CCAMLR

Conservation Measure 91/02 (2004) affords protection of the Cape Shirreff CCAMLR Ecosystem Monitoring Program (CEMP) site. Cape Shirreff is also protected as ASPA 149 through the Antarctic Treaty. The management plans for Cape Shirreff are due for review by CCAMLR in 2009 and by the ATCM in 2010. Both plans recognize the importance of the CEMP site and associated scientific research and afford area protection.

A multidisciplinary survey was conducted with the RV ‘G.O. Sars’ as part of the Antarctic Krill and Ecosystem Studies (AKES) from January to March 2008. Acoustical data were sampled continuously on six frequencies along one west-east and two south-north transects between latitudes 50 and 66.4 S in the sparsely studied CCAMLR subarea 48.6. The mean density of Antarctic krill, integrated to 270 m depth was 4.42 g/m2. The krill were mainly found in strong aggregations and were patchily distributed. The majority of the detected krill was distributed between 40 and 80 m depth, and approximately 14 % was distributed within a 100 x 100 km core area centered around the Bouvetøya.

of mean krill density in Subarea 48.4 there are premises for formation of the zones with increased density. These zones are located within the near-shore shelf-based SSMU and associated with meanders and eddy favorable for krill concentration. Here, in the cold water of the Weddell Sea, the main part of biomass of Subarea 48.4, are concentrated. In January-February, 2000, almost 60% of total biomass was concentrated here, the mean krill density was 65 g/m2, and on local grounds – greater than 150 g/m2.. Properties of the zones with increased density: these zones are associated with meanders and eddies favorable for krill concentration; observed quasistationary character of these eddies and meanders, caused by water dynamics; location of significant biomass that is formed by swarms fields, distributed in a rather narrow depth range, - obviously may promote above said zones, firstly, southern part of near-shore shelf based SSMU as an interesting to krill fishery in some seasons.

Generalized linear and additive models suggest that large proportions of inter-annual variability in the reproductive success of Adélie, gentoo, and chinstrap penguins can be explained by simple linear predictors based on local weather conditions and winter sea ice extent. Local weather variables selected by step-wise model fitting procedures corresponded to the incubation periods for each species. Sea ice extent measured during the winter prior to breeding also appears to be an important predictor of reproductive success in all species. Biological variables measured during the chick-rearing phase, like krill size, krill density at sea, and chlorophyll a concentrations appear less important, except for chinstrap penguins which breed later in the season than gentoo and Adélie penguins. In most cases, the final predictor variables detected in this analysis have exhibited directional trends, implying important effects of directional climate change on the future of reproductive success in monitored populations.

We present a quantitative food web of the Ross Sea as a step towards investigating ecosystem effects of the fishery for Antarctic toothfish (Dissostichus mawsoni). The model consolidates quantitative information on trophic links across all the major biota of the Ross Sea and tests for data consistency. The model has 38 trophic groups and is balanced in terms of annual flows of organic carbon in an average, recent year (1990–2000). The focus of the model is on the role of Antarctic toothfish in the food web, which means that the model has greater taxonomic resolution towards the top of the food web than the base. A survey of the available literature and both published and unpublished data provided an initial set of parameters describing the annual average abundance, imports, exports, energetics (growth, reproduction, consumption), and trophic linkages (diets, key predators) for each model group. We also estimated the relative level of uncertainty on these parameters. This set of parameters was not self consistent, and a method is described to adjust the initial parameter set to give a balanced model taking into account the estimates of parameter uncertainty and the large range of magnitude (>6 orders of magnitude) in trophic flows between groups. Parameters for biomass, production rate, growth efficiency, diet fractions, and other transfers of biomass between groups were adjusted simultaneously. We found that changes to the initial set of parameters needed to obtain balance were reasonably small for most groups and most parameters. The mean absolute change for all key parameters (biomass, production rate, growth efficiency) and all groups together was 1.7%, and for diet fractions was 0.6%. Large but not implausible changes in biomass, production/biomass, and production/consumption parameters were needed to balance the microzooplankton (34–47%), ice bacteria (61–72%), and ice protozoa (24–54%), components of the model. Trophic levels are in close agreement with those derived from isotopic analyses and other ecosystems. In the balanced model, there is only enough large (>100 cm) toothfish production to satisfy 6.6% of the diet of Weddell seals, 5.9% of the diet of orca, and 2.8% of the diet of sperm whales. The model does not support the hypothesis that depletion of Antarctic toothfish by fishing would change the diet of predators of toothfish (Weddell seals, orca, sperm whales) by large amounts throughout the Ross Sea, though the importance of toothfish as prey items to these predators is not tested. The model shows that large toothfish consume 61% of the annual production of medium sized demersal fishes and 14% of the annual production of small demersal fishes, implying a potential for the fishery to affect these prey through trophic cascades. There is a need to establish monitoring of medium and small demersal fishes in the Ross Sea, and to model potential changes to these groups due to the fishery.

