Krill Experts Discuss Need to Protect Southern Ocean’s Keystone Species

As a lead-up to World Krill Day, two scientists explain the urgency to improve fishery management

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Krill Experts Discuss Need to Protect Southern Ocean’s Keystone Species
: An underwater photo shows a swarm of tiny life forms—unidentifiable by their shape—suspended in blue ocean water beneath the bulbous, off-white edge of an iceberg. Sunlight filters into the water from above.
Antarctic larval krill, here feeding on algae that grow on the underside of sea ice, are under increasing threat from both climate change and concentrated fishing. Scientists are working to update the management of the krill fishery in order to take into account the needs of Southern Ocean predators.
Ulrich Freier Alfred-Wegener-Institut

Antarctic krill, the species at the center of the Southern Ocean food web, faces numerous threats.

Krill make up 96% of the calories consumed by certain seabirds and mammals in the region. But in recent decades, industrial krill fishing has become more and more concentrated in the Antarctic Peninsula, where predators such as humpback whales and chinstrap, Adelie, and gentoo penguins depend on krill. This fishing is now in competition with the species that need krill to survive.

Climate change is also directly affecting krill—which is doubly concerning because krill actually act to store atmospheric carbon in the deep ocean, helping to limit the impact of climate change. Research shows that warming waters are disrupting krill growth and reducing their suitable habitat in the Southern Ocean, and scientists project that krill will lose 30% of such habitat this century. What’s more, acidification from increased carbon dioxide has a negative impact on krill eggs hatching, which scientists predict could lead to the collapse of the region’s krill population by 2300.

In 2018, the Scientific Committee on Antarctic Research convened an expert group, the SCAR Krill Expert Group (SKEG), to improve understanding of the biology and ecology of Antarctic krill. The SKEG works as a link between the global community of krill scientists and the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR), which has recently committed to update the management of the krill fishery so that predator needs would be taken into account.

Bettina Meyer heads the ecophysiology of pelagic key species working group at the Alfred Wegener Institute for Polar and Marine Research in Bremerhaven, Germany. She was recently appointed the scientific representative from Germany to CCAMLR.

So Kawaguchi leads the Australian Antarctic Division’s krill research program and has attended CCAMLR meetings as part of both the Japanese and Australian delegations.

Although they started their marine science careers halfway around the world from each other, the small but mighty Southern Ocean crustacean brought SKEG co-chairs Meyer and Kawaguchi together for what might be their most important work—making sure enough krill remain in Antarctic waters to fulfill their ecological role in the nutrient cycle and to sustain predators that would cease to thrive without krill.

As a lead-in to this year’s World Krill Day, the Pew Bertarelli Ocean Legacy Project spoke to both scientists about their commitment to these Southern Ocean superheroes.

This interview with Meyer and Kawaguchi has been edited for length and clarity.

Bettina Meyer
So Kawaguchi

When did each of your research careers shift to a focus on krill? 

Meyer: In 1998 I was on a European Union Marie Curie Fellowship at the Plymouth Marine Laboratory in the U.K., working on the key North Atlantic pelagic copepod species Calanus finmarchicus. During this time, a colleague from the Alfred Wegener Institute (AWI) in Bremerhaven, Germany, asked if I could imagine setting up an Antarctic krill working group at AWI.

Until then, all I knew about krill was that they were the main food of whales. However, the more I read about this central species in the Southern Ocean, the more fascinated I became. I developed a project to study the overwintering of krill from an ecophysiological point of view, which was funded by the German Federal Ministry of Education and Research. That allowed me to start building up the krill group at AWI, which was the beginning of my krill career.

Kawaguchi: After obtaining my Ph.D. in 1990, I joined a Japanese fishing company as a research scientist. In those days, new hires were sent to various sections of the company to understand operations, and I was sent down south on an Antarctic krill fishing boat for six months. This changed the whole direction of my career.

Witnessing hundreds of tons of krill landing on deck every day, and having interesting conversations with the skipper and the officers, inspired me to study krill and its fishery management. After four years, I was fortunate enough to join the Japanese Fisheries Agency as a krill research scientist and also started attending CCAMLR meetings as part of the Japanese delegation.

Then in late 2002 I joined the Australian Antarctic Division, and my research went deeper into experimental krill biology—to understand their life cycle and impacts of environmental change. I continued to attend CCAMLR meetings, but now as part of the Australian delegation. My unique career path working for a krill fishing company, the Japanese Fisheries Research Agency, and the Australian Antarctic Division has allowed me to gain a range of perspectives and insights into krill, the krill fishery, and its management.

What can you tell us about the Scientific Committee on Antarctic Research’s krill expert group?

Meyer: The SCAR Krill Expert Group (SKEG) aims to improve our understanding of krill biology and ecology and to serve as the primary interface between the wider scientific krill community and CCAMLR, which manages and monitors the Antarctic krill fishery. SKEG also provides a forum for research direction; information exchange; dialogue between krill scientists, fisheries, and society; and collaboration within the krill community with a focus on early-career researchers.

Kawaguchi: SKEG is a group of scientists interested in krill biology and ecology. This definition is intentionally very loose, since krill research is broad and requires a variety of approaches, including traditional net sampling, modeling, and the use of ever-advancing technologies. We’re trying to understand important aspects of krill, such as their life cycle and the dynamics and impacts of climate change.

How did you end up as co-chairs of the group?

Meyer: The group grew out of discussions at the Third International Krill Symposium in St. Andrews, Scotland, in 2017, and a CCAMLR committee asked me to write a proposal for a krill action group under SCAR’s auspices. CCAMLR didn’t have any krill experts at the time. The proposal was approved the next year and CCAMLR recommended that the group would be most effective if it were led by two krill experts. For me, it was clear from the start that I would like to share the leadership of SKEG with So, with whom I’ve had a close and trusting relationship since 2003.

