What Is the Largest Fish?

Divers with whale shark

 Michael Aw / Getty Images

The largest fish in the world is a shark - the whale shark (Rhincodon typus).

The whale shark can grow to about 65 feet long and weigh up to 75,000 pounds. Imagine encountering this huge animal in the wild! Despite its huge size, though, whale sharks are pretty gentle. They move relatively slowly and feed on tiny plankton by sucking in water and filtering it through their gills and pharynx. These giants have over 20,000 teeth, but the teeth are tiny and thought not to even be used for feeding (you can see a photo of a whale shark's teeth here.)

Whale sharks have beautiful coloration - their backs and sides are bluish-gray to brown and they have a white belly. What's most striking about these sharks is their white spots, which are arranged among pale, horizontal and vertical stripes. This pigmentation pattern is used to identify individual whale sharks and learn more about the species.

Where Are Whale Sharks Found?

Whale sharks are found in warmer temperate and tropical waters and are widespread - they live in the Atlantic, Pacific and Indian Oceans. Diving with whale sharks is a popular activity in some areas, including Mexico, Australia, Honduras, and the Philippines.

Whale Sharks Are Cartilaginous Fish

Whale sharks, and all sharks, belong to the group of fish called the cartilaginous fish - fish that have a skeleton made of cartilage, rather than bone. Other cartilaginous fish include the skates and rays.

The second-largest fish is another plankton-eating cartilaginous fish - the basking shark. The basking shark is sort of a cold-water version of the whale shark. They grow to 30-40 feet and also feed on plankton, although the process is a little different. Instead of gulping water like whale sharks, basking sharks swim through the water with their mouths open. During this time, the water passes into the mouth, and out the gills, where gill rakers trap the prey.

The Largest Bony Fish

The cartilaginous fish is one out of two main groups of fish. The other is the bony fish. These fish have skeletons made of bone, and include fish such as cod, tuna and even seahorses.

The largest bony fish is another ocean dweller, although it is much smaller than the largest basking shark. The largest bony fish is the ocean sunfish (Mola mola). Ocean sunfish are a strange-looking fish who appear as if the back half of their body had been cut off. They are disk-shaped and have an unusual back end called a clavus, rather than a tail.

Ocean sunfish can grow over 10 feet across and weigh over 5,000 pounds. If you're a fisherman, though, don't get too excited - although in some areas, ocean sunfish are considered a delicacy, many consider these fish inedible and some even say their skin contains toxins, making them unsafe to eat. On top of this, these fish can host up to 40 different kinds of parasites (yuck!).

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Kennedy, Jennifer. "What Is the Largest Fish?" ThoughtCo, Feb. 16, 2021, thoughtco.com/what-is-the-largest-fish-2291876. Kennedy, Jennifer. (2021, February 16). What Is the Largest Fish? Retrieved from https://www.thoughtco.com/what-is-the-largest-fish-2291876 Kennedy, Jennifer. "What Is the Largest Fish?" ThoughtCo. https://www.thoughtco.com/what-is-the-largest-fish-2291876 (accessed March 30, 2023).

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