The circulation in the Ross Sea sector of the Southern Ocean is examined in three numberical models of intermediate to high resolution. Despite the model differences (including physics, forcing) the circulation representation is relatively consistent, both in terms of the mean and some aspects of monthly variability. This could point to strong bathymetric constraints on the circulation. In particular, the models sugges a pair of cyclonic gyres separated by shallow bathymetry around 180º E that redistribute water from the wider Southern Ocean into and out of the Ross Sea. The southermost gyre boundaries comprise the Antarctic Shelf Front and the Antarctic Coastal Current. To the north the gyres are bounded by the Antarctic Circumpolar Current. The model solutions also suggest that as the model Antarctic Circumpolar Current transport reduces, the gyral transport within the Ross Sea increases. Model flows at around 900 metres compare favourably with float data. Further, model depth-averaged flow on the Ross Sea shelf is relatively consistent with that reconstructed from longline fishing records.

This report is a synthesis of mostly existing information which has been compiled for the purposes of addressing items on the FEMA 2 agenda. It summarises the management of the fishery, catch and effort, size distribution, and tagging data collected from the Antarctic toothfish fishery up to the 2007/08 fishing year. It focuses in particular on Antarctic toothfish catches taken from the continental shelf of the Ross Sea itself, because this is the area where any ecosystem effects related to predators of toothfish are most likely to occur. Of the total catch from the fishery to date of almost 19 000 t, about 20% has been taken from the northern grounds, 70% from the continental slope, and 10% from the continental shelf of the Ross Sea. The shelf catch has been taken from three quite localised fishing grounds of deep water (mainly > 800 m) off Terra Nova Bay, Ross Island, and in the south of 88.1L (adjacent to the Ross Ice Shelf). The catch rates from the exploratory longline fishery typically show high temporal and spatial variability, even between consecutive sets within the main fishing grounds. There are no reliable estimates of Antarctic toothfish abundance on the shelf at the current time. In preparing this paper we have identified some data sources which could potentially be used to estimate the abundance of toothfish on the Ross Sea shelf. However, CPUE is inherently variable both within and between seasons on the various fishing grounds and different vessels have fished different grounds in different years making interpretation difficult. Tag-recapture data from the Terra Nova Bay fishing ground would also be difficult to interpret because of the movement of tagged fish. There is also other information on the distribution of Antarctic toothfish from the area derived from other research surveys and from studies focusing on other species. US Scientists at McMurdo Sound have collected Antarctic toothfish since 1971 using vertical set lines. Their sampling has shown significant within and between season variability in catch rates. Very few Antarctic toothfish have been caught in the Ross Sea by other research sampling. Indirect observations from cameras mounted on seals shows that Antarctic toothfish at McMurdo Sound can occupy the entire water column, but the spatial and temporal extent of its midwater distribution and the proportion of the population which occurs off the bottom are unknown.

This paper provides a brief summary of progress of inter-sessional by the Sub-group on Status and Trend Assessment of Predator Populations (WG-EMM-STAPP) as a follow-up to the Predator Survey Workshop.

It is widely recognised that the interpretation of counts of penguin populations at their breeding sites during the breeding period are strongly dependent on the timing within a breeding season at which they are undertaken. While the need to adjust raw penguin count data obtained at varying times within a breeding season to minimise bias in estimates of the breeding population has long been recognised, the considerable work in obtaining one-off counts for population surveys have not been matched by the collection of adjustment data. This was recognised at the recent Predator Survey workshop, where the collection of adjustment data to improve estimation of penguin abundance was identified as a priority for future work. This paper reports on the collection and development of adjustment factor data for Adélie penguins in east Antarctica.

The first international workshop on implementing a Southern Ocean Sentinel program was held at the CCAMLR Headquarters in Hobart in April 2009. The conclusions of that workshop are provided to WG-EMM for consideration along with an overview, the program and abstracts of the keynote presentations. A report of the workshop will be submitted to the Scientific Committee for its considerations in October 2009, including discussion on the following questions: A key conclusion of the workshop was that the Sentinel program could start now with qualitative assessments of current and future climate change impacts on Southern Ocean marine ecosystems and work towards a quantitative assessment of impacts by 2014. This process will fill an important gap in current discussions on climate change impacts on marine ecosystems by the Intergovernmental Panel on Climate Change. It will also assist CCAMLR in addressing climate change impacts on the conservation of Antarctic marine living resources. Another key conclusion of the workshop is that it should be possible to identify indicators of climate change impacts in the Southern Ocean that these could be used as early warning indicators of future change in both the Southern Ocean and elsewhere in the world. Importantly for CCAMLR, work in designing such a system should be complementary with developmental work being undertaken in the CCAMLR Ecosystem Monitoring Program. CCAMLR Members are invited to participate in the qualitative and quantitative assessments of current and future climate change impacts on the Southern Ocean marine ecosystems as well participating in designing and implementing an early-warning system to identify imminent climate change impacts on global ecosystem services.