DECEMBER 2000


U. S. Pacific 

Marine Mammal Stock Assessments: 2000 

by


Karin A. Forney, Jay Barlow, Marcia M. Muto, 


Mark Lowry, Jason Baker, Grant Cameron, 


Joseph Mobley, Charles Stinchcomb, and James V. Carretta


with contributions from


Susan Chivers, Joe Cordaro, Douglas DeMaster, 


Graeme Ellis, P. Scott Hill, Pierre Kleiber, Robert Read, 


Scott Spitz, and Tim Gerrodette


NOAA-TM-NMFS-SWFSC-300 

U. S. Department of Commerce


National Oceanic and Atmospheric Administration


National Marine Fisheries Service


Southwest Fisheries Science Center

TABLE OF CONTENTS


PREFACE .................................. .................................. ............. iv


PINNIPEDS 

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


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


HARBOR SEAL ( Phoca vitulina richardsi): Oregon & Washington Coastal Waters Stock ................. 13


HARBOR SEAL ( Phoca vitulina richardsi): Washington Inland Waters Stock .......................... 19


NORTHERN ELEPHANT SEAL ( Miroun ga ang ustirostris): California Breeding Stock .................. 25


GUADALUPE FUR SEAL (Arctocephalus townsendi) .................................. ........... 30


NORTHERN FUR SEAL (Callorhinus ursinus): San Miguel Island Stock .............................. 34


HAWAIIAN MO NK SEAL (Monachus schauinslandi) .................................. ........... 39


CETACEANS - U.S. WEST COAST 

HARBOR PORPOISE (Phocoena phocoena): Central California Stock ................................ 47


HARBOR PORPOISE (Phocoena phocoena): Northern California Stock ............................... 52


HARBOR PORPOISE (Phocoena phocoena): Oregon/Washington Coast Stock ......................... 56


HARBOR PORPOISE (Phocoena phocoena): Washington Inland Waters Stock ......................... 61


DALL'S PORPOISE (Phoco enoides dalli): California/Oregon/Washington Stock ........................ 68


PACIFIC WHITE-SIDED DOLPHIN (Lagenorhynchus obliquidens): 


California/Oregon/Washington, Northern and Southern Stocks ................................ 72


RISSO'S DOLPHIN (Grampus griseus): California/Oregon/Washington Stock .......................... 77


BOTTLENOSE DOLPHIN (Tursiops truncatus): California Coastal Stock ............................. 81


BOTTLENOSE DOLPHIN (Tursiops truncatus): California/Oregon/Washington Offshore Stock ............ 85


STRIPED DOLPHIN (Stenella coeruleoalba): California/Oregon/Washington Stock ..................... 89


SHORT-BEAKED COMMON DOLPHIN (Delphin us delph is): California/Oregon/Washington Stock ........ 93


LONG-BEAKED COMMON DOLPHIN (Delphin us cape nsis): California Stock ........................ 98


NORTHERN RIGHT-WHALE DOLPHIN (Lissodelp his borea lis): California/Oregon/Washington Stock .... 103


KILLER WHALE (Orcinus orca): Eastern North Pacific Transient Stock .............................. 107


KILLER WHALE (Orcinus orca): Eastern North Pacific Offshore Stock .............................. 114


KILLER WHALE (Orcinus orca): Eastern North Pacific Southern Resident Stock ....................... 119


SHORT-FINNED PILOT WHALE (Globicephala macrorhynchus): California/Oregon/Washington Stock ... 125


BAIRD'S BEAKED WHALE (Berard ius bairdii ): California/Oregon/Washington Stock .................. 129


MESOPLODO NT BEAKED WHALES ( Mesoplodon spp.): California/Oregon/Washington Stocks ......... 132


CUVIER'S BEAKED WHALE (Ziphius c avirostris ): California/Oregon/Washington Stock ............... 136


PYGMY SPERM WHALE (Kogia breviceps): California/Oregon/Washington Stock .................... 139


SPERM WHALE (Physeter macrocephalus): California/Oregon/Washington Stock ..................... 142


HUMPBACK WHALE (Megaptera novaeangliae): California/Oregon/Washington - Mexico Stock ......... 147


BLUE WHALE (Balaenoptera musculus): Eastern North Pacific Stock ................................ 153


FIN WHALE (Balaenoptera physalus): California/Oregon/Washington Stock .......................... 158


BRYDE'S WHALE (Balaenoptera edeni): Eastern Tropical Pacific Stock ............................. 162


SEI WHALE (Balaen optera b orealis ): Eastern North Pacific Stock .................................. 166


MINKE WHALE (Balaen optera a cutorostra ta): California/Oregon/Washington Stock ................... 170


ii 
CETACEANS - HAWAII 

ROUGH-TOOTHED DOLPHIN (Steno b redane nsis): Hawaiian Stock ................................ 174


RISSO'S DOLPHIN (Grampus griseus): Hawaiian Stock .................................. ......... 177


BOTTLENOSE DOLPHIN (Tursiops truncatus): Hawaiian Stock .................................. .. 180


PANTROPICAL SPOTTED DOLPHIN (Stenella a ttenuata ): Hawaiian Stock .......................... 184


SPINNER DOLPHIN (Stenella lo ngirostris ): Hawaiian Stock .................................. ..... 187


STRIPED DOLPHIN (Stenella coeruleoalba): Hawaiian Stock .................................. .... 190


MELON-HEADED WHALE (Pepono cephala electra ): Hawaiian Stock ............................... 193


PYGMY KILLER WHALE (Feresa a ttenuata ): Hawaiian Stock .................................. ... 196


FALSE KILLER WHALE (Pseudorca crassidens): Hawaiian Stock .................................. 198


KILLER WHALE (Orcinus orca): Hawaiian Stock .................................. ............. 201


SHORT-FINNED PILOT WHALE (Globicephala macrorhynchus): Hawaiian Stock .................... 204


BLAINVILLE'S BEAKED WHALE (Mesop lodon d ensirostris ): Hawaiian Stock ....................... 207


CUVIER'S BEAKED WHALE (Ziphius c avirostris ): Hawaiian Stock ................................. 210


PYGMY SPERM WHALE (Kogia breviceps): Hawaiian Stock .................................. .... 213


DWARF SPERM WHALE (Kogia sima): Hawaiian Stock .................................. ........ 215


SPERM WHALE (Physeter macrocephalus): Hawaiian Stock .................................. ..... 217


BLUE WHALE (Balaenoptera musculus): Hawaiian Stock .................................. ....... 221


FIN WHALE (Balaenoptera physalus): Hawaiian Stock .................................. .......... 224


BRYDE'S WHALE (Balaenoptera edeni): Hawaiian Stock .................................. ....... 226


APPENDICES 

APPE NDIX 1: Description of U.S . Commercial Fisheries .................................. ........ 228


APPE NDIX 2: Cetacea n Survey Effort .................................. ....................... 258


APPE NDIX 3: Summa ry of 2000 U.S. Pac ific Marine M ammal Sto ck Assessment Repo rts ................ 264


APPENDIX 4: Chronology of U. S. Pacific Stock Assessment Reports, 1995-2000 ....................... 268


APPE NDIX 5: U.S. Fish a nd W ildlife Service C alifornia & W ashington sea otter stock asse ssments ......... 272


iii 
PREFACE 

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

Service (NMFS) and the U.S. Fish and W ildlife 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. T his report p resents a comple te set of revised stock assessments for Pacific marine mammal stocks 

under NMF S jurisdiction (55 stocks ). Stock Asse ssments for Alaskan marine mammals are published by the National 

Marine Mammal Laboratory (NM ML) in a separate report . Stock assessment reports prepared by the USFWS for the 

California an d Wa shington state sto cks of sea otte rs appear in Appen dix 5. 

The assessments in this report include stocks studied by the Southwest Fisheries Science Center (SWFSC, La 

Jolla, California and Honolulu, Hawaii) and the National Marine Mammal Laboratory (NMML, Seattle, Washington). 

Staff of the National Ma rine Mamm al Laboratory wrote seve n reports, including two stocks of harb or seals in Oregon 

and Washington, northern fur seal (San Miguel Island stock), two stocks of harbor porpoise in Oregon and W ashington, 

and two stocks of Eastern North Pacific killer whales (Southern Resident and Transient stocks). Southwest Fisheries 

Science Center personnel prepared stock assessments for the remaining 48 stocks. A summary table for these revised 

stock assessm ent reports is p rovided in Appen dix 4. 

In the 2000 Stock Assessment Reports, descriptions of commercial fisheries that interact with or take marine 

mammals have been updated to include recent estimates of fishing effort and bycatch mortality (Appendix 1). Where 

possible, fishery mortality sections for individual species have been updated to include information on fishery mortality 

through 1998. Mortality estimates reflect the most recent 5 years of available data (1994-98), with the exception of the 

California drift gillnet fishery, where mortality estimates are based on data from 1 997-98 only. This reflects the fact that 

entanglement rates of marine mamma ls declined a fter impleme ntation of the Take Reduction Plan in 1997. New 

abundance estimates are available and have been included for 10 Hawaiian stocks and 25 U.S. West Coa st stocks. There 

were changes in the status of three stocks: (1) the C alifornia/Ore gon/W ashington sto ck of short-finne d pilot whale is no 

longer strategic, owing to a reductio n in driftnet mortality; (2) the central California stock of harbor porpoise is now 

strategic, owing to increased mortality in the halibut set gillnet fishe ry; and (3) the Hawaii stoc k of false killer wha le 

is now strategic, owing to serious injuries documented in the long line fishery. Of the remaining stoc ks, ten remain 

strategic and 42 non-strategic. T he 10 strateg ic stocks includ e 10 end angered sp ecies that are a utomatically considered 

strategic. The stock assessment report for the California/Oregon/Washington stock of dwarf sperm whale (Kogia sima) 

has been discontinued, reflecting its rarity in California waters. A change in the species name of the dwarf sperm wha le 

(from simus to sima) is briefly reviewed in the Hawaii report for this species (Rice 1998) . The stock of blue whale 

formerly known as the ‘California/Mexico stock’ has been renamed the ‘Eastern North Pacific stock’ to reflect current 

knowledge of whale movements between the U.S. west coast and the eastern tropical Pacific (Mate et al. 1999, Stafford 

et al. 1999) . Sighting plots for each species have been updated by eliminating older Minerals and Management Service 

(MMS) survey data from the 1970s and 1980s and by including more rec ent NMFS survey data from 1991-98. The 

exception to this is the sighting plot for the California/Oregon/Washington stock of short-finned pilot whale, which 

retains the MMS sighting data prior to the 1983-84 El Niño e vent, in part to reflect the rarity of pilot whales along the 

U.S. west co ast since that eve nt. 

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

Scientific Review Groups and by Doug DeMaster, Scott Hill, and Paul Wade; we thank them for their helpful comm ents. 

We thank the Marine Mam mal Commission, Center for Marine Conservation, and The Humane Society of the United 

States for their constructive criticism. The authors also wish to thank those who provided unpublished data. The cover 

photograph was provided by the SWF SC photogrammetry group. Any omissions or errors are the sole re sponsibility 

of the authors . 

This is a working d ocumen t and individu al stock assessm ent reports w ill be update d as new in formation 

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

or comm ents which wo uld impro ve future stock assessment re ports. 

iv 
References: 

Barlow, J., K. A. Fo rney, P. S. Hill, R. L . Browne ll, Jr., J. V. Carretta, D. P. DeMaster, F. Julian, M. S. Lowry, T. Ragen, 

and R. R. Ree ves. 1997 . U.S. Pacific Marine Mammal Stock Assessments: 1996. U.S. Department of 

Commerce, NOAA Technical Memorandum NMFS-SWFSC-248. 223 pp. 

Barlow, J., P. S. Hill, K. A. Forney, and D. P. DeMaster. 1998. U.S. Pacific Marine Mammal Stock Assessments: 1998. 

U.S. De partment o f Comme rce, NO AA Te chnical M emorand um NM FS-SW FSC-25 8. 42 pp . 

Forney, K. A., M. M. Muto, and J. Bake r. 1999. U.S. Pacific Marine Mammal Stock Assessments: 1999. U.S. 

Departm ent of Com merce, N OAA T echnical M emorand um NM FS-SW FSC-28 2. 62 pp . 

Hill, P. S. and D. P. DeMaster. 1998. Alaska Marine Mammal Stock Assessments, 1998. U. S. Department of 

Commerce, NOAA Technical Memorandum NMFS-AFSC-97. 166 pp. 

Mate, B.R., B.A . Lagerquist, a nd J. Calam bokidis. 19 99. Mo vements of N orth Pacific blue whales during the feeding 

season off southern California and their southern fall migration. Mar. Mamm. Sci. 15(4):1246-1257. 

Rice, D.W. 1998. Marine Mammals of the W orld, Systematics and Distribution. Special Publication Number 4 The 

Society of Marine Mammalogy. Douglas Wartzok (ed.). 231 pp. 

Stafford, K.M., S .L. Nieukirk, a nd C.G. F ox. 1999. A n acoustic link b etween blue whales in the eastern tro pical Pac ific 

and the northeast Pacific. Mar. Mamm. Sci. 15(4):1258-1268. 

v 
Revised 12/15/2000


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


STOCK DEFINITION AND GEOGRAPHIC RANGE 

The California sea lion Zalophus californianus includes 

three subspec ies: Z. c. wollebaeki (on the G alapago s Islands), Z. 

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


californianus (found from southern M exico 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). The se three geogra phic regio ns are used to


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


stock begins at the U.S./Mexico border and extends no rthward


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


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


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


Gulf of California from the southern tip of the Baja California


peninsu la and across to the mainland and extends to southern


Mexico (Lowry et al. 1992). Some movem ent has been


documented betwee n these ge ograph ic stocks, but rookeries in the


United States are widely separated from the major rookeries of


western Baja California, M exico. M ales from western B aja


California rookeries may spend most of the year in the United


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


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


There are no international agreements for joint management of Figure 1. Geographic range of California sea


California sea lions between the U.S., Mexico, and Canada. lions showing stock boundaries and locations of


major rook eries. 

POPULATION SIZE 

The entire population cannot be counted because all age 

and sex classes ar e never a shore at the same tim e. In lieu of c ounting all sea lions, pups are counted during the breeding 

season (b ecause th is is the only a ge class that is a shore in its en tirety), and th e num ber of birth s is estimated from the 

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

population. 

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

count in 1999 (42,388) w as adjusted for an estimated 15% pre-census m ortality (Boveng 1988; Low ry et al. 1992), 

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

23.9%) was estim ated from a life table derived for th e norther n fur seal ( Callorhinus ursinus) (Boveng 1988, L owry 

et al. 1992) which w as mod ified to acco unt for the growth rate of this Ca lifornia sea lio n popu lation (5.0% to 6.2% yr-1, 

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

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

Minimum Population Estimate 

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

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

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

rookeries in southern California and at the h aulout sites lo cated betw een Poin t Concep tion and th e Orego n/Californ ia 

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

censused. 

6 
Current Population Trend 

Records of pup counts from 1975 to 1999 

(Figure 2) were c ompile d from the literature, NMFS 

reports, unpublished NMFS data, and Lowry 1999 (the 

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

Pup counts from 1975 through 1999 were examined for 

four rookeries in southern California and for haulouts in 

central and northern California. Log-linear 

interpolation between adjace nt counts was u sed to 

estimate counts for rookeries when they were not 

censused in a given year: (1) 1980 a t Santa Ba rbara Is.; 

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

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

when more than one count was available for a given 

rookery. Also, an index was used for San Miguel Island 

because some years lacked da ta for certain are as. Three 

major declines in the number of pups counted occurred 

during El Niño events in 1983, 1992-93, and 1998 

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

pup counts against year indicates that the counts of pups Figure 2. U.S pup count index for California sea lions 

increased at an annual rate of 5.0% between 1975 and (1975-99). 

1999. The counts of pups between the 1976, 1983, and 

1992 El Niño e vents increased at 8.8% annually (from 

1976 to 1982 ) and at 10 .2% ann ually (from 19 83 to 19 91). Since 1983, th e counts of pups has increased at 6.2% 

annually. 

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

production decreased by 35 percent in 1983, 27 percent in1992, and 64 percent in 1998. After the 1992-93 and 1997-98 

El Niños, pup production rebounded by 52 percent and 185 percent, respectively, but there was no rebound after the 

1983-84 El Niño (Figure 2). Unlike the 1992-93 and 1997-98 El Niños, the 1983-84 El Niño a ffected adult fem ale 

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

were fewer adult females available in the population to produce a pup (it took five years fo r pup pro duction to re turn 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 pop ulation for the a ffected coho rts. The long term effects 

of the 1992-93 event, which resulted in fewer females being recruited into the adult population, is manifested in lower 

net productivity rates for 1997 and 1999 (relative to 1997; Figure 2) because fewer females reached reproductive age 

(females reach rep roductive a ge at 3 to 5 ye ars). Therefore, the effects of the 1992-93 and 1997-98 El Niños will resu lt 

in lower net productivity rates for several years due to a drop in adult female recruitment. The drop in net production 

shows the long-term effect of E l Niños and does not signal that the population has reached carrying capacity. The 

severity, timing, length, and frequency of future El Niños will govern the growth rate of the sea lion population in the 

future. 

CURRENT AND M AXIMUM NET PRODUCTIVITY RATES 

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

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

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

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

the total mortalities estimated fro m NM FS, Californ ia Dept. of Fish and Game , Columbia River A rea observer pro grams, 

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

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

respectively (Miller et al. 1983; Hanan et al. 1988; Hanan and Diamond 1989; Brown and Jeffries 1 993; B arlow et al. 

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

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

7 
Between 1980 and 1999 the net productivity rate averaged 16.1% (Figure 3). A regression (thin line) shows 

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

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

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

(thick line) and net p roduction averages 1 3.2%. M aximum ne t productiv ity rates cannot be estimated from availab le 

data. 

POTENTIAL BIOLOGICAL REMOVAL 

The potential biological removal (PBR) level 

for this stock is calcu lated as the minimum po pulation 

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

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

factor of 1.0 (for a stock of unknow n status that is 

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

of 6,591 sea lions per year. 

ANNUAL HUM AN-CAUSED MOR TALITY 

Fisheries Information 

California sea lions are killed incidentally in 

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

et al. 1994; Julian 1997; Julian and Beeson, 1998, 

Cameron and Forney 1999; Table 1). Detailed 

information on these fisheries is pro vided in Append ix 

1. Mortality estimates for the California the set and


drift gillnet fisheries are included in Table 1 for the five


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


Beeson 1998; Julian 1997; C ameron a nd Forne y 1999). Figure 1. Net productivity rates and regression lines


A controlled experiment during 1996-97 demonstrated estimated fro m pup co unts with corre ctions for incid ental 


that the use of acoustic warning devices (pingers) human related mortalities. Thick line excludes El Niño


reduced sea lion entanglement rates considera bly within years and El Niño recovery years (i.e., triangles); thin line


the drift gillnet fishery (Barlow and Cameron 1999). includes all years.


However, entangleme nt rates increase d 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 m ay have foraged further offshore in resp onse to limited food supp lies near rookeries,


which would provide opportu nity for increased interactions with the drift gillnet fishery (Barlow and Cameron 1999).


Because of interannual variability in entanglement rates, additional years of data will be required to fully evaluate the


effectiveness of pingers for reducing mo rtality of this particular species. Because of the changes in this fishery after


implementation of the Tak e Reduc tion Plan, m ean annua l takes in Tab le 1 are bas ed only on 199 7-98 da ta. This results


in an averag e estimate of 1 58 (CV = 0.23) C alifornia sea lion s taken annua lly.


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

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

Oregon and Washington non-salmon troll fisheries; (3) C alifornia herring purse seine fishe ry; (4) Californ ia anchovy, 

mackere l, and tuna pu rse seine fishery; (5 ) California sq uid purse se ine fishery, (6) W ashington, O regon, Ca lifornia and 

British Columbia, Canada salmon net pen fishery, (7) Washington, Oregon, California groundfish trawl fishery, and (8) 

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

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

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

database maintained by the National Marine Fisheries Service, Southwest Region contains records of human-related 

fishery mortalities of stranded California sea lions. These records show that at least 17 additional mortalities and 17 

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

and line fisheries. 

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

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

8 
fishery, which uses vessels, gear, and operational procedures similar to those in the U.S. drift gillnet fishery, although 

nets may be up to 4.5 km long (Holts and Sosa-Nishizaki 1998). The fleet has increased from two vessels in 1986 to 31 

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

data provided by these authors to be approximately 2,700, with an observed rate of marine mammal bycatch of 0.13 

animals per set (10 marine mammals in 77 observed sets; Sosa-N ishizaki et al. 19 93). Th is overall mo rtality rate is 

similar to that obser ved in Califo rnia 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. Ther e are curren tly efforts underway 

to convert th e Mexic an swordfish driftnet fishery to a lo ngline fishery (D . Holts, pers. c omm.). 

Table 1. Summary ofavailable informationon themortality and seriousinjuryofCalifornia sealionsin commercialfisheriesthatmighttakethis 

species(Julian1997,JulianandBeeson1998,CameronandForney1999,M.Perezper.comm,Appendix 1). Mean annualtakesarebasedon1994-98 

data unle ss noted o therwise. 

Fishery Name 

CA driftnet fishery 

for sharks and 

swordfish 

CA set gillnet fishery 

for halibut and angel 

shark 

WA, OR, CA 

domestic groundfish 

trawl fishery (At-sea 

processing Pacific 

whiting fishery only) 

WA, OR salmon net 

pen fishery 

Canada: BC salmon 

pen fishery 

Year(s) Data Type


1994


1995


1996 observer


1997


1998


1994 

1995 

1996 

1997 

1998 

observer 

estimate 

extrapolated 

estimate 

1994 

1995 

1996 

1997 

1998 

observer 

1996 

1997 

1998 

logbook 

1994 

1995 

1996 

reports 

Percent Observer 

Coverage 

Observed 

Mortality 

Estimated 

Mortality 

parentheses) 

Mean 

Annual Takes 

(CV in parentheses) 

17.9% 

15.6% 

12.4% 

23.0% 

20.0% 

5 

4 

4 

36 

23 

28 (0.40) 

26 (0.45) 

36 (0.55) 

201(0.34) 

114 (0.23) 

158 (0.23)1 

7.7% 

0% 

0% 

0% 

0% 

109 

-

-

-

-

905 (0.15) 

724 (0.08) 1 

999 (0.06) 1 

1,206 (0.06) 1 

1,228 (0.07) 1 

1,012 (0.04)2 

53.8% 

56.2% 

65.2% 

65.7% 

77.3% 

1 

0 

0 

0 

1 

2(0.68) 

0 

0 

0 

1(0.48) 

1(0.48) 

4 

9 

9 

4 

9 

9 

7(0.39) 

13 

23 

54 30(0.71) 

1,208 (0.05)

(CV in 

Minimum total annual takes 

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 in cluded the use of net extenders and acoustic warnin g devices (pingers).
 2 The CA set gillnets were not observed after 1994; mortality was extrapolated from effort estimates and previous entanglement rates. Changes in


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


Other M ortality 

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

at rookeries a nd haulou ts (Stewart and Yochem 1987, Oliver 1991). The proportion of those entangled ranged from 

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

9 
marine mammal rehabilitation center found that 87% of 87 rescued California sea lions were entangled in 4 to 4.5 inch 

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

and 5.4% in d rift gillnets were ob served to be released alive from the net by fishers during 1991-95 (Julian and Beeson 

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

as well as the mo rtality rate of these inju red anima ls, is unknown. 

Live strandings and dead beach-cast California sea lions have also been o bserved w ith gunshot wo unds in 

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

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

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

and shootings (70 mortalities and 8 injuries). Stranding records a re a gross un der-estimate o f injury and mo rtality. 

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

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

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

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

debris, or g affs, but the minim um numb er in 1998 was 144 . 

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

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

The tribes have agree d to cooperate w ith NMFS in ga thering and submitting data on takes o f marine mammals. 

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

neurotox in domoic acid (Scho lin et al. 2000). Future mortalities may be expected to occur, owing to the periodic nature 

of such harmful algal blooms. 

STATUS OF STOCK 

Lowry et al. (1992) concluded that there was no evidence of a density dependent signal in coun ts of Californ ia 

sea lions betw een 198 3 and 1 990, an d that it was n ot possible to determ ine the status of this stock relative to O SP. 

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

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

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

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

insignificant and approaching a zero mortality and serious injury rate. The population has been growing recently at 6.2% 

per year, and the fishery mortality is increasing. 

REFERENCES 

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

Burkanov. 1994. A review o f cetacean and pin niped m ortality in coastal fisheries along the west coast of the 

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

15:405-425. 

Barlow, Jay, and G. A . Came ron. 199 9. Field ex perime nts show that acoustic pingers reduce marine mammal bycatch 

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

1998 (unpublished). 20 pp. 

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

in central and northern California. (abstract). Tenth Biennial Conference on the Biology of M arine Mam mals, 

Galveston TX, November 11-15, 1993. 

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

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

26 pp. 

Brown, R. F. and S . J. Jeffries. 1993. P reliminar y report o n estimate d marin e mam mal m ortality in Co lumbia River 

fall and win ter salmo n gillnet fishe ries, 1991 -1992 . Columbia River Area Marine Mammal Observer Program, 

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

Cameron, G. A. an d K. A. F orney. 1 999. Prelimin ary estim ate of cetac ean mo rtality in the California gillnet fisheries 

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

14 pp. 

10 
Deiter, R. L. 1991. Recovery and necropsy of marine mammal carcasses in and near the Point Reyes national Seashore, 

May 1982-M arch 19 87. In J. E. Reynolds III and D. K. Odell (editors), Marine mammal strandings in the 

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

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

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

1982-1983 El Niño on sever al popu lation para meters an d diet of C alifornia sea lions on th e Californ ia Channel 

Islands. In F. Trillmich and K. A. Ono (ed itors), Pinnipeds and E l Niño: Respon ses to environm ental stress. 

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

Hanan, D. A., and S. L. Diamond. 1989. Estimates of sea lion, harbor se al, and ha rbor po rpoise m ortalities in Califo rnia 

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

NOAA/NMFS SW R, January 1989. 10 pp. 

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

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

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

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

NOAA/NMFS SW R October 1988. 10 pp. 

Holts, D. and O. Sosa-Nishizaki. 1998. Swordfish, Xiphias gladius, fisheries of the easte rn North P acific Ocean. In: 

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

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

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

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

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

40JGNF100597. 

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

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

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

fisheries: 19 90-19 95. Fish. B ull. 96:271-284. 

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

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

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

Diego County and San ta Catalina Isla nd, Califo rnia. Adm in. Rep. L J-87-15 . Southw est Fisheries Science 

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

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

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

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

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

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

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

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

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

Box 271, La Jolla, CA. 233 p. 

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

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

Commerce, Nationa l Ocean ic and Atmospheric Administration, National Marine Fisheries Service, Office of 

Protected Reso urces, June 199 5. 139 pp. + 4 Append ices. 

Oliver, C. W. 1991. 1988-1991 field studies on pinnipeds at San Clemente Island. Admin. Rep. LJ-91-2 7. Southwe st 

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

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

Voge laere, A., Harvey , J., Haulen a, M., Lefebv re, K., Lips comb , T., Loscu toff, S., Low enstine, L. J., M arin 

III, R., Miller, P. E., Mc Lellan, W . A., Mo eller, P. D. R ., Powell, C . L., Row les, T., Silvagni, P ., Silver, M ., 

Spraker, T., Trainer, V., and Van Dolah, F. M. 2000 . Mortality of sea lions alon g the central California c oast 

linked to a toxic diato m bloo m. Nature, 403:80-84. 

11 
Stewart, B. S. and P. K. Yochem. 1987. Entanglement of pinnipeds in synthetic debris and fishing net and line 

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

339. 

12

Revised 12/15/2000 

HARBOR SEAL (Phoca vitulina richardsi): California Stock 

STOCK DEFINITION AND GEOGRAPHIC RANGE 

Harbor seals (Phoca vitulina) are wide ly distribute d 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, M exico, 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 unpub lished data ). In California , 

approx imately 400-500 harbor seal hau lout sites are widely 

distributed along the mainland and on offshore islands, including 

intertidal san dbars, roc ky shor es and be aches (H anan 19 96). 

Within the subspecies P. v. richardsi, abundant evidence 

of geographic structure comes from differences in mitochondrial 

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

pupping dates (Temte 1986), pollutant loads (Ca lambo kidis et al. 

1985), pelage co loration (K elly 1981 ) and m ovem ent patte rns 

(Jeffries 1985; Brown 1 988). LaMon t (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 southeas tern Alask a. Althou gh we k now th at geogra phic Figure 1. Stock bo undaries for the California 

structure exists along an alm ost continuous distribution of harbor and Oregon/Washington coastal stocks of harbor 

seals from California to Alaska, stock boundaries are difficult to seals. Dashed line represents the U.S. EEZ. 

draw because any rigid line is (to a grea ter or lesser ex tent) 

arbitrary from a b iological p erspective . Noneth eless, failure to 

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

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

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

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

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

occur along the west coast of Baja California, but they are not considered to be a part of the Ca lifornia stock becau se 

no internationalagreements existforthe jointmanagement ofthisspeciesby theU.S.andMexico. Lackingany 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 Mamm al 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 c oastal and inland w aters. 

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 th e water alm ost imm ediately after birth. Population size is estimated by counting the 

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

of the estimated fraction of seals on land. Boveng (1988) reviewed studies estimating the prop ortion of se als 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 

13 
the peak pupping season. Hanan (1996) estimated 

that 83.3% (C V=0.17) o f harbor seals haul out at 

some time during the da y durin g the May/June 

molt, and he estimated a correction factor of 1.20 

based on those data. Neither correction factor is 

directly applicable to an aerial photographic count 

in California: the 1.53 factor was measured at the 

wrong time of year (when fewer seals are hauled 

out) and in a different area and the 1.20 factor was 

based on the fraction of seals hauled out over an 

entire 24 hr day (correction factors for aerial co unts 

should be based on the fraction of seals hauled out 

at the time of the survey). Hanan (pers. comm .) 

revised his haul-out correction factor to 1.3 by 

using only those seals hauled out between 0800 and 

1700 which better corresponds to the timing of his 

surveys. Based on the most recent harbor seal 

counts (23,302 in May/June 1995, Hanan 1996) and 

Hanan’s revised co rrection fac tor, the harbor seal Figure 2. Harbor seal haulout counts in California during

population in Californ ia is estimated to number May/June (Hanan 1996).

30,293. A harbor seal count in California was 

attempted in 1999, but was not successfu l due to 

bad weather and camera failure (Hanan, pers. comm.). Another survey is planned for 2000. 

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 equ al to that number, and thus fulfills the requirement of a minimum population estimate. The 

minim um size o f the Califo rnia harb or seal po pulation is th erefore 2 7,962. 

Current Population Trend 

Harbor seal coun ts have continu ed to 

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

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

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

Washington (see separate Stock AssessmentReport). 

CURRENT AN D MAXIMUM N E T 

PRODUCTIVITY RATES 

A realized rate of increase w as calculated 

for the 1982-1995 period by linear regression of the 

natural logarithm of total count versus year. The 

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

which gives an annualized growth rate estimate of 

3.5%. The current rate of net production is greater 

than this observed growth rate because fishery 

mortality takes a fraction of the net production. 

Annual gillnet mortality may have been as high as 5­

10% of the California harbor seal population in the 

mid-198 0s; a kill this large would have depressed Figure 3. Net production rates and regression line estimated 

population growth rates appreciably . Net from haulo ut counts and fishery mortality. 

14 
produ ctivity was therefore calculated for 1980-1994 as the realized rate of popula tion grow th (increase in seal cou nts 

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

year i divided by population size in year i). Between 1983 and 1994, the net productivity rate for the California stock 

averaged 9.2% (F ig. 3). A reg ression sho ws a dec rease in ne t produc tion rates, but the de cline is not statistica lly 

significant. Maximum net productivity rates cannot be estimated because measurements were not made when the stock 

size was v ery sma ll. 

POTENTIAL BIOLOGICAL REMOVAL 

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

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

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

HUMAN-CAUSED M ORTALITY 

Historical Takes 

Prior to state and fed eral protec tion and e specially d uring the nineteen th century , harbor se als along the we st 

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. 

Table 1. Summary ofavailable informationon themortality andseriousinjuryofharborseals(California stock)in commercialfisheriesthatmight 

takethisspecies(NMFS 1995;Julian1997;JulianandBeeson1998;CameronandForney1999). n/a indicatesthatdata arenotavailable. Mean annual 

takes are based on 1994-98 data unless noted otherwise. 

Fishery Name Year(s) Data 

Type 

1994-98 observer 

data 

1991 observer


1992 data


1993


1994


1995 extrapo­


1996 lated


1997 estimate


1998


1990-92 logbook 

data 

1990-92 logbook 

data 

1990-92 logbook 

data 

1991-95 observer 

data 

1990-92 logbook 

data 

1995-98 stranding 

data 

CA/OR thresher 

shark/swordfish drift 

gillnet fishery 

CA angel shark/halibut and 

other species large mesh 

(>3.5") set gillnet fishery 

CA, OR, and WA salmon 

troll fishery 

CA herring purse seine 

fishery 

CA anchovy, mackerel, and 

tuna purse seine fishery 

WA, OR, CA groundfish 

trawl 

CA squid purse seine 

fishery 

(unknown net and hook 

fisheries) 

Total annual takes 

Percent Observer 

Coverage 

Observed 

Mortality 

Estimated 

Mortality 

parentheses) 

(CV in 

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

9.8% 

12.5% 

15.4% 

7.7% 

0.0% 

0.0% 

0.0% 

0.0% 

42 

90 

71 

23 

-

-

-

-

601 (0.23) 

1,204 (0.47) 

475 (0.13) 

227 (0.33) 

228 (0.13)2 

296 (0.08)2 

349 (0.08)2 

392 (0.10)2 

n/a 

-

Avg. Annual 

take n/a 

-

Avg. Annual 

take n/a 

-

Avg. Annual 

take n/a 

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

-

Avg. Annual 

take n/a 

17 4 

n/a 

= 7.33 

= 0 

= 0.67 

= 0 

Mean 

Annual Takes 

(CV in parentheses) 

01 

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


Reduction Plan. Gear modifications in cluded the use of net extenders and acoustic warnin g devices (pingers).
 2

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


15 
Fishery Information 

A summary ofknownfisherymortalityandinjuryforthisstockofharborsealsisgiveninTable 1. More detailedinformation on these 

fisheriesisprovidedinAppendix 1. Because thevastmajority ofharborsealmortality inCalifornia fisheriesoccursinthesetgillnetfishery,because 

thatfisheryhasundergonedramaticreductionsandredistributionsofeffort, andbecause thatfisheryhasnotbeenobservedsince1994,averageannual 

mortality cannotbe accurately estimatedfortherecentyears(1995-98). Roughestimatesfor1995-1998 havebeenmade by extrapolationofpriorkill 

ratesusingrecenteffortestimates(Table 1). Preliminary gillnetobservationsfromApril toSeptember1999 in centralCalifornia included47 harbor 

sealsin24.6%ofthesetsforaroughextrapolatedestimate of191mortalitiesinthishalf-yearperiod. Strandingdata reportedtotheCalifornia Marine 

Mammal StrandingNetwork in1995-98includeharborsealdeathsandinjuriescausedby hook-and-line fisheries(17deaths, 4 injuries) andgillnet 

fisheries (1 d eath, 2 inju ries). 

Other Mor tality 

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

Southwe st Region, contains the following records of human-related harbor seal mortalities and injuries in 1995-98: (1) 

boat collision (10 mortalities, 2 injuries), (2) entrainment in power plants (20 mortalities), and (3) shootings (9 

mortalities). 

STATUS OF STOCK 

A review o f 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 a s "depleted " under the MM PA. To tal fishing m ortality cannot b e accurate ly estimate for recent ye ars, 

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

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

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

mortality cannot be considered insignificantand approachingzero mortality and seriousinjury rate. The population appears 

to be growing and the fishery mortality is declining. There are no knownhabitatissuesthat are of particular concern forthisstock. 

All west-coast harbor seals that were tested for morbilliviruses were found to be seronegative, indicating that this disease 

is not endemic in the population and that this population is extrem ely susceptible to an ep idemic of this disease (HamLamm é 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,andV.N.Burkanov. 1994. A reviewof 

cetaceanandpinnipedmortality incoastalfisheriesalongthewest coastoftheU.S.andCanadaandtheeast coast oftheRussianFederation. 

Rep. Int. Whal. Commn, Special Issue 15:405-425. 

Bartholomew,G.A.,R.A.Boolootian.1960.Numbers and populationstructureofthe pinnipedson theCalifornia ChannelIslands.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.StatusofthePacific harborsealpopulationon theU.S.west coast. Admin.Rep.LJ-88-06.SouthwestFisheriesScienceCenter, 

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. 199 6. Genetic analysis of eastern Pacific harbor seals (Phoca vitulina richardsi) from British Columb ia 

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 

mamma ls and marine birds: pop ulation health and evidence of pollution effects. U.S. Dep. Commer., NOAA 

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

Ham-Lamm é, 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. 199 9. The application of immuno-assays for serological detection of morbillivirus 

exposure in free ranging harb or seals (Phoca vitulina) and sea otters ( Enhyd ra lutris) from the w estern 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 

16 
National Marine Fisheries Service, Southwest Region. 27pp. 

Hanan, D. A. 199 6. Dynamics of Abundance and Distribution for Pacific Harbor Seal, Phoca vitulina richardsi, on the 

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

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

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

NOA A/NM FS SWR , January 198 9. 10 pages. 

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

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

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

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

NOA A/NM FS SWR October 19 88. 10 pag es. 

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

the Russian Rive r, California. MS T hesis. Humb olt State Univ. 52 p ages. 

Huber, H. 1995. The abund ance of harbor seals ( Phoca vitulina richardsi) in Washington, 19 91-1993. M S 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 Assessmen t Program , Office of Pro tected Res ources, N MFS , NOA A, 1335 EastWest Highway, Silver Spring, MD 20910. 

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

coastal waters of northern O regon and Washin gton. 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 f or marin e mam mal, turtle, an d seabird mortality for two California gillnet 

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

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

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

Genetic substructure o f the Pacific har bor 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. 1 983. Ca lifornia 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 Reso urces, June 199 5. 139 p. + 4 A ppendices. 

Perkins, P., J. Barlow, and M. Beeson. 1994. R eport on pinniped and cetac ean mo rtality in Califo rnia 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 porpo ises. Masters Thesis, O regon S tate Univ ., 

Corvallis, Oregon. 

17 
Revised 12/15/2000 

HARBOR SEAL (Phoca vitulina richardsi): 

Oregon/Washington Coast Stock 

STOCK DEFINITION AND GEOGRAPHIC RANGE 

Figure 1. Approximate distribution of harbor 

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 

migratory, with local movements associated with such factors as 

and reproduction 

(Scheffer and Slipp 1944; F isher 195 2; Bigg 19 69, 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. w est coast (up to 550 km) have been recorded 

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

Harbor seals have also displayed strong fidelity for haul 

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

For managem ent purpo ses, difference s in mean pupping 

(Jeffries 1985, Brown 

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

interactions have led to the recognition of 3 separate harbor seal 

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

1) inland wa ters of W ashington S tate (including the H ood Ca nal, 

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

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

1). Recent genetic analyses provide additional support for this 

occasion ally fresh waters. Harbor seals generally are nontides, weather, season, food availability, 

1986). 

date (Temte 1986), movement patterns 

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

Samples from W ashington, O regon, and California demonstrate a 

high level of genetic diversity and indicate that the harbor seals of 

inland Washington posse ss unique hap lotypes not fo und in seals 

from the coasts of Washington, Oregon, and California (Lamont et 

seals in the U.S. Pacific Northwest (shaded 

area). Stock boundaries separating the three 

stocks are shown. 

al. 1996). This report considers only the Oregon/Washington Coast stock. Three harbor seal stocks are also recognized 

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

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

POPU LATIO N SIZE 

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

Marine Mammal Laboratory (NM ML) and the Oregon and Washington D epartments of Fish and Wildlife (ODFW and 

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

surveys. In 1997, the mean count of harbor seals occurring along the Was hington coa st was 11,86 4 (CV= 0.028) a nimals 

(WDFW, unpubl. da ta; NMML, unp ubl. data). In 1997, the mean count of harbo r seals occurring along the Ore gon coast 

and in the Colum bia River w as 5,247 (CV=0 .042) anim als (ODF W, unp ubl. data; B rown 19 97). Combining these counts 

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

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

coastal sites) collected information on haulou t pattern from 63 harbo r seals in 1991 a nd 61 ha rbor seals in 1 992. D ata 

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 d uring the aerial su rveys (Hub er 1995 ). Using this 

correction factor results in a population estimate of 26,180 (17,111 x 1.53; CV= 0.069) for the Ore gon/Washingto n Coast 

18 
stock of harbor seals in 1997 (WDFW , unpubl. data; NMML, unpubl. data; ODF W, unpubl. data). 

Minimum Po pulation Estimate 

The log-norma l 20th percentile of the 1997 population estimate for this stock is 24,70 5 harbor seals. 

Current Population Trend 

Historical levels of harbor seal abundance in Oregon and Washington are unknown. The po pulation ap parently 

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

Washington by bounty hunters between 1943 and 1960 (Newby 1973). More than 3,800 ha rbor seals w ere killed in 

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

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

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

from 6,389 in 1977 to 17,111 in 199 7 (WDFW , unpubl. data; NMML, unpubl. data; ODF W, unpubl. data). 

Between 1983 and 1996, the annual rate of increase for this stock was 4%, with the peak cou nt of 18,66 7 seals 

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

1997), which may ind icate that this pop ulation has exceed ed equilibrium levels. Ana lyzing only the O regon da ta 

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

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

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

periods, or other unknown rea sons may have caused a larger number of seals to be in the water d uring the surve ys 

(Jeffries et al. 1997). 

CURRENT AND M AXIMUM NET PRODUCTIVITY RATES 

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

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

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

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

available, the pinniped default maxim um theore tical net prod uctivity rate (RMAX) of 12% will be employed for this harbor 

seal stock (Wade and Angliss 1997). 

POTENTIAL BIOLOGICAL REMOVAL 

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

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

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

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY 

Fisheries Information 

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

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

stock assessment report. For the entire fishery (coastal + inland waters), observer coverage ranged fro m appro ximately 

40 to 98% during those years. Fishing effort is conducted within the range o f both stocks o f harbor sea ls 

(Oregon/Washington Coast and Inland W ashington sto cks) occur ring in Wa shington State waters. Some o f the animals 

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

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

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

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

of the fishery are assu med to have belonged to the Oregon/Washington Coast stock. However, as noted, some movement 

of animals betw een W ashington’s co astal and inland waters is likely, although data from tagging studies have not shown 

movement of harbor s eals betwee n the two loca tions (Hub er 1995 ). Accord ingly, Table 1 includes d ata only from that 

portion of the northern Washington marine set gillnet fishery occurring within the range of the Orego n/Washington Coast 

stock (those waters south and west of Cape Flattery), where observer coverage was 100% in 1995-1 997. No fishing 

effort occurred in the coastal portion of the fishery in 1993 o r 1998. D ata from 19 93 to 19 98 are inclu ded in T able 1, 

although the mean estimated annual mortality is calculated using only the most recent 5 years for which data are 

19 
available. The mean estimated mortality for this fishery is 5 (CV=0.52) harbor seals per year from this stock. 

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

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

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

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

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

estimated mortality from 1 994 to 1 998 for m onitored h auls in this fishery is zero harbor seals per year from this stock, 

plus 0.4 animals per year from unmonitored haul data. 

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

Coast stock) in commercial and tribal fisheries that might take this sp ecies and c alculation of the mean annu al mortality 

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

are based on 1994-98 data unless otherwise noted. 

Fishery name 

Northern WA marine s et gillnet 

(tribal fishery: coastal waters) 

WA/OR/CA groundfish trawl 

(Pacific whiting component) 

WA Grays Harbor salmon drift 

gillnet 

WA Willapa Bay drift gi llnet 

WA Willapa Bay drift gi llnet 

Minimum total annual t akes 

Estimated 

mortality 

Percent 

observer Observed 

Years Data type coverage mortality 

93 obs data no fishery 0 0 

94 n/a n/a n/a 

95 100% 3 3 

96 100% 9 9 

97 100% 13 13 

98 no fishery 0 0 

94 

95 

96 

97 

98 

96 

97 

obs data 

unmonitored 

hauls 

53.8% 

56.2% 

65.2% 

65.7% 

77.3% 

0 

0 

0 

0 

0 

1 

1 

0 

0 

0 

0 

0 

0 

0.4 (n/a) 

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

91-93 obs data 1-3% 0, 0, 0 0, 0, 0 0 

Reported 

mortalities 

90-98 self 

reports 

n/a 0, 0, 6, 8, 

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

n/a, n/a 

n/a �3.5 (n/a) 

see text 

�15.6 (0.36) 

Mean annual 

takes (CV in 

parentheses) 

5 (0.52)1 

1

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

The Washin gton and O regon Lo wer Colum bia 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 mo rtalities, 

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

mortality. However, the structure of the fishery has changed substantially since th e 1991 -1992 fishin g seasons, an d this 

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

The Washington Grays Harbor salmon drift gillnet fishery was also monito red from 1 991-19 93 (He rczeg et al. 

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

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

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

in an extrapolated estimated total k ill of 10 seals (C V=1.0 ). In 1993 observers recorde d 1 harbo r seal mortality 

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

20 
and 4.4%, respectively) su ggests that 10 is also a reaso nable estimate of the total kill in 1993. Thus, the mean estimated 

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

available for this fishery after 199 3. 

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

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

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

The Washin gton W illapa Bay d rift gillnet fishery was also monitored at low levels of observer coverage from 

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

1994c, 1994d). In those years, 752, 576, and 452 sets we re observ ed repre senting app roximately 2.5%, 1.4% and 3.1% 

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

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

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

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

(3.5 harb or seals per year). 

An additional source of information on the numb er of harbo r seals killed or injured incidental to commercial 

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

period between 1 994 and 1998, the re were no fisher self-reports o f any harbor seal mortalities. However, because 

logbook records (fishe r self-reports req uired during 1990-9 4) are mo st likely negatively biased (Credle et al. 1994), these 

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

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

Other M ortality 

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

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

mortalities or serious inju ries occurre d in 1994 (4), 1997 (2) and 1998 (2), resulting in an estimated annual mortality of 

1.6 harbor seals (rounded to 2) from this stock during 1994 to 19 98. This estimate is considered a minimum because 

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

Subsistence Harvests by Northwest Treaty Indian Tribes 

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

and subsistence harvests of harbor seals and for the inciden tal take of marin e mammals during triba l fisheries. The tribes 

have agreed to co operate with NM FS in gathering and subm itting data on takes of marine mamm als. 

STATUS OF STOCK 

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

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

(16 + 2 = 18) does not exceed the PB R (1,482). Therefo re, the Oreg on/W ashington C oast stock o f harbor sea ls is not 

classified as a strategic stock. The minimum total fishery mortality and serious injury for this stock (16; based on 

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

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

insignificant and app roaching z ero morta lity and serious inj ury rate. The stock size increased until 1992, but has declined 

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

Popula tion (OSP ) level. 

REFERENCES 

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

Bigg, M. A. 1981. Harbour seal, Phoca vitulina, Linnaeus, 1758 and Phoca largha, Pallas, 181 1. Pp. 1-2 7, In: 

Ridgway, S. H., and R. J. Harriso n (eds.), Handbo ok of Marine M ammals. Vol. 2: Seals. Aca demic Press, 

New York. 

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

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

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

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

21 
Brown, R. F. 199 7. Abundance of Pacific harbor seals ( Phoca vitulina richardsi) in Orego n: 1977 -1996. O regon D ept. 

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

Brown, R. F., and B. R. Mate. 1983. Abunda nce, move ments, and fe eding hab its of the harbo r seal, Phoca vitulina, at 

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

Brown, R. F., and S. J. Jeffries. 1993. Preliminary report on estimated marine ma mmal mo rtality in Columbia River 

fall and winter salmon gilln et fisheries, 1991-1992. Unpub l. report. Columbia River Area Gillnet Fishery 

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

Burg, T. M. 1996 . Genetic analysis of eastern Pacific harbo r seals (Phoca vitulina richardsi) from British Columb ia 

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

Vancouver, BC. 77 pp. 

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

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

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

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

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

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

Fisher, H. D. 1952. The status of the harbour seal in British C olumbia, w ith particular reference to the Skeena River. 

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

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

Gearin, P. J., S. R. Melin, R. L. DeLong, H. Kajimura, and M. A. Johnson . 1994. H arbor po rpoise intera ctions with 

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

Gearin, P. J., M. E . Gosho, J. L. Laake, L. C ooke, R. L . DeLon g, and K. M . Hughes. 2 000. Ex perimenta l testing of 

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

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

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

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

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

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

gillnet fishery. Unpubl. report. Pacific States Marine Fisheries Co mmission, A storia, OR . 10 pp. A vailable 

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

Herder, M. J. 19 86. Seaso nal movem ents and hau ling site fidelity of harbo r seals, Phoca vitulina rich ardsi, tagged at 

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

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

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

Huber, H. 1995. T he abundance o f harbor seals (Phoca vitulina richardsi) in Washington, 1991-1993. MS Thesis, 

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

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

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

Resources, NMFS, N OAA, 1335 E ast-West Highway, Silver Spring, MD 209 10. Available at National Marine 

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

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

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

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

WA. 

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

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

1996. AFSC Processed Rep ort 97-10. 255 pp. Available at National Marine Mammal Laboratory, 7600 S and 

Point Way NE, Seattle, WA 98115. 

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

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

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

Matteson, K. M., and J. A. Langton. 1994a. Summary report on the 199 3 fall Columbia River sa lmon gillnet fishery. 

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

22 
SE 82nd Ave., Ste. 100, Gladstone, OR 97027. 

Matteson, K. M., and J. A. La ngton. 1994b . Summary report on the 1993 fall Grays Harbo r salmon gill net fishery. 

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

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

Matteson, K. M., and J. A. Langton. 1994c . Summar y report on the 1993 summer d ip-in salmon g illnet fisheries in 

Willapa Bay and Gra ys Harbor. Unp ubl. report. Pacific States Ma rine Fisheries Commission, Astoria, OR. 

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

Matte son, K. M., a nd J. A. Lan gton. 199 4d. Summ ary report o n the 199 3 fall Willap a Bay salmon gillnet fishery. 

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

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

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

in Willapa Bay and Grays Ha rbor. Un publ. repo rt. Pacific States Marine Fisheries Commission, Astoria, OR. 

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

Matteson, K. M., W. B. Barnett, and J. A. Langton. 1993a. Summary report on the 199 2 fall Grays Harbor salmon 

gillnet fishery. Unpu bl. report. Pacific States Marine F isheries Com mission, Asto ria, OR. 17 pp. Availab le 

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

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

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

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

Matteson, K. M., J. A . Langton, an d R. L. Ha dley. 1993c. Summary report on the 1993 winter Columbia River salmon 

gillnet fishery. Unp ubl. repor t. Pacific States M arine Fisherie s Comm ission, Astoria, O R. 29 pp. A vailable 

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

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

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

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

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

State Univ., Corvallis, OR. 23 pp. 

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

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

Pitcher, K. W., and D. C. M cAllister. 198 1. Mov ements and haul out beh avior of rad io-tagged ha rbor 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 puppin g in the Pacific h arbor sea l (Phoca vitulina richardsi) with 

notes on r epr odu ctio n in n orth ern fur s eals and Dal l's porpoise s. MS T hesis, Orego n State Univ. Corvallis, OR. 

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

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

Washington Departm ent of Fish and Wildlife, M arine Ma mmal Inve stigations, 780 1 Phillips Rd. SW, Tacom a, WA 

98498. 

23 
Revised 12/15/2000 

HARBOR SEAL (Phoca vitulina richardsi): 

Washington Inland Waters Stock 

STOCK DEFINITION AND GEOGRAPHIC RANGE 

Figure 1. Approximate distribution of harbor 

Harbor seals inhabit coastal and estuarine waters off Baja 

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

British Columbia, and S outheast 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 

migratory, with local mo vements associated with such factors as 

food availability, and reproduction 

(Scheffer and Slipp 1944; F isher 195 2; Bigg 19 69, 198 1). Harbor 

seals do not make extensive pelagic migrations though some long 

distance movement of tagged anim als in Alaska (174 km) and 

along the U.S. w est coast (up to 550 km) have been recorded 

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

Harbor seals have also displayed strong fidelity for haul 

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

For management purpose s, differences in mean pupping 

(Jeffries 1985, Brown 

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

interactions have led to the recognition of 3 separate harbor seal 

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

1) inland waters of Washington State (including the H ood Ca nal, 

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

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

1). Recent genetic analyses provide additional support for th is 

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

occasion ally fresh waters. Harbor seals generally are nontides, weather, season, 

1986). 

date (Temte 1986), movement patterns 

1996). Samples fro m Wa shington, O regon, and California 

demon strate a high level of ge netic diversity and indicate that the 

harbor seals of inland Washington possess unique haplotypes not 

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

seals in the U.S. Pacific Northwest (shaded 

area). Stock boundaries separating the three 

stocks are shown. 

California (Lamont e t al. 1996). T his report considers only the Inland Washington stock. Three harbor seal stocks are 

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

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

Region. 

POPU LATIO N SIZE 

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

time the total number of hauled-out seals (including p ups) were c ounted. In 1 997 the m ean coun t of harbor se als 

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

Radio-tagging studies conducted at6 locations (3 Washington inland waterssites and 3 Oregon and Washington 

coastal sites) collected information on haulout patterns from 63 harbor seals in 199 1 and 61 harbor sea ls in 1992. D ata 

from coastal and inland sites were not significantly different and were thus pooled, resulting in a correction factor of 1.53 

(CV=0.065) to account for animals in the water which are missed during the aerial surveys (Huber 1995). U sing this 

correction factor results in a population estimate of 16,056 (10,494 x 1.53; CV=0.067) for the Inland Washington stock 

of harbor seals (WDFW , unpubl. data; NMML, unpubl. data). 

Minimum Po pulation Estimate 

24 
The log-norma l 20th percentile of the 1997 population estimate for this stock is 15,17 4 harbor seals. 

Current Population Trend 

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

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

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

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

Protection Act (MMP A), harbor seal numbers in Washington have increased (Jeffries 1985). 

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

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

years may be du e to emigratio n of harbo r seals from the Canadian waters of the Strait of Georgia to the San Juan Islands 

(Jeffries et al. 1997). 

CURRENT AND M AXIMUM NET PRODUCTIVITY RATES 

From 1991 to 1996, c ounts of harb or seals in Washington State have increased at an annual rate of 10% (Jeffries 

et al. 1997). Because the popu lation was no t at a very low leve l, the observe d rate of increase will underestimate the 

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

theoretical net productivity rate (RMAX) of 12% will be employed for this harbor seal stock (Wade and Angliss 1997). 

POTENTIAL BIOLOGICAL REMOVAL 

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

(15,174) times one-half the de fault maximum net growth ra te for pinnipeds (1⁄2 of 12%) times a recovery fac tor of 1.0 

(for stocks of unknown status that are increasing in size, Wade a nd Angliss 1997), re sulting in a PB R of 910 harbor sea ls 

per year. 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY 

Fisheries Information 

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

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

stock assessment re port. For the entire fishery (co astal + inland waters), observer coverage ranged fro m appro ximately 

40 to 98% during those years. Fishing effort is condu cted within the ra nge of both stocks of harb or seals 

(Oregon/Washington Coast and Inland W ashington sto cks) occur ring in Washington State waters. Some of the animals 

taken in the inland waters portio n of the fishery ma y have been animals from the coastal stoc k. Similarly, some of the 

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

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

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

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

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

not shown movement of harbor seals between the two locations (Huber 1995). A ccording ly, Table 1 includes da ta only 

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

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

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

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

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

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

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

and Wildlife (W DFW ) monitore d all non-treaty c ompon ents of the W ashington Puget Sound Region salmon gillnet 

fishery (Pierce et a l. 1994). Observer coverage was 1.3% o verall, ranging fro m 0.9% to 7.3% for the variou s compo nents 

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

these mortalities to the entire Puget Sound fishery due to the low observer coverage and potential biases inherent in the 

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

67%. R esults of this pilot stud y were used to design the 19 94 obse rver prog rams discus sed below . 

25 
Table 1. Summary of available information on the incidental mortality and injury of harbor seals (Inland Washington 

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

n/a indicates that data are no t available. All en tanglements resulted in the death of the animal. Mean annual takes are 

based on 1994-98 data unless noted otherwise. 

Fishery name 

Northern WA marine s et gillnet 

(tribal fishery: inland waters) 

WA Puget Sound Region salmon 

set/drift gilln et (observer 

programs listed below covered 

segments of this fishery): 

Puget Sound non-treaty salmon 

gillnet (all areas and species) 

Puget Sound non-treaty chum 

salmon gillnet (areas 10/11 and 

12/12B) 

Puget Sound treaty chum 

salmon gillnet (areas 12, 12B, 

and 12C) 

Puget Sound treaty chum and 

sockeye salmon gillnet (areas 

4B, 5, and 6C) 

Puget Sound treaty and nontreaty sockeye salmon gi llnet 

(areas 7 and 7A) 

WA Puget Sound Region salmon 

set/drift gilln et 

WA salmon net pens 

unknown Puget Sound fishery 

Minimum total annual t akes 

Years 

93 

94 

95 

96 

97 

98 

-

93 

94 

94 

94 

94 

94-98 

97-98 

94-98 

Percent 

Data observer 

type coverage 

obs data 61% 

n/a 

24% 

6% 

80% 

40% 

- ­

obs data 1.3% 

obs data 11% 

obs data 2.2% 

obs data 7.5% 

obs data 7% 

Observed 

mortality 

Estimated 

mortality 

12 20 

n/a n/a 

0 0 

0 0 

0 0 

0 0 

- - ­

2 n/a see text 

1 10 10 (n/a) 

0 0 0 

0 0 0 

1 15 15 (1.0) 

Reported 

mortalities 

Mean annual 

takes (CV in 

parentheses) 

4.0 (1.0)1 

self 

reports 

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

n/a 

n/a see text 

self 

reports 

n/a 10, 5 n/a �7.5 (n/a) 

strand 

data 

n/a 3, 0, 2, 1, 1 n/a �1.4 (n/a) 

�37.9 (0.82) 

1

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

In 1994, NMFS in conjunction with WDFW conducted an observer program during the P uget Soun d non-treaty 

chum salmon gillnet fishe ry (areas 10 /11 and 1 2/12B). A total of 23 0 sets were o bserved d uring 54 b oat trips, 

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

as estimated from fish ticket landin gs (Erstad e t al. 1996). O ne harbo r seal was taken in the fishery, resulting in an 

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

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

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

monitored in 1994 (NW IFC 1995). No harbo r seal mortalities were reported in the observer programs covering these 

26 
treaty salmon gillnet fisheries, where observer coverage was estimated at 2.2% (based on % of total catch observed) and 

approx imately 7.5% (based o n % of ob served trips to total landings), re spectively. 

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

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

seal mortality (two o thers were en tangled and released un harmed) , resulting in a mo rtality rate of 0.00 045 har bor seals 

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

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

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

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

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

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

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

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

7 and 7A (15) fisheries results in an estimated minimum annual mo rtality rate in obser ved fisheries o f 29 harbo r seals 

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

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

include effort for the uno bserved se gments of this fishery. Therefore, 29 is an underestimate of the harbor seal mortality 

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

set/drift gillnet fishery was actually observed in 1994. However, the areas hav ing the highest salm on catches and in 

which a majority of the vessels operated in 1 994 were co vered by the 199 4 observer pro grams (J. Scordino, pers. 

comm.). 

An additional source of information on the numb er of harbo r seals killed or injured incidental to commercial 

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

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

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

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

annual mortality of 7.5 harbor sea ls from this stock in those two yea rs. Howev er, because logboo k records (fisher selfreports required during 1990-94) are most likely negatively biased (Credle et al. 1994), these are considered to be 

minimum estimates. Self-rep orted fisheries data are incomplete for 1994, not available for 1995, and considered 

unreliable afte r 1995 ( see App endix 4 in H ill and DeM aster 199 8). 

Strandings of harbor seals entangled in fishing gear or with injuries caused by interactions with gear are a final 

source of fishery-related mortality information. During the period from 1994 to 1998, small numbers of fishery-related 

strandings of harbor seals have occurred in most years. As the strandings could not be attributed to a particular fishery, 

they have been included in Table 1 as occurring in an unknown Puget Sound fishery. Fishery-related strandings during 

1994-1998 result in an estima ted annual m ortality of 1.4 ha rbor seals fro m this stock. This estimate is considered a 

minimum because not all stranded animals are found, rep orted, or e xamined fo r cause of de ath (via necropsy by trained 

personnel). 

The minimum estimated fishery mortality and serious injury for this stock is 37.9 (rounded to 38) harbor sea ls 

per year, based on observer program data (29), fisher self-reports (7.5), and stranding data (1.4) . Howev er, a reliable 

estimate of the total mortality rate incidental to commercial fisheries is currently unavailable due to the absence of 

observer placeme nts in segments o f the Wash ington Pug et Sound Region sa lmon set and drift gillnet fishery. 

Other M ortality 

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

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

mortalities occurred each year, with reports of 7, 1, 8, 7, and 2 animals for those years, respectively. These mortalities 

resulted in an estimated annual mortality of 5 harbor seals from this sto ck during 1 994-19 98. This estimate is considered 

a minimum because not all stranded animals are found , reported, or cause of death determined (via necropsy by trained 

personnel). 

Subsistence Harvests by Northwest Treaty Indian Tribes 

27 
Several Northwest Indian tribes have developed, or are in the process of developing, regulations for ceremonial 

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

have agreed to co operate with NM FS in gathering and subm itting data on takes of marine mamm als. 

STATUS OF STOCK 

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

under the Endan gered Sp ecies Act. Based o n currently available data, the level of human-caused mortality and serious 

injury (38 + 5 = 43) does not exceed the PBR (910). Therefore, the Inland Washington stock of harbor seals is not 

classified as a strategic stock. At present, the minimum estimated fishery mortality and serious injury for this stock (38) 

is less that 10% of the calculated PBR (91) and, therefore, can be considered to be insignificant and approaching zero 

mortality and seriou s injury rate. Th e stock size ha s increased in recent years, a lthough at this time it is not possib le to 

assess the status o f the stock relative to its Optimum Sustainable Popula tion (OSP ) level. 

REFERENCES 

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

Bigg, M. A. 19 81. Harbour seal, Phoca vitulina, Linnaeus, 1758 and Phoca largha, Pallas, 181 1. Pp. 1-2 7, In: 

Ridgway, S. H., and R . J. Harrison (eds.), Han dbook of Marine Mamm als. Vol. 2: Se als. Academic Press, 

New York. 

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

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

Brown, R. F. 1988. Assessment of pinniped populatio ns in Orego n. Processed Report 88-05, NM FS, Northwest and 

Alaska Fisheries Science Center, Seattle, WA. 

Brown, R. F., and B . R. Mate . 1983. Abundance, movements, and feeding habits of the ha rbor 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 Columb ia 

and parts of Alaska using mitochond rial DNA and microsatellites. MS The sis, Univ. of B ritish Columbia, 

Vancouver, BC. 77 pp. 

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

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

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

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

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

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

Erstad, P., S. J. Jeffries, and D. J. Pierce. 1996. 1994 Repo rt for the Puget Sound fishery observ er progra m 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. 19 52. The status of the harb our seal in B ritish Columb ia, with particular reference to the Skeena River. 

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

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

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

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

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

acoustic alarms (pingers) to reduce bycatch of ha rbour po rpoise, Phocoena phocoena, in the state of 

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

Herder, M. J. 1986. Seasonal movements and hauling site fidelity of harbor sea ls, Phoca vitulina rich ardsi, tagged at 

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

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

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

Huber, H. 1995. The abundance of harb or seals (Phoca vitulina richardsi) in Washington, 19 91-1993. M S Thesis, 

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

Huber, H., S. Jeffries, R. Brown, and R. DeLong. 19 94. Harbo r seal, Phoca vitulina richardsi, stock assessm ent in 

Washington and Ore gon, 199 3. 1993 Annual Re port to the MMPA Assessment Program, Office of Protected 

Resources, NMF S, NOA A, 1335 East-W est Highwa y, Silver Spring, MD 20910. Available at National Marine 

28 
Mammal Laboratory, 7600 Sand Point Way NE, Seattle, WA 98115. 

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

coastal waters of northern O regon and Washin gton. In: Marine mammals and their interactions with fisheries 

of the Columbia River and adjacent waters, 1980-1982. Processed Report 85-04, N MFS, Northwest and Alaska 

Fisheries Center, Seattle, WA. 

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

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

1996. AFSC Processed Report 97-10. 255 pp. Available at National Marine Mammal Laboratory, 7600 Sand 

Point Way NE, Seattle, WA 98115. 

Lamont, M. M., J. T. V ida, J. T. H arvey, S. Jeffries, R . Brown, H . H. Hub er, R. DeL ong, and W . K. Thomas. 1996. 

Genetic substructure o f the Pacific har bor seal ( Phoca vitulina richardsi) off Washington, Oregon, and 

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

Melvin, E. F., L. L. Conquest, and J. K. Parrish. 1997. Se abird bycatch reduc tion: new tools for Puget Sound drift 

gillnet salmon fisherie s. 1996 S ockeye and 199 5 Chum Salmon T est Fisheries Fin al Repor t. Washington Sea 

Grant Program, Seattle, WA. 48pp. 

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

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

Northwest Indian Fisheries Commission. 1995. Monitoring of marbled murrelet and marine mammal interactions with 

1994 tribal gillnet fisheries in northern P uget Soun d, Hoo d Canal, an d the Strait of Ju an de Fuc a. Final Report 

to NMFS Contract No. 52ABNF400087. Unpubl. report. Northwest Indian Fisheries Commission. 43 pp. 

Available at NWIFC, 6730 Martin Way E, Olympia, WA 98516. 

Pierce, D . J., W. P. R itchie, and R. K reuziger. 19 94. Preliminary findings of seabird interactions with the non-treaty 

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

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

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

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

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

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

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

Pitcher, K. W., and D. C. M cAllister. 198 1. Mov ements and haul out beh avior of rad io-tagged ha rbor seals, Phoca 

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

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

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

Temte, J. L. 1986. Photoperiod and the timing of pu pping in the P acific harbo r seal (Phoca vitulina richardsi) with 

notes on r epr odu ctio n in n orth ern fur s eals and Dal l's porpoise s. MS Thesis, Oregon State Univ., Corvallis, OR. 

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

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

Washington Departm ent of Fish and Wildlife, M arine Ma mmal Inve stigations, 780 1 Phillips Rd. SW, Tacom a, WA 

98498. 

29 
Revised 12/15/2000 

NORTHERN ELEPHANT SEAL (Mirounga angustirostris): 

California Breeding Stock 

STOCK DEFINITION AND GEOGRAPHIC RANGE 

Northern elephan t seals breed and give birth in California 

(U.S.) and Ba ja 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 45°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 retu rn to their fee ding area s again 

between their spring/summer molting and their winter breeding 

seasons. 

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

Mexico were all originally de rived 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 m ost rookeries, no genetic differentiation would be 

expected. Although movement and genetic exchange continues 

between rookeries, most elephant seals return to their natal 

rookeries when th ey start bree ding (H uber et al. 1 991). The 

California breeding population is now demographically isolated 

from the Baja California population. No internation al agreem ents 

exist for the joint management of this species by the U.S. and 

Mexico. The California breeding population is considered here to Figure 1. Stock boundary and major rookery be a separate stock.	 areas for northern elephant seals in the U.S. and 

Mexico. 

POPULATION SIZE 

A comp lete popu lation cou nt of eleph ant seals is no t possible be cause 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 1 985). Stew art et a l. (19 94) u sed M cCan n's 

multiplier of 4.5 to ex trapolate fro m 28,1 64 pups to a population estimate of 127,000 elephant seals in the U.S. and 

Mexico in 1991. The multiplier of 4.5 was based on a non-growing population. Boveng (1988) and Barlow et al.(1993) 

argue that a multiplier of 3.5 is more appropriate for a rapidly growing population such as the California stock of 

elephant seals. Based on the estim ated 24,0 00 pup s born in California in 1994 -96 (Fig. 2 ) and this 3 .5 multiplier, the 

California stock wa s approx imately 8 4,000 in 1996. 

Minimum Population Estimate 

The minim um po pulation siz e for north ern eleph ant seals can be estimated very conservatively as 51,625, twice 

the observed pup count (to account for the pups and their mothers) plus the peak number of males and juveniles counted 

at the Channel Island (Lowry, pers. comm .) and Año Nuev o (Le Boeuf 1996 ) sites in 1996. More sophisticated methods 

of estimating minimum population size could be applied if the variance of the multiplier used to estimate population 

size were known. 

Current Population Trend 

Based on trends in pup counts, northern elephant seal colonies were continuing to grow in California through 

1994 but app ear to be stab le or slowly decreasing in Mexico (Stewart et al. 1994). The number of pups born appears 

30 
Figure 1. Estimated number of northern elephant seal births in California 1958-98. Multiple independent estimates 

are presen ted for the C hannel Island s 1988-9 1. Total a nd central C alifornia cou nts are not yet av ailable for 19 98. 

Estimates are from Stewart et al. (1994), Lowry et al. (1996), and unpublished data from S. Allen, B. Hatfield, R. 

Jameson, B. Le Boeuf, M. Lowry, and W . Sydeman. 

to be leveling off in California over the last five years (Fig. 2). More tim e is required to determine whether the reduction 

in growth at the California rookeries is temporary (as was observed in 1985) or whether it represen ts an appr oach to 

carrying capacity. 

CURRE N T AND M AXIMUM N E T 

PRODUCTIVITY RATES 

Although growth rates as high as 16% per 

year have been documented for elephant seal 

rookeries in the U.S. from 1959 to 1981 (Cooper 

and Stewart 1983), much of this growth was 

supported by immigration from Mexico. The 

highest growth rate measu red for the whole 

U.S./Mexico population was 8.3% between 1965 

and 1977 (Cooper and Stewart 1983). A continuous 

growth rate of 8.3% is con sistent with an increase 

from approximately 100 animals in 1900 to the 

current population size. The "maximum estimated 

net productivity rate" as defined in the Marine 

Mammal Protection Act (MMPA) would therefore 

be 8.3%. In California , the net pro ductivity rate Figure 1. Net prod uction rates fo r northern ele phant seals in

appears to have d eclined in recent years [Figure 3; California based on pup births and fishery mortality. Annual 

net production rate was calculated as the realized mortality for 1980-1987 is assumed to be 300, the average of rate of population growth (increase in pup 1988-90 values (Perkins et al. 1994). abundance from year i to year i+1, divided by pup 

31 
abundance in year i) plus the harvest rate (fishery mortality in year i divided by population size in year i)]. 

POTENTIAL BIOLOGICAL REMOVAL 

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

(51,625) times one half the observed maximu m net growth rate for this stock (1⁄2 of 8.3%) times a recovery factor of 1.0 

(for a stock of unknown status that is increasing, Wade and Angliss 1997) resulting in a PBR of 2,142. 

HUMAN-CAUSED M ORTALITY 

Fisheries Information 

A summ ary of known fishery mortality and injury for this stock of northe rn elepha nt seals is give n in Tab le 

1. More detailed informa tion on these fisheries is prov ided in App endix 1. Beca use the set gillnet fishery has undergone 

drama tic reductions and redistributions of effort and because that fishery has not been observed since 1994, average 

annual mortality for that fishery cannot be accurately estimated for the recent years (1995-98). Rough estimates for 

1995-1998 have be en mad e by extra polation o f prior kill rates using recent effort estimates (Table 1). Preliminary set 

gillnet observations in Monterey Bay from April to September 1999 included 3 elephant seals in 24.6% of the sets for 

a rough extrapolatedestimate of 12 mortalitiesin this half-yearperiod. Strandingdata reported to theCalifornia Marine Mammal 

Stranding Network in 1995-98 include elephant seal injuries caused by hook-and-line fisheries (2 

Table 1. Summary ofavailable information on themortality andseriousinjuryofnorthern elephantseals(Californiabreedingstock)incommercial 

fisheriesthatmighttakethisspecies(Julian1997;JulianandBeeson1998;Cameron andForney 1999;Perez,in prep.; NMFS unpubl.data). n/a 

indicates information is not available. Mean annual takes are based on 1994-98 data unless noted otherwise. 

Fishery Name Year(s) Data Type 

Percent Observer 

Coverage 

Observed 

Mortality 

Estimated 

Mortality 

parentheses) 

Mean 

Annual Takes 

(CV in 

parentheses) 

CA/OR thresher 

shark/swordfish drift 

gillnet fishery 

1994 

1995 

1996 

1997 

1998 

observer 

data 

17.9% 

15.6% 

12.4% 

22.8% 

20.2% 

22 

14 

4 

8 

4 

123 (0.23) 

90 (0.25) 

37 (0.55) 

45 (0.33) 

20 (0.44) 

33 (0.27)1 

CA angel shark/halibut 

and other species large 

mesh (>3.5") set gillnet 

fishery 

1991 

1992 

1993 

1994 

1995 

1996 

1997 

1998 

observer 

data 

extrapolated 

estimate 

9.8% 

12.5% 

15.4% 

7.7% 

0.0% 

0.0% 

0.0% 

0.0% 

3 

7 

11 

2 

-

-

-

-

30 (0.55) 

51 (0.35) 

70 (0.27) 

16 (0.66) 

47 (0.29) 2 

46 (0.23) 2 

60 (0.24) 2 

70 (0.26) 2 

n/a 

WA, OR, CA 

groundfish trawl 

1991-95 observer 

data 

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

WA Willapa Bay drift 

gillnet fishery (salmon) 1991 

personal 

communica 

tion 

n/a 2 2 n/a 

Chehalis River salmon 

setnet fishery 1993 

personal 

communica 

tion 

n/a 4 4 n/a 

(CV in 

Total annual takes >33.0 (0.27)

1

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


Reduction Plan. Gearmodificationsincluded the use of net extenders and acousti c warning devices (pingers). Following these changes in the fishery,


entanglement rates of northern elephant seals declined.
 2

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


injuries) andgillnetfisheries(1injuries).The averageestimatedannualmortality fornorthern elephantsealsinthese fisheriesforthefivemost recent 

years ofmonitoring(1994-98)islikely to be substantially greaterthan 33 (thenumber estimatedforthedriftgillnetfisheryalone)but, basedon 

32 
extrapo lations from previou s years, is no t likely to be m ore than tw o or three times grea ter (ie. less than 1 00). 

AlthoughallofthemortalitiesinTable 1occurredinU.S.waters,somemay beofsealsfromMexico's breedingpopulationthataremigrating 

throughU.S.waters. Similardriftgillnetfisheriesforswordfish andsharksexistalongtheentirePacific coastofBajaCalifornia,Mexicoandprobably 

takenorthern elephantseal. Quantitativedata are available only fortheMexican swordfish driftgillnetfishery,which hasincreasedfromtwovessels 

in1986to29vesselsin1992(Sosa-Nishizakietal.1993).The totalnumber ofsetsinthisfisheryin1992 canbe estimatedfromdata providedby these 

authors to be approximately 2,700, with an observed rate of marine mammal bycatch 

of0.13animals perset(10marinemammalsin 77 observedsets;Sosa-Nishizakietal.1993). This overall mortality rate issimilartothatobserved 

inCalifornia driftnetfisheriesduring1990-95(0.14marinemammals perset),butspecies-specific information isnotavailable fortheMexican fisheries. 

There are currently efforts underway to convert the Mex ican swordfish driftnet fishery to a longline fishery (D. Holts, 

pers. comm.). The number ofset-gillnetvesselsin this partofMexico is unknown. The takeof northern elephantsealsin otherNorth Pacific 

fisheries that have been monitored appears to be trivial (Barlow et al. 1993, 1994). 

Other Mor tality 

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

Southwe st Region, contains the following records of human-related elephant seal mortalities and injuries in 1995-98: 

(1) boat collision (1 injury), (2) automobile collision (5 mortalities), and (3) shootings (3 mortalities). Protective 

measures were tak en to prev ent future automobile collisio ns in the vic inity of Pied ras Blanca s/San Sim eon (H atfield 

and Rathbun 199 9). 

STATUS OF STOCK 

A review of elephant seal dynamics through 1991 concluded that their status cou ld not be d etermin ed with 

certainty, but that they might be within their Optimal Sustainable Population (OSP) rang e (Barlow et al. 1993). They 

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

Because their annu al hum an-caus ed mo rtality is muc h less than th e calculated PBR fo r this stock (2 ,142), the y wou ld 

not be considered a "strategic" stock under the MMPA . The average rate of incidental fishery mortality for this stock 

over the last 5 years also appears to be less than 10% of the calculated PBR; therefore, the total fishery mortality appears 

to be insignificant and approaching a zero mortality a nd seriou s injury rate. The population is continuing to grow and 

fishery mortality is relatively constant. There are no known habitat issues that are of particular concern for this stock. 

REFERENCES 

Barlow, J., R. W. Ba ird, 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. S tatus of the n orthern e lephant se al popu lation alon g the U.S . west coas t in 1992 . Admin. 

Rept. LJ-93-01. Southwest Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La 

Jolla, CA. 3 2 pp. 

Boveng, P. 1988. Status of the northern elephant seal population on the U.S. West Coast. Admin. Rep. LJ-88-05 

Southwest Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA. 35pp. 

Cooper, C. F. and B. S. Stewart. 1983. Demography of northern elephant seals, 1911-1982. Science 219:969-971. 

Hatfield, B. B., and G. B. Rathbun. 1999. Interactions between northern elephant seals and vehicles near Point Piedras 

Blancas, California. Mar. Mamm. Sci. 15(2):598-600. 

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

Huber, H. R., A. C. Rovetta, L. A. Fry, an d S. John ston. 1991. Age-specific natality of northern elephant seals at the 

South Farallon Islands, California. J. Mamm. 72(3):525-534. 

Julian, F. and M . Beeson . 1998. E stimates fo r marine mam mal, turtle, and seabird mortality for two California gillnet 

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

Le Boeuf, B. J. 1996. Northern elephant seals at Año Nuevo during the breeding seasons of 1992-1996. Admin. Rep. 

LJ-96-12C. Southwest Fisheries Science Center, National Marine Fisheries Service, P. O. Box 271, La Jolla, 

California , 92038 . 8 pp. 

Le Boeuf, B. J., D. Crocker, S. Blackwell, and P. Morris. 1993. Sex differences in diving and foraging behaviour of 

33 
northern elephan t seals. In: I. Boyd (e d.). Marine Mam mal: Advances in Behavioural and Population 

Biology. Oxford U niv. Press. 

Lowry, M. S., W. L. Perryman, M. S. Lynn, R. L. Westlake, and F. Julian. 1996. Co unts of northern elephant seals, 

Mirounga angustiro stris, 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 demo graphy of southe rn elepha nt seal (Mirounga leonina) popula tions. In J. K. 

Ling and M. M. Bryden (eds.), Stud ies of Sea M amm als in South Latitudes. South Australian Museum. 132 

pp. 

Perez, M. A. (In prep.). Summary of marine mammal incidental catch data for domestic and joint ve nture groun dfish 

fisheries in the U.S. EEZ of the North Pacific, 1989-96. 

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

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

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

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

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

Int. CICESE, CTECT9306. 

Stewart, B . S., and H . R. Hub er. 1993 . Mirounga angustiro stris. 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 pre sent status of the north ern eleph ant seal po pulation. In: B. J. Le Boeuf and R. M. Laws 

(eds.) Elephant Seals. Univ. Calif. Press, Los A ngeles. 

34 
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 cap ture of tw o adult 

males at Guadalupe Island in 1928 established the species' return 

(Townsend 1931); however, they were not seen again until 1954 

(Hubbs 1956). Guadalupe fur seals pup and breed mainly at Isla 

Guadalupe, Mexico. In 1997, a second rookery was discovered at 

Isla Benito del Este, Baja California (Maravilla-Chavez and 

Lowry 1999) and a pup w as born at San M iguel Island , California 

(Melin and DeLong 1999). Individuals have stranded or been 

sighted as far north as Blind Beach, California (38N

 26' 10" N, 

123N

 07' 20" W); inside the Gulf of California and as far south as 

Zihuatanejo, Mexico (17N

 39' N, 101N

 34'W; Hanni et al. 1997 and 

Aurioles-Gamboa and Hernadez-Camacho 1999). The population 

is considered to be a single stock because all are recent 

descend ants from one breeding colony at Isla Guadalupe, Mexico. 

POPULATION SIZE 

The size of the population prior to the commercial 

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

from 20,000 to 100,000 animals (Wedgeforth 1928, Hubbs 1956, 

Fleischer 1987). The population was estimated by Gallo (1994) Figure 1. Geogr aphic range of the Guadalupe fur 

to be abou t 7,408 an imals in 1993. The population estimate was seal, showing loc ation of two roo keries at Isla 

derived by multiplying the numb er of pups ( counted and Guadalupe and Isla Benito Del Este. 

estimated) by a factor of 4.0. 

Minimum Population Estimate 

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

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

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

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

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

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

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

lion rook eries in the C hanne l Islands (Ste wart et al. 19 87). 

Current Population Trend 

Coun ts of Guadalupe fur seals have been m ade spo radically since 195 4. Recor ds of Gu adalupe fur seal cou nts 

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

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

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

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

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

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

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

35 
annual growth rate of 13.7% (Gallo 199 4; Figure 

2). 

CURRENT AND MAXIM UM N E T 

PRODUCTIVITY RATES 

The maximum net produc tivity rate can 

be assume d to be eq ual to the an nual gro wth rate 

observed over the last 30 years (13.7 %) becau se 

the population was at a very low level and should 

have been growing at nearly its maximum rate. 

POTENTIAL BIOLOGICAL REMOVAL 

The potential biological removal (PBR) 

for this stock is calculated as the minimum 

population size (3,028) times one half the defau lt 

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), Figure 2. Counts of Guadalupe fur seals at Guadalupe Island, resulting in a PBR of 104 G uadalup e fur seals per Mexico, and the estimated population growth curve derived 

year. The va st majority of this PBR would apply from counts made during the breeding season. towards incidental mortality in Mexico. 

