New Species of Giant Fish Discovered in Brazil

A new species of arapaima, a heavily armored, man-sized fish in South America's rivers, has been identified for the first time 166 years.

The new species was recently identified by Donald Stewart a professor of environmental science and forestry at the State University of New York after being collected from the waters of the central Amazon River in Brazil in 2001. Stewart, who published his find in the journal Copiea, has effectively challenged long-held beliefs about the giant fish. He contends that his latest find is the fifth species of arapaima, several more than previous estimates.

In the mid-1800s, there were four recognized species of arapaima, but in 1868 the German scientist Albert Günther suggested that those four were all one species. Günther's option went on to become the prevailing view of the fish.

"Everybody for 160 years had been saying there's only one kind of arapaima," Stewart said, adding that until this year, "no taxonomist has questioned Günther's opinion about these iconic fishes.".

"But we know now there are various species, including some not previously recognized," he said. "Each of these unstudied giant fishes needs conservation assessment."

Stewart said his find highlights conservation assessments necessary along different regions of the Amazonian waters.

"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 and the taxonomic records of the fish from the 19th century, Stewart concluded in a research paper published in Copiea earlier this year, all four of the original four species described were distinct.

The latest arapaima species, A. leptosoma, brings the total of distinct species to five. The fish is is distinguished among its brethren by the shape of sensory cavities on the head, a sheath that covers part of the dorsal fin and a distinctive color pattern. Its scientific name is a reference to its slender body.

"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."