Echizen kurage, or Nomura’s jellyfish are gathering in the Yellow Sea off China and the Korean peninsula. The swarm – or smack, as groups of jellyfish are properly termed – it is expected to drift into the Sea of Japan in the next few months.
The creatures are around 6ft wide and weigh up to 220kgs. When the Nomuras grow large they can destroy fishing nets, which are often community-owned on the coast of Japan. The fish caught alongside the jellyfish are poisoned and covered in a slime meaning that they are unable to be sold.
Some nuclear power plants along the Japan Sea coast are also finding that the jellyfish are being sucked into the pumps which take in sea water to cool the reactors.
There are several theories for why the jellyfish have been swarming more frequently in recent years including global warming, pollution, oxygen levels in the ocean, structures being built on the coast (which give the larvae more places to attach) and a lack of predators caused by overfishing. It is difficult to kill the jellyfish because they release millions of eggs and sperm when under stress which further causes the population to boom.