Antarctic krill and ecosystem monitoring survey off the South Orkney Islands in 2026

The Antarctic krill (Euphausia superba) fishery began in the early 1970s and peaked in the late 1980s, with catches up to around 500,000 tons per year, by USSR and Japanese vessels operating in various areas of the Southern Ocean. In response to the growing commercial interest in Antarctic krill resources, the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) was established in 1982. As an international commission CCAMLR is responsible for the conservation of Antarctic marine ecosystems. This does not exclude harvesting as long as such harvesting is carried out in a sustainable manner and takes account of the effects of fishing on other components of the ecosystem. Fishing activity declined during the period when the USSR dissolved. Since 1997, the Antarctic krill fishery has primarily concentrated within the Southwest Atlantic sector of the Southern Ocean, specifically in CCAMLR subareas 48.1, 48.2, and 48.3. In 1991, CCAMLR established a fixed precautionary annual catch limit (trigger level) for the sector including subareas 48.1-4, set at 620,000 tons. Additionally, a total catch limit of 440,000 tons has been set for subarea 58.4.1, and 260,000 tons are available for fishing in subarea 58.4.2. Unless otherwise specified, an exploratory catch limit for any statistical subarea in the Southern Ocean is set at 15,000 tons.

Figure 1. Annual total reported catch of Antarctic krill in the Southern Ocean (data source: ccamlr.org).

The 2024/25 fishing season marks the first time that the krill fishery has reached the trigger level for the subareas 48.1-4, since its introduction. Notably, the total allowable catch was attained already in August, resulting in an earlier closure of the fishery compared to previous seasons. This development coincides with regulatory changes within CCAMLR: due to a lack of consensus on maintaining the subdivision of the trigger level among Subareas 48.1–.4, Conservation Measure (CM) 51‑07 (previously governing the spatial distribution of catches) expired at the end of the 2023/24 fishing season (SC‑CAMLR‑43). As a consequence, the full 620,000‑tonne trigger level can now be harvested in any combination across these subareas. This regulatory shift may help explain the altered fishing pattern observed in 2024/25. Of the total krill catch of 624,920 tonnes, 57% was taken in Subarea 48.1, 42% in Subarea 48.2, and 1% in Subarea 48.3 (Figure 2). In addition, extensive pack ice conditions in Subarea 48.2 at the start of the season likely constrained early fishing activity in that area, contributing to a higher concentration of effort in Subarea 48.1, contrary to the typical pattern where the season often begins in Subarea 48.2.

Figure 2. Proportional historical distribution of the total reported catch of Antarctic krill in Subareas 48.1, 48.2, and 48.3 (48.1 = blue, 48.2 = red, 48.3 = green), (data source: ccamlr.org).

During the 2024/25 fishing season, the Norwegian krill industry accounted for 52% of the total catch, while Chinese vessels caught 37%. South Korea 5%, and Chile and Ukraine each contributed 3% (Figure 3).

Figure 3. Annual total catch per krill fishing participating flag state in CCAMLR subareas 48.1-4 from the 1994/95 season to the 2024/25 season (data source: ccamlr.org).

Two large-scale acoustic trawl surveys were conducted in the Southwest Atlantic sector of the Southern Ocean (subareas 48.1-48.4), estimating the total biomass of krill in these fishing areas to be 62.6 Mt in 2019 (Krafft et al., 2021), which was similar to the other synoptic survey in 2000 (60.3 Mt; CCAMLR, 2010). Regular meso-scale monitoring of krill distribution and demographic composition in these fishing areas has been carried out since 1996 in subarea 48.1 (Reiss et al., 2008, 2017; Yu et al., 2019; Krafft et al., 2021; Wang et al., 2021). Previously, these surveys were conducted during the austral summer, but they are now also performed during the austral winter. The British Antarctic Survey has been running an annual acoustic survey off the South Georgia/South Georgias Islands ("Western core-box" in subarea 48.3) since 1997 (Fielding et al., 2014) during the summer season.

