Using drones for surveying dolphins in the high seas

To test new methods for estimating abundance of dolphins in the eastern tropical Pacific (ETP), we conducted a 14-day trial survey on board the Mexican research vessel Dr Jorge Carranza Fraser off the western coast of Mexico in November 2019.

Part of the efforts consisted in testing if the newly installed flying bridge would be suitable for conducting line transect surveys (a form of distance sampling) in closing mode using the NMFS survey protocol (Kinzey et al. 2000). This protocol entails that the ship travels along predefined lines and observers record detections of cetacean schools along with their radial distances and angles to the detections. When a school is detected, the observers focus on the detected school while they approach it with the ship to collect information on species id, group composition and school size. While observers are allowed to miss schools that pass the ship at greater distances, distance sampling methods rely on that observers detect all schools on or near the transect line.

We are planning on using long range drones to test if this is indeed the case. For these purposes, a drone equipped with a video camera would be sent ahead of the ship to monitor the same area as the observers on the ship. Each detection made via the drone during real-time monitoring or post-survey image analyses would serve as a trial for the observers with two possible outcomes: the trial would be a success if observers detected the same school and a failure if they did not detect it. These double platform methods are usually referred to as mark-recapture distance sampling (MRDS, Borchers et al. 1998). As part of determining if this is feasible, we needed to test if drones could be launched and landed from the research vessel.

The results of these tests will be made publically available after review. Two of the species we encountered during the trial were the eastern spinner and short-beaked common dolphins.