Photograph by Joel Sartore, National Geographic Photo Ark
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The largest of all the gars, this megafish, photographed at the Tennessee Aquarium, earns its name with a wide, crocodilian head and rows of sharp teeth.

Photograph by Joel Sartore, National Geographic Photo Ark

Alligator gar


The alligator gar bears no relation to alligators, but with its wide, crocodilian head and razor-sharp teeth, it’s easy to see how this giant fish got its name.

Appearance

The largest of seven known gar species, this megafish has a torpedo-shaped body in olive brown and comes armored with glistening scales. It can grow up to 10 feet long, and historical reports suggest it may grow to weigh nearly 350 pounds. This makes it the largest fish species in North America that spends almost all its time in freshwater. (The white sturgeon is often considered North America’s largest freshwater fish, but it spends substantial time in salt water.)

Range and habitat

The prehistoric relatives of the species first appeared 157 million years ago and inhabited many parts of the world. Today, however, gars live only in North and Central America. Alligator gars were historically found throughout the Mississippi River Valley and may have even existed as far north as Iowa and as far west as Kansas and Nebraska.

Today alligator gars are known only to live in the lower Mississippi River Valley, from Oklahoma to the west, Arkansas to the north, Texas and portions of Mexico to the south, and east to Florida.

Alligator gars are able to tolerate brackish and even salt water, but they prefer the sluggish pools and backwaters of large rivers, swamps, bayous, and lakes. The fish’s thick, spongy, and highly vascular air bladder behaves like a lung to aerate the alligator gar’s blood. It also allows the fish to gulp air to “breathe” in waters with low oxygen. It may obtain as much as 70 percent of the oxygen it needs from the atmosphere.

Defenses

Although they may look ferocious, alligator gars pose no threat to humans and there are no known attacks on people.

They can pose a passive danger, though: The fish’s eggs are poisonous to humans if ingested. The toxicity of gar eggs serves as a defense mechanism against predators such as crustaceans.

Alligator gars have few natural predators, though alligators have been known to attack them, and young fish are preyed upon by other species.

Adult alligator gars primarily prey on fish, but they are opportunistic feeders who also eat blue crabs, small turtles, waterfowl or other birds, and small mammals.

Rehabilitated image

In the past, the gars developed a bad, but largely undeserved reputation as “trash fish” among anglers who believed they damaged nets and devoured game fish. Resource managers commonly recommending culling them, and throughout the 20th century the alligator gar numbers plummeted, with only Texas and Louisiana maintaining stable populations.

In recent years, however, the alligator gar’s reputation has improved and the fish has undergone something of an image makeover. Biologists have shown that the species presents no threat to game fish. In fact, the alligator gar itself has become a popular target fish for anglers, especially bowfishers, which is of concern to some conservationists. The fish is protected by law in parts of its range. There have also been efforts to reintroduce the alligator gar to some U.S. states where it was previously lost.

Saving the Alligator Gar

Watch as alligator gar are caught for a captive-breeding program.