CHANGES IN GROWTH OF NORTH-SEA PLAICE SINCE 1950 IN RELATION TO DENSITY, EUTROPHICATION, BEAM-TRAWL EFFORT, AND TEMPERATURE

Annual length increments of female North Sea plaice were back-calculat ed from distances between rings in otoliths. Growth of the smaller siz e classes (<25 cm) increased from the mid-1950s and decreased in the 1 980s. Length increments of intermediate size classes varied more or le ss randomly, and those of the larger size classes (>35 cm) increased f rom 1970. Growth changes of the smaller size classes were significantl y correlated with indices of plaice density, eutrophication, and seabe d disturbance by beam trawling. Moreover, they could be related to spa tial and temporal patterns in variations in eutrophication and beam tr awling. No correlation was observed with temperature. The analysis led to a consistent interpretation suggesting that eutrophication and bea m trawling have both affected the growth rate of plaice. The contribut ions of these factors differed in space. Effects of eutrophication dom inated in the shallow coastal waters, whereas beam trawling dominated in the waters further offshore. (C) 1996 International Council for the Exploration of the Sea