Depredation is a threat to the socioeconomic and ecological sustainability of pelagic longline fisheries, globally. Toothed whales (odontocetes) are anecdotally reported as responsible for annual revenue losses of AU$10–12 million in Australia’s Eastern Tuna and Billfish Fishery (ETBF), presenting a challenge for industry and management in developing avoidance and mitigation techniques. We trialled the use of electronic monitoring footage as a timely and cost-effective method for quantifying odontocete depredation interactions. Between March and July 2023, a mean of 5% of total catch of each set sampled (n = 27) was lost to odontocete depredation, but this was highly variable among sets (0 – 24% of catch). We used generalised additive models (GAMs) to explore the effects of operational, spatiotemporal and environmental factors on depredation rates. Our results reveal that odontocete depredation is more likely to occur when: (i) hauling process is initiated at night and completed after dawn, (ii) lines are set at shallower depths, (iii) light-sticks are used, (iv) sea-surface temperature is warmer, (v) lines are set and hauled between 24° and 27°S, and (vi) lines are set and hauled during Austral autumn. It remains difficult to disentangle the effects of spatial and temporal drivers due to our relatively small sample size, however, our work provides actionable information to guide fisher interaction-avoidance tactics and help promote fishery sustainability.

中文翻译：

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捕捞行为和环境变化影响齿鲸对远洋延绳钓渔获物的掠夺

掠夺对全球远洋延绳钓渔业的社会经济和生态可持续性构成威胁。据传闻，齿鲸（齿鲸）造成澳大利亚东部金枪鱼和旗鱼渔业 (ETBF) 年收入损失 10-1200 万澳元，这对行业和管理人员开发避免和缓解技术提出了挑战。我们尝试使用电子监控录像作为一种及时且经济有效的方法来量化齿鲸捕食相互作用。2023 年 3 月至 7 月期间，每组采样的总渔获量 (n = 27) 平均有 5% 因齿鲸捕食而损失，但这在各组之间差异很大（0 – 24% 的渔获量）。我们使用广义加性模型（GAM）来探索操作、时空和环境因素对掠夺率的影响。我们的结果表明，在以下情况下更有可能发生齿鲸捕食：（i）拖运过程在夜间开始并在黎明后完成，（ii）线设置在较浅的深度，（iii）使用荧光棒，（iv）海上-地表温度较温暖，(v) 线路在南纬 24° 至 27° 之间设置和拖运，(vi) 在澳大利亚秋季期间设置和拖运线路。由于我们的样本量相对较小，仍然很难理清空间和时间驱动因素的影响，但是，我们的工作提供了可操作的信息来指导渔民互动避免策略并帮助促进渔业可持续性。