Aerial Survey of Whale Sharks

Just off the northeastern tip of the Yucatan Peninsula is the largest whale shark aggregation site in the world. And marine biologists are conducting regular aerial surveys of this feeding zone to document key information about these wild ocean travelers….

According to Dr. Alistair Dove, Senior Scientist at the Georgia Aquarium, aerial surveys compliment other forms of whale shark study (such as swimming with them in the wild or documenting behaviors of animals on public display). “You get different information from an aerial study – you can’t determine sex and clouds may affect visibility, but you can get a better grasp on the population. When you’re out on a boat, you can get sex, size, tag, take photos, and look for injuries. So we look to both forms of study to assemble a story about these animals as a whole.”

How long have these giant fish been feeding in these waters? Rafael de la Parra, biologist and researcher with Project Domino, “according to old tradition of Isla Mujeres and Holbax, these animals have been here a long, long time…. they are present in stories from great-grandparents and fisherman.”

De la Parra adds that they “see large schools of tuna, and it appears the whale sharks are feeding on their eggs… And right now we are seeing a lot of sailfish and sardines in the same area where the whale sharks are going.”

Just a few weeks ago, I teamed up with Project Domino and Georgia Aquarium researchers to study whale sharks in the wild. On one clear afternoon we took to the sky in a little 4-person Cessna 206.7 to conduct an aerial study of these school bus-sized fish. Below, Dr. Alistair Dove and Cancun-based biologist Rafael de la Parra discuss aerial survey goals:

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We departed Cancun International Airport for the ‘afuera zone’ – with Diego as our pilot – anxious to find out how many animals would be feeding that morning.

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My door was taken off and I was harnessed inside so that I could capture footage. We
flew from 94-127 knots, maxing out at 3,000 feet.

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Photo Credit: Jodi Kendall

When we discovered the whale shark aggregation site, we dropped down to 1,500 feet and then 500 feet, circling them to double-check our counts – and the result? 39 whale sharks were feeding together in the ‘afuera.’ In this clip, you can see the ecotour/research boats and the gray whale sharks (they look a little bit like salamanders from above, don’t you think?)

While whale sharks are the largest fish in the ocean, remarkably little is known about the species. Currently, it’s uncertain where exactly these fish travel, how they reproduce and the total number of them in the wild. GAI-sponsored researchers are also studying the fish eggs in the water of the ‘afuera’ zone and the behavior of whale sharks before and after hurricanes pass through.

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Photo Credit: Jodi Kendall

Adds Dr. Dove, “We’re trying to collect as many different pieces of data as we can to get an accurate information about this species… It’s discovery-based science, not necessarily testing a hypothesis. But we are trying to learn new things and determine patterns. Often then, after describing it, we can start asking intelligent questions against that baseline.”

This particular aerial survey didn’t just shed light on whale sharks – we also documented the following sightings from our plane: 1 bull shark, 43 manta rays, 4 dolphin pods, 22 turtles, 3 mobula and 6 groups of cownose rays (about 500 individual rays).

After my initial survey experience, Dr. Dove participated in two more  aerial surveys later that week – one resulting in zero sightings, and the other with a staggering 300 whale sharks in the ‘afuera’ zone. And when they spotted the aggregation before the ecotour operators, Dr. Dove snapped this incredible image from the plane:

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Photo Credit: Dr. Alistair Dove

“I can only say that its remarkable that we saw nothing one day and 300 the next, without any major apparent difference in conditions,” he shares. “It just highlights the variability of life in the open ocean – one day its famine and the next day its a feast. The pelagic zone is characterized by these huge expanses of space and time with little going on, punctuated by occasional times and places of extraordinary activity. It’s one of the things that makes it such a rewarding and challenging place to study.”

If you enjoy studying wildlife from the air, check out this post on an aerial survey of wild manta ray populations off the coast of Florida.

Learn more about sharks and watch Ultimate Shark on Tuesday, December 28th at 10 PM et/pt!