Toothed whale swallow fishing hooks. Gillnetting and Seine netting are significant causes of mortality in cetaceans and other marine mammals. Porpoises are commonly entangled in fishing nets. Whales are also affected by marine pollution. High levels of organic chemicals accumulate in these animals since they are high in the food chain. They have large reserves of blubber, more so for toothed whales, as they are higher up the food chain than baleen whales. Lactating mothers can pass the toxins on to their young. These pollutants can cause gastrointestinal cancers and greater vulnerability to infectious diseases. They can also be poisoned by swallowing
Captive killer whales a limited area, such as Puget Sound or the Strait of Juan de Fuca, are termed "resident" whales, while "transient" whales roam the oceans at will. These "transient" types have to be more aggressive, in order to assert themselves in a wide range of territories and to prey on a variety of different species. This increased aggressiveness does not disappear in captivity. Furthermore, captivity itself has been asserted to aggravate aggressive behavior, resulting in a "cetacean equivalent of anxiety disorder." Captive killer whale attacks on humans seem to fall mostly into the categories of: biting during feeding, ramming in the