Researchers have received over 100 observations of the dangerous string jellyfish in Norway

Through the Marine Citizen Science (Dugnad for havet) portal, members of the public can report any interesting things they observe along the coast. So far this year, 110 observations of string jellyfish have been reported.

“But the big increase in reports only began in September–October,” marine scientist Tone Falkenhaug says.

From the Oslofjord to Troms

This is the same situation as we were in last autumn.

“Of the past 20 years, only last year had similarly high levels to this year,” Falkenhaug says.

The string jellyfish is an Atlantic species, and the researchers believe that it comes to the coast with inflows of Atlantic waters.

“We have received reports of observations along the whole coast, from the Oslofjord all the way up to Troms. Over the past week, we have received most reports from Trøndelag,” she says.

Like other jellyfish, string jellyfish can appear very suddenly, and then disappear for a number of years.

Killed many farmed fish in 1997 and 2001

The string jellyfish is a colonial jellyfish that can reach lengths of up to 30 metres. Within the colony, individuals have different roles. The ones whose job is to catch food or defend the colony have stinging cells.

“This means they may sting and cause harm to farmed fish,” Falkenhaug says.

If a colony hits a cage, it gets broken up, and small bits of jellyfish, including the stinging cells, may enter the cages.

On two previous occasions, string jellyfish have caused mass mortality events at fish farms. In 1997, jellyfish killed 12 tonnes of salmon, while 600 tonnes of fish died in 2001.

“That’s why we try to keep an eye on this species of jellyfish,” Falkenhaug says.

The researchers need help

Doing that, however, is not easy because jellyfish are difficult animals to study.

“This is mainly because they are made of jelly-like matter. It makes jellyfish hard to catch using normal gear, because they break up so easily,” Falkenhaug says.

This is why marine scientists need help from the general public.

“The Marine Citizen Science portal is a good tool. In addition, we have received great help from divers, as well as from the aquaculture industry, which has spotted these jellyfish in the vicinity of their farms,” she says.

In short: if you see a string jellyfish, report your observation to the Marine Citizen Science portal.

Marine Citizen Science

• Report your findings and see what others have found. Learn about new species and how the ocean is changing.
• Here you can either register individual findings or, for example, create longer time series. There may be records of Pacific oysters or litter in the same location over a long period of time. Such time series provide valuable information that researchers would otherwise not be able to obtain.
• If you register a single find, for example a crab or a jellyfish that you think may be rare, it will be looked at more closely by a researcher.
• The Marine Citizen Science portal is an initiative from the Institute of Marine Research (IMR) that gives the public the opportunity to contribute with observations of life in the sea.

Read more at dugnadforhavet.no

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