This paper is a revised version of WG-EMM-15/28, which uses a question and answer format to explain the management of the Antarctic krill (Euphausia superba) fishery in the subareas 48.1 to 48.4, and current knowledge about the state of the regional krill stock. The revisions provide a new, precautionary assessment of exploitation rate in this fishery. The effective regional catch limit (or “trigger level”), established in 1991, is 0.62 million tonnes year^-1, equivalent to ~1% of the regional biomass estimated in 2000. Additional subarea catch limits were established in 2009. There is some evidence for a decline in the abundance of krill in the 1980s, but no evidence of further decline over more recent decades. Biomass indices from local monitoring programmes established in the 1990s and 2000s also show no evidence of a further decline. Extrapolation from these local monitoring programmes provides conservative estimates of the regional biomass in recent years. This suggests that the trigger level would be equivalent to a long-term exploitation rate (catch divided by biomass) of <7%, which is below the 9.3% level considered precautionary for Antarctic krill. However, the permitted exploitation rate in each subarea, derived from the subarea catch limit, appears to exceed this level in up to 20% of years due to high variability in krill biomass indices. The actual exploitation rate in each subarea has remained <3% because annual catches have been <50% of the regional trigger level since 1991. The subarea catch limits help prevent higher exploitation rates.  The CAMLR Commission also needs to manage the risk of adverse impacts on the ecosystem which might occur as a result of climate change or concentrated fishing in sensitive areas. Frequent assessment of the krill stock will enhance the Commission’s ability to manage these risks. Continuing the local monitoring programmes will provide valuable information on krill variability, but more information is required on how the monitored biomass relates to biomass at the subarea scale. The most effective means to acquire this information is likely to be through the use of fishing vessels to collect data.

This paper briefly describes the rationale and structure of the research cruise that formed a key component of the co-ordinated, multi-national South Orkney Ecosystems Studies focusing on the krill-based ecosystem in the main fishing area in Subarea 48 undertaken in the austral summer of 2015-16. The research cruise consisted of collection of at-sea data on the distribution, abundance and behaviour of krill and its predators across a range of temporal and spatial scales using acoustics, nets and cameras. The research vessel data are linked to complementary studies undertaken from a commercial fishing vessel and field camps on Monroe Island, Powell Island and at Signy where satellite tracking of penguins and fur seals was undertaken. Taken together these data sets and the expected outputs will provide key information on important interactions between krill, krill predators and the commercial fishery that will be an important contribution to developing feedback management strategies.

The ability of Antarctic krill Euphausia superba Dana to withstand the overwintering period is critical to their success. Laboratory evidence suggests that krill may shrink in body length during this time in response to the low availability of food. Nevertheless, verification that krill can shrink in the natural environment is lacking because winter data are difficult to obtain. One of the few sources of winter krill population data is from commercial vessels. We examined length-frequency data of adult krill (>35 mm total body length) obtained from commercial vessels in the Scotia-Weddell region and compared our results with those obtained from a combination of science and commercial sampling operations carried out in this region at other times of the year. Our analyses revealed body-length shrinkage in adult females but not males during winter, based on both the tracking of modal size classes over seasons and sex-ratio patterns. Other explanatory factors, such as differential mortality, immigration and emigration, could not explain the observed differences. The same pattern was also observed at South Georgia and in the Western Antarctic Peninsula. Fitted seasonally modulated von Bertalanffy growth functions predicted a pattern of overwintering shrinkage in all body-length classes of females, but only stagnation in growth in males. This shrinkage most likely reflects morphometric changes resulting from the contraction of the ovaries and is not necessarily an outcome of winter hardship. The sex-dependent changes that we observed need to be incorporated into life cycle and population dynamic models of this species, particularly those used in managing the fishery.

