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Alligator gar (Atractosteus spatula)
Ecological Risk Screening Summary
U.S. Fish & Wildlife Service, August 2017
Web Version, 11/29/2017
Image: D. Raver, U.S. Fish and Wildlife Service. Public domain.
1 Native Range and Status in the United States
Native Range
From Froese and Pauly (2017):
“North America: ranges from Mississippi River basin from southwestern Ohio and southern
Illinois in USA south to Gulf of Mexico; Gulf of Mexico Coastal Plain from Enconfina River in
Florida, USA to Veracruz, Mexico.”
Status in the United States
Native populations exist in the United States.
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From NatureServe (2017):
“This gar is uncommon to rare throughout most of the range, except locally in swamps and
bayous of the south-central United States (Page and Burr 2011). […] Now the species is
extirpated or very rare in most of the northern part of the range north of the Gulf Coastal Plain.”
From Fuller (2017):
“A single Alligator Gar measuring 145.5 cm TL and weighing 18.6 kg was reported from Clifton
Court Forebay, a water storage reservoir located at the head of the California Aqueduct, near
Byron in Contra Costa County, California, on 17 September 1991 (Raquel 1992). Another
specimen was collected in July 2010 in Lake Wateree, South Carolina (R. Stroud,
pers.comm.).”
“This species is becoming fairly common in the aquarium trade (P. Fuller, pers. observation).”
Means of Introduction into the United States
From Fuller (2017):
“The introduction of the California individual was attributed to release by an aquarium hobbyist
(Raquel 1992). It is probably that the South Carolina specimen was also an aquarium release.”
Remarks
From Hassan-Williams and Bonner (2013):
“Listed as Vulnerable by the American Fisheries Society; categories of threats: present or
threatened destruction, modification, or reduction of habitat or range; and over-exploitation for
commercial, recreational, scientific, or educational purposes including intentional eradication or
indirect impacts of fishing (Jelks et al. 2008). Vulnerable in southern US (Warren et al. 2000).
Some states are listing alligator gar as a game fish to regulate harvest.”
2 Biology and Ecology
Taxonomic Hierarchy and Taxonomic Standing
From ITIS (2017):
“Kingdom Animalia
Subkingdom Bilateria
Infrakingdom Deuterostomia
Phylum Chordata
Subphylum Vertebrata
Infraphylum Gnathostomata
Superclass Actinopterygii
Class Holostei
Order Lepisosteiformes
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Family Lepisosteidae
Genus Atractosteus
Species Atractosteus spatula (Lacepède, 1803)”
“Current Standing: valid”
Size, Weight, and Age Range
From Froese and Pauly (2017):
“Max length : 305 cm OT male/unsexed; [McClanes 1974]; common length : 200 cm TL
male/unsexed; [Wiley 1978]; max. published weight: 137.0 kg [Stone 2007]”
Environment
From Froese and Pauly (2017):
“Freshwater; brackish; demersal; depth range 0 - ? m [Florida Museum of Natural History
2005].”
Climate/Range
From Froese and Pauly (2017):
“Subtropical, preferred ?; 44°N - 20°N, 101°W - 82°W [Florida Museum of Natural History
2005]”
From Fuller (2017):
“The California specimen was recorded in water with a temperature of 25°C […]”
Distribution Outside the United States
Native
From Froese and Pauly (2017):
“North America: […] Gulf of Mexico Coastal Plain from Enconfina River in Florida, USA to
Veracruz, Mexico.”
Introduced
From Muchlisin (2012):
“In April 2011, one specimen of alligator gar fish, A. spatula, was caught by a fisher using a
hook baited with shrimp in a coastal pond in the city of Meulaboh [Indonesia], and the specimen
was deposited at the Laboratory of Ichthyology, Syiah Kuala University.”
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From Esmaeili et al. (2017):
“A single specimen of the Alligator gar, Atractosteus spatula […] was caught by local fishermen
in March 2015 from Marivan (Zarivar) Lake, a Tigris River tributary of Iran (35°32'53.32"N,
46°7'19.08"E).”
“[…] a few notable sightings of alligator gar have been reported outside North America
including Turkmenistan (Salnikov 2010), Hong Kong, Singapore, and India.”
From Mutlak et al. (2017):
“The first record of a single specimen of alligator gar, Atractosteus spatula (Lacepède, 1803),
native to North America, is reported from the inland waters of Iraq. […] The fish examined was
an immature male, with gonad weight of 85.9 g.”
From Chong et al. (2010):
“Exotic freshwater fishes in Malaysia […] Atractosteus spatula”
Means of Introduction Outside the United States
From Muchlisin (2012):
“This fish [collected in Meulaboh, Indonesia] was probably released incidentally from the
aquarium during the tsunami in December 2004.”
