What Flounder Eat
As juveniles, flounder eat annelid worms known as polychaetes, small crustacean and small fish. As they grow larger, their primary diet becomes shrimp and small fish.
During the spring, flounder are the primary predator for shrimp in the Coastal Bend bay system. Studies have shown that the primary food source for adult flounder however are small fish such as menhaden, anchovies, pinfish, grunts, pigfish, croakers, and mullet. During those studies, about 1/3 of the flounder had shrimp in their digestive systems with the bulk of the flounder eating small fish.
Unlike other predator fish in the bay system, flounder don’t seem to eat larger fish as they grow larger. Instead they seem to just eat more small fish.
The most active feeding time for flounder are the three days before a new moon and the three days following a first quarter moon. They tend to stay in the deeper drop offs and ledges during the day and will move up on to sandy flats and feed prolifically at night. Alert anglers, wading the sandy flats, will recognize the depressions in the sand made by flounder (referred to as beds) as a sign that the area is home to a good flounder population.