Factors affecting marine growth of Bristol Bay sockeye salmon

Abstract

The growth of Bristol Bay sockeye salmon in freshwater and in the last few months at sea is dependent on their abundance (a negative correlate) and the prevailing water temperature (a positive correlate). In 1990 and 1991, the returning sockeye salmon to Bristol Bay were unusually small relative to their abundances and temperatures and this raised a concern for limited ocean carrying capacity because other stocks of salmon were also very numerous in those years. However, the inclusion of other stocks of sockeye salmon and the abundant runs of Asian chum salmon in a multiple regression analysis did not provide a better predictor of the body size of Bristol Bay sockeye salmon. Growth increments of Nushagak Bay sockeye salmon in their first and second years at sea (from scale measurements) were correlated with temperatures but not with the abundances since 1975. The growth increment in the third year of sea life was uncorrelated with temperature and abundance but was correlated with final adult length. This suggests that concerns for carrying capacity limitations should be placed on the migratory routes of returning adults when the fish are probably most concentrated and their growth most limited by their food supply.