Winter habitat of selected stream fishes and potential impacts from land-use activity

This paper reviews the habitat characteristics and the behaviour of selected stream fishes during winter in temperate-boreal ecosystems. Emphasis is placed on the salmonid fishes upon which most winter research has been directed. As space is the primary factor regulating stream fish populations in winter, aspects of winter habitat are considered at various spatial scales from microhabitat to stream reach to river basin. Choice of winter habitat is governed by the need to minimize energy expenditure, with the main criterion being protection from adverse physicochemical conditions (e.g., ice, spates, low oxygen). The distance moved to wintering habitats, and the continued activity by many fishes during winter, need to be considered when making management decisions regarding fish habitat. How habitat is affected by land-use activity in stream catchments is discussed with reference to impacts from water withdrawal, varying discharge regimes, and erosion or sedimentation. Even stream enhancement practices can deleteriously affect fish habitat if project managers are unaware of winter habitat requirements and stream conditions. Maintenance of habitat complexity, at least at the scale of stream sub-basin, is recommended to ensure the diversity of winter habitats for fish communities. Resume : Le document fait l'examen des caracteristiques de l'habitat et du comportement de certains poissons de cours d'eau pendant l'hiver en ecosystemes temperes ou boreaux. L'accent est mis sur les salmonides qui ont fait l'objet de la plus grande partie des recherches effectuees en hiver. L'espace etant le premier facteur regissant les populations de poissons de cours d'eau en hiver, les aspects de l'habitat d'hiver sont examines en fonction de diverses echelles spatiales allant du micro-habitat, au segment et au bassin du cours d'eau. Le choix de l'habitat d'hiver est regi par le besoin de minimiser les depenses energetiques et a pour critere principal la protection contre les conditions physiques et chimiques adverses (glaces, crues, faible teneur en oxygene). La distance parcourue pour atteindre les habitats d'hivernage et le maintien de l'activite d'un grand nombre de poissons pendant l'hiver doivent etre pris en compte au moment de la prise de decisions de gestion