Regional variability in the dynamics of reproduction and growth of Irish Sea plaice, Pleuronectes platessa L

Abstract

The differences in size-specific fecundity in relation to size/age at maturity, and in reproductive and somatic investment were analysed for female plaice caught in four regions of the Irish Sea (Cumbrian coast, Liverpool Bay, Cardigan Bay and western Irish Sea), each of which contains a spawning focus. Both the reproductive investment (gonad weight as a function of body size) and fecundity–size relationship of plaice in the western Irish Sea were significantly different from those in the other regions. Rates of annual somatic growth appeared to fall into three distinct groups (Cumbrian coast; Liverpool Bay and Cardigan Bay; western Irish Sea) and, in all cases, the rate of somatic growth fell rapidly after maturity. The data suggest that the highest surplus production (as spawned eggs) occurs in the sub-populations of plaice on the Cumbrian coast and in Liverpool Bay, and is linked to reduced intra-specific competition for food.