### ASA 130th Meeting - St. Louis, MO - 1995 Nov 27 .. Dec 01

## 2pAO6. Sensitivity of the inverse problem to size-class selection.

**J. Michael Jech
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*Great Lakes Ctr., Buffalo State College, 1300 Elmwood Ave., Buffalo, NY
14222-1095
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**John K. Horne
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*Buffalo State College, Buffalo, NY 14222-1095
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**Denise M. Schael
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*Univ. of Zululand, KwaZulu/Natal, South Africa
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Fisheries sonar systems typically operate at discrete frequencies between
38 and 420 kHz. Can length-frequency distributions of aggregated fish be
accurately estimated using available frequencies and the inverse problem? The
inverse problem requires measured fish lengths and realistic scattering models.
The size distribution of threadfin shad (Dorosoma petenense) in Lake Nornman was
estimated using 120-, 200-, and 420-kHz data, and a recently developed
scattering model [Jech et al., J. Acoust. Soc. Am. (in press 1995)]. Size
distribution estimates were compared to length frequency measurements from purse
seine catches. Fits of probability density functions (PDF's) using the inversion
technique to those using length frequency measures were sensitive to the choice
of fish size classes. Preliminary results indicate that estimation of length
frequencies using multi- frequency data and the inverse problem appears
dependent on the shape of measured length-frequency distributions. [Work
supported by NOAA Coastal Ocean Program (NA16RGO 492-01) and NSF (OCE-9115740).]