Fish and Wildlife Service biologist Tyler Yasenak taking flow measurements in the lower Fox River, Wisconsin. Photo by Rob Elliot

Biologist from the Fish and Wildlife Service’s Green Bay Ecological Services Office and Green Bay Fish and Wildlife Conservation Office worked together with the U.S. Army Corps of Engineers, Wisconsin DNR, and Thilmany Paper Company to collect flow data resulting from operational modifications of the De Pere Dam located on the Lower Fox River tributary to Green Bay.  Thilmany’s hydroelectric license requires that they develop an operational plan to protect lake sturgeon, which spawn below the dam.  The data collection efforts are in support of developing this plan.

Lake sturgeon are a species of special concern in Lake Michigan and this spawning area on the Fox River is the third largest spawning aggregation of sturgeon from Lake Michigan.  However, water level management within the Wolf River-Lake Winnebago-Fox River drainage basin is a highly regulated process that requires the Army Corps to accommodate a multitude of resource needs and user interests that include hydropower generation, pleasure boating, fishing, emergent plant restoration, and flood control.  The conflict in interest between these uses and users frequently results in the spawning grounds becoming dewatered during the egg incubation and larval development period.

The Army Corps did their best to satisfy these interests while maintaining a minimum flow to ensure the spawning habitat remained watered.  When the Corps could no longer maintain the minimum flows Thilmany modified their operations through the selective placement of flash boards and the occasional decrease in electric generation to maintain the minimum flows.  In fact, Thilmany stopped generation altogether when the flows were dangerously low and the sturgeon larvae were nearing the end of their emergence and downstream migration.  Through the cooperative efforts of all parties, the sturgeon had a successful spawning season despite a dry year.