What’s the Biggest Trout on Earth? You Might Be Surprised

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Man standing in the river holding a big trout.

The largest trout on earth are found swimming in the rivers from the Mongolian steppe north to Siberia. This trout is called a taimen, and these behemoths can grow to six feet long and weigh over 100 pounds. 

The brown trout, a native to Europe, has been introduced all over the world, and it gets very big. But it’s not the largest trout on earth. 

From the bow of a drift boat, I cast a long, yellow Clouser Minnow across upstream and across the river, letting the current grab the line and swing it through the deep water. 

It didn’t take long. In mere seconds, I was hooked up to the biggest trout of my life.

The trout — a massive Patagonian brown — rocketed down the river, pulling fly line and backing from my reel. I tightened my drag and slowed the big fish’s retreat. 

We engaged in a tug-of-war that lasted a good 20 minutes, but, with the help of my guide for the day, Peter, we brought the big trout to hand. 

The brown stretched the tape to 27 inches (almost 70 centimeters). At the time, it was my trout of a lifetime. 

The next day, on the Rio Limay in northern Patagonia, my buddy caught a brown that measured a full 30 inches (76 centimeters). It was the biggest trout I ever laid eyes on. 

But, while brown trout get very big, they are not the biggest trout on earth. That distinction belongs to the taimen, a trout that lives from the Mongolian steppe north into Russian Siberia. It is the biggest trout on the planet. 

A Behemoth From Central Asia

Mongolia's Taimen Fishing: A Big Adventure!
The taimen, a trout that lives in Mongolia and Siberia, is the largest trout on earth.

The taimen is a massive trout that has captured the imaginations of anglers all over the globe. It swims in rivers in Mongolia and Siberia. Taimen can grow to lengths of six feet and weigh more than 100 pounds

Taimen are found nowhere else on earth. If you want to catch one, you need to go to Mongolia and book a fishing trip. There, you can fish the rivers where these massive trout live. If you’re really lucky, you might even catch one. 

And, you might be surprised what you use to catch a taimen. In Mongolia, you’re only allowed to fish for taimen with fly fishing equipment. And the flies? They look more like rodents than they do like insects

Other Big Trout

Man holding the Sea trout above the water.
Sea trout are ocean-going brown trout. These giant fish are native to the North Atlantic and swim into the rivers from the British Isles to Scandinavia.

Brown Trout

Certainly, other species of trout can grow quite big. Brown trout can get absolutely massive, The world record for brown trout is 44 pounds, 5 ounces. It was caught in 2021 in a hydro canal in New Zealand. It measured 38.58 inches (almost 98 centimeters) long.

Some browns run from rivers into the sea, and these “sea trout” can get very big. In Iceland recently, I was fortunate enough to tangle with a sea trout that measured just over 30 inches (77 centimeters). 

But, even at this size, the brown trout doesn’t rival the taimen for sheer size. 

Rainbow Trout

Rainbow trout grow quite large, and steelhead trout — ocean-going rainbows — get even bigger.

The rainbow trout is prized by anglers all over the world. But, while it can get quite big, it doesn’t grow as big as a taimen. 

Like brown trout, some rainbow trout in coastal environments swim to the sea and come back to freshwater rivers to spawn. These ocean-going or “anadromous” rainbows are called steelhead trout. Steelhead, like sea trout, get very big.

But they don’t grow to the lengths that taimen do. 

What About Lake Trout?

Lake trout swimming under water.
Lake trout are actually a char, not a true trout. They get big, but not as big as taimen.

Lake trout grow to gargantuan lengths. Native to the boreal lakes of Canada, lake trout are prized by anglers of all stripes. But, did you know that lake trout aren’t really trout? Lake trout are a subspecies of char, like brook trout, bull trout, Dolly Varden and Arctic char

If you want to catch lake trout, your best bet is to visit lakes in Canada or the northern United States, where they’ve been introduced. You’ll likely need to fish deep with cutbait or troll big lures using a downrigger. Many anglers catch big lake trout while ice fishing, which can be very effective. 

It’s possible to catch lake trout on fly-fishing gear, in some places. But lakers tend to be deepwater fish, which makes fly fishing for them very challenging. 

Final Thoughts

There are many subspecies of trout that get very big. But the biggest trout swims in Mongolia and Siberia. Taimen are massive fish. If you want to catch a taimen, you need to book a trip to Mongolia or Siberia. They are found nowhere else in the world.

Other trout get big, too. Sea trout and steelhead can get very big over the course of their lives. Some species of char, like lake trout, can get very big, too. But char and trout, while both salmonids, are different from one another. 


What’s a Clouser Minnow?

A Clouser Minnow is a fly tied to imitate a baitfish. It’s named for its creator, renowned saltwater angler Bob Clouser of the United States. 

What Does “anadromous” Mean? 

Anadromous is Greek in origin, and it is applied to fish that migrate up rivers from the ocean to spawn. Salmon are anadromous, as are some species of trout (sea trout and steelhead). Arctic char and some brook trout are anadromous, too. 

Are Taimen Anadromous?

No. Taimen live only in freshwater rivers of Mongolia and Siberia. There are subspecies of taimen that live in some waters in eastern Europe, but they don’t get as big, and they, too, only live in freshwater.

Why Are Brown Trout Found All Over the World?

Brown trout are native to Europe and western Asia and a few high-elevation streams in the Atlas Mountains of north Africa. They have been introduced on all other continents except for Antarctica. They are prized by fly fishers from New Zealand to Patagonia and to the United States and southern Canada. 

Like brown trout, rainbow trout and brook trout (a subspecies of char) have been introduced around the world, too.

What’s the difference between a char and a trout? 

Trout and char are related. They are both members of the family Salmonidae, but they belong to a different genera. Trout belong to the genera Oncorhynchus and char belong to the genera Salvelinus

How can you tell trout and char apart?

Trout generally have light bodies and dark spots. Char, on the other hand, have lighter spots on darker bodies. 

Why do some brown and rainbow trout run to the sea?

Nobody, not even scientists, really knows why some rainbow trout run to the ocean and become steelhead. Genetically, rainbows and steelhead are identical. So, too, are brown trout and sea trout. The reason these fish migrate to the ocean? It’s one of life’s great mysteries. 

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