Krill: Euphausiacea

Physical characteristics: Adult Antarctic krill measure up to 2.5 inches (65 millimeters) in length and weigh up to 0.07 ounces (2 g). Their gut is green due to their diet of free-floating, microscopic plant organisms or phytoplankton.

Geographic range: They live in the oceans surrounding Antarctica.

Habitat: Antarctic krill are found from the surface to depths of 1,640 feet (500 meters). Their massive swarms are found under and around the edges of sea ice.

Diet: They eat mostly phytoplankton, but will also feed on small crustaceans.

Antarctic krill is fished commercially by several countries. Nearly 100,000 tons (90,000 metric tons) are caught each year. They are processed as food for humans, domestic animals, farm-raised fish, and sport fishing bait. (Photograph by John Shaw. Bruce Coleman, Inc. Reproduced by permission.)

Behavior and reproduction: Antarctic krill swarms may reach densities of 30,000 krill per 35 cubic feet (0.99 cubic meters). Some swarms are made up almost entirely of a single sex or age group. They rise to the surface at night to feed and sink to lower depths during the day.

Females lay several batches of eggs during the 5-month breeding season. Each batch may have up to 10,000 eggs. The eggs sink to the bottom. The larvae spend 10 days rising back to the surface to feed and develop. They reach maximum size in three to five years and may live for a total of seven years.

Antarctic krill and people: This krill species is fished commercially by several countries. Nearly 100,000 tons (90,000 metric tons) are caught each year. They are processed as food for humans, domestic animals, farm-raised fish, and sport fishing bait.

Conservation status: Antaractic krill are not considered endangered or threatened. However, krill fishing limits were set in 1982 by the Convention on the Conservation of Antarctic Marine Living Resources. Part of the Antarctic Treaty System, the Convention is intended to encourage the recovery of whale populations. ∎