In 2015, Conservation International launched a tagging program in Indonesia's Cenderawasih Bay to learn more about the behaviors of the largest fish species in the ocean: whale sharks. Whale sharks are often caught in nets and become victims of bycatch in the region. Now, a year later, scientists have learned a lot of new information about the large fish, and much of what they've found is rather shocking.
The fin-mounted tags gave researchers information about the whale sharks' locations, their depth under water and the temperature of the water they were swimming in. Over the course of the year, it became apparent to scientists that, like oceanic manta rays, whale sharks are homebodies for the most part. That means they don't typically have large migrations and instead feed on the local fish supply year round.
Nevertheless, some whale sharks were observed taking a few short, seemingly random "road trips," but researchers are still trying to figure out the motivations for the trips.
"We have no idea why they went so far — one shark covered 4,000 kilometers (2,485 miles) before returning to the bay — for such short periods of time," explains Conservation International's Dr. Mark Erdmann in a blog post. "Although we suspect that the journeys of some of the larger males might be related to mating, several of these traveling sharks have actually been juvenile males under 4.5 meters (15 feet), leaving us scratching our heads!"
The most shocking discovery about the gentle giants, though, has to do with depth. Whale sharks tend to stay above a 330-foot depth, as it's where most of the fish they eat are. However, scientists observed some of the tagged whale sharks diving as deep as 6,000 feet below the surface — and they have no idea why!
The baffling discoveries drive home how much more there is to learn about whale sharks (including where the females and babies are). Luckily, the tags will last another year so scientists can collect even more data. The more they can learn, the better equipped they'll be to learn how to protect the vulnerable species.