DIEL FEEDING CHRONOLOGIES IN TWO SONORAN DESERT STREAM FISHES, AGOSIA CHRYSOGASTER (CYPRINIDAE) AND PANTOSTEUS CLARKI (CATOSTOMIDAE)

Diel feeding chronologies in two desert fishes, Agosia chrysogaster (longfin dace) and Pantosteus clarki (Gila mountain sucker), were determined by examining the foregut contents of fishes taken from Sycamore Creek, Maricopa Co., Arizona. A comparison of algae in foreguts with algae collected from the stream suggests that these species have distinct feeding chronologies and foraging areas. Pantosteus clarki consumes benthic diatoms and small amounts of detritus while A. chrysogaster feeds on filamentous green algae, benthic and epiphytic diatoms, and detri- tus. Peaks of ingested food volume indicate that A. chrysogaster is a diurnal feeder whereas P. clarki feeds both day and night, with crepuscular peaks. Fishes may assume an important role in ecosystem metabolism through feeding activities. To evaluate their role in the metabolism of a desert