Feeding ecology of sterlet Acipenser ruthenus L. in the Hungarian section of the Danube River

The aim of the study was to describe the feeding habits of sterlet, Acipenser ruthenus L., in the mid section of the Danube (km 1676-1694). The fish were caught in the summers of 1991 and 1992. The food composition of 85 sterlets (mean body length BL = 37.1 cm; body weightW= 540 g) was analyzed. Most of the fish analyzed (98.8%) had full digestive tracts. Sterlet is considered to be a typical benthic feeder. The food analyzed contained insect larvae and pupae (Trichoptera, Chironomidae), amphipods (Corophium sp., Gammarus sp.), bivalves (Bivalvia), polychaetes (Annelida) and barbel, Barbus barbus (L.). The dominant food items in the digestive tracts were larval caddisflies (Trichoptera), Corophium (Amphipoda), and larval Chironomidae. Regardless of sterlet body size, the fish consumed Chironomidae followed by Trichoptera. The remaining components were noted in the food rarely and in small quantities. One exception were bivalves that were a considerable dietary component of the largest sterlet size group.