Fish habitat preferences in large streams of southern France

1. Relationships between fish and their habitat over whole geographic regio ns, which are evident from studies of many streams and species, can improve understanding of lotic communities and provide reliable management tools. Nevertheless, most habitat preference studies have been based on single sit es, and confined to small streams and to game species. 2. Regional habitat preference models, based on local velocity, depth and r oughness, were developed for twenty-four species and their size classes com monly found in large European streams. Fish surveys were conducted in six l arge streams in southern France over an 8-year period. To limit the influen ces of habitat variables other than those studied, we estimated fish prefer ences within each survey and averaged this information across surveys. Pref erences were fitted with confidence intervals and their sensitivity to fiel d uncertainty was evaluated. 3. Most species and size classes had significant preferences for local habi tat conditions which were consistent across the region. Habitat preferences predominant in the region overall were not always observed at any one site , but habitat conditions preferred on average in the region were never actu ally avoided locally. These results support the use of regional preference models for fish and the development of similar models for other lotic group s whose sensitivity to local habitat conditions has been reported elsewhere .