Feeding habits of two introduced fish species (Lepomis gibbosus, Pseudorasbora parva) in Neusiedler See (Austria), with special reference to chironomid larvae (Diptera: Chironomidae)

In Neusiedler See, a turbid shallow lake, Lepomis gibbosus (L.) and Pseudorasbora parva (Temminck & Schlegel) occur in large numbers within the reed belt. In April, June/July, August and September 1995, fishes were collected for gut analyses. The diet of both species consisted mainly of chironomid larvae. 0+ L. gibbosus whose total length exceeded 26 mm and 0+ P. parva larger than 32 mm preyed on chironomids almost exclusively. The food of > 0+ L. gibbosus, in addition to chironomids, was made up of other aquatic insects (e.g. Zygoptera nymphs, Corixidae and Trichoptera larvae), gastropods and Asellus aquaticus L. The diet of > 0+ L. gibbosus showed distinct seasonal variations. Detailed analyses of the chironomid larvae in the stomachs of the two fish species provided valuable information on their feeding grounds. Whereas L. gibbosus preyed mainly on sediment-dwelling chironomids, P. parva preferred epiphytic species. Diet overlaps between L. gibbosus and P. parva and other abundant fish species in the reed belt (Anguilla anguilla (L.), Blicca bjoerkna (L.), Gymnocephalus cernuus (L.)) are discussed.