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

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 per-recruitment; 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, L_t=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, L_t=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%。

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

Two Salangidae, Protosalanx hyalocranius (Abbott, 1901) and Neosalanx taihuensis (Chen, 1956) were sampled monthly from July 2015 to June 2016 in Hongze Lake. Catch per Unit Effort (CPUE) was estimated for these two species as the number of individuals or weight of each species collected per km2 of water area; growth and mortality parameters were estimated for both populations. The equilibrium output model was used to evaluate the appropriate onset timing of fishing to achieve the highest yield per-recruitment and to establish an optimized fishery management scheme. The spawner biomass per-recruitment (SBR) model was constructed to assess the fishing effects under two different fishery management schemes, the current one and the optimized one based on the equilibrium output model. Ranges of the body length and body weight for P. hyalocranius were 20.39—182.68 mm and 0.10—34.79 g, respectively; this fish had two rapid growth periods, from April to June and from August to November; the most fitted growth function was the von Bertalanffy equation, L_t=173.35×[1–e–1.972(t–0.092)]; fishing mortality and natural mortality coefficients for the population were estimated as 8.583/year and 3.292/year, respectively. Ranges of the body length and body weight for N. taihuensis were 20.4—82.7 mm and 0.04—3.40 g, respectively; this fish showed a relatively constant growth rate from April through November; the most fitted growth function was the Logistic equation, L_t=66.82/[1+e–5.386(t–0.124)]; fishing mortality and natural mortality coefficients for the populations were estimated as 7.006/year and 1.146/year, respectively. The current fishing management protocol on Salangidae in Hongze Lake has a banned fishing season between January 1 and August 8. Fishing is open for one week in mid-May. The equilibrium output model showed that the sum of yield per-recruitment for both species could reach the highest value when the banned fishing season is extended for 20 days, with the closure of one week fishing period in May and the onset of fishing period on August 29. Results of the SBR model showed that the SBR residues for P. hyalocranius were 20.23% and 36.72% of the unexploited state under the current protocol and the adjusted protocol, respectively, and those for N. taihuensis were 7.50% and 12.86%, respectively. In conclusion, the adjusted management protocol could effectively reduce fishing pressure for P. hyalocranius, but not for N. taihuensis.