F
Species Profile

Freshwater Drum

Aplodinotus grunniens

Hear the river: the freshwater drummer.
Roxana Gonzalez/Shutterstock.com

Freshwater Drum Distribution

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Freshwater drum are large freshwater fish

At a Glance

Wild Species
Also Known As Sheepshead, Sheephead, Gaspergou, Drumfish, Drum, Grunter
Diet Carnivore
Activity Cathemeral+
Lifespan 12 years
Weight 23 lbs
Status Least Concern
Did You Know?

It "drums" by contracting sonic muscles against its swim bladder-like many Sciaenidae, but it's the only species in its family that lives entirely in freshwater (USGS; Sciaenidae biology).

Scientific Classification

The freshwater drum is a widespread North American ray-finned fish in the drum/croaker family (Sciaenidae), notable for producing drumming sounds using specialized muscles against its swim bladder and for feeding heavily on mollusks and other benthic prey.

Kingdom
Animalia
Phylum
Chordata
Class
Actinopterygii
Order
Acanthuriformes
Family
Sciaenidae
Genus
Aplodinotus
Species
Aplodinotus grunniens

Distinguishing Features

  • Deep-bodied, silvery-gray fish with a slightly humped back and subterminal mouth
  • Single long dorsal fin with a distinct notch between spiny and soft portions
  • Produces audible ‘drumming’/croaking sounds via swim bladder vibration
  • Often has pavement-like pharyngeal teeth for crushing snails, mussels, and other hard prey

Physical Measurements

Length
1 ft 8 in (4 in – 3 ft 1 in)
Weight
6 lbs (0 lbs – 51 lbs)
Top Speed
9 mph
Estimated burst ~4 m/s

Appearance

Primary Colors
Secondary Colors
Skin Type Ray-finned fish with ctenoid scales (rough-edged) covering most of the body; lateral line conspicuous and extends onto the caudal fin (a typical sciaenid trait).
Distinctive Features
  • Deep-bodied, laterally compressed 'drum'-like profile with a slightly arched back; head blunt with a subterminal mouth adapted to benthic feeding.
  • Large otoliths (ear stones) typical of sciaenids; species name 'grunniens' refers to grunting/drumming sounds.
  • Specialized sonic (drumming) muscles vibrate the swim bladder to produce audible 'drum' sounds-most often associated with social/spawning behavior; sounds can be heard/recorded in rivers and lakes (including the Great Lakes).
  • Mollusk-crushing pharyngeal teeth (strong throat tooth plates) adapted for hard-shelled benthic prey (e.g., snails, mussels, clams) along with other bottom-dwelling invertebrates and small fishes.
  • No chin barbel (helps distinguish it from some other bottom-feeding sciaenids); lateral line scales extend onto the tail fin.
  • Size (reported maxima): up to 94 cm total length and ~23.4 kg (FishBase summary for Aplodinotus grunniens); commonly much smaller in most waters (often ~30-50 cm TL).
  • Longevity: maximum reported age commonly cited around 13 years in North American populations (e.g., regional age-and-growth studies; Becker-style Great Lakes references), with many fish harvested at younger ages.

Sexual Dimorphism

External sexual dimorphism is generally subtle; sexes look similar in overall coloration and shape. Differences are most evident during the spawning season and in sound production capability.

  • Typically more developed sonic (drumming) musculature associated with the swim bladder and more frequent/intense sound production during courtship/spawning (sex-linked behavior/physiology rather than obvious coloration).
  • May show slightly increased head/shoulder robustness in some populations during the breeding season, but not reliably diagnostic in the field.
  • Often attain slightly larger body size at the same age in some systems (common pattern in many fishes), but overlap is substantial; identification usually requires examination of gonads rather than external markings.
  • No consistent distinctive breeding coloration reported; overall appearance remains similar to males.

Did You Know?

