Like the gizzard shad, the threadfin shad has an elongated posterior dorsal ray, but its mouth is terminal and the lower margin of its upper jaw is not notched. The anal fin has 20 to 28 rays; the dorsal, 10 to 13. Lateral scales number 42 to 48; no lateral line is present. The back is bluish gray with a persistent black or purple shoulder spot. The venter is silver to creamy white. The caudal fin is distinctly yellow (hence the local name “yellowtails”). Other fins may be light yellow, dusky, or clear.
5.1 to 7.1 in (130 to 180 mm)
Threadfin shad are abundant in the Tennessee River and in all rivers of the Mobile basin. We encountered small numbers of threadfin shad in the Conecuh, Choctawhatchee, and Chattahoochee rivers. A purposeful introduction could explain the single collection from Big Creek Lake, a municipal reservoir of Mobile and a tributary to the Escatawpa River system. We have no records from the Perdido, Yellow, or Blackwater rivers, but future sampling will probably expand the species’ know range in these systems.
HABITAT AND BIOLOGY:
This pelagic, plankton-feeding species occurs in large, often single-size schools and with gizzard shad. The greatest numbers occur in rivers, reservoirs, and large streams, where they can be seen rippling the surface at dawn and dusk. Only rarely have we taken them in moderate and small streams. In Missouri, Pflieger (1975) notes that spawning occurs from dawn to sunrise, when water temperatures reach 70ºF (21.3ºC). Threadfin shad are sensitive to sudden changes in water temperature and oxygen content; for this reason, they frequently experience die-offs in late summer and winter.
Although the threadfin shad is native to Alabama, it has been widely introduced both here and elsewhere throughout the United States as a forage species for temperate basses and sunfishes.
Günther described threadfin shad in 1867.
Dorosoma means lance-shaped.
Petenense means from Lake Peten, Yucatan, the type locality.
The copyrighted information above is from Fishes of Alabama and the Mobile Basin. Alabama Wildlife and Freshwater Fisheries Division protects this fish from capture or possession.