Genetic variation for juvenile growth and survival in Atlantic cod ( Gadus morhua)

Body weights were recorded at tagging (∼200 days post-fertilization, dPF) of in total 6112 Atlantic cod ( Gadus morhua) offspring of parents caught in two regions off Norway, i.e., 3988 offspring of 20 dams and 28 sire (29 full-sib families) from region 1 (most likely Norwegian coastal cod) and 2124 offspring of 14 dams and 22 sires (22 full-sib families) from region 2 (most likely NE Arctic cod). The full-sib families were reared in separate tanks of same type and size from fertilization until tagging size (∼25 g). The regions 1 and 2 cod was not significantly different in body weight (−4.2±23.5 g) or survival in a 70-day period prior to tagging (−0.1±5.9 % units). The within and across population heritability estimates were 0.29±0.27 and 0.52±0.26 for body weight and 0.00±0.14 and 0.00±0.13 for survival, respectively. For both traits, the estimate of the effect common to full-sibs caused by factors other than additive genetics was quite high (varying from 0.03 to 0.12), indicating environmental effects common to full-sibs caused by the separate rearing of the families. Improvements in rearing technology will likely reduce these environmental effects. The results suggest good prospects for genetic improvement of growth rate in Atlantic cod through selective breeding.