NOAA Technical Memorandum NMFS 

JUNE 2011 

U.S. PACIFIC MARINE MAMMAL STOCK ASSESSMENTS: 2010 

James V. Carretta, Karin A. Forney, Erin Oleson, Karen Martien, Marcia M. Muto, 

Mark S. Lowry, Jay Barlow, Jason Baker, Brad Hanson, Deanna Lynch, Lilian 

Carswell, Robert L. Brownell Jr., Jooke Robbins, David K. Mattila, Katherine Ralls, 

and Marie C. Hill

with contributions from Patrick Opay, Brent Norberg, Jeff Laake, 

Dan Lawson, Joe Cordaro, Elizabeth Petras, Dale Sweetnam, and Chris Yates 

NOAA-TM-NMFS-SWFSC-476 

U. S. DEPARTMENT OF COMMERCE 

National Oceanic and Atmospheric Administration 

National Marine Fisheries Service 

Southwest Fisheries Science Center
NOAA Technical Memorandum NMFS 

This TM series is used for documentation and timely communication of preliminary results, interim reports, or special purpose information. The TMs 

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

U.S. PACIFIC MARINE MAMMAL STOCK ASSESSMENTS: 2010 

James V. Carretta1, Karin A. Forney2, Erin Oleson3, 

Karen Martien1, Marcia M. Muto4, Mark S. Lowry1, 

Jay Barlow1, Jason Baker3, , Brad Hanson5, 

Deanna Lynch6, Lilian Carswell7, Robert L. Brownell Jr.8, 

 Jooke Robbins9, David K. Mattila10, Katherine Ralls11, and Marie C. Hill12 

with contributions from 

 Patrick Opay, Brent Norberg, Jeff Laake, 

Dan Lawson, Joe Cordaro, Elizabeth Petras, 

Dale Sweetnam, and Chris Yates 

NOAA-TM-NMFS-SWFSC-476 

U. S. DEPARTMENT OF COMMERCE 

National Oceanic and Atmospheric Administration 

National Marine Fisheries Service 

Southwest Fisheries Science Center 

1 - NOAA Fisheries, Southwest Fisheries Science Center, 3333 N. Torrey Pines Ct., La Jolla, CA 92037 

2 - NOAA Fisheries, Southwest Fisheries Science Center, 110 Shaffer Road, Santa Cruz, CA 95060. 

3 - NOAA Fisheries, Pacific Islands Fisheries Science Center, 2570 Dole Street, Honolulu, HI 96822. 

4 - NOAA Fisheries, NOAA Fisheries, National Marine Mammal Laboratory, 7600 Sand Point Way, N.E., Seattle, WA 98115. 

5 - NOAA Fisheries, Northwest Fisheries Science Center, 2725 Montlake Boulevard, East Seattle WA 98112. 

6 - U.S. Fish and Wildlife Service, Western Washington Fish and Wildlife Office, 510 Desmond Drive SE, Suite 102, Lacey, WA 98503. 

7 - U.S. Fish and Wildlife Service, 2493 Portola Road, Suite B, Ventura, California, 9300 

8 - NOAA Fisheries, Southwest Fisheries Science Center, 1352 Lighthouse Ave., Pacific Grove, CA 93950. 

9 - Provincetown Center for Coastal Studies, 5 Holway Avenue, Provincetown, MA 02657. 

10 - NOAA Hawaiian Islands Humpback Whale National Marine Sanctuary, 6600 Kalaniana’ole Hwy, #301, Honolulu, HI 96825. 

11 - Center for Conservation and Evolutionary Genetics, National Zoological Park, Smithsonian Institution, PO Box 37012, MCR 5503, 

Washington DC 20013-7012. 

12 – Joint Institute for Marine and Atmospheric Research, University of Hawaii at Manoa, 1000 Pope Road, Marine Science Building 312, 

Honolulu, HI 96822. 
TABLE OF CONTENTS

Draft stock assessment reports and appendices revised in 2010 are highlighted; all others will be reprinted in the as 

they appear in the 2009 Pacific Region Stock Assessment Reports (Carretta et al. 2010). 

PINNIPEDS

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

HARBOR SEAL (Phoca vitulina richardsi): California Stock.....................................................................................9 

HARBOR SEAL (Phoca vitulina richardsi): Oregon & Washington Coast Stock....................................................15 

HARBOR SEAL (Phoca vitulina richardsi): Washington Inland Waters Stock .......................................................22 

NORTHERN ELEPHANT SEAL (Mirounga angustirostris): California Breeding Stock........................................28

GUADALUPE FUR SEAL (Arctocephalus townsendi) .............................................................................................33 

NORTHERN FUR SEAL (Callorhinus ursinus): San Miguel Island Stock ...............................................................37 

HAWAIIAN MONK SEAL (Monachus schauinslandi).............................................................................................42 

CETACEANS - U.S. WEST COAST

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

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

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

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

HARBOR PORPOISE (Phocoena phocoena vomerina): Northern Oregon/Washington Coast Stock ......................69 

HARBOR PORPOISE (Phocoena phocoena vomerina): Washington Inland Waters Stock .....................................74

DALL'S PORPOISE (Phocoenoides dalli dalli): California/Oregon/Washington Stock...........................................81 

PACIFIC WHITE-SIDED DOLPHIN (Lagenorhynchus obliquidens): 

 California/Oregon/Washington, Northern and Southern Stocks ...................................................................86 

RISSO'S DOLPHIN (Grampus griseus): California/Oregon/Washington Stock .......................................................92 

COMMON BOTTLENOSE DOLPHIN (Tursiops truncatus truncatus): California Coastal Stock ..........................96 

COMMON BOTTLENOSE DOLPHIN (Tursiops truncatus truncatus): 

California/Oregon/Washington Offshore Stock ........................................................................................................101 

STRIPED DOLPHIN (Stenella coeruleoalba): California/Oregon/Washington Stock............................................105 

SHORT-BEAKED COMMON DOLPHIN (Delphinus delphis delphis): California/Oregon/Washington Stock ...109 

LONG-BEAKED COMMON DOLPHIN (Delphinus capensis capensis): California Stock ..................................116 

NORTHERN RIGHT-WHALE DOLPHIN (Lissodelphis borealis): California/Oregon/Washington ....................121 

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

KILLER WHALE (Orcinus orca): Eastern North Pacific Southern Resident Stock ................................................132

SHORT-FINNED PILOT WHALE (Globicephala macrorhynchus): California/Oregon/Washington ..................138 

BAIRD'S BEAKED WHALE (Berardius bairdii): California/Oregon/Washington Stock .....................................143 

MESOPLODONT BEAKED WHALES (Mesoplodon spp.): California/Oregon/Washington Stocks ....................147 

CUVIER'S BEAKED WHALE (Ziphius cavirostris): California/Oregon/Washington Stock.................................151 

PYGMY SPERM WHALE (Kogia breviceps): California/Oregon/Washington Stock ...........................................155 

DWARF SPERM WHALE (Kogia sima): California/Oregon/Washington Stock....................................................159 

SPERM WHALE (Physeter macrocephalus): California/Oregon/Washington Stock .............................................163

HUMPBACK WHALE (Megaptera novaeangliae): California/Oregon/Washington Stock ....................................169 

BLUE WHALE (Balaenoptera musculus musculus): Eastern North Pacific Stock ..................................................177 

FIN WHALE (Balaenoptera physalus physalus): California/Oregon/Washington Stock........................................183

SEI WHALE (Balaenoptera borealis borealis): Eastern North Pacific Stock .........................................................188 

MINKE WHALE (Balaenoptera acutorostrata scammoni): California/Oregon/Washington Stock .......................193 
CETACEANS – HAWAII & WESTERN PACIFIC

ROUGH-TOOTHED DOLPHIN (Steno bredanensis): Hawaiian Stock ..................................................................198 

ROUGH-TOOTHED DOLPHIN (Steno bredanensis): American Samoa Stock (new)............................................201 

RISSO'S DOLPHIN (Grampus griseus): Hawaiian Stock ........................................................................................205 

COMMON BOTTLENOSE DOLPHIN (Tursiops truncatus truncatus): Hawaii Pelagic........................................209 

COMMON BOTTLENOSE DOLPHIN (Tursiops truncatus truncatus): Kauai and Niihau Stock (new)................209 

COMMON BOTTLENOSE DOLPHIN (Tursiops truncatus truncatus): Oahu Stock (new) ...................................209 

COMMON BOTTLENOSE DOLPHIN (Tursiops truncatus truncatus): 4 Islands Region Stock (new) .................209 

COMMON BOTTLENOSE DOLPHIN (Tursiops truncatus truncatus): Hawaii Island (new)................................209 

PANTROPICAL SPOTTED DOLPHIN (Stenella attenuata attenuata): Hawaiian Stock .......................................217 

SPINNER DOLPHIN (Stenella longirostris longirostris): Hawaii Pelagic Stock ....................................................222 

SPINNER DOLPHIN (Stenella longirostris longirostris): Hawaii (island) Stock (new)..........................................222 

SPINNER DOLPHIN (Stenella longirostris longirostris): Oahu / 4 Islands Stock (new) ........................................222 

SPINNER DOLPHIN (Stenella longirostris longirostris): Kauai / Niihau Stock (new)...........................................222 

SPINNER DOLPHIN (Stenella longirostris longirostris): Kure / Midway Stock (new)..........................................222 

SPINNER DOLPHIN (Stenella longirostris longirostris): Pearl and Hermes Reef Stock (new) .............................222 

SPINNER DOLPHIN (Stenella longirostris longirostris): American Samoa Stock (new).......................................226 

STRIPED DOLPHIN (Stenella coeruleoalba): Hawaiian Stock...............................................................................229 

FRASER’S DOLPHIN (Lagenodelphis hosei): Hawaiian Stock ..............................................................................233 

MELON-HEADED WHALE (Peponocephala electra): Hawaiian Stock ................................................................235 

PYGMY KILLER WHALE (Feresa attenuata): Hawaiian Stock ............................................................................238 

FALSE KILLER WHALE (Pseudorca crassidens): Pacific Islands Region Stocks (Hawaii Pelagic, 

 Hawaii Insular, and Palmyra Atoll).......................................241 

FALSE KILLER WHALE (Pseudorca crassidens): American Samoa Stock (new) ...............................................249 

KILLER WHALE (Orcinus orca): Hawaiian Stock .................................................................................................253 

SHORT-FINNED PILOT WHALE (Globicephala macrorhynchus): Hawaiian Stock ...........................................256 

BLAINVILLE’S BEAKED WHALE (Mesoplodon densirostris): Hawaiian Stock .................................................261 

CUVIER'S BEAKED WHALE (Ziphius cavirostris): Hawaiian Stock....................................................................265 

LONGMAN’S BEAKED WHALE (Indopacetus pacificus): Hawaiian Stock .........................................................268 

PYGMY SPERM WHALE (Kogia breviceps): Hawaiian Stock ..............................................................................271 

DWARF SPERM WHALE (Kogia sima): Hawaiian Stock ......................................................................................274 

SPERM WHALE (Physeter macrocephalus): Hawaiian Stock.................................................................................277 

BLUE WHALE (Balaenoptera musculus musculus): Central North Pacific Stock ..................................................281 

FIN WHALE (Balaenoptera physalus physalus): Hawaiian Stock...........................................................................285 

BRYDE'S WHALE (Balaenoptera edeni): Hawaiian Stock .....................................................................................288 

SEI WHALE (Balaenoptera borealis borealis): Hawaiian Stock .............................................................................291 

MINKE WHALE (Balaenoptera acutorostrata scammoni): Hawaiian Stock ..........................................................294 

HUMPBACK WHALE (Megaptera novaeangliae): American Samoa Stock ..........................................................297 

APPENDICES

APPENDIX 1: Description of U.S. Commercial Fisheries .......................................................................................301 

APPENDIX 2: Cetacean Survey Effort.....................................................................................................................330 

APPENDIX 3: Summary of 2010 U.S. Pacific Marine Mammal Stock Assessment Reports...................................333 

APPENDIX 4: Sea Otter stock assessments .............................................................................................................335 
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. The 2010 Pacific marine mammal stock assessments include 

revised stock assessments for 63 Pacific marine mammal stocks under NMFS jurisdiction, including 12 “strategic” 

stocks, 48 “non-strategic” stocks, and three stocks of unknown status (see summary table in Appendix 3). 

Information on the remaining 12 Pacific region stocks is reprinted without revision in the final 2010 reports and 

currently appears in the 2009 reports (Carretta et al. 2010). Twelve new stock assessments in the Pacific Islands 

region are included in the 2010 Pacific stock assessments for the first time, including six spinner dolphin stocks, 

four bottlenose dolphin stocks, one false killer whale stock, and one rough-toothed dolphin stock. New or revised 

abundance estimates are available for 41 stocks. Where available, information on subspecies designations has been 

included in these reports to reflect local taxonomic and conservation issues (Perrin 2009). Information updates for 

longline fisheries in the Pacific Islands region are also included in a fishery description appendix. Stock 

Assessments for Alaska region marine mammals are published by the National Marine Mammal Laboratory 

(NMML) in a separate report. USFWS sea otter stock assessments are included as Appendix 4 of this document. 

 Pacific region stock assessments include those studied by the Southwest Fisheries Science Center (SWFSC, 

La Jolla, California), the Pacific Islands Fisheries Science Center (PIFSC, Honolulu, Hawaii), the National Marine 

Mammal Laboratory (NMML, Seattle, Washington), and the Northwest Fisheries Science Center (NWFSC, Seattle, 

WA). 

 Draft versions of the 2010 stock assessment reports were reviewed by the Pacific Scientific Review Group 

at the November 2009 Pacific Scientific Review Group meeting and a 90-day public review process. The authors 

also wish to thank those who provided unpublished data, especially Robin Baird and Joseph Mobley, who provided 

valuable information on Hawaiian cetaceans. 

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

marine mammal stocks and fisheries becomes available. Background information and guidelines for preparing stock 

assessment reports are reviewed in Wade and Angliss (1997). The authors solicit any new information or comments 

which would improve future stock assessment reports. 

These Stock Assessment Reports summarize information from a wide range of original data 

sources and an extensive bibliography of all sources is given in each report. We strongly urge users of this 

document to refer to and cite original literature sources rather than citing this report or previous Stock 

Assessment Reports. If the original sources are not accessible, the citation should follow the format: 

[Original source], as cited in [this Stock Assessment Report citation]. 

Cover photograph: Short-beaked common dolphin (Delphinus delphis delphis): Southwest Fisheries Science Center 

References:

Carretta, J.V., K.A. Forney, M.S. Lowry, J. Barlow, J. Baker, D. Johnston, Brad Hanson, Robert L. Brownell Jr., 

Jooke Robbins, David. K. Mattila, Katherine Ralls, M.M. Muto, Deanna Lynch, and Lilian Carswell. 2010. 

U.S. Pacific Marine Mammal Stock Assessments: 2009. U.S. Department of Commerce, NOAA Technical 

Memorandum NMFS-SWFSC-453. 336p. 

Perrin, W.F. 2009. (ed.) World Cetacea Database. Available online at http://www.marinespecies.org/cetacea. 

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

workshop April 3-5, 1996, Seattle, Washington. NOAA Technical Memorandum NMFS-OPR-12. 

Available from Office of Protected Resources, National Marine Fisheries Service, Silver Spring, MD. 93p. 
Revised 10/30/2007 

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. 

Figure 1. Geographic range of California 

sea lions showing stock boundaries and 

locations of major rookeries. The U.S. stock 

ranges north into Canadian waters. 

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 2005 (48,277) was adjusted for an estimated 15% pre-census mortality (Boveng 1988; Lowry et al. 

1992), giving an estimated 55,519 live births in the population. The fraction of newborn pups in the population 

(23.3%) 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 (5.6% yr-1, see 

below). Multiplying the number of pups born by the inverse of this fraction (4.28) results in a population estimate 

of 238,000. 

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 2005 breeding season. The minimum population size of the U.S. 

stock is 141,842 (NMFS unpubl. data). It includes all California sea lions counted during the July 2005 census at 

the Channel Islands in southern California and at haulout sites located between Point Conception and the 

Oregon/California border. An additional unknown number of California sea lions are at sea or hauled out at 

locations that were not censused.

1
Current Population Trend

 Records of pup counts from 1975 to 2005 (Figure 2) were compiled from the literature, NMFS reports, 

unpublished NMFS data, and Lowry 1999 (the literature up to 2000 is listed in Lowry and Maravilla 2005). Pup 

counts from 1975 through 2005 were examined for four rookeries in southern California and for haulouts in central 

and northern California. The number of pups at rookeries not counted were estimated using multiple regressions 

derived from counts of two neighboring rookeries using data from 1975-2000 (Lowry and Maravilla 2005) : (1) 

1980 at Santa Barbara Is.; (2) 1978-1980 at San Clemente Is.; and (3) 1978 and 1979 at San Nicolas Is. The mean 

was used when more than one count was available for a given rookery. Four major declines in the number of pups 

counted occurred during El Niño events in 1983-1984, 1992-93, 1998, and 2003 (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 5.6% 

between 1975 and 2005 when pup counts for El Niño years (1983, 1984, 1992, 1993, 1998, and 2003) were removed 

from the 1975-2005 time series. 

CALIFORNIA SEA LION PUPS

United States 

0

10,000

20,000

30,000

40,000

50,000

60,000

1970 1975 1980 1985 1990 1995 2000 2005 2010

YEAR

COUNT

Counts

Counts and estimates

 The 1975-2005 time series of pup counts shows the effect of four El Niño events on the sea lion population. 

Pup production decreased by 35 percent in 1983, 27 percent in 1992, 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 1983-1984 El 

Niño affected adult female survivorship (DeLong 

et al 1991) which prevented the rebound in pup 

production because there were fewer adult females 

available in the population to produce pups (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 2002 and 2003 decline can 

be attributed to (1) reduced number of reproductive 

adult females being incorporated into the 

population as a result of the 1992-93 and 1997-98 

El Niños, (2) domoic acid poisoning (Scholin et al. 

2000, Lefebvre et al. 2000), (3) lower survivorship 

of pups due to hookworm infestations (Lyons et al. 

2001), and (4) the 2003 El Niño 

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

(1975-2005).

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

 A generalized logistic growth model indicated that the maximum population growth rate (Rmax) was 6.52 

percent when pup counts from El Niño years (1983, 1984, 1992, 1993, 1998, and 2003) were removed (Figure 3). 

POTENTIAL BIOLOGICAL REMOVAL

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

(141,842) 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 8,511 sea lions 

per year. 

ANNUAL HUMAN-CAUSED MORTALITY

Historical Depletion 

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. 

2
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; Carretta et al. 2005a; 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, 2000-2004 (Carretta and 

Chivers 2004, Carretta et al. 2005a, 2005b). 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 2000-

2004 observer data (~20% observer coverage). In past years, the largest source of sea lion mortality has been in the 

California halibut and angel shark set gillnet fishery, which currently operates south of Point Arguello, California 

and has not been observed throughout its range since 1994. Limited observer coverage occurred in Monterey Bay in 

2000 and 2001, but represented less than 5% of the total fishing effort. Given the lack of recent observer data, it is 

not possible to estimate sea lion mortality for this fishery. Evidence from fisher self-reports (Table 1) indicates that 

mortality of sea lions still occurs in this fishery, but it is not possible to extrapolate these self reports to overall 

mortality because these self reports have been shown to be grossly underreported. Logbook and observer data, and 

fisher reports, indicate that mortality of California sea lions occurs, or has occurred in the past 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, (8) Washington, Oregon and 

California commercial passenger fishing vessel fishery (NMFS 1995, M. Perez pers. comm, and P. Olesiuk pers. 

comm.) (9) the California small mesh drift gillnet fishery, and (10) the California purse seine fishery for anchovy, 

mackerel, and tuna. 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.). Stranding data from California, Oregon, and Washington 

during 2000-2004 shows that an additional 66 sea lions died from unknown entangling net fisheries (Table 1). 

Animals are typically found on the beach or sometimes at sea with portions of gillnet wrapped around the carcass. 

This represents a minimum number of animals killed, as many entanglements are likely unreported or undetected. 

 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 

1975 1980 1985 1990 1995 2000 2005

0 10000 20000 30000 40000 50000

Year

Abundance

1997

K = 4.6824e+04

MNPL = 3.9801e+04

Figure 3. Generalized logistic growth of California sea lion pup 

counts obtained during 1975-2005 (excluding El Niño years) 

indicating when Maximun Net Productivity Level (MNPL) was 

reached and that the population has reached carrying capacity (K). 

3
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 mortality and serious injury of California sea lions in commercial 

fisheries that might take this species (Carretta 2001; 2002, Carretta et al. 2005a, 2005b, Perez 2003, Perez 2003; 

Appendix 1). Mean annual takes are based on 2000-2004 data unless noted otherwise. In past years, the set gillnet 

fishery for halibut and angel shark has been responsible for the majority of fishery-related mortality. However, this 

fishery has not been observed recently and thus, current estimates of mortality are unknown. Because current 

mortality estimates are lacking for this fishery, overall mean annual takes reported in Table 1 are negatively biased 

by an unknown amount. 

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 large 

mesh drift gillnet fishery 

2000 

2001 

2002 

2003 

2004 

observer 

22.9% 

20.4% 

22.1% 

20.2% 

20.6% 

13 

2 

18 

4 

6 

50 (0.43) 

10 (0.67) 

81 (0.25) 

20 (0.50) 

29 (0.44) 

38 (0.18) 

CA angel shark/halibut 

and other species large 

mesh (>3.5 in) set gillnet 

fishery 

2001 

2002 

2003 

2004 

2005 

2000-2004 

No fisherywide observer 

program since 

1994 

MMAP self 

reports 

0% 

0% 

0% 

0% 

0% 

- 

n/a 

n/a 

n/a 

n/a 

n/a 

57 

n/a 

n/a 

n/a 

n/a 

n/a 

n/a 

n/a 

≥11.4 

CA small-mesh drift 

gillnet fishery for white 

seabass, yellowtail, 

barracuda, and tuna 

20031

20041 observer 11%1 11%1

2 

1 

18 (0.71) 

9 (0.94) 13.5 (0.57) 

CA anchovy, mackerel, 

and tuna purse seine 

fishery 

20042 observer n/a 1 ≥ 1 (n/a) ≥ 1 (n/a) 

WA, OR, CA domestic 

groundfish trawl fishery 

(At-sea processing Pacific 

whiting fishery only)

2000 

2001 

2002 

2003 

2004 

observer 

80.6% 

96.2% 

100% 

100% 

100% 

0 

0 

1 

2 

2 

0 

0 

1 

2 

2 

1.2 (0) 

WA, OR, CA domestic 

groundfish trawl fishery 

(bottom trawl) 

2000 

2001 

2002 

2003 

2004 

observer n/a 

n/a 

8 

6 

24 

6 

n/a ≥11 

WA, OR salmon net pen 

fishery

2000 

2001 

2002 

2003 

2004

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

Canada: BC salmon pen 

fishery

2000 

2001 

2002 

2003 

2004 

MMAP n/a 

225 

88 

19 

14 

6 

225 

88 

19 

14 

6 

≥70 

4
Fishery Name Year(s) Data Type

Percent Observer 

Coverage

Observed 

Mortality

Estimated 

Mortality (CV in 

parentheses)

Mean 

Annual Takes 

(CV in parentheses)

Unknown entangling net 

fishery 2000-2004 stranding n/a 66 n/a 13 (n/a) 

Minimum total annual takes ≥159 (n/a) 

1 A pilot observer program existed for two years in the small mesh drift gillnet fishery, where observer coverage ranged between 11-17%, based 

on logbook effort data and 22 observed sets in 2003 and 2004, respectively. 

Other Mortality 

 California sea lions 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 hauled out, with the majority (52%) entangled in monofilament gillnet. Data from a marine 

mammal rehabilitation center showed that 87% of 87 rescued California sea lions were entangled in 4-4.5 inch 

square-mesh monofilament gillnet (Howorth 1994). Of California sea lions entangled in gillnets, 0.8% in set gillnets 

and 5.4% in drift gillnets were observed to be released alive from the net by fishers during 1991-1995 (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 are regularly observed with gunshot wounds in 

California (Lowry and Folk 1987, Deiter 1991, Barocchi et al. 1993, Goldstein et al. 1999, NMFS unpublished 

stranding data). A summary of records for 2000-2004 from the California Marine Mammal Stranding Network 

(CMMSN) and the Oregon and Washington stranding databases shows the following non-fishery related mortality: 

boat collisions (17 deaths), entrainment in power plants (106 deaths), shootings (237 deaths), marine debris (three 

deaths), and unknown sources (seven deaths). Stranding records are a gross under-estimate of injury and mortality 

because many animals and carcasses are never recorded. 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 from 2000-2004 was 370. The average annual non-fishery related mortality of sea 

lions from 2000-2004 is a minimum of the 370 deaths listed above, divided by 5 years = 74 sea lions annually. 

 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 mortality in 1998 along the central California coast has recently been linked to the algal-produced 

neurotoxin domoic acid (Scholin et al. 2000). Future mortality may be expected to occur, due to the sporadic 

occurrence of such harmful algal blooms. 

STATUS OF STOCK

 A generalized logistic growth model of pup counts obtained during 1975-2005 (excluding El Niño years) 

indicated that the population reached its Maximum Net Productivity Level (MNPL) of 39,800 pups in 1997 and has 

reached carrying capacity (K) at 46,800 pups per year (z = 19.09, Rmax = 0.0652, n0 = 10,100, SE = 1,055) (Figure 

3). This determination should be taken with caution until more years of data have been collected to verify whether 

the flattening of the generalized logistic curve persists in future years. California sea lions in the U.S. are not listed 

as "endangered" or "threatened" under the Endangered Species Act or as "depleted" under the MMPA. Even 

though current total human-caused mortality is unknown (due a lack of observer coverage in the California set 

gillnet fishery that historically has been the largest source of human-caused mortality), California sea lions are not 

considered a "strategic" stock under the MMPA because (based on historical takes in the set gillnet fishery and 

current levels of fishing effort) total human-caused mortality is still likely to be less than the PBR (8,511). The total 

fishery mortality and serious injury rate for this stock likely remains above 10% of the calculated PBR and, 

therefore, cannot be considered to be insignificant and approaching a zero mortality and serious injury rate. 

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

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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. 

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

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NOAA/NMFS SWR October 1988. 10 pp. 

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

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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. 

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

SC/49/SM02 presented to the International Whaling Commission, September 1997 (unpublished). 13 pp. 

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

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

Lefebvre, K. C. Powell, G. Doucette, J. Silver, P. Miller, P. Hughes, M. Silver, and R. Tjeerdemma. 2000. Domoic 

acid-producing diatoms: probable cause of neuroexcitotoxicity in California sea lions. Marine 

Environmental Research 50:485-488. 

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. 

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Mexico and the United States. In D. K. Garcelon and C. A. Schwemm (editors), Proceedings of the Sixth 

California Islands Symposium, Ventura, California, December 1-3, 2003. p. 485-497. National Park 

Service Technical Publication CHIS-05-01, Institute for Wildlife Studies, Arcata, California. 

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adult Uncinaria spp. in northern fur seal (Callorhinus ursinus) and California sea lion (Zalophus 

californianus) pups on San Miguel Island, California, with notes on the biology of hookworms. Veterinary 

Parasitology 97:309-318. 

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. 

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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. 

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

33 pp. 

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

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

Memo. NMFS-AFSC-138. 145 pp. 

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. 

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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 

7
Symposium: Recent Advances in Research in the California Islands. Santa Barbara, CA, Santa Barbara 

Museum of Natural History. pp 501_516. 

8
Revised 11/01/2005 

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 400-600 harbor seal haulout sites are 

widely distributed along the mainland and on offshore 

islands, including intertidal sandbars, rocky shores and 

beaches (Hanan 1996; Lowry et al. 2005). 

 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; Westlake and O’CorryCrowe 2002; O’Corry-Crowe et al. 2003), mean 

pupping dates (Temte 1986), pollutant loads 

(Calambokidis et al. 1985), pelage coloration (Kelly 

1981) and movement patterns (Jeffries 1985; Brown 

1988). LaMont (1996) identified four discrete 

subpopulation differences in mtDNA between harbor 

seals from Washington (two locations), Oregon, and 

California. Another mtDNA study (Burg 1996) 

supported the existence of three separate groups of 

harbor seals between Vancouver Island and 

southeastern Alaska. Although we know that 

geographic structure exists along an almost continuous 

distribution of harbor seals from California to Alaska, stock boundaries are difficult to draw because any 

rigid line is (to a greater or lesser extent) arbitrary from a biological perspective. Nonetheless, failure to 

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

Previous assessments of the status of harbor seals have recognized three stocks along the west coast of the 

continental U.S.: 1) California, 2) Oregon and Washington outer coast waters, and 3) inland waters of 

Washington. Although the need for stock boundaries for management is real and is supported by biological 

information, the exact placement of a boundary between California and Oregon was largely a 

political/jurisdictional convenience. An unknown number of harbor seals also occur along the west coast 

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

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

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

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

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

separate stock in this report (Fig. 1). Other Marine Mammal Protection Act (MMPA) stock assessment 

reports cover the five other stocks that are recognized along the U.S. west coast: Oregon/Washington outer 

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

W132 W129 W126 W123 W120 W117

N30

N34

N38

N42

N46

WASHINGTON

OREGON

CALIFORNIA

OR/WA

COASTAL

STOCK

 CA

STOCK

PACIFIC

 OCEAN

Figure 1. Stock boundaries for the California 

and Oregon/Washington coastal stocks of 

harbor seals. Dashed line represents the U.S. 

EEZ.

POPULATION SIZE

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

from the haulout sites. A complete pup count (as is done for other pinnipeds in California) is also not 

possible because harbor seals are precocious, with pups entering the water almost immediately after birth. 

9
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 (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 

hrs which better corresponds to the timing of his surveys. Based on the most recent harbor seal counts 

(26,333 in May-July 2004; Lowry et al. 2005) and Hanan’s revised correction factor, the harbor seal 

population in California is estimated to number 34,233. 

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 31,600. 

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). 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 is approaching 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 humancaused mortality rate (fishery mortality in year i divided by population size in year i). Between 1983 and 

Figure 2. Harbor seal haulout counts in California during 

Figure 2. Harbor seal haulout counts in California during 

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

NMFS unpubl. data from 2002 and 2004 surveys).

0

5,000

10,000

15,000

20,000

25,000

30,000

Number Seals Counted

1955 1965 1975 1985 1995

TOTAL

Mainland

Channel Islands

2005

Year

10
1994, the net productivity rate for the 

California stock averaged 9.2% (Fig. 3). 

A regression shows a decrease in net 

production rates, but the decline is not 

statistically significant. Maximum net 

productivity rates cannot be estimated 

because measurements were not made 

when the stock size was very small. 

-0.2

-0.1

0

0.1

0.2

0.3

0.4

Net Production Rate

1982 1984 1986 1988 1990 1992 1994

Year

Harbor Seal Net Production in CA

POTENTIAL BIOLOGICAL 

REMOVAL

 The potential biological removal 

(PBR) level for this stock is calculated as 

the minimum population size (31,600) 

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 1,896. 

Figure 3. Net production rates and regression line 

estimated from haulout counts and fishery mortality. HUMAN-CAUSED MORTALITY 

AND SERIOUS INJURY

Historical Takes 

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

along the west coast of North America were greatly reduced by commercial hunting (Bonnot 1928, 1951; 

Bartholomew and Boolootian 1960). Only a few hundred individuals survived in a few isolated areas along 

the California coast (Bonnot 1928). In the last half of this century, the population has increased 

dramatically. 

Fishery Information

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

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

harbor seal mortality in California fisheries occurs in the set gillnet fishery, because that fishery has 

undergone dramatic reductions and redistributions of effort, and because the entire fishery has not been 

observed since 1994, average annual mortality cannot be accurately estimated for the recent years (1999-

2003). Rough estimates for 1999-2003 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 from 

1999-2003 include harbor seal deaths and injuries caused by hook-and-line fisheries (four deaths, two 

injuries) and gillnet fisheries (two deaths, two 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 mortality and 

injuries in 1999-2003: (1) boat collision (eight deaths, two injuries), (2) entrainment in power plants (26 

deaths), (3) shootings (15 deaths), and (4) all-terrain vehicle (ATV) collision (one injury). 

11
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 (Cameron and Forney 2000; Carretta 2001, 

2002; Carretta et al. 2003; Carretta and Chivers 2004). n/a indicates that data are not available. Mean 

annual takes are based on 1999-2003 data unless noted otherwise. 

Observed Estimated Mean 

Annual Takes Percent 

Observer 

Coverage

Fishery Name Year(s) Data Type Mortality Mortality (CV in 

parentheses) (CV in parentheses)

CA/OR thresher 

shark/swordfish drift 

gillnet fishery

1998-

2003

observer 

data

20-23% 0 0,0,0,0,0 01

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 (1999-2003) 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 2001-2003.

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 (388 

per year) is less than the calculated PBR for this stock (1,896), and thus they would not be considered a 

"strategic" stock under the MMPA. The average rate of incidental fishery mortality for this stock is likely 

to be greater than 10% of the calculated PBR; therefore, fishery mortality cannot be considered 

insignificant and approaching zero mortality and serious injury rate. The population appears to be 

stabilizing at what may be their carrying capacity and the fishery mortality is declining. There are no 

CA angel shark/halibut 

and other species large 

mesh (>3.5") set gillnet 

fishery

1999 

2000 

2001 

2002 

2003

observer 

data 

extrapolated 

estimate

4.0% 3

1.7%3

0.0%3 

0.0%3 

0.0%3

57 

24 

- 

- 

-

662 (0.10)1

415 (0.08)1

329 (0.09)1 

337 (0.11)1 

186 (0.09)1

386 (0.05)1

CA, OR, and WA salmon 

troll fishery

1990-92 logbook data - Avg. Annual 

take = 7.33 n/a

1990-92 logbook data - Avg. Annual 

take = 0

CA herring purse seine 

fishery 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

1999 

2000 

2001 

2002 

2003 

1999-

2003

observer data

unmonito ed r

hauls

68.6% 

80.6% 

96.2% 

100% 

100% 

0 

2 

0 

0 

0 

0 

1

3 (0.21) 

0 

0 

0 

1

0.6 (0.21) 

0.2 (n/a) 

1997-

2001 

Warden obs 

2-3 

trips/month

Avg. Annual 0 n/a CA squid purse seine 

fishery logbook data take = 0

1999- 6 1.5

2003

(unknown net and hook 

fisheries) stranding data

Total annual takes 388 (0.05)

12
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). 

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.] 

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

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

International Whaling Commission (unpublished). 21pp. 

Carretta, J. V. and S. J. Chivers. 2004. Preliminary estimates of marine mammal mortality and biological 

sampling of cetaceans in California gillnet fisheries for 2003. Paper SC/56/SM1 presented to the 

International Whaling Commission (unpublished). 20pp. 

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 

13
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 mortality 

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 mortality in 

California set net fisheries for 1983, 1984, and 1985. Final Report. Cooperative agreement No. 

NA-86-ABH-00018. NOAA/NMFS SWR October 1988. 10 pages. 

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

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

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

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

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

Oregon 1993. Annual report to the MMPA Assessment Program, Office of Protected Resources, 

NMFS, NOAA, 1335 East-West Highway, Silver Spring, MD 20910. 

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

adjacent coastal waters of northern Oregon and Washington. In: Marine Mammals and Adjacent 

Waters, 1980-1982. Processed Report 85-04, National Marine Fisheries Service, Northwest and 

Alaska Fisheries Center, Seattle, Washington. 

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

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

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

Lowry, M.S., J.V. Carretta, and K.A. Forney. 2005. Pacific harbor seal, Phoca vitulina richardsi, census in 

California during May - July 2004. Administrative Report LJ-05-06, available from Southwest 

Fisheries Science Center, 8604 La Jolla Shores Drive, La Jolla, CA 92037. 38 p. 

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. 

O’Corry-Crowe, G. M., K. K. Martien, and B. L. Taylor. 2003. The analysis of population genetic structure 

in Alaskan harbor seals, Phoca vitulina, as a framework for the identification of management 

stocks. Administrative Report LJ-03-08. Southwest Fisheries Sceeince Center, 8604 La Jolla 

Shores Drive, La Jolla, CA, 92037. 

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. 

Westlake, R. L. and G. M. O’Corry-Crowe. 2002. Macrogeographic structure and patterns of genetic 

diversity in harbor seals (Phoca vitulina) from Alaska to Japan. Journal of Mammalogy 83(4): 

1111-1126. 

14
Revised 01/15/2011

HARBOR SEAL (Phoca vitulina richardsi): 

Oregon/Washington Coast Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

 Harbor seals inhabit coastal and estuarine waters off 

Baja California, north along the western coasts of the 

continental U.S., British Columbia, and Southeast Alaska, west 

through the Gulf of Alaska and Aleutian Islands, and in the 

Bering Sea north to Cape Newenham and the Pribilof Islands. 

They haul out on rocks, reefs, beaches, and drifting glacial ice 

and feed in marine, estuarine, and occasionally fresh waters. 

Harbor seals generally are non-migratory, with local movements 

associated with such factors as tides, weather, season, food 

availability, and reproduction (Scheffer and Slipp 1944; Fisher 

1952; Bigg 1969, 1981). Harbor seals do not make extensive 

pelagic migrations, though some long distance movement of 

tagged animals in Alaska (174 km) and along the U.S. west 

coast (up to 550 km) have been recorded (Pitcher and 

McAllister 1981, Brown and Mate 1983, Herder 1986). Harbor 

seals have also displayed strong fidelity for haulout sites 

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

genetic evidence suggests that the population of 

OPULATION SIZE

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

arine M

ites and three Oregon 

d Was

 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 (Fig. 1). Genetic analyses provide additional support 

for this stock structure (Huber et al. 1994, 2010; 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 Washington inland waters 

possess unique haplotypes not found in seals from the coasts of 

Washington, Oregon, and California (Lamont et al. 1996). Recent 

harbor seals in Washington inland waters has more structure than is currently recognized (Huber et al. 2010). This 

report considers only the Oregon/Washington Coast stock. Stock assessment reports for Washington Inland Waters 

and California harbor seals also appear in this volume. Harbor seal stocks that occur in the inland and coastal waters 

of Alaska are discussed separately in the Alaska Stock Assessment Reports. Harbor seals occurring in British 

Columbia are not included in any of the U.S. Marine Mammal Protection Act (MMPA) stock assessment reports. 

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. 

P

Aerial surveys of

M ammal 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, unpublished 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 s

an hington 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 

15
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, 

unpublished data). However, because the most recent abundance estimate is >8 years old, there is no current 

estimate of abundance available for this stock. 

Minimum Population Estimate

on abundance is available to obtain a minimum population estimate for the 

regon/

urrent Population Trend

harbor seal abundance in Oregon and Washington are unknown. The population 

parent

URRENT AND MAXIMUM NET 

gton Coast 

5% CI = 12.9-26.8%) (Jeffries et al. 2003). When a logistic model was 

 No current information 

O Washington Coast stock of harbor seals. 

C

 Historical levels of 

ap ly 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 statehired 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 

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, unpublished data). Based 

on the analyses of Jeffries et al. (2003) 

and Brown et al. (2005), both the 

Washington and Oregon portions of this 

stock have reached carrying capacity and 

are no longer increasing (Fig. 2). 

C

PRODUCTIVITY RATES

 The Oregon/Washin

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% (9

fit to the Oregon portion of the 1977-2003 abundance data, estimates of RMAX ranged from 6.4% (95% CI = 4.6-

27%) for the south coast of Oregon to 10.1% (95% CI = 8.6-20%) for the north coast (Brown et al. 2005). Until a 

combined analysis for the entire stock is completed, the pinniped default maximum theoretical net productivity rate 

(RMAX) of 12% will be used for this harbor seal stock (Wade and Angliss 1997). 

Washington Coast Harbor Seals

0

2000

4000

6000

8000

10000

12000

14000

1970 1975 1980 1985 1990 1995 2000 2005

Year

Count

Oregon Harbor Seals

0

1000

2000

3000

4000

5000

6000

1970 1975 1980 1985 1990 1995 2000 2005

Year

Count

Figure 2. Generalized logistic growth curves of Washington 

Coast (Jeffries et al. 2003) and Oregon (Brown et al. 2005) harbor 

seals. 

16
POTENTIAL BIOLOGICAL REMOVAL

 Because there is no current estimate of minimum abundance, a potential biological removal (PBR) cannot 

be calculated for this stock. 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Fisheries Information

 Fishing effort in the northern Washington marine gillnet tribal fishery is conducted within the range of both 

stocks of harbor seals (Oregon/Washington Coast and Washington Inland Waters) occurring in Washington State 

waters. 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). For the 

purposes of this stock assessment report, the animals taken in waters south and west of Cape Flattery, WA, are 

assumed to have belonged to the Oregon/Washington Coast stock, and Table 1 includes data only from that portion 

of the fishery. Fishing effort in the coastal marine set gillnet tribal fishery has declined since 2004. There was one 

fisher self-report of a harbor seal death in a set gillnet in coastal waters in 2004 (Makah Fisheries Management, 

unpublished data). A test set gillnet fishery, with 100% observer coverage, was conducted in coastal waters in 2004 

and 2008. This test fishery required the use of nets equipped with acoustic alarms, and observers reported five 

harbor seal deaths in 2004 and one harbor seal death in 2008 (Makah Fisheries Management, unpublished data). 

The mean estimated mortality for the marine set gillnet tribal fishery in 2004-2008 is 1.2 (CV=0) harbor seals per 

year from observer data plus 0.2 seals per year from fisher self-reports. 

 The Washington/Oregon/California (WA/OR/CA) groundfish trawl fishery (Pacific hake at-sea processing 

component) was monitored for incidental take during 2002-2006 (NWFSC 2008), and harbor seal deaths were 

observed in 2005 and 2006. The mean estimated mortality for this fishery in 2002-2006 is 0.4 (CV=0.30) harbor 

seals per year. 

Table 1. Summary of available information on the incidental mortality and serious 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. Mean annual takes are based on 2004-2008 

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 test fishery in 

coastal waters) 

Northern WA marine set 

gillnet (tribal fishery in coastal 

waters)

2004 

2005 

2006 

2007 

2008 

2004

observer data 

fisher selfreports

100% 

no fishery 

no fishery 

no fishery 

100% 

5 

0 

0 

0 

1 

1

5 (0) 

0 (0) 

0 (0) 

0 (0) 

1 (0) 

n/a 

1.2 (0) 

>0.2 (n/a) 

WA/OR/CA groundfish trawl 

(Pacific hake at-sea processing 

component) 

2002 

2003 

2004 

2005 

2006

observer data 

100%1

100%1

100%1

100%1 

100%1 

0 

0 

0 

1 

1 

0 (0) 

0 (0) 

0 (0) 

1 (0.42) 

1 (0.44) 

0.4 (0.30) 

WA Grays Harbor salmon 

drift gillnet2 1991-1993 observer data 4-5% 0, 1, 1 0, 10, 10 see text2

WA Willapa Bay drift gillnet2 1991-1993 observer data 1-3% 0, 0, 0 0, 0, 0 see text2

WA Willapa Bay drift gillnet2 1990-1993 fisher selfreports n/a 0, 0, 6, 8 n/a see text2

Unknown West Coast fisheries 2004-2008 stranding data n/a 0, 0, 0, 0, 0 n/a 0

Minimum total annual takes >1.8 (0.08)

1

Percent observer coverage equals percent of vessels with observers. 

2

This fishery has not been observed since 1993 (see text); these data are not included in the calculation of recent minimum total annual takes. 

17
 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 

mortality, incidental to the fishery, was observed only in the winter season and was 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. Due to high steelhead bycatch in the 2002 fishery, harvest managers used 

in-season test fishing during the 2003 and 2004 fishing seasons to determine the optimum timing and gear 

requirements for each subsequent full-fleet commercial fishing period. Both large-mesh (8-9.75”) and small-mesh 

tangle net (<4.25”) fishing periods were adopted in each year, although the 2003 season was severely curtailed to 

limit the catch of spring chinook stocks listed under the Endangered Species Act (ESA). With the focus on greater 

selectivity in winter/spring commercial salmon fisheries, levels of observer coverage were much higher in 2002-

2004 than in previous years. To meet management needs, this increased level of observer coverage in test fisheries 

and full-fleet commercial fisheries is expected to continue into the foreseeable future (J. North and G. Whisler, pers. 

comm.). Data on marine mammal interactions (predation, entanglement) recorded by observers during the permit 

and demonstration commercial fisheries in 2001-2002 and the full-fleet commercial fisheries in 2003-2004 have not 

yet been summarized; however, no marine mammal deaths or serious injuries were reported to NMFS by vessel 

operators. 

 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 mortality was recorded in 1991. In 1992, observers recorded one harbor seal death incidental to the fishery, 

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

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

(4.2% and 4.4%, respectively) suggests that 10 is also a reasonable estimate of the total kill in 1993. Thus, the mean 

estimated mortality for this fishery in 1991-1993 is 6.7 (CV=0.50) harbor seals per year. 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. 

 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 mortality was reported by observers. However, 

because mortality was self-reported by fishers in 1992 and 1993, the low level of observer coverage failed to 

document harbor seal mortality that had apparently occurred. Due to the low level of observer coverage for this 

fishery, the self-reported fishery mortality has been included in Table 1 and represents 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). 

 Combining recent estimates from the northern Washington marine set tribal gillnet (1.2 from observer data 

+ 0.2 from fisher self-reports) and WA/OR/CA groundfish trawl (0.4 from observer data) fisheries results in an 

estimated mean mortality rate of 1.8 harbor seals per year from these fisheries. 

 The Marine Mammal Authorization Program (MMAP) fisher self-reports, required of commercial vessel 

operators by the MMPA, are an additional source of information on the number of harbor seals killed or seriously 

injured incidental to commercial fishery operations. Between 2002 and 2006, there were two fisher self-reports of 

harbor seal deaths in the WA/OR/CA groundfish trawl (Pacific hake at-sea processing) fishery. Since this is an 

observed fishery, these deaths are not included in Table 1. Although these reports are considered incomplete (see 

details in Appendix 1), they represent a minimum mortality. 

 Strandings of harbor seals entangled in fishing gear or with serious injuries caused by interactions with gear 

are a final source of fishery-related mortality information. According to Northwest Marine Mammal Stranding 

Network records, maintained by the NMFS Northwest Region (NMFS, Northwest Regional Office, unpublished 

data), there were no fishery-related strandings of harbor seals from this stock reported in 2004-2008, resulting in an 

18
average annual mortality of zero harbor seals. 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 (NMFS, Northwest Regional Office, unpublished data), a total of 10 human-caused harbor seal deaths or 

serious injuries were reported from non-fisheries sources in 2004-2008. Seven animals were shot, two animals were 

struck by boats, and one animal was entangled in line, resulting in an estimated mortality of 2.0 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

 Tribal subsistence takes of this stock may occur, but no data on recent takes are available. 

STATUS OF STOCK

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

“endangered” under the ESA. Based on currently available data, the level of human-caused mortality and serious 

injury is 3.8 (1.8 + 2.0) harbor seals per year. A PBR cannot be calculated for this stock because there is no current 

abundance estimate. The previous estimate of PBR was 1,343 (Carretta et al. 2009). Human-caused mortality 

relative to PBR is unknown, but it is considered to be small relative to the stock size. 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 (based on recent observer data (1.6) and self-reported fisheries information 

(0.2) or stranding data (0) where observer data were not available or failed to detect harbor seal mortality) is 1.8. 

Since a PBR cannot be calculated for this stock, fishery mortality relative to PBR is unknown. The stock is within 

its Optimum Sustainable Population (OSP) level (Jeffries et al. 2003, Brown et al. 2005). 

REFERENCES

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

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

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

New York. 359 pp. 

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

06. 43 pp. Available from Southwest Fisheries Science Center, 3333 North Torrey Pines Road, La Jolla, 

CA 92037. 

Brown, R. F. 1988. Assessment of pinniped populations in Oregon: April 1984 to April 1985. NWAFC Processed 

Report 88-05. 44 pp. Available at National Marine Mammal Laboratory, 7600 Sand Point Way NE, 

Seattle, WA 98115. 

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

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

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

River fall and winter salmon gillnet fisheries, 1991-1992. Unpublished Report. Columbia River Area 

Gillnet Fishery Observer Program. 13 pp. Available at Oregon Dept. Fish and Wildlife, 2040 SE Marine 

Science Dr., Newport, OR 97365. 

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

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

Brown, R. F., B. E. Wright, S. D. Riemer, and J. Laake. 2005. Trends in abundance and current status of harbor 

seals in Oregon: 1977-2003. Mar. Mammal Sci. 21(4):657-670. 

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

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

Carretta, J. V., K. A. Forney, M. S. Lowry, J. Barlow, J. Baker, D. Johnston, B. Hanson, M. M. Muto, D. Lynch, and 

L. Carswell. 2009. U.S. Pacific marine mammal stock assessments: 2008. U.S. Dep. Commer., NOAA 

Tech. Memo. NMFS-SWFSC-434. 336 pp. 

19
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. 

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. Unpublished Report. Pacific States Marine Fisheries 

Commission, Astoria, OR. 10 pp. Available at PSMFC, 205 SE Spokane Street, Suite 100, Portland, OR 

97202. 

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

salmon gillnet fishery. Unpublished Report. Pacific States Marine Fisheries Commission, Astoria, OR. 10 

pp. Available at PSMFC, 205 SE Spokane Street, Suite 100, Portland, OR 97202. 

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

at the Klamath River, California. MA Thesis, Humboldt State University, Arcata, 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. 

Huber, H. R., S. J. Jeffries, D. M. Lambourn, and B. R. Dickerson. 2010. Population substructure of harbor seals 

(Phoca vitulina richardsi) in Washington State using mtDNA. Can. J. Zool. 88:280-288. 

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

coastal waters of northern Oregon and Washington. Pp. 15-50, In: Beach, R. J., A. C. Geiger, S. J. Jeffries, 

S. D. Treacy, and B. L. Troutman, Marine mammals and their interactions with fisheries of the Columbia 

River and adjacent waters, 1980-1982. NWAFC Processed Report 85-04. 316 pp. Available at National 

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

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. 

Makah Fisheries Management, P.O. Box 115, Neah Bay, WA 98357. 

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

fishery. Unpublished Report. Pacific States Marine Fisheries Commission, Astoria, OR. 19 pp. Available 

at PSMFC, 205 SE Spokane Street, Suite 100, Portland, OR 97202. 

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

Unpublished Report. Pacific States Marine Fisheries Commission, Astoria, OR. 18 pp. Available at 

PSMFC, 205 SE Spokane Street, Suite 100, Portland, OR 97202. 

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. Unpublished Report. Pacific States Marine Fisheries Commission, 

Astoria, OR. 22 pp. Available at PSMFC, 205 SE Spokane Street, Suite 100, Portland, OR 97202. 

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

Unpublished Report. Pacific States Marine Fisheries Commission, Astoria, OR. 18 pp. Available at 

PSMFC, 205 SE Spokane Street, Suite 100, Portland, OR 97202. 

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. Unpublished Report. Pacific States Marine Fisheries 

Commission, Astoria, OR. 13 pp. Available at PSMFC, 205 SE Spokane Street, Suite 100, Portland, OR 

97202. 

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

gillnet fishery. Unpublished Report. Pacific States Marine Fisheries Commission, Astoria, OR. 17 pp. 

Available at PSMFC, 205 SE Spokane Street, Suite 100, Portland, OR 97202. 

20
Matteson, K. M., W. B. Barnett, and J. A. Langton. 1993b. Summary report on the 1992 fall Willapa Bay salmon 

gillnet fishery. Unpublished Report. Pacific States Marine Fisheries Commission, Astoria, OR. 17 pp. 

Available at PSMFC, 205 SE Spokane Street, Suite 100, Portland, OR 97202. 

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

salmon gillnet fishery. Unpublished Report. Pacific States Marine Fisheries Commission, Astoria, OR. 29 

pp. Available at PSMFC, 205 SE Spokane Street, Suite 100, Portland, OR 97202. 

National Marine Fisheries Service (NMFS), Northwest Regional Office, 7600 Sand Point Way NE, Seattle, WA 

98115. 

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

North, J. Ocean Salmon and Columbia River Program, Oregon Department of Fish and Wildlife, 17330 SE Evelyn 

Street, Clackamas, OR 97015. 

Northwest Fisheries Science Center (NWFSC). 2008. Report on the bycatch of marine mammals and seabirds by 

the U.S. West Coast groundfish fleet. At-sea Hake Observer Program, West Coast Groundfish Observer 

Program, Northwest Fisheries Science Center, NOAA Fisheries. Unpublished Report. 34 pp. Available at 

http://www.nwfsc.noaa.gov/research/divisions/fram/observer/datareport/index.cfm. 

Oregon Department of Fish and Wildlife (ODFW), 2040 SE Marine Science Dr., Newport, OR 97365. 

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

Oregon State University, Corvallis, OR. 23 pp. 

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

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

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

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

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

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

notes on reproduction in northern fur seals and Dall porpoises. MS Thesis, Oregon State University, 

Corvallis, OR. 147 pp. 

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

workshop April 3-5, 1996, Seattle, Washington. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR12. 93 pp. 

Whisler, G. Ocean Salmon and Columbia River Program, Oregon Department of Fish and Wildlife, 17330 SE 

Evelyn Street, Clackamas, OR 97015. 

21
Revised 01/15/2011

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). Genetic analyses 

provide additional support for this stock structure (Huber et al. 

1994, 2010; 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 

Washington inland waters possess unique haplotypes not found 

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

(Lamont et al. 1996). Recent genetic evidence suggests that the 

population of harbor seals in Washington inland waters has more structure than is currently recognized (Huber et al. 

2010). 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 th

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. 

e Alaska Region. 

POPULATION SIZE

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

which time the total numbers 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). However, because the most recent 

abundance estimate is >8 years old, there is no current estimate of abundance. 

22
Minimum Population Estimate

 No current information on 

abundance is available to obtain a 

minimum population estimate for the 

Washington Inland Waters stock of 

harbor seals. 

Current Population Trend

 Historical levels of harbor seal 

abundance in Washington are unknown. 

The population apparently decreased 

during the 1940s and 1950s due to a 

state-financed bounty program. 

Approximately 17,133 harbor seals were 

killed in Washington by bounty hunters 

between 1943 and 1960 (Newby 1973). 

The population remained relatively low 

during the 1970s but, since the 

termination of the harbor seal bounty 

program in 1960 and with the protection 

provided by the passage of the Marine 

Mammal Protection Act (MMPA) in 

1972, harbor seal numbers in Washington 

have increased (Jeffries 1985). 

0

2000

4000

6000

8000

10000

12000

14000

1975 1980 1985 1990 1995 2000

Year

Total count

Between 1983 and 1996, the 

annual rate of increase for this stock was 

6% (Jeffries et al. 1997). The peak count occurred in 1996 and, based on a fitted generalized logistic model (Fig. 2), 

the population is thought to be stable (Jeffries et al. 2003). 

Figure 2. Generalized logistic population growth curve for the 

Washington Inland Waters stock of harbor seals, 1978-1999 

(Jeffries et al. 2003).

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

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

(Jeffries et al. 1997). Because the population was not at a very low level by 1991, the observed rate of increase may 

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

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

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

12% will be employed for this harbor seal stock (Wade and Angliss 1997). 

POTENTIAL BIOLOGICAL REMOVAL

 Because there is no current estimate of minimum abundance, a potential biological removal (PBR) cannot 

be calculated for this stock. 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Fisheries Information

 Fishing effort in the northern Washington marine gillnet tribal fishery is conducted within the range of both 

stocks of harbor seals (Oregon/Washington Coast and Washington Inland Waters) occurring in Washington State 

waters. 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). For the 

purposes of this stock assessment report, the animals taken in waters east of Cape Flattery, WA, are assumed to have 

belonged to the Washington Inland Waters stock, and Table 1 includes data only from that portion of the fishery. 

There was no observer coverage in the northern Washington marine set gillnet tribal fishery in inland waters in 

2004-2008; however, there were two fisher self-reports of harbor seal deaths in this fishery in 2008 (Makah 

Fisheries Management, unpublished data). The mean estimated mortality for this fishery in 2004-2008 is 0.4 harbor 

seals per year from fisher self-reports. Fishing effort in the northern Washington marine drift gillnet tribal fishery in 

inland waters is also conducted within the range of the Washington Inland Waters stock of harbor seals. This 

fishery is not observed; however, there was one fisher self-report of a harbor seal death in 2008 (Makah Fisheries 

23
Management, unpublished data). The mean estimated mortality for this fishery in 2004-2008 is 0.2 harbor seals per 

year from fisher self-reports. 

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 deaths were reported. Pierce et al. (1994) cautioned against 

extrapolating this mortality to the entire Puget Sound fishery due to the low observer coverage and potential biases 

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

1993, approximately 67%. Results of this pilot study were used to design the 1994 observer programs discussed 

below. 

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

Inland Waters stock) in commercial and tribal fisheries that might take this species and calculation of the mean 

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

Mean annual takes are based on 2004-2008 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) 

Northern WA marine drift gillnet 

(tribal fishery in inland waters)

2004 

2005 

2006 

2007 

2008 

2008 

2008 

observer 

data 

fisher selfreports 

fisher selfreports

0% 

0% 

0% 

0% 

0% 

n/a 

n/a 

n/a 

n/a 

n/a 

2 

1 

n/a 

n/a 

n/a 

n/a 

n/a 

n/a 

n/a 

n/a 

>0.4 (n/a) 

>0.2 (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) 1993 observer data 1.3% 2 n/a see text

Puget Sound non-treaty chum 

salmon gillnet (areas 10/11 and 

12/12B)1

1994 observer 

data 11% 1 10 see text1

Puget Sound treaty chum 

salmon gillnet (areas 12, 12B, 

and 12C)1

1994 observer 

data 2.2% 0 0 see text1

Puget Sound treaty chum and 

sockeye salmon gillnet (areas 

4B, 5, and 6C)1

1994 observer 

data 7.5% 0 0 see text1

Puget Sound treaty and nontreaty sockeye salmon gillnet 

(areas 7 and 7A)1

1994 observer 

data 7% 1 15 see text1

Unknown Puget Sound fisheries 2004-2008 stranding 

data n/a 1, 0, 0, 8, 6 n/a >3.0 (n/a) 

Minimum total annual takes >3.6 (n/a) 

1

This fishery has not been observed since 1994 (see text); these data are not included in the calculation of recent minimum total annual takes.

 In 1994, NMFS, in conjunction with WDFW conducted an observer program during the Puget Sound nontreaty chum salmon gillnet fishery (areas 10/11 and 12/12B). A total of 230 sets were observed during 54 boat trips, 

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

24
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 deaths 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 mortality was reported in the 

observer programs covering these treaty salmon gillnet fisheries, where observer coverage was estimated at 2.2% 

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

respectively. 

 Also in 1994, NMFS, in conjunction with WDFW and the Tribes, monitored the Puget Sound treaty and 

non-treaty sockeye salmon gillnet fishery (areas 7 and 7A). During this fishery, observers monitored 2,205 sets, 

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

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

0.00045 harbor seals per set, which was extrapolated to 15 deaths (CV=1.0) for the entire fishery. 

 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. 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 

(Joe 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. 

 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 

deaths (one other was released alive with no apparent injuries). 

 Combining the estimates from the northern Washington marine set gillnet tribal fishery (0.4) and the 

northern Washington marine drift gillnet tribal fishery (0.2), results in an estimated mean annual mortality rate of 

0.6 harbor seals from this stock. One harbor seal also entangled in a tribal drift gillnet test fishery in area 8-2 in 

2006, resulting in an annual mortality of 0.2 harbor seals for this fishery. 

 The Marine Mammal Authorization Program (MMAP) fisher self-reports, required of commercial vessel 

operators by the MMPA, are an additional source of information on the number of harbor seals killed or seriously 

injured incidental to commercial fishery operations. Between 2004 and 2008, there were no fisher self-reports of 

harbor seal deaths 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). Although these reports are considered incomplete (see details in Appendix 1), they represent a 

minimum mortality. 

 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. According to Northwest Marine Mammal Stranding Network 

records, maintained by the NMFS Northwest Region (NMFS, Northwest Regional Office, unpublished data), there 

were 15 fishery-related strandings of harbor seals from this stock reported in 2004-2008, resulting in an average 

annual mortality of 3.0 harbor seals. Evidence of fishery interactions included entanglements in fishing nets (10), 

entanglements in fishing gear (three), hook injuries (one), and ingested hooks (one). As the strandings could not be 

attributed to a particular fishery, they have been included in Table 1 as occurring in unknown Puget Sound fisheries. 

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 (NMFS, Northwest Regional Office, unpublished data), a total of 46 human-caused harbor seal deaths or 

serious injuries were reported from non-fisheries sources in 2004-2008. Twenty-four animals were shot, 13 were 

struck by boats, two died in oil spills, three were killed by dogs, one was beaten by a fisherman, one was caught in 

the Ballard Locks, one entangled in wire, and one entangled in a scientific research capture net, resulting in an 

25
estimated mortality of 9.2 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

 Tribal subsistence takes of this stock may occur, but no data on recent takes are available. 

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 is 13.0 (3.8 + 9.2) harbor seals per year. A PBR cannot be calculated for this stock 

because there is no current abundance estimate. The previous estimate of PBR was 771 (Carretta et al. 2009). 

Human-caused mortality relative to PBR is unknown, but it is considered to be small relative to the stock size. 

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 is 3.8 (based on recent observer data (0) 

and self-reported fisheries information (0.8) or stranding data (3.0) where observer data were not available or failed 

to detect harbor seal mortality). Since a PBR cannot be calculated for this stock, fishery mortality relative to PBR is 

unknown. The stock is within its Optimum Sustainable Population (OSP) level (Jeffries et al. 2003). 

REFERENCES

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

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

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

New York. 

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

06. 43 pp. Available from Southwest Fisheries Science Center, 3333 North Torrey Pines Road, La Jolla, 

CA 92037. 

Brown, R. F. 1988. Assessment of pinniped populations in Oregon: April 1984 to April 1985. NWAFC Processed 

Report 88-05. 44 pp. Available at National Marine Mammal Laboratory, 7600 Sand Point Way NE, 

Seattle, WA 98115. 

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, University 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. 

Carretta, J. V., K. A. Forney, M. S. Lowry, J. Barlow, J. Baker, D. Johnston, B. Hanson, M. M. Muto, D. Lynch, and 

L. Carswell. 2009. U.S. Pacific marine mammal stock assessments: 2008. U.S. Dep. Commer., NOAA 

Tech. Memo. NMFS-SWFSC-434. 336 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. 

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 University, 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. 

Huber, H. R., S. J. Jeffries, D. M. Lambourn, and B. R. Dickerson. 2010. Population substructure of harbor seals 

(Phoca vitulina richardsi) in Washington State using mtDNA. Can. J. Zool. 88:280-288. 

26
Jeffries, S. J. 1985. Occurrence and distribution patterns of marine mammals in the Columbia River and adjacent 

coastal waters of northern Oregon and Washington. Pp. 15-50, In: Beach, R. J., A. C. Geiger, S. J. Jeffries, 

S. D. Treacy, and B. L. Troutman, Marine mammals and their interactions with fisheries of the Columbia 

River and adjacent waters, 1980-1982. NWAFC Processed Report 85-04. 316 pp. Available at National 

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

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. 

Makah Fisheries Management, P.O. Box 115, Neah Bay, WA 98357. 

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. 

National Marine Fisheries Service (NMFS), Northwest Regional Office, 7600 Sand Point Way NE, Seattle, WA 

98115. 

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

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. 

Unpublished Report. 41 pp. Available at NWIFC, 6730 Martin Way E, Olympia, WA 98516. 

Pierce, D. J., W. P. Ritchie, and R. Kreuziger. 1994. Preliminary findings of seabird interactions with the nontreaty salmon gill net fishery: Puget Sound and Hood Canal Washington. Unpublished 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 Report 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, Joe. National Marine Fisheries Service, Northwest Regional Office, 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 porpoises. MS Thesis, Oregon State University, 

Corvallis, OR. 

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

workshop April 3-5, 1996, Seattle, Washington. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR12. 93 pp. 

27
Revised 10/30/2007

NORTHERN ELEPHANT SEAL (Mirounga angustirostris): 

California Breeding Stock 

STOCK DEFINITION AND GEOGRAPHIC RANGE

Northern elephant seals breed and give 

birth in California (U.S.) and Baja California 

(Mexico), primarily on offshore islands (Stewart et 

al. 1994), from December to March (Stewart and 

Huber 1993). Males feed near the eastern Aleutian 

Islands and in the Gulf of Alaska, and females 

feed further south, south of 45o

N (Stewart and 

Huber 1993; Le Boeuf et al. 1993). Adults return 

to land between March and August to molt, with 

males returning later than females. Adults return 

to their feeding areas again between their 

spring/summer molting and their winter breeding 

asons.

tion is considered here to be a separate stock.

se 

 Populations of northern elephant seals in 

the U.S. and Mexico were all originally derived 

from a few tens or a few hundreds of individuals 

surviving in Mexico after being nearly hunted to 

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

recent derivation of most rookeries, no genetic 

differentiation would be expected. Although 

movement and genetic exchange continues 

between rookeries, most elephant seals return to 

their natal rookeries when they start breeding 

(Huber et al. 1991). The California breeding 

population is now demographically isolated from 

the Baja California population. No international 

agreements exist for the joint management of this 

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

breeding popula

W130 W125 W120 W115 W110 W105 W100

Longitude

N15

N20

N25

N30

N35

N40

N45

Latitude

WASHINGTON

OREGON

CALIFORNIA

MEXICO

UNITED STATES

PACIFIC OCEAN

CALIFORNIA BREEDING

 STOCK

 Isla 

Cedros

Isla Guadalupe

Isla Benito

 Del Este

SE Farallon Is.

Ano Nuevo

Channel

 Islands

Figure 1. Stock boundary and major rookery 

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

Mexico.

POPULATION SIZE

A complete population count of elephant seals is not possible because all age classes are not 

ashore at the same time. Elephant seal population size is typically estimated by counting the number of 

pups produced and multiplying by the inverse of the expected ratio of pups to total animals (McCann 

1985). Stewart et al. (1994) used McCann's multiplier of 4.5 to extrapolate from 28,164 pups to a 

population estimate of 127,000 elephant seals in the U.S. and Mexico in 1991. The multiplier of 4.5 was 

based on a non-growing population. Boveng (1988) and Barlow et al. (1993) suggest 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 35,549 pups born in California in 2005 (Fig. 2) and this 3.5 multiplier, the 

California stock was approximately 124,000 in 2005. 

Minimum Population Estimate

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

74,913, which is equal to twice the observed pup count (to account for the pups and their mothers) plus 

3,815 males and juveniles counted at the Channel Islands and central California sites in 2005 (Mark 

Lowry, NMFS unpubl. data) . More sophisticated methods of estimating minimum population size could 

be applied if the variance of the multiplier used to estimate population size were known. 

28
Current Population Trend

 Based on trends 

in pup counts, northern 

elephant seal colonies 

were continuing to grow 

in California through 2005 

(Figure 2), but appear to 

be stable or slowly 

decreasing in Mexico 

(Stewart et al. 1994). 

 

CURRENT AND 

Although growth 

rates as 

stic growth model 

OTENTIAL BIOLOGICAL REMOVAL

BR) level for this stock is calculated as the minimum 

latio

MAXIMUM NET 

PRODUCTIVITY 

RATE

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

indicates that the maximum population growth rate (Rmax) is 11.7 percent (SE = 2.7) (Figure 3). 

Northern Elephant Seal Births in U.S.

0

5,000

10,000

15,000

20,000

25,000

30,000

35,000

40,000

1950 1960 1970 1980 1990 2000 2010

Year

# Births

Total (U.S.)

Channel Islands

Central California

Figure 2. Estimated number of northern elephant seal births in California 

1958-2005. Multiple independent estimates are presented for the Channel 

Islands 1988-91. Estimates are from Stewart et al. (1994), Lowry et al. 

(1996), Lowry (2002) and unpublished data from Sarah Allen, Dan 

Crocker, Brian Hatfield, Ron Jameson, Bernie Le Boeuf, Mark Lowry, Pat 

Morris, Guy Oliver, Derek Lee, and William Sydeman. 

 1977 (Cooper and Stewart 1983). A generalized logi

P

 The potential biological removal (P

popu n size (74,913) times one half the observed maximum net growth rate for this stock (1⁄2 of 11.7%) 

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 4,382. 

HUMAN-CAUSED MORTALITY

own fishery mortality and injury for this stock of northern elephant seals is given 

 Table

Fisheries Information

 A summary of kn

in 1. More detailed information on these fisheries is provided in Appendix 1. Stranding data 

reported to the California, Oregon, and Washington Marine Mammal Stranding Networks in 2000-2004 

include elephant seal injuries caused by hook-and-line fisheries (two injuries) and gillnet fisheries (one 

injury). 

29
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 (Carretta and Chivers 2004, 

Carretta et al. 2005a, 2005b, Perez 2003 , Perez 2003; Perez, in prep.; NMFS unpubl. data). n/a indicates 

information is not available. Mean annual takes are based on 2000-2004 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 

2000 

2001 

2002 

2003 

2004 

observer 

data 

22.9% 

20.4% 

22.1% 

20.2% 

20.6%

6 

1 

1 

1 

0 

26 (0.39) 

5 (0.94) 

5 (0.92) 

5 (1.00) 

0 

8 (0.40) 

CA angel shark/halibut 

and other species large 

mesh (>3.5") set gillnet 

fishery1 

20011

20021

20031

20041

20051

observer 

data 

0% 

0% 

0% 

0% 

0% 

n/a 

n/a 

n/a 

n/a 

n/a 

n/a 

n/a 

n/a 

n/a 

n/a 

n/a

WA, OR, CA domestic 

groundfish trawl (At-sea 

processing Pacific 

whiting fishery only) 

2000 

2001 

2002 

2003 

2004 

observer 

data 

80.6% 

96.2% 

100% 

100% 

100% 

1 

0 

0 

0 

3 

1 (n/a) 

0 (n/a) 

0 (n/a) 

0 (n/a) 

3 (n/a) 

0.8 (n/a) 

WA, OR, CA domestic 

groundfish trawl fishery 

(bottom trawl) 

2000-2004 observer n/a 0 0 0 (n/a) 

Total annual takes > 8.8 (0.40)

1

 The most recent observer data for the halibut set gillnet fishery is from 2000 in Monterey Bay only and there has not been a fisherywide observer program since 1990-94. There are no current estimates of mortality for this fishery, as this would require assuming that 

current kill rates are comparable to kill rates observed between 1990-94 and extrapolation of mortality estimates using current

estimates of fishing effort. 

 

Although all of the mortality 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. 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). 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

 Stranding databases for California, Oregon, and Washington states that are maintained by the 

National Marine Fisheries Service contain the following records of human-related elephant seal mortality 

and injuries in 2000-2004: (1) boat collision (three deaths), (2) power plant entrainment (one death), (3) 

30
shootings (four deaths) and (4) entanglement in marine debris (10 injuries). This results in a minimum 

annual average of 1.6 non-fishery related deaths for 2000-2004.

STATUS OF STOCK

 A generalized logistic growth model of pup counts indicated that the population reached its 

Maximum Net Productivity Level (MNPL) of 19,000 pups in 1992, but has not reached carrying capacity 

(K) at 38,200 pups per year (z = 1, Rmax

= 0.117, n0 = 1,000, SE = 3,376, AICc 

= 500.3) (Figure 3). 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 (4,382), 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 (>8.8) 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. This annual rate of 

fishery mortality is negatively biased 

because it excludes mortality that likely 

occurs in the unobserved set gillnet 

fishery for halibut and angel shark, 

where average annual mortality was estimated at approximately 60 animals annually during the period 

1996-2000. 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. 

1960 1970 1980 1990 2000

0 10000 20000 30000 40000 50000

Year

Abundance

1992

K = 3.8e+04

MNPL = 1.9e+04

Figure 3. Generalized logistic growth model of elephant 

seal pup counts, 1958-2005. 

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. 

Carretta, J.V. and S.J. Chivers. 2004. Preliminary estimates of marine mammal mortality and biological 

sampling of cetaceans in California gillnet fisheries for 2003. Paper SC/56/SM1 presented to the 

IWC Scientific Committee, June 2004 (unpublished). [Available from Southwest Fisheries 

Science Center, National Marine Fisheries Service, 8604 La Jolla Shores Drive, La Jolla, CA 

92037, USA]. 

Carretta, J.V., S.J. Chivers, and K. Danil. 2005a. Preliminary estimates of marine mammal bycatch, 

mortality, and biological sampling of cetaceans in California gillnet fisheries for 2004. 

Administrative Report LJ-05-10, available from Southwest Fisheries Science Center, 8604 La 

Jolla Shores Drive, La Jolla, California, 92037. 17 p. 

Carretta, J.V., T. Price, D. Petersen, and R. Read. 2005b. Estimates of marine mammal, sea turtle, and 

seabird mortality in the California drift gillnet fishery for swordfish and thresher shark, 1996-

2002. Marine Fisheries Review 66(2):21-30. 

31
Cooper, C. F. and B. S. Stewart. 1983. Demography of northern elephant seals, 1911-1982. Science 

219:969-971. 

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. 

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. 2002. Counts of northern elephant seals at rookeries in the southern California Bight: 1981-

2001. NOAA Technical Memorandum NMFS, NOAA-TM-NMFS-SWFSC-345. Available at 

Southwest Fisheries Science Center, 8604 La Jolla Shores Drive, La Jolla, CA 92037 or at 

http://swfsc.noaa.gov/textblock.aspx?Division=PRD&ParentMenuId=148&id=1253#TechMemos. 

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

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

NOAA Tech. Memo. NMFS-AFSC-138. 145 pp.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
Revised 12/15/2000

GUADALUPE FUR SEAL (Arctocephalus townsendi) 

STOCK DEFINITION AND GEOGRAPHIC 

RANGE

 Commercial sealing during the 19th 

century reduced the once abundant Guadalupe fur 

seal to near extinction in 1894 (Townsend 1931). 

Prior to the harvest it ranged from Monterey Bay, 

California, to the Revillagigedo Islands, Mexico 

(Fleischer 1987, Hanni et al. 1997; Figure 1). The 

capture of two adult males at Guadalupe Island in 

1928 established the specie’s continued existence 

(Townsend 1931); however, they were not seen 

again until 1954 (Hubbs 1956). Guadalupe fur 

seals pup and breed mainly at Isla Guadalupe, 

Mexico. In 1997, a second rookery was 

discovered at Isla Benito del Este, Baja California 

(Maravilla-Chavez and Lowry 1999) and a pup 

was born at San Miguel Island, California (Melin 

and DeLong 1999). Individuals have stranded or 

been sighted as far north as Blind Beach, 

California (38o

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

the Gulf of California and as far south as 

Zihuatanejo, Mexico (17o

 39' N, 101o 34'W; Hanni 

et al. 1997 and Aurioles-Gamboa and HernadezCamacho 1999). The population is considered to 

be a single stock because all are recent descendants 

from one breeding colony at Isla Guadalupe, 

Mexico. 

W130 W125 W120 W115 W110 W105 W100

Longitude

N15

N20

N25

N30

N35

N40

N45

Latitude

WASHINGTON

OREGON

CALIFORNIA

MEXICO

UNITED STATES

PACIFIC OCEAN

Isla Guadalupe

Isla Benito

 Del Este

 Islas 

Revillagigedos

Figure 1. Geographic range of the Guadalupe fur 

seal, showing location of two rookeries at Isla 

Guadalupe and Isla Benito Del Este.

POPULATION SIZE

 The size of the population prior to the commercial harvests of the 19th century is not known, but 

estimates range from 20,000 to 100,000 animals (Wedgeforth 1928, Hubbs 1956, Fleischer 1987). The 

population was estimated by Gallo (1994) to be about 7,408 animals in 1993. The population estimate was 

derived by multiplying the number of pups (counted and estimated) by a factor of 4.0. 

Minimum Population Estimate

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

ashore at the same time and some individuals that are on land are not visible during the census. Subsampling portions of the rookery indicate that only 47-55% of the seals present (i.e., hauled out) are 

counted during the census (Gallo 1994). The 1993 count of all age classes plus the estimate of missed 

animals was 6,443 (Gallo 1994). The minimum size of the population in Mexico can be estimated as the 

actual count of 3,028 hauled out seals [The actual count data were not reported by Gallo (1994); this 

number is derived by multiplying the estimated number hauled out by 47%, the minimum estimate of the 

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

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

Current Population Trend

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

seal counts through 1984 were compiled by Seagars (1984), Fleischer (1987), and Gallo (1994). The count 

for 1988 was taken from Torres et al. (1990). A few of these counts were made during the breeding season, 

but the majority were made at other times of the year (Figure 1). Also, the counts that are documented in 

the literature generally provide only the total of all Guadalupe fur seals counted (i.e., the counts are not 

separated by age/sex class). The counts that were made during the breeding season, when the maximum 

33
number of animals are present at the 

rookery, were used to examine 

population growth (Gallo 1994). The 

natural logarithm of the counts was 

regressed against year to calculate the 

growth rate of the population. These 

data indicate that the population of 

Guadalupe fur seals is increasing 

exponentially at an average annual 

growth rate of 13.7% (Gallo 1994; 

Figure 2).

CURRENT AND MAXIMUM NET 

PRODUCTIVITY RATES

 The maximum net productivity 

rate can be assumed to be equal to the 

annual growth rate observed over the 

last 30 years (13.7%) because the 

population was at a very low level and 

should have been growing at nearly its 

maximum rate. 

0 

1000 

2000 

3000 

4000 

5000 

6000 

7000 

COUNTS

50 55 60 65 70 75 80 85 90 95

YEAR

Non-breeding season Breeding season Pop. growth curve

GUADALUPE FUR SEAL COUNTS

Guadalupe Island, Mexico

Figure 2. Counts of Guadalupe fur seals at Guadalupe 

Island, Mexico, and the estimated population growth curve 

derived from counts made during the breeding season. POTENTIAL BIOLOGICAL 

REMOVAL

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

size (3,028) times one half the default maximum net growth rate for pinnipeds (1⁄2 of 12%) times a recovery 

factor of 0.5 (for a threatened species, Wade and Angliss 1997), resulting in a PBR of 91 Guadalupe fur 

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

HUMAN-CAUSED MORTALITYAND SERIOUS INJURY

Fisheries Information

 Drift and set gillnet fisheries may cause incidental mortality of Guadalupe fur seals in Mexico and 

the United States. In the United States there have been no reports of mortality 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 mortality or injuries in Mexico. However, similar drift gillnet fisheries for 

swordfish and sharks exist along the entire Pacific coast of Baja California, Mexico and may take animals 

from the same population. Quantitative data are available only for the Mexican swordfish drift gillnet 

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

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

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

overall mortality rate is similar to that observed in California driftnet fisheries during 1990-93 (0.15 marine 

mammals per set), but species-specific information is not available for the Mexican fisheries. There are 

currently efforts underway to convert the Mexican swordfish driftnet fishery to a longline fishery (D. Holts, 

pers. comm.). The number of set gillnets used in Mexico is unknown. 

Other mortality

Juvenile female Guadalupe fur seals have stranded in central and northern California with net abrasions 

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

STATUS OF STOCK

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

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

Game Commission California Code of Regulations (Title 14, sec. 670.5, b, 6, H). The Endangered Species 

Act lists it as a threatened species, which automatically qualifies this as a "depleted" and "strategic" stock 

under the Marine Mammal Protection Act. There is insufficient information to determine whether the 

fishery mortality in Mexico exceeds the PBR for this stock. The total U.S. fishery mortality and serious 

34
injury for this stock is less than 10% of the calculated PBR and, therefore, can be considered to be 

insignificant and approaching zero mortality and serious injury rate. The population is growing at 

approximately 13.7% per year.

Table 1. Summary of available information on the incidental mortality and injury of Guadalupe fur seals in 

commercial fisheries that might take this species (Julian 1997, Julian and Beeson 1998, Cameron and 

Forney 1999, M. Perez per. comm, Appendix 1). Mean annual takes are based on 1994-98 data unless 

noted otherwise.

Fishery Name Year(s) Data Type

Percent 

Observer 

Coverage

Observed

Mortality

Estimated 

Mortality (CV in 

parentheses)

Mean 

Annual Takes 

(CV in parentheses)

CA driftnet fishery for 

sharks and swordfish

1994 

1995 

1996 

1997 

1998 

observer 

17.9% 

15.6% 

12.4% 

22.8% 

20.2% 

0 

0 

0 

0

0

0 

0 

0 

0

0

01

CA set gillnet fishery 

for halibut and angel 

shark

1994 

1995 

1996 

1997

1998

observer 

extrapolated 

estimates 

(1995-98)

7.7% 

0% 

0% 

0%

0%

0 

0 

0 

0

0

0 

02

02

02

02

02

WA, OR, CA ground 

fish trawl fishery (Atsea processing Pacific 

whiting fishery only)

1994 

1995 

1996 

1997

1998

observer 

53.8% 

56.2% 

65.2% 

65.7%

77.3%

0 

0 

0 

0

0

0 

0 

0 

0

0

0

Minimum total annual takes 0

1

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

of a 1997 Take Reduction Plan. Gear modifications included the use of net extenders and acoustic warning devices (pingers). 2

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

REFERENCES

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

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

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

V. N. Burkanov. 1994. A review of cetacean and pinniped mortality in coastal fisheries along the 

west coast of the USA and Canada and the east coast of the Russian Federation. Rept. Int. 

Whaling Comm., Special Issue 15:405-425. 

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

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

(unpublished). 14 pp. 

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

(eds.). Status, biology, and ecology of fur seals. Proceedings of an international symposium and 

workshop. Cambridge, England, 23-27 April 1984. p. 43-48. U.S. Dept. of Commerce, NOAA, 

NMFS, NOAA Tech. Rept. NMFS 51. 

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

(Merriam, 1897), at Isla de Guadalupe, Baja California, Mexico. Ph.D. Thesis, University of 

California, Santa Cruz, 199 p. 

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

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

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

CA 92038. 

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

35
Julian, F. 1997. Cetacean mortality in California gill net fisheries: Preliminary estimates for 1996. Paper 

SC/49/SM02 presented to the International Whaling Commission, September 1997 (unpublished). 

13 pp. 

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

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

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

Benito del 

 Este, Baja California, Mexico. Mar. Mamm. Sci. 15:239-241. 

Melin, S. R. and R. L. DeLong. 1999. Observations of a Guadalupe fur seal (Arctocephalus townsendi) 

female and pup at San Miguel Island, California. Mar. Mamm. Sci. 15:885-888. 

Perkins, P., J. Barlow, and M. Beeson. 1992. Pinniped and cetacean mortality in California gillnet 

fisheries: 1991. Rept. Int. Whaling Commission, Working Paper SC/44/SM14. 

Seagars, D. J. 1984. The Guadalupe fur seal: a status review. National Marine Fisheries Service, 

Southwest Region, Admin. Rep. SWR-84-6. 29pp. 

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

Velez. 1993. Estudio biologico pesquero del pez (Xiphias gladius) y otras especies de picudos 

(marlins y pez vela). Rep. Int. CICESE, CTECT9306. 

Stewart, B. S., P. K. Yochem, R. L. DeLong, and G.A. Antonelis Jr. 1987. Interactions between 

Guadalupe fur seals and California sea lions ant San Nicolas and San Miguel islands, California. 

In J. P. Croxall and R. L. Gentry (eds.). Status, biology, and ecology of fur seals. Proceedings of 

an international symposium and workshop. Cambridge, England, 23-27 April 1984. p. 103-106. 

U.S. Dept. of Commerce, NOAA, NMFS, NOAA Tech. Rept. NMFS 51. 

Torres-G., A., A. Aguayo-L., and N. Valdez-T. 1990. Tamaño y distribucion de la poblacion del lobo fino 

de Guadalupe, Arctocephalus townsendi (Merriam, 1897), durante el verano de 1988. [Abstracts] 

XV Reunion internacional para el estudio de los mamiferos marinos, 18-20 April 1990. La Paz, B. 

C. S., Mexico. 

Townsend, C. H. 1931. The fur seal of the California islands with new descriptive and historical matter. 

Zoologica 9:443-457. 

Wedgeforth, H. M. 1928. The Guadalupe fur seal (Arctocephalus townsendi). Zoonooz, S. D. Zool. Soc. 

3(3):4-9. 

36
Revised 01/15/2011

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 2007). 

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 this occurs outside of 

the breeding season (Fiscus 1983). 

Figure 1. Approximate distribution of northern fur seals in the North Pacific 

(shaded area). 

Due to differing requirements during the annual reproductive season, adult males and females typically 

occur ashore at different, though overlapping, times. Adult males usually occur on shore during the 4-month period 

from May-August, though some may be present until November (well after giving up their territories). Adult 

females are found ashore for as long as six months (June-November). After their respective times ashore, seals of 

both genders spend the next 7-8 months at sea (Roppel 1984). Adult females and pups from the Pribilof Islands 

migrate through the Aleutian Islands into the North Pacific Ocean, often to Oregon and California offshore waters. 

Many pups may remain at sea for 22 months before returning to their rookery of birth. Adult males from the 

Pribilof Islands generally migrate only as far south as the Gulf of Alaska (Kajimura 1984). There is considerable 

interchange of individuals between rookeries. 

 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 2007); 3) Phenotypic data: unknown; and 4) Genotypic data: little evidence of genetic 

differentiation among breeding islands (Ream 2002). 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, Lander’s (1981) life table analysis was used to estimate the number of yearlings, twoyear-olds, three-year-olds, and animals at least four years old. 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 

37
commercial harvest of juvenile males was terminated in 1984. A more appropriate expansion factor for the San 

Miguel Island stock is 4.0, because immigration of recruitment-age females is occurring in the population (DeLong 

1982) as well as mortality and possible emigration of adults associated with the El Niño Southern Oscillation events 

in 1982-1983 and 1997-1998 (Melin et al. 2008). A 1998 pup count resulted in an 80% decrease from the 1997 

count (Melin et al. 2005). In 1999, the population began to recover, and by 2007 the total pup count was 2,492 

(Melin et al. 2008). Based on the 2007 count and the expansion factor, the most recent population estimate of the 

San Miguel Island stock is 9,968 (2,492 x 4.0) northern fur seals. Currently, a coefficient of variation (CV) for the 

expansion factor is unavailable. 

Minimum Population Estimate

 The survey technique utilized for estimating the abundance of northern fur seals within the San Miguel 

Island stock is a direct count, with no associated CV, as sites are surveyed only once. Additional estimates of the 

overall population size (i.e., NBEST) and associated CV are also unavailable. Therefore, the minimum population 

size for this stock cannot be estimated by calculating the lower 20th percentile of the log-normal distribution of the 

population estimate. Rather, the minimum population size is estimated as twice the maximum number of pups born 

in 2007 (to account for the pups and their mothers) plus the maximum number of adult (147) and sub-adult (264) 

males counted for the 2007 season (Melin et al. 2008), which results in an estimate of 5,395 ((2,492 x 2) + 411). 

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 and 

Russian populations 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 et al. 

2005). El Niño events, which 

occur periodically along the California coast, impact population growth of northern 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, 2005, 2008). 

Figure 2. Number of live northern fur seal pups counted on San Miguel Island, 

1972-2007. 

 Specifically, live pup counts increased about 24% annually from 1972 through 1982 (Fig. 2), an increase 

due, in part, to immigration of females from the Bering Sea and the western North Pacific Ocean (DeLong 1982). 

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 or emigration 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 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 declined 80% from 1997 (Melin et al. 2005). Although total production increased to 2,492 in 

2007 (Melin et al. 2008), the population has not yet recovered. Recovery from the 1998 decline has been slowed by 

the adult female mortality or emigration which occurred in addition to the high pup mortality in 1997 and 1998 

(Melin et al. 2008). 

38
CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

 A growth rate of 20% was calculated for northern fur seals on San Miguel Island in 1972-1982 by linear 

regression of the natural logarithm of pup count against year. However, it is clear that this rate of increase was due 

in part to immigration of females from Russian and Pribilof Islands populations (DeLong 1982). In the absence of a 

reliable estimate of the maximum net productivity rate for the San Miguel Island stock of northern fur seals, the 

pinniped default maximum theoretical net productivity rate (RMAX) of 12% (Wade and Angliss 1997) is used as a 

conservative estimate of RMAX. 

POTENTIAL BIOLOGICAL REMOVAL

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

estimate (5,395) times one-half the default maximum net growth rate (1⁄2 of 12%) times a recovery factor of 1.0 (for 

stocks of unknown status that are increasing in size: Wade and Angliss 1997), resulting in a PBR of 324 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 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 observed fisheries that may have interacted with northern fur seals is listed in Table 1. 

There were no observer reports of northern fur seal deaths in any observed fishery along the west coast of the 

continental U.S. in 2004-2008 (Table 1; Carretta et al. 2005; Carretta and Enriquez 2006, 2007, 2009a, 2009b; 

NWFSC 2008). The estimated mean mortality rate in observed fisheries is zero northern fur seals per year from this 

stock. 

Table 1. Summary of available information on the incidental mortality and serious 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 2004-2008 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

2004 

2005 

2006 

2007 

2008 

observer 

data

20.6% 

20.9% 

18.5% 

16.4% 

13.5% 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 (n/a)

CA halibut/white seabass and 

other species large mesh (>3.5 

in) set gillnet

2003 

2004 

2005 

2006 

2007 

observer 

data

0% 

0% 

0% 

0% 

17.8% 

n/a 

n/a 

n/a 

n/a 

0 

n/a 

n/a 

n/a 

n/a 

0 

0 (n/a) 

WA/OR/CA groundfish trawl 

(Pacific hake at-sea processing 

component)

2002 

2003 

2004 

2005 

2006 

observer 

data

100%1 

100%1 

100%1

100%1

100%1 

0 

0 

0 

0 

0 

0 (0) 

0 (0) 

0 (0) 

0 (0) 

0 (0) 

0 (0)

Minimum total annual takes 0 (n/a) 

1

Percent observer coverage equals percent of vessels with observers. 

 The Marine Mammal Authorization Program (MMAP) fisher self-reports, required of commercial vessel 

operators by the MMPA, are an additional source of information on the number of northern fur seals killed or 

seriously injured incidental to commercial fishery operations. There were no fisher self-reports of northern fur seal 

deaths in any MMAP-listed fishery operating in waters off California, Oregon, or Washington between 2004 and 

39
2008. Although these reports are considered incomplete (see details in Appendix 1), they represent a minimum 

mortality. 

 Strandings of northern fur seals entangled in fishing gear or with serious injuries caused by interactions 

with gear are a final source of fishery-related mortality information. According to Marine Mammal Stranding 

Network records, maintained for California by the NMFS Southwest Region (NMFS, Southwest Regional Office, 

unpublished data) and for Oregon and Washington by the NMFS Northwest Region (NMFS, Northwest Regional 

Office, unpublished data), no fishery-related strandings were reported between 2004 and 2008. 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 

 In 2007 and 2008, four northern fur seals were incidentally killed in California waters during scientific 

sardine trawling operations conducted by NMFS (NMFS, Southwest Regional Office, unpublished data): one death 

occurred in 2007 and three in 2008. After marine mammal deaths, including one northern fur seal, occurred in April 

2008 trawls, NMFS scientists met to discuss and implement a mitigation plan to avoid future mortality. The initial 

mitigation plan included use of 162 dB acoustic pingers, a marine mammal watch, and scheduling trawls to occur 

when the ship first arrived on station to avoid attracting animals to a stationary vessel. Two additional northern fur 

seals were killed in subsequent 2008 trawls, including one in July and one in August. In 2009, a marine mammal 

excluder device was added to the trawls and no additional deaths were observed during 42 trawls. The average 

annual research-related mortality of northern fur seals from 2004 to 2008 is 0.8 animals. 

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

Southwest Regional Office, unpublished data) and Northwest (NMFS, Northwest Regional Office, unpublished 

data) Regions, two human-caused northern fur seal deaths were reported from non-fisheries sources in California in 

2004-2008. One animal was shot in 2007 and one was entangled in marine debris in 2008, resulting in an estimated 

annual mortality of 0.4 animals from this stock between 2004 and 2008. 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 (1.2) does not exceed the PBR (324). 

Therefore, the San Miguel Island stock of northern fur seals is not classified as a “strategic” stock. The minimum 

total fishery mortality and serious injury for this stock (0) is not known to exceed 10% of the calculated PBR (32.4) 

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

decreased 80% from 1997 to 1998, began to recover in 1999, and is currently at 77% 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. 

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Carretta, J. V., and L. Enriquez. 2006. Marine mammal bycatch and estimated mortality in California commercial 

fisheries during 2005. Administrative Report LJ-06-07. 14 pp. Available from Southwest Fisheries 

Science Center, 3333 North Torrey Pines Road, La Jolla, CA 92037. 

Carretta, J. V., and L. Enriquez. 2007. Marine mammal and sea turtle bycatch in the California/Oregon thresher 

shark and swordfish drift gillnet fishery in 2006. Administrative Report LJ-07-06. 9 pp. Available from 

Southwest Fisheries Science Center, 3333 North Torrey Pines Road, La Jolla, CA 92037. 

Carretta, J. V., and L. Enriquez. 2009a. Marine mammal and seabird bycatch in observed California commercial 

fisheries in 2007. Administrative Report LJ-09-01. 12 pp. Available from Southwest Fisheries Science 

Center, 3333 North Torrey Pines Road, La Jolla, CA 92037. 

Carretta, J. V., and L. Enriquez. 2009b. Marine mammal bycatch in the California/Oregon swordfish and thresher 

shark drift gillnet fishery in 2008. Administrative Report LJ-09-03. 10 pp. Available from Southwest 

Fisheries Science Center, 3333 North Torrey Pines Road, La Jolla, CA 92037. 

Carretta, J. V., S. J. Chivers, and K. Danil. 2005. Preliminary estimates of marine mammal bycatch, mortality, and 

biological sampling of cetaceans in California gillnet fisheries for 2004. Administrative Report LJ-05-10. 

17 pp. Available from Southwest Fisheries Science Center, 3333 North Torrey Pines Road, La Jolla, CA 

92037. 

40
DeLong, R. L. 1982. Population biology of northern fur seals at San Miguel Island, California. Ph.D. Thesis, 

University of California, Berkeley, CA. 185 pp. 

DeLong, R. L., and G. A. Antonelis. 1991. Impacts of the 1982-1983 El Niño on the northern fur seal population at 

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Responses to Environmental Stress. Springer-Verlag, New York. 293 pp. 

Dizon, A. E., C. Lockyer, W. F. Perrin, D. P. DeMaster, and J. Sisson. 1992. Rethinking the stock concept: a 

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

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

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. 

Kajimura, H. 1984. Opportunistic feeding of the northern fur seal, Callorhinus ursinus, in the eastern North Pacific 

Ocean and eastern Bering Sea. U.S. Dep. Commer., NOAA Tech. Report NMFS-SSRF-779. 49 pp. 

Lander, R. H. 1981. A life table and biomass estimate for Alaskan fur seals. Fisheries 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 

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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, 

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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 

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Commer., NOAA Tech. Memo. NMFS-AFSC-69. 144 pp. 

Melin, S. R., R. L. DeLong, and A. J. Orr. 2005. The status of the northern fur seal population at San Miguel 

Island, California, 2002-2003. Pp. 44-52, In: Testa, J. W. (ed.), Fur seal investigations, 2002-2003. U.S. 

Dep. Commer., NOAA Tech. Memo. NMFS-AFSC-151. 72 pp. 

Melin, S. R., A. J. Orr, and R. L. DeLong. 2008. The status of the northern fur seal population at San Miguel 

Island, California, 2006 and 2007. Pp. 41-54, In: Testa, J. W. (ed.), Fur seal investigations, 2006-2007. 

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seal (Callorhinus ursinus). National Marine Fisheries Service, Juneau, AK. Available at 

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the U.S. West Coast groundfish fleet. At-sea Hake Observer Program, West Coast Groundfish Observer 

Program, Northwest Fisheries Science Center, NOAA Fisheries. Unpublished Report. 34 pp. Available at 

http://www.nwfsc.noaa.gov/research/divisions/fram/observer/datareport/index.cfm. 

Ream, R. R. 2002. Molecular ecology of North Pacific otariids: genetic assessment of northern fur seal and Steller 

sea lion distributions. Ph.D. Thesis, University of Washington, Seattle, WA. 134 pp. 

Roppel, A. Y. 1984. Management of northern fur seals on the Pribilof Islands, Alaska, 1786-1981. U.S. Dep. 

Commer., NOAA Tech. Report NMFS-4. 32 pp. 

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

workshop April 3-5, 1996, Seattle, Washington. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR12. 93 pp. 

41
Revised 01/15/2011

HAWAIIAN MONK SEAL (Monachus schauinslandi)

STOCK DEFINITION AND GEOGRAPHIC RANGE

Hawaiian monk seals are distributed predominantly in six Northwestern Hawaiian Islands (NWHI) 

subpopulations at French Frigate Shoals, Laysan and Lisianski Islands, Pearl and Hermes Reef, and Midway and 

Kure Atoll. Small numbers also occur at Necker, Nihoa, and the main Hawaiian Islands (MHI). Genetic variation 

among NWHI monk seals is extremely low and may reflect both a long-term history at low population levels and 

more recent human influences (Kretzmann et al. 1997, 2001, Schultz et al. 2009). On average, 10-15% of the seals 

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

subpopulations are not isolated, though the different island subpopulations have exhibited considerable demographic 

independence. Observed interchange of individuals among the NWHI and MHI regions is rare, yet preliminary 

genetic stock structure analysis (Schultz et al. in review) suggests the species is appropriately managed as a single 

stock. 

