Evaluation of Growth, Survival, and Recruitment of Chinook Salmon in Southeast Alaska Rivers

Abstract

AbstractRecent reductions in the run sizes of Chinook Salmon Oncorhynchus tshawytscha in Southeast Alaska have resulted in social and economic hardships within the region. For Pacific salmon, including Chinook Salmon, brood year (BY) strength may be determined by size‐selective processes that occur during early marine residence. However, the relative importance of freshwater versus marine growth in determining recruitment success is unknown. We conducted a scale‐based retrospective analysis to examine the relative effects of freshwater and marine growth on survival to the age of reproduction for female Chinook Salmon by BY in the Taku (BYs 1979–1985, 1990–1999, 2002–2004) and Unuk (BYs 1981–1983, 1986–1988, 1994–2003, 2005–2006) rivers located in Southeast Alaska. First‐year marine growth of Chinook Salmon was positively related to total return, productivity (returns per spawner), and marine survival for stocks from both systems. In the Taku River, growth during the third year at sea was positively related to marine survival. Annual growth of Taku River Chinook Salmon was correlated with previous growth through the second year at sea; however, no correlations were detected between adjacent growth zones of Unuk River fish. These findings suggest that current declines in Chinook Salmon abundance in Southeast Alaska is attributed to changes in growth conditions during the first year at sea.