analyses. The committee recommends that NOAA/NMFS and ICCAT SCRS act to include transatlantic movement of fish and adaptive management techniques in future uncertainty analyses.
The committee cannot determine the maximum sustainable yield (MSY) for Atlantic bluefin tuna under a one-stock hypothesis with two spawning grounds. Available biological information on stock structure, mixing on the spawning and fishing grounds, spawning site fidelity, and spawner/recruit relationships is too sparse. We do know that the present abundance of bluefin tuna in the western Atlantic Ocean is lower than that in the early 1970s although the committee did not analyze similar data for the bluefin tuna in the eastern Atlantic Ocean. We also know that the present abundance and fishing mortality are much higher in the eastern Atlantic Ocean than in the west, and that some physical mixing occurs between the fishing grounds in the eastern and western Atlantic Ocean. The committee recommends that NOAA/NMFS reevaluate MSY for Atlantic bluefin tuna.
The committee notes that research on the biology of Atlantic bluefin tuna is not continuing at an intensity necessary to answer major biological questions pertaining to the management of the fisheries. Therefore, the committee recommends that NOAA/NMFS carry out the research described below using the best available science and techniques within and outside NOAA. For example, research supported by other U.S. government agencies, including the National Science Foundation, the Department of Energy, and the Office of Naval Research, could contribute to the goals of the studies funded by NOAA. Finally, the committee urges NOAA/NMFS to work cooperatively with ICCAT to implement these research recommendations. The following recommendations are not listed in order of importance or priority.
Tagging data show that there is movement of bluefin tuna between the eastern and western Atlantic fishing grounds, but the degree of gene flow between spawning areas is not known. Such knowledge is essential in defining population genetic structure and useful for refining stock assessments. The committee recommends that the one-stock hypothesis be tested rigorously, using the most appropriate technologies capable of detecting contemporary population genetic structure.
Estimates of spawning fidelity to a particular area are essential for stock assessments. The committee recommends that microconstituent analysis and archival tags be used to provide information on spawning fidelity.
Stock assessments can be refined by better estimates of life history characteristics such as spawning biomass, larval abundance, sex ratio, age at maturity, fecundity, and recruitment. The committee recommends that spawning