Herrings, 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 skipjack herring is a slender, streamlined fish with a large, terminal mouth; the lower jaw projects far beyond the tip of the snout; the lower jaw has dark speckles only near the tip; the teeth on the tongue are in 2 to 4 rows. The last ray of the dorsal fin is not prolonged into a slender filament. The dorsal fin has 16–18 rays (usually 17). The upperparts are bluish or greenish with silvery reflections, shading to silvery white on the sides and belly.
Similar species: Four species in the herring family are recorded for Missouri:
- Both the threadfin shad and gizzard shad may be separated from 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.
- The Alabama shad (Alosa alabamae) is uncommon in Missouri but is most similar to the skipjack herring. It 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 Alabama shad is anadromous, spending most of its adult life in the sea and entering freshwater streams only to spawn. It formerly occurred up the Mississippi River as far as Keokuk and Louisville, but Missouri may have the last spawning populations in the Mississippi River system. Collections of this species since the 1980s have been from the lower Mississippi River and the Missouri, Meramec, Gasconade, and Osage rivers.
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).
Adult length: commonly 12 to 16 inches; the maximum length is about 21 inches; maximum weight: about 3½ pounds.
Most abundant in the Mississippi River downstream from the mouth of the Ohio River; occasionally taken elsewhere in the state. This highly migratory species probably occurs at least occasionally in most of the large rivers of the state where its movements are not blocked by dams.
Habitat and Conservation
The skipjack herring inhabits the open waters of large rivers, often congregating in large numbers in the swift currents below dams. It seems to be intolerant of continuous high turbidity. Anglers fish for skipjack herring in the swift water below dams and around the ends of wing dikes.
The skipjack used to be more abundant farther north in the Mississippi River, but it appears only occasionally north of the Ohio River. Navigation impoundments seem to have decreased its numbers in the upper Mississippi.
The skipjack apparently is not native to the Missouri River, but now it is found there and in the Osage River. The construction of large dams upstream from our state apparently has reduced turbidity in the Missouri River to levels tolerable by skipjack, allowing it to ascend the Missouri from the Mississippi River.
Skipjack herring move about continuously in large schools. They often leap from the water when pursuing the minnows and other small fishes that make up the bulk of their diet. In Tennessee reservoirs, adult skipjacks have been observed feeding at the surface on small gizzard and threadfin shad.
A Species of Conservation Concern in Missouri. Ranked as "SU," meaning its status is as yet unrankable due to lack of information or due to substantially conflicting information about status or trends.
The timing and habitat of skipjack spawning is not well-known. This species might have an extended spawning season, possibly beginning early in May and ending soon after the first of July. Studies of skipjacks in the Mississippi River indicate that the young reach a length of about 3–5 inches by the end of their first summer of life.
The skipjack is bony, lacking in flavor, and seldom used as food. But it fights spectacularly when hooked, often leaping from the water, and can provide considerable sport on light tackle.
The oil present in its flesh is said by anglers to be attractive to catfishes, and many skipjacks are caught specifically for use as jug or trotline bait.
The herring family is primarily marine and includes some of the most valuable food fishes in the sea. Of the four members of the herring family in Missouri, none are commonly used as food. Only the skipjack is taken on hook and line.
The species name, chrysochloris, is Greek for “golden green,” in reference to the color of the back.
Human-built dams can have dramatic impacts on fish populations, as they seem to have done with this species: preventing its migrations up one river, and changing the water characteristics in another so much to allow the fish to inhabit it. It is well to remember that alterations of streams can have such repercussions on numerous plants and animals.
The herring family is primarily marine. Many herring and shad are anadromous, spending most of their adult life in saltwater but ascending freshwater streams to spawn. Of Missouri’s species, three out of four (the skipjack herring and gizzard and threadfin shads) are not anadromous; they can complete their entire life cycle in freshwater.
Skipjack herring consume, and therefore serve to limit, the populations of aquatic insects and small fishes. When they are young, skipjack provide food for a variety of larger fish, plus fish-eating birds, reptiles, and mammals. Footlong skipjacks have fewer predators.
A relative, the American shad (A. sapidissama) is native along the Atlantic Coast and has been a popular food fish (both for its flesh and its roe) since the early years of our nation. Prior to spawning, large schools of them swim up coastal rivers in “runs.” That species was long ago introduced to the West Coast and now also occurs from San Francisco Bay and northward.