| Located in the west of changxing island,chongming district,Shanghai,Qingcaosha reservoir is the largest water source of drinking water in Shanghai.According to the salt and turbidity of the water quality of the Yangtze river outside the reservoir,the principle is to remove salt from the water and remove turbidity from the water,so that the fish in the Yangtze river estuary will enter the reservoir and some fish in the reservoir will swim into the Yangtze river through drainage.But since 2018,in order to intercept clutter and make reservoir fish community structure is in a state of control,to control fish water ecological regulation,the fence in the intake adopted high density,lead to larger debris into the reservoir,fish and small fish of eggs,larvae only can enter the reservoirs,thus the reservoir fish in a state of artificial regulation.In order to control fish algae,the reservoir management department releases and catches fish every year according to the survey data of aquatic organisms and the water quality,and the fish community structure of the reservoir is in a dynamic change.We investigated the fish resources of qinghaosha reservoir,explored the changes and succession directions of the fish community structure over the years,and then mastered the ecological functions of the fish community on the water quality of qinghaosha reservoir.It provides scientific basis and management measures for the follow-up research of water sources and the sustainable development of fish resources.From 2015 to 2019,this study grass sand reservoir,gill nets and quarterly net cage fish sampling investigation,and the combination of fish in the laboratory for processing analysis,the results of the analysis proved the grass sand reservoir fish species composition,dominant species,ecological groups;The community stability in different years was analyzed by ABC curve,and the community similarity in different years was studied by cluster analysis and PCA.In April 2019,the molecular biological method of environmental DNA was applied to ecological research to extract fish DNA from water samples,obtain fish species information after high-throughput sequencing,and further analyze the structure and diversity of fish community.From 2015 to 2019,a total of 5158 fish samples were obtained from field sampling,and 51 species of fish were identified and analyzed,belonging to 9 orders,16 families and 41 genera.Order cyprinforma(34 species),order perciforma(8 species),order catfish(3 species),order plaice(1 species),order shad(1 species),order morbiforma(1 species),order anguilliforma(1 species),order anguilliforma(1 species),order sturgeon(1 species),order mullet(1 species).In terms of abundance,the highest proportion was 87.09% for cyprinformes,7.43% for perciformes,2.46% for shad and 2.15% for catfish,and only 0.87%,less than 1%,for other orders.In 2018,the maximum number of species to 12 families,7 orders,28 genera and 31 species,species number at least 2019,only survey to 28 species of fish,belonging to 4 orders,6 families and 23 genera in 2015-2019,grass sand reservoir fish in 4 ? 7 orders,6 ? 12 and 23 genera ? 28 genera,species,between 26 ? 31 kinds of change,the result shows that grass sand reservoir fish volatile on the level of the orders,and families,relatively stable in the genus and species levels.According to the life history of the fish species from 2015 to 20195,the ecological groups of the fish species were divided into four species: river and sea migration(D),river and lake semi-migration(P),estuarine(E),and fresh water settlement(R).The abundance ratio was 3%,0.1%,3.5%,and 93% respectively.According to the living water layer of fish,the fish species in qinghaosha can be divided into three types: pelagic fish,pelagic fish and pelagic fish,with the proportion of abundance being 25%,34% and 41%,and the proportion of biomass being 76%,17% and 7%,respectively.The species of fish in the grass grass sand can be divided into carnivorous fish,omnivorous fish,filter fish,and plant-eating fish according to their feeding habits,with the proportion of abundance being 32%,43%,11%,and 13%,respectively,and the proportion of biomass being 9%,15%,71%,and 5%,respectively.The proportion of the population of migratory fish in rivers and seas declined from 7.4% in 2015 to 0.8% in 2019.The proportion of quack semi-migratory fish was 0.5% in 2015 and 0.2% in 2016,and no quack semi-migratory fish were caught from 2017 to 2019.In 2015,the number of river mouth fish accounted for 6.6%,and in 2019,the number decreased to 2.5%.The proportion of freshwater sedentary fish increased from 85.6 percent in 2015 to 96.8 percent in 2019.The proportion of the abundance of Marine migratory fish,semi-migratory fish of rivers and lakes,and Percival fish was decreasing,while the proportion of the freshwater sedentary fish was increasing year by year.The whole qinghai-sha reservoir was inclined to the composition of freshwater fauna.From 2015 to 2019,five years sand reservoir of dominant species of grass carp,crucian carp,bighead,long Silver carp,bighead carp and crucian carp were the dominant species in all survey years,and their dominance increased year by year.In terms of fish diversity,Margalef index showed no obvious annual fluctuation pattern.From 2015 to 2019,pielou index and shannon-wiener index both showed a decreasing trend,but the range of variation was small.ABC curve results from 2015 to 2019,you can see that the grass sand reservoir every abundance of dominance curve in biomass dominance down to the bottom of the curve,that abundance of diversity is higher,shows that the community structure of green sand reservoir disturbance degree is low,W value from 0.205 to 0.311,but the two line spacing decreases year by year,shows the degree of reservoir interference is increased year by year,the grass sand reservoir at present community structure stability,but also should be alert to the possibility of community imbalance occurs.Cluster analysis results show that the community structure is similar in 2015 and 2016,and similar in 2017,2018 and 2019.Simper analysis results show that the average similarity of group A is 66.75%,and the average similarity of group B is 62.68%.There are 20 kinds of fish that contribute to more than 90% of the difference between the two groups.Crucian carp,big fin fish and lolly fish are the main causes of the difference between groups A and B Species.PCA analysis was conducted for each ecological group of fish.The first principal component was catadromous fish with a contribution rate of 91.4%,and the second was estuarine sedentary fish with a contribution rate of 8.4%.These two ecological types of fish were the main components causing the interannual community differences.The average body length of the typical estuarine settlement fish,the flower bass,has decreased from 40.8cm in 2015 to 21 cm in 2019,and the average body weight has decreased from 1,300 g in 2015 to 203 g in 2019.The size of the flower bass caught in the Qingcaosha reservoir has decreased year by year,which is related to the fact that only small fish can enter the reservoir when the fence is installed.The sampling eDNA method was used to analyze the fish community in April 2019 and classify the sequences obtained by high-throughput sequencing.The standard was to obtain 59,217 OTU sequences of effective fish according to the similarity of 97%.The OTU sequences were compared in NCBI and Fishbase database,and identified and analyzed as 31 species of fish belonging to 6 orders,11 families and 28 genera at 7 sites.Six orders were: cyprinformes,shad shad,fileferformes,perciformes,catfish formes,anguilliformes.Among them,17 species of cyprinoid fish were the largest,followed by 9 species of perch.In terms of abundance,the highest proportion was 79% for cyprinformes,13% for perciformes,5% for anguilliformes,and only a small proportion for other orders.By comparing the eDNA detection results with the fishing results,10 of the 11 species of fish caught in nets could be detected by eDNA method,and the detection rate of S1,S5 and S6 sites was 100%.The coincidence degree of the dominant species of the two survey methods was very high,which confirmed the feasibility of the application of eDNA in the investigation of fish community structure and diversity. |
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