Nature and Functions of Cover for Riverine Fish.

Abstract

This review attempts to assess the nature and the role of cover for riverine fish assemblages. Although early identified as a key factor for fish distribution, especially for salmonids, cover (i.e. woody debris, undercut banks, boulders, turbidity...) still remains the variable least considered in the studies of fish habitat relationships. This is mainly due to the diversity of ecological functions of cover structures in fish assemblages. Cover structures are structuring components of fish habitat and contribute to the biological productivity of streams. But, at the individual scale, cover fulfils three main functions: protection against predators, visual isolation reducing competition, and hydraulic shelter. In fact, the use of cover by fish results from a trade-off between the costs and the benefits associated with its use. Although the relationships between fish and cover appear extremely complex and context-specific, a growing body of evidence highlights the potential role of cover for management purposes.Key-words : cover, shelter, riverine fish, fish habitat. NATURE ET FONCTIONS DU COUVERT POUR LES POISSONS LOTIQUES. RÉSUMÉCet article décrit la typologie ainsi que les fonctions du couvert pour les poissons lotiques. Identifié très tôt comme un facteur explicatif de la distribution des poissons, principalement chez les salmonidés, le couvert (i.e. débris ligneux, sous-berges, blocs, turbidité...) demeure néanmoins la variable la moins considérée dans l'étude des relations habitat-poissons. Ceci s'explique notamment par les fonctions écologiques très diverses que le couvert remplit vis-à-vis des assemblages piscicoles. Les structures pourvoyeuses de couvert sont des agents structurants de l'habitat piscicole et contribuent à la productivité biologique des cours d'eau. Au niveau du microhabitat du poisson, le couvert remplit trois fonctions majeures : anti-prédation, isolation visuelle limitant la compétition, et abri hydraulique. En fait, l'utilisation du couvert par les poissons résulte d'un compromis entre les coûts et les bénéfices associés d'où l'extrême complexité de cette relation qui semble plutôt spécifique à un contexte donné. Malgré les difficultés d'extrapolation, de nombreux travaux mettent en évidence la signification écologique ainsi que l'utilisation potentielle du couvert pour une gestion optimale des ressources piscicoles.Mots-clés : couvert, abri, poissons lotiques, habitat piscicole.

Fish assemblage structure in urban streams of Puerto Rico: the importance of reach- and catchment-scale abiotic factors

“…High substrate diversity and depth coefficient of variation enhance overall species richness and biomass because individual species often require specific substrates and depths for their growth, survival, and reproduction. In other contexts, individual species use specific substrates for hydraulic and predatory refugia (Allouche, 2002), spawning (Tamada, 2011), and feeding (Fitzsimons et al, 2002). A reach with varied depths would be expected to provide predatory refugia for both small and large fish species (Power, 1987).…”

Can the presence of alien Ponto–Caspian gobies affect shelter use by the native European bullhead?

“…For both groups, the accessibility of shelter habitat is essential during the spawning period due to their similar reproductive strategies, including nest guarding and parental care of eggs (Goto 1982;Grabowska 2005). Moreover, shelters play also a significant role as a protection against predators, visual isolation and hydraulic cache (Allouche 2002). That is why for some species, shelter is fundamental not only during reproduction, but throughout the year (Mills and Mann 1983;Allouche 2002).…”

“…Moreover, shelters play also a significant role as a protection against predators, visual isolation and hydraulic cache (Allouche 2002). That is why for some species, shelter is fundamental not only during reproduction, but throughout the year (Mills and Mann 1983;Allouche 2002).…”

Optimal flow for brown trout: Habitat – prey optimization

“…Refugia can be vegetation (aquatic or overhanging), wood debris, undercut banks and many others (Allouche, 2002) but in the studied sites the discontinuities in the riverbed profile where the depth of water was higher than 0.30 m and the MSS was N0.5 m (boulders and blocks) were the only available refugia.…”