Sun, Nov 22, 2009 - Page 9 News List

Jellyfish swarm northward in warming world

Climate change has helped the poisonous, gelatinous creatures spawn faster and expand their range, posing a threat to fishermen’s livelihoods

By Michael Casey  /  AP , KOKONOGI, JAPAN

GOVERNMENT HELP

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

The invasions cost the industry up to ¥30 billion (US$332 million) a year, and tens of thousands of fishermen have sought government compensation, said scientist Shin-ichi Uye, Japan’s leading expert on the problem.

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.

“No one knew their life cycle, where they came from, where they reproduced,” said Uye, 59. “This jellyfish was like an alien.”

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 concluded China’s coastal waters offered a perfect breeding ground: Agricultural and sewage runoff are spurring plankton growth, and fish catches are declining. The waters of the Yellow Sea, meanwhile, have warmed as much as 1.7ºC over the past quarter-century.

“The jellyfish are becoming more and more dominant,” said Uye, as he sliced off samples of dead jellyfish on the deck of an Echizen fishing boat. “Their growth rates are quite amazing.”

The slight, bespectacled scientist is unafraid of controversy, having lobbied his government tirelessly to help the fishermen and angered Chinese colleagues by arguing their government must help solve the problem, comparing it to the effects of acid rain that reaches Japan from China.

“The Chinese people say they will think about this after they get rich, but it might be too late by then,” he said.

CORRELATION

A US marine scientist, Jennifer Purcell of Western Washington University, has found a correlation between warming and jellyfish on a much larger scale, in at least 11 locations, including the Mediterranean and North seas and Chesapeake and Narragansett bays.

“It’s hard to deny that there is an effect from warming,” Purcell said. “There keeps coming up again and again examples of jellyfish populations being high when it’s warmer.”

Some tropical species, on the other hand, appear to decline when water temperatures rise too high.

Even if populations explode, their numbers may be limited in the long term by other factors, including food and currents. In a paper last year, researchers concluded jellyfish numbers in the Bering Sea — which by 2000 were 40 times higher than in 1982 — declined even as temperatures have hit record highs.

“They were still well ahead of their historic averages for that region,” said co-author Lorenzo Ciannelli of Oregon State University. “But clearly jellyfish populations are not merely a function of water temperature.”

Addressing the surge in jellyfish blooms in most places will require long-term fixes, such as introducing fishing quotas and pollution controls, as well as capping greenhouse gas emissions to control global warming, experts said.

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