Ace technology keeps seals away, says Finnish trout farmer
04 July 2025
A Finnish trout farming business has solved its seal predation problem after installing five Ace Aquatec acoustic startle response devices at its two farms in the south-west of the country. Jannen Lohi Oy, a third-generation rainbow trout farmer, which harvests 200 tonnes of fish per year, had experienced historic issues with seals in the region, losing around four per cent of its stock a year to attacks, as well as sustaining significant damage to netting and equipment.
As seal populations continued to grow, the farmer tried various combinations of single and double predator nets, but they didn’t seem to work.
‘The predator nets were hard to handle and didn’t offer much protection against the seals, which are clever animals and found a way in,’ said Site Manager Matias Juslin. ‘Now we don’t need predator nets at all because the Acoustic Startle Response (A-ASR®) devices have been almost 100 per cent successful in keeping the seals away.
‘We still see the seals almost every day, about 200 metres from the pens, but now they don’t come near the fish.’
Jannen Lohi Oy learned about Ace Aquatec from another Finish trout farmer, Laitakarin Kala, which reported positive results with the A-ASR® USR devices. Laitakarin, which operates in Bothnian Bay in northern Finland, had also seen stocks depleted by predator attacks before installing Ace Aquatec technology across its farms in 2023.
Hearing first-hand about Laitakarin’s positive experiences, Jannen Lohi Oy approached Ace Aquatec, which recommended installing five A-ASR® US3 devices across two locations in Tiiraletto and Pukholma, which a have a total of 12 pens.
These mid-frequency A-ASR® devices produce low-volume noise through a triggered mechanism, inducing a startle response in seals. Using randomised, computer-generated sound patterns, the system avoids hearing damage and habituation risks associated with single-frequency devices. The emitted sounds are below levels that could harm or disturb the seals. Three A-ASR® devices were fitted at the bigger of the two sites, and two at the smaller farm, configured to provide effective coverage throughout.
Jannen Lohi Oy highlighted the simplicity of setting up the A-ASR® devices, noting how easy to use and install the system is, given the small team on-site. The flexibility of the deterrent is also proving to be a bonus, with all systems connected to the A-ASR® portal, enabling farmers to monitor and control the devices remotely. And they can also be run on batteries, an advantage at the Jannen Lohi Oy farms where power can be unreliable.
Since the installation in September, completed by an engineer from the north who had already fitted the system at Laitakarin, everyone in the Jannen Lohi Oy team can operate the system, said Matias. The company, which supplies its trout to the domestic market, has aspirations to expand its farms and, as Matias said, would have no hesitation in repeating its order with Ace Aquatec.
‘We have no complaints at all about the installation, and the ongoing support from Ace Aquatec, and would return for more devices if other sites required support for any future seal predation,’ said Matias.
Ace Aquatec’s Technical Sales Manager, Andrew Gillespie-McLean, who advised Jannen Lohi Oy, commented:
‘Unlike traditional deterrents that require long duty cycles to be effective and can cause deafness and habituation in seals, the A-ASR® devices work on creating conditioned avoidance.
‘This approach stops seals becoming habituated and forces a change in their behaviour, and because the sounds are well below acceptable thresholds, they do not cause any harm to the seals, or any non-target species.’
