The arapaima, native to the Amazon River basin, is one of the largest freshwater fish species globally. Known for its size and ancient lineage, it thrives in challenging aquatic environments, contributing to its presence in South American freshwater ecosystems.
Arapaima’s Typical Dimensions
A mature arapaima commonly measures between 7 and 8 feet (2.2 to 2.4 meters) in length, typically weighing around 200 pounds (90.7 kilograms). These fish exhibit rapid growth, reaching approximately 3 feet and 20 pounds in their first year, and growing to about five feet and 90 pounds by their fourth year. They achieve sexual maturity around 4 to 5 years of age, usually when they are about 1.65 meters long.
Record-Breaking Arapaima
While typical sizes are substantial, arapaima can reach even more impressive, record-breaking dimensions. Some individuals can extend to 9.8 feet (3 meters) and reach weights of up to 440 pounds (200 kilograms). The longest verified length for a specimen stands at 10 feet 1 inch (3.07 meters). Anecdotal accounts suggest lengths possibly reaching up to 14 or 15 feet, though these remain largely unverified. Among angler catches, a notable record includes a 13-foot long arapaima weighing 415 pounds 8 ounces caught in 2015. Another significant catch recorded 339 pounds 8 ounces and was 116.14 inches long.
Factors Influencing Growth
Several environmental and biological factors contribute to the arapaima’s ability to attain its considerable size. Their diet primarily consists of other fish, classifying them as piscivorous predators. They are also opportunistic feeders, consuming crustaceans, fruits, seeds, insects, birds, and even small mammals that venture near the water’s surface. Juveniles typically feed on insects and fish larvae, transitioning to a fish-heavy diet as adults, and can consume over 8% of their body weight daily.
Arapaima inhabit slow-moving rivers, floodplain lakes, and flooded forests within the Amazon and Essequibo basins. Their unique adaptation to breathe air, using a modified swim bladder as a lung, allows them to thrive in oxygen-deficient waters where other fish might struggle. This air-breathing capability means they frequently surface, making them more susceptible to fishing pressure.
The species can live for up to 20 years, with an average lifespan in captivity ranging from 15 to 20 years. Arapaima are sensitive to cold water, with temperatures below 61°F (16°C) proving fatal and optimal growth requiring temperatures above 24°C.