When you go hunting you don’t just walk to a random patch of trees and set up your stand (at least you shouldn’t). Fishing is much the same. Studying topographical maps of the lake and using sonar data can help ensure that you are not just casting into the abyss hoping a fish stops by.
Structure is what helps differentiate the lake for the fish who live in it. Structure is the topographical features in the bottom of the water. Holes, drop-offs, ledges, and other lake bottom features. Cover is weeds, logs, and old cars. Cover is often found near structure, but structure is what we are going to focus on here.
Why Do Fish Use Structure?
One of the best examples I have heard to explain why fish like structure is this: Imagine you are walking through the desert. There is nothing for miles. You come across a tree. You will probably walk by the tree and you may even stop at it. Now add a fence near this tree and you will invariably have to walk by the fence as well. Other people walking by will likely stop here too.
Fish use structure the same way. The natural terrain features that differentiate the lake bottom in an otherwise bland environment are like truck stops on an empty highway: they are natural places to stop. Also, structure often provides routes of travel between different parts of the lake.
Ledges and Drop-offs
Ledges and Drop-offs can be great spots to fish. These transitional zones where the depth changes can be spots where bass and walleye congregate. The shallower side of the ledge can be an area where baitfish congregate. Being close to the deeper water can provide an easy escape path for predator fish which greatly adds to their comfort level.
Fish, like most animals, need food and cover. Any areas underwater that can provide both of these will be good spots to start looking for fish.
So before you hit the water get out a topo map of the lake. Study it for underwater ridges, sudden elevation changes, humps, holes, and any other defining terrain features. Apps like OnX have topographical maps available. Also, you can check your local DNR agency for detailed lake maps. The Michigan DNR keeps a website with 27,000 maps of inland lakes which can be found here.
When you get to the water observe the landscape to search for any features you may have missed. Pay attention to any islands in the water, long thin shorelines that jut out into the lake, sand bars, or anything else that can signal the underwater structure you are looking for.
With these spots in mind, cruise the lake in your boat and use the sonar on your fish finder to see the features up close and confirm your suspicions. If you are nearing a ledge and see a lot of baitfish congregating, the odds are pretty good that you may find the fish you’re looking for there. Make sure you are marking the promising spots with pins on your map or fishfinder device. Throwdown marker buoys if you have them to help give you a surface visual on the boundaries of the structure.
You can do all the research in the world and fish all the right spots and still may not find fish on a particular day. The weather and water conditions also have a large impact on your success. However, taking a targeted approach to the lake instead of blindly fishing will improve your odds and help you narrow down the potential spots where fish are likely to be.