Slaughter isn't the only threat that we pose towards cetaceans. Fishing nets are very dangerous to dolphins and porpoises. Very often, dolphin or porpoise pods will be chasing a school of fish that fishermen in boats with nets are trying to catch. When the net is drawn up, the dolphins or porpoises will get tangled in the net and drown because they are unable to swim to the surface to breathe. We can not forget that they are mammals and need to breath air!
Fishing nets kill hundreds of dolphins and porpoises every day, and can be just as dangerous to species' populations as slaughter. Sometimes, divers will get in the water and help the pods out before the net is drawn up, but sometimes they won't either. Many other creatures become tangled in these fishing nets, such as seals, sealions, sharks and small whales.