Gars are elongated, cylindrical fish with long snouts with numerous prominent teeth. The body is covered with hard, diamond-shaped scales. The shortnose gar is named for its moderately short, broad snout: the least width of the snout goes only about 6–10 times into its length. The distance from the tip of the snout to the corner of the mouth is equal to or longer than the rest of the head. There is only a single row of teeth.
This species is brownish or olive above, grading to white below. If there are any black spots on the top of the head and on paired fins, they are only poorly defined. The unpaired fins often have definite roundish black spots. Individuals from clear water usually have better-defined spots than ones from murkier water. Young that are less than 10 inches long have a broad black stripe along the midside.
Similar species: Missouri has three other species of gars:
- The spotted gar (L. oculatus) is most similar, but it has well-defined roundish black spots on the top of the head and paired fins; the scales in a diagonal row, from the scale at the front of the anal fin to the scale on the midline of the back (both included) usually number 17–20 (while the shortnose numbers 20–23), and lateral line scales usually number 54–58 (the shortnose numbers 60–64).
- The longnose gar (L. osseus) has a relatively longer, narrower snout than all our other gars: the least width of the snout goes more than 10 times into its length, and the width of the upper jaw at the nostrils is less than the eye diameter.
- The alligator gar (Atractosteus spatula) has a short, broad snout: the distance from the tip of its snout to the corner of the mouth is shorter than the rest of the head, and the least width of the snout goes only about 3–5 times into its length; also, it is a very large fish, commonly exceeding 3 feet in length and 8 pounds in weight.
This is one of the smaller gars. Adult length: usually only to about 28 inches; weight: commonly only to 4½ pounds. The largest specimens in Missouri reach about 32 inches long and 6–11 pounds.
The commonest gar over much of Missouri outside of the Ozarks.
Habitat and Conservation
Often found along major rivers, in quiet pools, backwaters, and oxbow lakes. It also occurs in the large, permanent pools of prairie creeks. It is more tolerant of high turbidity than other gars. Gars are generally associated with warm, sluggish backwaters and are often seen basking quietly in the sun just beneath the surface. They frequently rise to the surface, opening and closing the jaws with a loud snap, then sinking below the surface. This behavior allows them to swallow air into their swim bladder, which is connected to the throat and is richly supplied with blood vessels — thus, the swim bladder functions much like a lung. This adaptation helps them survive in still or slow waters with relatively low oxygen levels.
The shortnose gar is somewhat more generalized in its food habits than the spotted and longnose gars, often feeding on insects and crayfish in addition to fish. Young shortnose gar eat insect larvae and small crustaceans, but they begin eating fish by the time they young gar are 1¼ inches long.
Gars pursue their prey by stalking, rather than by active pursuit. They rapidly vibrate their fins, propelling them toward their prey with little apparent movement; they look like a drifting stick or log. Once within striking distance, a gar makes a quick lunge and grasps the prey sideways in its jaws. The many thin sharp teeth are not useful for shredding or clipping apart the prey; instead, they simply make escape impossible. When the grasped prey has ceased to struggle, the gar turns it in its jaws and swallows it headfirst.
Spawning apparently occurs from mid-May into July, varying from year to year in response to differences in temperature and other annual variations in the weather. The eggs are scattered over vegetation and other submerged objects in quiet, shallow water. The spawning fish are sometimes in pairs, but often a single female is accompanied b two or more males. The yellowish eggs hatch about 8 days after spawning, and the young become active about 7 days later, when the yolk sac has been absorbed. The slender, slate-gray young resemble small sticks as they drift about near the water’s surface. They grow rapidly; by mid-July, they may be 3½ to 7 inches long. They become sexually mature at 3 years of age, and 15 or more inches long.
Because they feed upon or compete for food with more “desirable” fishes, gars are often considered a worthless nuisance. But they may also serve as a natural control in preventing overpopulation and unbalanced fish populations, which improves fisheries and aquatic ecosystems in general.
Gar are seldom taken on hook and line and are rarely used for food. The hard, bony jaws of gars do not readily take a hook, and special techniques are required to capture them consistently with rod and reel. Because they often bask near the surface, gars provide a ready target for the bow hunter.
The eggs (roe) of gar are highly toxic to warm-blooded animals, including humans.
Some species of gars have been kept as aquarium fish, but this species — potentially reaching nearly a yard in length — would require a very, very large tank. In Missouri, anyone with a fishing permit can possess native nongame species in aquaria, if they are collected according to the rules outlined in the Wildlife Code of Missouri.
Gars are a small group of primitive bony fishes that are a characteristic element in the fish fauna of the Mississippi Valley.
The armor of hard, diamond-shaped scales, and the hard, bony covering over the head and beak provide gars with a continuous, nearly inflexible sheath, making gars immune to the attacks of most wood-be predators.
The gar order (Lepisosteiformes) are an ancient group of fishes, with representatives dating back to the Late Jurassic period. Some ancestral (“primitive”) characteristics include the ganoid (hard, diamond-shaped, non-overlapping) scales, heterocercal tail (note how the spine extends upward into the top part of the tail), and unique characteristics of the pectoral girdle (bones supporting the pectoral fins).