Spatial distribution patterns of newly settled plaice (Pleuronectes platessa L.) along the Swedish Skagerrak archipelago

Spatial distribution patterns of newly settled plaice (Pleuronectes platessa) were investigated along a 200 km coastline of the Swedish Skagerrak archipelago. Juvenile plaice were sampled quantitatively with a drop-trap in 32 small (0.02–0.04 km2) nursery bays over a 13-day period in mid-May 1998. The investigated area was divided into four geographical regions along the coast, each with an inner and an outer archipelago zone. In each of the resulting eight sub-areas two randomly allocated pairs of closely situated (500–1000 m) bays were sampled, so that variation in post-settlement densities of plaice could be tested over different scales from hundreds of metres to tens of kilometres. density varied significantly on a regional scale, with order-of-magnitude higher densities in the northern (22.3 ind. m−2) than southern (2.3 ind. m−2) bays. Further, bays situated in the outer archipelago had significantly higher densities of juvenile plaice than bays in the inner archipelago. However, considerable variation was also found on a smaller spatial scale, with significant differences in plaice density within pairs of bays. asonal development in growth and mortality of juvenile plaice was studied in a sub-sample of bays characterised by high, medium and low post-settlement densities in May. Three bays from each group were revisited in July and August. Growth rates showed negative, and mortality rates positive, density-dependent relationships with plaice density. served patterns in settlement densities of plaice reflected the potential for variation in larval supply, local habitat characteristics and predation, over the spatial scales investigated. In addition, we outline the processes likely to produce density-dependent relationships in growth and mortality rates of juvenile plaice.