Induction of sterility in coho salmon (Oncorhynchus kisutch) by androgen immersion before first feeding

15 pages, 2 figures, 2 tables.Based on the observation that in coho salmon (Oncorhynchus kisutch) the sensitivity to the effects of exogenous steroids is highest around hatching, and that it decreases as ontogenetic development progresses, immersion in a dilute solution of androgen prior to first feeding was examined as a means of inducting sterility in this species. Two approaches were tested: 17α-methyltestosterone (MT) was administered either by continuous immersion for 30 days, from just before hatching to just before first feeding, at doses ranging from 3.12 to 100 μg/l, or as discrete 2-h immersions at doses of 1 or 10 mg/l, once or twice per week, for a total of 5 or 10 immersions, respectively. Sampling of fish at about 7 months of age showed that these treatments had no significant effect on survival or length, whereas weight was slightly reduced only in the groups exposed to the highest amount of androgen. At the doses tested, discrete immersions resulted in a higher yield of sterile fish (maximum 92.3%) than continuous immersions (maximum 51.2%). In a subsequent experiment, 17α-methyldihydrotestosterone was compared with MT in discrete immersions, but the percentage of sterile fish produced was not different from that obtained with MT. These results show that androgen immersion of coho salmon before first feeding can result in a high proportion of sterile fish without compromising their viability. The benefits for aquaculture derived from sterilizing salmon before first feeding are discussed.Part of these studies (Experiment 3) were made possible by NATO Collaborative Research Grant CRG-890958 to M.C. and E.M.D.Peer reviewe