Tarpon

Tarpon are large, powerful fish belonging to the genus Megalops. They are the only living members of the family Megalopidae. There are two distinct species within this genus. The Atlantic tarpon, Megalops atlanticus, lives in the Atlantic Ocean. Its range extends from Virginia to Brazil. It also inhabits the Caribbean and the Gulf of Mexico. The other species is the Indo-Pacific tarpon, Megalops cyprinoides. This fish lives along the eastern African coast and throughout Southeast Asia. You can also find it in Japan, Tahiti, and Australia.

One of the most remarkable features of the tarpon is its ability to breathe air. Most fish rely entirely on gills to extract oxygen from water. However, tarpon possess a specialized swim bladder that acts as an accessory respiratory organ. The swim bladder is a gas-filled sac located dorsally from the posterior pharynx. In tarpon, the respiratory surface of this bladder is coated with blood capillaries. This area has a thin epithelium, which is a type of tissue layer. This specialized structure allows the fish to perform gas exchange from the atmosphere.

This air-breathing ability is a vital survival mechanism. Tarpon often inhabit mangrove forests and salt marshes. These nursery habitats can have stagnant water with very low dissolved oxygen levels. During storms or king tides, young tarpon may even be carried into remote, landlocked ponds. In these isolated environments, oxygen levels can become so low that most other fish cannot survive. The tarpon survives by rising to the surface to take gulps of air. They use a rolling motion to gulp air, which provides a short burst of energy. This trait allows them to thrive in habitats with high aerobic metabolism needs.

The life cycle of a tarpon consists of three distinct developmental stages. The first stage is the leptocephalus stage. This lasts for 20 to 30 days and occurs in clear, warm oceanic waters near the surface. During this stage, the larvae do not forage for food. Instead, they use integumentary absorption to take nutrients directly from the seawater. The second stage is a shrunken larval form that develops by day 70. This happens because the fish goes through a negative growth phase followed by a sluggish growth phase. By day 70, the third stage begins. This is the juvenile growth phase, where the fish grows rapidly until it reaches sexual maturity.

As tarpon move through these stages, their diet and habitats change significantly. Stage-one larvae stay in the open ocean. Stage-two and stage-three juveniles move into salt marshes, tidal pools, and rivers. These juveniles feed on zooplankton, insects, and small fish. As they grow in freshwater environments, they begin eating more crabs and grass shrimp. Once they reach adulthood, tarpon become strictly carnivorous. They hunt midwater prey nocturnally and swallow their food whole.

The history of the Megalops genus stretches back millions of years. Fossil evidence shows that these fish existed during the Late Oligocene in Australia. There are also potential remains from the Late Cretaceous in Mississippi, known as Megalops nolfi. Scientists identify these ancient species using fossil otoliths. An otolith is a small bone found in the ear of a fish. Other fossil species include Megalops lissa from the Late Oligocene and Megalops vigilax from the Miocene. These fossils prove that the tarpon lineage is very old.

Tarpon are highly regarded as premier saltwater game fish. Anglers prize them for their massive size and their spectacular leaping ability. Because tarpon meat is not considered desirable for eating, most fish caught in tournaments are released. They are also very resilient to human environments. Atlantic tarpon can adapt to urban or suburban areas with heavy boat traffic. They also tolerate low water quality well. However, they are sensitive to temperature. They prefer water at 77 degrees Fahrenheit. If temperatures drop below 59 degrees, they become inactive. Temperatures under 50 degrees can be lethal to them.