M.Sc. (Freshwater Biology) / Please refer to full text to view abstract.

M.Sc. / Please refer to full text to view abstract

Seasonal utilization of sago pondweed (Potamogeton pectinatus L.) by waterfowl was studied at Bear River Miqratory Bird Refuge by comparing amounts of sago production on a series of plots on Unit Four. One plot was available to carp and waterfowl; one only to carp; and one available to neither. The cage used to eliminate carp and waterfowl use of a plot caused a significant increase in sago production. The increase was attributed to less turbidity and less wind and wave action within the cage. Carp distribution was limited to deep-water portions of Unit Four, a small area, and they had no significant effect on sago production. Therefore, sago production from carp and open plots was compared to determine utilization of sago by waterfowl. Waterfowl utilization of sago in summer and spring was not significant; however, 52 percent of the tuber crop was used by waterfowl in fall. The method of study did not allow detection of waterfowl use of windrowed or submersed seed. Water depths between 2 and 10 inches had little or no effect on waterfowl use of tubers in fall; however depths between 5 and 14 inches in spring and 4 and 13 inches in summer may have prevented full use of tubers. Tubers were most available to ducks in the first 6 inches of soil but were utili zed to 8 inch depths. A series of 50 foot-square pens (2,500 square feet) were stocked with semi-domestic mallards to determine the effect of certain levels of utilization on sago growth. Sago seemed to recover well after heavy spring utilization. Results concerning the effect of summer utilization on production were not conclusive. Sago recovered well in spring after waterfowl had consumed 52 percent of the tuber crop the previous fall.