Genetic and phenotypic effects on reproductive outcomes for captively-reared coho salmon, Oncorhynchus kisutch

Captive breeding programs are a common approach to preventing extinction and rehabilitating endangered stocks of Pacific salmonids. To minimize inbreeding in these typically small populations, genetic data from microsatellite loci have been used to estimate relatedness and choose spawning pairs. Phenotypic attributes (e.g., body size), that result at least in part from environmental conditions during rearing likely affect reproductive outcome as well. However, the combined effects of individual phenotype and genetic broodstock management have not been previously evaluated. This study assessed the influence of genetic background (source of original broodstock collection, and heterozygosity of both male and female parents), the molecular genetic-derived relatedness coefficient of mated pairs, and phenotypic attributes of female parents (body size, ovulation rate) on reproductive outcome for three brood years of endangered coho salmon, Oncorhynchus kisutch, from the Russian River, California. Over 1200 full-sibling family groups were created in total, whose survival was tracked individually from fertilization through the swim-up fry stage. Strong maternal influence on reproductive outcome was found, as increased female body mass resulted in lower progeny survival rates, and higher ovulation rates predicted improved progeny survival. Male and female heterozygosity was generally positively related to embryo survival, but this effect was not consistently observed across brood years or early life stages. The relatedness coefficient between mated pairs had a significant and negative effect on progeny survival, particularly after hatching, even though the most inbred matings were prevented. Thus, use of genetic broodstock management to guide selection of salmon breeding pairs increases offspring survival, in addition to reducing inbreeding.