Shark nets don't reduce attacks: expert

Installing shark nets on NSW's north coast will not lead to a reduction in attacks, according to an expert from Deakin University.

The addition of shark nets on NSW's north coast will not reduce the number of attacks, a marine expert says.

Deakin University Associate Professor Laurie Laurenson has analysed 50 years' of shark mitigation programs in places including Sydney to determine whether having fewer sharks in an area leads to a drop in attacks.

"We couldn't show that. We could not demonstrate that there is a statistically significant relationship between the density of sharks and the number of attacks," Assoc Prof Laurenson told AAP on Thursday.

"People are going to feel safer, but is it actually going to have any measurable effect? I doubt it."

However, only one person has died at a meshed beach in NSW (at Merewether in 1951) since nets were first dropped in Sydney in 1937.

A NSW Department of Primary Industries report in 2009 found 23 of the 139 unprovoked shark attacks in NSW since 1937 were at meshed beaches.

A follow-up report in 2015 said there were four attacks at meshed beaches between mid-2008 and mid-2015 that resulted in serious injury, but no fatalities.

There are 51 beaches currently netted between Newcastle and Wollongong from September 1 to April 30 each year.

Assoc Prof Laurenson's comments come a day after NSW Premier Mike Baird reversed his government's resistance to install nets off Ballina's beaches on the north coast after shark attacks on two surfers in the past fortnight.

Six surfers have been attacked in Ballina alone among 12 attacks on a 70km stretch of the north coast since January last year.

The government will now launch a six-month trial of the nets in the area.

Assoc Prof Laurenson, from Deakin's School of Life and Environmental Sciences, branded Mr Baird's decision a "political knee-jerk reaction" because shark nets don't always prevent attacks.

"By simply lumping a few more around the beaches of Ballina or other popular beaches up the coast, I can't see that it's going to work," he said.

Assoc Prof Laurenson said white and bull sharks, responsible for the majority of attacks, move four to five km/h so any shark removed from a beach can be replaced by another one within 100km in 24 hours.

"Our modelling shows ... you've got to basically wipe them out, if you want to use this process," he said.

"I am not suggesting they do this because it would have huge ecological consequences."

Nearly 200 marine animals were entangled in nets during the 2014-15 meshing season, according to a separate NSW DPI report.

Of those, more than three quarters were "threatened, protected and/or non-target animals" including 10 white sharks, four grey nurse sharks, three green turtles, and three dolphins.

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