Publication Abstract

An evaluation of management strategies for atlantic tuna stocks

L.T. Kell, D.J. Die, V.R. Restrepo, J.M. Fromentin, V. Ortiz de Zarate and P. Pallares

International agreements for the ICCAT convention area imply that Atlantic tuna stocks should be managed by strategies based on maximum sustainable yield (MSY), however, there is concern whether this will ensure sustainability with sufficiently high probability consistent with the principals of the precautionary approach. The performance of MSY management strategies based on current assessment procedures was evaluated using a computer simulation framework. The framework includes the data collection, assessment, prediction and management processes as well as the implementation of management regulations and thus allows the interaction between these processes to be investigated. It therefore provides an integrated way to evaluate the relative importance of each component of the system to the overall success of the management strategy.

The study attempts to elucidate guidelines about assessment and management that are general enough to be applied to all tunas in the Atlantic ocean. It does so by comparing different hypotheses about management and assessment for three stocks (North Atlantic albacore, Atlantic bigeye and East Atlantic skipjack), which are representative of the variety encountered (i.e. from data rich to poor and tropical to temperate) in ICCAT stocks.

The framework was useful in identifying the relative importance of different sources of uncertainty to the success of the management procedure. Management performance was especially sensitive to the initial status of the stock prior to the commencement of the management procedure. The type of proxy used for MSY was more important to the success of the procedure than the frequency of assessment or then the number of indices used during the assessment. The procedure was succesful at helping reaching the management objectives for albacore, was only partially succesful for bigeye and too conservative for skipjack. Many sources of uncertainty were purposedly ignored in this study, however, in future studies their impact on management will be tested with the framework.

Reference:

L.T. Kell, D.J. Die, V.R. Restrepo, J.M. Fromentin, V. Ortiz de Zarate and P. Pallares, 2003. An evaluation of management strategies for atlantic tuna stocks. Scientia Marina 67 (Suppl. 1)