Construction Update:

The Ozaukee County Planning and Parks Department (Department) is currently implementing a project to improve the form and function of the Milwaukee River Mequon-Thiensville Dam Fishway, located at river mile 20 in the Village of Thiensville, Ozaukee County, WI. The fishway was constructed in 2010 with support from multiple partners (e.g., Department, WDNR, City of Mequon (City), Village of Thiensville (Village), U.S. Fish and Wildlife Service, National Oceanic and Atmospheric Administration, etc.) and is currently operated and maintained by the Village and the Department.  The fishway design consists of pools and weirs within a meandering stream-like channel. Water to the fishway is supplied and controlled at the dam’s sluice gate where it flows for approximately 1,100 ft. before exiting at the river near the dam’s north spillway abutment under the pedestrian bridge.  Fish entering the fishway swim through these weirs and small resting pools before re-entering the Milwaukee River above the dam. The fishway has been very successful in meeting original project goals, as over 37 species of fish have been documented passing through the fishway to bypass the 6.5’ high dam. 

However, additional enhancements are being constructed so the fishway can perform at its full potential, particularly for larger-bodied fish such as Lake Sturgeon (Acipenser fulvescens), and to reduce annual operation and maintenance costs. The Village completes annual maintenance including weir adjustments and erosion controls; however, this work is dependent on staff availability and work may be limited by high flows or seasonal conditions.  Often, annual improvements and fishway optimization is delayed until after native fish migration and spawning periods (e.g., “ice-out” conditions typically in late-March for Northern Pike). A more permanent, stable fishway design will ensure that the fishway is optimized and/or fully functional prior to expected seasonal migration and spawning runs. 

Project activities include enlarging the weirs, increasing pool size and depth, significantly reducing the length of runs, and adding cover and velocity breaks. These improvements will optimize the number of fish attracted to and passing through the fishway by increasing fish-attracting flows through the fishway and at the fishway entrance, particularly for larger-bodied fish including Lake Sturgeon. These enhancements will also reduce recurring operation and maintenance costs, particularly costs associated with repairing erosion at the weirs.

Construction activities are being completed by the Ozaukee County Highway Department in cooperation with the Planning and Parks Department and Village.  The project is supported by grants from the US Fish and Wildlife Service Fish Passage Program, National Fish and Wildlife Sustain Our Great Lakes Program, Wisconsin Department of Natural Resources River Protection Management Program, and the Fund For Lake Michigan, in addition to in-kind support from the Department and the Village.  For more information please contact Matt Aho, Ozaukee County Planning and Parks Department Program Manager.