A marine conservation group has questioned the sight of tuna pens still being towed to Malta weeks after the EU closed the season after the quota for the species ended.

The Biological Conservation Research Foundation (Bicref) said it wondered how this could still be, given that tuna fishing had been stopped on June 9 after the EU's fishing fleet reached its quota.

"Bluefin tuna fishing in the Mediterranean has been clearly shown to require closer monitoring and enforcement of regulations to make sure responsible and sustainable fishing might slow down the rate of loss of Bluefin tuna in the Mediterranean spawning hot spots," BICREF said, accusing the authorities of doing "too little too late" to conserve the species.

However, reacting to this, a government spokesman said several checks were made before the pens could be towed, at a very slow pace.

"Towing can take a number of days or weeks, depending on weather conditions and on the positioning of the farming facility," he said.

"One should also consider that once a cage is being towed, the towing vessel has to sail at a very slow pace, contributing to the delay."

Tuna pens being towed to the island have recently also fallen in the crosshairs of conservation organisations, including Greenpeace International and the Sea Shepherd Conservation Society.

Of the three incidents reported, tuna was only freed in the second encounter between fishermen and a group from the Sea Shepherd. Two divers were hurt in that incident. The first, which came in the form of a protest by Greenpeace, was foiled by the armed forces and the third also by the Sea Shepherd crew, was repelled by the Libyan Navy.