Survival estimates for the Australian sea lion: Negativecorrelation of sea surface temperature with cohort survivalto weaning

Abstract

The Australian sea lion (Neophoca cinerea) population at Seal Bay ConservationPark, South Australia, is estimated to be declining at a rate of 1.14% per breedingseason. To better understand the potential causes of this decline, survival rates wereexamined to 14 yr of age for eight cohorts marked as pups (aged 0.17 yr) between1991 and 2002. Apparent yearly survival rates ( ) varied by cohort for pups frommarking to weaning at 1.5 yr ( =0.30–0.67). Postweaning juvenile survival(1.5–3 yr) was 0.89 and survival from 3 to 14 yr was constant ( female:male=0.96:0.89). of pup cohorts was negatively correlated to local sea surface temper-ature where the sea lions forage (SST) and was especially low for cohort 7 in 2000(0.30). It is possible that periods of unusually warm oceanographic conditions maybe limiting primary production and inhibiting maternal provisioning to pups. Pupsurvival to weaning is relatively low compared to other otariid species, is likelyto limit recruitment, and may be contributing to the decline in pup abundanceobserved in the colony.