Variability of fish densities in a small catchment

Temporal and spatial variability of fish communities were examined within a 91-km² catchment in central New York over four years. Riffle-dwelling species, slimy sculpin Cottus cognatus, longnose dace Rhinichthys cataractae, and young-of-the-year brown trout Salmo trutta, were more 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 atromacitlatiis. Canonical 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 discharge) separated fish communities among sites and years. The first axis represented a headwater-to-valley gradient; the second axis reflected habitat complexity, based on both geomorphic and hydraulic features. Temporal differences in fish densities were related to hydrological factors. Fish communities throughout the catchment showed similar responses to flood and drought.