How to Understand Fishfinders

How to Understand Fishfinders
Fishfinders are capable of displaying a large amount of information, including depth and temperature of water, contour and composition of the bottom, the presence of fish and the presence of vegetation. For the angler who knows how to understand them, fishfinders can offer a vast amount of information. While fishfinders alone will not result in anglers catching fish, they can provide anglers with pertinent information that will help them locate fish and understand more about their underwater world.


Difficulty: Moderate

How to Understand Fishfinders

Things You’ll Need:
  • Fishfinder
  • Boat
Step 1
Turn the unit on by pressing the "On" button.
Step 2
Look for the digital reading of the depth of the water. This is the distance between the surface of the water and the bottom of the lake, river or reservoir. The depth reading generally will be located in one of the four corners of the fishfinder screen.
Step 3
Watch the fishfinder as it graphs the bottom, its contours and its composition. A line curving upward indicates the water is getting shallower. A line curving downward indicates a drop off and deeper water. The thickness and darkness of the line gives you more information about the bottom. A thick, solid line portrays a hard bottom like rock or gravel. A thin, light-colored line, or one that is not fully connected, indicates a soft bottom, like mud.
Step 4
Examine the graphed bottom for cover or structure. A long line could be vegetation or submerged trees. Your fishfinder should also be able to accurately graph how sparse or dense the cover is. Verify the results from your fishfinder by casting a lure out and bumping the lure through the cover.
Step 5
Search the entire screen, and make special note of any icons that are not tied to the bottom. These likely are fish, or perhaps debris that is floating in the water column. Most fishfinders will display these items as fish, or as icons shaped like boomerangs. The fishfinder also will display them in various sizes, so a large icon could mean there is a large fish beneath the boat.

Tips & Warnings

Most anglers find the automatic, rather than the manual, mode on their fishfinder works best for them.

Article Written By Larry Anderson

Larry Anderson has been a freelance writer since 2000. He has covered a wide variety of topics, from golf and baseball to hunting and fishing. His work has appeared in numerous print and online publications, including "Fargo Forum" newspaper. Anderson holds a Bachelor of Arts in print journalism from Concordia College.

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