- Science: Explained
Why krill matter: Krill fishing and conservation in the Southern Ocean
The Southern Ocean is one of the most remote places on the planet.ย
Itย was only in 1911 that the first human, Roald Amundsen, reached the South Pole.ย For context, the first poweredย aircraft, theย Wright Flyer, took to the air in 1903.ย Humanity conquered the skies before it managed the southern continent.ย The waters here areย cold, barely above freezing, yet full of life. These are some of the richest waters in the world.ย ย
Theย main character is just 6cm long.ย Antarctic krillย (Euphausiaย superba)ย are small, shrimp-like crustaceans. Theyย snack on the phytoplankton that thrives in theย long hours ofย summerย sunlight,ย trapping and storingย similar amounts of carbon to seagrass and mangroves.ย ย
Their importance lies in their numbers: krillย swarmsย are vast.ย The rust-coloured cloudsย areย filled with billions of individualsย andย can beย visibleย fromย space. Theyย sustain most of the life around Antarctica. Penguins, seals, whales,ย fishย and sharks allย rely onย this buffet: krill are a keystone species. More recently,ย peopleย have joined the party.
Krill fishing has become aย divisive topic, being featured in David Attenboroughโs Ocean,ย calls to ban it being promoted at the United Nations Ocean Conferenceย and someย retailers withdrawing krill products from their shelves.ย Meanwhile, countries have appliedย to increase the catch limits andย the amounts of krill being fished are higher than ever.ย ย ย
To understand where we are going, first we can look at where we have been.ย Whyย areย krill important?ย What is our history in the Southern Ocean?ย What is our future?ย
How did we get here?ย
In 1775, Captain James Cook returned to England from a voyage around the world, in which he had searched forย new lands.ย Heย foundย thereย wasnโtย a new continent in the Pacific Oceanย (at least not where one was predicted to be)ย and hypothesised on the existence of Antarcticย land behind the iceย (which he was correct about).ย ย
Heย hadย discovered some land on his travels: an island populated by seals and penguins, which was named โIsle of Georgiaโ inย honour of King George III of England.ย We know it now as South Georgia.ย
Sealing and whaling in the Southern Oceanย
The element of Cookโs report that got attention was the abundance of fur seals on South Georgia and neighbouring islands.ย These pinnipeds were highly sought after, and between 1778 and 1822 an estimatedย 1.2 million fur seals were killedย for their pelts. The speciesย wasย almost completelyย wiped out on South Georgia and the islands.ย ย
The rise of industrial whaling then turned focus on to the waters of the Southern Ocean around Southย Georgia. Factory ships and explosive harpoons reduced the great whales toย 18% of their original population.ย 5% of blue whales were left, and just 3% of humpback whales survived. When the last two whaling stations closed on South Georgiaย in 1965,ย 175,250 whales had been killedย in those waters.ย ย ย

When did krill fishing start?ย
Industrial fishing had beenย largely unmanaged, and everyone raced toย benefitย from the natural resources the Southern Ocean had to offer. One by one theย marineย species of the south had been targeted toย great effect, and populations crashed. The focus then shifted to krill.ย ย
Industrial fishing for krill in the Southern Ocean increased through the 1960s and 1970s. As the species that formed the foundation of the ecosystem, theย alarm bells rang, loud,ย at the prospect of theย krill suffering the same fate as the seals and the whales.ย ย
Why are krill important?ย
Krill areย a keystone speciesย
The loss of krill would beย disastrous for many different species.ย Whales, seals,ย penguinsย and fish are all krill predators.ย Less krill means less food for these species.ย ย
Southern Right whale mothers have shown aย decrease in body condition over the past 40 years,ย suggesting ecological strainย on an animal heavily reliant on Antarctic krill.ย ย
Theย population of krill has been linked with Adelie and chinstrap penguin numbersย โ when there is less krill, the penguin populations decrease.ย ย And the fur seals, populations freshly rebounded from the hunting of the nineteenth century,ย areย showing declines due to krill availability.ย
Withoutย krill, lifeย in the Southern Ocean could collapse.ย ย
To relay it in economic terms, krill are a vital piece of an ecosystem that provides, conservatively,ย $180 billion annually in ecosystem servicesย โ aboutย 70% of Newย Zealandsย GDP in 2024.ย ย
Krill are climate championsย
Itย isnโtย just the animals in the Southern Ocean that depend on these.ย Krill are big players in the balancing of our atmosphere. They trap (sequester) a lot of carbon.ย ย
As phytoplankton photosynthesise, they take in carbon dioxide. When they are eaten by krill, the krill take on that carbon, some of which is then… dropped off. Krill faecal pellets (poo) alone areย estimated to sequester 20 million tonnes of carbon dioxide per year. Depending on the price of carbon, this is worth between $4 and $46 billion.ย
Marshes,ย mangrovesย and sea grass are estimated to absorb 13, 24 and 44 million tonnes per year respectively, so when you add in the extras of krill moults (20 million tonnes) and migration (26 million tonnes), as the researchers say: โit is likely that Antarctic krill is amongst the worldโs most important carbon-storing organisms.โย

