Bangai cardinalfish (Lakshmi Sawitri / CC BY)

Cardinalfish (Apogonidae) are relatively small fish with brightly colored bodies and two separated dorsal fins. Most cardinalfish species are less than 15 centimeters (5.9 inches) in length. Many species are mouth breeders, with males carrying eggs and hatchlings in their mouth cavities. Cardinalfish are typically nocturnal, feeding on zooplankton and small benthic invertebrates. Most species are reef associated.

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This supplemental online resource accompanies the book Scuba Diving Hand Signals by Lars Behnke, available on Amazon.