Sound waves are a non-lethal way to deter seals, but there is a debate over their use. Sandy Neil reports
It’s a simple question fish farmers face: how do you keep the salmon in and predators such as seals out?
The solutions, however, are many and complex, each with their own advantages and disadvantages that have to be weighed up carefully against harm, cost and other factors.
New net and scarer technologies are being developed all the time, all claiming to offer answers, and new research papers have to be kept on top of. All the while two drivers continue relentlessly: consumer demand for salmon and the natural cycles of predator and prey.
Seals can each eat 3–7kg (6.6–15.4lb) of food per day, depending on the species. Holes bitten through nets have let hundreds of thousands of farmed fish escape into the wild.
Salmon Scotland (formerly, the Scottish Salmon Producers Organisation) said that from May 2019 to May 2020 more than half a million farmed salmon in Scotland died as a result of seal attacks, either directly from a physical attack or indirectly from stress arising from being subjected to an attack.
In one such predator attack on 31 December 2020 at a Skye-based farm, 52,000 juvenile salmon were lost. The Portree site, managed by the Scottish Salmon Company, was due to have new “seal-proof” netting technology installed by the end of January.
What can be done? This month we look at where containment and protection are now. The biggest pressure facing Scottish fish farmers at the moment comes from more than 5,000km away in their second biggest market, the US, and its upcoming ban on importing salmon from countries that kill or injure marine mammals.
The story started back in 1972 when the US passed a landmark conservation law called the Marine Mammal Protection Act (MMPA), which prohibits activities that harass (i.e. injure), hunt, capture or kill marine mammals. It protects cetaceans such as whales, dolphins and porpoises, pinnipeds such as seals, and sea otters.
Fifty years later, on 1 January 2022, an amendment will come into force that will impact countries from Scotland to Samoa. The new rule will prohibit the US from importing fish and fish products from fisheries that cause intentional or incidental “mortality and serious injury of marine mammals”. The clock is ticking closer and closer to midnight on New Year’s Eve.
From 1 January 2017 each producer nation was given exactly five years to apply for and receive a “comparability finding” for each of its fisheries exporting to the US, confirming that each complies with the new law.
If the nation fails, it will lose the US as a customer. America is the world’s largest importer of seafood, buying about $20bn of product every year.
The US was the second largest market for Scottish salmon in 2019 with sales worth £179m, and in 2020 sales were worth £104m, down 40% due to the Covid-19 pandemic. It’s a loss Scotland’s economy could ill afford.
The need to comply will affect around 150 fish farms in Scotland. Before the deadline the Scottish Government must prove this higher standard of aquaculture welfare is on the statute book and being enforced. The spotlight has been focused on the ways fish farms reduce seal predation, such as licensed shooting and non-lethal acoustic deterrent devices (ADDs). These devices, also known as “seal scarers”, deter seals from attacking pens by emitting an unpleasant sound underwater as an alternative to the use of lethal force. A range of ADD-type products is available from manufacturers including OTAQ, Ace Aquatec and GenusWave.
Although ADDs offer a non-lethal solution, campaigners have called for them to be banned, arguing they cause hearing damage to acoustically sensitive cetaceans, such as whales and porpoises. In June this year a study carried out by the Scottish Association for Marine Science (SAMS) found the “wall of sound” created by conventional ADDs targeted at seals could harm porpoises up to 28 kilometres away.
Studies of the effects of ADDs have typically focused on single devices. The SAMS research modelled the cumulative effect of all the ADDs known to be deployed until recently by 120 fish farms along a stretch of the Scottish coast from Cape Wrath to the Clyde.
In March this year Salmon Scotland announced that no ADD devices of the type deemed to be harmful to marine mammals were being used by its members, so the SAMS study arguably does not reflect current practice.
Anne Anderson, then Director of Sustainability at the SSPO/Salmon Scotland, said at the time: “All devices the sector does not have total confidence in, with regards to the harming of protected species, have been turned off and removed from the marine environment… the Scottish salmon farming sector is committed to, where necessary, only using acoustic devices that have been scientifically proven to be compliant with the US Marine Mammals Protection Act.”
Since Marc, the salmon farming sector has gone further. Fish Farmer has been made aware that Salmon Scotland’s members have more recently agreed to stop using any ADDs – new or old generation – unless and until Marine Scotland can confirm that they can be used without harm to marine mammals, and also whether they will require a European Protected Species (EPS) licence.
So as of now the ADDs operated by the big aquaculture operators have been switched off, although it should be noted that ADDs are also used by other industries, such as offshore energy.
A spokesperson for Marine Scotland set out the organisation’s position: “Acoustic deterrent devices are one of the tools used by the aquaculture sector to manage seals. They have a range of applications in European waters – for example, including in relation to offshore wind farm construction. The technology is constantly evolving and we are fully supportive of the rapid innovation that is taking place.
“We will work closely with the sector and relevant stakeholders to ensure that the aquaculture industry can address the risks associated with seals interacting with finfish farms through a range of non-lethal methods, while ensuring that marine wildlife is provided with protection afforded through our environmental obligations.”
