The freshwater drum (Aplodinotus grunniens) is the only member of its marine family, Sciaenidae, to live entirely in North and Central American freshwaters. This adaptable fish is a common resident of many rivers and lakes, known for its distinctive characteristics.
Identifying Characteristics
The freshwater drum has a silvery to dusky-gray coloration. It possesses a deep, laterally compressed body, giving it a somewhat humpbacked appearance, with a long, sloping forehead and a blunt snout. A defining feature is its long dorsal fin, which is divided into two distinct parts, usually containing 10 spines and 29 to 32 rays. The fish’s lateral line, a sensory organ, uniquely extends all the way into its rounded caudal (tail) fin.
Adult freshwater drum are typically 10 to 30 inches in length and weigh 2 to 10 pounds, though some individuals can reach over 36 pounds. Within its head, the freshwater drum possesses large, bony structures called otoliths, often referred to as “lucky stones”. These otoliths, which aid in balance and hearing, were historically collected and used as jewelry by Native Americans.
Habitat and Behavior
The freshwater drum has an expansive geographical range, extending from Hudson Bay in the north to Guatemala in the south, and from the Appalachian Mountains westward into Texas, Kansas, and Oklahoma. This species thrives in various aquatic habitats, including large rivers, lakes, and reservoirs, often preferring areas with clean sand or gravel bottoms. While it prefers clear water, it demonstrates tolerance for turbid or murky conditions. Freshwater drum are primarily bottom feeders, using their snouts to dislodge prey from the substrate. Their diet primarily consists of mollusks like clams and snails, crayfish, and aquatic insects, though they will also consume small fish, particularly young gizzard shad, at certain times of the year.
The freshwater drum produces a “drumming” sound, which gives the fish its common name. This sound is generated by specialized muscles vibrating against the swim bladder. While the exact purpose is not fully understood, it is believed to be linked to spawning, as mature males produce these grunting noises during the breeding season. Spawning typically occurs once a year for about six to seven weeks in late spring to early summer, when water temperatures reach around 65-70°F (18-21°C). Females release a large quantity of eggs into the open water, which float and are randomly fertilized, with no parental care provided.
Freshwater Drum and People
The freshwater drum is a popular target for recreational anglers, valued for its strong fighting ability when hooked. Despite its reputation in some areas as a “rough fish,” it is edible and can be quite palatable. Its flesh is white and firm, and many anglers attest to its quality, particularly when properly prepared. The fish is known by numerous alternative common names across its range, including sheepshead, grunter, gaspergou, and croaker, reflecting its widespread presence and diverse regional perceptions.
Ecologically, the freshwater drum plays a role within its ecosystem, consuming various invertebrates and even invasive species like zebra mussels once they reach a certain size. Juvenile drum serve as forage for larger predatory fish, including walleye, smallmouth bass, and yellow perch. The species is not typically a conservation concern, as it maintains a widespread and stable population across its extensive range.