In American English the name gar (or garpike) is strictly applied to members of the Lepisosteidae, a family including seven living species of fish in two genera that inhabit fresh, brackish, and occasionally marine, waters of eastern North America, Central America, and the Caribbean islands. In British English the name gar was originally used for a species of needlefish, Belone belone, found in the North Atlantic. Further confusing matters, in both American and British English, some species of halfbeak are sometimes also called gar or garpikes. This article is concerned with the true gars of the family Lepisosteidae.
The gars are members of the Lepisosteiformes (or Semionotiformes), an ancient order of "primitive" ray-finned fish; fossil gars are known from the Permian onwards. Fossil gars are found in both Europe and North America, indicating that in Cretaceous and Tertiary times these fish had a wider distribution than they do today. Gars are considered to be among the most primitive bony fish and are most closely related to the bowfin, another archaic fish now found only in North America.
Gar bodies are elongate, heavily armored with ganoid scales, and fronted by similarly elongate jaws filled with long sharp teeth. Tails are heterocercal, and the dorsal fins are close to the tail. They have vascularised swim bladders that can function as lungs, and most gar surface periodically to take a gulp of air, doing so more frequently in stagnant or warm water when the concentration of oxygen in the water is low. As a result, they are extremely hardy and able to tolerate conditions that would kill most other fish.
All the gars are relatively big fish, but the alligator gar Atractosteus spatula is the champion, as specimens having been recorded up to 3 meters in length. Even the smaller species, such as Lepisosteus oculatus, are large, commonly reaching lengths of over 60 cm, and sometimes much more.
Gar tend to be slow, preferring shallow weedy areas of rivers, lakes, and bayous, but they are voracious predators, catching fish and crustaceans with their needle-like teeth. They are most abundant in tropical to subtropical freshwater, but several species are found in the more temperate parts of North America as far as southern Canada (for example Lepisosteus osseus). Most species inhabit brackish water in parts of their range, but only relatively few, most notably Atractosteus tristoechus, are regularly found in fully marine conditions.
Gar flesh is edible, and sometimes available in markets, but unlike the sturgeon that they resemble, gar roe is poisonous.
Gar in aquaria
Gar are popular fish for public aquaria where they are often kept alongside other large, "archaic" fish such as sturgeon and paddlefish. However, a few species, most commonly Lepisosteus oculatus, are sometimes offered to aquarists as pets. They do of course need very large tanks but in all other regards they are easy to keep. They are not much bothered by water quality or chemistry, and are tolerant of a wide range of temperatures. Gar must be allowed to breathe air, so some clearance between the surface of the water and the hood is essential.
Gar get on well with any other fish too big to be eaten (such as large catfish, cichlids, and centrachids). They do not like aggressive tankmates, and despite being predators are essentially peaceable, sociable fish that do well with their own kind. Sturdy aquarium plants and bogwood can also be used to create hiding places, since gars are very fond of lurking in slightly shady regions.
Feeding presents no problems. Most will take all kinds of meaty foods, including mealworms, crickets, earthworms, frozen lancefish and shrimps (defrosted), and strips of squid. Oily fish (like salmon and mackerel) as well as fish guts will quickly pollute an aquarium but are very effective at tempting newly introduced specimens to eat. Once settled in many specimens will also eat floating pellets as well. There is no nutritional reason to feed gar live fish, and cheap goldfish or guppies ("feeder fish") in particular tend to introduce parasites into an aquarium.
- Alligator gar Atractosteus spatula (305 cm)
Cuban gar Atractosteus tristoechus (200 cm)
Tropical gar Atractosteus tropicus (125 cm)
- Spotted gar Lepisosteus oculatus (112 cm)
Longnose gar Lepisosteus osseus (200 cm)
Shortnose gar Lepisosteus platostomus (88 cm)
Florida gar Lepisosteus platyrhincus (132 cm)