The alligator gar (Atractosteus spatula) is a euryhaline ray-finned fish in the clade Ginglymodi of the infraclass Holostei, being most closely related to the bowfins. It is the largest species in the gar family (Lepisosteidae), and is among the largest freshwater fish in North America. The fossil record traces its group's existence back to the Early Cretaceous over 100 million years ago. Gars are often referred to as "primitive fishes" or "living fossils," because they have retained some morphological characteristics of their early ancestors, such as a spiral valve intestine, which is also common to the digestive system of sharks, and the ability to breathe in both air and water. Their common name was derived from their resemblance to the American alligator, particularly their broad snouts and long, sharp teeth. It is suggested that an alligator gar can grow up to 10 ft (3.0 m) in length.
The body of an alligator gar is torpedo-shaped, usually brown or olive colored, fading to a lighter gray or yellow ventral surface. In very rare occurrences, they can also be black, seen in gars that have a high level of melanin. Their scales are not like the scales of other fishes; rather, they are ganoid scales, which are bone-like, rhomboidal-shaped scales, often with serrated edges, and covered by an enamel-like substance. Ganoid scales are nearly impenetrable, and are excellent protection against predation. Unlike other gar species, the upper jaw of an alligator gar has a dual row of large, sharp teeth that are used to impale and hold prey. Alligator gar are stalking, ambush predators, primarily piscivores, but they also ambush and eat waterfowl and small mammals they find floating on the water's surface.
Populations of alligator gar have been extirpated from much of their historic range as a result of 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 lakes and swamps to brackish marshes, estuaries, and bays along the Gulf of Mexico.
For nearly a half century, alligator gar were considered "trash fish", or a "nuisance species" detrimental to sport fisheries, and were targeted for elimination by state and federal authorities in the United States. The 1980s brought a better understanding of the ecological balance necessary to sustain an ecosystem, and an awareness that the alligator gar is an important element of the ecosystems they inhabit was eventually understood. Over time, alligator gar were afforded some protection by state and federal resource agencies. They are also protected under the Lacey Act, which makes transporting certain species of fish in interstate commerce illegal 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 gar 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.
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CarnivoreA carnivore meaning 'meat eater' is an organism that derives its energy and nutrient requirements from a diet consisting mainly or exclusively of a...
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PiscivoresA piscivore is a carnivorous animal that eats primarily fish. Piscivorous is equivalent to the Greek-derived word ichthyophagous. Fish were the die...
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OviparousOviparous animals are female animals that lay their eggs, with little or no other embryonic development within the mother. This is the reproductive...
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SolitaryA
starts withAlligator gar have gills, but unlike other species of fish, with few exceptions, they also have a highly vascularized swim bladder lung that supplements gill respiration. The bladder not only provides buoyancy, but also enables them to breathe in air. This capability allows alligator gar to inhabit stagnant and/or insufficiently aerated bodies of water that are poorly oxygenated or hypoxic, in which most other fishes would die of suffocation due to a lack of dissolved oxygen within the water. The swim bladder is connected to their fore gut by a small pneumatic duct, which allows them to breathe or gulp air when they break the water’s surface, an action seen quite frequently on lakes in the Southern United States during the hot summer.
The scales of alligator gar are not like the scales of other fishes, which have flexible elasmoid scales; gar bodies are protected by inflexible and articulated ganoid scales that are rhomboidal-shaped, often with serrated edges, and composed of a tough inner layer of bone and hard outer layer of ganoin, which is essentially homologous to tooth enamel, making them nearly impenetrable.
Alligator gar inhabit a wide variety of aquatic habitats, but most are found in the Southern United States in reservoirs and lakes, in the backwaters of lowland rivers, and in the brackish waters of estuaries, bayous, and bays. Gars occur southward along the Gulf Coast of Texas, into Tamaulipas and northern Veracruz, Mexico; however, records from Nicaragua and Costa Rica are considered "suspect and refuted." They have occasionally been seen in the Gulf of Mexico. In Texas and Louisiana, large gars are commonly seen breaking the surface in reservoirs, bayous, and brackish marshes. They are found throughout the lower Mississippi River Valley and Gulf Coast states of the Southern United States and Mexico as far south as Veracruz, and encompassing the following states in the US: Texas, Oklahoma, Louisiana, Kentucky, Mississippi, Alabama, Tennessee, Arkansas, Missouri, Illinois, Florida, and Georgia. Reports suggest alligator gar were once numerous throughout much of their northern range, but valid sightings today are rare, and may occur once every few years. Records of historical distribution indicate alligator gar once inhabited regions as far north as central Kansas, Nebraska, Ohio, Iowa, and west-central Illinois, where they are now listed as extirpated. The most northerly verified catch was in Meredosia, Illinois, in 1922. In 2016, there were efforts to reintroduce alligator gar between Tennessee and Illinois, as part of an effort to control invasive Asian carp.
