Norwegian salmon producer SalMar has reported another significant biological incident at its operations in Senja, as an "unusually intense influx" of stinging jellyfish resulted in the company culling approximately 1.2 million salmon.
The string-like colonies of jellyfish, called "Perlesnormanet" or "pearl-chain" jellyfish in Norwegian (Apolemia uvaria), have recently been sighted in increasing numbers along the Norwegian coast.
Because the jellyfish strings can break up into smaller fragments, they are able to drift through the lice skirts and other barriers around salmon pens, stinging and wounding the fish inside.
SalMar said it had observed unusually high numbers of the jellyfish at its Ørnfjordbotn site in Senja during November.
"In mid-November, our fishery guardians at the Ørnfjordbotn site in Senja observed a significant threatening influx of pearl-chain jellyfish. Some dead fish were also recorded. A few days later, the extent of the jellyfish increased further, and the damage to the fish intensified," the company said in a Norwegian-language statement on its website.
"For fish welfare reasons, SalMar decided to destroy all the fish at the site. Our employees worked intensively with personnel from an external emergency boat around the clock to manage the acute and regrettable situation that arose due to this unusual and intense influx of pearl-chain jellyfish. The operation was completed after 3-4 days."
The company noted that the jellyfish have been observed at other locations in mid and north Norway, but to a more limited extent.
"Jellyfish are one of several risk factors in fish farming, but they rarely cause harm to fish as in this case. About 20 years ago, a SalMar site in Frøya experienced a similar severe jellyfish attack. SalMar's contingency plans account for such events, ensuring they are handled safely and with fish welfare as a guiding principle when they occur."
"The incident will not have a financial impact on SalMar beyond the value of the destroyed fish. It will also not affect the guided slaughter volume. The site had approximately 1.2 million salmon with an average weight of 0.3 kilograms. Until the jellyfish attack, the mortality rate at the location was about 1 percent."
SalMar has also released more information on the incident at its fry facility in Jøvika, Senja, which WeAreAquaculture reported on last week.
The number of salmon fry involved in the incident were initially estimated at around 30,000, but SalMar has now confirmed that approximately 200,000 fry were killed or euthanized.
"The incident resulted from inadequate installation of barriers in a fish tank, specifically the center screens in the tank. As a result, the fish ended up in the RAS facility, biofilter, and fish trap," the company stated.
"The fish trap, an additional barrier to prevent escapes, captured most of the fry, but about 200 fry weighing 7 grams, not adapted to seawater, ended up in the sea. Eight of these were caught in recapture nets, while the rest are presumed dead as a result of the incident," SalMar said.
SalMar said it is keeping both the Norwegian Food Safety Authority (Mattilsynet) and the Norwegian Directorate of Fisheries (Fiskeridirektoratet) informed and will provide "a more detailed assessment of the extent and causes" to authorities in due course.
It also stated that it will work with its supplier to make adjustments to equipment to prevent future incidents.
"This regrettable incident is also being handled professionally by SalMar's employees. Analysis of the incident will be the basis for the company's ongoing work to improve safety and fish welfare in our facilities," the company said.
