Drum line (shark control)

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 1960s) there has only been one death caused by a shark attack on a protected beach.^[1][2][3][4] In January 2014, drum lines were introduced in Western Australia to catch potentially hazardous sharks. The topic of shark culling became a nationwide controversy and sparked public demonstrations and vocal opposition, particularly from environmentalists, animal welfare advocates and ocean activists.^[5][6][7][8]

Description

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.^[9] 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 only sharks from the immediate vicinity are attracted to the baits.^[10]

History

Drum lines were deployed to prevent shark attacks in Queensland, Australia in 1962.^[11] They continue to be used in Queensland, and continue to kill sharks (and also kill by-catch species such as dolphins).^[12][13] They were then used by KwaZulu-Natal (South Africa) and have been killing sharks there for the past 50 years.^[14] They were used intermittently in Western Australia in an "imminent threat" policy, having previously been used there for 4 months in 2014^[15][7]. However the use of drum lines ceased in March 2017 following a change in the state government.^[16] Since 2014 Réunion Island has used drum lines in conjunction with shark barriers.^[17]

Advantages

Permanent or semipermanent deployment of shark-fishing gear off high-use beaches (which includes drum lines) have been claimed to be successful in reducing the incidence of shark attack at the protected beaches,^[18][19] though this assertion has been disputed.^[20][21] 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.^[22] 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^[23] while shark nets allow the sharks to swim over or around them.^[24] The bycatch, or unintended catch, of drum lines is considerably less than that of shark nets.^[25]

Disadvantages

Drum lines are also responsible for bycatch. During shark attack mitigation off Recife, Brazil over a 4-year period (October 2007 to December 2011) the total bycatch and the percentage released alive was:^[22]

During the same period 38 potentially aggressive sharks were also hooked, including tiger sharks (34) and bull sharks (4). The overall survival rate of potentially aggressive sharks was 70% (relocated and released).^[22]

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.^[26]

Bycatch from drum lines is minor compared to bycatch from other human activities. For example, Australia’s commercial shark fishing industry is taking over 1200 tonne of shark out of our various fisheries each year: everything from gummy shark to mako, and very likely a few white sharks as well. The NSW prawn trawling industry alone results in 64 tonne of shark as bycatch each year. Six percent of what’s caught in the tuna longline fisheries in northern Australia is shark.^[27]

There is also evidence of dolphins stealing bait on numerous occasions, thus rendering the drum lines useless.^[2][28]

Drum lines have been claimed to be an ineffective strategy to keep people safe, while simultaneously killing thousands of sharks and other wildlife in the marine ecosystem,^[20] though this has been disputed.^[18][19] In particular, the ongoing killing of sharks in Queensland (under its "shark control" program) has been criticized.^[11] This program has been called a cull.^[5] Using drum lines to kill sharks negatively affects the marine ecosystem.^[20][21]

Smart drumlines

On Réunion regular operation of SMART (Shark-Management-Alert-in-Real-Time)^[29] drum lines began in August 2015 and they are used in conjunction with bottom long lines. A smart drum line is based on the traditional drum line design, but it includes technology that can alert rangers to the capture of marine life, who can then attend the device if sea conditions permit. In Reunion, fishermen usually attend the drum lines within 90 minutes of an alert and 90 per cent of animals caught on the hooks survive.^[30] There are now around 15 of these smart-drumlines along the coast of Réunion Island.^[31]

In December 2016 the NSW State government commenced a trial of smart drumlines,^[29] as part of a expansion of shark attack mitigation strategies along the NSW North coast.^[32] Twenty five drumlines were deployed at Ballina and Evans Head beaches (15 off Ballina; 10 off Evans Head).^[32] Once a target shark is caught it is tagged with a transmitter, relocated approximately 1km offshore and released. Non-targeted animals are immediately released. In addition, the tagged sharks provide an alert to the community if they pass within range of a series of listening stations located along the coast.^[33] In the first six months of the trial 36 target sharks (31 great white, 3 tiger, and 2 bull sharks) were caught with 35 (97%) successfully relocated.^[33] The trial has been effective in reducing shark attacks^[34][35] and in the 2017-18 summer the trial was expanded to 100 smart drumlines in six NSW regions.^[33]

In August 2018 a 12 month trial of SMART drumlines along Western Australia's South West coast, near Gracetown was announced.^[36]

Controversy

Great white sharks were 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.^[2][18] 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^[37] of its 20,000 km (12,000 mi) long coastline^[38] (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. Following a change in the West Australian state government in March 2017,^[16] the newly elected Premier Mark McGowan and Fisheries Minister David Kelly have stated that they do not support the previous governments' catch and kill policy.^[39]

Drum lines have been criticized on animal rights grounds, not only for its negative effect on the environment and killing of endangered species, but also for its possibly non-scientific approach.^{[6][7][8][21]}

A number of people opposed to the program have sabotaged various drum lines throughout Queensland to save sharks, despite the risk of being fined.^[40]

References