TOKYO >> Swarms of giant jellyfish are floating along the coastline of the Sea of Japan, and the damage they have been causing fisheries is feared to be the worst in more than a decade.
Nomura’s jellyfish is one of the world’s largest, with a bell of up to 6-1/2 feet in diameter and a weight that can hit 440 pounds.
When tangled in fishing nets, the jellyfish can damage catches and destroy the nets. In 2009, the last time a jellyfish bloom occurred, it caused some $89.6 million in damage to the industry nationwide.
Nomura’s jellyfish are usually found off the coast of China in the spring. They are pushed by ocean currents and arrive in the waters near Japan in summer.
Only about 10 Nomura’s jellyfish have been caught in Japan fishing nets in recent years, according to the Japan Fisheries Information Service Center.
But this year, about 1,000 jellyfish were caught in fixed nets in late August, near the Oki Islands in Shimane prefecture. Not only did they appear to be larger, but they affected a broader range of coastline, from Nagasaki to Aomori.
Off the coast of Fukui, up to hundreds of jellyfish have been sighted since mid-August, mainly in Wakasa Bay, where about 800 jellyfish were caught in fixed nets on Sept. 7. The Koshino fisheries cooperative in Fukui City suffered losses when its catch of Spanish mackerel and horse mackerel was damaged.
“It takes a lot of work to remove the jellyfish from the nets,” said Motoaki Kawabata, the head of the co-op. “Also, if the jellyfish’s tentacles touch the fish, they become discolored and damaged, making them unsalable.”
When the jellyfish bloom appeared in 2009, tens of thousands were caught in fixed nets in Fukui, forcing fishermen to end their season early.
Blooms have also affected crab fisheries in the prefecture.
Nomura’s jellyfish tend to appear in large numbers in Japan when there are warmer water temperatures in February along the coast of China, according to Shinichi Ue, a marine ecology professor at Hiroshima University.
“These jellyfish have been seen less and less since mid-September, but we need to keep an eye on them,” said Ue.