NOAA TECHNICAL MEMORANDUM 

NOAA-TM-NMFS-SWFSC-282 

U. S. Pacific 

Marine Mammal Stock Assessments: 1999

by 

Karin A. Forney, Marcia M. Muto and Jason Baker 

with contributions from

Jay Barlow, Nancy Black, John Calambokidis, Grant Cameron, Susan 

Chivers, Joe Cordaro, Douglas DeMaster, Graeme Ellis, 

Marilyn Fluharty, and P. Scott Hill.

U. S. Department of Commerce

National Oceanic and Atmospheric Administration

National Marine Fisheries Service

Southwest Fisheries Science Center

La Jolla, California 92038

December 1999
TABLE OF CONTENTS 

PREFACE ................................................................... iii

PINNIPEDS 

HAWAIIAN MONK SEAL (Monachus schauinslandi) ......................................................... 1

CETACEANS - U.S. WEST COAST 

HARBOR PORPOISE (Phocoena phocoena): Central California Stock ............................................. 8

HARBOR PORPOISE (Phocoena phocoena): Northern California Stock ........................................... 12

HARBOR PORPOISE (Phocoena phocoena): Oregon/Washington Coast Stock ..................................... 15

HARBOR PORPOISE (Phocoena phocoena): Inland Washington Stock ........................................... 20

KILLER WHALE (Orcinus orca): Eastern North Pacific Transient Stock ........................................... 27

KILLER WHALE (Orcinus orca): Eastern North Pacific Offshore Stock ........................................... 33

KILLER WHALE (Orcinus orca): Eastern North Pacific Southern Resident Stock .................................... 37

SHORT-FINNED PILOT WHALE (Globicephala macrorhynchus): California/Oregon/Washington Stock ................ 42

SPERM WHALE (Physeter macrocephalus): California/Oregon/Washington Stock ................................... 46

HUMPBACK WHALE (Megaptera novaeangliae): California/Oregon/Washington - Mexico Stock ...................... 51

APPENDICES 

APPENDIX 1: Chronology of U. S. Pacific Stock Assessment Reports, 1995-1999 ................................... 57

APPENDIX 2: Summary of 1999 Pacific Marine Mammal Stock Assessment Reports ................................ 62

ii 
PREFACE 

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

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

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

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

becomes available. This report presents updated information for several stocks in the Pacific Region under NMFS 

jurisdiction, including both strategic stocks and stocks for which new information on abundance and population 

structure has become available. These assessments 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). The southern sea otter, which is under the management jurisdiction of the USFWS, is covered in a 

separate report. A 1995-99 chronology of revision and publication dates for all Pacific Region stocks under NMFS 

jurisdiction is provided in Appendix 1. 

The National Marine Fisheries Service reviewed new information pertaining to the status of all stocks within 

the Pacific Region and, in consultation with the Pacific Scientific Review Group, decided that there was sufficient new 

information to warrant the revision of assessment reports for 11 stocks. The Stock Assessment Reports for 1999 include 

four written by staff of the National M arine Mammal Laboratory: Oregon & Washington Coast Harbor Porpoise, Inland 

Washington Harbor Porpoise, Eastern North Pacific Southern Resident Killer Whale and Eastern North Pacific Transient 

Killer Whale. Southwest Fisheries Science Center personnel prepared stock assessments for the following seven stocks: 

Hawaiian Monk Seal, Central California Harbor Porpoise, Northern California Harbor Porpoise, Eastern North Pacific 

Offshore Killer Whale, California/Oregon/ Washington Short-finned Pilot Whale, California/Oregon/ Washington Sperm 

Whale, and California/ Oregon/Washington-Mexico Humpback Whale. A summary table for these revised stock 

assessment reports is provided in Appendix 2. 

In the 1999 Stock Assessment Reports, the previous California/Oregon/Washington Killer Whale stock (Barlow 

et al. 1997) has been eliminated, based on new information on stock structure of eastern North Pacific killer whales. The 

animals from this stock have now been divided among two other stocks: 1) the existing Eastern North Pacific Transient 

stock, whose range description has been expanded southward to include California, and 2) a new ‘Eastern North Pacific 

Offshore’ stock, ranging from Southeast Alaska to California. The Eastern North Pacific Transient Killer Whale stock, 

which was previously published in the Stock Assessment reports for the Alaska Region (Hill and DeMaster 1998), has 

also been moved and is now included with the 1999 Pacific Region reports. 

Fishery mortality sections in the 1999 stock assessment reports have been updated to include information on 

fishery mortality through 1997, where possible. New abundance estimates are available and have been included for 10 

of the 11 stocks. Additional information on historic whaling has been included for sperm whales, and several distribution 

maps have been revised to include survey data through 1996 and to exclude data from the 1970s and early 1980s that are 

now considered outdated. The recovery factor was revised for four stocks (central California harbor porpoise, 

California/Oregon/Washington short-finned pilot whale, eastern North Pacific southern resident killer whale and eastern 

North Pacific transient killer whale). There were no changes in the status of any of the eleven stocks, with four remaining 

strategic and seven non-strategic. The four strategic stocks include three stocks of endangered species that are 

automatically considered strategic, and the California/Oregon/Washington short-finned pilot whale, for which a take 

reduction plan has been implemented. 

The following is the Final 1999 U.S. Pacific Stock Assessment Report. A draft version of this document was 

made available for public comment from May 28 - August 26, 1999 (Federal Register: May 28, 1999, Volume 64, Number 

103, Pages 29000-29005). No public comments were received. Earlier versions of these stock assessment reports were 

reviewed by members of the Pacific and Alaska Scientific Review Groups and by Jay Barlow, Doug DeMaster, Scott Hill, 

and Paul Wade; we thank them for their helpful comments. The authors also wish to thank those who provided 

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

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

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

or comments which would improve future stock assessment reports. 

iii 
References: 

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. Department of Commerce, 

NOAA Technical Memorandum NMFS-SWFSC-248. 223 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. 

iv 
Revised 9/30//99 

HAWAIIAN MONK SEAL (Monachus schauinslandi) 

STOCK DEFINITION AND GEOGRAPHIC RANGE 

Hawaiian monk seals are distributed throughout the Northwestern Hawaiian Islands (NWHI) in six main 

reproductive 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 centuries, the species has experienced two major declines which, presumably, have severely 

reduced its genetic variation. The tendency for genetic drift may have been (and continue to be) relatively large, due to 

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

(Johnson and Kridler 1983, National Marine Fisheries Service [NMFS] unpubl. data) and, to some degree, this movement 

should counter the development of separate genetic stocks. Genetic variation among the different island populations 

is low (Kretzmann et al., 1997). 

Demographically, the different island 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 

(Gerrodette and Gilmartin 1990). Current demographic variability among the island populations probably reflects a 

combination of different recent histories and varying environmental conditions. While research and recovery activities 

focus on the problems of single island/atoll 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 reproductive populations can be identified on the basis of those tags. In 1997, identification efforts were 

conducted during two- to six-month studies at all main reproductive sites except Midway Atoll, where the study period 

was 10 months. A total of 1295 seals (including pups) were observed at the main reproductive populations in 1997 

(NMFS, unpubl. data). Removal analyses in previous years and sighting probability calculations suggest that 90% or 

more of the seals were identified at each site (i.e., any negative bias should be less than 10%). 

Monk seals also occur at Necker and Nihoa Islands, where 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) counts (excluding pups) 

were 22 (±5.2) at Necker Island and 18 (±7.3) at Nihoa Island (Ragen and Finn 1996). The observed relationship between 

mean counts and total abundance at the reproductive sites indicates that the total abundance can be estimated by 

multiplying the mean count by a correction factor (±SE) of 2.89 (±0.06, NMFS unpubl. data). Resulting estimates (plus 

the number of pups born in 1993) are 65 (±15.1) at Necker Island and 56 (±21.1) at Nihoa Island. 

Finally, a small number of seals are distributed throughout the main Hawaiian Islands. These include an 

unknown number of seals, which naturally occur in the main Hawaiian Islands. In addition, twenty-one seals were 

released around these islands in 1994. All but two were subsequently resighted near their respective release sites, but 

their survival to 1997 is unknown. Sporadic reports indicate total abundance on the main Hawaiian Islands (including 

seals released in 1994) may be as high as 40 seals. 

Minimum Population Size 

The total number of seals identified at the main reproductive sites is the best estimate of minimum population 

size at those sites (i.e., 1295 seals). Minimum population sizes for Necker and Nihoa Islands (based on the formula 

provided by Wade and Angliss (1997)) are 54 and 41, respectively. If it is (arbitrarily) assumed that the abundance 

estimate for seals 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 estimates, or 1423 seals. 

1 
Current Population Trend 

Between 1958 and 1997, the total of 

mean beach counts at the main reproductive 

populations declined by 60%. From 1985 to 1997, 

the rate of decline was ca. 4% 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 MAXIMUM NET 

PRODUCTIVITY RATES 

Assuming mean beach counts are a 

reliable index of total abundance, then the current 

net productivity rate for this species is -0.04 yr-1 

(loglinear regression of beach counts of nonpups, 1985-97; R2 = 0.82, P<0.001). This trend is 

largely due to a catastrophic decline at French 

Frigate Shoals, where beach counts decreased by 

350 

400 

450 

500 

550 

600 

Mean Number of Non-Pups 

1984 1986 1988 1990 1992 1994 1996 1998 

Year 

Figure 1. Total of mean beach counts (non-pups) at the main 

reproductive populations (excluding Midway Atoll) of the 

Hawaiian monk seal, 1986-97. 

56% between 1989 and 1997. Populations at Laysan and Lisianski Islands have not grown, but have remained relatively 

stable since approximately 1990. 

Contrary to trends at the above sites, the population at Kure Atoll has grown at ca. 5% yr-1 since 1983 (loglinear 

regression of beach counts, 1983-97; R2 = 0.75, P<0.001), due largely to decreased human disturbance and introduced 

females. The population at Pearl and Hermes Reef has grown at approximately 7% yr-1 since 1975 (loglinear regression 

of beach counts, 1975-1997; R2 = 0.91, P<0.001). The latter annual growth rate is the best indicator of the maximum net 

productivity rate (Rmax) for this species. Finally, the small population at Midway Atoll is showing signs of incipient 

recovery. 

POTENTIAL BIOLOGICAL REMOVAL 

Using the values of Nmin and Rmax given above (1423 and 0.07 yr-1, respectively) and a recovery factor (FR) of 

0.1 (the Hawaiian monk seal was designated as both endangered and depleted in 1976), the potential biological removal 

(PBR) for this species is calculated as 1423 * (0.07 * (0.5)) * 0.1 = 5.0 seals. 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 1912, Wetmore 1925, 

Clapp and Woodward 1972). Several populations may have been driven extinct; for example, no seals were seen at 

Midway Atoll during a 14-month period in 1888-89, and only a single seal was seen during three months of observations 

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

half of this century (Rice 1960). However, subsequent surveys revealed that all 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 Laysan Islands. At Kure Atoll, Midway Atoll, and French Frigate Shoals, trends appear to have been 

determined by the pattern of human disturbance from military or U.S. Coast Guard activities. Such disturbance caused 

pregnant females to abandon prime pupping habitat and nursing females to abandon their pups (Kenyon 1972, Gerrodette 

and Gilmartin 1990). The result was a decrease in pup survival, which led to poor reproductive recruitment, low 

productivity, and population decline. 

Since 1979, disturbance from human activities on land has been limited primarily to Kure and Midway Atolls. 

The U.S. Coast Guard LORAN station at Kure Atoll was closed in 1992 and vacated in 1993. The U.S. Naval Air Facility 

at Midway was closed in 1993 and, following clean-up and restoration activities, jurisdiction was transferred in 1997 to 

the U.S. Fish and Wildlife Service, which manages the atoll as a National Wildlife Refuge. The refuge station and the atoll 

runway are maintained cooperatively with a commercial aircraft company, which supports its Midway operations, in part, 

2 
by establishing a tourism center at the site. Strict regulations have been established to prevent further human 

disturbance of the seals, but careful monitoring of human activities will be essential to ensure that the regulations are 

both adequate and observed (see Habitat Issues below). 

In addition to disturbance on land, disturbance at sea (e.g., direct and indirect fisheries interactions) may also 

impede recovery. As described below, however, the possible types of disturbance at sea can not yet be characterized 

or quantified. 

Fishery Information 

Detrimental fishery interactions with monk seals fall into four categories: operations/gear conflict, entanglement 

in fisheries debris (most of which likely originate in North Pacific fisheries outside the NWHI), seal consumption of 

potentially toxic discards, and competition for prey. Since 1982, a total of seven fishery-related monk seal deaths have 

been recorded, including four from entanglement in fisheries debris (Henderson 1990; NMFS, unpubl. data), one from 

entanglement in the bridle rope of lobster trap (1986; NMFS, unpubl. data), one from entanglement in an illegally set gill 

net off the western shore of Oahu (1994; NMFS, unpubl. data), and one from ingestion of a recreational fish hook and 

probable drowning off the island of Kauai (1995; NMFS, unpubl. data). In addition, 16 other seals have been observed 

with embedded fish hooks, 23 seals have been observed with wounds attributed to interactions with fishing gear, and 

154 cases of seals entangled in fishing gear or other debris have been observed. Importantly, the majority of these deaths 

and injuries have been observed incidentally during land-based research or other activities; monk seal/fisheries 

interactions need to be studied more thoroughly to assess the rate of fisheries-related injury or mortality for this species. 

Four fisheries interact with Hawaiian monk seals. The NWHI lobster fishery began in the late 1970s, and 

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

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

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

abundance of slipper lobster have increased in some areas. The number of vessels in the fishery increased from four 

in 1983 to 17 in 1985, then declined to 9, 12, 0, 5, 1, 5, and 9 in 1991through 1997, respectively (Dollar 1995, DiNardo et 

al.1998). Both effort and landings have been concentrated at Gardner Pinnacles, Maro Reef, Necker Island, and St. 

Rogatien Bank (Clarke and Todoki 1988, Polovina and Moffitt 1989). Seasonal and area differences in direct and indirect 

fisheries interactions remain to be evaluated, but neither incidental mortality nor serious injury were observed in 1997. 

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. However, the potential for indirect interaction due to competition 

for prey has not been thoroughly investigated (see Habitat Issues below). 

The NWHI bottomfish fishery also interacts with monk seals. This fishery occurred at low levels (< 50 t per 

year) until 1977, steadily increased to 460 t in 1987, and then dropped to ca. 140 to 190 t per year from 1988 to 1994 

(Kawamoto 1995). During 1995-1997 landings again increased to 384 to 486 t per year (Kawamoto, pers. comm.). The 

number of vessels rose from 19 in 1984 to 28 in 1987, and then varied from 10 to 17 in 1988 through 1997 (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. Importantly, the State logbook does not 

include information on protected species and, therefore, the nature and extent of interactions with monk seals cannot 

be reliably 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 events 

included seals damaging and removing hooked catch, seals being hooked in the process, and seals consuming discarded 

fish, which may contain high levels of ciguatoxin or other biotoxins. Mortality rates resulting from hooking or 

consumption of toxic discards cannot be estimated 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. 

A third fishery which interacts with monk seals is the pelagic longline fishery. This fishery targets swordfish 

and tunas, primarily, and does not compete with Hawaiian monk seals for prey. The fishery began in the 1940s, and 

operated at a relatively low level (< 5000 t per year) until the mid-1980s. In 1987, 37 vessels participated, but by 1991, the 

number had grown to 141 (Ito 1995). Entry is currently limited to a maximum of 167 vessels, and 124, 110, 103, and 105 

vessels were active in 1994-1997, respectively (Ito, pers. comm.). Total landings ranged from 9,100-13,500 tons during 

1991-1997. While much of the fishery has operated outside of the NWHI Exclusive Economic Zone, the rapid expansion 

raised concerns about the potential for interactions with protected species, including the monk seal. Evidence of 

interactions began to accumulate in 1990, including three hooked seals and 13 unusual seal wounds thought to have 

resulted from interactions. In October 1991, NMFS established a permanent Protected Species Zone extending 50 nautical 

miles around the NWHI and the corridors between the islands. Subsequent shore-based observations of seals suggest 

3 
that interactions decreased substantially after establishment of the Protected Species Zone, although they may still be

occurring; at French Frigate Shoals in 1994, a parturient female was observed with a hook in her mouth. At present,

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

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

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

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 

Current est. 

# of vessels Date type 

Range of 

observer 

coverag 

e 

Observed 

mort. (in 

given 

years) 

Estimated 

mort. (in 

given 

years) 

Mean 

annual 

mort. 

NWHI 

lobster 

91-97 9, 12, 0, 5, 1, 5, 9 Log book n/a n/a n/a n/a 

NWHI 

Bottomfish 

91-97 17, 13, 12, 16, 17, 

16, 14 n/a n/a n/a n/a n/a 

Pelagic 

longline 

91-97 141, 123, 122, 125, 

110, 103, 105 

Observer 

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

Recreational 91-95 n/a n/a n/a [0,0,0,1,1]† n/a n/a 

†

 Data collected incidentally. 

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

the main Hawaiian Islands. At least three seals have been hooked at Kure Atoll, but such incidents should no longer 

occur at this site because the atoll was vacated by the U.S. Coast Guard in 1993. In the main Hawaiian Islands, one seal 

was found dead in an offshore (non-recreational) gillnet in 1994 and a second seal was found dead with a recreational 

hook lodged in its esophagus. At least seven other seals have been hooked. Three of these incidents involved hooks 

used to catch ulua (Caranx spp.). One hooked seal had been translocated from Laysan Island to the main Hawaiian 

Islands in July 1994. The recent establishment of sport fishing at Midway clearly increases the potential for monk seals 

to be harmed by hooks at that site. 

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

monk seals. The removal of coral and the subsequent impact on monk seal prey resources is currently unknown. 

Fishery Mortality Rate 

Because monk seals continue to die as a result of entanglement in fishing debris and data are unavailable to 

assess interaction with specific fisheries, one must conclude that the total fishery mortality and serious injury for this 

stock is greater than 1) zero allowable take under the Endangered Species Act and 2) 10% of the calculated PBR. 

Therefore, total fishery mortality and serious injury can not be considered to be insignificant and approaching a rate of 

zero. 

Importantly, fishery interactions with this species have not been adequately studied and, therefore, the 

information above represents only the minimum level of interactions, not the true level. Without further study, the true 

level of interaction cannot be estimated. 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 have not been evaluated. 

Other Mortality 

Since 1982, 19 seals have died during rehabilitation efforts, five during research activities, three while held in 

permanent captivity, and two when captured for translocation. 

Seals have also died after encounters with marine debris from sources other than fisheries. In 1986, a weaned 

pup died at East Island, French Frigate Shoals, after becoming entangled in wire left when the U.S. Coast Guard 

abandoned the island three decades earlier. In 1991, a seal died after becoming trapped behind an eroding seawall on 

4 
Tern Island, French Frigate Shoals. This seawall continues to erode and poses an ongoing threat to the safety of seals 

and other wildlife. 

The only documented case of illegal killing of an Hawaiian monk seal occurred when a resident of Kauai killed 

an adult female in 1989. 

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

attacked seal. Since 1982, at least 64 seals have died or disappeared after being mobbed. The resulting increase in female 

mortality appears to be a major impediment to recovery at Laysan and Lisianski Islands. It has also been documented 

at French Frigate Shoals, Kure Atoll (although not recently), and Necker Island. The primary cause of mobbing is thought 

to be an imbalance in the adult sex ratio, with males outnumbering females. In 1994, 22 adult males were removed from 

Laysan Island, and only one seal is thought to have died from mobbing at this site since their removal (1995-97). Such 

imbalances in the adult sex ratio are more likely to occur when populations are reduced (Starfield et al. 1995). 

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

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

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

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 is probably not the primary cause of the recent decline at this site (Ragen 1993). 

The annual rate and number of shark-related mortalities is being investigated. Poisoning by ciguatoxin or related toxins 

is suspected as the primary cause of the Laysan die-off in 1978, and may have contributed to the high mortality of 

juvenile seals translocated to Midway Atoll in 1992 and 1993. While virtually all wild monk seals carry parasites after they 

begin to forage, the role of parasitism in monk seal mortality is unknown. The effect of disease on monk seal demographic 

trends is also uncertain. 

STATUS OF STOCK 

In 1976, the Hawaiian monk seal was designated depleted under the Marine Mammal Protection Act of 1972 and 

as endangered under the Endangered Species Act of 1973. The species is assumed to be well below its Optimum 

Sustainable Population (OSP) and, since 1985, has declined 4% per year. Therefore, the Hawaiian monk seal is 

characterized as a strategic stock. 

Habitat Issues 

The catastrophic decline at French Frigate Shoals is thought to be related to lack of available prey and 

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

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

capacity was simultaneously reduced by changes in oceanographic conditions and a resulting decrease in productivity 

(Polovina et al. 1994; Craig and Ragen, in press). Thus, this population may have significantly exceeded its carrying 

capacity, leading to a catastrophic increase in juvenile mortality. In addition, available prey also may have been reduced 

by competition with the NWHI lobster fishery. Monk seals forage at the four main banks where the fishery operates: 

Maro Reef, Gardiner Pinnacles, St. Rogatien Bank, and Necker Island. Thus, competition for prey merits investigation. 

This potential for competition cannot yet be evaluated because it is not known if lobster is an important component of 

the monk seal diet. 

A second important habit at issue is the management of human activities at Midway Atoll. Historically, human 

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

in the 1960s. The seal population failed to recover in the 1970s and 1980s, but is finally beginning to show some signs 

of growth due to immigration from nearby sites. Management jurisdiction of Midway Atoll has been transferred from 

the U.S. Navy to the Fish and Wildlife Service. The Fish and Wildlife Service maintains a refuge station at Midway Atoll 

by cooperating with a commercial aircraft company that uses the runway on Sand Island (the largest island at Midway 

Atoll), and support its operations, in part, by establishing an on-site eco-tourism destination. Tourist activities include 

a range of land-based and marine recreational activities (e.g., scuba diving and sport fishing), as well as harbor services 

to visiting vessels. As the tourism venture develops, so does a potential conflict of interest. The economic success of 

the venture may depend on the nature and variety of human activities or privileges allowed at the site. Importantly, those 

activities that are intended to enhance the Midway experience may be disruptive or detrimental to the refuge and its 

wildlife. The issue is whether such potential conflicts can be identified and resolved in a manner that allows for 

5 
continuation of the ecotourism venture but does not impede monk seal recovery. The Fish and Wildlife Service and 

NMFS are working cooperatively to ensure that human activities do not impede recovery at this important site. 

An important habitat issue is the degrading seawall at Tern Island, French Frigate Shoals. Tern Island is the 

site of the U.S. Fish and Wildlife refuge station, and is one of two sites in the NWHI accessible by aircraft. The island 

and the runway have played a key role in efforts to study the local monk seal population, and to mitigate its severe and 

ongoing decline. During World War II, the U.S. Navy enlarged the island to accommodate the runway. A sheet-pile 

seawall was constructed to maintain the modified shape of the island. Degradation of the seawall is creating entrapment 

hazards for seals and other wildlife, and is threatening to erode the runway. The loss of the runway could lead to the 

closure of the Fish and Wildlife Service station at the site and would thereby reduce on-site management of the refuge. 

The loss of the runway and refuge station would also hinder research and management efforts to recover the monk seal 

population. 

A fourth important habitat issue involves entanglement in marine debris as described above. Marine debris is 

removed from the beaches and from entangled seals during annual population assessment activities at the main 

reproductive sites. Efforts to remove potentially entangling marine debris from the reefs surrounding haulout sites 

utilized by monk seal have recently begun. In 1996, efforts commenced to assess and remove potentially entangling 

marine debris from reefs surrounding haulout sites utilized by monk seals. Preliminary surveys suggest a very large 

number of nets are fouled on nearshore reefs in the NWHI, and may pose a serious threat to seals foraging 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 (Boland, pers. comm.). Efforts to remove nets from monk seal 

habitat are continuing and will include several cooperating agencies. 

REFERENCES 

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

Boland, R., Joint Institute for Marine and Atmospheric Science, 2570 Dole St. Honolulu, HI 96822 

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

Bull. 164:303-304 

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

Northwestern Hawaiian Islands. Available Honolulu Lab., Southwest Fish. Sci. Cent., Natl. Mar. Fish. Serv., 

NOAA, Honolulu, HI 96822-2396. Southwest Fish. Sci. Cent. Admin. Rep. H-88-6, 30 p. 

Craig, M. P. and T. J. Ragen. In press. Size, survival, and decline of juvenile Hawaiian monk seals. Mar. Mamm. Sci. 

Dill, H. R., and W. A. Bryan. 1912. Report on an expedition to Laysan Island in 1911. U.S. Dept. of Agric. Surv. Bull. 42:1­

30. 

DiNardo, G. T., W. R. Haight, and J. A. Wetherall. 1998. Status of lobster stocks in the Northwestern Hawaiian Islands, 

1995-97, and outlook for 1998. Available Honolulu Lab., Southwest Fish. Sci. Cent., Natl. Mar. Fish. Serv., 

NOAA, Honolulu, HI 96822-2396. Southwest Fish. Sci. Cent. Admin. Rep. 98-05, 35 p. 

Gerrodette, T. M., and W. G. Gilmartin. 1990. Demographic consequences of changed pupping and hauling sites of the 

Hawaiian monk seal. Conserv. Biol. 4:423-430. 

