Transboundary movements of porbeagle sharks support need for continued cooperative research and management approaches

Distribution of species across jurisdictional and physical boundaries poses a challenge to management and research, and these transboundary species tend to suffer more-severe population declines from fisheries exploitation. Large pelagic sharks like the porbeagle shark, Lamna nasus, are particularly vulnerable to anthropogenic pressures due to their life history characteristics and their highly migratory behaviour. However, limited knowledge of their precise spatio-temporal movements is particularly challenging for management in situations where jurisdictional boundaries change over small spatial scales. We used satellite tags to demonstrate that porbeagle sharks tagged in the northern Northeast (NE) Atlantic (n = 3), display inter-individual variation in behaviour. Tagged sharks undertook rapid horizontal movements (up to 100 km per day) while transiting through multiple physical habitats and management jurisdictions in a matter of days along different paths. The spatial scale of these movements is important now that the population is deemed in recovery and a new catch advice for porbeagle sharks has been issued by ICES for the first time since 2009 in the NE Atlantic. These movement data highlight the value of existing, and need for continued, regional collaboration to inform sustainable fisheries and conservation management. This is achieved by maximising research impact through cross border funding mechanisms to fill knowledge gaps of species' life-history and ecology, and, in turn, improve respective outcomes for vulnerable and highly mobile shark species.