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.]