The Fish I.D. feature displays symbols on the screen in place of the ac- tual fish echoes. There are three symbol sizes: small, medium and large. These show the relative size between targets. In other words, it displays a small fish symbol when it thinks a target is a small fish, a medium fish symbol on a larger target and so forth.
Fish I.D. is an easier way for a sonar novice to recognize a fish signal return when he sees it. But, locating fish by symbol only does have some limitations.
Your sonar unit's microcomputer is sophisticated, but it can be fooled. It can not distinguish between fish and other suspended objects such as trotlines, turtles, submerged floats, air bubbles, etc. Individual tree limbs extending outward from a group of limbs are the hardest objects for the Fish I.D. feature to distinguish from fish.
Fish 
arches 
Fish I.D. symbols
Underwater scene in normal fish arch mode (left). Fish I.D. menu with
the feature turned on (right).
To see what is under your boat in maximum detail, we recommend you turn off Fish I.D. and begin learning to interpret fish arches.
You may see Fish I.D. symbols on the screen when actually, there are no fish. The reverse is also true — Fish I.D. can actually miss fish that are present. Does that mean Fish I.D. is broken? No — the feature is interpreting so- nar 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 informa- tion. This and other features can help you "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. This unit's default Fish I.D. setting is on.
Fish I.D. is most handy when you are in another part of the boat or per- forming some task that prevents you from watching the sonar screen. Then, you can turn on Fish I.D. and the audible fish alarm. When that lunker swims under your boat, you will hear it!
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