Heritability of life history and morphological traits in a wild pink salmon population assessed by DNA parentage analysis

Heritability estimates were calculated for body size and shape, day of entry onto the spawning grounds, and egg size for two brood years (1997 and 1998) of a wild population of pink salmon Oncorhynchus gorbuscha based on parentage analysis of DNA samples from breeding adults and their mature offspring in a small creek in Southeast Alaska. The majority of heritability estimates for size and shape were not significantly different from zero, probably as a result of the close association of these variables with fitness. The even- and odd-year brood lines are genetically isolated but heritability estimates from the two lines were significantly correlated, suggesting similar selection histories. Consistent with heritability estimates from controlled breeding and captive rearing of pink and other species of salmon, day of entry onto the spawning grounds had the highest heritabilities of the traits examined in this study, especially for males (h(2) = 0.6-1.38). One plausible method for the maintenance of genetic variation in entry timing (a trait important to fitness) is variation in the optimal spawning and emigration date from year to year owing to changes in flow rate, predation pressure, ocean conditions, and food availability for progeny.