Bathymetry and Ice Fishing: Tips for Finding Great Locations

A good set of bathymetry maps and a hand-held GPS can go a long way 

By Debbie Kay

There are a lot of ways to use technology to find fish in open water.  It becomes more difficult when that water is iced over.  A good set of bathymetry maps and a hand-held GPS can go a long way to making it easier, however.  Here is a look at what you need, and some of the best places to find fish when the water freezes over.

bathymetry
Photo Credit mattcatpurple from Hay River, Canada

GPS and Bathymetric Software

There is some precision needed for this technique, so a good hand-held GPS is an important place to start.  Read your degree of error on your GPS – it will show you the possible circle of error where your point is actually found.   Ten feet is pretty unavoidable, but thirty feet of error may not get you what you want.  GPS works by reading satellites, so most lakes provide a clear enough view of the sky to give you a good reading provided you have a halfway decent GPS.

Best Places to Find Bathymetry

The other trick is to have a GPS that uploads the kind of software you want to use.  USGS maps, National Geographic software and some others have some decent bathymetry these days, usually enough to get to the spots you’re looking for.   Many state agencies have bathymetry available for download too, if you know where to look.  If you don’t, a few well-placed phone calls to your state fish and wildlife agency will quickly get you in the right place.  It may be a smart play, if you haven’t bought the GPS yet, to find the software you want first and then choose the GPS based on its compatibility with that software.

Using Bathymetry

The best combination, to verify accuracy, is to use bathymetry to choose the location of your test hole, then add a down sounder to verify your bottom.  The reason this works so well is that it can get the features that bathymetry is too subtle to catch.  By swinging your down sounder in a line, you can extend the width of its view- keep doing this at different angles to get a full idea of the “cone” of area you’re looking for.  Clearly, the sign of fish is good news.  However, there are three other things to consider in looking for fish:

  • Shallow Vegetated Areas: This is the gimme spot.  Shallows with submerged vegetation provide a level of protection for smaller fish.  You will find them congregated here, but they probably won’t be big.  If you want a spot with likely bites but don’t care about size, this is a good choice.
  • Muddy Flats: These waters sit deeper than the vegetation, and are flat enough to get a nice collection of silt on the bottom.  That silt is perfect for aquatic insects, and will bring in some of your bigger fish. You can test the area for the needed mud by dipping weights on a string into the bottom and seeing what sticks.  Even the feeling of stickiness before you pull it up is a good sign.
  • Depressions: Within these two areas, the best locations for fish are the shallow depressions.  These small natural features may only be a foot or so below what’s around it, but fish tend to congregate to them.  Find these spots, and you’ll increase your chances for a good day on the ice.

Do you have additional tips for bathymetry?  Want to share your own stories?  Leave a note in the comments below.

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