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Spotted gar

Lepisosteus oculatus

What do they look like?

Spotted gar grow to a maximum length of 91 cm, the average length is 76 cm. The body is cylindrical and often mistaken for a log lying in shallow waters. They are covered with hard, diamond-shaped scales and spots on the top of the head and fins. Females are generally larger than males.

  • Sexual Dimorphism
  • female larger
  • Range mass
    1 to 4 kg
    2.20 to 8.81 lb
  • Range length
    100 to 914 mm
    3.94 to 35.98 in
  • Average length
    760 mm
    29.92 in

Where do they live?

Spotted gar are found throughout the rivers and streams that feed into Lake Michigan and Lake Erie, the Mississippi River, and rivers along the northern coast of the Gulf of Mexico from Texas east to Florida.

What kind of habitat do they need?

Spotted gar prefer shallow open waters, usually 3 - 5 m deep, as well as stagnant backwater. They are often found near the surface basking near fallen logs, trees, or brush. This species is also shoreline-oriented, meaning it can be found near banks that include some sort of brush covering. Spotted gar are rarely found in areas that do not include some form of brush covering. (Snedden, et al., 1999)

  • Range depth
    3 to 5 m
    9.84 to 16.40 ft

How do they grow?

Larval spotted gars hatch from eggs, and are about 2.5 cm long when they first emerge. They are slender and have a thread-like extension of the tail that vibrates, helping them to swim when they are small. They become fully developed by age 2. Females and males grow at different rates.

How do they reproduce?

Males gather in shallow (1.5 m) water with plants growing in it to compete for the largest females to mate with. Females allow more than one male to fertilize their eggs.

Most eggs are laid in October, when females lay about 14,000 eggs. Larger females lay more eggs.

  • How often does reproduction occur?
    Females lay eggs once yearly.
  • Breeding season
    Spawning occurs from February to June, varying with location.
  • Range number of offspring
    1772 to 13789
  • Average time to hatching
    7 days
  • Average age at sexual or reproductive maturity (female)
    1 years
  • Average age at sexual or reproductive maturity (male)
    1 years

Females deposit a lot of energy in the form of nutrients in their eggs to fuel the development of young. There is no parental care after the eggs are laid.

  • Parental Investment
  • pre-fertilization
    • provisioning
    • protecting
      • female

How long do they live?

It is not known how long spotted gar can live, but one study showed males living up to 8 years and females up to 10.

  • Average lifespan
    Status: captivity
    18 years
    AnAge

How do they behave?

Spotted gar are mainly active at night. Often, this species will remain still near fallen trees or brush throughout the day. At night they emerge and search for prey. Occasionally, they go to the surface of the water to take air into their specialized swim bladder. This specialized bladder acts as a primitive lung and allows them to live in waters with low levels of oxygen.

  • Range territory size
    0.9 to 162.73 km^2
  • Average territory size
    2.65 km^2

Home Range

Home range sizes change with the seasons in spotted gar because water depths change. In spring, home ranges are about 20 times larger than in other seasons. Spotted gar move away from their home areas to spawn.

How do they communicate with each other?

Methods of communication among spotted gars aren't well-studied. They have a lateral line system that may help them sense prey in the turbid waters they live in.

What do they eat?

Spotted gars are ambush predators, eating mainly crayfish (47% of diet in one study). They forage at night under the cover of floating logs or vegetation. Spotted gar also eat other species of fish including sunfish, gizzard shad, crappies, bass, catfish, and shiners.

  • Animal Foods
  • fish
  • insects
  • aquatic crustaceans

What eats them and how do they avoid being eaten?

Adult spotted gars do not have many natural predators, except for other types of gars. Eggs and juvenile spotted gars are probably attacked by a number of fish predators, although the eggs of gar are potentially toxic to many species. The spotted pattern on these fish may act as camouflage.

  • These animal colors help protect them
  • cryptic

What roles do they have in the ecosystem?

Spotted gars are important predators of crayfish, other crustaceans, and smaller fish in the low-oxygen level waters they inhabit.

Do they cause problems?

Spotted gars sometimes attack popular game fish species, but there is no evidence that they effect populations of game fish. Existing studies show they prey on mainly non-game species.

