Dietary overlap of invertivorous fishes and macroinvertebrates in the Gila River, New Mexico

The diets of stoneflies (Perlodidae) and hellgrammites (Corydalidae) from the Gila River, New Mexico, were quantified and compared to diets of three native fishes that also occupy riffle habitats along with stoneflies and hellgrammites: speckled dace (Rhinichthys osculus); longfin dace (Agosia chrysogaster); desert sucker (Catostomus clarkii). The highest overlap occurred among corydalids, desert sucker, and longfin dace, which had diets dominated by amorphous detritus. Speckled dace and perlodids consumed less amorphous detritus, with nymphs of mayflies and larval black flies dominating their respective diets. Our results suggest moderate to high overlap of resources among invertivorous fishes and invertebrates. Although we found high dietary overlap between corydalids and two fishes, it is unclear whether amorphous detritus is a limiting resource that drives competitive interactions. RESUMEN—Las dietas de las moscas de la roca (familia Perlodidae) y de la mosca Corydalidae (familia Corydalidae) del rı́o Gila, Nuevo México, fueron cuantificadas y comparadas con las dietas de tres peces 292 vol. 59, no. 2 The Southwestern Naturalist