洪泽湖大银鱼和太湖新银鱼的生长、死亡参数及资源利用状况

GROWTH,MORTALITY AND EVALUATION OF RESOURCE UTILIZATION FOR TWO SALANGIDAE,PROTOSALANX HYALOCRANIUS AND NEOSALANX TAIHUENSIS IN HONGZE LAKE

2015年7月至2016年6月采用银鱼拖网对洪泽湖大银鱼和太湖新银鱼进行周年逐月采样,确定单位水体面积(1 km2)捕捞渔获量,估算种群生长和死亡相关参数;利用平衡产量模型评估获得最高单位补充量渔产量时的最适开捕时间,并设定为优化的管理方案;构建单位补充量产卵群体生物量(Spawner biomass perrecruitment;SBR)模型,评估洪泽湖银鱼资源在当前和优化管理方案下的捕捞利用状况,为其资源管理提供指导。研究结果表明,大银鱼体长和体重分别为29.0—182.6 mm和0.10—34.79 g,世代周期中存在2个快速生长阶段,即4—6月和8—11月;最适生长方程为von Bertalanffy方程,Lt=173.35×[1–e–1.972(t–0.092)];捕捞死亡系数和自然死亡系数分别为8.583/year和3.292/year。太湖新银鱼体长和体重分别为20.4—82.7 mm和0.04—3.40 g,整个世代周期持续生长,最适生长方程为Logistic方程,Lt=66.82/[1+e–5.386(t–0.124)];捕捞死亡系数和自然死亡系数分别为7.006/year和1.146/year。平衡产量模型结果显示,当大银鱼开捕年龄为0.593 year,太湖新银鱼开捕年龄为0.420 year时,即将银鱼开捕时间由现行的8月9日,推迟20d,并取消现行的5月一周捕捞,可以获得最大总渔产量。SBR模型评估结果显示,在当前管理模式下,大银鱼SBR残存量相当于未开发状态的20.23%,优化管理方式后可达到36.72%,能有效缓解大银鱼的捕捞压力;在优化管理方式后,大湖新银鱼的SBR残存量从现行管理方式下相当于未开发状态的7.50%,提升至12.86%,但仍低于20%。

Two Salangidae,Protosalanx hyalocranius(Abbott,1901)and Neosalanx taihuensis(Chen,1956)weresampled monthly from July2015to June2016in Hongze Lake.Catch per Unit Effort(CPUE)was estimated for thesetwo species as the number of individuals or weight of each species collected per km2of water area;growth and mortalityparameters were estimated for both populations.The equilibrium output model was used to evaluate the appropriateonset timing of fishing to achieve the highest yield per-recruitment and to establish an optimized fishery managementscheme.The spawner biomass per-recruitment(SBR)model was constructed to assess the fishing effects undertwo different fishery management schemes,the current one and the optimized one based on the equilibrium outputmodel.Ranges of the body length and body weight for P.hyalocranius were20.39-182.68mm and0.10-34.79g,respectively;this fish had two rapid growth periods,from April to June and from August to November;the most fitted growthfunction was the von Bertalanffy equation,Lt=173.35×[1–e–1.972(t–0.092)];fishing mortality and natural mortality coefficientsfor the population were estimated as8.583/year and3.292/year,respectively.Ranges of the body length and bodyweight for N.taihuensis were20.4-82.7mm and0.04-3.40g,respectively;this fish showed a relatively constantgrowth rate from April through November;the most fitted growth function was the Logistic equation,Lt=66.82/[1+e–5.386(t–0.124)];fishing mortality and natural mortality coefficients for the populations were estimated as7.006/year and1.146/year,respectively.The current fishing management protocol on Salangidae in Hongze Lake has abanned fishing season between January1and August8.Fishing is open for one week in mid-May.The equilibrium outputmodel showed that the sum of yield per-recruitment for both species could reach the highest value when the bannedfishing season is extended for20days,with the closure of one week fishing period in May and the onset of fishing periodon August29.Results of the SBR model showed that the SBR residues for P.hyalocranius were20.23%and36.72%ofthe unexploited state under the current protocol and the adjusted protocol,respectively,and those for N.taihuensis were7.50%and12.86%,respectively.In conclusion,the adjusted management protocol could effectively reduce fishingpressure for P.hyalocranius,but not for N.taihuensis.