London, January 5 : Reports indicate that the arapaima, a giant species of fish that lurks in the Amazon river, may be threatened by overfishing.

According to a report by BBC News, studies reveal that errors in the classification of the species could mean that it is being pushed closer to the edge of extinction than thought.

The arapaima is the largest freshwater fish with scales in the world.

But there may actually be four species rather than one, and a lack of research and management may allow some to be fished to extinction.

The threat to the future of these fish has been revealed in research conducted by Dr Leandro Castello of the Woods Hole Research Center in Falmouth, Massachusetts, US, and Professor Donald Stewart of the State University of New York in Syracuse, US.

They have reviewed what is known about populations of the arapaima, and conducted detailed investigations into the status of the fish in the wild.

Previously, it was thought there was one species of arapaima, which also goes by the common names pirarucu or paiche.

However, in an ongoing study, Professor Stewart has analysed nearly all preserved specimens of supposed arapaima available in museums in the world.

So far, he has only found one specimen of Arapaima gigas.

The others are suspected to be closely related species, including some as yet unreported.

"Our new analyses indicate that there are at least four species of arapaima," said Dr Castello.

"So, until further field surveys of appropriate areas are completed, we will not know if Arapaima gigas is extinct or still swimming about," he added.

Research also shows that fishermen are putting populations of the fish under severe pressure.

Because of the fish''s huge size and habit of coming to the surface, it has long been a favoured fish to catch, with fisherman using harpoons and gill nets to land their prey.

Fishermen have been catching large numbers of arapaima in this way since the 1800s.

But now, while a few populations are increasing, others are being overfished, according to the researchers.

While Brazil implemented regulations to manage arapaima fisheries some 20 years ago, most fishermen do not follow the regulations.

"Arapaima can be viewed as badly overexploited and under some level of threat of extinction," said Dr Castello. (ANI)