Spatial and temporal distribution of fish in a small lowland stream

Abstract  The fish fauna and habitat characteristics in five reaches of a small lowland stream were studied through the summer and winter of one year. All species densities, except Atlantic salmon, Salmo salar L., were correlated with either instream or outstream cover, reaffirming the importance of cover to maintain the local abundance of fish populations. There were significant differences between reaches in the density of all the fish species studied, with the exception of the larger size group of dace. Leuciscus leuciscus (L.), and between sampling times for salmon, dace and eel, Anguilla anguilla (L.). There were significant differences between reaches for all the measured habitat variables apart from instream cover, and between sampling times for velocity. instream cover, and substrate particle size, but not depth, width:depth ratio and outstream cover. The implications of these variations for fish stock assessment and predictive fish habitat models such as PHABSIM and habitat suitability indices are discussed.