Pacific Salmon: Ecology and Management of Western Alaska’s Populations

Abstract

<em>Abstract.</em>—Data from high seas tagging experiments (external tags, coded-wire tags, electronic data storage tags) provide the only direct information on the distribution, biology, and ecology of immature and maturing Arctic-Yukon-Kuskokwim (AYK) salmon (<em>Oncorhynchus </em>spp.) migrating in the North Pacific Ocean and Bering Sea. Variation in the spatial and temporal distribution of tagging effort largely reflects changes in international salmon treaty research priorities over the past 52 years (1954–2006). Results of tagging studies indicate that in spring maturing AYK pink <em>O. gorbuscha </em>and coho <em>O. kisutch </em>salmon and immature and maturing AYK sockeye <em>O. nerka </em>and chum <em>O. keta </em>salmon are distributed primarily in the northeastern North Pacific Ocean and Gulf of Alaska, and in summer their distribution shifts to the west in the Gulf of Alaska and to the north and west in the Bering Sea. Immature and maturing AYK Chinook salmon <em>O. tshawytscha </em>are distributed in the eastern Bering Sea in winter, and immature Chinook salmon are distributed in the central and western Bering Sea in summer. Depth data from electronic tags indicated that Chinook and chum salmon have the deepest vertical distributions among the salmon species. Swimming depths might remain relatively constant across water masses and ocean areas. Bioenergetic simulations indicated that AYK salmon experiencing increased mean summer temperatures in the Bering Sea could suffer reduced growth at all age-maturity stages unless prey availability or prey energy density increased commensurately. Published conceptual models of the high seas distribution and migration patterns of AYK salmon need to be updated with new information from tagging, scale pattern, and genetic studies. New dynamic models would be useful for predicting climate-induced changes in carrying capacity, growth and survival, exploitation by marine fisheries, and timing of adult returns to the AYK region.