Ocean Acre Final Report: A Comparison of Volume Scattering Prediction Models
NAVAL UNDERWATER SYSTEMS CENTER NEW LONDON CT NEW LONDON United States
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Vertical profiles of scattering strength were successfully predicted for an ocean area off Bermuda from net trawl data on the vertical population density of 55 species of air bladdered, midwater fish collected during different years and seasons. The final predicted profiles compare favorably in shape and magnitude with measured profiles of scattering strength at 3.85, 5.0, 7.0, 9.0, and 15.5 kHz. At 3.85 kHz, only one of the predicted scattering strength values exceeds the measured scattering strength by more than 5 dB. For the predictions at 15.5 kHz, most values lie within 2 dB of the measured data. The surprisingly simple prediction model, using fish abundance as a function of depth correlated with measured profile data, achieves a notably superior attainment in its predictive capabilities over an earlier, more complicated model that required inputs on difficult-to-obtain swim bladder volume information. The success of the final prediction model is attributed largely to the fact that the vertical distribution density of the 55 species used serves as a reliable index to the total population of potential scatters within the insonified volume measured.