Other freshwater · Freshwater
Rainbow smelt
Osmerus mordax
Native to Atlantic coastal drainages and landlocked in some northern lakes; introduced through much of the Great Lakes and other inland systems.
Also called smelt, American smelt.
- Stillwater
- Ordinary target
- 4 of 4 overlays reviewed
- Reviewed 2026-08-27
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 Rainbow smelt there are 17 of them.
Named by a reviewer
14Somebody looked for this and wrote down that they did not find it.
- Behaviour
A generalisable rule for smelt position relative to the thermocline. The one lake study reached found them above it, in warm epilimnetic water, which contradicts the common assumption; the catalog's thermocline_edge holding class should be treated as lake-specific.
Cold-front, barometric and water-clarity responses with primary-source support.
Angling-pressure response with primary-source support.
Whether anadromous and landlocked forms differ behaviourally beyond the spawning migration.
Autumn behaviour and any pre-winter depth shift.
- Identification
A sourced typical weight; agency accounts report length only.
Spawning coloration or breeding tubercles as a field character.
Regional colour variation between anadromous and landlocked forms as a structured field.
Vernacular names beyond 'smelt' from an agency source.
- Forage
Season-by-season diet composition from a primary source; no sourced seasonal breakdown was found, so seasonalDiet is omitted.
Whether the fish-eating fraction of the adult diet is a general pattern or specific to large Great Lakes populations.
- Season
A fall entry. The agency sources reached describe winter, ice-out spring and stratified summer, but not autumn distribution or a pre-winter depth shift.
A defensible general rule for depth relative to the thermocline; the evidence reached is contradictory and lake-specific.
The catalog holding class 'inlet' is not connected to a season here, because the only sourced context for inlet-adjacent water is spawning movement, which is excluded from target guidance.
Absent from the record
3No reviewer wrote a gap here. The field is simply empty, which is its own answer.
- Water temperature
No agency or peer-reviewed temperature band for Rainbow smelt 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
Stillwater
5 reviewed holding classes- Suspended / open water
- Thermocline edge
- Basin
- Inlet
- Drop-off
DepthAdults use cool pelagic water and can make strong diel vertical movements; seasonal depth may range from nearshore to very deep basins.
Moving waterReviewed here as a lake / reservoir pelagic fish; spawning runs are intentionally not modeled as flowing-water targets.
LightLow light often permits higher positioning while clear bright conditions favor deeper pelagic layers.
Thermal band
Temperature
No reviewed temperature band
Nobody publishes a preferred or active temperature range for Rainbow smelt 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
New Hampshire Fish and Game describes smelt travelling in schools in the mid-water column. Michigan DNR describes offshore schools that move shallower on a seasonal cycle. This is a pelagic schooling forage species, not a structure-holding solitary fish.
Opportunistic zooplanktivores that add larger prey as they grow — amphipods, ostracods, mysids and aquatic insect larvae, then small fish including smaller smelt (USFWS, Michigan DNR). A Canadian Field-Naturalist study of an introduced population found smelt feeding primarily on calanoid copepods, the same prey as the native planktivores.
Michigan DNR describes nocturnal movement, and notes that winter fisheries use lights at night to draw smelt up from the bottom — direct evidence of upward movement in the water column after dark. Peer-reviewed hydroacoustic work on Osmerus mordax attributes this vertical movement to light rather than to temperature.
Seasonal activitySpawning occurs in spring shortly after ice-out (New Hampshire Fish and Game, Michigan DNR). USFWS gives onset near 4.4°C with peak activity near 10°C; Michigan DNR gives an April period lasting about three weeks. Outside that period the sourced accounts place smelt in deeper, cooler, offshore water.
Temperature-driven behaviourUSFWS gives a tolerance range of about −1.8°C to 20°C with an optimum of 6–18°C (roughly 43–64°F). The catalog band of 42–55°F sits inside that optimum. Agency accounts consistently describe smelt as a cool, clear-water species; Michigan DNR describes cool, dark water.
