莱州湾三疣梭子蟹生物学参数及生长特性研究

根据2012年5~11月使用单船底拖网进行的7个航次调查数据,运用FiSATⅡ软件相关模块对莱州湾三疣梭子蟹(Portunus trituberculatus)生长、死亡参数及生长特性、种群补充模式、资源量等进行研究。结果显示:7个航次共捕获三疣梭子蟹1128 ind,雌雄性比为0.96,雌性甲宽为27~227 mm,雄性为29~207mm;获得三疣梭子蟹雌性生长参数k=1.60、L_∞=241.50、W∞=639.29、t0=0.081,雄性为k=1.50、L∞=210.00、W∞=418.23、t0=0.091;经体长结构VPA(Length-Structured VPA)模块估算,稳定状态下莱州湾三疣梭子蟹雌性渔获尾数为734×10~4ind、种群尾数为1.15×10~8ind、资源量为2 682 t,雄性渔获尾数为810×10~4ind、种群尾数为1.19×10~8ind、资源量为1 929 t;经变换体长渔获曲线法(Length-Converted Catch Curve)及刀刃式选择假设模型(Knife-Edge)估算三疣梭子蟹雌性总死亡系数Z=4.17、自然死亡系数M=1.20、捕捞死亡系数F=2.97、资源开发利用率E=0.712、平均选择甲宽Lc=62.38mm、最大效益时开发利用率Emax=0.515;雄性总死亡系数Z=3.76、自然死亡系数M=1.19、捕捞死亡系数F=2.57、资源开发利用率E=0.684、平均选择体长Lc=40.84 mm、最大效益时开发利用率Emax=0.487。研究表明:1)莱州湾三疣梭子蟹雌雄性比、雌雄性幂指数均处在正常水平,总体生长状况良好;2)莱州湾三疣梭子蟹雌、雄性群体资源利用率均显著高于最适利用率与最大利用率,处于过度开发水平;3)莱州湾三疣梭子蟹现存资源量低于生态容量,上升空间较大。

On biological parameters and growth characteristics of Portunus trituberculatus in the Laizhou Bay

The Laizhou Bay is the spawning and feeding ground for many important economic marine species and thus, is rich in fishery resources.However, in recent years, frequent occurring of overfishing in this region leads to destruction of local fishery resources.As an important marine economic species and the main species for propagation and releasing, Portunus trituberculatus in the Laizhou Bay is also subject to severe impairment.Therefore, the study on the biological parameters and growth characteristics of Portunus trituberculatus is necessary.Based on the data of bottom trawl surveys on Portunus trituberculatus from May 2012 to November 2012, using FiSATⅡsoftware, the growth, mortality parameters as well as recruitment pattern, standing crop were studied.The results showed that 1 128 ind of Portunus trituberculatus were captured and the female-male ratio was 0.96.The carapace width of female Portunus trituberculatus ranged from 27 to 227 mm, and the male ranged from 46 to 185 mm.According to the measured data and then estimated by the Electronic Length Frequency Analysis, the growth parameters of Portunus trituberculatus were obtained as follows: for female Portunus trituberculatus: k=1.60,L∞=241.50,W∞=639.29,t0=0.081;for male Portunus trituberculatus:k=1.50,L∞=210.00,W∞=418.23,t0=0.091.All of the parameters conformed to the growth characteristics of Portunus trituberculatus.Through the Length-Structured VPA module, it was estimated that there were 115 million individuals of female Portunus trituberculatus for 2 682 tons and 119 million individuals of male Portunus trituberculatus for 1 929 tons in the Laizhou Bay, in which 7.34 million individuals of female Portunus trituberculatus and 8.10 million individuals of male Portunus trituberculatus had been captured.Through the Length-Converted Catch Curve, Pauly Empirical Formula and Beverton and Holt Y/R Analysis module, the mortality, the exploitation ratio and the optimum utilization rate of Portunus trituberculatus were estimated.The results were as follows: for female Portunu strituberculatus: total mortality (Z) =4.17, natural mortality (M) =1.20, mean selection length (Lc) =62.38 mm, fishing mortality (F) =2.97, exploitation rate (E) =0.712, optimum utilization rate (Emax) =0.515;for male Portunus trituberculatus: total mortality (Z) =3.76, natural mortality (M) =1.19, mean selection length (Lc) =40.84 mm, fishing mortality (F) =2.57, exploitation rate (E) =0.684, optimum utilization rate (Emax) =0.487.All these indices could well descripe the realities, indicating that there was serious overexploition.The results also showed that the level of sex ratio of Portunus trituberculatus in the Laizhou Bay was normal, which meant the growth of this species was in a good condition.The exploitation ratio of the Portunus trituberculatusis was significantly higher than the normal level(P<0.05), indicating the overdeveloping occurring to the Portunus trituberculatus in the Laizhou Bay.Finally, the resource amount of Portunus trituberculatusis was below the ecological capacity, which meant there could be more quantities of this species existing in the Laizhou Bay waters.