No boundaries for whales interacting with fishing activities targeting Patagonian toothfish (Dissostichus eleginoides)

Killer whale and sperm whale depredation interactions with longlines targeting Patagonian toothfish (Dissostichus eleginoides) have been documented as a severe issue in the Crozet EEZ since the late 90’s. Estimating depredation rates allows to correct catches and therefore to model the real impact of fishing activities on Patagonian toothfish stocks. Photo-identification of interacting marine mammals has been central to understand depredation and develop a mitigation scheme. Here we used photographs from the French vessels fishing in the Crozet EEZ as well as on Del Cano rise in the Southern Indian Ocean Fisheries Agreement (SIOFA), and a dataset from Spanish vessels operating on Del Cano rise. Photo-identification revealed movements of sperm whales and killer whales individuals across boundaries. Over the 2009 – 2019 period, and depredation rates were estimated to be around 8% in the Del Cano – SIOFA area.