HUMAN-CAUSEDMORTALITYAND SERIOUS INJURY 

Fisheries Information 

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

States. In the United States there have been no reports of mortalities or injuries for Guadalupe fur seals (Barlow et 

al.1994, Julian 1997, Julian and Beeson 1998, Cameron and Forney 1999. No information is available for humancaused m ortalities or inju ries in Mexic o. 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. Quantitativ e data 

are available only for the Mexican sw ordfish drift gillnet fishery (Sosa-Nishizaki et al. 1993 ). The total n umbe r of sets 

in this fishery in 1992 can be estimated from d ata provided by these authors to be approximately 2,700, with an observed 

rate of marin e mam mal by catch of 0 .13 anim als per set (10 marine mam mals in 77 ob served se ts; Sosa-N ishizaki et al. 

1993). This overall mortality rate is similar to that observed in California driftnet fisheries during 1990-93 (0.15 marine 

mam mals per set), but species-specific information is not available for the Mexican fisheries. There ar e currently efforts 

underway to convert the Mexica n swordfish d riftnet fishery to a long line fishery (D. H olts, pers. com m.). The number 

of set gillnets used in Mexico is unknown. 

Other morta lity 

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

neck, fish h ooks an d mon ofilame nt line, and polyfilam ent string (H anni et al. 19 97). 

STATUS OF STOCK 

The state of California lists the Guadalupe fur seal as a fully pro tected m amm al in the Fish and Game Code 

of California (Chap. 8, sec. 4 700, 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 a utoma tically qualifie s this as a "depleted" and "strategic" stock under the Marine Mammal Protection 

Act. There is ins ufficient info rmation to determ ine whe ther the fishe ry mo rtality in Mexic o excee ds the PB R for this 

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

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

is growing at approximately 13.7% per year. 

36 
Table 1. Summary ofavailable informationon theincidentalmortality andinjuryofGuadalupefursealsincommercialfisheriesthatmighttakethis 

species(Julian1997,JulianandBeeson1998,CameronandForney1999,M.Perezper.comm,Appendix 1).Mean annualtakesarebasedon1994-98 

data unless noted otherwise. 

Fishery Name 

CA driftnet fishery 

for sharks and 

swordfish 

CA set gillnet fishery 

for halibut and angel 

shark 

WA, OR, CA ground 

fish trawl fishery (Atsea processing Pacific 

whiting fishery on ly) 

Year(s) 

1994 

1995 

1996 

1997 

1998 

1994 

1995 

1996 

1997 

1998 

1994 

1995 

1996 

1997 

1998 

Percent Observer 

Data Type Coverage 

observer 17.9% 

15.6% 

12.4% 

22.8% 

20.2% 

observer 

extrapolated 

estimates 

(1995-98) 

7.7% 

0% 

0% 

0% 

0% 

observer 53.8% 

56.2% 

65.2% 

65.7% 

77.3% 

Estimated 

Observed Mortality (CV in 

Mortality parentheses) 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

02 

02 

02 

02 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

Mean 

Annual Takes 

(CV in parentheses) 

01 

02 

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 in cluded the use of net extenders and acoustic warnin g 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. H eyning , K. Wy nne, A. M . Manv ille II, L. F. Lo wry, D . Hanan , J. Sease, and V. N . 

Burkanov. 1994. A review of cetace an and pinn iped mortality in co astal fisheries along the we st coast of the 

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

15:405-425. 

Camero n, G., and K . A. Forney. 1 999. Estim ates of cetace an mortality in the California gillnet fisheries for 1997 and 

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

Fleischer, L. A. 19 87. Gu adalupe 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 po pulation sta tus of Gu adalupe fur seal, Arctocephalus townsendi (Merriam, 

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

p. 

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

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

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

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

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

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

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

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

Maravilla-Chavez, M. O. and M . S Low ry. 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. 19 99. Observations of a Guadalupe fur seal (Arctocephalus townsendi) female and 

37 
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-N ishizaki, 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. DeL ong, an d G.A. A ntonelis Jr. 19 87. Intera ctions betw een Gu adalupe fur seals 

and California sea lions ant San Nicolas and San Miguel islands, Califo rnia. 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 A pril 1984 . p. 103-1 06. U.S . Dept. of Commerce, NOAA, NMFS, NOAA Tech. 

Rept. NMFS 51. 

Torres-G., A., A. A guayo -L., and N . Valdez-T. 1990 . Tama ño y distrib ucion d e la pobla cion del lo bo fino de 

Guadalupe, Arctocephalus townsendi (Merriam , 1897), d urante 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. 

Wedg eforth, H . M. 192 8. The G uadalup e fur seal ( Arctocephalus townsendi). Zoonooz, S. D. Zool. Soc. 3(3):4-9. 

38 
Revised 12/15/2000 

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

STOCK DEFINITION AND GEOGRAPHIC RANGE 

Northern fur seals occu r from southe rn California 

north to the Bering Sea and west to the Okhotsk Sea and 

Honshu Island, Japan (Fig. 1). During the breeding season, 

approx imately 74% of the worldwide population is found 

on the Pribilof Island s in the southern Bering Se a, with the 

remaining animals spre ad through out the No rth 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 C alifornia 

(NMFS 1993). Northern fur seals may temporarily haul out 

on land at other sites in Alaska, British Columbia, and on 

islets along the coast of the continental United States, but 

generally outside of the breeding season (Fiscus 1983). 

Due to differing requirements during the annual 

reproductive season adult males and females typica lly 

occur ashore at different, thoug h overlapp ing times. Adult 

males usually occur on shore during the 4-month period 

from May-August, though some ma y be presen t until 

November (well after giving up their te rritories). Adu lt 

females are found ashore for as long as six months (June- Figure 1. Approximate distribution of northern fur 

November). After their respective times ashore, seals of seals in the eastern North Pacific (shaded area). 

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

1984). Adult females and pups from the Pribilof Isla nds migrate through the A leutian Islands in to the No rth Pacific 

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

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

(Kajimura 19 84). There is consid erable interchange of individuals b etween rookeries. 

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

phylogeo graphic approach: (1) Distributiona l data: geogr aphic distrib ution is continuo us during feed ing, geograp hic 

separation during the breedin g season, high natal site fidelity (DeLong 1982); (2) Population response data: substantial 

differences in population dynamics between Pribilofs and San M iguel Island (D eLong 1 982, D eLong an d Antone lis 

1991, NMFS 1993); (3) Phenotypic data: unknown; and (4) Genotypic data: unknown. Based on this information, two 

separate stocks of nor thern fur seals are recognize d 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. 

POPU LATIO N 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 se als, a life table analysis was performed to e stimate the number of yearlings, 2 year olds, 3 year olds, 

and animals at least 4 years old (Lander 1981). The resulting pop ulation estimate was equal to the pup count multiplied 

by 4.475. The expansion factors are based on a sex and age distribution estimated after the harvest of juvenile males 

was terminated. A more appropriate expansion factor for the San Miguel Island stock is 4.0, based on the known 

increased immigration of recruitment-age females (DeLong 1982) and mortality and possible emigration o f adults 

associated with the El Niño Southern Oscillation event in 1982-1983 (R. DeLong, pers. comm.). A 1998 pup count 

resulted in a total count of 627 pups, a 79.6% decrease from the 1997 co unt of 3,068 (Melin and DeLong 200 0). In 

1999, the population began to recover with a total pup count of 1,084 (S. Melin, unpubl. data). Based on the 1999 count 

and the expansion factor, the most recent population estimate of the San Miguel Island stock is 4,336 (1,084 x 4.0) 

northern fur se als. Currently, a C V for the ex pansion fac tor is unavailab le. 

39 
Minimum Po pulation Estimate 

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

stock is a direct count, with no associated CV(N ) as sites are surve yed only once. Ad ditional estima tes of the over all 

population size (i.e., N BEST) and associated CV are also unavailable. Therefore NMIN for this stock can not be estimated 

by calculating the log-normal 20th percentile of the population estimate. Rath er, NMIN is estimated as twice the maximum 

number of pups born in 1999 (to account for the pups and their mothers) plus the maximum number of adult and subadult males counted for the 1999 season, which results in an NMIN of 2,336 ((1,084 x 2) + 168). T his method provides 

a very conservative estimate of the northern fur seal population at San Miguel Island. 

Current Population Trend 

The population of northern fur seals on San Miguel Island originated from the Pribilof Islands population during 

the late 1950s or early 1960s (DeLong 1982). The colony has increased steadily, since its discovery in 1968, except for 

severe declines in 1983 and 1998 

associated with El Niño Southern 

Oscillation events in 1982-1983 

and 1997-1998 (DeL ong and 

Antonelis 1991, Melin and 

DeLong 2000). El N iño events, 

which occur periodically along 

the California coast, impact 

population growth of fur seals at 

San Miguel Island and are an 

important regulatory mechanism 

for this population (DeLong and 

Antonelis 1991; Melin and 

DeLong 1994, 2 000; M elin et al. 

1996). 

Specifically, live pup 

counts increased about 24% 

annually from 1972 through 1982, 

an increase due, in part, to 

immigration of females from the 

Bering Sea and the western North Figure 2. Northern fur seal live pup counts on S an Migu el Island, 19 72-199 9. 


Pacific Ocean (DeLong 1982) Counts from 1996 were incomplete and have not been included in the figure.


(Fig. 2). The 1982-1983 El Niño


event resulted in a 60.3% decline


in the northern fur seal population at San Miguel Island (DeLong and Antonelis 1991). It took the population 7 years


to recove r from this dec line, because adult female mortality occurred in addition to pup mortality (Melin and DeLong


1994). The 1992-1993 El N iño conditions resulted in reduced pup production in 1992, but the popu lation recov ered in


1993 and increased in 1994 (M elin et al. 1996).


From July 1997 through May 1998, the most severe El Niño event in recorded history affected California coastal 

waters (Lynn et al. 1998). In 1997, total fur seal pup production was 3,068 pups, the highest recorded since the colony 

has been monitored. However, it appears that up to 87% of the pups born in 1997 died before weaning, and total 

production in 1998 was only 627 pups, a decline of 79.6% from 1997 (Melin and DeLong 2000). Although total 

production increased to 1,084 in 1 999 (S. M elin, unpubl. d ata), a slow rec overy from the 1998 decline is anticipated if 

adult female mortality occurred in addition to the high pup mortality in 1997 and 1998 (Melin and DeLong 2000 ). 

CURRENT AND M AXIMUM NET PRODUCTIVITY RATES 

The northern fur seal population in the Pribilof Islands increased steadily during 1912-1924 after the 

commercial harvest no longer included pregnant females. During this period, the rate of population growth was 

approx imately 8.6% (SE=1.47) per year (A. York, unpub l. data), the maximum record ed for this species. This grow th 

rate is similar and slightly higher than the 8.12% rate of increase (a pproxim ate SE= 1.29) estim ated by G errodette e t al. 

(1985). Given the extremely low density of the population in the early 1900 s, the 8.6% rate of increas e is considered 

40 
a reliable estim ate of R MAX. 

POTENTIAL BIOLOGICAL REMOVAL 

The potential biological removal (PBR) level for this stock is calculated as the minimum p opulation e stimate 

(2,336) times one-half the observed maximum net growth rate (1⁄2 of 8.6%) times a recovery factor of 1.0 (for stocks of 

unknown status that are increasing in size, Wade and Angliss 1997), resulting in a PBR of 100 San Miguel Island 

northern fur seals per year. 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY 

Fisheries Information 

Northern fur seals taken during the winter/spring along the west coast of the continental U.S. could be from the 

Pribilofs and thus be long to the E astern Pac ific stock. Ho wever, it is the intentio n of NM FS to con sider any takes of 

northern fur seals by com mercial fisherie s in waters off Ca lifornia, Oreg on, and Washington as being from the San 

Miguel Island stock. Information concerning the three observed fisheries that may have interacted with northern fur seals 

are listed in Table 1. There were no reported mortalities of northern fur seals in any observed fishery along the west 

coast of the continental U.S. during the period from 1994-1998 (Table 1; Julian 1997, Julian and Beeson 1998, Cameron 

and Forney 1999). Overall entanglement rates in the California/Oregon thresher shark/swordfish drift gillnet fishery 

dropped considera bly after the 19 97 implementation o f a Take Reduction P lan, which includ ed skippe r education 

workshops and required the use o f pingers and minimum 6 -fathom extenders (Barlo w and Camero n 1999). Be cause 

of the changes in this fishery after imple mentation o f the Take R eduction P lan, mean an nual takes in T able 1 are based 

only on 1997-1998 data. Fishing effort in the California angel shark/halibut set gillnet fishery was substantially reduced 

as a result of a California voter proposition banning gillnet fishing in certain areas (Julian 1997, Julian and Beeson 1998). 

For this fishery, there were no observed sets after 1994. The estimated mean mortality rate in observed fisheries is zero 

northern fur se als per year fro m this stock. 

An additional source of information o n the numb er of norther n fur seals killed o r injured incid ental to 

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

During the period between 1994 and 1998 , there were no fisher self-reports of northern fur seal mortalities from any 

fisheries operating within the range of this stock. Self-reported fisheries data are incomplete for 1994, not available for 

1995, and considered unreliable after 1995 (see Appendix 4 of Hill and DeM aster 1998). 

Table 1. Summary of available information on the incidental mortality and injury of northern fur seals (San Miguel 

Island stock) in commercial fisheries that might take this species and calculation of the mean an nual mortality ra te; n/a 

indicates that data are not available. Mean annual takes are based on 1994-98 data unless noted otherwise. 

Fishery name Years Data type 

Percent 

observer 

coverage 

Observed 

mortality 

Estimated 

mortality 

Mean annual 

takes (CV in 

parentheses) 

CA/OR thresher shark/ 

swordfish drift gillnet 

94 

95 

96 

97 

98 

obs data 17.9% 

15.6% 

12.4% 

23.0% 

20.0% 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

01 

CA angel shark/h alibut set 

gillnet 

94 

95 

96 

97 

98 

obs data 

extrapolated 

estimates 

(1995-98) 

7.7% 

0% 

0% 

0% 

0% 

0 

0 

0 

0 

0 

0 

02 

02 

02 

02 

0 

0 

WA/OR/CA gr oundfi sh trawl 

(Pacific whiting component) 

94 

95 

96 

97 

98 

obs data 53.8% 

56.2% 

65.2% 

65.7% 

77.3% 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

41 
Fishery name Years Data type 

Percent 

observer 

coverage 

Observed 

mortality 

Estimated 

mortality 

Mean annual 

takes (CV in 

parentheses) 

CA/OR thresher shark/ 

swordfish drift gillnet 

94-98 self reports n/a n/a, n/a, n/a, n/a, 

n/a 

n/a ­

CA angel shark/h alibut set 

gillnet 

94-98 self reports n/a n/a, n/a, n/a, n/a, 

n/a 

n/a ­

unknown west coast fishery 94-98 strand data n/a 0, 0, 0, 0, 0 n/a 0 

Minimum to tal annual t akes 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 in cluded the use of net extenders and acoustic warnin g devices (pingers).
 2

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


Strandings of northern fur seals entangled in fishing gear or with injuries c aused by inte ractions with gear are 

a final source of fishery-related mortality information. During 1994-1998, no northern fur seal stran dings occu rred. 

Fishery-related strandings during 1994-1998 resulted in an estimated annual mortality of zero animals from this stock. 

This estimate is considered a minimum because not all stranded animals are found, reported, or examined for cause of 

death (via necropsy by trained personnel). 

STATUS OF STOCK 

The San Miguel Island northern fur seal stock is not considered to be “depleted” under the MMPA or listed as 

“threatened“ or “endangered” under the Endangered Species Act. Based on currently available data, the estimated annual 

level of total human-caused mortality and serious injury (0) does not exceed the PBR (100). Therefore, the San Miguel 

Island stock of nor thern fur seals is no t classified as a strate gic stock. The minimum total fishery mortality and serious 

injury for this stock (0) is not known to exceed 10% of the calculated PBR (10) and, therefore, can be considered to be 

insignificant and approaching zero mortality and serious injury rate. The stock size decreased 79.6% from 199 7 to 1998 

and began to recover in 1999. The status of this stock relative to its Optimum Sustainable Population (OSP) level is 

unknown, unlike the Eastern Pacific northern fur seal stock which is formally listed as “depleted” under the MMPA. 

REFERENCES 

Barlow, J., and G. A. Cam eron. 199 9. Field experiments show that acoustic pingers reduce marine mammal bycatch 

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

May 1998 (unpublished). 20 pp. 

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

for 1997 a nd 199 8. Pape r SC/51/O 4 presente d to the Intern ational W haling Commission, May 1999 

(unpublished). 14 pp. 

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

DeLong, R. L. 1982. Popula tion biolog y of northern fur seals at San M iguel Island, C alifornia. Ph.D . Thesis, U niversity 

of California, Berkeley, California. 185 pp. 

DeLong, R. L., and G. A. Antonelis. 1991. Impacts of the 1982-1983 El Niño on the northern fur seal population at San 

Miguel Island, Califo rnia. Pp. 75 -83, In: Trillmich, F., and K. Ono (eds.), Pinnipeds and El Niño: Responses 

to Environmental Stress. Springer-Verlag, New York. 293 pp. 

Dizon, A. E., C. Lockyer, W. F. Perrin, D. P. DeM aster, and J. S isson. 199 2. Rethinking the stock co ncept: a 

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

Fiscus, C. F. 198 3. Fur seals an d island. In: Background papers submitted by the United States to the 26th annual 

meeting of the Standing Scientific Committee of the North Pacific Fur Seal Com mission, W ashington, D .C., 

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

WA 98115. 

Gerrodette, T., D. Goodman, and J. Barlow. 1 985. Co nfidence limits for population projections when vital rates vary 

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

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

42 
Tech. Memo. NMFS-AFSC-97. 166 pp. 

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

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

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

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

Kajimura, H. 198 4. Opp ortunistic feedin g of the northe rn fur seal, Callorhinus ursinus, in the eastern N orth Pacific 

Ocean and eastern Bering Sea. NOAA Tech. Rep. NMFS-SSRF-779. 49 pp. 

Lander, R. H. 1981. A life table and biomass estimate for Alaskan fur seals. Fishery Research (Amsterdam) 1:55-70. 

Lander, R. H., and H. Kajimura. 1982. Status of northern fur seals. FAO Fisheries Series 5:319-345. 

Lynn, R. J., T. Baumgartner, J. Garcia, C. A. Collins, T. L. Hayward, K. D. Hyrenbach, A. W. Mantyla, T. Murphree, 

A. Shankle, F. B. Schwing, K. M. Sakuma, and M. J. Tegner. 1998. The state of the California Current, 1997­

1998: transition to El Niño conditions. CalCOFI Report 39:25-49. 

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

Melin, S. R., and R. L. DeLong. 1994. Population monitoring of northern fur seals on San Miguel Island, California. 

Pp. 137-14 1, In: Sinclair, E. H. (ed.), Fur seal investigations, 1992. U.S. Dep. Commer., NOAA Tech. Memo. 

NMFS-AFSC-45. 190 pp. 

Melin, S. R., and R. L. DeLong. 2000. Population monitoring studies of northern fur seals at San Miguel Island, 

California. Pp. 41-51, In: Robson, B. W. (ed.), Fur seal investigations, 1998. U.S. Dep. Commer., NOAA 

Tech. Memo. NMFS-AFSC-113. 101 pp. 

Melin, S. R., R. L. D eLong, an d J. R. Th omason . 1996. P opula tion monitoring studies of northern fur seals at San 

Miguel Island, Califo rnia. Pp. 87 -102, In: Sinclair, E.H. (ed.), Fur seal investigations, 1994. U.S. Dep. 

Commer., NOAA Tech. Memo. NMFS-AFSC-69. 144 pp. 

National Marine F isheries Servic e. 1993 . Final Conse rvation Pla n for the northe rn fur seal (Callorhinus ursinus). 

Prepared by the National Marine Mammal Laboratory, Alaska Fisheries Science Center, Seattle, WA, and the 

Office of Protected Resources, NMFS, Silver Spring, MD. 80 pp. 

Ropp el, A. Y. 198 4. Management of northern fur seals on the P ribilof Islands, A laska, 178 6-1981 . U.S. Dep . Comme r., 

NOAA Tech. Rep. NMFS-4. 32 pp. 

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

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

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

43 
Revised 12/15/2000 

HAWAIIAN MONK SEAL (Monachus schauinslandi) 

STOCK DEFINITION AND GEOGRAPHIC RANGE 

Hawaiian monk sea ls are distributed through out the N orthwe stern Haw aiian Island s (NWHI) in six m ain 

reproductive populations at French Frigate Shoals, Laysan Island, Lisianski Island, Pearl and Hermes Reef, Midway 

Atoll, and Kure Atoll. Small populations at Necker Island and Nihoa Island are maintained by immigration, and a few 

seals are distributed throughout the main Hawaiian Islands. Studies of Hawaiian monk seals have focused on their 

abundance and behavior on land during the reproductive season (spring and summer). Expanded research is underway, 

but currently the pelagic distribution and behavior of monk seals cannot be fully characterized. 

In the last two c enturies, the species ha s experien ced two majo r declin es which , presum ably, hav e severely 

reduced its genetic v ariation. Th e tenden cy for ge netic drift may have been (and continue to be) relatively large, due 

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

(Johnson and Kridler 1983; National Marine Fisher ies Service [NM FS] unp ubl. data) a nd, to som e degree , this 

movement should counter the development of separate genetic stocks. Genetic variation among the different island 

populations is low (Kretzmann et al., 1997). 

Demographically, the different island populations have exhibited considerable independence. For example, 

abundance at French Frigate Shoals grew rapidly during the 1950s to the 1980s, while other populations declined 

rapidly. However, variation in past population trends may be partially explained by changes in the level of human 

disturbance (Gerrod ette and G ilmartin 19 90). Cu rrent dem ograph ic variability a mong the island p opulation s probab ly 

reflects a combination of different re cent historie s and var ying en vironm ental con ditions. W hile research and recovery 

activities focus on the problems of single island/atoll populations, the species is managed as a single stock. 

POPULATION SIZE 

Abundance of the main reproductive populations is best estimated using the number of seals identified at each 

site. Individual seals are identified by applied flipper-tags and bleach-marks, and natural features such as scars and 

distinctive pelage patterns. Flipper-tagging of weaned pups began in the early 1980s, and the majority of the seals in 

the main rep roductiv e popu lations can be identified on the basis of those tags. In 1998, identification efforts were 

conducted during tw o- to five-m onth studies at all main reproductive sites except Midway Atoll, where the study period 

was 12 mon ths. A total of 1 308 sea ls (including 246 pups) were observed at the main reproductive populations in 1998 

(NMFS, unpubl. data). Removal analyses in previous years and sighting probability calculations suggest that 90% or 

more o f the seals w ere identified at each site (i.e., an y negativ e bias shou ld be less tha n 10% ). 

Monk seals also occur at Necker and Nihoa Islands, where repeated counts in a single year were last conducted 

in 1993. Single counts in subsequent years do not indicate abundance at those sites has changed appreciably. The 1993 

studies were not of sufficient duration to identify all individuals, so local abundance is best estimated by correcting mean 

beach counts and assuming that abundance at these sites has not changed. In 1993, mean (± SD) coun ts (excluding pu ps) 

were 22 (±5.2) at Necker Island and 18 (±7.3) at Nihoa Island (Ragen and Finn 1996). T he obse rved relatio nship 

between mean counts and total abundance at the reproductive sites indicates that the total abundance can be estimated 

by multiplying the mean count by a correction factor (±SE) of 2.89 (±0.06, NMFS unpubl. data). Resulting estimates 

(plus the n umbe r of pup s born in 1 993) are 65 (±1 5.1) at Ne cker Islan d and 5 6 (±21 .1) at Niho a Island. 

Finally, a small number of seals are distributed throughout the main Hawaiian Islands. These include an 

unknown numb er of seals, which naturally occur in the main Hawaiian Islands. In addition, twenty-one seals were 

released ar ound th ese islands in 1994. A ll but two w ere subse quently resighted near their respective release sites, but 

their survival to 1998 is unkno wn, bec ause there is no form al resighting effort in the m ain Hawa iian Islands. S poradic 

reports indicate total abundance on the main Hawaiian Islands (including seals released in 1994) may be as high as 40 

seals. 

Minimum Population Estimate 

The total number of seals identified at the main reproductive sites is the best estimate of minimum population 

size at those sites (i.e., 1308 seals). Minimum population sizes for Necker and Nihoa Islands (based on the form ula 

provided by Wade and A ngliss (1997)) are 54 an d 41, resp ectively. If it is assu med th at the abu ndanc e estimate fo r seals 

44 
in the main Hawaiian Islands is, say, 40 ±10 seals (i.e., a coefficient of variation of 0.25), then an estimate of the 

minimum population size in the main Islands is 33 seals. The minimum population size for the entire stock (species) 

is the sum of these estim ates, or 1436 seals. 

Current Population Trend 

Between 1958 and 1998, the total of mean non-pup beach counts at the main reproductive populations declined 

by 60%. From 1985 to 1998, the rate of decline was approximately 3% yr-1, although there has been little change since 

1993 (Fig. 1). Further decline is likely, due to extremely high juvenile mortality and an imminent drop in reproductive 

recruitment in the largest population (French Frigate Shoals). 

CURRENT AND M AXIMUM NET PROD UCTIVITY RATES 

Assuming mean beach cou nts are a reliable index of total abundance, then the current net productivity rate for 

this species is -0.03 yr-1

 (loglinear regression of 

beach counts o f non-p ups, 198 5-98; R2 = 0.82, 

P<0.001). This trend is largely due to a severe 

decline at French Frigate Shoals, where non-pup 

beach counts decreased by 60% between 1989 and 

1998. Populations at Laysan and Lisianski Islands 

have not grow n, but hav e remain ed relatively 

stable since a pprox imately 1 990. 

Contrary to trends at the above sites, the 

population at Kure Atoll has grown at ca. 5% yr-1 

since 1983 (logline ar regression of be ach counts, 

1983-98; R2

 = 0.79, P<0.001), due larg ely to 

decreased human disturbance and introduced 

females. The population at Pearl and Hermes Reef 

has grown at approximately 7% yr-1 since 1983 

(loglinear regression of beach counts, 1983-1998; 

R2

 = 0.81, P<0.001). The latter annual g rowth ra te 

is the best indicator of the maximum net 

produ ctivity rate (Rmax) for this species. Finally, 

the small population at Midway Atoll is showing Figure 1. Mean beach counts of Hawaiian monk seals (nonsigns of incipient recovery. pups) at the main reproductive rookeries (excluding Midway 

Atoll), 198 5-98. 

POTENTIAL BIOLOGICAL REMOVAL 

The potential b iological remova l (PBR) lev el for this stock is calculated as the minimum population size 

(1,436) times on e half the d efault ma ximum net grow th rate for this stock (1⁄2 of 7%) times a recovery factor of 0.1 (for 

an endangered species, Wade and Angliss 1997), resulting in a PBR of 5 monk seals per year. However, the 

Endangered Species Act takes precedence in the management of this species and, under the Act, allowable take is zero. 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY 

Human-related mortality has caused two major declines of the Hawaiian monk seal. In the 1800s, this species 

was decimated by sealers, crews of wrecked vessels, and guano and feather hunters (Dill and Bryan 191 2; Wetmore 

1925; Clapp and Woodward 1972). Several populations may have been driven extinct; for example, no seals were seen 

at Midway A toll during a 14-month period in 1888-89, and only a single seal was seen during three months of 

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

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

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

Pearl and Hermes Reef, or Lisianski and La ysan Islands. At Kure Atoll, Midway Atoll, and French Frigate Shoals, trends 

appear to have been determined by the pattern of human disturbance from military or U.S. Coast Guard activities. Such 

45 
disturbance caused pregnant females to abandon prime pupping habitat and nursing females to abandon their pups 

(Kenyon 1972; G errodette and Gilmartin 1990). The result was a decrease in pup survival, which led to poor 

reproductive recruitment, low productivity, and population decline. 

Since 1979, disturbance from human activities on land has been limited primarily to K ure and M idway Ato lls. 

The U.S. Coast Guard LORAN station at Kure Atoll was closed in 1992 and vacated in 1993. The U.S. N aval Air 

Facility at M idway w as closed in 1993 and , following clean-u p and restoration a ctivities, jurisdiction was transferred 

in 1997 to the U.S. Fish and Wildlife Service, which manages the atoll as a National Wildlife Refuge. The refuge station 

and the atoll runw ay are m aintained cooper atively w ith a com mercial a ircraft com pany, w hich sup ports its Midway 

operations, in part, by establishing a tourism center at the site. Strict regulations have been established to prevent further 

human disturbance of the seals, but careful monitoring of human activities will be essential to ensure that the regulations 

are both adequate and observed (see Habitat Issues below). 

In addition to disturbance on land, disturbance at sea (e.g., direct and indirect fisheries interactions) m ay also 

impede recovery. As described below, however, the possible types of disturbance at sea cannot yet be characterized or 

quantified . 

Fishery Information 

Detrimental fishery interactions with monk seals fall into four categories: operations/gear conflict, 

entanglement in fisheries debris (most of whic h likely originate in North Pacific fisheries outside the NWHI), seal 

consum ption of potentially tox ic discards, and competition for prey. Since 1982, a total of nine fishery-related monk 

seal deaths have been recorded, including six from entanglement in fisheries debris (Henderson 1990; NMFS, unpub l. 

data), one from entanglement in the bridle rope of lobster trap (1986; NMFS, unpub l. data), one from en tanglem ent in 

an illegally set gill net off the western shore of Oahu (1994; NM FS, unpubl. data), and one from ingestion of a 

recreational fish hook and probable drowning o ff the island of Kauai (1995; NMFS , unpubl. data). In addition, 17 other 

seals have been o bserved w ith embedd ed fish hooks, 2 3 seals have been observed with wounds suspected to have 

resulted from inte ractions w ith fisheries, an d 172 c ases of seals entangled in fishing gear or other debris have been 

observed through 1998 (NMFS, unpubl. data). Importantly, the majority of these deaths and injuries have been observed 

incidenta lly during land-based research or other activities; monk seal/fisheries intera ctions nee d to be m onitored to 

assess the rate of fisheries-related injury or mortality for this species. 

Four fisheries interact with Hawaiian monk seals. The NWHI lobster fishery began in the late 1970s, and 

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

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

due to low spawning stock biomass o f spiny lob ster. Since 1 994, lan dings rem ained low er than in th e mid- to late 

1980s, while catch of slipper lobster has increased in some areas. The number of vessels in the fishery increased from 

four in 1983 to 17 in 1985, then ranged from 0-12 during 1991-1998, with five vessels participating in 1998 (Dollar 

1995; DiNard o et al. 199 8; Kaw amoto and Pooley, 2000). Historically, both effort and landings have been concentrated 

at Gardner Pinnacles, Maro Reef, Necker Island, and St. Rogatien Bank (Clarke an d Tod oki 198 8; Polov ina and M offitt 

1989). However, spatial management of the NWHI lobster fishery began in 1998 with the formation of four management 

areas: Necker Island, Maro Reef, Gardner Pinnacle s, and all rem aining ba nks from Nihoa Is land in the east to Kure A toll 

in the west (called A rea 4). Th is approach was adopted in an effort to prevent local depletion of lobster stocks at Necker 

Island, Maro Reef, and Gardner Pinnacles and to disperse fishing effort, which in recent years has been limited to 

Necker Island and Maro Reef. As a result of the new management approach, 48,200 lobsters, comprising 21% of the 

total catch, were taken from Area 4, which had not been fished since the early 1990's (DiNardo et al.1998; Kawa moto 

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

the most recent being Kawamoto and Pooley (2000). A significant portion of the Area 4 catch in 1998 w as taken at 

locations where monk seal subpopulations occur. Neither incidental mortality nor serious injury have been observed 

by NMFS observers of the lobster fishery through 1998. As was noted, one mortality was documented in 1986; a monk 

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

potential for indirect interaction due to comp etition for prey is being investigated (see Habitat Issues below). 

A noteworthy event associated with the lobster fishery was the 16 October 1998 grounding of a transiting lobster 

vessel (Paradise Q ueen II) o n the fring ing reef at K ure Ato ll, near Gre en Island . As a resu lt of the shipwreck, 

approx imately 4,000 gallons of diesel fuel spilled but no significant direct impact from the fuel was detected on monk 

46 
seals or other wildlife in the vicinity. The hull of the vessel has since broken up, and pieces remain scattered on the reef 

and on shore. Trap line and several hundred lobster traps equipped w ith rope bridles were lost. Some of these have 

been recovered and removed after washing ashore. Salvage of the Paradise Q ueen II an d her ge ar were h alted due to 

inclement weathe r and insu fficient fun ding. Th is vessel gro unding represen ts a direct threa t to mon k seals via potential 

entanglement in derelict line and lob ster traps, and entrapm ent in piece s of the ship =s hull. Most of the traps and line 

which washed ashore have since been removed from the atoll as part of an ongoing marine debris m itigation effo rt. 

Indirect impacts on monks seals via habitat degradation is another threat, as the vessel da maged th e coral reef and lost 

lobster trap s were ob served to be gho st fishing for reef orga nisms tha t monk seals may prey up on. 

The NWH I bottom fish fishery also interacts with monk seals. This fishery occurred at low levels (< 50 t per 

year) until 197 7, steadily in creased to 460 m etric tons in 1987, then dropped to 284 metric tons in 1988, and varied from 

137 - 201 metric tons per year from 1989-1998 (Kawamoto 1995; Kawa moto p ers. com m.). Th e num ber of ve ssels 

rose from 19 in 1984 to 28 in 1987, and then varied from 10 to 17 in 1988 through 1998 (Kawamoto 1995; Kawamoto, 

pers. comm.). The fishery was monitored by observers from October 1990 to December 1993 (ca. 13% coverage), but 

is currently monitored by the State of Hawaii using logbooks. However, the State logbook does not include information 

on protected species and, therefore, the nature and extent of interactions with monk seals cannot be assessed. Nitta and 

Henderson (1993) evaluated observer data from 1991-92 and reported an interaction rate of one event per 34.4 hours 

of fishing, but they do not provide a confidence interval for their estimate. The authors documented one seal fo und w ith 

a bottom fish hook in her m outh at Fre nch Frig ate Shoals, observe r reports of seals taking bo ttomfish and bait off fishing 

lines, and observer reports of seals attracted to discarded bottom fish byca tch, whic h may contain ciguatoxin or other 

biotoxins. Injury or mortality resulting from hooking or consum ption of to xic discards cannot be determined with the 

available data. The ecological effects of this fishery on monk seals (e.g., competition for prey or alteration of prey 

assemblages by removal of key predator fishes) are unknown. However, published studies on monk seal prey selection 

based upon scat/spew analysis and seal-mounted video, rarely revealed evidence that monk seals fed on familie s of 

bottomfish which c ontain co mme rcial species (m any har d parts of scats and spews were identified only to the level of 

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

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

Table 1. Summary of incidental mortality of Hawaiian monk seals due to commercial and recreational fisheries since 

1990 and calculation of annual mortality rate. n/a indicates that sufficient data are not available. 

Fishery Name 

Years 

Range of 

# of vessels per year Date type 

Range of 

observer 

coverage 

Total 

observed 

mort. 

Estimated 

mort. (in 

given years) 

Mean 

annual 

mort. 

NWHI lobster 91-98 0-12 Observer 

Log book 

0-100% 0 n/a n/a 

NWHI 

Bottomfish 

91-98 12-17 

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

Pelagic longline 91-98 103-141 Observer 

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

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

† Data collected incidentally. 

A third fishery in which past interactions with monk seals were documented is the pelagic longline fish ery. This 

fishery targ ets sword fish and tu nas, prim arily, and d oes not co mpete with Hawaiian monk seals for prey. The fishery 

began in the 1940s, and operated at a relatively low level (< 5000 t per ye ar) until the mid-19 80s. In 1987 , 37 vessels 

participated, but by 1991, the number had grown to 141 (Ito, 1995). The number of active vessels ranged from 103-141 

during 1991-98 . Entry is currently limited to a maxim um of 16 4 vessels (Ito and Machado, 1999). Total landings 

ranged from 8,100-13,000 metric tons during 1991-1998. While most of the fishery has operated outside of the NWHI 

Exclusive Economic Zone, the rapid expansion raised concerns about the potential for interactions with protected 

species, including the mo nk seal. Ev idence o f interaction s began to accum ulate in 19 90, includ ing three h ooked seals 

47 
and 13 unu sual seal w ounds th ought to have resu lted from interactions. In response, NMFS established a permanent 

Protected Species Zone extending 50 nautical miles around the NWHI and the corridors between the islands in October 

1991. Subsequent shore-based observations of seals suggest thatinteractions decreased substantially after establishment 

of the Protected Species Zone. At present, interactions with protected species are assessed using Federal logbooks and 

observers (4-5% coverage), which may lack sufficient statistical power to estimate monk seal mortality/serious injury 

rates from longline interactions. However, since 199 1, there ha ve been no obse rved or re ported in teractions o f this 

fishery with m onk seals. 

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

the main Hawaiian Islands. At least three seals have been hooked at Kure Atoll, but such incidents should no longer 

occur at this site because the atoll was va cated by the U .S. Coast Guard in 1993. In the main Hawaiian Islands, one seal 

was found dead in an offshore (non-recreational) gillnet in 1994 and a second seal was found dead with a recreational 

hook lodged in its esophagus. At least seven other seals have been hooked. Three of these incidents involved hooks used 

to catch ulua (Caranx spp.). One hooked seal had been translocated from Laysan Island to the main Hawaiian Islands 

in July 1994. The recent establishment of sport fishing at Midway clearly increases the potential for monk seals to be 

harmed by hooks at that site. 

Recent interest in the h arvest of p recious co ral in the N WHI represen ts a potential for future interactions with 

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

is not kno wn. Ho wever, re cent studie s of seals with satellite transmitters and surveys using manned submersibles 

indicate that some monk seals forage at patches of precious gold corals occurring over 500m in de pth (Parrish, pers. 

comm.). Recruitment of gold coral is very slow (perhaps on the order of 100 years), so there is concern that harvesting 

could have a long term impact on monk seal foraging habitat. As a result, the Western Pacific Regional Fisheries 

Management Council has recommended regulations to suspend or set to zero annual quotas for gold coral harvest at 

specific locations until information on impacts of such harvests on monk seal foraging habitat become available. 

Fishery Mortality Rate 

Because monk seals contin ue to die as a result of en tanglement in North Pacific fishing debris and data are 

unava ilable to assess in teraction w ith specific fishe ries, one m ust conclu de that the to tal fishery m ortality and serious 

injury for this stock is greater than 1) zero allowable take under the Endangered Species Act and 2) 10% of the 

calculated PBR. Therefore, total fishery mortality and serious injury can not be considered to be insignifican t and 

approa ching a ra te of zero. 

Direct fishery interactions with this species remain to be thoroughly evaluated and, therefore, the information 

above represents only the observed level of interactions. Without further study, an accurate estimate cannot be 

determined. In addition, interactions may be indirect (i.e., involving competition for prey or consumption of discards 

from the bottomfish fishery) and, to date, the extent or consequences of such indirect interactions remain the topic of 

ongoing investigation. 

Other Mor tality 

Since 1982, 22 seals died during rehabilitation efforts, two died in captivity, two died when captured for 

translocation, one was euthanized (an aggressive male known to cause mortality), three died during captive research 

and three died during field research. 

Seals have also died after encounters with marine debris from sources other than fisheries. In 1986, a weaned 

pup died at East Island, French Frig ate Shoals, after becoming entangled in wire left when the U.S. Coast Gu ard 

abandoned the island three decades earlier. In 1991, a seal died after becoming trapped behind an eroding seawall on 

Tern Islan d, French Frigate Sh oals. This seawall continues to erode and poses an ongoing threat to the sa fety of seals 

and other wildlife. 

The only documented case of illegal killing of an Hawaiian monk seal occurred when a resident of Kauai killed 

an adult female in 1989. 

Other sources of mortality which are (or may be) impeding the recovery of this population include mobbing, 

sharks, poisoning by ciguatoxin or other biotoxins, and disease/parasitism. Mobbing occurs when multiple males attempt 

to mount and mate with an adult female or immature animal of either sex, often leading to the injury or death of the 

48 
attacked seal. Since 19 82, at least 66 seals have died or d isappeare d after bein g mob bed. Th e resulting in crease in 

female mortality appears to have been a major impediment to recovery at Laysan and Lisianski Islands. Mobbing has 

also been documented at French Frigate Shoals, Kure Atoll, and Necker Island. Th e prima ry cause o f mob bing is 

thought to be an imbalance in the adult sex ratio, with males outnumbering females. In 1994, 22 ad ult males were 

removed from Laysan Island, and only two seals are thought to have died from mobbing at this site since their removal 

(1995-98). Such imbalances in the adult sex ratio are more likely to occur when populations are reduced (Starfield et 

al. 1995). 

In addition to mobbin g, aggressive attacks b y single adult ma les have resulted in seve ral monk sea l mortalities. 

This was m ost notab le at French Frigate Sh oals in 199 7, wher e at least 8 pups died as a result of adult male aggression. 

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

who had bee n know n to kill pups in 1997 were observed exhibiting aggressive behavior toward pups at the beginning 

of the 1998 pupping season. These two males were translocate d to John ston Ato ll, 870 km to the south west. 

Subsequently, mounting injury to pups decreased and survival to weaning in 1998 was markedly higher than in 1997. 

The incidence of shark-related injury and mortality may have increased in the late 1980s and early 1990s at 

French Frigate Shoals, but such mortality was probably not the primary cause of the decline at this site (Ragen 1993). 

However, indications are that shark predation has accounted for a significant portion of pup mortality in the last few 

years. The potential causes of high pup mortality, including shark predation, disease, male aggression and food 

limitation are currently being inv estigated at F rench F rigate Sho als. Poisonin g by cig uatoxin or related to xins is 

suspected as the primary ca use of the Laysan die-off in 1978, and may have contributed to the high mortality of juvenile 

seals translocated to Midway Atoll in 1992 and 1993. W hile virtually all w ild mon k seals carry parasites after they beg in 

to forage, the role of parasitism in monk seal mortality is unknown. The effect of dise ase on m onk sea l demo graphic 

trends is also uncertain . 

STATUS OF STOCK 

In 1976, the Hawaiian monk seal was designated depleted under the Marine Mammal Protection Act of 1972 

and as endangered under the Endangered Species Act of 1973. The species is assumed to be well below its optimum 

sustainab le population (OSP) and, since 1985, has declined approximately 3% per year. Therefore, the Hawaiian monk 

seal is characterized as a strategic stock. 

Habitat Issues 

Availab le data indicate that the substantial decline at French Frigate Shoals was to some degree a ttributable 

to lack of available prey and subsequent emaciation and starvation. The two leading hypotheses to explain the lack of 

prey are 1) the local population reached its carrying c apacity in the 1970s and 1980s, and essentially diminished its own 

food supply, and 2) carrying capacity was simultaneously reduced by changes in oceanographic conditions and a 

resulting decrease in productivity (Polovina et al. 1994; Craig and Ragen 2000;). Thus, this population may have 

significantly exceeded its carrying capacity, leading to a catastrophic increase in juven ile mortality . In addition , available 

prey also may have been reduced by competition with the NWHI lobster fishe ry. Mo nk seals fo rage at the f our main 

banks where the fishery has primarily op erated: Maro R eef, Gardiner Pin nacles, St. Rogatien Bank, and Necker Island. 

In 1998, the fishery expanded into areas w here m onk sea l breeding popula tions are co ncentrate d within the fishery’s 

Area 4. Thus, competition for prey is under investigation. This potential for competition cannot yet be determined, 

however, because it is not know n if lobster is an importa nt com ponen t of the m onk sea l diet. Preliminar y research 

indicates that lobster hav e identifiable fatty ac id signatures, wh ich will potentially m ake possib le an assessm ent of its 

importance in the monk seal diet. This promising area of research is being actively pursued. 

A second importa nt habitat issu e is the management of human activities at Midway Atoll. Historically, human 

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

again in the 196 0s. The seal p opulation failed to reco ver in the 1970s and 1980s, but is finally beginning to show some 

signs of growth due to immigration from nearby sites. Mana geme nt jurisdiction of Mid way A toll has been transferred 

from the U.S. Navy to the Fish and W ildlife Service. The Fish an d Wildlife Service m aintains a refuge station at Midway 

Atoll by cooperating with a commercial aircraft company that uses the runway on Sand Island (the largest island at 

Midway Atoll), and sup port its operations, in part, by establishing an on-site eco-tourism destination. Tourist activities 

include a range of land-based and marine recreational activities (e.g., scuba diving and sport fishing), as well as harbor 

49 
services to visiting vessels. As the tourism venture develops, so does a potential conflict of interest. The economic 

success of the venture may depend on the nature and variety of human activities or privileges allowed at the site. 

Importantly, those activities that are intended to enhance the Midway experience may be disruptive or detrimen tal to 

the refuge and its wildlife. The issue is whether such potential conflicts can be identified and resolved in a manner that 

allows for continuation o f the ecotourism venture but do es not imped e monk seal recovery. Th e Fish and W ildlife 

Service and NMFS are working cooperatively to ensure that human activities do not impede recovery at this site. 

Another important habitat issue is the degrading seawall at Tern Island, French Frigate Shoals. Tern Island is 

the site of the U.S. Fish and Wildlife refuge station, and is one of two sites in the NWHI accessible by aircraft. The 

island and the runway have played a key role in efforts to study the local monk seal population, and to m itigate its severe 

and ongoing decline. During World War II, the U.S. Navy enlarged the island to accom moda te the runw ay. A sheet-pile 

seawall was constructed to maintain the modified shape of the island. Degradation of the seawall is creating entrapment 

hazards for seals and other wildlife, and is threatening to erode the runway. Erosion of the sea wall has also raised 

concerns about the poten tial release of to xic wastes into the aq uatic env ironme nt. The lo ss of the run way co uld lead to 

the closure of the Fish and Wildlife Service station at the site and would thereby reduce on-site management of the 

refuge. The loss of the runway and refuge station would also hinder research and management efforts to recover the 

monk seal population. 

A fourth important habitat issue involves entanglement in marine debris. Marine debris is removed from the 

beaches and entangled seals during annual population assessment activities at the m ain repro ductive sites . Efforts to 

remove potentially entangling marine debris from the reefs surrounding haulout sites utilized by monk seal are ongoing. 

In 1996, e fforts com menc ed to assess and remove potentially entangling marine debris from reefs surrounding haulout 

sites utilized by monk seals. Preliminary surveys suggest a very large number of nets are fouled on nearshore reefs in 

the NWHI, and may pose a serious threat to seals in these areas. During 1996-1998 debris survey and removal efforts, 

11,000 kg of derelict net and other debris were removed from coral reefs at French Frigate Shoals and Pearl and Hermes 

Reef (Bo land, pers . comm .). 

REFERENCES 

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

Clapp, R. B., and P. W . Woodw ard. 1972. T he natural history of Kure Atoll, No rthwestern Ha waiian Islands, Ato ll Res. 

Bull. 164:303-304 

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

Northwestern Hawaiian Islands. Admin. Rep. H-88-6. Southwest Fisheries Science Center, National Marine 

Fisheries Service, 2570 Dole St., Honolulu, HI 96822-2396. 30 pp. 

Craig, M. P. and T. J. Ragen. 1999. Body size, survival, and decline of juvenile Hawaiian monk seals, Monachus 

schauinslandi. .Marine Mammal Science 15(3): 786-809. 

Dill, H. R., and W. A. Bryan. 1912. Report o n an exp edition to L aysan Islan d in 191 1. U.S. D ept. of Ag ric. Surv. B ull. 

42:1-30. 

DiNardo, G. T., W. R. Haight, and J. A. Wetherall. 1998. Status of lobster stocks in the Northwestern Hawaiian 

Islands, 1995-97, and outlook for 1998. Admin. Rep. H-98-05. Southwest Fisheries Science Center, National 

Marine Fisheries Service, 2570 Dole St., Honolulu, HI 96822-2396. 35 pp. 

Gerrodette, T. M., and W. G. Gilmartin. 1990. Demographic consequences of changed pupping and hauling sites of the 

Hawaiian monk seal. Conserv. Biol. 4:423-430. 

Haight, W. R., and G. T . DiNard o. 1995 . Status of lob ster stocks in the North western H awaiian I slands, 19 94. Av ailable 

Honolulu Lab., Southwest Fish. Sci. Cent., Natl. Mar. Fish. Serv., NOAA, Honolulu, HI 96822-2396. 

Southwest Fish. Sci. Cent. Admin. Rep. H-95-03, 17 p. 

Henderson, J. R. 1990. Recent e ntanglem ents of H awaiian m onk sea ls in marin e debris. In R. S. Shomura and M. L. 

Godfrey (eds.), Proceedings of the Second International Conference on Marine Debris, April 2-7, 1989, 

Honolulu, Hawaii, p. 540-553. U.S. Dep. Commer., NOAA, Tech. Memo. NMFS-SWFSC-154. 

Ito, R. Y. 1995. Annual report of the 1994 Hawaii-based longline fishery. Admin. Rep. H-95-08 Southwest Fisheries 

Science Center, National Marine Fisheries Service, 2570 Dole St., Honolulu, HI 96822-2396. 36 pp. 

Ito, R. Y., and W. A. E. Machado. 1999. Annual report of the Hawaii-based longline fishery in 1998. Admin. Rep. 

50 
H-99-06. Southw est Fisheries Science Center, National Marine Fisheries Service, 2570 Dole St., Honolulu, 

HI 96822-2396. 62 pp. 

Johnson, A. M., and E. Kridler. 1983. Interisland movement of Hawaiian monk seals. 'Elepaio 44(5):43-45. 

Kawamoto, K. E. 1995. Northwestern Hawaiian Islands bottomfish fishery, 1994. Admin. Rep. H-95 -07. Southwe st 

Fisheries Science Center, National Marine Fisheries Service, 2570 Dole St., Honolulu, HI 96822-2396. 26 pp. 

Kawamoto, K. E., and S. G. Pooley. 2000. Annual report of the 1998 western Pacific lobster fishery. Admin. Rep. H00-02. Southwest Fisheries Sc ience Ce nter, Natio nal Ma rine Fisheries Service , 2570 D ole St., Honolulu, HI 

96822-2396. 38 pp. 

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

Kretzmann, M. B., W . G. Gilmartin, A. M eyer, G. P . Zegers, S . R. Fain, B. F . Taylor, and D. P. Costa. 1997. Low 

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

Goodman-Low e, G. D. 19 98. Diet o f the Haw aiian mo nk seal ( Monachus schauinslandi) from the Northwestern 

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

Nitta, E. T., and J. R. H ende rson . 199 3. A r eview of inte ractio ns be twee n Ha waii's fisheries and protected species. Mar. 

Fish. Rev. 55(2):83-92. 

Parrish, F. A., M. P. Craig, T. J. Ragen , G. J. Marshall, and B. M. Buhleier. 2000. Identifying diurnal foraging habitat 

of endangered Hawaiian monk seals using a seal-mounted video camera. Mar. Mamm. Sci. 16:392-412. 

Polovina, J. J. 1993. The lobster and shrimp fisheries in Hawaii. Mar. Fish. Rev. 55(2):28-33. 

Polovina, J. J., G. T. M itchum, N. E. Gr aham, M. P. Cra ig, E. E. DeMartini, and E. N. Flint. 1994. Physical and 

biological consequences of a climate event in the central North Pacific. Fish. Ocean. 3:15-21. 

Polovina, J. J., and R. B. Moffitt. 1989. Status of lobster stocks in the Northwestern Hawaiian Islands, 1988. Admin. 

Rep. H-89-3 . Southw est Fisheries S cience Center, Na tional M arine Fisheries Service, 2570 Dole St., Honolulu, 

HI 96822-2396. 10 pp. 

Pooley, S. G., and K. E. Ka wam oto. 199 8. 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., and M. A. Fin n. 1996. Th e Hawaiian m onk seal on N ihoa and N ecker Islands, 1993. Pages 89-104 in T. 

C. Johano s and T. J. R agen (ed s.), The H awaiian m onk sea l in the Northw estern Hawa iian Islands, 1993. U.S. 

Dep. Commer., NOAA, Tech. Memo. NMFS-SWFSC-227. 

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

Starfield, A. M., J. D. Roth , and K. Ralls. 199 5. "Mobb ing" in Haw aiian monk seals (Monachus schauinslandi): The 

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

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

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

93 pp. 

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

51 
Revised 12/15/2000 

HARBOR PORPOISE (Phocoena phocoena): Central California Stock 

STOCK DEFINITION AND GEOGRAPHIC RANGE 

In the Pacific, harbor porpoise are found in coastal and 

inland waters from Point Conception, California to 

Alaska and across to Kam chatka and Japan (G askin 

1984). Harbor porpo ise appear to have more restricted 

movem ents 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 (Calamb okidis and Barlow 1991). That 

study also showed so me region al differences w ithin 

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 (Polache ck et al. 

1995). A phyloge ographic analysis of gene tic data from 

northeast Pacific harbor porpoise did not show com plete 

concordance between D NA seq uence typ es and 

geograp hic 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 re sults 

demon strate that harbor porpo ise along the west coast of Figure 1. Stock boundaries and distributional 

North America are not panmictic or migratory, and range of harbor porpoise along the U.S. west co ast. 

movement is sufficiently restricted tha t genetic Shaded area represents harbor porpoise habitat (0­

differences have evolv ed. Rece nt preliminary g enetic 200 m) along the U .S. west coast. 

analyses of samples ra nging from M onterey B ay, 

California to Vanco uver Island, B ritish Columb ia indicate that there are at least nine genetically distinct 

populatio ns, including two within the prese nt central Califo rnia stock ran ge (S. Chive rs, pers. com m.). 

In their assessment of harbor porpoise, Barlow and Hanan (1995) recom mended that the animals inhabiting 

central California (d efined to be from Po int 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 Californ ia is not manag ed separa tely. 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 pop ulations. Follo wing the guida nce of Ba rlow and H anan (19 95), we will 

consider the harbor porpoise in central Califo rnia as a sepa rate stock. However, based o n recent gen etic 

findings (Chivers, pers. comm.), it ap pears likely that the central Califo rnia stock will be further sub divided into 

two stocks (with a division somewhere between Monterey Bay and San Francisco) once the ongoing analyses 

have been finalized and pee r-reviewed. Other U.S . West coast stocks are also likely to be re-evaluated at that 

time. For the 2000 Marine Mamm al Protectio n Act (M MPA ) Stock As sessment R eports, othe r Pacific coast 

harbor porpoise stocks include: 1) a northern California stock 2) an Oregon/Washington coast stock, 3) an 

Inland Washin gton stock, 4) a Southeast Alaska stock, 5) a Gulf of Alaska stock, and 6) a Bering Sea stock. 

Stock assessment re ports for no rthern Califor nia and the Oregon and Washington stocks appear in this volume. 

47 
The three Alaska harbor porpoise stocks are reported separately in the Stock Assessment Reports for the Alaska 

Region. 

POPU LATIO N SIZE 

Forney (1999a) estimates the abundance of central California harbor porpoise to be 5,732 (CV=0.39) based on 

aerial surveys in 1993-97. This estimate is not significantly different from the estimate of 4,120 (CV=0.22) 

presented by Barlow and F orney (1994). T he more recent estimate is less precise, because it was calculated 

using a more recently developed correction factor for submerged animals (3.42 = 1/g(0) with g(0)=0.292, 

CV=0.366; Laake et al. 1 997); this co rrection facto r is slightly higher than and has a larger estimated variance 

than the one used by Barlow and Forney (1994; g(0)=0.324, CV=0.173). Both of these estimates only include 

the region between the coa st and the 50-fathom (91m) isobath. Barlow (1988) found that the vast majority of 

harbor porpoise in California were within this depth range; however, Green et al.(1992) found that 24% of 

harbor porpoise seen during aerial surveys of Oregon and Washington were between the 100m and 200m 

isobaths (55 to 109 fathoms). A recent analysis of harbor porpoise trends including oc eanograp hic data sugg ests 

that the proportion of Ca lifornia harbor porpo ise in deeper waters may vary between years (Forney 1999b; see 

Current Popula tion Tren d below) . Therefo re, an unknown number o f animals from the central Ca lifornia 

population may have been in waters deeper than those covered by the surveys in 1993-97, and the above 

abundance estimate may u nderestima te the total population size by an unknown amount. Additional aerial 

surveys are planned in 1999 to cover waters deeper than 50 fathoms (91 m), and the results are expected to shed 

light on the magnitude of this potential bias. 

Minimum Po pulation Estimate 

The minimum population estimate for harbor porpoise in central Califo rnia is taken as the lower 20th percentile 

of the log-normal distribution of the abundance estimated from the 1993-97 aerial surveys (Forney 1999a) or 

4,172. 

Current Population Trend 

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

abundance in central Califo rnia (Forney, 1995; 1999b). After controlling for the effects of sea state, cloud 

cover, and area on sighting rates, Forney (1995) found a negative trend in population size; however, that trend 

was no longer significant when sea surface temperature (a proxy measure of oceanographic conditions) was 

included in an updated non-linear trend analysis (Forney 1999b). The negative correlation between harbor 

porpoise sighting rates and sea surface temperatures indicates that apparent trends could be caused by changing 

oceano graphic conditions and movement of animals into and out of the study area. Encounter rates for the 1997 

survey, however, were very high (Forney 1999a) despite the warmer sea surface temperatures caused by strong 

El Niño cond itions. These observatio ns suggest that p atterns of harb or porp oise move ment are no t directly 

related to sea surface temperature, but rather to the more complex distribution of potential prey species in this 

area. 

CURRENT AND M AXIMUM 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 pe r year until death ), the theoretica l, maximum -conceivab le growth rate of a closed harbor p orpoise 

population was estimated as 9.4% per year (Barlow and Boveng 1991). This maximum theoretical rate may 

not be achieva ble for any real population. [Woodley and Read (1991) calculate a maximum growth rate of 

approx imately 5% per year, but their argument for this being a maximum (i.e. that porpoise survival rates cannot 

exceed those of Himalayan thar) is not well justified.] Population growth rates have not actually been measured 

for any harbor porpoise population. Because a reliable estimate of the maximum net productivity rate is not 

available for central California harbor porpoise, it is recommended that the cetacean maximum theoretical net 

productivity rate (RMAX) of 4% (Wade and Angliss 1997) be employed. 

48 
POTENTIAL BIOLOGICAL REMOVAL 

The potential bio logical remo val (PB R) level for this stock is calculated as the minimum population size (4,172) 

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

a species of unknown status and a mortality rate CV�0.30; Wade and Angliss 1997), resulting in a PBR of 42. 

HUMAN -CAUSED MORTALITY 

Fishery Information 

The incidental capture of harbor porpoise is largely limited to the halibut set gillnet fishery in central Califo rnia 

(coastal setnets are not allowed in northern California, and harbor porpoise do not occur in southern California). 

Detailed information on this fishery is provided in Appendix 1. A summary of estimated fishery mortality and 

injury for this stock of ha rbor po rpoise is given in Table 1 . The mo rtality estimate for 1994 is based on actual 

1994 observer data (Julian and Beeson 1998). At the end of 1994, however, the observer program was 

discontinued, and mortality estimates for 1995-98 are therefore based on total estimated fishing effort and prioryear entangleme nt rate data. Forney et al. (in press) evaluated uncertainties in estimating mortality for 

unobserved years, and presented severa l alternate analyses of harbor porp oise mortality for this fisher y. Their 

analysis ‘C’, which includes data from both a 1987-90 California Department of Fish and Game observer 

program and a 1990-94 National Ma rine Fisheries Service observer program, best captures the range of 

variability in entanglement rates and is most consistent with the patterns observed more recently in the 1999 

observer program (for which on ly preliminary re sults are availab le at this time; Ta ble 1). Analysis ‘C’ is also 

stratified to reflect regional differences in bycatch rate s between Monterey Bay and Morro Bay. Table 1 

includes the 1995-98 mortality estimates from analysis ‘C’ in Forney et al. (in press), as was recommended by 

the Pacific Scientific Review Group at their December 1999 meeting. Although mortality estimates for the most 

recent five years (1994-98) are presented in Table 1, average annual takes in the setnet fishery are calculated 

using only 1996-98 data, because fishing effort approximately doubled after 1995, and the majority of recent 

effort has taken place in the southern areas of Monterey Bay, where very little effort took place prior to 1996. 

Table 1. Summary of available information on incidental mortality and injury of harbor porpoise (central CA stock) 

in commercial fisheries that might take this species (Julian and Beeson 1998; Forney et al., in press; 

NMFS/SWFSC, unpublished data). Mean annual takes are based on 1994-9 8 data unle ss noted oth erwise. n/a 

indicates that data are not available. 

49 
Fishery Name Year(s) 

CA angel shark / halibut 

and other 1994 

species large 

mesh (>3.5") set1995 

gillnet fishery 1996 

1997 

1998 

1999 

Unknown fishery 1994-98 

Minimum total annual takes 

Data Type 

Percent 

O 

b 

s 

er 

v 

er 

C 

o 

v 

er 

a 

g 

e 

Observed 

Mortality 

observer data 7.7% 1 

1987-90 0% -

and 0% -

1990-94 0% -

observer data 0% -

Prelim. 1999 22.0% 27 

ob 

ser 

ver 

dat 

a 

Strandings - 3 (in 1998)

Estimated 

Mortality (CV in 

parentheses) 

Mean Annual Ta kes 

(CV in parentheses) 

14 (0.96) 

42 (0.19) 

48 (0.19) 

80 (0.19) 

57 (0.19) 

approx. 123 (n/a) for 

JanSeptember 

62 (0.19) 1 

n/a �0.60 (n/a) 

63 (0.19) 

Only 1996-98 mortality estima tes are included in the average because of changes in the distribu tion and amount of fishing effort after 1995 (see text). 

The revised mo rtality data indicate that an average of 63 harbor porpoise (CV= 0.19) have been killed each year 

in central California during the period 1996-98. An observer program was initiated in the Monterey Bay area 

in April 1999, and the preliminary mortality estimate for January-September 1999 is 123 harbor porpoise (27 

mortalities observed in 22% o f total effort; NM FS, unpub lished data). Thus, it appears that entanglement rates 

have increa sed substan tially since the early 1 990's. 

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

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

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

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

Three fishery-related ha rbor po rpoise strand ings were rep orted in centralCalifornia in 1998, north of the known 

set gillnet fishing areas: two near Bodega Head and one inside San Francisco B ay (NMF S, Southwest Region, 

unpublished data). These mortalities were probably taken from the central California harbor porpoise stock, 

although it is possible that the northern two animals were taken from the northern California stock and drifted 

southward to the stranding location. Effo rts are under way to identify possible fisheries responsible for these 

mortalities. Based o n experien ce with other fishe ries (e.g. the set gillnet fishe ry), the prop ortion of incid entally 

killed animals that strand is generally only a fraction of the total mortality, and therefore these unidentified 

fisheries are likely to have taken more than the three observed harbor porpoise. 

STATUS OF STOCK 

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

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

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

the central California population could have been reduced to between 30% and 97% of K by incidental fishing 

50 
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 porpo ise 

relative to their Optim um Sustaina ble Population (OS P) levels in central California must be treated as unknown. 

The average annual mortality for 1996-98 (63 harbor porpoise) is greater than the calculated PBR (42) for 

central California harbor porpoise; therefore, the central California harbor porpoise population is “strategic” 

under the MM PA. Based on the succ ess of pingers for reducing harb or porpoise m ortality in east coast fisheries 

(Kraus et al. 1997; Trippel et al. 1999), efforts are presently underway to encourage voluntary use of pingers 

in the central California halibut set gillnet fishery. The observer program is scheduled to continue and will 

provide information o n the success o f any voluntary m easures. On Sep tember 1 3, 2000 , the Californ ia 

Depa rtment of F ish and G ame (C DFG ) restricted fishin g in the central California halibut set gillnet fishery 

to waters deeper tha n 60 fathom s, citing concerns over the continued mortality of common murres and decline 

of the southern sea otter population. The closure area extends from Po int Reyes to Yankee Point in Monterey 

Coun ty and from P oint Arguello to P oint Sal in Santa Barbara County. The area from Yankee Point to Point 

Sal will remain open to halibut fishing outside of 30 fathoms. This closure is effective for 120 days and may 

be extended or reissue d by the CD FG. The ex clusion of this fishery from insh ore waters less than 60 fathoms 

is expected to considerably reduce the mortality of harbor porpoise in Monterey Bay. Research activities will 

continue to monitor the population size and to investigate population trends. The average gillnet mortality for 

1996-98 (63 porpoise per year) is greater than the calculated PBR; therefore, the fishery mortality cannot be 

considered insignificant and approaching zero mortality and serious injury rate. There are no known habitat 

issues that are of particular concern for this stock. 

REFERENCES 

Barlow, J. 1988. Harb or porpoise (Phocoena phoco ena) abunda nce estimatio n in California, O regon and Washin gton: 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. Forne y. 1994. An assessmen t of the 1994 status of harbo r porpoise in California. U.S. Dep. Commer., NOAA 

Tech. Memo. NMFS-SWFSC-205. 17pp. 

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

16:123 -140. 

Calambokidis, J. and J. B arlow. 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. R ep. NM FS 98. 

Cameron, G. 199 8. Cetacean mortality in California gill net fisheries: Preliminary estimates for 1997. Paper SC/50/SM02 presented 

to the Internatio nal Wha ling Comm ission, June 1 998 (unp ublished). 1 5 pp. 

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

Forney, K. A. 1995. A decline in the abundance of harbor porpoise, Phocoena phocoena, in nearshore waters off California, 1986-93. 

Fish. Bull. 93: 741-748. 

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

LJ-99-02. Available from Southwest Fisheries Center, National Marine Fisheries Service, P.O. Box 271, La 

Jolla, CA 92038. 16pp. 

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

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

Forney, K. A., S. R. Benson, and G. A. Cameron. (in press). Central California gillnet effort and bycatch of sensitive species, 1990-98. 

In: E. F. Melvin and J. K. P arrish (eds.), Seabird Bycatch: Trends, Roadblocks and Solutions, Proceedings of 

an International Symposium of the Pacific Seabird Group, Semi-Ah-Moo, Wa shington, February 1999. 

University of Alaska Sea Grant, Fairbanks, AK. 

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

indirect catch es. Rep. int. W hal. Comm n 34:56 9-586. 

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. Brueg geman (ed .). Oregon and 

Washington Marine Mamma l and Seabird Surve ys. Minerals Management Service Contract Report 14-12­

51 
0001-30426 prep ared for the Pacific OCS Region. 

Julian, F. 19 97. Cetacean mortality in Califo rnia gill net fisheries: P reliminary estima tes for 199 6. Pape r SC/49/S M02 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. 

Kraus, S. D. A. J. Read, A. Solow, K. Baldwin, T. Spradlin, E. Anderson and J. Williamson. 1997. Acoustic alarms reduce porpoise 

mortality. Nature 388:525. 

Laake, J. L., J. C. Calambokidis, S. D. Osm ek, and D. J. Rugh. 19 97. Probab ility 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. 199 2. Genetic p opulation 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. 

Trippe l, E. A., M . B. Strong , J. M. Te rhune, and J. D. Con way. 1999. Mitigation of harbour porpoise (Phocoena phocoena) by-catch 

in the gillnet fishery in the lower Bay of Fundy. Can. J. Fish. Aquat. Sci. 56:113-123. 

Wade, P. R. and R. P. A ngliss. 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. 

52 
Revised 12/15/2000 

HARBOR PORPOISE (Phocoena phocoena): Northern California 

Stock 

STOCK DEFINITION AND GEOGRAPHIC RANGE 

In the Pacific, harbor porpoise are found in coastal and


inland waters from Po int Concep tion, California to


Alaska and acro ss to Kam chatka and Japan (G askin


1984). Harbor porpo ise 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 betw een California, Oregon,


and Washington (Calambokidis and Barlow 1991). That


study also showed some regional differences within


California (although the sample size was small). T his


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 Ba y of Fundy (P olacheck et al.


1995). A phyloge ographic analysis of gene tic data from


northeast Pacific harb or porp oise did no t show com plete


concordance between DNA sequence types and


geograp hic location (R osel 199 2). How ever, an ana lysis


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, Wa shington, British Figure 1. Stock boundaries and distributional


Columbia, and Alaska (Rosel et al. 1995) . These re sults range of harbor porpoise along the U.S. west co ast.


demon strate that harbor porpoise along the west coast of Shaded area repre sents harbor porpoise habitat (0 -


North America are not panmictic or migratory, and 200 m) along the U .S. west coast.


movement is sufficiently restricted tha t genetic


differences have evolv ed. Recent p reliminary gen etic


analyses of samples ranging from Monterey Bay, California to Vancouver Island, British Columbia indicate that


there are at lea st nine genetica lly distinct popu lations (S. Ch ivers, pers. co mm.). 


In their assessment of harbor porpoise, Barlow and Hanan (1995) recommended that the animals inhabiting


central California (d efined to be from Po int Concep tion to the Ru ssian River) b e 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 re stricted within C alifornia, and c onseque ntly 3) fishery mo rtality


could cause the local depletion of harbor porpoise if central California is not managed separately. Although


geograp hic structure exists along an almost c ontinuous d istribution of har bor por poise from California to


Alaska, stock boundaries are difficult to draw because any rigid line is (to a greater or lesser extent) arbitrary


from a biologica l perspective . Nonethe less, failure to reco gnize geog raphic structure by defining management


stocks can lead to depletion of local populations. Following the guidance o f Barlow a nd Hana n (1995 ), we will


consider the harbor porpoise in northern California as a separate stock. Based on recent genetic findings


(Chivers, pers. com m.), U.S. W est coast stock s are likely to be re-evaluated once ongoing analyses have been


finalized and peer-reviewed. For the 2000 Marine Mam mal Protection Act (MMPA ) Stock Assessment


Reports, other Pacific coast harbor porpoise stocks include: 1) a central California stock, 2) an


Oregon/Washington coast stock, 3) an Inland Washington stock, 4) a Southeast Alaska stock, 5) a Gulf of


Alaska stock, and 6 ) a Bering S ea stock. Stock assessment reports for central California and the Oregon and


Washington stocks appear in this volume. The three Alaska harb or porp oise stocks a re reporte d separate ly in


53 
the Stock Assessment Reports for the Alaska Region. 

POPU LATIO N SIZE 

Forney (1999a) estimates the abundance of northern California harbor porpoise to be 11,066 (CV=0.39) based 

on aerial surveys in 1 993-97 . This estimate is not significantly different from the estimate of 9,250 (CV=0.23) 

presented by Barlow and Forney (1994) based on a series of aeria l surveys from 1989 to 1993. The m ore recent 

estimate is less precise, because it was calculated using a more recently developed correction factor for 

submerged animals (3.42 = 1/g(0) with g(0)=0.292, CV=0.366; Laake et al. 1997 ); this correction factor is 

slightly higher than and has a larger estimated variance than the one used by Barlow and Forney (1994; 

g(0)=0.324, CV=0 .173). Both estimates only include the region between the coast and the 50-fathom (91m) 

isobath. Barlow (1988) found that the vast majority of harbor porpoise in California were within this depth 

range; however, G reen et al. (19 92) found that 24% of harbor p orpoise se en during ae rial surveys of Oregon 

and Washington were between the 100m and 200m isobaths (55 to 109 fathoms). A recent analysis of harbor 

porpoise trends including oc eanograp hic data sugg ests that the pro portion o f California har bor por poise in 

deeper waters may va ry between ye ars (Forne y 1999b ; see Curren t Populatio n Trend below). Therefore, an 

unknown number o f animals from the northern C alifornia pop ulation may ha ve been in waters deeper than those 

covered by the surveys in 1993-97, and the above abundance estimate may underestimate the total population 

size by an unknown amount. Additional aerial surveys are planned for waters deeper than 50 fathoms (91 m) 

during 1999, and the results may shed light on the magnitude of this po tential bias. 

Minimum Po pulation Estimate 

The minimum population estimate for harbor porpoise in northern C alifornia is taken a s the lower 20 th 

percentile of the log-normal distribution of the abundance estimated from the 1993-97 aerial surveys (Forney 

1999a) or 8,061. 

Current Population Trend 

Forney (1999b) exa mines trends in relative harbor po rpoise abundance in central and northern California based 

on aerial surveys from 1989-95. No significant trends were evident over this time period for the Northern 

California Stock. 

CURRENT AND M AXIMUM 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 pe r year until death ), the theoretica l, maximum -conceivab le growth rate of a closed harbor porpo ise 

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) ca lculate a maximum growth rate of 

approx imately 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 produ ctivity rate is not 

available for northern California harbor porpoise, it is recommended that the cetacean maximum theoretical net 

productivity rate (RMAX) of 4% (Wade and Angliss 1997) be employed. 

POTENTIAL BIOLOGICAL REMOVAL 

The potential biological removal (PBR) level for this stock is calculated as the minimum population size (8,061) 

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 Su stainable P opulation; W ade and Angliss 199 7), resulting in a P BR of 1 61. 

HUMAN -CAUSED MORTALITY 

Fishery Information 

The incidental cap ture of harbo r porpo ise in California is la rgely limited to se t gillnet fisheries in central 

California. Coastal setnets are no t allowed in no rthern Califor nia (to protect salmon resources there). However, 

one harbor porpoise mortality was documented from stranding reports for the Klamath River tribal salmon 

54 
gillnet fishery 

in 1995 (N MFS , Southwest Region, unp ublished d ata). Additionally, in 1998, two harbor porpoise strandings near 

Bodega Head were attributed to fishery-related mortality, but the responsible fishery is unknown. Although the 

stranding location falls within the range of the central California harbor porpoise stock and this is probably the 

source stock for the m ortalities, it is possible tha t these animals were taken from the northern California stock 

and subsequently drifted southward to the stranding loc ation. Efforts ar e underwa y to identifyfisheries that may 

have been responsible. 

Table 1. Summary of available information on incidental mortality and injury of harbor porpoise (northern CA stock) 

in fisheries that might take this species. n/a indicates that data are not available. 

Fishery Name Year(s) Data Type 

Percent Observer 

Cover 

age 

Observed Mortality 

Estimated Mortality 

(CV in 

parenthes 

es) 

Mean Annual Ta kes 

(CV in

parenthes

es) 

CA Klamath River tribal 

salmon gillnet 

fishery 

1994-98 

Stranding 

r 

e 

p 

o 

r 

t 

s 

n/a 1(1998) �1 �0.2 (n/a) 

Minimum total annual takes �0.2 (n/a) 

STATUS OF STOCK 

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

as depleted under the M arine Ma mmal Pro tection Act. There are no known habitat issues that are of particular 

concern for this stock. Because of the lack of recent or historical sources of human-caused mortality, the harbor 

porpoise stock in northe rn California h as been co ncluded to be within their Optimum Sustainable Population 

(OSP) level (Barlow and Forney 1994). Because the known human-caused mortality or serious injury (0.2 

harbor porpoise per year) is less than the PBR (161), 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) abunda nce estimatio n in California, O regon and Washin gton: 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 porpo ise 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. W hal., Special Issue 

16:123 -140. 

Calambokidis, J. and J. Barlow. 1991. Chlorinated hydroca rbon concentrations an d their use for describing pop ulation discreteness 

in harbor p orpoises fro m Wa shington, O regon, and California. pp. 101-110 In: J. E. Reynolds III and D. K. 

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

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

Forney, K. A. 1999a . The abundan ce of California harbor p orpoise estimated from 1993-97 aerial line-transect surveys. Admin. Rep. 

LJ-99-02. Southwest Fisheries Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA 92038. 

16 pp. 

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

55 
distribution? J. Cetacean Res. Manage. 1:73-80. 

Gaskin, D. E. 1984. The harbour porpoise (Phocoena phocoena L.): regional p opulations , status, and inform ation on dire ct and 

indirect catch es. Rep. int. W hal. Comm n 34:56 9-586. 

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. Brueg geman (ed .). Oregon and 

Washington Marine M ammal and Seabird S urveys. Minerals Management Service Contract Report 14-12­

0001-30426 prep ared for the Pacific OCS Region. 

Laake, J. L., J. C. Calambokidis, S. D. Osmek, and D . J. Rugh. 1997. P robability of detecting harbor p orpoise 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 . Wenz el, and G. E arly. 1995. W hat do strand ing data say about harbor porpoise (Phocoena phocoena). Rep. 

Int. Whal. Comm., Special Issue 16:169-179. 

Rosel, P. E. 1992. G enetic 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, an d M. G . Haygoo d. 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. 

56 
Revised 12/15/2000


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


STOCK DEFINITION AND GEOGRAPHIC RANGE 

In the eastern North Pacific Ocean, the harbor 

porpoise ranges from Point Barrow, along the 

Alaskan coast, and down the w est coast of N orth 

America to Point Conceptio n, California (G askin 

1984). Harbor po rpoise primarily frequent coastal 

waters. Harbor porpoise are known to occur yearround in the inland trans-boundary area of 

Washington and British Columbia, Canada 

(Osborne et al. 1988), and a long the 

Oregon/Washington coast (Ba rlow 198 8, Barlow et 

al. 1988, Green et al. 1992) . Aerial survey d ata 

from coastal Oregon and Washington, collected


during all seasons, suggests that harbor porpo ise


distribution varies by depth (Green et al. 1992).


Although distinct seasonal changes in abundance


along the west coast have been noted, and


attributed to possible shifts in distribution to deeper


offshore waters during late winter (Dohl et al. 1983,


Barlow 1988), harbor porpoise have also been


conspicu ously absent in offshore areas in late


November (B. Taylor, pers. comm.) leaving a gap


in the current understanding of their mo vements.


Stock discreteness in the eastern No rth Pacific was Figure 1. Approximate distribution of harbor porpo ise in


analyzed using mitochondrial DNA from samples the U.S. Pacific Northwest (shaded area). Stock


collected along the west coast (R osel 199 2) and is boundaries separating the stocks are shown.


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 clad es are not ge ographic ally distinct by latitude , the results may ind icate a low m ixing rate


for harbor porpoise along the west coast of North America. Investigation of pollutant loads in harbor po rpoise


ranging from California to the Canadia n borde r also suggests re stricted harb or porp oise move ments


(Calamb okidis and Barlow 199 1). Further ge netic testing of the same data mentioned a bove, alo ng with


additional samples, found significant genetic differences for four of the six pair-wise comparisons between the


four areas investiga ted: California , Washin gton, British C olumbia, a nd Alaska (Ro sel et al. 1995 ). These re sults


demonstrate that harbor porpoise along the west coast of North America are not panmictic or migratory, and


that movem ent is sufficiently restricted to evolve genetic differences. This is consistent with low movement


suggested by genetic analysis of harbor porpoise specimens from the North Atlantic, where numerous stocks


have been delineated with clinal differences over areas as small as the waters surroun ding the British Isles.


Using the 1990-91 aerial survey data of Calambokidis et al. (1993) for water depths < 50 fathoms, Osmek et


al. (1996) found significant differences in harbor porpoise mean densities (z=5.9, p<0.01) between the waters 

of coastal Oregon/W ashington and inland W ashington/southern British Columb ia, Canada (i.e., Strait of Juan 

de Fuca/San Juan Islands). Although differences in density exist between coastal Oregon/Washington and 

inland Washington, a specific stock boundary line cannot be identified based upon biological o r genetic 

differences. However, because harbor porpoise movem ents and rates of intermixing within the northeast Pacific 

are restricted, there has been a significant decline in harbor porpoise sightings within southern Puget Sound 

since the 1940s and, following a risk averse management strategy, two stocks are recognized to occur in Oregon 

and Washington waters (the Oregon/Washington Coast stock and the Inland Washington stock), with the 

boundary at Cape Flattery. Recent genetic evidence suggests that the population of eastern North Pacific harbor 

57 
porpoise is more finely struc tured than is cu rrently recognize d (S. Chive rs, pers. com m.). All relevan t data 

(e.g., genetic samp les, contamin ant studies, and satellite tagging) will be revie wed to de termine whe ther to 

adjust the stock bound aries for harbor porp oise in Oregon and Washington wa ters. 

In their assessment of California harbor porpoise, Barlow and Hanan (1995) recommended two stocks be 

recognized in California, with the stock boundary at the Russian River. Based on the above information, four 

separate harbor porpoise stocks are recognized to occur along the west coast of the continental U.S. (see Fig. 

1): 1) the Inland W ashington sto ck, 2) the O regon/W ashington C oast stock, 3 ) the North ern Californ ia stock, 

and 4) the Central California stock. This report considers only the Oregon/Washington Coast stock, with stock 

assessment reports for the Inland Washington and both California stocks appearing in this volume. Three 

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

Alaska, Gulf of Alaska, and Bering Sea stocks. The three Alaska harbor porpoise stocks are reported separately 

in the Stock Assessment Reports for the Alaska Region. The harb or porp oise occur ring in British Colu mbia 

have not been included in any stock assessment report from either the Alaska Region o r Pacific Northwest 

(Oregon/Washington). 

POPU LATIO N SIZE 

In August and September 1997, an aerial survey of Oregon, Washin gton, and so uthern British Columb ia coastal 

waters, from shore to 200 m depth, resulted in an observed abundance of 13,036 (CV=0.1 1) harbor porp oise 

in U.S. waters (Laake et al. 1 998a). Using a correction factor of 3.42 (1 /g(0); g(0)=0.292 , CV=0.36 6) to adjust 

for groups missed by aerial observers, the corrected estimate of abundance for harbor porpoise in coastal 

Oregon and Washington waters is 44,644 (CV=0.38). This estimate represents a substantial increase over the 

1991 estimate of 26,175 (Osmek et al. 1996) due to: 1) the larger sam pling region in the 1997 survey (out to 

water depths of 200 m vs. 91 m in 1991), and 2) a different estimate of g(0) (Laake et al. 1998a). 

Minimum Po pulation Estimate 

The minimum population estimate (NMIN) for this stock is calculated using Equation 1 from the PBR Guidelines 

(Wade and Angliss 199 7): N MIN = N/exp(0.842*[ln(1+[CV(N )]2

)]1⁄2). Using the population estimate (N) of 

44,644 and its associa ted CV (N) of 0.3 8, NMIN for the Oregon/Washington Coast stock of harbor p orpoise is 

32,769. 

Current Population Trend 

There are no reliab le data on population trends of harbor porpoise for coastal Oregon, Washington, or British 

Columbia waters. 

CURRENT AND M AXIMUM 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 O regon/Wash ington Coast 

harbor porpoise stock. 

POTENTIAL BIOLOGICAL REMOVAL 

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

(32,769) times one-half the de fault maximum net growth rate for cetaceans (1⁄2 of 4%) times a recovery factor 

of 0.5 (for a stock of unknown status, Wade and Angliss 1997), resulting in a PBR of 328 harbor porpoise per 

year. 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY 

Fisheries Information 

Within the EEZ boundaries of coastal Oregon and Washington, human-caused (fishery) mortalities of harbor 

porpoise are presen tly known to occur only in the northern Washington marine set gillnet fishery. During 1992­

1993 the WA /OR Lo wer Colum bia River, WA Grays Harbor, and WA Willapa Bay drift gillnet fisheries were 

58 
monitored at observer coverages of approximately 4% and 2%, respectively. There were no observed harbor


porpoise mo rtalities in these fisheries.


