Publication Abstract

THE GROWTH OF LARVAL ATLANTIC COD (Gadus morhua) AND HADDOCK (Melanogrammus aeglefinus) IN THE IRISH SEA: A MODEL WITH TEMPERATURE, PREY SIZE, AND TURBULENCE FORCING

 

 

Cod and haddock are commercially important whitefish species in the Irish Sea. As with many North Atlantic cod stocks, Irish Sea cod has undergone a continuous decline in spawning-stock biomass. In contrast, haddock has continued to experience relatively strong year classes at intervals, thus causing conflicting management requirements for the two stocks. Growth and survival through the early life-stages being of critical importance to successful recruitment in marine fishes, we need to understand better how cod and haddock larvae interact with their prey environments. We applied a physiological individual-based model for the foraging and growth of cod and haddock larvae using data from the Irish Sea, collected during the spawning season in 2006. The model was used to examine the different productivities of the cod and haddock stocks under the conditions encountered in the Irish Sea. Both larvae showed similar responses to changes in environmental conditions and survival was found to be better on the western side of the Irish Sea, covering the spawning ground for haddock and about half of that for cod. Prey availability was found to be the limiting factor of larval growth, but exploration of stock assessment data suggests that others factors have a role to play to ensure successful recruitment. We suggest that the increasing population of clupeids may have added predatory pressure on the eggs and larvae of gadoids in the Irish Sea, thus fitting the same pattern reported elsewhere, of forage fish being a significant factor impacting on recruitment success of demersal species.

S. Pitois*, M. Armstrong*