You are here

Alligator Gar (Atractosteus spatula)

 

Alligator Gar

Atractosteus spatula

(Order Somionotiformes; Family Lepisosteidae)

Juvenile Atractosteus spatula (photo by Justin Sullivan)

(Kansas: Sedgwick County.  Ninnescah River, WSU Ninnescah Reserve.  July 10, 2012).

 

Adult Diagnosis:

Ranging in length from 1.2-2.7 m and in weight from 68-159 kg, Alligator Gars are the largest species of gar. Like other gars, the Alligator Gar has a primitive, elongated body with dorsal and anal fins located very far back on the body. Gars have ganoid scales, which are tough, pointed scales that overlap one another, creating an armor-like covering. This species can be distinguished from other gars by the double row of teeth in the upper jaw, as opposed to a single row in other species. The snout of the Alligator Gar is shorter and stouter than that of the Long-Nosed Gar. Alligator Gars are dark, olive-green dorsally fading to yellowish-white ventrally. Juvenile Alligator Gars have a white mid-dorsal stripe and have speckles along the body, which adults lack. The dorsal, anal, and caudal fins of adults and juveniles often have dark, oval spots. Males and females are similar in appearance, but females tend to be larger.

Adult Atractosteus spatula. (from: http://www.outdooralabama.com/fishing/freshwater/fish/gar/alligator/)

 

Adult/Larval Natural History:

Gars have highly vascularized air bladders that are connected to the throat and allow them to gulp air at the surface of the water in addition to respiring through gills. Thus, they can survive in warm, oxygen-poor water where other fish cannot and have come to be associated with poor water quality.

 

Alligator Gars spawn from April through June as water temperature increases. Spawning seems to occur in flooded, backwater areas. Females will spread eggs over a wide area of shallow water in a flood plain while the river is high, which protects the young from predation when they emerge in remaining oxbow lakes. Two or more males follow each female and fertilize her eggs by coating them with sperm. The fertilized eggs sink and stick to the bottom substrate. Eggs are bright red and poisonous if eaten.

 

Each larva has an adhesive disk on the snout, which it will use to anchor itself while it absorbs the remaining yolk sac. Juveniles remain in backwater areas as they develop. Alligator Gar grow very quickly in the first year, but are slow-growing afterward. They are long-lived and regularly reach fifty years of age where not harvested too heavily.

 

Distribution:

Alligator Gars are found throughout the southeast coast of the U.S. They inhabit areas as far west as Texas and Oklahoma and as far north as the Mississippi River Basin and the lower Ohio and Missouri river systems. The southern extent of its range extends into Mexico.

KEY
Green - Naturally Sustaining Populations
Orange - Remnant Populations or Individual Observations
Red - Stocked Population
Yellow - Approximate Historic Range (Possibly Extirpated)

 

Habitat:

Alligator Gar inhabit estuaries, rivers, lakes, and reservoirs. Spawning occurs in shallow, backwater areas with vegetation.

 

Diet:

Alligator Gars are known for having a voracious appetite and are opportunistic feeders as well as scavengers. Food seems to consist primarily of forage fishes, although they will consume sport fishes where abundant. While gizzard shad seems to be the preferred food source, Alligator Gar have been known to eat invertebrates and even birds.

 

Conservation Status:

Alligator Gars are in decline in much of their native habitat and are in danger of becoming extirpated at the margins of their natural range. They are classified as rare in Missouri, threatened in Illinois, and endangered in Arkansas and Kentucky. This seems to be the result of modifications to aquatic habitats, such as levees and dams, which reduce spawning habitat and limit access to floodplain environments that serve as nurseries for juveniles.

 

Videos:

Alligator Gar, Atractosteus spatula in Its Natural Habitat

 

Links:

U.S. Geological Survey: Atractosteus spatula Fact Sheet: http://nas.er.usgs.gov/queries/factsheet.aspx?SpeciesID=755

 

Bioexpedition: Alligator Gar: http://bioexpedition.com/alligator-gar/

 

References:

 

Buckmeier, D. Life History and Status of Alligator Gar Atractosteus spatula with recommendations for management. Texas Parks and Wildlife Department, Inland Fisheries Division. Mountain Home, TX 78058.

 

Poly, W. 2001. Distribution of the Alligator Gar, Atractosteus spatula (Lacepede, 1803), in Illinois. Transactions of the Illinois State Academy of Science. 94: 185-190.

 

Garcia de Leon, F., L. Gonzalez-Garcia, J. Herrera-Castillo, K. Winemiller, and A. Bansa-Valdes. 2001. Ecology of the Alligator Gar, Atractosteus spatula in the Vicente Guerrero Reservoir, Tamaulipas, Mexico. The Southwestern Naturalist 46: 151-157.

 

Tomelleri, J. and M. Eberle. 2011. Fishes of the Central United States. University Press of Kansas. p.17-18.

 

Submitted by: Jessie Stark, July 2012

 

Wichita State University
Generated on 2011. This website is continuously updated.
Comments can be sent to Mary Liz Jameson.
Designed by Bioadventures.