Lake Yankton, a 332-acre backwater lake on the Nebraska/South Dakota border had a problem. In the summer of 2011, the Missouri River flooded, spilling into the lake a number of undesirable invasive rough fish, including large numbers of carp (silver, bighead, grass, and common), smallmouth buffalo, and gizzard shad. Notorious for stirring up lake bottoms while feeding and spawning — and for overeating zooplankton and aquatic plants — these species degrade water quality and fisheries.
Overrun by these invasive species, Lake Yankton soon looked like chocolate milk, with a water clarity of only three inches — that’s right, inches, not feet. So the cavalry was called in to assess the situation and provide a solution. Leading the effort was Nebraska Game and Parks Commission District Fisheries Manager Jeff Schuckman.
Fortunately for Nebraska anglers, this wasn’t Schuckman’s first rodeo. He knew the lake could be rehabilitated with careful application of Rotenone, a common fish-killing chemical. The challenge would be to determine just how much of the chemical was needed, and then purchase and apply just enough to do the job — no more, no less.
Overrun by these invasive species, Lake Yankton soon looked like chocolate milk, with a water clarity of only three inches — that’s right, inches, not feet. So the cavalry was called in to assess the situation and provide a solution. Leading the effort was Nebraska Game and Parks Commission District Fisheries Manager Jeff Schuckman.
Fortunately for Nebraska anglers, this wasn’t Schuckman’s first rodeo. He knew the lake could be rehabilitated with careful application of Rotenone, a common fish-killing chemical. The challenge would be to determine just how much of the chemical was needed, and then purchase and apply just enough to do the job — no more, no less.
Effects of chemicals in aquaria? Very predictable — Effects in lakes? Much more complicated
Advancements in chemical engineering and results from controlled experiments have resulted in a large number of selective aquatic pesticides with predictable effects in controlled environments. However, conditions in the field are rarely controlled. So in the past, success hinged on the intuition and experience of a grizzled aquatic weed applicator or fisheries manager using low-tech strategies not dissimilar to “winging-it.”
A common technique for successful rotenone applications is to first draw down a lake’s water level in order to concentrate both the pesticide and the fish species you’re targeting.
Still, past chemical-application failures — whether real or perceived — have put chemical control of aquatic species under an intense microscope by both the public and regulators, so the stakes were high for Schuckman, both environmentally and economically.
“Rotenone runs $50-86 a gallon and we estimated that we needed several hundreds of gallons for Yankton,” he explains. “We had to be precise.”
A common technique for successful rotenone applications is to first draw down a lake’s water level in order to concentrate both the pesticide and the fish species you’re targeting.
Still, past chemical-application failures — whether real or perceived — have put chemical control of aquatic species under an intense microscope by both the public and regulators, so the stakes were high for Schuckman, both environmentally and economically.
“Rotenone runs $50-86 a gallon and we estimated that we needed several hundreds of gallons for Yankton,” he explains. “We had to be precise.”
Precise treatment prescriptions require a detailed lake map
One key to successful pesticide application is achieving the correct concentration of chemical in the water. Because most riverine backwater lakes are not simple bowls that never change, Schuckman was not confident in the accuracy of his early-1980’s era, hand-drawn Lake Yankton contour map (Figure 1, below). Successful pesticide application, he knew, would require both speed and accuracy. Unfortunately, he didn’t have the time or budget to wait for a dedicated hydrographic survey crew. Thankfully, a colleague soon explained to him how he could use a Lowrance fish finder/GPS to create lake maps automatically.
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| Figure 1. Original 1980 hand-drawn contour map of Lake Yankton on the border of Nebraska and South Dakota. Depths are in meters. Basing fisheries-management decisions on maps like this is still common throughout the U.S. (but changing, thanks to easy and affordable sonar/GPS units like Lowrance and automated mapping with BioBase EcoSound). |
The Technique
Schuckman signed up for BioBase, updated his Lowrance HDS-5, popped in a SD card, hit “Record Sonar” and began motoring back and forth, keeping his passes spaced approximately 130 ft (40 m). It took him about 11 hours to map the lake, and another hour or two processing his recorded sonar data in BioBase to create perhaps the most detailed bathymetric map of Lake Yankton on the face of the Earth (Figure 2).
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| Figure 2. Most accurate and precise bathymetry map of Lake Yankton on Earth created in 11 hours with Lowrance HDS and BioBase. Data were collected by Nebraska Game and Parks fisheries biologists with no mapping experience. |
Using the EcoSound offset and polygon tools, Schuckman then estimated precise water volumes in targeted areas after the lake was drawn down 3.5 feet (e.g., -3.5 ft offset). Using the polygon tool, Schuckman digitized the simulated draw-down area to estimate water volumes (Figure 3, Table 1).
