Recovery of high mountain Alpine lakes after the eradication of introduced brook trout Salvelinus fontinalis using non-chemical methods

Fish stocking is a serious threat to originally fishless mountain lakes. We used non-chemical eradication methods (i.e. gillnetting and electrofishing) in four high mountain lakes in the Gran Paradiso National Park (Western Italian Alps) to eradicate alien brook trout Salvelinus fontinalis. Data of amphibians, macroinvertebrates, zooplankton, chlorophyll-a, nutrient concentrations, and water transparency were used as indicators of the recovery process. All treated lakes were returned to their original fishless condition in spite of their different sizes and habitat complexity, without permanent negative side-effects for native species. Several ecological indicators showed that many impacts of introduced fish can be reversed over a short time period following eradication. The present study adds to a still growing body of specialized literature on the recovery of habitats after the eradication of alien species and provides further evidence that physical eradication methods are effective and can be part of a more general strategy for the conservation of high mountain lake biota.