Few fish are produced in tributaries
ALGOMA - Beneath a canopy of black ash and white cedar, the tea-colored waters of Stoney Creek tumbled to Lake Michigan.
For humans, the cool stream was an antidote to the unseasonably hot and humid air on this late summer day.
Hundreds, perhaps thousands, of cold-water fish found the creek to be hospitable, too.
"Sixtty-three, 70, 85, 78, 110 (millimeters)," said Eric Wegleitner, a UW-Stevens Point graduate student. "All rainbows."
The juvenile rainbow trout, or steelhead, were among 144 salmonids captured by Wegleitner and a crew of other UW-Stevens Point researchers during an August assessment of a 100-meter stretch of Stoney.
They used electroshocking equipment to gather the fish in various sections of this and five other creeks.
The goal: Estimate how many trout and salmon are naturally produced in Wisconsin tributaries to Lake Michigan, as well as how many swim out to the lake.
The work is part of Wegleitner's master's thesis titled “Wild Juvenile Salmonid Abundance and Outmigration in Wisconsin tributaries to Lake Michigan.”
When non-native trout and salmon were first stocked in the Great Lakes, the fishery was considered "put-and-take."
Fisheries managers operated on the basis that the number of fish stocked was the population in the lake.
After a number of years, however, it became apparent that some of the non-native fish were able to naturally reproduce in the region.
In Lake Michigan, that was especially true in streams on the Michigan side of the lake. Michigan tributaries are generally longer, cooler and have more rocky bottom substrates, all of which are more conducive to natural reproduction of trout and salmon.
In a typical year, 3 to 4 million wild chinook smolts are produced in Lake Michigan, said Randy Claramunt, former fisheries biologist with the Michigan Department of Natural Resources. In 2015 the Michigan DNR estimated the number at 3.8 million, far outpacing stocked chinook.
In 2015, 69% of chinook sampled in Lake Michigan were wild, or naturally reproduced, according to the U.S. Fish and Wildlife Service.
To sustain a successful fishery and balance the predator-prey base, agencies around the lake need accurate data to guide their stocking programs.
Relatively little was known about the number of fish - if any - being contributed to Lake Michigan's trout and salmon populations from Wisconsin streams.
The first evidence of a naturally-reproduced coho salmon smolt in a Wisconsin stream was reported in 1992 by a game warden, said DNR fisheries biologist Pradeep Hirethota. This fish was captured in Mineral Springs, a tributary to Sauk Creek in Ozaukee County.
Subsequent searches by the DNR, including with elecro-shocking units, found minimal production of cohos, as well as chinook, brown trout and rainbow trout.
However, the DNR identified several streams with above-average potential for successful salmonid spawning.
Wegleitner credits the DNR's work with helping him focus on six streams: Pigeon Creek, Sauk Creek, Willow Creek, Fisher Creek, Stoney Creek and Hibbard Creek.
His work started in 2016 and will conclude in 2018. Dan Isermann of the Wisconsin Cooperative Fishery Research Unit at UW-Stevens Point is supervising the project.
The work is being funded by five Wisconsin Trout Unlimited chapters (Central, Fox Valley, Green Bay, Shaw-Paca and Southeastern) and the Algoma-Kewaunee Area Great Lakes Sport Fishermen. Wegleitner was awarded the Bill Beck Scholarship by Central Wisconsin Trout Unlimited.
On the hot August day, Wegleitner was joined by students Nic Brown of Kansas City, Kan., Ryan Eastman of Berlin, Wis., and Taylor Morlan of Crookston, Minn.
The researchers used nets to block off a 100-meter section of the creek, then made three passes up the stream with electro-shocking units.
As stunned fish rose to the surface, they were netted and placed in buckets and transported to a stream-side work station. Once there, the fish were identified, measured and recorded. Several dozen salmonids were implanted with passive integrated transponders (PITs). The tags, each about the size of a grain of rice, allow the fish to be tracked.
The fish were returned to the creek outside of the segregated area.
The passes yielded 83, 38 and 23 salmonids, respectively.
Of the 144 caught, 130 were steelhead, 10 were brown trout and four were coho salmon.
Dozens of native fish were caught, too, including mottled sculpins, long-nosed dace, central stonerollers and largemouth bass.
Wegleitner said Stoney Creek is the star of all the Wisconsin tributaries he has sampled. His preliminary estimate is Stoney is able to produce from 1,100 to 2,200 juvenile salmonids annually, with most being steelhead or rainbow trout.
Even so, its numbers are paltry compared to Michigan streams.
Steelhead also showed the greatest ability to naturally reproduce in the earlier DNR work. In southeastern Wisconsin, Sauk Creek produced the highest number of young steelhead. But once again, the numbers are low.
So relatively few trout and salmon are produced in Wisconsin's Lake Michigan tributaries. But do any of them contribute to the fishery on the big pond?
Wegleitner is attempting to answer that question, too.
He installed sensors near the mouths of Hibbard and Stoney creeks to detect movements of fish with tags.
Last year, only one fish on each stream was found to have out-migrated to the lake.
The results are preliminary; Wegleitner's work will continue through early 2018.
As the Lake Michigan fishery continues to evolve, solid research like this is critical to help natural resource managers make the best decisions for the future.