In the global context of an increase of Human Wildlife Conflict, due to space and resource competition, the ones occurring in marine environment might be exacerbated by the difficulty to assess their magnitude. Longline fisheries depredation is a growing issue confronted by such limitations. In most of the fisheries impacted by this behaviour, the number of individuals and their dynamics are unknown which limits the development of mitigation measures. The present study investigated the trends in abundance of killer whale (Orcinus orca) groups in the two zones most impacted by depredation in the southern Indian Ocean, the Crozet and Saint Paul/Amsterdam zones. The results indicate that the abundance of depredating killer whales in these zones has increased and is linked to an increase in depredation frequency and intensity. In the long-term, this behaviour by killer whales may modify their life history parameters as well as their social organisation. As top predators, changes in killer whale populations could also modify fish stock composition and size. Consequently, such changes could result in economical costs for fisheries by reducing their CPUE, leading to a need for mitigation measures adapted to the high abundance of killer whales in these zones.
Managing Thesis and Internship Exchanges
