

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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
161

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.
162

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.

Revised 12/15/2003

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. 1993) - referred to as the eastern North Pacific stock

(Figure 1); 2) winter/spring populations of the Hawaiian

Islands which migrate to northern British Columbia/Southeast

Alaska and Prince William Sound west to Kodiak (Baker et

al. 1990, Perry et al. 1990, Calambokidis et al. 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. 1993,

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).

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.
163

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. (2002) estimated humpback whale abundance in these feeding areas from 1991 to to 2001 using Petersen markrecapture 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 estimate.

The authors attributed this decline to non-random sampling and bias towards sampling in Monterey Bay in both 1999

and 2000 (Calambokidis et al. 2001); however, evidence of a decline persisted with the 2000/2001 estimate, and it is

likely that an actual decline did occur between 1998 and 1999 (Calambokidis et al. 2002). In general, mark-recapture

estimates are negatively biased due to heterogeneity in sighting probabilities (Hammond 1986); however, this bias is

likely to be minimal because the above mark-recapture estimate is based on data from over half of the entire population

(the 2000/2001 data contained 425 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 2000/2001 abundance estimated from mark-recapture methods

(Calambokidis et al. 2002) or approximately 681.

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 stock appears to have decreased in abundance between 1998

and 1999, but the most recent mark-recapture estimate shows that growth may have resumed (Calambokidis et al. 2002,

Figure 3). 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. Additional years of study will be needed to determine whether the population is continuing

to grow after the apparent decline between 1998 and 1999.

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

The proportion of calves in the California/Mexico stock from 1986 to 1994 appeared much lower than

previously measured for humpback whales in other areas (Calambokidis and Steiger 1994), but in 1995-97 a greater

proportion of calves were identified, and the 1997 reproductive rates for this population are closer to those reported for

humpback whale populations in other regions (Calambokidis et al. 1998). Despite the apparently low proportion of

calves, two independent lines of evidence indicate that this stock was growing in the 1980s and early 1990s (Barlow

1994; Calambokidis et al. 2000) with a best estimate of 8% growth per year (Calambokidis et al. 1999). The current net

productivity rate is unknown.
164

0

200

400

600

800

1000

1200

1400

1990 1992 1994 1996 1998 2000

Mark-recapture Estimates (+/- 2 SE)

Figure 3. Mark-recapture estimates of the abundance of humpback whales feeding off California, Oregon, and

Washington based on photo-identification studies (Calambokidis et al. 2002). 

POTENTIAL BIOLOGICAL REMOVAL

The potential biological removal (PBR) level for this stock is calculated as the minimum population size (681)

times one half the estimated population growth rate for this stock of humpback whales (1⁄2 of 8%) times a recovery factor

of 0.1 (for an endangered species), resulting in a PBR of 2.7. Because this stock spends approximately half its time

outside the U.S. EEZ, the PBR allocation for U.S. waters is 1.35 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 CaliforniaWashington stock includes at least the 2,000 taken in Oregon and Washington, the 3,400 taken in California, and the

2,800 taken in Baja California (Rice 1978). Shore-based whaling apparently depleted the humpback whale stock off

California twice: once prior to 1925 (Clapham et al. 1997) and again between 1956 and 1965 (Rice 1974). There has

been a prohibition on taking humpback whales since 1966.

Fishery Information

 A 1997-2001 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 1997- 2001 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 1996-

2000, 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.
165

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. 

Table 1. Summary of available information on the incidental mortality and injury of humpback whales (eastern North

Pacific stock) for commercial fisheries that might take this species (Julian 1997; Julian and Beeson 1998, Cameron and

Forney 1999, 2000; 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)

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

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

observer

data

10-15%

23.1% 2

26.9% 2

0%

0,0,0,0,0

0 2

0 2

01

0,0,0,0,0

0 1

0 1

01

0 1

Unidentified fisheries 1996-

2000

stranding

& sightings

n/a 0

(3)

n/a >0.6

CA salmon troll fishery 1997 incidental

report

0% (1) n/a Injury

>0.2 (n/a)

Total annual takes >0.8

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, 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.

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 deaths of at least two humpback whales in 1993, one in 1995, and one in

2000 (J. Cordaro, NMFS unpubl. data). 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 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 1997-2001 is at least
166

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 1996-2000.

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

1.35 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 probably greater than 10% of the PBR; therefore,

total fishery mortality may not be approaching zero mortality and serious injury rate. The eastern North Pacific stock

appears to be increasing in abundance. The increasing levels of anthropogenic noise in the world’s oceans, such as those

produced by ATOC (Acoustic Thermometry of Ocean Climate) or LFA (Low Frequency Active) Sonar, have been

suggested to be a habitat concern for whales, particularly for baleen whales that may communicate using low-frequency

sound.

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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.

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.

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 PB-280-794.

90pp.

Sosa-Nishizaki, O., R. De la Rosa Pacheco, R. Castro Longoria, M. Grijalva Chon, and J. De la Rosa Velez. 1993.
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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

W132 W129 W126 W123 W120 W117

N30

N34

N38

N42

N46

WASHINGTON

OREGON

CALIFORNIA

Figure 1. Blue whale sighting locations based on

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.

Revised 12/15/2003

BLUE WHALE (Balaenoptera musculus): Eastern North Pacific Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

The International Whaling Commission (IWC) has

formally considered only one management stock for blue

whales in the North Pacific (Donovan 1991), but now this

ocean is thought to include more than one population (Ohsumi

and Wada 1972; Braham 1991), possibly as many as five

(Reeves et al. 1998). This report covers one population that

feeds in California waters in summer/fall (from June to

November) and migrates south to productive areas off Mexico

(Calambokidis et al. 1990) and as far south as the Costa Rica

Dome (10o

 N) (Mate et al. 1999; Calambokidis, pers. comm.)

in winter/spring. Blue whales are occasionally seen or heard

off Oregon (McDonald et al. 1994, Stafford et al. 1998;

VonSaunder and Barlow 1999), but sightings there are rare.

Reilly and Thayer (1990) speculate that blue whales found

near the Costa Rica Dome from June to November are likely

to be part of a southern hemisphere population or an isolated

resident population; however, based on acoustic call

similarities, Stafford et al. (1999) linked these animals to the

population that feeds off California at the same time of year.

Rice (1974) hypothesized that blue whales from Baja

California migrated far offshore to fed in the eastern Aleutians

or Gulf of Alaska and returned to feed in California waters;

however, he has more recently concluded that the California

population is separate from the Gulf of Alaska population

(Rice 1992). Recently, blue whale feeding aggregations have

not been found in Alaska despite several surveys

(Leatherwood et al. 1982; Stewart et al. 1987; Forney and

Brownell 1996). One other stock of North Pacific blue whales

(in Hawaiian waters) is recognized in the Marine Mammal

Protection Act (MMPA) Stock Assessment Reports.

POPULATION SIZE

The size of the feeding stock of blue whales in

California was estimated recently by both line-transect and

mark-recapture methods. Barlow (2003) estimates 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. (2002) used photographic mark-recapture and

estimated population sizes of 744 (CV=0.58) based on 2000-2001 photographs of left sides and 1,251 (CV=0.51) based

on right sides. The average of the mark-recapture estimates 998 (CV=0.55) is considerably less than the line-transect

estimate but is not significantly different in a statistical sense. Mark-recapture estimates are often negatively biased by

individual heterogeneity in sighting probabilities (Hammond 1986); however, Calambokidis and Steiger (1994)

minimize such effects by selecting one sample that was taken randomly with respect to distance from the coast.

Similarly, the line-transect estimates may also be negatively biased because some blue whales in this stock are probably

along Baja California and, therefore, out of the study area at the time of survey (Wade and Gerrodette 1993). The best

estimate of blue whale abundance is the average of the line-transect and mark-recapture estimates, weighted by the

inverse of their variances, or 1,480 (CV=0.32).

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
171

1,138.

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. (2002) and Barlow (2003) declined in 2000/2001 compared to

previous years, but sample sizes were small and this apparent decline may not be real. 

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

No information exists on the rate of growth of blue whale populations in the Pacific (Best 1993).

POTENTIAL BIOLOGICAL REMOVAL

The potential biological removal (PBR) level for this stock is calculated as the minimum population size (1,138)

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 2.3. 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 1.2 whales per year.

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Historic Whaling 

The reported take of North Pacific blue whales by commercial whalers totaled 9,500 between 1910 and 1965

(Ohsumi and Wada 1972). Approximately 2,000 were taken off the west coast of North America between 1919 and 1929

(Tonnessen and Johnsen 1982). Partially overlapping with this is Rice's (1992) report of at least 1,378 taken by factory

ships off California and Baja California between 1913 and 1937. Between 1947 and 1987, reported takes of blue whales

in the North Pacific were approximately 2,400. Shore-based whaling stations in central California took 3 blue whales

between 1919 and 1926 (Clapham et al. 1997) and 48 blue whales between 1958 and 1965 (Rice 1974). Blue whales

in the North Pacific were given protected status by the IWC in 1966.

Fisheries Information 

The offshore drift gillnet fishery is the only fishery that is likely to take blue whales from this stock, but no

fishery mortalities or serious injuries have been observed (Table 1). Detailed information on this fishery is provided in

Appendix 1. After the 1997 implementation of a Take Reduction Plan, which included skipper education workshops

and required the use of pingers and minimum 6-fathom extenders, overall cetacean entanglement rates in the drift gillnet

fishery dropped considerably (Barlow and Cameron 2003). Mean annual takes for this fishery (Table 1) are based on

1997-2001 data. This results in an average estimate of zero blue whales taken annually. Some gillnet mortality of large

whales may go unobserved because whales swim away with a portion of the net; however, fishermen report that large

rorquals (blue and fin whales) usually swim through nets without entangling and with very little damage to the nets. 

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

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
172

(Berdegué 2002). . 

Table 1. Summary of available information on the incidental mortality and injury of blue whales (Eastern North Pacific

stock) for commercial fisheries that might take this species (Julian 1997; Julian and Beeson 1998; Cameron and Forney

1999, 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

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

0

0

0

0

0

0

0

0

0

Total annual takes 0

Ship Strikes

Ship strikes were implicated in the deaths of blue whales in 1980, 1986, 1987, and 1993 (J. Cordaro, Southwest

Region, NMFS and J. Heyning, pers. comm.). 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. Several blue whales

have been photographed in California with large gashes in their dorsal surface that appear to be from ship strikes (J.

Calambokidis, pers. comm.). The average number of blue whale mortalities in California attributed to ship strikes was

0.0 per year for 1997-2001.

STATUS OF STOCK

Previously, blue whales in the entire North Pacific were estimated to be at 33% (1,600 out of 4,900) of historic

carrying capacity (Mizroch et al. 1984). The initial abundance has never been estimated separately for the "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).

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ship survey and comparisons of passing and closing modes. Admin. Rept. LJ-97-11. Southwest Fisheries

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individuals. Rept. Int. Whal. Commn., Special Issue 12:343-348.

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

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

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from shore stations at Moss Landing and Trinidad, California, 1919-1926. Mar. Mamm. Sci. 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.

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

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Heyning, J. E., and T. D. Lewis. 1990. Fisheries interactions involving baleen whales off southern California. Rep.

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

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

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

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

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

Julian, F. 1997. Cetacean mortality in the California gill net fisheries: preliminary estimates for 1996. Paper

SC/49/SM2 presented to the International Whaling Commission, September 1997 (unpublished). 13 pp.

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

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Mate, B. R., B. A. Lagerquist, and J. Calambokidis. 1999. Movements of North Pacific blue whales during their feeding
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175

W132 W129 W126 W123 W120 W117

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N34

N38

N42

N46

WASHINGTON

OREGON

CALIFORNIA

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.

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).

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.

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 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”. 
176

Minimum Population Estimate

The minimum population estimate for fin whales is taken as the lower 20th percentile of the log-normal

distribution of abundance estimated from 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 20 vessels alternately

using longlines or driftnets, 23 using driftnets only, 22 using longlines only, and seven with unknown gear type

(Berdegué 2002).
177

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

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 (0.94)

0

0

1 (0.94)

Average 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).

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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.

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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.

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La Jolla CA 92037. 31p.

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

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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. Oregon-Washington Marine Mammal and

Seabird Survey: Information synthesis and hypothesis formulation. U.S. Department of the Interior, OCS

Study MMS 89-0030.

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

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

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

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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

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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.

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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-

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Donovan, G. P. 1991. A review of IWC stock boundaries. Rept. Int. Whal. Commn., Special Issue 13:39-68.

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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.

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Memorandum NOAA-TM-NMFS-SWFSC-300. 276p. 

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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.

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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.

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balaenopterid whales in the Canal de Ballenas, Gulf of California, Mexico. Rept. Int. Whal. Commn., Special

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California? Rev. Invest. Cient., Univ. Auton. de Baja California Sur. 1:69-71.

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180

Figure 1. Sighting locations of Bryde's whales

based on aerial and shipboard surveys off

California, Oregon, and Washington, 1991-96 (see

Appendix 2, Figures 1-5 for data sources and

information on timing and location of surveys).

Dashed line represents the U.S. EEZ; bold line

indicates the outer boundary of all surveys

combined.

Revised 12/15/2000 

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

STOCK DEFINITION AND GEOGRAPHIC RANGE

The International Whaling Commission (IWC) recognizes

3 stocks of Bryde's whales in the North Pacific (eastern, western,

and East China Sea), 3 stocks in the South Pacific (eastern, western

and Solomon Islands), and one cross-equatorial stock (Peruvian)

(Donovan 1991). Bryde's whales are distributed widely across the

tropical and warm-temperate Pacific (Leatherwood et al. 1982), and

there is no real justification for splitting stocks between the northern

and southern hemispheres (Donovan 1991). Recent surveys (Lee

1993; Wade and Gerrodette 1993) have shown them to be common

and distributed throughout the eastern tropical Pacific with a

concentration around the equator east of 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.

POPULATION SIZE

In the western North Pacific, Bryde's whale abundance in

the early 1980s was estimated independently by tag mark-recapture

and ship survey methods to be 22,000 to 24,000 (Tillman and

Mizroch 1982; Miyashita 1986). Bryde's whale abundance has

never been estimated for the entire eastern Pacific; however, a

portion of that stock in the eastern tropical Pacific was estimated

recently as 13,000 (CV=0.20; 95% C.I.=8,900-19,900) (Wade and

Gerrodette 1993), and the minimum number in the Gulf of California is 160 based on individually-identified whales

(Tershy et al. 1990). Only one confirmed sighting of Bryde's whales and five possible sightings (identified as sei or

Bryde's whales) were made in California waters during extensive ship and aerial surveys in 1991, 1992, 1993, and 1996

(Hill and Barlow 1992; Carretta and Forney 1993; Mangels and Gerrodette 1994; VonSaunder and Barlow 1999). Green

et al. (1992) did not report any sightings of Bryde's whales in aerial surveys off Oregon and Washington. The estimated

abundance of Bryde's whales in California, Oregon, and Washington coastal waters is 12 (CV=2.0) (Barlow 1997).

Minimum Population Estimate

The minimum population estimate for Bryde's whales is taken as the lower 20th percentile of the log-normal

distribution of abundance estimated from the summer/fall ship surveys in 1986-90 (Wade and Gerrodette 1993) plus the

minimum of 160 whales counted in the Gulf of California (Tershy et al. 1990), or 11,163.

Current Population Trend

There are no data on trends in Bryde's whale abundance in the eastern tropical Pacific.
181

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

There are no estimates of the growth rate of Bryde's whale populations in the Pacific (Best 1993).

POTENTIAL BIOLOGICAL REMOVAL

The potential biological removal (PBR) level for this stock cannot be calculated because the only relevant

abundance estimate (Wade and Gerrodette 1993) is more than 8 years old. Additional data on the abundance of Bryde’s

whales in the eastern Pacific was gathered in 1998-99, but their abundance has not yet been estimated from those data.

HUMAN CAUSED MORTALITY

Historic Whaling

The reported take of North Pacific Bryde's whales by commercial whalers totaled 15,076 in the western Pacific

from 1946-1983 (Holt 1986) and 2,873 in the eastern Pacific from 1973-81 (Cooke 1983). In addition, 2,304 sei-orBryde's whales were taken in the eastern Pacific from 1968-72 (Cooke 1983) (based on subsequent catches, most of these

were probably Bryde's whales). None were reported taken by shore-based whaling stations in central or northern

California between 1919 and 1926 (Clapham et al. 1997) or 1958 and 1965 (Rice 1974). There has been a prohibition

on taking Bryde's whales since 1988.

Table 1. Summary of available information on the incidental mortality and injury of Bryde’s whales (eastern tropical

Pacific stock) for commercial fisheries that might take this species (Julian 1997; Julian and Beeson 1998; Cameron

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

otherwise.

Fishery Name Year(s) Data Type

Percent Observer

Coverage

Observed

Mortality

Estimated

Mortality (CV in

parentheses)

Mean

Annual Takes

(CV in

parentheses)

CA/OR thresher

shark/swordfish drift

gillnet fishery

 1994-98 observer

data

 12-23% 0,0,0,0,0 0,0,0,0,0 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 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.). 
182

Ship Strikes

Ship strikes may occasionally kill Bryde's whales as they are known to kill their larger relatives: blue and fin

whales. No ship strikes have been reported for this species in this area.

STATUS OF STOCK

Commercial whaling of Bryde's whales was largely limited to the western Pacific. Bryde's whales are not listed

as "threatened" or "endangered" under the Endangered Species Act (ESA). Bryde's whales in the eastern tropical Pacific

would not be considered a strategic stock under the MMPA. The total human-caused mortality rate is estimated to be

zero; therefore, under the MMPA, total fishery mortality is approaching zero mortality and serious injury rate. The

increasing levels of anthropogenic noise in the world’s oceans has been suggested to be a habitat concern for whales,

particularly for baleen whales that may communicate using low-frequency sound.

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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

W132 W129 W126 W123 W120 W117

N30

N34

N38

N42

N46

WASHINGTON

OREGON

CALIFORNIA

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.

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.

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).

Minimum Population Estimate

The minimum population estimate for sei whales is taken as the lower 20th percentile of the log-normal

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, the possible effects of

continued unauthorized take (Yablokov 1994) and incidental ship strikes and gillnet mortality make this uncertain.
185

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

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 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
186

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.

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.
187

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. NMFS-SWFSC-221. 88 pp.

Masaki, Y. 1977. The separation of the stock units of sei whales in the North Pacific. Rept. Int. Whal. Commn.,

Special Issue 1:71-77.

Mizroch, S. A., D. W. Rice, and J. M. Breiwick. 1984. The sei whale, Balaenoptera borealis. Mar. Fish. Rev. 46:25-

29.

Ohsumi, S. and S. Wada. 1974. Status of whale stocks in the North Pacific, 1972. Rept. Int. Whal. Commn. 25:114-

126.

Rice, D. W. 1974. Whales and whale research in the eastern North Pacific. pp. 170-195 In: W. E. Schevill (ed.). The

Whale Problem: A Status Report. Harvard Press, Cambridge, MA.

Tillman, M. F. 1977. Estimates of population size for the North Pacific sei whale. Rept. Int. Whal. Commn., Special

Issue 1:98-106.

Von Saunder, A. and J. Barlow. 1999. A report of the Oregon, California and Washington Line-transect Experiment

(ORCAWALE) conducted in west coast waters during summer/fall 1996. U.S. Dep. Commer. NOAA Tech.

Memo. NMFS-SWFSC-264. 40 pp. 

Wade, P. R. and T. Gerrodette. 1993. Estimates of cetacean abundance and distribution in the eastern tropical Pacific.

Rept. Int. Whal. Commn. 43:477-493.

Yablokov, A. V. 1994. Validity of whaling data. Nature 367:108.
188

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.

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 year-round in California (Dohl et

al. 1983; Forney et al. 1995; Barlow 1997) and in the Gulf of

California (Tershy et al. 1990). Minke whales are present at

least in summer/fall along the Baja California peninsula

(Wade and Gerrodette 1993). Because the "resident" minke

whales from California to Washington appear behaviorally

distinct from migratory whales further north, minke whales in

coastal waters of California, Oregon, and Washington

(including Puget Sound) are considered as a separate stock.

Minke whales in Alaskan waters are considered in a separate

stock assessment report.

POPULATION SIZE

No estimates have been made for the number of

minke whales in the entire North Pacific. The number of

minke whales is estimated as 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.

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

There are no estimates of the growth rate of minke whale populations in the North Pacific (Best 1993).
189

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 

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

0

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 0.0

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 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.
190

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.

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.
191

Ford, D. H. Varoujean, D. Heinemann, and D. G. Chapman. 1990. Oregon-Washington Marine Mammal and

Seabird Survey: Information synthesis and hypothesis formulation. U.S. Department of the Interior, OCS

Study MMS 89-0030.

Calambokidis, J., S. Osmek, and J. L. Laake. 1997. Aerial surveys for marine mammals in Washington and British

Columbia inside waters. Final Contract Report to National Marine Mammal Laboratory, Seattle, WA. 

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

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.

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
192

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

Figure 1. Rough-toothed dolphin sighting locations during 1993-

98 aerial surveys within about 25 nmi of the main Hawaiian

Islands (see Appendix 2 for details on timing and location of

survey effort). Outer line indicates approximate boundary of

survey area.

Revised 12/15/2000

ROUGH-TOOTHED DOLPHIN (Steno bredanensis): Hawaiian Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

Rough-toothed dolphins are found

throughout the world in tropical and warmtemperate waters (Miyazaki and Perrin 1994). They

are present around all the main Hawaiian islands

(Shallenberger 1981; Tomich 1986) and have been

observed at least as far northwest as French Frigate

Shoals (Nitta and Henderson 1993). Recent sighting

locations around the main Hawaiian Islands are

shown in Figure 1. Five strandings have been

reported from Maui, Oahu, and the island of Hawaii

(Nitta 1991). Nothing is known about stock

structure for this species in the North Pacific. For

the Marine Mammal Protection Act (MMPA) stock

assessment reports, there is a single Pacific

management stock including only animals found

within the U.S. Exclusive Economic Zone of the

Hawaiian Islands.

POPULATION SIZE

A population estimate for this species has

been made in the eastern tropical Pacific (Wade and

Gerrodette 1993), but it is not known whether these

animals are part of the same population that occurs

around the Hawaiian Islands. As part of the Marine Mammal Research Program of the Acoustic Thermometry of Ocean

Climate (ATOC) study, a total of twelve aerial surveys were conducted within about 25 nmi of the main Hawaiian

Islands in 1993, 1995 and 1998. An abundance estimate of 123 (CV=0.63) rough-toothed dolphins was recently

calculated from the combined survey data (Mobley et al. 2000). This abundance underestimates the total number of

rough-toothed dolphins within the U.S. EEZ off Hawaii, because areas around the Northwest Hawaiian Islands (NWHI)

and beyond 25 nautical miles from the main islands were not surveyed.

Minimum Population Estimate

The log-normal 20th percentile of the combined 1993-98 abundance estimate is 76 rough-toothed dolphins. As

with the best abundance estimate above, this includes only areas within about 25 nmi of the main Hawaiian Islands and

is therefore an underestimate.

Current Population Trend

No data are available on current population trend.

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

No data are available on current or maximum net productivity rate.

POTENTIAL BIOLOGICAL REMOVAL

 The potential biological removal (PBR) level for this stock is calculated as the minimum population size (76)

times one half the default maximum net growth rate for cetaceans (1⁄2 of 4%) times a recovery factor of 0.50 (for a species

of unknown status with no known fishery mortality; Wade and Angliss 1997), resulting in a PBR of 0.8 rough-toothed

dolphins per year. 
194

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Fishery Information

No estimate of annual human-caused mortality and serious injury is available, as no mortality of this species

has been documented in Hawaiian fisheries (Nitta and Henderson 1993). However, mortality of other cetacean species

has been observed in Hawaiian fisheries, and the gear types used in these fisheries are responsible for marine mammal

mortality and serious injury in other fisheries throughout U.S. waters. Gillnets are used in Hawaiian waters and appear

to capture marine mammals wherever they are used, and float lines from lobster traps and longlines can be expected to

occasionally entangle whales (Perrin et al. 1994). 

Interactions with cetaceans have been reported for all Hawaiian pelagic fisheries, and some of these interactions

involved rough-toothed dolphins (Nitta and Henderson 1993). None were observed hooked in the Hawaiian longline

fishery between 1994 and 1998, with approximately 4.4% of all effort (measured as the number of hooks fished)

observed (Kleiber 1999). They are known to take bait and catch from Hawaiian sport and commercial fisheries operating

near the main islands and in a portion of the northwestern islands (Shallenberger 1981; Schlais 1984; Nitta and

Henderson 1993), and they have been specifically reported to interact with the day handline fishery for tuna (palu-ahi)

and the troll fishery for billfish and tuna (Schlais 1984; Nitta and Henderson 1993). Interaction rates between dolphins

and the NWHI bottomfish fishery have been estimated based on studies conducted in 1990-1993, indicating that an

average of 2.67 dolphin interactions, most likely involving bottlenose and rough-toothed dolphins, occurred for every

1000 fish brought on board (Kobayashi and Kawamoto 1995). Fishermen claim interactions with dolphins who steal

bait and catch are increasing. It is not known whether these interactions result in serious injury or mortality of dolphins.

Other Removals

At least 22 rough-toothed dolphins were live-captured in Hawaiian waters between 1963 and 1976

(Shallenberger 1981). 

STATUS OF STOCK

The status of rough-toothed dolphins in Hawaiian waters relative to OSP is unknown, and there are insufficient

data to evaluate trends in abundance. No habitat issues are known to be of concern for this species. They are not listed

as “threatened” or “endangered” under the Endangered Species Act (1973), nor as “depleted” under the MMPA.

Although information on rough-toothed dolphins in Hawaiian waters is limited, this stock would not be considered

strategic under the 1994 amendments to the MMPA given the absence of reported fisheries related mortality. However,

there is no systematic monitoring of gillnet fisheries that may take this species, and the potential effects of interactions

with the bottomfish fishery in the NWHI are not known. Insufficient information is available to determine whether the

total fishery mortality and serious injury for rough-toothed dolphins is insignificant and approaching zero mortality and

serious injury rate.

REFERENCES

Kleiber, P. 1999. Estimates of marine mammal takes in the Hawaiian longline fishery. (Unpublished). Southwest

Fisheries Science Center, NMFS, 2570 Dole St, Honolulu, HI, 96822-2396.

Kobayashi, D. R. and K. E. Kawamoto. 1995. Evaluation of shark, dolphin, and monk seal interactions with

Northwestern Hawaiian Island bottomfishing activity: a comparison of two time periods and an estimate of

economic impacts. Fisheries Research 23: 11-22.

Miyazaki, N. and W. F. Perrin. 1994. Rough-toothed dolphin Steno bredanensis (Lesson, 1828). In: S. H. Ridgway

and R. Harrison (eds.), Handbook of Marine Mammals, Vol.5: The First Book of Dolphins, pp. 1-21. Academic

Press, 416 pp.

Mobley, J. R. , Jr, S. S. Spitz, K. A. Forney, R. A. Grotefendt, and P. H. Forestall. 2000. Distribution and abundance

of odontocete species in Hawaiian waters: preliminary results of 1993-98 aerial surveys Admin. Rep. LJ-00-

14C. Southwest Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA

92038. 26 pp.

Nitta, E. 1991. The marine mammal stranding network for Hawaii: an overview. In: J.E. Reynolds III, D.K. Odell

(eds.), Marine Mammal Strandings in the United States, pp.56-62. NOAA Tech. Rep. NMFS 98, 157 pp.

Nitta, E. and J. R. Henderson. 1993. A review of interactions between Hawaii's fisheries and protected species. Mar.

Fish. Rev. 55(2):83-92.

Perrin, W.F., G. P. Donovan and J. Barlow. 1994. Gillnets and Cetaceans. Rep. Int. Whal. Commn., Special Issue 15,
195

629 pp.

Schlais, J.F. 1984. Thieving dolphins: A growing problem in Hawaii's fisheries. Sea Front. 30(5):293-298.

Shallenberger, E.W. 1981. The status of Hawaiian cetaceans. Final report to U.S. Marine Mammal Commission. MMC77/23, 79pp.

Tomich, P. Q. 1986. Mammals in Hawaii: A Synopsis and Notational Bibliography. Bishop Museum Press, Hawaii,

375 pp.

Wade, P. R. and R. P. Angliss. 1997. Guidelines for Assessing Marine Mammal Stocks: Report of the GAMMS

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

93 pp.

Wade, P. R. and T. Gerrodette. 1993. Estimates of cetacean abundance and distribution in the eastern tropical Pacific.

Rep. Int. Whal. Commn. 43:477-493.
196

Figure 1. Sighting location for the single Risso’s dolphin seen

during 1993-98 aerial surveys within about 25 nmi of the main

Hawaiian Islands (see Appendix 2 for details on timing and

location of survey effort). Outer line indicates approximate

boundary of survey area.

Revised 12/15/2000

RISSO'S DOLPHIN (Grampus griseus): Hawaiian Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

Risso's dolphins are found in tropical to

warm-temperate waters worldwide (Kruse et al.

1999). They appear to be rare in Hawaiian waters

(Figure 1). Of three reported sightings of this

species by Shallenberger (1981), only one was

verified. There are four stranding records from the

main islands (Nitta 1991). Balcomb (1987) referred

to a sighting of a large herd off the Kona Coast in

February 1985. For the Marine Mammal Protection

Act (MMPA) stock assessment reports, Risso's

dolphins within the Pacific U.S. Exclusive

Economic Zone are divided into two discrete, noncontiguous areas: 1) Hawaiian waters (this report),

and 2) waters off California, Oregon and

Washington.

POPULATION SIZE

Population estimates have been made off

Japan (Miyashita 1993) and in the eastern tropical

Pacific (Wade and Gerrodette 1993), but it is not

known whether these animals are part of the same

population that occurs around the Hawaiian Islands.

As part of the Marine Mammal Research Program of

the Acoustic Thermometry of Ocean Climate (ATOC) study, a total of twelve aerial surveys were conducted within about

25 nmi of the main Hawaiian Islands in 1993, 1995 and 1998 (Mobley et al. 2000). Only one sighting of a single Risso’s

dolphin was made, and therefore no meaningful abundance estimate could be calculated. Based on the locations of

interactions with the Hawaiian longline fishery (Figure 2), it is likely that Risso’s dolphins primarily occur in pelagic

waters tens to hundreds of miles from the main Hawaiian islands and are only occasionally found nearshore. 

Minimum Population Estimate

No data are available for a minimum population estimate.

Current Population Trend

No data are available on current population trend.

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

No data are available on current or maximum net productivity rate for Hawaiian animals.

POTENTIAL BIOLOGICAL REMOVAL

No PBR can be calculated for this species at this time.

HUMAN CAUSED MORTALITY AND SERIOUS INJURY

Fishery Information

No estimate of annual human-caused mortality and serious injury is available as there are no reports of direct

or incidental takes of Risso's dolphins in Hawaiian waters. However, mortality of other cetacean species has been

observed in Hawaiian fisheries, and the gear types used in these fisheries are responsible for marine mammal mortality

and serious injury in other fisheries throughout U.S. waters. Gillnets are used in Hawaiian waters and appear to capture

marine mammals wherever they are used, and float lines from lobster traps and longlines can be expected to occasionally

entangle whales (Perrin et al. 1994).
197

10 N 15 N 20 N 25 N 30 N 35 N 40 N 180 W 170 W 160 W 150 W 140 W

GG GGTT

UC

UW GM

GG GG

SL

PC

UW

PC

UW

TT T. truncatus

GG G. griseus

SL S longirostris

PC P. crassidens

GM G. macrorhynchus

UC Cetacean, unident.

