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
Whaling in Japan of extinction within a few decades according to IWC population estimates. In Japan, not only humpback, minke, and sperm whales, but many other smaller toothed whales, including species such as western gray, the endangered North Pacific right, and northern fin whales have been targets of illegal captures utilizing harpoons for dolphin hunts or intentionally drive whales into nets. Reports are later filed with administrative organs or research institutions as cases of "entanglements where fishermen tried their best to save whales". Products from internationally protected species' meat can also be found on markets even today mostly originating as "by-products" of entanglements,