Whale shark

About the Whale shark

It may come as a surprise that an animal as big as a school bus depends on some of the smallest creatures in the ocean to survive. But being the largest fish in the ocean (and the largest non-mammal vertebrate in the world) is just one of the surprising things about the whale shark.

Gliding peacefully through tropical surface waters, whale sharks open their large, flat mouths to filter huge quantities of zooplankton, fish larvae, and even small fish through sieve-like pads inside their gills. Unlike other large filter-feeders (like the basking shark), the whale shark also actively vacuums up water by rapidly opening and closing its mouth and expelling water through its gills. Some whale sharks migrate vast distances and seem to time their visits around the annual phytoplankton bloom or fish spawning events off of continental shelves.

Genetic analysis shows two distinct populations of whale sharks living in the Atlantic and the Indo-Pacific Oceans. These majestic creatures are most commonly found in areas where water temperatures exceed 21˚C (70˚F) but they have been spotted as far north as the Bay of Fundy and the Sea of Okhotsk.

While much of their food is found in the upper ocean, whale sharks are known to dive deep into the twilight zone. One study, on tagged whale sharks in an Indonesian bay, found the animals dove as deep as 1,800 meters (6,000 feet). These “extreme” dives make scientists think whale sharks visit the middle ocean for reasons other than food—perhaps to cool down, remove parasites, save energy, or even to calibrate their internal navigation. Whatever the reason, the unique star-like patterns on their sides (which kind of look like bioluminescent lights) allows researchers to identify individuals from underwater photographs while a white underside may help these gentle giants blend in as they cruise through the twilight zone.