Comparison of different European rainbow trout populations under intensive production conditions

Growth and carcass quality of European rainbow trout populations were compared in a full sib family test over five experimental periods. In total, 131 full-sib families of 17 different populations, (i.e. 19 500 fish), were included. A special system for family testing in trout was developed. This consisted of separate hatching of single pair matings, separate rearing of families up to marketable size and common fattening under two stocking densities. Thus, growth was studied separately for the rearing and the fattening period. The observed differences in rearing and fattening weight between and within populations were quite distinct and of significance for production and breeding efficiency. Similar ranking of populations after fattening in different years and under different stocking densities indicated that the final weight was highly genetically controlled. Carcass characteristics determined at marketable size showed somewhat smaller differences between populations. Populations with the highest fattening weight did not generally produce the most valuable carcasses. The results are discussed with respect to their impact on breeding strategies.