Brook trout

What it is, and why it matters

The brook trout is not a trout.

Salvelinus fontinalis is a char, the same genus as lake trout and Arctic char, and a different genus from every other fish in this challenge. The other four are Oncorhynchus or Salmo. That is not a technicality. It is why brook trout cannot hybridize with cutthroat, and why the harm they do here is competition and predation rather than genetic dilution. It is also why they are the easiest fish on this list to identify.

They are, by fairly broad agreement, the most beautiful fish in these mountains. Olive backs marked with dark wavy lines like worm tracks. Red spots ringed in pale blue. A white leading edge on the lower fins that looks painted on. In fall the flanks go orange-red.

And in a specific named list of conservation streams, New Mexico would like you to keep them.

Brook trout came to New Mexico's high country from the southern Appalachians in the late 1800s, stocked partly to replace native cutthroat that heavy harvest had already thinned. They thrived, and they did it in exactly the cold headwater streams the cutthroat had retreated into. They take food and space, they eat cutthroat eggs and fry, and cutthroat do not return the favor, probably because they did not evolve eating fish. Where the two overlap, brook trout generally win.

So the bag limit comes off in a short, bounded, well-marked list of waters. Everywhere else in the state they are an ordinary game fish under ordinary limits, and a well-regarded one.

None of which is the brook trout's fault. People moved this fish, on purpose, to solve a problem people had made. In its own range in the eastern United States it is the imperiled native, pushed out of its water by introduced rainbows and browns. Same story, opposite roles, different watershed.

Worth holding onto while you hold the fish.

Identifying it

The easiest identification in the challenge. Three marks, any one of them sufficient, all three photograph well.

The second mark is the taxonomy stated as a visual: char reverse the pattern. Notice it once and you will not mistake a brook trout again.

Brook trout and brown trout are the only two fish here with red spots in pale halos. The separation is instant: brook trout have vermiculations and light-on-dark spots, brown trout have neither, plus a square tail and a jaw that runs past the eye.

A mouth-based check separates char from trout by the arrangement of teeth on the roof of the mouth. Do not go looking for it. It means handling a fish that is probably going back, and the three external marks settle the question from a photograph.

For your challenge photo

Get the back and the flank in frame together. The vermiculations are the clearest confirmation a reviewer can get, and a straight side-on shot at water level can flatten them out of view. A slight angle showing the top of the back works better here than for any other species on the list.

Range and status in New Mexico

High-elevation streams and lakes in the northern mountains, generally above about 9,000 feet.

NMDOW's own characterization will surprise people: brook trout are "relatively uncommon in New Mexico and typically found in smaller, less accessible streams."

They are not overrunning the state. They are concentrated in precisely the small, cold, high headwaters that are the last refuge of the Rio Grande cutthroat. Locally abundant, in exactly the wrong places. That is a more useful picture than "invasive species spreading across the state," which is neither accurate nor the department's own word.

Status: not native, not listed, no conservation status, no special permit, no closed season. A fully legal game fish.

NMDOW publishes no typical size for New Mexico brook trout, and out-of-state figures describe different fish in different water. The New Mexico answer is more interesting anyway: brook trout overpopulate and stunt in the small streams they occupy here. A creek full of six-inch brook trout is a common outcome, and it is a worse fishery than the same creek holding cutthroat, which do not stunt that way and reach at least the size of other trout in the same water.

That moves the harvest argument from duty to self-interest, and it happens to be true.

Management in New Mexico

On this page, restoration means removal.

Why they win. Three mechanisms, in descending order of how well they are sourced.

Competition for food. NMDOW states this directly.

Predation on eggs and fry. This is what separates brook trout from brown trout, which the New Mexico evidence indicates do not prey on cutthroat at any life stage. Brook trout do, and they remain predacious on eggs and fry even when stunted by their own overpopulation.

Habitat. Researchers have found displacement severity tracking water temperature, fine sediment, and the abundance of pools and woody debris.

What removal looks like. The bag limit comes off brook trout, rainbow and brown together in a named set of conservation streams. Above barriers, agencies use mechanical removal. The recovery sequence is the same as for the natives generally: clear the nonnatives, install a barrier, repatriate pure native fish.

