As well as looking exactly like a real whale, the fibreglass orca also emits recordings of killer whale noises to enhance its effectiveness at scaring away seals.
The whale cost around £12,000 and came from Inverness-based aquaculture supplier Gael Force Group, which had it manufactured by a Shetland company.
Move with the current
Mowi spokesman Ian Roberts said the replica would be moored about four metres below the surface of the water and move with the current.
“We will review its effectiveness, and if it provides positive results will consider launching additional orcas,” said Roberts.
Roberts said hundreds of salmon could be killed by just one seal in a very short time, and that mortality due to seal predation has historically averaged around 1%.
Acoustic deterrent devices (ADDs), which generate a sound seals find unpleasant, are widely used by Scottish salmon farmers to deter the predators.
An “electric fish” is also being marketed by ADD manufacturer Ace Aquatec to deter seals which have become hard of hearing and are not put off by ADDs. The fish, which looks like a mort and is placed at the bottom of a salmon pen, is covered with electrodes which give a seal a shock when it touches them.
While some farmers such as Grieg Seafood Shetland and Scottish Sea Farms have also invested heavily in special netting that seals cannot penetrate, Roberts said this was not suitable for all sites.
Salmon farmers are licensed to shoot seals as a last resort, but this is something they try to avoid. The number of seals shot has dropped by 81% since 2011, and the industry wants to reach a stage where no seals are shot.
“We use several non-lethal methods of deterring seals, including acoustics and additional protective netting,” said Roberts.
“We hope that this replica killer whale will look menacing enough to encourage seals to keep swimming by.”