CCAMLR

A meso-scale zooplankton and krill net sampling survey was carried out in the north-western Weddell See and in Bransfield Strait/western Antarctic Peninsula during late January to early March 2013. The aim of the survey was to study the zooplankton composition and krill abundance and distribution in the outflow region of the Weddell Sea. Due to severe pack-ice conditions, more than half of the survey area was covered by ice during the summer season. Antarctic krill densities were found to be highest in the western Peninsula region and lower in ice-covered Weddell Sea waters. Overall krill density was below the longterm average of the area. New one-year-old recruits were scarce, the stock was dominated by two and three year old krill. Spawning occurred late and numbers of gravid females and larvae were low. Ice krill E. crystallorophias was abundant on the shelf of the north-western Weddell Sea. Thysanoessa macrura and salps Salpa thompsoni were far less abundant than the longterm average and were confined to the more northern, ice-free areas.

As part of the CCAMLR Scheme of International Scientific Observation, observers on-board Krill (Euphausia superba) fishing vessels measure the length of individual Krill sampled from commercial catches. These extremely valuable data may be used to monitor the state of harvested Krill populations. For instance, investigating length frequency distributions (LFDs) and their change over time provides insight into the underlying population dynamics. Three main processes drive temporal changes in LFDs: growth, mortality and recruitment. Understanding how these processes interact is a prerequisite to the interpretation of any observed trend. To illustrate these interactions a simple mechanistic individual-based model of krill population dynamics was subjected to a sensitivity analysis. Starting from a base scenario of cyclical annual recruitment, plausible ranges of growth, mortality and recruitment rates were tested and their effects on two length-based recruitment indices (the monthly median length and proportion of individuals smaller than 40mm, F40) were investigated. Results indicate that the annual span (maximum minus minimum) of F40 would be the best index of annual recruitment among those tested, and, that length-based indices may be used to determine the timing of recruitment events. However, since the population size structure at a given time is the result of a mixture of several annual cohorts, using such indices to quantify the intensity of a given recruitment event would need to take into account the relative magnitude of previous recruitment events.

In recent years, CCAMLR member states undertook substantial efforts to designate marine protected areas (MPAs) in the Southern Ocean. While MPA planning for six domains is underway, for three domains CCAMLR member states were asked to take the lead in MPA planning. At the CCAMLR meeting in 2012, the Commission welcomed the offer of Germany to take the lead in developing a Weddell Sea MPA for consideration in 2014. Subsequently, the German Federal Ministry of Food, Agriculture and Consumer Protection tasked the Alfred Wegener Institute (AWI) to compile and analyse scientific data for identifying potential conservation areas and measures in the Weddell Sea. The work under this project started mid-April 2013. Here, in our first conceptual outline, we (i) present the principal target area of our evaluation study aiming at a Weddell Sea MPA, (ii) give a systematic overview of our preliminary data retrieval accompanied by an invitation to all experts from within and outside CCAMLR to contribute relevant information and data sets and (iii) set out the project timeline in detail, i. a. to highlight an international expert workshop on the planning of a Weddell Sea MPA in 2014.

A  preliminary characterisation of available fishing information regarding catches and effort in Divisions 58.4.4a, 58.4.4b, 58.4.3a and 58.4.3b is presented. Information analysed corresponds to fishing logbooks recorded in the exploratory fisheries carried out between July 2000 and March 2012. During this period, a total of 9 countries registered fishing operations in which 1811 sets were recorded (79.3\% 58.4.3; 20.7\% 58.4.4) accounting of 1605 tons of toothfish. Division 58.4.3b (Banzare Bank) accumulated the highest proportion of allocated effort in which a total of 948 sets (52\%) were performed. Catches of toothfish have declined since fishing season 2006 and total allowed catch assigned has not been completed in most of the recent fishing seasons. Soaking time showed high variability and no seasonal pattern was detected and spatial coverage of fishing operations showed a reduction across time. Baseline analysis presented in this report provides relevant information for the exploratory fisheries and also for future research and management plans.