Drum lines

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Not to be confused with drumline. ‹See Tfd›

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 (used to offer further protection by enclosing designated swimming areas. The combination of drum lines and shark nets has been successful in reducing shark attacks in the areas protected by them. Since the shark nets and drum lines have been put into use, (in the 1960's) there has only been one death caused by a shark attack on a protected beach.[1][2][3] In January 2014, drum lines were introduced in Western Australia to catch sharks. The topic became a nation-wide controversy and sparked public demonstrations and vocal opposition, particularly from environmentalists, animal welfare advocates and ocean activists.

Description[edit]

The drum line consists of a floating drum (a barrel) with two lines attached to it. One line is attached to an anchor on the sea floor, while the other features a large baited shark hook. The drum is filled with a rigid polyurethane foam, which keeps it buoyant and prevents it from being stolen for use as a storage vessel.[4] In order to attract sharks, the hooks are baited with red mullet and false jacopever. Since the objective of the drum line is to prevent sharks from approaching popular beaches (and not to attract them) only about 500 grams of bait is added to each hook. Thus sharks are only attracted to the baits from the immediate vicinity.[5]

Advantages[edit]

Drum lines were first deployed to protect users of the marine environment from sharks in Queensland, Australia in 1962. During this time, they were just as successful in reducing the frequency of shark attacks as the shark nets on the beaches in New South Wales, Australia and KwaZulu-Natal, South Africa.[6][7] More recently, drumlines have also been used with great success in Recife, Brazil where the number of attacks has been shown to have reduced by 97% when the drumlines are deployed.[8] While shark nets and drum lines share the same purpose, drum lines are more effective at targeting the three sharks that are considered most dangerous to swimmers: the bull shark, tiger shark and Great white shark.[9] Drum Lines physically attract sharks from within the immediate vicinity using bait[10] while shark nets allow the sharks to swim over or around them.[11] Shark nets are responsible for significant bycatch mortalities including Dugongs, Dolphins and Sea Turtles all of which are protected species in Australian waters. Several harmless species of sharks are also caught.[12] The bycatch, or unintended catch, of drum lines is considerably less than that of shark nets.[13]

Disadvantages[edit]

Shark attacks themselves are extremely rare compared to other types of deaths; between 2004 and 2008 there was an average of 4 fatal shark attacks recorded per year.[14] Depending on their size, a minority of sharks survive being caught on a drum line. The combination of drum lines and shark nets do not directly lead to extinction, but they also may not give the population room to recover from being endangered of extinction.[15] Drum lines are also responsible for bycatch, possibly including dolphins[16] and sea turtles,[17] both of which are fully protected in Australian waters. There is evidence of dolphins stealing bait on numerous occasions, thus rendering the drum lines useless.[18][19]

Controversy[edit]

Great white sharks are targeted by Western Australia's controversial shark culling policy.

Prior to 2014, drum lines were only utilised on Australia's eastern coast and in South Africa where the numbers of attacks reduced dramatically.[20][21] In 2014, the Western Australian government reacted to the loss of seven human lives in the years 2010-2013 and installed drum lines along around 200 km[22] of its 20,000 km long coastline[23](around 1%). The policy has been the subject of national and international protests, coming under fire from marine conservationists and animal welfare advocates and their supporters. The policy is commonly referred to as the Western Australian shark cull.

References[edit]

  1. ^ Richard Shears Great White Shark attacked Retrieved on 1-22-09
  2. ^ http://www2.dpi.qld.gov.au/extra/pdf/fishweb/sharksafetyreport.pdf
  3. ^ http://www.shark.co.za/SharkNetsMore
  4. ^ Dudley, Haestier, Cox, Murray Shark control: experimental fishing with baited drumlines Retrieved on 1-22-09
  5. ^ Natal Sharks Board, Drumlines Frequently Asked Questions, archived from the original on 2010-02-15 
  6. ^ http://www2.dpi.qld.gov.au/extra/pdf/fishweb/sharksafetyreport.pdf
  7. ^ http://www.shark.co.za/SASharkAttacksMore
  8. ^ http://onlinelibrary.wiley.com/doi/10.1111/acv.12096/abstract
  9. ^ Dudley, Haestier, Cox, Murray Shark control: experimental fishing with baited drumlines Retrieved on 1-22-10
  10. ^ http://www.fish.wa.gov.au/Documents/occasional_publications/fop108.pdf
  11. ^ Marine Science Today Australian Shark Control Programs Indiscriminately Catch Marine Life Retrieved 2-10-10
  12. ^ Remove Shark Nets Focus on Removing Australian Shark Nets Retrieved on 1-22-10
  13. ^ http://www.shark.co.za/Downloads.aspx?c=4
  14. ^ Icthyology ISAF Statistics for the Top Ten Worldwide Locations with the Highest Shark Attack Activity Since 1990 Retrieved on 2-9-10
  15. ^ Remove Shark Nets Do the nets and drumlines really have a measurable impact on shark populations? Retrieved 2-10-10
  16. ^ Citation needed
  17. ^ http://www.shark.co.za/Uploads/Drumline%20FAQ.pdf
  18. ^ http://www2.dpi.qld.gov.au/extra/pdf/fishweb/sharksafetyreport.pdf
  19. ^ http://www.youtube.com/watch?v=yQtPnaWUPMA
  20. ^ http://www2.dpi.qld.gov.au/extra/pdf/fishweb/sharksafetyreport.pdf
  21. ^ http://www.shark.co.za/SASharkAttacksMore
  22. ^ http://www.abc.net.au/news/2013-12-10/protesters-oppose-tougher-shark-policy/5147288
  23. ^ http://www.ga.gov.au/education/geoscience-basics/dimensions/coastline-lengths.html