Conservation Society Sea Shepherd will today launch a "Blue Rage" campaign against the poaching of threatened bluefin tuna in the Mediterranean, the director of its French branch told AFP.

The group's boat Steve Irwin arrived in Malta on Saturday.

Director Lamya Essemlali and the group's founder, Paul Watson, are to join the vessel and its crew of about 40 people today to launch the campaign which would last until mid-July.

"We want to stop the poachers," Essemlali said, adding that Sea Shepherd's boat would consider sailing into Libyan waters, where many poachers operate, to protect the bluefin.

The legal fishing period for the fish is May 15 to June 15, but even during that period the catch is capped by strict international quotas.

Sea Shepherd says on the website www.seashepherd.org/blue-rage the Steve Irwin and its crew "will stand against the illegal overfishing of bluefin tuna."

"We will do everything possible within the boundaries of international law to protect the magnificent bluefin," it says.

Fishermen on Friday hurled a grappling hook at a Greenpeace dinghy trying to free endangered bluefin tuna from their nets off Malta, injuring an activist whose leg was pierced by the hook.

Essemlali said that Greenpeace had been right to target a ship that was fishing legally because, whether legal or not, "it's all endangering stocks of the fish."

"Targets are different before June 15, when illegal fishing is difficult to spot, and afterwards," Essemlali added.

In a May 16 statement on its website, the US-based Sea Shepherd said it suspected that four times the legal quota of 13,500 tons of blue fish tuna would be taken from the Mediterranean, "three-quarters falling into the hands of poachers."

Since the industrial fishing era began, stocks of bluefin tuna have fallen by at least 85 percent in the Mediterranean and eastern Atlantic, where they come to spawn in the warmer waters.

Many of the 100 boats that fish in the Mediterranean carry net cages to contain tuna, which are then towed to fish farms to be fattened and shipped in giant freezer ships to Japan, where they are a mainstay of sushi and sashimi.

Earlier this year the European Union and the United States attempted to ban the trade of the species, but Japan -- where bluefin tuna is a delicacy -- lobbied successfully and the proposal was defeated.

Sea Shepherd considers that France and Italy have made some progress on regulating bluefin tuna fishing, allowing inspectors from the international organisation in charge of managing Atlantic tuna (ICCAT) on board of fleets.

But Greenpeace recently accused ICCAT, as well as CITES, the UN body overseeing wildlife commerce, and the European Union of failing to protect the threatened species.