Toshio Katsukawa, a fisheries professor at Mie University in western Japan, said the industry has been allowed to pursue indiscriminate fishing for years.
"This is undermining Japan's own national interests," he said. "We have an international responsibility in this matter. It's a problem if we are not able to responsibly catch and consume these fish."
That may have been a valid criticism in the past, acknowledged Masanori Miyahara, the deputy director-general of the Japan Fisheries Agency. But over the past five or six years "our policy has changed," he said in an interview in his Tokyo office. "Now we are in the driver's seat."
"Previously, there was almost no control over the bluefin catch because so many fishermen were catching them. The JFA just gave up," Miyahara said. "But now we are in a position of control. We are serious about fishing management."
He noted that limits imposed in 2011 on domestic fishermen using large, encircling "purse seine" nets -- which scoop up vast amounts of fish, including many young ones -- during the summer spawning season in the Sea of Japan have reduced the catch of juveniles by more than a quarter.
Japan also has joined 2011 "effort limits" -- such as limiting the number of vessels -- called for by the Western and Central Pacific Fisheries Commission, the regional fisheries body that monitors the western two-thirds of the Pacific Ocean. The commission will meet in Tokyo in September to consider whether to strengthen catch restrictions.
Japan also has placed caps on the number of tuna farms, which take young tuna caught at sea and raise them in coastal waters, and is registering its 13,000 independent fishermen to better monitor their catch, Miyahara said.
But conservation groups say the measures are full of loopholes and not well enforced, while Japanese fishermen complain that South Korean boats are not similarly constrained.
"We wonder what the point is if others can catch the fish we can't," said Makoto Hotai, head of the Japan Purse Seiners Association, based in the southern city of Fukuoka.
While Japanese consumers are very sensitive about food safety and quality, awareness about resource management is still not very prevalent. Major retailer Aeon Co. has a lineup of 50 products with a special blue label from the Marine Stewardship Council, which certifies sustainable marine foods. However, MSC-labeled products account for only 3 percent of Aeon's total fish sales.
"Eating fish is a fundamental part of Japanese culture," said Kozo Ishii, the program director for MSC in Japan. "That fish is readily available is taken for granted."
A handful of U.S. and European sushi restaurants have removed bluefin from their menus, but Nagayama, the sushi chef, hasn't heard of that happening in Japan.
He tries to minimize the amount of the fish he uses, but says he needs to have it on hand because customers request it. A single piece of pink "o-toro" fatty tuna goes for 2,000 yen, or $21, at his shop, although customers visiting "conveyor belt" sushi shops can grab much lower quality bluefin for 100 yen, or just over a dollar.
"We're a top-end sushi bar, so we need to have it," said the 71-year-old sushi chef, who has written three books about fish. "If we don't, we can't really do business."
