Shark experts say a great white shark was likely responsible for the death of a 33-year-old Perth diver — an attack that had made Western Australia (WA) the deadliest place in the world for shark attacks.

Father of two Peter Kurmann was reportedly diving from a boat about a mile off Stratham Beach, 140 miles south of Perth, when a shark about 13 feet long attacked in overcast conditions around 9:30 a.m. Saturday.

It was the fourth fatal shark attack of WA in seven months.

Kurmann's mauled body was recovered from the water by his brother Gian, 34, and taken for analysis.

The WA's Fisheries Department confirmed Sunday the shark was likely to have been a great white, News.com.au reported.

"A Department of Fisheries scientist has advised police that, based on his experience, evidence he has examined indicates that a white shark was by all signs responsible for the attack," Shark Response Unit spokesman Tony Cappelluti reportedly said.

"It wasn't possible for the scientist to confirm the estimated size of the shark, but information given to police suggests it was around four meters in length."

Meanwhile, the Australian Associated Press cited WA Fisheries senior shark research scientist Rory McAuley as saying the attack was just the latest in an "unprecedented" number of fatal shark attacks off WA in the past two years.

"I'm not aware of any series of fatal shark attacks, this number, in such a short period of time anywhere in the world," McAuley told reporters in Perth on Sunday.

"Last year a large proportion of the global shark fatalities occurred in Western Australia. In other years we haven't even registered on the shark attack files statistics.

"This year has already started very tragically."

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He said the reduction of commercial fishing and protection of some shark species, such as the great white, might be responsible for the increase in attacks.

However, he said, other factors needed to be considered, including a rapid rise in WA's population.

"Just by the law of averages if there are more sharks in the water it's likely that there's going to be an increase in the number of encounters between humans and sharks," Mr McAuley said.

"But equally if there are more people in the water there's likely to be an increased number of encounters between those people and the sharks.

"What we've seen at a decadal level is that the number of shark attacks is very strongly correlated with the human population of Western Australia."

The other victims of recent fatal WA shark attacks were: Texan man George Thomas Wainwright, 32, killed scuba diving alone off Rottnest Island in October; businessman Bryn Martin, 64, killed while swimming off Perth's Cottesloe Beach the same month; and bodyboarder Kyle Burden, 21, killed near Bunker Bay in WA's southwest in September.

There's been little support at the political level for a shark cull in response to the attacks.

The WA Premier, Colin Barnett, said he would not be issuing a shoot-to-kill order. And opposition leader Mark McGowan said he was opposed to any cull or the hunting of individual sharks.

"I don’t support a cull," McGowan said, AAP reported. "I don’t support some sort of idea that you can just rid the oceans of predators — it’s not possible [or] reasonable.

‘‘An individual hunt for an individual shark is (also) very hard to do, because you don’t know it’s the same shark.’’

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McGowan was also opposed to shark netting: "They kill everything that swims down the coast," he said.

Cappelluti, meantime, said three set-lines were put in the water to try to catch any sharks that remained in the area where Kurmann was attacked, after an aerial patrol spotted a 10-13-foot shark on Saturday.

Beaches in the immediate area would remained closed until local authorities made a further safety assessment.