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The positive correlation of the adverse effects of the steady increase in the number of sport fishermen on the "biosphere" of fishing waters is now more often mentioned. While studies on the pressures caused by the presence of fisherman during the breeding period continue, up until now little is known of the effects of fishing pressure during the molting, resting (pause in migration), and over-wintering periods. The paper is concerned with the Häverner Marsh, made up of eight water-flooded gravel pits, which in the last 25 years, have been opened, enlarged, and because of technical advances, recultivated in recent years. One of the pits is still being quarried, and fishing is not allowed there because of safety concerns. Ziegler graphs the annual population of mallards and relates this to the presence of fishermen. From late summer in 1978, fishing has been suspended on four government-owned gravel pits serving as wildlife preserves. The suspension continues except for the pond "Wilddiebereien." With the exception of the molting period, it is possible for the mallards to avoid the disturbances found on the "fished ponds." Without such restrictions on fishing, it is not possible to prevent disturbances of the waterfowl. This is not an accusation against fishermen, but a simple fact, verified by observations in England by Tanner (1979). The paper ends by citing the decision of the DS-IRV at the 20th symposium in Ratzburg (1972) that at least 20% of the gravel pits are required to be set aside as nature preserves. (Translated from German)