The diet of a largemouth bass changes dramatically from the moment it hatches until it develops into a juvenile predator. Understanding the shifting nutritional needs of a baby bass, which includes the microscopic fry and the slightly larger fingerling stage, is helpful for managing aquatic ecosystems. The survival and rapid growth of these young fish depend entirely on the availability of appropriate-sized food items. This journey involves two major, rapid dietary shifts, moving from minuscule organisms to consuming other vertebrates.
The Earliest Diet (Fry Stage)
Newly hatched largemouth bass, known as fry, are initially sustained by the yolk sac for a few days. Once this internal food source is absorbed, typically when the fry are around eight days old, they must immediately seek external food. This first external diet is limited to the smallest, most abundant life forms in the water column: zooplankton.
The microscopic organisms consumed include rotifers, cladocerans, and copepods. These tiny crustaceans and filter-feeders are often less than a millimeter in size, requiring the fry to feed almost constantly to meet their high metabolic demands. Fry are visually oriented feeders, relying on sight to hunt these small, suspended animals.
Transition to Larger Invertebrates
As the bass grow to a length of roughly one to three inches, their mouths become large enough to capture bigger prey, triggering a major dietary transition. This shift moves the fingerlings away from filtering microscopic life toward actively hunting larger invertebrates. The increased size and energy expenditure necessitate food sources with higher caloric value than zooplankton alone.
The diet expands significantly to include aquatic insect larvae and small crustaceans found in bottom sediment and submerged vegetation. Prey items now feature the larvae of midges, small amphipods like Hyalella, and various aquatic insect nymphs. Fingerlings also consume bottom-dwelling organisms such as water boatmen and mosquito larvae.
This stage is marked by a preference for larger prey, including larger copepods such as Cyclops. As their foraging ability improves, they also target the young of larger crustaceans, including small crayfish, which offer a substantial energy boost. This invertebrate-focused diet fuels the rapid growth required for the next developmental stage.
Onset of Piscivory
The final major dietary change occurs as the bass reach a length of approximately 1.5 to 2 inches (38 to 50 millimeters), when they begin to incorporate other small fish into their diet. This aggressive feeding behavior, known as piscivory, establishes the largemouth bass as a true juvenile predator. Consuming fish allows for a much faster growth rate than an invertebrate-only diet permits.
The types of fish consumed are limited only by the size of the young bass’s mouth; the prey’s body depth must be smaller than the predator’s gape width for successful ingestion. Common targets include the fry and fingerlings of other species like sunfish (bluegill), shiners, and fathead minnows. Young bass also prey on the hatchlings of gizzard shad when available.
Cannibalism frequently occurs, where larger fingerlings actively prey upon smaller bass fry. This behavior is pronounced when food is scarce or when there is a significant size difference among the young bass. Once a young bass transitions to a fish-centric diet, it rarely returns to relying heavily on smaller prey like zooplankton or insects.