Dorosoma cepedianum
FAMILY
Clupeidae
TAXONOMY
Dorosoma cepedianum Lesueur, 1818, Baltimore, Maryland and Philadelphia, Pennsylvania, United States.
OTHER COMMON NAMES
English: American gizzard shad, eastern gizzard shad, gizzard mud, gizzard nanny shad, hickory shad, mud shad, nanny shad, skipjack winter shad; French: Alose à gésier, alose a gésier américaine, aloser noyer; Spanish: Sábalo molleja.
PHYSICAL CHARACTERISTICS
Maximum size 22.4 in (57 cm). Silver to brassy body with a bluish back and white belly. There is a large dark spot behind the operculum and above the pectoral fin. Snout is rounded and blunt. The last dorsal fin ray extends to a long filament.
DISTRIBUTION
Atlantic coast of the United States from New York, southward into the Gulf of Mexico and to the basin of the Rio Pánuco in Mexico. Found inland in the Great Lakes, St. Lawrence, Mississippi, Atlantic, and Gulf Slope drainages, with its east-west range extending from Quebec to North Dakota in the north and from Florida to New Mexico in the south.
HABITAT
Can tolerate salinities from fresh water to 33 or 34 parts per 1,000, but is most common in freshwater lakes, reservoirs, swamps, and slow-moving rivers. Adults are found in estuaries and protected bays; the young are sometimes found far upstream in small streams.
BEHAVIOR
Forms schools. Individuals may be seen leaping out of the water and skipping along the surface on their sides, giving rise to one common name for the species, the skipjack.
FEEDING ECOLOGY AND DIET
Young gizzard shad feed on zooplankton. As they mature, gizzard shad become herbivorous filter feeders, consuming phytoplankton and algae on the bottom of the water body.
REPRODUCTIVE BIOLOGY
Spawns from late winter through most of the summer; the exact spawning dates relate to latitude and water temperature. Adults spawn near the surface, usually in groups of two males and one female. The eggs, which are very small (0.03 in [0.75 mm] in diameter) sink and adhere to the bottom. They hatch in three days to one week, depending on temperature.
CONSERVATION STATUS
Not listed by the IUCN.
SIGNIFICANCE TO HUMANS
Young gizzard shad are important forage fishes that sustain other game and commercial fish species. In some areas, the abundance of gizzard shad creates a nuisance for humans when low temperatures, low oxygen, or disease trigger the death of a large number of fish that often wash onto shores and decay. Gizzard shad also create problems for fisheries; they entangle the nets of commercial fishermen and out-compete many preferred recreational species. The gizzard shad is used for fertilizer and as a component of cattle and hog food.
