Antarctic Krill: Facts, Diet & Where to See Them

1. What Is Antarctic Krill?

One of about 85 krill species, and the one that matters most here

Krill is a general name for a group of roughly 85 small crustaceans found in oceans worldwide. The word comes from Norwegian and loosely means "small fry of fish." Five krill species live in the Southern Ocean. When people talk about "krill" in an Antarctic context, they almost always mean one: Antarctic krill.

It lives south of the Antarctic Convergence, the boundary where cold polar water meets warmer water to the north. Much of the population is concentrated in the Atlantic sector, particularly the Scotia Sea and the waters around the Antarctic Peninsula and South Georgia. That's also where most tourist voyages go, which is no coincidence. Where krill gather, wildlife follows.

• Scientific name: Euphausia superba. The "superba" is earned: it's the largest of the Southern Ocean krill.
• Relatives: Krill are crustaceans, related to shrimp, crabs, and lobsters, though they aren't true shrimp.
• Color: Mostly transparent with reddish-orange pigment spots, which is why large swarms can tint the water pink or red.

2. Size, Lifespan & a Few Odd Tricks

Small, long-lived, and able to shrink on purpose

An adult Antarctic krill is roughly the length of a little finger and weighs a little over a gram. That's large for a krill. It's also long-lived for such a small animal, with estimates generally ranging from five to ten years.

Krill have a few habits that surprise most people:

• They glow: Krill carry light-producing organs and are bioluminescent, though you'd need to be in dark water at night to notice.
• They can shrink: Krill molt throughout their lives. When food runs short, they can molt into a smaller body rather than a larger one, which lowers their energy needs.
• They can go hungry for a long time: Lab studies suggest krill can survive more than 200 days without food.
• They escape by molting: A krill can shed its shell suddenly and dart away, leaving a predator with an empty decoy.

3. What Krill Eat

Phytoplankton in summer, ice algae in winter

Krill are mainly grazers. Their front legs form a fine-meshed feeding basket that filters phytoplankton, the microscopic plant-like algae that bloom across the Southern Ocean during the long summer days.

• Summer: Phytoplankton blooms, especially diatoms, make up most of the diet.
• Winter: Krill scrape algae from the underside of sea ice, which works a bit like a nursery and pantry for young krill.
• Lean times: They'll also eat small animal plankton and detritus from the seafloor.

That link to sea ice matters. Years with less winter ice generally mean fewer young krill survive, which ripples up through everything that eats them.

4. Swarms and Daily Migration

Tens of thousands in a single cubic metre

Krill live in swarms, and those swarms can be staggering. Densities of up to about 30,000 individuals per cubic metre of water have been recorded. Some swarms stretch for kilometres. A whale doesn't hunt krill one at a time. It finds a swarm and engulfs it.

Many krill also make a daily vertical trip. They generally sink to deeper, darker water during the day, where they're harder for visual predators to see, and rise toward the surface at night to feed. The pattern varies with season and location, and in the near-constant daylight of the Antarctic summer it can break down.

This is part of why krill are so hard to see from a ship. On most days, the swarms are below you. You'll see them on an echo sounder long before you'll see them with your eyes.

5. The Animals That Depend on Krill

Almost everything you came to see

The Antarctic food web is unusually short. In many oceans, several layers of small fish sit between plankton and the big predators. In the Southern Ocean, krill often fills that whole middle layer on its own. That's why it's called a keystone species.

• Baleen whales: Humpback, minke, fin, and blue whales migrate south to feed on krill in summer. NOAA notes the largest blue whales may eat up to 6 tons of krill a day.
• Crabeater seals: Despite the name, they eat almost nothing but krill, straining it through specially shaped teeth.
• Penguins: Adélie, chinstrap, gentoo, and macaroni penguins all rely heavily on krill, especially while feeding chicks.
• Leopard seals: Close to half of a leopard seal's diet is often krill. Our leopard seal guide covers how they sieve it through their teeth.
• Seabirds, fish, and squid: Albatrosses, petrels, Antarctic fish, and squid all eat krill, and many of them are eaten in turn by larger predators.

As whale populations recover from commercial whaling, their demand for krill is rising again. Scientists now study how whale recovery, a warming ocean, and a growing fishery all compete for the same food.

6. Krill and the Climate

A small animal with a large carbon footprint, in a good way

Krill help move carbon from the surface of the ocean into the deep. They eat carbon-rich phytoplankton near the surface, then release dense fecal pellets that sink quickly. They also shed their shells as they molt, and those sink too.

A 2024 study in Nature Communications, led by researchers at Imperial College London, estimated that Antarctic krill help store at least 20 million tonnes of carbon in the deep ocean each year. That's comparable to the carbon stored by coastal habitats like mangroves, salt marshes, and seagrass meadows.

Krill are also sensitive to warming. A 2019 study led by the British Antarctic Survey found that the center of the krill population in the southwest Atlantic had shifted south by roughly 440 km (about 4° of latitude) over four decades, as conditions at the northern edge of their range became harder for young krill to survive.

7. The Krill Fishery

Managed carefully, and closely watched

Krill is fished commercially, mostly for krill oil supplements and for feed used in fish farming. The fishery is managed by CCAMLR, the international commission responsible for conserving Antarctic marine life. Fishing is concentrated in the same waters around the Antarctic Peninsula and South Georgia where many penguins and whales feed.

• The catch trigger: CCAMLR sets a precautionary limit of 620,000 tonnes for the main fishing area. Once catches reach it, the fishery closes for the season.
• Recent seasons: The fishery hit that limit and closed early two years in a row, on August 1, 2025, and on August 12, 2026.
• The debate: Industry groups point to the closures as proof the precautionary system works. Conservation groups worry that catches are increasingly concentrated in small areas near penguin colonies and whale feeding grounds.
• What's next: Proposals for a Marine Protected Area around the Antarctic Peninsula and finer-scale fishery management are on CCAMLR's agenda.

For perspective, the catch is still a small fraction of the estimated total krill population. The concern is less about total numbers and more about where and when the fishing happens.

8. Where and How to See Krill on Your Trip

Look for the signs, not the animal

Krill mostly stay out of sight. But once you know what to look for, you'll notice their influence almost every day of the voyage.

• Pink guano: Penguin colonies stained pink or reddish-brown are a sure sign the birds are eating krill. It's also, fair warning, what you'll be smelling at most landings.
• Feeding whales: Humpbacks lunging at the surface or blowing bubble nets are almost always feeding on krill swarms just below. Your Zodiac driver will often cut the engine and let you watch.
• Red patches in the water: On calm days, dense swarms sometimes show near the surface as reddish or pinkish patches.
• Krill on the beach: After storms, you may find stranded krill along the tideline at landing sites.
• Onboard science: Many expedition ships run plankton tows or citizen-science programs. If yours does, it's the easiest way to see a live krill up close.

The best areas for krill-driven wildlife are the Antarctic Peninsula's channels and bays, especially later in the season (February to March), when humpback feeding activity is often at its peak.