Ctenophora predation by ctenophores may control the populations of small zooplanktonic organisms such as copepods, which might otherwise wipe out the phytoplankton (planktonic plants), which are a vital part of marine food chains. Almost all ctenophores are predators – there are no vegetarians and only one genus that is partly parasitic. If food is plentiful, they can eat 10 times their own weight per day. While "Beroe" preys mainly on other ctenophores, other surface-water species prey on zooplankton (planktonic animals) ranging in size from the microscopic, including mollusc and fish larvae, to small adult crustaceans such as copepods, amphipods, and even
Freshwater drum of the freshwater drum's diet. In August through November, they tend to eat fish (which are primarily young-of-the-year gizzard shad). The percentage of fish in their diet at this time ranges from 52-94 percent. Other items in the drum's diet are mollusks and crayfish. Freshwater drum tend to hang out with walleye. The freshwater drum competes with several organisms. During its early stages in Lake Erie, it has been shown to compete with yellow perch, the trout-perch, and the emerald shiner. During its adult lifetime, it competes with yellow perch and silver chub in deep water, and competes with black