Giant Blue Jellyfish Invade Vladivostok Waters: Why You Shouldn't Fear Them

Fishermen in Vladivostok captured an unusual encounter with giant sea creatures. While fishing for mackerel in Ajax Bay on Russky Island, the men noticed three enormous blue jellyfish slowly swimming from the beach side.

The footage quickly spread across social media, sparking debates among users about whether these jellyfish are dangerous to humans and what to do if such a formidable-looking giant appears nearby while swimming.

Alexander Olifirenko, a candidate of biological sciences and director of the ANO «Center for Environmental Initiatives,» told a VLADIVOSTOK1.RU correspondent that these are Rhopilema — one of the largest jellyfish in the Sea of Japan. He noted that despite their unusual appearance and impressive size — some individuals can weigh over 10 kilograms (22 lb) — these creatures pose virtually no threat to humans.

According to the scientist, their short, fleshy tentacles may cause a slight sting on the skin, but these sensations, the expert assures, are mild and quickly subside.

«It is completely harmless to humans. The tentacles do sting a bit, but nothing serious — even less than a nettle. Such contacts usually cause no severe consequences, except in rare cases of individual allergic reactions,» emphasized Alexander Olifirenko.

The biologist noted that in China, there is even an unusual method to test the quality of Rhopilema: the jellyfish is briefly applied to the skin. If it stings slightly, the product is considered fresh and suitable for further processing.

According to the scientist, Rhopilema began appearing en masse in Amur and Ussuri Bays in the early 2000s. In some years, their influx was so massive that industrial fishing was organized in the region. The jellyfish were harvested for export to China, where this product is considered a delicacy.

«They are indeed edible. In China, it»s called «crystal meat.» Though actually, in taste and texture, it resembles processed raw squid,« said Olifirenko.

The scientist noted that Chinese residents value Primorye Rhopilema higher than local ones. The wholesale price per kilogram of salted tentacles, according to the scientist, averaged $3 to $5 depending on quality and market conditions. Some of the products were then shipped from China to Japan.

The main value lies in the fleshy short tentacles — these are most often exported. The bell is also consumed but costs less, so it is often discarded during processing. After salting, the jellyfish loses up to 80–90% of its mass, as most of its body consists of water. What remains is dense protein tissue, which becomes the food product.

«Rhopilema fishing does not harm nature or the population. These jellyfish do not reproduce in Primorye waters; they arrive here with southern sea currents. They die anyway in autumn, so this species is not subject to quota,» explained the biologist.

No nets are used to catch Rhopilema. According to the specialist, jellyfish are collected with ordinary large landing nets. Before noon, one boat can prepare over three tons of catch. The jellyfish are then immediately brought ashore, where they are salted the same day with salt and alum — otherwise, they quickly spoil. After that, the product is shipped to China in barrels.

According to Alexander Olifirenko, in the best years, the fishery was quite profitable. Near Ugolnaya station, a jellyfish processing plant even operated. However, after COVID restrictions were introduced, exports almost ceased, and the business became unprofitable.