Japan is known as the biggest consumer of tuna. Be it raw for sushi or sashimi or fried, broiled or canned, tuna is an important element of the food culture.

But concerns are growing because tuna is disappearing, and this is putting Japan in a difficult diplomatic position.

How much tuna does Japan consume annually, and how does the rest of the world feel? Following are basic questions and answers:

How many types of tuna are there?

There are many different types, but the six main species are Atlantic bluefin, Pacific bluefin, southern bluefin, bigeye, yellowfin and albacore.

Conservationists warn in particular that the bluefin, known as “hon-maguro” or “kuro-maguro,” faces extinction because of overfishing.

Bluefin can be found in the Northern Hemisphere in the Pacific and the Atlantic. Served mainly as sashimi, bluefin fetches the highest prices on the market. In 2001, a 202-kg bluefin fetched a record ¥20.2 million at the Tsukiji fish market in Chuo Ward, Tokyo.

Then how much tuna does Japan consume annually?

In 2008, the nation consumed 411,000 tons, or 24 percent of the world’s total catch, according to data compiled by the Fisheries Agency.

Japan also accounted for some 70 to 80 percent of all bluefin tuna traded internationally.

Of Japan’s annual consumption, bigeye accounted for the most, at 159,000 tons, followed by 140,000 tons of yellowfin and 58,000 tons of albacore.

As for bluefin, Japan consumed 43,000 tons of the Atlantic and Pacific varieties and 10,000 tons of southern bluefin.

While the majority of Pacific bluefin is caught by the domestic fishing fleet, most of the Atlantic bluefin is imported. In 2008, Japan imported about 18,700 tons of the 21,400 tons it consumed.

How serious is the bluefin extinction threat and what caused it?

According to an estimate by Monaco, which advocates a ban on the international bluefin trade, Atlantic bluefin stocks plunged by about 75 percent from 1957 to 2007.

Experts blamed the disappearance on rampant fishing.

“Due to the excessive fishing of brood stock, the number of fish that can spawn has plummeted, making it difficult to reproduce resources,” said Aiko Yamauchi, a fisheries official at the World Wide Fund for Nature Japan.

“There is a large possibility that in general, Atlantic bluefin tuna may become (impossible to fish).”

Are only Atlantic bluefin tuna in trouble?

No. A recent study by Japanese researchers showed that the number of Pacific bluefin with reproductive capacity is also dropping at an alarming rate and environmentalists expressed grave concern that they may reach a “critical state” like Atlantic bluefin.

Eating tuna is part of the Japanese culture, isn’t it? When did Japanese start eating the fish?

The evidence suggests Japanese were eating tuna as early as in the mid-Jomon Period (10,000 B.C. to around 300 B.C.), according to a book this year by Hideki Nakano and Masakazu Oka titled “Maguro no Fushigi ga Wakaru Hon” (“Learning About the Wonders of Tuna”).

But tuna consumption saw a huge increase after the mid-Edo Period (1603-1867) with the spread of fixed fishing nets, which made it easier to catch large amounts of tuna at little cost.

Currently at the Tsukiji fish market in Tokyo, 250 out of about 750 wholesalers specialize in tuna.

Are there any global efforts to conserve tuna?

Some countries proposed a ban on Atlantic bluefin trade at the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) last spring in Doha, Qatar.

Monaco proposed that Atlantic bluefin be included in the CITES Appendix I with other marine species like minke whales, the dugong and sea turtles, to impose a ban on its international trade.

Supporters of the proposal included the United States, Norway and Kenya.

The EU, meanwhile, suggested that the Monaco proposal be amended so the ban would be delayed until next May.

In the end, a secret vote on the Monaco proposal was overwhelmingly rejected, with only 20 countries in favor, 68 against and 30 abstaining.

The EU amendment was also rejected, with 43 in favor, 72 opposed and 14 abstaining.

What was Japan’s position on the Monaco proposal?

Japan argued that a complete ban on international trade of Atlantic bluefin is unfair because it would benefit countries whose own fleets can meet their domestic demand. EU member states and the United States would be among them.

Masanori Miyahara, a councilor of the Fisheries Agency who was in Doha in March, said during a WWF Japan-hosted symposium on tuna consumption in Tokyo in early August that developing countries depend on the revenue they make from exporting bluefin, including to Japan.

“The Washington Convention only controls trade, so it has no effect on countries that can catch their own tuna supply,” Miyahara said.

“The proposal completely lacked fairness.”

Are there any international organizations to manage overall tuna stocks, and not just imports and exports of the fish?

Yes. There are five Tuna Regional Fisheries Management Organizations (RFMOs). They are tasked with managing fish stocks in the oceans and conserving them.

Of the five, the group managing Atlantic bluefin is called the International Commission for the Conservation of Atlantic Tunas (ICCAT).

But environmentalists say ICCAT is falling far short of proper management of tuna stocks.

“While the Atlantic bluefin are placed under the management of an international organization, there was no scientific-based management measures taken. Many fishing boats do not follow the rules, especially the one prohibiting use of (seine nets). It is difficult to grasp the actual situation of bluefin trade,” Yamauchi said.

Is Japan taking any action to preserve bluefin resources?

Yes — at least verbally. After the rejection of the proposal in Monaco, then farm minister Hirotaka Akamatsu issued a statement pledging Japan will play a leading role at ICCAT to prevent overfishing of Atlantic bluefin.

“Japan will continue to play a leading role at ICCAT and other RFMOs in preventing overfishing by adopting effective conservation and management measures, based on scientific stock assessments, and by establishing reliable monitoring systems to ensure compliance by RFMO member countries with the adopted measures,” he said.

What can consumers do?

WWF Japan advises that people learn more about the current situation, actively seek out companies or restaurants that provide sustainable tuna products, and ask restaurants and fishmongers where their tuna came from.

Yamauchi of WWF Japan stressed that tuna stocks could rebound if the fish have several years to reproduce naturally, even at during this “current excessive production and consumption state.”

But Yamaguchi added recovery will become extremely difficult if the reproductive rate falls too low.

“If managed properly, fish, by nature, can be a resource that increases naturally and can be used sustainably,” Yamauchi said. “We are now standing at the crossroads. . . . I believe it is necessary to refrain from consuming (Atlantic bluefin) for a few years.”

The Weekly FYI appears Tuesdays (Wednesday in some areas). Readers are encouraged to send ideas, questions and opinions to National News Desk