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How to discover the gender of the arapaima fish

George Chernilevsky / Wikicommons

Laparoscopy can be useful to distinguish the males and the females of this fish speciesGeorge Chernilevsky / Wikicommons

How can one tell whether an arapaima is a male or a female? This is important information for the management of fish farms. However, the subtle differences in  tone of the red scales are not enough to distinguish the gender of the Arapaima gigas, one of the largest freshwater fish in the world. Now, researchers from the Federal University of Ceara,  the Ocean Sciences Institute and the Rodolpho Von Ihering Aquaculture Research Center, also in Ceará, have found that laparoscopy – the technique used to remove the gall bladder in human beings – can be useful to determine the gender of this fish (Acta Amazonica, September). A test was conducted during which ten young fish were anesthetized with chloroform. Within three minutes, laparoscopic images 15-centimeter long by 5-millimeter wide were produced, allowing the researchers to accurately identify the gonads.