We use cetacean sightings data collected from the northern and eastern Scotia Arc (CCAMLR Subareas 48.3 and 48.4) during the 2018/19 international synoptic krill survey to provide preliminary density and relative abundance estimates for humpback whales (Megaptera novaeangliae), fin whales (Balaenoptera physalus) and for all other baleen whale species sighted. The survey was designed to collect data on the abundance of krill and so was not optimised for deriving design-based cetacean abundance estimates, but may provide a useful means of comparing whale densities and habitat use patterns between the present day and the CCAMLR-2000 synoptic survey. Humpback whales were the most frequently sighted cetacean species during the survey (226 sightings of a total count of 495 whales) and were widely distributed east of 42.5°W in all water depths surveyed, with fin whales the next most commonly sighted species (53 sightings and a cumulative count of 76 whales). Humpback whale abundance in South Georgia (Subarea 48.3) was estimated at 20,333 (95% CI 13,988-29,555) with all baleen whales estimated at 27,143 (95% CI 19,998-36,842). Humpback whale abundance around the South Sandwich Islands (Subarea 48.4) was estimated at 10,893 (95% CI 7,818-15,178) with all baleen whales estimated at 20,699 (95% CI 16,027-26,732). Fin whale abundance over all strata was estimated at 6,002 (95% CI 4,056-8,881). The estimates for humpback whales are consistent with the high recent estimates of abundance and trend from their Brazilian wintering grounds. These new estimates of abundance can also be used to re-assess the annual impact of krill-feeding whales within the Scotia Arc ecosystem, sensu Reilly et al. (2004).

Australia plans to conduct a krill biomass survey in Division 58.4.2 East during 23 January to 25 March 2021. The survey will estimate krill biomass with a view to update the precautionary catch limit for krill. A krill observatory mooring system will also be deployed during the survey to further monitor seasonal dynamics of krill in the seasonally ice covered area. The survey is also designed to improve our understanding on the connectivity of the krill population, and overlap between krill and predators. A deeper understanding of all these factors will support the design of a tractable and sustainable long-term monitoring plan and spatial management (small-scale management unit) of the krill fishery in East Antarctica. We welcome any suggestions and comments from the Members to improve our survey. Final survey plans will be submitted to SG-ASAM and WG-EMM in 2020.

The Mapping Application for Penguin Populations and Projected Dynamics (MAPPPD) is a web-based, open access, decision support tool designed to assist scientists, non-governmental organizations, and policymakers working to meet the management objectives as set forth by The Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) and other components of the Antarctic Treaty System (ATS) (i.e., Consultative Meetings and the ATS Committee on Environmental Protection). MAPPPD was designed specifically to complement existing efforts such as the CCAMLR Ecosystem Monitoring Program (CEMP) and the ATS's Visitor Site Guidelines. The database underlying MAPPPD includes all publicly available (published and unpublished) count data on Emperor, Gentoo, Adélie, and Chinstrap penguins in Antarctica. The structure of the database is designed to allow users to determine the nature and quality of the data they wish to use for management or exploratory purposes, giving stakeholders flexibility for decision making purposes.  A front-end web interface located at www.penguinmap.com provides free and ready access to all count data, which can be downloaded in easy-to-use formats thus facilitating transfer of information to Antarctic stakeholders.

CCAMLR has endorsed the use of the Risk Assessment framework to apportion the krill catch limits in order to minimise the risk of the fishery to krill dependent predators. We plan to apply the risk assessment framework across Subarea 48.1 at various spatial and temporal scales, in order to identify the most appropriate way to spread the catch from the fishery. The risk assessment framework requires data layers describing the distribution and krill consumption by krill-dependent predators. This paper describes the progress to-date in developing the data layers to input into the risk assessment framework.

CCAMLR has endorsed the use of the Risk Assessment framework to apportion the krill catch limits in order to minimise the risk of the fishery to krill dependent predators. We plan to apply the risk assessment framework across Subarea 48.1 at various spatial and temporal scales, in order to identify the most appropriate way to spread catch limits for the krill fishery. The risk assessment framework requires data layers describing the distribution and krill consumption by krill-dependent predators. This paper describes the analysis of cetacean observations from at-sea surveys, to estimate the abundance, distribution and consumption of krill by humpback whales, to be input into the risk assessment framework. 

We discuss a number of ecological issues in relation to CCAMLR’s aspiration for managing the krill fishery at small temporal and spatial scales. We highlight that the devil is in the detail, and a lot of detail is potentially necessary for managing at these smaller scales. Much of this detail is currently lacking, or only partial; consequently, we highlight an alternative approach, closed coastal areas.

Closed coastal areas potentially protect near-shore krill-dependent predators from the impacts of fishing, augmenting CCAMLR’s existing large-scale management framework. Seasonal, or year round closed coastal buffers will alter the potential levels of catch displacement, and therefore highlights the need for coupled research to ensure fishery displacement does not become too concentrated in other vulnerable habitats.

A body of research will be fundamental to understanding how to move beyond the current harvest levels, including the implementation of regular acoustic surveys at different times of year to better inform both ecological understanding and harvesting regimes. This is important as we demonstrate that krill demand from a range of predators in near-shore coastal habitats may only be met through oceanographic flow and krill movement. Krill flux and krill behaviour remains key to increased understanding.

