The outgoing head of the fisheries management body for the western and central Pacific has warned that some tuna stocks were now so low they should not be fished.

Glenn Hurry, executive director of the Western and Central Pacific Fisheries Commission (WCPFC), said the situation was not yet unrecoverable, but it was at a dangerous level and worsening.

"The Pacific bluefin is I would have thought at the biggest risk, it's at about 3.0 percent of its original spawning biomass, so the amount of adult fish in the water that can spawn ... it's at a pretty dangerous level," Hurry told AFP late Tuesday.

Hurry said other species were also depleted, with bigeye tuna below the critical level of about 20 percent of its original spawning biomass, and fishing this species should stop to allow it to recover.

"Of the big ones -- bigeye and skipjack tuna -- bigeye is about 16 percent of its original spawning biomass, so it's below the limit," he said.

Yellowfin tuna was below 40 percent of its original biomass.

Hurry, an Australian, welcomed Japan's plans to propose a 50 percent cut on catches of young bluefin tuna in the western and central Pacific in a historic shift aimed at safeguarding the at-risk species.

But he said fish stocks in the Pacific had slowly worsened in the four years he had spent in the job, which he expects to leave this month, and more tough decisions needed to be made.

Pacific island nations have complained that there are too many fishing boats catching too few fish.

"We started with one of the best stocks of fish in the world, and we've fished them down," Hurry said.

"And when it comes to the crunch and you've got to make hard decisions about reducing the catch on the stock, it gets really difficult.

"Take a little country like Tuvalu; 50 percent of the income of Tuvalu is the income they get from fishing. If you're going to reduce (its catch) it's going to hurt."

Hurry said fishing stocks could recover, but the more valuable fish became, the harder it would be for small countries dependant on the fishing industry to pull back on their hauls.

"They will bounce back so long as you restrict the fishing pressure on them and we're just increasing it," he said. "It's not looking particularly positive if you keep doing that."

With too many boats catching too few fish, Pacific island nations in June said they were ratcheting up the fees they charge tuna fishing boats to enter their waters by a hefty 33 percent.

The eight countries involved are from the Parties to the Nauru Agreement (PNA), which control waters covering more than half the world's skipjack tuna, the most commonly canned variety.

From January 1, 2015, the PNA will raise the fishing day fee for so-called "distant water" fleets from as far afield as Europe, China, South Korea, Japan and Taiwan, from US$6,000 to US$8,000.