Environmental groups and a Native American tribe accused the operator of a Maine dam on Monday of not fulfilling its obligation to protect the country's last remaining Atlantic salmon river run.

The last wild Atlantic salmon live in a group of rivers in Maine and have been listed under the Endangered Species Act since 2000. The Penobscot River, a 109-mile (175-kilometer) river in the eastern part of the state is one of the most important habitats for the fish.