Jellyfish outbreaks may last longer

JAPAN - Massive outbreaks of Echizen kurage giant jellyfish in the Sea of Japan may be prolonged this year, which could greatly damage local fishing industries, according to marine biologists.

Statistics show that the number of jellyfish outbreaks will be larger than usual for the first time in three years. Though the reason behind the increase is unknown, fishermen are preparing countermeasures, such as setting fishing nets to catch them.

Echizen jellyfish are born in the spring along Chinese coasts in the Yellow Sea, as well as the East China Sea. They move north along the Tsushima Current and arrive in Japanese waters starting in mid-July. Afterward, they usually drift out into the Pacific Ocean via the Tsugaru Channel in early October.

Some Echizen jellyfish have hoods two meters in diameter and weigh nearly 200 kilograms.

A research team led by Hiroshima University Prof. Shinichi Ue has conducted annual surveys of the number of jellyfish per 100 square meters in the Yellow Sea between June and November since 2006. The survey is used to predict how many jellyfish will arrive in Japanese waters.

This year, the team found 0.44 jellyfish per 100 square meters in July. The number is 730 times larger than the 0.0006 found in 2010, when hardly any jellyfish-related damage was reported, and about nine times larger than the 0.05 reported in 2011.

Usually, the number of jellyfish found in the Yellow Sea peaks in July. However, the figure has remained high this year, registering between 0.2 and 0.5 in August and 0.16 in September.

Compared to last year's figures, the number was 10 to 71 times larger in August and 2,285 times larger in September. The figures were close to those recorded years of jellyfish population explosions--0.21 in August 2007, 0.55 in August 2009 and 0.2 in September 2009.

According to JF Shimane, a fisheries cooperative in Matsue, Echizen jellyfish are usually caught in fixed fishing nets in early and mid-August. However, this year, 20 to 150 jellyfish were caught daily in fixed nets of Okinoshima island, even in September.

"We can't afford to let down our guard," an association official said.

"It's possible that the jellyfish will flood Japan's coastline if their numbers continue to increase in October or November," Ue said.

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