Eagle Electronics SeaFinder 480DF - Manual (Page 49)

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Fish Symbols vs. Full Sonar Chart
You may have noticed in the quick reference that we used fish arches in
full sonar chart mode for our example, and not the popular Fish I.D.

fish symbol feature. Here's why.
Fish I.D. is an easier way for a sonar novice to recognize a fishy signal
return when he sees it. However, locating fish by symbol only has some
limitations.
Your sonar unit's microprocessor is remarkably powerful, but it can be
fooled. Some of the echoes calculated to be fish could be tree limbs or
turtles! To see what's under your boat in maximum detail, we
recommend you turn off Fish I.D. and begin learning to interpret fish
arches.
Fish I.D. is most handy when you're in another part of the boat or
performing 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'll hear it!
Fish I.D. can also be useful when you want to screen out some of the
sonar detail gathered by your unit. For example, in one case fishermen
in San Francisco Bay saw clouds of clutter in the water but no fish
arches. When a down rigger was pulled up, it brought up several small
jellyfish. The fishermen switched their sonar to Fish I.D., which
screened out the schools of jellyfish and clearly showed the game fish
there as fish symbols.
Other Free Training Aids
The sonar options section discusses Fish I.D., fish alarms and other
features in greater detail. If you or a friend has Internet access, you can
also learn more about interpreting what you see on your sonar screen.
Visit our web site,
WWW.EAGLESONAR.COM . Be sure to check out the
free Sonar Tutorial, which includes animated illustrations and more
pictures of actual sonar returns, all described in detail. There's even a