LONGITUDINAL AND TEMPORAL COMPARISONS OF RIFFLE AND POOL FISH ASSEMBLAGES IN A NORTHEASTERN OKLAHOMA OZARK STREAM

I compared fish assemblages of riffles and pools in Battle Branch, a small upland stream in Delaware County, Oklahoma. Monthly seining collectiotions were made for a year at nine stations, each covering 200 m, along a 6 km total reach from extreme headwaters to near the confluence with a larger stream. In both riffle and pool habitat types, assemblage composition was related to water depth and substratum size and thus to longitudinal position in the stream. However, the commonly described longitudinal pattern of downstream increase in species richness and abundance was reflected better in assemblages of pools than of riffles. Temporal patterns were related to changes in species richness and fish abundance, especially of juveniles. Unlike pools, most of the variance in riffle assemblage structure was temporal. Riffles may be supplemental habitats or refuges for juveniles of taxa found primarily in pools, whereas pools serve as refuges during drought or floods for taxa found primarily in riffles.