Developing glider techniques for estimating krill biomass
The Weddell Sea is a potentially important area of spawning of Antarctic krill, contributing to the population of the significant fishing grounds of the Scotia Sea. Understanding the distribution of Antarctic krill (Euphausia superba) in the Weddell Sea is problematic, however, due to the difficulty and expense of accessing this remote and often ice-covered region and the limited seasonal window of Antarctic operations. In an effort to gain further insight into the distribution and transport of krill out of the Weddell Sea and north into the Scotia Sea, an ocean glider (an iRobot Seaglider) with an integrated echo sounder was deployed on the continental shelf, east of the Antarctic Peninsula.
Along with CTD and acoustic transects, net sampling and drifter deployment the GENTOO project (Gliders: Excellent New Tool for Observing the Ocean) deployed three Seagliders in the north-western Weddell Sea in late January and early February, 2012. One carried a bespoke Imagenex 120 kHz echo sounder designed to measure mean volume backscatter of Antarctic krill.
We discuss the calibration of the echo sounder using known targets and the validation of the krill swarm identification by mounting the echo sounder on a sampling net. The analysis of the acoustic data collected during the glider deployment is presented and we consider the potential and challenges of using Seagliders as platforms for estimating krill biomass and advective flux in Antarctic waters.