Native fish spawning habitat: It’s more than just rocks in the river - Part 2

Defining restoration goals of an adaptive management native fish spawning habitat in the Detroit River.

The rock was placed with a crane, scoop by scoop, to ensure accurate placement. Photo: Michigan Sea Grant

The rock was placed with a crane, scoop by scoop, to ensure accurate placement. Photo: Michigan Sea Grant

Part 1 of this series documented the beginning of a native fish habitat restoration project in the Detroit River. Now we will explore how a project team that included Michigan Sea Grant, Michigan State University Extension, United States Geological Survey and others developed a strategy for defining restoration goals. 

To begin, the team dumped some rocks in the river. Abracadabra, habitat restored! Well, not quite.

When referring to habitat, the term “restoration” can be confusing. In a sense, the project team is restoring a habitat feature that once existed somewhere in the river. The river bottom, especially in the lower Detroit River, was once rocky.

However, today, areas of the Detroit and St. Clair rivers are relatively smooth-bottomed — blasted away years ago to make way for large ships. Throughout the corridor (as the rivers are sometimes called, since they provide the connecting link from Lake Huron to Lake Erie) sections of the river bottoms were dredged and dynamited for navigation, stripping away the natural rock structure once found there.

While scientists don’t know for certain where fish spawned more than 100 years ago in the rivers, the team was able to use historical documents — an atlas of reputed spawning sites along the river and geologic maps showing where bedrock shelves are and were — to choose the best site. Reefs were not necessarily being built where they had once naturally existed, but by creating reefs, the team is restoring habitat that fish find desirable.

“We hope that by re-creating lost spawning habitat we will help restore native fish populations. These connecting channels are some of the only free-flowing rivers left in the Great Lakes,” said Lynn Vaccaro, coastal ecosystem research specialist at the University of Michigan Water Center and former Michigan Sea Grant researcher.

“They run through some of the most developed areas of the region, and yet, the corridor still continues to sustain the largest remaining population of sturgeon in the Great Lakes and vibrant populations of other species like walleye. The idea is to use the fairly strong population in the St. Clair and Detroit rivers to bolster populations throughout the corridor, and eventually they’ll spread out from there.”

So, when we talk about restoration here, Vaccaro said, we can easily mean both the rebuilding of habitat and the rebound of native fish populations.

Michigan Sea Grant helps to foster economic growth and protect Michigan’s coastal, Great Lakes resources through education, research and outreach. A collaborative effort of the University of Michigan and Michigan State University, Michigan Sea Grant is part of the NOAA-National Sea Grant network of 33 university-based programs.

Read the full series

“Native fish spawning habitat: It’s more than just rocks in the river”

Part 1: The beginning

Part 2: Strategy

Part 3: Assessment

Part 4: New projects

Part 5: Project benefits

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