How is krill fishing managedย in the Southern Ocean?ย
Those alarm bellsย over the fishing of krillย led to the creation ofย the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR). It was formed in 1980 and entered force in 1982.ย ย
The CCAMLR isย made up of 27ย member statesย (as of January 2026), with a further 10 โAccedingโ states โ that support butย donโtย contribute to the budget or take part in decision making.ย
Theย stated aim:ย to protect and conserve the ecosystem of the Southern Ocean. Article II of the convention states:ย ย
- Theย objectiveย of this Convention is the conservation of Antarctic marine living resources.ย
- For the purposes of this Convention, the term โconservationโ includes rational use.ย
This captures a crucial distinction: fishing is an element of conservation, ratherย than an adversary.ย ย
Howย doย youย preventย overfishing?ย
Catch Limitsย
A general rule of thumb is that youย canโtย remove so much the populationย canโtย sustain itself. That will vary with species โ some animals reproduce a lot faster than others.ย ย
Understanding how much of a resource there is, isย fundamental to managing it. This is one of the biggest obstaclesย in the Ocean:ย the water means youย canโtย just seeย (sea). In a field you can see how many cows there are, not true of a shoal of fish.ย ย
Acoustic surveying (using noise to find out what is there,ย like a bat) gives us estimates for theย amountย of krill. In short โ a lot. We estimate there are over 300 million tonnes of Antarctic krill,ย roughly theย same as the biomass of humans.ย ย
In the specific area targeted for krill fishing (known as Area 48), the biomass is estimated atย 62 million tonnesย (coincidentally,ย roughly theย same mass asย annual e-waste produced). So,ย CCAMLR adoptedย Conservation Measure 51-01. CM 51-01ย set a trigger level at 1% of thatย biomass (620,000 tonnes)ย โ when that is reached,ย all krill fishing stops, no questions asked. August 2025 was the first time this happened.ย

Marine Protected Areasย
Another tool in the toolbox is protected areas โ designated places with specific rules. Choosing to avoid fishing inย nursery areas, or places with high densities of predators, can ensure the health of theย fishery.ย ย
The Southern Ocean is home to the first MPA on the high-seas (outside of theย jurisdictionย of any one country) and the largest. Theย South Orkneyย Islands Southern Shelfย MPAย was created inย 2009, andย is a no-take zone protecting penguin foraging areas.ย ย
Theย Ross Sea MPAย wasย created in 2016 and is 2.09 million square kilometres,ย 72% ofย which is a no-take zone.ย The MPA has a controversial โsunset clauseโ,ย meaning the MPAย willย expire inย 35 yearsย unlessย renegotiated.ย ย
There areย four other MPAs that have been proposed,ย but not yet agreed on.ย ย
Hasย theย managementย of krillย worked?ย
The krill fishery is one of the mostย closely managedย in the world.ย Every single shipย has an independent scientific observer on boardย to ensure catch and bycatch amounts are accurately reported.ย There is zero illegal,ย unreportedย orย unregulated (known as IUU) fishing puttingย additionalย pressure on stocks.ย ย
Bycatch rates areย very low. In 2004,ย after pressure to report bycatch, it was revealed 292 fur seals had been killed as bycatch. This prompted the fishery to adopt mitigation measures, andย since 2010,ย 39 fur seals have been killed.ย This is alongside 7 humpback whales and 80 seabirds.ย ย
In many senses, this isย a great success. Krill populations are stable and thereย haveย been little ecological impact from fishing.ย No other large-scale fishery in the world is as well-monitored, as efficient (in avoiding byย catch)ย or conservative with catch limits. The industry refers to theseย points as support for increasing the limits.ย ย

Itโsย not just โhow muchโ:ย Why location-specific catch limitsย matterย
The numbers look excellent. However, the risk lies in local depletion. Taking 1%ย isnโtย much unless you take it all from one place.ย ย
Penguins,ย sealsย and whales need the krill withinย reach.ย They can travel to find them, but the further they go,ย the more energy they spend to get there and the less far the meal will go.ย ย
To make an analogy:ย ย
It is like buying sweets. If you have ยฃ10 to spend onย sweets,ย you could either buy lots ofย different typesย of sweets or spend all the moneyย just on fudge. If you do the latter, Timmy from down the road might not get the fudge he wants because you bought it all.ย
To avoid krill fisheries removing the entire quota from one area and leave the local penguins hungry, CCAMLRย introducedย Conservation Measure 51-07ย (CM 51-07). CM 51-07ย dividedย the catch limits inย area 48 intoย Subarea 48.1ย (25%, 155,000t), 48.2 (45%, 279,000t), 48.3 (45%,ย 279,000t) and 48.4 (15%, 93,000t).ย Itย added another layer of protection to CM 51-01, but was a temporary measureย with an expiry date, to incentiviseย agreementย on long term measures.ย ย
In 2024, theย CCAMLR failed to agreeย onย new โmove onโ rules.ย ย These would ensure fishing vessels leave an area once they have caught a certain amount, tackling the issues of local depletion.ย CM 51-07 expiredย without replacementย at the end of the 2024 fishing season,ย leaving theย krill fishery with onlyย CM 51-01ย (whenย ย 620,000ย tonnesย of krill is caught, fishing automatically stops)ย asย guidance.ย ย
The CCAMLR currentlyย doesnโtย have anyย special measuresย to prevent the full quota being taken from the same place.ย ย

