Besides the difficulties in gathering sufficiently reliable fisheries data for stock assessment, the problems of determining stock structure, the spatial distribution, the mixing zones remains the important factors to realize a stock assessment project. In parallel with other techniques like biological, chemical, parasitical tags (otolith, DNA and parasite), the tag could contribute towards providing a better knowledge on the migration pattern of swordfish betwe en the Indian Ocean towards the Atlantic (South Africa) or the Pacific (Australia). Within a particular stock, the knowledge of the individual behavior in a smaller area could help to model the spatial distribution following the size and/or the sex that ca n be indispensable for VPA Analysis. 'Research Group' Ifremer Laboratoire Ressources Halieutiques, B.P. 60, 97822 Le Port — Cedex — La Reunion (océan Indien) Email: fpoisson@guetali.fr, Marc.Taquet@ifrerner.fr.

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