An endangered species as indicator of freshwater quality: fractal diagnosis of fragmentation within a European mink, Mustela lutreola, population

Abstract

Decline of endangered species may be regarded as an indication of a deteriorating environment. European mink Mustela lutreola are freshwater predator populations which suffered a severe decline and are currently restricted to only two areas in Europe. A survey on distribution revealed that mink western population was highly fragmented. Watercourses occupied by mink significantly differed by their quality from watercourses where no mink were evidenced, with regard to most physico-chemical parameters studied, organic and oxidizable matters, nitrogenous matters, phosphorus concentration, heavy metals, pesticides and other micropollutants, and hydrobio-logical quality. A Gaussian representation of mink breeding dispersal was performed and, based on a ln-ln regression analysis, the fractal dimension D provided an accurate quantitative evaluation of the subdivision level. As revealed by low fractal dimension (D = 1.40), subdivision within the mink population may be reaching a critical threshold for European mink conservation. Fractal investigation constitutes a resourceful method for relating environmental deterioration and breeding dispersal in endangered species. Moreover, mink were found to avoid some watercourses which still provide domestic water supplies for human people and the level of fragmentation should be seen as a warning of the deterioration of freshwater ecosystems.