Salmon Aquaculture and Acoustic Deterrent Devices

Salmon Aquaculture and Acoustic Deterrent Devices

By Sally Campbell

On Wednesday 17 June 2020 the Scottish Government Parliament and MSPs completed the final stage of Animals and Wildlife (Penalties, Protections and Powers) (Scotland) Bill.

One area where the Scottish government has been convinced of the need to act was in recognition of US animal welfare law that from 2022 will prevent the import of fish from countries which allow seals to be killed to protect fisheries. Since 2011 salmon farming companies in Scotland have been licensed to shoot nearly 1,000 seals, including some that were pregnant. The Scottish Government is now intent on banning the fish farming industry from shooting seals in order to secure the economic value of the £180 million export business of farmed salmon to the US. So, some success in the Scottish Parliament of calling salmon aquaculture to account for wildlife protection. This is excellent news. The next step to follow should be that the Scottish Government ban the aquaculture industry from deploying high powered Acoustic Deterrent Devices (ADDs) to dissuade seals and other marine mammals from damaging fish pens, attacking fish through the cage or making holes through which fish can escape.

So what are ADDs, often referred to as pingers? They are intended to keep marine species, such as cetaceans (whales, dolphins and porpoises) and pinnipeds (seals etc.) away from marine structures including salmon farms. Fidra’s (Scottish Environmental NGO, named after an island and wildlife haven, made famous by writer of Treasure Island, Robert Louis Stevenson) have reported research into the environmental implications of the Scottish salmon farming industry using ADDs. These are a form of technology that sends out a high-pitched frequency of sound which is uncomfortable for the intended targets to hear. Due to the difference in hearing frequency between ages and species, ADDs are used to prevent unwanted marine mammals (e.g. seals and dolphins, porpoises, whales) from remaining in a particular area. ADDs have been developed for both the protection and deterrence of marine species. They are used on offshore wind farms to ensure marine species do not get trapped and confused in between pylons; on and around fishing nets to prevent animals from getting caught, and as a deterrent and “non-lethal” way of preventing predatory species approaching the salmon farms, damaging the nets in a bid to eat the farmed fish, which can then also result in fish escape.

Porpoises, dolphins and whales are being driven from feeding grounds and can also be deafened by these ADDs. These mammals echo-locate to find food, and if deafened can starve and become disorientated, sometimes beaching on the coast. Most Scottish farms use cheap single nets to enclose the growing fish. Dead fish accumulate at the bottom of the nets and tempt seals to bite salmon through the net. 121 of 172 farms use ADDs, outputting over 179 decibels, to deter seals, but because ADDs are not always very effective, farmers using ADDs have also shot seals. There are alternatives: Mowi use ADDs and shoot seals in Scotland even if Mowi did most recently undertake not to use ADDs in the Carradale, Kintyre expansion. But, they have now withdrawn plans for that expansion, so it is unclear about future policy in the company. However in British Columbia, Canada, where ADDs and seal shooting are banned, the same company uses double-skinned anti-predator nets, which also solve the problem of fish escapes. The salmon industry is unlawfully disturbing and excluding porpoise, whales and dolphins from inshore waters by using ADDs, so driving iconic animals away from feeding grounds on the west coast of Scotland, affecting their life expectancy in the Inner Hebrides and Minches SAC (Special Area of Conservation), designated for porpoises (Paper from David Ainsley to Rural Economy and Connectivity Committee). ADDs are not the most effective way of keeping seals and farmed salmon separated. In addition, there is a wealth of science data which shows ADDs disturb, exclude and cause hearing damage to porpoise and other cetaceans. One study found that 87.5% of porpoise were excluded from a 990 square kilometre area by a single ADD (SNH, 2011).


Map of Potential Extent of ADD Audibility to Harbour Porpoise (Mainland and Hebrides) (Coram, A. J. et al (2014).

Scottish Natural Heritage (called NatureScot from 1 May 2020), the government conservation agency, has told ministers there is significant scientific evidence that the ADDs, which emit tones underwater to primarily scare off seals, can cause hearing damage and stress in dolphins, porpoises and whales – breaching legislation to protect cetaceans. Scottish Natural Heritage (SNH) has also released 15 files containing 2,800 pages of internal reports and correspondence about ADDs. They show that SNH has repeatedly expressed concerns about the impact on cetaceans, including whales, dolphins and porpoises. In 2017 SNH was asked for “formal statutory advice” on ADDs by the Scottish Government’s Marine Scotland agency. “There is sufficient evidence, both empirical and modelled, to show that ADDs can cause disturbance and displacement of cetaceans,” SNH said in response. “There is sound scientific evidence to expect that hearing damage, stress and masking (hiding other sounds) may also occur but these are difficult to demonstrate empirically and would require further assessment. Accordingly we believe there is a strong case for managing ADD deployment and use.” SNH listed 12 studies that had suggested that ADDs disturb harbour porpoises, minke whales, killer whales and white-sided dolphins. “ADDs emit frequencies within the hearing range of cetaceans,” SNH concluded. The devices “have the potential to cause injury”, it added. “Current legislative protection requires a precautionary approach where a risk cannot be discounted beyond scientific doubt.”

