Bull Trout: How to ID the Threatened Char, and Where to Fish

A pale olive bull trout with small pink spots and white-edged lower fins swims among bright red spawning kokanee salmon in a clear Washington creek — Photo: Roger Tabor, U.S. Fish and Wildlife Service (public domain)

The bull trout is a char of the cold mountain rivers and lakes of the Northwest, and in the lower 48 it has been a threatened species since 1999. In most of its range you may not keep one, and in many waters you may not even fish for one. The few places that stay open are worth knowing, and so is the one look at the dorsal fin that keeps you legal.

One fin settles it. The field guide Oregon uses to sort bull trout from brook trout tells anglers to ignore every other feature and look only at the dorsal fin: plain on a bull trout, solid black marks on a brook trout.

Is a bull trout a trout?

No. Despite the name, it is a char, the branch of the salmon family that also holds the brook trout, the lake trout, the Dolly Varden and the Arctic char. The quick test works on every char: light spots on a dark body. A rainbow, a cutthroat or a brown is the reverse, dark spots on a lighter body.

For more than a century the bull trout was not even counted as its own species. The IGFA notes that it was described in 1858, then confused with the Dolly Varden for over a hundred years, so much of the older writing on Dolly Varden is really about bull trout. Montana’s field guide puts it plainly: the native bull trout is a separate species from the coastal Dolly Varden. The types of trout page shows where the chars sit among the true trout.

How do you identify a bull trout?

Start with the dorsal fin, the one on the middle of the back. Montana’s 2026 identification guide for anglers lists four marks:

No black spots or lines on the dorsal fin. This is the mark that matters most.
Pink, yellow or orange spots on the sides, on an olive-green to gray body. Washington’s biologists describe pale spots about the size of the pupil of the eye.
White leading edges on the lower fins, like every char.
A slightly forked tail.

The head gives it away too. Washington’s Department of Fish and Wildlife calls the head and mouth unusually large, and Oregon Sea Grant says that big head is where the name comes from.

Fish	Dorsal fin	Spots and body	Tail	Where it overlaps
Bull trout	No black at all	Pale yellow, pink or orange spots on olive-gray	Slightly forked	Montana, Idaho, Oregon, Washington, northern Nevada
Brook trout	Solid black marks with sharp edges	Pale marbling on the back; red spots with blue halos	Square	Introduced into many bull trout streams
Lake trout	Not the deciding mark	Cream spots on gray-green; no red spots	Deeply forked	Big lakes and reservoirs, often stocked
Dolly Varden	Very close to a bull trout	Very close to a bull trout	Very close to a bull trout	Olympic Peninsula and Puget Sound of Washington, north into Alaska

The brook trout is the fish that gets anglers in trouble, because it lives in the same streams. Oregon’s field guide, written by the Forest Service and Idaho Fish and Game, separates the two by the dorsal fin alone. A bull trout’s dorsal fin has no light or dark markings, apart from a few light marks along its base on some fish. A brook trout’s has solid black markings with distinct edges. A hybrid of the two shows dark marks that are not solid black and have no sharp edges. California’s biologists add that a bull trout lacks the worm-like marks on the back (vermiculations) of a brook trout. A lake trout has the deep fork in its tail that a bull trout lacks.

The Dolly Varden is the hard one. The IGFA says the two look alike and that a positive ID may take laboratory analysis. In practice the range decides it. The Dolly Varden lives along the Pacific coast from Washington north around Alaska, while the main bull trout populations of the lower 48 are inland, in Montana, Idaho, Oregon and Washington. Washington writes its rules for “Dolly Varden/bull trout” together, so in that state you treat them the same.

Why are bull trout threatened?

The U.S. Fish and Wildlife Service listed the bull trout as threatened across the lower 48 on November 1, 1999. Populations in the Klamath and Columbia River basins had been listed the year before. A final recovery plan for the lower 48 followed on September 30, 2015.

The Fish and Wildlife Service names three kinds of harm. Development and land use degrade habitat and water quality. Dams and weirs block migration. And non-native fish compete with bull trout for food or eat them. The brook trout does double damage. In Montana it crowds bull trout out, and the two interbreed into sterile hybrids.

Anglers are part of the story. Montana’s field guide says bull trout are vulnerable to overharvest because they feed opportunistically and mature late, and that poaching and accidental harvest through misidentification probably still hurt some populations. That is why Montana Fish, Wildlife & Parks offers a brief voluntary bull trout identification test online.

The field guide calls the bull trout the grizzly bear of the fish world, for how much unaltered habitat it needs. California has already lost it: the state’s last reported sighting was in 1975.

Where can you legally fish for bull trout?

In a handful of places, under strict rules. The table lists what the agency rules say for the waters they name; everything else in these states is closed to bull trout or catch-and-release only. Rules change every season, so read the current rules for your water before you go.

