Brachyplatystoma

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Brachyplatystoma is a group of very large South American catfish in the Pimelodidae family. They are often called goliath catfishes and include some of the Amazon’s biggest freshwater fish, such as the piraíba (Brachyplatystoma filamentosum).

What they are like
- Size: species range from about 60 cm to well over 3 meters. The piraíba can reach up to about 3.6 meters (12 feet) and very large weights; other species are usually 1–2 meters.
- Appearance: they are streamlined swimmers. Many have countershading (dark back, lighter belly). Juveniles can have spots or stripes that fade as they grow. Long barbels and, in many species, tail filaments are common.

Where they live
- They inhabit the Amazon and Orinoco basins and other tropical freshwater and even brackish waters in South America. They prefer soft substrates like mud or sand.
- Juveniles often live in brackish estuaries before moving to the main river as they grow.

Migration and life cycle
- Brachyplatystoma species are migratory. They travel long distances, sometimes thousands of kilometers, mainly to reach spawning areas.
- Maturation often coincides with the rising waters of the rainy season, and migrating fish may spawn in tributaries or floodplains.
- Juveniles drift downstream as larvae and gradually move back upriver as they mature.

What they eat and their role in the ecosystem
- They are mainly piscivores, feeding on smaller fish such as characins and cichlids, and occasionally other catfish.
- The largest species, especially some populations of B. filamentosum and B. rousseauxii, can have very large diets. There are occasional, unverified stories of very large individuals preying on humans.

Threats and relationship with people
- These fish are important food fish in the Amazon region, with large catches for local use and export.
- Overfishing, dams, and deforestation can disrupt their migrations and spawning. Some species are considered overfished or vulnerable in parts of their range.

In the aquarium
- They are rarely kept by fishkeepers because of their enormous size and active needs. When kept in captivity, only the largest public or specialty aquariums can house them. Some species, like B. tigrinum, are prized and expensive; breeding in home aquariums is not known.

Summary
Brachyplatystoma are among the Amazon’s most impressive catfish, known for their massive size, long migrations, and importance as a food fish. They live in large river systems, migrate to spawn, and face threats from overfishing and habitat change, making their conservation a concern in parts of their range.