Ridgway, S.H. 1995. The tides of change: Conservation of Marine Mammals, pp.407-424. In: 4 Conservation of Endangered Species In Captivity: M An Interdisciplinarv Approach. E.F. Gibbons Jr., l! 21 B.S. Durrant, and J. Demarest, (eds.) State University of New York Press, Albany. The Tides of Change: Conservation of Marine Mammals Sam H. Ridgway Marine mammals are represented in three taxonomic Orders of mammals: Cetacea, Sirenia, and Carnivora. Normally spending their entire lives in water, all extant members of Cetacea and Sirenia are designated marine mammals and include both fresh and salt water species. Some of the Order Carnivora spend considerable periods of time (many months) in the water, but none are totally aquatic. Within the Order Carnivora there are several families that include marine mammals: Otariidae or eared seals (fur seals and sea lions), Odobenidae (walrus), Phocidae (true seals), Mustelidae (chungungo and sea otters), and one member of the family Ursidae (polar bears). In the United States, all marine mammals are legally pro- tected by the Marine Mammal Protection Act of 1972. The U.S. Fish and Wildlife Service (FWS) of the U.S. Department of the Interior is responsible for administering regulations under this Act for polar bears, walrus, manatees, and sea otters, while the Na- tional Marine Fisheries Service of the U.S. Department of Com- merce is responsible for all whales, dolphins, seals, sea lions, and other marine mammals not regulated by FWS. In addition, another independent body, the Marine Mammal Commission, maintains a scientific committee to advise on scientific issues related to marine mammal conservation. Those species designated as endangered are further protected under the Endangered Species Act of 1973. Pressures that affect marine mammal populations worldwide are many and include fishing (gill nets, drift nets, ghost nets, the yellowfin tuna purse-seine fishery, rolling hooks), pollution 407 e