A Norwegian fishing company offered to carry out an annual krill monitoring survey commencing in 2011, for as long as they have commercial activity in the Southern Ocean (Jensen et al., 2010). This initiative is consistent with the broader CCAMLR framework, which relies on fishery-dependent data and places strong expectations on Members and industry to contribute to scientific data collection through vessel time and logistical support. Through discussions in CCAMLR WG-EMM (Working Group on Ecosystem Monitoring and Management) in 2010, it was agreed that the survey could be carried out in the CCAMLR statistical Subarea 48.2 according to similar standards as the annual scientific surveys undertaken in 48.1 and 48.3 and that the surveys should be executed by scientists from the Institute of Marine Research, Norway. The three surveys could form an integrated monitoring effort extending across the Scotia Sea (Figure 2), linking three of the areas with highest concentrations of krill and highest fishing activity. The results will help evaluate and develop the management of the krill fishery (Hill et al., 2016).

The first annual survey was conducted in January/February 2011 using the FV 'Saga Sea' (Aker Biomarine ASA). The results and study design from this survey were presented at the CCAMLR WG-EMM in 2011. The original survey design, suggested during WG-EMM 2010, consisted of six parallel north-south bound transects extending 100 nautical miles. During this first survey season, it was recognized that there was a need to extend the monitoring effort to cover the waters over the shelf edge, north of the South Orkney archipelago, where most krill in this region were observed to aggregate. During the WG-EMM meeting in 2011, it was agreed to extend the survey transects 20 nautical miles northwards and to omit the westernmost transect line from the 2011 survey. Before the survey in 2014, it was also agreed to extend the transect lines further to the south to cover the northern part of the Marine Protected Area south of the South Orkney Islands, and the design has remained unchanged since then (Figure 4).

Figure 4. CCAMLR Statistical Reporting Areas 48.1–48.3, with transect lines regularly surveyed for Antarctic krill abundance and demographic composition. A dispute exists between the Governments of Argentina and the United Kingdom of Great Britain and Northern Ireland concerning sovereignty over the Falkland Islands/Malvinas Islands (UN directive: ST/CS/SER.A/42).

Results and activities from these annual South Orkney surveys are reported to WG-EMM (e.g., Krafft et al., 2018b; Skaret et al., 2019) and are published in the primary literature (e.g., Krafft et al., 2018a, 2019; Skaret et al., 2023). This report presents the survey activities from the 2026 season off the South Orkney Islands.

2.1 - Survey design, area, and vessel

The cargo vessel “Antarctic Provider” (Aker BioMarine AS) departed Montevideo, Uruguay, on 27 January 2026. The survey was terminated upon arrival in Falkland/Malvinas Islands, on 18 February 2026. 

During the period when scientific personnel were physically onboard, an operational incident occurred during trawl station B1, where the trawl became entangled in the vessel’s propeller. As a result, the vessel lost propulsion and required assistance from another vessel for towing to the Falkland/Malvinas Islands. The trawl was subsequently released from the propeller upon arrival; however, it was severely damaged. Combined with the limited remaining survey time, this effectively truncated the survey. 

In addition, extensive pack-ice conditions south of the island group restricted transect coverage to areas north of the islands during the initial survey phase. Nevertheless, the completion of transects C, D, and E was carried out later through remote coordination when the vessel returned to the area in March, to the extent that ice conditions allowed access. No additional trawl stations were conducted following the incident.

The planned survey design covers 60 360 km2 of the waters around the South Orkney Islands and includes five parallel transects extending from the northernmost waypoints at 59.67°S and southernmost waypoint at 62.00°S. Longitudes for transects 1 through 5 are at 44°W, 45°W, 45.75°W, 46.5°W and 47.5° W, respectively.

Figure 5. Summary of the 2026 krill monitoring survey lines (A-E) with 6 trawl stations. Three moorings were deployed as denoted by the red stars. NASC values attributed to krill were only detected along transect B; this value is shown in white text (NASC = 682,456).

2.2 - Acoustic data collection

2.2.1 - Vessel mounted echosounders

During the survey, ‘Antarctic Provider’ was equipped with Simrad EK80, 18 kHz and EK60 echo sounders operating at 70, 120 and 200 kHz.

The echosounders were calibrated off Signy Island using the standard sphere calibration method (Foote et al., 1987). The echo sounder was operating with a ping interval at or close to 1 per second. Nominal vessel speed during surveying is 10 knots and could be kept during most of the survey. Acoustic data were collected down to 500 m on all four frequencies. Other transceiver settings are specified in Table 1.

