PACIFIC COD

General Biology

Geographical distribution

Pacific cod are found in continental shelf and upper continental slope waters of the North Pacific Ocean from off Port Arthur, China in the northern Yellow Sea, north around the North Pacific Rim, into the Bering Sea as far north as the Chukchi Sea, and south along the North America coast to Santa Monica Bay, California (Fig. 29) (Pinkas 1967, Hart 1973, Bakkala et al. 1984, Allen and Smith 1988, Love 1991, Stepanenko 1995, Westrheim 1996). Pacific cod are also found off the east coast of Japan from Tokyo Bay to northern Hokkaido, on the west coast of Japan in the Sea of Japan, and off the coasts of the Sakhalin and Kurile Islands (Bakkala et al. 1984, Fredin 1985). Off North America, the southern limit of specific commercial Pacific cod fishing occurs between Cape Flattery and Destruction Island on the Washington outer coast (Ketchen 1961).

Pacific cod in Puget Sound are generally categorized into three components: the North Sound component (located in U.S. waters north of Deception Pass, including the San Juan Islands, Strait of Georgia, and Bellingham Bay), the West Sound component (located west of Admiralty Inlet and Whidbey Island, and in the U.S. section of the Strait of Juan de Fuca, including Port Townsend), and the South Sound component (located south of Admiralty Inlet). The primary densities of numerous populations have historically been in the North Pacific, including the Bering Sea and the waters near northern Japan, suggesting that Pacific cod populations in Puget Sound are relatively isolated and distant (Table 14) (Westrheim 1996, Bakkala et al. 1984).

Adult Pacific cod are a member of the inner shelf-mesobenthal community (NOAA 1990). Adults occur as deep as 875 m (Allen and Smith 1988), but the vast majority occur between 50 and 300 m (Allen and Smith 1988, Hart 1973, Love 1991, NOAA 1990). Spawning occurs at depths of from 40 to 265 m (NOAA 1990, Palsson 1990).

Eggs are demersal and are found sublittorally (Palsson 1990). Larvae and small juveniles are pelagic; large juveniles and adults are parademersal (Dunn and Matarese 1987, NOAA 1990). Larvae are found in the upper 45 m of the water column; highest abundances are between 15 and 30 m (Garrison and Miller 1982, Matarese et al. 1981, NOAA 1990, Palsson 1990). Eggs and larvae are found over the continental shelf between Washington and central California from winter through summer (Dunn and Matarese 1987, Palsson 1990). Small juveniles (between 60 and 150 mm in length) usually settle into intertidal/subtidal habitats, commonly associated with sand and eel grass, and gradually move into deeper water with increasing age (NOAA 1990, Miller et al. 1976).

Pacific cod are historically an important groundfish of shallow, soft-bottom habitats in marine and estuarine environments along the west coast (Garrison and Miller 1982). Garrison and Miller (1982) reported that all life stages of Pacific cod occur in various bays in Puget Sound and in the Strait of Juan de Fuca. Adults and large juveniles prefer mud, sand and clay, although Palsson (1990) and Garrison and Miller (1982) found adults associated with coarse sand and gravel substrates.

Migrations

Although they are not considered to be a migratory species, individual adult Pacific cod have been found to move more than 1,000 km (NOAA 1990, Shimada and Kimura 1994). In the northern extent of the range, there exists a seasonal bathymetric movement from deep spawning areas of the outer shelf and upper slope in fall and winter to shallow middle-upper shelf feeding grounds in the spring and early summer (Dunn and Matarese 1987, Hart 1973, NOAA 1990, Shimada and Kimura 1994, Stepanenko 1995).

Larvae may be transported by tidal current to nursery areas (Garrison and Miller 1982). Juveniles are found in polyhaline to euhaline waters, whereas adults are found in marine waters. There is some evidence to suggest that the fish move to deeper water with growth (Hart 1973, NOAA 1990), but they are not found exclusively in deeper water (Brodeur et al. 1995, Palsson 1990).

Reproduction and development

In British Columbia waters, 50% of the male Pacific cod have been reported to be sexually mature at 41-53 cm, and 50% of the females have been reported to be mature at 47-56 cm (Westrheim 1996). For Pacific cod spawning near Port Townsend, both sexes mature by 2 years and 45 cm (NOAA 1990). A 60-cm female (3-4 years) may produce 1.2 million eggs. A 78-cm female (5-7 years) may have up to 3.3 million eggs. In general, fecundity in Pacific cod has been estimated between 225,000 and 5 million eggs per spawning female (Alderdice and Forrester 1971, Forrester 1969, Hart 1973, Palsson 1990, NOAA 1990).

Pacific cod are oviparous and have external fertilization (Hart 1973, NOAA 1990). They are single-batch spawners, releasing all ripe eggs in a single spawning event in a few minutes time (Sakurai 1989, Sakurai and Hattori 1996). Spawning occurs from late fall to early spring in Puget Sound (Garrison and Miller 1982); stocks further north in the Gulf of Alaska and the Bering Sea spawn in winter through spring (Klovach et al. 1995). Pacific cod in northern areas spawn at lower temperature (1-5^oC in the Bering Sea) than do fish in southern areas (7-9^oC around Japan; 6-9^oC in the Strait of Georgia). Eggs are demersal, weakly adhesive, and are found in polyhaline to euhaline waters between 1^oC and 10^oC (Thomson 1963, Alderdice and Forrester 1971, Dunn and Matarese 1987, Forrester 1969, Hart 1973, Sakurai 1989, Palsson 1990). Fertilized eggs are spherical, 0.98-1.08 mm in diameter (Forrester 1969, Hart 1973, Palsson 1990). Pacific cod eggs have been found associated with coarse sand and cobble bottoms (Phillips and Mason 1986), and because most winter concentration areas have bottom sediments consisting of coarse sand and cobble, it is inferred that Pacific cod preferentially spawn near these bottom types (Palsson 1990).

Conditions for optimal hatching were found to be in the range of 3-6^oC, salinities of 12.7-24.6%^o, and dissolved oxygen levels from three ppm to saturation (Alderdice and Forrester 1971, Forrester 1969). Alderdice and Forrester (1971) found that no spawning occurs below 0^oC or above 10_13^oC, speculating that eggs may experience high mortality or very decreased development at these temperatures. Embryonic development is indirect and external. Eggs hatch in 8-9 days at 11^oC, 20 days at 5^oC, and 28 days at 2^oC (Alderdice and Forrester 1971, Forrester 1969, Hart 1973, NOAA 1990). Larvae hatch at about 3-4 mm (Dunn and Matarese 1987, Palsson 1990) with a yolk sac that is absorbed in about 10 days. Larvae metamorphose at 20-25 mm (Alderdice and Forrester 1971, Dunn and Matarese 1987, Palsson 1990) and settle into the benthic community by 35 mm (Palsson 1990).

Karp (1982) reported that juvenile and adult Pacific cod in Hecate Strait, Strait of Georgia, and Puget Sound had growth rates that were similar, and that these rates were faster than those for Pacific cod in the Bering Sea and Gulf of Alaska. He also suggested that Georgia Basin Pacific cod had shorter life spans than subarctic Pacific cod stocks. Even though Pacific cod in Alaskan waters grow more slowly, their greater longevity allows them to reach a greater size (Table 15).

