Effects of regulated lake levels on northern pike spawning habitat and reproductive success in Namakan Reservoir, Voyageurs National Park
Kallemeyn LW. 1987. Effects of regulated lake levels on northern pike spawning habitat and reproductive success in Namakan Reservoir, Voyageurs National Park. Research/Resources Management Report MWR-8. National Park Service, Research and Science Division, Midwest Regional Office. Omaha, NE
The effects of regulated lake levels on northern pike spawning habitat availability and reproductive success were evaluated in Namakan Reservoir, Voyageurs National Park. Topographic maps of two tributary deltas and the results of vegetative cover type surveys were combined to quantify the amount of northern pike spawning habitat between 1112 and 1117 ft msl.[feet above mean sea level]. Total areas of the two deltas at the upper elevation were 148 and 203 acres of which 19% and 29% respectively consisted of emergent vegetation or potential northern pike spawning habitat. Since over 90% of the emergent vegetation occurs above 1115 ft msl., a 5 to 6 foot rise in lake level must occur to flood and provide access to the preferred substrate for egg deposition. Northern pike reproductive success was higher in years when this occurred. With the present water management program this would not occur during the spawning season in most years. The frequency with which lake levels reach the spawning grounds during the spawning season can be increased by providing higher water levels earlier in the spring and by having a summer drawdown of two to three feet that promotes the establishment of emergent vegetation at lower elevations.