It’s BROKE… again

One of the largest ventures of the Australian Antarctic programme will kick off next summer, in a bid to establish accurate catch limits for krill in the Southern Ocean. BROKE-West (Baseline Research on Oceanography, Krill and the Environment) will survey over 1 million km2 of ocean between 30° and 80° east in a region designated by the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) as Division 58.4.2 (see map). The survey will repeat krill abundance measurements made in 1981, which established a precautionary catch limit of 450 000 tonnes per year. Since that time, however, the methodology and acoustic technology used for estimating krill abundance has changed considerably and doubts about the validity of early estimates have arisen.

As an expanding krill fishery is one of the greatest potential threats to the Antarctic ecosystem, it is prudent to ensure that catch limits in the area of Australia’s national interest are based on the best scientific information available. Additionally, there is evidence from other areas of the Antarctic that considerable changes have been occurring in the marine ecosystem over the last 30 years. Consequently, in 2000, plans were laid to conduct a new survey of Division 58.4.2.

BROKE-West will follow in the footsteps of its 1996 predecessor, BROKE, which described krill distribution and abundance in CCAMLR Division 58.4.1 (South East Indian sector). While BROKE-West has been designed around the need to estimate krill distribution and abundance, it is also an opportunity to conduct large scale oceanographic experiments and to collect a suite of ecological information about this little visited stretch of the Antarctic coastline. The dataset will mimic that collected on the 1996 voyage, providing an integrated dataset which will stretch around one third of the Antarctic coast. The results will be used by the Antarctic Climate and Ecosystems Cooperative Research Centre to help determine the relationships between the physical environment and biological processes.

The BROKE-West voyage will sail from Fremantle in early January and begin sampling in the far west of the Division, at 30°E, conducting 11 transects as it moves eastwards, following the direction taken in the original BROKE survey. On every second transect there will be detailed oceanographic and biological sampling of the water column at fixed stations, using nets and oceanographic samplers (measuring salinity and temperature with depth). On all transects, continuous measurements will be conducted using underwater samplers and acoustic (echo-sounding) equipment. Observations of the abundance of seals, birds and whales will be carried out during daylight hours.

Fittingly, BROKE-West will take place during the 25th anniversary of the commencement of the Australian Antarctic marine research programme. It also occurs ten years after the original BROKE survey and many of the original 45 participants in that voyage are likely to devote the summer of 2006 to toiling up and down the Southern Ocean in search of the elusive krill.

Steve Nicol, Programme Leader, Southern Ocean Ecosystems, AAD