Switzerland as a hotspot for fish species diversity
In the "Projet Lac" research project, 35 lakes in the Alpine region were systematically examined for their fish stocks for the first time: In Switzerland alone, 106 fish species were detected. With almost 20 percent of all fish species known in Europe, Switzerland is thus one of the hotspots for fish species diversity. The results are now the basis for measures for sustainable fishing and the protection of this still preserved diversity.
Hidden at the bottom of Lake Maggiore, a rare Cagnetta (Salaria fluviatilis). Photo: Eawag, Ole Seehausen
"Between 2010 and 2020, the fish in many lakes on the edge of the Alps were told to take inventory. Within the framework of the "Projet Lac" a team of scientists from the Swiss Federal Institute of Aquatic Science and Technology (Eawag) and the University of Bern has for the first time carried out comprehensive and standardized surveys of fish stocks in 35 large lakes bordering the Alps. The work was carried out in collaboration with the Bern Museum of Natural History, cantonal agencies and numerous other partners, and with the support of the Federal Office for the Environment (FOEN). A huge amount of data on the species, their distribution and their distribution within the lakes was evaluated. The project is now completed with the publication of the synthesis report.
New and rediscovered diversity
Of a total of about 550 fish species now known in Europe, 106 were identified in the "Projet Lac". Although Switzerland accounts for only 0.4% of Europe's land area, it is home to almost 20% of the species. This makes it one of the regions in Europe with the highest diversity of fish species in freshwater. 15 (endemic) fish species, the majority of which are found only here, were detected and documented for the first time. In addition, five species were caught whose occurrence in Switzerland was previously unknown. Two species were found north of the Alps that were previously thought to occur only south of the Alps. And four fish species were rediscovered that were thought to be extinct, for example a char that lives at great depths in Lake Uri.
From the shallow shore to the greatest depths
Most of the (endemic) fish species found exclusively in the respective lake were detected in open water and in very deep habitats of the nutrient-poor lakes, such as the unique whitefish species in Lakes Brienz and Thun or a special bullhead that apparently still lives at depths of over 200 m in Lake Uri. In many nutrient-rich lakes, on the other hand, practically no fish were caught above 30 m depth - oxygen is lacking there in summer. In absolute terms, the researchers found the largest number of species in shallower shore areas and near river mouths, and these were mostly widespread species. For fish evolution researcher Ole Seehausen, who led the project, this shows how enormously important diverse, near-natural habitats are for fish diversity in addition to high water quality - from the lakeshores to the greatest depths.
Two bullheads (Cottus gobio) from Lake Thun. One (left) lives close to the shore, in shallow water; the other (right) was found in Projet Lac still at a depth of over 200 m. © zVg
Whitefish and perch dominant
While in the large alpine lakes such as Lake Lucerne, Lake Brienz or Lake Thun, the various whitefish species dominate in terms of the number of fish and their biomass, at higher levels of the nutrient phosphorus it is rather the eglis, together with roach, eel and red/black feather. An exception is Lake Maggiore, where agone, a freshwater herring, dominates in open water, and the alpine lakes of Sils and Poschiavo, where non-local Arctic char and native and introduced trout, also non-local, predominate.
Advice for fishing and protection measures
This synthesis report on the project provides an overview of the status of fish species diversity and fish stocks in all the larger lakes of the western Alpine region. It brings together the results from individual lakes, and since they were collected using the same methodology everywhere, the work provides a basis for comparisons between lakes and for analyzing larger contexts. "Above all, recommendations can now be derived for the preservation of the remaining fish species diversity in the lakes and for sustainable lake fisheries," says project leader Ole Seehausen. Also important for continuous monitoring and later comparisons is the scientific reference collection of all fish species from all lakes built up at the Natural History Museum in Bern. It is also available to the public in the new permanent exhibition "Wunderkammer" accessible.
The contribution Switzerland as a hotspot for fish species diversity first appeared on Environment perspectives.
