Trout & salmon · Freshwater
Bull trout
Salvelinus confluentus
Native coldwater char of northwestern North America with resident, fluvial, adfluvial, and anadromous life-history forms.
Also called bull char.
- Flowing water
- Stillwater
- Conservation-sensitive
- 4 of 4 overlays reviewed
- Reviewed 2026-08-27
Before you target this fish
Conservation-sensitive — presence is not permission
Lower-48 U.S. bull trout remain listed as threatened under the Endangered Species Act. Context only — no presentation guidance. This record is retained for biological context only; we do not give presentation guidance for it.
Where this applies Lower 48 United States; status and legal opportunity vary elsewhere in the species range.
The reviewed context, unedited
Conservation-sensitive context only. No presentation guidance, migration bottlenecks, spawning tributaries, or redd locations.
Rules for this fish change at a state line and sometimes inside one. Check the ones that apply to the exact water you are standing on before you act on anything here — this record is biology, not permission.
Take this somewhere
This page is the record. The reading is what happens when you add water, a season and a temperature to it — that is where the families below get ranked against each other instead of just listed.
Those three links carry the fish and nothing else. No conditions were declared on this page, so none travel, and the link says so rather than sending an empty reading.
The half nobody publishes
What this record does not know
Everything else on this page comes from a named agency or peer-reviewed source. This is the other side of that: the questions a reviewer went looking for an answer to and came back without, and the fields the record leaves empty because filling them would mean guessing.
It is here rather than at the bottom because a page that only shows what it knows is easy to read as a page that knows everything. For Bull trout there are 25 of them.
Named by a reviewer
19Somebody looked for this and wrote down that they did not find it.
- Behaviour
Nobody has sourced:
- adult diel pattern — the concealment and winter-diel work reached covers juveniles and subadults only
- current-facing / velocity-selection behavior for adults
- water clarity response
- cold-front or barometric response with primary-source support
- angling-pressure response with primary-source support
- water-level rise and fall response as a behavioral (not habitat-availability) finding
- Identification
Nobody has sourced:
- regional / vernacular names — no agency source reached supplied a name list, so the field is left empty rather than guessed
- spawning coloration — not described in any source reached
- sexual dimorphism outside the spawning period
- a field character separating bull trout from Dolly Varden; the agency key reached treats them together
- typical (as opposed to maximum) adult weight
- maximum documented age
- Forage
Nobody has sourced:
- crustaceans — the catalog forage list carries this class, but the sources reached document only 'benthic invertebrates and plankton' generically and no crustacean-specific diet record, so it is omitted from primaryForage rather than asserted
- season-by-season diet emphasis; the sources reached give ontogenetic rather than seasonal diet structure
- quantitative diet composition (percent by mass or number) for any life stage
- Season
Nobody has sourced:
- spring and fall habitat use are inferred from migration and general habitat statements rather than season-specific studies — the reason this record is partial
- stillwater seasonal structure beyond the littoral-in-spring-and-fall / deep-in-summer split
- adult (as opposed to subadult and juvenile) winter diel habitat use
- regional variation between the coastal, interior and adfluvial life-history forms
Absent from the record
6No reviewer wrote a gap here. The field is simply empty, which is its own answer.
- Presentation
No presentation family is reviewed for Bull trout in flowing water. The record documents the fish there; it does not yet say how to fish for it there.
No presentation family is reviewed for Bull trout in stillwater. The record documents the fish there; it does not yet say how to fish for it there.
No species-specific weighting rule is reviewed for Bull trout. Its ranking comes from the shared model — season, temperature, water type, holding and forage — with nothing added for this fish in particular.
- Water temperature
No agency or peer-reviewed temperature band for Bull trout was found that a review would accept. The reading runs without one rather than borrowing a number from a related fish.
- Identification
No reviewed image. A photograph is only in this catalog when an agency or a named creator labelled the subject, and nobody has cleared one for this species yet.
- Population context
No regional population profile is registered. The species-level reading stands on its own; it does not silently become a local one.
Where the record puts it
Water and range
Flowing water
6 reviewed holding classes- Deep pool
- Pool head
- Run
- Seam
- Boulder pocket
- Tributary mouth
Stillwater
5 reviewed holding classes- Drop-off
- Inlet
- Basin
- Thermocline edge
- Rocky shoreline
DepthOften associated with depth, cover, and cold-water refuge; larger migratory fish can be strongly piscivorous.
Moving waterUses cold connected rivers and tributaries with complex cover; migratory adults may move between large rivers or lakes and spawning tributaries.
LightLow light can support shallower movement, but habitat temperature and connectivity are more important constraints than light alone.
Thermal band
Temperature
No reviewed temperature band
Nobody publishes a preferred or active temperature range for Bull trout that a review would accept. Borrowing one from a related fish would look like knowledge and behave like a guess, so the reading runs without it and says which parts of the answer that weakens.
