Surveying Sector 58

One of the most comprehensive marine ecosystem research projects undertaken by the Australian Government Antarctic Division concluded on the 28th February 2006, 10 years after it began.

The Baseline Research on Oceanography, Krill and the Environment-West (BROKE-West) voyage, aboard the Aurora Australis, surveyed 1.5 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 aimed to describe the marine ecosystem of the region and determine krill distribution and abundance — to help calculate precautionary catch limits for the krill fishery in the region.

BROKE-West followed in the footsteps of BROKE which, in 1996, conducted a similar survey of the adjacent 4.7 million km2 CCAMLR Division 58.4.1. Together, the two surveys stretch around one third of the Antarctic coastline, adjacent to the Australian Antarctic Territory (Australian Antarctic Magazine 8:12).

The BROKE-West survey involved using a vast array of sensors whilst the ship was moving, together with information from satellites and samples obtained from Conductivity Temperature and Depth (CTD) probes and from nets. The CTD probes were deployed at 118 sampling stations and instrumented nets were lowered into the water 125 times. This concerted sampling strategy aimed to squeeze the maximum amount of information out of the ocean in the limited time available, and to use this information to build up a picture of the marine environment in this little-studied area. So what did we achieve?

Somewhat surprisingly we surveyed 50% more area than we thought we were attempting. We now have oceanographic and ecological information for this large region, which is compatible with information from BROKE and from a survey in the South West Atlantic — where four ships surveyed 2 million km2 in 2000. We are now in a position to piece together the ways in which Antarctic marine ecosystems function in summer.

The vast amount of data collected will take years to analyse. So far though, some of the results have been presented to international meetings: the International Whaling Commission, the Scientific Committee on Antarctic Research and CCAMLR. The results of the krill biomass survey were presented to CCAMLR’s Working Group on Ecosystem Monitoring and Management in July and the group recommended that the biomass estimate (15.9 million tonnes) should be used to calculate a precautionary catch limit on the krill fishery in this area.

STEVE NICOL, Programme Leader, Southern Ocean Ecosystems, AGAD