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Lepisosteus platyrhincusFlorida gar

By Stacy Lackey

Geographic Range

One of the most widespread and numerous of the gar species in Florida, Lepisosteus platyrhincus is found in the United States from the Savannah River drainage in Georgia to the Ocklockonee River drainage in Florida and Georgia. Lepisosteus platyrhincus is also found in peninsular Florida, generally north of and in Lake Okeechobee.

There is some evidence that L. platyrhincus hybridizes with the spotted gar (Lepisosteus oculatus) in the Apalachicola River drainage. (Agbayani, 2005; Conservation Commission, 1998; Schultz, 2004)

Habitat

Lepisosteus platyrhincus inhabits medium to large lowland streams, canals, and lakes with muddy or sandy bottoms, and must be near abundant underwater vegetation. Like all gars, L. platyrhincus uses an air bladder to breathe air to survive in poorly oxygenated or stagnant water that is intolerable to most other fish. Typically occurring between 43 to 28 degrees North, L. platyrhincus is subtropical, demersal and is also tolerant of brackish and estuarine environments.

The Tamiami Canal is a good example of the versatility and adaptability of L. platyrhincus. It is less developed than most, thus having fewer pollutants from urbanization. However, there are still some very stressful environmental conditions. The canal itself is extremely shallow, with high water temperatures, low dissolved oxygen levels, and low flow rates. Despite these overall poor conditions, Florida gars continue to be abundant in the Tamiami Canal.

Florida gars can be found at any depth in the habitats they occupy, from the surface to the bottom of the water body. (Agbayani, 2005; Conservation Commission, 1998; Schultz, 2004)

  • Range depth
    .6096 to 5.186 m
    2.00 to 17.01 ft
  • Average depth
    1.524-3.048 m
    ft

Physical Description

Florida gars are fusiform in overall body shape, with a broad snout that is less than 75% of the length of the head. There is a single row of irregularly spaced teeth on both the upper and lower jaws. They also have a single row of enlarged fangs along the outer jaw. The gill rakers are small and pear shaped, and there are 14 to 33 rakers in the outer row of the first arch. Lateral line scales are from 53 to 64, dorsal fin rays usually number 7 to 9 and caudal fin rays 11. Florida gars have a highly vascularized swim bladder that connects to the esophagus, which allows the swim bladder to function as a lung. This function allows Florida gars to inhabit otherwise low oxygen environments. The dorsal and anal fins are placed far back on the body, with the single dorsal fin placed directly above the anal fin. Their tough, ganoid scales form a firm external body covering in a brick-like pattern. They lack bony scales on the ventral surface of the isthmus, which has a concave posterior and a convex anterior. Coloration is typically a dark olive-brown along the back and upper sides, with a white to yellow belly. Young have dark stripes along the back and sides.

Like spotted gars (Lepsiosteus oculatus), Florida gars have irregular, round, black spots all over their head, body and fins. In Florida gars however, these spots sometimes fuse to form stripes. These two gar species can be distinguished from each other mainly by the distance from the front of the eye to the back of the gill cover. In Florida gars, the distance is less than two-thirds of the length of the snout; in spotted gars, the distance is more than two-thirds of the length of the snout.

Another similar species, and the only other gar found in Florida, is the longnose gar (Lepisosteus osseus). Longnose gars lack spots on the top of the head and have a much more elongated beak. There are two other species of North American gars: alligator gars, (Atractosteus spatula) and shortnose gars(Lepisosteus platostomus), but they vary greatly from Florida gars and confusion should not occur. (Agbayani, 2005; Community Based Fisheries Project and Conservation Commission, 2003; Conservation Commission, 1998; Etnier and Starnes, 1993; Schultz, 2004)

  • Sexual Dimorphism
  • female larger
  • Range mass
    1.36 to 4.28 kg
    3.00 to 9.43 lb
  • Average mass
    2.49 kg
    5.48 lb
  • Range length
    51.7 to 132.2 cm
    20.35 to 52.05 in
  • Average length
    71.5-109.7 cm
    in
  • Range basal metabolic rate
    not found (low) cm3.O2/g/hr

Development

Florida gar eggs are relatively large. Larvae possess an adhesive organ on the end of their snout and stay attached to vegetation until they are about 19 millimeters long. This is around the time the yolk sac is absorbed. Young typically feed on zooplankton, insect larvae, and small fish. With their high metabolism, growth and maturation occurs rapidly and a length of up to 762 millimeters is soon realized.

