Beschreibung:
<jats:p>To improve chances for discriminating and identifying fish and zooplankton species, more acoustic information is better. Multifrequency, digital echosounders increase information bandwidth by increasing the number discrete frequencies transmitted and received through multiple transducers. Multifrequency data provide a range of aural perspectives just as colored spotlights accent different components of a painting. Lake whitefish (Coregonus clupeaformis) represent an increasing biomass in Lake Michigan and have a disproportionately large, single-chambered swimbladder relative to the body volume. Frequency-dependent, echo amplitude predictions from a Kirchhoff-ray mode model were compared to in situ backscatter measurements of constrained and free ranging lake whitefish at five discrete frequencies (38, 50, 120, 200, and 420 kHz). In addition to geometric scattering, backscattering characteristics of whitefish in the resonance region were also modeled. This combination of theoretical model prediction and multifrequency measures allows the quantification of the importance of intraspecies backscatter variability due to fish sizes and behavior. [Work supported by ONR.]</jats:p>