Science Mission 3
Under sea-ice and pelagic surveys
Acoustics provide a powerful means for sampling aquatic environments and are used extensively for fisheries and ecological research. This project sought to capitalise on the unique capabilities of Autosub, an Automonous Underwater Vehicle (AUV), to conduct acoustic surveys in these otherwise impenetrable (operationally or physically) environments. Key research questions were addressed while demonstrating the utility of AUVs to the wider scientific community.
The precarious condition of the world’s fisheries makes increasing demands on the scientific assessment of fish stocks. Traditional assessments rely on commercial catch statistics, but there is an increasing need for fishery independent data. Acoustic surveys can provide such information; however ocean-going vessels have high operating costs and there is also a widespread concern that fish avoid these vessels because of the noise they make, thereby biasing abundance estimates.
The development of Autosub provided an opportunity to investigate whether AUVs could be used as a low-cost, unobtrusive platform for acoustic surveys of fish biomass, and also to investigate the concerns of fish avoidance.
Antarctic Marginal Ice Zone (MIZ) study
Due to inaccessibility and limitations with conventional sampling techniques, only limited observations have been conducted in the Marginal Ice Zone (MIZ). The development of Autosub provided an opportunity to collect continuous measurements under ice and explore three areas of research.
- Little knowledge of sea-ice thickness is available, yet such data are essential for the calculation of ice volume and water budget, which could lead to a greater understanding of the likely response of the Antarctic sea ice system to climate change.
- Circumstantial evidence suggests that sea ice is an important habitat for krill, and yet little quantitative data exist.
- Underwater illumination in the MIZ is influenced by edge effects under floes, and the illumination varies in a non-linear fashion as the proportion of ice cover changes. Understanding these changes is essential for modelling phytoplankton growth.
Fernandes P.G., Brierley A.S., Simmonds E.J., Millard N.W., McPhail S.D., Armstrong F., Stevenson P. and Squires M., 2000. Fish do not avoid survey vessels. Nature, 404, 35-36.
Fernandes P.G., Brierley A.S., Simmonds E.J., Millard N.W., McPhail S.D., Armstrong F., Stevenson P. and Squires M., 2000. Addendum to - Fish do not avoid survey vessels. Nature, 407, 152.
Brierley A.S. and Fernandes P.G., 2001. Diving depths of northern gannets: acoustic observations of Sula bassana from an autonomous underwater vehicle. The Auk, 118(2), 529-534.
Brierley A.S., Fernandes P.G., Armstrong E., Brandon M.A., Bone D.G., Millard N.W., Stevenson P., McPhail S.D., Pebody M., Perrett J.R. and Squires M., 2002. Antarctic krill under sea ice: elevated abundance in a narrow band just south of the ice edge. Science, 295(5561), 1789.
Brierley A.S., Fernandes P.G., Armstrong E., Brandon M.A., Bone D.G., Millard N.W., Stevenson P., McPhail S.D., Pebody M., Perrett J.R. and Squires M., 2003. An investigation of avoidance by Antarctic krill of RRS James Clark Ross using the Autosub-2 autonomous underwater vehicle. Fisheries Research, 60(2-3), 569-576.