Fish biodiversity in two Hungarian streams:: a landscape-based approach

We studied fish biodiversity using landscape- and island biogeography-based approaches in two relatively undisturbed Hungarian streams in the Danube drainage (Bernecei stream [2(nd) order] and Kemence stream [3(rd) order]). We asked whether season, patch type (riffle or pool), stream, and position in the landscape affected fish species richness, assemblage composition, fish density/biomass, and nestedness in these streams. We collected 9,678 fishes (14 species) in pool and riffle patches during the 15 month study. Kemence pool patches had the highest species richness, followed by Bernecei pool patches, then Kemence riffle patches and finally Bernecei riffle patches. Rarefaction curves confirmed the rank order in species richness among the four patch types and showed little evidence of seasonal effects. Path analysis demonstrated that location in the landscape had the strongest effect on species richness in pool patches. Pool patches showed a highly significant nested pattern (T = 2.9) indicating that assemblages of patches with low species richness represented subsets of more diverse assemblages. Cluster analysis indicated that stream and patch type affected fish assemblage structure; seasonal effects were minimal. Repeated-measure ANOVA on both density and biomass data identified significant patch type and seasonal effects, whereas stream effects were non-significant. Our results suggest that the location of a patch as well as its physical structure can have strong impacts on fish biodiversity.