CCAMLR

Acoustic and net sampling of Antarctic Krill and other euphausiids was conducted at 88 stations around the South Shetland Islands during a 30 day cruise between 10 August and 9 September 2013. Abundance and demographic patterns revealed that Antarctic krill were concentrated in the southern Bransfield Strait, and that these krill were approximately 33mm in length, about 10mm larger than found during the 2012 winter survey (Reiss and Jones 2013; WG-EMM 13/40) but similar in size to krill found in the German survey during summer in 2013 (Siegel 2013; WG-EMM 13/24). Large krill (>50mm), although present around Elephant Island, were not abundant in any area, and were also not abundant in the water column between 170 and 650m depth in the Antarctic Circumpolar Current. Sea ice extent and concentration was expansive (north of 60 S around Elephant Island) and the sea ice concentration was mostly more than 50%. Observations of birds and mammals showed that many species were found in southwestern Bransfield Strait, associated with the high concentrations of krill, an area targeted by the krill fishery in recent years. Species of note included Crabeater seals, Antarctic fur seal (sub-Adults), Leopard seal, and Adelie penguins. The high abundance of predators and prey in the Bransfield Strait, where the krill fishery is prosecuted into autumn, suggests that overlap between krill dependent predators and the fishery extends throughout the post reproductive period of many higher predators. Such overlap could impact the overwinter survival of predators if the fishery extracts prey from hotspots during autumn.

In June 2014, the ICED programme, the British Antarctic Survey and WWF co-hosted a two day workshop entitled “Understanding the objectives for krill fishing and conservation in the Scotia Sea and Antarctic Peninsula region” which involved participants from the science, conservation and fishing industry sectors. This report summarises the key initial conclusions and recommendations from the workshop. There is broad cross-sector commitment to maintaining a healthy ecosystem and support for management of the krill fishery that minimises the risk of the fishery negatively impacting ecosystem health. This accord could be strengthened by articulating a clear research and development strategy to support progress in the management of the krill fishery; broadening participation in WG-EMM to include other sectors and areas of expertise; and improving the availability of key information to all sectors.

We report on the first global census of the Adélie Penguin (Pygoscelis adeliae), achieved using a combination of ground counts and satellite imagery, and find a breeding population 53% larger (3.79 million breeding pairs) than the last estimate in 1993. We provide the first abundance estimates for 41 previously unsurveyed colonies, which collectively contain 420,000 breeding pairs, and report on 17 previously unknown colonies. We think 11 of these previously unknown colonies may be recent colonizations. These recent colonizations represent approximately 5% of the increase in known breeding population and provide insight into the ability of these highly philopatric seabirds to colonize new breeding territories. Additionally, we report on thirteen colonies not found in the survey, including eight we conclude have gone extinct. Our global population assessment provides a robust baseline for understanding future changes in abundance and distribution, and finds that Adélie Penguin declines on the Antarctic Peninsula are more than offset by increases in East Antarctica. These results represent a critically-needed contribution to ongoing negotiations regarding the design and implementation of Marine Protected Areas for the Southern Ocean.

We present preliminary analyses of krill fishery catch data covering the period December 2000 to November 2013. We show that fishing vessels in Subareas 48.2 and 48.3 are conservative in their behaviour, targeting fixed geographic locations in most years. In contrast, in Subarea 48.1, fishing locations show considerable variability between years. In Subarea 48.2 ice cover tends to increase rapidly from mid May, often extending to cover the whole core fishing area, forcing the fishery to relocate by late June. Much of the effort relocates to Subarea 48.3, where the shelf and shelf-break fishing areas are normally ice free throughout the winter. In Subarea 48.1 ice cover begins to increase earlier (often in April) but it increases more gradually and rarely covers the whole core fishing area. This often allows fishing to late June and, sometimes, throughout the winter. Overall, the mean catch location in Subarea 48.1 has shifted in recent years with most catch being taken south of the South Shetland Islands since 2008/09 in contrast to earlier years when the mean catch location was always to the north and west of the South Shetlands. We will continue to explore the relationship between catch location and ice dynamics during the inter-sessional period.

