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. Practice with the unit with the Fish I.D. mode on and off to become more skilled at interpreting sonar re- turns.
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.
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