Stay connected with us
around the nation »

License to Krill: A Story About Ecosystem-Based Management

Dr. Christian Reiss, a NOAA oceanographer, conducting an Antarctic Krill survey in the Southern Ocean. Photo credit: Christian Reiss.

Krill are a small, shrimp-like crustacean that are the most important link in the Antarctic marine food chain. Photo by NOAA.

 Watch this video, "Animals of  the Ice: Antarctic Krill" to learn more about these small crustaceans found throughout the ocean.

Gentoo penguins follow a well-worn path from the sea where they feed to their nesting area. Many species in Antarctica, among them penguins, seals, and humans, rely on krill as a food source.  Photo by Lt. Elizabeth Crapo, NOAA.

Ecosystem-based Fishery Management...

  • Considers many species and the interactions between them
  • Includes humans as one of the species interacting in the ecosystem
  • Considers how ecosystem dynamics play out in space and time
  • Attempts to balance the tradeoffs between fishing and other economic and environmental objectives
  • Requires collaboration between multiple stakeholders


Scientific krill catch aboard the South African R/V Africana near the South Orkney Islands. Photo by Roger Hewitt.


Antarctic krill are considered the greatest under-tapped biological resource in the ocean today. As humans increasingly turn to the oceans for food, we must be careful to not undermine the marine food chain. Ecosystem-based fishery management can help.

Every year in the ocean around Antarctica, as the southern hemisphere tilts back toward the sun after the long darkness of winter, there is a great burst of biological activity. Tiny shrimp-like creatures called krill begin their annual spawn. The krill support a multitude of other species including penguins, seals, and whales, some of which migrate great distances each year to feed in the rich waters of the Southern Ocean.

Krill eat phytoplankton, the microscopic marine organisms that convert sunlight into stored energy. Just about everything else eats krill. Scientists estimate that there are 170 to 300 million tons of krill in the Southern Ocean—that’s more than half the biomass of all humanity. Of that, about half is consumed by marine predators each year.

But Antarctic species aren’t the only animals that consume krill. Humans do as well. Krill are used to produce nutritional supplements like omega-3 fatty acid pills. They are used as bait in commercial and recreational fishing. Most importantly, they are an ingredient in feeds for poultry production, pet foods, and aquaculture.

During the coming decades, billions of people will move out of poverty and into the global middle class, and as their standards of living rise they will inevitably eat more meat and fish. The world population is projected to increase about 30 percent between now and 2050. During the same period, according to the United Nations Food and Agricultural Organization, demand for animal protein will grow by about 75 percent. Satisfying that demand without wrecking the planet is one of great challenges of this century, and Antarctic krill might play an important role in meeting that challenge.

But with other species also relying on krill, it’s important that the fishery be managed carefully so that there is enough to go around. How can we enable a viable krill fishery while also minimizing the impact on other species that prey on krill.

The Antarctic Marine Living Resources Program

“We’ve been monitoring the krill population continuously since 1987,” says Christian Reiss, an oceanographer with NOAA’s Antarctic Marine Living Resources Program. Every year, the AMLR team deploys to Antarctica to assess the size of the krill population and the health of the animals that prey on it.

Reiss points to a graph on his computer screen that looks like an EKG. The graph shows the krill population over time. This is one of the vital signs of the planet, and scientists have had their fingers on the pulse for 25 years. Reiss himself has been going since 2005.

The graph below shows the proportion of krill sizes during US AMLR krill survey net tows between 1988 and 2012. Source: Christian Reiss, NOAA.

“This is the longest continuous biological time series we have on the ecosystem in the Antarctic,” Reiss says, and it’s proven critical to understanding how the Antarctic is changing. A long time series is necessary to distinguish between year-to-year variations and trends that indicate a more fundamental change.

The Antarctic is Changing Rapidly

Things are changing rapidly in the Antarctic, though the changes aren’t uniform throughout the region. In some places, air and sea temperatures are dropping and winter ice cover is expanding. Around the Western Antarctic Peninsula, which is where most krill fishing takes place, the opposite is happening. There, the extent and duration of winter ice is rapidly declining.

Ice cover is important for krill, which take shelter under the ice and feed on algae that grow there. As winter ice cover has declined in extent and duration, the krill population has declined as well. By some estimates, krill abundance has dropped by as much as 80 percent since the 1970s. 

With ice cover retreating, fishing has picked up in winter. The AMLR team, after 25 years of summer surveys, has shifted to winter as well. Reiss and his colleagues conducted their first wintertime krill survey last year, and preliminary data indicate that as fishing activity shifts to winter, there is the potential for competition between fishing vessels and winter-resident animals such as gentoo penguins and several species of seals.

That’s because during winter, krill aggregate along the ice edge. The open water, which is dense with krill in summer, stays mostly clear. This boundary effect concentrates everything that’s looking for krill—animals and fishing vessels alike—into a relatively small area. If the ice continues to recede in coming years as projected, this boundary effect might become more pronounced.

Ecosystem-Based Management Can Help

The Southern Ocean, like the Antarctic continent itself, does not belong to any one nation. Instead, it is managed by an international Convention. The Commission for the Conservation of Antarctic Marine Living Resources, or CCAMLR (pronounced KAM-el-ar), has 25 member nations. This commission, which was formed in the late 1970s to manage Antarctic resources, specifically calls for an “ecosystem approach.” CCAMLR was the first international fishing convention to include this requirement.

For much of the 20th century, fish species were managed individually without fully considering the relationships between them. Ecosystem-based fishery management, on the other hand, is a more holistic approach that takes into account the interactions between species. When fishing reduces the population of one species, there are ripple effects throughout the marine food chain. For instance, if the human species takes more krill out of the ecosystem, the populations of other animals that prey on krill might decline.

But it’s not just a question of how much krill we take. Where and when we take it are also important. Penguin chicks need to find food when they fledge at the end of their first summer. For certain species of seals, which carry their pregnancies through winter, wintertime forage is critical. By identifying where and when these critical periods occur, scientists can advise fishery managers on how best to reduce the impacts of fishing on the other species we care about.

The United States is the world’s largest consumer of krill products. But that’s not the only reason NOAA sends scientists to the Antarctic. As the polar regions open up to increased activity, many nations are vying for control of the resources found there. Scientific research is one of the principal ways that the United States participates in CCAMLR, and this insures a continuing U.S. role in determining how Antarctic resources are managed.

Looking Forward

Currently about 200,000 tons of krill are harvested in the Southern Ocean each year.  That’s not nothing—if krill were landed in U.S. waters, it would be the nation’s fifth or sixth largest fishery by weight. But compared to the vast size of the resource, that’s a very low rate of fishing. Scientists estimate that the krill population could sustainably support harvests twenty times that size. But this would only work if we manage the timing and location of fishing carefully and if we monitor predator populations so that unexpected impacts can be caught early and addressed.

The very thing that makes the Antarctic krill situation so promising is what also makes it so risky. Because this vast resource is barely fished, it has the potential to help solve one of the great challenges of this century. But because it is barely fished, it supports one of the last great wild ecosystems on earth. When it comes to entering such places, we humans don’t have a very good track record of keeping them intact.

But maybe this time will be different. This time we have an ecosystem-based management framework already in place before fishing really picks up. And we have twenty-five year’s worth of data on krill and their predators that will help us to monitor and minimize the impact of fishing. As demand for animal protein intensifies during the coming decades, and as winter ice cover retreats around the West Antarctic Peninsula, will we manage to avoid the mistakes of our past?