From Esmaeili et al. (2017):
“It might have been released by local people [in Iran]. It is known that these fishes are kept in
aquaria all over the world including Iran, being sold in pet shops. It is also known that aquarists
frequently get rid of unwanted fish by releasing them into open water bodies.”
From Mutlak et al. (2017):
“Aquarium trade pathway is the suspected factor for the presence of this species in the Iraqi
freshwater area.”
From Chong et al. (2010):
“[…] released into the inland waters [of Malaysia] by pet owners.”
Short Description
From Froese and Pauly (2017):
“Large size and broad, short snout. Light dorsal stripe. Dark olivaceous brown above and white
to yellowish beneath. Dark brown blotches on all fins [Bigelow et al. 1963].”
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Biology
From Froese and Pauly (2017):
“Adults inhabit sluggish pools and backwaters of large rivers, swamps, bayous, and lakes. Rarely
enter brackish and marine waters [Page and Burr 1991]. Feed on blue crabs, turtles, waterfowl or
other birds and small mammals [Etnier and Starnes 1993].”
From NatureServe (2017):
“Spawning occurs April to June in Louisiana (Suttkus 1963), possibly January to September in
Oklahoma-Texas (Echelle and Riggs 1972). Seasonal variation in ovarian weight indicated peak
spawning in July-August in northeastern Mexico (Garcia de Leon et al. 2001). In Alabama,
females mature at age 11 and live to age 50; males mature at age 6 and live to age 26 (Irwin,
cited by Boschung and Mayden 2004).”
“Spawning occurs over vegetation in warm shallow water (e.g., see Garcia de Leon et al. 2001).
Spawning may occur in an impoundment (Lake Texoma) in Oklahoma (Boschung and Mayden
2004, Miller and Robison 2004). Young may float at the surface among twigs and leaves
(Boschung and Mayden 2004).”
Human Uses
From Froese and Pauly (2017):
“Fisheries: minor commercial; gamefish: yes; aquarium: public aquariums.”
“Marketed fresh [Bigelow et al. 1963].”
From NatureServe (2017):
“[…] Hoese and Moore (1998) stated that this gar is […] common as a market fish in Louisiana.
It is numerous enough to support a fishery in a reservoir in Tamaulipas, Mexico (Garcia de Leon
et al. 2001).”
Diseases
From Hassan-Williams and Bonner (2013):
“Cestoda: Proteocephalus ambloplitis. Trematoda: Clinostomum, Rhipidocotyle lepisostei.
Nemata: Contracaecum spiculigerum, Dechelyne lepisosteus (Wardle 1990; Mayberry et al.
2000), and Crustacea: Ergalis versicolor (Hoffman 1967).”
From Tkach et al. (2008):
“Macroderoides texanus n. sp. is described based on 16 specimens collected from the intestine of
the North American alligator gar, Atractosteus spatula.”
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No OIE-reportable diseases have been documented for this species.
Threat to Humans
From Froese and Pauly (2017):
“Harmless”
From Mutlak et al. (2017):
“The eggs of alligator gar are poisonous, but their consumption by people is unlikely (Boschung
and Mayden 2004, Goddard 2009). Additionally, this fish could damage fishing nets due to the
shape of its head and the sharp teeth.”
3 Impacts of Introductions
From Fuller (2017):
“Impact of Introduction: Unknown.”
From Mutlak et al. (2017):
“There has been no published information about established population alligator gar [sic] outside
its native America.”
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4 Global Distribution
Figure 1. Known global established locations of A. spatula. Map from GBIF (2017). Points in
central Mexico and the northern and western U.S. were excluded from this map and from the
climate matching analysis because they do not represent known established populations. The
points shown in South Carolina and peninsular Florida were also excluded from the climate
matching analysis because they do not represent documented established populations (Fuller
2017).
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5 Distribution Within the United States
Figure 2. Known distribution of A. spatula in the United States. Map from Fuller (2017).
6 Climate Matching
Summary of Climate Matching Analysis
The climate match (Sanders et al. 2014; 16 climate variables; Euclidean distance) was high
throughout the southeastern U.S. including peninsular Florida and Texas. Climate match was
medium in parts of the Southwest as well as the Mid-Atlantic states, the southern Midwest, and
the New England coast. Climate match was low in much of the West, northern New England,
and the Upper Midwest and north-central U.S. states. Climate 6 score indicated a high climate
match for the contiguous U.S. overall. Scores of 0.103 or greater are classified as high match;
Climate 6 score for A. spatula was 0.328.
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Figure 3. RAMP (Sanders et al. 2014) source map showing weather stations selected as source
locations (red) and non-source locations (gray) for A. spatula climate matching. Source locations
from GBIF (2017) and Fuller (2017).
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Figure 4. Map of RAMP (Sanders et al. 2014) climate matches for A. spatula in the contiguous
United States based on source locations reported by GBIF (2017) and Fuller (2017). 0=Lowest
match, 10=Highest match.