POPULATION SIZE

 The best estimate of the total population size is 1,161. This estimate is the sum of estimated abundance at 

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

and an estimate of minimum abundance in the main Hawaiian Islands. The number of individual seals identified 

was used as the population estimate at NWHI sites where total enumeration was achieved according to the criteria 

established by Baker et al. (2006). Where total enumeration was not achieved, capture-recapture estimates from 

Program CAPTURE were used (Baker 2004; Otis et al. 1978, Rexstad & Burnham 1991, White et al. 1982). When 

no reliable estimator was obtainable in Program CAPTURE (i.e., the model selection criterion was < 0.75, following 

Otis et al. 1978), the total number of seals identified was the best available estimate. Finally, sometimes capturerecapture estimates are less than the known minimum abundance (Baker 2004), and in these cases the total number 

of seals identified was used. In 2008, total enumeration was not definitively achieved at any site, however analysis 

of discovery curves (Baker et al. 2006) suggested that nearly all seals were identified at Laysan Island and Kure 

Atoll. Except at Midway Atoll, capture-recapture analysis either found no suitable estimator was available or the 

estimate was lower than known minimum abundance. Thus, abundance at the six main subpopulations was 

estimated to be 914 (including 138 pups). 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 2004 and 

2008 was 15.5 (±5.1) at Necker Island and 27.1 (±5.7) at Nihoa Island (Johanos and Baker in press, in prep., 

Johanos in prep.). 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 of 2.89 (NMFS unpubl. 

data). Resulting estimates (plus the average number of pups known to have been born during 2004-2008) are 47.8 

(±14.7) at Necker Island and 86.5 (±16.5) at Nihoa Island. 

 The only complete and systematic surveys for monk seals in the MHI were conducted in 2000 and 2001 

(Baker and Johanos 2004). The NMFS collects information on seal sightings reported by a variety of sources. 

Recently, the number of such reports has increased and related database improvement efforts have been underway. 

The total number of individually identifiable seals documented in this way in 2008 was 113, the current best 

minimum abundance estimate. 

Minimum Population Estimate

 The total number of seals (913) identified at the six main NWHI reproductive sites is the best estimate of 

minimum population size at those sites. Minimum population sizes for Necker and Nihoa Islands (based on the 

formula provided by Wade and Angliss (1997)) are 37 and 74, respectively. The minimum abundance estimate for 

the main Hawaiian Islands in 2008 is 113 seals. The minimum population size for the entire stock (species) is the 

sum of these estimates, or 1,136 seals. 

Current Population Trend 

Current population trend is based solely on the six NWHI subpopulations because these sites have 

historically comprised virtually the entire species, while information on the remaining smaller seal aggregations 

have been inadequate to reliably evaluate abundance or trends. The total of mean non-pup beach counts at the six 

main reproductive NWHI subpopulations in 2008 is 68% lower than in 1958. The trend in total abundance at the six 

main NWHI subpopulations estimated as described above is shown in Figure 1. A log-linear regression of estimated 

42
abundance on year for the past 10 years (1999-2008) estimates that abundance declined -4.5% yr-1 (95% CI = -5.0% 

to -3.9% yr-1). 

 The MHI monk seal population appears to be increasing with an intrinsic population growth rate estimated 

at 5.6% per year based upon Leslie matrix analysis (Baker et al., in review). Likewise, sporadic beach counts at 

Necker and especially Nihoa Islands, suggest positive growth. While these sites have historically comprised a small 

fraction of the total species abundance, the decline of the six main NWHI subpopulations, coupled with growth at 

Necker, Nihoa and the MHI may mean that these latter three sites now substantially influence the total abundance 

trend. Unfortunately, because we lack reliable abundance estimates for these areas, their influence cannot currently 

be determined. 

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

 Trends in abundance vary considerably among subpopulations. Mean non-pup beach counts are used as a 

long-term index of abundance for years when data are insufficient to estimate total abundance as described above). 

Prior to 1999, beach count increases of up to 7% yr-1 were observed at Pearl and Hermes Reef, and this is the highest 

estimate of the maximum net productivity 

rate (Rmax) observed for this species. 

Since 2000, low juvenile survival, thought 

to be due largely to food limitation, has 

resulted in population decline in the six 

main NWHI subpopulations (Fig. 1). 

 

POTENTIAL BIOLOGICAL 

REMOVAL

 Potential biological removal 

(PBR) is designed to allow stocks to 

recover to, or remain above, the maximum 

net productivity level (MNPL) (Wade 

1998). An underlying assumption in the 

application of the PBR equation is that 

marine mammal stocks exhibit certain 

dynamics. Specifically, it is assumed that 

a depleted stock will naturally grow 

toward OSP (Optimum Sustainable 

Population), and that some surplus growth 

could be removed while still allowing 

recovery. The Hawaiian monk seal 

population is far below historical levels 

and has declined 4.5 % yr-1 on average 

since 1999. Thus, the stock’s dynamics do 

not conform to the underlying model for 

calculating PBR such that PBR for the 

Hawaiian monk seal is undetermined. 

Figure 1. Trend in abundance of monk seals at the six main Northwestern 

Hawaiian Islands subpopulations, based on a combination of total 

enumeration and capture–recapture estimates. Error bars indicate ±2 s.e. 

(from variances of capture-recapture estimates). Fitted log-linear 

regression line is shown. 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

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

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

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

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

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

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

human activities in the NWHI are limited and human disturbance is relatively rare, but human-seal interactions have 

become an important issue in the MHI. 

Fishery Information

 Fishery interactions with monk seals can include direct interaction with gear (hooking or entanglement), 

seal consumption of discarded catch, and competition for prey. Entanglement of monk seals in derelict fishing gear, 

43
which is believed to originate outside the Hawaiian archipelago, is described in a separate section below. 

 Fishery interactions are a serious concern in the MHI, especially involving State of Hawaii managed 

nearshore fisheries. Three seals have been found dead in nearshore (non-recreational) gillnets (in 1994, 2006, and 

2007), and a seal was found dead in 1995 with a hook lodged in its esophagus. A total of 52 seals have been 

observed with embedded hooks in the MHI during 1989-2008 (including 9 in 2008, of which 3 constituted serious 

injuries entered in Table 1). Several incidents, including the dead hooked seal mentioned above, involved hooks 

used to catch ulua (jacks, Caranx spp.). Interactions in the MHI appear to be on the rise, as most reported hookings 

have occurred since 2000, and five seals have been observed entangled in nearshore gillnets during 2002-2008 

(NMFS unpubl. data). The MHI bottomfish handline fishery may also interact indirectly with monk seals as 

evidenced by fatty acid research, though no mortality or serious injuries have been attributed to the fishery (Table 

1). 

 In the past, monk seal interactions with fisheries in the NWHI were documented, but direct interactions 

have since become rare or non-existent, and issues related to competition have also somewhat abated. Possible 

reduction of monk seal prey by the NWHI lobster fishery has also been raised as a concern, though whether the 

fishery indirectly impacted monk seals remains unresolved. However, the NWHI lobster fishery closed in 2000 and 

on June 15, 2006, the Northwestern Hawaiian Islands (later renamed Papahanaumokuokea) Marine National 

Monument was established. Subsequent regulations prohibit commercial fishing in the Monument except for the 

bottomfish fishery (and associated pelagic species catch), which may continue until 2011 (U.S. Department of 

Commerce and Department of the Interior, 2006). In the past, interactions between the Hawaii-based domestic 

pelagic longline fishery and monk seals were documented (NMFS 2002). This fishery targets swordfish and tunas 

and does not compete with Hawaiian monk seals for prey. In October 1991, in response to 13 unusual seal wounds 

thought to have resulted from interactions with this fishery, NMFS established a Protected Species Zone extending 

50 nautical miles around the NWHI and the corridors between the islands. Subsequently, no additional monk seal 

interactions with either the swordfish or tuna components of the longline fishery have been observed. The NWHI 

bottomfish handline fishery landed between 66 and 201 metric tons per year from 1989-2008 (Kawamoto 1995; 

Kawamoto, pers. comm.) and the number of vessels is currently capped at 9 (8 made NWHI trips in 2008, 

Kawamoto, pers. comm.). Nitta and Henderson (1993) documented reports of seals taking bottomfish and bait off 

fishing lines, and reports of seals attracted to discarded bycatch. A Federal observer program of the fishery began in 

the fourth quarter of 2003 and no monk seal interactions were observed through the program's conclusion in 2006. 

NMFS 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 Biological 

Opinion has no incidental take statement. An EIS for the bottomfish fishery management plan has also been 

prepared. Fishermen indicate that they have engaged in mitigating activity over the past several years, e.g., holding 

discards on-board, etc. (NMFS pers. comm.). The ecological effects of this fishery on monk seals (e.g., competition 

for prey or alteration of prey assemblages) are unknown. However, published studies on monk seal prey selection 

based upon scat/spew analysis and seal-mounted video revealed some 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, Longenecker et al. 2006, Parrish et al. 2000). Recent quantitative 

fatty acid signature analysis (QFASA) results support previous studies illustrating that monk seals consume a wide 

range of species. However, deepwater-slope species, including two commercially targeted bottomfishes and other 

species not caught in the fishery, were estimated to comprise a large portion of the diet for some individuals. Similar 

species were estimated to be consumed by seals regardless of location, age or gender, but the relative importance of 

each species varied. Diets differed considerably between individuals. These results highlight the need to better 

understand potential ecological interactions with the Hawaiian bottomfish fishery. 

Fishery Mortality Rate

 Total fishery mortality and serious injury cannot be considered to be insignificant and approaching a rate of 

zero. Monk seals are being hooked and entangled in the MHI at a rate which has not been reliably assessed but is 

certainly greater than zero. The information above represents only reported direct interactions, and without purposedesigned observation effort the true interaction rate cannot be estimated. Monk seals also die from entanglement in 

fishing gear and other debris throughout their range (likely originating from various countries), and NMFS along 

with partner agencies is pursuing a program to mitigate entanglement (see below). Indirect interactions (i.e., 

involving competition for prey or consumption of discards) remain the topic of ongoing investigation. 

 

44
Table 1. Summary of mortality and serious injury of Hawaiian monk seals due to fisheries and calculation of annual 

mortality rate. n/a indicates that sufficient data are not available. 

Fishery Name Year Data 

Type 

% Obs. 

coverage 

Observed/Reported 

Mortality/Serious Injury 

Estimated 

Mortality/ 

Serious Injury 

Mean 

Takes 

(CV) 

 

Pelagic 

Longline 

 2004 

2005 

2006 

2007 

2008 

observer 

observer 

observer 

observer 

observer 

24.6% 

26.1% & 

100%1

22.1% & 100%1 

20.1% & 100%1 

21.7 %1 % & 100

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 (0) 

NWHI 

Bottomfish observer 3.9% 0 

0 (0) 

2004 

2005 

2006 

observer 

observer 

18.3% 

25.0% 

0 

0 

0 

0 

0 

MHI 

Bottomfish2 n/a none n/a n/a 

2004 

2005 

2006 

2007 

2008 

0 

0 

0 

0 

0 

Nearshore3 n/a none 

3 

n/a n/a 

2004 

2005 

2006 

2007 

2008 

2 

1 

1 

1 

 

Entanglement in Marine Debris

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

other pinnipeds (Henderson 2001). A total of 289 cases of seals entangled in fishing gear or other debris have been 

observed through 2008 (Henderson 2001; NMFS, unpubl. data), including eight documented deaths resulting from 

entanglement in marine debris (Henderson 1990, 2001; NMFS, unpubl. data). The fishing gear fouling the reefs and 

beaches of the NWHI and entangling monk seals only rarely includes types used in Hawaii fisheries. For example, 

trawl net and monofilament gillnet accounted for approximately 35% and 34% of the debris removed from reefs in 

the NWHI by weight, and trawl net alone accounted for 88% of the debris by frequency (Donohue et al. 2001). Yet 

tr heries have been prohibited in Hawaii since the 1980s. 

 The NMFS and partner agencies continue 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. Since 1996, annual debris survey and removal efforts 

awl fis

 the NWHI coral reef habitat have been ongoing (Donohue et al. 2000, Donohue et al. 2001). 

ther M

ought 

toll, 87

French Frigate Shoals, but such mortality was probably not the primary cause of the decline at this site (Ragen 

 

in

O ortality

 Since 1982, 23 seals died during rehabilitation efforts that ceased in 1994. Additionally, two died in 

captivity, two died when captured for translocation, one was euthanized (an aggressive male known to cause 

mortality), four died during captive research and four died during field research (Baker and Johanos 2002; NMFS 

unpubl. data). Other sources of mortality that impede recovery include food limitation (see Habitat Issues below), 

single and intra-species multiple-male aggression (mobbing), shark predation, and disease/parasitism. Multiple-male 

aggression has primarily been identified as a problem at Laysan and Lisianski Islands, though it has also been 

documented at other subpopulations. In 1994, 22 adult males were removed from Laysan Island, and 11 seals are 

th to have died from multiple-male aggression at this site since their removal (1995-2008). 

 Attacks by single adult male seals have resulted in several monk seal deaths, most notably at French Frigate 

Shoals in 1997, where at least 8 pups died from this cause. Many more pups were likely killed in the same way but 

the cause of their deaths could not be confirmed. Two males that killed pups in 1997 were translocated to Johnston 

A 0 km to the southwest. Subsequently, mounting injury to pups has decreased. 

 Shark-related injury and mortality incidents appeared to have increased in the late 1980s and early 1990s at 

1 Observer coverage for deep and shallow-set components of the fishery, respectively 2

 Data for MHI bottomfish and nearshore fisheries are based upon incidental observations (i.e., hooked seals). All 

hookings not clearly attributable to either fishery with certainty were attributed to the bottomfish fishery, and 

hookings which resulted in injury of unknown severity were classified as serious.

45
1993). However, shark predation has accounted for a significant portion of pup mortality in recent years. At French 

Frigate Shoals in 1999, 17 pups were observed injured by large sharks, and at least 3 were confirmed to have died 

from shark predation (Johanos and Baker 2001). As many as 22 pups of a total 92 born at French Frigate Shoals in 

1999 were likely 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. While disease 

effects on monk seal demographic trends are uncertain, there is concern that diseases of livestock, feral animals, pets 

or humans could be transferred to naive monk seals in the MHI and potentially spread to the core population in the 

NWHI. In 2003 and 2004, two deaths of free-ranging monk seals were attributable to diseases not previously found 

in the species: leptospirosis and toxoplasmosis (R. Braun, pers. comm.). Leptospira bacteria are found in many of 

Hawaii's streams and estuaries and are associated with livestock and rodents. Cats, domestic and feral, are a 

common source of toxoplasma. 

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 well below its OSP and has not 

recovered from past declines. Therefore, the Hawaiian monk seal is characterized as a strategic stock. 

Habitat Issues

 Poor juvenile survival rates and variability in the relationship between weaning size and survival suggest 

that prey availability is likely limiting recovery of NWHI monk seals (Baker and Thompson 2007, Baker et al. 2007, 

Baker 2008). A variety of strategies for improving juvenile survival are being considered and will be developed 

through an experimental approach in coming years (Baker and Littnan 2008). A major habitat issue involves loss of 

terrestrial habitat at French Frigate Shoals, where pupping and resting islets have shrunk or virtually disappeared 

(Antonelis et al. 2006). Projected increases in global average sea level may further significantly reduce terrestrial 

habitat for monk seals in the NWHI (Baker, Littnan and Johnston, 2006). 

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

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

satellite telemetry (Stewart et al. 2006). Preliminary studies to describe the foraging habitat of monk seals in the 

MHI are reported in Littnan et al. (2006). 

 Tern Island is the site of a USFWS refuge station and is one of two sites in the NWHI accessible by 

aircraft. During World War II, the U.S. Navy enlarged the island to accommodate the runway, and a sheet-pile 

seawall was constructed to maintain the modified shape of the island. Degradation of the seawall created entrapment 

hazards for seals and other wildlife. Erosion of the sea wall also raised concerns about the potential release of toxic 

wastes into the ocean. The USFWS began construction on the Tern Island sea wall in 2004 to reduce entrapment 

hazards and protect the island shoreline. Vessel groundings pose a continuing threat to monk seals and their habitat, 

through potential physical damage to reefs, oil spills, and release of debris into habitats. 

 Monk seal abundance is likely increasing in the main Hawaiian Islands (Baker et al. in review). Further, the 

excellent condition of pups weaned on these islands suggests that there may be ample prey resources available, 

perhaps in part due to fishing pressure that has reduced monk seal competition with large fish predators (sharks and 

jacks) (Baker and Johanos 2004). If the monk seal population continues to expand in the MHI, it may bode well for 

the species’ recovery and long-term persistence. In contrast, there are many challenges that may limit the potential 

for growth in this region. The human population in the MHI is approximately 1.2 million compared to fewer than 

100 in the NWHI, so that the potential impact of disturbance in the MHI is great. Also, the same fishing pressure 

that may have reduced the monk seal’s competitors, is a source of injury and mortality. Finally, vessel traffic in the 

populated islands carries the potential for collision with seals and impacts from oil spills. Thus, issues surrounding 

monk seals in the main Hawaiian Islands will likely become an increasing focus for management and recovery of 

this species. 

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Otis, D. L., K. P. Burnham, G. C. White, and D. R. Anderson. 1978. Statistical inference from capture data on 

closed animal populations. Wildl. Monogr. 62:1-135. 

Parrish, F. A., M. P. Craig, T. J. Ragen, G. J. Marshall, and B. M. Buhleier. 2000. Identifying diurnal foraging 

habitat of endangered Hawaiian monk seals using a seal-mounted video camera. Mar. Mamm. Sci. 16:392-

412. 

Pooley, S. G., and K. E. . 1998. Annual report of the 1995-97 western Pacific lobster fishery. Admin. Rep. H-98-

09. Southwest Fisheries Science Center, National Marine Fisheries Service, 2570 Dole St., Honolulu, HI 

96822-2396. 34 pp. 

Ragen, T. J. 1993. Status of the Hawaiian monk seal in 1992. Admin. Rep. H-93-05. Southwest Fisheries Science 

Center, National Marine Fisheries Service, 2570 Dole St., Honolulu, HI 96822-2396. 79 pp. 

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

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

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

Rexstad, E. A., and K. P. Burnham. 1991. User's manual for interactive Program CAPTURE. Colorado 

Cooperative Fish and Wildlife Research Unit, Colorado State University, Fort Collins, CO. 29 pp. 

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

Schultz J.K., Baker J.D., Toonen RJ, Bowen BW. 2009. Extremely low genetic diversity in the endangered 

Hawaiian monk seal (Monachus schauinslandi). Journal of Heredity 100:25-33. 

Schultz J.K., Baker J.D., Toonen RJ, Bowen BW (in review) Weak stock structure in a sea of connectivity: the case 

of the critically endangered Hawaiian monk sea. Conservation Biology . 

Stewart B. S., G. A. Antonelis, J. D. Baker, and P.Y.Yochem. 2006. Foraging biogeography of the Hawaiian monk 

seal in the Northwestern Hawaiian Islands. Atoll Res Bull 543:131-145. 

U.S. Department of Commerce and Department of the Interior. 2006. Northwestern Hawaiian Islands Marine 

National Monument. Federal Register 71:51,134-51,142. 

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

Workshop April 3-5, 1996, Seattle, Washington. U. S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR12. 93 pp. 

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

Mammal Science 14:1-37. 

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

White, G. C., D. R. Anderson, K. P. Burnham, and L. Otis. 1982. Capture-recapture and removal methods for 

sampling closed populations. Los Alamos National Laboratory, Los Alamos, New Mexico. 

48
Revised 10/15/2009 

HARBOR PORPOISE (Phocoena phocoena): Morro Bay Stock 

STOCK DEFINITION AND GEOGRAPHIC RANGE

 In the Pacific, harbor 

porpoise are found in coastal and 

inland waters from Point Conception, 

California to Alaska and across to 

Kamchatka and Japan (Gaskin 1984). 

Harbor porpoise appear to have more 

restricted movements along the 

western coast of the continental U.S. 

than along the eastern coast. 

Regional differences in pollutant 

residues in harbor porpoise indicate 

that they do not move extensively 

between California, Oregon, and 

Washington (Calambokidis and 

Barlow 1991). That study also 

showed some regional differences 

within California (although the 

sample size was small). This pattern 

stands as a sharp contrast to the 

eastern coast of the U.S. and Canada 

where harbor porpoise are believed to 

migrate seasonally from as far south 

as the Carolinas to the Gulf of Maine 

and Bay of Fundy (Polacheck et al. 

1995). A phylogeographic analysis 

of genetic data from northeast Pacific 

harbor porpoise did not show 

complete concordance between DNA 

sequence types and geographic location 

(Rosel 1992). However, an analysis of 

molecular variance (AMOVA) of the 

same data with additional samples 

found significant genetic differences for four of the six pair-wise comparisons between the four areas 

investigated: California, Washington, British Columbia, and Alaska (Rosel et al. 1995). These results 

demonstrate that harbor porpoise along the west coast of North America are not panmictic or migratory, 

and movement is sufficiently restricted that genetic differences have evolved. Recent preliminary genetic 

analyses of samples ranging from Monterey Bay, California to Vancouver Island, British Columbia indicate 

that there is small-scale subdivision within the U.S. portion of this range (Chivers et al., 2002, 2007). 

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, 2007), California coast stocks were re-evaluated, and 

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

presented here based on these genetic data and density discontinuities identified from aerial surveys, 

resulting in six California/Oregon/Washington stocks where previously there had been four (Carretta et al.

2001a). The stock boundaries for animals that occur in California/southern Oregon waters are shown in 

Figure 1. Stock boundaries and distributional range of 

harbor porpoise along the California and southern Oregon 

coasts. Dashed line represents harbor porpoise habitat (0-

200 m) in this region. 

OREGON

San Diego

CALIFORNIA Monterey

MORRO BAY

MONTEREY BAY

SAN FRANCISCO - 

RUSSIAN RIVER

NORTHERN CA -

SOUTHERN OR

Point Arena

Point Conception

Cape Blanco

1250’0"W 1200’0"W

450’0"N

400’0"N

Lincoln City

350’0"N

49
Figure 1. For the 2009 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, 

Northern Oregon/Washington coast, and Inland Washington waters harbor porpoise appear in this volume. 

The three Alaska harbor porpoise stocks are reported separately in the Stock Assessment Reports for the 

Alaska Region. 

POPULATION SIZE

 Previous estimates of abundance for California harbor porpoise were based on aerial surveys 

conducted between the coast and the 50-fm isobath during 1988-95 (Barlow and Forney 1994, Forney 

1999a). These estimates did not include an unknown number of animals found in deeper waters. Barlow 

(1988) found that the vast majority of harbor porpoise in California were within the 0-50-fm depth range; 

however, Green et al. (1992) found that 24% of harbor porpoise seen during aerial surveys of Oregon and 

Washington were between the 100m and 200m isobaths (55 to 109 fathoms). A systematic ship survey of 

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

waters deeper than 60 m (Carretta et al. 2001b). A recent analysis of harbor porpoise trends including 

oceanographic data suggests that the proportion of California harbor porpoise in deeper waters may vary 

between years (Forney 1999b). Since 1999 aerial surveys have 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 2002-2007 aerial surveys conducted under good survey 

conditions (Beaufort 2, cloud cover 25%) the estimate of abundance for this stock is 2,044 animals (CV 

= 0.40) (Carretta et al., 2009.). 

 

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 2002-2007 aerial 

surveys, or 1,478 animals. 

Current Population Trend

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

which is statistically significant (p < 0.002), Figure 2. The observed increase in abundance estimates for 

this stock since 1988 implies an annual population growth rate of approximately 13%, which is consistent 

with the median growth rate of 10% reported by Caswell et al. (1998) for Atlantic harbor porpoise and high 

reproductive rates reported for this species by Read and Hohn (1995). It is possible that some of the 

observed growth of the Morro Bay stock is partly due to emigration of animals from the Monterey Bay 

stock. 

 

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). 

50
1990 1995 2000 2005

0 1000 3000 5000 7000

Morro Bay

Year

Porpoise Abundance

Figure 2. Aerial survey annual estimates of abundance for the Morro Bay stock of harbor porpoise 

(inshore stratum only), 1988-2007. Error bars represent lower and upper 95% confidence intervals. Solid 

line represents a linear regression on the natural logarithm of abundance over time. The slope of this 

regression is statistically significant (p < 0.002, r2

 = 0.83). 

POTENTIAL BIOLOGICAL REMOVAL

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

population size (1,478) 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 

15. 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Fishery Information

 Gillnet fisheries for halibut and white seabass that historically operated in the vicinity of Morro 

Bay were eliminated in this stock’s range in 2002 by a ban on gillnets inshore of 60 fathoms (~110 m) from 

Point Arguello to Point Reyes, California. The large-mesh drift gillnet fishery for swordfish and thresher 

shark operates too far offshore to interact with harbor porpoise in this region. Since 2002, fishery-related 

strandings of harbor porpoise have been recorded north of this stock’s range. The responsible fisheries 

have not been identified and the locations of the strandings indicate that the animals are from stocks to the 

north (see Monterey Bay, San Francisco – Russian River, and Northern California/Southern Oregon stock 

assessments). 

STATUS OF STOCK

Harbor porpoise in California are not listed as threatened or endangered under the Endangered 

Species Act nor as depleted under the Marine Mammal Protection Act. Barlow and Hanan (1995) calculate 

the status of harbor porpoise relative to historic carrying capacity (K) using a technique called backprojection. They calculate that the central California population (including Morro Bay, Monterey Bay, and 

San Francisco-Russian River stocks) could have been reduced to between 30% and 97% of K by incidental 

fishing mortality, depending on the choice of input parameters. They conclude that there is no practical 

way to reduce the range of this estimate. New information does not change this conclusion, and the status 

51
of central California harbor porpoise populations relative to their Optimum Sustainable Population (OSP) 

levels must be treated as unknown. 

 No fishery-related mortality of harbor porpoise has been documented within this stock’s range 

between 2003 and 2007. Current fishery mortality is zero and can be considered insignificant and 

approaching zero mortality rate. The stock is considered non-strategic and the population appears to have 

grown at approximately 11% annually since surveys began in the late 1980s. 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., K.A. Forney, and S.R. Benson. 2009. Preliminary estimates of harbor porpoise abundance 

in California waters from 2002 to 2007. NOAA Technical Memorandum, NOAA-TM-NMFSSWFSC-435. 10 p. 

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

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

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

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

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

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

Bulletin 99:29-39. 

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

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

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

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

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

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

International Whaling Commission (unpublished). 21pp. 

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

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

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

Caswell, H., S. Brault, A. Read, and T. Smith. 1998. Harbor porpoise and fisheries: an uncertainty 

analysis of incidental mortality. Ecological Applications 84(4):1226-1238. 

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. 

Chivers, S.J., B. Hanson, J. Laake, P. Gearin, M.M. Muto, J. Calambokidis, D. Duffield, T. McGuire, J. 

Hodder, D. Greig, E. Wheeler, J. Harvey, K.M. Robertson, and B. Hancock. 2007. Additional 

genetic evidence for population structure of Phocoena phocoena off the coasts of California, 

Oregon, and Washington. Southwest Fisheries Science Center Administrative Report LJ-07-08. 

16pp. 

Forney, K. A. 1999a. The abundance of California harbor porpoise estimated from 1993-97 aerial linetransect surveys. Admin. Rep. LJ-99-02. Southwest Fisheries Center, National Marine Fisheries 

Service, P.O. Box 271, La Jolla, CA 92038. 16 pp. 

52
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. 

Read, A.J. and A.A. Hohn. 1995. Life in the fast lane: the life history of harbor porpoises from the Gulf 

of Maine. Marine Mammal Science 11(4):423-440. 

Rosel, P. E. 1992. Genetic population structure and systematic relationships of some small cetaceans 

inferred from mitochondrial DNA sequence variation. Ph.D. Dissertation, Univ. Calif. San Diego. 

191pp. 

Rosel, P. E., A. E. Dizon, and M. G. Haygood. 1995. Variability of the mitochondrial control region in 

populations of the harbour porpoise, Phocoena phocoena, on inter-oceanic and regional scales. 

Can. J. Fish. and Aquat. Sci. 52:1210-1219. 

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

GAMMS Workshop April 3-5, 1996, Seattle, Washington. U. S. Dep. Commer., NOAA Tech. 

Memo. NMFS-OPR-12. 93 pp. 

Woodley, T. H. and A. J. Read. 1991. Potential rates of increase of a harbour porpoise (Phocoena 

phocoena) population subjected to incidental mortality in commercial fisheries. Can. J. Fish. 

Aquat. Sci. 48:2429-2435.

53
Revised 10/15/2009 

HARBOR PORPOISE (Phocoena phocoena): Monterey Bay Stock 

STOCK DEFINITION AND GEOGRAPHIC RANGE

 In the Pacific, harbor 

porpoise are found in coastal and 

inland waters from Point Conception, 

California to Alaska and across to 

Kamchatka and Japan (Gaskin 1984). 

Harbor porpoise appear to have more 

restricted movements along the 

western coast of the continental U.S. 

than along the eastern coast. 

Regional differences in pollutant 

residues in harbor porpoise indicate 

that they do not move extensively 

between California, Oregon, and 

Washington (Calambokidis and 

Barlow 1991). That study also 

showed some regional differences 

within California (although the 

sample size was small). This pattern 

stands as a sharp contrast to the 

eastern coast of the U.S. and Canada 

where harbor porpoise are believed to 

migrate seasonally from as far south 

as the Carolinas to the Gulf of Maine 

and Bay of Fundy (Polacheck et al. 

1995). A phylogeographic analysis 

of genetic data from northeast Pacific 

harbor porpoise did not show 

complete concordance between DNA 

sequence types and geographic location 

(Rosel 1992). However, an analysis of 

molecular variance (AMOVA) of the 

same data with additional samples 

found significant genetic differences for 

four of the six pair-wise comparisons between the four areas investigated: California, Washington, British 

Columbia, and Alaska (Rosel et al. 1995). These results demonstrate that harbor porpoise along the west 

coast of North America are not panmictic or migratory, and movement is sufficiently restricted that genetic 

differences have evolved. Recent preliminary genetic analyses of samples ranging from Monterey Bay, 

California to Vancouver Island, British Columbia indicate that there is small-scale subdivision within the 

U.S. portion of this range (Chivers et al., 2002, 2007). 

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, 2007), California coast stocks were re-evaluated, and 

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

presented here based on these genetic data and density discontinuities identified from aerial surveys, 

resulting in six California/Oregon/Washington stocks where previously there had been four (Carretta et al.

Figure 1. Stock boundaries and distributional range of 

harbor porpoise along the California/southern Oregon 

coast. Dashed line represents harbor porpoise habitat (0-

200 m) along the U.S. west coast. 

OREGON

San Diego

CALIFORNIA Monterey

MORRO BAY

MONTEREY BAY

SAN FRANCISCO - 

RUSSIAN RIVER

NORTHERN CA -

SOUTHERN OR

Point Arena

Point Conception

Cape Blanco

1250’0"W 1200’0"W

450’0"N

400’0"N

Lincoln City

350’0"N

54
2001a). The stock boundaries for animals that occur in California/southern Oregon waters are shown in 

Figure 1. For the 2009 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 Morro Bay, San Francisco-Russian River, northern California/southern 

Oregon, Oregon/Washington coast, and Inland Washington waters harbor porpoise appear in this volume. 

The three Alaska harbor porpoise stocks are reported separately in the Stock Assessment Reports for the 

Alaska Region. 

POPULATION SIZE

 Previous estimates of abundance for California harbor porpoise were based on aerial surveys 

conducted between the coast and the 50-fm isobath during 1988-95 (Barlow and Forney 1994, Forney 

1999a). These estimates did not include an unknown number of animals found in deeper waters. Barlow 

(1988) found that the vast majority of harbor porpoise in California were within the 0-50-fm depth range; 

however, Green et al. (1992) found that 24% of harbor porpoise seen during aerial surveys of Oregon and 

Washington were between the 100m and 200m isobaths (55 to 109 fathoms). A systematic ship survey of 

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

waters deeper than 60 m (Carretta et al. 2001b). A recent analysis of harbor porpoise trends including 

oceanographic data suggests that the proportion of California harbor porpoise in deeper waters may vary 

between years (Forney 1999b). Starting 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 2002-2007 aerial surveys under good survey conditions 

(Beaufort 2, cloud cover 25%) the estimate of abundance for this stock is 1,492 animals (CV=0.40) 

(Carretta et al., 2009). 

 

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 2002-2007 aerial 

surveys, or 1,079 animals. 

Current Population Trend 

 Abundance estimates from aerial surveys conducted between 1988 and 2007 show evidence of a declining 

trend, though this decline is not statistically significant and it should be noted that survey effort in 2007 was 

sparse compared to previous years (Figure 2). 

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES 

 Based on what are argued to be biological limits of the species (i.e. females give birth first at age 4 

and produce one calf per year until death), the theoretical, maximum-conceivable growth rate of a closed 

harbor porpoise population was estimated as 9.4% per year (Barlow and Boveng 1991). This maximum 

theoretical rate may not be achievable for any real population. [Woodley and Read (1991) calculate a 

maximum growth rate of approximately 5% per year, but their argument for this being a maximum (i.e. that 

porpoise survival rates cannot exceed those of Himalayan thar) is not well justified.] Population growth 

rates have not actually been measured for any harbor porpoise population. Because a reliable estimate of 

the maximum net productivity rate is not available for 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 (1,079) times one half the default maximum net growth rate for cetaceans (1⁄2 of 4%) times

a recovery factor of 0.45 (for a stock of unknown status with known fishery mortality and unknown fishery 

mortality CV; Wade and Angliss 1997), resulting in a PBR of 10. 

55
1990 1995 2000 2005

0 1000 2000 3000 4000 5000

Monterey Bay

Year

Porpoise Abundance

Figure 2. Aerial survey annual estimates of abundance for the Monterey Bay stock of harbor porpoise, 

1988- 2007 (inshore stratum only). Error bars represent lower and upper 95% confidence intervals. Solid 

line represents a linear regression of the natural logarithm of abundance over time. The slope of this 

regression is not statistically significant (p = 0.08, r2

 = 0.24).

 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Fishery Information

 A 2002 ban on gillnets inshore of the 60 fathom (110 m) isobath was thought to eliminate the 

potential for harbor porpoise mortality to near zero in this stock’s range. However, there have been five 

observed harbor porpoise strandings in this stock’s range between 2003 and 2007 (three in 2004 and two in 

2005) that showed evidence of fishery interactions, such as gillnet-like markings on the carcass or fishing 

line and hooks wrapped around the body. The responsible fisheries are unknown. 

Table 1. Summary of available on incidental mortality and injury of harbor porpoise in commercial 

fisheries that might take this species. Mean annual takes are based on 2003-2007 data. 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)

Unidentified fisheries 2003-2007 Stranding n/a 5 n/a ≥5 ≥ 1.0 (n/a) 

Minimum total annual takes ≥ 1.0 (n/a)

56
STATUS OF STOCK

 Harbor porpoise in California are not listed as threatened or endangered under the Endangered 

Species Act nor as depleted under the Marine Mammal Protection Act. Barlow and Hanan (1995) calculate 

the status of harbor porpoise relative to historic carrying capacity (K) using a technique called backprojection. They calculate that the central California population could have been reduced to between 30% 

and 97% of K by incidental fishing mortality, depending on the choice of input parameters. They conclude 

that there is no practical way to reduce the range of this estimate. New information does not change this 

conclusion, and the status of harbor porpoise relative to their Optimum Sustainable Population (OSP) levels 

in central California must be treated as unknown. 

 Fishery-related mortality of harbor porpoise still occurs in this stock’s range, though the bycatch 

levels and responsible fisheries are unknown. Because the overall level of fishery mortality is unknown 

relative to the PBR it cannot be considered to be insignificant and approaching zero mortality and injury 

rate. Although there is uncertainty regarding the observed levels of fishery-related mortality for this stock, 

documented mortality is less than the PBR, thus this stock is not considered “strategic” under the MMPA. 

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., K.A. Forney, and S.R. Benson. 2009. . Preliminary estimates of harbor porpoise abundance 

in California waters from 2002 to 2007. NOAA Technical Memorandum, NOAA-TM-NMFSSWFSC-435. 10 p. 

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

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

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

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

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

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

International Whaling Commission (unpublished). 21pp. 

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

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

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

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

Bulletin 99:29-39. 

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

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

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

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

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

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

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

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

57
Forney, K. A. 1999a. The abundance of California harbor porpoise estimated from 1993-97 aerial linetransect surveys. Admin. Rep. LJ-99-02. Southwest Fisheries Center, National Marine Fisheries 

Service, P.O. Box 271, La Jolla, CA 92038. 16 pp. 

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

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

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

information on direct and indirect catches. Rep. int. Whal. Commn 34:569_586. 

Green, G. A., J. J. Brueggeman, R. A. Grotefendt, C. E. Bowlby, M. L. Bonnell, and K. C. Balcomb, III. 

1992. Cetacean distribution and abundance off Oregon and Washington, 1989-1990. Ch. 1 In: J. 

J. Brueggeman (ed.). Oregon and Washington Marine Mammal and Seabird Surveys. Minerals 

Management Service Contract Report 14-12-0001-30426 prepared for the Pacific OCS Region. 

Laake, J. L., J. C. Calambokidis, S. D. Osmek, and D. J. Rugh. 1997. Probability of detecting harbor 

porpoise from aerial surveys: estimating g(0). J. Wildl. Manag. 61:63-75. 

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

NMFS, Southwest Region, 501 West Ocean Blvd, Long Beach, CA 90802_4213 

Polacheck, T., F. W. Wenzel, and G. Early. 1995. What do stranding data say about harbor porpoise 

(Phocoena phocoena). Rep. Int. Whal. Comm., Special Issue 16:169-179. 

Rosel, P. E. 1992. Genetic population structure and systematic relationships of some small cetaceans 

inferred from mitochondrial DNA sequence variation. Ph.D. Dissertation, Univ. Calif. San Diego. 

191pp. 

Rosel, P. E., A. E. Dizon, and M. G. Haygood. 1995. Variability of the mitochondrial control region in 

populations of the harbour porpoise, Phocoena phocoena, on inter-oceanic and regional scales. 

Can. J. Fish. and Aquat. Sci. 52:1210-1219. 

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

GAMMS Workshop April 3-5, 1996, Seattle, Washington. U. S. Dep. Commer., NOAA Tech. 

Memo. NMFS-OPR-12. 93 pp. 

Woodley, T. H. and A. J. Read. 1991. Potential rates of increase of a harbour porpoise (Phocoena 

phocoena) population subjected to incidental mortality in commercial fisheries. Can. J. Fish. 

Aquat. Sci. 48:2429-2435. 

58
Revised 10/15/2009 

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, 2007). 

 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, 2007), California coast stocks were re-evaluated, and 

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

presented here based on these genetic data and density discontinuities identified from aerial surveys, 

Figure 1. Stock boundaries and distributional range 

of harbor porpoise along the California and southern 

Oregon coasts. Dashed line represents harbor 

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

OREGON

San Diego

CALIFORNIA Monterey

MORRO BAY

MONTEREY BAY

SAN FRANCISCO - 

RUSSIAN RIVER

NORTHERN CA -

SOUTHERN OR

Point Arena

Point Conception

Cape Blanco

1250’0"W 1200’0"W

450’0"N

400’0"N

Lincoln City

350’0"N

59
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 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). Since 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. Based on 2002-2007 aerial surveys under good survey 

conditions (Beaufort 2, cloud cover 25%) the estimate of abundance for this stock is 9,189 animals 

(CV= 0.38) (Carretta et al., 2009 ).

 

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 2002-

2007 aerial surveys, or 6,745 animals. 

Current Population Trend

 Abundance of the San Francisco - Russian River harbor porpoise stock appeared to be stable or declining 

between 1988-1991 and has steadily increased since 1993, however the slope of the linear regression on the 

natural logarithm of abundance over time is not statistically significant (p = 0.14, Figure 2). 

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

 Based on what are argued to be biological limits of the species (i.e. females give birth first at age 4 

and produce one calf per year until death), the theoretical, maximum-conceivable growth rate of a closed 

harbor porpoise population was estimated as 9.4% per year (Barlow and Boveng 1991). This maximum 

theoretical rate may not be achievable for any real population. [Woodley and Read (1991) calculate a 

maximum growth rate of approximately 5% per year, but their argument for this being a maximum (i.e. that 

porpoise survival rates cannot exceed those of Himalayan thar) is not well justified.] Population growth 

rates have not actually been measured for any harbor porpoise population. Because a reliable estimate of 

the maximum net productivity rate is not available for northern California harbor porpoise, we use the 

default maximum net productivity rate (RMAX) of 4% for cetaceans (Wade and Angliss 1997). 

POTENTIAL BIOLOGICAL REMOVAL

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

population size (6,745) 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 

67. 

60
1990 1995 2000 2005

0 5000 10000 15000 20000

San Francisco - Russian River

Year

Porpoise Abundance

Figure 2. Aerial survey annual estimates of abundance for the San Francisco – Russian River stock of 

harbor porpoise (inshore stratum only), 1988- 2007. Error bars represent lower and upper 95% confidence 

intervals. Solid line represents a linear regression of the natural logarithim of abundance over time. The 

slope of this regression line is not statistically significant (p = 0.24, r2

=0.17) 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Fishery Information

 Although coastal gillnets are prohibited throughout this stock’s range, there have been fisheryrelated strandings in past years. No fishery-related strandings occurred during the most recent five-year 

period (2003-2007) but did occur to the north and south of this stock’s range. It is possible that some of the 

fishery-related strandings recorded in the Monterey Bay area during the most recent five-year period were 

killed in the San Francisco – Russian River stratum and drifted south to their observed stranding locations. 

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. No fishery takes or 

fishery-related strandings were reported in this region between 2003 and 2007. 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

2003-2007 stranding n/a none n/a n/a 0 (n/a)

Minimum total annual takes 0 (n/a)

STATUS OF STOCK

 Harbor porpoise in California are not listed as threatened or endangered under the Endangered 

Species Act nor as depleted under the Marine Mammal Protection Act. Barlow and Hanan (1995) calculate 

the status of harbor porpoise relative to historic carrying capacity (K) using a technique called backprojection. They calculate that the central California population (including Morro Bay, Monterey Bay, and 

San Francisco-Russian River stocks) could have been reduced to between 30% and 97% of K by incidental 

61
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 (zero harbor porpoise per year) is less 

than the PBR (67), this stock is not considered a "strategic" stock under the MMPA. Because average 

annual fishery mortality is less than 10% of the PBR, the fishery mortality can be considered insignificant 

and approaching zero mortality and serious injury rate. 

REFERENCES

Barlow, J. 1988. Harbor porpoise (Phocoena phocoena) abundance estimation in California, Oregon and 

Washington: I. Ship surveys. Fish. Bull. 86:417-432. 

Barlow, J. and P. Boveng. 1991. Modeling age-specific mortality for marine mammal populations. Mar. 

Mamm. Sci. 7(1):84-119. 

Barlow, J. and K. A. Forney. 1994. An assessment of the 1994 status of harbor porpoise in California. 

U.S. Dep. Commer., NOAA Tech. Memo. NMFS-SWFSC-205. 17 pp. 

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

Rept. Int. Whal., Special Issue 16:123-140. 

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

describing population discreteness in harbor porpoises from Washington, Oregon, and California. 

pp. 101-110 In: J. E. Reynolds III and D. K. Odell (eds.) Marine mammal strandings in the United 

States. NOAA Tech. Rep. NMFS 98. 

Carretta, J.V., K.A. Forney, and S.R. Benson. 2009. Preliminary estimates of harbor porpoise abundance 

in California waters from 2002 to 2007. NOAA Technical Memorandum, NOAA-TM-NMFSSWFSC-435. 10 p. 

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

Stock Assessments: 2001. U.S. Dep. Commer. NOAA Technical Memorandum, NOAA-TMNMFS-SWFSC-317. 280 p. 

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

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

Bulletin 99:29-39. 

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

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

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

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

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

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

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

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

Chivers, S.J., B. Hanson, J. Laake, P. Gearin, M.M. Muto, J. Calambokidis, D. Duffield, T. McGuire, J. 

Hodder, D. Greig, E. Wheeler, J. Harvey, K.M. Robertson, and B. Hancock. 2007. Additional 

genetic evidence for population structure of Phocoena phocoena off the coasts of California, 

Oregon, and Washington. Southwest Fisheries Science Center Administrative Report LJ-07-08. 

16pp. 

Forney, K. A. 1999a. The abundance of California harbor porpoise estimated from 1993-97 aerial linetransect surveys. Admin. Rep. LJ-99-02. Southwest Fisheries Center, National Marine Fisheries 

Service, P.O. Box 271, La Jolla, CA 92038. 16 pp. 

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

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

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

information on direct and indirect catches. Rep. int. Whal. Commn 34:569_586. 

Green, G. A., J. J. Brueggeman, R. A. Grotefendt, C. E. Bowlby, M. L. Bonnell, and K. C. Balcomb, III. 

1992. Cetacean distribution and abundance off Oregon and Washington, 1989-1990. Ch. 1 In: J. 

J. Brueggeman (ed.). Oregon and Washington Marine Mammal and Seabird Surveys. Minerals 

Management Service Contract Report 14-12-0001-30426 prepared for the Pacific OCS Region. 

62
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. 

63
Revised 10/15/2009 

HARBOR PORPOISE (Phocoena phocoena): 

Northern California/Southern Oregon Stock 

STOCK DEFINITION AND 

GEOGRAPHIC RANGE

 In the Pacific, harbor porpoise are 

found in coastal and inland waters from 

Point Conception, California to Alaska and 

across to Kamchatka and Japan (Gaskin 

1984). Harbor porpoise appear to have more 

restricted movements along the western 

coast of the continental U.S. than along the 

eastern coast. Regional differences in 

pollutant residues in harbor porpoise 

indicate that they do not move extensively 

between California, Oregon, and 

Washington (Calambokidis and Barlow 

1991). That study also showed some 

regional differences within California 

(although the sample size was small). This 

pattern stands as a sharp contrast to the 

eastern coast of the U.S. and Canada where 

harbor porpoise are believed to migrate 

seasonally from as far south as the Carolinas 

to the Gulf of Maine and Bay of Fundy 

(Polacheck et al. 1995). A phylogeographic 

analysis of genetic data from northeast 

Pacific harbor porpoise did not show 

complete concordance between DNA 

sequence types and geographic location 

(Rosel 1992). However, an analysis of 

molecular variance (AMOVA) of the same 

data with additional samples found 

significant genetic differences for four of the 

six pair-wise comparisons between the four 

areas investigated: California, Washington, British Columbia, and Alaska (Rosel et al. 1995). These results 

demonstrate that harbor porpoise along the west coast of North America are not panmictic or migratory, 

and movement is sufficiently restricted that genetic differences have evolved. Recent preliminary genetic 

analyses of samples ranging from Monterey Bay, California to Vancouver Island, British Columbia indicate 

that there is small-scale subdivision within the U.S. portion of this range Chivers et al., 2002, 2007). 

 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, 2007), 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. The northern boundary of the Northern California/Southern 

Figure 1. Stock boundaries and distributional range of 

harbor porpoise along the California/southern Oregon 

coasts. Dashed line represents harbor porpoise habitat (0-

200 m) along the U.S. west coast.

OREGON

San Diego

CALIFORNIA Monterey

MORRO BAY

MONTEREY BAY

SAN FRANCISCO - 

RUSSIAN RIVER

NORTHERN CA -

SOUTHERN OR

Point Arena

Point Conception

Cape Blanco

1250’0"W 1200’0"W

450’0"N

400’0"N

Lincoln City

350’0"N

64
Oregon stock of harbor porpoise has been moved north to approximately the latitude of Lincoln City, 

Oregon, based on additional genetic analyses and a recommendation from the Pacific Regional Scientific 

Review Group to revise the boundary. 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 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). Since 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 2002-2007 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 39,581 harbor porpoise (CV=0.39). This estimate represents a combined estimate 

of aerial surveys completed between 2002-2007 by SWFSC (Carretta et al.2009) and unpublished data 

from the National Marine Mammal Laboratory. 

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 estimate obtained from 2002-

2007 aerial surveys, or 28,833 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

 Because the northern boundary of this stock has changed two times in recent years, trends in 

abundance have been examined only for the northern California portion of this stock. A possible increasing 

trend in abundance is apparent from surveys conducted between 1989 and 2007, but the trend is not 

statistically significant (Figure 2). 

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

 Based on what are argued to be biological limits of the species (i.e. females give birth first at age 4 

and produce one calf per year until death), the theoretical, maximum-conceivable growth rate of a closed 

harbor porpoise population was estimated as 9.4% per year (Barlow and Boveng 1991). This maximum 

theoretical rate may not be achievable for any real population. [Woodley and Read (1991) calculate a 

maximum growth rate of approximately 5% per year, but their argument for this being a maximum (i.e. that 

porpoise survival rates cannot exceed those of Himalayan thar) is not well justified.] Population growth 

rates have not actually been measured for any harbor porpoise population. Because a reliable estimate of 

the maximum net productivity rate is not available for northern California harbor porpoise, 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 (28,833) 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 577 . 

65
1990 1995 2000 2005

0 10000 20000 30000 40000

Northern California

Year

Porpoise Abundance

Figure 2. Aerial survey annual estimates of harbor porpoise abundance for the northern California inshore 

stratum, 1989-2007. Solid line represents a linear regression on the natural logarithim of abundance over 

time. The slope of this regression is not statistically significant (p = 0.21, r2

=0.22). 

HUMAN-CAUSED MORTALITY

Fishery Information

 There were 4 harbor porpoise strandings in this stock’s range that showed evidence of 

interactions with entangling net fisheries between 2003 and 2007. At least two of these were reported to be 

entangled in river salmon gillnet gear. There has been documented harbor porpoise mortality in the 

Klamath River tribal salmon gillnet fisheries as recently as 1995. It is possible that recent gillnet-related 

strandings in this area are attributable to that fishery. 

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)

Unknown fishery 2003-

2007 Stranding n/a 4 n/a ≥0.8 (n/a) 

Minimum total annual takes

≥0.8 (n/a)

 

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

66
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 (≥0.8 harbor porpoise per year) is less than the PBR (577), 

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., K.A. Forney, and S.R. Benson. 2009. Preliminary estimates of harbor porpoise abundance 

in California waters from 2002 to 2007. NOAA Technical Memorandum, NOAA-TM-NMFSSWFSC-435. 10 p. 

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

Stock Assessments: 2001. U.S. Dep. Commer. NOAA Technical Memorandum, NOAA-TMNMFS-SWFSC-317. 280p. 

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

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

Bulletin 99:29-39. 

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

describing population discreteness in harbor porpoises from Washington, Oregon, and California. 

pp. 101-110 In: J. E. Reynolds III and D. K. Odell (eds.) Marine mammal strandings in the United 

States. NOAA Tech. Rep. NMFS 98. 

Chivers, S.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. 

Chivers, S.J., B. Hanson, J. Laake, P. Gearin, M.M. Muto, J. Calambokidis, D. Duffield, T. McGuire, J. 

Hodder, D. Greig, E. Wheeler, J. Harvey, K.M. Robertson, and B. Hancock. 2007. Additional 

genetic evidence for population structure of Phocoena phocoena off the coasts of California, 

Oregon, and Washington. Southwest Fisheries Science Center Administrative Report LJ-07-08. 

16pp. 

Forney, K. A. 1999a. The abundance of California harbor porpoise estimated from 1993-97 aerial linetransect surveys. Admin. Rep. LJ-99-02. Southwest Fisheries Center, National Marine Fisheries 

Service, P.O. Box 271, La Jolla, CA 92038. 16 pp. 

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

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

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

information on direct and indirect catches. Rep. int. Whal. Commn 34:569_586. 

Green, G. A., J. J. Brueggeman, R. A. Grotefendt, C. E. Bowlby, M. L. Bonnell, and K. C. Balcomb, III. 

1992. Cetacean distribution and abundance off Oregon and Washington, 1989-1990. Ch. 1 In: J. 

J. Brueggeman (ed.). Oregon and Washington Marine Mammal and Seabird Surveys. Minerals 

Management Service Contract Report 14-12-0001-30426 prepared for the Pacific OCS Region. 

Laake, J. L., J. C. Calambokidis, S. D. Osmek, and D. J. Rugh. 1997. Probability of detecting harbor 

porpoise from aerial surveys: estimating g(0). J. Wildl. Manag. 61:63-75. 

Laake, J., J. Calambokidis, S. Osmek. 1998. Survey report for the 1997 aerial surveys for harbor porpoise 

and other marine mammals of Oregon, Washington, and British Columbia outside waters. Alaska 

Fisheries Science Center Processed Report 98-10. pp. 77-97. 

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

NMFS, Southwest Region, 501 West Ocean Blvd, Long Beach, CA 90802_4213 

67
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
Revised 10/15/2009

HARBOR PORPOISE (Phocoena phocoena): 

Northern Oregon/Washington Coast Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

 In the eastern North Pacific Ocean, harbor 

porpoise are found in coastal and inland waters from 

Point Barrow, along the Alaskan coast, and down the 

west coast of North America to Point Conception, 

California (Gaskin 1984). 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, suggest 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), seasonal 

movement patterns are not fully understood. 

 Investigation of pollutant loads in harbor 

porpoise ranging from California to the Canadian border 

suggests restricted harbor porpoise movements 

(Calambokidis and Barlow 1991). 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. Further genetic testing 

of the same data, 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 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, 2007). 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=6.9, P<0.001) between the waters of 

coastal Oregon/Washington and inland Washington/southern British Columbia, Canada (i.e., Strait of Juan de 

Fuca/San Juan Islands). Following a risk averse management strategy, two stocks were recognized in the waters of 

Oregon and Washington, with a boundary at Cape Flattery, Washington. Based on recent genetic evidence, which 

suggests that the population of eastern North Pacific harbor porpoise is more finely structured (Chivers et al. 2002, 

2007), stock boundaries on the Oregon/Washington coast have been revised, resulting in three stocks in 

Oregon/Washington waters: a Northern California/Southern Oregon stock (Point Arena, CA, to Lincoln City, OR), 

a Northern Oregon/Washington Coast stock (Lincoln City, OR, to Cape Flattery, WA), and the Washington Inland 

Figure 1. Stock boundaries (dashed lines) and 

approximate distribution (shaded areas) of harbor

porpoise along the coasts of Washington and 

northern Oregon.

Oregon

Washington

Lincoln City

Northern

Oregon/

Washington

Coast stock

Washington

Inland Waters

stock

Cape

Flattery

!

126°W

126°W 124°W 122°W 120°W

42°N

44°N

48°N

46°N

69
Waters stock (in waters east of Cape Flattery). Additional analyses are needed to determine whether to adjust the 

stock boundaries for harbor porpoise in Washington inland waters (Chivers et al. 2007). 

 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, 2007), 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 (e.g., Carretta et al. 2001): 1) the Washington Inland Waters stock, 2) the Northern 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. The stock boundaries for animals that occur in northern 

Oregon/Washington waters are shown in Figure 1. This report considers only the Northern Oregon/Washington 

Coast stock. Stock assessment reports for Washington Inland Waters, Northern California/Southern Oregon, San 

Francisco-Russian River, Monterey Bay, and Morro Bay harbor porpoise also appear in this volume. Stock 

assessment reports for the three harbor porpoise stocks in the inland and coastal waters of Alaska, including 1) the 

Southeast Alaska stock, 2) the Gulf of Alaska stock, and 3) the Bering Sea stock, 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 of the U.S. stock assessment reports. 

POPULATION SIZE

 In August and September 2002, an aerial survey of Oregon, Washington, and southern British Columbia 

coastal waters, from shore to 200 m depth, resulted in an uncorrected abundance estimate of 4,583 (CV=0.145) 

harbor porpoise in U.S. waters between Lincoln City, Oregon, and Cape Flattery, Washington (J. Laake, 

unpublished data). Using a correction factor of 3.42 (1/g(0); g(0)=0.292, CV=0.366) (Laake et al. 1997a), to adjust 

for groups missed by aerial observers, the corrected estimate of abundance for harbor porpoise in the coastal waters 

of northern Oregon (north of Lincoln City) and Washington is 15,674 (CV=0.394). 

Minimum Population Estimate

 The minimum population estimate for this stock is calculated as the lower 20th percentile of the log-normal 

distribution (Wade and Angliss 1997) of the 2002 population estimate of 15,674, which is 11,383 harbor porpoise. 

Current Population Trend

 There are no reliable data on population trends of harbor porpoise for coastal Oregon, Washington, or 

British Columbia waters; however, the uncorrected estimates of abundance for the Northern Oregon/Washington 

Coast stock in 1997 (6,406; SE=826.5) and 2002 (4,583) were not significantly different (Z=-1.73, P=0.08), 

although the survey area in 1997 (Regions I-S through III) was slightly larger than in 2002 (Strata D-G) (Laake et al. 

1998a; J. Laake, unpublished data). 

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 Northern 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 

(11,383) 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 114 harbor porpoise per year. 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Fisheries Information

 Within the EEZ boundaries of the coastal waters of northern Oregon and Washington, harbor porpoise 

deaths are known to occur in the northern Washington marine set (tribal) gillnet fishery. Total fishing effort in this 

fishery (areas 4, 4A, 4B, and 5) is conducted within the range of both harbor porpoise stocks (Northern 

Oregon/Washington Coast and Washington Inland Waters) occurring in Washington State waters (Gearin et al 

1994). 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. For the purposes of this stock assessment report, 

70
the animals taken in waters south and west of Cape Flattery, Washington (areas 4 and 4A), are assumed to have 

belonged to the Northern Oregon/Washington Coast stock, and Table 1 includes data only from that portion of the 

fishery. There has been a reduction in fishing effort in the coastal portion of this fishery due to reduced numbers of 

chinook salmon (a target species) in coastal waters. No fishing effort occurred in the coastal portion of the fishery in 

2001-2003 or 2005. Complete records of observer coverage and fishing effort in 2004 are not available; however, 

one vessel fished at least 60 net days (1 net day equals a 100-fathom-length net set for 24 hours) in areas 4 and 4A 

and the vessel operator reported two harbor porpoise deaths (P. Gearin, unpublished data; N. Pamplin, unpublished 

data). The mean estimated mortality for this fishery in 2001-2005 is 0 (CV=0) harbor porpoise per year from 

observer data plus 0.4 porpoise per year from fisher self-reports. 

Table 1. Summary of incidental mortality and serious injury of harbor porpoise (Northern 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 2003-2007 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)

2001 

2002 

2003 

2004 

2005 

2004 

observer data 

fisher selfreports 

no fishery 

no fishery 

no fishery 

unknown2

no fishery 

0 

0 

0 

n/a 

0 

2 

0 (0) 

0 (0) 

0 (0) 

n/a 

0 (0) 

0 (0)1 

>0.4 (n/a)

Unknown West Coast fisheries 2007 stranding 

data 

2 >0.4 (n/a) 

Minimum total annual takes >0.8 (n/a) 1

The 2001-2003 and 2005 mortality estimates are included in the average. 2

Complete records of observer coverage in 2004 are not available. 

 In 1995-1997, data were collected for the coastal portions (areas 4 and 4A) of the northern Washington 

marine set gillnet fishery 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 deaths occurred in alarmed nets (Gearin et al. 1996, 2000; Laake et al. 1997b). In 1997, 96% of the sets were 

equipped with acoustic alarms and 13 mortalities were observed (Gearin et al. 2000; P. Gearin, unpublished data). 

Harbor porpoise were displaced by an acoustic buffer around the alarmed nets, but it is unclear whether the porpoise 

or their prey were repelled by the alarms (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). For the past 

decade, Makah tribal regulations have required nets set in coastal waters (areas 4 and 4A) to be equipped with 

acoustic alarms. 

 A harbor porpoise death was also reported in a tribal steelhead gillnet fishery in the Chehalis River in 2006 

(NMFS, Northwest Regional Office, unpublished data), resulting in an average annual mortality of 0.2 for this 

fishery. 

 The Marine Mammal Authorization Program (MMAP) fisher self-reports, required of commercial vessel 

operators by the MMPA, are an additional source of information on the number of harbor porpoise killed or 

seriously injured incidental to commercial fishery operations. Current MMAP data are not available; however, there 

were no fisher self-reports of harbor porpoise deaths from any MMAP-listed fishery operating within the range of 

the Northern Oregon/Washington Coast stock between 2001 and October 2005. Although these reports are 

considered incomplete (see details in Appendix 1), they represent a minimum mortality. 

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

Region (NMFS, Northwest Regional Office, unpublished data), there were two fishery-related strandings of harbor 

porpoise from this stock reported on the northern Oregon/southern Washington coast in 2007, resulting in an 

average annual mortality of 0.4 harbor porpoise in 2003-2007. Evidence of fishery interactions included net marks, 

rope marks, and knife cuts. Since these deaths could not be attributed to a particular fishery, and they were the only 

confirmed fishery-related deaths in this area in 2007, they are listed in Table 1 as occurring in unknown West Coast 

fisheries. Nine additional strandings reported in 2003-2007 (5 in 2004, 1 in 2006, and 3 in 2007) were considered 

71
possible fishery-related strandings but were not included in the estimate of average annual mortality. 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

A significant increase in the number of harbor porpoise strandings reported throughout Oregon and 

Washington in 2006 prompted the Working Group on Marine Mammal Unusual Mortality Events to declare an 

Unusual Mortality Event (UME) on 3 November 2006 (Huggins 2008). A total of 114 harbor porpoise strandings 

were reported and confirmed throughout Oregon/Washington coast and Washington inland waters in 2006 and 2007 

(Huggins 2008). The cause of the UME has not been determined and several factors, including contaminants, 

genetics, and environmental conditions, are still being investigated. Cause of death, determined for 48 of 81 

porpoise that were examined in detail, was attributed mainly to trauma and infectious disease. Suspected or 

confirmed fishery interactions were the primary cause of adult/subadult traumatic injuries, while birth-related 

trauma was responsible for the neonate deaths. Although six of the Northern Oregon/Washington Coast harbor 

porpoise mortalities examined as part of the UME were suspected to have been caused by fishery interactions, only 

two could be confirmed as fishery-related deaths; these two deaths are listed in Table 1 as occurring in unknown 

West Coast fisheries in 2007. 

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 (1.0) does not exceed the PBR (114). Therefore, the Northern Oregon/Washington Coast stock of 

harbor porpoise is not classified as “strategic.” The total fishery mortality and serious injury for this stock (1.0: 

based on self-reported fisheries information (0.6) and stranding data (0.4) where observer data were not available or 

failed to detect harbor porpoise deaths) is not known to exceed 10% of the calculated PBR (11.4) and, therefore, can 

be considered to be insignificant and approaching zero mortality and serious injury rate. The status of this stock 

relative to its Optimum Sustainable Population (OSP) level and population trends is unknown. 

REFERENCES

Barlow, J. 1988. Harbor porpoise, Phocoena phocoena, abundance estimation for California, Oregon, and 

Washington: I. Ship surveys. Fish. Bull. 86:417-432. 

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

Whal. Commn. Special Issue 16:123-140. 

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

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

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

population discreteness in harbor porpoises from Washington, Oregon, and California. Pp. 101-110, In:

Reynolds, J. E., III, and D. K. Odell (eds.), Proceedings of the second marine mammal stranding workshop: 

3-5 December 1987, Miami, Florida. U.S. Dep. Commer., NOAA Tech. Rep. NMFS 98. 

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. 

Chivers, S. J., B. Hanson, J. Laake, P. Gearin, M. M. Muto, J. Calambokidis, D. Duffield, T. McGuire, J. Hodder, D. 

Greig, E. Wheeler, J. Harvey, K. M. Robertson, and B. Hancock. 2007. Additional genetic evidence for 

population structure of Phocoena phocoena off the coasts of California, Oregon, and Washington. 

Southwest Fisheries Science Center Administrative Report LJ-07-08. 14 pp. Available at SWFSC, NMFS, 

8604 La Jolla Shores Drive, La Jolla, CA 92037. 

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. 

72
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. 

Available at National Marine Mammal Laboratory, 7600 Sand Point Way NE, Seattle, WA 98115. 

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, III. 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 Report, OCS Study MMS 91-

0093, Minerals Management Service, U.S. Dept. of Interior, Los Angeles, CA. 

Huggins, J. 2008. Request for event closure: 2006-2007 Northwest harbor porpoise unusual mortality event. 

Unpublished report by Cascadia Research Collective to NMFS, Northwest Regional Office. 11 pp. 

Available at NMFS, Northwest Regional Office, 7600 Sand Point Way NE, Seattle, WA 98115. 

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

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

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

Laake, J. L., P. J. Gearin, M. E. Gosho, and R. L. DeLong. 1997b. 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. 

NMFS, Northwest Regional Office, 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., P. Rosel, A. Dizon, and R. DeLong. 1994. Harbor porpoise, Phocoena phocoena, population 

assessment in Oregon and Washington, 1993. Pp. 1-14, In: Braham, H. W., and D. P. DeMaster (eds.), 

Marine mammal assessment program: status of stocks and impacts of incidental take, 1993. National 

Marine Mammal Laboratory – MMPA Studies of 1993, NMML, AFSC, NMFS, NOAA. 153 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. 

Pamplin, N. Makah Fisheries Management, P.O. Box 115, Neah Bay, WA 98357. 

Rosel, P. E. 1992. Genetic population structure and systematic relationships of some small cetaceans inferred from 

mitochondrial DNA sequence variation. Ph.D. Thesis, University of California - 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. 

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. 

73
Revised 12/15/2006

HARBOR PORPOISE (Phocoena phocoena): 

Washington Inland Waters Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

 In the eastern North Pacific Ocean, harbor 

porpoise are found in coastal and inland waters from 

Point Barrow, along the Alaskan coast, and down the 

west coast of North America to Point Conception, 

California (Gaskin 1984). 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, suggest 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), seasonal 

movement patterns are not fully understood. 

 Investigation of pollutant loads in harbor 

porpoise ranging from California to the Canadian border 

suggests restricted harbor porpoise movements 

(Calambokidis and Barlow 1991). 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. Further genetic testing of 

the same data, 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 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). 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 

Figure 1. Stock boundaries (dashed lines) and 

approximate distribution (shaded areas) of harbor 

porpoise along the coasts of Washington and northern 

Oregon.

Oregon/

Washington

Coast stock

Washington

Inland Waters

stock

Oregon

Washington

Cape Blanco

126°W

126°W 124°W 122°W 120°W

42°N

44°N

48°N

46°N

74
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 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. The stock boundaries for animals that occur in Washington/northern Oregon waters are 

shown in Figure 1. This report considers only the Washington Inland Waters stock. Stock assessment reports for 

Oregon/Washington Coast, Northern California/Southern Oregon, San Francisco-Russian River, Monterey Bay, and 

Morro Bay harbor porpoise also appear in this volume. Stock assessment reports for the three harbor porpoise 

stocks in the inland and coastal waters of Alaska, including 1) the Southeast Alaska stock, 2) the Gulf of Alaska 

stock, and 3) the Bering Sea stock, 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 of the U.S. stock assessment 

reports. 

POPULATION SIZE

 Aerial surveys of the inside waters of Washington and southern British Columbia were conducted during 

August of 2002 and 2003 (J. Laake, unpubl. data). These aerial surveys included the Strait of Juan de Fuca, San 

Juan Islands, Gulf Islands, and Strait of Georgia, which includes waters inhabited by the Washington Inland Waters 

stock of harbor porpoise as well as harbor porpoise from British Columbia. An average of the 2002 and 2003 

estimates of abundance in U.S. waters results in an uncorrected abundance of 3,123 (CV= 0.10) harbor porpoise in 

Washington inland waters (J. Laake, unpubl. data). When corrected for availability and perception bias, using a 

correction factor of 3.42 (1/g(0); g(0)=0.292, CV=0.366) (Laake et al. 1997), the estimated abundance for the 

Washington Inland Waters stock of harbor porpoise is 10,682 (CV=0.38) animals (J. Laake, unpubl. data). 

Minimum Population Estimate

 The minimum population estimate for this stock is calculated as the lower 20th percentile of the log-normal 

distribution (Wade and Angliss 1997) of the average of the 2002 and 2003 population estimates (10,682), which is 

7,841 harbor porpoise. 

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, however, the uncorrected estimate of abundance in Washington inland waters was 

significantly greater in 2002/2003 than in 1996 (3,123 vs. 1,025; Z=6.16, P<0.0001) (Calambokidis et al. 1997; J. 

Laake, unpubl. data). 

 A different situation exists in southern Puget Sound where harbor porpoise are rarely observed, in contrast 

to 1942 when they were 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 factors (Osmek et al. 1995). Recently, however, 

there have been confirmed sightings of harbor porpoise in central Puget Sound (R. DeLong, pers. comm.). 

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 

(7,841) 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 63 

harbor porpoise per year.

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Fisheries Information

 Fishing effort in the northern Washington marine set gillnet fishery (areas 4, 4A, 4B, and 5) is conducted 

within the range of both harbor porpoise stocks (Oregon/Washington Coast and Washington Inland Waters) 

occurring in Washington State waters. 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. For the purposes of 

this stock assessment report, the animals taken in waters east of Cape Flattery (areas 4B and 5) are assumed to have 

belonged to the Washington Inland Waters stock, and Table 1 includes data only from that portion of the fishery. 

NMFS observers monitored 58% of the 36 net days (1 net day equals a 100-fathom length net set for 24 hours) of 

fishing effort in inland waters in 2000. There was no observer program in 1999 or 2001-2003 in inland waters; 

fishing effort was 4, 46, 4.5, and 7 net days (respectively) in those years, and no harbor porpoise takes were reported 

(Gearin et al. 1994; 2000; P. Gearin, unpubl. data). No mortality was reported in the inland portion of the fishery 

between 1999 and 2003, 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 non-treaty components (areas 7, 7A, 7B/7C, 8A/8D, 10/11, and 12/12A/12B) 

of the Washington Puget Sound Region salmon gillnet fishery (Pierce et al. 1994). Observer coverage was 1.5% 

overall, ranging from 0.9% to 7.3% for the various components of the fishery. No harbor porpoise mortality was 

reported (Table 1). Pierce et al. (1994) cautioned against extrapolating this mortality to the entire Puget Sound 

fishery due to the low observer coverage and potential biases inherent in the data. The area 7/7A sockeye landings 

represented the majority of the non-treaty salmon landings in 1993, approximately 67%. Results of this pilot study 

were used to design the 1994 observer programs discussed below. 

 In 1994, NMFS in conjunction with WDFW conducted an observer program during the Puget Sound nontreaty chum salmon gillnet fishery (areas 10/11 and 12/12B). A total of 230 sets were observed during 54 boat trips, 

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

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

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

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

monitored in 1994 (NWIFC 1995). No harbor porpoise mortality was 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 deaths (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 and serious injury 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 2000-2004 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)

1999 

2000 

2001 

2002 

2003 

observer

0% 

58% 

0% 

0% 

0% 

n/a 

0 

n/a 

n/a 

n/a 

n/a 

0 

n/a 

n/a 

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) 1993 observer 1.3% 0 0 see text

Puget Sound non-treaty chum 

salmon gillnet (areas 10/11 and 

12/12B)

1994 observer 11% 0 0 0

Puget Sound treaty chum 

salmon gillnet (areas 12, 12B, 

and 12C)

1994 observer 2.2% 0 0 0

Puget Sound treaty chum and 

sockeye salmon gillnet (areas 

4B, 5, and 6C)

1994 observer 7.5% 0 0 0

Puget Sound treaty and nontreaty sockeye salmon gillnet 

(areas 7 and 7A)

1994 observer 7% 1 15 15 (1.0)

Unknown Puget Sound fishery 2000-2004 stranding 1, 0, 0, 0, 0 ≥0.2 (n/a)

Minimum total annual takes ≥15.2 (1.0)

1

Only the 2000 mortality estimate is included in the average.

 Combining the estimates from the 1994 observer programs (15) with the northern Washington marine set 

gillnet fishery (zero) 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. 

 The Marine Mammal Authorization Program (MMAP) fisher self-reports, required of commercial vessel 

operators by the MMPA, are an additional source of information on the number of harbor porpoise killed or 

seriously injured incidental to commercial fishery operations. Between 2000 and 2004, there were no fisher selfreports of harbor porpoise mortality from any MMAP-listed Washington Puget Sound Region salmon set/drift 

gillnet fishery. Unlike the 1994 observer program data, the self-reported fisheries data cover the entire fishery. 

Although these reports are considered incomplete (see details in Appendix 1), they represent a minimum mortality. 

77
 Strandings of harbor porpoise wrapped in fishing gear or with serious injuries caused by interactions with 

gear are a final source of fishery-related mortality information. According to Northwest Marine Mammal Stranding 

Network records, maintained by the NMFS Northwest Region, one fishery-related stranding of a harbor porpoise 

occurred in 2000 in Bellingham Harbor. 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 2000-2004 

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 deaths) 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 2000-2004. 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 (63). 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 (6.3) 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 mortality rate is based on observer data from a 

subset of the Washington Puget Sound Region salmon set/drift gillnet fishery that was last observed in 1994. 

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) analysis of data from aerial surveys in 2002 and 2003 indicates that abundance has increased 

since 1996. 

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

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Island Publishers, Anacortes, WA. 191 pp. 

79
Osmek, S., P. Rosel, A. Dizon, and R. DeLong. 1994. Harbor porpoise, Phocoena phocoena, population 

assessment in Oregon and Washington, 1993. Pp. 1-14, In: Braham, H. W., and D. P. DeMaster (eds.), 

Marine mammal assessment program: status of stocks and impacts of incidental take, 1993. National 

Marine Mammal Laboratory – MMPA Studies of 1993, NMML, AFSC, NMFS, NOAA. 153 pp. 

Available at National Marine Mammal Laboratory, 7600 Sand Point Way NE, Seattle, WA 98115. 

Osmek, S., B. Hanson, J. L. Laake, S. Jeffries, and R. DeLong. 1995. Harbor porpoise Phocoena phocoena

population assessment studies for Oregon and Washington in 1994. Pp. 141-172, In: DeMaster, D. P., H. 

W. Braham, and P. S. Hill (eds.), Marine mammal assessment program: status of stocks and impacts of 

incidental take, 1994. National Marine Mammal Laboratory – MMPA Studies of 1994, NMML, AFSC, 

NMFS, NOAA. 244 pp. Available at National Marine Mammal Laboratory, 7600 Sand Point Way NE, 

Seattle, WA 98115. 

Osmek, S., J. Calambokidis, J. Laake, P. Gearin, R. DeLong, J. Scordino, S. Jeffries, and R. Brown. 1996. 

Assessment of the status of harbor porpoise, Phocoena phocoena, in Oregon and Washington waters. U.S. 

Dep. Commer., NOAA Tech. Memo. NMFS-AFSC-76. 46 pp. 

Pierce, D. J., W. P. Ritchie, and R. Kreuziger. 1994. Preliminary findings of seabird interactions with the nontreaty salmon gill net fishery: Puget Sound and Hood Canal Washington. Unpubl. Report, Washington 

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

98501. 

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

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

Washington Dept. Fish and Wildlife, Olympia, WA. 21 pp. Available at WDFW, 600 Capitol Way N, 

Olympia, WA 98501. 

Rosel, P. E. 1992. Genetic population structure and systematic relationships of some small cetaceans inferred from 

mitochondrial DNA sequence variation. Ph.D. Thesis, University of California - 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. 

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

workshop April 3-5, 1996, Seattle, Washington. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR12. 93 pp. 

80
Revised 01/15/2011

DALL'S PORPOISE (Phocoenoides dalli dalli): 

California/Oregon/Washington Stock

STOCK DEFINITION AND 

GEOGRAPHIC RANGE

 Dall’s porpoises are endemic to 

temperate waters of the North Pacific Ocean. 

Off the U.S. west coast, they are commonly 

seen in shelf, slope and offshore waters 

(Figure 1; Morejohn 1979). Sighting patterns 

from aerial and shipboard surveys conducted 

in California, Oregon and Washington at 

different times (Green et al. 1992, 1993; 

Mangels and Gerrodette 1994; Barlow 1995; 

Forney et al. 1995) suggest that north-south 

movement between these states occurs as 

oceanographic conditions change, both on 

seasonal and inter-annual time scales. The 

southern end of this population's range is not 

well-documented, but they are commonly seen 

off Southern California in winter, and during 

cold-water periods they probably range into 

Mexican waters off northern Baja California. 

The stock structure of eastern North Pacific 

Dall’s porpoises 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 porpoises are not restricted to 

U.S. territorial waters, there are no cooperative 

management agreements with Mexico or 

Canada for fisheries which may take this species 

(e.g. gillnet fisheries). For the Marine Mammal 

Protection Act (MMPA) stock assessment 

reports, Dall's porpoises within the Pacific U.S. 

Exclusive Economic Zone are divided into two 

discrete, non-contiguous areas: 1) waters off 

California, Oregon and Washington (this report), 

and 2) Alaskan waters. 

Figure 1. Dall’s porpoise sightings based on aerial 

and shipboard surveys off California, Oregon, and 

Washington, 1991-2008 (see Appendix 2 for data 

sources and information on timing and location of 

survey effort). Dashed line represents the U.S. 

EEZ, thin lines represent completed transect effort

of all surveys combined. Key: ● = summer/autumn 

ship-based sightings; ■ = winter/spring aerial-based 

sightings. 

POPULATION SIZE

 Dall’s porpoise distribution in 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 most recent 

estimate of Dall’s porpoise abundance is the geometric mean of estimates from 2005 (Forney 2007) and 

2008 (Barlow 2010) summer/autumn vessel-based line transect surveys of California, Oregon, and 

Washington waters, or 42,000 (CV = 0.33) animals. Additional numbers of Dall’s porpoises occur in the 

inland waters of Washington state, but the most recent abundance estimate obtained in 1996 (900 animals, 

81
CV=0.40) is over 8 years old (Calambokidis et al. 1997) and is not included in the overall estimate of 

abundance for this stock. 

Minimum Population Estimate

 The log-normal 20th percentile of the 2005-2008 average abundance estimate for the outer coast 

of California, Oregon and Washington waters is 32,106 Dall’s porpoises. 

Current Population Trend

 No information is available regarding trends in abundance of Dall’s porpoises 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 (32,106) 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 and mortality rate CV; Wade and Angliss 1997), 

resulting in a PBR of 257 Dall’s porpoises per year. 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Fishery Information

 A summary of recent fishery mortality and injury for this stock of Dall’s porpoises is given in 

Table 1. More detailed information on these fisheries is provided in Appendix 1. Mean annual takes for all 

fisheries for which mortality data are available are ≥0.4 animals per year. Mortality estimates for the 

California drift gillnet fishery are included for the five most recent years of monitoring, 2004-2008 

(Carretta et al. 2005, Carretta and Enriquez 2006, 2007, 2009a, 2009b). 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 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. 

Mortality of Dall’s porpoises has also been documented in the California/Oregon/Washington 

domestic groundfish trawl fisheries (Perez and Loughlin 1991; Perez 2003). Between 2002 and 2006 with 

100% of the fishing effort observed, one Dall’s porpoise was reported killed in the at-sea processing 

portion of the Pacific hake trawl fishery. 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). 

 

82
Table 1. Summary of available information on the incidental mortality of Dall's porpoises (California/ 

Oregon/Washington Stock) in commercial fisheries that might take this species. Coefficients of variation 

for mortality estimates are provided in parentheses; n/a = not available. Mean annual takes are based on 

2004-2008 data for the CA/OR swordfish drift gillnet fishery and 2002-2006 for groundfish fisheries. 

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 

2004 

2005 

2006 

2007 

2008 

20.6% 

20.9% 

18.5% 

16.4% 

13.5% 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 (n/a) 

WA/OR/CA domestic 

groundfish trawl (At-sea 

processing Pacific hake 

fishery). 

observer 

2002 

2003 

2004 

2005 

2006 

100% 

100% 

100% 

100% 

100% 

1 

0 

0 

0 

0 

1 

0 

0 

0 

0 

0.2 (n/a) 

Puget Sound salmon drift 

gillnet (tribal fishery, 

Area 5, Strait of Juan de 

Fuca) 

MMAP 2000-2004 n/a 1 1 0.2 (n/a) 

Minimum total annual takes 0.4 (n/a) 

STATUS OF STOCK

 The status of Dall's porpoises in California, Oregon and Washington relative to OSP is not known, 

and there are insufficient data to evaluate potential trends in abundance. No habitat issues are known to be 

of concern for this species. It is not listed as "threatened" or "endangered" under the Endangered Species 

Act nor as "depleted" under the MMPA. The average annual human-caused mortality (≥0.4 animals) is 

estimated to be less than the PBR (257), 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. 2010. Cetacean abundance in the California Current from a 2008 ship-based line-transect 

survey. NOAA Technical Memorandum, NMFS, NOAA-TM-NMFS-SWFSC-456. 

Barlow, J. and K.A. Forney. 2007. Abundance and population density of cetaceans in the California 

Current ecosystem. Fishery Bulletin 105:509-526. 

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. 1995. The abundance of cetaceans in California waters. Part I: Ship surveys in summer and fall 

of 1991. Fish. Bull. 93:1-14. 

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. 

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

and British Columbia inside waters. Final Contract Report for Contract 52ABNF-6-00092, 

available from Cascadia Research Collective, Waterstreet Building 218 1⁄2 West Forth Avenue, 

Olympia, Washington 98501. 

83
Carretta, J.V. and L. Enriquez. 2009a. Marine mammal and seabird bycatch observed in California 

commercial fisheries in 2007. Administrative Report LJ-09-01, available from Southwest 

Fisheries Science Center, 3333 North Torrey Pines Rd., La Jolla, CA 92037. 12 p. 

Carretta, J.V. and L. Enriquez. 2009b. Marine mammal bycatch observed in the California/Oregon 

swordfish and thresher shark drift gillnet fishery in 2008. Administrative Report LJ-09-03, 

available from Southwest Fisheries Science Center, 3333 North Torrey Pines Rd., La Jolla, CA 

92037. 10 p . 

Carretta, J.V. and L. Enriquez. 2007. Marine mammal and sea turtle bycatch in the California/Oregon 

thresher shark and swordfish drift gillnet fishery in 2006. Administrative Report LJ-07-06, 

available from Southwest Fisheries Science Center, 8604 La Jolla Shores Drive, La Jolla, CA 

92037. 9p. 

Carretta, J.V. and L. Enriquez. 2006. Marine mammal bycatch and estimated mortality in California 

commercial fisheries during 2005. Administrative Report LJ-06-07, available from Southwest 

Fisheries Science Center, 8604 La Jolla Shores Drive, La Jolla, CA 92037. 14p. 

Carretta, J.V., S.J. Chivers, and K. Danil. 2005. Preliminary estimates of marine mammal bycatch, 

mortality, and biological sampling of cetaceans in California gillnet fisheries for 2004. 

Administrative Report LJ-05-10, available from Southwest Fisheries Science Center, 8604 La 

Jolla Shores Drive, La Jolla, California, 92037. 17 p. 

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. 

Forney, K.A. 2007. Preliminary estimates of cetacean abundance along the U.S. west coast and within 

four National Marine Sanctuaries during 2005. U.S. Department of Commerce, NOAA Technical 

Memorandum NMFS-SWFSC-406. 27 p. 

Green, G., J. J. Brueggeman, R. A. Grotefendt, C. E. Bowlby, M. L. Bonnell, and K. C. Balcomb, III. 

1992. Cetacean distribution and abundance off Oregon and Washington. Ch. 1. In: Oregon and 

Washington Marine Mammal and Seabird Surveys. OCS Study 91-0093. Final Report prepared 

for Pacific OCS Region, Minerals Management Service, U.S. Department of the Interior, Los 

Angeles, California. 

Green, G., R. A. Grotefendt, M. A. Smultea, C. E. Bowlby, and R. A. Rowlett. 1993. Delphinid aerial 

surveys in Oregon and Washington waters. Final Report prepared for NMFS, National Marine 

Mammal Laboratory, 7600 Sand Point Way, NE, Seattle, Washington, 98115, Contract 

#50ABNF200058. 

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

Ocean. In: I. Barrett, O. Sosa-Nishizaki and N. Bartoo (eds.). Biology and fisheries of swordfish, 

Xiphias gladius. Papers from the International Symposium on Pacific Swordfish, Ensenada 

Mexico, 11-14 December 1994. U.S. Dep. Commer., NOAA Tech. Rep. NMFS 142, 276 pp. 

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

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

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

the eastern Pacific Ocean and Gulf of California aboard the NOAA ships McARTHUR and DAVID 

STARR JORDAN July 28 - November 6, 1993. U.S. Dep. Commer. NOAA Tech. Memo. NMFSSWFSC-211. 88 pp. 

Morejohn, G. V. 1979. The natural history of Dall's porpoise in the North Pacific Ocean. In: Winn, H. 

E. and B. L. Olla (eds.), Behavior of Marine Mammals, p. 45-83. Plenum Press, New York - 

London. 

Perez, M. A. and T. R. Loughlin. 1991. Incidental catch of marine mammals by foreign and joint venture 

trawl vessels in the U.S. EEZ of the North Pacific, 1973-88. U.S. Dep. Commer. NOAA Tech. 

Rep. 104. 57 p. 

84
Perez, M. 2003. Compilation of marine mammal incidental take data from the domestic and joint venture 

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

NOAA Tech. Memo. NMFS-AFSC-138. 145 pp. 

Perrin, W. F. and R. L. Brownell, Jr. 1994. A brief review of stock identity in small marine cetaceans in 

relation to assessment of driftnet mortality in the North Pacific. Rep. Int. Whal. Commn. Special 

Issue 15:393-401. 

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

Velez. 1993. Estudio biologico pesquero del pez (Xiphias gladius) y otras especies de picudos 

(marlins y pez vela). Rep. Int. CICESE, CTECT9306. 

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

GAMMS Workshop April 3-5, 1996, Seattle, Washington. U. S. Dep. Commer., NOAA Tech. 

Memo. NMFS-OPR-12. 93 pp. 

85
Revised 01/15/2011

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 (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). 

Figure 1. Pacific white-sided dolphin sightings 

based on aerial and shipboard surveys off 

California, Oregon, and Washington, 1991-2008

(see Appendix 2 for data sources and information on 

timing and location of survey effort). Dashed line 

represents the U.S. EEZ, thin lines indicate 

completed transect effort of all surveys combined. 

Key:  = summer/autumn ship-based sightings; ▲

= winter/spring aerial-based sightings. 

Although there is clear evidence that two forms of Pacific white-sided dolphins occur along the 

U.S. west coast, there are no known differences in color pattern, and it is not currently possible to 

distinguish animals without genetic or morphometric analyses. Geographic stock boundaries appear 

dynamic and are poorly understood, and therefore cannot be used to differentiate the two forms. Until 

means of differentiating the two forms for abundance and mortality estimation are developed, these two 

stocks must be managed as a single unit; however, this is an undesirable management situation. 

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

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

86
which may take this species (e.g. gillnet fisheries). Additional means of differentiating the two types must 

be found, and cooperative management with Mexico is particularly important for this species, given the 

apparently dynamic nature of geographical stock boundaries. Until these goals are accomplished, the 

management stock includes animals of both forms. For the Marine Mammal Protection Act (MMPA) stock 

assessment reports, Pacific white-sided dolphins within the Pacific U.S. Exclusive Economic Zone are 

divided into two discrete, non-contiguous areas: 1) waters off California, Oregon and Washington (this 

report), and 2) Alaskan waters. 

POPULATION SIZE

 The most recent estimates of abundance for Pacific white-sided dolphins are based on two 

summer/autumn shipboard surveys conducted within 300 nmi of the coasts of California, Oregon, and 

Washington in 2005 (Forney 2007) and 2008 (Barlow 2010). 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 multiyear average abundance estimate including California, Oregon and Washington is the most appropriate for 

management within U.S. waters. The 2005-2008 geometric mean abundance estimate for California, 

Oregon and Washington waters based on the two most recent ship surveys is 26,930 (CV=0.28) Pacific 

white-sided dolphins ( Forney 2007, Barlow, 2010). 

Minimum Population Estimate

 The log-normal 20th percentile of the 2005-2008 average abundance estimate is 21,406 Pacific 

white-sided dolphins. 

Current Population Trend

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

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

1993; Barlow 1995; Forney et al. 1995, Barlow and Forney 2007, Forney 2007). 

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 (21,406) 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 193 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. Including 

mortality from drift gillnet, groundfish trawl, and unknown fisheries, the average annual fishery-related 

mortality of Pacific white-sided dolphins is 10.5 (CV = 0.65) animals. Mortality estimates for the 

California drift gillnet fishery are included for the five most recent years of monitoring, 2004-2008 

(Carretta et al. 2005 Carretta and Enriquez 2006, 2007, 2009a, 2009b). 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. 

 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 

87
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). 

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 2004-2008 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 

2004 

2005 

2006 

2007 

2008 

20.6% 

20.9% 

18.5% 

16.4% 

13.5% 

0 

0 

0 

1 

5 

 0 

0 

0 

6 (1.00) 

37 (0.70) 

8.6 (0.77) 

WA/OR/CA domestic 

groundfish trawl (At-sea 

processing Pacific hake 

fishery ).

observer 

2002 

2003 

2004 

2005 

2006 

100% 

100% 

100% 

100% 

100% 

0 

1 

0 

0 

0 

0 

1 (n/a) 

0 

0 

0 

0.2 n/a) 

West Coast limited entry 

bottom trawl fishery observer 

2002 

2003 

2004 

2005 

10-33%, varies 

by reporting area 1 in 2003 7.5 (0.93) 1.9 (0.93) 

Unknown fishery stranding 

2004 

2005 

2006 

2007 

2008 

1 

0 

0 

0 

0 

n/a 0.2 (n/a) 

Minimum total annual takes 10.5 (0.65) 

 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; Northwest 

Fisheries Science Center 2008). Between 2004-2008, with 100% 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 

(NMFS,unpublished data). One white-sided dolphin death was reported in the limited entry bottom trawl 

fishery in 2003, resulting in a bycatch estimate of 7.5 animals (Table 1). 

Other removals 

In 2008, fifteen Pacific white-sided dolphin were incidentally killed in California waters during 

scientific sardine trawling operations conducted by NMFS (Southwest Regional Office Stranding Program, 

unpublished data). Three mortality events occurred in April trawls, after which NMFS scientists met to 

discuss & implement a mitigation plan to avoid future mortality events. The initial mitigation plan 

included use of 162 dB acoustic pingers, a marine mammal watch, and scheduling trawls to occur when the 

ship first arrived on station to avoid attracting animals to a stationary vessel. During August 2008 trawls, 

twelve additional Pacific white-sided dolphin were killed. One trawl caught 11 Pacific white-sided 

88
dolphins and six northern right whale dolphins. In 2009, a marine mammal excluder device was added to 

the trawls. In 2009, no additional mortality was observed during 42 trawls. However, a group of three 

Pacific white-sided dolphin became entangled in the trawl during retrieval. Two animals were brought 

aboard alive and immediately released, while a third animal escaped through the excluder device. Eight 

additional Pacific white-sided dolphins were killed in research surface trawls between 2005 and 2006 

(NMFS Northwest Region, unpublished data). The average annual research-related mortality of Pacific 

white-sided dolphin from 2004 to 2008 is 4.6 animals. 

 Additional removals of Pacific white-sided dolphins from the wild have occurred in live-capture 

fisheries off California. Brownell et al. (1999) estimate a minimum total live capture of 128 Pacific whitesided dolphins between the late 1950s and 1993. The most recent capture was in November 1993, when 

three animals were taken for public display (Forney 1994). No MMPA permits are currently active for 

live-captures of Pacific white-sided dolphins. 

STATUS OF STOCK

 The status of Pacific white-sided dolphins in California, Oregon and Washington relative to OSP 

is not known, and there is no indication of a trend in abundance for this stock. No habitat issues are known 

to be of concern for this species. They are not listed as "threatened" or "endangered" under the Endangered 

Species Act nor as "depleted" under the MMPA. Including commercial fishery (10.5/yr) and researchrelated mortality (4.6/yr), the average annual mortality for the 5-year period 2004-2008 is 15.1 animals. 

The average annual human-caused mortality in 2004-2008 (15.1 animals) is estimated to be less than the 

PBR (193), 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. 2010. Cetacean abundance in the California Current from a 2008 ship-based line-transect 

survey. NOAA Technical Memorandum, NMFS, NOAA-TM-NMFS-SWFSC-456. 

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. 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 K.A. Forney. 2007. Abundance and population density of cetaceans in the California 

Current ecosystem. Fishery Bulletin 105:509-526. 

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. 

Carretta, J.V. and L. Enriquez. 2009a. Marine mammal and seabird bycatch observed in California 

commercial fisheries in 2007. Administrative Report LJ-09-01, available from Southwest 

Fisheries Science Center, 3333 North Torrey Pines Rd., La Jolla, CA 92037. 12 p. 

Carretta, J.V. and L. Enriquez. 2009b. Marine mammal bycatch observed in the California/Oregon 

swordfish and thresher shark drift gillnet fishery in 2008. Administrative Report LJ-09-03, 

available from Southwest Fisheries Science Center, 3333 North Torrey Pines Rd., La Jolla, CA 

92037. 10 p . 

Carretta, J.V. and L. Enriquez. 2007. Marine mammal and sea turtle bycatch in the California/Oregon 

thresher shark and swordfish drift gillnet fishery in 2006. Administrative Report LJ-07-06, 

available from Southwest Fisheries Science Center, 8604 La Jolla Shores Drive, La Jolla, CA 

92037. 9p. 

Carretta, J.V. and L. Enriquez. 2006. Marine mammal bycatch and estimated mortality in California 

commercial fisheries during 2005. Administrative Report LJ-06-07, available from Southwest 

Fisheries Science Center, 8604 La Jolla Shores Drive, La Jolla, CA 92037. 14p. 

Carretta, J.V., S.J. Chivers, and K. Danil. 2005. Preliminary estimates of marine mammal bycatch, 

mortality, and biological sampling of cetaceans in California gillnet fisheries for 2004. 

89
Administrative Report LJ-05-10, available from Southwest Fisheries Science Center, 8604 La 

Jolla Shores Drive, La Jolla, California, 92037. 17 p. 

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. 

Forney, K.A. 2007. Preliminary estimates of cetacean abundance along the U.S. west coast and within 

four National Marine Sanctuaries during 2005. U.S. Department of Commerce, NOAA Technical 

Memorandum NMFS-SWFSC-406. 27p. 

Green, G., J. J. Brueggeman, R. A. Grotefendt, C. E. Bowlby, M. L. Bonnell, and K. C. Balcomb, III. 

1992. Cetacean distribution and abundance off Oregon and Washington. Ch. 1. In: Oregon and 

Washington Marine Mammal and Seabird Surveys. OCS Study 91-0093. Final Report prepared 

for Pacific OCS Region, Minerals Management Service, U.S. Department of the Interior, Los 

Angeles, California. 

Green, G., R. A. Grotefendt, M. A. Smultea, C. E. Bowlby, and R. A. Rowlett. 1993. Delphinid aerial 

surveys in Oregon and Washington waters. Final Report prepared for NMFS, National Marine 

Mammal Laboratory, 7600 Sand Point Way, NE, Seattle, Washington, 98115, Contract 

#50ABNF200058. 

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

Ocean. In: I. Barrett, O. Sosa-Nishizaki and N. Bartoo (eds.). Biology and fisheries of swordfish, 

Xiphias gladius. Papers from the International Symposium on Pacific Swordfish, Ensenada 

Mexico, 11-14 December 1994. U.S. Dep. Commer., NOAA Tech. Rep. NMFS 142. 276 pp. 

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

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

Lux, C. A., A. S. Costa, and A. E. Dizon. 1997. Mitochondrial DNA population structure of the Pacific 

white-sided dolphin. Rep. Int. Whaling. Commn. 47:645-652. 

Northwest Fisheries Science Center, NOAA Fisheries. 2008. Report on the bycatch of marine mammals 

and seabirds by the U.S. West Coast Groundfish Fleet. Northwest Fisheries Science Center, Atsea Hake Observer Program, West Coast Groundfish Observer Program. 34p. 

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. 

90
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. 

91
Revised 01/15/2011

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 welldocumented, but previous surveys have 

shown a conspicuous 500 nmi distributional 

gap 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, noncontiguous areas: 1) waters off California, 

Oregon and Washington (this report), and 2) 

Hawaiian waters.

POPULATION SIZE

 Current estimates of population size are derived from two shipboard surveys within 300 nmi of 

the coasts of California, Oregon, and Washington in summer/autumn of 2005 (Forney 2007) and 2008 

(Barlow 2010). 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 2005-2008 geometric mean abundance estimate for California, 

Oregon and Washington waters based on the two most recent ship surveys is 6,272 (CV=0.30) Risso’s 

dolphins (Forney, 2007, Barlow 2010). 

Figure 1. Risso’s dolphin sightings based on aerial 

and shipboard surveys off California, Oregon, and 

Washington, 1991-2008 (see Appendix 2 for data 

sources and information on timing and location of 

survey effort). Dashed line represents the U.S. EEZ, 

thin lines indicate completed transect effort of all 

surveys combined. Key:  = summer/autumn shipbased sightings; ■ = winter/spring aerial-based 

sightings. 

92
Minimum Population Estimate

 The log-normal 20th percentile of the 2005-2008 geometric mean abundance estimate is 4,913 

Risso's dolphins. 

Current Population Trend

 Barlow and Forney (2007) and Barlow (2010) report abundance estimates ranging from 

approximately 4,000 to 11,000 animals in California waters for five separate surveys conducted between 

1991 and 2008, with no apparent trend in abundance. Inter-annual variability in the distribution of Risso’s 

dolphin within the ship survey study area is likely responsible for the differences in estimated abundance 

between surveys. 

 

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 (4,913) 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 39 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, 2004-2008 

(Carretta et al. 2005, Carretta and Enriquez 2006, 2007, 2009a, 2009b). 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 2004-2008 data. This results in an average estimate 1.6 (CV = 0.99) Risso’s 

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 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, Risso’s dolphin mortality has been documented 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). An observer program in the squid purse seine fishery was initiated in 

2004 and a total of 377 sets have been observed through 2008 without a Risso’s dolphin interaction. 

Observer coverage in this fishery has been less than 10% of all fishing effort. 

93
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 2004-2008 data 

unless noted otherwise. 

Fishery Name Data Type

Year(s) 

Percent 

Observer 

Coverage

Observed

Mortality

Estimated Annual 

Mortality 

(CV)

Mean Annual 

Takes (CV)

CA/OR thresher 

shark/swordfish drift gillnet 

fishery

observer 

2004 

2005 

2006 

2007 

2008 

20.6% 

20.9% 

18.5% 

16.4% 

13.5% 

0 

0 

0 

0 

1 

0 

0 

0 

0 

7 (0.99)

1.4 (0.99)

CA shallow set longline 

fishery observer 

2004 

No fishery 

in 2005 

< 10% 0 0 

CA deep set longline fishery observer 2005-2008 100% 0 0 0 

Market squid purse seine observer 2004-2008 <10% 0 0 0 

Unknown fishery Stranding 2004-2008 1 ≥1 ≥0.2 

Minimum total annual takes 1.6 (0.99) 

 

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 (2004-2008), the 

average annual human-caused mortality (1.6 animals) is estimated to be less than the PBR (39), 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. 2010. Cetacean abundance in the California Current from a 2008 ship-based line-transect 

survey. NOAA Technical Memorandum, NMFS, NOAA-TM-NMFS-SWFSC-456. 

