Pacific Salmon: Ecology and Management of Western Alaska’s Populations

A Review of Growth and Survival of Salmon at Sea in Response to Competition and Climate Change

Gregory T. Ruggerone and Jennifer L. Nielsen


Abstract.—Studies have documented density-dependent growth of salmon in the ocean during early and late marine stages in response to competition between species. However, key questions remain as to whether competition and reduced growth at sea translate to lower survival of salmon, and whether changes in ocean regimes can alter this relationship. Few studies have tested these questions, in part, because the capacity of the ocean to support salmon is dynamic and smaller adult size has been associated with high abundance, which infers high overall survival. In support of salmon management activities in the Arctic-Yukon-Kuskokwim (AYK) region, we review evidence from recent studies suggesting that competition at sea can lead to reduced salmon growth and survival and to potentially lower reproductive potential of survivors. Climate change may, however, also affect prey availability and therefore influence the magnitude of competition. Salmon growth (and survival) responses to competition and climate shifts can vary with season and life stage of salmon. We conclude that growth of salmon is key to their survival and that competition at sea is an important, yet often elusive mechanism affecting salmon population dynamics.