Direct interactions between longline fisheries and many top predators such as toothed whales result in substatial impacts on fishing activity; depredating species and fish stocks. These issues continue to be a growing concern in fisheries worldwide, including the French Patagonian toothfish fishery. In this field study, researchers deployed data loggers on killer whales and sperm whales while aboard commercial toothfish demersal longline fishing vessels to gain insight into when, where and how depredation occurs. Data from odontocete tracking loggers and longline accelerometer loggers reveal both species are able to depredate longlines on the seafloor. Findings from this study suggest depredation can occur at anytime during the whole fishing process.