Diet of Gambusia affinis holbrooki, Xiphophorus helleri, X. maculatus and Poecilia reticulata (Pisces: Poeciliidae) in Streams of Southeastern Queensland, Australia

Abstract

The diets of four introduced Poeciliidae, Gambusia affinis holbrooki, Xiphophorus helleri, X. maculatus and Poecilia reticulata, were studied in subtropical streams, southeastern Queensland, Australia. The prey of greatest importance in G. affinis diets was usual]y of terrestrial origin, i.e. ants and adult nematoceran Diptera, but aquatic Hemiptera and other aquatic taxa were also important in some habitats. G. affinis ate invertebrate prey that were small relative to body size and mouth gape (mean prey width 0.3 x mouth gape, mean prey length 1.28 x mouth gape) and relative to the sfze range of prey present (mean prey ingested = 0.597 x mean length and 0.702 x mean width of availability prey in the environment equal to or smaller than the largest prey eaten). Some aquatic taxa (e.g., immature Trichoptera and Ephemeroptera, Oligochaeta, Crustacea and Mollusca) of the preferred size range which were abundant in the streams were eaten infrequently. X. helleri was omnivorous, consuming aquatic plant tissue, filamentous and other algae and aquatic and terrestrial invertebrates. X. maculatus consumed Crustacea and aquatic and terrestrial insects, with dominance of the atyid shrimp, Caridina. P. reticulata had a more diverse diet composed largely of terrestrial insects, particularly ants; chironomid larvae were the dominant aquatic taxon eaten. The four species of poeciliids had significantly different mean diet composition. The implications of poeciliid feeding for sympatric endemic fishes are briefly discussed.