A descriptive and experimental study of microhabitat use by young‐of‐the‐year benthic stream fishes

Abstract

Abstract– We studied microhabitat use of young‐of‐the‐year (YOY) benthic stream fishes (Cottus, Etheostoma, Percina) using underwater surveys conducted in the Little River of Tennessee, United States. At the upstream site, only Cottus was present and its density was low. Further downstream all genera were present, and YOY density was high and concentrated in deep water habitats. Microhabitat use by the species differed from microhabitat availability, with most species using deep, slow‐moving water with silt‐free, coarse substrates that lacked riverweed, Podostemum ceratophyllum. Despite differences in microhabitat use, there was substantial overlap among species. Because YOY were positively associated with coarse substrates and coarse substrates were uncommon in deep water, we tested their importance by adding cobbles to 3 deep water habitats. We found that YOY benthic fishes colonized areas with cobbles but not sand. After 2 months, however, many of the cobble areas were covered by sediment. These data suggest that YOY fish are substrate‐limited in deep water habitats and that the hydrological properties of pools preclude establishment of permanent instream cover. It is unclear why YOY occur in areas with little instream cover.