Oncorhynchus mykiss (Walbaum, 1792) (Salmoniformes, Salmonidae), a newly introduced fish recorded in natural freshwaters of Jiuzhaigou Valley, Sichuan, China

The Oncorhynchus mykiss is native to areas of the Pacific Ocean in Asian and North America,which in relatively short time has been introduced into at least 45 countries and territories. In someregions, it has established breeding populations in natural habitats and significantly disrupted nativeecosystems. The main reason of such a fast invasion is widely introduced as a farmed fish, but escapesfrom rearing ponds. The case of O. mykiss invasion demonstrates the risk of introduced fish, as well asurgent need of more caution and prevention in order to avoid further ecological problems.