延长拖网伏季休渔期的渔业资源养护效应

海洋伏季休渔制度是当前中国最主要的渔业资源管理制度之一,并在实践中得到不断调整与完善,新的海洋伏季休渔制度已于2017年发布实施。为论证新制度延长拖网休渔期的渔业资源养护效应,本研究依据2015—2017年每年5月东海区拖网大面定点调查资料,利用Ricker动态综合模型,从拖网的渔获结构特征和带鱼(Trichiurus japonicus)的种群动力学过程视角开展了相应的量化分析研究。研究结果表明, 5月拖网利用主体为带鱼和小黄鱼(Larimichthys polyactis),带鱼和小黄鱼的性成熟比例分别为92.04%～95.57%和13.82%～29.55%,幼鱼比例分别为74.94%～88.90%和0.03%～4.19%;带鱼种群经过4.5个月的休渔,其单位补充量资源量、单位补充量渔获量和平均渔获质量与3.5个月休渔期相比较,分别增加了7.04%、8.96%和20.78%。以上结果表明,提前并延长拖网休渔期,东、黄海主要经济渔业资源带鱼与小黄鱼的产卵群体和幼鱼得到进一步保护,资源增殖效果随着休渔期的不断延长而增加,新制度的休渔时间设置更趋合理。但由于开捕后的带鱼与小黄鱼渔获仍主要以当龄鱼为主,有必要同时配套执行现已颁布的最小网目尺寸和开捕标准等其他渔业资源管理措施,以确保伏季休渔制度主导下的渔业资源养护效果能真正得到巩固,渔业资源的种群结构能够得到切实好转与不断合理化。

Effects of prolonging the trawl net summer fishing moratorium period in the East China Sea on the conservation of fishery resources

The summer fishing moratorium system, the main fishing management system in China, has been continuously adjusted and perfected in practice. In order to evaluate the conservation effects of prolonging the trawl net summer fishing moratorium period, which is contained in the new summer fishing moratorium system and promulgated in 2017, on the fishery resources, the data from the bottom trawl surveys in May during 2015-2017 and the dynamic integrated Ricker model were used to quantitatively analyze the structural characteristics of trawl catches and the dynamics of fish species such as the hairtail (Larimichthys polyactis). The results showed that the hairtail and the small yellow croaker (Larimichthys polyactis) were the main organisms that were trawled in May, and their sex maturity ratios were 92.04%-95.57% and 13.82%-29.55%, respectively, while the proportion of juvenile fish for the two species were 74.94%-88.90% and 0.03%-4.19%, respectively. Compared with that from the previous 3.5 month fishing moratorium period, the biomass per recruit, yield per recruit, and the average catch weight of hairtail increased 7.04%, 8.96%, and 20.78%, respectively, after the newly enforced 4.5 month fishing moratorium period. According to our study, advancing and prolonging the trawl net moratorium period could further protect the spawning groups and juveniles of the hairtail and the small yellow croaker, which were the main economic fishery resources in the East China Sea and the Yellow Sea. The resource enhancement effect was more significant with the longer moratorium period, so the time setting of the new summer fishing moratorium system was reasonable. However, after the newly enforced summer fishing moratorium period, the main hairtail and little yellow croaker catch were still dominated by 1-year-old fish. Thus, it is necessary to support the implementation of other fishery resource management measures in addition to the new summer fishing moratorium system, such as the minimum mesh size and the open capture standard, to ensure that the conservation effects are firmly established and that the population structure of the fishery resources can continuously improve.