specifically for continuing scientific monitoring of the western stock. This scientific catch was allocated to ICCAT-participating nations that had active fisheries (including the United States, Canada, and Japan). Brazil and Cuba were exempted from the regulations because their total catches were small (less than 50 metric tons).

For the 1983 fishing season in the western North Atlantic Ocean, ICCAT established a total allowable catch of 2,660 metric tons. ICCAT also limited the catch of smaller fish, less than 120 cm in length, to no more than 15% in weight of the catch limit for the western stock. In addition, spawning areas such as the Gulf of Mexico were protected by prohibiting any directed fishery there.

In each year from 1983 to 1991, ICCAT approved a one-year extension of the existing management measures for both stocks of bluefin tuna. During the 1991 ICCAT meeting, new regulations were recommended to reduce the western stock's scientific monitoring quota by 10% in 1992 and again in 1993, with the possibility of additional reductions of up to 25% based on future SCRS analyses. Other measures were adopted by ICCAT at the 1991 meeting, including limiting catches of small fish, penalties for exceeding quotas, promoting tag and release efforts, and a bluefin tuna documentation and reporting program phasing in. Exporters of bluefin tuna will be required to provide documents that identify the location and nation of the vessel that caught the fish. To date, ICCAT has not recommended a quota for the eastern stock. However, measures for catch size limits and protection of spawning areas have been implemented for the eastern stock.

ICCAT management for Atlantic bluefin tuna has evolved according to the premise of a two stock structure that can be managed independently. Implementation of this assumption began in member nations in 1982. Since 1991, each stock has been alternately reviewed every second year by the commission. Because of the perceived decline in abundance of western Atlantic bluefin tuna, the two stocks have been subject to different regulations, the most striking difference being the lack of a quota for the eastern stock fishery and the imposition of a strict scientific quota only for the western stock fishery. The two most contentious issues concerning the management of Atlantic bluefin tuna are the definitions and sizes of management units and the indices of abundances that are now used to calculate stock assessments. Opposition to managing the western and eastern Atlantic bluefin tuna stocks as separate units has arisen primarily from lack of definitive scientific evidence for genetically-discrete populations, and alternative population structures have been suggested. The implications for management are significant-if there are more or fewer populations, the present ICCAT management, including the regulations, would have to be modified and new regulations agreed to by all member nations.