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 K.A. Forney. 2007. Abundance and population density of cetaceans in the California 

Current ecosystem. Fishery Bulletin 105:509-526. 

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. 

Carretta, J.V. and L. Enriquez. 2009a. Marine mammal and seabird bycatch observed in California 

commercial fisheries in 2007. Administrative Report LJ-09-01, available from Southwest 

Fisheries Science Center, 3333 North Torrey Pines Rd., La Jolla, CA 92037. 12 p. 

Carretta, J.V. and L. Enriquez. 2009b. Marine mammal bycatch observed in the California/Oregon 

swordfish and thresher shark drift gillnet fishery in 2008. Administrative Report LJ-09-03, 

available from Southwest Fisheries Science Center, 3333 North Torrey Pines Rd., La Jolla, CA 

92037. 10 p . 

Carretta, J.V. and L. Enriquez. 2007. Marine mammal and sea turtle bycatch in the California/Oregon 

thresher shark and swordfish drift gillnet fishery in 2006. Administrative Report LJ-07-06, 

available from Southwest Fisheries Science Center, 8604 La Jolla Shores Drive, La Jolla, CA 

92037. 9p. 

94
Carretta, J.V. and L. Enriquez. 2006. Marine mammal bycatch and estimated mortality in California 

commercial fisheries during 2005. Administrative Report LJ-06-07, available from Southwest 

Fisheries Science Center, 8604 La Jolla Shores Drive, La Jolla, CA 92037. 14p. 

Carretta, J.V., S.J. Chivers, and K. Danil. 2005. Preliminary estimates of marine mammal bycatch, 

mortality, and biological sampling of cetaceans in California gillnet fisheries for 2004. 

Administrative Report LJ-05-10, available from Southwest Fisheries Science Center, 8604 La 

Jolla Shores Drive, La Jolla, California, 92037. 17 p. 

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. 

Forney, K.A. 2007. Preliminary estimates of cetacean abundance along the U.S. west coast and within 

four National Marine Sanctuaries during 2005. U.S. Department of Commerce, NOAA Technical 

Memorandum NMFS-SWFSC-406. 27 p. 

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. 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. 

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

the eastern Pacific Ocean and Gulf of California aboard the NOAA ships McARTHUR and DAVID 

STARR JORDAN July 28 - November 6, 1993. U.S. Dep. Commer., NOAA Tech. Memo. NMFSSWFSC-211. 88 pp. 

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

1983-91. Bull. Southern California Acad. Sci. 93:13-29. 

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

Velez. 1993. Estudio biologico pesquero del pez (Xiphias gladius) y otras especies de picudos 

(marlins y pez vela). Rep. Int. CICESE, CTECT9306. 

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

GAMMS Workshop April 3-5, 1996, Seattle, Washington. U. S. Dep. Commerce, NOAA Tech. 

Memo. NMFS-OPR-12. 93 pp. 

95
Revised 12/15/2008

COMMON BOTTLENOSE DOLPHIN (Tursiops truncatus 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). Based on nuclear and mtDNA analyses, 

Lowther (2006) identified 5 haplotypes from 29 

coastal animals and 25 haplotypes from 40 offshore 

animals from the U.S. west coast. There were no 

shared haplotypes between coastal and offshore 

animals and significant genetic differentiation 

between the two ecotypes was evident. 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 San Quintin, Mexico. 

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 moving into and out of this area. 

There is little site fidelity of coastal bottlenose dolphins along the California coast; over 80% of the 

dolphins identified in Santa Barbara, Monterey, and Ensenada have also been identified off San Diego 

(Defran et al. 1999, Feinholz 1996, Defran, unpublished data). 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. 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. 

W123 W122 W121 W120 W119 W118 W117 W116

N31

N32

N33

N34

N35

N36

N37

N38

N39

N40

San Francisco

Monterey Bay

Point Conception

San Diego

Los Angeles

California

Pacific Ocean

Figure 1. Approximate range (in bold) of 

California coastal bottlenose dolphins based on 

aerial surveys along the coast of California from 

1990-2000. This population of bottlenose 

dolphins is found within about 1 km of shore. 

POPULATION SIZE

 Based on photographic mark-recapture surveys conducted along the San Diego coast in 2004 and 

2005, the most recent estimate of population size is 323 dolphins (CV = 0.13, 95% CI 259-430; Dudzik et 

al. 2006). This estimate does not reflect that approximately 35% of dolphins encountered lack identifiable 

dorsal fin marks (Defran and Weller 1999). If 35% of all animals lack distinguishing marks, then the true 

population size would be closer to 450-500 animals. Comparing the most recent population size estimate 

96
with those obtained from 1987-89 (354 dolphins, 95% CI 330 – 390) and 1996-98 (356 dolphins, 95% CI 

306 – 437; Dudzik 1999) suggests that the population size has been stable for approximately 20 years. 

Older estimates of population size for this stock range from 234 (95% CI 205-263) to 285 (95% CI 265-

306) animals for the period 1985-89 (Defran and Weller 1999). Because coastal bottlenose dolphins spend 

an unknown amount of time in Mexican waters, where they may be subject to mortality in Mexican 

fisheries, an average abundance estimate for California only is the most appropriate for U.S. management 

of this stock. 

Minimum Population Estimate

 The minimum number of dolphins photographically identified during 2004-2005 field studies was 

164, however, the discovery curve for new animals had not yet reached an asymptote during that study 

(Dudzik et al. 2006). The minimum population estimate for this stock is therefore taken as the lower 20th

percentile of the log-normal distribution of abundance obtained from the photographic mark-recapture 

estimate (Dudzik et al. 2006), or approximately 290 dolphins. 

Current Population Trend

 Based on a comparison of mark-recapture abundance estimates for the periods 1987-89 (Nˆ = 354), 

1996-98 (Nˆ = 356), and 2004-05 (Nˆ = 323), Dudzik et al. (2006) stated that the population size had remained 

stable over this 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 (290) times one half the default maximum net growth rate for cetaceans (1⁄2 of 4%) times a 

recovery factor of 0.50 (for a species of unknown status with no estimated fishery mortality; Wade and 

Angliss 1997), resulting in a PBR of 2.9 coastal bottlenose dolphins per year. Not all California coastal 

bottlenose dolphins are present in U.S. waters at any given moment and approximately 18% of the stock’s 

range occurs in Mexican waters. Thus, the PBR is prorated by a minimum factor of 0.82 to account for 

time that animals spend outside of U.S. waters. Without additional data on the residence times of dolphins 

in Mexican waters, this factor cannot be improved upon. Because this stock spends some of its time 

outside the U.S. EEZ, the PBR allocation for U.S. waters is 2.9 x 0.82 = 2.4 dolphins per year. 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Fishery Information

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

fishery-related mortality in coastal set net fisheries. A summary of information on fishery mortality and 

injury for this stock of bottlenose dolphin is shown in Table 1. More detailed information on the set gillnet 

fishery is provided in Appendix 1. From 1991-94, no bottlenose dolphins were observed taken in this 

fishery with 10-15% observer coverage (Julian and Beeson 1998). The observer program was discontinued 

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

coast. In 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. A 

renewed observer program began in the halibut set gillnet fishery in 2006. Through late 2007, a total of 

260 sets were observed without a cetacean interaction. In 2003, an immature female bottlenose dolphin 

stranded dead in San Diego, California, with 3.5-inch mesh gillnet wrapped around its tailstock (SWFSC 

stranding KXD0048). Perforation of the animal’s skin suggests the net was on the animal for some time. 

Mitochondrial DNA analysis showed that the haplotype for this animal matches that of known coastal

animals (Lowther 2006; Lowther et al. in prep). The fishery responsible for this mortality is unknown, but 

the location and type of gillnet found suggests either a set or drift gillnet targeting yellowtail, white seabass, 

or barracuda. In 2004, a bottlenose dolphin with missing flukes washed ashore near Newport Beach, 

California, suggestive of an interaction with an entangling net fishery. The haplotype of this animal 

97
matched those of known offshore bottlenose dolphins (Lowther 2006; Lowther et al., in prep). Coastal 

gillnet fisheries exist in Mexico and may take animals from this population, but no details are available. 

 

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. A renewed 

observer program began in the halibut set gillnet fishery in 2006 (12 sets observed total, <1% observer 

coverage).

Fishery Name Data Type

Year(s) 

Percent 

Observer 

Coverage

Observed

Mortality

Estimated 

Annual 

Mortality

Mean Annual 

Takes (CV in 

parentheses)

CA angel shark/ halibut and 

other species large mesh (>3.5in) 

set gillnet fishery

observer 

2002 

2003 

2004 

2005 

2006

0% 

0% 

0% 

0% 

<1% 

0 0 0

Unknown fishery stranding 2002-2006 

One bottlenose dolphin with a coastal stock 

haplotype stranded entangled in 3.5-inch mesh 

gillnet in 2003 

0.2 (n/a) 

Minimum total annual takes 0.2 (n/a)

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. Coastal bottlenose dolphins are not classified 

as a "strategic" stock under the MMPA because total annual fishery mortality and serious injury for this 

stock (0.2 per year) is less than the PBR (2.4). The total human-caused 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. 

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. 

98
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. 

Dudzik, K.J., K.M. Baker, and D.W. Weller. 2006. Mark-recapture abundance estimate of California 

coastal stock bottlenose dolphins: February 2004 to April 2005. SWFSC Administrative Report 

LJ-06-02C, available from Southwest Fisheries Science Center, 8604 La Jolla Shores Drive, La 

Jolla, CA 92037. 15p. 

Feinholz, D.M. 1996. Pacific coast bottlenose dolphins (Tursiops truncatus) in Monterey Bay, California. 

M.S. Thesis, San Jose State University, San Jose, CA. 78p.

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. 

Lowther, J. 2006. Genetic variation of coastal and offshore bottlenose dolphins, Tursiops truncatus, in the 

eastern North Pacific Ocean. M.S. Thesis, University of San Diego, San Diego, California, USA. 

126 p. 

Lowther, J.L., F.I. Archer, and D.W. Weller. Manuscript in preparation. Genetic variation of coastal and 

offshore bottlenose dolphins, Tursiops truncatus, in the eastern North Pacific Ocean. 

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. 

99
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. 

100
Revised 01/15/2011

COMMON BOTTLENOSE DOLPHIN (Tursiops truncatus 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; Lowther 2006; Lowther et al. in 

prep.). 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. 

Figure 1. Offshore bottlenose dolphin sightings based 

on shipboard surveys off California, Oregon, and 

Washington, 1991-2008 (see Appendix 2 for data 

sources and information on timing and location of 

survey effort). Dashed line represents the U.S. EEZ, 

thin lines indicate completed transect effort of all 

surveys combined. 

POPULATION SIZE

 The most recent shipboard surveys conducted within 300 nmi of the coasts of California, Oregon, 

and Washington were in 2005 (Forney 2007) and 2008 (Barlow 2010). 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 geometric mean abundance 

estimate for California, Oregon and Washington waters based on the 2005 and 2008 ship surveys, or 1,006 

(CV=0.48) offshore bottlenose dolphins (Forney 2007, Barlow 2010). 

101
Minimum Population Estimate

 The log-normal 20th percentile of the 2005-2008 average abundance estimate is 684 offshore 

bottlenose dolphins. 

Current Population Trend

 No information on trends in abundance of offshore bottlenose dolphins is available. 

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

 No information on current or maximum net productivity rates is available for this population of 

offshore bottlenose dolphins. 

POTENTIAL BIOLOGICAL REMOVAL

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

population size (684) 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 an unknown fishery mortality CV ; Wade 

and Angliss 1997), resulting in a PBR of 5.5 offshore bottlenose dolphins per year. 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Fishery Information

 A summary of known fishery mortality and injury for this stock of bottlenose dolphin is shown in 

Table 1. More detailed information on these fisheries is provided in Appendix 1. Mortality estimates for 

the California drift gillnet fishery are included for the five most recent years of monitoring, 2004-2008 

(Carretta et al. 2005, Carretta and Enriquez 2006, 2007, 2009a, 2009b). 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. In 2004, a bottlenose 

dolphin stranded dead near Newport Beach, California, with its flukes cut off, suggestive of an interaction 

with an entangling net fishery. The haplotype of this animal matched those of known offshore bottlenose 

dolphins (Lowther 2006, Lowther et al., in prep). Mean annual takes in Table 1 are based on 2004-2008 

data. This results in an average estimate of 0.2 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 2004-2008 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 

2004 

2005 

2006 

2007 

2008 

20.6% 

20.9% 

18.5% 

16.4% 

13.5% 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

Unknown fishery strandings 2004-

2008 1 ≥1 ≥0.2 (n/a) 

Minimum total annual takes ≥0.2 (n/a) 

 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, 

102
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 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 average annual fishery takes (0.2/year) are less than the calculated 

PBR (5.5), offshore bottlenose dolphins 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 PBR and thus can be considered to 

be insignificant and approaching zero. 

REFERENCES 

Barlow, J. 2010. Cetacean abundance in the California Current from a 2008 ship-based line-transect 

survey. NOAA Technical Memorandum, NMFS, NOAA-TM-NMFS-SWFSC-456. 19 p. 

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. 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. 

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commercial fisheries in 2007. Administrative Report LJ-09-01, available from Southwest 

Fisheries Science Center, 3333 North Torrey Pines Rd., La Jolla, CA 92037. 12 p. 

Carretta, J.V. and L. Enriquez. 2009b. Marine mammal bycatch observed in the California/Oregon 

swordfish and thresher shark drift gillnet fishery in 2008. Administrative Report LJ-09-03, 

available from Southwest Fisheries Science Center, 3333 North Torrey Pines Rd., La Jolla, CA 

92037. 10 p . 

Carretta, J.V. and L. Enriquez. 2007. Marine mammal and sea turtle bycatch in the California/Oregon 

thresher shark and swordfish drift gillnet fishery in 2006. Administrative Report LJ-07-06, 

available from Southwest Fisheries Science Center, 8604 La Jolla Shores Drive, La Jolla, CA 

92037. 9p. 

Carretta, J.V. and L. Enriquez. 2006. Marine mammal bycatch and estimated mortality in California 

commercial fisheries during 2005. Administrative Report LJ-06-07, available from Southwest 

Fisheries Science Center, 8604 La Jolla Shores Drive, La Jolla, CA 92037. 14p. 

Carretta, J.V., S.J. Chivers, and K. Danil. 2005. Preliminary estimates of marine mammal bycatch, 

mortality, and biological sampling of cetaceans in California gillnet fisheries for 2004. 

Administrative Report LJ-05-10, available from Southwest Fisheries Science Center, 8604 La 

Jolla Shores Drive, La Jolla, California, 92037. 17 p. 

103
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. 

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four National Marine Sanctuaries during 2005. U.S. Department of Commerce, NOAA Technical 

Memorandum NMFS-SWFSC-406. 27 p. 

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. 

Lowther, J. 2006. Genetic variation of coastal and offshore bottlenose dolphins, Tursiops truncatus, in the 

eastern North Pacific Ocean. M.S. Thesis, University of San Diego, San Diego, California, USA. 

126 p. 

Lowther, J.L., F.I. Archer, and D.W. Weller. Manuscript in preparation. Genetic variation of coastal and 

offshore bottlenose dolphins, Tursiops truncatus, in the eastern North Pacific Ocean. 

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. 

104
Revised 01/15/2011 

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. 

Figure 1. Striped dolphin sightings based on aerial and 

shipboard surveys off California, Oregon, and 

Washington, 1991-2008 (see Appendix 2 for data 

sources and information on timing and location of 

survey effort). Dashed line represents the U.S. EEZ, 

thin lines indicate the completed transect effort of all 

surveys combined. 

POPULATION SIZE

 Abundance is estimated from two summer/fall shipboard surveys conducted within 300 nmi of 

the coasts of California, Oregon and Washington in 2005 (Forney 2007) and 2008 (Barlow 2010). 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 2005-2008 geometric mean abundance estimate for California, Oregon and Washington waters 

105
based on the 2005 and 2008 ship surveys is 10,908 (CV=0.34) striped dolphins (Barlow and Forney 2007 , 

Forney 2007, Barlow 2010). 

Minimum Population Estimate

 The log-normal 20th percentile of the 2005-2008 mean abundance estimate is 8,231 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 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. Barlow and Forney (2007) reported striped dolphin abundance estimates of 32,370, 14,622, 

4,796, 12,570, and 25,561 for the years 1991, 1993, 1996, 2001, and 2005, respectively. The estimate from 

the most recent 2008 ship survey is 4,655 (CV=0.30) (Barlow 2010). 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 (8,231) 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 82 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, 2004-2008 ( 

Carretta et al. 2005, Carretta and Enriquez 2006, 2007, 2009a, 2009b). No striped dolphins 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 2004-2008 data. This results in an 

average estimate of zero striped 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 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). 

106
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. 

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 2004-2008 13-21% 0 0 0 

Minimum total annual takes 0

Other mortality 

One striped dolphin stranded in Oregon in 2006 with “bruising and trauma, possible impact or 

fisheries interaction” evidence. This results in a human-caused average annual mortality of 0.2 striped 

dolphins per year for the period 2004-2008. 

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. The average annual human-caused mortality in 2004-2008 is 0.2. Because 

recent fishery and human-caused mortality is less than 10% of the PBR (82), 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. 2010. Cetacean abundance in the California Current from a 2008 ship-based line-transect 

survey. NOAA Technical Memorandum, NMFS, NOAA-TM-NMFS-SWFSC-456. 19 p. 

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. 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. 

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. 

Carretta, J.V. and L. Enriquez. 2009a. Marine mammal and seabird bycatch observed in California 

commercial fisheries in 2007. Administrative Report LJ-09-01, available from Southwest 

Fisheries Science Center, 3333 North Torrey Pines Rd., La Jolla, CA 92037. 12 p. 

Carretta, J.V. and L. Enriquez. 2009b. Marine mammal bycatch observed in the California/Oregon 

swordfish and thresher shark drift gillnet fishery in 2008. Administrative Report LJ-09-03, 

available from Southwest Fisheries Science Center, 3333 North Torrey Pines Rd., La Jolla, CA 

92037. 10 p. 

Carretta, J.V. and L. Enriquez. 2007. Marine mammal and sea turtle bycatch in the California/Oregon 

thresher shark and swordfish drift gillnet fishery in 2006. Administrative Report LJ-07-06, 

available from Southwest Fisheries Science Center, 8604 La Jolla Shores Drive, La Jolla, CA 

92037. 9p. 

Carretta, J.V. and L. Enriquez. 2006. Marine mammal bycatch and estimated mortality in California 

commercial fisheries during 2005. Administrative Report LJ-06-07, available from Southwest 

Fisheries Science Center, 8604 La Jolla Shores Drive, La Jolla, CA 92037. 14p. 

Carretta, J.V., S.J. Chivers, and K. Danil. 2005. Preliminary estimates of marine mammal bycatch, 

mortality, and biological sampling of cetaceans in California gillnet fisheries for 2004. 

107
Administrative Report LJ-05-10, available from Southwest Fisheries Science Center, 8604 La 

Jolla Shores Drive, La Jolla, California, 92037. 17 p. 

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. 2007. Preliminary estimates of cetacean abundance along the U.S. west coast and within 

four National Marine Sanctuaries during 2005. U.S. Department of Commerce, NOAA Technical 

Memorandum NMFS-SWFSC-406. 27p. 

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., R. R. Reeves, W. F. Perrin, and W. E. Evans. 1982. Whales, dolphins and porpoises of 

the eastern North Pacific and adjacent Arctic waters. A guide to their identification. NOAA Tech. 

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

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

the eastern Pacific Ocean and Gulf of California aboard the NOAA ships McARTHUR and DAVID 

STARR JORDAN July 28 - November 6, 1993. U.S. Dep. Commer., NOAA Tech. Memo. NMFSSWFSC-211. 88 pp. 

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

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

28. Available from NMFS, Southwest Fisheries Science Center, P.O. Box 271, La Jolla, 

California, 92038. 28p. 

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

375. 

Smith, R. C., P. Dustan, D. Au, K. S. Baker, and E. A. Dunlap. 1986. Distribution of cetaceans and seasurface chlorophyll concentrations in the California Current. Marine Biology 91:385-402. 

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

Velez. 1993. Estudio biologico pesquero del pez (Xiphias gladius) y otras especies de picudos 

(marlins y pez vela). Rep. Int. CICESE, CTECT9306. 

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

GAMMS Workshop April 3-5, 1996, Seattle, Washington. U. S. Dep. Commer., NOAA Tech. 

Memo. NMFS-OPR-12. 93 pp. 

108
Revised 01/15/2011

SHORT-BEAKED COMMON DOLPHIN (Delphinus delphis 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 have been commonly 

sighted as far north as 42o

N during 1991-

2008 NMFS line-transect vessel surveys 

(Figure 1). Four strandings of common 

dolphins 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 shortbeaked 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 shortbeaked common dolphins off California 

may be an extension of the "northern 

common dolphin" stock defined for 

management of eastern tropical Pacific tuna 

fisheries (Perrin et al. 1985). However, 

preliminary data on variation in dorsal fin 

color patterns suggest there may be multiple 

stocks in this region, including at least two 

possible stocks in California (Farley 1995). 

The less abundant long-beaked common dolphin has only recently been recognized as a different species 

(Heyning and Perrin 1994; Rosel et al. 1994), and much of the available information has not differentiated 

between the two types of common dolphin. Although short-beaked common dolphins are not restricted to 

U.S. waters, cooperative management agreements with Mexico exist only for the tuna purse seine fishery 

and not for other fisheries which may take this species (e.g. gillnet fisheries). Under the Marine Mammal 

Protection Act (MMPA), short-beaked common dolphins involved in tuna purse seine fisheries in 

international waters of the eastern tropical Pacific are managed separately, and they are not included in the 

assessment reports. For the MMPA stock assessment reports, there is a single Pacific management stock 

including only animals found within the U.S. Exclusive Economic Zone of California, Oregon and 

Washington. 

Figure 1. Short-beaked common dolphin sightings 

based on shipboard surveys off California, Oregon, 

and Washington, 1991- 2008 (see Appendix 2, for 

data sources and information on timing and location of 

survey effort). Dashed line represents the U.S. EEZ, 

thin lines indicate completed transect effort of all 

surveys combined. 

109
POPULATION SIZE

 The most recent estimates of abundance estimates are based on two summer/fall shipboard 

surveys that were conducted within 300 nmi of the coasts of California, Oregon and Washington in 2005 

(Forney 2007) and 2008 (Barlow 2010.). The distribution of short-beaked common dolphins throughout 

this region is highly variable, apparently in response to oceanographic changes on both seasonal and 

interannual time scales (Heyning and Perrin 1994; Forney 1997; Forney and Barlow 1998). As 

oceanographic conditions vary, short-beaked common dolphins may spend time outside the U.S. Exclusive 

Economic Zone, and therefore a multi-year average abundance estimate is the most appropriate for 

management within U.S. waters. The 2005-2008 geometric mean abundance estimate for California, 

Oregon and Washington waters based on the two ship surveys is 411,211 (CV= 0.21) short-beaked 

common dolphins . 

Minimum Population Estimate

 The log-normal 20th percentile of the 2005-2008 abundance estimate is 343,990 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). 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 shortbeaked 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 (343,990) 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 3,440 short-beaked common dolphins per year. 

110
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. 

Mean annual takes in Table 1 are based on 2004-2008 data. This results in an average estimate of 64 

(CV=0.29) short-beaked common dolphins taken annually. 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, 2004-2008 (Carretta et al. 2005, Carretta and Enriquez 2006, 2007, 2009a, 

2009b). 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). Since the 

initial pinger experiments in 1996, short-beaked common dolphin entanglement rates have remained below 

pre-pinger levels, even though a time/area closure in 2001 shifted fishing effort south of Point Conception, 

California, where common dolphin densities are highest (Figure 2). Prior to the use of acoustic pingers in 

the fishery, short-beaked common dolphin were observed entangled at a rate of 6.7 animals per 100 sets 

(125 entanglements in 1,848 sets) in sets south of Point Conception. In the same region, sets with twenty 

or more pingers have an entanglement rate of 4.4 animals per 100 sets (137 entanglements in 3,104 sets). 

The difference between the two entanglement rates is statistically significant (Poisson probability < 0.002). 

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. Coefficients of variation for mortality estimates are 

provided in parentheses; n/a = not available. Mean annual takes are based on 2004-2008 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 

2004 

2005 

2006 

2007 

2008 

20.6% 

20.9% 

18.5% 

16.4% 

13.5% 

7 

12 

6 

9 

8 

34 (0.49) 

57 (0.30) 

32 (0.52) 

54 (0.41) 

59 (0.43) 

47 (0.19) 

CA squid purse seine observer 

2004 

2005 

2006 

2007 

2008 

unknown 

1.1% 

unknown 

<5% 

<5% 

0 

1 

0 

0 

0 

0 

87 (0.98) 

0 

0 

0 

17 (0.98) 

CA halibut /white 

seabass and other 

species set gillnet 

fishery2

Self-report 

Self-report 

Observer 

Observer 

Observer 

2004 

2005 

2006 

2007 

2008 

- 

- 

- 

n/a 

n/a 

~1% 

17% 

not observed

1 

0 

0 

0 

0 

≥1 

0 

0 

0 

0 

≥1 (n/a) 

111
Fishery Name Data Type Year 

Percent 

Observer 

Coverage

Observed 

Mortality

Estimated Annual 

Mortality

Mean 

Annual Takes 

(CV in 

parentheses)

Unknown fishery strandings 2004-2008 

 Two unidentified common and three short-beaked 

common dolphin stranded with evidence of fishery 

interactions. Evidence of fishery interactions included 

net marks and/or positive metal detector scans. None of 

the strandings could be linked to a specific commercial 

fishery. These strandings may have come from observed 

fisheries that already have bycatch estimates and thus are 

not included in the annual average to prevent doublecounting of fishery mortality. Mean annual takes are 

therefore based on stranded animals only if the stranding 

can be attributed to a fishery lacking an observer 

program or cases where stranded animals represent the 

only documented fishery-related deaths in a given year. 

≥ 0 (n/a) 

Minimum total annual takes 64 (0.29) 

 1The 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. There are no estimates of common dolphin mortality in this fishery because of a lack of recent observer effort. 

Observer coverage in this fishery resumed in 2006 (12 sets observed) and continued into 2007 (248 sets observed).

Short-Beaked Common Dolphin Entanglement 

Rates

0

5

10

15

1990199119921993199419951996199719981999200020012002200320042005200620072008

Year

Entanglement/100 

Sets

No pingers Pingers

Figure 2. Entanglement rates of short-beaked common dolphin per set fished in the California drift gillnet 

fishery for swordfish and thresher shark, 1990-2008. Entanglement 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- 2008, more than 99% of all observed sets utilized pingers. 

Common dolphin mortality has also been reported in halibut set gillnets in California (Julian and 

Beeson 1998). The fishery has been observed only four times since 1994 (in 1999, 2000, 2006, and 2007), 

at low levels of observer coverage (< 20% of fishing effort). No common dolphins were observed 

entangled in 2007, when the fishery had approximately 18% observer coverage (248 sets observed). 

There were 377 sets observed in the squid purse seine fishery from 2004-2008. One short-beaked 

common dolphin mortality was observed in 2005, with a resulting mortality estimate of 87 (CV=0.98) 

112
animals (Carretta and Enriquez 2006). In addition, there was one squid purse seine set in 2006 where 8 

unidentified dolphins were encircled. Seven were released alive and the eighth was seriously injured. 

 One unidentified and three short-beaked common dolphin stranded with evidence of fishery 

interaction (NMFS, Southwest Region, unpublished data) between 2004-2008. It is not known which 

fisheries were responsible for these deaths.

 Drift gillnet fisheries for swordfish and sharks exist along the entire Pacific coast of Baja 

California, Mexico and may take animals from this population. Quantitative data are available only for the 

Mexican swordfish drift gillnet fishery, which uses vessels, gear, and operational procedures similar to 

those in the U.S. drift gillnet fishery, although nets may be up to 4.5 km long (Holts and Sosa-Nishizaki 

1998). The fleet increased from two vessels in 1986 to 31 vessels in 1993 (Holts and Sosa-Nishizaki 1998). 

The total number of sets in this fishery in 1992 can be estimated from data provided by these authors to be 

approximately 2700, with an observed rate of marine mammal bycatch of 0.13 animals per set (10 marine 

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

observed in California driftnet fisheries during 1990-95 (0.14 marine mammals per set; Julian and Beeson, 

1998), but species-specific information is not available for the Mexican fisheries. Previous efforts to 

convert the Mexican swordfish driftnet fishery to a longline fishery have resulted in a mixed-fishery, with 

20 vessels alternately using longlines or driftnets, 23 using driftnets only, 22 using longlines only, and 

seven with unknown gear type (Berdegué 2002). 

Other Mortality

 In the eastern tropical Pacific, 'northern common dolphins' have been incidentally killed in 

international tuna purse seine fisheries since the late 1950's. Cooperative international management 

programs have dramatically reduced overall dolphin mortality in these fisheries during the last decade 

(Joseph 1994). Between 2000-2004, annual fishing mortality of northern common dolphins (potentially 

including both short-beaked and long-beaked common dolphins) ranged between 54 and 159 animals, with 

an average of 102 (IATTC, 2006). 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. The average annual human-caused mortality in 2004-2008 (64 animals) is estimated to be less 

than the PBR (3,440), and therefore they are not classified as a "strategic" stock under the MMPA. The 

total estimated fishery mortality and injury for short-beaked common dolphins is less than 10% of the 

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

serious injury rate. 

REFERENCES

Anganuzzi, A. A., S. T. Buckland, and K. L Cattanach. 1993. Relative abundance of dolphins associated 

with tuna in the eastern tropical Pacific Ocean: analysis of 1991 data. Rep. Int. Whal. Commn 

43:459-465. 

Barlow, J. 2010. Cetacean abundance in the California Current from a 2008 ship-based line-transect 

survey. NOAA Technical Memorandum, NMFS, NOAA-TM-NMFS-SWFSC-456. 19 p. 

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. 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 K.A. Forney. 2007. Abundance and population density of cetaceans in the California 

Current ecosystem. Fishery Bulletin 105:509-526. 

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, 

113
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. 

Carretta, J.V. and L. Enriquez. 2009a. Marine mammal and seabird bycatch observed in California 

commercial fisheries in 2007. Administrative Report LJ-09-01, available from Southwest 

Fisheries Science Center, 3333 North Torrey Pines Rd., La Jolla, CA 92037. 12 p. 

Carretta, J.V. and L. Enriquez. 2009b. Marine mammal bycatch observed in the California/Oregon 

swordfish and thresher shark drift gillnet fishery in 2008. Administrative Report LJ-09-03, 

available from Southwest Fisheries Science Center, 3333 North Torrey Pines Rd., La Jolla, CA 

92037. 10 p . 

Carretta, J.V. and L. Enriquez. 2007. Marine mammal and sea turtle bycatch in the California/Oregon 

thresher shark and swordfish drift gillnet fishery in 2006. Administrative Report LJ-07-06, 

available from Southwest Fisheries Science Center, 8604 La Jolla Shores Drive, La Jolla, CA 

92037. 9p. 

Carretta, J.V. and L. Enriquez. 2006. Marine mammal bycatch and estimated mortality in California 

commercial fisheries during 2005. Administrative Report LJ-06-07, available from Southwest 

Fisheries Science Center, 8604 La Jolla Shores Drive, La Jolla, CA 92037. 14p. 

Carretta, J.V., S.J. Chivers, and K. Danil. 2005. Preliminary estimates of marine mammal bycatch, 

mortality, and biological sampling of cetaceans in California gillnet fisheries for 2004. 

Administrative Report LJ-05-10, available from Southwest Fisheries Science Center, 8604 La 

Jolla Shores Drive, La Jolla, California, 92037. 17 p. 

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. 

Forney, K.A. 2007. Preliminary estimates of cetacean abundance along the U.S. west coast and within 

four National Marine Sanctuaries during 2005. U.S. Department of Commerce, NOAA Technical 

Memorandum NMFS-SWFSC-406. 27p. 

Heyning, J. E. and W. F. Perrin. 1994. Evidence for two species of common dolphins (Genus Delphinus) 

from the eastern North Pacific. Contr. Nat. Hist. Mus. L.A. County, No. 442. 

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

Commer., NOAA Tech. Memo. NMFS-AFSC-97. 166pp. 

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

Holts, D. 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. 2006. Annual Report of the Inter-American Tropical Tuna Commission, 2004, La Jolla, 

California. 96p. 

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. 

114
Julian, F. and M. Beeson. 1998. Estimates of mammal, turtle and bird mortality for two California gillnet 

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

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

the eastern Pacific Ocean and Gulf of California aboard the NOAA ships McARTHUR and DAVID 

STARR JORDAN July 28 - November 6, 1993. NOAA Technical Memorandum NMFS, NOAATM-NMFS-SWFSC-211. 

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

NMFS, Southwest Region, 501 West Ocean Blvd, Long Beach, CA 90802_4213. 

Norberg, B., NMFS, Northwest Region,.7600 Sand Point Way NE, BIN C15700,Seattle, WA 98115_0070. 

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

dolphins (Stenella spp. and Delphinus delphis) in the eastern Pacific. NOAA Technical Report 

NMFS 28. Available from NMFS, Southwest Fisheries Science Center, P.O. Box 271, La Jolla, 

California, 92038. 28p. 

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

375. 

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

common dolphin (genus Delphinus) utilizing mitochondrial DNA control region sequences. 

Marine Biology 119:159-167. 

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

Velez. 1993. Estudio biologico pesquero del pez (Xiphias gladius) y otras especies de picudos 

(marlins y pez vela). Rep. Int. CICESE, CTECT9306. 

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

GAMMS Workshop April 3-5, 1996, Seattle, Washington. U. S. Dep. Commer., NOAA Tech. 

Memo. NMFS-OPR-12. 93 pp. 

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

tropical Pacific. Rep. Int. Whal. Commn 43:477-493. 

115
Revised 01/15/2011

LONG-BEAKED COMMON DOLPHIN (Delphinus capensis capensis): 

California Stock 

STOCK DEFINITION AND GEOGRAPHIC RANGE

Long-beaked common dolphins 

have only recently been recognized as a 

distinct species (Heyning and Perrin 1994; 

Rosel et al. 1994). Along the U.S. west 

coast, their distribution overlaps with that 

of the short-beaked common dolphin, and 

much historical information has not 

distinguished between these two species. 

Long-beaked common dolphins are 

commonly found within about 50 nmi of 

the coast, from Baja California (including 

the Gulf of California) northward to about 

central California (Figure 1). Stranding 

data and sighting records indicate that the 

relative abundance of this species off 

California changes both seasonally and 

inter-annually. Although long-beaked 

common dolphins are not restricted to U.S. 

waters, cooperative management 

agreements with Mexico exist only for the 

tuna purse seine fishery and not for other 

fisheries which may take this species (e.g. 

gillnet fisheries). Under the Marine 

Mammal Protection Act (MMPA), longbeaked ("Baja neritic") common dolphins 

involved in eastern tropical Pacific tuna 

fisheries are managed separately as part of 

the 'northern common dolphin' stock (Perrin 

et al. 1985), and these animals are not 

included in the assessment reports. For the 

MMPA stock assessment reports, there is a 

single Pacific management stock including 

only animals found within the U.S. 

Exclusive Economic Zone of California. 

POPULATION SIZE

 The most recent abundance 

estimates are 11,714 (CV=0.99) and 62,447 

(CV=0.80) long-beaked common dolphins, based on 2005 and 2008 ship line transect surveys, respectively, 

of California, Oregon, and Washington waters ( Forney 2007; Barlow 2010). The distribution and 

abundance of long-beaked common dolphins off California appears to be variable on interannual and 

seasonal time scales (Heyning and Perrin 1994). As oceanographic conditions change, long-beaked 

common dolphins may move between Mexican and U.S. waters, and therefore a multi-year average 

abundance estimate is the most appropriate for management within the U.S. waters. The geometric mean 

abundance estimate for California, Oregon and Washington waters based on two ship surveys conducted in 

2005 and 2008 is 27,046 (CV=0.59) long-beaked common dolphins ( Forney 2007; Barlow 2010). 

Figure 1. Long-beaked common dolphin sightings based 

on shipboard surveys off California, Oregon, and 

Washington, 1991- 2008 (see Appendix 2 for information 

on timing and location of survey effort). No Delphinus 

sightings have been made off Washington. Dashed line 

represents the U.S. EEZ, thin lines indicate completed 

transect effort of all surveys combined. 

116
Minimum Population Estimate

 The log-normal 20th percentile of the weighted average abundance estimate is 17,127 long-beaked 

common dolphins. 

Current Population Trend

 California waters represent the northern limit for this stock and animals likely move between 

U.S. and Mexican waters. No information on trends in abundance are available for this stock because of 

high interannual variability in line-transect abundance estimates. Heyning and Perrin (1994) 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 (17,127) 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 164 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, 2004-2008 

(Carretta et al. 2005, Carretta and Enriquez 2006, 2007, 2009a, 2009b). 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. 

 Common dolphin mortality has also been reported in halibut set gillnets in California (Julian and 

Beeson 1998). This fishery has only been observed twice since 2004 (Table 1). Although no common 

dolphins were observed taken, fisherman self-reports in 2004 indicate that at least one common dolphin 

(type not specified) were killed (Marine Mammal Authorization Permit Program data). Although these 

reports are considered unreliable (see Appendix 4 of Hill and DeMaster 1998) they represent a minimum 

mortality for this fishery. 

 Twenty-four common dolphins (two unidentified common dolphin and 22 long-beaked common 

dolphins) stranded with evidence of fishery interaction (NMFS, Southwest Region, unpublished data) 

between 2004-2008. All but six of these strandings showed evidence of an interaction with an unknown 

entangling net fishery (severed flukes, knife cuts, net marks, or net fragments wrapped around the animal). 

One animal showed evidence of an interaction with an unknown hook and line fishery and five animals had 

either bullets removed from the carcass (3) or evidence of gunshot wounds (2). Mean annual takes in Table 

1 are based on 2004-2008 data. 

 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 

117
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 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. Coefficients of variation 

for mortality estimates are provided in parentheses, when available. Mean annual takes are based on 2004-

2008 data unless noted otherwise. n/a = information not available. 

Fishery Name Data Type Year(s) 

Percent 

Observer 

Coverage

Observed 

(or selfreported) 

Estimated Annual 

Mortality

Mean 

Annual Takes 

(CV in 

parentheses)

CA/OR thresher 

shark/swordfish drift 

gillnet fishery

observer 

2004 

2005 

2006 

2007 

2008 

20.6% 

20.9% 

18.5% 

16.4% 

13.5% 

0 

3 

1 

0 

1 

0 

14 (0.57) 

5 (1.04) 

0 

7 (1.08) 

5.2 (0.78) 

CA small mesh drift 

gillnet fishery for white 

seabass, yellowtail, 

barracuda, and tuna1 

observer 

2004 

2005 

2006 

2007 

2008 

17.6% 

not observed 

not observed 

not observed 

not observed 

1 

n/a 

n/a 

n/a 

n/a 

5 (1.18) 

n/a 

n/a 

n/a 

n/a 

5 (1.18) 

CA halibut /white 

seabass and other species 

set gillnet fishery 

Self report 

& observer 

2004 

2005 

2006 

2007 

2008 

not observed 

not observed 

~1% 

17% 

not observed 

(1) 

0 

0 

0 

0 

≥1 

0 

0 

0 

0 

≥1 (n/a) 

Undetermined strandings 2004-2008

24 common dolphins (two unidentified and 22 

longbeaked common dolphins) stranded with evidence 

of fishery interactions. Evidence of fishery interactions 

included severed flukes, net fragments, net marks, 

positive metal detector scans, and knife marks or cuts. 

Some strandings may have come from observed 

fisheries that already have bycatch estimates and these 

are not included in the annual average to prevent 

double-counting of fishery mortality. Mean annual 

takes are therefore based on stranded animals only if the 

stranding can be attributed to a fishery lacking an 

observer program or cases where stranded animals 

represent the only documented fishery-related deaths in 

a given year. This results in a minimum of 9 longbeaked common dolphin strandings over the 5 year 

period, or 1.8 animals annually. 

 1.8 (n/a) 

Minimum total annual takes

13.0 (0.51) 

1 Observer coverage in the small mesh drift gillnet fishery was estimated from logbook records. Logbook effort totaled 192, 134, 191, 

201, and 125 sets for 2000 through 2004, respectively. The fishery was not observed after 2004. 

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 2000-2004, annual fishing mortality of northern common dolphins (potentially 

including both short-beaked and long-beaked common dolphins) ranged between 54 and 159 animals, with 

an average of 102 (IATTC, 2006). Although it is unclear whether these animals are part of the same 

population as long-beaked common dolphins found off California, they are managed separately under a 

118
section of the MMPA written specifically for the management of dolphins involved in eastern tropical 

Pacific tuna fisheries. 

‘Unusual mortality events’ of long-beaked common dolphins due to domoic acid toxicity have 

been documented by NMFS as recently as 2007 along the California coast. 

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. The average annual 

human-caused mortality from 2004-2008 (13.0 animals) does not exceed the PBR (164), 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 (13.0) is less than 10% of the PBR and therefore, is considered to be 

insignificant and approaching zero mortality and serious injury rate. 

REFERENCES

Barlow, J. 2010. Cetacean abundance in the California Current from a 2008 ship-based line-transect 

survey. NOAA Technical Memorandum, NMFS, NOAA-TM-NMFS-SWFSC-456. 

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. 

Barlow, J. and K.A. Forney. 2007. Abundance and population density of cetaceans in the California 

Current ecosystem. Fishery Bulletin 105:509-526. 

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. 

Carretta, J.V. and L. Enriquez. 2009a. Marine mammal and seabird bycatch observed in California 

commercial fisheries in 2007. Administrative Report LJ-09-01, available from Southwest 

Fisheries Science Center, 3333 North Torrey Pines Rd., La Jolla, CA 92037. 12 p. 

Carretta, J.V. and L. Enriquez. 2009b. Marine mammal bycatch observed in the California/Oregon 

swordfish and thresher shark drift gillnet fishery in 2008. Administrative Report LJ-09-03, 

available from Southwest Fisheries Science Center, 3333 North Torrey Pines Rd., La Jolla, CA 

92037. 10 p . 

Carretta, J.V. and L. Enriquez. 2007. Marine mammal and sea turtle bycatch in the California/Oregon 

thresher shark and swordfish drift gillnet fishery in 2006. Administrative Report LJ-07-06, 

available from Southwest Fisheries Science Center, 8604 La Jolla Shores Drive, La Jolla, CA 

92037. 9p. 

Carretta, J.V. and L. Enriquez. 2006. Marine mammal bycatch and estimated mortality in California 

commercial fisheries during 2005. Administrative Report LJ-06-07, available from Southwest 

Fisheries Science Center, 8604 La Jolla Shores Drive, La Jolla, CA 92037. 14p. 

Carretta, J.V., S.J. Chivers, and K. Danil. 2005. Preliminary estimates of marine mammal bycatch, 

mortality, and biological sampling of cetaceans in California gillnet fisheries for 2004. 

Administrative Report LJ-05-10, available from Southwest Fisheries Science Center, 8604 La 

Jolla Shores Drive, La Jolla, California, 92037. 17 p. 

Forney, K.A. 2007. Preliminary estimates of cetacean abundance along the U.S. west coast and within 

four National Marine Sanctuaries during 2005. U.S. Department of Commerce, NOAA Technical 

Memorandum NMFS-SWFSC-406. 27p. 

Heyning, J. E. and W. F. Perrin. 1994. Evidence for two species of common dolphins (Genus Delphinus) 

from the eastern North Pacific. Contr. Nat. Hist. Mus. L.A. County, No. 442. 

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

Commer., NOAA Tech. Memo. NMFS-AFSC-97. 166 pp. 

Holts, D. 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, 

119
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. 2006. Annual Report of the Inter-American Tropical Tuna Commission, 2004, La Jolla, 

California. 96p. 

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. 

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. 

120
Revised 01/15/2011 

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. 

Figure 1. Northern right whale dolphin sightings based 

on aerial and shipboard surveys off California, Oregon, 

and Washington, 1991-2008 (see Appendix 2 for data 

sources and information on timing and location of 

survey effort). Dashed line represents the U.S. EEZ, 

thin lines indicates completed transect effort of all 

surveys combined. Key: ● = summer/autumn ship-based 

sightings; ■ = winter/spring aerial-based sightings. 

POPULATION SIZE

 The previous best estimates of abundance for northern right-whale dolphins (Barlow et al. 1997) 

were based on winter/spring 1991-92 aerial surveys (Forney et al. 1995) off California, which were 

presumed to include northern right-whale dolphins that are found off Oregon and Washington during 

summer and fall. Two summer/fall shipboard surveys were conducted within 300 nmi of the coasts of 

California, Oregon and Washington in 2005 (Forney 2007) and 2008 (Barlow 2010). The distribution of 

northern right-whale dolphins throughout this region is highly variable, apparently in response to 

121
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 2005-2008 geometric mean abundance estimate for California, 

Oregon and Washington waters based on the two ship surveys is 8,334 (CV=0.40) northern right-whale 

dolphins (Forney 2007, Barlow 2010). 

Minimum Population Estimate

 The log-normal 20th percentile of the 2005-2008 average abundance estimate is 6,019 northern 

right-whale dolphins. 

Current Population Trend

 Abundance estimates for all California, Oregon, and Washington waters from 1996, 2001, 2005, 

and 2008 surveys were 11,347 (CV = 0.27), 14,937 (0.21), 11,100 (0.60), and 6,258 (CV=0.58), 

respectively (Barlow and Forney 2007, Forney 2007, Barlow 2010). 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 (6,019) 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 48 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, 

2004-2008 (Carretta et al. 2005 Carretta and Enriquez 2006, 2007, 2009a, 2009b). 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 2004-2008 data. This results in an average estimate of 3.6 (CV= 0.96) 

northern right-whale 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 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). 

122
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 2004-

2008 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 

2004 

2005 

2006 

2007 

2008 

20.6% 

20.9% 

18.5% 

16.4% 

13.5% 

1 

0 

0 

1 

1 

 5 (0.99) 

0 

0 

6 (1.00) 

7 (0.99) 

3.6 (0.96) 

Minimum total annual takes 3.6 (0.96) 

Figure 2. Entanglement rates of northern right whale dolphin per set fished in the California drift gillnet 

fishery for swordfish and thresher shark, 1990-2008. 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 1998-2008, over 99% of all observed sets utilized pingers. 

Northern right whale dolphin entanglement rates

0

0.5

1

1.5

2

2.5

3

1990199119921993199419951996199719981999200020012002200320042005200620072008

Year

Entanglement/100 

Sets

No pingers Pingers

 

Other removals 

In 2008, six northern right whale dolphins were incidentally killed in California waters during 

scientific sardine trawling operations conducted by NMFS (Southwest Regional Office Stranding Program, 

unpublished data). All six animals were killed in a single trawl where 11 Pacific white-sided dolphin were 

also killed (see Pacific white-sided dolphin stock assessment). The average annual research-related 

mortality of northern right whale dolphin from 2004 to 2008 is 1.2 animals. 

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. The average annual human-caused mortality in 2004-

123
2008 (4.8 animals) is estimated to be less than the PBR ( 48), 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 does not exceed 10% of the calculated PBR and, therefore, can be considered to be insignificant 

and approaching zero mortality and serious injury rate. 

REFERENCES 

Barlow, J. 2010. Cetacean abundance in the California Current from a 2008 ship-based line-transect 

survey. NOAA Technical Memorandum, NMFS, NOAA-TM-NMFS-SWFSC-456. 19p. 

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. 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., 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 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 K.A. Forney. 2007. Abundance and population density of cetaceans in the California 

Current ecosystem. Fishery Bulletin 105:509-526.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. 

Carretta, J.V. and L. Enriquez. 2009a. Marine mammal and seabird bycatch observed in California 

commercial fisheries in 2007. Administrative Report LJ-09-01, available from Southwest 

Fisheries Science Center, 3333 North Torrey Pines Rd., La Jolla, CA 92037. 12 p. 

Carretta, J.V. and L. Enriquez. 2009b. Marine mammal bycatch observed in the California/Oregon 

swordfish and thresher shark drift gillnet fishery in 2008. Administrative Report LJ-09-03, 

available from Southwest Fisheries Science Center, 3333 North Torrey Pines Rd., La Jolla, CA 

92037. 10 p . 

Carretta, J.V. and L. Enriquez. 2007. Marine mammal and sea turtle bycatch in the California/Oregon 

thresher shark and swordfish drift gillnet fishery in 2006. Administrative Report LJ-07-06, 

available from Southwest Fisheries Science Center, 8604 La Jolla Shores Drive, La Jolla, CA 

92037. 9p. 

Carretta, J.V. and L. Enriquez. 2006. Marine mammal bycatch and estimated mortality in California 

commercial fisheries during 2005. Administrative Report LJ-06-07, available from Southwest 

Fisheries Science Center, 8604 La Jolla Shores Drive, La Jolla, CA 92037. 14p. 

Carretta, J.V., S.J. Chivers, and K. Danil. 2005. Preliminary estimates of marine mammal bycatch, 

mortality, and biological sampling of cetaceans in California gillnet fisheries for 2004. 

Administrative Report LJ-05-10, available from Southwest Fisheries Science Center, 8604 La 

Jolla Shores Drive, La Jolla, California, 92037. 17 p. 

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. 

124
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. 

Forney, K.A. 2007. Preliminary estimates of cetacean abundance along the U.S. west coast and within 

four National Marine Sanctuaries during 2005. U.S. Department of Commerce, NOAA Technical 

Memorandum NMFS-SWFSC-406. 27 p. 

Green, G., J. J. Brueggeman, R. A. Grotefendt, C. E. Bowlby, M. L. Bonnell, and K. C. Balcomb, III. 

1992. Cetacean distribution and abundance off Oregon and Washington. Ch. 1. In: Oregon and 

Washington Marine Mammal and Seabird Surveys. OCS Study 91-0093. Final Report prepared 

for Pacific OCS Region, Minerals Management Service, U.S. Department of the Interior, Los 

Angeles, California. 

Green, G., R. A. Grotefendt, M. A. Smultea, C. E. Bowlby, and R. A. Rowlett. 1993. Delphinid aerial 

surveys in Oregon and Washington waters. Final Report prepared for NMFS, National Marine 

Mammal Laboratory, 7600 Sand Point Way, NE, Seattle, Washington, 98115, Contract 

#50ABNF200058. 

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

Ocean. In: I. Barrett, O. Sosa-Nishizaki and N. Bartoo (eds.). Biology and fisheries of swordfish, 

Xiphias gladius. Papers from the International Symposium on Pacific Swordfish, Ensenada 

Mexico, 11-14 December 1994. U.S. Dep. Commer., NOAA Tech. Rep. NMFS 142, 276 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. 

125
Revised 01/15/2011

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; Barlow and 

Forney 2007). 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). 

Figure 1. Killer whale sightings based on shipboard 

surveys off California, Oregon and Washington, 1991-

2008 (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, thin lines

indicate completed transect effort of all surveys 

combined. 

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 

126
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. 

POPULATION SIZE

 Off British Columbia, approximately 200 offshore killer whales were identified between 1989 and 

1993 (Ford et al. 1994), and 20 of these individuals have also been seen off California (Black et al. 1997). 

Using only good quality photographs that clearly show characteristics of the dorsal fin and saddle patch 

region, an additional 11 offshore killer whales that were not previously known have been identified off the 

California coast, bringing the total number of known individuals in this population to 211. This is certainly 

an underestimate of the total population size, because not all animals in this population have been 

photographed. In the future, it may be possible estimate the total abundance of this transboundary stock 

using mark-recapture analyses based on individual photographs. Based on summer/fall shipboard linetransect surveys in 2005 (Forney 2007) and 2008 (Barlow 2010), the total number of killer whales within 

300 nmi of the coasts of California, Oregon and Washington is estimated to be 691 animals (CV=0.49). 

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 * 691 = 

240 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 

2005-2008 line-transect surveys as the 20th percentile of the geometric mean 2005-2008 abundance 

estimate, or 466 killer whales. Using the same prorating as above, a minimum of 56/161 * 466 = 162 

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 (162) 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 1.6 offshore killer whales per year. 

127
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 (Carretta et al. 2005, Carretta and Enriquez 2006, 2007, 2009a, 2009b). 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 and Chivers 2004, Carretta et al. 2005a, 2005b, Carretta and Enriquez 2006, 2007, 

2009a, 2009b), 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 and additional observations between 2000 and 2008 monitored 5-15% of all sets in the 

large mesh (>3.5") set gillnet fishery for halibut , and no killer whales were observed taken. Based on 

observations for longline fisheries in other regions (i.e. Alaska; Yano and Dahlheim 1995), fishery 

interactions may also occur with U.S. West coast pelagic longline fisheries, but no such interactions have 

been documented to date. 

Table 1. Summary of available information on the incidental mortality and injury of killer whales (Eastern 

North Pacific Offshore Stock) in commercial fisheries that might take this species. Mean annual takes are 

based on 2004-2008 data unless noted otherwise. 

Fishery Name Data Type Year(s) 

Percent 

Observer 

Coverage

Observed 

Mortality

Estimated An ual n

Mortality

Mean 

Annual Takes 

(CV in 

parentheses) 

CA/OR thresher 

shark/swordfish drift 

gillnet fishery

observer 

data

2004 

2005 

2006 

2007 

2008 

20.6% 

20.9% 

18.5% 

16.4% 

13.5% 

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). 

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 stock. 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. 

128
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Memo. NMFS-OPR-12. 93 pp. 

131
Revised 01/15/2011

KILLER WHALE (Orcinus orca): 

Eastern North Pacific Southern Resident Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

 Killer whales have been observed in all oceans and 

seas of the world (Leatherwood and Dahlheim 1978). 

Although reported from tropical and offshore waters, killer 

whales prefer the colder waters of both hemispheres, with 

greatest abundances found within 800 km of major 

continents (Mitchell 1975). Along the west coast of North 

America, killer whales occur along the entire Alaskan coast 

(Braham and Dahlheim 1982), in British Columbia and 

Washington inland waterways (Bigg et al. 1990), and along 

the outer coasts of Washington, Oregon, and California 

(Green et al. 1992; Barlow 1995, 1997; Forney et al. 1995). 

Seasonal and year-round occurrence has been noted for 

killer whales throughout Alaska (Braham and Dahlheim 

1982) and in the intracoastal waterways of British Columbia 

and Washington State, where pods have been labeled as 

‘resident,’ ‘transient,’ and ‘offshore’ (Bigg et al. 1990, Ford 

et al. 1994) based on aspects of morphology, ecology, 

genetics, and behavior (Ford and Fisher 1982, Baird and 

Stacey 1988, Baird et al. 1992, Hoelzel et al. 1998). 

Through examination of photographs of recognizable 

individuals and pods, movements of whales between 

geographical areas have been documented. For example, 

whales identified in Prince William Sound have been 

observed near Kodiak Island (Matkin et al. 1999) and 

whales identified in Southeast Alaska have been 

observed in Prince William Sound, British Columbia, 

and Puget Sound (Leatherwood et al. 1990, Dahlheim et 

al. 1997). 

Studies on mtDNA restriction patterns provide 

evidence that the ‘resident’ and ‘transient’ types are 

genetically distinct (Stevens et al. 1989, Hoelzel 1991, 

Hoelzel and Dover 1991, Hoelzel et al. 1998). Analysis of 73 samples collected from eastern North Pacific killer 

whales from California to Alaska has demonstrated significant genetic differences among ‘transient’ whales from 

California through Alaska, ‘resident’ whales from the inland waters of Washington, and ‘resident’ whales ranging 

from British Columbia to the Aleutian Islands and Bering Sea (Hoelzel et al. 1998). However, low genetic diversity 

throughout this species world-wide distribution has hampered efforts to clarify its taxonomy. At an international 

symposium in cetacean systematics in May 2004, a workshop was held to review the taxonomy of killer whales. A 

majority of invited experts felt that the Resident- and Transient-type whales in the eastern North Pacific probably 

merited species or subspecies status (Reeves et al. 2004). 

Figure 1. Approximate April-October distribution 

of the Eastern North Pacific Southern Resident killer 

whale stock (shaded area) and range of sightings 

(diagonal lines).

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, NWFSC unpubl. data). 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). These latter two pods have been sighted as far south as Monterey Bay 

and central California in recent years (N. Black, pers. comm., K. Balcomb, pers. comm.) They sometimes have also 

been seen entering the inland waters of Vancouver Island from the north–through Johnstone Strait–in the spring 

(Ford et al. 2000), suggesting that they may spend time along the entire outer coast of Vancouver Island during the 

winter. In May 2003, these pods were sighted off the northern end of the Queen Charlotte Islands, the furthest north 

they had ever been documented (J. Ford, pers. comm.). 

132
 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. 

POPULATION SIZE

 The Eastern North Pacific Southern Resident stock is a trans-boundary stock including killer whales in 

inland Washington and southern British Columbia waters. Photo-identification of individual whales through the 

years has resulted in a substantial understanding of this stock’s structure, behaviors, and movements. In 1993, the 

three pods comprising this stock totaled 96 killer whales (Ford et al. 1994). The population increased to 99 whales 

in 1995, then declined to 79 whales in 2001, and most recently numbered 85 whales in 2009 (Fig. 2; Ford et al. 

2000; Center for Whale Research, unpubl. data). The 2001-2005 counts included 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.). L-98 remained separate from L pod until 10 

March 2006 when he died due to injuries associated with a vessel interaction in Nootka Sound. L-98 has been 

subtracted from the official 2006 and subsequent population censuses. The most recent census includes three new 

calves and the deaths of two reproductive adult females and an adult male since 1 July 2008. It does not include a 

calf born last fall summer that did not survive to 1 July 2009 (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 85 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 declined to 79 

whales before increasing from 2002-2005 

to a total of 91 whales. The population 

declined for three years to 85 whales but 

remained unchanged in 2009 (Ford et al. 

2000; Center for Whale Research, 

unpubl. data). 

50

60

70

80

90

100

197419761978198019821984198619881990199219941996199820002002200420062008

Year

Total population

Figure 2. Population of Eastern North Pacific Southern Resident 

stock of killer whales, 1974-2009. 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).

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). For southern resident killer whales, estimates of the population growth rate have been made during 

the three periods when the population has been documented increasing since monitoring began in 1974. From 1974 

to 1980 the population increased at a rate of 2.6%/year, 2.3%/year from 1985 to 1996, and 3.6%/year from 2002 to 

2005 (Center for Whale Research, unpubl. data). However, a population increases at the maximum growth rate 

133
(RMAX) only when the population is at extremely low levels; thus, any of these estimates 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 

(85) 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 stock, Wade and Angliss 1997), resulting in a PBR of 0.17 whales per year. 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Fisheries Information

 NMFS observers have monitored the northern Washington marine set gillnet fishery since 1988 (Gearin et 

al. 1994, 2000; P. Gearin, unpubl. data). Observer coverage ranged from approximately 40 to 83% in the entire 

fishery (coastal + inland waters) between 1998 and 2002. There was no observer coverage in this fishery from 

1999-2003. However, the total fishing effort was 4, 46, 4.5 and 7 net days (respectively) in those years, it occurred 

only in inland waters, and no killer whale takes were reported. No killer whale mortality has 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 mortality was 

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 2004, there were no fisher self-reports of killer whale mortality from any 

fisheries operating within the range of this stock. However, because logbook records (fisher self-reports required 

during 1990-94) are most likely negatively biased (Credle et al. 1994), these are considered to be minimum 

estimates. Logbook data are available for part of 1989-1994, after which incidental mortality reporting requirements 

were modified. Under the new system, logbooks are no longer required; instead, fishers provide self-reports. Data 

for the 1994-1995 phase-in period is fragmentary. After 1995, the level of reporting dropped dramatically, such that 

the records are considered incomplete and estimates of mortality based on them represent minimums (see Appendix 

7 in Angliss and Lodge 2002 for details). 

 Due to a lack of observer programs, there are few data concerning the mortality of marine mammals 

incidental to Canadian commercial fisheries. Since 1990, there have been no reported fishery-related strandings of 

killer whales in Canadian waters. However, in 1994 one killer whale was reported to have contacted a salmon 

gillnet but did not entangle (Guenther et al. 1995). Data regarding the level of killer whale mortality related to 

commercial fisheries in Canadian waters are not available, though the mortality level is thought to be minimal. 

 During this decade there have been no reported takes from this stock incidental to commercial fishing 

operations (D. Ellifrit, pers. comm.), no reports of interactions between killer whales and longline operations (as 

134
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 mortality or serious injuries were reported from non-fisheries sources in 

1998-2004. There was documentation of a whale-boat collision in Haro Strait in 2005 which resulted in a minor 

injury to a whale. In 2006, whale L98 was killed during a vessel interaction. It is important to note that L98 had 

become habituated to regularly interacting with vessels during its isolation in Nootka Sound. The annual level of 

human-caused mortality for this stock over the past five years is 0.2 animals per year (reflecting the vessel strike 

mortality of animal L98 in 2006). 

STATUS OF STOCK

 On November 15, 2005 NMFS listed Southern Resident killer whales as endangered under the ESA. Total 

annual fishery mortality and serious injury for this stock (0) is not known to exceed 10% of the calculated PBR 

(0.17) 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 0.2 animals per year exceeds the PBR (0.17). 

Southern Resident killer whales are formally listed as “endangered” under the ESA and consequently the stock is 

automatically considered as a “strategic” stock under the MMPA. This stock was considered “depleted” prior to its 

2005 listing under the ESA. 

Habitat Issues 

Several of the potential risk factors identified for this population have habitat implications. The summer range of 

this population, the inland waters of Washington and British Columbia, is the home to a large commercial whale 

watch industry as well as high levels of recreational boating and commercial shipping. There continues to be 

concern about potential for masking effects by noise generated from these activities on the whales’ communication 

and foraging. This population appears to be Chinook salmon specialists (Ford and Ellis 2006, NWFSC 

unpubl.data), and there is some evidence that changes in coast–wide Chinook abundance has affected this population 

(Ford et al. 2009). In addition, the high trophic level and longevity of the animals has predisposed them to 

accumulate levels of contaminants that are high enough to cause potential health impacts. In particular, there is 

recent evidence of extremely high levels of flame retardants in young animals (Krahn et. al 2007, 2009). 

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137
Revised 01/15/2011 

SHORT-FINNED PILOT WHALE (Globicephala macrorhynchus): 

California/Oregon/Washington Stock 

STOCK DEFINITION AND 

GEOGRAPHIC RANGE

 Short-finned pilot whales were 

once common 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 

sightings of short-finned pilot whales off 

the U.S. west coast from 1991-2008. 

Although the full geographic range of the 

California, Oregon, and 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. 

Figure 1. Short-finned pilot whale sightings made 

during shipboard surveys conducted off California, 

Oregon, and Washington, 1991-2008. See Appendix 2 

for data sources and information on timing and location 

of survey effort. Dashed line represents the U.S. EEZ, 

thin lines indicate completed transect effort of all 

surveys combined. 

POPULATION SIZE

 Only two groups of pilot whales numbering approximately 26 and 43 animals, respectively were 

seen during the two most recent ship surveys conducted off California, Oregon, and Washington in 2005 

and 2008 (Barlow and Forney 2007; Forney 2007, Barlow 2010). Abundance is estimated at 489 

(CV=0.97) and 1,180 (CV=1.00) for the 2005 and 2008 surveys, respectively (Forney 2007, Barlow 2010). 

The abundance of short-finned pilot whales in this region is variable and may be influenced by prevailing 

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 2005-2008 

138
geometric mean abundance estimate for California, Oregon and Washington waters based on the two ship 

surveys is 760 (CV=0.64) short-finned pilot whales (Barlow and Forney 2007 ; Forney 2007; Barlow 

2010). 

Minimum Population Estimate

 The log-normal 20th percentile of the 2005-2008 geometric mean abundance estimate is 465 

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 incidental fishery mortality (Barlow and Gerrodette 1996; Carretta et al. 1995; 

Julian and Beeson 1998; Forney 2007; Barlow 2010). 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, or 

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 (465) 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 in the last 5 years; 

Wade and Angliss 1997), resulting in a PBR of 4.6 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, 

2004-2008 (Carretta et al. 2005, Carretta and Enriquez 2006, 2007, 2009a, 2009b). 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. There have been 11 pilot whale deaths observed in this fishery since 1990. In 1993, there were 8 

deaths observed, and one each in 1990, 1992, 1997 (in an unpingered net) and 2003. Mean annual takes in 

Table 1 are based on 2004-2008 data. This results in an average estimate of zero 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 

139
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), but these deaths occurred when pilot whales 

were still common in the region. An observer program in the squid purse seine fishery was initiated in 

2004 and a total of 377 sets have been observed through 2008 without a pilot whale interaction. Observer 

coverage in this fishery has been less than 10% of all fishing effort. 

 

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. 

Coefficients of variation for mortality estimates are provided in parentheses; n/a = not available. Mean 

annual takes are based on 2004-2008 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 

2004 

2005 

2006 

2007 

2008 

20.6% 

20.9% 

18.5% 

16.4% 

13.5% 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

Market squid purse seine observer 2004-2008 <10% 0 0 0 

Minimum total annual takes 0 

STATUS OF STOCK

 The status of short-finned pilot whales off California, Oregon and Washington in relation to OSP 

is unknown. They have declined in abundance in the Southern California Bight, likely a result of a change 

in their distribution since the 1982-83 El Niño, but the nature of these changes and potential habitat issues 

are not adequately understood. Short-finned pilot whales are not listed as "threatened" or "endangered" 

under the Endangered Species Act nor as "depleted" under the MMPA. The average annual human-caused 

mortality from 2004-2008 is zero animals, less than the PBR of 4.6, and therefore they are not classified as 

a "strategic" stock under the MMPA. Total annual human-caused mortality and serious injury for this stock 

is estimated at zero animals, therefore, mortality is considered to be approaching a zero mortality and 

serious injury rate. 

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Barlow, J. and K.A. Forney. 2007. Abundance and population density of cetaceans in the California 

Current ecosystem. Fishery Bulletin 105:509-526. 

Barlow, J. 1997. Preliminary estimates of cetacean abundance off California, Oregon and Washington 

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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. 

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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. 

Carretta, J.V. and L. Enriquez. 2009a. Marine mammal and seabird bycatch observed in California 

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Fisheries Science Center, 3333 North Torrey Pines Rd., La Jolla, CA 92037. 12 p. 

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Carretta, J.V. and L. Enriquez. 2009b. Marine mammal bycatch observed in the California/Oregon 

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available from Southwest Fisheries Science Center, 3333 North Torrey Pines Rd., La Jolla, CA 

92037. 10 p . 

Carretta, J.V. and L. Enriquez. 2007. Marine mammal and sea turtle bycatch in the California/Oregon 

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available from Southwest Fisheries Science Center, 8604 La Jolla Shores Drive, La Jolla, CA 

92037. 9p. 

Carretta, J.V. and L. Enriquez. 2006. Marine mammal bycatch and estimated mortality in California 

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Fisheries Science Center, 8604 La Jolla Shores Drive, La Jolla, CA 92037. 14p. 

Carretta, J.V., S.J. Chivers, and K. Danil. 2005. Preliminary estimates of marine mammal bycatch, 

mortality, and biological sampling of cetaceans in California gillnet fisheries for 2004. 

Administrative Report LJ-05-10, available from Southwest Fisheries Science Center, 8604 La 

Jolla Shores Drive, La Jolla, California, 92037. 17 p.Carretta, J.V., T. Price, D. Petersen, and R. 

Read. 2005b. Estimates of marine mammal, sea turtle, and seabird mortality in the California 

drift gillnet fishery for swordfish and thresher shark, 1996-2002. Marine Fisheries Review 

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Carretta, J. V. and K. A. Forney. 1993. Report of the two aerial surveys for marine mammals in California 

coastal waters using a NOAA DeHavilland Twin Otter aircraft, March 9-April 7, 1991, February 

8-April 6, 1992. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-SWFSC-185. 77p. 

Carretta, J. V., K. A. Forney. And J. Barlow 1995. Report of 1993-94 marine mammal surveys conducted 

within the U.S. Navy Outer Sea Test Range off Southern California. U.S. Dep. Commer., NOAA 

Tech. Memo. NMFS-SWFSC-217. 90p. 

Dohl, T. P., K. S. Norris, R. C. Guess, J. D. Bryant, and M. W. Honig. 1980. Summary of marine mammal 

and seabird surveys of the Southern California Bight area, 1975-1978. Part II. Cetacea of the 

Southern California Bight. Final Report to the Bureau of Land Management, NTIS Rep. No. 

PB81248189. 414p. 

Forney, K. A. 1997. Patterns of variability and environmental models of relative abundance for California 

cetaceans. Ph.D. Dissertation, Scripps Institution of Oceanography, University of California, San 

Diego. 

Forney, K. A. and J. Barlow. 1998. Seasonal patterns in the abundance and distribution of California 

cetaceans, 1991-92. Mar. Mamm. Sci. 14:460-489. 

Forney, K.A. 2007. Preliminary estimates of cetacean abundance along the U.S. west coast and within 

four National Marine Sanctuaries during 2005. U.S. Department of Commerce NOAA Technical 

Memorandum, NOAA-TM-NMFS-SWFSC-406. 27p. 

Green, G., J. J. Brueggeman, R. A. Grotefendt, C. E. Bowlby, M. L. Bonnell, and K. C. Balcomb, III. 

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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. and O. Sosa-Nishizaki. 1998. Swordfish, Xiphias gladius, fisheries of the eastern North Pacific 

Ocean. In: I. Barrett, O. Sosa-Nishizaki and N. Bartoo (eds.). Biology and fisheries of swordfish, 

Xiphias gladius. Papers from the International Symposium on Pacific Swordfish, Ensenada 

Mexico, 11-14 December 1994. U.S. Dep. Commer., NOAA Tech. Rep. NMFS 142, 276 p. 

Jones, P. A. and I. D. Szczepaniak. 1992. Report on the seabird and marine mammal censuses conducted 

for the long-term management strategy (LTMS), August 1990 through November 1991, for the 

U.S. Environmental Protection Agency, Region IX, San Francisco, July 1992. 

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

California gillnet fisheries: 1990-95. Fishery Bulletin 96:271-284. 

141
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. 

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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 

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

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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 

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Vojkovich, M. 1998. The California fishery for market squid (Loligo opalescens). CalCOFI Rep. 39:55-

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Wada, S. 1988. Genetic differentiation between forms of short-finned pilot whales off the Pacific coast of 

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

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142
Revised 01/15/2011 

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, noncontiguous 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 2005 

(Forney 2007) and 2008 (Barlow 2010). 

Because the distribution of Baird’s beaked 

whale 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 2005-

2008 geometric mean abundance estimate 

for California, Oregon and Washington 

waters based on the above two ship surveys is 907 (CV=0.49) Baird’s beaked whales (Forney 2007, Barlow 

2010). This abundance estimate includes correction factors for the proportion of animals missed, based on 

a model of their diving behavior, detection distances, and the searching behavior of observers (Barlow 

1999). About 96% of all trackline groups are estimated to be seen. 

Figure 1. Baird’s beaked whale sightings based on 

shipboard surveys off California, Oregon and 

Washington, 1991-2008 (see Appendix 2 for data 

sources and information on timing and location of 

survey effort). Dashed line represents the U.S. EEZ, 

thin lines indicate completed transect effort of all 

surveys combined. 

Minimum Population Estimate

 The log-normal 20th percentile of the 2005-2008 geometric mean abundance estimate is 615 

Baird’s beaked whales. 

143
Current Population Trend

 Due to the rarity of sightings of this species on surveys along the U.S. West coast, no information 

exists regarding trends in abundance of this population. Future studies of trends must take the apparent 

seasonality of the distribution of Baird's beaked whales into account. 

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

 No information on current or maximum net productivity rates is available for this species. 

POTENTIAL BIOLOGICAL REMOVAL

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

population size (615) 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 6.2 Baird’s beaked whales per year. 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Fishery Information

 The California large mesh drift gillnet fishery has been the only fishery known to interact with 

this stock. One Baird’s beaked whale was incidentally killed in this fishery in 1994 (Julian and Beeson 

1998), before acoustic pingers were first used in the fishery in 1996 (Barlow and Cameron 2003). Since 

1996, no beaked whale of any species have been observed entangled or killed in this fishery (Carretta et al. 

2008, Carretta and Enriquez 2009a, 2009b). Mean annual takes in Table 1 are based on 2004-2008 data. 

This results in an average estimated annual mortality of zero Baird’s beaked whales. 

 

Table 1. Summary of available information on the incidental mortality and injury of Baird's beaked whales 

(California/Oregon/Washington Stock) in commercial fisheries that might take this species. The single 

observed entanglement resulted in the death of the animal. Coefficients of variation for mortality estimates 

are provided in parentheses. Mean annual takes are based on 2004-2008 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

2004 

2005 

2006 

2007 

2008 

20.6% 

20.9% 

18.5% 

16.4% 

13.5% 

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). 

144
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). 

One Baird’s beaked whale stranded in Washington state in 2003 and the cause of death was attributed to a 

ship strike. No other human-caused mortality has been reported for this stock for the period 2004-2008. 

 Additional, unknown levels of injury and mortality of Baird’s beaked whales may occur as a result 

of anthropogenic sound, 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 injury or mortality 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. The average annual human-caused mortality during 

2004-2008 is zero animals/year. Because recent fishery and human-caused mortality is less than the PBR 

(6.2), Baird’s beaked whales are not classified as a "strategic" stock under the MMPA. The total fishery 

mortality and serious injury for this stock is zero and 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. 2010. Cetacean abundance in the California Current from a 2008 ship-based line-transect 

survey. NOAA Technical Memorandum, NMFS, NOAA-TM-NMFS-SWFSC-456. 19 p. 

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. 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 K.A. Forney. 2007. Abundance and population density of cetaceans in the California 

Current ecosystem. Fishery Bulletin 105:509-526. 

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. 

Carretta, J.V. and L. Enriquez. 2009a. Marine mammal and seabird bycatch observed in California 

commercial fisheries in 2007. Administrative Report LJ-09-01, available from Southwest 

Fisheries Science Center, 3333 North Torrey Pines Rd., La Jolla, CA 92037. 12 p. 

Carretta, J.V. and L. Enriquez. 2009b. Marine mammal bycatch observed in the California/Oregon 

swordfish and thresher shark drift gillnet fishery in 2008. Administrative Report LJ-09-03, 

available from Southwest Fisheries Science Center, 3333 North Torrey Pines Rd., La Jolla, CA 

92037. 10 p . 

Carretta, J.V., J. Barlow, and L. Enriquez. 2008. Acoustic pingers eliminate beaked whale bycatch in a gill 

net fishery. Marine Mammal Science 24(4):956-961. 

Frantzis, A. 1998. Does acoustic testing strand whales? Nature 392(5):29. 

145
Forney, K.A. 2007. Preliminary estimates of cetacean abundance along the U.S. west coast and within 

four National Marine Sanctuaries during 2005. U.S. Department of Commerce, NOAA Technical 

Memorandum NMFS-SWFSC-406. 27p. 

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. 

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. 

146
Revised 01/15/2011 

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), Gingko-toothed beaked whale 

(M. gingkodens), and Hubbs' beaked whale 

(M. carlhubbsi). Insufficient sighting 

records exist off the U.S. west coast (Figure 

1) to determine any possible spatial or 

seasonal patterns in the distribution of 

mesoplodont beaked whales. 

 Until methods of distinguishing 

these six species are developed, the 

management unit must be defined to 

include all Mesoplodon stocks in this 

region. However, in the future, specieslevel management is desirable, and a high 

priority should be placed on finding means 

to obtain species-specific abundance 

information. For the Marine Mammal 

Protection Act (MMPA) stock assessment 

reports, three Mesoplodon stocks are 

defined: 1) all Mesoplodon species off 

California, Oregon and Washington (this 

report), 2) M. stejnegeri in Alaskan waters, 

and 3) M. densirostris in Hawaiian waters. 

POPULATION SIZE

 Although mesoplodont beaked 

whales have been sighted along the U.S. 

west coast on several line transect surveys utilizing both aerial and shipboard platforms, sightings have 

generally been too rare to produce reliable population estimates, and species identification has been 

problematic (Barlow and Forney 2007, Forney 2007). 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 2005 (Forney 2007) and 

2008 (Barlow 2010), 2) whenever possible, assigning unidentified beaked whale sightings to Mesoplodon 

Figure 1. Mesoplodon beaked whale sightings based 

on shipboard surveys off California, Oregon and 

Washington, 1991-2008 (see Appendix 2 for data 

sources and information on timing and location of 

survey effort). Key:  = Mesoplodon spp.; ▲= 

identified Mesoplodon densirostris; ■ = identified

Mesoplodon carlhubbsi. Dashed line represents the 

U.S. EEZ, thin lines indicate completed transect effort

of all surveys combined. 

147
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, 

based on a model of their diving behavior, detection distances, and the searching behavior of observers 

(Barlow 1999). About 45% of all trackline groups are estimated to be seen. Of the 5 sightings of 

Mesoplodon made during 2005-2008 surveys [all 5 sightings were made during the 2005 survey] two were 

identified to the ‘probable’ species level (one Mesoplodon densirostris and one Mesoplodon carlhubbsi). 

The current estimate of Blainville’s beaked abundance is based on this one probable sighting, while the 

Hubb’s beaked whale sighting was not recorded during standard survey effort, and thus, there is no 

estimate of abundance. An updated estimate of abundance for unidentified mesoplodont beaked whales is 

also presented, based on 2005-2008 survey effort and 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 abundance of Blainville’s beaked 

whales for California, Oregon, and Washington, based on 2005-2008 surveys is 603 (CV=1.16). The 

abundance estimate for mesoplodont beaked whales of unknown species, based on the same 2005-2008 

surveys is 421 (CV=0.88). The combined estimate of abundance for all species of Mesoplodon beaked 

whales in California, Oregon, and Washington waters out to 300 nmi is 1,024 (CV=0.77) animals. This 

estimate does not include sightings of ‘unidentified beaked whales’ made during 2005 and 2008, some of 

which may have included beaked whales of the genus Mesoplodon (Forney 2007, Barlow 2010).

Minimum Population Estimate

 The minimum population estimate (defined as the log-normal 20th percentile of the abundance 

estimate) for mesoplodont beaked whales in California, Oregon, and Washington is 576 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 (576) 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 5.8 mesoplodont beaked whales per year. 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Fishery Information

 The California large mesh drift gillnet fishery has been the only fishery historically known to 

interact with Mesoplodon beaked whales in this region. Between 1990 and 1995, a total of eight 

Mesoplodon beaked whales (5 Hubb’s beaked whales (Mesoplodon carlhubbsi), one Stejneger’s beaked 

whale (Mesoplodon stejnegeri), and two unidentified whales of the genus Mesoplodon were observed 

entangled in approximately 3,300 sets (Julian and Beeson 1998, Carretta et al. 2008). Following the 

introduction of acoustic pingers into this fishery (Barlow and Cameron 2003), no beaked whales of any 

species have been observed entangled in over 4,000 observed sets (Carretta et al. 2008, Carretta and 

Enriquez 2009a, 2009b). Mean annual takes in Table 1 are based on 2004-2008 data. This results in an 

average estimated annual mortality of zero mesoplodont beaked whales. 

 Drift gillnet fisheries for swordfish and sharks exist along the entire Pacific coast of Baja 

California, 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 

148
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 Mesoplodon beaked 

whales (California/Oregon/Washington Stocks) in commercial fisheries that might take these species. 

Mean annual takes are based on 2004-2008 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 

2004 

2005 

2006 

2007 

2008 

20.6% 

20.9% 

18.5% 

16.4% 

13.5% 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

Minimum total annual takes of Mesoplodon beaked whales 0 

Other mortality

 Additional, unknown levels of injuries and mortality of mesoplodont beaked whales may occur as 

a result of anthropogenic sound, 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 

mortality would rarely be documented, due to the remote nature of many of these activities and the low 

probability that an injured or dead beaked whale would strand. 

STATUS OF STOCKS

 The status of mesoplodont beaked whales in California, Oregon and Washington waters relative to 

OSP is not known, and there are insufficient data to evaluate trends in abundance. No habitat issues are 

known to be of concern for this species, but in recent years questions have been raised regarding potential 

effects of human-made sounds on deep-diving cetacean species, such as mesoplodont beaked whales 

(Richardson et al. 1995). In particular, active sonar has been implicated in the mass stranding of beaked 

whales in the Mediterranean Sea (Frantzis 1998) and more recently in the Bahamas (U.S. Dept. of 

Commerce and Secretary of the Navy 2001).

 None of the six species is listed as "threatened" or "endangered" under the Endangered Species 

Act nor considered "depleted" under the MMPA. The average annual human-caused fishery mortality in 

2004-2008 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. 2010. Cetacean abundance in the California Current from a 2008 ship-based line-transect 

survey. NOAA Technical Memorandum, NMFS, NOAA-TM-NMFS-SWFSC-456. 

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 K.A. Forney. 2007. Abundance and population density of cetaceans in the California 

Current ecosystem. Fishery Bulletin 105:509-526. 

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, 

149
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. 

Carretta, J.V. and L. Enriquez. 2009a. Marine mammal and seabird bycatch observed in California 

commercial fisheries in 2007. Administrative Report LJ-09-01, available from Southwest 

Fisheries Science Center, 3333 North Torrey Pines Rd., La Jolla, CA 92037. 12 p. 

Carretta, J.V. and L. Enriquez. 2009b. Marine mammal bycatch observed in the California/Oregon 

swordfish and thresher shark drift gillnet fishery in 2008. Administrative Report LJ-09-03, 

available from Southwest Fisheries Science Center, 3333 North Torrey Pines Rd., La Jolla, CA 

92037. 10 p . 

Frantzis, A. 1998. Does acoustic testing strand whales? Nature 392(5):29. 

Forney, K.A. 2007. Preliminary estimates of cetacean abundance along the U.S. west coast and within 

four National Marine Sanctuaries during 2005. U.S. Department of Commerce, NOAA Technical 

Memorandum NMFS-SWFSC-406. 27p. 

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. 

150
Revised 01/15/2011 

CUVIER'S BEAKED WHALE (Ziphius cavirostris): 

California/Oregon/Washington Stock 

STOCK DEFINITION AND 

GEOGRAPHIC RANGE 

 Cuvier's beaked whales are 

distributed widely throughout deep waters 

of all oceans (Heyning 1989). Off the U.S. 

west coast, this species is the most 

commonly encountered beaked whale 

(Figure 1). No seasonal changes in 

distribution are apparent from stranding 

records, and morphological evidence is 

consistent with the existence of a single 

eastern North Pacific population from 

Alaska to Baja California, Mexico (Mitchell 

1968). However, there are currently no 

international agreements for cooperative 

management of this species. For the Marine 

Mammal Protection Act (MMPA) stock 

assessment reports, Cuvier's beaked whales 

within the Pacific U.S. Exclusive Economic 

Zone are divided into three discrete, noncontiguous areas: 1) waters off California, 

Oregon and Washington (this report), 2) 

Alaskan waters, and 3) Hawaiian waters. 

POPULATION SIZE

er's beaked whales 

ve bee

 Although Cuvi

ha n 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 2005 

(Forney 2007) and 2008 (Barlow 2010), 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, based on a model of their diving behavior, detection distances, and the searching 

behavior of observers (Barlow 1999). An estimated 23% of trackline 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 2005-2008 geometric 

mean abundance estimate for California, Oregon and Washington waters based on the above analyses is 

2,143 (0.65) Cuvier’s beaked whales. 

Figure 1. Cuvier’s beaked whale sightings based 

on shipboard surveys off California, Oregon and 

Washington, 1991-2008 (see Appendix 2, for data 

sources and information on timing and location of 

survey effort). Dashed line represents the U.S. 

EEZ, thin lines indicate completed transect effort

of all surveys combined. 

151
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 1,298 animals. 

Current Population Trend

 Due to the rarity of sightings of this species on surveys along the U.S. West coast, no information 

exists regarding trends in abundance of this population. 

 

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

 No information on current or maximum net productivity rates is available for this species. 

POTENTIAL BIOLOGICAL REMOVAL

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

population size (1,298) 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 13 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. The California large mesh drift gillnet fishery has been the only fishery historically 

known to interact with this stock. There have been no Cuvier’s beaked whales observed entangled in over 

4,000 drift gillnet fishery sets since acoustic pingers were first used in this fishery in 1996 (Barlow and 

Cameron 2003, Carretta et al. 2008, Carretta and Enriquez 2009a, 2009b). Prior to 1996, there were a total 

of 21 Cuvier’s beaked whales entangled in approximately 3,300 drift gillnet fishery sets: 1992 (six 

animals), 1993 (three), 1994 (six) and 1995 (six) (Julian and Beeson 1998). Mean annual takes in Table 1 

are based only on 2004-2008 data. This results in an average estimated annual mortality of zero Cuvier’s 

beaked whales. 

Table 1. Summary of available information on the incidental mortality and injury of Cuvier's beaked 

whales (California/ Oregon/Washington Stock) in commercial fisheries that might take this species. Mean 

annual takes are based on 2004-2008 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

2004 

2005 

2006 

2007 

2008

20.6% 

20.9% 

18.5% 

16.4% 

13.5%

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 

152
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 mortality of Cuvier’s beaked whales may occur as a 

result of anthropogenic sound, 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 mortality 

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 2004-2008 is zero. Because recent human-caused mortality is less than the PBR, Cuvier’s beaked 

whales 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 PBR and thus can be considered to be insignificant and 

approaching zero. 

REFERENCES 

Barlow, J. 2010. Cetacean abundance in the California Current from a 2008 ship-based line-transect 

survey. NOAA Technical Memorandum, NMFS, NOAA-TM-NMFS-SWFSC-456. 

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 K.A. Forney. 2007. Abundance and population density of cetaceans in the California 

Current ecosystem. Fishery Bulletin 105:509-526. 

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. 

Carretta, J.V. and L. Enriquez. 2009a. Marine mammal and seabird bycatch observed in California 

commercial fisheries in 2007. Administrative Report LJ-09-01, available from Southwest 

Fisheries Science Center, 3333 North Torrey Pines Rd., La Jolla, CA 92037. 12 p. 

Carretta, J.V. and L. Enriquez. 2009b. Marine mammal bycatch observed in the California/Oregon 

swordfish and thresher shark drift gillnet fishery in 2008. Administrative Report LJ-09-03, 

available from Southwest Fisheries Science Center, 3333 North Torrey Pines Rd., La Jolla, CA 

92037. 10 p . 

Carretta, J.V., J. Barlow, and L. Enriquez. 2008. Acoustic pingers eliminate beaked whale bycatch in a gill 

net fishery. Marine Mammal Science 24(4):956-961. 

Forney, K.A. 2007. Preliminary estimates of cetacean abundance along the U.S. west coast and within 

four National Marine Sanctuaries during 2005. U.S. Department of Commerce, NOAA Technical 

Memorandum NMFS-SWFSC-406. 27p. 

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. 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, 

153
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. 

154
Revised 01/15/2011 

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 probably reflects 

their pelagic distribution, small body size and 

cryptic behavior, rather than a measure of rarity. 

Strandings of pygmy sperm whales in this region are 

known from California, Oregon and Washington 

(Roest 1970; Caldwell and Caldwell 1989; NMFS, 

Northwest Region, unpublished data; NMFS, 

Southwest Region, unpublished data), while 

strandings of dwarf sperm whales (Kogia sima) are 

rare in this region. At-sea sightings in this region 

have all been either of pygmy sperm whales or 

unidentified Kogia sp. Available data are 

insufficient to identify any seasonality in the 

distribution of pygmy sperm whales, or to delineate 

possible stock boundaries. For the Marine Mammal 

Protection Act (MMPA) stock assessment reports, 

pygmy sperm whales within the Pacific U.S. 

Exclusive Economic Zone are divided into two 

discrete, non-contiguous areas: 1) waters off 

California, Oregon and Washington (this report), 

and 2) Hawaiian waters. 

POPULATION SIZE 

Although pygmy sperm whales have been 

sighted along the U.S. west coast on several line 

transect surveys, sightings have been too rare to 

produce reliable population estimates. The most 

recent abundance estimate of 1,157 (CV=1.02) 

animals is based on one sighting of an unidentified 

Kogia during a 2008 ship survey of California, Oregon, and Washington waters (Barlow 2010). Based on previous 

sighting surveys and historical stranding data, it is likely that these sightings were of pygmy sperm whales; K. 

breviceps. The 2008 estimate incorporate a correction factor for animals missed, based on a model of their diving 

behavior, detection distances, and the searching behavior of observers (Barlow 1999). About 35% of all trackline 

groups are estimated to be seen. The rarity of sightings likely reflects the cryptic nature of this species (they are 

detected almost exclusively in extremely calm sea conditions), rather than an absence of animals in the region. The 

best estimate of abundance for this stock is the mean of 2005 and 2008 shipboard line-transect surveys, or 579 

(CV=1.02) animals. 

Figure 1. Kogia sightings based on shipboard surveys 

off California, Oregon and Washington, 1991- 2008 (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, thin 

lines indicate completed transect effort of all surveys 

combined. 

 

155
Minimum Population Estimate 

 The minimum population estimate is taken as the log-normal 20th percentile of the 2005 and 2008 average 

abundance estimate for California, Oregon, and Washington waters, or 271 animals. 

Current Population Trend

 Due to the rarity of sightings of this species on surveys along the U.S. West coast, no information exists 

regarding trends in abundance of this population. 

 

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

 No information on current or maximum net productivity rates is available for this species. 

POTENTIAL BIOLOGICAL REMOVAL

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

(271) 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 during the last five years; Wade and Angliss 

1997), resulting in a PBR of 2.7 pygmy sperm whales per year. 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Fishery Information

 A summary of recent fishery mortality and injury for pygmy sperm whales and unidentified Kogia, which 

may have been pygmy sperm whales, is shown in Table 1. More detailed information on the drift gillnet fishery is 

provided in Appendix 1. In the California drift gillnet fishery, no mortality of pygmy sperm whales or unidentified 

Kogia was observed during the most recent five years of monitoring, ( Carretta et al. 2005, Carretta and Enriquez 

2006, 2007, 2009a, 2009b). 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 2004-2008 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). 

One pygmy sperm whale stranded in California in 2002 with evidence that it died as a result of a shooting 

(positive metal detector scan). Due to the cryptic and pelagic nature of this species, it is likely that the shooting 

resulted from an interaction with an unknown entangling net fishery. 

Other mortality

 No human-caused mortality of pygmy sperm whales has been documented during the most recent five-year 

period (2004-2008). Unknown levels of injuries and mortality of pygmy sperm whales may occur as a result of 

anthropogenic sound, 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 mortality 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. 

156
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. Given the 

rarity of sightings and fishery interactions in U.S. west coast waters, pygmy sperm whales are not classified as a 

“strategic” stock under the MMPA.

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 2004-

2008 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

2004 

2005 

2006 

2007 

2008 

20.6% 

20.9% 

18.5% 

16.4% 

13.5% 

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. 2010. Cetacean abundance in the California Current from a 2008 ship-based line-transect survey. 

NOAA Technical Memorandum, NMFS, NOAA-TM-NMFS-SWFSC-456. 

Barlow, J., R.L. Brownell, Jr., D.P. DeMaster, K.A. Forney, M.S. Lowry, S. Osmeck, T.J. Ragen, R.R. Reeves, and 

R.J. Small. 1995. U.S. Pacific Marine Mammal Stock Assessments. NOAA Technical Memorandum 

NOAA-TM-NMFS-SWFSC-219. 162p. 

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. NOAA 

Technical Memorandum NOAA-TM-NMFS-SWFSC-248. 223p. 

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. 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 K.A. Forney. 2007. Abundance and population density of cetaceans in the California Current 

ecosystem. Fishery Bulletin 105:509-526. 

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. 

Carretta, J.V. and L. Enriquez. 2009a. Marine mammal and seabird bycatch observed in California commercial 

fisheries in 2007. Administrative Report LJ-09-01, available from Southwest Fisheries Science Center, 

3333 North Torrey Pines Rd., La Jolla, CA 92037. 12 p. 

157
Carretta, J.V. and L. Enriquez. 2009b. Marine mammal bycatch observed in the California/Oregon swordfish and 

thresher shark drift gillnet fishery in 2008. Administrative Report LJ-09-03, available from Southwest 

Fisheries Science Center, 3333 North Torrey Pines Rd., La Jolla, CA 92037. 10 p . 

Carretta, J.V. and L. Enriquez. 2007. Marine mammal and sea turtle bycatch in the California/Oregon thresher 

shark and swordfish drift gillnet fishery in 2006. Administrative Report LJ-07-06, available from 

Southwest Fisheries Science Center, 8604 La Jolla Shores Drive, La Jolla, CA 92037. 9p. 

Carretta, J.V. and L. Enriquez. 2006. Marine mammal bycatch and estimated mortality in California commercial 

fisheries during 2005. Administrative Report LJ-06-07, available from Southwest Fisheries Science 

Center, 8604 La Jolla Shores Drive, La Jolla, CA 92037. 14p. 

Carretta, J.V., K.A. Forney, M.M. Muto, J. Barlow, J. Baker, and M. Lowry. 2004. U.S. Pacific Marine Mammal 

Stock Assessments: 2003. NOAA Technical Memorandum NOAA-TM-NMFS-SWFSC-358. 291p. 

Carretta, J.V., S.J. Chivers, and K. Danil. 2005. Preliminary estimates of marine mammal bycatch, mortality, and 

biological sampling of cetaceans in California gillnet fisheries for 2004. Administrative Report LJ-05-10, 

available from Southwest Fisheries Science Center, 8604 La Jolla Shores Drive, La Jolla, California, 

92037. 17 p. 

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. NOAA Technical Memorandum, 

NOAA-TM-NMFS-SWFSC-300. 230p. 

Forney, K.A. 2007. Preliminary estimates of cetacean abundance along the U.S. west coast and within four 

National Marine Sanctuaries during 2005. U.S. Department of Commerce NOAA Technical 

Memorandum, NOAA-TM-NMFS-SWFSC-406. 27 p. 

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. 

158
Revised 01/15/2011 

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. 

Figure 1. Kogia sightings based on shipboard 

surveys off California, Oregon and Washington, 

1991-2008 (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, thin lines indicate

completed transect effort of all surveys combined. 

 

POPULATION SIZE

 No information is available to estimate the population size of dwarf sperm whales off the U.S. 

west coast, as no sightings of this species have been documented despite numerous vessel surveys of this 

region (Barlow 1995; Barlow and Gerrodette 1996; Barlow and Forney 2007; Forney 2007; Barlow 2010). 

Based on previous sighting surveys and historical stranding data, it is likely that recent ship survey 

sightings were of pygmy sperm whales; K. breviceps. 

159
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. 

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, 2004-2008 (Carretta et al. 2005, Carretta and 

Enriquez 2006, 2007, 2009a, 2009b). 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 2004-2008 data. 

This results in an average estimated annual mortality of zero dwarf sperm whales. 

 Similar drift gillnet fisheries for swordfish and sharks exist along the entire Pacific coast of Baja 

California, Mexico and may take animals from this population. Quantitative data are available only for the 

Mexican swordfish drift gillnet fishery, which has increased from two vessels in 1986 to 29 vessels in 1992 

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

provided by these authors to be approximately 2700, with an observed rate of marine mammal bycatch of 

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

mortality rate is similar to that observed in California driftnet fisheries during 1990-95 (0.14 marine 

mammals per set; Julian and Beeson, 1998), but species-specific information is not available for the 

Mexican fisheries. Previous efforts to convert the Mexican swordfish driftnet fishery to a longline fishery 

have resulted in a mixed-fishery, with 20 vessels alternately using longlines or driftnets, 23 using driftnets 

only, 22 using longlines only, and seven with unknown gear type (Berdegué 2002). 

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. 

160
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 2004-2008 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

2004 

2005 

2006 

2007 

2008 

20.6% 

20.9% 

18.5% 

16.4% 

13.5% 

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. 2010. Cetacean abundance in the California Current from a 2008 ship-based line-transect 

survey. NOAA Technical Memorandum, NMFS, NOAA-TM-NMFS-SWFSC-456. 

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. 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 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 K.A. Forney. 2007. Abundance and population density of cetaceans in the California 

Current ecosystem. Fishery Bulletin 105:509-526. 

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. 

Carretta, J.V. and L. Enriquez. 2009a. Marine mammal and seabird bycatch observed in California 

commercial fisheries in 2007. Administrative Report LJ-09-01, available from Southwest 

Fisheries Science Center, 3333 North Torrey Pines Rd., La Jolla, CA 92037. 12 p. 

Carretta, J.V. and L. Enriquez. 2009b. Marine mammal bycatch observed in the California/Oregon 

swordfish and thresher shark drift gillnet fishery in 2008. Administrative Report LJ-09-03, 

available from Southwest Fisheries Science Center, 3333 North Torrey Pines Rd., La Jolla, CA 

92037. 10 p . 

Carretta, J.V. and L. Enriquez. 2007. Marine mammal and sea turtle bycatch in the California/Oregon 

thresher shark and swordfish drift gillnet fishery in 2006. Administrative Report LJ-07-06, 

available from Southwest Fisheries Science Center, 8604 La Jolla Shores Drive, La Jolla, CA 

92037. 9p. 

Carretta, J.V. and L. Enriquez. 2006. Marine mammal bycatch and estimated mortality in California 

commercial fisheries during 2005. Administrative Report LJ-06-07, available from Southwest 

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Carretta, J.V., S.J. Chivers, and K. Danil. 2005. Preliminary estimates of marine mammal bycatch, 

mortality, and biological sampling of cetaceans in California gillnet fisheries for 2004. 

Administrative Report LJ-05-10, available from Southwest Fisheries Science Center, 8604 La 

Jolla Shores Drive, La Jolla, California, 92037. 17 p. 

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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. 

