A new multifrequency acoustic method for the discrimination of biotic components in pelagic ecosystems: Application in a high diversity tropical ecosystem off Northeast Brazil

Underwater acoustics have an unrealized potential for multicomponent ecosystem characterization. Various methods are used for multifrequency classification. To improve scatter discrimination we propose a new method based on the distribution of scatters on multifrequency spatial planes. Groups of scatters are defined a priori (from in situ sampling). Then we apply a sensitivity analysis to maximize energy allocation within a given group when compared to the nearest one. This method was applied on four frequencies (38, 70, 120 and 200 kHz) data collected in the coastal and oceanic ecosystems of Northeast Brazil; an area characterized by a high biodiversity. By applying the method we discriminated six groups: Fish like, two types of High Resonant at 38 kHz associated with gelatinous, Fluid Like associated with crustacean macrozooplankton, High Resonant at 70 kHz associated with algae, and a group of Unclassified echoes. Results are coherent in terms of distribution pattern of each group. Among other, our res...