NL·0516Herbarium of the Nature Library
- Name
- Atractosteus spatula
- Family
- Lepisosteidae
- Native to
- Lower Mississippi basin and Gulf of Mexico coastal drainages from Florida to Veracruz, Mexico
- Habitat
- Large rivers, Bayous, Swamps, Brackish estuaries
Alligator gar
Atractosteus spatula
Also calledCatán (Mexican Spanish) · Gator gar · Garfish
A giant armoured fish of southern US rivers and bayous with a broad, alligator-like snout and a double row of fangs. It belongs to a lineage that has changed little for about 100 million years, and its eggs are poisonous.
The alligator gar is a euryhaline ray-finned fish in the clade Ginglymodi of the infraclass Holostei, being most closely related to the bowfins. It is the largest species in the gar family (Lepisosteidae), and is among the largest freshwater fishes in North America. The fossil record traces its group's existence back to the Early Cretaceous over 100 million years ago. Gars are often referred to as "primitive fishes" or "living fossils", because they have retained some morphological characteristics of their early ancestors, such as a spiral valve intestine, which is also common to the digestive system of sharks, and the ability to breathe in both air and water. Their common name was derived from their resemblance to the American alligator, particularly their broad snouts and long, sharp teeth. It is suggested that an alligator gar can grow up to 10 ft (3.0 m) in length. Wikipedia
What it can do
- iBreathes air with a vascularised swim bladder, so it survives warm, stagnant backwaters
- iiIts interlocking diamond-shaped ganoid scales form armour that resists most predators
- iiiLies motionless like a log, then sideswipes fish with its toothed snout
- ivLives for many decades: fish over 50 years old have been aged from their ear stones (otoliths), and ages near 95 have been reported
In the field
Field marks
- aBroad, short, alligator-like snout
- bTwo rows of large teeth in the upper jaw on each side (other gars have one)
- cLong, torpedo-shaped body armoured with diamond-shaped ganoid scales
- dDorsal and anal fins set far back near the rounded tail; olive-brown above
- Not to be confused with
- Longnose gar (Lepisosteus osseus) has a very long, needle-thin beak. Spotted and shortnose gars are smaller (under 1 m), with narrower snouts and a single row of large upper teeth. Florida gar has spots all over.
- Where to see it
- The Trinity River (Texas); Louisiana bayous and the Atchafalaya Basin; the lower Mississippi and its oxbow lakes
- When
- Resident; spawns April–June when floods inundate vegetation
Life & habits
- Diet
- Carnivore: fish, crabs, turtles and water birds; scavenges carcasses
- Habitat
- Slow, large rivers, oxbow lakes, bayous, reservoirs and brackish bays
- Size
- Commonly 1.5–2 m; up to about 3 m and 150 kg
- Lifespan
- Over 50 years; up to about 95
Floats near the surface and rolls to gulp air. In spring, groups spawn over flooded vegetation, scattering sticky green eggs that hatch within days.
Where it lives
Recorded sightings
—
geo-referenced records in GBIF, from museums, herbaria and field observers.
Native range
Lower Mississippi basin and Gulf of Mexico coastal drainages from Florida to Veracruz, Mexico
Drag the globe to turn it. Dots are where records exist, not a range map; darker means more records.
In the stacks
Searching the stacks…
Every page naming Atractosteus spatula in the Biodiversity Heritage Library →
Marginalia
Native peoples of the lower Mississippi used gar scales as arrowheads and the skin as armour. Early settlers covered wooden ploughshares with gar hide. In the 20th century gars were persecuted as 'trash fish' until research showed their role in river ecosystems.
Curiosity
Gar roe is toxic to mammals and birds, which may help protect the eggs from egg-eating predators.
Kinship
Fact-checked: 1 correction made to this sheet. Photographs: iNaturalist contributors under the licences shown. Records: GBIF.org. Historical plates: Source Library (CC BY-SA 4.0; originals public domain). Summary text: Nature Library editors and Wikipedia (CC BY-SA). Medicinal and edibility notes are historical and educational, not advice. iNaturalist taxon 54542.