Oregon Sea Grant

Hatcheries support fisheries and aid in the recovery of endangered wild populations. Evidence for reduced reproductive success (RS) of wild-spawning hatchery-reared salmon compared to wild-born fish invites questions about the impact on subsequent generations. Immune gene dependent mate preference is one mechanism known to influence salmonid fitness. We evaluated mate choice and correlates of RS to better understand fitness differences between hatchery reared and wild-born fish using a previously constructed genetic pedigree of coho salmon (Onchorhynchus kisutch) from the Umpqua River, Oregon. Two years (2005 and 2006) of three wild-spawning mate pair classes were examined: wild x wild (W x W), hatchery x hatchery (H x H), and wild x hatchery (W x H). We found no evidence for mate choice within mate pair class based on microsatellites linked to the Major Histocompatibility Complex (MHC) and immune relevant expressed sequence tags. Greater W x W mate pair RS was associated with increased MHC diversity in 2005 and 2006, while greater W x H mate pair RS was correlated to intermediate MHC diversity in 2006. We found no correlation between MHC diversity and H x H mate pair RS. Our results suggest greater MHC diversity between wild-born coho pairs may increase offspring survival.