Genetic improvement of Atlantic salmon for New Brunswick aquaculture

Atlantic salmon producers in New Brunswick wish to develop a strain characterised by fast growth, good carcass quality, and low grilse incidence. Genetic improvement strategies also need to be developed for new management practices wherein broodstock are reared in freshwater (FW) facilities, while market stocks are reared in seawater (SW) net pens.

Genetic parameters of body size, flesh quality (colour, astaxanthin, canthaxanthin, fat, and moisture), and age at sexual maturation (ASM) were estimated from data collected from full-sib families reared by the Atlantic Salmon Broodstock Development Program under commercial conditions. Most traits exhibited moderate heritability (h²) and therefore should show good response to selection, except for ASM which showed low h². Genetic correlations (r_G) indicated that selection to increase HWT will cause indirect increased flesh colour and pigmentation response, and undesirable increased flesh fat content. Most FW weights had positive r_G with HWT, and so could be used as indicators of HWT in a selection program. However, 1y weight and HWT had a negative r_G, therefore selecting on early weight may cause lower HWT. Negative r_G between FW weight and SW ASM suggested that selection on FW weights may cause higher market stock grilse incidence. Relationships between body size and ASM differed between environments, and estimates of r_G between ASM in FW and SW varied widely. FW ASM may be a different trait from SW ASM. An appropriately-weighted selection index should be therefore be used increase HWT while decreasing flesh fat content and market stock grilse incidence.

Computer simulations were used to predict effects of 10 generations of selection based on broodstock weight phenotype, estimated breeding values (EBV) for HWT calculated from best linear unbiased prediction (BLUP), and grilse culling, on broodstock weight, HWT, grilse rate, inbreeding, and economic returns for a range of genetic correlations. Selection on BLUP EBV combined with either no culling or culling grilse individuals resulted in higher HWT and lower grilse incidence, and thus higher revenues. However, selection on BUT EBVs also caused faster inbreeding accumulation, therefore some restrictions on selection and mating should be implemented in practice.