Depth movementUSFWS records smelt from the surface to about 425 m, though usually shallower than 150 m; New Hampshire Fish and Game records marine fish as far as 60 km offshore in depths to 77 m. Michigan DNR: deeper offshore water outside the spawning period, ascending seasonally. Vertical position within a stratified lake is lake-specific — a Canadian Field-Naturalist study found the largest numbers in a 6.1–11.3 m stratum in epilimnetic water at 18–21°C above an 11–13 m thermocline, so a general 'always below the thermocline' rule is not supported by the sources reached.
Open waterPelagic and mid-water rather than structure-associated. In lakes smelt function as a principal forage species for lake trout, walleye and other predators (Ontario, Michigan DNR), which is why their distribution is usually described in terms of the open water column rather than cover.
Spawning (conservation context)Spring spawner shortly after ice-out. Spawning takes place at night and lasts several days (New Hampshire Fish and Game). Adhesive, negatively buoyant eggs stick to substrate and hatch in about two to three weeks (USFWS). Spawning movements out of the lake, the waters used for them, and any structure that constricts them are conservation and regulatory context and are excluded from target guidance.
Where the general rule stops
- Tributary spawning concentrations are intentionally excluded from this angling presentation record.
- In many inland systems rainbow smelt are nonnative and can alter native food webs; local status matters.
What it can eat
Forage
- Zooplankton
- Crustaceans
- Aquatic insects
- Small forage fish
Smelt are opportunistic zooplanktivores that broaden with size. USFWS lists amphipods, ostracods, aquatic insect larvae, copepods, mysids and small fishes. Michigan DNR gives aquatic invertebrates and other fish including smaller rainbow smelt, sculpins, burbot and whitefish, and names shrimp-like crustaceans as a principal Great Lakes food. Ontario notes they compete for plankton and consume young native fish. This is dietary capacity, not evidence of a current forage event.
- Feeding style
- Opportunistic
- Feeding zone
- Pelagic
By life stage
- Young of year
- Copepods and cladocerans, plus rotifers, eggs and algae (Alaska Department of Fish and Game).
- Juvenile
- Zooplankton, with amphipods, ostracods and aquatic insect larvae added as size allows (USFWS).
- Adult
- Mysids and other shrimp-like crustaceans, copepods, amphipods, worms and small fish, including smaller smelt (Alaska Department of Fish and Game, USFWS, Michigan DNR).
Prey sizePrey size tracks fish size. The catalog small_forage_fish class belongs to larger adults; young-of-year smelt are on zooplankton.
Ontogenetic shiftZooplanktivory through the first year, then a widening diet that adds macro-crustaceans and small fish. Cannibalism on smaller smelt is reported by Michigan DNR.
SubstitutionsMysids and other shrimp-like crustaceans substitute for copepods and cladocerans in the Great Lakes (Michigan DNR); the Canadian Field-Naturalist study found calanoid copepods dominating in an inland lake. Substitution is system-specific.
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.
Through the year
Season
Winter
- Where they sit
- Open basin and suspended-open water in the main body of the lake; drop-offs and basin edges where the water column is deep enough to hold cool water.
- Depth
- Michigan DNR places smelt deep and offshore outside the spawning period; the same source notes they rise off the bottom after dark.
- Movement
- Vertical rather than lateral — smelt move up in the column at night and back down toward the bottom in daylight.
- Temperature
- USFWS tolerance extends to −1.8°C; cold water is not a constraint on this species.
- Light
- Strong. Michigan DNR records winter fisheries using lights at night specifically to draw smelt up from the bottom, and peer-reviewed hydroacoustic work attributes the vertical movement to light.
What that changesVertical jig and drop presentation are the reviewed still-water families that match a fish holding near bottom by day; suspended stationary matches a fish that has risen off the bottom after dark.
What would count against it
- searching horizontally for a fish whose sourced movement is vertical
- assuming a fixed depth — the sourced depth range is very wide and lake-specific
Spring
- Where they sit
- Upper and mid water column of the open basin as the lake warms from ice-out.
