Variation in Cyprinid Feeding Habits Mediated by Habitat and Morphology

The relationships between food availability, habitat, morphology, and consumer diet has long been of interest for ecologists.  Among fishes, there exists a high degree of diet variability, especially within Cyprinidae.  We investigated differences in the feeding habits of two ubiquitous cyprinids in central Texas streams, blacktail shiners (Cyprinella venusta) and Texas shiners (Notropis amabilis).  We recorded if individual fishes were captured from riffle or pool habitats and examined their alimentary digestive tract, measuring the head capsules of invertebrate prey remains when possible.  We sampled prey availability in both the benthos (Surber sampler) and the drift (pan traps and drift nets) for both riffle and pool habitats. Each species of fish was primarily found in riffle habitats and both mostly consumed prey items found in drift samples but the particular types of prey these two fish species consumed differed with respect to prey size.  The Texas shiner was found to have the greater average gape width to body size ratio and fed upon larger prey items but the blacktail shiner achieved larger sizes and fed upon a greater variety of prey.  The differences we observed in diets among these two minnows might be partially explained by subtle differences in their morphologies.