Young walleye growth rates decline by 12 to 14% in Minnesota lakes invaded by zebra mussels and spiny water fleas, researchers concluded in a study published recently.
Led by University of Minnesota Assistant Prof. Gretchen Hansen, it becomes one of the few studies to show impacts of aquatic invasive species on high-level fish such as walleye. A summary of the study in the journal Biological Invasions said slower growth makes it more difficult for baby walleyes to survive.
Fourteen percent might not seem like a big number, Hansen said, but a fish smaller than normal at the end of the first growing season can struggle to survive over winter.
The study out of the Minnesota Aquatic Invasive Species Research Center looked at a 35-year data set of first-year walleye growth in nine of Minnesota’s best walleye lakes. The numbers were routinely recorded over the years by the Department of Natural Resources. In the early years, none of the lakes was invaded. But seven of the lakes became invaded by spiny water fleas or zebra mussels (Mille Lacs was invaded by both).
It was another exciting and productive year at the Minnesota Aquatic Invasive Species Research Center! I continue to be inspired by our researchers – from the first semester students to the tenured professors – all working toward a common goal of finding research-based solutions to Minnesota’s AIS problems. As I look back on 2019, it is amazing what has been accomplished.
Six research projects concluded this year, each advancing our scientific understanding and providing new tools and options for managers, professionals, and the public. These projects included work on invasive bighead carp, non-native Phragmites, and zebra mussels – highlights are included in the following pages. The approaches to each project were as varied as the species, but all remained focused on solutions-oriented research and end user engagement. Congratulations to the project teams for getting their work over the finish line and beyond!
Inside a cramped shed alongside a lock and dam on the Mississippi River south of La Crosse, Wis., fisheries biologist Jeff Whitty flipped a switch.
A few yards away, at the foot of the lock, a dozen submerged speakers began blasting a repetitive drumbeat — a Pacman-like whomp, whomp, whomp — while underwater strobe lights began to pulse with bright flashes.
Researchers were about to discover what fish think about the best — and perhaps last — hope for keeping destructive Asian carp out of Minnesota’s rivers and lakes.
Imagine: It’s a hot summer day, and you’re surfing behind a boat as it cuts across the lake.
But this isn’t water skiing. You’re not being pulled by a rope tied to the boat. You’re riding a perfectly curled wake, created by the boat itself.
That’s wakesurfing, a relatively new water sport that’s been gaining popularity on Minnesota lakes.
A study is continuing in Lake Minnetonka this year on a potential new method to manage zebra mussel populations.
Researchers from the Minnehaha Creek Watershed District (MCWD) and the Minnesota Aquatic Invasive Species Research Center (MAISRC) are testing the use of a copper-based product to reduce the survival of zebra mussel veligers (larvae). By targeting the youngest zebra mussels, it’s hoped the overall zebra mussel population can be decreased. The study, funded by a $30,500 grant from Hennepin County, is the first known field test of its kind in the country.
"We're targeting veligers for this study for several reasons," said Dr. Michael McCartney, MAISRC Research Assistant Professor. "They're in a life stage that is more sensitive to our applications, we can lower the risk of larvae accidentally spreading through recreational boats, and we think we can significantly knock back zebra mussel populations by reducing the number of veligers in the lake."
Why is someone loading a fish into a tube?
That’s Whooshh. It’s a high-tech fish removal system, something like a cross between a potato gun and a pneumatic tube at a drive-in bank.
And that fish is a common carp, one the oldest and most invasive fish on the planet.
The annual migration of fish presents a unique opportunity for researchers at the University of Minnesota testing a new way to stop the spread of invasive carp.
The Minnesota Aquatic Invasive Species Research Center (MAISRC) is on Rice Creek experimenting with a Whooshh System.
A control research project on zebra mussels is planned for this summer on Lake Minnetonka. The study will begin in early May and will be completed in October, during which temporary lighted buoys will be installed at sampling locations.
The treated area will be in St. Alban’s Bay and the control area will be in Robinson’s Bay. The purpose is to evaluate the use of low-dose copper treatments, under the brand name EarthTec QZ, to manage zebra mussel populations by suppressing their early life stages.
A model created by MAISRC researchers to optimize watercraft inspection checkpoints to prevent the movement of starry stonewort and zebra mussels has now been pilot-tested with three counties: Crow Wing, Ramsey, and Stearns.
The model — a product of another MAISRC project — incorporates estimates of boater movement among lakes within each county and assesses risk of AIS spread based on boater movement and environmental suitability conditions. The model can be used by counties to allocate their limited inspection resources among various lakes and landings. It can help counties decide how many inspectors to hire, where to station them, even what times of days or days of the week they should be scheduled, for the optimal intervention of AIS.
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“So much of Minnesota’s culture and recreation is based around the water and enjoying our lakes and rivers,” says Dan Larkin, an Assistant Professor and Extension Specialist with the University of Minnesota. “And so, aquatic invasive species and other threats to those habitats really affect people personally.”