Trophic interactions

Larval feeding is poorly understood. It is known that at about 20 mm, larvae eat copepods (Hart 1973), but it is not known what they eat between yolk absorption and this size. Juveniles and adults are carnivorous, and feed at night (Allen and Smith 1988, Palsson 1990). Young juveniles in the Bering Sea eat copepods, small shrimps and amphipods, and switch to more crabs with increased size (Tokranov and Vinnikov 1991).

Adult Pacific cod have been described as euryphages because the main part of their diet is whatever prey species is most abundant (Kihara and Shimada 1988, Klovach et al. 1995). Klovach et al. (1995) found that 20-40 cm Pacific cod in the Bering Sea eat shrimp, mysids and amphipods; 40-50 cm Pacific cod eat crabs and amphipods; 50-70 cm Pacific cod prefer mainly sandlance; and 70+ cm Pacific cod consume almost exclusively walleye pollock when available.

Larval Pacific cod are eaten by pelagic fishes and sea birds. Juveniles are eaten by larger demersal fishes, including Pacific cod. Adults are preyed upon by toothed whales, Pacific halibut, salmon shark, and larger Pacific cod (Hart 1973, Love 1991, Stepanenko 1995, NOAA 1990, Palsson 1990). The closest competitor of Pacific cod for resources is the sablefish (Allen 1982).

Size and age distributions

Quinnell and Schmitt (1991) presented length distribution information for Pacific cod from Puget Sound. With the exception of Pacific cod from the Gulf of Bellingham (mean length of 54 cm), mean lengths of Pacific cod collected in the sampling areas of Puget Sound were relatively similar, ranging from 38 to 44 cm (Table 16). The authors also presented length/frequency data (Fig. 30), which indicated that the length distribution was bimodal, with most of Pacific cod being 30 to 46 cm, and a smaller number being 11 to 16 cm. Length/frequency distributions for Pacific cod collected from British Columbia waters are also frequently multi-modal; however, the length ranges are generally larger (Westrheim 1996). Alverson et al. (1964) presented length frequencies for Pacific cod in the Bering Sea, Gulf of Alaska, and British Columbia/Southeast Alaska. Few fish larger than 50 cm were reported in the Gulf of Alaska, although these large fish were common in the Bering Sea and British Columbia/Southeast Alaska samples (Alverson et al. 1964).

Phenetic and Genetic Information Relating to the Species Question

Phenetic and genetic information examined for evidence of DPS delineations of Pacific cod included presence of geographically-discrete and temporally-persistent spawning aggregations, stock structure, tagging studies, and variation in seasonal migrations, parasite incidence, growth rate, length and age-at-maturity, length frequency, fecundity, meristics and morphometrics, and genetic population structure.

Life History Information

Pre-historical and historical persistence in Puget Sound

Tunnicliffe et al. (in press) examined fish remains in a complete Holocene sediment core sequence from Saanich Inlet, Vancouver Island, British Columbia. Pacific cod first appear in the sediment record of Saanich Inlet around 6,000 BP (Tunnicliffe et al. in press). Fish abundance and species diversity peaked in Saanich Inlet between 7,500 and 6,000 BP, and the last 1,000 years have seen some of the lowest abundances of fishes in Saanich Inlet’s marine history (Tunnicliffe et al. in press). The close proximity of Saanich Inlet to Puget Sound would suggest that Pacific cod were also likely established in Puget Sound by approximately 6,000 BP.

Gadiform remains were identified in prehistoric fish skeletal remains from the Duwamish No. 1 archeological site (45-KI-23), located 3.8 km upstream from Elliott Bay on the Duwamish River, utilized by aboriginal humans between A.D. 15 and A.D. 1654 (Butler 1987). Gadiforms were present throughout the occupational history of this site, and were third and fourth in rank order of taxonomic abundance in two separate studies of fish bones performed at this site (following Salmonidae, Pleuronectiformes, and in one case Squalidae) (Butler 1987). Conversely, archaeological investigations of the West Point site on the north side of Discovery Park in Seattle (utilized by hunter-fisher-gatherers between 4,250 and 200 BP) found few remains of gadiforms, although some Pacific cod bones were identified at this site (Wigen 1995). Wigen (1995) postulated that differences in the frequency of gadiform remains found between the Duwamish and West Point sites may be related to the possible use of fish traps at West Point versus hook and line methods at the Duwamish site, or perhaps to differences in the season of human occupation between the two sites.

Pacific cod remains were also reported from the early component of the Bear Cove archaeological site on northeastern Vancouver Island that was occupied 6,500 to 5,000 years ago (Carlson 1979, Hebda and Frederick 1990) and from Namu, on the central coast of British Columbia from the same time period (Carlson 1979, Hebda and Frederick 1990).

Spawning location and spawn timing

Puget Sound to Dixon Entrance--Spawning locations of Pacific cod have been identified in Washington and British Columbia waters primarily on the basis of wintertime aggregations (Figs. 31, 32, Table A-3) (Palsson 1990). Spawning aggregations (several of these may no longer be viable) have been reported in Agate Passage northwest of Bainbridge Island (Bargmann 1980, Palsson 1991, WDFHMD 1992), Port Townsend Bay (Karp and Miller 1977, Karp 1982, WDFHMD 1992), Port Gamble (WDFHMD 1992), Dalco Passage near Tacoma, and Eliza Island off Bellingham, all in Puget Sound (Palsson 1990); Protection Island and Port Angeles in the Strait of Juan de Fuca (WDFHMD 1992); Nanoose Bay, Hornby Island/Cape Lazo in Minor Statistical Area (MSA) 14, and in the vicinity of Swanson Channel in the Gulf Islands in MSA 17s+18, all in the Strait of Georgia (Ketchen 1961, Westrheim 1996); Amphitrite and Clo-oose Banks off southwest Vancouver Island (Ware and McFarlane 1986); and White Rocks (Foucher and Westrheim 1990) and Bonilla Island in eastern Hecate Strait (Tyler and Westrheim 1986). In addition, Phillips and Mason (1986) identified Baynes Sound (in MSA 14) on eastern Vancouver Island as a Pacific cod spawning location by direct sampling of demersal Pacific cod eggs. This later area is in the vicinity of Hornby Island in MSA 14 (Figs. 13 and 15).

Puget Sound is near the southern limit of the range of Pacific cod (Pedersen and DiDonato 1982). Miller and Borton (1980) summarized distribution records of Pacific cod in Puget Sound as found in published records, museum collections, and various boat logs. Centers of collection of Pacific cod in Puget Sound were heavily influenced by fishing effort and ease of access, and centered around Point Roberts to Semiahmoo Bay, Bellingham Bay, west of Orcas Island in President Channel, in East Sound on Orcas Island, off the west side of Whidbey Island near Deception Pass and Point Partridge, Port Townsend, off Discovery Bay, Holmes Harbor, northern Hood Canal, the central Sound from Shilshole Bay to Port Madison, Elliott Bay, off Alki Point, Port Orchard, in the Tacoma Narrows, and between Fox and Anderson Islands at the mouth of Carr Inlet (Miller and Borton 1980). Historically, commercial and recreational fisheries for Pacific cod occurred throughout much of Puget Sound (see Figs. 33, 34) (Pedersen and DiDonato 1982).

