ASA 128th Meeting - Austin, Texas - 1994 Nov 28 .. Dec 02

4aAB10. Applications of multifrequency acoustics: Spatial patterns in a freshwater lake.

C. F. Greenlaw

R. W. Player

U. S. Samilo

Tracor Appl. Sci., Inc., 9150 Chesapeake Dr., San Diego, CA 92123

Vertical profiles of acoustical scattering at four frequencies were obtained at a mesh of points covering the major regions of a small, manmade freshwater lake. Inversion methods were used to estimate size-abundance profiles of zooplankters using a scattering model validated for oceanic zooplankton such as copepods. These profiles were then used to form estimates of lake-wide 3-D spatial patterns sorted by size classes of the dominant zooplankters. Results illustrate the value of multifrequency acoustical surveys as an adjunct to conventional sampling for rapid assessment of spatial distributional features of zooplankton populations in lakes. Problems with applications of ocean-based assessment techniques to lacustrine environments, such as the lack of validated scattering models for freshwater zooplankton, are discussed.