Table 1. Specification of transceiver settings on ‘Antarctic Provider’ applied during the 2026 survey.

2.2.2 - Acoustic Moorings

Mooring recovery:

Mooring 1: Nortek Signature 100, 2 CTDs at S 60°21.6814 and W 046°45.0552 – not recovered , no contact with release

Mooring 2: Nortek Signature 100, 2 CTDs, Aural M3 (PAM) at S 60°18.9248 and W46°44.7424

Mooring 3: ASL, 2 CTDs at S 60°21.3716 and W 046°39.6076

Mooring 4: Soundtrap ST600 at S 60°66928 and W 045°51249

Mooring deployment:

Mooring 1: Soundtrap ST 600 at S60° 40.157 and W 45°30.749

Mooring 2: Nortec Signature 100, 2 CTDs, Aural M3 (PAM) at S 60° 18.9248 and W 46° 44.7424

Mooring 3: ASL, 2 CTDs at S 60° 21.3716 and W 46° 39.6076

2.3 - Acoustic data analyses

In this work, only raw acoustic data were processed using the Large Scale Survey System (LSSS) (Korneliussen et al., 2016). NASC values at 120 kHz were interpreted as krill based on a standard swarm-based discrimination approach in accordance with the CCAMLR protocol (CCAMLR, 2017), including noise removal filtering and swarm detection. No further conversion of NASC to biomass was carried out, as the spatial coverage of the survey area was limited. During the survey period, dense pack ice south of the island group prevented the vessel from achieving adequate coverage. In addition, the incident where the trawl became entangled in the propeller restricted the coverage to only the northernmost parts of transects A and B. The northern sections (north of the island group) of transects C, D, and E were surveyed with the vessel operated remotely from shore, without scientific personnel onboard; in these areas, no acoustic signals were allocated to krill.

2.4 - Biological sampling

The survey design included trawl stations spaced ~20–25 nautical miles apart along the set parallel north-south oriented transect lines (Figure 5).

The standard survey trawl used was 42 m long, with a 36 m2 mouth opening, constructed of 7 mm (stretched) diamond shaped meshes from mouth to rear, or a 3 mm light opening (Figure 6). The trawl was towed using a 6 m wide steel beam with 200 kg weights at each lower wing tip to ensure fast deployment to depth and the best possible geometric stability of the trawl during sampling.

Figure 6. The survey trawl with a 7 mm meshed inner net made of polyamide (PA)

140 mm meshed PA net in the mouth, and 200 mm meshed outer support net in

polyethylene (PE). See also Figure 2. In Krafft et al.2018.

Attached on top of the steel beam was a 75x75 cm frame carrying a 180 µm meshed 3 m mesozooplankton net. A Hydro-Bios mechanical flowmeter was attached in the center of the mouth (Figure 7).

Figure 7. Trawl with a 180 µm plankton mesozooplankton net on the trawl beam, with mechanical flowmeter in the mouth. The right-side figure also shows the location on the beam with the SIMRAD Transceiver (WBAT) and forward-facing 120 kHz transducer.

At each station the trawl was lowered vertically from surface to ~200 m depth (or ~20 m above bottom if the depth was < 200 m) and then hauled in at 1.5 - 2.0 knots, including vessel and wire speed. When landed on the trawl deck, the cod end was opened, and the catch was removed. Thereby the towing rig was hung from a crane and flushed on deck to wash out biological remains stuck in the net. The macrozooplankton and micronekton were sorted, identified to species or to the nearest possible taxonomic group, and weighed. For E. superba, the body length was measured (± 0.1 mm) from the anterior margin of the eye to the tip of telson excluding the setae, according to the “Discovery” method of Marr (1962). Sex and maturity stages of E. superba were determined on fresh material using the classification methods outlined by Makorov and Denys (1981). In brief, juveniles were classified due to their lack of visible sexual characteristics. Males were divided into three subadult stages: M2A1, M2A2 and M2A3 and two adult stages: M3A and M3B; and females were divided into one subadult stage: F2A and five adult stages: F3A, F3B, F3C, F3D and F3E (Krafft et al., 2015).

