Each year, many cetaceans (300,000 a year) are victims of accessory catches, that is, bycatches in fishing nets or with hooks. Cetaceans can also be entangled in "ghost nets": these are abandoned nets (marine debris) that drift for years. Bycatches concern all cetacean species and are currently one of the most serious threats to them. Moreover, the extent of this phenomenon increases with the development of fishing and the increasing human population.