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

Abstract

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.

Reciprocal Role of Salamanders in Aquatic Energy Flow Pathways

“…The consumption of salamanders by fish is also well known [54,[86][87][88], with much research focusing on the effect of fish introductions on amphibian assemblages e.g., [89][90][91][92]. Overall, amphibian species richness is significantly lower in aquatic systems where fish have been introduced [93], demonstrating the importance of predatory fish species as consumers of salamanders.…”

Do alpine macroinvertebrates recover differently in lakes and rivers after alien fish eradication?

“…1) preventing upstream fish dispersion. Introduced fish were eradicated by intensive gillnetting and electrofishing (with an ELT62 II 160 GI backpack equipment) between June 2013 and August 2015 (last fish removed on the 11/08/2015; for detailed methods, see Tiberti et al, 2019a). Previously two intensive rod angling sessions had already enabled a substantial reduction of the initial density of adult fish (Tiberti et al, 2017a).…”

“…At the end of the eradication campaign, 15 221 fish were removed from the study area: 14 560 fish (biomass: 435.7 kg) from Lake Dres, 164 fish (7.1 kg) from the inlet (river section between Lake Dres and B1), 668 fish (24.0 kg) from the outlet (river section between Lake Dres and B2), and the remaining 848 fish (8.1 kg) from the small tributaries (data from Tiberti et al, 2019a).…”

“…The Gran Paradiso National Park (GPNP, Western Italian Alps) recently completed a fish eradication campaign (Tiberti et al, 2019a) with the aim of reducing the negative ecological effects of introduced brook trout (Salvelinus fontinalis, Mitchil 1814) already described in the GPNP lakes (Tiberti and Von Hardenberg, 2012;Magnea et al, 2013;Tiberti et al, 2014). Among the lakes treated for fish eradication, Lake Dres (Fig.…”

“…1) is the only one connected to any stream sections permanently inhabited by brook trout, which provides an interesting opportunity to compare the post-eradication recovery in adjacent lotic and lentic habitats. Intensive gill-netting and electrofishing were used as eradication methods without remarkable side effects for aquatic macroinvertebrates and other non-target species (Tiberti et al, 2019a).…”