The depth finder originated in the world of the submarines.
We know it as SONAR or “Sound Navigation Ranging”. You
might remember watching a movie that included submarines playing war
games.
In terms for the rest of us, this is how SONAR works.
Pulsed sound waves are sent through the water. When the wave strikes
an object, like the sea bottom, a fish, the Loch Ness Monster or some
other type of structure, the wave gets reflected back to the transducer.
The transducer then organizes the information and sends it to the
display.
The processor is programmed to know the rate of sound
transmission through the water. With this information it can extrapolate
the range or depth. Now that you have determined the depth, you can
also determine what the fishing technique will be. It will determine
what type of lure or bait you use.
In most cases you will look for underwater terrain
that tends to be a location where fish congregate. This can be stumps,
logs, underwater brush, drop-offs and channels. Fish activity might
also be an indicator to the experienced fisherman. A tight ball of
bait fish might indicate that a predator fish might be nearby.
SONAR cannot tell you what kind of fish is swimming
below you, but you can determine, based upon the features underwater
and the behavior of the fish, what is a bait fish and what is a fish
you would target as to catch.
There are many features that are not described here,
but that is up to you to decide now that you have a general understanding
of how the depth/fish finder works
