Specific growth rate and proximate body composition of Atlantic cod ( Gadus morhua L.)

Abstract

The effect of growth rate and maturation on the proximate composition and energy content of Atlantic cod, Gadus morhua L., was investigated over 10 months for each of two consecutive years, 1978–1980 at 5 and 8 °C. Relative energy and lipid content of whole cod increased with specific growth rate for all three sampling periods (November, January, March), each at 5 and 8 °C. Relative water content decreased with specific growth rate and temperature, and was lower in March than in January and November. Relative protein content was positively correlated with specific growth rate, but to a lesser degree than with temperature and age. Relative ash content was negatively correlated with specific growth rate. The effect of season and temperature on the proximate content of gonad, liver, muscle, and carcass was also determined. The major energy and lipid source in cod was the liver. Energy, lipid, and water were highly correlated to each other, and regressions are provided to allow for their prediction, given one of the components. Energy budgets for cod at 5 and 8 °C are calculated and the effect of increased ration size on the budget is estimated. The prediction of short-term specific growth rates of cod from the proximate composition is proposed. The proximate composition of cod is affected by growth rate and thus feeding level, and in turn directly affects behaviour. The relative proximate content of maturing and immature 3-yr-old cod was not found to be significantly different. Keywords: specific growth rate; proximate; bioenergetics; Atlantic cod; energy budget; temperature; season