A Greenpeace activist was yesterday beaten by fishermen as she tried to board two boats, moored at Grand Harbour, in search of illegally fished blue fin tuna.

An inspection by the Fisheries Control Division after the police had calmed the situation did not yield any illegal stocks of bluefin tuna, a breed that may be depleted within three years if overfishing continues.

What was meant to have been a peaceful protest staged by the international environmental group took a violent turn when Australian Emma Briggs was pulled by the hair, punched and thrown overboard from the Spanish fishing support vessel Cabo Tinoso Dos.

The 39-year-old later tried to get on the Maltese vessel Santina, which was moored next to the Spanish boat, but was again beaten by the fishermen as Greenpeace protested against unsustainable fishing activities.

A video taken by Greenpeace showed the fishermen hitting Ms Briggs as they swore while one of them shouted "hit her, hit her" in Maltese. She suffered a black eye and bruises to her neck and head but was not seriously injured.

Greenpeace international oceans campaigner François Provost said: "We were just trying to carry out an inspection on the boats".

Greenpeace US oceans campaigner John Hocevar said they wanted to see what tuna was on board and whether it was legal, adding that support vessels help the tuna ranching industry by transporting divers, supplies and material for cages.

According to Greenpeace, the two boats were being used by Ricardo Fuentes e Hijos, a major Spanish tuna ranching company which controls some 60 per cent of Mediterranean bluefin tuna production. This, together with the fact the boats had been in Libyan waters, fuelled the activists' suspicions.

When contacted, a spokesman for the Spanish company referred The Times to its local handler, Mareblu Tuna Farm, but its spokesman did not want to comment about the incident.

However, the secretary of the Federation of Maltese Aquaculture Producers, John Refalo, said when contacted that, while he did not condone violence, had the activists asked to go aboard they might have been allowed to do so.

The industry was highly regulated, he said in a statement. Aquaculture producers were committed to respect regulations and had to comply with a number of checks and procedures designed to guarantee transparency.

The Greenpeace activists, who arrived in Malta on their boat Rainbow Warrior on Saturday, started off by using two dinghies to block the Cabo Tinoso Dos and the Santina as they tried to leave their mooring spot at Ras Ħanżir.

Activists from the US, Australia and Lebanon carried posters saying "Bluefin Tuna Massacre" on the dinghies, as the fishermen hosed them with water jets.

The media, called to the Rainbow Warrior for a press conference, were instead taken aboard another small boat to watch the protest.

"The species is soon going to be made extinct and we need to stop this," Mr Provost said.

A number of activists managed to get on the quay, run by the Valletta Gateway Terminals, and remained there despite the protests of security officers. Police arrived and called the division to inspect the boats - but no illegal tuna was found.

The Rural Affairs Ministry said the division was committed to ensure the national quota for tuna fishing was respected.

Locally, the tuna fishing season closed earlier this month after Malta reached its quota - which Greenpeace still believes is too high - for this year.

Mr Provost said although scientists advised against catching more than 15,000 tonnes of tuna annually, an estimated 61,000 tonnes was caught in 2007, double the legal limit for that year and four times the recommended level to avoid the collapse of the bluefin tuna population.

The quotas were much higher than those recommended by scientists, he insisted.

In a statement the organisation said that as industrial fleets "continue to rampage across the spawning grounds" local fishermen were reduced to transferring the last of an endangered species to pens to be fattened, before being exported to the other side of the world.

Mr Hocevar said it was time to take this species' management away from the International Commission for the Conservation of Atlantic Tunas, an intergovernmental organisation.

"We want to see the US administration and other influential governments end international trade in this endangered species," he said.