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 Pseudor asbora parva (Temminck & Schlegel) occur in large numbers within the reed b elt. In April, June/July, August and September 1995, fishes were collected for gut analyses. The diet of both species consisted mainly of chironomid l arvae. 0+ L. gibbosus whose total length exceeded 26 mm and 0+ P. parva lar ger than 32 mm preyed on chironomids almost exclusively. The food of > 0+ L . gibbosus, in addition to chironomids, was made up of other aquatic insect s (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. pa rva preferred epiphytic species. Diet overlaps between L. gibbosus and P. p arva and other abundant fish species in the reed belt (Anguilla anguilla (L .), Blicca bjoerkna (L.), Gymnocephalus cernuus (L.)) are discussed.