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four National Marine Sanctuaries during 2005. U.S. Department of Commerce, NOAA Technical 

Memorandum NMFS-SWFSC-406. 27p. 

161
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(ed.), Whales, dolphins and porpoises. University of California Press, Berkeley. 

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Acad. Sci. 42:409-433. 

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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. 

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Noise. Academic Press, San Diego. 576 p. 

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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. 

162
Revised 01/15/2011 

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; Rice 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 

160o

W between 40-50oN, and ends up at 

180o

W north of 50oN; however, the IWC 

has not reviewed this stock boundary in 

many years (Donovan 1991). 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 midNovember (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) and between the Galapagos Islands and 

the southern Gulf of California (Jaquet et al. 2003), 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 2005). 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 

Figure 1. Sperm whale sighting locations based 

on shipboard surveys off California, Oregon, and 

Washington, 1991-2008. Dashed line represents 

the U.S. EEZ, thin lines indicate completed 

transect effort of all surveys combined. See 

Appendix 2 for data sources and information on 

timing and location of survey effort. 

163
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 in California, Oregon, and 

Washington waters during summer/fall based on pooled 1993 and 1996 ship line transect surveys within 

300 nmi of the coast and Barlow and Forney (2007) estimated 2,593 (CV= 0.30) sperm whales from a 

survey of the same area in 2001. A 2005 survey of this area resulted in an abundance estimate of 3,140 

(CV=0.40) whales, which is corrected for diving animals not seen during surveys (Forney 2007). The most 

recent ship survey of the same area in 2008 resulted in an estimate of only 300 (CV = 0.51) sperm whales 

(Barlow 2010). The 2008 estimate is lower than all previous estimates within this region and may be due 

to interannual variability of sperm whale distribution in this region. The most recent estimate of 

abundance for this stock is the geometric mean of the 2005 and 2008 summer/autumn ship survey 

estimates, or 971 (CV = 0.31) sperm whales. A large 1982 abundance estimate for the entire eastern 

North Pacific (Gosho et al. 1984) was based on a CPUE method which is no longer accepted as valid by the 

International Whaling Commission. A combined visual and acoustic line-transect survey conducted in the 

eastern temperate North Pacific in spring 1997 resulted in estimates of 26,300 (CV=0.81) sperm whales 

based on visual sightings, and 32,100 (CV=0.36) based acoustic detections and visual group size estimates 

(Barlow and Taylor 2005). 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 971 

(CV = 0.31) animals from the ship surveys conducted in 2005 (Forney 2007) and 2008 (Barlow 2010). 

This estimate is corrected for diving animals not seen during surveys. 

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 2005-2008 summer/fall ship surveys off 

California, Oregon and Washington (Barlow and Forney 2007; Forney 2007) or approximately 751. 

Current Population Trend

 Sperm whale abundance appears to have been rather variable off California between 1979/80 and 

1991 (Barlow 1994) and between 1991 and 2008 (Barlow and Forney 2007). The most recent estimate 

from 2008 is the lowest to date, in sharp contrast to the highest abundance estimates obtained from 2001 

and 2005 surveys. There is no reason to believe that the population has declined; the most recent survey 

estimate likely reflects interannual variability within the study area. To date, there has not been a 

statistical analysis to detect trends in abundance. 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 (751) times one half the default maximum net growth rate for cetaceans (1⁄2 

164
of 4%) times a recovery factor of 0.1 (for an endangered stock with Nmin <1,500, ; Taylor et al. 2003), 

resulting in a PBR of 1.5. 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY 

[Information on historic whaling has been moved to the Status of Stock section.]

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 summary of known fishery 

mortality and injury for this stock of sperm whales from 2004-2008 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. One 

sperm whale stranded dead in 2004 with 5 to 6-inch mesh nylon netting found in its stomach (NMFS 

Southwest Regional Office, unpublished data). The fishery source of this netting is unknown. Mean 

annual takes for this fishery (Table 1) are based on 2004-2008 data (Carretta et al. 2005; Carretta and 

Enriquez 2006, 2007, 2009a, 2009b). This results in an average estimate of 0.2 (CV = not available) sperm 

whale deaths 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 (Carretta et al. 2005). n/a 

indicates that data are not available. Mean annual takes are based on 2004-2008 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 

2004 

2005 

2006 

2007 

2008 

observer 

20.6% 

20.9% 

18.5% 

16.4% 

13.5% 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 (n/a) 

Unknown fishery 2004-2008 stranding n/a 1 1 0.2 

Total annual takes 0.2 (n/a) 

 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

 One sperm whale died as the result of a ship strike in Oregon in 2007 (NMFS Northwest Regional 

Stranding data, unpublished). Sperm whale mortality and serious injuries attributed to ship strikes 

averaged 0.2 per year for 2004-2008. 

165
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. Whaling removed at 

least 436,000 sperm whales from the North Pacific between 1800 and the end of commercial whaling for 

this species in 1987 (Best 1976; Ohsumi 1980; Brownell 1998; Kasuya 1998). Of this 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 approximately 1,000 were reported taken in land-based U.S. West coast whaling operations 

between 1919 and 1971 (Ohsumi 1980; 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. As 

a result of this whaling, sperm whales are formally listed as "endangered" under the Endangered Species 

Act (ESA), and consequently the California to Washington stock is automatically considered as a 

"depleted" and "strategic" stock under the MMPA. The annual rate of kill and serious injury (0.4 per year) 

is less than the calculated PBR for this stock (1.5). Total human-caused mortality is greater than 10% of 

the calculated PBR and, therefore, cannot be considered to be insignificant and approaching zero mortality 

and serious injury rate. Increasing levels of anthropogenic sound 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 

ocean’s “sound channel”. 

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168
Revised 01/15/2011 

HUMPBACK WHALE (Megaptera novaeangliae): 

California/Oregon/Washington 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). Humpback whales in the North Pacific 

feed in coastal waters from California to Russia and 

in the Bering Sea. They migrate south to wintering 

destinations off Mexico, Central America, Hawaii, 

southern Japan, and the Philippines. Mitochondrial 

and nuclear genetic markers show that considerable 

structure exists in humpback whale populations in the 

North Pacific (Baker et al. 1998). Significant levels 

of mitochondrial and nuclear genetic differences 

were found between central California and Southeast 

Alaska feeding areas (Baker et al. 1998). 

Mitochondrial genetic differences are also found 

between feeding area in the Atlantic (Palsboll et al. 

1995). 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). Individually identified whales have been 

found to move between winter breeding areas in 

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. Waters off 

northern Washington may be an area of mixing between 

the California/Oregon/Washington stock and a southern 

British Columbia stock. Alternatively, humpback 

whales in northern Washington and southern British 

Columbia may be a distinct feeding population 

(Calambokidis et al. 2008) and a separate stock. For humpback whales, maternally directed fidelity to specific 

feeding areas within an ocean basin appears to be so strong that genetic differences have evolved in both the 

Atlantic, where there is a single breeding area, and in the Pacific, where there are multiple breeding areas. Because 

fidelity appears to be greater in feeding areas than in breeding areas, the stock structure of humpback whales is 

defined based on feeding areas. 

Figure 1. Humpback whale sightings based on 

shipboard surveys off California, Oregon, and 

Washington, 1991-2008. Dashed line represents the 

U.S. EEZ, thin lines indicate completed transect effort

of all surveys combined. See Appendix 2 for data 

sources and information on timing and location of 

survey effort. 

For the Marine Mammal Protection Act (MMPA) stock assessment reports, the 

California/Oregon/Washington Stock is defined to include humpback whales that feed off the west coast of the 

United States. The winter migratory destination of this stock is primarily in coastal waters of Mexico and Central 

America. Three other stocks are recognized in the U.S. MMPA Pacific stock assessment reports: the Central North 

Pacific Stock (with feeding areas from Southeast Alaska to the Alaska Peninsula), the Western North Pacific Stock 

169
(with feeding areas from the Aleutian Islands, the Bering Sea, and Russia), and the American Samoa Stock (with 

largely undocumented feeding areas as far south as the Antarctic Peninsula). 

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). A photo-identification study in 2004-2006 estimated the abundance of humpback 

whales in the entire Pacific Basin to be approximately 18,000-20,000 (Calambokidis et al. 2008). Estimates of 

regional abundance in the California/Oregon stratum from that study (1,702) are less precise than estimates from 

dedicated west-coast studies. Barlow and Forney (2007) estimated 1,096 (CV=0.22) humpbacks in California, 

Oregon, and Washington waters based on summer/fall ship line-transect surveys in 2001. Forney (2007) estimated 

1,769 (CV=0.16) humpbacks in the same region based on a 2005 summer/fall ship line-transect survey, which 

included additional fine-scale coastal strata not included in the 2001 survey. Barlow (2010) recently estimated 

1,090 (CV=0.41) humpback whales from a 2008 summer/fall ship line-transect survey of the same region. The 

combined 2005 and 2008 line-transect estimate of abundance is the geometric mean of the two annual estimates, or 

1,389 (CV=0.21). Calambokidis et al. (2009) estimated humpback whale abundance in these feeding areas from 

1991 to 2008 using Petersen mark-recapture estimates based on photo-identification collections in adjacent pairs of 

years (Figure 2). The 2007/2008 mark-recapture population estimate for California and Oregon (2,043, CV=0.10) 

is higher than any previous mark-recapture estimates (Calambokidis et al. 2009). 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 nearly a third of the entire 

population (the 2007/2008 data contained 672 known individuals). The estimate of 2,043 humpback whales in 

2007/2008 is also a negatively biased estimate of this stock because it excludes some whales in Washington. The 

best estimate of abundance for this stock is the mark-recapture estimate of 2,043 (CV=0.10), which is also the most 

precise estimate. 

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 the 2007/2008 mark-recapture estimate (Calambokidis 2009) 

or 1,878. 

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 2005 (Barlow and Forney 2007; Forney 2007), but 

this increase was not steady, and estimates showed a slight dip in 2001. Mark-recapture population estimates have 

shown a long-term increase of approximately 7.5% per year (Calambokidis 2009, Figure 2), although there have 

been short-term declines during this period, probably due to oceanographic variability. Population estimates for the 

entire North Pacific have also increased substantially from 1,200 in 1966 to approximately 18,000 to 20,000 whales 

in 2004 to 2006 (Calambokidis et al. 2008). 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 California/Oregon/Washington stock. 

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

 The proportion of calves in the California/Oregon/Washington 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. 2003) with a best estimate of 8% growth per year (Calambokidis et 

al. 1999). The current net productivity rate is unknown. 

170
Figure 2. Mark-recapture estimates of humpback whale abundance in California and Oregon, 1991-2008 

(Calambokidis 2009). Horizontal bars indicate ±1 standard error of each abundance estimate. Solid line shows a 

linear regression of the natural logarithim of abundance over time. The slope of this regression is statistically 

significant (p < 0.001) and approximates an annual population growth rate of between 7% and 8%. 

POTENTIAL BIOLOGICAL REMOVAL

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

(1,878) times one half the estimated population growth rate for this stock of humpback whales (1⁄2 of 8%) times a 

recovery factor of 0.3 (for an endangered species, with Nmin > 1,500 and CV(Nmin) < 0.50), resulting in a PBR of 

22.5. Because this stock spends approximately half its time outside the U.S. EEZ, the PBR allocation for U.S. 

waters is 11.3 whales per year. 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

 Information on historic whaling has been moved to the Status of Stock section.

 

Fishery Information

 A summary of known fishery mortality and injury for this stock of humpback whales for 2004-2008 is 

given in Table 1. A total of 18 humpback whales were observed entangled in fishing gear during 2004-2008 in 

California, Oregon, and Washington (Table 1). No entanglements were reported from the observer program that 

monitors the large-mesh swordfish and thresher shark drift gillnet fishery ( Carretta et al. 2005, Carretta and 

Enriquez 2006, 2007, 2009a, 2009b); however, a free-swimming humpback was observed entangled in gillnet gear 

of unknown origin in 2006 (NMFS, Southwest Regional Stranding Program, unpublished data). Of the 18 

humpbacks entangled in fishing gear, 11 were reported entangled at sea in trap/pot fishery gear off California and 

Oregon, including two animals later found dead in Oregon (Northwest Regional Stranding Program, unpublished 

data). Seven humpbacks were reported entangled in unknown gillnet or other gear, including lines and buoys of 

unknown origin. Two of the 11 pot/trap gear entanglements could be attributed to specific fisheries: One whale was 

entangled in sablefish trap gear and another in spot prawn trap gear (NMFS, Southwest Regional Stranding 

Program, unpublished data). The whale entangled in sablefish trap gear was successfully disentangled by divers 

171
who removed all the gear, and the animal swam away immediately following disentanglement. Another whale 

entangled in crab pot gear in 2008 was successfully disentangled from gear. One of the sightings involving crab 

pot gear included a cow/calf pair where the cow was entangled. Due to the trailing gear, 14 of the humpbacks are 

considered as serious injuries in Table 1 (two released animals were not considered seriously injured). Including the 

14 serious injuries and two deaths, total mean annual serious injury and mortality for the commercial fisheries listed 

in Table 1 is 3.2 per year for the period 2004-2008. In addition to the humpback entanglements, there were 12 

unidentified whales observed entangled in pot/trap gear or unknown gillnet gear during 2004-2008. Some of these 

animals may represent re-sightings of entangled humpback whales described above. It is likely that most of the 

unidentified pot/trap fishery entanglements involved humpback whales. 

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

Mexico and may take animals from the same population. Quantitative data are available only for the Mexican 

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

gillnet fishery, although nets may be up to 4.5 km long (Holts and Sosa-Nishizaki 1998). The fleet increased from 

two vessels in 1986 to 31 vessels in 1993 (Holts and Sosa-Nishizaki 1998). The total number of sets in this fishery 

in 1992 can be estimated from data provided by these authors to be approximately 2700, with an observed rate of 

marine mammal bycatch of 0.13 animals per set (10 marine mammals in 77 observed sets; Sosa-Nishizaki et al. 

1993). This overall mortality rate is similar to that observed in California driftnet fisheries during 1990-95 (0.14 

marine mammals per set; Julian and Beeson, 1998), but species-specific information is not available for the Mexican 

fisheries. 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 

 Two humpback whale deaths were attributed to ship strikes during the period 2004-2008 (NMFS, 

unpublished stranding data). An additional animal that was struck in Washington waters in 2008 was reported to 

have broken the stabilizer on the vessel that struck it, but the condition of the whale is unknown. During 2004-

2008, there were an additional eight injuries 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 

documented humpback whale deaths by ship strikes for 2004-2008 is 0.4 per year, but it is apparent that animals 

struck by ships are unlikely to be reported. 

Other human-caused mortality

 There was no humpback whale mortality reported from non-commercial fishery sources for the period 

2004-2008. The average number of humpback deaths from unknown anthropogenic sources is zero per year from 

2004-2008. 

STATUS OF STOCK

 Approximately 15,000 humpback whales were taken from the North Pacific from 1919 to 1987 

(Tonnessen and Johnsen 1982; C. Allison, IWC unpubl. Data), and, of these, approximately 8,000 were taken from 

the west coast of Baja California, California, Oregon and Washington (Rice 1978), presumably from this stock. 

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. As a result of commercial whaling, humpback whales were listed as "endangered" 

under the Endangered Species Conservation Act of 1969. This protection was transferred to the Endangered Species 

Act (ESA) in 1973. The species is still listed as “endangered”, and consequently the California/Mexico stock is 

automatically considered as a "depleted" and "strategic" stock under the MMPA. The estimated annual mortality 

and serious injury due to entanglement (3.2/yr), other anthropogenic sources (zero), plus ship strikes (0.4/yr) in 

California is less than the PBR allocation of 11.3 for U.S. waters. Based on strandings and at sea observations, 

annual humpback whale mortality and serious injury in commercial fisheries is greater than 10% of the PBR; 

therefore, total fishery mortality and serious injury is not approaching zero mortality and serious injury rate. The 

eastern North Pacific stock appears to be increasing in abundance. 

172
Table 1. Summary of available information on the incidental mortality and injury of humpback whales 

(California/Oregon/Washington stock) for commercial fisheries that might take this species ( Carretta et al. 2005, 

Carretta and Enriquez 2006, 2007, 2009a, 2009b). 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 2004-2008 data unless noted otherwise. 

Fishery Name Year(s) Data Type 

Percent 

Observer 

Coverage 

Observed 

Mortality (and 

serious injury) 

Estimated mortality Mean Annual 

Takes 

CA/OR thresher 

shark/swordfish drift 

gillnet fishery 

2004 

2005 

2006 

2007 

2008 

Observer 

20.6% 

20.9% 

18.5% 

16.4% 

13.5% 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 (n/a) 

CA halibut and white 

seabass and other species 

large mesh (>3.5”) set 

gillnet fishery 

2004 

2005 

2006 

2007 

2008 

observer 

0% 

0% 

 ~1% 

17.8% 

0% 

n/a 

n/a 

n/a 

0 (0) 

n/a 

n/a 0 (n/a) 

Pot or trap fisheries 

2004 

2005 

2006 

2007 

2008 

Strandings 

& sightings n/a 

0 (0) 

0 (3) 

1 (1) 

1 (1) 

0 (2) 

n/a ≥1.8 

unidentified fisheries 

2004 

2005 

2006 

2007 

2008 

Strandings 

& sightings 

0 (1) 

0 (0) 

0 (2) 

0 (3) 

0 (1) 

n/a ≥ 1.4 

 Total Annual Takes ≥3.2 

Habitat Concerns 

Increasing levels of anthropogenic sound in the world’s oceans (Andrew et al. 2002), such as those produced by 

shipping traffic, 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 lowfrequency sound. Based on vocalizations (Richardson et al. 1995; Au et al. 2006), reactions to sound sources (Lien 

et al. 1990, 1992; Maybaum 1993), and anatomical studies (Hauser et al. 2001), humpback whales also appear to be 

sensitive to mid-frequency sounds, including those used in active sonar military exercises (Navy 2007). 

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106(1):506-514. 

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Steiger, G. H., J. Calambokidis, R. Sears, K. C. Balcomb, and J. C. Cubbage. 1991. Movement of humpback 

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Tonnessen, J. N., and A. O. Johnsen. 1982. The History of Modern Whaling. Univ. Calif. Press, Berkeley and Los 

Angeles. 798pp.7:306-310. 

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U.S. Pacific Fleet and Commander, Third Fleet. February 2007. 

176
Revised 01/15/2011

BLUE WHALE (Balaenoptera musculus 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 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). Blue whales in the North 

Pacific produce two distinct, stereotypic calls that 

have been termed the northwestern and northeastern 

call types, and it has been proposed that these 

represent two distinct populations with some degree 

of geographic overlap (Stafford et al. 2001, Stafford 

2003). The northeastern call predominates in the 

Gulf of Alaska, the U.S. West Coast, and the eastern 

tropical Pacific, and the northwestern call 

predominates from south of the Aleutian Islands to 

the Kamchatka Peninsula in Russia, though both call 

types have been recorded concurrently in the Gulf of 

Alaska (Stafford et al. 2001, Stafford 2003). Both 

call types are represented in lower latitudes in the 

central North Pacific but differ in their seasonal 

patterns (Stafford et al. 2001). Gilpatrick and 

Perryman (2008) showed that blue whales from 

California to Central America (the eastern North 

Pacific stock) are on average about two meters 

shorter than blue whales measured from historic 

whaling from the central and western north Pacific 

regions. Mate et al. (1999) used satellite tags to 

show that the eastern tropical Pacific is a migratory 

destination for blue whales that were tagged off 

southern California, and photographs of blue whales 

on the Costa Rica Dome in the eastern tropical 

Pacific have matched individuals that had been 

previously photographed off California 

(Calambokidis, pers. comm.). Photographs of blue 

whales in California have also been matched to 

individuals photographed off the Queen Charlotte 

Islands in northern British Columbia and to one 

individual photographed in the northern Gulf of 

Alaska (Calambokidis et al. 2009). 

Figure 1. Blue whale sighting locations based on 

aerial and summer/autumn shipboard surveys off 

California, Oregon, and Washington, 1991-2008 (see 

Appendix 2 for data sources and information on 

timing and location of surveys). Dashed line 

represents the U.S. EEZ; thin lines represent 

completed transect effort for all surveys combined.

For the Marine Mammal Protection Act (MMPA) stock assessment reports, the Eastern North Pacific Stock 

of blue whales includes animals found in the eastern North Pacific from the northern Gulf of Alaska to the eastern 

tropical Pacific. This definition is consistent with both the distribution of the northeastern call type, 

photogrammetric length determinations and with the known range of photographically identified individuals. Based 

on locations where the northeastern call type has been recorded, some individuals in this stock may range as far west 

as Wake Island and as far south as the Equator (Stafford et al. 1999, 2001). The U.S. West Coast is certainly one of 

the most important feeding areas in summer and fall (Figure 1), but, increasingly, blue whales from this stock have 

been found feeding to the north and south of this area during summer and fall. Most of this stock is believed to 

migrate south to spend the winter and spring in high productivity areas off Baja California, in the Gulf of California, 

177
and on the Costa Rica Dome. Given that these migratory destinations are areas of high productivity and given the 

observations of feeding in these areas, blue whales can be assumed to feed year round. Some individuals from this 

stock may be present year-round on the Costa Rica Dome (Reilly and Thayer 1990). However, it is also possible that 

some Southern Hemisphere blue whales might occur north of the equator during the austral winter. One other stock 

of North Pacific blue whales (the Central North Pacific stock in Hawaiian waters) is recognized in the Pacific 

Marine Mammal Protection Act (MMPA) Stock Assessment Reports. 

POPULATION SIZE 

The size of the feeding stock of blue whales off the U.S. West Coast was estimated recently by both linetransect and mark-recapture methods. Barlow and Forney (2007) estimated 603 (CV=0.29) blue whales off 

California, Oregon, and Washington based on ship line-transect surveys in 2001 and Forney (2007), estimated 721 

(CV=0.27) from a 2005 line-transect survey of the same area. More recently, Barlow (2010) estimated 442 

(CV=0.25) blue whales from a 2008 line-transect survey in the same region. The unweighted geometric mean of the 

2005 and 2008 line-transect estimates is 565 (CV=0.18) whales. Calambokidis et al. (2010) used photographic 

mark-recapture and estimated population sizes of 2,799 (CV=0.27) based on 2005-2008 photographs of left sides 

and 2,195 (CV=0.24) based on right sides. The average of the mark-recapture estimates is 2,497 (CV=0.24) whales. 

Mark-recapture estimates are often negatively biased by individual heterogeneity in sighting probabilities 

(Hammond 1986); however, Calambokidis et al. (2010) 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 outside of the study area at the time of survey (Calambokidis and 

Barlow 2004). Because some fraction of the population is always outside the survey area, the line-transect and mark 

recapture estimation methods provide different measures of abundance for this stock. Line transect estimates reflect 

the average density and abundance of blue whales in the study area during summer and autumn surveys, while mark 

recapture estimates provide an estimate of total population size. Therefore, the best estimate of blue whale 

abundance is the average of mark-recapture estimates, or 2,497 (CV=0.24). 

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 mark-recapture estimate, or approximately 2,046. 

Current Population Trend 

There is some indication that blue whales 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 in 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 IWC protected status in 1966, there is no evidence 

showing that the eastern North Pacific stock is currently growing. Estimates from line transect surveys declined 

between 1991-2005 (Figure 2), which is probably due to variability in the fraction of the population that utilizes 

California waters during the summer and autumn (Calambokidis et al. 2009). 

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

 No information exists on the overall rate of growth of blue whale populations in the Pacific (Best 1993). 

Based on mark-recapture estimates from the US West Coast and Baja California, Mexico, Calambokidis et al. 

(2010) estimate a rate of increase just under 3% per year, but it is not known if that corresponds to the maximum 

growth rate of this stock. 

POTENTIAL BIOLOGICAL REMOVAL

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

(2,046) times one half the default maximum net growth rate for cetaceans (1⁄2 of 4%) times a recovery factor of 0.3 

(for an endangered species which has a minimum abundance greater than 1,500 and a CVNmin<0.5), resulting in a 

PBR of 12.2. Because whales in this stock spends approximately three quarters of their time outside the U.S. EEZ, 

the PBR allocation for U.S. waters is one-quarter of this total, or 3.1 whales per year. 

178
Figure 2. Estimates of abundance from vessel-based line transect (LT) and mark-recapture (MR) surveys conducted 

in California waters, 1991-2005 (Barlow and Forney 2007; Calambokidis et al. 2003; Calambokidis and Barlow 

2004; Forney 2007; Calambokidis et al. 2007). The four line transect estimates are based on annual surveys 

conducted in 1991, 1993, 1996, 2001, and 2005, respectively. The three mark-recapture estimates are based on 

1991-1993, 1995-1997, 2000-2002, and 2004-2006 pooled estimates, respectively. Approximate 95% lognormal 

confidence intervals of the individual LT and MR estimates are also shown.

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY 

Fisheries Information 

 The offshore drift gillnet fishery is the only fishery that is likely to take blue whales from this stock, but no 

fishery mortality or serious injuries have been observed (Table 1). Detailed information on this fishery is provided 

in Appendix 1. After the 1997 implementation of a Take Reduction Plan, which included skipper education 

workshops and required the use of pingers and minimum 6-fathom extenders, overall cetacean entanglement rates in 

the drift gillnet fishery dropped considerably (Barlow and Cameron 1999). Mean annual takes for this fishery 

(Table 1) are based only on 2004-2008 data (Carretta et al. 2005 Carretta and Enriquez 2006, 2007, 2009a, 2009b). 

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 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 

179
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 blue whales (Eastern North 

Pacific stock) for commercial fisheries that might take this species ( Carretta et al. 2005, Carretta and Enriquez 

2006, 2007, 2009a, 2009b). Mean annual takes are based on 2004-2008 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 

2004 

2005 

2006 

2007 

2008 

observer 

20.6% 

20.9% 

18.5% 

16.4% 

13.5% 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 (n/a) 

 Total Annual Takes 0 (n/a) 

Ship Strikes 

Ship strikes were implicated in the deaths of five blue whales, from 2004-2008 (NMFS SWR Stranding 

Database). Four of these deaths occurred in 2007, the highest number recorded for any year. During 2004-2008, 

there were an additional eight injuries 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.). Blue whale mortality and injuries 

attributed to ship strikes in California waters averaged 1.0 per year for 2004-2008. The high number of ship strikes 

observed in 2007 resulted in NOAA implementing a mitigation plan that includes NOAA weather radio and U.S. 

Coast Guard advisory broadcasts to mariners entering the Santa Barbara Channel to be observant for whales, along 

with recommendations that mariners transit the channel at 10 knots or less. The Channel Islands National Marine 

Sanctuary also developed a blue whale/ship strike response plan, which involved weekly overflights to record whale 

locations. Additional plan information can be found at http://channelislands.noaa.gov/focus/alert.html. 

STATUS OF STOCK

 The reported take of North Pacific blue whales by commercial whalers totaled 9,500 between 1910 and 

1965 (Ohsumi and Wada 1972). Approximately 3,000 of these were taken from the west coast of North America 

from Baja California, Mexico to British Columbia, Canada (Tonnessen and Johnsen 1982; Rice 1992; Clapham et al. 

1997; Rice 1974). Blue whales in the North Pacific were given protected status by the IWC in 1966, but 

Doroshenko (2000) reported that a small number of blue whales were taken illegally by Soviet whalers after that 

date. As a result of commercial whaling, blue whales were listed as "endangered" under the Endangered Species 

Conservation Act of 1969. This protection was transferred to the Endangered Species Act (ESA) in 1973. They 

are still listed as “endangered”, and consequently the Eastern North Pacific stock is automatically considered as a 

"depleted" and "strategic" stock under the MMPA. The annual incidental mortality and injury rate (1.0/year) from 

ship strikes is less than the calculated PBR (3.1) for this stock, but this rate does not include unidentified large 

whales struck by vessels, some of which may have been blue whales. 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. 

Habitat Concerns 

Increasing levels of anthropogenic sound in the world’s oceans (Andrew et al. 2002) have been suggested 

to be a habitat concern for blue whales (Reeves et al. 1998).

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Revised 01/15/2011 

FIN WHALE (Balaenoptera physalus 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. 

Figure 1. Fin whale sighting locations based on 

shipboard surveys off California, Oregon, and 

Washington, 1991- 2008 (see Appendix 2 for data 

sources and information on timing and location of 

surveys). Dashed line represents the U.S. EEZ; thin

lines indicate completed transect effort of all surveys 

combined. 

183
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). The best estimate of fin whale abundance in California, Oregon, and 

Washington waters out to 300 nmi is the geometric mean of line transect estimates from summer/autumn 

ship surveys conducted in 2005 (3,281, CV=0.25) and 2008 (2,825, CV = 0.26) (Forney 2007, Barlow 

2010), or 3,044 (CV=0.18) whales. This is probably an underestimate because it almost certainly excludes 

some fin whales which could not be identified in the field and which were recorded as “unidentified 

rorqual” or “unidentified large whale”. 

Minimum Population Estimate

 The minimum population estimate for fin whales is taken as the lower 20th percentile of the lognormal distribution of abundance estimated from 2005 and 2008 summer/fall ship surveys (Forney 2007; 

Barlow 2010) or approximately 2,624. 

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 statistically 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. There is no evidence of a population trend 

from recent line-transect abundance surveys conducted in 1996, 2001, 2005, and 2008 in California, 

Oregon, and Washington waters out to 300 nmi. Estimates from these four surveys have been 2,042 (CV= 

0.13); 2,118 (CV= 0.18); 3,281 (CV=0.25); and 2,825 (CV=0.26) whales, respectively (Barlow and 

Forney 2007; Forney 2007; Barlow 2010). 

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 (2,624) 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 16. 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

 Information on historic whaling has been moved to the Status of Stock section. 

 

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 since 1990 when NMFS began observing the fishery . 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 2004-2008 data ( Carretta et al. 

2005, Carretta and Enriquez 2006, 2007, 2009a, 2009b). This results in an average estimate of zero 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 

184
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). 

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 . 

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 

2004 

2005 

2006 

2007 

2008 

observer 

20.6% 

20.9% 

18.5% 

16.4% 

13.5% 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 (n/a) 

Total annual takes 0 (n/a) 

Ship Strikes

 Ship strikes were implicated in the deaths of four fin whales and the injury of another from 2004 

to 2008, NMFS, unpublished stranding data). During 2004-2008, there were an additional eight injuries 

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 and injury due to ship strikes is 1.0 fin whales per year for 

the period 2004-2008. 

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. Approximately 

46,000 fin whales were taken from the North Pacific by commercial whalers between 1947 and 1987 (C. 

Allison, IWC, pers. comm.). Approximately 5,000 fin whales were taken from the west coast of North 

America from 1919 to 1965 (Rice 1974; Tonnessen and Johnsen 1982; Clapham et al. 1997). Fin whales in 

the North Pacific were given protected status by the IWC in 1976. 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 (zero) and ship strikes (1.0/yr) is less than the calculated PBR (16). 

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. Increasing levels of 

anthropogenic sound 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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survey. NOAA Technical Memorandum, NMFS, NOAA-TM-NMFS-SWFSC-456. 19 p. 

Barlow, J. 1994. Abundance of large whales in California coastal waters: a comparison of ship surveys in 

1979/80 and in 1991. Rept. Int. Whal. Commn. 44:399-406. 

Barlow, J. 1997. Preliminary estimates of cetacean abundance off California, Oregon, and Washington 

based on a 1996 ship survey and comparisons of passing and closing modes. Admin. Rept. LJ-97-

11 available from Southwest Fisheries Science Center, P.O. Box 271, La Jolla, CA. 25 pp. 

Barlow, J. 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. 

185
Barlow, J. and K.A. Forney. 2007. Abundance and population density of cetaceans in the California 

Current ecosystem. Fishery Bulletin 105:509-526. 

Berdegué, J. 2002. Depredación de las especies pelágicas reservadas a la pesca deportiva y especies en 

peligro de extinción con uso indiscriminado de artes de pesca no selectivas (palangres, FAD's, 

trampas para peces y redes de agallar fijas y a la deriva) por la flota palangrera Mexicana. 

Fundación para la conservación de los picudos. A.C. Mazatlán, Sinaloa, 21 de septiembre. 

Bérubé, M., J. Urban-R., A. E. Dizon, R. L. Brownell, and P. J. Palsbøll. 2002. Genetic identification of a 

small and highly isolated population of fin whales (Balaenoptera physalus) in the Sea of Cortez, 

México. Conservation Genetics 3:183-190. 

Best, P. B. 1993. Increase rates in severely depleted stocks of baleen whales. ICES J. Mar. Sci. 50:169-

186. 

Brueggeman, J. J., G. A. Green, K. C. Balcomb, C. E. Bowlby, R. A. Grotefendt, K. T. Briggs, M. L. 

Bonnell, R. G. Ford, D. H. Varoujean, D. Heinemann, and D. G. Chapman. 1990. OregonWashington Marine Mammal and Seabird Survey: Information synthesis and hypothesis 

formulation. U.S. Department of the Interior, OCS Study MMS 89-0030. 

Carretta, J.V. and L. Enriquez. 2009a. Marine mammal and seabird bycatch observed in California 

commercial fisheries in 2007. Administrative Report LJ-09-01, available from Southwest 

Fisheries Science Center, 3333 North Torrey Pines Rd., La Jolla, CA 92037. 12 p. 

Carretta, J.V. and L. Enriquez. 2009b. Marine mammal bycatch observed in the California/Oregon 

swordfish and thresher shark drift gillnet fishery in 2008. Administrative Report LJ-09-03, 

available from Southwest Fisheries Science Center, 3333 North Torrey Pines Rd., La Jolla, CA 

92037. 10 p. 

Carretta, J.V. and L. Enriquez. 2007. Marine mammal and sea turtle bycatch in the California/Oregon 

thresher shark and swordfish drift gillnet fishery in 2006. Administrative Report LJ-07-06, 

available from Southwest Fisheries Science Center, 8604 La Jolla Shores Drive, La Jolla, CA 

92037. 9p. 

Carretta, J.V. and L. Enriquez. 2006. Marine mammal bycatch and estimated mortality in California 

commercial fisheries during 2005. Administrative Report LJ-06-07, available from Southwest 

Fisheries Science Center, 8604 La Jolla Shores Drive, La Jolla, CA 92037. 14p. 

Carretta, J.V., S.J. Chivers, and K. Danil. 2005. Preliminary estimates of marine mammal bycatch, 

mortality, and biological sampling of cetaceans in California gillnet fisheries for 2004. 

Administrative Report LJ-05-10, available from Southwest Fisheries Science Center, 8604 La 

Jolla Shores Drive, La Jolla, California, 92037. 17 p. 

Clapham, P. J., S. Leatherwood, I. Szczepaniak, and R. L. Brownell, Jr. 1997. Catches of humpback and 

other whales from shore stations at Moss Landing and Trinidad, California, 1919-1926. Mar. 

Mamm. Sci. 13(3):368-394. 

Croll, D.A., C.W. Clark, A. Acevedo, B. Tershy, S. Flores, J. Gedamke, and J. Urban. 2002. Only male 

fin whales sing loud songs. Nature 417:809 

Dohl, T. P., R. C. Guess, M. L. Duman, and R. C. Helm. 1983. Cetaceans of central and northern 

California, 1980-83: Status, abundance, and distribution. Final Report to the Minerals 

Management Service, Contract No. 14-12-0001-29090. 284p. 

Donovan, G. P. 1991. A review of IWC stock boundaries. Rept. Int. Whal. Commn., Special Issue 13:39-

68. 

Forney, K. A., J. Barlow, and J. V. Carretta. 1995. The abundance of cetaceans in California waters. Part 

II: Aerial surveys in winter and spring of 1991 and 1992. Fish. Bull. 93:15-26. 

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

V. Carretta. 2000. U.S. Pacific Marine Mammal Stock Assessments: 2000. U.S. Dep. Commer. 

NOAA Technical Memorandum NOAA-TM-NMFS-SWFSC-300. 276p. 

Forney, K.A. 2007. Preliminary estimates of cetacean abundance along the U.S. west coast and within 

four National Marine Sanctuaries during 2005. U.S. Department of Commerce, NOAA Technical 

Memorandum NMFS-SWFSC-406. 27p. 

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. 

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California. Rep. int. Whal. Commn. 40:427-431. 

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

Ocean. In: I. Barrett, O. Sosa-Nishizaki and N. Bartoo (eds.). Biology and fisheries of swordfish, 

Xiphias gladius. Papers from the International Symposium on Pacific Swordfish, Ensenada 

Mexico, 11-14 December 1994. U.S. Dep. Commer., NOAA Tech. Rep. NMFS 142, 276p. 

Julian, F. 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. 

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array in the Northeast Pacific. (unpubl. ms.). 

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Rev. 46:20-24. 

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1998. Seasonal variation in reception of fin whale calls at five geographic areas in the North 

Pacific. Mar. Mamm. Sci. 14(3):617-627. 

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Commn. 25:114-126. 

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Schevill (ed.). The Whale Problem: A Status Report. Harvard Press, Cambridge, MA. 

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Velez. 1993. Estudio biologico pesquero del pez (Xiphias gladius) y otras especies de picudos 

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Tershy, B. R., D. Breese, and C. S. Strong. 1990. Abundance, seasonal distribution and population 

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Int. Whal. Commn., Special Issue 12:369-375. 

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Gulf of California? Rev. Invest. Cient., Univ. Auton. de Baja California Sur. 1:69-71. 

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and Los Angeles. 798pp. 

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

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187
Revised 01/15/2011 

SEI WHALE (Balaenoptera borealis 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 nine confirmed sightings of sei whales were made in California, Oregon, 

and Washington waters during extensive ship and aerial surveys between 1991- 2008 (Hill and Barlow 

1992; Carretta and Forney 1993; Mangels and Gerrodette 1994; VonSaunder and Barlow 1999; Barlow 

2003; Forney 2007; Barlow 2010). Green et al. (1992) did not report any sightings of sei whales in aerial 

surveys of Oregon and Washington. Abundance estimates for the two most recent line transect surveys of 

California, Oregon, and Washington waters out to 300 nmi are 74 (CV=0.88) and 215 (CV=0.71) sei 

whales, respectively (Forney 2007, Barlow 2010). The best estimate of abundance for California, Oregon, 

and Washington waters out to 300 nmi is the unweighted geometric mean of the 2005 and 2008 estimates, 

or 126 (CV=0.53) sei whales (Barlow and Forney 2007 ; Forney 2007; Barlow 2010). 

Figure 1. Sei whale sighting locations based on 

shipboard surveys off California, Oregon, and Washington, 

1991-2008 (see Appendix 2 for data sources and 

information on timing and location of surveys). Dashed 

line represents the U.S. EEZ; thin lines indicate completed

transect effort of all surveys combined. 

188
Minimum Population Estimate

 The minimum population estimate for sei whales is taken as the lower 20th percentile of the lognormal distribution of abundance estimated from 2005 and 2008 shipboard line-transect surveys, or 

approximately 83 whales. 

Current Population Trend

 There are no data on trends in sei whale abundance in the eastern North Pacific waters. Although 

the population in the North Pacific is expected to have grown since being given protected status in 1976, 

the possible effects of continued unauthorized take (Yablokov 1994) and incidental ship strikes and gillnet 

mortality make this uncertain. 

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

 There are no estimates of the growth rate of sei whale populations in the North Pacific (Best 

1993). 

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 0.1 (for an endangered species), resulting in a PBR of 0.17. 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

[Information on historic whaling has been moved to the Status of Stock section] 

Fishery Information

 The offshore drift gillnet fishery is the only fishery that is likely to take sei whales from this stock, 

but no fishery mortality 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 2004-2008 data (Carretta et al. 2005, 

Carretta and Enriquez 2006, 2007, 2009a, 2009b.). 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. n/a indicates that data are not 

available. Mean annual takes are based on 2004-2008 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 

2004 

2005 

2006 

2007 

2008 

observer 

20.6% 

20.9% 

18.5% 

16.4% 

13.5% 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 (n/a) 

Total annual takes 0 (n/a) 

Ship Strikes 

 One ship strike death was reported in Washington in 2003 (NMFS Northwest Regional Office, 

unpublished data). During 2004-2008, there were an additional eight injuries 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 zero sei whales per year for the period 2004-2008. 

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 

189
separately for the eastern North Pacific stock, but this stock was also probably depleted by 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, at least 410 were taken by-shore-based whaling stations in central 

California between 1919 and 1965 (Rice 1974; 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. 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. Although the current rate of ship strike deaths and 

serious injuries is zero, it is likely that some sei whale ship strikes are unreported. Increasing levels of 

anthropogenic sound 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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from SWFSC, 8604 La Jolla Shores Dr., La Jolla CA 92037. 31p. 

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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 L. Enriquez. 2009a. Marine mammal and seabird bycatch observed in California 

commercial fisheries in 2007. Administrative Report LJ-09-01, available from Southwest 

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Carretta, J.V. and L. Enriquez. 2009b. Marine mammal bycatch observed in the California/Oregon 

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available from Southwest Fisheries Science Center, 3333 North Torrey Pines Rd., La Jolla, CA 

92037. 10 p . 

Carretta, J.V. and L. Enriquez. 2007. Marine mammal and sea turtle bycatch in the California/Oregon 

thresher shark and swordfish drift gillnet fishery in 2006. Administrative Report LJ-07-06, 

available from Southwest Fisheries Science Center, 8604 La Jolla Shores Drive, La Jolla, CA 

92037. 9p. 

Carretta, J.V. and L. Enriquez. 2006. Marine mammal bycatch and estimated mortality in California 

commercial fisheries during 2005. Administrative Report LJ-06-07, available from Southwest 

Fisheries Science Center, 8604 La Jolla Shores Drive, La Jolla, CA 92037. 14p. 

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. 

Carretta, J.V., S.J. Chivers, and K. Danil. 2005. Preliminary estimates of marine mammal bycatch, 

mortality, and biological sampling of cetaceans in California gillnet fisheries for 2004. 

190
Administrative Report LJ-05-10, available from Southwest Fisheries Science Center, 8604 La 

Jolla Shores Drive, La Jolla, California, 92037. 17 p. 

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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68. 

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II: Aerial surveys in winter and spring of 1991 and 1992. Fish. Bull. 93:15-26. 

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192
Revised 01/15/2011 

MINKE WHALE (Balaenoptera acutorostrata scammoni): 

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. 

Figure 1. Minke whale sighting locations based on 

shipboard surveys off California, Oregon, and 

Washington, 1991-2008 (see Appendix 2 for data 

sources and information on timing and location of 

surveys). Dashed line represents the U.S. EEZ; thin

lines indicate completed transect effort of all surveys 

combined. 

POPULATION SIZE

 No estimates have been made for the number of minke whales in the entire North Pacific. Forney 

(2007) estimated 957 (CV=1.36) during a 2005 ship survey off California, Oregon, and Washington, while 

the most recent survey in 2008 did not record any minke whales while on survey effort (Barlow 2010). The 

number of minke whales off California Oregon, and Washington is estimated to be the arithmetic mean of 

two recent ship line transect surveys conducted in summer and autumn 2005 and 2008 (Barlow and Forney 

2007 ; Forney 2007; Barlow 2010); or 478 (CV=1.36) whales. 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. 

193
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 2005 and 2008 summer/fall ship surveys in 

California, Oregon, and Washington waters (Barlow and Forney 2007; Forney 2007; Barlow 2010) or 

approximately 202. 

Current Population Trend

 There are no data on trends in minke whale abundance in waters of California, Oregon and/or 

Washington. 

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

 There are no estimates of the growth rate of minke whale populations in the North Pacific (Best 

1993). 

POTENTIAL BIOLOGICAL REMOVAL

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

population size (202) 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 2.0 whales. 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

 Information on historic whaling has been moved to the Status of Stock section.

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 (Carretta et al. 2005, Carretta and 

Enriquez 2006, 2007, 2009a, 2009b). Mean annual takes are based on 2004-2008 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 

2004 

2005 

2006 

2007 

2008 

observer 

20.6% 

20.9% 

18.5% 

16.4% 

13.5% 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 (n/a) 

CA halibut and 

other species large 

mesh (>3.5”) set 

gillnet fishery 

2004 

2005 

2006 

2007 

2008 

0% 

0% 

~1% 

17.8% 

0% 

0 0 n/a 

Total annual takes 0 

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 for the period 2004-

2008. 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 California drift gillnet fishery 

dropped considerably (Barlow and Cameron 2003). Mean annual takes for this fishery (Table 1) are based 

on 2004-2008 data (Carretta et al. 2005, Carretta and Enriquez 2006, 2007, 2009a, 2009b). 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 coming from a minke whale using genetic sequencing methods. 

 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 

194
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 2004-2008. 

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

 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 (Rice 1974; Clapham et al. 1997). Reported aboriginal 

takes of minke whales in Alaska totaled 7 between 1930 and 1987 (C. Allison, IWC, pers. comm.). 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 westcoast stock is 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 (2.0), 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. Increasing levels of anthropogenic sound 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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west coast of the U.S. and Canada and the east coast of the Russian Federation. Rep. Int. Whal. 

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

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68. 

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197
Revised 01/15/2011 

ROUGH-TOOTHED DOLPHIN (Steno bredanensis): 

Hawaiian Stock 

STOCK DEFINITION AND GEOGRAPHIC RANGE 

 Rough-toothed dolphins are 

found throughout the world in tropical and 

warm-temperate waters (Perrin et al. 

2009). They are present around all the 

main Hawaiian islands (Shallenberger 

1981; Tomich 1986) and have been 

observed at least as far northwest as 

French Frigate Shoals (Nitta and 

Henderson 1993). Recent sighting 

locations of rough-toothed dolphins 

during a 2002 shipboard survey of waters 

within the U.S. Exclusive Economic Zone 

(EEZ) of the Hawaiian Islands (Barlow 

2006) are shown in Figure 1. Eight 

strandings have been reported from Maui, 

Oahu, and the island of Hawaii (Nitta 

1991; Maldini et al. 2005). Little is 

known about stock structure for this 

species in the North Pacific. Photographic 

identification studies around the main 

Hawaiian islands have indicated that 

dispersal rates between the islands of 

Kauai/Niihau and Hawaii do not exceed 

2% per year (Baird et al. 2008). 

Resighting rates off the island of Hawaii 

are high, with 75% of well-marked individuals resighted on two or more occasions, suggesting high site fidelity and 

low population size. Resighting data coupled with relatively high sighting rates within the Main Islands stratum 

versus the outer EEZ stratum (Barlow 2006) may suggest that there are island-associated populations of roughtoothed dolphins in the Hawaii EEZ. Rough-toothed dolphins have also been documented in American Samoan 

waters (NMFS, PIR, unpublished data). For the Marine Mammal Protection Act (MMPA) stock assessment reports, 

there are two Pacific management stocks: 1) The Hawaiian Stock (this report), and 2) the American Samoa Stock. 

The Hawaiian stock includes animals found both within the Hawaiian Islands EEZ and in adjacent international 

waters; however, because data on abundance, distribution, and human-caused impacts are largely lacking for 

international waters, the status of this stock is evaluated based on data from the U.S. EEZ waters of the Hawaiian 

Islands (NMFS 2005). 

W180 W175 W170 W165 W160 W155 W150

N10

N15

N20

N25

N30

N35

Figure 1. Rough-toothed dolphin sighting locations during the 2002 

shipboard cetacean survey of U.S. EEZ waters surrounding the 

Hawaiian Islands (Barlow 2006; see Appendix 2 for details on timing 

and location of survey effort). Outer line represents approximate 

boundary of survey area and U.S. EEZ.

POPULATION SIZE

 A population estimate for this species has been made in the eastern tropical Pacific (Wade and Gerrodette 

1993), but it is not known whether these animals are part of the same population that occurs around the Hawaiian 

Islands. Mark-recapture estimates for the islands of Kauai/Nihau and Hawaii were estimated from identification 

photographs obtained between 2003 and 2006, resulting in estimates of 1,665 (CV=0.33) around Kauai/Niihau and 

198 (CV=0.12) around the island of Hawaii (Baird et al. 2008). These estimates are specific to those island areas 

and do not represent the abundance of rough-toothed dolphins within the Hawaiian EEZ, as surveys were primarily 

conducted within 40km of shore. A 2002 shipboard line-transect survey of the entire Hawaiian Islands EEZ resulted 

in an abundance estimate of 8,709 (CV=0.45) rough-toothed dolphins (Barlow 2006). This is currently the best 

available abundance estimate for this stock. 

 

Minimum Population Estimate

 The log-normal 20th percentile of the 2002 abundance estimate for Hawaiian Islands EEZ waters (Barlow 

2006) is 6,067 rough-toothed dolphins within the Hawaiian Islands EEZ. 

198
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 

within the U.S. EEZ of the Hawaiian Islands (6,067) times one half the default maximum net growth rate for 

cetaceans (1⁄2 of 4%) times a recovery factor of 0.50 (for a stock of unknown status with no known fishery mortality 

or serious injury; Wade and Angliss 1997), resulting in a PBR of 61 rough-toothed dolphins per year. 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Fishery Information

Information on fishery-related mortality and serious injury of cetaceans in Hawaiian waters is limited, but 

the gear types used in Hawaiian fisheries are responsible for marine mammal mortality and serious injury in other 

fisheries throughout U.S. waters. Gillnets appear to capture marine mammals wherever they are used and lobster 

traps and longlines can be expected to occasionally entangle cetaceans (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). Rough-toothed dolphins are known to 

take bait and catch from Hawaiian sport and commercial fisheries operating near the main islands and in a portion of 

the northwestern islands (Shallenberger 1981; Schlais 1984; Nitta and Henderson 1993), and they have been 

specifically reported to interact with the day handline fishery for tuna (palu-ahi) and the troll fishery for billfish and 

tuna (Schlais 1984; Nitta and Henderson 1993). There are currently two distinct longline fisheries based in Hawaii: a 

deep-set longline (DSLL) fishery that targets primarily tunas, and a shallow-set longline fishery (SSLL) that targets 

swordfish. Both fisheries operate within U.S. waters and on the high seas. Between 2004 and 2008, no roughtoothed dolphins were observed hooked or entangled in the SSLL fishery (100% observer coverage) or the DSLL 

fishery (20-28% observer coverage) (McCracken & Forney 2010). Interaction rates between dolphins and the NWHI 

bottomfish fishery have been estimated based on studies conducted in 1990-1993, indicating that an average of 

2.67 dolphin interactions, most likely involving bottlenose and rough-toothed dolphins, occurred for every 1000 fish 

brought on board (Kobayashi and Kawamoto 1995). Fishermen claim interactions with dolphins that steal bait and 

catch are increasing. It is not known whether these interactions result in serious injury or mortality of dolphins. 

Baird et al. (2008) reported increased vessel avoidance of boats by rough-toothed dolphins off the island of Hawaii 

relative to those off Kauai or Niihau and attributed this to possible shooting of dolphins that are stealing bait or catch 

from recreational fisherman off the island of Hawaii (Kuljis 1983). 

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. It is 

not listed as “threatened” or “endangered” under the Endangered Species Act (1973), nor as “depleted” under the 

MMPA. Given the absence of recent fishery-related mortality or serious injuries, the Hawaiian stock of roughtoothed dolphins is not considered strategic under the 1994 amendments to the MMPA, and the total fishery 

mortality and serious injury can be considered to be insignificant and approaching zero. 

REFERENCES 

Baird, R.W., D.L. Webster, S.D. Mahaffy, D.J. McSweeney, G.S. Schorr, and A.D. Ligon. 2008. Site fidelity and 

association patterns in a deep-water dolphin: Rough-toothed dolphins (Steno bredanensis) in the Hawaiian 

Archipelago. Marine Mammal Science 24(3): 535-553. 

Barlow, J. 2006. Cetacean abundance in Hawaiian waters estimated from a summer/fall survey in 2002. Marine 

Mammal Science 22(2): 446-464. 

Forney, K.A. 2009. Serious injury determinations for cetaceans caught in Hawaii longline fisheries during 1994-

2008. Draft document PSRG-2009-09 presented to the Pacific Scientific Review Group, November 3-5, 

2009, Del Mar, CA. 

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 

199
economic impacts. Fisheries Research 23: 11-22. 

Kuljis, B.A. 1983. Porpoise/fisheries interactions within the Hawaiian islands. Southwest Fisheries Science Center 

Admin Rep H-83-19C. 16pp. 

Maldini, D., L. Mazzuca, and S. Atkinson. 2005. Odontocete stranding patterns in the Main Hawaiian Islands 

(1937-2002): How do they compare with live animal surveys? Pacific Science 59(1):55-67. 

McCracken M., and K.A. Forney. 2010. Preliminary assessment of incidental interactions with marine mammals in 

the Hawaii longline deep and shallow set fisheries. NMFS, Pacific Islands Fisheries Science Center 

Working Paper WP-10-001. 27p. 

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. 

Perrin, W.F., B. Würsig and J.G.M. Thewissen. 2009. Encyclopedia of Marine Mammals. Second Edition. 

Academic Press, Amsterdam. 

Schlais, J.F. 1984. Thieving dolphins: A growing problem in Hawaii's fisheries. Sea Front. 30(5):293-298. 

Shallenberger, E.W. 1981. The status of Hawaiian cetaceans. Final report to U.S. Marine Mammal Commission. 

MMC-77/23, 79pp. 

Tomich, P. Q. 1986. Mammals in Hawaii: A Synopsis and Notational Bibliography. Bishop Museum Press, Hawaii, 

375 pp. 

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

Workshop April 3-5, 1996, Seattle, Washington. U. S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR12. 93 pp. 

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

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

200
Revised 01/15/2011 

ROUGH-TOOTHED DOLPHIN (Steno bredanensis): 

American Samoa Stock 

STOCK DEFINITION AND GEOGRAPHIC RANGE 

Rough-toothed dolphins are found throughout 

the world in tropical and warm-temperate 

waters (Perrin et al. 2009). Rough-toothed 

dolphins are common in the South Pacific 

from the Solomon Islands, where they were 

taken by dolphin hunters, to French Polynesia 

and the Marquesas (reviewed by Reeves et al 

1999). Rough-toothed dolphins have been 

observed during summer and winter surveys 

around the American Samoan island of Tutuila 

(Johnston et al. 2008) and are thought to be 

common throughout the Samoan archipelago 

(Craig 2005). Rough-toothed dolphins were 

among the most commonly-sighted cetaceans 

during small boat surveys conducted from 

2003 to 2006 around Tutuila, though not 

observed during a 2006 survey of Swain’s 

Island and the Manu’a Group (Johnston et al. 

2008). Photo-identification data collected 

during the surveys suggest the presence of a 

resident population of rough-toothed dolphins 

in the waters surrounding Tutuila (Johnston et 

al. 2008). Approximately 1/3 of the 

individuals within the photo-id catalog were sighted in multiple years (Johnston et al. 2008). One rough-toothed 

dolphin was taken entangled near 40-fathom bank south of the islands by the American Samoa-based longline in 

2008 (Oleson 2009), indicating some rough-toothed dolphins maintain a more pelagic distribution. Nothing is 

known about stock structure for this species in the South Pacific. For the Marine Mammal Protection Act (MMPA) 

stock assessment reports, there are two Pacific management stocks: 1) The Hawaiian Stock, which includes animals 

found within the U.S. EEZ of the Hawaiian Islands, and 2) the American Samoa Stock, which include animals 

inhabiting the EEZ waters around American Samoa (this report). 

Figure 1. Rough-toothed dolphin sightings during cetacean 

sighting surveys around Tutuila, American Samoa, 2003-2006 

(Johnston et al, 2008). 

POPULATION SIZE 

No abundance estimates are currently available for rough-toothed dolphins in U.S. EEZ waters of American Samoa; 

however, density estimates for rough-toothed dolphins in other tropical Pacific regions can provide a range of likely 

abundance estimates in this unsurveyed region. Published estimates of rough-toothed dolphins (animals per km2

) in 

the Pacific are: 0.0035 (CV=0.45) for the U.S. EEZ of the Hawaiian Islands (Barlow 2006); 0.0017 (CV=0.63) for 

nearshore waters surrounding the main Hawaiian Islands (Mobley et al. 2000), 0.0076 (CV=0.32) and 0.0017 

(CV=0.16) for the eastern tropical Pacific Ocean (Wade and Gerrodette 1993; Ferguson and Barlow 2003). 

Applying the lowest and highest of these density estimates to U.S. EEZ waters surrounding American Samoa (area 

size = 404,578 km2

) yields a range of plausible abundance estimates of 692 – 3,115 rough-toothed dolphins. 

Minimum Population Estimate 

No minimum population estimate is currently available for waters surrounding American Samoa, but the roughtoothed dolphin density estimates from other tropical Pacific regions (Barlow 2003, Mobley et al. 2000, Wade and 

Gerrodette 1993, Ferguson and Barlow 2003, see above) can provide a range of likely values. The lognormal 20th

percentiles of plausible abundance estimates for the American Samoa EEZ, based on the densities observed 

elsewhere, range from 426 – 2,731 rough-toothed dolphins. 

Current Population Trend 

No data are available on current population trend. 

201
CURRENT AND MAXIMUM NET PRODUCTIVITY RATES 

No data are available on current or maximum net productivity rate. 

POTENTIAL BIOLOGICAL REMOVAL 

No PBR can presently be calculated for rough-toothed dolphins within the American Samoa EEZ, but based on the 

range of plausible minimum abundance estimates (426 – 2,731), a recovery factor of 0.40 (for a species of unknown 

status with a fishery mortality and serious injury rate CV > 0.50 within the American Samoa EEZ; Wade and 

Angliss 1997), and the default growth rate (1⁄2 of 4%), the PBR would likely fall between 3.4 and 22 rough-toothed 

dolphins per year. 

ANNUAL 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 American 

Samoan 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). The 

primary fishery in American Samoa is the 

commercial pelagic longline fishery that 

targets tunas, which was introduced in 1995 

(Levine and Allen 2009). In 2008, there were 

28 federally permitted vessels within the 

longline fishery in American Samoa. The 

fishery has been monitored since March 2006 

under a mandatory observer program, which 

records all interactions with protected species 

(Pacific Islands Regional Office 2009). One 

rough-toothed dolphin was seriously injured 

by the fishery in 2008 (Oleson 2009). 

Figure 2. Locations of observed rough-toothed dolphin takes 

(filled diamonds) in the American Samoa longline fishery, 

2006-2008. Solid lines represent the U.S. EEZ. Set locations 

in this fishery are summarized in Appendix 1. 

Table 1. Summary of available information on incidental mortality and serious injury of rough-toothed dolphins 

(American Samoan stock) in commercial fisheries within the U.S. EEZ (Oleson 2009). Longline fishery take 

estimates represent only those trips with at least 10 sets/trip (Oleson 2009). Mean annual takes are based on 2006-

2008 data unless otherwise indicated. 

Observed and estimated mortality and serious injury of rough-toothed 

dolphins in the American Samoa EEZ

Fishery Name Year American Samoa EEZ Data Type

Percent Observer 

Coverage

Obs. Estimated (CV) Mean Annual Takes 

(CV)

American 

Samoa-based 

longline fishery 

2006 

2007

2008

observer 

data

9.0% 

7.7%

8.5%

0 

0 

1 

0 (-) 

0 (-) 

10.9 (2.0) 3.6 (0.6)

Minimum total annual takes within U.S. EEZ waters 3.6 (0.6)

202
Prior to 1995, bottom fishing and trolling were the primary fisheries in American Samoa but they became 

less prominent after longlining was introduced (Levine and Allen 2009). Nearshore subsistence fisheries include 

spear fishing, rod and reel, collecting, gill netting, and throw netting (Craig 1993, Levine and Allen 2009). 

Information on fishery-related mortality of cetaceans in the nearshore fisheries is unknown, but the gear types used 

in American Samoan 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. Although boat-based 

nearshore fisheries have been randomly monitored since 1991, by the American Samoa Department of Marine and 

Wildlife Sources (DMWR), no estimates of annual human-caused mortality and serious injury of cetaceans are 

available. 

STATUS OF STOCK 

The status of rough-toothed dolphins in American Samoan 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. It is 

not listed as “threatened” or “endangered” under the Endangered Species Act (1973), nor as “depleted” under the 

MMPA. The status of the American Samoan stock of rough-toothed dolphins under the 1994 amendments to the 

MMPA cannot be determined at this time because no abundance estimates are available and PBR cannot be 

calculated. However, the estimated rate of fisheries-related mortality or serious injury within the American Samoa 

EEZ (3.6 animals per year) is between the range of likely PBRs (3.4 – 22) for this region. 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 

Barlow, J. 2006. Cetacean abundance in Hawaiian waters estimated from a summer/fall survey in 2002. Marine 

Mammal Science 22(2): 446-464. 

Craig, P., B. Ponwith, F. Aitaoto, and D. Hamm. 1993. The commercial, subsistence, and recreational fisheries of 

American Samoa –Fisheries of Hawaii and U.S. – associated pacific Islands. Marine Fisheries Review, 

Spring. 

Ferguson, M. C. and J. Barlow. 2003. Addendum: Spatial distribution and density of cetaceans in the eastern 

tropical Pacific Ocean based on summer/fall research vessel surveys in 1986-96. Administrative Report LJ01-04 (addendum), Southwest Fisheries Science Center, National Marine Fisheries Service, 8604 La Jolla 

Shores Drive, La Jolla, CA 92037. 

Johnston, D.W., J. Robbins, M.E. Chapla, D.K. Mattila, and K.R. Andrews. 2008. Diversity, habitat associations, 

and stock structure of odontocete cetaceans in the waters of American Samoa, 2003-2006. Journal of 

Cetacean Research and Management 10(1):59-66. 

Levine, A., and S. Allen. 2009. American Samoa as a fishing community. U.S. Dep. Commer., NOAA Tech. 

Memo., NOAA-TM-NMFS-PIFSC-19, 74 p. 

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. 

Oleson, E.M. 2009. Characteristics of the American Samoa Longline Fishery and Estimates of Cetacean Take, 

2006-2008. PSRG-2009-14. 

Pacific Islands Regional Office. 2009. Pacific Islands Regional Observer Program American Samoa longline annual 

status report, January 1, 2008 – December 31, 2008. 

http://www.fpir.noaa.gov/Library/PUBDOCs/ObserverQtrAnnRpts/obs_as_ll_rprts/2008/obs_as_ll_annual

_2008.pdf

Perrin, W.F., G. P. Donovan and J. Barlow. 1994. Gillnets and Cetaceans. Rep. Int. Whal. Commn., Special Issue 

15, 629 pp. 

Perrin, W.F., B. Würsig and J.G.M. Thewissen. 2009. Encyclopedia of Marine Mammals. Second Edition. 

Academic Press, Amsterdam. 

Reeves, R.R.S., S. Leatherwood, G.S. Stone, and G. Eldridge. 1999. Marine mammals in the area served by the 

South Pacific Regional Environmental Planning Programme (SPREP). South Pacific Regional 

Environmental Programme and United Nations Environment Programme. 48pp. 

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. 

203
Wade, P. R. and T. Gerrodette. 1993. Estimates of cetacean abundance and distribution in the eastern tropical 

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

204
Revised 01/15/2011

RISSO'S DOLPHIN (Grampus griseus): 

Hawaiian Stock 

STOCK DEFINITION AND GEOGRAPHIC RANGE 

Risso's dolphins are found in tropical to 

warm-temperate waters worldwide 

(Perrin et al. 2009). Although they have 

been considered rare in Hawaiian waters 

(Shallenberger 1981), six sightings were 

made during a 2002 survey of the U.S. 

Exclusive Economic Zone (EEZ) of the 

Hawaiian Islands (Figure 1). There are 

five stranding records from the main 

islands (Nitta 1991; Maldini et al. 2005). 

For the Marine Mammal Protection Act 

(MMPA) stock assessment reports, 

Risso's dolphins within the Pacific U.S. 

EEZ are divided into two discrete, noncontiguous areas: 1) Hawaiian waters 

(this report), and 2) waters off 

California, Oregon and Washington. 

The Hawaiian stock includes animals 

found both within the Hawaiian Islands 

EEZ and in adjacent international 

waters; however, because data on 

abundance, distribution, and humancaused impacts are largely lacking for 

international waters, the status of this 

stock is evaluated based on data from 

U.S. EEZ waters of the Hawaiian Islands (NMFS 2005). 

W180 W175 W170 W165 W160 W155 W150

N10

N15

N20

N25

N30

N35

Figure 1. Risso's dolphin sighting locations during the 2002 

shipboard cetacean survey of U.S. EEZ waters surrounding the 

Hawaiian Islands (Barlow 2006; see Appendix 2 for details on timing 

and location of survey effort). Outer line represents approximate 

boundary of survey area and U.S. EEZ.

POPULATION SIZE

 Population estimates have been made off Japan (Miyashita 1993), in the eastern tropical Pacific (Wade and 

Gerrodette 1993), and off the U.S. West Coast (Barlow and Forney 2007), but it is not known whether these animals 

are part of the same population that occurs around the Hawaiian Islands and in the central North Pacific. A 2002 

shipboard line-transect survey of the entire Hawaiian Islands EEZ resulted in an abundance estimate of 2,372 

(CV=0.97) Risso’s dolphins (Barlow 2006). This is currently the best available abundance estimate for this stock. 

Minimum Population Estimate

 The log-normal 20th percentile of the 2002 abundance estimate (Barlow 2006) is 1,195 Risso’s dolphins 

within the Hawaiian Islands 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 for Hawaiian animals. 

POTENTIAL BIOLOGICAL REMOVAL

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

within the U.S. EEZ of the Hawaiian Islands (1,195) times one half the default maximum net growth rate for 

cetaceans (1⁄2 of 4%) times a recovery factor of 0.50 (for a stock of unknown status with no known fishery mortality 

or serious injury within the U.S. EEZ of the Hawaiian Islands; Wade and Angliss 1997), resulting in a PBR of 12 

Risso’s dolphins per year. 

205
HUMAN CAUSED MORTALITY AND SERIOUS INJURY 

Fishery Information

Information on fishery-related 

mortality and serious injury of cetaceans 

in Hawaiian waters is limited, but the 

gear types used in Hawaiian fisheries are 

responsible for marine mammal 

mortality and serious injury in other 

fisheries throughout U.S. waters. 

Gillnets appear to capture marine 

mammals wherever they are used, and 

float lines from lobster traps and 

longlines can be expected to 

occasionally entangle cetaceans (Perrin 

et al. 1994). Interactions with cetaceans 

have been reported for all Hawaiian 

pelagic fisheries (Nitta and Henderson 

1993), and some of these interactions 

involved Risso’s dolphins. 

 There are currently two distinct 

longline fisheries based in Hawaii: a 

deep-set longline (DSLL) fishery that 

targets primarily tunas, and a shallowset longline fishery (SSLL) that targets 

swordfish. Both fisheries operate within 

U.S. waters and on the high seas. 

Between 2004 and 2008, 10 Risso’s 

dolphins were observed killed or 

seriously injured in the SSLL fishery 

(100% observer coverage), and 15 

Risso’s dolphins were observed killed or 

seriously injured in the DSLL fishery (20-28% observer coverage) (Forney 2009, McCracken & Forney 2010). 

Three Risso’s dolphin in the DSLL fishery and two in the SSLL fishery were killed; the remainder were determined 

to have been seriously injured (Forney 2009), based on an evaluation of the observer’s description of the interaction 

and following the most recently developed criteria for assessing serious injury in marine mammals (Andersen et al. 

2008). The total observed mortality and serious injury of cetaceans in the SSLL fishery (with 100% coverage), and 

the estimated annual and 5-yr average mortality and serious injury of cetaceans in the DSLL fishery are reported by 

McCracken and Forney (2010). Average 5-yr estimates of annual mortality and serious injury for 2004-2008 are 2.6 

(CV = 0.40) Risso’s dolphins outside of U.S. EEZs, and none within the Hawaiian Islands EEZ (Table 1, 

McCracken & Forney 2010). One additional unidentified cetacean, which may have been a Risso’s dolphin, was 

also taken in the DSLL fishery within U.S. EEZ waters during 2006 (Figure 2, Forney and McCracken 2008). 

Figure 1. Locations of Risso's dolphin takes (filled diamonds) and 

possible takes of this species (open diamonds) in Hawaii-based 

longline fisheries, 2004-2008 . Solid lines represent the U.S. EEZs.

Fishery descriptions are provided in Appendix 1. 

 

Table 1. Summary of available information on incidental mortality and serious injury of Risso’s dolphin (Hawaii 

stock) in commercial fisheries, within and outside of U.S. EEZs (McCracken & Forney 2010). Mean annual takes 

are based on 2004-2008 data unless indicated otherwise. 

Mortality and Serious In ry ju

outside of U.S. EEZ

Mortality and Serious Injury 

within Hawaiian Islands EEZ

Fishery Name Year Data Type

Percent 

Observer 

Coverage Observed Estimated 

(CV)

Mean Annual 

Takes 

(CV)

Observed Estimated 

(CV)

Mean Annual 

Takes 

(CV)

Hawaii-based 

deep-set longline 

fishery 

2004 

2005 

2006 

2007 

2008 

observer 

data 

25% 

28% 

22% 

20% 

22% 

0 

2 

4 

4 

5

0 (n/a) 

3 (0.6) 

5 (0.4) 

3 (1.0) 

2 (1.2)

2.6 (0.4) 

0 

0 

0 

0

0

0 (-) 

0 (-) 

0 (-) 

0 (-)

0 (-)

0 (-)

206
Mortality and Serious Injury 

outside of U.S. EEZ

Mortality and Serious Injury 

within Hawaiian Islands EEZ

Fishery Name Year Data Type

Percent 

Observer 

Coverage Observed Estimated 

(CV)

Mean Annual 

Takes 

(CV)

Observed Estimated 

(CV)

Mean Annual 

Takes 

(CV)

Hawaii-based 

shallow-set 

longline fishery 

2004 

2005 

2006 

2007 

2008 

observer 

data 

100% 

100% 

100% 

100% 

100% 

0 

1 

2 

3 

4 

Same as 

observed 

2.0 

0 

0 

0 

0

0

0 (-) 

0 (-) 

0 (-) 

0 (-)

0 (-)

0 (-)

Minimum total annual takes within U.S. EEZ waters 0 (-)

 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 stealing 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. It is not listed as 

“threatened” or “endangered” under the Endangered Species Act (1973), nor as “depleted” under the MMPA. Given 

the absence of recent fishery-related mortality or serious injuries within the Hawaiian Islands EEZ, the Hawaiian 

stock of Risso’s dolphins is not considered strategic under the 1994 amendments to the MMPA, and the total fishery 

mortality and serious injury can be considered to be insignificant and approaching zero. However, the potential 

effect of injuries sustained by Risso’s dolphins in U.S. pelagic longline fisheries in international waters is not 

known, because no abundance or bycatch estimates are available for international waters. 

REFERENCES

Andersen, M. S., K. A. Forney, T. V. N. Cole, T. Eagle, R. Angliss, K. Long, L. Barre, L. Van Atta, D. Borggaard, 

T. Rowles, B. Norberg, J. Whaley, and L. Engleby. 2008. Differentiating Serious and Non-Serious Injury 

of Marine Mammals: Report of the Serious Injury Technical Workshop, 10-13 September 2007, Seattle, 

Washington. NOAA Technical Memorandum NMFS-OPR-39. 94p. 

Barlow, J. 2006. Cetacean abundance in Hawaiian waters estimated from a summer/fall survey in 2002. Marine 

Mammal Science 22(2): 446-464.Barlow, J., and Forney, K.A. 2007. Abundance and density of cetaceans 

in the California Current ecosystem. Fishery Bulletin 105(4): 509-526. 

Forney, K.A. 2009. Serious injury determinations for cetaceans caught in Hawaii longline fisheries during 1994-

2008. Draft document PSRG-2009-09 presented to the Pacific Scientific Review Group, November 3-5, 

2009, Del Mar, CA.. 

Forney, K. A. and McCracken, M. 2008. Preliminary estimates of cetacean injury and mortality in Hawaii-based 

longline fisheries during 2006. Draft document PSRG-2008-16 presented to the Pacific Scientific Review 

Group, January 8-10, 2008, Monterey, CA. 

Kobayashi, D. R. and K. E. Kawamoto. 1995. Evaluation of shark, dolphin, and monk seal interactions with 

Northwestern Hawaiian Island bottomfishing activity: a comparison of two time periods and an estimate of 

economic impacts. Fisheries Research 23: 11-22. 

Maldini, D., L. Mazzuca, and S. Atkinson. 2005. Odontocete stranding patterns in the Main Hawaiian Islands 

(1937-2002): How do they compare with live animal surveys? Pacific Science 59(1):55-67. 

McCracken M. and K.A. Forney. 2010. Preliminary assessment of incidental interactions with marine mammals in 

the Hawaii longline deep and shallow set fisheries. NMFS, Pacific Islands Fisheries Science Center 

Working Paper WP-10-001. 27p. 

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. 

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. 

207
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. 

Perrin, W.F., B. Würsig and J.G.M. Thewissen. 2009. Encyclopedia of Marine Mammals. Second Edition. 

Academic Press, Amsterdam. 

Shallenberger, E.W. 1981. The status of Hawaiian cetaceans. Final report to U.S. Marine Mammal Commission. 

MMC-77/23, 79pp. 

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

Workshop April 3-5, 1996, Seattle, Washington. U. S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR12. 93 pp. 

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

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

208
Revised 01/15/2011

COMMON BOTTLENOSE DOLPHIN (Tursiops truncatus truncatus): 

Hawaiian Islands Stock Complex- Kauai/Niiahu, Oahu, 4-island, Hawaii 

Island, Hawaii Pelagic

STOCK DEFINITION AND GEOGRAPHIC RANGE 

 Common bottlenose dolphins are widely 

distributed throughout the world in tropical and 

warm-temperate waters (Perrin et al. 2009). The 

species is primarily coastal in much of its range, 

but there are populations in some offshore 

deepwater areas as well. Bottlenose dolphins are 

common throughout the Hawaiian Islands, from the 

island of Hawaii to Kure Atoll (Shallenberger 

1981). Twelve strandings have been reported 

within the main Hawaiian Islands (Nitta 1991, 

Maldini et al. 2005). Recent sighting locations 

based on a 2002 shipboard survey of waters within 

the U.S. Exclusive Economic Zone (EEZ) of the 

Hawaiian Islands (Barlow 2006) are shown in 

Figure 1. In the Hawaiian Islands, they are found 

in shallow inshore waters and deep water (Baird et 

al. 2009). W180 W175 W170 W165 W160 W155 W150

N10

N15

N20

N25

N30

N35

Separate offshore and coastal forms of 

bottlenose dolphins have been identified along 

continental coasts in several areas (Ross and 

Cockcroft 1990; Van Waerebeek et al. 1990), and 

there is some evidence that similar onshoreoffshore forms may exist in Hawaiian waters. In 

their analysis of sightings of bottlenose dolphins 

in the eastern tropical Pacific (ETP), Scott and Chivers (1990) noted that there was a large hiatus between the 

westernmost sightings and the Hawaiian Islands. 

These data suggest that bottlenose dolphins in 

Hawaiian waters belong to a separate stock from 

those in the ETP. Furthermore, recent photoidentification and genetic studies off Oahu, Maui, 

Lanai, Kauai, Niihau, and Hawaii suggest limited 

movement of bottlenose dolphins between islands 

and into offshore waters (Baird et al. 2009; 

Martien et al. in review). These data suggest the 

existence of demographically distinct resident 

populations at each of the four main Hawaiian 

Island groups – Kauai & Niihau, Oahu, the ‘4-

island Region (Molokai, Lanai, Maui, Kahoolawe), 

and Hawaii. In addition, the genetic data indicate 

that the deeper waters surrounding the main 

Hawaiian Islands are utilized by a larger pelagic 

population. 

Figure 1. Bottlenose dolphin sighting locations during the 

2002 shipboard cetacean survey of U.S. EEZ waters 

surrounding the Hawaiian Islands (Barlow 2006; see 

Appendix 2 for details on timing and location of survey 

effort). Outer line represents approximate boundary of 

survey area and U.S. EEZ. 

18.5

19

19.5

20

20.5

21

21.5

22

22.5

-160.5 -160 -159.5 -159 -158.5 -158 -157.5 -157 -156.5 -156 -155.5 -155 -154.5

Longitude (degrees W)

Latitude (degrees N)

1000 m 

500 m

O'ahu - 4-Island Region Boundary

O'ahu

Ni'ihau

Hawai'i

Kaua'i

4-island Region

Over 99% of the bottlenose dolphins 

known to be part of one of the insular populations 

photo-identified around the main Hawaiian Islands (Baird et al. 2009) have been documented in waters of 1000 m or 

less (Martien et al. 2009). Based on these data, Martien et al. (2009) suggested that the boundaries between the 

insular stocks and the Hawaii Pelagic stock be placed along the 1000 m isobath. Since that isobath does not separate 

Oahu from the 4-Islands Region, the boundary between those stocks would run approximately equidistant between 

the 500 m isobaths around Oahu and the 4-Islands Region, through the middle of Kaiwi Channel. These boundaries 

Figure 2. Insular bottlenose dolphin stock boundaries (red 

lines). Areas beyond the 1000 m isobath represent the 

pelagic stock range. 

209
(Figure 2) are provisionally applied in this report to recognize separate insular and pelagic bottlenose dolphin stocks 

for management (NMFS 2005). These boundaries may be revised in the future as additional information becomes 

available. To date, no data are available regarding population structure of bottlenose dolphins in the Northwest 

Hawaiian Islands (NWHI). However, given the existence of island resident populations in the main Hawaiian 

Islands, the larger distances between islands in the NWHI, and the finding of population structure with the NWHI in 

other dolphin species (Andrews 2010), it is likely that additional demographically independent populations of 

bottlenose dolphins exist in the NWHI. However, until data become available upon which to base stock 

designations in this area, the NWHI will remain part of the Hawaii Pelagic Stock. For the Marine Mammal 

Protection Act (MMPA) Pacific stock assessment reports, bottlenose dolphins within the Pacific U.S. EEZ are 

divided into seven stocks: 1) California, Oregon and Washington offshore stock, 2) California coastal stock, and five 

Pacific Islands Region management stocks (this report): 3) Kauai and Niihau, 4) Oahu, 5) the “4-Island Region” 

(Molokai, Lanai, Maui, Kahoolawe), 6) Hawaii Island and 7) the Hawaiian Pelagic Stock, including animals found 

both within the Hawaiian Islands EEZ and in adjacent international waters. Because data on abundance, distribution, 

and human-caused impacts are largely lacking for international waters, the status of the Hawaii pelagic stock is 

evaluated based on data from U.S. EEZ waters of the Hawaiian Islands (NMFS 2005). Estimates of abundance, 

potential biological removals, and status determinations for the five Hawaiian stocks are presented separately below. 

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 (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. 

 Interactions with cetaceans have 

been reported for all Hawaiian pelagic 

fisheries, and some of these interactions 

involved bottlenose dolphins (Nitta and 

Henderson 1993). There are currently two 

distinct longline fisheries based in 

Hawaii: a deep-set longline (DSLL) 

fishery that targets primarily tunas, and a 

shallow-set longline fishery (SSLL) that 

targets swordfish. Both fisheries operate 

within U.S. waters and on the high seas. 

Between 2004 and 2008, four bottlenose 

dolphins were observed hooked or 

entangled in the SSLL fishery (100% 

observer coverage), and one bottlenose dolphin was observed taken in the DSLL fishery (20-28% observer 

coverage) (Forney 2009, McCracken 2009). Based on the locations, these takes are all considered to have been from 

the Pelagic Stock of bottlenose dolphins. All five dolphins were determined to have been seriously injured (Forney 

2009), based on an evaluation of the observer’s description of the interaction and following the most recently 

developed criteria for assessing serious injury in marine mammals (Andersen et al. 2008). Average 5-yr estimates of 

annual mortality and serious injury for the Pelagic Stock during 2004-2008 are 0.6 (CV = 0) bottlenose dolphins 

outside of U.S. EEZs, and 0.4 (CV = 0.68) within the Hawaiian Islands EEZ (Table 1, McCracken 2009). 

 Bottlenose dolphins are one of the species commonly reported to steal bait and catch from several 

Hawaiian sport and commercial fisheries (Nitta and Henderson 1993; Schlais 1984). Observations of bottlenose 

Figure 3. Locations of observed Pelagic Stock bottlenose dolphin 

takes (filled diamonds) in the Hawaii-based longline fishery, 2004-

2008. Solid lines represent the U. S. EEZ. Fishery descriptions are 

provided in Appendix 1. 

210
dolphins stealing 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 that steal bait and catch are increasing, 

including anecdotal reports of bottlenose getting “snagged” (Rizzuto 2007). 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 stealing fish catches (Nitta and 

Henderson 1993). Nitta and Henderson (1993) also reported that one bottlenose dolphin calf was removed from a 

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. One 

bottlenose dolphin entangled in a gillnet was reported stranded on Maui in 1998 (NMFS/PIR, unpublished data; 

Maldini 2003). During 2009, one bottlenose dolphin was photographed off the Kona Coast of the island of Hawaii 

with a hook and line trailing out of its mouth (pers. comm. Robin Baird), but the responsible fishery is not known. 

No estimates of human-caused serious injury and mortality are available for nearshore hook-and-line fisheries, 

because these fisheries and not observed or monitored. 

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

(Hawaii stock) in commercial and gillnet fisheries, within and outside of the U.S. EEZs (McCracken 2009, Forney 

2009). Mean annual takes are based on 2004-2008 data unless otherwise indicated; n/a = not available. 

Mortality and Serious Injury 

outside of U.S. EEZ

Mortality and Serious Injury 

within Hawaiian Islands EEZ

Fishery Name Year Data Type

Percent 

Observer 

Coverage Observed Estimated

Mean Annual 

Takes 

(CV)

Observed Estimated 

(CV)

Mean Annual 

Takes 

(CV)

Hawaii-based 

deep-set longline 

fishery 

2004 

2005 

2006 

2007 

2008 

observer 

data 

25% 

28% 

22% 

20% 

22% 

0 

0 

0 

0 

0

0 (-) 

0 (-) 

0 (-) 

0 (-) 

0 (-)

0 (-)

0 

0 

1 

0 

0

0 (-) 

0 (-) 

1 (1.6) 

0 (-) 

0 (-)

0.2 (3.1) 

Hawaii-based 

shallow-set 

longline fishery 

2004 

2005 

2006 

2007 

2008 

observer 

data 

100% 

100% 

100% 

100% 

100% 

0 

0 

1 

2 

0 

Same as 

observed 0.6 (0.0) 

0 

0 

0 

1 

0

Same as 

observed 0.2

Minimum total annual takes within U.S. EEZ waters 0.4 (0.68)1

1 Takes were all from the Pelagic Stock of bottlenose dolphins

KAUAI AND NIIHAU STOCK

POPULATION SIZE

 A photo-identification study conducted in 2003, 2004 and 2005 identified 102 individual bottlenose 

dolphins around Kauai and Niihau (Baird et al. 2009). A Lincoln-Peterson mark-recapture analysis of the photoidentification data resulted in an abundance estimate of 147 (CV=0.11) (Baird et al. 2009). This abundance 

underestimates the total number of bottlenose dolphins around Kauai and Niihau because it only represents 

individuals with distinguishable marks. 

Minimum Population Estimate

 The log-normal 20th percentile of the Baird et al. (2009) mark-recapture estimate is 134. This is greater 

than the number of distinct individuals (102) identified during the photo-identification study. 

 Current Population Trend

 No data are available on current population trend. 

211
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 

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

(for a stock of unknown status with no reported fishery mortality or serious injury during the last five years; Wade 

and Angliss 1997), resulting in a PBR of 1.3 bottlenose dolphins per year. 

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. It is not listed as 

“threatened” or “endangered” under the Endangered Species Act (1973), nor as “depleted” under the MMPA. The 

Kauai and Niihau Stock of bottlenose dolphins is not considered strategic under the 1994 amendments to the 

MMPA, because there have been no reports of recent mortality or serious injuries of this stock. However, there is 

no systematic monitoring of near-shore fisheries that may take this species. 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. 

OAHU STOCK

POPULATION SIZE

 A photo-identification study conducted in 2002, 2003 and 2006 identified 67 individual bottlenose dolphins 

around Oahu (Baird et al. 2009). A Lincoln-Peterson mark-recapture analysis of the photo-identification data 

resulted in an abundance estimate of 594 (CV=0.54) (Baird et al. 2009). The estimate only represents individuals 

with distinguishable marks and does not include individuals from the Northeastern (windward) side of the island. 

The sample size of encounters (11) was small compared to encounters off other islands; therefore, this estimate is 

imprecise and should be considered provisional until additional abundance studies can be completed. 

Minimum Population Estimate

 The log-normal 20th percentile of the Baird et al. (2009) mark-recapture estimate is 388. This is 

substantially greater than the number of distinct individuals (67) identified during the photo-identification study. 

 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 

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

(for a stock of unknown status with no reported fishery mortality during the last five years; Wade and Angliss 1997), 

resulting in a PBR of 3.9 bottlenose dolphins per year. 

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. It is not listed as 

“threatened” or “endangered” under the Endangered Species Act (1973), nor as “depleted” under the MMPA. The 

Oahu stock of bottlenose dolphins is not considered strategic under the 1994 amendments to the MMPA, because 

there have been no reports of recent mortality or serious injuries of this stock. However, there is no systematic 

monitoring of near-shore fisheries that may take this species. 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. 

212
4-ISLANDS REGION STOCK

POPULATION SIZE

 A photo-identification study conducted from 2000-2006 identified 98 individual bottlenose dolphins around 

Maui and Lanai (Baird et al. 2009). A Lincoln-Peterson mark-recapture analysis of the photo-identification data 

resulted in an abundance estimate of 153 (CV=0.24) (Baird et al. 2009). This abundance underestimates the total 

number of bottlenose dolphins in the 4-islands region because it only represents individuals with distinguishable 

marks and does not include individuals from the Northeastern (windward) sides of Maui and Molokai. 

Minimum Population Estimate

 The log-normal 20th percentile of the Baird et al. (2009) mark-recapture estimate is 125. This is greater 

than the number of distinct individuals (98) identified during the photo-identification study. 

 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 

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

(for a stock of unknown status with no reported fishery mortality during the last five years; Wade and Angliss 1997), 

resulting in a PBR of 1.3 bottlenose dolphins per year. 

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. It is not listed as 

“threatened” or “endangered” under the Endangered Species Act (1973), nor as “depleted” under the MMPA. The 4-

Islands Region Stock of bottlenose dolphins is not considered strategic under the 1994 amendments to the MMPA, 

there have been no reports of recent mortality or serious injuries of this stock. However, there is no systematic 

monitoring of near-shore fisheries that may take this species. 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. 

HAWAII ISLAND STOCK

POPULATION SIZE

 A photo-identification study conducted from 2000-2006 identified 69 individual bottlenose dolphins around 

the island of Hawaii (Baird et al. 2009). A Lincoln-Peterson mark-recapture analysis of the photo-identification data 

resulted in an abundance estimate of 102 (CV=0.13) (Baird et al. 2009). This abundance underestimates the total 

number of bottlenose dolphins around the island of Hawaii because it only represents individuals with 

distinguishable marks and does not include individuals from the Northeastern (windward) side of the island. 

Minimum Population Estimate

 The log-normal 20th percentile of the Baird et al. (2009) mark-recapture estimate is 91. This is greater than 

the number of distinct individuals (69) identified during the photo-identification study. 

 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 

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

a stock of unknown status with no reported fishery mortality during the last five years; Wade and Angliss 1997), 

213
resulting in a PBR of 0.9 bottlenose dolphins per year. 

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. It is not listed as 

“threatened” or “endangered” under the Endangered Species Act (1973), nor as “depleted” under the MMPA. The 

Hawaii Island Stock of bottlenose dolphins is not considered strategic under the 1994 amendments to the MMPA, 

because there have been no reports of recent mortality or serious injuries of this stock. However, there is no 

systematic monitoring of gillnet fisheries that may take this species. Insufficient information is available to 

determine whether the total fishery mortality and serious injury for bottlenose dolphins is insignificant and 

approaching zero mortality and serious injury rate. 

HAWAIIAN PELAGIC 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. A 2002 shipboard line-transect survey of the entire Hawaiian Islands EEZ resulted in 

an abundance estimate of 3,215 (CV= 0.59) bottlenose dolphins (Barlow 2006), equivalent to a density of 1.31 

individuals per 1000 km2

. Applying this density to the 2,464,486 km2 area of the Pelagic Stock between the 1000m 

isobath and the Hawaiian Islands EEZ boundary (see Figures 1-2), the stock-specific abundance is estimated as 

3,178 (CV=0.59). This is currently the best available abundance estimate for the Hawaiian Pelagic stock. 

Minimum Population Estimate

 The log-normal 20th percentile of the 2002 line-transect abundance estimate for the Hawaiian Pelagic Stock 

is 2,006 bottlenose dolphins. 

 Current Population Trend

 No data are available on current population trend. 

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

 No data are available on current or maximum net productivity rate for this species in Hawaiian waters. 

POTENTIAL BIOLOGICAL REMOVAL

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

within the U.S EEZ of the Hawaiian Islands (2,006) times one half the default maximum net growth rate for 

cetaceans (1⁄2 of 4%) times a recovery factor of 0.45 (for a stock of unknown status with a Hawaiian Islands EEZ 

fishery mortality and serious injury rate between 0.60 and 0.80; Wade and Angliss 1997), resulting in a PBR of 18 

bottlenose dolphin per year. 

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. It is not listed as 

“threatened” or “endangered” under the Endangered Species Act (1973), nor as “depleted” under the MMPA. The 

Hawaiian Pelagic Stock of bottlenose dolphins is not considered strategic under the 1994 amendments to the 

MMPA, because the estimated rate of fisheries related mortality or serious injury within the Hawaiian Islands EEZ 

(0.4 animals per year) is less than the PBR (18). However, the potential effects of interactions with U.S. and 

international pelagic longline fisheries in international waters 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. 

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216
Revised 1/15/2011

PANTROPICAL SPOTTED DOLPHIN (Stenella attenuata attenuata): 

Hawaiian Stock 

STOCK DEFINITION AND GEOGRAPHIC RANGE 

 Pantropical spotted dolphins are 

primarily found in tropical and subtropical 

waters worldwide (Perrin et al. 2009). 

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 et al. 2009). These dolphins are 

common and abundant throughout the 

Hawaiian archipelago, particularly in 

channels between islands, over offshore 

banks (e.g. Penguin Banks), and off the lee 

shores of the islands (see Shallenberger 

1981). Recent sighting locations from a 

2002 shipboard survey of waters within the 

U.S. Exclusive Economic Zone (EEZ) of 

(Barlow 2006). Twelve strandings of this 

species have been documented in Hawaii 

(Nitta 1991, Maldini et al. 2005). 

Morphological differences and distribution 

patterns have been used to establish that 

the spotted dolphins around Hawaii belong 

to a stock that is distinct from those in the 

ETP (Perrin 1975; Dizon et al. 1994; Perrin et al. 1994b). Their possible affinities with other stocks elsewhere in the 

Pacific have not been investigated. 

W180 W175 W170 W165 W160 W155 W150

N10

N15

N20

N25

N30

N35

Figure 1. Pantropical spotted dolphin sighting locations during the 

2002 shipboard survey of U.S. EEZ waters surrounding the Hawaiian 

Islands (Barlow 2006; see Appendix 2 for details on timing and 

location of survey effort). Outer line represents approximate 

boundary of survey area and U.S. EEZ. 

the Hawaiian Islands are shown in Figure 1 

 Fishery interactions with pantropical spotted dolphins demonstrate that this species also occurs in U.S. EEZ 

waters around Palmyra Island, but it is not known whether these animals are part of the Hawaiian stock or a separate 

stock of pantropical spotted dolphins. Based on patterns of movement and population structure observed in other 

island-associated cetaceans (Norris and Dohl 1980; Norris et al.1994; Baird et al. 2008a, 2008b, 2009, Chivers et al 

2007, McSweeney et al. 2007, 2009), the animals around Palmyra Island may represent a separate stock. Efforts are 

currently underway to obtain additional tissue samples of pantropical spotted dolphins for further studies of 

population structure in the North Pacific Ocean. Analysis of 177 genetic samples collected throughout the main 

Hawaiian Islands suggests that spotted dolphins are not mating randomly across the main Hawaiian Islands, and 

there is clustering of genotypes, into Hawaii, Oahu, and 4-islands area regions, suggesting that individual islandassociated stocks may exist (Courbis et al., in prep.). Hawaiian spotted dolphins may be split into separate islandassociated stocks pending the outcome of on-going genetic analysis of these samples. For the Marine Mammal 

Protection Act (MMPA) stock assessment reports, there is a single Pacific management stock including animals 

found both within the Hawaiian Islands EEZ and in adjacent international waters. Because data on abundance, 

distribution, and human-caused impacts are largely lacking for international waters, the status of this stock is 

evaluated based on data from U.S. EEZ waters of the Hawaiian Islands (NMFS 2005). Spotted dolphins involved in 

eastern tropical Pacific tuna purse-seine fisheries are managed separately under the MMPA. Information on 

pantropical spotted dolphins around Palmyra Island will provisionally be included with this stock assessment report, 

recognizing that separate stock status may be warranted for these animals in the future. Estimates of abundance, 

potential biological removals, and status determinations will be presented separately for U.S. EEZ waters of the 

Hawaiian Islands and Palmyra Island. 

 

POPULATION SIZE

 Population estimates are available for Japanese waters (Miyashita 1993) and the eastern tropical Pacific 

217
(Wade and Gerrodette 1993). A 2002 shipboard line-transect survey of the entire Hawaiian Islands EEZ resulted in 

an abundance estimate of 8,978 (CV=0.48) pantropical spotted dolphins (Barlow 2006). This is currently the best 

available abundance estimate for pantropical spotted dolphins within the Hawaiian Islands EEZ. 

 No abundance estimates are currently available for pantropical spotted dolphins in U.S. EEZ waters of 

Palmyra Island; however, density estimates for pantropical spotted dolphins in other Pacific regions can provide a 

range of likely abundance estimates in this unsurveyed region. Published estimates of pantropical spotted dolphins 

(animals per km2

) in the Pacific are: 0.0040 (CV=0.48) for the U.S. EEZ of the Hawaiian Islands (Barlow 2006); 

0.0407 (CV=0.45) for nearshore waters surrounding the main Hawaiian Islands (Mobley et al. 2000), 0.0678 

(CV=0.15) and 0.1064 (CV=0.09) for the eastern tropical Pacific Ocean (Wade and Gerrodette 1993; Ferguson and 

Barlow 2003), and 0.0731 (CV=0.33) for the eastern tropical Pacific Ocean west of 120°W and north of 5°N 

(Ferguson and Barlow 2003). Applying the lowest and highest of these density estimates to U.S. EEZ waters 

surrounding Palmyra Island (area size = 352,821 km2

) yields a range of plausible abundance estimates of 1,414 - 

37,525 pantropical spotted dolphins. 

Minimum Population Estimate

 The log-normal 20th percentile of the 2002 abundance estimate for the Hawaiian Islands EEZ (Barlow 

2006) is 6,701 pantropical spotted dolphins. No minimum population estimate is currently available for waters 

surrounding Palmyra Island, but the pantropical spotted dolphin density estimates from other Pacific regions 

(Barlow 2006, Mobley et al. 2000, Wade and Gerrodette 1993, Ferguson and Barlow 2003; see above) can provide a 

range of likely values. The lognormal 20th percentiles of plausible abundance estimates for the Palmyra Island EEZ, 

based on the densities observed elsewhere, range from 964 - 34,792 pantropical spotted dolphins. 

Current Population Trend

 No data are available on current population trend. 

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

 No data are available on current or maximum net productivity rate. 

POTENTIAL BIOLOGICAL 

REMOVAL

The potential biological removal 

(PBR) level for the Hawaiian pantropical 

spotted dolphin stock is calculated as the 

minimum population size within the U.S. 

EEZ of the Hawaiian Islands (6,701) 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 61 pantropical spotted 

dolphins per year. No separate PBR can 

presently be calculated for pantropical 

spotted dolphins within the Palmyra Island 

EEZ, but based on the range of plausible 

minimum abundance estimates (964 - 

34,792), a recovery factor of 0.50 (for a 

species of unknown status with no 

documented mortality and serious injury 

within the Palmyra Islands EEZ during the 

past five years; Wade and Angliss 1997), 

and the default growth rate (1⁄2 of 4%), the 

PBR would likely fall between 9.6 and 347 

pantropical spotted dolphins per year. 

Figure 2. Locations of observed spotted dolphin takes (filled 

diamonds) in the Hawaii deep-set longline fishery, 2004-2008. Solid 

lines represent the U.S. EEZ. Set locations in this fishery are 

summarized in Appendix 1. 

218
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 cetaceans (Perrin et al. 1994a). Interactions with cetaceans 

have been reported for all Hawaiian pelagic fisheries (Nitta and Henderson 1993). There are currently two distinct 

longline fisheries based in Hawaii: a deep-set longline (DSLL) fishery that targets primarily tunas, and a shallow-set 

longline fishery (SSLL) that targets swordfish. Both fisheries operate within U.S. waters and on the high seas. 

Between 2004 and 2008, no pantropical spotted dolphins were observed hooked or entangled in the SSLL fishery 

(100% observer coverage), and one pantropical spotted dolphin was observed incidentally killed in international 

waters in the DSLL fishery (20-28% observer coverage) (Forney 2009, McCracken 2009) (Figure 2). Average 5-yr 

estimates of annual mortality and serious injury for 2004-2008 are 0.5 (CV=0.7) spotted dolphins outside of U.S. 

EEZs, and none within the Hawaiian Islands EEZ (Table 1, McCracken & Forney 2010). 

Commercial and recreational troll fisherman have been observed “fishing” dolphins off the island of Hawaii, 

including spotted dolphins, in order to catch tuna associated with the animals (Courbis et al. 2009, Rizzuto, 2007, 

Shallenberger 1981). Anecdotal reports from fisherman indicate that spotted dolphins are occasionally hooked 

(Rizzuto 1997) and photographs of dolphins suggest animals may be injured by both lines and propeller strikes 

(Barid unpublished data). Interaction rates between dolphins and the NWHI bottomfish fishery have been estimated 

based on studies conducted in 1990-1993, indicating that an average of 2.67 dolphin interactions, most likely 

involving bottlenose and rough-toothed dolphins, occurred for every 1000 fish brought on board (Kobayashi and 

Kawamoto 1995). Fishermen claim interactions with dolphins that steal bait and catch are increasing. It is not 

known whether these interactions result in serious injury or mortality of dolphins, nor whether pantropical spotted 

dolphins are involved. 