The catch sampled with the 180 µm net was split using a plankton splitter. One half was preserved in 4% buffered formaldehyde for onshore visual taxonomical analysis. The other half was blended in a 1000W mixer for 2-3 minutes until reaching complete homogeneity. Thereby, 2 ml homogenate were extracted using a 5 ml pipette, added to a cryovial pre-filled with TES buffer (Tris, EDTA and SDS solution) and preserved at -20°C. Two replicates were taken per homogenate. All cryovials were transported to an onshore lab for metabarcoding.

2.5 - Sampling and laboratory analyses (chlorophyll a and stable isotopes)

As part of a collaborative effort with Argentine scientists, water samples were collected for Chl-a analysis and processed using laboratory facilities in Argentina.

Water samples were collected for analysis of chlorophyll a (Chl-a). These analyses followed standard spectrophotometric procedures commonly used in studies of the Southern Ocean. Seawater was filtered onto glass fibre filters (in duplicate) and the pigments were extracted in organic solvents, typically acetone. Chl-a concentrations were quantified in order to estimate phytoplankton biomass, thereby providing a fundamental basis for understanding bottom-up ecosystem processes. In this study, Chl-a data are intended to support the interpretation of krill distribution and biomass by linking observed acoustic patterns to variability in food availability.

In addition, tissue samples from mesopelagic fish were collected and preserved for stable isotope analysis (e.g. δ¹³C and δ¹⁵N). These analyses provide information on trophic position and carbon sources, allowing assessment of food web structure and energy transfer within the ecosystem. Such data are particularly useful for evaluating the role of mesopelagic fish in relation to krill and higher predators.

The sampling represents an initial step in establishing a long-term international collaboration. Although the number of samples collected during this survey was limited, the successful implementation of shared protocols and sample exchange demonstrates strong potential for expanded cooperation in future field seasons.

2.6 - Installation of penguin observatory

A temporary observatory consisting of a camera (Reconyx HyperFire 4K Ultra HD Viltkamera) and an acoustic recorder (Song Meter® Mini 2 (Li-ion) Acoustic Recorder) was installed in a chinstrap penguin (Pygoscelis antarcticus) colony on Coronation Island (60°35′55.82″S, 46°00′45.88″W).

                          Figure 8. Location of the penguin observatory on Coronation Island. The satellite image also illustrates the dense pack-ice we encountered this season south of the South Orkney Islands.

The purpose of the installation was to support a multi-year monitoring programme aimed at quantifying the number of nests within the colony, estimating breeding success (i.e. the number of chicks that survive to the crèche stage, when parental guarding ceases), and determining the timing and duration of the breeding season. These data will be compared across years and evaluated in relation to krill biomass and spatial distribution derived from concurrent acoustic surveys.

A flat and stable location was selected adjacent to the penguin colony. The camera and recorder were pre-mounted on a wooden plank prior to deployment. This plank was securely fastened to one of three wooden pallets using screws, positioning the instruments at approximately head height to ensure adequate field of view.

The three pallets were then assembled into a triangular structure, with the camera oriented towards the penguin colony and adjacent beach area to allow simultaneous observation of penguins and seals. The structure was stabilized by tightening two ratchet straps around the pallets. To further secure the installation against strong winds and ice conditions, the interior of the pallet structure was completely filled with stones to add weight and prevent movement or collapse.

Figure 9. Installation of the penguin observatory (camera and acoustic recorder).

The camera and acoustic recorder were pre-activated prior to deployment, and no further calibration or adjustment was conducted in the field. In future years, drone-based surveys will be conducted to collect imagery along transects covering a larger proportion of the colony, enabling improved spatial estimates of nest abundance and distribution.

2.7 - Marine mammal observations

Marine mammal observations were carried out by dedicated observers during daylight hours, whenever visibility was sufficient. The observer was located on the bridge and continuously scanned the starboard forward quarter (0 – 90°), binoculars were used for species identification. Angles were estimated using a drawn angle board. Distance estimation was aided by using the reticles in the binoculars that marked one milliradian per line. Together with the platform and observer height (20.3+1.7m), each reticles line from the horizon marked a known distance.

Observations were only recorded on straight sections of the vessel track with a nominal vessel speed of 10 knots. The vessel GPS track and logged effort were recorded with custom software on a windows tablet (DOI 10.5281/zenodo.10228669). For each observation the species, time, location, distance, angle, visibility and number of individuals were noted. The observed marine mammal species were Fin whales (Balaenoptera physalus), Antarctic fur seals (Arctocephalus gazella), Weddell seals (Leptonychotes weddellii), Humpback whales (Megaptera novaeangliae) and Orcas (Orcinus orca).

