Sarah G. Allen

Entanglements of marine mammals and seabirds in central California and the north-west coast of the United States 2001–2005

Entanglement records for seabirds and marine mammals were investigated for the period 2001-2005. The entanglement records were extracted from databases maintained by seven organizations operating along the west coast of the United States of America. Their programmes included beach monitoring surveys, rescue and rehabilitation and regional pinniped censuses. Records of 454 entanglements were documented in live animals and in carcasses for 31 bird species and nine marine mammal species. The most frequently entangled species were Common Murres, Western Gulls and California sea lions. The entanglement materials identified were primarily fishing related. Entanglements were recorded every year suggesting that although the incidence level differs annually, entanglement is a persistent problem. It is recommended that each programme records details in standardized categories to determine entanglement material sources. Numbers of entanglements observed during these surveys are likely to be a conservative view of the actual entanglement rate taking place at sea.

PCB and DDE Contamination in Harbor Seals ( Phoca vitulina ) from North-Central California and Bristol Bay, Alaska

In recent years, concerns have increased regarding accumulation of persistent, lipophilic contaminants by marine mammals. We quantified blood levels of the two most prevalent organochlorine (OC) contaminants of the marine ecosystem in a model species, the harbor seal (Phoca vitulina) from three north-central California populations and a population in Bristol Bay, Alaska. Intensive sampling (n = 190) produced robust quantification of blood concentrations of selected PCBs and DDE, and allowed us to investigate factors affecting levels of these contaminants in seal populations with distinct environments and exposure histories. In the Alaskan samples, PCB and DDE levels were most strongly related to sex and age; OCs increased with age in males and decreased with age in females, likely due to cumulative exposure in males and load-dumping during lactation in females. Among females, an inverse relationship was observed between condition and PCB blood levels. In contrast, in the California seals, in which loads were generally much greater, pups had greater levels of PCBs and DDE than subadults and adults, suggesting stable to decreasing environmental contaminant levels. Spatial heterogeneity and seasonal differences also contributed substantially to variation among harbor seals in contaminant loads. These findings underscore the importance of accounting for demographic, geographic, seasonal, and physiological effects in toxicological studies of marine mammals.