# Rainbow Trout (*Oncorhynchus mykiss*)

> Rainbow trout are salmonid fish native to Pacific North America, named for the pink lateral stripe along silver sides. Stocked worldwide for sport fishing and aquaculture, they grow to 50 cm or more in rivers, leap at flies, and include steelhead populations that migrate to sea before returning to spawn.

- **Category:** Fish
- **Conservation status (IUCN):** Least Concern
- **Range:** Pacific drainages from Alaska through California and inland to Idaho and Nevada; introduced worldwide for sport fishing and aquaculture.
- **Canonical page:** https://globalanimalguide.org/animals/trout/
- **Last reviewed:** 2026-07-16

## Scientific classification

- **Kingdom:** Animalia
- **Phylum:** Chordata
- **Class:** Actinopterygii
- **Order:** Salmoniformes
- **Family:** Salmonidae
- **Genus:** Oncorhynchus

## Facts at a glance

| Attribute | Value |
| --- | --- |
| Scientific name | Oncorhynchus mykiss |
| Diet | Carnivore — insects, crustaceans, and small fish |
| Habitat | Cold rivers, lakes, and streams; anadromous steelhead in coastal rivers |
| Lifespan | 4–11 years in the wild (varies by population) |
| Weight | 0.5–9 kg (1–20 lb); steelhead and lake fish larger |
| Top speed | Strong swimmer; leaps waterfalls during spawning runs |
| Conservation status | Least Concern (IUCN) |

## Fly fishing icon

Rainbow trout rise to dry flies on the surface, making them the quintessential fly-fishing species. Clear mountain streams of the American West — Montana, Idaho, Colorado — built a global angling culture around wild rainbow and cutthroat trout.

## Steelhead life history

Some coastal populations ('steelhead') migrate to the ocean and return to natal rivers to spawn, growing larger and more silvery than resident river fish. Dams, water extraction, and warming streams threaten these anadromous runs across the Pacific Northwest.

## Global stocking

Rainbow trout have been introduced to every continent except Antarctica for food and sport. They can hybridise with native trout and outcompete local species, making introductions controversial in places like New Zealand, Chile, and the Appalachian Mountains.

## Aquaculture and wild genetics

Farm-raised rainbow trout supply supermarkets worldwide. Hatchery supplementation of wild streams raises questions about genetic dilution of native strains. Wild populations in the Pacific Northwest remain the evolutionary heartland of the species.

## Frequently asked questions

### Rainbow trout vs salmon?

Rainbow trout are in the same genus as Pacific salmon. Steelhead are sea-run rainbow trout. Salmon typically die after spawning; many trout survive to spawn again.

### What is a steelhead?

A rainbow trout that migrates to the ocean and returns to freshwater to spawn — larger and more silvery than river-resident rainbows.

### What do rainbow trout eat?

Aquatic insects, terrestrial insects that fall on the water, crustaceans, and small fish — diet shifts with size and habitat.

### Where are rainbow trout native?

Pacific drainages from Alaska through California and inland to Idaho and Nevada — not the eastern United States, where they are introduced.

### How big do rainbow trout get?

Stream fish often 30–40 cm; lake and steelhead forms can exceed 90 cm and 9 kg in rich waters.

## Sources

- [IUCN Red List — Oncorhynchus mykiss.](https://www.iucnredlist.org/search?query=Oncorhynchus%20mykiss&searchType=species)
- [Animal Diversity Web — Oncorhynchus mykiss. University of Michigan Museum of Zoology.](https://animaldiversity.org/accounts/Oncorhynchus_mykiss/)

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Source: Global Animal Guide (https://globalanimalguide.org/animals/trout/). Licensed CC BY-NC 4.0 — free for non-commercial reuse with attribution.