February 15-18, 2009 Washington State Convention Center Seattle ...

EVALUATION OF STRESS-INDUCED CORTISOL RESPONSE FOR USE IN A Morone
SELECTIVE BREEDING PROGRAM
S. Adam Fuller* and Matthew McEntire
United States Department of Agriculture
Agricultural Research Service
Harry K. Dupree Stuttgart National Aquaculture Research Center
Stuttgart, AR 72160 USA
Adam.Fuller@ars.usda.gov
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 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) (Figure 1). 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)
(Figure 2). 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.
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