Tropical Gar, Atractosteus tropicus
Tropical Gar, Atractosteus tropicus. Fish caught from a freshwater stream in Puerto Chomes, Costa Rica, March 2021. Length: 1.1 cm (3 feet 7 inches). Catch, photograph and identification courtesy of Eli (obsessiveangling.wordpress.com).
The Tropical Gar, Atractosteus tropicus, is a member of the Gar or Lepisosteidae Family, that is known in Mexico as pejelagarto. 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 found in the freshwater systems of Mexico that feed into the Atlantic Ocean and one (this species) that is found in the freshwater systems of both the Atlantic and the Pacific Oceans.
The Tropical Gar has an elongated moderately slender robust body. They vary in color from dark to pale brown with numerous dark brown blotches dorsally. They have a dark stripe along the flank and some fish have a dark spot on the upper base of the caudal fin. Juveniles are dark dorsally and white ventrally also with a dark stripe along the flank and another stripe that runs from the gill cover to the anal fin and then to the caudal fin; ventrally they have spots between the stripes. Their head has a long conical relatively broad snout and a mouth that has highly visible large fangs on each jaw that are set in two rows on the top jaw and one on the bottom. Their anal and dorsal fins are located far back in the body; their caudal fin is fan-like, their pectoral fins are low on the sides, and the pelvic fins are located mid-body. They have 57 to 62 large flattened gill rakers on the first arch. 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 Tropical Gar is found in large, slow moving rivers, lakes, and pools in both fresh and brackish water in areas that have abundant aquatic vegetation and are without strong current at depths up to 10 m (33 feet). They require access to flood plains for reproduction. They grow rapidly in the first two years but then the growth rates slow significantly. They reach a maximum of 1.25 m (4 feet 1 inch) in length and 2.9 kg (6 lbs 6 oz) in weight. They are very sluggish and docile and can be seen frequently lying on the surface and resemble floating logs. They are a lie in wait ambush predator that primarily consume a wide variety of cichlids and crustaceans. The Tropical accesses 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 temporary flooding in wetlands 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 which are left alone to defend from themselves as the waters recede. They grow rapidly during the first year.
The Tropical 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 both the Gulf of Mexico (in the State of Tabasco) and the Pacific Ocean (in the States of Oaxaca and Chiapas. They are absent from along the East Coast of the Yucatán Peninsula.
The Tropical Gar is often confused with the Longnose Gar, Lepiosteus osseus (longer thinner snout).
From a conservation perspective the Tropical Gar is currently considered to be of Least Concern with stable, widely distributed populations. They are prone to overfishing and habitat destruction of their breeding grounds. Both their meat and eggs are poisonous to humans. They are utilized on a limited basis by the aquarium trade and are not suitable for home aquariums and only found in large public aquariums. They are visually most intimidated but not considered to be hazardous to humans.