WIND-INDUCED TRANSPORT OF PLAICE (PLEURONECTES-PLATESSA) EARLY LIFE-HISTORY STAGES IN THE SKAGERRAK-KATTEGAT

Identifying mechanisms of exchange between adjacent fish populations i s important to understanding causes of fluctuations in abundance. This study addresses the hypothesis that the abundance of settled O-group plaice along the Danish coast of the Kattegat depends on transport fro m the Skagerrak. Abundance data are derived from annual (1957-1994; 10 -15 years missing depending on sample site) juvenile fish surveys cond ucted at four sites by the Danish Institute for Fisheries Research. Th e O-group abundance measured in July-August is significantly higher in years when wind conditions during the larval development period (Marc h-April) were moderate to strong. Meristic variation (number of anal f in rays) depends on wind conditions in a manner consistent with the ro le of wind on abundance. In years with strong winds, meristic variatio n along the coast is low due to influx of progeny from the Skagerrak; in years with weak winds (when influx of Skagerrak progeny is low), re gional variation in meristic counts is larger. These abundance and mer istic patterns are consistent with historical observations of stock di stribution and mixing in the area, and demonstrate the potential for p hysical processes to mediate exchange of eggs and larvae between areas . Abundances showed no evidence of long-term changes, even after allow ing for the significant role of wind on abundance, and despite eutroph ication of the Kattegat. (C) 1998 Elsevier Science B.V. All rights res erved.