Repeated acoustic assessments, ongoing research, couple with closed coastal areas has the potential to lead to a new management dynamic.

The South Orkney Islands region is a key location for understanding the distribution of Antarctic krill in CCAMLR Area 48. The local krill populations support krill-dependent higher predators and krill fisheries, and the regional oceanographic circulation provides connections between the Antarctic Peninsula, the South Orkney Islands and the central Scotia Sea and South Georgia. Furthermore, the South Orkney Islands lie in the seasonal sea ice zone. Sea ice is an important overwintering habitat for Antarctic krill, and how krill use the sea ice habitat can impact their distribution. To better determine the local ecosystem dynamics in this key region requires greater understanding of the extent to which krill - sea ice interactions influence the local distribution and retention of krill. Here we present results from a modelling study that suggest that the use of the sea ice habitat by krill affects the regional and local transport pathways to and in the South Orkneys region, and the residence time of krill on the South Orkney plateau. We found that including sea ice-associated behaviour of krill in the model provides additional source regions for the South Orkney Islands krill population than when krill are advected only with ocean currents, permitting episodic transport from much of the northern Antarctic Peninsula within a 9 month time period. Sea ice-associated behaviour also reduces retention time on the South Orkney plateau, with sea ice transferring material off the shelf rapidly. Variability in the source regions and retention timescales arises from variability in the regional and local sea ice dynamics. Our results demonstrate the importance of understanding the behaviour of krill under sea ice, including how the behaviour changes in response to different sea ice conditions and as krill mature, to better resolve the connectivity of krill populations in CCAMLR Area 48.

High-latitude ecosystems are among the fastest warming on the planet. Polar species may be sensitive to warming and ice loss, but data are scarce and evidence is conflicting. Here, we show that, within their main population centre in the southwest Atlantic sector, the distribution of Euphausia superba (hereafter, ‘krill’) has contracted southward over the past 90 years. Near their northern limit, numerical densities have declined sharply and the population has become more concentrated towards the Antarctic shelves. A concomitant increase in mean body length reflects reduced recruitment of juvenile krill. We found evidence for environmental controls on recruitment, including a reduced density of juveniles following positive anomalies of the Southern Annular Mode. Such anomalies are associated with warm, windy and cloudy weather and reduced sea ice, all of which may hinder egg production and the survival of larval krill. However, the total post-larval density has declined less steeply than the density of recruits, suggesting that survival rates of older krill have increased. The changing distribution is already perturbing the krill-centred food web and may affect biogeochemical cycling. Rapid climate change, with associated nonlinear adjustments in the roles of keystone species, poses challenges for the management of valuable polar ecosystems.

The biological carbon pump drives a flux of particulate organic carbon (POC) through the ocean and affects atmospheric levels of carbon dioxide. Short term, episodic flux events are hard to capture with current observational techniques and may thus be underrepresented in POC flux estimates. We model the potential hidden flux of POC originating from Antarctic krill, whose swarming behaviour could result in a major conduit of carbon to depth through their rapid exploitation of phytoplankton blooms and bulk egestion of rapidly sinking faecal pellets (FPs). Our model results suggest a seasonal krill FP export flux of 0.039 GT C across the Southern Ocean marginal ice zone, corresponding to 17–61% (mean 35%) of current satellite-derived export estimates for this zone. The magnitude of our conservatively estimated flux highlights the important role of large, swarming macrozooplankton in POC export and, the need to incorporate such processes more mechanistically to improve model projections.

Antarctic krill, Euphausia superba, have a circumpolar distribution but are concentrated within the south-west Atlantic sector, where they support a unique food web and a commercial fishery. Within this sector, our first goal was to produce quantitative distribution maps of all six ontogenetic life stages of krill (eggs, nauplii plus metanauplii, calyptopes, furcilia, juveniles, and adults), based on a compilation of all available post 1970s data. Using these maps, we then examined firstly whether “hotspots” of egg production and early stage nursery occurred, and secondly whether the available habitat was partitioned between the successive life stages during the austral summer and autumn, when krill densities can be high. To address these questions, we compiled larval krill density records and extracted data spanning 41 years (1976-2016) from the existing KRILLBASE-abundance and KRILLBASE-length-frequency databases. Although adult males and females of spawning age were widely distributed, the distribution of eggs, nauplii and metanauplii indicates that spawning is most intense over the shelf and shelf slope. This contrasts with the distributions of calyptope and furcilia larvae, which were concentrated further offshore, mainly in the Southern Scotia Sea. Juveniles, however, were strongly concentrated over shelves along the Scotia Arc. Simple environmental analyses based on water depth and mean water temperature suggest that krill associate with different habitats over the course of their life cycle. From the early to late part of the austral season, juvenile distribution moves from ocean to shelf, opposite in direction to that for adults. Such habitat partitioning may reduce intraspecific competition for food, which has been suggested to occur when densities are 39 exceptionally high during years of strong recruitment. It also prevents any potential cannibalism by adults on younger stages. Understanding the location of krill spawning and juvenile development in relation to potentially overlapping fishing activities is needed to protect the health of the south-west Atlantic sector ecosystem.