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


al. 1994, 2 000; P. G earin, unpub l. data); 199 4 observ er data rece ntly became available an d will be includ ed in 

a future stock assessment report. For the entire area fished (coastal + inland waters), observer coverage ranged 

from approximately 40 to 98% during tho se years. Fishing effo rt is conducte d within the range of both harbor 

porpoise stocks (Oregon/Washington Coast and Inland Washington stocks) occurring in Wa shington State 

waters. Some of the animals taken in the inland waters portion of the fishery (see the Inland Washington stock 

assessment report for details) ma y have been animals from the co astal stock. Sim ilarly, some of the animals 

taken in the coastal portion of the fishery may have been from the inland stock. For the purposes of this stock 

assessment report, the animals taken in the inland portion of the fishery are assumed to have belonged to the 

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

belonged to the Oreg on/W ashington C oast stock. Some movement of harbor porpoise between Washin gton’s 

coastal and inland waters is likely, but it is currently not possible to quantify the extent of such moveme nts. 

Accord ingly, Table 1 includes data only from that portion of the northern Washington marine set gillnet fishery 

occurring within the range of the Oregon/Washington Coast stock (those waters south and west of Cape 

Flattery), where observer coverage was 100 % in 199 5-1997 . No fishing effo rt occurred in the coastal portion 

of the fishery in 199 3 or 199 8. Data fro m 1993 to 1998 are included in Table 1, although the mean estimated 

annual mo rtality is calculated using the most recent 5 years of available data. The mean estimated mortality 

for this fishery is 12.4 (CV=0.46) harbor porpoise per year from this stock. 

Table 1. Summary of incidental mo rtality of harbor porpoise (Oregon/Washington Coast stock) in commercial and tribal 

fisheries and calcula tion of the mea n annual mo rtality rate; n/a indic ates that data are not available. Mean 

annual takes are based on 1994-98 data unless noted otherwise. 

Fishery name Years 

Data type 

Percent 

o 

b 

s 

e 

r 

v 

e 

r 

c 

o 

v 

e 

r 

a 

g 

e 

Observed 

mortality 

Estimated 

mortality 

Mean annual 

takes (CV in 

parenthes 

es) 

Northern WA marine s et gillnet 

(tribal fishery: coastal waters) 

93 

94 

95 

96 

97 

98 

obs data no fishery 

n/a 

100% 

100% 

100% 

no fishery 

0 

n/a 

20 

29 

13 

0 

0 

n/a 

20 

29 

13 

0 

12.4 (0.46)1 

Estimated t otal annual t akes 12.4 (0.46) 

1

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

The 1995-1997 data for the northern Washington marine set gillnet fishery were collected as part of an 

experime nt, 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 tha t the nets 

equipped with acoustic alarms had significantly lower entanglement rates, as only 2 of the 49 mortalities 

59 
occurred in alarmed n ets (Gearin et al. 1996 , 2000; L aake et al. 19 97). Harbor porpoise were displaced by an 

acoustic buffer aroun d the net, but it is unclear whether the porpoise were repe lled by the alarm s or whether it 

was their prey that were repelled (Kraus et al. 1997, Laake et al. 1998b). Because this fishery is likely to have 

acoustic devices on all nets in the future, the mean mortality estimated from non-alarmed nets may not be 

applicable. In 1997, 13 mortalities were observed (100% observer coverage) in this fishery and 96% of the sets 

were equipped with acoustic alarms (Gearin et al. 2000; P. Gearin, unpubl. data). 

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

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

the period between 1994 and 1998 , there were no fisher self-reports of harbor porpoise mortalities from any 

fisheries operating within the range of the Oregon/Washington Coast stock. However, because logbook records 

(fisher self-repo rts required during 19 90-94) are mo st likely negatively biased (Credle et al. 1994), these are 

considered to be minimum estimates. S elf-reported fisheries data ar e incomplete for 1994, not available for 

1995, a nd consid ered unre liable after 19 95 (see A ppendix 4 in Hill and D eMaste r 1998) . 

There have been no fishery-related strandings of h arbor po rpoise from this stock dating back to at least 1990. 

STATUS OF STOCK 

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

the Endangered Species Act. Based on the curre ntly available data, the level of human-caused mortality and 

serious injury (12) does not exceed the PBR (328). Therefore, the Oregon/Washington Coast stock of harbor 

porpoise is not classified as strategic. The total fishery mortality and serious injury for this stock (12; based 

on observer data) is not kno wn to exceed 10% o f the calculated PBR (33) and , therefore, can be consid ered to 

be insignificant and approaching zero mortality and seriou s injury rate. Th e status of this stock relative to its 

Optimum Sustainable Population (OSP) level and population trends is unknown. 

REFERENCES 

Barlow, J. 1988. H arbor po rpoise, Phoco ena ph ocoen a, abundance estimation for California, Oregon, and Washin gton: 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, a nd B. L. T aylor. 198 8. Harbo r porpo ise, Phoco ena ph ocoen a, 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 d iscreteness 

in harbor porpoises from Washington, Oregon, and California. Reynolds, J. E., III, and D. K. Odell (eds.), 

Proceedings of the second marine mammal stranding workshop: 3-5 December 1987, Miami, Florida. NMFS, 

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

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

1993. Abundance estimates of harbor porpo ise in Wash ington and O regon wate rs. Final Rep ort by Casc adia 

Research, Olympia, WA, to National Marine Mammal Laboratory, AFSC, NMFS, Seattle, WA. 55 pp. 

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

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

programs: minutes and recommendations from a workshop held in Galveston, Texas, November 10-11, 1993. 

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

Dohl, T. P., R. C. Guess, M. L. Duman, and R. C. Helm. 1983. Cetaceans of central and northern Ca lifornia, 1980-1983 : status, 

abundance, and distribution. OCS Study MMS 84-0045. Pacific OCS Region Minerals Management Service, 

1340 Sixth Street, Los Angeles, CA 90014. 284 pp. 

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

catches. Rep. Int. Whal. Commn. 34:569-586. 

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

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

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

Gearin, P. J., M. E. Gosho, L. Cooke, R. DeLong, and J. Laake. 1996. Acoustic alarm experiment in the 1995 northern Washington 

60 
marine setnet fishery: methods to reduce by-catch of harbor porpoise. Paper SC/48/SM1 0 presented to the 

International Whaling Commission, June 1996 (unpublished). 15 pp. 

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

(pingers) to reduce b ycatch of harb our porp oise, Phocoena phocoena, in the state of Washington. J. Cetacean 

Res. Manage. 2(1):1-9. 

Green, G. A., J. J. Brueggeman, R. A. Grotefendt, C. E. Bowlby, M. L. Bonnel, and K. C. Balcomb. 1992. Cetacean distribution and 

abundance off Oregon and Washington, 1989-1990 . Ch. 1, In: Brueggeman, J. J. (ed.), Oregon and Washington 

marine mammal and seabird surveys. Final Rep. OCS Study MMS 91-0093. 

Hill, P. S., and D. P. DeMaster. 1998. Alaska mar ine mamm al stock assessm ents, 1998 . U.S. Dep . Comme r., NOAA Tech. Memo. 

NMFS-AFSC-97. 166 pp. 

Kraus, S. D., A. J. Read, A. Solow, K. Baldwin, T. Spradlin, E. Anderson, and J. Williamson. 199 7. Acoustic alarms reduc e porpoise 

mortality. Nature 388:525. 

Laake, J. L., P. J. Gearin, M. E. Gosho, and R. L. DeLong. 1997. Evaluation of effectiveness of pingers to reduce incidental 

entanglement of harbor porpoise in a set gillnet fishery. Pp . 75-81, In: Hill, P. S., and D. P. DeMaster (eds.), 

MMPA and ESA Implementation Program, 1996. AFSC Processed Report 97-10. 255 pp. Available at 

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

Laake, J., J. Calamb okidis, and S . Osmek. 1 998a. Su rvey report for the 1997 aerial surveys for harbor porpoise and other marine 

mamma ls of Orego n, Wash ington and B ritish Columb ia outside wa ters. 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. 19 98b. O bservation s of harbor porpoise in the vicinity of aco ustic alarms on a set gillnet. 

U.S. Dep. Commer., NOAA Tech. Memo. NMFS-AFSC-84. 40 pp. 

Osborne, R., J. Calambokidis, and E . M. Dorsey. 19 88. A Guide to Marine M ammals of Greater P uget Sound. Island P ublishers, 

Anacortes, WA. 191 pp. 

Osmek, S. D., P. E. Rosel, A. E. Dizon, and R. L. DeLo ng. 1994 . Harbor porpoise , Phocoena phocoena, populatio n assessmen t in 

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

Resources, NMFS, NOAA , 1335 East-West Highway, Silver Spring, MD 20910. 14 pp. Available at National 

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

Osmek, S., J. Calambokidis, J. Laake, P. Gearin, R . DeLong, J. Sco rdino, S. Jeffries, and R. Brown. 1996. Assessment of the status 

of harbor p orpoises, Phocoena phocoena, in Oregon and Washington waters. U.S. Dep. Commer., NOAA 

Tech. Memo. NMFS-AFSC-76. 46 pp. 

Rosel, P. E. 1992. Genetic population structure and systematic relationships of some small cetaceans inferred from mitochond rial 

DNA sequence variation. Ph.D. Thesis, Univ. Calif. San Diego, La Jolla, CA. 191 pp. 

Rosel, P. E., A. E. Dizon, and M. G . Haygood. 1995. Variability of the mitochondrial control region in populations of the harbour 

porpoise, Phocoena phocoena, on inter-oceanic and regional scales. Can. J. Fish. and Aquat. Sci. 52:1210­

1219. 

Taylor, B. L. Southwest Fisheries Science Center, NMFS, P.O. Box 271, La Jolla, CA 92038. 

Wade, P. R., and R. Angliss. 1997. Guidelines for assessing marine mammal stocks: report of the GAMMS workshop April 3-5, 1996, 

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

61 
Revised 12/15/2000


HARBOR PORPOISE (Phocoena phocoena): Washington Inland Waters Stock


STOCK DEFINITION AND GEOGRAPHIC RANGE 

In the eastern North Pacific Ocean, the harbor 

porpoise ranges from Point Barrow, along the 

Alaskan coast, and dow n the west coa st of North 

America to Point C onceptio n, California (G askin 

1984). Harbor porpoise primarily frequent coastal 

waters. Harbor porpoise are known to occur yearround in the inland trans-boundary area of 

Washington and British Columbia, Canada 

(Osborne et al. 1988 ), and along the 

Oregon/Washington coast (Barlow 1988, Barlow 

et al. 1988, Green et al. 1992). Aerial survey data 

from coastal Oregon and Washington, collected 

during all seasons, suggests that harbor porpo ise 

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 s hifts in distribution to 

deeper offshore waters during late winter (Dohl et 

al. 1983, Barlow 1988), harbo r porpoise have also 

been conspicuo usly absent in offshore areas in late Figure 1. Approximate distribution of harbor porp oise


November (B. Taylor, pers. comm.) leaving a gap in the U.S. Pacific Northwest (shaded area). Stock


in the current understanding of their mo vements. boundaries separating the stocks are shown.


Stock discreteness in the eastern No rth Pacific was


analyzed using mitochondrial DNA from samples


collected along the we st coast (Ro sel 1992 ) and is summ arized 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 a re not geog raphically distinc t by latitude, the resu lts may indicate a low mixing ra te for harbor


porpo ise along the w est coast of N orth Ame rica. Investigation of pollutant loads in harbor porpoise ranging


from California to the Canadian border a lso suggests res tricted harb or porp oise move ments (Cala mbokid is and


Barlow 1991). Further genetic testing of the same data mentioned above, along with additional samples, found


significant genetic differences for four of the six pair-wise comparisons between the four areas investigated:


California, Washington, British Columbia, and Alaska (Rosel et al. 1995). These results demonstrate that


harbor porpoise along the west coast of North America are not pan mictic or migr atory, and that mo vement is


sufficiently restricted to evolve genetic differences. This is consistent with low movement suggested by genetic


analysis of harbor porpoise specimens from the North Atlantic, where numerous stocks have been delineated


with clinal differences over areas as small as the waters surrou nding 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 Island s). Although d ifferences in de nsity exist betwee n coastal O regon/W ashington and


inland Washin gton, a spec ific stock bou ndary line can not be iden tified based u pon bio logical or ge netic


differences. However, because harbor porpoise movements and rates of intermixing within the northeast Pacific


are restricted, there has been a significant decline in harbor porpoise sightings within southern Puget Sound


since the 1940s and, following a risk averse management strategy, two stocks are recognized to occur in Oregon


and Washington waters (the Oregon/Washington Coast stock and the Inland Washington stock), with the


boundary at Cape Flattery. Recent genetic evidence suggests that the population of eastern North Pacific harbor


porpoise is more finely structured than is currently recognized (S. Chivers, pers. comm.). All relevant data


62 
(e.g., genetic samples, contaminant studies, and satellite tagging) will be revie wed to de termine whe ther to 

adjust the stock bound aries for harbor porp oise in Oregon and Washington wa ters. 

In their assessment of California harbor porpoise, Barlow and Hanan (1995) recommended two stocks be 

recognized in California, with the stock boundary at the Russian River. Based on the above information, four 

separate harbor porpoise stocks are recognized to occur along the west coast of the continental U.S. (see Fig. 

1): 1) the Inland Washington stock, 2) the Oregon/W ashington Coast stock, 3) the Northern California stock, 

and 4) the Central California stock. This report considers only the Inland Washington stock, with stock 

assessment reports for the Oregon/Washington Coast and both California stocks appearing in this volume. 

Three harbor porpoise stocks are also recognized in the inland and coastal waters of Alaska, including the 

Southeast Alaska, Gulf of Alaska, and Bering Sea stocks. The three Alaska harbor porpoise stocks are reported 

separately in the Stock Assessment Reports for the Alaska R egion. The harbor p orpoise occurring in B ritish 

Columb ia have not been included in any stock assessment report from either the Alaska Region or Pacific 

Northwest (Oregon/Washington). 

POPU LATIO N SIZE 

Aerial surveys of the inside waters of Washington and southern British Columbia were conducted d uring August 

of 1996 (C alambok idis et al. 1997 ). These ae rial surveys included the Strait of Juan de Fu ca, San Juan Islands, 

Gulf Islands, and Strait of Georgia, which includes waters inhabited by harbor porpoise from British Columbia, 

as well as the Inland Washington stock. A total of 2,117 km of survey effort was completed within U .S. waters, 

resulting in an uncorrected abundance of 1,025 (CV=0.151) harbor porpoise in the inside waters of Washington 

(Calambokidis et al. 1997, Laake et al. 1997a). When corrected for availability and perception bias, using a 

correction factor of 3.42 (1/g(0); g(0)=0.292, CV=0.366), the estimated abundance for the Inland Washington 

stock of harbor porpoise is 3,509 (CV=0.396) animals (Laake et al. 1997a, 1997 b). 

Minimum Po pulation Estimate 

The minimum population estimate (NMIN) for this stock is calculated using Equation 1 from the PBR Guidelines 

(Wade and Angliss 199 7): N MIN = N/exp(0.842*[ln(1+[CV(N )]2

)]1⁄2). Using the population estimate (N) of 

3,509 a nd its associate d CV(N ) of 0.396 , NMIN for the Inland Washington stock of harbor porpoise is 2,545. 

Current Population Trend 

There are no reliable data on long-term population trends of harbor porpoise for most waters of Oregon, 

Washington, or British C olumbia. F or comp arability to the 199 6 survey, a re-analysis of the 1991 aerial survey 

data was cond ucted (Ca lambokid is et al. 1997 ). The abund ance of harbor po rpoise in the Inland Washington 

stock in 199 6 was not sign ificantly different than in 1991 (L aake et al. 19 97a). 

A different situation exists in southern Puget Sound where harbor porpoises are now rarely observed, a sharp 

contrast to 1942 when they were considered common in those waters (Scheffer and Slipp 1948). Although 

quantitative data for this area are lacking, marine mammal survey effort (Everitt et al. 1980), stranding records 

since the early 1 970s (O smek et al. 19 95), and th e results of harb or porp oise surveys o f 1991 (C alambok idis 

et al. 1992) and 199 4 (Osme k et al. 1995 ) indicate that ha rbor po rpoise ab undance 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 sig hting conditio ns produ ced no sigh tings of harbo r porpo ise in southern Puget Sound. 

Reasons for the apparent decline are unknown, but it may be related to fishery interactions, pollutants, vessel 

traffic, or other activities that may affect harbor p orpoise o ccurrence and distribu tion in this area (O smek et al. 

1995). Research to identify trends in harbor porpoise abundance is also needed for the other areas w ithin inland 

Washington. 

CURRENT AND M AXIMUM NET PRODUCTIVITY RATES 

A reliable estima te 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 

produc tivity rate (RMAX) of 4% (Wade and Angliss 1997) be employed for the Inland Washington harbor 

porpoise stock. 

63 
POTENTIAL BIOLOGICAL REMOVAL 

The potential bio logical remo val (PB R) level for this stock is calculated as the minimum population size (2,545) 

times one-half the default maximum net growth rate for cetaceans (1⁄2 of 4%) times a recovery factor of 0.40 

(for a stock of unknown status with a mortality rate CV�0.80, Wade and Angliss 1997), resulting in a PBR of 

20 harbor porpoise per year. 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY 

Fisheries Information 

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

al. 1994, 2 000; P. G earin, unpub l. data); 199 4 observ er data rece ntly became available and will be inc luded in 

a future stock assessment report. For the entire area fished (coastal + inland waters), observer coverage ranged 

from approximately 40 to 98% during those years. Fishing effo rt is conducte d within the range of both harbor 

porpoise stocks (Oregon/W ashington Coast and Inland Washington stocks) occurring in Wa shington State 

waters. Some of the animals taken in the inland waters portion of the fishery may have been animals from the 

coastal stock. Similarly, some of the animals taken in the coastal portion of the fishery (see the 

Oregon/Washington Coast stock assessment report for details) may have been from the inland stock. For the 

purposes of this stock assessment report, the animals taken in the inland portion of the fishery are assumed to 

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

assumed to have be longed to the Oregon/Washington Coast stock. Some movement of harbor porpoise between 

Washin gton’s coastal and inland waters is likely, but it is currently not possible to quantify the extent of such 

movements. Accord ingly, Table 1 includes d ata only from that portion of the northern Washington marine set 

gillnet fishery occurring within the range of the Inland W ashington stock (those waters east of Cape Flattery), 

where observer coverage ranged from 6 to 80% between 19 93 and 1998. Data from 1993-199 8 are included 

in Table 1, although the mean estima ted annual m ortality is calculated using the mos t recent 5 years of availab le 

data. No mortalities were observed in the inland po rtion of the fishery b etween 19 93 and 1 998. Little effort 

occurred in the inland po rtion of the fishery in 1 995, 19 97, or 19 98. The mean estimated morta lity for this 

fishery is zero harbor porpoise per year from this stock. 

In 1993, as a pilot for future ob server programs, N MFS in con junction with the Washingto n Department o f Fish 

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

gillnet fishery (Pierc e et al. 1994). O bserver co verage wa s 1.3% o verall, ranging from 0.9% to 7.3% for the 

various components of the fishery. No harbor porpoise mortalities were reporte d (Tab le 1). Pierce et al. 

(1994) cautioned against extrapolating these mortalities to the entire Puget Sound fishery due to the low 

observer coverage and potential biases inherent in the data. The area 7/7A sockeye landings represented the 

majority of the non-treaty salmon landings in 1993, approximately 67%. Results of this pilot study were used 

to design the 1 994 ob server pro grams discu ssed belo w. 

In 1994, NMFS in conjunction with WDFW conducted an observer program during the Puget Sound no n-treaty 

chum salmon gillnet fishery (areas 1 0/11 and 12/12B ). A total of 23 0 sets were observed d uring 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 land ings (Erstad et al. 1996 ). No harbor porpoise were reported within 

100 m of obse rved 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 (N WIFC 1995). No harbor porpoise mortalities were reported in the observer 

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

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

respectively. 

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

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

fishery (areas 7 and 7A). During this fishery, observers monitored 2,205 sets, representing approximately 7% 

of the estimated 33,086 sets occurring in the fishery (Pierce et al. 1996). There was one observed harbor 

porpoise mortality (one other was entangled and released alive with no indication the animal was injured), 

resulting in a mortality rate of 0.00045 harbor porpoise per set, which extrapolates to 15 mortalities (CV=1.0) 

for the entire fishery. In 1996 , Washington S ea Grant P rogram c onducted a test fishery in the non -treaty 

64 
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 lo w-frequenc y sound em itters attached to the corkline (M elvin et al. 1997 ). In 642 sets during 17 

vessel trips, 2 ha rbor po rpoise wer e killed in the 50 mesh gear. 

Combining the estimates from the 1994 observer programs (15) with the northern Washington marine set gillnet 

fishery (0) results in an estimated mean mortality rate in observed fisheries of 15 harbor porpoise per year from 

this stock. It should be noted that the 199 4 observ er programs did not sample all segments of the entire 

Washington Puget Sound Region salmon set/drift gillnet fishery, and further , the extrapo lation 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. Thou gh it is not possib le to quantify wha t percentag e of the 

Washington Puget Sound Region salmon set/drift gillnet fishery was actually observed in 1994, the observer 

programs cove red 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.). 

Accord ingly, the estimated harbor porpoise mortality (15) appears to be only a sli ght underestimate for the 

fishery. See Append ix 1 for additional information regard ing the Washington P uget Sound Reg ion salmon 

set/drift gillnet fishery. 

Table 1. Summary of incidental mortality of harbor porpoise (Inland Washington stock) due to commercial and tribal 

fisheries and calculation of the mean annual mortality rate; n/a indicates that data are not available. Mean 

annual takes are based on 1994-98 data unless noted otherwise. 

Fishery name Years 

Data type 

Percent 

observer 

c 

o 

v 

e 

r 

a 

g 

e 

Observed 

mortality 

Estimated 

mortality 

Mean annual 

takes 

(CV in 

parent 

heses) 

Northern WA marine s et gillnet 

(tribal fishery: inland waters) 

93 

94 

95 

96 

97 

98 

obs data 61% 

n/a 

24% 

6% 

80% 

40% 

0 

n/a 

0 

0 

0 

0 

0 

n/a 

0 

0 

0 

0 

01 

WA Puget Sound Region salmon 

set/drift gilln et 

(observer programs 

listed below covered 

segments of this 

fishery): 

- - - - - ­

Puget Sound non-treaty salmon 

gillnet (all areas and species) 

93 obs data 1.3% 0 0 see text 

Puget Sound non-treaty chum 

salmon gillnet (areas 10/11 and 

12/12B) 

94 obs data 11% 0 0 0 

Puget Sound treaty chum 

salmon gillnet (areas 12, 12B, 

and 12C) 

94 obs data 2.2% 0 0 0 

65 
Fishery name Years 

Data type 

Percent 

observer 

c 

o 

v 

e 

r 

a 

g 

e 

Observed 

mortality 

Estimated 

mortality 

Mean annual 

takes 

(CV in 

parent 

heses) 

Puget Sound treaty chum and 

sockeye salmon gillnet (areas 

4B, 5, and 6C) 

94 obs data 7.5% 0 0 0 

Puget Sound treaty and nontreaty sockeye salmon gi llnet 

(areas 7 and 7A) 

WA Puget Sound Region salmon 

set/drift gilln et 

Minimum total annual t akes 

94 obs data 7% 1 15 15 (1.0) 

Reported 

mort 

alitie 

s 

94-98 self 

reports 

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

n/a 

n/a see text 

�15 (1.0) 

1

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

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

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

the period between 1994 and 1998, there were no fishery self-reports of any harbor porpoise mortalities from 

the Washington Puget Sound Region salmon set and drift gillnet fishery (Tab le 1). Unlike the 1994 observer 

program data, the self-rep orted fisheries data cove r the entire fishery. H owever, because logbook records 

(fisher self-reports required during 1990-94) are most likely nega tively biased (C redle et al. 1994), these are 

considered to be minimum estimates of harbor p orpoise m ortality. Self-repo rted fisheries da ta are incom plete 

for 1994, not available for 1995, and considered unreliable after 1995 (see Appendix 4 of Hill and DeMaster 

1998). 

Strandings of harbor porpoise wrapped in fishing gear or with injuries caused by interactions with gear are a 

final source of fishery-related m ortality informatio n. No fishery-related strandings of harbor porpoise occurred 

during 1994-1998. 

There a re few data concernin g the mortality of marine m ammals incid ental to com mercial gillnet fishe ries in 

Canadian waters, which have no t been monitored b ut are known to have taken h arbor porpo ise in the past 

(Barlow et al. 1994, Stacey et al. 1997). As a result, the number of harbor porpoise from this stock curre ntly 

taken in the wa ters of souther n British Co lumbia is not k nown. 

STATUS OF STOCK 

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

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

injury (15) is not known to exceed the PBR (20). Therefore, the Inland Washingto n harbor porp oise stock is 

not classified as strategic. The minimum total fishery mortality and serious injury for this stock (15) exceeds 

10% of the calculated PBR (2.0) and, therefore, cannot be considered to be insignificant and approaching zero 

mortality and serious injury rate. The status of this stock relative to its Optimum Sustainable Population (OSP) 

level and population trends is unknown, although harbor porpoise sightings in southern Puget Sound have 

declined since the 194 0s. 

66 
Although this stock is not recognized as strategic at this time, there is cause for concern due to the following 

issues: 1) the estimated take level is close to exceeding the PBR, 2) the extent to which harbor porpoise from 

U.S. waters frequent the waters of British Columbia, and are therefore sub ject to fishery-relate d mortality, is 

unknown, and 3) the mortality rate is based on observer data from a subset of the Washington Puget Sound 

Region sa lmon set and gillnet fishery. 

REFERENCES 

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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 

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Barlow, J., C. W. O liver, T. D. J ackson, an d B. L. T aylor. 198 8. Harbo r porpo ise, Phoco ena ph ocoen a, abundance estimation fo r 

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

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and the east coast of the Russian Federation. Rep. Int. Whal. Commn. Special Issue 15:405-425. 

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

in harbor porpoises from Washin gton, Oreg on, and C alifornia. In: Reynolds, J. E., III, and D. K. Odell (eds.), 

Proceedings of the second marine mammal stranding workshop: 3-5 December 1987, Miami, Florida. NMFS, 

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

Calambokidis, J., J. R. Even son, J. C. Cu bbage, P . J. Gearin, an d S. D. O smek. 1992. Harbor porpoise distribution and abundance 

off Oregon and W ashington from aerial surve ys in 1991. F inal Repo rt by Cascad ia Research, Olympia, WA, 

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

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

1993. Abundance estimates of harbor porpoise in Washington and Oregon waters. Final Repo rt by Cascad ia 

Research, Olympia, WA, to National Marine Mammal Laboratory, AFSC, NMFS, Seattle, WA. 55 pp. 

Calambokidis, J., S. D. Osmek, and J. L. Laake. 1 997. Ae rial surveys for m arine mam mals in Washington and British Columbia inside 

waters. Final Report by Cascadia Research, Olympia, WA, to National Marine Mammal Laboratory, AFSC, 

NMFS, Seattle, WA. 96 pp. 

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

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

programs: minutes and recommendations from a workshop held in Galveston, Texas, November 10-11, 1993. 

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

Dohl, T. P., R. C. Guess, M . L. Duma n, and R. C. Helm. 19 83. Cetaceans of central and northe rn California, 1980-19 83: status, 

abundance, and distribution. OCS Study MMS 84-0045. Pacific OCS Region Minerals Management Service, 

1340 Sixth Street, Los Angeles, CA 90014. 284 pp. 

Erstad, P., S. J. Jeffries, and D. J. Pierce. 1996. 1994 Repo rt for the Puget Sound fishery observer program in management areas 10/11 

& 12/12B: nontreaty chum gill net fishery. Final Report, Washington Dept. Fish and Wildlife, Olympia, WA. 

14 pp. 

Everitt, R. D., C. H. Fiscus, and R. L. DeLong. 1980. Northern Puget Sound marine mamma ls. U.S. De p. Comm er., 

EPA-6000/7-80-139. 134 pp. 

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

indirect catches. Rep. Int. Whal. Commn. 34:569-586. 

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

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

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

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

(pingers) to reduce b ycatch of harb our porp oise, Phocoena phocoena, in the state of Washington. J. Cetacean 

Res. Manage. 2(1):1-9. 

Green, G. A., J. J. Brueggeman, R. A. Grotefendt, C. E. Bowlby, M. L. Bonnel, and K. C. Balcomb. 1992. Cetacean distribution and 

abundance off Oregon and Washington, 1989-1990 . Ch. 1, In: Brueggeman, J. J. (ed.), Oregon and Washington 

67 
Marine Mammal and Seabird Surveys. Final Rep. OCS Study MMS 91-0093. 

Hill, P. S., and D . P. DeM aster. 1998 . Alaska marine mammal stock assessments, 1998. U.S. Dep. Commer., NOAA Tech. Memo. 

NMFS-AFSC-97. 166 pp. 

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

and British Colu mbia inside waters, 199 6. Pp. 67 -73, In: MMP A and ESA Implementation Program, 1996. 

AFSC Processed Report 97-10. 255 pp. Available at National Marine Mammal Laboratory, 7600 Sand Point 

Way NE, Seattle, WA 98115. 

Laake, J. L., J. Calambokidis, S. D. Osmek, and D. J. Rugh. 19 97b. Prob ability of detecting harbor porp oise from aerial surveys: 

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

Melvin, E. F., L. L. Conquest, and J. K. Parrish. 1997. Seabird bycatch reduction: new tools for Puget Sound drift gillnet salmon 

fisheries. 1996 Sockeye and 199 5 Chum Salmon Test Fisheries Final Report. Washington Sea Grant Program, 

Seattle, WA. 48pp. 

Northwest Indian Fishe ries Comm ission. 1995 . Monito ring of marb led murrele t and marine mamma l interactions with 1 994 tribal 

gillnet fisheries in northern Puget Sound, Hood Canal, and the Strait of Jua n de Fuca . Final Report to NMFS 

Contract No. 52 ABNF 400087 . Unpubl. report. No rthwest Indian Fishe ries Comm ission. 43 pp. A vailable 

at NWIFC, 6730 Martin Way E, Olympia, WA 98516. 

Osborne, R., J. Calambokidis, and E. M. D orsey. 1988. A G uide to Marine M ammals of Greater P uget Sound. Island P ublishers, 

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. 199 3 Annual Rep ort to the MM PA Assessmen t Program, Office of P rotected Resourc es, 

NMFS, NOA A, 1335 East-W est Highwa y, Silver Spring , MD 2 0910. 1 4 pp. Available at National Marine 

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

Osmek, S. D., M. B. Hanson, J. L. Laake, S. J. Jeffries, and R. L. DeLong. 1995. Harbor porpoise Phocoena phocoena population 

assessment studies for Oregon and Washington in 1994. 1994 Annual Report to the MMPA Assessment 

Program, Office of Protected Resources, NMFS, NOAA, 1335 East-West Highway, Silver Spring, MD 20910. 

32 pp. Available at National Marine Mammal Laboratory, 7600 Sand Point Way NE, Seattle, WA 98115. 

Osmek, S., J. Calambokidis, J. Laake, P. Gearin, R. DeLong, J. Scordino, S. Jeffries, and R. Brown. 1996. Assessment of the status 

of harbor p orpoises, Phocoena phocoena, in Oregon and Washington waters. U.S. Dep. Commer., NOAA 

Tech. Memo. NMFS-AFSC-76. 46 pp. 

Pierce, D . J., W. P. Ritchie, and R. Kreuziger. 1994. Preliminary findings of seabird interactions with the non-treaty salmon gill net 

fishery: Puget So und and H ood Ca nal Wa shington. Un publ. 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 Rep ort, Wa shington D ept. Fish and 

Wildlife, Olympia, WA. 21 pp. 

Rosel, P. E. 1992. Genetic population structure and systematic relationships of some small cetaceans inferred from mitochondrial 

DNA sequence variation. Ph.D. Thesis, Univ. Calif. San Diego, La Jolla, CA. 191 pp. 

Rosel, P. E., A. E. Dizon, and M. G. Haygood. 1995. Variability of the mitochondrial control region in populations of the harbour 

porpoise, Phocoena phocoena, on inter-ocea nic and region al 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. Du ffus. 1997. A preliminary ev aluation of incidental mortality of small cetaceans in coastal 

fisheries in British C olumbia, C anada. M ar. Mam mal Sci. 13 :321-32 6. 

Taylor, B. L. Southwest Fisheries Science Center, NMFS, P.O. Box 271, La Jolla, CA 92038. 

Wade, P. R., and R. Angliss. 1997. Guidelines for assessing marine mammal stocks: report of the GAMMS workshop April 3-5, 1996, 

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

68 
Revised 12/15/2000 

DALL'S PORPOISE (Phocoenoides dalli): 

California/Oregon/Washington Stock 

STOCK DEFINITION AND GEOGRAPHIC RANGE 

Da ll's porpoise are endemic to temperate waters of the 

North Pacific Ocean. Off the U.S. west coast, they are 

commo nly seen in shelf, slope and offshore waters 

(Figure 1; Morejohn 1979). Sighting patterns from aerial 

and shipboard surveys conducted in California, Oregon 

and Washin gton 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 populatio n's range is not we lldocumented, but they are co mmonly s een off Southern 

California in winter, and during cold-water periods they 

probab ly range into Mexican waters off northern Baja 

California. The stock structure of eas tern North Pacific 

Da ll's porpoise is not known, but based on patterns of 

stock differentiation in the western North Pacific, where 

they have been more intensiv ely studied, it is expected 

that separate stocks will emerge when data become 

available (Perrin and Brownell 1994). Alth oug h Da ll's 

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

are no cooperative management agreements with Mexico 

or Canada for fisheries which may take this species (e.g. 

gillnet fisheries). For the Marine Mammal Protection 

Act (MMP A) 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 W ashington (this 

report), and 2) Alaskan waters. 

POPU LATIO N SIZE 

Figure 1. Dall’s porpoise sightings based on aerial 

and shipb oard surve ys off California, Oregon and 

Washington, 1991-96 (see Appendix 2, Figures 1­

5, for data sources and information on timing and 

location of survey effort). Dashed line represents 

the U.S. EEZ, thick line indicates the outer 

boundary of all surveys combined. 

Shipboard surveys are expected to be more reliable for this species than aerial surveys because of the large, 

unknown fraction of diving anima ls missed from the air (Forne y 1994). T hree summ er/fall shipboa rd surveys 

were conducted within 300 nmi of the coasts of Ca lifornia in 1991 and 1993 (B arlow and Gerrodette 1996) and 

California, Oregon and Washington in 1996 (Barlow 1997). The distribution of Dall’s po rpoise thro ughout 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 

oceano graphic conditions change, a multi-year average abundance estimate is the most appropriate for 

management within U.S. waters. The 1991-96 weighted average abundance estimate for California, Oregon 

and Washington waters based on the three ship surv eys is 116,0 16 (CV = 0.45) D all’s porpoise (Barlow 1997). 

Additional aerial surveys w ere cond ucted in the inlan d waters of W ashington in 1991 and 199 6, resulting in 

Dall’s porpoise abundance estimates of 2,747 (CV=0.48) in 1991, and 900 (C V=0.4 0) in 199 6 (Calam bokidis 

et al. 1997), with a weighted average estimate of 1,509 (CV=0.46). Both estimates include approx imate 

correction factors for animals missed due to perception and availab ility bias. Comb ining the avera ge estimate 

for inland W ashington wa ters with the 19 91-96 o uter coast estim ate of Barlow (1997) yields a total abundance 

estimate of 117,545 (CV=0.45) D all’s porpoise for the California/Oregon/Washington stock. 

69 
Minimum Po pulation Estimate 

The log-normal 20th perc entile of the 1991-96 we ighted average abund ance estimate for both the outer co ast 

of California, Oregon and Washington and inland Washington waters is 81,866 Dall's porpoise. 

Current Population Trend 

No information is available regarding trends in abundance of Dall's porpoise in California, Oregon and 

Washington. Their distrib ution and ab undance in this region varies consider ably at both seasonal and 

interannual time scales as oceanographic conditions vary (Forney 1997; Forney and Barlow 1998). 

CURRENT AND M AXIMUM NET PRODUCTIVITY RATES 

No information o n current or m aximum ne t productiv ity rates is available for Dall's porpoise off the U.S. west 

coast. 

POTENTIAL BIOLOGICAL REMOVAL 

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

(81,866) times one half the default maximum net growth rate for cetaceans (1⁄2 of 4%) times a recovery factor 

of 0.45 (for a species of unknown status and a mortality rate CV>0.60 and �0.80; Wade and Angliss 1997), 

resulting in a PB R of 737 Dall’s porp oise per yea r. 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY 

Fishery Information 

A summary of recent fishery mortality and injury for this stock of Dall’s porpoise is given in Table 1. More 

detailed info rmation on these fisheries is pro vided in A ppendix 1. Mortality estimates for the California d rift 

gillnet fishery are included for the five most recent years of monitoring, 1994-98 (Julian and Beeso n 1998; 

Julian 1997; Cameron and Forney 1999). After the 1997 implementation of a Take Reduction Plan, which 

included skipper education workshops and required the use of p ingers and m inimum 6-fatho m extende rs, overall 

cetacean entanglement rates in the drift gillnet fishery dropped considerably (Barlow and Cameron 1999). 

However, because of interannual variability in entanglement rates and the relative rarity of Dall’s porp oise 

entanglements, additional years of data will be required to fully evaluate the effectiveness of pingers for 

reducing mortality of this pa rticular specie s. Because of the change s in this fishery after implementation of the 

Take Reductio n Plan, mea n annual take s in Table 1 are based only on 1997-98 data. This results in an average 

estimate of 10 (CV = 0 .95) Da ll’s porpoise taken annua lly. 

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

and may take some Dall's porpoise from the same population during cold-water periods. Quantitative data are 

available only for the Mexican swordfish drift gillnet fishery, which uses vessels, gear, and operational 

procedures similar to those in the U.S. drift gillne t fishery, although n ets may be up to 4.5 km long (Holts and 

Sosa-Nishizaki 1998). T he fleet increased from two vessels in 1986 to 31 vessels in 1993 (Holts and SosaNishizaki 1998). The total number of sets in this fishery in 1992 can be estimated to be approximately 2700, 

with an observed rate of marine ma mmal byca tch of 0.13 animals per set (10 mar ine mamm als 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 spec ies-specific 

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

Mexica n swordfish d riftnet fishery to a long line fishery (D. H olts, pers. com m.). 

Low levels of mortality for Dall’s porpoise have a lso been documented in the California/Oregon/Washington 

domestic groundfish trawl fisheries (Perez and Loughlin 1991; Perez, in prep). Between 1994 and 1998, with 

54%-77% of the fishing effort observed, five Dall’s porpoise were reported killed in the at-sea processing 

portion of the Pacific whiting trawl fishery, and five animals were reported in unmonito red hauls.. Based o nly 

on the systematically observed hauls, Dall’s porpoise mortality was estimated to be five (CV=0.44) in 1997 and 

three (CV=0.33) in 1998 (Perez, in prep). Combining these estimates with the three reported mortalities for 

1994 and 1996 that are not accounted for in the estimates, the minimum average annual mortality for 1994-98 

70 
is 2.0 (CV =0.23) Dall’s porp oise per yea r. 

STATUS OF STOCK 

The status of Dall's porpoise in California, Oregon and Washington relative to OSP is not known, and there are 

insufficient data to eva luate potentia l trends in abundan ce. No ha bitat issues are kn own to be of concern for 

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

"deple ted" under the MMP A. Including driftnet mortality only for years after implementation of the Take 

Reduction Plan (1997-98), the average annual human-cau sed morta lity in 1994-9 8 (12 anim als) is estimated 

to be less than the PBR (737), and therefore they are not classified as a "strategic" stock under the MMPA. The 

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

can be considered to be insignificant and approaching zero mortality and serious injury rate. 

Table 1. Summary of available inform ation on the incidental mortality and injury of D all's porpoise (California/ 

Oregon/Washington Stock) in commercial fisheries that might take this species. All o bserved e ntanglemen ts 

of Dall's porpo ise resulted in the death of the anima l. Coefficients of variation for mortality estimates are 

provided in parenthese s; n/a = not ava ilable. Mean annual takes are based on 1994-98 data unless noted 

otherwise. 

Fishery Name 

CA/OR thresher 

shark/swordfish 

drift gillnet 

fishery 

WA/OR/CA domestic 

groundfish 

trawl fisheries 

(At-sea 

processing 

Pacific whiting 

fishery only). 

Data Type Year(s) 

Percent 

Ob 

ser 

ve 

r 

Co 

ve 

ra 

ge 

Observed 

Mortality 

Estimated Annual 

Mortalit 

y 

Mean Annual 

Takes 

(CV in 

parenthe 

ses) 

observer 

data 1994 

1995 

1996 

1997 

1998 

17.9% 

15.6% 

12.4% 

23.0% 

20.0% 

2 

1 

2 

4 

0 

11 (0.64) 

6 (0.92) 

24 (0.68) 

20 (0.95) 

0 10 (0.95)1 

observer data 

unmonitored 

hauls 

1994 

1995 

1996 

1997 

1998 

1994 

1996 

1997 

53.8% 

56.2% 

65.2% 

65.7% 

77.3% 

0 

0 

0 

3 

2 

2 

1 

2 

0 

0 

0 

5 (0.44) 

3 (0.33) 

1.6 (0.23) 

0.6 (n/a) 

Minimum total annual takes 12 (CV=0.79) 

1 Only 1997-98 mortality estimates are included in the average because overall cetacean entanglement rates dropped considerably after a Take 

Reduction Plan was implemented in 1997. 

REFERENCES 

Barlow, J. 1995. The ab undance of cetacean s in California w aters. Part I: Sh ip surveys in sum mer and fall o f 1991. Fish. Bull. 93:1­

14. 

Barlow, J. 	1997. Preliminary estimates of cetacean abundance off California, Oregon and Washington based on a 1996 ship survey 

and comparisons of passing and closing modes. Admin. Rep. LJ-97-11. Southwest Fisheries Science Center, 

National Marine Fisheries Service, P.O. Box 271, La Jolla, CA 92038. 25p. 

71 
Barlow, J. and T. Gerrodette. 1996. Abundance of cetaceans in California waters based on 1991 and 1993 ship surveys. U.S. Dep. 

Comm er., NOA A Tech . Memo . NMF S-SW FSC-23 3. 15 pp . 

Barlow, J. and G. A. Cameron. 1999. Field expe riments show that acoustic p ingers reduc e marine m ammal byc atch in the Ca lifornia 

drift gillnet fishery. Paper SC/51/SM2 presented to the International Whaling Commission, May 1998. 20 pp. 

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

waters. Final Contract Report for Contract 52ABNF-6-00092, available from Cascadia Research Collective, 

Waterstreet Building 218 1⁄2 West Forth Avenue, Olympia, Washington 98501. 

Cameron, G., and K . A. Forney. 1 999. E stimates of cetacean mortality in the California gillnet fisheries for 1997 and 1998. Paper 

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

Forney, K. A. 199 4. Recent in formation o n the status of od ontocetes in Californian w aters. U.S. Dep. Commer., NOAA Tech. Memo. 

NMFS-SWFSC-202. 87 pp. 

Forney, K. A. 199 7. 	 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 th e abundance and distribution of California cetaceans, 1991-92. Mar. 

Mamm. Sci. 14:460-489. 

Forney, K. A., J. B arlow and J. V. Carre tta. 1995. T he abund ance of ceta ceans in Ca lifornia waters. P art II: Aerial surv eys in winter 

and spring of 1991 and 1992. Fish. Bull. 93:15-26. 

Green, G., J. J. Brueggeman, R. A. Grotefendt, C. E. Bowlby, M. L. Bonne ll, and K. C. B alcomb, II I. 1992. Cetacean distribution and 

abundance off Orego n and W ashington. C h. 1. In: Oregon and Washington Ma rine Mammal and Seabird 

Surveys. OCS Study 91-0093. Final Report prepared for P acific OCS Region, Minerals Management Service, 

U.S. De partment o f the Interior, Lo s Angeles, C alifornia. 

Green, G., R. A. Grotefendt, M. A. Smultea, C. E. Bowlby, and R. A. Rowlett. 1993. Delphinid aerial surv eys in Oregon and 

Washington waters. Final Report prepared for NMFS, National Marine M ammal Laboratory, 7600 Sand Po int 

Way, NE, Seattle, Washington, 98115, Contract #50ABNF200058. 

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

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

Sosa-Nishizaki and N. B artoo (ed s.). Biology a nd fisheries of sw ordfish, Xiphias g ladius. Papers from the 

International Symposiu m on Pa cific Sword fish, Ensenad a Mexic o, 11-14 Decem ber 199 4. U.S. D ep. Commer., 

NOAA Tech. Rep. NMFS 142, 276 pp. 

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

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

Julian, F. and M. Beeson . 1998. E stimates 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 ma mmal surve y in the eastern Pacific Ocean 

and Gulf of California aboard the NOAA ships McARTHUR and DAVID STARR JORDAN July 28 - November 

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

Morejohn, G. V. 1979. The natural history of D all's porpoise in the North P acific Ocea n. In: Winn, H. E. and B. L. Olla (eds.), 

Behavior of Marine Mam mals, p. 45-83. Plenum Press, New York - London. 

Perez, M. A. and T. R. Loughlin. 1991. Incidental catch of marine mammals by foreign and joint venture trawl vessels in the U.S. EEZ 

of the North Pacific, 1973-88. U.S. Dep. Commer. NOAA Tech. Rep. 104. 57 p. 

Perez, M. A. (in prep). Summary of marine mammal incidental catch data for domestic and joint venture groundfish fisheries in the 

U.S. EEZ of the North Pacific, 1989-98. U.S. Dep. Commer. NOAA Tech. Memo. 

Perrin, W. F. and R. L. Brownell, Jr. 1994. A brief review of stock identity in small marine cetaceans in relation to assessment of 

driftnet mortality in the North Pacific. Rep. Int. Whal. Commn. Special Issue 15:393-401. 

Sosa-Nish izaki, 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 picudo s (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 W orkshop April 3-5, 

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

72 
Revised 12/15/2000 

PACIFIC WHITE-SIDED DOLPHIN (Lagenorhynchus obliquidens): 

California/Oregon/Washington, Northern and Southern Stocks 

STOCK DEFINITION AND GEOGRAPHIC RANGE 

Pacific white-sided d olphins are e ndemic to temperate 

waters of the North P acific Ocea n, and are co mmon b oth 

on the high seas and along the continental m argins. Off 

the U.S. west co ast, Pacific white -sided dolphins have 

been seen primarily in shelf and slope waters (Figure 1). 

Sighting patterns from recent aerial and shipboard 

surveys conducted in California, Oregon and 

Washington at different times of the year (Green et al. 

1992; 1993; Barlow 1995; Forney et al. 1995) suggest 

seasonal north-south movements, with animals found 

primarily off California during the colder water months 

and shifting northward into Oregon and Washington as 

water temperatures increase in late spring and summer 

(Green e t al. 1992; F orney 19 94). 

Stock structure throughou t the North P acific is poor ly


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 Figure 1. Pacific white-sided dolphin sightings


in the Southern California Bight, but it is unclear based on aerial and shipboar d surveys off


whether this indicates sympatry in this region or whether California, Oregon and Washington, 1991-96 (see


they may occur there at different times (seasonally or Appen dix 2, Figures 1-5, for data sources and


interannually). Recent gen etic analyses have confirmed information on timing and location of survey


the distinctness of anim als found off B aja Californ ia effort). Dashed line represents the U.S. EEZ,


from animals occ urring in U.S . waters north of Point thick line indicates the outer bou ndary of all


Conception, California an d in the high sea s of the Nor th surveys combined.


Pacific (Lux et al. 1997). Based on these genetic data,


a bounda ry or area o f mixing betwe en the two for ms appe ars to be located off Southern C alifornia (Lux et al.


1997).


Although there is clear evidence that two forms o f Pacific white-sid ed dolp hins occur a long the U .S. west coast,


there are no known differences in color pattern, and it is not currently pos sible to distinguish animals without


genetic or morphome tric analyses. Geographic stock boundaries appear dynamic and are poorly understood,


and therefore canno t 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. Furthe rmore, P acific white-sided dolphins ar e not restricted to


U.S. territorial waters, but cooperative mana gement agreemen ts with Mexico exist only for the tuna purse seine


fishery and not for other fisheries which may take this species (e.g. g illnet fisheries). Additional means of


differentiating the two types must be found, and cooperative management with Mexico is particularly important


for this species, give n the appa rently dynamic nature of geo graphical sto ck bound aries. Until these go als are


accomplished, the management stock includes animals of both forms. For the Marine Mammal Protection Act


(MMPA) stock assessm ent reports, P acific white-sided d olphins within the Pacific U .S. Exclusive Economic


Zone are divided into two discrete, non-contiguous areas: 1) waters off California, Oregon and W ashington (this


73 
report), and 2) Alaska n waters. 

POPU LATIO N SIZE 

The previous best estimates of abundance for Pacific white-sided 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 

Pacific white-sided dolphins that are found off Oregon and Washington during summer and fall. Three 

summer/fall shipboard surveys were conducted within 300 nmi of the coasts of California in 1991 and 1993 

(Barlow and Gerrodette 19 96) and California, Oregon and Washington in 1996 (Barlow 1997). The distribution 

of Pacific white-sid ed dolp hins througho ut this region is highly v ariable, app arently in response to 

oceano graphic changes on both seasonal and interannual time scales (Forney and Barlow 1998). As 

oceano graphic conditions v ary, Pacific wh ite-sided do lphins may spend time outside the U.S. Exclusive 

Econo mic Zone, and therefore a multi-year average abundance estimate including California, Oregon and 

Washington is the most appropriate for management within U.S. waters. The 1991-96 weighted average 

abundance estimate for California, Oregon and Wa shington waters based on the three ship surv eys is 25, 825 

(CV = 0.49) Pacific white-sided dolphins (Barlow 1997). 

Minimum Po pulation Estimate 

The log-normal 20th percentile of the 1991-96 weighted average abundance estimate is 17,4 75 Pac ific whitesided dolphins. 

Current Population Trend 

No long-term trends in the abundance of Pacific wh ite-sided do lphins in California, Oregon and Washington 

are suggested based on historical an d recent surv eys (Dohl et al. 1980; 1983; Green et al. 1992; 1993; Barlow 

1995; Forney et al. 1995;). 

CURRENT AND M AXIMUM NET PRODUCTIVITY RATES 

No information on current o r maximum net produ ctivity rates is available for Pacific wh ite-sided do lphins off 

the U.S. we st coast. 

POTENTIAL BIOLOGICAL REMOVAL 

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

(17,475) times one half the default m aximum ne t growth rate for cetaceans (1⁄2 of 4%) times a recovery factor 

of 0.45 (fo r a species o f unknown sta tus with a morta lity rate CV�0.60 and �0.80; Wade and Angliss 1997), 

resulting in a PB R of 157 Pacific white-sid ed dolp hins per year. 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY 

Fishery Information 

A summary of recent fishery mortality and injury for this stock of Pacific white-sided dolphin is shown in Table 

1.	 More detailed information on these fisheries is provided in Appendix 1. Mortality estimates for the 

California drift gillnet fishery are included for the five most recent years of monitoring, 1994-98 (Julian and 

Beeson 1998; Julian 1997; Cameron and Forney 1999). After the 1997 implementation of a Take Reduction 

Plan, which included skipper education workshops and required the use of pingers and minimum 6-fathom 

extenders, overall cetacean entanglement rates in the drift gillnet fishery dropped considerably (Barlow and 

Cameron 1999). However, because of interannual variability in entanglement rates and the relative rarity of 

Pacific white-sided dolphin entanglements, additional years of data will be required to fully evaluate the 

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

after implementation of the Take Reductio n Plan, mea n annual take s in Table 1 are based only on 1997-98 data. 

This results in a n average e stimate of 6.0 (CV = 0 .68) Pac ific white-sided d olphins take n annually. 

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

and probably take the southern form of this species. Quantitative data are available only for the Mexican 

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

74 
drift gillnet fishery, although nets may be up to 4.5 km long (Holts and Sosa-Nishizaki, 1998). The fleet 

increased from two ve ssels 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 p rovided by these autho rs to be app roximately 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 obser ved in California driftnet 

fisheries during 1990-95 (0.14 marine mammals per set; Julian and Beeson,1998), but species-sp ecific 

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

Mexica n swordfish d riftnet fishery to a long line fishery (D. H olts, pers. com m.). 

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 

entangleme nts of Pacific white-sided dolphins resulted in the death of the animal. Coefficients of variation for 

mortality estimates are provided in parentheses; n/a = not available. Mean annual takes are based on 1994-98 

data unless noted otherwise. 

Fishery Name Data TypeYear(s) 

Percent 

Ob 

ser 

ver 

Co 

ver 

age 

Observed 

M 

ort 

ali 

ty 

Estimated Annual 

Mortality 

Mean Annual 

Takes 

(CV in 

parenth 

eses) 

CA/OR thresher 

shark/swordfish 

drift gillnet 

fishery 

observer data 

1994 

1995 

1996 

1997 

1998 

17.9% 

15.6% 

12.4% 

23.0% 

20.0% 

3 

1 

3 

3 

0 

17 (0.67) 

6 (0.92) 

25 (0.96) 

12 (0.68) 

0 

6.0 (0.68)1 

WA/OR/CA domestic 

groundfish 

trawl fisheries 

(At-sea 

processing 

Pacific whiting 

fishery only). 

observer data 

other records 

1994 

1995 

1996 

1997 

1998 

1996 

53.8% 

56.2% 

65.2% 

65.7% 

77.3% 

0 

0 

0 

0 

1 

3 

0 

0 

0 

0 

1 (0.48) 

�3 

0.2 (0.48) 

0.6 (n/a) 

Minimum total annual takes 6.8 (0.60)

1 Only 1997-98 mortality estimates are included in t he average because overall cetacean entanglement rates dropped considerably after a Take 

Reduction Plan was implemented in 1997. 

Low levels of mortality for Pacific white-sided dolphins have also been documented in the California/Oregon/ 

Washington domestic groundfish trawl fisheries (Perez and Loughlin 1991; Perez, in prep;). Between 1994 and 

1998, with 54%-77% of the fishing effort observed, one Pacific white-sided dolphin was reported killed in the 

at-sea processing portion of the Pacific w hiting trawl fishery, and three additio nal animals we re reporte d in 

unmonitored hauls. Base d only on the systematically ob served hau ls, mortality was estim ated to be one Pac ific 

white-sided dolphin (CV=0.48, Perez, in prep) in 1998. Combining this estimate with the three additional 

reported mortalities for 1996 that are not accounted for in the estimate, the minimum average an nual mortality 

for 1994-98 is 0.8 (CV=0.4 8) Pacific white-sided dolph ins. 

Other remova ls 

Additional removals o f Pacific white-sid ed dolp hins from the w ild have oc curred in live-c apture fisherie s off 

California. B rownell et al. (1999) estimate a minimum total live capture of 128 Pacific white-sided dolphins 

75 
between the late 1950s and 1993. T he most rec ent capture was in November 1993 , when three animals were 

taken for public display (Forney 1994). No MMP A permits are currently active for live-captures of P acific 

white-sided dolphins. 

STATUS OF STOCK 

The status of Pacific white-sided dolphins in California, Oregon and Wa shington 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 M MPA . Including driftnet mortality only fo r years after imp lementation of the Take 

Reduction Plan (1997-9 8), the avera ge annual hu man-cause d mortality in 1994-98 (6.8 animals) is estimated 

to be less than the PBR (157), and therefore they are not classified as a "strategic" stock under the MMPA . The 

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

can be co nsidered to be insignificant an d appro aching zero mortality and se rious injury rate . 

REFERENCES 

Barlow, J. 1995. The abundance of cetaceans in California waters. Part I: Ship surveys in summer and fall of 1991. 

Fish. Bull. 93:1-14. 

Barlow, J. 1997. Preliminary estimates of cetacean abundance off California, Oregon and Washington based on a 1996 

ship survey and com parisons o f passing and closing mo des. Adm in. Rep. LJ-9 7-11, So uthwest Fisher ies 

Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA 92038. 25p. 

Barlow, J. and G. A. Cameron. 1999. Field experiments show that acoustic pin gers reduc e marine m ammal byc atch in 

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

1998 (unpublished). 20 pp. 

Barlow, J. and T. Gerrodette. 1996. Abundance o f cetaceans in California waters based on 1991 an d 1993 ship surv eys. 

NOA A Tech . Memo . NMF S-SW FSC-23 3. 15 pp . 

Barlow, J., K. A. Forney, P. S. Hill, R. L. Brownell, Jr., J. V. Carretta, D. P. DeMaster, F. Julian, M. S. Lowry, T. Ragen, 

and R. R. Reeves. 1997. U.S. Pacific Marine Mammal Stock Assessments: 1996. U.S. Dep. Commer., NOAA 

Tech. Memo. NMFS-SWFSC-248. 223 pp. 

Brown ell, R. L., Jr., W. A. Walker and K. A. Forney. 19 99. Pac ific white-sided d olphin, Lagenorhynchus obliquidens 

Gill, 1865. Pages 57-84 In: Ridgway, S. H. and R. Harrison (eds.), Handbook of Marine Mammals, Vol. 6. 

Academic Press, San Diego. 

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

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

Chivers, S. J., K. M . Peltier, W . T. Nor man, P. A . Akin, and J. Heyning. 1993. P opulation str ucture of ceta ceans in 

California coastal waters. Paper S OCCS 9 presente d at the Status o f California Cetacean Sto cks Wo rkshop, he ld 

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 Manageme nt 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 Souther n California B ight. 

Final Report to the Bureau of Land Management, NTIS Rep. No. PB81248189. 414p. 

Forney, K. A. 199 4. Recent information on the status of odontocetes in Californian waters. U.S. Dep. Commer., NOAA 

Tech. M emo. NM FS-SW FSC-20 2. 87 pp . 

Forney, K. A. 1997. Patterns of variability and environmental mo dels of relative abundance fo r California cetaceans. 

Ph.D. dissertation, Scripps Institution of Oceanography, University of California, San Diego. 

Forney, K. A. and J. Barlow. 1998. Seasonal patterns in the abundance and distribution of California cetaceans, 1991­

92. Mar. Mamm. Sci. 14:460-489. 

Forney, K. A., J. Barlow and J. V. Carretta. 1995. The abundance of cetaceans in California waters. Part II: Aerial 

surveys in winter and spring of 1991 and 1992. Fish. Bull. 93:15-26. 

Green, G., J. J. Bru eggeman , R. A. Gro tefendt, C. E . Bowlby, M. L. Bonnell, and K. C. Balcomb, III. 1992. Cetacean 

76 
distribution and abun dance o ff Oregon and Wa shington. Ch. 1. In: Oregon and Washington Marine Mammal 

and Seabird Surveys. OCS Study 91-0093. Final Repo rt prepared for Pacific O CS Reg ion, Mine rals 

Manag ement Ser vice, U.S. D epartmen t of the Interior, L os Angele s, California. 

Green, G., R. A. Grotefe ndt, M. A. Sm ultea, C. E. Bowlby, and R. A. Row lett. 1993. D elphinid aerial surveys in 

Oregon and W ashington wa ters. Final Report prepared for NMFS, National Marine Mammal Laboratory, 7600 

Sand Point Way, NE, Seattle, Washington, 98115, Contract #50ABNF200058. 

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

Holts, D. and O. S osa-Nishiza ki. 1998. S wordfish, Xiphias gladius, fisheries of the easte rn North P acific Ocea n. In: 

I. Barrett, O. Sosa-Nishizaki and N. B artoo (ed s.). Biology a nd fisheries of sw ordfish, Xiphias gladius. Papers 

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

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

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

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

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

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

Lux, C. A., A. S. Costa, and A. E. Dizon. 1997. Mitochondrial DNA population structure of the Pacific white-sided 

dolphin. Rep. Int. Whaling. Commn. 47:645-652. 

Perez, M. A. and T. R. Loughlin. 1991. Incidental catch of marine mammals by foreign and joint venture tra wl 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 dome stic and joint venture groundfish 

fisheries in the U.S. EEZ of the North Pacific, 1989-98. NOAA Tech. Memo. 

Sosa-Nish izaki, 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. 19 97. Guidelines for Assessing Marine Mammal Stocks: Report of the GAMMS 

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

93 pp. 

Walker, W. A., S. Leatherwood, K. R. Goodrich, W. F. Perrin and R. K. Stroud. 1986. Geographical variation and 

biology of the Pacific w hite-sided do lphin, Lagenorhynchus obliquidens, in the north-easte rn Pacific. In: 

Bryden, M. M. and R. Harrison (eds.), Research on Dolphins, p. 441-465. Clarendon Press, Oxford. 

77 
Revised 12/15/2000 

RISSO'S DOLPHIN (Grampus griseus): 

California/Oregon/Washington Stock 

STOCK DEFINITION AND GEOGRAPHIC RANGE 

Risso's dolphins are distributed world-wide in tropical 

and warm-temp erate waters. O ff the U.S. W est 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), a nimals found off California during 

the colder water months are thought to shift northward 

into Oregon and Wa shington as water temperatures 

increase in late spring and summer (G reen et al. 1992). 

The southern end of this population's range is not welldocumented, but on a recent joint U.S./M exican ship 

survey, Risso's dolphins were sighted off northern Baja 

California, and a conspicuous 500 nmi gap was present 

between these animals and Risso's dolphins sighted 

south of Baja California and in the Gulf of Califo rnia 

(Mang els and Ger rodette 19 94). Thus this population 

appears distinct from animals found in the eastern 

tropical Pacific and the Gulf of California. Although 

Risso's dolphins are not restricted to U.S. waters, 

cooperative management agreements with Mexico exist 

only for the tuna purse seine fishery and not for other 

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

fisheries). For the Marine Mammal Protection Act 

(MMPA) stock assessment reports, Risso's dolphins 

within the Pacific U.S. Exclusive Economic Zone are 

divided into two discrete, non-contiguous areas: 1) 

waters off California, Orego n and W ashington (this 

report), and 2) H awaiian waters. 

POPU LATIO N SIZE 

Figure 1. Risso’s dolp hin sightings based on 

aerial and shipboard surveys off California, Oregon 

and Washington, 1991-96 (see Append ix 2, 

Figures 1-5, for data sources and information on 

timing and location of survey effort). Dashed line 

represents the U.S. EEZ, thick line indicates the 

outer boundary of all surveys combined. 

The previous best estimates of abundance for Risso’s dolphins (Barlow et al. 1997) were based on 

winter/spring 1991-9 2 aerial surveys (Forney et al. 1995) off California, which were presumed to include 

Risso’s dolphins tha t are found o ff Oregon a nd Washington d uring summer and fall. Three summ er/fall 

shipboard surveys were conducted within 300 nmi of the coasts of California in 1991 and 1993 (Barlow and 

Gerrod ette 1996) a nd Californ ia, Orego n and W ashington in 1 996 (B arlow 19 97). Th e distribution o f Risso’s 

dolphins throughou t this region is highly variable, appare ntly in response to oceano graphic ch anges on b oth 

seasonal and interann ual time scales (F orney and Barlow 1 998). As oceano graphic co nditions vary, R isso’s 

dolphins may spend time outside the U.S. Exclusive Economic Zone, and therefore a multi-year average 

abundance estimate is the most appropriate for management within U.S. waters. The 1991-96 weighted average 

abundance estimate for California, Oregon and Washington waters based on the three ship surveys is 16,483 

(CV = 0.28) Risso’s dolphins (Barlow 1997). 

Minimum Po pulation Estimate 

The log-normal 20th perce ntile of the 1991-96 weighted average abunda nce estimate is 13,079 R isso's dolphins. 

78 
Current Population Trend 

Although sighting records of Risso's dolphins appear to have increased during the last two decades in some 

areas off the U.S. West co ast (Green et al. 1992; 1993; Shane 1994), sampling effort has also increased, and 

there are no statistical estimates of historical abundance on which to base a q uantitative com parison. T hus, it 

is possible that Risso's dolphin abundance off the U.S. West coast has increased, but no definitive statement 

regarding trends in abundance of Risso's dolphins off California, Oregon and Washington can be made. 

CURRENT AND M AXIMUM NET PRODUCTIVITY RATES 

No information o n current or m aximum ne t producti vity rates is available for Risso's dolphins in California, 

Oregon and W ashington. 

POTENTIAL BIOLOGICAL REMOVAL 

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

(13,079) times one half the default maximum net growth rate for cetaceans (1⁄2 of 4%) times a recovery factor 

of 0.40 (for a species of unknown status with a mortality rate CV�0.80; W ade and Angliss 199 7), resulting in 

a PBR of 105 R isso’s dolph ins 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 Appen dix 1. Mortality estim ates for the Ca lifornia drift 

gillnet fishery are included for the five most recent years of monitoring, 1994-98 (Julian and Beeson 1998; 

Julian 1997; Cameron and Forney 19 99). After the 1997 implementation of a Take Reduction Plan, which 

included skipper education workshops and required the use o f pingers and minimum 6 -fathom exten ders, overa ll 

cetacean entanglement rates in the drift gillnet fishery dropped considerably (Barlow and Cameron 1999 ). 

However, because of interannu al variability in entan glement rates and the relative rarity of Risso’s d olphin 

entanglements, additional years of data will be required to fully evaluate the effectiveness of pingers for 

reducing mortality of this particular species. Because of the change s in this fishery after implementation of the 

Take Reduction Plan, mean annual takes in Table 1 are based only on 1997-98 data. This results in an average 

estimate of 5.5 (CV = 0 .96) Risso ’s dolphins tak en annually. 

Drift gillnet fisheries for swordfish a nd sharks ex ist along the entire Pacific coast of Baja California, Mexico 

and probably take animals from the same population. Quantitative data are available only for the Mexican 

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

drift gillnet fishery, although nets may be up to 4.5 km long (Holts and Sosa-Nishizaki 1998). The fleet 

increased from two ve ssels 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-Nish izaki et al., 199 3). This overall mortality rate is similar to that observed in California driftnet 

fisheries during 1990-95 (0.14 marine mam mals per set; Julian and B eeson, 19 98), but sp ecies-specific 

information is not available for the Mexican fisheries. There are currently efforts underway to convert th e 

Mexica n swordfish d riftnet fishery to a long line fishery (D. H olts, pers. com m.). 

Table 1. Summary o f available information on the incidental m ortality and injur y of Risso's dolphin (California/ 

Oregon/Washington Stock) in commercial fisheries that might take this sp ecies. All obs erved enta nglements 

of Risso's dolphins resulted in the death of the animal. Coefficients of variation for mortality estimates are 

provided in parentheses; n/a = not available. Mean annual takes are based on 1994-98 data unless noted 

otherwise. 

79 
Fishery Name 

CA/OR thresher 

shark/swordfish 

drift gillnet 

fishery 

Minimum total annual takes 

Data Type 

observer 1994 

data 	 1995 

1996 

1997 

1998 

Year(s) 

Percent 

O 

b 

se 

r 

v 

er 

C 

o 

v 

er 

a 

g 

e 

Observed 

Mortality 

Estimated 

Annu 

al 

Mort 

ality 

17.9% 1 6 (0.91) 

15.6% 6 39 (0.57) 

12.4% 0 0 

23.0% 3 11 (0.96) 

20.0% 0 0 

Mean Annual Takes 

(CV in 

parentheses) 

5.5 (0.96) 1 

5.5 (0.96) 

1 Only 1997-98 mortality estimates are included in t he average because overall cetacean entanglement rates dropped considerab ly after a Take 

Reduction Plan was implemented in 1997. 

Additional mortality of unkn own extent h as been d ocumen ted for Risso 's dolphins in the squid purse seine 

fishery off Southern California (Heyning e t al. 1994). This mortality prob ably represented anima ls 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 e xpande d marked ly since 199 2 (California 

Department of Fish and Game, un publ. data). No recent Risso ’s dolphin m ortality has bee n reported for this 

fishery, but it is currently not monitored. 

STATUS OF STOCK 

The status of Risso's dolphins off California, Oregon and Wa shington 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 M MPA . Including driftnet mortality only for years after implementation of the Take 

Reduction Plan (1997-98), the average annual human-caused mortality in 1994-98 (5.5 animals) is estimated 

to be less than the PBR (105), and therefore they are not classified as a "strategic" stock under the MMPA. The 

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

can be co nsidered to be insignificant an d appro aching zero mortality and se rious injury rate . 

REFERENCES 

Barlow, J. 1997. Preliminary estimates of cetacean a bundanc e off California, Oregon and Washington based on a 1996 

ship survey and comparisons of passing and closing modes. Admin. Rep. LJ-97-11, Southwest Fisheries 

Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA 92038. 25p. 

Barlow, J. and G. A. Camero n. 1999 . Field expe riments show that acoustic p ingers reduc e marine mammal byc atch in 

the California d rift gillnet fishery. Pap er SC/51 /SM2 p resented to the International Whaling Commission, May 

1998 (unpublished). 20 pp. 

Barlow, J., K. A. Forney, P. S. Hill, R. L. Brownell, Jr., J. V. Carretta, D. P. DeMaster, F. Julian, M. S. Lowry, T. Ragen, 

and R. R. Reeves. 1 997. U.S. Pacific Marine Mammal Stock Assessments: 1996. U.S. Dep. Commer., NOAA 

Tech. Memo. NMFS-SWFSC-248. 223p. 

Barlow, J. and T. Gerrodette. 1996. Abundance o f cetaceans in California waters based on 1991 an d 1993 ship surv eys. 

NOAA Tech. Memo. NMFS-SWFSC-233. 15 pp. 

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

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

80 
Forney, K. A. and J. Barlow. 1998. S easonal pa tterns 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 w aters. Part II: Aerial 

surveys in winter and spring of 1991 and 1992. Fish. Bull. 93:15-26. 

Green, G., J. J. Brueggeman, R. A. Grotefendt, C. E. Bowlby, M. L. Bonnell, and K. C. Balcomb, III. 1992. Cetacean 

distribution and abun dance o ff Oregon a nd W ashington. Ch. 1. In: Oregon and Washington Marine Mammal 

and Seabird Surveys. OCS Study 91-0093. Final Report prepared for Pacific OCS Region, Mine rals 

Manag ement Ser vice, U.S. D epartmen t of the Interior, L os Angele s, California. 

Green, G., R. A. Grotefendt, M. A. Smultea, C. E. Bowlby, and R. A. Rowlett. 1993. Delphinid aeria l surveys in 

Oregon and Washington waters. Final Report prepared for NMFS, National Marine Mammal Laboratory, 7600 

Sand Point Way, NE, Seattle, Washington, 98115, Contract #50ABNF200058. 

Heyning, J. E., T. D. Lewis and C. D. Woodhouse. 1994. A note on odontocete mortality from fishing gear 

entanglements off Southern California. Rep. Int. Whal. Commn. Special Issue 15:439-442. 

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

Holts, D. and O. S osa-Nishiza ki. 1998. S wordfish, Xiphias gladius, fisheries of the eastern N orth Pacific O cean. In: 

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

from the Internation al Sympo sium on P acific 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. Be eson. 1998. Estimates of mammal, turtle and bird m ortality for two California gillnet fisheries: 

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

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

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

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

Shane, S. 1994. Occ urrence and habitat use of marine mammals at Santa C atalina Island, California from 1983-91. 

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

Sosa-Nish izaki, O., R. De la Rosa Pacheco, R. Castro Longoria, M. Grijalva Chon, and J. De la Rosa Velez. 1 993. 

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. 

81 
Revised 12/15/2000 

BOTTLENOSE DOLPHIN (Tursiops truncatus): California Coastal Stock 

STOCK DEFINITIO N AND GEOG RAPH IC 

RANGE 

Bottlenose dolphins are distributed worldwide in tropical and warm -temperate 

waters. In many regions, including 

California, separate co astal and offs hore 

populations are known (Walker 1981; 

Ross and Cockcroft 1990; Van Waerebeek 

et al. 1990). California coastal bottlenose 

dolphin s are found within about one 

kilometer of shore (Figure 1; Hansen, 

1990; Carretta et al. 1998; Defran and 

Weller 1999) primarily from Point 

Conception south into Mexican waters, at 

least as far south as Ensenada. 

Oceano graphic events appear to influence 

the distribution of animals alo ng 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 199 0; Wells e t al. 

1990). Since the 1982-83 El Niño, which 

increased water temperatures off 

California, they have be en consistently 

sighted in central California as far north as 

San Francisco . Photo-ide ntification 

studies have doc umented n orth-south 

movem ents 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 a re proba bly 

Figure 1. Range (in bold) of the coa stal bottlenose dolphin 

based on aerial surveys along the coast of California from 1990­

99 (see Appendix 2, Figure 7, for data sources and information 

on timing and distribution of survey effort). This population of 

bottlenose dolphins is found within about 1 km of shore. 

moving into and out of this area. Although coastal bottlenose dolphins are not restricted to U.S. waters, 

cooperative management agreements with Mexico exist only for the tuna purse seine fishery and not for other 

fisheries which may take this species (e.g. gillnet fisheries). Therefore, the management stock includes on ly 

animals found within U.S. waters. For the Marine Mammal Protection Act (MM PA) stock assessme nt 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. 

POPU LATIO N SIZE 

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

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

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

considered a minimum population estimate, however, because an unknown number of animals died during this 

period and rates o f acquisition o f dorsal fin char acters are no t known. M ark-recapture estimates based on 

82 
photo-identification studies in 1985-89 range from 234 (95% CI 205-263) to 285 (9 5% CI 265-30 6) animals 

for the entire California-Mexico population (Defran and W eller 1999). Because coastal bo ttlenose dolphins 

spend an unknow n amount o f time in Mexican waters, where they are subject to mortality in Mexica n fisheries, 

an average abundance estimate for California only is the most appropriate for U.S. management of this stock. 

Tandem aerial surveys were conducted in 1990-94 to estimate the abundance of coastal bottlenose dolphins 

throughout the southern California portion of their U.S. range. (Carretta et al. 1998). These estimates, which 

are corrected for the fraction o f animals missed by a single obser ver team, ran ge from 78 to 271 an imals, with 

a mean abu ndance e stimate of 140 b ottlenose d olphins (C V = 0.0 5). These surveys did not include the central 

California portion of this stock’s range, and therefore the published abundances underestimate the total number 

of animals is U.S. waters by an unknown amount. More recently, two surveys were conducted in 1994 and 

1999, covering virtu ally the entire U.S. range of this species, from the U.S./Mexican border to just south of San 

Francisco, California. Using the same methods and correction factors as in Carretta et al. (1998), the weighted 

average abundance estimate for these two surveys is 169 (CV=0.11) coastal bottlenose dolphins (NMFS, 

SWFSC, unpublished data). This presently is the best estimate of the average number of coastal bo ttlenose 

dolphins in U.S. waters. 

Minimum Po pulation Estimate 

The log-normal 20th percentile o f the above a verage ab undance estimate for U.S. waters based on the 1994 and 

1999 surveys is 154 coastal bottlenose dolph ins. 

Current Population Trend 

No trend in abundance of coastal bottlenose dolphins is apparent based on the available data. 

CURRENT AND M AXIMUM NET PRODUCTIVITY RATES 

No information o n current or m aximum ne t productiv ity rates is available fo r California co astal bottlenose 

dolphins. 

POTENTIAL BIOLOGICAL REMOVAL 

The potential biological removal (PBR) level for this stock is calculated as the minimum population size (154) 

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 m ortality; Wade and Angliss 1997), resulting in a PBR of 

1.5 coasta l bottlenose d olphins pe r year. 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY 

Fishery Information 

Due to its exclusive use of coastal hab itats, this bottlenose dolphin p opulation is su sceptible to fishery-related 

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

of bottlenose dolphin is sho wn in Tab le 1. More detailed information o n the set gillnet fishery is p rovided in 

Appen dix 1. From 1991-94, no bottlenose dolphins were observed taken in this fishery with 10-15% observer 

coverage (Julian and Beeson 1998). The observer program was discontinued at the end of 1994, when coastal 

set gillnet fishing was banned within 3 nmi of the southern California coast. In central California, gillnets have 

been restricted to waters deeper than 30 fathoms (56m) since 1991 in all areas except between Point Sal and 

Point Arguello. Because of these closures, the potential for mortality of coastal bottlenose dolphins in the 

California set gillnet fishery has b een greatly reduced since 1994. Fisher self-report data and stranding records 

for 1994-98 do not include any records of fishery interactions for this stock. Coastal gillnet fishe ries exist in 

Mexico and prob ably take anim als from this po pulation, bu t no details are available. 

Table 1. Summary o f available information on the incidental m ortality and injur y of bottlenos e dolphins (California 

Coastal Stock) in com mercial fisheries that might take this species. 

83 
Fishery Name 

CA angel shark/ halibut and other 

species large mesh 

(>3.5in) set gillnet 

fishery 

Minimum total annual takes 

Other remova ls 

Data Type Year(s) 

Percent 

O 

bs 

er 

ve 

r 

C 

ov 

er 

a 

ge 

Observed 

Mortality 

Estimated 

Annua 

l 

Mortal 

ity 

Mean Annual 

Takes 

observer 

data 

1991-94 

1995-98 

10-15% 

0% 

0 0 

0 

0 

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

Prescott 1961). T wenty-seven a dditional b ottlenose d olphins wer e captured off California between 1966 and 

1982 (Walker 1975; Reeves an d Leatherwood 1984), but base d 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-captu re permits ar e currently active for this 

species. 

STATUS OF STOCK 

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

of a trend in abundance. They are not listed as "threatened" or "endangered" under the Endangered Species 

Act nor as "depleted" under the MMPA. Because no recent fishery takes have been documented, coastal 

bottlenose dolphins are not classified as a "strategic" stock under the MMPA, and the total fishery mortality 

and serious injury for this stock can be considered to be insignificant and approaching zero. 

Habitat Issues 

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

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

the effects of polluta nts on cetaceans are not well understo od, they ma y affect reprod uction or make the animals 

more prone to other mortality factors (Britt and Howard 1983 ; O’Shea et al. 1999). This population of 

bottlenose dolphins m ay also be vu lnerable to the effects of morbillivirus outbreaks, which were im plicated 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. How ard. 1983. T issue residues of selected e nvironme ntal contam inants in marine ma mmals. 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 abunda nce of southern California coa stal bottlenose dolphins 

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

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

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

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

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

Hansen, L. J. 1990 . California coastal bottlenose dolphins. In: S. Leatherwood an d R.R. Reeves (ed s.), The Bottlenose 

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

Hansen, L. J. and R. H . Defran. 19 90. A comparison of photo-id entification studie s of California coastal bottlenose 

84 
dolphins. Rep. Int. Whal. Commn. Special Issue 12:101-104. 

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

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

Lipscomb, T. P., F. Y . Schulman , D. Mo ffett, and S. Ke nnedy. 1994. M orbilliviral disease in Atlantic bottlenose 

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

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

pollutants in small cetaceans from the Pac ific and South Atlantic Ocean s, November 1968-June 1976. 

Pesticides Monitoring Journal 14:35-46. 

O’Shea, T. J., R. R. Reeves, and A. Kirk Lo ng (eds.). 1 999. M arine Mamm als and Persistent Ocean Contaminants: 

Proceedings of the Marine Mammal Comm ission Workshop, Keystone, Colorado, 12-15 Octob er 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. 1 961. O bservation on Pacific c etaceans o f Californian an d Mex ican waters. University 

of California Publications in Zoology 63:291-402. University of California Press, Berkeley and Lo s 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. Comm ents on Australian bottlenose dolphins and the taxonomic status of 

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

101-12 8. Acade mic Press, 6 53pp. 

Schafer, H. A., R. W . Gossett, C. F. Ward, and A. M. Westcott. 1984. Chlorinated hydrocarbons in ma rine 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 o bservations of bottlenose 

dolphins from the Pacific coa st of South A merica. In: The Bottlenose D olphin (eds. S. Leatherwood and R. R. 

Reeves). p p. 143-1 54 Acad emic Pre ss, 653 pp . 

Walker, W. A. 1975. Review of the live-capture fishe ry for smaller ce taceans take n in Southern California waters for 

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

Walker, W. A. 198 1. Geograph ical variation in morphology and biology of bottlenose do lphins (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. 

Wells, R. S., L. J. Hansen, A. B. Baldridge, T . P. Dohl, D . L. Kelly and R. H De fran. 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. 

85 
Revised 12/15/2000 

BOTTLENOSE DOLPHIN (Tursiops truncatus): 

California/Oregon/Washington Offshore Stock 

STOCK DEFINITION AND GEOGRAPHIC RANGE 

Bottlenose dolphins ar e 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 

Cockcr oft 1990; Van Waerebeek et al. 1990). On 

surveys conducted off California, offshore bottlenose 

dolphins have been found at distances greater than a few 

kilometers from the mainland and throughout the 

Southern California Bight. They have also been 

documented in offshore waters as far north as about 

41o

N (Figure 1), and they may range into Oregon and 

Washington waters during warm-water perio ds. 

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 shipb oard surveys conducte d in 

summer/fall 1991 (B arlow 19 95), no sea sonality in 

distribution is apparent (Forney and Barlow 1998). 

Offshore bottlenose dolphins are not restricted to U.S. 

waters, but cooperative management agreeme nts 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. 

POPU LATIO N SIZE 

Figure 1. Offshore bottlenose dolphin sightings 

based on aerial and shipboar d surveys off 

California, Oregon and Washington, 1991-96 (see 

Appen dix 2, Figures 1-5, for data sources and 

information on timing and location of survey 

effort). All sightings were made at distances 

greater than a few kilometers from the mainland 

California coast. Dashed line represents the U.S. 

EEZ, thick line indicates the outer boundary of all 

surveys combined. 

The previous best estimates of abundance for offshore bottlenose dolphins (Barlow et al. 1997) were based on 

a weighted av erage for win ter/spring 19 91-92 a erial surveys (F orney et al. 19 95), and su mmer/fall ship surveys 

in 1991 and 1993 (Barlow and Gerrodette 1996) along the coast o f California. An additional summer/fall 

shipboard surveys was conducted within 300 nmi of the coasts of California, Oregon and Washington in 1996 

(Barlow 1997). Because the distribution of bottlenose dolphins appears to vary interannually and they may 

spend time outside the U.S. Exclusive E conomic Zon e, a multi-year average abunda nce estimate is the most 

approp riate for management within U.S. waters. The most comprehensive multi-year average abundance is the 

weighted average abundance estimate for California, Oregon and Washington waters based on the 199 1-96 ship 

surveys, 956 (CV = 0.14) offshore bottlenose dolphins (Barlow 1997). 

