Abstract
Currently, more than half of Pyrenean high mountain lakes are occupied by fish as a result of historical introductions that date back centuries and which have accelerated during the last 70 years. In the southern slope of these mountains, the main fish that have been introduced are Brown trout (Salmo trutta), Brook trout (Salvelinus fontinalis), Rainbow trout (Oncorhynchus mykiss), and European minnow (Phoxinus sp). The specific impacts of the introduction of fish include, among others, the transformation of the ecosystem structure and trophic relationships, and the reduction and extirpation of native species. The project LIFE RESQUE ALPYR (LIFE20 NAT/ES/000369), started in 2022 and ending in 2026, includes among its main objectives the restoration of ten high mountain lakes with fish (trout or minnow) and the recovery of native species of European interest by the eradication of introduced fish. We planned and executed continuous and sustained campaigns to achieve the complete removal of fish. From 2022, we began with operations in seven objective lakes by means of several capture techniques, mainly gill nets for trout and a combination of gill nets, fyke-nets, and electrofishing for minnows. In 2024 and 2025, in three other lakes, chemical treatments with rotenone were carried out to achieve rapid eradication of fish. Currently, we have already achieved the complete removal of fish in four lakes, either with sustained capture or chemical treatments. In the other three lakes, this objective is also expected to be achieved in 2026, and only few individuals persist in actuality. In the other two lakes, the European minnow has been removed, and trout are now the focus of a two-stage strategy. In the remaining lake, we have only achieved a reduction in the European minnow (>50% reduction), with trout still remaining. We present, in detail, the methodologies applied and the results obtained.
Author Contributions
Conceptualization, Q.P.-R., T.B., B.V., R.T. and M.V.; methodology, Q.P.-R., J.D., D.B., N.G., E.C., B.V., R.P., P.F., J.O.G., R.T. and M.V.; formal analysis, Q.P.-R., T.B., V.O., B.V. and M.V.; investigation, Q.P.-R., D.B., N.G., T.B., V.O., B.V., R.P., P.F., J.O.G. and M.V.; data curation, Q.P.-R. and J.D.; writing—original draft preparation, Q.P.-R., T.B., B.V. and M.V.; supervision, Q.P.-R., T.B., R.T. and M.V.; project administration, Q.P.-R., C.R., T.B., R.T. and M.V.; funding acquisition, Q.P.-R., T.B., R.T., C.R., B.V. and M.V. All authors have read and agreed to the published version of the manuscript.
Funding
The projects LIFE RESQUE ALPYR (LIFE20 NAT/ES/000369), RESTAURAPIR_SORELLONA and RESTAURAPIRCSIC were supported by the Fundación Biodiversidad of the Ministerio para la Transición Ecológica y el Reto Demográfico, through the call for grants to support projects under the LIFE program in the field of biodiversity and to promote the digitalisation of knowledge of natural heritage.
Institutional Review Board Statement
Not applicable.
Informed Consent Statement
Not applicable.
Data Availability Statement
Not applicable.
Conflicts of Interest
Author Q.P.-R. was employed by the company Sorelló, Estudis al medi aquatic SL. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content. |
© 2026 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license.