| Zhelin Reservoir,also known as Zhelin Lake,is the largest reservoir in Jiangxi province formed by Zhelin dam in Xiuhe river,the largest hydroelectric dam in Asia.The reservoir covers an area of 308km2,with the most water depth of 45m.An annual fishery investigation in the reservoir was conducted from December 2018 to December 2019.The fish assemblage including species composition,species diversity,and reproduction of two species economic fish was analyzed,and a preliminary study on fish species diversity based on eDNA was also conducted.It will provide basis of environment protection and scientific management for Zhelin Reservoir.The main results are as follows:1.42 species of fish were identified,belonging to 4 orders,8 families and 33 genera respectively in Zhelin Reservoir.There were 32 species of Cyprinidae,accounting for 76.16%of the total species.17 species carnivorous fish,accounting for 40.48%of the total of the species,30 species settled fish accounting for 71.43%,and 15 species in both upper and lower fish,accounted for 35.71%of the total of the species in the reservoir were found.The relative important index IRI showed that the dominant species are Hemiculter leucisculus,Xenocypris davidi,Cultrichthys erythropterus and Squalidus argentatus except for cultured fishes Hypophthalmichthys molitrix,Aristichthys nobilis,which account for 83.01%of the total catch;There were also 7 important species,5 common species,10 general species and 14 rare species.2.Zhelin Reservoir was rich in Gobioninae fish resources and is an important small economic fish in the surounding area of the reservoir.The reproductive characters on Squalidus argentatus and Saurogobio dabryi were studied,and the results showed that the sexual ratio(males to females)was 1.18:1 in Squalidus argentatus and 1.04:1 in Saurogobio dabryi.The female maturity coefficient of Squalidus argentatus appeared two peaks in May and July,and the spawning period was from April to September.The female sexual maturity coefficient of Saurogobio dabryi peaked in March and then gradually decreased.The spawning period should be from January to June.The absolute fertility of Squalidus argentatus was 760?16265 eggs and the relative fertility of individual body length was 8.2?105.6eggsˇmm-1,and the relative fertility of individual body weight was 91?693.5 eggsˇg-1.The absolute fertility of Saurogobio dabryi was 1564?20151 eggs,the relative fertility of individual body length was 12.9?117.2 eggsˇmm-1,and the relative fertility of individual body weight was 119.7?918.9 eggsˇg-1.3.Analysis of the growth characteristics of the main economic fish in the Zhelin Reservoir revealed that the relationship of body length and weight of Hemiculter leucisculus,Cultrichthys erytropterus,Culter alburnus,Xenocypris davidi,Squalidus argentatus,Saurogobio dabryi,Hypophthalmichthys molitrix,Aristichthys nobilis were all related,showing a power function relationship.Hemiculter leucisculus and Cultrichthys erythropterus grew at a constant rate,while Hypophthalmichthys molitrix,Aristichthys nobilis,Culter alburnus,Xenocypris davidi,Squalidus argentatus,Saurogobio dabryi grew at an allometric rate.The average CPUE of Zhelin Reservoir was 74.3 kg/d,and with the winter CPUE 17.8 kg/d and the spring and summer CPUE 57.7 kg/d and 61.4 kg/d,respectively,and however the autumn sharp rose to 160.2 kg/d.Based on the biomass of plankton,the fishery potential of Zhelin Reservoir was estimated to be 2.15×107 kg.Therefore,the reasonable stocking of Hypophthalmichthys molitrix,Aristichthys nobilis in Zhelin Reservoir will be 1.877 million and 6.075 million respectively.4.eDNA technology is a new method for biodiversity monitoring.This technique was used to detect the fish diversity in Zhelin Reservoir.Through sequence alignment in GeneBank,368 OTUs of the target species and 239356 OTU sequences related to fish were obtained.30 fish species belonging to 3 orders and 6 families were detected by using eDNA,of which 25 Cypriniformes fishes accounted for 83.33%of the tested fish species.Compared with traditional survey methods,from the point of view of composition,the number of Cypriniformes fish species was the largest.Judging from the OTU sequences of the fishes obtained,there were more Cyprinus carpio(71083 OTU sequences),followed by Aristichthys nobilis(70001 OTU sequences).Compared with traditional survey methods,the number of fish species detected by eDNA technology accounted for 71.43%of the traditional survey,and eDNA method also detected other 5 fishes not detected by the traditional method.If we add eDNA water samples,the more fish species will be detected. |
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