Minimum Po pulation Estimate 

86 
The log-normal 20th percentile of the 1991 -96 weighted average ab undance estimate is 850 offshore bo ttlenose 

dolphins. 

Current Population Trend 

No information on trends in abundance of offshore bottlenose dolphins is available. 

CURRENT AND M AXIMUM NET PRODUCTIVITY RATES 

No information on current or maximum net productivity rates is available for this population of offshore 

bottlenose dolphins. 

POTENTIAL BIOLOGICAL REMOVAL 

The potential biological removal (PBR) level for this stock is calculated as the minimum population size (850) 

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

a species of un known status w ith no known fishery mortality; Wade an d Angliss 1997), resulting in a PBR of 

8.5 offshor e bottlenos e dolphins per year. 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY 

Fishery Information 

A summary o f known fishery m ortality and injur y for this stock of b ottlenose d olphin is show n in Table 1. 

More detailed infor mation on these fisheries is pro vided in A ppendix 1. Mor tality estimates for the C alifornia 

drift gillnet fishery are included for the five most recent years of monitoring, 1994-98 (Julian and Beeson 1998; 

Julian 1997; Cameron and Forney 1999). After the 1997 implementation of a Take Reduction Plan, which 

included skipper education workshops and required the use of pingers and minimum 6 -fathom exten ders, overa ll 

cetacean entanglement rates in the drift gillnet fishery dropped considerably (Barlow and Cameron 1999). 

However, because of interannual variability in entanglement rates and the rarity o f bottlenose d olphin 

entanglements, additional ye ars of data will b e required to fully evaluate the effectiveness of pingers for 

reducing mortality of this pa rticular specie s. Because of the change s in this fishery after implementation of the 

Take Reduction Plan, mean annual takes in Table 1 are based only on 19 97-98 d ata. This resu lts in an average 

estimate of zer o offshore b ottlenose d olphins take n annually. 

Table 1. Summary o f available information on the incidental mortality and injury of bottlenose dolphins (California/ 

Oregon/Washington Offshore S tock) in com mercial fisherie s that might take this sp ecies. Mean annual takes 

are based on 1994-98 data unless noted otherwise. 

Fishery Name Data Type Year(s) 

Percent 

Observer 

Coverage 

Observed 

Mortality 

Estimated Annual 

Mortality 

Mean 

Annual Takes 

(CV in 

parenth 

eses) 

CA/OR thresher 

shark/swordfish 

drift gillnet 

fishery 

observer 

data 

1994 

1995 

1996 

1997 

1998 

17.9% 

15.6% 

12.4% 

23.0% 

20.0% 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 1 

Minimum total annual takes 0 

1 Only 1997-98 mortality estima tes are included in the average b ecause overall cetacean entanglement rates dropped considerably after a Take 

Reduction Plan was implemented in 1997. 

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

and may take anim als from the same population. Quantitative data are available only for the Mexica n swordfish 

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

87 
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 appr oximately 27 00, with an o bserved r ate 

of marine mammal bycatch of 0.13 animals per set (10 marine mammals in 77 observed sets; Sosa-Nishizaki 

et al. 1993) . This over all mortality rate is similar to that observed in California driftnet fisheries during 1990-95 

(0.14 marine mammals per set; Julian and Beeson, 1998), but species-specific information is not available for 

the Mexican fisheries. There are currently efforts underway to convert the Mexican swordfish driftnet fishery 

to a longline fishe ry (D. Ho lts, pers. comm .). 

Offshore bottlenose dolphins are often associated with Risso's dolphins and pilot whales, for which mor tality 

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 morta lity in this fishery. 

However these would probab ly 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 remova ls 

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 MM PA live-capture perm its are currently active for this species. 

STATUS OF STOCK 

The status of offshore bottlenose dolphins in California relative to OSP is not known, and there are insufficient 

data to evaluate trends in abundance. No habitat issues are known to be of concern for this species. They are 

not listed as "threatened" or "endangered" under the Endangered Species Act nor as "depleted" under the 

MMPA. Because no recent fishery takes have been documented, offshore bottlenose dolphins are not classified 

as a "strategic" stock under the MMPA, and the total fishery mortality and serious injury for this stock can be 

considered to be insignificant and approaching zero. 

REFERENCES 

Barlow, J. 1995. The abundance of cetaceans in California waters. Part I: Ship surveys in summer and fall of 1991. 

Fish. Bull. 93:1-14. 

Barlow, J. 1997. Preliminary estimates of cetacean abundance off California, Oregon and Washington based on a 1996 

ship survey and comparisons of passing and closing modes. Admin. Rep. LJ-97-11, Southwest Fisheries 

Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA 92038. 25p. 

Barlow, J. and G. A. Cameron. 1999. Field experiments show that acoustic pingers red uce marine mamma l bycatch in 

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

1998 (unpublished). 20 pp. 

Barlow, J., K. A. Forney, P. S. Hill, R. L. Brownell, Jr., J. V. Carretta, D. P. DeMaster, F. Julian, M. S. Lowry, T. Ragen, 

and R. R. Reeves. 1997. U.S. Pacific Marine Mammal Stock Assessments: 1996. U.S. Dep. Commer., NOAA 

Tech. Memo. NMFS-SWFSC-248. 223p. 

Barlow, J. and T. G errodette. 1 996. Ab undance of cetacean s in California waters based on 1991 an d 1993 ship surv eys. 

U.S. De p. Comm er., NOA A Tech . Memo . NMF S-SW FSC-23 3. 15 pp . 

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

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

Forney, K. A. and J. Barlow. 1998. Seasonal patterns in the abundance and distribution of California cetaceans, 1991­

92. Mar. Mamm. Sci. 14:460-489. 

Forney, K. A., J. Barlow and J. V. Carretta. 1995. The abundance of cetaceans in California waters. Part II: Aerial 

surveys in winter and spring of 1991 and 1992. Fish. Bull. 93:15-26. 

Heyning, J. E., T. D. Lewis and C. D. Woodhouse. 1994. A note on odontocete mortality from fishing gear 

entanglements off Southern California. Rep. Int. Whal. Commn. Special Issue 15:439-442. 

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

88 
Holts, D. and O . Sosa-Nish izaki. 1998 . Swordfish, Xiphias gladius, fisheries of the eas tern North Pacific Oc ean. 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 collec ted betwee n the years of 1 974 and 1985. U .S. Dep. Commer., 

NOAA Tech. Memo. NMFS-SWFSC-181. 184 pp. 

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

Pacific Ocean a nd Gulf of California aboard the N OAA 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 A ustralian bottlenose dolphins and the taxonomic status of 

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

101-12 8. Acade mic Press, 6 53pp. 

Sosa-Nish izaki, 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 Waer ebeek, K ., J. C. Reyes, A . J. Read, an d J. S. McKinnon . 1990. P reliminary ob servations o f bottlenose 

dolphins from the Pa cific coast of So uth Americ a. In: The Bottlenose D olphin (eds. S. Leatherwood and R. R. 

Reeves). p p. 143-1 54 Acad emic Pre ss, 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 an d biology of bottlenose d olphins (Tursiops) in the 

eastern North P acific. Admin . Rep. LJ-8 1-03C. S outhwest 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. 

89 
Revised 12/15/2000 

STRIPED DOLPHIN (Stenella coeruleoalba): 

California/Oregon/Washington Stock 

STOCK DEFINITION AND GEOGRAPHIC RANGE 

Striped dolphins are distributed world-wide in tropical 

and warm-temp erate pelagic waters. On recent 

shipboard surveys extend ing 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 

commo nly found in the ce ntral North Pacific, but 

sampling between this region and California has been 

insufficient to determin e 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; M angels and G errodette 

1994). No information on possible sea sonality in 

distribution is available, be cause the California surveys 

which extended 300 nmi offshore were cond ucted only 

during the summer/fall period. Although striped 

dolphins are not restricte d 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 on ly 

animals found within U.S. waters. For the Marine 

Mammal Protection Act (MMPA ) stock assessment 

reports, striped dolphins within the Pacific U.S. 

Exclusive Econo mic Zone are divided into two 

Figure 1. Striped do lphin sightings based on 

aerial and shipboard surveys off California, Oregon 

and Washington, 1991-96 (see Append ix 2, 

Figures 1-5, for data sources and information on 

timing and location of survey effort). Dashed line 

represents the U.S. EEZ, thick line indicates the 

outer boundary of all surveys combined. 

discrete, non-contigu ous areas: 1 ) waters off Ca lifornia, Oreg on and W ashington (this report), and 2) waters 

around H awaii. 

POPU LATIO N SIZE 

Three summer/fall shipboard surveys were conducted within 300 nmi of the coasts of California in 1991 and 

1993 (Barlow and Gerrodette 1996) and California, Oregon and W ashington in 1996 (Barlow 1997). The 

abundance of striped dolphins in this region appears to be variable between years and may be affected by 

oceano graphic conditions, as with other odontocete species (Forney 1997, Forney and Barlow 199 8). Because 

animals may spend time outside the U.S. Exclusive Economic Zone as ocea nograph ic condition s change, a 

multi-year average abundan ce estimate is the most appropriate for management within U.S. waters. The 1991­

96 weighted average abundance estimate for California, Oregon and Washington waters based on the above 

three ship surveys is 20,235 (CV = 0.14) striped dolphins (Barlow 1997). 

Minimum Po pulation Estimate 

The log-normal 20th perc entile of the 1991-96 we ighted average abund ance estimate is 17,995 striped dolphins. 

90 
Current Population Trend 

Prior to the 1991 shipboard survey (Barlow 1995), striped dolphins were not thought to be commo n off 

California (Leatherwo od et al. 1982), and two surv eys extending approx imately 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 strip ed dolp hin abund ance 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 abun dance were not ob tained for the earlier surveys. 

CURRENT AND M AXIMUM NET PRODUCTIVITY RATES 

No information on current or m aximum ne t productiv ity rates is available for striped dolphins off California. 

POTENTIAL BIOLOGICAL REMOVAL 

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

(17,995) times one half the default maximum net growth rate for cetaceans (1⁄2 of 4%) times a recovery factor 

of 0.50 (for a species of unknown status with no known fishery mortality; Wade and Angliss 1997), resulting 

in a PBR of 180 strip ed dolp hins per year. 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY 

Fishery Information 

A summary of recent fishery mortality and injury for this stock of stripe d dolph in is shown in T able 1. More 

detailed information on these fisheries is provided in Appen dix 1. Mortality estim ates for the Ca lifornia drift 

gillnet fishery are included for the five most recent years of monitoring, 1994-98 (Julian and Beeson 1998; 

Julian 1997; Cameron and Forney 1999). After the 1997 implementation of a Take Reduction Plan, which 

included skipper education workshops and required the use o f pingers and minimum 6 -fathom exten ders, overa ll 

cetacean entanglement rates in the drift gillnet fishery dropped considerably (Barlow and Cameron 1999 ). 

However, because of interannual variability in entanglement rates and the ra rity of striped do lphin 

entanglements, additional years of data will be required to fully evaluate the effectiveness of pingers for 

reducing mortality of this particular species. Because of the change s in this fishery after implementation of the 

Take Reduction Plan, mean annual takes in Table 1 are based only on 1997-98 data. This results in an average 

estimate of zer o striped d olphins take n annually. 

Table 1. Summary o f available information on the incidental m ortality and injur y of striped dolp hins (California/ 

Oregon/Washington Stock) in commercial fisheries that might take this species. The single observed 

entanglement of a striped dolphin resulted in the dea th of the anima l. Coefficients of va riation for mo rtality 

estimates are provid ed in paren theses. Mean annual takes are based on 1994-98 data unless noted otherwise. 

Fishery Name Data Type Year(s) 

Percent 

Observer 

Coverage 

Observed 

Mortality 

Estimated Annual 

Mortality 

Mean 

Annual Takes 

(CV in 

parenth 

eses) 

CA/OR thresher 1994 17.9% 1 6 (0.90) 

shark/swordfish observer 1995 15.6% 0 0 

drift gillnet data 1996 12.4% 0 0 0 1 

fishery 1997 23.0% 0 0 

1998 20.0% 0 0 

Minimum total annual takes 0 

1 Only 1997-98 mortality estimates are included in the average because overall cetacean entanglement rates dropped considerably after a Take 

Reduction Plan was implemented in 1997. 

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

and may take animals from the same population. Quantitative data are available only for the M exican swordfish 

91 
drift gillnet fishery, which use s vessels, gear, an d opera tional proc edures simila r 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 estim ated from d ata provid ed by these a uthors to be approx imately 270 0, with an ob served rate 

of marine mammal bycatch of 0 .13 anima ls per set (10 marine mammals in 77 observed sets; Sosa-Nishizaki 

et al. 1993) . This over all mortality rate is similar to that observed in California driftnet fisheries during 1990-95 

(0.14 marine mammals per set; Julian and Beeson, 1998), but species-specific information is not available for 

the Mexican fisheries. There are currently efforts underway to convert the M exican swordfish driftnet fishery 

to a longline fishe ry (D. Ho lts, pers. comm .). 

STATUS OF STOCK 

The status of striped dolphins in California relative to OSP is not known, and there are insufficient data to 

evaluate potential trends in abundance. No habitat issues are known to be of concern for this species. They 

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

MMPA. Including driftnet information only for years after implementation of the Take Reduction Plan (1997­

98), the average annual hum an-caused mortality in 19 94-98 is ze ro. Beca use recent m ortality is zero, striped 

dolphins are not classified as a "strategic" stock under the MMPA , and the total fishery mortality and serious 

injury for this stock can be considered to be insignificant and approaching zero. 

REFERENCES 

Barlow, J. 1995. T he abund ance of c etaceans in C alifornia waters. Part I: Ship surveys in summer and fall of 1991. 

Fish. Bull. 93:1-14. 

Barlow, J. 1997. Preliminary estimates of cetacean abundance off California, Oregon and Washington based on a 1996 

ship survey and comparisons of passing and closing modes. Admin. Rep. LJ-97-11. Southwest Fisherie s 

Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA 92038. 25p. 

Barlow, J. and G. A . Camero n. 1999 . Field expe riments show that acoustic pingers reduce m arine mam mal bycatch in 

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

1998 (unpublished). 20 pp. 

Barlow, J. and T. G errodette. 1 996. Ab undance of cetacean s in California waters based on 1991 an d 1993 ship surv eys. 

U.S. De p. Comm er., NOA A Tech . Memo . NMF S-SW FSC-23 3. 15 pp . 

Camero n, 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 1998 (unpublished). 14 pp. 

Forney, K. A. 1997. Patterns of variability and environmental models of relative abundance for California cetaceans. 

Ph.D. dissertation, Scripps Institution of Oceanography, University of California, San Diego. 

Forney, K. A. and J. Barlow. 1998. Seasonal patterns in the abundance and distribution of California cetaceans, 1991­

92. Mar. Mamm. Sci. 14:460-489. 

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

Holts, D. and O . Sosa-Nish izaki. 1998 . Swordfish, Xiphias gladius, fisheries of the easte rn North Pacific Oc ean. In: 

I. Barrett, O. Sosa-Nishizaki and N. Bartoo (eds.). Biology and fisheries o f 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. Cetacea n 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 m ortality 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. W hales, 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. Repo rt of cetacean sightings during a marine mammal survey in the eastern 

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

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

92 
Perrin, W. F., M. D. Scott, G. J. Walker and V. L. Cass. 1985. Review of geographical stocks of tropical dolphins 

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

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

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

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

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

Sosa-Nish izaki, 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. 19 97. Guid elines for Asse ssing Marine Mam mal Stock s: Report o f the GAMMS 

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

93 pp. 

93 
Revised 12/15/2000 

SHORT-BEAKED COMMON DOLPHIN (Delphinus delphis): 

California/Oregon/Washington Stock 

STOCK DEFINITION AND GEOGRAPHIC RANGE 

Short-beaked common dolphins are the most abundant 

cetacean off Califor nia, and a re 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 (Do hl et al. 1986; Barlow 1995; F orney e t al. 

1995). Historically , they we re reporte d prima rily south 

of Pt. Conc eption (D ohl et al. 19 86), but on recent 

(1991/93/96) summer/fall surveys, they were comm only 

sighted as far north as 42o

N (Figure 1). Four strandings 

of common dolphins have been reported in Oregon and 

Washington since 1942 (B. Norberg, pers. comm .). Of 

these, three were not identified to the species level, and 

one animal, which stranded in 198 3, was identified as a 

short-beaked common dolphin (J. Hodder, pers. comm .). 

Significant seasonal shifts in the abundance and 

distribution of commo n 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; 

Mang els and Gerrodette 1994), and short-beaked 

common dolphins off California may be an extension of 

the "northern common dolphin" stock defined for 

management of eastern tro pical Pacific tuna fisheries 

(Perrin et al. 1985). However, preliminary data on 

variation in dorsal fin color patt erns suggest there may 

be multiple stocks in this region, including at least two 

possible stocks in California (Farley 19 95). The less 

abundant long-beaked common dolphin has only 

recently been recognized as a different species (Heyning 

Figure 1. Short-bea ked com mon do lphin sightings 

based on shipbo ard surveys off California, Oregon 

and Washington, 1991-96 (see Append ix 2, Figures 

3-5, for data sources and information on timing and 

location of survey effort). No Delphinus sightings 

have been mad e off Orego n and W ashington. 

Dashed line represents the U.S. EEZ, thick line 

indicates the outer bo undary of all sur veys 

combined. 

and Perrin 1994; Rosel et al. 1994), and much of the available information has not differentiated between the 

two types of com mon do lphin. Althoug h short-beake d comm on dolphin s are not restricted to U.S. w aters, 

cooperative manag emen t agreem ents with M exico ex ist only for the tuna purse seine fishery and not for other 

fisheries which m ay take this species (e.g. gillnet fisheries). Under the Marine Mammal Protection Act 

(MMPA ), short-beaked common dolphins involved in tuna pu rse seine fish eries in international waters of the 

eastern tropical Pacific are managed separately, and they are not included in the assessment repo rts. For the 

MMPA stock assessment reports, there is a single Pacific management stock including only animals found 

within the U.S. Ex clusive E conom ic Zone of Californ ia, Orego n and W ashingto n. 

POPULATION SIZE 

Aerial line transect su rveys co nducted in winter/sp ring of 19 91-92 resulted on ly in a com bined abundance 

estimate of 305,694 (CV=0.3 4) animals for sho rt-beaked and long-beake d comm on dolphin s, because specieslevel identification was no t possible from the air (Forney et al. 1995). Based o n sighting locations, th e major ity 

of these we re proba bly short- beaked comm on dolp hins. A be tter, species-sp ecific abu ndanc e estimate is 

93 
available based on three summer/fall shipboa rd surveys that w ere cond ucted within 3 00 nmi of t he coasts of 

California (in 1991 and 1993; Barlow and Gerrodette 1996) and California, Oregon and Washington (in 1996; 

Barlow 1997). The distribution of short-beaked common dolphins throughout this region is highly variable, 

apparen tly in response to oceanographic changes on both seasonal and interannual time scales (Heyning and 

Perrin 1994; Forne y 1997; Forney an d Barlow 19 98). As oceano graphic conditions vary, short-beaked common 

dolphins may spend time outside the U.S. Exclusive Economic Zone, and therefore a multi-year average 

abundance estimate is the most appropriate for management within U.S. waters. The 1991-96 weighted average 

abundance estimate for California, Oregon and Washington waters based on the three ship su rveys is 373,573 

(CV=0.19) short-beaked comm on dolphins (Barlow 1997). 

Minimum Population Estimate 

The log-normal 20th percentile of the 1991-96 weighted average abundance estimate is 318,795 short-beaked 

comm on dolphin s. 

Current Population Trend 

In the past, common dolphin abundance has been shown to increase off California during the warm-wa ter 

months (Dohl et a l. 1986). Surveys conducted during both cold-water and warm-water conditions in 1991 and 

1992 (Barlow 1995, Forney et al. 1995) resulted in overall abundance estimates (for both types of common 

dolphins combined) which were considerably greater than historical estimates (Dohl et al. 1986). The recent 

combined abundance estimate for the 1991-96 summer/fall surveys (Barlow 1997) is the highest and most 

precise to date. Environmental models (Forney 1997) and seasonal comparisons (Forney and Barlow 1998) 

have shown that the abundance o f 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 sh ort-beaked comm on dolphins) in the eastern tropical Pacific and 

along the Pacific coast of M exico suggests a possible northward shift in the distribution of common dolphins 

(IATTC 1997) during this period of gradual warming of the waters off California (Roemmich 1992). The 

majority of this is likely to reflect an increase in the abundance of short-beaked common dolphins. Heyning 

and Perrin (19 94) hav e detected change s in the pro portion o f short-be aked 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 (w hich increased water temperatures off California), and the long-beaked common 

dolphin more comm only observed for several years afterwards. Thus, it appears that both relative and absolute 

abundan ces of these species off C alifornia may ch ange with va rying ocean ographic co nditions. 

CURRENT AND M AXIMUM NET PROD UCTIVITY RATES 

There are no estimates of current o r maxim um net pro ductivity rates for short-be aked com mon do lphins. 

POTENTIAL BIOLOGICAL REMOVAL 

The potential biological remova l (PBR) level for this stock is calculated as t he minimum population size 

(318,795) times one half the d efault maximum net grow th rate for cetaceans (1⁄2 of 4%) times a recovery factor 

of 0.50 (for a species of unknown status with a mortality rate CV< 0.30; Wade and Angliss 1997), resulting in 

a PBR of 3,188 short-beake d comm on dolp hins per year. 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY 

Fishery Information 

A summ ary of rec ent fishery mortality a nd injury for short-b eaked c omm on dolp hins is shown in Table 1. 

More detailed inform ation on th ese fisheries is p rovided in App endix 1 . Mortality of com mon d olphins 

primarily has been observed in California drift gillnet fisheries (Julian and Beeson 1998; Julian 1997; Cameron 

and Forney 1999). Because of the difficu lty in distinguishing short-beaked and long-beaked common dolphins 

in the field, tissue samples have been collected for most of the animals observed killed. These tissue samples 

have enabled positive identification using genetic techniques for all except two of the common dolphins killed 

94 
(NMFS, unpublished data). Based on past patterns (Barlow et al. 1997), these two animals are likely to have 

been a short-beaked common dolphin, and they are included belo w for this species. After the 1997 

implementation of a Take Reduction Plan, which included skipp er education worksho ps and required the use 

of pingers and minimum 6 -fathom exten ders, common do lphin entanglement rates in the drift gillnet fishery 

dropped considerably (Barlow and Cameron 1999). However, because of interannual variability in 

entanglement rates additional years of data will be required to fully evaluate the effectiveness of pingers for 

reducing mortality of this spe cies in the long te rm. Because of the changes in this fishery after implementation 

of the Take Reduction Plan, mean annual takes in Table 1 are based only on 1997-98 data. This results in an 

average es timate of 78 ( CV=0 .23) short-b eaked co mmon d olphins take n annually. 

Table 1. Summ ary of av ailable info rmation on the inc idental m ortality and injury of short-beaked common dolphins 

(California/Oregon/Washington Stock), in commercial fisheries that migh t take this spec ies. All entan glemen ts 

resulted in the death of the animal. The observer program for the set gillnet fishery was discontinued during 

1994. Coefficien ts of variation for mortality estimates are provided in parentheses; n/a = not available. Mean 

annua l takes are ba sed on 1 994-9 8 data un less noted o therwise. 

Fishery Name Data Type Year 

1994 

observer 1995 

data	 1996 

1997 

1998 

observer 

d 

at 

a 

MMAP 

selfre 

p 

o 

1994 

1995-98 

1995 

1996 

1998 

strandings 1994-98 

CA/OR thresher 

shark/swordf 

ish drift 

gillnet 

fishery 

CA angel shark/ halibut 

and other 

species large 

mesh (>3.5in) 

set gillnet 

fishery 

Undetermined 

Percent 

Observer 

Coverage 

Observed 

Mortality 

Estimated Annual 

Mortality 

Mean 

Annual Takes 

(CV in 

parent 

heses) 

17.9% 

15.6% 

1 

2. 

4 

% 

23.0% 

20.0% 

26 

36 

27 

21 

9 

146 

231 (0.29) 

319 (0.23) 

105 (0.30) 

51 (0.33) 

(includes prorated) 

78 (0.23)1 

Common dolphins, species not determined 

n/a 

�0.8 (n/a) 

7.7% 

0% 

-

-

-

0 

n/a 

1 

1 

2 

0 

n/a 

�1 

�1 

�2 

2 common dolphins (species not determined) stranded with 

evidence of fishery interactions 

�0.4 (n/a) 

79 (0.23)

(0.18) 

rt Minimum total annual takes i 1

Only 1997-98 mortality estima tes are inclu n ded 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 warn ing devices (pi ngers). Following these c hanges g

in the fishery, entanglement rates of short-beaked common dolphin declined. 

Additional common dolphin mortality has been reported for set gillnets in California (Julian and Beeson 1998); 

however, because of a 1994 ban on gillnets in nearshore areas of Southern California, the size of this fishery 

decreased by about a factor of two (see Appendix 1), and the observer program was disco ntinued. No 

observer data are av ailable for th e set gillnet fishe ry after 19 94, but Marine Mammal Authorization Permit 

(MMAP) fisher self-reports for 1994-98 indicate that at least four comm on dolphins (type not specified) were 

killed betwee n 1995 and 19 98. Although the se reports a re conside red unreliab le (see App endix 4 of Hill and 

95 
DeM aster 199 8) they repre sent a minimu m mortality for th is fishery. 

Two common dolphins (type not specified) stranded with evidence of fishery interaction (NM FS, Southw est 

Region, unpublished data); one animal had a hook and line in its mouth and a slit ventrum, and the other animal 

had its flukes cut off. It is not kno wn wh ich fisheries were respo nsible for these deaths. 

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

take short-beaked common dolphins from the same population. Quantitative data are available only for the 

Mexican swordfish drift gillnet fishery, which uses vessels, gear, and operationa l procedures similar to those 

in the U.S. drift gillne t fishery, although n ets may be up to 4.5 km lo ng (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 estim ated from d ata provid ed by these a uthors to be approx imately 

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 over all mortality rate is sim ilar to that observe d in California 

driftnet fisheries during 19 90-95 (0 .14 marine mamma ls per set; Julian a nd Bee son, 199 8), but spec ies-specific 

information is not available for the Me xican fisheries. T here are cu rrently efforts underway to convert the 

Mexica n swordfish d riftnet fishery to a long line fishery (D. H olts, pers. com m.). 

Other Mor tality 

In the eastern tropical Pacific, 'northe rn comm on dolphin s' have been incidentally killed in international tuna 

purse seine fisheries since the late 1950's. Cooperative international management program s have dr amatically 

reduced overall dolphin mortality in these fisheries during the last decade (Joseph 1994). Between 1994 and 

1998, annual mortality of northern common dolphins (potentially including both short-beaked and long-beaked 

common dolphins) ranged between 9 and 261 animals, with an average of 91 (IA TTC, in prep). A lthough 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 inv olved in eastern trop ical 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 abun dance o f this species off California over the last decade probably reflects a distributional shift 

(Anganuzzi et al. 1993; Barlow 1995; Forney et al. 1995; Forney and Barlow 1998), rath er than an overall 

population increase due to growth. No habitat issues are kn own to be of con cern for th is species. They are not 

listed as "threatened" or "endangered" under the Endangered Species Act nor as "depleted" under the MMPA. 

Including driftnet mortality o nly for years after implementati on of the Take Reduction Plan (1997-98), the 

average annual human-caused mortality in 19 94-98 (7 9 animals) is estimated to be less than the PBR (3,188), 

and therefore they a re 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 co nsidered to be insignificant an d appro aching zero mortality and se rious injury rate . 

REFERENCES 

Anganuz zi, A. A., S. T. Buckland, and K. L Cattanach. 1993. Relative ab undance of dolphins associated with tuna in 

the eastern tropical Pacific Ocean: analysis of 1991 data. Rep. Int. Whal. Commn 43:459-465. 

Barlow, J. 1995. The abund ance of ceta ceans in Ca lifornia waters. P art I: Ship surve ys in summer a nd fall of 1991. 

Fish. Bull. 93:1-14. 

Barlow, J. 1997. Preliminary estimates of cetacean abundance off California, Oregon and Washington based on a 1996 

ship survey and c ompariso ns of passing a nd closing modes. Administrative Repo rt LJ-97-11, Southwe st 

Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA 92038. 25p. 

Barlow, J. and G. A. Cameron. 1999. Field experiments show that acoustic pingers reduce marine mamma l bycatch in 

the California d rift gillnet fishery. Pap er SC/51 /SM2 p resented to the International Whaling Commission, May 

1998 (unpublished). 20pp. 

Barlow, J., K. A. Fo rney, P. S. H ill, R. L. Brow nell, Jr., J. V. Carretta, D. P. DeMaster, F. Julian, M. S. Lowry, T. Ragen, 

and R. R. Reeves. 199 7. U.S. Pacific M arine Mamm al Stock Assessments: 1996. U.S. Dep. Commer., NOAA 

96 
Tech. Memo. NMFS-SWFSC-248. 223p. 

Barlow, J. and T. Gerrodette. 1996. Abun dance of cetaceans in C alifornia waters based on 19 91 and 199 3 ship surveys. 

NOA A Tech nical Me morand um NM FS, NO AA-TM -NMF S-SW FSC-23 3. 

Dohl, T. P., M. L. Bonnell, and R. G. Ford. 1986. D istribution and abundan ce on com mon do lphin, Delphin us delph is, 

in the Souther n 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-beake d comm on dolp hins, Delphin us delph is, in 

the eastern Pacific Oc ean. Adm inistrative Rep ort LJ-95 -06, Availab le 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 environmen tal models of relative abundan ce for California cetaceans. 

Ph.D. Dissertation, Scripps Institution of Oceanography, University of California, San Diego. 

Forney, K. A. and J. Barlow. 1998. Seasonal patterns in the abundance and distribution of California cetaceans, 1991­

92. Mar. Mamm. Sci. 14:460-489. 

Forney, K. A., J. Barlow and J. V. Carretta. 1995. The abundance of cetaceans in California waters. Part II: Aerial 

surveys in winter and spring of 1991 and 1992. Fish. Bull. 93:15-26. 

Heyning, J. E. and W. F. Perrin. 1994. Evidence for two spec ies of common d olphins (Genus Delphinus) from the 

eastern North Pacific. Contr. Nat. Hist. Mus. L.A. County, No. 442. 

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

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

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

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

Holts, D. and O. S osa-Nishiza ki. 1998. S wordfish, Xiphias gladius, fisheries of the easte rn North P acific Ocea n. In: 

I. Barrett, O. Sosa-Nishizaki and N. B artoo (ed s.). Biology a nd fisheries of sw ordfish, Xiphias gladius. Papers 

from the Internation al Sympo sium on P acific Swordfish, Ensenada Mexico, 11-14 December 1994. U.S. Dep. 

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

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

IATTC. (in prep). Annual Report of the Inter-American Tropical Tuna Commission, 1998, La Jolla, California. 

Joseph, J. 1994. The tuna-dolphin controversy in the eastern Pacific Ocean: bio logical, econom ic and political impac ts. 

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. E stimates of mammal, turtle and bird mortality for two California gillnet fisheries: 

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

Mange ls, K. F. and Gerrod ette, T. 199 4. Report of cetacean sightings during a marine mamm al survey in the eastern 

Pacific Ocean and Gulf of California a board the N OAA ships McARTHUR and DAVID STARR JORDAN July 

28 - November 6, 1993. NOAA Technical Memorandum NMFS, NOA A-TM-NMFS-SWFSC-211. 

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

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

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

Perrin, W. F., M. D. Scott, G. J. Walker and V. L. Cass. Review of geograp hical stocks of tropical do lphins (Stenella 

spp. and Delphin us delph is) in the eastern Pacific. NOAA T echnica l 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 a nd J. E. H eyning . 1994. Population genetic analysis of two forms o f the com mon d olphin 

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

Sosa-Nishiza ki, 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. 1 997. G uidelines 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. 

97 
93 pp. 

Wade, P. R. and T . Gerrod ette. 1993 . Estimates o f cetacean abund ance an d distributio n in the eastern tropical Pacific. 

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

98

Revised 12/15/2000 

LONG-BEAKED COMMON DOLPHIN (Delphinus capensis): 

California Stock 

STOCK DEFINITION AND GEOGRAPHIC RANGE 

Long-beaked common dolphins have only recently been 

recognized as a distinct spe cies (Hey ning an d Perrin 

1994; Rosel et al. 19 94). Alo ng the U .S. west co ast, 

their distribution overlaps with that of the short-beaked 

common dolphin, and much historical information has 

not distinguish ed betw een these two spec ies. Longbeaked common dolphin s are com monly found w ithin 

about 50 nm i of the coa st, from B aja Californ ia 

(including the Gulf of California) northward to about 

central California (Figure 1). Stranding data and 

sighting records indicate that the relative abundance of 

this species off California changes both seasonally and 

inter-annually, with highest densities observed during 

warm-water events (Heyning and Perrin 1994). 

Although long-beaked common dolphins are not 

restricted to U.S. waters, cooperative management 

agreemen ts 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 (M MPA ), long-be aked ("B aja 

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 m anagem ent stock in cluding only 

animals found within the U.S. Exclusive Economic Zone 

of California. 

POPULATION SIZE 

Aerial line transect surveys conducted in winter and 

spring of 1991 and 1992 resulted only in a combined 

Figure 1. Long-beaked common dolphin sightings 

based on shipbo ard surveys off California, Oregon 

and Washington, 1991-96 (see Append ix 2, 

Figures 3-5, for data sources and information on 

timing and location of survey effort). No 

Delphinus sightings have been made off Oregon 

and Washington. Dashed line represents the U.S. 

EEZ, thick line indicates the outer bounda ry of all 

surveys combined. 

abundance estimate of 305,694 (CV=0.34) long-beaked and short-beaked common dolphins, becau se specieslevel identification was no t possible fro m the air (F orney e t al. 1995). Based o n sighting locations, th e major ity 

of these anim als were p robably short-bea ked com mon d olphins. A better, specie s-specific ab undan ce estimate 

is available based on three summer/fall ship board su rveys that were c onducted within 300 nmi of the coasts of 

California (in 1991 and 1993; Barlow and G errodette 1996) and California, Oregon and Washington (in 1996; 

Barlow 1997). The distribution and abundance of long-beaked common dolphins off California appears to be 

variable on interannual and seasonal time scales (Heyning and Perrin 1994). As oceanographic conditions 

change, long-beaked common dolphins may spend time in Mexican waters, and therefore a multi-year average 

abundance estimate is the most appropriate for management within the U.S. waters. The 1991-96 weighted 

average abundance estimate for California, Oregon and W ashington wa ters based o n the three ship surveys is 

32,239 (CV=0 .18) long-beaked common dolphins (Barlow 199 7). 

Minimum Population Estimate 

99 
The log-normal 20th percentile of the 1991-96 weighted average abundance estimate is 27,739 long-beaked 

comm on dolphin s. 

Current Population Trend 

Due to the historical lack of distinction between the two sp ecies of co mmo n dolph ins, it is difficult to establish 

trends in abundance for this species. In the past, common dolphins have been shown to increase in abundance 

off California during the warm-water months (Dohl et al. 1986). Surveys conducted during both cold-water 

and warm-water conditions in 1991 and 1992 (Barlow 1995, Forney et al. 1995) resulted in overall abundance 

estimates (for both types of common dolphins combined) which were considerably greater than historical 

estimates (Dohl et al. 1986). The combined abundance estimate for the 1991-96 summer/fall surveys (Barlow 

1997) is the highest and most precise to date. An ongoing decline in the abundance of ‘northern common 

dolphins’ (including both long-beaked and short-beaked comm on dolp hins) in the eastern tropical Pacific and 

along the Pacific coast of M exico (IATTC 199 7) suggests a possib le northward shift in the distribution of 

common dolphins during this period of gradual warming of the waters off California (Roemm ich 1992). 

However, it is unclear how much of this increase reflects an increase in the abundance of the long-beaked 

common dolphin . Heynin g and P errin (1994) have detected changes in the proportion of short-beaked to longbeaked common d olphins stra nding a long the C alifornia co ast, with the sh ort-beak ed com mon d olphin 

stranding more frequently prior to the 1982-83 El Niño (which increased water temperatures off California), 

and the long-beaked comm on dolphin more co mmonly o bserved for several years afterwards. Thus, it appears 

that both relativ e and absolute abundance of these species off California may change with varying 

oceanogra phic conditions. 

CURRENT AND M AXIMUM NET PROD UCTIVITY RATES 

There are no estimates of current o r maxim um net pro ductivity rates for long-b eaked com mon do lphins. 

POTENTIAL BIOLOGICAL REMOVAL 

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

(27,629) times one half the default m aximum ne t growth rate for cetaceans (1⁄2 of 4%) times a recovery factor 

of 0.45 (fo r a species o f unknown sta tus with a morta lity rate CV�0.60 and �0.80; Wade and Angliss 1997), 

resulting in a PB R of 250 long-beake d comm on dolp hins per year. 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY 

Fishery Information 

A summ ary of rec ent fishery mortality a nd injury for long-beaked common dolphins is shown in Table 1. 

More detailed information on these fisheries is provided in Appendix 1. Mortality of common dolph ins 

primarily has been observed in California drift gillnet fisheries(Julian 1997; Julian and Beeson 1998; Cameron 

and Forney 1999). Because of the difficulty in distinguishing short-beaked and long-beaked common dolphins 

in the field, tissue samples have been collected for most of the animals observed killed. These tissue samples 

have enabled positive identification using genetic techniques for all except two of the common dolphins killed 

(NMFS, unpublished data). Based on past patterns (Barlow et al. 1997), these two animals are likely to have 

been a short-beaked common dolphin, and they have not been included in the mortality calculations below for 

long-beaked comm on dolphin s. After the 199 7 implementation of a T ake Red uction 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 Camero n 1999). 

However, because of interannual variability in entanglement rates additional years of data will be required to 

fully evaluate the effe ctiveness of p ingers for red ucing morta lity of this species in the lo ng term. Because of 

the changes in this fishery after implementation of the Take Reduction Plan, mean annual takes in Table 1 are 

based only on 1997-98 data. This results in an average estimate of 13 (CV=0.74) long-beaked common 

dolphins tak en annually. 

Additional comm on dolp hin mo rtality has be en repo rted for set g illnets in California (Julian and Beeson 1998); 

100 
however, because of a 1994 ban on gillnets in nearshore areas of Southern California, the size of this fishery 

decreased by about a factor of two (see Appendix 1), and the observer program was discontinued. No 

observer data are av ailable for th e set gillnet fishe ry after 19 94, but Marine Mamm al Authorization Permit 

(MMAP) fisher self-reports for 1994-98 indicate that at least four common dolphins (type not specified) were 

killed betwee n 1995 and 19 98. Although these reports are considered unreliable (see Appendix 4 of Hill and 

DeM aster 199 8) they repre sent a minimu m mortality for th is fishery. 

Two comm on dolp hins (type not specifie d) strande d with evidence of fishery interaction (NM FS, Southw est 

Region, unpublished data); one animal had a hook and line in its mouth and a slit ventrum, and the other animal 

had its flukes cut off. It is not kno wn wh ich fisheries were respo nsible for these deaths. 

Table 1. Summary of available information on the incidental mortality and injury of long-beaked common dolphins 

(Californ ia Stock) an d prorate d unide ntified com mon d olphins in comm ercial fisheries that might take this 

species. All observ ed entan glements resulted in the death of the animal. The observer program for the set 

gillnet fishery w as discon tinued du ring 199 4. Coefficients of variation for mortality estimates are provided 

in parenth eses, whe n availab le. Mean annual ta kes are ba sed on 1 994-9 8 data un less noted o therwise. 

Fishery Name Data Type Year(s) 

Percent 

Observer 

Co 

ver 

age 

Observed Estimated Annual 

Mortality 

Mean 

Annual Takes 

(CV in 

parenth 

eses) 

CA/OR thresher 

shark/swordfish 

drift gillnet 

fishery 

observer 

data 

1994 

1995 

1996 

1997 

1998 

17.9% 

15.6% 

12.4% 

23.0% 

20.0% 

1 

6 

1 

4 

0 

6 (0.91) 

39 (0.65) 

12 (0.96) 

25 (0.74) 

0 

13 (0.74)1 

CA angel shark/ halibut 

and other 

species large 

mesh (>3.5in) 

set gillnet 

fishery 

observer 

d 

at 

a 

MMAP 

selfre 

p 

o 

rt 

i 

Common dolphins, species not determined 

n/a 

�0.8 (n/a) 

1994 

1995-98 

1995 

1996 

1998 

7.7% 

0% 

-

-

-

0 

n/a 

1 

1 

2 

0 

n/a 

�1 

�1 

�2 

Undetermined strandings 1994-98 2 common dolphins (species not determined) stranded 

with evidence of fishery interactions 

�0.4 (n/a) 

Minimum total annual takes 14 (0.74) 

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

g Reduction Plan. Gear modifications included the use of net extenders and acoustic warning devices. Following these changes in the 

fishery, entanglement rates of long-beaked common dolphin declined. 

Drift gillnet fisheries for swordfish and sharks exist along the entire Pacific c oast of Ba ja California , Mexico 

and may take long-beaked common dolphins from the same pop ulation. Quantitative data are available o nly 

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 198 6 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 

approx imately 2700, w ith an observ ed rate of marine ma mmal b ycatch of 0.13 animals per set (10 marine 

101 
mamma ls in 77 obse rved sets; So sa-Nishizak i et al. 1993 ). This ove rall 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-spe cific information is not available for the Mexican fisheries. There are currently efforts underway 

to convert th e Mexic an swordfish driftnet fishery to a lo ngline fishery (D . Holts, pers. c omm.). 

Other Mor tality 

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 dr amatically 

reduced overall dolphin mortality in these fisheries during the last decade (Joseph 1994). Between 1994 and 

1998, annual mortality of northern common dolphins(potentially including both short-beaked and long-beaked 

common dolphins) rang ed between 9 and 261 animals, with an average of 91 (IAT TC, in pr ep). Altho ugh it 

is likely that the long-beaked common dolphins included in the 'northern common dolphin' stock are part of 

the same population as those found off Califor nia, they ar e mana ged sep arately under a section of the MMPA 

written specifically for the m anagem ent of dolphins in volved in eastern tropical Pacific tuna fisheries. 

STATUS OF STOCK 

The status of long-beaked common dolphins in California waters relative to OSP is not known, and there are 

insufficient data to eva luate poten tial trends in ab undan ce 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 th e MM PA. Including driftnet mortality only for years after 

implementation of the Take Reduction Plan (1997-98), the average annual human-caused mortality in 1994-98 

(14 animals) is estima ted to be less than the PB R (250 ), and therefore they are not classified as a "strategic" 

stock under the M MPA . The average total fishery mortality and injury for long-beaked common dolphins is 

less than 10% of the PBR and, therefore, can be considered to be insignificant and approaching zero m ortality 

and serio us injury ra te. 

REFERENCES 

Barlow, J. 1995. The abundance o f cetaceans in California waters. Part I: Ship surveys in summer and fall of 1991. 

Fish. Bull. 93:1-14. 

Barlow, J. 1997. Preliminary estimates of cetacean a bundanc e off California, Oregon and Washington based on a 1996 

ship survey and comparisons of passing and closing modes. Administrative Report LJ-97-11 , Southwest 

Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA 92038. 25p. 

Barlow, J. and G. A. Camero n. 1999 . Field expe riments show that acoustic p ingers reduc e marine mammal byc atch in 

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

1998 (unpublished). 20pp. 

Barlow, J., K. A. Forney, P. S. Hill, R. L. Brownell, Jr., J. V. Carretta, D. P. DeMaster, F. Julian, M. S. Lowry, T. Ragen, 

and R. R. Reeves. 1 997. U.S. Pacific Marine Mammal Stock Assessments: 1996. U.S. Dep. Commer., NOAA 

Tech. Memo. NMFS-SWFSC-248. 223p. 

Barlow, J. and T. Gerr odette. 19 96. Abu ndance o f cetaceans in C alifornia waters based on 1991 a nd 199 3 ship surveys. 

U.S. De p. Comm er., NOA A Tech . Memo . NMF S-SW FSC-23 3. 

Cameron, G., and K. A. Forney. 1999. Estimates of cetacean m ortality in the Califo rnia gillnet fisheries for 1997 and 

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

Dohl, T. P., M. L. Bonnell, and R. G. Ford. 1986. Distribution and abundance on com mon d olphin, Delphin us delph is, 

in the South ern Califo rnia Bigh t: A quantitative assessment based upon aerial transect data. Fish. Bull. 84:333­

343. 

Forney, K. A., J. Barlow and J. V. Carretta. 1995. The abundance of cetaceans in California waters. Part II: Aerial 

surveys in winter and spring of 1991 and 1992. Fish. Bull. 93:15-26. 

Heyning, J. E. and W. F. Pe rrin. 1994. Evid ence for two sp ecies of comm on dolphin s (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 

102 
Tech. Memo. NMFS-AFSC-97. 166 pp. 

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

Holts, D. and O . Sosa-Nish izaki. 1998 . Swordfish, Xiphias gladius, fisheries of the easte rn North Pacific Oc ean. In: 

I. Barrett, O. Sosa-Nishizaki and N. Bartoo (eds.). Bio logy and fisher ies of sword fish, Xiphias gladius. Papers 

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

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

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

IATTC. (in prep). Annual Report of the Inter-American Tropical Tuna Commission, 1998, La Jolla, California. 

Joseph, J. 1994. The tuna-dolphin controversy in the eastern Pacific Ocea n: biological, econo mic and po litical 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 m ammal, turtle and bird mo rtality 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 geograp hical stocks of tropical do lphins (Stenella 

spp. and Delphin us delph is) in the easter n Pacific. N OAA Techn ical Repo rt 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 form s of the com mon d olphin 

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

Sosa-N ishizaki, 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. 19 97. Guid elines for Asse ssing Marine Mam mal Stock s: Report of the GAMMS 

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

93 pp. 

103 
Revised 12/15/2000 

NORTHERN RIGHT-WHALE DOLPHIN (Lissodelphis borealis): 

California/Oregon/Washington Stock 

STOCK DEFINITION AND GEOGRAPHIC RANGE 

Northern right-whale dolphins ar e endem ic to temper ate 

waters of the North Pacific Oc ean. 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 199 8). 

The southern en d of this pop ulation's range is no t welldocumented, but during cold-water periods, they 

probab ly range into Mexican waters off northern Baja 

California. Genetic an alyses have no t 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 

agreeme nts 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 E conom ic 

Zone of California, Oregon and Washington. 

POPU LATIO N SIZE 

Figure 1. Northern right-whale dolphin do lphin 

sightings based on aerial and ship board su rveys off 

California, Oregon and Washington, 1991-96 (see 

Appen dix 2, Figures 1-5, for data sources and 

information on timing and location of survey 

effort). Dashed line represents the U.S. EEZ, 

thick line indicates the outer bou ndary of all 

surveys combined. 

The previous best estimates of abundance for northern right-whale dolphins (Barlow et al. 1997) were based 

on winter/spr ing 1991 -92 aerial surv eys (Forney et al. 1995) off California, which were presumed to include 

northern right-whale dolphins that are found off Oregon and Washington during summer and fall. Three 

summer/fall shipboard surveys were conducted within 300 nmi of the coasts of California in 1991 and 1993 

(Barlow and Gerrodette 1996) and California, Oregon and Washington in 1996 (Barlow 1997). The distribution 

of northern righ t-whale dolp hins througho ut this region is highly v ariable, apparently in response to 

oceano graphic 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 

Econo mic Zone, and therefore a m ulti-year average abundan ce estimate is the most app ropriate for management 

within U.S. waters. The 1991-96 weighted average abundance estimate for California, Oregon and Washington 

waters based on the three ship surveys is 13,705 (CV=0.38 ) northern right-whale dolphins (Barlow 1997). 

104 
Minimum Po pulation Estimate 

The log-norma l 20th perc entile of the 19 91-96 w eighted ave rage abun dance estim ate is 10,06 0 northern rightwhale dolphins. 

Current Population Trend 

No information is available regarding trends in abundance of northern right-whale dolphins in California, 

Oregon and W ashington. 

CURRENT AND M AXIMUM NET PRODUCTIVITY RATES 

No information on current or maximum net productivity rates is available for northern righ t-whale dolp hins off 

the U.S. we st coast. 

POTENTIAL BIOLOGICAL REMOVAL 

The po tential biologic al remova l (PBR) level for this stock is calculated a s the minimum population size 

(10,060) times one half the d efault maximum net growth rate for cetaceans (1⁄2 of 4%) times a recovery factor 

of 0.48 (for a species of unknown status with a mortality rate CV>0.30; Wade and Angliss 1 997), resu lting in 

a PBR of 97 north ern right-whale d olphins pe r year. 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY 

Fishery Information 

A summary of recent fishery mortality and injury for this stock of northern right-whale dolphin is shown in 

Table 1. More detailed information on these fisheries is provided in Appendix 1. Mortality estimates for the 

California drift gillnet fishery are included for the five most recent years of monitoring, 1994-98 (Julian and 

Beeson 1998; Julian 1997; Cameron and Forney 1999). After the 1997 implementation of a Take Reduction 

Plan, which included skipper education workshops and required the use of pingers and minimum 6-fathom 

extenders, overall cetacean entanglement rates in the drift gillnet fishery dropped considerably (Barlow and 

Cameron 1999). However, because of interannual variability in entanglement rates and the relative rarity of 

northern right-whale do lphin entanglements, add itional years of data will be required to fully evaluate the 

effectiveness of pingers for reducing mo rtality of this particular species. Because of the changes in this fishery 

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

This results in a n average e stimate of 15 (CV=0 .42) northe rn right-whale d olphins take n annually. 

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

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

entangle ments of northern right-whale dolphins resulted in the death of the animal. Coefficients of variation 

for mortality estimates are provided in parentheses. Mean annual takes are based on 1994-98 data unless noted 

otherw ise. 

Fishery Name Data Type Year(s) 

Percent 

Observer 

C 

o 

v 

er 

a 

g 

e 

Observed 

M 

ort 

ali 

ty 

Estimated Annual 

Mortality 

Mean 

Annual Takes 

(CV in 

parenth 

eses) 

CA/OR thresher 

shark/swordfish 

drift gillnet 

fishery 

observer 

data 

1994 

1995 

1996 

1997 

1998 

17.9% 

15.6% 

12.4% 

23.0% 

20.0% 

7 

9 

5 

5 

0 

39 (0.42) 

58 (0.59) 

27 (0.68) 

29 (0.42) 

0 

15 (0.42)1 

Minimum total annual takes 15 (0.42) 

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 extend ers and acoustic warnin g devices (pingers). Following these changes 

within the fishery, entanglement rates of northern right-whale dolphin declined. 

105 
Drift gillnet fisheries for swordfish and sharks exist along the entire Pacific coa st of Baja C alifornia, Mexico 

and may take animals from the same popula tion durin g cold-w ater period s. Quantitativ e data are a vailable only 

for the Me xican sw ordfish d rift 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 

approx imately 2700, with an observed rate of marine mammal bycatch of 0.13 animals per set (10 marine 

mamma ls in 77 observed sets; Sosa-Nishizaki et al. 1993). This over all 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 Mexica n fisheries. The re are curre ntly efforts underway 

to convert th e Mexic an swordfish driftnet fishery to a lo ngline fishery (D . Holts, pers. c omm.). 

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 "de pleted" u nder the M MPA . Including d riftnet mortality only for years after implementation of the 

Take Reduction Plan (1997-98), the average an nual human -caused m ortality in 199 4-98 (15 animals) is 

estimated to be less than the PBR (97), and therefore they are not classified as a "strategic" stock under the 

MMPA. The total fishery mortality and serious injury for northern right-whale dolphins is greater than 10% of 

the calculated PBR and, therefo re, cannot b e consider ed to be insig nificant and ap proachin g zero mo rtality and 

serious injury ra te. 

REFERENCES 

Barlow, J. 1995. T he abund ance of ceta ceans in Ca lifornia waters. P art I: Ship surve ys in summer a nd fall of 1991. 

Fish. Bull. 93:1-14. 

Barlow, J. 1997. Preliminary estimates of cetacean abundance off California, Oregon and Washington based on a 1996 

ship survey and comparisons of p assing and closing mod es. Administrative Report LJ-97-11, Southwest 

Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA 92038. 25p. 

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

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

1998 (unpublished). 20pp. 

Barlow, J., K. A. Forney, P. S. Hill, R. L. Brownell, Jr., J. V. Carretta, D. P. DeMaster, F. Julian, M. S. Lowry, T. Ragen, 

and R. R. Reeves. 1997. U.S. Pacific Marine Mammal Stock Assessments: 1996. U.S. Dep. Commer., NOAA 

Tech. Memo. NMFS-SWFSC-248. 223p. 

Barlow, J. and T. Gerrodette. 1996. Abundance of cetaceans in California waters based on 1991 and 1993 ship surveys. 

U.S. De p. Comm er., NOA A Tech . Memo . NMF S-SW FSC-23 3. 

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, 1998 (unpublished). 14pp. 

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

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 B ight. 

106 
Final Report to the Bureau of Land Management, NTIS Rep. No. PB81248189. 414p. 

Forney, K. A. 1994. Recent information on the status of odontocetes in Californian waters. NOAA Techni cal 

Memorandum NMFS, NOAA-TM-NMFS-SW FSC-202. Available from NMFS, Southwest Fisheries Science 

Center, P.O. Box 271, La Jolla, California, USA. 

Forney, K. A. and J. Barlow. 1998. Seasonal patterns in the abundance and distribution of California cetaceans, 1991­

92. Mar. Mamm. Sci. 14:460-489. 

Forney, K. A., J. Barlow and J. V. Carretta. 1995. The abundance of cetaceans in California waters. Part II: Aerial 

surveys in winter and spring of 1991 and 1992. Fish. Bull. 93:15-26. 

Green, G., J. J. Brueggeman, R. A. Grotefendt, C. E. Bowlby, M. L. Bonnell, and K. C. Balcomb, III. 1992. Cetacean 

distribution and abundance off Oregon and Washington. Ch. 1. In: Oregon and Washington Marine Mammal 

and Seabird Surveys. O CS Stud y 91-009 3. Final Rep ort prepa red for Pa cific OCS Region, M inerals 

Manag ement Ser vice, U.S. D epartmen t of the Interior, L os Angele s, California. 

Green, G., R. A. G rotefendt, M . A. Smultea , C. E. Bowlby, a nd R. A. Rowlett. 199 3. Delph inid aerial surve ys in 

Oregon and Washington waters. Final Report prepared for NMFS, National Marine Mammal Laboratory, 7600 

Sand Point Way, NE, Seattle, Washington, 98115, Contract #50ABNF200058. 

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

Holts, D. a nd O. So sa-Nishizak i. 1998. Swordfish, Xiphias gladius, fisheries of the eastern North Pacific Ocean. In: 

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

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

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

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

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

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

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

Leatherwood, S. and W. A. Walker. 1979. The northern right-whale dolphin Lissodelp his borea lis Peale in the eastern 

North Pacific. In: Winn, H. E. and B. L. Olla (eds.), Beha vior of Marin e Mam mals, p. 85-14 1. Plenum P ress, 

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. Su mma ry of the 1 988 W ashingto n/Oreg on exp erimen tal thresher shark gill net 

fishery. State of Washington, Department of Fisheries, Progress Report 275. 40p. 

Wade, P. R. and R. P. A ngliss. 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. 

107 
108

Figure 1. Approximate distribution of killer whales in the

eastern North Pacific (shaded area). stribution of

the Eastern N orth Pacific Northern Resident and Transient

stocks are larg ely overlapp ing (see text). 

Revised 12/15/2000

KILLER WHALE (Orcinus orca): 

Eastern North Pacific Transient Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

Killer whales have been observed in all oceans

and seas of the world (Leatherwood and

Dahlheim 1978). reported from

tropical and offshore waters, killer whales prefer

the colder wa ters of both hemisphe res, 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 waterw ays (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 w aterways 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

morpho logy, ecology, genetics, and behavior

(Ford and Fisher 1982, Baird and Stacey 1988,

Baird et al. 1992, Hoelzel et al. 1998). 

examination of photographs o f recognizable individuals and pods, movements of whales between geographical

areas have been documented. e, whales identified in Prince William Sound have been observed near

Kodiak Island (M atkin et al. 199 9) and wh ales identified in S outheast Ala ska have b een obse rved in Prince

William Sound, British Columbia, and Puget Sound (Leatherwood et al. 1990, Dahlheim et al. 1997).

Movements of killer whales between the waters of Southeast Alaska and central California have also been

documented (Goley and Straley 1994).

Studies on mtDNA restriction patterns provide evidence that the ‘resident’ and ‘tra nsient’ types are g enetically

distinct (Stevens et al. 1989, Hoelzel 1991, Hoelzel and Dover 1991, Hoelzel et al. 1998). sis 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 Washin gton, and ‘re sident’ whales ranging from British Columbia to the Aleutian Islands

and Bering Sea (Hoelzel et al. 1998).

Based on data regarding association patterns, acoustics, movements, genetic differences and potential fishery

interactions, five killer whale stocks are recognize d within the Pa cific U.S. EE Z: 1) the Ea stern 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

Columb ia, but also in co astal waters from British Columbia throu gh California , 3) the Easte rn North P acific

Transient stock - occurring from Alaska through California (see Fig. 1), 4) the Eastern North Pacific Offshore

stock - occurring from Southeast Alaska through California, and 5) the Hawaiian stock. ient’ whales in

Canadian waters are considered part of the Eastern North Pacific Transient stock. 

Reports for the Alaska Region contain information concerning the Eastern North Pacific Northern Resident

stock

The di

Although 

Through

For exampl

Analy

‘Trans

The Stock Assessment
POPU LATIO N SIZE 

The Eastern North Pacific Transient stock is a trans-boundary stock, including killer whales from British 

Columbia. Preliminary analysis of photographic data resulted in the following minimum c ounts for ‘transie nt’ 

killer whales belonging to the Eastern North Pacific Transient stock (Note: individual whales have been 

matched between geographical regions and missing animals likely to be dead have b een subtracted). In British 

Columb ia and southeastern Alaska, 219 ‘transient’ whales have been cataloged (Ford and Ellis 1999). In the 

Gulf of Alaska, 21 ‘transient’ killer whales have been identified genetically and/or acoustically (Matkin et al. 

1999). The ‘transien t’ group AT1, commonly seen in Prince William Sound/Kenai Fjords, had only 11 

remaining whales in 19 98 (M atkin et al. 1999 ). Based on data collected from all Alaska waters west of Seward 

(Dahlheim and Waite 1993; Dahlheim 1994, 1997), 68 whales are considered ‘residents’ as they have been 

linked by associatio n to ‘resident’ whales from Prince William Sound (G. Ellis, pers. comm.), and the remainder 

are provisiona lly classified as 17 4 ‘residents’ an d 53 ‘transie nts.’ Provisional classifications were based 

primarily on morphological differences identified from the photographs. Accordingly, the numbers of 

‘residents’ and ‘transients’ in A laska waters w est of Seward are consid ered pre liminary at this time. O ff the 

coast of California, 105 ‘transient’ whales have been identified (Black et al. 1997): 10 whales were matched 

to photos of ‘transients’ in other catalogs and the remaining 95 were linked by association. An additional 14 

whales in southeastern Alaska (M . Dahlheim , unpubl. da ta) and 16 whales off the coast of California (N. Black, 

pers. comm.) have been provisionally classified as ‘transient’ whales by associatio n. Combining the counts of 

cataloged ‘transient’ whales gives a minimum number of 346 (219 + 21 + 11 + 95) killer whales be longing to 

the Eastern North Pacific Transient stock. 

Minimum Po pulation Estimate 

The abundan ce estimate o f killer whales is a dire ct count of ind ividually identifi able animals. However, the 

number of cataloged whales does not necessarily represent the number of live animals. Some animals may have 

died, but whales can not be presumed dead if not resighted because long periods of time between sightings is 

common for some ‘tr ansient’ animals. On the other hand, given that researchers continue to identify new 

whales, the estim ate of abundance based on the number of uniquely ide ntified individu als cataloged is likely 

conservative. However, the rate of discovering new whales within Southeast Alaska and Prince William Sound 

is relatively low. In addition, the abundance estimate does not include 53 whales from western Alaska, 14 

whales from southeastern Alaska, and 16 whales off the co ast of California that have be en provisio nally 

classified as ‘transie nts.’ 

Other estimates of the o verall pop ulation size (i.e., N BEST) and associated CV(N) are not currently available. 

Thus, the minimum population estimate (NMIN) for the Eastern North Pacific Transient stock of killer whales 

is 346 animals, which includes animals found in Canadian waters (see PBR Guidelines regarding the status of 

migratory trans-boun dary stocks, W ade and Angliss 199 7). Informa tion on the p ercentage o f time animals 

typically encountered in Canadian waters spend in U.S. waters is unknown. Ho wever, as no ted abov e, this 

minimum population estimate is considered conservative. This approach is consistent with the 

recomm endations o f the Alaska Sc ientific Review G roup (D eMaste r 1996) . 

Current Population Trend 

At present, reliable data on trends in population abundance for the Eastern North Pacific Transient stock of 

killer whales are unavailable. 

CURRENT AND M AXIMUM NET PRODUCTIVITY RATES 

A reliable estimate of the maximum net produ ctivity rate is currently un available for this stock of killer whales. 

Studies of ‘resid ent’ killer whale po ds in the Pacific Northwest resulted in estimated population growth rates 

of 2.92% and 2.54% over the period from 1973 to 1987 (O lesiuk et al. 1990, Brault and Caswell 1993). 

However, a population increases at the maximum growth rate (RMAX) only when the po pulation is at ex tremely 

low levels; thus, the estima te of 2.92% is not a reliable e stimate of R MAX. Hence, un til additional data become 

available, it is recommended that the cetacean maximum theoretical net productivity rate (RMAX) of 4% be 

109 
employed for this stock (Wade and Angliss 1997). 

POTENTIAL BIOLOGICAL REMOVAL 

The potential biological removal (PBR) level for this stock is calculated as the minimum population size (346) 

times one-half the default maximum net growth rate for cetaceans (1⁄2 of 4%) times a recovery factor of 0.40 

(for a cetacean stock of unknown status with a mortality rate CV�0.80, W ade and Angliss 199 7), resulting in 

a PBR of 2.8 whales per year. The proportion of time that this trans-boundary stock spends in Canadian waters 

cannot be determined (G. Ellis, pers. comm.). 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY 

Fisheries Information 

Six different commercial fisheries in Alaska that could have interacted with killer whales were monitored for 

incidental take by fishery observers from 1994 to 1998: Bering Sea/Aleutian Islands (BSAI) and Gulf of Alaska 

groundfish trawl, longline, and pot fisheries. Of the six observed fisheries, killer whale mortalities occurred 

only in the Bering Sea groundfish trawl and longline fisheries (Table 1; Perez in prep.). From 1994 to 1998, 

one killer whale mo rtality was obser ved in 19 97 in the Bering S ea ground fish trawl fishery. Th e 1995 mortality 

in the longline fishery occurred during an unmonitor ed haul and could not be used to estimate tota l mortality 

for the fishery. 

NMFS observers also monitored the California/Oregon thresher shark/swordfish drift gillnet fishery from 1994 

to 1998 (Table 1; Julian 1997, Julian and Be eson 199 8, Came ron and F orney 19 99). Th e observe d mortality 

in this fishery, in 1995 , was a transient w hale as deter mined by g enetic testing (S. Chivers, pers. comm.). 

Overall entanglement rates in the California/Oregon thresher shark/swordfish drift gillnet fishery dropped 

considera bly after the 1997 implementation of a Take Reduction Plan, which included skipper education 

workshops and required the use of pingers and minimum 6-fathom extenders (Barlow and Cameron 1999). 

Because of the changes in this fishery after implementation of the Take Reduction Plan, mean annu al takes in 

Table 1 are based only on 1997-199 8 data. Additional fisheries that could interact with the Easte rn North 

Pacific Transient stock of killer whales are listed in Appendix 1. 

The mean annual mortality was 0.4 (CV=1.0) for the Bering Sea groundfish trawl fishery, 0.2 (0 from monitored 

hauls + 0.2 from unmonitored haul data) for the combined Bering Sea longline fishery, and zero for the 

California/Oregon thresher shark/swordfish drift gillnet fishery (1997-1998 data), resulting in a mean annual 

mortality rate of 0.6 killer whales per year from ob served fisheries. 

An additional source of information on the number of killer whales killed or injured incidental to commercial 

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

the period b etween 19 94 and 1 998, there were no fisher self-reports of killer whale mortalities from any Alaska 

fisheries operatin g within the range of this stock. Ho wever, bec ause logbo ok record s (fisher self-repo rts 

required during 1990-94) are most likely negatively biased (Credle et al. 1994), these are considered to be 

minimum estimates. Self-rep orted fisheries data are incomplete for 1994, not available for 1995, and 

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

The estimated minimum mo rtality rate incidental to recently monitored U.S. co mmercial fisheries is 0.6 animals 

per year, based on observer data (0.4 from m onitored h auls + 0.2 fro m unmon itored hauls). As the anima ls 

which were taken inc idental to comm ercial fisheries in Alaska have not been identified genetically, it is not 

possible to determine whether they belonged to the Eastern North Pacific Northern Resident or the Eastern 

North Pacific Transient killer wha le stock. Acc ordingly, these same mortalities can be found in the stock 

assessment re port for the N orthern Re sident stock. 

Table 1. Summary of incidental mo rtality of killer whales (E astern No rth Pacific T ransient stock ) due to commercial 

fisheries and calculation of the mean annual mortality rate. Mean annual takes are based on 19 94-98 data unless 

noted otherwise. 

110 
Fishery name Years Data type 

Percent 

o 

b 

s 

e 

r 

v 

e 

r 

c 

o 

v 

e 

r 

a 

g 

e 

Observed 

mortality 

Estimated 

mortality 

Mean annual 

takes 

(CV in 

parenth 

eses) 

Beri ng Sea /Aleu tian Is. (B SAI) 

groundf ish trawl 

94 

95 

96 

97 

98 

obs data 65.5% 

67.3% 

66.2% 

63.9% 

67.0% 

0 

0 

0 

1 

0 

0 

0 

0 

2 

0 

0.4 (1.0) 

BSAI groundfish longline 

(incl. misc. finfish 

and sablefish 

fisheries) 

94 

95 

96 

97 

98 

95 

obs data 

unmonitored 

h 

a 

u 

l 

27.3% 

28.0% 

28.7% 

32.5% 

36.2% 

0 

0 

0 

0 

0 

1 

0 

0 

0 

0 

0 

0 

0.2 

CA/OR thresher shark/ 

swordfish drift gillnet 

94 

95 

96 

97 

98 

obs data 17.9% 

15.6% 

12.4% 

23.0% 

20.0% 

0 

1 

0 

0 

0 

0 

6 

0 

0 

0 

01 

Estimated t otal annual t akes 0.6 (1.0) 

1

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

Reduction Plan. Gear modifications in cluded the use of net extenders and acoustic warnin g devices (pingers). 

Due to a lack of Canadian observer programs, there are few data concerning the mortality of marine ma mmals 

incidental to Canadian commercial fisheries, which are analogous to U.S. fisheries that are known to interact 

with killer whales. The sablefish longline fishery accounts for a large proportion of the commercial 

fishing/killer whale interactions in Alaska waters. Such interactions have not been reported in Canadian waters 

where sablefish are taken via a po t fishery. Since 1990, there have been no reported fishery-related strandings 

of killer whales in Canadian waters. However, in 1994, one killer whale was reported to have contacted a 

salmon gillnet, but it did not en tangle (Gue nther et al. 1995). D ata regardin g the level of killer w hale mortality 

related to commercial fisheries in Canadian w aters, though th ought to be small, are not re adily available or 

reliable which results in an underestimate of the annual mortality for this stock. 

Subsistence/Native Harvest Information 

There are no reports of a subsistence harvest of killer whales in Alaska or Canada. 

111 
Other M ortality 

There is considerable interaction between killer whales and longline vessels in the Bering Sea (Dahlheim 1988;


Yano and Dahlheim 1995; Perez in prep.; M. Perez, unpubl. data), as well as reports of killer whales consuming


the processing waste of Be ring Sea gro undfish trawl fishing vessels (M. Perez, unpubl. data). H owever, it most


likely is the ‘resident’ stock of killer whales that is involved in such fishery interactions since these whales are


known to be fish eaters, while ‘transient’ whales have only bee n observed feeding o n marine mamm als.


The shooting of killer whales in Canadian waters has also been a concern in the past. However, in recent years


there have been no repor ts of shooting inc idents in Can adian water s. In fact, the likelihood of shooting


incidents involving ‘transie nt’ killer whales is thou ght to be minimal since c ommerc ial fishermen are most likely


to observe ‘transients’ feeding on seals or sea lions instead of interacting with their fishing gear (G. Ellis, pers.


comm.).


Collisions with boats are another source of mortality. One mortality due to a ship strike occurred in 1998, when


a killer whale struck the propeller of a vessel in the Bering Sea groundfish trawl fishery, resulting in an


estimated annual mortality of 0.2 killer whales from this stock in 1994-1998.


STATUS OF STOCK 

Killer whales are not listed as “depleted” under the MMPA or listed as “threatened” or “endangered” under the 

Endangered Species A ct. Recall that the h uman-caus ed morta lity has been und erestimated , primarily due to 

a lack of information on Canadian fisheries, and that the minimum abundance estimate is considered 

conservative (because researchers continue to encounter new whales and provisiona lly classified whales from 

western Alaska, southeastern Alaska, and off the coast of California were not included), resulting in a 

conservative PBR estimate. Ba sed on cur rently available data, the estima ted annual fishe ry-related mo rtality 

level (0.6) exce eds 10% of the PBR (0.28 ) and, therefo re, can not b e consid ered to be insignificant and 

approaching zero mortality and serious injury rate. The estimated annual level of human-caused mortality and 

serious injury (0.6 + 0.2 = 0.8 animals per year) is not known to exceed the PBR (2.8). Therefore, the Eastern 

North Pacific Transient stock of killer whales is not classified as a strategic stock. Population trends and status 

of this stock relative to its Optimum Sustainable Population (OSP) level are currently unknown. 

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Individuals. Day M oon Press, Seattle, W A. 82 pp. + ap pendices. 

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Anchorage, AK. 20 pp + appendices. Available upon request - D. P. DeMaster, National Marine Mammal 

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

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University of Washington Press, Seattle. 102 pp. 

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killer whales (Orcinus orca) previously identified in Glacier Bay, Alaska. Can. J. Zool. 72:1528-1530. 

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distribution and abundance off Oregon and Washington, 1989-1990. Pp. 1-100, In: Brueggeman, J. J. (ed.), 

Oregon and Washington Marine Mammal and Seabird Surveys. Final Rep. OCS Study MMS 91-0093. 

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fishing gear entanglements of cetaceans on the west coast of Canada in 1994. Paper SC/47/O6 p resented to the 

International Whaling Commission, May 1995 (unpublished). 7 pp. 

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

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conservation. Rep. Int. Whal. Commn. Special Issue 13:225-233. 

Hoelze l, A. R., and G . A. Dove r. 1991. G enetic differentia tion betwee n sympatric kille r whale po pulations. H eredity 

113 
66:191-195. 

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the Eastern North Pacific, and genetic differentiation between foraging specialists. J. Heredity 89:121-128. 

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

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fisheries: 1990-1995. Fish. Bull. 96(2):271-284. 

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Prince William Sound, Alaska 1976 to 1987. Can. Field Nat. 104:362-371. 

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Gulf Oceanic Society. 96 pp. 

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32:914-916. 

Olesiuk, P. F., M. A . Bigg, and G . M. Ellis. 19 90. Life history and population dynamics of resident killer whales 

(Orcinus orca) in the coastal w aters of British C olumbia and Washington State. Rep. Int. Whal. Commn. 

Special Issue 12:209-242. 

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groundfish fisheries in the U.S. EEZ of the North Pacific, 1989-99. 

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67:2592-2595. 

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

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114 
Revised 12/15/2000 

KILLER WHALE (Orcinus orca): 

Eastern North Pacific Offshore Stock 

STOCK DEFINITION AND GEOGRAPHIC 

RANGE 

Killer whales have been observed in all oceans 

and seas of the world (Leatherwood and 

Dahlheim 1978). Although reported from 

tropical and offshore waters, killer whales prefer 

the colder waters of both hemisp heres, 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 Colu mbia 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 

morpho logy, ecology, genetics and behavior 

(Ford and Fisher 1982; Baird and Stacey 1988; 

Baird et al. 1992, Hoelze l et al. 1998). Through 

examination of photog raphs of rec ognizable 

individuals and pod s, 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 

Figure 1. Killer whale sightings based on aerial and 

shipboard surveys off California, Oregon and Washington, 

1991-96 (see Appendix 2, Figures 1-5, for data sources 

and information on timing and location of survey effort). 

Sightings include kille r whales from all stock s found in 

this region. Da shed line rep resents the U .S. EEZ, thic k 

line indicates the outer boundary of all surveys combined. 

identified in Southeast Alaska have been observed in Prince William Sound, British Columbia, and Puget Sound 

(Leatherwood et al. 1990, Dahlheim et al. 1997). Movements of killer whales between the waters of Southeast 

Alaska and central California have also been documented (Goley and Straley 1994). 

Offshore killer whales hav e more rec ently also bee n identified off the coasts of Ca lifornia, Oreg on, and rar ely, 

in Southeas t Alaska (Fo rd et al. 199 4, Black e t al. 1997, Dahlheim et al. 1997). They app arently do no t 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 clos ely related gen etically, morphologically, behaviorally, and vocally to the ‘resident’ type killer 

whales (Black et al. 1997, Hoelzel et al. 1998; J. Ford, pe rs. comm.; L. Barrett-Lennard, pers. comm.). Based 

on data regarding association patterns, acoustics, movements, genetic differences, and potentia l fishery 

interactions, five k iller whale stock s are recog nized within the Pacific U.S. EEZ 1) the Eastern N orth Pacific 

Northern Resident stock - occurring from British Columbia through Alaska, 2) the Eastern North Pacific 

Southern Resident stock - occurring within the inland waters of Washington State and southern B ritish 

Columbia, 3) the Eastern North Pacific Transient stock - occurring from Alaska through California, 4) the 

Eastern N orth Pacific Offshore stock - occurring from Southeast Alaska through California (this report), and 

5) the Hawaiian stock. ‘Offshore’ whales in Canadian waters are consid ered par t of the Eastern North P acific 

115 
Offshore stock. The Stock Assessment Reports for the Alaska Region contain assessments o f the Eastern N orth 

Pacific Northern Resident sto ck, and the m ost recent asse ssment for the H awaii Stock is included in this 

volume. 

POPU LATIO N SIZE 

Off British Colu mbia, app roximately 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 o f known indiv iduals in this po pulation to 2 11. This is c ertainly an underestimate of the total 

population size, becaus e not all anima ls in this popula tion have be en photo graphed. In the future, it may be 

possible estimate the total abundance of this transboundary stock using mark-recapture analyses based on 

individual photographs. Based on summer/fall shipboard line-transect surveys in 1991, 1993 and 1996 (Barlow 

1997), the total number of killer whales within 300 nmi of the coasts of California, Oregon and Washington was 

recently estimated to b e 819 an imals (CV =0.38) . There is cu rrently no way to reliably distinguish the different 

stocks of killer whales from sightings at sea, but photographs of individual a nimals can prov ide a rough estimate 

of the proportion of whales in each stock. A total of 16 1 individua l killer whales pho tographe d off Californ ia 

and Oregon have been determined to belong to the transient (105 whales) and offshore (56 whales) stocks 

(Black et al. 1997). Using these p roportio ns to prora te the line transec t abundan ce estimate yield s an estimate 

of 56/161 * 819 = 2 85 offshor e killer whales alo ng the U.S. w est 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 a ssessment pu rposes, this co mbined v alue is currently the best available estimate of abundance for 

offshore killer whales off the coasts of California, Oregon and Washington. 

Minimum Po pulation Estimate 

The total number of known offshore killer whales along the U.S. West coast, Can ada and Alaska is 21 1 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 W ashington can be estimated from the 1991-1996 line-transect 

surveys as the 20th percentile of the abundance estimate, or 601 killer whales. Using the same prorating as 

above, a minimum of 56/161 * 601 = 209 o ffshore killer whales are estimated to be in U .S. waters off 

California, Oregon and Washington. 

Current Population Trend 

No information is available reg arding trends in abunda nce of Eastern No rth Pacific offshore killer whales. 

CURRENT AND M AXIMUM NET PRODUCTIVITY RATES 

No inform ation on cur rent or max imum net pr oductivity rates is available for k iller whales in this reg ion. 

POTENTIAL BIOLOGICAL REMOVAL 

The potential biological re moval (P BR) leve l for this stock is calculated as the minimum population size (209) 

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

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

2.1 offshor e killer whales p er year. 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY 

Fishery Information 

A summary o f information o n fisheries that ma y take animals fro m this killer whale stock is shown in Table 1. 

More detailed information on these fisheries is provided in Appendix 1. In the Californ ia drift gillnet fishery, 

no offshore killer whales have been observed entangled ( Julian 1997; Julian and Beeson 1998; Cameron and 

116 
Forney 1999), but one killer whale from the Eastern North Pacific Transient Stock was observed taken in 1995, 

and offshore killer w hales may also occasiona lly be entangled. Additional poten tial sources of k iller whale 

mortality are set gillnets and longlines. In California, an observer program between July 1990 and December 

1994 monitored 5-15% of all sets in the large mesh (>3.5") set gillnet fishery for halibut and angel sharks, and 

no killer whales were observed taken. Based on observations for longline fisheries in other regions (i.e. Alaska; 

Yano and Dahlheim 1995), fishe ry interactions m ay also occu r with U.S. W est coast pela gic longline fisheries, 

but no such interactions have been documented to date. 

Table 1. Summary of available information on the incidental mortality and injury of k iller whales (Ea stern North Pacific 

Offshore Stock) in commercial fisheries that might take this species. Mean annual takes are based on 1994-98 

data unless no ted otherwise . 

Fishery Name Data TypeYear(s) 

Percent 

Ob 

ser 

ver 

Co 

ver 

age 

Observed 

M 

ort 

ali 

ty 

Estimated Annual 

Mortality 

Mean 

Annual Takes (CV 

in 

parenth 

eses) 

CA/OR thresher 

shark/swordfish 

drift gillnet 

fishery 

observer 

data 

1994 

1995 

1996 

1997 

1998 

17.9% 

15.6% 

12.4% 

23.0% 

20.0% 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

01 

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 in cluded the use of net extenders and acoustic warnin g devices (pingers). 

Set and drift gillnet fisheries for swordfish and sharks exist along the entire Pacific coast of Baja California, 

Mexico and may tak e animals from the same po pulation. Q uantitative data are available only for the Mexican 

swordfish drift gillnet fishery, which uses vessels, gear, and operational proc edures 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 c an be estima ted from d ata provid ed by these a uthors 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 B eeson 19 98), but sp ecies-specific 

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

Mexica n swordfish d riftnet fishery to a long line fishery (D. H olts, pers. com m.). 

Historical mortality 

California coastal whaling operations killed five killer whales between 1962 and 1967 (Rice 1974). An 

additional killer whale was taken by whalers in British Columbian waters (Hoyt 19 81). It is unknown whether 

any of these animals belonged to the Eastern North Pacific Offshore stock. 

STATUS OF STOCK 

The status of killer whales in California in relation to OSP is unknown, and there are insufficient data to 

evaluate trends in abundance. No habitat issues are known to be of concern for this species. They are not 

listed as "threatened" or "endangered" under the Endangered Species Act nor as "depleted" under the MMPA. 

There has been no documented human-caused mortality of this stock, and therefore they are not classified as 

a "strategic" stock under the MMPA . The total fishery mortality and serious injury for offshore killer whales 

is zero and can be co nsidered to be insignificant an d appro aching zero mortality and se rious injury rate . 

117 
REFERENCES 

Baird, R. W., and P. J. Stacey. 1988. Variation in sad dle patch pigmentation in po pulations of killer whales (Orcinus 

orca) from British Columbia, Alaska, and Washington State. Can. J. Zool. 66:2582-2585. 

Baird, R. W., A brams, P . A., and L. M. Dill. 1992. Possible indirect interactions between transient and resident killer 

whales: implications for the evolution of foraging spec ializations in the genus Orcinus. Oecologia 89:125-132. 

Barlow, J. 1995. The abundance of cetaceans in California waters. P art I: Ship surveys in summer and fall of 1991. 

Fish. Bull. 93:1-14. 

Barlow, J. 1997. Preliminary estimates of cetacean abundance off California, Oregon and Washington based on a 1996 

ship survey and comparisons of passing and closing modes. Administrative Report LJ-97-11, Southwest 

Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA 92038. 25p. 

Barlow, J., K. A. Forney, P. S. Hill, R. L. Brownell, Jr., J. V. Carretta, D. P. DeMaster, F. Julian, M. S. Lowry, T. Ragen, 

and R. R. Reeves. 1997. U.S. Pacific marine mammal stock assessments: 1996. U.S. Dep. Commer., NOAA 

Tech. Memo. NMFS-SWFSC-248. 223 pp. 

Barrett-Lennard, L. Univ. of British Columbia, 6270 University Blvd., Vancouver, BC V6T1Z4. 

Bigg, M. A., P. F. Olesiuk, G. M. Ellis, J. K. B. Ford, and K. C. Balcomb III. 1990. Social organization and genealogy 

of resident killer whales (Orcinus orca) in the coastal water s of British Co lumbia and Washington State. Rep. 

int. Whal. Commn Special Issue 12:386-406. 

Black, N. A., A. Schulman-Janiger, R. L. Ternullo, and M. Guerrero-Ruiz. 1997. Killer whales of California and western 

Mexico: A Catalog ofphoto-identified individuals. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-SWFSC247. 174p. 

Braham, H. W., a nd M. E . Dahlheim. 1982. Killer whales in Alaska docu mented in the Platforms o f Oppo rtunity 

Program. Rep. Int. Whal. Commn., 32:643-646. 

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

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

Dahlheim, M. E., D. Ellifrit, and J. Swenson. 1997. Killer Whales of Southeast Alaska: A Catalogue of Photoidentified 

Individuals. Day M oon Press, Seattle, W A. 82 pp. + ap pendices. 

