More than one million farmed salmon have died at Mowi Scotland's sites in Loch Seaforth, marking the largest mass die-off of farmed salmon in Scotland in a decade, reports The Guardian. 

The deaths, which occurred during the standard year-and-a-half production cycle beginning in spring 2023, were attributed to rising sea temperatures and subsequent jellyfish blooms, according to Mowi.

Ben Hadfield, Mowi Scotland's chief operating officer, confirmed the total death count of 1.05 million fish from the two sites, known as Seaforth and Noster. He emphasized that the mass mortality is "very false and misleading" if linked to poor farming practices.

"This is caused by an unprecedented rise in sea temperatures," he said, explaining that jellyfish stings to the fish's eyes, skin, and gills can lead to health complications and death.

The troubling data was revealed through an analysis by Scotland's Coastal Communities Network (CCN) and the NGO Free Salmon.

"This is the first time since 2014 that more than a million farmed salmon deaths have been reported at a single farm site in one production cycle," said John Aitchison, representing CCN.

He also highlighted that such mass deaths could be indicative of poor animal welfare and expressed concern that larger farms may exacerbate these issues in the future.

Despite the mass die-off, Mowi maintains that the welfare of its fish remains a priority. Hadfield noted that salmon mortality at Mowi "has decreased by two-thirds this year as temperatures have normalized."

The incident has drawn attention to the welfare practices in the Scottish salmon farming industry. The Royal Society for the Prevention of Cruelty to Animals (RSPCA), which certifies many of Mowi's farms under the RSPCA Assured label, has recently suspended three Scottish salmon farming sites after reports of welfare regulation breaches.

However, a spokesperson for the RSPCA clarified that the jellyfish-related health issues at Mowi's sites are considered beyond the supplier's control and do not jeopardize its welfare certification.