Effects of organohalogen contaminants on Steller sea lion survival and female reproduction in the Russian Far East

Abstract

The presence of persistent organohalogen contaminants (OCs) in the habitats of Steller sea lions, Eumetopias jubatus, may influence reproductive rates and possibly survival. The lack of recovery and the reduction in natality for the western stock has no apparent cause and OCs may be potential contributing factors. Among the most common synthetic OCs measured in marine mammal tissues are polychlorinated biphenyls (PCBs), dichlorodiphenyltrichloroethane (DDT), polybrominated diphenyl ethers (PBDEs), and hexachlorobenzene (HCB). This project's focus was on the relationship between OCs and the western stock's lack of recovery. A suite of OCs were quantified from 239 hot-branded pups from 2001-2007 at nine Russian Far East rookeries. The use of brand-resighting data provided the opportunity to contrast pup survival, movement, reproductive success, and age at first reproduction between rookeries and among individuals with varying post-natal loads of OCs. Survival and movement were not affected by OC concentrations, but the estimated probability of survival within the first year was lower than expected at some rookeries. The effects of OCs on reproduction were less clear and no consistent pattern of negative effects emerged. Rookery specific differences indicated that location may be an important variable when considering survival, movement, and reproduction.