STATUS OF STOCK

The status of pantropical spotted dolphins in Hawaiian waters relative to OSP is unknown, and there are insufficient 

data to evaluate trends in abundance. No habitat issues are known to be of concern for this species. It is not listed as 

“threatened” or “endangered” under the Endangered Species Act (1973), nor as “depleted” under the MMPA. Given 

the absence of recent fishery-related mortality or serious injuries within U.S. EEZs, the Hawaiian stock of spotted 

dolphins is not considered strategic under the 1994 amendments to the MMPA, and the total fishery mortality and 

serious injury can be considered to be insignificant and approaching zero. However, the potential effect of injuries 

sustained by pantropical spotted dolphins in U.S. pelagic longline fisheries in international waters is not known, 

because no abundance estimates or international bycatch estimates are available. 

Table 1. Summary of available information on incidental mortality and serious injury of pantropical spotted 

dolphins (Hawaiian stock) in commercial fisheries, within and outside of the U.S. EEZs (McCracken & Forney 

2010). Mean annual takes are based on 2004-2008 data unless otherwise indicated. 

Observed and estimated mortality and serious injury of pantropical spotted dolphins, 

by EEZ region 

Outside of U.S. EEZs Hawaiian Islands EEZ 

Fishery Name Year Data 

Type 

Percent 

Observer 

Coverage 

Obs Estimated 

(CV) 

Mean 

Annual 

Takes 

(CV) 

Obs Estimated 

(CV) 

Mean 

Annual 

Takes 

(CV) 

Hawaii-based 

deep-set longline 

fishery 

2004 

2005 

2006 

2007 

2008 

observer 

data 

25% 

28% 

22% 

20% 

22% 

0 

0 

0 

0 

1 

0 (-) 

0 (-) 

0 (-) 

0 (-) 

2 (0.3) 

0.5 (0.7) 

0 

0 

0 

0 

0 

0 (-) 

0 (-) 

0 (-) 

0 (-) 

0 (-) 

0 (-) 

Hawaii-based 

shallow-set 

longline fishery 

2004 

2005 

2006 

2007 

2008 

observer 

data 

100% 

100% 

100% 

100% 

100% 

0 

0 

0 

0 

0 

Same as 

observed 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

Same as 

observed 0 

Minimum total annual takes within U.S. EEZ waters 0 (-) 

219
REFERENCES

Baird, R. W., Ligon, A. D., Hooker, S. K., and A. M. Gorgone. 2001. Subsurface and nighttime behaviour of 

pantropical spotted dolphins in Hawai’i. Can. J. Zool. 79:988-996. 

Baird, R.W., A.M. Gorgone, D.J. McSweeney, D.L. Webster, D.R. Salden, M.H. Deakos, A.D. Ligon, G.S. Schorr, 

J. Barlow and S.D. Mahaffy. 2008a. False killer whales (Pseudorca crassidens) around the main Hawaiian 

Islands: long-term site fidelity, inter-island movements, and association patterns. Marine Mammal Science 

24:591-612. 

Baird, R.W., D.L. Webster, S.D. Mahaffy, D.J. McSweeney, G.S. Schorr and A.D. Ligon. 2008b. Site fidelity and 

association patterns in a deep-water dolphin: rough-toothed dolphins (Steno bredanensis) in the Hawaiian 

Archipelago. Marine Mammal Science 24:535-553. 

Baird, R.W., A.M. Gorgone, D.J. McSweeney, A.D. Ligon, M.H. Deakos, D.L. Webster, G.S. Schorr, K.K. Martien, 

D.R. Salden, and S.D. Mahaffy. 2009. Population structure of island-associated dolphins: evidence from 

photo-identification of common bottlenose dolphins (Tursiops truncatus) in the main Hawaiian Islands. 

Marine Mammal Science 25:251-274. 

Barlow, J. 2006. Cetacean abundance in Hawaiian waters estimated from a summer/fall survey in 2002. Marine 

Mammal Science 22(2): 446-464. 

Courbis, S, R.W. Baird, F. Cipriano, D. Duffield. In prep. Population Structure of Pantropical Spotted Dolphins 

Near the Main Hawaiian Islands: Evidence of Multiple Genetic Stocks for Management. 

Chivers, S. J., R. W. Baird, D. J. McSweeney, D. L. Webster, N. M. Hedrick, and J. C. Salinas. 2007. Genetic 

variation and evidence for population structure in eastern North Pacific false killer whales (Pseudorca 

crassidens). Can. J. Zool. 85: 783-794. 

Dizon, A. E., W. F. Perrin, and P. A. Akin. 1994. Stocks of dolphins (Stenella spp. and Delphinus delphis) in the 

eastern tropical Pacific: a phylogeographic classification. NOAA Tech. Rep. NMFS 119, 20 pp. 

Ferguson, M. C. and J. Barlow. 2003. Addendum: Spatial distribution and density of cetaceans in the eastern 

tropical Pacific Ocean based on summer/fall research vessel surveys in 1986-96. Administrative Report LJ01-04 (addendum), Southwest Fisheries Science Center, National Marine Fisheries Service, 8604 La Jolla 

Shores Drive, La Jolla, CA 92037. 

Forney, K.A. 2009. Serious injury determinations for cetaceans caught in Hawaii longline fisheries during 1994-

2008. Draft document PSRG-2009-09 presented to the Pacific Scientific Review Group, November 3-5, 

2009, Del Mar, CA. 

Kobayashi, D. R. and K. E. Kawamoto. 1995. Evaluation of shark, dolphin, and monk seal interactions with 

Northwestern Hawaiian Island bottomfishing activity: a comparison of two time periods and an estimate of 

economic impacts. Fisheries Research 23: 11-22. 

Maldini, D., L. Mazzuca, and S. Atkinson. 2005. Odontocete stranding patterns in the Main Hawaiian Islands 

(1937-2002): How do they compare with live animal surveys? Pacific Science 59(1):55-67. 

McCracken M. and K.A. Forney 2010. Preliminary assessment of incidental interactions with marine mammals in 

the Hawaii longline deep and shallow set fisheries. NMFS, Pacific Islands Fisheries Science Center 

Working Paper WP-10-001. 27p. 

McSweeney, D.J., R.W. Baird and S.D. Mahaffy. 2007. Site fidelity, associations and movements of Cuvier’s 

(Ziphius cavirostris) and Blainville’s (Mesoplodon densirostris) beaked whales off the island of Hawai‘i. 

Marine Mammal Science 23:666-687. 

McSweeney, D.J., R.W. Baird, S.D.Mahaffy, D.L. Webster, and G.S. Schorr. 2009. Site fidelity and association 

patterns of a rare species: Pygmy killer whales (Feresa attenuata) in the main Hawaiian Islands. Marine 

Mammal Science 25(4): 557-572. 

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. 

Norris, K. S., B. Würsig, R. S. Wells, and M. Würsig. 1994. The Hawaiian Spinner Dolphin. University of 

California Press, 408 pp. 

220
Norris, K. S. and T. P. Dohl. 1980. Behavior of the Hawaiian spinner dolphin, Stenella longirostris. Fish. Bull.

77:821-849. 

Perrin, W. F. 1975. Variation of spotted and spinner porpoise (genus Stenella) in the eastern tropical Pacific and 

Hawaii. Bull. Scripps Inst. Oceanogr. 21, 206 pp. 

Perrin, W.F., 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. 

Perrin, W.F., B. Würsig and J.G.M. Thewissen. 2009. Encyclopedia of Marine Mammals. Second Edition. 

Academic Press, Amsterdam. 

Rizzuto, J. 2007. Big fish await HIBT teams. West Hawaii Today 39(218):1B, 4B-5B. 

Shallenberger, E.W. 1981. The status of Hawaiian cetaceans. Final report to U.S. Marine Mammal Commission. 

MMC-77/23, 79pp. 

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

Workshop April 3-5, 1996, Seattle, Washington. U. S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR12. 93 pp. 

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

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

221
Revised 01/15/2011

SPINNER DOLPHIN (Stenella longirostris longirostris): 

Hawaiian Islands Stock Complex- Hawaii Island, Oahu/4-islands, 

Kauai/Niihau, Pearl & Hermes Reef, Midway Atoll/Kure, Hawaii Pelagic 

STOCK DEFINITION AND GEOGRAPHIC RANGE

 Six morphotypes within four subspecies of spinner dolphins have been described worldwide in tropical and 

warm-temperate waters (Perrin et al. 2009). The Gray’s (or pantropical) spinner dolphin (Stenella longirostris 

longirostris) is the most widely distributed subspecies and is found in the Atlantic, Indian, central and western 

Pacific Oceans (Perrin et al. 1991). Within the central and western Pacific, spinner dolphins are island-associated 

and use shallow protected bays to rest and socialize during the day then move offshore at night to feed (Norris and 

Dohl 1980; Norris et al. 1994). They are common and abundant throughout the entire Hawaiian archipelago 

(Shallenberger 1981; Norris and Dohl 1980; Norris et al. 1994), and 26 strandings have been reported (Maldini 

2005). Recent sighting locations from a 2002 shipboard survey of waters within the U.S. Exclusive Economic Zone 

(EEZ) of the main Hawaiian Islands (Barlow 2006) are shown in Figure 1. 

Hawaiian spinner dolphins belong to a stock that is separate from those involved in the tuna purse-seine 

fishery in the eastern tropical Pacific (Perrin 1975; Dizon et al. 1994). The Hawaiian form is referable to the 

subspecies S. longirostris longirostris, which occurs pantropically (Perrin 1990). Recent studies on the genetic 

structure of spinner dolphins in the Hawaiian archipelago found significant genetic distinctions between spinner 

dolphins sampled at five different islands/atolls- Hawaii, Oahu/4-islands, Kauai/Niihau, Pearl and Hermes Reef, 

Midway Atoll/Kure (Andrews 2009, Andrews et al. 2010) and these distinctions are supported by available photo-ID 

and animal movement data (Karczmarski 2005). In particular, mitochondrial and microsatellite DNA data from 

individuals sampled along the Kona Coast of the Island of Hawaii show marked distinctions from individuals 

sampled at all other Hawaiian Islands including Maui (Andrews 2009, Andrews et al. 2010). Hill et al. (2009) 

suggest an offshore boundary for each island-associated stock at 10nmi from shore based on anectodal accounts of 

spinner dolphin distribution. This offshore boundary is likely to be revised as new information on the movements of 

island-associated spinner dolphins becomes available. For the Marine Mammal Protection Act (MMPA) stock 

assessment reports, there are six stocks found within the U.S. EEZ of the Hawaiian Islands 1) Hawaii Island, 2) 

Oahu/4-islands, 3) Kauai/Niihau, 4) Pearl & Hermes Reef, 5) Kure/Midway, and 6) Hawaii Pelagic, including 

animals found both within the Hawaiian Islands EEZ and in adjacent international waters. Because data on 

abundance, distribution, and human-caused impacts are largely lacking for international waters, the status of all 

stocks combined is evaluated based on 

data from U.S. EEZ waters of the 

Hawaiian Islands (NMFS 2005). 

Spinner dolphins involved in eastern 

tropical Pacific tuna purse-seine fisheries 

are managed separately under the 

MMPA. 

POPULATION SIZE

 No data on current population 

sizes for any of the Hawaiian Island 

stocks are available. A 2002 shipboard 

line-transect survey of the entire 

Hawaiian Islands EEZ resulted in an 

abundance estimate of 3,351 (CV=0.74) 

spinner dolphins (Barlow 2006); 

however, this estimated assumed a single 

Hawaiian Islands stock. Over the past 

few decades abundance estimates have 

been produced from several studies 

along the Kona coast of the Island 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) photo-identified 677 individual spinner dolphins in the same area from 1989 to 1992. Using the 

Figure 2. Spinner dolphin stock boundaries. Animals outside of the 

defined island areas represent the pelagic stock range 

222
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. In the Northwestern Hawaiian Islands, a multi-year photo-identification study 

at Midway Atoll resulted in a population estimate of 260 spinner dolphins based on 139 identified individuals 

(Karczmarski et al 1998). As part of the Marine Mammal Research Program of the Acoustic Thermometry of Ocean 

Climate (ATOC) study, a total of twelve aerial surveys were conducted within about 25 nmi of the main Hawaiian 

Islands in 1993, 1995 and 1998. An abundance estimate of 3,184 (CV=0.37) spinner dolphins was calculated from 

the combined survey data (Mobley et al. 2000). These data may be used to produce abundance estimates for each 

new stock area; however, the data are now more than 8 years old and abundance estimates from these data would be 

out of date. 

Minimum Population Estimate

 Abundance data for each new stock is not yet available, but estimates will be incorporated into this report 

as estimates based on photo-identification data become available. The log-normal 20th percentile of the 2002 

abundance estimate for all stocks combined (Barlow 2006) is 1,920 spinner dolphins. 

Current Population Trend

 No data on current population trend are available. 

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES 

No information on current or maximum net productivity rate is currently available for any stock in the 

Hawaiian Islands stock complex. 

 

POTENTIAL BIOLOGICAL REMOVAL

 The potential biological removal (PBR) level for the combined Hawaiian Islands stock complex is 

calculated as the minimum population size within the U.S EEZ of the Hawaiian Islands (1,920) times one half the 

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

status with no estimated fishery mortality or serious injury within the U.S. EEZ of the Hawaiian Islands; Wade and 

Angliss 1997), resulting in a total PBR of 19 spinner dolphins from all stocks 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 cetaceans (Perrin et al. 1994). In Hawaii, some 

entanglements of spinner dolphins have been observed (Nitta and Henderson 1993; NMFS/PIR, unpublished data), 

but no estimate of annual human-caused mortality and serious injury is available, because the nearshore gillnet 

fisheries are not observed or monitored. 

 Interactions with cetaceans have been reported for all Hawaiian pelagic fisheries (Nitta and Henderson 

1993). There are currently two distinct longline fisheries based in Hawaii: a deep-set longline (DSLL) fishery that 

targets primarily tunas, and a shallow-set longline fishery (SSLL) that targets swordfish. Both fisheries operate 

within U.S. waters and on the high seas. Between 2004 and 2008, no spinner dolphins were observed hooked or 

entangled in the SSLL fishery (100% observer coverage) or the DSLL fishery (20-28% observer coverage) (Forney 

2009, McCracken & Forney 2010). 

 Interaction rates between dolphins and the NWHI bottomfish fishery have been estimated based on studies 

conducted in 1990-1993, indicating that an average of 2.67 dolphin interactions, most likely involving bottlenose 

and rough-toothed dolphins, occurred for every 1000 fish brought on board (Kobayashi and Kawamoto 1995). 

Fishermen claim interactions with dolphins that steal bait and catch are increasing. It is not known whether these 

interactions result in serious injury or mortality of dolphins, nor whether spinner dolphins are involved. 

STATUS OF STOCK 

The status of spinner dolphins in Hawaiian waters relative to OSP is unknown, and there are insufficient 

data to evaluate trends in abundance for any stock. 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 

(Danil et al. 2005, Courbis and Timmel 2009). Spinner dolphins are not listed as “threatened” or “endangered” 

under the Endangered Species Act (1973), nor as “depleted” under the MMPA. The Hawaiian stocks of spinner 

223
dolphins are not considered a strategic stock under the 1994 amendments to the MMPA, because the estimated rate 

of mortality and serious injury within the Hawaiian Islands EEZ is zero. However, there is no systematic 

monitoring of nearshore fisheries that may take animals from both island-assocated and pelagic regions of the stock 

complex. Insufficient information is available to determine whether the total fishery mortality and serious injury for 

any Hawaiian spinner dolphin stock is insignificant and approaching zero mortality and serious injury rate.

REFERENCES 

Andrews, K.R. 2009. Barriers to gene flow in the spinner dolphin (Stenella longirostris). PhD dissertation, 

University of Hawaii, Manoa. 99 pp. 

Andrews, K.R., Karczmarski, L., Au, W.W.L., Rickards, S.H., Vanderlip, C.A., Bowen, B.W., Grau, E.G., and 

Toonen, R.J. 2010. Rolling stones and stable homes: social structure, habitat diversity and population 

genetics of the Hawaiian spinner dolphin (Stenella longirostris). Molecular Ecology 19:732-748. 

Barlow, J. 2006. Cetacean abundance in Hawaiian waters estimated from a summer/fall survey in 2002. Marine 

Mammal Science 22(2): 446-464. 

Courbis, S. and G. Timmel. 2009. Effects of vessels and swimmers on behavior of Hawaiian spinner dolphins 

(Stenella longirostris) in Kealake’akua, Honaunau, and Kauhako bays, Hawai’i. Marine Mammal Science 

25(2):430-440. 

Danil, K., D. Maldini, and K. Marten. 2005. Patterns of use of Maku’a Beach, O’ahu, Hawai’i, by spinner dolphins 

(Stenella longirostris) and potential effects of swimmers on their behavior. Aquatic Mammals 31(4):403-

412. 

Dizon, A. E., W. F. Perrin, and P. A. Akin. 1994. Stocks of dolphins (Stenella spp. and Delphinus delphis) in the 

eastern tropical Pacific: a phylogeographic classification. NOAA Tech. Rep. NMFS 119, 20 pp. 

Forney, K.A. 2009. Serious injury determinations for cetaceans caught in Hawaii longline fisheries during 1994-

2008. Draft document PSRG-2009-09 presented to the Pacific Scientific Review Group, November 3-5, 

2009, Del Mar, CA. 

Hill, M.C., E.M. Oleson, K.R. Andrews. 2009. A proposal to introduce new stock boundaries for Hawaiian spinner 

dolphins. PSRG-2009-12. 

Karczmarski, L., B. Würsig and B. Winning. 1998. Socio-ecology and population biology of spinner dolphins 

Stenella longirostris in Midway Atoll, Northwest Hawaiian Chain, Central Pacific. Unpublished report to 

U.S. Fish and Wildlife Service and National Marine Fisheries Service. 41 pp. 

Karczmarski, L., B. Wursig, G. Gailey, K.W. Larson, and C. Vanderlip. 2005. Spinner dolphins in a remote 

Hawaiian atoll: Social grouping and population structure. Behavioral Ecology 16(4):675-685. 

Kobayashi, D. R. and K. E. Kawamoto. 1995. Evaluation of shark, dolphin, and monk seal interactions with 

Northwestern Hawaiian Island bottomfishing activity: a comparison of two time periods and an estimate of 

economic impacts. Fisheries Research 23: 11-22. 

Maldini, D., L. Mazzuca, and S. Atkinson. 2005. Odontocete stranding patterns in the Main Hawaiian Islands 

(1937-2002): How do they compare with live animal surveys? Pacific Science 59(1):55-67. 

McCracken M., and K.A. Forney. 2010. Preliminary assessment of incidental interactions with marine mammals in 

the Hawaii longline deep and shallow set fisheries. NMFS, Pacific Islands Fisheries Science Center 

Working Paper WP-10-001. 27p. 

Mobley, J. R. , Jr, S. S. Spitz, K. A. Forney, R. A. Grotefendt, and P. H. Forestall. 2000. Distribution and 

abundance of odontocete species in Hawaiian waters: preliminary results of 1993-98 aerial surveys Admin. 

Rep. LJ-00-14C. Southwest Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La 

Jolla, CA 92038. 26 pp. 

Nitta, E. and J. R. Henderson. 1993. A review of interactions between Hawaii's fisheries and protected species. 

Mar. Fish. Rev. 55(2):83-92. 

Norris, K. S., B. Würsig, R. S. Wells, and M. Würsig. 1994. The Hawaiian Spinner Dolphin. University of 

California Press, 408 pp. 

Norris, K. S. and T. P. Dohl. 1980. Behavior of the Hawaiian spinner dolphin, Stenella longirostris. Fish. Bull.

77:821-849. 

NMFS, Pacific Islands Region, Observer Program, 1602 Kapiolani Blvd, Suite 1110, Honolulu, HI 96814. 

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. 

224
Perrin, W. F. 1990. Subspecies of Stenella longirostris (Mammalia: Cetacea: Delphinidae). Proc. Biol. Soc. Wash. 

103:453-463. 

Perrin, W.F., P.A. Akin, and J.V. Kashiwada. 1991. Geographic variation in external morphology of the spinner 

dolphin Stenella longirostris in the Eastern Pacific and implications for conservation. Fishery Bulletin 

89:411-428 

Perrin, W.F., G. P. Donovan and J. Barlow. 1994. Gillnets and Cetaceans. Rep. Int. Whal. Commn., Special Issue 

15, 629 pp. 

Perrin, W.F., B. Würsig and J.G.M. Thewissen. 2009. Encyclopedia of Marine Mammals. Second Edition. 

Academic Press, Amsterdam. 

Shallenberger, E.W. 1981. The status of Hawaiian cetaceans. Final report to U.S. Marine Mammal Commission. 

MMC-77/23, 79pp. 

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

Workshop April 3-5, 1996, Seattle, Washington. U. S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR12. 93 pp. 

225
Revised 01/15/2011 

SPINNER DOLPHIN (Stenella longirostris longirostris): 

American Samoa Stock 

STOCK DEFINITION AND 

GEOGRAPHIC RANGE 

Gray’s spinner dolphins (Stenella 

longirostris longirostris) are the most widely 

distributed subspecies of spinner dolphins 

and are found in tropical and subtropical 

waters of the Atlantic, Indian, central and 

western Pacific Oceans (Perrin et al. 1991, 

Norris et al. 1994, Oremus et al. 2007, 

Johnston et al. 2008). Spinner dolphins are 

considered common in American Samoa 

(Reeves et al. 1999). During small-boat 

surveys from 2003 to 2006 in the waters 

surrounding the island of Tutuila, the spinner 

dolphin was the most frequently encountered 

species (i.e., 34 of 52 sightings) and was 

found in waters with a mean depth of 44m 

(Johnston et al. 2008). Photo-identification 

data collected during the surveys indicate the 

presence of a resident population of spinner 

dolphins in the waters surrounding Tutuila 

(Johnston et al. 2008). Approximately 1/3 of 

the individuals within the photo-id catalog 

were sighted in multiple years (Johnston et 

al. 2008). In addition, some of these 

individuals demonstrated strong site fidelity 

and were encountered within only a few 

kilometers from one year to the next 

(Johnston et al. 2008). During a shipboard 

survey in 2006 spinner dolphins were also 

encountered just south of the island of Ta‘u, 

American Samoa (Johnston et al. 2008). 

Figure 1. Spinner dolphin sightings from visual sighting surveys, 

2003-2006 (Johnston et al 2008). 

Genetic analyses of biopsy samples 

collected during the 2003-2006 small boat surveys around Tutuila indicate that spinner dolphins in American Samoa 

are distinct from those of the Hawaiian Archipelago. Pairwise F-statistical analyses revealed significant (p<0.001) 

genetic distinction, at both mtDNA and microsatellite loci, between spinner dolphins sampled in American Samoa 

and those sampled in the Hawaiian Islands (Johnston et al. 2008, Andrews 2009). For the Marine Mammal 

Protection Act (MMPA) stock assessment reports, there are eight Pacific management stocks, six of these extend 

from the Hawaiian archipelago to 10 nmi offshore: 1) Kure/Midway, 2) Pearl and Hermes Reef, 3) French Frigate 

Shoals, 4) Kauai/Niihau, 5) Oahu/4-Islands, and 6) Hawaii Island, The Hawaii Pelagic Stock, which includes 

animals within the U.S. EEZ of the Hawaiian Islands, but more than 10 nmi from the shore where insular 

populations exist, and 8) the American Samoa Stock, which include animals inhabiting the EEZ waters around 

American Samoa (this report). Spinner dolphins involved in eastern tropical Pacific tuna purse-seine fisheries are 

managed separately under the MMPA. 

POPULATION SIZE

No abundance estimates are currently available for spinner dolphins in U.S. EEZ waters of American 

Samoa; however, density estimates for spinner dolphins in other tropical Pacific regions can provide a range of 

likely abundance estimates in this unsurveyed region. Published estimates of spinner dolphins (animals per km2

) in 

the Pacific are: 0.0014 (CV=0.74) for the U.S. EEZ of the Hawaiian Islands (Barlow 2006); 0.0443 (CV=0.37) for 

nearshore waters surrounding the main Hawaiian Islands (Mobley et al. 2000), 0.0532 (CV=0.19) and 0.0473 

226
(CV=0.15) for the eastern tropical Pacific Ocean (Wade and Gerrodette 1993; Ferguson and Barlow 2003), and 

0.1280 (CV=0.27) for eastern tropical Pacific waters west of 120o

W and north or south of 10o, a region with similar 

oceanographic conditions to those around American Samoa. Applying the lowest and highest of these density 

estimates to U.S. EEZ waters surrounding American Samoa (area size = 404,578 km2

) yields a range of plausible 

abundance estimates of 553 – 51,773 spinner dolphins. 

Minimum Population Estimate 

No minimum population estimate is currently available for waters surrounding American Samoa, but the spinner 

dolphin density estimates from other tropical Pacific regions (Barlow 2003, Mobley et al. 2000, Wade and 

Gerrodette 1993, Ferguson and Barlow 2003, see above) can provide a range of likely values. The lognormal 20th

percentiles of plausible abundance estimates for the American Samoa EEZ, based on the densities observed 

elsewhere, range from 317 – 41,483 spinner dolphins. 

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 American Samoan waters. 

POTENTIAL BIOLOGICAL REMOVAL

No PBR can presently be calculated for spinner dolphins within the American Samoa EEZ, but based on the range 

of plausible minimum abundance estimates (317 – 41,483), a recovery factor of 0.50 (for a species of unknown 

status with no fishery mortality and serious injury within the American Samoa EEZ; Wade and Angliss 1997), and 

the default growth rate (1⁄2 of 4%), the PBR would likely fall between 3.2 and 415 spinner dolphins per year. 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY 

Fishery Information

Information on fishery-related mortality of cetaceans in American Samoan waters is limited, but the gear 

types used in American Samoa’s 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). The primary 

fishery in American Samoa is the commercial pelagic longline fishery that targets tunas, which was introduced in 

1995 (Levine and Allen 2009). In 2008, there were 28 federally permitted vessels within the longline fishery in 

American Samoa (Levine and Allen 2009). The fishery has been monitored since March 2006 under a mandatory 

observer program, which records all interactions with protected species (Pacific Islands Regional Office 2009). No 

interactions with spinner dolphins have been recorded. Prior to 1995, bottomfishing and trolling were the primary 

fisheries in American Samoa but became less prominent after longlining was introduced (Levine and Allen 2009). 

Nearshore subsistence fisheries include spear fishing, rod and reel, collecting, gill netting, and throw netting (Craig 

1993, Levine and Allen 2009). Information on fishery-related mortality of cetaceans in the nearshore fisheries is 

unknown, but the gear types used in American Samoan 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. Although boat-based nearshore fisheries have been randomly monitored since 1991, by the American 

Samoa Department of Marine and Wildlife Sources (DMWR), no estimates of annual human-caused mortality and 

serious injury of cetaceans are available. 

STATUS OF STOCK

 The status of spinner dolphins in American Samoan waters relative to OSP is unknown, and there are 

insufficient data to evaluate trends in abundance. No habitat issues are known for spinner dolphins in American 

Samoa. Spinner dolphins are not listed as “threatened” or “endangered” under the Endangered Species Act (1973), 

nor as “depleted” under the MMPA. The American Samoan stock of spinner dolphins is not considered a strategic 

stock under the 1994 amendments to the MMPA because the estimated rate of mortality and serious injury within 

the American Samoa EEZ is zero. 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. 

227
REFERENCES 

Andrews, K.R. 2009. Barriers to gene flow in the spinner dolphin (Stenella longirostris). PhD dissertation, 

University of Hawaii, Manoa. 99 pp. 

Craig, P., B. Ponwith, F. Aitaoto, and D. Hamm. 1993. The commercial, subsistence, and recreational fisheries of 

American Samoa –Fisheries of Hawaii and U.S. – associated pacific Islands. Marine Fisheries Review, 

Spring. 

Fisheries Monitoring and Socioeconomics Division, Pacific Islands Fisheries Science Center. 2008. PIFSC Report 

on the American Samoa Longline Fishery, January-March 2008. Pacific Islands Fisheries Science Center, 

PIFSC Data Report, DR-08-005, 12 p. 

Johnston, D.W., J. Robbins, M.E. Chapla, D.K. Mattila, and K.R. Andrews. 2008. Diversity, habitat associations, 

and stock structure of odontocete cetaceans in the waters of American Samoa, 2003-2006. Journal of 

Cetacean Research and Management 10(1):59-66. 

Levine, A., and S. Allen. 2009. American Samoa as a fishing community. U.S. Dep. Commer., NOAA Tech. 

Memo., NOAA-TM-NMFS-PIFSC-19, 74 p. 

Norris, K.S., B. Wursig, R.S. Wells, and M. Wursig. 1994. The Hawaiian Spinner Dolphin. University of 

California Press, Berkley. 408pp. 

Oremus, M., M.M. Poole, D. Steel, and C.S. Baker. 2007. Isolation and interchange among insular spinner dolphin 

communities in the South Pacific revealed by individual identification and genetic diversity. Marine 

Ecological Progress Series 336: 275-89. 

Pacific Islands Regional Office. 2009. Pacific Islands Regional Observer Program American Samoa longline annual 

status report, January 1, 2008 – December 31, 2008. 

http://www.fpir.noaa.gov/Library/PUBDOCs/ObserverQtrAnnRpts/obs_as_ll_rprts/2008/obs_as_ll_annual

_2008.pdf

Perrin, W.F. and J.W. Gilpatrick. 1994. Spinner dolphin Stenella longirostris. Pages 99-128 in S. H. Ridgeway and 

R. Harrison, editors. Handbook of Marine Mammals. Academic Press, London. 

Reeves, R., S. Leatherwood, G.S. Stone, and L.G. Eldredge. 1999. Marine mammals in the area served by the South 

Pacific Regional Environment Programme (SPREP). South Pacific Regional Environment Programme, 

Apia, Samoa. 48pp. 

228
Revised 01/15/2011

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. 2009). 

They have been documented in the 

Hawaiian Islands from 20 strandings (Nitta 

1991, Maldini et al. 2005), although 

sightings have historically been infrequent 

(Shallenberger 1981, Mobley et al. 2000). 

A comprehensive shipboard survey of the 

Hawaiian Exclusive Economic Zone 

(EEZ), resulted in 15 sightings of striped 

dolphins (Figure 1; Barlow 2006). 

 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 tropical 

Pacific all striped dolphins are 

provisionally considered to belong to a 

single stock (Dizon et al. 1994). For the 

Marine Mammal Protection Act (MMPA) 

stock assessment reports, striped dolphins 

within the Pacific U.S. EEZ are divided 

into two discrete, non-contiguous areas: 1) 

waters off California, Oregon and 

Washington, and 2) waters around Hawaii (this report), including animals found both within the Hawaiian Islands 

EEZ and in adjacent international waters. Because data on abundance, distribution, and human-caused impacts are 

largely lacking for international waters, the status of all stocks combined is evaluated based on data from U.S. EEZ 

waters of the Hawaiian Islands (NMFS 2005). Striped dolphins involved in eastern tropical Pacific tuna purse-seine 

fisheries are managed separately under the MMPA. 

W180 W175 W170 W165 W160 W155 W150

N10

N15

N20

N25

N30

N35

Figure 1. Striped dolphin sighting locations during the 2002 

shipboard survey of U.S. EEZ waters surrounding the Hawaiian 

Islands (Barlow 2006; see Appendix 2 for details on timing and 

location of survey effort). Outer line represents approximate 

boundary of survey area and U.S. EEZ. 

POPULATION SIZE

 Population estimates are available for Japanese waters (Miyashita 1993) and the eastern tropical Pacific 

(Wade and Gerrodette 1993), but it is not known whether any of these animals are part of the same population that 

occurs around the Hawaiian Islands. A 2002 shipboard line-transect survey of the entire Hawaiian Islands EEZ 

resulted in an abundance estimate of 13,143 (CV=0.46) striped dolphins (Barlow 2006). This is currently the best 

available abundance estimate for this stock. 

Minimum Population Estimate

 The log-normal 20th percentile of the 2002 abundance estimate (Barlow 2006) is 9,088 striped dolphins. 

Current Population Trend 

 No data are available on current population trend. 

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

 No data are available on current or maximum net productivity rate. 

POTENTIAL BIOLOGICAL REMOVAL

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

within the U.S. EEZ of the Hawaiian Islands (9,088) times one half the default maximum net growth rate for 

229
cetaceans (1⁄2 of 4%) times a recovery factor of 0.45 (for a stock of unknown status with a Hawaiian Islands EEZ 

fishery mortality and serious injury rate CV between 0.60 and 0.80; Wade and Angliss 1997), resulting in a PBR of 

82 striped dolphins per year. 

 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Fishery Information

Information on fishery-related 

mortality and serious injury of cetaceans 

in Hawaiian waters is limited, but the gear 

types used in Hawaiian fisheries are 

responsible for marine mammal mortality 

and serious injury in other fisheries 

throughout U.S. waters. Gillnets appear 

to capture marine mammals wherever 

they are used, and float lines from lobster 

traps and longlines can be expected to 

occasionally entangle cetaceans (Perrin et 

al. 1994). 

 Interactions with cetaceans have 

been reported for all Hawaiian pelagic 

fisheries (Nitta and Henderson 1993). 

There are currently two distinct longline 

fisheries based in Hawaii: a deep-set 

longline (DSLL) fishery that targets 

primarily tunas, and a shallow-set 

longline fishery (SSLL) that targets 

swordfish. Both fisheries operate within 

U.S. waters and on the high seas. 

Between 2004 and 2008, one striped 

dolphin was seriously injured on the high 

seas in the SSLL fishery (100% observer 

coverage), and one striped dolphin was 

killed within the Hawaiian Islands EEZ in 

the DSLL fishery (20-28% observer coverage) (Figure 2, Forney 2009, McCracken & Forney 2010). Average 5-yr 

estimates of annual mortality and serious injury for 2004-2008 are zero dolphins outside of U.S. EEZs, and 0.9 

(CV=0.6) within the Hawaiian Islands EEZ (Table 1). 

Figure 2. Locations of striped dolphin takes (filled diamonds) in 

Hawaii-based longline fisheries, 2004-2008 Solid lines represent the 

U.S. EEZs. Fishery descriptions are provided in Appendix 1. 

 Interaction rates between dolphins and the NWHI bottomfish fishery have been estimated based on studies 

conducted in 1990-1993, indicating that an average of 2.67 dolphin interactions, most likely involving bottlenose 

and rough-toothed dolphins, occurred for every 1000 fish brought on board (Kobayashi and Kawamoto 1995). 

Fishermen claim interactions with dolphins that steal bait and catch are increasing. It is not known whether these 

interactions result in serious injury or mortality of dolphins, nor whether 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. It is not listed as 

“threatened” or “endangered” under the Endangered Species Act (1973), nor as “depleted” under the MMPA. The 

Hawaiian stock of striped dolphins is not considered strategic under the 1994 amendments to the MMPA, because 

the estimated rate of fisheries related mortality and serious injury within the Hawaiian Islands EEZ (0.9 animals per 

year) is less than the PBR (82). Total fishery mortality and serious injury for striped dolphins can be considered 

insignificant and approaching zero, because the average annual takes are less than 10% of the PBR. 

230
Table 1. Summary of available information on incidental mortality and serious injury of striped dolphin (Hawaii 

stock) in commercial fisheries, within and outside of U.S. EEZs (McCracken & Forney 2010). Mean annual takes 

are based on 2004-2008 data unless otherwise indicated. 

Mortality and Serious In ry ju

outside of U.S. EEZ

Mortality and Serious Injury 

within Hawaiian Islands EEZ

Fishery Name Year Data Type

Percent 

Observer 

Coverage Observed Estimated Mean Annual 

Takes (CV) Observed Estimated 

(CV)

Mean Annual 

Takes (CV)

Hawaii-based 

deep-set longline 

fishery 

2004 

2005 

2006 

2007 

2008 

observer 

data 

25% 

28% 

22% 

20% 

22% 

0 

0 

0 

0 

0

0 (-) 

0 (-) 

0 (-) 

0 (-)

0 (-)

0 (-) 

0 

0 

1 

0

0

0 (-) 

0 (-) 

5 (0.3) 

0 (-)

0 (-)

0.9 (0.6)

Hawaii-based 

shallow-set 

longline fishery 

2004 

2005 

2006 

2007 

2008 

observer 

data 

100% 

100% 

100% 

100% 

100% 

0 

0 

0 

0 

1 

Same as 

observed 

0.2 

0 

0 

0 

0

0

0 

0 

0 

0

0

0

Minimum total annual takes within U.S. EEZ waters 0.9 (0.6)

REFERENCES

Barlow, J. 2006. Cetacean abundance in Hawaiian waters estimated from a summer/fall survey in 2002. Marine 

Mammal Science 22(2): 446-464. 

Dizon, A. E., W. F. Perrin, and P. A. Akin. 1994. Stocks of dolphins (Stenella spp. and Delphinus delphis) in the 

eastern tropical Pacific: a phylogeographic classification. NOAA Tech. Rep. NMFS 119, 20 pp. 

Forney, K.A. 2009. Serious injury determinations for cetaceans caught in Hawaii longline fisheries during 1994-

2008. Draft document PSRG-2009-09 presented to the Pacific Scientific Review Group, November 3-5, 

2009, Del Mar, CA. 

Kishiro, T. and T. Kasuya. 1993. Review of Japanese dolphin drive fisheries and their status. Rep. Int. Whal. 

Commn. 43:439-452. 

Kobayashi, D. R. and K. E. Kawamoto. 1995. Evaluation of shark, dolphin, and monk seal interactions with 

Northwestern Hawaiian Island bottomfishing activity: a comparison of two time periods and an estimate of 

economic impacts. Fisheries Research 23: 11-22. 

McCracken M. and K.A. Forney 2010. Preliminary assessment of incidental interactions with marine mammals in 

the Hawaii longline deep and shallow set fisheries. NMFS, Pacific Islands Fisheries Science Center 

Working Paper WP-10-001. 27p. 

Maldini, D., L. Mazzuca, and S. Atkinson. 2005. Odontocete stranding patterns in the Main Hawaiian Islands 

(1937-2002): How do they compare with live animal surveys? Pacific Science 59(1):55-67. 

Miyashita, T. 1993. Abundance of dolphin stocks in the western North Pacific taken by the Japanese drive fishery. 

Rep. Int. Whal. Commn. 43:417-437. 

Mobley, J. R. , Jr, S. S. Spitz, K. A. Forney, R. A. Grotefendt, and P. H. Forestall. 2000. Distribution and 

abundance of odontocete species in Hawaiian waters: preliminary results of 1993-98 aerial surveys Admin. 

Rep. LJ-00-14C. Southwest Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La 

Jolla, CA 92038. 26 pp. 

Nitta, E. 1991. The marine mammal stranding network for Hawaii: an overview. In: J.E. Reynolds III, D.K. Odell 

(eds.), Marine Mammal Strandings in the United States, pp.56-62. NOAA Tech. Rep. NMFS 98, 157 pp. 

Nitta, E. and J. R. Henderson. 1993. A review of interactions between Hawaii's fisheries and protected species. 

Mar. Fish. Rev. 55(2):83-92. 

Perrin, W.F., G. P. Donovan and J. Barlow. 1994. Gillnets and Cetaceans. Rep. Int. Whal. Commn., Special Issue 

15, 629 pp. 

Perrin, W.F., B. Würsig and J.G.M. Thewissen. 2009. Encyclopedia of Marine Mammals. Second Edition. 

Academic Press, Amsterdam. 

Shallenberger, E.W. 1981. The status of Hawaiian cetaceans. Final report to U.S. Marine Mammal Commission. 

MMC-77/23, 79pp. 

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

Workshop April 3-5, 1996, Seattle, Washington. U. S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR12. 93 pp. 

231
Wade, P. R. and T. Gerrodette. 1993. Estimates of cetacean abundance and distribution in the eastern tropical 

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

232
Revised 01/15/2011 

FRASER'S DOLPHIN (Lagenodelphis hosei):

Hawaiian Stock 

STOCK DEFINITION AND GEOGRAPHIC RANGE

Fraser’s dolphins are distributed 

worldwide in tropical waters (Dolar 2009 

in Perrin et al. 2009). They have only 

recently been documented within the U.S. 

Exclusive Economic Zone (EEZ) of the 

Hawaiian Islands, during a 2002 cetacean 

survey (Barlow 2006, Figure 1). No 

strandings of Fraser’s dolphins have been 

documented in the Hawaiian Islands 

(Nitta 1991; Maldini et al. 2005), though 

there is one sighting off the island of 

Hawaii from April 2008 (Baird 

unpublished). For the Marine Mammal 

Protection Act (MMPA) stock assessment 

reports, there is a single Pacific 

management stock including animals 

found both within the Hawaiian Islands 

EEZ and in adjacent international waters. 

Because data on abundance, distribution, 

and human-caused impacts are largely 

lacking for international waters, the status 

of this stock is evaluated based on data 

from U.S. EEZ waters of the Hawaiian 

Islands (NMFS 2005). 

W180 W175 W170 W165 W160 W155 W150

N10

N15

N20

N25

N30

N35

Figure 1. Fraser’s dolphin sighting locations during the 2002 

shipboard cetacean survey of U.S. waters surrounding the Hawaiian 

Islands (Barlow 2006; see Appendix 2 for details on timing and 

location of survey effort). Outer line indicates approximate boundary 

of survey area and U.S. EEZ.

POPULATION SIZE

 Population estimates for Fraser’s dolphins have been made in the eastern tropical Pacific (Wade and 

Gerrodette 1993), but it is not known whether these animals are part of the same population that occurs around the 

Hawaiian Islands and in the central North Pacific. A 2002 shipboard line-transect survey of the entire Hawaiian 

Islands EEZ resulted in an abundance estimate of 10,226 (CV=1.16) Fraser’s dolphins (Barlow 2006). This is 

currently the best available abundance estimate for this stock. 

Minimum Population Estimate

 The log-normal 20th percentile of the 2002 abundance estimate (Barlow 2006) is 4,700 Fraser’s dolphins. 

Current Population Trend

 No data are available on current population trend. 

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

 No data are available on current or maximum net productivity rate for the Hawaiian stock of Fraser’s 

dolphin. 

POTENTIAL BIOLOGICAL REMOVAL

 The potential biological removal (PBR) level for this stock of Fraser’s dolphin is calculated as the 

minimum population size within the U.S. EEZ of the Hawaiian Islands (4,700) times one half the default maximum 

net growth rate for cetaceans (1⁄2 of 4%) times a recovery factor of 0.50 (for a stock of unknown status with no 

known fishery mortality or serious injury within the Hawaiian Islands EEZ; Wade and Angliss 1997), resulting in a 

PBR of 47 Fraser’s dolphins per year. 

233
HUMAN CAUSED MORTALITY AND SERIOUS INJURY 

Fishery Information

 Information on fishery-related mortality and serious injury of cetaceans in Hawaiian waters is limited, but 

the gear types used in Hawaiian fisheries are responsible for marine mammal mortality and serious injury in other 

fisheries throughout U.S. waters. Gillnets appear to capture marine mammals wherever they are used, and float lines 

from lobster traps and longlines can be expected to occasionally entangle cetaceans (Perrin et al. 1994). Interactions 

with cetaceans have been reported for all Hawaiian pelagic fisheries (Nitta and Henderson 1993), but none of these 

interactions are known to have involved Fraser’s dolphins. There are currently two distinct longline fisheries based 

in Hawaii: a deep-set longline (DSLL) fishery that targets primarily tunas, and a shallow-set longline fishery (SSLL) 

that targets swordfish. Both fisheries operate within U.S. waters and on the high seas. Between 2004 and 2008, no 

Fraser’s dolphins were observed hooked or entangled in the SSLL fishery (100% observer coverage) or the DSLL 

fishery (20-28% observer coverage) (McCracken & Forney 2010). 

 Interaction rates between dolphins and the NWHI bottomfish fishery have been estimated based on studies 

conducted in 1990-1993, indicating that an average of 2.67 dolphin interactions, most likely involving bottlenose 

and rough-toothed dolphins, occurred for every 1000 fish brought on board (Kobayashi and Kawamoto 1995). 

Fishermen claim interactions with dolphins that steal bait and catch are increasing. It is not known whether these 

interactions result in serious injury or mortality of dolphins, nor whether Fraser’s dolphins are involved. 

STATUS OF STOCK 

 The status of Fraser's dolphins in Hawaiian waters relative to OSP is unknown, and there are insufficient 

data to evaluate trends in abundance. No habitat issues are known to be of concern for this species. It is not listed as 

“threatened” or “endangered” under the Endangered Species Act (1973), nor as “depleted” under the MMPA. Given 

the absence of recent fishery-related mortality or serious injuries, the Hawaiian stock of Fraser’s dolphins is not 

considered strategic under the 1994 amendments to the MMPA, and the total fishery mortality and serious injury can 

be considered to be insignificant and approaching zero. 

REFERENCES

Barlow, J. 2006. Cetacean abundance in Hawaiian waters estimated from a summer/fall survey in 2002. Marine 

Mammal Science 22(2): 446-464. 

Forney, K.A. 2009. Serious injury determinations for cetaceans caught in Hawaii longline fisheries during 1994-

2008. Draft document PSRG-2009-09 presented to the Pacific Scientific Review Group, November 3-5, 

2009, Del Mar, CA. 

Kobayashi, D. R. and K. E. Kawamoto. 1995. Evaluation of shark, dolphin, and monk seal interactions with 

Northwestern Hawaiian Island bottomfishing activity: a comparison of two time periods and an estimate of 

economic impacts. Fisheries Research 23: 11-22. 

Maldini, D., L. Mazzuca, and S. Atkinson. 2005. Odontocete stranding patterns in the Main Hawaiian Islands 

(1937-2002): How do they compare with live animal surveys? Pacific Science 59(1):55-67. 

McCracken M., and K.A. Forney. 2010. Preliminary assessment of incidental interactions with marine mammals in 

the Hawaii longline deep and shallow set fisheries. NMFS, Pacific Islands Fisheries Science Center 

Working Paper WP-10-001. 27p 

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. 

Perrin, W.F., B. Würsig and J.G.M. Thewissen. 2009. Encyclopedia of Marine Mammals. Second Edition. 

Academic Press, Amsterdam. 

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

Workshop April 3-5, 1996, Seattle, Washington. U. S. Dept. Commer., NOAA Tech. Memo. NMFS-OPR12. 93 pp. 

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

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

234
Revised 01/15/2011

MELON-HEADED WHALE (Peponocephala electra): 

Hawaiian Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

 Melon-headed whales are found 

in tropical and warm-temperate waters 

throughout the world. The distribution 

of reported sightings suggests that the 

oceanic habitat of this species is 

primarily equatorial waters (Perryman et 

al. 1994). Small numbers have been 

taken in the eastern tropical Pacific, and 

they are occasionally killed in direct 

fisheries in Japan and elsewhere in the 

western Pacific. Large herds are seen 

regularly in Hawaiian waters, especially 

off the Waianae coast of Oahu, the north 

Kohala coast of Hawaii, and the leeward 

coast of Lanai (Shallenberger 1981). A 

comprehensive shipboard survey of the 

Hawaiian Exclusive Economic Zone 

(EEZ), resulted in only one sighting of 

melon-headed whales (Figure 1; Barlow 

2006). Inter-island movements from 

Kauai to Hawaii have been documented 

and genetic samples from at least 82 

animals are available for future stock 

structure analyses (R.W. Baird, pers. 

comm.). Little is known about this 

species elsewhere in its range, and most knowledge about its biology comes from mass strandings (Perryman et al. 

1994). Fourteen strandings are known from Hawaii (Nishiwaki and Norris 1966; Shallenberger 1981; Nitta 1991; 

Maldini et al. 2005). For the Marine Mammal Protection Act (MMPA) stock assessment reports, there is a single 

Pacific management stock including animals found both within the Hawaiian Islands EEZ and in adjacent 

international waters. Because data on abundance, distribution, and human-caused impacts are largely lacking for 

international waters, the status of this stock is evaluated based on data from U.S. EEZ waters of the Hawaiian 

Islands (NMFS 2005). 

W180 W175 W170 W165 W160 W155 W150

N10

N15

N20

N25

N35

N30

Figure 1. Melon-headed whale sighting location during the 2002 

shipboard survey of U.S. EEZ waters surrounding the Hawaiian 

Islands (Barlow 2006; see Appendix 2 for details on timing and 

location of survey effort). Outer line represents approximate 

boundary of survey area and U.S. EEZ. 

 

POPULATION SIZE

 An abundance estimate of melon-headed whales is available for the eastern tropical Pacific (Wade and 

Gerrodette 1993), but it is not known whether any of these animals are part of the same population that occurs 

around the Hawaiian Islands. A 2002 shipboard line-transect survey of the entire Hawaiian Islands EEZ resulted in 

an abundance estimate of 2,950 (CV=1.17) melon-headed whales (Barlow 2006). This is currently the best available 

abundance estimate for this stock. 

Minimum Population Estimate

 The log-normal 20th percentile of the 2002 abundance estimate (Barlow 2006) is 1,350 melon-headed 

whales in the Hawaiian Islands 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. 

235
POTENTIAL BIOLOGICAL REMOVAL

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

within the U.S. EEZ of the Hawaiian Islands (1,350) 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 14 melon-headed whales per year. 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY 

Fishery Information

 Information on fishery-related mortality and serious injury of cetaceans in Hawaiian waters is limited, but 

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 cetaceans (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. There are currently two distinct 

longline fisheries based in Hawaii: a deep-set longline (DSLL) fishery that targets primarily tunas, and a shallow-set 

longline fishery (SSLL) that targets swordfish. Both fisheries operate within U.S. waters and on the high seas. 

Between 2004 and 2008, no melon-headed whales were observed hooked or entangled in the SSLL fishery (100% 

observer coverage) or the DSLL fishery (20-28% observer coverage) (McCracken & Forney 2010). Interaction rates 

between dolphins and the NWHI bottomfish fishery have been estimated based on studies conducted in 1990-1993, 

indicating that an average of 2.67 dolphin interactions, most likely involving bottlenose and rough-toothed dolphins, 

occurred for every 1000 fish brought on board (Kobayashi and Kawamoto 1995). Fishermen claim interactions with 

dolphins that steal bait and catch are increasing. It is not known whether these interactions result in serious injury or 

mortality of dolphins, nor whether melon-headed whales are involved. 

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 (Cox et al. 2006) and other cetaceans, including melon-headed 

whales (Southall et al. 2006) and pygmy killer whales (Feresa attenuata) (Wang and Yang 2006). The use of active 

sonar from military vessels has been implicated in mass strandings of beaked whales and recent mass-stranding 

reports suggest some delphinids may be impacted as well. A 2004 mass-stranding of melon-headed whales in 

Hanalei Bay, Kauai occurred during a multi-national sonar training event around Hawaii (Southall et al. 2006). 

Although data limitations preclude a conclusive finding regarding the role of Navy sonar in triggering this event, 

sonar transmissions were considered a plausible, if not likely cause of the mass stranding based on the 

spatiotemporal link between the sonar exercises and the stranding, the direction of movement of the transmitting 

vessels near Hanalei Bay, and propagation modeling suggesting the sonar transmissions would have been audible at 

the mouth of Hanalei Bay (Southall et al 2006; Brownell et al. 2009). Additional research on the behavioral response 

of delphinids in the presence of sonar transmissions is needed in order to understand the level of impact. No 

estimates of potential mortality or serious injury are available for U.S. waters. 

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. It is 

not listed as “threatened” or “endangered” under the Endangered Species Act (1973), nor as “depleted” under the 

MMPA. Given the absence of recent fishery-related mortality or serious injuries, the Hawaiian stock of melonheaded whales is not considered strategic under the 1994 amendments to the MMPA, and the total fishery mortality 

and serious injury can be considered to be insignificant and approaching zero. 

REFERENCES 

Barlow, J. 2006. Cetacean abundance in Hawaiian waters estimated from a summer/fall survey in 2002. Marine 

Mammal Science 22(2): 446-464. 

Brownell, R.L, Jr., K. Ralls, S. Baumann-Pickering, and M.M. Poole. 2009. Behavior of melon-headed whales, 

Peponocephala electra, near oceanic islands. Marine Mammal Science 25(3):639-658. 

Cox, T.M., T.J. Ragen, A.J. Read, E. Vos, R.W. Baird, K. Balcomb, J. Barlow, J. Caldwell, T. Cranford, L. Crum, 

A. D’Amico, G. D’Spain, A. Fernandez, J. Finneran, R. Gentry, W. Gerth, F. Gulland, J.A. Hildebrand, D. 

Houser, T. Hullar, P.D. Jepson, D. Ketten, C.D. Macleod, P. Miller, S. Moore, D. Mountain, D. Palka, P. 

Ponganis, S. Rommel, T. Rowles, B. Taylor, P. Tyack, D. Wartzok, R. Gisiner, J. Mead, and L. Brenner. 

236
A. D’Amico, G. D’Spain, A. Fernandez, J. Finneran, R. Gentry, W. Gerth, F. Gulland, J.A. Hildebrand, D. 

Houser, T. Hullar, P.D. Jepson, D. Ketten, C.D. Macleod, P. Miller, S. Moore, D. Mountain, D. Palka, P. 

Ponganis, S. Rommel, T. Rowles, B. Taylor, P. Tyack, D. Wartzok, R. Gisiner, J. Mead, and L. Brenner. 

2006. Understanding the impacts of anthropogenic sound on beaked whales. J.Cetacean Res. Manag. 7: 

177-187. 

Forney, K.A. 2009. Serious injury determinations for cetaceans caught in Hawaii longline fisheries during 1994-

2008. Draft document PSRG-2009-09 presented to the Pacific Scientific Review Group, November 3-5, 

2009, Del Mar, CA. 

Kobayashi, D. R. and K. E. Kawamoto. 1995. Evaluation of shark, dolphin, and monk seal interactions with 

Northwestern Hawaiian Island bottomfishing activity: a comparison of two time periods and an estimate of 

economic impacts. Fisheries Research 23: 11-22. 

Maldini, D., L. Mazzuca, and S. Atkinson. 2005. Odontocete stranding patterns in the Main Hawaiian Islands 

(1937-2002): How do they compare with live animal surveys? Pacific Science 59(1):55-67. 

McCracken M., and K.A. Forney. 2010. Preliminary assessment of incidental interactions with marine mammals in 

the Hawaii longline deep and shallow set fisheries. NMFS, Pacific Islands Fisheries Science Center 

Working Paper WP-10-001. 27p 

McSweeney, D.J., R.W. Baird, S.D.Mahaffy, D.L. Webster, and G.S. Schorr. 2009. Site fidelity and association 

patterns of a rare species: Pygmy killer whales (Feresa attenuata) in the main Hawaiian Islands. Marine 

Mammal Science 25(4): 557-572. 

Nitta, E. 1991. The marine mammal stranding network for Hawaii: an overview. In: J.E. Reynolds III, D.K. Odell 

(eds.), Marine Mammal Strandings in the United States, pp.56-62. NOAA Tech. Rep. NMFS 98, 157 pp. 

Nitta, E. and J. R. Henderson. 1993. A review of interactions between Hawaii's fisheries and protected species. 

Mar. Fish. Rev. 55(2):83-92. 

Perrin, W.F., G. P. Donovan and J. Barlow. 1994. Gillnets and Cetaceans. Rep. Int. Whal. Commn., Special Issue 

15, 629 pp. 

Pryor, T., K. Pryor and K. S. Norris. 1965. Observations on a pygmy killer whale (Feresa attenuata Gray) from 

Hawaii. J. Mamm. 46:450-461. 

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. 

Schofield, D. 2007. Pygmy killer whale (Feresa attenuata) stranding of July 23, 2006. National Marine Fisheries 

Service, Honolulu, HI. 

Shallenberger, E.W. 1981. The status of Hawaiian cetaceans. Final report to U.S. Marine Mammal Commission. 

MMC-77/23, 79pp. 

Southall, B. R. Braun, F.M.D. Gulland, A.D. Heard, R.W. Baird, S.M. Wilkin, T.K. Rowles. 2006. Hawaiian melonheaded whale (Peponocephala electra) mass stranding event of July 3-4, 2004. NOAA Technical 

Memorandum NMFS-OPR-31. 73 pp. 

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

Workshop April 3-5, 1996, Seattle, Washington. U. S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR12. 93 pp. 

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

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

Wang, J.Y., and S.-C. Yang. 2006. Unusual cetacean stranding events in Chinese waters in early 2004 and 2005. J. 

Cetacean Res. and Manag. 8:283-292.

237
Revised 01/15/2011

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. More recently, pygmy 

killer whales have also been seen off the 

islands of Niihau and Lanai 

(McSweeney et al. 2009). Three 

sightings of pygmy killer whales were 

made during a 2002 shipboard survey of 

U.S. Exclusive Economic Zone (EEZ) 

waters surrounding the Hawaiian Islands (Figure 1; Barlow 2006). Six strandings have been documented from Maui 

and the island of Hawaii (Nitta 1991, Maldini et al. 2005). A 22-year study off the island of Hawaii suggested this 

species is relatively rare (1.2% of all sightings) yet occurs year-round and in stable groups. High resighting rates 

suggest a small-island associated population off the island of Hawaii (McSweeney et al. 2009), which may warrant 

division of this population into a separate island-associated stock in the future. For the Marine Mammal Protection 

Act (MMPA) stock assessment reports, there is a single Pacific management stock including animals found both 

within the Hawaiian Islands EEZ and in adjacent international waters. Because data on abundance, distribution, and 

human-caused impacts are largely lacking for international waters, the status of this stock is evaluated based on data 

from U.S. EEZ waters of the Hawaiian Islands (NMFS 2005). 

W180 W175 W170 W165 W160 W155 W150

N10

N15

N20

N25

N30

N35

Figure 1. Pygmy killer whale sighting locations during the 2002 

shipboard survey of U.S. EEZ waters surrounding the Hawaiian 

Islands (Barlow 2006; see Appendix 2 for details on timing and 

location of survey effort). Outer line represents approximate 

boundary of survey area and U.S. EEZ. 

 

POPULATION SIZE

 A population estimate has been made for this species in the eastern tropical Pacific (Wade and Gerrodette 

1993), but it is not known whether any of these animals are part of the same population that occurs around the 

Hawaiian Islands. A 2002 shipboard line-transect survey of the entire Hawaiian Islands EEZ resulted in an 

abundance estimate of 956 (CV=0.83) pygmy killer whales (Barlow 2006). This is currently the best available 

abundance estimate for this stock. 

Minimum Population Estimate

 The log-normal 20th percentile of the 2002 abundance estimate (Barlow 2006) is 520 pygmy killer whales 

within the Hawaiian EEZ. 

Current Population Trend

 No data are available on current population trend. 

238
CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

 No data are available on current or maximum net productivity rate. 

POTENTIAL BIOLOGICAL REMOVAL

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

within the U.S. EEZ of the Hawaiian Islands (520) times one half the default maximum net growth rate for cetaceans 

(1⁄2 of 4%) times a recovery factor of 0.50 (for a stock of unknown status with no known fishery mortality or serious 

injury within the Hawaiian Islands EEZ; Wade and Angliss 1997), resulting in a PBR of 5.2 pygmy killer whales per 

year. 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Fishery Information

Information on fishery-related mortality and serious injury of cetaceans in Hawaiian waters is limited, but 

the gear types used in Hawaiian fisheries are responsible for marine mammal mortality and serious injury in other 

fisheries throughout U.S. waters. Gillnets appear to capture marine mammals wherever they are used, and float lines 

from lobster traps and longlines can be expected to occasionally entangle cetaceans (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. There are currently two distinct 

longline fisheries based in Hawaii: a deep-set longline (DSLL) fishery that targets primarily tunas, and a shallow-set 

longline fishery (SSLL) that targets swordfish. Both fisheries operate within U.S. waters and on the high seas. 

Between 2004 and 2008, no pygmy killer whales were observed hooked or entangled in the SSLL fishery (100% 

observer coverage) or the DSLL fishery (20-28% observer coverage) (McCracken & Forney 2010). Interaction rates 

between dolphins and the NWHI bottomfish fishery have been estimated based on studies conducted in 1990-1993, 

indicating that an average of 2.67 dolphin interactions, most likely involving bottlenose and rough-toothed dolphins, 

occurred for every 1000 fish brought on board (Kobayashi and Kawamoto 1995). Fishermen claim interactions with 

dolphins that steal bait and catch are increasing. It is not known whether these interactions result in serious injury or 

mortality of dolphins, nor whether pygmy killer whales are involved. A stranded pygmy killer whale from Oahu 

showed signs of hooking injury (Schofield 2007) and mouthline injuries have also been noted in some individuals 

(Baird unpublished data), though it is not known if these interactions result in serious injury or mortality. 

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 (Cox et al. 2006) and other cetaceans, including melon-headed 

whales (Southall et al. 2006, Brownell et al. 2009) and pygmy killer whales (Wang and Yang 2006). The use of 

active sonar from military vessels has been implicated in mass strandings of beaked whales, and recent massstranding reports suggest some delphinids may be impacted as well. Two mass-strandings of pygmy killer whales 

occurred in the coastal areas of southwest Taiwan in February 2005, possibly associated with offshore naval training 

exercises (Wang and Yang 2006). A necropsy of one of the pygmy killer whales revealed hemorrhaging in the 

cranial tissues of the animal. Additional research on the behavioral response of delphinids in the presence of sonar 

transmissions is needed in order to understand the level of impact. No estimates of potential mortality or serious 

injury are available for U.S. waters. 

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. Given the absence of recent fishery-related mortality or serious injuries, the Hawaiian stock of 

pygmy killer whales is not considered strategic under the 1994 amendments to the MMPA, and the total fishery 

mortality and serious injury can be considered to be insignificant and approaching zero. 

REFERENCES 

Barlow, J. 2006. Cetacean abundance in Hawaiian waters estimated from a summer/fall survey in 2002. Marine 

Mammal Science 22(2): 446-464. 

Brownell, R.L, Jr., K. Ralls, S. Baumann-Pickering, and M.M. Poole. 2009. Behavior of melon-headed whales, 

Peponocephala electra, near oceanic islands. Marine Mammal Science 25(3):639-658. 

Cox, T.M., T.J. Ragen, A.J. Read, E. Vos, R.W. Baird, K. Balcomb, J. Barlow, J. Caldwell, T. Cranford, L. Crum, 

239
A. D’Amico, G. D’Spain, A. Fernandez, J. Finneran, R. Gentry, W. Gerth, F. Gulland, J.A. Hildebrand, D. 

Houser, T. Hullar, P.D. Jepson, D. Ketten, C.D. Macleod, P. Miller, S. Moore, D. Mountain, D. Palka, P. 

Ponganis, S. Rommel, T. Rowles, B. Taylor, P. Tyack, D. Wartzok, R. Gisiner, J. Mead, and L. Brenner. 

2006. Understanding the impacts of anthropogenic sound on beaked whales. J.Cetacean Res. Manag. 7: 

177-187. 

Forney, K.A. 2009. Serious injury determinations for cetaceans caught in Hawaii longline fisheries during 1994-

2008. Draft document PSRG-2009-09 presented to the Pacific Scientific Review Group, November 3-5, 

2009, Del Mar, CA. 

Kobayashi, D. R. and K. E. Kawamoto. 1995. Evaluation of shark, dolphin, and monk seal interactions with 

Northwestern Hawaiian Island bottomfishing activity: a comparison of two time periods and an estimate of 

economic impacts. Fisheries Research 23: 11-22. 

Maldini, D., L. Mazzuca, and S. Atkinson. 2005. Odontocete stranding patterns in the Main Hawaiian Islands 

(1937-2002): How do they compare with live animal surveys? Pacific Science 59(1):55-67. 

McCracken M., and K.A. Forney. 2010. Preliminary assessment of incidental interactions with marine mammals in 

the Hawaii longline deep and shallow set fisheries. NMFS, Pacific Islands Fisheries Science Center 

Working Paper WP-10-001. 27p 

McSweeney, D.J., R.W. Baird, S.D.Mahaffy, D.L. Webster, and G.S. Schorr. 2009. Site fidelity and association 

patterns of a rare species: Pygmy killer whales (Feresa attenuata) in the main Hawaiian Islands. Marine 

Mammal Science 25(4): 557-572. 

Nitta, E. 1991. The marine mammal stranding network for Hawaii: an overview. In: J.E. Reynolds III, D.K. Odell 

(eds.), Marine Mammal Strandings in the United States, pp.56-62. NOAA Tech. Rep. NMFS 98, 157 pp. 

Nitta, E. and J. R. Henderson. 1993. A review of interactions between Hawaii's fisheries and protected species. 

Mar. Fish. Rev. 55(2):83-92. 

Perrin, W.F., G. P. Donovan and J. Barlow. 1994. Gillnets and Cetaceans. Rep. Int. Whal. Commn., Special Issue 

15, 629 pp. 

Pryor, T., K. Pryor and K. S. Norris. 1965. Observations on a pygmy killer whale (Feresa attenuata Gray) from 

Hawaii. J. Mamm. 46:450-461. 

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. 

Schofield, D. 2007. Pygmy killer whale (Feresa attenuata) stranding of July 23, 2006. National Marine Fisheries 

Service, Honolulu, HI. 

Shallenberger, E.W. 1981. The status of Hawaiian cetaceans. Final report to U.S. Marine Mammal Commission. 

MMC-77/23, 79pp. 

Southall, B. R. Braun, F.M.D. Gulland, A.D. Heard, R.W. Baird, S.M. Wilkin, T.K. Rowles. 2006. Hawaiian melonheaded whale (Peponocephala electra) mass stranding event of July 3-4, 2004. NOAA Technical 

Memorandum NMFS-OPR-31. 73 pp. 

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

Workshop April 3-5, 1996, Seattle, Washington. U. S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR12. 93 pp. 

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

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

Wang, J.Y., and S.-C. Yang. 2006. Unusual cetacean stranding events in Chinese waters in early 2004 and 2005. J. 

Cetacean Res. and Manag. 8:283-292.

240
Revised 1/15/2011 

FALSE KILLER WHALE (Pseudorca crassidens): 

Pacific Islands Region Stock Complex - Hawaii Insular, 

Hawaii Pelagic, and Palmyra Atoll Stocks 

STOCK DEFINITIONS AND GEOGRAPHIC RANGES 

 False killer whales are found 

worldwide mainly in tropical and warmtemperate waters (Stacey et al. 1994). In the 

North Pacific, this species is well known from 

southern Japan, Hawaii, and the eastern 

tropical Pacific. There are six stranding 

records from Hawaiian waters (Nitta 1991; 

Maldini 2005). One on-effort sighting of false 

killer whales was made during a 2002 

shipboard survey of waters within the U.S. 

Exclusive Economic Zone (EEZ) of the 

Hawaiian Islands (Figure 1; Barlow 2006). 

Smaller-scale surveys conducted around the 

main Hawaiian Islands (Figure 2) show that 

false killer whales are also encountered in 

nearshore waters (Baird et al. 2005, Mobley et 

al. 2000, Mobley 2001, 2002, 2003, 2004). 

This species also occurs in U.S. EEZ waters 

around Palmyra Atoll (Figure 1), Johnston 

Atoll (NMFS/PIR/PSD unpublished data), and 

American Samoa (Johnston et al. 2008, Oleson 

2009). 

 Genetic analyses of tissue samples 

collected within the Eastern North Pacific 

(ENP) indicate restricted gene flow between 

false killer whales sampled near the main 

Hawaiian Islands and false killer whales 

sampled in all other regions of the ENP 

(Chivers et al. 2007). Since 2003, observers of 

the Hawaii-based longline fishery have also 

been collecting tissue samples of caught 

cetaceans for genetic analysis whenever 

possible. Between 2003 and 2008, five false 

killer whale samples, three collected outside the Hawaiian EEZ and two collected within the EEZ but more than 

100 nautical miles (185km) from the main Hawaiian Islands (see Figure 3), were determined to have ENP-like 

haplotypes. Based on sighting locations and results of the genetic analyses, Chivers et al. (2008) suggested 

implementing a stock boundary coincident with the longline exclusion zone, which is at about 75 nmi (139 km) 

from the main Hawaiian Islands, until more information is available about the ecology of false killer whales, and 

especially the movement patterns of the insular stock animals. 

Figure 1. False killer whale sighting locations during standardized 

shipboard surveys of the Hawaiian U.S. EEZ (2002, black diamond, 

Barlow 2006), the Palmyra U.S. EEZ and pelagic waters of the 

central Pacific south of the Hawaiian Islands (2005, open squares, 

Barlow and Rankin 2007). Outer lines represent approximate 

boundary of U.S. EEZs; shaded gray area is the insular false killer 

whale stock area, including overlap zone between insular and pelagic 

false killer whale stocks . 

For the 2008-2009 stock assessment reports, a provisional stock boundary for insular and pelagic stocks of 

false killer whales was recognized as the February-September longline exclusion boundary (at roughly 75 miles 

from the islands), with the expectation that this boundary would be refined as additional studies of false killer whale 

movements became available. Recent satellite telemetry studies, boat-based surveys, and photo-identification 

analyses of false killer whales around Hawaii have demonstrated that these two stocks have overlapping ranges, 

rather than a clear separation in distribution. 

241
Insular false killer whales have been 

documented as far as 100 km from the main 

Hawaiian islands, and pelagic stock animals 

have been documented as close as 42 km to 

the islands (Baird et al. 2008, Baird 2009, 

Baird et al. 2010). Based on a review of 

new information (Forney et al. 2010), this 

stock assessment report recognizes a new, 

overlapping stock structure for insular and 

pelagic stocks of false killer whales around 

Hawaii: animals within 40 km of the main 

Hawaiian Islands are considered to belong 

to the insular stock; animals beyond 140 km 

of the main Hawaiian Islands are 

considered to belong to the pelagic stock, 

and the two stocks overlap between 40 km 

and 140 km from shore (Figure 1). 

 This report also clarifies that the 

pelagic stock includes animals found both 

within the Hawaiian Islands EEZ and in 

adjacent international waters; however, 

because data on false killer whale 

abundance, distribution, and human-caused 

impacts are largely lacking for international 

waters, the status of this stock is evaluated 

based on data from U.S. EEZ waters of the 

Hawaiian Islands (NMFS 2005). The 

Palmyra Atoll stock of false killer whales remains a separate stock, because comparisons amongst false killer whales 

sampled at Palmyra Atoll and those sampled from the insular stock of Hawaii and the pelagic ENP revealed 

restricted gene flow, although the sample size remains low for robust comparisons (Chivers et al. 2007). NMFS will 

continue to obtain and analyze additional tissue samples for genetic studies of stock structure, and will evaluate new 

information on stock ranges as it becomes available. 

Figure 2. Sighting, biopsy, and telemetry records of false killer whales 

identified as being from insular (closed symbols) vs. pelagic (open 

symbols) stocks. The dark gray area is the 40-km insular stock core area; 

light gray area is the 40-km to 140-km overlap zone (Baird et al. 2010; 

Baird, unpublished data; reproduced from Forney et al. 2010).

For the Marine Mammal Protection Act (MMPA) stock assessment reports, there are currently four Pacific 

Islands Region management stocks (Chivers et al. 2008): 1) the Hawaii insular stock, which includes animals 

inhabiting waters within 140 km (approx. 75 nmi) of the main Hawaiian Islands, and 2) the Hawaii pelagic stock, 

which includes false killer whales inhabiting waters greater than 40 km (22 nmi) from the main Hawaiian Islands, 3) 

the Palmyra Atoll stock, which includes false killer whales found within the U.S. EEZ of Palmyra Atoll, and 4) the 

American Samoa stock, which includes false killer whales found within the U.S. EEZ of American Samoa. 

Estimates of abundance, potential biological removal, and status determinations for the first three stocks are 

presented below; the American Samoa Stock is covered in a separate report. 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY 

Fishery Information 

Interactions with cetaceans have been reported for Hawaiian pelagic fisheries, and false killer whales have 

been identified in fishermen's logs and NMFS observer records as taking catches from pelagic longlines (Nitta and 

Henderson 1993, NMFS/PIR unpublished data). False killer whales have also been observed feeding on mahi mahi, 

Coryphaena hippurus, and yellowfin tuna, Thunnus albacares, and they have been reported to take large fish (up to 

70 pounds) from the trolling lines of both commercial and recreational fishermen (Shallenberger 1981). There are 

anecdotal reports of interactions with marine mammals in the commercial Hawaii shortline fishery, which was 

developed to target bigeye tuna, Thunnus obesus, and lustrous pomfret, Eumegistus illustris, at Cross Seamount and 

may also set gear around the main Hawaiian Islands. Fishing is permitted through the State of Hawaii Commercial 

Marine License program, and until recently there were no reporting systems in place to document marine mammal 

interactions. This fishery was added to the 2010 List of Fisheries as a Category II fishery (Federal Register Vol. 74, 

No. 219, p. 58859-58901, November 16, 2009), and efforts are underway to obtain further information on the extent 

of interactions between shortlines and marine mammals and to document the species involved. Baird and Gorgone 

(2005) documented a high rate of dorsal fin disfigurements that were consistent with injuries from unidentified 

fishing line for false killer whales belonging to the insular stock. At the present time, however, it is unknown 

242
whether these injuries might have been 

caused by longline gear, shortline gear, or 

other hook-and-line gear used around the 

main Hawaiian Islands. 

There are two distinct longline 

fisheries based in Hawaii: a deep-set 

longline (DSLL) fishery that targets 

primarily tunas, and a shallow-set 

longline fishery (SSLL) that targets 

swordfish. Both fisheries operate within 

U.S. waters and on the high seas, within 

the ranges of both insular and pelagic 

stocks. Between 2004 and 2008, one false 

killer whale was observed hooked or 

entangled in the SSLL fishery (100% 

observer coverage) within the U.S. EEZ 

of the Hawaiian Islands, and 19 false 

killer whales were observed taken in the 

DSLL fishery (≥20% observer coverage) 

(Forney 2010). Two of the false killer 

whale takes in the DSLL fishery in 

Hawaiian EEZ waters resulted in the 

death of the animal. Based on an 

evaluation of the observer’s description 

of each interaction and following the 

most recently developed criteria for 

assessing serious injury in marine 

mammals (Andersen et al. 2008), the 

single animal taken in the SSLL fishery 

was considered not seriously injured. In 

the DSLL fishery, one false killer whale 

taken within the range of the insular 

stock, one taken in Hawaiian waters 

within the range of the pelagic stock, and 

one taken in international waters were 

considered not seriously injured. The remaining 15 false killer whales (six in international waters, seven in the 

Hawaiian Islands EEZ pelagic stock range, and one in the EEZ of Palmyra Atoll) were considered seriously injured 

(Forney 2010). Eight additional unidentified cetaceans that may have been false killer whales were also seriously 

injured during 2004-2008 (Forney 2010). Seven of these were taken in the DSLL fishery within U.S. EEZ waters, 

including two animals within the insular stock range, and one was taken in the SSLL fishery in international waters 

(Figure 3). 

Figure 3. Locations of observed false killer whale takes (filled 

symbols) and possible takes of this species (open symbols) in the 

Hawaii-based longline fisheries, 2004-2008. Deep-set fishery takes 

are shown in black; shallow-set fishery takes are shown in gray.

Stars are locations of genetic samples from fishery-caught false 

killer whales. Solid gray lines represent the U.S. EEZ; the dotted 

line is the outer (140-km) boundary of the overlap zone between 

insular and pelagic false killer whale stocks. Fishery descriptions 

are provided in Appendix 1.

 The total observed mortality and serious injury of cetaceans in the SSLL fishery (with 100% coverage), 

and the estimated annual and 5-yr average mortality and serious injury of cetaceans in the DSLL fishery are reported 

by McCracken and Forney (2010). Their methodology includes prorating all estimated takes of false killer whales 

based on the proportions of observed interactions that resulted in death or serious injury (89%), or non-serious injury 

(11%). Further, takes of false killer whales of unknown stock origin within the insular/pelagic stock overlap zone 

are prorated based on the density of each stock in that area. No genetic samples are available to establish stock 

identity for these takes, but both stocks are considered at risk of interacting with longline gear within this region. 

The pelagic stock is known to interact with longline fisheries in waters offshore of the overlap zone based on two 

genetic samples obtained by fishery observers (Chivers et al. 2008). Insular false killer whales have been 

documented via telemetry to move sufficiently far offshore (112 km) to reach longline fishing areas, and animals 

from this stock have a high rate of dorsal fin disfigurements consistent with injuries from unidentified fishing line 

(Baird and Gorgone 2005). Based on these considerations, and as outlined in the NMFS Guidelines for Assessing 

Marine Mammal Stocks (NMFS 2005), bycatch within the overlap zone has been prorated based on the estimated 

densities of each stock (McCracken and Forney 2010). This introduces an additional element of uncertainty into the 

bycatch estimates, but until methods of determining stock identity for animals observed taken within the overlap 

zone are available (e.g., photos, tissue samples), this approach ensures that potential impacts to both stocks are 

243
assessed. 

Based on these bycatch analyses, estimates of annual and 5-yr average annual mortality and serious injury 

of false killer whales, by stock and EEZ area, are shown in Table 1. Estimates of mortality and serious injury do not 

include any of the unidentified animals that may have been false killer whales and are therefore minimum estimates. 

Efforts are currently underway to develop methods of prorating the unidentified animals by species and stock, taking 

into account geographic differences in their ranges and observed rates of documented interactions with each species. 

Table 1. Summary of available information on incidental mortality and serious injury of false killer whales (Pacific 

Islands Stock Complex) in commercial fisheries, by stock and EEZ area, as applicable (McCracken and Forney 

2010). Mean annual takes are based on 2004-2008 estimates unless otherwise indicated. Information on all 

observed mortality events (M), serious injuries (SI) and non-serious injuries (NSI) is included, because total takes 

were prorated to deaths, serious injuries, and non-serious injuries based on the observed proportions of each 

outcome (see McCracken and Forney 2010 for details). 

Observed mortality events (M), serious injuries (SI) and non-serious injuries (NSI), and total 

estimated mortality and serious injury (M&SI) of false killer whales by stock / EEZ region 

Hawaii Pelagic Stock 

Outside of U.S. EEZs Hawaiian Islands EEZ

Hawaii Insular 

Stock

Palmyra Atoll Stock

Fishery Name Year Data Type 

Percent 

Observer 

Coverage Obs. 

M/SI/NSI

Estimated 

M&SI 

(CV)

Obs. 

M/SI/NSI

Estimated 

M&SI 

(CV)

Obs. 

M/SI/NSI

Estimated 

M&SI 

(CV)

Obs. 

M/SI/NSI

Estimated 

M&SI 

(CV)

Hawaii-based 

deep-set 

longline fishery 

2004 

2005 

2006 

2007 

2008 

Observer 

data 

25% 

28% 

22% 

20% 

22% 

0/3/0 

0/1/0 

0/2/0 

0/0/1 

0/0/0 

13 (0.4) 

3 (1.6) 

8 (0.7) 

2 (3.7) 

0 (-) 

1/2/0 

1/0/0 

0/1/1* 

0/1/1 

0/3/1 

12 (0.3) 

3 (1.9) 

3 (1.7) 

8 (0.8) 

11 (0.4) 

0/0/0 

0/0/0 

0/0/1* 

0/0/0 

0/0/0 

0 (-) 

0 (-) 

3 (0.7) 

0 (-) 

0 (-) 

0/0/0 

0/0/0 

0/0/0 

0/1/0 

0/0/0 

0 (-) 

0 (-) 

0 (-) 

2 (0.7) 

0 (-) 

Mean Estimated Annual Takes (CV) 5.3 (0.5) 7.3 (0.3) 0.6 (1.3) 0.3 (1.3) 

Hawaii-based 

shallow-set 

longline fishery 

2004 

2005 

2006 

2007 

2008 

Observer 

data 

100% 

100% 

100% 

100% 

100% 

0/0/0 

0/0/0 

0/0/0 

0/0/0 

0/0/0 

0 

0 

0 

0 

0 

0/0/0 

0/0/0 

0/0/0 

0/0/0 

0/0/1 

0 

0 

0 

0 

0 

0/0/0 

0/0/0 

0/0/0 

0/0/0 

0/0/0 

0 

0 

0 

0 

0 

No fishing effort 

Mean Annual Takes (100% coverage) 0 0 0 

Minimum total annual takes within U.S. EEZs 7.3 (0.3) 0.6 (1.3) 0.3 (1.3) 

* The single NSI take within insular/pelagic stock overlap zone is shown once for each stock, but total estimates derived from this take are 

prorated by stock based on insular/pelagic false killer whale densities within the overlap zone (see text above, and McCracken and Forney 2010). 

HAWAII INSULAR STOCK

POPULATION SIZE

A mark-recapture study of photo-identification data obtained during 2000-2004 around the main Hawaiian 

Islands produced an estimate of 123 (CV=0.72) insular false killer whales (Baird et al. 2005). 

Minimum Population Estimate

The minimum population estimate for the insular stock false killer whales is the number of distinct 

individuals identified in this population during the 2002-2004 photo-identification studies, 76 individuals (Baird et 

al. 2005). This is similar to the log-normal 20th percentile of the mark-recapture abundance estimate, 71 false killer 

whales. 

Current Population Trend

A recent study (Reeves et al. 2009) summarized information on false killer whale sightings near Hawaii 

between 1989 and 2007, based on various survey methods, and suggested that the insular stock of false killer whales 

may have declined during the last two decades. More recently, Baird (2009) reviewed trends in sighting rates of 

false killer whales from aerial surveys conducted using consistent methodology around the main Hawaiian Islands 

between 1994 and 2003 (Mobley et al. 2000, Mobley 2001, 2002, 2003, 2004). Sighting rates during these surveys 

exhibited a statistically significant decline that could not be attributed to any weather or methodological changes. 

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES 

No data are available on current or maximum net productivity rate for this species in Hawaiian waters.

POTENTIAL BIOLOGICAL REMOVAL 

The potential biological removal (PBR) level for the insular false killer whale 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 

244
recovery factor of 0.40 (for a stock of unknown status with a human-caused mortality and serious injury rate 

CV>0.80; Wade and Angliss 1997), resulting in a PBR of 0.61 false killer whales per year. 

STATUS OF STOCK

The status relative to OSP of false killer whales belonging to the insular stock is unknown, although this stock 

appears to have declined during the past two decades (Reeves et al. 2009; Baird 2009). A recent study (Ylitalo et 

al. 2009) documented elevated levels of polychlorinated biphenyls (PCBs) in three of nine insular false killer whales 

sampled, and biomass of some false killer whale prey species may have declined around the main Hawaiian Islands 

(Boggs & Ito 1993, Reeves et al. 2009). False killer whales are not listed as “threatened” or “endangered” under the 

Endangered Species Act (1973), nor as “depleted” under the MMPA. In September 2009, a petition was submitted 

to NMFS to list the Hawaiian insular false killer whale stock as an endangered species under the ESA, and NMFS 

has initiated a status review to determine if such a listing is warranted. The estimated average annual human-caused 

mortality and serious injury for this stock (0.60 animals per year) is slightly less than the PBR (0.61); therefore, the 

insular false killer whale stock is not considered “strategic” under the 1994 amendments to the MMPA. However, 

the current estimate of mortality and serious injury does not include additional unidentified animals that may have 

been false killer whales and were taken within the insular stock range, and the status of this stock is likely to change 

once methods have been developed to prorate these additional takes. 

HAWAII PELAGIC STOCK

POPULATION SIZE

 Analyses of a 2002 shipboard line-transect survey of the Hawaiian Islands EEZ (HICEAS survey) resulted 

in an abundance estimate of 236 (CV=1.13) false killer whales (Barlow 2006) outside of 75 nm of the main 

Hawaiian Islands. A recent re-analysis of the HICEAS data using improved methods and incorporating additional 

sighting information obtained on line-transect surveys south of the Hawaiian EEZ during 2005, resulted in a revised 

estimate of 484 (CV = 0.93) false killer whales within the Hawaiian Islands EEZ outside of about 75 nmi of the 

main Hawaiian Islands (Barlow & Rankin 2007). This is the best available abundance estimate for the pelagic stock 

of false killer whales. The 2005 survey (Barlow and Rankin 2007) also resulted in a separate abundance estimate of 

906 (CV=0.68) false killer whales in international waters south of the Hawaiian Islands EEZ and within the EEZ of 

Johnston Atoll, but it is unknown how many of these animals might belong to the Hawaii pelagic stock. 

 

Minimum Population Estimate

 The log-normal 20th percentile of the 2002 abundance estimate for the Hawaiian Islands EEZ outside of 75 

nmi from the main Hawaiian Islands (Barlow & Rankin 2007) is 249 false killer whales. 

Current Population Trend

 No data are available on current population trend. 

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

 No data are available on current or maximum net productivity rate for this species in Hawaiian waters. 

POTENTIAL BIOLOGICAL REMOVAL

 Following the NMFS Guidelines for Assessing Marine Mammal Stocks (NMFS 2005), the PBR is 

calculated only within the U.S. EEZ of the Hawaiian Islands, because estimates of human-caused mortality and 

serious injury are not available from all U.S. and non-U.S. sources in international waters where this stock may 

occur. The potential biological removal (PBR) level for the Hawaii pelagic stock of false killer whale is thus 

calculated as the minimum population size within the U.S. EEZ of the Hawaiian Islands (249) times one half the 

default maximum net growth rate for cetaceans (1⁄2 of 4%) times a recovery factor of 0.50 (for a stock of unknown 

status with a Hawaiian Islands EEZ mortality and serious injury rate CV≤0.30; Wade and Angliss 1997), resulting in 

a PBR of 2.5 false killer whales per year. 

STATUS OF STOCK

 The status of the Hawaii pelagic stock of false killer whale 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 stock. The 

stock is not listed as “threatened” or “endangered” under the Endangered Species Act (1973), nor as “depleted” 

under the MMPA. Following the NMFS Guidelines for Assessing Marine Mammal Stocks (NMFS 2005), the status 

of this transboundary stock of false killer whales is assessed based on the estimated abundance and estimates of 

mortality and serious injury within the U.S. EEZ of the Hawaiian Islands, because estimates of human-caused 

245
mortality and serious injury from all U.S. and non-U.S. sources in international waters are not available, and because 

the geographic range of this stock beyond the Hawaiian Islands EEZ is poorly known. Because the rate of mortality 

and serious injury to false killer whales within the Hawaiian Islands EEZ (7.3 animals per year) exceeds the PBR 

(2.5), this stock is considered a “strategic stock” under the 1994 amendments to the MMPA. Furthermore, 

additional injury or mortality of unidentified cetaceans that may have been false killer whales is known to occur in 

the U.S. longline fisheries, but these animals have not yet been included in the Hawaii pelagic stock status 

assessment. The total fishery mortality and serious injury for the Hawaii pelagic stock of false killer whales cannot 

be considered to be insignificant and approaching zero, because it exceeds the PBR. . 

The National Marine Fisheries Service recognizes that the assessment of this transboundary stock based 

only on abundance and human-caused mortality and serious injury within the U.S. EEZ of Hawaii introduces 

uncertainty and has considered whether the status assessment would change if animals outside the Hawaiian Islands 

EEZ are considered. Using all available peer-reviewed information on the abundance of false killer whales on the 

high-seas and within the EEZ of Johnston Atoll , a PBR can be calculated as the lower 20th percentile of the Barlow 

and Rankin (2007) abundance estimate (530), 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 with a mortality and serious injury rate 

CV≤0.30; Wade and Angliss 1997), resulting in 5.3 false killer whales per year. The abundance estimate may be 

based on a smaller geographic area than the (unknown) full range of the pelagic stock, because areas to the north of 

the Hawaiian Islands EEZ are not included; however, the estimate meets the definition of a ‘minimum population 

estimate’ under the MMPA. Bycatch information for the high seas is incomplete, because the levels of false killer 

whale takes in non-U.S. fisheries are not known. The average annual estimated mortality and serious injury by U.S. 

longline vessels operating on the high seas and within the EEZ of Johnston Atoll is 5.4 (CV=0.3; McCracken and 

Forney 2010). This value is greater than the PBR of 5.3, and the combined U.S. and international mortality and 

serious injury is likely substantially higher, because fishing effort by foreign vessels may be up to six times greater 

than that of the US fleet (NMFS, unpublished data). Better information on the full geographic range of this stock and 

quantitative estimates of bycatch in international fisheries are needed to reduce the uncertainties regarding impacts 

of false killer whale takes on the high seas, but these uncertainties do not change the current assessment that the 

pelagic false killer whale stock is strategic. 

PALMYRA STOCK

POPULATION SIZE

 Recent line transect surveys in the U.S. EEZ waters of Palmyra Atoll produced an estimate of 1,329 (CV = 

0.65) false killer whales (Barlow & Rankin 2007). This is the best available abundance estimate for false killer 

whales within the Palmyra Atoll EEZ. 

Minimum Population Estimate

 The log-normal 20th percentile of the 2002 abundance estimate for the Palmyra Atoll EEZ (Barlow & 

Rankin 2007) is 806 false killer whales. 

Current Population Trend

 No data are available on current population trend. 

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

 No data are available on current or maximum net productivity rate for this species in Palmyra Atoll waters. 

POTENTIAL BIOLOGICAL REMOVAL

 The potential biological removal (PBR) level for the Palmyra Atoll false killer whale stock is calculated as 

the minimum population size (806) 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 and serious injury rate CV >0.80; 

Wade and Angliss 1997), resulting in a PBR of 6.4 false killer whales per year. 

STATUS OF STOCK

 The status of false killer whales in Palmyra Atoll EEZ 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 stock. The 

stock is not listed as “threatened” or “endangered” under the Endangered Species Act (1973), nor as “depleted” 

under the MMPA. The rate of mortality and serious injury to false killer whales within the Palmyra Atoll EEZ in 

the Hawaii-based longline fishery (0.3 animals per year) does not exceed the PBR (6.4) for this stock and thus, this 

stock is not considered “strategic” under the 1994 amendments to the MMPA. The total fishery mortality and 

246
serious injury for Palmyra Atoll false killer whales is less than 10% of the PBR and, therefore, can be considered to 

be insignificant and approaching zero. Additional injury and mortality of false killer whales is known to occur in 

U.S and international longline fishing operations in international waters, and the potential effect on the Palmyra 

stock is unknown. 

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Revised 01/15/2011 

FALSE KILLER WHALE (Pseudorca crassidens): 

American Samoa Stock 

STOCK DEFINITION AND GEOGRAPHIC 

RANGE 

False killer whales are found worldwide 

mainly in tropical and warm-temperate waters 

(Stacey et al. 1994). The species is welldocumented throughout the tropical and sub-tropical 

south Pacific, from Papua New Guinea and 

Australia to the line islands (Reeves et al. 1999). 

The species has been taken in the drive hunt in the 

Solomon Islands (Reeves et al 1999). ). During 

small-boat surveys from 2003 to 2006 in the waters 

surrounding the island of Tutuila, American Samoa, 

false killer whales were observed during summer 

surveys on five occasions (Johnston et al 2008). 

During a shipboard survey in 2006 false killer 

whales were also encountered just north of the 

island of Ta‘u, in the Manu’a Group within 

American Samoa (Johnston et al. 2008). Two false 

killer whales were entangled near 40-Fathom Bank 

south of the islands by the American Samoa-based 

longline fishery in 2008 (Oleson 2009), indicating 

some false killer whales maintain a more pelagic 

distribution. Five genetic samples collected near 

Tutuila are available for comparison to other false 

killer whale populations throughout the Pacific 

(Johnston et al 2008). For the Marine Mammal 

Protection Act (MMPA) stock assessment reports, 

there are four Pacific management stocks: 1) The 

Hawaii Insular Stock, which includes animals found 

within the 25-75 nmi longline exclusion boundary 

surrounding the main Hawaiian Islands, 2) The 

Hawaii Pelagic Stock, which includes animals 

found within the U.S. EEZ of the Hawaiian Islands 

but outside the 25-75 nmi longline exclusion zone, 

3) The Palmyra Stock, which includes animals 

found within the U.S. EEZ of the Palmyra Atoll, 

and 4) The American Samoa Stock, which includes 

animals found within the U.S. EEZ A

Figure 1. False killer whale sightings during visual 

surveys from 2003-2006 (Johnston et al 2008). 

merican 

amoa (this report). 

POPUL

Samoa (area size = 404,578 km2

) 

ields a range of plausible abundance estimates of 87 – 1,538 false killer whales. 

S

ATION SIZE 

No abundance estimates are currently available for false killer whales in U.S. EEZ waters of American 

Samoa; however, density estimates for false killer whales in other tropical Pacific regions can provide a range of 

likely abundance estimates in this unsurveyed region. Published estimates of false killer whales (animals per km2

) 

in the Pacific are: 0.0002 (CV= 0.93) for the U.S. EEZ of the Hawaiian Islands (Barlow and Rankin 2007); 0.0038 

(CV=0.65) for the U.S. EEZ around Palmyra, (Barlow and Rankin 2007), 0.0021 (CV=0.64) and 0.0016 (CV=0.31) 

for the eastern tropical Pacific Ocean (Wade and Gerrodette 1993; Ferguson and Barlow 2003). Applying the lowest 

and highest of these density estimates to U.S. EEZ waters surrounding American

y

249
Minimu

he American Samoa EEZ, based on the densities observed 

lsewhere, range from 45 – 936 false killer whales. 

Current

No data are available on current population trend. 

CURRE

No data are available on current or maximum net productivity rate. 

POTEN

d the default growth rate (1⁄2 of 4%), the PBR would likely fall between 0.4 and 7.5 false killer 

hales per year. 

ANNUA

ercial fisheries for false killer whales in American Samoa waters is 7.8 (CV=1.7) 

animals 

life 

Sources (DMWR), no estimates of annual human-caused mortality and serious injury of cetaceans are available. 

m Population Estimate 

No minimum population estimate is currently available for waters surrounding American Samoa, but the 

false killer whale density estimates from other tropical Pacific regions (Barlow and Rankin 2007, Wade and 

Gerrodette 1993, Ferguson and Barlow 2003, see above) can provide a range of likely values. The lognormal 20th

percentiles of plausible abundance estimates for t

e

 Population Trend 

NT AND MAXIMUM NET PRODUCTIVITY RATES 

TIAL BIOLOGICAL REMOVAL 

No PBR can presently be calculated for false killer whales within the American Samoa EEZ, but based on 

the range of plausible minimum abundance estimates (45 - 936), a recovery factor of 0.40 (for a species of unknown 

status with a fishery mortality and serious injury rate CV > 0.80 within the American Samoa EEZ; Wade and 

Angliss 1997), an

w

L HUMAN-CAUSED MORTALITY AND

Information on fishery-related 

mortality of cetaceans in American Samoan 

waters is limited, but the gear types used in 

American Samoas 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 cetaceans 

(Perrin et al. 1994). The primary fishery in 

American Samoa is the commercial pelagic 

longline fishery that targets tunas, which 

was introduced in 1995 (Levine and Allen 

2009). In 2008, there were 28 federally 

permitted vessels within the longline fishery 

in American Samoa. The fishery has been 

monitored since March 2006 under a 

mandatory observer program, which records 

all interactions with protected species 

(Pacific Islands Regional Office 2009). 

Two false killer whales were killed or 

seriously injured by the fishery in 2008 

(Oleson 2009). The average annual serious 

injury and mortality in comm

 SERIOUS INJURY 

Figure 2. Locations of observed false killer whale takes (filled 

diamonds) in the American Samoa longline fishery, 2006-2008. 

Solid line represents the U.S. EEZ. Set locations in this fishery 

are summarized in Appendix 1. 

per year (Table 1). 

Prior to 1995, bottomfishing and trolling were the primary fisheries in American Samoa but became less 

prominent after longlining was introduced (Levine and Allen 2009). Nearshore subsistence fisheries include spear 

fishing, rod and reel, collecting, gill netting, and throw netting (Craig 1993, Levine and Allen 2009). Information on 

fishery-related mortality of cetaceans in the nearshore fisheries is unknown, but the gear types used in American 

Samoan 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. Although boat-based nearshore 

fisheries have been randomly monitored since 1991, by the American Samoa Department of Marine and Wild

250
STATU

ales is 

significant and approaching zero, but this appears unlikely given the estimated takes and likely PBR range. 

th at least 10 sets/trip (Oleson 2009). Mean annual takes are based on 

2006-2008 data unless otherwise indicated. 

Observed and estimated of false killer whales in 

t

S OF STOCK 

The status of false killer whales in American Samoan 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 stock. False 

killer whales are not listed as “threatened” or “endangered” under the Endangered Species Act (1973), nor as 

“depleted” under the MMPA. The status of the American Samoa stock of false killer whales under the 1994 

amendments to the MMPA cannot be determined at this time because no abundance estimates are available and PBR 

cannot be calculated. However, the estimated rate of fisheries related mortality and serious injury within the 

American Samoa EEZ (7.8 animals per year) exceeds the range of likely PBRs (0.4 – 7.5) for this region, suggesting 

that this stock would probably be strategic if abundance estimates were available. Additional research on the 

abundance of false killer whales in American Samoa is required to resolve this stock's status. Insufficient 

information is available to determine whether the total fishery mortality and serious injury for false killer wh

in

Table 1. Summary of available information on incidental mortality and serious injury of false killer whales 

(American Samoa stock) in commercial fisheries operating within the U.S. EEZs (Oleson 2009). Longline fishery 

take estimates represent only those trips wi

mortality and serious injury 

he American Samoa EEZ

Fishery Name Year American Samoa EEZ Data Type

Per er 

Coverage

Obs. Estimated (CV) Mean Annual Takes 

(CV)

cent Observ

American 

Samoa-based 

longline fishery 2008

o r 

data 8.5% 2 23.5 (1.9) 7.8 (1.7)

2006

2007 bserve 9.0%7.7% 

0

0 

0 (-) 

0 (-) 

Minimum total annual takes within U.S. EEZ waters 7.8 (1.7)

REFERENCES 

J. and S. Rankin. False killer whale abundance and density: Preliminary estimates for PICEAS study area 

south of Hawaii and new estimates for the U.S. EEZ around Hawaii. Administrative Report LJ-07-02, 

Southwest Fisherie

Barlow, 

s Science Center, National Marine Fisheries Service, 8604 La Jolla Shores Drive, La 

Craig, P

n Samoa –Fisheries of Hawaii and U.S. – associated pacific Islands. Marine Fisheries Review, 

Ferguson

ries Science Center, National Marine Fisheries Service, 8604 La Jolla 

Johnston

e waters of American Samoa, 2003-2006. Journal of 

Levine, a fishing community. U.S. Dep. Commer., NOAA Tech. 

