Jump to content

Shark net

From Wikipedia, the free encyclopedia
For other uses, see Shark net (disambiguation).
Simplified diagram of shark net in New South Wales, Australia

A shark net is a submerged section of gillnets placed at beaches designed to intercept large marine animals including sharks, with the aim to reduce the likelihood of shark attacks on swimmers. Shark nets used are gillnets which is a wall of netting that hangs in the water and captures the marine animals by entanglement, however only around 10% of catch is the intended target shark species.[1][2] The nets in Queensland, Australia, are typically 186m long, set at a depth of 6m, have a mesh size of 500mm and are designed to catch sharks longer than 2m in length.[3] The nets in New South Wales, Australia, are typically 150m long, set on the sea floor, extending approximately 6m up the water column, are designed to catch sharks longer than 2m in length.[4] Shark nets do not create an exclusion zone between sharks and humans, and 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 aim to reduce occurrence via shark mortality. Shark nets such as those in New South Wales are designed to entangle and capture sharks that pass near them.[5] Reducing the local shark populations reduces 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.[6][7][8] However a 2019 study argued this conclusion overlooks key factors.[9] 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.[10]

Shark nets have been criticized by environmentalists, conservationists and animal rights activists — they say shark nets are unethical and harm the marine ecosystem.[11][12][5][13][14][15] They also argue there is no science showing that nets make the ocean safer for people.[5]

History

[edit]

Shark net meshing was developed by the New South Wales Fisheries in 1937, after a decade and a half of repeated shark attacks off Sydney beaches. In March 1935, for example, two people — one at North Narrabeen and one at Maroubra — perished after great white shark attacks in a single week. The meshing was never designed to enclose a piece of water, as barrier nets couldn't survive a surf zone. Instead, it was designed to catch large 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, many of which are released alive.[16]

Nets were first deployed off certain beaches in KwaZulu-Natal (formerly Natal), South Africa, in 1952.[7]

Shark nets were also used off Dunedin, New Zealand for roughly 40 years, and were removed in 2011. The nets were found to be detrimental to the environment; 700 non-target species were killed.[17] No shark attacks have occurred since their removal.[18]

As of 2018, shark nets are used in New South Wales, Queensland and KwaZulu-Natal.[15][19][20] In August 2018, it was announced that the nets in northern New South Wales would be removed, but that the nets in Sydney, Newcastle and Wollongong would stay.[12][21] The New South Wales Green party said they wanted all shark nets removed.[21]

Effectiveness

[edit]

Ongoing shark control programs have been very successful in reducing the incidence of shark attack at the protected beaches.[7][22][8] In the years from 1900 to 1937, 13 people died off New South Wales surf beaches after shark attacks; 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 New South Wales human population rose from 1.4 million to seven million — and when more people began going to the beach.[16]

In Queensland, there has been only one fatal attack on a controlled beach since 1962, compared to 27 fatal attacks between 1919 and 1961. Statistics from the New South Wales Department of Primary Industries indicate that before nets were introduced in New South Wales in 1936 there was an average of one fatal shark attack every year. There has been only one fatal attack on a protected beach since then and that was in 1951. Similarly, between 1943 and 1951 the South African city of Durban experienced seven fatal attacks but there have been none since nets were introduced in 1952. A more recent comparison shows that in South Africa there were three shark attacks, none fatal, at protected beaches in KwaZulu-Natal between 1990 and 2011, while there were 20 fatal attacks in the same period at unprotected beaches in the Eastern and Western Cape Provinces.[6]

However, the net program in New South Wales has been called "outdated and ineffective" by environmental groups;[12] they argue that shark nets do not protect swimmers.[5] 65% of shark attacks in New South Wales occurred at netted beaches.[13]

Environmental impact

[edit]

Shark nets result in incidence of bycatch, including threatened and endangered species like sea turtles, dugongs, dolphins and whales.[23] In Queensland in the 2011/12 summer season there were 700 sharks caught, 290 above 4 metres in shark nets and drum lines.[24]