It "drums" by contracting sonic muscles against its swim bladder-like many Sciaenidae, but it's the only species in its family that lives entirely in freshwater (USGS; Sciaenidae biology).

Maximum reported size: 94 cm total length (FishBase) and an IGFA all-tackle record of 23.6 kg.

Longevity is about 13 years (USGS), with age commonly read from its large otoliths ("ear stones").

It has strong pharyngeal (throat) teeth that crush hard prey such as snails and mussels-one reason it can heavily utilize invasive zebra/quagga mussels in the Great Lakes.

Those oversized otoliths are often found by anglers and beachcombers and are widely kept as "lucky stones" or used in jewelry in Great Lakes communities.

Local common names include "freshwater drum" and "sheepshead" (Great Lakes)-the latter referencing its blunt head profile, not actual sheep-like habits.

Unique Adaptations

  • Freshwater specialization within Sciaenidae: unlike most drums/croakers that are marine or estuarine, Aplodinotus grunniens is fully adapted to freshwater across a huge North American range (USGS distribution summaries).
  • Sonic-muscle + swim-bladder "instrument": a reinforced swim bladder functions as a resonator, making low-frequency sounds that travel well in turbid rivers and lakes.
  • Pharyngeal tooth plates for durophagy: specialized throat teeth allow efficient crushing of hard prey (mollusks/crustaceans), enabling exploitation of benthic shell beds.
  • Large otoliths (sagittae): exceptionally big "ear stones" aid hearing/balance and preserve annual growth rings used for precise age estimation in fisheries science.
  • Lateral line extension: the sensory lateral line continues onto the tail fin, improving detection of vibrations/pressure changes-useful for bottom-feeding in low visibility.

Interesting Behaviors

  • Sound production ("drumming"/croaking): males commonly vocalize during the spawning season, using rapid contractions of sonic muscles on the swim bladder (a hallmark behavior of drums/croakers, family Sciaenidae).
  • Benthic foraging: typically feeds along the bottom, using its inferior mouth and small chin barbel to help locate prey in sediment.
  • Mollusk-crushing feeding: captures hard-shelled prey (mussels, snails) and crushes them with robust pharyngeal teeth before swallowing.
  • Seasonal movement: in large lakes and rivers, individuals often shift between deeper/offshore areas and shallower nearshore or tributary habitats with temperature and spawning conditions.
  • Schooling: juveniles and adults may form loose schools, especially in open-water areas of large lakes and big rivers.

Cultural Significance

Freshwater drum (Aplodinotus grunniens) are common in the Mississippi Basin and Great Lakes. Called “sheepshead,” they are seen as rough but good sport and food. Fishers keep their large ear stones as charms and they eat invasive dreissenid mussels.

Myths & Legends

In the Great Lakes region, large white otoliths from the freshwater drum Aplodinotus grunniens are called "lucky stones" and kept as good-luck charms, given to kids, or worn as simple pendants.

For the freshwater drum (Aplodinotus grunniens), Great Lakes dockside stories call it "sheepshead." Some say its blunt, high forehead looks like a sheep's head; others point to bleating drumming sounds underwater.

Boaters and anglers tell campfire tales that lakes 'hum' or 'thump' on warm nights; people often blame schooling Freshwater drum (Aplodinotus grunniens) calling during spawning, saying the water is 'speaking'.

Conservation Status

LC Least Concern

Widespread and abundant in the wild.

Population Stable

Life Cycle

Birth 500000 frys
Lifespan 12 years

Lifespan

In the Wild
6–72 years
In Captivity
5–20 years

Reproduction

Mating System Polygynandry
Social Structure Aggregation Group
Breeding Pattern Transient
Fertilization Broadcast Spawning
Birth Type Broadcast_spawning

Freshwater drum (Aplodinotus grunniens) spawn in groups, releasing eggs and sperm into open water. Eggs float and drift; no pair bonds or care for young. Males drum. Spawning May–Aug (~18–25°C); eggs hatch in 1–2 days. Both sexes have many mates.

