Tracking whale sharks from the air

In 2022, after several false starts, our research took a leap forward. We partnered with our friends at the Georgia Aquarium to set up an expedition on a local fishing vessel with several objectives – to tag and track yellowfin tuna, blue sharks and hammerheads around some of the central islands, and to act as a floating platform from which to move rapidly in a speedboat to intercept any whale sharks that might be seen from the air. We would base our operations at the location where the whale sharks had been seen by the Galapagos National Park’s aerial patrol a couple of years earlier. Julio would fly his ultralight aircraft from coastal Ecuador and then operate daily out of the airport in San Cristobal. The expedition would last a week.

We struck gold before the aerial support even got here! Sofía saw a whale shark just below the surface on the way out of San Cristobal and was able to jump in and tag her. It was the perfect start to the trip and seemed to be a good omen for the upcoming days. Unfortunately, we ran into logistical problems immediately. Although we successfully tagged and tracked four each of the hammerhead, blue sharks and tuna, Julio was unable to leave mainland Ecuador. It turns out that Guayaquil airport doesn’t like to handle ultralights, so they sent him to Manta airport… where there was no quarantine facility for flights to Galapagos… so they promptly sent him back to Guayaquil. This went on for several days, while the tension on the boat grew, as we sat and waited and hoped for him to appear on the horizon. Finally, our colleagues from Georgia had to catch their flights home, so we headed back to port, somewhat dejected.

I called Julio to give him the news and tell him that we had to pull the plug, but there was no answer. One explanation for this might be that he had finally made it into the air and out to sea. I opted to stay in Galapagos a little longer in case he was on his way. An hour later, we got a photo from Elaine from Georgia Aquarium as she went up the steps onto the aircraft for her flight home. It showed an ultralight on the tarmac! Julio had finally made it here.

We immediately called our friend and collaborator Manuel Yepez, a local fisherman and Mission Blue Hope Spot Champion for Galapagos, and he placed his fishing skiff at our service, so we decided to make daily trips out of San Cristobal. It was too far to go all the way to Isabela, but we felt that it would be worth exploring the area to the south of Española and Floreana, where the island platform shelves off. We agreed on a series of daily flight plans and how to communicate between the ultralight and the speedboat. Finally, it was going to happen.

The next four days were amazing. Not only did we find whale sharks, but we also had close encounters with a Bryde’s whale and its calf, bottlenose dolphins, and the aerial observers even reported blue whales. The best moment, however, was when the ultralight flew over us, dipping its wings. This was the agreed signal for a whale shark.

We followed it until it began to circle over a point. We all jumped up and scanned the water. It only took us a few minutes before we saw a large shadow under the surface. Sofía and I got our fins on and grabbed a tag each. We slipped into the water and there beneath us was an adult whale shark, just sitting at around 8 metres depth. Sofi didn’t think twice, and within seconds she was onto the shark and had clamped the tag onto the fin. The shark didn’t even react. We’d done it! After years of trying, we had shown that with aerial support, we were able to locate and communicate the position of a shark, intercept it and successfully tag it.

We ended up with nine individual whale shark reports from the air, and were able to intercept six of them, with four successful tags. They were all large females, similar to the ones seen at Darwin later in the year. Surprisingly, none of the sharks were tracked to Darwin. Instead, three of them headed out west, traveling 1,500 – 3,000 km before we lost track of them. A fourth shark looped around to the south and was heading north when her signal was lost, and the final shark must have encountered a fishing vessel sometime between mid-March and mid-May, because her tag appeared in a fishing port on mainland Ecuador. In any case, as a National Geographic Explorer, I felt I had proof of concept and we could now submit a proposal to National Geographic to begin a large-scale study.