Off the coast of Malta, bobbing in the Mediterranean waters, a flotilla of fishing boats is waiting to net swarms of bluefin tuna before the catching season ends in the middle of this month.
The tuna aren't the only ones being hunted.
Environmental campaigners are waiting too, their binoculars and monitoring devices trained not on the sea but on the trawlers.
"Actually, I want them to start fishing," said Oliver Knowles, a campaigner for Greenpeace, which wants a moratorium on bluefin tuna fishing and has sent two ships to the Mediterranean to try to disrupt the hunt.
"You want a little environmental destruction, so you get to say something about it," he told his young crew of 26 on board the organisation's flagship Rainbow Warrior.
At any one time there are a dozen or more vessels in an area large enough for them to remain out of sight of each other. From France, Spain, Turkey and elsewhere. Some barely move, others shift constantly.
Many of the boats carry net cages used to encircle the tuna swarms, which are then towed offshore to be fattened and shipped in giant freezer ships to Japan, where it is a mainstay of sushi and sashimi.
The larger and fatter, the more valuable they are - the biggest specimens can fetch more than 100,000 dollars (€80,000) at the Tsukiji fish market in Tokyo.
Industrial-scale fishing and harvesting on the high seas has caused stocks to plunge by up to 80 per cent in the Mediterranean and eastern Atlantic, where they come to spawn in the warmer waters.
Earlier this year, the EU and the US attempted to ban the trade of the species, but Japan lobbied successfully and the proposal was defeated.
The focus has now returned to the open waters until the tuna season ends on June 15, and Greenpeace flew reporters, including AFP, by helicopter onto the Rainbow Warrior to follow its side of the chase.
Leaning over nautical maps and compasses, Mr Knowles and his crew monitor the trawlers, looking for signs they might have found a swarm.
"If they start circling or their speed slows down," he said, "it's usually an indication that they at least think they've got a shoal of fish."
That's the point when the Greenpeace activists want to step in to disrupt any fishing to "stop them taking the fish out of the water," said Mr Knowles.
Greenpeace refuses to divulge what kind of tactics it might employ. Last month, activists on board rafts temporarily blocked three tuna fishing vessels from leaving the port of Sete, in southern France.