• SharkieSophie

Attack of the Drones

Updated: Apr 27

Protecting ocean-users from unprovoked shark attacks are a major priority for many nations that have many sharks in their waters. For example, Australia has the NSW Shark Meshing Program (est. 1937) and the Queensland Shark Control program (est. 1962), and South Africa has the KwaZulu–Natal shark control program (est. 1952). Mostly, these initiatives involve stringing nets along beaches to ensure sharks cannot access popular areas, but these actually kill sharks in huge numbers. Therefore, there is a real need to develop protective programs which are not also a serous conservation concern (Butcher et al, 2019).


Great white shark sighted from a drone (Butcher et al, 2019)

Aerial surveys, using planes and helicopters, to patrol coasts have been used in the past. The idea is that a manned aircraft flies up and down a coastline, with those on board searching the water for sharks. If a shark is sighted in the vicinity of ocean users an alert is sounded, to inform them to leave the water. However, these programs can be troublesome because sometimes sharks can be challenging to spot. If water is turbid or the weather is particularly bad, it can be difficult to see sharks through the water. Whatsmore, unlike air-breathing aquatic animals, sharks do not necessarily need to swim near to the surface, so can go unseen. Three of the species which are most commonly involved in unprovoked attacks upon humans; the bull shark (Carcharhinus leucas), tiger shark (Galeocerdo cuvier) and the great white (Carcharodon carcharias), often spend considerable time swimming at depths and cannot be sighted from aircrafts. Scientists studying the efficacy of aerial shark spotting have estimated that as few as 12.5% of sharks were successfully sighted from planes and only 17.1% were spotted from helicopters (Robbins et al, 2014).


Drone image captured by Butcher et al (2019)

Therefore, scientists have recently been looking for other methods, which are more successful and can be used to patrol beaches and protect bathers... Recently, Unmanned Aerial Vehicles (AUV) or Remotely Piloted Aircraft Systems (RPAS), more commonly known as drones, have been trialled for shark spotting.


Scientists in Australia have recently assessed how effective drones can be for detecting sharks across a range of environmental conditions; including different wind speeds and bearings, barometric pressures, air temperatures, amounts of rainfall, wave swell heights and directions, and humidities. They found that drones were very successful for spotting sharks in shallow waters with good water visibility, but they also found that this method could be very successful even in more challenging weather and ocean conditions. In fact, they reported that no environmental variable except water depth was related to being able to detect sharks; as water depth increased by 1 m, the probability of spotting a shark dropped by 57% and when water was 3.5 m or deeper, the odds of being able to see a shark were less than 50/50 (Butcher et al, 2019).

Success of sighting sharks at different water depths (Butcher et al, 2019)

The researchers concluded that drones could be a very effective method for spotting sharks swimming near to bather beaches, moreso than manned flights. They suggested that this was the case because drones fly at much lower air speeds and at lower altitudes compared to manned aircrafts and therefore, are much more efficient for spotting sharks.


Drones have many advantages over manned patrols because they can operate on a smaller scale (at individual beaches, rather than along long stretches of coastline), which would increase the coverage at popular swimming sites. Whatsmore, drones can be fitted with polarising filters or digital-enhancing sensors, which can improve the visibility at deeper water depths, compared to what is possible by human observers. Drones are also significantly cheaper to run compared to lite aircraft (Butcher et al, 2019).


The scientists also stated that using drones for shark patrols could have applications beyond just beach protection because drones can record footage. These videos can be observed in a lab in real- time or at a later date and can be used for scientific studies. This video data could be valuable for assessing which species of sharks live within a certain region and how abundant they are.


Drone images captured by Butcher et al (2019)

Whilst the drones were excellent for spotting potentially dangerous sharks, this study also found that many other species of sharks could be sighted on the footage. During the study the drone caught footage of a type of ray called the white-spotted guitarfish (Rhinobatos albomaculatus) swimming in rocky, shallow waters. This species is classified as 'vulnerable' on the International's Union for the Conservation of Nature Red List of Threatened Species (IUCN) and its populations are declining globally. Therefore, this study highlights how shark patrol programs could also simultaneously be used to assess populations of endangered sharks (Butcher et al, 2019).




References

Butcher PA, Piddocke TP, Colefax AP, Hoade B,Victor M. Peddemors VM, Lauren Borg L & Brian R. Cullis BR (2019). Beach safety: can drones provide a platform for sighting sharks? Wildlife Research, 46, 701–712. Access online.


Robbins WD, Peddemors VM, Kennelly SJ, & Ives MC (2014). Experimental evaluation of shark detection rates by aerial observers. PLoS One, 9, e83456. Access online.


Web Resources

IUCN (2020). Access online.


By Sophie A. Maycock for SharkSpeak.

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