The researchers analysed nearly all preserved museum specimens of supposed arapaima and found only one specimen of Arapaima gigas. The others are suspected to be closely related species. "Our new analyses indicate that there are at least four species of arapaima," said Castello. "So, until further field surveys of appropriate areas are completed, we will not know if Arapaima gigas is extinct or still swimming about."

Fishermen ignore regulations intended to manage stocks, he said, and there is a lack of data about population numbers. "The present situation may be one in which one species of arapaima is recovering in certain areas, while unrecognised species are going extinct."