Head to head
Cutthroat Trout vs Rainbow Trout
The cutthroat trout and rainbow trout are close relatives within the same genus, sharing much of their range across western North America, but their relationship has become a genuine conservation problem wherever introduced rainbow trout meet native cutthroat populations.
| Cutthroat Trout | Rainbow Trout | |
|---|---|---|
| Scientific name | Oncorhynchus clarkii | Oncorhynchus mykiss |
| Throat marking | Bold red or orange slash | None |
| Native range | Widespread across the West | Originally narrower, Pacific coast |
| Introduced status | Native throughout its range | Widely introduced worldwide |
| Hybridisation risk | High where rainbow trout are introduced | High where cutthroat trout are native |
| Subspecies diversity | Numerous distinct subspecies | Fewer distinct subspecies |
| Population trend | Decreasing | Stable |
| Diet | Carnivore | Carnivore |
Cutthroat Trout vs Rainbow Trout: common questions
How can you tell a cutthroat trout from a rainbow trout?
Look at the underside of the jaw: the cutthroat trout displays a bold red or orange slash there, a feature the rainbow trout lacks entirely, though the two species can still be difficult to separate in areas where they have hybridised, since the resulting offspring can show a mix of features from both parents.
Why do cutthroat trout and rainbow trout hybridise?
The two species are close relatives within the same genus and share enough of their genetics and breeding behaviour that they readily interbreed wherever their ranges overlap, a situation that has become far more common since rainbow trout have been introduced so widely into rivers and lakes where cutthroat trout are native.
Why is hybridisation a bigger problem for cutthroat trout than rainbow trout?
Cutthroat trout exist as numerous genetically distinct subspecies, each shaped by isolation within a separate river drainage or lake basin, so hybridisation with the more widely introduced rainbow trout threatens to gradually erode that specific genetic distinctiveness, a conservation concern that does not apply in the same way to the more broadly distributed rainbow trout.