CCAMLR

This paper outlines plans for a co-ordinated, multi-national study focusing on the krill-based ecosystem in Area 48 during the 2015-16 austral summer. The studies will include at-sea data collection from research and fishing vessels, together with remotely sensed data obtained from moorings and gliders, with links to land-based predator foraging behaviour, diet and reproductive success. The aims of this note are both to inform CCAMLR members of the proposed activities and also to stimulate any additional participation of members in this developing study.

This paper presents a description of the statistical approach developed to estimate abundance of Antarctic fur seals at South Georgia. The estimate is based on photographic counts of all the breeding beaches in the fur seal’s distribution range. The images were obtained during comprehensive helicopter surveys conducted during 2006 and 2008. The proposed Bayesian analysis scales up in situ counts to total population size carrying over multiple sources of uncertainty from estimates of proportions of unobserved animals.

Many of the key oceanographic and ecological processes that determine the structure and functioning of ecosystems in the regions around South Georgia and the South Orkney Islands operate over small scales of <10 km.  This paper reports the initiation of a project to develop high-resolution hydrodynamic models that will be used to examine the detailed oceanography of the South Georgia and South Orkney Islands shelves and surrounding regions.  The models will be based on the NEMO-Shelf model, with the capability to resolve tides, atmospheric forcing, and sea ice processes, and with a ~3 km horizontal resolution.  They 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 ICED programme is investigating how climate change might impact Southern Ocean ecosystems in order to help inform management of Southern Ocean fisheries. As part of this ICED convened a workshop in November 2013 on “Southern Ocean food webs and scenarios of change”, and is currently preparing an academic paper detailing the outputs, which are summarised here. ICED recognises the key role for CCAMLR in improving the basis for future monitoring and management of Southern Ocean ecosystems, and encourages active two-way engagement between the scientific community and CCAMLR.

Within Drake Passage, the southern flank of the Antarctic Circumpolar Current (ACC) hosts the ventilation of deep water, the injection of Antarctic shelf waters and interactions between westward and eastward boundary cur rents. This exchange is explored through the trajectories of forty surface drifters released in January 2012 in the northwestern Weddell Sea. The drifters detail Lagrangian transport pathways between the eastern Antarctic Peninsula and sites of elevated chlorophyll in the Scotia Sea. ACC frontal currents, in particular the  Southern ACC Front, act as dynamical transport barriers to the drifters and influence surface chlorophyll distributions, indicating that ACC fronts partition Weddell source waters in the Scotia Sea. Interannual fluctuations in surface chlorophyll in the south Scotia Sea and the northern Weddell Sea covary. This suggests that Scotia Sea ecosystem dynamics are linked to water properties injected from the tip of the Antarctic Peninsula and respond to Weddell Gyre circulation changes.

A calibrated 120 kHz single-beam echo-sounder was integrated into an ocean glider and deployed in the Weddell Sea, Southern Ocean. The glider was deployed for two short periods in January 2012, in separate survey boxes on the continental shelf to the east of the Antarctic Peninsula, to assess the distribution of Antarctic krill (Euphausia superba). During the glider missions, a research vessel undertook acoustic transects using a calibrated, hull-mounted, multi-frequency echo-sounder. Net hauls were taken to validate acoustic targets and parameterize acoustic models. Krill targets were identified using a thresholded schools analysis technique (SHAPES), and acoustic data were converted to krill density using the stochastic distorted-wave Born approximation (SDWBA) target strength model. A sensitivity analysis of glider pitch and roll indicated that, if not taken into account, glider orientation can impact density estimates by up to 8-fold. Glider-based, echo-sounder–derived krill density profiles for the two survey boxes showed features coherent with ship-borne measurements, with peak densities in both boxes around a depth of 60 m. Monte Carlo simulation of glider subsampling of ship-borne data showed no significant difference from observed profiles. Simulated glider dives required at least an order of magnitude more time than the ship to similarly estimate the abundance of krill within the sample regions. These analyses highlight the need for suitable sampling strategies for glider-based observations and are our first steps toward using autonomous underwater vehicles for ecosystem assessment and long-term monitoring. With appropriate survey design, gliders can be used for estimating krill distribution and abundance.

This paper presents the results of at-sea monitoring of seabirds and cetaceans over five summer seasons, 2010 to 2014, at the Scotia Sea, Antarctica, covering a total of 1463 nautical miles with 1100 ten-min counts. Among birds, six species of Procellariiformes were abundant: Black-browed Albatross, Cape petrel, Southern Fulmar petrel, Antarctic Prion, Wilson’s Storm petrel, and Black-bellied Storm Petrel. Antarctic Prion was the dominant species within the 5 years whereas Cape petrel showed successive decreases in abundance. Five baleen whales where recorded: Humpback, Sei, Southern Right, Fin and Minke, which had different abundances during our study. Fin whale had the highest mean encounter rate in the five years (0.29 ± 1.57 whale/nautical mile), followed by Humpback whale (0.09 ± 0.54). Annual dissimilarity in abundance of both birds and cetaceans occurred in conjunction with changes in sea surface temperature and ice cover, showing the dependence of top predators to environmental changes. The largest aggregations of all top predators (seabirds and cetaceans) were recorded mainly in two regions: west and south of South Orkney Is., suggesting important prey availability, especially krill, in those areas.

A multi-year plan for research by Japan and South Africa aimed at yielding a tag-based assessment of the Dissostichus resource in statistical Subarea 48.6 was adopted in 2012 and formulated in CM 41-04. This paper submits a work plan for the South African contribution to the third year of this research in 2014/15 and is to be read in conjunction with WG-SAM-14/10.

Japan and South Africa are undertaking a multi-year research plan in Statistical Subarea 48.6 as outlined in CM 41-04 (2012 & 2013). Progress achieved during the 2012/13 season is reported and achievements for the first two months of the 2013/14 season are briefly mentioned.

Over the first 14 months of the Research fishery a total of 318 Dissostichus eleganoides and 1660 D. mawsoni have been tagged and released, and 31 tagged toothfish have been recaptured. Even though almost 50% of the recaptures are within season the progress is encouraging and the indications are that sufficient tagged toothfish could be recaptured by the end of the current season to enable a tag-based assessment of the Dissostichus resource in Subarea 48.6 to be undertaken next year.

Concern is expressed over the rise of IUU activity in Subarea 48.6 and the possible negative consequences for the Research being undertaken.

In this paper we provide WG-EMM with an update on aerial survey methods used to provide new estimates of penguin population distribution and abundance. This project will continue to develop over the coming years and we will provide similar updates at regular intervals.