基于双重拔靴法拟合拖网网囊选择性的不确定性

研究拖网网囊选择性对于渔业的科学管理和资源的合理利用都有重要意义。拖网网囊选择性的研究一般先开展捕捞实验,然后使用选择性模型拟合和处理实验数据,最后得出选择性参数和选择性曲线。主要的选择性参数包括50%选择体长(L50)和选择范围(SR)。但是,仅仅提供选择性参数和曲线是不够的,还需要拟合它们的不确定性,并以置信区间的形式展现。双重拔靴法是拟合网囊选择性不确定性的重要方法。本研究在阐述双重拔靴法基本原理的基础上,选取2组实验数据为实例,用常规方法和双重拔靴法进行拟合,通过比较拟合结果诠释双重拔靴法的特点和优势。结果表明,双重拔靴法能够很好地拟合网囊选择性参数L50、SR和曲线的不确定性。同时,本研究还就应用双重拔靴法的重大误区进行了分析和讨论。本研究可为研究人员开展渔具选择性研究提供方法参考。

Estimation uncertainties of the size selectivity of trawl codends based on the double-bootstrapping technique

Codend size selectivity is the keystone for management of trawling fisheries and sustainable exploitation of fisheries resources. In order to assess the size selectivity of trawl codends, experimental sea trials are often conducted and fishing data is manipulated using some mathematical models to obtain selectivity parameters, such as 50% retention length (L50) and selection range (SR), and selectivity curves. Providing the values of this information, however, is highly inadequate. It needs to account for the uncertainties in size selectivity and represent them in confidence intervals. To do this, the double-bootstrapping technique is intensively applied in fishing gear selectivity studies. In this study, the basic principle of the double-bootstrapping technique was firstly introduced, then two set of fishing data involved two different fishing species were used as case studies to show and compare how this technique was used to estimate the uncertainties of codend size selectivity. Our results demonstrated that the uncertainties of codend size selectivity could be easily estimated applying the double-bootstrapping technique. Additionally, the most commonly wrong practice of using the doublebootstrapping technique was discussed. Our study will provide a guideline for conducting trawl codend selectivity studies, improve the level of selectivity researches, and contribute to the sustainable development of marine fisheries in China.