Other freshwater · Freshwater
Freshwater drum
Aplodinotus grunniens
Native large-river and lake sciaenid of central/eastern North America; a benthic generalist with strong mollusk and invertebrate use.
Also called sheephead, gaspergoo, gou, thunder pumper, croaker, drum, sheepshead, gaspergou.
- Flowing water
- 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 Freshwater drum there are 22 of them.
Named by a reviewer
19Somebody looked for this and wrote down that they did not find it.
- Behaviour
Nobody has sourced:
- no telemetry- or gut-content-based diel activity study was reached; the nocturnal class rests on agency narrative and one state encyclopedia
- no primary source found for cold-front / barometric response
- no primary source found for water-level or flow-change response
- no primary source found for angling-pressure response
- territoriality, aggression, and predator avoidance are not described in the sources reached; fields omitted
- social structure outside the spawning period is not characterised
- Identification
Nobody has sourced:
- longevity is badly unresolved — 13 years versus 50-plus years across agency sources — and needs a human decision
- typical weight ranges disagree by an order of magnitude between state agency and encyclopedia accounts
- no sourced description of juvenile appearance or spawning coloration was found; those fields are omitted
- sexual dimorphism is only indirectly indicated (sound production attributed to mature males in one source) and is not written as a field key
- one state source describes small barbels beside the mouth, which no other source supports; that character is deliberately excluded
- no sourced seasonal clarity/turbidity response; turbidity tolerance is recorded in the behavior record only
- Forage
Nobody has sourced:
- only the fall seasonal diet entry is sourced; no winter, spring, or summer diet composition was reached
- the mollusk-dominance question is genuinely contested between a Great Lakes dreissenid record and a mid-continent state agency account; both are recorded rather than reconciled
- no quantitative diet study for riverine (as opposed to Great Lakes) populations was reached
- Season
Nobody has sourced:
- seasonal habitat class is largely inferred from year-round habitat statements plus the movement record; only the movement and thermal contexts are directly seasonal in the sources
- no sourced winter or spring diet composition
- no sourced late_fall material, and no early_spring / early_summer / late_summer material
- the movement figures come from a single large lake–river system and may not generalise to reservoir or small-river populations
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 Freshwater drum 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
4 reviewed holding classes- Deep pool
- Run
- Current break
- Pool tail
Stillwater
4 reviewed holding classes- Basin
- Drop-off
- Riprap
- Point
DepthPredominantly lower-column and bottom-oriented; larger fish commonly use deeper water while moving shallower to feed under favorable conditions.
Moving waterUses large-river current and channel habitat but commonly feeds along bottom transitions, holes, and current-washed structure.
LightFeeds by day and night, with low-light and nighttime benthic feeding often increasing shallow accessibility.
Thermal band
Temperature
No reviewed temperature band
Nobody publishes a preferred or active temperature range for Freshwater drum 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
Adults are described as schooling around the spawning period, and acoustic telemetry shows highly mobile individuals rather than fixed-lie holders. Outside the spawning period the sources reached do not characterise group structure, so treat this as a loosely grouped bottom fish rather than a tight school.
A true bottom forager. The underslung mouth is used to root through substrate, and the fish is repeatedly described as flipping stones and moving bottom material with its blunt snout and forehead to dislodge prey. Behind the mouth sit heavy molar-like pharyngeal teeth that crush shelled prey — a capability that develops with size and reshapes the diet.
Agency and state-encyclopedia accounts describe drum as feeding through the night, with one calling the species strongly nocturnal. Daytime bottom feeding also occurs — one state agency notes fish visible feeding in shallow areas. No telemetry-grade diel activity study for this species was reached, so read the nocturnal label as an emphasis rather than an exclusive pattern.
Seasonal activityRemarkably mobile. Acoustic telemetry in a large lake–river system recorded mean monthly movement rates among the highest on record for any freshwater fish — roughly 27–45 km per month in winter, rising through spring, and reaching about 87–219 km per month in summer and fall, with some individuals covering over 620 km in four months. Fish enter rivers in spring ahead of spawning, then move into lake habitat and range laterally. Site fidelity to the natal river across successive years is nearly complete.
Temperature-driven behaviourStress appears when water exceeds about 25.6°C (78°F), particularly when it coincides with prolonged low dissolved oxygen. This is a warm-tolerant species relative to the rest of this dossier set, consistent with the catalog's 65–75°F preferred band.
Depth movementOccupies the bottom of medium to large rivers and lakes to roughly 40–60 ft; one state agency records fish frequently at about 30 ft in large river pools and reservoirs.
