Drumfish
Juvenile Pareques acuminatus (Peter Leahy / shutterstock.com)
The drumfish (Scianidae), also called drum or croaker, has a long dorsal fin with a deep notch between the spinous and soft portion. Drumfish use their swim bladder as resonance chamber for producing drumming sounds. The largest species (Totoaba macdonaldi) can grow up to 2 meters (6.6 feet) in length and 100 kilograms (220 pounds) in weight. However, most species are much smaller.
This supplemental online resource accompanies the book Scuba Diving Hand Signals by Lars Behnke, available on
Amazon.