The effect of sediment dredging on the distribution of diving ducks at Lake Myvatn, Iceland

Abstract

Sediment dredging in Lake Myvatn, Iceland, which commenced in 1967, poses a threat to the populations of breeding and moulting waterfowl in the area. Detailed mapping of diving ducks on the lake was carried out in order to evaluate the impact of the dredging. Densities of diving ducks in the dredged area were among the lowest in the lake. Positions of ducks diving for food were mapped in a 4·8-km 2 area in the North Basin of the lake, which included the area distrubed by dredging. In June 1990 relatively few dives were recorded in the dredged area except by red-breasted mergansers Mergus serrator. In August numerous dives were recorded in the dredged area, yet they were significantly fewer than outside the area. The loss of habitat is still small in comparison with fluctuations which occur in the breeding populations, but dredging in areas close to the present dredging activities will have a disproportionately large impact on the waterfowl populations.