Growth, survival, diet, and on-growing husbandry of haddock Melanogrammus aeglefinus in tanks and netpens

Growth of haddock (Melanogrammus aeglefinus) was assessed in onshore tanks in West Scotland. Fish were stocked at a mean weight of 15 g in July 2002, with a second stocking in October 2002 at 25 g. Fish had a mean weight of 755 ± 150 (s.d.) g at 20 months after stocking and were harvested. The specific growth rate of haddock was similar to Atlantic cod (Gadus morhua) during the first year but decreased by 20% after that. Liver biomass was 17.6% of the whole body weight, suggesting haddock had difficulty in utilizing dietary lipid. Reduced lipid levels in the diet had only a short-term effect on hepatosomatic index (HSI). Haddock that were held under 24-h light from the first summer solstice did not mature at an age of two years when compared with complete maturation of fish reared under ambient light. Mortality during the on-growing stage was high (28% of stock) and was attributed to Vibrio anguillarum infection, and possibly to enlarged livers. An assessment of quality found taste and texture to be as good or equal to wild North Sea haddock, and quality was improved with a five-day starvation period. Haddock mean weight, six months after transfer to netpens, was not significantly different from that of fish of the same age grown in tanks.