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3.4 Surface Noise/Aeration
When the waters are rough or the boat passes over a wake, surface noise may appear near the zero line. As surface turbulence is acous- tically equivalent to running into a brick wall, the bottom echo will be displayed intermit- tently. Similar noise sometimes appears when a water temperature difference (thermocline) exists. Different species of fish tend to prefer different temperature zones, so the ther- mocline may be useful to help identify target fish. 200 kHz tends to show shallow ther- moclines better than 50 kHz.
In rough waters the display is occasionally in- terrupted due to
Surface noise
Caused by aerated water
Thermocline
Figure 3-4 Surface noise/aeration
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