Cardinalfish

Photo: Margarida · CC BY-NC

Mediterranean cardinalfish fill the interior of Caverna dos Peixes in clouds of hundreds, their translucent orange bodies pulsing through the cave's dimmer zones as they shelter from daytime predators outside and emerge at dusk to feed on zooplankton. Male cardinalfish are oral brooders, incubating fertilised eggs in the buccal cavity for 4 to 7 days without feeding, and this behaviour has been observed at the cave entrance where the lower current levels within provide a stable environment for incubating males to remain stationary. Their aggregation density inside the cave is one of the highest anywhere in Macaronesian waters, a function of the undisturbed refuge that the cave structure provides against both predators and fishing pressure.