Genotype by Environment Interaction for Growth in Atlantic Cod (Gadus morhua L.) in Four Farms of Norway

We studied genotype by environment interaction (G x E) for body weight (BW) of Atlantic cod (Gadus morhua L.) from the National cod breeding program in Norway. Records of 13,811 fish in a nucleus farm (NUC) and two test farms (PENorth, PESouth) in year-class (YC) 2007, and for 9149 fish in NUC and one test farm in YC 2010 were available. Heterogeneity of variances and heritabilities (h(2)) were estimated using a univariate animal model with environmental effects common to full-sibs (full-model). Genetic correlations (r(g)) between farms were estimated using a multivariate full-model and a reduced-model (without c(2)) for each YC. Heterogeneity of h(2) was observed in both YC 2007 (0.10 to 0.16) and YC 2010 (0.08 to 0.26). The estimates of r(g) between NUC and test farms were relatively high for both models (0.81 +/- 0.19 to 0.96 +/- 0.17) and (0.81 +/- 0.08 to 0.86 +/- 0.04), suggesting low re-ranking of genotypes. Strong re-ranking of genotypes between PESouth and PENorth may be less important because most cod producers are situated close to the breeding nucleus. In conclusion, G x E between NUC and test farms were low and at present there is no need for separate breeding programs for BW in cod.