Variability in biological distributions and hydrography from concurrent acoustic Doppler current profiler and SeaSoar surveys

Concurrent Acoustic Doppler Current Profiler (ADCP)/SeaSoar surveys can provide a range of quantitative and qualitative biological data at the same time and space scales as hydrographic data. The data resolve mesoscale variability for both biology and physics and can be displayed in real time-thereby allowing targeting of conventional sampling programmes. Examples from such surveys in a range of oceanic conditions and from different oceans demonstrate the complex patterns of biological distributions, and thereby acoustic variability, which change in space and time in response to both biological and physical forcing. Direct comparison of data from different areas requires absolute acoustic data. A method for converting relative ADCP backscatter to mean volume backscattering strength that includes using concurrent temperature and salinity data from SeaSoar is described; the resultant data sets can be directly compared in time and space. (C) 1996 International council for the Exploration of the Sea