How do they interact with us?

Juvenile spotted gar eat mosquito larvae. The species is not particular popular for sport fishing, although gars are considered good fish for eating.

  • Ways that people benefit from these animals:
  • food

Are they endangered?

Spotted gars are not generally considered in need of special conservation efforts, except at the edges of their range, where numbers have shrunk due to habitat destruction. They have not been evaluated by the IUCN. Spotted gar are Species of Special Concern in Michigan, Threatened in Canada (Ontario Province), and may have protected status in other states on the northern, eastern, and western limits of theirrange.

Some more information...

Contributors

George Hammond (editor), Animal Diversity Web.

Lana Hall (author), Radford University, Thomas Meade (author), Radford University, Drew Paulette (author), Radford University, Josh Albert (author), Radford University, Karen Francl (editor, instructor), Radford University.

Stephanie Givinsky (author), University of Michigan-Ann Arbor.

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends.

brackish water

areas with salty water, usually in coastal marshes and estuaries.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

cryptic

having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.

ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

fertilization

union of egg and spermatozoan

food

A substance that provides both nutrients and energy to a living thing.

freshwater

mainly lives in water that is not salty.

intertidal or littoral

the area of shoreline influenced mainly by the tides, between the highest and lowest reaches of the tide. An aquatic habitat.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

motile

having the capacity to move from one place to another.

natatorial

specialized for swimming

native range

the area in which the animal is naturally found, the region in which it is endemic.

nocturnal

active during the night

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

piscivore

an animal that mainly eats fish

poisonous

an animal which has a substance capable of killing, injuring, or impairing other animals through its chemical action (for example, the skin of poison dart frogs).

polyandrous

Referring to a mating system in which a female mates with several males during one breeding season (compare polygynous).

seasonal breeding

breeding is confined to a particular season

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

solitary

lives alone

swamp

a wetland area that may be permanently or intermittently covered in water, often dominated by woody vegetation.

tactile

uses touch to communicate

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

territorial

defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement

visual

uses sight to communicate

References

Hubbs, Carl L., and Lagler, Karl F. 1964. Fishes of the Great Lakes Region. University of Michigan Press.

Bowler, 1987. Recent observations of the distribution and status of the Freckled Madtom and the first record of Spotted Gar in Iowa. The Journal of the Iowa Academy Science, 3-4: 40-43.

Love, J. 2004. Age, growth, and reproduction of spotted gar Lepisosteus oculatus (Lepisosteidae) from the Lake Pontchartrain estuary, Louisiana. Southwestern Naturalist, 49/1: 18-23.

Ostrand, K., B. Braeutigam, D. Wahl. 2004. Consequences of vegetation density and prey species on Spotted Gar foraging. Transactions of the American Fisheries Society, 133/3: 794-800.

Pope, K., G. Wilde. 2003. Variation in spotted gar (Lepisosteus oculatus) mass-length relationships in Texas reservoirs. The Texas Journal of Science, 55.1: 43-49.

Schultz, K. 2004. Ken Schultz's Field Guide to Freshwater Fish. Hoboken, NJ: John Wiley & Sons, Inc. (US).

Snedden, G., W. Kelso, D. Rutherford. 1999. Diel and seasonal patterns of Spotted Gar movement and habitat use in the Lower Atchafalaya River Basin, Louisiana. Transactions of the American Fisheries Society, 128: 144-154.

Tyler, J., M. Granger. 1984. Notes on food habits, size, and spawning behavior of Spotted Gar in Lake Lawtonka, Oklahoma. Proceedings of the Oklahoma Academy of Science, Volume 64: 8.

 
University of Michigan Museum of ZoologyNational Science Foundation

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Givinsky, S.; T. Meade; D. Paulette and J. Albert 1999. "Lepisosteus oculatus" (On-line), Animal Diversity Web. Accessed April 24, 2014 at http://www.biokids.umich.edu/accounts/Lepisosteus_oculatus/

BioKIDS is sponsored in part by the Interagency Education Research Initiative. It is a partnership of the University of Michigan School of Education, University of Michigan Museum of Zoology, and the Detroit Public Schools. This material is based upon work supported by the National Science Foundation under Grant DRL-0628151.
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