Abstract The incidental mortality of seabirds from fisheries ranks as the greatest threat impacting seabirds globally. However, its impact on seabird populations may have been substantially underestimated due to lost, undetected bycatch. To estimate the full extent of the bycatch problem, knowledge about the magnitude and variability of lost bycatch is necessary. Based on a long-term dataset, this study aims to facilitate the loss-corrected bycatch estimates for pelagic longline fisheries that do not have a concurrent bycatch loss observation component. We analyze information from all types of fishery interactions of seabirds to improve the estimate of bycatch loss rate and also reveal its variability. Specifically, we analyze how environmental and ecological factors affect seabird bycatch loss rate using Bayesian state-space models. Results show strong species effects in the bycatch loss rate. Inclement weather and strong competition among seabird species also affect bycatch loss rate. Estimates of the species-specific bycatch loss rate indicate that, for some species, the loss can well exceed the average loss rate, suggesting that seabird bycatch loss cannot be further ignored in assessing the fishery impact on seabird populations. To gauge the full scale of seabird bycatch, it is critical to account for this lost bycatch in bycatch assessments, at minimum, using an average loss rate with the ultimate goal of species-specific loss-corrected assessments.

中文翻译：

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远洋延绳钓渔业中的海鸟兼捕损失率变化

摘要 渔业海鸟的意外死亡是影响全球海鸟的最大威胁。然而，由于兼捕丢失、未被发现，它对海鸟种群的影响可能被大大低估了。为了估计兼捕问题的全部范围，需要了解兼捕损失的幅度和可变性。基于长期数据集，本研究旨在促进对没有并发兼捕损失观察组成部分的远洋延绳钓渔业进行损失校正的兼捕估计。我们分析了来自海鸟所有类型渔业相互作用的信息，以改进对兼捕损失率的估计并揭示其可变性。具体来说，我们使用贝叶斯状态空间模型分析环境和生态因素如何影响海鸟兼捕损失率。结果表明，兼捕损失率有很强的物种效应。恶劣的天气和海鸟物种之间的激烈竞争也会影响兼捕损失率。特定物种兼捕损失率的估计表明，对于某些物种，损失可能远远超过平均损失率，这表明在评估渔业对海鸟种群的影响时不能进一步忽略海鸟兼捕损失。为了衡量海鸟兼捕的全面规模，在兼捕评估中考虑这种损失的兼捕至关重要，至少使用平均损失率，最终目标是针对特定物种的损失校正评估。损失可能远远超过平均损失率，这表明在评估渔业对海鸟种群的影响时不能进一步忽略海鸟兼捕损失。为了衡量海鸟兼捕的全面规模，在兼捕评估中考虑这种损失的兼捕至关重要，至少使用平均损失率，最终目标是针对特定物种的损失校正评估。损失可能远远超过平均损失率，这表明在评估渔业对海鸟种群的影响时不能进一步忽略海鸟兼捕损失。为了衡量海鸟兼捕的全面规模，在兼捕评估中考虑这种损失的兼捕至关重要，至少使用平均损失率，最终目标是针对特定物种的损失校正评估。