UW Whale, unident.

Figure 2. Locations of observed cetacean interactions in the

Hawaiian longline fishery, 1994-98 (modified from Kleiber 1999).

Dashed line is the U.S. Exclusive Economic Zone (EEZ); GG =

Risso’s dolphin.

Interactions with cetaceans have been

reported for all Hawaiian pelagic fisheries (Nitta

and Henderson 1993), and some of these

interactions involved Risso’s dolphins in waters

outside the U.S. EEZ. Four Risso’s dolphins

were observed hooked in the Hawaiian longline

fishery between 1994 and 1998, with

approximately 4.4% of all effort (measured as the

number of hooks fished) observed. This

interaction rate extrapolates to a total 5-year

estimate of 90 (95% CI = 27-213) Risso’s

dolphins, or an average of 18 per year (Kleiber

1999). Three of the observed Risso’s dolphins

were reported to have been hooked in the mouth

or to have ingested the hook, and they were

released with hook and line still attached.

Following the guidelines of a 1997 Serious Injury

Workshop (Angliss and DeMaster 1998), these

three animals have been considered seriously

injured (defined under the MMPA as likely to

result in mortality). The fourth animal was

hooked in an unknown location and swam

normally, but was released with 20m of trailing

line and a light stick. Because a substantial length of line was still attached when the animal was released, this animal

is likely to have sustained serious injury. Reports for other odontocetes indicate they may also become hooked in other

parts of their body, and that they may occasionally become entangled in the fishing line. 

Interaction rates between dolphins and the NWHI bottomfish fishery have been estimated based on studies

conducted in 1990-1993, indicating that an average of 2.67 dolphin interactions, most likely involving bottlenose and

rough-toothed dolphins, occurred for every 1000 fish brought on board (Kobayashi and Kawamoto 1995). Fishermen

claim interactions with dolphins who steal bait and catch are increasing. It is not known whether these interactions result

in serious injury or mortality of dolphins, nor whether Risso’s dolphins are involved.

STATUS OF STOCK

The status of Risso's dolphins in Hawaiian waters relative to OSP is unknown, and there are insufficient data

to evaluate trends in abundance. No habitat issues are known to be of concern for this species. They are not listed as

“threatened” or “endangered” under the Endangered Species Act (1973), nor as “depleted” under the MMPA. Although

information on Risso's dolphins in Hawaiian waters is limited, this stock would not be considered strategic under the

1994 amendments to the MMPA given the absence of reported fisheries related mortality within the U.S. EEZ and the

species’ apparent offshore distribution. The potential effect of injuries sustained by Risso’s dolphins in the Hawaiian

longline fishery in international waters is not known. Insufficient information is available to determine whether the total

fishery mortality and serious injury for Risso’s dolphins is insignificant and approaching zero mortality and serious injury

rate.

REFERENCES

Angliss, R. P. and D. P. DeMaster. 1998. Differentiating Serious and Non-Serious Injury of Marine Mammals Taken

Incidental to Commercial Fishing Operations: Report of the Serious Injury Workshop 1-2 April 1997, Silver

Spring, Maryland. U. S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-13. 48 pp.

Balcomb, K. C., III. 1987. The Whales of Hawaii. Marine Mammal Fund, 99 pp.

Kruse, S. K., D. K. Caldwell, and M. C. Caldwell. 1999. Risso's dolphin Grampus griseus. Pages 183-212 In: S. H.

Ridgway and R. Harrison (eds.), Handbook of Marine Mammals, Volume 6. Academic Press, San Diego.

Kleiber, P. 1999. Estimates of marine mammal takes in the Hawaiian longline fishery. (Unpublished). Southwest

Fisheries Science Center, NMFS, 2570 Dole St, Honolulu, HI, 96822-2396.

Kobayashi, D. R. and K. E. Kawamoto. 1995. Evaluation of shark, dolphin, and monk seal interactions with
198

Northwestern Hawaiian Island bottomfishing activity: a comparison of two time periods and an estimate of

economic impacts. Fisheries Research 23: 11-22.

Miyashita, T. 1993. Abundance of dolphin stocks in the western North Pacific taken by the Japanese drive fishery.

Rep. Int. Whal. Commn. 43:417-437.

Mobley, J. R. , Jr, S. S. Spitz, K. A. Forney, R. A. Grotefendt, and P. H. Forestall. 2000. Distribution and abundance

of odontocete species in Hawaiian waters: preliminary results of 1993-98 aerial surveys Admin. Rep. LJ-00-

14C. Southwest Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA

92038. 26 pp.

Nitta, E. 1991. The marine mammal stranding network for Hawaii: an overview. In: J.E. Reynolds III, D.K. Odell

(eds.), Marine Mammal Strandings in the United States, pp.56-62. NOAA Tech. Rep. NMFS 98, 157 pp.

Nitta, E. and J. R. Henderson. 1993. A review of interactions between Hawaii's fisheries and protected species. Mar.

Fish. Rev. 55(2):83-92.

Perrin, W.F., G. P. Donovan and J. Barlow. 1994. Gillnets and Cetaceans. Rep. Int. Whal. Commn., Special Issue 15,

629 pp.

Shallenberger, E.W. 1981. The status of Hawaiian cetaceans. Final report to U.S. Marine Mammal Commission. MMC77/23, 79pp.

Wade, P. R. and T. Gerrodette. 1993. Estimates of cetacean abundance and distribution in the eastern tropical Pacific.

Rep. Int. Whal. Commn. 43:477-493.
199

Figure 1. Bottlenose dolphin sighting locations during 1993-98

aerial surveys within about 25 nmi of the main Hawaiian Islands

(see Appendix 2 for details on timing and location of survey

effort). Outer line indicates approximate boundary of survey

area.

Revised 12/15/2003

BOTTLENOSE DOLPHIN (Tursiops truncatus): Hawaiian Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

Bottlenose dolphins are widely distributed

throughout the world in tropical and warmtemperate waters. The species is primarily coastal

in much of its range, but there are populations in

some offshore deepwater areas as well. Separate

offshore and coastal forms have been identified

along continental coasts in several areas (Ross and

Cockcroft 1990; Van Waerebeek et al. 1990), and

similar onshore-offshore forms may exist in

Hawaiian waters. 

Although only three strandings have been

reported (Nitta 1991), bottlenose dolphins are

common throughout the Hawaiian Islands, from the

island of Hawaii to Kure Atoll (Shallenberger

1981). Recent sighting locations for systematic

aerial surveys within about 25nmi of the main

Hawaiian Islands in 1993-98 (Mobley et al. 2000)

are shown in Figure 1. In the Northwestern

Hawaiian Islands, they are found primarily in

relatively shallow inshore waters (Rice 1960). In

the main Hawaiian Islands, they are found in both

shallow inshore waters and deep channels between

islands. 

In their analysis of sightings of bottlenose

dolphins in the eastern tropical Pacific (ETP), Scott and Chivers (1990) noted that there was a large hiatus between the

westernmost sightings and the Hawaiian Islands. These data suggest that the bottlenose dolphins in Hawaiian waters

belong to a separate stock from those in the ETP. Recent nearshore photo-identification studies off Oahu, Maui, Lanai,

and Hawaii suggest limited movement of bottlenose dolphins between islands and into offshore waters (Baird et al.

2002), but insufficient data are available to evaluate whether separate stocks may exist around the different islands and

in offshore waters. For the Marine Mammal Protection Act (MMPA) stock assessment reports, bottlenose dolphins

within the Pacific U.S. Exclusive Economic Zone (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). As part of the Marine Mammal Research Program of

the Acoustic Thermometry of Ocean Climate (ATOC) study, a total of twelve aerial surveys were conducted within about

25 nmi of the main Hawaiian Islands in 1993, 1995 and 1998. An abundance estimate of 743 (CV=0.56) bottlenose

dolphins was recently calculated from the combined survey data (Mobley et al. 2000). This abundance underestimates

the total number of bottlenose dolphins within the U.S. EEZ off Hawaii, because areas around the Northwest Hawaiian

Islands (NWHI) and beyond 25 nautical miles from the main islands were not surveyed. A line-transect vessel survey

of the Hawaiian archipelago EEZ was completed in 2002 and is expected to provide a more comprehensive estimate of

abundance for Hawaiian bottlenose dolphins in the near future.

Minimum Population Estimate

The log-normal 20th percentile of the combined 1993-98 abundance estimate is 479 bottlenose dolphins. As

with the best abundance estimate above, this includes only areas within about 25 nmi of the main Hawaiian Islands and
200

Figure 5 Locations of observed bottlenose dolphin interactions (!) and

possible bottlenose dolphin interactions (") in the Hawaiian longline

fishery, 1997-2001. The solid line surrounding the Hawaiian Islands

represents the U. S. Exclusive Economic Zone (EEZ).

is therefore an underestimate. 

Current Population Trend

No data are available on current population trend.

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

No data are available on current or maximum net productivity rate for this species in Hawaiian waters.

POTENTIAL BIOLOGICAL REMOVAL

The potential biological removal (PBR) level for this stock is calculated as the minimum population size (479)

times one half the default maximum net growth rate for cetaceans (1⁄2 of 4%) times a recovery factor of 0.50 (for a species

of unknown status with no estimated fishery mortality within the U.S. EEZ of the Hawaiian Islands; Wade and Angliss

1997), resulting in a PBR of 4.8 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, but no

estimate of annual human-caused mortality

and serious injury is available, because

these fisheries are not observed or

monitored. Regulations governing the use

of nearshore gillnets (lay nets) are

currently under review by the State of

Hawaii.

Interactions with cetaceans have been reported for all Hawaiian pelagic fisheries, and some of these interactions

involved bottlenose dolphins (Nitta and Henderson 1993). Between 1997 and 2001, one bottlenose dolphin was observed

hooked in the Hawaiian longline fishery (Figure 2), with approximately 4-23% of all effort observed each year. This

extrapolates to an average interaction rate of 2.3 (95% CI = 1-11) bottlenose dolphins per year for the entire fishery

(NMFS unpublished data, Kleiber 1999); however, not all interactions with longlines lead to the death or serious injury

of cetaceans. Cetaceans may ingest a hook, become hooked in the mouth or other body part, or become entangled in

fishing line, causing varying levels of injury. Following the guidelines of a 1997 Serious Injury Workshop (Angliss and

DeMaster 1998), small cetaceans that ingest a hook, are hooked in the mouth or head, are swimming abnormally, or are

entangled and released trailing gear are considered seriously injured (defined under the MMPA as likely to result in

mortality). The single observed bottlenose dolphin was reported to have ingested the hook and is, therefore, considered

to have been seriously injured. The estimate of serious injury or mortality for bottlenose dolphins in the entire fishery

during the five most recent years for which data are available (1997-2001) is 12 (95% CI = 1-55), or an average of 2.3

dolphins per year (NMFS, unpublished data, Kleiber 1999). Within the Hawaiian Islands EEZ, the annual rate of serious

injury or mortality for bottlenose dolphins in the Hawaiian longline fishery during 1997-2001 is zero. Two additional

unidentified cetaceans that may have been bottlenose dolphins were taken outside the Hawaiian Islands EEZ and were

not considered to have been seriously injured. Their inclusion would not increase the annual rate of serious injury or
201

mortality for bottlenose dolphins within Hawaiian waters. 

Bottlenose dolphins are one of the species commonly reported to take bait and catch from several Hawaiian

sport and commercial fisheries (Nitta and Henderson 1993; Schlais 1984). Observations of bottlenose dolphins taking

bait or catch have also been made in the day handline fishery (palu-ahi) for tuna, the handline fishery for mackerel scad,

the troll fishery for billfish and tuna, and the inshore set gillnet fishery (Nitta and Henderson 1993). Nitta and Henderson

(1993) indicated that bottlenose dolphins remove bait and catch from handlines used to catch bottomfish off the island

of Hawaii and Kaula Island and on several banks of the Northwestern Hawaiian Islands. Fishermen claim interactions

with dolphins who steal bait and catch are increasing. Interaction rates between dolphins and the NWHI bottomfish

fishery have been estimated based on studies conducted in 1990-1993, indicating that an average of 2.67 dolphin

interactions, most likely involving bottlenose and rough-toothed dolphins, occurred for every 1000 fish brought on board

(Kobayashi and Kawamoto 1995). It is not known whether these interactions result in serious injury or mortality of

dolphins. Beginning in the early 1970s the National Marine Fisheries Service received reports of fishermen shooting at

bottlenose dolphins to deter them from taking fish catches (Nitta and Henderson 1993). Nitta and Henderson (1993) also

reported that one bottlenose dolphin calf was removed from small-mesh set gillnet off Maui in 1991 and expressed

surprise that bottlenose dolphins are "rarely reported entangled or raiding set gill nets in Hawaii," considering that they

so often remove fish from fishing lines.

Other Removals

At least 36 bottlenose dolphins were live-captured in Hawaiian waters between 1963 and 1981 (Shallenberger

1981). The main capture area was around Oahu. One juvenile bottlenose dolphin was entangled in a mooring line and

stranded dead along the coast of Maui in 1998 (H. Bernard, pers. comm.).

STATUS OF STOCK

The status of bottlenose dolphins in Hawaiian waters relative to OSP is unknown, and there are insufficient data

to evaluate trends in abundance. No habitat issues are known to be of concern for this species. They are not listed as

“threatened” or “endangered” under the Endangered Species Act (1973), nor as “depleted” under the MMPA. Although

information on bottlenose dolphins in Hawaiian waters is limited, this stock would not be considered strategic under the

1994 amendments to the MMPA because the estimated rate of fisheries related mortality or 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 effects of interactions with the Hawaiian longline fishery in international waters or the bottomfish

fishery in the NWHI are not known. Insufficient information is available to determine whether the total fishery mortality

and serious injury for bottlenose dolphins is insignificant and approaching zero mortality and serious injury rate.

REFERENCES

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 Southwest

Fisheries Science Center, National Marine Fisheries Service, 8604 La Jolla Shores Drive, La Jolla, CA 92037,

USA. 10p.

Bernard, H. Hawai'i Wildlife Fund, P.O. Box 637, Paia, HI 96779.

Kleiber, P. 1999. Estimates of marine mammal takes in the Hawaiian longline fishery. (Unpublished). Southwest

Fisheries Science Center, NMFS, 2570 Dole St, Honolulu, HI, 96822-2396.

Kobayashi, D. R. and K. E. Kawamoto. 1995. Evaluation of shark, dolphin, and monk seal interactions with

Northwestern Hawaiian Island bottomfishing activity: a comparison of two time periods and an estimate of

economic impacts. Fisheries Research 23: 11-22.

Miyashita, T. 1993. Abundance of dolphin stocks in the western North Pacific taken by the Japanese drive fishery.

Rep. Int. Whal. Commn. 43:417-437.

Mobley, J. R. , Jr, S. S. Spitz, K. A. Forney, R. A. Grotefendt, and P. H. Forestall. 2000. Distribution and abundance

of odontocete species in Hawaiian waters: preliminary results of 1993-98 aerial surveys Admin. Rep. LJ-00-

14C. Southwest Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA

92038. 26 pp.
202

Nitta, E. 1991. The marine mammal stranding network for Hawaii: an overview. In: J.E. Reynolds III, D.K. Odell

(eds.), Marine Mammal Strandings in the United States, pp.56-62. NOAA Tech. Rep. NMFS 98, 157 pp.

Nitta, E. and J. R. Henderson. 1993. A review of interactions between Hawaii's fisheries and protected species. Mar.

Fish. Rev. 55(2):83-92.

Perrin, W.F., G. P. Donovan and J. Barlow. 1994. Gillnets and Cetaceans. Rep. Int. Whal. Commn., Special Issue 15,

629 pp.

Rice, D. W. 1960. Distribution of the bottle-nosed dolphin in the leeward Hawaiian Islands. J. Mamm. 41:407-408.

Ross, G.J.B. and V. G. Cockcroft. 1990. Comments on Australian bottlenose dolphins and the taxonomic status of

Tursiops aduncus (Ehrenberg, 1832). In: The Bottlenose Dolphin (eds. S. Leatherwood and R. Reeves). pp.

101-128. Academic Press, 653pp. 

Schlais, J.F. 1984. Thieving dolphins: A growing problem in Hawaii's fisheries. Sea Front. 30(5):293-298.

Scott, M. D. and S. J. Chivers. 1990. Distribution and herd structure of bottlenose dolphins in the eastern tropical

Pacific Ocean. In: The Bottlenose Dolphin (eds. S. Leatherwood and R. Reeves). pp. 387-402. Academic Press,

653pp. 

Shallenberger, E.W. 1981. The status of Hawaiian cetaceans. Final report to U.S. Marine Mammal Commission. MMC77/23, 79pp.

Van Waerebeek, K., J. C. Reyes, A. J. Read, and J. S. McKinnon. 1990. Preliminary observations of bottlenose dolphins

from the Pacific coast of South America. In: The Bottlenose Dolphin (eds. S. Leatherwood and R. Reeves). pp.

143-154. Academic Press, 653 pp. 

Wade, P. R. and R. P. Angliss. 1997. Guidelines for Assessing Marine Mammal Stocks: Report of the GAMMS

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

93 pp.

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.
203

Figure 1. Pantropical spotted dolphin sighting locations during

1993-98 aerial surveys within about 25 nmi of the main

Hawaiian Islands (see Appendix 2 for details on timing and

location of survey effort). Outer line indicates approximate

boundary of survey area.

Revised 12/15/2003

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

aerial surveys around the main Hawaiian Islands

(Mobley et al. 2000) are shown in Figure 1. Nitta

(1991) only documented three strandings of this

species in Hawaii. Morphological differences and

distribution patterns have been used to establish that

the spotted dolphins around Hawaii belong to a stock

that is distinct from those in the ETP (Perrin 1975;

Dizon et al. 1994; Perrin et al. 1994b). Their possible

affinities with other stocks elsewhere in the Pacific

have not been investigated. For the Marine Mammal

Protection Act (MMPA) stock assessment reports,

there is a single Pacific management stock including only animals found within the U.S. Exclusive Economic Zone

(EEZ) of the Hawaiian Islands. Spotted dolphins involved in eastern tropical Pacific tuna purse-seine fisheries are

managed separately under the MMPA.

POPULATION SIZE

Population estimates are available for Japanese waters (Miyashita 1993) and the eastern tropical Pacific (Wade

and Gerrodette 1993). As part of the Marine Mammal Research Program of the Acoustic Thermometry of Ocean Climate

(ATOC) study, a total of twelve aerial surveys were conducted within about 25 nmi of the main Hawaiian Islands in

1993, 1995 and 1998. An abundance estimate of 2,928 (CV=0.45) pantropical spotted dolphins was recently calculated

from the combined survey data (Mobley et al. 2000). This abundance underestimates the total number of pantropical

spotted dolphins within the U.S. EEZ off Hawaii, because areas around the Northwest Hawaiian Islands (NWHI) and

beyond 25 nautical miles from the main islands were not surveyed. A line-transect vessel survey of the Hawaiian

archipelago EEZ was completed in 2002 and is expected to provide a more comprehensive estimate of abundance for

Hawaiian pantropical spotted dolphins in the near future.

Minimum Population Estimate

The log-normal 20th percentile of the combined 1993-98 abundance estimate is 2,040 pantropical spotted

dolphins. As with the best abundance estimate above, this includes only areas within about 25 nmi of the main Hawaiian

Islands and is therefore an underestimate. 

Current Population Trend

No data are available on current population trend.
204

Figure 2. Locations of observed pantropical spotted dolphin interactions

(!) and possible interactions with this species (") in the Hawaiian

longline fishery, 1997-2001. The solid line surrounding the Hawaiian

Islands represents the U. S. Exclusive Economic Zone (EEZ).

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 (2,040)

times one half the default maximum net

growth rate for cetaceans (1⁄2 of 4%) times

a recovery factor of 0.50 (for a species of

unknown status with no known fishery

mortality within the U.S. EEZ of the

Hawaiian Islands; Wade and Angliss

1997), resulting in a PBR of 20 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). In Hawaii, no

mortality of pantropical spotted dolphins has been observed in inshore gillnets, but these fisheries are not observed or

monitored. Regulations governing the use of nearshore gillnets (lay nets) are currently under review by the State of

Hawaii. 

Interactions with cetaceans have been reported for all Hawaiian pelagic fisheries (Nitta and Henderson 1993).

Between 1997 and 2001, one pantropical spotted dolphin was observed killed in the Hawaiian longline fishery (Figure

2), with approximately 4-23% of all effort observed each year. Although this animal was killed, not all interactions result

in the death or serious injury of cetaceans. Cetaceans may ingest a hook, become hooked in the mouth or other body

part, or become entangled in fishing line, causing varying levels of injury. Following the guidelines of a 1997 Serious

Injury Workshop (Angliss and DeMaster 1998), small cetaceans that ingest a hook, are hooked in the mouth or head,

are swimming abnormally, or are entangled and released trailing gear are considered seriously injured (defined under

the MMPA as likely to result in mortality). The estimate of serious injury or mortality for pantropical spotted dolphins

in the entire fishery during the five most recent years for which data are available (1997-2001) is 12 (95% CI = 1-55),

or an average of 2.3 dolphins per year (NMFS, unpublished data, Kleiber 1999). Within the Hawaiian Islands EEZ, the

annual rate of serious injury or mortality for pantropical spotted dolphins in the Hawaiian longline fishery during 1997-

2001 is zero. One additional unidentified cetacean that may have been a pantropical spotted dolphins was hooked and

injured outside the Hawaiian Islands EEZ. The inclusion of this take would not increase the annual rate of serious injury

or mortality for pantropical spotted dolphins within Hawaiian waters. 

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.
205

Other Removals

At least 52 pantropical spotted dolphins were live-captured in Hawaii between 1963 and 1978 (Shallenberger

1981).

STATUS OF STOCK

The status of pantropical spotted dolphins in Hawaiian waters relative to OSP is unknown, and there are

insufficient data to evaluate trends in abundance. No habitat issues are known to be of concern for this species. They

are not listed as “threatened” or “endangered” under the Endangered Species Act (1973), nor as “depleted” under the

MMPA. Although information on pantropical spotted dolphins in Hawaiian waters is limited, this stock would not be

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 is zero. However, there is no systematic monitoring of gillnet fisheries

that may take this species, and the potential effects of interactions with the Hawaiian longline fishery in international

waters are not known. Insufficient information is available to determine whether the total fishery mortality and serious

injury for pantropical spotted dolphins is insignificant and approaching zero mortality and serious injury rate. 

REFERENCES

Angliss, R. P. and D. P. DeMaster. 1998. Differentiating Serious and Non-Serious Injury of Marine Mammals Taken

Incidental to Commercial Fishing Operations: Report of the Serious Injury Workshop 1-2 April 1997, Silver

Spring, Maryland. U. S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-13. 48 pp.

Dizon, A. E., W. F. Perrin, and P. A. Akin. 1994. Stocks of dolphins (Stenella spp. and Delphinus delphis) in the eastern

tropical Pacific: a phylogeographic classification. NOAA Tech. Rep. NMFS 119, 20 pp.

Kleiber, P. 1999. Estimates of marine mammal takes in the Hawaiian longline fishery. (Unpublished). Southwest

Fisheries Science Center, NMFS, 2570 Dole St, Honolulu, HI, 96822-2396.

Kobayashi, D. R. and K. E. Kawamoto. 1995. Evaluation of shark, dolphin, and monk seal interactions with

Northwestern Hawaiian Island bottomfishing activity: a comparison of two time periods and an estimate of

economic impacts. Fisheries Research 23: 11-22.

Miyashita, T. 1993. Abundance of dolphin stocks in the western North Pacific taken by the Japanese drive fishery.

Rep. Int. Whal. Commn. 43:417-437.

Mobley, J. R. , Jr, S. S. Spitz, K. A. Forney, R. A. Grotefendt, and P. H. Forestall. 2000. Distribution and abundance

of odontocete species in Hawaiian waters: preliminary results of 1993-98 aerial surveys Admin. Rep. LJ-00-

14C. Southwest Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA

92038. 26 pp.

Nitta, E. 1991. The marine mammal stranding network for Hawaii: an overview. In: J.E. Reynolds III, D.K. Odell

(eds.), Marine Mammal Strandings in the United States, pp.56-62. NOAA Tech. Rep. NMFS 98, 157 pp.

Nitta, E. and J. R. Henderson. 1993. A review of interactions between Hawaii's fisheries and protected species. Mar.

Fish. Rev. 55(2):83-92.

Perrin, W. F. 1975. Variation of spotted and spinner porpoise (genus Stenella) in the eastern tropical Pacific and

Hawaii. Bull. Scripps Inst. Oceanogr. 21, 206 pp.

Perrin, W. F. and A. A. Hohn. 1994. Pantropical spotted dolphin Stenella attenuata. In: S. H. Ridgway and R. Harrison

(eds.), Handbook of Marine Mammals, Vol.5: The First Book of Dolphins, pp 71-98. Academic Press, 416 pp.

Perrin, W.F., G. P. Donovan and J. Barlow. 1994a. Gillnets and Cetaceans. Rep. Int. Whal. Commn., Special Issue 15,

629 pp.

Perrin, W. F., G. D. Schnell, D. J. Hough, J. W. Gilpatrick, Jr., and J. V. Kashiwada. 1994b. Re-examination of

geographical variation in cranial morphology of the pantropical spotted dolphin, Stenella attenuata, in the

eastern Pacific. Fish. Bull. 92:324-346.

Shallenberger, E.W. 1981. The status of Hawaiian cetaceans. Final report to U.S. Marine Mammal Commission. MMC77/23, 79pp.

Wade, P. R. and R. P. Angliss. 1997. Guidelines for Assessing Marine Mammal Stocks: Report of the GAMMS

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

93 pp.

Wade, P. R. and T. Gerrodette. 1993. Estimates of cetacean abundance and distribution in the eastern tropical Pacific.

Rep. Int. Whal. Commn. 43:477-493.
206

Figure 1. Spinner dolphin sighting locations during 1993-98

aerial surveys within about 25 nmi of the main Hawaiian Islands

(see Appendix 2 for details on timing and location of survey

effort). Outer line indicates approximate boundary of survey area.

Revised 12/15/2003

SPINNER DOLPHIN (Stenella longirostris): Hawaiian Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

Spinner dolphins are found throughout the

world in tropical and warm-temperate waters (Perrin

and Gilpatrick 1994). They are common and

abundant throughout the entire Hawaiian archipelago

(Shallenberger 1981; Norris and Dohl 1980; Norris et

al. 1994). Recent sighting locations around the main

Hawaiian Islands (Mobley et al. 2000) are shown in

Figure 1. There is some suggestion from an intensive

study of spinner dolphins off the Kona Coast of

Hawaii that the waters surrounding this island may

have a large, relatively stable "resident" population

(Norris et al. 1994). 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 purseseine fishery in the eastern tropical Pacific (Perrin

1975; Dizon et al. 1994). The Hawaiian form is

referable to the subspecies S. longirostris

longirostris, which occurs pantropically (Perrin

1990). For the Marine Mammal Protection Act

(MMPA) stock assessment reports, there is a single

Pacific management stock including only animals found within the U.S. Exclusive Economic Zone (EEZ) of the

Hawaiian Islands. Spinner dolphins involved in eastern tropical Pacific tuna purse-seine fisheries are managed separately

under the MMPA.

POPULATION SIZE

Although spinner dolphins are clearly among the most abundant cetaceans in Hawaiian waters, previously

available population estimates apply only to the west coast of Hawaii. Norris et al. (1994) photoidentified 192

individuals along the west coast of Hawaii and estimated 960 animals for this area in 1979-1980. Östman (1994)

photoidentified 677 individual spinner dolphins in the same area from 1989 to 1992. Using the same estimation

procedures as Norris et al. (1994), Östman (1994) estimated a population size of 2,334 for his study area along the Kona

coast of Hawaii. As part of the Marine Mammal Research Program of the Acoustic Thermometry of Ocean Climate

(ATOC) study, a total of twelve aerial surveys were conducted within about 25 nmi of the main Hawaiian Islands in

1993, 1995 and 1998. An abundance estimate of 3,184 (CV=0.37) spinner dolphins was recently calculated from the

combined survey data (Mobley et al. 2000). This abundance underestimates the total number of spinner dolphins within

the U.S. EEZ off Hawaii, because areas around the Northwest Hawaiian Islands (NWHI) and beyond 25 nautical miles

from the main islands were not surveyed. A line-transect vessel survey of the Hawaiian archipelago EEZ was completed

in 2002 and is expected to provide a more comprehensive estimate of abundance for Hawaiian spinner dolphins in the

near future.

Minimum Population Estimate

The log-normal 20th percentile of the combined 1993-98 abundance estimate is 2,355 spinner dolphins. As with

the best abundance estimate above, this includes only areas within about 25 nmi of the main Hawaiian Islands and is

therefore an underestimate.

Current Population Trend

No data on current population trend are available.
207

Figure 2. Locations of observed spinner dolphin interactions (!) and

possible interactions with this species (") in the Hawaiian longline

fishery, 1997-2001. The solid line surrounding the Hawaiian Islands

represents the U. S. Exclusive Economic Zone (EEZ).

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

No information on current or maximum net productivity rate is currently available for the Hawaiian stock. 

POTENTIAL BIOLOGICAL REMOVAL

The potential biological removal (PBR) level for this stock is calculated as the minimum population size (2,355)

times one half the default maximum net growth rate for cetaceans (1⁄2 of 4%) times a recovery factor of 0.50 (for a species

of unknown status with no estimated fishery mortality within the U.S. EEZ of the Hawaiian Islands ; Wade and Angliss

1997), resulting in a PBR of 24 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, 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. Regulations

governing the use of nearshore gillnets (lay

nets) are currently under review by the State of Hawaii.

Interactions with cetaceans have been reported for all Hawaiian pelagic fisheries (Nitta and Henderson 1993).

Between 1997 and 2001, two spinner dolphins were observed hooked in the Hawaiian longline fishery (Figure 2), with

approximately 4-23% of all effort observed each year. This extrapolates to an average interaction rate of 4.6 (95% CI

= 1-15) spinner dolphins per year for the entire fishery (NMFS unpublished data, Kleiber 1999); however, not all

interactions with longlines lead to the death or serious injury of cetaceans. Cetaceans may ingest a hook, become hooked

in the mouth or other body part, or become entangled in fishing line, causing varying levels of injury. Following the

guidelines of a 1997 Serious Injury Workshop (Angliss and DeMaster 1998),small cetaceans that ingest a hook, are

hooked in the mouth or head, are swimming abnormally, or are entangled and released trailing gear are considered

seriously injured (defined under the MMPA as likely to result in mortality). One of the spinner dolphins, taken outside

of the Hawaiian Islands EEZ, was reported to have been hooked in the fluke and was released alive; this animal would

not be considered seriously injured. Interaction details are not available for the second spinner dolphin interaction, which

occurred within the Hawaiian Islands EEZ, and the severity of injury cannot be determined. Depending on the nature

of this injury, the estimate of serious injury or mortality for spinner dolphins in the entire fishery during the five most

recent years for which data are available (1997-2001) is either zero or 12 (95% CI = 1-55), or an average of 0-2.3

dolphins per year (NMFS, unpublished data, Kleiber 1999). The same rates apply if only takes within the Hawaiian

Islands EEZ are considered. One additional unidentified cetacean that may have been a spinner dolphin was hooked and

injured outside the Hawaiian Islands EEZ. The inclusion of this take would not increase the annual rate of serious injury

or mortality for spinner dolphins within Hawaiian waters. 

