Antarctic Marine Living Resources Research Articles

Changing the focus: The need for cross-scale dynamic management in the Southern Ocean and implications for holistic conservation of Antarctic marine living resources

The Convention on the Conservation of Antarctic Marine Living Resources (CCAMLR) establishes the regulatory framework for fisheries management and the establishment of Marine Protected Areas (MPA) in the Southern Ocean. Identifying foraging areas regularly used by penguins provides valuable information for the small-scale management of the krill fishery and the design of MPAs, currently under discussion in CCAMLR. We used geolocators to identify the areas used by Adélie penguins from Ardley Island (South Shetlands Islands) during the non-breeding season and Stable Isotope Analysis (SIA) (δ13 C and δ15 N) on feathers to study the trophic niche. Adélie penguins depended on resources available in CCAMLR subareas 48.1 and 48.5 during the post-breeding and molting stage, the subarea 48.5 during the post-molting stage and subareas 48.1, 48.2 and 48.5 during the pre-breeding stage, critical moments of the species’ annual cycle. The Domain 1, Weddell Sea and SOISS MPA proposal areas were extensively used. SIA results show the use of coastal and off-shore foraging areas in 2022, but principally off-shore areas in 2021. Adélie penguins dependence on resources from different subareas in different times of the year emphasizes the need of incorporating the temporal dimension of resources utilization when designing conservation measures in the Southern Ocean. With an increasing pressure on Adélie penguin colonies in the western Antarctic Peninsula, its long-term protection might depend on both 1) well designed and managed MPAs in the Domain 1 and the Weddell Sea, and 2) small-scale fisheries management that simultaneously consider activities undertaken in different small-scale management units.

Establishing marine protected areas in the southern ocean, lessons for the BBNJ agreement

This paper first gives a brief overview of the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR)’s struggle to establish Antarctic Marine Protected Areas (MPAs). The paper then addresses the question: what lessons can countries learn from CCAMLR’s experience in establishing high seas MPAs under the Biodiversity in Areas Beyond National Jurisdiction (BBNJ) Agreement? The paper finds that the final text of the BBNJ Agreement did largely reflect CCAMLR’s experience when it comes to MPAs. This is particularly so with respect to 1) clarification of the relationship between conservation and use; 2) the interpretation and application of a science-based precautionary approach; and 3) consensus-based decision-making process. The paper concludes that the insights CCAMLR provides for navigating geopolitical tensions between major powers is an important reference for the future operation of the BBNJ Agreement.

Evaluating the impacts of the Ross Sea region marine protected area for Antarctic toothfish (Dissostichus mawsoni) with a spatially-explicit population model

In 2016, the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) adopted what was then the world's largest marine protected area (MPA), the Ross Sea region marine protected area or “RSrMPA.” Only one fishery operates in the Ross Sea region (RSr). This fishery targets Antarctic toothfish (Dissostichus mawsoni), which has an ontogenically-segregated life-history spanning both the RSrMPA and areas fully open to fishing. Here, we present a spatially-explicit population model for RSr Antarctic toothfish, which we use to run projections to evaluate the impacts of the RSrMPA for the species. We considered six alternative scenarios, which consisted of the combination of two spatial management scenarios (MPA versus no-MPA situations) and three different spatial patterns of future fishing. The same CCAMLR decision rules were employed to determine a total catch limit in each case. Our results indicate that access to productive fishing grounds continues to exist with the RSrMPA, the total catch limit and fishery catch rates are not impacted, and the RSrMPA specific objectives relating to Antarctic toothfish are being met. The no-take fraction of the RSrMPA (the “General Protection Zones”) protects areas of ecological importance for the species (juvenile settlement areas, migration corridors for maturing individuals, and adult feeding areas), while the partial-take fraction of the MPA (the “Special Research Zone”) allows for the continuity and integrity of a critical tagging program. Our modelling framework provides valuable information to inform resource management at CCAMLR and could be employed to explore other proposed large-scale MPAs in the Southern Ocean.

