THE MAXIMUM GROWTH OPTIMAL FOOD CONDITION HYPOTHESIS - A TEST FOR 0-GROUP PLAICE PLEURONECTES-PLATESSA IN THE DUTCH WADDEN SEA

A test of the 'maximum growth/optimal food condition' (MG/OFC) hypothe sis is described for 0-group plaice Pleuronectes platessa L. in the we stern Dutch Wadden Sea. The MG/OFC hypothesis assumes optimal food con ditions (i.e. no competition for superfluous food and hence no negativ e density-dependent growth) and consequently a maximum growth rate onl y determined by prevailing water temperature conditions. Growth of 0-g roup plaice subpopulations was determined for a number of areas differ ing in food abundance and composition (benthic biomass of potential fo od items) and density of 0-group plaice in both the intertidal and the sublittoral. Growth showed a positive relationship with food abundanc e, in both the intertidal and the sublittoral, falsifying the MG/OFC h ypothesis. At similar food abundance, growth in the intertidal was alw ays higher than in the sublittoral due to the presence of the lugworm Arenicola marina in the intertidal only. In the intertidal, growth was positively related to density of A. marina. The assumption of the MG/ OFC hypothesis of no negative density-dependent growth was confirmed b oth in the intertidal and in the sublittoral, although it did not resu lt in maximum growth rate for 0-group plaice everywhere in the field. Differences in growth rate therefore do not necessarily reflect compet ition for food and density-dependent growth, but they might reflect di fferences in food composition and availability (searching and handling time).