Over the North Pacific Ocean as a whole, Pacific cod spawn within the period from December to May (see Table A-3). Spawning seasons appear to be somewhat earlier for Pacific cod in higher latitudes and earlier in lower latitudes. Within British Columbia the Pacific cod spawning season occurs from February to March (Foucher and Westrheim 1990). Principal spawning occurs off southwest Vancouver Island in February and in Hecate Strait in March (Foucher and Westrheim 1990). Within northern Hecate Strait (Area 5D), Pacific cod spawn later than elsewhere in British Columbia, while Pacific cod in southern Hecate Strait (Area 5C) spawn substantially earlier, possibly indicating that two separate stocks exist within Hecate Strait (Fig. 12) (Foucher and Westrheim 1990). Spawning is completed by April in most areas of British Columbia but not until May in northern Hecate Strait (Foucher and Westrheim 1990).

Gulf of Alaska--Hirschberger and Smith (1983) and Dunn and Matarese (1987) reported on observations of spawning Pacific cod in the Gulf of Alaska at Shelikof Strait, on the outer edge of the continental shelf from Yakutat Bay to Chirikof Island, and especially south of Kodiak Island in the Chirikof Island and outer Albatross Bank areas (Fig. 29). Spawning fish were most prevalent from February to May, and occurred between 73 and 265 m depth and in water of 4.5-5.9EC (Hirschberger and Smith 1983). Young-of-the-year Pacific cod ($80 mm) are the dominate fish in nearshore eelgrass communities in Prince William Sound (Laur and Haldorson 1996, Dean et al. 2000) indicating significant Pacific cod spawning is occurring in, or near, Prince William Sound.

Bering Sea--Within the eastern Bering Sea, spawning Pacific cod have been taken in fisheries along the continental slope south of the Pribilof Islands in late January through March and in bays and nearshore waters in the eastern Aleutians and along the north side of Unimak Island to False Pass, from late December to April (Fredin 1985). In the western Bering Sea, Pacific cod spawn from January to May in various locations from Anadyr Bay southwesterly to the Commander Islands (Fig. 29, Table A-3) (Moiseev 1953, Musienko 1970, Vinnikov 1996)

Sea of Okhotsk to Korea--In the eastern part of the Sea of Okhotsk, off western Kamchatka, Pacific cod spawn from the end of February to the end of May in depths of 170 to 280 m (Rovnina et al. 1997). In Japanese coastal waters Pacific cod spawn along the coasts of Hokkaido and northern Honshu primarily from December to March (Fig. 29, Table A-3) over bottom areas consisting of hard or gravelly mud (Mishima 1984). Off the east coast of Korea in the Sea of Japan, Pacific cod spawn in a number of locations, particularly in Yeongil and Chinhoe Bays from late December to late January in water temperatures of 5-9EC (Zhang 1984). In the Yellow Sea, Pacific cod do not concentrate in any given spawning areas but instead spawn over broad areas along the west coast of the Korean Peninsula (Zhang 1984) (Fig. 29, Table A-3).

Pacific cod management stocks

Palsson (1990) identified three Pacific cod stocks in Puget Sound (North, West, and South), based on tagging studies and spawning ground location. The North stock included Pacific cod in the Gulf-Bellingham and San Juan Marine Fish Management Regions (Fig. 14). Pacific cod in the Juan de Fuca and West Juan de Fuca Management Regions comprised the West stock, which included Pacific cod that spawn in Port Townsend Bay. The South stock was comprised of Pacific cod in Hood Canal, Central Puget Sound, and South Sound Management Regions (Palsson 1990). Tagging studies indicated that some of the fish in the North stock spawn at Nanoose Bay in the Strait of Georgia, north of Nanaimo on Vancouver Island (Palsson 1990).

Nine Pacific cod stocks have been provisionally identified in British Columbia waters; four in the Strait of Georgia (Nanoose Bay, Gulf Islands, MSA 14, and MSA 19), one off the southwest coast of Vancouver Island (La Perouse Bank/Amphitrite Bank), two in Queen Charlotte Sound (Areas 5A and 5B); and two in Hecate Strait (a northern and a southern stock) (Figs. 12, 13, 15) (Westrheim 1996). The itinerant MSA 19 stock has been identified as a transitory grouping of Pacific cod apparently lured inshore by spawning Pacific herring and is not associated with a particular Pacific cod spawning ground (Westrheim and Foucher 1987). The stocks in the Gulf Islands and MSA 14 are considered to consist of year-round residents in the Strait of Georgia (Westrheim and Foucher 1987). Pacific cod that spawn in Nanoose Bay, north of Nanaimo on the east coast of Vancouver Island, are considered an itinerant stock that disperses widely beyond Nanoose Bay into the southeast Strait of Georgia, Gulf Islands, and MSA 14 (Figs. 13, 15) (Westrheim and Foucher 1987).

Definitive stock structure analysis of Pacific cod in Alaska has not occurred, although separate Gulf of Alaska and Aleutian Islands/East Bering Sea stocks are recognized for management purposes (Westrheim 1996). Wilimovsky et al. (1967) tentatively identified four separate stocks, based on meristic measurements: southern British Columbia, southeastern Alaska/northern British Columbia, eastern Aleutian Islands/Bering Sea, and western Aleutian Islands.

Numerous stocks of Pacific cod have been identified by researchers in the northwestern Pacific. Moiseev (1960) concluded, based on length frequency differences, that at least 10 local stocks of Pacific cod exist off the Asian coast, but he did not identify them. Zhang (1984) reviewed size at first spawning and morphological differences between the two recognized Korean Pacific cod stocks; an east coast and a west coast stock, which are presumably isolated from one another by warm water at the southern end of the Korean Peninsula. Pacific cod in Japanese waters are differentiated as either "bank cod" or "offshore cod" on the basis of differences in age composition and condition factors (Matsubara 1938, 1939; Mishima 1984). Mishima (1984) noted that Pacific cod in various regions of Japan obtain sexual maturity at different sizes, but he also postulated that these differences were likely due to variable rates of growth affected by biotic and abiotic factors, and by implication not indicative of genetic differences between stocks. Hattori et al. (1992b) cited diverging catch rates between Pacific cod in the Sea of Japan and Pacific cod off the east coast of Japan as evidence of separate stocks occurring in these regions. According to Moiseev (1960), Pacific cod stocks off Asia are believed to have resulted following isolation during the quaternary period when island chains and deep-sea canyons were forming. This resulted in many individual stocks that do not mix, undergo short spawning migrations, and occupy relatively small areas.

Tagging and distribution

Unlike Pacific hake and walleye pollock, numerous tagging studies of adult Pacific cod have occurred in the Northwest Pacific Ocean, including within Puget Sound (Gosho 1976, Bargmann 1980, Westrheim 1982, Karp 1982, Palsson 1990); however, few of these studies have tagged Pacific cod during the spawning season and on the spawning grounds. In the context of delineation of Pacific cod population structure, key questions that tagging studies may help answer are: 1) To what degree do the same fish return to spawn on the same grounds year after year? and 2) How much interchange (gene flow) occurs between spawning populations? Unfortunately, adult tagging studies cannot help answer another important question: do adult Pacific cod return to the same spawning grounds where they were hatched?

