Department Fish Ecology and Evolution

Projet Lac Synthesis report

Projet Lac was a large project conducted by Eawag and the University of Bern, and funded by Eawag, the University of Bern, BAFU and Cantons with the aim to survey whole-lake fish communities in the large lakes in and around the Alps. The project combined multiple, standardised sampling methods and identification of fish to species and ecotype level, supported by genetics, with detailed documentation of phenotype. In total, 32 lakes were sampled across Switzerland, Italy and France. A large museum collection was created with vouchers of every lake population of each species.

Lake-specific reports were written to summarise the fish data from each of the Swiss lakes, to evaluate the state of biodiversity and the ecological state of the fish community of each lake and to provide recommendations for biodiversity conservation, fisheries managers and environmental protection authorities. A synthesis report is now in progress to bring together key findings from the lake-specific reports, to compare fish communities among lakes and their relationship to environmental parameters, and provide an overview of the diversity and conservation status of fish in this important ecosystem across the region.

One of the unique aspects of Projet Lac was the use of the same methods in all lakes. The use of consistent fishing and identification methods allows quantitative comparisons of the fish communities among lakes. Analyses for the synthesis report will involve establishing relationships between key aspects of the fish community and lake characteristics such as altitude, depth, surface area, temperature, productivity, pollution history and current human use. This will include documenting effects of fisheries on lake fish communities.



Eawag und BAFU

Synthese report

The final report will be published in cooperation with BAFU in English (with summaries in German, French and Italian) by autumn 2021.

The report will further investigate physical and biotic factors that explain the distribution of the different species within a lake. Examples include temperature and oxygen, which drive the fish depth distributions in some lakes, major river inflows, which may influence fish horizontal distribution, while fish-habitat associations likely shape the distribution of fish especially in the littoral zone. The report will investigate to what extent such patterns are consistent among the lakes and whether environmental drivers or biological traits of populations can explain variation in these relationships among lakes and among populations of the same species.

An important part of the report will also be to compare the sampling methods, to discuss the strengths and weaknesses of each method, to provide guidance on how to interpret the data collected by the project and recommendations for future monitoring of the fish communities.

A final goal will be to highlight gaps in our knowledge and identify the most urgent directions for further research.