FISHERY BULLETIN: VOL 77. NO, 4 



E_ 



I 

 I- 

 CL 

 LU 

 Q 



TIME 



1658 1702 1706 1710 1714 1718 1722 1726 1730 1734 1738 1742 1746 1750 1754 1758 1802 1806 



DISTANCE [m] < > > . 



 ■• n Rnn ^'>nr\ ^a^^n OArtn 



Sy (dB/m3) 



.-^^ 



« — TRAWL- 



r-W 



•""-^^ 



■. 0°. 



.->. 



* Plankton only 



° Fish layer in 

 center of window 



Figure 2. — A qualitative 102 kHz echogram showing a migrating scattering layer in San Clemente basin, southern California. 26 

 January 1977. and calculated volume scattering strengths (Sv I at 102 kHz for selected 20 m depth intervals ( horizontal solid lines on 

 echogram). The volume scattering strengths are shown when the scattering layer is in the center of the integration window (open 

 circle), partially in the window (solid circle), and absent from the window (asterisk). The towing period for trawi 25660 is shown. 



DC 



< 



o 



Z 



cr 



< 

 o 



05 



(X 

 LU 



o 



X 

 I- 

 □. 



UJ 



o 



1700 



1 



TIME 



1730 1745 



SALINITY 



Figure 3. — Left: Depth of the center of the 102 kHz scattering layer plotted against time. Right: The temperature-salinity diagram 



for the water column immediately after trawl 25660. 



938 



