Contrary to previous beliefs that only one kind of Arapaima existed, a new species of the giant Amazonian freshwater fish has been discovered in Brazil.
The Arapaima is a family of freshwater osteoglossiform fishes known as the bonytongues, native to the Amazon River in Brazil. They are also the largest freshwater fish in South America. Contrary to previous beliefs that only that one kind of Arapaima existed, a new species of the giant Amazonian fish has been discovered in Brazil. This species has been discovered 160 years after the first one was found.
"Everybody for 160 years had been saying there's only one kind of arapaima. But we know now there are various species, including some not previously recognized. Each of these unstudied giant fishes needs conservation assessment," said Dr. Donald Stewart of the SUNY College of Environmental Science and Forestry (ESF), who made the discovery.
For centuries now, the Arapaima has been one of the most commercially viable fish in the world and has high economical value. However, not much is known about their diversity. Though in the 1880s, four species were reportedly discovered, Albert Günther, a scientist at the British Museum of Natural History, revealed that the four species were actually all one species - Arapaima gigas.
Until last year, no one questioned Günther's opinion. However, when Stewart began a study on the genus in Guyana and Brazil, he was forced to question Günther's theory.
"If you're going to do conservation biology, you have to be sure about the taxonomy of the animals being studied," he said. "If each study area has a different species, then results from one area should not be applied to manage populations in the next area."
After studying scientific literature from the 19th century and examining original specimens preserved at the National Museum of Natural History in Paris, Steward found that the four species previously discovered were, in fact, distinct. The author published a re-description of one of the species and a summary of the other species discovered in a paper in the March issue of Copeia.
After examining preserved arapaima at the Instituto Nacional de Pesquisas da Amazônia in Manaus, Brazil, Steward discovered the latest species, bringing the total number of species currently known to five. The shape of sensory cavities on the head, a sheath that covers part of the dorsal fin, and a distinctive color pattern sets the newly discovered species apart from the others and has been given the scientific name A. leptosome.
The new discovery also highlights the ecological hazards of relocating animals in their habitat. It also questions what other species remain undiscovered.
"Failure to recognize that there are multiple species has consequences that are far reaching," Stewart said. "For example, there is a growing aquaculture industry for arapaima, so they are being moved about and stocked in ponds for rearing. Eventually pond-reared fishes escape and, once freed, the ecological effects are irreversible. A species that is endangered in its native habitat may become an invasive species in another habitat. The bottom line is that we shouldn't be moving these large, predatory fishes around until the species and their natural distributions are better known. Given the uncertainties, precaution is needed."
Overfishing is held responsible for the lack of diversity knowledge of the Arapaima. For years now, it has been the most exploited fish in the Amazon basin. The number of Arapaima fish living in their natural habitat is close to zero and this could be one of the reasons why such species discoveries remain rare.
The newly discovered species is on display in a public aquarium in the Ukraine.