Pacific Salmon in Alaska
by
Carl V. Burger
National Biological Service
Alex C. Wertheimer
National Marine Fisheries Service
Pacific Salmon in Alaska | ||
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by Carl V. Burger National Biological Service Alex C. Wertheimer National Marine Fisheries Service |
| Pacific salmon (Salmonidae) have played a major role in the history and economy of Alaska and its commercial, sport, and subsistence fisheries; Alaska currently produces about 80% of all salmon harvested in the western United States and Canada. Before commercial exploitation in the late 1800's, salmon were a main food source for Alaska's Native peoples, who subsisted by using an estimated 12 million salmon annually (Pennoyer 1988). By the end of the century, the total commercial harvest in Alaska had expanded to an estimated 56,000 salmon in 1878 but rose to more than 21 million by 1900 (Rigby et al. 1991). Since 1980 the annual commercial harvest has exceeded 100 million salmon in all but one year and is presently at a record high of more than 190 million (Fig. 1). The annual sport harvest of salmon in Alaska has averaged about 1 million fish over the past several years (Mills 1993), as has the subsistence harvest (INPFC 1992). Science-based management, "limited-entry" fishing, effective law enforcement, and establishment of fixed escapement goals for specific rivers are among the factors responsible for increased salmon abundance. | ||
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| Fig. 1. Statewide commercial salmon harvest for all species of Alaskan salmon (excluding hatchery-produced fish), 1891-1991 (Rigby et al. 1991). | ||
| Apart from their economic, recreational, and subsistence importance, salmon are a vital link in various Alaskan ecosystems. Large populations of bears (Ursidae) and eagles (Accipitridae) in some parts of Alaska, for example, depend on late-spawning salmon as a food source before winter. Also, the carcasses of spawned-out salmon are a key element in otherwise nutrient-poor lakes and rivers. Because Alaska has a comparatively greater amount of unaltered habitat and a larger number of wild salmon stocks than do other parts of the Northwest, monitoring population status and trends is particularly important to alert managers to problems before irreversible losses occur. | ||
| We summarize trends in harvest and escapement (fish that survive sport, commercial, and subsistence fishing) for five species of salmon in Alaska: pink (Oncorhynchus gorbuscha), chum (O. keta), sockeye (O. nerka), chinook (O. tshawytscha), and coho salmon (O. kisutch). We present historical records and data for three major regions of the state: southeastern, central, and western (Fig. 1). This summary is based on data from similar efforts completed or in progress by the Alaska Chapter of the American Fisheries Society, the Alaska Department of Fish and Game, the National Marine Fisheries Service, and the U.S. Forest Service. | ||
| The data we present originate from the Alaska Department of Fish and Game (various Area Management Reports). Information on the annual status of Alaskan salmon populations comes from numerous state and federal publications and is presented in three ways. First, we tabulate the trends in salmon escapement by species. This tabulation was done for species in central and western Alaska from 1968 to 1984 (Konkel and McIntyre 1987), for pink and chum salmon in southeast Alaska from 1960 to 1993 (Wertheimer in press), and for southeast sockeye, chinook, and coho stocks from 1960 to 1992 (C. Halupka, U.S. Forest Service, personal communication). These trend summaries do not include all populations, but are limited to those for which escapement data are readily available in a usable format. | ||
| Second, we graph the historical harvest for each species from 1891 to 1991 (Rigby et al. 1991). Because of Alaska's limited-entry fishing policy (since 1975) and the use of fixed-escapement goals, these summaries of commercial harvest may be a useful indicator of population trends. | ||
