There have been several sightings of a large shark in the Dawesville Channel, near popular school holiday spot Mandurah.
A 3.2 metre shark was spotted five metres off the north groin rock in the Channel at 11am on Thursday, with a member of the public reporting it to Water Police on Friday morning.
The Department of Fisheries then advised a tagged white shark had been detected two kilometres off a Scarborough receiver on Thursday night.
Water Police could not say if the same shark was sighted at both locations.
The SharkSmart website has reported two other shark sightings in the Dawesville Channel in the past 30 days.
A member of the public reported a possible shark sighting at 2pm on October 1 in the boat ramp abalone landing, although the caller was unsure if it was a shark or whale.
A 2.5 metre shark was sighted 20 metres off the channel September 19.
On the same day, a Dawesville resident saw a shark lurking behind the Dawesville yacht club.