Research On Species Diversity And Early-stage Resources Of Fish Status Of Xiajiang Hydro-junction In The Middle And Lower Reaches Of Ganjiang River

The total length of the Ganjiang River is 823km,which is the largest river in Jiangxi Province and have rich fish resources.At the same time,the Ganjiang River is an important habitat for migratory fish.Currently,Wanan Dam,Shihutang Dam and Xiajiang Dam were constructed in the middle of Ganjiang River.Dam constructions have been regarded as the main factor to destroy the river habitat and fish resources.Although the fish resource investigation has been done before the dam constructions in the middle reaches of the Ganjiang River,fish resources investigation after dam constructions are little,especially the data of early fish resources are seriously lack.It is necessary to monitor the effect on fish diversity after dam constructions.Here,we investigated the fish diversity,early fish resources and distribution of spawing in the middle and lower reaches of the Ganjiang River.The main conclusions are as follows:(1)87 species were collected in the middle and lower reaches of Ganjiang River,belonging to 5 orders,21 families and 62 genera.Cyprinidae is the greatest(39),accounting for 55.17%of total number of fish species.Comparing with the historical data,the number of fish species decreased 22.Eurytopia fish were greater,migratory fish were fewer,such as Myxocyprinus asiaticus,Mylopharyngodon piceus,Ctenopharyngodon idellus,Hypophthalmichthys molitrix,Aristichthys nobilis,Ochetobius elongatus,Squaliobarbus curriculus.The analysis of ecological type showed that omnivore fish(59.17%),demersal fish(37.93%)and sticky egg fish(34.48%)were great in the middle and lower reaches of Ganjiang River.(2)The dominant species were Parabramis pekinensis,Cyprinus capio,Culter alburnus,Squaliobarbus curriculus,Xenocypris argentea,Hypophthalmichthys molitrix,Aristichthys nobilis.The fish diversity in wet season and normal season higher than dry season.(3)11215 ind.fish eggs and 12645 ind.larvae fish were collected in Fengcheng reach of the Ganjiang River,belonging to 4 orders,8 families and 36 species.The fish eggs were classified into 21 species and larvae fish were classified into 22 species.24species were the drifting eggs of fish,accounting for 66.7%.Cyprinidae was the greatest(22),accounting for 61.1%of the total number of fish species.The main dominant species were Parabramis pekinensis,Hemiculter bleekeri,Pseudolaubuca sinensis,Rhinogobius giurinus,Squalidus argentatus,Parabramis pekinensis and so on.(4)The total quantity of early-stage fish in Fengcheng section was 66.66×10~8ind.The quantity of fish eggs was 63.84×10~8 ind and fish larvae were 2.82×10~8 ind.Compared with fish quantity in 2009,the quantity of major four Chinese carps increased significantly in the middle and lower reaches of Ganjiang River.The dominant species of major four Chinese carps were Hypophthalmichthys molitrix.Fish species composition was differences in each month,Squalidus argentatus mainly breed in May,Parabramis pekinensis,Parabramis pekinensis,Squaliobarbus curriculus,major four Chinese carps and so on mainly breed in June.(5)The small fish spawning grounds were widely distributed in the middle reaches of Ganjiang River.Compared with major four Chinese carps spawning ground(12)in the historical data,current periods have decreased to 3 site in the middle and lower reaches of Ganjiang River.The spawning ground of major four Chinese carps mainly distributed in Renghe to Xingan section of Ganjiang River.