Trends in Abundance and Biological Characteristics for North Pacific Sockeye Salmon

摘要

Trends in abundance, productivity, and average size were reviewed for sockeye salmon populations from Washington, British Columbia, southeast Alaska, central Alaska, western Alaska, and Russia. Aggregate catch estimates were reasonable indicators of overall stock status, but in areas toward the southern extent of their range, population-specific return and escapement estimates are also needed by fishery managers. Sockeye abundance in Russia and western and central Alaska declined coincident with a regime shift in 1949. Declines also occurred in the eastern North Pacific although they were less severe. Abundance increases were ubiquitous around the time of the regime shift in 1977. Short-term reductions in abundance in western Alaska and parts of central Alaska followed the 1989 shift but were not evident in Russia or the eastern North Pacific. The status of many North American stocks recently declined, with severest declines in southernmost areas. Trends in survival rate indices were similar to trends in catch and abundance. Average body size was inversely related to aggregate abundance, implying that growth was density-dependent. The coherence in trends in abundance, catch, and average weight among stocks suggests that large-scale environmental processes are major factors controlling sockeye salmon survival and production around the North Pacific Rim, and probably restrict the total production from particular ocean zones. However, local-scale environmental processes can result in regional differences in productivity.