Antarctica is often closer than you think. From the fish in your supermarket to the supplements in your health food store, traces of its most important animal are everywhere, hidden in plain sight. Krill, the tiny crustacean at the centre of the Antarctic food web eaten by everything from gentoo penguins to whales, is being targeted by fishing fleets in ever-increasing numbers. It’s turned into fish meal for the world’s industrial salmon farms, into food for livestock and pets, and even transformed to omega-3 supplements for the diet industry. But could this growing hunger for Antarctic krill threaten the fragility of Antarctica’s ecosystem?
To find out more, we spoke to Dr Ryan Reisinger from the University of Southampton, who is leading a new project to help better understand the complicated dynamics between Antarctic krill, whales and the growing number of ships fishing for krill.
Whales and fisheries
‘We’re collecting new data on krill distribution and whale movements during two expeditions to the Western Antarctic Peninsula, in March 2024 and March 2025,’ explained Dr Reisinger, whose research is being carried in partnership with the British Antarctic Survey, the Scottish Association for Marine Science and the University of California Santa Cruz. The data collected during the project, called ‘Safeguarding Antarctic krill stocks for baleen whales’ will then be used to build up a more detailed picture for ensuring the krill fishery is as sustainable as possible.
These tiny crustaceans are one of the most abundant animals on Earth and are a major food source for many higher predators including penguins, seals and baleen whales. In addition to this, their swarms act as amazing carbon sinks, capturing many megatons of carbon every year, which is sequestered in their moulted exoskeletons and faecal pellets that sink to the ocean floor. It’s this outsized role that makes managing the fishery so important.
‘Krill fishing happens almost exclusively in the southwest Atlantic now, focussed on South Georgia, the South Orkney Islands and the Western Antarctic Peninsula including the South Shetland Islands,’ said Dr Reisinger. ‘The fishery is open all year, but vessels usually only fish off the Western Antarctic Peninsula in late summer and autumn.’
This forms a big overlap with the parts of Antarctica visited by the polar cruise industry. It seems that where there is krill, there’s a draw for tourists and fishing vessels alike. This was particularly observed in 2022 when biologists onboard the expedition cruise ship National Geographic Endurance observed commercial krill fishing taking place within a foraging supergroup of nearly one thousand fin whales.
Fin whales are part of the focus of the current research project. They are enormous consumers of krill, but their ecology remains poorly understood even as their numbers slowly recover from the devastation wrought upon them by industrial whaling in the 20th Century. Researchers have been satellite tagging fin whales, to look at their location and diving behaviour as well as recording them by hydrophone.
A hungry whale eats a lot of krill. It’s estimated that an adult Antarctic blue whale requires about 4.2 tonnes of krill per day, with fin whales consuming only marginally less. The numbers are staggering, Dr Reisenger explained. ‘Before being decimated by commercial whaling, large whales consumed about 430 million tonnes of krill per year in the Southern Ocean.’
Antarctica’s most populous animal
It’s estimated that in the southwest Atlantic, the corner of the Southern Ocean pierced by the Antarctic Peninsula, where almost all krill fishing takes place, the biomass of krill adds up to about 62.6 million tonnes.
It’s essential to understand how that krill is distributed, to prevent conflicts between whales and man. At the same time as tagging fin whales then, the research team uses active acoustic echo sounding surveys to measure the distribution of krill swarms to better understand where they form – as well as how whales interact with them. While echo sounding is traditionally done from a ship, the team is using ImpYaks, small remote-controlled echosounders, that enable surveys to be safely carried out in near-shore areas, and other locations that are inaccessible to large research vessels.
Previous research has already established that the distribution of humpback and minke whales around the Antarctic Peninsula is best explained by krill distribution, with humpbacks ranging throughout continental shelf waters bays along the western Peninsula – particularly along the Bransfield and Gerlache Straits. Minke whales prefer sheltered bays and areas where sea ice is present. Both of these areas currently overlap with the krill fishery.
Who regulates krill fishing?
Thankfully, safeguards are already in place to regulate how much krill can be fished in Antarctic waters. The Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) was established in 1982 as part of the Antarctic Treaty system. It was created in direct response to growing commercial interest in Antarctic krill, against the historical backdrop of over-exploitation of the region’s marine resources.
CCAMLR’s mandate is to manage the krill fishery with an ecosystem approach, so that krill stocks are maintained at productive levels and fishing activities should not interfere with krill-dependent consumers. CCAMLR sets limits on how much krill can be caught in the Southern Ocean, based on this principle. The catch limit set in the southwest Atlantic is 5.61 million tonnes but has been set to an even more precautionary 620,000 tonne trigger level, which acts as the current catch limit, to avoid negative effects on krill-dependent predators. As catches have been increasing over the last decade, the precautionary principle has been key to setting limits.
‘The catch limits represent only a very small proportion of the estimated total krill biomass in the southwest Atlantic,’ said Dr Reisenger. ‘The trigger level of 620,000 tonnes is less than 1% of the estimated biomass. Nonetheless, there is a concern that the fishery is becoming more and more spatially concentrated in a few areas that are also favoured by krill predators including whales. This can cause local depletion of krill, where predators in these areas aren’t able to find sufficient krill to eat. We therefore suggest that krill fishery management needs to be more fine-scale and needs to consider the behaviour and distribution of whales, which are increasing towards their abundance pre-whaling.’
The final part of the research project therefore involves marrying the data collected in the field from the whales and the krill swarms, to data from CCAMLR and the non-profit organisation Global Fishing Watch on the distribution and activity of the krill fishing fleet.
There is already precedent for restricting the krill fishery along the Antarctic Peninsula. In 2018, buffer zones were established extending from 18-25 miles (30-40 km) from penguin colonies during breeding season, protecting significant swathes of the ocean there.
‘We need a better understanding of how whales, Antarctic krill and the krill fishery interact in space and time,’ said Dr Reisinger. ‘This is especially important as baleen whale populations are recovering from historical exploitation and climate change is affecting krill distribution.’
It’s an irony that the majority of travellers to Antarctica on an expedition cruise ship never get to see any krill up close. But the evidence of their centrality to the polar ecosystem is absolutely everywhere, whether that’s in the penguins porpoising through the water on the way back from collecting food for their chicks, or the whales who gather here every Antarctic summer to gorge themselves on this small but mighty crustacean. Even the leopard seal, one of Antarctica’s top predators, tops up its diet with krill, as well as the penguins who rely on it. Without krill, there would be a lot fewer reasons to visit Antarctica.
Dr Reisinger’s research team will be back in the Peninsula in early 2025. While it’s too early for the results of the research project to be put into place, it’s hoped that the new data being collected will go a long way towards adding a much needed extra level of protection for krill – and all of Antarctica’s wildlife as a result.
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