The influence of Antarctic governance on marine protected areas in the Biodiversity Beyond National Jurisdiction Agreement negotiations

With the Biodiversity Beyond National Jurisdiction (BBNJ) Agreement adopted, the negotiations process left questions related to what would be included in the final text and how the BBNJ Agreement architecture would function. The Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR), an international body, has successfully established high seas marine protected areas (MPAs), a key aspect of the BBNJ Agreement. Here, we investigate if and how CCAMLR has influenced negotiations on the BBNJ Agreement and how it may influence the forthcoming structure. This work used ethnographic notes and documents from the negotiations and interviews with actors who overlapped at both the BBNJ negotiations and the CCAMLR meetings to elucidate themes of influence that CCAMLR has had on the BBNJ negotiations. We found that CCAMLR is influencing the BBNJ negotiations in several ways, including through setting precedent and as an example for lessons learned. Additionally, we found that there was a divergence of views on whether CCAMLR would be considered a competent body by the decision-making mechanism of the BBNJ Agreement to establish MPAs due to the issues CCAMLR faces on reaching consensus. We found that some aspects of CCAMLR, such as the exclusivity (i.e., restricted to only actors working within the CCAMLR space) was perceived negatively by interviewees, thus affecting the BBNJ Agreement negotiations through hidden red lines. With the BBNJ Agreement adopted, there is still the potential for CCAMLR to be an example for the BBNJ structure and to be a participant in the BBNJ Agreement architecture.

Managing for climate resilient fisheries: Applications to the Southern Ocean

Climate change is having profound effects on populations of fished species and the ecosystems on which they depend, lending to a growing body of work that advocates for climate resilience to be a priority in fishery management. Here, we provide a comprehensive analysis of the tools needed to manage for climate resiliency. The Antarctic region is among the most vulnerable to climate change, and thus, we then consider climate resilient management tools utilized by the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR), the body responsible for the management of Antarctic marine living resources as part of the Antarctic Treaty System. We note progress, gaps, and opportunities for implementation. Across the literature, ecosystem-based management was cited as an appropriate tool for climate resilience of marine ecosystems, as was the use of climate model outputs (projections and simulations), marine protected areas (MPAs), and dynamic stock assessments. CCAMLR has a unique position where its Convention effectively mandates the principles of an ecosystem-based precautionary approach for managing fisheries, and many of its Member States have been advocating for climate initiatives within this approach. While CCAMLR has made limited overall progress towards ensuring climate resilience, it has advanced in some areas, such as MPA implementation, developing a risk assessment for krill, and including statements on climate change in fishery reports, although there is much work to be done. While climate change remains a worldwide issue that must be addressed on a global scale, CCAMLR holds the responsibility for adaptively managing Southern Ocean marine living resources for climate resilience.

Commercial krill fishing within a foraging supergroup of fin whales in the Southern Ocean.

Commercial krill fishing within a foraging supergroup of fin whales in the Southern Ocean.

Circumpolar sampling reveals high genetic connectivity of Antarctic toothfish across their spatial distribution

Antarctic Toothfish are a circumpolar species which are targeted in multiple fisheries around Antarctica covering nine statistical areas within the Convention for the Conservation of Antarctic Marine Living Resources. Despite this, it is still unclear whether the species forms a single stock across its circumpolar distribution, shows a pattern of isolation by distance, or exhibits discrete stock structure between different regions. Recent genetics studies of Antarctic toothfish have shown connectivity between two areas (Ross Sea and Antarctic Peninsula), but earlier studies with smaller number of markers produced inconsistent results with regards to genetic connectivity between other geographic locations. Here we present a range-wide population genetic study of Antarctic toothfish using > 11,000 nuclear single nucleotide polymorphisms from 715 fish collected. Our results indicate that genetic diversity of the Antarctic toothfish is very low, with only 0.1% of genetic variability associated with geographic location. Multiple clustering methods, both supervised and unsupervised, indicated no distinct breeding populations. These results are consistent with current theories of egg and larval dispersal by the predominant Antarctic currents.