Behavior & Ecology

Social School Group: 20
Activity Cathemeral, Crepuscular
Diet Carnivore Hard-shelled benthic mollusks-especially bivalves (mussels; often zebra mussels in invaded systems) crushed with pharyngeal teeth.
Seasonal Migratory, Hibernates 31 mi

Temperament

Generally non-territorial toward conspecifics outside reproduction; social tolerance supports shoaling/schooling in open habitats (observational summaries in Becker 1983).
Seasonally gregarious: can form dense concentrations/aggregations during spawning and at times of movement or habitat compression (Becker 1983; Etnier & Starnes 1993).
Predatory/benthic-foraging disposition: persistent substrate-oriented feeding and strong prey-handling behavior (notably mollusc crushing with pharyngeal teeth), often with repeated localized foraging passes rather than active defense of a feeding territory (Becker 1983).
Freshwater drum (Aplodinotus grunniens) are long-lived; otolith aging shows many live for decades, often up to 70+ years in large lakes, so they often reuse the same seasonal gathering sites yearly.

Communication

Low-frequency swim-bladder 'drumming'/grunting produced by specialized sonic muscles; used most prominently in reproductive/aggregation contexts Classic sciaenid mechanism; described for A. grunniens in Fish & Mowbray 1970
Acoustic signaling is typically strongest at close range in turbid/low-light habitats where visual signals are limited; sounds function in mate attraction and/or social spacing during aggregations Fish & Mowbray 1970; general sciaenid behavioral ecology
Schooling/shoaling coordination via hydrodynamic and mechanosensory cues detected by the lateral line Common across Actinopterygii; relevant to freshwater drum's frequent aggregation behavior
Chemical cues likely contribute to reproductive synchronization and habitat selection Inference consistent with freshwater teleost ecology; species-specific experimental quantification for A. grunniens is limited in the primary literature
Tactile/near-field interactions occur in dense aggregations Body proximity/contact), especially during spawning, but are not typically described as elaborate ritualized contact behaviors for this species (Becker 1983

Habitat

Terrain:
Riverine Plains Valley Coastal Muddy Sandy
Elevation: Up to 1640 ft 5 in

Ecological Role

Benthic mesopredator and major molluscivore in freshwater food webs (lakes and large rivers).

Regulates benthic invertebrate populations, particularly mollusks (including invasive zebra mussels in invaded waters). Transfers energy from benthic production to higher trophic levels (prey base for larger piscivores and fish-eating birds). Bioturbation and nutrient recycling through bottom foraging and processing of shelled prey, contributing to benthic-pelagic coupling.

Diet Details

Main Prey:
Bivalve mussels Aquatic snails Crayfish Aquatic insect larvae Benthic macroinvertebrates Small fish

Human Interaction

Domestication Status

Wild

Freshwater drum (Aplodinotus grunniens) has no domestication history or farmed lines. It is taken from rivers and lakes by recreational and commercial fishers. A benthic predator, it can reach ~94 cm and ~23.5 kg but is usually smaller; wild individuals have lived up to 72 years. Sciaenidae relatives are fished for food, bycatch, or recreation and make sounds.

Danger Level

Low
  • Minor puncture/laceration risk from fin spines and gill covers during handling (typical of many spiny-rayed fishes).
  • Food safety risk depends on waterbody: potential bioaccumulation of contaminants (e.g., mercury/PCBs) in some systems-follow local fish-consumption advisories.
  • Potential for fish-borne parasites if eaten raw/undercooked; proper cooking mitigates risk.

As a Pet

Not Suitable as Pet

Legality: Freshwater drum (Aplodinotus grunniens) can be kept where legally caught, but follow local fishing rules, live transport limits, and bans on moving fish between waters; permits may be needed. Check rules first.

