Why saving our salmon distresses the dolphins
Noise devices to scare predators also put marine mammals at risk
SOUND machines being used to scare seals away from salmon farms pose a threat to whales, dolphins and porpoises, experts warn.
The growing use of acoustic deterrent devices (ADDs) has led to a ‘significant and chronic source of underwater noise’ along the West Coast, a report shows.
The low frequency kit had been regarded as an acceptable, non-lethal method of deterring seals from hunting farmed fish.
But campaigners and academics are calling for a ban, claiming ADDs are causing sea mammals severe health and social problems – including hearing damage and stress.
They are urging the Scottish Government and Joint Nature Conservation Committee to record the ‘loud and pervasive’ noise pollution on the UK’s Marine Noise Registry.
The use of ADDs has soared in the past decade, with 164 salmon farms using them – 112 leaving them on permanently.
The devices were proposed following a backlash against the shooting of predatory seals but concerns have been raised over the lack of research into the impact they have on the wider marine population.
The Marine Pollution Bulletin journal yesterday published a paper warning against the use of ADDs in Scotland.
It states that ‘over the last decade, underwater noise from ADDs has markedly increased’ and refers to the devices as ‘an important source of chronic underwater noise in western Scotland’.
The article says: ‘Results indicated a steady increase in ADD detections from 2006 (0.05 per cent) to 2016 (6.8 per cent).’
The paper states the impact on seals and other cetaceans – aquatic mammals such as dolphins, whales and porpoises – needs further study, along with improved monitoring and regulatory strategies.
The warning follows concerns raised by Scottish Natural Heritage.
In an email to Marine Scotland, released under Freedom of Information laws, officials said: ‘There is sufficient evidence, both empirical and modelled, to show that ADDs can cause disturbance and displacement of cetaceans.
‘There is sound, scientific evidence to expect that hearing damage, stress and masking may also occur.’
Experts fear that ‘masking’ – when the mammals are unable to hear certain sounds – could lead to individuals being split up from their pods.
The Scottish Association of Marine Science has warned that the ‘chronic underwater noise pollution’ could ‘negatively affect animals’ individual fitness, potentially with long-term consequences’ for population numbers.
Don Staniford, director of Scottish Salmon Watch, has demanded that officials capture the sounds emitted from ADDs on the Marine Noise Registry.
He said: ‘ADDs used by salmon farms could be the loudest and most pervasive noise on the West Coast of Scotland and must be turned off immediately. Scientific research has shown that salmon farms using ADDs can be heard by cetaceans such as harbour porpoises perhaps as far as 50km [30 miles] away.
‘Unless ADDs are switched off completely the UK is in danger of a hefty fine from Europe for deliberately and recklessly breaching the EU Habitats Directive.’
Ministers are working on strict new guidelines for the troubled Scottish salmon industry, with plans to help tackle the mortality rate and the spread of sea lice.
A spokesman for the Scottish Government said: ‘Acoustic deterrent devices are one of a number of measures used by fish farms to reduce seal predation, and when used appropriately can be an effective non-lethal method.
‘We are aware of concerns regarding their use and are working with Scottish Natural Heritage to consider the potential impact they have on the environment and marine mammals.
‘We take our duty to protect Scotland’s iconic marine species extremely seriously, and will carefully consider the available evidence.’
‘Can be heard 30 miles away’