Dams hurt native fish by blocking their access to rivers — but removing dams to let the fish through would open the way for invasive species.
A first-of-its-kind barrier designed to deal with this problem by sorting fish will be tested on the Boardman River in downtown Traverse City. If it’s successful, it could be a model for rivers all over the world.
What to do with dams
Frank Dituri is the director of Public Works for Traverse City, Michigan. Standing on the downtown Union Street Dam, he says the city didn’t always know what it was going to do with the leaky, aging structure.
“If you walk along the base of the dam come springtime, you can see water is actually seeping, weeping through it in places,” says Dituri. “It needs to be replaced.”
Union Street Dam is the last remaining dam on the Boardman River. Three others have been removed as part of Michigan’s largest ever river reconnection project. Local governments, state and federal agencies, and the Grand Traverse Band of Ottawa and Chippewa Indians teamed up to take dams out so native fish could swim freely up and down.
However, the Union Street Dam can’t just be removed. It’s blocking native fish, yes, but it’s also the only thing separating the Boardman from invasive fish downstream in Lake Michigan.
“We kept looking for ways to modify or understand how this could be modified to allow movement of fish up and downstream, while keeping out the fish we didn't want,” says Dituri.
A big challenge
One of those fish is the dreaded sea lamprey, which actually looks more like an eel than a fish. Sea lampreys latch onto other fish and suck their blood. Native to the Atlantic Ocean, they’re devastating to the fish of the Great Lakes, who often die from sea lamprey injuries.
Marc Gaden is with the Great Lakes Fishery Commission, the international agency in charge of controlling sea lampreys. He says they need river access to spawn, so dams in the region have played an unintended but important role in curbing them.
“There are thousands and thousands of barriers around the Great Lakes basin that keep invasive species, most notably the sea lamprey, in check,” says Gaden. “If those barriers didn't exist, we would not have a fishery to speak of because the lamprey are just indiscriminate pests.”
He says even beyond the Great Lakes, figuring out how to “sort” fish — to let desired fish swim up rivers while blocking invasives — is the biggest fisheries management challenge of our time.
“And that applies not just in the Great Lakes, but it also applies to big river systems like the Columbia River, or the Mekong River, or the Amazon or any other river system where you have big structures that are inhibiting fish movement,” he says.
In fact, the Great Lakes Fishery Commission was looking for a place to test fish-sorting technology — just about the time Traverse City was looking for a solution for the last dam on the Boardman. That's how the FishPass project came to be.
Passing fish
FishPass (Giiigook Mah-Jowag in Anishinaabemowin) is the planned new barrier to replace the Union Street Dam — plus more.
It’s a collaboration between the Great Lakes Fishery Commission, the Grand Traverse Band of Ottawa and Chippewa, the City of Traverse City, the Michigan Department of Natural Resources, and the US Army Corps of Engineers.
A weir and associated waterfall will span a little over half the river. The weir will block all fish, pass flood flows and maintain the elevation of downtown Boardman Lake.
Next to the weir will be adjustable gates. Downstream of those gates will be a thirty-foot-wide concrete research channel. There, for the next 10 years, scientists will test ways to separate fish species from each other, the goal being to control which ones make it through the channel.
Dan Zielinski is an engineer with the Great Lakes Fishery Commission, and the FishPass project lead.
“So this is really the first opportunity where we can look at combining all these technologies that have been under research over the last 50 years by the Great Lakes Fishery Commission and, you know, over 100 years of research on just fish passage in general,” he says.
The sorting technologies will be tested alone and in combination. They’ll range from the advanced, like using facial recognition on the fish, to the more simple, like using lights or changing the speed of the water in the channel.
Zielinski says it’s important to test this stuff on an actual river.
“A lot of research around what might guide fish in certain ways has been done in the lab,” he says. “So you have to take fish out of their natural environment, bring them into a lab, and their behavior is not gonna be the same as in nature.”
He says technology that can pass even a small number of native fish while blocking others will be considered a success, and useful throughout the Great Lakes basin.
“If you're only passing, say, 10% of the native fish at this site, but you're able to pass 10% of native fish at all those tributaries where you had zero, that's a pretty monumental improvement,” says Zielinski.
Looking out for the river
To be clear, the upstream gates will be closed completely during this 10-year time period. So, a failed experiment won’t accidentally send unwanted fish up the river. In the meantime, some of the native fish that make it through the sorting channel will be trapped and released on the other side of the gates.
Still, some Traverse City residents have concerns. Perhaps one of the largest is not the FishPass project itself, but which fish will eventually be allowed to pass. Which fish are “desired” fish?
Clearly, nobody is going to start passing sea lamprey — but there’s a question mark over introduced sportfishing species, like salmon or steelhead.
"I've been fishing steelhead for 51 years,” says Gary Marek of the Brook Trout Coalition. “I know something about them. I do not want them in the Boardman River.”
Marek’s organization is against passing any fish that could compete with the Boardman’s resident brook trout population — like salmon or steelhead.
The final decision on which fish to pass rests with the Michigan Department of Natural Resources and the Grand Traverse Band of Ottawa and Chippewa Indians. The tribe has passed a resolution saying that they want passage for native species only. The DNR says they’ll make a decision after the 10-year testing phase.
But Tom White, also of the Brook Trout Coalition, is worried the DNR is already planning to pass nonnative fish, and is just biding its time.
“I think our biggest concern is that their decision has already been made, and it's just being held for implementation until the research is done,” says White.
The DNR, for its part, maintains that it will wait to decide until after the research is done and discuss the decision with interested parties.
In reality, the DNR could pass nonnative species without FishPass. Salmon and steelhead can jump, unlike fish native to the Great Lakes. The Union Street Dam is equipped with something called a fish ladder, which lets fish jump up barriers using a series of pools. It was closed when the other dams were removed, in order to keep jumping fish out of those upper river reaches (for the time being).
FishPass also includes new park space and an educational building. Some think there hasn’t been enough scrutiny on the project's impacts to the local landscape.
Frank Dituri says he appreciates residents' concerns.
“I think people just really care about it and that's shown in the folks that show up,” says Dituri. “Whether they're pro or con, they care about the river, and that right there is an amazing thing.”
He also says he believes this is the best thing for the river.