Herrings and shads, as a group, are silvery, flat-sided fish, easily recognized by the row of sharp-edged, spiny scales (or scutes) along the midline of the belly. These scutes are readily apparent when you rub your fingers forward along the fish’s belly.
The Alabama shad is similar to the skipjack herring, but the Alabama shad has the lower jaw equal to or projecting only slightly beyond the tip of the snout; its lower jaw has dark speckles along much of its length (not just near the tip); the teeth on the tongue are in a single row down the middle; and the gill rakers on the lower half of the first arch usually number more than 30 (the skipjack usually has fewer than 30). The last ray of the dorsal fin is not elongated into a long, slender filament. The principal rays of the dorsal fin usually number 16 or more.
Coloration is very similar to the skipjack herring: both have upperparts bluish or greenish with silvery reflections, shading to silvery white on the sides and belly. Both lack the dark spot behind the upper end of the gill opening, which is present on our other herrings.
Similar species: Four species in the herring family are recorded for Missouri:
- The skipjack herring (Alosa chrysochloris), as noted above, is the Missouri fish most similar to the Alabama shad. It is much more commonly encountered than the Alabama shad. The skipjack has the lower jaw projecting far beyond the tip of the snout; dark speckles only near the tip of the lower jaw; teeth on the tongue in 2–4 rows; and gill rakers on the lower half of the first arch usually fewer than 30.
- Both the threadfin shad and gizzard shad may be separated from both the Alabama shad and the skipjack herring by their last dorsal fin ray being elongated into a long, slender filament and by a dark spot present behind the upper end of the gill opening. Also, the principal rays of the dorsal fin usually are 14 or fewer.
Members of the herring family might be mistaken for the mooneye and goldeye (which are in a different family), but herrings have the following key characters: The dorsal fin is far forward of the anal fin. The head is without scales, but the body is covered with thin, smooth-edged (cycloid) scales that are easily dislodged. The lateral line is absent. A small, triangular projection (an axillary process) is present just above the base of the pelvic fin, and the eyes are partly covered by transparent membranes (adipose eyelids).