Tiny Animals That Hold the Ocean Together
Imagine a pregnant humpback whale, all 40 tons of her, moving through cold blue water toward a cloud of pink. The cloud is dense enough to have edges and to slow the light. The whale opens her mouth, and the ocean pours through her baleen in rivers.
In a single lunge, she consumes hundreds of thousands of tiny Antarctic krill from the pink cloud. And then she turns and does it again — she is eating for two. The calf she is carrying and the seals, fish, seabirds, and countless other species depend on this feast.
For a few short months each year, humpback whales arrive in Antarctica to replenish their energy reserves to sustain their migration, pregnancy, birth, and nursing. Every mouthful matters. Scientists who study these whales think something may be starting to change.
“The health of humpback whales is directly tied to the health of Antarctic krill populations,” said Ari Friedlaender, PhD, a marine ecologist who has spent decades studying humpback whales in Antarctic waters.
Research from his team and others suggests that pregnancy rates in humpback whales may be declining. Hormonal indicators associated with successful pregnancies are showing troubling trends. At the same time, the krill these whales depend on appear to be under increasing pressure. The whales may be telling us something: Food matters.
Every humpback calf begins as a gamble. A mother must feed intensively during a brief Antarctic summer, build enormous fat reserves, migrate thousands of miles to tropical breeding grounds, give birth, and then nurse her calf while eating little or nothing. If food becomes scarce at the beginning of that cycle, the consequences can echo for years.
The challenge is that humpback whales are not the only animals depending on Antarctic krill. Penguins, seals, and nearly the entire Southern Ocean depends on this one small creature that many people have never heard of.
Tiny Giant of the Southern Ocean
Antarctic krill (Euphausia superba) are crustaceans that share a distant evolutionary history with shrimp. They reach only about 2 inches (5 centimeters) in length, roughly the size of your little finger. They are translucent, tinged with shades of pink and red, and have large black eyes. Their feathery feeding appendages allow them to filter microscopic phytoplankton from the water.
At first glance, they seem unremarkable. Look closer, and they become extraordinary.
Krill have evolved to survive in one of Earth’s most extreme environments. They inhabit a world of endless summer daylight followed by months of darkness and ice. Over millions of years, they have developed remarkable adaptations that sound almost impossible.
For starters, they glow. Krill possess specialized light-producing organs called photophores. Located near their eyes, mouthparts, and abdomen, the photophores emit a soft, blue-green light. Scientists believe krill use this light for a form of camouflage known as counterillumination. By matching the faint light filtering down from above, they effectively erase their silhouettes and make themselves harder for predators below to see.
They look like millions of tiny living lanterns drifting beneath the Antarctic ice. The ghostly shimmer that divers sometimes observe around feeding whales may be the collective glow of countless krill, each one running its own biological stealth system.
Their winter survival strategy is equally astonishing. When sea ice forms and phytoplankton disappear, krill do not migrate away. Instead, they gather beneath the ice and graze on microscopic algae growing within it. They often swim upside down, scraping food from the underside of the ice.
When food becomes scarce, krill shrink. Rather than starve, they reduce their metabolism and become smaller with each molt, consuming their own body tissues for energy. Adult krill can survive for months in this diminished state before growing again when food returns. Scientists often monitor the ratio between eye size and body size in krill populations. Large eyes on shrinking bodies can indicate nutritional stress.
Krill are also remarkably productive. A single female can release thousands of eggs in one spawning event. Those eggs sink deep into the ocean before hatching, and then the krill begin a long journey back toward the surface.
If sea ice forms properly and seasonal blooms occur on schedule, young krill survive. If environmental conditions fail, an entire generation can be lost. Their lives are both resilient and fragile, yet their abundance has shaped an entire ocean.
The Foundation of Antarctica
There may be no animal on Earth more important to a marine ecosystem than Antarctic krill. Blue whales consume up to 17.6 tons (16 metric tons) of krill each day during feeding season. Humpback whales migrate thousands of miles specifically to reach Antarctic krill swarms. Minke, fin, and southern right whales depend heavily upon them.
Crabeater seals, despite their name, eat almost exclusively krill. Their specialized teeth function like sieves, filtering tiny crustaceans from seawater. Penguins, fish, squids, seabirds, and countless other animals rely on krill directly or indirectly. Remove krill, and the Southern Ocean begins to unravel.
Krill are also important climate allies. As they feed on phytoplankton near the surface, they help move carbon deeper into the ocean through fast-sinking waste products and biological processes that contribute to long-term carbon storage. Scientists are still working to understand the full scale of this contribution, but it is increasingly clear that krill play a significant role in regulating Earth’s climate.
In many ways, Antarctic krill are the foundation upon which one of the planet’s greatest wildlife spectacles is built, which is why what is happening now matters.
A Growing Industry
Commercial krill fishing began in the 1970s. Advances in technology have transformed the fishery into a highly efficient industrial enterprise. The harvested krill become krill meal and krill oil, which are used in aquaculture feed, nutritional supplements, and premium pet foods.
The marketing for these products is compelling. Krill oil is promoted as a superior source of omega-3 fatty acids. Pet products advertise healthier joints, shinier coats, improved cognition, and enhanced wellness. Most consumers never consider where the ingredient originated.