Sex ratios initally lean more towards males but females live longer and grow to be much larger. Other than size, there is easy way to distinguish the sexes.

The roe (eggs) are highly toxic to humans, animals and birds. (Etnier and Starnes, 1993; Orlando, et al., 2003)

Reproduction

Environmental factors such as photoperiod, water temperature, and rainfall are known to influence internal rhythms in fishes, including patterns of reproduction.

Although Florida gars often travel in groups of 2 to 10 or more, males and females have no specific mates. A female will deposit her eggs on vegetation or rocks and a many males follow to fertilize them. There is no paternal investment, as both males and females swim downstream after spawning occurs. (Agbayani, 2005; Orlando, et al., 2003)

In Lepisosteus platyrhincus, groups of both sexes congregate in shallow weedy waters where the females place their adhesive eggs among aquatic plants. Males release sperm over the eggs and both sexes leave the spawning area. Following a dormant period in the summer, there is an increase is the testosterone of the males. Female gar also show reproductive hormone increases during this time. Following a single spawning event during the early spring (February to March), reproductive parameters return to basal levels. This indicates that seasonal changes in photoperiod and temperature activate hormone production and declines. (Conservation Commission, 1998; Orlando, et al., 2003)

  • Breeding interval
    Florida gar spawn once a year.
  • Breeding season
    Spawning occurs from February to April.
  • Range number of offspring
    6,000 (high)
  • Average age at sexual or reproductive maturity (female)
    3-4 years
  • Average age at sexual or reproductive maturity (male)
    2 years

There is no parental involvement in raising the young. The only investment males and females have is traveling upstream to deposit eggs and fertilize them.

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

Lifespan/Longevity

No information was found on lifespans of Florida gars.

Behavior

Florida gars tend to live in groups of 2 to 10 or more. They burrow into marsh sediments and aestivate through the dry season. Movement patterns are determined by varying water depths and hydroperiods. They will travel further distances if they inhabit deeper, more extensive bodies of water. Most movements have no intended or specific direction, however, in shallow water, they become more active at night and travel further distances. In one study, Florida gars were found in alligator holes and deeper areas of a marsh during the day and moved into shallower areas during the night. ("An ecological characterization of the lower everglades, Florida bay and the Florida keys", 1982; Conservation Commission, 1998; Wolski, et al., 2003)

  • Range territory size
    no real territory (high) cm^2

Home Range

In 2002, a radio transmitter study was done on the movement of Florida gars. The results showed that Florida gar traveled considerably shorter distances in areas with shorter hydroperiods or low water depths. When the gar were tracked during the wet season, some of the individuals traveled much farther. This was believed to be the result of deeper water, which allows more movement. Florida gars do not have a specific home range, but one that varies in relation to water depths and availability. (Wolski, et al., 2003)

Communication and Perception

No information on communication between Florida gars was found. They use their sense of vision and tactile cues for perceiving the environment, as well as chemical cues.

Food Habits

Florida gars use ram feeding, which is the use of a high velocity lunge or chase to kill prey. This feeding behavior in consists of a slow stalk, resulting in the close, lateral positioning of the head relative to prey. It uses a sideways lunge of the head during the strike, which lasts only 25 to 40 ms and is extremely fast. Prey capture in adults is also characterized by the jaws closing on the prey, then slashing their mouth from side to side. This is followed by manipulation and repositioning of the prey so that the gar can eat them head first.

Young Florida gars feed on zooplankton, insect larvae and small fish. Adults primarily feed on fish, shrimp (17% of the diet), and crayfish. (Porter, 2004)

Predation

When wetlands recede, shore birds are a major predator of Florida gar. They gather in huge numbers wherever there is remaining water, and the birds take advantage of this density. There has been a recorded 75% consumption of gar by shorebirds and other predators during these periods.