In 2019, CCAMLR decided to develop a revised management approach for krill. At present, the SCAR Action Group has become an established Expert Group (SKEG) and is now a valued institution supporting CCAMLR in its process of reforming the management of the krill fishery.

Kawaguchi: Bettina and I have been collaborators and friends for 20 years, so when she asked me to co-chair SKEG it was more than a great pleasure for me. Our strengths, approaches, and characteristics are complementary, which works really well as a team.

Why do krill need a dedicated group of scientific experts?

Meyer: Krill is the keystone species of the Southern Ocean. Almost all large animals, from seabirds and fish to penguins, seals, and whales, feed on this species, which serves as a direct energy transfer from primary producers to top predators. And through their high biomass, krill have a major impact on the biological carbon pump in terms of carbon sequestration and remineralization of iron, the trace element in the Southern Ocean that promotes phytoplankton growth.

Kawaguchi: Any effects of changes in krill biomass and distribution are likely to cascade through the ecosystem. We’re in a period of rapid environmental change that’s already affecting krill dynamics. At the same time, increasing commercial interest in krill is driving annual catch levels to historic highs, fishing technology is advancing, and fishing effort is being locally concentrated more than ever. So it’s vital for us to understand the impact of climate change and fishing on krill and its ecosystem at a range of scales in space and time to better inform krill fishery management. We also need to be able to monitor and predict how the krill ecosystem may look into the future to inform policy in the longer term.

Meyer: Yes, not only do we need high-experience krill experts, we have to train the upcoming generation of researchers to meet the challenges of the future.

Speaking of climate change, how is it affecting krill?

Meyer: Krill biomass has been declining since the mid-1970s and has been shifting to higher latitudes toward the Antarctic Peninsula since the late 1990s. We don’t yet know why, but data collection is essential for predictive models so we can understand how the population will change in the future based on projected climate changes.

The reason for the large knowledge gap in krill biology and ecology is that, until 2019, CCAMLR focused primarily on the krill stock to serve predators’ needs. However, given the importance of krill to the ecosystem and the increasing pressures on the stock, it’s crucial to gain a mechanistic understanding of krill biology in general and its resilience to climate change in particular. Only with this data will we be able to build predictive models that will give us insight into population declines due to predicted climate change scenarios and fishing impacts in addition to predation.

CCAMLR is currently updating its management approach for the Antarctic krill fishery. Why is that important?

Meyer: We face several challenges, including climate change, the growth of fisheries in general, and a new generation of fisheries that use pumping systems to collect krill very effectively on small scales almost all year round. At the same time, we have a growing whale population whose main food source is krill. With these challenges, it’s not enough—and too short-sighted—to just look at how predators might be affected by fishing. It’s time to also focus on the krill population itself and its resilience to climate change, which is now partially integrated into the updated management approach.

You recently led a workshop (supported by Pew Bertarelli Ocean Legacy) on the “krill stock hypothesis.” What is that and why does it matter?

Meyer: A krill stock hypothesis, or KSH for short, is a conceptual model of the biology of the krill population (stock) in terms of spawning, recruitment (or the number of young that survive to adulthood), vertical and horizontal movement, and migration (connectivity) between regions. If we understand the biology of the krill population, we may be able to define the appropriate size of fishery management units and, in combination with biomass estimates, harvest rates in such a way that the stock is not adversely affected by any stressors.

Kawaguchi: The KSH is a conceptual model describing the movements Bettina just described. This can be represented on a map with arrows showing movement and connection between areas used by different life stages (for example, areas where eggs and larvae move, overwintering habitat, etc.) with the goal of understanding important habitat in space and time and how life stages are connected spatially. It’s a hypothesis so it doesn’t have to be perfect, and in fact there can be alternative hypotheses and possibly something in between; the important point is to develop a management approach that protects the ecosystem given a scenario or hypothesis. Having a stock hypothesis also helps identify the gaps in our knowledge about krill stock dynamics and will help us design research and monitoring to close such gaps—which in turn will improve and refine the stock hypothesis.

What are the next steps now that you’ve developed this hypothesis?

Meyer: It will be a long time before the development of a krill stock hypothesis is complete—a five-to-10-year process. In the SKEG report, we’ll summarize what we already have and where there are gaps in knowledge and data we need to further develop the KSH. This will enable CCAMLR members and the SKEG community to develop a work program and projects to collect the missing data in an internationally collaborative effort.

Kawaguchi: This is just the beginning of a concerted effort by SKEG scientists. The hypothesis provides an excellent opportunity for the community to collaborate and coordinate our research efforts and systematically fill the knowledge gaps to advance our overall understanding of krill dynamics in the area.

Next week marks the second World Krill Day. What does this awareness day mean to you?

Meyer: It’s a big deal—and we need it now. We are already seeing signs of population changes due to climate change. And we have increasing fishing pressure on krill—and feeding pressure due to a growing whale population. There are many unanswered questions about how, for example, the increasing fishing pressure will affect the krill population itself and not just the predators. I hope that World Krill Day will bring krill more into focus because, due to its central role in the marine Antarctic ecosystem, a massive decline of krill would have cascading effects on the functional biodiversity, biogeochemical cycles, and carbon flux in the Southern Ocean.

Kawaguchi: Who would have thought 20 years ago that krill would get this popular? Having an awareness day gives us a moment to seriously consider what climate change means to krill and the Antarctic ecosystem, and the importance of the conservation of our precious planet.

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