BRUSSELS France and Spain banned industrial fishing of endangered bluefin tuna late on Tuesday for the rest of this season after fishermen from both countries exhausted their quotas more quickly than anticipated.
Western scientists say stocks of the Atlantic bluefin - which can sell for up to $100,000 each at market - have fallen by about 80 percent since the 1970s.
Most tuna caught by EU vessels are sent to Japan, where they are highly prized by sushi and sashimi lovers.
High-tech vessels using sonar or echo-sounders have become so efficient at locating and netting the fish in huge "purse seine" nets that a season's quota can be filled in just 10 days. The current season runs from May 16 to June 14.
"The purse seine quota allocated to both countries was exhausted yesterday... and both member states have decided to call back their vessels to port," the European Union's executive, the European Commission, said in a statement.
The nine French and six Spanish purse seine vessels were involved in joint operations, which meant their quotas were filled more quickly, the Commission said.
Small-scale fishing for bluefin tuna using traps, hooks and spears will be allowed to continue for the moment.
This year's total quota for Atlantic bluefin was set at 12,900 metric tons (14220 tons) by the International Commission for the Conservation of Atlantic Tunas (ICCAT).
The European Union's quota for 2012 was fixed at 5,756 metric tons. Spain received the largest share - 2,411 metric tons - followed by Italy with 1,787 metric tons and France with 958 metric tons.
The warm-blooded Atlantic bluefin are found throughout the North Atlantic from the Gulf of Mexico to the Mediterranean Sea, where they go each year to spawn.
They are known for their size and speed, reaching weights of more than 600 kg (1,300 pounds) and speeds of up to 70 km per hour (112 miles per hour).
(Reporting by Charlie Dunmore; editing by Rex Merrifield and Mark Heinrich)