Relation entre habitat et peuplements de poissons: Essai de definition d'une methode numerique pour des rivieres nordiques

Abstract

A study of fish communities was conducted in downstream sections of the Nottaway, Broadback and Rupert Rivers, northern Québec, in order to establish a relationship between communities and their habitat. The areas sampled are relatively homogenous and the number of species present is limited to 18, of which 11 are not abundant. Physical similarity between the 163 sampling stations is established using 5 characteristics observed in the field and is computed using a coefficient derived from the metric of Canberra. Six types of habitat are identified from the complete linkage clustering of the matrix of similarities between stations. Discriminant analysis of fish communities results in a prediction success of about 60% in classifying samples in their own habitat. This proposed numerical procedure may therefore be used as management tool.

The community structure is interpreted in terms of the physical characteristics of the environment. Relative abundances of the 4 most discriminating species between habitats seem to be determined by water transparency, current speed and abundance of aquatic vegetation, these two last variables interacting in a complex fashion. Changes in community structure that arise because of predictable physical alterations to the environment may therefore be predicted only by relatively sophisticated numerical procedures, at least when the physical environment is relatively homogeneous and the species diversity low, as in northern rivers.