Ford, J. K. B., Vancouver Aquarium, P.O. Box 3232, Vancouver, BC V6B 3XB, Canada. 

Ford, J. K. B., G. M. Ellis, and K.C. Balcom b. 1994 . Killer whales. T he natural histo ry and gene alogy of Orcinus orca 

in British Columbia and Washington State. UBC Press, Vancouver, Canada 

Ford, J. K. B., and H. D. Fisher. 1982. Killer whale (Orcinus orca) dialects as an indicator o f stocks in Br itish 

Columbia. Rep. Int. Whal. Commn 32:671-679. 

Forney, K. A., J. Barlow and J. V. Carretta. 1995. The abundance of cetaceans in California waters. Part II: Aerial 

surveys in winter and spring of 1991 and 1992. Fish. Bull. 93:15-26. 

Goley, P. D., and J. M. Strale y. 1994. Attack on gray whales ( Eschrichtius robustus) in Monterey Bay, California, by 

killer whales (Orcinus orca) previously identified in Glacier Bay, Alaska. Can. J. Zool. 72:1528-1530. 

Green, G., J. J. Brueggeman, R. A. Grotefendt, C. E. Bowlby, M. L. Bonn ell, and K. C. Balcom b, III. 1992. Cetacean 

distribution and abundance off Oregon and W ashington. Ch. 1. In: Oregon and Washington Marine Mammal 

and Seabird Surveys. OCS Study 91-0093. Final Report prepared for Pacific OCS Region, M inerals 

Manag ement Ser vice, U.S. D epartmen t of the Interior, L os Angele s, California. 

Heise, K., G. Ellis, and C. M atkin. 1991 . A catalogue of Prince W illiam Sound Killer Whales. North Gulf Oce anic 

Society, Homer, AK. Pub lished for th e National Marine Mammal Laboratory, 7600 Sand Point Way NE, 

Seattle, WA 98115. 

Hoelze l, A. R., M. E . Dahlheim , and S. J. Ster n. 1998. Low ge netic variation among killer whales ( Orcinus orca) in 

the Eastern North Pacific, and genetic differentiation between foraging specialists. J. Heredity 89:121-128. 

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

Holts, D. and O . Sosa-Nish izaki. 1998 . Swordfish, Xiphias gladius, fisheries of the easte rn North Pacific Oc ean. In: 

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

from the Internation al Sympo sium on P acific Swordfish, Ensenada Mexico, 11-14 December 1994. U.S. Dep. 

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

Hoyt, E. 1981. The W hale Called Killer. E. P. Dutton, New York. 

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

118 
presented to the International Whaling Commission, 1997 (unpublished). 13 pp. 

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

1990-1995. Fishery Bulletin 96:271-284. 

Leatherwood, J. S., and M. E. Dahlheim. 1978. Worldwide distribution of pilot whales and killer whales. Naval Ocean 

Systems Center, Tech. Rep. 443:1-39. 

Leatherwood, S., C. O. M atkin, J. D. H all, and G. M . Ellis. 1990 . Killer whales, Orcinus orca, photo-ide ntified in 

Prince William Sound, Alaska 1976 to 1987. Can. Field Naturalist 104:362-371. 

Mitchell, E. D. 19 75. Rep ort on the meeting on small cetaceans, Montre al, April 1-11, 1974. J. Fish. Res. Board 

Canada, 32:914-916. 

Rice, D. W. 1974. Whales and whale research in eastern North Pacific. p. 170-195 In: W. E. Schevill (ed.), The Whale 

Problem - A Status Report. Harvard University Press, Cambridge, MA. 

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

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

Int. CICESE, CTECT9306. 

Yano, K. and M . E. Dahlhe im. 1995 . Killer whale, Orcinus orca, depredation on lon gline catches of bottomfish in the 

southeastern Bering Sea and adjacent waters. Fishery Bulletin 93:355-372. 

Wade, P. R. and R . P. Angliss. 19 97. Guid elines for Asse ssing Marine Mam mal Stocks: Report of the GAMMS 

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

93 pp. 

119 
Revised 12/15/2000 

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 (Le atherwoo d and D ahlheim 1978). Although


reported from tropical and offshore waters, killer whales


prefer the colder waters of both hem ispheres, with greatest


abundances found within 800 k m of majo r continents


(Mitchell 1975). Along the west coast of North America,


killer whales occur along the entire Alaskan coast (Braham


and Dahlheim 198 2), 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) a nd in the


intracoastal waterways of B ritish Columb ia 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


recogniza ble individuals and pods, movements of whales


between geograp hical areas ha ve been d ocumen ted. For Figure 1. Approximate distribution of the


example, whales identified in Prince William Sound have Eastern North P acific Southe rn Residen t killer


been observed near Kodiak Island (Matkin et al. 1999) and whale stock (shaded area).


whales identified in Southeast A laska have b een obse rved in


Prince William Sound, British Columbia, and Puget Sound


(Leatherwood et al. 1990, Dahlheim et al. 1997). Movements of killer whales between the waters of Southeast


Alaska and central California have also been documented (Goley and Straley 1994).


Studies on mtDNA restriction patterns provide evidence that the ‘resident’ and ‘tra nsient’ types are g enetically


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 Califor nia through Alaska, ‘resident’ whales from


the inland waters of Washington, and ‘resident’ whales ranging from British Colu mbia to the Aleutian Islands


and Bering Sea (Hoelzel et al. 1998). Most sightings of the Eastern North Pacific Southern Resident stock of


killer whales have occurred in inland waters of Washington and southern British Columbia. However, pods


belonging to this stock have also been sighted in coastal waters off Vancouver Island and Washington (Bigg


et al. 1990, Ford et al. 2000), as far south as Grays Harbor (Bigg et al. 1990), and members of two pods were


observed in Monterey Bay, California, in January 2000 (N. Black, pers. comm.).


Based on data regarding association p atterns, acoustics, movements, genetic differences and potential fishery


interactions, five killer whale stoc ks are reco gnized within the Pacific U .S. EEZ: 1 ) the Eastern North P acific


Northern Resident stock - occurring from British Columbia through Alaska, 2) the Eastern North Pacific


Southern Resident stock - occurring m ainly within the inland waters of Wash ington State and southern B ritish


Columbia, but also in co astal waters from British Colu mbia throu gh California (see Fig. 1), 3 ) the Eastern North


Pacific Transient stock - occurring from Alaska through California, 4) the Eastern North Pacific Offshore stock


- occurring from Southeast Alaska through California, and 5) the Hawaiian stock. The Stock Assessment


Reports for the Alaska Region contain information concerning the Eastern North Pacific Northern Resident


stock. 


120 
POPU LATIO N SIZE 

The Eastern North P acific Southe rn Residen t stock is a trans-boundary stock including killer whales in inland 

Washington and southe rn British Co lumbia waters. Photo-identification of individual whales through the years 

has resulted in a substantial und erstanding o f this stock’s structure, behaviors, and movements. In 1993, the 

three pods comprising this stock totaled 96 killer whales (Ford et al. 1994). The population increased to 99 

whales in 1995, then declined to the current population of 84 whales in 1999 (Fig. 2; Ford et al. 2000). 

Minimum Po pulation Estimate 

The abundance estimate for this 

stock of killer whales is a direct 

count o f individuall y 

identifiable animals. Other 

estimates of the overall 

population size (i.e., NBEST) and 

associated CV(N) are not 

currently available. Thus, the 

minimum population estimate 

(NMIN) for the Easter n North 

Pacific Southern Resident stock 

of killer whales is 84 animals. 

Figure 2. Popula tion of Easte rn North Pacific Southern Resident stock of 

Current Population Trend killer whales, 1976-1 999. Ea ch year’s count includes animals first seen and 

During the live-capture fishery first missed; a whale is considered first missed the year after it was last seen


that existed from 1967 to 1973, alive (Ford et al. 2000 ). 


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 repre sents a net annual growth rate of 1.8% during those years.


Since 1995, the population has declined to 84 whales (Ford et al. 2000). A Southern Resident Killer W hale


Workshop, sponsored by the AFS C’s National M arine Ma mmal Lab oratory (N MM L), the Cente r for Wh ale


Research, Six Flags Ma rine Wo rld Vallejo , and The Whale Museum , was held at the NMML in Seattle, WA,


on 1-2 April 2000. Workshop participants discussed possible factors influencing killer whale populations


including contamin ant levels (Ross et al. 2000; G. Ylitalo, pers. comm.), whale-watching activities, and the


availability of prey resources (NMML 2000).


CURRENT AND M AXIMUM NET PRODUCTIVITY RATES 

A reliable estima te of the maxim um net pro ductivity 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 

populatio n growth rates of 2.92% and 2.54% over the period from 197 3 to 198 7 (Olesiuk et al. 1990 , Brault 

and Caswell 1993). However, a population increases at the maximum growth rate (RMAX) only when the 

population is at extremely low levels; thus, the estimate of 2.92% is not considered a reliable estimate of RMAX. 

Hence, u ntil additional d ata becom e 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 (84) 

times one-half the default maximum net growth rate for cetaceans (1⁄2 of 4%) times a recovery factor of 0.5 (for 

a cetacean stock of unknown status, Wade and Angliss 1997), resulting in a PBR of 0.8 whales per year. 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY 

Fisheries Information 

121 
NMFS observers have monitored the northern Washin gton marine set gillnet fishery since 1 988 (G earin et al. 

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

future stock assessment report. Observer coverage ranged from approximately 40 to 98% in the entire fishery 

(coastal + inland waters) between 1993 and 1998. Data from 1993 to 1998 are included in Table 1, although 

the mean estimated annual mortality is calculated using only the most recent 5 years for which data are 

available. No killer whale mortalities have been recorded in this fishery since the inception of the observer 

program. 

In 1993, as a pilot for future observer programs, NMFS in conjunction with the W ashington Departm ent of Fish 

and W ildlife (WD FW) m onitored a ll 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 W DFW 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 co mprising the to tal 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, 1 2B, and 

12C) and Pug et Sound treaty sockeye /chum gillnet fisher y 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 wha le mortalities we re reporte d in either treaty sa lmon gillnet fishery. 

Also in 1994, NMFS, WDFW , and the Tribes conducted an observer program to examine seabird and marine 

mammal interactions with th e Puget So und treaty and non-treaty sockeye salmon gillnet fishery (areas 7 and 

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

number of sets in the fishery (Pierce et al. 1996). Killer whales were observed within 10 m of the gear during 

10 observed sets (32 animals in all), though none were observed to have been entangled. 

An additional source of information on the number of killer whales killed or injured incidental to commercial 

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

the period b etween 19 94 and 1 998, there were no fisher self-reports of kille r whale mo rtalities from any 

fisheries operating within the range of this stock. However, because logbook reco rds (fisher self-rep orts 

required during 1990-94) are most likely negatively biased (Credle et al. 1994), these are considered to be 

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

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

Table 1. Summary of incidental morta lity of killer whales (E astern No rth Pacific So uthern Resid ent stock) du e to 

commercial and tribal fisheries and calculation of the mean annual mortality rate; n/a indicates that data are not 

available. Mean annual takes are based on 1994-98 data unless noted otherwise. 

122 
Fishery name Years 

Data type 

Percent 

o 

b 

s 

e 

r 

v 

e 

r 

c 

o 

v 

e 

r 

a 

g 

e 

Observed 

mortality 

Estimated 

mortality 

Mean annual 

takes 

(CV in 

parent 

heses) 

Northern WA marine s et gillnet 

(tribal fishery: coastal + inland 

waters) 

93 

94 

95 

96 

97 

98 

obs data 61% 

n/a 

87% 

59% 

98% 

40% 

0 

n/a 

0 

0 

0 

0 

0 

n/a 

0 

0 

0 

0 

01 

WA Puget Sound Region salmon 

set/drift gilln et 

(observer programs 

listed below covered 

segments of this 

fishery): 

- - - - - -

Puget Sound non-treaty salmon 

gillnet (all areas and species) 

93 obs data 1.3% 0 0 0 

Puget Sound non-treaty chum 

salmon gillnet (areas 10/11 and 

12/12B) 

94 obs data 11% 0 0 0 

Puget Sound treaty chum 

salmon gillnet (areas 12, 12B, 

and 12C) 

94 obs data 2.2% 0 0 0 

Puget Sound treaty chum and 

sockeye salmon gillnet (areas 

4B, 5, and 6C) 

94 obs data 7.5% 0 0 0 

Puget Sound treaty and nontreaty sockeye salmon gi llnet 

(areas 7 a nd 7A) 

94 obs data 7% 0 0 0 

Minimum to tal annual t akes 0 

1 1993 and 1995-98 m ortality estimat es are included in the average. 

Due to a lack of observer programs, there are few data concerning the mortality of marine mammals incidental 

to Canadian commercial fisheries. Since 1990, there have been no reported fishery-related strandings of killer 

whales in Canadian waters. However, in 1994 o ne killer whale w as reporte d 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, tho ugh the mo rtality level is thought to be minima l. 

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 

123 
(as occurs in Alaskan waters; see Ya no and Dahlhe im 1995), no rep orts of stranded animals with net marks, 

and no photographs of individual whales carrying fishing gear. The total fishery mortality and serious injury 

for this stock is zero. 

STATUS OF STOCK 

Killer whales are not listed as “depleted” under the MMPA or listed as “threatened “ or “endangered” under 

the Endangered Species Act. Based on currently available data, the total fishery mortality and serious injury 

for this stock (0) is not known to exceed 10% of the calculated PBR (0.08) and, therefore, can be considered 

to be insignificant and approaching zero mortality and serious injury rate. The estimated annual level of humancaused mortality and serious injury of zero animals per year is not known to exceed the PBR (0.8). Therefore, 

the Eastern North Pacific Southern Resident stock of killer whales is not classified as a strategic stock. The 

stock size has dec reased in rec ent years, althou gh at this time it is not possible to assess the status of this stock 

relative to its Op timum Sustain able Po pulation (O SP) level. 

REFERENCES 

Baird, R. W., and P. J. Stacey. 1988. Variation in saddle patch pigmentation in populations of killer whales (Orcinus 

orca) from British Columbia, Alaska, and Washington State. Can. J. Zool. 66 (11):2582-2585. 

Baird, R. W., P. A. Abrams, and L. M. Dill. 1992. Possible indirect interactions between transient and resident killer 

whales: implications for the evolution of foraging specializations in the genus Orcinus. Oecologia 89:125-132. 

Barlow, J. 1995. T he abund ance of ceta ceans in Ca lifornia waters. P art I: Ship surveys in summer and fall of 1991. 

Fish. Bull. 93:1-14. 

Barlow, J. 1997. Preliminary estimates of cetacean abundance off California, Oregon and Washington based on a 1996 

ship survey and comparisons of passing and closing modes. Adm inistrative Report LJ-97-11 , Southwest 

Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA 92038. 25 pp. 

Bigg, M. A., P. F. Olesiuk, G. M. Ellis, J. K. B. Ford, and K. C. Balcomb III. 1990. Social organization and genealogy 

of resident killer whales (Orcinus orca) in the coastal waters of British Columbia and Washington State. Pp. 

386-406, In: Hammond, P. S., S. A. Mizroch , and G. P. Do novan (eds.), Individual Re cognition of Cetaceans: 

Use of Photo-identification and Other Techniques to E stimate Population Pa rameters. Rep. Int. Whal. Commn. 

Special Issue 12. 

Black, N. A. P.O. Box 52001, Pacific Grove, CA 93950. 

Braham, H. W., and M. E. Dahlheim. 1982. Killer whales in Alaska documented in the Platforms o f Oppo rtunity 

Program. Rep. Int. Whal. Commn. 32:643-646. 

Brault, S., and H. C aswell. 1993. Pod -specific demography o f killer whales (Orcinus orca). Ecology 74(5):1444-1454. 

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

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

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

Dahlheim, M. E., D . Ellifrit, and J. Swe nson. 199 7. Killer Whales of Southeast Alaska: A Catalogue of Photoidentified 

Individuals. Day M oon Press, Seattle, W A. 82 pp. + ap pendices. 

Dahlheim, M., D. Bain, C. Sims, and D. DeMaster (compilers). 2000. Southern resident killer whale workshop, 

National Marine M ammal Laborato ry, Seattle, WA, 1-2 April 2000. AFSC Processed Report 2000-08. 

Available at National Marine Mammal Laboratory, 7600 Sand Point Way NE, Seattle, WA 98115-6349. 

Ellifrit, D. Center for Whale Research, 1359 Smugglers Cove Rd., Friday Harbor, WA 98250. 

Erstad, P., S. J. Jeffries, and D. J. Pierce. 19 96. 199 4 Repo rt for the Puge t Sound fishe ry observe r program in 

management areas 10/1 1 & 12 /12B: no ntreaty chum g ill net fishery. Final R eport, Washington Dept. Fish and 

Wildlife, Olympia, WA. 14 pp. 

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Ford, J. K. B., G. M. Ellis, and K. C. Balcomb. 1994. Killer Whales: The N atural History and Genealogy of Orcinus 

orca in British Columbia and Washington State. University of British Columbia Press, Vancouver, BC, and 

University of Washington Press, Seattle. 102 pp. 

Ford, J. K. B., G. M. Ellis, and K. C. Balcomb. 2000. Killer Whales: The Natural History and Gen ealogy of Orcinus 

124 
orca in British Columbia and Washin gton. 2nd e dition. Unive rsity of British Columbia Press, Vancouver, BC, 

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surveys in winter and spring of 1991 and 1992. Fish. Bull. 93:15-26. 

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

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125 
restriction fragment differences in mitochondrial DN A among killer whales ( Orcinus orca). Can. J. Zo ol. 

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126 
Revised 12/15/2000 

SHORT-FINNED PILOT WHALE (Globicephala macrorhynchus): 

California/Oregon/Washington Stock 

Figure 1. Short-finned pilot whale sightings made 

STOCK DEFINITION AND GEOGRAPHIC RANGE 

Short-finned pilot whales were once commonly seen 

off Southern California, with a n appare ntly resident 

population around Santa Catalina Island, as well as 

seasonal migrants (Dohl et al. 1980). 

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 

After a strong 

(Jones and Szczepaniak 1992; Barlow 1997; 

Carretta and Forney 1993; Shane 19 94; Gre en et al. 

1992, 1993). In 1993, six groups of short-finned 

pilot whales were again seen off California 

(Carretta et al. 1995; Barlow and Gerrodette 1996), 

and mortality in drift gillnets increased (Julian and 

Beeson 1998) but sightings remain rare (Barlow 

1997). Figure 1 summarizes the sighting history of 

short-finned pilot whales off the U.S. west coast. 

Although the full geograp hic range of the 

California/Oregon/Washington population is not 

known, it may be continuous with animals found off 

Baja California, and its individuals are 

morpho logically 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 during aerial and shipboard surveys cond ucted off 

also been documented for the western North P acific California in 1975-83 (+) and off California, Oregon 

(Kasuya et al. 1988; Wada 198 8; Miyazaki and and Washin gton, 1991-96 (!). See Appendix 2, 

Amano 1994). For the Marine Mammal Protection Figures 1-5, for data sources and information on timing 

Act (MMPA) stock assessment reports, short-finned and location of survey effort. Dashed line represents the 

pilot whales within the Pacific U.S. Exclusive U.S. EEZ, thick line indicates the outer bou ndary of all 

Econo mic Zone are divided into two discrete, non- surveys com bined. 


contiguous areas: 1) waters off California, Oregon


and Wa shington (this report), and 2) Ha waiian waters.


POPU LATIO N SIZE 

Three summer/fall ship board su rveys were co nducted w ithin 300 nm i of the coasts o f California (in 1991 and 

1993; Barlow a nd Gerr odette 19 96) and California, O regon and Washin gton (in 199 6; Barlow 1997). The 

abundance of short-finned pilot whales in this re gion app ears to be v ariable and may relate to o ceanogra phic 

conditions, as with other odontocete species (Forney 1997, Forney and Barlow 1 998). Because animals may 

spend time outside the U.S. Exclusive Economic Zone as oceanographic conditions change, a multi-year 

average abundance estimate is the most appropriate for management within U.S. waters. The 1991-96 weighted 

average abundance estimate for California, Oregon and Washington waters b ased on the above thre e ship 

surveys is 970 (CV=0.37) short-finned pilot whales (Barlow 1997). 

Minimum Po pulation Estimate 

The log-normal 20th percentile of the 1991-96 weighted average abundance estimate is 717 short-finned pilot 

127 
whales. 

Current Population Trend 

Appro ximately nine years after the virtual disapp earance o f short-finned p ilot whales follow ing the 1982-83 

El Niño, they ap pear to hav e returned to California waters, as indicated by an increase in sighting records as 

well as incidental fishe ry mortality (B arlow and Gerrod ette 1996; Carretta et al. 1995; Julian and Beeson 1998). 

However, this cannot be consid ered a true g rowth in the po pulation, be cause it mere ly reflects large-scale, longterm movements of this species in response to changing o ceanographic co nditions. It is not known where the 

animals went after the 82-83 El Niño, nor where the recently observed animals came from. Until the range of 

this populatio n and the m ovemen ts 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 M AXIMUM NET PRODUCTIVITY RATES 

No information o n current or m aximum ne t producti vity rates is available for short-finned pilot whales o ff 

California, Oregon and Washington. 

POTENTIAL BIOLOGICAL REMOVAL 

The potential biological removal (PBR) level for this stock is calculated as the minimum population size (717) 

times one half the default maximum net growth rate for cetaceans (1⁄2 of 4%) times a recovery factor of 0.40 (for 

a species of unknown status with a mortality rate CV>0.80; Wad e and Ang liss 1997), re sulting in a PB R of 5.7 

short-finned p ilot whales pe r year. 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY 

Fishery Information 

A summary of known fishery mortality and injury for this stock of short-finned pilot whale is shown in Table 

1. More detailed information on these fisheries is provided in Appendix 1. Mortality estimates for the 

California drift gillnet fishery are included for the five most recent years of monitoring, 1994-98 (Julian and 

Beeson 1998; Julian 1997; Cameron and Forney 1999). After the 1997 implementation of a Take Reduction 

Plan, which included skipper ed ucation workshops a nd required the use of ping ers and minimum 6-fathom 

extenders, overall cetacean entanglement rates in the drift gillnet fishery dropped considerably (Barlow and 

Cameron 1999). However, because of interannual variability in entanglement rates and the relative rarity of 

short-finned pilot whale entanglements, additional years of data will be required to fully evaluate the 

effectiveness of pingers for reducing mortality of this particular sp ecies. The observed mortality of a single 

short-finned pilot whale in 1997 was in a pingered net. Because of the changes in this fishery after 

implementation of the Take Reductio n Plan, mea n annual take s in Table 1 are based only on 19 97-98 d ata. This 

results in an aver age estimate o f 3.0 (CV =0.96) short-finned p ilot whales taken annually. 

Table 1. Summary of available information on the incidental mortality and injury of short-finned pilot whales 

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

entangleme nts of pilot whales resulted in the d eath of the animal. Coefficien ts of variation for mortality 

estimates are provided in parentheses; n/a = not available. Mean annual takes are based on 1994-98 data unless 

noted otherwise. 

128 
Fishery Name 

CA/OR thresher 

shark/swordfish 

drift gillnet 

fishery 

Undetermined (probably 

squid purse 

seine fishery) 

Data Type Year(s) 

Percent 

Observer 

C 

ov 

er 

a 

ge 

Observed 

Mortality 

observer 1994 17.9 % 0 

data 1995 15.6 % 0 

1996 12.4 % 0 

1997 22.8 % 1 

1998 20.2 % 0 

strandings 

Estimated Annual 

Mortality 

0


0


0


6 (0.96)


0


Mean 

Annual Takes 

(CV in 

parenth 

eses) 

3.0 (0.96)1 

n/a 

3.0 (0.96) 

1975-90 14 short-finned pilot whales stranded in Sou thern 

California with evidence of fishery 

interactions, probably with the squid purse 

seine fishery 

Minimum total annual takes 

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 in cluded the use of net extenders and acoustic warnin g devices (pingers). 

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

and may take anim als from the sam e popula tion. Quantitativ e data are a vailable only for the Mexican swo rdfish 

drift gillnet fishery, which uses vessels, gea r, and ope rational pro cedures sim ilar 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 b e appro ximately 270 0, with an ob served rate 

of marine m ammal byc atch of 0.13 animals per set (10 marine mammals in 77 observed sets; Sosa-Nishizaki 

et al. 1993) . This over all mortality rate is similar to that observed in California driftnet fisheries during 1990-95 

(0.14 ma rine mamm als per set; Julian a nd Bee son, in press), b ut species-spe cific information is n ot available 

for the Mexican fisheries. There are currently efforts underway to convert the Mexican swordfish driftnet 

fishery to a longline fishery (D. H olts, pers. com m.). 

Historically, short-finned pilot whales were also killed in squid purse seine operation s off Southern California 

(Miller et al. 1983; Heyning et al. 1994). No recent mortality has been reported, presumably because sh ortfinned pilot whales are no longer common in the areas of squ id purse sein e fishing activity; however, there have 

been recent anecdotal reports of pilot whales seen near squid fishing operations off Southern California during 

the October 1997- April 98 fishin g season. T his fishery is not curren tly monitored , and has exp anded m arkedly 

since 1992 (Vojkovich 1998). 

STATUS OF STOCK 

The status of short-finned pilot whales off California, Oregon and Washington in relation to OSP is unknown. 

They have declined in abundance in the Southern California B ight, likely a result of a ch ange in their 

distribution since the 1982-83 El Niño, but the nature of these changes and potential habitat issues are not 

adequa tely understood. Short-finned pilot whales are not listed as "threatened" or "endangered" under the 

Endangered Species Act nor as "depleted" under the MMPA . Including driftnet mortality only for years after 

implementation of the Take Reduction Plan (1997-98), the average annual human-caused mortality in 1994-98 

(3.0 animals) is estimated to be less than the PB R (5.7), and therefore they are not classified as a "strategic" 

stock under the MMPA. The total fishery mortality and serious injury for short-finned pilot whales is greater 

than 10% of the calculated PBR and, therefore, cannot b e conside red to be insignificant and approaching zero 

mortality and serio us injury ra te. 

REFERENCES 

129 
Barlow, J. 1997. Preliminary estimates of cetacean abundance off California, Oregon and Washington based on a 1996 

ship survey and comparisons of passing and closing modes. Administrative Report LJ-97-11, Southwest 

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Barlow, J. and G. A. Cameron. 1999. Field experiments show that acoustic pingers reduce marine mamma l bycatch in 

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

1998 (unpublished). 20pp. 

Barlow, J. and T. Gerrodette. 199 6. Abundance of cetaceans in California waters based on 1991 an d 1993 ship surv eys. 

U.S. De p. Comm er., NOA A Tech . Memo . NMF S-SW FSC-23 3. 

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, 1998 (unpublished). 14pp. 

Carretta, J. V. and K . A. Forney. 1 993. Re port of the two aerial surveys fo r marine mammals in Ca lifornia coasta l 

waters using a NOAA DeH avilland Twin O tter aircraft, M arch 9-Ap ril 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 ma mmal surve ys conducted within the 

U.S. Navy Outer Sea Test Range off Southern California. U.S. Dep. Commer., NOAA Tech. Memo. NMFSSWFSC-217. 90p. 

Dohl, T. P., K. S. Norris, R. C. Guess, J. D. Bryant, and M. W. Honig. 1980. Summary of marine mammal and seabird 

surveys of the Southern California Bight area, 1975-1978. Part II. Cetacea of the Southern C alifornia Bigh t. 

Final Report to the Bureau of Land Management, NTIS Rep. No. PB81248189. 414p. 

Forney, K. A. 1997. Patterns of variability and environmental mo dels of relative abundance fo r California cetaceans. 

Ph.D. Dissertation, Scripps Institution of Oceanography, University of California, San Diego. 

Forney, K. A. and J. Barlow. 1998. Seasonal patterns in the abundance and distribution of California cetaceans, 1991­

92. Mar. Mamm. Sci. 14:460-489. 

Green, G., J. J. Brueggeman, R. A. Grotefendt, C. E. Bowlby, M. L. Bonnell, and K. C. Balcomb, III. 1992. Cetacean 

distribution and abundance off Oregon and W ashington. Ch. 1. In: Oregon and Washington Marine Mammal 

and Seabird Surveys. OCS Study 91-0093. Final Report prepared for Pacific OCS Region, Mine rals 

Manag ement Ser vice, U.S. D epartmen t of the Interior, L os Angele s, California. 

Green, G., R. A. G rotefendt, M . A. Smultea, C . E. Bow lby, and R. A . Rowlett. 19 93. Delp hinid aerial surveys in 

Oregon and Washington waters. Final Report prepared for NMFS, N ational Marine Mamm al Labora tory, 7600 

Sand Point Way, NE, Seattle, Washington, 98115, Contract #50ABNF200058. 

Heyning, J. E., T. D. Lewis and C. D. Woodhouse. 1994. A note on odontocete mortality from fishing gear 

entanglements off Southern California. Rep. Int. Whal. Commn. Special Issue 15:439-442. 

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

Holts, D. and O. Sosa-Nishizaki. 1998. Swordfish, Xiphias gladius, fisheries of the eastern North P acific Ocea n. In: 

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

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

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

Jones, P. A. and I. D. Szczepaniak. 1992. Report on the seabird and marine mammal censuses conducted for the longterm management strategy (LTMS), August 1990 through Novem ber 1991, for th e U.S. Environmental 

Protection Agency, Region IX, San Francisco, July 1992. 

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

SC/49/SM02 presented to the International Whaling Commission, September 1997, Bournemouth, UK. 

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

fisheries: 1990-95. Fishery Bulletin 96:271-284. 

Kasuya, O., T. M iyashita, and F. K asamatsu. 19 88. Segregation of two forms of short-finned p ilot whales off the P acific 

coast of Japan. Sci. Rep. Whales Res. Inst. 39:77-90. 

Miller, D. J., M. J. Herder a nd J. P Sc holl. 1983 . California ma rine mamm al - fishery interaction study, 1979-1981. 

Administrative Report LJ-83-13C. Available from NMFS, Southwest Fisheries Science Center, P.O. Box 271, 

La Jolla, California, 92038. 233p. 

Miyazaki, N. and M. Amano. 1 994. Sku ll morpho logy of two forms of short-finne d pilot whale s off the Pacific coast 

of Japan. Rep. Int. Whaling Commn. 44:499-508. 

130 
Polisini, J. M. 19 81. A co mparison of Globic ephala macrorhyncha (Gray, 18 46) with the p ilot whale of the N orth 

Pacific Ocean: An analysis of the skull of the broad-rostrum pilot whales of the genus Globice phala . 

Dissertation Abstracts International Vol. 41, No. 08, February 1981, p. 2928-B. 

Shane, S. 1994. O ccurrence and habita t use of marine mamma ls at Santa Ca talina Island, California from 1983-9 1. 

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

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

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

Int. CICESE, CTECT9306. 

Vojkovich, M. 1998. The California fishery for market squid (Loligo opalescens). CalCOFI Rep. 39:55-60. 

Wada, S. 1988 . Genetic differentiation between forms of short-finned pilot whales off the Pacific coa st of Japan. S ci. 

Rep. Whales Res. Inst. 39:91-101. 

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

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

93 pp. 

131 
Revised 12/15/2000 

BAIRD'S BEAKED WHALE (Berardius bairdii): 

California/Oregon/Washington Stock 

STOCK DEFINITION AND GEOGRAPHIC RANGE 

Baird's beaked whales are distributed throughout deep 

waters and along the continental slopes of the Nor th 

Pacific Ocean (B alcomb 1 989). They have been 

harvested and studied in Japanes e 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 M arine Ma mmal Protection Act 

(MMPA) stock assessment reports, Baird's beaked 

whales within the Pacific U.S. Exc lusive Eco nomic 

Zone are divided into two discrete, non-contiguous 

areas: 1) waters off California, Oregon and Washington 

(this report), and 2) Alaskan waters. 

POPU LATIO N SIZE 

Three summer/fall shipboard surveys were conducted 

within 300 nm i of the coasts o f California (in 1991 and 

1993; Barlow a nd Gerr odette 19 96) and California, 

Oregon and Washington (in 1996; Barlow 1997), 

resulting in a combined total of 10 Baird’s beaked 

whale sightings. Because their distribution varies and 

animals probably spend time outside the U.S. Exclusive 

Economic Zone, a multi-year average abundance 

estimate is the most app ropriate for managem ent within 

U.S. waters. The 1991-96 weighted average abundance 

estimate for California, Oregon and Washington waters 

Figure 1. Baird’s beaked whale sightings based on 

aerial and shipboard surveys off California, Oregon and 

Washington, 1991-96 (see Appendix 2, Figures 1-5, for 

data sources and information on timing and location of 

survey effort). Dashed line represents the U.S. EEZ, 

thick line indicates the outer boundary of all sur veys 

combined. 

based on the above three ship surveys is 379 (CV=0.23) Baird’s beaked whales (Barlow 1997). This abundance 

estimate includes correction factors for the proportion of anima ls missed (g(0) = 0.90 fo r groups of 1-3 animals, 

g(0)=1.0 for larger groups), which are similar to the estimate of g(0)=0.96 calculated more recently (Barlow 

1999) based on dive-interval stud ies. 

Minimum Po pulation Estimate 

The log-normal 20th percentile of the 1991-96 weighted average ab undance estimate is 313 Baird’s beaked 

whales. 

Current Population Trend 

Due to the rarity of sighting s of this specie s on surveys along the U .S. West c oast, no inform ation exists 

regarding trends in abundan ce of this pop ulation. Future studie s of trends mu st take the app arent seaso nality 

of the distributio n of Baird 's beaked wh ales into acco unt. 

CURRENT AND M AXIMUM NET PRODUCTIVITY RATES 

No information on current or maximum n et productivity rates is available for this species. 

132 
POTENTIAL BIOLOGICAL REMOVAL 

The potential biological removal (PBR) level for this stock is calculated as the minimum population size (313) 

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

a species of unknown statu s with no fishery mortality; Wa de and A ngliss 1997 ), resulting in a PB R of 3.1 

Baird’s beaked whales per year. 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY 

Fishery Information 

A summary of recent fishery mortality and injury for Baird’s beaked whales in this region is show n in Table 

1. More detailed information on these fisheries is provided in Appendix 1. Mortality estimates for the 

California drift gillnet fishery are included for the five most recent years of monitoring, 1994-98 (Julian and 

Beeson 1998; Julian 1997; Cameron and Forney 1999). After the 1997 implementation of a Take Reduction 

Plan, which included skipper education workshops and required the use of pingers and minimum 6-fathom 

extenders, overall cetacean entanglement rates in the drift gillnet fishery dropped considerably (Barlow and 

Cameron 1999). However, because of interannual variability in entanglement rates and the relative rarity of 

Baird’s beaked whale entang lements, add itional years of d ata will be require d to fully evaluate the effectiveness 

of pingers for reducing mortality of this particular species. Because of the changes in this fishery after 

implementation of the Take Reduction Plan, mean annual takes in Table 1 are based only on 1997-9 8 data. T his 

results in an average estimated annual m ortality of zero Baird’s beaked whales. 

Table 1. Summary of available information on the incidental mortality and inju ry of Ba ird's beaked whales (California/ 

Oregon/Washington Stock) in commercial fisheries that might take this species. The single observed 

entanglement resulted in the death of the animal. Coefficients of variation for mortality estimates are provided 

in parentheses. Mean annual takes are based on 1994-98 data unless noted otherwise. 

Fishery Name Data Type Year(s) 

Percent 

Observer 

C 

o 

v 

er 

a 

g 

e 

Observed 

Mortality 

Estimated Annual 

Mortality 

17.9% 1 6 (0.90) 

15.6% 0 0 

12.4% 0 0 

23.0% 0 0 

20.0% 0 0 

Mean 

Annual Takes (CV 

in 

parenth 

eses) 

01 

0 

CA/OR thresher 

shark/swordfish 

drift gillnet 

fishery 

1994 

observer 1995 

data 	 1996 

1997 

1998 

Minimum total annual takes 

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 in cluded the use of net extenders and acoustic warnin g devices (pingers). 

Drift gillnet fisheries for swordfish and sharks exist along the e ntire Pacific coast of B aja Californ ia, Mexico 

and may take animals from the same population. Quantitative data are available only for the Mexican sword fish 

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 appr oximately 27 00, with an o bserved r ate 

of marine mammal bycatch of 0.13 animals per set (10 marine mammals in 77 observed sets; Sosa-Nishizaki 

et al. 1993) . This over all mortality rate is similar to that observed in California driftnet fisheries during 1990-95 

(0.14 marine mammals per set; Julian and Beeson, 1998), but species-specific information is not available for 

the Mexican fisheries. There are currently efforts underway to convert the Mexican swordfish driftnet fishery 

133 
to a longline fishe ry (D. Ho lts, pers. comm .). 

Other mortality 

California coasta l whaling operations killed 15 Baird's beaked whales between 1956 and 1970, and 29 

additional Baird's beaked whales were taken by whalers in British Columbian waters (Rice 1974). 

STATUS OF STOCK 

The status o f Ba ird's beaked whales in California, Oregon and Washington waters relative to OSP is not known, 

and there are insufficient data to evaluate trends in abundance. No habitat issues are known to be of concern 

for this species, but in recent years questions have been raised regarding potential effects of human-made 

sounds on deep-diving cetacean species, such as Baird’s beaked whales (Richardson et al. 1995). They are not 

listed as "threatened" or "endangered" under the Endangered Species Act nor as "depleted" under the MMPA. 

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

average annual hum an-caused mortality in 1994-9 8 is zero. Because recent mortality is zero, Baird’s beaked 

whales are not classified as a "strategic" stock unde r the MM PA, and the total fishery mortality and serious 

injury for this stock can be considered to be insignificant and approaching zero. 

REFERENCES 

Balcomb, K. C., III. 1989. Baird's beaked whale Berard ius bairdii Ste jneger, 18 83: Arn oux 's beaked whale Berardius 

arnuxii Duverno y, 1851. In: Ridgway, S. H. and Harrison, R. (eds.), H andboo k of Marine Mam mals, Vol. 4 ., 

p. 261-288. Academic Press Limited. 

Barlow, J. 1997. Preliminary estimates of cetacean abundance off California, Oregon and Washington based on a 1996 

ship survey and comp arisons of passing and closing m odes. Administrative Rep ort LJ-97-11, Sou thwest 

Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA 92038. 25p. 

Barlow, J. 1999 . Trackline detection probability for long-diving whales. p. 209-224 In: G. W. Garner, S. C. Amstrup, 

J. L. Laake, B. F. J. Manly, L. L. McDonald, and D. G. Robertson (eds.) Marine Mammal Survey and 

Assessment Methods. A. A. Balkema, Rotterdam. 287 pp. 

Barlow, J. and G. A . Camero n. 1999 . Field experime nts show that ac oustic pinge rs reduce m arine mam mal bycatch in 

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

1998 (unpublished). 20pp. 

Barlow, J. and T. Gerrodette. 199 6. Abundance of cetaceans in California waters based on 1991 an d 1993 ship surv eys. 

U.S. De p. Comm er., NOA A Tech . Memo . NMF S-SW FSC-23 3. 

Cameron, G., and K. A. Forney. 1999. Estimates of c etacean m ortality in the California gillnet fisheries for 1997 and 

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

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

Holts, D. and O . Sosa-Nish izaki. 1998 . Swordfish, Xiphias gladius, fisheries of the easte rn North Pacific Oc ean. In: 

I. Barrett, O. Sosa-Nishizaki and N. Bartoo (eds.). Biology and fisheries of swor dfish, 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. Cetacea n mortality in California gill net fisheries: Preliminary estimates for 1996. Paper SC/49/SM02 

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

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

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

Rice, D. W. 1 974. W hales and w hale researc h in eastern N orth Pacific. p. 170-195 In: W. E. Schevill (e d.), The W hale 

Problem - A Status Report. Harvard University Press, Cambridge, MA. 

Richardson, W. J., C. R. Greene, Jr., C. I. Malme, and D. H . Thomp son. 199 5. Marin e Mammals and N oise. Acad emic 

Press, San Diego. 576 p. 

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

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

Int. CICESE, CTECT9306. 

Wade, P. R. and R. P. A ngliss. 1997. Guidelines for A ssessing Marine Mammal Stocks: Report of the GAMMS 

134 
Workshop April 3-5, 1996, Seattle, Washington. U. S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-12. 

93 pp. 

135

Revised 12/15/2000 

MESOPLODONT BEAKED WHALES (Mesoplodon spp.): 

California/Oregon/Washington Stocks 

STOCK DEFINITION AND GEOGRAPHIC RANGE 

Mesoplodont beaked whales are distributed throughout 

deep waters and a long the con tinental slopes o f the North 

Pacific Ocean. At least 5 species in this genus have been 

recorded off the U.S. we st coast, but due to the rarity of 

records and the difficulty in identifying these animals in the 

field, virtually no species -specific inform ation is availab le 

(Mead 1989). The five sp ecies know n to occur in this 

region are: Blainville's beaked whale (M. den sirostris), 

He ctor's beaked whale, (M. hectori ), Stejneger's beaked 

whale (M. stejnegeri ), Gingko-toothed beaked whale (M. 

gingkodens), and Hubb s' beaked whale (M. carlhubb si). 

Insufficient sighting records exist off the U.S. west coast 

(Figure 1) to determine any possible spatial or seasonal 

patterns in the distribution of mesoplodo nt beaked whales. 

Until methods of distinguishing these five species are 

developed, the management unit must be defined to include 

all Mesoplodon stocks in this region. However, in the 

future, species-level management is desirable, and a high 

priority should be placed on finding means to obtain 

species-spe cific abundance information. For the Marine 

Mammal Protection Act (MMPA ) stock assessment reports, 

three Mesoplodon stocks are defined: 1) all Mesoplodon 

species off California, O regon and Washin gton (this 

report), 2) M. stejnegeri in Alaskan waters, and 3) M. 

densirostris in Hawaiian waters. 

POPU LATIO N SIZE 

Although mesoplodont beaked whales have been sighted 

along the U.S. west coast on several line trans ect surveys 

utilizing both aerial a nd shipbo ard platform s, sightingshave 

generally been too rare to produce reliable population 

estimates, and species identification has been problematic. 

Figure 1. Mesoplodon beaked whale sightings 

based on aerial and shipboar d surveys off 

California, Oregon and Washington, 1991-96 (see 

Appen dix 2, Figures 1-5, for data sources and 

information on timing and location of survey 

effort). Key: ! = Mesoplodon d ensirostris, + = 

Mesoplodon spp. Dashed line represen ts the U.S. 

EEZ, thick line indicates the outer bounda ry of all 

surveys combined. 

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 no t include anim als 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 c avirostris ). Recent analyses (Barlow and Gerrodette 1996, Barlow and 

Sexton 1996, Barlow 1997) have resulted in improved estimates of abundance by 1) combining data from three 

surveys conducte d within 300 nmi of the co asts of California (in 1991 and 1993; Barlow and Gerrodette 1996) 

and California, Oregon and Washington (in 1996; Barlow 1997), 2) whenever possible, assigning unidentified 

beaked whale sightings to Mesoplodon spp. or Ziphius c avirostris based on written descriptions, size estimates, 

and ‘most prob able identifications’ made by the observers at the time of the sightings, and 3) estimating a 

correction factor for animals missed because they are submerged, based on div e-interval data collected for 

mesoplodont whales in 1993-95 (about 26% of all trackline gro ups are estim ated to be seen). The first speciesspecific abundance estimate is now available for Blainville’s beaked whale, which was identified once during 

the 1993 cruise. Because their distribution varies and animals probably spend time outside the U.S. Exclusive 

136 
Econo mic Zone, a mu lti-year average abundan ce estimate is the most app ropriate for manage ment within U.S. 

waters. The 1991-96 weighted average abundance estimates for California, Oregon and Washington waters 

based on the above analyses are 3,738 (CV=0.50) mesoplodont beaked whales of unknown species plus 360 

(CV=2.0) Blainville's beaked whales (Barlow 1997, with corrected CV). 

Minimum Po pulation Estimate 

Based on the combined abundance estimate of 4,098 (CV=0.50), the minimum population estimate (defined 

as the log-normal 20th percentile of the abundance estimate) for mesoplodont beaked whales in California, 

Oregon, and W ashington is 2,734 anima ls. This includes a species-specific minimum abundance estimate of 

123 B lainville’s beake d whales. 

Current Population Trend 

Due to the rarity of sightings of these species on surveys along the U.S. W est coast, no info rmation exists 

regarding possible trends in abundance. 

CURRENT AND M AXIMUM NET PRODUCTIVITY RATES 

No information on current or maximum n et productivity rates is available for mesoplo dont beaked w hales. 

POTENTIAL BIOLOGICAL REMOVAL 

The potential biological removal (PBR) level for this stock is calculated as the minimum population size (2,734) 

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

a species of unknown st atus with no known recent fishery mortality; Wade and Angliss 1997), resulting in a 

PBR o f 27 mesoplod ont beaked whales p er year. This includes at least 1.1 Blainville’s beake d whales. 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY 

Fishery Information 

A summary of recent fishery mortality and injury for mesoplodont beaked whales in this region is sho wn in 

Table 1. More detailed information on these fisheries is provided in Appendix 1). Mortality estimates for the 

California drift gillnet fishery are included for the five most recent years of monitoring, 1994-98 (Julian and 

Beeson 1998; Julian 1997; Cameron and Forn ey 1999 ). A recently co mpleted g enetic analysis of tissue samples 

has allowed the reliable identification of the majority of these animals (Hensh aw et al. 1997). Base d on past 

patterns of identification (NMFS, unpublished data), the remaining unidentified beaked whale is likely to have 

been a Mesoplodon sp. After the 1997 imp lementation of a Take Reduction Plan, which included skipper 

education workshops and required the use of pingers and minimum 6-fathom extenders, overall cetacean 

entanglement rates in the drift gillnet fishery dropped considerably (Barlow and Cameron 1999). However, 

because of interannual variability in entanglement rates and the relative rarity of mesoplod ont beake d whale 

entanglements, additional ye ars of data will b e required to fully evaluate the effectiveness o f pingers for 

reducing mortality of this group of species. Because of the changes in this fishery after implementation of the 

Take Reduction Plan, mean annual takes in Table 1 are based only on 19 97-98 d ata. This resu lts in an average 

estimated annual mortality of zero m esoplodont be aked whales. 

Drift gillnet fisheries for swo rdfish and sha rks exist along th e entire Pac ific coast of Baja C alifornia, and may 

take animals from the same populations. Quantitative data are available only for the Mexican swordfish dr ift 

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 1 993 (H olts and Sosa-Nishizaki 1998). The total number of sets in this fishery 

in 1992 can b e estimated from data pro vided by these authors to be app roximately 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 over all mortality rate is similar to that observed in California driftnet fisheries during 1990-95 

(0.14 marine mammals per set; Julian and B eeson, 19 98), but sp ecies-specific info rmation is not available for 

the Mexican fisheries. There are currently efforts underway to convert the Mexican swordfish driftnet fishery 

to a longline fishe ry (D. Ho lts, pers. comm .). 

137 
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 humanmade sounds on Table 1. Summary o f available information on the incidental m ortality and injur y of 

Mesoplodon beaked whales (Ca lifornia/Oregon/Washington Stocks) in commercial fisheries that might take 

these species. All ob served enta nglements o f Mesoplodon beaked whales resulted in the death of the animal. 

Coefficients of variation for mortality estimates are provided in parentheses. Mean annual takes are based on 

1994-98 data unless noted otherwise. 

Fishery Name 

Data Type Year(s) 

Percent 

Observer 

C 

o 

v 

er 

a 

g 

e 

Observed 

Mortality 

Estimated Annual 

Mortali 

ty 

Mean 

Annual Takes 

(CV in parentheses) 

CA/OR thresher 

shark/swordfish 

drift gillnet 

fishery 

Hubbs’ beaked whale, Mesoplodon carlhubbsi 

observer 

data 

1994 

1995 

1996 

1997 

1998 

17.9% 

15.6% 

12.4% 

23.0% 

20.0% 

2 

0 

0 

0 

0 

11 (0.64) 

0 

0 

0 

0 

01 

Stejneger’s beaked whale, Mesoplodon stejnegeri 

observer 

data 

1994 

1995 

1996 

1997 

1998 

17.9% 

15.6% 

12.4% 

23.0% 

20.0% 

Unident ified bea ked whale ( probabl y Mesoplodon) 

observer 

data 

1994 

1995 

1996 

1997 

1998 

17.9% 

15.6% 

12.4% 

23.0% 

20.0% 

6 (0.91) 

0 

0 

0 

0 

01 

6 (0.90) 

0 

0 

0 

0 

01 

0 

1 

0 

0 

0 

0 

1 

0 

0 

0 

0 

Minimum total annual takes of Mesoplodon beaked whales 

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 in cluded the use of net extenders and acoustic warnin g devices (pingers). 

deep-diving cetacean species, such as mesoplodont beaked whales (Richardson et al. 1995). In particular, Low 

Frequency Active Sonar (LFAS) has been implicated in the mass stranding of beaked whales in the 

Mediterranean Sea (Frantzis 1998) and more recently in the Caribbean. None of the five species is listed as 

"threatened" or "endangered" under the Endangered Species Act nor considered "depleted" under the MMPA. 

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

average annual human-caused mortality in 1994-98 is zero. Because recent mortality is zero, mesoplodont 

beaked whales are no t classified as a "str ategic" stoc k under the M MPA , and the total fishe ry mortality and 

serious injury for this stock can be co nsidered to be insignificant an d appro aching zero. It is likely that the 

difficulty in identifying these a nimals in the field w ill remain a critica l obstacle to obtaining s pecies-spe cific 

abunda nce estimates and stock a ssessments in the future. 

138 
REFERENCES 

Barlow, J. 1997. Preliminary estimates of cetacean abundance off California, Oregon, and Washington based on a 1996 

ship survey and comparisons of passing and closing mo des. Southwest Fisheries Science Center Administrative 

Report. LJ-97-11. 25pp. 

Barlow, J. 1997. Preliminary estimates of cetacean abundance off California, Oregon and Washington based on a 1996 

ship survey and c ompariso ns of passing a nd closing m odes. Administrative Re port LJ-9 7-11, Southwest 

Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA 92038. 25p. 

Barlow, J. and G. A. Cameron. 1999. Field expe riments show that acoustic p ingers reduc e marine m ammal byc atch in 

the California d rift gillnet fishery. Pap er SC/51 /SM2 p resented to the International Whaling Commission, May 

1998 (unpublished). 20pp. 

Barlow, J. and T. G errodette. 1 996. Ab undance of cetacean s in California waters based on 1991 and 1 993 ship surveys. 

NOA A Tech nical Me morand um NM FS, NO AA-TM -NMF S-SW FSC-23 3. 

Barlow, J. and S. Sexton. 1996. The effect of diving and searching behavior on the probability of detecting track-line 

groups, g0, of long-diving w hales during lin e transect surve ys. Administrativ e Repo rt LJ-96-14 . Available from 

NMFS, Southwest Fisheries Science Center, P.O. Box 271, La Jolla, California, 92038, USA. 21 p. 

Camero n, G., and K . A. Forney. 1 999. Estim ates of cetace an mortality in the California gillnet fisheries for 1997 and 

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

Frantzis, A. 1998. Does acoustic testing strand whales? Nature 392(5):29. 

Henshaw, M. D., R. G. LeDuc, S. J. Chivers, and A. E. Dizon . 1997. Identifying beaked whales (family Ziphiidae) 

using mtDNA sequences. Marine Mammal Science 13:487-495. 

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

Holts, D. and O. Sosa-Nishizaki. 1998. Swordfish, Xiphias gladius, fisheries of the eastern North P acific Ocea n. In: 

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

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

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

Julian, F. 1997 . Cetacean mortality in California gill net fisheries: preliminary estimates for 1996. Int. Whal. Commn. 

Working Paper SC/49/SM2. 13pp. 

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

1990-1995. Fishery Bulletin 96:271-284. 

Mead, J. G. 1989. B eaked 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. Tho mpson. 1 995. M arine Ma mmals and Noise. Ac ademic 

Press, San Diego. 576 p. 

Sosa-Nish izaki, 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, W ashington. U. S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-12. 

93 pp. 

139 
Revised 12/15/2000 

CUVIER'S BEAKED WHALE (Ziphius cavirostris): 

California/Oregon/Washington Stock 

STOCK DEFINITION AND GEOGRAPHIC RANGE 

Cuv ier'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 chang es in 

distribution are appa rent from stranding records, and 

morphological evidenc e is consisten t with the existence of 

a single eastern North Pacific population from Alaska to 

Baja California, Mexico (Mitchell 1968). Howe ver, there 

are currently no international agreements for cooperative 

management of this species. For the Marine Mammal 

Protection Act (MMPA) stock assessment repo rts, Cu vier's 

beaked whales w ithin the Pacific U.S . Exclusiv e Econ omic 

Zone are divided into three discrete, non-contiguous areas: 

1)	 waters off California, Oregon and W ashingto n (this 

report), 2) Alaskan waters, and 3) H awaiian waters. 

POPULATION SIZE 

Although Cuvier's beaked whales have been sighted along 

the U.S. west coast on several line transect surveys 

utilizing both aerial and shipboard platforms, sightings 

have generally been too rare to produce reliable population 

estimates. Previous abundance estimates have been 

imprecise and biased downward by an unknown amount 

because of the large proportion of time this species spends 

submerged, and because the ship surveys on which they 

were based co vered o nly Califo rnia waters, an d thus co uld 

not observe animals o ff Orego n/Wash ington. Furthermore, 

there were a large number of unidentified beaked whale 

Figure 1. Cuvier’s beaked whale sightings based 

on aerial and ship board su rveys off California, 

Oregon and Washington, 1991-96 (see Append ix 2, 

Figures 1-5, for data sources and information on 

timing and location of survey effort). Dashed line 

represents the U.S. EEZ, thick line indicates the 

outer boundary of all surveys combined. 

sightings, which were probab ly either Mesoplodon sp. or Cuvier's beak ed whales ( Ziphius cavirostris ). Recent 

analyses (Barlow and Gerrodette 1996, Barlow and Sexton 1996) have resulted in improved estimates of 

abundance by 1) combining data from three surveys conducted within 300 nmi of the coasts of C alifornia (in 

1991 and 1993; Barlow and G errodette 1996) and California, Oregon and Washington (in 1996; Barlow 1997), 

2) whenever possible, assigning unidentified beaked whale sightings to Mesoplodon spp. or Ziphius c avirostris 

based on written description s, size estimates, and ‘m ost probable iden tifications’ made by the observers at the 

time of the sightings, and 3) estimating a correction factor for animals missed because they are submerged, 

based on dive-interval data collected for Cuvier’s beaked whales in 1993-95 (an estimated 13% o f all groups 

are estimated to be seen ). Because animals probably spend time outside the U.S. Exclusive Economic Zone, 

a multi-year avera ge abund ance estima te is the most ap propriate for manage ment within U.S. waters. The 1991­

96 weighted average abu ndance estimate for California, O regon and W ashington waters based on the above 

analyses is 5,870 (CV= 0.38) Cuv ier’s beaked w hales (Barlow 1997, with corrected CV). 

Minimum Population Estimate 

Based on the above abundance estimate and CV, the minimum population estimate (defined as the log-normal 

20th percentile of the abundance estimate) for Cuvier's beaked whales in California, Oregon, and Washington 

is 4,309 anim als. 

140 
Current Population Trend 

Due to the rarity of sighting s of this spec ies on surv eys along the U.S. W est coast, no information exists 

regardin g trends in abund ance of th is popula tion. 

CURRENT AND M AXIMUM NET PROD UCTIVITY RATES 

No inform ation on curren t or maxim um net pro ductivity rates is available for this species. 

POTENTIAL BIOLOGICAL REMOVAL 

The potential biological removal (PBR) level for this stock is calculated as the minimum population size (4,309) 

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

a species of un known status w ith no known recent fishery mortality; Wa de and A ngliss 1997 ), resulting in a 

PBR of 43 Cuv ier’s beaked whales per ye ar. 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY 

Fishery Information 

A summary of recent fishery mortality and injury for Cuvier’s beaked whales in this region is shown in Table 

1. More d etailed information on th ese fisheries is p rovided in App endix 1 . Mortality estimates for the 

California drift gillnet fishery are included for the five most recent years of monitoring, 1994-98 (Julian and 

Beeson 1998; Julian 1997; C ameron a nd Forne y 1999). A fter the 1997 implemen tation of a Take Reduction 

Plan, which included skipper education workshops and required the use of pingers and minimum 6-fathom 

extenders, overall cetac ean entangle ment rates in the drift gillnet fishery dro pped co nsiderably (Barlow and 

Cameron 1999). However, because of interannual variability in entanglement rates and the relative rarity of 

Cuvier’s beaked whale entanglements, additional years of data will be required to fully evaluate the 

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

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

This results in an average estimated an nual mortality of zero Cuvier’s beake d whales. 

Table 1. Summary of available information on the incidental mortality and injury of Cuvier's beaked whales 

(California/ Oregon/W ashington Stoc k) in comm ercial fisheries that might take this species. One Cuvier’s 

beaked whale was released aliv e in the driftn et fishery in 1995; a ll other entan glemen ts resulted in th e death 

of the animal. Coefficients of variation for mortality estimates are provided in parentheses. Annual mortality 

estimates for 1995 are shown both including and excluding the animal released alive. Mean annual takes are 

based o n 1994 -98 data u nless noted otherw ise. 

Fishery Name Data Type Year(s) 

Percent 

Observer 

Co 

ve 

ra 

ge 

Observed 

Mortality + 

Release 

dAlive 

Estimated Annual 

Mortality / 

Mortality + 

Entanglemen 

ts 

Mean 

Annual Takes 

(CV in 

parent 

heses) 

CA/OR thresher 

shark/swor 

dfish drift 

gillnet 

fishery 

observer 

data 

1994 

1995 

1996 

1997 

1998 

17.9% 

15.6% 

12.4% 

23.0% 

20.0% 

6 

5+1 

0 

0 

0 

34 (0.36) 

32 (0.40) / 39 (0.36) 

0 

0 

0 

01 

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 in cluded the use of net extenders and acoustic warnin g devices (pingers). 

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

141 
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 198 6 to 31 ve ssels in 1993 (Holts and Sosa-Nishizaki 1998). The total number 

of sets in this fishery in 199 2 can be e stimated from data provided by these authors to be approximately 2700, 

with an observed rate of marine ma mmal byca tch of 0.13 animals per set (10 mar ine mamm als in 77 observed 

sets; Sosa-Nish izaki et al. 199 3). This ov erall mortality rate is similar to that observed in California driftnet 

fisheries during 1990-95 (0.14 marine mammals per set; Julian and B eeson, 19 98), but sp ecies-specific 

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

Mexica n swordfish d riftnet fishery to a long line fishery (D. H olts, pers. com m.). 

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 humanmade sou nds on deep -diving cetacean species, such as Cuvier’s beaked whales (Richardson et al. 1995). In 

particular, Low F requen cy Activ e Sonar (LFAS ) has been implicated in the mass stranding of beaked whales 

in the Mediterranean Sea (Fran tzis 1998 ) and m ore recen tly in the Ca ribbean . They ar e not listed as 

"threatened" or "enda ngered " under the End angered Species A ct nor as "d epleted" u nder the M MPA . Including 

driftnet mortality only for years after implementation of the Take Reduction Plan (1997-98), the average annual 

human-caused mortality in 1994-98 is zero. Because recent mortality is zero, Cuvier’s beaked whales are not 

classified as a "strategic" stock under the MMPA, and the total fishery mortality and serious injury for this stock 

can be considered to be insignificant and approaching zero. 

REFERENCES 

Barlow, J. 1997. Preliminary estimates of cetacean abundance off California, Oregon and Washington based on a 1996 

ship survey and comparisons of passing and closing mo des. Administrative Repo rt LJ-97-11, Southwe st 

Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA 92038. 25p. 

Barlow, J. and G. A. Cameron. 1999. Field experiments show that acoustic pingers red uce marine mamma l bycatch in 

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

1998 (unpublished). 20pp. 

Barlow, J. and T. Gerrodette. 1996. Abundance of cetaceans in California waters based on 1991 and 1993 ship su rveys. 

NOA A Tech nical Me moran dum N MFS , NOA A-TM -NM FS-SW FSC-2 33. 

Barlow, J. and S. Sexton. 1996. The effect of diving and searching behavior on the probability of detecting track-line 

group s, g0, of long-diving whales during line transect surveys. A dministra tive Repo rt LJ-96-1 4. Availab le 

from NMFS, Southwest Fisheries Science Center, P.O. Box 271, La Jolla, California, 92038, USA. 21 p. 

Camero n, G., and K . A. Forney. 1 999. Estim ates of cetace an mortality in the California gillnet fisheries for 1997 and 

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

Frantzis, A. 1998. Does acoustic testing strand whales? Nature 392(5):29. 

Heyning, J. E. 1989. Cuvier’s beaked whale Ziphius c avirostris G. Cuvier , 1823. pp. 289-308 In: Ridgway, S. H. and 

R. Harrison (ed s.), Handboo k of Marine Mam mals, Vol. 4. Ac ademic Press. 

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

Holts, D. and O. S osa-Nishiza ki. 1998. S wordfish, Xiphias gladius, fisheries of the eastern N orth Pacific O cean. In: 

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

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

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

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

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

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

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

Mitche ll, E. 1968. Northeast Pacific stranding distribution an d season ality of Cu vier's beak ed wha le, Ziphius 

142 
cavirostris . Can. J. Zool. 46:265-279. 

Richardson, W. J., C. R. Greene, Jr., C. I. Malm e, and D . H. Thompso n. 1995 . Marine Mam mals and Noise. A cadem ic 

Press, San Diego. 576 p. 

Sosa-N ishizaki, O., R. De la Rosa-Pache co, 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. 

143 
Revised 12/15/2000 

PYGMY SPERM WHALE (Kogia breviceps): 

California/Oregon/Washington Stock 

STOCK DEFINITION AND GEOGRAPHIC RANGE 

Pygmy sperm whales are distributed throughout deep 

waters and along the continental slopes of the North 

Pacific and other o cean basins (Ro ss 1984; Caldw ell 

and Caldw ell 1989) . Along th e U.S. w est coast, 

sightings of this species an d of anim als identified only 

as Kogia sp. have been very rare (Figure 1). 

However, this is probably a reflection o f their pelag ic 

distribution, small body size and cryptic behavior, 

rather than an indication of true rareness. Strandings 

of pygmy sperm whales in this region are known from 

California, Oregon and Washington (Roest 1970; 

Caldw ell and Caldwell 1989 ; NMFS , Northwest 

Region, unpublished data; NMFS, Southwest Region, 

unpublished data). Available data are insufficient to 

identify any seasonality in the distribution of pygmy 

sperm whales, or to delineate possible stock 

boundaries. For the Marine Mammal Protection Act 

(MMPA) stock assessment reports, pygmy sperm 

whales within the Pacific U.S . Exclusiv e Econ omic 

Zone are divided into two discrete, non-contiguous 

areas: 1) waters off California, Oregon and 

Washin gton (this re port), and 2) Haw aiian wate rs. 

POPULATION SIZE Figure 1. Kogia sightings based on aerial and

Although pygmy sperm wh ales have been sighted shipboard surveys off California, Oregon and 

along the U.S. west coast on several line transect Washington, 1991-96 (see Appendix 2, Figures 1-5, for 

surveys utilizing both aerial and sh ipboard platform s, data sources and information on timing and location of 

sightings have generally been too rare to produce survey effort). Key: ! = Kogia b reviceps, + = Kogia reliable population estimates. Previous abundance spp. Dashed line represents the U.S. EEZ, thick line 

estimates have been imprecise and biased downward indicates the o uter bound ary of all surveys co mbined. 

by an unknown amount because pygmy sperm whales 

spend a large proportion of time submerged and are very difficult to detect at the surface unless seas are calm. 

Furthermore, the ship survey covered only California waters, and thus could not observe animals off 

Oregon/Washington. Recent analyses (Barlow and Gerrod ette 1996, Barlow and Sexton 1996) have resulted 

in improved estimates of abundance by 1) combining data from three surveys conducted within 300 nmi of the 

coasts of California (in 1991 and 1993; Barlow and G errodette 1996) and California, Oregon and Washington 

(in 1996; Barlow 1997), and 2) estimating a correction factor for animals missed because they are submerged, 

based on dive-interval data collected for Kogia simus in 1993-95 (about 19% of all groups are estimated to be 

seen). Because animals probably spend time outside the U.S. Exclusive Economic Zone, a multi-year average 

abundance estimate is the most appropriate for management within U.S. waters. The 1991-96 weighted average 

abundance estimate for California, Oregon and Washington waters based on the above analyses is 2,933 

(CV=0.54) pygmy sperm whales plus an estimated 1,813 (CV=1.53) pygmy or dwarf sperm whales, based on 

sightings that could only b e identified to the genu s Kogia (Barlow 1997, with corrected C V). Because there 

have been no reported sightings, strandings, or entanglements of dwarf sperm whales along the U.S. West coast 

since the early 1 970s, it is alm ost certain th at these add itional Kogia were pygmy sperm whales, bringing the 

total abundance estimate to 4,746 (CV=0 .67). 

144 
Minimum Population Estimate 

Based on the above abundance estimate and CV, the minimum population estimate (defined as the log-normal 

20th percentile o f the total Kogia abundance estimate) for pygmy sperm whales in California, Oregon, and 

Washing ton is 2,837 anim als. 

Current Population Trend 

Due to the rarity of sightin gs of this spe cies on sur veys alon g the U.S . West coa st, no inform ation exists 

regardin g trends in abund ance of th is popula tion. 

CURRENT AND M AXIMUM NET PROD UCTIVITY RATES 

No inform ation on curren t or maxim um net pro ductivity rates is available for this species. 

POTENTIAL BIOLOGICAL REMOVAL 

The potential biological removal (PBR) level for this stock is calculated as the minimum population size (2,837) 

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

a species of unknown status with no known recent fishery mortality; Wade and Angliss 1997), resulting in a 

PBR of 28 pygmy sperm whales per year. 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY 

Fishery Information 

A summ ary of rec ent 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 provide d in Ap pendix 1. In the Californ ia drift gillnet fishery, no m ortality of pygmy sperm whales or 

unidentified Kogia was observed during the most recent five years of monitoring, 1994-98 (Julian 1997; Julian 

and Beeson 1998; Cameron and Forney 1999). After the 1997 implementation of a Take Reduction Plan, which 

included skipper education workshops and required the use of pingers and minimum 6-fathomextenders, overa ll 

cetacean entanglement rates in the drift gillnet fishery dropped considerably (Barlow and Cameron 1999). 

However, because of interannual variab ility in entanglemen t rates and the ra rity of Kogia entanglements, 

additional years of data will be req uired to fully eva luate the effectiven ess of pingers for reducing mortality of 

pygmy sperm whales. Because of the changes in this fishery after implementation of the Take Reduction Plan, 

mean annual takes in Table 1 are based only on 1997-98 data. This results in an average estimated annual 

mortality of zero pygmy sperm whales. 

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

and may take animals from the same population. Quantitative data are available only for the Mexican 

swordfish drift gillnet fishery, which uses vessels, gea r, and ope rational pro cedures sim ilar 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 fro m two vesse ls 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 prov ided by thes e authors to b e appro ximately 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 over all mortality rate is similar to that observed in California driftnet 

fisheries during 1990-95 (0.14 marine mamm als per set; Julian and Be eson, 199 8), but spec ies-specific 

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

Mexica n swordfish d riftnet fishery to a long line fishery (D. H olts, pers. com m.). 

STATUS OF STOCK 

The status of py gmy sp erm w hales in California, Oregon and Washington waters relative to OSP is not known, 

and there are in sufficient d ata to evalua te potential tre nds 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 humanmade 

145 
sounds on deep-diving cetacean species, such as pygmy sperm whales (Richardson et al. 1995). They are not listed as 

"threatened" or "endangered" under the Endangered Species Act nor as "depleted" under the MMPA. Including 

driftnet mortality only for years after implementation of the Take Reduction Plan (1997-98), the average annual 

human-caused mortality in 1994-98 is zero. Because recent mortality is zero, pygmy sperm whales are not 

classified as a "strategic" stock under the MMPA, and the total fishery mortality and serious injury for this stock 

can be considered to be insignificant and approaching zero. 

Table 1. Summ ary of av ailable info rmation on the in cidental mortality and injury of pygmy sperm whales and 

unidentified Kogia sp. (Californ ia/Orego n/Wash ington S tock) in co mme rcial fisheries th at migh t take this 

species. Coefficien ts of variation for mortality estimates are provided in parentheses. Mean annu al takes are 

based on 1994-98 data unless noted otherwise. 

Fishery Name Data TypeYear(s) 

Percent 

Observer 

C 

o 

ve 

ra 

ge 

Observed 

Mortality 

K. breviceps 

/Ko 

gia 

sp. 

Estimated Annual 

Mortality of 

K. 

breviceps/K 

ogia sp. 

Mean 

Annual Takes 

(CV in 

parenth 

eses) 

CA/OR thresher 

shark/swordfish 

drift gillnet 

fishery 

observer 

data 

1994 

1995 

1996 

1997 

1998 

17.9% 

15.6% 

12.4% 

23.0% 

20.0% 

0 / 0 

0 / 0 

0 / 0 

0 / 0 

0 / 0 

0 / 0 

0 / 0 

0 / 0 

0 / 0 

0 / 0 

01 

Minimum total annual takes 0 

1

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

Reduction Plan. Gear modifications in cluded the use of net extenders and acoustic warnin g devices (pingers). 

REFERENCES 

Barlow, J. 1997. Preliminary estimates of cetacean abundance off California, Oregon and Washington based on a 1996 

ship survey and comparisons of passing and closing modes. Administrative Report LJ -97-11, Southwest 

Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA 92038. 25p. 

Barlow, J. and G. A. Cameron. 1999. Field expe riments show that acoustic p ingers reduc e marine m ammal byc atch in 

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

1998 (unpublished). 20pp. 

Barlow, J. and T. Gerrodette. 1996. Abundan ce of cetaceans in California waters based on 1991 and 1993 ship surveys. 

NOA A Tech nical Me moran dum N MFS , NOA A-TM -NM FS-SW FSC-2 33. 

Barlow, J. and S. Sexton. 1996. The effect of diving and searching behavior on the probability of detecting track-line 

group s, g0, of long-diving whales during line transect surveys. Administrative Report LJ-96-14. Availab le 

from NMFS, Southwest Fisheries Science Center, P.O. Box 271, La Jolla, California, 92038, USA. 21 p. 

Caldw ell, D. K. an d M. C . Caldwe ll. 1989. Py gmy sp erm w hale 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 

Mam mals, Vol. 4. Ac ademic Press. 

Camero n, G., and K . A. Forney. 1 999. Estim ates of cetace an mortality in the California gillnet fisheries for 1997 and 

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

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

Holts, D. a nd O. So sa-Nishizak i. 1998. S wordfish, Xiphias gladius, fisheries of the eastern North P acific Ocea n. In: 

I. Barrett, O. Sosa-Nishizaki and N. Bartoo (eds.). Bio logy and fisheries of sword fish, 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. C etacean m ortality in Californ ia gill net fisheries: Preliminary estimates for 1996. Paper SC/49/SM02 

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

146 
Julian, F. and M . Beeson . 1998. E stimates 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. Malm e, and D . H. Thompso n. 1995 . Marine Mam mals and Noise. A cadem ic 

Press, San Diego. 576 p. 

Roest, A. I. 197 0. Kogia simus and other cetaceans from San Luis Obispo County, California. J. Mammal. 51:410-417. 

Ross, G. J. B. 1984. Th e smaller cetaceans o f the south east coast of southe rn Africa . Ann. C ape Pro v. Mus . Nat. Hist. 

15:173-410. 

Sosa-Nish izaki, 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 (m arlins y pez vela). Rep. 

Int. CICESE, CTECT9306. 

147 
Revised 12/15/2000 

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 1 974; G osho et al. 

1984; Miyashita et al. 1995) . For mana gement, the 

International Whaling Commission (IWC) had 

divided the North Pacific into two management 

regions (Donovan 1991) d efined by a zig-zag line 

which starts at 150o

W at the equator, is 160oW 

between 40-50o

N, and ends up at 180oW north of 

50o

N; however, the IWC has not review ed this 

stock boundary in many years (Donovan 1991). 

Sperm whales are fo und year-ro und in Califo rnia 

waters (Dohl et al. 1983; Barlow 1995; Forney et al. 

1995), but they reach peak ab undance from April 

through mid-June a nd from th e end of August 

through mid-November (Rice 1974). They were 

seen in every season excep t 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 wha lers: one off northern 

California in June, one off Washin gton 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 distrib uted in 

the tropics, their rela tive abund ance tape rs 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 structur e of sperm whale 

popula tions in the eastern tropical Pacific is not 

known, but the only photographic matches of 

known individuals from this area have been 

Figure 1. Sperm wh ale sighting locations based on 

aerial and shipboard surveys off California, Oregon, and 

Washington, 1989-96. Dashed line represents the U.S. 

EEZ, thick line indicates the oute r bounda ry of all 

surveys combined. Gre ater effort was co nducted o ff 

California (south of 42�N) and in the insho re half of the 

U.S. EEZ. Se e Appe ndix 2 of Barlow et al. (1997) and 

Barlow (1997) for data sources and information on 

timing and lo cation of surv ey effort. 

between the Galapagos Islands and coastal waters of South America (Dufault and Whitehead 1995), suggesting 

that the eastern tropical animals constitute a distinct stock. A recent surv ey designed specifically to inve stigate 

stock structure and abundance of sperm whales in the northeastern temperate Pacific revealed no apparent hiatus 

in distribution between the U.S. EEZ off California and areas farther west, out to Hawaii (Barlow and Taylor 

1998). Recent analyses of genetic relationships of animals in the eastern Pacific found that mtDNA and 

microsatellite DNA of animals sam pled in the California Curr ent is significantly different from animals sampled 

further offshore and that genetic differences appeared larger in an east-west direction than in a north-sou th 

direction (Mesnick et al., in press). 

For the Marine Mammal Protection Act (MM PA) stoc k assessmen t reports, spe rm whales with in the Pacific 

U.S. EEZ are divided into three discrete, non-contiguous areas: 1) California, Oregon and Washington waters 

(this report), 2 ) waters arou nd Haw aii, and 3) Ala ska waters. 

142 
POPU LATIO N SIZE 

Barlow (1997) estimates 1 ,191 (CV=0.22) sperm whales along the coasts of California, Oregon, and 

Washington during summer/fall based on ship line transect surveys in 1991, 1993, and 1996 (lognormal 95% 

C.I.= 778-1,824). Forney et al. (1995) estimate 892 (CV=0.99) sperm whales off California during 

winter/spring based on aerial line-transect surveys (95% C.I.=176-4,506), but this estimate does not correct for 

diving whales that were missed. Because of the long dive time of sperm wh ales (Leathe rwood e t al. 1982), it 

is reasonable to assume that a corrected estimate would be three to eight times the estimates from aerial surveys. 

Green et al. (1992) report that sperm whales were the third most abundant large whale (after gray and humpback 

whales) in aerial surveys off Oregon and Washington, but they did not estimate population size for that area. 

A large 1982 abundance estimate for the entire eastern North Pacific (Gosho et al. 1984) was based on a CPUE 

method which is no longer accepted as valid by the International Whaling Commission. Recently, a combined 

visual and acoustic line-transect survey conducted in the eastern temperate North Pacific in spring 1997 resulted 

in estimates of 24,000 (CV=0.46) sperm whales based on visual sightings, and 39,200 (CV=0.60) based 

acoustic detections a nd visual gro up size estima tes (Barlow and Ta ylor 1998 ). Howev er, it is not known 

whether any or all of these an imals routinely e nter 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 Ger rodette 1993), b ut this 

area does not include areas where sperm whales are taken by drift gillnet fisheries in the U.S. EEZ and there 

is no eviden ce of sperm whale mov ements from the eastern tro pical Pac ific to the U.S. E EZ. 

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 co vered 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 evide nce of sper m whale mo vement from California to 

northern areas off British Columb ia, but there are no abundance estimates for this area. The most precise 

estimate of sperm wh ale abund ance for this stoc k is therefore fro m the ship surv ey estimate of Barlow (1997); 

however, this is probably an underestimate of true abundance because recent studies suggest sperm whale group 

sizes may have b een unde restimated o n past line-transe ct surveys (Barlow and Taylor 1 998; B . Taylor, unp ubl. 

data). 

Minimum Po pulation Estimate 

The minimum population estimate for sperm whales is taken as the lower 20th percentile of the log-normal 

distribution of abunda nce estimated from the sum mer/fall ship surv eys off California, Oregon and Washington 

(Barlow 1997) or approximately 992. More sophisticated methods of estimating minimum population size 

would be available if a correction factor (and associated variance) were available to correct the aerial survey 

estimates for m issed anima ls. 

Current Population Trend 

Sperm whale abundance appears to have been rather variable off California between 1979/80 and 1996 (Barlow 

1994; Barlow 1997) but does not show any obvious trends. Although the population in the e astern No rth 

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 mak e this uncertain. 

CURRENT AND M AXIMUM 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 (992) times one half the default maximum net growth rate for cetaceans (1⁄2 of 4%) 

times a recover y factor of 0.1 (the default valu e for an end angered sp ecies), resulting in a PBR of 2.0. 

HUMAN -CAUSED MORTALITY 

143 
Historic Whaling 

Between 1800 and 1909 , about 60,842 sperm whales were estimated taken in the North Pacific (Best 1976). 

The reported take o f North P acific sperm whales by co mmercial w halers betwe en 1947 and 198 7 totaled 

258,000 (C. Allison, pers. comm.). Ohsumi (1980) lists an additional 28,198 sperm whales taken mainly in 

coastal whaling op erations from 1910 to 1946. Based on the massive under-reporting of So viet catches, 

Brown ell 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 com mercial wha ling for this specie s in 1987 . Of this grand to tal, an estimated 33,842 were taken by 

Soviet and Japanese pelagic whaling op erations in the e astern No rth 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 operation s between 1 947 and 1971 (O hsumi 198 0). In 

addition, 13 sperm whales were taken by shore whaling stations in California between 1919 and 1926 (Clapham 

et al. 1997) . There ha s been a pr ohibition o n taking sperm whales in the N orth Pacific since 1988, but largescale pelagic whaling stopped earlier, in 1980. 

Fishery Information 

The offshore drift gillne t fishery is the only fishery tha t is likely to take sperm whales from this stock. Detailed 

information on this fishery is provided in Appendix 1. A 1994-98 summary of known fishery mortality and 

injury for this stock of sp erm whales is given in Ta ble 1. After the 1997 implementation of a Take Reduction 

Plan, which included skipper education workshops and required the use of pingers and minimum 6-fathom 

extenders, overall cetacean entanglement rates in the drift gillnet fishery dropped considerably (Barlow and 

Cameron 1999). However, two sperm whales have been observed taken in nets with pingers (1996 and 1998). 

Because sperm whale entanglement is rare and because those nets which took sperm whales did n ot use the full 

mandated complement of pingers, it is difficult to evaluate w hether pinge rs have any effec t on sperm whale 

entanglement in drift gillnets. Because of the changes in this fishery after implementation of the Take 

Reduction Plan, mean annual takes for this fishery (Table 1) are based only on 1997-98 data. This results in an 

average estimate of 2.5 (CV = 0.89) sperm whale mortalities per year. 

Table 1. Summary of available information on the incidental mortality and injury of sperm whales (CA/OR/WA stock) 

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

Forney 1999). Injury includes any entanglement that does not result in immediate death and may include 

serious injury resulting in death. The injured whale obs erved in 19 96 was no t expected to survive . n/a 

indicates that d ata are not av ailable. M ean annua l takes are ba sed on 19 94-98 d ata unless note d otherwise . 

Fishery NameYear(s) Data Type Percent Observer 

Cover 

age 

Observed 

Mortality 

(and injury in 

par 

ent 

hes 

es) 

Estimated 

Mortality (CV in 

parent 

heses) 

Mean Annual Takes 

(CV in parentheses) 

CA/OR thresher 

shark/swordfish 

drift gillnet 

fishery 

1994 

1995 

1996 

1997 

1998 

observer 

data 

17.9% 

15.6% 

12.4% 

23.0% 

20.0% 

0 

0 

0 (1) 

0 

1 

Mortality 

0,0,0,0,5 

(0.89) Injury 

0,0,1,0,0 

Mortality 

2.5 (0.89)1 

Injury

0.0 (n/a) 

Total annual takes 2.5 (0.89) 

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 in cluded the use of net extenders and acoustic warnin g devices (pingers). 

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

take animals from the same population. Quantitative data are available only for the Mexica n swordfish drift 

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

144 
fishery, although nets may be up to 4.5 km long (Holts and Sosa-Nishizaki 1998). The fleet increased from two 

vessels in 1986 to 31 vessels in 1993 (Holts and Sosa-Nishizaki 1998). The total number of sets in this fishery 

in 1992 can be estimated from data provided by these authors to be approximately 2,700, with an obse rved rate 

of marine mammal bycatch of 0.13 animals per set (10 marine mammals in 77 observed sets; Sosa-Nishizaki 

et al. 1993) . This over all mortality rate is similar to that observed in California driftnet fisheries during 1990-95 

(0.14 marine mammals per set; Julian and Beeson,1998), but species-specific information is not available for 

the Mexican fisheries. There are currently efforts underway to convert the Mexican swordfish driftnet fishery 

to a longline fishe ry (D. Ho lts, pers. comm .). 

Ship Strikes 

No sperm whale mortalities have been attributed to ship strikes during the period 1994-98 (J. Cordaro, 

Southwest R egion, NM FS, pers. co mm.). 

STATUS OF STOCK 

The only estimate of the status of North Pacific sperm whales in relation to carrying capacity (Gosho et al. 

1984) is based on a CPUE method which is no longer accepted as valid. Sperm whales are formally listed as 

"endangered" under the Endangered Species Act (ESA), and consequently the California to Washington stock 

is automatically considered as a "depleted" and "strategic" stock under the MMPA. The annual rate of kill and 

serious injury (2.5 per year) is greater than the calculated PBR for this stock (2.0) which would also result in 

the classification of this stock as “strategic”. Total fishery takes are not approaching zero mortality and serious 

injury rate. The increasing levels of anthropogenic noise in the world’s oceans has been suggested to be a 

habitat concern for whales, particularly for deep-divin g whales like sp erm whales that feed in the oceans “sound 

channel”. 

REFERENCES 

Allison, C. International Whaling Commission. The Red House, 135 Station Road, Impington, Cambridge, UK CB4 

9NP. 

