Spatial variability in diet, condition and growth of juvenile plaice (Pleuronectes platessa) at sandy beach nursery grounds on the south-west coast of Ireland

Characterization of suitable habitat for settlement of juvenile flatfish is important for the management of nursery areas. Food availability is one important determinant of habitat quality that can affect the condition and growth, and thus survival, of flatfish. Spatial and temporal variation in diet has been widely studied for several species of flatfish. However, levels of intraspecific variation in diet at small spatial scales are relatively unknown, with most studies focusing only on large scale variability. This study investigates how diet, growth and condition of juvenile plaice, Pleuronectes platessa, varies over two spatial scales (10s of kilometres and 100s of metres). Juvenile plaice were collected from three beaches and from three replicate hauls on each beach using a beach seine in September 2007 and 2008. Gut content analyses of 108 juvenile plaice within the size-range of 70-90 mm were carried out. Diet composition in plaice guts differed among beaches and hauls suggesting that food abundance and availability differed at both spatial scales. A significant positive correlation was observed between a morphological condition index and the prey diversity in the gut. This suggests that fish which specialize on a limited number of prey items (perhaps due to a greater abundance of certain prey) may do better than fish which feed on a wide range of prey types. Significant differences in condition were observed between hauls and between beaches, while recent and total otolith growth varied between beaches but not between hauls. The results highlight the importance of considering small scale variation when attempting to link habitat quality to feeding, growth and condition of juvenile flatfish.