Several specimens of the deep-water char, declared extinct in 2008, have been discovered by surprised scientists in Lake Constance as part of a study into fish biodiversity in Alpine lakes.
“Projet Lac” was carried out from 2010 to 2015 by the Swiss Federal Institute of Aquatic Science and Technology (Eawag), together with the cantons, the Federal Office for the Environment, the University of Bern and the Bern Natural History Museum.
Researchers determined the taxonomy of some 50,000 fish in 17 Swiss lakes and several bodies of water in northern Italy and France.
More than 70 fish species were documented in the study, with whitefish dominating down to great depths but only in the cleanest lakes. Perch and carp dominate in the lakes that are now, or were in the past, nutrient rich.
In most of the lakes, however, former deep-water fish species have been lost. In the 197-metre deep Lake Zug, for example, there are hardly any fish below 30 metres.
But Projet Lac also brought good news: thanks to a targeted search in Lake Constance, several specimens of the deep-water char (Salvelinus profundus) native to the lake were rediscovered.
This species, frequently caught by Lake Constance fishermen until the 1960s, was declared extinct by the International Union for Conservation of Nature (IUCN) in 2008.
The deep-water char is found at a depth of about 80 metres and feeds on flatworms, small crustaceans and mussels. The size of the population from which these recently found specimens come will be investigated in the future.
swissinfo.ch and agencies