BANGKOK » Environmentalists want tougher restrictions on the industrial-scale fishing of bigeye tuna in the Pacific Ocean after new research showed current measures are failing and will do little to sustain stocks of a fish that is popular in sushi bars the world over.

The findings will intensify a debate between the multibillion-dollar fishing industry and conservationists over the best ways to protect 23 tuna species, nine of which are threatened with extinction.

Bigeye and yellowfin tuna, which can grow to 8 or 9 feet long and weigh more than 450 pounds, are not in immediate danger of being wiped out, but have been hit hard by overfishing. The fish are used mostly for steaks and, in the case of bigeye, sushi.

The western and central Pacific region accounts for 55 percent of the world's tuna production.

In December the Western and Central Pacific Fisheries Commission, which regulates commercial fishing from Indonesia to Hawaii, approved measures supposed to reduce catches of bigeye tuna by 30 percent over three years and limit catches of yellowfin tuna to 2001-2004 levels.

But scientists working for the commission found the measures were undermined by numerous territorial exemptions from the catch limits, including coastal waters that surround archipelagic states such as Indonesia, Papua New Guinea and the Philippines.

It also found limits on purse seine fishing are ineffective, as they are based on catch rates from 2004 that were higher than average.

Fisheries experts with the World Wildlife Fund say the research shows the current restrictions are inadequate, and are calling for tough and swift action by the industry to protect bigeye tuna, which are in danger of being overfished. Yellowfin are less threatened.