In New South Wales, the meshing averages one humpback whale every two years; the whale is almost always released alive. In Queensland in 2015, the bycatch included one bottlenose and seven common dolphin (one released alive), 11 catfish, eight cow-nose rays, nine eagle rays, 13 loggerhead turtles, five manta rays (all but one survived), eight shovelnose rays, three toadfish, four tuna, and a white spotted eagle, which was safely released.[16]

New South Wales and Queensland also utilize acoustic pingers attached to the nets to reduce bycatch of dolphins, whales and other marine mammals.[25] Use of the pingers has been shown to significantly reduce marine mammal bycatch.[26]

The current net program in New South Wales has been described as being "extremely destructive" to marine life.[27] Between September 2017 and April 2018, more than 403 animals perished in the nets in New South Wales, including 10 critically endangered grey nurse sharks, 7 dolphins, 7 green sea turtles and 14 great white sharks.[12] Between 1950 and 2008, 352 tiger sharks and 577 great white sharks died in the nets in New South Wales — also during this period, a total of 15,135 marine animals perished in the nets.[15] More than 5,000 marine turtles have been caught on the nets.[13] The New South Wales government prohibits people from rescuing entangled animals — this prohibition has been called "heartless and cruel".[14]

In a 30-year period, more than 33,000 sharks have perished in KwaZulu-Natal's shark net program.[20] During the same 30-year period, 2,211 turtles, 8,448 rays, and 2,310 dolphins died in KwaZulu-Natal's shark net program.[20]

Animal welfare groups note the suffering and cruelty that nets inflict upon animals, such as lacerations, stress, pain, and disease.[13] They suggest alternatives such as surf lifesaving patrols, public education on shark behaviour, radio signals, sonar technology and electric nets.

Political scientist Christopher Neff notes, "Internationally, shark nets have been labeled a 'key threatening process' for killing endangered species." He adds: " ... killing endangered species to boost public confidence or to show government action is not workable. It is a disservice to the public."[11] Jessica Morris of Humane Society International calls shark nets a "knee-jerk reaction" and says, "sharks are top order predators that play an important role in the functioning of marine ecosystems. We need them for healthy oceans."[13] Sea World Research & Rescue Foundation also oppose the use of shark nets to cull shark populations "In an ideal world we would like for there to be no culling of sharks in Australia and around the world however, this is not a reality. We understand the pressure on governments to protect swimmers through the use of shark control programs. We continue our stance against shark nets and maintain our rescue operations to save dolphins, whales, turtles that become entrapped within them, along with working with the authoritative agencies to research improved methods which will lessen the impact on our marine life".[28]

However bycatch from shark nets is minor compared to bycatch from other activities. On average 15 Great white sharks are caught by the NSW and Queensland shark control programme each year, compared to 186 caught in Australia from other activities.[29] Australia's commercial shark fishing industry is catching over 1200 tonne of shark each year,[16] of which 130 are Great white sharks.[29] The NSW prawn trawling industry alone results in 64 tonne of shark as bycatch each year,[16] with two thirds dying.[30] Tuna and swordfish longline fishing off the coast of South Africa reported 39,000 to 43,000 sharks died each year between 1995 and 2005.[30] Sharksavers estimates that in total 50 million sharks are caught unintentionally each year as bycatch by the commercial fishing industry.[31]

Cost

[edit]

Total cost for the Shark netting program in NSW for the 2009/10 year was approximately AUD $1m, which included the cost of the nets, contractors, observers and shark technician, shark meshing equipment (dolphin pingers and whale alarms etc.), and compliance audit activities.[10] For the 51 beaches protected,[10] this represents a financial cost of approximately AUD$20,000 per beach per year.

Australia

[edit]
Graph of sharks caught in Queensland's Shark Control Program (by type) July 1997- June 2014

In New South Wales, Australia, 51 beaches are netted.[32] 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.[33] From 1950 to 2008, hundreds of great white sharks and tiger sharks perished in the nets in New South Wales.[15]

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.[24] Since 1997, 500-900 sharks perished annually in the program, including several shark species of conservation concern. They include the following:

Common name Scientific name IUCN Redlist status EPBC conservation listing (AUS)
Great hammerhead Sphyrna mokarran Endangered[34]
Great white shark Carcharodon carcharias Vulnerable[35] Vulnerable[36]
Grey nurse shark Carcharias taurus Vulnerable[37] Critically Endangered (East Coast) Population[36]
Scalloped hammerhead Sphyrna lewini Endangered[38]