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| Figure 3. Polygon created in BioBase to estimate the size and volume of specific areas targeted for Rotenone application. Polygons can be exported as .shp files and converted to .gpx to view on Lowrance GPS chartplotters on treatment boats, making applications more precise. |
Table.1 Cost and volume estimates based on simulated draw-down scenarios from BioBase of Lake Yankton for Rotenone applications (data courtesy Nebraska Game and Parks).
Further, Schuckman printed maps and zones for each staffer involved in the project (Figure 4).
“Detailed [depth] maps generated by the BioBase technology allowed us to simulate lake draw-down scenarios and maps for our partners, such as the U.S. Army Corps of Engineers, U.S. Fish and Wildlife Service, and South Dakota Game Fish and Parks,” he says. “This allowed our partners to visualize different draw-down scenarios and [us to] convince them to cooperate with the project. We were also able to segment the lake and generate volume estimates for precise chemical application to kill the [invasive] fish.”
“Detailed [depth] maps generated by the BioBase technology allowed us to simulate lake draw-down scenarios and maps for our partners, such as the U.S. Army Corps of Engineers, U.S. Fish and Wildlife Service, and South Dakota Game Fish and Parks,” he says. “This allowed our partners to visualize different draw-down scenarios and [us to] convince them to cooperate with the project. We were also able to segment the lake and generate volume estimates for precise chemical application to kill the [invasive] fish.”
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| Figure 4. BioBase map of a drawn-down Lake Yankton, complete with staff assignments for Rotenone application. (Map courtesy Nebraska Game and Parks) |
The Result
In early September 2014, Schuckman (seen perhaps by his invasive fish victims as an evil Dr. Nefario) had the lake drawn down while his Minions conducted precision strikes with the toxic piscicide (Figure 5). Shortly after the treatments, all the rough fish were dead and quickly became food for scavengers or decomposed and returned to the Earth (Figures 6 and 7).
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| Figure 5. Fisheries staff donned in Personal Protective suits while applying precise quantities of rotenone to treatment areas on Lake Yankton (Disclosure: in the above photo staff are rinsing the barrels after the treatments were done. Actual treatments took place from sprayers on airboats or drip stations). Photo credit: Yankton Daily Press & Dakotan |
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Figure 6. Common carp and other rough fish killed by rotenone treatments on Lake Yankton in September 2014
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| Figure 6. Fisheries staff proudly displaying trophy kills of invasive Big Head Carp. These invasive fish were eradicated shortly after the Rotenone application to Lake Yankton |
The success of the project is chronicled in the Yankton Daily Press and Dakotan (Search “Lake Yankton Renovation”), with the capstone story one year later celebrating the amazing recovery of the lake. Stocked largemouth bass, bluegill, walleye, black crappie and catfish have now replaced the carp, which Schuckman believes were completely wiped out by the treatments. Further, clarity in Lake Yankton increased 24-fold, going from three to six inches before renovation to over eight feet a year after renovation. Abundant aquatic plants are now providing sustainable habitat and food sources for fish and waterfowl.
“It’s like a brand new lake,” Schuckman says of the Lake Yankton renovation. “[In 2016], anglers will be harvesting two-year-old bluegill that have already spawned and will be over eight inches”
“It’s like a brand new lake,” Schuckman says of the Lake Yankton renovation. “[In 2016], anglers will be harvesting two-year-old bluegill that have already spawned and will be over eight inches”
The Upshot: Employee of the Year!
The success of the Lake Yankton project proved to be one of Schuckman’s biggest career achievements — the director of The Nebraska Game and Parks Dept. awarded him a prestigious Employee of the Year award in November 2015. Schuckman, in turn, extended ample praise for the cooperation of partners, stakeholders, competent staff, and technology that allowed him to focus on more important details.
“BioBase mapping took all the guesswork out of this project and allowed us to make good, precise plans to undertake a very successful project,” Schuckman says.
“BioBase mapping took all the guesswork out of this project and allowed us to make good, precise plans to undertake a very successful project,” Schuckman says.
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| When he’s not standing sentinel over Nebraska’s Sandhill Lakes, you may find Jeff Schuckman chasing both small and large game throughout the Rockies and plains of the Midwest (Antelope from Wyoming shown here) |
Awesome post !