We review the state of ecological knowledge for Subarea 48.2 and suggest that the development of any new management approach based on ecological indicators is limited by the current level of relevant ecological information. We propose that there is therefore an urgent need to improve the ecological knowledge base, but identify that this will take time. We conclude that if the krill fishery in Subarea 48.2 is to expand beyond its current level, a new experimental approach must be developed that will help provide the ecological and management information needed. This paper therefore outlines one possible framework that has the potential to provide the types of information required. We suggest that the experimental framework should be a CCAMLR community project involving as many Members as possible. This will be necessary if the experimental framework is to have a high probability of success. The proposed framework identifies some of the main data requirements, including oceanographic modelling, predator monitoring, and fisheries acoustics. We propose that the experimental framework should be evaluated periodically in order to explore initial results and to determine if the framework should be continued.

We explore CCAMLR Catch and Effort data from the fishery for Antarctic krill for the period 1999/2000 to 2014/2015. We show that since 2013, both the number of hauls as well as the associated level of catch has increased in Subarea 48.1 during the penguin breeding season. We explore in detail, the fishing patterns in Subarea 48.1 during 2014/2015, showing that two areas of fishing aggregation took place, one in the Bransfield Strait and one in Hughes Bay, on the Danco Coast. The latter took place from 27 December until 28 May, over 153 days of elapsed time. During this period 4 vessels operated, collectively taking over 42,000 tonnes of krill from an area less than 30 km in diameter. The fishing aggregation comprised 3 periods of harvesting; catch rates per hour showed evidence of decline at the end of the first two periods, but were increasing at the end of the third period when the Subarea was closed having reached the Subarea trigger allocation. Though the collective catch comprised 27% of the Subarea trigger allocation, it is uncertain whether any ecological impact ensued, as there was no ecological or CEMP monitoring in the vicinity. We pose a number of questions, answers to which we believe will help WG-EMM in its deliberations related to the subdivision of harvesting and the prevention of impacts upon krill eating predators.

In this paper we consider whether the CCAMLR fishing season for Antarctic krill should start at a time of year that is based upon ecological events, rather than upon a date that is convenient for management. We review data on the breeding phenology of predators, and use data from the CCAMLR Statistical Bulletin (Version 28) to explore whether there are times of year that would reduce the potential for competition between land-based krill-eating predators and the fishery.

The marine ecosystem associated with the ocean shelves around South Georgia and the South Orkney Islands is highly productive, with a history of commercial exploitation. Many of the key oceanographic and ecological processes that determine the structure and functioning of this ecosystem operate over small scales of <10 km. Historically, these fine spatial scales have been poorly represented in numerical models. Here we describe the development of two regional ocean models that will be used to examine the detailed oceanography of the South Georgia and South Orkney Islands shelves and surrounding regions. The models are regional applications of NEMO with a ~3 km horizontal resolution, and include key physical processes of relevance to the local ecosystems including tides, atmospheric forcing from reanalysis, a seasonal glacial melt cycle, and with sea ice processes incorporated using LIM3.  The models will be used to generate a ~20 year time series of oceanographic flows and water mass properties, which 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 Antarctic toothfish (Dissostichus mawsoni Norman, 1937) is one of the main target species of commercial fisheries in the Antarctic. It is an endemic and is found along the shelf of Antarctica, as well as on the slopes of seamounts, underwater elevations and islands in the sub-Antarctic. It feeds on a variety of fish and cephalopods and can be an intermediate/paratenic host of some helminthes, whose final hosts are whales, seals, large rays and sharks. This article presents new data on toothfish infection in the Pacific sector of the Antarctic. Specimens were examined during commercial longline fishing in the Ross Sea and the Amundsen Sea in January-February 2013. Fourteen species of parasites were found using standard parasitological methods and genetic analysis.

Lipid metabolism and indices of oxidation processes obtained during examination of specimens of Antarctic toothfish Dissostichus mawsoni (Perciformes: Nototheniidae) caught in the Ross Sea are given. Blood plasma, tissues mesonephric kidney, liver and spleen were studied for the content of total lipids and lipid composition, products of lipid peroxidation and level of antioxidant protection. Biochemical status of immune organs depending on the structural and functional characteristics of tissues was established.