2.8 - Satellite tagging of cetaceans

As part of a multi-year undertaking, humpback whales were approached using a MOB boat and satellite transmitters were deployed using a compressed-air-powered rifle, which projected a carrier containing the tag into the dorsal blubber of the whale. Tagging procedures followed established best practices and ethical guidelines to minimize disturbance and ensure secure attachment. In this study, SPLASH tags manufactured by Wildlife Computers were used. These tags transmit geolocation data via the Argos satellite system when the animal surfaces and record dive profile information, including dive depth and duration. Together, these data provide a combined description of horizontal movements and vertical habitat use over time.

The primary objective of the analyses is to describe movement patterns and diving behavior of humpback whales and to investigate how these relate to krill distribution, environmental variability, and the presence of other predators. By combining movement, dive, acoustic, and biological data, it is possible to assess predator–prey overlap, habitat use, and foraging behavior, and to infer aspects of energetic requirements.

Humpback whales are among the dominant predators of Antarctic krill in the Southern Ocean, and their distribution and feeding behavior are therefore of direct relevance to ecosystem-based management. Improved knowledge of whale movements and their overlap with krill resources and fisheries activity contributes to assessing predator demand, understanding ecosystem dynamics, and informing sustainable management of the krill fishery.

                          Figure 10. Example track of a satellite-tagged humpback whale (Megaptera novaeangliae) in 2026. Positions derived from Argos transmissions are shown with dates indicated along the track, illustrating movement patterns within the study area.

Glider deployment

An autonomous underwater glider (Seaglider, Kongsberg Maritime) was deployed during the survey to collect high-resolution oceanographic data over the northwestern South Orkney Island Plateau. The glider was deployed over a canyon area off Coronation Island and operated along the northern shelf edge of the island group.

                           Figure 11. Seaglider (Kongsberg Maritime) used for autonomous oceanographic measurements during the survey, deployed off Coronation Island.

The Seaglider is a buoyancy-driven autonomous vehicle designed for long-duration missions, navigating in a sawtooth (vertical profiling) pattern through the water column while progressing horizontally. The platform was equipped with a standard oceanographic sensor suite, including conductivity-temperature–depth (CTD) sensors for measuring salinity, temperature, and pressure, as well as additional sensors for dissolved oxygen, providing information on water mass properties.

The glider was remotely piloted via satellite communication, allowing continuous adjustment of its trajectory and sampling strategy throughout the mission. Following deployment, the glider operated as planned, traversing the shelf break in a cross-slope pattern along the northern side of the island group. The system transmitted data regularly via satellite, and high-quality datasets were received throughout the deployment period.

Figure 12. Track of the Seaglider at the South Orkney Islands from deployment in early February to recovery in March. The buoyancy-driven platform profiled the water column in a sawtooth pattern to characterize water mass properties.

Recovery of the glider was originally planned as part of the regular survey operations using R/V Antarctic Provider. However, due to the premature termination of the survey following the incident where the trawl became entangled in the vessel’s propeller, this plan could not be completed as intended. After disembarkation of the scientific personnel, the vessel crew made an attempt to recover the glider.

The glider was successfully navigated to a predefined recovery position and was visually observed from the bridge. However, for unknown reasons, communication and visual contact with the glider was lost and the vehicle disappeared shortly before it could be retrieved by crew members deploying a MOB boat.

Despite the loss of the platform, all transmitted data had been successfully received via satellite during the mission and are therefore considered secured.

3.1 - Biological sampling

A total of 5 trawl stations were successfully completed during the survey, all of them situated in the deep canyon area north-west of the South Orkney Islands. Twenty-two taxonomic groups were recorded, 10 of which were identified to species level. The westernmost stations (A1, A2 and A3) were dominated by large catches of the tunicate Salpa thompsoni. These stations were sampled during the night. In particular, the maximum catch weight was 126.45 kg at station A1. At stations B3 and B2, catches were less than 2 kg, more diverse and dominated by the hyperiid amphipod Themisto gaudichaudii and the euphausiid Thysanoessa macrura. These stations were sampled during the day. The largest catch (108 g) of Euphausia superba was caught at the shelf station B3 and was present at all stations except A1, but in smaller amounts (>20 g ). The most frequent species found were the myctophid fish Electrona antarctica, the siphonophore Diphyes antarctica and the hyperiid amphipod Vibilia sp.