Facing the currentAssociated with slow to moderate current over sand or mud, and with deep pools and backwaters of sluggish current in rivers. Not a fast-water fish.
ClarityTolerates turbid and murky water well and is often more abundant in turbid systems than clear ones, though it occurs across both. Body colour shifts with water condition.
CoverSubstrate rather than structure. Sand, mud, and mixed mud-and-sand bottoms are the repeatedly named associations; the fish works the bottom material itself rather than holding to cover objects.
Open waterIn lake habitat, telemetered fish made extensive lateral movements rather than settling into a home area, which is unusual for a benthic species and is the most striking behavioral finding in the record.
Spawning (conservation context)Late spring to early summer broadcast spawner — accounts range from April–May through June–July depending on latitude — at water temperatures around 18–26°C (roughly 65–79°F). No nest and no parental care. Uniquely among most freshwater fishes, the eggs and newly hatched larvae are buoyant and drift at the surface, sometimes for miles, before the fry emerge. Sound production intensifies during the spawning period. All of this is conservation context; spawning water and spawning aggregations are excluded from target guidance.
Where the general rule stops
- A school or seasonal movement is not a hotspot map; freshwater drum can be mobile and forage-linked.
- Large adults may be much more mollusk-focused than juveniles, so forage class should remain falsifiable in the field.
What it can eat
Forage
- Mollusks
- Crustaceans
- Aquatic insects
- Small forage fish
- Zooplankton
A benthic generalist whose diet is strongly system-dependent, and the sources disagree in an instructive way. A federal profile gives adults immature insects, crayfish, minnows, amphipods, and mollusks. A state agency explicitly pushes back on the assumption that drum are primarily mollusk eaters, reporting fish, crayfish, and immature aquatic insects as the mainstay in its waters. In dreissenid-invaded systems the picture flips: large drum can become overwhelmingly molluscivorous. Do not assume mollusk dominance from the pharyngeal teeth alone. Capacity is not a current prey event.
- Feeding style
- Opportunistic
- Feeding zone
- Benthic
Through the year
- Fall
- Young-of-year gizzard shad are reported to make up over half the diet during autumn where that forage exists — the clearest seasonal signal in the record.
By life stage
- Young of year
- Larvae and small fish take microcrustaceans, zooplankton, copepods, chironomids, and fish fry — soft-bodied prey.
- Juvenile
- The transition stage. A dietary shift from small soft prey toward larger, harder-bodied prey occurs above roughly 7 cm standard length, alongside allometric changes in mouth position, gape, and head depth.
- Adult
- Immature insects, crayfish, amphipods, minnows and other small fish, and mollusks — with the balance set by what the system offers.
Prey sizeGape and mouth position change with growth: larger fish have a more anteriorly positioned mouth, a more expansive gape, and greater body depth, all of which enlarge the prey they can take.
Ontogenetic shiftOne of the better-documented ontogenetic shifts in this catalog, and it is a shift in processing hardware as much as in prey. Pharyngeal teeth change with size: the smallest fish have only cardiform and villiform teeth; the first molariform teeth appear around 17 cm total length, and by about 25 cm molariform teeth make up roughly 85% of pharyngeal tooth surface area, which is where shell crushing begins. In one Great Lakes study no shell fragments appeared in fish under 25 cm, while dreissenid mussels rose from about 6% of the diet in the 25–29 cm size class to about 88% in the 38–50 cm class.
SubstitutionsIn dreissenid-invaded systems, large drum substitute mussels for much of the diet. Where gizzard shad are produced, young shad carry the autumn diet. In systems without either, the diet reverts to crayfish, immature insects, and small fish. Substitution is system-specific and size-gated: a fish under about 25 cm cannot make the mussel substitution at all.
Diet capacity is not proof that a mussel, crayfish, or baitfish event is occurring. Observed current forage still comes from a user observation or Hatch Match.
Through the year
Season
Winter
- Where they sit
- Bottom-associated water: deep pools and runs in rivers, basins and drop-offs in lakes.
- Movement
- The lowest movement rates of the year in the telemetry record — roughly 27–45 km per month, against 87–219 km in summer and fall — and the smallest home ranges.
- Feeding
- No sourced winter diet composition; treat forage as unresolved for this season.
What that changesBottom contact and slow drag in still water; bottom-contact drift and stationary bait in flow.
What would count against it
- reading reduced winter movement as a change in feeding zone — the fish is still benthic
Spring
- Where they sit
- River habitat — deep pools, runs, and current breaks — as fish enter rivers ahead of spawning.
- Movement
- Movement rises sharply from winter levels; fish enter rivers, then move into lake habitat a few weeks later. Site fidelity to the same river across successive years is near-complete.