In January 2020 SNH raised concerns about the use of ADDs at three salmon farms in Argyll. In November 2019 SNH warned Highland Council that ADDs at a proposed fish farm off the Isle of Skye were “likely to have a significant effect on harbour porpoises”. The released documents show that SNH also repeatedly criticised the use of ADDs at fish farms in May, June, July, August and September 2019. In 2018 SNH described an online claim that it backed one particular acoustic device as “inaccurate and misleading” and demanded it be deleted. ( Rob Edwards June 2020). Mark Ruskell MSP of Scottish Greens welcomed SNH’s moves. “This is clear confirmation from Scottish Natural Heritage that these devices cause considerable harm to marine life,” and pointed out that there were “far more humane alternatives” such as stronger nets designed to prevent seals from eating caged salmon.” “I hope this revelation will convince MSPs to back my amendment 55 to the Wildlife Bill to extend the seal culling ban to include these torture devices. Otherwise it will be clear that market forces have driven the legislation, not real concerns over animal welfare.” Mairi Gougeon, Minister of Rural Affairs and Natural Environment in response to this Amendment on ADDs replied “The Scottish Government is undertaking a comprehensive programme of work on this matter, including a review of the current regulation and management of ADD use in this sector, and it is my view that that review should be completed before we determine what any next steps might be.”

She continued, “The Scottish Government is supporting scientific research that will establish the full extent of current ADD use across the Scottish finfish sector. Furthermore, that research will underpin the development of robust, science-based industry guidance and any regulatory reform that is deemed necessary in relation to the future use of ADDs. There is already a significant body of work under way in this important area.” Mairi Gougeon concluded “It is important that the national and international context that we are operating in is recognised, and my amendments place on Scottish ministers a duty to report on that broad framework. Amendments 55A and 55B to the Animals and Wildlife (Penalties, Protections and Powers) (Scotland) Bill make the reporting requirement (on ADDs) better reflect the breadth of work that is currently being undertaken by the Scottish Government, and I welcome the obligation to report the outcomes to Parliament. Therefore, I can support Mark Ruskell’s amendment 55, but only on the condition that my amendments 55A and 55B are accepted.” So Mark Ruskell’s Amendment to ban ADDs did not succeed but as a result of all this evidence Ministers in Edinburgh have undertaken to table plans to licence and control the use of ADDs by the end of March 2021. We must keep them to that timetable and not allow continually delay in the process at the behest of the salmon aquaculture companies.

It is interesting that during the Pandemic lockdown and reductions in shipping it has been noticed that more marine mammals are appearing nearer the British coasts. But international concern is ramping up fast as evidence grows about problems arising from the din created by ADDs, military sonar, seismic surveys, oil drilling, dredging and ship engines. Short, loud blasts of sound as with ADDs can cause physical damage; persistent background noise, such as that from shipping, can alter a host of systems and behaviours, from communication to feeding. Work has shown “As underwater noise increases, it is literally shrinking the whales’ and other marine mammals’ world, and the range over which their calls are audible, which means it is shrinking the range at which the whales can stay in contact, coordinate their movements, share their prey.” (Nature 2019)

While sound moves at a much faster speed in the water than in air, the distance that sound waves travel is primarily dependent upon ocean temperature and pressure. These factors have a curious effect on how (and how far) sound waves travel. Sound travels about 1500 meters per second in seawater. That is approximately 15 soccer fields end-to-end in one second. Sound travels much more slowly in air, at about 340 meters per second, only 3 soccer fields a second.

So let us continue to put pressure on the Scottish Government and our MSPs to outlaw ADDs from salmon aquaculture at the latest by the end of March 2021. There is an obvious solution !

Rural Economy And Connectivity Committee, Salmon Farming In Scotland Submission, From David Ainsley
SNH Publication, EPS Licensing Guidance – Test 2 (2011) 2.3
Ocean uproar: saving marine life from a barrage of noise (10 April 2019)
Coram, A. J. et al (2014). Evaluating and Assessing the Relative Effectiveness of Acoustic Deterrent Devices and other Non-Lethal Measures on Marine Mammals. Scottish Government. 145pp.

Sally Campbell
June 2020

Featured image credit: Don Staniford