Antarctic krill one of the world’s most abundant multi-celled animals.

Scientists estimate the biomass of Antarctic krill to be around 380 million tonnes – greater than the weight of all humans on Earth. They are the key species of most food webs in the Southern Ocean.

Harvested krill is mainly used for the production of krill meal and krill oil, which in turn is used for animal feed and for direct human consumption through health products.

How they behave

Female krill lay up to 10,000 eggs at one time. As krill grow to maturity they gather into swarms (the collective name), sometimes stretching for kilometres in every direction, with many thousands of krill packed into each cubic metre of water, turning the water orange.

These swarms form columns that rise and fall, staying deep in the water during the day and rising to the surface at night. Why swarms are sometimes seen on the surface during daylight hours is unknown.

Antarctic krill, Weddell Sea, Antarctica
© / Ingo Arndt / WWF

What they eat

Antarctic krill eat microscopic phytoplankton, single-celled plants that drift up near the ocean’s surface. In their larval or juvenile stages of life krill feed on the green algae that grows on the underside of pack ice. Krill are the staple diet of hundreds of different animals, from fish to birds to seals and whales.

Why are krill ecologically important?

Krill plays a key role in the Antarctic ecosystem and are a critical food source for many Southern Ocean species such as whales, seals, fish, penguins and other seabirds. Hence it is important to avoid food competition from the fishery with predators, especially in the vicinity of breeding colonies. There are many current and emerging threats to their conservation and management, including climate change, and future increases in catch limits. Antarctic krill are very sensitive to climate change, including increased temperatures, the loss of sea ice and ocean acidification driven by rising carbon dioxide concentrations in seawater. Find out more here.