Research On The Status Of Fish Community,Species Diversity And Early-stage Resources Of Ganjiang River

As the largest river in Poyang Lake system,Ganjiang River plays an irreplaceable role in the protection and restoration of fish diversity in Poyang Lake system.With the gradual construct of water conservancy project,the aggravation of water environment pollution,sand mining,over fishing and other factors,the fish resources in Ganjiang River are facing a severe threat.Based on the survey data of catches in Ganjiang River from 2014 to 2018,and combined with literature,this paper analyzed the distribution pattern of fish community and species diversity in Ganjiang River by using the methods of cluster analysis,sorting,taxonomic diversity and beta diversity;Meanwhile,based on the survey data of early fish resources in lower reaches of Ganjiang River from May to June in 2019,the species composition,spawning scale and spawning ground of early fish resources in Ganjiang River were analyzed.The results are as follows:(1)The fish species in 15 families and 75 species were captured in the upper reaches of Ganjiang River,and the most common species belonging to Cyprinidae;In addition,the ecological types are mainly composed of omnivorous,mountain and stream type and viscous eggs.The relative importance index analysis shows that Hemiculter leucisculus is the common species of all sampling sites.Cluster analysis and n MDS analysis show that the habitat in the upper reaches of Ganjiang River can be divided into four regions.In addition,the distribution of fish species in the upper reaches of Ganjiang River is more discrete with the decrease of latitude through the analysis of TINCL_iand taxonomic diversity index.(2)The G-F index of fish species diversity in Ganjiang River showed that the middle reaches>upper reaches>lower reaches,which was higher in 2000-2018 than in 1982-1999;The analysis of taxonomic diversity showed that the evenness of fish composition in the upper and middle reaches was higher than that in the lower reaches,and the level of?~+in 1982-1999 was lower than that in 2000-2018;The results of beta diversity showed that turnover process was the main driving factor in spatial variations,and changed significantly with the region,the relationship between species turnover and spatial variations was significant.(3)From May to June in 2019,111 eggs and 3864 fish larvae were collected in Fengcheng section of Ganjiang River.All samples were sorted to 29 species,7families and 4 orders,mainly composed by Cyprinidae.In addition,there are 20species of fish that produce drifting eggs,accounting for 69.96%of the total species.According to statistics,Main spawning period in Fengcheng section of Ganjiang River appeared in the middle of May and the period with the most larvae is early June.The dominant species were mainly Hemiculter bleekeri,Parabramis pekinensis,Xenocypris macrolepis,Squalidus argentatus.At the same time,the size of spawning and the location of spawning grounds of the four major carps were estimated.It was found that the spawning scale and the number of spawning grounds of the four species of major carps were reduced.