Japan's bluefin tuna trade

A fishing boat waves in the waters of the Tsugaru strait off Oma. Oma is well known in Japan as being the landing place for the country's finest quality 'hon maguro' or Pacific bluefin tuna, which is also known as 'black diamonds' in Japan Photograph: Robert Gilhooly

A fishing boat heads out in the early morning. The waters off the Tsugaru strait are some of Japan's most perilous. Around 100 fishermen in the area employ a sustainable method of fishing known as 'ippon-zuri', or single-hook hand-line fishing, to land giant tuna Photograph: Robert Gilhooly

Fisherman Atsushi Sasaki examines a monitor showing sonar-generated read-outs of the marine life below and around his boat as he heads out into the Tsugaru strait. The 'ippon-zuri' fishermen catch tuna with a combination of a rod and line and a basic sonar system Photograph: Robert Gilhooly

Lights hang from a squid fishing boat in Oma port. Many boats formerly used for squid fishing in the area are now used for the more profitable tuna fishing Photograph: Robert Gilhooly

Fisherman Masayoshi Kikuchi unloads six Pacific bluefin tuna from his boat at Oma port. Kikuchi's haul of six tuna is a rarity these days in Oma, a town that has long been synonymous with high-quality tuna in Japan Photograph: Robert Gilhooly

A fishermen carries the innards of a 100kg Pacific bluefin tuna from a boat at Oma port. Tuna caught off Oma, a town of 6,000 people on the northern coast of Aomori prefecture, typically fetch twice as much as imported fish at auction Photograph: Robert Gilhooly

The tail of a Pacific bluefin tuna stands above a wash basin at the offices of the local fisherman's union in Oma. Oma’s average tuna catch of 2,500 fish a year is worth about 1.6bn yen to the local economy Photograph: Robert Gilhooly

A market worker uses an axe to chop off the frozen tails of tuna set to go to auction at Tsukiji fish market in Tokyo. Some 2,300 tons of fish pass through the market daily Photograph: Robert Gilhooly

Customers enjoy tuna sushi and other seafood at a hole-in-the-wall sushi eatery located in the grounds of Tsukiji fish market in Tokyo Photograph: Robert Gilhooly

A market worker drags frozen tuna fish auctioned at Tsukiji fish market in Tokyo. High fuel prices, lower profit margins and stricter quotas in other parts of the world, combined with rising demand in Europe, the US and, increasingly, Russia and China, have created an irresistible urge to take bigger numbers of bluefin from Japan's waters Photograph: Robert Gilhooly