Marine mammal bycatch in southwest England: Taking a holistic approach to assess causes, impacts and evidence-based solutions

背景：ZSL的鲸类搁浅调查计划（CSIP）自1990年以来一直在运行，由Defra和威尔士地方政府资助。它负责协调对所有搁浅在英格兰和威尔士海岸线上的鲸鱼、海豚和鼠海豚、海龟、海豹和大型鲨鱼的调查。除了记录每一个搁浅的个体，他们还进行尸检以调查死亡原因，并了解更多关于大型海洋脊椎动物在英国水域面临的威胁。自1990年成立以来，CSIP注意到，在每年的研究中，商业渔业中意外捕获海洋哺乳动物（副渔获物）一直是一个一致的发现，并且代表了尸检中搁浅鲸类动物死亡的最大直接人为驱动因素（n=782, 1990-2019，数据英国搁浅数据集）。英格兰西南部和威尔士，尤其是康沃尔郡，是副渔获相关死亡的热点地区。例如，在英国（1990年至2019年）尸检中诊断出的搁浅普通海豚的副渔获物病例中，有64%记录在康沃尔。在2020年期间，康沃尔郡搁浅鲸类动物的尸检中约有三分之一被诊断为副渔获病例。该区域的副渔获物很可能是由影响整个区域物种的多个部门和多个船队驱动的；以及英国专属经济区（EEZ）内外。来自北大西洋广大地区的海洋哺乳动物，包括普通海豚、港鼠海豚和灰海豹，都在这一地区被误捕。因此，副渔获是一个在区域、国家和国际各级影响海洋哺乳动物的国际问题。此外，局部分散的小型海洋哺乳动物种群（例如沿海/近岸宽吻海豚群落）将极易受到任何与副渔获有关的死亡的影响。因此，副渔获物也可能对某些物种/种群构成重大的保育问题。目前，关于该地区副渔获的主要驱动因素的信息相对有限，而诸如物种分布与渔业之间的空间和时间重叠以及使用的渔具类型等信息对于为旨在管理这一威胁的政策提供信息至关重要。目的和方法：该项目将采用跨学科的方法来提高我们对西南水域海洋哺乳动物兼捕物的认识。学生可以根据自己的技能和兴趣，制定项目的具体目标，但建议的目标包括：1)生态学/病理学：评估被认为影响该地区鲸类的渔具类型的现有证据基础。确定是否可以在调查搁浅期间收集额外的副渔获物法医证据，以帮助改进数据收集和诊断。该学生将与来自CSIP和更广泛的英国搁浅网络的搁浅科学家和兽医病理学家合作，设计一系列实验，以测试与不同类型的齿轮相互作用如何在被捕获的动物中出现。评估现有的副渔获物来源、搁浅和其他辅助数据，以综合更全面地了解副渔获物对不同海洋哺乳动物物种的影响，包括时间和空间变化。2)海洋学：研究确定可能影响副渔获相关搁浅时空格局的潜在因素的方法。在沿海海洋数值模型中，通过反向粒子跟踪，从被捕获动物的搁浅位置向后跟踪，以估计动物与渔具相互作用的潜在位置。利用若干数据来源（如近海船舶监测数据和登陆信息）确定西南区域水域“高风险”捕鱼活动的空间范围。3)政策分析：制定政策选项以支持设计改进和潜在的解决方案

Background: The Cetacean Strandings Investigation Programme (CSIP) at ZSL has been running since 1990 and is funded by Defra and the Devolved Government of Wales. It coordinates the investigation of all whales, dolphins and porpoises, marine turtles, seals and large bodied sharks that strand around the English and Welsh coastline. As well as documenting each individual stranding, they conduct post-mortem examinations to investigate causes of death and learn more about the threats large marine vertebrates face in UK waters. Since its inception in 1990, CSIP have noted that accidental entrapment of marine mammals in commercial fisheries (bycatch) has been a consistent finding in every year of study and represents the largest direct anthropogenic driver of mortality in stranded cetaceans examined at necropsy (n=782, 1990-2019, data UK strandings dataset). The southwest of England and Wales, particularly Cornwall, is a hotspot for bycatch-related mortality. For example, 64% of all bycatch cases diagnosed in UK of stranded common dolphins examined at post-mortem examination (1990-2019) were recorded in Cornwall. During 2020, approximately one-third of post-mortem examinations of stranded cetaceans in Cornwall were diagnosed as bycatch cases.It is likely that bycatch in the region is driven by multiple sectors and multiple fleets impacting on species across the region; and inside/outside of the UK Exclusive Economic Zone (EEZ). Marine mammals from across the wider north Atlantic region, including common dolphins, harbour porpoises and grey seals, are known to succumb to bycatch in this area. Bycatch is therefore an international issue impacting marine mammals at regional, national and international levels. In addition, locally discrete and small marine mammal populations (e.g. coastal/inshore bottlenose dolphin communities) will be highly vulnerable to any bycatch-related mortality. Bycatch may therefore also pose a significant conservation issue for some species/populations.There is currently relatively limited information on the main drivers of bycatch in the area, and information such as the spatial and temporal overlap between species distributions and fisheries, and the types of gear used are essential for informing policies aimed at managing the threat.Aims and Approach: This project would take an interdisciplinary approach to informing our understanding of marine mammal bycatch in southwest waters. There is scope for the student to develop the specific objectives of the project depending on their skills and interests but suggested aims include;1) Ecology/Pathology: Assess the existing evidence base for gear types thought to impact on cetaceans in the region. Determine whether additional forensic evidence of bycatch could be gathered during investigation of strandings to help improve data collection and diagnosesa. The student would work with strandings scientists and veterinary pathologists from CSIP and the wider UK strandings network to design a series of experiments to test how interactions with different gear types may present in bycaught animals.b. Assess existing sources of bycatch, strandings and other ancillary data to synthesise a more holistic understanding of bycatch related impacts across different marine mammal species, including temporal and spatial variation.2) Oceanography: Develop methods for identifying potential factors that may influence the spatio-temporal patterns of bycatch-related strandingsa. By inverted particle tracking within a numerical coastal ocean model, backwards track bycaught animals from their stranding location to estimate the potential location for the animals interacting with fishing gearb. Identify the spatial extent of 'high risk' fishing activities in southwest regional waters using a number of data sources (e.g. Inshore Vessel Monitoring data and landings information).3) Policy analysis: Develop policy options to support design improvement and potential solutions