Three species of Carassius are considered to occur in the perialpine region: Carassius carassius (Crucian carp), C. gibelio (Prussian carp) and C. auratus (goldfish). According to the Ordinance of the Swiss Fisheries Act none of these species are native to Switzerland. C. auratus is native to East Asia and has been introduced throughout Europe and most of the world. The native distributions of C. carassius and C. gibelio are uncertain. C. carassius is believed to be native to eastern and central Europe, as far west as the Rhine [9]. C. gibelio may be native to the central European lowlands or introduced from Asia [9]. C. carassius can be identified by a convex rear edge of the dorsal fin and 31-36 scales along the lateral line, while the rear edge of the dorsal fin in the other two species is concave or straight and they have fewer scales along the lateral line (26-33). C. auratus and C. gibelio are distinguished by colour (golden-bronze and silvery brown, respectively). The three species are however often confused with one another. [9] [9] All Carassius caught in Projet Lac except some from Lake Garda, were C. gibelio. This species was recorded in all southern perialpine lakes, as well as lakes Rousses, Constance Upper and Morat in the north. In most cases, DNA barcoding was not able to distinguish whether these fish were C. gibelio or C. auratus (3 from Maggiore, 1 from Lugano, 2 from Constance Upper and 1 from Morat), but clearly ruled out any C. carassius. Barcoding did however confirm the presence of two individuals of Carassius auratus in Lake Garda.

Published as part of Alexander, Timothy & Seehausen, Ole, 2021, Diversity, distribution and community composition of fish in perialpine lakes – " Projet Lac " synthesis report, Eawag: Swiss Federal Institute of Aquatic Science and Technology on page 118, DOI: 10.5281/zenodo.5779569