ASA 130th Meeting - St. Louis, MO - 1995 Nov 27 .. Dec 01

2aAO3. Acoustic backscattering by complex zooplankton assemblages on Georges Bank.

Peter H. Wiebe

Dept. of Biol., Woods Hole Oceanogr. Inst., Woods Hole, MA 02543

Timothy K. Stanton

Woods Hole Oceanogr. Inst., Woods Hole, MA 02543

Charles H. Greene

Cornell Univ., Ithaca, NY 14853-2701

High-frequency (420 kHz) sound was used to study the volume backscattering from plankton and micronekton over Georges Bank as part of a study designed to understand the relationship between volume backscattering and the composition of the plankton. Volume backscattering levels at stratified sites were factors of 4 to 7 times higher than at a well mixed site. However, there was no significant difference in MOCNESS sampled biomass between the locations and the regression between volume backscattering and total biovolume was not significant. The difference in volume backscattering is due to differences in the acoustic scattering properties of zooplankton taxa and the fact that the taxonomic composition of the plankton differed between the sites. When taxa-specific model predictions of acoustic backscattering cross section were used with field size and abundance data to predict measured volume backscattering data, a highly significant relationship between observed and predicted volume backscattering was obtained. [Work supported by ONR, NSF, and NOAA.]