Ireland has a rich Antarctic history, with Bransfield, Crozier, Shackleton, Crean and others acting as key Irish individuals in Antarctic exploration. Recognized as a source of Irish national pride, memorials, stamps, coins and a government research vessel all commemorate their polar feats. Today, a large proportion of Ireland's citizens visit the Antarctic region and Irish researchers produce high levels of academic outputs on Antarctic topics relative to many other nations. However, Ireland has not acceded to any Antarctic Treaty System instruments, despite a 20 year campaign to do so by cross-party Irish politicians. Ireland has the largest population of any nation in the European Union (EU) yet to accede to the Treaty and is much larger than some existing Treaty signatory states. However, Treaty accession provides no entitlement to participate in Antarctic governance, which is reserved for Consultative Parties, and therefore undertaking the associated legal and administrative work may be considered a poor use of available resources. Ireland's attainment of consultative status would be an even more complex and resource-intensive goal, but collaboration with the EU and other global partners could be a cost-effective solution that may also indirectly support Ireland's ambitions for Observer status at the Arctic Council.

Sea ice is the major constraint on human activities in the Southern Ocean. Depending on a vessel's ice class, human mobility may be restricted or even prevented altogether by sea-ice conditions. This may imply limited access to research or monitoring stations, preferred fishing grounds or attractive tourist sites. Here, we introduce a statistical model that evaluates the sea-ice cover with two measures: 1) accessibility (i.e. the probability that a given area is navigable by vessels at a given time) and 2) repeated accessibility (i.e. the probability that a given area is navigable by vessels at a given time and again at least once within a defined timespan). We use daily sea-ice concentration data from 2002 to 2020 to demonstrate this tool and its functioning regarding the spatiotemporal variability of sea-ice cover in the wider Weddell Sea region. These findings reflect known characteristics of sea-ice distribution and dynamics in the Weddell Sea, confirming the functionality of our simple tool for determining repeated accessibility of certain areas. Such a tool may facilitate the planning of research and monitoring activities in the Southern Ocean, as well as in Arctic seas.

Several recent papers have criticized the scientific robustness of the fisheries management system used by the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR), including that for Ross Sea toothfish. Here we present a response from the wider CCAMLR community to address concerns and to correct some apparent misconceptions about how CCAMLR acts to promote conservation whilst allowing safe exploitation in all of its fisheries. A key aspect of CCAMLR’s approach is its adaptive feedback nature; regular monitoring and analysis allows for adjustments to be made, as necessary, to provide a robust management system despite the statistical uncertainties inherent in any single assessment. Within the Ross Sea, application of CCAMLR’s precautionary approach has allowed the toothfish fishery to develop in a steady fashion with an associated accumulation of data and greater scientific understanding. Regular stock assessments of the fishery have been carried out since 2005, and the 2013 stock assessment estimated current spawning stock biomass to be at 75% of the pre-exploitation level. There will always be additional uncertainties which need to be addressed, but where information is lacking the CCAMLR approach to management ensures exploitation rates are at a level commensurate with a precautionary approach.

Krill consumption by natural predators represents a critical link between surveys and models of standing krill biomass and the design of a sustainable krill fishery for the Scotia Sea. Antarctic krill (Euphausia superba) is a significant component of diet for penguins breeding in this region and, consequently, uncertainties regarding penguin population abundances contribute to uncertainties in krill predation estimates. We use a comprehensive database of Antarctic penguin abundances to identify 14 breeding colonies that contribute most significantly to uncertainty regarding the total number of pygoscelid penguins breeding in this region. We find that a high quality survey of Zavodovski Island alone would decrease uncertainty in total population by 24.8%, whereas high quality surveys of all 14 “high-influence” locations would decrease uncertainty by almost 72%. Updated population estimates at these sites should be considered top priority for future fieldwork in the region. Our results are based on a robust quantitative method for assessing data priorities in estimating krill consumption that is easily extended to other groups of krill predators.

Muscle tissue samples were collected from Antarctic toothfish (Dissostichus mawsoni Norman) and Patagonian toothfish (D. eleginoides Smitt) in 1998 and from D. mawsoni and three of its prey species - Whitson's grenadier (Macrourus whitsoni (Regan)), ice fish (Chionobathyscus dewitti Andriashev & Neyelov), and blue antimora (Antimora rostrata (Günther)) - in 2006 to determine their mercury. Mercury levels were highly variable both within and between the five species studied but were positively correlated with fish length in four of the species. Once the factors length and year had been accounted for, the mercury levels in D. eleginoides were more than four times greater than in D. mawsoni. The low levels of mercury in D. mawsoni relative to its prey species and the four-fold difference in mercury concentrations between it and D. eleginoides were unexpected. Reasons for these different levels of bioaccumulation were explored including differences in diet, growth and longevity, and location. Differences in bioaccumulation between the two toothfish species could be explained partly through differences in their geographic distribution and differences in trophic position. However, the low levels of mercury in D. mawsoni relative to its prey species can only be explained by a lower rate of mercury assimilation and/or a higher rate of mercury elimination by D. mawsoni.