Advancing Antarctic climate change policy: upcoming opportunities for scientists and policymakers to work together

AbstractClimate change is increasingly affecting Antarctica and the rest of the world. Urgent policy responses are needed to mitigate its associated impacts. Engagement of the Antarctic Treaty Consultative Meeting (ATCM), Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) and Committee for Environmental Protection (CEP) with the issue of climate change has culminated in several important meetings planned for 2023/2024. Researchers play a crucial role in the provision of the best available science to inform action by Antarctic policymakers, and the Scientific Committee on Antarctic Research (SCAR) clearly will play an important role in representing the Antarctic science community and delivering the latest science into the upcoming meetings. However, recognizing the ATCM's call for Parties and other stakeholders to bring experts to its meeting to support the work and with acknowledgement by CCAMLR and CEP of the value of including a range of scientific experts, we highlight the opportunity for and importance of researchers engaging proactively to offer further bespoke scientific support. Given the urgency of addressing climate change in Antarctica and beyond, every effort is needed from researchers and policymakers to work together to facilitate the necessary policy responses at both the national and international level.

Ant-ICON - ‘Integrated Science to Inform Antarctic and Southern Ocean Conservation’: a new SCAR Scientific Research Programme

AbstractAntarctic and Southern Ocean environments are facing increasing pressure from multiple threats. The Antarctic Treaty System regularly looks to the Scientific Committee on Antarctic Research (SCAR) for the provision of independent and objective advice based on the best available science to support decision-making, policy development and effective environmental management. The recently approved SCAR Scientific Research Programme Ant-ICON - ‘Integrated Science to Inform Antarctic and Southern Ocean Conservation‘ - facilitates and coordinates high-quality transdisciplinary research to inform the conservation and management of Antarctica, the Southern Ocean and the sub-Antarctic in the context of current and future impacts. The work of Ant-ICON focuses on three research themes examining 1) the current state and future projections of Antarctic systems, species and functions, 2) human impacts and sustainability and 3) socio-ecological approaches to Antarctic and Southern Ocean conservation, and one synthesis theme that seeks to facilitate the provision of timely scientific advice to support effective Antarctic conservation. Research outputs will address the most pressing environmental challenges facing Antarctica and offer high-quality science to policy and advisory bodies including the Antarctic Treaty Consultative Meeting, the Committee for Environmental Protection and the Scientific Committee of the Commission for the Conservation of Antarctic Marine Living Resources.

Using a risk assessment framework to spatially and temporally spread the fishery catch limit for Antarctic krill in the west Antarctic Peninsula: A template for krill fisheries elsewhere

The west Antarctic Peninsula is an important breeding and foraging location for marine predators that consume Antarctic Krill (Euphasia superba). It is also an important focus for the commercial fishery for Antarctic krill, managed by the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR). Aiming to minimise ecosystem risks from fishing, whilst enabling a sustainable fishery, CCAMLR has recently endorsed a new management framework that incorporates information about krill biomass estimates, sustainable harvest rates and a risk assessment to spatially and temporally distribute catch limits. We have applied a risk assessment framework to the west Antarctic Peninsula region (Subarea 48.1), with the aim of identifying the most appropriate management units by which to spatially and temporally distribute the local krill catch limit. We use the best data currently available for implementing the approach, recognising the framework is flexible and can accommodate new data, when available, to improve future estimates of risk. We evaluated 36 catch distribution scenarios for managing the fishery and provide advice about the scale at which the krill fishery can be managed. We show that the spatial distribution with which the fishery currently operates presents some of the highest risks of all scenarios evaluated. We highlight important issues that should be resolved, including data gaps, uncertainty and incorporating ecosystem dynamics. We emphasize that for the risk assessment to provide robust estimates of risk, it is important that the management units are at a similar scale to ecosystem function. Managing the fishery at small scales has the lowest risk but may necessitate a high level of management interaction. Our results offer advice to CCAMLR about near-term management and this approach could provide a template for the rest of the southwest Atlantic (Area 48), or fisheries elsewhere. As each data layer influences the outcome of the risk assessment, we recommend that updated estimates of the distribution, abundance and consumption of krill, and estimates of available krill biomass will be key as CCAMLR moves forward to develop a longer-term management strategy.

