| In recent years,due to changes in the water environment,invasion of alien species,overfishing,etc.,which have severely affected fish resources.Fish diversity has shown a downward trend.Traditional fish diversity survey methods are often time-consuming,labor-intensive and have low target catch rates,Unable to meet the animal welfare requirements of no damage to fish.eDNA metabarcoding technology shows the advantages of time-saving,labor-saving,high sensitivity,and standardization in fish monitoring,which has great application prospects.This study uses traditional fishing methods and eDNA metabarcoding technology to investigate and compare the diversity of fish in Daye Lake,and explore the reliability and effectiveness of eDNA metabarcoding technology for lake fish monitoring.Therefore,it will pave the way for the development and improvement of the new technology in application research.The main results are as follows:1.Based on traditional fishing methods to investigate the fish resources of Daye Lake,a total of 4 orders,6 families,18 genera and 24 species of fish were caught.Among them,1 species of Herringoides,17 species of Cypriformes,2 species of Siluriformes,4 species of Perciformes,the species accounted for 4.2%,70.8%,8.3%,and 16.7% respectively.Through the analysis of relative importance index IPI value,Hypophthalmichthys molitrix and Hypophthalmichthys nobilis are the dominant species in Daye Lake.Coilia brachygnathus,Megalobrama amblycephala,Carassius auratus,Culter dabryi and Hemiculter leucisculus are important species in Daye Lake.Through the analysis of fish diversity in Daye Lake,the Shannon-Wiener diversity index(H)of the fish is 0.714～2.237,and the Simpson dominance concentration index(C)is 0.457～0.879.Both indexes indicate Daye Lake cowhide.The fish diversity in NPG waters is the highest,and the fish diversity in BSW waters is the lowest.2.Based on eDNA metabarcoding technology,chosing two gene regions of mitochondrial cytochrome C oxidase subunit I(Cytochrome Oxidase I,COI)and 12 S r RNA,The research amplified eDNA to study the fish diversity of Daye Lake.The high-throughput sequencing of eDNA-COI samples adopts the method of direct splicing first and then quality control.The effective sequence pairs used for subsequent analysis of the chimera removed are between 49252～69776.The eDNA-12 S sample adopts the method of quality control first and then splicing,and the effective sequence pair number for the subsequent analysis after removing the chimera is between 69264～74224.Performing cluster analysis on the effective sequences,COI got 3113 OTU,12 S got 3683 OTU.3.The Alpha diversity analysis of eDNA-COI samples showed that Shannon index is 3.168-5.003;Simpon index varied from 0.019 to 0.158;ACE index varys from 577.031 to 1563.512;Chao index varys from 579.222 to 1553.881.Among them,the minimum value of ACE index and Chao index appeared in the SJW waters,indicating the lowest species diversity in the SJW waters.The highest value of Shannon index,ACE index and Chao index appeared in the DW waters,which indicates the highest species diversity in the DW waters.The Alpha diversity index analysis of eDNA-12 S samples showed that Shonnon index is 3.610-4.978,Simpon index varys from 0.023 to 0.107;ACE index varys from 424.076 to 1428.967,Chao index variation is 422.000-1392.707.The lowest values of ACE index and Chao index are in the TBH waters,and the highest value is in the LJH waters,which indicates that the species diversity of TBH is the lowest and that of LJH waters is the highest.4.Beta diversity analysis of eDNA-COI samples showed: PCA analysis,PCo A analysis and NMDS analysis all show that the difference between DW and NPG is small;PCA analysis and PCo A analysis show that the community species composition of the GJQ waters and BSW waters are quite different,while the NMDS analysis of SJW and LJH are quite different.Beta diversity analysis of eDNA-12 S samples showed that: PCA analysis showed that the community species composition of the GJQ and BSW waters are quite different,and the community species composition of LJH and BSW waters is relatively small.PCo A analysis showed that the species composition of the GJQ and LJH waters are quite different,while the species composition of NPG and the GJQ is relatively small.According to NMDS analysis,the difference between LJH and BSW is relatively small,while the difference between NPG and BSW is relatively large.5.After species annotation,eDNA-COI annotated to 2 classes of fishes,13 orders,17 families,20 genera and 20 species.Among them,there are 7 species of freshwater lake fishes,accounting for 35.0%.They are silver carp Hypophthalmichthys molitrix,Carassius auratus,Ctenopharyngodon idellus,Cyprinus carpio,Silurus ast OTU,and Hemibarbus maculatus,Ladislavia taczanowskii.eDNA-12 S is annotated to 2 classes of fishes,17 orders,26 families,29 genera and 29 species.Among them,there are 3 species of freshwater lake fishes,accounting for 10.3%.They are Hypophthalmichthys nobilis,Hypseleotris swinhonis and Opsariichthys bidens.10 species of freshwater lake fishes monitored by eDNA metabarcoding technology belong to 3 orders,3 families and 10 genera.There are 5species of fish that can be monitored jointly with traditional methods,namely Hypophthalmichthys molitrix,Hypophthalmichthys nobilis,Carassius auratus,Ctenopharyngodon idellus,Hemibarbus maculatus. |
