Precocious maturation of Atlantic salmon (Salmo salar) continues to be a source of economic loss for farmers due to the associated decreased growth performance, poor feed conversion efficiency, and reduced product quality (e.g., pale fillets), among other things. Given the natural life history of the species, and the numerous factors (photoperiod, temperature, fish size, growth rate, nutritional status, genetics, etc.) that can influence the onset of puberty, early sexual maturation can be difficult to prevent. This problem has been particularly prevalent in land-based, closed containment recirculation aquaculture system (RAS) facilities raising Atlantic salmon; reported early maturation has ranged from 2% to 100% in surveyed RAS facilities. With the increasing investment in land-based salmon farm projects over the past several years, the issue of early maturation will likely be of major economic significance for land-based salmon producers unless reliable preventive methods are developed.
Well-defined, RAS-specific water temperature thresholds that maintain high fish growth performance while minimizing early maturation are needed to accurately forecast bioplans, operational costs, and gains from reduced maturation downgrades. Accordingly, the objective of this research was to compare growth performance and maturation status of diploid, mixed-sex Atlantic salmon grown to ~1.3 kg in land-based RAS at a standard production temperature of 14 °C or at a cooler temperature of 12 °C. Survival, final weight, condition factor, feed consumption, and feed conversion ratio were similar between temperature treatments while thermal growth coefficient was significantly higher at 12 °C. Maturation prevalence and gonadosomatic index of immature fish was significantly higher at 14 °C. Overall, lower water temperature reduced prevalence of maturation in RAS while maintaining similar production performance; however, more than 20% of salmon cultured at 12 °C matured indicating even lower temperature, additional manipulations to the RAS environment, or use of all-female stocks are needed to optimize Atlantic salmon growout in RAS for reduced maturation.