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
208

in serious injury or mortality of dolphins, nor whether spinner dolphins are involved. 

Other Removals

At least 85 spinner dolphins were live-captured in Hawaiian waters from 1962 to 1981 (Shallenberger 1981).

The main capture area was around Oahu.

STATUS OF STOCK

The status of spinner dolphins in Hawaiian waters relative to OSP is unknown, and there are insufficient data

to evaluate trends in abundance. A habitat issue of increasing concern is the potential effect of swim-with-dolphin

programs and other tourism activities on spinner dolphins around the main Hawaiian Islands. Spinner dolphins are not

listed as “threatened” or “endangered” under the Endangered Species Act (1973), nor as “depleted” under the MMPA.

The Hawaiian stock is not considered a strategic stock under the 1994 amendments to the MMPA, because the

estimated rate of serious injury within the Hawaiian Islands EEZ (0-2.3 spinner dolphins per year), is less than the PBR

(24) . However, there is no systematic monitoring of gillnet fisheries that may take this species, and the potential effect

of interactions with the Hawaiian longline fishery in international waters is not known. Insufficient information is

available to determine whether the total fishery mortality and serious injury for spinner dolphins is insignificant and

approaching zero mortality and serious injury rate.

REFERENCES

Angliss, R. P. and D. P. DeMaster. 1998. Differentiating Serious and Non-Serious Injury of Marine Mammals Taken

Incidental to Commercial Fishing Operations: Report of the Serious Injury Workshop 1-2 April 1997, Silver

Spring, Maryland. U. S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-13. 48 pp.

Dizon, A. E., W. F. Perrin, and P. A. Akin. 1994. Stocks of dolphins (Stenella spp. and Delphinus delphis) in the eastern

tropical Pacific: a phylogeographic classification. NOAA Tech. Rep. NMFS 119, 20 pp.

Kleiber, P. 1999. Estimates of marine mammal takes in the Hawaiian longline fishery. (Unpublished). Southwest

Fisheries Science Center, NMFS, 2570 Dole St, Honolulu, HI, 96822-2396.

Kobayashi, D. R. and K. E. Kawamoto. 1995. Evaluation of shark, dolphin, and monk seal interactions with

Northwestern Hawaiian Island bottomfishing activity: a comparison of two time periods and an estimate of

economic impacts. Fisheries Research 23: 11-22.

Mobley, J. R. , Jr, S. S. Spitz, K. A. Forney, R. A. Grotefendt, and P. H. Forestall. 2000. Distribution and abundance

of odontocete species in Hawaiian waters: preliminary results of 1993-98 aerial surveys Admin. Rep. LJ-00-

14C. Southwest Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA

92038. 26 pp.

Nitta, E. and J. R. Henderson. 1993. A review of interactions between Hawaii's fisheries and protected species. Mar.

Fish. Rev. 55(2):83-92.

Norris, K. S., B. Würsig, R. S. Wells, and M. Würsig. 1994. The Hawaiian Spinner Dolphin. University of California

Press, 408 pp.

Norris, K. S. and T. P. Dohl. 1980. Behavior of the Hawaiian spinner dolphin, Stenella longirostris. Fish. Bull. 77:821-

849.

Östman, J. S. O. 1994. Social organization and social behavior of Hawaiian spinner dolphins (Stenella longirostris).

Ph.D. dissertation, University of California, Santa Cruz, 114 pp.

Perrin, W. F. 1975. Variation of spotted and spinner porpoise (genus Stenella) in the eastern tropical Pacific and

Hawaii. Bull. Scripps Inst. Oceanogr. 21, 206 pp.

Perrin, W. F. 1990. Subspecies of Stenella longirostris (Mammalia: Cetacea: Delphinidae). Proc. Biol. Soc. Wash.

103:453-463.

Perrin, W. F. and J. W. Gilpatrick, Jr. 1994. Spinner dolphin Stenella longirostris (Gray, 1828). In: S. H. Ridgway and

R. Harrison (eds.), Handbook of Marine Mammals, Vol.5: The First Book of Dolphins, pp. 99-128. Academic

Press, 416 pp.

Perrin, W.F., G. P. Donovan and J. Barlow. 1994. Gillnets and Cetaceans. Rep. Int. Whal. Commn., Special Issue 15,

629 pp.

Shallenberger, E.W. 1981. The status of Hawaiian cetaceans. Final report to U.S. Marine Mammal Commission. MMC77/23, 79pp.

Wade, P. R. and R. P. Angliss. 1997. Guidelines for Assessing Marine Mammal Stocks: Report of the GAMMS

Workshop April 3-5, 1996, Seattle, Washington. U. S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-12.
209

93 pp.
210

Figure 1. Location of the single sighting of striped dolphins

during 1993-98 aerial surveys within about 25 nmi of the main

Hawaiian Islands (see Appendix 2 for details on timing and

location of survey effort). Outer line indicates approximate

boundary of survey area.

Revised 12/15/2000

STRIPED DOLPHIN (Stenella coeruleoalba): Hawaiian Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

Striped dolphins are found in tropical to

warm-temperate waters throughout the world (Perrin

et al. 1994). There is an incongruity between the

frequency of strandings and the infrequency of

sightings of this species in Hawaii. Nitta (1991)

found more stranding records of striped dolphins

(13) than of any other species between 1936 and

1988, yet Shallenberger (1981) was aware of only

two at-sea sightings, one near Niihau and one west

of Oahu. A single sighting was made during recent

systematic surveys within about 25 nmi of the main

Hawaiian Islands (Figure 1). The Sea Life Park

collecting crew never encountered striped dolphins

from the early 1960s through the late 1970s, during

their live-capture operations (Shallenberger 1981).

Striped dolphins have been intensively

exploited in the western North Pacific, where three

migratory stocks are provisionally recognized

(Kishiro and Kasuya 1993). In the eastern Pacific

all striped dolphins are provisionally considered to

belong to a single stock (Dizon et al. 1994). For the

Marine Mammal Protection Act (MMPA) stock

assessment reports, striped dolphins within the

Pacific U.S. Exclusive Economic Zone are divided into two discrete, non-contiguous areas: 1) waters off California,

Oregon and Washington, and 2) waters around Hawaii (this report). Striped dolphins involved in eastern tropical Pacific

tuna purse-seine fisheries are managed separately under the MMPA.

POPULATION SIZE

Population estimates are available for Japanese waters (Miyashita 1993) and the eastern tropical Pacific (Wade

and Gerrodette 1993), but it is not known whether any of these animals are part of the same population that occurs

around the Hawaiian Islands. As part of the Marine Mammal Research Program of the Acoustic Thermometry of Ocean

Climate (ATOC) study, a total of twelve aerial surveys were conducted within about 25 nmi of the main Hawaiian

Islands in 1993, 1995 and 1998. An abundance estimate of 114 (CV=1.19) striped dolphins was recently calculated from

the combined survey data (Mobley et al. 2000). This abundance underestimates the total number of striped dolphins

within the U.S. EEZ off Hawaii, because areas around the Northwest Hawaiian Islands (NWHI) and beyond 25 nautical

miles from the main islands were not surveyed.

Minimum Population Estimate

No data are available for a minimum population estimate. The log-normal 20th percentile of the combined 1993-

98 abundance estimate is 52 striped dolphins. As with the best abundance estimate above, this includes only areas within

about 25 nmi of the main Hawaiian Islands and is therefore an underestimate.

Current Population Trend

No data are available on current population trend.

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

No data are available on current or maximum net productivity rate.
211

POTENTIAL BIOLOGICAL REMOVAL

The potential biological removal (PBR) level for this stock is calculated as the minimum population size (52)

times one half the default maximum net growth rate for cetaceans (1⁄2 of 4%) times a recovery factor of 0.50 (for a species

of unknown status with no known fishery mortality; Wade and Angliss 1997), resulting in a PBR of 0.5 striped dolphins

per year.

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Fishery Information

No estimate of annual human-caused mortality and serious injury is available as there are no reports of direct

or incidental takes of striped dolphins in Hawaiian waters (Nitta and Henderson 1993). However, mortality of other

cetacean species has been observed in Hawaiian fisheries, and the gear types used in these fisheries are responsible for

marine mammal mortality and serious injury in other fisheries throughout U.S. waters. Gillnets are used in Hawaiian

waters and appear to capture marine mammals wherever they are used, and float lines from lobster traps and longlines

can be expected to occasionally entangle whales (Perrin et al. 1994).

Interactions with cetaceans have been reported for all Hawaiian pelagic fisheries (Nitta and Henderson 1993),

but no interactions with striped dolphins have been documented. None were observed hooked in the Hawaiian longline

fishery between 1994 and 1998, with approximately 4.4% of all effort (measured as the number of hooks fished)

observed (Kleiber 1999). Interaction rates between dolphins and the NWHI bottomfish fishery have been estimated based

on studies conducted in 1990-1993, indicating that an average of 2.67 dolphin interactions, most likely involving

bottlenose and rough-toothed dolphins, occurred for every 1000 fish brought on board (Kobayashi and Kawamoto 1995).

Fishermen claim interactions with dolphins who steal bait and catch are increasing. It is not known whether these

interactions result in serious injury or mortality of dolphins, nor whether striped dolphins are involved.

STATUS OF STOCK

The status of striped dolphins in Hawaiian waters relative to OSP is unknown, and there are insufficient data

to evaluate trends in abundance. No habitat issues are known to be of concern for this species. They are not listed as

“threatened” or “endangered” under the Endangered Species Act (1973), nor as “depleted” under the MMPA. Although

information on striped dolphins in Hawaiian waters is limited, this stock would not be considered strategic under the

1994 amendments to the MMPA given the absence of reported fisheries related mortality. Insufficient information is

available to determine whether the total fishery mortality and serious injury for striped dolphins is insignificant and

approaching zero mortality and serious injury rate. 

REFERENCES

Dizon, A. E., W. F. Perrin, and P. A. Akin. 1994. Stocks of dolphins (Stenella spp. and Delphinus delphis) in the eastern

tropical Pacific: a phylogeographic classification. NOAA Tech. Rep. NMFS 119, 20 pp.

Kishiro, T. and T. Kasuya. 1993. Review of Japanese dolphin drive fisheries and their status. Rep. Int. Whal. Commn.

43:439-452.

Kleiber, P. 1999. Estimates of marine mammal takes in the Hawaiian longline fishery. (Unpublished). Southwest

Fisheries Science Center, NMFS, 2570 Dole St, Honolulu, HI, 96822-2396.

Kobayashi, D. R. and K. E. Kawamoto. 1995. Evaluation of shark, dolphin, and monk seal interactions with

Northwestern Hawaiian Island bottomfishing activity: a comparison of two time periods and an estimate of

economic impacts. Fisheries Research 23: 11-22.

Miyashita, T. 1993. Abundance of dolphin stocks in the western North Pacific taken by the Japanese drive fishery.

Rep. Int. Whal. Commn. 43:417-437.

Mobley, J. R. , Jr, S. S. Spitz, K. A. Forney, R. A. Grotefendt, and P. H. Forestall. 2000. Distribution and abundance

of odontocete species in Hawaiian waters: preliminary results of 1993-98 aerial surveys Admin. Rep. LJ-00-

14C. Southwest Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA

92038. 26 pp.

Nitta, E. 1991. The marine mammal stranding network for Hawaii: an overview. In: J.E. Reynolds III, D.K. Odell

(eds.), Marine Mammal Strandings in the United States, pp.56-62. NOAA Tech. Rep. NMFS 98, 157 pp.

Nitta, E. and J. R. Henderson. 1993. A review of interactions between Hawaii's fisheries and protected species. Mar.

Fish. Rev. 55(2):83-92.

Perrin, W. F., C. E. Wilson, and F. I. Archer, II. 1994. Striped dolphin Stenella coeruleoalba (Meyen, 1833). In: S.

H. Ridgway and R. Harrison (eds.), Handbook of Marine Mammals, Vol.5: The First Book of Dolphins, pp 129-
212

159. Academic Press, 416 pp.

Perrin, W.F., G. P. Donovan and J. Barlow. 1994. Gillnets and Cetaceans. Rep. Int. Whal. Commn., Special Issue 15,

629 pp.

Shallenberger, E.W. 1981. The status of Hawaiian cetaceans. Final report to U.S. Marine Mammal Commission. MMC77/23, 79pp.

Wade, P. R. and R. P. Angliss. 1997. Guidelines for Assessing Marine Mammal Stocks: Report of the GAMMS

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

93 pp.

Wade, P. R. and T. Gerrodette. 1993. Estimates of cetacean abundance and distribution in the eastern tropical Pacific.

Rep. Int. Whal. Commn. 43:477-493.
213

Figure 1. Melon-headed whale sighting locations during 1993-

98 aerial surveys within about 25 nmi of the main Hawaiian

Islands (see Appendix 2 for details on timing and location of

survey effort). Outer line indicates approximate boundary of

survey area.

Revised 12/15/2000

MELON-HEADED WHALE (Peponocephala electra): Hawaiian Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

Melon-headed whales are found in tropical

and warm-temperate waters throughout the world.

The distribution of reported sightings suggests that

the oceanic habitat of this species is primarily

equatorial waters (Perryman et al. 1994). Small

numbers have been taken in the eastern tropical

Pacific, and they are occasionally killed in direct

fisheries in Japan and elsewhere in the western

Pacific. Large herds are seen regularly in Hawaiian

waters, especially off the Waianae coast of Oahu,

the north Kohala coast of Hawaii, and the leeward

coast of Lanai (Shallenberger 1981). Recent sighting

locations around the main Hawaiian Islands

(Mobley et al. 2000) are shown in Figure 1. Little is

known about this species elsewhere in its range, and

most knowledge about its biology comes from mass

strandings (Perryman et al. 1994). Ten strandings

are known from Hawaii (Nishiwaki and Norris

1966; Shallenberger 1981; Nitta 1991). For the

Marine Mammal Protection Act (MMPA) stock

assessment reports, there is a single Pacific

management stock including only animals found

within the U.S. Exclusive Economic Zone of the

Hawaiian Islands.

POPULATION SIZE

An estimate of melon-headed whales is available for the eastern tropical Pacific (Wade and Gerrodette 1993),

but it is not known whether any of these animals are part of the same population that occurs around the Hawaiian Islands.

As part of the Marine Mammal Research Program of the Acoustic Thermometry of Ocean Climate (ATOC) study, a total

of twelve aerial surveys were conducted within about 25 nmi of the main Hawaiian Islands in 1993, 1995 and 1998. An

abundance estimate of 154 (CV=0.88) melon-headed whales was recently calculated from the combined survey data

(Mobley et al. 2000). This abundance underestimates the total number of melon-headed whales within the U.S. EEZ

off Hawaii, because areas around the Northwest Hawaiian Islands (NWHI) and beyond 25 nautical miles from the main

islands were not surveyed.

Minimum Population Estimate

The log-normal 20th percentile of the combined 1993-98 abundance estimate is 81 melon-headed whales. As

with the best abundance estimate above, this includes only areas within about 25 nmi of the main Hawaiian Islands and

is therefore an underestimate.

Minimum Population Estimate

No data are available for making a minimum population estimate. 

Current Population Trend

No data are available on current population trend.

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

No data are available on current or maximum net productivity rate.
214

POTENTIAL BIOLOGICAL REMOVAL

The potential biological removal (PBR) level for this stock is calculated as the minimum population size (81)

times one half the default maximum net growth rate for cetaceans (1⁄2 of 4%) times a recovery factor of 0.50 (for a species

of unknown status with no known fishery mortality; Wade and Angliss 1997), resulting in a PBR of 0.8 melon-headed

whales per year.

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Fishery Information

 Melon-headed whales are not known to be taken directly or incidentally in Hawaiian waters and no mortality

of this species has been documented in Hawaiian fisheries (Nitta and Henderson 1993). However, mortality of other

cetacean species has been observed in Hawaiian fisheries, and the gear types used in these fisheries are responsible for

marine mammal mortality and serious injury in other fisheries throughout U.S. waters. Gillnets are used in Hawaiian

waters and appear to capture marine mammals wherever they are used, and float lines from lobster traps and longlines

can be expected to occasionally entangle whales (Perrin et al. 1994).

Interactions with cetaceans have been reported for all Hawaiian pelagic fisheries (Nitta and Henderson 1993),

but no interactions with melon-headed whales have been documented. None were observed hooked in the Hawaiian

longline fishery between 1994 and 1998, with approximately 4.4% of all effort (measured as the number of hooks fished)

observed (Kleiber 1999). Interaction rates between dolphins and the NWHI bottomfish fishery have been estimated based

on studies conducted in 1990-1993, indicating that an average of 2.67 dolphin interactions, most likely involving

bottlenose and rough-toothed dolphins, occurred for every 1000 fish brought on board (Kobayashi and Kawamoto 1995).

Fishermen claim interactions with dolphins who steal bait and catch are increasing. It is not known whether these

interactions result in serious injury or mortality of dolphins, nor whether melon-headed whales are involved.

Historical Mortality

Peale (1848) reported that 60 whales of this species were driven ashore by natives in Hilo Bay, Hawaii in 1841.

At least three melon-headed whales were live-captured for public display between 1966 and 1978 (Shallenberger 1981).

STATUS OF STOCK

The status of melon-headed whales in Hawaiian waters relative to OSP is unknown, and there are insufficient

data to evaluate trends in abundance. No habitat issues are known to be of concern for this species. They are not listed

as “threatened” or “endangered” under the Endangered Species Act (1973), nor as “depleted” under the MMPA.

Although information on melon-headed whales in Hawaiian waters is limited, this stock would not be considered

strategic under the 1994 amendments to the MMPA given the absence of reported fisheries related mortality. 

Insufficient information is available to determine whether the total fishery mortality and serious injury for melon-headed

whales is insignificant and approaching zero mortality and serious injury rate. 

REFERENCES

Kleiber, P. 1999. Estimates of marine mammal takes in the Hawaiian longline fishery. (Unpublished). Southwest

Fisheries Science Center, NMFS, 2570 Dole St, Honolulu, HI, 96822-2396.

Kobayashi, D. R. and K. E. Kawamoto. 1995. Evaluation of shark, dolphin, and monk seal interactions with

Northwestern Hawaiian Island bottomfishing activity: a comparison of two time periods and an estimate of

economic impacts. Fisheries Research 23: 11-22.

Mobley, J. R. , Jr, S. S. Spitz, K. A. Forney, R. A. Grotefendt, and P. H. Forestall. 2000. Distribution and abundance

of odontocete species in Hawaiian waters: preliminary results of 1993-98 aerial surveys Admin. Rep. LJ-00-

14C. Southwest Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA

92038. 26 pp.

Nishiwaki, M. and K. S. Norris. 1966. A new genus, Peponocephala, for the odontocete cetacean species Electra electra.

Sci. Rep. Whales Res. Inst. 20:95-100.

Nitta, E. 1991. The marine mammal stranding network for Hawaii: an overview. In: J.E. Reynolds III, D.K. Odell

(eds.), Marine Mammal Strandings in the United States, pp.56-62. NOAA Tech. Rep. NMFS 98, 157 pp.

Nitta, E. and J. R. Henderson. 1993. A review of interactions between Hawaii's fisheries and protected species. Mar.

Fish. Rev. 55(2):83-92.

Peale, T. R. 1848. United States Exploring Expedition. During the Years 1838, 1839, 1840, 1841, 1842. Under the

Command of Charles Wilkes, U.S.N. Vol. VIII. Mammalia and Ornithology. C Sherman, Philadelphia, 338
215

pp.

Perrin, W.F., G. P. Donovan and J. Barlow. 1994. Gillnets and Cetaceans. Rep. Int. Whal. Commn., Special Issue 15,

629 pp.

Perryman, W. L., D. W. K. Au, S. Leatherwood, and T. A. Jefferson. 1994. Melon-headed whale Peponocephala

electra Gray, 1846. In: S. H. Ridgway and R. Harrison (eds.), Handbook of Marine Mammals, Vol.5: The First

Book of Dolphins, pp. 363-386. Academic Press, 416 pp.

Shallenberger, E.W. 1981. The status of Hawaiian cetaceans. Final report to U.S. Marine Mammal Commission. MMC77/23, 79pp.

Wade, P. R. and R. P. Angliss. 1997. Guidelines for Assessing Marine Mammal Stocks: Report of the GAMMS

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

93 pp.

Wade, P. R. and T. Gerrodette. 1993. Estimates of cetacean abundance and distribution in the eastern tropical Pacific.

Rep. Int. Whal. Commn. 43:477-493.
216

Revised 12/15/2000

PYGMY KILLER WHALE (Feresa attenuata): Hawaiian Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

Pygmy killer whales are found in tropical and subtropical waters throughout the world (Ross and Leatherwood

1994). They are poorly known in most parts of their range. Small numbers have been taken directly and incidentally

in both the western and eastern Pacific. Most knowledge of this species is from stranded or live-captured specimens.

Pryor et al. (1965) stated that pygmy killer whales have been observed several times off the lee shore of Oahu, and that

"they seem to be regular residents of the Hawaiian area." Although all sightings up to that time had been off Oahu and

the Big Island, Shallenberger (1981) stated that this species might be found elsewhere in Hawaii, as well. No pygmy

killer whales were seen during 1993-98 aerial surveys within about 25 nmi of the main Hawaiian Islands (Mobley et al.

2000; see Appendix 2 for detailed information on timing and location of effort), suggesting that they are uncommon in

these nearshore regions. Nitta (1991) documented five strandings from Maui and the island of Hawaii. For the Marine

Mammal Protection Act (MMPA) stock assessment reports, there is a single Pacific management stock including only

animals found within the U.S. Exclusive Economic Zone of the Hawaiian Islands. 

POPULATION SIZE

A population estimate has been made for this species in the eastern tropical Pacific (Wade and Gerrodette 1993),

but no data are available to estimate population size in any other area of the North Pacific. As part of the Marine

Mammal Research Program of the Acoustic Thermometry of Ocean Climate (ATOC) study, a total of twelve aerial

surveys were conducted within about 25 nmi of the main Hawaiian Islands in 1993, 1995 and 1998 (Mobley et al. 2000).

No sightings of pygmy killer whales were made, and therefore no abundance estimate for nearshore Hawaiian waters

is presently available. It is likely that pygmy killer whales occur primarily in pelagic waters greater than 25 nmi from

the main Hawaiian islands.

Minimum Population Estimate

No data are available for a minimum population estimate.

Current Population Trend

No data are available on current population trend.

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

No data are available on current or maximum net productivity rate.

POTENTIAL BIOLOGICAL REMOVAL

No PBR can be calculated for this species at this time.

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Fishery Information

No estimate of annual human-caused mortality and serious injury is available as there are no reports of direct

or incidental takes of pygmy killer whales in Hawaiian waters. However, mortality of other cetacean species has been

observed in Hawaiian fisheries, and the gear types used in these fisheries are responsible for marine mammal mortality

and serious injury in other fisheries throughout U.S. waters. Gillnets are used in Hawaiian waters and appear to capture

marine mammals wherever they are used, and float lines from lobster traps and longlines can be expected to occasionally

entangle whales (Perrin et al. 1994).

 Interactions with cetaceans have been reported for all Hawaiian pelagic fisheries (Nitta and Henderson 1993),

but no interactions with pygmy killer whales have been documented. None were observed hooked in the Hawaiian

longline fishery between 1994 and 1998, with approximately 4.4% of all effort (measured as the number of hooks fished)

observed (Kleiber 1999). Interaction rates between dolphins and the NWHI bottomfish fishery have been estimated based

on studies conducted in 1990-1993, indicating that an average of 2.67 dolphin interactions, most likely involving

bottlenose and rough-toothed dolphins, occurred for every 1000 fish brought on board (Kobayashi and Kawamoto 1995).

Fishermen claim interactions with dolphins who steal bait and catch are increasing. It is not known whether these

interactions result in serious injury or mortality of dolphins, nor whether pygmy killer whales are involved.
217

Other Removals

Three specimens were live-captured by Sea Life Park between 1963 and 1971 (Pryor et al. 1965; Pryor 1975;

Shallenberger 1981).

STATUS OF STOCK

The status of pygmy killer whales in Hawaiian waters relative to OSP is unknown, and there are insufficient

data to evaluate trends in abundance. No habitat issues are known to be of concern for this species. This species is not

listed as “threatened” or “endangered” under the Endangered Species Act (1973), nor as “depleted” under the MMPA.

Although information on pygmy killer whales in Hawaiian waters is limited, this stock would not be considered strategic

under the 1994 amendments to the MMPA given the absence of reported fisheries related mortality. Insufficient

information is available to determine whether the total fishery mortality and serious injury for pygmy killer whales is

insignificant and approaching zero mortality and serious injury rate.

REFERENCES

Kleiber, P. 1999. Estimates of marine mammal takes in the Hawaiian longline fishery. (Unpublished). Southwest

Fisheries Science Center, NMFS, 2570 Dole St, Honolulu, HI, 96822-2396.

Kobayashi, D. R. and K. E. Kawamoto. 1995. Evaluation of shark, dolphin, and monk seal interactions with

Northwestern Hawaiian Island bottomfishing activity: a comparison of two time periods and an estimate of

economic impacts. Fisheries Research 23: 11-22.

Mobley, J. R. , Jr, S. S. Spitz, K. A. Forney, R. A. Grotefendt, and P. H. Forestall. 2000. Distribution and abundance

of odontocete species in Hawaiian waters: preliminary results of 1993-98 aerial surveys Admin. Rep. LJ-00-

14C. Southwest Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA

92038. 26 pp.

Nitta, E. 1991. The marine mammal stranding network for Hawaii: an overview. In: J.E. Reynolds III, D.K. Odell

(eds.), Marine Mammal Strandings in the United States, pp.56-62. NOAA Tech. Rep. NMFS 98, 157 pp.

Nitta, E. and J. R. Henderson. 1993. A review of interactions between Hawaii's fisheries and protected species. Mar.

Fish. Rev. 55(2):83-92.

Perrin, W.F., G. P. Donovan and J. Barlow. 1994. Gillnets and Cetaceans. Rep. Int. Whal. Commn., Special Issue 15,

629 pp.

Pryor, K. 1975. Lads Before the Wind: Adventures in Porpoise Training. Harper and Row, New York, 278 pp.

Pryor, T., K. Pryor and K. S. Norris. 1965. Observations on a pygmy killer whale (Feresa attenuata Gray) from Hawaii.

J. Mamm. 46:450-461.

Ross, G. J. B. and S. Leatherwood. 1994. Pygmy killer whale Feresa attenuata Gray, 1874. In: S. H. Ridgway and R.

Harrison (eds.), Handbook of Marine Mammals, Vol.5: The First Book of Dolphins, pp.387-404. Academic

Press, 416 pp.

Shallenberger, E.W. 1981. The status of Hawaiian cetaceans. Final report to U.S. Marine Mammal Commission. MMC77/23, 79pp.

Wade, P. R. and T. Gerrodette. 1993. Estimates of cetacean abundance and distribution in the eastern tropical Pacific.

Rep. Int. Whal. Commn. 43:477-493. 
218

Figure 1. False killer whale sighting locations during 1993-98

aerial surveys within about 25 nmi of the main Hawaiian Islands

(see Appendix 2 for details on timing and location of survey

effort). Outer line indicates approximate boundary of survey

area.

 Revised 12/15/2003

FALSE KILLER WHALE (Pseudorca crassidens): Hawaiian Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

False killer whales are found worldwide

mainly in tropical and warm-temperate waters

(Stacey et al. 1994). In the North Pacific, this

species is well known from southern Japan, Hawaii,

and the eastern tropical Pacific. It occurs around all

the main Hawaiian Islands, but its presence around

the Northwestern Hawaiian Islands has not yet been

established (Nitta and Henderson 1993). Recent

sighting locations around the main Hawaiian Islands

(Mobley et al. 2000) are shown in Figure 1. There

are only 4 stranding records from Hawaiian waters

(Nitta 1991). Large numbers of false killer whales

have been taken in direct fisheries in southern

Japan, and small numbers have been taken

incidental to fishing operations in the eastern

tropical Pacific. Most knowledge about this species

comes from outside Hawaiian waters (Stacey et al.

1994). Recent genetic analyses of tissue samples

from Hawaiian false killer whales indicate that they

may be genetically distinct from animals found in

both the eastern and western North Pacific (S.

Chivers, NMFS unpublished data); however, the

offshore range of this Hawaiian population is

unknown. Efforts are currently underway to obtain additional 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 a single Pacific management stock including only animals found within the U.S. Exclusive Economic

Zone (EEZ) of the Hawaiian Islands.

POPULATION SIZE

Population estimates for this species have been made from shipboard surveys in Japan (Miyashita 1993) and

the eastern tropical Pacific (Wade and Gerrodette 1993), but evidence suggests that false killer whales around Hawaii

form a distinct population (S. Chivers, NMFS 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 recently calculated from the combined survey data (Mobley et al. 2000). This abundance underestimates

the total number of false killer whales within the U.S. EEZ off Hawaii, because areas around the Northwest Hawaiian

Islands (NWHI) and beyond 25 nautical miles from the main islands were not surveyed and estimates are uncorrected

for the proportion of diving animals missed from the survey aircraft. A line-transect vessel survey of the Hawaiian

archipelago EEZ was completed in 2002 and is expected to provide a more comprehensive estimate of abundance for

Hawaiian false killer whales in the near future.

Minimum Population Estimate

The log-normal 20th percentile of the combined 1993-98 abundance estimate is 83 false killer whales. As with

the best abundance estimate above, this includes only areas within about 25 nmi of the main Hawaiian Islands and is

therefore an underestimate.

Current Population Trend

No data are available on current population trend.
219

Figure 2. Locations of observed false killer whale interactions (!) and

possible interactions with this species (") in the Hawaiian longline

fishery, 1997-2001. The solid line surrounding the Hawaiian Islands

represents the U. S. Exclusive Economic Zone (EEZ).

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

No data are available on current or maximum net productivity rate for this species in Hawaiian waters.

POTENTIAL BIOLOGICAL REMOVAL

The potential biological removal (PBR) level for this stock is calculated as the minimum population size (83)

times one half the default maximum net growth rate for cetaceans (1⁄2 of 4%) times a recovery factor of 0.5 (for a species

of unknown status; Wade and Angliss 1997), resulting in a PBR of 0.8 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. Regulations governing the use of

nearshore gillnets (lay nets) are currently

under review by the State of Hawaii.

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 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.).

The Hawaiian longline fishery currently operates under new restrictions which prohibit swordfish style fishing

methods in an effort to reduce sea turtle mortality (NMFS Western Pacific Pelagic Fisheries Biological Opinion 2001).