| In our third approach, we graph the escapements of pink, sockeye, chinook, and chum salmon (data for coho salmon were inadequate) in key areas of Alaska based on Department of Fish and Game Annual Management reports (1960 to 1992). This method provides an index of salmon abundance and is particularly relevant in determining sockeye salmon trends because management of this species is often based on in-season escapement enumeration. It also allows us to compare a species escapement trend in a specific area (for example, Prince William Sound) with its overall trend in other areas of Alaska. Because many Alaskan stocks are managed to meet a target escapement goal, however, a decreasing trend may not indicate a decrease in overall productivity. | ||
Population Trends for Five Species |
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| Pink Salmon | ||
| The plot of statewide harvest of pink salmon over time (Fig. 2a) was similar to the 100-year statewide harvest totals for all species (Fig. 1). Hatchery production of pink salmon is considerable in the central portion of Alaska and may account for up to 51% of the catch (Wertheimer in press). Statewide, a record catch occurred in 1991, when 93 million wild pink salmon and 35 million hatchery pink salmon were harvested (Fig. 2a; Wertheimer in press). | ||
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Fig. 2 a-e. Statewide commercial harvest of Alaskan salmon by species, 1891-1991 (Rigby et al. 1991). | |
| Pink salmon management in Prince William Sound is extremely complex. Record harvests of pink salmon (30-50 million fish) in Prince William Sound during 1990 and 1991 declined to 9 million in 1992. The decline in catch and recent declines in escapement (Fig. 3a) may be a result of density-dependent mortality from increased hatchery releases, environmental alterations, or changing oceanic currents. It should be noted, however, that the pink salmon escapements in Prince William Sound, Cook Inlet, and Kodiak increased in 1993 (Fig. 3a). The 1989 peak in the combined escapements for pink salmon in Cook Inlet and Kodiak reflects fishery closures related to the Exxon Valdez oil spill. |
Fig. 3 a-d. Salmon escapements over time in select areas of Alaska. (BB--Bristol Bay; CI--Cook Inlet; K--Kodiak; PWS--Prince William Sound; Y--Yukon.) |
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| Chum Salmon | ||
| The trend summary for chum salmon was available for all regions of Alaska. Decreasing trends were more common than increases (Table). The statewide harvest of chum salmon attained record levels through the mid-1980's (Fig. 2b) and has generally increased in all areas of Alaska since the mid-1970's. Although the catch in western Alaska is almost all from wild populations, hatchery contributions are now about 12% of the catch in the central region and about 33% in southeastern Alaska (Wertheimer in press). | ||
| Chum salmon escapements (1979-93) in central and western Alaska (Fig. 3b) have generally declined, as have the escapements of fall-run chum salmon in the Yukon River. These declines have directly affected western Alaska commercial and subsistence users who depend on the chum salmon resource. Several factors could be responsible for this decline, including oceanographic change, density-dependent competition at sea with large numbers of chums released by hatcheries in Russia and Japan (Ishida et al. 1993), and interception by high seas drift-net fisheries (Olsen 1994). In addition, fishing effort has increased in recent years from expanding in-river commercial and subsistence chum salmon fisheries. | ||
| Sockeye Salmon | ||
| A trend summary was possible for sockeye salmon in all regions of Alaska. Most populations were either stable or increasing (Table). Statewide sockeye salmon harvest is at a record level (Fig. 2c), and the catch throughout Alaska has risen substantially since the early 1970's (Wertheimer in press). Escapement also appears to be increasing for most populations (Fig. 3c). In addition to the few stocks in southeast Alaska that have declined, a decline in Cook Inlet sockeye salmon is predicted over the next 2 years. After many spawning adults escaped harvest when fisheries were closed in 1989 because of the Exxon Valdez oil spill, too many fry were produced to be supported by their habitat (D. Schmidt, Alaska Department of Fish and Game, personal communication). The resulting increase in fry mortality will probably be a factor in the abundance of Cook Inlet sockeye salmon in the immediate future. | ||
| Chinook Salmon | ||
