Award of CR/2020/18 - Improving understanding of the use, impact and efficacy of acoustic deterre...

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Introduction1. The Scottish Government is committed to a clean, healthy, safe, productive and biologically diverse marine and coastal environment that meets the long-term needs of people and nature. This includes managing our seas sustainably to protect their rich biological diversity and to ensure that our marine ecosystems continue to provide economic, social and wider benefits for people, industry and society.Background & Context2. Acoustic Deterrent Devices (ADDs) are one of a number of management measures used by the aquaculture industry to reduce seal depredation at fish farms, but in recent years there has been increasing concern about the potential for impacts on cetaceans. Despite the long-term use of ADDs in aquaculture there is 1) a poor understanding of the practical effectiveness of current and new ADDs in terms of deterring seals and reducing predation events at Scottish aquaculture sites, and 2) limited empirical data on the disturbance and displacement of cetaceans as a result of ADD use at Scottish aquaculture sites. These were raised as significant knowledge gaps in a Scottish Government review of ADDs in Scotland , therefore the aim of this project is to address some of the recommendations made by Coram et al (2014) in an effort to further develop our understanding of the issue.3. To address some of these issues requires a greater understanding of the extent of ADD use at aquaculture sites in Scotland. Currently there is limited information on their use (for example, the number, type of device(s) used and mode of operation) which may vary considerably between aquaculture sites. Increasing our understanding of where and how ADDs are used at fish farms will not only enable better mapping of devices, but will also help to inform investigations into the effectiveness of ADDs in reducing seal depredation and the potential for impacts on cetaceans.4. Assessing the potential for impacts on cetaceans from ADDs, and their effectiveness in reducing seal depredation, can be difficult. They will vary widely based on a number of factors, including sound characteristics of the devices, how they are used (e.g., duration, source level, frequency, duty cycle), the environment in which they are used, as well as species behaviour. Our understanding of the effectiveness of ADDs on seal depredation events in the long-term and the variables that may influence this effectiveness is still limited. Similarly, while a number of studies have been undertaken over the years which have demonstrated that certain devices have the potential to affect some cetacean species (particularly harbour porpoise), there is still a poor understanding of the occurrence of behavioural responses around ADDs in situ at fish farms in Scotland and the consequences of any disturbance or displacement of cetaceans.5. Consequently, there is a need to improve our understanding of the use, impact and efficacy of ADDs in aquaculture in order to balance the sustainability of our growing aquaculture industry whilst protecting biodiversity and the environment.