Variability Of Pink Salmon Family Size Has Implications For Conservation And Management Models

Abstract

In several populations of pink salmon, the short-term dynamics population size was related to both the mean and variance of individual family sizes, because not all families were equally productive. In the marine lifestage, population increases came disproportionately from the most productive families, especially in populations with the highest average marine survival. Moreover, the trait of marine survival itself had a statistically detectable genetic component. This implies that the most favored phenotypes change from generation to generation, and that the marine environment is unpredictable and changing. These results, together with laboratory studies of freshwater survival and measurements of wild pink salmon in Prince William Sound, Alaska, seemed to indicate that family-specific variation in marine survival and variation in egg retention within the redd were the most important potential influences on variation of pink salmon family size in the studied populations, when density was controlled to intermediate levels. These results provide more justification for maintaining stock sizes at intermediate or high levels, and for protecting metapopulation structure. These results also show the importance of variation and instability in the recruitment process of Pacific salmon, and highlight the inadequacy of current models of salmon recruitment, which emphasize stability and long-term averages.