Abundance of fishes was determined at stations located in several western Manitoba streams. By use of a multivariate classification procedure, groups of species were identified which were similar in their distribution among arbitrarily defined habitat types. The largest group of species was associated with areas of low current speed, but within high gradient sections of the streams. Species diversity (defined as the number of fish species present) was related to structural features of the environment. By an analysis of variance technique, it was concluded that stream gradient and current speed explained most of the variation in diversity. When a predator (Esox lucius) was present, diversity and abundance of the remaining species were both reduced.