(ocean age .0, before January 1 of their second year at sea).1 Information on the ocean life history of immature and maturing AYK salmon is based largely on extensive high-seas research gill net, purse seine, longline, and trawl surveys; tagging experiments; and stock identification studies conducted as part of the research programs of the International North Pacific Fisheries Commission (INPFC) from 1953 to 1992 and the North Pacific Anadromous Fish Commission (NPAFC) from 1993 to present. Detailed research methods and results are presented in the annual report, bulletin, statistical yearbook, and technical report series of INPFC and NPAFC (also see reviews by Burgner 1992, Myers et al. 2000). Broad syntheses of the INPFC/NPAFC data were used to develop conceptual models of the movements of immature and maturing salmon on the high seas (coho salmon, Godfrey et al. 1975; sockeye salmon, French et al. 1976; chum salmon, Neave et al. 1976; Chinook salmon, Major et al. 1978; pink salmon, Takagi et al. 1981), although these models need to be updated with new information. Additional sources of information are cited throughout the text.

General Life History Characteristics

The life histories of all five species of Pacific salmon found in the AYK region share several general characteristics. All species are anadromous: spawning occurs in the fall, usually in freshwater, and juveniles then migrate to the marine environment. In the ocean, salmon grow to maturity, and mature adults return to freshwater to spawn. Individuals in all species typically home rather precisely to their natal area to spawn. All species are semelparous, spawning only once and dying a few days or weeks later.

Within this general framework, many other life history characteristics are common to all species. Mature females bury their relatively


Age and life history are designated by the European method. For example, an age 1.3 Chinook salmon spent one winter in freshwater (F) and three winters in the ocean (W). The number before the dot designates the number of winter annuli laid down on the fish’s scales while in freshwater, and the number after the dot designates the number of winter annuli formed in the ocean. The Alaska Department of Fish and Game may designate the age of an adult salmon by its total age (T) at return, where T = F + W + 1 (for example, a 1.3 Chinook is 5 years old). This calculation accounts for the fact that scales do not form until after the fish hatch, so the first winter of life spent as a developing egg and alevin in the stream gravels is not recorded on the scales.

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