Measuring ADD Noise in TIdal Streams (MANTIS): Could Acoustic Deterrent Devices (ADDs) reduce risk of marine mammal collisions with tidal turbines?

扩大潮汐流海洋可再生能源（MRE）部门是可取的，但对周围的海洋环境构成潜在风险。一个潜在的风险是海洋哺乳动物和其他物种与旋转的潮汐涡轮机叶片相撞。由于担心这些有吸引力的受保护物种可能因碰撞而死亡或受伤，监管机构（包括项目合作伙伴苏格兰海洋[MS]、苏格兰自然遗产[SNH]和威尔士自然资源[NRW]）在考虑同意申请时采取了预防措施，导致MRE场地开发放缓。如果动物要避免碰撞，它们就需要对涡轮机的存在给予足够的警告，以便及时采取行动。由于水流和游泳速度严重限制了视觉探测范围，因此将通过声学手段进行远程探测（即警告）。然而，在这些能量充沛的地方，动物是否能听到涡轮机的声音，而不是自然产生的环境噪音（来自水流、床载运输和湍流），这是不确定的。因此，开发商和监管机构（包括微软）正在考虑是否在涡轮机上增加额外的噪声源，以确保动物能够感知和避开它们。其他行业，如水产养殖，渔业和建筑业使用声学威慑装置（add），通过发出响亮的，令人厌恶的声音来吓唬海豹和其他动物远离潜在的危险区域。因此，add目前被认为是减少潮汐涡轮机之间潜在碰撞风险的一种缓解方法。然而，存在对潜在的不适当的长期将动物排除在大面积区域之外的担忧，特别是潮汐流MRE涡轮机打算运行数十年而不是短期。此外，考虑到涡轮机放置的嘈杂环境，目前尚不清楚增压器在多大范围内可以听到，以及这在潮汐周期中可能会如何变化。因此，迫切需要评估这些环境中add的可检测性（或不可检测性）。整个项目的目标是澄清在真实的潮汐流环境中，商业上可用的add的可探测性如何在碰撞相关的空间尺度（至少几十到几百米，但可能进一步取决于环境噪声水平）以及在退潮-洪水和春季-小潮周期中变化。对来自潮汐流环境的现有声学数据集的详细分析将使我们能够了解环境噪声水平如何在潮汐周期中变化，以及与海洋哺乳动物听力相关的频率。这将允许开发改进的距离相关声音传播模型，描述潮汐流环境中的ADD信号传输。然后，将在不同的流量条件下对不同ADD信号的传输进行实验测试，以评估声学可探测范围，验证传播模型，并考虑对海洋哺乳动物的可能影响。这将提高我们对add是否可以提供一种适当的缓解技术来减少海洋哺乳动物与潮汐涡轮机的潜在碰撞率的理解。该提案的预期结果的影响将是允许监管项目合作伙伴（苏格兰海洋，苏格兰自然遗产和威尔士自然资源）制定长期的基于证据的政策，将添加物作为一种实用和相称的手段，以减轻潮汐涡轮机可能造成的海洋哺乳动物碰撞风险。这些政策将有助于海洋资源部门的长期环境可持续性，并提高苏格兰和威尔士在保护海洋哺乳动物和其他流动海洋物种方面履行其（国际）国家义务的能力。

Expansion of the tidal-stream marine renewable energy (MRE) sector is desirable but poses potential risks to the surrounding marine environment. One potential risk involves marine mammals and other species colliding with rotating tidal turbine blades. Concern about potential collision-driven mortality or injury of these charismatic protected species has led to regulators (including project partners Marine Scotland [MS], Scottish Natural Heritage [SNH] and Natural Resources Wales [NRW]) adopting a precautionary approach when considering consent applications, resulting in a slowdown in MRE site development. If animals are to avoid collision they will need sufficient warning of turbines' presence to take timely action. With water flow and swimming speeds significantly restricting visual detection ranges, long-range detection (i.e. warning) will be through acoustic means. However there is uncertainty over whether animals can hear turbines over naturally occurring ambient noise in these energetic sites (from water flow, bed load transport and turbulence). As a result, developers and regulators (incl. MS) are considering whether to add extra noise sources to their turbines to ensure animals can perceive and avoid them. Other industries such as aquaculture, fishing and construction use Acoustic Deterrent Devices (ADDs) to scare seals and other animals away from potentially dangerous areas by producing loud, aversive sounds. For this reason ADDs are currently being considered as a mitigation method to reduce potential collision risk among tidal turbines. However, concerns exist regarding potential undue long-term exclusion of animals from large areas, especially as tidal-stream MRE turbines are intended to operate for decades rather than short periods. Furthermore it is not clear over what range ADDs will be audible given the already noisy environments targeted for turbine placement, and how this might vary over the tidal cycle. There is therefore an urgent need to assess the detectability (or not) of ADDs in these environments.The overall project objective is to clarify how the detectability of commercially available ADDs in real tidal-stream environments varies across collision-relevant spatial scales (at least tens to hundreds of metres, but potentially further dependent on ambient noise levels) and across the ebb-flood and spring-neap tidal cycles. A detailed analysis of existing acoustic datasets from tidal-stream environments will allow us to understand how ambient noise levels vary across tidal cycles across frequencies relevant to marine mammal hearing. This will allow development of improved range-dependent sound propagation models describing ADD signal transmission in tidal-stream environments. The transmission of different ADD signals will then be experimentally tested under varying flow conditions to assess ranges of acoustic detectability, validate propagation models and consider likely impacts on marine mammals. This will improve our understanding of whether or not ADDs could provide a suitable mitigation technique to reduce potential collision rates of marine mammals with tidal turbines. The impact of the expected outcomes of this proposal will be to allow the regulatory project partners (Marine Scotland, Scottish Natural Heritage and Natural Resources Wales) to develop long-term evidence-based policies concerning the use of ADDs as a practical and proportionate means to mitigate marine mammal collision risk potentially posed by tidal turbines. Such policies will contribute towards long-term environmental sustainability of the MRE sector and improve Scotland's and Wales' ability to fulfil their (inter-)national obligations in terms of conservation of marine mammals and other mobile marine species.