Figure 13. The five most common macrozooplankton species from the catch in grammes (g). The smallest circle represents catches less than 100 g.

A total of 160 individual E. superba were length measured and staged. The mean body length was 47.0 mm (SD: 5.0), with a range between 32.5 – 55.7 mm (Figure 11). The demographic composition was dominated by adult females F3A (25.6%) and F3B (17.5%), and males M3B (16.9%) (Table 2).

Figure 14. Length distribution of E. superba caught during the survey.

Table 2. Sexual maturity stages of E. superba, number of observations (N), proportion (%), mean and range (MM) of body length. F: females, M: males, TL: total length, SD: standard deviation. Maturity stages according to Makorov and Denys (1981).

Due to the limited spatial coverage and relatively small number of samples collected during this survey, results should be considered preliminary. Chl a concentrations showed variability between stations, indicating spatial heterogeneity in phytoplankton biomass across the study area. These patterns are consistent with the observed variability in hydrographic conditions and may contribute to explaining the distribution of krill detected acoustically.

Tissue samples from mesopelagic fish were successfully collected and archived for subsequent isotope analysis, but laboratory results are not yet available. These analyses are expected to provide valuable insights into trophic linkages once completed.

3.2 - Fin and Humpback whale density estimates

Due to the premature end of the survey and sea ice conditions only a fraction of the survey stratum could be covered. Density estimates based on this data are not valid for the entire stratum.

We calculated the density and abundance estimates for fin and humpback whales from the limited data to give an indication of their presence in the area. Standard line transect distance sampling methods (Buckland et al., 2001) were used to analyse the fin and humpback whale sightings data using the Distance and mrds packages (Thomas et al., 2010, Miller et al., 2019) for the R language. We fitted a series of half-normal detection functions with a truncation distance of 4000 m to the observations from all survey years, setting year as co-variable.

For the 2026 survey the effective strip width was 820m.  Fin and humpback whale abundance was estimated using a Horvitz-Thompson estimator. For the 2026 survey the fin whale density in the SOF-N stratum was estimated as 0.63 ind. m-2 (0.34 – 1.21 95% confidence intervals) and humpback whale density as 0.12 ind. m-2 (0.04 - 0.12 95% confidence intervals).

Figure 15. Map of observations efforts and marine mammal sightings. Blue tracks mark the observation effort, circles the species and group size of the sightings. Background map from IBSCO v2.  

Table 3. Summary of observed species.

This work is financed by the project KRILL (IMR, Ministry of Trade, Industry and Fisheries). We extend our gratitude to Aker Biomarine AS for providing ‘Antarctic Provider’ and its crew for disposal for this research survey free of charge. We are most grateful to the captain, officers, and crew on board for all the help provided during the cruise.

CCAMLR (Convention on the Conservation of Antarctic Marine Living Resources). (2010) Report of the 29th meeting of the scientific committee, Hobart, TAS, Australia, 25-29th October, 2010. SC-CAMLR- XXIX. CCAMLR, Hobart, TAS, Australia.

Fielding, S., Watkins, J.L., Trathan, P.N., Enderlein, P., Waluda, C.M., Stowasser, G.,  Tarling, G.A. & Murphy, E.J. 2014. Interannual variability in Antarctic krill (Euphausia superba) density at South Georgia, Southern Ocean: 1997–2013. ICES Journal of Marine Science, 71: 2578–2588.

Foote, K.G., H.P. Vestnes, D.N. MacLennan and E.J. Simmonds. 1987. Calibration of acoustic instruments for fish density estimation: a practical guide. ICES Cooperative Research Report, 144, 69 pp.

