Body weight, sexual maturity, and spinal deformity in strains and families of Atlantic cod ( Gadus morhua ) at two years of age at different locations along the Norwegian coast

Kolstad, K., Thorland, I., Refstie, T., and Gjerde, B. 2006. Body weight, sexual maturity, and spinal deformity in strains and families of Atlantic cod (Gadus morhua) at two years of age at different locations along the Norwegian coast. e ICES Journal of Marine Science, 63: 246e252. Body weight, occurrence of spinal deformity, and sexual maturity were recorded in 51 fullsib families of the strains coastal and Arctic cod at two years of age. The family groups were located at three sites along the Norwegian coast including Hordaland, More and Romsdal (M&R), and Nordland County to detect genetic variation in important production traits and to investigate interactions between genetic composition and production environment. Body weight varied among locations partly owing to different production conditions. There were also large differences among the locations with respect to spinal deformity. M&R had the highest occurrence of spinal deformity ( p < 0.001). Comparison of sexual maturity among the locations was made difficult owing to the different ways the trait was recorded. Only small differences were found between coastal and Arctic cod in spinal deformity ( p < 0.05 in Hordaland) and sexual maturity ( p ¼ 0.06 in M&R), while no differences were found for body weight. Heritability estimates for body weight (0.51), spinal deformity (0.27), and sexual maturity (0.21) indicate the potential for improvement of all three traits by selective breeding using a family-based selection programme. Final recordings at the end of the growing period will provide further information. Genetic correlations estimated between weight and occurrence of spinal deformity (rg ¼ 0.50) suggest that caution be used when selecting for growth, and that a need exists for including spinal deformity in the selection index. No significant correlations were found between these two traits and the incidence of sexual maturity.