Changes in this fishery have not been in place long enough to assess their influence on the rate of false killer whale

interactions, but overall cetacean take rates are similar. Between 1997 and 2001, five false killer whales were observed

hooked in the Hawaiian longline fishery (Figure 2), with approximately 4-23% of all effort observed each year. This

extrapolates to an average interaction rate of 11.6 (95% CI = 4-25) false killer whales per year for the entire fishery

(NMFS unpublished data, Kleiber 1999); however, not all interactions with longlines lead to the death or serious injury

of cetaceans. Cetaceans may ingest a hook, become hooked in the mouth or other body part, or become entangled in

fishing line, causing varying levels of injury. Following the guidelines of a 1997 Serious Injury Workshop (Angliss and

DeMaster 1998), small cetaceans that ingest a hook, are hooked in the mouth or head, are swimming abnormally, or are

entangled and released trailing gear are considered seriously injured (defined under the MMPA as likely to result in

mortality). Three of the false killer whales, two of which were taken inside of the Hawaiian Islands EEZ, would thus

be considered seriously injured. The resulting estimate of serious injury or mortality for false killer whales in the entire

fishery during the five most recent years for which data are available (1997-2001) is 35 (95% CI = 8-92), or an average

of 6.9 false killer whales per year (NMFS, unpublished data, Kleiber 1999). Considering only animals taken within the

Hawaiian Islands EEZ, this rate drops to 23 (95% CI = 3-74) animals during the 5-yr period, or 4.6 false killer whales

per year. In addition, five unidentified cetacean that may have been false killer whales were taken in the longline fishery,

including one animal with injuries of unknown severity taken within the Hawaiian Islands EEZ, one animal considered

seriously injured and taken outside the Hawaiian Islands EEZ, and three animals with injuries of unknown severity taken
220

outside the Hawaiian Islands EEZ. If the single unidentified cetacean taken within EEZ waters was a false killer whale,

this would yield a Hawaiian Islands EEZ rate of serious injury or mortality of 4.6-6.9 false killer whales per year,

depending on whether this animal is considered to have been seriously injured.

Interaction rates between dolphins and the NWHI bottomfish fishery have been estimated based on studies

conducted in 1990-1993, indicating that an average of 2.67 dolphin interactions, most likely involving bottlenose and

rough-toothed dolphins, occurred for every 1000 fish brought on board (Kobayashi and Kawamoto 1995). Fishermen

claim interactions with dolphins who steal bait and catch are increasing. It is not known whether these interactions result

in serious injury or mortality of dolphins, nor whether false killer whales are involved. 

Other Removals

Since the early 1960's, at least 12 false killer whales have been live-captured by aquaria or the Navy (Pryor

1975; Shallenberger 1981; J. Thomas pers. comm.).

STATUS OF STOCK

The status of false killer whales in Hawaiian waters relative to OSP is unknown, and there are insufficient data

to evaluate trends in abundance. No habitat issues are known to be of concern for this species. They are not listed as

“threatened” or “endangered” under the Endangered Species Act (1973), nor as “depleted” under the MMPA. Because

the rate of serious injury to false killer whales within the Hawaiian Islands EEZ in the Hawaiian longline fishery (4.6-6.9

animals per year) exceeds the PBR (0.8), this stock is considered a strategic stock under the 1994 amendments to the

MMPA. The total fishery mortality and serious injury cannot be considered to be insignificant and approaching zero,

because it exceeds the PBR. However, the available abundance estimate, on which PBR is based, applies only to a

portion of this species’ range in Hawaiian waters, and additional studies of abundance, distribution, and fishery-related

mortality and injury of false killer whales in Hawaiian waters will be required to re-evaluate this species’ status in the

future. A line-transect vessel survey of the Hawaiian archipelago EEZ was completed in 2002 and is expected to

provide a more comprehensive estimate of abundance for this stock in the near future.

REFERENCES

Angliss, R. P. and D. P. DeMaster. 1998. Differentiating Serious and Non-Serious Injury of Marine Mammals Taken

Incidental to Commercial Fishing Operations: Report of the Serious Injury Workshop 1-2 April 1997, Silver

Spring, Maryland. U. S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-13. 48 pp.

Kleiber, P. 1999. Estimates of marine mammal takes in the Hawaiian longline fishery. (Unpublished). Southwest

Fisheries Science Center, NMFS, 2570 Dole St, Honolulu, HI, 96822-2396.

Kobayashi, D. R. and K. E. Kawamoto. 1995. Evaluation of shark, dolphin, and monk seal interactions with

Northwestern Hawaiian Island bottomfishing activity: a comparison of two time periods and an estimate of

economic impacts. Fisheries Research 23: 11-22.

Miyashita, T. 1993. Abundance of dolphin stocks in the western North Pacific taken by the Japanese drive fishery.

Rep. Int. Whal. Commn. 43:417-437.

Mobley, J. R. , Jr, S. S. Spitz, K. A. Forney, R. A. Grotefendt, and P. H. Forestall. 2000. Distribution and abundance

of odontocete species in Hawaiian waters: preliminary results of 1993-98 aerial surveys Admin. Rep. LJ-00-

14C. Southwest Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA

92038. 26 pp.

Nitta, E. 1991. The marine mammal stranding network for Hawaii: an overview. In: J.E. Reynolds III, D.K. Odell

(eds.), Marine Mammal Strandings in the United States, pp.56-62. NOAA Tech. Rep. NMFS 98, 157 pp.

Nitta, E. and J. R. Henderson. 1993. A review of interactions between Hawaii's fisheries and protected species. Mar.

Fish. Rev. 55(2):83-92.

NMFS Western Pacific Pelagic Fisheries Biological Opinion 2001.

Perrin, W.F., G. P. Donovan and J. Barlow. 1994. Gillnets and Cetaceans. Rep. Int. Whal. Commn., Special Issue 15,

629 pp.

Pryor, K. 1975. Lads Before the Wind: Adventures in Porpoise Training. Harper and Row, New York, 278 pp.

Shallenberger, E.W. 1981. The status of Hawaiian cetaceans. Final report to U.S. Marine Mammal Commission. MMC77/23, 79pp.

Stacey, P. J., S. Leatherwood, and R. W. Baird. 1994. Pseudorca crassidens. Mamm. Spec. 456:1-6.

Wade, P. R. and R. P. Angliss. 1997. Guidelines for Assessing Marine Mammal Stocks: Report of the GAMMS

Workshop April 3-5, 1996, Seattle, Washington. U. S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-12.
221

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.
222

Revised 12/15/2000

KILLER WHALE (Orcinus orca): Hawaiian Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

Killer whales have been observed in all oceans and seas of the world (Leatherwood and Dahlheim 1978).

Although reported from tropical and offshore waters (Heyning and Dahlheim 1988), killer whales prefer the colder

waters of both hemispheres, with greatest abundances found within 800 km of major continents (Mitchell 1975). They

are rare in Hawaiian waters. No killer whales were seen during 1993-98 aerial surveys within about 25 nmi of the main

Hawaiian Islands (Mobley et al. 2000; see Appendix 2 for detailed information on timing and location of effort),

suggesting that they are uncommon in these nearshore regions. One stranding from the island of Hawaii was reported

in 1950 (Richards 1952). Two sightings have been reported, one in January 1978 off the Waianae Coast of Oahu and

another in December 1979 near Kauai (Shallenberger 1981). Except in the northeastern Pacific where "resident",

"transient", and “offshore” stocks have been described for coastal waters of Alaska, British Columbia, and Washington

to California (Bigg 1982; Leatherwood et al. 1990, Bigg et al. 1990, Ford et al. 1994), little is known about stock

structure of killer whales in the North Pacific. For the Marine Mammal Protection Act (MMPA) stock assessment

reports, five killer whale stocks are recognized within the Pacific U.S. EEZ 1) the Eastern North Pacific Northern

Resident stock - occurring from British Columbia through Alaska, 2) the Eastern North Pacific Southern Resident stock -

occurring within the inland waters of Washington State and southern British Columbia, 3) the Eastern North Pacific

Transient stock - occurring from Alaska through California, 4) the Eastern North Pacific Offshore stock - occurring from

Southeast Alaska through California, and 5) the Hawaiian stock (this report). The Stock Assessment Reports for the

Alaska Region contains the assessment of the Eastern North Pacific Northern Resident stock; all other killer whale stock

assessments are included in this report.

POPULATION SIZE

Population sizes for killer whales in the coastal waters of British Columbia and Washington are known from

photo-identification studies (Bigg et al. 1990). The population of killer whales in the eastern tropical Pacific has been

estimated from shipboard sightings surveys (Wade and Gerrodette 1993). No data to estimate population size are

available for the central Pacific. As part of the Marine Mammal Research Program of the Acoustic Thermometry of

Ocean Climate (ATOC) study, a total of twelve aerial surveys were conducted within about 25 nmi of the main Hawaiian

Islands in 1993, 1995 and 1998 (Mobley et al. 2000). No sightings of killer whales were made, and therefore no

abundance estimate for Hawaiian waters is presently available. 

Minimum Population Estimate

No data are available to provide a minimum population estimate.

Current Population Trend

No data are available on current population trend.

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

No data are available on current and maximum net productivity rate in Hawaiian waters.

POTENTIAL BIOLOGICAL REMOVAL

No PBR can be calculated for this stock at this time.

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Fishery Information

No estimate of annual human-caused mortality and serious injury is available for killer whales in Hawaiian

waters (Nitta and Henderson 1993). However, mortality of other cetacean species has been observed in Hawaiian

fisheries, and the gear types used in these fisheries are responsible for marine mammal mortality and serious injury in

other fisheries throughout U.S. waters. Gillnets are used in Hawaiian waters and appear to capture marine mammals

wherever they are used, and float lines from lobster traps and longlines can be expected to occasionally entangle whales

(Perrin et al. 1994). 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
223

removed the catch from a longline in Hawaii (Dollar 1991). None were observed hooked in the Hawaiian longline fishery

between 1994 and 1998, with approximately 4.4% of all effort (measured as the number of hooks fished) observed

(Kleiber 1999). Interaction rates between dolphins and the NWHI bottomfish fishery have been estimated based on

studies conducted in 1990-1993, indicating that an average of 2.67 dolphin interactions, most likely involving bottlenose

and rough-toothed dolphins, occurred for every 1000 fish brought on board (Kobayashi and Kawamoto 1995).

Fishermen claim interactions with dolphins who steal bait and catch are increasing. It is not known whether these

interactions result in serious injury or mortality of dolphins, nor whether killer whales are involved.

STATUS OF STOCK

The status of killer whales in Hawaiian waters relative to OSP is unknown, and there are insufficient data to

evaluate trends in abundance. No habitat issues are known to be of concern for this species. This species is not listed

as “threatened” or “endangered” under the Endangered Species Act (1973), nor as “depleted” under the MMPA. 

Although information on killer whales in Hawaiian waters is limited, this stock would not be considered strategic under

the 1994 amendments to the MMPA given the insignificance of reported fisheries related mortality. Insufficient

information is available to determine whether the total fishery mortality and serious injury for killer whales is

insignificant and approaching zero mortality and serious injury rate.

REFERENCES

Bigg, M. A. 1982. An assessment of killer whale (Orcinus orca) stocks off Vancouver Island, British Columbia. Rep.

Int. Whal. Commn. 32:655-666.

Bigg, M. A., P. F. Olesiuk, G. M. Ellis, J. K. B. Ford, and K. C. Balcomb, III. 1990. Social organization and genealogy

of resident killer whales (Orcinus orca) in the coastal waters of British Columbia and Washington State. Rep.

Int. Whal. Commn. (Spec. Iss. 12):383-405.

Dollar, R. A. 1991. Summary of swordfish longline observations in Hawaii, July 1990-March 1991. Southwest Fish.

Cent. Admin. Rep. H-91-09, 13 pp.

Ford, J. K. B., G. M. Ellis, and K.C. Balcomb. 1994. Killer whales. The natural history and genealogy of Orcinus orca

in British Columbia and Washington State. UBC Press, Vancouver, Canada

Kleiber, P. 1999. Estimates of marine mammal takes in the Hawaiian longline fishery. (Unpublished). Southwest

Fisheries Science Center, NMFS, 2570 Dole St, Honolulu, HI, 96822-2396.

Kobayashi, D. R. and K. E. Kawamoto. 1995. Evaluation of shark, dolphin, and monk seal interactions with

Northwestern Hawaiian Island bottomfishing activity: a comparison of two time periods and an estimate of

economic impacts. Fisheries Research 23: 11-22.

Leatherwood, J. S., and M. E. Dahlheim. 1978. Worldwide distribution of pilot whales and killer whales. Naval Ocean

Systems Center, Tech. Rep. 443:1-39.

Heyning, J. E. and M. E. Dahlheim. 1988. Orcinus orca. Mamm. Spec.304:1-9.

Leatherwood, S., C. O. Matkin, J. D. Hall, and G. M. Ellis. 1990. Killer whales, Orcinus orca, photo-identified in

Prince William Sound, Alaska, 1976 through 1987. Can Field-Nat. 104:362-371.

Mitchell, E. D. 1975. Report on the meeting on small cetaceans, Montreal, April 1-11, 1974. J. Fish. Res. Board

Canada, 32:914-916.

Mobley, J. R. , Jr, S. S. Spitz, K. A. Forney, R. A. Grotefendt, and P. H. Forestall. 2000. Distribution and abundance

of odontocete species in Hawaiian waters: preliminary results of 1993-98 aerial surveys Admin. Rep. LJ-99-

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

92038. 26 pp.

Nitta, E. and J. R. Henderson. 1993. A review of interactions between Hawaii's fisheries and protected species. Mar.

Fish. Rev. 55(2):83-92.

Perrin, W.F., G. P. Donovan and J. Barlow. 1994. Gillnets and Cetaceans. Rep. Int. Whal. Commn., Special Issue 15,

629 pp.

Richards, L. P. 1952. Cuvier's beaked whale from Hawaii. J. Mamm. 33:255. 

Shallenberger, E.W. 1981. The status of Hawaiian cetaceans. Final report to U.S. Marine Mammal Commission. MMC77/23, 79pp.

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

Figure 1. Short-finned pilot whale sighting locations during

1993-98 aerial surveys within about 25 nmi of the main

Hawaiian Islands (see Appendix 2 for details on timing and

location of survey effort). Outer line indicates approximate

boundary of survey area.

Revised 12/15/2003

SHORT-FINNED PILOT WHALE (Globicephala macrorhynchus): 

Hawaiian Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

Short-finned pilot whales are found in all

oceans, primarily in tropical and warm-temperate

waters. They are commonly observed around the main

Hawaiian Islands and are probably also present around

the Northwestern Hawaiian Islands (Shallenberger

1981). Recent sighting locations around the main

Hawaiian Islands (Mobley et al. 2000) are shown in

Figure 1. Several mass strandings have been reported

from the main islands (Tomich 1986; Nitta 1991).

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." Recent genetic analyses of tissue

samples from Hawaiian short-finned pilot whales

indicate that they may be genetically distinct from

animals found in both the eastern and western North

Pacific (S. Chivers, NMFS unpublished data);

however, the offshore range of this Hawaiian

population is unknown. Efforts are currently

underway to obtain additional samples of short-finned pilot whales for further studies of population structure in the North

Pacific Ocean. Preliminary photo-identification work with pilot whales in Hawaii indicated a high degree of site fidelity

around the main island of Hawaii (Shane and McSweeney 1990). For the Marine Mammal Protection Act (MMPA)

stock assessment reports, short-finned pilot whales within the Pacific U.S. Exclusive Economic Zone (EEZ) are divided

into two discrete, non-contiguous areas: 1) Hawaiian waters (this report), and 2) waters off California, Oregon and

Washington.

POPULATION SIZE

Estimates of short-finned pilot whale populations have been made off Japan (Miyashita 1993) and in the eastern

tropical Pacific (Wade and Gerrodette 1993), but it is not known whether any of these animals are part of the same

population that occurs around the Hawaiian Islands. As part of the Marine Mammal Research Program of the Acoustic

Thermometry of Ocean Climate (ATOC) study, a total of twelve aerial surveys were conducted within about 25 nmi of

the main Hawaiian Islands in 1993, 1995 and 1998. An abundance estimate of 1,708 (CV=0.32) short-finned pilot

whales was recently calculated from the combined survey data (Mobley et al. 2000). This abundance underestimates

the total number of short-finned pilot whales within the U.S. EEZ off Hawaii, because areas around the Northwest

Hawaiian Islands (NWHI) and beyond 25 nautical miles from the main islands were not surveyed. A line-transect vessel

survey of the Hawaiian archipelago EEZ was completed in 2002 and is expected to provide a more comprehensive

estimate of abundance for Hawaiian short-finned pilot whales in the near future.

Minimum Population Estimate

The log-normal 20th percentile of the combined 1993-98 abundance estimate is 1,313 short-finned pilot whales.

As with the best abundance estimate above, this includes only areas within about 25 nmi of the main Hawaiian Islands

and is therefore an underestimate.
225

Figure 2. Locations of observed short-finned pilot whale interactions

(!) and possible interactions with this species (") in the Hawaiian

longline fishery, 1997-2001. The solid line surrounding the Hawaiian

Islands represents the U. S. Exclusive Economic Zone (EEZ).

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 (1,313)

times one half the default maximum net growth rate for cetaceans (1⁄2 of 4%) times a recovery factor of 0.50 (for a species

of unknown status with no known fishery mortality within the U.S. EEZ off Hawaii; Wade and Angliss 1997), resulting

in a PBR of 13 short-finned pilot whales per year.

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Fishery Information

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 short-finned pilot whales has

been observed in inshore gillnets, but these

fisheries are not observed or monitored.

Regulations governing the use of nearshore

gillnets (lay nets) are currently under review by

the State of Hawaii. 

Interactions with cetaceans have been

reported for all Hawaiian pelagic fisheries

(Nitta and Henderson 1993). Between 1997

and 2001, four short-finned pilot whales were

observed hooked in the Hawaiian longline

fishery (Figure 2), with approximately 4-23% of

all effort observed each year. This extrapolates to an average interaction rate of 9.3 (95% CI = 3-22) short-finned pilot

whales per year for the entire fishery (NMFS unpublished data, Kleiber 1999); however, not all interactions with

longlines lead to the death or serious injury of cetaceans. Cetaceans may ingest a hook, become hooked in the mouth

or other body part, or become entangled in fishing line, causing varying levels of injury. Following the guidelines of

a 1997 Serious Injury Workshop (Angliss and DeMaster 1998), small cetaceans that ingest a hook, are hooked in the

mouth or head, are swimming abnormally, or are entangled and released trailing gear are considered seriously injured

(defined under the MMPA as likely to result in mortality). Two of the short-finned pilot whales, both taken outside the

Hawaiian Islands EEZ, were dead or considered seriously injured. The resulting estimate of serious injury or mortality

for short-finned pilot whales in the entire fishery during the five most recent years for which data are available (1997-

2001) is 23 (95% CI = 3-74), or an average of 4.6 short-finned pilot whales per year (NMFS, unpublished data, Kleiber

1999). Considering only animals taken within the Hawaiian Islands EEZ, this rate drops to zero. In addition, four

unidentified cetaceans that may have been short-finned pilot whales were taken in the longline fishery, including one

animal taken within the Hawaiian Islands EEZ with injuries of unknown severity, and three animals taken outside the

Hawaiian Islands EEZ with undetermined, non-serious, and serious injuries, respectively. If the single unidentified

cetacean taken within EEZ waters was a short-finned pilot whale, this would yield a Hawaiian Islands EEZ rate of

serious injury or mortality of 0-2.3 short-finned pilot whales per year, depending on whether this animal is considered

to have been seriously injured.

 Interaction rates between dolphins and the NWHI bottomfish fishery have been estimated based on studies
226

conducted in 1990-1993, indicating that an average of 2.67 dolphin interactions, most likely involving bottlenose and

rough-toothed dolphins, occurred for every 1000 fish brought on board (Kobayashi and Kawamoto 1995). Fishermen

claim interactions with dolphins who steal bait and catch are increasing. It is not known whether these interactions result

in serious injury or mortality of dolphins, nor whether short-finned pilot whales are involved. 

Other Removals

Since 1963, at least 20 short-finned pilot whales have been live-captured from Hawaiian waters by Sea Life

Park/Oceanic Foundation (Shallenberger 1981).

STATUS OF STOCK

The status of short-finned pilot whales in Hawaiian waters relative to OSP is unknown, and there are insufficient

data to evaluate trends in abundance. No habitat issues are known to be of concern for this species. They are not listed

as “threatened” or “endangered” under the Endangered Species Act (1973), nor as “depleted” under the MMPA.

Although information on short-finned pilot whales in Hawaiian waters is limited, this stock would not be considered

strategic under the 1994 amendments to the MMPA, because the estimated rate of serious injury within the Hawaiian

Islands EEZ (0-2.3 short-finned pilot whales per year), is less than the PBR (13). However, there is no systematic

monitoring of gillnet fisheries that may take this species, and the potential effect of mortality in the Hawaiian longline

fishery in international waters is not known. Insufficient information is available to determine whether the total fishery

mortality and serious injury 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.

Kasuya, T., T. Miyashita, and F. Kasamatsu. 1988. Segregation of two forms of short-finned pilot whales off the Pacific

coast of Japan. Sci. Rep. Whales Res. Inst. 39:77-90.

Kleiber, P. 1999. Estimates of marine mammal takes in the Hawaiian longline fishery. (Unpublished). Southwest

Fisheries Science Center, NMFS, 2570 Dole St, Honolulu, HI, 96822-2396.

Kobayashi, D. R. and K. E. Kawamoto. 1995. Evaluation of shark, dolphin, and monk seal interactions with

Northwestern Hawaiian Island bottomfishing activity: a comparison of two time periods and an estimate of

economic impacts. Fisheries Research 23: 11-22.

Miyashita, T. 1993. Abundance of dolphin stocks in the western North Pacific taken by the Japanese drive fishery.

Rep. Int. Whal. Commn. 43:417-437.

Mobley, J. R. , Jr, S. S. Spitz, K. A. Forney, R. A. Grotefendt, and P. H. Forestall. 2000. Distribution and abundance

of odontocete species in Hawaiian waters: preliminary results of 1993-98 aerial surveys Admin. Rep. LJ-00-

14C. Southwest Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA

92038. 26 pp.

Nitta, E. 1991. The marine mammal stranding network for Hawaii: an overview. In: J.E. Reynolds III, D.K. Odell

(eds.), Marine Mammal Strandings in the United States, pp.56-62. NOAA Tech. Rep. NMFS 98, 157 pp.

Nitta, E. and J. R. Henderson. 1993. A review of interactions between Hawaii's fisheries and protected species. Mar.

Fish. Rev. 55(2):83-92.

Perrin, W.F., G. P. Donovan and J. Barlow. 1994. Gillnets and Cetaceans. Rep. Int. Whal. Commn., Special Issue 15,

629 pp.

Shallenberger, E.W. 1981. The status of Hawaiian cetaceans. Final report to U.S. Marine Mammal Commission. MMC77/23, 79pp.

Shane, S. H. and D. McSweeney. 1990. Using photo-identification to study pilot whales social organization. Rep. Int.

Whal. Commn. (Spec. Iss. 12):259-263.

Tomich, P. Q. 1986. Mammals in Hawaii: A Synopsis and Notational Bibliography. Bishop Museum Press, Hawaii,

375 pp.

Wade, P. R. and R. P. Angliss. 1997. Guidelines for Assessing Marine Mammal Stocks: Report of the GAMMS

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

Wade, P. R. and T. Gerrodette. 1993. Estimates of cetacean abundance and distribution in the eastern tropical Pacific.

Rep. Int. Whal. Commn. 43:477-493.
227

Figure 1. Blainville’s beaked whale (!) and unidentified

Mesoplodon (+) sighting locations during 1993-98 aerial surveys

within about 25 nmi of the main Hawaiian Islands (see Appendix

2 for details on timing and location of survey effort). Outer line

indicates approximate boundary of survey area.

Revised 12/15/2003 

BLAINVILLE'S BEAKED WHALE (Mesoplodon densirostris): 

Hawaiian Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

Blainville's beaked whale has a

cosmopolitan distribution in tropical and temperate

waters, apparently the most extensive known

distribution of any Mesoplodon species (Mead

1989). Two strandings were reported in 1961 from

Midway Island (Galbreath 1963) and another in

1983 from Laysan Island (Nitta 1991). Sixteen

sightings were reported from the main islands by

Shallenberger (1981), who suggested that

Blainville's beaked whales were present off the

Waianae Coast of Oahu for prolonged periods

annually. Balcomb (1987) speculated that this

species is "more common in Hawaii than anywhere

else in the world." Recent sighting locations around

the main Hawaiian Islands (Mobley et al. 2000) are

shown in Figure 1. Although all identified

Mesoplodon records from Hawaiian waters are of

M. densirostris, several other species in the genus

Mesoplodon are known from the North Pacific and

may be recorded in Hawaiian waters in the future

(see Mead 1989). There is no information on stock

structure of Blainville's beaked whale. For the

Marine Mammal Protection Act (MMPA) stock

assessment reports, three Mesoplodon stocks are defined within the Pacific U.S. Exclusive Economic Zone (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.

POPULATION SIZE

As part of the Marine Mammal Research Program of the Acoustic Thermometry of Ocean Climate (ATOC)

study, a total of twelve aerial surveys were conducted within about 25 nmi of the main Hawaiian Islands in 1993, 1995

and 1998. Seven sightings of Blainville’s beaked whales were made. An abundance estimate of 68 (CV=0.60)

Blainville’s beaked whales was recently calculated from the combined survey data (Mobley et al. 2000). This abundance

underestimates the total number of Blainville’s beaked whales within the U.S. EEZ off Hawaii, because areas around

the Northwest Hawaiian Islands (NWHI) and beyond 25 nautical miles from the main islands were not surveyed.

Furthermore, this species is known to spend a large proportion of time diving, causing additional downward bias in the

abundance estimate. A line-transect vessel survey of the Hawaiian archipelago EEZ was completed in 2002 and is

expected to provide a more comprehensive estimate of abundance for Blainville’s beaked whales in the near future.

Minimum Population Estimate

The log-normal 20th percentile of the combined 1993-98 abundance estimate is 43 Blainville’s beaked whales.

As with the best abundance estimate above, this includes only areas within about 25 nmi of the main Hawaiian Islands

and does not include a large proportion of animals that were diving and therefore unavailable to be seen.

Current Population Trend

No data are available on current population trend.
228

Figure 2. Location of a single observed interaction with a possible

beaked whale (") in the Hawaiian longline fishery, 1997-2001. The

solid line surrounding the Hawaiian Islands represents the U. S.

Exclusive Economic Zone (EEZ).

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 (43)

times one half the default maximum net growth rate for cetaceans (1⁄2 of 4%) times a recovery factor of 0.50 (for a species

of unknown status with no known fishery mortality; Wade and Angliss 1997), resulting in a PBR of 0.4 Blainville’s

beaked whales per year.

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Fishery Information

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 Blainville's beaked

whales has been observed in inshore gillnets,

but these fisheries are not observed or

monitored. Regulations governing the use of

nearshore gillnets (lay nets) are currently

under review by the State of Hawaii.

Interactions with cetaceans are

reported for all pelagic fisheries (Nitta and

Henderson 1993), but no takes of Blainville's

beaked whales have been documented.

Between 1997 and September 2001, no

identified Blainville’s beaked whales were

observed taken in the Hawaiian longline fishery (Figure 2), with approximately 4-23% of all effort observed each year.

However, there was one interaction with an unidentified whale that may have been a Blainville’s beaked whale, outside

the Hawaiian Islands EEZ. Not all interactions result in the death or serious injury of cetaceans. Cetaceans may ingest

a hook, become hooked in the mouth or other body part, or become entangled in fishing line, causing varying levels of

injury. Following the guidelines of a 1997 Serious Injury Workshop (Angliss and DeMaster 1998), small cetaceans that

ingest a hook, are hooked in the mouth or head, are swimming abnormally, or are entangled and released trailing gear

are considered seriously injured (defined under the MMPA as likely to result in mortality). The unidentified cetacean

was hooked in the fluke and released alive; therefore, it would not be considered seriously injured. During the five most

recent years for which data are available (1997-2001), the estimated mortality or serious injury for Blainville’s beaked

whale in the entire fishery is zero.

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).

No estimates of potential mortality or serious injury are available for U.S. waters.
229

STATUS OF STOCK

The status of Blainville's beaked whales in Hawaiian waters relative to OSP is unknown, and there are

insufficient data to evaluate trends in abundance. They are not listed as “threatened” or “endangered” under the

Endangered Species Act (1973), nor as “depleted” under the MMPA. Although information on Blainville's beaked

whales in Hawaiian waters is limited, this stock would not be considered strategic under the 1994 amendments to the

MMPA because there has been no reported fisheries related mortality within the Hawaiian Islands EEZ. However, the

effect of potential interactions of unidentified beaked whales (which may have been Blainville’s beaked whales) with

the Hawaiian longline fishery in international waters is not known. Insufficient information is available to determine

whether the total fishery mortality and serious injury for 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

Angliss, R. P. and D. P. DeMaster. 1998. Differentiating Serious and Non-Serious Injury of Marine Mammals Taken

Incidental to Commercial Fishing Operations: Report of the Serious Injury Workshop 1-2 April 1997, Silver

Spring, Maryland. U. S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-13. 48 pp.

Balcomb, K. C., III. 1987. The Whales of Hawaii. Marine Mammal Fund, 99 pp.

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.

Kleiber, P. 1999. Estimates of marine mammal takes in the Hawaiian longline fishery. (Unpublished). Southwest

Fisheries Science Center, NMFS, 2570 Dole St, Honolulu, HI, 96822-2396.

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.

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.

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.
230

Figure 1. Cuvier’s beaked whale sighting locations during

1993-98 aerial surveys within about 25 nmi of the main

Hawaiian Islands (see Appendix 2 for details on timing and

location of survey effort). Outer line indicates approximate

boundary of survey area.

Revised 12/15/2003 

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

STOCK DEFINITION AND GEOGRAPHIC RANGE

Cuvier's beaked whales occur in all oceans

and major seas (Heyning 1989). In Hawaii,

strandings have been reported from Midway

Islands, Pearl and Hermes Reef, Oahu, and Hawaii

Islands (Shallenberger 1981; Galbreath 1963;

Richards 1952; Nitta 1991). Sightings have been

reported off Lanai and Maui (Shallenberger 1981).

Recent sighting locations around the main Hawaiian

Islands (Mobley et al. 2000) are shown in Figure 1.

Nothing is known about stock structure for this

species. For the Marine Mammal Protection Act

(MMPA) stock assessment reports, Cuvier's beaked

whales within the Pacific U.S. Exclusive Economic

Zone (EEZ) are divided into three discrete, noncontiguous areas: 1) Hawaiian waters (this report),

2) Alaskan waters, and 3) waters off California,

Oregon and Washington.

