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While krill may be small to look at, these shrimp-like crustaceans play an outsized role in the global food web. They support the nutrition of several whale species, including the largest animals to ever exist: seabirds, seals and more. Humans have also developed a taste for krill. They come in the form of some omega-3 supplements, despite the fact that they usually exist speculative health benefits. This increased human demand for the krill could spell trouble for the whale species as they continue to recover from the days of industrial whaling.
A new one perspective study published on September 10 in the journal Nature communication found that continuing krill harvesting in the Southern Ocean could jeopardize the whale’s continued recovery from whaling. The authors also call for new recommendations to protect the marine mammals and other Antarctic species that these small ship-like crustaceans need to survive.
Krill the mighty
Krill is a collective name for about 86 species found throughout the world’s open oceans. They are about the size of a human thumb, but play an important role in the global food web. Antarctic krill (Euphausia superba) occurs only in the Southern Ocean and is among the most important animals in the Antarctic ecosystem. It forms the diet of most marine mammals and seabirds and also stores carbon. Krill can remove as much as 23 megatons of carbon dioxide annually from the atmosphere.
The crustacean also plays an economic role and is the focus of the largest fishery in the Southern Ocean. Ask about krill as a nutritional supplement shot up from 104,728 tons in 2007 to 415,508 tons in 2022.
According to the Associated press10 to 12 trawlers from Chile, China, Norway, South Korea and Ukraine harvest krill. Its largest commercial use is as an ingredient fed to farm-raised fish. Aker BioMarine from Norway is responsible for about 70 percent of the krill catch and is behind changes in the way it is caught and marketed in recent years. The small red krill oil capsules the company sells contain omega-3 vitamins that claim to support brain, heart and joint health.
At the same time, baleen whales, including humpback whales (Megaptera novaeangliae), fin whales (Balaenoptera physalus), and Antarctic blue whales (Balaenoptera musculus ssp. Intermediate product), have begun to recover from 200 years of commercial whaling. Because they are not hunted in large quantities, they have had a chance to repopulate after they were almost wiped out.
[Related: Biologists vastly underestimated how much whales eat and poop.]
Conservation biologist from Stanford University Matthew Savoca and his team previously discovered that Antarctic whales eat significantly more krill than scientists expected. Whale foraging in Antarctica also overlaps directly with human fishing for krill in some cases proposals to increase the allowable catch of krill.
“Taken together, this is all very worrying,” says Sovca Popular science. “Antarctic krill are among the most biomass-rich macroscopic species in the world. To give you an idea of how much mass this is, there are about 400 million tons of Antarctic krill in the Southern Ocean (much more than before whaling), while the entire human population weighs about 600 million tons.”
Back-of-the-envelope calculations
Sovca is also co-author of this latest study that calculates the overlap between the krill that whales must eat to survive and what human fishermen catch.
“We have multiplied how much whales eat how many whales there are now and before whaling,” Savoca explains. “We then compared those numbers to the estimated amount of krill in the Southern Ocean, focusing specifically on the SW Atlantic sector.”
The southwestern Atlantic sector of the Southern Ocean is important because this is the region where most krill are found in this area.
According to their results, current krill biomass cannot support both growing krill fisheries and the recovery of whale populations to their pre-whaling sizes. The calculations highlight a growing conflict between humans and wildlife at the bottom of the Earth.
Savoca is surprised “that we allow industrial supertrawlers to drag their nets through pods of feeding whales. Imagine if that happened off the coast of the US or Europe, there would be an uproar!”
[Related: How do blue whales find food? They check the weather.]
They also saw that both whales were specifically hunting dense swarms of krill. Other predators, including penguins and seals, do not go after flocks in this way. This means that the trawlers and the whales occupy the same spots.
“They are forced to compete directly for krill unless there are guardrails to prevent this,” says Savoca.
The This is what the Association of Responsible Krill Harvesting Companies (ARK) says. that it adheres to catch limits and fishing in designated areas. They also monitor and report vessels’ use of marine mammal exclusion equipment, including rigid or flexible grilles on their fishing gear. However, four humpback whales became entangled in one of Aker BioMarine’s nets in 2021 and 2022.A 2022 study discovered that krill fishing in Antarctica has a low bycatch.
Avoid further conflict
In October the Convention on the Conservation of Antarctic Marine Living Resources (CCAMLR) meets in Hobart, Australia. Savoca hopes that some of their recommendations can be presented at this annual meeting. They recommend that whale populations and prey needs be taken into account when calculating annual catch limits.
“As whale populations recover, it is now essential that CCAMLR include recovered whales (humpback whales) and recovering whales (blue and fin whales) as monitoring species,” the authors write in the study. “CCAMLR and the IWC [International Whaling Commission] should work together to quantify and incorporate whale prey requirements into any updated krill harvesting regulations.”
Savoca and his team are also calling for more monitoring of krill and larvae hotspots, using the United Nations High Seas Treaty as a framework to hold individual parties accountable, and ensuring more voices come from the South. These countries do not receive as many financial benefits from luxury tourism and fishing, and are more affected by the degraded Southern Ocean.
“Most people I talked to about this didn’t even know we were fishing for krill in Antarctica, and awareness is so important,” says Savoca. “Additionally, we know there are very few regulations to protect wildlife from fishing, and we know we can do better [is important]. With common sense, we can get our krill and the whales (and penguins and seals, etc.) can get it too.”