If you want to find freshwater drum, put on your listening ears! Mature male freshwater drum can make a loud grunting noise. Their swim bladder has two chambers and thick walls with body-wall muscles attached to it. The croaking or drumming sound grows in intensity around dusk creating a low, rumbling noise in chorus. This behaviour is most common in mid-to-late June, during the spawning season, and is assumed to serve as a mating call.
The freshwater drum plays a role in the reproduction and distribution of mussels by acting as a host for their larvae or glochidia. A mussel will attract and lure a drum by fluttering part of its flesh in the water. When the drum draws near, the mussel releases the glochidia that attach to the gills of the fish using tiny hooks. Later, the larvae mature and release from the gills to begin their adult life on bottom.
Drum have large otoliths, stone-like objects found in the ear of many animals. Often used to age fish, otoliths help the drum to orient themselves in water too cloudy to see. Their otoliths can be more than an inch in diameter, and have been used by humans for currency, jewelry and good luck charms.
Freshwater drum are known to eat zebra mussels. They are not an effective means to eradicate this invasive species but they do provide some measure of population control. Fish over 14 inches in length are known to consume all sizes of zebra mussels, limited by their ability to remove them in clumps.