The 'maximum growth/optimal food condition' hypothesis: a test for 0-group plaice Pleuronectes platessa in the Dutch Wadden Sea

Abstract

A test of the 'maximum growth/optimal food condition' (MG/OFC) hypothesis is described for 0-group plaice Pleuronectes platessa L. in the western Dutch Wadden Sea. The MG/OFC hypothesis assumes optimal food conditions (i.e. no competition for superfluous food and hence no negative density-dependent growth) and consequently a maximum growth rate only determined by prevailing water temperature conditions. Growth of 0-group plaice subpopulations was determined for a number of areas differing in food abundance and composition (benthic biomass of potential food items) and density of 0-group plaice in both the intertidal and the sublittoral. Growth showed a positive relationship with food abundance, in both the intertidal and the sublittoral, falsifying the MG/OFC hypothesis. At similar food abundance, growth in the intertidal was always 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 densitydependent growth was confirmed both in the intertidal and in the sublittoral, although it did not result in maximum growth rate for 0-group plaice everywhere in the field Differences in growth rate therefore do not necessarily reflect competition for food and density-dependent growth, but they might reflect differences in food composition and availability (searching and handling time).