Antarctic krill (Euphausia superba)—one of the most abundant animal species on Earth—exhibits a five to six year population cycle, with oscillations in biomass exceeding one order of magnitude. Previous studies have postulated that the krill cycle is induced by periodic climatological factors, but these postulated drivers neither show consistent agreement, nor are they supported by quantitative models. Here, using data analysis complemented with modelling of krill ontogeny and population dynamics, we identify intraspecific competition for food as the main driver of the krill cycle, while external climatological factors possibly modulate its phase and synchronization over large scales. Our model indicates that the cycle amplitude increases with reduction of krill loss rates. Thus, a decline of apex predators is likely to increase the oscillation amplitude, potentially destabilizing the marine food web, with drastic consequences for the entire Antarctic ecosystem.

A dominant Antarctic ecological paradigm suggests that winter sea ice is generally the main feeding ground for krill larvae. Observations from our winter cruise to the southwest Atlantic sector of the Southern Ocean contradict this view and present the first evidence that the pack-ice zone is a food-poor habitat for larval development. In contrast, the more open marginal ice zone provides a more favourable food environment for high larval krill growth rates. We found that complex under-ice habitats are, however, vital for larval krill when water column productivity is limited by light, by providing structures that offer protection from predators and to collect organic material released from the ice. The larvae feed on this sparse ice-associated food during the day. After sunset, they migrate into the water below the ice (upper 20 m) and drift away from the ice areas where they have previously fed. Model analyses indicate that this behaviour increases both food uptake in a patchy food environment and the likelihood of overwinter transport to areas where feeding conditions are more favourable in spring.

In Division 58.4.3a, since 2012, research fishing has been conducted in the research block by three vessels using longline: “Shinsei Maru No. 3” (Japan), “Saint André” (France) and “Mascareignes III” (France). The first Franco-Japanese exploratory longline fishery research plan for Dissostichus spp. in Division 58.4.3a (WG-FSA-16/55) was presented to WG-FSA-16, which included research objectives, methods and milestones in accordance with Conservation Measure 41-06 and associated measures. In October 2017, the Scientific Committee agreed that the research plan is appropriate to achieve its objectives (SC-CAMLR-XXXVI, para. 3.121). France and Japan commonly notifies their intention to continue their exploratory fisheries in Division 58.4.3a over the coming years in order to contribute to the tagging program and to achieve a robust stock assessment. We present here a proposal for the continuation of the research plan as set out in WG-FSA-17/55, and taking into account the Scientific Committee’s recommendations.

A proposal from Spain to join the current research proposal coordinated between JAP and ZAF is presented. 

In the SC-2017 report, the Scientific Committee noted that the future inclusion of an ice strengthened vessel, in an expanded research plan for this area, would address the capacity issues that the research conducted by Japan and South Africa were experiencing (parag 3.109) and recommended that research in this subarea should continue, focussing on D. mawsoni in research blocks 486_2 to 486_5 (parag 3.112).

Taking into account the above recommendations made by CCAMLR WGs and SC and in order to speed up the acquisition and data analysis, Spain proposes their collaboration with ZAF and JAP so that the united research effort will help to achieve a fully integrated assessments of the D.mawsoni stock in the Subarea 48.6. The proposed Spanish vessel “TRONIO”, with extensive experience in fisheries in CCAMLR area, is an ice strengthened vessel that could contribute to achieve the catch limit by research blocks, especially those with more difficult access due to difficult ice condition, and therefore increase the acquisition of data necessary to achieve a fully stock assessment in the subarea in the scheduled time.

Exploratory fishing for toothfish (Dissostichus spp.) in East Antarctica (Divisions 58.4.1 and 58.4.2) began in 2003. Robust stock assessments and catch limits according to CCAMLR decision rules remain to be determined for these Divisions. WG-FSA-16/29 outlined the first multi-member toothfish exploratory fishery research plan up to 2017/18 for East Antarctica, which the Scientific Committee agreed was appropriate to achieve the research objectives (SC-CAMLR-XXXV, para. 3.244). Subsequent research progress including evaluation of standard approaches to identify precautionary catch limits (WG-FSA-17 para. 4.28-4.38) and bycatch mitigation (Maschette et al. 2017), suggests a low risk profile for this fishery. Furthermore, examination of bycatch data and underwater video footage have not led to the identification of vulnerable marine ecosystem (VME) indicator species (Maschette et al. 2017). Final milestone results for the current research plan will be presented to WG-FSA-18. Here, we present a succeeding research proposal for 2018/19 to 2021/22, in accordance with ANNEX 24-01/A, Format 2. This succeeding plan has been designed as a 4-year plan, based on the low risk profile of this fishery and to allow more time for review by Working Groups of major reporting and review years in non-stock-assessment years. In this document we propose draft research objectives and an approach to review the locations of research blocks based on WG-SAM-11 para. 2.40. Based on WG-SAM-18 discussions and final milestone results for the current research plan, we will further develop the objectives and the locations of research blocks of this research plan for WG-FSA-18. In addition, the current genetics work (Maschette et al. 2018) will provide information on the stock structure of Antarctic toothfish in East Antarctica in relation to the wider Southern Ocean, and whether the species is suitable for an abundance estimate using a close-kin mark-recapture method.