The threadfin shad (''Dorosoma petenense'') is a small

pelagic The pelagic zone consists of the water column of the open ocean and can be further divided into regions by depth. The word ''pelagic'' is derived . The pelagic zone can be thought of as an imaginary cylinder or water column between the sur ...

freshwater Fresh water or freshwater is any naturally occurring liquid or frozen water containing low concentrations of dissolved salts and other total dissolved solids. The term excludes seawater and brackish water, but it does include non-salty mi ...

forage fish Forage fish, also called prey fish or bait fish, are small pelagic fish that feed on planktons (i.e. planktivores) and other small aquatic organisms (e.g. krill). They are in turn preyed upon by various predators including larger fish, seabirds ...

common in lakes, large streams and reservoirs of the

Southeastern United States The Southeastern United States, also known as the American Southeast or simply the Southeast, is a geographical List of regions in the United States, region of the United States located in the eastern portion of the Southern United States and t ...

. Like the American gizzard shad, the threadfin shad has an elongated

dorsal fin A dorsal fin is a fin on the back of most marine and freshwater vertebrates. Dorsal fins have evolved independently several times through convergent evolution adapting to marine environments, so the fins are not all homologous. They are found ...

, but unlike the gizzard shad, its mouth is more terminal without a projecting upper jaw. The fins of threadfin shad often have a yellowish color, especially the caudal fin. The back is grey to blue with a dark spot on the shoulder. ''D. petenense'' is more often found in moving water, and is rarely found deep in the water column. It occurs in large schools, sometimes with gizzard shad, and can be seen on the surface at dawn and dusk. The threadfin shad may reach lengths of , but only rarely. This fish is very sensitive to changes in temperature and dissolved oxygen, and die-offs are frequent in late summer and fall, especially when water temperature drops to 42 °F. The threadfin shad is a favorite food for many game fishes, including

striped bass The striped bass (''Morone saxatilis''), also called the Atlantic striped bass, striper, linesider, rock, or rockfish, is an anadromous perciform fish of the family Moronidae found primarily along the Atlantic coast of North America. It has ...

largemouth bass The largemouth bass (''Micropterus nigricans'') is a carnivorous, freshwater fish, freshwater, ray-finned fish in the Centrarchidae (sunfish) family, native to the eastern United States, eastern and central United States, southeastern Canada an ...

smallmouth bass The smallmouth bass (''Micropterus dolomieu'') is a species of freshwater fish in the Centrarchidae, sunfish family (biology), family (Centrarchidae) of the order (biology), order Centrarchiformes. It is the type species of its genus ''Micropterus ...

, and

catfish Catfish (or catfishes; order (biology), order Siluriformes or Nematognathi) are a diverse group of ray-finned fish. Catfish are common name, named for their prominent barbel (anatomy), barbels, which resemble a cat's whiskers, though not ...

. This fish is widely introduced throughout the United States as a forage for game fish.

Description

Adult shad grow to a maximum size of , but most specimens are about long. They have yellowish fins.

Geographic distribution

The threadfin shad is native to the U.S., west of the eastern

Appalachian Mountains The Appalachian Mountains, often called the Appalachians, are a mountain range in eastern to northeastern North America. The term "Appalachian" refers to several different regions associated with the mountain range, and its surrounding terrain ...

, through the

Mississippi basin The Mississippi River is the primary river of the largest drainage basin in the United States. It is the second-longest river in the United States, behind only the Missouri. From its traditional source of Lake Itasca in northern Minnesota, ...

all along the

Gulf of Mexico The Gulf of Mexico () is an oceanic basin and a marginal sea of the Atlantic Ocean, mostly surrounded by the North American continent. It is bounded on the northeast, north, and northwest by the Gulf Coast of the United States; on the southw ...

down to

Belize Belize is a country on the north-eastern coast of Central America. It is bordered by Mexico to the north, the Caribbean Sea to the east, and Guatemala to the west and south. It also shares a maritime boundary with Honduras to the southeast. P ...

. This species tends to do best in large lakes and rivers. The construction of

dam A dam is a barrier that stops or restricts the flow of surface water or underground streams. Reservoirs created by dams not only suppress floods but also provide water for activities such as irrigation, human consumption, industrial use, aqua ...

s has created more reservoirs, providing more water bodies for the shad to inhabit. This has expanded the home range of the fish, as has the rise in temperatures in northern lakes.Green, B. W., et al. (2010)
Threadfin shad impacts phytoplankton and zooplankton community structures in channel catfish ponds.
''Aquaculture Research'' 41:e524-e536. Threadfin shad have been introduced outside of their original as a supplemental forage. Populations have become established on the American West Coast from

Oregon Oregon ( , ) is a U.S. state, state in the Pacific Northwest region of the United States. It is a part of the Western U.S., with the Columbia River delineating much of Oregon's northern boundary with Washington (state), Washington, while t ...

south to

San Diego Bay San Diego Bay is a natural harbor and deepwater port in San Diego County, California, near the Mexico–United States border. The bay, which is long and wide, is the third largest of the three large, protected natural bays on California's of ...

and the

Gulf of California The Gulf of California (), also known as the Sea of Cortés (''Mar de Cortés'') or Sea of Cortez, or less commonly as the Vermilion Sea (''Mar Vermejo''), is a marginal sea of the Pacific Ocean that separates the Baja California peninsula from ...

Ecology

The threadfin lives a

life in natural lakes, reservoirs, and large streams. In addition to freshwater habitats, it also inhabits brackish waters such as estuaries and lagoons. It prefers areas with limited vegetation. It is found to a depth of , and moves between deep water during the day and shallow areas at night. The young and adults feed on a variety of planktonic organisms and organic debris. Many researchers believe that threadfin shad often compete for plankton with young-of-the-year predator species, especially largemouth bass.Higginbotham, B
Forage Species: Range, Description, and Life History.
Oklahoma State University. Oklahoma Cooperative Extension Service. Threadfin shad is a very important food source for many game fish such as the largemouth bass. It has little known competition, but one species known to have a similar lifestyle is the gizzard shad (''Dorosoma cepedianum'').Mettee, M. F., et al. ''Fishes of Alabama and the Mobile Basin.'' Birmingham, Alabama. Oxmoor House, Inc. 1996.

Life history

The shad spawns in the spring when the water temperature is in the upper 60s (°F). Threadfin shad are a pelagic (open water) schooling species that is typically found in large numbers. The shad spawn occurs in the spring and early summer with a secondary spawn often occurring in the early fall. Spawning usually occurs early in the morning on available vegetation. The eggs adhere to submerged and floating objects. Females lay from 2,000 to 24,000 eggs. The young reach reproductive adulthood at one year of age. Life expectancy seldom exceeds 2 to 3 years.

Current management

Many populations of threadfin shad have been introduced by humans to the far north, resulting in large die-offs in the winter when water temperatures fall below 42 °F. This die-off affects both humans and wildlife. A tide of dead fish floats ashore, creating a strong odor unpleasant to humans. The die-off also gives some bird species an unnatural feeding habit, as well. The species should not be transplanted into water bodies that drop below 42 °F. This species is not endangered and has relatively healthy populations.

References

{{Authority control Dorosoma Fish of North America Fish described in 1867 Taxa named by Albert Günther Freshwater fish of North America