POPULATION SIZE

Wade and Gerrodette (1993) made an

estimate for Cuvier's beaked whales in the eastern

tropical Pacific, but it is not known whether any of

these animals are part of the same population that

occurs around the Hawaiian Islands. As part of the

Marine Mammal Research Program of the Acoustic Thermometry of Ocean Climate (ATOC) study, a total of twelve

aerial surveys were conducted within about 25 nmi of the main Hawaiian Islands in 1993, 1995 and 1998. Seven

sightings of Cuvier’s beaked whales were made. An abundance estimate of 43 (CV=0.51) Cuvier’s beaked whales was

recently calculated from the combined survey data (Mobley et al. 2000). This abundance underestimates the total

number of Cuvier’s beaked whales within the U.S. EEZ off Hawaii, because areas around the Northwest Hawaiian

Islands (NWHI) and beyond 25 nautical miles from the main islands were not surveyed. Furthermore, this species is

known to spend a large proportion of time diving, causing additional downward bias in the abundance estimate. A linetransect vessel survey of the Hawaiian archipelago EEZ was completed in 2002 and is expected to provide a more

comprehensive estimate of abundance for Cuvier’s beaked whales in the near future.

Minimum Population Estimate

The log-normal 20th percentile of the combined 1993-98 abundance estimate is 29 Cuvier’s beaked whales.

As with the best abundance estimate above, this includes only areas within about 25 nmi of the main Hawaiian Islands

and does not include a large proportion of animals that were diving and therefore unavailable to be seen.

Current Population Trend

No data are available on current population trend.

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

No data are available on current or maximum net productivity rate.

POTENTIAL BIOLOGICAL REMOVAL

The potential biological removal (PBR) level for this stock is calculated as the minimum population size (29)

times one half the default maximum net growth rate for cetaceans (1⁄2 of 4%) times a recovery factor of 0.50 (for a species

of unknown status with no known fishery mortality; Wade and Angliss 1997), resulting in a PBR of 0.3 Cuvier’s beaked
231

Figure 2.Location of a single observed interaction with a possible

beaked whale (") in the Hawaiian longline fishery, 1997-2001. The

solid line surrounding the Hawaiian Islands represents the U. S.

Exclusive Economic Zone (EEZ).

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 Cuvier's beaked

whales has been observed in inshore gillnets,

but these fisheries are not observed or

monitored. Regulations governing the use of

nearshore gillnets (lay nets) are currently

under review by the State of Hawaii.

Interactions with cetaceans are

reported for all pelagic fisheries (Nitta and

Henderson 1993), but no takes of Cuvier's

beaked whales have been documented. 

Between 1997 and September 2001, no

identified Cuvier’s beaked whales were

observed taken in the Hawaiian longline fishery (Figure 2), with approximately 4-23% of all effort observed each year.

However, there was one interaction with an unidentified whale that may have been a Cuvier’s beaked whale, outside the

Hawaiian Islands EEZ. Not all interactions result in the death or serious injury of cetaceans. Cetaceans may ingest a

hook, become hooked in the mouth or other body part, or become entangled in fishing line, causing varying levels of

injury. Following the guidelines of a 1997 Serious Injury Workshop (Angliss and DeMaster 1998), small cetaceans that

ingest a hook, are hooked in the mouth or head, are swimming abnormally, or are entangled and released trailing gear

are considered seriously injured (defined under the MMPA as likely to result in mortality). The unidentified cetacean

was hooked in the fluke and released alive; therefore, it would not be considered seriously injured. During the five most

recent years for which data are available (1997-2001), the estimated mortality or serious injury for Cuvier’s beaked whale

in the entire fishery is zero.

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).

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. Although information on Cuvier's beaked whales in Hawaiian waters

is limited, this stock would not be considered strategic under the 1994 amendments to the MMPA because there has been

no reported fisheries related mortality within the Hawaiian Islands EEZ. However, the effect of potential interactions

of unidentified beaked whales (which may have been Cuvier’s beaked whales) with the Hawaiian longline fishery in

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.
232

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

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.

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.

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 

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.

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. MMC77/23, 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-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.
233

Figure 1. Pygmy or dwarf sperm whale sighting locations

during 1993-98 aerial surveys within about 25 nmi of the main

Hawaiian Islands (see Appendix 2 for details on timing and

location of survey effort). Outer line indicates approximate

boundary of survey area.

Revised 12/15/2000

PYGMY SPERM WHALE (Kogia breviceps): Hawaiian Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

Pygmy sperm whales are found throughout

the world in tropical and warm-temperate waters

(Caldwell and Caldwell 1989). Between the years

1949 and 1982, at least nine strandings of this

species were reported in the Hawaiian Islands

(Tomich 1986; Nitta 1991). Shallenberger (1981)

reported three sightings off Oahu and Maui. Two

sightings of pygmy or dwarf sperm whales were

made between Hawaii and Maui during 1993-98

aerial surveys within about 25 nmi of the main

Hawaiian Islands (Figure 1; Mobley et al. 1999). A

stranded calf was held for several days at Sea Life

Park (Pryor 1975:94). Nothing is known about

stock structure for this species. For the Marine

Mammal Protection Act (MMPA) stock assessment

reports, pygmy sperm whales within the Pacific U.S.

Exclusive Economic Zone are divided into two

discrete, non-contiguous areas: 1) Hawaiian waters

(this report), and 2) waters off California, Oregon

and Washington.

POPULATION SIZE

No data are available to estimate

population size for this species in the central Pacific. As part of the Marine Mammal Research Program of the Acoustic

Thermometry of Ocean Climate (ATOC) study, a total of twelve aerial surveys were conducted within about 25 nmi of

the main Hawaiian Islands in 1993, 1995 and 1998. Two sightings of five pygmy or dwarf sperm whales were made;

however these sightings were excluded during recent abundance analyses (Mobley et al. 2000), because they were made

during poor observation conditions. Therefore, no abundance estimate is available for pygmy sperm whales within

Hawaiian waters.

Minimum Population Estimate

No data are available to provide a minimum population estimate.

Current Population Trend

No data are available on current population trend.

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

No data are available on current or maximum net productivity rate.

POTENTIAL BIOLOGICAL REMOVAL

No PBR can be calculated for this stock at this time.

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Fishery Information

No estimate of annual human-caused mortality and serious injury is available as there are no reports of direct

or incidental takes of pygmy sperm whales in Hawaiian waters (Nitta and Henderson 1993). However, mortality of other

cetacean species has been observed in Hawaiian fisheries, and the gear types used in these fisheries are responsible for

marine mammal mortality and serious injury in other fisheries throughout U.S. waters. Gillnets are used in Hawaiian

waters and appear to capture marine mammals wherever they are used, and float lines from lobster traps and longlines
234

can be expected to occasionally entangle whales (Perrin et al. 1994).

Interactions with cetaceans have been reported for all Hawaiian pelagic fisheries (Nitta and Henderson 1993),

but no interactions with pygmy sperm whales have been documented. None were observed hooked in the Hawaiian

longline fishery between 1994 and 1998, with approximately 4.4% of all effort (measured as the number of hooks fished)

observed (Kleiber 1999). 

STATUS OF STOCK

The status of pygmy sperm whales in Hawaiian waters relative to OSP is unknown, and there are insufficient

data to evaluate trends in abundance. They are not listed as “threatened” or “endangered” under the Endangered Species

Act (1973), nor as “depleted” under the MMPA. Although information on pygmy sperm whales in Hawaiian waters is

limited, this stock would not be considered strategic under the 1994 amendments to the MMPA because there has been

no reported fisheries related mortality. The total fishery mortality and serious injury for pygmy sperm whales is zero and

therefore can be considered to be insignificant and approaching zero mortality and serious injury rate. The increasing

levels of anthropogenic noise in the world’s oceans has been suggested to be a habitat concern for whales, particularly

for deep-diving whales like pygmy sperm whales that feed in the oceans’ “sound channel”.

REFERENCES

Caldwell, D. K. and M. C. Caldwell. 1989. Pygmy sperm whale Kogia breviceps (de Blainville, 1838): Dwarf sperm

whale Kogia simus Owen, 1866. In: S. H. Ridgway and R. Harrison (eds.), Handbook of Marine Mammals,

Vol. 4: The River Dolphins and Larger Toothed Whales, pp. 235-260. Academic Press, 442 pp.

Kleiber, P. 1999. Estimates of marine mammal takes in the Hawaiian longline fishery. (Unpublished). Southwest

Fisheries Science Center, 2570 Dole St, Honolulu, HI, 96822-2396.

Mobley, J. R., Jr., R. A. Grotefendt, P. H. Forestell, and A. Frankel. 1999. Results of aerial surveys of marine mammals

in the major Hawaiian Islands (1993-98): Report to the Acoustic Thermometry of Ocean Climate Marine

Mammal Research Program (ATOC MMRP) (unpublished). 39 pp.

Mobley, J. R., Jr, S. S. Spitz, K. A. Forney, R. A. Grotefendt, and P. H. Forestall. 2000. Distribution and abundance

of odontocete species in Hawaiian waters: preliminary results of 1993-98 aerial surveys Admin. Rep. LJ-00-

14C. Southwest Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA

92038. 26 pp.

Nitta, E. 1991. The marine mammal stranding network for Hawaii: an overview. In: J.E. Reynolds III, D.K. Odell

(eds.), Marine Mammal Strandings in the United States, pp.56-62. NOAA Tech. Rep. NMFS 98, 157 pp.

Nitta, E. and J. R. Henderson. 1993. A review of interactions between Hawaii's fisheries and protected species. Mar.

Fish. Rev. 55(2):83-92.

Perrin, W.F., G. P. Donovan and J. Barlow. 1994. Gillnets and Cetaceans. Rep. Int. Whal. Commn., Special Issue 15,

629 pp.

Pryor, K. 1975. Lads Before the Wind: Adventures in Porpoise Training. Harper and Row, New York, 278 pp.

Shallenberger, E.W. 1981. The status of Hawaiian cetaceans. Final report to U.S. Marine Mammal Commission. MMC77/23, 79pp.

Tomich, P. Q. 1986. Mammals in Hawaii: A Synopsis and Notational Bibliography. Bishop Museum Press, Hawaii,

375 pp.
235

Figure 1. Pygmy or dwarf sperm whale sighting locations

during 1993-98 aerial surveys within about 25 nmi of the main

Hawaiian Islands (see Appendix 2 for details on timing and

location of survey effort). Outer line indicates approximate

boundary of survey area.

Revised 12/15/2000

DWARF SPERM WHALE (Kogia sima): Hawaiian Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

Dwarf sperm whales are found throughout

the world in tropical to warm-temperate waters

(Nagorsen 1985). One sighting in an unspecified

locality, one stranding on Oahu (Tomich 1986), and

one stranding on Lanai (Nitta 1991) constitute the

only evidence that this species inhabits Hawaiian

waters (Tomich 1986). Two sightings of pygmy or

dwarf sperm whales were made between Hawaii and

Maui during 1993-98 aerial surveys within about 25

nmi of the main Hawaiian Islands (Figure 1; Mobley

et al. 1999). The difficulty of detecting and

identifying it at sea, as well as its confusion with the

pygmy sperm whale, may partially explain the

paucity of records. For the Marine Mammal

Protection Act (MMPA) stock assessment reports,

there is a single Pacific management stock of dwarf

sperm whales including only animals found within

the U.S. Exclusive Economic Zone of the Hawaiian

Islands. Rice (1998) recently argued that the

species name simus, is incorrect and should be

replaced by sima. This change is not taxonomic, but

merely reflects rules of Latin usage.

POPULATION SIZE

Wade and Gerrodette (1993) provided an estimate for the eastern tropical Pacific, but no data are available to

estimate population size for this species in the central Pacific. As part of the Marine Mammal Research Program of the

Acoustic Thermometry of Ocean Climate (ATOC) study, a total of twelve aerial surveys were conducted within about

25 nmi of the main Hawaiian Islands in 1993, 1995 and 1998. Two sightings of five pygmy or dwarf sperm whales were

made; however these sightings were excluded during recent abundance analyses (Mobley et al. 2000), because they were

made during poor observation conditions. Therefore, no abundance estimate is available for dwarf sperm whales within

Hawaiian waters.

Minimum Population Estimate

No data are available for a minimum population estimate.

Current Population Trend

No data are available on current population trend.

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

No data are available on current or maximum net productivity rate.

POTENTIAL BIOLOGICAL REMOVAL

No PBR can be calculated for this species at this time.

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Fishery Information

No estimate of annual human-caused mortality and serious injury is available as there are no reports of direct

or incidental takes of dwarf sperm whales in Hawaiian waters (Nitta and Henderson 1993). However, mortality of other

cetacean species has been observed in Hawaiian fisheries, and the gear types used in these fisheries are responsible for
236

marine mammal mortality and serious injury in other fisheries throughout U.S. waters. Gillnets are used in Hawaiian

waters and appear to capture marine mammals wherever they are used, and float lines from lobster traps and longlines

can be expected to occasionally entangle whales (Perrin et al. 1994).

Interactions with cetaceans have been reported for all Hawaiian pelagic fisheries (Nitta and Henderson 1993),

but no interactions with dwarf sperm whales have been documented. None were observed hooked in the Hawaiian

longline fishery between 1994 and 1998, with approximately 4.4% of all effort (measured as the number of hooks fished)

observed (Kleiber 1999).

STATUS OF STOCK

The status of dwarf sperm whales in Hawaiian waters relative to OSP is unknown, and there are insufficient

data to evaluate trends in abundance. They are not listed as “threatened” or “endangered” under the Endangered Species

Act (1973), nor as “depleted” under the MMPA. Although information on dwarf sperm whales in Hawaiian waters is

limited, this stock would not be considered strategic under the 1994 amendments to the MMPA because there has been

no reported fisheries related mortality. The total fishery mortality and serious injury for dwarf sperm whales is zero and

therefore can be considered to be insignificant and approaching zero mortality and serious injury rate. The increasing

levels of anthropogenic noise in the world’s oceans has been suggested to be a habitat concern for whales, particularly

for deep-diving whales like dwarf sperm whales that feed in the oceans’ “sound channel”.

REFERENCES

Kleiber, P. 1999. Estimates of marine mammal takes in the Hawaiian longline fishery. (Unpublished). Southwest

Fisheries Science Center, NMFS, 2570 Dole St, Honolulu, HI, 96822-2396.

Mobley, J. R., Jr., R. A. Grotefendt, P. H. Forestell, and A. Frankel. 1999. Results of aerial surveys of marine mammals

in the major Hawaiian Islands (1993-98): Report to the Acoustic Thermometry of Ocean Climate Marine

Mammal Research Program (ATOC MMRP) (unpublished). 39 pp.

Mobley, J. R. , Jr, S. S. Spitz, K. A. Forney, R. A. Grotefendt, and P. H. Forestall. 2000. Distribution and abundance

of odontocete species in Hawaiian waters: preliminary results of 1993-98 aerial surveys Admin. Rep. LJ-00-

14C. Southwest Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA

92038. 26 pp.

Nagorsen, D. 1985. Kogia simus. Mamm. Spec. 239:1-6.

Nitta, E. 1991. The marine mammal stranding network for Hawaii: an overview. In: J.E. Reynolds III, D.K. Odell

(eds.), Marine Mammal Strandings in the United States, pp.56-62. NOAA Tech. Rep. NMFS 98, 157 pp.

Nitta, E. and J. R. Henderson. 1993. A review of interactions between Hawaii's fisheries and protected species. Mar.

Fish. Rev. 55(2):83-92.

Perrin, W.F., G. P. Donovan and J. Barlow. 1994. Gillnets and Cetaceans. Rep. Int. Whal. Commn., Special Issue 15,

629 pp.

Rice, D.W. 1998. Marine Mammals of the World Systematics and Distribution. Special Publication Number 4 The

Society of Marine Mammalogy. Douglas Wartzok (ed.). 231 pp.

Tomich, P. Q. 1986. Mammals in Hawaii: A Synopsis and Notational Bibliography. Bishop Museum Press, Hawaii,

375 pp.

Wade, P. R. and T. Gerrodette. 1993. Estimates of cetacean abundance and distribution in the eastern tropical Pacific.

Rep. Int. Whal. Commn. 43:477-493. 
237

Figure 1. Sperm whale sighting locations during 1993-98 aerial

surveys within about 25 nmi of the main Hawaiian Islands (see

Appendix 2 for details on timing and location of survey effort).

Outer line indicates approximate boundary of survey area.

Revised 12/15/2003

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 150o

W 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).

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 five strandings have been reported

from Oahu, Kauai (Nitta 1991) and Kure Atoll (Woodward 1972). Sperm whales have also been sighted around several

of the Northwestern Hawaiian Islands (Rice 1960), off the main island of Hawaii (Lee 1993; Mobley et al. 2000, see

Figure 1), in the Kauai Channel and in the Alenuihaha Channel between Maui and the island of Hawaii (Shallenberger

1981). In addition, the sounds of sperm whales have been recorded throughout the year off Oahu (Thompson and Friedl

1982).

The stock identity of sperm whales in the North Pacific has been inferred from historical catch records

(Bannister and Mitchell 1980) and from trends in CPUE and tag-recapture data (Ohsumi and Masaki 1977), but much

uncertainty remains. A 1997 survey designed specifically to investigate stock structure and abundance of sperm whales

in the northeastern temperate Pacific revealed no apparent hiatus in distribution between the U.S. Exclusive Economic

Zone (EEZ) off California and areas farther west, out to Hawaii (Barlow and Taylor 1998). Very preliminary genetic

analyses revealed significant differences between sperm whales off the coast of California, Oregon and Washington and

those sampled offshore to Hawaii (Mesnick et al., unpubl. data); analyses of additional genetic samples are ongoing at

the NMFS, Southwest Fisheries Science Center. For the Marine Mammal Protection Act (MMPA) stock assessment

reports, sperm whales within the Pacific U.S. EEZ are divided into three discrete, non-contiguous areas: 1) waters around

Hawaii (this report), 2) California, Oregon and Washington waters, and 3) Alaskan waters.

POPULATION SIZE

A large 1982 abundance estimate for the entire eastern North Pacific (Gosho et al. 1984) was based on a CPUE

method which is no longer accepted as valid by the International Whaling Commission. Recently, a combined visual

and acoustic line-transect survey conducted in the eastern temperate North Pacific in spring 1997 resulted in estimates

of 24,000 (CV=0.46) sperm whales based on visual sightings, and 39,200 (CV=0.60) based acoustic detections and visual

group size estimates (Barlow and Taylor 1998). In the eastern tropical Pacific, the abundance of sperm whales has been

estimated as 22,700 (95% C.I.=14,800-34,600; Wade and Gerrodette 1993). However, it is not known whether any or

all of these animals routinely enter the U.S. EEZ of Hawaii. As part of the Marine Mammal Research Program of the

Acoustic Thermometry of Ocean Climate (ATOC) study, a total of twelve aerial surveys were conducted within about

25 nmi of the main Hawaiian Islands in 1993, 1995 and 1998. An average abundance estimate of 66 (CV=0.56) sperm
238

Figure 2. Locations of observed sperm whale interaction (!) in the

Hawaiian longline fishery, 1997-2002. The solid line surrounding the

Hawaiian Islands represents the U. S. Exclusive Economic Zone (EEZ).

whales was recently calculated from the combined survey data (Mobley et al. 2000). This abundance underestimates

the total number of sperm whales within the U.S. EEZ off Hawaii, because areas around the Northwest Hawaiian Islands

(NWHI) and beyond 25 nautical miles from the main islands were not surveyed. Furthermore, this species is known to

spend a large proportion of time diving, causing additional downward bias in the abundance estimate. A line-transect

vessel survey of the Hawaiian archipelago EEZ was completed in 2002 and is expected to provide a more comprehensive

estimate of abundance for the Hawaiian stock of sperm whales in the near future.

Minimum Population Estimate

The log-normal 20th percentile of the combined 1993-98 abundance estimate is 43 sperm whales. As with the

best abundance estimate above, this includes only areas within about 25 nmi of the main Hawaiian Islands and does not

include a large proportion of animals that were diving and therefore unavailable to be seen.

Current Population Trend

No data on current population trend are available.

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

No data on current or maximum net productivity rate are available.

POTENTIAL BIOLOGICAL REMOVAL

The potential biological removal (PBR) level for this stock is calculated as the minimum population size (43)

times one half the default maximum net growth rate for cetaceans (1⁄2 of 4%) times a recovery factor of 0.1 (the default

value for an endangered species; Wade and

Angliss 1997), resulting in a PBR of 0.4

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). In

Hawaii, no mortality of sperm whales has

been observed in inshore gillnets, but these

fisheries are not observed or monitored.

Regulations governing the use of nearshore

gillnets (lay nets) are currently under review

by the State of Hawaii.

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 unpublished data). Between 1997 and September

2001, one sperm whale was observed taken within the Hawaiian Islands EEZ in the Hawaiian longline fishery (Figure

2), with approximately 4-23% of all effort observed each year. This extrapolates to an average interaction rate of 2.3

(95% CI = 1-11) sperm whales per year for the entire fishery (NMFS unpublished data, Kleiber 1999); however, not all

interactions result in the death or serious injury of cetaceans. Cetaceans may ingest a hook, become hooked in the mouth

or other body part, or become entangled in fishing line, causing varying levels of injury. Following the guidelines of a

1997 Serious Injury Workshop (Angliss and DeMaster 1998), if large cetaceans are entangled and released trailing gear

that could impede feeding or locomotion, they are considered seriously injured (defined under the MMPA as likely to
239

result in mortality). The sperm whale was entangled but appeared to free itself from the line; therefore, it would not be

considered seriously injured. During the five most recent years for which data are available (1997-2001), the estimated

mortality or serious injury for sperm whales in the entire fishery is zero.

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 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. 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 Hawaiian 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 deep-diving whales like sperm whales that

feed in the oceans’ “sound channel”.

REFERENCES

Allen, K. R. 1980. Size distribution of male sperm whales in the pelagic catches. Rep. Int. Whal. Commn. Special

Issue 2:51-56.

Allison, C. International Whaling Commission. The Red House, 135 Station Road, Impington, Cambridge, UK CB4

9NP.

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. 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-
240

394.

Donovan, G. P. 1991. A review of IWC stock boundaries. Rept. Int. Whal. Commn., Special Issue 13:39-68.

Gilmore, R. M. 1959. On the mass strandings of sperm whales. Pac. Nat. 1(9-10):3-15.

Gosho, M. E., D. W. Rice, and J. M. Breiwick. 1984. The sperm whale Physeter macrocephalus. Mar. Fish. Rev.

46(4):54-64.

Kasuya, T. 1998. Evidence of statistical manipulations in Japanese coastal sperm whale fishery. Paper SC/50/CAWS10

presented to the International Whaling Commission, June 1998 (unpublished).

Kleiber, P. 1999. Estimates of marine mammal takes in the Hawaiian longline fishery. (Unpublished). Southwest

Fisheries Science Center, NMFS, 2570 Dole St, Honolulu, HI, 96822-2396.

Lee, T. 1993. Summary of cetacean survey data collected between the years of 1974 and 1985. NOAA Tech.Mem.

NMFS 181, 184pp.

Mesnick, S. Southwest Fisheries Science Center, NMFS, P.O. Box 271, La Jolla, California, 92038.

Miyashita, T., H. Kato, and T. Kasuya (Eds.). 1995. Worldwide map of cetacean distribution based on Japanese

sighting data. Volume 1. National Research Institute of Far Seas Fisheries, Shizuoka, Japan. 140pp.

Mobley, J. R. , Jr, 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.

Ohsumi, S. 1980. Catches of sperm whales by modern whaling in the North Pacific. Rep. Int. Whal. Commn. (Spec.

Iss. 2):11-18.

Ohsumi, S. and Y. Masaki. 1977. Stocks and trends of abundance of the sperm whale in the North Pacific. Rep. Int.

Whal. Commn. 27:167-175.

Perrin, W.F., G. P. Donovan and J. Barlow. 1994. Gillnets and Cetaceans. Rep. Int. Whal. Commn., Special Issue 15,

629 pp.

Rice, D. W. 1960. Distribution of the bottle-nosed dolphin in the leeward Hawaiian Islands. J. Mamm. 41:407-408.

Rice, D. W. 1974. Whales and whale research in the eastern North Pacific. pp. 170-195 In: W. E. Schevill (ed.). The

Whale Problem: A Status Report. Harvard Press, Cambridge, MA.

Rice, D. W. 1989. Sperm whale Physeter macrocephalus Linneaus, 1758. In: S. H. Ridgway and R. Harrison (eds.),

Handbook of Marine Mammals, Vol. 4: The River Dolphins and Larger Toothed Whales, pp. 177-233.

Academic Press, 442 pp.

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. MMC77/23, 79pp.

Thompson, P. O. and W. A. Friedl. 1982. A long term study of low frequency sound from several species of whales off

Oahu, Hawaii. Cetology 45:1-19.

Townsend, C. H. 1935. The distribution of certain whales as shown by logbook records of American whaleships.

Zoologica 19:1-50.

Wade, P. R. and R. P. Angliss. 1997. Guidelines for Assessing Marine Mammal Stocks: Report of the GAMMS

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

93 pp.

Wade, P. R. and T. Gerrodette. 1993. Estimates of cetacean abundance and distribution in the eastern tropical Pacific.

Rep. Int. Whal. Commn. 43:477-493.

Woodward, P. W. 1972. The natural history of Kure Atoll, northwestern Hawaiian Islands. Atoll Res. Bull. 164:302.
241

Revised 12/15/2000

BLUE WHALE (Balaenoptera musculus): Hawaiian Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

Blue whales are extremely rare in Hawaii. The only published sighting record is that of Berzin and Rovnin

(1966) north of the Hawaiian Islands. Additional evidence that blue whales occur in this area comes from acoustic

recordings made off Oahu and Midway Islands (Northrop et al. 1971; Thompson and Friedl 1982; McDonald and Fox

1999). Although the exact positions of the whales producing the sounds could not be determined, at least some of them

were within the U.S. Exclusive Economic Zone. The recordings made off Oahu showed bimodal peaks throughout the

year, suggesting that the animals were migrating into the area in summer and winter. 

The stock structure of blue whales in the North Pacific is uncertain (Mizroch et al. 1984; Reilly and Thayer

1990; Reeves et al. 1998). The International Whaling Commission (IWC) has formally considered only one management

stock for blue whales in the North Pacific (Donovan 1991), but now this ocean is thought to include up to five

populations (Reeves et al. 1998), with two occurring within the U.S. EEZ. One group of animals feeds in California

waters in summer/fall (from June to November) and migrates south to productive areas off Mexico and as far south as

the Costa Rica Dome (10o

 N) in winter/spring (Mate et al. 1999, Stafford et al. 1999). Rice (1974) hypothesized that

blue whales from Baja California migrated far offshore to fed in the eastern Aleutians or Gulf of Alaska and returned

to feed in California waters; however, he has more recently concluded that the California population is separate from

the Gulf of Alaska population (Rice 1992). Length frequency analyses (Gilpatrick et al. 1996) and photo-identification

studies (Calambokidis et al. 1995) support separate population status for blue whales feeding off California and those

feeding in Alaskan waters. Whaling catch data indicate that whales feeding along the Aleutian Islands are probably part

of a central Pacific stock (Reeves et al. 1998), which may migrate to offshore waters north of Hawaii in winter (Berzin

and Rovnin 1966). Recently, however, blue whale feeding aggregations have not been found in Alaska despite several

surveys (Leatherwood et al. 1982; Stewart et al. 1987; Forney and Brownell 1996). For management in U.S. Pacific

waters outside the continental EEZ, the Hawaiian stock includes only those whales within the EEZ of the Hawaiian

Islands. One other stock of North Pacific blue whales (off California and Mexico) is recognized in the Marine Mammal

Protection Act (MMPA) stock Assessment Reports.

POPULATION SIZE

From ship line-transect surveys, Wade and Gerrodette (1993) estimated 1,400 blue whales for the eastern

tropical Pacific. A weighted average estimate of 1,940 blue whales is available for California, Oregon and Washington,

based on 1991-96 shipboard line-transect surveys (Barlow 1997) and photographic mark-recapture estimates

(Calambokidis and Steiger 1994). No data are available to estimate population size for any other North Pacific blue

whale population, including the putative central stock that apparently summered along the Aleutians and wintered north

of Hawaii. A summer 1994 shipboard survey within the historical whaling grounds south of the Aleutian Islands yielded

no blue whale sightings (Forney and Brownell 1996), nor did a total of twelve aerial surveys conducted in 1993-98

within about 25 nmi of the main Hawaiian Islands as part of the Marine Mammal Research Program of the Acoustic

Thermometry of Ocean Climate (ATOC) study (Mobley et al. 2000).

Minimum Population Estimate

No data are available to provide a minimum population estimate.

Current Population Trend

No data are available on current population trend.

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

No data are available on current or maximum net productivity rate.

POTENTIAL BIOLOGICAL REMOVAL

No PBR can be calculated for this stock at this time.
242

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Fishery Information

No estimate of annual human-caused mortality and serious injury is available as there are no reports of recent

direct or incidental takes of blue whales in Hawaiian waters. However, mortality of other cetacean species has been

observed in Hawaiian fisheries, and the gear types used in these fisheries are responsible for marine mammal mortality

and serious injury in other fisheries throughout U.S. waters. Gillnets are used in Hawaiian waters and appear to capture

marine mammals wherever they are used, and float lines from lobster traps and longlines can be expected to occasionally

entangle whales (Perrin et al. 1994). Interactions with dolphins are reported for all pelagic fisheries, and humpback

whales have been entangled in longlines off the Hawaiian Islands, but no takes of blue whales have been documented

(Nitta and Henderson 1993). None were observed hooked or entangled in the Hawaiian longline fishery between 1994

and 1998, with approximately 4.4% of all effort (measured as the number of hooks fished) observed (Kleiber 1999). 

Historical Mortality

 At least 9,500 blue whales were taken by commercial whalers throughout the North Pacific between 1910 and

1965 (Ohsumi and Wada 1972). Some proportion of this total may have been from a population or populations that

migrate seasonally into the Hawaiian EEZ. The species has been protected in the North Pacific by the IWC since 1966.

STATUS OF STOCK

The status of blue whales in Hawaiian waters relative to OSP is unknown, and there are insufficient data to

evaluate trends in abundance. Blue whales are formally listed as "endangered" under the Endangered Species Act (ESA),

and consequently the Hawaiian stock is automatically considered as a "depleted" and "strategic" stock under the MMPA.

The total fishery mortality and serious injury for blue whales is zero and therefore can be considered to be insignificant

and approaching zero mortality and serious injury rate. The increasing levels of anthropogenic noise in the world’s

oceans has been suggested to be a habitat concern for blue whales (Reeves et al. 1998).

REFERENCES

Barlow, J. 1997. Preliminary estimates of cetacean abundance off California, Oregon, and Washington based on a 1996

ship survey and comparisons of passing and closing modes. Admin. Rept. LJ-97-11. Southwest Fisheries

Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA. 25 pp.

Berzin, A. A. and A. A. Rovnin. 1966. Distribution and migration of whales in the northeastern part of the Pacific

Ocean, Bering and Chukchi Seas. Izv. Tikhookean. Nauchno-issled, Inst. Rybn. Khoz. Okeanogr. (TINRO)

58:179-207. {In Russian}. (Translated by U.S. Dep. Inter., Bur. Commer. Fish., Seattle, Washington, 1966, pp.

103-106 In: Panin, K. I. (ed) Soviet Research on marine mammals of the Far East).

