UPDATE 4pm: An injured sea-lion at Mullaloo Beach has made his way out to seas after forcing the closure of the beach earlier today.
It is now thought the injured animal was hurt by a boat's propeller rather than a shark, as originally suspected.
City of Joondalup rangers had earlier closed the beach, believing that the animal had been attacked by a shark.
Officers from the Department of Parks and Wildlife and the Perth Zoo were monitoring the sea-lion which had been lying on the shore.
Surf Life Saving WA tweeted earlier in the day that the Fisheries Department had advised there was an injured seal at Mullaloo Beach, with possible bite marks.
“Council rangers will be closing Mullaloo Beach due to the seal's injuries indicating shark activity in the area,” Surf Life Saving WA said.
Yesterday, the Fisheries Department said one of the receivers in the Shark Monitoring Network was out of position, after the buoy to which it was attached broke free of its mooring and was found washed ashore south of Scarborough Beach.
Staff attended the Peasholm Dog Beach to retrieve the equipment and assess the situation.The Westpac lifesaver helicopter also sighted three whales 400m south of Scarborough, about 250m offshore, tracking north.