The Resource Evaluation Of Trichiurus Japonicus On East China Sea In Summer Close Season

Trichiurus japonicus is an important fish in the East China Sea. China have carried the Summer Close Season from 1995 for the fact that the resource of Trichiurus japonicus had declined day by day. The Summer Close Season have protected the Trichiurus japonicus and achieved significant ecosystem benefit, economy benefit and society benefit.Based on the dynamic monitoring data of Trichiurus japonicus in 1990~2007 and the research in the East China Sea in 2008~2009, the stock dynamic situation of Trichiurus japonicus was analyzed after the Summer Close Season in the East China Sea, discussed the utilizing situation of its resource, and provided scientific basis for rational using of the resource.Firstly, the stock dynamic situation of Trichiurus japonicus was analysed after the Summer Close Season in the East China Sea. The result shows that the total catch of Trichiurus japonicus remains at a high-yield level. The density index of juvenile individual also remains at a high level. The ratio of the elder individual has increased and the average anal length of Trichiurus japonicus tends to be an increasing situation after 13 years'summer close season in the East China Sea.Secondly, growth equation of Von Bertalanffy was computed by the Walford's method. The result shows that asymptotic anus length(AL∞) is 497.9mm, growth coefficient(K) is 0.332, and age at zero length(t0) is -0.465, the turning point of body weight is at 2.68year, the turning point of weight is 523.66g. The mortality parameters were estimated by using Length-converted catch curve technique in FISATⅡ. The instantaneous rate of total mortality(Z) is 3.148, the fishing mortality(F) is 2.71, and the exploit rate is 0.86.Thirdly, the rational utilization of Trichiurus japonicus resource in the East China Sea was approached by using the catch per recruit theory of Beverton-Holt model. The result shows that the unit catch will increase 93.16% if the tc changed from 0.375 to 1. And the unit catch increase 198.8% if the tc changed from 0.375 to 2 at the exploitation rate of Trichiurus japonicus(E)=0.86.Lastly, the Stock-Recruitment(SR) Relationship of Trichiurus japonicus was fitted by six statistical SR models. And the best relationships were selected by using AIC(Akaike Information Criterion) and BIC(Bayesian Information Criterion) methods respectively. The result shows that the Shepherd model is considered the best model. And the maximum recruitment stock(Rmax) is 68.92×10~8ind, the maximum spawn stock(Smax) is 16.39×10~8ind, the spawn number of maximum sustainable yield(SS) is 16.02×10~8ind, the recruitment number of maximum sustainable yield(RS) is 68.74×10~8ind, and the maximum sustainable yield(MSY) is 52.72×10~8ind.