Whale shark sightings by ordinary citizens provide useful data to researchers

Because of citizen scientists and NASA, researchers have a clearer picture of the habits and whereabouts of the largest, very elusive fish: the endangered whale shark.

Over a 22-year period, more than 28,000 encounters with this spotted, filter-feeding shark by citizen scientists from 54 countries have been recorded and contributed to the Wildbook for Whale Sharks database, out of which nearly 6,000 individual sharks were identified, according to a new study recently published in the peer-reviewed journal BioScience.

“The value of that is that the scientists can’t always be everywhere at once, and by being able to take advantage of people who see whale sharks when they’re diving, we’re actually able to put together a picture of the worldwide distribution and what we call the populations structure of the species,” said Robert Hueter, director of Mote Marine Laboratory’s Center for Shark Research.

Hueter, who has been studying sharks for about 40 years, was one of 38 researchers to contribute to the study, which compared how many and how often Rhincodon typus was seen in any of the 20 known aggregation sites around the world. The study’s lead author, Brad Norman, also heads the organization responsible for the database.

The boom in whale shark ecotourism has helped with this collection process, in which divers, snorkelers or scientists alike can submit photos of the whale sharks they encounter to whaleshark.org. In order to keep track of the resurgence of identified individuals or discover new ones, the submitted images taken with an underwater camera have to concentrate on the area behind the gills to capture a specific smattering of spots.

“The pattern is sort of like a fingerprint and is unique,” Hueter said. “The (Wildbook) group used a computer program that was adapted from a NASA program to navigate by the stars and figure out where a space craft is based on star patterns.”

This method of identification is as non-invasive and inexpensive as it gets, especially when compared to other tagging methods like satellite trackers that can cost thousands of dollars. Whale sharks aren’t dangerous to swim with, Hueter said, minding that people keep a safe distance. Contributors to the database can also submit information on the date and location of the encounter, its estimated length and sex. They will be notified if the shark is spotted again.

Sharks in the Gulf region are also on average slightly larger than most of the other ones around the world at 8 meters, with the Galapagos harboring the largest average shark at 11 meters.

With this information, researchers were able to identify insights into their movements. The group of states that line the Gulf of Mexico, particularly Louisiana and Mississippi, is one of the 20 shark hotspots. Of the 419 encounters submitted to the Wildbook, 101 individuals have been identified, 45 of which have been identified by their sex.

The region that had the most identified sharks — 1,101 out of 6,017 submissions — was in the Mexico-Atlantic region near Cancun, which is also where Hueter has done the bulk of his whale shark research.

Juvenile males often dominated aggregation sites, often keeping toward the coasts with an abundance of food. Only a few places, such as the Galapagos, had were dominated by females.

For the most part, researchers found that identified sharks generally weren’t photographed moving between countries, save for a few like H-021, who was pinged as moving 1,300 kilometers between Belize, Honduras, Mexico-Atlantic and the Gulf states regions over a 14-year period.

There are limitations to the study, as detailed in its conclusion. It’s more likely that the contributions will come from popular snorkeling and dive spots as well as particular times of the year when tourism is high. A big part of the whale shark’s life cycle, where females give birth, is largely unknown, Hueter said.

Whale sharks are listed as endangered by the International Union of Conservation of Nature, as boat strikes and bycatch threaten their futures. Through the continued collection of information on sharks from the public, researchers hope it can help to suggests areas that are in most need of protection efforts.

“This effort is increasing our knowledge of whale shark abundance and geographic range, trends in site fidelity and frequency,” Norman said in a press release. “That information is vital for prioritizing conservation areas for the species.”

This story was originally published November 30, 2017 at 4:54 PM with the headline "Whale shark sightings by ordinary citizens provide useful data to researchers."