The relationship between Ephemeroptera and presence of the white-clawed crayfish (Austropotamobius pallipes). Case study in the Poitou-Charentes region (France)
Résumé
Nowadays, the distribution of the European native white-clawed crayfish (Austropotamobius pallipes) is restricted, fragmented and mainly located in headwater streams. To preserve this indigenous species, it is necessary to characterize its habitat preferences. Although this species is endangered, little was known about its ecological requirements until recently. Recent studies conducted throughout its distribution area indicate that water pollution is the main cause of its disappearance. In particular, A. pallipes seems very sensitive to organic pollution. However, no study has focused on the macroinvertebrate assemblages that co-occur with A. pallipes. In this study, seven streams located in the Deux-Sevres Departement (western France) containing wild populations of A. pallipes were qualitatively sampled in April 2004 and Ephemeroptera were identified to species level. These sites were also sampled according to the French biotic index "IBGN" during the summer of 2004. Several chemical parameters were also analyzed e.g. Dissolved Oxygen, pH, Ca, Turbidity, UV254mm, Conductivity, Total Organic Carbon (TOC) and Total Suspended Solids (TSS) The objectives of this study were: 1) to analyze the benthic invertebrate assemblage by determining the IBGN index in both reference zone (presence of A. pallipes) and zone without crayfish, 2) to identify the Ephemeroptera community in both zones to find some match with the presence of A. pallipes. The applied issue of this study is to use both physico-chemical criteria and Ephemeroptera communities to select suitable streams for a crayfish relocation program in the Poitou-Charentes region of France. It was found that (i) the IBGN scores did not separate the sites with/without A. pallipes (ii) Ephemeroptera diversity is statistically higher in sites with crayfish than in sites without (iii) there was a strong correlation between A. pallipes, species of Ephemeroptera mainly of Leptophlebiidae family (Habrophlebia fusca, Habrophlebia lauta and Paraleptophlebia submarginata) and dissolved oxygen at the study sites.