Résumé
Billfishes are not targeted by tuna purse seiners, but they can be taken incidentally during the setting operation. Because by-catch information is not recorded in the commercial logbooks, it is important to quantify by-catches taken by the purse seine fishery in the Atlantic Ocean. In this paper, we attempted to estimate the total by-catch of billfishes generated by the European tropical tuna purse seine fishery in the eastern Atlantic Ocean from 1991 to 2000. Information on the by-catch of billfish was collected by scientific observers at sea during the European Union Bigeye Program. A Monte Carlo simulation was performed to account for some uncertainties in the changes over time of the fishing strategies adopted by the purse seine fishermen operating in this ocean. This study indicates that the temporary moratorium on fishing with FADs adopted by the European purse seiners, combined with a decrease in the number of fishing operations, produced a substantial decrease in incidental catches of marlins from 450 - 520t/year to less than 300t/year. For the sailfishes, the by-catch was very low (between 40t and 70t per year).