To hunt for its prey, the Candirú lies at the bottom of the river testing and sniffing the water for certain chemicals, such as urea and ammonia from the gills of other fish. Once they have found a fish nearby they rush with a burst of speed to the gill cavity and attaches itself with its spines. Then, it begins to gnaw a hole towards a major blood vessel and stuffs itself for no more than a few minutes, which usually causes the victim to die. It will then release itself and sink back to the river bed in order to digest its food and wait for its next meal. 