Care Level: Expert Only

Purchase Cost: Up to $50
Lifetime Cost: $2,000 - $15,000

Economic Value

Uses:
Recreational angling species (common in rivers and large lakes; often caught from shore/boats) Commercial fishery species in parts of its range (variable market demand; sometimes sold as food fish or processed product) Bait/forage and bycatch in multi-species inland fisheries Scientific/educational value (otoliths used for age/growth studies; sound production used in behavior/physiology research)
Products:
  • Fresh/frozen fillets and whole fish (food use varies regionally; flesh quality is widely regarded as acceptable to good when properly handled)
  • Fish meal/animal feed (where processed)
  • Cut bait (local use)
  • Otoliths ("lucky stones") collected for curios/education (non-food cultural/economic minor use)

Relationships

Related Species 5

Red drum
Red drum Sciaenops ocellatus Shared Family
Black drum Pogonias cromis Shared Family
Atlantic croaker Micropogonias undulatus Shared Family
Weakfish
Weakfish Cynoscion regalis Shared Family
Spot
Spot Leiostomus xanthurus Shared Family

Ecological Equivalents 5

Animals that fill a similar ecological role in their ecosystem

Redear sunfish
Redear sunfish Lepomis microlophus Overlapping niche as a freshwater molluscivore: both species specialize on hard-shelled benthic invertebrates and commonly use pharyngeal teeth to crush snails and mussels; they often co-occur in warm lakes and reservoirs where snails and unionids are abundant.
Sheepshead
Sheepshead Archosargus probatocephalus Functional analogue in coastal and brackish systems: a strong-crushing benthic feeder that consumes mollusks and crustaceans and occupies a 'shellfish predator' role analogous to the freshwater drum in freshwater.
Channel catfish Ictalurus punctatus Frequently co-occurs in large rivers and reservoirs as a generalist benthic feeder. Both commonly forage on the bottom for invertebrates (insects, crayfish, mollusks) and small fishes, and can be caught together in the same habitats.
Common carp
Common carp Cyprinus carpio Share benthic foraging habitat (soft substrates in lakes and slow rivers) and have overlapping diets of bottom-dwelling invertebrates. Both can significantly influence benthic communities through intense bottom-feeding.
Black drum Pogonias cromis Both are sciaenids (drums) that produce sounds with swim-bladder muscles and feed on benthic mollusks and crustaceans. The freshwater drum, Aplodinotus grunniens, is a widespread freshwater sciaenid that can reach about 94 cm and 23.6 kg.

The freshwater drum is native to Central and North America. It is the only species belonging to the genus Aplodinotus. These interesting fish inhabit freshwater rivers and lakes with rocky beds and sand on the bottom. They go by many names, like grunter, croaker, Russell fish, grinder, Gaspergou, Gasper goo, grinder, and wuss fish.

Freshwater drums’ appearance will differ depending on their habitat. For example, they appear brown in transparent water, but in muddy water, they look silvery or grayish. These fish move in groups and are mostly active at night. They aren’t the easiest fish to catch, as they show strong fighting abilities when trapped and often escape, especially from anglers. But if you are wondering if you can eat these drums, the answer is yes.

Five Amazing Freshwater Drum Facts

  • The biggest recorded freshwater drum weighed around 54 pounds and measured over three feet in length.
  • They are often called grunters because males produce a grunting noise during the breeding season.
  • These fish prefer inhabiting the bottoms of lakes and rivers and spend most of their lives down there looking for food.
  • The current can sweep their eggs for miles, often carrying them to other lakes, rivers, and waterways until they eventually hatch.
  • These fish have strong pharyngeal teeth in their throats, which they use to crush clams, snails, and other mollusks.

 Freshwater Drum Scientific Name

The freshwater drum’s scientific name is Aplodinotus grunniens, and it belongs to the order Acanthuriformes. This order includes a diverse group of ray-finned fishes, and the freshwater drum belongs to the family Sciaenidae. It includes groups like Surgeonfishes, Moorish Idols, and Louvars. In addition, members of this order have sexual reproduction.

