Saltwater performance of triploid Atlantic salmon Salmo salar L. brown trout Salmo trutta L. hybrids

Survival and growth in a saltwater net-pen of sexually immature triploid Atlantic salmon Salmo salar L. brown trout Salmo trutta L. hybrids was comparable to that of immature diploid Atlantic salmon. Following 17 months of freshwater rearing, the experimental fish were individually tagged and transferred to a saltwater net-pen where they were raised communally for 376 days. Initial and final average weights were 158 and 760 g per fish for the diploid Atlantic salmon and 209 and 1010 g per fish for the triploid hybrids; weights for the hybrids were significantly larger in both cases (α= 0.05). Survival from transfer to harvest was 43% for the Atlantic salmon and 48% for the hybrids. Average specific growth rate of fish which survived to harvest was 0.42% day^-1 for Atlantic salmon and 0.41% day^-1 for hybrids; these values were not significantly different. No significant differences were observed in average condition factor and dress-out percentage between crosses. Average gonadal weights and gonadosomatic indices were not significantly different for male diploid Atlantic salmon, female triploid hybrids and male triploid hybrids, but were significantly greater for female Atlantic salmon.