In my precious spare time, I like to calculate weird numbers and statistics. For example, based on the approximate volume of a single Antarctic krill (they’re about 2 inches long), it would take around 743 of them to fill a venti coffee cup from a very popular coffee store chain.
It would take approximately 2.7 trillion venti coffees to fill the Empire State Building once – that’s 2 quadrillion, 6 trillion, 100 billion krill. There are enough Antarctic krill in the Southern Ocean to fill the Empire State Building more than 200 times.
If there are that many krill in the Southern Ocean, why are we concerned that fishing for krill might not leave enough for the seals and penguins that depend on them for survival during their breeding season?
Well, krill are a little bit like people. They prefer living in places with comfortable temperatures and lots of good food to eat. Our study area—the South Shetland Islands and the Bransfield Strait—is prime real estate for krill. The ocean there is cold and highly productive, meaning there’s lots of high-quality food sources, such as phytoplankton or small zooplankton. This area is also far enough north that winters are not completely dark, so photosynthesis and phytoplankton production continue year-round (although production is less during winter than during summer because of limited daylight). And, until recently, the Bransfield Strait was mostly ice-covered during winter, which provided krill with a smorgasbord of sea-ice algae to feast on when phytoplankton production was low. These days, the Bransfield Strait has less winter sea ice because of warming temperatures.
Because the Bransfield Strait is an ideal krill habitat, krill concentrate there, especially during winter when they can take advantage of feeding in the sea ice. They aren’t evenly spread throughout the Southern Ocean. Krill fishing vessels know this, which makes the Bransfield Strait one of the most heavily fished areas in Antarctica. The Bransfield Strait is also a crucial feeding area for seals and penguins, which have to compete with fishing vessels for krill.
A still image captured from a video logger attached to a chinstrap penguin's back. The image shows the back of the penguin's head as it swims through a krill swarm and eats a krill. Credit: NOAA Fisheries
So, while there are more than four hundred quadrillion krill in the Southern Ocean—likely more than the fishery could ever catch—overfishing in certain areas, such as the Bransfield Strait, could have devastating consequences for animals that must eat krill to survive. We already know that penguin populations suffer when the fishery catches large amounts of krill from small areas where penguins feed.
Though the South Shetland Islands and the Bransfield Strait are more than 7,000 miles from the United States, we have an economic interest in Antarctica. Americans are among the top consumers of dietary supplements made from krill; in 2021, we spent more than $250M on krill oil supplements. Even before the krill oil market took off, Congress enacted the Antarctic Marine Living Resources Convention Act of 1984 to establish a way for the U.S. to conduct research aimed at managing Antarctic marine living resources. This act paved the way for NOAA’s U.S. Antarctic Marine Living Resources Program, which has now been studying krill and krill predators around the Antarctic Peninsula every year for almost 40 years. One of the most important jobs of this program is to estimate the amount of krill around the South Shetland Islands each year. We provide these estimates to the Commission for the Conservation of Antarctic Marine Living Resources, which is an international commission that decides where, when, and how much krill can be caught in Antarctica. Catch limits are broken down into small areas to prevent the fishery from taking too much krill from any one spot.
Our program used to go to sea on a research vessel every year to estimate the amount of krill around the South Shetland Islands. However, we had to stop going out to sea in 2016 because ship time became cost-prohibitive.
That left us in a pickle: how would we continue to study krill without a ship?
Answer: autonomous underwater gliders.
The two transducers on the bottom of the glider are the AZFP. The big transducer emits the high and medium frequencies, while the small transducer emits the low frequency.(Images: NOAA)
I’ve described in a past blog how acoustic sensors on our gliders help us estimate the amount of krill in our study area each year. Without gliders, we wouldn’t have been able to keep providing these critical estimates for managing the krill fishery and safeguarding the resources seals and penguins need to survive and reproduce.
So, when a glider sends us pilots an urgent text message in the middle of the night that drags us out of bed to fix a problem, we remind ourselves that the data we collect and the management advice we provide is well worth the few hours of lost sleep. We know we’re making a difference for this amazing continent and the animals that live there.
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