Survival estimates for the Australian sea lion: Negative correlation of sea surface temperature with cohort survival to weaning

Abstract

The Australian sea lion (Neophoca cinerea) population at Seal Bay Conservation Park, South Australia, is estimated to be declining at a rate of 1.14% per breeding season. To better understand the potential causes of this decline, survival rates were examined to 14 yr of age for eight cohorts marked as pups (aged 0.17 yr) between 1991 and 2002. Apparent yearly survival rates ( ) varied by cohort for pups from marking 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 temperature 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 may be limiting primary production and inhibiting maternal provisioning to pups. Pup survival to weaning is relatively low compared to other otariid species, is likely to limit recruitment, and may be contributing to the decline in pup abundance observed in the colony.

Intrinsic and extrinsic influences on standard metabolic rates of three species of Australian otariid

“…The habitats of the Australian fur seal and the Australian sea lion do not overlap, but the New Zealand fur seal occurs across both the feeding and breeding ranges of the other two species ( Page et al ., 2005a ; Campbell et al ., 2014 ). The ranges of the Australian fur seal and the New Zealand fur seal are currently expanding as they begin to reoccupy territory they held before commercial sealing ( Goldsworthy et al ., 2003 ), whereas the Australian sea lion is listed as endangered, and the population continues to decline ( McIntosh et al ., 2013 ). By investigating how marine mammals occupying similar habitats but using different reproductive and foraging strategies vary their primary energy expenditure over the course of a year, we can begin to understand how they might respond to environmental changes.…”

A retrospective socio‐ecological analysis of seal strandings in the Gulf of Maine

“…Changing water temperatures may have indirect effects on marine mammal distribution or health, and thus influence stranding rates by altering habitat suitability, including prey distribution and availability. Climate variability, including SST, has been shown to significantly affect pup production and survival in several other pinniped species worldwide (Forcada et al, 2005; Laake et al, 2018; McIntosh et al, 2012). In our study system, where the strongest correlation between seal stranding density and SST was observed at a 4‐month lag, the modeled effect of SST on harbor seal pup strandings most likely reflects the effects experienced by the adult female during pregnancy.…”

Effect of environmental variables on the number of births at California sea lion (Zalophus californianus) rookeries throughout the Gulf of California, Mexico

“…The use of remote estimates of SST and CHL‐a as indicators of food availability has been established previously for other pinnipeds (Mitchell‐Innes & Pitcher, 1992; Castillo, Barbieri & González, 1996; McIntosh et al, 2013). The SST is one factor that modulates the abundance and distribution of marine organisms at different trophic levels.…”