Westrheim (1982) reviewed results of Pacific cod tagging studies in British Columbia from 1944 to 1968 that tagged and released over 6,800 Pacific cod in the Strait of Georgia, over 1,600 off southwest Vancouver Island, and over 13,000 in Hecate Strait, with respective area recapture rates of 16%, 18%, and 27%. For the Strait of Georgia releases, 90.8% of recoveries occurred in the Strait of Georgia, 8.5% in Puget Sound, 0.6% off Southwest Vancouver Island, and 0.2% off the outer coast of Washington. For the southwest Vancouver Island releases, 97.9% of recaptures occurred in the area of release, 1.8% in the Strait of Georgia, and 0.4% in Hecate Strait. For Hecate Strait releases, 99.7% of recaptures occurred in Hecate Strait, 0.2% in Queen Charlotte Sound, and 0.1% off northwest Vancouver Island. Pacific cod tagged on the Nanoose Bay spawning grounds appeared to disperse more widely than other stocks: 45% of Nanoose Bay releases were recaptured at Nanoose Bay, 26% in the southeast Strait of Georgia and north Puget Sound, 13% in the Gulf Islands, 7% in MSA 14, and 4% from offshore waters (Westrheim 1982). Westrheim (1982) stated that "Overall, there was little migration of tagged cod among the three tagging regions."

Gosho (1976) summarized Pacific cod tagging in Washington waters from 1955 to 1970. The majority of tagged fish in these studies were recovered in or near the area of release in the fishery that was underway during tagging operations. Palsson (1990) reanalyzed the results of Washington tagging studies of 1955 to 1979 and the Canadian Nanoose Bay tagging by eliminating all recoveries that occurred in the season of tagging. Results of tagging recoveries on apparent spawning aggregations, as reported in Palsson (1990), are reproduced in Table A-4. Palsson (1990) concluded that tagging results suggested that most Pacific cod remained in the area of spawning after tagging, although some out of area movements did occur. Palsson (1990) pointed out problems with interpretation of these tagging studies due to the unquantified and non-uniform recovery efforts among areas and that significant recoveries of tagged fish occurred immediately after tagging in the same areas.

Bargmann (1980) reported on tagging of Pacific cod aggregated for spawning in Agate Passage. Overall recoveries of tags during the year after tagging indicated dispersion of this stock throughout Puget Sound. Figure 35 illustrates tag recoveries as reported in Bargmann (1980) from fish tagged in February and March 1977 in Agate Passage that occurred one or two years later during the months of February and March when spawning aggregations occur. Most spawning season recoveries occurred in or near Agate Passage (74%), although recoveries during February or March also occurred at Port Townsend and in Dalco Passage, known spawning areas of Pacific cod. Shimada and Kimura (1994) reported on tagging studies of Pacific cod between 1982 and 1990 in the eastern Bering Sea and adjacent waters and found "sufficient migration to explain Grant et al.’s (1987a) findings of genetic homogeneity in Pacific cod over broad areas of the North Pacific." Direct evidence was found that Pacific cod migrate from the eastern Bering Sea into the Gulf of Alaska during winter. Shimada and Kimura (1994) stated that tag-recapture data and inferred seasonally directed movements suggest a single winter spawning population of Pacific cod occurs in the eastern Bering Sea, nearby Aleutian Island waters, and in the Western Gulf of Alaska between 157EW and 170EW.

Seasonal migrations

The spawning migrations of Pacific cod in offshore waters of Washington and southwest Vancouver Island and in Puget Sound differ from the migration pattern of Pacific cod in northern British Columbia (Palsson 1990). In all cases, Pacific cod migrate from areas where they feed during most of the year to winter spawning areas, where the water is between 6º-7º C. At the southern extent of its range, off Korea, Japan, Washington, Vancouver Island, and in Puget Sound, Pacific cod move from deep water to cool shallow water to spawn in the winter and then return to deeper offshore waters to feed when the shallower coastal waters warm (Bargmann 1980, Westrheim and Tagart 1984). In northern British Columbia, Pacific cod follow a reverse pattern, migrating to deeper waters to spawn during the winter and returning to shallower waters to feed at other times of the year (Ketchen 1961, Palsson 1990).

Likewise, Pacific cod in the eastern Bering Sea appear to conduct seasonal migrations to deeper warmer water in the winter to avoid cooling of inshore waters (Bakkala 1984). Spring feeding migrations are shoreward in the Bering Sea towards the coastal shelf environment. The southern coastal stocks of Pacific cod can achieve these seasonal migrations with short inshore-offshore depth migrations; however, in the Bering Sea, seasonal migrations are necessarily much longer due to the extensive area covered by the Bering Sea shelf (Shimada and Kimura 1994).

Juvenile Pacific cod are found in nearshore kelp and sand-eelgrass habitats in Puget Sound (Miller et al. 1976, WDFHMD 1992). Laur and Haldorson (1996) and Dean et al. (2000) reported that juvenile Pacific cod were utilizing inshore eelgrass habitat in Prince William Sound. These observations indicate that there is a migration of juvenile Pacific cod to inshore nursery habitats at least in fjord-like environments like Puget and Prince William Sounds, followed by migration to deeper waters as fish mature.

Parasite incidence

A protistan parasite, tentatively placed in the Family Hartmannelidae has been identified as the cause of parabranchial X-cell lesions in Pacific cod (Westrheim 1996). Palsson (1990) reported that the incidence of parabranchial lesions in Pacific cod in all Marine Fish Management Regions in Puget Sound was 0%, except in the San Juan (0.04%; n=2,374) and Juan de Fuca (0.86%; n=700) Regions. Since Westrheim (1987) reported a parabranchial lesion frequency of 3.4% for trawl-caught Pacific cod off southwest Vancouver Island and incidence of lesions was 0% in Puget Sound, Palsson (1990) concluded that little intermingling of Puget Sound and southwest Vancouver Island Pacific cod occurred.

Growth rate

Westrheim (1996) presented an historical review of age determination studies in Pacific cod and stated that although numerous structures have been investigated for age determination of Pacific cod no validated method currently exists. Age determination of Pacific cod has been attempted through examination of otoliths (Ketchen 1970, LaLanne 1975, Lai et al. 1987, Kimura and Lyons 1990, Hattori et al. 1992a, Tok 1994), scales (Kennedy 1970, Lai et al. 1987, Kimura and Lyons 1990), fin rays (Beamish 1981b, Chilton and Beamish 1982, Lai et al. 1987, Beamish et al. 1990, Tok 1994), and length frequency analysis (Foucher and Fournier 1982, Lai et al. 1987, Beamish et al. 1990). Ketchen (1984) indicated that age of Pacific cod cannot be reliably estimated from either scales or otoliths in Canadian waters. Fish age calculated from scales often disagrees with age computed from otoliths (Tok 1994). In Canada, ageing of Pacific cod is currently done by computerized analysis of length-frequencies (Foucher and Fournier 1982, Foucher et al. 1984, Westrheim 1996).

Ketchen (1961) suggested that the initial high growth rate, early sexual maturity, and short life span exhibited by Pacific cod along the Canadian coast was a result of the species being at the southern limit of its range where it is subject to relatively high water temperatures and consequent environmental stress. Karp’s (1982) analysis of age and growth data for Port Townsend Bay Pacific cod indicated that this stock was short lived and fast growing compared to other populations further north. Karp (1982) presented mean length-at-age data for several stocks of Pacific cod (Table 15, Fig. 36). Although ageing errors, as discussed above, may occur and selective behavior of different trawl gear may confound the results, the data presented in Table 15 and Figure 36 and discussed in Karp (1982) indicate that Port Townsend, Hecate Strait, and Strait of Georgia Pacific cod are relatively fast growing compared to Pacific cod from the Bering Sea, especially. Karp (1982) suggested that rapid growth rates evident in Washington and British Columbia Pacific cod stocks may be "a function of increased metabolic activity and longer growing seasons in warmer waters of these southernmost limits of Pacific cod distribution."