- Temperature
- Spawning begins as water reaches roughly 18–26°C (65–79°F), which is at and above the catalog's 65–75°F preferred band.
What would count against it
- using spawning-period movement as a targeting cue
Spawning season begins in the late-spring window in southern waters. Spawning water and spawning aggregations are excluded from target guidance.
Summer
- Where they sit
- Bottom of medium-to-large rivers and lakes over sand, mud, and mixed substrate; basins, drop-offs, points, and riprap in still water; deep pools and current breaks in flow.
- Depth
- Bottom to roughly 40–60 ft, with about 30 ft frequently reported in large river pools and reservoirs.
- Movement
- The most mobile season, with extensive lateral movement through lake habitat rather than settled occupancy.
- Feeding
- Benthic rooting — flipping stones and working substrate to dislodge prey.
- Temperature
- Preferred band 65–75°F; stress appears above about 78°F, and worsens where prolonged low dissolved oxygen coincides.
- Current
- Slow to moderate current over sand or mud; deep pools and backwaters of sluggish current.
- Light
- Feeding is described as running through the night, though daytime bottom feeding also occurs.
What that changesBottom contact, slow drag, and drop presentation match a fish rooting through substrate in still water; vertical jig over deep basin and drop-off. In flowing water, bottom-contact drift, tight-line drift, and stationary bait.
What would count against it
- working the mid-column for a fish that feeds on the bottom
- assuming mollusk forage in a system with no mollusk record, or for fish under about 25 cm
Fall
- Where they sit
- Bottom-associated river and lake habitat; movement remains high.
- Movement
- Movement rates stay at or near the summer peak.
- Forage
- Young-of-year gizzard shad are reported to make up over half the diet in autumn where that forage exists. That is a sourced seasonal emphasis, not a declared current event.
What that changesBottom contact and slow drag remain the reviewed stillwater families; bottom-contact drift and tight-line drift in flow. Subsurface slow roll only where a baitfish emphasis is actually observed.
What would count against it
- assuming a shad-forage pattern in a system that does not produce shad
Spawning · Early summer, Summer
Late-spring through summer broadcast spawner as water warms; eggs and larvae are pelagic rather than nest-associated.
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
- The lateral line runs all the way onto and through the rounded caudal fin — unusual among North American freshwater fishes and the single best confirming character.
- One long dorsal fin with a deep notch dividing it into a spiny forward portion (about ten spines) and a long soft-rayed rear portion (about 26–32 rays).
- Blunt, underslung, subterminal mouth built for taking food off the bottom.
- Heavy molar-like pharyngeal teeth in the throat, used to crush shelled prey. Not visible externally but definitive on examination.
- Milky-white lips; pelvic fins often tinged orange.
- Very large otoliths — the ear bones long collected as 'lucky stones'.
- Produces a drumming, grunting, or croaking sound by vibrating muscles against the swim bladder; one account attributes the sound to mature males.
- Average adult length
- Commonly 12–20 in; one agency account gives 10–14 in as typical and another gives a common length near 45 cm (18 in).
- Common angling size
- 12–20 in in most river and reservoir fisheries.
- Typical weight
- 12 oz to 5 lb over the common length range. One state encyclopedia gives an average of 5–15 lb, which is well above the state-agency figures and is treated here as large-river specific.
- Maximum documented
- Documented to about 95 cm (37 in). Record weights reported by agencies and encyclopedias range from roughly 28 lb through 45 lb to a world record near 50 lb.
- Longevity
- Sources disagree sharply. One federal profile gives a maximum of 13 years with an average of 6–8; a federal agency story and a state encyclopedia both report individuals living past 50 years, with 'into a seventh decade' cited. Sexual maturity at 4–6 years, around 20 cm.
What it gets confused with
- Red drum
- The saltwater relative is closely similar in form. Red drum carries a dark caudal spot; freshwater drum has none, and differs in coloration.
- Bigmouth buffalo and carps
- Buffalo and carp lack a notched, spine-bearing dorsal fin and do not carry the lateral line onto the caudal fin. Drum has ten dorsal spines ahead of the notch and the lateral line running into the tail.
- White bass
- White bass has fully separated spiny and soft dorsal fins, a slimmer body, and horizontal stripes. Drum has a single notched dorsal, a humped back, an underslung mouth, and the caudal lateral line.
What follows from all of that
Presentation families
Flowing water
Bottom-contact drift
Tick or crawl a food form along the substrate through a feeding lane without snagging constantly.
