Aquatic Habitats and Fish Distribution in a Large Oklahoma River, the Cimarron, from 1975 to 1986

were established and a 200-meter area was sampled two or three times yearly. A total of 50 species and 347,902 specimens were used to compare the four major ecoregions and the ten sampling sites. The composition, abundance, seasonal and spatial distribution, and diversity of the fish populations were determined for each station. The ichthyofaunal data were used to correlate certain water quality parameters with spatial and temporal components of fish communities. Alterations of these community parameters were most pronounced in areas of elevated mineralization due to high levels of chlorides and sulfates. Overall fish abundance, species diversity, species counts, and species distribution at sites of elevated salinity were significantly affected. The changing patterns of the community characteristics during the ten-year period were summarized with special emphasis on their connection with certain chemical and physical changes in the river. A new fish community richness rating scale was utilized, and showed a distinct relationship in the spatial distribution and the ratings during this study. Most of the upper stations were rated as "poor " fish communities; the downstream stations were rated as "fair".