Selection of priority areas for fish conservation in Guadiana River basin, Iberian Peninsula

We developed a species-by-species approach for selecting protected areas for conservation of native freshwater fishes in semiarid regions, with catchment as the fundamental landscape unit for conservation efforts. Input data were composed of occurrences of freshwater fishes and landscape variables, and general quantification of occurrence, abundance, and endemicity of each fish species, to derive an index of conservation value for each species. Probability of occurrence of each species was performed with logistic-regression analysis based on the landscape variables and extrapolated to the entire study area with a geographic information system. We estimated the conservation value of a stream reach by summing the predicted probability of occurrence of each species multiplied by its corresponding conservation value. To define and select reserves, we used a threshold that maximizes conservation value of the stream reaches but identifies the minimum number of reaches for protection. The approach was applied to native freshwater fishes in the Guadiana River basin (southern Iberian Peninsula), which are threatened by the construction of two major dams. We used the data from 1 sampling year (1999) to produce the models, which were validated based on data collected in 2000 and 2001. We used variables of climate (3), geomorphology (4), hydrology (7), and human influence (6) to build the predictive models, which revealed that native species occur over a wide range of riverine habitats, with stream order and location in the basin the most frequently selected variables. The conservation value of species varied considerably, with Anaecypris hispanica the highest-ranked species. The catchments selected for reserves were the mainstream of the Guadiana River (upstream and downstream of the Alqueva and Pedrogao reservoirs) and the Degebe, Ardila, and Enxoe catchments. Our approach is a pragmatic way to address the urgent need to protect Guadiana native fish species in light of the ongoing anthropogenic degradation of aquatic environments.