Meeting Abstract
Although the practice of selective breeding in aquaculture facilities has been essential for maximizing growth and survival, it has also led to increased differentiation from wild strains and a loss of genetic diversity, with potential deleterious effects. Understanding how outbreeding with wild stocks impacts the mechanisms underlying fish growth and survival in captivity is therefore vital for maximizing aquaculture success. Cortisol is a major energetic hormone that oscillates with a circadian rhythm in response to diel variation in energetic demands. We hypothesized that if different outbred crosses between wild and captive chinook salmon stocks manage cortisol differently across the day, this may impact growth rates, and therefore terminal size and potentially survival. We measured baseline plasma cortisol levels across a 24-hour period in pre-smolt individuals from hybrid (outbred) stocks created via crosses between eggs from domestic (captive) females and multiple individual males within each of seven different wild stocks (using cryopreserved milt). While all stocks showed a clear diel rhythm in baseline plasma cortisol levels, we found a significant additive genetic effect of the sire on the management of baseline cortisol across the 24-hour cycle. We will next investigate whether these stock-level differences in cortisol impact early growth to determine the influence of outbreeding on salmon fitness and aquaculture productivity.
