The waters around the island of Holbox are one of the few areas on our planet, where whale sharks are frequent visitors. Every year, although usually solitary, whale sharks congregate here between June and September, when the ocean becomes especially plankton rich. As predictable whale shark aggregations are very rare, they are extremely valuable for researchers to study the world’s largest fish and for the local community of Holbox eco tourism has become one the most important activities in recent years.

Sharks and rays, known collectively as elasmobranches, have skeletons made of cartilage. Sharks’ origins are not well known and few fossil records exist to tell their story, yet they are believed to have evolved around 350 million years ago.

The whale shark, Rhincodon typus, is a slow filter feeding shark that is the largest living fish species. This distinctively-marked shark is the only member of its genus Rhincodon and its family, Rhincodontidae. The whale shark is found in tropical and warm oceans and lives in the open sea; it is thought to have evolved around 200 million years ago.

The whale shark reaches 20 mt, although the most accurate measurement made is 14/15 m. Whale sharks feed on a variety of tiny animals including zooplankton, thimble jellyfish, baitfish and squid. The whale shark is ovoviviparous, where the young develop in eggcases in the uterus and are then born live. Although sharks in general produce very few young compared to bony fish, whale sharks have been known to produce an estimated 300 live young in one litter. Although no one knows how long they live or where they reproduce, they are thought to reach sexual maturity at about 30 years of age, or when they reach close to 30 ft/9-10m in length, and may live beyond 100 years old. World population estimates are unknown but they are thought by shark scientists to be very low.