Freshwater drums are members of the Sciaenidae family, which is a diverse group of elongated, compressed fishes. They primarily inhabit subtropical coastal and shallow temperate waters.

Freshwater Drum Appearance

The freshwater drum fish is distinguished by its silver scales and grayish-blue overcast. They have deep, compressed bodies with a prominent lateral line that spans the entire length of their bodies. Additionally, other identifying features include:

  • A small horizontal mouth situated at the bottom of the head
  • Blunt nose
  • Prominent arched top
  • White belly
  • Spiny and elongated dorsal fin, divided into two

The freshwater drum varies in size, but its average weight ranges from 1 to 8 pounds, and it can measure between 10 and 24 inches in length.

Man h holding a freshwater drum

Freshwater drums are the only species of their family to occur in only freshwater in North America.

Freshwater Drum Behavior

This species of drum generally moves in large clusters. The juveniles try to gain superiority in their habitat by rivaling other species like trout-perch, emerald shiner, and yellow perch. Additionally, these fish are very vocal, and males make a rumbling or grunting noise during mating season to attract a mate. Their sounds have generated many unique nicknames like pumper, thunder, grunter, croaker, grinder, and bubbler.

Freshwater Drum Habitat

The freshwater drum is the only one in its family in North America to inhabit only freshwater. They generally spend most of their lives on the bottom of medium to large-sized rivers and lakes with depths of around 40 to 60 feet. While they are found in turbid and murky water, they prefer clear water. Anglers can find freshwater drum throughout the central and eastern United States, including the Mississippi River basin, the Great Lakes, and parts of southern Canada.

Freshwater Drum Diet

These mysterious fish are carnivorous and like to feed on mussels, crayfish, and insects. However, their primary source of food is organisms living in the river or lake beds. For example, insect larvae and mussels make up most of their diet. However, juveniles’ eating habits vary depending on the season. Therefore, in spring, during April and May, they eat dipterans. But, from August to November, their diet consists of small fish. In addition, they are strong enough and have sharp teeth to prey on hard-shelled snail species.

Freshwater Drum Predators and Threats

The only animals that prey on freshwater drums are humans and other fish. In fact, during their first year of life, they serve as forage fish for several predatory fish species like the smallmouth bass and walleye. However, once they pass the first year mark, their primary predator is humans. But, for now, they are listed as Least Concern on IUCN’s Redlist.

Freshwater Drum Reproduction, Babies, and Lifespan

These bottom dwellers usually prefer open water to breed. They mate once a year, and their breeding period can last for six or seven weeks. Sexual maturity varies between the sexes of these fish. For example, female drums reach reproductive maturity at five or six years old, while males reach sexual maturity at four. Once females mature, they swim around 33 feet deep into shallow water. Their preferred water temperature is between 65 to 68 °F.

Their breeding season is usually between June and July. During this period, females will release their eggs into open water while the males swim overhead while disposing of their sperm. This behavior is known as spawning, which is common in many fish species. Females can release about 34,000 to 66,500 eggs at once, and fertilization occurs randomly. Once the eggs are fertilized, they float to the surface and only take two to three days to hatch. The larvae emerge and measure around 0.13 inches long. They will stay on the surface for a few more days until they have grown to approximately 0.17 inches. It only takes five to eight days for these fish to transform into their adult form, measuring 0.59 inches. During this stage, they become independent and swim around in search of food.

Lifespan/Longevity

Freshwater drums have a relatively long lifespan of 6 to 13 years in the wild. Unfortunately, there are no records of how long they live in captivity.

Freshwater Drum Population

There are no exact recordings of the freshwater drum’s population size, but researchers assume their numbers exceed 100,000 individuals.

Similar Fish Species

There are several fish species that resemble the freshwater drum, and they are often misidentified. Here are three similar fish species.