Oleson, s of the American Samoa Longline Fishery and Estimates of Cetacean Take, 2006-

Perrin, W onovan and J. Barlow. 1994. Gillnets and Cetaceans. Rep. Int. Whal. Commn., Special Issue 

Reeves, 

vironment Programme (SPREP). South Pacific Regional Environment Programme, 

Jolla, CA 92037. 

., B. Ponwith, F. Aitaoto, and D. Hamm. 1993. The commercial, subsistence, and recreational fisheries of 

America

Spring. 

, M. C. and J. Barlow. 2003. Addendum: Spatial distribution and density of cetaceans in the eastern 

tropical Pacific Ocean based on summer/fall research vessel surveys in 1986-96. Administrative Report LJ01-04 (addendum), Southwest Fishe

Shores Drive, La Jolla, CA 92037. 

, D.W., J. Robbins, M.E. Chapla, D.K. Mattila, and K.R. Andrews. 2008. Diversity, habitat associations, 

and stock structure of odontocete cetaceans in th

Cetacean Research and Management 10(1):59-66. 

A., and S. Allen. 2009. American Samoa as

Memo., NOAA-TM-NMFS-PIFSC-19, 74 p. 

E.M. 2009. Characteristic

2008. PSRG-2009-14. 

.F., G. P. D

15, 629 pp. 

R., S. Leatherwood, G.S. Stone, and L.G. Eldredge. 1999. Marine mammals in the area served by the South 

Pacific Regional En

Apia, Samoa. 48pp. 

Stacey, P. J., S. Leatherwood, and R. W. Baird. 1994. Pseudorca crassidens. Mamm. Spec. 456:l-6. 

251
n. U. S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR12. 93 pp. 

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

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

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

Workshop April 3-5, 1996, Seattle, Washingto

252
Revised 01/15/2011

KILLER WHALE (Orcinus orca): 

Hawaiian Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

 Killer whales have been observed 

in all oceans and seas of the world 

(Leatherwood and Dahlheim 1978). 

Although reported from tropical and 

offshore waters (Heyning and Dahlheim 

1988), killer whales prefer the colder 

waters of both hemispheres, with greatest 

abundances found within 800 km of major 

continents (Mitchell 1975). They are 

considered rare in Hawaiian waters. No 

killer whales were seen during 1993-98 

aerial surveys within about 25 nmi of the 

main Hawaiian Islands, but one sighting 

was reported during subsequent surveys 

(Mobley et al. 2000, 2001). Two 

sightings of killer whales were made 

during a 2002 shipboard survey of waters 

within the U.S. Exclusive Economic Zone 

(EEZ) of the Hawaiian Islands (Figure 1; 

Barlow 2006). One stranding from the 

island of Hawaii was reported in 1950 

(Richards 1952) and 21 additional 

sightings or strandings were reported 

around the main Hawaiian Islands, French 

Frigate Shoals, and offshore of the 

Hawaiian islands (Baird et al. 2006). 

Except in the northeastern Pacific where "resident", "transient", and “offshore” stocks have been described for 

coastal waters of Alaska, British Columbia, and Washington to California (Bigg 1982; Leatherwood et al. 1990, 

Bigg et al. 1990, Ford et al. 1994), little is known about stock structure of killer whales in the North Pacific. Baird 

et al. ( 2006) report a sighting of this species off the island of Hawaii in 2003 and also note analyses of genetic 

results from two samples collected, indicating a haplotype similar to the Gulf of Alaska “transient” killer whales 

and one similar to that of mammal eating killer whales in coastal Alaska. For the Marine Mammal Protection Act 

(MMPA) stock assessment reports, eight killer whale stocks are recognized within the Pacific U.S. EEZ: 1) the 

Eastern North Pacific Alaska Resident stock - occurring from southeastern Alaska to the Aleutian Islands and 

Bering Sea, 2) the Eastern North Pacific Northern Resident stock - occurring from British Columbia through part of 

southeastern Alaska, 3) the Eastern North Pacific Southern Resident stock – occurring mainly within the inland 

waters of Washington State and southern British Columbia, but also in coastal waters from British Columbia 

through California, 4) the Eastern North Pacific Gulf of Alaska, Aleutian Islands, and Bering Sea Transient stock - 

occurring mainly from Prince William Sound through the Aleutian Islands and Bering Sea, 5) the AT1 Transient 

stock - occurring in Alaska from Prince William Sound through the Kenai Fjords, 6) the West Coast Transient stock 

- occurring from California through southeastern Alaska, 7) the Eastern North Pacific Offshore stock - occurring 

from California through Alaska, and 8) the Hawaiian stock (this report). The Hawaii stock includes animals found 

both within the Hawaiian Islands EEZ and in adjacent international waters; however, because data on abundance, 

distribution, and human-caused impacts are largely lacking for international waters, the status of this stock is 

evaluated based on data from U.S. EEZ waters of the Hawaiian Islands (NMFS 2005).Stock assessment reports for 

the Southern Resident, Eastern North Pacific Offshore, and Hawaiian stocks can be found in the Pacific Region 

stock assessment reports; all other killer whale stock assessments are included in the Alaska Region stock 

assessments. 

W180 W175 W170 W165 W160 W155 W150

N10

N15

N20

N25

N30

N35

Figure 1. Killer whale sighting locations during the 2002 shipboard 

survey of U.S. EEZ waters surrounding the Hawaiian Islands 

(Barlow 2006; see Appendix 2 for details on timing and location of 

survey effort). Outer line represents approximate boundary of survey 

area and U.S. EEZ. 

253
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). A 2002 shipboard line-transect 

survey of the entire Hawaiian Islands EEZ resulted in an abundance estimate of 349 (CV=0.98) killer whales 

(Barlow 2006). This is currently the best available abundance estimate for this stock. 

Minimum Population Estimate

 The log-normal 20th percentile of the 2002 abundance estimate (Barlow 2006) is 175 killer whales within 

the Hawaiian Islands EEZ. 

Current Population Trend

 No data are available on current population trend. 

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

 No data are available on current and maximum net productivity rate in Hawaiian waters. 

POTENTIAL BIOLOGICAL REMOVAL

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

within the U.S. EEZ of the Hawaiian Islands (175) times one half the default maximum net growth rate for cetaceans 

(1⁄2 of 4%) times a recovery factor of 0.50 (for a stock of unknown status with no known fishery mortality or serious 

injury within the Hawaiian Islands EEZ; Wade and Angliss 1997), resulting in a PBR of 1.8 killer whales per year. 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Fishery Information

 Information on fishery-related mortality and serious injury of cetaceans in Hawaiian waters is limited, but 

the gear types used in Hawaiian fisheries are responsible for marine mammal mortality and serious injury in other 

fisheries throughout U.S. waters. Gillnets appear to capture marine mammals wherever they are used, and float lines 

from lobster traps and longlines can be expected to occasionally entangle cetaceans (Perrin et al. 1994). 

 Interactions with cetaceans have been reported for all Hawaiian pelagic fisheries (Nitta and Henderson 

1993), but killer whale interactions appear to be rare. In 1990, a solitary killer whale was reported to have removed 

the catch from a longline in Hawaii (Dollar 1991). There are currently two distinct longline fisheries based in 

Hawaii: a deep-set longline (DSLL) fishery that targets primarily tunas, and a shallow-set longline fishery (SSLL) 

that targets swordfish. Both fisheries operate within U.S. waters and on the high seas. Between 2004 and 2008, no 

killer whales were observed hooked or entangled in the SSLL fishery (100% observer coverage) or the DSLL 

fishery (20-28% observer coverage) (McCracken & Forney 2010). Interaction rates between dolphins and the NWHI 

bottomfish fishery have been estimated based on studies conducted in 1990-1993, indicating that an average of 2.67 

dolphin interactions, most likely involving bottlenose and rough-toothed dolphins, occurred for every 1000 fish 

brought on board (Kobayashi and Kawamoto 1995). Fishermen claim interactions with dolphins that steal bait and 

catch are increasing. It is not known whether these interactions result in serious injury or mortality of dolphins, nor 

whether killer whales are involved. 

STATUS OF STOCK

 The status of killer whales in Hawaiian waters relative to OSP is unknown, and there are insufficient data to 

evaluate trends in abundance. No habitat issues are known to be of concern for this stock. This species is not listed 

as “threatened” or “endangered” under the Endangered Species Act (1973), nor as “depleted” under the MMPA. 

Given the absence of recent fishery-related mortality or serious injuries, the Hawaiian stock of killer whales is not 

considered strategic under the 1994 amendments to the MMPA, and the total fishery mortality and serious injury can 

be considered to be insignificant and approaching zero. 

REFERENCES 

Baird, R.W., D.J. McSweeney, C. Bane, J. Barlow, D.R. Salden, L.K. Antoine, R.G. DeLuc, and D.L. Webster. 

2006. Killer whales in Hawaiian waters: Information on population identity and feeding habits. Pacific 

Science 60(4): 523-530.

Barlow, J. 2006. Cetacean abundance in Hawaiian waters estimated from a summer/fall survey in 2002. Marine 

Mammal Science 22(2): 446-464. 

254
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. 

Forney, K.A. 2009. Serious injury determinations for cetaceans caught in Hawaii longline fisheries during 1994-

2008. Draft document PSRG-2009-09 presented to the Pacific Scientific Review Group, November 3-5, 

2009, Del Mar, CA. 

Heyning, J. E. and M. E. Dahlheim. 1988. Orcinus orca. Mamm. Spec.304:1-9. 

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. 

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. 

McCracken M., and K.A. Forney. 2010. Preliminary assessment of incidental interactions with marine mammals in 

the Hawaii longline deep and shallow set fisheries. NMFS, Pacific Islands Fisheries Science Center 

Working Paper WP-10-001. 27p 

Mitchell, E. D. 1975. Report on the meeting on small cetaceans, Montreal, April 1-11, 1974. J. Fish. Res. Board 

Canada, 32:914-916. 

Mobley, J. R., Jr, S. S. Spitz, K. A. Forney, R. A. Grotefendt, and P. H. Forestall. 2000. Distribution and 

abundance of odontocete species in Hawaiian waters: preliminary results of 1993-98 aerial surveys Admin. 

Rep. LJ-00-14C. Southwest Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La 

Jolla, CA 92038. 26 pp. 

Mobley, J. R. , L. Mazzuca, A. S. Craig, M. W. Newcomer, and S. S. Spitz. 2001. Killer whales (Orcinus orca) 

sighted West of Ni'ihau, Hawai'i. Pacific Science 55:301_303. 

Nitta, E. and J. R. Henderson. 1993. A review of interactions between Hawaii's fisheries and protected species. 

Mar. Fish. Rev. 55(2):83-92. 

Perrin, W.F., G. P. Donovan and J. Barlow. 1994. Gillnets and Cetaceans. Rep. Int. Whal. Commn., Special Issue 

15, 629 pp. 

Richards, L. P. 1952. Cuvier's beaked whale from Hawaii. J. Mamm. 33:255. 

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

Workshop April 3-5, 1996, Seattle, Washington. U. S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR12. 93 pp. 

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

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

255
Revised 01/15/2011

SHORT-FINNED PILOT WHALE (Globicephala macrorhynchus): 

Hawaiian Stock 

STOCK DEFINITION AND GEOGRAPHIC RANGE 

 Short-finned pilot whales are found in all 

oceans, primarily in tropical and warm-temperate 

waters. They are commonly observed around the 

main Hawaiian Islands and are also present around 

the Northwestern Hawaiian Islands (Shallenberger 

1981; Barlow 2006). During a 2002 shipboard 

survey of waters within the U.S. Exclusive 

Economic Zone (EEZ) of the Hawaiian Islands, 25 

sightings of short-finned pilot whales were made 

(Figure 1; Barlow 2006). Fourteen strandings of 

short-finned pilot whales have been documented 

from the main Hawaiian Islands, including five 

mass strandings (Tomich 1986; Nitta 1991; 

Maldini et al. 2005). Stock structure of shortfinned pilot whales has not been adequately 

studied in the North Pacific, except in Japanese 

waters, where two forms have been identified 

based on pigmentation patterns and differences 

in the shape of the heads of adult males (Kasuya 

et al. 1988). The pilot whales in Hawaiian 

waters are similar morphologically to the 

Japanese "southern form." Preliminary photoidentification work with pilot whales in Hawaii indicated a high degree of site fidelity around the main island of 

Hawaii (Shane and McSweeney 1990) and around Kauai and Niihau (Baird et al. 2006). 

 Genetic analyses of tissue samples collected near the main Hawaiian Islands indicate that Hawaiian shortfinned pilot whales are reproductively isolated from short-finned pilot whales found in the eastern Pacific Ocean (S. 

Chivers, NMFS/SWFSC, unpublished data); however, the offshore range of this Hawaiian population is unknown. 

Fishery interactions with short-finned pilot whales demonstrate that this species also occurs in U.S. EEZ waters of 

Palmyra Atoll and Johnston Atoll (Figure 2), but it is not known whether these animals are part of the Hawaiian 

stock or whether they represent separate stocks of short-finned pilot whales. Based on patterns of movement and 

population structure observed in other island-associated cetaceans (Norris and Dohl 1980; Norris et al.1994; Baird et 

al. 2008a, 2008b, 2009, Chivers et al 2007, McSweeney et al. 2007, 2009), it is possible that the animals around 

Palmyra Atoll and Johnston Atoll are one or more separate stocks. Efforts are currently underway to obtain 

additional samples of short-finned pilot whales for further studies of population structure in the North Pacific Ocean. 

For the Marine Mammal Protection Act (MMPA) stock assessment reports, short-finned pilot whales within the 

Pacific U.S. EEZ are divided into two discrete, non-contiguous areas: 1) Hawaiian waters (this report), and 2) waters 

off California, Oregon and Washington. Information on short-finned pilot whales around Palmyra Atoll and 

Johnston Atoll will provisionally be included with this stock assessment report, recognizing that separate stock 

status may be warranted for these animals in the future. Estimates of abundance, potential biological removals, and 

status determinations will be presented separately for U.S. waters of the Hawaiian Islands, Palmyra Atoll, and 

Johnston Atoll. The Hawaii, Johnston, and Palmyra stocks each include animals found both within the Hawaiian 

Islands EEZ and in adjacent international waters; however, because data on abundance, distribution, and humancaused impacts are largely lacking for international waters, the status of each stock is evaluated based on data from 

U.S. EEZ waters (NMFS 2005). 

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. A 2002 shipboard line-transect survey of the entire 

Hawaiian Islands EEZ resulted in an abundance estimate of 8,846 (CV=0.49) short-finned pilot whales (Barlow 

Figure 1. Short-finned pilot whale sighting locations during 

the 2002 shipboard survey of U.S. EEZ waters surrounding the 

Hawaiian Islands (Barlow 2006); see Appendix 2 for details on 

timing and location of survey effort). Outer line represents 

approximate boundary of survey area and U.S. EEZ. 

W180 W175 W170 W165 W160 W155 W150

N10

N15

N20

N25

N30

N35

256
2006). This is currently the best available abundance estimate for short-finned pilot whales within the Hawaiian 

Islands EEZ. 

No abundance estimates are currently available for short-finned pilot whales in U.S. EEZ waters of 

Palmyra Atoll; however, density estimates for short-finned pilot whales in other Pacific regions can provide a range 

of likely abundance estimates in this unsurveyed region. Published estimates of short-finned pilot whale density 

(animals per km2

) in the Pacific are: 0.0040 (CV=0.38) for the U.S. EEZ of the Hawaiian Islands (Barlow 2006); 

0.0237 (CV=0.32) for nearshore waters surrounding the main Hawaiian Islands (Mobley et al. 2000), 0.0084 

(CV=0.14) and 0.0040 (CV=0.23) for the eastern tropical Pacific Ocean (Wade and Gerrodette 1993; Ferguson and 

Barlow 2003), and 0.0025 (CV=0.29) for the eastern tropical Pacific Ocean west of 120°W and north of 5°N 

(Ferguson and Barlow 2003). Applying the lowest and highest of these density estimates to U.S. EEZ waters 

surrounding Palmyra Atoll (area size = 352,821 km2

) yields a range of plausible abundance estimates of 891-8,362 

short-finned pilot whales. Similarly, there are no abundance estimates for short-finned pilot whales in U.S. EEZ 

waters of Johnston Atoll. Applying the lowest and highest of the above density estimates to U.S. EEZ waters 

surrounding Johnston Atoll (area size = 443,586 km2

) yields a range of plausible abundance estimates of 1,121-

10,513 short-finned pilot whales. 

 

Minimum Population Estimate

 The log-normal 20th percentile of the 2002 abundance estimate for the Hawaiian Islands EEZ (Barlow 

2006) is 5,986 short-finned pilot whales. No minimum population estimate is currently available for waters 

surrounding Palmyra Atoll or Johnston Atoll, but the short-finned pilot whale density estimates from other Pacific 

regions (Barlow 2006, Mobley et al. 2000, Wade and Gerrodette 1993, Ferguson and Barlow 2003; see above) can 

provide a range of likely values. The lognormal 20th percentiles of plausible abundance estimates for the Palmyra 

Atoll EEZ, based on the densities observed elsewhere, range from 701 to 6,429 short-finned pilot whales. The 

lognormal 20th percentiles of plausible abundance estimates for the Johnston Atoll EEZ, based on the densities 

observed elsewhere, range from 882 to 8,083 short-finned pilot whales. 

Current Population Trend

 No data are available on current population trend. 

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

 No data are available on current or maximum net productivity rate. 

POTENTIAL BIOLOGICAL REMOVAL 

 The potential biological removal (PBR) level for the Hawaiian short-finned pilot whale stock is calculated 

as the minimum population size (5,986) times one half the default maximum net growth rate for cetaceans (1⁄2 of 4%) 

times a recovery factor of 0.40 (for a species of unknown status with a Hawaiian Islands EEZ fishery mortality and 

serious injury rate CV> 0.80; Wade and Angliss 1997), resulting in a PBR of 48 short-finned pilot whales per year. 

No separate PBR can presently be calculated for Palmyra Atoll waters, but based on the range of plausible minimum 

abundance estimates (701-6,429), a recovery factor of 0.50 (for a species of unknown status with no known fishery 

mortality and serious injury within the Palmyra Atoll EEZ; Wade and Angliss 1997), and the default growth rate (1⁄2 

of 4%), the PBR would likely fall between 7.0 and 64 short-finned pilot whales per year. Similarly, based on the 

range of plausible minimum abundance estimates for Johnston Atoll (882-8,083), a recovery factor of 0.40 (for a 

species of unknown status with a fishery mortality and serious injury rate CV>0.80 within the Johnston Atoll EEZ; 

Wade and Angliss 1997), and the default growth rate (1⁄2 of 4%), the PBR would likely fall between 7.1 and 65 

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 cetaceans (Perrin et al. 1994). 

257
Figure 2. Locations of short-finned pilot whale takes (filled 

diamonds) and possible takes of this species (open diamonds) in 

Hawaii-based longline fisheries, 2004-2008 . Solid lines represent 

the U. S. EEZ. Fishery descriptions are provided in Appendix 1. 

Interactions with cetaceans 

have been reported for all Hawaiian 

pelagic fisheries (Nitta and Henderson 

1993). There are currently two distinct 

longline fisheries based in Hawaii: a 

deep-set longline (DSLL) fishery that 

targets primarily tunas, and a shallowset longline fishery (SSLL) that targets 

swordfish. Both fisheries operate within 

U.S. waters and on the high seas. 

Between 2004 and 2008, no shortfinned pilot whales were observed 

hooked or entangled in the SSLL 

fishery (100% observer coverage), and 

eight short-finned pilot whales were 

observed taken in the DSLL fishery 

(20-28% observer coverage) (Forney 

2009, McCracken 2009). Based on an 

evaluation of the observer’s description 

of the interaction and following the 

most recently developed criteria for 

assessing serious injury in marine 

mammals (Andersen et al. 2008), two 

short-finned pilot whales taken in 

international waters were considered not 

seriously injured, and the remaining six 

(four in international waters, one in the 

Hawaiian Islands EEZ, and one in the 

EEZ of Johnston Atoll) were considered 

seriously injured (Forney 2009). Average 

5-yr estimates of annual mortality and serious injury for 2004-2008 are 2.0 (CV = 0.5) short-finned pilot whales 

outside of U.S. EEZs, 0.7 (CV=1.4) within the Hawaiian Islands EEZ, and 0.5 (CV=0.8) within the Johnston Atoll 

EEZ (McCracken & Forney 2010). Eight additional unidentified cetaceans, which may have been short-finned-pilot 

whales, were also taken during 2004-2008. Six of these were taken in the DSLL fishery in Hawaiian Islands EEZ 

waters, one was taken in the DSLL fishery in international waters, and one was taken in the SSLL fishery in 

international waters (Figure 2). Interaction rates between dolphins and the NWHI bottomfish fishery have been 

estimated based on studies conducted in 1990-1993, indicating that an average of 2.67 dolphin interactions, most 

likely involving bottlenose and rough-toothed dolphins, occurred for every 1000 fish brought on board (Kobayashi 

and Kawamoto 1995). Fishermen claim interactions with dolphins that steal bait and catch are increasing. It is not 

known whether these interactions result in serious injury or mortality of dolphins, nor whether short-finned pilot 

whales are involved. 

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. 

It is not listed as “threatened” or “endangered” under the Endangered Species Act (1973), nor as “depleted” under 

the MMPA. The Hawaiian stock of short-finned pilot whales is not considered strategic under the 1994 

amendments to the MMPA, because the estimated rate of mortality and serious injury within the Hawaiian Islands 

EEZ (0.7 animals per year) is less than the PBR (52). Although no estimates of abundance or PBR are currently 

available for short-finned pilot whales around Johnston Atoll, the estimated average rate of mortality and serious 

injury of short-finned pilot whales within the EEZ of Johnston Atoll ( 0.5 animals per year) is below the range of 

likely PBRs (7.1 to 65) for this region. There have been no serious injuries or mortality of short-finned pilot whales 

within the Palmyra Atoll EEZ. The potential effects of mortality and serious injuries of short-finned pilot whales in 

the Hawaii-based fishery in international waters is not known, because no abundance estimates or international 

bycatch estimates are available. Based on the available data, which indicate total fishery-related takes are less than 

10% of PBR, the total fishery mortality and serious injury for short-finned pilot whales can be considered to be 

258
insignificant and approaching zero. 

Table 1. Summary of available information on incidental mortality and serious injury of short-finned pilot whales 

(Hawaiian stock) in commercial fisheries, within and outside of the U.S. EEZs (McCracken & Forney 2010). Mean 

annual takes are based on 2004-2008 data unless otherwise indicated. 

Observed and estimated mortality and serious injury of short-finned pilot whales, by EEZ region 

Outside of U.S. EEZs Hawaiian Islands EEZ Johnston Atoll EEZ 

Fishery 

Name Year Data Type 

Percent 

Observer 

Coverage 

Obs. Estimated 

(CV) 

Mean 

Annual 

Takes 

(CV) 

Obs. Estimated 

(CV) 

Mean 

Annual 

Takes 

(CV) 

Obs. Estimated 

(CV) 

Mean 

Annual 

Takes 

(CV) 

Hawaiibased 

deep-set 

longline 

fishery 

2004 

2005 

2006 

2007 

2008 

observer 

data 

25% 

28% 

22% 

20% 

22% 

0 

1 

1 

1 

1 

0 (-) 

4 (0.4) 

1 (2.1) 

2 (1.5) 

3 (0.8) 

2.0 (0.5) 

0 

0 

1 

0 

0 

0 (-) 

0 (-) 

4 (0.7) 

0 (-) 

0 (-) 

0.7 

(1.4) 

1 

0 

0 

0 

0 

3 (0.2) 

0 (-) 

0 (-) 

0 (-) 

0 (-) 

0.5 

(0.8) 

Hawaiibased 

shallow-set 

longline 

fishery 

2004 

2005 

2006 

2007 

2008 

observer 

data 

100% 

100% 

100% 

100% 

100% 

0 

0 

0 

0 

0 

Same as 

observed 

0 (n/a) 

0 

0 

0 

0 

0 

Same as 

observed 

0 

0 

0 

0 

0 

0 

Same as 

observed 

0 

Minimum total annual takes within U.S. EEZ waters 1.2 (1.02) 

REFERENCES 

Andersen, M. S., K. A. Forney, T. V. N. Cole, T. Eagle, R. Angliss, K. Long, L. Barre, L. Van Atta, D. Borggaard, 

T. Rowles, B. Norberg, J. Whaley, and L. Engleby. 2008. Differentiating Serious and Non-Serious Injury 

of Marine Mammals: Report of the Serious Injury Technical Workshop, 10-13 September 2007, Seattle, 

Washington. NOAA Technical Memorandum NMFS-OPR-39. 94p. 

Baird, R.W., G.S. Schorr, D.L. Webster, S.D. Mahaffy, A.B. Douglas, A.M. Gorgone, and D.J. McSweeney. 2006. 

A survey for odontocete cetaceans off Kaua'i and Ni'ihau, Hawai'i, during October and November 2005: 

evidence for population structure and site fidelity. Report prepared under contract #AB133F05SE519 to 

Pacific Islands Fisheries Science Center, National Marine Fisheries Service, 2570 Dole Street, Honolulu, 

HI 96822, USA. 16p. 

Baird, R.W., A.M. Gorgone, D.J. McSweeney, D.L. Webster, D.R. Salden, M.H. Deakos, A.D. Ligon, G.S. Schorr, 

J. Barlow and S.D. Mahaffy. 2008a. False killer whales (Pseudorca crassidens) around the main Hawaiian 

Islands: long-term site fidelity, inter-island movements, and association patterns. Marine Mammal Science 

24:591-612. 

Baird, R.W., D.L. Webster, S.D. Mahaffy, D.J. McSweeney, G.S. Schorr and A.D. Ligon. 2008b. Site fidelity and 

association patterns in a deep-water dolphin: rough-toothed dolphins (Steno bredanensis) in the Hawaiian 

Archipelago. Marine Mammal Science 24:535-553. 

Baird, R.W., A.M. Gorgone, D.J. McSweeney, A.D. Ligon, M.H. Deakos, D.L. Webster, G.S. Schorr, K.K. Martien, 

D.R. Salden, and S.D. Mahaffy. 2009. Population structure of island-associated dolphins: evidence from 

photo-identification of common bottlenose dolphins (Tursiops truncatus) in the main Hawaiian Islands. 

Marine Mammal Science 25:251-274. 

Barlow, J. 2006. Cetacean abundance in Hawaiian waters estimated from a summer/fall survey in 2002. Marine 

Mammal Science 22: 446–464. 

Chivers, S. J., R. W. Baird, D. J. McSweeney, D. L. Webster, N. M. Hedrick, and J. C. Salinas. 2007. Genetic 

variation and evidence for population structure in eastern North Pacific false killer whales (Pseudorca 

crassidens). Can. J. Zool. 85: 783-794. 

Ferguson, M. C. and J. Barlow. 2003. Addendum: Spatial distribution and density of cetaceans in the eastern 

tropical Pacific Ocean based on summer/fall research vessel surveys in 1986-96. Administrative Report LJ01-04 (addendum), Southwest Fisheries Science Center, National Marine Fisheries Service, 8604 La Jolla 

Shores Drive, La Jolla, CA 92037. 

Forney, K.A. 2009. Serious injury determinations for cetaceans caught in Hawaii longline fisheries during 1994-

2008. Draft document PSRG-2009-09 presented to the Pacific Scientific Review Group, November 3-5, 

2009, Del Mar, CA. 

Kasuya, T., T. Miyashita, and F. Kasamatsu. 1988. Segregation of two forms of short-finned pilot whales off the 

259
Pacific coast of Japan. Sci. Rep. Whales Res. Inst. 39:77-90. 

Kobayashi, D. R. and K. E. Kawamoto. 1995. Evaluation of shark, dolphin, and monk seal interactions with 

Northwestern Hawaiian Island bottomfishing activity: a comparison of two time periods and an estimate of 

economic impacts. Fisheries Research 23: 11-22. 

Maldini, D., L. Mazzuca, and S. Atkinson. 2005. Odontocete stranding patterns in the Main Hawaiian Islands 

(1937-2002): How do they compare with live animal surveys? Pacific Science 59(1):55-67. 

McCracken M., and K.A. Forney. 2010. Preliminary assessment of incidental interactions with marine mammals in 

the Hawaii longline deep and shallow set fisheries. NMFS, Pacific Islands Fisheries Science Center 

Working Paper WP-10-001. 27p. 

McSweeney, D.J., R.W. Baird and S.D. Mahaffy. 2007. Site fidelity, associations and movements of Cuvier’s 

(Ziphius cavirostris) and Blainville’s (Mesoplodon densirostris) beaked whales off the island of Hawai‘i. 

Marine Mammal Science 23:666-687. 

McSweeney, D.J., R.W. Baird, S.D.Mahaffy, D.L. Webster, and G.S. Schorr. 2009. Site fidelity and association 

patterns of a rare species: Pygmy killer whales (Feresa attenuata) in the main Hawaiian Islands. Marine 

Mammal Science 25(4): 557-572. 

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. 

Norris, K. S., B. Würsig, R. S. Wells, and M. Würsig. 1994. The Hawaiian Spinner Dolphin. University of 

California Press, 408 pp. 

Norris, K. S. and T. P. Dohl. 1980. Behavior of the Hawaiian spinner dolphin, Stenella longirostris. Fish. Bull.

77:821-849. 

Perrin, W.F., G. P. Donovan and J. Barlow. 1994. Gillnets and Cetaceans. Rep. Int. Whal. Commn., Special Issue 

15, 629 pp. 

Shallenberger, E.W. 1981. The status of Hawaiian cetaceans. Final report to U.S. Marine Mammal Commission. 

MMC-77/23, 79pp. 

Shane, S. H. and D. McSweeney. 1990. Using photo-identification to study pilot whales social organization. Rep. 

Int. Whal. Commn. (Spec. Iss. 12):259-263. 

Tomich, P. Q. 1986. Mammals in Hawaii: A Synopsis and Notational Bibliography. Bishop Museum Press, Hawaii, 

375 pp. 

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

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

pp. 

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

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

260
Revised 01/15/2011

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. 

Resightings of individual Blainville’s 

beaked whales during a 21-yr study 

suggests long-term site fidelity and year 

round occurrence off the island of 

Hawaii (McSweeney et al. 2007). Three 

sightings were made during a 2002 

shipboard survey of waters within the 

U.S. Exclusive Economic Zone (EEZ) of 

the Hawaiian Islands (Figure 1; Barlow 

2006). Recent analysis of Blainville’s 

beaked whale movements off the Island 

of Hawaii suggest the existence of 

insular and offshore populations of this 

species in Hawaiian waters; however, further movement and genetic studies are needed to better understand 

individual movements and stock structure of Blainville’s beaked whales in Hawaii (McSweeney et al. 2007, Baird et 

al. 2009, Schorr et al., 2009).. Some genetic samples have been collected recently from around the main Hawaiian 

islands, (R.W. Baird, pers. comm.). For the Marine Mammal Protection Act (MMPA) stock assessment reports, 

three Mesoplodon stocks are defined within the Pacific U.S. EEZ: 1) M. densirostris in Hawaiian waters (this 

report), 2) M. stejnegeri in Alaskan waters, and 3) all Mesoplodon species off California, Oregon and Washington. 

The Hawaiian stock of Blainville’s beaked whales includes animals found both within the Hawaiian Islands EEZ 

and in adjacent international waters; however, because data on abundance, distribution, and human-caused impacts 

are largely lacking for international waters, the status of this stock is evaluated based on data from U.S. EEZ waters 

f the Hawaiian Islands (NMFS 2005). 

W180 W175 W170 W165 W160 W155 W150

N10

N15

N20

N25

N30

N35

Figure 1. Sighting locations of Mesoplodon densirostris (filled 

circles), Indopacetus pacificus (triangle), and unidentified 

Mesoplodon beaked whales (cross) during the 2002 shipboard

cetacean survey of U.S. EEZ waters surrounding the Hawaiian 

Islands (Barlow 2006; see Appendix 2 for details on timing and 

location of survey effort). Outer line indicates approximate boundary 

of survey area and U.S. EEZ.

o

POPULATION SIZE

 Based on the photo-identification catalog for the island of Hawaii, a minimum of 55 individuals are 

known to occur there (McSweeney et al. 2007). A 2002 shipboard line-transect survey of the entire Hawaiian 

Islands EEZ resulted in an abundance estimate of 2,872 (CV=1.17) Blainville’s beaked whales (Barlow 2006), 

including a correction factor for missed diving animals. This is currently the best available abundance estimate for 

this stock. 

Minimum Population Estimate

 The log-normal 20th percentile of the 2002 abundance estimate (Barlow 2006) is 1,314 Blainville’s beaked 

whales within the Hawaiian Islands EEZ. 

 

261
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 

within the U.S. EEZ of the Hawaiian Islands (1,314) 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 recent fishery 

mortality or serious injury within the Hawaiian Islands EEZ; Wade and Angliss 1997), resulting in a PBR of 13 

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 cetaceans (Perrin et al. 1994). 

 Interactions with cetaceans are 

reported for all pelagic fisheries (Nitta and 

Henderson 1993). There are currently two 

distinct longline fisheries based in Hawaii: a 

deep-set longline (DSLL) fishery that targets 

primarily tunas, and a shallow-set longline 

fishery (SSLL) that targets swordfish. Both 

fisheries operate within U.S. waters and on 

the high seas. Between 2004 and 2008, no 

Blainville’s beaked whale was observed 

killed or seriously injured in the SSLL 

fishery (100% observer coverage) or the 

DSLL fishery (20-28% observer coverage) 

(Forney 2009, McCracken 2009) and one 

Blainville’s beaked whale was observed taken, 

but not seriously injured, in international 

waters in the DSLL fishery (20-28% observer 

coverage) (McCracken & Forney 2010). 

Average 5-yr estimates of annual mortality and 

serious injury for 2004-2008 are 0.7 (CV=0.9) Blainville’s beaked whales outside of the U.S. EEZs, and zero within 

the Hawaiian Islands EEZ (Table 1

Figure 2. Location of the Blainville’s beaked whale take 

(filled diamond) and the possible take of this species (open 

diamonds) in Hawaii-based longline fisheries, 2004-2008.

Solid lines represent the U.S. EEZ. Fishery descriptions are 

provided in Appendix 1. 

). 

Other Mortality

 In recent years, there has been increasing concern that loud underwater sounds, such as active sonar and 

seismic operations, may be harmful to beaked whales (Malakoff 2002). The use of active sonar from military vessels 

has been implicated in mass strandings of beaked whales in the Mediterranean Sea during 1996 (Frantzis 1998), the 

Bahamas during 2000 (U.S. Dept. of Commerce and Secretary of the Navy 2001), and the Canary Islands 2002 

(Martel 2002). Similar military active sonar operations occur around the Hawaiian islands. It has been suggested 

that quick ascent from deep dives in response to acoustic exposure could lead to death in beaked whales (Cox et al.

2006). A modeling exercise based on dive data from Blainville’s, Cuvier’s and northern bottlenose whales suggest 

that the dive habits of all three species produce tissue nitrogen saturation levels that would normally cause 

262
decompression sickness in terrestrial mammals (Hooker et al. 2009). The impact of sonar exercises on resident 

versus offshore beaked whales may be significantly different with offshore animals less frequently exposed, possibly 

subject to more extreme reactions (Baird et al. 2009). No estimates of potential mortality or serious injury are 

available for U.S. waters. 

Table 1. Summary of available information on incidental mortality and serious injury of Blainville’s beaked whales 

(Hawaiian stock) in commercial fisheries, within and outside of the Hawaiian Islands EEZ (McCracken & Forney 

2010). Mean annual takes are based on 2004-2008 data unless otherwise indicated. 

Mortality and Serious In ry ju

outside of U.S. EEZ

Mortality and Serious Injury 

within Hawaiian Islands EEZ

Fishery Name Year Data Type

Percent 

Observer 

Coverage

Observed Estimated 

(CV)

Mean Annual 

Takes 

(CV)

Observed Estimated 

(CV)

Mean Annual 

Takes 

(CV)

Hawaii-based 

deep-set longline 

fishery 

2004 

2005 

2006 

2007 

2008 

Observer 

data 

25% 

28% 

22% 

20% 

22% 

0 

0 

0 

0 

0 

0 (-) 

3 (0.3) 

0 (-) 

0 (-) 

0 (-) 

0.7 (0.9) 

0 

0 

0 

0 

0 

0 (-) 

0 (-) 

0 (-) 

0 (-) 

0 (-) 

0 (-) 

Hawaii-based 

shallow-set 

longline fishery 

2004 

2005 

2006 

2007 

2008 

Observer 

data 

100% 

100% 

100% 

100% 

100% 

0 

0 

0 

0 

0 

Same as 

observed 0 

0 

0 

0 

0 

0 

Same as 

observed 0 

Minimum total annual takes within U.S. EEZ waters 0 (-)

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. It is not listed as “threatened” or “endangered” under the 

Endangered Species Act (1973), nor as “depleted” under the MMPA. . Given the absence of recent fishery-related 

mortality or serious injuries within U.S. EEZs, the Hawaiian stock of Blainville’s beaked whales is not considered 

strategic under the 1994 amendments to the MMPA, and the total fishery mortality and serious injury can be 

considered to be insignificant and approaching zero. However, the effect of potential interactions of Blainville’s 

beaked whales and unidentified beaked whales (some of which may have been Blainville’s beaked whales) with the 

Hawaii-based longline fishery in international waters is not known. The increasing level 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

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population of Blainville’s beaked whales. Report to Southwest Fisheries Science Center, 15p. 

Barlow, J. 2006. Cetacean abundance in Hawaiian waters estimated from a summer/fall survey in 2002. Marine 

Mammal Science 22: 446–464. 

Cox, T.M., T.J. Ragen, A.J. Read, E. Vos, R.W. Baird, K. Balcomb, J. Barlow, J. Caldwell, T. Cranford, L. Crum, 

A. D’Amico, G. D’Spain, A. Fernandez, J. Finneran, R. Gentry, W. Gerth, F. Gulland, J.A. Hildebrand, D. 

Houser, T. Hullar, P.D. Jepson, D. Ketten, C.D. Macleod, P. Miller, S. Moore, D. Mountain, D. Palka, P. 

Ponganis, S. Rommel, T. Rowles, B. Taylor, P. Tyack, D. Wartzok, R. Gisiner, J. Mead, and L. Brenner. 

2006. Understanding the impacts of anthropogenic sound on beaked whales. J.Cetacean Res. Manag. 7: 

177-187. 

Forney, K.A. 2009. Serious injury determinations for cetaceans caught in Hawaii longline fisheries during 1994-

2008. Draft document PSRG-2009-09 presented to the Pacific Scientific Review Group, November 3-5, 

2009, Del Mar, CA. 

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. 

263
Hooker, S.K., R.W. Baird, F.A. Fahlman. 2009. Could beaked whales get the bends? Effect of diving behavior and 

physiology on modeled gas exchange for three species: Ziphius cavirostris, Mesoplodon densirostris, and 

Hyperoodon ampulata.. Respiration Physiology and Neurobiology 117(2009): 235-246. 

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. 

McCracken M., and K.A. Forney. 2010. Preliminary assessment of incidental interactions with marine mammals in 

the Hawaii longline deep and shallow set fisheries. Pacific Islands Science Center Working Paper WP-09-

007. Draft document PSRG-2009-10 presented to the Pacific Scientific Review Group, November 3-5, 

2009, Del Mar, CA 

McSweeney, D.J., R.W. Baird, and S.D. Mahaffy. 2007. Site fidelity, associations, and movements of Cuvier’s 

(Ziphius cavirostris) and Blainville’s (Mesoplodon densirostris) beaked whales off the island of Hawaii. 

Mar. Mamm. Sci. 23(3):666-687. 

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. 

Schorr, G.S., R.W. Baird, M.B. Hanson, D.L. Webster, D.J. McSweeney, and R.D. Andrews. 2009. Movements of 

satellite-tagged Blainville’s beaked whales off the island of Hawaii. Endangered Species Res.10:203-213. 

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. 

264
Revised 01/15/2011 

CUVIER'S BEAKED WHALE (Ziphius cavirostris): 

Hawaiian Stock 

STOCK DEFINITION AND GEOGRAPHIC RANGE

 Cuvier's beaked whales occur in 

all oceans and major seas (Heyning 

1989). In Hawaii, five strandings have 

been reported from Midway Islands, 

Pearl and Hermes Reef, Oahu, and 

Hawaii Islands (Shallenberger 1981; 

Galbreath 1963; Richards 1952; Nitta 

1991; Maldini et al. 2005). Sightings 

have been reported off Lanai and Maui 

(Shallenberger 1981) and Hawaii, 

Ni’ihau, and Kauai (Mobley 2000, Baird 

et al. 2004, 2009). Four sightings were 

made during a 2002 shipboard survey of 

waters within the U.S. Exclusive 

Economic Zone (EEZ) of the Hawaiian 

islands (Figure 1; Barlow 2006). While 

nothing is known about stock structure, 

some genetic samples have been 

collected recently from around the island 

of Hawaii. Resightings of individual 

Cuvier’s beaked whales during a 21-yr 

study suggests long-term site fidelity and 

year round occurrence off the island of 

Hawaii (McSweeney et al 2007). For the 

Marine Mammal Protection Act 

(MMPA) stock assessment reports, Cuvier's beaked whales within the Pacific U.S. EEZ are divided into three 

discrete, non-contiguous areas: 1) Hawaiian waters (this report), 2) Alaskan waters, and 3) waters off California, 

Oregon and Washington. The Hawaiian stock includes animals found both within the Hawaiian Islands EEZ and in 

adjacent international waters; however, because data on abundance, distribution, and human-caused impacts are 

largely lacking for international waters, the status of this stock is evaluated based on data from U.S. EEZ waters of 

the Hawaiian Islands (NMFS 2005). 

W180 W175 W170 W165 W160 W155 W150

N10

N15

N30

N35

N20

N25

Figure 1. Cuvier’s beaked whale sighting locations during the 2002 

shipboard survey of U.S. EEZ waters surrounding the Hawaiian 

Islands (Barlow 2006; see Appendix 2 for details on timing and 

location of survey effort). Outer line represents approximate 

boundary of survey area and U.S. EEZ. 

POPULATION SIZE

 Wade and Gerrodette (1993) made an estimate for Cuvier's beaked whales in the eastern tropical Pacific, 

but it is not known whether any of these animals are part of the same population that occurs around the Hawaiian 

Islands. The data on which this estimate was based are now over 8 years old. Based on the photo-identification 

catalog for the island of Hawaii, a minimum of 35 individuals are known to occur there (McSweeney et al. 2007). . 

A 2002 shipboard line-transect survey of the entire Hawaiian Islands EEZ resulted in an abundance estimate of 

15,242 (CV=1.43) Cuvier’s beaked whales (Barlow 2006), including a correction factor for missed diving animals. 

This is currently the best available abundance estimate for this stock. 

Minimum Population Estimate

 The log-normal 20th percentile of the 2002 abundance estimate (Barlow 2006) is 6,269 Cuvier’s beaked 

whales within the Hawaiian Islands 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. 

265
POTENTIAL BIOLOGICAL REMOVAL

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

within the U.S. EEZ of the Hawaiian Islands (6,269) times one half the default maximum net growth rate for 

cetaceans (1⁄2 of 4%) times a recovery factor of 0.50 (for a species of unknown status with no known fishery 

mortality within the Hawaiian Islands EEZ; Wade and Angliss 1997), resulting in a PBR of 63 Cuvier’s beaked 

whales per year. 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY 

Fishery Information 

 Information on fishery-related mortality of cetaceans in Hawaiian waters is limited, but the gear types used 

in Hawaiian fisheries are responsible for marine mammal mortality and serious injury in other fisheries throughout 

U.S. waters. Gillnets appear to capture marine mammals wherever they are used, and float lines from lobster traps 

and longlines can be expected to occasionally entangle cetaceans (Perrin et al. 1994). 

 Interactions with cetaceans are reported for all pelagic fisheries (Nitta and Henderson 1993). There are 

currently two distinct longline fisheries based in Hawaii: a deep-set longline (DSLL) fishery that targets primarily 

tunas, and a shallow-set longline fishery (SSLL) that targets swordfish. Both fisheries operate within U.S. waters 

and on the high seas. Between 2004 and 2008, no Cuvier’s beaked whales were observed hooked or entangled in 

the SSLL fishery (100% observer coverage) or the DSLL fishery (20-28% observer coverage) (McCracken & 

Forney 2010) .However, one unidentified cetacean, which may have been a Cuvier’s beaked whale, was taken in 

the DSLL fishery in international waters (Forney 2009). . 

Other Mortality

 In recent years, there has been increasing concern that loud underwater sounds, such as active sonar and 

seismic operations, may be harmful to beaked whales (Malakoff 2002). The use of active sonar from military vessels 

has been implicated in mass strandings of beaked whales in the Mediterranean Sea during 1996 (Frantzis 1998), the 

Bahamas during 2000 (U.S. Dept. of Commerce and Secretary of the Navy 2001), and the Canary Islands 2002 

(Martel 2002). Similar military active sonar operations occur around the Hawaiian islands. It has been suggested 

that quick ascent from deep dives in response to acoustic exposure could lead to death in beaked whales (Cox et al.

2006). A modeling exercise based on dive data from Blainville’s, Cuvier’s and northern bottlenose whales suggest 

that the dive habits of all three species produce tissue nitrogen saturation levels that would normally cause 

decompression sickness in terrestrial mammals (Hooker et al. 2009). The longer dives and shorter surface intervals 

of Cuvier’s beaked whales may put them at higher risk for decompression sickness than other species, possibly 

increasing their susceptibility to high-intensity underwater noise (Hooker et al. 2009). 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. It is not listed as “threatened” or “endangered” under the 

Endangered Species Act (1973), nor as “depleted” under the MMPA. Because there have been no reported fishery 

related mortality or injuries within the Hawaiian Islands EEZ, the Hawaiian stock of Cuvier’s beaked whales is not 

considered strategic under the 1994 amendments to the MMPA, and the total mortality and serious injury can be 

considered to be insignificant and approaching zero. The increasing level of anthropogenic noise in the world’s 

oceans has been suggested to be a habitat concern for whales (Richardson et al. 1995), particularly for deep-diving 

whales like Cuvier’s beaked whales that feed in the oceans’ “sound channel”. 

REFERENCES 

Baird, R.W., D.J. McSweeney, A.D. Ligon and D.L. Webster. 2004. Tagging feasibility and diving of Cuvier's 

beaked whales (Ziphius cavirostris) and Blainville's beaked whales (Mesoplodon densirostris) in Hawai'i.

Report prepared under Order No. AB133F-03-SE-0986 to the Hawai'i Wildlife Fund, Volcano, HI, from 

the Southwest Fisheries Science Center, National Marine Fisheries Service, La Jolla, CA, 92037 USA. 

Baird, R.W., G.S. Schorr, D.L. Webster, S.D. Mahaffy, D.J. McSweeney, M.B. Hanson, and K.D. Andrews. 2009. 

Movements of satellite-tagged Cuvier’s and Blainville’s beaked whales in Hawaii: Evidence for an offshore 

population of Blainville’s beaked whales. Report to Southwest Fisheries Science Center, 15p. 

Barlow, J. 2006. Cetacean abundance in Hawaiian waters estimated from a summer/fall survey in 2002. Marine 

Mammal Science 22: 446–464. 

266
Cox, T.M., T.J. Ragen, A.J. Read, E. Vos, R.W. Baird, K. Balcomb, J. Barlow, J. Caldwell, T. Cranford, L. Crum, 

A. D’Amico, G. D’Spain, A. Fernandez, J. Finneran, R. Gentry, W. Gerth, F. Gulland, J.A. Hildebrand, D. 

Houser, T. Hullar, P.D. Jepson, D. Ketten, C.D. Macleod, P. Miller, S. Moore, D. Mountain, D. Palka, P. 

Ponganis, S. Rommel, T. Rowles, B. Taylor, P. Tyack, D. Wartzok, R. Gisiner, J. Mead, and L. Brenner. 

2006. Understanding the impacts of anthropogenic sound on beaked whales. J.Cetacean Res. Manag. 7: 

177-187. 

Forney, K.A. 2009. Serious injury determinations for cetaceans caught in Hawaii longline fisheries during 1994-

2008. Draft document PSRG-2009-09 presented to the Pacific Scientific Review Group, November 3-5, 

2009, Del Mar, CA. 

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. 

Hooker, S.K., R.W. Baird, F.A. Fahlman. 2009. Could beaked whales get the bends? Effect of diving behavior and 

physiology on modeled gas exchange for three species: Ziphius cavirostris, Mesoplodon densirostris, and 

Hyperoodon ampulata.. Respiration Physiology and Neurobiology 117(2009): 235-246. 

Malakoff, D. 2002. Suit ties whale deaths to research cruise. Science 298:722-723. 

Maldini, D., L. Mazzuca, and S. Atkinson. 2005. Odontocete stranding patterns in the Main Hawaiian Islands 

(1937-2002): How do they compare with live animal surveys? Pacific Science 59(1):55-67. 

McCracken M., and K.A. Forney. 2010. Preliminary assessment of incidental interactions with marine mammals in 

the Hawaii longline deep and shallow set fisheries. NMFS, Pacific Islands Fisheries Science Center 

Working Paper WP-10-001. 27p. 

McSweeney, D.J., R.W. Baird, and S.D. Mahaffy. 2007. Site fidelity, associations, and movements of Cuvier’s 

(Ziphius cavirostris) and Blainville’s (Mesoplodon densirostris) beaked whales off the island of Hawaii. 

Mar. Mamm. Sci. 23(3):666-687. 

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. 

MMC-77/23, 79pp. 

U.S. Department of Commerce and Secretary of the Navy. 2001. Joint Interim Report, Bahamas Marine Mammal 

Stranding Event of 15_16 March 2000. Available from NOAA, NMFS, Office of Protected Resources, 

Silver Spring, MD. 

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

Workshop April 3-5, 1996, Seattle, Washington. U. S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR12. 93 pp. 

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

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

267
Revised 01/15/2011 

LONGMAN’S BEAKED WHALE (Indopacetus pacificus): 

Hawaiian Stock 

STOCK DEFINITION AND GEOGRAPHIC RANGE

 Longman’s beaked whale is 

considered one of the rarest and least 

known cetacean species (Jefferson et al. 

1993; Rice 1998; Dalebout et al 2003). 

Until recently, it was known only from 

two skulls found in Australia and 

Somalia (Longman 1926; Azzaroli 

1968). Recent genetic studies (Dalebout 

et al. 2003) have revealed that sightings 

of ‘tropical bottlenose whales’ 

(Hyperoodon sp.; Pitman et al. 1999) in 

the Indopacific region were in fact 

Longman’s beaked whales, providing 

the first description of the external 

appearance of this species. Although 

originally described as Mesoplodon 

pacificus (Longman 1926), it has been 

proposed that this species is sufficiently 

unique to be placed within its own 

genus, Indopacetus (Moore 1968; 

Dalebout et al. 2003). The distribution 

of Longman’s beaked whale, as 

determined from stranded specimens and 

sighting records of ‘tropical bottlenose 

whales’, includes tropical waters from 

the eastern Pacific westward through the 

Indian Ocean to the eastern coast of 

Africa. No strandings of Longman’s beaked whales have been documented in Hawaiian waters, although numerous 

strandings of unidentified beaked whales have been reported (Nitta 1991; Maldini et al. 2005). One sighting of 

Longman’s beaked whale was made during a 2002 survey of waters within the U.S. Exclusive Economic Zone 

(EEZ) of the Hawaiian Islands (Figure 1; Barlow 2006). For the Marine Mammal Protection Act (MMPA) stock 

assessment reports, there is one Pacific stock of Longman’s beaked whales, found within waters of the Hawaiian 

Islands EEZ. This stock includes animals found both within the Hawaiian Islands EEZ and in adjacent international 

waters; however, because data on abundance, distribution, and human-caused impacts are largely lacking for 

international waters, the status of this stock is evaluated based on data from U.S. EEZ waters of the Hawaiian 

slands (NMFS 2005). 

W180 W175 W170 W165 W160 W155 W150

N10

N15

N20

N35

N25

N30

Figure 1. Sighting locations of Indopacetus pacificus (triangle), 

Mesoplodon densirostris (circle) and unidentified Mesoplodon

beaked whales (crosses) during the 2002 shipboard cetacean survey 

of U.S. waters surrounding the Hawaiian Islands (Barlow 2006; see 

Appendix 2 for details on timing and location of survey effort). 

Outer line indicates approximate boundary of survey area and U.S. 

EEZ.

I

POPULATION SIZE

 A 2002 shipboard line-transect survey of the entire Hawaiian Islands EEZ resulted in an abundance 

estimate of 1,007 (CV=1.25) Longman’s beaked whales (Barlow 2006). This is currently the best available 

abundance estimate for this stock. 

Minimum Population Estimate

 The log-normal 20th percentile of the 2002 abundance estimate (Barlow 2006) is 443 Longman’s beaked 

whales within the Hawaiian Islands EEZ. 

Current Population Trend

No data are available on current population trend. 

268
C NT AND MAXIMUM N URRE ET PRODUCTIVITY RATES

No data are available on current or maximum net productivity rate for Longman’s beaked whales. 

 

POTENTIAL BIOLOGICAL REMOVAL

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

within the U.S. EEZ of the Hawaiian Islands (443) times one half the default maximum net growth rate for cetaceans 

(1⁄2 of 4%) times a recovery factor of 0.50 (for a stock of unknown status with no known fishery mortality or serious 

injury within the Hawaiian Islands EEZ; Wade and Angliss 1997), resulting in a PBR of 4.4 Longman’s beaked 

hales per year. 

ORTALITY AND SERIOUS INJURY 

 float 

r, one unidentified cetacean, which may have been a Longman’s 

eaked whale, was taken in the DSLL fishery. . 

ther M

 mammals (Hooker et al. 2009). No estimates of potential mortality or serious 

jury are available for U.S. waters.

95), particularly for deep-diving whales like 

ongman’s beaked whales that feed in the oceans’ “sound channel”. 

Azzaroli of Mesoplodon pacificus, the rarest living beaked whale. Monitore 

Barlow, Hawaiian waters estimated from a summer/fall survey in 2002. Marine 

Cox, T.M

erstanding the impacts of anthropogenic sound on beaked whales. J.Cetacean Res. Manag. 7: 

w

HUMAN CAUSED M

Fishery Information

 Information on fishery-related mortality and serious injury of cetaceans in Hawaiian waters is limited, but 

the gear types used in Hawaiian fisheries are responsible for marine mammal mortality and serious injury in other 

fisheries throughout U.S. waters. Gillnets appear to capture marine mammals wherever they are used, and

lines from lobster traps and longlines can be expected to occasionally entangle cetaceans (Perrin et al. 1994). 

 Interactions with cetaceans have been reported for all Hawaiian pelagic fisheries (Nitta and Henderson 

1993). There are currently two distinct longline fisheries based in Hawaii: a deep-set longline (DSLL) fishery that 

targets primarily tunas, and a shallow-set longline fishery (SSLL) that targets swordfish. Both fisheries operate 

within U.S. waters and on the high seas. Between 2004 and 2008, no Longman’s beaked whales were observed 

hooked or entangled in the SSLL fishery (100% observer coverage) or the DSLL fishery (20-28% observer 

coverage) (McCracken & Forney 2010). Howeve

b

O ortality

 In recent years, there has been increasing concern that loud underwater sounds, such as active sonar and 

seismic operations, may be harmful to beaked whales (Malakoff 2002). The use of active sonar from military vessels 

has been implicated in mass strandings of beaked whales in the Mediterranean Sea during 1996 (Frantzis 1998), the 

Bahamas during 2000 (U.S. Dept. of Commerce and Secretary of the Navy 2001), and the Canary Islands 2002 

(Martel, 2002). Similar military active sonar operations occur around the Hawaiian Islands. It has been suggested 

that quick ascent from deep dives in response to acoustic exposure could lead to death in beaked whales (Cox et al.

2006). A modeling exercise based on dive data from Blainville’s, Cuvier’s and northern bottlenose whales suggest 

that the dive habits of all three species produce tissue nitrogen saturation levels that would normally cause 

decompression sickness in terrestrial

in

STATUS OF STOCK

 The status of Longman's beaked whales in Hawaiian waters relative to OSP is unknown, and there are 

insufficient data to evaluate trends in abundance. It is not listed as “threatened” or “endangered” under the 

Endangered Species Act (1973), nor as “depleted” under the MMPA. Given the absence of recent fishery-related 

mortality or serious injuries, the Hawaiian stock of Longman’s beaked whales is not considered strategic under the 

1994 amendments to the MMPA, and the total fishery mortality and serious injury can be considered to be 

insignificant and approaching zero. The increasing level of anthropogenic noise in the world’s oceans has been 

suggested to be a habitat concern for whales (Richardson et al. 19

L

REFERENCES

, M. L. 1968. Second specimen 

Zoologico Italiano (N.S.) 2:67-79. 

J. 2006. Cetacean abundance in

Mammal Science 22: 446–464. 

., T.J. Ragen, A.J. Read, E. Vos, R.W. Baird, K. Balcomb, J. Barlow, J. Caldwell, T. Cranford, L. Crum, 

A. D’Amico, G. D’Spain, A. Fernandez, J. Finneran, R. Gentry, W. Gerth, F. Gulland, J.A. Hildebrand, D. 

Houser, T. Hullar, P.D. Jepson, D. Ketten, C.D. Macleod, P. Miller, S. Moore, D. Mountain, D. Palka, P. 

Ponganis, S. Rommel, T. Rowles, B. Taylor, P. Tyack, D. Wartzok, R. Gisiner, J. Mead, and L. Brenner. 

2006. Und

269
177-187. 

t, M. L., G. J. B. Ross, C. S. Baker, R. C. Anderson, P. B. Best, V. G. Cockcroft, H. L. Hinsz, V. Peddemors 

and R. L. Pitman. 2003. Appearance, distribution and genetic

Dalebou

 distinctiveness of Longman’s beaked whale, 

Forney, 

mber 3-5, 

Hooker,

n densirostris, and 

Jefferson

ronment Programme; Food and Agriculture Organization of the United 

Longma ecords of Cetacea, with a list of Queensland species. Memoirs of the Queensland 

Maldini,

Martel, V

iety for the Study of the Cetaceans in the Canary 

McCrac

hallow set fisheries. NMFS, Pacific Islands Fisheries Science Center 

NMFS 2 ific Islands Region, 1602 

Nitta, E. ll 

Nitta, E A review of interactions between Hawaii's fisheries and protected species. 

Perrin, W ono n and J. Barlow. 1994. Gillnets and Cetaceans. Rep. Int. Whal. Commn., Special Issue 

Pitman, 

ottlenose whale in the tropical Indo-Pacific: Indopacetus pacificus? Marine Mammal Science 

Rice, D. matics and distribution. Special Publication 4. The Society 

Richards alme, and D. H. Thompson. 1995. Marine Mammals and Noise. 

U.S. De

15_16 March 2000. Available from NOAA, NMFS, Office of Protected Resources, 

Wade, P

pril 3-5, 1996, Seattle, Washington. U. S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR12. 93 pp. 

Indopacetus pacificus. Marine Mammal Science 19:421-461. 

K.A. 2009. Serious injury determinations for cetaceans caught in Hawaii longline fisheries during 1994-

2008. Draft document PSRG-2009-09 presented to the Pacific Scientific Review Group, Nove

2009, Del Mar, CA..Frantzis, A. 1998. Does acoustic testing strand whales? Nature 392(5):29. 

 S.K., R.W. Baird, F.A. Fahlman. 2009. Could beaked whales get the bends? Effect of diving behavior and 

physiology on modeled gas exchange for three species: Ziphius cavirostris, Mesoplodo

Hyperoodon ampulata.. Respiration Physiology and Neurobiology 117(2009): 235-246. 

, T. A., S. Leatherwood, and M. A. Webber. 1993. FAO species identification guide: marine mammals of 

the world. United States Envi

Nations (FAO), Rome. 320p. 

n, H.A. 1926. New r

Museum 8:266-278. 

Malakoff, D. 2002. Suit ties whale deaths to research cruise. Science 298:722-723 

 D., L. Mazzuca, and S. Atkinson. 2005. Odontocete stranding patterns in the Main Hawaiian Islands

(1937-2002): How do they compare with live animal surveys? Pacific Science 59(1):55-67. 

. M. 2002. Summary of the report on the atypical mass stranding of beaked whales in the Canary Islands 

in September 2002 during naval exercises. Soc

Archipelago (SECAC). Unpublished report. 11p. 

ken M., and K.A. Forney. 2010. Preliminary assessment of incidental interactions with marine mammals in 

the Hawaii longline deep and s

Working Paper WP-10-001. 27p. 

Moore J. C. 1968. Relationships among the living genera of beaked whales. Fieldiana Zoology 53:209-298. 

001. Western Pacific Pelagic Fisheries Biological Opinion. Available from Pac

Kapiolani Blvd, Suite 1110, Honolulu, HI 96814 (http://swr.nmfs.noaa.gov/pir). 

1991. The marine mammal stranding network for Hawaii: an overview. In: J.E. Reynolds III, D.K. Ode

(eds.), Marine Mammal Strandings in the United States, pp.56-62. NOAA Tech. Rep. NMFS 98, 157 pp. 

. and J. R. Henderson. 1993. 

Mar. Fish. Rev. 55(2):83-92. 

. F., G. P. D va

15, 629 pp. 

R. L., D. M. Palacios, P. L Brennan, K.C. III. Balcomb, and T. Miyashita. 1999. Sightings and possible 

identity of a b

15:531-549. 

 W. 1998. Marine Mammals of the world: syste

for Marine Mammalogy, Lawrence, KS, USA. 

on, W. J., C. R. Greene, Jr., C. I. M

Academic Press, San Diego. 576 p. 

partment of Commerce and Secretary of the Navy. 2001. Joint Interim Report, Bahamas Marine Mammal 

Stranding Event of 

Silver Spring, MD. 

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

Workshop A

270
Revised 01/15/2011 

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 2008, at least 35 strandings of 

this species were reported in the 

Hawaiian Islands (Shallenberger 1981, 

Tomich 1986; Nitta 1991; Maldini et al. 

2005, NMFS database). A stranded calf 

was held for several days at Sea Life 

Park (Pryor 1975). Shallenberger (1981) 

reported three sightings off Oahu and 

Maui. Two sightings of pygmy or dwarf 

(Kogia sima) sperm whales were made 

between Hawaii and Maui during 1993-

98 aerial surveys within about 25 nmi of 

the main Hawaiian Islands (Mobley et 

al. 2000). Two sightings were made 

during a 2002 shipboard survey of 

waters within the U.S. Exclusive 

Economic Zone (EEZ) of the Hawaiian 

Islands (Figure 1; Barlow 2006). Baird 

(2005) reported one sighting off Niihau 

and another off the island off Hawaii 

(R.W. Baird, pers. comm.). Nothing is 

known about stock structure for this species. For the Marine Mammal Protection Act (MMPA) stock assessment 

reports, pygmy sperm whales within the Pacific U.S. EEZ are divided into two discrete, non-contiguous areas: 1) 

Hawaiian waters (this report), and 2) waters off California, Oregon and Washington. The Hawaiian stock includes 

animals found both within the Hawaiian Islands EEZ and in adjacent international waters; however, because data on 

abundance, distribution, and human-caused impacts are largely lacking for international waters, the status of this 

stock is evaluated based on data from U.S. EEZ waters of the Hawaiian Islands (NMFS 2005). 

W180 W175 W170 W165 W160 W155 W150

N10

N15

N20

N25

N30

N35

Figure 1. Sighting locations of pygmy sperm whales (filled circle)

and unidentified Kogia (cross) during the 2002 shipboard cetacean 

survey of U.S. EEZ waters surrounding the Hawaiian Islands 

(Barlow 2006; see Appendix 2 for details on timing and location of 

survey effort). Outer line indicates approximate boundary of survey 

area and U.S. EEZ.

 

POPULATION SIZE

 A 2002 shipboard line-transect survey of the entire Hawaiian Islands EEZ resulted in an abundance 

estimate of 7,138 (CV=1.12) pygmy sperm whales (Barlow 2006), including a correction factor for missed diving 

animals. This is currently the best available abundance estimate for this stock. 

Minimum Population Estimate

 The log-normal 20th percentile of the 2002 abundance estimate (Barlow 2006) is 3,341 pygmy sperm 

whales within the Hawaiian Islands 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 

271
within the U.S EEZ of the Hawaiian Islands (3,341) times one half the default maximum net growth rate for 

cetaceans (1⁄2 of 4%) times a recovery factor of 0.50 (for a stock of unknown status with no known fishery mortality 

or serious injury within the Hawaiian Islands EEZ; Wade and Angliss 1997), resulting in a PBR of 33 pygmy sperm 

whales per year. 

HUMAN-CAUSED MORTALITY 

AND SERIOUS INJURY

Fishery Information

 Information on fishery-related 

mortality of cetaceans in Hawaiian waters 

is limited, but the gear types used in 

Hawaiian fisheries are responsible for 

marine mammal mortality and serious 

injury in other fisheries throughout U.S. 

waters. Gillnets appear to capture marine 

mammals wherever they are used, and 

float lines from lobster traps and longlines 

can be expected to occasionally entangle 

cetaceans (Perrin et al. 1994). 

Interactions with cetaceans have been 

reported for all Hawaiian pelagic fisheries 

(Nitta and Henderson 1993). There are 

currently two distinct longline fisheries 

based in Hawaii: a deep-set longline 

(DSLL) fishery that targets primarily 

tunas, and a shallow-set longline fishery 

(SSLL) that targets swordfish. Both 

fisheries operate within U.S. waters and 

on the high seas. Between 2004 and 2008, 

one pygmy or dwarf sperm whale was 

observed hooked in the SSLL fishery 

(100% observer coverage) (Figure 2, 

McCracken & Forney 2010). Based on an 

evaluation of the observer’s description of the interaction and following the most recently developed criteria for 

assessing serious injury in marine mammals (Andersen et al. 2008), this animal was considered not seriously injured 

(Forney 2009). No pygmy sperm whales were observed hooked or entangled in the DSLL fishery (20-28% observer 

coverage). 

Figure 2. Location of pygmy or dwarf sperm whale take (filled 

diamond) in Hawaii-based longline fisheries, 2004-2008. Solid lines 

represent the U.S. EEZs. Fishery descriptions are provided in 

Appendix 1. 

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. It is not listed as “threatened” or “endangered” under the 

Endangered Species Act (1973), nor as “depleted” under the MMPA. Given the absence of recent fishery-related 

mortality or serious injuries within the Hawaiian Islands EEZ, the Hawaiian stock of pygmy sperm whales is not 

considered strategic under the 1994 amendments to the MMPA, and the total fishery mortality and serious injury can 

be considered to be insignificant and approaching zero. The increasing level of anthropogenic noise in the world’s 

oceans has been suggested to be a habitat concern for whales (Richardson et al. 1995), particularly for deep-diving 

whales like pygmy sperm whales that feed in the oceans’ “sound channel”. 

272
Table 1. Summary of available information on incidental mortality and serious injury of pygmy sperm whales 

(Hawaiian stock) in commercial fisheries, within and outside of the Hawaiian Islands EEZ (McCracken & Forney 

2010). Mean annual takes are based on 2004-2008 data unless otherwise indicated; n/a = not available. 

Mortality and Serious In ry ju

outside of U.S. EEZ

Mortality and Serious Injury 

within Hawaiian Islands EEZ

Fishery Name Year Data Type

Percent 

Observer 

Coverage Observed Estimated 

(CV)

Mean Annual 

Takes 

(CV)

Observed Estimated 

(CV)

Mean Annual 

Takes 

(CV)

Hawaii-based 

deep-set longline 

fishery 

2004 

2005 

2006 

2007 

2008 

observer 

data 

25% 

28% 

22% 

20% 

22% 

0 

0 

0 

0 

0 

0 (-) 

0 (-) 

0 (-) 

0 (-) 

0 (-) 

0 (-) 

0 

0 

0 

0 

0 

0 (-) 

0 (-) 

0 (-) 

0 (-) 

0 (-) 

0 (-) 

Hawaii-based 

shallow-set 

longline fishery 

2004 

2005 

2006 

2007 

2008 

observer 

data 

100% 

100% 

100% 

100% 

100% 

0 

0 

0 

0 

1* 

Same as 

observed 0.2 

0 

0 

0 

0 

0 

Same as 

observed 0 

Minimum total annual takes within U.S. EEZ waters 0 

*One animal, which was either a pygmy sperm whale or dwarf sperm whales, observed not seriously injured. 

REFERENCES 

Baird, R.W. 2005. Sightings of dwarf (Kogia sima) and pygmy (K. breviceps) sperm whales from the main 

Hawaiian Islands. Pacific Science 59: 461-466..

Barlow, J. 2006. Cetacean abundance in Hawaiian waters estimated from a summer/fall survey in 2002. Marine 

Mammal Science 22: 446–464. 

Forney, K.A. 2009. Serious injury determinations for cetaceans caught in Hawaii longline fisheries during 1994-

2008. Draft document PSRG-2009-09 presented to the Pacific Scientific Review Group, November 3-5, 

2009, Del Mar, CA..Caldwell, D. K. and M. C. Caldwell. 1989. Pygmy sperm whale Kogia breviceps (de 

Blainville, 1838): Dwarf sperm whale Kogia simus Owen, 1866. In: S. H. Ridgway and R. Harrison (eds.), 

Handbook of Marine Mammals, Vol. 4: The River Dolphins and Larger Toothed Whales, pp. 235-260. 

Academic Press, 442 pp. 

Maldini, D., L. Mazzuca, and S. Atkinson. 2005. Odontocete stranding patterns in the Main Hawaiian Islands 

(1937-2002): How do they compare with live animal surveys? Pacific Science 59(1):55-67. 

McCracken M., and K.A. Forney. 2010. Preliminary assessment of incidental interactions with marine mammals in 

the Hawaii longline deep and shallow set fisheries. NMFS, Pacific Islands Fisheries Science Center 

Working Paper WP-10-001. 27p. 

Mobley, J. R., Jr, S. S. Spitz, K. A. Forney, R. A. Grotefendt, and P. H. Forestall. 2000. Distribution and 

abundance of odontocete species in Hawaiian waters: preliminary results of 1993-98 aerial surveys Admin. 

Rep. LJ-00-14C. Southwest Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La 

Jolla, CA 92038. 26 pp. 

NMFS Pacific Islands Regional Office Stranding Database. Available from NMFS-PIRO 1601 Kapiolani Blvd, Ste. 

1110, Honolulu, HI 96814. 

Nitta, E. 1991. The marine mammal stranding network for Hawaii: an overview. In: J.E. Reynolds III, D.K. Odell 

(eds.), Marine Mammal Strandings in the United States, pp.56-62. NOAA Tech. Rep. NMFS 98, 157 pp. 

Nitta, E. and J. R. Henderson. 1993. A review of interactions between Hawaii's fisheries and protected species. 

Mar. Fish. Rev. 55(2):83-92. 

Perrin, W.F., G. P. Donovan and J. Barlow. 1994. Gillnets and Cetaceans. Rep. Int. Whal. Commn., Special Issue 

15, 629 pp. 

Pryor, K. 1975. Lads Before the Wind: Adventures in Porpoise Training. Harper and Row, New York, 278 pp. 

Richardson, W. J., C. R. Greene, Jr., C. I. Malme, and D. H. Thompson. 1995. Marine Mammals and Noise. 

Academic Press, San Diego. 576 p. 

Shallenberger, E.W. 1981. The status of Hawaiian cetaceans. Final report to U.S. Marine Mammal Commission. 

MMC-77/23, 79pp. 

Tomich, P. Q. 1986. Mammals in Hawaii: A Synopsis and Notational Bibliography. Bishop Museum Press, Hawaii, 

375 pp. 

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. 

273
Revised 01/15/2011

DWARF SPERM WHALE (Kogia sima): 

Hawaiian Stock 

STOCK DEFINITION AND GEOGRAPHIC RANGE

 Dwarf sperm whales are found 

throughout the world in tropical to 

warm-temperate waters (Nagorsen 

1985). Rice (1998) recently argued that 

the species name simus, was incorrect 

and should be replaced by sima to reflect 

rules of Latin usage. At least four 

strandings of dwarf sperm whales have 

been documented in Hawaii (Tomich 

1986; Nitta 1991; Maldini et al. 2005). 

Two sightings of pygmy or dwarf 

sperms whales were made between 

Hawaii and Maui during 1993-98 aerial 

surveys within about 25 nmi of the main 

Hawaiian Islands (Mobley et al. 2000), 

and dwarf sperm whales were seen near 

Niihau, Kauai, Lanai, and Hawaii during 

small boat surveys between 2000 and 

2003 (Baird et al 2005). Five sightings 

of dwarf sperm whales were made 

during a 2002 shipboard survey of 

waters within the U.S. Exclusive 

Economic Zone (EEZ) of the Hawaiian 

Islands (Figure 1; Barlow 2006). For the 

Marine Mammal Protection Act 

(MMPA) stock assessment reports, 

dwarf sperm whales within the Pacific 

U.S. EEZ are divided into two discrete, non-contiguous areas: 1) Hawaiian waters (this report), and 2) waters off 

California, Oregon and Washington. The Hawaiian stock includes animals found both within the Hawaiian Islands 

EEZ and in adjacent international waters; however, because data on abundance, distribution, and human-caused 

impacts are largely lacking for international waters, the status of this stock is evaluated based on data from U.S. EEZ 

waters of the Hawaiian Islands (NMFS 2005). 

W180 W175 W170 W165 W160 W155 W150

N10

N15

N20

N25

N30

N35

Figure 1. Sighting locations of dwarf sperm whales (filled circle) 

and unidentified Kogia (cross) during the 2002 shipboard cetacean

survey of U.S. waters surrounding the Hawaiian Islands (Barlow 

2006; see Appendix 2 for details on timing and location of survey 

effort). Outer line indicates approximate boundary of survey area 

and U.S. EEZ.

 

POPULATION SIZE

 Wade and Gerrodette (1993) provided an estimate for the eastern tropical Pacific, but it is not known 

whether these animals are part of the same population that occurs in the central North Pacific. Baird (2005) reports 

that dwarf sperm whales are the sixth most commonly sighted odontocete around the Main Hawaiian Islands. This 

species’ small size, tendency to avoid vessels, deep-diving habits, combined with the high proportion of Kogia

sightings that are not identified to species, may result in negatively biased relative abundances in this region (R.W. 

Baird, pers. comm.). A 2002 shipboard line-transect survey of the entire Hawaiian Islands EEZ resulted in an 

abundance estimate of 17,519 (CV=0.74) dwarf sperm whales (Barlow 2006), including a correction factor for 

missed diving animals. This is currently the best available abundance estimate for this stock. 

Minimum Population Estimate

 The log-normal 20th percentile of the 2002 abundance estimate (Barlow 2006) is 10,043 dwarf sperm 

whales within the Hawaiian Islands EEZ. 

 

Current Population Trend

 No data are available on current population trend. 

274
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 

within the U.S. EEZ of the Hawaiian Islands (10,043) times one half the default maximum net growth rate for 

cetaceans (1⁄2 of 4%) times a recovery factor of 0.50 (for a stock of unknown status with no known fishery mortality 

or serious injury within the Hawaiian Islands EEZ; Wade and Angliss 1997), resulting in a PBR of 100 dwarf sperm 

whales per year. 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Fishery Information 

 Information on fishery-related 

mortality of cetaceans in Hawaiian waters is 

limited, but the gear types used in Hawaiian 

fisheries are responsible for marine mammal 

mortality and serious injury in other fisheries 

throughout U.S. waters. Gillnets appear to 

capture marine mammals wherever they are 

used, and float lines from lobster traps and 

longlines can be expected to occasionally 

entangle cetaceans (Perrin et al. 1994). 

Interactions with cetaceans have been 

reported for all Hawaiian pelagic fisheries 

(Nitta and Henderson 1993). There are 

currently two distinct longline fisheries 

based in Hawaii: a deep-set longline (DSLL) 

fishery that targets primarily tunas, and a 

shallow-set longline fishery (SSLL) that 

targets swordfish. Both fisheries operate 

within U.S. waters and on the high seas. 

Between 2004 and 2008, one pygmy or 

dwarf sperm whale was observed hooked in 

the SSLL fishery (100% observer coverage) 

(Figure 2, McCracken & Forney 2010). 

Based on an evaluation of the observer’s 

description of the interaction and following 

the most recently developed criteria for 

assessing serious injury in marine mammals 

(Andersen et al. 2008), this animal was 

considered not seriously injured (Forney 2009). No dwarf sperm whales were observed hooked or entangled in the 

DSLL fishery (20-28% observer coverage). 

Figure 2. Location of pygmy or dwarf sperm whale take (filled 

diamond) in Hawaii-based longline fisheries, 2004-2008. Solid 

lines represent the U.S. EEZs. Fishery descriptions are provided 

in Appendix 1. 

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. It is not listed as “threatened” or “endangered” under the Endangered Species 

Act (1973), nor as “depleted” under the MMPA. Because there have been no reported fishery related mortality or 

injuries within the Hawaiian Islands EEZ, the Hawaiian stock of dwarf sperm whales is not considered strategic 

under the 1994 amendments to the MMPA, and the total mortality and serious injury can be considered to be 

insignificant and approaching zero. The increasing levels of anthropogenic noise in the world’s oceans has been 

suggested to be a habitat concern for whales (Richardson et al. 1995), particularly for deep-diving whales like dwarf 

sperm whales that feed in the oceans’ “sound channel”. 

275
Table 1. Summary of available information on incidental mortality and serious injury of pygmy sperm whales 

(Hawaiian stock) in commercial fisheries, within and outside of the Hawaiian Islands EEZ (McCracken & Forney 

2010). Mean annual takes are based on 2004-2008 data unless otherwise indicated; n/a = not available. 

Mortality and Serious In ry ju

Outside of U.S. EEZ

Mortality and Serious Injury 

within Hawaiian Islands EEZ

Fishery Name Year Data Type

Percent 

Observer 

Coverage Observed Estimated 

(CV)

Mean Annual 

Takes 

(CV)

Observed Estimated 

(CV)

Mean Annual 

Takes 

(CV)

Hawaii-based 

deep-set longline 

fishery 

2004 

2005 

2006 

2007 

2008 

observer 

data 

25% 

28% 

22% 

20% 

22% 

0 

0 

0 

0 

0 

0 (-) 

0 (-) 

0 (-) 

0 (-) 

0 (-) 

0 (-) 

0 

0 

0 

0 

0 

0 (-) 

0 (-) 

0 (-) 

0 (-) 

0 (-) 

0 (-) 

Hawaii-based 

shallow-set 

longline fishery 

2004 

2005 

2006 

2007 

2008 

observer 

data 

100% 

100% 

100% 

100% 

100% 

0 

0 

0 

0 

1* 

Same as 

observed 0.2 

0 

0 

0 

0 

0 

Same as 

observed 0 

Minimum total annual takes within U.S. EEZ waters 0 (-)

*One animal, which was either a pygmy sperm whale or dwarf sperm whales, observed not seriously injured. 

REFERENCES 

Baird, R.W. 2005. Sightings of dwarf (Kogia sima) and pygmy (K. breviceps) sperm whales from the main 

Hawaiian Islands. Pacific Science 59: 461-466.

Barlow, J. 2006. Cetacean abundance in Hawaiian waters estimated from a summer/fall survey in 2002. Marine 

Mammal Science 22: 446–464. 

Forney, K.A. 2009. Serious injury determinations for cetaceans caught in Hawaii longline fisheries during 1994-

2008. Draft document PSRG-2009-09 presented to the Pacific Scientific Review Group, November 3-5, 

2009, Del Mar, CA..Maldini, D., L. Mazzuca, and S. Atkinson. 2005. Odontocete stranding patterns in the 

Main Hawaiian Islands (1937-2002): How do they compare with live animal surveys? Pacific Science 

59(1):55-67. 

McCracken M., and K.A. Forney. 2010. Preliminary assessment of incidental interactions with marine mammals in 

the Hawaii longline deep and shallow set fisheries. NMFS, Pacific Islands Fisheries Science Center 

Working Paper WP-10-001. 27p. 

Mobley, J. R. , Jr, S. S. Spitz, K. A. Forney, R. A. Grotefendt, and P. H. Forestall. 2000. Distribution and 

abundance of odontocete species in Hawaiian waters: preliminary results of 1993-98 aerial surveys Admin. 

Rep. LJ-00-14C. Southwest Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La 

Jolla, CA 92038. 26 pp. 

Nagorsen, D. 1985. Kogia simus. Mamm. Spec. 239:1-6. 

Nitta, E. 1991. The marine mammal stranding network for Hawaii: an overview. In: J.E. Reynolds III, D.K. Odell 

(eds.), Marine Mammal Strandings in the United States, pp.56-62. NOAA Tech. Rep. NMFS 98, 157 pp. 

Nitta, E. and J. R. Henderson. 1993. A review of interactions between Hawaii's fisheries and protected species. 

Mar. Fish. Rev. 55(2):83-92. 

Perrin, W.F., G. P. Donovan and J. Barlow. 1994. Gillnets and Cetaceans. Rep. Int. Whal. Commn., Special Issue 

15, 629 pp. 

Rice, D.W. 1998. Marine Mammals of the World Systematics and Distribution. Special Publication Number 4 The 

Society of Marine Mammalogy. Douglas Wartzok (ed.). 231 pp. 

Richardson, W. J., C. R. Greene, Jr., C. I. Malme, and D. H. Thompson. 1995. Marine Mammals and Noise. 

Academic Press, San Diego. 576 p. 

Tomich, P. Q. 1986. Mammals in Hawaii: A Synopsis and Notational Bibliography. Bishop Museum Press, Hawaii, 

375 pp.

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

Workshop April 3-5, 1996, Seattle, Washington. U. S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR12. 93 pp. 

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

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

276
Revised 01/15/2011 

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 160o

W between 40-50oN, and 

ends up at 180o

W north of 50oN; 

however, the IWC has not reviewed this 

stock boundary in many years (Donovan 

1991). Summer/fall surveys in the 

eastern tropical Pacific (Wade and 

Gerrodette 1993) show that although 

sperm whales are widely distributed in 

the tropics, their relative abundance 

tapers off markedly westward towards 

the middle of the tropical Pacific (near 

the IWC stock boundary at 150o

W) and 

tapers off northward towards the tip of Baja California. The Hawaiian Islands marked the center of a major 

nineteenth century whaling ground for sperm whales (Gilmore 1959; Townsend 1935). Since 1936, at least 18 

strandings have been reported from Oahu, Kauai and Kure Atoll (Woodward 1972; Nitta 1991; Maldini et al. 2005). 

Sperm whales have also been sighted around several of the Northwestern Hawaiian Islands (Rice 1960; Barlow 

2006), off the main island of Hawaii (Lee 1993; Mobley et al. 2000) in the Kauai Channel and in the Alenuihaha 

Channel between Maui and the island of Hawaii (Shallenberger 1981). In addition, the sounds of sperm whales 

have been recorded throughout the year off Oahu (Thompson and Friedl 1982). A summer/fall 2002 shipboard 

survey of waters within the U.S. Exclusive Economic Zone (EEZ) of the Hawaiian Islands resulted in 43 sperm 

whale sightings throughout the study area (Figure 1; Barlow 2006). 

W180 W175 W170 W165 W160 W155 W150

N10

N15

N20

N25

N30

N35

Figure 1. Sperm whale sighting locations during the 2002 shipboard 

survey of U.S. EEZ waters surrounding the Hawaiian Islands 

(Barlow 2006; see Appendix 2 for details on timing and location of 

survey effort). Outer line represents approximate boundary of survey 

area and U.S. EEZ. 

The stock identity of sperm whales in the North Pacific has been inferred from historical catch records 

(Bannister and Mitchell 1980) and from trends in CPUE and tag-recapture data (Ohsumi and Masaki 1977), but 

much uncertainty remains. A 1997 survey designed specifically to investigate stock structure and abundance of 

sperm whales in the northeastern temperate Pacific revealed no apparent hiatus in distribution between the U.S. EEZ 

off California and areas farther west, out to Hawaii (Barlow and Taylor 2005). 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. This stock 

includes animals found both within the Hawaiian Islands EEZ and in adjacent international waters; however, 

because data on abundance, distribution, and human-caused impacts are largely lacking for international waters, the 

status of this stock is evaluated based on data from U.S. EEZ waters of the Hawaiian Islands (NMFS 2005).

POPULATION SIZE

 A large 1982 abundance estimate for the entire eastern North Pacific (Gosho et al. 1984) was based on a 

277
CPUE method which is no longer accepted as valid by the International Whaling Commission. A spring 1997 

combined visual and acoustic line-transect survey conducted in the eastern temperate North Pacific resulted in 

estimates of 26,300 (CV=0.81) sperm whales based on visual sightings, and 32,100 (CV=0.36) based on acoustic 

detections and visual group size estimates (Barlow and Taylor 2005). Sperm whales appear to be a good candidate 

for acoustic surveys due to the increased range of detection; however, visual estimates of group size are still required 

(Barlow and Taylor 2005). 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 the Hawaiian Islands. A 2002 shipboard line-transect survey of the entire 

Hawaiian Islands EEZ resulted in an abundance estimate of 6,919 (CV=0.81) sperm whales (Barlow 2006), 

including a correction factor for missed diving animals. This is currently the best available abundance estimate for 

this stock. 

Minimum Population Estimate

 The log-normal 20th percentile of the 2002 abundance estimate (Barlow 2006) is 3,805 sperm whales 

within the Hawaiian Islands EEZ. 

 

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 

(3,805) within the U.S. EEZ of the Hawaiian Islands times one half the default maximum net growth rate for 

cetaceans (1⁄2 of 4%) times a recovery factor of 0.2 (for an endangered species with Nmin > 1,500 and CVNmin > 0.50, 

with low vulnerability to extinction (Taylor et al. 2003)), resulting in a PBR of 15 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 cetaceans (Perrin et al. 1994). 

 Interactions with cetaceans are reported for all pelagic fisheries, and large whales have been entangled in 

longlines off the Hawaiian Islands (Nitta and Henderson 1993; Forney 2009). There are currently two distinct 

longline fisheries based in Hawaii: a deep-set longline (DSLL) fishery that targets primarily tunas, and a shallow-set 

longline fishery (SSLL) that targets swordfish. Both fisheries operate within U.S. waters and on the high seas. 

Between 2004 and 2008, no sperm whales were observed hooked or entangled in the SSLL fishery (100% observer 

coverage) or the DSLL fishery (20-28% observer coverage) (McCracken & Forney 2010).

 

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 under-reporting of Soviet catches, Brownell et al. (1998) estimate that about 89,000 whales were 

additionally taken by the Soviet pelagic whaling fleet between 1949 and 1979. The Japanese coastal operations 

apparently also under-reported catches by an unknown amount (Kasuya 1998). Thus a total of at least 436,000 

sperm whales were taken between 1800 and the end of commercial whaling for this species in 1987. Of this grand 

total, an estimated 33,842 were taken by Soviet and Japanese pelagic whaling operations in the eastern North Pacific 

from the longitude of Hawaii to the U.S. West coast, between 1961 and 1976 (Allen 1980, IWC statistical Areas II 

and III), and 965 were reported taken in land-based U.S. West coast whaling operations between 1947 and 1971 

(Ohsumi 1980). In addition, 13 sperm whales were taken by shore whaling stations in California between 1919 and 

1926 (Clapham et al. 1997). There has been a prohibition on taking sperm whales in the North Pacific since 1988, 

but large-scale pelagic whaling stopped earlier, in 1980. Some of the whales taken during the whaling era were 

278
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. Given the absence of recent 

fishery-related mortality or serious injuries within the Hawaiian Islands EEZ, the Hawaiian stock of sperm whales is 

not considered strategic under the 1994 amendments to the MMPA, and the total fishery mortality and serious injury 

can be considered to be insignificant and approaching zero. The increasing level of anthropogenic noise in the 

world’s oceans has been suggested to be a habitat concern for whales (Richardson et al. 1995), particularly for deepdiving whales like sperm whales that feed in the oceans’ “sound channel”. 

REFERENCES

Allen, K. R. 1980. Size distribution of male sperm whales in the pelagic catches. Rep. Int. Whal. Commn. Special 

Issue 2:51-56. 

Allison, C. International Whaling Commission. The Red House, 135 Station Road, Impington, Cambridge, UK CB4 

9NP. 

Barlow, J. 2006. Cetacean abundance in Hawaiian waters estimated from a summer/fall survey in 2002. Marine 

Mammal Science 22: 446–464. 

Barlow, J and B. Taylor. 2005. Estimates of sperm whale abundance in the northeast temperate Pacific from a 

combined visual and acoustic survey. Mar. Mamm. Sci. 21(3):429-445. 

Bannister, J. and E. Mitchell. 1980. North Pacific sperm whale stock identity: distributional evidence from Maury 

and Townsend charts. Rep. Int. Whal. Commn. (Spec. Iss. 2):219-230. 

Best, P. B. 1976. A review of world sperm whale stocks. Paper ACMRR/MM/SC/8 Rev.1, FAO Scientific 

Consultation of Marine Mammals, Bergen, Norway. 

Brownell, R. L., Jr., A. V. Yablokov and V. A. Zemmsky. 1998. USSR pelagic catches of North Pacific sperm 

whales, 1949-1979: Conservation implications. Paper SC/50/CAWS27 presented to the International 

Whaling Commission, June 1998 (unpublished). 

Clapham, P. J., S. Leatherwood, I. Szczepaniak, and R. L. Brownell, Jr. 1997. Catches of humpback and other 

whales from shore stations at Moss Landing and Trinidad, California, 1919-1926. Marine Mammal 

Science 13(3):368-394. 

Donovan, G. P. 1991. A review of IWC stock boundaries. Rept. Int. Whal. Commn., Special Issue 13:39-68. 

Forney, K.A. 2009. Serious injury determinations for cetaceans caught in Hawaii longline fisheries during 1994-

2008. Draft document PSRG-2009-09 presented to the Pacific Scientific Review Group, November 3-5, 

2009, Del Mar, CA..Gilmore, R. M. 1959. On the mass strandings of sperm whales. Pac. Nat. 1(9-10):3-

15. 

Gosho, M. E., D. W. Rice, and J. M. Breiwick. 1984. The sperm whale Physeter macrocephalus. Mar. Fish. Rev. 

46(4):54-64. 

Kasuya, T. 1998. Evidence of statistical manipulations in Japanese coastal sperm whale fishery. Paper 

SC/50/CAWS10 presented to the International Whaling Commission, June 1998 (unpublished). 

Lee, T. 1993. Summary of cetacean survey data collected between the years of 1974 and 1985. NOAA Tech.Mem. 

NMFS 181, 184pp. 

Maldini, D., L. Mazzuca, and S. Atkinson. 2005. Odontocete stranding patterns in the Main Hawaiian Islands 

(1937-2002): How do they compare with live animal surveys? Pacific Science 59(1):55-67. 

McCracken M., and K.A. Forney. 2010. Preliminary assessment of incidental interactions with marine mammals in 

the Hawaii longline deep and shallow set fisheries. NMFS, Pacific Islands Fisheries Science Center 

Working Paper WP-10-001. 27p. 

Mesnick, S. Southwest Fisheries Science Center, NMFS, 8604 La Jolla Shores Drive, La Jolla, California, 92037. 

Miyashita, T., H. Kato, and T. Kasuya (Eds.). 1995. Worldwide map of cetacean distribution based on Japanese 

sighting data. Volume 1. National Research Institute of Far Seas Fisheries, Shizuoka, Japan. 140pp. 

Mobley, J. R. , Jr, S. S. Spitz, K. A. Forney, R. A. Grotefendt, and P. H. Forestall. 2000. Distribution and 

abundance of odontocete species in Hawaiian waters: preliminary results of 1993-98 aerial surveys Admin. 

Rep. LJ-00-14C. Southwest Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La 

Jolla, CA 92038. 26 pp. 

279
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. 

MMC-77/23, 79pp. 

Taylor, B.L., M. Scott, J. Heyning, and J. Barlow. 2003. Suggested guidelines for recovery factors for endangered 

marine mammals. U.S. Dep. Commerce, NOAA Tech. Memo., NMFS-TM-NMFS-SWFSC-354. 6 p. 

Thompson, P. O. and W. A. Friedl. 1982. A long term study of low frequency sound from several species of whales 

off Oahu, Hawaii. Cetology 45:1-19. 

Townsend, C. H. 1935. The distribution of certain whales as shown by logbook records of American whaleships. 

Zoologica 19:1-50. 

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

Workshop April 3-5, 1996, Seattle, Washington. U. S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR12. 93 pp. 

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

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

Woodward, P. W. 1972. The natural history of Kure Atoll, northwestern Hawaiian Islands. Atoll Res. Bull. 

164:302. 

280
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BLUE WHALE (Balaenoptera musculus musculus): 

Central North Pacific Stock 

STOCK DEFINITION AND GEOGRAPHIC RANGE 

 The International Whaling 

Commission (IWC) has formally 

considered only one management stock 

for blue whales in the North Pacific 

(Donovan 1991), but up to five 

populations have been proposed (Reeves 

et al. 1998). Rice (1974) hypothesized 

that blue whales from Baja California 

migrated far offshore to fed in the 

eastern Aleutians or Gulf of Alaska and 

returned to feed in California waters; 

however, he has more recently 

concluded that the California population 

is separate from the Gulf of Alaska 

population (Rice 1992). Length 

frequency analyses (Gilpatrick et al. 

1996) and photo-identification studies 

(Calambokidis et al. 1995) support 

separate population status for blue 

whales feeding off California and those 

feeding in Alaskan waters. Whaling 

catch data indicate that whales feeding 

along the Aleutian Islands are probably 

part of a central Pacific stock (Reeves et 

al. 1998), which may migrate to offshore 

waters north of Hawaii in winter (Berzin 

and Rovnin 1966). Blue whale feeding 

aggregations have not been found in 

Alaska despite several surveys 

(Leatherwood et al. 1982; Stewart et al. 

1987; Forney and Brownell 1996); 

however, blue whale calls have been recorded there between 1995 and 2001 (Stafford et al. 2001, Stafford 2003). 

Figure 1. Locations of four blue whale sightings made by observers 

aboard Hawaii-based longline fishing vessels between July 1994 

and December 2009 (NMFS/PIR unpublished data). Solid lines 

represent the U.S. Exclusive Economic Zone (EEZ). 

Recent analyses of acoustic data obtained throughout the North Pacific Ocean (Stafford et al. 2001; 

Stafford 2003) has revealed two distinct blue whale call types, suggesting two North Pacific stocks: eastern and 

central (formerly western). The regional occurrence patterns indicate that blue whales from the eastern North 

Pacific stock winter off Mexico, central America, and as far south as 8o S (Stafford et al. 1999), and feed during 

summer off the U. S. West Coast and to a lesser extent in the Gulf of Alaska, . This stock has previously been 

documented to feed in waters off California (and occasionally as far north as British Columbia; Calambokidis et al. 

1998) in summer/fall (from June to November) migrating south to productive areas off Mexico (Calambokidis et al. 

1990) and as far south as the Costa Rica Dome (10 N) in winter/spring (Mate et al. 1999, Stafford et al. 1999). 

Blue whales belonging to the central Pacific stock appear to feed in summer southwest of Kamchatka, south of the 

Aleutians, and in the Gulf of Alaska (Stafford 2003; Watkins et al. 2000), and in winter they migrate to lower 

latitudes in the western Pacific and less frequently in the central Pacific, including Hawaii (Stafford et al. 2001). The 

only published sighting record of blue whales near Hawaii is that of Berzin and Rovnin (1966). Two sightings have 

been made by observers on Hawaii-based longline vessels (Figure 1; NMFS/PIR, unpublished data). Additional 

evidence that blue whales occur in this area comes from acoustic recordings made off Oahu and Midway Islands 

(Northrop et al. 1971; Thompson and Friedl 1982), which included at least some within the U.S. Exclusive 

Economic Zone (EEZ). The recordings made off Hawaii showed bimodal peaks throughout the year (Stafford et al. 

2001), with central Pacific call types heard during winter and eastern Pacific calls heard during summer. For the 

Marine Mammal Protection Act (MMPA) stock assessment reports, there are two blue whale stocks within the 

281
Pacific U.S. EEZ: 1) the central North Pacific stock (this report), which includes whales found around the Hawaiian 

Islands during winter and 2) the eastern North Pacific stock, which feeds primarily off California.

POPULATION SIZE

 From ship line-transect surveys, Wade and Gerrodette (1993) estimated 1,400 blue whales for the eastern 

tropical Pacific. No blue whale sightings were made during a summer 1994 shipboard survey south of the Aleutian 

Islands (Forney and Brownell 1996), during twelve aerial surveys conducted in 1993-98 within about 25 nmi of the 

main Hawaiian Islands (Mobley et al. 2000), or during a summer/fall 2002 shipboard surveys of the entire Hawaiian 

Islands EEZ (Barlow 2006). Therefore, no estimate of abundance is available for the central Pacific blue whale 

stock. 

Minimum Population Estimate

 No data are available to provide a minimum population estimate. 

Current Population Trend 

 No data are available on current population trend. 

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES 

No data are available on current or maximum net productivity rate.

POTENTIAL BIOLOGICAL REMOVAL

 No PBR can be calculated for this stock at this time. 

 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Fishery Information 

 Information on fishery-related mortality of cetaceans in Hawaiian waters is limited, but the gear types used 

in Hawaiian fisheries are responsible for marine mammal mortality and serious injury in other fisheries throughout 

U.S. waters. Gillnets appear to capture marine mammals wherever they are used, and float lines from lobster traps 

and longlines can be expected to occasionally entangle cetaceans (Perrin et al. 1994). Interactions with cetaceans 

are reported for all pelagic fisheries, and large whales have been entangled in longline gear off the Hawaiian Islands 

(Nitta and Henderson 1993, Forney 2009). . There are currently two distinct longline fisheries based in Hawaii: a 

deep-set longline (DSLL) fishery that targets primarily tunas, and a shallow-set longline fishery (SSLL) that targets 

swordfish. Both fisheries operate within U.S. waters and on the high seas. Between 2004 and 2008, no blue whales 

were observed hooked or entangled in the SSLL fishery (100% observer coverage) or the DSLL fishery (20-28% 

observer coverage) (McCracken & Forney 2010).