Hill SL, Atkinson A, Darby C, Fielding S, Krafft BA, Godø OR, Skaret G, Trathan P, Watkins J. 2016. Is current management of the Antarctic krill fishery in the Atlantic sector of the Southern Ocean precautionary? CCAMLR Science 23:31-51

Jensen N, Nicoll R, Iversen SA (2010) The importance of obtaining annual biomass information in CCAMLR Sub-area 48.2 to inform management of the krill fishery. WG-EMM-10/9, 5 pp

Korneliussen, R.J., Ona, E., Eliassen, I., Heggelund, Y., Patel, R., Godø, O.R., Giertsen, C., Patel, D., Nornes, E., Bekkvik, T., Knudsen, H.P., & Lien, G. (2006).The Large Scale Survey System (LSSS). Proceedings of the 29th Scandinavian Symposium on Physical Acoustics, Ustaoset, Norway

Krafft BA, Macaulay GJ, Skaret G, Knutsen T, Bergstad OA, Lowther A, Huse G, Fielding S, Trathan P, Murphy E, Choi S-G, Chung S, Han I, Lee K, Zhao X, Wang X, Ying Y, Yu X, Demianenko K, Podhornyi V, Vishnyakova K, Pshenichnov L, Chuklin A, Shyshman H, Cox MJ, Reid K, Watters GM, Reiss CS, Hinke JT, Arata J, Godø OR, Hoem N. 2021. Standing stock of Antarctic krill (Euphausia superba Dana 1850 (Euphausiacea)) in the Southwest Atlantic sector of the Southern Ocean, 2019. 2021. Journal of Crustacean Biology. 41:1-17. https://doi.org/10.1093/jcbiol/ruab046

Krafft BA, Krag LA, Knutsen T, Skaret G, Jensen KHM, Krakstad JO, Larsen SH, Melle W, Iversen SA, Godø OR. 2018a. Summer distribution and demography of Antarctic krill (Euphausia superba) (Dana, 1852) (Euphausiacea) at the South Orkney Islands, 2011–2015. Journal of Crustacean Biology. P 1-7- Doi: 10.1093/jcbiol/ruy061

Krafft BA, Skaret G, Krag LA, Pedersen R. 2018b. Antarctic krill and ecosystem monitoring survey off the South Orkney Islands in 2018. WG-EMM CCAMLR 2018/04, 32 pp.

Makorov RR, Denys CJI (1981) Stages of sexual maturity of Euphausia superba. BIOMASS Handbook No. 11, pp 1-13

Marr J (1962) The natural history and geography of the Antarctic krill (Euphausia superba Dana). In: Discovery reports vol 32. National Institute of Oceanography, Cambridge University Press, Cambridge pp 33-464

Reiss C.S., A.M. Cossio, V. Loeb and D.A. Demer 2008. Variations in the biomass of Antarctic krill (Euphausia superba) around the South Shetland Islands, 1996-2006. ICES Journal of Marine Science. 65: 497-508.

Reiss C. S., A. Cossio, J. A. Santora, K. S. Dietrich, A. Murray, B. G. Mitchell, J. Walsh, E. L. Weiss, C. Gimpel, C. D. Jones, and G. M. Watters. 2017. Overwinter habitat selection by Antarctic krill under varying sea-ice conditions: Implications for top predators and fishery management. Marine Ecology - Progress Series 568:1-16.

Skaret G, Krafft BA, Macaulay G, Knutsen T, Bergstad OA. 2019. Results from the 2019 annual acoustic krill monitoring off the South Orkney Islands. CCAMLR WG-EMM-2019/69. 8 pp.

Skaret G, Macaulay GJ, Pedersen R, Wang X, Klevjer TA, Krag LA, Krafft BA.2023. Distribution and biomass estimation of Antarctic krill (Euphausia superba) off the South Orkney Islands during 2011-2020. ICES Journal of Marine Science, 2023, 0, 1–15 DOI: 10.1093/icesjms/fsad076

Wang X., X. Yu, X. Zhao, J. Zhang, G. Fan, Y. Ying and J. Zhu. 2021. Biomass estimates of Antarctic krill around the South Shetland Islands based on surveys conducted by a Chinese fishing vessel from 2013 to 2019. WG-ASAM-2021/13.

Yu X., X. Wang, X. Zhao, J. Zhang, G. Fan, Y. Ying and J. Zhu. 2019. Time series of Antarctic krill estimates around the South Shetland Islands from 2013 to 2019. SG-ASAM-2019/04 Rev. 1.

6.1 - Mooring 1

6.2 - Mooring 2

6.3 - Mooring 3