Right: Move on please! Where traditional "drumlines" were basically a line, a baited hook and a large float used to kill sharks, "Smart" drumlines use modern technology to capture and move sharks to an area where they would be considered to be less of a threat to humans.
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Background information
Shark nets and drum lines
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 in Queensland, Australia, 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.
A drum line is an unmanned aquatic trap used to lure and capture large sharks using baited hooks. They are typically deployed near popular swimming beaches with the intention of reducing the number of sharks in the vicinity and therefore the probability of shark attack. Drum lines are often used in association with shark nets, with the intent of killing sharks. However SMART drum lines can be used to move sharks, which greatly reduces shark and bycatch mortality. The use of drum lines has been successful in reducing shark attacks in the areas where they are installed. The topic of shark culling has become an international controversy and sparked public demonstrations and vocal opposition, particularly from environmentalists, animal welfare advocates and ocean activists.
Shark nets such as those in New South Wales are designed to entangle and kill sharks and other animals that pass near them. 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 drum lines 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 or A$20,000 per beach per year.
History of shark nets
Shark net meshing was first devised by the New South Wales Fisheries in 1936, after a decade and a half of 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 as 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 New South Wales meshing annual average catch is 143 sharks, quite a number of which are released alive.
Nets were also deployed off certain beaches off KwaZulu-Natal (KZN, formerly Natal) South Africa, in 1952.
Shark barriers
A shark barrier (otherwise known as a 'shark-proof enclosure' or 'beach enclosure') is seabed-to-surface protective barrier that is placed around a beach to protect people from shark attacks. Often confused with shark nets, shark barriers form a fully enclosed swimming area that prevents sharks from entering (nets aim to reduce shark populations). Shark barrier design has evolved from rudimentary fencing materials to netted structures held in place with buoys and anchors. Recent designs have used plastics to increase strength, versatility and to reduce the environmental damage of bycatch.
Shark barriers work on the principle of excluding sharks from a designated swimming area. Shark barriers form an "underwater fence" from seabed-to-surface, beach-to-beach. Shark barriers are seen as a more environmentally friendly option as they largely avoid bycatch, however they cannot protect the same sized area as culling methods.
Shark barriers are not generally used on surf beaches because they usually disintegrate in the swell and so are normally constructed only around sheltered areas such as harbour beaches. It should be noted that where there are surf conditions at Hong Kong beaches, the swell is 'typically small'. Even if they were in place at surf beaches, they would not protect surfers who go some distance from shore.
The shark nets are more suitable for surf beaches as they can be anchored beyond the deepest sandbank and can be easily taken out of the water when ever any big swell is forecast.
Shark net and barrier use in different Australian states
New South Wales responses
In New South Wales, Australia, 51 beaches are netted. The nets are maintained by the New South Wales Department of Primary Industries. The nets are generally 150 metres long, 6 m wide and 'bottom-set' on the seabed in depths of 10 m. The nets can be 500 metres from the beach. The mesh is sized 50-60 centimetres. Nets are lifted every 24 to 48 hours for servicing so as to prevent rotting, to clean out debris and to remove dead sharks and other marine life. It is said that 35-50% of the sharks are entangled from the beach side. Acoustic 'pingers' have been fitted to the nets to warn off dolphins and whales and the nets are not in place in winter, the whale migration season. The Department states that the nets have 'never been regarded as a means of absolutely preventing any attacks', but help to deter sharks from establishing territories.
Shark meshing on Sydney beaches began in 1937 to reduce the numbers of sharks and thereby reduce the risk of shark attacks. Originally beaches from Palm Beach to Cronulla were meshed. In 1949 beaches in Wollongong and Newcastle were added, with Central Coast beaches added in 1987. Today 200 km of coastline are meshed. The nets are set for eight months of the year from September to April inclusive.
There have been trials of shark enclosures or barriers proposed for two northern New South Wales beaches - off Seven Mile Beach at Lennox Head and at Ballina's Lighthouse Beach. Neither proceeded because it was judged that conditions made them unworkable.
SMART (Shark-Management-Alert-in-Real-Time) drum lines are one of the measures currently being tested and trialled as part of the NSW Government's $16M Shark Management Strategy.
The state-of the artš technology differs greatly from the operation of traditional drum lines as they are designed and operated to maximise the survival of sharks and other marine animals caught. Trials of SMART drum lines have been undertaken at multiple locations on the NSW North Coast by DPI scientists since December 2015.
Queensland responses
In Queensland, Australia, drum lines are used in combination with shark nets. Queensland's Shark Control Program has been in place since the early 1960s. In Queensland's 2011/12 summer season there were 714 sharks caught, 281 above 2 metres in shark nets and drum lines. Since 1997, the program catches 500-900 sharks annually, including several shark species of conservation concern.
A fatal attack in Queensland occurred in January 2006 at Amity Point on North Stradbroke Island. The water at this location drops off to 30 metres depth, and bull sharks are known to frequent the area. Other beaches around the island were protected with drum lines at the time.
In November, 2017, there was another fatal attack off Whitsunday Island. This is an area not protected by drum lines.
Western Australia responses
In 2017/18 the Western Australian Government provided Surf Life Saving WA (SLSWA) with nearly $3.7 million for the delivery of shark mitigation strategies, which includes funding for aerial patrols provided by SLSWA's Westpac Life Saver Rescue Helicopter.
Surf lifesavers are watching from the beaches, on the water and in the air and public officers are ready to respond to sightings. Swimming between the flags at patrolled beaches means that if a shark is sighted, the information will be communicated quickly to the front line responders and the beach can be closed by lifesavers.
SLSWA has State-wide standard operating procedures for shark sightings, including guidelines on when to clear the water and close a beach, and how long a beach should remain closed.
When swimming at an unpatrolled beach, beachgoers are warned that Rangers are not always close-by to respond quickly to a shark sighting (particularly in regional areas), So that it is important water users take responsibility for their own safety and check the latest reported sighting and tagged shark detection information on the shark activity map .
The Western Australian Government provides funding to SLSWA to operate two lifesaving helicopter services, the metropolitan based Westpac Lifesaver Helicopter and the South-West Lifesaver Helicopter.
The metropolitan service based at Rous Head, North Fremantle patrols between Port Bouvard and Yanchep, and Rottnest Island to the west. Patrols are scheduled on weekends throughout September and daily from 1 October 2018 to 30 April 2019.
The South-West service based in Busselton covers popular coastal destinations between Bunbury and Margaret River. Patrols are focused on weekends, and public and school holidays between 1 September 2018 to 28 April 2019, including daily flights from 19 November to 3 February.
The helicopter service provides many benefits including the ability to directly communicate with the public; when a shark is sighted at an unpatrolled beach, the helicopter will sound its alert siren from the air. In addition, the crew are medically trained and equipped to assist in a real time emergency when needed.