Earlier this month, Findhorn-based conservation charity Trees for Life called on the Scottish government to leave the beavers or relocate them.
But the government said the animals would have to be trapped and removed as they were released illegally.
Public agency SNH has been trying to find out how many beavers there are.
It said a family of animals were thought to be at the river, but individual numbers were still not known.
A spokesman for SNH said that, once trapped, the beavers would be moved but it was not yet known when, or where they would be moved to, or what period of quarantine would be involved for health checks.
Trees for Life has asked that the animals either be allowed to stay where they are, or be relocated to another part of the Highlands, but not kept in captivity.
It believes the family involves a mother and at least two kits.
The charity also said it was thought there had been beavers at the river for at least five years.
Native Scottish beavers were hunted to extinction in the 16th Century.
Individual numbers of a family of beavers spotted in a river near Beauly are still unknown, Scottish Natural Heritage (SNH) has said.