Wildlife charity Clyde Porpoise CIC claims that even more up-to-date ADDs generate an unacceptable level of underwater “noise”. Earlier this year Clyde Porpoise carried out its own acoustic testing in the Firth of Clyde and it says that the results show even the ADDs introduced in recent years are unacceptable.
The organisation stated: “The acoustic data indicate there is no significant difference between 2019 and 2021 ADD signal outputs (i.e., frequency content). Based on this evidence we dispute any assertion from operators that this ‘new-generation system’ used in 2021 is somehow more compliant than ADD outputs used in 2019… the ADD source levels are well above the 120dB value advised by Marine Scotland to cause disturbance and warrant immediate application for EPS licence.”
Marine Scotland has declined to comment as the concerns raised by Clyde Porpoise “are currently part of an active investigation”.
So how can a new generation of ADDs deter seals without collateral damage to cetaceans? Aquaculture technology businesses, such as Ace Aquatec and GenusWave, claim they have the answer: “startle” devices that target seals when they approach rather than relying on a “wall of sound”.
Nathan Pyne-Carter, Chief Executive of Ace Aquatec, explained how its anti-predator technology works: “Ace Aquatec’s acoustic startle response devices were first developed in 2001 by John Ace-Hopkins with a key difference over alternatives: they made a discrete noise when triggered by the presence of a seal, which created an acoustic startle response (ASR) in the predator. This was a major departure from alternatives on the market, which relied on a permanent fence of sound.
“Over the years we have refined our ASR systems, adding lower-frequency transducers that play sounds outside the hearing range of cetaceans such as porpoises, and thanks to Scottish Government grants totalling nearly £1m, we have been able to create a highly modular anti-predator approach with intelligent triggering as well as electric startle response (ESR) systems.
“The ESR devices include a submerged electric net, an electric fish that sits on the mort sock, and surface electric fences to prevent seals breaching the surface net and becoming trapped in a pen. The triggering devices utilised a combination of thermal imaging and advanced image-recognition technology to automatically identify and track seals or non-target species. The rationale of the ESR technology was to complement the acoustic systems by creating sensitisation (an avoidance of habituation) and a conditioned avoidance response to the general area of predation.
“It is the same intelligent systems that have recently been shortlisted for the Global Aquaculture Alliance’s Innovation award.”
Compliance with the Marine Mammal Protection Act is clearly a key issue. Pyne-Carter said: “NOAA has a website where the characteristics of deterrent devices can now be plugged in to assess the compliance of a device (albeit the website is a work in progress and certificates are provisional pending final approval). Unlike traditional barrier systems that rely on a continuous fence of sound, Ace Aquatec’s systems rely on the opposite: an effect of a rapid pulse lasting no more than a few milliseconds, which creates a startle response that is hard-wired into the mammalian nervous system and cannot be overcome with learning.
“This necessarily means we have the lowest duty cycle (the time where sound is played compared with when it is not), the lowest acoustic energy output (average volumes across the emission) and a targeted frequency that is responsive to marine mammals’ sensitive hearing thresholds. Beyond this, every ASR and ESR device used is connected to the internet, allowing all transmission to be monitored and recorded for inspection. Furthermore, the development of our intelligent triggering systems allows marine wildlife around the farms to be counted and tracked. All of these combined mean that we currently receive a pass for all variants of our equipment on the NOAA deterrent portal (certificates are provisional until the final model is approved) and we have no concerns about compliance going forward.”
This is also the approach adopted by GenusWave. The company’s founder, Steven Alevy, said: “Targeted Acoustic Startle Technology (TAST) is an innovative technology that leverages Mother Nature to safely ‘tickle’ an animal’s startle reflex – a natural bio-reflex innate to all mammals. A specific frequency – tailored to each species – triggers an instinctive flight response and naturally conditions the targeted animals to avoid the protected area.”
Initially funded by the Scottish Government to provide an animal-friendly method to keep seals at bay, the TAST technology was developed at the University of St. Andrews.
Alevy says that TAST is the only acoustic seal deterrent approved for use by the Aquaculture Stewardship Council, and TAST meets all the rigorous demands of the US Marine Mammal Protection Act. The technology is currently being used by NOAA off the coast of Alaska in some of the most environmentally sensitive waters in the US.
As he explains: “TAST broadcasts a specific frequency. In response seals demonstrate clear avoidance conditioning, an uncontrollable flight response is triggered and conditions the animals to avoid the area. Seals do not habituate to the reflex and repeated exposure only leads to increased responsiveness.
“ADDs make predation worse. Conventional ADDs operate on the premise that causing pain will deter animals. This is now proven to be ineffective over the long term. Published research has established that seals habituate to the deterrent sound of the ADDs, and that ADDs can cause hearing damage and harm non-target species.
“Peer-reviewed research published in the journal Animal Conservation shows that, unlike ADDs, the Targeted Acoustic Startle Technology can be used to deter seals without adversely affecting whales and porpoises.”
All these new technologies will come at a cost, but the manufacturers hope it will be paid for by the value of the fish not lost to seal attacks.