February 20th, 2022 - The barrel jellyfish is mostly harmless to humans, but sure seems to be a menace to fishing nets due to its size - and numbers. Fishermen have been struggling with an invasion of huge jellyfish in the north of Istria that shows no sign of subsiding

An infestation of large jellyfish has been a source of headache for fishermen in Umag and Savudrija for two months now, so much so that some have given up and are not even going out to sea anymore. There are so many of them, and they’re so big and heavy that they destroy the nets as the fishermen lift them out of the sea, reports Jutarnji list.

Danilo Latin, a fisherman from Savudrija, says it’s not uncommon for them to pull out one ton of jellyfish at a time. He’s never seen such a thing before, and fishermen in general don’t know how to go about it. 

‘This has been going on for two months. It’s never been this way. Last year, [the jellyfish] appeared for a short while in March and that was that. This year they just won’t leave, and we don’t know when we’ll be able to go out to sea again. There are so many of them that even us fishermen are starting to feel uneasy. A friend of mine was recently at sea and told me that he’s never been scared to look at the sea before. He had a feeling as if it were ghosts under the surface’, said Latin.

Latin and other fishermen who are dealing with the jellyfish invasion in northern Istria are calling for the situation to be declared a natural disaster.

‘We can’t go out to sea as we only suffer damage. Some of the jellyfish weigh up to eight kilograms. And we don’t even know when we’ll be able to sail out. We informed experts at the Institute of Agriculture and Tourism in Poreč of this, and invited the Ruđer Bošković Centre for Marine Research in Rovinj as we wish for this to be declared a natural disaster. As far as I know, the scientists from the Rovinj institute haven’t yet arrived to see what’s going on. We reached out to the Department of Agriculture of Istria County and they told us they had never dealt with this issue. It’s new to everyone’, Latin said, adding it wasn’t only an issue in Umag and Savudrija, but also in the waters of Slovenia and the Italian region Friuli Venezia Giulia.

Scientist Barbara Sladonja from the Centre for Invasive Species of the Institute of Agriculture and Tourism in Poreč wasn’t able to say with certainty when the jellyfish would pull back and if it would happen before summer.

‘It’s the barrel jellyfish (Lat. Rhizostoma pulmo). This jellyfish is naturally found in our waters, and over the last hundred years or so, it has made an occasional appearance in large numbers. It’s the so-called jellyfish bloom phenomenon, seen in many jellyfish species, including the barrel jellyfish. In recent years, such blooms have been lasting longer and longer. It can’t be said for sure when it will pull back. Judging by the last few years, they already should have retreated, but their population remains large. We hope this won’t last until summer’, said the scientist.

She explained there were several reasons why the jellyfish would appear in such large numbers.

‘One reason is the sea temperature being too high. The barrel jellyfish population should decrease significantly in winter due to low temperatures. This year, it apparently hasn’t dropped low enough, and the population kept growing. In addition, marine food chains have been disrupted by several factors’, said Sladonja.

Experts from the Ruđer Bošković Institute from Rovinj said they were monitoring the phenomenon and that this jellyfish species is among the bigger ones found in the Adriatic. They can weigh up to 10 kilos each.

Until they fall back, it’s only the Ministry of the Sea that can help the fishermen. According to Ezio Pinzan, head of Istria’s Department of Agriculture, Istria County doesn’t have the funds for it.

‘We have to see what’s going on and how to prevent it from happening again next year. The Ministry has an aid package of 50 million kuna in the works, which they’ll distribute to our fishermen for this difficult situation’, said Pinzan.

As the tourist season approaches in Dalmatia, the compass jellyfish makes an appearance.

As Morski writes on the 14th of May, 2019, potentially harmful compass jellyfish (Chrysaora hysoscella) have made an appearance in the sea near Betina, experts warn that if one sees this jellyfish they should give it a very wide berth and make no attempt whatsoever to go near it or touch it as a sting from this animal is very painful.

Chrysaora hysoscella, known as the compass jellyfish, is a species that typically lives in the coastal waters of the Atlantic ocean and the Mediterranean sea, often appearing along the coast of the United Kingdom, especially in the North sea, Ireland, and as far south as Turkey. It is characterised by a yellow-brown ''cap'' that resembles a compass and it can grow to up to thirty centimetres in diameter, with tentacles reaching up to one metre long. The compass jellyfish has 24 tentacles that are divided into three groups of eight, as was described by the Centre for Invasive Species, which reported that the same had jellyfish appeared near Poreč in Istria last summer.

Although during spring compass jellyfish may occur in slightly larger numbers, a small number of individuals reach sexual maturity and continue to survive until the summer. This type of compass jellyfish belongs to a group of jellyfish which possess their cnidocite on their tentacles and thus, if one comes into contact with it, it can cause painful burns and marks on the skin. 

Compass jellyfish tend to appear in cycles but not each and every year, and their lifespan is one year. They feed on zooplankton, and the natural enemies are sea turtles and the Ocean sunfish (Mola Mola) - a large fish that feeds on them.

The aforementioned centre advises that if you do come across and come into accidental contact with a compass jellyfish while swimming, then you need to cool the burned area with aloe vera or a similar gel which soothes burns.

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Experts from the Oceanography and Fishing Institute from Split send a calming message to the concerned locals and tourists