Distinct patterns of inheritance shape life-history traits in steelhead trout

Life-history variation is the raw material of adaptation, and understanding its genetic and environmental underpinning is key to designing effective conservation strategies. We used large-scale genetic pedigree reconstruction of anadromous steelhead trout (Oncorhynchus mykiss) from the Russian River, California, USA to elucidate sex-specific patterns of life-history traits and their heritability. SNP data from adults returning from sea over a 14-year period were used to identify 13,474 parent-offspring trios. These pedigrees were used to determine age structure, size distributions, and family sizes for these fish, as well as to estimate the heritability of two key life-history traits, spawn date and age at maturity (first reproduction). Spawn date was highly heritable (h2 = 0.73) and had a cross-sex genetic correlation near unity. We provide the first estimate of heritability for age at maturity in ocean-going fish from this species and found it to be high heritable (h2 from 0.29–0.62, ...