 

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 central Pacific stock is automatically considered as a "depleted" and "strategic" stock 

under the MMPA. Because there have been no reported fishery related mortality or serious injuries of blue whales 

within the Hawaiian Islands EEZ, the total fishery-related mortality and serious injury of this stock can be 

considered to be insignificant and approaching zero. 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. 2006. Cetacean abundance in Hawaiian waters estimated from a summer/fall survey in 2002. Marine 

Mammal Science 22: 446–464. 

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. 

282
(TINRO) 58:179-207. {In Russian}. (Translated by U.S. Dep. Inter., Bur. Commer. Fish., Seattle, 

Washington, 1966, pp. 103-106 In: Panin, K. I. (ed) Soviet Research on marine mammals of the Far East). 

Calambokidis, J, T. Chandler, K. Rasmussen, G.H. Steiger, and L. Schlender. 1998. Humpback and blue whale 

photographic identification: Report of research in 1997. Final report to Southwest Fisheries Science 

Center, Olympic Coast National Marine Sanctuary, University of California at Santa Cruz, and Cornell 

University. Cascadia Research, 2181⁄2 W. Fourth Ave., Olympia, WA 98501. 41pp. 

Calambokidis, J., R. Sears, G. H. Steiger, and J. Evenson. 1995. Movement and stock structure of blue whales in the 

eastern North Pacific. P.19 In: Proceedings of the Eleventh Biennial Conference on the Biology of Marine 

Mammals, Orlando, FL, 14-18 December 1995 (Abstract). Society for Marine Mammalogy, Lawrence, KS. 

Calambokidis, J., G. H. Steiger, J.C. Cubbage, K.C. Balcomb, C. Ewald, S. Kruse, R. Wells, and R. Sears. 1990. 

Sightings and movement of blue whales off central California 1986-88 from photo-identification of 

individuals. Rep. Int. Whaling. Commn., Special Issue 12:343-348. 

Donovan, G. P. 1991. A review of IWC stock boundaries. Rept. Int. Whal. Commn., Special Issue 13:39-68. 

Forney, K.A. 2009. Serious injury determinations for cetaceans caught in Hawaii longline fisheries during 1994-

2008. Draft document PSRG-2009-09 presented to the Pacific Scientific Review Group, November 3-5, 

2009, Del Mar, CA.. 

Forney, K. A. and Brownell, R. L., Jr. 1996. Preliminary report of the 1994 Aleutian Island Marine Mammal 

Survey. Paper SC/48/O11 presented to the International Whaling Commission, June 1996 (unpublished). 

Gilpatrick, J., W. Perryman, M. Lynn, and M. A. DeAngelis. 1996. Geographic populations of blue whales 

(Balaenoptera musculus) in the North Pacific Ocean investigated from whaling records and aerial 

photogrammetry. Paper SC/47/NP4 presented to the International Whaling Commission, May 1995 

(unpublished). 

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

eastern North Pacific and adjacent Arctic waters: A guide to their identification. NOAA Technical Rept. 

NMFS Circular 444. 245 pp. 

Mate, B.R., B.A. Lagerquist, and J. Calambokidis. Movements of North Pacific blue whales during the feeding 

season off southern California and their southern fall migration. Mar. Mamm. Sci. 15(4):1246-1257. 

McCracken M., and K.A. Forney. 2010. Preliminary assessment of incidental interactions with marine mammals in 

the Hawaii longline deep and shallow set fisheries. NMFS, Pacific Islands Fisheries Science Center 

Working Paper WP-10-001. 27p 

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. 

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. 

Stafford, K.M., S. L. Nieukirk, and G.G. Fox. 2001. Geographic and seasonal variation of blue whale calls in the 

North Pacific. J. Cetacean Res. Manage. 3(1):65-76. 

Stafford. K.M. 2003. Two types of blue whale calls recorded in the Gulf of Alaska. Mar. Mamm. Sci. 19:682-693 

Stewart, B. S., S. A. Karl, P. K. Yochem, S. Leatherwood, and J. L. Laake. 1987. Aerial surveys for cetaceans in 

the former Akutan, Alaska, whaling grounds. Arctic 40(1):33-42. 

283
Thompson, P. O. and W. A. Friedl. 1982. A long term study of low frequency sound from several species of whales 

off Oahu, Hawaii. Cetology 45:1-19. 

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

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

Watkins, W. A., J. E. George, M. A. Daher, K. Mullin, D. L. Martin, S. H. Haga, and N. A. DiMarzio. 2000. Whale 

call data for the North Pacific November 1995 through July 1999: Occurrence of calling whales and source 

locations from SOSUS and other acoustic systems. Technical Report WHOI_00_02 available from Woods 

Hole Oceanographic Institution. 160pp. 

284
Revised 01/15/2011 

FIN WHALE (Balaenoptera physalus physalus): 

Hawaiian Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

Fin whales are found 

throughout all oceans and seas of the 

world from tropical to polar latitudes. 

They have been considered rare in 

Hawaiian waters and are absent to rare 

in eastern tropical Pacific waters 

(Hamilton et al. 2009). Balcomb (1987) 

observed 8-12 fin whales in a 

multispecies feeding assemblage on 20 

May 1966 approx. 250 mi. south of 

Honolulu. Additional sightings were 

reported north of Oahu in May 1976 and 

in the Kauai Channel in February 1979 

(Shallenberger 1981). More recently, a 

single fin whale was observed north of 

Kauai in February 1994 (Mobley et al. 

1996), and five sightings were made 

during a 2002 survey of waters within 

the U.S. Exclusive Economic Zone 

(EEZ) of the Hawaiian Islands (Barlow 

2003; Figure 1). A single stranding has 

been reported on Maui (Shallenberger 

1981). Thompson and Friedl (1982; and 

see Northrop et al. 1968) suggested that 

fin whales migrate into Hawaiian waters 

mainly in fall and winter, based on 

acoustic recordings off Oahu and 

Midway Islands. Although the exact positions of the whales producing the sounds could not be determined, at least 

some of them were almost certainly within the U.S. EEZ. More recently, McDonald and Fox (1999) reported an 

average of 0.027 calling fin whales per 10002

 km (grouped by 8-hr periods) based on passive acoustic recordings 

within about 16 km of the north shore of Oahu. 

W180 W175 W170 W165 W160 W155 W150

N10

N15

N20

N25

N30

N35

Figure 1. Fin whale sighting locations during the 2002 shipboard 

survey of U.S. EEZ waters surrounding the Hawaiian Islands 

(Barlow 2003; see Appendix 2 for details on timing and location of 

survey effort). Outer line represents approximate boundary of survey 

area and U.S. EEZ. 

The International Whaling Commission (IWC) recognized two stocks of fin whales in the North Pacific: 

the East China Sea and the rest of the North Pacific (Donovan 1991). Mizroch et al. (1984) cite 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. The Hawaiian stock includes 

animals found both within the Hawaiian Islands EEZ and in adjacent international waters; however, because data on 

abundance, distribution, and human-caused impacts are largely lacking for international waters, the status of this 

stock is evaluated based on data from U.S. EEZ waters of the Hawaiian Islands (NMFS 2005).

POPULATION SIZE

 Using passive acoustic detections from a hydrophone north of Oahu, MacDonald and Fox (1999) estimate 

an average density of 0.027 calling fin whales per 1000 km2

 within about 16 km from shore. However, the 

relationship between the number of whales present and the number of calls detected is not known, and therefore this 

acoustic method does not provide an estimate of absolute abundance for fin whales. A 2002 shipboard line-transect 

survey of the entire Hawaiian Islands EEZ resulted in an abundance estimate of 174 (CV=0.72) fin whales (Barlow 

2003). This is currently the best available abundance estimate for this stock. 

285
Minimum Population Estimate

 The log-normal 20th percentile of the 2002 abundance estimate is 101 fin whales within the Hawaiian 

Islands 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 

within the U.S EEZ of the Hawaiian Islands (101) times one half the default maximum net growth rate for cetaceans 

(1⁄2 of 4%) times a recovery factor of 0.1 (the default value for an endangered species; Wade and Angliss 1997), 

resulting in a PBR of 0.2 fin whales per year. 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Fishery Information 

 Information on fishery-related mortality of cetaceans in Hawaiian waters is limited, but the gear types used 

in Hawaiian fisheries are responsible for marine mammal mortality and serious injury in other fisheries throughout 

U.S. waters. Gillnets appear to capture marine mammals wherever they are used, and float lines from lobster traps 

and longlines can be expected to occasionally entangle cetaceans (Perrin et al. 1994). Interactions with cetaceans 

are reported for all pelagic fisheries, and large whales have been entangled in longline gear off the Hawaiian Islands 

(Nitta and Henderson 1993, Forney 2009). There are currently two distinct longline fisheries based in Hawaii: a 

deep-set longline (DSLL) fishery that targets primarily tunas, and a shallow-set longline fishery (SSLL) that targets 

swordfish. Both fisheries operate within U.S. waters and on the high seas. Between 2004 and 2008, no fin whales 

were observed hooked or entangled in the SSLL fishery (100% observer coverage) or the DSLL fishery (20-28% 

observer coverage) (McCracken & Forney 2010).

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. Because there have been no reported fishery related mortality or serious injuries within the Hawaiian 

Islands EEZ, the total fishery-related mortality and serious injury of this stock can be considered to be insignificant 

and approaching zero. The increasing level of anthropogenic noise in the world’s oceans has been suggested to be a 

habitat concern for whales (Richardson et al. 1995). 

REFERENCES

Allison, C. International Whaling Commission. The Red House, 135 Station Road, Impington, Cambridge, UK CB4 

9NP. 

Balcomb, K. C., III. 1987. The Whales of Hawaii. Marine Mammal Fund, 99 pp. 

Barlow, J. 2003. Cetacean abundance in Hawaiian waters during summer/fall 2002. Admin. Rep. LJ-03-13. 

Southwest Fisheries Science Center, National Marine Fisheries Service, 8604 La Jolla Shores Drive, La 

Jolla, CA 92037. 

Donovan, G. P. 1991. A review of IWC stock boundaries. Rept. Int. Whal. Commn., Special Issue 13:39-68. 

Forney, K.A. 2009. Serious injury determinations for cetaceans caught in Hawaii longline fisheries during 1994-

2008. Draft document PSRG-2009-09 presented to the Pacific Scientific Review Group, November 3-5, 

286
2009, Del Mar, CA. 

Hamilton, T.A., J.V. Redfern, J. Barlow, L.T. Balance, T. Gerrodette, R.S. Holt, K.A. Forney, and B.L. Taylor. 

2009. Atlas of cetacean sightings for Southwest Fisheries Science Center Cetacean and Ecosystem 

Surveys: 1986 – 2005. U.S. Dep. of Commerce, NOAA Technical Memorandum, NOAA-TM-NMFSSWFSC-440. 70 p. 

McCracken M., and K.A. Forney. 2010. Preliminary assessment of incidental interactions with marine mammals in 

the Hawaii longline deep and shallow set fisheries. NMFS, Pacific Islands Fisheries Science Center 

Working Paper WP-10-001. 27p 

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. 

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. 

Richardson, W. J., C. R. Greene, Jr., C. I. Malme, and D. H. Thompson. 1995. Marine Mammals and Noise. 

Academic Press, San Diego. 576 p. 

Shallenberger, E.W. 1981. The status of Hawaiian cetaceans. Final report to U.S. Marine Mammal Commission. 

MMC-77/23, 79pp. 

Thompson, P. O. and W. A. Friedl. 1982. A long term study of low frequency sound from several species of whales 

off Oahu, Hawaii. Cetology 45:1-19. 

Tønnessen, J. N. and A. O. Johnsen. 1982. The History of Modern Whaling. Hurst, 789 pp. 

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

Workshop April 3-5, 1996, Seattle, Washington. U. S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR12. 93 pp. 

287
Revised 01/15/2011 

BRYDE'S WHALE (Balaenoptera edeni): 

Hawaiian Stock 

STOCK DEFINITION AND GEOGRAPHIC RANGE 

 Bryde's whales occur in tropical 

and warm temperate waters throughout 

the world. Shallenberger (1981) 

reported a sighting of a Bryde's whale 

southeast of Nihoa in April 1977 (see 

DeLong and Brownell 1977; 

Leatherwood et al. 1982: Fig. 39c). 

Leatherwood et al. (1982) described the 

species as relatively abundant in summer 

and fall on the Mellish and Miluoki 

banks northeast of Hawaii and around 

Midway Islands, but the basis for this 

statement was not explained. Ohsumi 

and Masaki (1975) reported the tagging 

of "many" Bryde's whales between the 

Bonin and Hawaiian Islands in the 

winters of 1971 and 1972 (Ohsumi 

1977). A summer/fall 2002 shipboard 

survey of waters within the U.S. 

Exclusive Economic Zone (EEZ) of the 

Hawaiian Islands resulted in 13 Bryde’s 

whale sightings throughout the study 

area (Figure 1; Barlow 2006).With 

presently available evidence, there is no 

biological basis for defining separate 

stocks of Bryde's whales in the central North Pacific. Bryde's whales also occasionally occur off southern California 

(Morejohn and Rice 1973). For the MMPA stock assessment reports, Bryde's whales within the Pacific U.S. EEZ 

are divided into two areas: 1) Hawaiian waters (this report), and 2) the eastern Pacific (east of 150o

W and including 

the Gulf of California and waters off California). The Hawaiian stock includes animals found both within the 

Hawaiian Islands EEZ and in adjacent international waters; however, because data on abundance, distribution, and 

human-caused impacts are largely lacking for international waters, the status of this stock is evaluated based on data 

from U.S. EEZ waters of the Hawaiian Islands (NMFS 2005). 

W180 W175 W170 W165 W160 W155 W150

N10

N15

N20

N25

N30

N35

Figure 1. Bryde’s whale sighting locations during the 2002 

shipboard survey of U.S. EEZ waters surrounding the Hawaiian 

Islands (Barlow2006; see Appendix 2 for details on timing and 

location of survey effort). Outer line represents approximate 

boundary of survey area and U.S. EEZ. 

POPULATION SIZE

 Tillman (1978) concluded from Japanese and Soviet CPUE data that the stock size in the North Pacific 

pelagic whaling grounds, mostly to the west of the Hawaiian Islands, declined from approximately 22,500 in 1971 to 

17,800 in 1977. An estimate of 13,000 (CV=0.202) Bryde's whales was made from vessel surveys in the eastern 

tropical Pacific between 1986 and 1990 (Wade and Gerrodette 1993). The area to which this estimate applies is 

mainly east and somewhat south of the Hawaiian Islands, and it is not known whether these animals are part of the 

same population that occurs around the Hawaiian Islands. A 2002 shipboard line-transect survey of the entire 

Hawaiian Islands EEZ resulted in an abundance estimate of 469 (CV=0.45) Bryde’s whales (Barlow 2006). This is 

currently the best available abundance estimate for this stock. 

Minimum Population Estimate

 The log-normal 20th percentile of the 2002 abundance estimate (Barlow 2006) is 327 Bryde’s whales 

within the Hawaiian Islands EEZ. 

 

Current Population Trend

 No data are available on current population trend. 

288
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 

within the U.S EEZ of the Hawaiian Islands (327) times one half the default maximum net growth rate for cetaceans 

(1⁄2 of 4%) times a recovery factor of 0.50 (for a stock of unknown status with no known fishery mortality or serious 

injury within the Hawaiian Islands EEZ; Wade and Angliss 1997), resulting in a PBR of 3.3 Bryde’s whales per 

year. 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY 

Fishery Information

 Information on fishery-related mortality of cetaceans in Hawaiian waters is limited, but the gear types used 

in Hawaiian fisheries are responsible for marine mammal mortality and serious injury in other fisheries throughout 

U.S. waters. Gillnets appear to capture marine mammals wherever they are used, and float lines from lobster traps 

and longlines can be expected to occasionally entangle cetaceans (Perrin et al. 1994). Interactions with cetaceans are 

reported for all pelagic fisheries, and large whales have been entangled in longline gear off the Hawaiian Islands 

(Nitta and Henderson 1993, Forney 2009). There are currently two distinct longline fisheries based in Hawaii: a 

deep-set longline (DSLL) fishery that targets primarily tunas, and a shallow-set longline fishery (SSLL) that targets 

swordfish. Both fisheries operate within U.S. waters and on the high seas. Between 2004 and 2008, one Bryde’s 

whale was observed hooked or entangled in the SSLL fishery (100% observer coverage) in international waters 

(McCracken & Forney 2010). Based on an evaluation of the observer’s description of the interaction and following 

the most recently developed criteria for assessing serious injury in marine mammals (Andersen et al. 2008), this 

animal was considered not seriously injured (Forney 2009). No Bryde’s whales were observed hooked or entangled 

the DSLL fishery (20-28% observer coverage). 

Table 1. Summary of available information on incidental mortality and serious injury of Bryde’s whales (Hawaiian 

stock) in commercial fisheries, within and outside of the Hawaiian Islands EEZ (McCracken & Forney 2010). Mean 

annual takes are based on 2004-2008 data unless otherwise indicated; n/a = not available. 

Mortality and Serious In ry ju

outside of U.S. EEZ

Mortality and Serious Injury 

within Hawaiian Islands EEZ

Fishery Name Year Data Type

Percent 

Observer 

Coverage Observed Estimated 

(CV)

Mean Annual 

Takes 

(CV)

Observed Estimated 

(CV)

Mean Annual 

Takes 

(CV)

Hawaii-based 

deep-set longline 

fishery 

2004 

2005 

2006 

2007 

2008 

observer 

data 

25% 

28% 

22% 

20% 

22% 

0 

0 

0 

0 

0 

0 (-) 

0 (-) 

0 (-) 

0 (-) 

0 (-) 

0 (-) 

0 

0 

0 

0 

0 

0 (-) 

0 (-) 

0 (-) 

0 (-) 

0 (-) 

0 

Hawaii-based 

shallow-set 

longline fishery 

2004 

2005 

2006 

2007 

2008 

observer 

data 

100% 

100% 

100% 

100% 

100% 

0 

0* 

0 

0 

0 

Same as 

observed 0.2 

0 

0 

0 

0 

0 

Same as 

observed 0 

Minimum total annual takes within U.S. EEZ waters 0 

*One animal observed not seriously injured. 

Historical Mortality

 Small numbers of Bryde's whales were taken near the Northwestern Hawaiian Islands by Japanese and 

Soviet whaling fleets during the early 1970s (Ohsumi 1977). Pelagic whaling for Bryde's whales in the North 

Pacific ended after the 1979 season (IWC 1981), and coastal whaling for this species ended in the western Pacific in 

1987 (IWC 1989).

STATUS OF STOCK

The status of Bryde's whales in Hawaiian waters relative to OSP is unknown, and there are insufficient data 

to evaluate trends in abundance. It is not listed as “threatened” or “endangered” under the Endangered Species Act 

(1973), nor as “depleted” under the MMPA. Given the absence of recent fishery-related mortality or serious injuries 

within the Hawaiian Islands EEZ, the Hawaiian stock of Bryde’s whales is not considered strategic under the 1994 

289
amendments to the MMPA, and the total fishery mortality and serious injury can be considered to be insignificant 

and approaching zero. The increasing level of anthropogenic noise in the world’s oceans has been suggested to be a 

habitat concern for whales (Richardson et al. 1995). 

REFERENCES 

Andersen, M. S., K. A. Forney, T. V. N. Cole, T. Eagle, R. Angliss, K. Long, L. Barre, L. Van Atta, D. Borggaard, 

T. Rowles, B. Norberg, J. Whaley, and L. Engleby. 2008. Differentiating Serious and Non-Serious Injury 

of Marine Mammals: Report of the Serious Injury Technical Workshop, 10-13 September 2007, Seattle, 

Washington. NOAA Technical Memorandum NMFS-OPR-39. 94p. 

Barlow, J. 2006. Cetacean abundance in Hawaiian waters estimated from a summer/fall survey in 2002. Marine 

Mammal Science 22: 446–464. 

DeLong, R. L. and R. L. Brownell, Jr. 1977. Hawaiian monk seal (Monachus schauinslandi) habitat and population 

survey in the northwestern (Leeward) Hawaiian Islands, April 1977. Northwest Alaska Fish Cent. Proc. 

Rep., 43 pp. 

Forney, K.A. 2009. Serious injury determinations for cetaceans caught in Hawaii longline fisheries during 1994-

2008. Draft document PSRG-2009-09 presented to the Pacific Scientific Review Group, November 3-5, 

2009, Del Mar, CA..International Whaling Commission. 1981. Japan. Progress report on cetacean 

research June 1979-May 1980. Rep. Int. Whal. Commn. 31:195-200. 

International Whaling Commission. 1989. Japan. Progress report on cetacean research June 1987 to April 1988. 

Rep. Int. Whal. Commn. 39:201-204. 

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

North Pacific and adjacent arctic waters: A guide to their identification. NOAA Tech. Rep. NMFS 444, 

245 pp. 

McCracken M., and K.A. Forney. 2010. Preliminary assessment of incidental interactions with marine mammals in 

the Hawaii longline deep and shallow set fisheries. NMFS, Pacific Islands Fisheries Science Center 

Working Paper WP-10-001. 27p 

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. 

Richardson, W. J., C. R. Greene, Jr., C. I. Malme, and D. H. Thompson. 1995. Marine Mammals and Noise. 

Academic Press, San Diego. 576 p. 

Shallenberger, E.W. 1981. The status of Hawaiian cetaceans. Final report to U.S. Marine Mammal Commission. 

MMC-77/23, 79pp. 

Tillman, M. F. 1978. Modified Delury estimates of the North Pacific Bryde's whale stock. Rep. Int. Whal. 

Commn. 28:315-317. 

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

Workshop April 3-5, 1996, Seattle, Washington. U. S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR12. 93 pp. 

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

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

290
Revised 01/15/2011 

SEI WHALE (Balaenoptera borealis borealis): 

Hawaiian Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

 The International Whaling 

Commission (IWC) only considers one 

stock of sei whales in the North Pacific 

(Donovan 1991), but some evidence 

exists for multiple populations (Masaki 

1977; Mizroch et al. 1984; Horwood 

1987). Sei whales are distributed far out 

to sea in temperate regions of the world 

and do not appear to be associated with 

coastal features. Whaling effort for this 

species was distributed continuously 

across the North Pacific between 45-

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. There is still insufficient 

information to accurately determine 

population structure, but from a 

conservation perspective it may be risky 

to assume panmixia in the entire North 

Pacific. Four sightings of sei whales 

were recently made during a summer/fall 

2002 shipboard survey of waters within 

the U.S. Exclusive Economic Zone (EEZ) of the Hawaiian Islands (Figure 1; Barlow 2003). For the Marine 

Mammal Protection Act (MMPA) stock assessment reports, sei whales within the Pacific U.S. EEZ are divided into 

three discrete, non-contiguous areas: 1) waters around Hawaii (this report), 2) California, Oregon and Washington 

waters, and 3) Alaskan waters. The Hawaiian stock includes animals found both within the Hawaiian Islands EEZ 

and in adjacent international waters; however, because data on abundance, distribution, and human-caused impacts 

are largely lacking for international waters, the status of this stock is evaluated based on data from U.S. EEZ waters 

of the Hawaiian Islands (NMFS 2005). 

W180 W175 W170 W165 W160 W155 W150

N10

N15

N20

N25

N30

N35

Figure 1. Sei whale sighting locations during the 2002 shipboard 

cetacean survey of U.S. EEZ waters surrounding the Hawaiian 

Islands (Barlow 2003; see Appendix 2 for details on timing and 

location of survey effort). Outer line indicates approximate boundary 

of survey area and U.S. EEZ. 

POPULATION SIZE

 Ohsumi and Wada (1974) estimate the pre-whaling abundance of sei whales to be 58,000-62,000 in the 

North Pacific. Later, Tillman (1977) used a variety of different methods to estimate the abundance of sei whales in 

the North Pacific and revised this pre-whaling estimate to 42,000. His estimates for the year 1974 ranged from 

7,260 to 12,620. All methods depend on using the history of catches and trends in CPUE or sighting rates; there 

have been no direct estimates of sei whale abundance in the entire North Pacific based on sighting surveys. A 2002 

shipboard line-transect survey of the entire Hawaiian Islands EEZ resulted in a summer/fall abundance estimate of 

77 (CV=1.06) sei whales (Barlow 2003). This is currently the best available abundance estimate for this stock, but 

the majority of sei whales would be expected to be at higher latitudes in their feeding grounds at this time of year. 

Minimum Population Estimate

 The log-normal 20th percentile of the 2002 abundance estimate is 37 sei whales within the Hawaiian 

Islands EEZ. 

Current Population Trend

 No data are available on current population trend. Although the population in the North Pacific is expected 

291
to have grown since being given protected status in 1976, the possible effects of continued unauthorized takes 

(Yablokov 1994) make this uncertain. 

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

 No data are available on current or maximum net productivity rate for sei whales. 

POTENTIAL BIOLOGICAL REMOVAL

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

within the U.S. EEZ of the Hawaiian Islands (37) times one half the default maximum net growth rate for cetaceans 

(1⁄2 of 4%) times a recovery factor of 0.1 (the default value for an endangered species; Wade and Angliss 1997), 

resulting in a PBR of 0.1 sei whales per year. 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Fishery Information 

 Information on fishery-related mortality of cetaceans in Hawaiian waters is limited, but the gear types used 

in Hawaiian fisheries are responsible for marine mammal mortality and serious injury in other fisheries throughout 

U.S. waters. Gillnets appear to capture marine mammals wherever they are used, and float lines from lobster traps 

and longlines can be expected to occasionally entangle cetaceans (Perrin et al. 1994). Interactions with cetaceans are 

reported for all pelagic fisheries, and large whales have been entangled in longline gear off the Hawaiian Islands 

(Nitta and Henderson 1993; Forney 2009). There are currently two distinct longline fisheries based in Hawaii: a 

deep-set longline (DSLL) fishery that targets primarily tunas, and a shallow-set longline fishery (SSLL) that targets 

swordfish. Both fisheries operate within U.S. waters and on the high seas. Between 2004 and 2008, no sei whales 

were observed hooked or entangled in the SSLL fishery (100% observer coverage) or the DSLL fishery (20-28% 

observer coverage) (McCracken & Forney 2010).

Historical Whaling

 The reported take of North Pacific sei whales by commercial whalers totaled 61,500 between 1947 and 

1987 (C. Allison, IWC, pers. comm.). There has been an IWC prohibition on taking sei whales since 1976, and 

commercial whaling in the U.S. has been prohibited since 1972. 

STATUS OF STOCK 

Previously, sei whales were estimated to have been reduced to 20% (8,600 out of 42,000) of their prewhaling abundance in the North Pacific (Tillman 1977). Sei whales are formally listed as "endangered" under the 

Endangered Species Act (ESA), and consequently the Hawaiian stock is automatically considered as a "depleted" 

and "strategic" stock under the MMPA. Because there have been no reported fishery related mortality or serious 

injuries of sei whales within the Hawaiian Islands EEZ, the total fishery-related mortality and serious injury can be 

considered to be insignificant and approaching zero. The increasing level of anthropogenic noise in the world’s 

oceans has been suggested to be a habitat concern for whales (Richardson et al. 1995). 

REFERENCES

Allison, C. International Whaling Commission. The Red House, 135 Station Road, Impington, Cambridge, UK CB4 

9NP. 

Barlow, J. 2003. Cetacean abundance in Hawaiian waters during summer/fall 2002. Admin. Rep. LJ-03-13. 

Southwest Fisheries Science Center, National Marine Fisheries Service, 8604 La Jolla Shores Drive, La 

Jolla, CA 92037. 

Donovan, G. P. 1991. A review of IWC stock boundaries. Rept. Int. Whal. Commn., Special Issue 13:39-68. 

Forney, K.A. 2009. Serious injury determinations for cetaceans caught in Hawaii longline fisheries during 1994-

2008. Draft document PSRG-2009-09 presented to the Pacific Scientific Review Group, November 3-5, 

2009, Del Mar, CA..Horwood, J. 1987. The Sei Whale: Population Biology, Ecology and Management. 

Croom Helm, London, U.K. 375pp. 

Masaki, Y. 1977. The separation of the stock units of sei whales in the North Pacific. Rept. Int. Whal. Commn., 

Special Issue 1:71-77. 

McCracken M., and K.A. Forney. 2010. Preliminary assessment of incidental interactions with marine mammals in 

the Hawaii longline deep and shallow set fisheries. NMFS, Pacific Islands Fisheries Science Center 

Working Paper WP-10-001. 27p 

Mizroch, S. A., D. W. Rice, and J. M. Breiwick. 1984. The sei whale, Balaenoptera borealis. Mar. Fish. Rev. 

292
46:25-29. 

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. and S. Wada. 1974. Status of whale stocks in the North Pacific, 1972. Rept. Int. Whal. Commn. 

25:114-126. 

Perrin, W.F., G. P. Donovan and J. Barlow. 1994. Gillnets and Cetaceans. Rep. Int. Whal. Commn., Special Issue 

15, 629 pp. 

Rice, D. W. 1974. Whales and whale research in the eastern North Pacific. pp. 170-195 In: W. E. Schevill (ed.). 

The Whale Problem: A Status Report. Harvard Press, Cambridge, MA. 

Richardson, W. J., C. R. Greene, Jr., C. I. Malme, and D. H. Thompson. 1995. Marine Mammals and Noise. 

Academic Press, San Diego. 576 p. 

Tillman, M. F. 1977. Estimates of population size for the North Pacific sei whale. Rept. Int. Whal. Commn., 

Special Issue 1:98-106. 

Yablokov, A. V. 1994. Validity of whaling data. Nature 367:108. 

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

Workshop April 3-5, 1996, Seattle, Washington. U. S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR12. 93 pp. 

293
Revised 01/15/2011

MINKE WHALE (Balaenoptera acutorostrata scammoni): 

Hawaiian Stock 

STOCK DEFINITION AND GEOGRAPHIC RANGE

 The International Whaling 

Commission (IWC) recognizes 3 stocks of 

minke whales in the North Pacific: one in the 

Sea of Japan/East China Sea, one in the rest of 

the western Pacific west of 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 have only been 

recently confirmed to occur seasonally around 

the Hawaiian Islands (Barlow 2003, Rankin 

and Barlow, 2005), and their migration routes 

or destinations are not known. Minke whales 

were observed within 22km of Kauai during a 

nearshore survey in February 2005 (Rankin et 

al. 2007) and four reliable sightings of minke 

whales were made by observers in the Hawaiibased longline fishery during the months of December-March, 2000-2002 (Figure 1; NMFS/PIR unpublished data). 

One confirmed sighting of a minke whale was made in November 2002 during a survey of waters within the U.S. 

Exclusive Economic Zone (EEZ) of the Hawaiian Islands (Barlow 2003), and additional acoustic detections of this 

species’ distinctive call (known as the ‘boing’) were made that could not be visually verified (Figure 1). There are 

no known stranding records of this species from the main islands (Nitta 1991; Maldini et al. 2005). For the Marine 

Mammal Protection Act (MMPA) stock assessment reports, there are three stocks of minke whale within the Pacific 

U.S. EEZ: 1) a Hawaiian stock (this report), 2) a California/Oregon/ Washington stock, and 3) an Alaskan stock. 

The Hawaiian stock includes animals found both within the Hawaiian Islands EEZ and in adjacent international 

waters; however, because data on abundance, distribution, and human-caused impacts are largely lacking for 

international waters, the status of this stock is evaluated based on data from U.S. EEZ waters of the Hawaiian 

Islands (NMFS 2005). 

Figure 1. Locations of minke whale sightings from longline 

observer records (diamonds; NMFS/PIR, unpublished data), and 

sighting (closed circle) and acoustic detections (open circles) 

made during the 2002 shipboard survey of U.S. EEZ waters 

surrounding the Hawaiian Islands (Barlow 2003; see Appendix 

2 for details on timing and location of survey effort). Solid lines 

represent the U.S. EEZ. 

POPULATION SIZE

 A summer/fall 2002 shipboard line-transect survey of the entire Hawaiian Islands EEZ resulted in one ‘off 

effort’ sighting of a minke whale following the acoustic detection of a so-called ‘boing’ (Barlow 2003; Rankin and 

Barlow, 2005). This sighting was not part of regular survey operations and, therefore, could not be used to calculate 

an estimate of abundance (Barlow 2003). Furthermore, the majority of this survey took place during summer and 

early fall, when the Hawaiian stock of minke whale would be expected to be farther north. There currently is no 

abundance estimate for this stock of minke whales, which appears to occur seasonally (about November - March) 

294
around the Hawaiian Islands. 

Minimum Population Estimate

 There is no minimum population estimate for the Hawaiian stock of minke whales. 

Current Population Trend

 No data are available on current population trend. 

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

 No data are available on current or maximum net productivity rate for Hawaiian minke whales. 

POTENTIAL BIOLOGICAL REMOVAL

 No PBR can be calculated for this stock at this time. 

HUMAN CAUSED MORTALITY AND SERIOUS INJURY 

Fishery Information

 Information on fishery-related mortality and serious injury of cetaceans in Hawaiian waters is limited, but 

the gear types used in Hawaiian fisheries are responsible for marine mammal mortality and serious injury in other 

fisheries throughout U.S. waters. Gillnets appear to capture marine mammals wherever they are used, and float lines 

from lobster traps and longlines can be expected to occasionally entangle cetaceans (Perrin et al. 1994). Interactions 

with cetaceans have been reported for all Hawaiian pelagic fisheries (Nitta and Henderson 1993), but none of these 

interactions are known to have involved minke whales (Forney 2009). There are currently two distinct longline 

fisheries based in Hawaii: a deep-set longline (DSLL) fishery that targets primarily tunas, and a shallow-set longline 

fishery (SSLL) that targets swordfish. Both fisheries operate within U.S. waters and on the high seas. Between 

2004 and 2008, no minke whales were observed hooked or entangled in the SSLL fishery (100% observer coverage) 

or the DSLL fishery (20-28% observer coverage) (McCracken & Forney 2010). 

STATUS OF STOCK

 The status of minke whales in Hawaiian waters relative to OSP is unknown, and there are insufficient data 

to evaluate trends in abundance. It is not listed as “threatened” or “endangered” under the Endangered Species Act 

(1973), nor as “depleted” under the MMPA. Although information on minke whales in Hawaiian waters is limited, 

this stock would not be considered strategic under the 1994 amendments to the MMPA because there has been no 

reported fisheries related mortality or serious injury within the Hawaiian Islands EEZ. Insufficient information is 

available to determine whether the total fishery mortality and serious injury for minke whales is insignificant and 

approaching zero mortality and serious injury rate. The increasing levels of anthropogenic sound in the world’s 

oceans has been suggested to be a habitat concern for whales (Richardson et al. 1995). 

REFERENCES

Barlow, J. 2003. Cetacean abundance in Hawaiian waters during summer/fall 2002. Admin. Rep. LJ-03-13. 

Southwest Fisheries Science Center, National Marine Fisheries Service, 8604 La Jolla Shores Drive, La 

Jolla, CA 92037. 

Brueggeman, J. J., G. A. Green, K. C. Balcomb, C. E. Bowlby, R. A. Grotefendt, K. T. Briggs, M. L. Bonnell, R. G. 

Ford, D. H. Varoujean, D. Heinemann, and D. G. Chapman. 1990. Oregon-Washington Marine Mammal 

and Seabird Survey: Information synthesis and hypothesis formulation. U.S. Department of the Interior, 

OCS Study MMS 89-0030. 

Donovan, G. P. 1991. A review of IWC stock boundaries. Rept. Int. Whal. Commn., Special Issue 13:39-68. 

Dorsey, E. M., S. J. Stern, A. R. Hoelzel, and J. Jacobsen. 1990. Minke whale (Balaenoptera acutorostrata) from 

the west coast of North America: individual recognition and small-scale site fidelity. Rept. Int. Whal. 

Commn., Special Issue 12:357-368. 

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

eastern North Pacific and adjacent Arctic waters: A guide to their identification. NOAA Technical Rept. 

NMFS Circular 444. 245pp. 

Forney, K.A. 2009. Serious injury determinations for cetaceans caught in Hawaii longline fisheries during 1994-

2008. Draft document PSRG-2009-09 presented to the Pacific Scientific Review Group, November 3-5, 

2009, Del Mar, CA..McCracken M., and K.A. Forney. 2010. Preliminary assessment of incidental 

interactions with marine mammals in the Hawaii longline deep and shallow set fisheries. NMFS, Pacific 

295
Islands Fisheries Science Center Working Paper WP-10-001. 27p 

Maldini, D., L. Mazzuca, and S. Atkinson. 2005. Odontocete stranding patterns in the Main Hawaiian Islands 

(1937-2002): How do they compare with live animal surveys? Pacific Science 59(1):55-67. 

NMFS, Pacific Islands Region, Observer Program, 1602 Kapiolani Blvd, Suite 1110, Honolulu, HI 96814. 

Nitta, E. 1991. The marine mammal stranding network for Hawaii: an overview. In: J.E. Reynolds III, D.K. Odell 

(eds.), Marine Mammal Strandings in the United States, pp.56-62. NOAA Tech. Rep. NMFS 98, 157 pp. 

Nitta, E. and J. R. Henderson. 1993. A review of interactions between Hawaii's fisheries and protected species. 

Mar. Fish. Rev. 55(2):83-92. 

Perrin, W. F., G. P. Donovan and J. Barlow. 1994. Gillnets and Cetaceans. Rep. Int. Whal. Commn., Spec. Issue 15, 

629p. 

Rankin, S. and J. Barlow. 2005. Source of the North Pacific “boing” sound attributed to minke whales. J. Acous. 

Soc. Am. 118(5):3346-335. 

Rankin, S., T.F. Norris, M.A Smultea, C. Oedokoven, A.M. Zoidis, E. Silve, J. Rivers. 2007. A visual sighting and 

acoustic detections of minke whales, Balaenoptera acutorostrata. (Cetacea: Balaenopteridae), in nearshore 

Hawaiian waters. Pacific Science 612(3):395-398. 

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. 

296
Revised 10/15/2009 

 HUMPBACK WHALE (Megaptera novaeangliae) 

IUCN Oceania subpopulation – American Samoa Stock 

 

STOCK DEFINITION AND GEOGRAPHIC RANGE 

The humpback whale has a global 

distribution. Humpback whales migrate 

long distances between their feeding 

grounds at mid- to high latitudes and 

their calving and mating grounds in 

tropical waters. The Oceania 

subpopulation (as defined by the IUCN 

Red List process, see Childerhouse et 

al. 2008) ranges throughout the South 

Pacific, except the west coast of South 

America, and from the equator to the 

edges of the Antarctic ice. Humpback 

whales have been recorded across most 

of the lower latitudes of the South 

Pacific from approximately 30°S 

northwards to the equator during the 

austral autumn and winter. Although 

there have been no comprehensive 

surveys of this huge area, humpback 

whale densities are known to vary 

extensively from high densities in East 

Australia to low densities at many 

island groups. Many regional research 

projects have documented the presence 

of these whales around various island 

groups, but they are also found in open water away from islands (SPWRC 2008). Movements of individual whales 

between the tropical wintering grounds and the Antarctic summer feeding grounds have been documented by a 

variety of methods including Discovery tagging, photo-identification, matching genotypes from biopsies or 

carcasses, and satellite telemetry (Mackintosh 1942; Chittleborough 1965; Dawbin 1966; Mikhalev 2000; Rock et 

al. 2006, Franklin et al. 2007, Robbins et al. 2008). However, migratory routes and specific destinations remain 

poorly known. Unlike the other humpback stocks found in U. S. waters, the IUCN Oceania subpopulation is defined 

by structure on its calving grounds (Garrigue et al. 2006b, Olavarria et al. 2006, 2007) rather than on its feeding 

grounds. The Oceania subpopulation consists of breeding stocks E (including E1, E2 and E3) and F recognized by 

the International Whaling Commission (IWC). It is found in the area defined by the following approximate 

boundaries: 145°E (eastern Australia) in the west, 120°W (between French Polynesia and South America) in the 

east, the equator in the north, and 30°S in the south (Childerhouse et al. 2008). 

Figure 1. Western Pacific Exclusive Economic Zones for selected U.S. 

territories, including American Samoa. Information on the American 

Samoa stock of humpback whales in this report is derived from survey 

work conducted within the American Samoa EEZ, although animals range 

well outside this area (see text).

For the Marine Mammal Protection Act (MMPA) stock assessment reports, there is need for only one 

South Pacific Island region management stock of humpback whales, the American Samoa stock. American Samoa 

lies at the boundary of breeding stocks E3 and F. Surveys have been undertaken annually at the primary island of 

Tutuila since 2003. A total of 150 unique individuals were identified by fluke photographs during 58 days at sea, 

2003-2008 (D. Mattila and J. Robbins, unpublished data). Individuals have been resighted on multiple days in a 

single breeding season, but only three inter-annual re-sightings have been made to date (two based on dorsal fin 

photographs) (D. Mattila and J. Robbins, unpublished data). Breeding behavior and the presence of very young 

calves has been documented in American Samoa waters. One whale that was sighted initially without a calf was resighted later in the season with a calf. Individual exchange has been documented with Western Samoa (SPWRC 

2008), as well as Tonga, French Polynesia and the Cook Islands (Garrigue et al. 2007). Although the feeding range 

of American Samoan whales has not yet been defined, there has been one photo-ID match to the Antarctic Peninsula 

(IWC Antarctic Area I, Robbins et al. 2008). Whales at Tonga have exhibited exchange with both Antarctic Area V 

(Dawbin 1959) and Area I (Brown 1957, Dawbin 1956) and so whales from American Samoa may have a similarly 

297
wide feeding range. 

 On-going photographic studies indicate a higher frequency of certain types of skin lesions on humpback 

whales at American Samoa as compared to humpback whale populations at Hawaii or the Gulf of Maine (Mattila 

and Robbins, 2008). However, the cause and implications have yet to be determined. Some similar skin lesions on 

blue whales in Chilean waters have been observed (Brownell et al. 2008). 

 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY 

Historic whaling 

 Southern Hemisphere humpback whales were hunted extensively during the last two centuries, and it is 

thought that populations have been reduced to a small percentage of their former levels (Chapman 1974). After 

correcting catch records for illegal Soviet whaling, (Clapham & Baker 2002) estimated that over 200,000 Southern 

Hemisphere humpback whales were killed from 1904 to 1980. Humpback whales were protected from commercial 

whaling in 1966 by the IWC but they continued to be killed illegally by the Soviet Union until 1972. Illegal Soviet 

catches of 25,000 humpback whales in two seasons (1959/60 and 1960/61) precipitated a population crash and the 

closure of land stations in Australia and New Zealand, including Norfolk Island (Mikhalev 2000; Clapham et al. 

2005). 

 

POPULATION SIZE 

 There is currently no estimate of abundance for humpback whales in American Samoan waters. The South 

Pacific Whale Research Consortium produced a number of preliminary mark-recapture estimates of abundance for 

Oceania and its subregions (SPWRC, 2006). A closed population estimate of 3,827 (CV 0.15) was calculated for 

eastern Oceania (breeding stocks E3 and F) for 1999-2004 and this may be the most relevant of those currently 

available, given observed exchange between American Samoa, Tonga, the Cook Islands, and French Polynesia 

(Garrigue et al. 2006a). However, the extent and biological significance of the documented interchange is still 

poorly understood. 

Minimum Population Estimate 

The minimum population estimate for this stock is 150 whales, which is the number of individual 

humpbacks identified in the waters around American Samoa between 2003-2008 by fluke photo identification (J. 

Robbins, personal communication). This is clearly an underestimation of the true minimum population size as photo 

ID studies have been conducted over a few weeks per year and there is also evidence of exchange with other areas 

in Oceania. There are also insufficient data to estimate the proportion of time Oceania humpback whales spend in 

waters of American Samoa. 

Current Population Trend 

 No data are available on current population trend. 

 

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES 

 No estimates of current or maximum net productivity rates are available for this species in Samoan waters. 

However, the maximum plausible growth rate for Southern Hemisphere humpback whale populations is estimated 

as 10.6% (Clapham et al. 2006). 

 

POTENTIAL BIOLOGICAL REMOVAL 

 The potential biological removal (PBR) for this stock is calculated as the minimum population size (150) 

times one half the estimated maximum growth rate for humpback whales in the Southern Hemisphere (1/2 of 

10.6%) times a recovery factor of 0.1 (for an endangered species with a total population size of less than 1,500), 

resulting in a PBR of 0.8. This stock of humpback whales is migratory and thus, it is reasonable to expect that 

animals spend at least half the year outside of the relatively small American Samoa EEZ. Therefore, the PBR 

allocation for U.S. waters is half of 0.8, or 0.4 whales. 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY 

No human-related mortalities of humpback whales have been recorded in American Samoan waters. 

Human-related mortality of humpback whales due to entanglements in fishing gear and collisions with ship have 

been reported elsewhere in the Southern Hemisphere. Entanglement of humpback whales in pot lines has been 

reported in both New Zealand and Australia but there are no estimated rates available. There is little information 

298
from the rest of the South Pacific but a humpback mother (with calf) was reported entangled in a longline in 2007 in 

the Cook Islands (N. Hauser, reported in SPWRC 2008). 

 A photographic-based scar study of the humpback whales of American Samoa has been initiated and there is 

some indication of healed entanglement and ship strike wounds, although perhaps not at the levels found in some 

Northern Hemisphere populations (D. Mattila and J. Robbins, unpublished data). However, the sample size to date 

is insufficient for robust comparison and the study is ongoing. 

 

STATUS OF STOCK 

 The status of humpback whales in American Samoan EEZ waters relative to OSP is unknown and there are 

insufficient data to estimate trends in abundance. However, humpback whale populations throughout the South 

Pacific were drastically reduced by historical whaling and IUCN classifies the Oceania subpopulation as 

“Endangered” (Childerhouse et al. 2008). Worldwide humpback whales are listed as “endangered” under the 

Endangered Species Act (1973) so the Samoan stock is automatically considered a "depleted" and “strategic” stock 

under the MMPA. There are no habitat concerns for the stock. 

 Japan has proposed killing 50 humpback whales as part of its program of scientific research under special 

permit (scientific whaling) called JARPA II in the IWC management areas IV and V in the Antarctic (Gales et al.

2005). Areas IV and V have demonstrated links with breeding stock E. Japan postponed their proposed catch in the 

2007/08 and 2008/09 seasons but have not removed them from their future whaling program. The JARPA II 

program has the potential to negatively impact the recovery of humpbacks in Oceania.

REFERENCES 

Brownell, R. L., Jr., C. A. Carlson, B. Galletti Vernazzani, and E. Cabrera. 2008. Skin lesions on blue whales off 

southern Chile. Paper SC/60/SH25 presented to the Scientific Committee of the International Whaling 

Commission, Santiago, Chile. 

Chapman, D.G. 1974. Status of Antarctic rorqual stocks. Pages 218-238 in W.E. Schevill, (ed.), The whale problem. 

Harvard University Press, Cambridge. 

Childerhouse, S., J. Jackson, C. S. Baker, N. Gales, P. J. Clapham, and R. L. Brownell, Jr. 2008. Megaptera 

novaeangliae, Oceania subpopulation. IUCN Red List of Threatened Species 

(http://www.iucnredlist.org/details/132832 ). 

Chittleborough, R.G. 1965. Dynamics of two populations of humpback whales, Megaptera novaeangliae

(Borowski). Aust. J. Mar. and Freshw. Res. 16:33-128. 

Clapham, P. J. and C. S. Baker. 2002. Modern whaling. Pages 1328-1332 in W.F. Perrin, B. Würsig and J.G.M. 

Thewissen, (eds.) Encyclopedia of Marine Mammals. Academic Press, New York. 

Clapham, P., Yu. Mikhalev, W. Franklin, D. Paton, C. S. Baker, and R. L. Brownell, Jr. 2005. Catches of 

humpback whales in the Southern Ocean, 1947-1973. Paper SC/57/SH6 presented to the Scientific 

Committee of the International Whaling Commission, Uslan, Korea. 

Clapham, P., P. Wade, and A. Zerbini. 2006. Plausible rates of population growth in humpback whales revisited. 

SC/58/SH4 presented to the Scientific Committee of the International Whaling Commission, St. Kitts & 

Nevis. 

Dawbin, W.H. 1966. The seasonal migratory cycle of humpback whales. Pages 145-171 in K.S. Norris (ed.), 

Whales, dolphins and porpoises. University of California Press, Berkeley. 

Franklin, T., F. Smith, N. Gibbs, S. Childerhouse, D. Burns, D. Paton, W. Franklin, C. S. Baker, and P. Clapham. 

2007. Migratory movements of humpback whales (Megaptera novaeangliae) between eastern Australia 

and the Balleny Islands, Antarctica, confirmed by photo-identification. Paper SC/59/SH18 presented to the 

Scientific Committee of the International Whaling Commission Annual Meeting 2007, Anchorage, Alaska. 

Garrigue, C., C. S. Baker, R. Constantine, M. Poole, N. Hauser, P. Clapham, M. Donoghue, K. Russell, D. Paton, 

and D. Mattila. 2006a. Interchange of humpback whales in Oceania (South Pacific), 1999 to 2004. Paper 

SC/A06/HW55 presented to IWC Comprehensive Assessment of Southern Hemisphere Humpback whales 

2006, Hobart, Australia. 

Garrigue, C., C. Olavarría, C. S. Baker, D. Steel, R. Dodemont, R. Constantine and K. Russell. 2006b. Demographic 

and genetic isolation of New Caledonia (E2) and Tonga (E3) breeding stocks. Report SC/A06/HW19 for 

consideration of the Inter-sessional Workshop for the Comprehensive Assessment of Southern Hemisphere 

humpback whales. Scientific Committee of the International Whaling Commission. Hobart, Australia. 

Garrigue, C., T. Franklin, K. Russell, D. Burns, M. Poole, D. Paton, N. Hauser, M. Oremus, R. Constantine, S. 

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Childerhouse, D. Mattila, N. Gibbs, W. Franklin, J. Robbins, P. Clapham, and C. S. Baker. 2007. First 

assessment of interchange of humpback whales between Oceania and the east coast of Australia. Paper 

SC/59/SH15 presented to the Scientific Committee of the International Whaling Commission Annual 

Meeting 2007, Anchorage, Alaska. 

Gales, N. J., Kasuya, T., Clapham, P. J. and Brownell, R. L., Jr. 2005. Japan’s whaling plan under scrutiny. Nature 

435:883-884. 

Mackintosh, N.A. 1942. The southern stocks of whalebone whales. Disc. Rep. 22:197-300. 

Mattila, D.K. and J. Robbins. 2008. Incidence of raised and depressed ovoid skin lesions on humpback whales of 

American Samoa. Paper SC/60/DW3 presented to the Scientific Committee of the International Whaling 

Commission, Santiago, Chile. 

Mikhalev, Y.A. 2000. Biological characteristics of humpbacks taken in Antarctic Area V by the whaling fleets 

Slava and Sovietskaya Ukraina. Paper SC/52/IA presented to the Scientific Committee of the International 

Whaling Commission, Adelaide, Australia. 

Olavarría, C., M. Anderson, D. Paton, D. Burns, M. Brasseur, C. Garrigue, N. Hauser, M. Poole, S. Caballero, L. 

Flórez-González, and C. S. Baker. 2006. Eastern Australia humpback whale genetic diversity and their 

relationship with Breeding Stocks D, E, F and G. Paper SC/58/SH25 presented to the Scientific Committee 

of the International Whaling Commission , St Kitts & Nevis. 

Olavarría, C., C. S. Baker, C. Garrigue, C., M. Poole, N. Hauser, S. Caballero, L. Flórez-González, M. Brasseur, J. 

Bannister, J. Capella, J., P. Clapham, R. Dodemont, M. Donoghue, C. Jenner, M. Jenner, D. Moro, M. 

Oremus, D. Paton, and K. Russell. 2007. Population structure of humpback whales throughout the South 

Pacific and the origins of the eastern Polynesian breeding grounds. Marine Ecology Progress Series 

330:257-268. 

Robbins, J., L. Dalla Rosa, J. M. Allen, D. K. Mattila, and E. R. Secchi. 2008. Humpack whale photo-identification 

reveals exchange between American Samoa and the Antarctic Peninsula, and a new mammalian distance 

record. Paper SC/60/SH5 presented to the Scientific Committee of the International Whaling Commission, 

Santiago, Chile. 

Robbins, J. and D. K. Mattila. 2006. Summary of humpback whale research at American Samoa, 2003-2005. Paper 

SC/58/SH5 presented to the Scientific Committee of the International Whaling Commission, St. Kitts & 

Nevis. 

Rock, J., L. A. Pastene, G. Kaufman, P. Forestell, K. Matsuoka, and J. Allen, 2006. A note on East Australia Group 

V Stock humpback whale movement between feeding and breeding areas based on photo-identification. 

Journal of Cetacean Research and Management 8: 301-305. 

South Pacific Whale Research Consortium (C. S. Baker, C. Garrigue, R. Constantine, B. Madon, M. Poole, N. 

Hauser, P. Clapham, M. Donoghue, K. Russell, T. O’Callahan, D. Paton and D. Mattila). 2006. Abundance 

of humpback whales in Oceania (South Pacific), 1999 to 2004. Unpublished report to the IWC Intersessional workshop for the Comprehensive Assessment of Southern Hemisphere Humpback Whales. 

Hobart, Australia. 

South Pacific Whale Research Consortium. 2008. Report of the Annual Meeting of the South Pacific Whale 

Research Consortium, Auckland, 5-8 February 2008. South Pacific Whale Research Consortium, P.O. Box 

3069, Avarua, Rarotonga, Cook Islands. 36 pp. 

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Revised 01/15/2011 Appendix 1. Description of U.S. Commercial Fisheries 

The Marine Mammal Protection Act (MMPA) requires NMFS to publish a list of commercial fisheries (List Of 

Fisheries or “LOF”) and classify each fishery based on whether incidental mortality and serious injury of marine mammals 

is frequent (Category I), occasional (Category II), or unlikely or unknown (Category III). The LOF is published annually in 

the Federal Register. The categorization of a fishery in the LOF determines whether participants in that fishery are subject 

to certain provisions of the MMPA, such as registration, observer coverage, and take reduction plan requirements. The 

categorization criteria as they appear in the LOF is reprinted below: 

 The fishery classification criteria consist of a two-tiered, stock-specific approach that first addresses the total impact 

of all fisheries on each marine mammal stock, and then addresses the impact of individual fisheries on each stock. This 

approach is based on consideration of the rate, in numbers of animals per year, of incidental mortality and serious injury of 

marine mammals due to commercial fishing operations relative to the Potential Biological Removal (PBR) level for each 

marine mammal stock. The MMPA (16 U.S.C. 1362 (20)) defines the PBR level as the maximum number of animals, not 

including natural mortality, that may be removed from a marine mammal stock while allowing that stock to reach or 

maintain its optimum sustainable population. This definition can also be found in the implementing regulations for section 

118 at 50 CFR 229.2. 

 Tier 1: If the total annual mortality and serious injury across all fisheries that interact with a stock is less than or 

equal to 10 percent of the PBR level of the stock, all fisheries interacting with the stock would be placed in Category III. 

Otherwise, these fisheries are subject to the next tier (Tier 2) of analysis to determine their classification. 

 Tier 2, Category I: Annual mortality and serious injury of a stock in a given fishery is greater than or equal to 50 

percent of the PBR level. 

 Tier 2, Category II: Annual mortality and serious injury of a stock in a given fishery is greater than 1 percent and 

less than 50 percent of the PBR level. 

 Tier 2, Category III: Annual mortality and serious injury of a stock in a given fishery is less than or equal to 1 

percent of the PBR level. 

While Tier 1 considers the cumulative fishery mortality and serious injury for a particular stock, Tier 2 considers fisheryspecific mortality and serious injury for a particular stock. Additional details regarding how the categories were determined 

are provided in the preamble to the final rule implementing section 118 of the MMPA (60 FR 45086, August 30, 1995). 

Since fisheries are categorized on a per-stock basis, a fishery may qualify as one Category for one marine mammal stock 

and another Category for a different marine mammal stock. A fishery is typically categorized on the LOF at its highest level 

of classification (e.g., a fishery that qualifies for Category III for one marine mammal stock and for Category II for another 

marine mammal stock will be listed under Category II). 

Other Criteria That May Be Considered

 In the absence of reliable information indicating the frequency of incidental mortality and serious injury of marine 

mammals by a commercial fishery, NMFS will determine whether the incidental serious injury or mortality qualifies for 

Category II by evaluating other factors such as fishing techniques, gear used, methods used to deter marine mammals, 

target species, seasons and areas fished, qualitative data from logbooks or fisher reports, stranding data, and the species and

distribution of marine mammals in the area, or at the discretion of the Assistant Administrator for Fisheries (50 CFR 229.2). 

This appendix describes commercial fisheries that occur in California, Oregon, Washington, and Hawaiian waters 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 as a proposed rule in the Federal Register, 71 FR 20941, 24 April 2006. 

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 

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Revised 01/15/2011 Appendix 1. Description of U.S. Commercial Fisheries 

Program (MMAP) data, and the NMFS Marine Mammal Stranding Network (MMSN) data. Each of these data sources has 

an unique objective. Data on mammal mortality and injury are reported to the MMAP by fishers in any commercial 

fisheries. Marine mammal mortality and injury is also monitored by the NMFS Marine Mammal Stranding Network 

(MMSN). Data provided by the MMSN is not duplicated by either the NMFS Observer Program or MMAP reporting. 

Human-related data from the MMSN include occurrences of mortality due to entrainment in power station intakes, ship 

strikes, shooting, evidence of net fishery entanglement (net remaining on animal, net marks, severed flukes), and ingestion 

of hooks. 

2. Marine Mammal Reporting from Fisheries 

 In 1994, the MMPA was amended to implement a long-term regime for managing mammal interactions with 

commercial fisheries (the Marine Mammal Authorization Program, or MMAP). Logbooks are no longer required - instead 

vessel owners/operators in any commercial fishery (Category I, II, or III) are required to submit one-page pre-printed 

reports for all interactions (including those that occur while an observer is onboard) resulting in an injury to or death of a 

marine mammal. The report must include owner/operator’s name and address, vessel name and ID, where and when the 

interaction occurred, the fishery, species involved, and type of injury (if the animal was released alive). These postage-paid

report forms are mailed to all Category I and II fishery participants that have registered with NMFS, and must be completed 

and returned to NMFS within 48 hours of returning to port for trips in which a marine mammal injury or mortality 

occurred. The number of self-reported marine mammal interactions is considerably lower than the number reported by 

fishery observers, even though observer reports are typically based on 20% observer effort. For example, from 2000-2004, 

there were 112 fisher self-reports of marine mammal interactions in the California swordfish/thresher shark drift gillnet 

fishery. This compares with 141 observed interactions over the same period, based on only 20% observer coverage. This 

suggests that fisher self-reports are negatively-biased. 

3. NMFS Marine Mammal Stranding Network data

 From 2000-2004, there were 1,022 cetacean and 13,215 pinniped strandings recorded in California, Oregon, and 

Washington states. Approximately 10% of all cetacean and 6% of all pinniped strandings showed evidence of humancaused 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. 

4. Fishery Descriptions

Category I, CA/OR thresher shark/swordfish drift gillnet fishery (≥14 inch mesh)

Number of permit holders: The numbers of eligible permit holders in California for 2002-2006 were 106, 100, 96, 90, and 

88, respectively (data source: California Deparment of Fish and Game website: www.dfg.ca.gov/licensing). Permits are 

non-transferable and are linked to individual fishermen, not vessels. 

Number of active permit holders: The numbers of vessels active in this fishery from 2002-2006 were 50, 43, 43, 40, and 

43 respectively. Information on the number of permit holders is obtained from the Status of the U.S. west coast fisheries 

for Highly Migratory Species through 2004; Stock Assessment and Fishery Evaluation report available from the Pacific 

Fishery Management Council website (www.pcouncil.org) and the California Department of Fish and Game. 

Total effort: Both estimated and observed effort for the drift-net fishery during the calendar years 1990 through 2006 are 

shown in Figure 2. 

Geographic range: Effort in this fishery ranges from the U.S./Mexico border north to waters off the state of Oregon. For 

this fishery there are area-season closures (see below). Figures 1-5 show locations of observed sets and Figure 6 shows 

approximate locations of observed marine mammal entanglements for the period 1998-2002. 

Seasons: This fishery is subject to season-area restrictions. From February 1 to May 15 effort must be further than 200 

nautical miles (nmi) from shore; from May 16 to August 14, effort must be further than 75 nmi from shore, and from 

August 15 to January 31 there is only the 3 nmi off-shore restriction for all gillnets in southern California (see halibut and 

white seabass 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') to 

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Revised 01/15/2011 Appendix 1. Description of U.S. Commercial Fisheries 

N 34o 27' W 123o

 35', west to W129o, north to N 45o, then east to the Oregon coast. An additional season-area closure south 

of Point Conception and east of W120 degrees longitude is effective during the months of June, July, and August during El 

Niño years to protect loggerhead turtles (Federal Register, 68 FR 69962, 16 December 2003). 

Gear type and fishing method: Typical gear used for this fishery is a 1000-fathom gillnet with a stretched mesh size 

typically ranging from 18-22 inches (14 inch minimum). The net is set at dusk and allowed to drift during the night after 

which, it is retrieved. The fishing vessel is typically attached to one end of the net. Soak duration is typically 12-14 hours 

depending on the length of the night. Net extender lengths of a minimum 36 ft. became mandatory for the 1997-1998 

fishing season. The use of acoustic warning devices (pingers) became mandatory 28 October 1997. 

Regulations: The fishery is managed under a Fishery Management Plan (FMP) developed by the Pacific Fishery 

Management Council and NMFS. 

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 stocks 

including short-finned pilot whales, beaked whales, sperm whales and humpback whales, a Take Reduction Team was 

formed in 1996. Since then, the implementation of increased extender lengths and the deployment of pingers have 

substantially decreased cetacean entanglement. The fraction of active vessels in this fishery that are not observed owing 

to a lack of berthing space for observers has been increasing as larger vessels drop out of this fishery. 

Category I1

, CA halibut/white seabass and other species set gillnet fishery (>3.5 inch mesh).

Note: This fishery has not targeted angel sharks since 1994, when regulatory changes resulted in nets being fished >3 nmi 

from shore in southern California. Thus, there is a proposed name change to this fishery to reflect current fishing practices.

Halibut are typically targeted using 8.5 inch mesh while the remainder of the fishery targets white seabass and yellowtail 

using 6.5 inch mesh. In recent years, there has been an increasing number of 6.0-6.5 inch mesh sets fished using drifting 

methods; this component is now identified as a separate fishery (see “CA yellowtail, barracuda, white seabass, and tuna 

drift gillnet fishery (>3.5 and <14 in mesh)” fishery described below). 

Number of permit holders: There is no specific permit category for this fishery. Overall, the current number of legal 

permit holders for gill and trammel nets, excluding swordfish drift gillnets and herring gillnets for 2002-2006 are, 209, 

193, 187, 172, and 166, respectively. Information on permit numbers is available from the California Department of Fish 

and Game website (http://www.dfg.ca.gov/licensing). 

Number of active permit holders: Based on logbook data, there were at least 62 active permit holders during the period 

2002-2006. Annual participation in the fishery appears to have declined, as the number of active permit holders by 

individual year (43, 42, 41, 31, 28) has declined. 

Total effort: Fishing effort in the halibut fishery has declined from over 3,200 sets in 2002 to approximately 1,400 sets in 

2006. A summary of estimated fishing effort and observer coverage for the years 1990-2003 is shown in Figure 8. Effort 

in the white seabass and yellowtail portion of this fishery has ranged between 456 and 948 days annually for the period 

2002-2006. A portion of the effort in the white seabass and yellowtail fishery utilizes drifting nets (see “CA yellowtail, 

barracuda, white seabass, and tuna drift gillnet fishery (>3.5 and <14 in mesh)” fishery description in the Category II 

fishery section below). 

Geographic range: Effort in this fishery previously ranged from the U.S./Mexico border north to Monterey Bay and was 

localized in more productive areas: San Ysidro, San Diego, Oceanside, Newport, San Pedro, Ventura, Santa Barbara, Morro 

Bay, and Monterey Bay. Fishery effort is now predominantly in the Ventura Flats area off of Ventura, the San Pedro area 

between Pt. Vicente and Santa Catalina Island and in the Monterey Bay area. The central California portion of the fishery 

 

1

 Due to the closure of the fishery in central California, which has reduced the threat to stocks of harbor porpoise in this 

region, the draft 2009 NMFS MMPA List of Fisheries proposes to recategorize this fishery to ‘Category II’. 

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Revised 01/15/2011 Appendix 1. Description of U.S. Commercial Fisheries 

from Point Arguello to Point Reyes has been closed since September 2002 when a ban on gillnets inshore of 60 fathoms 

took effect. 

Seasons: This fishery operates year round. Effort generally increases during the summer months and declines during the 

last three months of a year. 

Gear type and fishing method: Typical gear used for this fishery is a 200 fathom gillnet with a stretched mesh size of 8.5 

inches. The component of this fishery that targets white seabass and yellowtail utilizes 6.5 inch mesh. The net is generally 

set during the day and allowed to soak for up to 2 days. Soak duration is typically 8-10, 19-24, or 44-49 hours. The depth 

of water ranges from 15-50 fathoms with most sets in water depths of 15-35 fathoms. 

Regulations: This fishery is managed by the California Dept. of Fish and Game in accordance with state and federal laws. 

Management type: The halibut and white seabass set-net fishery is a limited-entry fishery with gear restrictions and area 

closures. 

Comments: An observer program for the halibut and white seabass portion of this fishery operated from 1990-94 and was 

discontinued after area closures were implemented in 1994, which prohibited gillnets within 3 nmi of the mainland and 

within 1 nmi of the Channel Islands in southern California. NMFS re-established an observer program for this fishery in 

Monterey Bay in 1999-2000 due to a suspected increase in harbor porpoise mortality in Monterey Bay. In 1999 and 2000, 

fishery mortality exceeded PBR for the Monterey Bay harbor porpoise stock, which at that time, was designated as 

strategic [the stock is currently non-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 in response to concerns over mortality of common murres and threats to sea otters. This effectively reduced fishing 

effort to negligible levels in 2001 and 2002 in Monterey Bay. A ban on gill and trammel nets inside of 60 fathoms from 

Point Reyes to Point Arguello became effective in September 2002. Mortality of marine mammals continues in the 

southern California portion of this fishery, as evidenced by fisher self-reports under the Marine Mammal Authorization 

Program (MMAP) from 2000-2005. During this time, fishermen reported mortality of 60 California sea lions, 20 harbor 

seals, one northern elephant seal and one unidentified common dolphin. NMFS renewed observer coverage in 

halibut/white seabass set gillnet fishery in 2006 and through 2007, observers recorded bycatch data from 260 sets. No 

cetaceans were observed entangled during this period, but there were 34 California sea lions, two harbor seals, and one 

unidentified pinniped observed killed. 

 

Category I, Hawaii deep-set (tuna target) longline/set line fishery

Note: The Hawaii-based longline fisheries of the Pelagic Fishery Ecosystem Plan (FEP) consist of two separately managed 

longline fisheries. One is the deep-set (tuna targeted) fishery which is classified as a Category I fishery under the MMPA. 

This fishery is discussed here. The classification of this fishery was elevated to Category I in 2004 based on revised PBR 

levels of false killer whales and observed false killer whale mortality in this fishery (Federal Register 69 FR 48407 1, 10 

August 2004). The other Hawaii-based longline fishery is the Hawaii shallow-set longline (swordfish targeted) fishery 

which is classified as a Category II fishery under the MMPA and is discussed in the Category II section of this Appendix. 

Number of permit holders: The number of Hawaii longline limited access permit holders is 164. Not all such permits are 

renewed and used every year. Permit holders may use the permits for either deep-set or shallow-set fishing, but must notify 

NMFS how they will fish before each trip. Most holders of Hawaii longline limited access permits are based in, or operate 

out of, Hawaii. 

Number of active deep-set longline vessels targeting tuna: From 2005 to 2008, the number of active longline vessels based 

and landing in Hawaii was 124, 127, 129, and 127, respectively (http://www.pifsc.noaa.gov/fmsd/reports.php). 

 

Total effort: The number of trips ranged from a low of approximately 500 (in 1992) to 1,400 in 2005. Figure 4 shows the 

number of fishing trips by longline vessels based and landing in Hawaii, by year and trip type, 1991-2009. The number of 

sets for the deep-set tuna fishery in 2005, 2006, 2007, and 2008 was 16,549, 16,397, 17,809, and 17,881, respectively. The 

number of hooks set in 2005, 2006, 2007, and 2008 was 33.7 million, 34.5 million, 38.8 million, and 40.1 million, 

respectively. 

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Geographic range: The Hawaii-based pelagic, deep-set longline fishery operates inside and outside the EEZ, primarily 

around the main Hawaiian Islands and Northwestern Hawaiian Islands, with some trips to the EEZs around the remote U.S. 

Pacific islands (however there are restricted areas, please refer to “Regulations”). Vessels vary their fishing grounds 

depending on their target species. Most of the deep-set fishing occurs south of 20° N. 

Seasons: This fishery operates year-round, although vessel activity increases during the fall and is greatest during the 

winter and spring months. 

Gear type: Deep-set longline gear typically consists of a continuous main line set on the surface and supported in the water 

column horizontally by floats with branch lines connected at intervals to the main line. In addition radio buoys are also used 

to keep track of the mainline as it drifts at sea. A line shooter is used on deep-sets to deploy the mainline faster than the 

speed of the vessel, thus allowing the longline gear to sink to its target depth (average target depth is 167 m, target depth for 

bigeye tuna is approximately 400 m). The main line is typically 30 to 100 km (18 to 60 nm) long. A minimum of 15, but 

typically 20 to 30, weighted branch lines (gangions) are clipped to the mainline at regular intervals between the floats. 

Each gangion terminates with a single baited hook. The branch lines are typically 11 to 15 meters (35 to 50 feet) long. 

Sanma (saury) or sardines are used for bait. Lightsticks are not typically attached to the gangions on this type of longline 

set. Deep-set longline gear is set in the morning and hauled in the afternoon.

Regulations: This fishery is managed under the Pelagics FEP and subject to Federal regulation. Measures that are currently 

applicable to the fishery include, but are not limited to, limited access (requirement for a permit), vessel and gear marking 

requirements, vessel length restrictions, Federal catch and effort logbooks, large longline restricted areas around the 

Hawaiian Archipelago, vessel monitoring system (VMS), annual protected species workshops, and the use of sea turtle, 

seabird, and marine mammal handling and mitigation gear and techniques. The vessel operator must notify NMFS prior to 

departure whether the vessel is undertaking a deep-set or shallow-set trip. Once the trip type is set, it cannot be changed 

during the trip. Vessel operators must take a NMFS contracted observer if requested by NMFS – target observer coverage 

is 20 percent of trips. If any marine mammal interaction (hooking or entanglement) resulting in injury or mortality occurs, 

the vessel operator must complete and mail a pre-addressed, postage paid form to NOAA Fisheries within 48 hours of the 

end of the trip. Additional information on all applicable regulations for the deep-set longline fishery is available at 

http://www.fpir.noaa.gov/SFD/SFD_regs_2.html.

Management type: Federal limited access program. This fishery is managed under a Fishery Ecosystem Plan (FEP)

developed by the Western Pacific Fishery Management Council and NMFS. 

Comments: Non-target species are caught incidentally. Interactions with common bottlenose dolphins, false killer whales, 

humpback whales, short-finned pilot whales, pantropical spotted dolphins, Blainville’s beaked whale, and Risso’s dolphins 

have been documented. Longline hooks have also been recovered from Hawaiian monk seals, but these were not observed 

during longline fishing operations. 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 exceeded 

20% in 2001, 2002, and 2003. Observer coverage was 20.1 %, 21.7%, and 20.6% in 2007, 2008, and 2009 respectively. 

Observed marine mammal injures in 2007 included 4 false killer whales, 1 short-finned pilot whale, and 2 unidentified 

cetaceans. Observed mortality included 1 Risso’s dolphin. Observed marine mammal injuries in 2008 included 3 false 

killer whales, 3 short-finned pilots whales, 1 Risso’s dolphin, 2 unidentified cetaceans, and 2 unidentified whales. 

Observed mortality in 2008 included 1 spotted dolphin. Observed injuries of marine mammals in 2009 included 9 false 

killer whales, 1 bottlenose dolphin, and 3 unidentified whales. Observed mortality of marine mammals in this fishery in 

2009 included 1 false killer whale. 

Category II, Hawaii shallow-set (swordfish target) longline/set line fishery 

Note: The Hawaii-based longline fisheries of the Pelagic Fishery Ecosystem Plan (FEP) consist of two separately managed 

longline fisheries. One is the deep-set (tuna targeted) fishery which is classified as a Category I fishery under the MMPA. 

The other is the Hawaii shallow-set longline (swordfish targeted) fishery which is classified as a Category II fishery under 

the MMPA and is discussed here. 

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Number of permit holders: The number of Hawaii longline limited access permit holders is 164. Not all such permits are 

renewed and used every year. Permit holders may use the permits for either deep-set or shallow-set fishing, but must notify 

NMFS how they will fish before each trip. Most holders of Hawaii longline limited access permits are based in, or operate 

out of, Hawaii. Longline general permits are not limited by number. These general permits are open access and usable in 

Guam, CNMI, and the Pacific Remote Island Areas; they are usually not more than a half dozen a year. 

Number of active shallow-set longline vessels targeting swordfish: From 2005 to 2008, the number of active shallow-set 

longline vessels based in and landing in Hawaii was 33, 35, 28, and 27, respectively 

Total effort: The number of trips since 1991 has ranged from zero (2002-2003) to approximately 300 in 1993. Figure 4 

shows the number of fishing trips by longline vessels based and landing in Hawaii, by year and trip type, 1991-2009. The 

number of sets for the shallow-set swordfish fishery in 2005, 2006, 2007, and 2008 was 1,645, 850, 1,570, and 1,587, 

respectively. The number of hooks set in 2005, 2006, 2007, and 2008 was 1.4 million, 0.7 million, 1.4 million, and 1.5 

million, respectively. 

Geographic range: 

The most productive swordfishing areas for Hawaii-based longline vessels are north of Hawaii outside the U.S. Exclusive 

Economic Zone (EEZ) on the high seas, and this fishery operates almost entirely north of Hawaii (north of approximately 

20° N). In some years, when influenced by seawater temperature, this fishery may operate mostly north of 30° N. 

Seasons: Shallow-set effort is highest in either the first or second quarter of the calendar year and drops off substantially in 

the latter half of the year. 

Gear type: Shallow-set longline gear typically consists of a continuous main line set on the surface and supported in the 

water column horizontally by floats with branch lines connected at intervals to the main line. In addition radio buoys are 

also used to keep track of the mainline as it drifts at sea. Longline fishing for swordfish is known as shallow-set longline 

fishing as the bait is set at depths of 30–90 m. The portion of the mainline with branchlines attached is suspended between 

floats at about 20–75 m of depth, and the branchlines hang off the mainline another 10–15 m. Only 4-6 branchlines are 

clipped to the mainline between floats, and a typical set for swordfish uses about 700–1,000 hooks. Shallow-set longline 

gear is set at night, with luminescent light sticks attached to the branchlines. Formerly, J-hooks and squid bait were used, 

but since 2004, circle hooks and mackerel-type bait have been required. These gear restrictions were implemented to 

reduce sea turtle bycatch. 

Regulations: This fishery is managed under the Pelagics FEP and subject to Federal regulation. Measures that are 

currently applicable to the fishery include, but are not limited to, limited access (requirement for a permit), vessel and gear

marking requirements, vessel length restrictions, Federal catch and effort logbooks, 100-percent observer coverage, large 

longline restricted areas around the Hawaiian Archipelago, vessel monitoring system (VMS), annual protected species 

workshops, and the use of sea turtle, seabird, and marine mammal handling and mitigation gear and techniques. The vessel 

operator must notify NMFS prior to departure whether the vessel is undertaking a shallow-set or a deep-set trip. Once the 

trip type is set, the type cannot be changed during the trip. All shallow-set trips must have a NMFS contracted observer. If 

any marine mammal interaction (hooking or entanglement) resulting in injury or mortality occurs, the vessel operator must 

complete and mail a pre-addressed, postage paid form to NOAA Fisheries within 48 hours of the end of the trip. More 

information on all applicable regulations is available at http://www.fpir.noaa.gov/SFD/SFD_regs_2.html. 

Management type: Federal limited access program. This fishery is managed under a Fishery Ecosystem Plan (FEP) by the 

Western Pacific Fishery Management Council and NMFS. 

Comments: Non-target species are caught incidentally. Interactions with common bottlenose dolphins, false killer whales, 

humpback whales, short-finned pilot whales, striped dolphins, Bryde’s whales, Risso’s dolphins, sperm whales, spinner 

dolphins, pygmy sperm or dwarf sperm whales, and common dolphins have been documented. The shallow-set fishery 

was completely closed in 2001 and reopened in 2004. One hundred percent observer coverage is required in this fishery. 

Observed injuries of marine mammals in this fishery October 2007 through 2008 included 1 false killer whale, 3 Risso’s 

dolphins, 1 humpback whale, 1 pygmy sperm whale, 1 striped dolphin, and 1 unidentified whale. Observed mortality for 

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the period included 1 Risso’s dolphin. Observed injuries of marine mammals in 2009 included 1 false killer whale, 3 

Risso’s dolphins, and 1 unidentified whale. No observed mortality was reported in 2009. 

Category II, Hawaii Shortline Fishery 

Note: The Hawaii shortline fishery was added to the 2010 List of Fisheries as a Category II fishery under the MMPA based 

on analogy with the Category I “HI deep-set (tuna-target) longline/set line” and Category II “HI shallow-set (swordfishtarget) longline/set line” fisheries (Federal Register 74 FR 58859, 16 November 2009). 

Number of permit holders: There are no specific fishing permits issued for this fishery. However, all persons with a State 

of Hawaii Commercial Marine License (CML) may participate in any fishery, including the “HI shortline” fishery. 

Number of active shortline vessels: Of those persons possessing CMLs, shortline participation has varied between 5 and 11 

vessels from 2003 - 2008. 

Total effort: From 2003-2008, there was an average of 135,757 pounds (lbs) of fish landed each year. In 2008 alone, 

104,152 lbs of fish were landed. 

Geographic range: The Category II “HI shortline” fishery is a small-scale system operating off the State of HI, and 

targeting bigeye tuna (Thunnus obesus) or the lustrous pomfret (Eumigistes illustris). This fishery was developed to target 

these fish species when they concentrate over the summit of Cross Seamount, 290 km (180 mi) south of the State of HI. 

Seasons: This fishery has no seasonal component and may operate year-round. 

Gear type: The gear style is designed specifically to target the aggregating fish species over seamount structures. The 

primary gear type used is a horizontal main line (monofilament) less than 1 nautical mile long, and includes two baskets of 

approximately 50 hooks each. The gear is set before dawn and has a short soak time, with the gear retrieved about two 

hours after it is set. 

Regulations: All persons with a State of Hawaii Commercial Marine License (CML) may participate in the “HI shortline” 

fishery. The mainline length must be less than 1 nautical mile. 

Management type: Hawaii State managed fishery. 

Comments: Currently, there is no reporting system in place to document potential marine mammal interactions in this 

fishery. However, there are anecdotal reports of interactions off the north side of Maui, but the species and extent of 

interactions are unknown. 

Category II, CA yellowtail, barracuda, white seabass, and tuna drift gillnet fishery (>3.5 and <14 in mesh) 

Note: This fishery has developed recently as an offshoot of the “CA other species, large mesh (>3.5 in) set gillnet 

fishery” (see Category I fishery section above). Fishermen use the same gear as in the set gillnet fishery (typically 6.5 inch 

mesh nets, 100-200 fathoms in length, except that they instead utilize drifting nets to target white seabass and yellowtail. 

Albacore tuna and barracuda are also targeted in this fishery. 

Number of permit holders: There are approximately 24 active permit holders in this fishery. 

Total effort: From 2002-2006, there were 221, 193, 120, 184, and 175 small-mesh drift gillnet sets fished, respectively, 

as determined from California Department of Fish and Game logbook data. 

Geographic range: This drift gillnet component of this fishery operates primarily south of Point Conception. Observed sets 

have been clustered around Santa Cruz Island, the east Santa Barbara Channel, and Cortez and Tanner Banks. Some effort 

has also been observed around San Clemente Island and San Nicolas Island. 

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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 to 200-fathom gillnet, which is allowed to drift. 

The mesh size depends on the target species but typical values observed are 6.0 and 6.5 inches. 

Regulations: This fishery is managed by the California Dept. of Fish and Game in accordance with State and Federal laws. 

Management type: This fishery is a limited-entry fishery with gear restrictions and area closures. 

Comments: This fishery primarily targets white seabass and yellowtail but also targets barracuda and albacore tuna. 

From 2002-2004, there have been 63 sets observed from 17 vessel trips. Marine mammal mortality includes two longbeaked common dolphin and 3 California sea lions. Also, 4 California sea lions were entangled and released alive during 

this period. In 2003, there was one coastal bottlenose dolphin stranded with 3.5-inch gillnet wrapped around its tailstock, 

the responsible fishery is unknown. Observer coverage in this fishery was 12% in 2002, 10% in 2003, and 17% in 2004. 

Category II, CA swordfish longline fishery 

Number of permit holders: As recently as 2004, there were 20-30 vessels participating in the fishery. Only one vessel was 

active in 2005. This decline in participation was due to the prohibition in shallow set swordfishing east of W150 longitude. 

Number of active permit holders: In January 2006, there was only one vessel participating in this fishery, which fished for 

tuna using deep set methods outside the U.S. EEZ. The remaining vessels from this fishery now participate in the Hawaii 

longline fishery. 

Total Effort: An estimated 1 - 1.5 million hooks were fished annually when 20-30 California-based vessels participated in 

the fishery. In 2005, there were only two trips fished by one vessel. Ten sets were observed in the first trip and it is 

unknown how many sets were made during the second trip because no observer was present. 

Geographic range: The fishery management plan (FMP) for highly migratory species prohibits targeting swordfish with 

shallow set fishing methods east of W150 longitude. In March 2006, the Pacific Fishery Management Council approved an 

application for an exempted fishing permit (EFP) that would allow one vessel to utilize shallow set longline methods within 

the U.S. EEZ, with the same shallow-set regulations used in the Hawaii fishery (circle hooks and fish bait). An 

environmental assessment of this proposal will be prepared by the Highly Migratory Species Management Team (HMSMT) 

for review at a future Council meeting. This EFP will be effective no sooner than 2007 if it receives final approval. 

Seasons: The fishery operates year-round. 

Gear type: Typically, vessels fish 24 to 72 km of mainline, rigged with 22-m gangions at approximately 60-m intervals. 

Anywhere from 800 to 1,300 hooks are deployed in a set, with large squid (Illex sp.) used for bait. Variously colored 

lightsticks are used, for fishing takes place primarily during the night when more swordfish are available in surface waters. 

The mainline is deployed in 4-7 hours and left to drift unattached for 7-10 hours. Retrieval typically takes about 7-10 

hours. A description of the gear used for deep sets targeting tuna is given in the Hawaii longline fishery section. 

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 managed under a Highly Migratory Species Fishery Management 

Plan (FMP) developed by the Pacific Fishery Management Council and NMFS. . The FMP was partially approved by 

NMFS on February 4, 2004. NMFS published a final rule on March 11, 2004 which prohibits shallow longline sets of the 

type normally targeting swordfish on the high seas in the Pacific Ocean east of 150 ̊ W. longitude. A mandatory observer 

program became effective for this fishery in August 2002. 

Comments: Between October 2001 and February 2004, 23 trips were observed by California-based longline observers, 

with 469 sets observed (<15% observer coverage). Between October 2001 and November 2003 the longline observer 

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program reported one injured Risso’s dolphin and one unidentified dolphin killed. Examination of photographs of the dead 

dolphin led marine mammal identification experts to conclude that the animal was most likely a striped dolphin. 

Category II, California Anchovy, Mackerel, and Sardine Purse Seine Fishery. 2

Number of permit holders: There are 63 limited-entry permits (Pacific Fishery Management Council. 2005. Status of the 

Pacific Coast coastal pelagic species fishery and recommended acceptable biological catches. Stock Assessment and 

Fishery Evaluation Report 2005). 

Number of active permit holders: There are 61 vessels actively fishing. 

Total effort: The fishery is managed under a capacity goal, with gross tonnage of vessels used as a proxy for fishing 

capacity. Capacity for the fleet is approximately 5,400 gross tons. Harvest guidelines for sardine and mackerel are also set 

annually. 

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: This is a limited-entry fishery. 

Management type: The fishery is managed under a Coastal Pelagic Species Fisheries Management Plan developed by the 

Pacific Fishery Management Council and NMFS. 

 

A NMFS pilot observer program began in July 2004 and continued through January 2006. A total of 93 sets have been 

observed. Observed marine mammal interactions with the fishery have included one California sea lion killed, 54 sea lions 

released alive, and one sea otter released alive. Under the MMAP self-reporting program, the following mortality was 

reported: In 2003, four California sea lions drowned after chewing through a bait barge net used by the anchovy lampara 

net fishery. 

 

Category II, California tuna purse seine fishery. 

Note: This fishery was previously included in the CA anchovy, mackerel, and sardine purse seine fishery (see above). 

Vessels in the anchovy, mackerel, and sardine fishery target tuna when oceanographic conditions result in an influx of tuna 

into southern California waters. Data for this fishery were obtained from the ‘Status of the U.S. West Coast Fisheries for 

Highly Migratory Species through 2004’, available at the Pacific Fishery Management Council website 

(http://www.pcouncil.org). 

Number of permit holders: There are 63 limited-entry permits (Pacific Fishery Management Council. 2005. Status of the 

Pacific Coast coastal pelagic species fishery and recommended acceptable biological catches. Stock Assessment and 

Fishery Evaluation Report 2005). 

Number of active permit holders: Between one and 23 vessels actively purse seined for tunas during the period 2000-2004. 

 

2 Information for this fishery came from the following sources: Pacific Fishery Management Council. 2005. Status of the Pacific Coast coastal pelagic 

species fishery and recommended acceptable biological catches. Stock assessment and fishery evaluation – 2005; California Coastal Pelagic Species Pilot 

Observer Program Informational Report 12 October 2005 (NMFS SW Region, unpublished); Lyle Enriquez NMFS Southwest Regional Office (personal 

communication) and the Marine Mammal Authorization Program, Registration and Reporting System. This fishery was formerly known as the “CA 

anchovy, mackerel, and tuna purse seine fishery” and was renamed in the NMFS MMPA List of Fisheries for 2007 (Federal Register Volume 72, No. 59, 

14466). The “tuna” component of this fishery was designated as a separate fishery in the 2007 List of Fisheries and is named the “CA tuna purse seine 

fishery” (see fishery description below). 

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Total effort: The number of vessels landing bluefin, yellowfin, skipjack, and albacore in 2000-2004 varied between one 

and 23. Logbooks are not required for this fishery, and the overall number of sets fished is unknown. 

 

Geographic range: Observed sets in this fishery have occurred in the southern California Bight. 

Seasons: Observed sets occurred in August and September. The timing of fishing effort varies with the availability of tuna 

species in this region. 

Gear type and fishing method: Small coastal purse seine vessels with a <640 mt carrying capacity target bluefin, yellowfin, 

albacore and skipjack tuna during warm-water periods in southern California. 

Regulations: This is a limited-entry fishery. 

Management type: This fishery is managed under a Highly Migratory Species Management Plan developed by the Pacific 

Fishery Management Council and NMFS. 

Comments: A pilot observer program for this fishery began in July 2004 and ended in January 2006. A total of 9 trips and 

15 sets were observed with no marine mammal interactions. 

Category II, WA Puget Sound Region salmon drift gillnet fishery.

Number of permit holders: This commercial fishery includes all inland waters south of the US-Canada border and east of 

the Bonilla/Tatoosh line, at the entrance to the Strait of Juan de Fuca. Treaty Indian salmon gillnet fishing is not included 

in this commercial fishery. In 1999, the U.S. and Canada reached an agreement that significantly reduced the U.S. share of 

sockeye salmon. In order to compensate the non-treaty U.S. fishermen for the impact of this reduction, a federally funded 

buyback program was established. By the 2001 fishing season, the number of available drift gillnet permits had been 

reduced from 675 (1999) to 216. The intent of the buyback program was to reduce the number of drift gillnet permits to 

200 (pers. comm., David Cantillon, NMFS, Northwest Region). 

Number of active permit holders: Under the cooperative program that integrates issuance of Marine Mammal 

Authorization Certificates into the existing State license process, NMFS receives data on vessels that have completed the 

licensing process and are eligible to fish. These vessels are a subset of the total permits extant (725 in 2001), and the 

remainder of the permits are inactive and do not participate in the fishery during a given year. The number of "active" 

permits is assumed to be equal to or less than the number of permits that are eligible to fish. From 1997-2001, the number 

of active permits was 633, 559, 199, 248, and 182, respectively. 

Total effort: Effort in the Puget Sound salmon drift gillnet fishery is regulated by systematic openings and closures that are 

specific to area and target salmon species. Since 1994, the number of active vessels in the Puget Sound drift gillnet fishery

has declined. In addition, at least one major portion of the fishery, the previously observed sockeye fishery in areas 7 and 

7A, has experienced reductions in available fishing time (openings). The number of days and total number of hours that the 

sockeye fishery remained open, approached the 1994 level only once (1997) in the period from 1995 through 1998. In the 

remaining years the available sockeye fishing time was less than half of the 1994 level. In recent years, poor sockeye 

returns and market conditions have combined to reduce participation in the fishery beyond the reductions created originally 

by the federal buyback program. In 2001, drift gillnets fished for only one opening, and 182 gear units were fished in all 

areas as compared to the 559 cited for 1998. Owing to the buyback program and reduced salmon runs, it is expected that 

the number of active permits will remain low. 

Geographic Range: The fishery occurs in the inland marine waters south of the U.S./Canada border and east of the 

Bonilla/Tatoosh line at the entrance to the Strait of Juan de Fuca. The inland waters are divided into smaller statistical 

catch areas which are regulated independently. 

Seasons: This fishery has multiple seasons throughout the year that vary among local areas dependent on local salmon 

runs. The seasons are managed to access harvestable surplus of robust stocks of salmon while minimizing impacts on weak 

stocks. 

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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 Inseason Orders issued by the NMFS Regional Administrator of the NMFS Northwest Region. These regulations are filed in 

the Federal Register post-season. 

Comments: In 1993, observers were placed onboard vessels in a pilot program to monitor seabird and marine mammal 

interactions with fishing effort for several target salmon species in a number of areas throughout the Puget Sound region. 

In 1994 observer effort was concentrated in the sockeye fishery in areas 7 and 7A, where interactions with seabirds and 

marine mammals were most likely to occur. Incidental takes of harbor porpoise, Dall’s porpoise and harbor seals have been 

documented in the fishery. The overall take of marine mammals for the salmon drift gillnet fisheries in Puget Sound is 

unlikely to have increased since the fisheries were last observed, owing to reductions in the number of participating vessels 

and available fishing time. 

Category II, OR swordfish surface longline fishery.

Number of permit holders: The number of permits issued annually from 2000-2005 has ranged between one and seven 

(pers. comm., Jean 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 2000-2005. 

Total effort: From 2000-2005, there were no reported swordfish landings using longline gear. 

Geographic range: The Fishery Management Plan prohibits targeting highly migratory species such as swordfish with 

longlines within the U.S. EEZ, thus any fishing would have to occur outside the EEZ. However, shallow set methods used 

for swordfish are also prohibited east of W150 longitude. 

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: The fishery is managed under a Highly Migratory Species Fisheries Management Plan developed by 

the Pacific Fishery Management Council and NMFS. 

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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 2000-2005, there were fewer than 5 permits issued annually for this fishery (pers. comm., 

Jean 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 2000-

2005. 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: From 2000-2005, there were no reported landings of blue sharks using longline gear. 

Geographic range: This fishery occurs off the coast of Oregon. The Fishery Management Plan prohibits targeting highly 

migratory species such as blue sharks with longlines within the U.S. EEZ, thus any fishing would have to occur outside the 

EEZ. 

 

Seasons: This fishery occurs year-round, however, effort in this fishery generally terminates by late fall. 

Gear type: Fishing gear consists of a buoyed mainline fitted with leaders and baited hooks. The mainline is fished near the 

surface suspended from buoys (rather than anchored to the bottom as in groundfish longline fisheries). Shark longlines 

must be marked at each terminal surface end with a pole and flag, an operating light, a radar reflector, and a buoy showing 

clear identification and gear owner. The gear is typically set in the evening and retrieved in the morning. 

Regulations: The fishery is a limited-entry fishery with gear and bycatch restrictions. 

Management type: The fishery is managed under a Highly Migratory Species Fisheries Management Plan developed by 

the Pacific Fishery Management Council and NMFS. 

Category II, CA squid purse seine fishery.3

Number of Permit Holders: A permit has been required to participate in the squid fishery since April 1998. Originally, 

only two types of permits were issued, either a vessel or light boat permit during the moratorium period from 1998 to 2004. 

Since the adoption of the Market Squid Fishery Management Plan (MSFMP) in 2005, a total of seven different permit types 

are now allowed under the restricted access program. Permit types include both transferable and non-transferable vessel, 

brail and light boat permits whose qualifying criteria are based on historical participation in the fishery during the 

moratorium period. Market squid vessel and brail permits allow a vessel to use lights to attract and capture squid using 

either purse seines or brail gear. Light boat owner permits only allow the use of attracting lights to attract and aggregate 

squid. In addition, three experimental non-transferable permits are allowed for vessel fishing outside of historical fishing 

areas north of San Francisco. In the 2006/2007 season there were 91 vessel permits, 14 brail permits, 64 light boat permits 

and 3 experimental permits issued. A permit is not required when fishing for live bait or when landing two short tons or 

less, which is considered incidental. 

Number of Active Permit Holders: The number of active permits varies by year depending on market conditions and 

availability of squid. During the 2006/2007 season (1 April 2006 – 31 March 2007) there were approximately 84 vessels 

active during some portion of the year. Twenty-nine vessels harvested 86% of the total landings greater than two tons. The 

1999/2000 season had the highest squid landings to date (115,437mt), with 132 vessels making squid landings. 

Total Effort: Logbooks have been mandatory for the squid fishery since May 2000. Results for the 2006 calendar year 

indicate that each hour of fishing required 1.4 hours of search time by light boats. Combined searching and fishing effort 

 

3

This fishery description was provided by Dianna Porzio and Dale Sweetnam, California Department of Fish and Game. 

Details of marine mammal interactions with this fishery were obtained from NOAA Fisheries, Southwest Regional Office. 

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resulted in 6.9 metric tons (mt) of catch per hour. In the 2006/2007 season, the fishery made 1,611 landings. This is a 47% 

decrease from the previous season. In addition, the average landing decreased from 23.9 mt to 21.7 mt.

Geographic Range: Since the 1960’s there have been two distinct fisheries in operation north and south of Point 

Conception. Since the mid-1980’s the majority of the squid fishing harvest has occurred in the southern fishery, with 

efforts focused around the Channel Islands and along the mainland from Port Hueneme to La Jolla. In the 2006/2007 

season, the southern fishery landed 98% of the catch with the majority of landings occurring around the northern Channel 

Islands. In contrast, during the 2005/2006 season, landings in the southern fishery were primarily around Catalina Island. 

The northern fishery, centered primarily in Monterey Bay, has been in operation since the mid-1860’s and has historical 

significance to California. During the 2002/2003 season, a moderate El Niño condition resulted in nearly 60% of the catch 

being landed in northern California. 

Seasons: The fishery can occur year-round; however, fishing efforts differ north and south of Point Conception. Typically, 

the northern fishery operates from April through September while the southern fishery is most active from October through 

March. El Niño conditions generally hamper the fishery in the southern fishery and squid landings are minimal during 

these events. In contrast, landings in the northern fishery often increase during El Niño events and then are depressed for 

several years after. 

Gear Type: There are several gears employed in this fishery. From 1996 to 2006, the vast majority (95%) of vessels use 

either purse (69%) or drum (26%) seine nets. Other types of nets used include brail (5%) and lampara nets (<1%). Another 

gear type associated with the fishery is attracting lights (30,000 watts maximum) that are used to attract and aggregate 

spawning squid in shallow waters. 

Regulations: Since March 2005, the fishery operates under a restricted access program that requires all vessels to be 

permitted. A mandatory logbook program for fishing and lighting vessels has been in place since May 2000. A 

/monitoring program has been in place since 2000 that samples the landings is designed to evaluate the impact of the 

fishery on the resource. Attracting lights were regulated with each vessel restricted to no more than 30,000 watts of light 

during fishing activities. These lights must also be shielded and oriented directly downward to reduce light scatter. The 

lighting restrictions were enacted to avoid risks to nesting brown pelicans and interactions with other seabird species of 

concern. A seabird closure area restricting the use of attracting lights for commercial purposes in any waters of the Gulf of

the Farallones National Marine Sanctuary was enacted. A seasonal catch limitation of 107,047 mt (118,000 short tons) was 

established to limit further expansion of the fishery. Commercial squid fishing is prohibited between noon on Friday and 

noon on Sunday of each week to allow an uninterrupted consecutive two-day period of spawning. Additional closure areas 

to the fishery to protect squid spawning habitat include the Channel Islands Marine Protected Areas (MPAs) and the newly 

established MPAs along the central California coast as well as areas closed to the use of purse seine gear including the 

leeward side of Catalina Island, Carmel and Santa Monica Bays. 

Management Type: The market squid fishery is under California State management. The fishery was largely unregulated 

until 1998 when it came under regulatory control of the California Fish and Game Commission and the Department of Fish 

and Game. The MSFMP was enacted on March 28, 2005. The MSFMP was developed to ensure sustainable long-term 

conservation and to be responsive to environmental and socioeconomic changes. Market squid is also considered a 

monitored species under the Pacific Fishery Management Council’s (PFMC) Coastal Pelagic Species Fishery Management 

Plan. 

