Dartmoor National Park Authority is to enact a permanent ban on dogs in parts of the park.
The authority is opening up the West Dart Valley between Two Bridges and Hexworthy under new right to roam laws which are to start in August.
The authority says though that dogs pose a threat to otters, and salmon spawning grounds there.
Geoff Haynes, director of understanding and enjoyment, said the authority has to consider the area's wildlife.
He said, "Dogs may not be a danger if they are on a lead and well away from the riverbank, but we have to work out how best to manage access and get the message about the importance of this area of land as a wildlife corridor."
Dartmoor dog walker Harriet Wymark commented, "This is a great sadness. Dogs are a good companion and if you are walking alone you feel a bit safer with a dog.
"My dog has never caught an otter or a salmon and wouldn't even know what it looked like."
However another walker, Brian Vessey, said, "I have walked on the moor for years, but I never take my dog because of the wildlife, as well as sheep and lambs.
"It should be kept for the wildlife, especially at this time of year when you have young birds. Why let Fido chase them around?"