Calambokidis, J., R. Sears, G. H. Steiger, and J. Evenson. 1995. Movement and stock structure of blue whales in the

eastern North Pacific. P.19 In: Proceedings of the Eleventh Biennial Conference on the Biology of Marine

Mammals, Orlando, FL, 14-18 December 1995 (Abstract). Society for Marine Mammalogy, Lawrence, KS.

Calambokidis, J., and G. H. Steiger. 1994. Population assessment of humpback and blue whales using photoidentification from 1993 surveys off California. Final Contract Report to Southwest Fisheries Science Center,

National Marine Fisheries Service, P.O. Box 271, La Jolla, CA 92038. 31 pp.

Donovan, G. P. 1991. A review of IWC stock boundaries. Rept. Int. Whal. Commn., Special Issue 13:39-68.

Forney, K. A. and Brownell, R. L., Jr. 1996. Preliminary report of the 1994 Aleutian Island Marine Mammal Survey.

Paper SC/48/O11 presented to the International Whaling Commission, June 1996 (unpublished).

Gilpatrick, J., W. Perryman, M. Lynn, and M. A. DeAngelis. 1996. Geographic populations of blue whales

(Balaenoptera musculus) in the North Pacific Ocean investigated from whaling records and aerial

photogrammetry. Paper SC/47/NP4 presented to the International Whaling Commission, May 1995

(unpublished). 

Kleiber, P. 1999. Estimates of marine mammal takes in the Hawaiian longline fishery. (Unpublished). Southwest

Fisheries Science Center, NMFS, 2570 Dole St, Honolulu, HI, 96822-2396.

Leatherwood, S., R. R. Reeves, W. F. Perrin, and W. E. Evans. 1982. Whales, dolphins, and porpoises of the eastern

North Pacific and adjacent Arctic waters: A guide to their identification. NOAA Technical Rept. NMFS

Circular 444. 245 pp.

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.
243

Mizroch, S. A., D. W. Rice, and J. M. Breiwick. 1984. The blue whale, Balaenoptera musculus. Mar. Fish. Rev.

46(4):15-19.

Mobley, J. R. , Jr, S. S. Spitz, K. A. Forney, R. A. Grotefendt, and P. H. Forestall. 2000. Distribution and abundance

of odontocete species in Hawaiian waters: preliminary results of 1993-98 aerial surveys Admin. Rep. LJ-00-

14C. Southwest Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA

92038. 26 pp.

Nitta, E. and J. R. Henderson. 1993. A review of interactions between Hawaii's fisheries and protected species. Mar.

Fish. Rev. 55(2):83-92.

Northrop, J., W. C. Cummings, and M. F. Morrison. 1971. Underwater 20-Hz signals recorded near Midway Island.

J. Acoust. Soc. Am. 49:1909-1910.

Ohsumi, S. and S. Wada. 1972. Stock assessment of blue whales in the North Pacific. Int. Whal. Commn. Sci. Comm.

Rep., 20 pp.

Perrin, W.F., G.P. Donovan and J. Barlow. 1994. Gillnets and Cetaceans. Rep. Int. Whal. Commn., Spec. Iss. 15, 629pp.

Reeves, R. R., P. J. Clapham, R. L. Brownell, Jr., and G. K. Silber. 1998. Recovery plan for the blue whale

(Balaenoptera musculus). Office of Protected Resources, NMFS, NOAA, Silver Spring, Maryland. 30 pp.

Reilly, S. B. and V. G. Thayer. 1990. Blue whale (Balaenoptera musculus) distribution in the eastern tropical Pacific.

Mar. Mamm. Sci. 6:265-277.

Rice, D. W. 1974. Whales and whale research in the eastern North Pacific. pp. 170-195 In: W. E. Schevill (ed.). The

Whale Problem: A Status Report. Harvard Press, Cambridge, MA.

Rice, D. W. 1992. The blue whales of the southeastern North Pacific Ocean. pp. 1-3 In. Alaska Fisheries Science

Center, Quart. Rept. Oct.-Dec.

Stafford, K.M., S.L. Nieukirk, and C.G. Fox. 1999. An acoustic link between blue whales in the eastern tropical Pacific

and the northeast Pacific. Mar. Mamm. Sci. 15(4):1258-1268.

Stewart, B. S., S. A. Karl, P. K. Yochem, S. Leatherwood, and J. L. Laake. 1987. Aerial surveys for cetaceans in the

former Akutan, Alaska, whaling grounds. Arctic 40(1):33-42.

Thompson, P. O. and W. A. Friedl. 1982. A long term study of low frequency sound from several species of whales off

Oahu, Hawaii. Cetology 45:1-19.

Wade, P. R. and T. Gerrodette. 1993. Estimates of cetacean abundance and distribution in the eastern tropical Pacific.

Rep. Int. Whal. Commn. 43:477-493.
244

Revised 12/15/2000 

FIN WHALE (Balaenoptera physalus): Hawaiian Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

Fin whales are found throughout all oceans and seas of the world from tropical to polar latitudes. They are rare

in Hawaiian waters. Balcomb (1987) observed 8-12 fin whales in a multispecies feeding assemblage on 20 May 1966

approx. 250 mi. south of Honolulu. Additional sightings were reported north of Oahu in May 1976 and in the Kauai

Channel in February 1979 (Shallenberger 1981). More recently, a single fin whale was observed north of Kauai in

February 1994 (Mobley et al. 1996). A single stranding has been reported on Maui (Shallenberger 1981). Thompson

and Friedl (1982; and see Northrop et al. 1968) suggested that fin whales migrate into Hawaiian waters mainly in fall

and winter, based on acoustic recordings off Oahu and Midway Islands. Although the exact positions of the whales

producing the sounds could not be determined, at least some of them were almost certainly within the U.S. Exclusive

Economic Zone. More recently, McDonald and Fox (1999) reported an average of 0.027 calling fin whales per 10002

km (grouped by 8-hr periods) based on passive acoustic recordings within about 16 km of the north shore of Oahu.

The International Whaling Commission (IWC) recognized two stocks of fin whales in the North Pacific: the

East China Sea and the rest of the North Pacific (Donovan 1991). Mizroch et al. (1984) cites evidence for additional

fin whale subpopulations in the North Pacific. There is still insufficient information to accurately determine population

structure, but from a conservation perspective it may be risky to assume panmixia in the entire North Pacific. In the

North Atlantic, fin whales were locally depleted in some feeding areas by commercial whaling (Mizroch et al. 1984),

in part because subpopulations were not recognized. The Marine Mammal Protection Act (MMPA) stock assessment

reports recognize three stocks of fin whales in the North Pacific: 1) the Hawaii stock (this report), 2) the

California/Oregon/Washington stock, and 3) the Alaska stock. 

POPULATION SIZE

No data are available to estimate population size. As part of the Marine Mammal Research Program of the

Acoustic Thermometry of Ocean Climate (ATOC) study, a total of twelve aerial surveys were conducted within about

25 nmi of the main Hawaiian Islands in 1993-98 (Mobley et al. 2000). Only one sighting of a single fin whale was made

(Mobley et al. 1996), and therefore no meaningful abundance estimate could be calculated. Using passive acoustic

detections from a hydrophone north of Oahu, MacDonald and Fox (1999) estimate an average density of 0.027 calling

fin whales per 1000 km2

 within about 16 km from shore. However, the relationship between the number of whales

present and the number of calls detected is not known, and therefore this acoustic method does not provide an estimate

of absolute abundance for fin whales. 

Minimum Population Estimate

No data are available to provide a minimum population estimate.

Current Population Trend

No data are available on current population trend.

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

No data are available on current or maximum net productivity rate.

POTENTIAL BIOLOGICAL REMOVAL

No PBR can be calculated for this stock at this time.

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Fishery Information

No estimate of annual human-caused mortality and serious injury is available as there are no reports of recent

direct or incidental takes of fin whales in Hawaiian waters. However, mortality of other cetacean species has been

observed in Hawaiian fisheries, and the gear types used in these fisheries are responsible for marine mammal mortality

and serious injury in other fisheries throughout U.S. waters. Gillnets are used in Hawaiian waters and appear to capture

marine mammals wherever they are used, and float lines from lobster traps and longlines can be expected to occasionally

entangle whales (Perrin et al. 1994).
245

Interactions with dolphins are reported for all pelagic fisheries, and humpback whales have been entangled in

longlines off the Hawaiian Islands (Nitta and Henderson 1993), but no takes of fin whales have been documented. None

were observed hooked or entangled in the Hawaiian longline fishery between 1994 and 1998, with approximately 4.4%

of all effort (measured as the number of hooks fished) observed (Kleiber 1999).

Historical Mortality

Large numbers of fin whales were taken by commercial whalers throughout the North Pacific from the early

20th century until the 1970s (Tønnessen and Johnsen 1982). Approximately 46,000 fin whales were taken from the North

Pacific by commercial whalers between 1947 and 1987 (C. Allison, IWC, pers. comm.). Some of the whales taken may

have been from a population or populations that migrate seasonally into the Hawaiian EEZ. The species has been

protected in the North Pacific by the IWC since 1976.

STATUS OF STOCK

The status of fin whales in Hawaiian waters relative to OSP is unknown, and there are insufficient data to

evaluate trends in abundance. Fin whales are formally listed as "endangered" under the Endangered Species Act (ESA),

and consequently the Hawaiian stock is automatically considered as a "depleted" and "strategic" stock under the MMPA.

The total fishery mortality and serious injury for fin whales is zero and therefore can be considered to be insignificant

and approaching zero mortality and serious injury rate. The increasing levels of anthropogenic noise in the world’s

oceans has been suggested to be a habitat concern for whales.

REFERENCES

Allison, C. International Whaling Commission. The Red House, 135 Station Road, Impington, Cambridge, UK CB4

9NP.

Balcomb, K. C., III. 1987. The Whales of Hawaii. Marine Mammal Fund, 99 pp.

Donovan, G. P. 1991. A review of IWC stock boundaries. Rept. Int. Whal. Commn., Special Issue 13:39-68.

Kleiber, P. 1999. Estimates of marine mammal takes in the Hawaiian longline fishery. (Unpublished). Southwest

Fisheries Science Center, NMFS, 2570 Dole St, Honolulu, HI, 96822-2396.

McDonald, M. A., and C. G. Fox. 1999. Passive acoustic methods applied to fin whale population density estimation.

J. Acoust. Soc. Am. 105: 2643-2651.

Mizroch, S. A., D. W. Rice, and J. M. Breiwick. 1984. The fin whale, Balaenoptera physalus Mar. Fish. Rev. 46(4):20-

24.

Mobley, J. R., Jr., M. Smultea, T. Norris, and D. Weller. 1996. Fin whale sighting north of Kaua’i, Hawai’i. Pacific

Science 50:230-233.

Mobley, J. R., Jr, S. S. Spitz, K. A. Forney, R. A. Grotefendt, and P. H. Forestall. 2000. Distribution and abundance

of odontocete species in Hawaiian waters: preliminary results of 1993-98 aerial surveys Admin. Rep. LJ-00-

14C. Southwest Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA

92038. 26 pp.

Nitta, E. and J. R. Henderson. 1993. A review of interactions between Hawaii's fisheries and protected species. Mar.

Fish. Rev. 55(2):83-92.

Northrop, J., W. C. Cummings, and P. O. Thompson. 1968. 20-Hz signals observed in the central Pacific. J. Acoust.

Soc. Am. 43:383-384.

Perrin, W.F., G. P. Donovan and J. Barlow. 1994. Gillnets and Cetaceans. Rep. Int. Whal. Commn., Special Issue 15,

629 pp.

Shallenberger, E.W. 1981. The status of Hawaiian cetaceans. Final report to U.S. Marine Mammal Commission. MMC77/23, 79pp.

Thompson, P. O. and W. A. Friedl. 1982. A long term study of low frequency sound from several species of whales off

Oahu, Hawaii. Cetology 45:1-19.

Tønnessen, J. N. and A. O. Johnsen. 1982. The History of Modern Whaling. Hurst, 789 pp.
246

Revised 12/15/2000 

BRYDE'S WHALE (Balaenoptera edeni): Hawaiian Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

Bryde's whales occur in tropical and warm temperate waters throughout the world. Shallenberger (1981)

reported a sighting of a Bryde's whale southeast of Nihoa in April 1977 (see DeLong and Brownell 1977; Leatherwood

et al. 1982: Fig. 39c). Leatherwood et al. (1982) described the species as relatively abundant in summer and fall on the

Mellish and Miluoki banks northeast of Hawaii and around Midway Islands, but the basis for this statement was not

explained. Ohsumi and Masaki (1975) reported the tagging of "many" Bryde's whales between the Bonin and Hawaiian

Islands in the winters of 1971 and 1972 (Ohsumi 1977). With presently available evidence, there is no biological basis

for defining separate stocks of Bryde's whales in the central North Pacific. Bryde's whales also occasionally occur off

southern California (Morejohn and Rice 1973). For the MMPA stock assessment reports, Bryde's whales within the

Pacific U.S. Exclusive Economic Zone are divided into two areas: 1) Hawaiian waters (this report), and 2) the eastern

tropical Pacific (east of 150o

W and including the Gulf of California and waters off California).

POPULATION SIZE

Tillman (1978) concluded from Japanese and Soviet CPUE data that the stock size in the North Pacific pelagic

whaling grounds, mostly to the west of the Hawaiian Islands, declined from approximately 22,500 in 1971 to 17,800 in

1977. An estimate of 13,000 (CV=0.202) Bryde's whales was made from vessel surveys in the eastern tropical Pacific

between 1986 and 1990 (Wade and Gerrodette 1993). The area to which this estimate applies is mainly east and

somewhat south of the Hawaiian Islands, and it is not known whether these animals are part of the same population that

occurs around the Hawaiian Islands. As part of the Marine Mammal Research Program of the Acoustic Thermometry

of Ocean Climate (ATOC) study, a total of twelve aerial surveys were conducted within about 25 nmi of the main

Hawaiian Islands in 1993, 1995 and 1998 (Mobley et al. 2000). No sightings of Bryde’s whales were made, and

therefore no abundance estimate is available for Hawaiian waters.

Minimum Population Estimate

No data are available for a minimum population estimate.

Current Population Trend

No data are available on current population trend.

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

No data are available on current or maximum net productivity rate.

POTENTIAL BIOLOGICAL REMOVAL

No PBR can be calculated for this stock at this time.

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY 

Fishery Information

No estimate of annual human-caused mortality and serious injury is available as there are no reports of recent

direct or incidental takes of Bryde's whales in Hawaiian waters. However, mortality of other cetacean species has been

observed in Hawaiian fisheries, and the gear types used in these fisheries are responsible for marine mammal mortality

and serious injury in other fisheries throughout U.S. waters. Gillnets are used in Hawaiian waters and appear to capture

marine mammals wherever they are used, and float lines from lobster traps and longlines can be expected to occasionally

entangle whales (Perrin et al. 1994). 

Interactions with dolphins are reported for all pelagic fisheries, and humpback whales have been entangled in

longlines off the Hawaiian Islands (Nitta and Henderson 1993), but no takes of Bryde's whales have been documented.

None were observed hooked or entangled in the Hawaiian longline fishery between 1994 and 1998, with approximately

4.4% of all effort (measured as the number of hooks fished) observed (Kleiber 1999).

Historical Mortality

Small numbers of Bryde's whales were taken near the Northwestern Hawaiian Islands by Japanese and Soviet
247

whaling fleets during the early 1970s (Ohsumi 1977). Pelagic whaling for Bryde's whales in the North Pacific ended

after the 1979 season (IWC 1981), and coastal whaling for this species ended in the western Pacific in 1987 (IWC 1989).

STATUS OF STOCK

The status of Bryde's whales in Hawaiian waters relative to OSP is unknown, and there are insufficient data

to evaluate trends in abundance. They are not listed as “threatened” or “endangered” under the Endangered Species Act

(1973), nor as “depleted” under the MMPA. Although information on Bryde's whales in Hawaiian waters is limited, this

stock would not be considered strategic under the 1994 amendments to the MMPA because there has been no reported

fisheries related mortality. The total fishery mortality and serious injury for Bryde’s whales is zero and therefore can

be considered to be insignificant and approaching zero mortality and serious injury rate. The increasing levels of

anthropogenic noise in the world’s oceans has been suggested to be a habitat concern for whales.

REFERENCES

DeLong, R. L. and R. L. Brownell, Jr. 1977. Hawaiian monk seal (Monachus schauinslandi) habitat and population

survey in the northwestern (Leeward) Hawaiian Islands, April 1977. Northwest Alaska Fish Cent. Proc. Rep.,

43 pp.

International Whaling Commission. 1981. Japan. Progress report on cetacean research June 1979-May 1980. Rep. Int.

Whal. Commn. 31:195-200.

International Whaling Commission. 1989. Japan. Progress report on cetacean research June 1987 to April 1988. Rep.

Int. Whal. Commn. 39:201-204.

Kleiber, P. 1999. Estimates of marine mammal takes in the Hawaiian longline fishery. (Unpublished). Southwest

Fisheries Science Center, NMFS, 2570 Dole St, Honolulu, HI, 96822-2396.

Leatherwood, S., R. R. Reeves, W. F. Perrin, and W. E. Evans. 1982. Whales, dolphins, and porpoises of the eastern

North Pacific and adjacent arctic waters: A guide to their identification. NOAA Tech. Rep. NMFS 444, 245

pp.

Mobley, J. R. , Jr, S. S. Spitz, K. A. Forney, R. A. Grotefendt, and P. H. Forestall. 2000. Distribution and abundance

of odontocete species in Hawaiian waters: preliminary results of 1993-98 aerial surveys Admin. Rep. LJ-00-

14C. Southwest Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA

92038. 26 pp.

Morejohn, G. V. and D. W. Rice. 1973. First record of Bryde's whale (Balaenoptera edeni) off California. Cal. Fish

Game 59:313-315.

Nitta, E. and J. R. Henderson. 1993. A review of interactions between Hawaii's fisheries and protected species. Mar.

Fish. Rev. 55(2):83-92.

Ohsumi, S. 1977. Stocks and trends of abundance of the sperm whale in the North Pacific. Rep. Int. Whal. Commn.

27:167-175.

Ohsumi, S. and Y. Masaki. 1975. Japanese whale marking in the North Pacific, 1963-72. Bull. Far Seas Fish. Res. Lab.

12:171-219.

Perrin, W.F., G. P. Donovan and J. Barlow. 1994. Gillnets and Cetaceans. Rep. Int. Whal. Commn., Special Issue 15,

629 pp.

Shallenberger, E.W. 1981. The status of Hawaiian cetaceans. Final report to U.S. Marine Mammal Commission. MMC77/23, 79pp.

Tillman, M. F. 1978. Modified Delury estimates of the North Pacific Bryde's whale stock. Rep. Int. Whal. Commn.

28:315-317.

Wade, P. R. and T. Gerrodette. 1993. Estimates of cetacean abundance and distribution in the eastern tropical Pacific.

Rep. Int. Whal. Commn. 43:477-493.
248

Revised 12/15/2003

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. 66, no. 14 dated 22

January 2001.

1. Sources of Mortality/Injury Data

There are three major sources of marine mammal mortality/injury data for the active commercial fisheries in

California, Oregon, and Washington. These sources are the NMFS Observer Programs, the Marine Mammal

Authorization Program (MMAP) data, and the NMFS Marine Mammal Stranding Network (MMSN) data. Each of these

data sources has a unique objective. The National Marine Fisheries Service (NMFS) currently observes about 20% of

the annual CA swordfish drift-net fishery (based on the five-year period 1997-2001, Figure 1). The set gillnet fishery

for halibut/angel shark was observed from 1990-94, after which the observer program was discontinued owing to

legislation which banned set gillnets within 3 nmi of the mainland in southern California and a consequent reduction in

fishing effort. A regional set gillnet observer program was reinstated in Monterey Bay in 1999 and 2000 in response

to evidence of increasing harbor porpoise mortalities in this fishery. Observer coverage in Monterey Bay for 1999 and

2000 was 21% and 27%, respectively (this represented <5% of the entire California fishery). The set gillnet observer

program was discontinued in 2001, owing to an area closure implemented by the California Department of Fish and

Game (CDFG), which effectively eliminated most set gillnet fishing in Monterey Bay. Permanent year-round regulations

currently prohibit the use of gillnet and trammel net fishing inshore of 60 fathoms from Pt. Reyes to Pt. Arguello. Data

from observer programs are combined with estimates of total effort provided by the CDFG, to estimate marine mammal

mortality. Data on mammal mortality and injury are reported to the MMAP by fishers in any commercial fisheries. 

Marine mammal mortality and injury is also monitored by the NMFS Marine Mammal Stranding Network (MMSN).

Data provided by the MMSN is not duplicated by either the NMFS Observer Program or MMAP reporting. Humanrelated 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

The Marine Mammal Exemption Program (MMEP) was put into place in mid-1989 as a result of the 1988

amendments to the MMPA. It required fishers to register with NMFS and to complete annual logbooks detailing each

day’s fishing activity, including: date fished, hours fished, area fished, marine mammal species involved, injured and

killed due to gear interactions, and marine mammal species harassed, injured and killed due to deterrence from gear or

catch. If the marine mammal was deterred, the method of deterrence was required, as well as indication of its

effectiveness. Fishers were also required to report whether there were any losses of catch or gear due to marine

mammals. These logbooks were submitted to NMFS on an annual basis, as a prerequisite to renewing their registration.

Logbook data are available for part of the 1989 and 1991-1994. Logbook data received for part of 1994 and 1995 was

not entered into the MMEP logbook database in order to focus staff efforts on implementing the 1994 amendments to

the MMPA.

In 1994, the MMPA was amended again to implement a long-term regime for managing mammal interactions

with commercial fisheries (the Marine Mammal Authorization Program, or MMAP). Logbooks are no longer required -

instead vessel owners/operators in any commercial fishery (Category I, II, or III) are required to submit one-page preprinted reports for all interactions (including those that occur while an observer is onboard) resulting in an injury or

mortality to a marine mammal. The report must include owner/operator’s name and address, vessel name and ID, where
Appendix 1. Fishery Descriptions

2

Read, R. B. 2002. Effort estimates of California gill net fisheries: halibut-angel shark set net, sharkswordfish drift net, white seabass-yellowtail set/drift net, for January through December, 2001. Report submitted to

NOAA Fisheries/National Marine Fisheries Service, Southwest Region in partial fulfillment of Cooperative

Agreement No. NA77FX0349. Available from Southwest Fisheries Science Center, La Jolla, CA.

249

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. Since the inception of this system in April 1996, the number of interactions have been

grossly under-reported by drift-net fishers. During 1997-2001, the number of self-reported interactions from the

California swordfish/shark drift gillnet fishers was 199. By comparison, there were 247 interactions recorded by

observers, which is based on observing approximately one-fifth of the total fishing effort (Table 1). In the California

halibut/angel shark set gillnet fishery, the number of self-reported interactions for 1999-2000 was 74, compared to 122

reported by observers over the same period with approximately 25% observer coverage. 

3. NMFS Marine Mammal Stranding Network data

In California, for the years 1997 through 2001 there were 101,120, 154, 152, and 100 cetacean strandings

respectively and 2,061, 3,568, 1,066, 1,857 and 1,482 pinniped strandings respectively. In Oregon/Washington from

1997-2001, there were 20, 43, 50, 48, and 28 reported cetacean strandings and 254, 321, 267, 235, and 250 pinniped

strandings, respectively. Approximately 8% of all cetacean and 6% 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 1997-2001 is given in Table 2 of this Appendix.

4. Fishery Descriptions

Category I, CA/OR thresher shark/swordfish drift gillnet fishery

Number of permit holders: The number of eligible permit holders in California for1997-2001 are 120, 148, 136, 126,

and 113 respectively.

Number of active permit holders: The number of active permit holders observed by NMFS from 1997-2001 were98,

92, 84, 89, and 75 respectively.1

Total effort: Both estimated and observed effort for the drift-net fishery during the calendar years 1990 through 2001

are shown in Figure 7. In 2001 there was an estimated 1,665 effort-days, where an effort-day is defined to be one day

of effort by one vessel.2

 (In this fishery, 1 effort-day is equivalent to 1 set.). There were 339 (65 trips) observed effortdays in 2001. 

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 1997-2001.

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 season-area 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')
Appendix 1. Fishery Descriptions

3

Barlow, Jay and Grant Cameron. 1999. Field experiments show that acoustic pingers reduce marine

mammal bycatch in the California drift gillnet fishery. IWC working paper SC/51/SM2.

250

to N 34o 27' W 123o

 35', west to W129o, north to N 45o, then east to the Oregon coast. Additional season-area closures

south of Point Conception are being considered to protect loggerhead turtles in this region. 

Gear type and fishing method: Typical gear used for this fishery is a 1000 fathom gillnet with a stretched mesh size

typically ranging from 18-22 inches (14 inch minimum). The net is set at dusk and allowed to drift during the night after

which, it is retrieved. The fishing vessel is typically attached to one end of the net. Soak duration is typically 12-14

hours depending on the length of the night. Net extender lengths of a minimum 36 ft. became mandatory for the 1997-

1998 fishing season. The use of acoustic warning devices (pingers) became mandatory 28 October 1997. 

Regulations: This fishery is managed by the California Dept. of Fish and Game and by Oregon Dept. of Fish and

Wildlife in accordance with state and federal laws.

Management type: The drift-net fishery is a limited entry fishery with seasonal closures and gear restrictions (see above).

The state of Oregon restricts landing to swordfish only. 

Comments: This fishery has had a NMFS observer program in place since July 1990. Due to bycatch of strategic stock

including short-finned pilot whale, beaked whales, sperm whale and humpback whale, a Take Reduction Team was

formed February 12, 1996. Since then, the implementation of increased extender lengths and the deployment of pingers

has substantially decreased cetacean entanglement3

.

Category I, CA angel shark/halibut large mesh (>8.0 in) set gillnet fishery.

Number of permit holders: There is no specific permit category for this fishery.Overall, the current number of legal

permit holders for gill and trammel nets, excluding swordfish drift gillnets and herring gillnets for1997 through 2001

are, respectively,219, 255, 245, 232, and 212. This general permit category includes the fishery, “CA. large mesh (>3.5")

for other species” described below.

Number of active permit holders: For the period 1997-2001, there were 52, 45, 66, 62, and 57 active permit holders in

this fishery.

Total effort: Effort in the 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 1990-2001 is shown in Figure 8. 

Geographic range: Effort in this fishery previously ranged from the U.S./Mexico border north to Monterey Bay and was

localized in more productive areas: San Ysidro, San Diego, Oceanside, Newport, San Pedro, Ventura, Santa Barbara,

Morro Bay, and Monterey Bay. Fishery effort is now predominantly in the Ventura Flats area off of Ventura, the San

Pedro area between Pt. Vicente and Santa Catalina Island and in the Monterey Bay area.

Seasons: This fishery operates year round. Effort generally increases during the summer months and declines during

the last three months of a year.

Gear type and fishing method: Typical gear used for this fishery is a 200 fathom gillnet with a stretched mesh size of

8.5 inches. The net is generally set during the day and allowed to soak for up to 2 days. Soak duration is typically 8-10,

19-24, or 44-49 hours. The depth of water ranges from 15-50 fathoms with most sets in water depths of 15-35 fathoms.
Appendix 1. Fishery Descriptions

251

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 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. NMFSre-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

in Monterey Bay. A permanent ban on gill and trammel nets inside of 60 fathoms from Point Reyes to Point Arguello

became effective in September 2002. This area closure effectively bans gillnet fishing in most harbor porpoise habitat

in central California.

Category I, CA other species, large mesh (>3.5 in) set gillnet fisheries.

Note: This fishery was previously combined with the California halibut/angel shark fishery. Because marine mammal

mortality estimates were determined specifically for that fishery, other large mesh set gillnet fisheries have been

separately described here. White seabass is the primary target of this fishery. This fishery is now prohibited from

operating inshore of 60 fathoms from Pt. Reyes to Pt. Arguello, essentially eliminating the fishery from that portion of

the central California coast.

Number of permit holders: There is no specific permit category for this fishery. See the fishery “CA halibut/angel shark,

large mesh (>8 in)” for the number of legal permit holders in the category gill/trammel nets.

Number of active permit holders:. In the gillnet fishery for white sea bass and yellowtail, the number of vessels actively

fishing in1997-2000 were 28, 59, 30and 44, respectively (source: White Seabass Fishery Management Plan, California

Department of Fish and Game, www.dfg.ca.gov). An estimated 43 vessels participated in this fishery in 20012

. 

Total effort: Total effort for these set-net fisheries is not currently estimated but the majority of effort is due to the white

sea bass and yellowtail fishery. For this fishery, 1997-2001, there were an estimated 411,761, 460, 657, and 551 days

of effort. The fisheries comprising this category are further described in Table 3.

Geographic range: Effort in this fishery ranges from the U.S./Mexico border north to Monterey Bay and is localized in

more productive areas: San Ysidro, San Diego, Oceanside, Newport, San Pedro, Ventura, Santa Barbara, Morro Bay,

and Monterey Bay. Effort from Pt. Arguello south to the U.S./Mexico border is restricted to waters farther than 3 nmi

offshore and greater than 1 nmi from any of the Channel Islands and waters deeper than 60 fathoms north of Pt. Arguello.

Seasons: This fishery operates year round. Targeted species is typically determined by market demand on a short-term

basis.

Gear type and fishing method: Typical gear used for this fishery is a 150-200 fathom gillnet. The mesh size depends

on the target species but typical values observed are 6.0 and 6.5 inches. Typical characteristics for these fisheries are

found in Table 3. Fishing methods vary according to target species but are similar to methods used in the halibut/angel

shark fishery.

Regulations: This fishery is managed by the California Dept. of Fish and Game in accordance with state and federal

laws.

Management type: These fisheries have gear restrictions and area closures.
Appendix 1. Fishery Descriptions

252

Comments: This fishery is not currently observed by NMFS or the state of California. Mortalities and injuries reported

to the MMAP for California set gill net fisheries are given in Table 1. In April of 2000, the California Marine Mammal

Stranding Network reported a dead gray whale near Seal Beach, CA with “white seabass gillnet” wrapped around its

flukes.

Category II, CA swordfish longline fishery

Number of permit holders: The number of vessels currently unloading in California since 1999 is approximately 40-50.

No permit is currently required to participate in this fishery, but permits will be required under a Fishery Management

Plan expected to be completed in 2003. 

Number of active permit holders: As of 2001, approximately 45 vessels participated in this fishery. Between 1991-93

only 3 high-seas longline vessels participated in this fishery; by 1994 this number had risen to 31 vessels (Vojkovich

and Barsky 1998).

Total Effort: From August 1, 1995 through December 31, 1999, 30 different vessels fished a total of 2,090 days,

deploying a total of 7,071,745 hooks (CDFG unpublished data).

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, typically. 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 not covered by a fishery management plan (FMP).

However, the Pacific Fishery Management Council is in the process of developing a pelagic FMP that will include the

California longline fishery. The FMP is expected to be finalized in 2003. A draft of the FMP can be found at the Pacific

Fishery Management Council website: http://www.pcouncil.org/hms/draftfmp.html. 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, 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. Currently, approximately

40-50 longline vessels unload in California, and of these, 40 boats originating from Hawaii (and which also have Hawaii

longline limited entry permits) have unloaded their catch in California ports since December, 1999 (D. Petersen, NMFS,

personal communication, April, 2000). Between October 2001 and March 2003, eleven trips were observed by

California-based longline observers, with 240 sets observed (<10% observer coverage). To date, one cetacean interaction
Appendix 1. Fishery Descriptions

253

with a Risso’s dolphin (outside the U.S. EEZ) has been observed. 

