The American or yellow perch begins life by eating the zooplankton in the lake. These are tiny animals that float along the surface of the water. When the fish are mature, they eat animals found at the bottom of the lake, such as crabs, snails, isopods and insect larvae. When they are large enough, they eat other fish.

The teeth of the yellow perch are small and slant backwards, which makes it easy for them to strain tiny particles of food from the water. Gill rakers also help the American perch ingest its food, as does a mouth positioned in a way that makes bottom feeding easier. The European perch follows the same pattern and usually hunts during the day.

Although the diet of the larvae of the Pacific Ocean perch is not well known, scientists believe that these young perch eat copepods, which are minute crustaceans that make up part of the zooplankton. The older fish eat krill, an animal very much like a shrimp, and amphipods, another tiny, shrimp-like crustacean. They also eat mysid shrimp and fish that live in the mid-level of the ocean. Sea perch larvae eat zooplankton. Like their cousins, they later eat benthic crustaceans and other fish.