Acoustics plays a crucial role in providing rapid surveys and long- term time series of distributions of marine organisms. Echo sounders are typically used to 1) map the spatial distribution of volume scatterers, 2) interpolate between data collected by nets or pumps, and 3) provide data when net or pumps are not practical for use(such as in logistically dificult regions) and/or cost- effective. In order that these acoustic methods be quantitative, accurate scattering models need to be used which relate the echo levels to meaningful biological parameters such as animal size, spatial, and temporal distributions. The models that are currently available are not at a sufficiently advanced state for reliable use.
