Shark net
Encyclopedia
Net (device)
A net, in its primary meaning, comprises fibers woven in a grid-like structure, and is very infrequently mentioned in discussions of philosophy. It blocks the passage of large items, while letting small items and fluids pass...
placed around beach
Beach
A beach is a geological landform along the shoreline of an ocean, sea, lake or river. It usually consists of loose particles which are often composed of rock, such as sand, gravel, shingle, pebbles or cobblestones...
es to reduce shark attack
Shark attack
A shark attack is an attack on a human by a shark. Every year around 60 shark attacks are reported worldwide, although death is quite unusual. Despite the relative rarity of shark attacks, the fear of sharks is a common phenomenon, having been fueled by the occasional instances of serial attacks,...
s on swimmers.
Shark nets do not offer complete protection but work on the principle of "fewer shark
Shark
Sharks are a type of fish with a full cartilaginous skeleton and a highly streamlined body. The earliest known sharks date from more than 420 million years ago....
s, fewer attacks". They reduce occurrence via shark mortality. Reducing the local shark populations is believed to reduce the chance of an attack. 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 4m or more below the surface and do not connect with the shoreline (excluding Hong Kong
Hong Kong
Hong Kong is one of two Special Administrative Regions of the People's Republic of China , the other being Macau. A city-state situated on China's south coast and enclosed by the Pearl River Delta and South China Sea, it is renowned for its expansive skyline and deep natural harbour...
's shark barrier nets) thus allowing sharks the opportunity to swim over and around nets.
Bycatch
One downside to shark nets is the high incidence of bycatchBycatch
The term “bycatch” is usually used for fish caught unintentionally in a fishery while intending to catch other fish. It may however also indicate untargeted catch in other forms of animal harvesting or collecting...
, including threatened and endangered species
Endangered species
An endangered species is a population of organisms which is at risk of becoming extinct because it is either few in numbers, or threatened by changing environmental or predation parameters...
like sea turtle
Sea turtle
Sea turtles are marine reptiles that inhabit all of the world's oceans except the Arctic.-Distribution:...
s, dugong
Dugong
The dugong is a large marine mammal which, together with the manatees, is one of four living species of the order Sirenia. It is the only living representative of the once-diverse family Dugongidae; its closest modern relative, Steller's sea cow , was hunted to extinction in the 18th century...
s, dolphin
Dolphin
Dolphins are marine mammals that are closely related to whales and porpoises. There are almost forty species of dolphin in 17 genera. They vary in size from and , up to and . They are found worldwide, mostly in the shallower seas of the continental shelves, and are carnivores, mostly eating...
s and whale
Whale
Whale is the common name for various marine mammals of the order Cetacea. The term whale sometimes refers to all cetaceans, but more often it excludes dolphins and porpoises, which belong to suborder Odontoceti . This suborder also includes the sperm whale, killer whale, pilot whale, and beluga...
s.
Animal welfare
Animal welfare
Animal welfare is the physical and psychological well-being of animals.The term animal welfare can also mean human concern for animal welfare or a position in a debate on animal ethics and animal rights...
groups suggest alternatives such as surf lifesaving, public education on shark behaviour, radio signals, sonar technology and electric nets. Drum lines
Drum lines
A drum line is an aquatic device used to reduce the amount of shark attacks in popular beaches by capturing the shark on the drum line's hook. While most drum lines are used in addition to the shark net, it has been proven that the drum line is more effective at catching the three more deadly sharks...
are also viewed, by some people, as an alternative: they consist of baited hooks aimed at catching only large sharks (though turtles are sometimes hooked).
Australia
In New South WalesNew South Wales
New South Wales is a state of :Australia, located in the east of the country. It is bordered by Queensland, Victoria and South Australia to the north, south and west respectively. To the east, the state is bordered by the Tasman Sea, which forms part of the Pacific Ocean. New South Wales...
, Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
, 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. The netting program began in 1937. During 70 years while the nets have been in operation, there has been only one fatal attack on a netted beach.
In Queensland
Queensland
Queensland is a state of Australia, occupying the north-eastern section of the mainland continent. It is bordered by the Northern Territory, South Australia and New South Wales to the west, south-west and south respectively. To the east, Queensland is bordered by the Coral Sea and Pacific Ocean...
, Australia, drum lines are used. The Shark Safety Program has been in place since the early 1960s. A fatal attack in January 2006 on a North Stradbroke Island
North Stradbroke Island
North Stradbroke Island is an Australian island in the state of Queensland, 30 km southeast of the capital Brisbane. Before 1896 the island was part of the Stradbroke Island. In that year a storm separated it from South Stradbroke Island, forming the Jumpinpin Channel. It is known...
beach, was on a beach protected by drum lines.
Hong Kong
In Hong KongHong Kong
Hong Kong is one of two Special Administrative Regions of the People's Republic of China , the other being Macau. A city-state situated on China's south coast and enclosed by the Pearl River Delta and South China Sea, it is renowned for its expansive skyline and deep natural harbour...
, after the shark-attack death of 3 swimmers over 10 days in 1995, the government installed shark nets on all 32 gazetted beaches. Unlike the long-line and gill-net designs common in Australia and South Africa, these are permanent installations and are barrier nets. There have been zero fatalities since installation in 1995.
The Hong Kong nets are generally 35 mm square on the surface 2 m and 100 mm square thereafter. They are suspended off 225 mm HDPE pipe or BL14 Marine Float Lines, and anchored strongly to resist the many typhoons and waves up to 10 m. They are anti-fouled, and spend an average of 9 months a year in the water. An average net enclosure would be 500 m long and either semi-circular or rectangular in shape. They are diver-inspected a minimum of two times a week, and independent verification is required. They also exclude floating refuse, and clearly define the swimming area. They can be clearly picked out on Google Earth
Google Earth
Google Earth is a virtual globe, map and geographical information program that was originally called EarthViewer 3D, and was created by Keyhole, Inc, a Central Intelligence Agency funded company acquired by Google in 2004 . It maps the Earth by the superimposition of images obtained from satellite...
- at 22^14'38" North, 114^11'26" East, see "Repulse Bay".
South Africa
In South AfricaSouth Africa
The Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...
, numerous beaches in KwaZulu-Natal
KwaZulu-Natal
KwaZulu-Natal is a province of South Africa. Prior to 1994, the territory now known as KwaZulu-Natal was made up of the province of Natal and the homeland of KwaZulu....
province are protected by the KwaZulu-Natal Sharks Board
KwaZulu-Natal Sharks Board
thumb|A notice at a beach protected by the BoardThe KwaZulu-Natal Sharks Board, previously the Natal Sharks Board and Natal Anti-Shark Measures Board is an organisation that maintains shark nets and drum lines off the coast of KwaZulu-Natal Province, South Africa, to protect bathers and surfers...
http://www.shark.co.za/nsb2.htm.