FISH ASSOCIATIONS WITH 4 HABITAT TYPES IN A SOUTH-DAKOTA PRAIRIE STREAM

Fish were collected from riffles, runs, pools and woody habitats in th e Vermillion River, South Dakota, to examine the temporal dynamics of habitat use during non-flood summer months. The densities of small fis hes (30-75 mm; cyprinids and young-of-the-year individuals) were great est in riffles and woody habitats during periods of moderate discharge (1.14 and 1.44 m(3)/s); however, their densities were greater in riff les than other habitats during late summer low now (0.49 m(3)/s). Larg e fishes (> 75 mm; juvenile and adult individuals of several species) were distributed evenly among habitats across flow levels. During mode rate stream flows, 89% and 95% of the individual species and size clas ses exhibited random use of habitats. In contrast, 35% of the individu al species collected during late summer low stream flows exhibited pre ferences for two or three habitats, but only one species (central ston eroller Campostoma anomalum) exhibited a preference for a single habit at type (riffles). We found Little evidence for the existence of discr ete habitat guilds of fish because neither individual species nor grou ps of species consistently associated with a single habitat type. We s uggest a community-level approach based on the combined densities of s mall and young-of-the-year fishes, rather than an individual species o r guild approach, be used to define fish associations with habitat in hydrologically variable prairie streams because discrete patterns of h abitat use exist at the community level.