Aerial patrols touted as the cornerstone of State Government efforts to protect swimmers against sharks detect as few as one in eight, research has found.
In a NSW Government study that casts serious doubts on the Government-funded aerial beach patrols, researchers found crews in spotter planes and helicopters were unreliable in identifying sharks.
Using artificial sharks placed at various depths and locations along a stretch of southern NSW, the study noted plane crews spotted just 12.5 per cent of the dummies.
Helicopters, which are used for all WA's aerial patrols, were marginally better, identifying 17.1 per cent of the dummy sharks.
Crews were largely unable to spot sharks below a shallow depth, with most of the dummies that were seen no deeper than 2.7m.
The researchers also found that though helicopter patrols were more likely to see sharks up to 250m away, neither aircraft was effective at spotting them beyond 300m.
"We conclude that aerial observers have limited ability to detect the presence of submerged animals such as sharks," they said.
"This raises serious concerns about the utility of programs such as aerial beach patrols as a warning system for sharks."
They said sighting records from 20 actual aerial patrols confirmed this, with low shark sighting rates a likely underestimate of the presence of many shark species known to be in the patrol areas.
Colin Barnett, whose Government significantly increased funding for aerial shark patrols, stood by the practice as an "important and effective tool" to safeguard swimmers.
The Premier said aerial surveys were only one part of the State's shark hazard mitigation strategy, with other measures including a $300,000 observation tower planned for Cottesloe beach.
Chris Peck, from Surf Life Saving WA, defended aerial patrols, saying it was better to spot 17 per cent of sharks off beaches than none.
He also questioned the NSW study, saying there was nothing to compare it with and it did not take into account WA conditions.
At Floreat beach yesterday, Wembley father Paul Joyce said the ineffectiveness of the patrols was a surprise but it was unlikely to affect whether he went swimming with his family.
"I actually don't see sharks as a huge risk when you look at the context of things out there," he said.