Abstract To assess the exploitation status of marine resources and to formulate scientific advice for fisheries management, reliable fishery data are required. When dealing with data-poor stocks, like skates and rays (Rajiformes) caught by multispecies and multigear fisheries in Portugal, strategies need to be defined to surpass data limitations, like species misidentification and the lack of fishing gear information in landings data. This paper presents a stepwise statistical procedure, involving factor analysis for mixed data and flexible discriminant analysis, to estimate the total number of trips and the correspondent total landed weight by species. Interviews and self-sampling that took place under a pilot study (2011 – 2013) focused on skate and ray fisheries showed that collaborative research is a low cost and valuable tool to improve our knowledge on fisheries and their catches and may contribute to increase the accuracy. Given the persistence of species misidentification errors in the official statistics, the procedure here presented is currently used to report the Portuguese annual estimates of species-specific landed weight. This procedure may be considered to be applied to data deficient fishery bycatch resources for which dedicated sampling programs are not priority.

中文翻译：

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多品种和多网具渔业中鱼形目副渔获物估计

摘要 为了评估海洋资源的开发状况并为渔业管理制定科学建议，需要可靠的渔业数据。在处理数据贫乏的种群时，例如葡萄牙多物种和多网具渔业捕获的鳐鱼和鳐鱼（Rajiformes），需要制定策略以超越数据限制，例如物种识别错误和上岸数据中缺乏渔具信息。本文提出了一种逐步统计程序，包括混合数据的因子分析和灵活的判别分析，以估计总旅行次数和相应的物种总着陆重量。在一项针对滑冰和鳐鱼渔业的试点研究（2011-2013 年）下进行的访谈和自我抽样表明，合作研究是一种低成本且有价值的工具，可以提高我们对渔业及其捕捞量的了解，并可能有助于提高准确性. 鉴于官方统计数据中物种识别错误的持续存在，此处介绍的程序目前用于报告葡萄牙对特定物种登陆重量的年度估计。该程序可被认为适用于数据不足的渔业兼捕资源，专门的抽样计划不是优先事项。此处介绍的程序目前用于报告葡萄牙对特定物种着陆重量的年度估计。该程序可被认为适用于数据不足的渔业兼捕资源，专门的抽样计划不是优先事项。此处介绍的程序目前用于报告葡萄牙对特定物种着陆重量的年度估计。该程序可被认为适用于数据不足的渔业兼捕资源，专门的抽样计划不是优先事项。