Steelhead vs Rainbow Trout: What’s the Difference?

Rainbow trout and steelhead are the same species, Oncorhynchus mykissquite. They are to distinguish from each other as they look very similar but they lead very different lives.

Join me as we compare steelhead vs rainbow trout so that you can target them more effectively when fly fishing, identify each species easily and assist in protecting their natural habitat.

Rainbow Trout And Steelhead Life Cycle

Rainbow Trout vs Steelhead – Life Cycles

Freshwater rainbow trout and steelhead belong to the same trout species, Oncorhynchus mykiss, and genetically both fish, being part of Oncorhynchus mykiss are identical and they start their life in the same way too.

Steelhead, rainbow trout, salmon, and almost all other types of trout and salmon are born in the same way. They hatch from eggs laid by older spawning fish in rivers, streams, and lakes.

For the first year of their lives, both rainbows and steelhead spend their time in the river, stream, or lake they were born in and feed on insects just like normal rainbow trout, sipping dry flies off the surface and eating nymphs.

After having spent around 1-3 years in their river, lake, or streams, a switch flips and some of the rainbows decide to leave freshwater and migrate out to sea, becoming a steelhead and anadromous, like a salmon.

This is the key difference between a steelhead and a rainbow trout, a steelhead has decided to leave fresh water and live in saltwater whereas true rainbows will stay in freshwater for their entire lives.

Why Do Steelhead Leave For The Sea?

Scientists are still in search of why rainbow trout leave the rivers, lakes, and streams and head for the sea. They don’t know whether it’s an inbuilt genetic reaction or due to environmental factors.

My personal opinion, and the opinion of a lot of fly fishing anglers around the world, is that the reason rainbow trout migrate to the sea is that there isn’t enough food in the freshwater system they live and their search for food takes them to saltwater where food is far more abundant.

This is excellent if you’re into fly fishing, as steelhead like salmon, grow far bigger feeding in the Pacific ocean than they ever would by staying in the freshwater rivers, and lakes, eating insects in the streams they started in.

An average rainbow trout might grow to be 2-4 pounds whereas a steelhead trout can grow more than 20 pounds, depending on how long they have spent in the ocean.

How long do steelhead spend in the ocean

How Long Do Steelhead Spend in the Ocean?

Steelhead generally spend between one and five years at sea before returning home to spawn in the freshwater they started in. The longer the steelhead spends in the ocean the bigger the fish get and in the fly fishing world are split into categories.

  • “One Salt” fish migrate back to freshwater to spawn after a year in salt water and if you catch them at this point they will be about 2-6 pounds, depending on how much they have eaten in the ocean.
  • Two salt fish spend around two years in the ocean before returning to freshwater to spawn and usually weigh around 10 pounds.
  • Three to five salt fish are the largest of the species and usually weigh around 20 lbs and up to 40 lb fish are also possible.

What Steelhead Do After They Spawn?

Once these anadromous rainbow steelheads migrate back for spawning season they will lay their eggs in gravel and either remain anadromous and head back to the sea for another season or two of feeding but return for spawning season again.

Others decided not to go back to the slat and stay in freshwater and live the rest of their lives there. Steelhead does not die after spawning like salmon, all steelhead will be spawning up to 6 times in their life, whereas only 2% of salmon are repeat spawners.

difference between a steelhead and a rainbow trout

How to Distinguish Between Steelhead and Rainbow Trout

Working out whether the fish you have just caught while fly fishing is a steelhead or rainbow trout isn’t easy. The fish look extremely similar but there are a few tell-tale signs and tips that can help with identification.

  • Generally, the first thing anglers should look at is the size of the fish. Steelhead, as we now know, are a lot bigger than rainbow trout and if you catch a fish over 2 lbs or 26 inches in length, chances are it’s a steelhead. Average rainbows are 12 inches in length so a fish of 26 inches is a rare catch, and is most likely a steelhead.
  • Steelhead tends to develop a rainbow line or stripe down the middle of their body which is far deeper in color and larger in size than the rainbow line that rainbow trout form.
  • Another way to identify a steelhead is by looking for a silvery sheen on its body. Fish that are fresh from the sea will be much more silvery than fish that have been in the river for a while. So this is only a noticeable difference if the fish are fresh out of salty water.
  • A very easy difference top spot between these two types of fish is that male steelhead will develop a kype when it’s time to spawn which is a kind of hook-shaped lower jaw, whereas male rainbow trout will not.
Where are steelhead found in the world

Where Are Steelhead Found in the World?

Steelhead is only found on the Pacific coast of America and you can find these fish in California. Steelhead is also found in British Columbia, that’s one of the reasons why you should also consider BC fly fishing.

For some reason, despite being found all over the planet in rivers, it’s only in these locations where rainbow trout decided to go to sea and become steelhead trout.

In the fly fishing world, you like to hear about the steelhead that lives in the great lakes but it’s a contentious issue as to whether these great lakes steelhead are steelhead at all.

Rainbow trout were introduced to the great lakes, grow to be larger than the average size of rainbow trout, and migrate into the rivers from the great lakes to spawn every year which is why they got the name steelhead. The difference is, that these rainbow trout, or “steelhead trout”, never go to sea meaning they are not anadromous.

If you want to start a good fishing debate at the dinner table, especially if you have some east coast fishing enthusiasts at the table, pose the questions as to whether the great lakes steelhead are just rainbows.

From a scientific and ecological perspective, a rainbow trout is only a steelhead if it migrates to the ocean and I wholeheartedly agree with this.

All trout that live in a lake have to move into a river to spawn, so all the rainbow trout in the great lakes doing this aren’t doing anything different from a normal tout, so they are not steelhead trout.

Why are they called steelhead

Is The Steelhead Population Declining?

Local fisheries across the western US have noticed a significant drop in the population of steelhead and this is mainly due to damming the water for hydroelectric purposes which means steelhead can’t migrate up the rivers to their spawning grounds. You can help by acting and joining to protect these fish by petitioning against dams and asking for current ones to be removed.

Do Rainbow Trout and Steelhead Eat the Same Flies?

To a point, these fish eat the same flies but when fishing for steelhead you will probably be swinging steelhead flies, orange or other color streamers and not fishing dry flies on the surface of the water. But, being trout at their core, steelhead trout might take a fly off the surface from time to time, as a salmon does rarely too.

Does Steelhead Taste Like Rainbow Trout?

This is kind of like asking if salmon taste like trout and the answer is no. Fish tend to taste differently depending on the water they live in and thus their diet. Since rainbow trout stay in freshwater eating insects and steelhead go to the ocean and eat crustaceans, they taste very different. Steelhead tastes a lot more like salmon than they do trout. Whereas a rainbow trout tastes, well, like a trout.

Why Are They Called Steelhead?

These fish got their name because when they return from the salt the fish are extremely silvery and thus look a bit like steel. You will have heard of them and salmon being referred to as chrome which is for the same reasons. So the name comes from them looking a bit like steel instead of spotted and darker like a rainbow trout.

Photo of author

Jamie Melvin

Growing up fly fishing on trout streams in Kenya and the UK, Jamie has traveled the world in search of fly fishing nirvana. From his time managing bonefish lodges in the Bahamas and running fishing safaris in East Africa, all the way to guiding on the flats of Seychelles, there aren't many species or environments he hasn't experienced firsthand.

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