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

Honolulu Lab., Southwest Fish. Sci. Cent., Natl. Mar. Fish. Serv., NOAA, Honolulu, HI 96822-2396. Southwest 

Fish. Sci. Cent. Admin. Rep. H-95-03, 17 p. 

Henderson, J. R. 1990. Recent entanglements of Hawaiian monk seals in marine debris. In R. S. Shomura and M. L. 

Godfrey (eds.), Proceedings of the Second International Conference on Marine Debris, April 2-7, 1989, 

Honolulu, Hawaii, p. 540-553. U.S. Dep. Commer., NOAA, Tech. Memo. NMFS-SWFSC-154. 

Ito, R. Y., Southwest Fisheries Science Center, NMFS, 2570 Dole St., Honolulu, HI 96822-2396. 

Ito, R. Y. 1995. Annual report of the 1994 Hawaii-based longline fishery. Available Honolulu Lab., Southwest Fish. Sci. 

Cent., Natl. Mar. Fish. Serv., NOAA, Honolulu, HI 96822-2396. Southwest Fish. Sci. Cent. Admin. Rep. H-95-08, 

36 p. 

Johnson, A. M., and E. Kridler. 1983. Interisland movement of Hawaiian monk seals. 'Elepaio 44(5):43-45. 

Kawamoto, K. E., Southwest Fisheries Science Center, NMFS, 2570 Dole St., Honolulu, HI 96822-2396. 

Kawamoto, K. E. 1995. Northwestern Hawaiian Islands bottomfish fishery, 1994. Available Honolulu Lab., Southwest 

Fish. Sci. Cent., Natl. Mar. Fish. Serv., NOAA, Honolulu, HI 96822-2396. Southwest Fish. Sci. Cent. Admin. Rep. 

H-95-07, 26 p. 

6 
Kenyon, K. W. 1972. Man versus the monk seal. J. of Mammal. 53(4):687-696. 

Kretzmann, M. B., W. G. Gilmartin, A. Meyer, G. P. Zegers, S. R. Fain, B. F. Taylor, and D. P. Costa. 1997. Low genetic 

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

Nitta, E. T., and J. R. Henderson. 1993. A review of interactions between Hawaii's fisheries and protected species. Mar. 

Fish. Rev. 55(2):83-92. 

Polovina, J. J. 1993. The lobster and shrimp fisheries in Hawaii. Mar. Fish. Rev. 55(2):28-33. 

Polovina, J. J., G. T. Mitchum, N. E. Graham, M. P. Craig, E. E. DeMartini, and E. N. Flint. 1994. Physical and biological 

consequences of a climate event in the central North Pacific. Fish. Ocean. 3:15-21. 

Polovina, J. J., and R. B. Moffitt. 1989. Status of lobster stocks in the Northwestern Hawaiian Islands, 1988. Available 

Honolulu Lab., Southwest Fish. Sci. Cent., Natl. Mar. Fish. Serv., NOAA, Honolulu, HI 96822-2396. Southwest 

Fish. Sci. Cent. Admin. Rep. H-89-3, 10 p. 

Pooley, S. G., and K. E. Kawamoto. 1998. Annual report of the 1995-97 western Pacific lobster fishery. Available 

Honolulu Lab., Southwest Fish. Sci. Cent., Natl. Mar. Fish. Serv., NOAA, Honolulu, HI 96822-2396. Southwest 

Fish. Sci. Cent. Admin. Rep. H-98-09, 34 p. 

Ragen, T. J. 1993. Status of the Hawaiian monk seal in 1992. Available Honolulu Lab., Southwest Fish. Sci. Cent., Natl. 

Mar. Fish. Serv., NOAA, Honolulu, HI 96822-2396. Southwest Fish. Sci. Cent. Admin. Rep. H-93-05, 79 p. 

Ragen, T. J., and M. A. Finn. 1996. The Hawaiian monk seal on Nihoa and Necker Islands, 1993. Pages 89-104 in T. C. 

Johanos and T. J. Ragen (eds.), The Hawaiian monk seal in the Northwestern Hawaiian Islands, 1993. U.S. Dep. 

Commer., NOAA, Tech. Memo. NMFS-SWFSC-227. 

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

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

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

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

April 3-5, 1996, Seattle, Washington. NOAA Technical Memorandum NMFS-OPR-12 available from Office of 

Protected Resources, National Marine Fisheries Service, Silver Springs, MD. 93pp. 

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

7 
Revised 09/30/99 

HARBOR PORPOISE (Phocoena phocoena): Central California Stock 

STOCK DEFINITION AND GEOGRAPHIC RANGE 

In the Pacific, harbor porpoise are found in coastal and 

inland waters from Point Conception, California to Alaska and 

across to Kamchatka and Japan (Gaskin 1984). Harbor porpoise 

appear to have more restricted movements along the western 

coast of the continental U.S. than along the eastern coast. 

Regional differences in pollutant residues in harbor porpoise 

indicate that they do not move extensively between California, 

Oregon, and Washington (Calambokidis and Barlow 1991). 

That study also showed some regional differences within 

California (although the sample size was small). This pattern 

stands as a sharp contrast to the eastern coast of the U.S. and 

Canada where harbor porpoise are believed to migrate 

seasonally from as far south as the Carolinas to the Gulf of 

Maine and Bay of Fundy (Polacheck et al. 1995). A 

phylogeographic analysis of genetic data from northeast Pacific 

harbor porpoise did not show complete concordance between 

DNA sequence types and geographic location (Rosel 1992). 

However, an analysis of molecular variance (AMOVA) of the 

same data with additional samples found significant genetic 

differences for four of the six pair-wise comparisons between 

the four areas investigated: California, Washington, British 

Columbia, and Alaska (Rosel et al 1995). These results Figure 1. Stock boundaries and distributional range 

demonstrate that harbor porpoise along the west coast of North of harbor porpoise along the U.S. west coast. 

America are not panmictic or migratory, and movement is 

sufficiently restricted that genetic differences have evolved. 

In their assessment of harbor porpoise, Barlow and Hanan (1995) recommended that the animals inhabiting 

central California (defined to be from Point Conception to the Russian River) be treated as a separate stock. Their 

justifications for this were: 1) fishery mortality of harbor porpoise is limited to central California, 2) movement of 

individual animals appears to be restricted within California, and consequently 3) fishery mortality could cause the local 

depletion of harbor porpoise if central California is not managed separately. Although geographic structure exists along 

an almost continuous distribution of harbor porpoise from California to Alaska, stock boundaries are difficult to draw 

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

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

the guidance of Barlow and Hanan (1995), we will consider the harbor porpoise in central California as a separate stock. 

Other Pacific coast Marine Mammal Protection Act (MMPA) stock assessment reports for harbor porpoise include: 1) 

a northern California stock 2) an Oregon/Washington coast stock, 3) an Inland Washington stock, 4) a Southeast Alaska 

stock, 5) a Gulf of Alaska stock, and 6) a Bering Sea stock. Stock assessment reports for northern California and the 

Oregon and Washington stocks appear in this volume. The three Alaska harbor porpoise stocks are reported separately 

in the Stock Assessment Reports for the Alaska Region. 

POPULATION 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 Forney (1994). The more recent estimate is higher and 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 of these 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, Green et al.(1992) found that 24% of harbor porpoise seen during aerial surveys of Oregon and Washington 

8 
were between the 100m and 200m isobaths (55 to 109 fathoms). The above abundance estimates are likely to 

underestimate the total abundance of harbor porpoise by an unknown, but non-trivial amount. 

Minimum Population Estimate 

The minimum population estimate for harbor porpoise in central California is taken as the lower 20th percentile 

of the log-normal distribution of the 

abundance estimated from the 1993-97 

aerial surveys (Forney 1999a) or 4,172. 

Current Population Trend 

An analysis of a 1986-95 time 

series of aerial surveys was 

conducted to examine trends in harbor 

porpoise abundance in central 

California (Forney 1999b). After 

controlling for the effects of sea state, 

cloud cover, and area on sighting 

rates, Forney (1999b) found a 

negative trend in population size, but 

that trend was not statistically 

significant (p=0.15) (Figure 2). 

Between 1986 and 1995, harbor 

porpoise abundance was negatively 

correlated with sea surface 

temperature (Forney 1999b), 

indicating that apparent trends could 

be caused by changing 

0.00 

0.10 

0.20 

Porpoise/km 

85 86 87 88 89 90 91 92 93 94 95 96 

Year 

HPAS 86-95 adjusted relative abundance 

Central CA Avg. 

North Central 

South Central 

Figure 2. Harbor porpoise relative abundance in central California from 

1986-95 aerial surveys (corrected for effects of sea state and cloud cover, 

Forney 1999b). 

oceanographic conditions and movement of animals into and out of the study area. Encounter rates for the 1997 survey, 

however, were very high (Forney 1999a) despite the warmer sea surface temperatures caused by strong El Niño 

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

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

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES 

Based on what are argued to be biological limits of the species (i.e. females give birth first at age 4 and produce 

one calf per year until death), the theoretical, maximum-conceivable growth rate of a closed harbor porpoise population 

was estimated as 9.4% per year (Barlow and Boveng 1991). This maximum theoretical rate may not be achievable for any 

real population. [Woodley and Read (1991) calculate a maximum growth rate of approximately 5% per year, but their 

argument for this being a maximum (i.e. that porpoise survival rates cannot exceed those of Himalayan thar) is not well 

justified.] Population growth rates have not actually been measured for any harbor porpoise population. We therefore 

conclude that the current and maximum net productivity rates are unknown for the central California population of harbor 

porpoise. 

POTENTIAL BIOLOGICAL REMOVAL 

The potential biological removal (PBR) 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 with 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 set gillnet fisheries in central California (coastal 

setnets are not allowed in northern California, and harbor porpoise do not occur in southern California). Detailed 

information on this fishery is provided in Appendix 1 of Barlow et al. (1997). A summary of estimated fishery mortality 

and injury for this stock of harbor porpoise is given in Table 1, based on analyses of entanglement rate data for a 1990-94 

9 
observer program (Julian 1997, Cameron 1998, Julian and Beeson 1998). These data indicate that an average of 24 harbor 

porpoise (range 13-49, CV=0.27) have been killed in all of central California (including both Morro Bay and Monterey Bay 

regions) each year for the period 1993-1997. However, since 1994, there has been a shift in set gillnet effort, with more 

effort in areas of high harbor porpoise density (Monterey Bay) and less effort in the lower density regions around Morro 

Bay, where no harbor porpoise mortalities were observed after 1990. Therefore, the mortality estimates presented below 

(Table 1) may be negatively biased. In a more recent preliminary analysis of mortality using effort and entanglement data 

only for the Monterey Bay region and including additional 1987-90 entanglement data for the areas presently being 

fished, Forney (1998) suggests that mortality could be substantially higher. Average annual estimates of mortality for 

1993-97 in that study are 107 harbor porpoise (range 49 to 202; CV=0.12) using a stratified analysis, or 99 harbor porpoise 

(range 62-160, CV=0.19) using an unstratified analysis for the entire Monterey Bay region. An observer program was 

initiated this area in April 1999, and more accurate data are expected to be available in the near future. 

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 (Barlow and Hanan 1995; Julian 1997, Cameron 1998, Julian and Beeson 

1998). n/a indicates that data are not available. 

Fishery Name Year(s) Data 

Type 

Percent 

Observer 

Coverage 

Observed 

Mortality 

Estimated 

Mortality (CV 

in 

parentheses) 

Mean Annual Takes 

1993-97 

(CV in parentheses) 

CA angel shark / 

halibut and other 

species large mesh 

(>3.5") set gillnet 

fishery 

1993 

1994 

1995 

1996 

1997 

NMFS 

observer 

data 

15.4% 

7.7% 

0.0% 

0.0% 

0.0% 

2 

1 

-

-

-

13 (0.64) 

14 (0.96) 

14 (0.64) 1 

32 (0.28) 1 

49 (0.27) 1 

24 (0.27) 

CA set and drift 

gillnet fishery that 

use a stretched mesh 

size of 3.5" or less 

(white croaker) 

1980s 

CDFG 

observer 

data 

n/a 1 in 200 

sets 

n/a n/a 

Total annual takes 24 (0.27) 

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

entanglement rates. 

STATUS OF STOCK 

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

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

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

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

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

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

Sustainable Population (OSP) levels in central California must be treated as unknown. The average mortality rate over 

the last five years (24) is less than the calculated PBR (42) for central California harbor porpoise; therefore, the central 

California harbor porpoise population is not "strategic" under the MMPA. The Pacific Scientific Review Group 

(established by the MMPA) recommended that this stock be considered strategic because it was thought to be declining. 

Because the apparent decline in the population is likely to be natural and is no longer statistically significant, the NMFS 

does not believe that a strategic status is justified at this time. However, this determination should be reviewed after 

additional mortality data become available at the end of 1999 for the Monterey Bay area set gillnet fishery, because true 

mortality may be higher than the currently published estimates. Research activities will continue to monitor the 

population size and to investigate population trends. The average gillnet mortality for the last 5 years (24 porpoise per 

year) is greater than 10% of 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 

10 
this stock. 

REFERENCES 

Barlow, J. 1988. Harbor porpoise (Phocoena phocoena) abundance estimation in California, Oregon and Washington: 

I. Ship surveys. Fish. Bull. 86:417-432. 

Barlow, J. and P. Boveng. 1991. Modeling age-specific mortality for marine mammal populations. Marine Mammal Sci. 

7(1):84-119. 

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 K. A. Forney. 1994. An assessment of the 1994 status of harbor porpoise in California. NOAA Technical 

Memorandum NOAA-TM-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. 

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. 

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

discreteness in harbor porpoises from Washington, Oregon, and California. pp. 101-110 In: J. E. Reynolds III 

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

Cameron, G. 1998. Cetacean mortality in California gill net fisheries: Preliminary estimates for 1997. Paper SC/50/SM02 

presented to the International Whaling Commission, June 1998 (unpublished). 15 pp. 

Forney, K. A. 1998. A review of 1990-97 set gillnet fisheries in the Monterey Bay area and revised estimates of mortality 

for harbor porpoise, Phocoena phocoena, and sea otters, Enhydra lutris. Background paper 98-PSRG-4 

submitted to the Pacific Scientific Review Group Meeting, Seattle, WA, November 16-18, 1998. 

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, 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? Journal of Cetacean Research and Management 1:73-80. 

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

direct and indirect catches. Rep. int. Whal. Commn 34:569-586. 

Green, G. A., J. J. Brueggeman, R. A. Grotefendt, C. E. Bowlby, M. L. Bonnell, and K. C. Balcomb, III. 1992. Cetacean 

distribution and abundance off Oregon and Washington, 1989-1990. Ch. 1 In: J. J. Brueggeman (ed.). Oregon 

and Washington Marine Mammal and Seabird Surveys. Minerals Management Service Contract Report 14-12­

0001-30426 prepared for the Pacific OCS Region. 

Julian, F. 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. Fishery Bulletin 96:271-284. 

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

surveys: estimating g(0). Journal of Wildlife Management 61:63-75. 

Polacheck, T., F. W. Wenzel, and G. Early. 1995. What do stranding data say about harbor porpoise (Phocoena 

phocoena)? Report International Whaling Commission, Special Issue 16:169-179. 

Rosel, P. E. 1992. Genetic population structure and systematic relationships of some small cetaceans inferred from 

mitochondrial DNA sequence variation. Ph.D. Dissertation, Univ. Calif. San Diego. 191pp. 

Rosel, P. E., A. E. Dizon, and M. G. Haygood. 1995. Variability of the mitochondrial control region in populations of the 

harbour porpoise, Phocoena phocoena, on inter-oceanic and regional scales. Can. J. Fish. and Aquat. Sci. 

52:1210-1219. 

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

Workshop April 3-5, 1996, Seattle, Washington. U. S. Dep. Commerce, NOAA Technical Memorandum NMFSOPR-12. 93 pp. 

Woodley, T. H. and A. J. Read. 1991. Potential rates of increase of a harbour porpoise (Phocoena phocoena) population 

11 
subjected to incidental mortality in commercial fisheries. Can. J. Fish. Aquat. Sci. 48:2429-2435. 

12
Revised 09/30/99 

HARBOR PORPOISE (Phocoena phocoena): Northern California Stock 

STOCK DEFINITION AND GEOGRAPHIC RANGE 

In the Pacific, harbor porpoise are found in coastal 

and inland waters from Point Conception, California to Alaska 

and across to Kamchatka and Japan (Gaskin 1984). Harbor 

porpoise appear to have more restricted movements along the 

western coast of the continental U.S. than along the eastern 

coast. Regional differences in pollutant residues in harbor 

porpoise indicate that they do not move extensively between 

California, Oregon, and Washington (Calambokidis and Barlow 

1991). That study also showed some regional differences 

within California (although the sample size was small). This 

pattern stands as a sharp contrast to the eastern coast of the 

U.S. and Canada where harbor porpoise are believed to migrate 

seasonally from as far south as the Carolinas to the Gulf of 

Maine and Bay of Fundy (Polacheck et al. 1995). A 

phylogeographic analysis of genetic data from northeast 

Pacific harbor porpoise did not show complete concordance 

between DNA sequence types and geographic location (Rosel 

1992). However, an analysis of molecular variance (AMOVA) 

of the same data with additional samples found significant 

genetic differences for four of the six pair-wise comparisons 

between the four areas investigated: California, Washington, 

British Columbia, and Alaska (Rosel et al 1995). These results Figure 1. Stock boundaries and distributional range demonstrate that harbor porpoise along the west coast of of harbor porpoise along the U.S. west coast. North America are not panmictic or migratory, and movement 

is sufficiently restricted that genetic differences have evolved. 

In their assessment of harbor porpoise, Barlow and Hanan (1995) recommended that the animals inhabiting 

central California (defined to be from Point Conception to the Russian River) be treated as a separate stock. Their 

justifications for this were: 1) fishery mortality of harbor porpoise is limited to central California, 2) movement of 

individual animals appears to be restricted within California, and consequently 3) fishery mortality could cause the local 

depletion of harbor porpoise if central California is not managed separately. Although geographic structure exists along 

an almost continuous distribution of harbor porpoise from California to Alaska, stock boundaries are difficult to draw 

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

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

the guidance of Barlow and Hanan (1995), we will consider the harbor porpoise in northern California as a separate 

stock. Other Pacific coast Marine Mammal Protection Act (MMPA) stock assessment reports for harbor porpoise 

include: 1) a central California stock, 2) an Oregon/Washington coast stock, 3) an Inland Washington stock, 4) a 

Southeast Alaska stock, 5) a Gulf of Alaska stock, and 6) a Bering Sea stock. Stock assessment reports for central 

California and the Oregon and Washington stocks appear in this volume. The three Alaska harbor porpoise stocks are 

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

POPULATION SIZE 

Forney (1999a) estimates the abundance of northern California harbor porpoise to be 11,066 (CV=0.39) based 

on aerial surveys in 1993-97. 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 aerial surveys from 1989 to 1993. The more recent estimate is higher 

and 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, Green et al. (1992) found that 24% of harbor porpoise seen 

13 
during aerial surveys of Oregon and Washington were between the 100m and 200m isobaths (55 to 109 fathoms). The 

above abundance estimates are likely to underestimate the total abundance of harbor porpoise by an unknown, but nontrivial amount. 

Minimum Population Estimate 

The minimum population estimate for harbor porpoise in northern California is taken as the lower 20th percentile 

of the log-normal distribution of the abundance estimated from the 1993-97 aerial surveys (Forney 1999a) or 8,061. 

Current Population Trend 

Forney (1999b) examines trends in relative harbor porpoise abundance in central and northern California based 

on aerial surveys from 1989-95. No significant trends were evident over this time period for the Northern California Stock. 

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES 

Based on what are argued to be biological limits of the species (i.e. females give birth first at age 4 and produce 

one calf per year until death), the theoretical, maximum-conceivable growth rate of a closed harbor porpoise population 

was estimated as 9.4% per year (Barlow and Boveng 1991). This maximum theoretical rate may not be achievable for any 

real population. [Woodley and Read (1991) calculate a maximum growth rate of approximately 5% per year, but their 

argument for this being a maximum (i.e. that porpoise survival rates cannot exceed those of Himalayan thar) is not well 

justified.] Population growth rates have not actually been measured for any harbor porpoise population. We therefore 

conclude that the current and maximum net productivity rates are unknown for the northern California stock of harbor 

porpoise. 

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 0.5 (for a species 

of unknown status), resulting in a PBR of 81. 

HUMAN-CAUSED MORTALITY 

Fishery Information 

The incidental capture of harbor porpoise in California is largely limited to set gillnet fisheries in central 

California. Coastal setnets are not allowed in northern California (to protect salmon resources there). 

Fishery Mortality Rates 

Because there is no known fishery mortality in northern California, the fishery mortality can be considered 

insignificant and approaching zero mortality and serious injury rate. 

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. Because of the lack of recent or historical sources of humancaused mortality, the harbor porpoise stock in northern California has been concluded to be within their Optimum 

Sustainable Population (OSP) level (Barlow and Forney 1994). Because there is no known human-caused mortality or 

serious injury, this would not be considered a "strategic" stock under the MMPA. There are no known habitat issues 

that are of particular concern for this stock. 

REFERENCES

Barlow, J. 1988. Harbor porpoise (Phocoena phocoena) abundance estimation in California, Oregon and Washington:

I. Ship surveys. Fish. Bull. 86:417-432. 

Barlow, J. and P. Boveng. 1991. Modeling age-specific mortality for marine mammal populations. Marine Mammal Sci. 

7(1):84-119. 

Barlow, J. and K. A. Forney. 1994. An assessment of the 1994 status of harbor porpoise in California. NOAA Technical 

Memorandum NOAA-TM-NMFS-SWFSC-205. 17pp. 

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

14 
Special Issue 16:123-140. 

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

discreteness in harbor porpoises from Washington, Oregon, and California. pp. 101-110 In: J. E. Reynolds III 

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

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, 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? Journal of Cetacean Research and Management 1:73-80. 

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

direct and indirect catches. Rep. int. Whal. Commn 34:569-586. 

Green, G. A., J. J. Brueggeman, R. A. Grotefendt, C. E. Bowlby, M. L. Bonnell, and K. C. Balcomb, III. 1992. Cetacean 

distribution and abundance off Oregon and Washington, 1989-1990. Ch. 1 In: J. J. Brueggeman (ed.). Oregon 

and Washington Marine Mammal and Seabird Surveys. Minerals Management Service Contract Report 14-12­

0001-30426 prepared for the Pacific OCS Region. 

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

surveys: estimating g(0). Journal of Wildlife Management 61:63-75. 

Polacheck, T., F. W. Wenzel, and G. Early. 1995. What do stranding data say about harbor porpoise (Phocoena 

phocoena). Report International Whaling Commission, Special Issue 16:169-179. 

Rosel, P. E. 1992. Genetic population structure and systematic relationships of some small cetaceans inferred from 

mitochondrial DNA sequence variation. Ph.D. Dissertation, Univ. Calif. San Diego. 191pp. 

Rosel, P. E., A. E. Dizon, and M. G. Haygood. 1995. Variability of the mitochondrial control region in populations of the 

harbour porpoise, Phocoena phocoena, on inter-oceanic and regional scales. Can. J. Fish. and Aquat. Sci. 

52:1210-1219. 

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. 

15 
16

O R /W A

C oa st

stock

Inla nd W A stoc k

N orth er n C A stock

Figure 1. Approximate distribution of harbor porpoise in

the U.S. Pacific Northwest (shaded 

boundaries separating the stocks are shown.

Revised 09/30/99

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

STOCK DEFINITION AND GEOGRAPHIC RANGE

In the eastern North Pacific Ocean, the harbor

porpoise ranges from Point Barrow, along the Alaskan coast,

and down the west coast of North America to Point

Conception, California (Gaskin 1984). 

primarily frequent coastal waters. Harbor porpoise are

known to occur year-round in the inland trans-boundary area

of Washington and British Columbia, Canada (Osborne et al.

1988), and along the Oregon/Washington coast (Barlow

1988, Barlow et al. 1988, Green et al. 1992). 

from coastal Oregon and Washington, collected during all

seasons, suggests that harbor porpoise distribution varies

by depth (Green et al. 1992). 

changes in abundance along the west coast have been

noted, and attributed to possible shifts in distribution to

deeper offshore waters during late winter (Dohl et al. 1983,

Barlow 1988), harbor porpoise have also been conspicuously

absent in offshore areas in late November (B. Taylor, pers.

comm.) leaving a gap in the current understanding of their

movements.

Stock discreteness in the eastern North Pacific was

analyzed using mitochondrial DNA from samples collected

along the west coast (Rosel 1992) and is summarized in

Osmek et al. (1994). 

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. 

geographically distinct by latitude, the results may indicate a low mixing rate for harbor porpoise along the west coast

of North America. 

also suggests restricted harbor porpoise movements (Calambokidis and Barlow 1991). 

data mentioned above, along with additional samples, found significant genetic differences for four of the six pair-wise

comparisons between the four areas investigated: California, Washington, British Columbia, and Alaska (Rosel et al.

1995). These results demonstrate that harbor porpoise along the west coast of North America are not panmictic or

migratory, and that movement is sufficiently restricted to evolve genetic differences. This is consistent with low

movement suggested by genetic analysis of harbor porpoise specimens from the North Atlantic, where numerous stocks

have been delineated with clinal differences over areas as small as the waters surrounding the British Isles.

