The Smallest Catch In The Southern Ocean

AAntarctic krill, Euphausia superba, is a shrimp-like crustacean rarely longer than six centimetres, yet the swarms it forms are among the largest gatherings of animal life on the planet. It is the hinge on which the Southern Ocean turns, since whales, seals, penguins and fish alike convert krill into something larger. Since the 1970s it has also been a commodity. Modern vessels no longer haul nets onto the deck; they draw the catch aboard continuously through a hose, and the product is divided between meal for farmed salmon and capsules of krill oil sold for their omega-3 content. Regulation falls to the Southern Ocean Commission, which since 1991 has capped the annual catch in Area 48, the sector lying north of the Antarctic Peninsula, at 5.6 million tonnes. The Commission also set a much lower trigger level of 620,000 tonnes, which may not be exceeded until the allowance has been divided among smaller management units. Reported landings in 2023 came to 415,000 tonnes.

BIngrid Solheim, a fisheries oceanographer at the Bergen Polar Institute, reads those numbers as evidence of restraint. Between 2019 and 2024 her group repeated acoustic surveys along fixed transects each January, and arrived at a standing stock of 62 million tonnes for Area 48. Set against that, the reported catch removes about 0.7 per cent of the biomass a year, a share that would be thought negligible in any temperate fishery. Solheim is careful, however, about what an acoustic estimate can and cannot show. A survey records the animals present in one summer; krill live five or six years, and the number entering the population each season varies with the extent of winter sea ice, so a single figure describes a moment rather than a trend. What troubles her about the modern fishery is not the size of the catch but its footprint. The fleet, she points out, took more than 70 per cent of last season's tonnage from an area smaller than one-tenth of the sector open to it.

CTomás Reyes, a seabird ecologist at the Punta Delgada field station, works at the other end of the chain. A chinstrap penguin feeding a chick cannot go far: the adult must be back at the nest within a day or two, which in practice confines it to waters some thirty kilometres from the colony. Reyes's counts at Cape Renard record a fall of 27 per cent in breeding pairs between 2004 and 2020. He does not offer this as a verdict on the fishery. Winter sea ice retreated over the same years, and the two pressures cannot be separated by counting birds alone. His argument is narrower and, he believes, harder to dismiss. Whatever is driving the decline, a colony that is already losing pairs can absorb no further pressure, and the months in which the fleet works closest to the shore, January and February, are exactly the weeks in which a breeding adult's range is at its smallest.

DThe fishery of today does not resemble the one the 5.6-million-tonne ceiling was written for. Continuous pumping allows a vessel to sit on a single swarm for weeks, processing as it goes, where an older trawler had to break off to empty its nets. Onboard freezing has extended the season, and since 2018 a growing share of the effort has moved into autumn and winter, when the ice edge is closer to land. The Commission's own reporting shows the tonnage taken within thirty kilometres of the coast climbing from 21 per cent of the total in 2010 to 58 per cent in 2022, while the total itself grew only modestly over the same period. Concentration, rather than volume, is what has changed, and the rules were written to restrain volume.

EAt a workshop convened in 2024 the two positions proved less opposed than the published papers implied. Solheim accepted that a limit expressed for an entire sector says nothing about conditions in a single bay, and that her 0.7 per cent is meaningless at the scale on which a penguin forages. Reyes accepted that the six seasons of foraging data he relies on come from two colonies only, and that the overlap he documents holds where the continental shelf is narrow and need not hold elsewhere. They parted over what should be done while the evidence remains incomplete. For Reyes, a predator that breeds once a year cannot wait for certainty, so the burden of proof belongs with the fleet; for Solheim, closing grounds where no link has been demonstrated simply pushes vessels into waters that have been surveyed less well still.

FA newer argument has arrived from an unexpected quarter. Krill feed at the surface at night and descend by day, and their faecal pellets sink faster than most particles, carrying carbon beyond the reach of the atmosphere; one modelling study put the annual flux for Area 48 at 23 million tonnes of carbon, though its authors described the estimate as provisional. If the figure holds, the animals are worth more in the water than on a deck, and the case for restraint no longer rests on penguins at all. The practical difficulty is older than the argument. The biomass survey on which every limit ultimately depends has been repeated only twice since 2000, and the subdivision of the trigger level among four subareas, agreed in 2023, lapses in 2028 unless it is renewed. Neither researcher disputes the conclusion that follows: a fishery that has changed its habits within a decade is being managed from a description of the ocean drawn before those habits changed.