Rusty parrotfish (Derek Keats / CC BY)

Parrotfish (Scaridae) are named for their parrotlike beaks, which are used for rasping algae from the skeletons of dead coral. Parrotfish species range from 19 centimeters (7.5 inches, raggedtooth parrotfish) to 80 centimeters (32 inches, spotted parrotfish) in length. After nightfall some species, including the queen parrotfish (Scarus vetula), form a cocoon by secreting mucus from their mouths. This “sleeping bag” most likely hides their scent from potential predators.

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