The Biggest Shark

The largest fish in the sea is a shark. It’s the size of a bus, and it eats plankton.

Meet the whale shark. It’s not a whale — it’s a shark, and it’s the biggest fish alive today. Most adults grow to around 10 to 12 metres long, roughly the length of a city bus, and the largest one reliably measured stretched to about 18 metres. Bigger ones are sometimes reported, but they’re hard to confirm.

For all that size, a whale shark is a gentle filter feeder. It swims with its enormous mouth open, taking in plankton, tiny fish and fish eggs, and strains the food out through its gills. Its mouth can be more than a metre wide, but its throat is surprisingly narrow — nothing about it is built for eating anything big.

Despite its fame, the whale shark keeps plenty of secrets. It’s a slow swimmer and a long-distance traveller, crossing whole oceans, and scientists are still working out exactly where it goes and how long it lives.

Second place, and the ghost of the biggest

The runner-up for largest fish is the basking shark, another filter feeder, which can reach around 12 metres. It looks a little like a floating submarine with a mouth you could nearly walk into.

And the biggest shark that ever lived? That title probably belongs to megalodon, an extinct giant estimated at somewhere between 15 and 18 metres. But megalodon lived millions of years ago — it’s a fossil, not a neighbour. The biggest shark you could actually meet today is the whale shark, munching plankton and minding its business.

So the next time someone says the ocean is full of monsters, you can tell them the biggest shark in it eats some of the smallest food in it. That’s the real story.

Did you know? Whale sharks have a pattern of spots on their skin that is unique to each one. Scientists use it like a fingerprint to tell individuals apart.