Alligator Gars are an ancient group of predatory fish belonging to the family Lepisosteidae, native to North America, Central America, and parts of the Caribbean. Often referred to as "primitive fishes" or "living fossils", they have retained some morphological characteristics of their early ancestors. This article delves into the diet and feeding habits of the alligator gar, along with various aspects of its biology, habitat, and conservation.
Alligator Gar: An Overview
There are several species of gar, including the Alligator Gar, Spotted Gar, Shortnose Gar, and Longnose Gar, each with unique characteristics. The Alligator Gar (Atractosteus spatula) is the largest species in the gar family (Lepisosteidae), and is among the largest freshwater fishes in North America. Mature alligator gar commonly measure 6 ft (1.8 m) in length, and weigh over 100 lb (45 kg). However, anecdotal reports suggest they can grow up to 10 ft (3 m) in length, and weigh as much as 350 lb (159 kg). The largest alligator gar officially recorded was 8 ft 5+1⁄4 in (2.572 m) long, weighed 327 lb (148 kg), and its girth was 47 in (120 cm).
Gars are also unique in their ability to breathe air, thanks to a specialized swim bladder that functions like a lung. This allows them to survive in low-oxygen environments, where many other fish would struggle. All gars have torpedo-shaped bodies. Alligator 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.
Their common name was derived from their resemblance to the American alligator, particularly their broad snouts and long, sharp teeth. The English common name for Atractosteus spatula are alligator gar, gator, greater gar, garpike, garfish, and Mississippi alligator gar.
Alligator gars have about 80 teeth in total. Their teeth get replaced by new ones as they wear down. On average, an alligator gar goes through 2,000 to 3,000 teeth in a lifetime. 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.
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Habitat and Distribution
Gars live in freshwater habitats such as rivers, lakes, and swamps, often preferring slow-moving waters with plenty of vegetation and submerged structures like logs or debris. They can be found in both warm and moderate climates across North and Central America.
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. 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, and Florida.
They mostly live in slower-moving rivers, reservoirs, and brackish waters. Texas is king, followed by Mississippi, Oklahoma, Arkansas and Florida. Estuaries along the Gulf of Mexico for coast states are prime locations. They can also be found in saltwater, usually further out. The habitat of alligator gars varies by season. They prefer to reside in coves with no current off main rivers in the winter. In Spring, they begin a journey to the river’s main channel, frequently returning to the cove. Later in Spring, they will finally begin their descent further away from the cove. They could go as far 250 miles north during these times. As example, in Florida the Escambia Bay during this time of the year is prime for big Gar but also travel as far north as Alabama. Each state has these migration location, you just need to find them and get the time correct.
Diet and Feeding Habits in Detail
Alligator gar are carnivorous and require a diet rich in protein to support their growth and health. They 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, other birds, 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. 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.
In their natural habitat, they primarily feed on smaller fish, crustaceans, and invertebrates. Brackish water populations of alligator gar are known to feed heavily on blue crabs in addition to fish such as the hardhead catfish. This gar is also known to prey on waterfowl and other birds, small mammals, turtles, and carrion.
Read also: Opportunistic Carnivore
Conservation Status and Threats
Populations of alligator gar have been extirpated from much of their historic range as a result of habitat destruction, indiscriminate culling, and unrestricted harvests. 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. 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.
The alligator gar is disappearing from many parts of the range, and declining in population everywhere due to over-fishing and the construction of dikes, dams, and other flood control devices, resulting in loss of key breeding habitat.
Alligator Gar in Captivity
Keeping an alligator gar as a pet is a rewarding experience, but it requires careful attention to their unique needs.
Tank Size and Setup
Alligator gars require specific and spacious aquarium conditions to thrive, as they are large, predatory fish. Tank size is crucial. Alligator gars can grow up to 10 feet in length, so they need an expansive tank to accommodate their size and swimming habits. A minimum of 1,890 liters (500 gallons) is recommended for juveniles, but as they grow, a tank size of 3,785 liters (1,000 gallons) or more is ideal. This ensures the gar has enough room to swim freely and prevents overcrowding, which could lead to stress or aggression.
Water temperature plays a significant role in their health and activity. Alligator gars prefer warm water, with temperatures maintained between 75-82°F (24-28°C). Consistent temperature control is important, as sudden temperature fluctuations can stress the fish. In terms of water hardness, alligator gars thrive in soft to moderately hard water, with a general hardness (GH) level between 4-12 dGH. The hardness of the water influences their overall health and immune system, so it’s important to monitor and adjust if needed.
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The aquarium should have plenty of open swimming areas to allow the gar to move freely. While they are solitary and territorial, having some hiding spots like rocks, logs, or plants can help the gar feel more secure, especially when they are young or stressed. However, it’s important not to overcrowd the tank with too much decoration, as this could limit the gar’s movement. A tank lid is essential, as alligator gars are known to jump. Having a tight-fitting lid will prevent the gar from escaping the tank, ensuring it stays safe within its environment.
