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
Ultrasound whistle is a whistle that emits ultrasound, used for training and calling dogs. The frequency of most dog whistles is within the range of 23 to 54 kHz. Toothed whales, including dolphins, can hear ultrasound and use such sounds in their navigational system (biosonar) to orient and to capture prey. Porpoises have the highest known upper hearing limit at around 160 kHz. Several types of fish can detect ultrasound. In the order Clupeiformes, members of the subfamily Alosinae (shad) have been shown to be able to detect sounds up to 180 kHz, while the other subfamilies (e.g. herrings) can hear