Influence of Hydrological Factors on the Distribution of Methane Fields in the Water Column of the Bransfield Strait: Cruise 87 of the R/V “Academik Mstislav Keldysh”, 7 December 2021–5 April 2022

Within the framework of the expedition research “Complex studies of the Antarctic marine ecosystem in the areas of the transport and interaction of water masses in the Atlantic sector of Antarctica, the Scotia Sea and the Drake Strait” (cruise 87 of the R/V “Academik Mstislav Keldysh”, 7 December 2021–5 April 2022), the distribution of gas-geochemical fields of methane in the Bransfield Strait was studied in detail for the first time. The connection of the methane distribution in water with the complex hydrological regime of the strait has been revealed. Elevated values of methane concentrations brought to the Bransfield Strait in the warm current flow from the Bellingshausen Sea have been established. Low concentrations of methane also mark the cold waters of the Weddell Sea, which carry out the transit of water masses into the Atlantic Ocean. The research was carried out within the framework of the theme FWMM-2022-033 “Integrated environmental studies of the Southern Ocean” AAAA17-117030110035-4 and international obligations of the Russian Federation as a party to the Antarctic Treaty and the Convention on the Conservation of Antarctic Marine Living Resources.

Оценка биологической безопасности антарктического криля Euphausia superba (Dana, 1852) из вод Атлантического океана

The development of the Antarctic krill fishery is a promising direction of Russian food industry. Euphausia superba is the largest source of animal protein in the global oceans. According to the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR), the year of 2021 saw a steady increase in the global catch of krill. The Government of the Russian Federation approved a program for the development of the oceanic fishery for crustaceans. The assessment of its biological safety is of particular interest because the extraction of this raw material in Russia is currently undergoing a restoration process. The purpose of the study was to analyze samples of Antarctic krill E. superba for parasites and microorganisms that could affect its sanitary condition.
 The study featured the microplankton of E. superba crustaceans (n = 130) caught in 2019–2020 by the Federal Agency for Fishery. The methods included an incomplete helminthological analysis, as well as compressor, microbiological, and histological studies.
 The visual inspection, helminthological dissection, and compressor microscopy revealed no helminth larvae or protozoa. In a microbiological study for safety indicators according to CU TR 021/2011, EAEU TR 040/2016 and Sanitary Rules and Norms SanPiN 2.3.2.1078-01, the quantity of mesophilic aerobic and facultative anaerobic microorganisms (QMAFAnM) were did not exceed 1.0×103 at 37 and 25°C. Opportunistic and pathogenic microorganisms were not detected. When examining cultivate for the isolation of Staphylococci, were found Cocci, but we did not identify them. When the material was sown on the Sabouraud nutrient medium at 24°C, Penicillium microscopic fungi grew on the plates in the amount of 3.0×102. Histological examination of carapace, gills, and internal organs detected no parasitological organisms, pathological inclusions, or any tissue changes.
 The Antarctic krill contained no parasites and was microbiologically safe. After tests on Vibrio parahemolyticus and Listeria monocytogenes, it can be used in the food industry.

Two scales of distribution and biomass of Antarctic krill (Euphausia superba) in the eastern sector of the CCAMLR Division 58.4.2 (55°E to 80°E).

Regular monitoring is an important component of the successful management of pelagic animals of interest to commercial fisheries. Here we provide a biomass estimate for Antarctic krill (Euphausia superba) in the eastern sector of the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) Division 58.4.2 (55°E to 80°E; area = 775,732 km2) using data collected during an acoustic-trawl survey carried out in February and March 2021. Using acoustic data collected in day-time and trawl data, areal biomass density was estimated as 8.3 gm-2 giving a total areal krill biomass of 6.48 million tonnes, with a 28.9% coefficient of variation (CV). The inaccessibility of the East Antarctic makes fisheries-independent surveys of Antarctic krill expensive and time consuming, so we also assessed the efficacy of extrapolating smaller surveys to a wider area. During the large-scale survey a smaller scale survey (centre coordinates -66.28°S 63.35°E, area = 4,902 km2) was conducted. We examine how representative krill densities from the small-scale (Mawson box) survey were over a latitudinal range by comparing krill densities from the large-scale survey split into latitudinal bands. We found the small scale survey provided a good representation of the statistical distribution of krill densities within its latitudinal band (KS-test, D = 0.048, p-value = 0.98), as well as mean density (t-test p-value = 0.44), but not outside of the band. We recommend further in situ testing of this approach.

