Japanese marine experts have given warning that the country’s northern coastline is under threat from a plague of Giant jellyfish.
The first wave of GIANT jellyfish have been reported off the coasts of Shimane, Kyoto and Niigata.
Fishermen in northern Japan are braced for a “massive” inundation of huge Nomura’s jellyfish this autumn.
One of the largest jellyfish in the world, the species can grow up to 2 meters in diameter and weigh 200 kg.
The last time the phenomenon occured on a similar scale was in the summer of 2005 when the jellyfish damaged nets, rendered fish inedible with toxic stings and injured fishermen.
The first jellyfish have been reported off the coasts of Shimane, Kyoto and Niigata prefectures.
“We have reports of massive bloomings of young jellyfish near the Chinese coast, where the ecosystems of the Yellow Sea and the East China Sea are favorable for breeding,” said Professor Shinichi Uye, a leading expert on the species at the Graduate School of Biosphere Science of
Hiroshima University.
Relatively little is known about Nomura’s jellyfish, such as why some years see thousands of the creatures floating across the Sea of Japan on the Tsushima Current, but last year there were virtually no sightings.
In 2007, there were 15,500 reports of damage to fishing equipment caused by the creatures.
“It is possible that they have a ‘rest stage’ or hibernation period in their development over several years, but then their numbers shoot up given certain environmental stimuli,” said Professor Uye.
But there are no explanations for why the jellyfish are becoming more regular visitors to Japan’s shores, he said. In the early 1900s, for example, large numbers were only reported every 40 years or so.
One contributing factor may be a decline in the number of predators, which include sea turtles and certain species of fish. In addition, the creatures appear to favour warmer water and research suggests that the temperature of the East China Sea is 1 degree centigrade higher than last year.
That also helps the jellyfish grow so large, so quickly, Professor Uye believes. The creatures are extremely efficient at filtering zooplankton out of the water around them and while the jellyfish is healthy it devotes all its energies to eating. Only if it is injured or sick does it switch to producing offspring, he said.
