Many ponds and reservoirs in Ohio contain little or no natural underwater structure that could, if present, concentrate fish and increase angling success. Ponds treated with aquatic herbicides are essentially without any type of vegetation that could provide structure for fish. Most reservoirs in Ohio had natural structure (such as trees) removed prior to filling to ensure safe navigation. Natural structure may also be lacking because age has decayed any remaining timber and fluctuating water levels prevent growth of submerged vegetation. Placement of artificial structure in ponds and reservoirs is an effective way to concentrate fish. In the absence of structure, fish are often widely dispersed or travel in hard-to-locate groups known as schools. Angling is often difficult when fish exhibit these behaviors. Research done at Ohio State University has shown that artificial structures can concentrate fish and increase angling success.