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Whither whale sharks? What 9-year study reveals so far about mammoth fish.

One tidbit is that the plankton-eating whale sharks like to feed in waters northeast of the Yucatán Peninsula. The study's aim is to learn the species' migration patterns in the western Atlantic region.

By Staff writer / August 22, 2013

A whale shark swims looking for food off the coast of Tan-awan, Oslob, in the southern Philippines island of Cebu, in March.

David Loh/Reuters

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Hundreds of whale sharks can't be wrong: Dine off the northeast tip of the Yucatán Peninsula.

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In what may be the largest study of its kind globally, and certainly the largest for the western North Atlantic region, researchers have tracked the travels and travails of these enormous sharks to and from feeding grounds off Mexico's state of Quintana Roo – a whale-shark hot spot that the scientists describe as one of the most important population centers in the world for the species.

Over nine years, scientists tracked the sharks as they spread throughout the Gulf of Mexico, the Caribbean, and out through the Florida Strait after the Quintana Roo's offshore diner shuts down at summer's end. One adult female, dubbed Rio Lady, ventured as far as the central South Atlantic off the coast of Brazil. In 150 days, she covered just shy of 4,500 miles as the crow flies – but far more as the fish swims – before she shed her tracking tag. There, the researchers suggest, she may have given birth to pups.

The scientists also note that a significant number of whale sharks bear scars from collisions with boats, raising concerns that collisions with larger vessels that ply the shipping lanes off the coast may be killing some of these creatures.

Even the 2010 Deepwater Horizon blowout and subsequent oil spill may have affected these plankton-eaters.

Early in the summer of 2010, a "pulse" of sightings was reported along Florida's Gulf Coast, indicating that the whales were traveling much closer to shore than they typically do, notes the team, led by Robert Hueter, a marine biologist at the Mote Marine Laboratory in Sarasota, Fla. It remains unclear if the whales were avoiding oil and dispersants, or merely were attracted to waters rich in plankton, one of the whales' staple foods.

The study's immediate aim is to unravel the mysteries behind whale-shark migration in the western Atlantic region. This study and comparable ones around the globe are aimed at preventing the sharks from slipping into further trouble on the International Union for Conservation of Nature's conservation-status list. Whale sharks are listed as vulnerable – the lowest of three levels within the IUCN's "endangered" category.

Until about 10 years ago, whale sharks were targets for commercial fishermen in parts of Asia. They reportedly are still hunted in the region, although much less intensively.

Concerns over the sharks' future stem from the length of time it takes for them to reach reproductive maturity, about 30 years. They also stem from increasing coastal development, which can introduce pollutants to the whales' feeding grounds.

Even ecotourism, a key reason for conserving the fish, represents a mixed blessing. Snorkeling tourists visiting whale-shark feeding grounds can help researchers by photographing the fish or noting the information on tracking tags and passing any photos or other information back to scientists. But the boat traffic can get so heavy that it may affect whale-shark behavior.

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