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

Spatial distribution patterns of newly settled plaice (Pleuronectes platess a) were investigated along a 200 km coastline of the Swedish Skagerrak arch ipelago. Juvenile plaice were sampled quantitatively with a drop-trap in 32 small (0.02-0.04 km(2)) 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 re sulting sight sub-areas two randomly allocated pairs of closely situated (5 00-1000 m) bays were sampled, so that variation in post-settlement densitie s of plaid could be tested over different scales from hundreds of metres to tens of kilometres. Plaice density varied significantly on a regional scale, with order-of-magn itude 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 sign ificantly higher densities of juvenile plaid than bays in the inner archipe lago. However, considerable variation was also found on a smaller spatial s cale, with significant differences in plaice density within pairs of bays. The seasonal development in growth and mortality of juvenile plaice was stu died in a sub-sample of bays characterised by high, medium and low post-set tlement densities in May. Three bays from each group were revisited in July and August. Growth rates showed negative, and mortality rates positive, de nsity-dependent relationships with plaice density. The observed patterns in settlement densities of plaice reflected the poten tial for variation in larval supply, local habitat characteristics and pred ation, over the spatial scales investigated. In addition, we outline the pr ocesses likely to produce density-dependent relationships in growth and mor tality rates of juvenile plaice. (C) 2000 Elsevier Science B.V. All rights reserved.