The Jellyfish population in Japanese waters is 100 times greater than 20 years ago.

Nomura’s Jellyfish swarm   © Amazing Story’s

Nomura’s Jellyfish are in the same size class as the lion’s mane jellyfish, the largest jellyfish in the world.
They reside primarily in the waters between China and Japan, centralized in the Yellow Sea and East China Sea. They grow up to 2 meters (over 6 feet) in diameter and weigh up to 300 kilograms (ca. 660 pounds). Though it is considered low quality, the species is edible and gets fished regularly for food. But this animal is mostly described as an unwanted by catch that destroys fishing gear and will crush, slime, and poison valuable fish in the nets, such as the tuna and salmon.

Like other species of jellyfish, its population appears to be increasing. Recent reports have documented massive swarms, so called blooms, hitting the coast of Japan. Blooms have affected the fishing industry as well as the environment directly in those regions.

In 2006 a nuclear plant was shut down by a Numora swarm and in 2009, a 10-ton fishing trawler was sunk as its three-man crew tried to haul in a net containing dozens of Nomura’s Jellyfish. The crew were rescued by another trawler.

The increase in population is connected to climate change and decline in predator (sea turtle) population. Changes of temperature and salinity in the ocean have created an ideal environment for jellyfish to thrive.

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