Krill biomass estimation: Sampling and measurement variability

Krill are the subject of growing commercial fisheries and therefore fisheries management is necessary to ensure long-term sustainability. Krill catch limits, set by Commission for the Conservation of Antarctic Marine Living Resources, are based on absolute krill biomass, estimated from acoustic-trawl surveys. In this work, we develop a method for determining an error budget for acoustic-trawl surveys of krill which includes sampling and measurement variability. We use our error budget method to examine the sensitivity of biomass estimates to parameters in acoustic target strength (TS) models, length frequency distribution and length to wetmass relationships derived from net data. We determined that the average coefficient of variation (CV) of estimated biomass was 17.7% and the average CV due from scaling acoustic observations to biomass density was 5.3%. We found that a large proportion of the variability of biomass estimates is due to the krill orientation distribution, a parameter in the TS model. Orientation distributions with narrow standard deviations were found to emphasise the results of nulls in the TS to length relationship, which has to potential to lead to biologically implausible results.

Guiding marine protected area network design with comparative phylogeography and population genomics: An exemplary case from the Southern Ocean

AbstractAimNetworks of connected marine protected areas (MPAn) are recognized as the key area‐based management tool to preserve biodiversity, moderate exploitation of marine resources and increase ecological resilience to climate change. Although population genetic studies could greatly benefit connectivity assessments between MPAs, genetic data are rarely used in MPAn planning. Here, we aim to illustrate the use of a multispecies and multilocus approach to provide recommendations for MPAn design, highlighting the importance of the species selected and the analyses performed. Our study is focused on the Southern Ocean, an area of keen multinational interest given its scientific significance, economic importance and its unique, shared legal status.LocationSouth Georgia and South Sandwich Islands MPA (SGSSI MPA), the South Orkney Islands and the Western Antarctic Peninsula (WAP)—where an MPA was proposed in 2018 (Domain 1 MPA) but has not been approved by the Commission for the Conservation of the Antarctic Marine Living Resources (CCAMLR).MethodsOur datasets include 819 individuals from five different species with contrasting life‐history strategies: two nemerteans (Antarctonemertes valida and A. riesgoae), two annelids (Pterocirrus giribeti and Neanthes kerguelensis) and one sponge (Mycale [Oxymycale] acerata). To identify genetic connectivity patterns in our study area, spanning roughly 2500 km, we used the COI mitochondrial marker and genome‐wide ddRADseq‐derived SNPs.ResultsA consistent lack of connectivity between SGSSI MPA and the WAP was found for all studied species. Additionally, our data indicated a stepping‐stone role for the South Orkney Islands between these two genetically differentiated regions.Main conclusionsOur results reveal how the application of comparative phylogeography and population genomics can guide policymakers in their decision‐making process during MPAn design. We detected priority areas for conservation in Antarctica, including the South Orkney Islands and the WAP, providing strong evidence for the implementation of the Domain 1 MPA.

Research funding and economic aspects of the Antarctic krill fishery

The Antarctic krill fishery has increased in recent years to more than two-thirds of an interim catch level of 620,000 tonnes in the Atlantic Sector, FAO Fishery Area 48. Members of the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) have expressed concern that catches at these levels, if taken from small areas, could impact krill-dependent predators. In recent years, CCAMLR has been unable to agree on small-scale spatial management measures influencing the spatial distribution of krill catch. Some krill-fishing Members contend that more science is needed as CCAMLR is obliged to use the precautionary approach informed by the best available science. The availability of scientific information is dependent on funding and these considerations should be included in decision-making to ensure the costs for the necessary research to manage the fishery will be met. In this article we review the economics of the Antarctic krill fishery, the beneficiaries of the fishery, the costs of producing the scientific information currently available and the extent of current contributions. Based on this analysis, we propose that CCAMLR Scientific Committee designs a research strategy for the krill fishery in which research needs are identified, costed and implemented. This should include a funding mechanism to sustain these research activities and ensure appropriate contributions from those benefiting from the fishery.

A Summary of United States Research and Monitoring in Support of the Ross Sea Region Marine Protected Area

Due to the remarkable ecological value of the Ross Sea, the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) adopted a large-scale Ross Sea region marine protected area (RSRMPA) in 2016. Since then, many CCAMLR Members have conducted research and monitoring in the region. In 2021, the U.S. Ross Sea science community convened a workshop to collate, synthesize, and coordinate U.S. research and monitoring in the RSRMPA. Here we present workshop results, including an extensive synthesis of the peer-reviewed literature related to the region during the period 2010–early 2021. From the synthesis, several things stand out. First, the quantity and breadth of U.S. Ross Sea research compares to a National Science Foundation Long Term Ecological Research project, especially involving McMurdo Sound. These studies are foundational in assessing effectiveness of the RSRMPA. Second, climate change and fishing remain the two factors most critical to changing ecosystem structure and function in the region. Third, studies that integrate ecological processes with physical oceanographic change continue to be needed, especially in a directed and coordinated research program, in order to effectively separate climate from fishing to explain trends among designated indicator species.

