Shark nets

A shark net is a submerged net placed around beaches to reduce shark attacks on swimmers. The majority of Shark nets used are Gillnets which is a wall of netting that hangs in the water and captures the targeted sharks by entanglement. The nets are typically 186m long, set at a depth of 6 m, have a mesh size of 500 mm and are designed to catch sharks longer than 2m in length. Shark nets are not to be confused with shark barriers.

Shark nets do not offer complete protection but work on the principle of "fewer sharks, fewer attacks". They reduce occurrence via shark mortality. Reducing the local shark populations is believed to reduce the chance of an attack. Historical shark attack figures suggest that the use of shark nets and drumlines does markedly reduce the incidence of shark attack when implemented on a regular and consistent basis. The large mesh size of the nets is designed specifically to capture sharks and prevent their escape until eventually, they drown. Due to boating activity, the nets also float 4 metres or more below the surface and do not connect with the shoreline (excluding Hong Kong's shark barrier nets) thus allowing sharks the opportunity to swim over and around nets. Shark nets can cost A$1 million dollars or A$20,000 per beach per year.

Shark net meshing was thought up by the NSW Fisheries in 1936, after a decade and a half of relentless Shark attacks off Sydney beaches. In March 1935, for example, two people — one at North Narrabeen and one at Maroubra — were killed by great white sharks in a single week. The meshing was never designed to enclose a piece of water — even back then, they knew barrier nets would never survive a surf zone. Instead, it was designed to catch large dangerous sharks as they swam within range of the surf. At first, the catch was huge; over 600 sharks in the first year of operation, off just a few Sydney beaches. But over time, even without adjusting for the spread of the program across almost all Sydney beaches and into Wollongong and Newcastle, the catch declined. Today's NSW meshing annual average catch is 143 sharks, quite a number of which are released alive.

Nets were also first deployed off certain beaches off KwaZulu-Natal (KZN, formerly Natal) South Africa, in 1952.

Ongoing shark control programs have been very successful in reducing the incidence of shark attack at the protected beaches. In the years from 1900 to 1937, 13 people were killed off NSW surf beaches by sharks; over the next 72 years, the death rate fell to eight, only one of which was at a meshed beach. This in a period when the NSW human population rose from 1.4 million to seven million — and when more people began going to the beach.

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Wikipedia