Environmental Factors Influencing Local Fish Species Richness and Differences between Hydroregions in South‐Western France

Abstract

AbstractThe aim of this study was to investigate the influence of 5 typological variables on the spatial distribution patterns of fish species richness in south‐western France, and, subsequently, to analyse differences in the number of species occurring in 6 major hydroregions located within the overall study area. The data were collected at 329 sampling sites. General Linear Modelling was used to assess the influence of each typological variable on local fish species richness, and to determine the differences in local fish species richness between the 6 hydroregions. Local species richness was significantly influenced by altitude, slope and catchment area, whereas distance from the source and stream width showed no significant relations with local richness. The Côteaux de Gascogne hydroregion had a significantly lower species richness, whereas no significant differences occurred among other neighbouring hydroregions. These results were congruent with the spatial distribution patterns of freshwater invertebrate species richness in the area, which were analysed in previous studies. At such a regional scale, we suggest that congruent patterns between fish and invertebrate species richness are almost certainly a result of similar responses by different taxa to environmental conditions, rather than to biotic interactions. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)