Alligator Gar is quite a unique and exciting type of fish. It falls into the category of ‘ray-finned species’ and is one of the largest freshwater fish found in North America. It is related to bowfin in the infraclass Holostei and is the largest in size in the gar family.
Its fossil record traces back to the time of the Early Cretaceous more than a million years ago. This is why they are often known as ‘primitive fishes’ or the ‘Living Fossils’ as they have still retained some of their earlier morphological characteristics of their ancestors.
This includes the spiral valve intestine which is also found in sharks and their ability to breathe in both water and air. Their common name, ‘Alligator Gar’, is derived from their resemblance to the American alligator, with their long sharp teeth and their broad snout.
- Class: Actinopterygii
- Order: Lepisosteiformes
- Family: Lepisosteidae
- Genus: Atractosteus
- Adult Size: 5.9 to 9.8 ft (1.8 to 3 m)
They typically have about 57 to 62 lateral line scales and around 23 scale rows which are diagonal between their anal-fin origin and their dorsal midline. They always have about two rows of sharp teeth in their upper jaw, as compared to one row in all other gar species. The younger Alligator gars may only have one row.
The Alligator Gar can grow really big in size. It can grow as long as about 10 ft (3.0 m) in their length. The largest Alligator Gar ever found was recorded to be 8 ft 5 1⁄4 in (2.572 m) long, it weighed about 327 pounds (148 kg), and it was 47 inches (120 cm) around the circumference.
Their body is torpedo-shaped and is in a brown to light olive and has a grey or yellow ventral surface. Their scales are not similar to other fish. In fact, they are ganoids scales that are diamond-shaped and bone-like, covered by an enamel-like substance with serrated edges.
These scales provide excellent protection against predators and are almost impenetrable. The upper jaw of the Alligator Gar as a dual row of sharp and large teeth, unlike the other gar species. It uses its sharp teeth to impale and to hold its prey.
Habitat and Biology
The Alligator Gars live in the coastal estuaries of Alabama as well as in the major streams and rivers. They are also found in the Conecuh River site which is characterized by a moderate level of current, and there is predominantly gravel and sand substrates. The process of spawning for the Alligator Gar occurs around spring.
They have gills, but unlike other types of fish, they have a vascular swim bladder lung which supplements their gill respiration. The bladder provides it with buoyancy, but it also enables it to breathe in air through which they can inhabit bodies of water where most types of fish would end up dying of suffocation.
Through a small pneumatic duct, their swim bladder is connected to their foregut through which they can breathe or gulp air when they are on the surface, which is seen often on the lakes during summertime in the Southern United States.
As a result of habitat destruction, unrestricted harvests and indiscriminate culling, the population of these fish has been extirpated from most of their historic range. Currently, the population of Alligator Gar is located mostly towards the southern portion of the USA extending towards Mexico.
The Alligator Gars are considered euryhaline since they can adapt quite quickly to the varying salinities that can range from swamps to brackish marshes, estuaries, freshwater lakes and bays along the Gulf of Mexico.
Taxonomy and evolution
This fish was first described in 1803 with its original name being Lepisosteus spatula and the name was changed later to Atractosteus spatula in 1976 after two distinct taxa of gars were recognized.
There have been fossils from Lepisosteiformes which have been collected from Europe from the Oligocene and Cretaceous period and in India and Africa from the Cretaceous as well as in North America from recent times. The Lepisosteidae are the only family of gars that have about seven different species and all are located in Central and North of America.
From the fossil record, the fish can be traced back to the early Cretaceous which is over a hundred million years ago. For the longest period, the Alligator Gar was not paid attention to and were thought to be as ‘nuisance species’ or ‘trash fish’ that were detrimental to the sports fisheries.
They were targeted by the federal authorities in the USA for elimination. Over time, however, they were offered protection as there was more awareness regarding the protection of the ecosystem and the ecological balance.
They are now protected under the Lacey Act which makes it illegal to transport particular species of fish in interstate commerce. The Alligator Gars are currently cultured in pools, ponds, tanks, and raceways by the federal hatcheries for mitigation stocking by universities for research and in Mexico for consumption.
The Alligator gars are entirely passive, sluggish and solitary fish, while at the same time ambush predators and are piscivores. They do however ambush and eat small mammals which may be floating about on the surface and also feed on waterfowl.
The way they attack their prey is by hovering a few feet away below the surface of the water and wait for the unsuspecting victim to swim towards their reach. Then they make a forward lunge, and along with a sweeping motion, they grab their prey and attack with their teeth.
They occasionally eat sports fish, but most of the studies of their stomach suggest that they predominantly feed on forage fishes like the gizzard shad as well as invertebrates.
The alligator gars, like their ancestral species, are long-living, but they sexually mature later as compared to other fish. Most of the female species of the fish does not attain sexual maturity until the first decade of their lives, while the males reach in about half that time.
There are precise conditions for the spawning to be successful. The preparation for breeding begins in the spring season with the rising water temperature, but to trigger the event, flooding is also necessary.
As the rivers rise and it spreads over the floodplain, it creates sloughs and oxbow lakes, and it ends up inundating terrestrial vegetation, which provides protection and nutrient-rich habitat for the larval fish and the fry. As the water temperature reaches 68 to 82 °F (20 to 28 °C) while having the rest of the criteria met the alligator gar moves towards weed laden and grassy shallows for the process of spawning.
The actual spawning happens as the males gather around the females and begin twisting, writhing, slithering and bumping all over the females. This is an activity that triggers the release of eggs.
The males, on the other hand, release clouds of milt which fertilizes the eggs in the water column. The sticky eggs are then attached to the sticky vegetation, and the process of development begins. Within a few days, the eggs are hatched into larval fish and in another ten days or so, the larval fish detaches itself from the vegetation and starts moving as fry.
The number of eggs that the female would lay varies on the size of the female and a standard formula used to determine the volume of eggs that the female would produce is 4.1 eggs/gram of the total body weight. This is an average of about 150,000 eggs per spawn. The alligator gar eggs are bright red in color and poisonous to human beings if ingested.
Aquarium trade and commercial uses
Even with their large size, the Alligator Gars can be kept as aquarium fish, also though many of the fish labeled as the Alligator Gars in the aquarium trade are much smaller in size. These fish require a vast aquarium or a pond and an abundance of resources for them to grow and thrive in captivity.
They are also quite popular when it comes to public aquariums or for the zoo. In many places, keeping the Alligator Gars as pets is illegal, but they are still available in fish stores. They are quite sought after in Japan for the aquarium trade and are quite expensive as well.
Moreover, Alligator Gar meat is also eaten by many people. It is sold to wholesale and retail distributors by supermarkets and can be cooked into grilled or boiled fillets along with crab boil seasoning which is a favorite dish in the South.
The scales of the Alligator Gar is also used in making jewelry, and the tan gar hides are used for making leather lampshades, purses, and many other expensive items. The Alligator Gars are also very popular with the bow fishers due to their large size, fighting ability and trophy potential. As such, it is also considered as a good sports fish and the long time, negative perception of being a ‘trash fish’ has changed.