Electric fence concept trains seals to stay away
18 December 2024
Fish farmers can now deploy an anti-predation system similar to that used by terrestrial farmers to protect livestock, that is both humane and highly effective. Ace Aquatec’s A-EFENCE® works on the same principle as an electric cattle fence except that it safeguards fish from seal and sea lion attacks on marine farms. The A-EFENCE® produces a low voltage, harmless force of electricity upon contact that conditions would-be predators to change their behaviour. It functions in much the same way as Ace Aquatec’s acoustic protection devices, but uses electric fields (rather than underwater acoustics) to produce an instinctive startle response that trains marine mammals to avoid jumping onto walkways to enter the salmon pens.
The A-EFENCE® cable is mounted above the walkway and is secured around the pen by custom made fasteners, which are attached to the uprights. A control box with a beacon also sits on the pen, so that site personnel can see if the device is switched on or off, and it has the same remote functionality as the A-ASR® devices. This means that whoever has access to the portal can control A-EFENCE® at the touch of a button.
Ace Aquatec Marine Protection Products Business Manager, Andrew Gillespie-McLean, said the A-EFENCE® has evolved from earlier versions of the same concept.
‘A-EFENCE® is a streamlined, practical and easy-to-install means of protecting the pens. The seal doesn’t feel any pain because the voltage is set as low as possible. When a seal climbs onto the walkway, its whiskers would likely come into contact with the electric pulse, which provokes a startle response, guiding the seal away from the pen.
The system is currently being deployed at two Scottish salmon farms and a third site will be added early next year, involving 30 fences in total in the North of Scotland, where seal predation is a constant challenge.
The system is safe to use with cetaceans in protected zones and unlike other non-lethal seal control options available to farmers and fishery boards.
Seals were responsible for more than one million farmed salmon mortalities in the two years to the end of 2021, according to statistics published by Salmon Scotland, the trade body for Scotland’s farmed salmon sector. In addition to the salmon killed directly by seal attacks, many hundreds of thousands more fish die from stress after the event.
Farmers using the A-EFENCE® have reported encouraging results to date. At one site, the farm manager said there had been no mortalities from seals and no breaching of the pens, in an area historically prone to predation.
