Species Spotlight: Krill, small but vital

These tiny crustaceans play a big role in the ocean food web as both consumer and prey. They feed on phytoplankton, or microscopic algae, and are in turn a major food source for many marine animals including whales, seals, squids, seabirds, and fish. This places krill in the important position of transferring large amounts of energy up the food chain.

Krill travel in large swarms near the ocean’s surface. So while they may be small in size, in large amounts, they feed large animals. In fact, the largest animal to ever live, the blue whale, feeds almost exclusively on krill. Blue whales have been known to eat up to 8,000 pounds of krill per day during peak feeding times!

Krill can be found in all of the world’s oceans, but one species—Pacific krill (Euphausia pacifica)—is most common and abundant in the Greater Farallones National Marine Sanctuary and along the California coast. Pacific krill are strong vertical migrators, descending as far as 1,300 feet during the day and swarming at the surface at night. During the ocean upwelling season, from March to August, the population peaks, luring whales and other marine life to feed.

A krill on a finger. Photo credit: Sophie Webb | NOAA SWFSC
A krill on a finger. Photo credit: Sophie Webb | NOAA SWFSC

Conservation Concerns 

While krill harvesting is prohibited along the US west coast within 200 nautical miles of shore, significant commercial fisheries exist in South Korea, Japan, Poland, and Norway. The harvested krill are primarily used to feed livestock and fish, as bait, or to make omega-3 fish oil for human consumption.

Overfishing is not the only threat to krill populations. Krill need stable ocean conditions to thrive. But with changing climate comes changing ocean conditions, leaving researchers concerned that climate change could put krill at risk. This could have potentially disastrous implications for the greater ocean ecosystem, starting in areas where large amounts of krill feed large amounts of ocean animals, like in the Greater Farallones National Marine Sanctuary.

Krill and Ecosystem Health in the Sanctuary

Through the ACCESS Partnership, Greater Farallones and Cordell Bank National Marine Sanctuaries, Point Blue Conservation Science, and Association staff, collect data on the size and abundance of krill and other zooplankton in the Sanctuary. This information provides insight into the health of the marine ecosystem and is used to inform important management and conservation decisions.

Check out this video from NOAA to learn more!

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