Length and age at maturity

Table A-5 summarizes length at first maturity, at 50% maturity, and at 100% maturity for selected Pacific cod populations. Thomson (1962) stated that length at 50% maturity for male and female Pacific cod in Hecate Strait in 1960-61 was 50 and 55 cm, respectively. This was compared to Pacific cod from West Kamchatka (Sea of Okhotsk) where males and females reach 50% maturity at 69 and 73 cm, respectively. Similar lengths at 50% maturity in Strait of Georgia Pacific cod were reported to be 48-49 cm and 55 cm for male and females, respectively (Ketchen 1961). Males appear to mature at an earlier age, as well as a smaller size, with 50% of males mature at age-2 and all mature by age-3 in the Strait of Georgia (Ketchen 1961). By comparison, only 15-25% of females are mature at age-2, although almost all are mature by 3-years-of-age (Ketchen 1961). Moiseev (1953) stated that Pacific cod in the Sea of Okhotsk reach sexual maturity at age-5, and some are still immature age-9. By contrast, Pacific cod off the east coast of Korea are more comparable to Pacific cod in the Strait of Georgia, reaching maturity at age-3, with all mature by age-5 (Ketchen 1961).

Fredin (1985) reported that both male and female Pacific cod in the eastern Bering Sea first reach maturity at slightly greater than 50 cm and that 50% of the fish are mature at a length of 60 cm for males and 62 cm for females. By comparison, Pacific cod from Hecate Strait mature at a smaller size and Pacific cod from the west coast of Kamchatka mature at a greater size than eastern Bering Sea Pacific cod (Fredin 1985).

Length frequencies

Westrheim (1996) examined length-frequency samples from both research and commercial catches of Pacific cod in British Columbia and Puget Sound, as well as elsewhere. Palsson (1990) also presented length-frequency data for trawl (Gulf-Bellingham, Juan de Fuca, Port Townsend), setnet (Port Townsend), and recreational (Juan de Fuca, Central Puget Sound, South Puget Sound) Pacific cod fisheries in Puget Sound in the 1970s and 1980s. Length frequencies were usually multi-modal but "revealed that fisheries depend upon one or two year classes" for most of the catch (Palsson 1990). Palsson (1990) examined mean lengths of Pacific cod in these fisheries since 1970 but did not find long term patterns. Figure 37 presents a comparison of length frequencies for Pacific cod from Canadian commercial catches near known spawning grounds at White Rocks-Bonilla Island (Hecate Strait), Amphitrite Bank (off southwest Vancouver Island), Nanoose Bay, and MSA 14 (Strait of Georgia) (Figs. 13, 31, 32) during the spawning months of January-March (data from Foucher [1987]). Although these data are from commercial catch records and not survey cruises they suggest little intermingling of White Rocks-Bonilla Island and Amphitrite Bank Pacific cod with each other or with the two Strait of Georgia stocks occurred during the years analyzed (Fig. 37).

Fecundity and egg size

Thomson (1962) concluded that since there was no apparent difference in fecundity at similar body lengths between Pacific cod in Hecate Strait and West Kamchatka, the Pacific cod stocks in Hecate Strait had reduced reproductive potential compared to other populations in the North Pacific. Foucher and Tyler (1990) examined fecundity in Pacific cod from the west coast of Vancouver Island and Hecate Strait and found that Hecate Strait fish showed a slightly higher fecundity at length than did Pacific cod from the west coast of Vancouver island. Hecate Strait Pacific cod, in this later study, also showed a higher fecundity at length than was reported by Thomson (1962).

Karp (1982) found the fecundity-length relationship in Pacific cod in Port Townsend Bay to be represented by the relationship F=12.024L^2.959, which results in 40, 50, and 60 cm female Pacific cod producing 661,000, 1,280,000, and 2,195,000 eggs, respectively. Karp (1982) compared fecundity in Port Townsend Pacific cod to stocks from Kamchatka and Hecate Strait (Fig. 38) and suggested that southern locations have higher size-specific fecundities than northern stocks and this could provide some compensation for southern populations that appear to grow and mature at faster rates and die at a younger age than do Pacific cod from northern areas (Ketchen 1961).

Tyler (1995) compared reproductive biology between Pacific cod stocks from Hecate Strait and Amphitrite Bank (off southwestern Vancouver Island) and found that Hecate Strait fish had greater fecundity at the same size than did Amphitrite Bank fish (Foucher and Tyler 1990). A larger proportion of mature female Pacific cod from the Amphitrite Bank stock (14%) go through a resting stage (failing to spawn in any one year), than do female Pacific cod from the Hecate Strait stock (0.2%) (Tyler 1995). Tyler (1995) hypothesized that these stock differences could be due to the warmer water temperatures interfering with reproductive activity at Amphitrite Bank or to differences in feeding opportunity between the two stocks. Tyler (1995) did not consider the possibility that genetic differences in reproductive capacity may exist between these two stocks.

Morphological Differentiation

Morphometric discrimination

Wilimovsky et al. (1967) analyzed Pacific cod from Alaska and British Columbia for morphometric and meristic characters, and initially subdivided specimens into four geographic areas: British Columbia, Southeast Alaska, Aleutian Islands, and Bering Sea. Morphometric characters (interorbital width, depth of caudal peduncle, length of barbel, length of first dorsal fin, and body depth at the pelvic and anal fins) showed no consistent clinal trends and did not serve to differentiate stocks of Pacific cod from British Columbia to the Bering Sea (Wilimovsky et al. 1967). However, meristic counts of dorsal and anal fin rays, left pectoral fin, gill rakers, and total vertebrae showed varying degrees of an irregular clinal trend that suggested separate stocks of Pacific cod in southern British Columbia, Southeast Alaska, and the Bering Sea (Wilimovsky et al. 1967). Wilimovsky et al. (1967) were unable to delimit the stocks precisely due to insufficient sample sizes.

Genetic Information

Pacific cod

Grant et al. (1987a) examined ocean-wide genetic variation at 40 allozyme loci (seven of which were polymorphic) in Pacific cod collected at 11 locations, ranging from Puget Sound to the Yellow Sea. Two genetically distinct groupings were revealed, a North American group (including the eastern Bering Sea, Aleutian Islands, Gulf of Alaska, Southeast Alaska, and Puget Sound) and a western north Pacific (Asian) group. Nei’s genetic distance, D, between the North American and Asian groups was 0.025, and it was suggested that this level of differentiation reflects isolation of these two groups during coastal Pleistocene glaciation (Grant et al. 1987a). Among the North American samples, Nei’s D averaged 0.0007 (± 0.0006) among pairs of North American samples. Nei’s D for the two Asian samples, Yellow Sea and Sea of Japan, averaged 0.0041 (± 0.0026).

There was "a highly significant amount of allele-frequency heterogeneity between western (Asia) and eastern ( North America including the Bering Sea) North Pacific samples"; however, comparisons of the amount of genetic heterogeneity between "regions" in the North American samples (Puget Sound/Gulf of Alaska compared to Bering Sea/Aleutian Islands) were not significant (Grant et al. 1987a). Comparisons of the amount of genetic heterogeneity between Gulf of Alaska and eastern North Pacific samples and between Bering Sea and Aleutian Islands samples were also not significant. At the population level, significant allele-frequency differences were detected between Yellow Sea and Sea of Japan Pacific cod at three loci, GDA*, ME2*, and PEPA*; between Bering Sea samples for ADA-2*; and among Gulf of Alaska samples for PEPA*.

