ST. JOHN'S — About 400,000 fish recently died across three salmon farming sites operated by Mowi Canada East along the south coast of Newfoundland, the second major die-off the company has reported this summer.
The company said the "abnormal mortality incident" affected about 23 per cent of the Atlantic salmon at the three sites near Harbour Breton, N.L., which is at the southern tip of the Connaigre Peninsula, about 230 kilometres west of St. John's.
"Although we know the approximate scale of the loss we cannot determine an exact figure after only a few days," Mowi said in a Facebook post Thursday. "It is an unfortunate fact that all livestock farmers will encounter and must manage environmental mortality events from time to time."
The post said the salmon were killed by a thermocline inversion, during which cold, low-oxygen water swells up to the surface.
Newfoundland and Labrador's Department of Fisheries, Forestry and Agriculture said Mowi first contacted officials on Aug. 25 to report a die-off of over three per cent but less than 10 per cent of its stock at the three farming sites. Five days later, the company said more than 10 per cent of its 1.7 million salmon at the sites had died, the department said in an emailed statement. Mowi issued a public notice a day later.
On Thursday, the company said an estimated 133,334 salmon had died at each of the three farms, the email said.
"Mortalities are currently being removed and properly disposed of, while some of the remaining fish within the population are being harvested," said spokesperson Sara Rideout. "The (department) continues to work closely with Mowi throughout its investigation."
Mowi did not respond to questions about how it is disposing of the dead fish.
This is the second fish die-off at Mowi farms in Newfoundland in as many months. The company reported an "abnormal mortality event" exceeding 10 per cent of salmon on July 20 at a site near Rencontre East, also along Newfoundland's south coast.
Neville Crabbe with the Atlantic Salmon Federation said the deaths pose serious questions about Mowi's current bid to grow its operations in Newfoundland and Labrador. The company is looking to expand its hatchery in western Newfoundland, and the project cleared the province's environmental assessment process on Friday.
The two salmon die-offs this summer underline the federation's position that expanding the aquaculture industry in the province is "unwarranted, unnecessary and too risky," Crabbe said in an interview Friday.
"Companies are struggling to keep fish alive long enough in the cages to harvest them for market," he said. "Companies and regulators need to address the causes of these issues and demonstrate a track record of success and sustainability before they're expanding."
In its Facebook post, Mowi noted that the die-offs came after "several years of successful, incident-free production."
"2025 is proving to be an environmentally tough year for everyone (in) Newfoundland, including salmon farmers," the post said.
This report by The Canadian Press was first published Sept. 5, 2025.
The Canadian Press