Does keeping a few actually matter?

At the scale of a whole watershed, angler harvest alone will not eradicate an established brook trout population. It will not. Agencies use barriers, mechanical removal and in some places genetic techniques, because that is what the job requires. Anyone who tells you your creel saves a species is flattering you.

What angler harvest does is reduce competition and buy time above a barrier where a cutthroat population is being re-established. That is specific, real, and worth doing.

New Mexico has been evaluating a genetic approach to brook trout control with university and federal partners. The details are not published here; the primary source could not be retrieved.

A wildfire in 2011 cleared a stream of nonnative brook trout, and the recovery team took the opening and restocked Rio Grande cutthroat there. A catastrophic fire did what a removal project would have done. That is not a strategy. It is what working on the margin looks like.

The spawn. Brook trout spawn in fall, later than browns, from late October into December, and they are obligate groundwater spawners: the redd goes over an upwelling spring or at the tail of a pool. New Mexico protects none of it. Clean, light-colored gravel is a redd. Walk around it.

Handling this fish, and when not to fish for it

Most of what follows is about the fish you are not keeping. In the conservation waters the state asks you to harvest brook trout, and there the ethic is a clean, quick dispatch rather than a careful release. Everywhere else, which is most of New Mexico, the ordinary ethic applies.

Do not let "nonnative" become a license for careless handling. A fish you are going to release deserves to survive it, whatever its passport.

When not to fish

Brook trout are the least heat-tolerant of the five, which matters because they live in the water anglers assume is automatically cold. Two state agencies give different preferred bands, one about 53°F or less, another 50–65°F. They agree on the ranking.

How to handle it

Steps 1 through 8 are NMDOW's own published Catch and Release Tips, 2026–2027 rules booklet, p. 21.

1. Land the fish quickly and don't play it to exhaustion.
2. Use a landing net whenever possible.
3. Keep the fish in the water.
4. Do not squeeze or grab any part of the fish. Wet your hands first if you must handle the fish.
5. Gently remove the hook.
6. If the hook is swallowed deeply, cut the leader.
7. Let a tired fish recover. Hold it by the tail in the water, supported from below, until it swims away.
8. Never toss or throw a fish back into the water.

The law does not require the following. We are asking you to. Pinch your barbs, which the conservation waters require anyway. Keep air exposure to a few seconds. Never lift a fish by the jaw or hold it vertically; these are small, light-boned fish. Wet everything the fish touches.

If you are keeping them, dispatch them promptly and use them. A fish taken under a conservation rule and then wasted has not served the purpose the rule exists for. Keeping brook trout is a legitimate contribution. Leaving them on the bank is littering.

Your challenge photo

Back and flank in frame together, so the vermiculations show. Camera ready before the fish is, shot over the water or the net, one or two frames.

What the law requires

No special permit exists for brook trout, and there is no closed season anywhere in New Mexico. Standard license, validations and stamps. Stamps are required on Forest Service and Bureau of Land Management land, which covers nearly all of this fish's New Mexico range.

In a named set of conservation waters the bag limit on brook trout is removed entirely. The rule reads "bag limit unlimited for rainbow trout, brown trout and brook trout." Those same waters require artificial fly or lure with a single, barbless hook.

Chumming and baitfish are prohibited in every Special Trout Water.

Stocking fish anywhere in New Mexico without a permit is illegal, as is transporting live game fish away from the water where they were caught. The reason brook trout are in these headwaters at all is that people moved them, and moving them is now a crime.

Consumption advisories exist by water and by species.

What the law does not require

Nothing requires you to keep a single brook trout. New Mexico encourages harvest by removing the limit. It never mandates it. The only mandatory-kill rule in the state applies to northern pike at one lake. If anyone tells you New Mexico requires you to kill brook trout, they are wrong.

There is no spawning protection. Brook trout spawn in fall over upwelling groundwater and no rule protects those redds.

No temperature rule exists.

Nothing requires you to pinch a barb outside the waters that specify it.