Protecting ocean-users from unprovoked shark attacks is a major priority for many nations that have sharks in their waters. In the past it was common to net or hook and simply kill any threatening sharks Therefore, there is a real need to develop protective programs which are not also a serous conservation concern. In recent years, technological advancements mean drones might be a more sustainable option. But how does this work? Can drones really be used to monitor beaches for sharks?
Gotcha!
The earliest forms of shark safety programs usually involved implementing long nets along stretches of coastline or deploying baited drumlines to hook sharks. 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). The problem is that these methods kill sharks in enormous numbers and, as they are indiscriminate, also kill all kinds of other marine life in the process (Robbins et al, 2014).
Come Fly with Me
As technologies developed, governments have employed aerial surveys, using planes and helicopters, to patrol their coasts for sharks. 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 (Robbins et al, 2014).
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. For example, three of the shark 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).
A New Hope
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 (Butcher et al, 2019).
yeia 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, humidities, rainfall and swell heights. 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, and when sharks were swimming in deeper wate (Butcher et al, 2019).
Eye in the Sky
It seems drones are much more successful at spotting sharks compared to what is possible from human observers. This is because drones fly at slower speeds and lower altitudes compared to planes or helicopters, so we can see more in real time (Butcher et al, 2019).
Additionally, drones can be fitted with polarising filters or digital-enhancing sensors, which can improve the visibility at deeper water depths, to spot more sharks (Butcher et al, 2019).
Drones also have many other advantages over manned patrols. Firstly, they can operate on a smaller scale - at individual beaches, rather than along long stretches of coastline. This means we could increase the coverage at popular swimming sites. Drones are also significantly cheaper to run compared to lite aircraft (Butcher et al, 2019).
Two Birds with One Stone
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. Drone footage can be used to study hunting and scavenging behaviours, social interactions, movement ecology migrations, schooling events, habitat use, population demographics. They can also be used to identify critical habitats, like feeding and breeding grounds and to monitor endangered species (Butcher et al, 2019; Butcher et al, 2021).
For instance, during the aforementioned 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 Critically Endangered 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 very rarely sighted animals (Butcher et al, 2019; Butcher et al, 2021).
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.
Butcher PA, Colefax AP, Gorkin III RA, Kajiura SM, López NA, Mourier J, Cormac R. Purcell CR, Skomal GB, Tucker JP, Walsh AJ, Williamson JE, & Raoult V. (2021). The drone revolution of shark science: A review. Drones, 5(1): 8. Access online.
IUCN (2020). International Union for the Conservation of Nature Red list of Threatened Species. 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.
By Sophie A. Maycock for SharkSpeak
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