Alligator Gar, Atractosteus spatula
Alligator Gar, Atractosteus spatula. Fish caught from a freshwater stream in Puerto Chomes, Costa Rica, March 2021. Length: 1.1 m (3 feet 7 inches). Catch, photograph and identification courtesy of Eli (obsessiveangling.wordpress.com).
Alligator Gar, Atractosteus spatula. Fish caught from the Richland-Chambers Reservoir, Richland, Texas. June 2021. Length: 1.1 cm (3 feet 7 inches). Catch, photograph and identification courtesy of Luke Ovgard, Klamath Falls, Oregon.
The Alligator Gar, Atractosteus spatuls, is a member of the Gar or Lepisosteidae Family, that is known in Mexico as catán. The gars are scientifically interesting as they are very primitive and date to the Cretaceous Period, 145 to 66 million years ago. There are currently seven living gars that have been placed in two genera of which three species are in the genus Atractosteus, with one (this species) found in the freshwater systems of Mexico that feed into the Atlantic Ocean and one that is found in the freshwater systems of both the Atlantic and the Pacific Oceans.
The Alligator Gar appears as a prehistoric living fish but they are actually highly evolved. They have an elongated and torpedo-shaped body. They are olive-brown dorsally and transition to a lighter gray or yellow ventrally. The juveniles have a light mid-dorsal stripe bordered by thin dark line that extend from the tip of the snout to the dorsal fin and a dark lateral band that extends along the sides with irregular borders. Their anal, caudal and dorsal fins have oval black spots. The adults lack spotting on the body. Their head has a broad snout. Unlike other gar species, the upper jaw of an alligator gar has two rows of large, sharp teeth that are used to impale and hold prey. Their anal and dorsal fins are located far back in the body; their caudal fin is asymmetrical, their pectoral fins are low on the sides, and the pelvic fins are located mid-body. The have 59 to 66 gill rakers. They are covered with unique ganoid scales that are thick and overlapping, which provide them with a suit of armor and allow adults to be free from predation.
The Alligator Gar is found in large, slow moving rivers, reservoirs, lakes, bayous and bays in both fresh and brackish water. They are the largest species in the Gar Family and the second only to the White Sturgeon, Acipenser transmontanus, as the largest freshwater fish found in North America. They grow rapidly in the first two years but then the growth rates slow significantly. A two-meter (6-foot) gar is between 10 and 30 years of age and will weight 45 kg (100 pounds). They can reach 3.05 m (10 feet 0 inches) in length and 159 kg (350 lbs) in weight. They are very sluggish and docile. They are sexually dimorphic with females being larger than males in length and weight. They are nighttime lie-in-wait ambush predators that primarily consume various fishes including buffalos, carp and shad, blue crabs and a limited number of birds, small mammals, turtles and carrion. As such they are an important apex predator in many ecosystems. In turn they are known to be preyed upon by the American Alligator, Alligator mississippiensis. The Alligator Gar is long-lived, and sexually late maturing. They access oxygen via its gills, but unlike most other species of fish, they also have a highly vascularized swim bladder lung. The bladder not only provides buoyancy, but also enables them to breathe in air, which is why they are able to inhabit bodies of water in which most other fishes would die of suffocation. Reproduction occurs in the spring when water temperature reach 20oC (68oF) with flooding necessary to trigger the event which provides protection from predation and nutrient rich terrestrial vegetation for larval fish and fry. The female and males gather in groups and simultaneously release eggs and sperm. The eggs are stick and adhere to the substrate. The eggs hatch quickly into larval fish. On average each female will only once or twice each decade and will release 150,000 bright red eggs on annual cycles. They are covered with a coating of slime. They have life spans of up to 100 years.
The Alligator Gar is a resident of Mexican waters but has a limited distribution being found in coastal brackish waters and within the freshwater systems that drain into the Gulf of Mexico from northern Veracruz northward to the United States border.
The Alligator Gar is often misidentified. They can be confused with the Longnose Gar, Lepiosteus osseus (long, narrow snout, thinner bodies), as-well-as the Shortnose Gar, Lepiosteus platostomus (lack spotting on the top of the head and pectoral and pelvic fins), and the Spotted Gar, Lepiosteus oculatus (dark spots on their head, body and fins and small in stature).
From a conservation perspective the Alligator Gar is currently considered to be of Least Concern with stable, widely distributed populations. Historically they have a reputation of being a “trash fish” or “nuisance species” and they have been deliberately slaughtered by the thousands. Recently this perception has changed and they have become of enhanced interest to national and international attention on the species as a sport fish. Although widespread, there is a long-term concern for the survival of the species due to overfishing and human-caused habitat destruction. The Alligator Gar is heavily targeted by commercial fishermen, recreational anglers and bow fishermen. They are prone to overfishing and habitat destruction of their breeding grounds. Their flesh has been used for centuries by Native Americans for food, their scales have been used to make arrow heads and jewelry, and their skin has been used to make leather products. Their eggs are poisonous to humans. They are utilized on a limited basis by the aquarium trade and found primarily in large public aquariums and they require large bodies of water; in some areas their use as pets has been banned. They are a current focus and being raised in several locations via aquaculture. They are visually most intimidated but not considered to be hazardous to humans.