North American river otters (Lontra canadensis) are useful indicators of aquatic ecosystem health, but obtaining information on populations is difficult and expensive. By combining non-invasive faecal sampling with DNA genotyping techniques, I investigated: (i) environmental contaminant exposure, (ii) diet, and (iii) population metrics of river otters along the urban coast of southern Vancouver Island, British Columbia, Canada. In Victoria Harbour, mean faecal concentrations of polychlorinated biphenyls (PCBs) exceeded criteria thought to inhibit otter reproduction. However, individual faecal PCB concentrations varied with otter movement and landscape use. Intertidal fish dominated the diet, but otters in the regional harbours consumed proportionally more upper trophic-level fish than otters outside the harbours. Genetic and demographic analyses provided no conclusive evidence of PCB-induced population-level effects. Concurrent monitoring of contaminant exposure and population metrics of river otters is important to detect effects of pollutants on populations, and to guide river otter conservation and ecosystem management.
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