Most of the bluefin will end up in Japanese markets such as Tsukiji in Tokyo
Measures to prevent illicit fishing of Mediterranean bluefin tuna have been strengthened at the annual meeting of governments involved in the industry.
The International Commission for the Conservation of Atlantic Tunas (Iccat) decided to implement an electronic system for recording bluefin catches.
Research shows catches have been far higher than skippers have declared.
The meeting, in Turkey, also gave extra protection to the silky shark, whose numbers are falling because of fishing.
Tuna boats often snare this species by accident; and now, fishermen will have to release them alive.
Government delegates also voted through a minimum legal size for swordfish, and will draw up a comprehensive recovery plan in 2013.
But proposals for protecting the porbeagle shark, classified as vulnerable to extinction on the internationally recognised Red List, were rebuffed.
The most controversial issue on the agenda - illegal fishing for the lucrative bluefin in Libyan waters during the height of this year's civil conflict, which BBC News revealed earlier this month - will be addressed in a separate meeting next year.
Conservation groups gave a mixed reception to the outcomes.
"Iccat's new bluefin tuna electronic catch documentation scheme is an important and positive leap forwards in the monitoring of the fishery and protection of the species," said Sergi Tudela, head of fisheries for WWF in the Mediterranean region.
A report from the Pew Environment Group last month showed that last year 140% more bluefin meat entered the market from the Mediterranean than was declared, largely because the paper-based catch recording system was open to abuse.
New EU rules on shark finning should give extra protection to vulnerable species
The new system will not, however, track bluefin through the "farms" or "ranches" where they are fattened for eventual sale, usually to Japan.
"The continued absence of data on quantity and size of bluefin tuna caged in fattening farms creates a black hole and provides an easy facility for the laundering of illegal, unregulated and unreported catches of Mediterranean bluefin tuna," said Dr Tudela.
Although the focus of Iccat meetings is often on the Mediterranean, the body also regulates fishing across a huge swathe of the Atlantic Ocean.
This includes waters off the west coast of Africa which are beginning to see heavy fishing.
Here, Iccat governments voted to restrict the use of fish aggregating devices (Fads) which attract tuna and sharks, and whose use often leads to significant catch of unwanted species and juveniles.
The Istanbul meeting also produced some good news for birds in the south Atlantic.
Longline boats, which tow lines tens of kilometres long carrying thousands of baited hooks, will have to use at least two out of three methods proven to reduce the accidental catch of albatrosses and other ocean-going giants.
The three strategies comprise deploying streamers from the back of the boat to scare birds away, setting lines at night, and adding weights to their hooks so they sink too deep for the birds to reach.
"This is a great day for albatrosses and other seabirds which die needlessly every minute of the day, accidental casualties in the tuna and swordfish fisheries," said Dr Cleo Small of the RSPB and BirdLife International.
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