The Spotted Bass (Micropterus punctulatus) is a freshwater species native primarily to the southeastern United States, including the Mississippi River and Ohio River basins. It is an opportunistic predator that occupies an ecological niche often between that of the Largemouth Bass and the Smallmouth Bass. This species is distinguished by its smaller average size and a jaw that does not extend past the rear of the eye, which influences the maximum size of prey it can consume. Spotted Bass typically favor areas with current, such as rocky reservoirs, flowing streams, and river systems, where they feed throughout the water column and on the bottom. Its diet is varied, shifting based on the bass’s size, the availability of local forage, and seasonal changes.
Dominant Prey: Fish and Crustaceans
The primary, high-calorie components of an adult Spotted Bass’s diet consist of crustaceans and forage fish. Crayfish are a particularly significant food source in many habitats, sometimes accounting for a large portion of the overall diet. The consumption of these crustaceans is often linked to their molting cycle, as a crayfish with a newly shed, soft exoskeleton is easier to digest and less likely to cause injury.
Crayfish shells resist digestion, meaning their remnants are frequently found in stomach analyses. This can sometimes overrepresent their actual dietary importance compared to soft-bodied prey that are quickly broken down. Spotted Bass effectively prey on these bottom-dwelling arthropods, especially in the rocky, current-swept areas they prefer.
Forage fish also form a substantial part of the adult diet. Common prey include small sunfish, such as Bluegill and Green Sunfish, as well as various minnow species. Shad, particularly the Threadfin Shad, are favored open-water prey because they are schooling fish that rarely exceed five inches in length, making them an ideal meal for the Spotted Bass’s smaller mouth structure. Gizzard Shad are also consumed, but they often grow too large for most Spotted Bass to manage, unlike the larger-mouthed Largemouth Bass.
Seasonal Foods: Insects and Amphibians
While fish and crayfish provide consistent energy, insects and amphibians serve as important supplementary prey, especially when they become seasonally abundant or vulnerable. Aquatic insects, such as the larvae and nymphs of Mayflies, Caddisflies, and Dragonflies, are consumed year-round, but often in greater quantities during their emergence periods. These small invertebrates help sustain the bass population when primary forage may be less active.
The Spotted Bass will also opportunistically feed on terrestrial insects that fall into the water. Consumption of large surface insects like grasshoppers, cicadas, and beetles spikes during the summer months. These meals are frequently intercepted near the water’s surface, offering a quick, accessible source of calories.
Amphibians and small reptiles, while not staples, are eaten when the opportunity arises. Small frogs, tadpoles, salamanders, and even small snakes that venture into the water become prey. These items are typically consumed near the shoreline or emergent vegetation.
Dietary Changes from Juvenile to Adult
The diet of the Spotted Bass progresses as the fish increases in size. Newly hatched fry, which are only a few millimeters in length, begin feeding on zooplankton once their yolk sac is absorbed. The initial diet consists of the smallest forms, such as rotifers, which are quickly replaced by slightly larger micro-invertebrates like copepods and cladocerans (e.g., Daphnia).
As the young fish grow, their mouth size increases, allowing for a swift transition to a more carnivorous diet. This shift begins when the juvenile bass reaches approximately 25 to 35 millimeters (about one to one-and-a-half inches) in total length. At this stage, they begin to consume small aquatic insect larvae and the fry of other fish species.
By the time the bass reaches six inches in length, its diet strongly resembles that of the adult, consisting primarily of larger prey like forage fish and crayfish. The shift from micro-invertebrates to larger prey is essential for the rapid growth and survival of the sub-adult fish.