The armor-like scales and sharp teeth are the main defenses of adults. There is some camoflauge with dark colors blending into the water, but this typically only works in greater depths. However, the roe/eggs, are toxic to humans, mammals, and birds. ("An ecological characterization of the lower everglades, Florida bay and the Florida keys", 1982; Agbayani, 2005; Etnier and Starnes, 1993)

  • Anti-predator Adaptations
  • cryptic

Ecosystem Roles

Lepisosteus platyrhincus is an important prey species for alligators, osprey, and bald eagles, and shore birds during certain times. They are also important predators of fish. ("An ecological characterization of the lower everglades, Florida bay and the Florida keys", 1982)

Mutualist Species

Economic Importance for Humans: Positive

Florida gars are sporty fighters, however they are not fished to a great extent. Those that do fish Florida gar are normally fishing specifically for sport. Although edible, Florida gar are not highly esteemed as food, but they have a mild flavor and firm white flesh. They are consumed in considerable numbers in Louisiana, and are supposed to be a relatively good substitute for lobster. (Community Based Fisheries Project and Conservation Commission, 2003; Etnier and Starnes, 1993)

  • Positive Impacts
  • food

Economic Importance for Humans: Negative

Lepisosteus platyrhincus eggs are reported to be toxic to humans, mammals, and birds. In large numbers, some people see these fish as pests. With their high metabolism, they can eat a large amount of fish in a short period of time, devastating populations of other fish. (Community Based Fisheries Project and Conservation Commission, 2003; Orlando, et al., 2003)

Conservation Status

Florida gar populations seem to be relatively stable. They are not fished to an extreme extent and have an exceptional ability to overcome high death rates and low quality environments. They are in no danger of being threatened or endangered in the near future. ("An ecological characterization of the lower everglades, Florida bay and the Florida keys", 1982; Agbayani, 2005)

Other Comments

None.

Contributors

Tanya Dewey (editor), Animal Diversity Web.

Stacy Lackey (author), Eastern Kentucky University, Sherry Harrel (editor, instructor), Eastern Kentucky University.

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. Synapomorphy of the Bilateria.

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

coastal

the nearshore aquatic habitats near a coast, or shoreline.

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.

diurnal
  1. active during the day, 2. lasting for one day.
ectothermic

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

estuarine

an area where a freshwater river meets the ocean and tidal influences result in fluctuations in salinity.

external fertilization

fertilization takes place outside the female's body

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.

heterothermic

having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.

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).

marsh

marshes are wetland areas often dominated by grasses and reeds.

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

nomadic

generally wanders from place to place, usually within a well-defined range.

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).

polygynandrous

the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.

seasonal breeding

breeding is confined to a particular season

sexual

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

social

associates with others of its species; forms social groups.

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).

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

visual

uses sight to communicate

zooplankton

animal constituent of plankton; mainly small crustaceans and fish larvae. (Compare to phytoplankton.)

References

United States Fish and Wildlife Service. An ecological characterization of the lower everglades, Florida bay and the Florida keys. FWS/OBS-82/58.1. Washington, DC: Office of Biological Services. 1982.

Agbayani, E. 2005. "Lepisosteus platyrhincus, Florida Gar" (On-line). Accessed October 01, 2005 at http://www.fishbase.com/Summary/SpeciesSummary.php?genusname=Lepisosteus&speciesname=platyrhincus.

Community Based Fisheries Project, , F. Conservation Commission. 2003. "The City Fisher" (On-line). Accessed October 01, 2005 at http://www.floridaconservation.org/Fishing/offices/cityfish/CITFSH14.pdf#search='florida%20gar%20depth'.

Conservation Commission, F. 1998. "Gar" (On-line). Accessed September 08, 2005 at http://floridafisheries.com/Fishes/gar.html.

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

Orlando, E., G. Binczik, P. Thomas, L. Guillette, Jr. 2003. Reproductive seasonality of the male Florida gar, Lepisosteus platyrhincus. General and Comparative Endocrinology, Volume 131, Issue 3: 365-371.

Porter, H. 2004. A comparison of strike and prey capture kinematics of three species of piscivorous fishes: Florida gar (Lepisosteus platyrhincus), redfin needlefish (Strongylura notata), and great barracuda (Sphyraena barracuda). Marine Biology, 145, no. 5: 989-1000.

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

Wolski, L., J. Trexler, J. Knouft, C. Ruetz III, W. Loftus. 2003. "Patterns of Movement of Florida Gar (Lepisosteus platyrhincus) in the Everglades Revealed by Radio Telemetry" (On-line). Accessed October 01, 2005 at http://conference.ifas.ufl.edu/jc/papers/geer/3oralgr/WolskiLF.doc.

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