Biological Effects Associated with El Niño Southern Oscillation, 1982–83, on Northern Elephant Seals Breeding at Año Nuevo, California

Abstract

This chapter presents vital statistics on northern elephant seals, Mirounga angustirostris, inhabiting the rookery at Año Nuevo, California over a period that included EN 1982–83. Our approach involves comparisons of baseline data collected routinely in the years before, during, and after EN 1982–83. Specifically, we examine:

• 1. Direct effects on mortality and distribution of adults caused by a rise in sea surface level, high coastal winds, high surf, and winter storms associated with El Niño (Fahrbach et al., this Vol.), and

• 2. Indirect or long-term effects on mortality, reproduction, and foraging effort associated with fluctuations in water currents, upwelling, and water temperature—perturbations that might have caused changes in the composition, distribution, abundance, and availability of the food base of these phocids (Arntz et al., this Vol.).