The use of the French long line CPUE to provide an abundance index for porbeagle in the North East Atlantic

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A porbeagle catch per unit of effort (cpue) series of the French longline fishery was presented at the 2009 ICES Working Group on Elasmobranch Fishes (WGEF). This fishery has targeted porbeagle in the Northeast Atlantic up to 2009, mainly along the continental edge of the Bay of Biscay shelf and of the south of Ireland shelf. This cpue series was used to carry out exploratory assessments at the 2009 WGEF. Days at sea was adopted for fishing effort unit in order to get a series as long as possible and consequently the cpue is expressed in catch per day at sea. The aggregative behaviour of the porbeagle and the fishing practices in response to this behaviour, however, raise the question of the ability of this cpue index to track changes in stock abundance accurately. This question has been investigated in recent years, from 2000 onwards, by analysing the logbooks of several vessels.