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.[39] Drum lines were installed at beaches around the island at the time.[40] Another shark attack occurred at Greenmount Beach on the Gold Coast in 2020. Drumlines and shark nets were installed at the beach at this time.[41]

South Africa

[edit]

In South Africa, shark nets are installed at numerous beaches in KwaZulu-Natal by the KwaZulu-Natal Sharks Board.[42] Shark nets have been installed in KwaZulu-Natal since the 1950s[20] and have greatly reduced the number of shark attacks along the beaches where they are installed.[8] However more than 33,000 sharks have perished in KwaZulu-Natal's nets in a 30-year period.[20] KwaZulu-Natal's shark net program has been called "archaic" and "disastrous to the ecosystem".[20]

See also

[edit]

References

[edit]
  1. ^ Fisheries, NOAA. "Gillnets: Fishing Gear and Risks to Protected Species :: NOAA Fisheries". Retrieved 22 April 2017.
  2. ^ "Council calls for removal of shark nets on the Northern Beaches". 28 April 2021. Retrieved 19 March 2022.
  3. ^ "Shark control equipment and locations". Retrieved 22 April 2017.
  4. ^ "Shark Nets - SharkSmart - NSW Government". 2 August 2021. Retrieved 19 March 2022.
  5. ^ a b c d Forrest, Alice (2014-09-10). "Shark Nets in Australia – What Are They and How Do They Work?". sealifetrust.org. Archived from the original on October 16, 2018. Retrieved October 17, 2018.
  6. ^ a b "Can governments protect people from killer sharks?". ABC News. 22 December 2013. Retrieved 22 April 2017.
  7. ^ a b c Curtis; et al. (2012). "Responding to the risk of white shark attack: updated statistics, prevention, control, methods and recommendation. Chapter 29 In: M. L. Domeier (ed). Global Perspectives on the Biology and Life History of the White Shark". CRC Press. Boca Raton, FL. Retrieved 18 January 2020.
  8. ^ a b c "Shark attacks on the South African coast between 1960 and 1990". South African Journal of Science. 87 (10): 513–518. October 1991. Retrieved 22 November 2018.
  9. ^ Gibbs, Leah; Fetterplace, Lachlan; Rees, Matthew; Hanich, Quentin (2 December 2019). "Effects and effectiveness of lethal shark hazard management: The Shark Meshing (Bather Protection) Program, NSW, Australia". People and Nature. 2: 189–203. doi:10.1002/pan3.10063. S2CID 213735780.
  10. ^ a b c Green, M., Ganassin, C. and Reid, D. D. "Report into the NSW Shark Meshing (Bather Protection) Program" (PDF). State of New South Wales through NSW Department of Primary Industries. Retrieved 21 December 2016.{{cite web}}: CS1 maint: multiple names: authors list (link)
  11. ^ a b Pepin-Neff, Christopher (12 October 2011). "The Untold Story of Shark Nets in Australia". theconversation.com. Retrieved October 17, 2018.
  12. ^ a b c d Mackenzie, Bruce (August 4, 2018). "Sydney Shark Nets Set to Stay Despite Drumline Success". swellnet.com. Retrieved October 17, 2018.
  13. ^ a b c d e Morris, Jessica (December 8, 2016). "Shark Nets – Death Traps For Marine Animals". hsi.org.au. Retrieved October 17, 2018.
  14. ^ a b Eddie, Rachel (January 9, 2018). "Threat to Cut Shark Nets if Government Fails to Act". thenewdaily.com. Retrieved October 17, 2018.
  15. ^ a b c d "Shark Culling". marineconservation.org.au. Retrieved October 17, 2018.
  16. ^ a b c d e Media, Australian Community Media - Fairfax (8 November 2016). "Beyond the panic: the facts about shark nets". Retrieved 22 April 2017.
  17. ^ Benson, Nigel (2011-11-17). "Dunedin shark-nets film 'positive environmental story'". Otago Daily Times Online News. Retrieved 2024-09-13.
