Common porpoise (Phocaena phocaena)
Common porpoises appear in shallow coastal waters and inland bays and sometimes move upstream into rivers. They feed on fish, squid and crustaceans, and used to be widely distributed in the coastal waters of the North Atlantic and the Baltic, White, Greenland and Black seas. Porpoises, like dolphins, are seriously threatened by sea pollution, especially by chlorinated hydrocarbons and heavy metals. Since these animals are situated at the top of the food-chain, they tend to accumulate relatively large quantities of these substances. Another threat is oil which can enter the breathing hole. The species has also been reduced by excessive commercial fishing.