A tuna is sliced carefully with a long sword-like knife – the choicest cuts will be served as sashimi or sushi.
As the world has developed a taste for these Japanese delicacies, the pressure on tuna stocks has grown.
Japan has introduced a scheme to track where the most highly prized species, Bluefin tuna, was caught.
It hopes this will help to stamp out illegal catches.
Text: Chris Hogg
Pictures: James Cope