How it uses water
Behaviour
Biological context only. Bull trout are a conservation-sensitive record in this catalog and this dossier carries no targeting guidance.
Fry feed on or near the bottom, in the water column, and at the surface, taking mostly aquatic insects off the bottom or in drift. From about 110 mm, juveniles begin taking small fish and forage near the substrate and in the water column but not at the surface. Most adults become piscivorous. Stream residents in systems without fish prey subsist on benthic invertebrates and plankton.
Documented for juveniles and subadults. Thurow et al. (2020) found juveniles 14.5 times less likely to be concealed in constant darkness than in constant light, with 70–82% concealed during daylight where large substrate was available, and concealment 6.2 times less likely in small (26–51 mm) than in larger (52–102 mm) substrate. Muhlfeld and Marotz (2003) found wintering subadults concealed in deep midchannel water by day and emerging to shallow, low-velocity channel margins without overhead cover at night, with emergence immediately at the onset of night and concealment at daybreak. Adult diel pattern is not established in the sources reached.
Seasonal activityAdfluvial adults forage in the littoral zone in fall and spring and move to deep water in summer once temperatures exceed 15°C. Juvenile emigration from natal areas begins in spring and continues through most of summer. Spawning migration occurs in late summer and fall and is conservation context only.
Temperature-driven behaviourUSFWS frames the species requirement as cold, clean, complex and connected habitat with water below about 59–64°F. Bull trout are uncommon wherever water rises above 15°C (59°F) for extended periods. Juvenile rearing is associated with summer temperatures under 15°C, and spawning with water below about 8–9°C. Thurow et al. (2020) found juvenile concealment declining as temperature rose toward about 13.3°C, near the species' peak growth temperature. The catalog preferred band of 44–54°F sits inside these agency limits and does not contradict them.
Depth movementJuvenile focal sites sit close to the bottom — about 4 cm off it. Wintering subadults used deep midchannel water by day and shallow margins at night, with a median day-to-night displacement of 86 m (range 27–594 m). Lacustrine adults move from the littoral zone into deep water in summer above 15°C.
Change in flowMuhlfeld and Marotz (2003) recommended flow management that maximizes and stabilizes channel-margin habitat at night, on the basis that wintering subadults use those margins after dark. Dewatering of channel margins therefore removes the habitat this life stage occupies at night. This is a habitat-availability finding, not a feeding response.
CoverComplex cover is the documented rearing requirement — deep pools, large woody debris, rocky stream beds, and undercut banks. Juvenile focal sites are strongly associated with instream and especially overhead cover, and concealment depends on interstitial space, which larger substrate (52–102 mm) supplies and small substrate does not.
Open waterLacustrine and adfluvial fish forage in the littoral zone in spring and fall and hold in deep water in summer. No pelagic schooling form is documented in the sources reached.
Predator avoidanceDaytime concealment in interstitial spaces of larger substrate; the authors interpret nocturnal emergence as energy conservation or predator avoidance.
TerritoryFry hold focal sites about 4 cm off the bottom, strongly associated with instream cover and especially overhead cover, and defend them against individuals that take the site.
Spawning (conservation context)Fall spawner. USFWS gives spawning between August and November, sometimes as late as December; the Montana AFS account gives late August through early November, with spawning associated with water below about 8–9°C. Females deposit roughly 5,000 eggs in gravel redds; eggs may incubate up to about 210 days and juveniles rear one to four years before migrating. Spawning substrate, redds, and any pre-spawn holding water are conservation context and are excluded from this record's habitat guidance. No spawning area, aggregation, or migration bottleneck is described here.
Where the general rule stops
- Do not use this record to infer targetable spawning tributaries, redds, or migration bottlenecks.
- Dolly Varden is a different species and must not resolve to this record.
What it can eat
Forage
- Small forage fish
- Larger prey fish
- Aquatic insects
- Crustaceans
Biological context only; this catalog withholds presentation guidance for bull trout. Fry take mostly aquatic insects off the bottom and in drift and will also feed at the surface. From about 110 mm, juveniles add small fish — sculpins, mountain whitefish and trout fry are the taxa named in the life-history review — and stop feeding at the surface. Most adults become piscivorous, with a documented propensity for sculpins, kokanee and mountain whitefish where those are present, and for Dolly Varden in sympatric systems. Stream residents in systems without fish prey remain on benthic invertebrates and plankton. Capacity is not a current hatch or a current forage event.
- Feeding style
- Mixed
- Feeding zone
- Mixed
By life stage
- Young of year
- Mostly aquatic insects taken off the bottom and in drift, with some surface feeding.
- Juvenile
- Aquatic insects plus small fish from about 110 mm, foraging near the substrate and in the water column but not at the surface.