This paper, now in press in ICES Journal of Marine Science, presents krill density estimates for a 17 year time series of acoustic surveys of the Western Core Box at South Georgia.  Krill targets were identified in acoustic data using the approved CCAMLR protocol, that is using a multi-frequency identification window and converted to krill density using the Stochastic Distorted-Wave Born Approximation (SDWBA) target strength model. Krill density ranged over several orders of magnitude (0 to 10 000 g m^-2) and its distribution was highly skewed with many zero observations. Within each survey the mean krill density was significantly correlated with the top 7% of the maximum krill densities observed. Hence, only the densest krill swarms detected in any one year drove the mean krill density estimates for the WCB in that year. WCB krill density (µ, mean density for the area) showed several years (1997-8, 2001-2003, 2005-2007) of high values (µ > 30 g m^-2) interspersed with years (1999-2000, 2004, 2009-2010) of low density (µ < 30 g m^-2). This pattern showed three different periods, with fluctuations every 4 to 5 years. Cross correlation analyses of variability in krill density with current and lagged indices of ocean (Sea Surface Temperature, SST) and atmospheric variability (Southern Annular Mode, SAM and El Niño/Southern Oscillation, ENSO) found the highest correlation between krill density and winter sea-surface temperature (August SST) from the preceding year. A quadratic regression (r² = 0.42, P<0.05) provides a potentially valuable index for forecasting change in this ecosystem.

In addition to the paper, we present an additional table (Table 0) which takes the values of krill density from the paper, derives the total krill biomass for the survey area and provides commercial krill catches for SSMUs within subarea 48.3. Note that commercial catches within SGW are very small in comparison to the biomass in the WCB and even total commercial catch in subarea 48.3 is frequently less than 10% of the biomass within the WCB.

This paper outlines plans for a co-ordinated, multi-national study focusing on the krill-based ecosystem in Area 48 during the 2015-16 austral summer. The studies will include at-sea data collection from research and fishing vessels, together with remotely sensed data obtained from moorings and gliders, with links to land-based predator foraging behaviour, diet and reproductive success. The aims of this note are both to inform CCAMLR members of the proposed activities and also to stimulate any additional participation of members in this developing study.

This paper presents a description of the statistical approach developed to estimate abundance of Antarctic fur seals at South Georgia. The estimate is based on photographic counts of all the breeding beaches in the fur seal’s distribution range. The images were obtained during comprehensive helicopter surveys conducted during 2006 and 2008. The proposed Bayesian analysis scales up in situ counts to total population size carrying over multiple sources of uncertainty from estimates of proportions of unobserved animals.

Many of the key oceanographic and ecological processes that determine the structure and functioning of ecosystems in the regions around South Georgia and the South Orkney Islands operate over small scales of <10 km.  This paper reports the initiation of a project to develop high-resolution hydrodynamic models that will be used to examine the detailed oceanography of the South Georgia and South Orkney Islands shelves and surrounding regions.  The models will be based on the NEMO-Shelf model, with the capability to resolve tides, atmospheric forcing, and sea ice processes, and with a ~3 km horizontal resolution.  They will provide a numerical basis for detailed examination of the controls on the distribution of krill and fish around the islands, their interactions with predators and availability to fisheries.  Such detailed analyses will help inform WG-EMM activities aimed at developing spatial and feedback management procedures.

The ICED programme is investigating how climate change might impact Southern Ocean ecosystems in order to help inform management of Southern Ocean fisheries. As part of this ICED convened a workshop in November 2013 on “Southern Ocean food webs and scenarios of change”, and is currently preparing an academic paper detailing the outputs, which are summarised here. ICED recognises the key role for CCAMLR in improving the basis for future monitoring and management of Southern Ocean ecosystems, and encourages active two-way engagement between the scientific community and CCAMLR.

Within Drake Passage, the southern flank of the Antarctic Circumpolar Current (ACC) hosts the ventilation of deep water, the injection of Antarctic shelf waters and interactions between westward and eastward boundary cur rents. This exchange is explored through the trajectories of forty surface drifters released in January 2012 in the northwestern Weddell Sea. The drifters detail Lagrangian transport pathways between the eastern Antarctic Peninsula and sites of elevated chlorophyll in the Scotia Sea. ACC frontal currents, in particular the  Southern ACC Front, act as dynamical transport barriers to the drifters and influence surface chlorophyll distributions, indicating that ACC fronts partition Weddell source waters in the Scotia Sea. Interannual fluctuations in surface chlorophyll in the south Scotia Sea and the northern Weddell Sea covary. This suggests that Scotia Sea ecosystem dynamics are linked to water properties injected from the tip of the Antarctic Peninsula and respond to Weddell Gyre circulation changes.