MACKINAC COUNTY, MI -- As once-abundant Great Lakes whitefish slide toward population collapse, biologists are trying something that would have sounded far-fetched a decade ago: hauling live fish upriver and simply letting them go.
This month, the Sault Ste. Marie Tribe of Chippewa Indians and partner scientists released nearly 200 adult whitefish into the upper Carp River. The "translocation" effort aims to get the fish to do what their ancestors did before the logging era destroyed Michigan river habitat -- spawn and produce babies that eventually return on their own.
"We're trying to get whitefish to imprint in the rivers," said Matt Herbert, a senior aquatic ecologist with The Nature Conservancy who helped coordinate the project. "Our rivers can produce a lot of fish. Every walleye in Saginaw Bay is produced from rivers."
"Our rivers still carry a lot of nutrients."
Whitefish, a backbone of tribal and commercial fisheries, have suffered a steep collapse in the lower Great Lakes as invasive zebra and quagga mussels strip out phytoplankton at the base of the food chain, leaving less food for native zooplankton and baby fish.
According to the Great Lakes Fishery Commission, whitefish recruitment has crashed by 70-80 percent since the late 1990s in Lake Michigan and Lake Huron due to the combined effects of mussel-driven food scarcity and declining winter ice cover.
Newly introduced bipartisan Congressional legislation introduced this month would devote $500 million over the next decade to battling invasive mussels and scaling up large-scale suppression technologies on part with lamprey control efforts launched in the 1950s.
The translocation experiment is part of a wider scramble among tribal nations, state agencies and conservation groups to find resilient pathways for whitefish recovery.
One of those is reintroduction to rivers.
"There is habitat below dams in Michigan that that they can use," said Herbert. River-spawning efforts may not boost populations into pre-decline numbers, but "it stops the bleeding, and I think it actually starts to build things in a positive direction."
The Sault Tribe conducted two translocation events involving 50 fish on Nov. 1 and 142 more on Nov. 10. The fish, captured in a tribal commercial trap-net in northern Lake Huron, were transported by truck and fitted with acoustic transmitters before release.
"They were really close to spawning," said Rusty Aikens, a fisheries coordinator with the Sault Tribe. "A couple of females actually expressed eggs while we handled them and most of the males were ready to go."
Eight receivers placed along the river allow biologists to track how long the fish remain in the system. This fall is the second attempt to translocate fish into the Carp River. Last year, transmitters showed fish stayed about nine days before a rainstorm raised the river and flushed most downstream. That departure coincided with peak spawn timing, leaving researchers unsure whether the fish left because they spawned or because the river surged.
"That's why you do more than one year of data collection," Aikens said. "Year one opened up more questions than it answered."
The Carp River is an ideal testbed for the project that's close to tribal headquarters, small enough to monitor effectively and full of the cobble substrate whitefish prefer.
This fall, tribal staff placed a dozen egg mats in the river's rocky spawning habitat which they'll retrieve in December. Finding fertilized eggs would be a big win. Finding larval drift in the spring would be another. In five to seven years, the hope is that adults return.
The project is part of a cross-tribe working group that includes the Sault Tribe, Little Traverse Bay Bands, Bay Mills Indian Community, the Michigan DNR and the Nature Conservancy. The group meets monthly to trade data and coordinate efforts.
Much of the early restoration push has centered on the Jordan River in the Lower Peninsula, where the tribal and conservation partners have tested multiple techniques to get whitefish to imprint on tributaries again. In the last few years, crews stocked fertilized eggs using in-stream incubators and later tried placing eggs directly into rocky habitat.
Those trials produced larval fish drifting from the Jordan River mouth, but not enough data to determine which method works best.
"We had high waters, so we had a difficult time like measuring that the way we wanted to," Herbert said. With the Carp River, the hope is to get the fish to do the spawning themselves.
"That's easier and cheaper than dealing with spawning and the eggs."
"It's all kind of the same concept," Herbert said.
Herbert and Aikens said Michigan has far more potential whitefish habitat in its rivers than most people realize. Whitefish prefer the same rocky, cobble-bottom spawning grounds used by walleye and lake sturgeon and many Michigan tributaries still contain those features despite dams and industrial-era damage.
Herbert pointed to the Muskegon, Grand, Kalamazoo and St. Joseph rivers in lower Michigan as having suitable reaches below hydro dams. Restoration projects have already improved substrate conditions in places like the Kalamazoo River.
The strongest proof-of-concept comes from Wisconsin's Green Bay tributaries where whitefish spontaneously re-established river runs in the last 10 to 15 years. Despite flowing through urban Green Bay with agricultural runoff and contaminated site issues, the Fox River now produces a "nice whitefish run," Herbert said.
In the Upper Peninsula, the Menominee River has only a few miles of habitat below a dam in downtown Menominee but still supports productive spawning, Herbert said. The clearest sign Michigan rivers can still host whitefish came from the Escanaba River, where a spawning adult was found while electrofishing during early project surveys.
"It would be nice to do this stuff in bigger tributaries," said Aikens. "Measuring success in those big ones is kind of hard, so you start with these smaller ones. If we find out it works, then you can just apply it to bigger and scale it up."
"The goal is to help nature along," Aikens said. "We see the decline of whitefish as something we probably just can't stock our way out of."
"Nature is capable of doing huge and amazing things if the conditions are right, and so it's just a matter of getting the right conditions."