PORTLAND, Maine (AP) - Environmental groups and a Native American tribe have accused the operator of a Maine hydroelectric dam 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-long river in the eastern part of the state is one of the most important habitats for the fish.

The Penobscot is also the site of the Milford Dam, which is owned by renewable energy giant Brookfield Renewa...