In this paper we review evidence for, and anticipated consequences of, climate change in Antarctic marine communities, examining the potential impacts on invertebrates and vertebrates alike and exploring plausible outcomes for species, with examples principally from the Antarctic literature. We suggest that industries with the greatest potential to aggravate climate change impacts on marine communities are marine capture fisheries. In the Southern Ocean, harvesting is governed under the Convention for the Conservation of Antarctic Marine Living Resources (CCAMLR). CCAMLR espouses an ecological management framework and so has the capacity to mitigate harvesting impacts such that they do not worsen impacts from climate change. We discuss some of the implications of climate change and advocate that CCAMLR address certain key issues if it is to fulfil its international obligations. It will be essential for CCAMLR to determine relative risks (uncertainties), impacts and timescales, of various processes consequent on climate change. Such risk assessments should be feasible with current knowledge and should provide a focus for future work. We believe it will be important to prioritize issues that reduce impacts and uncertainties by the greatest degree, and propose that future plans should involve shared responsibility (e.g. with SCAR etc.) for each of the risks described.

Uncertainty exists over the importance of Antarctic toothfish (Dissostichus mawsoni) as prey of top predators in the Ross Sea. In this paper we assess relative weight given to direct, observational evidence of prey taken, as opposed to indirect evidence from scat and biochemical analysis, and conclude that toothfish are important to Weddell seals (Leptonychotes weddellii). The seals eat only the flesh of large toothfish and therefore they are not detected in scat or stomach samples; biochemical samples have been taken from seal sub-populations where toothfish seldom occur. Using direct observations of non-breeding seals away from breeding haulouts in McMurdo Sound, 0.8–1.3 toothfish were taken per day. Based on these and other data, the non-breeding portion of the McMurdo Sound seal population, during spring and summer, consume about 52 tonnes of toothfish. Too many unknowns exist to estimate the non-trivial amount consumed by breeders. We discuss why reduced toothfish availability to Weddell seals, for energetic reasons, cannot be compensated by a switch to silverfish (Pleuragramma antarcticum) or squid. The Ross Sea toothfish fishery should be reduced including greater spatial management, with monitoring of Weddell seal populations by CCAMLR. Otherwise, probable cascades will lead to dramatic changes in the populations of charismatic megafauna.

Antarctic krill has been studied for many decades, but we are still long way from understanding their biology to be able to make reliable predictions about the reaction of their populations to environmental change. This is partly due to certain difficulties in relation to logistics, operations and survey design associated with scientific surveys that have been obstacles for us to better understand krill biology. The krill fishery is the largest fishery in the Southern Ocean, continuously operating since early 1970s. Recent studies revealed its potential to be used as a unique source for scientific discussions to understand krill biology. In this paper, after a brief overview of krill fishery operation and krill biology, we examine how current data collection through the fishery operation could contribute to a greater understanding of krill biology, and then suggest future priorities for fisheries-related research in relation to recent changes in the Southern Ocean environment.

Man's activities have impacted on the Southern Ocean ecosystem for more than 200 years. The exploitation of Southern Ocean resources has followed the same pattern as in other parts of the World Ocean with exploitation starting at the highest trophic levels when seals and whales were taken in the 19th and 20th centuries. After serious over-exploitation of these groups attention moved down the food web to begin exploitation of fish and krill from the late 1960s onwards. The establishment of international management regimes for whales (International Whaling Convention) in 1948 and the remaining marine resources (Convention for the Conservation of Antarctic Marine Living Resources) in 1982 were based on different perceptions of management, the former only considering management by species whilst the latter adopted management at an ecosystem level. These fundamentally different approaches, together with major political interference, have resulted in very different outcomes for management. The Scientific Committee of the IWC developed a sustainable management system, the Revised Management Procedure, in the first half of the 1990s which, however, is still awaiting inclusion into an overall management regime, the Revised Management Scheme, and its acceptance by the Commission. The IWC is now paralysed by political agendas that have nothing to do with scientific management. In contrast, after an early period of slow progress, CCAMLR has improved its performance substantially from the beginning of the 1990s onwards and is now hailed worldwide for its ecosystem approach to sustainable management.

The ecosystem approach to fisheries recognises the interdependence between harvested species and other ecosystem components. It aims to account for the propagation of the effects of harvesting through the food-web. The formulation and evaluation of ecosystem-based management strategies requires reliable models of ecosystem dynamics to predict these effects. The krill-based system in the Southern Ocean was the focus of some of the earliest models exploring such effects. It is also a suitable example for the development of models to support the ecosystem approach to fisheries because it has a relatively simple food-web structure and progress has been made in developing models of the key species and interactions, some of which has been motivated by the need to develop ecosystem-based management. Antarctic krill, Euphausia superba, is the main target species for the fishery and the main prey of many top predators. It is therefore critical to capture the processes affecting the dynamics and distribution of krill in ecosystem dynamics models. These processes include environmental influences on recruitment and the spatially variable influence of advection. Models must also capture the interactions between krill and its consumers, which are mediated by the spatial structure of the environment. Various models have explored predator-prey population dynamics with simplistic representations of these interactions, while others have focused on specific details of the interactions. There is now a pressing need to develop plausible and practical models of ecosystem dynamics that link processes occurring at these different scales. Many studies have highlighted uncertainties in our understanding of the system, which indicates future priorities in terms of both data collection and developing methods to evaluate the effects of these uncertainties on model predictions. We propose a modelling approach that focuses on harvested species and their monitored consumers and that evaluates model uncertainty by using alternative structures and functional forms in a Monte Carlo framework.

