Comparison of growth in Atlantic cod (Gadus morhua) originating from the northern and southern coast of Iceland reared under common conditions

Counter-gradient variation in growth has been documented for several commercial fish species. This phenomenon was tested for Atlantic cod (Gadus morhua) when forming the base population for a cod-breeding program in Iceland. In 2004, wild brood fish from five locations off the Icelandic coast were captured using gillnets from commercial fishing vessels. The eggs were hatched at the Marine Research Institute (MRI) and transferred to sea cages at 322 days post hatch dPH. Growth rate, maturation and conditional factor were measured at a commercial scale among the fishes originating from these five locations. The measurements taken at 322 days post hatch (dPH) showed a significant different in weight, but measurements taken at 729 and 952 dPH showed no difference in growth rate, length or maturation.Analysis of gene diversity among the brood fish showed a significant genetic structure, but all FST were below 0.006 and were significant. Moreover, the hatching success among the females from these locations was not significant.The main conclusion is that Atlantic cod originating from the North and South coast of Iceland show no quantitative differences in growth, proportion of maturation or length. These results need to be considered when forming the base population of Atlantic cod.