Eagle FISHMARK 640C, Installation And Operation Instructions Manual

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There are several fish symbol sizes. These are used to designate the
relative size between targets. In other words, Fish I.D. displays a small
fish symbol when it thinks a target is a small fish, a medium fish sym-
bol on a larger target and so on.
The sonar's microcomputer is sophisticated, but it can be fooled. It can't
distinguish between fish and other suspended objects such as trotlines,
turtles, submerged floats, air bubbles, etc. Individual tree limbs ex-
tending outwards from a group of limbs is the hardest object for the
Fish I.D. feature to distinguish from fish.
You may see fish symbols on the screen when actually, there are no
fish. The reverse is also true. The illustrations on the next page show
how Fish I.D. can be turned on. Does that mean Fish I.D. is broken?
No, the feature is interpreting sonar returns in a specific way to help
take some of the work out of reading the screen. Remember, Fish I.D. is
one of the many tools we provide so you can analyze your sonar returns
for maximum fish finding information.
This and other features can help you successfully "see" beneath the
boat under various water and fishing conditions. So, practice with the
unit in both the Fish I.D. mode and without to become more familiar
with the feature. The default for Fish I.D. is off.
Sonar Features menu with Fish I.D. Symbols selected (at left, dual-
frequency menu; at right, single-frequency menu). When the check box
to the right is checked the feature is on.