By-catch is the most significant direct threat marine megafauna face at the global scale. However, the magnitude and spatial patterns of megafauna by-catch are still poorly understood, especially in regions with very limited monitoring and expanding fisheries. The Indian Ocean is a globally important region for megafauna biodiversity and for tuna fisheries, but has limited by-catch data. Anecdotal and scattered information indicates high by-catch could be a major threat. Here, we adapt a Productivity Susceptibility Analysis tool designed for data-poor contexts to present the first spatially explicit estimates of by-catch risk of sea turtles, elasmobranchs, and cetaceans in the three major tuna fishing gears (purse seines, longlines, and drift gill nets). Our assessment highlights a potential opportunity for multi-taxa conservation benefits by concentrating management efforts in particular coastal regions. Most coastal waters in the northern Indian Ocean, including countries that have had a minimal engagement with regional management bodies, stand out as high risk for fisheries interactions. In addition to species known to occur in tuna gears, we find high vulnerability to multiple gear types for many poorly known elasmobranchs that do not fall under any existing conservation and management measures. Our results indicate that current by-catch mitigation measures, which focus on safe-release practices, are unlikely to adequately reduce the substantial cumulative fishing impacts on vulnerable species. Preventative solutions that reduce interactions with non-target species (such as closed areas or seasons, or modifications to gear and fishing tactics) are crucial for alleviating risks to megafauna from fisheries.

中文翻译：

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海洋巨型动物对印度洋金枪鱼渔业脆弱性的空间明确风险评估

副渔获物是全球范围内海洋巨型动物面临的最重要的直接威胁。然而，人们对大型动物副渔获物的规模和空间格局仍然知之甚少，特别是在监测和渔业扩张非常有限的地区。印度洋是大型动物生物多样性和金枪鱼渔业的全球重要区域，但副渔获物数据有限。轶事和零散的信息表明，高副渔获物可能是一个主要威胁。在这里，我们采用了一种专为数据匮乏的环境而设计的生产力敏感性分析工具，以首次在空间上明确估计三种主要金枪鱼渔具（围网、延绳钓和漂流）中海龟、弹性鳃和鲸类的副渔获风险刺网）。我们的评估强调了通过将管理工作集中在特定沿海地区来实现多类群保护效益的潜在机会。印度洋北部的大多数沿海水域，包括与区域管理机构接触最少的国家，都被认为是渔业互动的高风险。除了已知存在于金枪鱼渔具中的物种外，我们发现许多不属于任何现有保护和管理措施的鲜为人知的弹性鳃鱼很容易受到多种渔具类型的影响。我们的研究结果表明，目前侧重于安全释放做法的副渔获物缓解措施不太可能充分减少对脆弱物种的大量累积捕捞影响。