Blue Zoo: Whale Shark


Featuring one amazing marine animal per week.

The whale shark (Rhincodon typus) is a shark (not a whale!) and it’s the largest fish in the world.

Divers in Cocos Island are joined by a huge, but gentle, whale shark. Photo by Shmulik Blum. 

These massive sharks can grow to 40 feet (12 m) long and can weigh around 27,550 lbs (12,500 kg). As enormous as these animals are, they aren’t at all ferocious. They got the confusing name “whale shark” because of their massive size, and because they eat by filter feeding like whales do.  They swim slowly through the water holding open their big mouths, catching tiny fish and plankton for food. There are two other species of sharks that feed the same way: the basking shark and the megamouth shark

Whale sharks eat plankton by filtering water while they swim. Photo by Shmulik Blum.

Whale sharks migrate long distances and can be found in tropical waters all around the world. Although they can dive to deeper than 1,000 m (3,280 feet), where the water may be as cold as 3oC (37.4oF), they usually spend their time in warm water, near the surface.

Whale sharks usually travel alone but sometimes gather in large groups. Individual whale sharks are often accompanied by many smaller fish. Since they’re so big and fairly slow, whale sharks act like a moving “reef” for these fish, which live around it.

A passing whale shark spotted during a deep dive in a submersible. Photo by Shmulik Blum.

While very little is known about these sharks otherwise, it is known that whale sharks are vulnerable to overfishing. Their meat is highly valuable in some places in Asia. Since they live for a long time and are slow reproducers, they don’t rebound easily from exploitation.

The species is listed by IUCN as Vulnerable, and is on the CITES list of species for which trade should be regulated due to conservation concerns.Many other organizations also recognize whale sharks as being at risk.

Photo by Shmulik Blum.

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