Man bitten by a shark in WA's north

An unknown species of shark has bitten a man while he was swimming in Western Australia's Pilbara region.

A shark warning has been issued for Sams Creek following the incident at 3pm on Sunday.

The man was treated at Roebourne District Hospital for minor injuries but the incident was not reported until Monday.

Meanwhile, a shark warning remains in place near Admiralty Crescent at Halls Head in Mandurah, south of Perth, after a whale carcass washed ashore.

Beaches are closed between Falcon Bay and Doddies Beach.

"It is possible the carcass will act as an attractant that could lead to sharks coming close into shore along this stretch of coast," the Primary Industries and Regional Development Department warns.