Genotype-by-environment interaction for growth in seawater and freshwater in Atlantic salmon (Salmo salar)

Abstract

A severe outbreak of infectious salmon anemia (ISA) virus in Chile in 2007 led to considerable changes in breeding practices and regulations for the salmon industry. The Atlantic salmon (Salmo salar) broodstock reproductive cycle, from birth to maturity, is now wholly carried out in freshwater in some companies while commercial salmon are finished in saltwater. The genetic differences pertaining to growth between fish reared in freshwater and seawater are unknown. The objective of this work was to evaluate the genotype by environment interaction for body weight in two independent Atlantic salmon populations (year class 2012 and 2014), both reared in seawater and freshwater. Heritability estimates and genetic correlations for body weight in both environments were estimated through a linear bivariate animal model. Estimated heritabilities were moderate to high (0.23 ± 0.04 to 0.46 ± 0.08); indicating that body weight improvement is feasible through genetic selection. The genetic correlations for body weight between freshwater and saltwater rearing were low: 0.31 ± 0.13 for year class 2012 and 0.26 ± 0.14 for year class 2014; indicating a considerable genotype by environment interaction for growth in Atlantic salmon. The genotype by environment interaction causes a re-ranking of selection candidates, reducing the potential to maximize genetic gain for growth when broodstock is reared in freshwater and production is done in seawater.