The “High”, “Medium”, and “Low” climate match categories are based on the following table:
Climate 6: Proportion of
(Sum of Climate Scores 6-10) / (Sum of total Climate Scores)
Climate Match
Category
0.000<X<0.005
Low
0.005<X<0.103
Medium
>0.103
High
7 Certainty of Assessment
The biology and ecology of A. spatula are well understood. A. spatula has been introduced
outside of its native range in multiple locations in the U.S. and internationally; however,
established populations or impacts from introduction have not been documented. The certainty of
this assessment is low because of the lack of information on introductions.
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8 Risk Assessment
Summary of Risk to the Contiguous United States
Atractosteus spatula is a large fish native to the Mississippi River basin and Gulf of Mexico
coastal drainages in the U.S. and Mexico. It has become rare in much of its native range.
Individuals have been collected in California and South Carolina, outside the native range, but no
introduced established populations are known in the U.S. Several individuals have been collected
in Asian countries, as well, but again no established populations have been documented. Impacts
of introduction remain unknown. Aquarium releases appear to be the predominant pathway of
introduction. Climate match to the contiguous U.S. is high. Without information on impacts of
introductions, the overall risk posed by A. spatula is uncertain.
Assessment Elements
History of Invasiveness (Sec. 3): Uncertain
Climate Match (Sec. 6): High
Certainty of Assessment (Sec. 7): Low
Overall Risk Assessment Category: Uncertain
9 References
Note: The following references were accessed for this ERSS. References cited within
quoted text but not accessed are included below in Section 10.
Chong, V. C., P. K. Y. Lee, and C. M. Lau. 2010. Diversity, extinction risk and conservation of
Malaysian fishes. Journal of Fish Biology 76:2009-2066.
Esmaeili, H. R., M. Masoudi, M. Amini Chermahini, A. H. Esmaeili, F. Zarei, and M. Ebrahimi.
2017. Invasion of the Neotropical and Nearctic fishes to Iran. FishTaxa 2(3):126-133.
Froese, R., and D. Pauly, editors. 2017. Atractosteus spatula (Lacepède, 1803). FishBase.
Available: http://www.fishbase.org/summary/Atractosteus-spatula.html. (July 2017).
Fuller, P. 2017. Atractosteus spatula (Lacepède, 1803). U.S. Geological Survey, Nonindigenous
Aquatic Species Database, Gainesville, Florida. Available:
https://nas.er.usgs.gov/queries/FactSheet.aspx?SpeciesID=755. (August 2017).
GBIF (Global Biodiversity Information Facility). 2017. GBIF backbone taxonomy: Atractosteus
spatula (Lacepède, 1803). GBIF Secretariat, Copenhagen. Available:
https://www.gbif.org/species/2346754. (August 2017).
Hassan-Williams, C., and T. H. Bonner. 2013. Atractosteus spatula. Texas Freshwater Fishes,
Texas State University, San Marcos. Available:
http://txstate.fishesoftexas.org/atractosteus%20spatula.htm. (August 2017).
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ITIS (Integrated Taxonomic Information System). 2017. Atractosteus spatula (Lacepède, 1803).
Integrated Taxonomic Information System, Reston, Virginia. Available:
https://www.itis.gov/servlet/SingleRpt/SingleRpt?search_topic=TSN&search_value=201
897#null. (July 2017).
Muchlisin, Z. A. 2012. First report on introduced freshwater fishes in the waters of Aceh,
Indonesia. Archives of Polish Fisheries 20:129-135.
Mutlak, F., L. Jawad, and A. Al-Faisal. 2017. Atractosteus spatula (Actinopterygii:
Lepisosteiformes: Lepisosteidae): a deliberate aquarium trade introduction incidence in
the Shatt Al-Arab River, Basrah, Iraq. Acta Ichthyologica et Piscatoria 47(2):205-207.
NatureServe. 2017. NatureServe Explorer: an online encyclopedia of life, version 7.1.
NatureServe, Arlington, Virginia. Available: http://explorer.natureserve.org. (August
2017).
Sanders, S., C. Castiglione, and M. H. Hoff. 2014. Risk Assessment Mapping Program: RAMP.
U.S. Fish and Wildlife Service.
Tkach, V. V., E. J. Strand, and L. Froese. 2017. Macroderoides texanus n. sp. (Digenea:
Macroderoididae) from alligator gar, Atractosteus spatula in Texas. Parasitology
Research 104(1):27-33.
10 References Quoted But Not Accessed
Note: The following references are cited within quoted text within this ERSS, but were not
accessed for its preparation. They are included here to provide the reader with more
information.
Bigelow, H. B., M. G. Bradbury, J. R. Dymond, J. R. Greeley, S. F. Hildebrand, G. W. Mead, R.
