4.4 Swiss fish diversity: A complex matter with many unknowns
Results from Projet Lac and Progetto Fiumi indicate that fish diversity in Switzerland is much more complex than previously thought. Many fish groups, such as whitefish or common minnows, include cryptic species that look virtually the same, but may occur at different depths, require different nutrients or have different breeding times.
The apparently well-known Swiss fish fauna, is actually full of surprises. As in the tropics and other species-rich habitats, however, these species may disappear before we have the chance to document them.
4.5 Whitefish
The whitefish fillet we eat belongs not to a particular whitefish species, but to a complex fish group. Collections allow scientist to keep documenting and updating the diversity of whitefish, which as of 2020, stands at 31 species. Many of these species occur in only one or few lakes, and nowhere else.
4.6 The Lake Constance deep water char
In 2014, the Projet Lac stumbled upon a fish believed to be extinct since the 1970s: The Lake Constance deep water char. This species requires deep, oxygen-rich water to breed, conditions that almost completely disappeared due to the past massive over-fertilization of the lakes.
‘If we continue to experience summer temperatures as in 2018, then soon we’ll find the grayling only in museums’ (Patrick Wasem, fisheries officer for the canton of Schaffhausen, 2019). These fish require cool, flowing, oxygen-rich water. Extremely hot summers such as those in 2003 and 2018 led to the death of virtually all animals in some places.
