Copepods can sense many food items with their long antennae. Utilizing water currents, the long, very thin hairs that grow from these antennae allow them to sense food particles in the water before they can actually grab them. Copepods eat microzooplankton, phytoplankton, and detritus. They are a very important food source for many fish. Striped Bass and many other commercial fish feed on copepods as larvae, while other fish like bay anchovies and silversides remain plankton feeders their entire lives.
Copepods occur in freshwater, estuarine, and marine ecosystems.
Very small, newly hatched fish are not strong enough to swim substantially on their own, and are carried around the bay with the water currents. It is only for this early stage that fish are zooplankton. Fish larvae feed mainly on other zooplankton, especially copepods. Fish larvae are also very abundant in marshed and aquatic grass beds. The reason is that these locations provide the larvae with many places to hide from their predators.