Introducing acoustic devices to protect fish pens from seal predation: a case study from Finland
01 April 2025
Operating in the south of Finland, Jannen Lohi Oy is a third-generation rainbow trout farmer with decades of industry experience, harvesting 200 tonnes of fish per year.
Challenge
Jannen Lohi Oy discovered that they were losing up to 4% of their fish stock to seal predation, with daily attacks reported. This not only stressed both the fish and on-site workers, but also caused significant damage to their netting and equipment. Seeking a welfare-first solution, Jannen Lohi Oy were determined to find a way to discourage seals from approaching their net pens.
Solution
Jannen Lohi Oy learned about Ace Aquatec’s solutions from Laitakarin Kala’s positive experiences with the A-ASR® (Acoustic Startle Response) USR devices. After completing the site configuration, experts from Ace Aquatec recommended installing five A-ASR® US3 devices across two locations in Tiiraletto and Pukholma. 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.
Results and Benefits
Jannen Lohi Oy highlighted the simplicity of setting up the A-ASR® (US3) devices, noting how easy to use and install the system is, given the small team on-site. All systems were connected to the A-ASR® portal, enabling farmers to monitor and control the devices remotely. Since installation, the Finnish trout producer reported that the seals have “vanished by almost 100%,” with the site manager adding that seal sightings only occured when the devices are switched off. The site manager commended the process and support, and confirmed he’d return to Ace Aquatec if other sites required support for any future seal predation. “We wanted to address the mortalities as a result of seal predation, which were around 4% of our entire fish stock. Since installing the A-ASR® devices, we have not recorded any seal attacks and only spotted seals when the device was switched off.” - Matias Juslin (Site Manager)
