Porbeagle (Lamna nasus) is an ubiquist, highly mobile and long-living shark species with spatial and temporal sex and size segregation observed in catches. Porbeagle sharks were targeted by commercial fisheries in the European waters until the closure of the fishery in 2010. Most of the French fleet catches were located in Bay of Biscay, Celtic Sea and the English Channel. The aim of the study was to find out occurrences of spatial segregation within the shark population in the Northeast Atlantic Ocean based on the stable isotope method. Carbon and nitrogen stable isotopes (delta 13C, delta 15N) were measured in muscle of porbeagle sharks fished in the Bay of Biscay and the Celtic Sea between April and September 2008, and April and June 2009. Neither influence of sex nor ontogenic isotopic shift was detected in the sampled sharks, but muscle delta 13C and delta 15N values increased significantly from offshore towards coastal area, which reflected inter-areas variability. Realized isotopic niches were similar amongst offshore areas whilst in St Georges' Channel muscle isotopic composition exhibited higher interindividual variability. This underpins the lack of information on life history of porbeagle sharks and underlines the need of more information on the species movements to support population management in European waters.