Aplodinotus grunniens
Freshwater drum
(Also: Sheephead; Sheepshead)

Freshwater drum are the only members of the family Sciaenidae that inhabit freshwater. They have a vast distribution range that extends from as far north as the Hudson Bay to their extreme southern range in the Rio Usumacinata Basin of Guatemala. They are found as far east as the western banks of the Appalachian Mountain range in the eastern U.S. and extending as far west as Texas, Oklahoma and Kansas. They are considered to be one of the most wide-ranging fish species in North America. (Minnesota Department of Natural Resources, 2005; Ohio Department of Natural Resources Division of Wildlife, 2005; Ross and Brenneman, 2001; Texas Parks and Wildlife Department, 2005; Trautman, 1981)

Freshwater drum inhabit backwaters and areas of slack current in a wide range of habitats including deep pools in medium to large rivers and large, deep to shallow lacustrine environments. They are a benthic fish that particularly like silty to rocky substrates. (Etnier and Starnes, 1993; Hubbs and and Lagler, 1947; Minnesota Department of Natural Resources, 2005; Robison and Buchanan, 1988; Ross and Brenneman, 2001; Texas Parks and Wildlife Department, 2005; Trautman, 1981; Etnier and Starnes, 1993; Hubbs and and Lagler, 1947; Minnesota Department of Natural Resources, 2005; Robison and Buchanan, 1988; Ross and Brenneman, 2001; Texas Parks and Wildlife Department, 2005; Trautman, 1981)

Freshwater drum have a distinctive appearance. They are a silver, deep-bodied fish that are compressed laterally. An unusual characteristic of these fish is that their lateral line extends into their rounded caudal fin. They also have a long dorsal fin relative to their total length that contains a deep notch. According to Smith (2001) the mouth is sub terminal with a blunt rounded snout. The scales are ctenoid and the lateral line scales can range from 49 to 53. The anal fin has two spines, the first being much shorter than the second, and seven soft rays. Freshwater drum can reach lengths up to .91 m (three feet) and weights up to 24 kg (55 pounds). On average they range in size from 31 cm to 71 cm ( 12 to 28 inches) and weights from .45 kg to 3.6 kg (1 to 8 pounds). (Etnier and Starnes, 1993; Minnesota Department of Natural Resources, 2005; Ohio Department of Natural Resources Division of Wildlife, 2005; Robison and Buchanan, 1988; Ross and Brenneman, 2001; Texas Parks and Wildlife Department, 2005; Trautman, 1981)

Freshwater drum begin life when the female's egg becomes fertilized by the male. The fertilized egg then hatches after 48 to 96 hours. The larvae are 3 mm at hatching and stay at the surface for three days, or until they are capable of swimming on their own. They then proceed to move into deeper waters to begin feeding and are considered juveniles at 15 mm. They can reach lengths up to 85 mm during their first year, and reach sizes up to 150 mm the next. The size of freshwater drum varies based on food and habitat availability. The sexes are not dimorphic. (Etnier and Starnes, 1993; Robison and Buchanan, 1988; Ross and Brenneman, 2001; Trautman, 1981)

Freshwater drum breed seasonally in open water. The eggs are fertilized and left floating near the surface of the water, where the eggs, and subsequently the larvae, are carried by currents. This unique characteristic is thought to be the explanation of their wide distribution. Freshwater drum are seemingly promiscuous because males and females disperse eggs and sperm into the water column where fertilization is rather random. However scientific evidence to justify this statement has not been documented. (Minnesota Department of Natural Resources, 2005)

Males generally reach maturity at the age of four while females usually reach maturity around age five and into their sixth year of life. Spawning takes place when water temperatures reach 20° C, usually between the months of May and June. The fish spawn within the water column. According to Etnier and Starnes (1993) one female can produce 40,000 to 60,000 ova, although most of these eggs are preyed on almost immediately. Fertilized eggs float near the surface of the water for two to four days before hatching. Larvae stay attached to the surface film until they obtain enough muscle strength to swim into deeper water. This usually requires at least three more days. Growth is rapid in young fish and tends to slow down with age. (Etnier and Starnes, 1993; Minnesota Department of Natural Resources, 2005; Ohio Department of Natural Resources Division of Wildlife, 2005; Robison and Buchanan, 1988; Ross and Brenneman, 2001; SWEDBERG and WALBURG, 1970; Texas Parks and Wildlife Department, 2005; Trautman, 1981)

