SHARK nets are controversial because the proof that they work has been debatable since they were first installed off New South Wales beaches in 1937.
According to the Department of Primary Industries, there has been only one fatality at a netted beach between Newcastle and Wollongong in the past 70 years.
It also says the frequency of shark interactions with people "dropped considerably" after nets were installed around Sydney and in Queensland.
But according to statistics from the DPI compiled by Sea Shepherd, there has been 39 shark encounters off netted beaches since nets were introduced in 1937.
> More than half of those (21) have occurred since 1992, at a rate of almost one a year.
> These include the well-documented white shark attack on Glenn Orgias, who lost his left hand while surfing off Bondi in 2009, and a bull shark attack on Glenn Folkard off Newcastle's Redhead Beach in 2012.
> Between 1990 and 2008 there were also 3259 non-target animals entangled.
> These included 1292 hammerhead sharks, 1269 stingrays, 259 angel sharks, 107 Port Jackson sharks, 52 dolphins, 47 turtles, 40 thresher sharks, 15 critically-endangered grey nurse sharks, six whales, four seals, a penguin and a dugong.
In the 52 years from 1950 to 2002 ...
> More than 11,500 sharks were caught and killed in the nets - and only a third were target species: Great whites, bull and tiger sharks. This is according to the Fisheries Scientific Committee from a report dated 2002.
About NSW nets:
> Shark nets are 150m long and 6m high. They are positioned on the ocean floor at depths of 10-12m. Their mesh size is between 50-60cm.
> The NSW Government has announced four trial nets will be installed at Ballina beaches: Seven Mile Beach at Lennox Head, as well as Sharpes, Shelly and Lighthouse beaches.
> One net will be installed off Main Beach at Evans Head.
> There are 51 beaches netted across Newcastle (10 beaches), the Central Coast (11 beaches), Sydney North (15 beaches), Sydney South (10 beaches) and the Illawarra (five beaches).
> The netting of the Far North Coast will bring that number to 56.
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