El Niño is a meteorological and oceanographic phenomenon, which occurs at irregular intervals in the eastern tropical Pacific. Its most obvious characteristic is the warming of surface waters, which causes enormous disturbances of the marine environment. A severe Niño may also affect continental systems worldwide. This book gathers in a comprehensive way the information available on the effects of the exceptionally strong 1982-83 Niño on a group of marine mammals, the pinnipeds. It presents an analysis of the effects of environmental stress on the populations of top predators. Data and interpretations are based on a most unusual collection of long-term studies of pinniped population dynamics, behavior and ecology which spanned the El Niño event. The responses of pinniped populations to the El Niño disturbance of the marine ecosystem also has important implications for the management and conservation of marine mammal populations.

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I.- 1 The Time Sequence and Magnitude of Physical Effects of El Niño in the Eastern Pacific.- 2 Biological Consequences of the 1982-83 El Niño in the Eastern Pacific.- II. Otariid Pinnipeds, General.- 3 Introductory Remarks on the Natural History of Fur Seals.- 4 El Niño Effects on Pinnipeds in Northern Chile.- 5 El Niño Effects on Pinnipeds in Peru.- 6 The Effects of El Niño on Galapagos Pinnipeds.- 7 Impact of the 1982-1983 El Niño on the Northern Fur Seal Population at San Miguel Island, California.- 8 El Niño Effects on Adult Northern Fur Seals at the Pribilof Islands.- 9 Sea Surface Temperatures and Their Relationship to the Survival of Juvenile Male Northern Fur Seals from the Pribilof Islands.- III. California Sea Lion.- 10 Introductory Remarks and the Natural History of the California Sea Lion.- 11 Effects of the El Niño 1982-1983 on California Sea Lions in Mexico.- 12 Population Abundance, Pup Mortality, and Copulation Frequency in the California Sea Lion in Relation to the 1983 El Niño on San Nicolas Island.- 13 Changes in the Distribution of California Sea Lions North of the Breeding Rookeries During the 1982-83 El Niño.- 14 The Influence of El Niño on Female Attendance Patterns in the California Sea Lion.- 15 Effects of El Niño 1983 on the Foraging Patterns of California Sea Lions (Zalophus californianus) near San Miguel Island, California.- 16 Effects of El Niño on the Foraging Energetics of the California Sea Lion.- 17 Effects of the 1982-1983 El Niño on Several Population Parameters and Diet of California Sea Lions on the California Channel Islands.- 18 The Effect of El Niño on Pup Development in the California Sea Lion (Zalophus californianus) I. Early Postnatal Growth.- 19 The Effect of El Niño on Pup Development in the California Sea Lion (Zalophus californianus) II. Milk Intake.- 20 The Influence of El Niño on Mother-Pup Behavior, Pup Ontogeny, and Sex Ratios in the California Sea Lion.- 21 The Effects of El Niño on the Frequency and Sex Ratio of Suckling Yearlings in the California Sea Lion.- IV. The Elephant Seal.- 22 The Natural History of the Northern Elephant Seal.- 23 Biological Effects Associated with El Niño, Southern Oscillation 1982-83, on Northern Elephant Seals Breeding at Año Nuevo, California.- 24 Effects of the 1982-83 El Niño on Northern Elephant Seals on the South Farallon Islands, California.- 25 Northern Elephant Seals on the Southern California Channel Islands and El Niño.- V. Summary and Conclusion.- 26 The Effects of El Niño on Pinniped Populations in the Eastern Pacific.- References.