Detection and quantitative estimation of krill concentrations by hydroacoustic instruments
The limited capabilities of existing hydroacoustic instruments in detecting dispersed and surface concentrations of krill lead to considerable underestimates of krill biomass in areas surveyed. The task of detecting surface concentrations of krill can be solved with the help of towed acoustic antennae. The practical possibility of detecting dispersed krill by hydroacoustic instruments was established on board the research vessel Odissey during the international expedition under the FIBEX program. It was shown that the hydroacoustic device Simrad SK-120, with TVG switched off, is capable of registering individual krill at a depth of 50–60 m while the vessel is in motion. According to theoretical calculations, the range of detection of individual specimens can be considerably increased at the expense of a rise in the acoustic power of emission.