What is next in the Southern Ocean?ย
The krill fisheryย isnโtย just dealing with changing policies, but also a changing Ocean.ย ย
The Southern Ocean isย getting warmer.ย ย
The areas of sea ice coverage are decreasing, and aย record low in 2023ย was 1.02 million square kilometres less than the 1979-2022 average daily minimum.ย That is the same size as Egypt.ย The previous four years have seen the minimum sea ice extent dropย below 2 million square kilometres.ย ย
Krillย dependย on sea ice.ย Theย changing amounts of ice impact theย krill’sย foodย โ phytoplankton.ย As juveniles, they stay close for protection and graze off the algae that can grow on it.ย Less ice means less shelter and less food, which leadsย to a lot less krill before any fishing has happened.ย Maximum sea ice extentsย impactย the following summer blooms of krill โ more ice means more food and shelter for young krill, who then visibly blossom in the summer. 2025 had theย third lowest sea ice maximum, behind only 2023 and 2024.ย ย
Since the 1970s, we have been seeing aย reduction in the density of krill adults, and in the occurrence of very dense swarms around the Antarctic peninsula.ย These environmental changes also meanย the krill are moving southย โ staying closer to the pole, where it is colder.ย This means that the northern ecosystems are losing access to their main food supply.ย It also means the areas divided up for krill fishing may not capture where the krill are anymore.ย

One of the biggest wins for nature and conservation is the return of the whales.ย ย
Afterย populationย depletionย by industrial whaling, whale populations are increasingย to their historic levels.ย As whalesย return,ย theย amountย of krill they eat increases.ย ย
Acceptableย krillย catch limits from 20 year ago may no longer cater for the larger whale populations, which is why re-assessment is so important.ย ย
Even if the amounts of krill taken are acceptable, the fishing vessels can still affect the whales. The vesselsย disturb theย whales andย can spread krill swarms out more. This means that whales can spend more energy getting the same amount of food, which decreases their body condition and reducesย their capacity to reproduce.ย ย
The situation gets more complicated when you combine the changes.ย Less krill is likely to disturb the recovery of whale populations.ย ย
ย Where do we standย on the future of krill?ย
The warming world and returning whales need to be factored into our management of krill fishing. But recent progress has been slow.ย
There is a lot of disagreement over the future of the krill fishery. In the meeting of the CCALMR in October 2025,ย Norway proposed a doubling of the catch limits for krill. At the same time,ย scientists are calling for a re-evaluation of the limits, as they are based on old data and assumptions. Meanwhile, concernย about the exploitation of the Southern Ocean resulted inย UK retailerย Holland and Barrett withdrawingย all krill productsย by April 2026.ย
The challenge of consensusย
The CCAMLR operates on a consensus decision making model. Everyoneย has toย agree before new measures can be introduced.ย New MPAsย havenโtย been agreed becauseย oneย or two countriesย have blocked themย on the grounds of a lack of scientific evidence and their right to fish for krill and other target species.ย ย
What have we learned from exploitation in the Southern Ocean?ย ย
There is a lot of hope to be found in the Southern Ocean. Fur seals were given protection in 1909, and their numbers have nowย recovered toย over 3 million.ย Whaling stations on South Georgia are relics of the past, rusting microcosms ofย the industry they supported.ย ย
The CCAMLR is different to any other fishery. It has learned fromย previousย mistakes andย has madeย decisions based in robust science.ย A well-managed fishery will always beย called too conservative, too limiting, too safe, because it will never reach the point of collapse or decline.ย So far, krill populations haveย remainedย steady, unaffected by us.ย ย
The Southern Ocean is changing, and so the fishery must change with it.ย Climate change, moreย whalesย andย improvedย understanding of the ecosystem should all be considered in new fishery management.ย ย There are three things to take from this:ย ย
- Weย are capable of facilitatingย the recovery of the Ocean.ย ย
- The Southern Ocean, and its krill,ย areย facing new challenges.ย
- We allย benefitย from the Southern Ocean, and its krill,ย flourishing.ย
Krill are small but mighty. They fuel giantsย and balance our climate. The continuing battle to protect themย demonstratesย how far we have come. We can understandย better than everย the benefits this tiny crustacean impartsย as a part of its ecosystem.ย ย
Weย donโtย have all the answers, but the progress is reassuring.ย A relationship with the Ocean that is based in our understanding of the impacts of our actions will be much more productive than one based on theย potentialย profits.ย ย
Krill areย not theย impressive,ย charismaticย Ocean animals that whales and penguins are.ย But if we fail krill, we stand to lose the rest.ย Krill can be the species that marks a new chapter in our relationship with the Oceanย โ one in which we work with our Ocean rather than at the cost of it.ย ย




























































