Community Structure Of Small-scale Fishery Resources And Biological Study Of Dominate Species In Dianshan Lake

Dianshan Lake is the only natural fresh lake and important water sourceprotection area. It has many functions in transportation, irrigation, aquaculture,playing a significant role in people’s life and economic development. In recent years,the ecological environment of Dianshan Lake had suffered great damage, the numberof aquatic animals species declined and traditional economical fish stock is alsodestroyed. Shanghai government conducted a comprehensive rectification and spent alot of manpower, material on fishery enhancement and releasing activities inDianshan Lake since2005. It has played positive effect on protecting the watersecological remediation and protecting fishery resource and enhancing fishermanincome. Many problems still exist in Dianshan Lake, such as over-fishing, thedecrease of water quality.The study last one year from August2010to July2011, exploring various area:investigating and analyzing the community structure，density and diversity ofsmall-scale fishes, estimating the growth and mortality parameters of Cloilia ectentelin Dianshan Lake by used ELLEFAN technique. Discussing the propagation ofP．nitidus, one kind of dominant fish species in Dianshan Lake, covering itsspawning colony, sexual maturation. This paper aimed to supply historicalinformation and reference for the jobs of fishery enhancement in future, to provide thescientific basis to future research work.The community structure，density and diversity of small-scale fishes wereinvestigated with trawl in Dianshan Lake.15species were collected. Cloilia ectentes,Plagiognathops microlepis, Neosalanx taihuensis chen,Hypouham phus intemediusand Acheilognathus taenianlis were the dominant species. The density ofsmall—sized fishes in the lake was0.82ind/m²,4.64g/m². Diversity of fishcommunity in the seine was low．The diversity index（H’），dominance index（λ）andevenness index（J’） of small-sized fish community were0.669，0.738and0.247 respectively. The growth of Cloilia ectentel，Neosalanx taihuensis chen andAcheilognathus taenianlis was allometric growth and the others were isometricgrowth among these6fishes.Wild fish can be use reasonably， In order to increaseeconomic and ecological benefit， through optimizing fish community structure.Based on the investigation data in2010to2011, and by using ELLEFANtechnique, the growth and mortality parameters of Cloilia ectentel in Dianshan Lakewere estimated. The estimated parameter for Von Bertalanffy growth equation wereL_∞=35.7cm、K=0.54、t₀=-0.48. The turning point for body weight growth curve of thestock was situated at t=1.1in Dianshan Lake. The natural mortality calculated withPaulys empirical equation was M=0.94, and the total mortality estimated by lengthconverted catch curve was Z=2.12and exploitation rate （E） was0.55. Yeild-perrecruit analysis applying Beverton-Holt model indicated, if the optimum body-lengthshould be increased,we could get the most value to achieve the sustainable use ofCloilia ectentel．Based on the biological data of130P．nitidus collected from Dianshan Lakebetween2010to2011, we analyzed the P．nitidus’s length distribution, full weightdistribution, relationships between length and weight, t, sex ratio, maturity stages ofthe gonad, gonad somatic index, feeding intensity. The results indicate:（1） Thedistribution of length are4.7cm¹6cm, with a dominant were8cm¹2cm; Thedistribution of weight are1.3g²8.4g, with a dominant were5g¹5g;（2） Themean length of females and males are10.93cm and11.37cm, with a mean weight of15.1g and15.88g,respectively;（3） The relationship between length and weight offemales and males were expressed as，R²=0.8418，（N=96），，R2=0.8690，（N=37）, After covariance analysis, therelationship between length and weight of female and male showing Significantdifference.（4）)Based on Pearson test, there is positive correlation in relationship ofgonad weight and length, weight of females and males, and the gonad weight ofP．nitidus increased with the total length or round weight;（5） the female–male ratio is2.6:1, not accordance with1:1,（6） The length of minimum sexual maturity of famleand male P．nitidus is8.6cm and9.4cm,with the weight is6.9g and8.9g,respectively.（7） There is difference in gonad somatic index between females and males, the matureindividuals’s gonad somatic index is greater than immature individuals’, the gonadsomatic index of immature individuals increased with total length, but for the mature individuals showing negative correlation;...