Black drum are heavy-bodied fish with large heads. Fish up to about 15 pounds have 4 or 5 wide vertical black bars set on a silver-gray body. The bars fade as the fish grow larger, eventually disappearing. All sizes of black drum can be identified by the whisker-like barbels under their chin.

Black drum have large heavy pharyngeal teeth in the back of their throat that they use to crush mollusk shells. Young black drum under 8 inches long feed mostly on marine worms and small fish. After 8 inches, they switch their diet to mollusks such as oysters, clams, and mussels. Research has shown that drum captured from oyster reef areas prefer to eat oysters over clams and mussels. Research has also shown that black drum can average eating one oyster per pound of body weight per day.

Feeding black drum swim with their heads slightly lowered, drifting their barbels (chin whiskers) over possible food items. When the barbels touch a food item, the drum stops swimming and inhales in the food item by creating a suction with its gill covers and mouth. The drum slowly swims forward while crushing the food item with its massive pharyngeal teeth. As the food item is crushed, small shell particles fall from the drum's gills. After finishing, the drum ejects the rest of the shell from its mouth. Black drum can break apart and crush oyster clusters, but seem to select singles for ease of feeding. They feed both during daylight hours and at night, but feeding is less intensive during early morning hours. While feeding, schools of black drum often dredge up the bottom, creating muddy plumes in the water which can be easily seen from the air.

Black drum are a prolific species, with females producing 11-60 million eggs each over a 14-week spawning season. Generally, spawning takes place in or near passes, as well as in channels in open water in depths between 10 and 165 feet. The locations change with seasons and environmental conditions.

Black drum spawn between January and April. Spawning activity takes place between 7 p.m. and 10 p.m. and at water temperatures of 59 to 75°F. Black drum spawning sites are closely tied to the amount of dissolved oxygen in the water, with the more oxygen the better. During this period, each female spawns 20 to 30 times. Spawning peaks seem to occur at new and full moon phases and spawning takes place in the early evening, one to two hours after sunset. After being spawned, the eggs are carried seaward by currents until they hatch. Larval (baby) and small black drum then tend to travel inland with incoming tides where they settle out in marshes to grow.

At 24 to 26 inches and 4 to 5 years of age, they become sexually mature and begin to spawn. Mature black drum form large schools before the beginning of spawning season. Often 20,000 - 60,000 pounds of fish will be in one of these offshore schools, frequently mixed with cownose rays and occasionally with crevalle jacks and red drum. After spawning season, these schools seem to disperse. Black drum are long-lived fish, with most studies indicating a maximum age of over 40 years and one study in Florida estimating a maximum of 58 years of age.