Fish IdentifierTrout identification: know your trout at a glance
Trout identification comes down to pattern direction and three or four signature marks. Dark spots on a light body point to true trout (rainbow, brown, cutthroat); light spots on a dark body point to char (brook, lake trout). This trout identifier guide walks the marks species by species, with a comparison chart.
Trout ID in four checks
- Pattern direction - dark spots on light body = trout; light spots on dark body = char.
- Flank color - pink-red stripe = rainbow; golden-brown with haloed spots = brown.
- Throat - orange-red slash under the jaw = cutthroat.
- Fins and tail - white-edged lower fins = brook; deeply forked tail = lake trout.
The main species, one by one
Rainbow trout
Oncorhynchus mykiss. Field marks: a pink to red lateral stripe, dense small black spots over the back, dorsal fin, and across the whole tail in radiating rows, and a white belly. Sea-run and lake-run fish (steelhead) turn silver and can nearly lose the stripe, but keep the spotted, squarish tail.
Brown trout
Salmo trutta. Field marks: buttery golden-brown flanks with large black and red spots, often surrounded by pale halos, few or no spots on a square tail, and an adipose fin often tinged orange. Browns tolerate warmer water than most trout and grow wary and large.
Brook trout
Salvelinus fontinalis - a char. Field marks: worm-like light squiggles (vermiculations) across a dark olive back, red spots with blue halos on the flanks, and white leading edges backed by black on the lower fins. Spawning males glow orange below.
Cutthroat trout
Oncorhynchus clarkii. Field marks: the namesake orange-red slash under each side of the jaw, spots that grow denser toward the tail, and a longer jaw that reaches past the eye. Many regional subspecies vary in color; the throat slash is the constant.
Lake trout
Salvelinus namaycush - a char. Field marks: a deeply forked tail (unique among this group), light cream spots over a dark gray-green body, and a big head. Fish of deep, cold lakes; commonly 3–15 lb and capable of much more.
Golden trout and tiger trout
Golden trout (a rainbow relative from high Sierra streams) are small and vivid: golden flanks, red lateral band, and dark oval parr marks kept into adulthood. Tiger trout are a brown × brook hybrid with bold maze-like markings - if the pattern looks like tiger stripes drawn in a labyrinth, that is your fish.
Trout identification chart
| Species | Group | Pattern | Signature mark | Tail | Typical size |
|---|---|---|---|---|---|
| Rainbow trout | Trout | Black spots on silver-olive body | Pink-red lateral stripe | Square, fully spotted | 1–5 lb |
| Brown trout | Trout | Black + red haloed spots on golden body | Buttery flanks, haloed spots | Square, few spots | 1–6 lb |
| Brook trout | Char | Light spots/squiggles on dark body | Vermiculated back; white-edged fins | Square-ish | 0.5–2 lb |
| Cutthroat trout | Trout | Black spots, denser toward tail | Orange-red throat slash | Square, spotted | 1–4 lb |
| Lake trout | Char | Cream spots on dark body | Deeply forked tail | Deeply forked | 3–15 lb+ |
| Golden trout | Trout | Golden flanks, parr marks | Red band + retained parr marks | Square, spotted | < 1 lb |
| Tiger trout | Hybrid | Maze-like stripes | Labyrinth pattern | Square | 1–4 lb |
Trout or salmon?
In rivers that hold both, use the anal fin rule: trout carry a short anal fin of about 12 or fewer rays, Pacific salmon a longer one of roughly 13–19. Trout tails are squarer, salmon tails more forked. The full breakdown, including how steelhead fit in, is in the salmon identification guide.
Using a trout identifier on the water
Trout are delicate, so make the photo quick: keep the fish wet, support it horizontally, take one clear side-on frame in daylight, and return it promptly. That single frame - stripe, spots, fins, tail - contains every mark in the chart above. The Fish Identifier app reads those marks and suggests the species with its traits, size, habitat, and season, and files the catch in your collection. Fishing wider than trout streams? Browse the freshwater fish identification chart for the rest of the lake’s cast.
Trout identification FAQ
What is the fastest way to identify a trout?
Start with the flank pattern. A pink-red lateral stripe with small black spots means rainbow trout. Buttery flanks with red and black spots, often haloed in pale rings, mean brown trout. Light worm-like squiggles on a dark back with white-edged lower fins mean brook trout. An orange-red slash under the jaw means cutthroat. A deeply forked tail with light spots on a dark body means lake trout.
How do I tell a rainbow trout from a cutthroat?
Lift the lower jaw and look underneath: cutthroat trout show a distinct orange-to-red slash on each side of the throat, which rainbows lack. Rainbows have a stronger pink lateral stripe and usually white tips on the pelvic and anal fins. Beware hybrids ("cutbows"), which can show a faint slash plus a rainbow stripe.
What is the difference between brook trout and brown trout?
Spot direction. Brook trout have light markings on a dark background, including worm-like vermiculations across the back, plus white leading edges on the lower fins. Brown trout are the reverse: dark red and black spots on a light golden-brown background. The two do not really overlap in pattern once you know which way the contrast runs.
Are brook trout and lake trout actually trout?
Biologically they are char (genus Salvelinus), together with Arctic char, Dolly Varden, and bull trout. Char share the light-spots-on-dark-body pattern. True trout (rainbow, cutthroat, brown) show dark spots on a lighter body. For identification purposes the char rule is handy: if the spots are lighter than the body, think char.
How is a steelhead different from a rainbow trout?
Same species (Oncorhynchus mykiss), different life history. A steelhead spends part of its life at sea or in a great lake and returns larger and chrome-silver, with the pink stripe faint or absent. The structure is unchanged: small black spots radiating in rows across a squarish tail, and a short anal fin that separates it from salmon.
Can the Fish Identifier app tell trout species apart?
Yes - trout patterns (stripe, spots, vermiculations, throat slash) are exactly the kind of visual field marks a photo shows well. Take a side-on shot in daylight with the fish wet, and check the suggested species against the traits the app lists. For jaw-slash cases such as cutthroat, add a photo of the underside of the jaw.
Your pocket trout identifier
One wet, side-on photo and Fish Identifier suggests the species - rainbow, brown, brook, cutthroat, or something rarer - with the marks to verify it yourself.
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