| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Actinopterygii |
| Infraclass: | Holostei |
| Order: | Lepisosteiformes |
| Family: | Lepisosteidae |
| Genus: | Atractosteus |
| Species: | A. spatula |
Alligator gar, Atractosteus spatula, are ray-finned euryhaline fishes related to bowfin in the infraclass Holostei (ho'-las-te-i). The fossil record traces the existence of alligator gars back to the Early Cretaceous over a hundred million years ago. They are the largest in the gar family, and among the largest freshwater fishes in North America. Gars are often referred to as "primitive fishes", or "living fossils" because they have retained some morphological characters of their earliest ancestors, such as a spiral valve intestine which is also common to the digestive system of sharks, and they can breathe both air and water. Their common name was derived from their resemblance to American alligators, particularly their broad snout and long sharp teeth. Anecdotal scientific reports suggest that alligator gars can grow up to 10 ft (3.0 m) in length and weigh as much as 300 lb (140 kg), however in 2011 the largest alligator gar ever caught and officially recorded was 8 ft 5
1⁄4 in (2.572 m) long, weighed 327 lb (148 kg), and was 47 in (120 cm) around the girth. Their bodies are torpedo shaped, usually brown or olive fading to a lighter gray or yellow ventral surface. They do not have scales like other fishes, rather they are armored for protection against predation with hard, enamel-like, jagged diamond-shapedganoid scales that are nearly impenetrable. Unlike other gar species, mature alligator gars have a dual row of large sharp teeth in the upper jaw which they use for impaling and holding prey. They are stalking, ambush predators that are primarily piscivores, but will also ambush and eat water fowl and small mammals that may be floating on the surface.
Alligator gars have been extirpated from much of their historic range through habitat destruction, indiscriminate culling, and unrestricted harvests. Populations are now located primarily in the southern portions of the United States extending into Mexico. They are considered euryhaline because they can adapt to varying salinities ranging from freshwater lakesand swamps to brackish marshes, estuaries, and bays along the Gulf of Mexico.
For nearly a half-century, alligator gars were considered "trash fish",[1] or a "nuisance species" that were detrimental tosport fisheries, and therefore targeted for elimination by state and federal authorities in the United States, but the last ten years has seen a greater emphasis placed on the importance of alligator gars to the ecosystems they inhabit. As a result, they were afforded protection by restricted licensing. They are also protected under the Lacey Act which makes it illegal to transport fish in interstate commerce when in violation of state law or regulation. Several state and federal resource agencies are monitoring populations in the wild, and have initiated outreach programs to educate the public. Alligator gars are being cultured in ponds, pools, raceways and tanks by federal hatcheries for mitigation stocking, by universities for research purposes, and in Mexico for consumption.[2]
Evolution:
Lacépède first described the alligator gar in 1803. The original name was Lepisosteus spatula, but was later changed by E.O. Wiley in 1976 to Atractosteus spatulain order to recognize two distinct extant taxon of gars. Synonyms of Atractosteus spatula include Lesisosteus [sic] ferox (Rafinesque 1820), and Lepisosteus spatula(Lacepede 1803). Fossils from the order Lepisosteiformes have been collected in Europe from the Cretaceous to Oligocene periods, in Africa and India from the Cretaceous, and in North America from the Cretaceous to recent times. Lepisosteidae is the only extant family of gar which has seven species all located in North and Central America.[3] The fossil record traces the existence of alligator gars back to the Early Cretaceous over a hundred million years ago.[8][9] Despite being a highly evolved species, alligator gars are often referred to as "primitive fishes", or "living fossils"[10][11] because they have retained a few morphologicalcharacteristics of their earliest ancestors with seemingly little to no apparent changes, such as a spiral valve intestine which is also common to the digestive system of sharks, an abbreviate-heterocercal tail, and a swim bladder lung for breathing in both air and water.
Feeding:
Alligator gars are relatively passive, seemingly sluggish solitary fish, but voracious ambush predators. They are opportunistic night predators and are primarily piscivores, but they will also ambush and eat water fowl and smallmammals that may be floating on the surface. Their method of ambush is to float a few feet below the surface, and wait for unsuspecting prey to swim within reach. They lunge forward, and with a sweeping motion grab their prey, impaling it on their double rows of sharp teeth.[7]
Diet studies have shown alligator gars to be opportunistic piscivores, and even scavengers depending on the availability of their preferred food source. They occasionally ingest sport fishes, but the majority of stomach content studies suggest they feed predominately on forage fishes such as gizzard shad as well as invertebrates, and water fowl. Diet studies have also revealed fishing tackle and boat engine parts in their stomachs.
