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Page 112 CPF180i and CPF300i
17.1.1 Understanding the Fish Finder display
Figure 17.1.1 - The Fish Finder display
Fishes
Fishes are represented as arcs because of the cone angle of the transducer. In fact as
the boat passes over the fish the leading edge of the cone strikes the fish, causing a
display pixel to be turned on. As the boat passes over the fish, the distance to the fish
decreases turning each pixel on at a shallower depth on the display. When the boat is
directly over the fish, the first half of the arch is formed and since the fish is closer to
the boat, the signal is stronger and the arch is thicker. As the boat moves away from
the fish, the distance increases and the pixels appear at progressively deeper depths
forming the remaining half of the arch.
Thermoclines
Are the zones where two layers of different water temperatures meet. The greater the
temperature differential, the denser the thermocline shows on the screen. Thermo-
clines are represented as horizontal stripes of noise. They are very important for fishing
since often many species of game fish like to suspend in, just above, or just below the
thermoclines.
White Line
The White Line shows the difference between hard, soft bottoms and even distinguish-
es between fishes and structures located near the bottom. In this way it is easier to tell
the difference between a hard and soft bottom and even to distinguish fishes and
structures located nearby the bottom. For example, a soft, muddy or weedy bottom
returns a weaker echo that is shown with a narrow white line while a hard bottom returns
a strong echo that causes a wide white bottom line.
Surface Clutter
Appears like noise at the top of the screen extending many feet below the surface. It’s
caused by many things, including air bubbles, bait fish, plankton and algae.
Structures
Generally, the term “structure” is used to identify objects like wrecks and weeds rising
from the bottom.
Bottom Echo Profile
Bottom profile recorded by the Fish Finder. When the echo sounder is set in Auto
Range mode, the bottom is kept in the lower half in the display.