Scientists track sharks with everyday drones
Small consumer drones can be used to detect and monitor marine megafauna (big sea animals, basically) in shallow waters, according to new research from North Carolina State University. The team has shown that a quadcopter drone can be an affordable, easy and non-invasive means to collect reliable data about the abundance and distribution of species from numerous sites.
Many marine megafauna species are difficult to monitor because of their large home ranges and the inherent difficulty of capturing and handling such large creatures. Though aerial surveys are by no means a new idea in marine wildlife research, they tend to involve observation from small aircraft, or older types of Unmanned Aerial Vehicles (UAV), which are expensive to use.
But advances in off-the-shelf consumer drones have seen increasing image definition at range at a relatively small cost. The drone used in this study was a DJI Phantom 2 Vision+ drone.
"Demonstrating the viability of drones for this work matters, because these are inexpensive tools for collecting accurate abundance estimates," says Enie Hensel, a Ph.D candidate at NC State and co-author of the paper. "Those estimates are important for both informing the development of conservation efforts and for assessing the effectiveness of those efforts."
"Drone surveys are also a good way to monitor shallow water, megafauna species because they are not intrusive," Hensel adds. "More traditional monitoring methods – such as boat surveys or gill nets – are more invasive, and have the potential to harm individuals or alter their movement patterns."
With the drone, it was possible to detect and identify different species of elasmobranchs at all sites: lemon sharks, nurse sharks, bonnethead sharks, southern stingrays, and spotted eagle rays. Hawksbill and green turtle species were also evident in the footage but it was not possible to distinguish between them.
Surprisingly, the team of scientists also demonstrated that water quality doesn't affect detectability. Placing decoy sharks underwater in two locations with different water clarity, they were able to identify all of the decoys. "We chose grey shark decoys because they would be the most difficult to spot in these environments, but we were able to spot them all," Hensel says.
In the past, similar studies have been limited to a single site. For this study, several locations were chosen to include a variety of shoreline development and other environmental factors. The researchers looked at whether human activity might affect local populations and indeed it did – higher numbers of megafauna were found at the low human population sites.
"One reason we chose these sites, all of which were on Great Abaco Island in The Bahamas, was because The Bahamas are interested in using several of the sites as a pilot for a managed conservation effort," Hensel says. "Our surveys provide baseline data for marine megafauna abundances within these newly established parks and we show that drones offer a new management tool for the park service of The Bahamas. And, of course, the technology certainly opens doors for us to explore a range of conservation issues."
The team's research paper, "Using a small, consumer-grade drone to identify and count marine megafauna in shallow habitats," appears in the Latin American Journal of Aquatic Research. A PDF version is available to read online.
Source: North Carolina State University