DIET AND DENTITION IN TROPICAL ARID CATFISHES FROM AUSTRALIA

The diets of 13 species of ariid catfishes from the tropical waters of the Gulf of Carpentaria are described and compared. Fishes were colle cted from two estuaries and inshore and offshore marine areas. Up to 1 0 species have been recorded from a single estuary. Although all are c arnivorous and consume a variety of prey, diet analyses and statistica l ordination reveal three feeding guilds - piscivores, polychaete-eate rs and molluscivores. The diets of most species are similar between si tes. There are strong relationships between dietary guild and the size and arrangement of the palatine teeth. The piscivorous group of catfi sh (guild 1) have large mouths with relatively large multiple palatine tooth plates, either in a band or in a triangular pattern and armed w ith sharp recurved teeth. The primarily polychaete-feeding group (guil d 2) have a variable mouth size but it is usually smaller than that of guild 1 fish; their palatine teeth plates are fewer and smaller, and they have small, sharp recurved teeth. Guild 3 eat mainly molluscs, an d have a small mouth and large posteriorly situated palatine plates wi th globular, truncated teeth. Overlaps in diet between species are pro bably reduced by differential distribution patterns within estuaries a nd different habitat preferences. The mouth-width and tooth-plate arra ngements of ariids in tropical Australia are suitable for dealing with broad classes of prey rather than specific items, conferring dietary flexibility. This probably optimizes the trade-off for most species be tween occupation of broad feeding niches and the ability to shift diet easily.