In another step forward for fisheries management on the Milwaukee River, last week a sensor array detected five lake sturgeon moving upriver.
The “hits” were the first on sturgeon since the high-tech system was installed across the river bottom in July 2021, according to the Department of Natural Resources.
“It’s definitely exciting,” said Aaron Schiller, DNR fisheries biologist who helped install and monitors the array. “This confirms (the sensor) is working on sturgeon and it’s doing what it’s designed to do.”
The array is a permanent, cross-stream system to detect fish implanted with passive integrated transponders (PIT) tags. It’s installed 4 miles north of the river mouth and upstream of the old North Avenue dam site.
The PIT tags are the size of a grain of rice and work very similarly to the “chips” put into dogs and cats.
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The technology carries a unique 15-digit number and links to data on tagging date, location, species and length and weight of the fish when handled.
One PIT tag has been injected into each of the approximately 19,000 young sturgeon raised at the Riveredge Nature Center and released into the Milwaukee River or harbor since 2006 as part of the restoration project called Return the Sturgeon.
The DNR has also implanted the tags in an assortment of other species of fish in the Milwaukee, including northern pike, brown trout, brook trout, steelhead (rainbow trout), redhorse, suckers and walleye.
Due to its multiple sensors spaced across the river bottom, the system can also determine if a fish is moving upstream or down.
Although sturgeon, including a PIT-tagged fish, were observed in the Milwaukee River last spring, the sensor system had not yet been installed and fisheries crews and sturgeon advocates have been intently watching this year for signs of a potential spawning migration.
The remote design is preferable because it’s far more efficient for scientists and it doesn’t require fish to be netted or handled, thereby eliminating risk of injuring fish.
And in theory, it can detect all tagged fish moving through the river, not just a cohort that can be electro-shocked or netted.
Schiller has been checking the data daily and at 4 a.m. Wednesday the first PIT-tagged sturgeon passed upstream through the array.
The sturgeon’s 15-digit code identified it as a fish raised at Riveredge and stocked in the river in 2011, Schiller said.
It was followed by another sturgeon hours later; the second fish was a Riveredge fish stocked in 2007.
Then on Thursday three more Riveredge-reared sturgeon passed upriver, from the 2008, 2010 and 2011 year classes, respectively.
At mid-week the river’s water temperature was 47 degrees Fahrenheit and the flow was 1,030 feet per second.
Schiller said the DNR will continue to monitor the array as well as visit the river to look for signs of sturgeon spawning. It’s likely more fish will move upriver as water warms.
Sturgeon spawning typically occurs when water temps reach from 53 to 59 degrees, according to DNR data from the Wolf River.
Several aspects of the Milwaukee River sturgeon restoration project, including stocking and fish detection, are now in place.
It remains to be seen if the fish will attempt to spawn – they take 15 to 20 years to mature, and no spawning behavior has been documented on the Milwaukee – and if the river will have sufficient habitat to allow successful reproduction.
A river mapping project by Ozaukee County Planning and Parks Department has attempted to identify suitable sturgeon spawning sites in the Milwaukee.
The fish are known to successfully spawn on rocky substrate with flows about 2 feet per second and higher, according to a habitat guide by Fred Binkowski, sturgeon expert at the UWM School of Freshwater Sciences.
Limestone rocks from 6 to 18 inches in diameter are particularly good for sturgeon spawning, said Ron Bruch, retired DNR sturgeon biologist and fisheries director who helped restore spawning sites on the Wolf River. Bruch said adult sturgeon also require a staging area of deeper water relatively close to the spawning site.
“It’s wonderful to have sturgeon moving up the Milwaukee,” Bruch said. “Now it will be a matter of the fish showing us if they have what they need.”
A “significant amount” of input was collected online Monday through Thursday for the 2022 Department of Natural Resources Spring Hearings and Wisconsin Conservation Congress County Meetings, according to Kari Lee-Zimmermann, DNR liaison to the congress.
This year’s questionnaire featured 63 advisory questions on topics including chronic wasting disease management, deer farms, walleye management and wolf hunting tactics.
Lee-Zimmerman said the DNR and WCC were working through the data and results should be available on the DNR’s webpage in the coming week.
Waterfowl regulations set
The Natural Resources Board on Wednesday approved the 2022 Wisconsin migratory bird hunting season framework and regulations.
Hunters will have a 60-day duck season with a six-duck daily bag limit.
Opening days will be Sept. 24 for the North Zone, Oct. 1 for the South Zone and Oct. 15 for the Open Water Zone. A youth hunt will be held statewide Sept. 17 and 18.
In addition, a statewide early teal season (Sept. 1-9, limit six teal) and a statewide early Canada goose season (Sept. 1-15, limit five geese) will be held.
The daily duck bag limit during the normal seasons may include no more than four mallards (including a maximum of two hens), three wood ducks, two black ducks, two canvasbacks, two redheads and one pintail.
In addition, special regulations apply to scaup. Hunters in the North Zone and Open Water Zone will be allowed to take two scaup for the first 45 days of the season and one scaup for the final 15 days, while hunters in the South Zone will be allowed one scaup for the first 15 days and 2 scaup for the final 45.
The DNR received more than 1,400 public comments as it worked to establish this year’s regulations, according to Taylor Finger, DNR migratory bird ecologist.
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This article originally appeared on Milwaukee Journal Sentinel: Sturgeon migrating up Milwaukee River, sensor system shows