MULTISCALE ANALYSIS OF HABITAT USE DURING LATE SUMMER FOR 0+ FISHES IN THE RIVER GARONNE (FRANCE)

Relationships between environmental variables and O+fish in the upper River Garonne (France) were studied at different habitat scales during late August 1995. In total, 39110+fish representing 21 species were s ampled using point abundance sampling by electrofishing. Fish reproduc tive function of floodplain channels was evaluated using principal com ponents analysis of O+fish distributions (in absence/presence), with d istinction of the three main channel types (flowing, partially abandon ed and abandoned channels). A descriptive model of microhabitat use an d microhabitat profiles of O+fish was developed for the more frequentl y encountered species using canonical correspondence analysis and an e lectivity index combined with chi-square analysis. Water velocity, wat er depth and distance from the bank were the mast important microhabit at variables, followed by bank gradient and bottom composition. Partia lly-abandoned channels provide conditions particularly suitable to O+f ish, with submerged vegetation in these side-channels serving many of the fishes as refuge and feeding areas. Similarities in microhabitat u se were found with respect to O+juvenile fish in the Danube flood plai n (Slovakia/Hungary), the upper River Rhone (France) and the River Gre at Ouse catchment (England).