The effects of two water temperature regimes on Atlantic salmon (Salmo salar) growth performance and maturation in freshwater recirculating aquaculture systems

There is increasing investment in and use of land-based recirculating aquaculture systems (RAS) to produce market-size Atlantic salmon (Salmo solar) despite limited understanding of economic feasibility at commercial scale. High incidence of early maturing fish in RAS growout is one obstacle to profitability for this production method. 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 similar to 1.3 kg in land-based RAS at a standard production temperature of 14 degrees C or at a cooler temperature of 12 degrees C. Survival (97.7 +/- 0.6 vs 98.1 +/- 0.3%), final weight (1292 +/- 25 vs 1355 +/- 31 g), condition factor (1.57 +/- 0.01 vs 1.58 +/- 0.01), feed consumption (409.2 +/- 6.2 vs 449.3 +/- 15.8 kg/RAS), and feed conversion ratio (1.11 +/- 0.02 vs 1.15 +/- 0.01) were similar between temperature treatments while thermal growth coefficient (2.45 +/- 0.02 vs 2.18 +/- 0.02) was significantly higher at 12 degrees C. Maturation prevalence (20.4 +/- 3.5 vs 32.1 +/- 1.4%) was significantly higher at 14 degrees C and gonadosomatic index of immature fish skewed higher at 14 degrees 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 degrees 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.

Automated summary

Despite limited understanding of economic feasibility, there is increasing investment and use of land-based recirculating aquaculture systems (RAS) for producing market-size Atlantic salmon. High incidence of early maturing fish is a profitable obstacle for this production method, therefore well-defined RAS-specific water temperature thresholds are needed to minimize early maturation.