Brachyplatystoma filamentosum

Brachyplatystoma filamentosum
Piraíba in a fish market. Note the very long maxillary barbel
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Actinopterygii
Order:	Siluriformes
Family:	Pimelodidae
Genus:	Brachyplatystoma
Species:	B. filamentosum
Binomial name
Brachyplatystoma filamentosum (Lichtenstein, 1819)
Synonyms
Brachyplatystoma goeldii Pimelodus filamentosus Piratinga piraaiba Platystoma affine Platystoma gigas Sorubimichthys gigas

Brachyplatystoma filamentosum, commonly called piraíba, kumakuma, valentón or lau lau, is a species of catfish of the family Pimelodidae and genus Brachyplatystoma that is native to Amazon and Orinoco River basins and rivers in the Guianas and northeastern Brazil. It is an important predator in its ecosystem, and in turn is a food fish.

Description

The name "piraíba" is used by locals to define B. filamentosum specimens larger than 1.6 m (50kg), while the term "filhote" is used for smaller individuals.

The piraíba reaches up to 3.6 metres (12 ft) in length and 200 kilograms (440 lb) in weight, though most individuals of B. filamentosum don't reach these dimensions, more commonly being 120 centimetres (47 in). Juveniles exhibit dark body spots or blotches.

B. capapretum was recognized as distinct from B. filamentosum and described in 2005. These two species are very closely related, being sister genera. They can be differentiated through premaxillary dentition, juvenile and adult coloration, and adult maxillary barbel length and caudal fin shape. Both species exhibit spotting in their juvenile stages, though in B. filamentosum these spots are about the same size as the eye, while in B. capapretum these spots are much larger in size. The adult B. capapretum has a very dark or even black dorsum (its species name is derived from Portuguese which means black cape), as opposed to the relatively lighter dorsal surface of B. filamentosum.

Adults have dark gray coloration on the dorsal side of the body, with a lighter white underside. They have paired pectoral fins, pelvic fins, a single unpaired dorsal fin, anal fin, and an adipose fin. The caudal fin is forked. While their body structure is somewhat reminiscent of a shark, they can be identified by their 3 pairs of barbels around the mouth.

Distribution

The species is found in rivers and estuaries of Amazon and Orinoco watersheds, Guianas and northeastern Brazil.

Ecology

Brachyplatystoma filamentosum is found in both freshwater and brackish water systems. The species is a demersal potamodromous fish that commonly inhabits deeper, flowing channels with soft bottoms.

Despite being sizeable predators themselves, surubí may fall prey to the piraíba

The piraíba is strongly predatory, mainly preying on a wide variety of fish. The fish preyed upon include Achirus soles; characins from the genera Brycon, Colossoma, Hemiodus, Leporinus, Myleus, Mylossoma, Prochilodus, Schizodon, Semaprochilodus, Rhytiodus, Triportheus, along with indeterminate Curimatidae; catfish such as Ageneiosus, Calophysus vulture catfish, Hypophthalmus, Pareiodon candiru, Pimelodella, Pimelodus, Sorubim, and indeterminate members of the families Cetopsidae, Pimelodidae, and Trichomycteridae; Cichlids, Gymnotiformes, Pellona, and drums like Pachypops and Plagioscion. The piraíba is notable for tackling difficult prey items, such as toxic Colomesus pufferfish and stingrays; armored catfish among the Doradidae and Loricariidae, such as Doras and Oxydoras; and other predatory fish like Pseudoplatystoma and Rhaphiodon are all taken by the piraíba, solidifying its position as top-order carnivore. However, stomach contents are said to include parts of monkeys, and even people have been reported to fall prey to them. Only the river dolphins has been recounted to prey on the piraíba, but even then, they may fail at killing and consuming much of the catfish; the doomed piraíba is then left crippled and at the mercy of the currents and riverine scavengers, such as the two genera of catfish referred to as candiru, and the aptly-named vulture catfish.

Juvenile piraíba

Piraíba begin their life as ichthyoplankton, metamorphosing through their larval stages as they drift downriver The young take aquatic invertebrates, such as diplostracans, rotifers, and aquatic insects, along with other arthropods adrift in the current. Eventually, they reach the estuary, where they remain for some time to continue growing and maturing. Eventually, the immature fish swim up the river to return to their spawning grounds. Mature adults may then return to the estuary to feed.

Spawning tends to occur in rising and high water periods, typically between February to June. In their larval stage, their diet consists mostly of insect remains and plankton, similar to other fish that are piscivorous as adults. Piraiba migrate across the amazon basin throughout their life. They rear their young in both upstream and estuarine environments.

Conservation status

Piraiba, along with other large amazon catfish species, are important apex predators in the Amazon Basin. This water body serves as a central source for fisheries in South America, providing food for communities in the area.

However, this species, along with several other South American catfishes, are declining in population. Local fisheries are struggling due to overfishing, with records of decreasing catches being a primary indicator of their decline. These catfish are migratory, meaning they are especially sensitive to dam construction and habitat degradation, which impede their ability to migrate throughout the waterways.

Piraiba, along with other predator fish, are also susceptible to mercury contamination; this, along with their role as an important food source, puts many local communities at risk.

Fisheries there are poorly studied and we know relatively little about these species, so our understanding of the ecological impacts are also limited. Chemical analysis of otoliths within specimens has proven to help researchers study migratory patterns of Piraiba, helping provide evidence of their life stages at different regions. This serves as an alternative method to physically monitoring their behavior, which eliminates several difficulties the latter method raises.

Relation to humans

Piraíba are considered to be game fish, but are more valuable as a food fish; it was considered to be the 6th most important species fished in the Brazilian Amazon in 1998. Due to overfishing, catches have been declining.

These large species are used as food for people in South America, specifically the communities that are housed around the rivers. The skin residue is high in fatty acids and proteins, and is a usable alternative for several products, including gelatin. Gelatin is primarily produced using cows, which may introduce the risk of bovine spongiform encephalopathy. Fish residue as an alternative would mitigate this risk, as well as the other consequences of using cattle products.

Piraíba are sometimes kept in aquaria, although the adults need a very large tank to accommodate their swimming.

Conversely, there have been recorded incidents where large B. filamentosum have preyed on humans. In one account documented on the television series River Monsters, a local fisherman was found having been swallowed head-first up to his waist by one of these catfish, with neither the fish nor the fisherman survived the encounter.