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New Zealand University Uses Drones to Study Endangered Manta Rays

Manta rays could be getting the lift they need from technology after all. An innovation developed by a University of Auckland PhD student has the potential of helping scientists monitor endangered manta rays.

Improved monitoring can help scientists to better gauge the health of manta ray populations in the face of overfishing and climate change. The problem is manta rays are particularly hard to monitor. That is where a pioneering study by a University of Auckland postgraduate student came in handy.

The PhD student got the idea during fieldwork in 2019 in Raja Ampat, Indonesia, as he flew drones over the giant fish. Manta rays are often difficult to observe via in-water surveys, but using drones they are very obvious.

It was manta season, and I flew a drone over a squadron of 20 to 30 reef manta rays feeding on the sea surface, getting clear visuals of size variations and distinguishing features such as the mating scars on sexually mature females.

University of Auckland PhD Student

 The advantage of the drone approach is stealth. It avoids disruption to the animals unlike alternative methods of monitoring such as divers entering the water to assess the rays’ size. To help researchers assess the animals better, the technique was finessed with the addition of a length of PVC pipe – dubbed the “MantaMeasure” – which floats in the vicinity of the rays to serve as a size reference for the images captured by drone.

Internationally, the ingenious method is starting to attract serious attention. For example, researchers affiliated with the Manta Trust charity are interested in adopting the method. The research paper was entitled “How Big Is That Manta Ray? A Novel and Non-Invasive Method for Measuring Reef Manta Rays Using Small Drones.” The University of Auckland research team affirmed their success. They felt confident they have demonstrated conclusively the value of using small, commercially available drones to accurately measure the body size of surface-feeding or cruising Mobula Alfredi (reef manta rays) with minimal or no impact on the animals.

While reef manta rays are distributed widely across the tropical and subtropical regions of the Indian and Western Pacific Oceans, they are not as prevalent in New Zealand waters. The study could help grow the population of the larger oceanic manta ray (Mobula Birostris), which reaches an impressive wingspan of 7 metres and is considered “endangered” on the IUCN Red List.

The giant manta ray (or oceanic manta ray) has been classified by the International Union for the Conservation of Nature (IUCN) as endangered joining 30% of sharks in the soon-to-be-extinct list. The main threat to the giant manta ray is commercial fishing, with the species both targeted and caught as bycatch in a number of global fisheries throughout its range. Manta rays are particularly valued for their gill rakers, which are traded internationally.

Technology-wise, a drone can fly without WiFi or cell service. Instead, they are controlled by remote ground control systems (GSC), also referred to as a ground cockpit. The Unmanned Aerial Vehicle (UAV) system has two parts, the drone itself and the control system. The nose of the unmanned aerial vehicle is where all the sensors and navigational systems are present. Today, drones have been extensively used for military and commercial purposes.

UAVs have been greatly utilised in ICT. Their smaller size, quick deployment and dropping cost make them ideal for a growing list of areas. For instance, their inputs are considered crucial in smart agriculture as they can be equipped with a lot more sensors than just a regular camera (e.g., multispectral, infrared). That should provide timely data for more analytics than just the regular camera.

Indeed, this is excellent news for New Zealand, a country that has continually pursued its digital transformation. Just recently, Wellington has chosen to upgrade internet access in rural areas to improve connectivity and get everyone closer as the pandemic winds down.

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