November 29, 2016
Water Center restoration partners received welcome news this spring – the team discovered lake sturgeon eggs on four different constructed spawning reefs in the St. Clair and Detroit rivers. These results delighted team members because it meant that this state endangered fish species found the new habitat structures and deemed them suitable for spawning.
Egg mats collected 1300 sturgeon eggs per square meter from the team’s most recent and largest project to date, a 4-acre spawning reef upstream of Grassy Island in the Detroit River, near Wyandotte, Michigan. Although lake sturgeon were known to pass by this area, monitoring efforts detected no eggs prior to restoration efforts. Importantly, sturgeon eggs appear to be incubating and hatching successfully on the reefs, producing viable larvae that are showing up in nets downstream of the constructed reefs.
These results are particularly encouraging as Water Center partners begin building another spawning habitat project near the head of Belle Isle in the Detroit River this fall. The project is part of a comprehensive remediation plan under the Area of Concern program, supported by the Great Lakes Restoration Initiative. The upcoming Belle Isle project will be the seventh spawning reef constructed within the St. Clair and Detroit rivers over the past twelve years.
The restoration team has taken an adaptive management approach to restoring spawning reefs. Through rigorous monitoring integrated into an adaptive process, the team has built on lessons learned from prior fish habitat restoration projects. Scientists from the USGS Great Lakes Science Center, US Fish and Wildlife Service, the University of Michigan, and Michigan Department of Natural Resources have spearheaded the biological and physical monitoring of restoration projects. The Water Center has served as group facilitator to ensure that the team bases its decisions on sound science and incorporates the group’s collective best judgment into project design, permitting, and construction.
The reef restoration team also works with hydrodynamics experts from the University of Michigan College of Engineering and the USGS Geomorphology and Sediment Transport Laboratory (see: winter 2016 article). These experts in river dynamics have helped the team improve their site selection and reef design process by better predicting and avoiding in-filling from excessive sediment. Annual sidescan sonar and video surveys of recent projects show that reef rock in recent projects has remained relatively clear of sand and silt.
Constructed reefs help replace rocky spawning habitat that was destroyed during the construction of shipping channels or made inaccessible by dams in tributary rivers. A spawning reef is essentially a bed of loose limestone cobble placed on the river bottom. For more information about current and past projects and the science that has guided restoration efforts, visit: