Involvement of recreational anglers in the eradication of alien brook trout from high altitude lakes

Abstract

Stocking programs for recreational angling are primarily responsible of the spread and ecological impact of introduced fish in high altitude, originally fishless lakes. In 2013, the Gran Paradiso National Park started an eradication campaign of brook trout by intensive gill-netting. Local anglers were invited to attend two angling sessions to start the eradication before gill-netting in an experimental lake, as part of an education action devoted to these critical stakeholders. The angling sessions turned out to be a valuable help for the eradication campaign and the aim of this study is to report on the outcomes of these angling sessions. Angling techniques were highly size selective, removing a substantial part of the adult population and of the fish biomass, but their contribution to the eradication of small fish (<15cm) was irrelevant. Therefore, angling cannot completely eradicate age-structured populations. However there is scope to use angling sessions as a support for eradication campaigns and as an emergency measure for recent fish introductions. Similar actions should be considered whenever a fish eradication programme is planned. These findings however do not imply a general endorsement for angling within protected areas.