Scientists and fishermen team up for the krill | Polarjournal
A dozen vessels from different nations fish for krill (Photo: Daniel Beltrá / Greenpeace)

Krill is a key resource in the icy Antarctic Ocean. The trawlers that go after it are keeping their catch under the precautionary threshold, a fact confirmed by a study that involves fishermen in scientific monitoring

The South Orkney Islands, off the Antarctic Peninsula, are surrounded by krill-rich currents that attract penguins, seals, whales — and trawlers. Georg Skaret, of Havforskningsinstituttet, a Norwegian marine-research outfit, and his colleagues have taken advantage of the presence of these ships to monitor the changes in the krill population over the decade 2011-2020. In the Scotia Sea in 2019 kril data were provided by the Association of Responsible Krill Harvesting Companies, a group of shipowners representing 90% of the krill catch. These observations are in addition to those of the research vessels.

Their results have just been published in the Journal of Marine Science. The waters of the South Orkney Islands are the most prolific for krill in the Scotia Sea and based on the measured biomass, fishermen catch less than 9.3% of the krill in this region, which is in line with the precautionary principle of the Convention on the Conservation of Antarctic Marine Living Resources.

CCAMLR has not yet established management objectives for krill fisheries that take into account the marine predators that depend on them, other than this precautionary principle. “Still, it is very important that the industry, scientists, managers and other stake-holders have a mutual understanding of the compromises underlying the existing management,” Mr Skaret said.

In science mode

The researchers found it convenient to use fishing vessels because they are present in this remote area almost all year round. Norwegian fishermen spend most of the year off South Georgia, South Orkney and South Shetland. Oceanographic vessels are expensive, and there are few cruises. The presence of fishing vessels therefore increases the ability to do measurements.

“The fishing vessels have echo sounders and sonars as important fish finding equipment, and we can calibrate and use these instruments, sometimes slightly modified, for scientific monitoring. The experience of the fishermen and historical catch data are used as part of the background knowledge to decide how we allocate the survey effort,” Mr Skaret said.

In Norway, companies with a krill licence are required to carry out annual monitoring. “It goes without saying that the fishermen are eager to fish and not necessarily to conduct scientific surveys, but in a larger context the collaboration and mutual understanding between fishermen and scientists has proven to be very fruitful and might also help to improve the management of krill,” he said.

Krill are small organisms that can swim, but, over long distances, currents move them and determine their distribution. Aggregations of krill are typically associated with shelf edges where a combination of small-scale eddies and the lack of currents that transport away from the coast lead to krill retention, Mr Skaret explained. The krill aggregations in such areas can reach several kilometres at the most extreme and extend hundreds of metres deep. “What is indicated from the few studies that have been done and the reports from the fishermen is that big aggregations can persist for days and even weeks and then dissolve,” he said.

Camille Lin, PolarJournal

Skaret, G., Macaulay, G.J., Pedersen, R., Wang, X., Klevjer, T.A., Krag, L.A., Krafft, B.A., 2023. Distribution and biomass estimation of Antarctic krill (Euphausia superba) off the South Orkney Islands during 2011–2020. ICES Journal of Marine Science fsad076.

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