by Bob Thomas
One of the most primitive groups of fish alive today are the gars, survivors whose ancestors were abundant in the Triassic Period some 200 million years ago, sharing the earth with the dinosaurs. Of the four species that occur in Louisiana today, the alligator gar (Lepisosteus spatula) is the most widely known species. It occurs statewide and is common in the Mississippi River delta. Though they start out quite small, the largest on record measured almost ten feet in length and weighed 300 pounds!
Garfish have cylindrical bodies that are covered with very tough scales (called ganoid) that are such efficient protection that gars have few enemies. Their elongate mouths are packed with sharp, cone-shaped teeth that slash through the water to impale prey. Gar appear to feed primarily on fish, but they will consume almost any critter they can get into their mouths, including frogs, turtles, small mammals and birds, snakes, and insects. Though it is especially tempting to think that a ten foot alligator gar would attack and eat people, there are no documented records that anyone has been consumed. There have been, however, a few bites!
With their long, camouflaged, counter-shaded bodies, gar like to lie quietly amidst floating vegetation and debris, patiently waiting for some unsuspecting animal to move within range of their tooth-filled jaws. A quick, sideward slash dooms the hapless prey. Gar normally immediately swallow their food, but I once watched a four foot long alligator gar at the Louisiana Nature Center swim about for an hour with a large bluegill in its mouth that appeared too large for the gar’s throat. Eventually, the fish was either swallowed or released back to the pond.
Gar normally obtain oxygen via gills, as do other fish. Yet, they have a connection between their gut and swim bladder that allows them to gulp air at the surface and absorb oxygen in much the same way as do our lungs. Their swim bladder even has a roughened surface with many tiny blood vessels that increase the surface area, mimicking the alveolar air sacs in mammalian lungs. It is known that gar will take air from the surface even when there is plenty of oxygen in the water. Everyone who frequents ponds and bayous is familiar with the gar’s occasional lazy pop at the water’s surface. This ability to breathe air becomes important to the species when enclosed bodies of water begin to dry and oxygen levels drop. When this happens, many types of fish abruptly die due to the lack of oxygen. Gar, however, shift to airborne oxygen and frequently outlive the drought.
The combination of near-perfect camouflage, impenetrable armor, omnivorous diet, and the ability to take oxygen from the air have allowed gars to be among the earth’s most durable species. They are very important predators in their habitat.
Also published in Delta Journal, The Times Picayune, July 5, 1989.
The above photo is courtesy of Captain Kirk Kirkland, Texas fishing guide.