A MAN has been fatally attacked by a shark in West Australia's southwest while diving with his brother.

The attack sparked the closure of beaches in the area and an investigation was launched by the by the state's Department of Fisheries, The Australian reports.

On Saturday afternoon police confirmed the victim was Busselton man Peter Kurmann. He was attacked around 9.30am (AWST) while diving about 1.8km offshore at Stratham Beach, 230km south of Perth.

It is believed Kurmann's mauled body was recovered from the water by his brother and conveyed via boat to the Port Geographe Marina, near the town of Busselton. He was 33.

Mr Kurmann's brother Gian Kurmann said his family had suffered a terrible loss.

"We have lost a son, a brother, a husband and a wonderful father," the 34-year-old said in a statement.

Full report The Australian.