- Movement
- Spawning movement occurs shortly after ice-out. That movement is conservation context and is not described here as target water.
- Temperature
- USFWS gives spawning onset near 4.4°C with peak activity near 10°C; Michigan DNR gives an April period of about three weeks.
What would count against it
- treating spawning timing as a location cue
- moving smelt between waters
Spring spawning period. The spawning movement, the waters used for it, and any structure that concentrates spawning fish are excluded from target guidance. Smelt are also a regulated and, in many inland waters, an invasive species with transport and possession restrictions — check the local rule before handling.
Summer
- Where they sit
- Suspended open water and basin, with drop-offs and thermocline edges as the boundary of usable water in stratified lakes.
- Depth
- USFWS places young-of-year in warmer nearshore water at roughly 2–6 m and yearlings in cooler pelagic water. Adult depth within a stratified lake is lake-specific; one study found the bulk of fish in a 6.1–11.3 m stratum above the thermocline.
- Forage
- Zooplankton, with mysids and other shrimp-like crustaceans where present.
- Temperature
- Optimum 6–18°C (about 43–64°F), tolerance to about 20°C (USFWS). The catalog band of 42–55°F sits inside that optimum.
- Light
- Nocturnal ascent in the column continues to structure where fish are found at a given hour.
What that changesTrolling and suspended stationary are the reviewed still-water families that match a pelagic open-basin distribution; vertical jig and drop presentation apply where fish are located over a drop-off or a thermocline edge.
What would count against it
- assuming smelt sit below the thermocline as a rule — the one sourced lake study found them above it
- treating a single depth as transferable between lakes
Spawning · Early spring, Spring
Spawning follows ice-out in very cold tributaries or shoreline habitat; this record excludes tributary aggregation targeting from its reviewed presentation set.
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
- A small fleshy adipose fin sits between the dorsal fin and the tail. Minnows and shiners have no adipose fin (Ontario).
- Well-developed canine-like teeth on the tongue and on the roof of the mouth. Lake whitefish and cisco also carry an adipose fin but are deeper-bodied and lack teeth on the tongue and palate (Ontario, Alaska Department of Fish and Game).
- Large terminal mouth with the lower jaw projecting slightly beyond the upper (Alaska Department of Fish and Game).
- Fewer than 75 scales along the lateral line; scales are small and shed very easily when handled (Maine IFW, Ontario).
- The single dorsal fin is set near the middle of the back (Ontario).
- Average adult length
- USFWS gives adults at 100–350 mm (about 4–14 in). Michigan DNR gives 3–6 in in the Great Lakes. Maine IFW gives 3–5 in in most waters and 6–8 in in northern Maine lakes. Ontario gives an average near 19 cm.
- Common angling size
- State accounts put most fish handled well under 10 in — New Hampshire Fish and Game states they rarely exceed 10 in (250 mm), and Maine reports 3–8 in as typical depending on the water.
- Typical weight
- Not established in the agency sources reached. State and federal smelt accounts report length and age rather than weight, and no sourced typical weight is asserted here.
- Maximum documented
- USFWS gives up to 35.6 cm (about 14 in) in large lakes under optimal conditions. Maine IFW reports occasional fish to 14 in.
- Longevity
- USFWS gives 7+ years in large lakes under optimal conditions, with shorter lifespans in smaller systems. New Hampshire Fish and Game describes smelt as short-lived and maturing in their second year; Michigan DNR reports most Great Lakes fish mature by the end of two growing seasons.
What it gets confused with
- Cisco and lake whitefish (Coregonus spp.)
- Coregonines share the adipose fin but are deeper-bodied and have no teeth on the tongue or the roof of the mouth. Smelt is slim, big-eyed, and obviously toothed (Ontario).
- Minnows and shiners (Cyprinidae)
- Minnow-family fish have no adipose fin and no prominent teeth. Smelt has both (Ontario).
