Head to head
Brook Trout vs Brown Trout
Anglers across North America catch both of these in the same rivers, and they are constantly compared. But they are not even the same kind of fish. The brook trout is a char, native to eastern North America, and the brown trout is a true trout, native to Europe and introduced to North America in the 1880s.
| Brook Trout | Brown Trout | |
|---|---|---|
| Trout or char | A char (Salvelinus) | A true trout (Salmo) |
| Native to | Eastern North America | Europe and western Asia |
| Spot pattern | Pale spots and blue-haloed red spots on a dark body | Dark spots, and red spots with pale halos, on a light body |
| Back markings | Wavy worm-track vermiculation | None |
| Lower fin edges | Bold white edge backed by black | Plain |
| Water it needs | Cold and clean, generally below 20 degrees C | Tolerates warmer, siltier water |
| Maximum size | Smaller; often stream fish of under 30 cm | Larger; can exceed several kg, sea trout larger still |
| Where they meet | Retreats to the coldest headwaters | Out-competes and displaces brook trout downstream |
Brook Trout vs Brown Trout: common questions
Is a brook trout really not a trout?
Correct, in the strict sense. The brook trout belongs to the genus Salvelinus, the chars, along with the Arctic char, lake trout, bull trout, and Dolly Varden. True trout and salmon belong to the genera Salmo and Oncorhynchus. The clearest visible sign is the spotting: chars have light spots, cream, pink, or red, on a darker background, while trout and salmon have dark spots on a lighter background. The brook trout also has the worm-track markings and the white-and-black edged fins typical of char. Its common name simply predates the sorting out of these groups and has stuck, and anglers happily fish for brook trout and brown trout together as trout regardless of the technicality.
How do I tell a brook trout from a brown trout?
Check the spots and the back. A brook trout has light-coloured spots, plus red spots ringed in blue, on a dark green to olive body, a maze-like pattern of pale worm-track lines over the back and dorsal fin, and lower fins with a sharp white front edge lined in black. A brown trout has dark spots, some of them red with a pale halo, scattered over a lighter golden or bronze body, a plain back with no worm-track pattern, and plain fins with no white edging. Tail shape is a supporting clue, roughly square on a brook trout and square to slightly forked on a brown. If you catch a small, jewelled fish in a cold mountain headwater in the eastern United States it is very likely a brook trout; a larger, browner, dark-spotted fish lower down is likely a brown.
Why does the brown trout push out the brook trout?
Several factors stack up in the brown trout's favour where the two share a stream. Brown trout tolerate warmer water and lower oxygen than brook trout, so as a river warms, through the removal of streamside trees, water abstraction, or climate change, the lower reaches become better for browns and worse for brookies. Brown trout also tend to grow faster and larger, are more aggressive in defending feeding stations, and the larger individuals prey on small brook trout. The result across much of the eastern United States is that introduced brown trout, along with introduced rainbow trout, have progressively replaced native brook trout in the main rivers and confined them to the coldest, steepest headwater sections. Conservation efforts focus on protecting and reconnecting those headwater refuges.