The Amazon and its tributaries are home to almost one tenth of the world’s freshwater fish biodiversity, 2500 species being recorded. The giant fish Arapaima gigas is one of the most emblematic of these.Catches in the wild have been declining substantially and fish farming is gradually being developed in the Brazilian and Colombian Amazon to alleviate this. Captive reproduction is one of the main problems hampering aquaculture of Arapaima notably because it is almost impossible to distinguish the sex of the reproductive adults. A new, practically non-invasive, method based on testing of a straightforward blood sample, enabled an IRD team and its Peruvian partner to determine accurately the sex of 100% of nearly 30 specimens. The technique should help improve breeding programmes of this species and at the same time facilitate study and monitoring of wild populations to improve conservation and management strategies.
Arapaima gigas is a giant air-breathing fish, emblematic in the rivers of South America. Known to Brazilians as pirarucu, it inhabits natural lagoons and low-current reaches of Amazonian rivers and is the largest freshwater fish of the South American continent. At adult stage, some specimens can reach several hundred kilograms for a length that sometimes exceeds four metres. This fish with tasty bone-free meat has been the target of intensive fishing since the early XVIIIth Century. One century ago, over 1 200 tonnes of Arapaima was landed each year in the Brazilian port of Belém alone. In 2006, declared catches for the whole of the Amazon Basin reached only 380 tonnes.
Today, it is estimated that the natural population of Arapaima gigas ranges between 50 000 and 100 000 individuals. The species has been put on the IUCN Red List of Endangered Species, and fishing is now strictly regulated. Yet commercial demand is constantly on the increase and, in order to meet this, aquaculture stations for the species are starting up in the Peruvian and the Brazilian Amazon.
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