Atractosteus spatula

Geographic Range

Atractosteus spatula is found in the Ohio River in southwestern Ohio and the Mississippi river south to the Gulf of Mexico. They are found in drainages throughout the southeastern coastal United States (Alligator Gar, 2005). They are found in parts of Florida, Georgia, Alabama, Tennessee, Arkansas, Oklahoma, and Texas (Knopf, 2002; Shultz, 2004). Their range is from 44° to 20° north latitude and 101° to 82° west longitude (Agbayani, 2005).

• Biogeographic Regions
• nearctic nearctic
  • native native

Habitat

Alligator gar are found in large lakes, rivers, and bayous. Typically they are found in backwaters and bottomland swamps. They are found in both freshwater and brackish waters, they rarely enter marine waters (Etnier, 1993; Knopf, 2002).

• Habitat Regions
• temperate temperate
• freshwater freshwater

• Aquatic Biomes
• lakes and ponds
• rivers and streams
• brackish water brackish water

• Other Habitat Features
• estuarine estuarine

Physical Description

Alligator gar are grayish green to brown color on their dorsal surface and yellowish or white colored ventrally (Page and Burr, 1991). They may also have brownish spots on their dorsal surface. They are alligator-like in appearance, with their long, slender body, jaws armed with many teeth, and their habit of floating at the water surface (Goddard 2005). Their eyes are small. They have a heterocercal tail. Their swim bladder can function as a lung. The snout is short and broad with two rows of teeth on the upper jaw (Etnier 1993, Knopf, 2002). They are protected by a thick set of ganoid scales (Knopf 2002). This species is the largest of the gars and one of the largest freshwater fishes in North America, growing to nearly 3 meters long and up to 137 kg. Lateral line scales number 58 to 62 (Etnier, 1993).

• Other Physical Features
• ectothermic ectothermic
• heterothermic heterothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• female larger

Development

Young alligator gars develop from eggs and then float to the water's surface, resembling sticks (Shultz, 2004). They have a disc on the bottom of their snouth that allows them to attach to rocks and other objects until their yolk is absorbed (Goddard, 2005). Shortly afterwards, the young begin searching for food.

Reproduction

Mating behaviors in this species are not known.

Female alligator gars lay eggs that are dark green or red and stick to rocks and vegetation. The eggs are poisonous if eaten. Alligator gar may take many years to reach sexual maturity, although little is known about reproduction in this species.

• Key Reproductive Features
• iteroparous iteroparous
• seasonal breeding seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual sexual
• fertilization fertilization
  • external external
• oviparous oviparous

Alligator gars are oviparous. Once the eggs are laid, the young are left to survive on their own (Shultz, 2004).

• Parental Investment
• no parental involvement
• pre-fertilization
  • provisioning
  • protecting
    • female

Lifespan/Longevity

Females generally live longer than males and are larger, they may live from 26 to 50 years in the wild (Etnier and Starnes, 1993).

Behavior

Little is known about alligator gar behavior. They are not known to be extensively social or to migrate.

• Key Behaviors
• natatorial natatorial
• motile motile
• solitary solitary

Home Range

Home ranges of alligator gar are unknown.

Communication and Perception

Not much information is known about communication in alligator gars. Their lateral line system is used to detect motion in the water. They are also likely to use chemical cues and vision to some extent.

• Perception Channels
• visual visual
• tactile tactile
• chemical chemical

Food Habits

Alligator gars are opportunistic carnivores and sit-and-wait predators. They appear to be sluggish, but can ambush prey with short bursts of speed (Goddard, 2005). They feed on almost anything, including fish, ducks, turtles, small mammals, and carrion (Schultz, 2004).

• Primary Diet
• carnivore carnivore
  • eats terrestrial vertebrates
  • piscivore piscivore

• Animal Foods
• birds
• mammals
• amphibians
• reptiles
• fish
• carrion carrion
• aquatic crustaceans

Predation

Alligator gars have few predators. They may be eaten by larger fish as eggs, fry, and juveniles . Because of their large size, their only natural predators as adults are American alligators ( Alligator mississippiensis ). Humans also prey on adult alligator gars.

Ecosystem Roles

Alligator gars are generalist predators and eat anything they can find. They are especially important as top predators in aquatic systems (Goddard, 2005).

Economic Importance for Humans: Positive

Alligator gars have been fished commercially (Knopf, 2002). In Lousiana, they are fished for food, acting as a substitute for lobster (Etnier and Starnes, 1993). Like many other fish, they are also collected for aquaria.

• Positive Impacts
• pet trade pet trade
• food food

Economic Importance for Humans: Negative

Because these fish are predators, they consume gamefish, (Shultz, 2004). In turn, they cause a problem for humans in terms of sport fishing and consumption. There are several undocumented reports of injuries to humans. Their eggs are poinsonous if consumed (Goddard, 2005).

• Negative Impacts
• injures humans
  • bites or stings
  • poisonous poisonous

Conservation Status

Alligator gar are not currently listed as endangered, threatened, or of special concern. There are some concerns about overfishing and indications that populations have declined in areas where their preferred habitat, bottomland swamps, has been destroyed through channelization and and the building of levees.

Additional Links

Encyclopedia of Life

Contributors

Tanya Dewey (editor), Animal Diversity Web.

Denise Roberts (author), Eastern Kentucky University, Sherry Harrel (editor, instructor), Eastern Kentucky University.

References

Agbayani, E. 2005. "Atractosteus spatula" (On-line). Accessed October 20, 2005 at http://www.fishbase.org/Summary/SpeciesSummary.php?id=1073 .

Etnier, D., W. Starnes. 1993. The Fishes of Tennessee . Knoxville, TN: University OF Tennessee Press.

Goddard, N. 2005. "Alligator Gar" (On-line). Ichthyology at the Florida Museum of Natural History. Accessed December 03, 2005 at http://www.flmnh.ufl.edu/fish/Gallery/Descript/AlligatorGar/AlligatorGar.html .

Knopf, A. 2002. National Audubon Society: Field Guide to Fishes . New York: Chanticleer Press, Inc..

Page, L., B. Burr. 1991. Peterson Field Guides: Freshwater Fishes . Boston, Massachusetts: Houghton Mifflin Company.

Schultz, K. 2004. Ken Shultz’s Field Guide to Freshwater Fish . Hoboken, New Jersey: John Wiley & Sons, Inc..

2005. "Alligator Gar" (On-line). Accessed October 20, 2005 at http://en.wikipedia.org/wiki/Alligator_gar .