Photo: Shrimp krill
Integral to the food chain, tiny shrimp krill are the primary food source for many marine mammals and fish.
Photograph by George F. Mobley
Map: Locator map for the krill
 Krill range

Fast Facts

Type: Invertebrate
Diet: Herbivore
Average lifespan in the wild: 5 years or more
Size: 2.4 in (6 cm)
Weight: 0.035 oz (1 g)
Did you know? Scientists estimate that the total weight of all the Antarctic krill is more than the total weight of all humans on Earth.

The lowly krill averages only about two inches (5 centimeters) in length, but it represents a giant-sized link in the global food chain. These small, shrimp-like crustaceans are essentially the fuel that runs the engine of the Earth’s marine ecosystems.

Krill feed on phytoplankton, microscopic, single-celled plants that drift near the ocean’s surface and live off carbon dioxide and the sun’s rays. They in turn are the main staple in the diets of literally hundreds of different animals, from fish, to birds, to baleen whales.

Simply put, without krill, most of the life forms in the Antarctic would disappear.

Alarmingly, there are recent studies that show Antarctic krill stocks may have dropped by 80 percent since the 1970s. Scientists attribute these declines in part to ice cover loss caused by global warming. This ice loss removes a primary source of food for krill: ice-algae.

Pink and opaque, Antarctic krill are among the largest of the 85 known krill species. Their estimated numbers range from 125 million tons to 6 billion tons in the waters around Antarctica. Congregating during certain times of year, in swarms so dense and widespread, they can be seen from space.

Antarctic krill can live up to 10 years, an amazing longevity for such a heavily hunted creature. They spend their days avoiding predators in the cold depths of the Southern Ocean, some 320 feet (100 meters) below the surface. During the night, they drift up the water column toward the surface in search of phytoplankton.