Sheepshead

The sheepshead is not just a nickname for the freshwater drum; it’s actually its own species. They are found in the coastal waters of the Western Atlantic, southwest Florida, and the Gulf of Mexico. In addition, smaller populations are also spread throughout Central and South America, all the way to the southern tip of Brazil. Furthermore, they can also occur in brackish waters. They are close relatives of the yellowfin bream and belong to the same family.

Sheepsheads have greenish-yellow or silvery bodies with vertical markings that are evidently prominent in juveniles. Their teeth look eerily similar to humans as they have molars in their upper and lower jaws. Additionally, their dorsal and anal fins contain spines. These fish are omnivores, and their diet consists of plant matter and several species of vertebrates and invertebrates. The sheepshead is caught in large numbers around Florida because people love their taste. The best time for fishermen to catch these fish is during March and April, during their mating season. However, they are caught in the Gulf of Mexico for commercial and recreational purposes.

Carp

The common carp inhabits freshwater bodies over Asia and Europe. Carps have excellent hearing, and their massive mouth helps them to consume larger prey. Their diet includes animals like

However, they also eat plant matter and algae.

These fish are covered in large, thick scales and vary in color from bronze to silver and olive green. Unfortunately, they are preyed on by larger fish and are currently listed as a Vulnerable species because of overfishing. But, even so, they are an invasive species and can easily outcompete other fish for food and space. While many US citizens don’t like the taste of carp, many cultures around the world enjoy the taste of its mild, pink flesh. These fish breed throughout the year, and females can lay a whopping 300,000 eggs at a time.

Channel Bass

The channel bass (Sciaenops ocellatus) goes by many names, such as redfish, red drum, puppy drum, red, and spot tail bass. They are species of game fish primarily found in certain areas of the Atlantic Ocean, Florida, the Gulf of Mexico, and northern Mexico. Channel bass are closely connected to black drums. In fact, these two species can reproduce and form a robust hybrid.

Some of their most distinguishing features include dark red backs that dramatically fade into a white underbelly. Additionally, channel bass have a prominent black spot or eyespot on the base of their tails and streamlined bodies. Because of their common reddish-bronze coloring, they have inherited nicknames like the redfish, but they actually come in an array of colors like copper, silvery-gray, and deep black.

The channel bass population has recovered in some areas due to effective fisheries management. They prefer habitats in shallow waters, with submerged seagrass and other vegetation. In addition, they also enjoy occupying oyster reefs and have been found several miles upriver.

Channel bass’s lifecycle is unique. Once the female is sexually mature, she will release her egg into the water, where the male will take them and fertilize them externally. It takes the eggs around 22 to 28 hours to hatch, which produces tiny larvae that feed on plankton. It takes these larvae about two weeks to fully mature into their adult forms; from then on, growth is rapid.

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Sources

  1. Wikipedia / Accessed January 29, 2023
  2. Kidadl / Accessed January 29, 2023
  3. Guidesly / Accessed January 29, 2023
Chanel Coetzee

About the Author

Chanel Coetzee

Chanel Coetzee is a writer at A-Z Animals, primarily focusing on big cats, dogs, and travel. Chanel has been writing and researching about animals for over 10 years. She has also worked closely with big cats like lions, cheetahs, leopards, and tigers at a rescue and rehabilitation center in South Africa since 2009. As a resident of Cape Town, South Africa, Chanel enjoys beach walks with her Stafford bull terrier and traveling off the beaten path.
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Freshwater Drum FAQs (Frequently Asked Questions)

The freshwater drum is the only one in its family in North America to inhabit only freshwater. They generally spend most of their lives on the bottom of medium to large-sized rivers and lakes with depths of around 40 to 60 feet. While they are found in turbid and murky water, they prefer clear water. Anglers will venter to the Appalachian mountains, Rockies, Guatemala, and Canada to find these drum.