It was the second incident at the site in under a year, following the escape of 24,572 fish with an average weight of 1.1kg during storms in November 2018.
According to details on the Marine Scotland website, the most recent escape of 23,970 fish occurred on October 10 and 11 last year. When Mowi notified Marine Scotland on October 14 it cited equipment damage as the reason for the escape, but in its final notification on November 14 the incident was blamed on “net failure (not including hole)”.
Ben Hadfield, Mowi’s chief operating officer farming Scotland & Ireland, said: “We are very disappointed that a further loss has occurred at Hellisay, which due to weather conditions is one of our most exposed farms.
“Our ambition at Mowi is to realise 100% containment for all our stock and we have regrettably fallen short of this goal in recent years, but are determined to prevent future escapes at all our sites.”
The previous escape in November 2018 was caused by a tear in netting that occurred during a sustained storm event.
The company said at the time that the equipment on site was new, robust and exceeded the Scottish Technical Standards, but suffered due to the high wave heights experienced in the storm events.
“We are very disappointed that our infrastructure was unable to withstand these severe weather challenges,” farming director Gideon Pringle said after the 2018 event. “Our priority is to keep our employees safe during these extreme events, but admittedly we need to do a better job at keeping our fish contained, especially at our high-energy sites.”
The company said in 2018 that it would review the site’s moorings, nets and cages used at offshore locations, and make any changes required to ensure the site could effectively withstand the most challenging weather conditions.
Hellisay was the first of Mowi’s sites that could truly be considered “high-energy”. It has since successfully developed high-energy farms off Muck and Rum.
The most recent escape is a costly one. Even at October’s unusually low spot prices, the escaped fish would have been worth around €500,000.