There is a better than 50/50 chance that people enjoying tuna sushi half a world away in Japan are eating not wild fish but fish that have been fattened on tuna farms in the Mediterranean Sea.

A total of 12 tuna farms now operating in the Mediterranean produced 11,000 tons of tuna fish in 2001 - more than half the traded blue fin tuna in the world.

Two international conservation groups and the largest environmental group in Spain's Murcia province today attempted to sound a warning that an expansion in tuna farming threatens to destroy the already overfished wild tuna in the Mediterranean.

Together with representatives of Greenpeace, and the Asociacion de Naturalistas del Sureste (ANSE), the conservation group WWF tried to call the attention of 15 European Union Agriculture Ministers to the "harmful new trend."

The ministers were onboard the Spanish Navy flag ship Juan Sebastián El Cano on a visit to a bluefin tuna farm located near Tiñoso Cape at Cartagena in Spain's Murcia province.

On their sailboat, the environmental groups displayed a banner with the message "STOP Blue Fin Tuna Overfishing."

Their intention was to reach the Spanish Navy ship in a lifeboat displaying a second banner saying "STOP tuna farms" and give the ministerial delegation a document with several petitions concerning tuna farming.

But the Spanish government delegation in Murcia stopped the sailboat and prevented the environmentalists from presenting the document to the ministers.

Tuna farming - caging of wild tuna for fattening - is a phenomenon driven mainly by Japanese market demands. Farmed tuna is higher in oil content than wild tuna, which makes it desirable for sushi.

The Murcian coast is the biggest producer of fattened captive tuna in the world. Six authorized facilities are currently operating in the area with three new facilities going through the environmental impact assessment process.

Most of the tuna farms are located in what the environmentalists term "highly ecological sensitive areas," such as the Azohía-Tiñoso Cape.

Tuna farms are also located in Croatia and Malta. France, Tunisia, and Algeria are interested in developing this activity.

Tuna farming contributes to the growing overfishing of the world's most important bluefin tuna breeding population, which lives along the Levantine and Balearic Spanish coast, the groups warn.

WWF, Greenpeace, and ANSE fear that the new tuna farming facilities waiting for permission in Murcia, Catalonia, Valencia, and the Balearic Islands will increase the pressure on the bluefin tuna breeding population.

But proponents of tuna farming, also known as tuna penning and tuna aquaculture, view the practice as a proactive means to increase the efficiency of the tuna industry while reducing the exploitation of tuna species.

The three environmental groups are denouncing tuna farming as unsound and warn that it could lead to disturbance of local and regional food chains due to the large number of small pelagic fish caught to feed the captive tuna.

From April 15 to 19, THE International Commission for the Conservation of Atlantic Tunas and the General Fisheries Commission of the Mediterranean met in Malta to consider for the first time the effects of bluefin tuna farming on statistics and stock assessment. The report, which was not made public, will become part of the next bluefin tuna stock assessments planned for July 22 to 30 in Madrid.

In addition to a moratorium on the development of new tuna farming in Mediterranean countries, the environmental groups are calling for "establishment of a No Take Zone" for the Mediterranean bluefin tuna breeding population.

The groups say there should be "proper and harmonized regulations for tuna farming practices, since these are large scale agro-industrial operations with major environmental impacts."

Dr. Simon Cripps, director of WWF's Endangered Seas Program, said, "The highly migratory blue-fin tuna is already threatened by direct fishing in the Mediterranean. This so-called tuna farming avoids every regional and international rule set up to conserve and manage the fishery. Governments must urgently take action to close yet another loophole within European fisheries management and step up controls on this growing practice while there is still time."