The last bits of the Union Street Dam are removed as work on its replacement and FishPass program continue on the Boardman/Ottaway River in downtown Traverse City.
TRAVERSE CITY -- With construction at the midway point, scientists are working out how Fishpass can solve a perplexing fish migration quandary.
The Great Lakes Fishery Commission wants to create a sorting system that would let desired species like lake sturgeon, longnose suckers and other species that can't jump a traditional fish ladder upstream to their spawning grounds. But the system also must block invasive species like the parasitic sea lamprey, which also seek out rivers and streams to reproduce.
But how to sort one fish species from another? It's a problem the fish science community hasn't solved before, having focused on setups that block or allow a single species, GLFC Prinicipal Engineer and Scientist Dan Zielinski said. Those translate poorly to other fish that can't swim as fast, jump as high or have some other trait that keeps them from getting through.
A University of Toronto researcher looked at all 220 fish species in the Great Lakes for sortable attributes, and identified 21 that can be used to separate one from the other, Zielinski said. Those include their size, relative eye position, whether they're more sensitive to sound or light than other fish, where they sit in the food chain and how well they can swim.
From there, the researcher ran what's called a guild analysis to look for overlaps among those 21 traits, Zielinski said. That narrowed them down to five guilds, each with its own group of traits.
One, for example, includes relatively larger fish that mostly migrate in the spring and are sensitive to electrical fields in the water. Another is small minnows that tend to migrate later in the year and a third is hearing specialists, or fish that are more sensitive to sound cues than others.
Those guilds provide a useful starting point for determining how to sort fish more broadly, even sorting different species within a guild, Zielinski said. That'll be crucial to blocking undesirable species from passing through the sorting system.
Plus, it's a process that can be exported to different streams that have a different cross-section of Great Lakes fish migrating into them -- the Boardman-Ottaway has 45 out of the 220.
"The guild analysis just gives you the broad starting point, and we still need to refine it through the actual research at Fishpass to refine it down to within-guild sorting," he said.
Grouping fish into guilds will also help researchers make educated guesses about sorting species for which there's not a lot of data, Zielinski said. Fish with a high commercial interest tend to be the focus of the most research, whereas those like white and longnose suckers don't get the same attention.
"When we make decisions on what tools to consider, we have at least some confidence it would apply to other species within that guild," he said.
Figuring out what fish goes in which guild is one consideration, but going from theories about sortable traits to actual sorting techniques is the next challenge, Zielinski said.
Another researcher is looking at how to combine 18 different methods to sort one species from another. They include bubbles for guidance, lights, sounds, pheromones and traps.
The possible combinations are many, so another method can help researchers figure out the most promising arrangements, Zielinski said. Known as the Beijing sorting technique, it looks at each step as a sort of two-way gate: either a fish is passed on further through the system, or it's sent back to the beginning.
"It essentially boils that all down into a very large system of equations you can evaluate to see what the predicted outcome would be," he said.
Construction on Fishpass should be complete in 2027, and after some commissioning studies to further evaluate the movement of fish into the river, the first sorting technique trials should begin in spring 2028, Zielinski said. That'll kick off 10 years of optimization, during which fish will only be passed in deliberate, controlled movements.
"Any level of passage that happens during the 10-year optimization phase will be very strategic in its planning and studied, because this does provide us an opportunity to be able to tag the fish that would be passed, so we can understand where they go in the upper watershed, how they contribute to the fish community and also return downstream for many of the fish species," he said.
Any fish passed through would be species native to the upper Great Lakes -- no stocked species like salmon or rainbow trout -- and could vary from a handful to larger groups, Zielinski said. Either way, each fish will be manually assessed to avoid passing anything that should have been sorted out. That would be one of several layers of safeguards to avoid passing the wrong fish by mistake.
Even modest success, where Fishpass is able to reliably allow 10% of migratory desired species upstream while blocking undesirables, would add up quickly if duplicated elsewhere.
"If we're able to implement that 10% passage of native species at the majority of these sites, that becomes a lot of increased habitat for native fish species that they were blocked from," Zielinski said.
If scientists can't figure out a reliable sorting strategy, Fishpass would be set to act as a barrier to all passage, Zielinski said. Decisions on how to allow species like lake sturgeon through would need to be made, with manually trapping and sorting fish as the fallback.
"If we're largely unsuccessful, the stakes are that this site in particular is, it's a new, improved dam, it has new facilities around it, but it still just functions as a sea lamprey barrier," he said.
Jay Wesley, the Lake Michigan basin coordinator for the state Department of Natural Resources, said Fishpass holds the promise to solve a pressing dilemma.
While dams keep migratory fish from their spawning grounds, they also keep sea lampreys from theirs.
That question has grown in urgency as dams throughout the Great Lakes basin reach the end of their useful lives, or are already well past it -- Wesley said a dam in Manistique is so decrepit that sea lampreys can get through the cracks into the Manistique River. Lampricide has to be applied throughout the entire watershed, which fans out across a wide stretch of the central Upper Peninsula.
Plans are to replace that dam with a low-head barrier dam to stop sea lampreys, Wesley said. It still wouldn't allow for passage of other species, and he agreed the river could someday be a candidate for Fishpass 2.0 -- as could many others around the globe.
"So this would be valuable anywhere throughout the world because we're all dealing with fish passage issues around dams," he said, "so it's very innovative and we're hoping something comes out of it that can be useful in other systems."