The largest known populations, which are very small and isolated, are in the Meramec, Bourbeuse, and Gasconade Rivers of Missouri.
Mississippi River | River Thames | Amazon River | Columbia River | Hudson River | Colorado River | Potomac River | river | Ohio River | Missouri River | Delaware River | Murray River | River Tyne | Madeira River | Volga River | River Nene | River Clyde | River Trent | River Severn | Amur River | River Wear | Allegheny River | Red River | Dnieper River | Yarra River | Paraná River | River Tees | Fraser River | Yangtze River | Tocantins River |