Trends and Factors Influencing the Length, Compensatory Growth, and Size-Selective Mortality of Juvenile Bristol Bay, Alaska, Sockeye Salmon at Sea

AbstractThe productivity of Bristol Bay, Alaska, Sockeye Salmon Oncorhynchus nerka increased during the mid-1970s. This increase is believed to be partially due to an increase in early marine growth associated with the 1976–1977 cool-to-warm shift in summer sea surface temperature (SST). The body size of juvenile salmon during their first year at sea is believed to regulate their ability to survive over winter. The back-calculated smolt length, first-year ocean growth, and total juvenile length of Sockeye Salmon from five Bristol Bay river systems (Egegik, Kvichak, Naknek, Ugashik, and Wood) and two smolt ages were used to examine trends and factors influencing total juvenile length, compensatory growth, and size-selective mortality in the first year in the ocean from 1962 to 2007. Juvenile length increased in relation to summer sea temperature, the 1977–2001 and 2002–2007 warm temperature regimes, smolt length, and compensatory growth. Compensatory growth—an inverse relationship between first-year ocean ...