Like the sea otter, the Northern river otter was hunted to the extreme for their rich, dense fur. When the early European settlers in America began cutting down trees and threatening the river otter's habitat, the river otter population declined severly, and by 1980's, the river otter became extinct in 13 of the states it had once lived in. Now, many organizations and programs have been formed to build back their population and restrict farming in some areas to stop the use of pesticides and fertilizers that threaten river otters.

Even so, the northern river otters probably have the largest population of otters.