Growth-related changes in diet and foraging behavior of the yellow wrasseThalassoma lutescens at Kuchierabu Island

Ontogenetic changes in diet and foraging behavior ofThalassoma lutescens were examined in shallow reef habitats around Kuchierabu Island, southern Japan. This species mainly took small benthic invertebrates, including gammarids, polychaetes, sipunculids, chitons, crabs, gastropods, pelecypods and urchins from algal mats. Larger fish consumed correspondingly larger prey, although most of the latter were armored with hard exoskeletons, shells or body plates (e.g., crabs, gastropods, pelecypods and urchins). Such hard parts were crushed with the molar-like, pharyngeal teeth which develop with fish growth, allowing exploitation of such larger, hard-bodied prey. Because the densities of larger prey species were relatively low in the initial habitats foraged, larger fish shifted their foraging attention to rock and coral crevices, where the prey species dwelt in greater numbers, as well as foraging over larger areas. Such behavioral changes maintained high foraging efficiency in larger fish.