Editing Lake Constance (section)

===== Well-known non-native species =====
Even the [[rainbow trout]] (''Oncorhynchus mykiss'') is not a native fish. It was introduced into Lake Constance around 1880 for economic reasons to enhance the local fauna.<ref name="Eingewanderte Arten">Angela Schneider: ''Gepanzerte Truppe erobert den Bodensee.'' In: ''Südkurier.'' dated 9 October 2010.</ref>

Among the foreign species of animal in Lake Constance are the [[zebra mussel]] (''Dreissena polymorpha'') which, since the 18th century, has spread from the Black Sea region across most of Europe and was carried into Lake Constance between 1960 and 1965. After a huge increase in numbers during the 1980s in the Rhine and large lakes, this species is now in retreat today. The zebra mussel causes problems because, among other things, it blocks water extraction pipes. In addition, the species can be a disaster for domestic shellfish, because it competes for their food.<ref name="Neozoen">Angela Schneider: ''Drei von vielen, die sich bereits im Bodensee etabliert haben.'' In: ''Südkurier.'' dated 9 October 2010.</ref> Today, according to the Institute for Lake Research (''Institut für Seenforschung'', ISF), the zebra mussel is also an important food for overwintering waterfowl. In fact, the number of overwinterers has more than doubled in around 30 years.<ref name="Eingewanderte Arten"/>

The [[killer shrimp]] (''Dikerogammarus villosus'') has spread since 2002 from two sections of shoreline near Hagnau and Immenstaad, over the whole Lake Überlingen (2004), the whole of the Upper Lake (2006) and almost the whole Lake Constance and Rheinsee shore (2007).<ref>''Invasion des Höckerflohkrebses.'' In: ''Südkurier.'' dated 9 October 2010.</ref> As its name implies, it is a voracious burglar of fish larvae and fish eggs.<ref name="Eingewanderte Arten"/>

The most recent example is the little [[opossum shrimp]] (''Limnomysis benedeni''), only six to eleven millimeters long, which was found in 2006 in the Vorarlberg region of Hard, and can now be found almost all over Lake Constance.<ref name="Eingewanderte Arten"/> It comes from the waters around the Black Sea. It was presumably first transported by ships up the Danube before it spread into the Rhine river system and entered Lake Constance. The opossum shrimp, which occurs in many places in shoals of several million in winter, are already an influential link in the food chain in Lake Constance. They consume dead animal and plant material as well as [[phytoplankton]], but are also eaten by fish themselves.<ref name = "Neozoen"/>

Today, in western Lake Constance are found: the North American [[spinycheek crayfish]] (''Orconectes limosus''), which was introduced into European waters in the mid-19th century to increase the yield,<ref name="Eingewanderte Arten" /> occasionally the [[Chinese mitten crab]] (''Eriocheir sinensis''), and in the lake's tributaries, the [[signal crayfish]] (''Pacifastacus leniusulus''). As these species of large crayfish are immune to [[crayfish plague]], but spread the pathogen, they are a great danger to native species such as [[noble crayfish]], [[white-clawed crayfish]] or [[stone crayfish]]. The animals are often undemanding, multiply rapidly and lead predatory lives, thus also posing a threat to various small species of fish.<ref name="Neozoen"/> The ISF has been systematically researching the subject since 2003.<ref name="Eingewanderte Arten"/>