A predator-prey size relationship for Plaice larvae feeding on <i>Oikopleura</i>

Abstract

SUMMARY Pelagic plaice larvae in the southern North Sea normally feed exclusively on the appendicularian Oikopleura dioica, and the size of prey eaten can be estimated from the Oikopleura faecal pellets found in the larval gut Predator-prey size measurements show that smaller plaice larvae are restricted to smaller prey, and that, as larval growth proceeds, so their feeding versatility increases, to include all sizes of Oikopleura at a late pelagic stage of development. Competition for food will therefore be keenest in the early larval stages, when prey-size restriction prevails. This accords with Hjort's hypothesis regarding brood strengths. As growth proceeds, so plaice larvae begin to discriminate for prey size. At the close of the pelagic phase, the degree of size selection is roughly equal to that of a 6o-mesh to i in. plankton net.