Stepwise Increases in Maximum Prey Size of Larval Creek Chubs, Semotilus atromaculatus, in an Urbanized Ohio Stream

Abstract

Abstract The diet of larval Semotilus atromaculatus (Creek Chubs) was examined in fish collected from an urbanized stream with a limited food base. Chironomids comprised nearly 90% of food items. They appeared in the gut of early larvae and continued to be the main food source as size increased; cladocerans were the second most abundant food item. Both average and maximum prey size were examined. Overall, average prey size increases significantly with standard length (SL). Maximum prey size is gape-limited twice, from the early to mid-mesolarval stage and again in the late mesolarval stage. Significant differences were observed in the maximum size of chironomids ingested among fish of four size ranges, 14.1 mm SL, indicating maximum prey size increases rapidly at 8.0 mm SL, 9.6 mm SL, and again at 14.1 mm SL, yet maximum prey size within each group remains constant. The degree of cranial ossification and fin development at these break points was examined wit...