The project to eliminate fish in the Pyrenean lakes of the Natural Park of the Alt Pirineu was successful. The work began in September 2025, through a European LIFE project, and consisted of the application of rotenone, a biodegradable ichthyocide, in lakes Tres Estanys del Mig and Tres Estanys de Baix.
The change in water color constitutes the main evidence of the success of the intervention. The water went from a greenish and turbid tone, characteristic of recent years, to a clearer appearance, a sign that the ecosystem is beginning to recover the lost balance.
The cause of environmental degradation was the expansion of the minnow, a small fish introduced by humans in the lakes. The presence of this fish had altered the natural balance of the aquatic ecosystems of the region.
The project managers affirm that the results demonstrate that it is possible to restore degraded ecosystems through this biodegradable chemical method.
