FISH ARCHES
Fish arches are created when the cone of sound passes over a fish. The distance to a fish when the cone first strikes it is shown as "A" below. When the center of the cone strikes the fish, the distance is shorter as shown "B". As the cone leaves the fish, the distance increases again as shown in "C".
When the Fish I.D. mode is off, the depth of the water will affect the size and shape of the fish arch due to the cone angle diameter. For example, if the cone passes over a fish in shallow water, the signal displayed on the unit may not arch at all. This is due to the narrow cone diameter and the resolution limitations of the display.
Very small fish probably will not arch at all. Medium sized fish will show a partial arch, or a shape similar to an arch if they’re in deep water. Large fish will arch, but turn the sensitivity up in deeper water to see the arch. Because of water conditions, such as heavy surface clutter, ther- moclines, etc., the sensitivity sometimes cannot be increased enough to get fish arches.
BOAT'S DIRECTION OF TRAVEL
AB
C
ABC
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