Size-dependent mortality of juvenile Atlantic cod, estimated from recaptures of released reared cod and tagged wild cod

The recapture rate and survival of reared cod Gadus morhua L. (15-45 cm) re leased in fjords and open coastal areas of Norway increased with increasing size at release, while release area and season also had a significant infl uence on the results. High mortality soon after release reduced the number of released fish by more than two-thirds within 6 months, and reduced the p otential commercial yield to a low level. In most cases the recapture yield was lower than the released biomass and the net yield increased little or not at all with increasing size at release. In western Norway high fishing mortality of young fish reduced the numbers of surviving fish rapidly and t he growth overfishing reduced the potential yield still further. Natural mo rtality decreased with increasing size at release, and became low when the fish approached their size refuge, i.e. when they could not be eaten by the ir usual predators. (C) 2000 The Fisheries Society of the British Isles.