Krill are small, shrimplike animals that live in oceans throughout the world. Krill are crustaceans, a type of animal with a shell and jointed legs (see Crustacean). There are more than 90 species of krill. They range in length from 3/8 inch to 6 inches (1 to 15 centimeters). Krill are abundant in plankton, the mass of tiny organisms that provides an important source of food for marine life (see Plankton). Blue, fin, and humpback whales eat vast amounts of krill and other planktonic organisms daily.
Many species of krill are surface dwellers, and others live at deeper levels or migrate up or down in the water. Animals that eat krill, including whales, seals, fish, and squids, follow along.
Young krill hatch from eggs as larvae, immature animals that do not resemble the adults. The larvae molt (shed their shell) as they grow. Krill larvae may go through as many as 10 molts before reaching the adult stage.
As food, krill is rich in protein. Most of the krill that people catch is used as fish bait or as feed for fish farms. Krill is also used as a food additive and a dietary supplement. Some people eat krill directly, but the shell must first be removed because it contains high levels of a chemical called fluoride. Some scientists worry that catching large numbers of krill may jeopardize the food supply of whales and other animals.
