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首页> 外文期刊>ICES Journal of Marine Science >The influence of trawl efficiency assumptions on survey-based population metrics
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The influence of trawl efficiency assumptions on survey-based population metrics

机译：拖网效率假设对基于测量的人口指标的影响

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摘要

Catch data from bottom trawl surveys are used in various ways (e.g. stock assessments, fisheries management, and ecosystem studies) to represent trends in fish populations across space, time, season, or size. Relative abundance indices assume constant capture efficiency, and area-swept abundance requires an estimate of capture efficiency. Therefore, it is important to develop a predictive understanding of the interaction between fish and survey gear. We conducted experiments to test two primary factors that influence the efficiency of survey trawls at capturing demersal groundfish: (1) footrope escapement-estimated by attaching a collection bag beneath the primary trawl, and (2) herding of the sweeps/doors-estimated by varying sweep length. Random forest models were used to disentangle the herding effect from patterns caused by environmental variables. Contrary to common assumptions, footrope efficiency was incomplete ( 100%) and herding was non-trivial (0%), which introduces a bias in population metrics that rely on such assumptions. This bias varied by species and depended upon the relative strength of the counteracting effects of footrope escapement and herding. Our findings suggest that trawl efficiency should be estimated (not assumed) to derive area-swept abundance, and relative abundance indices should account for size-based efficiency and changing size compositions.
机译：从底部拖网调查捕获数据以各种方式使用（例如股票评估，渔业管理和生态系统研究）来代表空间，时间，季节或尺寸的鱼群趋势。相对丰富指数假设恒定捕获效率，并且区域扫描丰度需要捕获效率的估计。因此，重要的是要制定对鱼和调查齿轮之间相互作用的预测理解。我们进行了实验，以测试两个主要因素，影响捕获过度纹理的调查拖网的效率：（1）通过在主要拖网下附着收集袋和（2）扫描/门的放牧估计估计脚步率变化的扫描长度。随机森林模型用于解开环境变量引起的模式的牧群效果。与常见的假设相反，脚踏效率不完全（＆ 100％），掠夺性是非琐碎的（＆ 0％），这引入了依赖于这种假设的人口指标中的偏差。这种偏差因物种而变化，依赖于脚踏脱落和放牧的抵抗效果的相对强度。我们的研究结果表明，应估计拖网效率（未假设）来派生地区席位丰富，而相对丰富指数应考虑基于尺寸的效率和变化尺寸组成。

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