The Huron-Erie Corridor, consisting of the St. Clair River, Lake St. Clair and the Detroit River, is a regular spawning site for many fish species in the Great Lakes. But dredging operations to increase shipping navigability through the corridor have changed this vital ecosystem. With native species on the line, ongoing research funded by the Great Lakes Fishery Trust seeks to determine the best route for restoration, and demonstrate why a well-maintained corridor is so valuable to the entire Great Lakes region.
Restoration efforts have targeted the Huron-Erie Corridor extensively since 2010, said Darryl Hondorp, a research fishery biologist with the U.S. Geological Survey. Dredging removed desirable spawning substrate from the channel bottom and modified its shorelines.
“There’s also been a considerable amount of shoreline hardening, where natural shorelines have been replaced by wood or steel,” Hondorp said. “That’s removed quite a bit of access and completely destroyed some wetland habitat.”
Lacking wetlands to filter its waters and with fewer hydrological inputs and outputs, the corridor suffered further from already-burdensome waste discharge. Populations of fish and other wildlife in the corridor have diminished, and many of those that remain are unfit for human consumption.
Hondorp, along with Edward Roseman and Bruce Manny of the USGS, conducted a study that tracked lake sturgeon throughout the corridor. Lake sturgeon have drawn particular attention among the corridor’s impacted species for several reasons, Hondorp explained.
“They’re a native species, number one, and there’s a large emphasis placed on restoring populations and habitats for native species,” Hondorp said. “They’re the largest and longest-lived native species in the Great Lakes, so they’ve become the poster child for restoration efforts.”
Lake sturgeon are highly migratory, spending most of their time in the lakes when not spawning. This makes it difficult to address issues that the species faces in relation to the Huron-Erie corridor. Furthermore, the researchers were unsure if the sturgeon migrated as one population, or split into smaller groups.
“Where do you restore a habitat, and which populations are you going to help when you actually complete the restoration process?” Hondorp said. “That wasn’t entirely clear for lake sturgeon.”
To answer these questions, the researchers captured and marked sturgeon with acoustic transmitters. Their hypothesis, Hondorp explained, stated that if multiple spawning groups existed, then the transmitters would reveal multiple movement patterns between the lakes and rivers in the region.
In its prime, the Huron-Erie corridor possessed a unique hydrology that suited it perfectly to spawning. The corridor receives cold, clean and well-oxygenated water from Lake Huron — “exactly what you want for incubating fish eggs,” Hondorp said. Floods and droughts, capable of wreaking havoc on fish habitats, are rare in the corridor.
The study is split into two separate phases. In the first, from April to June, researchers collect sturgeon on set lines, tagging any large adult individuals. The second phase requires the researchers to travel around the Huron-Erie Corridor and download data from hydrophones that listen in on the tagged sturgeon’s movements. The hydrophones weren’t marked above water, and Hondorp said a few of the instruments were expectedly lost, along with their data.
The study began in 2012, and is currently set to continue through 2016. But Hondorp believes there will be more work to be done, and he seems confident that the team will attain the resources necessary to continue.
“I anticipate the results are going to garner enough interest that we should be able to get a 5-year extension,” Hondorp said.
So far, Hondorp said that the sturgeon appear to maintain two distinct spawning populations: one from the Detroit River, and one from the St. Clair River. Their research has also found that Lake St. Clair is an important winter feeding ground for lake sturgeon and other fish.
“We expect that, number one, this is going to inform the choice of habitat that fishery managers will … restore,” Hondorp said. “Now that we have a sense of what the population structure looks like, we can begin to put spawning reefs in the rivers and at the sites of the particular population that we want to restore.”