Using the 1990-91 aerial survey data of Calambokidis et al. (1993) for water depths < 50 fathoms, Osmek et al.

(1996) found significant differences in harbor porpoise mean densities (z=5.9, p<0.01) between the waters of coastal

Oregon/Washington and inland Washington/southern British Columbia, Canada (i.e., Strait of Juan de Fuca/San Juan

Islands). Although differences in density exist between coastal Oregon/Washington and inland Washington, a specific

stock boundary line cannot be identified based upon biological or genetic differences. 

p orpoise 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 Washingt on waters (the Oregon/Washington

Coast stock and the Inland Washington stock), with the boundary at Cape Flattery. 

that a population of animals at Spike Rock (on the northern coast of Washington, south of Cape Flattery) is more similar

to the Inland Washington stock of harbor porpoise than to the Oregon/Washington Coast stock (S. Chivers, pers.

comm.). All relevant data (e.g., additional genetic samples, contaminant studies, and 

to determine whether to adjust the stock boundaries for harbor porpoise in Oregon and Washington waters.

In their assessment of California harbor porpoise, Barlow and Hanan (1995) recommended two stocks be

area). Stock

Harbor porpoise

Aerial survey data

Although distinct seasonal

Two distinct mtDNA groupings or

Although these two clades are not

Investigation of pollutant loads in harbor porpoise ranging from California to the Canadian border

Further genetic testing of the same

However, because harbor

Recent genetic evidence suggests

satellite tagging) will be reviewed
recognized in California, with the stock boundary at the Russian River. Based on the above information four separate 

harbor porpoise stocks are recognized to occur along the west coast of the continental U.S. (see Fig. 1): 1) the Inland 

Washington stock, 2) the Oregon/Washington Coast stock, 3) the Northern California stock, and 4) the Central California 

stock. This report considers only the Oregon/Washington Coast stock, with stock assessment reports for the Inland 

Washington and both California stocks appearing in this volume. Three harbor porpoise stocks are also recognized in 

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

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

The harbor porpoise occurring in British Columbia have not been included in any stock assessment report from either 

the Alaska Region or Pacific Northwest (Oregon/Washington). 

POPULATION SIZE 

In August and September 1997, an aerial survey of Oregon, Washington, and southern British Columbia coastal 

waters, from shore to 200 m depth, resulted in an observed abundance of 13,036 (CV=0.11) harbor porpoise in U.S. waters 

(Laake et al. 1998a). Using a correction factor of 3.42 (1/g(0); g(0)=0.292, CV=0.366) to adjust for groups missed by aerial 

observers, the corrected estimate of abundance for harbor porpoise in coastal Oregon and Washington waters is 44,644 

(CV=0.38). This estimate represents a substantial increase over the 1991 estimate of 26,175 (Osmek et al. 1996) due to: 

1) the larger sampling region in the 1997 survey (out to water depths of 200 m vs. 91 m in 1991), and 2) a different estimate 

of g(0) (Laake et al. 1998a). 

Minimum Population Estimate 

The minimum population estimate (NMIN) for this stock is calculated using Equation 1 from the PBR Guidelines 

(Wade and Angliss 1997): NMIN = N/exp(0.842*[ln(1+[CV(N)]2

)]1⁄2). Using the population estimate (N) of 44,644 and its 

associated CV(N) of 0.38, NMIN for the Oregon/Washington Coast stock of harbor porpoise is 32,769. 

Current Population Trend 

There are no reliable data on population trends of harbor porpoise for coastal Oregon, Washington, or British 

Columbia waters. 

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES 

A reliable estimate of the maximum net productivity rate is currently not available for harbor porpoise. Therefore, 

until additional data become available, it is recommended that the cetacean maximum theoretical net productivity rate 

(RMAX) of 4% (Wade and Angliss 1997) be employed for the Oregon/Washington Coast harbor porpoise stock. 

POTENTIAL BIOLOGICAL REMOVAL 

Under the 1994 re-authorized Marine Mammal Protection Act (MMPA), the potential biological removal (PBR) 

is defined as the product of the minimum population estimate, one-half the maximum theoretical net productivity rate, 

and a recovery factor: PBR = NMIN × 0.5RMAX × FR. The recovery factor (FR) for this stock is 0.5, the value for a cetacean 

stock with an unknown population status (Wade and Angliss 1997). Thus, for the Oregon/Washington Coast stock of 

harbor porpoise, PBR = 328 animals (32,769 × 0.02 × 0.5). 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY 

Fisheries Information 

Within the EEZ boundaries of coastal Oregon and Washington, human-caused (fishery) mortalities of harbor 

porpoise are presently known to occur only in the northern Washington marine set gillnet fishery. During 1992-93 the 

WA/OR Lower Columbia River, WA Grays Harbor, and WA Willapa Bay drift gillnet fisheries were monitored at observer 

coverages of approximately 4% and 2%, respectively. There were no observed harbor porpoise mortalities in these 

fisheries. 

With the exception of 1994, NMFS observers monitored the northern Washington marine set gillnet fishery 

during 1992-97 (Gearin et al. 1994; P. Gearin, unpubl. data). For the entire area fished, observer coverage ranged from 

approximately 59 to 98% during those years. Fishing effort is conducted within the range of both harbor porpoise stocks 

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

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

17 
details) may have been animals from the coastal stock. Similarly, some of the animals taken in the coastal portion of the 

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

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

coastal portion of the fishery are assumed to have belonged to the Oregon/Washington Coast stock. Some movement 

of harbor porpoises between Washington’s coastal and inland waters is likely, but it is currently not possible to quantify 

the extent of such movements. Accordingly, Table 1 includes data only from that portion of the northern Washington 

marine set gillnet fishery occurring within the range of the Oregon and Washington Coast stock (those waters south and 

west of Cape Flattery), where observer coverage ranged from 70-100% between 1992 and 1997. No fishing effort occurred 

in the coastal portion of the fishery in 1993 and, as noted above, no observer program occurred in 1994. Data from 1992 

to 1997 are included in the Table 1, although the mean estimated annual mortality is calculated using the most recent 5 

years of available data. The mean estimated mortality for this fishery is 12.4 (CV=0.46) harbor porpoise per year from this 

stock. 

Table 1. Summary of incidental mortality of harbor porpoise (Oregon and Washington Coast stock) due to commercial 

fisheries from 1992 through 1997 and calculation of the mean annual mortality rate. Only data from 1993 to 1997 (or the 

most recent 5 years of available data) are used to calculate mean annual mortality (n/a indicates that data are not 

available). 

Fishery 

name Years 

Data 

type 

Range of 

observer 

coverage 

Observed 

mortality (in 

given yrs.) 

Estimated 

mortality (in 

given yrs.) 

1993-97 

Mean annual 

mortality 

Northern WA marine set 

gillnet 

(coastal waters) 

92-97 obs data 70-100% 0, 0, n/a, 20, 

29, 13 

0, 0, n/a, 20, 

29, 13 

12.4 

(CV= 0.46) 

Observer program total 12.4 

(CV=0.46) 

Estimated total annual 

mortality 

12.4 

(CV=0.46) 

The 1995-96 data for the northern Washington marine set gillnet fishery were collected as part of an experiment, 

conducted in cooperation with the Makah Tribe, designed to explore the merits of using acoustic alarms to reduce 

bycatch of harbor porpoise in salmon gillnets. The nets equipped with acoustic alarms had significantly lower 

entanglement rates, as only two of the 49 mortalities occurred in alarmed nets (Gearin et al. 1996, Laake et al. 1997). 

Harbor porpoise were displaced by an acoustic buffer around the net, but it is unclear whether the porpoise were repelled 

by the alarms or whether it was their prey that were repelled (Kraus et al. 1997, Laake et al. 1998b). Because this fishery 

is likely to have acoustic devices on all nets in the future, the mean mortality estimated from non-alarmed nets may not 

be applicable. In 1997, 13 mortalities were observed (100% observer coverage) in this fishery and 96% of the sets were 

equipped with acoustic alarms. 

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 1990 and 1997, there were no fisher self-reports of harbor porpoise mortalities from any fisheries 

operating within the range of the Oregon/Washington Coast stock. However, because logbook records (fisher selfreports required during 1990-94) are most likely negatively biased (Credle et al. 1994), these are considered to be minimum 

estimates. Self-reported fisheries data are incomplete for 1994, not available for 1995, and considered unreliable after 1995 

(see Appendix 4 in Hill and DeMaster 1998). 

There have been no fishery-related strandings of harbor porpoise from this stock dating back to at least 1990. 

STATUS OF STOCK 

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

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

injury (12) does not exceed the PBR (328). Therefore, the Oregon/Washington Coast stock of harbor porpoise is not 

classified as strategic. The total fishery mortality and serious injury for this stock (12; based on observer data) is not 

18 
known to exceed 10% of the calculated PBR (33) and, therefore, can be considered to be insignificant and approaching 

zero mortality and serious injury rate. The status of this stock relative to its Optimum Sustainable Population and 

population trends is unknown. 

REFERENCES 

Barlow, J. 1988. Harbor porpoise, Phocoena phocoena, abundance estimation for California, Oregon and Washington: 

I. Ship surveys. Fish. Bull. 86:417-432. 

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

Commn. Special Issue 16:123-140. 

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

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

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

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

(eds.), Proceedings of the Second Marine Mammal Stranding Workshop: 3-5 December 1987, Miami, Florida. 

NMFS, NOAA Technical Rep. NMFS 98:101-110. 

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

F. Brown. 1993. Abundance estimates of harbor porpoise in Washington and Oregon waters. Final Rep. by 

Cascadia Research, Olympia, WA, to National Marine Mammal Laboratory, AFSC, NMFS, Seattle, WA. 55 pp. 

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

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

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

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

Dohl, T. P., R. C. Guess, M. L. Duman, and R. C. Helm. 1983. Cetaceans of central and northern California, 1980-1983: 

Status, abundance, and distribution. OCS study MM S 84-0045. Pacific OCS Region Minerals Management 

Service, 1340 Sixth Street, Los Angeles, CA 90014. 284 pp. 

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

direct and indirect catches. Rep. Int. Whal. Commn. 34:569-586. 

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

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

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

Gearin, P. J., M. E. Gosho, L. Cooke, R. DeLong, and J. Laake. 1996. Acoustic alarm experiment in the 1995 northern 

Washington marine setnet fishery: methods to reduce by-catch of harbor porpoise. Paper SC/48/SM10 

presented to the International Whaling Commission, June 1996 (unpublished). 15 pp. 

Green, G. A., J. J. Brueggeman, R. A. Grotefendt, C. E. Bowlby, M. L. Bonnel, and K. C. Balcomb. 1992. Cetacean 

distribution and abundance off Oregon and Washington, 1989-1990. Ch. 1, In: Brueggeman, J. J. (ed.), Oregon 

and Washington Marine Mammal and Seabird Surveys. Final Rep. OCS Study MMS 91-0093. 

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

Memo. NMFS-AFSC-97. 166 pp. 

Kraus, S. D., A. J. Read, A. Solow, K. Baldwin, T. Spradlin, E. Anderson, and J. Williamson. 1997. Acoustic alarms 

reduce porpoise mortality. Nature 388:525. 

Laake, J. L., P. J. Gearin, M. E. Gosho, and R. L. DeLong. 1997. Evaluation of the effectiveness of pingers to reduce 

incidental entanglement of harbor porpoise in a set gillnet fishery. Annual Report to the MMPA Assessment 

Program, Office of Protected Resources, NMFS, NOAA, 1335 East-West Highway, Silver Spring, MD 20910. 

7 pp. Available at National Marine Mammal Laboratory, 7600 Sand Point Way NE, Seattle, WA 98115. 

Laake, J., J. Calambokidis, and S. Osmek. 1998a. Survey report for the 1997 aerial surveys for harbor porpoise and other 

marine mammals of Oregon, Washington and British Columbia Outside Waters. Pp. 77-97, In: Hill, P. S., and 

D. P. DeMaster (eds.), 1997 MMPA/ESA Implementation Program. U.S. Dep. Commer., AFSC Processed Report 

98-10. 246 pp. 

Laake, J. L., D. J. Rugh, and L. S. Baraff. 1998b. Observations of harbor porpoise in the vicinity of acoustic alarms on 

a set gillnet. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-AFSC-84. 40 pp. 

Osborne, R., J. Calambokidis, and E. M. Dorsey. 1988. A Guide to Marine Mammals of Greater Puget Sound. Island 

Publishers, Anacortes, WA. 191 pp. 

19 
Osmek, S. D., P. E. Rosel, A. E. Dizon, and R. L. DeLong. 1994. Harbor porpoise, Phocoena phocoena, population 

assessment studies for Oregon and Washington in 1993. Annual Report to the MMPA Assessment Program, 

Office of Protected Resources, NMFS, NOAA, 1335 East-West Highway, Silver Spring, MD 20910. 14 pp. 

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

Osmek, S., J. Calambokidis, J. Laake, P. Gearin, R. DeLong, J. Scordino, S. Jeffries, and R. Brown. 1996. Assessment of 

the status of harbor porpoises, Phocoena phocoena, in Oregon and Washington waters. U.S. Dep. Commer., 

NOAA Tech. Memo. NMFS-AFSC-76. 46 pp. 

Rosel, P. E. 1992. Genetic population structure and systematic relationships of some small cetaceans inferred from 

mitochondrial DNA sequence variation. Ph.D. Dissertation, 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. 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. 

20 
21

OR /W A

C oast

sto ck

Inlan d W A sto ck

N o rth er n C A stock

Figure 1. Approximate distribution of harbor porpoise

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

boundaries separating the stocks are shown.

Revised 09/30/99

HARBOR PORPOISE (Phocoena phocoena): Inland Washington Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

In the eastern North Pacific Ocean, the harbor

porpoise ranges from Point Barrow, along the Alaskan coast,

and down the west coast of North America to Point

Conception, California (Gaskin 1984). Harbor porpoise

primarily frequent coastal waters. 

known to occur year-round in the inland trans-boundary

area of Washington and British Columbia, Canada (Osborne

et al. 1988), and along the Oregon/Washington coast

(Barlow 1988, Barlow et al. 1988, Green et al. 1992). Aerial

survey data from coastal Oregon and Washington, collected

during 

distribution varies by depth (Green et al. 1992). 

distinct seasonal changes in abundance along the west

coast have been noted, and attributed to possible shifts in

distribution to deeper offshore waters during late winter

(Dohl et al. 1983, Barlow 1988), harbor porpoise have also

been conspicuously absent in offshore 

November (B. Taylor, pers. comm.) leaving a gap in the

current understanding of their movements.

Stock discreteness in the eastern North Pacific was

analyzed using mitochondrial DNA from samples collected

along the west coast (Rosel 1992) and is summarized in

Osmek et al. (1994). 

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. 

geographically distinct by latitude, the results may indicate a low mixing rate for harbor porpoise along the west coast

of North America. 

also suggests restricted harbor porpoise movements (Calambokidis and Barlow 1991). 

data mentioned above, along with additional samples, found significant genetic differences for four of the six pair-wise

comparisons between the four areas investigated: California, Washington, British Columbia, and Alaska (Rosel et al.

1995). These results demonstrate that harbor porpoise along the west coast of North America are not panmictic or

migratory, and that movement is sufficiently restricted to evolve genetic differences. This is consistent with low

movement suggested by genetic analysis of harbor porpoise specimens from the North Atlantic, where numerous stocks

have been delineated with clinal differences over areas as small as the waters surrounding the British Isles.

Using the 1990-91 aerial survey data of Calambokidis et al. (1993) for water depths < 50 fathoms, Osmek et al.

(1996) found significant differences in harbor porpoise mean densities (z=5.9, p<0.01) between the waters of coastal

Oregon/Washington and inland Washington/southern British Columbia, Canada (i.e., Strait of Juan de Fuca/San Juan

Islands). Although differences in density exist between coastal Oregon/Washington and inland Washington, a specific

stock boundary line cannot be identified based upon biological or genetic differences. 

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. 

that a population of animals at Spike Rock (on the northern coast of Washington, south of Cape Flattery) is more similar

to the Inland Washington stock of harbor porpoise than to the Oregon/Washington Coast stock (S. Chivers, pers.

comm.). All relevant data (e.g., additional genetic samples, contaminant studies, and 

to determine whether to adjust the stock boundaries for harbor porpoise in Oregon and Washington waters.

In their assessment of California harbor porpoise, Barlow and Hanan (1995) recommended two stocks be

recognized in California, with the stock boundary at the Russian River. Based on the above information four separate

Stock

Harbor porpoise are

all seasons, suggests that harbor porpoise

Although

areas in late

Two distinct mtDNA groupings or

Although these two clades are not

Investigation of pollutant loads in harbor porpoise ranging from California to the Canadian border

Further genetic testing of the same

However, because harbor

Recent genetic evidence suggests

satellite tagging) will be reviewed
harbor porpoise stocks are recognized to occur along the west coast of the continental U.S. (see Fig. 1): 1) the Inland 

Washington stock, 2) the Oregon/Washington Coast stock, 3) the Northern California stock, and 4) the Central California 

stock. This report considers only the Inland Washington stock, with stock assessment reports for the 

Oregon/Washington Coast and both California stocks appearing in this volume. Three harbor porpoise stocks are also 

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

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

Region. The harbor porpoise occurring in British Columbia have not been included in any stock assessment report from 

either the Alaska Region or Pacific Northwest (Oregon/Washington). 

POPULATION SIZE 

Aerial surveys of the inside waters of Washington and southern British Columbia were conducted during 

August of 1996 (Calambokidis et al. 1997). These aerial surveys included the Strait of Juan de Fuca, San Juan Islands, 

Gulf Islands, and Strait of Georgia, which includes waters inhabited by harbor porpoise from British Columbia, as well 

as the Inland Washington stock. A total of 2,117 km of survey effort was completed within U.S. waters, resulting in an 

uncorrected abundance of 1,025 (CV=0.151) harbor porpoise in the inside waters of Washington (Calambokidis et al. 1997, 

Laake et al. 1997a). When corrected for availability and perception bias, using a correction factor of 3.42 (1/g(0); 

g(0)=0.292, CV=0.366), the estimated abundance for the Inland Washington stock of harbor porpoise is 3,509 (CV=0.396) 

animals (Laake et al. 1997a, 1997b). 

Minimum Population Estimate 

The minimum population estimate (NMIN) for this stock is calculated using Equation 1 from the PBR Guidelines 

(Wade and Angliss 1997): NMIN = N/exp(0.842*[ln(1+[CV(N)]2

)]1⁄2). Using the population estimate (N) of 3,509 and its 

associated CV(N) of 0.396, NMIN for the Inland Washington stock of harbor porpoise is 2,545. 

Current Population Trend 

There are no reliable data on long-term population trends of harbor porpoise for most waters of Oregon, 

Washington, or British Columbia. For comparability to the 1996 survey, a re-analysis of the 1991 aerial survey data was 

conducted (Calambokidis et al. 1997). The abundance of harbor porpoise in the Inland Washington stock in 1996 was 

not significantly different than in 1991 (Laake et al. 1997a). 

A different situation exists in southern Puget Sound where harbor porpoises are now rarely observed, a sharp 

contrast to 1942 when they were considered common in those waters (Scheffer and Slipp 1948). Although quantitative 

data for this area are lacking, marine mammal survey effort (Everitt et al. 1980), stranding records since the early 1970s 

(Osmek et al. 1995), and the results of harbor porpoise surveys of 1991 (Calambokidis et al. 1992) and 1994 (Osmek et al. 

1995) indicate that harbor porpoise abundance has declined in southern Puget Sound. In 1994 a total of 769 km of vessel 

survey effort and 492 km of aerial survey effort conducted during favorable sighting conditions produced no sightings 

of harbor porpoise in southern Puget Sound. Reasons for the apparent decline are unknown, but it may be related to 

fishery interactions, pollutants, vessel traffic, or other activities that may affect harbor porpoise occurrence and 

distribution in this area (Osmek et al. 1995). Research to identify trends in harbor porpoise abundance is also needed 

for the other areas within inland Washington. 

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES 

A reliable estimate of the maximum net productivity rate is not currently available for harbor porpoise. Hence, 

until additional data become available, it is recommended that the cetacean maximum theoretical net productivity rate 

(RMAX) of 4% (Wade and Angliss 1997) be employed for the Inland Washington harbor porpoise stock. 

POTENTIAL BIOLOGICAL REMOVAL 

Under the 1994 re-authorized Marine Mammal Protection Act (MMPA), the potential biological removal (PBR) 

is defined as the product of the minimum population estimate, one-half the maximum theoretical net productivity rate, 

and a recovery factor: PBR = NMIN × 0.5RMAX × FR. The recovery factor (FR) for this stock is 0.4, the value for a cetacean 

stock with an unknown population status and with a CV of mortality estimates greater than 0.8 (Wade and Angliss 1997). 

Thus, for the Inland Washington stock of harbor porpoise, PBR = 20 animals (2,545 × 0.02 × 0.4). 

22 
HUMAN-CAUSED MORTALITY AND SERIOUS INJURY 

Fisheries Information 

With the exception of 1994, NMFS observers monitored the northern Washington marine set gillnet fishery 

during 1992-97 (Gearin et al. 1994; P. Gearin, unpubl. data). For the entire area fished, observer coverage ranged from 

approximately 59 to 98% during those years. Fishing effort is conducted within the range of both harbor porpoise stocks 

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

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

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

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

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

in the coastal portion of the fishery are assumed to have belonged to the Oregon/Washington Coast stock. Some 

movement of harbor porpoise between Washington’s coastal and inland waters is likely, but it is currently not possible 

to quantify the extent of such movements. Accordingly, Table 1 includes data only from that portion of the northern 

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

Cape Flattery), where observer coverage ranged from 6-80% between 1992 and 1997. Data from 1992-97 are included in 

Table 1, although the mean estimated annual mortality is calculated using the most recent 5 years of available data. No 

mortalities were observed in the inland portion of the fishery between 1992 and 1997. As noted above, there was no 

observer program in 1994. Little effort occurred in 1995 and observer coverage was lower than usual (24%). Effort 

increased in 1996, however, the observer coverage decreased to a low of 6%. In 1997, observer coverage increased to 

80%, although little effort occurred. The mean estimated mortality for this fishery is zero harbor porpoise per year from 

this stock. 

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

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

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

of the fishery. No harbor porpoise mortalities were reported (Table 1). Pierce et al. (1994) cautioned against extrapolating 

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

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

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

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

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

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

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

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

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

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

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

Also in 1994, NMFS in conjunction with the WDF&W and the Tribes conducted an observer program to 

examine seabird and marine mammal interactions with the Puget Sound treaty and non-treaty sockeye salmon gillnet 

fishery (areas 7 and 7A). During this fishery, observers monitored 2,205 sets, representing approximately 7% of the 

estimated 33,086 sets occurring in the fishery (Pierce et al. 1996). There was one observed harbor porpoise mortality (one 

other was entangled and released alive with no indication the animal was injured), resulting in a mortality rate of 0.00045 

harbor porpoise per set, which extrapolates to 15 mortalities (CV=1.0) for the entire fishery. In 1996, Washington Sea 

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

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

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

or upper eighth (20 mesh gear) of the net or had low-frequency sound emitters attached to the corkline (Melvin et al. 

1997). In 642 sets during 17 vessel trips, 2 harbor porpoise were killed in the 50 mesh gear. 

Combining the estimates from the 1994 observer programs (15) with the northern Washington marine set gillnet 

fishery (0) results in an estimated mean mortality rate in observed fisheries of 15 harbor porpoise per year from this stock. 

It should be noted that the 1994 observer programs did not sample all segments of the entire Washington Puget Sound 

Region salmon set/drift gillnet fishery, and further, the extrapolation of total kill did not include effort for the unobserved 

segments of this fishery. Therefore, 15 is an underestimate of the harbor porpoise mortality due to the entire fishery. 

Though it is not possible to quantify what percentage of the Washington Puget Sound Region salmon set/drift gillnet 

23 
fishery was actually observed in 1994, the observer programs covered those segments of the fishery which had the 

highest salmon catches, the majority of vessel participation, and the highest likelihood of interaction with harbor 

porpoise (J. Scordino, pers. comm.). Accordingly, the estimated harbor porpoise mortality (15) appears to be only a 

slight underestimate for the fishery. See Appendix 1 of Barlow et al. (1997) for additional information, including a map 

depicting fishing areas, regarding the Washington Puget Sound Region salmon set/drift gillnet fishery. 

Table 1. Summary of incidental mortality of harbor porpoise (Inland Washington stock) due to commercial fisheries from 

1992 through 1997 and calculation of the mean annual mortality rate. Only data from 1993 to 1997 (or the most recent 5 

years of available data) are used to calculate mean annual mortality (n/a indicates that data are not available). 

Fishery 

name Years 

Data 

type 

Range of 

observer 

coverage 

Observed 

mortality (in 

given yrs.) 

Estimated 

mortality (in 

given yrs.) 

