VARIABILITY OF FISH DENSITIES IN A SMALL CATCHMENT

Temporal and spatial variability of fish communities were examined wit hin a 91-km(2) catchment in central New York over four years. Riffle-d welling species, slimy sculpin Cottus cognatus, longnose dace Rhinicht hys cataractae, and young-of-the-year brown trout Salmo trutta, were m ore strongly affected by flood and drought than pool-adapted species, adult brown trout, blacknose dace Rhinichthys atratulus, white sucker Catostomus commersoni, and creek chub Semotilus atromaculatus. Canonic al correspondence analysis using seven abiotic variables (mean width, residual pool depth, water surface slope, mean Froude number, variance in Froude number, maximum monthly discharge and minimum monthly disch arge) separated fish communities among sites and years. The first axis represented a head water-to-valley gradient; the second axis reflecte d habitat complexity, based on both geomorphic and hydraulic features. Temporal differences in fish densities were related to hydrological f actors. Fish communities throughout the catchment showed similar respo nses to flood and drought.