- Adult
- Predominantly fish. Stream residents without fish prey remain invertebrate and plankton feeders.
Prey sizePrey size steps with fish size: small fish enter the diet at about 110 mm, and a sudden acceleration in growth around 550 mm coincides with a shift onto kokanee-scale prey.
Ontogenetic shiftAquatic insects to mixed insect-and-small-fish at about 110 mm to predominantly piscivorous adults, with the terminal stage conditional on fish prey being available in the system.
SubstitutionsPrey emphasis is system-specific. Where forage fish are present the review names sculpins, mountain whitefish, trout fry and kokanee; where they are absent, resident fish remain on benthic invertebrates and plankton rather than substituting a different fish prey.
Diet capacity is not proof that a hatch or prey event is occurring. Observed current forage still comes from a user observation or Hatch Match. For this species the rule is doubly binding: bull trout are conservation-sensitive here and no forage record in this dossier is a targeting cue.
Through the year
Season
Winter
- Where they sit
- Deep midchannel water by day; shallow, low-velocity channel margins without overhead cover at night. In lakes, deep water outside the littoral zone.
- Depth
- Deep by day, shallow at night for subadults in a large river system.
- Movement
- 92% of tracked subadults made at least one diel movement, moving on about 73% of occasions, with a median day-to-night displacement of 86 m (range 27–594 m).
- Cover
- Interstitial concealment in larger substrate (52–102 mm) by day; no overhead cover at the night margin positions.
- Light
- Nocturnal emergence began immediately at the onset of night; daytime concealment resumed at daybreak.
What would count against it
- reading the daytime midchannel position as the whole winter picture
- converting any part of this entry into targeting guidance — presentation guidance is withheld for this species
Conservation-sensitive record. Channel-margin dewatering removes the habitat this life stage uses after dark.
Spring
- Where they sit
- Littoral zone for lacustrine adults; complex stream cover — deep pools, large woody debris, rocky beds, undercut banks — for rearing juveniles.
- Movement
- Juvenile emigration from natal areas begins in spring and continues through most of summer.
- Temperature
- Below the 15°C (59°F) limit that bounds the species across its range.
What would count against it
- treating juvenile spring emigration as a concentration cue
Conservation-sensitive record; no presentation implication is given for any season.
Summer
- Where they sit
- Deep water in lakes once surface temperatures exceed 15°C; in streams, the coldest complex habitat available with instream and overhead cover.
- Depth
- Lacustrine adults move off the littoral zone into deep water as surface temperature rises.
- Temperature
- Uncommon where water exceeds 15°C (59°F) for extended periods; juvenile rearing associated with summer temperatures under 15°C. Juvenile concealment declines as temperature approaches about 13.3°C, near peak growth temperature.
- Cover
- Deep pools, large woody debris, rocky stream beds and undercut banks.
What would count against it
- assuming bull trout will use warm water because other salmonids in the system do
Thermal compression in summer concentrates this species in the little cold habitat that remains. Conservation-sensitive record; no presentation implication.
Fall
- Where they sit
- Littoral foraging continues in lakes. In streams the spawning period is under way; spawning substrate and pre-spawn holding water are conservation context and are excluded from this record's habitat description.
- Temperature
- Spawning is associated with water dropping below about 8–9°C.
What would count against it
- using spawning substrate as holding water
- reading the fall spawning period as an activity or opportunity window
Fall spawner. Spawning gravel, redds and any pre-spawn holding water are excluded from target guidance, and no spawning area or aggregation is named. Presentation guidance is withheld for this species in every season.
Late fall
- Where they sit
- Movement out of spawning reaches toward wintering habitat, then the winter deep-by-day / margin-by-night pattern.
What would count against it
- assuming spawning has finished because the calendar has turned
USFWS records spawning between August and November and sometimes as late as December, so late-fall spawning overlap remains conservation caution. Presentation guidance is withheld.
Spawning · Late summer, Fall, Late fall
Late-summer through fall spawning in very cold, clean, connected tributary habitat; redds and spawning concentrations are never targeting outputs.
Recorded as conservation context. No spawning site, staging concentration or migration bottleneck is named anywhere in this catalog, because naming one is how a population gets fished out.
Telling it apart
Identification
What to look at
- Dorsal fin carries no black spots or lines; some fish show a few light markings along the base of the dorsal fin. Brook trout show solid black dorsal markings with distinct edges, and bull trout × brook trout hybrids show markings that are neither solid black nor sharply edged. ODFW notes this key applies to fish of at least 125 mm.
- Sides carry pale spots — cream, pink, yellow, orange, sometimes crimson — with no blue halo around them.
- White leading edges on the fins. WDFW's char key gives white leading edges on the lower fins for brook trout as well, so this trait alone is not diagnostic against brook trout.
