Variability of family size and marine survival in pink salmon (Oncorhynchus gorbuscha) has implications for conservation biology and human use

The short-term dynamics of salmonid populations are directly related to the mean sizes of individual families. The amount of genetic variation maintained in the population is directly related to the: variance in sizes of individual families. Both the mean and variance of individual family sizes have important implications for conservation actions and sustainable levels of harvest of salmonid fishes. We develop a context for examining variation in family size. and we provide estimates of mean and variance of family size from five groups of marked pink salmon (Oncohynchus gorbuscha) released into the north Pacific Ocean. We then present two important results: (1) a statistically detectable genetic component of marine survival exists in groups with high marine survival and (2) ratios of variance-to-mean family size are linearly related to mean family size over the interval that we observed. These results imply that short-term population increases come from a small fraction of the population's families, that salmon encounter a fluctuating marine environment, and that the most favored phenotype changes from generation to generation. These results also support the widely held view that protecting genetic variation in recovering or exploited salmon populations has important economic benefits.