Cutthroat trout vs Rainbow trout
How to tell them apart, and what follows from getting it right.
Why they get confused
They hybridise. That is the honest answer, and it is why this pair is harder than any other on this list: in much of the cutthroat's range the fish in front of you may be genetically intermediate, and no field character will resolve it.
Cutthroat trout
Oncorhynchus clarkii — Salmonidae
Rainbow trout
Oncorhynchus mykiss — Salmonidae
The differences
Each difference is marked with how far it can be trusted on its own. A single diagnostic character settles the identification; suggestive ones only narrow it.
| Character | Cutthroat trout | Rainbow trout | Reliability |
|---|---|---|---|
| The cutthroat markIdentification | Red or orange slashes under each side of the lower jaw. | No jaw slash, though a faint mark is occasionally present and misleads. | Supporting — use with others |
| Basibranchial teethIdentification | Small teeth present at the base of the tongue, behind the tongue's main patch. | Absent — there are no teeth at the base of the tongue behind the main patch. | Diagnostic on its own |
| Flank colourIdentification | Spotting typically heavier towards the tail, with no strong pink lateral band in most forms. | Pink or red lateral band along the flank in most fish, strongest in spawning condition. | Suggestive only — varies |
| Conservation positionConservation status | Several subspecies are of serious conservation concern, and hybridisation with introduced rainbows is among the causes. | Globally secure and very widely introduced, including into cutthroat waters. | Supporting — use with others |
Why it matters
This is the one pair on the list where the honest answer is often 'cannot be determined in the field'. Where native cutthroat conservation is active, that uncertainty is the reason to treat the fish as the more sensitive of the two rather than the less.
The full records
This page compares two species. Each of them has a complete record covering biology, behaviour, handling and the evidence behind all of it.
More about cutthroat trout
Where it lives, how it is caught, and what else it is confused with.
Similar and related fish
What these connections rest on (1)
Scientific evidence — 1 connection
Supported by peer-reviewed research or fisheries science. The sources are listed and can be checked.
Rainbow trout
A comparison whose substance is the hybridisation, which is the species' principal conservation problem.
- FishBase: a global information system on fishes — Froese, R. and D. Pauly, eds. — FishBase Consortium (Scientific institute)Relied on for: That Oncorhynchus clarkii and Oncorhynchus mykiss are congeners in the genus Oncorhynchus with overlapping western North American ranges.States this directlyPassage read and verified
- Check Clean Dry — biosecurity guidance for water users — GB Non-native Species Secretariat (Conservation authority)Relied on for: That hybridisation with introduced congeners is a recognised harm in the assessment of non-native fish.FishingHQ's interpretation of what it saysPassage read and verified
How it is caught
What these connections rest on (1)
Practitioner consensus — 1 connection
Widely and independently recommended by experienced anglers and specialist sources. This is real angling knowledge, not proof: controlled evidence for it is limited, and FishingHQ records it as convention rather than as a demonstrated effect.
Dry fly fishing
A practitioner claim about relative willingness, labelled as convention.
- Freshwater Fishing — Macdonald & Jane's, 1975 (Specialist angling publication)Relied on for: Practitioner treatment of dry fly technique and of variation in rise willingness between trout species.Citation checked — the work exists and is described correctly
- Trout & Salmon — Bauer Media (Specialist angling publication)Relied on for: Contemporary practitioner treatment of dry fly fishing for western North American trout.Citation checked — the work exists and is described correctly
Gear for this fish
- Dry fliesCutthroat are noted for rising freely and unselectively to a well-presented dry, which is why they are the species most western dry-fly fishing is learned on.
- NymphsCutthroat feed on drifting invertebrates in the cold western rivers they are native to, and nymph fishing is the approach that matches their ordinary rather than their occasional feeding.
What these connections rest on (2)
Practitioner consensus — 2 connections
Widely and independently recommended by experienced anglers and specialist sources. This is real angling knowledge, not proof: controlled evidence for it is limited, and FishingHQ records it as convention rather than as a demonstrated effect.
Dry flies
A practitioner claim about which lure family answers this species' feeding or holding behaviour.
- Trout & Salmon — Bauer Media (Specialist angling publication)Relied on for: Fly categories and their application to salmonids in running and still water.States this directlyCitation checked — the work exists and is described correctly
- Still Water Fly-Fishing — Andre Deutsch, 1952 (Specialist angling publication)Relied on for: Still-water fly categories, and the feeding observations they are chosen from.Background and mechanism onlyCitation checked — the work exists and is described correctly
Nymphs
A practitioner claim about which lure family answers this species' feeding or holding behaviour.
- Trout & Salmon — Bauer Media (Specialist angling publication)Relied on for: Fly categories and their application to salmonids in running and still water.States this directlyCitation checked — the work exists and is described correctly
- Still Water Fly-Fishing — Andre Deutsch, 1952 (Specialist angling publication)Relied on for: Still-water fly categories, and the feeding observations they are chosen from.Background and mechanism onlyCitation checked — the work exists and is described correctly
Reviewed 2026-08-10. FishingHQ does not state what any rule is or where any rule applies. Where this page says the two species are managed differently, that is a reason to check the authority for the water you are on — not a statement of what it requires.