- Slightly forked tail; pure fish have spotless dorsal and tail fins, the basis of the fishery-manager phrase 'fins black, put it back'.
- Head and mouth are large relative to the body — a consistent field impression separating bull trout from stream trout of similar length.
- Average adult length
- Life-history dependent. USFWS gives stream residents reaching about 10 in and migratory forms reaching about 35 in. Oregon Sea Grant cites migratory populations up to 41 in.
- Common angling size
- Not a target species in this catalog — bull trout are ESA-listed as threatened across much of their U.S. range and encounters here are incidental. As a size frame only, Montana FWP's guide separates stream juveniles under 20 in from lake adults over 20 in, and states that all bull trout must be released immediately where catch-and-release seasons apply.
- Typical weight
- The sources reached give maxima rather than a typical weight. USFWS gives migratory forms to about 32 lb; the Montana AFS species account gives 20+ lb for large fish. No sourced typical weight for stream residents.
- Maximum documented
- USFWS: about 35 in and 32 lb for migratory forms. Montana AFS: 37 in and 20+ lb. Oregon Sea Grant: up to 41 in and 32 lb. Maxima are population-specific and these three agency figures do not resolve to one number.
- Longevity
- USFWS gives maturity at four to seven years; the Montana AFS account gives a minimum breeding age of five. Maximum age was not found in the sources reached.
What it gets confused with
- Brook trout
- Brook trout carry solid, sharply edged black markings on the dorsal fin and crimson spots ringed with blue halos, plus worm-trail vermiculations on the back. Bull trout have an unmarked dorsal fin and pale spots with no blue halo. Bull trout × brook trout hybrids show intermediate dorsal markings that are neither solid black nor distinctly edged — a hybrid is not a bull trout and should not be forced into this record.
- Dolly Varden
- The agency keys reached for this record (WDFW) treat bull trout and Dolly Varden together as light-spotted char with no blue halos and do not supply a field character separating them. Where ranges overlap, this record does not support a reliable field separation from Dolly Varden.
- Lake trout
- Lake trout carry irregular white or gray spots rather than the orange-to-cream spotting of bull trout and Dolly Varden.
What follows from all of that
Presentation families
Flowing water
The record documents Bull trout in flowing water but has no reviewed presentation family for it. Presence and a method are different claims and only the first one is made here.
Stillwater
The record documents Bull trout in stillwater but has no reviewed presentation family for it. Presence and a method are different claims and only the first one is made here.
What moves them for this fish
No species-specific rule is reviewed for Bull trout. Its ranking comes from the shared model — season, temperature, water type, holding water, forage — with nothing added for this fish in particular. That is a gap, not a claim that nothing is special about it.
Where every sentence came from
Sources
Agency
USFWS species profile: Bull Trout (Salvelinus confluentus)
Used for identification; behaviour; forage; season. Read 2026-08-30, next check 2026-11-28.
Agency
Used for behaviour; forage; season. Read 2026-08-30, next check 2026-11-20.
Agency
U.S. Fish & Wildlife Service bull trout species profile and 5-year status review
Used for habitat, thermal band and presentation families. Read 2026-08-27, next check 2026-11-27.
Agency
USFWS bull trout Species Status Assessment
Used for habitat, thermal band and presentation families. Read 2026-08-27, next check 2026-11-27.
Agency
Oregon Department of Fish and Wildlife bull trout identification guide (dorsal-fin marking key)
Used for identification. Read 2026-08-30, next check 2026-11-28.
Agency
Montana Fish, Wildlife & Parks bull trout identification guide
Used for identification. Read 2026-08-30, next check 2026-11-28.
Agency
WDFW, Salmon and Trout: The Identification Guide (char section)
Used for identification. Read 2026-08-30, next check 2026-11-28.
Agency
Oregon Sea Grant native fishes account: bull trout
Used for identification. Read 2026-08-30, next check 2026-11-28.
Agency
Idaho Governor's Office of Species Conservation — bull trout account (listing status and threats)
Used for behaviour. Read 2026-08-30, next check 2026-11-20.
Peer reviewed
Used for behaviour; season. Read 2026-08-30, next check 2026-11-20.
Peer reviewed
Used for behaviour; season. Read 2026-08-30, next check 2026-11-20.
Peer reviewed
Rieman & McIntyre bull trout habitat and conservation literature
Used for habitat, thermal band and presentation families. Read 2026-08-27, next check 2026-11-27.
Synthesis
Montana Chapter, American Fisheries Society — bull trout species of concern status account
Used for identification; behaviour; forage; season. Read 2026-08-30, next check 2026-11-28.
A source with no link predates the rule that one has to carry a URL. It is still a real citation and still checkable; it just takes a search rather than a click, and that is worth knowing before you rely on it.