Allen, K. R. 1980. Size distribution of male sperm whales in the pelagic catches. Rep. Int. Whal. Commn. Special Issue 

2:51-56. 

Barlow, J. 1994. Abunda nce of large w hales in Califor nia coastal waters: a comparison of ship surveys in 1979/80 and 

in 1991. Rept. Int. Whal. Commn. 44:399-406. 

Barlow, J. 1995. T he abund ance of ceta ceans in Ca lifornia waters. Part I: S hip surveys in summer and fall of 1991. 

Fish. Bull. 93:1-14. 

Barlow, J. 1997. Preliminary estimates of cetacean abundance off California, Oregon and Washington based on a 1996 

ship survey and comparisons of passing and closing mo des. Administrative Repo rt LJ-97-11, Southwe st 

Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA 92038. 25p. 

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

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

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

425. 

Barlow, J. and G. A. Came ron. 199 9. Field exp eriments sho w that acoustic pingers red uce marine mamma l bycatch in 

the California drift gillnet fishery. Report SC/51/SM2 to the Scientific Committee of the International Whaling 

Commission, May 1999. 20pp. 

Barlow, J., K. A. Forney, P. S. Hill, R. L. Brownell, Jr., J. V. Carretta, D. P. DeMaster, F. Julian, M. S. Lowry, T. Ragen, 

and R. R. Reeves. 1997. U.S. Pacific Marine Mammal Stock Assessments: 1996. U.S. Dep. Commer., NOAA 

Tech. Memo. NMFS-SWFSC-248. 223p. 

Barlow, J. and B. L . Taylor. 19 98. Prelim inary abund ance of spe rm whales in the northeastern temperate Pacific 

estimated from a combined visual and acoustic survey. Paper SC/50/CAWS20 presented to the International 

Whaling Comm ission, June 1 998 (unp ublished). 

Best, P. B. 1976. A review of world sperm whale stocks. Paper ACMRR/MM/SC/8 Rev. 1, FAO Scientific 

Consultatio n of Mar ine Mam mals, Berg en, Norw ay. 

145 
Best, P. B. 1993. Increase rates in severely depleted stocks of baleen whales. ICES J. Mar. Sci. 50:169-186. 

Brown ell, R. L., Jr., A. V . Yablok ov and V . A. Zemm sky. 1998 . USSR pelagic catc hes of No rth Pacific sperm whales, 

1949-1979: Conservation implications. Paper SC/50/CAWS27 presented to the International Whaling 

Commission, June 1998 (unpublished). 

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

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

(unpublished). 14 pp. 

Clapham, P. J., S. Leatherwood, I. Szczepaniak, and R. L. Brownell, Jr. 1997. Catches of humpback and other whales 

from shore stations at Moss Landing and Trinidad, California, 1919-1926. Marine Mammal Science 13(3):368­

394. 

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

Dohl, T. P., R. C. Guess, M. L. Duman, and R. C. Helm. 1983. Cetaceans of central and northern California, 1980-83: 

Status, abundance, and distribution. Final Report to the Minerals Management Service, Contract No. 14-12­

0001-29090. 284p. 

Donovan, G. P. 1991. A review of IWC stock boundaries. Rept. Int. Whal. Commn., Special Issue 13:39-68. 

Dufault, S. and H . Whitehe ad. 199 5. The geo graphic stoc k structure of fem ale and imm ature sperm whales in the South 

Pacific. Rep. Int. Whal. Commn. 45:401-405. 

Forney, K. A., J. B arlow, and J. V. Carre tta. 1995. T he abund ance of ceta ceans in Ca lifornia waters. Part II: Aerial 

surveys in winter and spring of 1991 and 1992. Fish. Bull. 93:15-26. 

Gosho, M. E., D. W. Rice, and J. M. Breiwick. 1984. The sperm whale. Mar. Fish. Rev. 46(4):54-64. 

Green, G. A., J. J. B rueggema n, R. A. Gro tefendt, C. E . Bowlby, M. L. Bonnell, K. C. Balcomb, III. 1992. Cetacean 

distribution and abundance off Oregon and W ashington, 1989-1990. Ch. 1 In: J. J. Brueg geman (ed .). Oregon 

and WashingtonMarine Mammal and Seabird Surveys. Minerals Management Service Contract Report 14-12­

0001-30426. 

Hanan, D. A. 1986. California Department of Fish and Game coastal marine mammal study, annual report for the period 

July 1, 1983 - June 30, 1 984. Admin. Rept. LJ-86-16 available from Southwest Fisheries Science Center, P.O. 

Box 271, La Jolla, CA. 55pp. 

Hanan, D. A., D. B . Holts, and A . L. Coan, Jr . 1993. The California drift gill net fishery for sharks and swordfish, 1981­

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

Heyning, J. E., and T. D. Lewis. 1990. Fisheries interactions involving baleen whales off sou thern Californ ia. Rep. int. 

Whal. Commn. 40:427-431. 

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

Holts, D. a nd O. So sa-Nishizak i. 1998. S wordfish, Xiphias gladius, fisheries of the easte rn North Pacific Oc ean. In: 

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

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

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

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

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

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

fisheries: 1990-95. Fishery Bulletin 96:271-284. 

Kasuya, T. 1998. Evidence of statistical manipu lations in Japa nese coasta l sperm wha le fishery. Paper SC/50/CAWS10 

presented to the International Whaling Commission, June 1998 (unpublished). 

Leatherwood, S., K. Goodrich, A. L. Kinter, and R. M. Trupp o. 1982. Resp iration patterns and 'sightability' of whales. 

Rep. Int. Whal. Commn. 32:601-613. 

Mesnick, S. L., B. L. T aylor, B. N achenbe rg, A. Rose nberg, S. Peterson, a nd A. E. Dizon. (In press.). Population 

structure of sperm wh ales in the eastern temperate North Pacific: preliminary findings. Admin. Rep. LJ-xx-xx. 

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

Miyashita, T., H. Kato, and T. Kasu ya (Eds.). 1995. W orldwide map o f cetacean distribution based o n Japanese 

sighting data. Volume 1. National Research Institute of Far Seas Fisheries, Shizuoka, Japan. 140pp. 

Ohsumi, S. 1980. Catches of sperm whales by modern whaling in the North Pacific. Rep. Int. Whal. Commn. Special 

Issue 2: 11-18. 

146 
Rice, D. W . 1988. Sperm whale Physeter macrocephalus, Linnaeus 1758. pp. 177-233 In: S. H. Ridgway and R. J. 

Harrison (eds.). Handbook of Marine Mamma ls, Vol. 4. Academic Press, London. 

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

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

Int. CICESE, CTECT9306. 

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

Rept. Int. Whal. Commn. 43:477-493. 

147 
Revised 12/15/2000 

HUMPBACK WHALE (Megaptera novaeangliae): 

California/Oregon/Washington - Mexico Stock 

STOCK DEFINITION AND GEOGRAPHIC RANGE 

Although the International Whaling Commission 

(IWC) only considered one stock (Donovan 1991), 

there is now goo d evidenc e for multiple populations 

of humpback whales in the North Pacific (Johnson 

and Wolman 1984 ; Baker et al. 1990). Aerial, 

vessel, and photo-identificatio n surveys, and genetic 

analyses indicate that within the U.S. EEZ, there are 

at least three relatively separate populations that 

migrate between the ir respective su mmer/fall 

feeding areas and winter/spring calving and mating 

areas (Calambokidis et al. 1997, Baker et al. 1998): 

1) winter/spring populations in coastal Central 

America and Mexico which migrate to the coast of 

California to southern B ritish Columb ia in 

summer/fall (Steiger et al. 1991, Calambokidis et al. 

1993) - referred to as the California / 

Oregon/Washington - Mexic o stock (Figure 1); 2) 

winter/spring populations of the Hawaiian Islands 

which m igrate to northern B ritis h 

Columbia/Sou theast Alaska and Prince William 

Sound west to Kodia k (Baker et al. 1990, Perry et 

al. 1990, Calambokidis et al. 1997) - referred to as 

the Central North Pacific stock; and 3) winter/spring 

populati ons of Japan which, based on Discovery 

Tag information, p robably m igrate to waters west of 

the Kodiak Archipelago (the Bering Sea and 

Aleutian Islands) in summer/fall (Berzin a nd Rovn in 

1966, Nishiwaki 1966, D arling 199 1) - referred to 

as the Western North Pacific stock. Winter/spring 

populations of humpback whales also occur in 

Mexico ’s offshore islands; the migratory destination 

of these whales is not well known (Calambokidis et 

al. 1993, Calambokidis et al. 1997), but Norr is et al. 

(1999) speculate that they may travel to the Bering 

Sea or Aleutian Islands. Significant levels of 

Figure 1. Humpb ack whale sigh ting locations 

based on aerial and shipboard surveys off California, 

Oregon, and Washington, 1989-96. Dashed line 

represents the U.S. EEZ, thick line indicates the 

outer boundary of all surveys combined. Greater 

effort was conducted off California (south of 42�N) 

and in the inshore half of the U.S. EEZ. See 

Appendix 2 of Barlow et al. (1997) and Barlow 

(1997) for data sou rces and in formation on timing 

and locatio n of survey effor t. 

genetic differences were found between the California and Alaska feeding groups based on analyses of 

mitochondrial DNA (Baker et al. 1990) and nuclear DNA (Baker et al. 199 3). The g enetic excha nge rate 

between California an d Alaska is estimated to be less than 1 female per generation (Baker 1992). Two b reeding 

areas (Hawaii and coastal Mexico) showed fewer genetic differences than did the two feeding areas (Baker 

1992). This is substantiated by the observed movement of individually-identified whales between Hawaii and 

Mexico (Baker et al. 1990). There have been no individual matches between 597 humpbacks photographed 

in California an d 617 h umpba cks photo graphed in Alaska (C alambok idis 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 po pulations. 

Until further information becomes available, three management units of humpback whales (as described above) 

are recognized within the U.S. EEZ of the North Pacific: the California/Oregon/Washington - Mexico Stock 

148 
(this report), the Central North Pacific Stock, and the Western North Pacific Stock. The Central and Western 

North P acific stocks are reported separately in the Stock Asse ssment Rep orts for the Ala ska Regio n. 

POPU LATIO N SIZE 

Based on whaling statistics, the pre-1905 population of humpback whales in the North Pacific was estimated 

to be 15,000 (Rice 1978), but this population was reduced by whaling to approximately 1,200 by 1966 (Johnson 

and Wolman 1984). The North Pacific total now almost certainly exceeds 6,000 humpback whales 

(Calamb okidis et al. 1997). Dohl et al. (1983) first estimated the central California feeding population to be 

338 (CV=0 .29) base d on aerial su rveys in August through November of 1980-83; however, this estimate does 

not include a co rrection for su bmerged animals. More r ecently, the size of the "California" feeding stock of 

humpback whales has been estimated b y three indep endent me thods. 1) C alambok idis et al. (1999) estimated 

the number of humpback whales in California-Washington to be 905 (CV=0.06 ) based on mark-recapture 

estimates comparing their 1997 and 1998 photo-identification catalogs. 2) Barlow (1997) estimates 1,152 

(CV=0.15) humpba cks in California, Oregon and W ashington wa ters based o n ship line-transe ct surveys in 

summer/autumn of 1991, 1993, and 1996. 3) Forney et al. (1995) estimate 319 (CV=0.41) humpback whales 

in California coastal waters based on aerial line-transect surveys in winter/spring of 1991 and 1992 (not 

corrected for diving whales). In addition, Green et al. (1992) report that humpback whales were the second 

most abundant large whale (after the gray whale) in aerial surveys off Oregon and Washington, but they did not 

estimate populatio n size. Thes e estimates for th e west-coast sto ck are not sign ificantly different from each 

other. The shipboard estimates are likely to be the most unbiased, and the aerial surveys are likely to be the 

most negatively biased because sub merged animals are missed. Mark-recapture estimates may also be 

negatively biased du e to heterog eneity in sighting pr obabilities (H ammon d 1986 ). Howev er, given that the 

above mark-recap ture estimate is based on a large fraction of the entire population (1997-98 catalog contained 

544 known individuals), this bias is likely to be minimal. Also, in previous mark-recapture analyses on the 

same population, when methods were used which account for heterogeneity, estimates were comparable or 

smaller (Calambokidis et al. 199 3). The most pre cise and least biased estimate is likely to be the markrecapture estimate of 90 5 (CV= 0.06) hum pback w hales for this po pulation. 

Minimum Po pulation Estimate 

The minimum p opulation e stimate for hum pback w hales in the California/Mexico stock is taken as the lower 

20th percentile of the log-normal distribution of 1997-98 abundance estimated from mark-recapture methods 

(Calambokidis et al. 1999) or approximately 861. 

Current Population Trend 

Ship surveys provide some indication thathumpback whales increased in abundance in California coastalwaters 

between 1979/80 and 1991 (Barlow 1994) and between 199 1 and 1996 (B arlow 1997). Mark-recapture 

population estimates increased steadily from 1988 /90 to 19 97-98 a t about 8% per year (C alambok idis et al. 

1999). Population estimates for the entire North Pacific have also increased substantially from 1,200 in 1966 

to 6,000-8,000 circa 1992. Although these estimates are based on different metho ds and the e arlier estimate 

is extremely u ncertain, the grow th rate implied by these estima tes (6-7% ) is consistent with the recently 

observed growth rate o f the California/O regon/W ashington sto ck. 

CURRENT AND M AXIMUM NET PRODUCTIVITY RATES 

The proportion of calves in the California/Mexico stock from 1986 to 1994 appeared much lower than 

previously measured for humpback whales in other areas (Calambokidis and Steiger 1994), but in 1995-97 a 

greater pro portion o f calves were id entified, and the 1997 re produc tive rates for this po pulation are closer to 

those reported for humpback whale populations in other regions (Calambokidis et al. 1998). Despite the 

apparen tly low proportion of calves, two independent lines of evidence indicate that this stock appears to be 

growing (Barlow 1994; C alambok idis et al. 1999 ) with a best estim ate of 8% growth per year (Calamb okidis 

et al. 1999). 

149 
POTENTIAL BIOLOGICAL REMOVAL 

The potential bio logical remo val (PB R) level for this stock is calculated as the minimum population size (861) 

times one half the estimated population growth rate for this stock of humpback whales (1⁄2 of 8%) times a 

recovery factor of 0.1 (for an endang ered species), resulting in a PB R of 3.4. Becau se this stock spends 

approximately half its time outside the U.S. EEZ, the PBR allocation for U.S. waters is 1.7 whales per year. 

HUMAN -CAUSED MORTALITY 

Historic Whaling 

The reported take of North Pacific humpback whales by commercial whalers totaled approximately 7,700 

between 1947 and 1987 (C. Allison, pers. comm.). In addition, approximately 7,30 0 were taken along the west 

coast of North America from 1919 to 1929 (Tonnessen and Johnsen 1982). To tal 1910-1965 catches from the 

California-Washington stock includes at least the 2,000 taken in Oregon and Washington, the 3,400 taken in 

California, and the 2,800 taken in Baja California (Rice 1978). Shore-based whaling apparently depleted the 

humpback whale stock off California twice: once prior to 1925 (Clapham et al. 1997) and again between 1956 

and 1965 (Rice 1974). There has been a prohibition on taking humpback whales since 1966. 

Fishery Information 

A 1994-98 summary of known fishery mortality and injury for this stock of humpback whales is given in T able 

1. Detailed information on these fisheries is provided in Appendix 1. After the 1997 implementation of a Take 

Reduction Plan, which included skipper education workshops and required the use of pingers and minimum 6­

fathom extenders, overall cetacean entanglement rates in the drift gillnet fishery dropped considerably (Barlow 

and Cameron 1999). Because of the changes in this fishery after implementation of the Take Reduction Plan, 

mean annual takes for this fishery (Table 1) are based only on 1997-98 data. This results in an average es timate 

of zero humpback whales taken annually. Some gillnet mortality of large whales may go unobserved because 

whales swim away with a portion of the net. The deaths of two humpback whales that stranded in the Southern 

California Bight have been attributed to entanglement in fishing gear (Heyning and Lewis 1990), and a 

humpback whale was observed off Ventura, CA in 1993 with a 20 ft section of netting wrapped around and 

trailing behind, but no other gillnet-caused strandings or entanglements were reported for the period 1994-98 

(J. Cordero, NMF S SW Region, pers. comm.). Other unobserved fisheries may also result in injuries or deaths 

of humpback whales. In 1997, one humpback whale was snagged by a central California salmon troller, and 

the animal swam away with the ho ok and many feet of trailing monofilame nt (NM FS, Southwest Region, 

unpublishe d data); this type of injury is not likely to b e serious. 

Table 1. Summary of available information on the incidental mortality and injury of humpback whales (CA/OR/WA -

Mexico stock) for co mmercial fishe ries that might take this species (Julian 1997, Julian and Beeson 1998, 

Cameron and Forn ey 1999 ). Injury include s any entanglem ent 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 1994-98 data unless noted otherwise. 

Fishery NameYear(s) Data Type 

Percent Observer 

Cover 

age 

Observed 

Mortality 

(and Inju ry) 

Estimated 

Mortality (CV 

in 

pare 

nthe 

ses) 

Mean Annual Takes 

(CV in parentheses) 

CA/OR thresher 

shark/swordfish 

drift gillnet 

fishery 

1994 

1995 

1996 

1997 

1998 

observer 

data 

17.9% 

15.6% 

12.4% 

23.0% 

20.0% 

0 (1) 

0 

0 

0 

0 

Mortality 

0,0,0,0,0 

Injury

6,0,0,0,0 

(0.91) 

Mortality 

0 

Injury 

01 

CA angel shark/halibut and 

other species large 

mesh (>3.5") set 

gillnet fishery 

1990-94 observer 

data 

10-15% 0,0,0,0,0 0,0,0,0,0 n/a 

150 
Fishery NameYear(s) Data Type 

Percent Observer 

Cover 

age 

Observed 

Mortality 

(and Inju ry) 

Estimated 

Mortality (CV 

in 

pare 

nthe 

ses) 

Mean Annual Takes 

(CV in parentheses) 

CA salmon troll fishery 1997 incidental 

r 

e 

p 

o 

r 

t 

0% (1) n/a Injury 

>0.2 (n/a) 

Total annual takes >0.2 

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 in cluded the use of net extenders and acoustic warnin g devices (pingers). 

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

take animals from the same population. Quantitative data are available only for the Mexica n swordfish d rift 

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

fishery, although nets m ay be up to 4 .5 km long (H olts and Sosa-Nishizaki 1998). The fleet increased from two 

vessels in 1986 to 31 vesse ls 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 approx imately 2,70 0, with an ob served rate 

of marine m ammal byc atch of 0.13 animals per set (10 mar ine mamm als in 77 observed sets; Sosa-Nishizaki 

et al. 1993) . This over all 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 Mexica n fisheries. There are currently efforts underway to convert the Mexican swordfish driftnet fishery 

to a longline fishe ry (D. Ho lts, pers. comm .). 

Ship Strikes 

Ship strikes were implicated in the deaths of at least two humpback whales in 1993 and one hump back wha le 

in 1995, and o ne unidentified whale, which m ay have bee n a humpb ack whale, w as struck and injured by a 

small boat in 1997 (J . Cordaro, pers. comm.). Additional mortality from ship strikes probably goes unreported 

because the whales do not strand or, if they do, they do not have obvious signs of trauma. Several humpback 

whales have been photographed in California with large gashes in their dorsal surface that appear to be from 

ship strikes (J. Calambokidis, pers. comm.). The average number of humpback whale deaths by ship strikes 

for 1994-98 is at least 0.2 per year. 

STATUS OF STOCK 

Humpback whales in the North Pacific were estimated to have been reduced to 13% of carrying capacity (K) 

by commercial whaling (Braham 1991). C learly the No rth Pacific po pulation wa s severely dep leted. The initial 

abundance has never been estimated separately for the "California" stock, but this stock was also depleted 

(probab ly twice) by whaling (Rice 1974; Clapham et al. 1997). Humpback whales are formally listed as 

"endangered" under the Endangered Species Act (ESA), and consequently the California/Mexico stock is 

automatica lly considered as a "depleted" and "strategic" stock under the MMPA . The estimated annual 

mortality and injury due to entanglement (0.2/yr) plus ship strikes (0.2/yr) in California is less than the PBR 

allocation of 1.7 for U.S. waters. In a review of the severity of injury to the humpback whale entangled in 1994, 

the Pacific Scientific Review Group determined that this animal was not seriously injured. Based on strandings 

and gillnet observations, annual hum pback w hale mortality an d serious inju ry in California's drift gillnet fishery 

is probably greater than 10% of the PBR; therefore, total fishery mortality is not appro aching zero mortality 

and serious injury rate. Th e California sto ck appe ars to be increasing in abundance. The increasing levels of 

anthropo genic noise in the world’s oceans, such as those prod uced by A TOC (Acoustic Thermometry of Ocean 

Climate) or LFA (Low Frequenc y Active) Sonar, have be en suggested to be a hab itat concern for whales, 

particularly for baleen whales that may communicate using low-frequency sound. 

151 
REFERENCES 

Allison, C. International Whaling Commission. The Red House, 135 Station Road, Impington, Cambridge, UK CB4 

9NP. 

Baker, C. S. 1992. Genetic variability and stock identity of humpback whales, world-wide. Final Contract Report to 

Int. Whal. Commn. 45pp. 

Baker, C. S., D. A. G ilbert, M. T. W einrich, R. Lambertsen, J. Calam bokidis, B. McArdle, G. K. Chambers, and S. J. 

O'Brien. 1993. Population characteristics of DNA fingerprints in hump back whales (Megaptera novaeangliae). 

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154 
Revised 12/15/2000 

BLUE WHALE (Balaenoptera musculus): Eastern North Pacific Stock 

STOCK DEFINITION AND GEOGRAPHIC RANGE 

The International Whaling Commission (IWC) has 

formally considered only one management stock for blue 

whales in the North P acific (Donovan 1991), but now this 

ocean is thought to include more than one population 

(Ohsumi and Wada 1972; Braham 1991), possibly as 

many as five (Reeves et al. 1998). This report covers one 

population that feeds in Califo rnia waters in summer/fall 

(from June to Nove mber) an d migrates so uth to 

productive areas off Mexic o (Calam bokidis et al. 1990) 

and as far south as the Costa Rica Dome (10o N) (Mate et 

al. 1999; Calambokidis, pers. comm.) in winter/spring. 

Blue whales are o ccasionally seen or heard off Oregon 

(McD onald et al. 1994, Stafford et al. 1998; VonSaunder 

and Barlow 1 999), bu t sightings there are rare. Reilly 

and Thayer (1990) speculate that blue whales found near 

the Costa Rica Dome from June to Nove mber are likely 

to be part of a southern hemisphere population or an 

isolated resident populatio n; however , based on acoustic 

call similarities, Stafford et al. (1999) linked these 

animals to the population that feeds off California at the 

same time of year. Rice (1974) hypothesized that blue 

whales from Baja California migrated far offshore to fed 

in the eastern A leutians or G ulf of Alaska an d returned to 

feed in California waters; however, he has mor e recently 

concluded that the California population is separate from 

the Gulf of Alaska population (Rice 1 992). Re cently, 

blue whale feeding aggregations have not been found in 

Alaska despite several surveys (Leatherwood et al. 1982; 

Stewart et al. 1987; Forney and Brownell 1996). One 

other stock of North Pacific blue whales (in Hawaiian 

waters) is recognized in the Marine Mammal Protection 

Act (MM PA) Stock A ssessment Reports. 

POPU LATIO N SIZE 

Figure 1. Blue whale sighting locations based on 

aerial and shipboard surveys off California, 

Oregon, and Washington, 19 91-96(s ee App endix 

2, Figures 1-5 , for data sources and information on 

timing and location of surveys). Dashed line 

represents the U.S. E EZ; bold line indicates the 

outer boundary of all surveys combined. 

The size of the feeding stock of blue whales in Califo rnia was estima ted recently by both line-transect and markrecapture methods. Barlow (1997) estimates 1,927 (CV=0.16) blue whales off California, Oregon, and 

Washington based on ship line-transect surveys in 1991-96. Calambokidis and Steiger (1994) used 

photogra phic mark-recapture and estimated population sizes of 2,038 (CV=0.33) based on photographs of left 

sides and 1,997 (CV=0 .42) based on right sides. The average of the mark-recapture estimates (2,017, CV=0.38) 

is in surprisingly good agreement with the line-transec t estimate. Mark-recap ture estimates a re often nega tively 

biased by individua l heterogene ity in sighting prob abilities (Ham mond 1 986); ho wever, Ca lambokid is and 

Steiger (1994) minimize such effects by se lecting one sa mple that was taken randomly with respect to distance 

from the coast. Sim ilarly, the line-transect estimates may also be negatively biased because some blue whales 

in this stock are probably along Baja California and, therefore, out of the study area at the time of survey (Wade 

and Gerrod ette 1993 ). The be st estimate of blue whale abundance is the average of the line-transect and markrecapture estimates, weighted by their variances, or 1,940 (CV=0.15). 

Minimum Po pulation Estimate 

155 
The minimum population estimate for blue whales is taken as the lower 20th percentile of the log-normal 

distribution of abunda nce estimated from the combined m ark-recap ture and line-transect estimates, or 

approximately 1,716. 

Current Population Trend 

There is some indication that blue whales have increased in abundance in California coastal waters between 

1979/80 and 199 1 (regressio n p<0.0 5, Barlo w 1994 ) and betw een 199 1 and 19 96 (not sign ificant, Barlow 

1997). Although this may be due to an increase in the stock as a whole, it could also be the result of an 

increased use of California as a feeding area. The size of the apparent increase abundance seen by Barlow 

(1994) is too large to be accounted for by population growth alone. Also, Larkman and Veit (1998) did not 

detect any increase along con sistently surveyed tracklines in the S outhern C alifornia Bight from 1987 to 1995. 

Although the population in the North Pacific is expected to have grown since being given protected status in 

1966, the possibility of continued unauthorized takes after blue whales were protected (Yablokov 1994) and 

the existence of incidental ship strikes and gillnet mortality makes this uncertain. 

CURRENT AND M AXIMUM NET PRODUCTIVITY RATES 

No information exists on the rate of growth of blue whale populations in the Pacific (Best 1993). 

POTENTIAL BIOLOGICAL REMOVAL 

The potential biological removal (PBR) level for this stock is calculated as the minimum population size (1,716) 

times one half the default maximum net growth rate for cetaceans (1⁄2 of 4%) times a recovery factor of 0.1 (for 

an endangered specie s), resulting in a PB R of 3.4 . Because this stoc k spends a pproxim ately half its time 

outside the U.S. EEZ, the PBR allocation for U.S. waters is half this total, or 1.7 whales per year. 

HUMAN CAUSED MOR TALITY 

Historic Whaling 

The reported take of No rth Pacific blue whales by commercial whalers totaled 9,500 between 1910 and 1965 

(Ohsumi and Wada 1972). Approximately 2,000 were taken off the west coa st of North America between 1919 

and 1929 (T onnessen and Jo hnsen 1982). P artially overlapping with this is Rice's (1992) repo rt of at least 

1,378 taken by factory ships off California and Baja California between 1913 and 1937. Between 1947 and 

1987, reported takes of blue whales in the North Pacific were approximately 2,400. Shore-based whaling 

stations in central California took 3 blue whales between 1919 and 1926 (Clapham et al. 1997) and 48 blue 

whales between 1 958 and 1965 (R ice 1974 ). Blue wha les in the North Pacific were given protected status by 

the IWC in 1966. 

Fisheries Information 

The offshore drift gillnet fishery is the only fishery that is likely to take blue whales from this stock, but no 

fishery mortalities or serious injuries have been observed (Table 1). Detailed information o n this fishery is 

provided in Appendix 1. After the 1997 implementation of a Take Reduction Plan, which included skipper 

education workshops and required the use of pingers and minimum 6-fathom extenders, overall cetacean 

entanglement rates in the drift gillnet fishery dropped considerably (Barlow and Cameron 1999). Because of 

the changes in this fishery after implementation of the Take Reduction Plan, mean annual takes fo r this fishery 

(Table 1) are base d only on 1 997-98 data. This re sults in an average estimate of zero blue whales taken 

annually. Some gillne t mortality of large whales may go unobserv ed beca use whales sw im away with a portion 

of the net; however, fishermen report that larg e rorquals (blue and fin whales) usually swim through nets without 

entangling and with very little dama ge to the nets. 

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

take animals from the same po pulation. Quantitative d ata are availa ble only for the Me xican sword fish drift 

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

fishery, although nets m ay be up to 4 .5 km long (H olts and Sosa-Nishizaki 1998). The fleet increased from two 

156 
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 autho rs to be app roximately 2 ,700, with an observed rate 

of marine mammal bycatch of 0.13 animals per set (10 marine mammals in 77 observed sets; Sosa-Nishizaki 

et al. 1993). This overall mortality rate is similar to that observed in California driftnet fisheries during 1990-95 

(0.14 marine mammals per set; Julian and Beeson 1998), but species-specific information is not available for 

the Mexican fisheries. There are currently efforts underway to convert the Mexican swordfish driftnet fishery 

to a longline fishe ry (D. Ho lts, pers. comm .). 

Table 1. Summary of available information on theincidentalmortality and injuryofbluewhales(EasternNorth Pacific stock)forcommercial 

fisheriesthatmighttakethisspecies(Julian1997;JulianandBeeson1998;CameronandForney 1999). Mean annualtakesarebasedon 

1994- 98 data u nless noted otherw ise. 

Fishery Name Yar(s) Data Type 

Percent Observer 

Cover 

age 

Observed 

Mortality 

Estimated 

Mortality 

parent 

heses) 

Mean 

Annual Takes 

(CV in 

parent 

heses) 

CA/OR thresher 

shark/swordf 

ish drift 

gillnet 

fishery 

1994-98 observer 

data 

12-23% 0,0,0,0,0 0,0,0,0,0 01 

Total annual takes 0 

(CV in 

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 in cluded the use of net extenders and acoustic warnin g devices (pingers). 

Ship Strikes 

Ship strikes were implicated in the deaths of blue whales in 1980, 198 6, 1987, and 1 993 (J. Cord aro, Southwest 

Region, NMFS and J. Heyning, pers. comm.). Additional mortality from ship strikes probably goes unreported 

because the whales do not strand or, if they do, they do not always have o bvious signs o f trauma. Several blue 

whales have been photographed in California with large gashes in their dorsal surface that appea r to be from 

ship strikes (J. Calambokidis, pers. comm.). The average number of blue whale mortalities in California 

attributed to ship strikes was 0.0 per year for 1994-98. 

STATUS OF STOCK 

Previous ly, blue whales in the entire North Pacific were estimated to be at 33% (1,600 o ut of 4,900 ) of historic 

carrying capacity (M izroch et al. 19 84). Th e initial abund ance has ne ver been e stimated sep arately for the 

"California" stock, but this stock was almost certainly depleted by whaling. Blue whales are formally listed as 

"endangered" under the Endangered Species A ct (ESA) , and conse quently the E astern No rth Pacific stoc k is 

automatica lly considered as a "depleted" and "strategic" stock under the MM PA. The annual incidental 

mortality from ship strikes is apparently less than the calculated P BR for this sto ck. To d ate, no blue w hale 

mortality has been associated with California gillnet fisheries; therefore , total fishery morta lity is approaching 

zero mortality and serious injury rate. The population appears to be growing. The increasing levels of 

anthropo genic noise in the world’s oceans has been suggested to be a habitat concern for blue whales (Reeves 

et al. 1998). 

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Mate, B. R., B. A . Lagerquist, a nd J. Calam bokidis. 19 99. Movements of North Pacific blue whales during their feeding 

season off southern California and their southern fall migration. Mar. Mamm. Sci. 15(4):1246-1257. 

McDonald, M. A., J. A. Hildebrand, and S. C. Webb. 1994. Blue and fin whales observer on a seafloor array in the 

Northeast Pacific. (unpubl. ms.). 

Mizroch, S. A., D. W . Rice, and J . M. Bre iwick. 1984 . The blue whale, Balaenoptera musculus. Mar. Fish. Rev. 

46:15-19. 

Ohsumi, S. and S. Wada. 1972. Stock assessment of blue whales in the North P acific. Work ing Pape r for the 24th 

Meeting of the International Whaling Commission. 20 pp. 

Reilly, S. B. and V. G. Thayer. 1990. Blue whale (Balaenoptera musculus) distribution in the eastern tropical Pacific. 

Mar. Mamm. Sci. 6(4):265-277. 

Reeves, R. R., P. J. C lapham, R . L. Brown ell, Jr., and G . K. Silber. 1 998. Re covery pla n for the blue w hale 

(Balaenoptera musculus). Office of Protected Resources, NMFS, NOAA, Silver Spring, Maryland. 30 pp. 

Rice, D. W. 1 974. Whales and whale research in the eastern North Pacific. pp. 170-195 In: W. E. S chevill (ed.). The 

Whale Problem: A Status Report. Harvard Press, Cambridge, MA. 

Rice, D. W. 1992. T he blue whales of the southeastern North Pacific Ocea n. pp. 1-3 In. Alaska Fisheries Science 

Center, Quart. Rept. Oct.-Dec. 

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

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

Int. CICESE, CTECT9306. 

Stafford, K. M., C. G. Fox, an d D. S. Clark. 1998 . Long-rang e acoustic d etection and localization o f blue whale ca lls 

in the northeast Pacific Ocean. J. Acoust. Soc. Am. 104(6):3616-3625. 

Stafford, K. M., S . L. Nieukirk, a nd C. G. F ox. 1999 . An acoustic link between blue whales in the eastern tropical 

Pacific and the Northeast Pacific. Mar. Mamm. Sci. 15(4):1258-1268. 

Stewart, B. S., S. A. Karl, P. K. Yochem, S. Leatherwood, and J. L. Laake. 1987. Aerial surveys for cetaceans in the 

former Akutan, Alaska, whaling grounds. Arctic 40(1):33-42. 

Tonnesse n, J. N., and A . O. Johnse n. 1982. The History of Modern Whaling. Univ. Calif. Press, Berkeley and Los 

Angeles. 798 pp. 

Von Saunder, A. and J. Barlow. 1999. A report of the Oregon, California and Washington Line-transect Experiment 

(ORCAWALE) conducted in west coast waters during summer/fall 1996. U.S. Dep. Commer. NOAA Tech. 

Memo . NMF S-SW FSC-26 4. 40 pp . 

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

Rept. Int. Whal. Commn. 43:477-493. 

Yablokov, A. V. 1994. Validity of whaling data. Nature 367:108. 

159 
Revised 12/15/2000 

FIN WHALE (Balaenoptera physalus): 

California/Oregon/Washington Stock 

STOCK DEFINITION AND GEOGRAPHIC RANGE 

The International Whaling Commission (IWC) 

recognized two stocks o f fin whales in the N orth Pacific: 

the East China Sea and the rest of the Nor th Pacific 

(Donovan 1991). Mizroch e t al. (1984) cites evidence 

for additional fin whale subp opulations 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 O regon (G reen et al. 1992; 

McD onald 1994), and in summer/autumn in the Shelikof 

Strait/Gulf of Alaska (B rueggema n et al. 1990 ). Acoustic 

signals from fin whale a re detected year-round off 

northern California, Oregon and Washington, with a 

concentra tion 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 informatio n to accura tely 

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 (M izroch et al. 1984), in part 

because subpopulations were not reco gnized. T his 

assessment will cover the stock of fin whales which is 

found along the coasts of California, Oregon, and 

Figure 1. Fin whale sighting locations based on 

aerial and shipboard surveys off California, 

Oregon, and Washin gton, 199 1-96 (see Append ix 

2, Figures 1-5 for data sources and information on 

timing and location of surveys). Dashed line 

represents the U.S. E EZ; bold line indicates the 

outer boundary of all surveys combined. 

Washington. Because fin whale abundance appears lower in winter/spring in California (Dohl et al. 1983; 

Forney et al. 1995) and in O regon (Green et al. 19 92), it is likely that the distribution of this stock extends 

seasonally outside these coastal waters. Coincidentally, fin whale abundance in the Gulf of California increases 

seasonally in winter and spring (Tershy et al. 1993). It is premature, however, to conclude that the Gulf whales 

are part of the U .S. west coast p opulation. T he Marine Mammal Protection Act (MMP A) stock assessment 

reports recognize three stocks o f fin whales in the North Pacific: 1) the California/Oregon/Washington stock 

(this report), 2) the Hawaii stock, and 3) the Alaska stock. 

POPU LATIO N 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 P acific popu lation was estimated to hav e been red uced to 

13,620-18,680 (Ohsumi a nd Wada 197 4), of which 8 ,520-10 ,970 wer e estimated to belong to th e eastern P acific 

stock. A minimum of 148 individually-identified fin whales are found in the Gulf of California (T ershy et al. 

1990). Recently, 1,236 (CV=0.20) fin whales were estimated to be off California, Oregon and Washington 

based on ship surve ys in summer/autumn of 1991, 1993, a nd 199 6 (Barlo w 1997 ). Fin whale ab undance in 

160 
California was estimated as only 49 (C V=1.0 ) based o n aerial surveys in winter/spring of 1991/92 (Forney et 

al. 1995); however, this estimate does not include a correction for diving animals that were missed. 

Minimum Po pulation Estimate 

The minimum population estimate for fin whales is taken as the lower 20th percentile of the log-normal 

distribution of abundance estimated from summer/fall ship survey (Barlow 1997) or approximately 1,044. 

Current Population Trend 

There is some indication that fin whales have increased in abundance in California coastal waters between 

1979/80 and 1991 (Barlow 1994) and between 1991 and 1996 (Barlow 1997), but these trends are not 

significant. Although the population in the North Pacific is expected to have grown since receiving protected 

status in 1976, the possible effec ts of continued unauthorized take (Yablokov 1994) and incidental ship strikes 

and gillnet mortality make this uncertain. 

CURRENT AND M AXIMUM NET PRODUCTIVITY RATES 

There are no estimates of the growth rate of fin whale populations in the North Pacific (Best 1993). 

POTENTIAL BIOLOGICAL REMOVAL 

The potential biological removal (PBR) level for this stock is calculated as the minimum population size (1,044) 

times one half the default maximum net growth rate for cetaceans (1⁄2 of 4%) times a recovery factor of 0.1 (for 

an endangered species), resulting in a PBR of 2.1. 

HUMAN CAUSED MOR TALITY 

Historic Whaling 

Appro ximately 46,000 fin whales were taken from the North Pacific by commercial whalers between 1947 and 

1987 (C. Allison, IWC , pers. com m.), including 1 ,060 fin wha les taken by co astal whalers in central Califo rnia 

between 1958 and 1965 (Rice 1974). In addition, approximately 3,800 were taken o ff the west coast o f North 

America between 1919 and 1929 (Tonnessen and Johnsen 1982), and 177 were taken by coastal whalers off 

California between 1919 and 1926 (Clapham et al. 1997) . Fin whales in the North Pacific were given protected 

status by the IWC in 1976. 

Fisheries Information 

The offshore drift gillnet fishery is the only fishery tha t is likely to take fin whales from this stock, but no fishery 

mortalities or serious injuries have been observed (Table 1). Detailed information on this fishery is provided 

in Appendix 1. After the 1997 implementation of a Take Reduction Plan, which included skipper education 

workshops and required the use of pingers and minimum 6-fathom extenders, overall cetacean entanglement 

rates in the drift gillnet fishery droppe d conside rably (Barlow and Cam eron 19 99). Be cause of the c hanges in 

this fishery after implementation of the Take Reduction Plan, mean annual takes for this fishery (Table 1) are 

based only on 1997-98 data. This results in an average estimate of zero 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 larg e rorquals (blue and fin w hales) usually swim through nets without enta ngling and w ith 

very little damag e to the nets. 

Table 1. Summary of available information on theincidentalmortality andinjuryoffinwhales(CA/OR/WA stock)forcommercialfisheriesthat 

mighttakethisspecies(Julian 1997;JulianandBeeson1998;CameronandForney 1999). Mean annualtakesarebasedon 1994-98data 

unless no ted otherw ise. 

161 
Fishery Name Year(s) Data Type 

Percent Observer 

Coverage 

Observed 

Mortality 

Estimated 

Mortality 

parentheses 

) 

Mean 

Annual Takes 

(CV in parentheses) 

CA/OR thresher 

shark/swordfish 

drift gillnet 

fishery 

1994-98 

observer 

data 12-23% 0,0,0,0,0 0,0,0,0,0 01 

Average annual takes 0 

(CV in 

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 in cluded the use of net extenders and acoustic warnin g devices (pingers). 

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

take animals from the same population. Quantitative data are available only for the Mexican swordfish dr ift 

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 vesse ls 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 autho rs to be app roximately 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). T his overall mo rtality rate is similar to that observed in California driftnet fisheries during 1990-95 

(0.14 marine mammals per set; Julian and Beeson 1998), but species-specific information is not available for 

the Mexican fisheries. There are currently efforts underway to convert the M exican swordfish driftnet fishery 

to a longline fishe ry (D. Ho lts, pers. comm .). 

Ship Strikes 

Ship strikes were implicated in the deaths o f one fin whale in 1991, one in 1996, and one in 1997 (J. Heyning 

and J. Cordaro, So uthwest Region, NMFS, pers. comm.). Additional mortality from ship strikes probably goes 

unreported because the whales do not strand or, if they do, they do not always have obvious signs of trauma. 

The average observed annual mortality due to ship strikes is 0.4 fin whales per year for the period 1 994-98 . 

STATUS OF STOCK 

Fin whales in the en tire North P acific were estimated to be at less than 38% (16,625 out of 43,5 00) of histor ic 

carrying capacity (Mizroch et al. 1984). The initial abund ance has never been estimated separately for the 

"west coast" stoc k, but this stock was also probably depleted by whaling. Fin whales are formally listed as 

"endangered" under the Endangered Species Act (ESA), and consequently the California to Washington stock 

is automatically considered as a "depleted" and "strate gic" stock under the MMPA. The total incidental 

mortality due to fisheries (0.0/yr) and ship strikes (0.4 /yr) appear s to be less than the calculated PBR (2.1). In 

fact, no fin whale m ortality has bee n associated with California g illnet fisheries; therefo re, total fishery mo rtality 

is approaching zero mortality and serious injury rate. There is some indication that the population may be 

growing. The increasing leve ls of anthrop ogenic no ise 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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Fisheries Science Center, P.O. Box 271, La Jolla, CA. 25 pp. 

162 
Barlow, J., R. W. B aird, J. E. H eyning, K. W ynne, 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 

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Barlow, J. and G. A . Camero n. 1999. Field expe riments show that acoustic p ingers reduc e marine m ammal byc atch in 

the California d rift gillnet fishery. Report SC/51/SM2 to the Scientific Committee of the International Whaling 

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Best, P. B. 1993. Increase rates in severely depleted stocks of baleen whales. ICES J. Mar. Sci. 50:169-186. 

Brueggeman, J. J., G. A. Green, K. C. Balcomb, C. E. Bowlby, R. A. Grotefendt, K. T. Briggs, M. L. Bonnell, R. G. 

Ford, D. H. Varoujean, D. Heinemann, and D. G. Chapman. 1990. Oregon-Washington M arine Mammal and 

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

for 1997 a nd 199 8. Pape r SC/51/O 4 presente d to the Intern ational Whalin g Commission, May 1998 

(unpublished). 14 pp. 

Clapham, P. J., S. Leatherwo od, I. Szcz epaniak, an d R. L. Brownell, Jr. 1997. Catches of humpback and other whales 

from shore stations at Moss Landing an d Trinida d, California , 1919-1 926. Mar. Mamm. Sci. 13(3):368-394. 

Dohl, T. P., R. C. Guess, M. L. Duman, and R. C. Helm. 1983. Cetaceans of central and northern California, 1980-83: 

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Forney, K. A., J. Barlow, and J. V. Carretta. 1995. The abundance of cetaceans in California waters. Part II: Aerial 

surveys in winter and spring of 1991 and 1992. Fish. Bull. 93:15-26. 

Green, G. A., J. J. Brueggeman, R. A. Grotefend t, C. E. Bo wlby, M. L. B onnell, K. C. Balcom b, III. 1992. Cetacean 

distribution and abundance off Oregon and W ashington, 1989-1990. Ch. 1 In: J. J. Bruegge man (ed.). Oregon 

and WashingtonMarine Mammal and Seabird Surveys. Minerals Management Service Contract Report 14-12­

0001-30426. 

Hanan, D. A. 1986. California Department of Fish and Game coastal marine mammal study, annual report for the period 

July 1, 1983 - June 30, 1984. Admin. Rept. LJ-86-16 available from Southwest Fisheries Science Center, P.O. 

Box 271, La Jolla, CA. 55pp. 

Hanan, D. A., D. B. Holts, and A. L. Coan, Jr. 1 993. T he California drift gill net fishery for sharks and swordfish, 1981­

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

Heyning, J. E., and T . D. Lewis. 19 90. Fisherie s interactions invo lving baleen w hales off southern California. Rep. 

int. Whal. Commn. 40:427-431. 

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

Holts, D. and O. Sosa-Nish izaki. 1998 . Swordfish, Xiphias gladius, fisheries of the eastern No rth Pacific O cean. In: 

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

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

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

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

SC/49/SM2 presented to the International Whaling Commission, September 1997 (unpublished). 13pp. 

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

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

Lee, T. 1 993. Summary of cetacean survey data collected between the years of 1974 and 1985. U.S. Dep. Commer. 

NOAA Tech. Memo. NMFS-SWFSC-181. 184 pp. 

McDonald, M. A., J. A . Hildebrand, and S. C. Webb. 1994 . Blue and fin whales observer on a seafloor array in the 

Northeast Pacific. (unpubl. ms.). 

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Whale Problem: A Status Report. Harvard Press, Cambridge, MA. 

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Int. CICESE, CTECT9306. 

Tershy, B. R., D. Breese, and C. S. Strong. 1990. Abundance, seasonal distribution and population composition of 

balaenop terid whales in the Canal d e Ballenas , Gulf of Califo rnia, Mex ico. Rept. Int. Whal. Commn., Special 

Issue 12:369-375. 

Tershy, B. R., J. U rbán-R., D . Breese, L. Rojas-B., and L. T. F indley. 199 3. Are fin wha les resident to the Gulf of 

California? Rev. Invest. Cient., Univ. Auton. de Baja California Sur. 1:69-71. 

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Angeles. 798pp. 

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

Rept. Int. Whal. Commn. 43:477-493. 

Yablokov, A. V. 1994. Validity of whaling data. Nature 367:108. 

164 
Revised 12/15/2000 

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

Stock 

STOCK DEFINITION AND GEOGRAPHIC RANGE 

The International Whaling Commission (IWC) recognizes 

3 stocks of Bryde's whales in the North Pacific (eastern, 

western, and East C hina Sea), 3 stocks in the So uth Pacific 

(eastern, western and Solomon Islands), and one crossequatorial stock (Peruvian) (Donovan 1 991 ). Bryde's 

whales are distributed widely across the tropical and 

warm-temp erate Pacific (Leatherwood et al. 1982), and 

there is no real justification for splitting stocks between the 

northern and southern hemispheres (Donovan 1991). 

Recent surveys (Lee 1993; Wade and Gerrodette 1993) 

have shown them to be common and distributed throughout 

the eastern tropical Pacific with a concentration around the 

equator east of 110o

W (correspond ing appro ximately to 

the IWC's "Pe ruvian stock") and a red uction west of 

140oW. They are also the mo st commo n baleen wh ale in 

the central Gulf of California (Tershy et al. 1990). Only 

one was positively identified in surveys o f California 

coastal waters (Barlow 1997). Bryde's whale s in 

California are likely to belong to a larger population 

inhabiting at least the eastern part of the trop ical Pacific. 

For the Marine Mammal Protection Act (MMPA) stock 

assessment reports, B ryde's whales within the Pacific U.S. 

Exclusive Economic Zone are divided into two areas: 1) 

the eastern trop ical Pacific (ea st of 150o

W and including 

the Gulf of Califo rnia and wa ters off California ; this 

report), and 2) H awaiian waters. 

POPU LATIO N SIZE 

Figure 1. Sighting locations of Bryde's whales 

based on aerial and shipboar d surveys off 

California, Oregon, and Washington, 1991-96 (see 

Appen dix 2, Figures 1-5 for data sources and 

information on timing and location of surveys). 

Dashed line represents the U.S. EEZ; bold line 

indicates the outer boundary of all surv eys 

combined. 

In the western North Pacific, Bryde's whale abundance in the early 1980s was estimated independently by tag 

mark-recapture and ship survey methods to be 22,000 to 24,000 (Tillman and Mizroch 1982; M iyashita 1986). 

Bry de's whale abundance has never been estimated for the entire eastern Pacific; however, a portion of that 

stock in the eastern tropical Pacific was estimated recently as 13,000 (CV=0.20; 95% C.I.=8,900-19,900) 

(Wade and Gerrodette 1993), and the minimum number in the Gulf of California is 160 based on individuallyidentified whales (Tershy et al. 1990). Only one confirmed sighting of Bryde's whales and five possible 

sightings (ide ntifi ed a s sei or Bryde's whales) were made in California waters during extensive ship and aerial 

surveys in 1991, 1992, 1993, and 1996 (Hill and Barlow 199 2; Carretta and Forney 1993; Mangels and 

Gerrod ette 1994; VonSaunder and B arlow 1999). Green et al. (1992) did not report any sightings of Bryde's 

whales in aerial surveys off Oregon and Washington. The estimated abundance of Bryde's whales in California, 

Oregon, and Washington coastal waters is 12 (CV=2.0) (Barlow 199 7). 

Minimum Po pulation Estimate 

The minimum population estimate for Bryde's whales is taken as the lower 20th percentile of the log-normal 

distribution of abundance estimated from the summer/fall ship surveys in 198 6-90 (W ade and Gerrod ette 1993) 

plus the minimum of 160 whales counted in the Gulf of California (Tershy et al. 1990), or 11,163. 

165 
Current Population Trend 

There are no data on trends in Bryde's whale abundance in the eastern tropical Pacific. 

CURRENT AND M AXIMUM NET PRODUCTIVITY RATES 

There are no estimates of the growth rate of Bryde's whale populations in the Pacific (Best 1993). 

POTENTIAL BIOLOGICAL REMOVAL 

The potential biological removal (PBR) level for this stock cannot be calculated because the only relevant 

abundance estimate (Wade and Ger rodette 19 93) is mor e than 8 years old. Additional data on the abundance 

of Bryde’s wh ales in the eastern Pacific was g athered in 1 998-99 , but their abundance has not yet been 

estimated fro m those da ta. 

HUMAN CAUSED MOR TALITY 

Historic Whaling 

The reported take of North Pacific Bryde's whales by commercial whalers totaled 15,076 in the western P acific 

from 1946-1 983 (H olt 1986 ) and 2,87 3 in the eastern Pacific from 1973-81 (Cooke 1983). In addition, 2,304 

sei-or-B ryde's whales were taken in the eastern Pacific from 1968-72 (Cooke 1983) (based on subsequent 

catches, most of these were probably Bryde's whales). None were reported taken by shore-based whaling 

stations in central or northern California between 1919 and 1926 (Clapham et al. 1997) or 1958 and 1965 (Rice 

1974). There has been a prohibition on taking Bryde's whales since 1988. 

Table 1. Summary ofavailable informationon theincidentalmortality and injuryofBryde’swhales(easterntropicalPacific stock)forcommercial 

fisheriesthatmighttakethisspecies(Julian1997;JulianandBeeson1998;Cameronand Forney 1999). n/a indicatesthatdata are not 

available. Mean annual takes are based on 1994-98 data unless noted otherwise. 

Fishery Name Year(s) Data Type 

Percent Observer 

Coverage 

Observed 

Mortality 

12-23% 

Estimated 

Mortality 

parenthese 

s) 

(CV in 

Mean 

Annual Takes 

(CV in parentheses) 

01 

n/a 

0 

n/a 

0,0,0,0,0 

Total annual takes 

CA/OR thresher 

shark/swordfish 

drift gillnet 

fishery 

Mexico thresher 

shark/swordfish 

drift gillnet 

fishery 

1994-98 observer 

data 

observer 

data 

1991-95 

0,0,0,0,0 

n/a n/a 

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 in cluded the use of net extenders and acoustic warnin g devices (pingers). 

Fishery Information 

The offshore drift gillnet fishery is the only fishery that is likely to take Bryde’s whales from this stock, but no 

fishery mortalities or serious injuries have bee n observe d (Tab le 1). Detailed information o n this fishery is 

provided in Appen dix 1. After the 1997 im plementatio n of a Tak e Reduc tion Plan, which included skipper 

education workshop s and requ ired the use o f pingers and m inimum 6-fathom extenders, overall cetacean 

entanglement rates in the drift gillnet fishery dropped considerably (Barlow and Cameron 1999). Because of 

the changes in this fishery after implementation of the Take Reduction Plan, mean annual takes for this fishery 

(Table 1) are based only on 1997-98 data. This results in an average estimate of zero Bryde’s whales ta ken 

annually. However, some gillnet mortality of large whales may go unobserved because whales swim away with 

a portion o f the net. 

166 
Drift gillnet fisheries for swordfish and sharks exist along the entire Pacific coast of Baja California and may 

take animals from the same population. Quantitative data are available only for the Mex ican sword fish 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 o f 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 m ammal byc atch of 0.13 animals per set (10 marine mammals in 77 observed sets; Sosa-Nishizaki 

et al. 1993). This over all mortality rate is simila r to that obse rved in Ca lifornia driftnet fisheries during 1990-95 

(0.14 marine mammals per set; Julian and Beeson 1998), b ut species-spe cific information is not available for 

the Mexican fisheries. There are currently efforts underway to convert the Mexican swordfish driftnet fishery 

to a longline fishe ry (D. Ho lts, pers. comm .). 

Ship Strikes 

Ship strikes may oc casionally kill B ryde's whales as the y are known to kill their larger relatives: blue an d fin 

whales. No ship strikes have been reported for this species in this area. 

STATUS OF STOCK 

Commercial whaling of Bryde's whales was largely limited to the western Pacific. Bryde's whales are not listed 

as "threatened" or "endangered" under the Endangered Species Act (ESA). Bryde's whales in the eastern 

tropical Pacific would not be considered a strategic stock under the MM PA. Th e total human -caused m ortality 

rate is estimated to be zero; therefore, under the M MPA , total fishery morta lity is approac hing zero m ortality 

and serious injury rate. The increasing levels of anthropogenic no ise in the world’s oceans has been suggested 

to be a habitat concern for whales, particularly for baleen whales that may communicate using low-frequency 

sound. 

REFERENCES 

Barlow, J. 1997. Preliminary estimates of cetacean abundance off California, Oregon, and Washington based on a 1996 

ship survey and comparisons of passing and closing modes. Adm in. Rept. LJ-97-11 ava ilable from Southwest 

Fisheries Science Center, P.O. Box 271, La Jolla, CA. 25pp. 

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

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

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

425. 

Barlow, J. and G. A. Cameron. 1999. F ield experim ents show that a coustic ping ers reduce marine mammal byca tch in 

the California drift gillnet fishery. Report SC/51/SM2 to the Scientific Committee of the International Whaling 

Commission, May 1999. 20pp. 

Best, P. B. 1993. Increase rates in severely depleted stocks of baleen whales. ICES J. Mar. Sci. 50:169-186. 

Cameron, G. A. and K. A. Forney. 1999. Preliminary estimates of cetacean m ortality in the California gillnet fisheries 

for 1997 and 1998 . Paper SC/51/O4 presented to the International Whaling Commission, May 1998 

(unpublished). 14 pp. 

Carretta, J. V. and K. A. Forney. 1993. Report on two aerial surveys for marine mammals in California coastal waters 

utilizing a NOAA DeHavilland Twin Otter Aircraft: March 9-April7, 1991 and February 8-April 6, 1992. 

NOAA Tech. Memo. NOAA-TM-NMFS-SWFSC-185. 77pp. 

Clapham, P. J., S. Leatherwood, I. Szczepaniak, and R. L. Brownell, Jr. 1997. Catches of humpback and other whales 

from shore stations at Moss Landing and Trinidad, California, 1919-1926. Mar. Mamm. Sci. 13(3):368-394. 

Cooke, J. G. 198 3. Estimates of the stock of Bryde's whales fished off the coast of Peru. Rept. Int. Whal. Commn. 

33:453-456. 

Donovan, G. P. 1991. A review of IWC stock boundaries. Rept. Int. Whal. Commn., Special Issue 13:39-68. 

Green, G. A., J. J. Brueggeman, R. A. Grotefendt, C. E. Bowlby, M. L. Bonnell, K. C. Balcomb, III. 1992. Cetacean 

distribution and abundance off Oregon and Washington, 1989-1990 . Ch. 1 In: J. J. Brueg geman (ed .). Oregon 

167 
and WashingtonMarine Mammal and Seabird Surveys. Minerals Management Service Contract Report 14-12­

0001-30426. 

Hanan, D. A. 1986. California Department of Fish and Game coastal marine mammal study, annual report for the period 

July 1, 1983 - June 30, 1984. Admin. Rept. LJ-86-16 available from Southwest Fisheries Science Center, P.O. 

Box 271, La Jolla, CA. 55pp. 

Hanan, D. A., D. B. Holts, and A. L. Coan, Jr. 1993. The California drift gill net fishery for sharks and swordfish, 1981­

82 through 1990-91. Calif. Dept. Fish and Game Fish. Bull. No. 175. 95pp. 

Heyning, J. E ., and T. D . Lewis. 199 0. Fisheries interactions involving baleen whales off southern California. Rep. 

int. Whal. Commn. 40:427-431. 

Hill, P. S. and J. Barlow. 1992. Report of a marine mammal survey of the California coast aboard the research vessel 

McARTHUR July 28-November 5, 1991. NOAA Technical Memorandum NOAA-TM-NMFS-SWFSC-169. 

NTIS #PB93-109908. 103pp. 

Holt, S. 	1986. Aspe cts of the assessment and regulation of B ryde's whales in the Northwest Pacific. Rept. Int. W hal. 

Commn. 36:257-262. 

Holts, D. Southwest Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA 92038. 

Holts, D. and O . Sosa-Nish izaki. 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 swor dfish, Xiphias gladius. Papers 

from the International Symposium on Pacific Swordfish, Ensenada Mexico, 11-14 December 1994. U.S. Dep. 

Commer., NOAA Tech. Rep. NMFS 142, 276 p. 

Julian, F. 1997. Cetacean mortality in the California gill net fisheries: preliminary estimates for 1996. P aper 

SC/49/SM2 presented to the International Whaling Commission, September 1997 (unpublished). 13pp. 

Julian, F. and M. Beeson. 1998. Estimates for marine m ammal, turtle, and seabird mortality for two California gillnet 

fisheries: 1990-95. Fish. Bull. 96:271-284. 

Leatherwood, S., R. R. Reeves, W. F. Perrin, and W. E. Evans. 1982. Whales, dolphins, and porpoises of the eastern 

North Pacific and adjacent Arctic waters: A guide to their identification. NOAA Technical Rept. NMFS 

Circular 444. 245 pp. 

Lee, T. 1993. Summary o f cetacean sur vey data co llected betw een the years o f 1974 an d 1985 . NOAA Tech. Memo. 

NOAA-TM-NMFS-SWFSC-181. 184 pp. 

Mangels, K. F. and T. Gerr odette. Re port of ceta cean sightings d uring a marin e mammal survey in the ea stern Pacific 

Ocean and the Gulf of California aboard the N OAA ships McArthur and David Starr Jordan July 28 -

November 6, 1993. U.S. Dep. Commer. NOAA Tech. Memo. NMFS-SWFSC-221. 88 pp. 

Miyashita, T. 1986. Sighting estimate for the Bryde's whale stock in the western N orth Pacific. R ept. Int. W hal. 

Commn. 36:249-252. 

Rice, D. W. 1974. Whales and whale r esearch in the eastern No rth Pacific. pp. 170-195 In: W. E. S chevill (ed.). The 

Whale Problem: A Status Report. Harvard Press, Cambridge, MA. 

Sosa-Nish izaki, O., R. De la Rosa Pacheco, R. Castro Longoria, M. Grijalva Chon, and J. De la Rosa Velez. 1993. 

Estudio biologico pesquero del pez (Xiphias gladius) y otras especies de picudos (marlins y pez vela). Rep. 

Int. CICESE, CTECT9306. 

Tershy, B. R., D. B reese, and C . S. Strong. 19 90. Abu ndance, se asonal distribution and population composition of 

balaenop terid whales in the Canal de Ballenas, Gulf of California, Mexico. Rept. Int. Whal. Commn., Special 

Issue 12:369-375. 

Tillman, M. F. and S. A. Mizroch. 1982. Mark-recapture estimates of abundance for the western Northern Pacific stock 

of Bryde's whales. Rept. Int. Whal. Commn. 32:335-337. 

Von Saunder, A. and J. Barlow. 1999. A report of the Oregon, California and Washington Line-transect Experiment 

(ORC AWA LE) con ducted in w est coast wate rs during sum mer/fall 199 6. U.S. Dep. Commer. NO AA Tech. 

Memo . NMF S-SW FSC-26 4. 40 pp . 

Wade, P. R. and T. Gerrodette. 1993. Estimates of cetacean abundance and distribution in the eastern tropical Pacific. 

Rept. Int. Whal. Commn. 43:477-493. 

168 
Revised 12/15/2000 

SEI WHALE (Balaenoptera borealis): Eastern North Pacific Stock 

STOCK DEFINITION AND GEOGRAPHIC RANGE 

The International Whaling Commission (IWC) only 

considers one stock of sei wha les in the Nor th 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 continuous ly across the N orth 

Pacific between 45-55o

N (Masaki 1977). Two sei whales 

that were tagged off California w ere later killed o ff 

Washington and British C olumbia (R ice 1974 ) and the 

movement of tagged an imals 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 

Gerrod ette 1993; Lee 1993). Lacking additional 

information on sei whale population structure, sei whales 

in the eastern N orth Pacific (east of longitude 180o

) will 

be considered as a separate stock. 

POPU LATIO N SIZE 

Ohsumi and Wada (197 4) 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 P acific and revised this pre-whaling estimate 

Figure 1. Sei whale sighting locations based on 

aerial and shipboard surveys off California, 

Oregon, and Washin gton, 199 1-96 (see Append ix 

2, Figures 1-5 for data sources and information on 

timing and location of surveys). Dashed line 

represents the U.S. E EZ; bold line indicates the 

outer boundary of all surveys combined. 

to 42,000. His estimates for the year 1974 ranged from 7,260 to 12,62 0. All methods depend on using the 

history of catches and trends in CPUE or sighting rates; the re have be en no direc t estimates of sei wh ale 

abundance in the entire (or eastern) North Pacific based on sighting surveys. Only one confirmed sighting of 

sei whales and 5 possible sightings (identified as sei or Bryd e's whales) were made in California waters during 

extensive ship and aerial surveys in 1991, 1992, 1993, and 1996 (Hill and Barlow 1992 ; Carretta and Forney 

1993; Mangels and Gerrodette 1994; VonSaunder and Barlow 1999). Green et al. (1992) did not report any 

sightings of sei whales in aerial surveys of Oregon and Washington. There are no abundance estimates for sei 

whales along the west coast of the U.S. or in the eastern North Pacific. 

Minimum Po pulation Estimate 

Minimum population estimates do not exist for sei whales in the eastern North Pacific. 

Current Population Trend 

There are no data on tren ds in sei whale a bundanc e in the eastern N orth Pacific waters. Although the population 

in the North Pacific is expected to have grown since being g iven protec ted status in 19 76, the po ssible effects 

of continued unauthorize d take (Y ablokov 1994) a nd inciden tal ship strikes and gillnet mortality ma ke this 

uncertain. 

169 
CURRENT AND M AXIMUM NET PRODUCTIVITY RATES 

There are no estimates of the growth rate of sei whale populations in the North Pacific (Best 1993). 

POTENTIAL BIOLOGICAL REMOVAL 

No estimate exists for the minimu m abund ance of the e astern No rth Pacific stock of sei whales. Estimates for 

the entire North Pacific are mo re than 10 years old and do not include statistical estimates of precision. 

Consequently, PBR levels cannot be calculated. 

HUMAN CAUSED MOR TALITY 

Historic Whaling 

The reported take of North Pacific sei whales by commercial whalers totaled 61,500 between 1947 and 1987 

(C. Allison, IWC, pers. comm.). Of these, 3 84 were ta ken by-shore -based wh aling stations in ce ntral California 

between 1958 and 1965 (Rice 1974). An additional 26 were taken off central and northern California between 

1919 and 1926 (Clapham et al. 1997). There has been an IW C prohibition on taking sei whales since 1976, and 

comme rcial whaling in the U.S. has b een proh ibited since 1 972. 

Fishery Information 

The offshore drift gillnet fishery is the only fishery that is likely to take sei whales from this stock, but no fishery 

mortalities or serious injuries have been observed (Table 1). Detailed information on this fishery is provided 

in Appendix 1. After the 1997 implementation of a Take Reduction Plan, which included skipper education 

workshops and required the use of pingers and minimum 6-fathom extenders, overall cetacean entanglement 

rates in the drift gillnet fishery dropped considerably (Barlow and Cameron 1999). Because of the changes in 

this fishery after implementation of the Take Reduction Plan, mean annual takes for this fishery (Table 1) are 

based only on 1997-98 data. This results in an average estimate of zero sei whales taken annually. However, 

some gillnet mortality of large whales may go unobserv ed beca use whales sw im away with a p ortion of the n et. 

Table 1. Summary ofavailable information on theincidentalmortality andinjuryofseiwhales(easternNorth Pacific stock)forcommercialfisheries 

thatmighttake thisspecies(Julian1997;JulianandBeeson1998;Cameron andForney1999). n/a indicatesthatdata arenotavailable. 

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 

parenthese 

s) 

Mean 

Annual Takes 

(CV in parentheses) 

CA/OR thresher 

shark/swordfish 

drift gillnet 

fishery 

1994-98 observer 

data 

12-23% 0,0,0,0,0 0,0,0,0,0 01 

Total annual takes 0 

(CV in 

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 in cluded the use of net extenders and acoustic warnin g devices (pingers). 

Ship Strikes 

Ship strikes may occasionally kill sei whales as they have been show n to kill their larger re latives: blue and fin 

whales. No ship strikes have been reported for this species in this area. 

STATUS OF STOCK 

Previous ly, sei whales were estimated to have been reduced to 20% (8,600 out of 42,000) of their pre-whaling 

abundance in the North Pacific (Tillman 1977). The initial abundance has never been reported separately for 

the eastern No rth Pacific stock, but this stoc k was also pr obably d epleted b y whaling. Sei whales ar e formally 

170 
listed as "endangered" under the E ndangere d Specie s Act (ESA ), and cons equently the eastern N orth Pacific 

stock is automatically considered as a "depleted" and "strategic" stock under the Marine Mammal Protection 

Act (MM PA). Total estim ated fishery mo rtality is zero and therefore is “ap proachin g zero mo rtality and serious 

injury rate”. The increasing leve ls of anthropogenic noise in the world’s oceans has been suggested to be a 

habitat concern for whales, particularly for baleen whales that may communicate using low-frequency sound. 

REFERENCES 

Barlow, J. 1997. Preliminary estimates of cetacean abundance off California, Oregon, and Washington based on a 1996 

ship survey and comparisons of passing and closing modes. Admin. Rept. LJ-97-11. Southwest Fisheries 

Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA. 25 pp. 

Barlow, J., R. W. B aird, J. E. H eyning, K. W ynne, A. M. M anville, 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 Can ada and the east coast o f the Russian F ederation . Rep. Int. W hal. Commn, Special Issue 15:405­

425. 

Barlow, J. and G. A. Cameron. 1999. Field experiments show that acoustic pingers red uce marine mamma l bycatch in 

the California drift gillnet fishery. Report SC/51/SM2 to the Scientific Committee of the International Whaling 

Commission, May 1999. 20pp. 

Best, P. B. 1993. Increase rates in severely depleted stocks of baleen whales. ICES J. Mar. Sci. 50:169-186. 

Carretta, J. V. and K. A . Forney. 19 93. Rep ort on two a erial surveys for m arine mammals in Califor nia coastal waters 

utilizing a NOAA DeHavilland Twin Otter Aircraft: March 9-April7, 1991 and Feb ruary 8-Ap ril 6, 1992. U.S. 

Dep. Commer. NOAA Tech. Memo. NMFS-SWFSC-185. 77 pp. 

Cameron, G. A. and K. A. Forney. 1999. Preliminary estimates of cetacean mortality in the California gillnet fisheries 

for 1997 and 1998. Paper SC/51/O4 presented to the International Whaling Commission, May 1998 

(unpublished). 14 pp. 

Clapham, P. J., S. Leatherwood, I. Szczepaniak, and R. L. Brownell, Jr. 1997. Catches of humpback and other whales 

from shore stations at Moss Landing and Trinidad, California, 1919-1926. Mar. Mamm. Sci. 13(3):368-394. 

Dohl, T. P., R. C. Guess, M. L. Duman, and R. C. Helm. 1983. Cetaceans of central and northern California, 1980-83: 

Status, abundance, and distribution. Final Report to the Minerals Management Service, Contract No. 14-12­

0001-29090. 284 pp. 

Donovan, G. P. 1991. A review of IWC stock boundaries. Rept. Int. Whal. Commn., Special Issue 13:39-68. 

Forney, K. A., J. Barlow, and J. V. Carretta. 1995. The abundance of cetaceans in California waters. Part II: Aerial 

surveys in winter and spring of 1991 and 1992. Fish. Bull. 93:15-26. 

Green, G. A., J. J. Brueg geman, R . A. Grotefe ndt, C. E. B owlby, M . L. Bonne ll, K. C. Balcomb, III. 1992. Cetacean 

distribution and abundance off Oregon and W ashington, 1989-1990. Ch. 1 In: J. J. Brueg geman (ed .). Oregon 

and WashingtonMarine Mammal and Seabird Surveys. Minerals Management Service Contract Report 14-12­

0001-30426. 

Hanan, D. A. 1986. California Department of Fish and Game coastal marine mammal study, annual report for the period 

July 1, 1983 - June 30, 1984. Admin. Rept. LJ-86-16. Southwest Fisheries Science Center, National Marine 

Fisheries Service, P.O. Box 271, La Jolla, CA. 55pp. 

Hanan, D. A., D. B . Holts, and A . L. Coan, Jr . 1993. The California drift gill net fishery for sharks and swordfish, 1981­

82 through 1990-91. Calif. Dept. Fish and Game Fish. Bull. No. 175. 95pp. 

Heyning, J. E., and T. D. Lewis. 1990. Fisheries interactions involving ba leen whales o ff southern California. Rep. 

Int. Whal. Commn. 40:427-431. 

Hill, P. S. and J. Barlow . 1992. Report of a marine mammal survey of the California coast aboard the research vessel 

McARTHUR July 28-November 5, 1991 . U.S. Dep . Comme r. NOA A Tech . Memo . NMF S-SWFSC-16 9. 103 

pp. 

Holts, D. and O. Sosa-Nishizaki. 1998. Swordfish, Xiphias gladius, fisheries of the easte rn North P acific Ocean. In: 

I. Barrett, O. Sosa-Nishizaki and N. Bartoo (eds.). Bio logy and fisheries of sword fish, 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. 

171 
Horwood, J. 1987. The Sei Whale: Population Biology, Ecology and Management. Croom Helm, London, U.K. 

375pp. 

Julian, F. 1997. Cetacean mortality in the California gill net fisheries: preliminary estimates for 1996. Paper 

SC/49/SM2 presented to the International Whaling Commission, September 1997 (unpublished). 13pp. 

Julian, F. and M. Beeson. 1998. Estimates for marine mammal, turtle, and seab ird mortality for two California gillnet 

fisheries: 1990-95. Fish. Bull. 96:271-284. 

Lee, T. 1993. Summary of cetacean survey data collected between the years of 1974 and 1985. U.S. Dep. Commer. 

NOAA Tech. Memo. NMFS-SWFSC-181. 184 pp. 

Mangels, K. F. and T . Gerrod ette. Report of cetacean sigh tings during a m arine mam mal survey in the eastern Pa cific 

Ocean and the Gulf of California abo ard the NOA A ships McArthur and David Starr Jordan July 28 -

November 6, 1993. U.S. Dep. Commer. NOAA Tech. Memo. NMFS-SWFSC-221. 88 pp. 

Masak i, Y. 1977. The separation of the stock units of sei whales in the North Pacific. Rept. Int. Whal. Commn., Special 

Issue 1:71-77. 

Mizroch, S. A., D. W . Rice, and J. M. Bre iwick. 1984 . The sei wha le, Balaenoptera borealis. Mar. Fish. Rev. 46:25­

29. 

Ohsumi, S. and S. Wada. 1974. Status of whale stocks in the North Pacific, 1972. Rept. Int. Whal. Commn. 25:114­

126. 

Rice, D. W. 1974. W hales and whale research in the eastern North Pacific. pp. 170-195 In: W. E. S chevill (ed.). The 

Whale Problem: A Status Report. Harvard Press, Cambridge, MA. 

Tillman, M. F. 1977. Estimates of population size for the North Pacific sei whale. Rept. Int. Whal. Commn., Special 

Issue 1:98-106. 

Von Saunder, A. and J. Barlow. 1999. A report of the Oregon, California and Washington Line-transect Experiment 

(ORCAWALE) conducte d in west coast waters during summer/fall 1996. U.S. Dep. Commer. NOA A Tech. 

Memo . NMF S-SW FSC-26 4. 40 pp . 

Wade, P. R. and T. Gerrodette. 1993. Estimates of cetacean abundance and distribution in the eastern tropical Pacific. 

Rept. Int. Whal. Commn. 43:477-493. 

Yablokov, A. V. 1994. Validity of whaling data. Nature 367:108. 

172 
Revised 12/15/2000 

MINKE WHALE (Balaenoptera acutorostrata): 

California/Oregon/Washington Stock 

STOCK DEFINITION AND GEOGRAPHIC RANGE 

The International Whaling Commission (IWC) 

recognizes 3 stocks of m inke whales in the North 

Pacific: one in the Sea of Japan/East China Sea, one 

in the rest of the we stern Pacific west of 180oN, and 

one in the "remainder" of the Pacific (Donovan 

1991). The "remainder" stock only reflects the lack 

of exploitation in the eastern Pacific and does not 

imply that only one population exists in that area 

(Donovan 1991). In the "remainder" area, minke 

whales are relatively common in the Bering and 

Chukchi seas and in the Gulf of Alaska, but are not 

considered abundant in any other part of the eastern 

Pacific (Leatherwood et al. 1982; Brueggeman et al. 

1990). In the Pacific, minke whales are usually seen 

over continental shelves (Brueggeman et al. 1990). 

In the extreme north, minke whales are believed to be 

migratory, but in inland waters of Washington and in 

central California they appear to establish home 

ranges (Dorsey et al. 1990). Minke whales occur 

year-round in California (D ohl et al. 1983; Forney et 

al. 1995; Barlow 1997) a nd in the Gu lf of California 

(Tershy et al. 1990). Minke whales are present at 

least in summer/fall alo ng the Baj a California 

peninsula (Wade and Gerrod ette 1993). Bec ause the 

"resident" minke whale s from Califo rnia to 

Washington appear b ehaviorally d istinct from 

migratory whales further north, minke whales in 

coastal waters of Ca lifornia, Oregon, and Washington 

(including Puget Sound) w ill be considered as a 

separate stock. Minke whales in Alaskan waters are 

considere d in a separ ate stock asse ssment repo rt. 

POPU LATIO N SIZE 

Figure 2. Minke wh ale sighting locations based on 

aerial and shipboard surveys off California, Oregon, 

and Washington, 1991-96 (see Append ix 2, Figures 1 -5 

for data sources and information on timing and location 

of surveys). Dashed line represen ts the U.S. E EZ; bold 

line indicates the o uter bound ary of all surveys 

combined. 

No estimates have been made for the number of minke whales in the entire North Pacific. The number of minke 

whales is estimated as 6 31 (CV = 0.45) b ased on sh ip surveys in 199 1, 1993 , and 199 6 off Californ ia and in 

1996 off Orego n and W ashington (B arlow 19 97). Forn ey et al. (199 5) estimate at to tal of 73 (CV =0.62) in 

California based on an aerial survey, but this estimate is negatively biased because it excludes diving w hales. 

In addition, Green et al. (1992) report 4 sightings of minke whales in aerial surveys of Oregon and Washington, 

but they did not estimate population size for that area. Two minke whales were seen during 1996 aerial surveys 

in Washington and British Columbia inland waters (Calambokidis et al. 1997), but no abundance estimates are 

available for this area. 

Minimum Po pulation Estimate 

The minimum population estimate for minke whales is taken as the lower 20th percentile of the log-normal 

distribution of abunda nce estimated from the sum mer/fall ship survey in California, Oregon, and Washington 

waters (Barlow 1997 ) or approximately 440. More sophisticated methods of estimating minimum population 

173 
size would be available if a correction factor (and associate d variance) were available to correct the aerial 

survey estimates for missed animals. 

Current Population Trend 

There are no data on trends in minke whale abundance in waters of California, Oregon and/or Washington. 

CURRENT AND M AXIMUM NET PRODUCTIVITY RATES 

There are no estimates of the growth rate of minke whale populations in the North Pacific (Best 1993). 

POTENTIAL BIOLOGICAL REMOVAL 

The potential biological removal (PBR) level for this stock is calculated as the minimum population size (440) 

times one half the d efault maximu m net grow th rate for cetaceans (1⁄2 of 4%) times a recovery factor of 0.5 (for 

a stock of unknown status), resulting in a PBR of 4.4. 

HUMAN CAUSED MOR TALITY 

Historic Whaling 

The estimated take of western North Pacific minke whales by commercial whalers was approximately 31,000 

from 1930 to 1987 (C. Allison, IWC, pers. comm.). Minke whales were not harvested commercially in th e 

eastern North Pacific: none were reported taken by shore-based whaling stations in central or northern 

California between 1919 and 1926 (Clapham et al. 1997) or between 1958 and 1965 (Rice 1974). Reported 

aboriginal takes of minke whales in Alaska totaled 7 betwee n 1930 and 1987 (C. A llison, IWC, pers. comm.). 

Table 1. Summary ofavailable informationon theincidentalmortality andinjuryofminkewhales(CA/OR/WAstock)forcommercialfisheriesthat 

mighttakethisspecies(Pierceetal.1996;Julian1997,JulianandBeeson1998;CameronandForney 1999). Mean annualtakesarebased 

on 1994-98 data unless noted otherwise. 

Fishery Name Year(s) Data Type 

Percent Observer 

Covera 

ge 

Observed 

Mortality 

Estimated 

Mortality (CV in 

parenthe 

ses) 

Mean 

Annual Takes 

(CV in parentheses) 

CA/OR thresher 

shark/swordfish 

drift gillnet 

fishery 

1994 

1995 

1996 

1997 

1998 

observer 

data 

17.9% 

15.6% 

12.4% 

23.0% 

20.0% 

1 

0 

1 

0 

0 

6 (0.91) 

0 

12 (0.96) 

0 

0 

01 

WA Puget Sound Region 

salmon drift 

gillnet fishery 

(areas 7 and 7A) 

1994 observer 

d 

at 

a 

7% 0 0 0 

CA angel shark/halibut 

and other 

species large 

mesh (>3.5") set 

gillnet fishery 

1991-94 observer 

data 

10-18% 0,0,0,0 0,0,0,0 n/a 

Total annual takes 0.0 

1

 Only 1997-98 mortality estimates are included in the average because of gear modifications implemented within the fishery as part of a 1997 Take 

Reduction Plan. Gear modifications in cluded the use of net extenders and acoustic warnin g devices (pingers). 

Fishery Information 

Minke whales may occasiona lly be caught in c oastal set gillnets o ff California, in salm on drift gillnet in Puget 

Sound, Wash ington, and in offshore drift gillnets off California and Oregon. A summary of known fishery 

174 
mortality and injury for this stock of mink e whales is given in Table 1 . Detailed info rmation on this fishery is 

provided in Appen dix 1. After the 1997 implementation of a Take Reduction Plan, which included skipper 

education workshops and required the use of pingers and minimum 6-fathom extenders, overall cetacean 

entanglement rates in the drift gillnet fishery dropped considerably (Barlow and Cameron 1999). Because of 

the changes in this fishery after implementation of the Take Reduction Plan, mean annual takes for this fishery 

(Table 1) are based only on 1997-98 data. This results in an average estimate of zero minke whales taken 

annually. Total fishery mortality for minke whales was not estimated for the 1980-86 California Department 

of Fish and Game observer program for the drift gillnet fishery, but based on the 2 observed deaths in 1% of 

the total sets, the total mortality during this time may have been on the order of 200 minke whales or 40 per 

year. 

Drift gillnet fisheries for swordfish and sharks exist along the entire Pacific coast of Baja California and may 

take animals from the same po pulation. Q uantitative data are available only for the M exican swo rdfish 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 o f sets in this fishery 

in 1992 can be estimated from data provided by these authors to be approximately 2,700, with an obse rved rate 

of marine mammal bycatch of 0 .13 anima ls per set (10 marine mammals in 77 observed sets; Sosa-Nishizaki 

et al. 1993). This overall mortality rate is similar to that observed in California driftnet fisheries during 1990-95 

(0.14 marine mammals per set; Julian and Beeson 1998), but species-specific information is not available for 

the Mexican fisheries. There are currently efforts underway to convert the Mexican swordfish driftnet fishery 

to a longline fishe ry (D. Ho lts, pers. comm .). 

Ship Strikes 

Ship strikes were implicated in the death of one minke whale in 1977 (J. Heyning and J. Cordaro, pers. comm.). 

The reported minke whale mortality due to ship strikes is zero for the period 1994-98. A dditional mortality 

from ship strikes probably goes unreported because the whales do not strand or, if they do, they do not always 

have obvious signs of trauma. 

STATUS OF STOCK 

There were no known comm ercial whaling harvests of minke whales from Baja California to Washington. 

Minke whales are not listed as "endangered" under the Endangered Species Act and are not considered 

"depleted" under the MMPA . The greatest uncertainty in their status is whether entanglement in commercial 

gillnets and ship strikes could have red uced this relatively small population. Bec ause of this, the status of the 

west-coast stock should be considered "unknown" . The annu al mortality due to fisheries (0.0 /yr) and ship 

strikes (0.0/yr) is less than the calculated PBR for this stock (4.4), so they are not considered a "strategic" stock 

under the MMPA. Fishery mortality is less than 1 0% of the PBR; therefore, total fishe ry mortality is 

approaching zero mortality and serious injury rate. There is no information on trends in the abundan ce of this 

stock. The increasing levels of anthropogenic noise in the world’s oceans has been suggested to be a habitat 

concern for whales, particularly for baleen whales that may communicate using low-frequency sound. 

