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Variable effects of climate and density on the juvenile ecology of two salmonids in an Alaskan lake
Despite concerns over rapidly warming temperatures, an empirical understanding of climatic impacts on wild salmonid populations is limited. We tested how temperature and density affected juvenile coho (Oncorhynchus kisutch) and sockeye salmon (Oncorhynchus nerka) using a 31 year census from an Alaskan lake. There were positive effects of temperature on overall salmon biomass, sockeye biomass, and the length of age 2 sockeye smolts. There was, however, little evidence for relationships between temperature or length of growing season and coho biomass, coho length, smolts per spawner (both species), and age structure (both species). In some cases there were temporal changes contrary to what is generally expected in a warming Alaskan lake with longer growing seasons (e.g., increasing proportions of age 2 smolts). Intraspecific density was negatively related to sockeye length at out-migration, but there was no evidence for relationships between density and other response variables. Overall, patterns observed here and in other studies emphasize that responses to climatic variation can vary substantially across locations, between similar species occupying the same habitats, and among alternative life history strategies within populations.
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