Atlantic tarpon – Megalops atlanticus (Distribution – biology – conservation) – Video

This video was taken in June 2012 at the World of the Sea aquarium, Sea World, San Diego, California, USA

Introduction: Atlantic tarpon, Megalops atlanticus that belongs to the family Megalopidae is also known as the silver king and Sábalo in Spanish. Although this species has no commercial value as a food fish due to its bony flesh, it is a premier sport fish species not only because of their size, but also because of their fighting spirit when hooked. When they occur in high abundance, tarpons would be of economic significance. Their average life span is about 50-55 years for females and 30-40 years for males. Being a prized game fish, tarpon would be present in fishing festivals. In fact, there is a special International annual tarpon Fishing Contest that is held in Tecolutla on Mexico’s Costa Esmeralda. The tarpon is the official state saltwater fish of Alabama.

Distribution and habitats: The Atlantic tarpon (Megalops atlanticus) populates a wide variety of habitats, but are primarily found in coastal waters, bays, estuaries, mangrove-lined lagoons and rivers on both sides of the Atlantic Ocean, typically in tropical and subtropical regions, though it has been reported as far north as Nova Scotia and the Atlantic coast of southern France, and as far south as Argentina. They are also found throughout the Gulf of Mexico and the Caribbean, and in the Eastern Central Pacific off Coiba Island. The species migrated through the Panama Canal from the Atlantic to the Pacific and back. The normal habitat depth for tarpon extends to 30 m.   

Tarpons tolerate wide ranges in salinity (0 – 47 g/l) throughout their lives and hence they often enter river mouths and bays and travel upstream into fresh water. The modification in their air bladder allows tarpon to inhale atmospheric oxygen and hence to tolerate oxygen-poor environments.

In regard to temperature, tarpons prefer water temperatures of 22 to 28°C, below 16°C they become inactive, and temperatures below 5°C can be lethal and so tarpons seek warmer refuges in deeper water whenever temperature drops to such risky levels.

Description: Tarpon, Megalops atlanticus are large, beautiful, fish that can reach up to 2.5 m and weigh up to about 160 kg for female with males generally smaller. They have bluish-gray color on their dorsal side with very bright silvery sides and belly. Tarpon has a large and superior mouth with the lower mandible extending far beyond the upper jaw. Tarpon have very large scales with 40-48 scales along their lateral line. Tarpon possess a swim bladder attached to their esophagus which enables them to live in oxygen-poor (hypoxic) water.  Tarpon also uses its swim bladder in producing sound in the form of thumps in case of attack.  

Feeding behavior: During their larval stages, tarpon larvae absorb nutrients directly from seawater. As fish grows reaching small juveniles, they consume zooplankton (copepods and ostracods), insects, and small fish while adult tarpon become carnivorous and prey on midwater fish, shrimp and crabs. Tarpon feed during both the day and the night. Because of their small teeth, they generally swallow their prey whole. The ability of tarpon to tolerate low dissolved oxygen levels due to the structure of its swim bladder, the species would enjoy a predatory advantage when oxygen levels are low. On the other hand, different life stages of tarpon are vulnerable to predation that range and include from zooplankton, small fishes, piscivorous birds, and sharks.

Reproduction:  Tarpon reach sexual maturity at 6-7 years of age and By 10 years of age; all females were found to be sexually mature.  They breed offshore in warm, isolated areas. On the average, adult female tarpon produces more than 12 million eggs at once in an annual spawning cycle.

Threats and conservation:

Threats: Tarpon fishery is exposed to variety of threats. The catch and release fishing by recreational anglers may be a source of adult tarpon mortality even at low rate. Habitat degradation due to whatever reasons (e.g. pollution) represents a significant threat to tarpon fishery. Tarpon estuarine fishery may be threatened by runoff from agriculture and urbanization.

Conservation measures: According to situations and types of threats, the followings are examples of conservation measures which are taken in different tarpon fishery:

Declaring tarpon as a game fish in South Carolina in 1991 led to not only the banning of the sale of tarpon but also limiting recreational anglers to a possession limit of one fish per person per day.

In Florida and Alabama, a special permit is required to kill and keep a tarpon.

Promoting and creating awareness on the conservation ethics upon the handling of tarpon should go side by side with fishermen education on the best practices when releasing the fish.

References: Florida Museum of Natural History, MarineBio, NAS – Nonindigenous Aquatic Species, Wikipedia


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