Beluga Whale: The species Delphinapterus leucas, in the family Monodontidae, found primarily in the Arctic Ocean and adjoining seas. They are small WHALES lacking a dorsal fin.Whales: Large marine mammals of the order CETACEA. In the past, they were commercially valued for whale oil, for their flesh as human food and in ANIMAL FEED and FERTILIZERS, and for baleen. Today, there is a moratorium on most commercial whaling, as all species are either listed as endangered or threatened.Fin Whale: The species Balaenoptera physalus, in the family Balaenopteridae, characterized by a large, strongly curved, dorsal fin. It is the second largest of the WHALES, highly migratory, but rarely seen near the shore.