Nutrient requirements of Atlantic cod (Gadus morhua) larvae at first-feeding

Intensively cultured cod larvae, which are fed rotifers and formulated feed, grow slower and develop more deformities than larvae cultured semi-extensively with the natural diet, copepods. This shows that the present knowledge is insufficient for optimal intensive juvenile production. Suboptimal nutrition is one possible reason for the inferior performance of intensive compared to extensive culture of cod larvae. Nutrient requirement studies with marine fish larvae are scarce, because of the difficulty in controlling nutrient levels in the live feed organisms and due to the difficulties of producing a formulated diet where water-soluble nutrients do not leak. The group behind this application has developed methods for controlling rotifer nutrient composit ion, which enable us to run nutrient requirement studies with cod larvae at first-feeding. We have shown that total protein, phospholipid levels, taurine and several minerals are potentially deficient in rotifers, when we compare with copepods. In the pre sent project we will identify which of these nutrients are actually deficient with regard to growth, survival and deformities in cod larvae and run requirement studies to determine how much the rotifers must be enriched to cover the requirements. The resu lts will be used to produce a rotifer that is balanced in as many nutrients as possible. This rotifer will be used in a full scale trial with cod larvae.