Evaluation of stress-induced cortisol response for use in a Morone selective breeding program

Authors: Fuller, Adam; McEntire, Matthew - Matt

Submitted to: Book of Abstracts Aquaculture America
Publication Type: Abstract Only
Publication Acceptance Date: 8/12/2008
Publication Date: 2/15/2009
Citation: Fuller, S.A., Mcentire, M.E. 2009. Evaluation of stress-induced cortisol response for use in a Morone selective breeding program [abstract]. Book of Abstracts Aquaculture America. p.111.

Interpretive Summary:

Technical Abstract: Harry K. Dupree Stuttgart National Aquaculture Research Center (HKDSNARC) has initiated a selective breeding program aimed at improving production traits for sunshine bass, Morone chrysops X M. saxatilis, via multi-trait selection in the two parental species, white bass, Morone chrysops (Rafinesque), and striped bass, Morone saxatilis (Walbaum). We are interested in understanding the physiological and genetic impact of many production trait phenotypes that are currently being characterized in white bass and striped bass for the hybrid striped bass National Breeding Program. Cortisol is a hormone steroid with many biological effects, including gluconeogenesis and immunosupression. If selective breeding could be used to reduce the severity of the physiological stress response it would be a benefit to those culturing hybrid striped bass. A cortisol dose response curve was created using three year-old white bass exposed to a low water stressor for 0, 5, 10, 15, 20, 25, 30, 40, 50, 60, 70, or 80 minutes. At each time interval, a blood sample was taken from each of the five fish with a heparinized syringe using no anesthetic, the blood centrifuged and the plasma stored frozen. Plasma cortisol concentrations were determined by radioimmunoassay (RIA). Relative stress response was then determined for three year-old white bass broodstock representing 80 crosses produced at the North Carolina State University’s Pamlico Aquaculture Field Laboratory. Male (n = 49) and female (n = 85) white bass were segregated, tagged, then weighed, measured, and stocked into 700-L tanks at a rate of ten same sex fish per tank. Fish were exposed to a low-water stress event for 40-minutes then captured and bled without anesthesia. This was done once per month for two consecutive months. Cortisol concentrations were determined as described. There was a significant difference in mean cortisol/g body weight response between the male (0.409 ± 0.020) and female (0.224 +/- 0.016) white bass (P < 0.0001). The lowest-responding 25% of females (cortisol/g < 0.329) and males (cortisol/g < 0.548) will be selectively bred to determine heritability of low cortisol response.