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 t o the mean sizes of individual families. The amount of genetic variati on maintained in the population is directly related to the: variance i n sizes of individual families. Both the mean and variance of individu al family sizes have important implications for conservation actions a nd sustainable levels of harvest of salmonid fishes. We develop a cont ext for examining variation in family size. and we provide estimates o f mean and variance of family size from five groups of marked pink sal mon (Oncohynchus gorbuscha) released into the north Pacific Ocean. We then present two important results: (1) a statistically detectable gen etic component of marine survival exists in groups with high marine su rvival and (2) ratios of variance-to-mean family size are linearly rel ated to mean family size over the interval that we observed. These res ults imply that short-term population increases come from a small frac tion 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 v iew that protecting genetic variation in recovering or exploited salmo n populations has important economic benefits.