1pUW6. Effects of absorptivity due to fish on transmission loss in shallow water.

Session: Monday Afternoon, December 2

Time: 3:04

Author: Orest Diachok
Location: Naval Res. Lab., Washington, DC 20375


Absorption losses of up to about 10 dB at night and 25 dB at twilight at the resonance frequency of pelagic fish, at a range of 12 km were observed during MODAL LION, a multidisciplinary experiment designed to test the feasibility of isolating biological scattering from other effects on long-range propagation at a relatively shallow (83 m) site in the Gulf of Lion. Comparison of measurements with a theoretical model that incorporates absorption layers in the water column permitted estimation of the average fish length (or bladder size), the number of fish/m[sup 3], and the depth of the layers. Good agreement between estimated parameters and echosounder and direct sampling results suggests the possibility of long-term tomographic mapping of fish parameters over large areas.

ASA 132nd meeting - Hawaii, December 1996