There is no parental involvement among freshwater drum after spawning. (Schultz, 2004)

Not much information is available on the lifespan of freshwater drum in captivity. It is known that they can reach the age of 13 in the wild and average between 6 to 8 years natural longevity. (Etnier and Starnes, 1993; Ross and Brenneman, 2001)

Freshwater drum congregate in large schools to feed and breed. They are primarily active in feeding at night. (Etnier and Starnes, 1993; Minnesota Department of Natural Resources, 2005; Ohio Department of Natural Resources Division of Wildlife, 2005; Ross and Brenneman, 2001; Texas Parks and Wildlife Department, 2005; Trautman, 1981)

Freshwater drum communicate by making drumming, or croaking sounds with specialized muscles that vibrate against their air bladders. This feature gives the species its name, grunniens, latin for "grunting". These muscles only develop in males. Drumming is thought to excite males and females to assemble in a breeding area. (Etnier and Starnes, 1993; Robison and Buchanan, 1988; Ross and Brenneman, 2001; Trautman, 1981)

Freshwater drum feed on prey at all hours of the night. They peruse the bottom in schools in search of many different items. They generally root around and move rocks and other substrates to flush their prey. Adults feed primarily on aquatic insects such as mayflies, small fish (in particular shad (Alosa) and immature drum) and mollusks. During the early larval stage freshwater drum feed primarily on the larval stages of other fishes. After reaching 12 mm they begin to feed on zooplankton (Clark and Pearson, 1979; as cited in Etnier and Starnes, 1993). Juveniles feed on larval stages of mayflies and caddisflies. Freshwater drum are equipped with heavy pharyngeal teeth that aid in the consumption of snails and the introduced Dreissena polymorpha. (Etnier and Starnes, 1993; Hubbs and and Lagler, 1947; Minnesota Department of Natural Resources, 2005; Ohio Department of Natural Resources Division of Wildlife, 2005; Ross and Brenneman, 2001)

Humans contribute to a great amount of predation on freshwater drum. Commercially up to 453,592 kg (1 million pounds) is harvested per year. Immature drum are preyed on by many different predatory fishes such as Sander vitreus, Esox masquinongy, Esox lucius, Aplodinotus grunniens, and gulls (Larus), such as Larus argentatus. (Minnesota Department of Natural Resources, 2005)

Freshwater drum are known for their feeding on the notorious zebra mussels Dreissena polymorpha. They do not control populations however they may contribute to high numbers of mortality in these nuisance mussells. It is documented that many types of mussels use freshwater drum as a host in their reproductive cycle. (French and Bur, 2005; Molluscs Division of the Museum of Biological Diversity at the Ohio State University, 2004)

Freshwater drum are growing in popularity and in some cases they are recognized as a sport fish. They are known for their great fighting ability and their large size. They are popular meat in some areas. In some cases drum make a great bait to catch other fish species. These fish also have exceptionally large inner ear bones called otoliths. They are called “lucky stones” and are collected for good luck. Many otoliths have been found around old Indian settlements and were traded far outside of their natural range. Archeologists believe that they were collected by indigenous peoples and worn as jewelry. (Etnier and Starnes, 1993; Minnesota Department of Natural Resources, 2005; Robison and Buchanan, 1988; Texas Parks and Wildlife Department, 2005; Trautman, 1981)

There are no known adverse effects of freshwater drum on humans.

The IUCN Red List, CITES appendices, and the United States Endangered Species Act list the status of Aplodinotus grunniens as being a species of “least concern” or having “no special status.” This indicates that populations are not threatened in the near future.