1993-97 

Mean annual 

mortality 

Northern WA marine set 

gillnet 

(inland waters) 

92-97 obs data 6-80% 0, 0, 

n/a, 0, 0, 0 

0, 0, 

n/a, 0, 0, 0 

0 

WA Puget Sound Region 

salmon set/drift gillnet 

(observer programs listed below 

covered segments of this 

fishery): 

- - - - - -

Puget Sound non-treaty 

salmon 

gillnet (all areas and species) 

93 obs data 1.3% 0 0 see text 

Puget Sound non-treaty 

chum 

salmon gillnet (areas 10/11 

and 

12/12B) 

94 obs data 11% 0 0 0 

Puget Sound treaty chum 

salmon 

gillnet (areas12,12B, 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 gill 

net 

(areas 7 and 7A) 

94 obs data 7% 1 15 15 

(CV=1.0) 

Observer program total 15 

(CV=1.0) 

Reported 

mortalities 

WA Puget Sound Region 

salmon set/drift gillnet 

90-97 self 

reports 

n/a 6, 4, 6, 2, 

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

n/a see text 

Minimum total annual 

mortality 

$15 

(CV=1.0) 

24 
An additional source of information on the number of harbor porpoises killed or injured incidental to commercial 

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

fishery data from 1990 to 1997 for the Washington Puget Sound Region salmon set and drift gillnet fishery are shown 

in Table 1. Unlike the 1994 observer program data, the self-reported fisheries data cover the entire fishery. However, 

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

1994), these are considered to be minimum estimates of harbor porpoise mortality. 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). Though the 1994 observer program data may underestimate the total fishery mortality for this stock, it is 

considered more reliable than the self-reported data. Thus, the self-reported fisheries data were not used in the mortality 

rate calculation. 

Strandings of harbor porpoise wrapped in fishing gear or with injuries caused by interactions with gear are a 

final source of fishery-related mortality information. During the period from 1992 to 1997 the only reported fishery-related 

strandings of harbor porpoise occurred in 1992 (1 animal) and 1993 (1 animal). The mortalities likely occurred in the 

Washington Puget Sound Region salmon set and drift gillnet fishery. As the 1994 observer program already accounts 

for 15 harbor porpoise mortalities per year from this fishery, these strandings have not been included in Table 1. 

There are few data concerning the mortality of marine mammals incidental to commercial gillnet fisheries in 

Canadian waters, which have not been monitored but are known to have taken harbor porpoise in the past (Barlow et 

al. 1994, Stacey et al. 1997). As a result, the number of harbor porpoise from this stock currently taken in the waters of 

southern British Columbia is not known. 

STATUS OF STOCK 

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

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

(15) is not known to exceed the PBR (20). Therefore, the Inland Washington harbor porpoise stock is not classified as 

strategic. The minimum total fishery mortality and serious injury for this stock (15) exceeds 10% of the calculated PBR 

(2.0) and, therefore, cannot be considered to be insignificant and approaching zero mortality and serious injury rate. The 

status of this stock relative to its Optimum Sustainable Population and population trends is unknown, although harbor 

porpoise sightings in the southern Puget Sound have declined since the 1940s. 

Although this stock is not recognized as strategic at this time, there is cause for concern due to the following 

issues: 1) the estimated take level is close to exceeding the PBR (i.e., one additional observed mortality or serious injury 

in the area 7/7A sockeye drift gillnet fishery would increase the estimated annual take level above the PBR), 2) the extent 

to which harbor porpoise from U. S. waters frequent the waters of British Columbia, and are therefore subject to fisheryrelated mortality, is unknown, and 3) the mortality rate is based on observer data from a subset of the Washington Puget 

Sound Region salmon set and gillnet fishery. 

REFERENCES

Barlow, J. 1988. Harbor porpoise, Phocoena phocoena, abundance estimation for California, Oregon and Washington:

I. Ship surveys. Fish. Bull. 86:417-432. 

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

Commn. Special Issue 16:123-140. 

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

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

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

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

Canada and the east coast of the Russian Federation. Rep. Int. Whal. Commn. Special Issue 15:405-425. 

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. 

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

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

(eds.), Proceedings of the Second Marine Mammal Stranding Workshop: 3-5 December 1987, Miami, Florida. 

NMFS, NOAA Technical Rep. NMFS 98:101-110. 

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

25 
abundance off Oregon and Washington from aerial surveys in 1991. Final Rep. by Cascadia Research, Olympia, 

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

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

F. Brown. 1993. Abundance estimates of harbor porpoise in Washington and Oregon waters. Final Rep. by 

Cascadia Research, Olympia, WA, to National Marine Mammal Laboratory, AFSC, NMFS, Seattle, WA. 55 pp. 

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

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

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

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

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

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

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

Dohl, T. P., R. C. Guess, M. L. Duman, and R. C. Helm. 1983. Cetaceans of central and northern California, 1980-1983: 

Status, abundance, and distribution. OCS study MMS 84-0045. Pacific OCS Region Minerals Management 

Service, 1340 Sixth Street, Los Angeles, CA 90014. 284 pp. 

Erstad, P., S. L. Jeffries, and D. J. Pierce. 1996. 1994 Report for the Puget Sound fishery observer program in management

areas 10/11 & 12/12B: nontreaty chum gill net fishery. Wash. Dept. Fish and Wildlife., Olympia, WA. 14 pp.

Everitt, R. D., C. H. Fiscus, R. L. DeLong. 1980. Northern Puget Sound marine mammals. U.S. Department of Commerce

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. 

Green, G. A., J. J. Brueggeman, R. A. Grotefendt, C. E. Bowlby, M. L. Bonnel, and K. C. Balcomb. 1992. Cetacean 

distribution and abundance off Oregon and Washington, 1989-1990. Ch. 1, In: Brueggeman, J. J. (ed.), Oregon 

and Washington Marine Mammal and Seabird Surveys. Final Rep. OCS Study MMS 91-0093. 

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

Memo. NMFS-AFSC-97. 166 pp. 

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

Washington and British Columbia inside waters, 1996. Annual rep. to the MMPA Assessment Program, Office 

of Protected Resources, NMFS, NOAA, 1335 East-West Highway, Silver Spring, MD 20910. 7 pp. Available 

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

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

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

Melvin, E. F., L. L. Conquest, and J. K. Parrish. 1997. Seabird bycatch reduction: New tools for Puget Sound drift gillnet 

salmon fisheries. 1996 Sockeye and 1995 Chum Salmon Test Fisheries Final Report. Washington Sea Grant 

Program, Seattle, WA. 48pp. 

Northwest Indian Fisheries Commission. 1995. Monitoring of marbled murrelet and marine mammal interactions with 

1994 tribal gillnet fisheries in northern Puget Sound, Hood Canal, and the Strait of Juan de Fuca. Final Report 

to NMFS Contract No. 52ABNF400087. Unpubl. report. Northwest Indian Fisheries Commission. 43 pp. 

Available at NWIFC, 6730 Martin Way E, Olympia, WA 98516. 

Osborne, R., J. Calambokidis, and E. M. Dorsey. 1988. A Guide to Marine Mammals of Greater Puget Sound. Island 

Publishers, Anacortes, WA. 191 pp. 

Osmek, S. D., P. E. Rosel, A. E. Dizon, and R. L. DeLong. 1994. Harbor porpoise Phocoena phocoena population 

assessment studies for Oregon and Washington in 1993. Annual Rep. to the MMPA Assessment Program, 

Office of Protected Resources, NMFS, NOAA, 1335 East-West Highway, Silver Spring, MD 20910. 14 pp. 

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

Osmek, S. D., M. B. Hanson, J. L. Laake, S. J. Jeffries, and R. L. DeLong. 1995. Harbor porpoise Phocoena phocoena 

population assessment studies for Oregon and Washington in 1994. Annual Rep. 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. 

26 
Osmek, S., J. Calambokidis, J. Laake, P. Gearin, R. DeLong, J. Scordino, S. Jeffries, and R. Brown. 1996. Assessment of 

the status of harbor porpoises, Phocoena phocoena, in Oregon and Washington waters. U.S. Dep. Commer., 

NOAA Tech. Memo. NMFS-AFSC-76. 46 pp. 

Pierce, D. J., W. P. Ritchie, and R. Kreuziger. 1994. Preliminary findings of seabird interactions with the non-treaty 

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

of 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, Wash. Dept. 

Fish and Wildlife, Olympia, WA. 21 pp. 

Rosel, P. E. 1992. Genetic population structure and systematic relationships of some small cetaceans inferred from 

mitochondrial DNA sequence variation. Ph.D. Dissertation, 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. 

Scheffer, V. B., and J. W. Slipp. 1948. The whales and dolphins of Washington state with a key to the cetaceans of the 

west coast of North America. Am. Midl. Nat. 39(2):257-337. 

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

Stacey, P. J., R. W. Baird, and D. A. Duffus. 1997. A preliminary evaluation of incidental mortality of small cetaceans, 

in coastal fisheries in British Columbia, Canada. Mar. Mamm. Sci. 13:321-326. 

Taylor, B. 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. 

27 
28

Figure 1. Approximate distribution of killer whales in

the eastern North Pacific (shaded area). 

of the Eastern North Pacific Northern Resident and

Transient stocks are largely overlapping (see text). 

Revised 09/30/99

KILLER WHALE (Orcinus orca): 

Eastern North Pacific Transient Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

Killer whales have been observed in all oceans

and seas of the world (Leatherwood and Dahlheim 1978).

Although reported from tropical and offshore waters, killer

whales prefer the colder waters of both hemispheres, with

greatest abundances found within 800 

continents (Mitchell 1975). Along the west coast of North

America, killer whales occur along the entire Alaskan coast

(Braham and Dahlheim 1982), in British Columbia and

Washington inland waterways (Bigg et al. 1990), and along

the outer coasts of Washington, Oregon, and California

(Green et al. 1992; Barlow 1995, 1997; Forney et al. 1995).

Seasonal and year-round occurrence has been noted for

killer whales throughout Alaska (Braham and Dahlheim

1982) and in the intracoastal waterways of British Columbia

and Washington State, where pods have been labeled as

‘resident,’ ‘transient,’ and ‘offshore’ (Bigg et al. 1990, Ford

et al. 1994) based on aspects of morphology, ecology,

genetics, and behavior (Ford and Fisher 1982, Baird and

Stacey 1988, Baird et al. 1992, Hoelzel et al. 1998). Through

examination of photographs of recognizable individuals

and pods, movements of whales between geographical

areas have been documented. 

identified in Prince William Sound have been observed

near Kodiak Island (Heise et al. 1991) and whales identified

in Southeast Alaska have been observed in Prince William Sound, British Columbia, and Puget Sound (Leatherwood et

al. 1990, Dahlheim et al. 1997). Movements of killer whales between the waters of Southeast Alaska and central California

have also been documented (Goley and Straley 1994).

Studies on mtDNA restriction patterns provide evidence that the ‘resident’ and ‘transient’ types are genetically

distinct (Stevens et al. 1989, Hoelzel 1991, Hoelzel and Dover 1991, Hoelzel et al. 1998). 

from eastern North Pacific killer whales from California to Alaska has demonstrated significant genetic differences among

‘transient’ whales from California through Alaska, ‘resident’ whales from the inland waters of Washington, and ‘resident’

whales ranging from British Columbia to the Aleutian Islands and Bering Sea (Hoelzel et al. 1998).

Based on data regarding association patterns, acoustics, movements, genetic differences and potential fishery

interactions, five killer whale stocks are recognized within the Pacific U.S. EEZ: 1) the Eastern North Pacific Northern

Resident stock - occurring from British Columbia through Alaska, 2) the Eastern North Pacific Southern Resident stock -

occurring within the inland waters of Washington State and southern British Columbia, 3) the Eastern North Pacific

Transient stock - occurring from Alaska through California (see Fig. 1), 4) the Eastern North Pacific Offshore stock -

occurring from Southeast Alaska through California, and 5) the Hawaiian stock. ‘Transient’ whales in Canadian waters

are considered part of the Eastern North Pacific Transient stock. The Stock Assessment Reports for the Alaska Region

contain information concerning the Eastern North Pacific Northern Resident stock

POPULATION SIZE

The Eastern North Pacific Northern Transient stock is a trans-boundary stock, including killer whales from

British Columbia. Preliminary analysis of photographic data resulted in the following minimum counts for ‘transient’ killer

whales belonging to the Eastern North Pacific Transient stock (Note: individual whales have been matched between

geographical regions and missing animals likely to be dead have been subtracted). In British Columbia and southeastern

Alaska, 213 ‘transient’ whales have been cataloged (Ford and Ellis 1999). In the Gulf of Alaska, 17 ‘transient’ killer

The distribution

km of major

For example, whales

Analysis of 73 samples collected
whales have been identified genetically and acoustically (L. Barrett-Lennard, pers. comm.). The ‘transient’ group AT1, 

commonly seen in Prince William Sound, was thought to have 11 whales alive in 1997 (Matkin et al. 1998). Based on data 

collected from all Alaska waters west of Seward (Dahlheim and Waite 1993, Dahlheim 1994, 1997), 68 whales are 

considered ‘residents’ as they have been linked by association to ‘resident’ whales from Prince William Sound (G. Ellis, 

pers. comm.), and the remainder are provisionally classified as 174 ‘residents’ and 53 ‘transients.’ Provisional 

classifications were based primarily on morphological differences identified from the photographs. Accordingly, the 

numbers of ‘residents’ and ‘transients’ in Alaska waters west of Seward are considered preliminary at this time. Off the 

coast of California, Black et al. (1997) identified 105 ‘transient’ whales: 10 whales were matched to photos of ‘transients’ 

in other catalogs and the remaining 95 were linked by association. Combining the counts of ‘transient’ whales gives a 

minimum number of 336 (213 + 17 + 11 + 95) killer whales belonging to the Eastern North Pacific Transient stock. 

Minimum Population Estimate 

The survey technique utilized for obtaining the abundance estimate of killer whales is a direct count of 

individually identifiable animals. Given that researchers continue to identify new whales, the estimate of abundance 

based on the number of uniquely identified individuals known to be alive 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 unclassified whales from western Alaska that have been provisionally classified as 

‘transients’. 

Other estimates of the overall population size (i.e., NBEST) and associated CV(N) are not currently available. 

Thus, the minimum population estimate (NMIN) for the Eastern North Pacific Transient stock of killer whales is 336 animals, 

which includes animals found in Canadian waters (see PBR Guidelines regarding the status of migratory trans-boundary 

stocks, Wade and Angliss 1997). Information on the percentage of time animals typically encountered in Canadian 

waters spend in U.S. waters is unknown. However, as noted above, this minimum population estimate is considered 

conservative. This approach is consistent with the recommendations of the Alaska Scientific Review Group (DeMaster 

1996). 

Current Population Trend 

At present, reliable data on trends in population abundance for the Eastern North Pacific Transient stock of 

killer whales are unavailable. 

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES 

A reliable estimate of the maximum net productivity rate is currently unavailable for this stock of killer whales. 

Studies of ‘resident’ killer whale pods in the Pacific Northwest resulted in estimated population growth rates of 2.92% 

and 2.54% over the period from 1973 to 1987 (Olesiuk et al. 1990, Brault and Caswell 1993). However, a population 

increases at the maximum growth rate (RMAX) only when the population is at extremely low levels; thus, the estimate of 

2.92% is not a reliable estimate of RMAX. Hence, until additional data become available, it is recommended that the 

cetacean maximum theoretical net productivity rate (RMAX) of 4% be employed for this stock (Wade and Angliss 1997). 

POTENTIAL BIOLOGICAL REMOVAL 

Under the 1994 re-authorized Marine Mammal Protection Act (MMPA), the potential biological removal (PBR) 

is defined as the product of the minimum population estimate, one-half the maximum theoretical net productivity rate, 

and a recovery factor: PBR = NMIN × 0.5RMAX × FR. The recovery factor (FR) for this stock is 0.45, the value for cetacean 

stocks with unknown population status and a mortality estimate CV between 0.6 and 0.8 (Wade and Angliss 1997). Thus, 

for the Eastern North Pacific Transient killer whale stock, PBR = 3.0 animals (336 × 0.02 × 0.45). 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 1993 to 1997: Bering Sea (and Aleutian Islands) 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. For the fisheries with observed takes, the range of observer coverage over the 

5-year period, as well as the annual observed and estimated mortalities, are presented in Table 1. The 1995 mortality in 

29 
the longline fishery occurred during an unmonitored haul and could not be used to estimate total mortality for the fishery 

(28% observer coverage in 1995). For computational purposes, the estimated mortality in 1995 was set at 1, because at 

a minimum, one whale is known to have perished in that year. The 1993 mortality in the trawl fishery occurred under 

similar circumstances and was treated in the same manner (66% observer coverage in 1993). 

NMFS observers also monitored the California/Oregon thresher shark/swordfish drift gillnet fishery from 1993 

to 1997 (Table 1; Julian 1997, Cameron 1998, Julian and Beeson 1998). The observed mortality in this fishery, in 1995, was 

a transient whale as determined by genetic testing (S. Chivers, pers. comm.). Additional fisheries that could interact with 

the Eastern North Pacific Transient stock of killer whales are listed in Appendix 1 of Barlow et al. (1997). 

The mean annual mortality was 0.6 (CV=0.67) for the Bering Sea groundfish trawl fishery, 0.2 (CV=1.0) for the 

combined Bering Sea longline fishery, and 1.2 (CV=1.0) for the California/Oregon thresher shark/swordfish drift gillnet 

fishery, resulting in a mean annual mortality rate of 2.0 (CV=0.64) killer whales per year from observed fisheries. 

An additional source of information on the number of killer whales killed or injured incidental to commercial 

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

period between 1990 and 1997, fisher self-reports from all Alaska fisheries operating within the range of this stock 

indicated only one killer whale mortality, which occurred in the Bering Sea groundfish trawl fishery in 1990. However, 

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

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

for 1995, and considered unreliable after 1995 (see Appendix 4 of Hill and DeMaster 1998). Thus, the observer program 

provides more reliable estimates of mortality than the fisher self-reports. 

The estimated minimum mortality rate incidental to U.S. commercial fisheries recently monitored is 2.0 animals 

per year, based exclusively on observer data. As the animals which were taken incidental to commercial fisheries in 

Alaska have not been identified genetically, it is not possible to determine whether they belonged to the Eastern North 

Pacific Northern Resident or the Eastern North Pacific Transient killer whale stock. Accordingly, these same mortalities 

can be found in the stock assessment report for the Northern Resident stock. 

Table 1. Summary of incidental mortality of killer whales (Eastern North Pacific Northern Transient stock) due to 

commercial fisheries from 1993 through 1997 and calculation of the mean annual mortality rate. Only data from 1993 to 

1997 (or the most recent 5 years of available data) are used to calculate mean annual mortality. 

Fishery 

name Years 

Data 

type 

Range of 

observer 

coverage 

Observed 

mortality (in 

given yrs.) 

Estimated 

mortality (in 

given yrs.) 

1993-97 

Mean annual 

mortality 

Bering Sea/Aleutian Is. (BSAI) 

groundfish trawl 

93-97 obs data 64-67% 1, 0, 0, 0, 1 1, 0, 0, 0, 2 0.6 

(CV=0.67) 

BSAI groundfish longline 

(incl. misc. finfish and 

sablefish fisheries) 

93-97 obs data 27-33% 0, 0, 1, 0, 0 0, 0, 1, 0, 0 0.2 

(CV=1.0) 

CA/OR thresher 

shark/swordfish drift gillnet 

93-97 obs data 12-27% 0, 0, 1, 0, 0 0, 0, 6, 0, 0 1.2 

(CV=1.0) 

Estimated total annual 

mortality 

2.0 

(CV=0.64) 

Due to a lack of Canadian observer programs, there are few data concerning the mortality of marine mammals 

incidental to Canadian commercial fisheries, which are analogous to U.S. fisheries that are known to interact with killer 

whales. The sablefish longline fishery accounts for a large proportion of the commercial fishing/killer whale interactions 

in Alaska waters. Such interactions have not been reported in Canadian waters where sablefish are taken via a pot 

fishery. Since 1990, there have been no reported fishery-related strandings of killer whales in Canadian waters. However, 

in 1994, one killer whale was reported to have contacted a salmon gillnet but did not entangle (Guenther et al. 1995). Data 

regarding the level of killer whale mortality related to commercial fisheries in Canadian waters, though thought to be 

small, are not readily available or reliable which results in an underestimate of the annual mortality for this stock. 

30 
Subsistence/Native Harvest Information 

There are no reports of a subsistence harvest of killer whales in Alaska or Canada. 

Other Mortality 

Since 1986, research efforts have been made to assess the nature and magnitude of killer whale/blackcod 

(sablefish; Anoplopoma fimbria) fishery interactions (Yano and Dahlheim 1995, Dahlheim 1988). Fishery interactions 

have occurred each year in the Bering Sea and Prince William Sound, with the number of annual reports varying 

considerably. Data collected from the Japan/U.S. cooperative longline research surveys operating in the Bering Sea 

indicate that interactions may be increasing and expanding into the Aleutian Island region (Yano and Dahlheim 1995). 

During the 1992 surveys conducted in the Bering Sea and western Gulf of Alaska, 9 of 182 (4.9%) individual whales in 

7 of the 12 (58%) pods encountered had evidence of bullet wounds (Dahlheim and Waite 1993). The relationship 

between wounding due to shooting and survival is unknown. In Prince William Sound, the pod responsible for most 

of the fishery interactions has experienced a high level of mortality: between 1986 and 1991, 22 whales out of a pod of 

37 (59%) are missing and considered dead (Matkin et al. 1994). The cause of death for these whales is unknown, but may 

be related to gunshot wounds or effects of the Exxon Valdez oil spill (Dahlheim and Matkin 1994). 

The shooting of killer whales in Canadian waters has also been a concern in the past. However, in recent years 

there have been no reports of shooting incidents in Canadian waters. In fact, the likelihood of shooting incidents 

involving ‘transient’ killer whales is thought to be minimal since commercial fishermen are most likely to observe 

‘transients’ feeding on seals or sea lions instead of interacting with their fishing gear (G. Ellis, pers. comm.). 

Other Issues 

Although only small numbers of killer whales are taken in the Bering Sea fisheries, there is considerable 

interaction between the whales and the fisheries. Interactions between killer whales and longline vessels have been well 

documented (Dahlheim 1988, Yano and Dahlheim 1995). In 1997, the first year that predation data were collected in the 

Bering Sea and Gulf of Alaska groundfish trawl, longline and pot fisheries, NMFS observers recorded killer whale 

predation and/or deterrence events during 187 longline sets: 179 in the Bering Sea and 8 in the Gulf of Alaska. A total 

of 183 whales were deterred (through the use of seal bombs or acoustic alarms suspended from the vessels) from 20 sets 

in the Bering Sea and one group of 35 whales was deterred from a set in the Gulf of Alaska. Less has been documented 

regarding interactions with the trawl fishery, but several observers reported that large groups of killer whales in the 

Bering Sea followed vessels for days at a time, actively consuming the processing waste (Fishery Observer Program, 

unpubl. data). However, it may be the ‘resident’ stock of killer whales that is involved in such fisheries interactions since 

these whales are known to be fish eaters, while ‘transient’ whales have only been observed feeding on marine mammals. 

STATUS OF STOCK 

Killer whales are not listed as “depleted” under the MMPA or listed as “threatened” or “endangered” under 

the Endangered Species Act. Recall, that the human-caused mortality has been underestimated primarily due to a lack 

of information on Canadian fisheries, and that the minimum abundance estimate is considered conservative (because 

researchers continue to encounter new whales and unclassified whales from western Alaska were not included), resulting 

in a conservative PBR estimate. Based on currently available data, the estimated annual fishery-related mortality level 

(2.0) exceeds 10% of the PBR (0.30) and, therefore, can not be considered to be insignificant and approaching zero 

mortality and serious injury rate. The estimated annual level of human-caused mortality and serious injury (2.0 animals 

per year) is not known to exceed the PBR (3.0). 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 are currently unknown. 

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. 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 

31 
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. 25pp. 

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 waters of British Columbia and Washington State. Pp. 386­

406, In: Hammond, P. S. , S. A. Mizroch, and G. P. Donovan (eds.), Individual Recognition of Cetaceans: Use 

of Photo-identification and Other Techniques to Estimate Population Parameters. Rep. Int. Whal. Commn. 

Special Issue 12. 

Black, N. A., A. Schulman-Janiger, R. L. Ternullo, and M. Guerrero-Ruiz. 1997. Killer whales of California and western 

Mexico: a catalog of photo-identified individuals. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-SWFSC-247. 

174 pp. 

Braham, H. W., and M. E. Dahlheim. 1982. Killer whales in Alaska documented in the Platforms of Opportunity Program. 

Rep. Int. Whal. Commn. 32:643-646. 

Brault, S., and H. Caswell. 1993. Pod-specific demography of killer whales (Orcinus orca). Ecology 74(5):1444-1454. 

Cameron, G. 1998. Cetacean mortality in California gill net fisheries: Preliminary estimates for 1997. Paper SC/50/SM02 

presented to the International Whaling Commission, June 1998 (unpublished). 15 pp. 

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

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

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

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

Dahlheim, M. E. 1988. Killer whale (Orcinus orca) depredation on longline catches of sablefish (Anoplopoma fimbria) 

in Alaskan waters. NWAFC Processed Rep. 88-14. 31 pp. (available upon request - Alaska Fisheries Science 

Center, 7600 Sand Point Way NE, Seattle, WA 98115). 

