Ecological Factors Influencing Lifetime Productivity of Pink Salmon (Oncorhynchus Gorbuscha) in an Alaskan Stream
Ecological factors underlying freshwater productivity and marine survival of pink salmon (Oncorhynchus gorbuscha) were evaluated by analyzing a 30 year time series of local environmental data and censuses of migrating adult and juvenile fish collected at Auke Creek, Alaska. Freshwater productivity was influenced primarily by spawning habitat limitation and less so by stream temperature and flow. Furthermore, a trend of declining freshwater productivity was detected over the time series, which may be related to observed declines in spawning substrate quality and in the duration of the adult migration. Marine survival was highly variable among brood years and was influenced by physical conditions in the nearshore marine environment; warm sea-surface temperatures during nearshore residency were associated with higher marine survival rates, whereas high stream flows late in the fry emigration period were associated with reduced marine survival. Simulations of adult recruitment, based on ecological factors in the freshwater and marine environments, indicated that the productivity of pink salmon in this stream is determined primarily by early marine survival.
The anadromous life cycle of Pacific salmon (Oncorhynchus spp.) entails exposure to a diverse array of ecological factors during their freshwater and marine stages. An understanding of which of these factors drive productivity can provide a basis for addressing fisheries research topics, such as the extent to which habitat availability and seasonal environmental variation control reproduction and survival and whether lifetime productivity is primarily limited by the freshwater or marine stage. Additionally, the identification of links between environmental variation and demographic processes can enhance our understanding of how salmonid populations will respond to climate change. These research topics have important implications for the development of salmonid management strategies.