and porpoises, found worldwide. While no cetacean species has been driven to extinction by human endeavors (Perrin, 1988), four species of the smaller cetaceans are in jeopardy in the coming decades if certain human activities in their habitats are not changed (Brownell, 1991; Norris, 1992). These include the baiji, Lipotes vexillifer; the Chilean dolphin, Cephalorhynchus eutropia; the Indus River dolphin, Platanista minor; and the vaquita, Phocoena sinus, of the Gulf of California.

The marine Carnivora all spend some time on land or sea ice to breed and bear their young. The breeding areas are therefore especially sensitive to human encroachment. A few species live in freshwater. Marine mammals in the order Carnivora include fur seals and sea lions, true seals, walrus, chungungo and sea otters, and polar bears (Table B-2).

Pinniped means ''feather footed,'' and the suborder Pinnipedia includes three families: Otariidae (fur seals and sea lions), Odobenidae (walrus), and Phocidae (true seals). Historically, almost all pinnipeds were hunted for fur, meat, oil, or ivory. Brownell (1991) suggests that, although most pinniped species will probably experience an increase in number during the 1990s, at least three species—northern fur seal, Callorhinus ursinus; Steller sea lion, Eumetopias jubatus; and Mediterranean monk seal, Monachus monachus—will continue to decline in the absence of stronger corrective measures. One pinniped species, the Caribbean monk seal, Monachus tropicalis, has apparently become extinct during this century (Kenyon, 1977).

The sea otter of the North Pacific, Enhydra lutris, is a coastal animal that is often associated with kelp beds just off the coasts of California, British Columbia, and Alaska.

The marine otter off the coasts of Peru and Chile, chungungo, Lutra felina, is severely endangered because the animals are hunted for their prized pelts on the Chilean coast and because Peruvians often shoot them as a menace to fishing (Miller and Rottmann, 1983). Another large otter, Lutra longicaudis of northeast Brazil, is threatened by fishing, clandestine hunting, and habitat degradation (Almeida et al., 1991).

FRONT MATTER (R1-R16)

EXECUTIVE SUMMARY (1-7)

1 A REVIEW OF CURRENT KNOWLEDGE (8-24)

2 REGULATORY BARRIERS AND POSSIBLE ALTERNATIVES (25-39)

3 TOPICS FOR FUTURE RESEARCH (40-62)

APPENDIX A COMPARISON OF SOUND-PRESSURE REFERENCE LEVELS IN AIR AND WATER (63-64)

APPENDIX B AN INTRODUCTION TO MARINE MAMMALS (65-73)

APPENDIX C COMPARISON OF YEARLY SOUND ENERGY FROM OCEANOGRAPHIC RESEARCH AND SUPERTANKERS (74-75)