Fish community successions in Lake Ulungur: a case of fish invasions in fragile oasis.
Lake Ulungur, located in the desert region of northwest China, is one of the most important fishing grounds in the Chinese inland area. Ulungur possessed a simple fish assemblage of 7 indigenous species of fish, dominated by the common perch, Perca fluviatilis Linnaeus and Leuciscus dzungaricus. Over the last 40 years, 14 non-indigenous species of fish have been introduced into this fragile ecosystem via intentional or unintentional human activities. Over the decades since these introductions, the fish community of Ulungur has been severely altered. Most of the niches that had inhabited by the native species of fishes are now occupied by these non-native species. The two, once dominate species, the common perch and Leuciscus dzungaricus, have become endangered and threatened with extinction, while the non-native Pond smelt (Hypomesus olidus Pallas), the Aral bream (Abramis brama orientalis Berg) and the Northern pike (Esox lucius Linnaeus), have become the most prevalent species. In this paper, non-indigenous fish introductions and the corresponding changes in native fish communities in Ulungur are outlined. Possible mechanisms of community succession were analyzed to provide information for the management of fish introduction.