| The trend summary for chinook salmon suggests that most populations are either stable or increasing (Table). Although present commercial harvest of chinook salmon statewide is slightly lower than the average historical level (Fig. 2d), the catch appears to be more stable than for all species combined (Fig. 1). A recent decrease in the quota for southeastern Alaska troll fisheries may be a factor in the stable catch of chinook salmon. Sport harvest of chinook salmon has increased substantially over the past several years (Mills 1993) and now exceeds 10% of the commercial catch (Wertheimer in press). Catches of chinook salmon declined in nearly all regions of Alaska in the early 1970's, rebounded through the early 1980's, and have begun to decrease since that time. High seas drift-net and trawl fisheries that target other species may be factors in the minor decline in chinook salmon harvest in western Alaska (Olsen 1994; Table). When actual escapements are plotted for several areas of Alaska, however, the trends are generally increasing (Fig. 3d). | ||
| Coho Salmon | ||
| Sockeye salmon return to spawn in numerous Alaskan streams each summer. Courtesy M. Wenger, USFWS | |
A trend summary was possible for coho salmon stocks only in the southeastern and central regions of Alaska (Table). Overall, fewer data have been collected for coho than for other species of salmon because of their late run timing, smaller population sizes, and use of remote, heavily vegetated watersheds. Most populations analyzed in southeastern Alaska showed no trend: some increased and some decreased (Table). Of the eight populations examined from central Alaska, half increased and none decreased. |
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| Statewide harvest of coho salmon is at a record level (Fig. 2e), as is the catch in all regions of Alaska (Wertheimer in press). Data were insufficient to plot coho salmon escapements in key areas of Alaska. Based on catch data alone, abundance of coho salmon is generally increasing (Wertheimer in press). For some of the populations that are declining in southeastern Alaska (Table), habitat effects associated with logging may be a factor; however, an equal number of declining populations in southeast Alaska are in pristine areas (C. Halupka, U.S. Forest Service, personal communication). | ||
Conclusions |
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| The population trends and escapements of pink, sockeye, chinook, and coho salmon in Alaska are generally stable or increasing based on the data analyzed. A recent decline in chum salmon escapements has occurred in central and western Alaska, the cause of which may be related to density-dependent factors and oceanic change in the marine environment. In many Alaskan streams, salmon abundance has not been determined or analysis of data is incomplete. | ||
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National Biological Service Alaska Science Center 1011 East Tudor Rd. Anchorage, AK 99503 |
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| References | |
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INPFC. 1992. Statistical yearbook, 1989. International North Pacific Fisheries Commission, Vancouver, BC. 123 pp. Ishida, Y., S. Ito, M. Kaeriyama, S. McKinnell, and K. Nagasawa. 1993. Recent changes in age and size of chum salmon (Oncorhynchus keta) in the North Pacific Ocean and possible causes. Canadian Journal of Fisheries and Aquatic Sciences 50:290-295. Konkel, G.W., and J.D. McIntyre. 1987. Trends in spawning populations of Pacific anadromous salmonids. U.S. Fish and Wildlife Service Tech. Rep. 9. 25 pp. Mills, M.J. 1993. Harvest, catch, and participation in Alaska sport fisheries during 1992. Fishery Data Series Rep. 93-42. Alaska Department of Fish and Game, Anchorage. 228 pp. |
Olsen, J.C. 1994. Alaska salmon resources. Pages 77-89 in L. Low, J. Olsen, and H. Braham, eds. Status of living marine resources off Alaska, 1993. National Oceanic and Atmospheric Administration, Tech. Memorandum NMFS-AFSC-27. U.S. Department of Commerce, Alaska Fisheries Science Center, Seattle, WA. Pennoyer, S. 1988. Early management of Alaska fisheries. Marine Fisheries Review 50:194-197. Rigby, P., J. McConnaughey, and H. Savikko. 1991. Alaska commercial salmon catches, 1878-1991. Alaska Department of Fish and Game Regional Information Rep. 5J91-16. 88 pp. Wertheimer, A.C. Status of Alaska salmon. In D.J. Stounder, P.A. Bisson, and R.J. Naiman, eds. Pacific salmon and their ecosystems: status and future options. Chapman and Hall, Inc., New York. 18 pp. In press. |