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Krill are small, shrimp-like crustaceans found in every ocean.
Roughly the size and weight of a paperclip, krill are responsible for sustaining some of our most iconic marine species, including seals, penguins and whales.
There are approximately 85 krill species, with most spending their lives swimming and feeding in the open ocean.
Most krill species are filter feeders. They have five pairs of swimming limbs located on their abdomen, which propel them through the water in short bursts. Their front-most appendages vary between 6–8 depending on species and use small combs to ‘catch’ food when drawn through the water.
Almost all krill feed on plankton and zooplankton, but some species utilise other food sources.
Credit: Credit: NOAA Office of National Marine Sanctuaries/Flickr
Antarctic krill feed on microalgae growing on the underside of sea ice during spring, when plankton is less abundant. Other species feed on organic matter in the ocean sediments.
Krill are a keystone species and play an integral role in the ocean food web. The largest concentration of krill – estimated to be 300 million tonnes – is found in the Southern Ocean.
Here, they are the primary food source for many species, including fish, whales, seals, penguins and seabirds.
Thanks in part to the abundance of krill, they are responsible for storing as much carbon as the world’s seagrass mangroves, salt marshes and seagrass beds.
Coming in for the krill
Despite their abundance, krill populations face increasing pressure. They are commercially fished, primarily for aquarium and aquaculture feed, and utilised in pharmaceuticals.
Driven largely by technological advancement, the krill fishing industry has expanded rapidly over the last two decades.
Industrialised krill-fishing fleets not only disrupt krill populations, they also disrupt ocean ecosystems through overfishing and entanglement in fishing nets.
Credit: Youenn Kerdavid (CC BY-ND)/Sea Shepherd Global
Krill-cial to protect
Krill are currently not listed as endangered, but looming threats of climate change and expiring commercial fishing regulations in some regions could change this.
Scientists and conservation groups are calling for strict fishing limits, updated regulations, expanded marine protected areas and improved monitoring of krill populations.
For such a small animal, krill carry an enormous responsibility to support some of the largest and most iconic species on Earth.
