Resource sharing among darters in an Ohio stream [Etheostoma caeruleum, Etheostoma zonale, Etheostoma blennioides, fishes, predator-prey interactions]

This study quantified predator-prey interactions involving three darter species (Etheostoma caeruleum, E. zonale and E. blennioides) and macroinvertebrates of the upper Little Miami River, Ohio, and the extent of seasonal food and habitat partitioning among these fishes. Food overlap values (Cλ) based on biomass were generally lower than those computed from the numbers of prey items in the annual diets (Cλ= 0.41-0.75 and 0.72-0.84, respectively). These differences reflected size-selective feeding behavior and variability in the dry weights of food organisms. Feeding intensity was influenced by water temperature, while the contributions of the various invertebrate taxa to the diets shifted with changes in the abundances of these forms. Etheostoma zonale and E. blennioides selected food items in the size ranges of 1-5 and 1-6 mm, respectively; the range for E. caeruleum was 1-9 mm. Darter numbers in the riffles changed seasonally in response to the timing of reproduction. These shifts resulted in low overlap values (Cλ= 0.41-0.44) based on habitat use. We concluded that the darters coexist through resource sharing which reduces interspecific competition for food and space.