Category II, California Round Haul Fisheries. 6

Note: This category includes purse seine, drum seine and lampara net fisheries for wetfish (anchovy, mackerel, and

sardine), and tuna. Choice of targeted species is primarily driven by availability and varying market demand.

Number of permit holders: Number of permit holders is estimated at 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).

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
Appendix 1. Fishery Descriptions

254

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.

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.
Appendix 1. Fishery Descriptions

255

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, respectively, for this fishery (pers.

comm., Jane McCrae, Oregon Department of Fish and Wildlife, Marine Resources Program).

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
Appendix 1. Fishery Descriptions

7

 Pers. Comm. Diana Watters, biologist at CDFG Menlo Park and California’s Living Marine Resources, A

Status Report, CDFG December 2001.

8

This fishery description was provided by Annette Henry, biologist at CDFG La Jolla.

256

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.7

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 midMarch. There are 10 permits available for the fresh herring round haul fishery (purse seine or lampara nets). This fishery

is restricted to the non-spawning season, or approximately mid-March through the end of November. Fishing may take

place in open ocean areas ( e.g. Monterey Bay) or inside bays (e.g. San Francisco Bay). 

Category II, CA squid purse seine fishery.8

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 light and/or catch squid. Light boat owner

permits allow the use of attracting lights to aggregate market squid. In the 2001/2002 season there were 214 market

squid vessel permits and 47 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 2001/2002 season, there were approximately 95 vessels active during some portion of the year.

During the 2001/2002 season, there were approximately 95 vessels active during some portion of the year. Forty-seven

vessels harvested 90% of the total landings greater than two tons. The 1999/2000 season had the highest squid landings

to date; 132 vessels made squid landings greater than two tons.

Total effort: Beginning in May 2000, logbooks were required for the squid fishery. Preliminary results for the 2001

calendar year indicate that each hour of fishing required 5.5 hours of search time by light boats. Combined searching
Appendix 1. Fishery Descriptions

257

and fishing effort resulted in 3.7 mt of catch per hour. In the 2001/2002 season, the fishery made 3,402 landings. This

is a 21.7% decrease from the previous season. On the other hand, the average landing increased from 27.2 mt to 28.2

mt.

Geographic range: The majority of the squid fishing harvest occurs south of Point Conception. During the 2001/2002

season, slightly more than 90% of the catch was taken from this region with the majority (80%) harvested near the

Channel Islands. Squid catch north of Point Conception accounted for almost 10% of the 2001/2002 landings. Although

the northern fishery operates from Lopez Point to Half Moon Bay, the majority of fishing activity takes place 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.

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. 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.

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 2002. The plan considers seasonal and daily catch limitations; weekend

closures, research and monitoring programs, harvest replenishment areas, live bait and 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.
Appendix 1. Fishery Descriptions

258

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. 

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
Appendix 1. Fishery Descriptions

259

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.

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
Appendix 1. Fishery Descriptions

260

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. Noncommercial salmon enhancement pens are not included in the list of commercial fisheries.

Number of active permit holders: Twelve salmon net pen facilities in Washington. 

Total effort: The 12 licensed facilities on Washington operate year-round. 

Geographic range: In Washington, net pens are found in protected waters in the Straits (Port Angeles), northern Puget

Sound (in the San Juan Island area) as well as in Puget Sound south of Admirality Inlet. There are currently no

commercial salmon pens in Oregon.

Seasons: Salmon net pens operate year-round.

Gear type: Net pens are large net impoundments suspended below a floating dock-like structure. The floating docks

are anchored to the bottom and may also support guard (predator) net systems. Multiple pens are commonly rafted

together and the entire facility is positioned in an area with adequate tidal flow to maintain water quality.

Regulations: Specific regulations unknown.

Management type: In Washington, the salmon net pen fishery is managed by the Washington Department of Natural

Resources through Aquatic Lands Permits as well as the Washington Department of Fish and Wildlife. 
Appendix 1. Fishery Descriptions

261

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 at-sea

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.

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
Appendix 1. Fishery Descriptions

9

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.

10 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.

262

lion, harbor seal, northern fur seal, and northern elephant seal have been documented in the whiting fishery. From1997-

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.9

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, non-commercial 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.

Category III, Hawaii swordfish, tuna, billfish, mahi mahi, wahoo, and oceanic shark longline/set line fishery.10

Number of permit holders: There are 164 permits under a (1994) federal limited entry program.

Number of active permit holders: From 1997-2001 there were 105, 115, 122, 125, and 101 vessels actively fishing,

respectively.

Total effort: For the years 1997-2001, there were1,162, 1,181, 1,165, 1,135, and 1,075 trips made respectively. The

number of hooks set has steadily increased since 1997 (15.5 million) andpeaked in 2001 with22.3 million hooks set.

In 2001, most effort occurred within the U.S. EEZ (13.7 million hooks set), while 8.6 million hooks were set outside the

U.S. EEZ. At Kingman Reef and Palmyra Atoll there were 1.8 million hooks set in 2001.
Appendix 1. Fishery Descriptions

11Kawamoto, K. and Samuel G. Pooley. 1999. Draft Annual report of the 1998 western pacific lobster

fishery.

12Kawamoto, K. 1999. Summary of the 1999 NWHI Lobster Fishing Season. NMFS Honolulu Laboratory.

263

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 tuna-style 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.

Category III, Hawaii lobster trap fishery.

10 11 12

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
Appendix 1. Fishery Descriptions

264

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.

Category III, Hawaii deep sea bottomfish handline and jig fishery.

Note: There are two commercial bottomfish fisheries in Hawaii: a distant water Northwestern Hawaiian Islands (NWHI)

limited entry fishery under federal jurisdiction and the main Hawaiian Islands bottomfish fishery primarily under the

State of Hawaii jurisdiction.

Number of permit holders: The main Hawaiian Islands fishery is open access with close to 2,000 bottomfish vessels

registered with the State of Hawaii, whereas the NWHI is restricted to a maximum of 17 vessels. 

Number of active permit holders: In 1997 in the MHI a total of 750 fishers were active. The NWHI are divided into

the Mau Zone (closer to MHI) and the Hoomalu Zone. The Hoomalu Zone is a limited entry zone with 6 vessels

participating in 1998, 7 vessels fished the Mau Zone in the same year. Restrictions on new entry into the Mau Zone were

implemented in 1998.

Total effort: In 1998 in the MHI approximately 8,500 trips were made with a total catch of 424,000 pounds for an exvessel landing value of $1,336,000. This fishery occurs primarily in offshore banks and pinnacles. In the NWHI
Appendix 1. Fishery Descriptions

265

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 re-categorizing the

NWHI bottomfish fishery from Category III to Category II due to concerns for potential interactions between bottomfish

fishing vessels and Hawaiian monk seals, although there were none observed during 26 NWHI bottomfish trips during

1990-1993, and none reported. On 12 of the 26 trips, bottlenose dolphins have been observed 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 mid-ocean

seamounts and pinnacles. The principal catches are small to medium sized bigeye, yellowfin and albacore tuna. There

are several types of handline methods in the Hawaiian fisheries. Baited lines with chum are used in day fishing

operations (palu-ahi), another version uses squid as bait during night operations (ika-shibi), and an operation called

“danglers” uses multiple lines with artificial lures suspended or dangled over the water. Interactions have been

documented for rough-toothed dolphin, bottlenose dolphin, and Hawaiian monk seal.
Appendix 1. Fishery Descriptions

266

Table 1. The number of animals injured (I) and killed (K) reported to the Marine Mammal Authorization Program (MMAP) comfrom the NMFS Observer Program for two California gillnet fisheries for the years 1997-2001.

Category I, CA/OR thresher shark/swordfish drift gillnet fishery

1997 1998 1999 2000 

Species

MMAP NMFS MMAP NMFS MMAP NMFS MMAP NMFS MMIK IK IK IK IK IK IK IK I

Minke whale 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 

Sperm whale 0 0 0 0 0 1 0 1 0 0 0 0 0 0 0 0 0 

Gray whale 0 0 0 0 0 1 0 1 0 1 0 0 0 0 0 0 0 

Humpback whale 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 

Pacific white-sided dolphin 1 3 0 3 0 0 0 0 0 0 0 0 0 1 0 2 0 

Common dolphin spp. 1 20 1 24 2 5 0 9 8 29 0 35 3 15 0 25 1 

Risso’s dolphin 0 0 0 3 0 0 0 0 0 0 0 0 0 2 0 3 0 

Northern right-whale

dolphin

0 4 0 5 0 0 0 0 0 1 0 3 0 6 0 11 0 

Dall’s porpoise 0 0 0 4 0 0 0 0 0 0 0 0 0 0 0 0 0 

Unidentified Small

cetacean

00 00 00 00 03 00 41 00 2

California sea lion 4 15 2 37 3 19 0 23 0 5 0 6 0 14 0 13 1 

Steller sea lion 0 0 0 0 0 1 0 0 0 1 0 0 0 0 0 0 0 

Northern elephant seal 0 6 1 8 0 0 0 4 2 1 0 2 1 1 0 6 0 

Harbor seal 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 

Unidentified seal 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 

Unidentified baleen whale 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 

Unidentified toothed whale 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 

Total Occurrences

Reported 6 48 4 81 1 28 0 38 10 41 1 46 8 40 0 60 4 
Appendix 1. Fishery Descriptions

267

Table 1 (continued). Category I, CA large mesh (>3.5in) set gillnet fisheries (angel shark/halibut and other species)

1997 1998 1999 2000 

Species

MMAP NMFS MMAP NMFS MMAP NMFS MMAP NMFS MM

IK IK IK IK IK IK IK IK I

Common dolphin 0 3 0 2 0 0 0 0 0 0 0 0 0 

Harbor porpoise 0 0 0 0 6 5 0 27 0 0 0 7 0 

California sea lion 0 4 0 2 3 20 0 13 0 25 0 28 0 

Harbor seal 0 0 0 0 6 17 0 57 0 3 0 24 0 

Total Occurrences

Reported

0 7 0 4 9 37 0 70 0 28 0 52 0 

Not Observed

Not Observed
Appendix 1. Fishery Descriptions

268

Table 2. Strandings reported to the NMFS Marine Mammal Stranding Network 1997-2001. %HR = Percent human-related strandings.

Species

1997 1998 1999 2000 

CA OR/WA CA OR/WA CA OR/WA CA OR/WA 

n %HR (#) n % HR (#) n %HR (#) n % HR (#) n %HR (#) n % HR (#) n %HR (#) n % HR 

Harbor Porpoise 26 0 (0) 3 0 (0) 37 10.8(4) 25 0 (0) 31 6.4 (2) 7 0 (0) 20 10 (2) 6 16

Dall’s Porpoise 4 0 (0) 10 0 (0) 2 0 (0) 2 0 (0) 4 0 (0) 3 0 (0) 3 0 (0) 9 11

Pac. White-sided Dolphin 5 20.0(1) 0 0 (0) 5 0 (0) 1 0 (0) 4 25(1) 1 0 (0) 3 0 (0) 0 

Risso’s Dolphin 2 0 (0) 0 0 (0) 3 0 (0) 0 0 (0) 2 0 (0) 1 0 (0) 6 0 (0) 1 

Bottlenose Dolphin 3 0 (0) 0 0 (0) 4 0 (0) 0 0 (0) 3 0 (0) 0 0 (0) 12 0 (0) 0 

Common Dolphin 15 6.7(1) 0 0 (0) 35 2.9(1) 0 0 (0) 37 10.8(4) 0 0 (0) 30 3.3(1) 0 

Striped Dolphin 1 0 (0) 1 0 (0) 2 0 (0) 0 0 (0) 0 0 (0) 0 0 (0) 0 0 (0) 0 

N. Right Whale Dolphin 0 0 (0) 0 0 (0) 1 0 (0) 0 0 (0) 2 0 (0) 0 0 (0) 0 0 (0) 0 

Rough-toothed Dolphin 0 0 (0) 0 0 (0) 1 0 (0) 0 0 (0) 2 0 (0) 0 0 (0) 0 0 (0) 0 

Killer Whale 1 0 (0) 0 0 (0) 0 0 (0) 1 0 (0) 1 0 (0) 1 0 (0) 0 0 (0) 0 

Short-finned Pilot Whale 0 0 (0) 0 0 (0) 0 0 (0) 0 0 (0) 0 0 (0) 0 0 (0) 1 0 (0) 0 

Stejneger’s Beaked Whale 0 0 (0) 0 0 (0) 0 0 (0) 0 0 (0) 1 0 (0) 0 0 (0) 0 0 (0) 0 

Cuvier’s Beaked Whale 2 0 (0) 0 0 (0) 2 0 (0) 1 0 (0) 0 0 (0) 0 0 (0) 1 0 (0) 0 

Peruvian Beaked Whale 0 0 (0) 0 0 (0) 1 100(1) 0 0 (0) 0 0 (0) 0 0 (0) 0 0 (0) 0 

Unident. Beaked Whale 0 0 (0) 0 0 (0) 0 0 (0) 0 0 (0) 1 0 (0) 0 0 (0) 0 0 (0) 0 

Pygmy Sperm Whale 0 0 (0) 0 0 (0) 6 0 (0) 0 0 (0) 1 0 (0) 0 0 (0) 0 0 (0) 0 

Dwarf Sperm Whale 0 0 (0) 0 0 (0) 0 0 (0) 0 0 (0) 0 0 (0) 0 0 (0) 1 0 (0) 0 

Sperm Whale 1 0 (0) 0 0 (0) 0 0 (0) 0 0 (0) 1 0 (0) 0 0 (0) 0 0 (0) 1 

Gray Whale 10 60.0(6) 4 0 (0) 3 100(3) 4 25 (1) 47 12.7(6) 31 6.0 (2) 58 13.7(8) 25 

Minke Whale 0 0 (0) 0 0 (0) 1 0 (0) 1 0 (0) 1 0 (0) 0 0 (0) 0 0 (0) 0 

Blue Whale 0 0 (0) 0 0 (0) 0 0 (0) 0 0 (0) 0 0 (0) 0 0 (0) 0 0 (0) 0 

Fin Whale 1 100(1) 1 0 (0) 1 0 (0) 0 0 (0) 0 0 (0) 0 0 (0) 0 0 (0) 0 

Humpback Whale 3 33.3(1) 0 0 (0) 2 0 (0) 2 0 (0) 0 0 (0) 0 0 (0) 4 75(3) 0 

Unidentified Cetacean 3 0 (0) 0 0 (0) 0 0 (0) 0 0 (0) 0 0 (0) 3 0 (0) 1 0 (0) 4 2

Unidentified Porpoise 0 0 (0) 0 0 (0) 0 0 (0) 0 0 (0) 0 0 (0) 0 0 (0) 0 0 (0) 0 

Unidentified Dolphin 16 0 (0) 1 0 (0) 12 0 (0) 5 0 (0) 13 15(2) 2 0 (0) 11 0 (0) 2 

Unidentified Whale 7 14.3(1) 1 100(1) 2 0 (0) 0 0 (0) 3 33(1) 0 0 (0) 1 0 (0) 0 

Unident. Balaenopterid 1 100(1) 0 0 (0) 0 0 (0) 1 0 (0) 0 0 (0) 1 0 (0) 0 0 (0) 0 

Northern Fur Seal 50 0(0) 1 0 (0) 21 0 (0) 1 0 (0) 7 14(1) 3 0 (0) 3 0 (0) 6 

Guadalupe Fur Seal 2 0(0) 0 0 (0) 3 0 (0) 0 0 (0) 5 0(0) 0 0 (0) 1 0 (0) 0 

Steller (Nthn) Sea Lion 7 0(0) 3 33.3(1) 10 20.0(2) 7 0 (0) 11 9(1) 3 0 (0) 10 20(2) 5 

California Sea Lion 1262 10.6(134) 10 30.0(3) 2576 7.7(199) 75 12.0(9) 596 8.7(52) 35 (3) 1268 5.2(67) 32 

Unidentified Sea Lion 0 0(0) 0 0 (0) 0 0 (0) 0 0 (0) 0 0 (0) 9 11.1 (1) 1 0 (0) 8 

Harbor Seal 297 5.7(17) 127 9.4(12) 313 6.7(21) 121 5.8(7) 135 5.1(7) 176 2.2 (4) 230 5.6(13) 148 5

Northern Elephant Seal 241 0.4(1) 0 0 (0) 409 1.5(6) 24 0 (0) 200 0.5(1) 2 0 (0) 211 1.4(3) 11 

Unidentified Seal 0 0(0) 0 0 (0) 0 0 (0) 5 0 (0) 0 0 (0) 26 3.8 (1) 0 0 (0) 17 5

Unidentified Pinniped 202 0(0) 113 0 (0) 236 0 (0) 88 0 (0) 112 0(0) 13 0 (0) 133 0 (0) 8 

Totals for Cetaceans 101 11.9(12) 20 5.0(1) 120 6.1(9) 43 2.3(1) 1220 10.3(16) 50 4.0 (2) 2009 9.2(14) 48 6

Totals for Pinnipeds 2061 7.3(152) 254 6.3(16) 3568 6.3(228) 321 5.0(16) 2286 5.8(62) 317 3.3 (9) 3866 4.4(83) 283 5.9 
Appendix 1. Fishery Descriptions

269

Table 3. Characteristics of Category I Gillnet Fisheries in California.

Fishery Species Mesh Size Water Depth Set Duration Deployment 

Category ICA/OR ThresherShark/Swordfish drift gillnet fishery

Swordfish/Shark

14" - 22" Ranges from 50fms to

 2500fms

Typically 8-15 hrs. Drift Net

Only

1000fms c

opah, lou

Category I CA angel shark/ halibut andother species large mesh(>3.5in) set gillnet fisheries

Halibut/angel shark 8.5" < 40 fms 24 hrs Set NetBarracuda 3.5" -- < 12 hrs Drift Net Leopard Shark 7.0" - 9.0" < 50 fms -- – Fished simPerch/Croaker 3.5" - 4.0" < 15 - 20 fms < 24 hrs Set Net Few bRockfish 4.5" - 7.5" > 50 fms 12 - 18 hrs Set Net Net length

is a majo

Soupfin Shark 6.0" - 8.5" > 30 fms 24 hrs Set Net Few b

White Sea bass/Yellowtail

Usually 6.5"

6.0" - 7.0"

Usually 10 - 50 fms 

or Shallow 3 - 4 fms

8 - 24 hrs. Mostly Drift Net White s

spec

Miscellaneous Shark 6.0" - 14" < 40 fms 8 - 24 hrs Drift, some Set Net Species inc

Additional Notes:1. In southern California, gillnets are generally prohibited within three miles of shore.2. In central California, there are 30 or 40 fathom closures depending on area.3. In northern California, set gillnets are not allowed.
Appendix 1. Fishery Descriptions

270

W129 W126 

N30N34N38N42N46Figure 3. Locatin the swordfisgillnet fishery i2,634 sets were 

W129 W126 W123 W120 W117

N30N34N38N42N46

WASHINGTON

OREGON

CALIFORNIA

Figure 1. Locations of 692 observed setsin the swordfish/thresher shark driftgillnet fishery in 1997. An estimated3,039 sets were fished in 1997.

W129 W126 W123 W120 W117

N30N34N38N42N46

WASHINGTON

OREGON

CALIFORNIA

Figure 2. Locations of 587 observed setsin the swordfish/thresher shark driftgillnet fishery in 1998. An estimated3,353 sets were fished in 1998.
Appendix 1. Fishery Descriptions

271

W129 W126 W123 W120 W117

N30N34N38N42N46

WASHINGTON

OREGON

CALIFORNIA

Figure 4. Locations of 444 observed setsin the swordfish/thresher shark driftgillnet fishery in 2000. An estimated1,936 sets were fished in 2000.

W129 W126 W123 W120 W117

N30N34N38N42N46

WASHINGTON

OREGON

CALIFORNIA

Figure 5. Locations of 339 observed setsin the swordfish/thresher shark driftgillnet fishery in 2001. An estimated1,665 sets were fished in 2001.

W129 W126 W1

N30N34N38N42N46

WA

OR

Figure 6. Observemarine mammal endrift gillnet fishery, 1
Appendix 1. Fishery Descriptions

272

D rift Gillnet Fishery 1990-2001

20.4% 22.9%

20.0%

17.5%

22.8%

12.4%

15.6%

17.9%

13.4%

13.6%

9.8%

4.4%

0

1000

2000

3000

4000

5000

6000

1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001

Days

Figure 7. Estimated (gray) and observed (black) days of effort in the California

swordfish/shark drift gillnet fishery for 1990-2001. Percent values above bars

represent fraction of observer coverage in the fishery for a given year.

S et Gilln et Fish ery 1990-2001

0.0%

0.0% 0.0%

4.0% 1.8%

0.0%

7.7% 0.0%

15.4% 12.5%

9.8%

5.2%

0

1000

2000

3000

4000

5000

6000

7000

8000

1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001

Days

Figure 8. Estimated (gray) and observed (black) days of effort in the

halibut/angel shark set gillnet fishery for 1990-2001. Percent values above bars

represent fraction of observer coverage in the fishery for a given year. The set

gillnet fishery was observed only in Monterey Bay in 1999-2000, where 20-25%

of the local fishery was observed.
Appendix 1. Fishery Descriptions

273

W123 W122 W121 W120 W119 W118 W117

N31N32N33N34N35N36N37N38

Monterey Bay

Pt. Arguello

Long Beach

S.D.

Morro Bay

42 22 104

142 61

43

1

1 1

38

15

2

2 9

7 113 18

157 105576

121 1 10 36 5 7

5 50 2

1 11739

1 39 288258 4

2 1

1 3 5 273 5

13 196 2

26

Reported days of effort by CDFG block in the set gillnet fishery for halibut and angel shark in 1997. A total of 2,978 days are shown.There were an additional 89, 22, and 3 effort days reported without block number from Monterey Bay, Morro Bay, and Long Beach, respectively.

Figure 9. Reported effort in the halibut/angel shark setgillnet fishery for 1997.

W123 W122 W121 W120 

N31N32N33N34N35N36N37N38

Monterey Bay

Pt. Arguello

Morro Bay

63 26 16

178

54

5

1 4

3 9 18

276220

34 

12 68 21

2 

2

3 

Reported days of effort by CDFG block in the set gihalibut/angel shark in 1998. A total of 2,821 days arwere an additional 15 effort days reported without bMorro Bay.

14

21 14 7

5

1

10

2 1 4

5

2

1 8 

Figure 10. Reported effort in the halibgillnet fishery for 1998.
Appendix 1. Fishery Descriptions

274

W123.5 W122.5 W121.5 W120.5 W119.5 W118.5 W117.5

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 5 576 143

61 7 15 20 1 307

3 4 35 4 1 1

162 1

1 2 43 527 600 1

2 1

1 1 1 49

182 1 6

220 2

3

Monterey Bay

Morro Bay

Pt. Arguello

Long Beach

S.D.

Reported days of effort by CDFG block in the set gillnet fishery for halibut/angel shark in 1999. A total of 4,057 days are shown. There were an additional 3 effort days reported without block number from Monterey Bay, 8 days from Morro Bay, and 2 days from Long Beach.

Figure 11. Reported effort in the halibut/angel shark setgillnet fishery for 1999.

W123.5 W122.5 W121.5 W120.5 W119.5 

N31N32N33N34N35N36N37N38

46 141 608 

45 5 2 12 26

10 2 

4

Monterey Bay

Morro Bay

Pt. Arguello

2 1

85 33 17

90

2

24

1 1

1

150

88

8

5

41

5

3

2 2 156

Reported days of effort by CDFG block halibut/angel shark in 2000. A total of 3were an additional 2 effort days reporteMonterey Bay and 21 days from Morro 

Figure 12. Reported effort in the halibugillnet fishery for 2000.
Appendix 1. Fishery Descriptions

275

W123.5 W122.5 W121.5 W120.5 W119.5 W118.5 W117.5

N31N32N33N34N35N36N37N38

3 38 665 41

24 18 2 5 190

6 1 23

101

5 27 651 368 13

206

240

Monterey Bay

Morro Bay

Pt. Arguello

Long Beach

S.D.

26

272

105

166 125

1

Reported days of effort by CDFG block in the set gillnet fishery forhalibut/angel shark in 2001. A total of 3,408 days are shown. Therewere an additional 7 effort days reported without block number from Morro Bay.

2

1

2 2

1

4 59

7

1

2 1

1

Figure 13. Reported effort in the halibut/angel shark setgillnet fishery for 2001.
Revised 12/15/2003

Appendix 2. Cetacean Survey Effort

276

W132 W129 W126 W123 W120 W117

N30

N34

N38

N42

N46

WASHINGTON

OREGON

CALIFORNIA

Figure 1. Transect lines completed

during a 1991 winter/spring aerial

survey of California waters (Forney

et al. 1995).

W132 W129 W126 W123 W120 W117

N30

N34

N38

N42

N46

WASHINGTON

OREGON

CALIFORNIA

Figure 2. Transect lines completed

during a 1992 winter/spring aerial

survey of California waters (Forney

et al. 1995).

W132 W129 W126 W123 W120 W117

N30

N34

N38

N42

N46

WASHINGTON

OREGON

CALIFORNIA

Figure 3. Transect lines completed

during a 1991 summer/autumn vessel

survey of California waters (Barlow

1995).

W132 W129 W126 W123 W120 W117

N30

N34

N38

N42

N46

WASHINGTON

OREGON

CALIFORNIA

Figure 4. Transect lines completed

during a 1993 summer/autumn vessel

survey of California waters (Mangels

and Gerrodette 1994).

W132 W129 W126 W123 W120 W117

N30

N34

N38

N42

N46

WASHINGTON

OREGON

CALIFORNIA

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).

W132 W129 W126 W123 W120 W117

N30

N34

N38

N42

N46

WASHINGTON

OREGON

CALIFORNIA

Figure 6. Transect lines completed

during a 2001 summer/autumn vessel

survey of California, Oregon, and

Washington waters (Barlow 2003).

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.
Revised 12/15/2003

Appendix 2. Cetacean Survey Effort

277

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

N34.0N36.0N38.0N40.0N42.0N44.0

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 7. Harbor porpoise stock boundaries in California andsouthern Oregon. Stippled area shows approximate harborporpoise habitat between 0- 200 m. Thick solid lines representsurvey transects flown during 1989-2002 aerial surveys (Forneyet al. 1991; Forney 1995; NMFS unpubl. data). Survey coveragenorth of the California/Oregon border is completed by NationalMarine Mammal Laboratory personnel.

W123 W122 W121 W120 W119 W118 W117 

N31N32N33N34N35N36N37N38N39N40

San Francisco

Monterey Bay

Point Conception

San Di

Los Angeles

California

Pacific Ocean

Figure 8. Coastline section (in bold) surveyed during 2000 coastal bottlenose dolphin aerial surveys in southecentral California (Carretta et al. 1998, NMFS unpubl. da
Revised 12/15/2003

Appendix 2. Cetacean Survey Effort

278

W160o W158o W156o W154o

CES

N18o

N20o

N22o

0 40 80 120 NAUTICAL MILES

HAWAII

NORTH

PACIFIC OCEAN

Figure 9. Area covered by 1993-98 aerial surveys around the main Hawaiian

Islands (Mobley et al. 1999).

References

Barlow, J. 1995. The abundance of cetaceans in California waters. Part I: Ship surveys in summer and fall of 1991. 

Fish. Bull. 93:1-14.

Barlow, J. 1997. Preliminary estimates of cetacean abundance off California, Oregon, and Washington based on a

1996 ship survey and comparisons of passing and closing modes. Admin. Rep. LJ-97-11. Southwest

Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA 92038. 25 pp.

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. 

Carretta, J.V., K.A. Forney, and J.L. Laake. 1998. Abundance of southern California coastal bottlenose dolphins

estimated from tandem aerial surveys. Mar. Mamm. Sci. 14(4):655-675.

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

using analysis of covariance. Fish. Bull. 89:367-377.

Forney, K.A. 1995. A decline in the abundance of harbor porpoise, Phocoena phocoena, in nearshore waters off

California, 1986-93. Fish. Bull. 93(4):741-748.

Forney, K.A., J. Barlow, and J.V. Carretta. 1995. The abundance of cetaceans in California waters. Part II: Aerial

surveys in winter and spring of 1991 and 1992. Fish. Bull. 93(4):15-26.

Mobley, J.R., R.A. Grotefendt, P.H. Forestell, and A. Frankel. 1999. Results of aerial surveys of marine mammals

in the major Hawaiian Islands (1993-98): Report to the Acoustic Thermometry of Ocean Climate Marine

Mammal Research Program (ATOC MMRP). University of Hawaii-West Oahu 96-129 Ala Ike, Pearl City,

HI 96782. 39 pp.

Mangels, K.F. and T. Gerrodette. 1994. Report of cetacean sightings during a marine mammal survey in the eastern

Pacific Ocean and the Gulf of California aboard the NOAA ships McArthur and David Starr Jordan July 28

- November 6, 1993. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-SWFSC-221. 88 pp.

Von Saunder, A. and J. Barlow. 1999. A report of the Oregon, California, and Washington line-transect experiment

(ORCAWALE) conducted in west coast waters during summer/fall 1996. U.S. Dep. Commer., NOAA

Tech. Memo. NMFS-SWFSC-264. 49 pp.
APPENDIX 3 (revised 12/15/2003) 

Stocks for which assessment reports were revised in 2003 are .

SUMMARY OF 2003 PACIFIC MARINE MAMMAL STOCK ASSESSMENT

REPORTS (FOR STOCKS UNDER NMFS JURISDICTION)

279

Species Stock Area Region

NMFS

Center Nmin Rmax Fr PBR

Total

Annual

Mortality +

Serious

Injury

Annual

Fish.

Mortality +

Serious

Injury

Strategic

Status

California sea

lion

U.S. PAC SWC 138,881 0.12 1.0 8,333 1,562 1,476 N

Harbor Seal California PAC SWC 25,720 0.12 1.0 1,543 $443 433 N

Harbor Seal Oregon/

Washington

Coast

PAC AKC 22,380 0.12 1.0 1,343 17 15 N ≥ ≥

Harbor Seal Washington

Inland Waters

PAC AKC 12,844 0.12 1.0 771 34 30 N ≥ ≥

Northern

Elephant Seal

California

breeding

PAC SWC 60,547 0.083 1.0 2,513 88 86 N ≥ ≥

Guadalupe Fur

Seal

Mexico to

California

PAC SWC 3,028 0.12 0.5 91 0.0 0.0 Y

Northern Fur

Seal

San Miguel

Island

PAC AKC 4,190 0.086 1.0 180 0.8 0.6 N ≥

Monk seal Hawaii PAC SWC 1,378 0.07 0.1 4.8 n/a n/a Y

Harbor porpoise Morro Bay PAC SWC 669 0.04 0.5 7 4.8 4.8 N

Harbor porpoise Monterey Bay PAC SWC 1,142 0.04 0.5 11 3 3 N

Harbor porpoise San FranciscoRussian RiverPAC SWC 4,858 0.04 0.5 49 0.8 0.8 N ≥ ≥

Harbor porpoise Northern

CA/Southern

OR

PAC SWC 12,940 0.04 1.0 259 0 0 N ≥ ≥

Harbor porpoise Oregon/

Washington

Coast

PAC AKC 28,967 0.04 0.5 290 3.2 3.2 N

Harbor porpoise Washington

Inland Waters 

PAC AKC 2,545 0.04 0.4 20 15.2 15.2 N

Dall’s Porpoise California/

Oregon/

Washington

PAC SWC 75,915 0.04 0.48 729 7 7 N

Pacific Whitesided DolphinCalifornia/

Oregon/

Washington

PAC SWC 39,822 0.04 0.48 382 5.4 5.4 N ≥ ≥

Risso’s Dolphin

California/

Oregon/

Washington

PAC SWC 12,748 0.04 0.4 115 3.6 3.6 N
APPENDIX 3 (revised 12/15/2003) 

Stocks for which assessment reports were revised in 2003 are .