In summary, Grant et al. (1987a) stated that, in contrast to the two Asian samples, "there was virtually no regional genetic differentiation among North American stocks of Pacific cod." The small average genetic distance between samples (0.0007) and the small fraction of total gene diversity due to all sources of population subdivision serve to illustrate this lack of differentiation among North American stocks (Grant et al. 1987a). One factor that complicates the interpretation of this study is that all samples were collected outside of the spawning season and some samples have the potential to represent mixed populations (Grant et al. 1987a).

Gong et al. (1991) examined genetic variation for 21 polymorphic loci in Pacific cod sampled at various times and subsequently pooled (some collections occurred on spawning aggregations and others did not) from five localities; Yellow Sea, Sea of Japan off Korea, Sea of Japan off Hokkaido, Pacific Ocean off Hokkaido, and Bering Sea. Significant allele frequency differences were detected between all population pairs except for the comparison between Pacific cod on the Pacific and Sea of Japan coasts of Hokkaido (Gong et al. 1991). Two major clusters were revealed from this analysis corresponding to the Hokkaido/Bering Sea and the Yellow Sea/Korean coast of the Sea of Japan. Gong et al. (1991) stated that the large genetic distance (Roger’s D of 0.020) between samples from the Yellow Sea and Sea of Japan indicate a divergence time between these populations of about 110,000 years ago. The Yellow Sea population is currently isolated from other Pacific cod populations by a high temperature barrier that exists in shallow waters around the southern tip of the Korean Peninsula (Zhang 1984).

Saitoh (1998) analyzed RAPD markers and haplotype diversity at the mtDNA control region using RFLP and SSCP techniques (see "Glossary" for description) in Pacific cod from the Bering Sea and 3 putative Japanese spawning sites; Noto-shima (Ishikawa Prefecture), Wakinosawa (Aomori Prefecture), and Joban (Fukushima Prefecture). Samples from the first two Japanese sites were of individuals extruding gametes when collected. The Joban and Bering Sea collections were of juveniles (possible descendants of spawning in nearby Sendai Bay) and adults, respectively (Saitoh 1998). The mtDNA analysis revealed low variability and no local differentiation among Japanese samples, but did show genetic divergence between Japanese coastal areas and the Bering Sea. Saitoh (1998) concluded that "this study gives no evidence for genetic identity among the Japanese localities analyzed."

Comparative genetic information for Atlantic cod

Although Atlantic cod spawn pelagic eggs, in contrast to the demersal eggs released by Pacific cod, the comparison of genetic population structure studies from Atlantic cod (with what little is known concerning population structure in Pacific cod) is thought to be informative due to these species’ close systematic relationship and more comprehensive treatment Atlantic cod have received. Grant et al. (1999) recently reviewed studies of genetic variability in Atlantic cod. Surveys of genetic population structure of Atlantic cod across the North Atlantic using allozymes, mtDNA, and anonymous nuclear DNA loci showed differing results. Fine scale population structure in Atlantic cod has not been detected in allozyme (Mork et al. 1985) or mtDNA (Carr and Marshall 1991, Arnason and Rand 1992, Carr et al. 1995) studies. However, analyzes of nuclear DNA have revealed greater levels of genetic differentiation between regional populations (Pogson et al. 1995, Galvin et al. 1995). Analysis of microsatellite loci have revealed even finer scale population structure of Atlantic cod in the northwest Atlantic Ocean (Bentzen et al. 1996; Ruzzante et al. 1996, 1997, 1998). Bentzen et al. (1996) stated that rather than comprised of a "single, panmictic assemblage," northern cod "are composed of genetically distinguishable subunits, each of which appear to be geographically affiliated with spawning area."

Information Relevant to the Pacific Cod DPS Question

As stated in the previous "Approaches to the Species Question and to Determining Risk" section, four broad types of information were analyzed by the BRT in its determinations of whether Pacific cod in Puget Sound represent a "discrete" and "significant" population and therefore qualifies as a DPS under the ESA; habitat characteristics, phenotypic and life-history traits, mark-recapture studies, and analysis of neutral genetic markers. As such data can only be properly evaluated in relation to similar information for the biological species as a whole, Puget Sound Pacific cod data were compared with data from Pacific cod from throughout the species’ range.

As detailed in the previous sections on "Environmental Features..." and "Phenetic and Genetic Information Relating to the Species Question," specific information for Puget Sound Pacific cod was available in the following categories; physical habitat, spawning time and location, migration patterns, tagging, parasite incidence, growth rate and body size, size and age at maturity, length frequency, fecundity, and very limited data on genetic population structure. Data on year-class strength, meristics and morphometrics, and local genetic population structure were largely unavailable for Pacific cod in Puget Sound. Specific information on Pacific cod in the Strait of Georgia was available for physical habitat, spawning time and location, migration patterns, tagging, parasite incidence, growth rate and body size, size and age at maturity, length frequency, and meristics and morphometrics. No data on year-class strength, fecundity, or genetic population structure were available for Strait of Georgia Pacific cod. Within the region from southwest Vancouver Island north to Dixon Entrance, specific information for Pacific cod was available on physical habitat, spawning time and location, migration patterns, tagging, parasite incidence, growth rate and body size, size and age at maturity, length frequency, fecundity, and meristics and morphometrics. No data on year-class strength or genetic population structure were available for Pacific cod in this region. Only very limited data on meristics and morphometrics and genetic population structure were available for Pacific cod in Southeast Alaska. The previous section on "Approaches to the Species Question and to Determining Risk" should be consulted for a general discussion of the relative usefulness of the various categories of data for DPS delineation. Issues of data quality are addressed for each category of biological data for Pacific cod in the preceding section on "Phenetic and Genetic Information Relating to the Species Question."

Discussion and Conclusions on Pacific Cod DPS Determinations

The BRT considered several possible DPS configurations for populations of Pacific cod in the northeastern Pacific Ocean in its attempt to identify a "discrete" and "significant" segment of the biological species that incorporates Puget Sound fish. It is the majority opinion of the BRT that Pacific cod from Puget Sound are part of a DPS that extends well beyond Puget Sound and north to at least Dixon Entrance, although many BRT members were unable to rule out the possibility that the northern boundary of the Pacific cod DPS occurs at the level of the Georgia Basin, or at the other extreme, Southeast Alaska. A high level of uncertainty concerning the northern boundary of the DPS was expressed in the decision-making process, and the BRT agreed that there is insufficient information available at present to identify DPSs of Pacific cod with any certainty. The BRT struggled with this decision and noted that the lack of suitable data to answer the DPS question for Pacific cod was a cause for concern.

The conclusion that the Pacific cod DPS is larger than Puget Sound was supported by the following considerations: 1) Genetic data that show a lack of significant heterogeneity among Pacific cod sampled, largely during summer and fall, at various locations in the northeastern Pacific Ocean (although it is possible that if collections had been of spawning fish the data might have shown greater population structure); 2) results of adult tagging studies in the Strait of Georgia and Puget Sound that show movement amongst inshore locations and some limited movement between inshore and coastal areas (although rare tagging studies on spawning fish do show some level of spawning site fidelity); and 3) the ecological similarity of fjord-type marine habitat in Puget Sound to habitats along the coasts of British Columbia and southern Alaska. In particular, the BRT noted that ecosystems where Pacific cod spawn north of the Georgia Basin are similar to Puget Sound and that the physical habitat is similar from Washington to Southeast Alaska. The BRT did not preclude the possibility that further information on the behavior, ecology, and genetic population structure of Pacific cod might provide a basis for delineating smaller DPSs.