In the 2024–2025 fishing season, approximately 683,433 tons (620,000 metric tons) of krill were harvested from Antarctic waters. The fishery reached its allowable catch limit for the first time in history, forcing an early seasonal closure.
Fishery supporters point out that this harvest still represents only a small fraction of the estimated total krill biomass. The larger concern, however, is where fishing occurs and whether it overlaps with the feeding grounds of whales, penguins, and seals.
Competing with Whales
The greatest challenge facing Antarctic krill may not be the total harvest but rather the concentration of fishing effort in the same areas where predators gather to feed. Management measures distributed fishing activity across multiple regions of the Antarctic Peninsula for years. The goal was simple: to prevent excessive harvesting in locations that are especially important to krill predators.
In 2024, those spatial protections lapsed. Fishing efforts have become increasingly concentrated in Area 48.1, where roughly 80% of the catch now occurs — often later in the season when predators are actively feeding.
Those places are often exactly where humpback whales, penguins, and crabeater seals have evolved to feed. Concentrated prey is easy prey. The same dense krill swarms that attract whales also attract fishing vessels. For perhaps the first time in human history, we find ourselves competing directly with some of Antarctica’s most iconic wildlife for access to the resource that sustains them.
This is no longer an abstract conservation issue. It is a question of who gets the krill: feeding whale mothers and growing calves or industrial supply chains. A humpback whale cannot simply move hundreds of miles to find food elsewhere. A penguin colony cannot relocate because fishing activity has intensified nearby. The consequences of localized depletion can be profound.
Friedlaender’s research examining humpback whale reproductive health has identified troubling patterns. Reduced prey availability appears to be associated with lower pregnancy rates in a species that invests enormous energy into producing and raising a single calf.
Every missing pregnancy represents more than a statistic. It represents a calf that may never be born, a migration that never happens, or a future generation that never joins the population. The warning signs are there. When food becomes less predictable, mothers struggle. And when mothers struggle, populations feel the effects.
Two Threats, One Future
Fishing pressure is only one challenge. Climate change is creating another. Antarctic sea ice has declined significantly in recent decades, particularly along the western Antarctic Peninsula. Sea ice is more than frozen water for krill. It is a nursery habitat, a winter feeding ground, and a key driver of ecosystem productivity.
As sea ice shrinks, krill habitats shrink with it. Scientists project that warming oceans may push krill populations south toward colder waters. Predators that evolved around reliable krill availability may find themselves increasingly separated from their food source.
At the same time, gelatinous salps are becoming more common in some warming regions. Unlike krill, salps provide little nutritional value to whales, penguins, or seals. Blue whales and penguins cannot thrive on salps.
Krill are therefore caught between two forces: a changing climate from below and increasing harvest pressure from above. Together, those pressures create uncertainty for the future of the Southern Ocean.
Rethinking Pet Food
It is difficult to look at a humpback whale and a premium pet food additive in the same sentence. Yet that is precisely the connection.
In one of the most remote oceans on Earth, industrial vessels are harvesting krill from waters where whales, penguins, and seals have depended on them for millennia. Much of that harvest ultimately becomes krill meal, krill oil, aquaculture feed, nutritional supplements, and premium pet food ingredients.
Most consumers have no idea this connection exists. This is not an argument against healthy pets or human nutrition. It is a question of priorities. At a time when Antarctic krill face growing pressure from climate change and concentrated fishing effort, we should ask whether harvesting the foundation of an ecosystem for consumer products is the best use of this extraordinary resource.
What We Can Do
The future of Antarctic krill will not be decided solely in scientific journals or international policy meetings. Informed citizens will help shape it. Scientists like Friedlaender continue to call for stronger ecosystem-based management and the reinstatement of spatial protections that prevent concentrated harvesting in critical feeding areas.
Consumers also have influence. Read labels. Ask questions. Learn where marine ingredients come from. Consider alternatives to krill-based supplements and pet products. Most important, share the story. Talk to your supplement store owner or producer. Ask your grocer about sourcing. Consumer awareness matters.
As divers, we have a unique stake in this issue. We are among the few communities that experience the ocean as a living system rather than as an abstraction. Many of us have had the privilege of watching humpback whales glide through blue water. We have seen penguins rocket through the sea.
We understand that every spectacular encounter is supported by countless unseen connections. A whale is connected to a krill swarm. A penguin is connected to sea ice. A diver is connected to both. The smallest animals often carry the greatest weight. Antarctic krill glow in the dark. They survive brutal winters, feed countless animals, and help regulate our climate, just as they have for millions of years.
The question before us is remarkably simple: Will we leave enough krill for the ocean? When we protect krill, we are not merely protecting a tiny crustacean. We are protecting whale mothers and their future calves. We are protecting Antarctica’s living heartbeat.
Perhaps most important, we are recognizing a simple truth: The smallest creatures often hold together the largest worlds. In Antarctica, the future of whales may depend on whether we choose to leave enough krill in the sea.
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Learn more about the importance of krill in these videos.
© Alert Diver – Q3 2026