Alligator gar is an invasive species in Mainland China, where it can be purchased as an exotic pet fish. Due to its large size and armored scales, it has few natural predators even within its natural range, and its poisonous eggs may pose a passive threat to other fish. The fish has been sighted in eight provinces, and authorities have worked to remove it.
In November 2008, a broadhead gar, genus Atractosteus, measuring 5.2 to 6.4 ft (1.6 to 2.0 m) was caught in the Caspian Sea north of Esenguly, Turkmenistan, by two officials of Turkmenistan Fishery Protection.
On September 4, 2009, a 3 ft 3 in (0.99 m) alligator gar was found in Tak Wah Park in Tsuen Wan, Hong Kong. Over the next two days, at least 16 other alligator gar, the largest measuring 4.9 ft (1.5 m), were found in ponds within public parks in Hong Kong. Nearby residents reported the alligator gar had been released into the ponds by aquarium hobbyists, and had lived there for several years. However, after a complaint made by a citizen who falsely identified alligator gar as crocodiles, the use of terms like "horrible man-eating fish" had begun appearing in the headlines of some major local newspapers. Officials with Leisure and Cultural Services in Tak Wah Park removed all the alligator gar from the ponds because they were concerned the large, carnivorous fish might harm children. Not unusually, the large, sharp teeth and outward appearance of alligator gar can precipitate unreasonable fear in those unfamiliar with the species. Sensationalized reports have contributed to the misconception of predatory attacks by alligator gar on humans, though none of the reports have been confirmed.
On January 21, 2011, an alligator gar measuring 4 ft 11 in (1.50 m) was caught in a canal in Pasir Ris, Singapore, by two recreational fishermen. The fish was taken to a nearby pond, where the owner confirmed it was an alligator gar rather than an arapaima, as the men had initially thought.
Anecdotal reports have been made of alligator gar captured in various parts of India, but are believed to be the result of incidental releases by aquarium hobbyists and the like. In August 2015, an alligator gar was found entangled in cloth inside a well in Dadar, where it had been living for quite some time. It was rescued by animal activists and returned to the well unharmed. In June 2016, a 3.5-ft alligator gar was caught from Subhash Sarovar Lake in Kolkata. Other incidents over the years have been random, ranging from captures in coastal waters during environmental assessments to captures in private ponds.
On June 27, 2020, an alligator gar measuring 112 cm (3 ft 8in) was reported dead on the shore of Gonyeli Baraji reservoir, North Cyprus. Specialists from Cyprus Wildlife Research Institute collected the fish, and explained its species to be alligator gar (Atractosteus spatula). It is suspected that the fish had been released recently, and could not cope with the environment and died; however, it could be that the fish was resident there for years. A necropsy will be applied to find out more.
Similarly, on May 12, 2023, an alligator gar measuring less than 2 feet was caught during a deweeding process in Dal Lake of Kashmir near the Sher-i-Kashmir International Conference Centre (SKICC), sparking concerns about potential effects on the ecosystem.
Alligator gar are relatively passive, seemingly sluggish solitary fish, but voracious ambush predators. They are opportunistic night predators and are primarily piscivores, but gar will also ambush and eat water fowl, turtles, and small mammals 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. The gar will then lunge forward, and with a sweeping motion, grab their prey, impaling it on their double rows of sharp teeth.
Diet studies have shown alligator gar to be opportunistic piscivores, and even scavengers depending on the availability of their preferred food source. They occasionally ingest sport fish, 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. However, brackish water populations of alligator gar are known to feed heavily on blue crabs, in addition to fish such as the hardhead catfish (Ariopsis felis). Diet studies have also revealed fishing tackle and boat-engine parts in their stomachs.