Dahlheim, M. E. 1994. Abundance and distribution of killer whales (Orcinus orca) in Alaska in 1993. Annual Report 

to the MMPA Assessment Program, Office of Protected Resources, NMFS, NOAA, 1335 East-West Highway, 

Silver Spring, MD 20910. 

Dahlheim, M. E. 1997. A photographic catalogue of killer whales (Orcinus orca) from the Central Gulf of Alaska to the 

southeastern Bering Sea. U.S. Dep. Commer., NOAA Tech. Rep. NMFS-131. 54 pp. 

Dahlheim, M. E., and J. M. Waite. 1993. Abundance and distribution of killer whales (Orcinus orca) in Alaska in 1992. 

Annual Report to the MMPA Assessment Program, Office of Protected Resources, NMFS, NOAA, 1335 EastWest Highway, Silver Spring, MD 20910. 

Dahlheim, M. E., and C. O. Matkin. 1994. Assessment of injuries to Prince William Sound killer whales. Pp. 163-171, In 

Loughlin, T. R. , (ed.), Marine Mammals and the Exxon Valdez. Academic Press, Inc., San Diego, CA. xix +395 

pp. 

Dahlheim, M. E., D. Ellifrit, and J. Swenson. 1997. Killer Whales of Southeast Alaska: A Catalogue of Photoidentified 

Individuals. Day Moon Press, Seattle, WA. 82 pp. + appendices. 

DeMaster, D. P. 1996. Minutes from the 11-13 September 1996 meeting of the Alaska Scientific Review Group, 

Anchorage, AK. 20 pp + appendices. (available upon request - D. P. DeMaster, National Marine Mammal 

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

Ellis, G. Pacific Biological Station, Nanaimo, BC V9R 5K6. 

Fishery Observer Program. AFSC, NMFS, 7600 Sand Point Way NE, Seattle, WA 98115 

Ford, J. K. B., and G. M. Ellis. 1999. Transients: Mammal-Hunting Killer Whales of British Columbia, Washington, and 

Southeastern Alaska. University of British Columbia Press, Vancouver, BC. 96 pp. 

Ford, J. K. B., and H. D. Fisher. 1982. Killer whale (Orcinus orca) dialects as an indicator of stocks in British Columbia. 

Rep. Int. Whal. Commn. 32:671-679. 

Ford, J. K. B., G. Ellis, and K. C. Balcomb. 1994. Killer Whales: The Natural History and Genealogy of Orcinus orca in 

British Columbia and Washington State. University of British Columbia Press and University of Washington 

Press. 102 pp. 

Forney, K. A., J. Barlow, and J. V. Carretta. 1995. The abundance of cetaceans in California waters. Part II: Aerial 

32 
surveys in winter and spring of 1991 and 1992. Fish. Bull. 93:15-26. 

Goley, P. D., and J. M. Straley. 1994. Attack on gray whales (Eschrichtius robustus) in Monterey Bay, California, by 

killer whales (Orcinus orca) previously identified in Glacier Bay, Alaska. Can. J. Zool. 72:1528-1530. 

Green, G. A., J. J. Brueggeman, R. A. Grotefendt, C. E. Bowlby, M. L. Bonnel, and K. C. Balcomb. 1992. Cetacean 

distribution and abundance off Oregon and Washington, 1989-1990. Pp. 1-100, In: Brueggeman, J.J. (ed.), 

Oregon and Washington Marine Mammal and Seabird Surveys. Final Rep. OCS Study MMS 91-0093. 

Guenther, T. J., R. W. Baird, R. L. Bates, P. M. Willis, R. L. Hahn, and S. G. Wischniowski. 1995. Strandings and fishing 

gear entanglements of cetaceans on the west coast of Canada in 1994. Paper SC/47/O6 presented to the 

International Whaling Commission, May 1995 (unpublished). 7pp. 

Heise, K., G. Ellis, and C. Matkin. 1991. A catalogue of Prince William Sound Killer Whales. North Gulf Oceanic Society, 

Homer, AK. Published for the National Marine Mammal Laboratory, 7600 Sand Point Way NE, Seattle, WA 

98115. 

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

Memo. NMFS-AFSC-97. 166 pp. 

Hoelzel, A. R. 1991. Analysis of regional mitochondrial DNA variation in the killer whale; implications for cetacean 

conservation. Rep. Int. Whal. Commn. Special Issue 13:225-233. 

Hoelzel, A. R., and G. A. Dover. 1991. Genetic differentiation between sympatric killer whale populations. Heredity 66: 

191-195. 

Hoelzel, A. R., M. E. Dahlheim, and S. J. Stern. 1998. Low genetic variation among killer whales (Orcinus orca) in the 

Eastern North Pacific, and genetic differentiation between foraging specialists. J. Heredity 89:121-128. 

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: 1990-1995. Fish. Bull. 96(2):271-284. 

Leatherwood, J. S., and M. E. Dahlheim. 1978. Worldwide distribution of pilot whales and killer whales. Naval Ocean 

Systems Center, Tech. Rep. 443:1-39. 

Leatherwood, S., C. O. Matkin, J. D. Hall, and G. M. Ellis. 1990. Killer whales, Orcinus orca, photo-identified in Prince 

William Sound, Alaska 1976 to 1987. Can. Field Naturalist 104:362-371. 

Matkin, C. O., G. M. Ellis, M. E. Dahlheim, and J. Zeh. 1994. Status of killer whales in Prince William Sound, 1985-1992. 

Pp. 141-162, In: Loughlin, T. R. (ed.), Marine Mammals and the Exxon Valdez . Academic Press, Inc., San Diego, 

CA. xix + 395 pp. 

Matkin, C.O., D. Scheel, G. Ellis, L. Barrett-Lennard, H. Jurk, and E. Saulitis. 1998. Comprehensive Killer Whale 

Investigation, Exxon Valdez Oil Spill Restoration Project Annual Report (Restoration Project 97012), North Gulf 

Oceanic Society, Homer, AK. 58 pp. 

Mitchell, E. D. 1975. Report on the meeting on small cetaceans, Montreal, April 1-11, 1974. J. Fish. Res. Bd. Can. 32:914­

916. 

Olesiuk, P. F., M. A. Bigg, and G. M. Ellis. 1990. Life history and population dynamics of resident killer whales (Orcinus 

orca) in the coastal waters of British Columbia and Washington State. Rep. Int. Whal. Commn. Special Issue 

12:209-242. 

Stevens, T. A., D. Duffield, E. Asper, K. Hewlett, A. Bolz, L. Gage, and G. Bossart. 1989. Preliminary findings of 

restriction fragment differences in mitochondrial DNA among killer whales (Orcinus orca). Can. J. Zool. 

67:2592-2595. 

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

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

Yano, K., and M. E. Dahlheim. 1995. Killer whale, Orcinus orca, depredation on longline catches of bottomfish in the 

southeastern Bering Sea and adjacent waters. Fish. Bull. 93:355-372. 

33 
Revised 09/30/99 

KILLER WHALE (Orcinus orca): 

Eastern North Pacific Offshore Stock 

STOCK DEFINITION AND GEOGRAPHIC RANGE 

Killer whales have been observed in all oceans and 

seas of the world (Leatherwood and Dahlheim 1978). 

Although reported from tropical and offshore waters, killer 

whales prefer the colder waters of both hemispheres, with 

greatest abundances found within 800 km of major continents 

(Mitchell 1975). Along the west coast of North America, killer 

whales occur along the entire Alaskan coast (Braham and 

Dahlheim 1982), in British Columbia and Washington inland 

waterways (Bigg et al. 1990), and along the outer coasts of 

Washington, Oregon and California (Green et al. 1992; Barlow 

1995, 1997; Forney et al. 1995). Seasonal and year-round 

occurrence has been noted for killer whales throughout 

Alaska (Braham and Dahlheim 1982) and in the intracoastal 

waterways of British Columbia and Washington State, where 

pods have been labeled as 'resident', 'transient' and ‘offshore’ 

(Bigg et al. 1990, Ford et al. 1994) based on aspects of 

morphology, ecology, genetics and behavior (Ford and Fisher 

1982; Baird and Stacey 1988; Baird et al. 1992, Hoelzel et al. 

1998). Through examination of photographs of recognizable 

individuals and pods, movements of whales between 

geographical areas have been documented. For example, 

whales identified in Prince William Sound have been 

observed near Kodiak Island (Heise et al. 1991) and whales 

identified in Southeast Alaska have been observed in Prince 

William Sound, British Columbia, and Puget Sound 

(Leatherwood et al. 1990, Dahlheim et al. 1997). Movements 

of killer whales between the waters of Southeast Alaska and 

central California have also been documented (Goley and 

Straley 1994). 

Offshore killer whales have more recently also been 

identified off the coasts of California, Oregon, and rarely, in 

Southeast Alaska (Ford et al. 1994, Black et al. 1997, Dahlheim 

et al. 1997). They apparently do not mix with the transient 

and resident killer whale stocks found in these regions (Ford 

et al. 1994, Black et al. 1997). Studies indicate the ‘offshore’ 

type, although distinct from the other types (‘resident’ and 

‘transient’), appears to be more closely related genetically, 

Figure 1. Killer whale sightings based on aerial and 

shipboard surveys off California, Oregon and 

Washington, 1989-96. Sightings include killer whales 

from all stocks found in this region. Dashed line 

represents the U.S. EEZ , thick line indicates the outer 

boundary of all surveys combined. 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 sources 

and information on timing and location of survey 

effort. 

morphologically, behaviorally, and vocally to the ‘resident’ type killer whales (Black et al. 1997, Hoelzel et al. 1998; J. 

Ford, pers. comm.; L. Barrett-Lennard, pers. comm.). Based on data regarding association patterns, acoustics, 

movements, genetic differences, and potential fishery interactions, five killer whale stocks are recognized within the 

Pacific U.S. EEZ 1) the Eastern North Pacific Northern Resident stock - occurring from British Columbia through Alaska, 

2) the Eastern North Pacific Southern Resident stock - occurring within the inland waters of Washington State and 

southern British Columbia, 3) the Eastern North Pacific Transient stock - occurring from Alaska through California, 4) 

the Eastern North Pacific Offshore stock - occurring from Southeast Alaska through California (this report), and 5) the 

Hawaiian stock. ‘Offshore’ whales in Canadian waters are considered part of the Eastern North Pacific Offshore stock. 

The Stock Assessment Reports for the Alaska Region contain assessments of the Eastern North Pacific Northern 

Resident stock, and the most recent assessment for the Hawaii Stock can be found in Barlow et al. (1997). 

34 
POPULATION SIZE 

Off British Columbia, approximately 200 offshore killer whales were identified between 1989 and 1993 (Ford et 

al. 1994), and 20 of these individuals have also been seen off California (Black et al. 1997). Using only good quality 

photographs that clearly show characteristics of the dorsal fin and saddle patch region, an additional 11 offshore killer 

whales that were not previously known have been identified off the California coast, bringing the total number of known 

individuals in this population to 211. This is certainly an underestimate of the total population size, because not all 

animals in this population have been photographed. In the future, it may be possible estimate the total abundance of 

this transboundary stock using mark-recapture analyses based on individual photographs. Based on summer/fall 

shipboard line-transect surveys in 1991, 1993 and 1996 (Barlow 1997), the total number of killer whales within 300 nmi of 

the coasts of California, Oregon and Washington was recently estimated to be 819 animals (CV=0.38). There is currently 

no way to reliably distinguish the different stocks of killer whales from sightings at sea, but photographs of individual 

animals can provide a rough estimate of the proportion of whales in each stock. A total of 161 individual killer whales 

photographed off California and Oregon have been determined to belong to the transient (105 whales) and offshore (56 

whales) stocks (Black et al. 1997). Using these proportions to prorate the line transect abundance estimate yields an 

estimate of 56/161 * 819 = 285 offshore killer whales along the U.S. west coast. This is expected to be a conservative 

estimate of the number of offshore killer whales, because offshore whales apparently are less frequently seen near the 

coast (Black et al. 1997), and therefore photographic sampling may be biased towards transient whales. For stock 

assessment purposes, this combined value is currently the best available estimate of abundance for offshore killer whales 

off the coasts of California, Oregon and Washington. 

Minimum Population Estimate 

The total number of known offshore killer whales along the U.S. West coast, Canada and Alaska is 211 animals, 

but it is not known what proportion of time this transboundary stock spends in U.S. waters, and therefore this number 

is difficult to work with for PBR calculations. A minimum abundance estimate for all killer whales along the coasts of 

California, Oregon and Washington can be estimated from the 1991-1996 line-transect surveys as the 20th percentile of 

the abundance estimate, or 601 killer whales. Using the same prorating as above, a minimum of 56/161 * 601 = 209 

offshore killer whales are estimated to be in U.S. waters off California, Oregon and Washington. 

Current Population Trend 

No information is available regarding trends in abundance of Eastern North Pacific offshore killer whales. 

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES 

No information on current or maximum net productivity rates is available for killer whales in this region. 

POTENTIAL BIOLOGICAL REMOVAL 

Based on this stock's unknown status and growth rate and the lack of observed fishery mortality, the recovery 

factor (Fr) is 0.5. 1⁄2Rm ax is the default value of 0.02. Multiplying these two values times the minimum population estimate 

of 209 yields a potential biological removal (PBR) of 2.1 animals per year. 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY 

Fishery Information 

A summary of recent fishery mortality and injury for this killer whale stock is shown in Table 1. More detailed 

information on these fisheries is provided in Appendix 1 of Barlow et al. (1997). In the California drift gillnet fishery, no 

offshore killer whales have been observed entangled (Julian and Beeson 1998, Julian 1997, Cameron 1998), but one killer 

whale from the Eastern North Pacific Transient Stock was observed taken in 1995, and offshore killer whales may also 

occasionally be entangled. 

Additional potential sources of killer whale mortality are set gillnets and longlines. In California, an observation 

program between July 1990 and December 1994 monitored 5-15% of all sets in the large mesh (>3.5") set gillnet fishery 

for halibut and angel sharks, and no killer whales were observed taken. Based on observations for longline fisheries in 

other regions (i.e. Alaska; Yano and Dahlheim 1995), fishery interactions may also occur with U.S. West coast pelagic 

longline fisheries, but no such interactions have been documented to date. 

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

Mexico and may take animals from the same population. Quantitative data are available only for the Mexican swordfish 

35 
drift gillnet fishery, which increased from two vessels in 1986 to 29 vessels in 1992 (Sosa-Nishizaki et al. 1993). The total 

number of sets in this fishery in 1992 can be estimated from data provided by these authors to be approximately 2700, 

with an observed rate of marine mammal bycatch of 0.13 animals per set (10 marine mammals in 77 observed sets; SosaNishizaki et al. 1993). This overall mortality rate is similar to that observed in California driftnet fisheries during 1990-95 

(0.14 marine mammals per set; Julian and Beeson, in press), but species-specific information is not available for the 

Mexican fisheries. 

Table 1. Summary of available information on the incidental mortality and injury of killer whales (Eastern North Pacific 

Offshore Stock) in commercial fisheries that might take this species. 

Fishery Name Data Type Year(s) 

Percent 

Observer 

Coverage 

Observed 

Mortality 

Estimated 

Annual 

Mortality 

Mean 

Annual Takes 

1993-97 

CA/OR thresher 

shark/swordfish drift 

gillnet fishery 

observer 

data 

1993 

1994 

1995 

1996 

1997 

13.4% 

17.9% 

15.6% 

12.4% 

26.6% 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 0 

Minimum total annual takes 1993-97 0 

Historical mortality 

California coastal whaling operations killed five killer whales between 1962 and 1967 (Rice 1974). An additional 

killer whale was taken by whalers in British Columbian waters (Hoyt 1981). It is unknown whether any of these animals 

belonged to the Eastern North Pacific Offshore stock. 

STATUS OF STOCK 

The status of killer whales in California in relation to OSP is unknown, and there are insufficient data to evaluate 

trends in abundance. No habitat issues are known to be of concern for this species. They are not listed as "threatened" 

or "endangered" under the Endangered Species Act nor as "depleted" under the MMPA. There has been no 

documented human-caused mortality of this stock, and therefore they are not classified as a "strategic" stock under the 

MMPA. The total fishery mortality and serious injury for offshore killer whales is zero and can be considered to be 

insignificant and approaching zero mortality and serious injury rate. 

REFERENCES 

Baird, R. W., and P. J. Stacey. 1988. Variation in saddle patch pigmentation in populations of killer whales (Orcinus 

orca) from British Columbia, Alaska, and Washington State. Can. J. Zool. 66:2582-2585. 

Baird, R. W., Abrams, P. A., and L. M. Dill. 1992. Possible indirect interactions between transient and resident killer 

whales: implications for the evolution of foraging specializations in the genus Orcinus. Oecologia 89:125-132. 

Barlow, J. 1995. The abundance of cetaceans in California waters. Part I: Ship surveys in summer and fall of 1991. Fish. 

Bull. 93:1-14. 

Barlow, J. 1997. Preliminary estimates of cetacean abundance off California, Oregon and Washington based on a 1996 

ship survey and comparisons of passing and closing modes. Administrative Report LJ-97-11, Southwest 

Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA 92038. 25p. 

Barlow, J., K. A. Forney, P. S. Hill, R. L. Brownell, Jr., J. V. Carretta, D. P. DeMaster, F. Julian, M. S. Lowry, T. Ragen, and 

R. R. Reeves. 1997. U.S. Pacific marine mammal stock assessments: 1996. U.S. Dep. Commer., NOAA Tech. 

Memo. NMFS-SWFSC-248. 223 pp. 

Barrett-Lennard, L. Univ. of British Columbia, 6270 University Blvd., Vancouver, BC V6T1Z4. 

Bigg, M. A., P. F. Olesiuk, G. M. Ellis, J. K. B. Ford, and K. C. Balcomb III. 1990. Social organization and genealogy of 

resident killer whales (Orcinus orca) in the coastal waters of British Columbia and Washington State. Rep. int. 

Whal. Commn Special Issue 12:386-406. 

Black, N. A., A. Schulman-Janiger, R. L. Ternullo, and M. Guerrero-Ruiz. 1997. Killer whales of California and western 

36 
Mexico: A Catalog of photo-identified individuals. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-SWFSC247. 174p. 

Braham, H. W., and M. E. Dahlheim. 1982. Killer whales in Alaska documented in the Platforms of Opportunity Program. 

Rep. Int. Whal. Commn., 32:643-646. 

Cameron, G. 1998. Cetacean mortality in California gill net fisheries: Preliminary estimates for 1997. Paper SC/50/SM02 

presented to the International Whaling Commission, June 1998 (unpublished). 15 pp. 

Dahlheim, M. E., D. Ellifrit, and J. Swenson. 1997. Killer Whales of Southeast Alaska: A Catalogue of Photoidentified 

Individuals. Day Moon Press, Seattle, WA. 82 pp. + appendices. 

Ford, J. K. B., Vancouver Aquarium, P.O. Box 3232, Vancouver, BC V6B 3XB, Canada. 

Ford, J. K. B., G. M. Ellis, and K.C. Balcomb. 1994. Killer whales. The natural history and genealogy of Orcinus orca 

in British Columbia and Washington State. UBC Press, Vancouver, Canada 

Ford, J. K. B., and H. D. Fisher. 1982. Killer whale (Orcinus orca) dialects as an indicator of stocks in British Columbia. 

Rep. Int. Whal. Commn 32:671-679. 

Forney, K. A., J. Barlow and J. V. Carretta. 1995. The abundance of cetaceans in California waters. Part II: Aerial surveys 

in winter and spring of 1991 and 1992. Fish. Bull. 93:15-26. 

Goley, P. D., and J. M. Straley. 1994. Attack on gray whales (Eschrichtius robustus) in Monterey Bay, California, by 

killer whales (Orcinus orca) previously identified in Glacier Bay, Alaska. Can. J. Zool. 72:1528-1530. 

Green, G., J. J. Brueggeman, R. A. Grotefendt, C. E. Bowlby, M. L. Bonnell, and K. C. Balcomb, III. 1992. Cetacean 

distribution and abundance off Oregon and Washington. Ch. 1. In: Oregon and Washington Marine Mammal 

and Seabird Surveys. OCS Study 91-0093. Final Report prepared for Pacific OCS Region, Minerals Management 

Service, U.S. Department of the Interior, Los Angeles, California. 

Heise, K., G. Ellis, and C. Matkin. 1991. A catalogue of Prince William Sound Killer Whales. North Gulf Oceanic Society, 

Homer, AK. Published for the National Marine Mammal Laboratory, 7600 Sand Point Way NE, Seattle, WA 

98115. 

Hoelzel, A. R., M. E. Dahlheim, and S. J. Stern. 1998. Low genetic variation among killer whales (Orcinus orca) in the 

Eastern North Pacific, and genetic differentiation between foraging specialists. J. Heredity 89:121-128. 

Hoyt, E. 1981. The Whale Called Killer. E. P. Dutton, New York. 

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

presented to the International Whaling Commission, 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. Fishery Bulletin 96:271-284. 

Leatherwood, J. S., and M. E. Dahlheim. 1978. Worldwide distribution of pilot whales and killer whales. Naval Ocean 

Systems Center, Tech. Rep. 443:1-39. 

Leatherwood, S., C. O. Matkin, J. D. Hall, and G. M. Ellis. 1990. Killer whales, Orcinus orca, photo-identified in Prince 

William Sound, Alaska 1976 to 1987. Can. Field Naturalist 104:362-371. 

Mitchell, E. D. 1975. Report on the meeting on small cetaceans, Montreal, April 1-11, 1974. J. Fish. Res. Board Canada, 

32:914-916. 

Rice, D. W. 1974. Whales and whale research in eastern North Pacific. p. 170-195 In: W. E. Schevill (ed.), The Whale 

Problem - A Status Report. Harvard University Press, Cambridge, MA. 

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

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

CICESE, CTECT9306. 

Yano, K. and M. E. Dahlheim. 1995. Killer whale, Orcinus orca, depredation on longline catches of bottomfish in the 

southeastern Bering Sea and adjacent waters. Fishery Bulletin 93:355-372. 

37 
38

Figure 1. Approximate distribution of the Eastern North

Pacific Southern Resident killer whale stock, April

through October (shaded area).

Revised 09/30/99

KILLER WHALE (Orcinus orca): 

Eastern North Pacific Southern Resident Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

Killer whales have been observed in all oceans and

seas of the world (Leatherwood and Dahlheim 1978).

Although reported from tropical and offshore waters, killer

whales prefer the colder waters of both hemispheres, with

greatest abundances found within 800 

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 

1982) and in the intracoastal waterways of British Columbia

and Washington State, where pods have been labeled as

‘resident,’ ‘transient,’ and ‘offshore’ (Bigg et al. 1990, Ford

et al. 1994) based on aspects of morphology, ecology,

genetics, and behavior (Ford and Fisher 1982, Baird and

Stacey 1988, Baird et al. 1992, Hoelzel et al. 1998). 

examination of photographs of recognizable individuals and pods, movements of whales between geographical areas

have been documented. For example, whales identified in Prince William Sound have been observed near Kodiak Island

(Heise et al. 1991) and whales identified in Southeast Alaska have been observed in Prince William Sound, British

Columbia, and Puget Sound (Leatherwood et al. 1990, Dahlheim et al. 1997). Movements of killer whales between the

waters of Southeast Alaska and central California have also been documented (Goley and Straley 1994).

Studies on mtDNA restriction patterns provide evidence that the ‘resident’ and ‘transient’ types are genetically

distinct (Stevens et al. 1989, Hoelzel 1991, Hoelzel and Dover 1991, Hoelzel et al. 1998). 

from eastern North Pacific killer whales from California to Alaska has demonstrated significant genetic differences among

‘transient’ whales from California through Alaska, ‘resident’ whales from the inland waters of Washington, and ‘resident’

whales ranging from British Columbia to the Aleutian Islands and Bering Sea (Hoelzel et al. 1998). 

belonging to the Eastern North Pacific Southern Resident stock have been sighted off the outer Washington coast as

far south as Grays Harbor (Bigg et al. 1990), most killer whale sightings in Washington have occurred in the inland

waters.

Based on data regarding association patterns, acoustics, movements, genetic differences and potential fishery

interactions, five killer whales 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 (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. 

Region contain information concerning the Eastern North Pacific Northern Resident stock. 

POPULATION SIZE

The Eastern North Pacific Southern Resident stock is a trans-boundary stock including killer whales in inland

Washington and southern British Columbia waters. Photo-identification of individual whales through the years has

resulted in a substantial understanding of this stock’s structure, behaviors, and movements. 

comprising this stock totaled 96 killer whales (Ford et al. 1994). Counts remained in the mid-high 90s until a recent

decrease to 89 whales (Fig. 2; Center for Whale Research, unpubl. data).

km of major

(Braham and Dahlheim

Through

Analysis of 73 samples collected

Although some pods

The Stock Assessment Reports for the Alaska

In 1993, the three pods
Minimum Population Estimate 

The survey technique utilized for obtaining 

the abundance estimate for this stock of killer 

whales is a direct count of individually 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 Eastern North Pacific 

Southern Resident stock of killer whales is 89 

animals. 

