Citation: Butcher, P. A., Piddocke, T. P., Colefax, A. P., Hoade, B., Peddemors, V. M., Borg, L., & Cullis, B. R. (2020). Beach safety: can drones provide a platform for sighting sharks? Wildlife Research, 46(8), 701-712. DOI 10.1071/WR18119
Shark attacks, while rare, do happen at beaches around the world. As the number of people on the planet grows, especially in coastal areas, the number of people swimming in the ocean also grows. With more people swimming, there is more of a chance that sharks and people will cross paths. Between 1982 and 2011, global shark attacks increased by a factor of 3. The majority of shark attacks take place along the coasts of Recife, Reunion Island, North and South Carolina, and Western Australia, and New South Wales. White, bull, and tiger sharks are responsible for most attacks. Shark attacks, though rare, usually gain a lot of media attention and give sharks a bad reputation, which can be harmful to conservation efforts. Shark conservation is important because as a species at the top of the food chain, they play an important role in keeping the oceans functioning properly.
Many shark attacks are attributed to white, bull, and tiger sharks, pictured above in that order, giving the species a bad reputation.
Given the ecological importance of sharks and the increase in attacks, environmental managers are under pressure to do what is necessary to keep beachgoers safe. This has historically meant that nets were deployed around beaches to keep sharks out or baited hooks were placed off the coast to catch and kill sharks, reducing their population sizes and presence. However, these methods have negative impacts on the environment. Aside from sharks being killed, which we know is not good for the oceans, other marine animals can be caught up in the nets or caught on the hooks. As a result, managers are looking for safer methods of reducing the likelihood of shark attacks. Other methods have included baited hooks with satellite communications so that animals can be released or relocated quickly, physical barriers, visual barriers, and electrical and electromagnetic barriers. Since these methods are often costly and unsuccessful, managers have moved towards detection of sharks rather than trying to deterrence. Some of these methods include using trained observers, automated sonar systems, acoustic tagging and monitoring programs, and aircraft or helicopter patrols. These methods also have their weaknesses, which is why a team of researchers from Australia wanted to see if using drones could help improve shark detection.
To do this, the researchers created 54 realistic shark models, put them in the water along the coast of New South Wales, and attempted to detect them using a drone in a variety of environmental conditions. The models were placed in sand and rock habitats in water 2 – 6.3m deep in a line along the coast and 27 drone flights were conducted with 2 passes over the models each flight over a period of 3 weeks. The pilot of the drone attempted to detect the sharks as the drone was flying and the footage was also sent to a lab for analysis by another observer.
Out of a possible 108 detections, 41 models were detected in total. The observer in the lab had a 2.5-times higher chance of detecting the shark models than the pilot and observed an additional 10 that the pilot did not see. Deeper water also resulted in fewer detections. The water throughout the study area and study period had high turbidity and low visibility, which may have contributed to the models only being observed about 40% of the time. Sandy ocean bottom, no wind, low turbidity (good visibility), and smooth sea conditions were optimal for detecting sharks, both by the pilot and the observer in the lab. While detection rates went down in adverse conditions, which is also true of detection by manned aircraft, drones fly lower and slower than manned aircraft, which may increase the rate of detection comparably. Overall, this study shows that drones may be useful in detecting sharks (in fact, they are already being used), but given the high turbidity levels throughout the study, additional research in different water conditions is needed to fully evaluate the effectiveness of drones in detecting sharks and keeping beachgoers safe.