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

2aAO5. Dominant scattering mechanisms and associated scattering models for several zooplankton types.

Timothy K. Stanton

Dept. of Appl. Ocean Phys. and Eng., Woods Hole Oceanogr. Inst., Woods Hole, MA 02543

Dezhang Chu

Peter H. Wiebe

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

The shape and material properties of zooplankton can vary widely from species to species and, as a result, the acoustic scattering properties vary accordingly. Because of the great complexity of the boundary conditions of the animals, determination of the conditions is difficult, if not impossible, by direct measurement. Through a series of controlled laboratory measurements of acoustic backscatter by live individual animals, the boundary conditions of several different types of animals have been inferred. Dominant scattering mechanisms of the animals have been identified and incorporated into approximate scattering models. Data and models are presented for live individual euphausiids (weakly scattering fluidlike), gastropods (hard elastic shelled), and siphonophores (gas-bearing). In particular, relative scattering efficiency (echo energy per unit biomass) and patterns of target strength versus frequency for both single echoes from individuals as well as averages from many echoes will be shown. [Work supported by ONR and NSF.]