Fish Community Structure And Growth Characteristics Of H.molitrix And A.nobilis In Qingcaosha Reservoir

The Qingcaosha reservoir is a large reservoir at the Changjiang Estuary in the northwest of changxing island,Shanghai.It is an important source of water in Shanghai with long east-west and narrow north-south.Since the reservoir has been fully put into operation in June 2011,the water is frequently transferred,and water and water drainage could cause the fish in the Yangtze River estuary to enter the reservoir and reservoir fish enter the Yangtze River.and for water control and water solution of H.molitrix?Hypophthalmichthys molitrix?,A.nobilis?Aristichthys nobilis?and fisheries effect of irregular,etc.,lead to changes of fish species composition and community structure in the reservoir.Therefore,regular fish surveys are conducted on the Qingcaosha Reservoir to study the succession pattern of fish communities in the new reservoir.Operation provides scientific basis for continuous supply of quality drinking water.From June 2015 to May 2017,a quarterly survey was conducted on fish resources in reservoirs.The survey method included three quarters of screen-wide storage,monthly samples provided by reservoir fishing teams.Data,etc.,used various methods to analyze fish species composition,dominance,food habits,species diversity,etc.,and at the same time studied the age growth of the major fishes,H.molitrix and A.nobilis in reservoirs,and established corresponding growth.The model provides reliable fishing basis and recommendations.In January,March,May,July,and November of 2017,used Dual-frequency identification sonar?DIDSON?to detect the reservoir,directly acquired the temporal and spatial distribution characteristics of fish population and the distribution relationship between plankton and rotifers,and further clarification the dynamic relationship between fish and plankton.The main results are as follows:1.Composition and analysis of reservoir fish.In the reservoir survey sample collection,analysis 60 batches,3601 individuals,897 kg fish,37 different species of fish were collected,belonging to 10 families and 12families.34 genera.The largest number of fishes in the fish is the carp,accounting for64.84%of the total number of fishes.In addition,there were 4 types o f perciformes,10.81%,and lusiformes,which accounted for 8.11%,and all other species were only one species.The dominant species of reservoir are H.molitrix,A.nobilis and other freshwater fishes.The construction of the reservoir also changed the ecolo gical environment and fish structure of the Qingcaosha Reservoir.The breeding,growth and feeding of the fish in the Yangtze River estuary were hindered,and the reproduction of migratory fishes was particularly affected.In our survey cycle,only one Chinese sturgeon was found in the Yangtze River migratory fish,and one Japanese migratory fish was found in the sea.According to the life of fish,the reservoir fish could be roughly divided into four groups:river-sea migratory type,river-lake migratory type,mountain stream,.sedentary,ecological types is given priority to with.sedentary type of fish,which are mainly freshwater fish.According to the food analysis of fish,the fish can be divided into five types:herbivore,piscivores,planktotrophic,invertivores and omnivorous.According to fish fauna composition analysis,the fish can be divided into four fish fauna complex:southern plains fish fauna complex,China plain,neogene early fish,northern plains.Origin of reservoir fish has obvious nature o f tropical and subtropical plains,freshwater fish in China plains are the kinds of complex and southern plains department is given priority to,the kinds of complex early and late tertiary,northern plains region is a complex of several.Thus,the composition of the reservoir fish is a Oriental world.During the summer of 2015 to the spring of 2017,the season of the total amount of fish species,fish and biological diversity index of the Qingcaosha reservoir,community diversity index,richness index,evenness index appeared different degree of change.In each season of the Qingcaosha reservoir,the specie of catcheswere the most in summer and autumn,followed by spring,and the least in winter.2 Study and Analysis of H.molitrix and A.nobilis's growth characteristics.In this paper,the biological characteristics of the main fishes of Qingcaosha Reservoir are analyzed.The growth equations of Von Bertalanffy of H.molitrix and A.nobilis is fitted by the relationship between body length,body weight and age.?1?VonBertalanffy growth equation of H.molitrix:The least squares method is used to obtain the growth equation as follows:asymptote length=77.73,growth coefficient k=0.183,and t0=-0.600.Then the length and weight equations of H.molitrix were calculated as:L_t=77.73^{[1-e-0.183?t+0.60?]},W_t=20024.3^{[1-e-0.183?t+0.60?]3.027},t represents the age of the fish.?2?Von Bertanlanffy Growth equation of A.nobilis:Asymptote length=92.11,growth coefficient k=0.172,t0=-1.266 and then the length and weight equation of A.nobilis were calculated as:L_t=92.11^{[1-e-0.172?t+1.27?]},W_t=23875.2^{[1-e-0.172?t+1.27?]2.946},Where t represents the age of the fish.It has great significance to make scientific breeding and fishing for the H.molitrix and A.nobilis of the reservoir,to the rational utilization of fishery resources and the protection of water sources.Generally speaking,the age growth inflection point of H.molitrix in the reservoir is 5.,4,and A.nobilis is 5.0.The growth advantage is not fully played before the growth inflection point.After growth inflection point,as the growth of the age,the growth slows down,and the bait coefficient increases,conversion efficiency,it is not economy.Recommend the fishery utilization of H.molitrix,A.nobilis to 5 for the hunting age after age,it can make the best use of nitrogen and phosphorus in water body,cutting the algae.3 Fish level distribution assessment of Dual-frequency identification sonar DIDSONUsing Dual-frequency identification sonar DIDSON to evaluate the fish level distribution of Qingcaosha Reservoir for one year,it was found that the density of fish groups under different months has change in the distribution.The combination of the fish distribution density and plankton distribution of the same period shows that at the same time the density of fish and plankton and density distribution of the rotifer is consistent,both were positively correlated.