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Kirchoff-ray Mode Model Applications

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Models to Measures

The KRM model was developed independent of any empirical measurements. When completed, the model was verified using two independent data sets. In the left panel, maximum backscatter observations at 38 kHz from Nakken and Olsen (1977) were compared to backscatter predictions from five Atlantic cod scaled from 8 to 96 cm. On the right panel Jech et al. (1995) compared KRM backscatter model predictions to empirical target strength measurements of threadfin shad (Dorosoma petenense) at 120 kHz (squares), 200 kHz (circles), and 420 kHz (triangles). In both cases the data fit the independent model predictions well.


plot of TS vs. fish length Other KRM backscatter models have been compared to empirical measures (not all are published). Predicted target strengths of a group of 15 lavnun were compared to measurements of 8 tethered fish at 120 kHz. The plot to the left shows the mean and standard deviation of target strength plotted as a function of fish length. The set of points below the line are the overall mean target strength values for each of the 8 fish.
The upper set of points are the mean values for each fish with a minimum target strength of -50 dB. The original target strength frequency distributions were bimodally distributed. A threshold filter of -50 dB removes the small target strengths due to extreme tilt angles of the fish while tethered.


Cited References
Jech, J.M., Schael, D.M. and Clay, C.S. 1995. Application of three sound
scattering models to threadfin shad (Dorosoma petenense). J. Acoust. Soc. Am. 98: 2262-2269.
Nakken, O. and Olsen, K. 1977. Target strength measurements of fish. Rapp.
P.-v. Réun. Cons. Int. Explor. Mer 170: 52-69.
Relevant Publications
Horne, J.K., P.D. Walline, and J.M. Jech. 2000. Comparing acoustic
model predictions to in situ backscatter measurements of fish with dual-chambered swimbladders. Journal of Fish Biology (in press).
Haro, A., J. Horne, D. Degan, B. Kulik, and J. Boubee. 1999. An Investigtion
of the Feasibility of Employing Hydroacoustic Monitoring as a Means to Detect the Presence and Movement of Large, Adult Eels (Genus Anguilla). CARFC Internal Report No. 99-01.

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