Current Population Trend 

During the live-capture fishery that existed 

from 1967 to 1973, it is estimated that 47 killer 

whales, mostly immature, were taken out of this 

stock (Ford et al. 1994). The first complete census of 

this stock occurred in 1974. Between 1974 and 1993 

the Southern Resident stock increased 

50 

60 

70 

80 

90 

100 

1976 1978 1980 1982 1984 1986 1988 1990 1992 1994 1996 1998 

Year 

Total population 

Figure 2. Population of Eastern North Pacific Southern Resident 

stock of killer whales, 1976-1998. Each year’s count includes 

animals first seen and first missed; a whale is considered first 

missed the year after it was last seen alive (Center for Whale 

Research, unpubl. data). 

approximately 35%, from 71 to 96 individuals (Ford et al. 1994). This represents an annual growth rate of 1.8% during 

those years. The population peaked at 99 whales in 1995 then decreased to 89 whales from 1995 to 1998 (Center for 

Whale Research, unpubl. data). 

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES 

A reliable estimate of the maximum net productivity rate is currently unavailable for this stock of killer whales. 

Studies of ‘resident’ killer whale pods in British Columbia and Washington waters resulted in estimated population 

growth rates of 2.92% and 2.54% over the period from 1973 to 1987 ( Olesiuk et al. 1990, Brault and Caswell 1993). 

However, a population increases at the maximum growth rate (RMAX) only when the population is at extremely low levels; 

thus, the estimate of 2.92% is not considered a reliable estimate of RMAX. Hence, until additional data become available, 

it is recommended that the cetacean maximum theoretical net productivity rate (RMAX) of 4% be employed for this stock 

(Wade and Angliss 1997). 

POTENTIAL BIOLOGICAL REMOVAL 

Under the 1994 re-authorized Marine Mammal Protection Act (MMPA), the potential biological removal (PBR) 

is defined as the product of the minimum population estimate, one-half the maximum theoretical net productivity rate, 

and a recovery factor: PBR = NMIN × 0.5RMAX × FR. The recovery factor (FR) for this stock is 0.5, the value for cetacean 

stocks of unknown status (Wade and Angliss 1997). Thus, for the Eastern North Pacific Southern Resident killer whale 

stock, PBR = 0.9 animals (89 × 0.02 × 0.5). 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY 

Fisheries Information 

NMFS observers have monitored the northern Washington marine set gillnet fishery since 1988. No killer whale 

mortalities have been recorded in this fishery since the inception of the observer program. Observer coverage has 

ranged from approximately 59 to 98% in this fishery between 1992 and 1997, excluding 1994 in which no observer program 

occurred (Gearin et al. 1994, P. Gearin, unpubl. data). 

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

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

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

of the fishery. Encounters (whales within 10 meters of a net) with killer whales were reported, but not quantified, though 

no entanglements occurred. 

In 1994, NMFS and WDF&W conducted an observer program during the Puget Sound non-treaty chum salmon 

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

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

from fish ticket landings (Erstad et al. 1996). No interactions with killer whales were observed during this fishery. The 

39 
Puget Sound treaty chum salmon gillnet fishery in Hood Canal (areas 12, 12B, and 12C) and Puget Sound treaty 

sockeye/chum gillnet fishery in the Strait of Juan de Fuca (areas 4B, 5, and 6C) were also monitored in 1994 at 2.2% 

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

coverage, respectively (NWIFC 1995). No interactions resulting in killer whale mortalities were reported in either treaty 

salmon gillnet fishery. 

Also in 1994, NMFS, WDF&W, and the Tribes conducted an observer program to examine seabird and marine 

mammal interactions with the Puget Sound treaty and non-treaty sockeye salmon gillnet fishery (areas 7 and 7A). During 

this fishery, observers monitored 2,205 sets, representing approximately 7% of the estimated number of sets in the fishery 

(Pierce et al. 1996). Killer whales were observed within 10 meters of the gear during 10 observed sets (32 animals in all), 

though none were observed to have been entangled. 

An additional source of information on the number of killer whales killed or injured incidental to commercial 

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

period between 1990 and 1997, there were no fisher self-reports of killer whale mortalities from any fisheries operating 

within the range of this stock. However, because logbook records (fisher self-reports required during 1990-94) are most 

likely negatively biased (Credle et al. 1994), these are considered to be minimum estimates. Self-reported fisheries data 

are incomplete for 1994, not available for 1995, and considered unreliable after 1995 (see Appendix 4 of Hill and DeMaster 

1998). 

Table 1. Summary of incidental mortality of killer whales (Eastern North Pacific Southern Resident stock) due to 

commercial fisheries from 1992 through 1997 and calculation of the mean annual mortality rate. Only data from 1993 to 

1997 (or the most recent 5 years of available data) are used to calculate mean annual mortality (n/a indicates that data 

are not available). 

Fishery 

name Years 

Data 

type 

Range of 

observer 

coverage 

Observed 

mortality (in 

given yrs.) 

Estimated 

mortality (in 

given yrs.) 

1993-97 

Mean annual 

mortality 

Northern WA marine set 

gillnet 

92-97 obs data 59-98% 0, 0, n/a, 0, 0, 0 0, 0, n/a, 0, 0, 0 0 

WA Puget Sound Region 

salmon set/drift gillnet 

(observer programs listed below 

covered segments of this 

fishery): 

- - - - - -

Puget Sound non-treaty 

salmon 

gillnet (all areas and species) 

93 obs data 1.3% 0 0 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 (areas12,12B, 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 

40 
Fishery 

name Years 

Data 

type 

Range of 

observer 

coverage 

Observed 

mortality (in 

given yrs.) 

Estimated 

mortality (in 

given yrs.) 

1993-97 

Mean annual 

mortality 

Puget Sound treaty and nontreaty sockeye salmon gill 

net 

(areas 7 and 7A) 

94 obs data 7% 0 0 0 

Observer program total 0 

Minimum total annual 

mortality 

0 

Due to a lack of observer programs, there are few data concerning the mortality of marine mammals incidental 

to Canadian commercial fisheries. Since 1990, there have been no reported fishery-related strandings of killer whales in 

Canadian waters. However, in 1994 one killer whale was reported to have contacted a salmon gillnet but did not entangle 

(Guenther et al. 1995). Data regarding the level of killer whale mortality related to commercial fisheries in Canadian waters 

are not available, though the mortality level is thought to be minimal. 

During this decade there have been no reported takes from this stock incidental to commercial fishing 

operations (D. Ellifrit, pers. comm.), no reports of interactions between killer whales and longline operations (as occurs 

in Alaskan waters; see Yano and Dahlheim 1995), no reports of stranded animals with net marks, and no photographs 

of individual whales carrying fishing gear. The total fishery mortality and serious injury for this stock is zero. 

STATUS OF STOCK 

Killer whales are not listed as “depleted” under the MMPA or listed as “threatened “ or “endangered” under 

the Endangered Species Act. Based on currently available data, the total fishery mortality and serious injury for this 

stock (0) is not known to exceed 10% of the calculated PBR (0.09) and, therefore, can be considered to be insignificant 

and approaching zero mortality and serious injury rate. The estimated annual level of human-caused mortality and 

serious injury of zero animals per year is not known to exceed the PBR (0.9). Therefore, the Eastern North Pacific 

Southern Resident stock of killer whales is not classified as a strategic stock. The stock size has decreased in recent 

years, although at this time it is not possible to assess the status of this stock relative to its Optimum Sustainable 

Population. 

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. The abundance of cetaceans in California waters. Part I: Ship surveys in summer and fall of 1991. Fish. 

Bull. 93:1-14. 

Barlow, J. 1997. Preliminary estimates of cetacean abundance off California, Oregon and Washington based on a 1996 

ship survey and comparisons of passing and closing modes. Administrative Report LJ-97-11, Southwest 

Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA 92038. 25pp. 

Bigg, M. A., P. F. Olesiuk, G. M. Ellis, J. K. B. Ford, and K. C. Balcomb III. 1990. Social organization and genealogy of 

resident killer whales (Orcinus orca) in the coastal waters of British Columbia and Washington State. Pp. 386­

406, In: Hammond, P. S. , S. A. Mizroch, and G. P. Donovan (eds.), Individual Recognition of Cetaceans: Use 

of Photo-identification and Other Techniques to Estimate Population Parameters. Rep. Int. Whal. Commn. 

Special Issue 12. 

Braham, H. W., and M. E. Dahlheim. 1982. Killer whales in Alaska documented in the Platforms of Opportunity Program. 

Rep. Int. Whal. Commn. 32:643-646. 

Brault, S., and H. Caswell. 1993. Pod-specific demography of killer whales (Orcinus orca). Ecology 74(5):1444-1454. 

Center for Whale Research. 1359 Smugglers Cove Rd., Friday Harbor, WA 98250.

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

41 
observer programs: minutes and recommendations from a workshop held in Galveston, Texas, November 10-11, 

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

Dahlheim, M. E., D. Ellifrit, and J. Swenson. 1997. Killer Whales of Southeast Alaska: A Catalogue of Photoidentified 

Individuals. Day Moon Press, Seattle, WA. 82 pp. + appendices. 

Ellifrit, D. Center for Whale Research, 1359 Smugglers Cove Rd., Friday Harbor, WA 98250. 

Erstad, P., S. L. Jeffries, and D. J. Pierce. 1996. 1994 Report for the Puget Sound fishery observer program in management

areas 10/11 & 12/12B: nontreaty chum gill net fishery. Wash. Dept. Fish and Wildlife., Olympia, WA. 14 pp.

Ford, J. K. B., and H. D. Fisher. 1982. Killer whale (Orcinus orca) dialects as an indicator of stocks in British Columbia.

Rep. Int. Whal. Commn. 32:671-679. 

Ford, J. K. B., G. Ellis, and K. C. Balcomb. 1994. Killer Whales: The Natural History and Genealogy of Orcinus orca in 

British Columbia and Washington State. University of British Columbia Press and University of Washington 

Press. 102 pp. 

Forney, K. A., J. Barlow, and J. V. Carretta. 1995. The abundance of cetaceans in California waters. Part II: Aerial 

surveys in winter and spring of 1991 and 1992. Fish. Bull. 93:15-26. 

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

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

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

Goley, P. D., and J. M. Straley. 1994. Attack on gray whales (Eschrichtius robustus) in Monterey Bay, California, by 

killer whales (Orcinus orca) previously identified in Glacier Bay, Alaska. Can. J. Zool. 72:1528-1530. 

Green, G. A., J. J. Brueggeman, R. A. Grotefendt, C. E. Bowlby, M. L. Bonnel, and K. C. Balcomb. 1992. Cetacean 

distribution and abundance off Oregon and Washington, 1989-1990. Pp. 1-100, In: Brueggeman, J.J. (ed.), 

Oregon and Washington Marine Mammal and Seabird Surveys. Final Rep. OCS Study MMS 91-0093. 

Guenther, T. J., R. W. Baird, R. L. Bates, P. M. Willis, R. L. Hahn, and S. G. Wischniowski. 1995. Strandings and fishing 

gear entanglements of cetaceans on the west coast of Canada in 1994. Paper SC/47/O6 presented to the 

International Whaling Commission, May 1995 (unpublished). 7pp. 

Heise, K., G. Ellis, and C. Matkin. 1991. A Catalogue of Prince William Sound Killer Whales. North Gulf Oceanic Society, 

Homer, AK. Published for the National Marine Mammal Laboratory, 7600 Sand Point Way NE, Seattle, WA 

98115. 

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

Memo. NMFS-AFSC-97. 166 pp. 

Hoelzel, A. R. 1991. Analysis of regional mitochondrial DNA variation in the killer whale; implications for cetacean 

conservation. Rep. Int. Whal. Commn. Special Issue 13:225-233. 

Hoelzel, A. R., and G. A. Dover. 1991. Genetic differentiation between sympatric killer whale populations. Heredity 

66:191-195. 

Hoelzel, A. R., M. E. Dahlheim, and S. J. Stern. 1998. Low genetic variation among killer whales (Orcinus orca) in the 

Eastern North Pacific, and genetic differentiation between foraging specialists. J. Heredity 89:121-128. 

Leatherwood, J. S., and M. E. Dahlheim. 1978. Worldwide distribution of pilot whales and killer whales. Naval Ocean 

Systems Center, Tech. Rep. 443:1-39. 

Leatherwood, S., C. O. Matkin, J. D. Hall, and G. M. Ellis. 1990. Killer whales, Orcinus orca, photo-identified in Prince 

William Sound, Alaska 1976 to 1987. Can. Field Naturalist 104:362-371. 

Mitchell, E. D. 1975. Report on the meeting on small cetaceans, Montreal, April 1-11, 1974. J. Fish. Res. Bd. Can. 32:914­

916. 

Northwest Indian Fisheries Commission. 1995. Monitoring of marbled murrelet and marine mammal interactions with 

1994 tribal gillnet fisheries in northern Puget Sound, Hood Canal, and the Strait of Juan de Fuca. Final Report 

to NMFS Contract No. 52ABNF400087. Unpubl. report. Northwest Indian Fisheries Commission. 43 pp. 

Available at NWIFC, 6730 Martin Way E, Olympia, WA 98516. 

Olesiuk, P. F., M. A. Bigg, and G. M. Ellis. 1990. Life history and population dynamics of resident killer whales (Orcinus 

orca) in the coastal waters of British Columbia and Washington State. Rep. Int. Whal. Commn. Special Issue 

12:209-242. 

Pierce, D. J., W. P. Ritchie, and R. Kreuziger. 1994. Preliminary findings of seabird interactions with the non-treaty 

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

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

42 
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, Wash. Dept. 

Fish and Wildlife, Olympia, WA. 21 pp. 

Stevens, T. A., D. Duffield, E. Asper, K. Hewlett, A. Bolz, L. Gage, and G. Bossart. 1989. Preliminary findings of 

restriction fragment differences in mitochondrial DNA among killer whales (Orcinus orca). Can. J. Zool. 

67:2592-2595. 

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

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

Yano, K., and M. E. Dahlheim. 1995. Killer whale, Orcinus orca, depredation on longline catches of bottomfish in the 

southeastern Bering Sea and adjacent waters. Fish. Bull. 93:355-372. 

43 
Revised 09/30/99 

SHORT-FINNED PILOT WHALE (Globicephala macrorhynchus): 

California/Oregon/Washington Stock 

STOCK DEFINITION AND GEOGRAPHIC RANGE 

Short-finned pilot whales were once commonly seen 

off Southern California, with an apparently resident 

population around Santa Catalina Island, as well as seasonal 

migrants (Dohl et al. 1980). After a strong El Niño event in 

1982-83, short-finned pilot whales virtually disappeared from 

this region, and despite increased survey effort along the 

entire U.S. west coast, few sightings were made from 1984­

1992 (Jones and Szczepaniak 1992; Hill and Barlow 1992; 

Carretta and Forney 1993; Shane 1994; Green et al. 1992, 

1993). In 1993, six groups of short-finned pilot whales were 

again seen off California (Mangels and Gerrodette 1994; 

Carretta et al. 1995), and mortality in drift gillnets increased 

(Julian and Beeson, 1998). Figure 1 summarizes the sighting 

history of short-finned pilot whales off the U.S. west coast. 

Although the full geographic range of the 

California/Oregon/Washington population is not known, it 

may be continuous with animals found off Baja California, 

and its individuals are morphologically distinct from shortfinned pilot whales found farther south in the eastern tropical 

Pacific (Polisini 1981). Separate southern and northern forms 

of short-finned pilot whales have also been documented for 

the western North Pacific (Kasuya et al. 1988; Wada 1988; 

Miyazaki and Amano 1994). For the Marine Mammal 

Protection Act (MMPA) stock assessment reports, shortfinned pilot whales within the Pacific U.S. Exclusive 

Economic Zone are divided into two discrete, noncontiguous areas: 1) wat ers off California, Oregon and 

Washington (this report), and 2) Hawaiian waters. 

POPULATION SIZE 

Based on surveys conducted within 300 nmi of the 

California, Oregon and Washington coast in 1991, 1993, and 

1996, Barlow (1997) has recently calculated an abundance 

estimate of 970 (CV = 0.37) short-finned pilot whales. 

Minimum Population Estimate 

Figure 1. Short-finned pilot whale sightings made 

during aerial and shipboard surveys conducted off 

California in 1975-83 (+) and off California, Oregon and 

Washington, 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 sources and information on 

timing and location of survey effort. 

The log-normal 20th percentile of the above abundance estimate is 717 short-finned pilot whales. 

Current Population Trend 

Approximately nine years after the virtual disappearance of short-finned pilot whales following the 1982-83 El 

Niño, they appear to have returned to California waters, as indicated by an increase in sighting records as well as 

incidental fishery mortality (Mangels and Gerrodette 1994; Carretta et al. 1995; Julian and Beeson, 1998). However, this 

cannot be considered a true growth in the population, because it merely reflects large-scale, long-term movements of this 

species in response to changing oceanographic conditions. It is not known where the animals went after the 82-83 El 

Niño, nor where the recently observed animals came from. Until the range of this population and the movements of 

animals in relation to environmental conditions are better documented, no inferences can be drawn regarding trends in 

abundance of short-finned pilot whales off California, Oregon and Washington. 

44 
CURRENT AND MAXIMUM NET PRODUCTIVITY RATES 

No information on current or maximum net productivity rates is available for short-finned pilot whales off 

California, Oregon and Washington. 

POTENTIAL BIOLOGICAL REMOVAL 

Based on this stock's unknown status and growth rate and given the precision of the estimate of annual fishery 

mortality (CV= 0.50), the recovery factor (Fr) is 0.48. 1⁄2Rm ax is the default value of 0.02. Multiplying these two values 

times the minimum population estimate of 717 yields a potential biological removal (PBR) of 6.9 animals per year. 

HUMAN-CAUSED MORTALITY AND SERIOUS INJURY 

Fishery Information 

A summary of known fishery mortality and injury for this stock of short-finned pilot whale is shown in Table 

1. More detailed information on these fisheries is provided in Appendix 1 of Barlow et al. (1997). The average estimated 

annual mortality for short-finned pilot whales in this fishery for the five most recent years of monitoring, 1993-97, is 13 

(CV= 0.50) animals (Julian and Beeson 1998; Julian 1997, Cameron 1998). In 1996-97, a pinger experiment was conducted 

to evaluate whether these acoustic alarms may reduce cetacean entanglement rates in the drift gillnet fishery. Based on 

the positive results of this study (Cameron 1998), pingers were made mandatory in this fishery in November 1997. The 

observed mortality of a single short-finned pilot whale in 1997 was in a pingered net. 

Table 1. Summary of available information on the incidental mortality and injury of short-finned pilot whales (California/ 

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

whales resulted in the death of the animal. Coefficients of variation for mortality estimates are provided in parentheses; 

n/a = not available. 

Fishery Name Data Type Year(s) 

Percent 

Observer 

Coverage 

Observed 

Mortality 

Estimated 

Annual Mortality 

Mean 

Annual Takes 

1993-97 

CA/OR thresher 

shark/swordfish drift 

gillnet fishery 

observer 

data 

1993 

1994 

1995 

1996 

1997 

13.4% 

17.9% 

15.6% 

12.4% 

26.6% 

8 

0 

0 

0 

1 

60 (0.54) 

0 

0 

0 

6 (0.96) 13 (0.50) 

Undetermined 

(probably squid purse 

seine fishery) 

strandings 1975-90 14 short-finned pilot whales stranded in 

Southern California with evidence of fishery 

interactions, probably with the squid purse 

seine fishery 

n/a 

Minimum total annual takes 1993-97 13 (0.50) 

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

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

fishery, which has increased from two vessels in 1986 to 29 vessels in 1992 (Sosa-Nishizaki et al. 1993). The total number 

of sets in this fishery in 1992 can be estimated from data provided by these authors to be approximately 2700, with an 

observed rate of marine mammal bycatch of 0.13 animals per set (10 marine mammals in 77 observed sets; Sosa-Nishizaki 

et al. 1993). This overall mortality rate is similar to that observed in California driftnet fisheries during 1990-95 (0.14 marine 

mammals per set; Julian and Beeson 1998), but species-specific information is not available for the Mexican fisheries. 

Historically, short-finned pilot whales were also killed in squid purse seine operations off Southern California 

(Miller et al. 1983; Heyning et al. 1994). No recent mortality has been reported, presumably because short-finned pilot 

whales are no longer common in the areas of squid purse seine fishing activity; however, there have been recent 

anecdotal reports of pilot whales seen near squid fishing operations off Southern California during the October 1997­

45 
April 98 fishing season. This fishery is not currently monitored, and has expanded markedly since 1992 (California 

Department of Fish and Game, unpubl. data). 

STATUS OF STOCK 

The status of short-finned pilot whales off California, Oregon and Washington in relation to OSP is unknown. 

They have declined in abundance in the Southern California Bight, likely a result of a change in their distribution since 

the 1982-83 El Niño, but the nature of these changes and potential habitat issues are not adequately understood. Shortfinned pilot whales are not listed as "threatened" or "endangered" under the Endangered Species Act nor as "depleted" 

under the MMPA. Because the average annual human-caused mortality for 1993-97 (13 animals per year) exceeds the 

PBR (6.9) short-finned pilot whales off California are a "strategic" stock under the MMPA, and the total fishery mortality 

and injury cannot be considered to be insignificant and approaching zero. A take reduction plan for the drift gillnet 

fishery, including mandatory pingers and a minimum 6-fathom suspender length, was implemented in 1997, and 

preliminary results indicate that cetacean mortality has decreased markedly (Cameron 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. 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. 223p. 

Cameron, G. 1998. Cetacean mortality in California gill net fisheries: Preliminary estimates for 1997. Paper SC/50/SM02 

presented to the International Whaling Commission, June 1998 (unpublished). 15 pp. 

Carretta, J. V. and K. A. Forney. 1993. Report of the two aerial surveys for marine mammals in California coastal waters 

using a NOAA DeHavilland Twin Otter aircraft, March 9-April 7, 1991, February 8-April 6, 1992. U.S. Dep. 

Commer., NOAA Tech. Memo. NMFS-SWFSC-185. 77p. 

Carretta, J. V., K. A. Forney. And J. Barlow 1995. Report of 1993-94 marine mammal surveys conducted within the U.S. 

Navy Outer Sea Test Range off Southern California. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-SWFSC217. 90p. 

Dohl, T. P., K. S. Norris, R. C. Guess, J. D. Bryant, and M. W. Honig. 1980. Summary of marine mammal and seabird 

surveys of the Southern California Bight area, 1975-1978. Part II. Cetacea of the Southern California Bight. 

Final Report to the Bureau of Land Management, NTIS Rep. No. PB81248189. 414p. 

Green, G., J. J. Brueggeman, R. A. Grotefendt, C. E. Bowlby, M. L. Bonnell, and K. C. Balcomb, III. 1992. Cetacean 

distribution and abundance off Oregon and Washington. Ch. 1. In: Oregon and Washington Marine Mammal 

and Seabird Surveys. OCS Study 91-0093. Final Report prepared for Pacific OCS Region, Minerals Management 

Service, U.S. Department of the Interior, Los Angeles, California. 

Green, G., R. A. Grotefendt, M. A. Smultea, C. E. Bowlby, and R. A. Rowlett. 1993. Delphinid aerial surveys in Oregon 

and Washington waters. Final Report prepared for NMFS, National Marine Mammal Laboratory, 7600 Sand 

Point Way, NE, Seattle, Washington, 98115, Contract #50ABNF200058. 

Heyning, J. E., T. D. Lewis and C. D. Woodhouse. 1994. A note on odontocete mortality from fishing gear 

entanglements off Southern California. Rep. Int. Whal. Commn. Special Issue 15:439-442. 

Hill, P. S. and J. Barlow. 1992. Report on a marine mammal survey of the California coast aboard the research vessel 

McARTHUR July 28 - November 5, 1991. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-SWFSC-169. 

Jones, P. A. and I. D. Szczepaniak. 1992. Report on the seabird and marine mammal censuses conducted for the longterm management strategy (LTMS), August 1990 through November 1991, for the U.S. Environmental Protection 

Agency, Region IX, San Francisco, July 1992. 

Julian, F. 1997. Cetacean mortality in California gill net fisheries: Preliminary estimates for 1996. 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, O., T. Miyashita, and F. Kasamatsu. 1988. Segregation of two forms of short-finned pilot whales off the Pacific 

coast of Japan. Sci. Rep. Whales Res. Inst. 39:77-90. 

46 
Mangels, K. F. and Gerrodette, T. 1994. Report of cetacean sightings during a marine mammal survey in the eastern 

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

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

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

Administrative Report LJ-83-13C. Available from NMFS, Southwest Fisheries Science Center, P.O. Box 271, La 

Jolla, California, 92038. 233p. 

Miyazaki, N. and M. Amano. 1994. Skull morphology of two forms of short-finned pilot whales off the Pacific coast of 

Japan. Rep. Int. Whaling Commn. 44:499-508. 

Polisini, J. M. 1981. A comparison of Globicephala macrorhyncha (Gray, 1846) with the pilot whale of the North Pacific 

Ocean: An analysis of the skull of the broad-rostrum pilot whales of the genus Globicephala. Dissertation 

Abstracts International Vol. 41, No. 08, February 1981, p. 2928-B. 

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

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

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

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

CICESE, CTECT9306. 

Wada, S. 1988. Genetic differentiation between forms of short-finned pilot whales off the Pacific coast of Japan. Sci. 

Rep. Whales Res. Inst. 39:91-101. 

47 
Revised 09/30/99 

SPERM WHALE (Physeter macrocephalus): 

California/Oregon/Washington Stock 

STOCK DEFINITION AND GEOGRAPHIC RANGE 

Sperm whales are widely distributed across the 

entire North Pacific and into the southern Bering Sea in 

summer but the majority are thought to be south of 40oN in 

winter (Rice 1974; Gosho et al. 1984; Miyashita et al. 1995). 

