Antarctic krill are a source of food for many species of fish, seabirds, seals and whales in the Southern Ocean. There is debate amongst scientists as to how, and to what extent, this ecosystem is being affected by climate change.
Young krill are dependent on the protection and food afforded by the ice before they head out into the open ocean. Higher surface temperatures reduce the sea ice area, diminishing their chances of survival. Some researchers also believe that temperature increases have led to greater competition from a transparent sea squirt that can appear in large numbers if the conditions are right.
However, little is known for certain about this enormous ecosystem, as there is a shortage of data and the ecosystem is constantly changing. Scientific expeditions to these areas require a lot of resources, and are hence rare. The Norwegian contribution is therefore being well received by the international scientific community.
Just after Christmas, we travelled from Montevideo, Uruguay, down to the South Orkney Islands (60°S, 45°W), where we did our research on krill, before recently returning to Ushuaia, Argentina.
The South Orkney Islands were discovered by seal hunters in 1821. In 1903 a meteorological station was established on one of the islands, which is still operational, and is the oldest of its kind in the Antarctic. There is also another onshore research station.
Norwegian place names such as Sandefjord Bay, Larsen Island, Tønsberg Cove, Norway Bay and Sørlie Rock are proud monuments to our ancestors, who in their day ruled these waters with their sharp harpoons.
The climate is cold, with lots of precipitation and powerful winds. During the summer, which lasts from December to March, the average temperature is +2 °C. In winter the average is around -10 °C. The waters around the islands are covered in ice from late in April until November. Currently both Argentina and the United Kingdom claim sovereignty over the islands.
One of the goals was to estimate how much krill is carried through the fishing zone where we were located. That information will help make it easier to calculate fishing quotas for other areas that will ensure long-term, sustainable harvesting. We measured the route and size of the krill swarm using echo-sounders and sonar. We also took samples of krill from the catch to look at how gender distributions and reproduction status change by area and over time.
We also took samples of the water and of the krill’s food. This forms part of a larger research project, and is a follow-up to the Institute of Marine Research’s major scientific expedition last year, when the “G.O. Sars” was sent to the Southern Ocean for three months to do research on krill.
Life on board
Our research was adapted to the day-to-day operations on the “Saga Sea”, so as not to interfere with its fishing. It is great to be able to use a commercial fishing vessel as a base for some aspects of field research. There is also a lot of interesting information to be gained by talking to the crew, most of whom have many years’ experience of this type of fishing.
Data that the “Saga Sea” has collected during five years of krill fishing in the Southern Ocean reveals that krill are most abundant around the shelf edges by islands or underwater ridges. During the day they tend to gather in dense swarms deep below sea level, whilst at night they spread out close to the surface, which is rich in nutrients.
There is a fine balance between being eaten, and obtaining enough food. In the deep waters lurk the best divers such as whales, which are also equipped with sonar to detect the krill, and in the upper water layers there are predators that require light to see them.
To what extent the krill move up and down through the water in order to make use of ocean currents for transport purposes is another question that we would like to be able to answer. After a successful expedition, we have now returned home with a bag full of data that needs to be analysed further.
Small animals – big appeal
Various species of krill are found in all of the oceans, but the Antarctic krill (Euphasia superba) is the largest, reaching up to 6 cm in length.
In general krill are rich in protein, omega 3 fatty acids, carotenoids and antioxidants, and are potentially an attractive resource. New areas of application are constantly being investigated, including research into the potential health benefits of krill products. The pharmaceutical, cosmetic and food industries are currently very interested in krill products.
The total quantity of krill in the Southern Ocean is estimated to be between 80 and 1000 million tonnes, mostly found in large swarms with very high krill densities. In recent years the total catch has varied between 100,000 and 150,000 tonnes. The CCAMLR (Convention for the Conservation of Antarctic Marine Living Resources) has set a low limit on the catch until more is known about the size of the krill population. For the 2008-09 season, Japan, Korea, Russia and Norway have been allocated quotas for krill fishing in the Southern Ocean.