Eagle 480 Installation And Operation Instructions Manual page 59

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
symbol 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
extending 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 actually miss fish that are present.
Does that mean Fish I.D. is broken? No — the feature is simply
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 varied 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 left is checked, the feature is on.
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