A simple rule-of-thumb method to define environmental flow for the Pyrenean desman ( Galemys pyrenaicus )

Résumé fourni par la source

Abstract The Pyrenean desman ( Galemys pyrenaicus ) is a semiaquatic insectivore that is critically endangered due to inbreeding, predation by the invasive American mink, and habitat fragmentation and degradation, among many other causes. Many of the streams currently occupied by the Pyrenean desman, even those protected within the Natura 2000 network, are affected by hydropower. However, the environmental flows (eflows) set by the water administrations within its distribution areas do not account for the specific needs of this species. Unfortunately, the small size, nocturnal habits and low population density of this animal make it impossible to gather the information necessary to draw habitat preference curves as detailed as those obtained for many fish and invertebrate species. As an alternative, given the urgent need to prevent the extinction of this endangered species, we propose to combine the Pyrenean desman preference for riffles, runs and pools with maps of these habitats under different flow conditions in the Leitzaran, a stream affected by diversion hydropower. We show how habitat suitability drops as riffle area decreases with flow reduction, and how this information can be used to provide a simple, rule-of-thumb method for defining eflows for the species. This method can be adapted to other populations differing in their habitat preferences, as well as to rivers with contrasting habitat characteristics.

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