Yesterday, February 29, 2024, the defense of the doctoral thesis entitled ‘The role of non-native fish on littoral macroinvertebrates of Pyrenean high mountain lakes’ took place by Victor Osorio, PhD student at the Blanes Center of Advanced Studies (CEAB) of the Spanish National Research Council (CSIC).

Although the effects of the introduction of trout have been the subject of many studies, the effects of minnows are poorly understood. One of the objectives of the thesis has been to investigate the effects of the introduction of non-native fish, and especially minnows, on the littoral macroinvertebrate communities of Pyrenees high mountain lakes.

Through the study of 54 lakes, he evaluated the impact of minnow and trout densities on macroinvertebrates community compositions and abundacnce, relative to other biotic and abiotic factors In the lakes with veron, the macroinvertebrate community was tipically limited to a small number of taxa, predominantly composed of small, semi-sessile burrower organisms. Metabarcoding tools have been used to explore the impact of trout and minnows.

The recovery of macroinvertebrate communities in eight lakes where fish populations were eradicated or controlled has also been evaluated over nine years. A few years after eradication, rapid signs of recovery were already observed, with communities gradually resembling those typical of fishless lakes.

The thesis has been directed by Dr. Marc Ventura from the CEAB-CSIC and Dr. Maria Àngels