Tarpon, Megalops atlanticus
The Tarpon, Megalops atlanticus, whose common Spanish name is sábalo, is a species in the Tarpon or Megalopidae Family, known collectively as sábalos in Mexico. This fish is also known as the Atlantic Tarpon and the Silver King. It is the only global species in the genus Megalops.
The Tarpons have oblong, elongated, and strongly compressed bodies. They are blue-green dorsally and transition to silver on their sides and ventrally. Their caudal and dorsal fins have dusky margins. Their head is short and deep with a straight profile above and a convex profile below. They have large eyes and a large superior mouth oriented upwards with a longer lower jaw and small villiform teeth. They lack fin spines. Their anal fin is deep and triangular and has 22 to 25 rays with the last ray being slightly elongated in adults. Their caudal fin is deeply forked with lobes of equal length. Their dorsal fin is high anteriorly and has 13 to 16 rays with the last ray being elongated. Their pectoral fins are long and their pelvic fins are large. They are covered with extraordinarily large scales.
The Tarpons are found in coastal waters including estuaries, lagoons, and freshwater rivers at depths up to 100 feet with water temperatures between 22oC (72oF) and 28oC (82oF). They reach 2.5 meters (8 feet 2 inches) in length and 161 kg (355 pounds) in weight. Males are smaller than females. They are highly migratory and make long runs to follow water temperatures. They have a high sensitivity to low temperatures and will quickly expire in waters that are less than 10oC (50oF). They form large schools and will frequent the same locations annually. Juveniles consume zooplankton, small crustaceans, and insects. Older juveniles and adults transition to consuming larger crustaceans (shrimp and crab), polychaetes, and schooling fish (anchovies, cichlids, mullets, sardines, and snooks, which they swallow whole). In turn their eggs and larvae are preyed upon by shore birds, small fish, zooplankton and by alligators, porpoises, and sharks as they mature. They can tolerate a wide range of salinities and oxygen concentrations. They have a swim bladder that allows them to gulp atmospheric oxygen, which is essential for their survival and gives them a competitive advantage as they can reside in areas with low predation rates and little competition for prey. Reproduction involves batch spawning and occurs at sea with each female capable of releasing 12 million eggs on average. The eggs hatch quickly and larvae migrate into estuaries. They have a maximum lifespan of 80 years in captivity. Females are known to live longer than males in the wild, 55 years versus 43 years.
In Mexican waters the Tarpons are found in all waters of the Atlantic. They are one of the few species who navigated the Panama Canal and have become established in the Pacific.
The Tarpon is very easy to recognize and cannot be confused with any other species.
The Tarpons are considered one of the world’s great saltwater game fish due to their size, inshore habitats, fighting abilities (including tremendous endurance which can take one to three hours to land), long runs, and spectacular airborne leaps when pursued in shallow flats with fly rods. They are considered a marginal food fish due to the abundance of bones and the presence of Cigua Toxin, however, they are served for Christmas dinner in some cultures. In Mexico they are retained by subsistence fishermen and sold fresh. They are also retained when caught as a by-catch by commercial fishermen utilizing purse seines, longlines, and gill nets. They are heavily regulated in some areas, including in the United States where most fish are handled as “catch and release.” In Mexico there is a two fish per person per day limit without a minimum size requirement, which is poorly understood and poorly enforced. The International Sábalo Fishing Tournament is held every May in Tecolutla in Mexico’s Costa Esmeralda. From a conservation perspective, they are currently considered Vulnerable to extinction. Although widely distributed, their populations are believed to have declined by at least 30% over the last decade, which has been attributed to overfishing, habitat degradation, and by-catch mortality. They mature late and have long generation times making their recovery difficult. They are used by the aquarium trade on a limited basis requiring very large tanks. Their large scales are used in ornamental objects such as artificial pearls.
Tarpon, Megalops atlanticus. Fish caught from coastal waters off Key West, Florida, March 2017. Length: 1.27 meters (4 feet 2 inches). Weight: 12.7 kg (28 pounds). Catch, photo, and identification courtesy of Dean Kimberly, Atlanta, GA.