The attraction to Holbox is whale sharks, Rhincodon typus, the world’s largest living fish.  How Big Are They?  While stories of whale sharks as large as 70 feet or more exists, the largest verifiable record is 40 feet with an approximated weight of 30,000 pounds. Most of the ones we saw were probably closer to 20 feet, and we may have seen one approaching 30 feet.

Little is known about this gentle giant, but studies are now under way in many places where they are found to aggregate including off the coast of Belize, the Yucatan of Mexico, and Honduras.  Tagging, photo identification, and placement of satellite transmitters are the tools now being used to unravel the mysteries that surround this animal, and will allow us to understand their migrations, their population status and their behavior.

But the rich planktonic waters attract other filter feeders too.  Out in the waters made green and red by different species of plankton, we found dozens of giant manta rays, Manta birostris, many with wingspans exceeding 12 feet, and schools of Cownose rays, Rhinoptera bonasus, a small ray that seemed to be flying through the water in formation.  Devil rays, Mobula mobula,r looking a lot like smaller versions of mantas were also abundant.
The guided experience inside the marine protected area was very nice.  Our guides, licensed by the Mexican government were very conscientious, making sure no one touched a whale shark and preventing visitors from coating their bodies with sunscreen that could harm the marine wildlife.  The Park Guard boat was present numerous times, and though carrying US researchers, its presence no doubt kept visitors on their best behavior.

But on our second trip out, no Park Guard vessel was present, and some tourists could be seen touching and even “riding” the whale sharks.  Our guide informed us that those boats were not licensed,  and not from Holbox, but had come from Isla Mujeres or possibly from Cancun.

Another problem-more than one whale shark was seen to have a ragged dorsal fin, probably the result of propeller cut.  Too many boats and too many visitors is an issue that will have to be carefully monitored and controlled to ensure the safety of the marine species.