| Sanshan bay is located in the northeast of Fujian Province,which is surrounded by the Dongchong peninsula and Jianjiang peninsula.It has a total area of 720.36 km2.It has many harbors and islands which include GuanJingyang,Dongwuyang,Fudingyang,Sanduao.Sanshan bay has a vast water area and rich aquatic resources.But the composition and structure of Sanshan bay's resources are destroyed by overfishing,water pollution,reclamation and other marine development activities.Many economic fish resources decline.Stock enhancement is a direct way to supplement the fishery resources and repair the ecological environment.It will improve the structure of groups and ecological system and achieve the goal of ecological benefit and economic benefit by means of throwing cultured fishs,shrimps,crabs,etc into natural water.the main results were showed as follow:(1)The Ecopath model contained 20 functional groups which include primary producers,dedritus and others.The Effective Trophic level of these functional groups ranged from 1 to 4.089;the EE values of planktivorous fish,shrimp,crab and large yellow croaker were relatively high,and the primary producers,echinoderms and dedritus were low.(2)The average transfer efficiency of Sansha bay ecosystem was 10.8%.The total throughput of the ecosystem was 2344.409 t/km2·y.Flows from primary producers and dedritus accounted for 51.2%and 48.8%of the total throughput,indicating that grazing food chain slightly higher than detritus food chain.(3)The TPP/TR value was 2.766,SOI value was 0.247,CI value is 0.399 and the TB/TT value was 0.009,Finn's cycling index and Finn's mean path length were relative low which were 5.15%and 2.509.These indicators indicating that the ecosystem has a low maturity and poor stability.(4)According to the results of Ecopath,combining with traditional selection principle,we set up eight screening indicators:local important species,economic value,artificial seedling maturity,historical releasing species,serious recession species,major advantages of fishing,key species of ecosystem and bait biological of key species.Based on these indicators,we selected the appropriate releasing species of sansha bay.The releasing capacity of large yellow croaker stock enhancement which was estimated by the Ecopath model was 5.52 million.(5)The large yellow croaker as the test object,Based on the fishery resources monitoring data collected in Sansha bay from 2015-2016,The results indicate that the average body length is 132.56 mm,with the group of predominant body length 100-150 mm,accounting for 60.12%;the average body weight is 49.59 g,with the group of dominant weight 10-50 g,representing 72.3%.The relationship between length and weight was expressed as:W=1.766×10-5L2.987(R2=0.982).The growth parameters of von Bertalanffy formula estimated by ELEFAN were L?=320.25mm,k=0.52 and t0=-0.27 a;Total death coefficient(Z),natural death coefficient(M)and the coefficient of fishing death(F)are 2.35,0.534 and 1.816,the exploitation rate in recent years was 0.773,and flexion age is 1.83 years.(6)The results of fishery production investigation showed that the total capture of Large Yellow Croakerthe in 2015 is 120.461 t,the economic output is 4.44 million yuan,the ratio of intput and ouput in first years close to 1:5 by estimate the catch in theory;finally,an overall assessment is given from aspects of economy and society. |
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