State	Water	What the rule says	Season
Montana	Hungry Horse Reservoir	1 bull trout per license year; catch-and-release the rest of the year; catch card required	Harvest from the third Saturday in May to Aug. 15
Montana	Lake Koocanusa	Catch-and-release only; catch card required	Open all year
Montana	South Fork Flathead River, Cross-over boat ramp up to Youngs and Danaher creeks	Catch-and-release only; single-point hooks only; catch card required	July 1–31
Montana	All other waters	Closed to intentional angling for bull trout	All year
Idaho	Lake Pend Oreille	Bull trout catch-and-release	Open all year (Fishing Rules 2025–2027)
Oregon	Lake Billy Chinook, balance of reservoir	Trout limit may include 1 bull trout, 24 in (61 cm) minimum	See the Central Zone rules
Oregon	Metolius River	Catch-and-release for trout, including bull trout	Open all year below Allingham Campground Bridge; above it May 22–Oct 31
Oregon	Other Central Zone waters	Closed to angling for bull trout unless an exception says otherwise	–
Washington	Most waters	May not be fished for or kept; open only in the river reaches the pamphlet names	–

Montana’s catch cards are free, from the FWP office in Kalispell or the Spotted Bear Ranger Station, or by mail; there is no digital option. You pick one area, Lake Koocanusa or Hungry Horse with the South Fork. Every bull trout you catch, kept or released, goes on the card with the date, the zone and its length. It is unlawful in Montana to keep a bull trout alive for any reason: a fish you keep is killed at once, and every other one is released unharmed without delay.

Washington adds a rule worth remembering anywhere. A bull trout hooked in water closed to bull trout fishing may not be taken out of the water; you unhook it and let it go. The catch-and-release water rules elsewhere differ, but the habit travels well.

How do you catch a bull trout?

Adult bull trout eat fish. In Montana’s Flathead Lake, fish made up more than 99% of their food by weight, and Washington’s biologists call them aggressive predators that take lures and flies that look like fish, such as spoons and Rapalas. Where the open water is a river, Washington names casting as the method of choice. The trout lures page covers the spoons, spinners and minnow baits that imitate that prey.

Timing follows the rules more than the fish. In Montana the harvest window on Hungry Horse runs from mid-May to mid-August, and the South Fork Flathead opens only in July. In Oregon, the state’s own guide to the Central Zone points to a winter bull trout fishery on the Metolius River.

Handle every fish as if it will be released, because nearly all of them must be. Montana’s regulations advise barbless hooks, a short fight and the fish kept in the water while you unhook it. On a deep hook, cut the line and leave about 1 in (2.5 cm) of leader hanging from the mouth rather than pulling the hook out. An Idaho study of 278 bull trout found no difference in survival after up to 60 seconds in the air, but in Washington’s closed waters the fish may not leave the water at all. How to hold a trout shows the grip that does the least harm.

How big do bull trout get?

It depends on the life the fish leads. Montana’s field guide puts stream-resident adults at 6–12 in (15–30 cm), while migratory adults commonly pass 24 in (60 cm). Washington’s biologists give an average of 12–20 in (30–51 cm). In Flathead Lake they reach trophy sizes of up to 25 lb (11 kg).

The IGFA all-tackle world record is a 32 lb (14.51 kg) bull trout caught by N. Higgins in Lake Pend Oreille, Idaho, on October 27, 1949. Idaho’s Fishing Planner for the lake still names it as the home of that record. Today the same lake is catch-and-release for bull trout. Washington’s state record is 22.50 lb (10.2 kg), caught by Louis Schott in the Tieton River on April 23, 1961.

The IGFA also keeps length records for released fish. Its fly length record for bull trout is 81 cm (32 in), from near Fernie, British Columbia, in 2011.

How cold does the water need to be?

Colder than most cold-water fish need, by Oregon Sea Grant’s account. Idaho’s Office of Species Conservation says bull trout are rarely found in water warmer than around 60 °F (16 °C). Oregon Sea Grant gives 52–59 °F (11–15 °C) as the range they need to survive, and says spawning begins in the fall when the water drops below 48 °F (9 °C).

A water temperature scale from 40 to 66 °F: spawning begins below 48 °F, bull trout need 52 to 59 °F, and they are rarely found above about 60 °F

That is why bull trout water is mountain water: cold rivers and lakes, and the headwater streams where they spawn. The trout water temperature chart gives the limits for rainbow, brown, brook and lake trout to set beside these. The Fish and Wildlife Service sums up the habitat in four words: cold, clean, complex and connected.

Are bull trout good to eat?

You will rarely get the chance to find out. Across most of their range bull trout must be released, and the waters that allow harvest cap it hard. Hungry Horse Reservoir in Montana allows one fish a license year. Lake Billy Chinook in Oregon allows one fish of 24 in or more within the trout limit. If you do keep a legal fish in Montana, kill it at once and log it on your catch card, as the rules require.

How do bull trout live and spawn?

Bull trout follow four life histories, by the Fish and Wildlife Service’s count. Resident fish stay in one stream. Fluvial fish move between small streams and rivers. Adfluvial fish live in a lake and spawn in its tributaries. And some go to sea and come back to fresh water to spawn. Montana’s field guide records migratory bull trout moving up to 156 miles (250 km) between lakes, rivers and tributaries.

They mature late, at four to seven years by the Fish and Wildlife Service’s count, and may spawn every year or every other year, so a spawner can return to spawn again. Spawning runs from August to November, sometimes into December. The female digs a redd in clean gravel and lays an average of 5,000 eggs. The eggs stay in the gravel for up to 210 days, and the young spend one to four years in their home stream before moving down to a river, a lake or the sea.

Montana’s field guide says bull trout do not tolerate high sediment in their spawning streams, because it can suffocate the eggs before they hatch. The trout hub covers the other trout that share their rivers.