We examined the annual number of pups born, pup mortality, and pup weights of California sea lions (Zalophus californianus) at San Miguel Island, California, and related them to large and small-scale oceanographic indices in the central California Current System (CCS) between 1997 and 2011. Annual variability in the number of pups born and pup mortality was best explained by the mutlitvariate ENSO index (MEI) that tracks the El Niño/La Niña cycle. Annual variability in average pup weights was best explained by a sea surface temperature anomaly index (SSTA); average pup weights were lower in years when the SSTA was greater than 1˚C above normal. We demonstrated that California sea lions are sensitive to large and small-scale changes in ocean conditions through changes in their reproductive success, pup growth, and pup mortality. Therefore, California sea lions are an ideal indicator species for the IEA of the CCS.