The BRT examined several scenarios as to where the northern boundary for a Pacific cod DPS may occur, including: 1) the Georgia Basin, 2) the north end of Vancouver Island (encompassing the Georgia Basin and Amphitrite Bank spawning aggregations), 3) Dixon Entrance, and 4) Southeast Alaska (Fig. 2). Although many BRT members expressed some level of support for each of these scenarios, the BRT had the greatest overall support for scenarios 3 and 4. Therefore, the majority opinion of the BRT was that the northern boundary of the Pacific cod DPS extends at least as far north as Dixon Entrance. In addition, the BRT recognized that the DPS that includes Puget Sound Pacific cod may represent fish that are uniquely adapted to survive at the southern end of the species’ range.

Within the area south of Dixon Entrance, Pacific cod encompass several geographically-discrete, current and historical spawning aggregations, including (but not necessarily limited to): Agate Passage, Port Townsend Bay, Port Gamble, Dalco Passage, and Bellingham Bay/Eliza Island in Puget Sound; Nanoose Bay, Hornby Island/Cape Lazo, and Swanson Channel in the Strait of Georgia; off southwest Vancouver Island; and in Hecate Strait (Figs. 2, 31, 32). Therefore, the BRT considered whether there is evidence for multiple populations or stocks of Pacific cod within this area and, perhaps, multiple DPSs within Puget Sound, Georgia Basin, or the area south of Dixon Entrance. Such evidence included: 1) the persistence of geographically and temporally discrete spawning aggregations of Pacific cod, 2) the Pacific cod reproductive traits of demersal spawning and adhesive eggs that would tend to concentrate eggs in the vicinity of the spawning grounds, 3) results of limited adult tagging studies indicating some degree of spawning site fidelity, and 4) demographic differences amongst Pacific cod sampled from discrete spawning locations. Although the BRT could not with any certainty identify multiple populations or DPSs of Pacific cod within the region south of Dixon Entrance, they acknowledged the possibility that significant structuring does exist within the proposed DPS and that such structure might be revealed by new information in the future.

Assessment of Extinction Risk

Population Status and Trends

Since the geographic extent of the DPS that includes Pacific cod in Puget Sound is uncertain, the BRT considered three potential areas, extending from Puget Sound to Southeast Alaska in their analysis of extinction risk for the DPS. Consequently, known information about the status of stocks in these areas is described in following sections and considered in determining extinction risk. The status of Pacific cod stocks beyond southeast Alaska were not considered in analyses of extinction risk.

Puget Sound

The assessment of the status of Pacific cod in Puget Sound is based primarily on trends in fishery statistics since 1970 (Palsson 1990, Palsson et al. 1997). In general, recreational and commercial fishing effort increased during the 1970s and stabilized during the 1980s. These fisheries are dependent on one or two age classes, based on length frequency data. Palsson (1990) reported that mean lengths estimated from biological samples collected since 1970 did not show long-term patterns. However, catches showed alternating periods of good catch years with periods of poor catch years. Six cycles have occurred since 1942, with a peak catch of 1,588 mt in 1980 (see Fig. 39). Catches fluctuated around a 900 mt level between the mid-1970s and mid-1980s (Fig. 39, Palsson 1990). Due to concerns for the status of Pacific cod, commercial fishing for Pacific cod was prohibited in Puget Sound south of Admiralty Inlet, in 1987. Catches then declined fairly steadily to low levels, about 13.6 mt in 1994 (Palsson et al. 1997).

The primary stock indicator for Puget Sound, north of Admiralty Inlet, was the catch rate from the commercial bottom trawl fishery (Palsson et al. 1997). Catch rates (Table 17) ranged between 42 and 73 kg/hour during the 1970s, stabilized at about 39 kg/hour until 1988, but then declined continuously to a low of 12 kg/hour by 1994. Trends in trawl effort (hours) were similar. Since 1994, unpublished data (W. Palsson ^[27]) indicate that catch rates in the bottom trawl fishery were somewhat higher than the low in 1994, ranging from 36 kg/hr in 1995 to 17.2 kg/hr in 1998 (Table 17). The primary stock indicator for Puget Sound south of Admiralty Inlet was the catch rate from the recreational fishery. Since the late 1970s, catch rates in the recreational fishery (Table 18) have declined fairly steadily from 0.6 Pacific cod/angler trip to less than 0.05 Pacific cod/angler trip following the 1989-1994 period (Palsson 1997). Unpublished data (W. Palsson^[28]) indicate that the catch rate in the recreational fishery was less than 0.01 Pacific cod/angler trip every year during 1994-1998 (Table 18). Recreational catches estimated from the National Marine Recreational Fisheries Statistical Survey in Puget Sound were 2,430 and 920 Pacific cod in 1996 and 1997, respectively (WDFW 1998).

Bottom trawl surveys were conducted throughout Puget Sound in 1987, 1989, and 1991. Surveys covering various regions of Puget Sound were conducted in 1994, 1995, 1996, and 1997. Estimated biomass and numbers in the population vulnerable to the survey trawl, and average size of Pacific cod within each WDFW management region (see Fig. 14) are shown in Table 19 (W. Palsson^[29]). Estimates for biomass and numbers of fish in 1987 were much higher than in other years, but this may be due to other factors than a change in fish abundance. The 1987 survey was exploratory, being the first such survey ever conducted in Puget Sound. Also, the survey vessel used in 1987 was much larger than those used in subsequent years and the survey was conducted in the fall, whereas other surveys were presumably conducted in the spring. Otherwise, there is no apparent trend in the estimated abundance of Pacific cod in Puget Sound, both in number and weight, since the 1987 survey. In the three years when all management regions were surveyed, the estimated biomass of Pacific cod exceeded 2,500 mt and estimated numbers of Pacific cod exceeded 4.7 million fish each year (Table 19).

South Sound includes both Port Townsend Bay, where Pacific cod once supported bottom trawl and set net fisheries during the winter, and Agate Passage, where a popular sport fishery once harvested Pacific cod on their spawning grounds. The abundance of adult Pacific cod that aggregate on or near spawning grounds has declined, based on fishery statistics. Relatively intense fisheries for Pacific cod occurred in Port Townsend Bay and at Agate Passage during the winter spawning period in the 1970s and early 1980s (Palsson et al. 1997).

Pacific cod aggregate during the late winter to spawn demersal eggs in or near Agate Passage. This aggregation has supported a recreational fishery, which was monitored for Pacific cod catches and fishing effort during most years between 1977 and 1989 (Palsson 1990). Catch rates and estimated catches and effort fluctuated during this period (Table 20). The highest catch estimated in this fishery was 32,800 Pacific cod taken during 8,100 angler trips during 1981. Estimated catch and effort reached a low of 146 Pacific cod taken during 393 angler trips in 1989 (Palsson 1990). After 1989, catches and effort remained at low levels (W. Palsson^[30]) and several restrictions were placed on recreational and commercial fisheries for Pacific cod in Puget Sound. The Agate Passage area was closed to Pacific cod fishing in 1991 due to concerns over the low numbers of Pacific cod. The daily bag limit in the recreational fishery for Pacific cod in other areas of Puget Sound south of Admiralty Inlet was reduced from fifteen fish to two fish in 1991 and to zero in 1997. In addition, the bottom trawl fishery near Port Townsend and Protection Island was closed during the winter to protect Pacific cod and other marine fish, beginning in 1991.

