| Summary: | A high-priority research issue identified by the Arctic-Yukon-Kuskokwim (AYK) Sustainable Salmon Initiative (SSI) is to determine whether the ocean environment is a more important cause of variation in the abundance of AYK Pacific salmon (Oncorhynchus spp.) populations than marine fishing mortality. At the outset of this project, however, data on ocean life history of AYK salmon were too limited to test hypotheses about the effects of environmental conditions versus fishing on marine survival. Our goal was to identify and evaluate life history patterns of use of marine resources (habitat and food) by Chinook salmon (O. tshawytscha) and to explore how these patterns are affected by climate-ocean conditions, including documentation of local traditional knowledge (LTK) of this high-priority issue. Synthesis of LTK from the Bering Straits region identified important changes in adult AYK Chinook salmon biological characteristics, climate, and fishing. Local experts observed later run timing, a decrease in body size and stomach contents, and an increase in diseases, parasites, and deformities in adult salmon; environmental changes, including strength and direction of wind, timing of freeze- and break-up, warming of ocean and river temperatures, accompanied by increases in algae, water grasses, jellyfish, and erosion events; an increase in marine subsistence harvests of salmon; and salmon bycatch in Bering Sea/Aleutian Islands (BSAI) trawl fisheries for walleye pollock. Multiple lines of scientific evidence indicated that Chinook salmon respond to variation in climate-ocean conditions and fishing by changes in distribution, diet, size and age at maturation, growth, and survival. Evidence from tagging and other stock identification methods suggested that AYK Chinook spend most of their ocean life in the Bering Sea. Distribution of immature AYK Chinook is farthest offshore in their second summer-fall at sea, extending into the Russian Exclusive Economic Zone in the northwestern Bering Sea. Unlike other species of AYK ...
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