SUMMARY OF 2003 PACIFIC MARINE MAMMAL STOCK ASSESSMENT

REPORTS (FOR STOCKS UNDER NMFS JURISDICTION)

Species Stock Area Region

NMFS

Center Nmin Rmax Fr PBR

Total

Annual

Mortality +

Serious

Injury

Annual

Fish.

Mortality +

Serious

Injury

Strategic

Status

280

Bottlenose

Dolphin

California

coastal PAC SWC 186 0.04 0.5 1.9 0 0 N

Bottlenose

Dolphin

California/

Oregon/

Washington

Offshore

PAC SWC 3,053 0.04 0.5 31 0 0 N

Striped Dolphin

California/

Oregon/

Washington

PAC SWC 9,165 0.04 0.5 92 0 0 N

Common

dolphin,

 short-beaked

California/

Oregon/

Washington

PAC SWC 365,617 0.04 0.5 3,656 93 93 N

Common

dolphin,

 long-beaked

California PAC SWC 25,163 0.04 0.48 242 11 11 N

Northern rightwhale dolphin

California/

Oregon/

Washington

PAC SWC 16,417 0.04 0.50 164 23 23 N

Killer whale

Eastern North

Pacific

Offshore

PAC SWC 361 0.04 0.5 3.6 0 0 N

Killer whale

Eastern North

Pacific

Southern

Resident

PAC AKC 80 0.04 0.5 0.8 0 0 Y

Short-finned 

pilot whale

California/

Oregon/

Washington

PAC SWC 149 0.04 0.4 1.19 1.2 1.2 Y

Baird’s Beaked

Whale

California/

Oregon/

Washington

PAC SWC 152 0.04 0.5 1.5 0 0 N

Mesoplodont

Beaked Whales

California/

Oregon/

Washington

PAC SWC 645 0.04 0.5 6.5 0 0 N

Cuvier’s Beaked

Whale

California/

Oregon/

Washington

PAC SWC 1,121 0.04 0.5 11 0 0 N

Pygmy Sperm

Whale

California/

Oregon/

Washington

PAC SWC 119 0.04 0.5 1 0 0 N
APPENDIX 3 (revised 12/15/2003) 

Stocks for which assessment reports were revised in 2003 are .

SUMMARY OF 2003 PACIFIC MARINE MAMMAL STOCK ASSESSMENT

REPORTS (FOR STOCKS UNDER NMFS JURISDICTION)

Species Stock Area Region

NMFS

Center Nmin Rmax Fr PBR

Total

Annual

Mortality +

Serious

Injury

Annual

Fish.

Mortality +

Serious

Injury

Strategic

Status

281

Sperm whale

California/

Oregon/

Washington

PAC SWC 885 0.04 0.1 1.8 1.0 1.0 Y

Humpback

whale

Eastern North

Pacific PAC SWC 681 0.08 0.1 1.35 1.2 0.8 Y ≥ ≥

Blue whale Eastern North

Pacific PAC SWC 1,138 0.04 0.1 1.2 0.0 0 Y

Fin whale

California/

Oregon/

Washington

PAC SWC 2,541 0.04 0.1 5.1 1.4 1.0 Y

Bryde’s whale Eastern

Tropical Pacific PAC SWC 11,163 0.04 0.5 n/a 0 0 N

Sei whale

California/

Oregon/

Washington

PAC SWC 35 0.04 0.1 0.1 0 0 Y

Minke whale 

California/

Oregon/

Washington

PAC SWC 585 0.04 0.45 5.8 0 0 N

Rough-Toothed

Dolphin Hawaii PAC SWC 76 0.04 0.5 0.8 n/a n/a N

Risso’s Dolphin Hawaii PAC SWC n/a 0.04 0.5 n/a n/a n/a N

Bottlenose

Dolphin Hawaii PAC SWC 479 0.04 0.5 4.8 0 0 N

Pantropical

spotted dolphin Hawaii PAC SWC 2,040 0.04 0.5 20 0 0 N

Spinner dolphin Hawaii PAC SWC 2,355 0.04 0.5 24 0 - 2.3 0 - 2.3 N

Striped dolphin Hawaii PAC SWC 52 0.04 0.5 0.5 n/a n/a N

Melon-headed

whale Hawaii PAC SWC 81 0.04 0.5 0.8 n/a n/a N

Pygmy killer

whale Hawaii PAC SWC n/a 0.04 0.5 n/a n/a n/a N

False killer

whale Hawaii PAC SWC 83 0.04 0.5 0.8 4.6 - 6.9 4.6 - 6.9 Y

Killer whale Hawaii PAC SWC n/a 0.04 0.5 n/a n/a n/a N
APPENDIX 3 (revised 12/15/2003) 

Stocks for which assessment reports were revised in 2003 are .

SUMMARY OF 2003 PACIFIC MARINE MAMMAL STOCK ASSESSMENT

REPORTS (FOR STOCKS UNDER NMFS JURISDICTION)

Species Stock Area Region

NMFS

Center Nmin Rmax Fr PBR

Total

Annual

Mortality +

Serious

Injury

Annual

Fish.

Mortality +

Serious

Injury

Strategic

Status

282

Pilot whale,

short-finned Hawaii PAC SWC 1,313 0.04 0.5 13 0 - 2.3 0 - 2.3 N

Blainville’s

beaked whale Hawaii PAC SWC 43 0.04 0.5 0.4 0 0 N

Cuvier’s

beaked whale Hawaii PAC SWC 29 0.04 0.5 0.3 0 0 N

Pygmy sperm

whale Hawaii PAC SWC n/a 0.04 0.5 n/a n/a n/a N

Dwarf sperm

whale Hawaii PAC SWC n/a 0.04 0.5 n/a n/a n/a N

Sperm whale Hawaii PAC SWC 43 0.04 0.1 0.4 0 0 Y

Blue whale Hawaii PAC SWC n/a 0.04 0.1 n/a n/a n/a Y

Fin whale Hawaii PAC SWC n/a 0.04 0.1 n/a n/a n/a Y

Bryde’s whale Hawaii PAC SWC n/a 0.04 0.5 n/a n/a n/a N

n/a indicates that data are not available. Values appearing in Annual Fishery Mortality + Serious Injury columns

represent mortalities/injuries occurring only within the U.S. EEZ.
APPENDIX 4 (revised 12/15/2003)

CHRONOLOGY OF U.S. PACIFIC MARINE MAMMAL STOCK ASSESSMENT REPORTS, 1995-2003.

Key: X = Revised with new information; R = Reprinted without revision, N = New stock, E = Eliminated stock,

Shading indicates that a stock was not defined for that year.

283

U.S. PACIFIC MARINE MAMMAL STOCK 1995 1996 19981 1999 2000 2001 2002 2003

PINNIPEDS

CALIFORNIA SEA LION (Zalophus californianus californianus): 

U.S. Stock

XX XRRX

HARBOR SEAL (Phoca vitulina richardsi): 

California Stock

XX XXRX

HARBOR SEAL (Phoca vitulina richardsi): 

Oregon & Washington Coastal Waters Stock

XXX XRXX

HARBOR SEAL (Phoca vitulina richardsi): 

Washington Inland Waters Stock

XXX XRXX

NORTHERN ELEPHANT SEAL (Mirounga angustirostris): 

California Breeding Stock

XX XRXR

GUADALUPE FUR SEAL (Arctocephalus townsendi) XR XRRR

NORTHERN FUR SEAL (Callorhinus ursinus): 

San Miguel Island Stock

XXX XRRX

HAWAIIAN MONK SEAL 

(Monachus schauinslandi)

XX XXXXX

CETACEANS - U. S. WEST COAST

HARBOR PORPOISE (Phocoena phocoena): Morro Bay Stock N X

HARBOR PORPOISE ((Phocoena phocoena): Monterey Bay Stock N X

HARBOR PORPOISE ((Phocoena phocoena): San FranciscoRussian River StockN X

HARBOR PORPOISE ((Phocoena phocoena): N California/S

Oregon Stock

N R

HARBOR PORPOISE (Phocoena phocoena): 

Central California Stock

XX XXXEE

HARBOR PORPOISE (Phocoena phocoena): 

Northern California Stock

XX XXXEE

HARBOR PORPOISE (Phocoena phocoena): 

Oregon/Washington Coast Stock

XXXXX RX2 X

HARBOR PORPOISE (Phocoena phocoena): 

Washington Inland Waters Stock

XXXXXRXX

DALL'S PORPOISE (Phocoenoides dalli): 

California/Oregon/Washington Stock

XX XRRX

PACIFIC WHITE-SIDED DOLPHIN (Lagenorhynchus

obliquidens): California/ Oregon/Washington, Northern and

Southern Stocks

XX XRRX

RISSO'S DOLPHIN (Grampus griseus): 

California/Oregon/Washington Stock

XX XRRX

BOTTLENOSE DOLPHIN (Tursiops truncatus): 

California Coastal Stock

XX XXRX

BOTTLENOSE DOLPHIN (Tursiops truncatus): 

California/Oregon/Washington Offshore Stock

XX XRRX
APPENDIX 4 (revised 12/15/2003)

CHRONOLOGY OF U.S. PACIFIC MARINE MAMMAL STOCK ASSESSMENT REPORTS, 1995-2003.

Key: X = Revised with new information; R = Reprinted without revision, N = New stock, E = Eliminated stock,

Shading indicates that a stock was not defined for that year.

U.S. PACIFIC MARINE MAMMAL STOCK 1995 1996 19981 1999 2000 2001 2002 2003

284

STRIPED DOLPHIN (Stenella coeruleoalba): 

California/Oregon/Washington Stock

XX XRRX

SHORT-BEAKED COMMON DOLPHIN (Delphinus delphis):

California/Oregon/Washington Stock

XX XRRX

LONG-BEAKED COMMON DOLPHIN (Delphinus capensis): 

California Stock

XX XRRX

NORTHERN RIGHT-WHALE DOLPHIN (Lissodelphis borealis):

California/Oregon/Washington Stock

XX XRRX

KILLER WHALE (Orcinus orca): 

California/Oregon/Washington Pacific Coast Stock

XX EEEEE

KILLER WHALE (Orcinus orca): 

Eastern North Pacific Southern Resident Stock

XX XXXXX

KILLER WHALE (Orcinus orca): 

Eastern North Pacific Transient Stock

(INCLUDED IN ALASKA REPORTS) X X R (IN

ALASKA

REPORTS)

(IN

ALASKA

REPORTS)

KILLER WHALE (Orcinus orca): 

Eastern North Pacific Offshore Stock

NXRRX

SHORT-FINNED PILOT WHALE (Globicephala macrorhynchus):

California/Oregon/Washington Stock

XX XXRRX

BAIRD'S BEAKED WHALE (Berardius bairdii): 

California/Oregon/Washington Stock

XX XRRX

MESOPLODONT BEAKED WHALES (Mesoplodon spp.): 

California/Oregon/Washington Stocks

XXX XRRX

CUVIER'S BEAKED WHALE (Ziphius cavirostris): 

California/Oregon/Washington Stock

XX XRRX

PYGMY SPERM WHALE (Kogia breviceps): 

California/Oregon/Washington Stock

XX XRRX

DWARF SPERM WHALE (Kogia sima): 

California/Oregon/Washington Stock

XX EEEX

SPERM WHALE (Physeter macrocephalus): 

California/Oregon/Washington Stock

XX XXXRX

HUMPBACK WHALE (Megaptera novaeangliae): 

Eastern North Pacific Stock

XX XXXXX

BLUE WHALE (Balaenoptera musculus): 

Eastern North Pacific Stock

XX XRRX

FIN WHALE (Balaenoptera physalus): 

California/Oregon/Washington Stock

XX XXRX

BRYDE'S WHALE (Balaenoptera edeni): 

Eastern Tropical Pacific Stock

XX XRRR

SEI WHALE (Balaenoptera borealis): 

Eastern North Pacific Stock

XX XRRX

MINKE WHALE (Balaenoptera acutorostrata): 

California/Oregon/Washington Stock

XXX XRRX

CETACEANS - HAWAII
APPENDIX 4 (revised 12/15/2003)

CHRONOLOGY OF U.S. PACIFIC MARINE MAMMAL STOCK ASSESSMENT REPORTS, 1995-2003.

Key: X = Revised with new information; R = Reprinted without revision, N = New stock, E = Eliminated stock,

Shading indicates that a stock was not defined for that year.

U.S. PACIFIC MARINE MAMMAL STOCK 1995 1996 19981 1999 2000 2001 2002 2003

285

ROUGH-TOOTHED DOLPHIN (Steno bredanensis): 

Hawaiian Stock

XR XRRR

RISSO'S DOLPHIN (Grampus griseus): 

Hawaiian Stock

XR XRRR

BOTTLENOSE DOLPHIN (Tursiops truncatus): 

Hawaiian Stock

XR XRRX

PANTROPICAL SPOTTED DOLPHIN (Stenella attenuata): 

Hawaiian Stock

XR XRRX

SPINNER DOLPHIN (Stenella longirostris): 

Hawaiian Stock

XR XRRX

STRIPED DOLPHIN (Stenella coeruleoalba): 

Hawaiian Stock

XR XRRR

MELON-HEADED WHALE (Peponocephala electra): 

Hawaiian Stock

XR XRRR

PYGMY KILLER WHALE (Feresa attenuata): 

Hawaiian Stock

XR XRRR

FALSE KILLER WHALE (Pseudorca crassidens): 

Hawaiian Stock

XR XXXX

KILLER WHALE (Orcinus orca): 

Hawaiian Stock

XR XRRR

SHORT-FINNED PILOT WHALE (Globicephala macrorhynchus): 

Hawaiian Stock

XR XRRX

BLAINVILLE'S BEAKED WHALE (Mesoplodon densirostris): 

Hawaiian Stock

XR XRRX

CUVIER'S BEAKED WHALE (Ziphius cavirostris): 

Hawaiian Stock

XR XRRX

PYGMY SPERM WHALE (Kogia breviceps): 

Hawaiian Stock

XR XRRR

DWARF SPERM WHALE (Kogia sima): 

Hawaiian Stock

XR XRRR

SPERM WHALE (Physeter macrocephalus): 

Hawaiian Stock

XR XRRX

BLUE WHALE (Balaenoptera musculus): 

Hawaiian Stock

XR XRRR

FIN WHALE (Balaenoptera physalus): 

Hawaiian Stock

XR XRRR

BRYDE'S WHALE (Balaenoptera edeni): 

Hawaiian Stock

XR XRRR

APPENDIX TITLES APPENDIX NUMBERS

Summary of Pacific Stock Assessment Reports 1 3 1 2 3 3 3 3

Description of U.S. Commercial Fisheries 1 1 1 1 1
APPENDIX 4 (revised 12/15/2003)

CHRONOLOGY OF U.S. PACIFIC MARINE MAMMAL STOCK ASSESSMENT REPORTS, 1995-2003.

Key: X = Revised with new information; R = Reprinted without revision, N = New stock, E = Eliminated stock,

Shading indicates that a stock was not defined for that year.

U.S. PACIFIC MARINE MAMMAL STOCK 1995 1996 19981 1999 2000 2001 2002 2003

286

Cetacean Survey Effort 2 2222

Chronology of U. S. Pacific Stock Assessment Reports 14444

U.S. Fish and Wildlife Service California & Washington sea otter

stock assessments

5555

1

The public comment, review and revision process has necessitated about a one year time lag between the draft revision and final publication of

Marine Mammal Stock Assessment Reports. Therefore, in 1997, the Stock Assessment Report dates were changed to ‘1998' to match the 1998

publication year of the report.

2

The Oregon/Washington coast stock of harbor porpoise previously included animals south to the California/Oregon border. Stock revisions based

on genetic and sighting density data resulted in the southern boundary of this stock being moved north to Cape Blanco, Oregon (see stock assessment

report for Oregon/Washington coast harbor porpoise).
Appendix 5. The following stock assessment reports were prepared by the U.S.Fish and

Wildlife Service. NMFS includes these reports in this Technical Memorandum as a

convenience to interested readers and in response to a recommendation from regional

Scientific Review Groups.

Revised 10/4/1995

SOUTHERN SEA OTTER (Enhydra lutris nereis):

California Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

Southern sea otters breed and give birth in California year round, however the seasonality is not highly

synchronous and the birth peak may extend over several months (Siniff and Ralls 1991, Riedman et al. 1994). The

population ranges along the mainland coast from Pt. Ano Nuevo, Santa Cruz County south to Purisima Point, Santa

Barbara County; an experimental population currently exists at San Nicolas Island, Ventura County. The initial

translocation of sea otters to San Nicolas Island occurred in August 1987.

The population of southern sea otters historically ranged from northern California or Oregon to approximately

Punta Abreojos, Baja California (Wilson el al. 1991). Harvest of sea otters during the 1700's and 1800's reduced the

species throughout its range. In 1914, the total California population was estimated to be about 50 animals (California

Department of Fish and Game 1976). The estimated carrying capacity in California ranges between 13,500 and 30,000

sea otters (Marzin and DeMaster, In prep.).

POPULATION SIZE

Data on population size and distribution of the southern sea otter have been gathered for more than 50 years.

In 1982, a standardized survey technique was adopted to eliminate variation from future counts (Estes and Jameson

1988). This method involves shore-based censuses of approximately 80 percent of the population, supplemented with

aerial surveys of the remaining 20 percent. These surveys are conducted twice each year (in spring and fall). The San

Nicolas Island experimental population is surveyed approximately every two months.

Minimum Population Estimate

Based on the 1994 spring survey (actual count), the minimum southern sea otter population size of the mainland

population is 2,359 individuals. Based on the most recent survey of the San Nicolas Island experimental population, the

minimum sea otter population size is 17 individuals. Counts of sea otters at San Nicolas Island during 1994 and 1995

have ranged between 10 and 17 individuals.

Current Population Trend

Based on annual spring count totals since 1983, the southern sea otter population is continuing to increase. The

mean growth rate from 1983 through 1994 is 5.7 percent (R. Jameson, National Biological Service, pers. comm., Estes

et al., In press) (The 1994 count represented a 5.4 percent increase over 1993). Recent counts of the San Nicolas Island

experimental population indicate a slight increase in the population; available information is inadequate to determine

trends at this time.

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

The maximum growth rate (rmax) for sea otter populations is about 20 percent (Estes 1990). Except for

California and Washington, all increasing sea otter populations for which data are available have grown at about this

rate. Since the early 1900's, the California sea otter population increased at about 4 to 5 percent a year until the mid1970's. Available information suggests that between 1976 and 1982 population growth ceased and possibly declined

by as much as 20 percent. Counts from 1983 to 1994 have increased at about 5 to 6 percent per year (Estes et al., In

press). In California, the rmax appears to be 6 percent.

287
Appendix 5.

288

ANNUAL HUMAN-CAUSED MORTALITY

Incidental drowning of sea otters in gill and trammel entangling nets has been a significant source of mortality

(Wendell et al. 1985). Mortality assessments for southern sea otters in California's commercial fisheries have been based

on direct observations. Monitoring of commercial fisheries was initiated in 1982. Extrapolations from the number of

otters observed drowned and the proportion of the set-net fishery sampled indicated that from June 1982 to June 1984,

an average of 80 sea otters drowned in gill and trammel nets each year (Wendell et al. 1985). The first of several State

restrictions of gill and trammel net fishing to protect sea otters was enacted in 1985. The most recent restriction,

California Senate Bill No. 2563, was enacted in 1990 and became effective on January 1, 1991. This bill prohibits the

use of gill and trammel nets in waters shallower than 30 fathoms between Waddell Creek in Santa Cruz County and Point

Sal in Santa Barbara County. Gill and trammel net fishing are prohibited within 30 fathoms around San Nicolas Island,

Ventura County.

Since 1988, 26 otters have been observed or otherwise known to have drowned in legally set commercial fishing

nets: 5 in 1988, 11 in 1989, 9 in 1990, and 0 in 1991 and 1992, 1 in 1993, and 0 in 1994. The net responsible for the

1993 mortality is of unknown origin. It may have been legally or illegally set, or a piece of netting set adrift in which

the otter became entangled. In 1992, a dead sea otter was recovered by a California Department of Fish and Game

warden in a crab pot located in 30 to 60 feet of water off Point Santa Cruz, Santa Cruz County. The level of take of

southern sea otters in lobster and crab fisheries in California is unknown. Although the level of take is unknown, it

has been postulated by some to have made a significant contribution to the lack of population growth in the colony

of sea otters translocated to San Nicolas Island.

Other sources of human-caused mortality include shooting, boat strikes, capture and relocation efforts, oil spills

and possibly elevated levels of polychlorinated biphenyls (PCBs) and other toxic contaminants. 

FISHERIES INFORMATION

Fishing with set gillnets has been restricted throughout most of the range of the southern sea otter with one

exception. Set gillnets are used by approximately 6 vessels (T. Price, National Marine Fisheries Service, pers. comm.)

to catch halibut and flounder, along the coastline from Point Sal to Point Arguello, Santa Barbara County. Because this

area is remote and difficult to access, this fishery is not monitored and no data exists on the level of take of southern sea

otters. 

Lobster and crab fishing occur within the range of the southern sea otter. Available information suggests that

sea otters are accidentally caught and drowned in lobster and crab traps. 

As part of the southern sea otter recovery effort, the Fish and Wildlife Service has attempted to establish a sea

otter colony at San Nicolas Island. Public Law 99-625, which provided the legislative authority for the translocation

of sea otters from the mainland to San Nicolas Island, specified that the area surrounding the translocation zone be

designated a "management zone" from which sea otters are to be excluded by non-lethal means to prohibit range

expansion and protect fishery resources south of Point Conception.

STATUS OF STOCK

The southern sea otter was designated as a threatened species in 1977 (42 FR 2965-2968) pursuant to the

Endangered Species Act of 1973, as amended (16 U.S.C. 1531 et seq.). Because of its threatened status, the southern

sea otter also is designated as depleted under the Marine Mammal Protection Act of 1972, as amended (16 U.S.C. 1361

et seq.). Furthermore, the southern sea otter population is below its Optimum Sustainable Population level. 

If the restrictions on the use of gill and trammel nets in areas inhabited by southern sea otters were lifted, the

southern sea otter population would be designated as a "strategic stock" as defined by the Marine Mammal Protection

Act, requiring constitution of a Take Reduction Team to advise on measures that could and should be taken to ensure

that the incidental take of sea otters, by itself and in combination with other possible sources of non-natural mortality,

does not exceed the calculated potential biological removal level.

POTENTIAL BIOLOGICAL REMOVAL

The Potential Biological Removal (PBR) for the California stock is 7 animals. PBR is the product of three

elements: the minimum population estimate (Nmin); half the maximum net productivity rate (0.5 Rmax); and a recovery
Appendix 5.

289

factor (Fr

). For the California sea otter stock, Nmin=2,376; Rmax= 6 percent; and Fr=0.1.

 Calculating a PBR for the southern sea otter serves no practical purpose. Incidental take of the southern sea

otter is not governed under section 118 of the Marine Mammal Protection Act.

REFERENCES

California Department of Fish and Game. 1976. A proposal for sea otter protection and research, and request for return

of management to the State of California, January 1976. 2 Vols. Unpubl. rep.

Estes, J. A. 1990. Growth and equilibrium in sea otter populations. J. Anim. Ecol. 59:358-401.

Estes, J. A. and R. J. Jameson. 1988. A double-survey estimate for sighting probability of sea otters in California. J.

Wildl. Manage. 52:70-76.

Estes, J. A., R. J. Jameson, J. L. Bodkin, and D. R. Carlson. (In Press) California sea otters. Our Living Resources

1995 - Mammals. National Biological Service.

Marzin, C. G. and D. P. DeMaster. (In prep.) Estimating the carrying capacity of sea otters (Enhydra lutris) along the

California coast. 

Riedman M. L, J. A. Estes, M. M. Staedler, A. A. Giles, and D. R. Carlson. 1994. Breeding patterns and reproductive

success of California sea otters. J. Wildl. Manage. 58:391-399.

Siniff, D. B., and K. Ralls. 1991. Reproduction, survival and tag loss in California sea otters. Marine Mammal Science

7(3):211-229.

Wendell, F. E., R. A. Hardy, and J. A. Ames. 1985. Assessment of the accidental take of sea otters, Enhydra lutris, in

gill and trammel nets. Mar. Res. Branch, Calif. Dep. Fish Game. Unpubl. rep. 30 pp.

Wilson, D. E., M. A. Bogan, R. L. Brownell, Jr., A. M. Burdin, and M. K. Maminov. 1991. Geographic variation in

sea otters, Enhydra lutris. J. Mammal. 72(1):22-36.
Appendix 5.

290

Revised 10/4/1995

 SEA OTTER (Enhydra lutris kenyoni):

Washington Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

Sea otters breed and give birth year-round (Riedman and Estes 1990). The peak pupping period for the

Washington population is not defined; however, breeding and pupping seasons peak about 2-3 months later in

Alaska than in California. The Washington population ranges from Neah Bay south to Destruction Island.

Enhydra lutris kenyoni historically ranged throughout the Aleutian Islands, originally as far north as the

Pribilof Islands and in the eastern Pacific Ocean from the Alaskan Peninsula south along the coast to Oregon

(Wilson el al. 1991). This subspecies was extirpated from most of its range during the 1700's and 1800's as the

species was exploited for its fur. In 1969 and 1970, a total of 59 sea otters captured at Amchitka Island, Alaska were

released in Washington (Jameson et al. 1982). The estimated carrying capacity in Washington has not been

determined.

For management purposes pursuant to the Marine Mammal Protection Act of 1972, the range of this stock

currently is being considered as within the boarders of the state of Washington.

POPULATION SIZE

The reintroduced population was not surveyed between 1970 and 1977. In 1977, the U.S. Fish and Wildlife

Service surveyed the coast and counted only 19 sea otters. The population was surveyed again in 1978. Between

1981 and 1989 the population was surveyed every other year. Since 1989, data on size and distribution of the

Washington sea otter population have been gathered annually using combined aerial and ground counts. 

Minimum Population Estimate

Based on the 1994 spring survey (actual count), the minimum population size is 360. Survey conditions

during 1994 were less than optimal and the Service believes that the population is probably slightly larger than this

count. 

Current Population Trend

Based on count totals from 1977 to the present, the Washington sea otter population is continuing to

increase. Since 1989 (when the current survey method was initiated) through 1994, the population has grown at an

average rate of 12 percent per year (R. Jameson, National Biological Service, pers. comm.).

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

 The maximum growth rate (rmax) for sea otter populations is about 20 percent. Except for California and

Washington sea otter populations, all increasing populations for which data are available have grown at about this

rate (Estes 1990). In Washington, the rmax appears to be 12 percent.

ANNUAL HUMAN-CAUSED MORTALITY

Incidental drowning of sea otters in gill and trammel entangling nets has been a significant source of

mortality for southern sea otters (Wendell et al. 1985). In 1992, a dead sea otter was recovered by a California

Department of Fish and Game warden in a crab pot located in 30 to 60 feet of water off Point Santa Cruz. The level

of take of southern sea otters in lobster and crab fisheries in California is unknown. Reports from Alaska further

substantiate the incidental take of sea otters in traps fisheries.
Appendix 5.

291

Sea otters are susceptible to drowning in gill nets in Washington's coastal gill net fisheries, but documented

incidental takes are rare. In Washington, one sea otter was killed in a tribal chinook salmon set-net in the vicinity of

the mouth of the Ozette River on the north Washington coast. However, as the sea otter population expands,

mortality in crab pot and tribal set-net fisheries may increase.

Other sources of human-caused mortality affecting the Washington population of sea otters are not

well documented. Documented sources of human-caused mortality for the southern sea otter include shooting,

boat strikes, capture and relocation efforts, oil spills and possibly elevated levels of polychlorinated biphenyls

(PCBs) and other toxic contaminants. In Washington , an uncertain number of sea otters may have been killed

in recent years by small oil spills. 

Native Americans of the Pacific northwest have Tribal Rights to wildlife resources. These resources are

claimed by the tribes to include sea otters. Currently there is no harvest of sea otters by the Native Americans;

however, there is an interest to develop such a program.

FISHERIES INFORMATION

At present, there has been only one recorded otter-fishery interaction in Washington. Set gill nets are used

by Native Americans to catch salmon along the north coast of Washington and the Strait of Juan de Fuca. This

fishery operates out of Neah Bay. As the Washington sea otter population moves north, or if the fishery moves

south, the probability of fisheries-related incidental take will increase. 

As sea otters expand their range north or south, they will encounter several sport and commercial shellfish

fisheries (urchins, razor clams, Dungeness crabs) along the coast. Evidence from California and Alaska suggests

that incidental take of sea otter in crab traps may occur.

STATUS OF STOCK

The Washington sea otter has no formal Federal designation. It is legally designated as endangered by the

State of Washington (Washington Administrative Code 232-12-014). The Washington sea otter population is

below its Optimum Sustainable Population level. 

POTENTIAL BIOLOGICAL REMOVAL

The Potential Biological Removal (PBR) for the Washington stock is 11 animals. PBR is the product

of three elements: the minimum population estimate (Nmin); half the maximum net productivity rate (0.5 Rmax);

and a recovery factor (Fr

). For the Washington sea otter stock, Nmin=360; Rmax=12 percent; and Fr=0.5.

REFERENCES

Estes, J. A. 1990. Growth and equilibrium in sea otter populations. J. Anim. Ecol. 59:358-401.

Jameson, R. J., K. W. Kenyon, A. M. Johnson, and H. M. Wight. 1982. History at status of translocated sea otter

populations in North America. Wildl. Soc. Bull. 10:100-107.

Riedman, M. L., and J. A. Estes. 1990. The sea otter (Enhydra lutris): behavior, ecology, and natural history. U.S.

Fish and Wildlife Service, Washington, D.C., Biological Report 90(14). 126 pp.

Wendell, F. E., R. A. Hardy, and J. A. Ames. 1985. Assessment of the accidental take of sea otters, Enhydra lutris,

in gill and trammel nets. Mar. Res. Branch, Calif. Dep. Fish Game. Unpubl. rep. 30 pp.

Wilson, D. E., M. A. Bogan, R. L. Brownell, Jr., A. M. Burdin, and M. K. Maminov. 1991. Geographic variation in

sea otters, Enhydra lutris. J. Mammal. 72(1):22-36.