Tank Mates
When selecting tank mates for an alligator gar, it is important to choose large, robust fish that can withstand the gar’s predatory nature. Alligator gars are solitary and territorial, especially as they mature, and they may view smaller fish or invertebrates as prey. Suitable tank mates include other large fish such as catfish, large cichlids, or other species of gar, which can tolerate the gar's size and occasional aggressive behavior. Fish like pacu, arowanas, and large tilapia can also coexist with gars, as long as they are of similar size and strength. It is important to avoid small or slow-moving fish, as they may be eaten by the gar. Additionally, any tank mates should have similar water requirements, such as warm water temperatures and good water quality, to ensure the health and well-being of all the species in the tank.
Diet and Feeding in Captivity
When kept in captivity, it’s essential to provide them with similar food sources to mimic their natural diet. A primary food source for alligator gars is fresh or frozen fish, such as tilapia, trout, herring, and other meaty fish. These are ideal because they provide the necessary nutrients, including proteins and fats. Shrimp (both fresh and frozen) is another excellent choice, as it is rich in protein and helps keep the gar's diet varied. Squid and other types of shellfish can also be offered. Earthworms and nightcrawlers are a good option for additional protein and help maintain the gar's interest in different food textures.
Occasionally, frozen or freeze-dried foods like krill, mealworms, or bloodworms can be offered as treats, but these should not make up the main diet. Pellets designed for carnivorous fish can also be an option, but many gars may not readily accept them, so they are best used in combination with fresh or frozen food. Feeding an alligator gar requires careful attention to portion sizes. Juvenile gars can be fed smaller amounts, while adult gars need larger portions to meet their energy demands. It’s generally best to feed the gar every 2-3 days, as they have a slower metabolism. Overfeeding should be avoided, as uneaten food can degrade water quality and lead to health issues for both the gar and other tank inhabitants.
Health Monitoring
Alligator gars can face various health issues, including skin infections and fungal diseases, often caused by poor water quality or injuries. Bacterial infections like Aeromonas can lead to sores or redness, while parasites such as Ich and flukes can cause scratching or abnormal behavior. Swim bladder disorders may occur from overfeeding or constipation, affecting swimming. Malnutrition can result from an imbalanced diet, leading to weight loss or lethargy. Stress-related issues, such as hiding or loss of appetite, can weaken the immune system. Preventing these problems requires maintaining clean water, offering a balanced diet, and minimizing stress. Regular water testing, good filtration, and suitable tank mates are key to keeping gars healthy.
Breeding Considerations
Breeding alligator gars in captivity is challenging, as it requires specific conditions that replicate their natural environment. In the wild, gars typically spawn during the spring in shallow, calm waters with dense vegetation. They lay eggs in nests built by males, who guard them until they hatch. Gars are slow to mature, and they often don’t breed until they reach several years of age, typically around 5-6 years for males and 7-10 years for females. In aquariums, breeding is rare, as it requires a large tank, optimal water conditions, and an appropriate environmental setup. Successful breeding is often a result of mimicking the seasonal changes in temperature and water levels found in their natural habitat.
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 fish and fry. Actual spawning occurs when 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. The sticky eggs then attach to submerged vegetation, and development begins. Only a few days are needed for the eggs to hatch into larval fish, and another 10 days or so for the larval fish to detach from the vegetation, and start moving about as young fry. Egg production is variable, and believed to be dependent on the size of the female. A common formula used for predicting the number 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.
Alligator Gar and Humans
Due to its large size and sharp teeth, the alligator gar is capable of delivering a serious bite wound to fisherman or swimmers. However, there is no documentation of attacks on man by alligator gars. Not unusually, the large, sharp teeth and outward appearance of alligator gar can precipitate unreasonable fear in those unfamiliar with the species.
Native Americans in the South and Caribbean peoples used the alligator gar's ganoid scales for arrow heads, breastplates, and as shielding to cover plows. Early settlers tanned the skins to make a strong, durable leather to cover their wooden plows, make purses, and craft various other items.
Alligator gar have a high yield of white-meat fillets and a small percentage of waste relative to body weight. Fried gar balls, grilled filets, and fillets boiled in water with crab boil are popular dishes in the southern United States.
Sport Fishing and Management
The long-time public perception of alligator gar as trash fish or a nuisance species has changed, with increasing national and international attention on the species as a sport fish, which some have attributed to features on popular television shows. Oklahoma, Texas, Arkansas, Mississippi, and Louisiana allow regulated sport fishing of alligator gar. Texas has one of the best remaining fisheries for alligator gar, and in concert with its efforts to maintain a viable fishery, imposed a one-per-day bag limit on them in 2009. Alligator gar are also quite popular among bowfishers because of their large size, trophy potential, and fighting ability. Declining populations of alligator gar throughout their historic range have resulted in the need to monitor wild populations and regulate commercial harvests.