Lake Constance whitefish

Lake Constance whitefish inhabited the lake’s deep zones

The freshwater fish Lake Constance whitefish was once native to the deep parts of Lake Constance. The olive-green or brown fish could reach a length of around 29 centimetres and weighed about 125 grams.

Initially, the physician and naturalist Johann Friedrich Gmelin described the Lake Constance whitefish in 1818 as a subspecies of the maraena whitefish (Salmo maraena). In the same year, the Lake Constance whitefish was elevated to its own species: Coregonus gutturosus.

In 1854, the physician Wilhelm Ludwig von Rapp gave the Lake Constance whitefish a new Latin name: Coregonus acronius. The reason: Rapp regarded the different kilch populations in Ammersee, Lake Geneva and Attersee as a single species. Later, the Swiss ichthyologist Maurice Kottelat reverted to the scientific name introduced by Gmelin, because he restricted the species concept to the kilch in the deep parts of Lake Constance.

Lake Constance whitefish – fact sheet

alternative name	Strumose whitefish, Bodensee kilch, Kilch
scientific names	Coregonus gutturosus, Salmo gutturosus, Coregonus acronius, Salmo maraena gutturosa
native range	Lake Constance (Germany, Austria and Switzerland)
time of extinction	1970s
causes of extinction	Eutrophication of Lake Constance
IUCN status	extinct

Eutrophication of Lake Constance harmed the kilch

Today, Lake Constance is considered to have very good water quality, but after the Second World War the pollution of the lake increased steadily. Due to high phosphate inputs from fertilisers and wastewater, eutrophication of Lake Constance occurred in the 1950s. Eutrophication causes algae and other plants in the lake to grow unchecked and deprive other organisms of the basis for life.

Despite various measures, the phosphorus concentration around 1980 was still ten times higher than the standard value. At the beginning of the 1980s, dangerously low oxygen concentrations were even measured in some parts near the lake bed – the Lake Constance whitefish lived at the bottom of the lake. The lack of oxygen also meant that the eggs of many fish could not develop.

The Lake Constance whitefish probably went extinct as early as the 1970s due to eutrophication. The IUCN also classifies the species as extinct. A similar fate befell the Gravenche, an extinct whitefish that once lived in Lake Geneva.

Was the kilch affected by commercial fishing?

The IUCN notes that the Lake Constance kilch is a fish species that was also commercially caught in the 1960s. Whether this actually contributed to the species’ extinction is questionable, because catching the animals was complicated. Caught kilch were often disfigured, because the abdomen would bloat strongly as the fish was hauled up from depth and the water pressure dropped, and could even burst.

But perhaps there is a glimmer of hope: researchers rediscovered the Lake Constance deepwater char (Salvelinus profundus), which had also been thought extinct, in Lake Constance in 2016 after targeted searches, according to an article in the Südkurier. That makes it not entirely impossible that the Lake Constance kilch might also have survived.