The Only Whale Shark to Be Tagged Twice by Scientists Has Traveled Nearly 10,000 Miles in Just Over 600 Days

The only whale shark to have been tagged with a monitoring device on two separate occasions by researchers has travelled more than 9,700 miles in just over 600 days.

Scientists from Nova Southeastern University's Guy Harvey Research Institute (GHRI) and Mexican conservation non-profit Ch'ooj Ajauil AC tagged the mature, 26 feet long whale shark, dubbed "Rio Lady," in August, 2018 in the waters off Cancún, Mexico, and have now been following her movements for 20 months.

This is the longest period of time that scientists have tracked a member of this globally endangered species using high-resolution positioning data, the researchers said.

From August 2018 to the latest "ping" from her satellite tag, Rio Lady has covered vast distances, spending long periods of time in the Caribbean, the Gulf of Mexico and even making a short trip to the waters off the coast of Apalachicola in the Florida Panhandle.

"As of May 12, 2020, Rio Lady has travelled 620 days and at least 9,689 miles in that time," Mahmood Shivji, Director of the Guy Harvey Research Institute & Save Our Seas Shark Research Center at Nova Southeastern University, told Newsweek.

"Her actual distance travelled is even longer; we can only estimate distance travelled based on connecting the detection dots with a straight line, but in the ocean she has not traveled in a straight line between detections."

"Tracking data are demonstrating that long distance travels of a few thousand miles per year by whale sharks are not unusual," he said. "Rio Lady's travel distance is the longest of the 10 whale sharks we have tracked/are tracking, but we have also tracked her for a longer period than any other whale shark—so far."

In August, 2007, a team from Mote Marine Laboratory in Florida and Ch'ooj Ajauil AC's Executive Director Rafael de la Parra tagged Rio Lady for the first time near Isla Mujeres in the waters off Cancún—an area where whale sharks gather every year to feed. While research has shown that whale sharks tend to travel alone they sometimes aggregate in large numbers for feeding purposes.

The team fitted her with a "pop-up" satellite tag, which detached itself from the animal five months later, around 5,000 miles away in the southern Atlantic Ocean near the Saint Peter and Saint Paul Archipelago—located between Brazil and West Africa.

At the time, scientists suspected that the shark was pregnant due to her large girth, and thus, this journey out into the open ocean—away from near-shore feeding grounds—provided researchers with an important clue as to where females of this species give birth.

whale shark
A whale shark. Guy Harvey Ocean Foundation

Then, in 2018, de la Parra, in collaboration with a GHRI team, tagged her again in almost exactly the same location. This time though, the researchers fitted her with a higher resolution Smart Position and Temperature (SPOT) satellite tag that was attached to her dorsal fin, located on her back.

"This is the only known case of the same whale shark being satellite tag tracked twice, each at different times," Shivji said.

The SPOT tag provided researchers with more accurate data regarding her position and movements than the "pop-up" tag. Tracking whale sharks over long periods using this kind of data can yield important information, the scientists said.

"The strikingly different travel patterns of Rio Lady over the past 20 months compared to her five-month journey into the Atlantic when she was first tracked in 2007-2008, suggests that whale shark individuals may not repeat the same migration pathway annually like many other wildlife species do," Shivji said.

"The migration path by individual whale sharks may be different every year but they clearly travel really long distances which is energetically very costly, so the question is what is driving these annually different migration patterns?

"The only way we'll find out is by tracking many individuals over a long period of time, at least two or more years. Rio Lady has been tracked for the longest time period of any whale shark in the Atlantic Ocean. It will be interesting to see if she will head back later this summer to the feeding aggregation site where she was tagged in 2007 and 2018," he said.

It's also clear that whale sharks spend a lot of time at the surface otherwise the scientists would no be receiving so many "pings" from the fin-mounted SPOT satellite tags, Shivji said. Furthermore, the tracking data could have implications for conservation efforts. The species is classified as "Endangered" on the International Union for Conservation of Nature's Red List of Threatened Species.

"We're following four other whale sharks that have been tracked for eight-to-nine months so far; hopefully we will be able to follow them as long as we have Rio Lady so we can get a good understanding of the travel behavior of these endangered species and determine how much their travel paths intersect with busy shipping lanes where there is a risk of collision causing shark injury and mortality," Shivji said.

"The long distance travels of these sharks are also taking them through the jurisdictional waters (Exclusive Economic Zones) of multiple countries, underscoring that conservation efforts for whale sharks will require international cooperation."

whale shark, Rio Lady
A researcher tagging the whale shark Rio Lady. Guy Harvey Ocean Foundation

Whale sharks (Rhincodon typus) are both the largest fish and largest sharks in the oceans, growing to around 30 feet in length on average, and weighing as much as 20 tons. Despite their large size, these animals—which are not whales—are harmless, feeding mostly on tiny plankton and fish eggs that they consume while swimming along with their giant mouths wide open. In fact, the animals are one of only three species of filter-feeding shark, according to non-profit conservation group Oceana.

Unlike other large sharks, whale sharks—which have a life expectancy of between 70 and 100 years—are thought to give birth to hundreds of very small babies, however, this process has never been directly observed. The animals are found in tropical oceans all over the world, often travelling large distances to abundant food sources, such as plankton blooms or a mass spawning of fish.

Whale sharks are under threat from hunting—the animals are harvested for their fins, oils, meat and other body parts—as well as ship strikes that occur during their long migrations.