What follows from all of that
Presentation families
Stillwater
Vertical jig
Work a compact bait up and down through a marked depth, basin, or timber pocket.
- stay over the target
- measured lift
- controlled drop
- watch slack
What it asks of the tackle
- Depth control
- High
- Sensitivity
- High
- Casting distance
- Vertical
- Weight range
- 1/8–3/4 oz
- Cover resistance
- Moderate
- Line visibility
- Low
- Retie frequency
- Moderate
Suspend / pause
Leave a neutrally buoyant bait hanging in place where fish are already holding.
- reach the band
- long pause
- tiny pulse only if needed
- do not leave the zone
What it asks of the tackle
- Depth control
- High
- Sensitivity
- High
- Casting distance
- Moderate
- Weight range
- 1/8–3/8 oz suspending
- Cover resistance
- Low
- Line visibility
- Low
- Retie frequency
- Low
Horizontal retrieve
Move a swimming bait through a chosen depth band along structure or open water.
- count down
- steady or pulsing retrieve
- keep the band
- cover the edge
What it asks of the tackle
- Depth control
- Moderate
- Sensitivity
- Moderate
- Casting distance
- Moderate to long
- Weight range
- 1/8–1/2 oz
- Cover resistance
- Moderate
- Line visibility
- Low
- Retie frequency
- Low
Trolling
Cover a depth contour or basin at a controlled speed to intercept mobile fish.
- speed control
- depth control
- follow the contour
- turn to change action
What it asks of the tackle
- Depth control
- High
- Sensitivity
- Low
- Casting distance
- Boat
- Weight range
- Varies with speed and depth
- Cover resistance
- Low
- Line visibility
- Moderate
- Retie frequency
- Low
What moves them for this fish
Reviewed rules that push particular families up when the conditions match. Each one names the conditions it needs and why it exists, so you can disagree with it.
Rainbow smelt are strongly pelagic with diel vertical movement; reinforce depth-band mechanics and keep tributary spawning runs outside the model.
When
Stillwater · Suspended / open water, Thermocline edge, Basin, Drop-off
Moves up
Vertical jig, Suspend / pause, Trolling, Horizontal retrieve
Reviewed 2026-08-27
Where every sentence came from
Sources
Agency
USFWS Ecological Risk Screening Summary, rainbow smelt (Osmerus mordax), 2025
Used for identification; behaviour; forage; season. Read 2026-08-30, next check 2026-11-21.
Agency
Michigan DNR Michigan species, smelt
Used for identification; behaviour; forage; season. Read 2026-08-30, next check 2026-11-21.
Agency
New Hampshire Fish and Game rainbow smelt species account
Used for identification; behaviour; season. Read 2026-08-30, next check 2026-11-21.
Agency
Government of Ontario rainbow smelt invasive species profile
Used for behaviour; forage; season. Read 2026-08-30, next check 2026-11-20.
Agency
Alaska Department of Fish and Game rainbow smelt species profile
Used for identification; forage. Read 2026-08-30, next check 2026-11-21.
Agency
USGS Nonindigenous Aquatic Species rainbow smelt profile
Used for habitat, thermal band and presentation families. Read 2026-08-27, next check 2026-11-27.
Agency
Maine Department of Marine Resources rainbow smelt biology
Used for habitat, thermal band and presentation families. Read 2026-08-27, next check 2026-11-27.
Agency
Government of Ontario rainbow smelt invasive species profile (identification and lookalikes)
Used for identification. Read 2026-08-30, next check 2026-11-21.
Agency
Maine Department of Inland Fisheries and Wildlife rainbow smelt species information
Used for identification. Read 2026-08-30, next check 2026-11-21.
Peer reviewed
Used for behaviour; forage; season. Read 2026-08-30, next check 2026-11-20.
Peer reviewed
Used for behaviour. Read 2026-08-30, next check 2026-11-20.
Peer reviewed
Used for season. Read 2026-08-30, next check 2026-11-27.
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.