Studies On Fish Resoures And The Fishes Of Early Life History Stage In The Upper Yangtze River

Investigations on the fishes and the fishery of early life history stage were carried out in 2000-2006 in order to reveal the pres(?)nt status of the fishery resources in the upper Yangtze River and the impacts of the Three Gores Dam.The main results are as follows:(ⅰ) One hundren and ninten species of fishes belonging to 76 genera,20 families and 8 orders were collected in the main channels and tributaries of the upper Yangtze River in 2000-2006.Of these,18 species are endemic and 7 species are alien,and 67.23% species belongs to Cypriniformes.The catch compositions in the different reaches of the channels in the upper Yangtze River have few differences,maily comprising Coreius heterodon(Bleeker),Coreius guichenoti(Sauvage et Dabry),Pelteobagrus vachelli (Richardson),Silurus meridionalis(Chen) and Cyprinus(Cyprinus) carpio Linnaeus. However,The catch compositions in the different tributaries have significant differences.(ⅱ) Comparison with the results before the filling of the Three Gores Reservoir, there are no significant changes in species number of Yibin and Banan reaches of the Upper Yangtze River,but in Wanzhou reach(?)s,weight percents of some glide species such as Coreius heterodon(Bleeker) and Coreius guichenoti(Sauvage et Dabry) in the catches showes a falling tendency after the filling of the Three Gores Reservior,while those of some lentic species such as Silurus meridionalis(Chen),Pelteobagrus vachelli (Richardson),and Cyprinus(Cyprinus) carpio Linnaeus showes a rising tendency.(ⅲ) The results of Hydro-acoustic survey on fishes from December in 2006 to January in 2007 showes that the densities ot the fishes in the tributaries are greater than those in the main channels of the upper Yangtze River.Daninghe Tributary has the greatest desity in all the tributaries,with the density of 363.8 ind./km~3.In the main channels Fenjie-Wanzhou reaches and Banan reaches have the greater density,with the density of more than 40 ind./km~3,and the density in other reaches are low,with the range form 15 to 30 ind./km~3.(ⅳ) According to the investigation on the fishery of early life history stage in Yunyang reaches from May to June in 2002,the species of the four major Chinese carps include Ctenopharyngodon idellus(Cuvier et Valenciennes),Hypophthalmichthys molitrix (Cuvier et Valenciennes) and Aristichthys nobilis(Richardson) except Mylopharyngodon piceus.The numbers of egg and larvae of the four major Chinese carps were 3.56×10~8 in 2002 and 2.90×10~8 in 2003,separately.Analysis basing on the embryo development periods of the collected eggs and larvae and the velocity of flow showed that there are spawning grounds of the four major Chinese carps in Jiangjin-Mudong,Fengdu-Fuling, Zhongxian,Wanzhou-Yunyang reaches of the upper Yangtze River.However,these spawning grounds disappeared after the filling of the Three Gores Reservoir.(ⅴ) According to the investigation on the fishery of early life history stage in Jiangjin reaches in 2006-2007,the species of the four major Chinese carps maily include Ctenopharyngodon idellus(Cuvier et Valenciennes) and Hypophthalmichthys molitrix(Cuvier et Valenciennes).The numbers of egg and larvae of the four major Chinese carps were 1.67×10~8 in 2006 and 7.42×10~8 in 2007,separately.Analysis basing on the embryo development periods of the collected eggs and larvae and the velocity of flow showes that the spawning grounds of the four major Chinese carps located in Hejiang-Mituo reaches of the upper Yangtze River with the distance of the 80-120 km from Youxi reaches.