Yield Loss of Western Alaska Chinook Salmon Resulting from the Large Catch by the Japanese Salmon Mothership Fleet in the North Pacific Ocean and Bering Sea in 1980

Abstract

The Japanese salmon mothership fleet, fishing with gill nets in the North Pacific Ocean and Bering Sea in 1980, took a record 704,000 chinook salmon (Oncorhynchus tshawytscha), an estimated 380,000 of which originated in western Alaska. On the basis of information coalesced from earlier studies, non-catch mortality of western Alaska chinook salmon (referring to fish that die at sea because of their encounter with the gill nets but are not taken aboard ship as part of the catch) also was set at 380,000 fish. Nearly all were 1, 2, or 3 years from maturity. By balancing growth against mortality over time to maturity, it was estimated that the survivors of western Alaska chinook salmon caught or killed at sea as a result of the gill-net fishery would have weighed 6.52 times (range 3.53-11.58) the original high-seas catch had they been allowed to mature and enter the coastal fisheries of western Alaska. This ratio is, by far, the highest yet reported for Pacific salmon. The aggregate 1980-1983 chinook salmon runs to western Alaska (catch plus escapement) were reduced by 5,712 t (range 1,986-13,288) because of the 1980 mothership fishery.