Encountering rare whale sharks

Miami HeraldAugust 14, 2013 

When a diver or angler encounters a whale shark in southeast Florida’s offshore waters, the incident is rare enough to be news. It’s even better if the observer is lucky enough to shoot photos or video of the world’s largest fish.

About 500 miles away, in the Gulf and Caribbean waters off Mexico’s Yucatan Peninsula, swims the largest aggregation of the giant brown creatures with white polka dots known to science. From late May to early September, hundreds of whale sharks – which grow to 45 feet – glide slowly near the surface with their front-end loader maws gaping wide, sucking up zooplankton that consists mostly of the spawn of the little tunny, known as the bonito. A few manta rays often join the party, as do gaggles of wide-eyed tourists from around the globe.

The phenomenon drew little public attention until about 10 years ago when Bob Hueter, director of the Center for Shark Research at Sarasota’s Mote Marine Laboratory, described it in a research paper. Then fellow shark researchers, vacationers and videographers began flocking to the Gulf waters off tiny Isla Holbox and the Caribbean off Isla Mujeres to jump in the water with the gentle giants.

What began as a sort of ecotourism cottage industry employing a few dozen commercial fishermen as guides has grown exponentially, with more than 240 vessels conducting as many as 18,000 passengers per year on whale shark snorkeling excursions. While there are no current figures available on the industry’s economic impact to Mexico, a recent study in nearby Belize (where the sharks do not show up as frequently) found each animal is worth about $35,000 annually in local ecotourism revenues and about $3.7 million annually to the country’s economy.

Snorkeling alongside slow-moving, behemoth whale sharks and mantas is heart-poundingly exciting. It can be a little too exciting when seas are rough and a couple hundred boats are idling around, jockeying for position to unload their passengers into the water close to the large animals. The hustle-bustle seems to drive the sharks deeper where they can not be seen as easily. Best viewing is early morning on calm days with no rain when the sharks don’t seem as bothered by human interlopers and remain near the surface for long periods.

The upside of the Yucatan region’s whale shark tourism industry is that local residents are making money, and the creatures are not killed for consumption. The downside, according to Hueter, is that the burgeoning number of admirers could end up loving them to death.

Hueter applauds the Mexican government and conservationists for implementing a code of conduct for whale shark encounters. For example, there is no touching or chasing; the use of scuba gear or flash photography is prohibited; only one guide and two tourists from each boat may interact with a whale shark at one time and they must keep at least six feet away.

“The key to these things is not to overdo it and keep control over it,” Hueter said. “The rules, if you stick to them, are good. But they seem to have difficulty limiting the number of boats. On top of that, you have private boats and interlopers who don’t have licenses. Ecotourism is regulated but not controlled. The concern is all this activity will drive these animals off their feeding grounds. This is a very important gas station for whale sharks. It’s very worrisome.”

Hueter and colleagues have tagged more than 800 whale sharks in the Yucatan with conventional tags since 2003. Another 35 are equipped with satellite tags that precisely track their movements. The researchers have compiled a photo database of more than 950 whale sharks that identifies each individual by spots, prop scars and other features.

What the scientists have learned is that the 1,000 to 1,500 animals that show up each season spread out all over the western and northern Gulf of Mexico and disperse to the Florida Straits and southern Caribbean. One female tagged in 2007 headed to the South Atlantic between Brazil and Africa.

In 2008, the Mexican government established a whale shark biosphere reserve off the Yucatan, but the animals refuse to stay within its boundaries.

Hueter proposes increasing the size of the reserve, setting limits on the number of boats permitted to conduct whale shark tours, and strengthening and enforcing the code of conduct. He also recommends the Mexican government work with the maritime industry to move shipping lanes away from sharks, mantas and other surface swimmers.

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