Diets of Pacific Salmon in the Sea of Okhotsk, Bering Sea, and Northwest Pacific Ocean

摘要

Since the 1950s the food habits of Pacific salmon have been studied from samples representing multiple salmon life-history stages, collected from principal feeding areas (Sea of Okhotsk, Bering Sea, and Northwest Pacific Ocean) within Russia's 200-mile economic zone. Data have been gathered by various types of fishing gear designed to catch juvenile and adult salmon. Using a comparative analysis, we examined feeding habits of pink, chum and sockeye salmon. Our results showed that in the 1950s, in offshore waters, the principal prey of these salmon consisted of energetically valued hyperiids and euphausiids. The basic juvenile salmon diet consisted of copepods, which also contributed substantially to the food of returning adults. Diets were stable until the 1980s, when the contribution of pteropods and juvenile fish to salmon diets became more significant. Since that time, low-energy organisms, including arrow worms, appendicularia, and salps, have appeared in the diets of salmon in relatively high numbers, particularly in the Bering Sea. Chum salmon have the most varied diet, and may be the best indicator of plankton production. Research shows that changes in diet can be associated with changes in plankton and nekton abundance. Regional variables and salmon abundance have also affected salmon diet composition. The composition of salmon diets has affected the size and average age at maturity toward the end of the last century, which has influenced the productivity of salmon stocks and populations.