Rocks in the River: More About Native Fish Restoration

It was just before Thanksgiving 2001 when Michigan Sea Grant was asked to take the lead on a potential project in the Detroit River. On the surface it was simple — one time, very specific, a chance to construct habitat in the river to restore native fish populations. Sea Grant, USGS and others had just days to put together a team and to come up with a proposal. From the beginning, the team agreed that performing assessments, before and after the restoration work, was critical to the viability of the project.

An Experiment

That meant that the team approached the project in two ways: as a research project — what would happen if…? And as a restoration project — here’s an existing population of sturgeon and other native fish, they are spawning on similar rock types, if we build spawning habitat in the right areas, out of the right materials, will the populations be sustained and will they grow?

The team carefully considered where to put the rocks, place them specifically and then record what happened. The team approached this effort as an experiment because they were uncertain about what would work.

substrateStarting out, they didn’t know what kinds of rocks to use, or what size. They didn’t know where a reef should go. Spawning requirements are one thing, but what happens when the fish hatch? They need a hospitable environment to hide, feed and grow. What happens when they get bigger? Will they be poached? Will they survive to spawn? That’s what the post-restoration assessment work would help figure out.

The assembled team, consisting of specialists from the USGS, U.S. Fish and Wildlife Service, Michigan Department of Environmental Quality and Department of Natural Resources as well as others, had decades of experience working with fish and aquatic habitats.

After significant assessment, lining up the science, laying out objectives and loads of research on spawning and juvenile fish survival needs, the team built reefs. In 2004, they installed a series of rock reefs in the Detroit River, near Belle Isle. The reefs were created with different sizes and types of rocks to learn what might draw the most fish. They monitored the reefs for spawning activity.


Abracadabra: Restored!

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 structure once found there.

credit Adam Lintz Blue Visions Media - Sturgeon bluewaterWhile 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, Michigan Sea Grant coastal research specialist.

“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.


Testing the Spawning Waters

AInspectingEggMatsfter the reefs were created, the researchers performed post-restoration assessment. Essentially, they check the area for evidence of fish and fish spawning. Assessment of this kind mostly consists of collecting fish in the project area, using set lines and nets to check for spawning-ready adults as well as young fish.

Laying down fish egg mats, usually modified furnace filters, to collect eggs is another tactic to confirm spawning reefs are being used. The researchers were particularly interested in whether desirable species, meaning native species especially those that are relatively rare (e.g., lake sturgeon) or commercially important (e.g., walleye), are using the new reefs. The eggs are later hatched in the lab to confirm which species were successful.

In some cases, underwater cameras are sent below the surface to record whatever action may be found there. Scuba divers are sent to investigate the reefs to ensure they were constructed properly or subsequently to check the condition of reefs and may also report visual confirmation of fish on or near the rocks.

What Happened

Before the Belle Isle reefs were constructed, only two species of fish were collected in the defined space. After construction, 20 species of fish were collected, including 14 native fish species. Many of the fish that were collected were ready for spawning (had eggs or sperm).

Something else happened. People were paying attention to the project. And the project gained momentum; media picked up on the story.

“Ecologically, this kind of thing is super important because, one, it can right some of the wrongs that were done historically to the river and, two, it can help native fish species recover,” said Vaccaro. “Among those species are fish like the northern madtom, an extremely rare native catfish species, and the lake sturgeon, a fish that is incredibly charismatic, and of course walleye and other commercially important fish.”

The project blossomed from one, stand-alone reef project to an ecosystem wide approach with more fish habitat restoration projects following behind.


Spawning More Restoration

GLRI st clair detroit river system-8x11The Belle Isle reefs were the first step and provided the team with on-the-ground, real life answers to some questions about fish habitat construction. It largely showed that restoration of fish spawning habitat in the corridor was possible and brought managers closer to solving the riddles that each restoration project faces (location, rock sizes, nursery habitat, etc.).

In 2008, more reefs were constructed in the Detroit, near a place called Fighting Island. A few years after that, in 2012, a series of reefs were constructed across the Middle Channel in the St. Clair River, just north of Lake St. Clair.

Each reef was constructed using different types of rock material. Based on these three projects, the team discovered that target fish species — lake sturgeon, walleye and lake whitefish — didn’t seem to have a preference for one type of rock. What they did prefer were rocks piled deep enough to form crevices that protect the eggs from predators and from being washed downstream, and that remain relatively free of silt, algae and mussels.

The conclusion: 4-8 inch limestone works best to encourage native species development, while discouraging invasive species.

The reef projects are an example of adaptive management in action.

“We’re not just doing this work for the sake of knowledge alone,” said Read. “This is real, actionable science that people really respond to because they can see it and they can see results. It’s also science that supports management decisions. That’s what sets our adaptive management approach to restoration apart.”


Economy and Ecology: Not-So-Strange Bedfellows

What also sets restoration apart is the far-reaching and direct benefits. While the fish that are using the reefs to spawn are seeing a discernible benefit — as is the surrounding ecosystem — the advantage to humans may be more difficult to spot.

A recent study published in the journal Marine Policy[1] looked at the connection between restoring coastal habitat and the economy. The study determined that, on average, habitat restoration projects directly generate 17 jobs per million dollars spent.

To put it in context, that figure is similar to other conservation industry job impacts, but is much higher than the per-million-dollar return of other industries like coal, oil and gas (non-pipeline building), where the same investment results in an average of 1-2 direct jobs. Of course, that is over the short term.

Long term, other studies cited in the article suggest that investing in habitat restoration also leads to future job creation in rebuilt fisheries and coastal tourism, as well as other long-term benefits to coastal economies, including higher property values and better water quality.

Michigan Sea Grant Sturgeon Reef Construction tour 2012Jim Felgenauer, current president and one of the founders of the St. Clair-Detroit River Sturgeon for Tomorrow group, said he has seen encouraging results in the community as a result of the habitat restoration projects.

“There certainly has been some direct economic impact because local contractors are being used on the projects,” he said. “The willingness for others to make such a large investment in our river adds to our understanding of how important and special it is.”

Felgenauer went on to say that the restoration has also created many opportunities for the community to become involved in the process and to forge a stronger connection with the river and its fishy inhabitants. For example, the Blue Water Sturgeon Festival in Port Huron will be held for a second year this May.

Read agreed. “Festivals, higher quality of life, tourism, a desirable, healthy environment — these things all add up to creating attractive places to live, and that in turn creates a stronger economy. You can live in this neighborhood,” she said, “Or you can live in this other community where there are cool things happening, a community that’s known for its environmental amenities. Which would you choose?”


What Comes Next?

The project team has three more reef construction projects planned for summer and fall 2014. The St. Clair River will see two new reefs near Pointe aux Chenes in Algonac and Harts Light in East China; and either East Belle Isle or Grassy Island will be the home of new spawning reefs in the Detroit River.


[1] P.E.T. Edwards, A.E. Sutton-Grier, G.E. Coyle, Investing in Nature: Restoring coastal habitat, blue infrastructure and green job creation, Marine Policy, Volume 38, March 2013, Pages 65-71, ISSN 0308-597X.