REFERENCES


Barlow, J. 1997. Preliminary estimates of cetacean abundance off California, Oregon, and Washington based on a 1996


ship survey and compariso ns of passing and closing modes. Admin. Rep. LJ-97-11. Southwest Fisheries 

Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA 92038. 25 pp. 

Barlow, J., K. A. Forney, P. S. Hill, R. L. Brownell, Jr., J. V. Carretta, D. P. DeMaster, F. Julian, M. S. Lowry, T. Ragen, 

and R. R. Reeves. 1997. U.S. Pacific Marine Mammal Stock Assessments: 1996. U.S. Dep. Commer. NOAA 

Tech. Memo. NMFS-SWFSC-248. 223 pp. 

Barlow, J., R. W. B aird, J. E. H eyning, K. W ynne, 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 Can ada and the east coast o f the Russian F ederation . Rep. Int. W hal. Commn, Special Issue 15:405­

425. 

175 
Barlow, J. and G. A. Cameron. 1999. F ield experim ents show that a coustic ping ers reduce marine ma mmal byca tch in 

the California drift gillnet fishery. Report SC/51/SM2 to the Scientific Committee of the International Whaling 

Commission, May 1999. 20pp. 

Best, P. B. 1993. Increase rates in severely depleted stocks of baleen whales. ICES J. Mar. Sci. 50:169-186. 

Brueggeman, J. J., G. A. Green, K. C. Balcomb, C. E. Bowlby, R. A. Grotefendt, K. T. Briggs, M. L. Bonnell, R. G. 

Ford, D. H. Varoujean, D. Heinemann, and D. G. Chapman. 1990. Oregon-Washington M arine Mammal and 

Seabird Survey: Information synthesis and hypothesis formulation. U.S. Department of the Interior, OCS Study 

MMS 89-0030. 

Calambokidis, J., S. Osmek, and J. L. Laake. 1997. Aerial surveys for marine mamma ls in Washington an d British 

Columb ia inside waters . Final Contra ct Repor t to Nationa l Marine M ammal La boratory, S eattle, WA . 

Cameron, G. A. and K. A. Forney. 1999. Preliminary estimates of cetacean mortality in the California gillnet fisheries 

for 1997 and 1998 . Paper SC/51/O4 presented to the International Whaling Commission, May 1998 

(unpublished). 14 pp. 

Dohl, T. P., R. C. Guess, M. L. Duman, and R. C. Helm. 1983. Cetaceans of central and northern California, 1980-83: 

Status, abundance, and distribution. Final Report to the Minerals Management Service, Contract No. 14-12­

0001-29090. 284p. 

Donovan, G. P. 1991. A review of IWC stock boundaries. Rept. Int. Whal. Commn., Special Issue 13:39-68. 

Dorsey, E. M., S. J. Stern, A. R . Hoelzel, and J. Jacobsen. 1990. Minke whale (Balaenoptera acutorostra ta) from the 

west coast o f North Am erica: individu al recognitio n and sma ll-scale site fidelity. Rept. Int. Whal. C ommn., 

Special Issue 12:357-368. 

Forney, K. A., J. Barlow, and J. V. Carretta. 1995. The abundance of cetaceans in California waters. Part II: Aerial 

surveys in winter and spring of 1991 and 1992. Fish. Bull. 93:15-26. 

Green, G. A., J. J. Brueggeman, R. A. Grotefendt, C. E. Bowlby, M. L. Bonnell, K. C. Balcomb, III. 1992. Cetacean 

distribution and abundance off Oregon and Washington, 1989-1990. Ch. 1 In: J. J. Brueg geman (ed .). Oregon 

and WashingtonMarine Mammal and Seabird Surveys. Minerals Management Service Contract Report 14-12­

0001-30426. 

Hanan, D. A. 1986. California Department of Fish and Game coastal marine mammal study, annual report for the period 

July 1, 1983 - June 30, 1984. Admin. Rept. LJ-86-16. Southwest Fisheries Science Center, National Marine 

Fisheries Service, P.O. Box 271, La Jolla, CA. 55 pp. 

Hanan, D. A., D. B. Holts, and A. L. Coa n, Jr. 1993 . The California drift gill net fishery for sharks and swordfish, 1981­

82 through 1990-91. Calif. Dept. Fish and Game Fish. Bull. No. 175. 95 pp. 

Heyning, J. E., and T. D. Lewis. 1990. Fisheries interactions involving baleen whales off southern California. Rep. 

Int. Whal. Commn. 40:427-431. 

Holts, D. Southwest Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA 92038. 

Holts, D. and O . Sosa-Nish izaki. 1998. S wordfish, Xiphias gladius, fisheries of the eastern No rth Pacific O cean. 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. Cetace an mortality in the California gill net fisheries: preliminary estimates for 1996. Paper 

SC/49/SM2 presented to the International Whaling Commission, September 1997 (unpublished). 13 pp. 

Julian, F. and M . Beeson . 1998. E stimates for ma rine mamm al, turtle, and seabird mortality for two California gillnet 

fisheries: 1990-95. Fish. Bull. 96:271-284. 

Leatherwood, S., R. R. Reeves, W. F. Perrin, and W. E. Evans. 1982. W hales, dolphins, and porpoises of the eastern 

North Pacific and adjacent Arctic waters: A guide to their identification. NOAA Technical Rept. NMFS 

Circular 444. 245pp. 

Pierce, D. J., M. Alexandersdottie, S. J. Jeffries, P. Erstad, W. Beattie, and A. Chapman. 1996. Interactions of marbled 

murrelets and marine mamma ls with the 199 4 Puget S ound soc keye gill net fishery. Fin al Repor t, Wash. D ept. 

Fish and Wildlife, Olympia, WA. 21pp. 

Rice, D. W. 1974. Whales and whale research in the eastern North Pacific. pp. 170-195 In: W. E. S chevill (ed.). The 

Whale Problem: A Status Report. Harvard Press, Cambridge, MA. 

176 
Sosa-Nish izaki, O., R. De la Rosa P acheco, R. Castro Longoria, M. Grijalva Chon, and J. De la Rosa Velez. 1993. 

Estudio biologico pesquero del pez (Xiphias gladius) y otras especies de picudos (marlins y pez vela). Rep. 

Int. CICESE, CTECT9306. 

Tershy, B. R., D. Breese, and C. S. Strong. 1990. Abundance, seasonal distribution and population composition of 

balaenop terid whales in the Canal de Ballenas, Gulf of California, Mexico. Rept. Int. Whal. Commn., Special 

Issue 12:369-375. 

Von Saunder, A. and J. Barlow. 1999. A report of the Oregon, California and Washington Line-transect Experiment 

(ORCAWALE) conducted in west coa st waters during summer/fall 1996. U.S. Dep. Commer. NOAA Tech. 

Memo . NMF S-SW FSC-26 4. 40 pp . 

Wade, P. R. and T. Gerrodette. 1993. Estimates of cetacean abundance and distribution in the eastern tropical Pacific. 

Rept. Int. Whal. Commn. 43:477-493. 

177 
Revised 12/15/2000 

ROUGH-TOOTHED DOLPHIN (Steno bredanensis): Hawaiian Stock 

STOCK DEFINITION AND GEOGRAPHIC RANGE 

Rough-toothed dolphins are found 

throughout the world in tropical and warmtemperate waters (M iyazaki and P errin 

1994). They are present around all the 

main Hawaiian islands (Shallenberger 

1981; Tomich 1986) and have been 

observed at least as far northwest as French 

Frigate Shoals (Nitta and Henderson 

1993). Recent sighting locations around the 

main Hawaiian Islands are shown in Figure 

1. Five strandings have been reported from 

Maui, Oahu, and the island of Hawaii 

(Nitta 1991). Nothing is known about 

stock structure for this species in the North 

Pacific. For the Marine Mammal 

Protection Act (MMPA) stock assessment 

reports, there is a single Pacific 

management stock including only animals 

found within the U.S. Exclusive E conom ic 

Zone of the Haw aiian Islands. 

POPU LATIO N SIZE 

A population estimate for this species h as 

Figure 1. Rough-toothed dolphin sighting locations during 

1993-9 8 aerial surve ys within about 2 5 nmi of the m ain 

Hawaiian Islands (see Appendix 2 for details on timing and 

location of su rvey effort). Ou ter line indicates a pproxim ate 

boundary of survey area. 

been made in the e astern tropic al Pacific (W ade and Gerrod ette 1993 ), but it is not known whether these 

animals are part of the same population that occurs around the Hawaiian Islands. As part of the Marine 

Mammal Research Program of the Acoustic Thermometry of Ocean Climate (ATOC) study, a total of twelve 

aerial surveys were conducted within about 25 nmi of the main Hawaiian Islands in 1993, 1995 and 1998. An 

abundance estimate of 123 (CV=0.63) rough-toothed dolphins was recently calculated from the combined 

survey data (M obley et al. 20 00). This abundance underestimates the total number of rough-toothed dolphins 

within the U.S. EEZ off Hawaii, because areas around the Northwest Hawaiian Islands (NWH I) and beyond 

25 nautical miles from the main islands were not surveyed. 

Minimum Po pulation Estimate 

The log-nor mal 20 th percentile of the combined 1993-98 abundan ce estimate is 76 rou gh-toothed d olphins. 

As with the best abun dance e stimate ab ove, this inc ludes on ly areas w ithin about 25 nmi of the main Hawaiian 

Islands and is therefore an underestimate. 

Current Population Trend 

No data are available on current population trend. 

CURRENT AND M AXIMUM NET PRODUCTIVITY RATES 

No data are available on current or maximum net productivity rate. 

POTENTIAL BIOLOGICAL REMOVAL 

The po tential biologic al remova l (PBR ) level for this stock is calculated as the minimum population size (76) 

timesone half the default maximum net growth rate for cetaceans (1⁄2 of 4%) times a recovery factor of 0.50 (for 

174 
a species of unknown status with no kno wn fishery mortality; Wade and Angliss 1997), re sulting in a PBR of 

0.8 rough -toothed d olphins pe r year. 

HUMAN -CAUSED MORTALITY AND SERIOUS INJURY 

Fishery Information 

No estimate of annual human-caused mortality and serious injury is available, as no mortality of this species 

has been documented in Hawaiian fisheries (Nitta and Henderson 1993). However, mortality of other cetacean 

species has been observed in Hawaiian fisheries, and the gear types use d in these fisherie s are respo nsible for 

marine mammal mortality and serious injury in other fisheries th roughou t U.S. waters. G illnets are used in 

Hawaiian waters and appear to capture marine mammals wherever they are used, and float lines from lobster 

traps and lo nglines can b e expecte d to occa sionally entangle whales (Pe rrin et al. 199 4). 

Interactions with cetaceans have been reported for all Hawaiian pelagic fisheries, and some of these interactions 

involved ro ugh-toothed dolphins (N itta and Henderson 1993). None were observed hooked in the Hawaiian 

longline fishery between 1994 and 1998, with approximately 4.4% of all effort (measured as the number of 

hooks fished) observed (Kleiber 1 999). T hey are kno wn to take ba it and catch from Hawa iian sport and 

commercial fisheries operating near the main islands and in a portion of the northwestern islands (Shallenberger 

1981; Schlais 198 4; Nitta and Hende rson 199 3), and they h ave been specifically reported to interact with the 

day handline fishery for tuna (palu-ahi) and the troll fishery for billfish and tuna (Schlais 1984; Nitta and 

Henderson 1993). Interaction rates between dolphins and the NWHI bottomfish fishery have been estimated 

based on studies conducted in 1990-1 993, indic ating that an ave rage of 2.6 7 dolph in interactions, m ost likely 

involving bottlenose and rough-toothed dolphins, occurred for every 1000 fish brought on board (Kobayashi 

and Kawam oto 199 5). Fisherm en claim intera ctions with dolphins who steal bait and catch are increasing. It 

is not known whether these interactions res ult in serious injury o r mortality of do lphins. 

Other Remov als 

At least 22 rough-toothed dolphins were live-captured in Hawaiian waters between 1963 and 1976 

(Shallenbe rger 198 1). 

STATUS OF STOCK 

The status of rough-toothed dolphins in Hawaiian waters relative to OSP is unknown, and there are insufficient 

data to evaluate trends in abundance. No habitat issues are known to be of concern for this species. They are 

not listed as “threatened” or “endangered” under the Endangered Species Act (1973), nor as “depleted” under 

the MMP A. Although information on rough-toothed dolphins in Hawaiian waters is limited, this sto ck would 

not be considered strategic under the 1994 amendments to the MMPA given the absence of reported fisheries 

related mortality. However, there is no systematic monitoring of gillnet fisheries that may take this species, and 

the potential effects of interactions with the bottomfish fishery in the NWHI are not known. Insufficient 

information is available to determine whether the total fishery mortality and serious injury for rough-toothed 

dolphins is insignificant and approaching zero mortality and serious injury rate. 

REFERENCES


Kleiber, P. 1999 . Estimate s of marine mammal takes in the Hawaiian longline fishery. (Unpub lished). Southwest


Fisheries Science Center, NMFS, 2570 Dole St, Honolulu, HI, 96822-2396. 

Kobayashi, D. R. and K. E. Ka wamoto . 1995. E valuation of sh ark, dolph in, and mon k seal interactio ns with 

Northwestern Hawaiian Island bottomfishing activity: a comparison of two time periods and an estimate of 

economic impacts. Fisheries Research 23: 11-22. 

Miyazaki, N. and W. F. Perrin. 19 94. Rou gh-toothed dolphin Steno b redane nsis (Lesson, 1828). In: S. H. Ridgway 

and R. Harrison (eds.), Handbook of Marine M ammals, Vol.5: The First Boo k of Dolp hins, pp. 1-2 1. Acade mic 

Press, 416 pp. 

Mob ley, J. R. , Jr, S. S. Sp itz, K. A. Fo rney, R. A. G rotefendt, 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

175 
14C. Southwest Fisheries Science Center, N ational Marine Fisheries Service, P.O. Box 271, La Jolla, CA 

92038. 26 pp. 

Nitta, E. 1991 . The marine mammal stranding netw ork for H awaii: an ove rview. In: J.E. Reyno lds 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. Dono van and J. B arlow. 199 4. Gillnets and Cetaceans. Rep. Int. Whal. Commn., Special Issue 15, 

629 pp. 

Schlais, J.F. 1984. Thieving dolphins: A growing problem in Hawaii's fisheries. Sea Front. 30(5):293-298. 

Shallenberger, E.W. 1981. The status of Hawaiian cetaceans. Final report to U.S. Marine Mammal Commission. MMC77/23, 79pp. 

Tomich, P. Q. 1986. Mammals in Hawaii: A Synopsis and Notational Bibliogra phy. 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, 1 996, Se attle, Wash ington. U. S. D ep. Com mer., 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. 

176 
Revised 12/15/2000 

RISSO'S DOLPHIN (Grampus griseus): Hawaiian Stock 

STOCK DEFINITION AND GEOGRAPHIC RANGE 

Risso's dolphins ar e found in tro pical to 

warm-temperate waters worldwide (Kruse 

et al. 1999). They app ear to be ra re in 

Hawaiian waters (Figure 1). Of three 

reported sightings of this species by 

Shallenberger (1981), only one was 

verified. There are four stranding records 

from the main islands (Nitta 1991). 

Balcomb (1987) referred to a sighting of a 

large herd off the Kona Coast in February 

1985. For the Marine Mammal Protection 

Act (MMPA) stock assessme nt reports, 

Risso 's dolphins within the Pacific U.S. 

Exclusive Economic Zone are divided into 

two discrete, non-contiguous areas: 1) 

Hawaiian waters (this report), and 2) 

waters off California, Oregon and 

Washington. 

POPU LATIO N SIZE 

Population estimates have been mad e off 

Japan (Miyashita 1993) and in the eastern 

tropical Pacific (Wade and Gerro dette 

Figure 1. Sighting location for the single Risso’s dolphin seen 

during 19 93-98 a erial surveys within about 25 nmi of the ma in 

Hawaiian Islands (see Appendix 2 for details on timing and 

location of su rvey effort). Ou ter line indicates a pproxim ate 

boundary of survey area. 

1993), but it is not know n whether thes e animals are part of the sam e popula tion that occurs around the 

Hawaiian Islands. As part of the Marine Mammal Research Program of the Acoustic Thermometry of Ocean 

Climate (ATO C) study, a tota l of twelve aerial su rveys were conducted within about 2 5 nmi of the m ain 

Hawaiian Islands in 19 93, 199 5 and 19 98 (M obley et al. 20 00). Only one sighting o f a single Risso’s dolp hin 

was made, and therefore no meaningful abundance estimate could be calculated. Based on the locations of 

interactions with the Haw aiian longline fishe ry (Figure 2), it is likely tha t Risso’s dolp hins primarily o ccur in 

pelagic waters tens to hundreds of miles from the main Hawaiian islands and are only occasionally found 

nearshore . 

Minimum Po pulation Estimate 

No data are available for a minimum population estimate. 

Current Population Trend 

No data are available on current population trend. 

CURRENT AND M AXIMUM NET PRODUCTIVITY RATES 

No data are ava ilable on current or maximu m net productivity rate for Haw aiian animals. 

POTENTIAL BIOLOGICAL REMOVAL 

No PBR can be calculated for this species at this time. 

HUMAN CAUSED MORTALITY AND SERIOUS INJURY 

Fishery Information 

177 
No estimate of annual human-cau sed morta lity and serious injury is available as there are no reports of direct


or incidental takes of Risso's dolphins in Hawaiian waters. However, mortality of other cetacean species has


been observed in Hawaiian fisheries, and the gear types use d in these fisherie s are responsible for marine


mammal mortality and serious injury in other fisheries throughout U.S. waters. Gillnets are used in Hawaiian


waters and app ear to cap ture marine m ammals wherever they are used, and float lines from lobster traps and


longlines can be expected to occasionally entangle whales (Perrin et al. 1994).


Interactions with cetaceans have been


reported for all Hawa iian pelagic


fisheries (Nitta and Henderson 1993),


and some of these interactions involved


Risso’s dolphins in waters outside the


U.S. EEZ. Four Risso’s dolphins were


observed hooked in the Hawaiian


longline fishery between 1994 and


1998, with appro ximately 4.4% of all


effort (measured as the number of hooks


fished) observed. This interaction rate


extrapolates to a total 5-year estimate of


90 (95% CI = 27-213) Risso’s dolphins,


or an average of 18 per year (Kleiber


1999). Three of the observed Risso’s


dolphins were reported to have been


hooked in the mouth or to have ingested


the hook, and they were released with Figure 2. Locations of observed cetacean interactions in the


hook and line still attached. Following Hawaiian longline fishery, 1994-98 (modified from Kleiber


the guidelines of a 1997 Serious Injury 1999). Dashed line is the U.S. Exclusive Economic Zone (EEZ);
 Workshop (Angliss and DeMaster GG = Risso’s dolphin.
 1998), these three animals have been


considered seriously injured (defined


under the MM PA as likely to result in mortality). The fourth animal was hooked in an unknown location and


swam normally, but was released with 20m of trailing line and a light stick. Because a substantial length of line


was still attached when the animal was released, this animal is likely to have sustained serious injury. Reports


for other odontocetes indicate they may also become hooked in other parts of their body, and that they may


occasion ally becom e entangled in the fishing line. 


Interaction rates between dolphins and the NWH I 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


Kawam oto 1995). Fishermen claim interactio ns with dolph ins who steal b ait 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 o f Risso's dolphins in Hawaiian waters relative to OSP is unknown, and there are insufficient data 

to evaluate trends in abundance. No habitat issues are known to be of concern for this species. They are not 

listed as “threatened” or “endangered” under the Endangered Species Act (1973), nor as “depleted” under the 

MMPA. Although information on Risso's dolphins in Hawaiian waters is limited, this stock would not be 

considered strategic under the 1994 amendments to the MMPA given the absence of reported fisheries related 

mortality within the U.S. EEZ and the species’ apparent offshore distribution. The potential effect of injuries 

sustained by Risso’s dolphins in the Hawaiian longline fishery in inte rnational wate rs is not known. Insufficient 

information is available to determine whether the total fishery mortality and serious injury for Risso’s dolphins 

is insignificant and approaching zero mortality and serious injury rate. 

178 
REFERENCES 

Angliss, R. P. and D. P. DeMaster. 1998. Differentiating Serious and Non-Serious Injury of Marine Mammals Taken 

Incidental to Commercial Fishing Operations: Report of the Serious Injury Workshop 1-2 April 1997, Silver 

Spring, Maryland. U. S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-13. 48 pp. 

Balcomb, K. C., III. 1987. The Whales of Hawaii. Marine Mammal Fund, 99 pp. 

Kruse, S. K., D. K . Caldwell, an d M. C . Caldwell. 19 99. Risso's do lphin Gram pus griseu s. Pages 183-212 In: S. H. 

Ridgway and R. Harrison (eds.), Handbook of Marine Mammals, Volume 6. Academic Press, San Diego. 

Kleiber, P. 1999. Estimates of marine mammal takes in the Ha waiian longline fishery. (Unpublished). So uthwest 

Fisheries Science Center, NMFS, 2570 Dole St, Honolulu, HI, 96822-2396. 

Koba yashi, D. R. and K. E. Kawamoto. 1995. Evaluation of shark, dolphin, and monk seal interaction s with 

Northwestern Hawaiian Island bottomfishing activity: a comparison of two time periods and an estimate of 

economic impacts. Fisheries Research 23: 11-22. 

Miyashita, T. 199 3. Abundance of dolphin stocks in the western North Pacific taken by the Japanese drive fishery. Rep. 

Int. Whal. Commn. 43:417-437. 

Mob ley, J. R. , Jr, S. S. Spitz, K. A. Forney, R. A. Grotefendt, and P. H. Forestall. 2000. Distribution and abundance 

of odonto cete 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. Reyno lds 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 H awaii's fisheries and protected species. Mar. 

Fish. Rev. 55(2):83-92. 

Perrin, W.F., G. P. Dono van and J. Barlow . 1994. Gillnets and C etaceans. Rep. Int. Whal. Commn., Special Issue 15, 

629 pp. 

Shallenberger, E.W. 1981. T he status of Hawaiian cetaceans. Final report to U.S. Marine Mammal Co mmission. MMC77/23, 79pp. 

Wade, P. R. and T. Gerrodette. 1993. Estimates of cetacean abundance and distribution in the eastern tropical Pacific. 

Rep. Int. Whal. Commn. 43:477-493. 

179 
Revised 12/15/2000 

BOTTLENOSE DOLPHIN (Tursiops truncatus): Hawaiian Stock 

STOCK DEFINITION AND GEOGRAPHIC RANGE 

Bottlenose dolphins are widely distributed 

throughout the world in tropical and warmtemperate waters. The species is primarily 

coastal in much of its range, but there are 

populations in some offshore deepwater 

areas as well. Separate offshore and 

coastal forms have been identified along 

continental coasts in several areas (Ross 

and Cockcroft 1990; Van Waerebeek et al. 

1990), and similar onshore-offshore forms 

may exist in H awaiian wate rs. 

Although only three strandings have been 

reported (Nitta 1991), bottlenose dolphins 

are common throughout the Hawaiian 

Islands, from the island of H awaii to Kure 

Atoll (Shallenberger 1981). Recent 

sighting locations for sys tematic aeria l 

surveys within about 2 5nmi of the m ain 

Hawaiian Islands in 1993-98 are shown in 

Figure 1. In the Northwestern Hawaiian 

Islands, they are found primarily in 

relatively shallow inshore waters (Rice 

1960). In the main Hawaiian Islands, they 

Figure 1. Bottlenose dolphin sighting locations during 1993­

98 aerial surveys within about 25 nmi of the main Hawaiian 

Islands (see Appendix 2 for details on timing and location of 

survey effort). Outer line indicates approximate boundary of 

survey area. 

are found in both shallow inshore wate rs and dee p channe ls between islan ds. 

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 westernm ost sightings and the Hawaiian Islands. These 

data suggest that the bottlenose dolphins in H awaiian wate rs belong to a separate sto ck from tho se in the ETP. 

For the Marine Mammal Protection Act (MMPA) stock assessment reports, bottlenose dolphins within the 

Pacific U.S. Exc lusive Eco nomic Zo ne are divid ed into three stocks: 1) Hawaiian stock (this report), 2) 

California, Oregon and Washington offshore stock, and 3) California coastal stock. 

POPU LATIO N SIZE 

Population estimates have bee n made in J apanese w aters (Miya shita 1993 ) and the eastern tropica l Pacific 

(Wade and Gerro dette 199 3), but it is not kno wn whether th ese animals a re part of the same pop ulation that 

occurs around the Hawaiian Islands. As pa rt of the Marine Ma mmal Re search Pr ogram o f the Acoustic 

Thermometry of Ocean Climate (ATOC) study, a total of twelve aerial surveys were conducted within about 

25 nmi of the main Hawaiian Islands in 1993, 1995 and 1998. An abundance estimate of 743 (CV=0.56) 

bottlenose dolphins w as recently c alculated from the combined su rvey data (M obley et al. 20 00). Th is 

abundance underestimates the total num ber of bo ttlenose do lphins within the U.S. EEZ o ff Hawaii, because 

areas around the Northwest Hawaiian Islands (NWHI) and beyo nd 25 na utical miles from the main islands were 

not surveyed. 

Minimum Po pulation Estimate 

The log-normal 20th percentile of the combined 1993-98 abundance estimate is 479 bottlenose dolph ins. As 

with the best abundance estimate above, this includes only areas within about 25 nmi of the main Hawaiian 

Islands an d is therefo re an un derestim ate. 

180 
Current Population Trend 

No data are available on current population trend. 

CURRENT AND M AXIMUM NET PRODUCTIVITY RATES 

No data are ava ilable on current or maximu m net productivity rate for this species in Haw aiian waters. 

POTENTIAL BIOLOGICAL REMOVAL 

The potential biological removal (PBR) level for this stock is calculated as the minimum population size (479) 

times one half the default maximum net growth rate for cetaceans (1⁄2 of 4%) times a recovery factor of 0.50 (for 

a species of un known status w ith no estimated fishery mortality; Wade and Angliss 1997), resulting in a PBR 

of 4.8 bo ttlenose do lphins per yea r. 

HUMAN CAUSED MORTALITY AND SERIOUS INJURY 

Fishery Information 

Although some mo rtality of bottlenose 

dolphins has been observed in inshore 

gillnets, no estimate of annual humancaused mortality and serious injury is 

available. The gea r types used in 

Hawaiian fisheries are responsible for 

marine mamma l mortality and serious 

injury in other fisheries throughout U.S. 

waters. Gillnets are used in Hawaiian 

waters and appear to capture marine 

mamma ls wherever they are used, and 

float lines from lobster traps and 

longlines can be expected to 

occasion ally entangle wha les (Perrin et 

al. 1994). 

Interactions with cetaceans have been 

reported for all Hawa iian pelagic 

fisheries, and many of these interactions Figure 2. Locations of observed cetacean interactions in the 

involved bottlenose dolphins (Nitta and Hawaiian longline fishery, 1994-98 (modified from Kleiber 

Henderson 1993). One bottlenose 1999). Dashed line is the U.S. Exclusive Economic Zone (EEZ); 

dolphin was observed hooked in the TT = bottlenose dolphin.


Hawaiian longline fishery between 1994


and 1998 in waters outside the U.S. EEZ (Figure 2), with approximately 4.4% of all effort (measured as the


number of hooks fished) observed. This interaction rate extrapolates to a total 5-year estimate of 23 (95% CI


= 1-108) bottlenose dolphins, or an average of 4.6 interactions per year (Kleiber 1999). The single observed


bottlenose dolphin was reported to have ingested the hook. Following the guidelines of a 1997 Serious Injury


Workshop (Angliss and DeMaster 1998), this animal has been considered seriously injured (defined under the


MMPA as likely to result in mortality). Reports for other odontocetes indicate they may also become hooked


in the mouth o r other part o f their body, and that they may occasionally become entangled in the fishing line.


Bottlenose dolphins are one of the species commonly reported to take bait and catch from several Hawaiian


sport and commercial fisheries (Nitta and Henderson 1993; Schlais 1984). Observations of bottlenose dolphins


taking bait or catch have also been made in the day handline fishery (palu-ahi) for tuna, the handline fishery for


mackerel scad, the troll fishery for billfish and tuna, and the inshore set gillnet fishery (Nitta and Henderson


1993). Nitta and Henderson (1993) indicated that bottlenose dolphins remove bait and catch from handlines


used to catch bottomfish off the island of Hawaii and Kaula Island and on several banks of the Northwestern


Hawaiian Islands. Fishermen claim interactions with dolphins who steal bait and catch are increasing.


181 
Interaction rates betwee n dolphin s 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 

Kawam oto 1995). It is not known whether these interactions result in serious injury or mortality of dolphins. 

Beginning in the early 1970s the National M arine Fisherie s Service rec eived rep orts of fishermen shooting at 

bottlenose dolphins to deter them from taking fish catches (Nitta and Henderson 1993). Nitta and Henderson 

(1993) also reported that one bottlenose dolphin calf was removed from small-mesh set gillnet off Maui in 1991 

and expressed surprise that bo ttlenose do lphins are "r arely repor ted entangle d or raiding set gill nets in Haw aii," 

considering that they so often remov e fish from fishing lines. 

Other Remov als 

At least 36 bottlenose dolphins were live-captured in Hawaiian waters between 1963 and 1981 (Shallenberger 

1981). The main capture area was around Oahu. O ne juvenile b ottlenose d olphin was entangled in a mooring 

line and stranded dead along the coast of Maui in 1998 (H. Bernard, pers. comm.). 

STATUS OF STOCK 

The status of bottlenose dolphins in Hawaiian waters relative to OSP is unknown, and there are insufficient data 

to evaluate trends in abundance. No habitat issues are known to be of concern for this species. They are not 

listed as “threatened” or “endangered” under the Endangered Species Act (1973), nor as “depleted” under the 

MM PA. Altho ugh informa tion on bo ttlenose do lphins in Hawaiian waters is limited, this stock would not be 

considered strategic under the 1994 amendments to the MMPA given the absence of reported fisheries related 

mortality within the U.S. EEZ. However, there is no systematic monitoring of gillnet fisheries that may take 

this species, and the potential effects of interactions with the Hawaiian longline fishery in international waters 

or the bottomfish fishery in the NWHI are not known. Insufficient information is available to determine 

whether the total fishery mortality and serious injury for bottlenose dolphins is insignificant and approaching 

zero mortality and serious injury rate. 

REFERENCES 

Bernard, H. Hawai'i Wildlife Fund, P.O. Box 637, Paia, HI 96779. 

Kleiber, P. 1999. Estimates of marine mamma l takes in the Hawaiian longline fishery. (Unpub lished). Southwest 

Fisheries Science Center, NMFS, 2570 Dole St, Honolulu, HI, 96822-2396. 

Koba yashi, D. R. and K. E. Ka wamoto . 1995. E valuation of shark, dolphin, a nd monk seal interaction s with 

Northwestern Hawaiian Island bottomfishing activity: a comparison of two time periods and an estimate of 

economic impacts. Fisheries Research 23: 11-22. 

Miyashita, T. 1993. Abundance of dolphin stocks in the western North Pacific taken by the Japanese drive fishery. Rep. 

Int. Whal. Commn. 43:417-437. 

Mob ley, 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. Reyno lds 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. Dono van and J. B arlow. 199 4. Gillnets and Cetaceans. Rep. Int. Whal. Commn., Special Issue 15, 

629 pp. 

Rice, D. W. 1960. Distribution of the bottle-nosed dolphin in the leeward Hawaiian Islands. J. Mamm. 41:407-408. 

Ross, G.J.B. and V. G. Cockcroft. 1990. Comments on Australian bottlenose dolphins and the taxonomic status of 

Tursiops aduncus (Ehrenb erg, 1832 ). In: The Bottlenose D olphin (eds. S. Leatherwood and R. Reeves). pp. 

101-12 8. Acade mic Press, 6 53pp. 

Schlais, J.F. 1984. Thieving dolphins: A growing problem in Hawaii's fisheries. Sea Front. 30(5):293-298. 

182 
Scott, M. D. and S. J. Chivers. 1990. Distribution and herd structure of bottlenose dolphins in the eastern tropical 

Pacific Ocean. In: The Bottlenose Dolphin (eds. S. Leatherwood and R. Reeves). pp. 387-402 . Academic Pre ss, 

653pp . 

Shallenberger, E.W. 1 981. T he status of H awaiian cetac eans. Final report to U.S. Marine Mammal Commission. MMC77/23, 79pp. 

Van Waerebeek, K., J. C. Reyes, A. J. Read, and J. S. McKinnon. 1990 . Preliminary observations of bottlenose dolphins 

from the Pacific co ast of South A merica. In: The Bottlenose Dolphin (eds. S. Leatherwood and R. Reeves). pp. 

143-15 4. Acade mic Press, 6 53 pp. 

Wade, P. R. and R. P. Angliss. 1997. Guidelines for Assessing Marine Mammal Stocks: Report of the GAMMS 

Workshop April 3-5, 1996, Seattle, Washington. U. S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-12. 

93 pp. 

Wade, P. R. and T. Gerrodette. 1993. Estimates of cetacean abundance and distribution in the eastern tropical Pacific. 

Rep. Int. Whal. Commn. 43:477-493. 

183 
Revised 12/15/2000 

PANTROPICAL SPOTTED DOLPHIN (Stenella attenuata): Hawaiian Stock 

STOCK DEFINITION AND GEOGRAPHIC RANGE 

Pantropical spotted do lphins are pr imarily 

found in tropical and subtropical waters 

worldwide (Perrin and Hohn 1994). Much 

of what is known about the species in the 

North Pacific has been learned from 

specimens obtained in the large directed 

fishery in Japan and in the eastern tropical 

Pacific (ETP) tuna purse-seine fishery 

(Perrin and Hohn 1994). The se dolphins 

are common and abundant throughout the 

Hawaiian archipelag o, particularly in 

channels between islands, over offshore 

banks (e.g. Penguin Banks), and off the lee 

shores of the islands (see Shallenberger 

1981). Recent sighting locations around 

the main Hawaiian Islands are shown in 

Figure 1. Nitta (1991) only documented 

three strandings of this species in Hawaii. 

Morpho logical differences and distribution 

patterns have been used to e stablish that 

the spotted dolphins around H awaii belong 

to a stock that is distinct from those in the 

ETP (Perrin 1975; Dizon et al. 1994; 

Figure 1. Pantropical spotted dolphin sighting locations 

during 19 93-98 a erial surveys within about 25 nmi of the ma in 

Hawaiian Islands (see Appendix 2 for details on timing and 

location of su rvey effort). Ou ter line indicates a pproxim ate 

boundary of survey area. 

Perrin et al. 1994b). Their possible affinities with other stocks elsewhere in the Pacific have not been 

investigated. For the Marine Mammal Pro tection Act (MMPA) stock assessment reports, there is a single 

Pacific management stock including only animals found within the U.S. Exclusive Economic Zone of the 

Hawaiian Islands. Spotted dolphins inv olved in eastern tropical Pacific tuna purse-seine fisheries are managed 

separately under the MMPA. 

POPU LATIO N SIZE 

Population estimates are a vailable for Japanese waters (Miyashita 1993) and the eastern tropical Pacific (Wade 

and Gerrod ette 1993 ). As part of the Marine Mammal Research Program of the Acoustic Thermometry of 

Ocean Climate (ATOC) study, a total of twelve aerial surveys were conducted within about 25 nmi of the main 

Hawaiian Islands in 1993, 1995 and 1998. An abundance estimate of 2,928 (CV=0.45) pantropical spotted 

dolphins was recently calculated from the combined survey data (Mobley et al. 2000). This abundance 

underestimates the total numbe r of pantrop ical spotted d olphins within the U.S. EEZ off Hawaii, because areas 

around the Northwest Hawaiian Islands (NWHI) and beyond 2 5 nautical mile s from the ma in islands were not 

surveyed. 

Minimum Po pulation Estimate 

The log-normal 20th percentile of the combined 1993-98 abundance estimate is 2,040 pantropical spotted 

dolphins. As with the best abund ance estima te above, this inc ludes only are as within abo ut 25 nmi o f the main 

Hawaiian Islands and is therefore an u nderestima te. 

Current Population Trend 

No data are available on current population trend. 

184 
CURRENT AND M AXIMUM NET PRODUCTIVITY RATES 

No data are available on current or maximum net productivity rate. 

POTENTIAL BIOLOGICAL REMOVAL 

The potential biological removal (PBR) level for this stock is calculated as the minimum population size (2,040) 

times one half the default maximum net growth rate for cetaceans (1⁄2 of 4%) times a recovery factor of 0.50 (for 

a species of un known status w ith no known fishery mortality; W ade and Angliss 199 7), resulting in a PBR of 

20 pantropical spotted dolphins per year. 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY 

Fishery Information 

No estimate of annual human-caused mortality and serious injury is available as there are no reports of direct 

or incidental takes of pantropical spotted dolphins in Hawaiian waters (Nitta and Hende rson 199 3). However, 

mortality of other cetacean species ha s been observed in Hawaiian fisheries, and the gear types used in these 

fisheries are responsib le for marine mammal mortality and serious injury in other fisheries throughout U.S. 

waters. Gillnets are used in Hawaiian waters and appear to capture marine mammals wherever they are used, 

and float lines from lobster traps and longline s can be ex pected to occasiona lly entangle whale s (Perrin et al. 

1994a). 

Interactions with cetaceans have been reported for all Hawaiian pelagic fisheries (Nitta and Henderson 1993), 

but no interactions with pantropical spotted dolphins have been documented. None were observed hooked in 

the Hawaiian longline fishery between 1994 and 1998, with approximately 4.4% of all effort (measured as the 

number of hooks fished) observed (Kleiber 1999 ). Interaction rates between dolp hins and the NW HI bottomfish 

fishery have been estimated based on studies conducted in 1990-1993, in dicating that an average of 2.67 

dolphin interactions, most likely involving bottlenose and rough -toothed dolphins, occu rred for every 1000 fish 

brought on board (K obayashi an d Kawa moto 19 95). Fisherm en claim intera ctions with dolphins w ho steal bait 

and catch are increasing. It is not known whether these interactions result in serious injury or mortality of 

dolphins, nor whether pantropical spotted dolphins are involved. 

Other Remov als 

At least 52 pantropical spotted dolphins were live-captured in Hawaii between 1963 and 1978 (Shallenberger 

1981). 

STATUS OF STOCK 

The status of pantropical spotted dolphins in Hawaiian waters relative to OSP is unknown, and there are 

insufficient data to eva luate trends in abundance. No habitat issues are known to be of con cern for this species. 

They are not listed as “threatened” or “endangered” under the Endangered Species Act (1973), nor as 

“depleted” under the MMPA. There has been no documented human-caused mortality of this stock, and 

therefore they are not classified as a "strategic" stock under the MMPA. Insufficient informa tion is available 

to determine whether the total fishery mortality and serious injury for pantropical sp otted dolp hins is 

insignificant and approa ching zero mortality and se rious injury rate . 

REFERENCES 

Dizon, A. E., W. F. Perrin, and P. A. Akin. 1994. Stocks of dolphins (Stenella spp. and Delphin us delph is) in the eastern 

tropical Pacific: a phylogeographic classification. NOAA Tech. Rep. NMFS 119, 20 pp. 

Kleiber, P. 1999. Estimates of marine marine mammal takes in the Hawaiian longline fishery. (Unpub lished). Southwest 

Fisheries Science Center, NMFS, 2570 Dole St, Honolulu, HI, 96822-2396. 

Kobayash i, D. R. and K . E. Kawamoto. 19 95. Evalu ation of shark , dolphin, an d monk se al interactions w ith 

Northwestern Hawaiian Island bottomfishing activity: a comparison of two time periods and an estimate of 

economic impacts. Fisheries Research 23: 11-22. 

185 
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. 

Mob ley, J. R. , Jr, S. S. Spitz, K. A. For ney, R. A. Grotefendt, and P. H. Forestall. 2000. Distribution and abundance 

of odontocete spe cies 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 mar ine mamm al stranding ne twork for H awaii: an ove rview. In: J.E. Reynolds III, D.K. O dell 

(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. 197 5. Variation of spotted and spinner porpoise (ge nus Stenella ) in the eastern tropical Pacific and 

Hawaii. Bull. Scripps Inst. Oceanogr. 21, 206 pp. 

Perrin, W. F. and A. A. Hohn. 1994. Pantropical spotted dolphin Stenella a ttenuata . In: S. H. Ridgway and R. Harrison 

(eds.), Handboo k of Marine M ammals, Vol.5: T he First Book of D olphins, pp 71-98 . Academic Pre ss, 416 pp. 

Perrin, W.F., G. P. Donov an and J. B arlow. 199 4a. 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 cra nial morph ology of the p antropica l spotted do lphin, Stenella a ttenuata, in the 

eastern Pacific. Fish. Bull. 92:324-346. 

Shallenberger, E.W. 1981. T he status of Hawaiia n cetacean s. Final report to U.S. Marine Mammal Commission. MMC77/23, 79pp. 

Wade, P. R. and R . P. Angliss. 19 97. Guid elines 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. 

186 
Revised 12/15/2000 

SPINNER DOLPHIN (Stenella longirostris): Hawaiian Stock 

STOCK DEFINITION AND GEOGRAPHIC RANGE 

Spinner dolphins are found throughout the 

world in tropical and warm-temperate 

waters (Perrin and Gilpatrick 1994). They 

are common and abundant throughout the 

e ntire Hawaii an archipelag o 

(Shallenberger 1981; Norris and Dohl 

1980; Norris et al. 1994). Recent sighting 

locations around the main Hawaiian 

Islands (Mobley et al. 2000) a re shown in 

Figure 1. There is some suggestion from an 

intensive study of spinner dolphins off the 

Kona Coast of Hawaii that the waters 

surrounding this island may have a large, 

relatively stable "resident" population 

(Norris et al. 1994). 

Hawaiian spinner dolphins belong to a 

stock that is separate fro m 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 occu rs pantrop ically 

(Perrin 1990). For the Marine Mammal 

Figure 1. Spinner dolphin sighting locations during 1993-98 

aerial surveys within about 25 nmi of the main Hawaiian 

Islands (see Appendix 2 for details on timing and location of 

survey effort). Outer line indicates approximate boundary of 

survey area. 

Protection Act (MMPA) stock assessment re ports, there is a sin gle Pacific manageme nt stock includ ing only 

animals found within the U.S. Exclusive Economic Zone of the Hawaiian Islands. Spinner dolphins involved 

in eastern tropical Pacific tuna purse-seine fisheries are managed separately under the MMPA. 

POPU LATIO N SIZE 

Although spinner dolphins are clearly am ong the mo st abundan t cetaceans in H awaiian wate rs, previously 

available populatio n estimates ap ply only to the west c oast of Ha waii. 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 ) photoid entified 677 individual sp inner dolp hins in the same area from 1 989 to 1992. Using the same 

estimation procedures as Norris et al. (1994), Östman (1994) estimated a population size of 2,334 for his study 

area along the Kona coast of Hawaii. As part of the Marine Mam mal Resea rch Prog ram of the A coustic 

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 w as recently calc ulated from the comb ined survey d ata (Mobley et al. 2000). This abundance 

underestimates the total number of spinner dolphins within the U.S. EEZ off Hawaii, because areas around the 

Northwest Hawaiian Islands (NWHI) and beyond 25 nautical miles from the main islands were not surveyed. 

Minimum Po pulation Estimate 

The log-normal 20th percentile of the combined 1993-98 abundance estimate is 2,355 spinner dolphins. As 

with the best abundance estimate above, this includes only areas within about 25 nmi of the main Hawaiian 

Islands and is therefore an underestimate. 

Current Population Trend 

No data on current population trend are available. 

187 
CURRENT AND M AXIMUM NET PRODUCTIVITY RATES 

No inform ation on cur rent or max imum net pr oductivity rate is c urrently availab le for the Ha waiian stock. 

POTENTIAL BIOLOGICAL REMOVAL 

The potential bio logical remo val (PB R) level for this stock is calculated as the minimum population size (2,355) 

times one half the default maximum net growth rate for cetaceans (1⁄2 of 4%) times a recovery factor of 0.50 (for 

a species of unknown status with no estimated fishery mortality; Wade and Angliss 1997), resulting in a PBR 

of 24 spinner dolphins per year. 

HUMAN -CAUSED MORTALITY AND SERIOUS INJURY 

Fishery Information 

Although some mortality of spinner dolphins has been observed in inshore gillnets, no estimate of annual


human-caused mortality and se rious injury is ava ilable. The gear types used in Hawaiian fisheries are


responsib le for marine mammal mortality and serious injury in o ther fisheries thro ughout U .S. waters. Gillnets


are used in Hawaiian waters and appear to capture marine mammals wherever they are used, and float lines from


lobster traps and longlines can be expected to occasionally entangle whales (Perrin et al. 1994).


Interactions with cetaceans have been


reported for all Hawaiian pelagic


fisheries, and there are records of


spinner dolphins tak en in inshore


monofilament gillnets and net fragments


in Hawaiian waters (Nitta and


Henderson 1993). One spinn er dolphin


was observed hooked in the Hawaiian


longline fishery between 1994 and 1998


in waters outsid e the U.S. E EZ, with


approx imately 4.4% o f all effort


(measured as the number of hooks


fished) observed . This interactio n rate


extrapolates to a total 5-year estimate of


23 (95% CI = 1-108) spinne r dolphins,


or an average of 4.6 interactions per


year (Kleiber 1 999). T he single


observed spinner do lphin was reported Figure 2. Locations of observed cetacean interactions in the


to have been hooked in the fluke. Hawaiian longline fishery, 1994-98 (modified from Kleiber


Following the guidelines of a 1997 1999). Dashed line is the U.S. Exclusive Economic Zone (EEZ);
 Serious Injury Workshop (Angliss and SL = spinner dolphin.
 DeMaster 1998), this animal would not


be considered seriously injured (defined


under the MM PA as likely to result in mortality). Reports for other odontocetes indicate they may also become


hooked in the mouth or ingest the hook, and they may occasionally become entangled in the fishing line.


Interaction rates between dolphins and the NWHI bottomfish fishery have been estimated based on studies


conducted in 1990-1993, indicating that an average of 2.67 dolphin interactions, most likely involving


bottlenose and rough-toothed dolphins, occurred for every 1000 fish brought on board (Kobayashi and


Kawam oto 1995). Fishermen claim interactions with dolphins who steal bait and catch are increasing. It is not


known whether these interactions result in serious injury or mortality of dolphins, nor whether spinner dolphins


are involved . 


Other Remov als 

188 
At least 85 spinner dolphins were live-captured in Hawaiian waters from 1962 to 1981 (Shallenberger 1981). 

The main capture area was around Oahu. 

STATUS OF STOCK 

The status of spinner dolphins in H awaiian wate rs relative to OSP is unknown, a nd there are insufficient data 

to evaluate trends in abundance. A habitat issue of increasing concern is the potential effect of swim-withdolphin programs and other tourism activities on spinner d olphins around the ma in Hawaiian Islands. Spinner 

dolphins are not listed as “threatened” or “endangered” under the Endangered Species Act (1973), nor as 

“deplete d” under the MMPA. The Hawaiian stock is not considered a strategic stock under the 1994 

amendm ents to the MM PA, bec ause there ar e no estimate s of mortality within the U.S. EEZ. However, there 

is no systematic monitoring of gillnet fisheries that may take this species, and the potential effect of interactions 

with the Hawaiian longline fishery in international waters is not kno wn. Insufficient inform ation is available 

to determine whether the total fishery mortality and serious injury for spinner dolphins is insignificant and 

approaching zero mortality and serious injury rate. 

REFERENCES 

Angliss, R. P. and D. P. DeMaster. 1998. Differentiating Serious and Non-Serious Injury of Marine Mammals Taken 

Incidental to Commercial Fishing Operations: Report of the Serious Injury Workshop 1-2 April 1997, Silver 

Spring, Maryland. U. S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-13. 48 pp. 

Dizon, A. E., W. F. Perrin, and P. A. Akin. 1994 . Stocks of dolphins (Stenella spp. and Delphin us delph is) in the eastern 

tropical Pacific: a phylogeographic classification. NOAA Tech. Rep. NMFS 119, 20 pp. 

Kleiber, P. 1999. Estimates of marine marine mammal takes in the Hawaiian longline fishery. (Unpub lished). Southwest 

Fisheries Science Center, NMFS, 2570 Dole St, Honolulu, HI, 96822-2396. 

Kobayashi, D. R. and K. E. Ka wamoto . 1995. E valuation of sh ark, dolph in, and mon k seal interactio ns with 

Northwestern Hawaiian Island bottomfishing activity: a comparison of two time periods and an estimate of 

economic impacts. Fisheries Research 23: 11-22. 

Mob ley, 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 . Hender son. 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. T he Hawa iian Spinner Dolphin . University of C alifornia 

Press, 408 pp. 

Norris, K. S. and T. P. Dohl. 1980. Behavior of the Hawa iian spinner d olphin, Stenella lo ngirostris . Fish. Bull. 77:821­

849. 

Östman, J. S. O. 19 94. Social organization a nd social behavior o f Hawaiian spinner dolp hins (Stenella longirostris). 

Ph.D. dissertation, University of California, Santa Cruz, 114 pp. 

Perrin, W. F. 1975. Varia tion of spotted and spinner p orpoise (genus Stenella ) in the eastern tropical Pacific and 

Hawaii. Bull. Scripps Inst. Oceanogr. 21, 206 pp. 

Perrin, W. F. 19 90. Subs pecies of Stenella longirostris (Mammalia: Cetacea: Delphinidae). Proc. Biol. Soc. Wash. 

103:453-463. 

Perrin, W. F. and J. W. Gilpatrick, Jr. 1994. Spinner dolphin Stenella lo ngirostris (Gray, 1828). In: S. H. Ridgway and 

R. Harrison (eds.), Han dbook of M arine Mamm als, Vol.5: The First Book o f Dolphins, p p. 99-12 8. Acade mic 

Press, 416 pp. 

Perrin, W.F., G. P. Donovan and J. Barlow. 1994. G illnets and Cetaceans. Rep. Int. Whal. Commn., Special Issue 15, 

629 pp. 

Shallenberger, E.W. 1981. T he status of Hawaiia n cetacean s. Final report to U.S. Marine Mammal Commission. MMC77/23, 79pp. 

189 
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. 

190 
Revised 12/15/2000 

STRIPED DOLPHIN (Stenella coeruleoalba): Hawaiian Stock 

STOCK DEFINITION AND GEOGRAPHIC RANGE 

Striped dolphins are found in tropic al to


warm-temp erate waters throughout the


world (Perrin et al. 1 994). T here is an


incongruity between the frequency of


strandings and the infrequency of sightings


of this species in Hawaii. Nitta (1991)


found more stranding records of striped


dolphins (13) than of any other species


between 1936 and 1988, yet Shallenberger


(1981) was aware of only two at-sea


sightings, one near Niihau and one west of


Oahu. A single sighting was made during


recent systematic surveys within about 25


nmi of the main Hawaiian Islands (Figure


1). The Sea Life Park collecting crew never


encountered striped dolphins from the early


1960s th rough the late 1970s, d uring their


live-capture operations (Shallenberger Figure 1. Location of the single sighting of striped dolphins


1981) . during 19 93-98 a erial surveys within about 25 nmi of the ma in


Striped dolphins ha ve been inte nsively Hawaiian Islands (see Appendix 2 for details on timing and


exploited in the western North Pacific, location of su rvey effort). Ou ter line indicates a pproxim ate


where three migratory stocks are boundary of survey area.


provisiona lly recognized (Kishiro and


Kasuya 1993). In the eastern Pacific all striped dolphins are provisionally considered to belong to a single stock


(Dizon et al. 1994 ). For the M arine Ma mmal P rotection A ct (MMPA) stock assessment reports, striped


dolphins within the Pacific U.S. Exclusive Economic Z one are divided into two discrete, non-contiguous areas:


1) waters off California, Oregon and Washington, and 2) waters around Hawaii (this report). Striped dolphins 

involved in eastern tropical Pacific tuna purse-seine fisheries are managed separately under the MMPA. 

POPU LATIO N SIZE 

Population estimates are a vailable for Japanese waters (Miyashita 1993) and the eastern tropical Pacific (Wade 

and Gerrod ette 1993 ), but it is not know n whether an y of these anima ls are part of the same population that 

occurs around th e Hawaiian Islands. As p art of the M arine Ma mmal Re search Pr ogram o f the Acoustic 

Thermometry of Ocean Climate (ATOC) study, a total of twelve aerial surveys were conducted within about 

25 nmi of the ma in Hawaiian Islands in 19 93, 199 5 and 19 98. An abundance estimate of 114 (CV=1.19) 

striped dolphins was recently calculated from the combined survey data (Mobley et al. 2000). This abundance 

underestimates the total number of striped dolphins within the U.S. EEZ off Hawaii, because areas around the 

Northwest Hawaiian Islands (NWHI) and beyond 25 nautical miles from the main islands were not surveyed. 

Minimum Po pulation Estimate 

No data are av ailable for a m inimum po pulation estim ate. The log-normal 20th percentile of the combined 

1993-98 abund ance estim ate is 52 striped dolphin s. As with the best abundance estimate above, this includes 

only areas within about 25 nmi of the main Hawaiian Islands and is therefore an underestimate. 

Current Population Trend 

No data are available on current population trend. 

191 
CURRENT AND M AXIMUM 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 (52) 

times one half the default maximum net growth rate for cetaceans (1⁄2 of 4%) times a recovery factor of 0.50 (for 

a species of unknown sta tus with no known fishery mortality; Wade and Angliss 1997), resulting in a PBR of 

0.5 striped dolphins per year. 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY 

Fishery Information 

No estimate of ann ual human-c aused mo rtality and serious injury is available as there are no reports of direct 

or incidental takes of striped dolphins in Hawaiian waters (Nitta and Henderson 1993). However, mortality of 

other cetacean species ha s been observed in Hawaiian fisheries, and the gear types used in these fisheries are 

responsib le for marine mammal mortality and serious injury in other fisheries throughout U.S. waters. Gillnets 

are used in Hawaiian waters and appear to capture marine mammals wherever they are used, and float lines from 

lobster traps and longlines can be expected to occasionally entangle whales (Perrin et al. 1994). 

Interactions with cetaceans have been reported for all Hawa iian pelagic fishe ries (Nitta and Henderson 1993), 

but no interactions with striped dolphins have been documented. None were observed hooked in the Hawaiian 

longline fishery between 1994 a nd 199 8, with appr oximately 4.4 % of all effort ( measured as the number of 

hooks fished) observed (Kleiber 1999). Interaction rates between dolphins and the NWH I bottomfish fishery 

have been estima ted based on studies co nducted in 1990-1 993, indic ating that an ave rage of 2.6 7 dolph in 

interactions, most likely involving bottlenose and rough-toothed dolphins, occurred for every 1000 fish brought 

on board (Kobayashi and Kawamoto 1 995). Fishermen claim interactions with dolphins who steal bait and 

catch are increasing . It is not known whether these interactions res ult in serious injury o r mortality of dolphins, 

nor whether striped dolphins are involved. 

STATUS OF STOCK 

The status of striped dolphins in Hawaiian waters relative to OSP is un known, and there are insufficie nt data 

to evaluate trends in abundance. No habitat issues are known to be of concern for this species. They are not 

listed as “threatened” or “endangered” under the Endangered Species Act (1973), nor as “depleted” under the 

MMPA. Although information on striped dolphins in Hawaiian waters is limited, this stock would not be 

considered strategic under the 1994 amendments to the MMPA given the absence of reported fisheries related 

mortality. Insufficient information is available to determine whether the total fishery mortality and serious 

injury for striped dolphins is insig nificant and ap proachin g zero mo rtality and seriou s injury rate. 

REFERENCES 

Dizon, A. E., W. F. Perrin, and P. A. Akin. 1994. Stock s of dolphins (Stenella spp. and Delphin us delph is) in the eastern 

tropical Pacific: a phylogeographic classification. NOAA Tech. Rep. NMFS 119, 20 pp. 

Kishiro, T. and T. Kasuya. 1993. R eview of Jap anese do lphin drive fishe ries and their sta tus. Rep. Int. Whal. Commn. 

43:439-452. 

Kleiber, P. 1999. Estimates of marine mammal takes in the Hawaiian longline fishery. (Unpub lished). Southwest 

Fisheries Science Center, NMFS, 2570 Dole St, Honolulu, HI, 96822-2396. 

Koba yashi, D. R. and K. E. Kawamoto. 19 95. Evalu ation of shark , dolphin, an d monk se al interactions w ith 

Northwestern Hawaiian Island bottomfishing activity: a comparison of two time periods and an estimate of 

economic impacts. Fisheries Research 23: 11-22. 

Miyashita, T. 199 3. Abund ance of do lphin 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 odonto cete species in Hawaiian waters: preliminary results of 1993-98 aerial surveys Admin. Rep. LJ-00­

192 
14C. Southwest Fisheries Science Center, N ational Marine Fisheries Service, P.O. Box 271, La Jolla, CA 

92038. 26 pp. 

Nitta, E. 1991 . The marine mammal stranding netw ork for H awaii: an ove rview. In: J.E. Reyno lds III, D.K . Odell 

(eds.), Marine Mammal Strandings in the United States, pp.56-62. NOAA Tech. Rep. NMFS 98, 157 pp. 

Nitta, E. and J. R. Henderson. 1993. A review of interactions between Hawaii's fisheries and protected species. Mar. 

Fish. Rev. 55(2):83-92. 

Perrin, W. F., C. E. Wilson, and F. I. Archer, II. 1994. Striped dolphin Stenella coeruleoalba (Meyen , 1833). In: S. 

H. Ridgway a nd R. Ha rrison (eds.), H andboo k of Marine Mam mals, Vol.5 : The First B ook of D olphins, pp 

129-159. Academic Press, 416 pp. 

Perrin, W.F., G. P. Donovan and J. Barlow. 1994. Gillnets and Cetaceans. Rep. Int. Whal. Commn., Special Issue 15, 

629 pp. 

Shallenberger, E.W. 1981. T he status of Hawaiian cetaceans. Final report to U.S. Marine Mammal Commission. MMC77/23, 79pp. 

Wade, P. R. and R. P. Angliss. 1997. Guidelines for Assessing Marine Mammal Stocks: Report of the GAMMS 

Workshop April 3-5, 1996, Seattle, Washington. U. S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-12. 

93 pp. 

Wade, P. R. and T. Gerrodette. 1993. Estimates of cetacean abundance and distribution in the eastern tropical Pacific. 

Rep. Int. Whal. Commn. 43:477-493. 

193 
Revised 12/15/2000 

MELON-HEADED WHALE (Peponocephala electra): Hawaiian Stock 

STOCK DEFINITION AND GEOGRAPHIC RANGE 

Melon-headed whales are fo und in tropical 

and warm-temp erate waters throughout the 

world. The distribution of reported 

sightings suggests that the oceanic habitat 

of this species is primarily equatorial 

waters (Perryma n et al. 1994 ). Small 

numbers have been taken in the eastern 

tropical Pacific, and they are occ asionally 

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 K ohala coa st of Hawaii, 

and the leeward coast of Lanai 

(Shallenberger 1981). Recent sighting 

locations around the main Hawaiian 

Islands (Mobley et al. 2000) are shown in 

Figure 1. Little is known about this species 

elsewhere in its range, and most knowledge 

about its biology comes from ma ss 

strandings (Perryman et al. 1994). Ten 

strandings are known from Ha waii 

(Nishiwaki and Norris 1966; Shallenberger 

Figure 1. Melon-headed whale sighting locations during 

1993-9 8 aerial surve ys within about 2 5 nmi of the m ain 

Hawaiian Islands (see Appendix 2 for details on timing and 

location of su rvey effort). Ou ter line indicates a pproxim ate 

boundary of survey area. 

1981; Nitta 1991). For the Marine Mammal Protection Act (MMPA) stock assessment re ports, there is a single 

Pacific management stock including only animals found within the U.S. Exclusive Economic Zone of the 

Hawaiian Islands. 

POPU LATIO N SIZE 

An estimate of melon-headed whales is available for the eastern tropical Pacific (Wade and Gerrodette 1993), 

but it is not known whether any of these animals are part of the same population that occurs around the 

Hawaiian Islands. As part of the Marine Mammal Research Pro gram of the Acoustic Thermometry of Ocean 

Climate (ATOC) study, a total of twelve aerial surveys were co nducted w ithin about 25 nmi of the ma in 

Hawaiian Islands in 1993, 1995 and 1998. An abundance estimate of 154 (CV=0.88) melon-headed whales 

was recently calculated from the combined survey data (Mobley et al. 2000). This abundance underestimates 

the total number of melon-headed whales within the U.S. EEZ o ff Hawaii, because areas aro und the Northwest 

Hawaiian Islands (NWHI) and beyond 25 nautical miles from the main islands were not surveyed. 

Minimum Po pulation Estimate 

The log-normal 20th percentile of the combined 1993-98 abundance estimate is 81 melon-he aded wh ales. As 

with the best abund ance estim ate abov e, this includ es only ar eas within about 2 5 nmi o f the main Hawaiian 

Islands and is therefore an underestimate. 

Minimum Po pulation Estimate 

No data are available for making a minimum p opulation e stimate. 

Current Population Trend 

No data are available on current population trend. 

194 
CURRENT AND M AXIMUM 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 (81) 

times one half the default maximum net growth rate for cetaceans (1⁄2 of 4%) times a recovery factor of 0.50 (for 

a species of unknown sta tus with no known fishery mortality; Wade and Angliss 1997), resulting in a PBR of 

0.8 melon-headed whales per year. 

HUMAN -CAUSED MORTALITY AND SERIOUS INJURY 

Fishery Information 

Melon -headed w hales are no t known to be taken directly or incid entally in Haw aiian waters an d no mo rtality 

of this species has been documented in Hawaiian fisheries (Nitta and H enderson 1993). H owever, m ortality 

of other cetacean species has been observed in Hawaiian fisheries, and the gear types used in these fisheries are 

responsib le for marine mammal mortality and serious injury in other fisheries throughou t U.S. waters. G illnets 

are used in Hawaiian waters and appear to capture marine mammals wherever they are used, and float lines from 

lobster traps and longlines can be expected to occasionally entangle whales (Perrin et al. 1994). 

Interactions with cetaceans have been reported for all Hawaiian pelagic fisheries (Nitta and Henderson 1993), 

but no interactions with melon-headed whales have been documented. None were observed hooked in the 

Hawaiian longline fishery between 1994 and 1998, with approximately 4.4% of all effort (measured as the 

number of hooks fished) observed (Kleiber 1999). Interaction rates between dolphins and the NWH I bottomfish 

fishery have been estimated b ased on stud ies conduc ted in 199 0-1993 , indicating that an average of 2.67 

dolphin interactions, most likely involving bottlenose and rou gh-toothed dolphins, occurred for every 1000 fish 

brought on board (Kobayashi and Kawam oto 1995). Fishermen claim interactio ns with dolphins w ho steal bait 

and catch are increasing. It is not known whether these interactions result in serious injury or mortality of 

dolphins, nor whether melon-headed whales are involved. 

Historical Mortality 

Peale (1848) reported that 60 whales of this species were driven ashore by n atives in Hilo Bay, Hawaii in 1841. 

At least three melon-headed whales were live-captured for public display between 1966 and 1978 

(Shallenberger 1981). 

STATUS OF STOCK 

The status of melon-headed whales in Ha waiian waters re lative to OSP is unknown, and there are insufficient 

data to evaluate trends in abundance. No habitat issues are known to be of concern for this species. They are 

not listed as “threatened” or “endangered” under the Endangered Species Act (1973), nor as “depleted” under 

the MMP A. Although information o n melon-he aded wh ales in Haw aiian waters is limited, this stock would not 

be considered strategic under the 1994 amendments to the MMPA given the absence of reported fisheries 

related mortality. Insufficient information is available to determine whether the total fishery mortality and 

serious injury for melo n-headed whales is insignificant and approaching zero mortality and serious injury rate. 

REFERENCES 

Kleiber, P. 1999. Estimates of marine mammal takes in the Hawaiian lon gline fishery. (Unpublished). Southwe st 

Fisheries Science Center, NMFS, 2570 Dole St, Honolulu, HI, 96822-2396. 

Koba yashi, D. R. and K. E. Kawamoto. 19 95. Evalu ation of shark , dolphin, an d monk se al interactions w ith 

Northwestern Hawaiian Island bottomfishing activity: a comparison of two time periods and an estimate of 

economic impacts. Fisheries Research 23: 11-22. 

Mob ley, 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 1993-9 8 aerial surve ys Admin. Rep. LJ-00­

14C. Southwest F isheries Scien ce Center, N ational M arine Fisheries Service, P.O. Box 271, La Jolla, CA 

92038. 26 pp. 

195 
Nishiwaki, M. and K. S. Norris. 1966. A new gen us, Pepon oceph ala, for the odontocete cetace an species Electra electra . 

Sci. Rep. Whales Res. Inst. 20:95-100. 

Nitta, E. 1991 . The marine mammal stranding netw ork for H awaii: an ove rview. In: J.E. Reyno lds III, D.K . Odell 

(eds.), Marine Mammal Strandings in the United States, pp.56-62. NOAA Tech. Rep. NMFS 98, 157 pp. 

Nitta, E. and J. R. Henderson. 1993. A review of interactions between Hawaii's fisheries and protected species. Mar. 

Fish. Rev. 55(2):83-92. 

Peale, T. R. 1848. United States Exploring Expedition. During the Years 1838, 1839, 1840, 1841, 1842. Under the 

Command of Charles Wilkes, U.S.N. Vol. VIII. Mamm alia and Ornithology. C Sherman, Philadelphia, 338 

pp. 

Perrin, W.F., G. P. Donovan and J. Barlow. 1994. Gillnets and Cetaceans. Rep. Int. Whal. Commn., Special Issue 15, 

629 pp. 

Perryman, W. L., D. W. K. Au, S. Leatherwood, and T. A. Jefferson. 1994. Melon-headed whale Pepon oceph ala 

electra Gray, 1846. In: S. H. Ridgway and R. Harrison (eds.), Handbook of Marine Mamma ls, Vol.5: The First 

Book of Dolphins, pp. 363-386. Academic Press, 416 pp. 

Shallenberger, E.W. 1981. The status of Hawaiian cetaceans. Final report to U.S. Marine Mammal Commission. MMC77/23, 79pp. 

Wade, P. R. and R. P. Angliss. 1997. Guidelines for Assessing Marine Mammal Stocks: Report of the GAMMS 

Workshop April 3-5, 1 996, Se attle, Wash ington. U. S. D ep. Com mer., NOAA Tech. Memo. NMFS-OPR-12. 

93 pp. 

Wade, P. R. and T. Gerrodette. 1993. Estimates of cetacean abundance and distribution in the eastern tropical Pacific. 

Rep. Int. Whal. Commn. 43:477-493. 

196 
Revised 12/15/2000 

PYGMY KILLER WHALE (Feresa attenuata): Hawaiian Stock 

STOCK DEFINITION AND GEOGRAPHIC RANGE 

Pygmy killer whales are found in tropical and subtropical waters throughout the world (Ross and Leatherwood 

1994). They are p oorly know n in most par ts of their range. S mall numbers have been taken directly and 

incidentally in both the western and eastern Pacific. Most knowledge of this species is from stranded or livecaptured specimens. Pryor et al. (1965) stated that pygm y killer whales hav e been ob served sev eral times off 

the lee shore o f Oahu, and that "they seem to be regula r residents of the Hawaiian area." Although all sightings 

up to that time had been off O ahu and the Big Island, Shallenberger (1981) stated that this species might be 

found elsewhere in Hawaii, as we ll. No pygm y killer whales wer e seen durin g 1993 -98 aerial surv eys within 

about 25 nmi of the main Hawaiian Islands (M obley et al. 2000; see Appendix 2 for detailed information on 

timing and location of effort), suggesting that they are uncommon in these nearshore regions. Nitta (1991) 

documented five strandings from Maui and the island of Hawaii. For the Marine Mammal Protection Act 

(MMPA) stock assessment reports, there is a single Pacific management stock including only animals found 

within the U.S . Exclusive E conom ic Zone of the Hawaiian Islands. 

POPU LATIO N SIZE 

A population estimate has been made for this species in the eastern tropical Pacific (Wad e and Ge rrodette 

1993), but no data are available to estimate population size in any other area of the North Pacific. As part of 

the Marine Mammal Research Program of the Acoustic Thermometry of Ocean Climate (ATOC) study, a total 

of twelve aerial surveys were conducted within about 25 nmi of the main Hawaiian Islands in 1993, 1995 and 

1998 (Mob ley et al. 2000 ). No sightings of pygmy killer w hales were m ade, and therefore no abundance 

estimate for nearshore Hawaiian waters is presently available. It is likely that pygmy killer whales occur 

primarily in pelagic waters greater than 25 n mi from the main Haw aiian islands. 

Minimum Po pulation Estimate 

No data are available for a minimum population estimate. 

Current Population Trend 

No data are available on current population trend. 

CURRENT AND M AXIMUM NET PRODUCTIVITY RATES 

No data are available on current or maximum net productivity rate. 

POTENTIAL BIOLOGICAL REMOVAL 

No PBR can be calculated for this species at this time. 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY 

Fishery Information 

No estimate of annual human-caused mortality and serious injury is available as there are no reports of direct 

or incidental takes of pygmy killer whales in Ha waiian waters. H owever, m ortality of other cetacean species 

has been observed in Hawaiian fisheries, and the gear types used in these fisheries are responsible for marine 

mammal mortality and serious injury in other fisheries throughout U.S. waters. Gillnets are used in Hawaiian 

waters and app ear to capture marine mammals wherever they are used, and float lines from lobster traps and 

longlines can be expected to occasionally entangle whales (Perrin et al. 1994). 

Interactions with cetaceans have been reported for all Hawa iian pelagic fishe ries (Nitta and Henderson 1993), 

but no interactions with pygmy killer whales have been documented. None were observed hooke d in the 

Hawaiian longline fishery between 1994 and 1998, with approximately 4.4% of all effort (measured as the 

number of hooks fished) observed (K leiber 1999). Interaction ra tes between dolphins and the NWH I bottomfish 

197 
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 rou gh-toothed dolphins, occurred for every 1000 fish 

brought on board (Koba yashi and K awamoto 1995). F ishermen cla im interactions with dolphins w ho steal bait 

and catch are in creasing. It is not known whether these interactions result in serious injury or mortality of 

dolphins, nor whether pygmy killer whales are involved. 

Other Remov als 

Three specimens were live-captured by Sea Life Park between 1963 and 1971 (Pryor et al. 1965; Pryor 1975; 

Shallenberger 1981). 

STATUS OF STOCK 

The status of pygmy k iller whales in Hawaiian waters relative to OSP is unknown, a nd there are insufficient data 

to evaluate trend s in abundance. No habitat issues are known to be of concern for this species. T his species is 

not listed as “threatened” or “endangered” under the Endangered Species Act (1973), nor as “depleted” under 

the MMPA . Although information on pygmy killer whales in Hawaiian waters is limited, this stock would not 

be considered strategic under the 1994 amendments to the MMPA given the absence of reported fisheries 

related mortality. Insufficient information is available to determine whether the total fishery mortality and 

serious injury for pygmy killer whales is insignificant and approaching zero mortality and serious injury rate. 

REFERENCES 

Kleiber, P. 1999. Estimates of m arine mammal takes in the H awaiian longline fishery. (Unpublished). So uthwest 

Fisheries Science Center, NMFS, 2570 Dole St, Honolulu, HI, 96822-2396. 

Koba yashi, D. R. and K. E. Ka wamoto . 1995. E valuation of sh ark, dolph in, and mon k seal interactio ns with 

Northwestern Hawaiian Island bo ttomfishing activity: a comparison of two time periods and an estimate of 

economic impacts. Fisheries Research 23: 11-22. 

Mob ley, J. R. , Jr, S. S. Sp itz, K. A. Fo rney, R. A. G rotefendt, an d P. H. F orestall. 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, C A 

92038. 26 pp. 

Nitta, E. 1991. The marine mammal stranding network for Hawaii: an overview. In: J.E. Reyno lds III, D.K . Odell 

(eds.), Marine Mammal Strandings in the United States, pp.56-62. NOAA Tech. Rep. NMFS 98, 157 pp. 

Nitta, E. and J. R. Henderson. 1993. A review of interactions between Hawaii's fisheries and protected species. Mar. 

Fish. Rev. 55(2):83-92. 

Perrin, W.F., G. P. Donovan and J. Barlow. 1994. Gillnets and Cetaceans. Rep. Int. Whal. Commn., Special Issue 15, 

629 pp. 

Pryor, K. 1975. Lads Before the Wind: Adventures in Porpoise Training. Harper and Row, New York, 278 pp. 

Pryor, T., K. Pryor and K. S. No rris. 1965. O bservation s on a pygmy killer whale (Feresa a ttenuata Gray) from Hawaii. 

J. Mamm. 46:450-461. 

Ross, G. J. B. and S. Leatherwood. 1994. Pygmy killer whale Feresa a ttenuata Gray, 1874. In: S. H. Ridgway and R. 

Harrison (eds.), Handbook of Marine Mammals, Vol.5: The First Book of Dolph ins, pp.387 -404. Aca demic 

Press, 416 pp. 

Shallenberger, E.W. 1981. T he status of Hawaiian cetaceans. Final report to U.S. Marine Mammal Commission. MMC77/23, 79pp. 

Wade, P. R. and T. Gerrodette. 1993. Estimates of cetacean abundance and distribution in the eastern tropical Pacific. 

Rep. Int. Whal. Commn. 43:477-493. 

198 
Revised 12/15/2000 

FALSE KILLER WHALE (Pseudorca crassidens): Hawaiian Stock 

STOCK DEFINITION AND GEOGRAPHIC RANGE 

False killer whales are found worldwide 

mainly in tropical and w arm-temp erate 

waters (Stacey et al. 199 4). In the No rth 

Pacific, this species is well kn own from 

southern Japan, Hawaii, and the e astern 

tropical Pacific. It occurs around all the 

main Hawaiian Islands, but its presence 

around the Northwestern Hawaiian Islands 

has not yet been established (Nitta and 

Henderson 1993). Recent sighting 

locations around the main Hawaiian 

Islands (M obley et al. 20 00) are sho wn in 

Figure 1. There are only 4 stranding 

records from Haw aiian waters (N itta 

1991). Large numbers of false killer 

whales have been taken in direct fisheries 

in southern Japan, and small numbers have 

been taken inciden tal to fishing operations 

in the eastern tro pical Pacific. Most 

knowledge about this species comes from 

outside Hawaiian waters (Stace y et al. 

1994). For the Marine Mammal 

Protection Act (MMP A) stock assessment 

Figure 1. False killer whale sighting locations during 1993-98 

aerial surveys within about 25 nmi of the main Hawaiian 

Islands (see Appendix 2 for details on timing and location of 

survey effort). Outer line indicates approximate boundary of 

survey area. 

reports, there is a single Pacific management stock including only animals found within the U.S. Exclusive 

Economic Z one of the Hawaiian Island s. 

POPU LATIO N SIZE 

Population estimates for this species have been made from shipboard surveys in Japan (Miyashita 1993) and 

the eastern tropical Pa cific (Wa de and G errodette 1 993), bu t it is not known whether these animals are part of 

the same population that occurs around the Hawaiian Islands. As part of the Marine Mammal Research 

Program of the Acoustic Thermometry of Ocean Climate (ATOC) study, a total of twelve aerial surveys were 

conducted within about 25 nmi of the main Hawaiian Islands in 19 93, 199 5 and 19 98. An ab undance estimate 

of 121 (CV=0.47) false killer whales w as recently calc ulated from the comb ined survey d ata (Mo bley et al. 

2000). This abundance underestimates the total number of false killer whales within the U.S. E EZ off Ha waii, 

because areas around the N orthwest Hawaiian Islands (N WHI) a nd beyond 25 nautical miles from the main 

islands were not surveyed. 

Minimum Po pulation Estimate 

The log-normal 20th percentile of the combined 1993-98 abundance estimate is 83 false killer whales. As with 

the best abundance estimate above, this include s only are as within a bout 25 nmi of th e main Hawaiian Islands 

and is therefore an underestimate. 

Current Population Trend 

No data are available on current population trend. 

CURRENT AND M AXIMUM NET PRODUCTIVITY RATES 

No data are ava ilable on current or maximu m net productivity rate for this species in Haw aiian waters. 

199 
POTENTIAL BIOLOGICAL REMOVAL 

The potential biological removal (PBR) level for this stock is calculated as the minimum population size (83) 

times one half the default maximum net growth rate for cetaceans (1⁄2 of 4%) times a recovery factor of 0.50 (for 

a species of unknown status with no known fishery m ortality; Wade and Angliss 1997), resulting in a PBR of 

0.8 false killer wh ales per year . 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY 

Fishery Information 

Mortality of other cetacean species has been observed in Hawaiian fisheries, and the gear types used in these 

fisheries are responsible for marine mammal mortality and serious injury in other fisheries throughout U.S. 

waters. Gillnets are used in Ha waiian waters a nd appe ar to capture marine mammals wherever they are used, 

and float lines from lobster traps and 

longlines can be expected to 

occasio nally entangle whales (Perrin et 

al. 1994). Interactions with cetaceans 

have been reported for all Hawaiian 

pelagic fisheries, and false killer whales 

have been identified in fishermen's logs 

as taking catches from pelag ic longlines 

(Nitta and Henderson 1993). T hey have 

also been observed feeding on mahi 

mahi, Coryphaena hippurus, and 

yellowfin tuna, Thunnus albacares, and 

frequently steal large fish (up to 70 

pounds) (Shallenberger 1981) from the 

trolling lines of both co mmercial and 

recreational fishermen (S. Kaiser, pers. 

comm.). 

Two false killer whales were observed 

hooked in the Hawaiian longline fishery Figure 2. Locations of observed cetacean interactions in the between 1994 and 1998 w ithin the U.S. Hawaiian longline fishery, 1994-98 (modified from Kleiber

EEZ (Figure 2), w ith approx imately 1999). Dashed line is the U.S. Exclusive Economic Zone (EEZ); 4.4% of all effort (measured as the PC = false killer whale. number of hooks fished) observed. This


interaction rate extrapolates to a total 5­


year estimate of 45 (95% C I = 7-146 ) false killer whales, o r an averag e of 9 interac tions per ye ar (Kleiber


1999). Both of the observed false killer whales were reported to have been hooked in the mouth or to have


ingested the hook, an d they were re leased with trailing gear. Reports for other odontocetes indicate they may


also become hooked in other parts o f their body, and that they may occasionally become entangled in the fishing


line. Following the guidelines of a 1997 Serious Injury Workshop (Angliss and DeMaster 1998), the two


observed false killer whales have been considered seriously injured (defined un der the M MPA as likely to result


in mortality), and , therefore, the inte raction rate o f 9 animals per year represents an estimate of mortality and


serious injury fo r this stock. 


Interaction rates betwee n dolphins and the NWH I bottomfish fishery have been estimated based on studies


conducted in 1990-1 993, indic ating that an average of 2.67 dolphin interactions, most likely involving


bottlenose and rough-toothed d olphins, occurred for eve ry 1000 fish brought on board (Kobayashi and


Kawam oto 1995). Fishermen claim interactions with dolphins who steal bait and catch are increasing. It is not


known whether these interactions result in serious injury or mortality of dolphins, nor whether false killer


whales are inv olved. 


Other Remov als 

200 
Since the early 1960's, at least 12 false killer whales have been live-captured by aquaria or the Navy (Pryor 

1975; Shallenberger 1981; J. Thomas pers. comm .). 

STATUS OF STOCK 

The status of false killer whales in Hawaiian waters relative to OSP is unknown, and there are insufficient data 

to evaluate trend s in abunda nce. No h abitat issues are known to be of conc ern for this species. They are not 

listed as “threatened” or “endangered” under the Endangered Species Act (1973), nor as “depleted” under the 

MMPA. Because the rate of serious injury to false killer whales within the U.S. EEZ in the Hawaiian longline 

fishery (9 animals p er year) exce eds the PB R (0.8), this sto ck is considered a strategic stock under the 1994 

amendm ents to the MM PA. Th e total fishery mo rtality and seriou s injury canno t be consid ered to be 

insignificant and approaching zero, because it exceeds the PBR. However, the available abundance estimate, 

on which PB R is based, ap plies only to a p ortion of this sp ecies’ range w ithin the U.S. EEZ around Hawaii, and 

additional studies of abundance, distribution, and fishery-related mortality and injury of false killer whales in 

Hawaiian waters will be required to re-evaluate this species’ status in the future. 

REFERENCES 

Angliss, R. P. and D. P. DeMaster. 1998. Differentiating Serious and Non-Serious Injury of Marine Mammals Taken 

Incidental to Commercial Fishing Operations: Report of the Serious Injury Workshop 1-2 April 1997, Silver 

Spring, Maryland. U. S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-13. 48 pp. 

Kleiber, P. 1999. Estima tes of marine mamma l takes in the Hawaiian longline fishery. (Unpublished). Southw est 

Fisheries Science Center, NMFS, 2570 Dole St, Honolulu, HI, 96822-2396. 

Koba yashi, D. R. and K. E. Kawamoto. 199 5. Evaluation of shark, dolphin, and monk seal interactio ns with 

Northwestern Hawaiian Island bottomfishing activity: a comparison of two time periods and an estimate of 

economic impacts. Fisheries Research 23: 11-22. 

Miyashita, T. 1993. Abundance of dolphin sto cks in the wester n North P acific taken by the Japanese drive fishery. Rep. 

Int. Whal. Commn. 43:417-437. 

Mob ley, 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 mamm al stranding ne twork for H awaii: an ove rview. In: J.E. Reyno lds 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. G illnets and Ce taceans. Re p. Int. Wh al. Commn., Special Issue 15, 

629 pp. 

Pryor, K. 1975. Lads Before the Wind: Adventures in Porpoise Training. Harper and Row, New York, 278 pp. 

Shallenberger, E.W. 1981. The status of Hawaiian cetaceans. Final report to U.S. Marine Mammal Commission. MMC77/23, 79pp. 

Stacey, P. J., S . Leatherwo od, and R . W. Ba ird. 1994 . Pseudorca crassidens. Mamm. Spec. 456:1-6. 

Wade, P. R. and R. P. Angliss. 1997. Guidelines for Assessing Marine Mammal Stocks: Report of the GAMMS 

Workshop April 3-5, 1996, Seattle, Washington. U. S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-12. 

93 pp. 

