Bioacoustic surveys of planktonic sound scatterers and of their diel and seasonal variability in the northwest Gulf of Mexico

A vessel-mounted 150 kHz acoustic Doppler current profiler (ADCP), which is employed to gather underway data on near-surface current velocity, was used in March and June 1992 to survey plankton stocks using backscattered ADCP signal intensity. Relative backscatter intensity was calibrated with salinity-temperature-depth data from CTD casts to determine an absolute backscatter intensity in decibels (dB) in 8 m bins, from 16 to 320 m. Time versus depth matrices were then constructed to display temporal and spatial patterns of aggregations of sound scatterers.<>