Krill thrill in the chillComment on this story
Cape Town - It was unbelievably cold on the ice – down to a mind-numbing, body-freezing, frostbite-inducing –56°C at times – so getting into the seawater that was “only” –2°C felt positively balmy by comparison.
Well, only in a manner of speaking, of course.
That was the recent experience of two marine scientists from the Department of Agriculture, Forestry and Fisheries during an international research cruise deep into Antarctic waters to investigate bio-ecological aspects of krill, the tiny crustacean that looks something like a shrimp, and that forms the basis of the food-chain in the vast Southern Ocean surrounding Antarctica.
The staple food of the great baleen whale species like southern rights, blue whales and humpbacks, krill probably constitute the largest total biomass (living weight) of any animal species on the plant, with stock estimates ranging anywhere between 60 and 155 million tons.
Professors Lutz Auerswald and Sven Kerwath were taking part in the nine-nation expedition ANT-XXIX-7, done under the auspices of the famous German research institution, the Alfred Wegener Institute, and specifically its Helmholtz Centre for Polar and Marine Research, using its polar research vessel RV Polarstern, which has ice-breaking capability.
The aim of the nine-week research cruise was to investigate the importance of winter sea ice coverage for the development of krill, Euphasia superba, and especially its larval stages, in the Southern Ocean. Part of their work involved diving under the ice during two dive camps of nine and 14 days duration, set up on sea ice floes in the one-year pack ice.
This chilly work was aimed at helping them achieve a better understanding of the importance of sea ice coverage for krill development in winter, explained Auerswald, who has worked with Antarctic krill specialist Professor Bettina Meyer and her research group at the Alfred Wegener Institute since 2004.
“And I introduced Sven Kerwath (to them) a while ago,” he added.
Kerwath said he was grateful that Minister Tina Joemat-Pettersson had given them permission to join the prestigious research expedition, “and to be able to apply my expertise in such an extreme and challenging environment”.
“Although it was mentally and physically demanding to be on the ice at –56 ºC and to dive under the ice at –2 ºC, it was also a great experience.”
The under-ice landscape was “bizarre, alien and almost psychedelic with amazing colours”, he said.
“The natural light penetrates through the ice and illuminates the upper part of the crystal-clear water. The visibility seems endless but then fades away into the dark abyss of the 5 000m water column underneath. It took some nerve to do this work, and everybody was feeling a bit apprehensive at first.”
Auerswald, co-author of the expedition’s final report to the Alfred Wegener Institute, said he was proud to have been given the opportunity to contribute to the success of what he described as “this challenging but exciting research expedition”.
Dive studies had involved sampling krill from under the sea ice, and had also provided information on behaviour, distribution patterns and abundance of krill under the ice, he explained.
The dive operations were supplemented by research on the physical and biological composition of the sea ice habitat, using an remotely operated vehicle.
“After weeks of hard work, the results were very satisfying,” he said.
The RV Polarstern had sailed from the bunker station Cabo Negro, near the Chilean “Antarctic gateway” city of Punta Arena on August 16, then headed east on a transect from Patagonia to South Georgia.
After calibrating the vessel’s fish eco-sounder in the shelter of the Sunset Fjord of South Georgia, the cruise followed a north-south transect towards the South Orkney Islands, and the first dive camp was set up on an ice floe of the pack ice south-east of the islands.
Nine days later the expedition moved east towards the South Sandwich Islands, where the second, two-week dive camp was established on a suitable, stable ice floe.
Then the researchers moved northwards along the South Sandwich Islands into the transition zone between one-year pack ice and the so-called marginal ice zone, where they did another set of dives from inflatable craft in this “changing ice habitat”.
From there, the cruise headed in a north-easterly direction, and was concluded with a transect on the Greenwich Meridian, ending in Cape Town on October 16.
Joemat-Pettersson said she recognised the importance of this research cruise, and there was renewed interest in the South African fishing industry to look at this “massive, under-used resource”.
“With relative proximity to South Africa of the area with highest stock densities, new technologies are available to harvest krill more economically than in the past.
“South Africa already possesses a sophisticated fishing industry and industrial processing infrastructure, so it could easily benefit from harvesting krill.”
Concern over overfishing of southern krill
While krill is the basis of a substantial fishery, with about 70 percent of the catch being used as animal feed, there have been major concerns about the impacts of over-harvesting in the Southern Ocean/Antarctic waters ecosystem.
The krill catch rocketed during the five years from 1978 to 1982, dropped dramatically, and then climbed very quickly again between 1984 and 1992, after which harvesting crashed again.
The Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) was established by international convention in 1982 with the objective of conserving Antarctic marine life, and specifically in response to the increasing commercial interest in krill.
Since then, the krill fishery has been carefully regulated by CCAMLR, of which South Africa is a founder member.
Conservation measures of the commission, which has its headquarters in Hobart, Tasmania, include compulsory notification and permission prior to fishing for krill, and for other target species like Patagonian toothfish, Antarctic toothfish and mackerel icefish.
The convention area, which covers around 10 percent of Earth’s surface, is defined in the CCAMLR convention as the area south of the Antarctic Convergence – the constantly shifting, natural oceanographic “boundary” feature where cold, northwards-flowing Antarctic waters meet the relatively warmer waters of the Subantarctic. The convention also applies in the area south of 60°S, to which the 1959 Antarctic Treaty applies.
The status and management of the fisheries are reviewed annually by the convention’s Scientific Committee and its specialist working groups, using the best available science and information that includes detailed data from the fisheries and fishery surveys, and the CCAMLR Scheme of International Scientific Observation.
There are established krill fishing areas in zones all around Antarctica, but at present there is fishing only in five zones between about 20°W and 80°W. The total allowable catch for this area is 620 000 tons. There is also a major exploratory krill fishing zone between 20°W and 30°E – directly in line with South Africa’s area of interest in Antarctica – but no legal fishing is being done here at present. - Sunday Argus