  18. ^ "Recorded shark attacks in New Zealand to 2014 - Te Ara". Retrieved 19 March 2022.
  19. ^ "Shark Defence Campaign". Sea Shepherd Australia. Retrieved 2024-09-13.
  20. ^ a b c d e f "Shark Angels - Turning Fear Into Fascination". SHARK ANGELS. Retrieved 2024-09-13.
  21. ^ a b "Shark nets to be removed from all NSW north coast beaches". The Guardian. 2018-08-17. ISSN 0261-3077. Retrieved 2024-09-13.
  22. ^ Dudley, S.F.J. (1997). "A comparison of the shark control programs of New South Wales and Queensland (Australia) and KwaZulu-Natal (South Africa)". Ocean Coast Manag. 34 (34): 1–27. Bibcode:1997OCM....34....1D. doi:10.1016/S0964-5691(96)00061-0.
  23. ^ "Baby whale dies in shark net". News24. July 19, 2004. Archived from the original on March 22, 2005. Retrieved March 22, 2005.
  24. ^ a b "Data Tables: Shark control program: Sharks caught by area, Queensland, 2002–03 to 2012–13 (OESR, Queensland Treasury)". Oesr.qld.gov.au. 2013-07-26. Retrieved 2013-09-11.
  25. ^ "Subscribe - theaustralian". Retrieved 22 April 2017.
  26. ^ Barlow, Jay; Cameron, Grant A. (2003). "Field experiments show that acoustic pingers reduce marine mammal bycatch in the California drift gill net fishery". Marine Mammal Science. 19 (2): 265–283. doi:10.1111/j.1748-7692.2003.tb01108.x. S2CID 26969713.
  27. ^ Scott, Elfy (July 5, 2018). "Here's What You Need To Know About Australia's SMART Drum Lines Being Used To Prevent Shark Attacks". BuzzFeed. Retrieved October 17, 2018.
  28. ^ "Sea World Research & Rescue Foundation - What is the Foundation's opinion of the Shark Control Program?". Retrieved March 19, 2022.
  29. ^ a b H. Malcolm, B. D. Bruce and J. D. Stevens (September 2001). "A Review of the Biology and Status of White Sharks in Australian Waters". CSIRO Marine Research, Hobart: 93. Retrieved 8 December 2018.
  30. ^ a b Stephanie M. Bettis (July 2017). "Shark Bycatch in Commercial Fisheries: A Global Perspective". Nova Southeastern University. Retrieved 8 December 2018.
  31. ^ "Shark fin trade myths and truths" (PDF). Sharksavers. Retrieved 8 December 2018.
  32. ^ "Summer is coming and so are the sharks". Smh.com.au. 2012-10-19. Retrieved 2013-09-11.
  33. ^ "NSW Shark Meshing publications | NSW Department of Primary Industries". Dpi.nsw.gov.au. Retrieved 2013-09-11.
  34. ^ "Sphyrna mokarran". The IUCN Red List of Threatened Species. International Union for the Conservation of Nature. Retrieved 2014-09-14.
  35. ^ "Carcharodon carcharias". The IUCN Red List of Threatened Species. International Union for the Conservation of Nature. Retrieved 2014-09-14.
  36. ^ a b "EPBC Act List of Threatened Fauna". Department of the Environment. Australian Government. 2014. Retrieved 2014-09-14.
  37. ^ "Carcharias taurus". The IUCN Red List of Threatened Species. International Union for the Conservation of Nature. Retrieved 2014-09-14.
  38. ^ "Sphyrna lewini". The IUCN Red List of Threatened Species. International Union for the Conservation of Nature. Retrieved 2014-09-14.
  39. ^ Wikinews:Woman killed in shark attack at Amity Point, Australia
  40. ^ Sarah Vogler. "Monster shark spreads fear off Queensland coast". Couriermail.com.au. Retrieved 2013-09-16.
  41. ^ "Gold Coast shark attack victim named as Nick Slater, Greenmount and Burleigh beaches closed". ABC News. abc.com.au. 8 September 2020. Retrieved 2022-10-29.
  42. ^ [1] Archived March 31, 2009, at the Wayback Machine
[edit]
Wikimedia Commons has media related to Shark nets.
Retrieved from "https://en.wikipedia.org/w/index.php?title=Shark_net&oldid=1251804763"