Voluntary actions by the Antarctic krill fishing industry help reduce potential negative impacts on land-based marine predators during breeding, highlighting the need for CCAMLR action

Abstract The Commission for the Conservation of Antarctic Marine Living Resources is responsible for management of the Antarctic marine ecosystem, including its living resources. The Commission has yet to implement precautionary measures that protect predators dependent upon Antarctic krill from potential food competition with fisheries where these now increasingly spatially aggregate. Here, we describe voluntary buffer zones (VBZ) implemented in 2018 by the Association of Responsible Krill harvesting companies (ARK) following negotiations with environmental NGOs. The VBZ now prohibit krill fishing during the penguin-breeding season around important penguin colonies along the Antarctic Peninsula. We describe the background of the VBZ and further actions that would ensure ongoing ecological benefits. Lack of data and delays in the implementation of the Commission's revised krill fishery management framework continue to concern NGOs and other stakeholders, especially as part of the management framework will expire in November 2022. Without action by CCAMLR, the ARK VBZ will be the only regulation providing precautionary protection at relevant spatial and temporal scales. The VBZ are an example of how responsible industry can help to protect marine ecosystems when regional management is unable to act given lack of data, and/or associated legal and political constraints.

Applying Marine Protected Area Frameworks to Areas beyond National Jurisdiction

Marine protected areas (MPAs) can provide a range of ecological benefits. Frameworks—including the IUCN protected area categories and The MPA Guide—offer tools towards evaluating an MPA’s objectives, types, Level of Protection, and potential effectiveness. However, the majority of MPAs exist in national waters, raising the question of how these frameworks apply in areas beyond national jurisdiction (ABNJ). We evaluated the existing ABNJ MPAs in the Antarctic designated through the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) using the two above mentioned frameworks. The newly released The MPA Guide, which complements guidance from the IUCN protected area categories, provides perhaps the most exhaustive framework as it seeks to evaluate implementation, enabling conditions, and outcomes. The CCAMLR MPAs ranged from Category 1A (for IUCN)/Highly Protected (for The MPA Guide) to Category IV (for IUCN)/Lightly Protected (for The MPA Guide) due to differences in management objectives and activities occurring within the zones of the MPAs. Given ongoing negotiations for a new international, legally binding treaty for high seas biodiversity, evaluating an MPA using these existing frameworks will prove useful to allow for a full comprehensive picture of an MPA and what it can expect to achieve.

Contrasting life-history traits of two toothfish (Dissostichus spp.) species at their range edge around the South Sandwich Islands

The South Sandwich Islands (SSI), a chain of volcanic islands in the Atlantic sector of the Southern Ocean, are home to two large notothenoid species: the Patagonian toothfish Dissostichus eleginoides and the Antarctic toothfish Dissostichus mawsoni. Both species support valuable fisheries throughout the Southern Ocean under management of the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR). The SSI region, which is located south of the Southern Antarctic Circumpolar Current Front, has a diverse and distinct biodiversity and it represents a range edge for the distribution of both toothfish species. In this paper we have updated and expanded previous biological analyses with recent data, explored the stock hypotheses and links of these species to other regions, and investigated the role of the SSI archipelago in the life cycles of both toothfish species, where they overlap in their distribution. We conclude that Patagonian toothfish around the SSI are linked to the adjacent South Georgia population, but have some unique characteristics, including faster growth and better somatic condition, possibly reflecting ‘Bergmann's rule’ which states that body size increases with decreasing temperature and increasing latitude. By comparison, the Antarctic toothfish at the SSI appear to be the northern extent of a larger stock connecting further south towards the Antarctic continent. Finally, we consider the relative importance of the SSI in the life cycle of both species, including in the context of climatic changes to this region.