COMPARISON OF RAINBOW-TROUT (ONCORHYNCHUS-MYKISS) STRAINS FOR BODY-WEIGHT, LENGTH AND AGE AT MATURITY IN DIFFERENT SWEDISH PRODUCTION SYSTEMS

The relative suitabilities of four rainbow trout strains for rearing in Sweden were evaluated. After spending their first year at the research station, the offspring were divided into groups and reared until slaughter, at an age of 2.5 years, on four commercial fish farms differing in latitude and water salinity. Pronounced strain- and production system-related differences were found in performance. Growth traits were strongly influenced by sex and maturity. A small, but significant, interaction between strain and production system was found for the tested traits. The heritabilities for weight at 1.5 years of age, and weight, length and maturity at 2.5 years of age, estimated from sire components (39 sires [113 dams]), were low, with estimates of 0.13, 0.12, 0.11 and 0.02, respectively. The condition factor showed only moderate heritability (0.21 ). The weight, length, condition factor, and maturity of a given sex were genetically and phenotypically correlated with production ability.