Swapping:
As with most ancestral species, alligator gars are long living, and sexually late maturing. Most females do not reach sexual maturity until after their first decade of life while males reach sexual maturity in half that time. The conditions must be precise for a successful spawning to occur. Preparation for spawning begins in the spring with the extended photoperiod and rising water temperatures, but flooding is also necessary to trigger the event. When rivers rise and spread over the floodplain, they create oxbow lakes and sloughs, and inundate terrestrial vegetation which in turn provides protection and a nutrient rich habitat for larval fishes, and fry. Once the water temperature has reached 68 to 82 °F (20 to 28 °C), and all the other criteria are met, gars will move into the grassy, weed-laden shallows to spawn.[15][16]
Actual spawning occurs when a collection of males gather around gravid females, and begin writhing, twisting, bumping into and slithering over the tops of females, an activity which triggers the release of eggs. Males release clouds of milt to fertilize the eggs as they are released into the water column.[15] The sticky eggs then attach to submerged vegetation, and development begins. It takes only a few days for the eggs to hatch into larval fish, and another ten days or so for the larval fish to detach from the vegetation and start moving about as young fry.[16] Egg production is variable, and believed to be dependent on the size of the female. A common formula used for predicting the volume of eggs a female can produce is 4.1 eggs/gram of body weight which gives an average of about 150,000 eggs per spawn. The eggs of alligator gars are bright red and poisonous to humans if ingested.[7]
Aquaria[edit]
Despite the large size alligator gars can attain, they are kept as aquarium fish, though many fish labeled as "alligator gar" in the aquarium trade are actually smaller species. Alligator gars require a very large aquarium or pond, and ample resources in order for them to thrive in captivity. They are also a popular fish for public aquaria, and zoos. It is illegal in many areas to keep alligator gars as pets, but they will occasionally show up in fish stores. Alligator gars are highly prized and sought after for private aquaria, particularly in Japan. According to some reports, large alligator gars could fetch as much as US$40,000 in what some consider the "Japanese black market".[29] In June 2011, three men from Florida and Louisiana were indicted on charges of illegally removing wild alligator gars from the Trinity River in Texas, and attempting to ship them to Japan for private collectors. The indictments resulted from an undercover sting operation by special agents with the U.S. Fish & Wildlife Service, the Texas Parks and Wildlife Department, and theFlorida Fish and Wildlife Conservation Commission.[30] The charges included violations of three separate provisions of the Lacey Act, specifically conspiracy to submit a false label for fish transported in interstate commerce; conspiracy to transport fish in interstate commerce in violation of state law or regulation; and conspiracy to transport and sell fish in interstate commerce in violation of state law or regulation.[31] Two of the conspirators entered guilty pleas to one count, and the government dropped the other two charges against them. A third conspirator went to trial on all three counts, was acquitted on one count, and found guilty on two. The district court sentenced him to serve nine months in prison followed by one year of supervised release.[32] The case was appealed, and on April 15, 2014, the appellate court affirmed the judgment of the district court.[33]
Commercialization and aquaculture[edit]
Declining populations of alligator gars throughout their historic range has resulted in the need to monitor wild populations and regulate commercial harvests. Alligator gars have a high yield of white meat fillets and a small percentage of waste relative to body weight. The meat is sold to wholesale distributors, and also sold retail by a few supermarkets with prices starting at around $3.00/lb. Fried gar balls, grilled fillets, and fillets boiled in water with crab boil seasoning are popular dishes in the south. There is also a small cottage industry that makes jewelry out of ganoid scales, and tans gar hides to produce leather for making lamp shades, purses, and a host of novelty items.[7][13]
Atractosteus gars, including alligator gars, tropical gars, and Cuban gars are considered good candidates for aquaculture particularly in developing regions where their rapid growth, disease resistance, easy adaptation to artificial feeds as juveniles, and ability to tolerate low water quality are essential. Their ability to breathe in both air and water eliminates the need for costly aeration systems and other technology commonly used in aquaculture. In the Southern United States, as well as in parts of Mexico and Cuba, broodstocks have already been established, and are being maintained in their respective regions where they already are a popular food fish.[28]
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