Measurements of the volume scattering strength in the Beaufort and Chukchi Seas

Measurements of the acoustic volume scattering strength were made in the Marginal Ice Zone of the Beaufort and Chukchi Seas in the summers of 1971 and 1972. During the 1971 cruise, the measurements were made from the USCGC NORTHWIND using a 105 kHz pulsed cw vertically directed sonar, and during the 1972 cruise the measurements were made from the USCGC STATEN ISLAND using the 105 kHz echo sounder as well as a 38 kHz echo sounder. Approximately 60 data files were recorded on magnetic tape in 1971, and 100 data files in 1972. Selective biological sampling was performed with vertical net hauls and horizontal trawls. The data indicate that the Marginal Ice Zone is an area of great biological activity-at least during the summer months. Volume scattering strengths as great as -42 dB were observed. Detailed examination of the magnetic tapes and the echograms reveals many distinct fish as well as numerous plankton layers at all depths.