Antarctic krill are individually small but collectively mighty. Each one is only a few centimeters long, but they gather in groups so large that during certain times of year, the swarms can be seen from space.
But these tiny shrimp-like creatures may not be so numerous forever. In at least some areas of the Southern Ocean, krill populations appear to be in a period of long-term decline. And a loss of this keystone species would be devastating for the Antarctic’s marine ecosystem.
Fortunately, emerging technologies are helping scientists monitor krill more effectively. One example is the Signature100, a device that combines an acoustic Doppler current profiler (which measures ocean currents) and a scientific echo sounder (which measures krill biomass).
David Velasco, lead author of a paper describing the technology, said that because krill generally move with ocean currents, measuring currents and krill biomass at the same time can tell scientists not only how many krill there are but also where they’re going.
The devices can also operate autonomously—scientists can attach them to stationary moorings or slow moving underwater robots called gliders, where they will quietly collect data for several months. This autonomous data collection, said Velasco, could provide substantial cost savings compared with ship-based research as well as allow for longer-term observations.
The Impact of the Krill Fishery
The krill fishery is important to both the Antarctic ecosystem and the human economy, so monitoring and sustainably maintaining its health has taken on increased importance. Leopard seals, blue whales, albatrosses, penguins, squid, and many species of fish all consume vast quantities of krill.
“Antarctic krill are central to the Antarctic food web,” said Simeon Hill, a senior scientist with the British Antarctic Survey who studies the ecosystem of the Southern Ocean. “A wide variety of species covering a whole range of different sizes, from things that are about the same size as krill themselves, right up to the baleen whales, all feed on Antarctic krill. So it’s a key food item for almost all of the biodiversity that is visible to us as visitors to the Southern Ocean.”
Since the 1990s, the amount of krill harvested by the fishing industry has been on the rise. By the late 2010s, more than 300,000 tons of krill were being harvested from the Southern Ocean each year. Once harvested, krill can be used as a food source in aquaculture or used to make krill oil, a popular dietary supplement high in omega-3 fatty acids.
“The fishery for Antarctic krill is the most important fishery in the Southern Ocean,” said Hill. “And yet unlike most fisheries that have advanced management in the world, [the krill] fishery is managed without a clear idea about how the population size changes from year to year.”
—Hannah Thomasy (@HannahThomasy), Science Writer