The role of seagrass as preferred habitat for juvenile sillaginodes punctata (cuv. & val.) (sillaginidae, pisces): habitat selection or feeding?

Abstract

Previous experiments have shown that the relationship between abundance of juvenile fishes and seagrass density is the result of habitat selection rather than direct predation, but have not distinguished between habitat selection and simple feeding. The simple feeding model, in which fish swim until they find food, eat it, and swim again, predicts that fish will be found where the most food is available regardless of the presence or density of seagrass. Food availability was manipulated in tanks in which juvenile Sillaginodes punctata (Cuv. & Val.) (King George whiting) were offered the choice of two habitats, live eelgrass ( Zostera muelleri Irmisch ex Aschers.) or unvegetated sand. When food was available, fish were initially distributed in a way that strongly supported the feeding model, but once they were satiated, the distribution of fish fitted the predictions of neither model. In the absence of food, fish selected eelgrass habitat. At night, the distribution of fish showed that they took little account of food availability or habitat.