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Freshwater Drum


SCIENTIFIC NAME: Aplodinotus grunniens

CHARACTERISTICS: Also known as the gaspergou, the freshwater drum has a ventral surface that is essentially flat when viewed from the side. The body reaches its greatest depth near the dorsal fin origin, then tapers downward toward a somewhat slender caudal peduncle. The head is small with large eyes and an inferior mouth. The dorsal fin is long, extending from the pectoral fins almost to the base of the convex caudal fin. Most fins are dark gray to black on large individuals. Scales along the back are variously edged in black, producing a body color that varies from dusky gray to dull silvery white. Aplodinotus grunniens has marble-sized bony structures known as otoliths, or “head rocks,” in its head that assist in maintaining balance. Anglers occasionally collect these curious objects from larger specimens.

ADULT SIZE: 28 in (711 mm) in length and 10 lb (4.6 kg) in weight. The state angling record (41 lb, 8 oz) was caught in Wilson Reservoir on the Tennessee River in 1949.

DISTRIBUTION: Freshwater drums are distributed across southern Canada, the central United States from the Mississippi basin eastward to the Appalachian Mountains, and southward to Guatemala. This species is known from numerous main-river collections in the Mobile basin, primarily below the Fall Line, and from the Tennessee River drainage. Records of this species are strangely absent from coastal drainages east of the Mobile basin.

HABITAT AND BIOLOGY: We routinely encounter small freshwater drum in backwaters and along the margins of rivers, reservoirs, and their large tributaries. Large individuals prefer swift areas below dams. Pelagic spawning occurs from May through mid-summer. Males produce a low-frequency drumming sound during spawning, perhaps to attract females and organize the reproduction activities. Females release large quantities of floating eggs during spawning. The freshwater drum is a bottom feeder, consuming aquatic insects, amphipods, fish, crayfish, and mollusks. This is a commercially important species for some freshwater fishermen, generally providing a major source of income. The life span of this species is estimated at 10 to 11 years.

ORIGINAL DESCRIPTION: Rafinesque described the freshwater drum in 1819.

Aplodinotus means simple back, probably in reference to the single dorsal fin.
Grunniens means grunting, for the sounds they make.

The copyrighted information above is from Fishes of Alabama and the Mobile Basin.

ADDITIONAL COMMON NAMES: In the southeast, anglers also call freshwater drum: sheepshead, croaker, grunt, gaspergou, gou, whiter perch, campbellite, according to Cloutman and Olmstead in Fisheries (Vol. 8, No. 2).

Note: In Alabama, it is illegal to stock or move any fish, mussel, snail or crayfish to any public water without a permit.

From Montana Outdoors:

  • Freshwater drum have the ability to grunt. By vibrating a unique set of muscles and tendons against its balloon-like swim bladder, a male drum creates a grunting sound in the spring during breeding season.  Presumably, the sound attracts females from a distance.
  • The lateral line on a drum extends to the end of the tail, rather than just to the base of the tail.  The lateral line allos the drum to pick up extra vibrations and better locate food and enemies.
  • The otolith on a freshwater drum is larger than on most fish.  This white half-sphere of rock-hard calcium, is found in the inner ear of all vertebrates. Smooth on one side and rough on the other, the otolith floats on cilia and helps the fish stay balanced and oriented in murky water.
  • The eggs of freshwater drum float on the surface until they hatch, sometimes traveling fo miles on rivers or wind-swept lakes before the tiny fry emerge.  The uniquely buoyant eggs may help account for the drum's continent-wide range.

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