DIFFERENCES IN GROWTH-PERFORMANCE BETWEEN ARCTO-NORWEGIAN AND NORWEGIAN COASTAL COD REARED UNDER IDENTICAL CONDITIONS

Offspring from seven family groups of Arcto-Norwegian cod (AN) and a g enetically marked Norwegian coastal cod (NC) broodstock, were mixed at metamorphosis and raised in the same rearing unit. The fish were tran sferred subsequently to a net-pen and held under standard farming cond itions. In December 1992, 466 cod juveniles were measured, weighed, an d tagged individually. Length and weight changes were monitored until the fish matured (January 1994). Genotyping of each individual was per formed using enzyme electrophoresis to identify the fish to strain. Pr espawning females were examined for organ weights and stage of maturit y. There were population specific differences in growth performance. N C displayed significantly higher specific growth rate (SGR) and daily length increment (DLI) during spring/summer season. The AN had signifi cantly lower hepatosomatic and gonadosomatic indices, and were thinner than the NC, indicating differences in body form and energy allocatio n pattern between the two strains. All NC (both sexes) became sexually mature at the age of 2 years while 2% of fish in the AN group were st ill immature at the end of the experiment. (C) 1996 The Fisheries Soci ety of the British Isles.