The threadfin shad (Dorosoma petenense) is a small pelagic freshwater forage fish common in lakes, large streams and reservoirs of the Southeastern United States.

[4] The threadfin shad is native to the U.S., west of the eastern Appalachian Mountains, through the Mississippi basin all along the Gulf of Mexico down to Belize.

[4] Populations have become established on the American West Coast from Oregon south to San Diego Bay and the Gulf of California.

It is found to a depth of 50 metres (160 ft), and moves between deep water during the day and shallow areas at night.

Many researchers believe[citation needed] that threadfin shad often compete for plankton with young-of-the-year predator species, especially largemouth bass.

[6] Threadfin shad are a pelagic (open water) schooling species that is typically found in large numbers.

[4] 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.

A tide of dead fish floats ashore, creating a strong odor unpleasant to humans.