Fishery Resources, Environment, and Conservation in the Mississippi and Yangtze (Changjiang) River Basins

<em>Abstract</em>.—A total of 13 alien fish species were introduced to the middle reaches of the Yarlung Zangbo River with the development of aquaculture in recent years. Eight of these species now have established populations and five have not established. To explore the mechanism for alien fish species establishment in this river, we compiled 23 biological traits of those species and tested for differences in biological trait and ecological niche between the established and nonestablished fish species. The trait analysis results showed that successfully established fish species have smaller body length, smaller egg diameter, earlier sexual maturity, and wider diet breadth than the nonestablished species. Ecological niches between established and nonestablished fish species also differed significantly. Our results support the vacant niche hypothesis that the successfully established species could occupy the vacant niches in the introduced range. We also used a model to predict the invasion risk of 27 potentially introduced fish species in the middle reaches of the Yarlung Zangbo River. The model predicted that there was a higher risk of establishment for 15 of the 27 species.