- feel the bottom
- short hops
- reset after hang
- weight just enough
What it asks of the tackle
- Depth control
- High
- Sensitivity
- High
- Casting distance
- Moderate
- Weight range
- 1/8–3/8 oz
- Cover resistance
- Moderate
- Line visibility
- Low
- Retie frequency
- Moderate
Pulse / jig
Lift and drop a compact bait so it occupies a pocket, seam, or head without leaving the water column.
- short lift
- controlled drop
- stay in the pocket
- repeat on the same piece
What it asks of the tackle
- Depth control
- High
- Sensitivity
- High
- Casting distance
- Short to moderate
- Weight range
- 1/8–3/8 oz
- Cover resistance
- Moderate
- Line visibility
- Low
- Retie frequency
- High
Stationary bait
Hold a scent or food form in one feeding station and wait for a fish to move to it.
- anchor the presentation
- keep bait in the pocket
- detect takes without sweeping
- refresh often
What it asks of the tackle
- Depth control
- High
- Sensitivity
- Moderate
- Casting distance
- Short
- Weight range
- 1/4–1 oz
- Cover resistance
- High
- Line visibility
- Moderate
- Retie frequency
- High
Stillwater
Bottom contact
Keep a bait on or just above the substrate along a break, flat, or inside a weed edge.
- feel bottom
- drag or hop
- pause on the break
- stay in contact
What it asks of the tackle
- Depth control
- High
- Sensitivity
- High
- Casting distance
- Moderate
- Weight range
- 1/8–1/2 oz
- Cover resistance
- High
- Line visibility
- Low
- Retie frequency
- High
Slow drag
Move a bait along the bottom slowly enough that it stays in the feeding layer of inactive fish.
- continuous contact
- very slow travel
- pause at changes in bottom
- do not hop out of the zone
What it asks of the tackle
- Depth control
- High
- Sensitivity
- High
- Casting distance
- Moderate
- Weight range
- 1/8–3/8 oz
- Cover resistance
- Moderate
- Line visibility
- Low
- Retie frequency
- Moderate
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
Live / natural bait suspension
Present a natural food form with enough life or scent to hold in a station without looking mechanical.
- keep it alive or fresh
- match the holding depth
- minimize hardware bulk
- detect without pulling it away
What it asks of the tackle
- Depth control
- High
- Sensitivity
- High
- Casting distance
- Short to moderate
- Weight range
- As light as conditions allow
- Cover resistance
- Moderate
- Line visibility
- Low
- Retie frequency
- High
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.
Freshwater drum, especially larger adults, can be strongly benthic and mollusk-focused; reinforce substrate contact.
When
Deep pool, Pool tail, Basin, Drop-off, Riprap, Point · Mollusks, Crustaceans
Moves up
Bottom-contact drift, Bottom contact, Slow drag, Stationary bait, Vertical jig
Reviewed 2026-08-27
Where every sentence came from
Sources
Agency
USGS Nonindigenous Aquatic Species — Freshwater Drum (Aplodinotus grunniens) species profile
Used for identification; behaviour; forage; season. Read 2026-08-30, next check 2026-11-25.
Agency
Missouri Department of Conservation — Field Guide: Freshwater Drum
Used for identification; behaviour; forage; season. Read 2026-08-30, next check 2026-11-25.
Agency
U.S. Fish and Wildlife Service — 'Freshwater Drum: The Great Grunting Gaspergoo'
Used for identification; behaviour; forage; season. Read 2026-08-30, next check 2026-11-25.
Agency
West Virginia Division of Natural Resources — Freshwater Drum species page
Used for identification; behaviour; forage. Read 2026-08-30, next check 2026-11-25.
Agency
National Park Service, Mississippi National River and Recreation Area — Freshwater Drum / Sheepshead
Used for identification; behaviour; season. Read 2026-08-30, next check 2026-11-25.
Agency
Used for forage; season. Read 2026-08-30, next check 2026-11-24.
Agency
USGS Nonindigenous Aquatic Species freshwater drum profile
Used for habitat, thermal band and presentation families. Read 2026-08-27, next check 2026-11-27.
Peer reviewed
Used for behaviour; season. Read 2026-08-30, next check 2026-11-25.
Peer reviewed
USGS freshwater drum temperature, growth, and life-history literature
Used for habitat, thermal band and presentation families. Read 2026-08-27, next check 2026-11-27.
Peer reviewed
Used for forage. Read 2026-08-30, next check 2026-11-24.
Synthesis
Encyclopedia of Arkansas (Central Arkansas Library System) — Freshwater Drum
Used for identification; behaviour. Read 2026-08-30, next check 2026-11-25.
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.