As lakes age (specifically reservoirs) many types of structure (particularly woody debris) deteriorate. The end result is lakes lose areas that used to concentrate fish for the angler. Without these sites angler success often declines. A similar situation occurs in the trout streams of Northeast Iowa. Natural pools, undercut banks, and logs disappear with time. Fishery management teams often place habitat in the form of trees, rock or other artificial structure in lakes or in the form of half-cut logs, bank hides, or stabilized shorelines in streams to improve angler success. Examples of habitat improvement structures

An important part of habitat improvement is marking the structure so everyone can easily find it once the lake refills. Buoys, markers, and putting the location on contour maps of the lake help the anglers locate the structure to optimize fishing.

Some habitat is available commercially. This structure is made of plastic planks that snap together. It is much more durable than wooden structures, providing many years of use by fish.

<Habitat improvements aren't just made in lakes. In many trout streams, we often build structures called bank hides which produce crevices under the stream bank for the fish to hide.

Beds of wooden stakes provide excellent habitat for fish to hide and reproduce in.

As soon as the structure is covered by water, it will begin to attract fish.