Enhancing the reproductive potential of local populations of coastal Atlantic cod (Gadus morhua)

Abstract

We investigate the feasibility of enhancing the reproductive potential of northern Atlantic cod (Gadus morhua L.) populations resident in Newfoundland and Labrador bays by "catch, grow out, and release". This entails trapping juvenile and young adult fish from the local population, increasing their growth, maturation rate, and potential fecundity by feeding them a natural diet in net pens, and then returning the fish to their natal bay habitat to spawn. To determine whether multiyear farming affects spawning success, we determined the spawning period and egg quality of cod held in captivity for three growth seasons. Farmed cod spawned in a net pen concurrently with wild cod in Trinity Bay during 1995 and produced fertilized eggs from which viable larvae hatched. Sonic tracking showed that cod farmed for 3 years and then released reintegrated with wild cod aggregations over known spawning grounds. Recaptures of tagged fish several years after release suggest that farmed fish remained in the bay as members of the resident population. Fishing mortality (bycatch in coastal fisheries for lumpfish (Cyclopterus lumpus) and winter flounder (Pseudopleuronectes americanus)) of released farmed cod was not negligible, emphasizing that any enhancement effort must be carried out under a complete fishing moratorium.