The southern half of Iowa is well supplied with artificial impoundments in the form of water supply reservoirs, industrial pits, farm ponds and State owned artificial lakes. Individually these water areas arc relatively small, but collectively they furnish several thousand acres of fishing water. One important aspect of the management of these waters has been concerned with the education of the fisherman in the values of increased harvest of pan fish. An unknown share of the success of the harvest is related to the reaction of fish to the stratification of these artificial lakes and ponds. The fisherman must be informed of the nature of this phenomenon and how it may affect his fishing