V 



SHEEP-HEAD 



Acoustic intensity contours provide a frequency-time 

 plot of signals reflected from a large sheep-head, 

 Pimelometopon pulchrum. The analysis shows intri- 

 cate patterns which differentiate this fish from 

 other targets. 



JACK MACKEREL 

 Similar acoustic intensity contours were 

 recorded and analyzed from a school of jack 

 mackerel, Trachurus symmetricus. Other 

 fish studied were: halfmoon, Medialuna 

 californiensis ; grunion, leuresthes tenuis; 

 jacksmelt, Atherinopsis californiensis; and 

 topsmelt, Atberinops affinis. 



Even individual targets as large as scuba divers 

 may be identified from analysis of echo intensity 

 contours and frequency. Contours left are for a 

 female scuba diver 10 feet away. 



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