Rainbow Trout Vs. Steelhead – The Difference

Genetically, Rainbow Trout and Steelhead are the same species, Oncorhynchus mykiss (O, mykiss), but both fish live vastly different lives. The most basic difference between both fish is quite simple; rainbow trout reside and always stay in freshwater, while steelhead are anadromous, meaning that they migrate to the ocean.

To make this a little more confusing, these trout are also often considered steelhead when they migrate from lakes to rivers to spawn. The best example of this is in the great lakes where the “steelhead” are completely freshwater fish, but they live in the lake, and spawn in the connecting rivers. (All, if not nearly all of the successful reproduction of these fish is due to fisheries, and not natural spawning).

Scientists are still puzzled to this day as to what causes these fish to be anadromous vs freshwater dwelling. Some theories and correlations have arisen:

  • Steelhead have higher metabolic rates
  • Food availability seems to be a factor. Areas with high food availability will have less anadromous fish as there is no need to migrate.
  • When water is cold, summer water flows stay high, and food availability is high, there tends to be less migrating fish.

There are known different strains of rainbow trout, some of which appear to have a better likelihood of being anadromous.

Physically, steelhead get much larger than rainbow trout. This is shown in more detail below.

Rainbow Trout

Size

Adult freshwater stream rainbow trout average between 1 and 5 lb (0.5 and 2.3 kg)

Rainbow Trout

Rainbow Trout from South Western Montana

Steelhead

Size

Adults average between 8-11 pounds (3.6-5.0 kg), but can get as large as 40 pounds (18.1 kg)

Spawning

During the spawning season from January through April, female steelhead build redds (gravel nests) at the top of a riffle and lay their eggs. Generally, the young fish will stay in the streams for years, grow large enough, and head out to sea. From this point, the trout spend 1-4 years growing in the sea before returning to spawn.

Steelhead are very closely related to salmon, but they are able to spawn, and continue spawning, unlike salmon, which spawn and die.

Rainbow Trout Head

Fishing for Steelhead

Fishing for steelhead vastly varies depending on where you are in the world. It is notoriously one of the favorite fish for fly anglers to target in winter months (for those bold enough to fly fish in the winter).

Generally speaking, steelhead require larger rods, and you will see many anglers with two handed rods for swinging large flies. A nymph and indicator rig is also a common method for targeting steelhead.

Non fly fishing techniques are also used frequently.

Fishing for Rainbows

Rainbows, being smaller, enable anglers to use lighter rods. Generally, a 5 weight rod will be able to handle most all rainbow trout situations. They are targeted with just about every fly fishing technique, and are located nearly everywhere in the world.

Whatever species you are targeting, you are sure to have an amazing time. Rainbow and steelhead are both beautiful fish.

Looking to get into fly fishing? Check out our post about the best beginner fly rod and reel combos. Or our complete guide to fly fishing for beginners.