Parr–smolt transformation in out-of-season triploid Atlantic salmon (Salmo salar L.)
Taylor, J.F. | Leclercq, E. | Preston, A.C. | Guy, D. | Migaud, H.
Production of sterile triploid Atlantic salmon (Salmo salar) would appear to be the best strategy to address the growing concerns on environmental impacts of escapees. However, the industry relies on a year round supply of smolts to ensure continual production and to date the production of out-of-season (S0+) triploid smolts has not been reported. The present study demonstrates that S0+ triploid smolts can be produced using an accelerated “square-wave” photoperiod (LL–LD 9.5:14.5–LL) under ambient water temperature. Such a regime advanced the timing of smoltification by 3months (S0+) relative to their siblings under an ambient photoperiod (S1+) as observed through body silvering, fin darkening, decrease in condition and significantly increased gill Na⁺, K⁺-ATPase activity. Importantly, triploid S0+ fish smolted 4weeks earlier than their diploid siblings. In S1+ populations, no difference in smolt time was observed although triploid fish also achieved a higher weight. Furthermore, deformity prevalence was very low during the fresh (≤5%) and seawater (≤2.5%) stages within both ploidies mainly represented by spinal deformity and operculum shortening. Family effects for growth and condition were clear, however, no significant family/ploidy interactions were observed although this was based on only two full-sib crosses. These results are promising but there is still a long way to go before triploid can become a commercial reality. Further studies are required to optimize and refine husbandry protocols, define breeding strategies especially regarding family selection and overall better understand triploid salmon physiology.
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