Alligator Gar

Atractosteus spatula (formerly Lepisosteus spatula)

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Alligator gar side view photo with black background
Alligator gar, Atractosteus spatula
Lance Merry
Family

Lepisosteidae (gars) in the order Lepisosteiformes (gars)

Description

Gars are elongated, cylindrical fish with long snouts with numerous prominent teeth. The body is covered with hard, diamond-shaped scales. The alligator gar is our largest gar and has a distinctively short, broad snout: the least width of the snout goes only about 3–5 times into its length. The distance from the tip of the snout to the corner of the mouth is shorter than the rest of the head. The large teeth in the upper jaw are in two rows on each side.

Adults are brownish or dark olive above, becoming lighter toward the belly. The unpaired fins often have numerous roundish black spots. Young have a blackish band along the midside and a narrow, white stripe along the midline of the back.

Similar species: Missouri has three other species of gars:

  • The shortnose gar (Lepisosteus platostomus) is named for its moderate short, broad snout that is nevertheless not as short and broad as the alligator gar’s. In the shortnose, the least width of the snout goes only about 6–10 times into its length. It and all our other gars, does not reach the large size of the alligator gar.
  • The spotted gar (L. oculatus) is similar to the shortnose, but it has many well-defined roundish black spots on top of the head and on the paired fins; also, its lateral line and diagonal row scale counts are different. In Missouri, it occurs mostly in the Bootheel.
  • 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.
Size

This is by far the largest of the gars. It is one of the largest freshwater fishes in North America. Adult length: can reach 10 feet; weight: can reach 300 pounds.

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Closeup of alligator gar held in a person's hands prior to being released into water
Alligator Gar
The alligator gar is our largest gar and has a distinctively short, broad snout. They are one of the few native animals that grow large enough to eat invasive Asian carp.

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Alligator Gar
Alligator Gar

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Man holding an alligator gar in his hands prior to placing it into the water
Alligator Gar Stocking
The alligator gar once occurred in the Mississippi River at least as far upstream as the mouth of the Illinois River and in major tributaries. It has been declining in abundance.

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Man in a boat placing an alligator gar into water with lilypads
Alligator Gar Stocking
The alligator gar is one of the few native fishes that reaches a size large enough to help control invasive, human-introduced Asian carp, which is one big reason many conservation departments are working to reintroduce it and prevent further decline.

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Chris Kennedy works with Alligator Gar.
Alligator Gar Wrangler
Chris Kennedy has a wild job. He wrangles alligator gars for a living.
Habitat and conservation

In Missouri, the alligator gar lives in sluggish pools and overflow eaters of large rivers. It tolerates higher salinities than the other gar species, and it is abundant in brackish waters along the Gulf Coast.

Gars are generally associated with warm, sluggish backwaters and are often seen basking quietly in the sun just beneath the surface. They frequently rist 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.

Foods

In freshwater, alligator gar probably eat mainly fish, but they are also known to eat ducks and other water birds. In brackish water (along the Gulf Coast), they feed heavily on marine catfish but also eat dead fish and other refuse discarded around docks and piers.

Distribution in Missouri

The alligator gar once occurred in the Mississippi River at least as far upstream as the mouth of the Illinois River and in major tributaries. Apparently it is declining in abundance. In nearby Arkansas, its numbers have declined drastically in the last years of the twentieth century.

Status

Non-game species. In much of their former range — including central Kansas, Nebraska, Ohio, Iowa, and Illinois — alligator gar have been extirpated due to habitat destruction, indiscriminate culling of them as “trash” or “nuisance” fish, and unrestricted harvest. Also, levees and dams prevent gar from moving between the river and critical floodplain spawning habitat. Some states have strict regulations to prevent overfishing. In many places, reintroduction efforts are being made so that the native alligator gar may help control invasive Asian carp and other invasive species. MDC has been restocking this dwindling species in areas near the Mississippi River for more than a decade.

Life cycle

Little is known about the habits and life history of this huge fish: because of its great size and strength, it often breaks up fishing nets, making it hard for biologists to collect data about them. Based on an observation of young gar in Lake Texoma, Oklahoma, in July, and larval specimens in a backwater of the Red River, Oklahoma, we presume that spawning occurs in that region during the first half of May. The larval alligator gar were beautifully patterned with sharply defined white and jet-black areas.

Human connections

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.

The alligator gar is one of the few native fishes that reaches a size large enough to help control invasive, human-introduced Asian carp, which is one big reason many conservation departments are working to reintroduce it and prevent further decline.

Many people believe Missouri should declare the alligator gar endangered, so that it can be protected from overfishing and its numbers increased or at least stabilized. For many reasons unrelated to its value in balancing the ecosystem against invasive Asian carp, people instinctively fear this gar, and efforts to protect it can be a tough “sell” for conservationists.

Historically, Native Americans used the tough scales, and the scale-covered skins, of alligator gar for arrowheads, as a tough covering for plows, and in breastplates. Settlers tanned the skin and used it as a tough leather covering for wooden tools and for making purses.

Alligator gar have a fierce look, and they have often been blamed for attacking people — but there are no authenticated attacks. There have been occasional injuries, however, when people attempt to capture these large, strong fish, and the fish thrash around on boats.

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, and they have been gaining in popularity as a sport fish. The large size of alligator gars generally causes them to ruin nets.

Some species of gars have been kept as aquarium fish, but this species — capable of reaching 6 feet or more in length — would require a room-sized 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.

In regions where they are more numerous, alligator gar are harvested, and even farmed, for commercial purposes. People make various craft items, such as earrings or lamp shades, out of the unusual ganoid scales.

The eggs (roe) of gar are highly toxic to warm-blooded animals, including humans.

Alligator gar have been caught in places far from their native North American range, including Turkmenistan, Hong Kong, Singapore, and India. In almost all these cases, they were apparently released by aquarium hobbyists. Never release aquarium fish or plants into native waters!

Ecosystem connections

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.

Fossils show this species of gar dates back to the early Cretaceous period, more than 100 million years ago.

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 upwards into the top part of the tail), and unique characteristics of the pectoral girdle (bones supporting the pectoral fins).