Pilot hydro-acoustic surveys were conducted in Agate Passage and nearby Port Madison and Port Orchard in 1987 before, during, and after the historic peak fishing period (Lemberg et al. 1988). Four surveys were conducted to determine the feasibility of assessing Pacific cod aggregations, the timing of the population increase and decrease, the distribution of fish schools, and to relate the results to concurrent recreational fishery monitoring. Fish targets and schools were observed in all three areas during most surveys; however, these fish could not be positively identified by species because fish were not collected during the surveys. The acoustic signals corresponded to typical signals for British, such as Pacific herring in the upper water column, and some relatively large individual targets and dense small schools along the bottom that may have been Pacific cod. More signals were observed in Port Orchard than in Agate Passage.

During the late 1990's, similar acoustic surveys were conducted for one night each year during the former peak fishing period in Agate Passage. No acoustic sign that could be interpreted as Pacific cod were observed in any of the surveys (W. Palsson^[31]).

British Columbia

Within British Columbia, four stocks of Pacific cod are defined for management purposes: Strait of Georgia, west coast Vancouver Island, Queen Charlotte Sound, and Hecate Strait. Tagging studies indicate that there is very little movement of Pacific cod among areas (DFO 1999). Catches in each of these areas between 1955 and 1991 are given in (Table 21) (Westrheim 1996) and updated through 1999 (Table 22). The status of Pacific cod stocks in British Columbia has not been recently evaluated, except for Hecate Strait, where Pacific cod stocks are at low levels.

Pacific cod in Hecate Strait are fished mainly with trawls. Annual yields have varied between a high of 8,870 mt in 1987 to a low of 403 mt in 1996 (DFO 1999). The most recent assessment of Pacific cod in Hecate Strait indicates that stock biomass was at historically low levels in 1994-96 (Haist and Fournier 1998) and that there has been a slight increase in the past two years. Recruitment estimates are low, with the last nine year classes falling below the long-term average. The 1998 year class is the smallest ever. This is the longest run of below-average year-classes in the time series, which goes back to 1956. Projections for Pacific cod in Hecate Strait indicate that the stock will decline in the next two years (DFO 1999).

For the Strait of Georgia during 1955-91, catch, effort, and catch rates for Pacific cod in the commercial trawl fishery generally fluctuated without trend, except for a precipitous decline after 1988 (Westrheim 1996). During 1970-1991 when catch data were available for Puget Sound and the Strait of Georgia, catch patterns in the Strait of Georgia closely matched those in Puget Sound, as shown in Fig. 40A (Schmitt et al. 1994). In both areas, catches synchronously ranged between 500 and 1,000 mt during the early 1970s, then rose to about 1,500 mt per year during the late 1970s and early 1980s. After a peak in 1981, catches fell to less than 100 mt by 1991. Catches in the Strait of Georgia continued to decline, to zero by 1999 (Table 22).

Gulf of Alaska

Pacific cod in the Gulf of Alaska are of medium abundance and are fully exploited. The estimated spawning biomass of Pacific cod is 111,000 mt in 2000, down about 15% from the 1999 estimate (Thompson et al. 1999). The estimated biomass of age 3+ Pacific cod in the Gulf of Alaska is 567,000 mt, down about 13% from the previous year’s estimate. However, estimated spawning biomass and age 3+ biomass in the late 1990s are about the same as they were during the late 1970s (Table 23). Estimates were about one-third larger during the mid-1980s (Thompson et al. 1999). The stock is projected to decline as a result of poor year-classes produced from 1990-1994. Preliminary indications of the 1995 year class suggest it may be above average (Witherell 1999).

Information on the status of Pacific cod in Southeast Alaska is limited. The assessment of Pacific cod for the Gulf of Alaska does not provide estimates of abundance, catches or catch rates for subareas within the Gulf. However, area-swept biomass estimates from triennial bottom trawl surveys during 1984-1999 indicate that the abundance of Pacific cod in Southeast Alaska fluctuated between 4,000 mt in 1984 to 11,000 mt in 1990. In 1999, the biomass of Pacific cod was near its highest level, about 10,000 mt, with a confidence interval of 4,000 to 16,000 mt. (M. Martin^[32]).The catch history for Pacific cod in inside waters of Southeast Alaska fluctuated generally without trend between 64 mt and 436 mt during 1987-1998 (Table 24). The catch in 1998 was 294 mt. (ADFG^[33]).

West Coast of U.S.

Commercial landings of Pacific cod off the U.S. west coast peaked in 1988 at 3,343 mt and have steadily declined since that peak to an estimated 404 mt in 1998 (Table 25). The majority of these landings are reported from Washington State ports (PFMC 1999). The bulk of the large catches from 1987 to 1989 was composed of an exceptionally strong 1985 year class that was also present in the west Vancouver Island and Hecate Strait stocks (Dorn 1993). The stock off the U.S. west coast reportedly is more prone to recruitment failure than the northern stocks of Pacific cod, suggesting that the environmental conditions necessary for successful spawning and larval success occur infrequently in this area (Dorn 1993).

Table 17. Fishery trends for Pacific cod in Northern Puget Sound (modified from Palsson et al. 1997). The commercial trawl catch includes fisheries in the Strait of Juan de Fuca. A new fishery targeted on Pacific cod of unknown origin began in the western Strait of Juan de Fuca in 1995. Data since 1994 courtesy of W. Palsson (WDFW, 16018 Mill Creek Blvd., Mill Creek, WA 98012-1296, pers. commun. to C. Schmitt). Dashes indicate data were not available.

Table 18. Fishery trends for Pacific cod in Southern Puget Sound (modified from Palsson et al. 1997). The Pacific cod sport fishery in Southern Puget Sound was closed beginning in 1997. Data since 1994 courtesy of W. Palsson (WDFW, 16018 Mill Creek Blvd., Mill Creek, WA 98012-1296, pers. commun. to C. Schmitt). Dashes indicate data were not available.

Table 19. Estimated biomass, number and size of Pacific cod in the Puget Sound population from WDFW trawl surveys (W. Palsson, WDFW, 16018 Mill Creek Blvd., Mill Creek, WA 98012-1296. Pers. commun. to W. Lenarz.). Dashes indicate data were not available.

Table 19. (Continued).

Table 20. Standardized results from Agate Passage fishery monitoring for Pacific cod. Modified from Palsson (1990). Dashes indicate data were not available.

Table 21. Canadian or Canada-U.S. annual nominal catch (t), equivalent effort (h), and median CPUE (kg/h), by region, for Pacific cod in British Columbia waters, 1955-91 (modified from Table 7.3.1.2 in Westrheim (1996)). Dashes indicate data were unavailable. (Please click on the link to view Table 21).

Table 22. Annual landings (metric tons) of Pacific cod in British Columbia waters by major area, 1992-99 (J. Fargo, DFO, Pacific Biological Station, Nanaimo, British Columbia, Canada. Pers. commun. to C. Schmitt.).

Table 23. Time series of estimates for Pacific cod age 3+ biomass, spawning biomass, and survey biomass (in 1000's of mt) in the Gulf of Alaska (Modified from Thompson et al. (1999)). Dashes indicate data were not available.