Bluefin tuna population has fallen 97%

A prospective buyer inspects the quality of tuna before the first auction of the year at Tsukiji fish market in Tokyo, on Jan. 5, 2016. (AP Photo/Eugene Hoshiko)

TOKYO -- The latest scientific assessment paints a likely bleak future for the Pacific bluefin tuna, a sushi lovers' favourite whose population has dropped by more than 97 per cent from its historic levels.

A draft summary of a report by the International Scientific Committee for Tuna and Tuna-like Species in the North Pacific Ocean seen by The Associated Press shows the current population of bluefin tuna is estimated at 2.6 per cent of its "unfished" size. A previous assessment put the population at an already dire 4.2 per cent.

Overfishing has continued despite calls to reduce catches to allow the species to recover. In some areas, bluefin tuna is harvested at triple the levels considered to be sustainable.

"The situation is really as bad as it appears," said Amanda Nickson, director for Global Tuna Conservation at The Pew Charitable Trusts.

Limits imposed after the previous estimates actually allowed some countries to up their catches, she said.

"If those managers again fail to act in a conservation-minded way this time, it may be time for other actions, such as an international trade ban or complete fishing moratorium," Nickson said.

The independent scientists who compiled the report said improved data make them more confident in their latest estimates than in previous ones. The report is due to be reviewed by the committee in July.

The report estimated that in 2014, the total recruitment level of the fish, or the percentage of new fish that survive each year, was below 3.7 million fish, the second lowest level ever.

Under current levels of reproduction and management of the fisheries in the Pacific, the likelihood of rebuilding stocks to healthy levels is only 0.1 per cent, the report says.

Cutting catches by a fifth would improve those odds to only 3 per cent.

Japanese eat about 80 per cent of all bluefin tuna caught worldwide, and stocks of all three bluefin species -- the Pacific, Southern and Atlantic -- have fallen over the past 15 years as demand for the luscious, buttery pink-to-red fleshed fish has soared globally.

Organizations charged with helping to manage bluefin fisheries have set a goal of rebuilding the species' population to 6.4 per cent, or 42,592 metric tons, of unfished levels by 2024.

But 6.4 per cent levels for a species like the Pacific bluefin, which can live for up to 40 years, are no guarantee of a recovery. Many experts believe 20 per cent of historic levels is the minimum size for a sustainable fishery.

The international body that monitors fisheries in most of the Pacific Ocean, the Western and Central Pacific Fisheries Commission, was unable to reach consensus last year on either short-term or long-term measures to help restore the bluefin population.

In Europe, officials have agreed last month on implementing a recovery plan for bluefin tuna in the eastern Atlantic and the Mediterranean.

A next step by conservationists could include efforts to get Pacific bluefin tuna banned from international trading.

Pacific bluefin tuna are spawned in the western parts of the northern Pacific but migrate throughout the ocean, complicating management of catches. The population of the species is estimated to have peaked in 1960.

An earlier estimate put the 2014 population of the bluefin at 26,000 tons. The most recent reduced that estimate by 9,000 tons, to 17,000 tons.

If the population of Pacific bluefins drops much further, it may no longer be economically feasible to fish for them.

At that point, "Pacific bluefin would be considered commercially extinct," Nickson said.