R. Miller, L. R. Rivas, W. L. Schroeder, R. D. Suttkus, and V. D. Vladykov. 1963. Fishes
of the western North Atlantic, part three. Sears Foundation for Marine Research, Yale
University, New Haven, Connecticut.
Boschung H. T., and R. L. Mayden. 2004. Fishes of Alabama. Smithsonian Institution Press,
Washington, D. C.
Echelle, A. A., and C. D. Riggs. 1972. Aspects of the early history of gars (Lepisosteus) in Lake
Texoma. Transactions of the American Fisheries Society 101:106-112.
Etnier, D. A., and W. C. Starnes. 1993. The fishes of Tennessee. The University of Tennessee
Press, Knoxville, Tennessee.
Florida Museum of Natural History. 2005. Biological profiles: alligator gar. Ichthyology at the
Florida Museum of Natural History: Education-Biological Profiles. Florida Museum of
Natural History, University of Florida, Gainesville. Available:
www.flmnh.ufl.edu/fish/Gallery/Descript/AlligatorGar/AlligatorGar.html. (August 2005).
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Garcia de Leon, F. J., L. Gonzalez-Garcia, J. M. Herrera-Castillo, K. O. Winemiller, and A.
Banda-Valdes. 2001. Ecology of the alligator gar, Atractosteus spatula, in the Vicente
Guerrero Reservoir, Tamaulipas, Mexico. Southwestern Naturalist 46(2):151-157.
Goddard, N. 2009. Alligator gar. Ichthyology at the Florida Museum of Natural History.
University of Florida, Gainesville. Available: https://www.
floridamuseum.ufl.edu/fish/discover/species-profiles/ atractosteus-spatula.
Hoese, H. D., and R. H. Moore. 1998. Fishes of the Gulf of Mexico: Texas, Louisiana, and
adjacent waters. Texas A&M University Press, College Station.
Hoffman, G. L. 1967. Parasites of North American freshwater fishes. University of California
Press, Berkeley.
Jelks, H. L., S. J. Walsh, N. M. Burkhead, S. Contreras-Balderas, E. Diaz-Pardo, D. A.
Hendrickson, J. Lyons, N. E. Mandrak, F. McCormick, J. S. Nelson, S. P. Platania, B. A.
Porter, C. B. Renaud, J. J. Schmitter-Soto, E. B. Taylor, and M.L. Warren, Jr. 2008.
Conservation status of imperiled North American freshwater and diadromous fishes.
Fisheries 33(8):372-407.
Mayberry, L. F., A. G. Canaris, and J. R. Bristol. 2000. Bibliography of parasites and vertebrate
host in Arizona, New Mexico, and Texas (1893-1984). University of Nebraska Harold W.
Manter Laboratory of Parasitology Web Server, Lincoln.
McClanes, A. J., editor. 1974. Field guide to freshwater fishes of North America. Holt, Rinehart
and Winston, New York.
Miller, R. J., and H. W. Robison. 2004. Fishes of Oklahoma. University of Oklahoma Press,
Norman.
Page, L. M., and B. M. Burr. 1991. A field guide to freshwater fishes of North America north of
Mexico. Houghton Mifflin Company, Boston.
Raquel, P. F. 1992. Record of the alligator gar (Lepisosteus spatula) from the Sacramento-San
Joaquin Delta. California Fish and Game 78(4):169-171.
Salnikov, V. 2010. First finding of gar Atractosteus sp. (Actinopterygii, Lepisosteiformes,
Lepisosteidae) in the Caspian Sea near the coast of Turkmenistan. Russian Journal of
Biological Invasions 1(1):17-20.
Stone, R. 2007. The last of the leviathans. Science 316:1684-1688.
Suttkus, R. D. 1963. Order Lepostei. Pages 61-88 in H. B. Bigelow and W. C. Schroeder, editors.
Fishes of the western North Atlantic, part 3. Sears Foundation for Marine Research, New
Haven, Connecticut.
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Wardle, W. J. 1990. Experimental verification of the matecercarial stage of Rhipdocotyle
lepisostei (Trematoda: Bucephalidae) with notes on the natural occurrence of its adult
stage in gars in Texas and Virginia. Journal of Parasitology 76(2):293-295.
Warren, M. L. Jr., B. M. Burr, S. J. Walsh, H. L. Bart Jr., R. C. Cashner, D. A. Etnier, B. J.
Freeman, B. R. Kuhajda, R. L. Mayden, H. W. Robison, S. T. Ross, and W. C. Starnes.
2000. Diversity, distribution and conservation status of the native freshwater fishes of the
southern United States. Fisheries 25(10):7-29.
Wiley, E. O. 1978. Lepisosteidae. In W. Fischer, editor. FAO species identification sheets for
fishery purposes, volume 3. Western Central Atlantic (Fishing Area 31). FAO, Rome.
