Multi-scale analysis of habitat use during late summer for 0+ fishes in the River Garonne (France)

Abstract

Relationships between environmental variables and 0+fish in the upper River Garonne (France) were studied at different habitat scales during late August 1995. In total, 3911 0+ fish representing 21 species were sampled using point abundance sampling by electrofishing. Fish reproductive function of floodplain channels was evaluated using principal components analysis of 0+ fish distributions (in absence/presence), with distinction of the three main channel types (flowing, partially abandoned and abandoned channels). A descriptive model of microhabitat use and microhabitat profiles of 0+ fish was developed for the more frequently encountered species using canonical correspondence analysis and an electivity index combined with chi-square analysis. Water velocity, water depth and distance from the bank were the most important microhabitat variables, followed by bank gradient and bottom composition. Partially-abandoned channels provide conditions particularly suitable to 0+ fish, with submerged vegetation in these side-channels serving many of the fishes as refuge and feeding areas. Similarities in microhabitat use were found with respect to 0+ juvenile fish in the Danube flood plain (Slovakia/Hungary), the upper River Rhone (France) and the River Great Ouse catchment (England).