WHAT IS THE BIGGEST FISH IN THE WORLD?

If you are talking about fish - and definitely don't mean to include whales - then the answer is easy as there is only one contender, the Whale Shark - Rhincodon typus.

However, unlike the sharks you would normally think off, the whale shark is almost completely harmless. Why? Because the largest fish (and therefore the largest shark) in the world alive today is a slow-moving filter feeding shark. The largest confirmed individual was 12.65 metres (41.50 ft) in length and the heaviest weighed more than 36 tonnes (79,000 lb), however there have been unconfirmed claims reports of considerably larger whale sharks. The whale shark is found in tropical and warm oceans, lives in the open sea with a lifespan of about 70 years.

Originating from about 60 million years ago, they feed mainly, though not exclusively, on plankton, microscopic plants and animals. However, the BBC program Planet Earth filmed a whale shark feeding on a school of small fish.

Largest freshwater fish

But if you want to know what is the largest freshwater fish then it's a different story as Whale sharks are only found in the ocean. The biggest freshwater fish in the world is the Giant Mekong catfish - Pangasius gigas.

The biggest one ever captured and measured was caught in Thailand in May of 2005. It was 9 feet long and weighed 646 pounds.

Unfortunately the Mekong catfish is in decline and although research projects are currently ongoing, relatively little is known about this species. Historically, the fish had a natural range that reached from the lower Mekong in Vietnam (above the tidally influenced brackish water of the river’s delta) all the way to the northern reaches of the river in the Yunnan province of China, spanning almost the entire 4,800 km length of the river. Due to threats, this species no longer inhabits the majority of its original habitat. It is now believed to only exist in small, isolated populations in the middle Mekong region.

But what about the sturgeon?

This is a good question because as a freshwater fish the beluga sturgeon (Huso huso)  it is considerably larger than the Giant Mekong catfish measuring a hugely impressive 24 ft long and weighing in at 3,250 lb.

The trouble is that  it doesn't count as sturgeons are not truly freshwater fish as they also spend a great deal of time in brackish water and as well as switching between saltwater and freshwater during their life cycle. Unless of course you want to know what the world's largest brackish fish is, but then where do you stop?

For related articles click onto the following links:
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WHAT IS THE BIGGEST FISH IN THE WORLD?
WHAT IS THE WORLD'S FASTEST FISH?
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