The Tibet Plateau is the main part of the Qinghai-Tibet Plateau.It is the highest plateau in the world and usually called"the Third Pole" because its average altitude is over 4000m.Numerous renowned rivers in Asia or in the world,such as the Changyiang,Lancangjiang,Nujiang,Irrawaddy,Yarlongzangbo,Indus Rivers,ect.,and interior waters, such as the Nam Co,Silling Co,Banggong Co,Yamzhonyum Co,Maphamyum Co Lakes,ect.,rise or flow here.They constitute a very complex water system.The special topography and harsh climate on the plateau make the ichthyofauna existing here show obvious regionality and unique.According to the composition and distribution of the fishes and the features of the regional natural geography relating to the fishery production in Tibet,three first-class fishery regions and five fishery subregions are divided.They are:(a).The Northern Tibet Region.It can be divided into three subregions:the Ngari Subregion,The Nagqu Subregion and the Qiangtang Subregion:(b).The Upper and Middle Yarlongzangbo River Region and(c).The Southeastern Tibet Region.It includes two subregions:the Lower Yarlongzangbo River Subregion and the Sanjiang Gorge Subregion of Eastern Tibet.