基于多源数据的东海小黄鱼资源评估与管理

为建立稳定环境和波动环境机制下预防性渔业管理生物参考点, 整合调查设计和渔捞日志等多源资源指标构建混合矩阵, 利用logistic和Fox剩余产量模型的两步分析技术, 对东海区小黄鱼(Larimichthys polyactis)渔业资源动态进行评估。模型估算参数和管理参考点显示, Fox模型对渔获量和CPUE拟合的方差贡献率高于logistic模型, 两者分别为68%和57%, 环境承载力和内禀增长率相差较大。logistic模型估算了相对较低的承载力和较高的内秉增长率、初始开发率以及MSY。稳定环境下资源状况评判结果表明: 1999―2008年间多数年份的捕捞强度超过捕捞水平限制参考点, 渔业遭受过度开发, 平均资源量保持在中位水平且未达到过度捕捞状态, 但已超过目标参考点; 波动环境条件下的判别结果显示: logistic和Fox模型拟合的渔业水平均已达到过度捕捞。采用保护性捕捞参考点可增强渔业资源稳定性, 当捕捞死亡从参考点F_MSY降至预防性参考点F_opt, logistic模型估算资源量从8.1 t上升到10.1 t, 而渔获量从13.1 t下降至12.3 t; Fox模型资源量则从11 t增加到15.9 t, 相应的捕捞产量从12.8 t下降到11.6 t。Fox模型评估结果较为保守, 适合预防性渔业管理。

Stock assessment of small yellow croaker in the East China Sea based on multi-source data

Integrating the standardization of abundance indices into stock assessment models to examine the population dynamics of small yellow croaker, Larimichthys polyactis, was tested through a fisheries mixture matrix constructed with multiple data types. A precautionary approach to fishery control rules was adopted based on the logistic and Fox surplus production models, incorporating data from fishery-independent surveys, fishery-    dependent catch-per-unit-of-effort(CPUE), and regional harvests. A risk-averse control rule, derived from model parameters and associated uncertainty, was developed to manage fisheries for maximum sustainable yield (MSY) and rapid rebuilding of overfished stocks. The proposed control rule consists of relative biomass and relative fishing mortality rate in a deterministic environment and conservative harvest in a fluctuating environment. The results of the Fox model explained 68% of the variance observed for the stock abundance, while the logistic model explained 57%. The parameter estimates were different and the Fox model predicted a much larger decrease in population abundance at the MSY, intrinsic growth rates(r), and initial exploited levels. We compared the fishing mortality/current stock biomass from 1998 to 2006 with the fishing- and stock-related reference points, respectively. The results in a determined environment revealed that small yellow croaker stock in the East China Sea was overfished in most years, while the population was not always overfished during the entire period, although its biomass has been decreasing since 1999. However, both the Fox and logistic surplus production models indicate that the small yellow croaker fishery has been consistently over harvested in the fluctuating environment. Harvesting at a conservative level with either the Fox or logistic model could increase small yellow croaker abundance substantially with little decrease in harvest. At a conservative harvest level, there is a 24.7% increase in biomass with a 6.1% decrease in yield with the logistic model and a 44.5% increase in biomass with a 9.4% decrease in yield with the Fox model. The MSY assessment results from the Fox surplus production model was more conservative than that of logistic model, which is concordant with precautionary fisheries management strategies.