Hydrographic surveys and acoustic Doppler current profiler measurements collected to monitor fish spawning reef placements, Detroit and St. Clair Rivers, Michigan, September 13-16, 2021 and May 2-5, 2022

The U.S Geological Survey conducted hydrographic surveys from September 13-16, 2021 and May 2-5, 2022 to monitor fish spawning substrate placements (reefs) in the Detroit and St. Clair Rivers, Michigan. This work was conducted as part of a reimbursable agreement with the Environmental Protection Agency to provide technical assistance in areas of concern. A multibeam echosounder was used from the Great Lakes Science Center research vessel Cisco in 2021 and Desmid in 2022 to collect the hydrographic data. These data were used to generate maps of river bottom topography in locations where spawning substrates have been placed. The reefs surveyed in the Detroit River in 2021 included: Fort Wayne, New (East) Belle Isle, Belle Isle, and Grassy Island. The reefs surveyed in the St. Clair River in 2021 included: Middle Channel, Pointe Aux Chenes, and Harts Light. In 2022, the same reefs that were surveyed in 2021 were resurveyed. The Fighting Island reef in the Detroit River was also surveyed in 2022. The data for each study reach were produced in LAS format supported by most geospatial software. Additionally, in May 2022 an acoustic Doppler current profiler was used to collect measurements of river discharge and depth-averaged flow velocity near the Middle Channel reef.