Alosa aestivalis

Common Name

Blueback Shad

Year Described

Mitchill, 1814


Dorsal Fin: 15-20
Anal Fin: 15-21
Pectoral Fin: 14-18
Pelvic Fin: 9-11
Vertebrae: 47-53
Scales: 46-54 (transverse rows)
Ventral Scutes: 31-36
Gill Rakers: 41-51 (lower limb of first arch)

Body fusiforme and compressed. Depth of body quite variable with size. Ventral profile extremely convex from pelvic fin to lower jaw. Head moderate. Eye diameter less than snout length. Mouth large, extending to rare margin of eye. Upper jaw distinctly notched (unique to Brevoortia, Alosa, and Dorosoma. Lower jaw fits into upper jaw notch, and not strongly projecting beyond upper and rises steeply within mouth (forming an obtuse angle with upper jaw margin). Teeth absent in jaws (adults). Dorsal fin at midbody with a strongly concave margin. Anal fin origin well behind last dorsal ray. Pelvic fin under dorsal fin. Pectoral fin low on side. Tail forked. Body fully scaled. Pre-dorsal scales not enlarged, modified, or fringed. Axillary scale of pelvic fin about half fin length. Belly scutes keeled.


Body bluish above, grading to silvery on the sides and whitish on the belly. A small dark spot usually present posterior to the upper opercular edge. Dark stripes follow scale rows on the dorsum. Dorsal and caudal fins are yellowish. Peritoneum is dark.


Maximum size 38cm SL, but common to 30cm SL.


Adults found at sea in coastal waters. Anadromous: spawns in freshwater and young return to saltwater.


Nova Scotia to northeastern Florida.


Hildebrand, S.F. 1964. Engraulidae and Clupeidae (pp. 152-454). In: Fishes of the Western North Atlantic. Mem. Sears Fnd. Mar. Res. 1 (Vol. 3): 1-630.

Munroe, T.A. & M.S. Nizinski. 2002. Clupeidaeidae (pp 804-830). In: Carpenter. 2002. The living marine resources of the Western Central Atlantic. Vol. 2: Bony fishes part 1 (Acipenseridae-Grammatidae). FAO Species Identification Guides for Fisheries Purposes. American Society of Ichthyologists and Herpetologists Special Publication No. 5.

Other Notes

Closely related to Alosa pseudoharengus but can be distinguished by eye diameter, color pattern differences and ecological separation.