FEEDING, GROWTH, AND SURVIVAL OF ATLANTIC COD (GADUS-MORHUA) LARVAE REARED IN REPLICATE PLASTIC ENCLOSURES

Feeding, growth, and survival of Atlantic cod (Gadus morhua) larvae we re examined during their first 2 mo of life. The experiment was carrie d out in eight plastic enclosures of 10 m3 volume each. Larval cod, at an initial stocking density of 10 larvae/L, were fed rotifers (Brachi onus plicatilis) and natural zooplankton collected from the sea. The e nclosures replicated well with regard to hydrography, feeding conditio ns, and larval growth and survival. Larval mortality was low during th e first month, with a mean mortality rate (Z) of 0.02/d. Growth, howev er, was very slow and mortality increased significantly after about 4 wk, possibly due to starvation. Brachionus plicatilis dominated the gu t content during the first 3-4 wk. The zooplankton concentration avera ged 15-80 rotifers/L during the first 2 wk, which seemed to be insuffi cient under the present rearing conditions. Most of the larvae were di stributed in the upper parts of the rearing enclosures, while rotifers were distributed deeper. This, together with the high larval density, inadequate rotifer enrichment, and low temperature probably amplified the unfavourable feeding conditions.