Great Basin Naturalist


Native fishes in Aravaipa Creek, Arizona, cropped foods proportional to abundance of those foods within the system. Ephemeropteran nymphs and adults comprised the major prey of 5 of 7 fishes (Gila robusta, Meda fulgida, Rhinichthys osculus, Tiaroga cobitis, and Catostomus insignis). The omnivorous Agosia chrysogaster ate almost as many nymphal mayflies as did the carnivores. Pantosteus clarki was herbivorous, taking animals only when they were abundant. When ephemeropterans decreased in abundance, a shift by some fish species occurred to other locally or seasonally abundant items. Other fishes continued to feed upon the same foods throughout the year. Abundance of invertebrates in Aravaipa Creek, coupled with marked spatial partitioning of habitat by fishes present, seemingly precluded severe interspecific interactions for food.