For management, the International Whaling Commission 

(IWC) had divided the North Pacific into two management 

regions (Donovan 1991) defined by a zig-zag line which starts 

at 150oW at the equator, is 160o

W between 40-50oN, and ends 

up at 180o

W north of 50oN; however, the IWC has not 

reviewed this stock boundary in many years (Donovan 1991). 

Sperm whales are found year-round in California waters (Dohl 

et al. 1983; Barlow 1995; Forney et al. 1995), but they reach 

peak abundance from April through mid-June and from the 

end of August through mid-November (Rice 1974). They 

were seen in every season except winter (Dec.-Feb.) in 

Washington and Oregon (Green et al. 1992). Of three sperm 

whales that were marked off southern California in January, 

one was caught by whalers off northern California in June, 

one off Washington in June, and another far off British 

Columbia in April (Rice 1974). Recent summer/fall surveys 

in the eastern tropical Pacific (Wade and Gerrodette 1993) 

show that although sperm whales are widely distributed in 

the tropics, their relative abundance tapers off markedly 

westward towards the middle of the tropical Pacific (near the 

IWC stock boundary at 150o

W) and tapers off northward 

towards the tip of Baja California. The structure of sperm 

whale populations in the eastern tropical Pacific is not 

known, but the only photographic matches of known 

individuals from this area have been between the Galapagos 

Islands and coastal waters of South America (Dufault and 

Whitehead 1995), suggesting that the eastern tropical 

animals constitute a distinct stock. A recent survey 

designed specifically to investigate stock structure and 

abundance of sperm whales in the northeastern temperate 

Figure 1. Sperm whale sighting locations based on 

aerial and shipboard surveys off California, Oregon, and 

Washington, 1989-96. Dashed line represents the U.S. 

EEZ, thick line indicates the outer boundary of all 

surveys combined. Greater effort was conducted off 

California (south of 42/N) and in the inshore half of the 

U.S. EEZ. See Appendix 2 of Barlow et al. (1997) and 

Barlow (1997) for data sources and information on 

timing and location of survey effort. 

Pacific revealed no apparent hiatus in distribution between the U.S. EEZ off California and areas farther west, out to 

Hawaii (Barlow and Taylor 1998). Very preliminary genetic analyses revealed significant differences between sperm 

whales off the coast of California, Oregon and Washington and those sampled offshore to Hawaii (Mesnick et al., 

unpubl. data); analyses of additional genetic samples are ongoing at the NMFS, Southwest Fisheries Science Center. 

For the Marine Mammal Protection Act (MMPA) stock assessment reports, sperm whales within the Pacific U.S. 

EEZ are divided into three discrete, non-contiguous areas: 1) California, Oregon and Washington waters (this report), 

2) waters around Hawaii, and 3) Alaska waters. 

POPULATION 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 whales (Leatherwood et al. 1982), it is reasonable to assume that the true abundance would be three to 

48 
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 and visual group size estimates (Barlow and Taylor 1998). However, it is not known whether any or all of 

these animals routinely enter the U.S. EEZ. In the eastern tropical Pacific, the abundance of sperm whales has been 

estimated as 22,700 (95% C.I.=14,800-34,600; Wade and Gerrodette 1993), but this area does not include areas where 

sperm whales are taken by drift gillnet fisheries in the U.S. EEZ and there is no evidence of sperm whale movements from 

the eastern tropical Pacific to the U.S. EEZ. The most precise estimate of sperm whale abundance within the area of the 

drift gillnet fishery is therefore from the ship survey estimate of Barlow (1997); however, this is probably an 

underestimate of true abundance because recent studies suggest sperm whale group sizes may have been 

underestimated on past line-transect surveys (Barlow and Taylor 1998). 

Minimum Population Estimate 

The minimum population estimate for sperm whales is taken as the lower 20th percentile of the log-normal 

distribution of abundance estimated from the summer/fall ship surveys off California, Oregon and Washington (Barlow 

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 missed animals. 

Current Population Trend 

Sperm whale abundance appears to have been fairly stable in California coastal waters between 1979/80 and 

1991 (Barlow 1994). Although the population in the eastern North Pacific is expected to have grown since large-scale 

pelagic whaling stopped in 1980, the possible effects of large unreported catches are unknown (Yablokov 1994) and the 

ongoing incidental ship strikes and gillnet mortality make this uncertain. 

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES 

There are no published estimates of the growth rate for any sperm whale population (Best 1993). 

POTENTIAL BIOLOGICAL REMOVAL 

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

population size ( 992) times one half the default maximum net growth rate for cetaceans (1⁄2 of 4%) times a recovery factor 

of 0.1 (the default value for an endangered species), resulting in a PBR of 2.0. 

HUMAN-CAUSED MORTALITY 

Historic Whaling 

Between 1800 and 1909, about 60,842 sperm whales were estimated taken in the North Pacific (Best 1976). The 

reported take of North Pacific sperm whales by commercial whalers between 1947 and 1987 totaled 258,000 (C. Allison, 

pers. comm.). Ohsumi (1980) lists an additional 28,198 sperm whales taken mainly in coastal whaling operations from 1910 

to 1946. Based on the massive under-reporting of Soviet catches, Brownell et al. (1998) estimate that about 89,000 whales 

were additionally taken by the Soviet pelagic whaling fleet between 1949 and 1979. The Japanese coastal operations 

apparently also under-reported catches by an unknown amount (Kasuya 1998). Thus a total of at least 436,000 sperm 

whales were taken between 1800 and the end of commercial whaling for this species in 1987. Of this grand total, an 

estimated 33,842 were taken by Soviet and Japanese pelagic whaling operations in the eastern North Pacific from the 

longitude of Hawaii to the U.S. West coast, between 1961 and 1976 (Allen 1980, IWC statistical Areas II and III), and 965 

were reported taken in land-based U.S. West coast whaling operations between 1947 and 1971 (Ohsumi 1980). In 

addition, 13 sperm whales were taken by shore whaling stations in California between 1919 and 1926 (Clapham et al. 1997). 

There has been a prohibition on taking sperm whales in the North Pacific since 1988, but large-scale pelagic whaling 

stopped earlier, in 1980. 

Fishery Information 

Sperm whales in this stock are likely to be caught only in offshore drift gillnets. Detailed information on this 

49 
fishery is provided in Appendix 1 of Barlow et al. (1997). A summary of known fishery mortality and injury for this stock 

of sperm whales is given in Table 1. In 1996-97, a pinger experiment was conducted to evaluate whether these acoustic 

alarms may reduce cetacean entanglement rates in the drift gillnet fishery. Based on the positive results of this study 

(Cameron 1998), pingers were made mandatory in this fishery in November 1997. The 1996-97 mortality estimates were 

stratified for pingered and unpingered drift gillnets. Only one whale was observed in a pingered net in 1996; this whale 

sustained significant injuries and was not expected to survive (Cameron 1998). The average annual fishery mortality is 

estimated to be 3.0 sperm whales for the five most recent years of monitoring (1993-97). In addition, an estimated 1.6 

sperm whales per year were entangled but released alive. In addition, some gillnet mortality of large whales may go 

unobserved because whales swim away with a portion of the net. The deaths of two stranded sperm whales in California 

were attributed to entanglement in fishing gear between 1983 and 1991 (J. Cordaro, pers. comm.). Drift gillnet fisheries 

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

same population. Quantitative data are available only for the Mexican swordfish drift gillnet fishery, which has increased 

from two vessels in 1986 to 29 vessels in 1992-(Sosa-Nishizaki et al. 1993). The total number of sets in this fishery in 1992 

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

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

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

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

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 and Beeson 1998; Julian 1997; Cameron 1998). Injury includes 

any entanglement that does not result in immediate death and may include serious injury resulting in death. The injured 

whale observed in 1996 was not expected to survive . n/a indicates that data are not available. 

Fishery Name Year(s) Data Type Percent 

Observer 

Coverage 

Observed 

Mortality 

(and injury in 

parentheses) 

Estimated 

Mortality (CV 

in parentheses) 

Mean Annual Takes 

1993-97 

(CV in parentheses) 

CA/OR thresher 

shark/swordfish drift 

gillnet fishery 

1993 

1994 

1995 

1996 

1997 

observer 

data 

13.4% 

17.9% 

15.6% 

12.4% 

26.6% 

2 (1) 

0 

0 

0 (1) 

0 

Mortality 

15,0,0,0,0 

(0.66,0) 

Injury 

7,0,0,1,0 

Mortality 

3.0 (0.66) 

Injury 

1.6 (n/a) 

Total annual takes 4.6 (0.66) 

Ship Strikes 

Ship strikes were implicated in the deaths of two unidentified whales in 1990 (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 always have obvious signs of trauma. 

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 (3.0 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”. In 

addition, an annual average of 1.6 sperm whales are estimated to be entangled and injured, but released alive. Total 

fishery mortality is not approaching zero mortality and serious injury rate. In comparing gillnet mortality with the PBR, 

it should be remembered that the PBR does not include sperm whales found further offshore which possibly belong to 

the same population. A fishery interaction problem appears to exist for sperm whales taken in the drift gillnet fishery, 

but enough uncertainties exist that one should not conclude from this information that sperm whales are necessarily 

declining in abundance off the U.S. West Coast. A take reduction plan for the drift gillnet fishery, including mandatory 

pingers and a minimum 6-fathom suspender length, was implemented in 1997, and preliminary results indicate that 

cetacean mortality has decreased markedly (Cameron 1998). The increasing levels of anthropogenic noise in the world’s 

oceans has been suggested to be a habitat concern for whales, particularly for deep-diving whales like sperm whales that 

50 
feed in the oceans “sound channel”. 

REFERENCES 

Allison, C. International Whaling Commission. The Red House, 135 Station Road, Impington, Cambridge, UK CB4 9NP. 

Allen, K. R. 1980. Size distribution of male sperm whales in the pelagic catches. Rep. Int. Whal. Commn. Special Issue 

2:51-56. 

Barlow, J. 1994. Abundance of large whales in California coastal waters: a comparison of ship surveys in 1979/80 and 

in 1991. Rept. Int. Whal. Commn. 44:399-406. 

Barlow, J. 1995. The abundance of cetaceans in California waters. Part I: Ship surveys in summer and fall of 1991. Fish. 

Bull. 93:1-14. 

Barlow, J. 1997. Preliminary estimates of cetacean abundance off California, Oregon and Washington based on a 1996 

ship survey and comparisons of passing and closing modes. Administrative Report LJ-97-11, Southwest 

Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA 92038. 25p. 

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

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

Canada and the east coast of the Russian Federation. Rep. Int. Whal. Commn, Special Issue 15:405-425. 

Barlow, J., K. A. Forney, P. S. Hill, R. L. Brownell, Jr., J. V. Carretta, D. P. DeMaster, F. Julian, M. S. Lowry, T. Ragen, and 

R. R. Reeves. 1997. U.S. Pacific Marine Mammal Stock Assessments: 1996. U.S. Dep. Commer., NOAA Tech. 

Memo. NMFS-SWFSC-248. 223p. 

Barlow, J. and B. L. Taylor. 1998. Preliminary abundance of sperm whales in the northeastern temperate Pacific estimated 

from a combined visual and acoustic survey. Paper SC/50/CAWS20 presented to the International Whaling 

Commission, June 1998 (unpublished). 

Best, P. B. 1976. A review of world sperm whale stocks. Paper ACMRR/MM/SC/8 Rev. 1, FAO Scientific Consultation 

of Marine Mammals, Bergen, Norway. 

Best, P. B. 1993. Increase rates in severely depleted stocks of baleen whales. ICES J. Mar. Sci. 50:169-186. 

Brownell, R. L., Jr., A. V. Yablokov and V. A. Zemmsky. 1998. USSR pelagic catches of North Pacific sperm whales, 1949­

1979: Conservation implications. Paper SC/50/CAWS27 presented to the International Whaling Commission, 

June 1998 (unpublished). 

Cameron, G. 1998. Cetacean mortality in California gill net fisheries: Preliminary estimates for 1997. Paper SC/50/SM02 

presented to the International Whaling Commission, June 1998 (unpublished). 15 pp. 

Clapham, P. J., S. Leatherwood, I. Szczepaniak, and R. L. Brownell, Jr. 1997. Catches of humpback and other whales from 

shore stations at Moss Landing and Trinidad, California, 1919-1926. Marine Mammal Science 13(3):368-394. 

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

Dohl, T. P., R. C. Guess, M. L. Duman, and R. C. Helm. 1983. Cetaceans of central and northern California, 1980-83: 

Status, abundance, and distribution. Final Report to the Minerals Management Service, Contract No. 14-12­

0001-29090. 284p. 

Donovan, G. P. 1991. A review of IWC stock boundaries. Rept. Int. Whal. Commn., Special Issue 13:39-68. 

Dufault, S. and H. Whitehead. 1995. The geographic stock structure of female and immature sperm whales in the South 

Pacific. Rep. Int. Whal. Commn. 45:401-405. 

Forney, K. A., J. Barlow, and J. V. Carretta. 1995. The abundance of cetaceans in California waters. Part II: Aerial 

surveys in winter and spring of 1991 and 1992. Fish. Bull. 93:15-26. 

Gosho, M. E., D. W. Rice, and J. M. Breiwick. 1984. The sperm whale. Mar. Fish. Rev. 46(4):54-64. 

Green, G. A., J. J. Brueggeman, R. A. Grotefendt, C. E. Bowlby, M. L. Bonnell, K. C. Balcomb, III. 1992. Cetacean 

distribution and abundance off Oregon and Washington, 1989-1990. Ch. 1 In: J. J. Brueggeman (ed.). Oregon 

and Washington Marine Mammal and Seabird Surveys. Minerals Management Service Contract Report 14-12­

0001-30426. 

Hanan, D. A. 1986. California Department of Fish and Game coastal marine mammal study, annual report for the period 

July 1, 1983 - June 30, 1984. Admin. Rept. LJ-86-16 available from Southwest Fisheries Science Center, P.O. Box 

271, La Jolla, CA. 55pp. 

Hanan, D. A., D. B. Holts, and A. L. Coan, Jr. 1993. The California drift gill net fishery for sharks and swordfish, 1981-82 

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

Heyning, J. E., and T. D. Lewis. 1990. Fisheries interactions involving baleen whales off southern California. Rep. int. 

51 
Whal. Commn. 40:427-431. 

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

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

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

fisheries: 1990-95. Fishery Bulletin 96:271-284. 

Kasuya, T. 1998. Evidence of statistical manipulations in Japanese coastal sperm whale fishery. Paper SC/50/CAWS10 

presented to the International Whaling Commission, June 1998 (unpublished). 

Leatherwood, S., K. Goodrich, A. L. Kinter, and R. M. Truppo. 1982. Respiration patterns and 'sightability' of whales. 

Rep. Int. Whal. Commn. 32:601-613. 

Miyashita, T., H. Kato, and T. Kasuya (Eds.). 1995. Worldwide map of cetacean distribution based on Japanese sighting 

data. Volume 1. National Research Institute of Far Seas Fisheries, Shizuoka, Japan. 140pp. 

Ohsumi, S. 1980. Catches of sperm whales by modern whaling in the North Pacific. Rep. Int. Whal. Commn. Special 

Issue 2: 11-18. 

Rice, D. W. 1988. Sperm whale Physeter macrocephalus, Linnaeus 1758. pp. 177-233 In: S. H. Ridgway and R. J. 

Harrison (eds.). Handbook of Marine Mammals, Vol. 4. Academic Press, London. 

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

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

CICESE, CTECT9306. 

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

Rept. Int. Whal. Commn. 43:477-493. 

52 
Revised 09/30/99 

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 good evidence for multiple populations of humpback 

whales in the North Pacific (Johnson and Wolman 1984; 

Baker et al. 1990). Aerial, vessel, and photo-identification 

surveys, and genetic analyses indicate that within the U.S. 

EEZ, there are at least three relatively separate populations 

that migrate between their respective summer/fall feeding 

areas and winter/spring calving and mating areas 

(Calambokidis et al. 1997, Baker et al. 1998): 1) winter/spring 

populations in coastal Central America and Mexico which 

migrate to the coast of California to southern British Columbia 

in summer/fall (Steiger et al. 1991, Calambokidis et al. 1993) ­

referred to as the California/ Oregon/Washington - Mexico 

stock (Figure 1); 2) winter/spring populations of the Hawaiian 

Islands which migrate to northern British Columbia/Southeast 

Alaska and Prince William Sound west to Kodiak (Baker et al. 

1990, Perry et al. 1990, Calambokidis et al. 1997) - referred to as 

the Central North Pacific stock; and 3) winter/spring 

populations of Japan which, based on Discovery Tag 

information, probably migrate to waters west of the Kodiak 

Archipelago (the Bering Sea and Aleutian Islands) in 

summer/fall (Berzin and Rovnin 1966, Nishiwaki 1966, Darling 

1991) - referred to as the Western North Pacific stock. 

Winter/spring populations of humpback whales also occur in 

Mexico’s offshore islands, but the migratory destination of 

these whales is not well known (Calambokidis et al. 1993, 

Calambokidis et al. 1997). Significant levels of genetic 

differences were found between the California and Alaska 

feeding groups based on analyses of mitochondrial DNA 

(Baker et al. 1990) and nuclear DNA (Baker et al. 1993). The 

genetic exchange rate between California and Alaska is 

Figure 1. Humpback whale sighting locations 

based on aerial and shipboard surveys off California, 

Oregon, and Washington, 1989-96. Dashed line 

represents the U.S. EEZ, thick line indicates the outer 

boundary of all surveys combined. Greater effort 

was conducted off California (south of 42/N) and in 

the inshore half of the U.S. EEZ. See Appendix 2 of 

Barlow et al. (1997) and Barlow (1997) for data 

sources and information on timing and location of 

survey effort. 

estimated to be less than 1 female per generation (Baker 1992). Two breeding areas (Hawaii and coastal Mexico) showed 

fewer genetic differences than did the two feeding areas (Baker 1992). This is substantiated by the observed movement 

of individually-identified whales between Hawaii and Mexico (Baker et al. 1990). There have been no individual matches 

between 597 humpbacks photographed in California and 617 humpbacks photographed in Alaska (Calambokidis et al. 

1996). Only two of the 81 whales photographed in British Columbia have matched with a California catalog (Calambokidis 

et al. 1996), indicating that the U.S./Canada border is an approximate geographic boundary between feeding populations. 

Until further information becomes available, three management units of humpback whales (as described above) 

are recognized within the U.S. EEZ of the North Pacific: the California/Oregon/Washington - Mexico stock (this report), 

the Central North Pacific Stock, and the Western North Pacific Stock. The Central and Western North Pacific stocks are 

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

POPULATION SIZE 

Based on whaling statistics, the pre-1905 population of humpback whales in the North Pacific was estimated 

53 
to be 15,000 (Rice 1978), but this population was reduced by whaling to approximately 1,200 by 1966 (Johnson and 

Wolman 1984). The North Pacific total now almost certainly exceeds 6,000 humpback whales (Calambokidis et al. 1997). 

Dohl et al. (1983) first estimated the central California feeding population to be 338 (CV=0.29) based on aerial surveys 

in August through November of 1980-83; however, this estimate does not include a correction for submerged animals. 

More recently, the size of the "California" feeding stock of humpback whales has been estimated by three independent 

methods. 1) Calambokidis et al. (1998) estimated the number of humpback whales in California-Washington to be 843 

(CV=0.06) based on mark-recapture estimates comparing their 1996 and 1997 photo-identification catalogs. 2) Barlow 

(1997) estimates 1,152 (CV=0.15) humpbacks in California, Oregon and Washington waters based on ship line-transect 

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 population size. These estimates 

for the west-coast stock are not significantly 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 submerged animals are missed. 

Mark-recapture estimates may also be negatively biased due to heterogeneity in sighting probabilities (Hammond 1986). 

However, given that the above mark-recapture estimate is based on a large fraction of the entire population (the 1996-97 

catalog contained 492 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. 1993). The most precise and least biased estimate is likely to be the mark-recapture estimate of 843 

(CV=0.06) humpback whales for this population. 

Minimum Population Estimate 

The minimum population estimate for humpback whales in the California/Mexico stock is taken as the lower 20th 

percentile of the log-normal distribution of 1996-97 abundance estimated from mark-recapture methods (Calambokidis 

et al. 1998) or approximately 802. 

Current Population Trend 

There is some indication that humpback whales increased in abundance in California coastal waters between 

1979/80 and 1991 (Barlow 1994) and between 1991 and 1993 (Barlow and Gerrodette 1996), but these trends are not 

statistically significant. Mark-recapture population estimates increased steadily from 1988/90 to 1992/93 at about 5% 

per year (Calambokidis and Steiger 1994), and the even higher 1996-97 estimate suggests a continued population increase 

(Calambokidis et al. 1998). Although the population in the North Pacific is expected to have grown since being given 

protected status in 1966, the possible effects of continued unauthorized take (Yablokov 1994) and incidental ship strikes 

and gillnet mortality make this uncertain. 

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES 

There are no estimates of the growth rate of humpback whale populations in the North Pacific (Best 1993). The 

proportion of calves in the California/Mexico stock from 1986 to 1994 appeared much lower than previously measured 

for humpback whales in other areas (Calambokidis and Steiger 1994), but in 1995-97 a greater proportion of calves were 

identified, and the 1997 reproductive rates for this population are closer to those reported for humpback whale 

populations in other regions (Calambokidis et al. 1998). 

POTENTIAL BIOLOGICAL REMOVAL 

The potential biological removal (PBR) level for this stock is calculated as the minimum population size (802) 

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 1.6. Because this stock spends approximately half its time in Mexican waters, 

the PBR allocation for U.S. waters is 0.8 whales per year. 

HUMAN-CAUSED MORTALITY 

Historic Whaling 

The reported take of North Pacific humpback whales by commercial whalers totaled approximately 7,700 between 

1947 and 1987 (C. Allison, pers. comm.). In addition, approximately 7,300 were taken along the west coast of North 

America from 1919 to 1929 (Tonnessen and Johnsen 1982). Total 1910-1965 catches from the California-Washington 

54 
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 

Humpback whales are known to be killed only in offshore drift gillnets. A summary of known fishery mortality 

and injury for this stock of humpback whales is given in Table 1. Detailed information on this fishery is provided in 

Appendix 1 of Barlow et al. (1997). The average fishery mortality and injury is estimated to be 1.4 humpback whales per 

year for the five most recent years of monitoring (1993-97) based on the observation of one entangled whale (released 

alive). 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). A humpback whale was observed off Ventura, CA in 1993 with a 20 ft section 

of netting wrapped around and trailing behind. Other unobserved fisheries may also result in injuries or deaths of 

humpback whales. In 1997, one humpback whale was snagged by a central California salmon troller, and the animal swam 

away with the hook and many feet of trailing monofilament (NMFS, Southwest Region, unpublished data). 

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

probably take animals from the same population. Quantitative data are available only for the Mexican swordfish drift 

gillnet fishery, which has increased from two vessels in 1986 to 29 vessels in 1992 (Sosa-Nishizaki et al. 1993). The total 

number of sets in this fishery in 1992 can be estimated from data provided by these authors to be approximately 2,700, 

with an observed rate of marine mammal bycatch of 0.13 animals per set (10 marine mammals in 77 observed sets; SosaNishizaki et al. 1993). This overall mortality rate is similar to that observed in California driftnet fisheries during 1990-95 

(0.14 marine mammals per set, Julian and Beeson 1998), but species-specific information is not available for the Mexican 

fisheries. 

Table 1. Summary of available information on the incidental mortality and injury of humpback whales (CA/OR/WA -

Mexico stock) for commercial fisheries that might take this species (Julian and Beeson 1998, Julian 1997, Cameron 1998). 

Injury includes any entanglement that does not result in immediate death and may include serious injury resulting in 

death. n/a indicates that data are not available. 

Fishery Name Year(s) Data Type 

Percent 

Observer 

Coverage 

Observed 

Mortality 

(and Injury) 

Estimated 

Mortality 

(CV in 

parentheses) 

Mean Annual Takes 

1993-97 

(CV in parentheses) 

CA/OR thresher 

shark/swordfish drift 

gillnet fishery 

1993 

1994 

1995 

1996 

1997 

observer 

data 

13.4% 

17.9% 

15.6% 

12.4% 

26.6% 

0 

0 (1) 

0 

0 

0 

Mortality 

0,0,0,0,0 

Injury 

0,6,0,0,0 

(0.91) 

Mortality 

0 

Injury 

1.2 (0.91) 

CA angel shark/halibut 

and other species large 

mesh (>3.5") set gillnet 

fishery 

1991-95 observer 

data 

0-15% 0,0,0,0,0 0,0,0,0,0 0 

CA salmon troll fishery 1997 incidental 

report 

0% (1) n/a Injury 

0.2 (n/a) 

Total annual takes 1.4 (0.91) 

Ship Strikes 

Ship strikes were implicated in the deaths of at least two humpback whales in 1993 and one humpback whale 

in 1995, and one unidentified whale, which may have been a humpback whale, was struck and injured by a small boat in 

1997 (J. Cordaro, pers. comm.). Additional mortality from ship strikes probably goes unreported because the whales do 

not strand or, if they do, they do not have obvious signs of trauma. Several humpback whales have been photographed 

in California with large gashes in their dorsal surface that appear to be from ship strikes (J. Calambokidis, pers. comm.). 

