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Jellyfish Head North For Warmer Waters

November 16, 2009

Fishermen have been pulling net after net of jellyfish out of the ocean off the coast of Kokonogi, Japan recently.

The Nomura jellyfish, the largest of the creatures, can be up to two meters in diameter and can weigh up to 450 pounds. The venom of these jellyfish can ruin a whole day’s catch by killing fish stung when entangled with them in the maze of nets.

Fisherman Taiichiro Hamano told the Associated Press, “Some fishermen have just stopped fishing. When you pull in the nets and see jellyfish, you get depressed.”

He says this year’s swarm is one of the worst he has seen. What was once a rare occurrence, is now an almost annual event along several thousand kilometers of Japanese coast.

Scientists believe the warming of oceans has allowed some of the almost 2,000 jellyfish species to expand their ranges, appear earlier in the year and increase overall numbers.

The U.S. National Science Foundation says these creatures are blamed for abolishing fishing industries in the Bering and Black seas and terrorizing beachgoers worldwide.

A 2008 study estimated that people are stung over half a million times every year, sometimes multiple times, and 20 to 40 people die each year in the Phillippines from jellyfish stings.

The increase of pollution in our waters boosts the growth of the microscopic plankton that the jellyfish feed upon.

Lucas Brotz, a researcher from the University of British Columbia, told AP, “These increases in jellyfish should be a warning sign that our oceans are stressed and unhealthy.”

The jellyfish began inundating Kokonogi Bay in 2002 and reduced fish catches by 30 percent, slashing prices by half over concerns and quality.

Fumio Oma and his crew are out of work after their net broke under the weight of thousands of jellyfish. He told AP, “We have been getting rid of jellyfish. but no matter how hard we try, the jellyfish keep coming and coming. We need the government’s help to get rid of the jellyfish.”

Scientist Shin-ichi Uye says the invasions cost the industry up to $349 million a year, and tens of thousands of fishermen have sought government compensation.

Hearing fishermen’s pleas, Uye, who had been studying zooplankton, became obsessed with the little-studied Nomura’s jellyfish, scientifically known as Nemopilema nomurai, which, at its biggest, looks like a giant mushroom trailing dozens of noodle-like tentacles.

“This jellyfish was like an alien,” he says. “No one knew their life cycle, where they came from, where they reproduced.”

He artificially bred Nomura’s jellyfish in his Hiroshima University lab, learning about their life cycle, growth rates and feeding habits. He traveled by ferry between China to Japan this year to confirm they were riding currents to Japanese waters.

He came to the conclusion that the Coastal waters of China offer a perfect breeding ground: sewage runoff are spurring plankton growth, and fish catches are declining.

“The jellyfish are becoming more and more dominant,” Uye told AP. “Their growth rates are quite amazing.”

Image Caption: Nemopilema nomurai in the Kaiyukan-aquarium of Osaka. Courtesy Wikipedia

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