The marine resources of the Antarctic region are of global significance. In managing Southern Ocean marine resources, especially fisheries, the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) has adopted principles that aim: to balance harvesting and conservation; to protect the needs of dependent species, and to avoid changes that are irreversible in 20–30 years. CCAMLR has pioneered ecosystem approaches to fishery and environmental management, through the incorporation of precaution and uncertainty into its management procedures and by establishing an ecosystem monitoring programme using indicator species and processes. This pioneering application of precautionary and ecosystem approaches in the management of harvesting has met with some success, notably in applying conservative yield models for toothfish and krill stocks and in establishing strict rules for undertaking new and exploratory fisheries. However, toothfish management has been recently compromised by Illegal, Unreported and Unregulated (IUU) fishing which is driven by forces outside the Southern Ocean. Southern Ocean harvestable resources are also subject to other global forces such as environmental changes, and their management systems remain very vulnerable to rapid shifts in worldwide fishery economics, and to inadequate management in adjacent areas, particularly high seas. CCAMLR needs quickly to develop the basis of more flexible and effective management to cater for rapid shifts in capacity and demand. The complementary task, however, is to raise the management standard of other Regional Fisheries Management Organisations (RFMOs) to those of CCAMLR if global high seas marine resources are to be sustainable for the rest of this century.

Samples of Chaenocephalus aceratus (Lönnberg) were collected during a trawl survey carried out around the South Shetland Islands in January–February 2002. Fish were caught by commercial bottom trawl fishing down to 500 m depth, using a stratified randomized sampling design. As observed in other recent surveys within the same area, C. aceratus represented one of the predominant species. Overall, 357 specimens ranging from 13 and 67 cm (TL) were selected for the present study. Ages were estimated by counting annuli present in the sagittal otoliths, exposed by grinding and polishing along their sagittal plane. To estimate the precision of age data, we compared blind readings by readers from different institutions. The age range was 1–17 years for females and 1–15 years for males. Von Bertalanffy growth curves were fitted to the estimated age-length data for each sex. The estimated values of asymptotic length L∞ (cm) and K (year−1) were respectively 79.8 and 0.07 for females and 60.0 and 0.09 for males. The growth performance index ranged between 2 and 2.5, similar to that reported in other icefish. Sexual maturity was attained by females and males at about 10 and 9 years old respectively, at about 60% of their maximum estimated age. These results are compared with age and growth data available in the literature for C. aceratus, and discussed in the light of recent commercial exploitation.

Commercial krill fishing has been undertaken in the Southern Ocean for twenty years. Recently the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) introduced a reporting scheme to summarize catch data from half degree of latitude by one degree of longitude rectangles. These data demonstrate that commercial fishing in the southwest Atlantic is concentrated in the shelf zone. Certain krill predators are also restricted to this area whilst collecting food for their young during the summer. Krill fishing takes place year round, moving northwards in winter as the ice edge advances.

Dissostichus eleginoides spawn over the continental slope from June to September. The eggs, 4.3–4.7 mm diameter, were found in the upper 500 m of the water column over waters 2200–4400 m deep. Incubation of eggs is likely to take about three months. Hatching is probably in October/November. Embryos in egg development stages III and IV are described. Scales are not present until the fish are about 64–74 mm long.

The Convention on the Conservation of Antarctic Marine Living Resources states as part of its objective the maintenance of ecological relationships and the prevention of irreversible changes to the ecosystem. The Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) has implemented an Ecosystem Monitoring Programme (CEMP) for the Antarctic marine environment to give effect to this requirement. The design phase of the programme took three years. The programme has been fully implemented since 1987 and involves monitoring selected predator, prey and environmental indicators of ecosystem performance. The central aim of the programme is the detection of changes in these indicators and the interpretation as to whether these changes are due to natural events or the harvesting of marine living resources. The core of the programme is the acquisition, centralised storage and analysis of standardised monitoring data combined with a strong emphasis on empirical and modelling based research. This both modifies the monitoring approach in line with changing requirements and creates a sound scientific background against which to test the effects of management options on components of the Antarctic ecosystem. The development of procedures for translating monitoring results into management advice is a critical part of the programme. Management takes the form of the regulation of fishing activities. Since 1987 CEMP has collected data on six bird and seal species at 15 sites around the Antarctic. Up to 14 parameters of predator performance and 10 parameters of prey and environmental performance are collected at each site. The data sets collected by CEMP form an extremely powerful tool for understanding and managing the Antarctic marine ecosystem.