The average number of humpback whale deaths by ship strikes from 1993-97 is at least 0.6 per year. 

55 
STATUS OF STOCK 

Humpback whales in the North Pacific were estimated to have been reduced to 13% of carrying capacity (K) 

by commercial whaling (Braham 1991). Clearly the North Pacific population was severely depleted. The initial abundance 

has never been estimated separately for the "California" stock, but this stock was also depleted (probably twice) by 

whaling (Rice 1974; Clapham et al. 1997). Humpback whales are formally listed as "endangered" under the Endangered 

Species Act (ESA), and consequently the California/Mexico stock is automatically considered as a "depleted" and 

"strategic" stock under the MMPA. The estimated annual mortality and injury due to entanglement (1.4/yr) plus ship 

strikes (0.6/yr) in California is greater than the PBR allocation of 0.8 for U.S. waters. If none of the injuries from fishing 

gear entanglement resulted in death, the known mortality due to ship strikes alone would not exceed the PBR. In a review 

of the severity of injury to the humpback whale entangled in 1994, the Pacific Scientific Review Group determined that 

it this animal was not seriously injured. Based on strandings and gillnet observations, annual humpback whale mortality 

and serious injury in California's drift gillnet fishery is probably greater than 10% of the PBR; therefore, total fishery 

mortality is not approaching zero mortality and serious injury rate. The California stock appears to be increasing in 

abundance. The increasing levels of anthropogenic noise in the world’s oceans, such as those produced by ATOC 

(Acoustic Thermometry of Ocean Climate) or LFA (Low Frequency Active) Sonar, have been suggested to be a habitat 

concern for whales, particularly for baleen whales that may communicate using low-frequency sound. 

REFERENCES 

Allison, C. International Whaling Commission. The Red House, 135 Station Road, Impington, Cambridge, UK CB4 9NP. 

Baker, C. S. 1992. Genetic variability and stock identity of humpback whales, world-wide. Final Contract Report to Int. 

Whal. Commn. 45pp. 

Baker, C. S., D. A. Gilbert, M. T. Weinrich, R. Lambertsen, J. Calambokidis, B. McArdle, G. K. Chambers, and S. J. O'Brien. 

1993. Population characteristics of DNA fingerprints in humpback whales (Megaptera novaeangliae). J. 

Heredity 84:281-290. 

Baker, C. S., L. Medrano-Gonzalez, J. Calambokidis, A. Perry, F. Pichler, H. Rosenbaum, J. M. Straley, J. UrbanRamirez, M. Yamaguchi, and O. von Ziegesar. 1998. Population structure of nuclear and mitochondrial DNA 

variation among humpback whales in the North Pacific. Mol. Ecol. 7: (in press). 

Baker, C. S., S. R. Palumbi, R. H. Lambertsen, M. T. Weinrich, J. Calambokidis, and S. J. O'Brien. 1990. Influence of 

seasonal migration on geographic distribution of mitochondrial DNA haplotypes in humpback whales. Nature 

344(15):238-240. 

Barlow, J. 1994. Abundance of large whales in California coastal waters: a comparison of ship surveys in 1979/80 and 

in 1991. Rept. Int. Whal. Commn. 44:399-406. 

Barlow, J. 1995. The abundance of cetaceans in California waters. Part I: Ship surveys in summer and fall of 1991. Fish. 

Bull. 93:1-14. 

Barlow, J. 1997. Preliminary estimates of cetacean abundance off California, Oregon and Washington based on a 1996 

ship survey and comparisons of passing and closing modes. Administrative Report LJ-97-11, Southwest 

Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, CA 92038. 25p. 

Barlow, J., 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., K. A. Forney, P. S. Hill, R. L. Brownell, Jr., J. V. Carretta, D. P. DeMaster, F. Julian, M. S. Lowry, T. Ragen, and 

R. R. Reeves. 1997. U.S. Pacific Marine Mammal Stock Assessments: 1996. U.S. Dep. Commer., NOAA Tech. 

Memo. NMFS-SWFSC-248. 223p. 

Barlow, J. and T. Gerrodette. 1996. Abundance of cetaceans in California waters based on 1991 and 1993 ship surveys. 

U.S. Dep. Commer., NOAA Tech. Memo. NMFS-SWFSC-233. 15p. 

Berzin, A. A., and A. A. Rovnin. 1966. The distribution and migrations of whales in the northeastern part of the 

Pacific, Chukchi and Bering Seas. Izvestiya Tikhookeanskogo Nauchno-Issledovatel’skogo Institut Rybnogo 

Khozyaistva I Okeanografii 58:179-207. (Translated by Bureau of Commercial Fisheries, U. S. Fish and Wildlife 

Service, Seattle, 1968, pp. 103-136 In: K. I. Panin (ed.), Soviet Research on Marine Mammals of the Far East). 

Best, P. B. 1993. Increase rates in severely depleted stocks of baleen whales. ICES J. Mar. Sci. 50:169-186. 

Braham, H. W. 1991. Endangered whales: status update. A Report on the 5-year status of stocks review under the 1978 

amendments to the U.S. Endangered Species Act. NMFS Unpublished Report. 

Calambokidis, J. Cascadia Research Collective, 218 1⁄2 West Fourth Avenue, Olympia, WA 98501. 

56 
Calambokidis, J., T. Chandler, K. Rasmussen, G. H. Steiger, and L. Schlender. 1998. Humpback and blue whale 

photographic identification: Report on research in 1997. Report prepared by Cascadia Research, 2181⁄2 W. 

Fourth Ave, Olympia, WA 98501. 41p. 

Calambokidis, J., and G. H. Steiger. 1994. Population assessment of humpback and blue whales using photoidentification from 1993 surveys off California. Final Contract Report to Southwest Fisheries Science Center, 

P.O. Box 271, La Jolla, CA 92038. 31pp. 

Calambokidis, J., G. H. Steiger, and J. R. Evenson. 1993. Photographic identification and abundance estimates of 

humpback and blue whales off California in 1991-92. Final Contract Report 50ABNF100137 to Southwest 

Fisheries Science Center, P.O. Box 271, La Jolla, CA 92038. 67pp. 

Calambokidis, J., G. H. Steiger, J. R. Evenson, K. R. Flynn, K. C. Balcomb, D. E. Claridge, P. Bloedel, J. M. Straley, C. S. 

Baker, O. von Ziegesar, M. E. Dahlheim, J. M. Waite, J. D. Darling, G. Ellis, and G. A. Green. 1996. Interchange 

and isolation of humpback whales in California and other North Pacific feeding grounds. Mar. Mamm. Sci. 

12(2):215-226. 

Calambokidis, J., G. H. Steiger, J. M. Straley, T. J. Quinn, II, L. M. Herman, S. Cerchio, D. R. Salden, M. Yamaguchi, F. 

Sato, J. Urbán R., J. Jacobsen, O. von Ziegesar, K. C. Balcomb, C. M. Gabriele, M. E. Dahlheim, N. Higashi, S. 

Uchida, J. K. B. Ford, Y. Miyamura, P. Ladrón de Guevara P., S. A. Mizroch, L. Schlender and K. Rasmussen. 

1997. Abundance and population structure of humpback whales in the North Pacific Basin. Final Contract 

Report 50ABNF500113 to Southwest Fisheries Science Center, P.O. Box 271, La Jolla, CA 92038. 72p. 

Cameron, G. 1998. Cetacean mortality in California gill net fisheries: Preliminary estimates for 1997. Paper SC/50/SM02 

presented to the International Whaling Commission, June 1998 (unpublished). 15 pp. 

Clapham, P. J., S. Leatherwood, I. Szczepaniak, and R. L. Brownell, Jr. 1997. Catches of humpback and other whales from 

shore stations at Moss Landing and Trinidad, California, 1919-1926. Marine Mammal Science 13(3):368-394. 

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

Darling, J. D. 1991. Humpback whales in Japanese waters. Ogasawara and Okinawa. Fluke identification catalog 1987­

1990. Final Contract Report, World Wildlife Fund for Nature, Japan. 22 pp. 

Dizon, A. E., C. Lockyer, W. F. Perrin, D. P. DeMaster, and J. Sisson. 1992. Rethinking the stock concept: a 

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

Dohl, T. P., R. C. Guess, M. L. Duman, and R. C. Helm. 1983. Cetaceans of central and northern California, 1980-83: 

Status, abundance, and distribution. Final Report to the Minerals Management Service, Contract No. 14-12­

0001-29090. 284p. 

Donovan, G. P. 1991. A review of IWC stock boundaries. Rept. Int. Whal. Commn., Special Issue 13:39-68. 

Forney, K. A., J. Barlow, and J. V. Carretta. 1995. The abundance of cetaceans in California waters. Part II: Aerial 

surveys in winter and spring of 1991 and 1992. Fish. Bull. 93:15-26. 

Green, G. A., J. J. Brueggeman, R. A. Grotefendt, C. E. Bowlby, M. L. Bonnell, K. C. Balcomb, III. 1992. Cetacean 

distribution and abundance off Oregon and Washington, 1989-1990. Ch. 1 In: J. J. Brueggeman (ed.). Oregon 

and Washington Marine Mammal and Seabird Surveys. Minerals Management Service Contract Report 14-12­

0001-30426. 

Hammond, P. S. 1986. Estimating the size of naturally marked whale populations using capture-recapture techniques. 

Rept. Int. Whal. Commn., Special Issue 8:253-282. 

Hanan, D. A. 1986. California Department of Fish and Game coastal marine mammal study, annual report for the period 

July 1, 1983 - June 30, 1984. Admin. Rept. LJ-86-16 available from Southwest Fisheries Science Center, P.O. Box 

271, La Jolla, CA. 55pp. 

Hanan, D. A., D. B. Holts, and A. L. Coan, Jr. 1993. The California drift gill net fishery for sharks and swordfish, 1981-82 

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

Heyning, J. E., and T. D. Lewis. 1990. Fisheries interactions involving baleen whales off southern California. Rep. int. 

Whal. Commn. 40:427-431. 

Johnson, J. H., and A. A. Wolman. 1984. The humpback whale, Megaptera novaeangliae. Mar. Fish. Rev. 46(4):30-37. 

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

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

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

fisheries: 1990-95. Fishery Bulletin 96:271-284. 

Nishiwaki, M. 1966. Distribution and migration of the larger cetaceans in the North Pacific as shown by Japanese 

57 
whaling results. Pp. 172-191 In: K. S. Norris (ed.), Whales, Dolphins and Porpoises. University of California 

Press, Berkeley, CA. Academic Press, New York. 

Perry, A., C. S. Baker, L. M. Herman. 1990. Population characteristics of individually identified humpback whales in 

the central and eastern North Pacific: a summary and critique. Rep. Int. Whal. Commn. (Special Issue 12):307­

317. 

Rice, D. W. 1974. Whales and whale research in the eastern North Pacific. pp. 170-195 In: W. E. Schevill (ed.). The 

Whale Problem: A Status Report. Harvard Press, Cambridge, MA. 

Rice, D. W. 1978. The humpback whale in the North Pacific: distribution, exploitation, and numbers. pp. 29-44 In: K. 

S. Norris and R. R. Reeves (eds.). Report on a Workshop on Problems Related to Humpback Whales 

(Megaptera novaeangliae) in Hawaii. Contr. Rept. to U. S. Marine Mammal Commn. NTIS PB-280-794. 90pp. 

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

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

CICESE, CTECT9306. 

Steiger, G. H., J. Calambokidis, R. Sears, K. C. Balcomb, and J. C. Cubbage. 1991. Movement of humpback whales 

between California and Costa Rica. Mar. Mamm. Sci. 7:306-310. 

Tonnessen, J. N., and A. O. Johnsen. 1982. The History of Modern Whaling. Univ. Calif. Press, Berkeley and Los 

Angeles. 798pp. 

Yablokov, A. V. 1994. Validity of whaling data. Nature 367:108. 

58 
APPENDIX 1 

CHRONOLOGY OF U.S. PACIFIC MARINE MAMMAL STOCK ASSESSMENT REPORTS, 1995-1999.

Key: X=Revised with new information, R=Reprinted without revision, N=New stock, 

E=Eliminated Stock; Shading indicates that a stock was not defined for that year.

U.S. PACIFIC MARINE MAMMAL STOCK 1995 1996 1998 1 1999 

PINNIPEDS 

CALIFORNIA SEA LION (Zalophus californianus californianus): 

U.S. Stock 

X X 

HARBOR SEAL (Phoca vitulina richardsi): 

California Stock 

X X 

HARBOR SEAL (Phoca vitulina richardsi): 

Oregon & Washington Coastal Waters Stock 

X X X 

HARBOR SEAL (Phoca vitulina richardsi): 

Washington Inland Waters Stock 

X X X 

NORTHERN ELEPHANT SEAL (Mirounga angustirostris): 

California Breeding Stock 

X X 

GUADALUPE FUR SEAL (Arctocephalus townsendi) X R 

NORTHERN FUR SEAL (Callorhinus ursinus): 

San Miguel Island Stock 

X X X 

HAWAIIAN MONK SEAL 

(Monachus schauinslandi) 

X X X 

CETACEANS - U. S. WEST COAST 

HARBOR PORPOISE (Phocoena phocoena): 

Central California Stock 

X X X 

HARBOR PORPOISE (Phocoena phocoena): 

Northern California Stock 

X X X 

HARBOR PORPOISE (Phocoena phocoena): 

Oregon/Washington Coast Stock 

X X X X 

HARBOR PORPOISE (Phocoena phocoena): 

Inland Washington Stock 

X X X X 

DALL'S PORPOISE (Phocoenoides dalli): 

California/Oregon/Washington Stock 

X X 

PACIFIC WHITE-SIDED DOLPHIN (Lagenorhynchus obliquidens): 

California/ Oregon/Washington, Northern and Southern Stocks 

X X 

59 
APPENDIX 1 

CHRONOLOGY OF U.S. PACIFIC MARINE MAMMAL STOCK ASSESSMENT REPORTS, 1995-1999.

Key: X=Revised with new information, R=Reprinted without revision, N=New stock, 

E=Eliminated Stock; Shading indicates that a stock was not defined for that year.

U.S. PACIFIC MARINE MAMMAL STOCK 1995 1996 1998 1 1999 

RISSO'S DOLPHIN (Grampus griseus): 

California/Oregon/Washington Stock 

X X 

60 
CHRONOLOGY OF U.S. PACIFIC MARINE MAMMAL STOCK ASSESSMENT REPORTS, 1995-1999. 

Key: X=Revised with new information, R=Reprinted without revision, 

E=Eliminated Stock; Shading indicates that a stock was not defined for that year. 

N=New stock, 

APPENDIX 1 APPENDIX 1 (continued) 

CHRONOLOGY OF U.S. PACIFIC MARINE MAMMAL STOCK ASSESSMENT REPORTS, 1995-1999.

Key: X=Revised with new information, R=Reprinted without revision, N=New stock, 

E=Eliminated Stock; Shading indicates that a stock was not defined for that year.

U.S. PACIFIC MARINE MAMMAL STOCK 1995 1996 1998 1 1999 

BOTTLENOSE DOLPHIN (Tursiops truncatus): 

California Coastal Stock 

X X 

BOTTLENOSE DOLPHIN (Tursiops truncatus): 

California/Oregon/Washington Offshore Stock 

X X 

STRIPED DOLPHIN (Stenella coeruleoalba): 

California/Oregon/Washington Stock 

X X 

SHORT-BEAKED COMMON DOLPHIN (Delphinus delphis): 

California/Oregon/Washington Stock 

X X 

LONG-BEAKED COMMON DOLPHIN (Delphinus capensis): 

California Stock 

X X 

NORTHERN RIGHT WHALE DOLPHIN (Lissodelphis borealis): 

California/Oregon/Washington Stock 

X X 

KILLER WHALE (Orcinus orca): 

California/Oregon/Washington Pacific Coast Stock 

X X E 

KILLER WHALE (Orcinus orca): 

Eastern North Pacific Southern Resident Stock 

X X X 

KILLER WHALE (Orcinus orca): 

Eastern North Pacific Transient Stock 

(INCLUDED IN 

ALASKA REPORTS) 

X 

KILLER WHALE (Orcinus orca): 

Eastern North Pacific Offshore Stock 

N 

SHORT-FINNED PILOT WHALE (Globicephala macrorhynchus): 

California/Oregon/Washington Stock 

X X X 

BAIRD'S BEAKED WHALE (Berardius bairdii): 

California/Oregon/Washington Stock 

X X 

MESOPLODONT BEAKED WHALES (Mesoplodon spp.): 

California/Oregon/Washington Stocks 

X X X 

CUVIER'S BEAKED WHALE (Ziphius cavirostris): 

California/Oregon/Washington Stock 

X X 

PYGMY SPERM WHALE (Kogia breviceps): 

California/Oregon/Washington Stock 

X X 

DWARF SPERM WHALE (Kogia simus): 

California/Oregon/Washington Stock 

X X 

61 
CHRONOLOGY OF U.S. PACIFIC MARINE MAMMAL STOCK ASSESSMENT REPORTS, 1995-1999. 

Key: X=Revised with new information, R=Reprinted without revision, 

E=Eliminated Stock; Shading indicates that a stock was not defined for that year. 

N=New stock, 

APPENDIX 1 APPENDIX 1 (continued) 

CHRONOLOGY OF U.S. PACIFIC MARINE MAMMAL STOCK ASSESSMENT REPORTS, 1995-1999.

Key: X=Revised with new information, R=Reprinted without revision, N=New stock, 

E=Eliminated Stock; Shading indicates that a stock was not defined for that year.

U.S. PACIFIC MARINE MAMMAL STOCK 1995 1996 1998 1 1999 

SPERM WHALE (Physeter macrocephalus): 

California/Oregon/Washington Stock 

X X X 

HUMPBACK WHALE (Megaptera novaeangliae): 

California/Oregon/Washington - Mexico Stock 

X X X 

BLUE WHALE (Balaenoptera musculus): 

California/Mexico Stock 

X X 

FIN WHALE (Balaenoptera physalus): 

California/Oregon/Washington Stock 

X X 

BRYDE'S WHALE (Balaenoptera edeni): 

Eastern Tropical Pacific Stock 

X X 

SEI WHALE (Balaenoptera borealis): 

Eastern North Pacific Stock 

X X 

MINKE WHALE (Balaenoptera acutorostrata): 

California/Oregon/Washington Stock 

X X X 

CETACEANS - HAWAII 

ROUGH-TOOTHED DOLPHIN (Steno bredanensis): 

Hawaiian Stock 

X R 

RISSO'S DOLPHIN (Grampus griseus): 

Hawaiian Stock 

X R 

BOTTLENOSE DOLPHIN (Tursiops truncatus): 

Hawaiian Stock 

X R 

PANTROPICAL SPOTTED DOLPHIN (Stenella attenuata): 

Hawaiian Stock 

X R 

SPINNER DOLPHIN (Stenella longirostris): 

Hawaiian Stock 

X R 

STRIPED DOLPHIN (Stenella coeruleoalba): 

Hawaiian Stock 

X R 

MELON-HEADED WHALE (Peponocephala electra): 

Hawaiian Stock 

X R 

PYGMY KILLER WHALE (Feresa attenuata): 

Hawaiian Stock 

X R 

62 
CHRONOLOGY OF U.S. PACIFIC MARINE MAMMAL STOCK ASSESSMENT REPORTS, 1995-1999. 

Key: X=Revised with new information, R=Reprinted without revision, 

E=Eliminated Stock; Shading indicates that a stock was not defined for that year. 

N=New stock, 

APPENDIX 1 APPENDIX 1 (continued) 

CHRONOLOGY OF U.S. PACIFIC MARINE MAMMAL STOCK ASSESSMENT REPORTS, 1995-1999.

Key: X=Revised with new information, R=Reprinted without revision, N=New stock, 

E=Eliminated Stock; Shading indicates that a stock was not defined for that year.

U.S. PACIFIC MARINE MAMMAL STOCK 1995 1996 1998 1 1999 

FALSE KILLER WHALE (Pseudorca crassidens): 

Hawaiian Stock 

X R 

KILLER WHALE (Orcinus orca): 

Hawaiian Stock 

X R 

SHORT-FINNED PILOT WHALE (Globicephala macrorhynchus): 

Hawaiian Stock 

X R 

BLAINVILLE'S BEAKED WHALE (Mesoplodon densirostris): 

Hawaiian Stock 

X R 

CUVIER'S BEAKED WHALE (Ziphius cavirostris): 

Hawaiian Stock 

X R 

PYGMY SPERM WHALE (Kogia breviceps): 

Hawaiian Stock 

X R 

DWARF SPERM WHALE (Kogia simus): 

Hawaiian Stock 

X R 

SPERM WHALE (Physeter macrocephalus): 

Hawaiian Stock 

X R 

BLUE WHALE (Balaenoptera musculus): 

Hawaiian Stock 

X R 

FIN WHALE (Balaenoptera physalus): 

Hawaiian Stock 

X R 

BRYDE'S WHALE (Balaenoptera edeni): 

Hawaiian Stock 

X R 

APPENDIX TITLES APPENDIX NUMBERS 

Summary of Pacific Stock Assessment Reports 1 3 1 2 

Description of U.S. Commercial Fisheries 1 

Cetacean Survey Effort 2 

Review of New Information for Pacific Marine Mammal Stocks 2 

Chronology of U. S. Pacific Stock Assessment Reports, 1995-1999 1 

1 The public comment, review and revision process has necessitated about a one-year time lag between the draft revision 

and final publication of Marine Mammal Stock Assessment Reports. Therefore, in 1997, the Stock Assessment Report 

dates were changed to ‘1998’ to match the 1998 publication year of the report. 

63 
APPENDIX 1 (continued) 

REFERENCES 

Pacific Region 

1995: Barlow, J., R. L. Brownell, Jr., D. P. DeMaster, K. A. Forney, M. S. Lowry, S. Osmek, T. J. Ragen, R. R. Reeves, 

and R. J. Small. 1995. U.S. Pacific marine mammal stock assessments. U.S. Department of Commerce, NOAA 

Technical Memorandum, NMFS-SWFSC-219. 162 pp. 

1996: 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. 

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

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

Assessments: 1998. U.S. Department of Commerce, NOAA Technical Memorandum, NMFS-SWFSC-258. 42 

pp. 

1999: Forney, K. A., M. M. Muto and J. Baker. 1999. U. S. Pacific Marine Mammal Stock Assessments: 1999. (This 

report). 

Alaska Region: 

1995: Small, R. J. and D. P. DeMaster. 1995. Alaska Marine Mammal Stock Assessments 1995. U.S. Department of 

Commerce, NOAA Technical Memorandum NMFS-AFSC-57, 93 pp. 

1996: Hill, P. S., D. P. DeMaster and R. J. Small. 1996. Alaska Marine Mammal Stock Assessments, 1996. U.S. 

Department of Commerce, NOAA Technical Memorandum NMFS-AFSC-78, 150 pp. 

1998: 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. 

64 
APPENDIX 2 

SUMMARY OF 1999 PACIFIC MARINE MAMMAL STOCK ASSESSMENT REPORTS 

(FOR STOCKS UNDER NMFS JURISDICTION). 

Species Stock Area Regio 

n 

NMFS 

Cente 

r 

Nmin Rmax Fr PBR 

Total 

Annual 

Mortality 

Annual 

Fish. 

Mortality 

Strategic 

Status 

Monk seal 

Harbor 

porpoise 

Harbor 

porpoise 

Harbor 

porpoise 

Harbor 

porpoise 

Killer whale 

Killer whale 

Killer whale 

Short-finned 

pilot whale 

Sperm whale 

Humpback 

whale 

Hawaii 

Central 

California 

Northern 

California 

Oregon/ 

Washington 

Coast 

Inland 

Washington 

Eastern North 

Pacific 

Transient 

Eastern North 

Pacific 

Offshore 

Eastern North 

Pacific 

Southern 

Resident 

California/ 

Oregon/ 

Washington 

California/ 

Oregon/ 

Washington 

California/ 

Oregon/ 

Washington -

Mexico 

PAC 

PAC 

PAC 

PAC 

PAC 

PAC 

PAC 

PAC 

PAC 

PAC 

PAC 

SWC 

SWC 

SWC 

AKC 

AKC 

AKC 

SWC 

AKC 

SWC 

SWC 

SWC 

1,423 

4,172 

8,061 

32,769 

2,545 

336 

209 

89 

717 

992 

802 

0.07 

0.04 

0.04 

0.04 

0.04 

0.04 

0.04 

0.04 

0.04 

0.04 

0.04 

0.1 

0.50 

0.5 

0.5 

0.4 

0.45 

0.5 

0.5 

0.48 

0.1 

0.1 

5.01 

42 

81 

328 

20 

3.0 

2.1 

0.9 

6.9 

2.0 

0.8 

N/A 

24 

0.0 

12 

15 

2.0 

0.0 

0.0 

13 

3.0 

2.0 

N/A 

24 

0.0 

12 

15 

2.0 

0.0 

0.0 

13 

3.0 

1.4 

Y 

N 

N 

N 

N 

N 

N 

N 

Y 

Y 

Y 

1

The Endangered Species Act takes precedence in the management of this species and, under the Act, allowable take 

is zero. 

65