Growth Characteristics Of Portunus Trituberculatus In Zhejiang Fishing Ground

Portunus trituberculatus belongs to Crustacea,Decapoda,Portunidae and Portunus.It is one of the important marine fishing species in Zhejiang Province,and plays an important role in marine fishing industry and protein supply.According to the samples of PR trituberculatus collected from May 2015 to May 2016 in Yueqing sea area,zhoushan and zhouwai fishing grounds and the observation data from aquaculture farm,we studied the biological characteristics of P.trituberculatus and its seasonal changes in these sea area,we also analyzed the stepwise growth characteristics of P.trituberculatus,and compared the results with previous research.Totally 769.trtuberculatus were collected in Yueqing sea area,zhoushan and zhouwai fishing grounds,the distribution of the carapace width(L)ranged from 4cm to 20.2 cm,and the average value was 12.5 cm.The body weight(W)ranged from 4.04g to 357.96g,with average of 116g,The ratio of male and female was 1:0.77,female individuals were in the dominant position.We built 3 growth functions to demonstrate the features of continuous and discontinuous growth,and then made comparison among them.The v-B growth function(VBGF)and v-B seasonal growth function(VBSGF)were built according to the collected sample data using FiSAT II and length frequency distribution analysis(LFDA 5.0)software packages,respectively.While,the observation data from aquaculture farm were used to build the stepwise growth function(SWGF)of P.trituberculatus.The results showed the relationship of W and L was W=0.06438L2.9111(Combination),W?=0.0704L28772 and W?= 0.05923L2.9421 respectively;The VBGF of P.trituberculatus were Lt ?21(1-e-0.83(t+0.373))(Combination),Lt=21(1-e-0.72(t+0.449))(Male)and Lt =21(1-e-0.97(t+0.304))(Female)respectively;The VBSGF of P.trituberculatus were Lt?18.68[1-e[-1.55(T+0.07)-1.023/2?sin(2?(t+03-.38))+1.023/2?sin(0.62?)]](Combination),Lt=17.62[1-e[-1.19(t+0.75)-1.0472/2?sin(2?(t-0.01))+1.0472/2?sin(-1.527?)]/(Male)and Lt=17.65[1-e[-169(t+0.12)-1.7407/2?s'n(2?(t+0.42))+1.7407/2?sin(0.6?)]](Female)respectively;The SWGF of P.trituberculatus was:Lt(Li,min-Li,max)RAND + Li,max,when t?(ti,min,ti,max)RAND?N(0.5,0.29).Compared with the previous research results,the parameters of a and b estimated in this research were larger,and b was closer to 3.Parameter K>1 in the seasonal growth equation,and the results showed that the P.trituberculatus grew faster,which conform to its biological characteristics.The difference between any 2 of above 3 functions(VBGF,VBSGF and SWGF)were significant,t(P<0.05).This may be related to the change of the marine environment,stock enhancement and releasing,as well as the difference of sexual maturity between male and female.Therefore,on the basis of biology,scientific stock assessment of P,trituberculatus should be carried out in the future,and provide scientific suggestions for the effective management of this resource.