Wade, P. R. and T. Gerrodette. 1993. Estimates of cetacean abundance and distribution in the eastern tropical Pacific. 

Rep. Int. Whal. Commn. 43:477-493. 

201 
Revised 12/15/2000 

KILLER WHALE (Orcinus orca): Hawaiian Stock 

STOCK DEFINITION AND GEOGRAPHIC RANGE 

Killer whales have been observed in all oceans and seas of the world (Leatherwood and Dahlheim 1978). 

Although reported from tropical and offshore waters (Heyning and Dahlheim 1988), killer whales prefer the 

colder waters of bo th hemispher es, with greatest ab undance s found within 8 00 km o f major co ntinents (Mitchell 

1975). They are rare in Hawaiian waters. No killer whales were seen during 1993-9 8 aerial surve ys within 

about 25 nmi of the main Hawaiian Islands (Mobley et al. 2000; see Appendix 2 for detailed information on 

timing and location of effort), suggesting that they are uncommon in these nearshore regions. One stranding 

from the island of Hawaii was reported in 1950 (Richards 1952). Two sightings have been reported, one in 

January 1978 off the W aianae Coast of Oahu and another in December 1979 near Kauai (Shallenberger 1981). 

Except in the northeastern Pacific where "resident", "transient", and “offshore” stocks have been described for 

coastal waters of Alaska, British Columbia, and Washington to California (Bigg 1982; Leatherwood et al. 1990, 

Bigg et al. 1990, Ford et al. 1994), little is known about stock structure of killer whales in the North Pacific. 

For the Marine Mammal Protection Act (MM PA) stock assessment reports, five killer whale stocks are 

recognized within the Pacific U.S. EEZ 1) the Eastern North Pacific Northern Resident stock - occurring from 

British Columbia through Alaska, 2) the Eastern North Pacific Southern Resident stock - occurring within the 

inland waters of Washington State and southern British Columbia, 3) the Eastern North Pacific Transient stock ­

occurring from Alaska through California, 4) the Eastern North Pacific Offshore stock - occurring from 

Southeast Alaska through California, and 5) the Hawaiian stock (this repo rt). The Sto ck Assessm ent Repo rts 

for the Alaska Region contains the assessment of the Eastern North Pacific Northern Resident stock; all other 

killer whale stoc k assessmen ts are included in this report. 

POPU LATIO N 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 po pulation of killer whales in the ea stern tropica l Pacific 

has been estima ted from ship board sig htings surveys (W ade and Gerrod ette 1993 ). No data to estimate 

population size are available for the central Pacific. As part of the Marine Mammal Research Program of the 

Acoustic Thermometry of Ocean Climate (ATO C) study, a total of twelve aerial surveys were conducted within 

about 25 nmi of the main Hawaiian Islands in 1993, 1995 and 1998 (Mobley et al. 2000). No sightings of killer 

whales were made, and therefore no abundan ce estimate fo r Hawaiian waters is prese ntly available. 

Minimum Po pulation Estimate 

No data are available to provide a minimum population estimate. 

Current Population Trend 

No data are available on current population trend. 

CURRENT AND M AXIMUM NET PRODUCTIVITY RATES 

No data are ava ilable on current and max imum net produc tivity rate in Hawaiian waters. 

POTENTIAL BIOLOGICAL REMOVAL 

No PBR can be calculated for this stock at this time. 

HUMAN -CAUSED MORTALITY AND SERIOUS INJURY 

Fishery Information 

No estimate of annual human-caused mortality and serious injury is available for killer whales in Hawaiian 

waters (Nitta and Hend erson 1993). How ever, morta lity of other cetac ean specie s has been o bserved in 

Hawaiian fisheries, and the gear types used in these fisheries are responsible for marine mammal mortality and 

202 
serious injury in other fisheries throug hout U.S. w aters. Gillnets are used in Ha waiian waters a nd appe ar to 

capture marine mammals wherever they are used, and float lines from lobster traps and longlines can be 

expected to occasio nally entangle wh ales (Perrin et al. 1994 ). 

Interactions with cetaceans have been rep orted for all H awaiian pela gic fisheries (Nitta and Henderson 1993), 

but killer whale interactions appear to be rare. In 1990, a solitary killer whale was reported to have removed 

the catch from a longline in Hawaii (Dollar 1991). None were observed hoo ked in the Hawaiian longline fishery 

between 1994 and 1998, with approximately 4.4% of all effort (measured as the number of hooks fished) 

observed (Kleiber 1999). Interaction rates between dolphins and the NWHI bottomfish fishery have been 

estimated based on studies conducted in 1990-1993, indicating that an average of 2.67 dolphin interactions, 

most likely involving bottlenose and rough-toothed dolphins, occurred for every 1000 fish brought on board 

(Kobayashi and Kaw amoto 1 995). Fish ermen claim interactions with dolphins who steal bait and catch are 

increasing. It is not known w hether these inte ractions resu lt in serious injury o r mortality of dolphins, nor 

whether killer whales are involved. 

STATUS OF STOCK 

The status of killer whales in Hawaiian waters relative to OS P is unknow n, and there a re insufficient data to 

evaluate trends in abundance. No habitat issues are known to be of concern for this species. This species is not 

listed as “threatened” or “endangered” under the Endangered Species Act (1973), nor as “depleted” under the 

MMPA. Although info rmation on killer whales in Hawaiian waters is limited, this stock would not be 

considere d strategic und er the 199 4 amend ments to the MMPA given the insignificance of reported fisheries 

related mortality. Insufficient information is available to determine whether the total fishery mortality and 

serious injury for killer whales is insignificant and approaching zero mortality and serious injury rate. 

REFERENCES 

Bigg, M. A. 1982. An assessment of killer whale (Orcinus orca) stocks off Vancouver Island, British Columbia. Rep. 

Int. Whal. Commn. 32:655-666. 

Bigg, M. A., P. F. Olesiuk, G. M. Ellis, J. K. B. Ford, and K. C. Balcomb, III. 1990. Social organization and genealogy 

of resident killer whales (Orcinus orca) in the coastal w aters of British C olumbia 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. T he natural histo ry and gene alogy of Orcinus orca 

in British Columbia and Washington State. UBC Press, Vancouver, Canada 

Kleiber, P. 1999. Estimates of marine mammal takes in the Hawaiian longline fishery. (Unpu blished). Southwest 

Fisheries Science Center, NMFS, 2570 Dole St, Honolulu, HI, 96822-2396. 

Kobayashi, D. R. and K. E. Kawamoto. 1995. Evaluation of shark, dolphin, and monk seal interactions with 

Northwestern Hawaiian Island botto mfishing activity: a co mparison of two time periods and an estimate of 

economic impacts. Fisheries Research 23: 11-22. 

Leatherwood, J. S., and M. E. Dahlheim. 197 8. Worldw ide distribution of pilot whales and killer whales. Naval Ocean 

Systems Center, Tech. Rep. 443:1-39. 

Heyning, J. E . and M. E . Dahlheim . 1988. Orcinus orca. Mamm. Spec.304:1-9. 

Leatherwood, S., C. O. Matkin, J. D. Hall, and G. M. E llis. 1990. K iller whales, Orcinus orca, photo-ide ntified in 

Prince William Sound, Alaska, 1976 through 1987. Can Field-Nat. 104:362-371. 

Mitchell, E. D. 1975. Report on the meeting on small cetaceans, Montreal, April 1-11, 1974. J. Fish. Res. Board 

Canada, 32:914-916. 

Mob ley, J. R. , Jr, S. S. Spitz, K. A. Forney, R. A. Grotefendt, and P. H. Forestall. 2000. Distribution and abundance 

of odontocete species in Hawaiian waters: preliminary results of 1993-98 aerial surveys Admin. Rep. LJ-99-

XXC. Southwest Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA 

92038. 26 pp. 

Nitta, E. and J. R. Henderson. 1993. A review of interactions between Hawaii's fisheries and protected species. Mar. 

Fish. Rev. 55(2):83-92. 

203 
Perrin, W.F., G. P. Donovan and J. Barlow. 1994. Gillnets and Cetaceans. Rep. Int. Whal. Commn., Special Issue 15, 

629 pp. 

Richards, L. P. 1952. Cuvier's beaked whale from Hawaii. J. Mamm. 33:255 . 

Shallenberger, E.W. 1 981. T he status of H awaiian cetac eans. Final rep ort to U.S. Marine Mamm al Commission. MMC77/23, 79pp. 

Wade, P. R. and T . Gerrod ette. 1993 . Estimates of ce tacean ab undance and distribu tion in the eastern tropical Pacific. 

Rep. Int. Whal. Commn. 43:477-493. 

204 
Revised 12/15/2000 

SHORT-FINNED PILOT WHALE (Globicephala macrorhynchus): 

Hawaiian Stock 

STOCK DEFINITION AND GEOGRAPHIC RANGE 

Short-finned pilot whales ar e found in all


oceans, primarily in tropical and warm­


temperate waters. The y are comm only


observed around the main Hawaiian Islands


and are probably also present around the


N o rthwestern Hawaiian Island s


(Shallenberger 1981). Recent sighting


locations around the main Hawaiian Islands


(Mobley et al. 2000) are shown in Figure 1.


Several mass strandings have been reported


from the main island s (Tom ich 1986 ; Nitta


1991). In Japanese waters, two stocks have


been identified based on pigmentation


patterns and differences in the shape of the


heads of adult male s (Kasuya e t al. 1988).


The pilot whales in Hawaiian waters are


similar to the Japa nese "sou thern form." Figure 1. Short-finned pilot whale sighting locations during
 Stock structure of short-finned pilot whales 1993-9 8 aerial surve ys within about 2 5 nmi of the m ain


has not been adequately studied in the Hawaiian Islands (see Appendix 2 for details on timing and
 North Pacific, except in Japanese waters. location of su rvey effort). Ou ter line indicates a pproxim ate


Preliminary photo-identification work with boundary of survey area.
 pilot whales in Hawaii indicated a high


degree of site fidelity around the m ain


island of Hawaii (Shane and McSweeney 1990). For the Marine Mammal Protection Act (MMPA) stock


assessment reports, short-finned pilot whales within the Pacific U.S. Exclusive Economic Zone are divided into


two discrete, non-contiguous areas: 1) Hawaiian waters (this report), and 2) waters off California, Oregon and


Washington.


POPU LATIO N SIZE 

Estimates of short-finned pilot whale populations have been made off Japan (Miyashita 1993) and in the eastern 

tropical Pacific (Wade and Gerrod ette 1993), but it is not known whether any of these animals are part of the 

same population that occurs around the Hawaiian Islands. As part of the Marine Mammal Research Program 

of the Acoustic Thermometry of Ocean Climate (ATOC) study, a total of twelve aerial surveys were conducted 

within about 25 nmi of the main Hawaiian Islands in 1993, 1995 and 1998. An abundance estimate of 1,708 

(CV= 0.32) short-finned p ilot whales was re cently calculate d from the c ombined survey data (M obley et al. 

2000). This abundance underestimates the total numbe r of short-finned pilot whales with in the U.S. E EZ off 

Hawaii, because areas around the Northwest Hawaiian Islands (NWHI) and beyond 25 nautical miles from the 

main islands were not surveyed. 

Minimum Po pulation Estimate 

The log-normal 20th percentile of the combined 1993-98 abundance estimate is 1,313 short-finned pilot 

whales. As with th e best abu ndanc e estimate a bove, th is includes o nly areas within about 25 nmi of th e main 

Hawaiian Islands and is therefore an underestimate. 

Current Population Trend 

No data are available on current population trend. 

205 
CURRENT AND M AXIMUM NET PRODUCTIVITY RATES 

No data are available on current or maximum net productivity rate. 

POTENTIAL BIOLOGICAL REMOVAL 

The potential bio logical remo val (PB R) level for this stock is calculated as the minimum population size (1,313) 

times one half the default maximum net growth rate for cetaceans (1⁄2 of 4%) times a recovery factor of 0.50 (for 

a species of unknown status with a known fishery mortality within the U.S. EEZ off Hawaii; Wad e and Angliss 

1997), resulting in a PBR of 13 short-finned pilot whales per year. 

HUMAN -CAUSED MORTALITY AND SERIOUS INJURY 

Fishery Information 

Mortality of cetaceans has been observed in Hawaiian fisheries, and the gear types used in these fisheries are 

responsib le for marine mammal mortality and serious injury in o ther fisheries thro ughout U .S. waters. Gillnets 

are used in Ha waiian waters a nd appe ar to capture marine mammals wherever they are used, and float lines from 

lobster traps and longlines can be 

expected to occasio nally entangle whales 

(Perrin et al. 1 994). 

One short-finned pilot whale was 

observed killed outside the U.S. EEZ in 

the Hawaiian longline fishery between 

1994 and 1998 (Figure 2), with 

approx imately 4.4% of all effort 

(measured as the number of hooks 

fished) observed . This mortality rate 

extrapolates to a total 5-year estimate of 

23 (95% CI = 1-108) short-finned pilot 

whales, or an average of 4.6 animals 

killed per year (Kleiber 1999). The 

single observed short-finned p ilot whale 

was reported to have been entangled in 

the fishing line. Reports for other 

odontocetes indicate animals may also 

ingest the hook or beco me hook ed in the 

mouth or o ther part of the ir body. 

Interactions with cetaceans have been 

reported for all Hawa iian pelagic 

fisheries (Nitta and Henderson 1993), 

but no other interactions with shortFigure 2. Locations of observed cetacean interactions in the 

Hawaiian longline fishery, 1994-98 (modified from Kleiber 

1999). Dashed line is the U.S. Exclusive Economic Zone (EEZ); 

GM = short-finned pilot whale. 

finned pilot whales have been documented. Interaction rates between dolphins and the NWHI bottomfish 

fishery have been estimated based on studies conducted in 1990-1993, indicating that an average of 2.67 

dolphin interactions, most likely involving bottlenose and rough -toothed dolphins, occu rred for every 1000 fish 

brought on board (Kobayashi and Kawamoto 1995). Fishermen claim interactions with dolphins who steal bait 

and catch are increasing. It is not known whether these interactions result in serious injury or mortality of 

dolphins, no r whether sho rt-finned pilot wh ales are invo lved. 

Other Remov als 

Since 1963, at least 20 short-fin ned pilot wh ales have be en live-captur ed from H awaiian wate rs by Sea Life 

Park/Oceanic Foundation (Shallenberger 1981). 

STATUS OF STOCK 

206 
The status of short-finned pilot whales in Hawaiian waters relative to OSP is unknown, and there are insufficient 

data to evaluate tre nds in abun dance. N o habitat issue s are known to be of co ncern for this species. They are 

not listed as “threatened” or “endangered” under the Endangered Species Act (1973), nor as “depleted” under 

the MMPA . Although information on short-finned pilot whales in Hawaiian waters is limited, this sto ck would 

not be considered strategic under the 1994 amendments to the MMPA given the absence of reported fisheries 

related mortality within the U.S. EEZ. However, the potential effect of mortality in the Hawaiian longline 

fishery in international w aters is not known. Insufficient information is available to determine whether the total 

fishery mortality and serious injury for short-finned pilot whales is insign ificant and ap proachin g zero mo rtality 

and serious injury rate. 

REFERENCES 

Kasuya, T., T. Miyashita, and F. Kasamatsu. 1988. Segregation of two forms o f short-finned p ilot whales off the P acific 

coast of Japan. Sci. Rep. Whales Res. Inst. 39:77-90. 

Kleiber, P. 1999. Estimates of marine mamma l takes in the Hawaiian longline fishery. (Unpub lished). Southwest 

Fisheries Science Center, NMFS, 2570 Dole St, Honolulu, HI, 96822-2396. 

Kobayashi, D. R. and K. E . Kawamoto. 19 95. Evaluation of shark, do lphin, and monk seal interactions with 

Northwestern Hawaiian Island bottomfishing activity: a comparison of two time periods and an estimate of 

economic impacts. Fisheries Research 23: 11-22. 

Miyashita, T. 1993. A bundanc e of dolph in stocks in the western North Pacific taken by the Japanese drive fishery. Rep. 

Int. Whal. Commn. 43:417-437. 

Mob ley, J. R. , Jr, S. S. Sp itz, K. A. Fo rney, R. A. G rotefendt, and P. H. Forestall. 2000. Distribution and abundance 

of odontocete spe cies in Hawaiian waters: preliminary results of 199 3-98 aerial surveys Admin. Rep. LJ-00­

14C. Southwest F isheries Scien ce Center, N ational Marine Fisheries Service, P.O. Box 271, La Jolla, CA 

92038. 26 pp. 

Nitta, E. 1991 . The mar ine mamm al stranding ne twork for H awaii: an ove rview. In: J.E. Reyno lds 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. Don ovan and J. Barlow . 1994. G illnets and Cetaceans. Rep. Int. Whal. Commn., Special Issue 15, 

629 pp. 

Shallenberger, E.W. 1981. The status of Hawaiian cetaceans. Final report to U.S. Marine Mammal Commission. MMC77/23, 79pp. 

Shane, S. H. and D. McSweeney. 1990. Using photo-identification to study pilot whales so cial organiza tion. Rep. Int. 

Whal. Commn. (Spec. Iss. 12):259-263. 

Tomich, P. Q. 19 86. Ma mmals in H awaii: 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, 1 996, Se attle, 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. 

207 
Revised 12/15/2000 

BLAINVILLE'S BEAKED WHALE (Mesoplodon densirostris): 

Hawaiian Stock 

STOCK DEFINITION AND GEOGRAPHIC RANGE 

Bla invi lle'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 island s by Shallenberger


(1981), who sugg este d that Blain ville 's


beaked whales were present off the


Waianae Coast of Oahu for prolonged


periods annually. Balcomb (1987)


specula ted that this species is "more


common in Hawaii than anywh ere else in


the world." Recent sighting locations


around the main Hawaiian Islands (Mobley Figure 1. Blainville’s beaked whale (!) and unidentified


et al. 2000) are shown in Figure 1. Mesoplodon (+) sighting locations during 1993-98 aerial


Although all identified Mesoplodon surveys within about 25 nmi of the main Hawaiian Islands (see


records from Haw aiian waters are of M. Appen dix 2 for de tails on timing and location of su rvey effort). 


densirostris, several other species in the Outer line indicates approximate boundary of survey area.


genus Mesoplodon are known from the


North Pacific and may be rec orded in H awaiian wate rs in the future (see Mead 1989). There is no information


on stock structure of Blainville's be aked wha le. For the Marine Mammal Protection Act (MMPA) stock


assessment reports, three Mesoplodon stocks are defined: 1) M. densirostris in Hawaiian waters (this report),


2) M. stejnegeri in Alaskan wa ters, and 3) a ll Mesoplodon species off California, Oregon and W ashington. 

POPU LATIO N SIZE 

As part of the M arine Ma mmal Re search Pr ogram o f the Acousti c Thermometry of Ocean Climate (ATOC) 

study, a total of twelve aerial surveys were c onducted within about 2 5 nmi of the m ain Hawa iian Islands in 

1993, 1995 and 1998. Seven sightings of Blainville’s beaked whales were made. An abundance estimate of 

68 (CV=0.60) Blainville’s beaked whales was recently calculated from the combined survey data (Mobley et 

al. 2000). This abundance underestimates the total number of Blainville’s beaked whales within the U.S. EEZ 

off Hawaii, because areas around the Northwest Hawaiian Islands (NWHI) and beyond 25 nautical miles from 

the main islands were not surveyed. Furthermore, this species is known to spend a large proportion of time 

diving, causing additional downward bias in the abundance estimate. 

Minimum Po pulation Estimate 

The log-normal 20th percentile of the combined 1993-98 abund ance estim ate is 43 Blainville’s beaked whales. 

As with the b est abund ance estim ate above, this includes only areas within about 25 nmi of the main Hawaiian 

Islands and does not include a large proportion of animals that were diving and therefore unavailable to be 

seen. 

Current Population Trend 

No data are available on current population trend. 

208 
CURRENT AND M AXIMUM NET PRODUCTIVITY RATES 

No data are available on current or maximum net productivity rate. 

POTENTIAL BIOLOGICAL REMOVAL 

The potential biological removal (PBR) level for this stock is calculated as the minimum population size (43) 

times one half the default maximum net growth rate for cetaceans (1⁄2 of 4%) times a recovery factor of 0.50 (for 

a species of unknown status with no known fishery mortality; Wade and Angliss 1997), resulting in a PBR of 

0.4 Blainville’s beaked whales per year. 

HUMAN -CAUSED MORTALITY AND SERIOUS INJURY 

Fishery Information 

No estimate of annual human-caused mortality and serious injury is available as there are no reports of direct 

or incidenta l takes of Blain ville's beaked w hales in Hawaiian waters (Nitta and Henderson 1993). However, 

mortality of other cetacean species has been observed in Hawaiian fisheries, and the gear types used in these 

fisheries are responsible for marine mammal mortality and serious injury in other fisheries throughout U.S. 

waters. Gillnets are used in Hawaiian waters and appear to capture marine mammals wherever they are used, 

and float lines from lobste r traps and lo nglines can b e expecte d to occa sionally entangle wha les (Perrin et a l. 

1994). 

Interactions with dolphins are reported 

for all pelagic fisheries, and humpback 

whales have been entangled in longlines 

off the Hawaiian Islands (Nitta and 

Henderson 1993), but no takes of 

Bla inville's beaked whales have been 

documented. However, thre e 

unidentified whales and one unidentified 

cetacean were observed hooked in the 

Hawaiian longline fishery between 1994 

and 1998 (Figure 2), with approximately 

4.4% of all effort (measured as the 

number of hooks fished) observed. 

Observer descriptions and photographs 

of these interactio ns indicate that at least 

two of the unidentified whales may have 

been beaked whales, including one 

within the U.S. EEZ. The total 

interaction rate based on these two 

possible beaked whales extrapolates to 

a 5-year estimate of 45 (95% CI = 7­

108), or an average of 9 interactions per 

year (Kleiber 1999). One of the two 

possible beaked whales was hoo ked in 

the fluke, and following the guidelines 

Figure 2. Locations of observed cetacean interactions in the 

Hawaiian longline fishery, 1994-98 (modified from Kleiber 

1999). Dashed line is the U.S. Exclusive Economic Zone (EEZ); 

UW = unidentified whale; UC = unidentified cetacean. The two 

westernmo st unidentified w hales may ha ve been B lainville’s 

beaked whales. 

of a 1997 Serious Injury Workshop (Angliss and DeM aster 1998), this would not be considered a serious injury 

(defined under the M MPA as likely to result in morta lity). The other interaction, whic h took plac e within the 

U.S. EEZ, involved a possible beaked whale that was hooked but broke the line and swam away before the 

location of the hook could be ascertained. Therefore, no determination can be made regarding the severity of 

this second injury. Repo rts for other odontocetes indica te they may also become hooked in the mouth or ingest 

the hook, and that they may occasionally become entangled in the fishing line. Insufficient infor mation is 

available to evaluate whether som e of these unidentified whales may have b een Blainville’s beaked wha les. 

STATUS OF STOCK 

209 
The status of Blainville's beaked whales in Hawaiian waters relative to OSP is unknown, and there are 

insufficient data to evaluate trends in abundance. They are not listed as “threatened” or “endangered” under 

the Endangered Species Act (1973), nor as “depleted” under the MMPA. Alth oug h inf ormatio n on Bla inville's 

beaked whales in Hawaiian waters is limited, this stock would not be considered strategic under the 1994 

amendm ents to the MM PA bec ause there ha s been no r eported fisheries related m ortality within the U.S. EEZ. 

However, the effect of potential interactions of unidentified beaked whales (which may have been B lainville’s 

beaked whales) with the Hawaiian longline fishery in U.S. and international waters is not known. Insufficient 

information is available to determine whether the total fishery mo rtality and seriou s injury for Bla inville’s 

beaked whales is insignificant and approac hing zero m ortality and serio us injury rate. T he increasing levels 

of anthropogenic noise in the world’s oceans has been suggested to be a habitat con cern for whales, particularly 

for deep-diving whales like Blainville’s beaked whales that feed in the oceans’ “sound channel”. 

REFERENCES 

Angliss, R. P. and D . P. DeM aster. 1998 . Differentiating S erious and Non-Se rious Injury o f Marine M ammals Taken 

Incidental to Commercial Fishing Operations: Report of the Serious Injury Work shop 1-2 April 1997, Silver 

Spring, Maryland. U. S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-13. 48 pp. 

Balcomb, K. C., III. 1987. The Whales of Hawaii. Marine Mammal Fund, 99 pp. 

Galbreath, E. C. 1963. Three beaked whales stranded on the Midway Islands, central Pacific Ocean. J. Mamm. 44:422­

423. 

Kleiber, P. 1999. Estimates of marine mammal takes in the Hawaiian longline fishery. (Unpublished). Southwe st 

Fisheries Science Center, NMFS, 2570 Dole St, Honolulu, HI, 96822-2396. 

Mob ley, J. R. , Jr, S. S. Sp itz, K. A. Fo rney, R. A. G rotefendt, an d P. H. F orestall. 2000. Distribution and abundance 

of odonto cete specie s in Hawaiian waters: preliminary results of 1993-98 aerial surveys Admin. Rep. LJ-00­

14C. Southwest Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA 

92038. 26 pp. 

Mead, J. G . 1989. Beak ed 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 netw ork for H awaii: an ove rview. In: J.E. Reyno lds 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. 1 994. G illnets and Ce taceans. Re p. Int. Whal. Commn., Special Issue 15, 

629 pp. 

Shallenberger, E. W. 1981. The status of Hawaiian cetaceans. Final report to U.S. Marine Mammal Commission. MMC77/23, 79pp. 

Wade, P. R. and R . P. Angliss. 19 97. Guid elines 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. 

210 
Revised 12/15/2000 

CUVIER'S BEAKED WHALE (Ziphius cavirostris): Hawaiian Stock 

STOCK DEFINITION AND GEOGRAPHIC RANGE 

Cuv ier's beaked whales occ ur in all oceans 

and major seas (Heyning 1989). In 

Hawaii, strandings have been reported 

from Midway Islands, Pearl and Hermes 

Reef, Oahu, and Hawaii Isl ands 

(Shallenberger 1981; Galbreath 1963; 

Richards 1952; Nitta 1991). Sightings 

have been reported off Lanai and Maui 

(Shallenberger 1981). Recent sighting 

locations around the main Hawaiian 

Islands (Mobley et al. 2000) are shown in 

Figure 1. Nothing is known about stock 

structure for this species. For the Marine 

Mammal Protection Act (MMPA) stock 

assessment reports, Cuvier's beaked 

whales within the Pacific U.S. Exclusive 

Econo mic Zone are divided into three 

discrete, non-contigu ous areas: 1) 

Hawaiian waters (this rep ort), 2) Ala skan 

waters, and 3) waters off California, 

Oregon and W ashington. 

POPU LATIO N SIZE 

Figure 1. Cuvier’s beaked whale sighting locations during 

1993-9 8 aerial surve ys within about 2 5 nmi of the m ain 

Hawaiian Islands (see Appendix 2 for details on timing and 

location of su rvey effort). Ou ter line indicates a pproxim ate 

boundary of survey area. 

Wade and Gerrod ette (19 93) mad e an estimat e for Cu vier's beaked whales in the eastern tropical Pacific, but 

it is not known whether any of these animals are part of the same population that occurs around the Hawaiian 

Islands. As part of the Marine Mammal Research Program of the Acoustic Thermometry of Ocean Climate 

(ATOC) study, a total of twelve aerial surveys were conducted within about 25 nmi of the main Haw aiian 

Islands in 1993, 1995 and 199 8. Seven sightings of Cuvier’s beaked whales were made. An abundance 

estimate of 43 (CV=0.51) Cuvier’s beaked w hales was rec ently calculated from the combined su rvey data 

(Mobley et al. 2000). This abundance underestimates the total number of Cuvier’s beaked whales within the 

U.S. EEZ off Haw aii, because areas around the Northwest Hawaiian Islands (NWHI) and beyond 25 nautical 

miles from the main islands were not surveyed. Furthermore, this species is known to spend a large proportion 

of time diving, causing additional downward bias in the abundance estimate. 

Minimum Po pulation Estimate 

The log-normal 20th percentile of the combined 1993-98 abund ance estim ate is 29 Cuvier’s beaked whales. 

As with the b est abund ance estim ate abov e, this includes only areas within about 25 nmi of the main Hawaiian 

Islands and does not include a large proportion of animals that were diving and therefore unavailable to be 

seen. 

Current Population Trend 

No data are available on current population trend. 

CURRENT AND M AXIMUM NET PRODUCTIVITY RATES 

No data are available on current or maximum net productivity rate. 

POTENTIAL BIOLOGICAL REMOVAL 

211 
The potential bio logical remo val (PB R) level for this stock is calculated as the minimum population size (29) 

times one half the default maximum net growth rate for cetaceans (1⁄2 of 4%) times a recovery factor of 0.50 (for 

a species of unknown status with no known fishery mortality; Wade and Angliss 1997), resulting in a PBR of 

0.3 Cuvier’s beaked whales per year. 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY 

Fishery Information 

No estimate of annual human-cau sed morta lity and serious injury is available as there are no reports of direct 

or incidental takes of C uvier's beaked whales in Hawaiian waters (Nitta and Henderson 1993). Howeve r, 

mortality of other cetacean species has been observed in Hawaiian fisheries, and the gear types used in these 

fisheries are responsible for marine mammal mortality and serious injury in other fisheries throughout U.S. 

waters. Gillnets are used in Hawaiian waters and appear to capture marine mammals wherever they are used, 

and float lines from lob ster traps and longlines can be expec ted to occasiona lly entangle whale s (Perrin et al. 

1994). 

Interactions with dolphins are reported 

for all pelagic fisheries, and humpback 

whales have been entangled in longlines 

off the Hawaiian Islands (Nitta and 

Henderson 1993), but no takes of 

Cuv ier's beaked whales have been 

docum ented. How ever, thre e 

unidentified whales and one unidentified 

cetacean were observed hooked in the 

Hawaiian longline fishery between 1994 

and 1998 (Figure 2), with appro ximately 

4.4% of all effort (measured as the 

number of hooks fished) observed. 

Observer descriptions and photographs 

of these interactions indicate that at least 

two of the unidentified whales may have 

been beaked whales, including one 

within the U.S. EEZ. The total 

interaction rate based on these two 

possible beaked whales extrapolates to a 

5-year estimate of 45 (95% CI = 7-108), 

or an average of 9 interactions per year 

(Kleiber 1999). One of the two possible 

beaked whales was hooked in the fluke, 

and following the guidelines of a 1997 

Figure 2. Locations of observed cetacean interactions in the 

Hawaiian longline fishery, 1994-98 (modified from Kleiber 

1999). Dashed line is the U.S. Exclusive Economic Zone (EEZ); 

UW = unidentified whale; UC = unidentified cetacean. The two 

westernmost unidentified whales may have been Cuvier’s beaked 

whales. 

Serious Injury Workshop (Angliss and DeMaster 1998), this would not be considered a serious injury (defined 

under the MMPA as likely to result in mortality). The other interaction, which took place within the U.S. EEZ, 

involved a possible beaked whale that was hooked but broke the line and swam away before the location of the 

hook could be ascertained . Therefore, no determination can be made regarding the severity of this second 

injury. Reports for other odontocetes indicate they may also become hooked in the mouth or ingest the hook, 

and that they may occasionally become entangled in the fishing line. Insufficient inform ation is availab le to 

evaluate whether some o f these unidentified whales may have bee n Cuvier’s beaked wh ales. 

STATUS OF STOCK 

The status of Cuvier's beaked whales in Hawaiian waters relative to OSP is unknown, and there are insufficient 

data to evaluate trends in abundance. They are not listed as “threatened” or “endangered” under the Endangered 

Species Act (197 3), nor as “d epleted” u nder the M MPA . Although information on Cuvier's beaked whales in 

Hawaiian waters is limited, this stock would not be considered strategic under the 1994 amendments to the 

212 
MMPA because the re has been no reported fisheries relate d mortality within the U.S. EEZ. However, the effect 

of potential interactions of unidentified b eaked wh ales (which m ay have bee n Cuvier’s beaked whales) with the 

Hawaiian longline fishery in U.S. and international wa ters is not know n. Insufficient inform ation is availab le 

to determine whether the total fishery mortality and serious injury for Cuvier’s beaked whales is insignificant 

and approaching zero mortality and serious injury rate. The increasing levels of anthropogenic noise in the 

world’s oceans has been suggested to be a habitat concern for whales, particularly for deep-diving whales like 

Cuvier’s beaked whales that feed in the oceans’ “sound channel”. 

REFERENCES 

Angliss, R. P. and D. P. DeM aster. 1998. Differentiating Serious and Non-Serious Injury of Marine Mammals Taken 

Incidental to Commercial Fishing Operations: Report of the Serious Injury Workshop 1-2 April 1997, Silver 

Spring, Maryland. U. S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-13. 48 pp. 

Galbreath, E. C. 1963. Three beaked whales stranded on the Midway Islands, central Pacific Oc ean. J. Mamm. 44:422­

423. 

Heyning, J. E. 1989. Cuvier's beaked whale Ziphius c avirostris G. Cuvier , 1823. In: S. H. Ridgway and R. Harrison 

(eds.), Handbook of Marine Mammals, Vol. 4: The River Dolphins and Larger Toothed Whales, pp. 289-308. 

Academic Press, 442 pp. 

Kleiber, P. 1999. Estimates of marine mammal takes in the Hawaiian longline fishery. (Unpublished). Southwest 

Fisheries Science Center, NMFS, 2570 Dole St, Honolulu, HI, 96822-2396. 

Mob ley, J. R. , Jr, S. S. Spitz, K. A. Forney, R. A. Grotefendt, and P. H. Forestall. 2000. Distribution and abundance 

of odonto cete specie s in Hawaiian waters: preliminary results of 1993-98 aerial surveys Admin. Rep. LJ-00­

14C. Southwest Fisheries Science Center, National Marine Fisherie s Service, P.O. Box 271, La Jolla, CA 

92038. 26 pp. 

Nitta, E. 1991 . The mar ine mamm al stranding ne twork for H awaii: an ove rview. In: J.E. Reynolds III, D .K. Ode ll 

(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 b etween H awaii's fisheries and protected species. Mar. 

Fish. Rev. 55(2):83-92. 

Perrin, W.F., G. P. Donovan and J. Barlow. 1994. Gillnets and Cetaceans. Rep. Int. Whal. Commn., Special Issue 15, 

629 pp. 

Richards, L. P. 1952. Cuvier's beaked whale from Hawaii. J. Mamm. 33:255 . 

Shallenberger, E.W. 1981. The status of Hawaiian cetaceans. Final report to U.S. Marine Mammal Commission. MMC77/23, 79pp. 

Wade, P. R. and R. P. Angliss. 1997. Guidelines for Assessing Marine Mammal Stocks: Report of the GAMMS 

Workshop April 3-5, 1996, Seattle, Washington. U. S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-12. 

93 pp. 

Wade, P. R. and T. Gerrodette. 1993. Estimates of cetacean abundance and distribution in the eastern tropical Pacific. 

Rep. Int. Whal. Commn. 43:477-493. 

213 
Revised 12/15/2000 

PYGMY SPERM WHALE (Kogia breviceps): Hawaiian Stock 

STOCK DEFINITION AND GEOGRAPHIC RANGE 

Pygmy sperm whales are found throughout 

the world in tropical and warm-te mperate 

waters (Caldwell and Caldwell 1989). 

Between the years 1949 and 1982, at least 

nine strandings of this species were 

reported in the Hawaiian Islands (Tomich 

1986; Nitta 1991). Shallenberger (1981) 

reported three sightings off Oahu and 

Maui. Two sightings of pygmy or dwarf 

sperm whales were made between H awaii 

and Maui during 1993-98 aerial surveys 

within about 25 nmi of the main Hawaiian 

Islands (Figure 1; Mobley et al. 1999 ). A 

stranded calf was held for several days at 

Sea Life Park (Pryor 1975:9 4). Nothin g is 

known about stock structure for this 

species. For the Marine Mammal 

Protection Act (MMP A) stock assessment 

reports, pygmy sperm whales within the 

Pacific U.S. Exc lusive Eco nomic Zone are 

divided into two discre te, non-contiguous 

areas: 1) Hawa iian waters (this report), and 

2) waters off Calif ornia, Oregon and 

Washington. 

POPU LATIO N SIZE 

Figure 1. Pygmy or dwarf sperm whale sighting locations 

during 19 93-98 a erial surveys within about 25 nmi of the ma in 

Hawaiian Islands (see Appendix 2 for details on timing and 

location of su rvey effort). Ou ter line indicates a pproxim ate 

boundary of survey area. 

No data are available to estimate population size for this species in the central Pacific. As part of the Marine 

Mammal Research Program of the Acou stic Thermometry of O cean Clima te (ATOC) study, a total of twelve 

aerial surveys were conducted within about 25 nmi of the main Hawaiian Islands in 1993, 1995 and 1998. Two 

sightings of five pygmy or dwarf sperm whales were made; however these sightings were excluded during recent 

abundance analyses (Mob ley et al. 2000), because they were made during p oor observation co nditions. 

Therefore, no ab undance estimate is available for pygm y sperm whales within Hawaiian w aters. 

Minimum Po pulation Estimate 

No data are available to provide a minimum population estimate. 

Current Population Trend 

No data are available on current population trend. 

CURRENT AND M AXIMUM 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 

214 
No estimate of annual human-caused mortality and serious injury is available as there are no reports of direct 

or incidental takes of pygmy sperm whales in Hawaiian waters (Nitta a nd Hend erson 19 93). Ho wever, mo rtality 

of other cetacean species has been observed in Hawaiian fisheries, and the gear types used in these fisheries are 

responsib le for marine m ammal mo rtality and serious injury in other fisheries throughout U .S. waters. Gillnets 

are used in Hawaiian waters and appear to capture marine mammals wherever they are used, and float lines from 

lobster traps and longlines can be expected to occasionally entangle whales (Perrin et al. 1994). 

Interactions with cetaceans have been rep orted for all H awaiian pela gic fisheries (N itta and Henderson 1993), 

but no interactions with pygmy sperm whales have been documented. None were observed hooked in the 

Hawaiian longline fishery between 1994 and 1998, with approximately 4.4% of all effort (measured as the 

number o f hooks fished ) observe d (Kleibe r 1999) . 

STATUS OF STOCK 

The status o f pygmy sperm whales in Hawaiian waters relative to OSP is unknown, and there are insufficient 

data to evaluate trends in abundance. They are not listed as “threatened” or “endangered” under the Endangered 

Species Act (1973), nor as “depleted” under the MMPA. Although informatio n on pygmy sperm wha les 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. Th e total fishery mo rtality and serious 

injury for pygmy sperm whales is zero and therefore can be considered to be insignificant and approaching zero 

mortality and seriou s injury rate. Th e increasing lev els of anthrop ogenic noise in the world’s oceans has been 

suggested to be a habitat concern for whales, particularly for deep-diving whales like pygmy sperm whales that 

feed in the oceans’ “sound channel”. 

REFERENCES 

Caldwell, D. K. and M. C. Caldwell. 1989. Pygmy sperm whale Kogia breviceps (de Blainville, 1838): Dwarf sperm 

whale Kogia simus Owen, 18 66. In: S. H. Ridgway and R. Harrison (eds.), Ha ndbook of M arine Mamm als, 

Vol. 4: The River Dolphins and Larger Toothed Whales, pp. 235-260. Academic Press, 442 pp. 

Kleiber, P. 1999. Estima tes of marine mamma l takes in the Hawaiian longline fishery. (Unpub lished). Southwest 

Fisheries Science Center, 2570 Dole St, Honolulu, HI, 96822-2396. 

Mob ley, J. R., Jr., R. A. Grotefendt, P. H. Forestell, and A. Fra nkel. 199 9. Results of ae rial surveys of ma rine mamm als 

in the major Hawaiian Islands (1993-98): Report to the Acoustic Thermometry of Ocean Climate Marine 

Mammal Research Program (ATOC MMRP) (unpublished). 39 pp. 

Mob ley, 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 overv iew. In: J.E. Reyno lds 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. Donov an and J. Barlow. 199 4. Gillnets and Cetacean s. Rep. Int. Whal. Commn., Special Issue 15, 

629 pp. 

Pryor, K. 1975. Lads Before the Wind: Adventures in Porpoise Training. Harper and Row, New York, 278 pp. 

Shallenberger, E.W. 1981. T he status of Hawaiian cetaceans. Final report to U.S. Marine Mammal Commission. MMC77/23, 79pp. 

Tomich, P. Q. 1986. Mammals in Hawaii: A Synopsis and Notational Bibliography. Bishop Museum P ress, Hawaii, 375 

pp. 

215 
Revised 12/15/2000 

DWARF SPERM WHALE (Kogia sima): Hawaiian Stock 

STOCK DEFINITION AND GEOGRAPHIC RANGE 

Dwarf sperm whales are found throughout 

the world in tropical to warm-temperate 

waters (Nagor sen 1985 ). One sighting in 

an unspecified locality, one stranding on 

Oahu (Tomich 1986), and one stranding on 

Lanai (Nitta 1991) co nstitute the only 

evidence that this species inhab its 

Hawaiian waters (Tomich 1986). Two 

sightings of pygmy or dwarf sperm whales 

were made between Hawaii and Maui 

during 1993-98 aerial surveys within about 

25 nmi of the main Hawaiian Islands 

(Figure 1; Mobley et al. 1999). The 

difficulty of detecting and identifying it at 

sea, as well as its confusion with the 

pygmy sperm wha le, may partially ex plain 

the paucity of records. For the Marine 

Mammal Protectio n Act (M MPA ) stock 

assessment reports, there is a single Pacific 

management stock of dwarf sperm whales 

including only animals fo und within the 

U.S. Exclusive Economic Zone of the 

Hawaiian Islands. Rice (1998) rece ntly 

Figure 1. Pygmy or dwarf sperm whale sighting locations 

during 19 93-98 a erial surveys within about 25 nmi of the ma in 

Hawaiian Islands (see Appendix 2 for details on timing and 

location of su rvey effort). Ou ter line indicates a pproxim ate 

boundary of survey area. 

argued that the species name simus, is incorrect and should be replaced by sima. 

but merely reflects rules of Latin usage. 

POPU LATIO N SIZE 

This change is not taxonomic, 

Wade and Ger rodette (1 993) pr ovided a n estimate for the eastern tropical Pacific, but no data are av ailable to 

estimate population size for this species in the central Pacific. As part of the Marine Mammal Research 

Program of the Acoustic Thermometry of Ocean Climate (ATOC) study, a total of twelve aerial surveys were 

conduc ted within abo ut 25 nmi o f the main Ha waiian Island s in 1993, 1995 and 19 98. Two sightings of five 

pygmy or dwarf sperm whales were made; however these sightings were excluded during recent abundance 

analyses (Mobley et al. 2000), because they were made during poor observation conditions. Therefore, no 

abundance estimate is ava ilable for dwarf sperm whales within H awaiian waters. 

Minimum Po pulation Estimate 

No data are available for a minimum population estimate. 

Current Population Trend 

No data are available on current population trend. 

CURRENT AND M AXIMUM NET PRODUCTIVITY RATES 

No data are available on current or maximum net productivity rate. 

POTENTIAL BIOLOGICAL REMOVAL 

No PBR can be calculated for this species at this time. 

216 
HUMAN -CAUSED MORTALITY AND SERIOUS INJURY 

Fishery Information 

No estimate of annual human-caused mortality and serious injury is available as there are no reports of direct 

or incidental takes of dwarf sperm whales in Hawaiian waters (Nitta and Hende rson 199 3). How ever, morta lity 

of other cetacean species has been observed in Hawaiian fisheries, and the gear types used in these fisheries are 

responsib le for marine mammal mortality and serious injury in other fisheries thr oughout U .S. waters. Gillne ts 

are used in Hawaiian waters and appear to capture marine mammals wherever they are used, and float lines from 

lobster traps and longlines can be expected to occasionally entangle whales (Perrin et al. 1994). 

Interactions with cetaceans have been reported for all Hawaiian pelagic fisheries (Nitta and Henderson 1993), 

but no interactions with dwarf sperm whales have been documented. None were observed hooked in the 

Hawaiian longline fishery between 1994 and 1998, with approximately 4.4% of all effort (measured as the 

number of hooks fished) observed (Kleiber 1999). 

STATUS OF STOCK 

The status of dwarf sperm whales in Hawaiian waters relative to OSP is unknown, and there are insufficient da ta 

to evaluate trends in abundance. They are not listed as “threatened” or “endangered” under the Endangered 

Species Act (1973), nor as “depleted” under the MMPA. Although info rmation on dwarf sperm whales in 

Hawaiian waters is limited, this stock would not be considered strategic under the 1994 amendments to the 

MMPA because there has been no reported fisheries related m ortality. The total fishery mortality and serious 

injury for dwarf sperm whales is zero and therefore can be considered to be insignificant and approaching zero 

mortality and serious injury rate. The increasing lev els of anthropogenic no ise in the world’s oceans has been 

suggested to be a habitat concern for whales, particularly for deep-diving whales like dwarf sperm whales that 

feed in the oceans’ “sound channel”. 

REFERENCES 

Kleiber, P. 1999. Estimates of marine mamma l takes in the Hawaiian longline fishery. (Unpub lished). Southwest 

Fisheries Science Center, NMFS, 2570 Dole St, Honolulu, HI, 96822-2396. 

Mob ley, J. R., Jr., R. A. G rotefendt, P . H. Foreste ll, and A. Fran kel. 1999 . Results of aerial surveys of marine mamma ls 

in the major Hawaiian Islands (1993-98): Report to the Acoustic Thermometry of Ocean Climate Marine 

Mammal Research Program (ATOC MMRP) (unpublished). 39 pp. 

Mob ley, J. R. , Jr, S. S. Sp itz, K. A. Fo rney, R. A. G rotefendt, and P. H. Forestall. 2000. Distribution and abundance 

of odontocete species in Hawaiian waters: prelim inary results of 1993-98 aerial surveys Admin. Rep. LJ-00­

14C. Southwest Fisheries Science Cen ter, 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. Reyno lds 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. Dono van and J. B arlow. 1994. Gillnets and Cetaceans. Rep. Int. Whal. Commn., Special Issue 15, 

629 pp. 

Rice, D.W. 1998. Marine M ammals of the World Systematics and Distribution. Special Publication Number 4 The 

Society of Marine Mammalogy. Douglas Wartzok (ed.). 231 pp. 

Tomich, P. Q. 1986. Mamm als in Hawaii: A Synopsis and Notational Bibliography. Bishop Museum Press, Hawaii, 375 

pp. 

Wade, P. R. and T. Gerrodette. 1993. Estimates of cetacean abundance and distribution in the eastern tropical Pacific. 

Rep. Int. Whal. Commn. 43:477-493. 

217 
Revised 12/15/2000 

SPERM WHALE (Physeter macrocephalus): Hawaiian Stock 

STOCK DEFINITION AND GEOGRAPHIC RANGE 

Sperm whales are wid ely 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, 1 989; Gosh o et al. 

1984; Miyashita et al. 1995). For 

management, the International Whaling 

Commission (IWC ) had divid ed the No rth 

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 

180oW north of 50oN; however, the IWC 

has not reviewed this sto ck bound ary in 

many years (Do novan 19 91). Sum mer/fall 

surveys in the eastern tro pical Pac ific 

(Wade and Gerrodette 1993) show that 

although sperm whales a re widely 

distributed in the tropics, their relative 

abundance tapers off ma rkedly westward 

towards the middle of the tropical Pacific 

(near the IWC stock boundary at 150o

W) 

and tapers off northward towards the tip of 

Figure 1. Sperm whale sighting locations during 1993-98 

aerial surveys within about 25 nmi of the main Hawaiian 

Islands (see Appendix 2 for details on timing and location of 

survey effort). Outer line indicates approximate boundary of 

survey area. 

Baja California. The Hawaiian Islands marked the center of a major nineteenth century whaling ground for 

sperm whales (Gilmore 1959; Townsend 19 35). Since 1936, at least five strandings have been reported from 

Oahu, Kauai (Nitta 1991) and Kure Atoll (Woodward 1972). Sperm whales have also been sighted around 

several of the Northwestern Hawaiian Islands (Rice 1960), off the main island of Hawaii (Lee 1993; Mobley 

et al. 1999, see Figure 1), in the Kauai Channel and in the Alenuihaha Channel between Maui and the island 

of Hawaii (Shallenberger 1981). In addition, the sounds of sperm whales have been recorded throughout the 

year off Oahu (Thompson and Friedl 1982). 

The stock identity of sperm whales in the North Pacific has been inferred from historical catch records 

(Bannister and Mitchell 1980) and from trends in CPUE and tag-recapture data (Ohsumi and Masaki 1977), 

but much uncertainty remains. A 1997 survey designed specifically to investigate stock structure and 

abundance of sperm whales in the northeastern temperate Pacific revealed no apparent hiatus in distribution 

between the U.S. EEZ off California and areas farther west, out to Hawaii (Barlow and Taylor 1998). Very 

preliminary genetic analyses revealed significant differences between sperm whales off the coast of California, 

Oregon and Wash ington 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 discr ete, non-con tiguous area s: 1) waters aro und Haw aii (this report), 2) California, Oregon 

and Wa shington waters, and 3) Alaskan waters. 

POPU LATIO N SIZE 

A large 1982 abundance estimate for the entire eastern North Pacific (Gosho et al. 1984) was based on a CPUE 

method which is no longer a ccepted as valid by the In ternational W haling Com mission. Rec ently, a combined 

visual and acou stic line-transect surv ey conduc ted in the eastern temperate North Pacific in spring 1997 resulted 

in estimates of 24,000 (CV=0.46) sperm whales based on visual sightings, and 39,200 (CV=0.60) based 

acoustic detections and visual group size estimates (Barlow and Taylor 1998). In the eastern tropical Pacific, 

218 
the abundan ce of sperm whales has b een estimated as 22,70 0 (95% C.I.=14 ,800-34 ,600; W ade and Gerrod ette 

1993). Howev er, it is not known whether any o r all of these animals routinely enter the U.S. EEZ of Hawaii. 

As part of the Marine Mammal Research Program of the Acoustic Thermometry of Ocean Climate (ATOC) 

study, a total of twelve a erial surveys were co nducted w ithin about 25 nmi of the ma in Hawaiian Islands in 

1993, 1995 and 1998 . An average abundance estimate of 66 (CV=0.56) sperm whales was recently calculated 

from the combined survey data (Mobley et al. 2000). This abundance underestimates the total number of sperm 

whales within the U.S. EEZ off Hawaii, because areas around the Northwest Hawaiian Islands (NWHI) and 

beyond 25 nautical miles from the main islands were not surveyed. Furthermore, this species is known to spend 

a large proportion of time diving, causing additional downward bias in the abundance estimate. 

Minimum Po pulation Estimate 

The log-normal 20th percentile of the combined 1993-98 abundan ce estimate is 43 sperm whales. As with the 

best abundance estimate above, this includes only areas within about 25 nmi of the main Hawaiian Islands and 

does not include a large proportion of animals that were diving and therefore unavailable to be seen. 

Current Population Trend 

No data on current population trend are available. 

CURRENT AND M AXIMUM NET PRODUCTIVITY RATES 

No data on current or maximum net productivity rate are available. 

POTENTIAL BIOLOGICAL REMOVAL 

The potential biological removal (PBR) level for this stock is calculated as the minimum population size (43) 

times one half the default maximum net growth rate for cetaceans (1⁄2 of 4%) times a recovery factor of 0.1 (the 

default value for an endangered species), resulting in a PBR of 0.4 sperm whales per year. 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY 

Fishery Information 

No estimate of annual human-caused mortality and serious injury is available as there are no reports of recent 

direct or incidental takes of sperm whales in Hawaiian waters (Nitta a nd Hend erson 19 93). Howev er, mortality 

of other cetacean species has been observed in Hawaiian fisheries, and the gear types used in these fisheries are 

responsib le for marine m ammal mo rtality and serious injury in other fisheries throughout U .S. waters. Gillnets 

are used in Hawaiian waters and appear to capture marine mammals wherever they are used, and float lines from 

lobster traps and longlines can be expected to occasionally entangle whales (Perrin et al. 1994). 

Interactions with dolphin s are repo rted for all pe lagic fisheries, and hump back wha les have bee n entangled in 

longlines off the Hawaiian Islands (Nitta and Henderson 1993), but no takes of sperm whales have been 

documented. None were observed ho oked in the H awaiian long line fishery betwe en 1994 and 199 8, with 

approximately 4.4% of all effort (measured as the number of hooks fished) observed (Kleiber 1999). 

Historical Mortality 

Between 1800 and 1909 , about 60,842 sperm whales were estimated taken in the North Pacific (Be st 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 20°N (Ohsumi 1980). Ohsumi (1980) 

lists an additional 28,198 sperm whales taken mainly in c oastal whaling operation s from 191 0 to 1946. Based 

on the massive under-reporting of Soviet catches, Brownell et al. (1998) estimate that about 89,000 whales were 

additiona lly taken by the S oviet pelagic whaling fleet between 1949 and 1979. The Japanese coastal operations 

apparen tly also under -reported catches by an unknown a mount (K asuya 199 8). Thus a total of at least 436,000 

sperm whales were taken betwe en 1800 and the end of commercial whaling fo r this specie s in 1987 . Of this 

grand total, an estimate d 33,84 2 were take n by Soviet a nd Japa nese pelag ic whaling operations in the eastern 

North Pacific from the longitude of Hawaii to the U.S. West coast, between 1961 and 197 6 (Allen 1980, IWC 

statistical Areas II and III), and 96 5 were rep orted taken in land-based U.S. W est coast whaling operations 

219 
between 1947 and 1971 (Ohsumi 1980). In addition, 13 sperm whales were taken by shore whaling stations 

in California between 1919 and 1926 (Clapham et al. 1997). There has been a prohibition on taking sperm 

whales in the North Pacific since 1988, but large-scale pelagic whaling stopped earlier, in 1980. Some of the 

whales taken during the whaling era were certainly from a population or populations that occur within Hawaiian 

waters. 

STATUS OF STOCK 

The only estimate of the status of N orth Pacific sp erm whales in relation to ca rrying capac ity (Gosho e t al. 

1984) is based on a CPUE method which is no longer accepted as valid. The status o f sperm wha les in 

Hawaiian waters relative to OSP is un known, and there are insufficie nt data to eva luate trends in abundance. 

Sperm whales are formally listed as "endangered" under the Endangered Species Act (ESA), an d conseq uently 

the Hawa iian stock is automatically considered as a "depleted" and "strategic" stock under the MMPA . The 

total fishery mortality and serious injury for sperm whales is zero and therefore can be considered to be 

insignificant and app roaching z ero morta lity and serious inj ury rate. The increasing levels of anthro pogenic 

noise in the world’s oceans has been suggested to be a habitat concern for whales, particularly for deep-diving 

whales like sperm whales that feed in the oceans’ “sound channel”. 

REFERENCES 

Allen, K. R. 1980. Size distribution of male sperm whales in the pelagic catches. Rep. Int. Whal. Commn. Special Issue 

2:51-56. 

Allison, C. International Whaling Commission. The Red House, 135 Station Road, Impington, Cambridge, UK CB4 

9NP. 

Barlow, J. and B. L . Taylor. 19 98. Prelim inary abund ance of spe rm whales in the northeastern temperate Pacific 

estimated from a combined visual and acoustic survey. Paper SC/50/CAWS20 presented to the International 

Whaling Comm ission, June 1 998 (unp ublished). xx pp. 

Bannister, J. and E. Mitchell. 1980. North Pacific sperm whale stock identity: distributional evidence from Maury and 

Townsend charts. Rep. Int. Whal. Commn. (Spec. Iss. 2):219-230. 

Best, P. B. 1976. A review of world sperm whale stocks . Paper A CMR R/MM /SC/8 Re v. 1, FAO Scientific 

Consultatio n of Mar ine Mam mals, Berg en, Norw ay. 

Brown ell, R. L., Jr., A. V . Yablok ov and V . A. Zemm sky. 1998 . USSR pelagic catches of North Pacific sperm whales, 

1949-1979: Conservation implications. Paper SC/50/CAWS27 presented to the International Whaling 

Commission, June 1998 (unpublished). 

Clapham, P. J., S. Leatherwood, I. Szczepaniak, and R. L. Brownell, Jr. 1997. Catches of humpback and other whales 

from shore stations at Moss Landing and Trinidad, California, 1919-1926. Marine Mammal Science 13(3):368­

394. 

Donovan, G. P. 1991. A review of IWC stock boundaries. Rept. Int. Whal. Commn., Special Issue 13:39-68. 

Gilmore, R. M. 1959. On the mass strandings of sperm whales. Pac. Nat. 1(9-10):3-15. 

Gosho, M. E., D. W. Rice, and J. M. Breiwick. 1984. The sperm whale Physeter macrocephalus. Mar. Fish. Rev. 

46(4):54-64. 

Kasuya, T. 199 8. Evidence of statistical manipulations in Japanese coastal sperm whale fishery. Paper SC/50/CAWS10 

presented to the International Whaling Commission, June 1998 (unpublished). 

Kleiber, P. 1999. Estimates of marine mammal takes in the Ha waiian longline fishery. (Unpublished). So uthwest 

Fisheries Science Center, NMFS, 2570 Dole St, Honolulu, HI, 96822-2396. 

Lee, T. 1993. Summary of cetacean survey data collected between the years of 1974 and 1985. NOAA Tech.Mem. 

NMFS 181, 184pp. 

Mesnick, S. Southwest Fisheries Science Center, NMFS, P.O. Box 271, La Jolla, California, 92038. 

Miyashita, T., H. Kato, and T. Kasuya (Eds.). 1995. W orldwide map of cetacean distribution based on Japanese 

sighting data. Volume 1. National Research Institute of Far Seas Fisheries, Shizuoka, Japan. 140pp. 

Mob ley, J. R., Jr., R. A. Grotefendt, P. H. Forestell, and A. Frankel. 1 999. Re sults of aerial surve ys of marine mammals 

in the major Hawaiian Islands (1993-98): Report to the Acoustic Thermometry of Ocean Climate Marine 

Mammal Research Program (ATOC MMRP) (unpublished). 39 pp. 

220 
Mob ley, J. R. , Jr, S. S. Sp itz, K. A. Fo rney, R. A. G rotefendt, an d P. H. F orestall. 2000. Distribution and abundance 

of odonto cete specie s 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. Reyno lds 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. 199 3. A review o f inte rac tion s be twee n Ha waii'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. M asaki. 197 7. Stocks an d trends of a bundanc e of the sperm whale in the N orth Pacific. R ep. Int. 

Whal. Commn. 27:167-175. 

Perrin, W.F., G . P. Dono van and J. B arlow. 1994. G illnets and Ce taceans. Re p. Int. Wh al. Comm n., 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 (e d.). The 

Whale Problem: A Status Report. Harvard Press, Cambridge, MA. 

Rice, D. W. 1989. Sperm whale Physeter macrocephalus Linneaus, 17 58. In: S. H. Ridgway and R. Harrison (eds.), 

Handbook of Marine Mamm als, Vol. 4: T he River D olphins and Larger T oothed W hales, pp. 177-233. 

Academic Press, 442 pp. 

Shallenberger, E.W. 1981. The status of Hawaiian cetaceans. Final report to U.S. Marine Mammal Commission. MMC77/23, 79pp. 

Thompson, P. O. and W. A. Friedl. 1982. A long term study of low frequency sound from several species of wh ales off 

Oahu, Hawaii. Cetology 45:1-19. 

Townsend, C. H. 1935. The distribution of certain whales as shown by logboo k records of Ame rican whaleships. 

Zoologica 19:1-50. 

Wade, P. R. and R. P. Angliss. 1997. Guidelines for Assessing Marine Mammal Stocks: Report of the GAMMS 

Workshop April 3-5, 1996, Seattle, Washington. U. S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-12. 

93 pp. 

Wade, P. R. and T. Gerrodette. 1993. Estimates of cetacean abundance and distribution in the eastern tropical Pacific. 

Rep. Int. Whal. Commn. 43:477-493. 

Woodward, P. W. 1972. The natural history of Kure Atoll, northwestern Hawaiian Islands. Atoll Res. Bull. 164:302. 

221 
Revised 12/15/2000 

BLUE WHALE (Balaenoptera musculus): Hawaiian Stock 

STOCK DEFINITION AND GEOGRAPHIC RANGE 

Blue whales are ex tremely rare in Hawaii. The only p ublished sigh ting record is that of Berz in and Ro vnin 

(1966) north of the Hawaiian Islands. Additional evidence that blue whales occur in this area comes from 

acoustic recordings made off Oahu and Midway Islands (Northrop et al. 1971; Thomp son and Friedl 1982; 

McD onald and Fox 1999). Although the exact positions of the whales producing the sounds could not be 

determined, at least some of them were within the U.S. Exc lusive Eco nomic Zo ne. The re cordings m ade off 

Oahu sho wed bimo dal peaks th roughou t the year, suggestin g that the anima ls were migrating into the area in 

summer an d winter. 

The stock structure of blue whales in the North Pacific is uncertain (Mizroch et al. 1984; Reilly and Thayer 

1990; Reeves et al. 1998). The International Whaling Comm ission (IWC) has formally considered only one 

management stock for blue whales in the North Pacific (Dono van 199 1), but now this ocean is tho ught to 

include up to five populations (Reeves et al. 1998), with two occurring within the U.S. EEZ. One group of 

animals feed s in California waters in summer/fall (from June to November) and migrates south to productive 

areas off Mexico and as far south as the Costa Rica Dome (10o

 N) in winter/sp ring (Ma te et al. 1999, Stafford 

et al. 1999). Rice (1974) hypothesized that blue whales from Baja C alifornia migra ted far offshor e 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 ind icate that whales feeding along the Aleutian Island s are prob ably part of a c entral Pacific 

stock (Reeves et al. 1998), which may migrate to offshore waters north o f Hawaii in winte r (Berzin a nd Rovn in 

1966). Recently, however, blue whale feeding aggregations have not been found in Alaska despite several 

surveys (Leatherwood et al. 1982; S tewart et al. 1987; Forney and Brownell 1996). For management in U.S. 

Pacific waters outside the continental EEZ, the Hawaiian stock includes only those whales within the EEZ of 

the Hawaiian Islands. One other stock of North Pacific blue whales (off California and Mexico) is recognized 

in the Marine M ammal Protection A ct (MMP A) stock Assessment R eports. 

POPU LATIO N SIZE 

From ship line-transect surveys, Wade and Gerrodette (1993) e stimated 1,400 blue whales for the eastern 

tropical Pacific. A weighted average estimate of 1,940 blue whales is available for California, Oregon and 

Washington, based on 1991-96 shipboard line-transect surveys (Barlow 1997) and photographic mark-recapture 

estimates (Calambokidis and Steiger 1994). No data are available to estimate population size for any other 

North Pacific blue whale population, including the putative central stock that apparently summered along the 

Aleutians and wintered north of Hawaii. A summer 1994 shipboard survey within the historical whaling 

grounds south of the Aleutian Islands yielded no blue whale sightings (Forney and Brownell 1996), nor did a 

total of twelve aeria l surveys conducted in 1993-98 within about 25 nmi of the main Hawaiian Islands as part 

of the Marin e Mam mal Resea rch Prog ram of the A coustic T hermom etry of Ocean Climate (ATOC) study 

(Mobley et al. 2000). 

Minimum Po pulation Estimate 

No data are available to provide a minimum population estimate. 

Current Population Trend 

No data are available on current population trend. 

CURRENT AND M AXIMUM NET PRODUCTIVITY RATES 

No data are available on current or maximum net productivity rate. 

222 
POTENTIAL BIOLOGICAL REMOVAL 

No PBR can be calculated for this stock at this time. 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY 

Fishery Information 

No estimate of ann ual human-c aused mo rtality and seriou s injury is available as there are no reports of recent 

direct or incidental takes of blue whales in Hawaiian waters. However, mortality of other cetacean species has 

been observed in Hawaiian fisheries, and the gear types used in these fisheries are responsible for marine 

mammal mortality and serious injury in other fisheries throughout U.S. waters. Gillnets are used in Hawaiian 

waters and a ppear to c apture ma rine mamm als wherever they are used, and float lines from lobster traps and 

longlines can be exp ected to occasiona lly entangle whales (Perrin et al. 1994). Interactions with dolphins are 

reported for all pelagic fishe ries, and humpback whales have been entangled in longlines off the Hawaiian 

Islands, but no takes of blue whales have been documented (Nitta and Henderson 1993). None were observed 

hooked or entangled in the Hawaiian longline fishery between 1994 and 1998, with appro ximately 4.4% of all 

effort (measu red as the nu mber of ho oks fished) o bserved ( Kleiber 1 999). 

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 wh ales in Haw aiian waters rela tive to OSP is unknown, a nd there are insufficient data to 

evaluate trends in abu ndance. B lue whales are formally listed as "endangered" under the Endangered Species 

Act (ESA), and consequently the Hawaiian stock is automatically considered as a "depleted" and "strategic" 

stock under the MMPA. The total fishery mortality and serious injury for blue whales is zero and therefore can 

be considered to be insignificant and approaching zero mortality and se rious injury rate . The incre asing levels 

of anthropogenic noise in the world’s oceans has been suggested to be a habitat concern for blue whales (Reeves 

et al. 1998). 

REFERENCES 

Barlow, J. 1997. Preliminary estimates of cetacean abundance off California, Oregon, and Washington based on a 1996 

ship survey and comparisons of passing and closing modes. Admin. Rept. LJ-97-11. Southwest Fisheries 

Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA. 25 pp. 

Berzin, A. A. and A. A. Rovnin. 1966. D istribution and migration of w hales in the northeastern pa rt of the Pacific 

Ocean, Bering and Chukchi Seas. Izv. Tikhoo kean. Nau chno-issled, In st. Rybn. Khoz. Okeanogr. (TINRO) 

58:179-207. {In Russian }. (Transla ted by U.S . Dep. Inter ., Bur. Com mer. Fish., Seattle, Washington, 1966, pp. 

103-106 In: Panin, K. I. (ed) Soviet Research on marine mammals of the Far East). 

Calambokidis, J., R. Sears, G. H. Steiger, and J. Evenson. 1995. Movement and stock structure of blue whales in the 

eastern North P acific. P.19 In: Proceedings of the Eleventh Biennial Conference on the Biology of Marine 

Mammals, Orlando, FL, 14-18 December 1995 (Abstract). Society for Marine Mammalogy, Lawrence, KS. 

Calambokidis, J., and G. H. Steiger. 1994. Population assessment of humpback and blue whales using photoidentification from 1993 surveys off California. Final Contract Report to Southwest Fisheries Science Center, 

National Marine Fisheries Service, P.O. Box 271, La Jolla, CA 92038. 31 pp. 

Donovan, G. P. 1991. A review of IWC stock boundaries. Rept. Int. Whal. Commn., Special Issue 13:39-68. 

Forney, K. A. and Browne ll, R. L., Jr. 1996. Preliminary report of the 1994 A leutian Island M arine Ma mmal Surv ey. 

Paper SC/48/O11 presented to the International Whaling Commission, June 1996 (unpublished). 

223 
Gilpatrick, J., W. Perryman, M. Lynn, and M. A. DeAngelis. 1996. Geographic populations of blue whales 

(Balaenop tera 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 

(unpublishe d). 

Kleiber, P. 1999 . Estimates of m arine mammal takes in the H awaiian long line fishery. (Unp ublished). Southwest 

Fisheries Science Center, NMFS, 2570 Dole St, Honolulu, HI, 96822-2396. 

Leatherwood, S., R. R. Re eves, W . F. Perrin, and W. E. E vans. 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. 

Mizroch, S. A., D. W . Rice, and J. M. Breiwick. 1 984. The blue wha le, Balaenoptera musculus. Mar. Fish. Rev. 

46(4):15-19. 

Mob ley, J. R. , Jr, S. S. Spitz, K. A. Forney, R. A. Grotefendt, and P. H. Forestall. 2000. Distribution and abundance 

of odonto cete specie s in Hawaiian waters: preliminary results of 1993-98 aerial surveys Admin. Rep. LJ-00­

14C. Southwest F isheries Scien ce Center, N ational M arine Fisherie s Service, P.O. Box 271, La Jolla, CA 

92038. 26 pp. 

Nitta, E. and J. R . Hender son. 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 w hale 

(Balaenoptera musculus). Office of Protected Resources, NMFS, NOAA, Silver Spring, Maryland. 30 pp. 

Reilly, S. B. and V. G. Thayer. 1990. Blue whale (Balaenoptera musculus) distribution in the eastern tropical Pacific. 

Mar. Mamm. Sci. 6:265-277. 

Rice, D. W. 1974. W hales and whale research in the eastern North Pacific. pp. 170-195 In: W. E. S chevill (ed.). The 

Whale Problem: A Status Report. Harvard Press, Cambridge, MA. 

Rice, D. W. 19 92. The blue wh ales 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 tro pical Pac ific 

and the northeast Pacific. Mar. Mamm. Sci. 15(4):1258-1268. 

Stewart, B. S., S. A. Karl, P. K. Yochem, S. Leatherw ood, and J. L. Laake. 1987. Aerial surveys for cetaceans in the 

former Akutan, Alaska, whaling grounds. Arctic 40(1):33-42. 

Thompson, P. O. and W. A. Friedl. 1982. A long term study of low frequency sound from several species of whales off 

Oahu, Hawaii. Cetology 45:1-19. 

Wade, P. R. and T . Gerrod ette. 1993 . Estimates of cetacean abundance and distribution in the eastern tropical Pacific. 

Rep. Int. Whal. Commn. 43:477-493. 

224 
Revised 12/15/2000 

FIN WHALE (Balaenoptera physalus): Hawaiian Stock 

STOCK DEFINITION AND GEOGRAPHIC RANGE 

Fin whales are fo und throug hout all oceans and seas of the world from tropical to polar latitudes. They are rare 

in Hawaiian waters. Balcomb (1987) observed 8-12 fin whales in a multispecies feeding assemblage on 20 May 

1966 approx. 250 mi. south of Honolulu. Additional sightings were reported north of Oahu in May 1976 and 

in the Kauai Channel in February 1979 (Shallenberger 1981). More recently, a single fin whale was observed 

north of Kauai in February 1994 (Mobley et al. 1996). A single stranding has been reported on Maui 

(Shallenberger 1981). Thompson and Friedl (1982; and see Northrop et al. 1968) suggested that fin whales 

migrate into Hawaiian waters mainly in fall and winter, based on acoustic recordings off Oahu and Midway 

Islands. Although the exact positions of the whales producing the sounds could not be determined, at least some 

of them were a lmost certainly w ithin the U.S. E xclusive Ec onomic Z one. More recently, McDonald and Fox 

(1999) reported an average of 0.027 calling fin whales per 10002

 km (grouped by 8-hr periods) based on passive 

acoustic recordings within about 16 km of the north shore of Oahu. 

The International Whaling Commission (IWC) recognized two stocks of fin whales in the North Pacific: the 

East China Sea and the rest of the North Pacific (Donovan 1991). Mizroch et al. (1984) cites evidence for 

additional fin whale subp opulations in the North P acific. There is still insufficient informatio n to accura tely 

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 

Mamm al Protectio n Act (M MPA ) stock assessm ent reports re cognize thre e stocks of fin wh ales in the No rth 

Pacific: 1) the Hawaii stock (this report), 2) the California/Oregon/Washington stock, and 3) the Alaska stock. 

POPU LATIO N SIZE 

No data are av ailable to estim ate popu lation size. As part of the Marine Mammal Research Program of the 

Acoustic Thermometry of Ocean Climate (ATOC) study, a total of twelve aerial sur veys were co nducted w ithin 

about 25 nmi of the main Hawaiian Islands in 1993-98 (Mobley et al. 2000). Only one sighting of a single fin 

whale was made (Mobley et al. 1996), and therefore no meaningful abundance estimate could be calculated. 

Using passive aco ustic detections from a hydrophone north of Oahu, MacDonald and Fox (1999) estimate an 

average density of 0.027 calling fin whales per 1000 km 2 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 m ethod do es not prov ide an estima te of absolute abundan ce for fin whales . 

Minimum Po pulation Estimate 

No data are available to provide a minimum population estimate. 

Current Population Trend 

No data are available on current population trend. 

CURRENT AND M AXIMUM NET PRODUCTIVITY RATES 

No data are available on current or maximum net productivity rate. 

POTENTIAL BIOLOGICAL REMOVAL 

No PBR can be calculated for this stock at this time. 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY 

Fishery Information 

No estimate of ann ual human-c aused mo rtality and serious injury is available as there are no reports of recent 

direct or incidental takes of fin whales in Hawaiian waters. However, mortality of other cetacean species has 

225 
been observed in Ha waiian fisheries, and the gear types used in these fisheries are responsible for marine 

mammal mortality and serious injury in other fisheries throughout U.S. waters. Gillnets are used in Hawaiian 

waters and appear to capture marine mammals wherever they are used, and float lines from lobster traps and 

longlines can be expected to occasionally entangle whales (Perrin et al. 1994). 

Interactions with dolphin s are repo rted for all pelagic fisheries, and hu mpbac k whales hav e been enta ngled in 

longlines off the Hawaiian Islands (Nitta and Henderson 1993), but no takes of fin whales have been 

documented. None were observed hooked or entangled in the Hawaiian longline fishery between 1994 and 

1998, with approximately 4.4% of all effort (measured as the number of hooks fished) observed (Kleiber 1999). 

Historical Mortality 

Large numbers of fin whales were taken by commercial whalers throughout the No rth Pacific from the early 

20th century until the 1970 s (Tønne ssen and Jo hnsen 198 2). App roximately 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 H awaiian wate rs relative to O SP is unkno wn, 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 MM PA. Th e total fishery mo rtality and seriou s injury for fin whales is zero and therefore can 

be considered to be insignificant and approaching zero mortality and serious injury rate. The inc reasing levels 

of anthropogenic no ise in the world’s oceans has been suggested to be a habitat con cern for whales. 

REFERENCES 

Allison, C. International Whaling Commission. The Red House, 135 Station Road, Impington, Cambri dge, UK CB4 

9NP. 

Balcomb, K. C., III. 1987. The Whales of Hawaii. Marine Mammal Fund, 99 pp.


Donovan, G. P. 1991. A review of IWC stock boundaries. Rept. Int. Whal. Commn., Special Issue 13:39-68.


Kleiber, P. 1999. E stimates of marine mamma l takes in the Hawaiian longline fishery. (Unpub lished). Southwest 

Fisheries Science Center, NMFS, 2570 Dole St, Honolulu, HI, 96822-2396. 

McDonald, M. A., and C. G. Fox. 1999. Passive acoustic methods applied to fin whale population density estimation. 

J. Acoust. Soc. Am. 105: 2643-2651. 

Mizroch, S. A., D. W . Rice, and J . M. Bre iwick. 1984 . The fin wha le, Balaenoptera physalus Mar. Fish. Rev. 46(4):20­

24. 

Mobley, J. R., Jr., M. Smultea, T. Norris, and D. We ller. 1996. F in whale sighting n orth of Ka ua’i, Hawai’i. P acific 

Science 50:230-233. 

Mobley, J. R., Jr, S. S. Spitz, K. A. Forney, R. A. Grotefend t, and P. H. Forestall. 2000. Distribution and abundance 

of odonto cete specie s in Hawaiian waters: preliminary results of 1993-98 aerial surveys Admin. Rep. LJ-00­

14C. Southwest F isheries Scien ce Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA 

92038. 26 pp. 

Nitta, E. and J. R. Henderson. 199 3. A review o f inte rac tion s be twee n Ha waii's fisheries and protected species. Mar. 

Fish. Rev. 55(2):83-92. 

Northrop, J., W. C. Cummings, and P. O. Thompso n. 1968. 2 0-Hz signa ls observed in the central P acific. J. Acou st. 

Soc. Am. 43:383-384. 

Perrin, W.F., G . P. Dono van and J. B arlow. 1994. Gillnets and Cetaceans. Rep. Int. Whal. Commn., Special Issue 15, 

629 pp. 

Shallenberger, E.W. 1981. T he status of Hawaiian cetaceans. Final report to U.S. Marine Mammal Co mmission. MMC77/23, 79pp. 

Thompson, P. O. and W. A. Friedl. 1982. A long term study of low frequency sound from several species of whales off 

Oahu, Hawaii. Cetology 45:1-19. 

226 
Tønnessen, J. N. and A. O. Johnsen. 1982. The History of Modern Whaling. Hurst, 789 pp. 

227

Revised 12/15/2000 

BRYDE'S WHALE (Balaenoptera edeni): Hawaiian Stock 

STOCK DEFINITION AND GEOGRAPHIC RANGE 

Bry de's whales occur in tropical and warm temperate waters throughout the world. Shallenberger (1981) 

reported a sighting of a Bryde's whale sou theast 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 abun dant 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 "ma ny" Bry de's 

whales between the Bonin and Haw aiian Islands in the winters of 19 71 and 1 972 (O hsumi 197 7). With 

presently available evidence, there is no biological basis for defining separate stocks of Bryde's whales in the 

centralNorth Pacific. Bryde's whales also occasionally occur offsouthern California (Morejohn and Rice 1973). 

For the MM PA stock assessment re ports, Bryd e's whales within the P acific U.S. Exclusive Economic Zone are 

divided into two areas: 1) Hawaiian waters (this report), and 2) the eastern tropical Pacific (east of 150o

W and 

including the Gulf of California and waters off California). 

POPU LATIO N SIZE 

Tillman (1978) concluded from Japanese and Soviet CPUE data that the stock size in the N orth Pacific p elagic 

whaling grounds, mostly to the west of the Hawaiian Islands, dec lined from a pproxim ately 22,50 0 in 1971 to 

17,800 in 1977. An estimate of 13,000 (CV=0.202) B ryde's whales was made from vessel surveys in the eastern 

tropical Pacific between 1986 and 1990 (W ade and Gerrodette 1993). The area to which this estimate applies 

is mainly east and somewhat south of the Hawaiian Islands, and it is not known whether these animals are part 

of the same population that occurs around the Hawaiian Islands. As part of the Marine Mammal Research 

Program of the Acoustic Thermometry of Ocean Climate (ATOC) study, a total of twelve aerial surveys were 

conducted within about 25 nmi of the main Hawaiian Islands in 1993, 1995 and 199 8 (Mobley et al. 2000). 

No sightings of Bryde’s whales were made, and therefore no abundance estimate is available for Hawaiian 

waters. 

Minimum Po pulation Estimate 

No data are available for a minimum population estimate. 

Current Population Trend 

No data are available on current population trend. 

CURRENT AND M AXIMUM NET PRODUCTIVITY RATES 

No data are available on current or maximum net productivity rate. 

POTENTIAL BIOLOGICAL REMOVAL 

No PBR can be calculated for this stock at this time. 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY 

Fishery Information 

No estimate of annual human-cau sed morta lity and serious injury is available as there are no reports of recent 

direct or incidental takes of Bryde's whales in H awaiian waters. However, mortality of other cetacean species 

has been observed in Hawaiian fisheries, and the gear types used in these fisheries are responsible for marine 

mammal mortality and serious injury in other fisheries throughout U.S. waters. Gillnets are used in Hawaiian 

waters and appear to capture marine mammals wherever they are used, and float lines from lobster traps and 

longlines can be expec ted to occ asionally entan gle whales (P errin et al. 199 4). 

Interactions with dolphins are reported for all pelagic fisheries, and humpback whales have been entangled in 

longlines off the Hawaiian Islands (Nitta and Henderson 1993), but no takes of Bryde's whales have been 

228 
documented. None were observed hooked or entangled in the Hawaiian longline fishery between 1994 and 

1998, with approximately 4.4% of all effort (measured as the number of hooks fished) observed (Kleiber 1999). 

Historical Mortality 

Small numbers of Bryde's whales were taken near the Northwestern Hawaiian Islands by Japanese and Soviet 

whaling fleets during the e arly 1970 s (Ohsum i 1977). P elagic whaling for B ryde's whales in the North P acific 

ended after the 1979 season (IWC 19 81), and coastal whalin g for this specie s ended in the western Pa cific in 

1987 (IWC 1989). 

STATUS OF STOCK 

The status of Bryde's whales in Hawaiian waters relative to OSP is unknown, and there are insufficient data to 

evaluate trends in abundance. They are not listed as “threatened” or “endangered” under the Endangered 

Species Act (1973), nor as “depleted” under the MMPA. Although information on Bryde's whales in Hawaiian 

waters is limited, this stock would not be considered strategic under the 1994 amendments to the MMPA 

because there has been no reported fisheries related mortality. The total fishery mortality and serious injury 

for Bryde’s whales is zero and therefore can be considered to be insignificant and a pproac hing zero m ortality 

and serious injury rate. The increasing levels of anthropogenic noise in the world’s oceans has been suggested 

to be a habitat concern for w hales. 

REFERENCES 

DeLong, R. L. and R. L. Brownell, Jr. 1977. Hawaiian monk sea l (Monachus schauinslandi) habitat and population 

survey in the northwestern (Leeward) Hawaiian Islands, April 19 77. Northwest Alaska Fish C ent. Proc. R ep., 

43 pp. 

International Whaling Commission. 1981. Japan. Progress report on cetacean research June 1979-May 1980. Rep. Int. 

Whal. Commn. 31:195-200. 

International Whaling Comm ission. 1989. Ja pan. Pro gress repo rt on cetacea n research J une 198 7 to April 1988. Rep. 

Int. Whal. Commn. 39:201-204. 

Kleiber, P. 1999 . Estimates of marine mamm al takes in the Hawaiian longline fishery. (Unpub lished). Southwest 

Fisheries Science Center, NMFS, 2570 Dole St, Honolulu, HI, 96822-2396. 

Leatherwo od, S., R. R . Reeves, W . F. Perrin, and W. E. E vans. 198 2. Whales, dolphins, and porpoises of the eastern 

North Pacific and adjacen t arctic waters: A guide to their identification. NOAA Tech. Rep. NMFS 444, 245 

pp. 

Mob ley, 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. 1 975. Jap anese whale marking in the N orth Pacific, 1 963-72 . Bull. Far Seas Fish. Res. Lab. 

12:171-219. 

Perrin, W.F., G . P. Dono van and J. B arlow. 1994. Gillnets and Cetaceans. Rep. Int. Whal. Commn., Special Issue 15, 

629 pp. 

Shallenberger, E.W. 1981. T he status of Hawaiian cetaceans. Final report to U.S. Marine Mammal Co mmission. MMC77/23, 79pp. 

Tillman, M . F. 197 8. M odified Del ury e stimates of th e No rth P acific Bryde's whale stock. Rep. Int. Whal. Commn. 

28:315-317. 

229 
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. 

230