Bluefin tuna face global warming threat: experts

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Tuesday, Dec. 26, 2006

 

Bluefin tuna face global warming threat: experts

Kyodo News

 

Bluefin tuna stocks in the Pacific could be hit

seriously by the end of this century if global warming

progresses at the current pace and threatens the

breeding ground, researchers said Monday.

 

The group, led by Shingo Kimura, a professor of marine

environmental science at the University of Tokyo,

warned that the tuna population, already hit hard by

overfishing, could be dealt a further blow as seawater

temperatures rise above the level comfortable for tuna

growth.

 

Pacific bluefin migrate over a wide range from east to

west while they grow, but their breeding ground is

believed to be limited to a rather small area from

eastern Taiwan to areas around Amami Oshima Island in

Kagoshima Prefecture.

 

Kimura's group tested young bluefin tuna in different

water temperatures and found that most are likely to

die when the seawater temperatures rise close to 30.

 

While 26 degrees, near the average temperature in the

species' spawning ground, is best suited for their

growth, their survivability remains unchanged even if

temperatures drop to 20, the study says.

 

Based on a computer analysis of how global warming

will affect seawater temperatures in the breeding

ground, the group has found that the area with the

proper temperature will shrink by 2099 and surviving

young tuna will make up 37 percent of today's level.

 

Kimura said it is possible that a new spawning ground

will develop in the Sea of Japan by then.

 

" While bluefin tuna catches may grow in the Sea of

Japan in this case, the fight over fish resources may

become more serious among Japan, China, Taiwan and

South Korea, " he said.

 

Japan has the world's largest catches of bluefin tuna.