Submitted to: Annual Meeting World Aquaculture Society
Publication Type: Abstract Only
Publication Acceptance Date: August 30, 2003
Publication Date: March 1, 2004
Citation: Weber, G.M., Silverstein, J. 2004. Evaluating rainbow trout (onchorynchus mykiss) families for a stress response for use in a selective breeding program.. Annual Meeting World Aquaculture Society. Book of Abstracts. p.631. Technical Abstract: A breeding program to develop improved germ plasm for the US rainbow trout aquaculture industry is being conducted at the USDA, ARS National Center for Cool and Cold Water Aquaculture (NCCCWA). A stake holders meeting held at NCCCWA in July of 2001 identified mitigation of problems associated with stress as an objective for research at NCCCWA. As a first step in that effort our broodstock families are being characterized for a stress response. It is well accepted that stress has a negative impact on many traits important to aquaculture including growth rate, feed efficiency, disease resistance, and reproductive performance; all of which are performance traits we are in the process of characterizing for our broodstock. Previous work has shown that differences in stress response among rainbow trout families can be identified by measuring blood levels of the stress hormone cortisol in the fish following exposure to a three hour crowding stress. This stress response is highly heritable and lines of low and high responding fish can be generated. Surprisingly, studies of lines of rainbow trout with such disparate stress responses have failed to identify substantial benefits of altering stress response through breeding. Our approach is to characterize the stress response of our broodstock families, generate a limited number of low and high responding lines, then look for correlates with various performance traits as we characterize these traits for our broodstock. If correleates of stress response and a performance trait are identified, the connection will be investigated in greater detail. We are measuring plasma cortisol concentrations by radioimmunoassay following a combined netting and crowding stress in 64 families of rainbow trout. The trout were bred from three commercial strains of rainbow trout to generate pure strain families and crosses among the strains. Eight fish from each family were sampled four times at monthly intervals beginning in September when the fish were approximately seven months of age and 200 g body weight. Once a month the fish were netted and transferred from a 120 L tank to a 15 L tank and left undisturbed for three hours. The fish were then netted again into anesthesia and quickly bled. Cortisol measurements have been completed for the September samples from all fish. Significant differences in September plasma cortisol levels were identified among families within a cross but not among crosses. Mean cortisol levels for the highest families were approximately four fold those of the lowest families. Cortisol measurements have also been completed for the subsequent months for six families that had low cortisol concentrations in September and six families that had high cortisol concentrations. Differneces in cortisol response observed in September were maintained over four months of sampling. The family means for the low and high responding families were 21.7+/-2.8 and 57.8+/-3.6 ng/ml cortisol (mean+/-SEM)respectively for September, and the means over four months were 24.3+/-3.2 and 58.7+/-9.1 ng/ml respectively.