Anatomy of a lake

One of the most difficult skills that novice anglers need to develop is to imagine what is under the water as they look out at the placid surface of a lake.  The bottom of the lake is not uniform. It has a variety of depths, different bottom types, open water and water close to shore. In addition, it may have: rock piles; mud flats and sand flats; shallow aquatic weed beds; deep weed beds; steep cliffs and gradual slopes; old stream channels; boat docks; old roadbeds; tree stumps; standing flooded timber; old house foundations; and a variety of other items. Each of these items is important to the fish species that inhabit the lake. Some fish will use one or several of these items extensively and avoid the others; while other species will use different features almost exclusively.

While this list may seem daunting to first-timers, do not let it overwhelm them. Lakes can be “dissected” into manageable parts, and there are likely visual clues on the lakeshore to help identify underwater features. It is far more productive to become very familiar with one smaller section of a large lake than trying to learn the entire lake at one time. 

Obtaining a hydrographic map of any lake, even if it is not the lake they will ultimately fish, is a great learning tool. The best maps will also show topographic features on land as well.

Careful study of a hydrographic map will identify many of the features listed above. If the map shows topographic contours on the land, you will likely note a strong relationship between the features on the land and those under water. For example, a ridge or hill that descends to the lakeshore also very likely extends under water. This likely indicates that there are steep drop-offs along the side of the underwater ridge, and potentially a turn in any channel that flows along the underwater base of the ridge. A flat area that abuts the lakeshore likely extends into the water as well, and likely indicates a shallow “flat” under the water. 

Natural lakes tend to have fewer features than man-made lakes. They also tend to be shallower, but likely will have deeper areas. Most lakes will have at least one in-flow stream and an out-flow stream. In between these two points there may be a deeper channel. The channel rarely flows in a straight line; it likely will meander based on the contours of the surrounding land. Areas with stronger current will likely have a gravel bottom; those with slower water flow will likely be mud or silt.

In glacial areas, natural lakes will likely have additional features, such as scattered areas of large rocks, deeper “basins,” and sunken islands.

Man-made lakes can have numerous features not found in natural lakes, such as old roadbeds, flooded house foundations, and flooded tree stumps or standing timber. In some situations, old pre-construction topographic maps may be available to help identify underwater features. Observing features on the land adjacent to the lake (including soil type) will often reveal similar features under water.

For example, if you observe a steep slope with a lot of basketball-sized rocks along the shore, you can reasonably assume that this extends into the water. The steep slope with rocks for both prey species and predator fish to hide behind would make this location a prime area to fish in the summer when panfish are holding a bit deeper, and may be associating with other forms of cover like rocks.

The dam area of a man-made lake often contains rocks to prevent erosion and a steep dam face. Both of these features may attract sunfish and crappie.

Time on the water will help hone observation and interpretation skills so a person can make better judgments about where to fish.

Unfortunately, shore access may limit where you actually can fish. Often fishing piers will have additional fish holding habitat, such as brush piles, sunken Christmas trees and artificial reef material.

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