Fish Diversity And Its Conservation In Dongjiang Lake,Hunan Province

Biological diversity the basis for human survival and development.As an important part of biodiversity,fish diversity plays a pivotal role in maintaining the balance of watershed ecosystem and promoting sustainable development of fisheries.Dongjiang Lake is located in the upper reaches of Lei Shui,a first-class tributary of Xiangjiang River,and is the largest deep-water reservoir in Hunan Province,which was also an important fishery base.2020,a ten-year fishing ban was implemented in the waters of Dongjiang Lake,prohibiting net-pen aquaculture and all productive fishing activities.In order to further protect the fish resources of Dongjiang Lake and provide a basis for scientific assessment of the effect of the fishing ban,this study jointly used field visits and eDNA technology to evaluate the fish species composition and diversity of Dongjiang Lake,analyze the main problems it faces,and propose targeted conservation recommendations.The main conclusions are as follows:A total of 68 species of fish were identified in the survey,with the largest number of 39 species of Cypriniformes(57.35%),followed by 14 species of Perciformes(20.59%),6species of Siluriformes(8.82%),and 2 species each of Acipenseriformes and Osmeriformes.Among them,42 species of fish belonging to 5 orders,14 families and 31 genera were collected and recorded during the visit survey,and 38 species of fish belonging to 10 orders,16 families and 31 genera were annotated based on eDNA technology.Compared with the historical data before the construction of Dongjiang Power Station in 1986,the number of indigenous species decreased by 27 species,including Hypophthalmichthys molitrix,Hypophthalmichthys nobilis,Magalobrana terminalis,Culter alburnus,Erythroculter dabryi,Neosalanx taihuensis,and introduced species such as Oreochromis mossambicus,Oncorhynchus mykiss,and Lepomis macrochirus and other introduced or invasive species.The results show that the fish community structure in Dongjiang Lake has changed to a certain extent compared with that before the construction of the power station,and the problem of alien species invasion is more prominent.Nonetheless,under the background of a total fishing ban,especially in the new situation where fishing gear survey methods are strictly restricted,more scientific and accurate techniques for monitoring fish diversity in large deep-water lakes are worthy of further exploration and optimization.The eDNA-based fish diversity analysis revealed that the Shannon,Simpson,Observed＿species,Pieloue and Chao1 indices of the Alpha diversity index of fish in Dongjiang Lake were 3.69±1.19,0.81±0.13,398.00±352.90,0.44±0.09 and 556.00,respectively.The PCA analysis of Beta diversity index explained a total of 62.9% of the variation.A total of 30 species of fish were annotated in the waters above the dam.The Shannon index of fish was 3.82 ± 1.39;the Simpson index was 0.81 ± 0.13;the Observed＿species index was 488.20±405.80;the Pieloue index was 0.44±0.10;the Chao1 index was 684.20±551.20;Fish Shannon index was 3.42±0.64;Simpson index was 0.80±0.13;Observed＿species index was 217.60±21.31;Pieloue index was 0.44±0.08;Chao1index was 299.60±32.66.A total of 31 species of fish were annotated in the water below the dam,Shannon index of fish was 3.42 ± 0.64;Simpson index was 0.80 ± 0.13;Observed＿species index was 217.60±21.31;Pieloue index was 0.44±0.08;Chao1 index was 299.60 ± 32.66.The Alpha diversity index of fish in the waters above the dam was generally higher than that under the dam,but the difference was not significant(P > 0.05).PCA analysis showed that the Beta diversity index of the sampling points above the dam(S1～ S16)were mainly concentrated in the second and fourth quadrants,while the sampling points below the dam(S17 ～ S24)were mainly concentrated in the first and second quadrants.The results show that there are certain differences in the composition and diversity of fish in the waters above and below the dam of Dongjiang Lake.In response to the changes in the composition of fish species and their diversity in the Dongjiang Lake,as well as the changes in the community structure and the invasion of introduced species and alien species,we put forward the following five protection suggestions: 1.Strengthen fishery management and do a good job in policy publicity;2.Take restoration measures 3.Regular ecological monitoring and strengthening of environmental protection;4.Scientific proliferation and release to protect indigenous fish;5.Control biological invasion and reduce ecological hazards.