SummaryFor Greater Scaup Aythya marila, classified as ‘Vulnerable’ on the European Red List of Birds, the south-western Baltic Sea is one of the most important wintering sites in Europe. In this area, a large concentration of gillnet fishery temporally overlaps periods of the most abundant occurrence of foraging diving birds. The aim of the article is to show how bycatch can impact the population of a diving duck. To assess this, we calculate the Potential Biological Removal (PBR) for the studied Greater Scaup population and we model the population change according to age-structured matrix models. Summing all the available recent figures on Greater Scaup bycatch in north-west Europe yields an estimated mean annual total of 3,991 individuals (2% of the flyway population). For a baseline stable population, an age-structured matrix model indicates that at this bycatch level the Greater Scaup population that winters in north-west Europe will decrease by 36% over the next 30 years, qualifying the status of the population as ‘Vulnerable’ according to IUCN criteria. As this population also experiences decline prior to bycatch, this decrease will be 57%, which qualifies the status as ‘Endangered’. PBR as an indicator of population vitality does not work in our case because the PBR-informed allowable bycatch values have a significantly negative impact on the population. Our results indicate unambiguously that fishery bycatch is among the most important threats responsible for the Greater Scaup’s decline. While recent data suggest that some improvement has taken place in the species’ status over the last 10 years, measures to protect Greater Scaup from bycatch are required. The solution should involve the prohibition of gillnet fishing in selected key sites and the use of mitigation techniques in other areas.

中文翻译：

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渔业兼捕是大 Scaup Aythya marila 欧洲人口面临的最重要威胁之一

总结为了更大的 Scaup大马里拉波罗的海西南部被欧洲鸟类红色名录列为“易危”，是欧洲最重要的越冬地点之一。在该地区，刺网渔业的大量集中在时间上与觅食潜水鸟最丰富的时期重叠。这篇文章的目的是展示兼捕如何影响潜水鸭的数量。为了评估这一点，我们计算了所研究的大 Scaup 种群的潜在生物去除 (PBR)，并根据年龄结构矩阵模型对种群变化进行建模。将所有可用的关于西北欧大 Scaup 兼捕的最新数据加起来，估计平均每年共有 3,991 人（占飞行路线人口的 2%）。对于基线稳定的人群，一个年龄结构的矩阵模型表明，在这个兼捕水平上，在欧洲西北部越冬的大 Scaup 种群将在未来 30 年内减少 36%，根据 IUCN 标准，该种群的状态为“弱势”。由于这一人口在兼捕之前也经历了下降，这一下降将是 57%，这使状态为“濒危”。PBR 作为种群活力的指标在我们的案例中不起作用，因为 PBR 告知的允许兼捕值对种群具有显着的负面影响。我们的研究结果明确表明，渔业兼捕是导致Greater Scaup 衰退的最重要威胁之一。虽然最近的数据表明该物种的状况在过去 10 年中有所改善，需要采取措施保护 Greater Scaup 免受兼捕。解决方案应包括在选定的关键地点禁止刺网捕鱼，并在其他地区使用缓解技术。