Wildlife authorities are trying to free a humpback whale tangled in rope off Rottnest Island, but they say the whale is moving too quickly to detangle it.

It was first reported on Saturday morning near Rottnest Island's Parker Point by a marine ranger conducting routine patrols.

A Parks and Wildlife spokeswoman said the animal did not appear to be in distress.

"It appears quite healthy — we first spotted it yesterday morning at around 11:15am," she said.

"The ranger was out doing routine sea lion monitoring when the whale was spotted and by [that] afternoon it had a satellite tag on it."

The whale was first spotted on Saturday morning. ( Supplied: Parks and Wildlife )

She said authorities were hoping satellite data would track the humpback whale's location and help determine how best to free it; however, they said on Sunday afternoon the whale was moving too fast to attempt to disentangle it.

Parks and Wildlife said they would work closely with Department of Fisheries officers in the coming days to free the whale from the rope.

Authorities are closely monitoring the situation and have said the whale is currently in good condition and not at risk of stranding.

The Fremantle Sea Rescue volunteer group advised vessels to stay clear of the area to avoid causing distress to the animal.