River otters in the lower Columbia River have elevated levels of PCBs and the pesticide DDE in their livers. Data indicates that river otter populations in the lower Columbia River have declined over the past 20 years, but data on population trends and general health are not extensive enough to make accurate assessments of the current status of populations.
River otters are a top predator and play a key role in the food chain in many riverine environments.
River otters are a good indicators of environmental health because they are especially susceptible to habitat changes and human disturbance. Since river otters primarily consume resident fish, they provide an excellent indication of water quality, particularly accumulations of toxic contaminants in the lower levels of the food chain. They feed primarily on fish, including carp, sucker, crappie, sculpin, salmon and crayfish. They also consume amphibians, insects, birds and small mammals. They are opportunistic feeders and will feed on whatever is most available.