Norwegian researchers are collaborating with aquaculture companies such as Grieg Seafood through the FHF-funded JellySafe project to develop early-warning systems and protective measures. Pictured: Researcher Marius Andersen of SINTEF Ocean.
Photo: Bendik Skogli / FHF
A harmful jellyfish known for killing farmed salmon has reappeared along parts of the Norwegian coast this autumn, and aquaculture firms now say early warnings from fishermen could be crucial to preventing another mass die-off.
The species, Apolemia sp., is often called the string jellyfish or “pearl-chain” jellyfish because it forms colonies of long, thread-like chains. According to the Norwegian Institute of Marine Research (IMR), it possesses potent venom capable of injuring fish, and outbreaks in both 2023 and 2024 caused significant damage.
A major bloom in 2023 is believed to have killed about three million farmed fish, the first large-scale event in more than two decades to severely affect the aquaculture sector. IMR researcher Tone Falkenhaug recently noted that sightings follow a clear pattern: “This lasts from September through January, peaking in November. We’ve seen this pattern every year since we first started receiving observations in 2019.”
Benn-Levi Thomassen, operations manager for operational services at sea for the aquaculture company Grieg Seafood in Finnmark.
Photo: Bendik Skogli / FHF
At Grieg Seafood’s site in Øksfjord, Finnmark, operations manager Benn-Levi Thomassen says the jellyfish continue to pose a serious threat.
“In recent years, we have had problems at several facilities in the area. We see how the fish suffer when the jellyfish get inside the cages. The fish are exposed to both skin and eye damage as a result of the jellyfish,” Thomassen explained. “We have ordered several types of systems that we are now testing out. But it is important for us to get notified early so that we can prepare for it to arrive.”
The jellyfish have been observed this season in Troms and western Finnmark. Although numbers appear lower than in previous years, Marine Institute researchers say vigilance remains essential. More than 2,000 public sightings have been logged since 2019 on the Dugnad for havet reporting platform, with the highest number recorded in 2023.
A sighting of Apolemia sp. logged via the reporting channel Dugnad for havet.
Photo: IMR
Researchers from SINTEF Ocean are working with Grieg Seafood in Øksfjord through the FHF-funded Jellysafe project to find ways to protect fish in aquaculture facilities. Marius Andersen, a researcher at SINTEF Ocean, warned of the "serious damage" an influx of jellyfish can cause.
“In 2023 and 2024, several locations had to cull entire cages of fish. But we need help from fishermen. Early observations can give us valuable time to take measures and protect the facilities before the jellyfish arrive,” Andersen said.
Trials at the Grieg Seafood site include brush walls that filter incoming seawater, lice skirts, and other barrier systems. Early-warning communication between neighbouring farms is also being tested.
The project team has also produced an animated film, “Warn the Coast”, aimed at encouraging fishermen, sailors and coastal residents to report sightings quickly.
"We hope to reach as many fishermen as possible – both in Norway and in our neighbours in Scotland, Shetland and the Faroe Islands. Everyone who reports findings directly contributes to preventing new incidents," said project manager Tina Oldham at the Institute of Marine Research.
IMR researchers said they are currently modelling how Atlantic inflow may be transporting the jellyfish toward Norway, with early simulations suggesting they may drift northwards through the Faroe–Shetland Channel after originating west of Scotland.
However, Oldham said much remains unknown about the species’ movements and origins. “We lack knowledge about these organisms. We therefore need information about where it comes from, and why and where it appears off the coast," she said.
"Therefore, it is important for us that as many people as possible notify us if fishermen see something similar,” Oldham explained.
The JellySafe project aims to understand and reduce the impact of the “pearl-chain” jellyfish on Norwegian aquaculture, following a series of damaging blooms in recent winters. Researchers and industry partners are testing a range of protective measures, including brush walls, electric and bubble barriers, and lice skirts, while also working to develop a coastal warning system.
The project consortium involves the Institute of Marine Research, SINTEF Ocean, Akvaplan-niva, NIVA, the University of Bergen, NCE Aquaculture, PatoGen, Åkerblå and several farming companies. It is funded primarily by the Fisheries and Aquaculture Industry Research Fund (FHF) with NOK 35 million, alongside contributions of NOK 2.5 million from the Institute of Marine Research and the University of Bergen.