Comments: During the 1980’s, California’s squid fishery grew rapidly in fleet size and landings when international 

demand for squid increased due to declining fisheries in other parts of the world. In 1997 industry-sponsored legislation 

halted the growth of fleet size with a moratorium on new permits. Landing records were set several times during the 

1990’s, but landings seem to fluctuate with changing environmental and atmospheric conditions of the California Current. 

Encounters with marine mammals and sea birds are documented in logbooks. Seal bombs are used regularly, but fishermen 

report that they no longer have an effect. A pilot observer program began in July 2004 and has documented one 

unidentified common dolphin death in 135 sets through January 2006. In addition, there have been 96 California sea lions 

and three harbor seals released alive (NMFS, Southwest Region, unpublished data). In addition to the observed death, there 

were three strandings of Risso’s dolphin from 2002-2003 where evidence of gunshot wounds was confirmed, suggesting 

interaction with this fishery (NMFS Southwest Regional Office, unpublished data). The squid fishery operates primarily at 

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night and targets spawning aggregations of adult squid. In recent years the amount of daylight fishing has increased, 

especially in Monterey, in part due to better sonar gear, but also to reduce interactions with California sea lions. The PFMC 

adopted the egg escapement method to monitor the impact of market squid fishery since no reliable biomass estimate has 

been developed. It is a proxy for Maximum Sustainable Yield (MSY), setting an egg escapement threshold level at which to 

evaluate the magnitude of fishing mortality on the spawning potential of the squid stock. The egg escapement method was 

developed on conventional spawning biomass “per-recruit” theory. In general, the MSY Control Rule for market squid is 

based on evaluating levels of egg escapement associated with the exploited population. The egg escapement threshold, 

initially set at 30%, represents a biological reference point from which to evaluate fishery related impacts. 

Category III, CA Dungeness crab pot 

Notes: NMFS is reviewing several pot and trap fisheries along the U.S. west coast, in response to entanglements of 

humpback whales in pot and trap gear. An update on these fisheries will appear in the MMPA Proposed List of Fisheries 

for 2009. For all commercial pot and trap fisheries in California, a general trap permit is required, in addition to any 

specific permits required for an individual fishery. All traps are required to be tended and serviced at least every 96 hours,

weather permitting. Descriptions of those pot and/or trap fisheries for which interactions with marine mammals have been 

documented or suspected are included in this Appendix. 

Number of permit holders: The Dungeness crab fishery is a limited access fishery requiring a vessel-based permit that is 

transferable. This program was initiated in 1994 based on landing histories. The number of vessels participating on an 

annual basis does vary, but approximately 400 vessels have been landing crab in recent years. 

Number of active permit holders: Approximately 400 vessels have been landing crabs in recent years. 

Total effort: There is no restriction on the number of traps that may be fished at one time by a single vessel. Some vessels 

use as many as 1000 or more traps at the peak of the season (December/January). 

Geographic range: This fishery operates in central and northern California. 

Seasons: The fishery is divided into two management areas. The central region (south of the Mendocino-Sonoma county 

line) fishery opens November 15 and continues through June 30. The northern region (north of the Mendocino-Sonoma 

county line) is annually scheduled to open on December 1, but may be delayed by CDF&G based on the condition of 

market size crabs, and continues until July 15. 

Gear type: For each trap fished there is one vertical line in the water, though only in the northern region, is fishing strings 

illegal. All traps are required to be marked with buoys bearing the commercial fishing license number. The normal 

operating depth for Dungeness crab is between 35 and 70 m. Traps are typically tended on a daily basis. 

Regulations: There is no daily logbook requirement for the commercial Dungeness crab fishery. There is a recreation 

fishery for Dungeness crab, which allows for 10 crab per day to be harvested except when fishing on a commercial 

passenger fishing vessel (CPFV) in central California, the limit is 6 crab per person. There is no reliable estimate for the 

effort or landings in the sport fishery except that CPFVs are required to track catch and effort by species. 

Management type: The Dungeness crab pot fishery is managed by the California legislature, CDF&G and also by the tristate committee for Dungeness, which includes the states of Oregon and Washington. 

Comments: Humpback whale entanglements with Dungeness crab gear have not been confirmed, but are suspected as the 

responsible fishery based on the location and timing of fishing effort and observed humpback entanglements. 

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Category III, OR Dungeness crab pot 

Notes: Dungeness crab is the most significant pot/trap fishery in the state of Oregon. Over the long term, the fishery has 

averaged around 10 million lb of landings per year; although since 2003, annual landings have been approximately 25 to 30 

million lb. This fishery requires an Oregon issued limited-entry permit, which is transferable. 

Number of permit holders: There were 433 permit holders in 2006. 

Number of active permit holders: A total of 364 vessels landed crabs in 2006. 

Total effort: In 2006, the fishery made a transition to a three-tiered pot limitation program which allows a maximum of 

200, 300, or 500 pots to be fished at any one time depending on previous landing history. The pot limitation is 

implemented through a buoy tag requirement. All Dungeness crab pots require buoy tags with the identifying associated 

permit attached. The expected result of the buoy tags and tier limits is to reduce the number of pots in Oregon waters down 

from 200,000 to approximately 150,000. 

Geographic range: Oregon waters. 

Seasons: The Dungeness crab season runs from December 1 to August 14. The highest landings are always recorded in 

December through February, at the beginning of the season. 

Gear type: Pots. 

Regulations: All Oregon pot/trap gear must be marked on its terminal ends with pole and flag, light, radar reflector, and 

buoy with the owner/operator number clearly marked. By law, gear may not be left unattended for more than seven days. 

All vessel operators and deck hands must have a commercial fishing license or crewmembers license. 

Management type: State management, Oregon Department of Fish and Wildlife. 

Comments: Humpback whale entanglements with Dungeness crab gear have not been confirmed, but are suspected as the 

responsible fishery based on the location and timing of fishing effort and observed humpback entanglements. 

Category III, CA spot prawn fishery 

Number of permit holders: A three-tiered limited access permit system is used in this fishery to accommodate changes in 

the fishery that occurred when trawling methods were banned and replaced with trap fishing in 2003. Permits are linked to 

the vessel owner and only Tier 1 permits are transferable. Tier 1 permits allow a maximum of 500 traps in use at a time. 

Eighteen vessels had Tier 1 permits in 2007. Tier 2 permits allow 150 traps in use at a time. There were three vessels 

utilizing Tier 2 permits in 2007. Tier 3 permits were issued to allow vessels that previously used trawl gear to switch to 

trap gear to target spot prawn. There were nine Tier 3 permits issued in 2007. Information on 2007 license statistics was 

obtained from the CA Department of Fish and Game website, http://www.dfg.ca.gov/licensing/statistics/statistics.html. 

Number of active permit holders: A total of 30 vessels participated in this fishery in 2007. 

Total effort: Landings have increased every year since 2003. The total number of traps set is unknown, although the 

theoretical maximum number of traps that may be fished annually is approximately 13,000. 

Geographic range: The fishery operates from Monterey south. Over half of the landings are made in Los Angeles and San 

Diego. Traps are typically set in waters of 182 m (100 fathoms) or more. South of Point Arguello, traps must be fished in 

waters 91 m (50 fathoms) or deeper. 

Seasons: North of Point Arguello, the fishery is open from February 1 to October 30. North of Point Arguello, the open 

season is August 1 to April 30. 

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Gear type: Strings of 25 to 50 traps are fished in deep waters (>182 m). 

Regulations: For all commercial pot and trap fisheries in California, a general trap permit is required, in addition to any 

specific permits required for an individual fishery. All traps are required to be tended and serviced at least every 96 hours,

weather permitting. There is a daily logbook requirement in this fishery. There is no buoy marking requirement and no 

recreational fishery for this species. 

Management type: This fishery is managed under state authority by the California Department of Fish and Game. 

Comments: One humpback whale was seriously injured in 2006 as a result of entanglement in spot prawn trap gear. 

Category III, WA/OR/CA sablefish pot

Notes: Sablefish is likely the most commonly targeted groundfish caught in pot gear in off the U.S. west coast. 

Number of permit holders: There are 32 limited-entry permits (LEPs) to catch sablefish with pot gear. Open access 

privileges are also available to fishermen. 

Number of active permit holders: Including all vessels which made landings with an LEP or under open access rules, a 

total of about 150 vessels participated in this fishery in 2007. This total fluctuates on an annual basis. 

Total effort: Estimated annual landings indicate usually over 1 million lbs of sablefish are landed per year in this fishery. 

Geographic range: The fishery is well distributed from central California north to the U.S./Canadian border. Most of the 

effort occurs out in deeper waters (200-400 m). 

Seasons: Most fishing effort occurs January through September. 

Gear type: Traps <6 ft. in any dimension. 

Regulations: A general trap permit is all that is required for open access to this fishery by the states along the U.S. west 

coast. LEPs are divided into a three-tiered system which allocates annual landing limits to individual permits based on the 

status of the stock. Daily logbook reporting is required. 

Management type: Sablefish is managed under the federal Groundfish Fishery Management Plan. This is the only trap 

fishery regulated by the federal government; all others are managed by the states. 

Comments: One humpback whale was seriously injured in 2006 as a result of entanglement in sablefish trap gear. 

Category III, CA rock crab 

Number of permit holders: There were 134 permits issued in 2007. 

Number of active permit holders: Unknown, but it is likely that most issued permits are active. 

Total effort: Annual landings averaged approximately 1 million pounds from 2000 to 2005. 

Geographic range: The fishery operates throughout California waters. Most landings are made south of Morro Bay, 

California, with approximately 65% of all landings coming from the Santa Barbara area. 

Seasons: There are no seasonal restrictions, though some area closures exist. 

Gear type: There is no restriction on the number of traps that may be fished at one time by the vessel but the typical number 

of traps operated at any given time is less than 200. Traps are usually buoyed singularly or in pairs, but fishing strings 

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(multiple traps attached together between two buoys) is allowed. Buoys are required to be marked with the license number 

of the operator. The normal working depth of traps in this fishery is 10 to 35 fathoms. 

Regulations: There is no daily logbook requirement for the commercial rock crab fishery. 

Management type: The fishery is managed by the California Department of Fish and Game. 

Comments: The recreational bag limit is 35 crabs per day, but there is no reliable estimate of the effort or landings in the 

sport fishery. 

Category III, CA halibut bottom trawl. 

Notes: This is a newly-listed fishery in the 2007 MMPA NMFS List of Fisheries (Federal Register Volume 72, No. 59, 

14466). Information on fishing effort was provided by Stephen Wertz, California Department of Fish and Game. 

Number of permit holders: There were 60 permits issued in 2006. 

Number of active permit holders: There were 31 active permit holders in 2006. 

Total effort: Thirty one vessels made 3,711 tows statewide in 2006, totaling 3,897 tow hours, in 332 days of fishing effort. 

Geographic range: The fishery operates from Bodega Bay in northern California to San Diego in southern California, from 

3 to 200 nautical miles offshore. Trawling is prohibited in state waters (0 to 3 nmi offshore) and within the entire Monterey 

Bay, except in the designated “California halibut trawl grounds”, between Point Arguello and Point Mugu beyond 1 

nautical mile from shore. Trawls used in this region must have a minimum mesh size of 7.5 in and trawling is prohibited 

here between 15 March and 15 June to protect spawning adults. 

 

Seasons: Fishing is permitted year-round, except in state waters. State waters are closed between 15 March and 15 June. 

Gear type: Otter trawls, with a minimum mesh size of 4.5 inches are required in federal waters, while fishing in state 

waters has a 7.5 inch mesh size requirement. 

Regulations: Fishing in state waters is limited to the period 14 March – 16 June in the ‘California halibut trawl grounds’ in 

southern California between Point Arguello and Point Mugu. All other fishing must occur in federal waters beyond 3 

nautical miles from shore. 

Management type: The fishery is managed by the California Department of Fish and Game. 

Comments: No marine mammal interactions have been documented for this fishery, but the gear type and fishing methods 

are similar to the WA/OR/CA groundfish trawl fishery (also category III), which is known to interact with marine 

mammals. 

Category III, CA herring gillnet fishery.4

 The herring fishery is concentrated in four spawning areas which 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 largest spawning aggregations occur in San Francisco Bay and produces more than 90% of the herring catch. 

Smaller spawning aggregations are fished in Tomales Bay, Humboldt Bay, and Crescent City Harbor. During the early 

1990's, there were 26 round haul permits (either purse seine or lampara nets). Between 1993 and 1998, all purse seine 

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 fishery is managed through a limited-entry program. The 

California Department of Fish and Game website lists a total of 447 herring gillnet permits for 2005 

 

4

 Pers. Comm. Becky Ota, State Herring Manager, Senior Biologist. 

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(http://www.dfg.ca.gov/mrd/herring/index.html). Of these, 406 permits exist for San Francisco Bay, 34 in Tomales Bay, 4 

in Humboldt Bay, and 3 in Crescent City Harbor. This fishery begins in December (San Francisco Bay) or January 

(northern California) and ends when the quotas have been reached, but no later than mid-March. 

 

Category III, WA Willapa Bay salmon drift gillnet fishery. 

Number of permit holders: The total number of permit holders for this fishery in 1995 and 1996 was 300, but this number 

has declined in subsequent years. In 1997 there were 264 total permits and 243 in 1998. The NMFS 2001 List of Fisheries 

lists an estimate of 82 vessels/persons in this fishery. 

Number of active permit holders: The number of active permit holders is assumed to be equal to or less than the number of 

permits eligible to fish in a given year. The number of permits renewed and eligible to fish in 1996 was 300 but declined to 

224 in 1997 and 196 permits were renewed for 1998. The 1996-98 counts do not include permits held on waivers for those 

years, but do include permits that were eligible to fish at some point during the year and subsequently entered into a 

buyback program. The number of permits issued for this fishery has been reduced through a combination of State and 

federal permit buyback programs. Vessels permitted to fish in the Willapa Bay are also permitted to fish in the lower 

Columbia River drift gillnet fishery. 

 

Total effort: Effort in this fishery is regulated through area and species openings. The fishery was observed in 1992 and 

1993 when fishery opening were greater than in recent years. In 1992 and 1993 there were 42 and 19 days of open fishing 

time during the summer "dip-in" fishery. The "dip-in" fishery was closed in 1994 through 1999. Available openings have 

also declined in the fall chinook/coho fisheries. In 1992/93 respectively there were 44 and 78 days of available fishing 

time. There were 43, 45, 22 and 16.5 available open fishing days during 1995 through 1998. 

Geographic range: This fishery includes all inland marine waters of Willapa Bay. The waters of the Bay are further 

divided into smaller statistical catch areas. 

Seasons: Seasonal openings coincide with local salmon run timing and fish abundance. 

Gear type: Fishing gear used in this fishery is a drift gillnet of single web construction, not exceeding 250 fathoms in 

length, with a minimum stretched mesh size ranging upward from 5 inches depending on target salmon species. The gear is 

commonly set during periods of low and high slack tides. It is the intention of the fisher to keep the net off the bottom. 

The vessel is attached to one end of the net and drifts with the net. The entire net is periodically retrieved onto the vessel

and catch is removed. Drift times vary depending on fishing area, tidal condition, and catch. 

Regulations: This fishery is a limited-entry fishery with seasonal openings and gear restrictions. 

Management type: The salmon drift gillnet fishery is managed by the Washington Department of Fish and Wildlife. 

Comments: Observers were placed onboard vessels in this fishery to monitor marine mammal interactions in the early 

1980s and in 1990-93. Five incidentally taken harbor seals were recovered by observers in the fishery from 1991through 

1993 (3 in ‘92 and 2 in ‘93). Two incidentally taken northern elephant seals were recovered by observers from the fishery 

in 1991 but no takes of this species were observed. The summer fishery (July- August) in Willapa Bay has been closed 

since it was last observed in 1993 and available fishing time declined from 1996 through 1998. 

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 

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permits were renewed for 1998. The 1996-98 counts do not include permits held on waivers for those years but do include 

permits that were eligible to fish at some point during the year and subsequently entered a buyback program. The number 

of permits issued for this fishery has been reduced through a combination of State and federal permit buyback programs. 

Vessels permitted to fish in Grays Harbor are also permitted to fish in the lower Columbia River salmon drift gillnet 

fishery. 

Total effort: Effort in this fishery is regulated through area and species openings. The fishery was observed in 1992 and 

1993 when fishery openings were greater than in recent years. In 1992 and 1993 there were 42 and 19 days of open fishing 

time during the summer "dip-in" fishery. The "dip-in" fishery was closed in 1994 through 1999. Available openings have 

also declined in the fall chinook/coho fisheries. There were 11, 17.5, 9 and 5 available open fishing days during the 1995 

through 1998 fall season. 

Geographic range: Effort in this fishery includes all marine waters of Grays Harbor. The waters are further divided into 

smaller statistical catch areas. 

Seasons: This fishery is subject to seasonal openings which coincide with local salmon run timing and fish abundance. 

Gear type: Fishing gear used in this fishery is a drift gillnet of single web construction, not exceeding 250 fathoms in 

length, with a minimum stretched mesh size ranging of 5 inches depending on target salmon species. The gear is 

commonly set during periods of low and high slack tides and retrieved periodically by the tending vessel. It is the intention 

of the fisher to keep the net off the bottom. The vessel is attached to one end of the net and drifts with the net. The entire 

net is periodically retrieved onto the vessel and catch is removed. Drift times vary depending on fishing area, tidal 

condition, and catch. 

Regulations: The fishery is a limited-entry fishery with seasonal openings and gear restrictions. 

Management type: The salmon drift gillnet fishery is managed by the Washington Department of Fish and Wildlife. 

Comments: Observers were placed onboard vessels in this fishery to monitor marine mammal interactions in the early 

1980s and in 1990-93. Incidental take of harbor seals was observed during the fishery in 1992 and 1993. In 1992, one 

harbor seal was observed entangled dead during the summer fishery and one additional seal was observed entangled during 

the fall fishery but it escaped uninjured. In 1993, one harbor seal was observed entangled dead and one additional seal was 

recovered by observers during the summer fishery. The summer fishery (July-August) in Grays Harbor has been closed 

since it was last observed in 1993. Available fishing time in the fall chinook fisheries declined from 1996 through 1998. 

Category III, WA, OR lower Columbia River salmon drift gillnet fishery.

Number of permit holders: The total number of permit holders was 856 (344 from Oregon and 512 from Washington) 

when the fishery was last observed in 1993. In 1995 through 1998 the number of permits was 747, 693, 675 and 620 

respectively. The number of permits issued for this fishery by Washington has been reduced through a combination of 

State and federal buy-back programs. This reduction is reflected in the overall decline in the total number of permits. 

 

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 mortality was observed in 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. 

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Geographic range: This fishery occurs in the main stem of the Columbia river from the mouth at the Pacific Ocean 

upstream to river mile 140 near the Bonneville Dam. The lower Columbia is further subdivided into smaller statistical 

catch areas which can be regulated independently. 

Seasons: This fishery is subject to season and statistical area openings which are designed to coincide with run timing of 

harvestable salmon runs while protecting weak salmon stocks and those listed under the Endangered Species Act. In recent 

years, early spring (winter) fisheries have been sharply curtailed for the protection of listed salmon species. In 1994, for 

example, the spring fishery was open for only three days with approximately 1900 fish landed. In 1995 the spring fishery 

was closed and in 1996 the fishery was open for one day but fishing effort was minimal owing to severe flooding. Only 

100 fish were landed during the one day in 1996. 

Gear type: Typical gear used in this fishery is a gillnet of single web construction, not exceeding 250 fathoms in length, 

with a minimum stretched mesh size ranging upwards from 5 inches depending on target salmon species. The gear is 

commonly set during periods of low and high slack tides. It is the intention of the fisher to keep the net off the bottom. 

The vessel is attached to one end of the net and drifts with the net. The entire net is periodically retrieved onto the vessel

and catch is removed. Drift times vary depending on fishing area, tidal condition, and catch. 

Regulations: The fishery is a limited-entry fishery with seasonal openings, area closures, and gear restrictions. 

Management type: The lower Columbia River salmon drift gillnet fishery is managed jointly by the Washington 

Department of Fish and Wildlife and the Oregon Department of Fish and Wildlife. 

Comments: Observers were placed onboard vessels in this fishery to monitor marine mammal interactions in the early 

1980s and in 1990-93. Incidental takes of harbor seals and California sea lions were documented, but only during the 

winter seasons (which have been reduced dramatically in recent years to protect ESA-listed salmon). No mortality was 

observed during the fall fisheries. 

Category III, WA, OR salmon net pens.

Number of permit holders: There were 12 commercial salmon net pen (“grow out”) facilities licensed in Washington in 

1998. There are no commercial salmon net pen or aquaculture facilities currently licensed in Oregon. Non-commercial 

salmon enhancement pens are not included in the list of commercial fisheries. 

Number of active permit holders: Twelve salmon net pen facilities in Washington. 

Total effort: The 12 licensed facilities on Washington operate year-round. 

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. 

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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 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 hake. The annual 

hake 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. Hake 

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 

hake deliveries landed at shore-based processors were monitored. The following is a description of the commercial hake 

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. The number of limited-entry permits is limited to 404. 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 hake, 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 hake during the regular season. In addition, 6 

unpermitted mothership processors received unsorted hake catch. 

 

Total effort: The hake 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 hake in 17 days, catcher/processors took 70,365 mt of hake in 54 days and 

shore-based processors received 87,862 mt of hake 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 hake 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 hake 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 dolphins, Dall's porpoise, California sea 

lions, harbor seals, northern fur seals, and northern elephant seals have been documented in the hake fishery. From 1997-

2001, 4 California sea lions, 2 harbor seals, 2 northern elephant seals, 1 Pacific white-sided dolphin, and 6 Dall’s porpoise 

were reported taken in California/Oregon/Washington regions by this fishery. 

 

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Revised 01/15/2011 Appendix 1. Description of U.S. Commercial Fisheries 

Category III, Hawaii gillnet fishery.5

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 are 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 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 dolphins and spinner dolphins. 

 

Category III, Hawaii lobster trap fishery.

6 7

Note: The portion of this fishery managed by the State of Hawaii and operating in the MHI is about 1% of the size (total 

pounds of lobster caught) of the federally managed fishery operating primarily in the NWHI. The description that follows 

refers to the NWHI fishery unless stated otherwise. 

Number of permit holders: There are 15 permit holders under a (1991) federal limited access program. 

Number of active permit holders: In 1998 and 1999 there were 5 and 6 vessels that participated, respectively. In the MHI 

there were 5 active fishers in 1997. 

Total effort: The number of trap hauls for 1999 is not available at this time. However, the majority of the effort took place 

in the 4 harvest guideline areas; Necker Bank, Gardner Pinnacles and Maro Reef, with the remaining effort spread out over 

10 unique areas. In 1998 171,000 trap hauls were made by the 5 vessels during 9 trips and in 1997 a total of 177,700 hauls 

were made. In the MHI 19 trips were made in 1997. 

Geographic range: Lobster permits allow fishing operations in the US EEZ from 3 to 200 nmi offshore American Samoa, 

Guam and Hawaii (including the EEZ areas of the NWHI and MHI). However, no vessels have operated in the EEZ’s of 

American Samoa or Guam since 1983. 

 

5

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.

6

Kawamoto, K. and Samuel G. Pooley. 1999. Draft Annual report of the 1998 western pacific lobster fishery.

7

Kawamoto, K. 1999. Summary of the 1999 NWHI Lobster Fishing Season. NMFS Honolulu Laboratory.

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Revised 01/15/2011 Appendix 1. Description of U.S. Commercial Fisheries 

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 of 750 fishers made 8,526 fishing trips in the main Hawaiian Islands, 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 dolphins. 

 

Category III, Hawaii deep sea bottomfish handline and jig fishery. 

Note: There are two commercial bottomfish fisheries in Hawaii: a distant water Northwestern Hawaiian Islands (NWHI) 

limited-entry fishery under federal jurisdiction and the main Hawaiian Islands bottomfish fishery primarily under the State 

of Hawaii jurisdiction. 

 

Number of permit holders: The main Hawaiian Islands fishery is open-access with close to 2,000 bottomfish vessels 

registered with the State of Hawaii, whereas the NWHI is restricted to a maximum of 17 vessels. 

Number of active permit holders: In 1997 in the MHI a total of 750 fishers were active. The NWHI are divided into the 

Mau Zone (closer to MHI) and the Hoomalu Zone. The Hoomalu Zone is a limited-entry zone with 6 vessels participating 

in 1998, 7 vessels fished the Mau Zone in the same year. Restrictions on new entry into the Mau Zone were implemented 

in 1998. 

Total effort: In 1998 in the MHI approximately 8,500 trips were made with a total catch of 424,000 pounds for an exvessel landing value of $1,336,000. This fishery occurs primarily in offshore banks and pinnacles. In the NWHI 332,000 

pounds ($894,000) were caught in 1998, below average since 1990. 

Seasons: Year round. 

Gear type: This fishery is a hook-and-line fishery that takes place in deep water. In the NWHI fishery, vessels are 30 ft or 

greater and conduct trips of about 10 days. In the MHI the vessels are smaller than 30 ft and trips last from 1 to 3 days. 

323
Revised 01/15/2011 Appendix 1. Description of U.S. Commercial Fisheries 

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 no 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 are 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 roughtoothed dolphins, bottlenose dolphins, and Hawaiian monk seals. 

324
Revised 01/15/2011 Appendix 1. Description of U.S. Commercial Fisheries 

Table 1. Characteristics of Category I and Category II gillnet fisheries in California. Fishery Species Mesh Size Water Depth Set Duration Deployment Category I CA/OR thresher shark and swordfish drift gillnet fishery 

swordfish/shark 14 to 22 inches Ranges from 90 to 

4600 meters 

Typically 8 to 15 hrs 

Drift net only 

Halibut 8.5 inch < 70 meters 24 hrs Set net Barracuda 3.5 inch < 12 hrs Drift net Leopard Shark 7.0 to 9.0 inch < 90 meters Perch/Croaker 3.5 to 4.0 inch < 40 meters < 24 hrs Set net Rockfish 4.5 to 7.5 inch > 90 meters 12 to 18 hrs Set net Soupfin shark/white seabass 

6.0 to 8.5 inch > 50 meters 24 hrs Set net 

Category I CA halibut and white seabass set gillnet fishery (>3.5 inch mesh) 

Miscellaneous shark 6.0 to 14 inch < 70 meters 8 to 24 hrs Drift, some set ne

Category II CA Yellowtail, barracuda, white seabass, and tuna drift gillnet fishery 

White seabass, yellowtail, barracuda, white seabass, and tuna 

Typically 6.5 inch 15 to 90 meters 8 to 24 hrs Mostly drift net 
Revised 

Figure 1. Locations of 7,660 sets observed in the California/Oregon large-mesh drift gillnet fishery for thresher shark and 

swordfish, 1990-2006. The cross-hatched area has been closed to gillnetting from 15 August to 15 November each year 

since 2001 to protect leatherback turtles. The outer dashed line represents the U.S. Exclusive Economic Zone. Total 

estimates of fishing effort over this period are approximately 48,000 sets.

01/15/2011 Appendix 1. Description of U.S. Commercial Fisheries 

326
01/15/2011 Appendix 1. Description of U.S. Commercial Fisheries 

CA thresher shark and swordfish drift gillnet 

fishery

19% 16%

12%23%18%20%

23% 20%

22%

4%

10%14%

13%

18%

16%

20%

21% 21%

0

100020003000400050006000

1990

1991

1992

1993

1994

1995

1996

1997

1998

1999

2000

2001

2002

2003

2004

2005

2006

2007

Year

Effort (Sets)

Fiin

gure 2. Estimated (gray) and observed (black) days of fishing effort for 1990-2007 in the California/Oregon thresher shark/swordfis

ch mesh). One fishing day is equal to one set in this fishery. Percent observer coverage for each year is shown above the bars. 

Revised 
Revised 01/15/2011 Appendix 1. Description of U.S. Commercial Fisheries 

CA halibut and white seabass set gillnet fishery

18%

2% 0%0% 4%

0% 0% 0% 0% 8%

13%15%

10%

5% 0% 0%0% 1%

0

2000400060008000

1990

1991

1992

1993

1994

1995

1996

1997

1998

1999

2000

2001

2002

2003

2004

2005

2006

2007

Year

Effort (days)

Figure 3. Estimated (gray) and observed (black) days of fishing effort for 1990- 2007 in the California halibut/white seabass set gillne

mesh). The fishery has been observed only sporadically since 1994. Percent observer coverage for each year is shown above the barsestimate for 2007 is based on the number of sets observed in 2007 (n=248 sets) and 2006 fishing effort obtained from logbooks (n = 1,3
Figure 4. Number of fishing trips by longline vessels based and landing in Hawaii, by year and 

Revised 01/15/2011 Appendix 1. Description of U.S. Commercial Fisheries 

trip type, 1991-2009. Source: http://www.pifsc.noaa.gov/fmsd/reports.php. 
Revised 12/15/2008 

Appendix 2. Cetacean Survey Effort 

Documentation of cetacean abundance estimates used in the 2008 draft Pacific Marine Mammal 

Stock Assessments. 

Cetacean abundance estimates reported in the Pacific Marine Mammal Stock 

Assessments originate from several sources: vessel line-transect surveys of U.S. west 

coast and Pacific Island Exclusive Economic Zone (EEZ) waters (Barlow 2006, Barlow 

and Rankin 2007, Barlow and Forney 2007, Forney 2007); aerial line-transect surveys of 

harbor porpoises (Carretta and Forney 2004, Laake et al. 1998); photographic markrecapture analyses of large whales (Calambokidis et al. 2007); Hawaiian small cetaceans 

(Baird et al. 2005); and southern resident killer whales (Center For Whale Research, 

unpublished data). Often, multiple abundance estimates are available for a given 

cetacean stock and decisions about which estimates to utilize in the stock assessment 

report must be made, based on what is known about the stock. Considerable interannual 

variability in abundance estimates can occur because the range of many cetacean stocks 

extends beyond the U.S. EEZ boundaries where surveys are conducted. For this reason, 

multi-year averages are utilized in the stock assessments when possible. 

Abundance estimates for U.S. west coast coast cetacean stocks are available in 

two separate publications (Barlow and Forney 2007, Forney 2007). The Barlow and 

Forney (2007) paper presents a 1991-2005 time series of abundance estimates, based on 

large-scale vessel line-transect surveys of California, Oregon, and Washington waters out 

to 300 nmi. The Forney (2007) report presents estimates from a 2005 vessel line transect 

survey that is included in the Barlow and Forney (2007) paper, however, the Forney 

(2007) report includes additional analyses from fine-scale strata from coastal waters of 

the Olympic, Farallones, and Monterey Bay Na al Marine Sanctuaries. These coastal 

strata appear to represent seasonally important habitat for some species as Dall’s 

porpoise, northern right whale dolphin, humpback whales, Pacific white-sided dolphin, 

and blue whales. Inclusion of these coastal resulted in improved estimates of 

abundance for several species and thus, the Forney (2007) report is used for reporting 

2005 abundance estimates, while the Barlow and Forney (2007) paper is used for 2001 

estimates. For most U.S. west coast cetaceans, ge abundances reported in the draft 

2008 Pacific Marine Mammal Stock Assessmen resent the geometric mean* of 2001 

estimates reported by Barlow and Forney (2007) and 2005 estimates reported by Forney 

(2005). In the case of humpback and blu les, mark-recapture estimates may 

sometimes be substituted for line-transect estim the precision of the mark-recapture 

estimate is superior. 

* Current stock assessment preparation guide rrently recommend reporting a weighted 

arithmetic mean, weighted by the inverse of the variances individual abundance estimates. However, 

the authors of the Pacific stock assessment reports have found that the unweighted geometric mean is a 

more appropriate measure of mean abundance for cases where estimates are log-normally distributed. The 

problem with the weighted arithmetic mean is easily understood by example. Consider a case where two 

equally precise abundance estimates are available; one relatively large, the other small (e.g., N1 = 20,000, 

CV1 = 0.3; N2 = 5,000, CV2 = 0.3). Calculating a me nce using the inverse variance method 

arbitrarily underweights the larger estimate (due to its ariance), resulting in a negatively biased 

mean estimate (Nmean = 5,882). By comparison, the ge c mean of the two estimates is Ngeomean = 

10,000, which is equivalent to calculating the mean of the hms of N1 and N2. 

tion

strata 

 avera

ts rep

e wha

ates if

lines cu

 of the 

an abunda

larger v

ometri

 logarit

330
Revised 12/15/2008 

Appendix 2. Cetacean Survey Effort 

References

ransect expedition (ORCAWALE) conducted aboard the NOAA ships McARTHUR and 

 JORDAN, July - December 2001. NOAA Techinal Memorandum NOAA-TM-NMFSSWFSCBaird, R.W., A.M

Barlow, 

Barlow, 

Barlow, 

Barlow, vey in 2002. Mar. 

Mamm. 

Barlow, 

Barlow, 

Calambo

Carretta,

Carretta,

Forney, 

Forney, 

Forney, 

Forney, 

uaries during 2005. U.S. Department of Commerce, NOAA Technical 

Memora NMFS-SWFSC-406. 27p. 

Laake, J., J. Calam

Mangels

Mobley,

Mobley, oustic Laboratory 

Appler, J., J. Barlow, and S. Rankin, 2004. Marine mammal data collected during the Oregon, California and

Washington line-t

DAVID STARR

359. 32p. 

. Gorgone, D.L. Webster, D.J. McSweeney, J.W. Durban, A.D. Ligon, D.R. Salden, and M.H. 

Deakos. 2005. False killer whales around the Main Hawaiian Islands: An assessment of inter-island 

movements and population size using individual photo-identification. Contract Report JJ133F04SE0120 

prepared for the Pacific Islands Fisheries Science Center, National Marine Fisheries Service, 2570 Dole 

Street, Honolulu, Hawaii, 96822. 24pp. 

J. 1995. The abundance of cetaceans in California waters. Part I: Ship surveys in summer and fall of 1991. 

Fish. Bull. 93:1-14. 

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. 

J., S. Rankin, E. Zele, and J. Appler. 2004. Marine mammal data collected during the Hawaiian Islands 

Cetacean and Ecosystem Assessment Survey (HICEAS) conducted aboard the NOAA ships McArthur and 

David Starr Jordan, July - December 2002. U.S. Department of Commerce, NOAA Technical 

Memorandum, NMFS-SWFSC-362. 39 p. 

J. 2006. Cetacean abundance in Hawaiian waters estimated from a summer/fall sur

Sci. 22(2):446-464. 

J. and S. Rankin. 2007. False killer whale abundance and density: Preliminary estimates for the PICEAS 

study area south of Hawaii and new estimates for the US EEZ around Hawaii. Administrative Report LJ07-02. Southwest Fisheries Science Center, National Marine Fisheries Service, 8604 La Jolla Shores 

Drive, La Jolla, CA 92037. 

J. and K.A. Forney. 2007. Abundance and population density of cetaceans in the California Current 

ecosystem. Fishery Bulletin 105:509-526. 

kidis, J., A. Douglas, E. Falcone, and L. Schlender. 2007. Abundance of blue whales off the U.S. west 

coast using photo identification. Contract Report AB133F06SE3906 to Southwest Fisheries Science 

Center. 13p. 

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

estimated from tandem aerial surveys. Mar. Mamm. Sci. 14(3):655-675. 

 J.V. and K.A. Forney. 2004. Preliminary estimates of harbor porpoise abundance in California from 1999 

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

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

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. 

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. 

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. 

K.A. 2007. Preliminary estimates of cetacean abundance along the U.S. west coast and within four 

National Marine Sanct

ndum

bokidis, 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. 

, 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. 

 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. LJ00-14C. Southwest Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, 

CA 92038. 26 pp. 

J.R. 2001. Results of 2001 aerial surveys north of Kauai. Report to North Pacific Ac

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program. 20 pp. Available as downloadable pdf file at: 

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Mobley, 2003 aerial surveys north of Kauai. Report to North Pacific Acoustics Laboratory 

Mobley, 

i/jmobley/2004NPAL.pdf

d in west coast waters during summer/fall 1996. U.S. Dep. Commer., NOAA 

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program. 20 pp. Available as downloadable pdf file at: 

http://socrates.uhwo.hawaii.edu/SocialSci/jmobley/2002NPAL.pdf 

J.R. 2003. Results of

program. 20 pp. Available as downloadable pdf file at: 

http://socrates.uhwo.hawaii.edu/SocialSci/jmobley/2003NPAL.pdf 

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program. 25 pp. Available as downloadable pdf file at: 

http://socrates.uhwo.hawaii.edu/SocialSc

Von Saunder, A. and J. Barlow. 1999. A report of the Oregon, California, and Washington line-transect experiment 

(ORCAWALE) conducte

Tech. Memo. NMFS_SWFSC_264. 49 pp.

332
Appendix 3. 2010 Pacific Marine Mammal Stock Assessment Reports summary.

Shaded lines indicate reports revised in 2010.

Total Annual

Annual Fishery

Mortality Mortality 

NMFS + Serious + Serious Strategic 

Species Stock Area Center N est CV N est N min R max Fr PBR Injury Injury Status California sea lion U.S. SWC 238,000 n/a 141,842 0.12 1 8,511 232 159 N 

Harbor seal California SWC 34,233 n/a 31,600 0.12 1 1,896 389 389 N 

Harbor seal Oregon/Washington Coast AKC unk unk unk 0.12 1 unk 3.8 1.8 N Harbor seal Washington Inland Waters AKC unk unk unk 0.12 1 unk 13.0 3.8 N 

Northern Elephant Seal California breeding SWC 124,000 n/a 74,913 0.117 1 4,382 10.4 8.8 N 

Guadalupe Fur Seal Mexico to California SWC 7,408 n/a 3,028 0.12 0.5 91 0 0 Y Northern Fur Seal San Miguel Island AKC 9,968 n/a 5,395 0.12 1 324 1.2 0 N Hawaiian Monk Seal Hawaii PIC 1,161 n/a 1,136 0.07 0.1 undet unk unk Y Harbor porpoise Morro Bay SWC 2,044 0.40 1,478 0.04 0.4 15 0 0 N 

Harbor porpoise Monterey Bay SWC 1,492 0.4 1,079 0.45 10   N 

Harbor porpoise San Francisco – Russian River SWC 9,189 0.38 6,745 0.04 0.5 67   N 

Harbor porpoise Northern CA/Southern OR SWC 39,581 0.39 28,833 0.04 1 577   N 

Harbor porpoise Northern Oregon/Washington Coast AKC 15,674 0.39 11,383 0.04 0.5 114   N 

Harbor porpoise Washington Inland Waters AKC 10,682 0.38 7,841 0.04 0.4 63 15.2 15.4 N Dall’s porpoise California/Oregon/Washington SWC 42,000 0.33 32,106 0.04 0.4 257   N 

Pacific white-sided dolphin California/Oregon/Washington SWC 26,930 0.28 21,406 0.04 0.45 193 15.1 10.5 N 

Risso’s dolphin California/Oregon/Washington SWC 6,272 0.30 4,913 0.04 0.4 39 1.6 1.6 N 

Common Bottlenose dolphin California Coastal SWC 323 0.13 290 0.04 0.5 2.4 0.2 0.2 N 

Common Bottlenose dolphin California/Oregon/Washington Offshore SWC 1,006 0.48 684 0.04 0.4 5.5   N 

Striped dolphin California/Oregon/Washington SWC 10,908 0.34 8,231 0.04 0.5 82 0 0 N Common dolphin, short-beaked California/Oregon/Washington SWC 411,211 0.21 343,990 0.04 0.5 3,440 64 64 N Common dolphin, long-beaked California SWC 27,046 0.59 17,127 0.04 0.48 164 13 13 N Northern right whale dolphin California/Oregon/Washington SWC 8,334 0.40 6,019 0.04 0.4 48 4.8 3.6 N 

Killer whale Eastern North Pacific Offshore SWC 240 0.49 162 0.04 0.5 1.6 0 0 N Killer whale Eastern North Pacific Southern Resident AKC 85 und 85 0.04 0.1 0.17 0.2 0 Y Short-finned pilot whale California/Oregon/Washington SWC 760 0.64 465 0.04 0.4 4.6 0 0 N 

Baird’s beaked whale California/Oregon/Washington SWC 907 0.49 615 0.04 0.5 6.2 0 0 N 

Mesoplodont beaked whales California/Oregon/Washington SWC 1,024 0.77 576 0.04 0.5 5.8 0 0 N 

Cuvier’s beaked whale California/Oregon/Washington SWC 2,143 0.65 1,298 0.04 0.5 13 0 0 N 

Pygmy Sperm whale California/Oregon/Washington SWC 579 1.02 271 0.04 0.5 2.7 0 0 N 

Dwarf sperm whale California/Oregon/Washington SWC unk unk unk 0.04 0.5 undet 0 0 N 

Sperm whale California/Oregon/Washington SWC 971 0.31 751 0.04 0.1 1.5 0.4 0.2 Y Humpback whale California/Oregon/Washington SWC 2,043 0.10 1,878 0.08 0.3 11.3 ≥ 3.6 ≥ 3.2 Y 

Blue whale Eastern North Pacific SWC 2,497 0.24 2,046 0.04 0.3 3.1 1.0 0 Y Fin whale California/Oregon/Washington SWC 3,044 0.18 2,624 0.04 0.3 16 1.0 0 Y 

Sei whale Eastern North Pacific SWC 126 0.53 83 0.04 0.1 0.17 0 0 Y Minke whale California/Oregon/Washington SWC 478 1.36 202 0.04 0.5 2.0 0 0 N Rough-toothed dolphin Hawaii PIC 8,709 0.45 6,067 0.04 0.5 61 unk unk N 

Rough-toothed dolphin American Samoa (new stock) PIC unk unk unk 0.04 0.5 unk unk unk unk 

unk = unknown; undet = undetermined; n/a = not applicable
Appendix 3. 2010 Pacific Marine Mammal Stock Assessment Reports summary.

Shaded lines indicate reports revised in 2010.

Total Annual

Annual Fishery

Mortality Mortality 

NMFS + Serious + Serious Strategic 

Species Stock Area Center N est CV N est N min R max Fr PBR Injury Injury Status Risso’s dolphin Hawaii SWC 2,372 0.97 1,195 0.04 0.5 12 0 0 N Common Bottlenose dolphin Hawaii Pelagic SWC 3,178 0.59 2,006 0.04 0.45 18 0.4 0.4 N Common Bottlenose dolphin Kauai and Niihau (new stock) SWC 147 0.11 134 0.04 0.5 1.3 unk unk N Common Bottlenose dolphin Oahu (new stock) SWC 594 0.54 388 0.04 0.5 3.9 unk unk N Common Bottlenose dolphin 4 Islands Region (new stock) SWC 153 0.24 125 0.04 0.5 1.3 unk unk N Common Bottlenose dolphin Hawaii Island (new stock) SWC 102 0.13 91 0.04 0.5 0.9 unk unk N Pantropical Spotted dolphin Hawaii PIC 8,978 0.48 6,701 0.04 0.5 61.0 0 0 N Spinner dolphin Hawaii Pelagic PIC 3,351 0.74 1,920 0.04 0.5 19 0 0 N Spinner dolphin Hawaii Island (new stock) PIC unk unk unk 0.04 0.5 unk unk unk N Spinner dolphin Oahu / 4 Islands (new stock) PIC unk unk unk 0.04 0.5 unk unk unk N Spinner dolphin KauaI / Niihau (new stock) PIC unk unk unk 0.04 0.04 unk unk unk N Spinner dolphin Kure / Midway (new stock) PIC unk unk unk 0.04 0.04 unk unk unk N Spinner dolphin Pearl and Hermes Reef (new stock) PIC unk unk unk 0.04 0.04 unk unk unk N Spinner dolphin American Samoa (new stock) PIC unk unk unk 0.04 0.04 unk unk unk unk Striped dolphin Hawaii Pelagic PIC 13,143 0.46 9,088 0.04 0.45 82 unk unk N Fraser’s dolphin Hawaii PIC 10,226 1.16 4,700 0.04 0.5 47 0 0 N Melon-headed whale Hawaii PIC 2,950 1.17 1,350 0.04 0.5 14 0 0 N Pygmy killer whale Hawaii SWC 956 0.83 520 0.04 0.5 5.2 0 0 N False killer whale Hawaii Pelagic SWC 484 0.93 249 0.04 0.5 2.5 7.3 7.3 Y False killer whale Palmyra Atoll SWC 1,329 0.65 806 0.04 0.4 6.4 0.3 0.3 N False killer whale Hawaii Insular SWC 123 0.72 76 0.04 0.4 0.61 0.60 0.60 N False killer whale American Samoa (new stock) PIC unk unk unk 0.04 0.5 unk unk unk unk Killer whale Hawaii PIC 349 0.98 175 0.04 0.5 1.8 0 0 N Pilot whale, short-finned Hawaii PIC 8,846 0.49 5,986 0.04 0.4 48 0.7 0.7 N Blainville’s beaked whale Hawaii PIC 2,872 1.17 1,314 0.04 0.5 13.0 0 0 N Longman's Beaked Whale Hawaii PIC 1,007 1.25 443 0.04 0.5 4.4 0 0 N Cuvier’s beaked whale Hawaii PIC 15,242 1.43 6,269 0.04 0.5 63 0 0 N Pygmy sperm whale Hawaii PIC 7,138 1.12 3,341 0.04 0.5 33 0 0 N Dwarf sperm whale Hawaii PIC 17,519 0.74 10,043 0.04 0.5 100 0 0 N Sperm whale Hawaii PIC 6,919 0.81 3,805 0.04 0.2 15.0 0 0 Y Blue whale Central North Pacific PIC unk unk unk 0.04 0.1 undet 0 0 Y Fin whale Hawaii PIC 174 0.72 101 0.04 0.1 0.2 0 0 Y Bryde’s whale Hawaii PIC 469 0.45 327 0.04 0.5 3.3 0 0 N Sei whale Hawaii PIC 77 1.06 37 0.04 0.1 0.1 0 0 Y Minke whale Hawaii PIC unk unk unk 0.04 0.5 undet 0 0 N Humpback whale American Samoa SWC unk unk 150 0.106 0.1 0.4 0 0 Y Sea Otter Southern USFWS 2,826 n/a 2,723 0.06 0.1 8 0.8 0.8 Y 

Sea Otter Washington USFWS n/a n/a 1,125 0.20 0.1 11   N 

unk = unknown; undet = undetermined; n/a = not applicable
Revised: 12/2008 

SOUTHERN SEA OTTER (Enhydra lutris nereis) 

U.S. Fish and Wildlife Service, Ventura, California 

STOCK DEFINITION AND 

GEOGRAPHIC RANGE 

Southern sea otters are listed as 

threatened under the Endangered Species 

Act. They occupy nearshore waters along 

the mainland coastline of California from 

San Mateo County to Santa Barbara 

County (Figure 1). A small colony of 

southern sea otters also exists at San 

Nicolas Island, Ventura County, as a result 

of translocation efforts initiated in 1987. 

The San Nicolas Island colony is 

considered to be a “non-essential 

experimental” population under the 

Endangered Species Act. 

Historically, southern sea otters 

ranged from Punta Abreojos, Baja 

California, Mexico to northern California 

(Wilson et al. 1991) or Oregon, or 

possibly as far north as Prince William 

Sound, Alaska (reviewed in Riedman and 

Estes 1990). During the 1700s and 1800s, 

the killing of sea otters for their pelts 

extirpated the subspecies throughout most 

of its range. A small population of 

southern sea otters survived near Bixby 

Creek in Monterey County, California, 

numbering an estimated 50 animals in 

1914 (Bryant 1915). Since receiving 

protection under the International Fur Seal Treaty in 1911, southern sea otters have gradually 

expanded northward and southward along the central California coast. The estimated carrying 

capacity of California is approximately 16,000 animals (Laidre et al. 2001). 

Mating and pupping of southern sea otters takes place year round, but a birth peak 

extending over several months occurs in the spring, and a secondary birth peak occurs in the fall 

(Siniff and Ralls 1991; Riedman et al. 1994). Male sea otters typically aggregate at the northern 

and southern limits of the range in winter and early spring, when some males that have 

maintained breeding territories in the predominantly female center of the range abandon their 

territories and join other males at its ends (Jameson 1989; Ralls et al. 1996). 

All sea otters of the subspecies Enhydra lutris nereis are considered to belong to a single 

stock because of their recent descent from a single remnant population. Southern sea otters are 

geographically isolated from the other two recognized subspecies of sea otters, E. l. lutris and E. 

l. kenyoni, and have been shown to be distinct from these subspecies in studies of cranial 

Figure 1. Current range and densities of the southern sea 

otter (2008 sea otter census). Data source: U.S. 

Geological Survey, http://www.werc.usgs.gov/otters/casurveys.html. 

Appendix 4. Sea Otter Stock Assessments 335
2

morphology (Wilson et al. 1991) and variation at the molecular level (Sanchez 1992; Cronin et 

al. 1996; Larson et al. 2002). 

POPULATION SIZE 

 Data on population size have been gathered for more than 50 years. In 1982, a 

standardized survey technique was adopted to ensure that subsequent counts were comparable 

(Estes and Jameson 1988). This survey method involves shore-based censuses of approximately 

60% of the range, with the remainder surveyed from the air. These surveys are conducted twice 

each year (in spring and fall). At San Nicolas Island, counts are conducted from shore on a 

quarterly basis. The highest of the four counts is used as the official count for the year. 

Minimum Population Estimate

 The 2007 3-year running average (2006-2008) is 2,826 individuals (U.S. Geological 

Survey, http://www.werc.usgs.gov/otters/ca-surveys.html) for the mainland population. The San 

Nicolas Island colony numbers about 42 animals (based on the high count for 2008), 37 

independent sea otters and 5 dependent pups (U.S. Geological Survey unpub. data). Given the 

log-normal distribution of combined counts for the mainland and San Nicolas Island for 2006-

2008, the estimate corresponding to the 20th percentile of this distribution, or Nmin, is 2723 for 

the southern sea otter stock. 

 

Current Population Trend 

 As recommended in the Final Revised Recovery Plan for the Southern Sea Otter (U.S. 

Fish and Wildlife Service 2003), three-year running averages are used to characterize population 

trends to dampen the effects of anomalous counts in any given year. Based on three-year 

running averages of the annual spring counts, the mainland southern sea otter population 

increased by an average of about three percent per year from 2003 to the present (Figure 2). 

Growth rates are highest at the southern end of the range, whereas growth in the northern and 

central portions of the range has been more sluggish, suggesting that sea otters may be 

approaching local carrying capacity in some areas (Tinker et al. 2006). The colony at San 

Nicolas Island has grown by an average of approximately nine percent annually since the early 

1990s (Tinker et al. 2008). 

CURRENT AND MAXIMUM 

NET PRODUCTIVITY 

RATES 

 The maximum growth 

rate (Rmax) for southern sea 

otters along the mainland 

coastline appears to be six 

percent per year. Recovering or 

translocated populations at Attu 

Island, southeast Alaska, British 

Columbia, and Washington state 

have all exhibited growth rates 

of up to 17 or 20 percent 

annually (Estes 1990, Jameson 

Figure 2. Southern sea otter counts 1983-2008 (mainland 

population). Data source: U.S. Geological Survey,

http://www.werc.usgs.gov/otters/ca-surveys.html. 

Southern Sea Otter Spring Counts 

1983-2008

0

500

1000

1500

2000

2500

3000

3500

1983

1985

1987

1989

1991

1993

1995

1997

1999

2001

2003

2005

2007

Year

Number of Sea Otters i

Spring

Count

3-Year

Running

Average

Appendix 4. Sea Otter Stock Assessments 336
3

and Jeffries 1999, Jameson and Jeffries 2005), but the mainland southern sea otter population has 

grown much more slowly. From the early 1900s to the mid-1970s, it increased at about five 

percent annually (Estes 1990). From 1983 to 1995, annual growth averaged about six percent. 

The population declined during the late 1990s but resumed growth in the early 2000s. Recent 

growth has leveled off, averaging approximately three percent per year from 2003 to the present. 

Growth rates at San Nicolas Island are higher, averaging approximately nine percent annually 

(Tinker et al. 2008), but these higher rates have never been seen in the mainland population as a 

whole. The sea otters at San Nicolas Island are a very small component of the southern sea otter 

stock. This small population is geographically removed from the mainland range and is subject 

to different threats and limitations than the mainland range. The higher growth rate for the San 

Nicolas Island animals is not representative of the overall stock, and it is not foreseeable that the 

mainland population will ever achieve the growth rate of the San Nicolas Island animals. 

Therefore, for the overall stock, we use an Rmax of 6 percent. This Rmax reflects the threats and 

limitations to which approximately 98 percent of the stock is exposed and is the maximum 

observed rate for that 98 percent of the stock. 

POTENTIAL BIOLOGICAL REMOVAL 

Potential Biological Removal (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 southern sea otter stock, Nmin = 2,723, Rmax = 6 percent, and Fr = 0.1. A 

recovery factor of 0.1 is used for the southern sea otter stock because, although its numbers are 

currently increasing, Nmin is below 5,000 and the species is vulnerable to a natural or humancaused catastrophe, such as an oil spill, due to its restricted geographic distribution in nearshore 

waters (Taylor et al. 2002). Therefore, the PBR for the southern sea otter stock is 8 animals. It 

should be noted that because southern sea otters are not covered under section 118 of the 

MMPA, PBR does not apply to the governance of incidental take of southern sea otters in 

commercial fisheries. 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Fishery Information 

Sea otters are susceptible to entanglement and drowning in gill nets. The set gill net 

fishery in California is estimated to have killed from 48 to 166 (average of 103) southern sea 

otters per year from 1973 to 1983 (Herrick and Hanan 1988) and 80 sea otters annually from 

June 1982 to June 1984 (Wendell et al. 1986). A 1991 closure restricted gill and trammel nets to 

waters deeper than 30 fathoms throughout most of the southern sea otter’s range (California 

Senate Bill No. 2563). In 1990, NMFS started an observer program using at-sea observers, 

which provided data on incidental mortality rates relative to the distribution of fishing effort. 

The observer program was active through 1994, discontinued from 1995 to 1998, and reinstated 

in the Monterey Bay area in 1999 and 2000 because of concern over increased harbor porpoise 

mortality. Based on a detailed analysis of fishing effort, sea otter distributions by depth, and 

regional entanglement patterns during observed years, NMFS estimated southern sea otter 

mortality in the halibut set gill net fishery to have been 64 in 1990, zero from 1991 to 1994, 3 to 

13 in 1995, 2 to 29 in 1996, 6 to 47 in 1997, 6 to 36 in 1998, 5 in 1999, and zero in 2000 

(Cameron and Forney 2000; Carretta 2001; Forney et al. 2001). The increase in estimated 

mortality from 1995 to 1998 was attributed to a shift in set gill net fishing effort into areas where 

sea otters are found in waters deeper than 30 fathoms. 

Appendix 4. Sea Otter Stock Assessments 337
4

Fishing with set gill nets has since been further restricted throughout the range of the 

southern sea otter. An order prohibiting the use of gill and trammel nets year-round in ocean 

waters of 60 fathoms or less from Point Reyes, Marin County, to Point Arguello, Santa Barbara 

County was made permanent in September 2002. In the waters south of Point Arguello, the 

Marine Resources Protection Act of 1990 (California Constitution Article 10B) defined a Marine 

Resources Protection zone in which the use of gill and trammel nets is banned. This zone 

includes waters less than 70 fathoms (128 meters) or within one mile, whichever is less, around 

the Channel Islands, and waters generally within three nautical miles offshore of the mainland 

coast from Point Arguello to the Mexican border. Although sea otters occasionally dive to 

depths of 100 meters, the vast majority (>99 percent) of dives are to depths of 40 meters or less.1

 

Therefore, because of these restrictions and the current extent of the southern sea otter’s range, 

southern sea otter mortalities resulting from entanglement in gill nets are believed to be currently 

at or near zero. An estimated 58 vessels participate in the CA angel shark/halibut and other 

species set gillnet (>3.5” mesh) fishery [72 FR 66048, November 27, 2007]. Approximately 24 

vessels participate in the CA yellowtail, barracuda, and white seabass drift gillnet fishery (mesh 

size ≥3.5” and <14”) [72 FR 66048, November 27, 2007]. 

Three southern sea otter interactions with the California purse seine fishery for Northern 

anchovy and Pacific sardine have been documented during the past five years. In 2005, a 

contract observer in the NOAA Fisheries California Coastal Pelagic Species observer program 

documented the incidental, non-lethal capture of two sea otters that were temporarily encircled in 

a purse seine net targeting Northern anchovy but escaped unharmed by jumping over the 

corkline. In 2006, a contract observer in the same program documented the incidental, nonlethal capture of a sea otter in a purse seine net targeting Pacific sardine. Again, the sea otter 

escaped the net at end of the haul without assistance.2

 Based on these observations and the levels 

of observer coverage in each year, 58 and 20 such interactions are estimated to have occurred in 

the CA sardine purse seine fishery in 2005 and 2006, respectively, but these estimates are 

accompanied by considerable uncertainty because of the low levels of observer coverage.3 In 

documented interactions, sea otters have been able to escape purse seine nets without assistance, 

but these incidents do not preclude mortality or serious injury. There are no additional data 

available to assess the risk of mortality or serious injury resulting from interactions with this 

fishery. The 2007 list of fisheries reorganized purse seine fisheries targeting anchovy and 

sardines into the “CA anchovy, mackerel, sardine purse seine” fishery. An estimated 63 vessels 

participate in the CA anchovy, mackerel, and sardine purse seine fishery [72 FR 66048, 

November 27, 2007]. 

The potential exists for sea otters to drown in traps set for crabs, lobsters, and finfish, but 

only limited documentation of mortalities is available. Hatfield and Estes (2000) summarize 

records of 18 sea otter mortalities in trap gear, 14 of which occurred in Alaska. With the 

exception of one sea otter, which was found in a crab trap, all of the reported Alaska mortalities 

involved Pacific cod traps and were either recorded by NMFS observers or reported to NMFS 

observers by fishers. Four sea otters are known to have died in trap gear in California: one in a 

 

1

 Personal communication, M. Tim Tinker, 2008. Research Wildlife Biologist, USGS-Western Ecological Research 

Center, Santa Cruz Field Station, and Department of Ecology & Evolutionary Biology, University of California at 

Santa Cruz, 100 Shaffer Road, Santa Cruz, CA 95060. 

2

 Personal communication, Lyle Enriquez, 2006. Southwest Regional Office, NOAA, U.S. National Marine 

Fisheries Service, 501 West Ocean Boulevard, Long Beach, CA 90802. 3

 Personal communication, Jim Carretta, 2008. Southwest Fisheries Science Center, NOAA, U.S. National Marine 

Fisheries Service, 8604 La Jolla Shores Drive, La Jolla, CA 92037. 

Appendix 4. Sea Otter Stock Assessments 338
5

lobster trap near Santa Cruz Island in 1987; a mother and pup in a trap with a 10-inch diameter 

opening (presumed to be an experimental trap) in Monterey Bay in 1987; and one in a rock crab 

trap 0.5 miles off Pt. Santa Cruz, California (Hatfield and Estes 2000). In 1995, the U.S. 

Geological Survey began opportunistic efforts to observe the finfish trap fishery in California. 

These efforts were supplemented with observations by the California Department of Fish and 

Game (CDFG) in 1997 and two hired observers in 1999. No sea otters were found in the 1,624 

traps observed (Hatfield and Estes 2000). However, a very high level of observer coverage 

would be required to see any indication of trap mortality, even if mortality levels were high 

enough to substantially reduce the rate of population recovery (Hatfield et al., in prep.). 

Controlled experiments conducted by the U.S. Geological Survey and the Monterey Bay 

Aquarium demonstrated that sea otters would enter a baited commercial finfish trap with inner 

trap funnel openings of 5.5 inches in diameter (Hatfield and Estes 2000). Hatfield et al. (in 

prep.) confirmed that some sea otters exposed to finfish, lobster, and mock Dungeness crab traps 

in a captive setting would succeed in entering them. Based on experiments with carcasses and 

live sea otters, they concluded that finfish traps with 5-inch-diameter circular openings would 

largely exclude diving sea otters; that circular openings of 5.5 to 6 inches in diameter and 

rectangular openings 4 inches high (typical of Dungeness crab pots) would allow the passage of 

sea otters up to about 2 years of age; and that the larger fyke openings of spiny lobster pots and 

finfish traps with openings larger than 5 inches would admit larger sea otters. Reducing the 

fyke-opening height of Dungeness crab traps by one inch (to 3 inches) would exclude nearly all 

diving sea otters while not significantly affecting the number or size of harvested crabs (Hatfield 

et al. in prep.). 

Since January 2002, CDFG has required 5-inch sea-otter-exclusion rings to be placed in 

live-fish traps used along the central coast from Pt. Montera in San Mateo County to Pt. Arguello 

in Santa Barbara County. No rings are required for live-fish traps used in the waters south of 

Point Conception, and no rings are currently required for lobster or crab traps regardless of their 

location in California waters. 

Data on the number of participating vessels in these fisheries are provided by CDFG and 

represent those vessels making at least one landing in each of the respective fisheries. Numbers 

of participating vessels are given by region, North (Oregon Border to Cape Mendocino), NorthCentral (Cape Mendocino to Point Año Nuevo), South-Central (Point Año Nuevo to Point 

Conception), and South (Point Conception to Mexico). From North to South, the average 

number of vessels participating in the Dungeness and rock crab fisheries from 2002-2006 was 

215, 240, 43, and 113, respectively. The average number of vessels participating in the 

California spiny lobster fishery during this period was 0, 0, 2, and 163, respectively. The 

average number of vessels participating in the live-fish trap fishery during this period was 213, 

86, 58, and 212, respectively. It should be noted that most of the sea otter range is coincident 

with the two central coast regions. 

Available information on incidental mortality and serious injury of southern sea otters in 

commercial fisheries is very limited. Fisheries believed to have the potential to kill or injure 

southern sea otters are listed in Table 1. It should be noted that, due to the nature of potential 

interactions (entrapment or entanglement followed by drowning), serious injury is unlikely to be 

detected prior to the death of the animal. 

Appendix 4. Sea Otter Stock Assessments 339
6

Table 1. Summary of available information on incidental mortality and serious injury of southern sea otters in 

commercial fisheries that might take southern sea otters. n/a indicates that data are not available or are insufficient 

to estimate mortality/serious injury. 

Fishery Name DataType Year(s) Percent 

Observer 

Coverage 

Observed 

Mortality/Serious 

Injury 

Estimated 

Mortality/Serious 

Injury 

Mean 

Takes 

CA angel 

shark/halibut and 

other species set 

gillnet fishery 

(>3.5”)1 

no fisherywide 

observer 

program 

since 1994 

2002 

2003 

2004 

2005 

2006 

0% 

0% 

0% 

0% 

<10% 

n/a 

n/a 

n/a 

n/a 

0 

n/a n/a 

CA yellowtail, 

barracuda, and 

white seabass drift 

gillnet fishery 

(≥3.5” and <14”) 

observer 

2002 

2003 

2004 

2005 

2006 

11.5% 

10.4% 

17.6% 

0% 

0% 

0 

0 

0 

n/a 

n/a 

n/a n/a 

CA anchovy, 

mackerel, and tuna 

purse seine 

observer

(since July 

2004) 

2002 

2003 

2004 

2005 

2006 

0% 

0% 

0% 

1.3% 

<5% 

n/a 

n/a 

n/a 

0 

0 

n/a n/a 

CA sardine purse 

seine 

observer 

(since July 

2004) 

2002 

2003 

2004 

2005 

2006 

0% 

0% 

0% 

1.7% 

<5% 

n/a 

n/a 

n/a 

0 

0 

n/a n/a 

CA lobster, prawn, 

shrimp, rock crab, 

fish pot 

n/a 

2002 

2003 

2004 

2005 

2006 

not 

observed2 n/a n/a n/a 

WA/OR/CA 

crab pot 

(central CA portion 

only) 

n/a 

2002 

2003 

2004 

2005 

2006 

not 

observed2 n/a n/a n/a 

CA finfish and 

shellfish live 

trap/hook and line 

n/a 

2002 

2003 

2004 

2005 

2006 

not 

observed2 n/a n/a n/a 

Unknown hook 

and line fishery 

stranding 

data 

2002 

2003 

2004 

2005 

2006 

- 

0 

1 

2 

1 

0 

≥4 ≥0.8 

1The 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. Observer coverage in this fishery resumed in 2006 (12 sets observed) and continued into 2007 (248 sets observed). Despite no or low 

observer coverage in some years, mortality/serious injury of sea otters in this fishery is estimated to be at or near zero because of depth 

restrictions in place throughout the current mainland range of the southern sea otter. 

2This fishery is classified as a Category III fishery [72FR66048]. Category III fisheries are not required to accommodate observers aboard 

vessels due to the remote likelihood of mortality and serious injury of marine mammals. 

Appendix 4. Sea Otter Stock Assessments 340
7

Other Mortality 

 A study of 3,105 beach-cast carcasses salvaged from 1968 through 1999 identified 

several patterns in the strandings that occurred during periods of population decline: increased 

percentages of (1) prime-age (3 to 10 years) animals, (2) deaths caused by white shark bites, (3) 

carcasses recovered in spring and summer, and (4) animals for which the cause of death was 

unknown (Estes et al. 2003). Analysis of beach-cast carcasses recovered from October 1997 to 

May 2001 showed that 13 percent of the mortalities resulted directly or indirectly from infection 

by acanthocephalans of the genus Profilicollis (Mayer et al. 2003). Common causes of death 

identified for fresh beach-cast carcasses necropsied from 1998 to 2001 included protozoal 

encephalitis, acanthocephalan-related disease, shark attack, and cardiac disease (Kreuder et al.

2003, Kreuder et al. 2005). Encephalitis caused by Toxoplasma gondii was associated with 

shark attack and heart disease, and these causes of death were more common in prime-age 

animals than in juveniles (Kreuder et al. 2003). Diseases (due to parasites, bacteria, fungi, or 

unspecified causes) were identified as the primary cause of death in 63.8 percent of the sea otter 

carcasses examined (Kreuder et al. 2003). 

 An unusually high number of stranded southern sea otters was recovered in 2003, 

prompting declaration of an Unusual Mortality Event for the period from 23 May to 1 October 

2003. The number of strandings relative to the spring sea otter count from 1983 to 2007 is 

shown in Figure 3. In 2003, the relative number of strandings exceeded 10 percent of the spring 

count. No one cause appears to have been responsible for the increase in mortality. Relative 

mortality has remained nearly as high in subsequent years. The relative number of strandings in 

2004, 2005, 2006, and 2007 constituted approximately 9.9 percent of the spring count. 

 Shootings and boat strikes are relatively low but persistent sources of mortality. Other 

rare sources of mortality include debris entanglement and complications associated with research 

activities. During the period from 2002-2006, 13 sea otters were shot, 17 were suspected to have 

been struck by boats, 1 was found entangled in plastic debris, and 2 died as a result of 

complications related to research activities (U.S. Geological Survey and CDFG unpub. data). 

Total observed mortality due to anthropogenic causes, excluding fisheries, is 33, yielding an 

estimated mortality of ≥33 and a mean annual mortality of ≥6.6. 

It should be noted that 

mean annual mortalities reported 

here and in Table 1 are minimum 

estimates. Documentation of these 

sources of mortality comes 

primarily from necropsies of 

beach-cast carcasses. Because it is 

unknown to what extent the levels 

of human-caused mortality 

documented in beach-cast 

carcasses are representative of the 

relative contributions of known 

causes or of human-caused 

mortality as a whole, we are unable 

to give upper bounds for these 

estimates. Disease has been 

identified as the primary cause of 

Figure 3. Southern sea otter strandings relative to the spring 

count, 1983-2007. Data source: U.S. Geological Survey unpub. 

data. 

Relative Number of Sea Otter Strandings

1983 - 2007

0

2

4

6

8

10

12

1983

1985

1987

1989

1991

1993

1995

1997

1999

2001

2003

2005

2007

Percent of Spring Count

Appendix 4. Sea Otter Stock Assessments 341
8

death in more than half of the beach-cast carcasses necropsied (Kreuder et al. 2003), but the 

anthropogenic contribution to disease levels in sea otters is currently unknown. Therefore, 

animals that died of disease are not included in the number of mortalities reported here. 

STATUS OF STOCK

The southern sea otter is designated a fully protected mammal under California state law 

(California Fish and Game Code §4700) and was listed as a threatened species in 1977 (42 FR 

2965) pursuant to the federal Endangered Species Act, as amended (16 U.S.C. 1531 et seq.). As 

a consequence of its threatened status, the southern sea otter is considered by default to be a 

“strategic stock” and “depleted” under the Marine Mammal Protection Act of 1972, as amended 

(16 U.S.C. 1361 et seq.). 

The status of the southern sea otter in relation to its optimum sustainable population 

(OSP) level has not been formally determined, but population counts are well below the 

estimated lower bound of the OSP level for southern sea otters, about 8,400 animals (U.S. Fish 

and Wildlife Service 2003), which is roughly 50 percent of the estimated carrying capacity of 

California (Laidre et al. 2001). Because of the lack of observer data for several fisheries that 

may interact with sea otters, it is not possible to determine whether the total fishery mortality and 

serious injury for sea otters is insignificant and approaching zero mortality and serious injury 

rate. 

Habitat Issues 

Sea otters are particularly vulnerable to oil contamination (Kooyman and Costa 1979; 

Siniff et al. 1982), and oil spill risk from large vessels that transit the California coast remains a 

primary threat to the southern sea otter. Studies of contaminants have documented 

accumulations of dichlorodiphenyltrichloro-ethane (DDT), dichlorodiphenyl-dichloroethylene 

(DDE) (Bacon 1994; Bacon et al. 1999), and polychlorinated biphenyls (PCBs) in stranded sea 

otters (Nakata et al. 1998), as well as the presence of butyltin residues, which are known to be 

immunosuppressant (Kannan et al. 1998). Kannan et al. (2006, 2007) found a significant 

association between infectious diseases and elevated concentrations of perfluorinated 

contaminants and polychlorinated biphenyls (PCBs) in the livers of sea otters, suggesting that 

chemical contaminants may play a role in driving patterns of sea otter mortality. Food limitation 

and nutritional deficiencies may also contribute to sea otter mortality (Bentall 2005, Tinker et al.

2006, Tinker et al. 2008). 

REFERENCES

Bacon, C.E. 1994. An ecotoxicological comparison of organic contaminants in sea otters among 

populations in California and Alaska. M.S. thesis, University of California, Santa Cruz. 

Bacon, C.E., W.M. Jarman, J.A. Estes, M. Simon, and R.J. Norstrom. 1999. Comparison of 

organochlorine contaminants among sea otter (Enhydra lutris) populations in California 

and Alaska. Environ. Toxicology and Chemistry 18(3):452-458. 

Bentall, G.B. 2005. Morphological and behavioral correlates of population status in the 

southern sea otter: a comparative study between central California and San Nicolas 

Island. Masters Thesis, University of California, Santa Cruz, CA, unpublished. 

Bryant, H.C. 1915. Sea otters near Point Sur. California Department of Fish and Game Bull. 

1:134-135. 

Appendix 4. Sea Otter Stock Assessments 342
9

Cameron, G.A. and K.A. Forney. 2000. Preliminary estimates of cetacean mortality in 

California/Oregon gillnet fisheries for 1999. Paper SC/S2/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. Paper SC/53/SM9 presented to the International Whaling Commission, 2001 

(unpublished). 21 pp. Available from NMFS, Southwest Fisheries Science Center, P.O. 

Box 271, La Jolla, California, 92038, USA. 

Cronin, M.A., J. Bodkin, B. Bellachey, J.A. Estes, and J.C. Patton. 1996. Mitochondrial-DNA 

variation among subspecies and populations of sea otters (Enhydra lutris). J. Mammal. 

77:546-557. 

Estes, J.A. 1990. Growth and equilibrium in sea otter populations. J. Anim. Ecol. 59:385-401. 

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., B.B. Hatfield, K. Ralls, and J. Ames. 2003. Causes of mortality in California sea 

otters during periods of population growth and decline. Marine Mammal Science 

19(1):198-216. 

Forney, K.A., S.R. Benson, and G.A. Cameron. 2001. Central California gill net effort and 

bycatch of sensitive species, 1990-1998. Pages 141-160 in Seabird Bycatch: Trends, 

Roadblocks, and Solutions, E.F. Melvin and J.K. Parrish, eds. Proceedings of an 

International Symposium of the Pacific Seabird Group, University of Alaska Sea Grant, 

Fairbanks, Alaska, 212 pp. 

Hatfield, B.B. and J.A. Estes. 2000. Preliminary results of an evaluation of the potential threat 

to sea otters posed by the nearshore finfish trap fishery. Unpublished. 6 pp. + 

appendices. 

Hatfield, B.B., J.A. Ames, J.A. Estes, M.T. Tinker, A.B. Johnson, M.M. Staedler, and M.D. 

Harris. Manuscript in preparation. The potential for sea otter mortality in fish and 

shellfish traps. 22 pp. + appendices. 

Herrick, S.F. Jr. and D. Hanan. 1988. A review of California entangling net fisheries, 1981-

1986. National Oceanic and Atmospheric Administration Technical Memorandum. 

National Marine Fisheries Service. NOAA-TM-NMFS-SWFC-108. 39 pp. 

Jameson, R.J. 1989. Movements, home range, and territories of male sea otters off central 

California. Marine Mammal Science 5:159-172. 

Jameson, R.J. and S. Jeffries. 1999. Results of the 1999 survey of the Washington sea otter 

population. Unpublished report. 5 pp. 

Jameson, R.J. and S. Jeffries. 2005. Results of the 2005 survey of the reintroduced Washington 

sea otter population. Unpublished report. 6 pp. 

Kannan, K., E. Perrotta, and N.J. Thomas. 2006. Association between perfluorinated 

compounds and pathological conditions in southern sea otters. Environmental Science & 

Technology 40:4943-4948. 

Kannan, K., E. Perrotta, N.J. Thomas, and K.M. Aldous. 2007. A comparative analysis of 

polybrominated diphenyl ethers and polychlorinated biphenyls in southern sea otters that 

died of infectious diseases and noninfectious causes. Archives of Environmental 

Contamination and Toxicology 53:293–302. 

Appendix 4. Sea Otter Stock Assessments 343
10

Kannan K., K.S. Guruge, N.J. Thomas, S. Tanabe, J.P. Giesy. 1998. Butyltin residues in 

southern sea otters (Enhydra lutris nereis) found dead along California coastal waters. 

Environmental Science and Technology 32:1169-1175. 

Kooyman, G.L. and D.P. Costa. 1979. Effects of oiling on temperature regulation in sea otters. 

Yearly progress report, Outer Continental Shelf Energy Assessment Program. 

Kreuder, C., M.A. Miller, D.A. Jessup, L.J. Lowenstein, M.D. Harris, J.A. Ames, T.E. Carpenter, 

P.A. Conrad, and J.A.K. Mazet. 2003. Patterns of mortality in southern sea otters 

(Enhydra lutris nereis) from 1998-2001. Journal of Wildlife Diseases 39(3):495-509. 

Kreuder, C., M.A. Miller, L.J. Lowenstine, P.A. Conrad, T.E. Carpenter, D.A. Jessup, and J.A.K. 

Mazet. 2005. Evaluation of cardiac lesions and risk factors associated with myocarditis 

and dilated cardiomyopathy in southern sea otters (Enhydra lutris nereis). American 

Journal of Veterinary Research 66:289-299. 

Laidre, K.L., R.J. Jameson, and D.P. DeMaster. 2001. An estimation of carrying capacity for 

sea otters along the California coast. Marine Mammal Science 17(2):294-309. 

Larson, S., R. Jameson, J. Bodkin, M. Staedler, and P. Bentzen. 2002. Microsatellite DNA and 

mitochondrial DNA variation in remnant and translocated sea otter (Enhydra lutris) 

populations. J. Mammal. 83(3):893-906. 

Mayer, K.A., M.D. Dailey, and M.A. Miller. 2003. Helminth parasites of the southern sea otter 

Enhydra lutris nereis in central California: abundance, distribution, and pathology. 

Diseases of Aquatic Organisms 53:77-88. 

Nakata, H., K. Kannan, L. Jing, N. Thomas, S. Tanabe, and J.P. Giesy. 1998. Accumulation 

pattern of organochlorine pesticides and polychlorinated biphenyls in southern sea otters 

(Enhydra lutris nereis) found stranded along coastal California, USA. Environ. Poll. 

103:45-53. 

Ralls, K., T.C. Eagle, and D.B. Siniff. 1996. Movement and spatial use patterns of California 

sea otters. Canadian Journal of Zoology 74:1841-1849. 

Riedman, M.L. and J.A. Estes. 1990. The sea otter (Enhydra lutris): behavior, ecology, and 

natural history. U.S. Fish and Wildlife Service, Biol. Rep. 90(14). 126 pp. 

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. 

Sanchez, M.S. 1992. Differentiation and variability of mitochondrial DNA in three sea otter, 

Enhydra lutris, populations. M.S. Thesis, University of California Santa Cruz. 

Siniff, D.B. and K. Ralls. 1991. Reproduction, survival, and tag loss in California sea otters. 

Marine Mammal Science 7(3):211-229. 

Siniff, D.B., T.D. Williams, A.M. Johnson, and D.L. Garshelis. 1982. Experiments on the 

response of sea otters, Enhydra lutris, to oil contamination. Biol. Conserv. 2: 261-272. 

Taylor, B.L., M. Scott, J. Heyning, and J. Barlow. 2002. Suggested guidelines for recovery 

factors for endangered marine mammals. Unpublished report submitted to the Pacific 

Scientific Review Group. 7 pp. 

Tinker, M.T., G. Bentall, and J.A. Estes. 2008. Food limitation leads to behavioral 

diversification and dietary specialization in sea otters. PNAS 105:560-565. 

Tinker, M.T., J.A. Estes, K. Ralls, T.M. Williams, D. Jessup, and D.P. Costa. 2006. Population 

Dynamics and Biology of the California Sea Otter (Enhydra lutris nereis) at the Southern 

End of its Range. MMS OCS Study 2006-007. Coastal Research Center, Marine Science 

Appendix 4. Sea Otter Stock Assessments 344
11

Institute, University of California, Santa Barbara, California. MMS Cooperative 

Agreement Number 14-35-0001-31063. 

U.S. Fish and Wildlife Service. 2003. Final Revised Recovery Plan for the Southern Sea Otter 

(Enhydra lutris nereis). Portland, Oregon. xi + 165 pp. 

Wendell, F.E., R.A. Hardy, and J.A. Ames. 1986. An assessment of the accidental take of sea 

otters, Enhydra lutris, in gill and trammel nets. California Department of Fish and Game, 

Mar. Res. Tech. Rep. No. 54, 31 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 4. Sea Otter Stock Assessments 345
August 2008 

SEA OTTER (Enhydra lutris kenyoni)

WASHINGTON STOCK

U.S. Fish and Wildlife Service 

 Lacey, Washington 

STOCK DEFINITION AND GEOGRAPHIC RANGE 

The northern sea otter, Enhydra lutris kenyoni, 

historically ranged throughout the North Pacific, from 

Asia along the Aleutian Islands, originally as far north 

as the Pribilof Islands and in the eastern Pacific Ocean 

from the Alaska Peninsula south along the coast to 

Oregon (Wilson et al. 1991). In Washington, areas of 

sea otter concentration were reported from the 

Columbia River to along the Olympic Peninsula coast 

(Scheffer 1940). Sea otters were extirpated from most 

of their range during the 1700s and 1800s as the species 

was exploited for its fur. Washington’s sea otter 

population was extirpated by the early 1900s. In 1969 

and 1970, a total of 59 sea otters were captured at 

Amchitka Island, Alaska, and released near Point 

Grenville and LaPush off Washington’s Olympic 

Peninsula coast (Jameson et al. 1982; Jameson et al. 

1986). Washington’s current sea otter population 

originated from the Amchitka Island genotype 

(Enhydra lutris kenyoni). 

For management purposes pursuant to the Marine 

Mammal Protection Act (MMPA), the range of the Washington sea otter stock is within the 

marine waters of Washington State. However, if the stock expands southward into Oregon or 

northward into British Columbia, a revised stock assessment would consider this expanded 

range. 

Figure 1. Approximate distribution 

of Washington sea otter stock.

In 2006, the distribution of the majority of the Washington sea otter stock ranged from 

Pillar Point in the Strait of Juan de Fuca, west to Cape Flattery and as far south as Cape Elizabeth 

on the outer Olympic Peninsula coast (Figure 1). However, scattered individuals (usually one or 

two individuals at a time) have been seen outside of this range. For example, sick or injured sea 

otters have come ashore as far south as Ocean Shores and repeated sightings have been reported 

in Grays Harbor and as far east as Port Townsend. Sightings around the San Juan Islands, near 

Deception Pass, off Dumas Bay, off the Nisqually River, and in southern Puget Sound near 

Squaxin and Hartstene Islands have also been reported. Several of the sea otters in Puget Sound 

became relatively “tame,” and in some cases local residents were feeding these individuals and 

promoting their “friendly” behavior. The U. S. Fish and Wildlife Service (USFWS) and 

Washington Department of Fish and Wildlife (WDFW) intervened, to the extent necessary, when 

these individual sea otters exhibited behaviors that presented a danger to themselves or to human 

health and safety. 

1

Appendix 4. Sea Otter Stock Assessments 346
In waters to the north of the Washington stock is the British Columbia sea otter 

population, which originated from animals also translocated from Amchitka Island and 

additional individuals from Prince William Sound, Alaska (Watson 2000). British Columbia’s 

sea otter population, which is also increasing, includes at least 3,180 animals distributed mainly 

along the west coast of Vancouver Island from Barkley Sound to Cape Scott with a separate 

population along the mainland coast near Goose Island in Queen Charlotte Sound (COSEWIC 

2007). Although most of the British Columbia sea otter population remains north of Estevan 

Point along the west coast of Vancouver Island, groups of 100 to 150 animals have recently been 

observed south of Estevan Point near Hesquiat Harbor and Flores Island just north of Tofino. 

Small numbers of animals have also been reported in Barkley Sound and scattered along the 

coast of the Strait of Juan de Fuca to Victoria. Currently there is no evidence of interchange 

between the Washington and British Columbia sea otter populations. However, as the 

Washington and British Columbia populations grow and expand their respective ranges, 

movement between these populations can be expected. 

Sea otters breed and give birth year-round (Riedman and Estes 1990). Pupping period for 

Washington’s sea otter stock is not well defined, with dependent pups observed in all months. 

However, births in Washington sea otters are believed to occur primarily from March to April, 

with peak numbers of dependent pups expected to be present from May to September (Ron 

Jameson, pers. comm.). 

POPULATION SIZE 

Original Washington Translocation 

Fifty-nine sea otters were released off the Washington coast in 1969 and 1970, although 

almost half of the otters released in 1969 died. Sightings of sea otters were sporadic for several 

years after the translocations and during surveys through 1976, no more than 10 otters were 

observed at a time (Jameson et al. 1982). The current Washington sea otter population 

descended from no more than 43 otters and possibly as few as 10 (Jameson et al. 1982). 

Reproduction was first documented in 1974 (Jameson et al. 1982) and pups have been observed 

in all subsequent surveys. 

Minimum Population Estimate

 The first comprehensive post-release surveys of Washington’s sea otter population were 

conducted by boat in 1977 and again in 1981 (Jameson et al. 1986). Boat, ground, and aerial 

surveys for sea otters were conducted biennially from 1981 to 1989. Starting in 1989 and 

continuing to present, Washington’s sea otter population estimate has been developed from a 

combined aerial and ground survey conducted in early July by United States Geological Survey 

and/or WDFW. Based on the 2007 survey (actual count), the minimum population estimate of 

the Washington sea otter population is 1,125 individuals (Jameson and Jeffries 2008). No 

correction factor for missed animals has been applied to count data to determine a total 

population estimate from survey counts for Washington. 

2

Appendix 4. Sea Otter Stock Assessments 347
Current Population Trend 

 Based on count totals from 1977 to 1989, the 

Washington sea otter population increased at an annual

rate of 20 percent (Jameson and Jeffries 1999). As has 

been done for the southern sea otter (Enhydra lutris 

nereis), three-year running averages are used to 

characterize population trends to dampen the effects of 

anomalous counts in any given year (U.S. Fish and 

Wildlife Service 2003). Jameson and Jeffries (2006) 

indicate “the finite rate of increase for this population 

since 1989 is 8 percent.” Survey data indicate the 

Washington stock is nearing equilibrium density north of 

La Push, where the rate of increase has shown no growth since 2000 (Jameson and Jeffries 

2008). South of La Push, the stock has been growing at about 20 percent per year since 1989 

(Jameson and Jeffries 2006). 

0

200

400

600

800

1000

1200

1989

1991

1993

1995

1997

1999

2001

2003

2005

2007

Year

Number of Sea Otters

Count

3-Year

Running

Average

Figure 2. Annual and three-year running average 

of population estimates (1989-2007).

Laidre et al. (2002) provides a carrying capacity (K) estimate of 1,019 sea otters (95 

percent CI 754-1,284) for Washington’s sea otter stock to reoccupy rocky habitat from 

Destruction Island to Neah Bay (e.g., Seal and Sail Rocks). Laidre et al. (2002) also provide a 

total carrying capacity estimate for Washington of 1,836 sea otters (95 percent CI 1,386-2,286) 

based on an assumption that sea otters will reoccupy most of their historic habitat along the outer 

Washington coast (excluding reoccupation of the Columbia River, Willapa Bay, and Grays 

Harbor estuaries due to significant human alterations and use) and eastward into the Strait of 

Juan de Fuca as far as Protection Island. The Washington sea otter stock appears to be 

approaching equilibrium in the rocky habitat along the Olympic Peninsula coast; the reasons why 

the population has not dispersed into the unoccupied portions of its historic range are unclear. 

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

 The maximum annual growth rate (Rmax) for sea otter populations for which data are 

available has been reported as 17 to 20 percent (Estes 1990). From 1977 to 1989, the 

Washington stock grew at 20 percent (Jameson and Jeffries 1999) and appears to still be growing 

at this rate south of La Push (Jameson and Jeffries 2008). However, between 1989 and 2007, the 

growth rate of the entire Washington sea otter stock has slowed to an annual rate of 8 percent 

(Jameson and Jeffries 2008). 

POTENTIAL BIOLOGICAL REMOVAL

 The Potential Biological Removal (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=1,125; Rmax uses a maximum sea otter 

growth rate of 20 percent; and Fr=0.1. A Fr of 0.1 was used for the Washington sea otter stock 

because even though the population is increasing, the minimum population size is less than 1,500 

and the population is restricted in its geographical range making it vulnerable to natural or 

human-caused catastrophe (Taylor et al. 2002). Therefore, the calculated PBR for the 

Washington sea otter stock is 11 animals. 

3

Appendix 4. Sea Otter Stock Assessments 348
ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY 

Fisheries Information 

 Sea otters are susceptible to drowning in gillnets and have been taken in the Makah 

Northern Washington Marine Set-gillnet Fishery (Gearin et al. 1996). Based on observer data 

collected from 1988 through 2001, a total of 11 sea otters were taken when fishing effort 

occurred (Makah Tribe/Makah Tribal Resources and National Marine Fisheries Service 

(NMFS)/National Marine Mammal Lab (NMML) observer data). Although the fishing effort in 

this fishery began declining in the mid 1990s, sea otters continue to be taken in this fishery 

(Table 1). Pre-2000 data indicates sea otter mortalities are likely to occur when there is fishing 

effort in Areas 4 and 4A (Makah Bay). Only mortalities, not serious injuries, are reflected in 

Table 1 because the nets set by the Makah fishery do not rise to the surface of the water and any 

otters that get caught in the nets will likely drown. Due to inconsistent reporting between fishing 

areas, years, and the associated fishing effort, observer coverage, and otter mortalities (see Table 

1), a reliable estimation of the annual sea otter mortality and serious injury in the Makah 

Northern Washington Marine Set Gillnet Fishery is assumed to be a minimum of 2 when there is 

fishing effort. In order to provide a more accurate estimate of the annual mortality and serious 

injury associated with this fishery, the USFWS requested information from the NMFS and the 

Makah Tribe. The information provided by the NMFS and the Makah Tribe was not sufficient to 

provide a more accurate estimate. 

Table 1. Summary of sea otter incidental mortality in Northern Washington Marine Set-Gillnet 

Fishery. (Source: NMFS/NMML observer program, BIA, and Makah Tribe) 

Fishery Name Year Fishing 

Efforta

(Yes/No) 

Observer Coverage Observed/Reported 

mortality 

(Number of Otters) 

2003 Yes None - 

2004 Yes 

1-11 net days 

observedb 2 

2005 Yes None - 

2006 Yes None - 

Northern WA 

Marine Set 

Gillnet Areas 

4/4A/4B/5 

2007 Yes None - a

Overall fishing effort is not available

b

Observer coverage is presented in format supplied to USFWS 

Other fisheries that occur within the range of the sea otter in Washington include treaty 

and non-treaty gillnet fisheries in the Strait of Juan de Fuca, Puget Sound, and Grays Harbor. 

Neither the USFWS or the NMFS have received any voluntary or observer reports of sea otters 

killed or seriously injured in these fisheries. However, the lack of information cannot be 

interpreted to mean that no sea otters have been killed or seriously injured because there has not 

been marine mammal observer coverage of these fisheries since 1994, rather, incidental takings 

of marine mammals in these fisheries are reported to NMFS through self-reporting (Sources: 

Treaty/Non-treaty sum of landings submitted to the USFWS as part of Biological Opinion 

reporting requirements, USDC NMFS 2003). The fisheries subject to self-reporting do not 

4

Appendix 4. Sea Otter Stock Assessments 349
include tribal fisheries. An accurate estimate of sea otter mortality and serious injury associated 

with these fisheries requires instituting an observer program and obtaining fishing effort data. 

Because this information is not currently available, we cannot provide an accurate estimate of the 

annual mortality and serious injury associated with these fisheries. Sea otter densities along the 

Strait of Juan de Fuca in the summer and fall are low, when the fisheries generally operate, so 

few entanglements would be expected. However, as the Washington sea otter population 

continues to grow, the possibility of fisheries-related incidental take in these gillnet fisheries will 

grow. 

Other fisheries that also occur within the range of the Washington sea otter stock include: 

1) treaty set-gillnet fisheries that occur in the coastal rivers (Quinault, Queets, Hoh, Quillayute, 

Hoko, and Waatch); 2) treaty and non-treaty groundfish trawl fisheries that occur offshore of the 

Olympic Peninsula coast; and 3) treaty and non-treaty drift gillnet fisheries that occur in Willapa 

Bay. These fisheries are unlikely to result in mortality or serious injury because sea otters are 

unlikely to occur in these areas. 

As sea otters expand their range eastward into the Strait of Juan de Fuca or south along 

the outer Washington coast, they will also encounter important sport and commercial shellfish 

fisheries (urchins, razor clams, Dungeness crabs, steamer clams, geoducks). “Evidence from 

California and Alaska suggests that the potential for incidental take of sea otters in crab traps will 

increase as the population expands its range south of Destruction Island into prime Dungeness 

crab habitat” (Lance et al. 2004). In addition, the potential exists for increased interactions with 

invertebrate fisheries, particularly sea urchins and geoducks, as the sea otter population expands 

eastward into the Strait of Juan de Fuca (Gerber and VanBlaricom 1999). 

Other Human-Caused Mortality and Serious Injury

 Other sources of human-caused mortality and serious injury affecting the Washington sea 

otter population 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 and other toxic contaminants. In 2003, one 

Washington sea otter death was presumed to have been caused by a boat strike because of the 

type of injuries observed during necropsy. However, these injuries could also have been 

sustained in a variety of other ways. 

In the past decade, a number of oil spills have occurred within the range of Washington’s 

sea otter population, with one documented oil related death recorded during one of these spills 

(Jameson 1996). Additionally, with the increasing volume of shipping traffic into and out of the 

Strait of Juan de Fuca, the potential for a catastrophic spill exists and most, if not all, of the 

Washington sea otter population and range is vulnerable to the effects of such a spill. Significant 

oil-related mortalities and habitat damage would be expected to occur if an oil spill of this nature 

were to happen and impinge directly on sea otter habitat along Washington’s Olympic Peninsula 

and Strait of Juan de Fuca coastlines. 

However, due to the lack of documented mortalities or serious injuries resulting from 

other human-caused sources and the unpredictability of oil spills, we are unable to provide an 

estimate of the annual mortality and serious injuries associated with other human-caused 

mortality and serious injury. 

Harvest by Northwest treaty Indian tribes 

5

Appendix 4. Sea Otter Stock Assessments 350
 A number of Native American tribes of the Pacific Northwest have treaty rights to 

harvest various fish and wildlife resources in Washington State. Currently there is no 

authorization for harvest of sea otters by Native Americans; however, there is a developing 

interest in such a program. As affirmed by the Court of Appeals for the Ninth Circuit in 

Anderson v. Evans (9th Cir. June 7, 2004), any take of sea otters by Native Americans other than 

Alaskan natives residing in Alaska has to be authorized under the MMPA. 

STATUS OF STOCK

The Washington sea otter stock is not listed as “depleted” under the MMPA nor listed as 

“threatened” or “endangered” under the Endangered Species Act. Sea otters are listed by the 

State of Washington as “State endangered” under Revised Code of Washington 77.12.020 and 

Washington Administrative Code (WAC) 232.12.014 due to small population size, restricted 

distribution, and vulnerability (Lance et al. 2004). The WDFW finalized their sea otter recovery 

plan in 2004 (Lance et al. 2004). 

This stock is not classified as strategic because the population is growing and is not listed 

as “depleted” under the MMPA or “threatened” or “endangered” under the Endangered Species 

Act of 1973. 

The lower end of the Optimum Sustainable Population (OSP) range is assumed to occur 

at approximately 60 percent of the maximum population size the environment will support (i.e. 

carrying capacity) (DeMaster et al. 1996). The total carrying capacity estimate for Washington 

is 1,836 sea otters (95 CI 1,386 – 2,286) (Laidre et al. 2002). The current population estimate of 

1,125 (Jameson and Jeffries 2008) is above the lower end of the OSP (60 percent of 1,836). 

The mortality and serious injury for the Makah Northern Washington Marine Set Gillnet 

Fishery is estimated to be a minimum of two mortalities annually when there is fishing effort. 

We are unable to provide an estimate of the annual mortality and serious injury associated with 

other fisheries and other sources of human-caused mortality and serious injury, due to the lack of 

information. Therefore, we are unable to determine whether the level of human-caused 

mortalities and serious injuries are insignificant and approaching a zero mortality and serious 

injury rate. 

REFERENCES

COSEWIC 2007. COSEWIC assessment and update status report on the sea otter Enhydra lutris

in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa. vii + 

36 pp. (www.sararegistry.gc.ca/status/status_e_cfm). 

DeMaster, D.P., C. Marzin, and R.J. Jameson. 1996. Estimating the historical abundance of sea 

otters in California. Endangered Species Update 13(12):79-81. 

Estes, J. A. 1990. Growth and equilibrium in sea otter populations. J. Anim. Ecol. 59:358-401. 

Gearin, P.J., M. E.Gosho, J. Laake, and R. L. Delong. 1996. Acoustic alarm experiments in the 

northern Washington marine set-net fishery, method to reduce by-catch of harbor 

porpoise. Rept. Int. Whal. Commn. SC/48/SM10, 13 pp. 

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Appendix 4. Sea Otter Stock Assessments 351
Gerber, L.R. and G.R. VanBlaricom. 1999. Potential fishery conflicts involving sea otters 

(Enhydra lutris [L.] in Washington State waters. Final report to the Marine Mammal 

Commission, Contract T30917202, October 1999, 69pp. 

Jameson, R. J., K. W. Kenyon, A. M. Johnson, and H. M. Wight. 1982. History and status of 

translocated sea otter populations in North America. Wildl. Soc. Bull. 10:100-107. 

Jameson, R. J., K. W. Kenyon, S. Jeffries and G. R. VanBlaricom. 1986. Status of a 

translocated sea otter and its habitat in Washington. Murrelet 67:84-87. 

Jameson, R.J. 1996. Status reports: West Coast translocation projects, Oregon and Washington. 

The Otter Raft No. 55, Page 8. 

Jameson, R.J., and S. Jeffries 1999. Results of the 1999 Survey of the Washington Sea Otter 

Population. Unpublished Report. 5pp. 

Jameson, R.J. and S. Jeffries. 2006. Results of the 2006 Survey of the Reintroduced Sea Otter 

Population in Washington State. Unpublished Report. 7pp. Copies may be obtained 

from the Washington Department of Fish and Wildlife. 

Jameson, R.J. and S. Jeffries. 2008. Results of the 2007 Survey of the Reintroduced Sea Otter 

Population in Washington State. Unpublished Report. 7pp. Copies may be obtained 

from the Washington Department of Fish and Wildlife. 

Laidre, K., R.J. Jameson, S.J. Jeffries, R.C. Hobbs, C.E. Bowlby, and G.R. VanBlaricom. 2002. 

Estimates of carrying capacity for sea otters in Washington state. Wildl. Soc. Bull. 

30(4):1172-1181. 

Lance, M.M., S.A. Richardson, and H. Allen. 2004. State of Washington sea otter recovery 

plan. WDFW, Olympia WA. 91 pp. 

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 

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Scheffer, V.B. 1940. The sea otter on the Washington coast. Pacific Northwest Quarterly, 

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Taylor, B.L., M. Scott, J. Heyning, and J. Barlow. 2002. Suggested guidelines for recovery 

factors for endangered marine mammals. Unpublished report submitted to the Pacific 

Scientific Review Group. 7 pp. 

U.S. Department of Commerce (USDC). National Marine Fisheries Service 2003. Harbor seal 

(Phoca vitulina richardsi): Washington inland waters stock, stock assessment report. 

6pp. 

U.S. Fish and Wildlife Service. 2003. Final revised recovery plan for the southern sea otter 

(Enhydra lutris nereis). Portland, Oregon. xi + 165pp. 

Watson, J.C. 2000. The effects of sea otters (Enhydra lutris) on abalone (Haliotis spp.) 

populations. Pages 123-132 In: Workshop on rebuilding abalone stocks in British 

Columbia. Ed. A. Campbell. Canadian Special Publication of Fisheries and Aquatic 

Sciences 130 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. 

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Appendix 4. Sea Otter Stock Assessments 352