Variability in the early life stages of juvenile plaice (Pleuronectes platessa) on west of Ireland nursery grounds: 2000–2007

Plaice (Pleuronectes platessa) are the most abundant juvenile flatfish present on west of Ireland nursery grounds. o-group plaice were collected from eleven sandy beach nursery areas along the west coast of Ireland by beach seining (2000-2007). In the majority of years examined, certain beaches were found to support a higher abundance of juvenile plaice, or individuals that were larger in size and exhibited good condition, suggesting that differences in habitat quality exist between beaches. Monthly mean densities of plaice ranged from 2.4 (+/- 2.4) to 100 (+/- 1.3) individuals 1000 m(-2). Mean lengths of plaice ranged between 6.0 (+/- 1.0) and 10.1 (+/- 0.5) cm. No evidence of density dependent growth was detected over the eight years of the study. The length and condition of juvenile plaice also differed between hauls, indicating the existence of micro-habitat effects and emphasizing the importance of selecting an appropriate spatial resolution to adequately assess an area. Similar to other locations in Europe, juvenile plaice abundances on nursery grounds were inversely related to mean spring seawater temperatures during the pelagic stage. Abundances of o-group plaice were not related to the number of either 1- or 2-group individuals collected during bottom-trawl surveys off the Irish west coast, demonstrating the difficulties associated with developing a recruitment index for plaice.