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Removing Carp from Cherry County Lakes

It is early morning in the heart of the Sandhills as a Nebraska Game and Parks Fisheries crew assembles on the edge of Vrenders Marsh in Cherry County. The pink and orange sunrise reflects off the water, and the sound of an airboat drowns out the morning bird song. The day has finally arrived. After years of meetings, negotiations, and setbacks, the Rat and Beaver Lakes watershed renovation is nearing completion. Today, airboats and prop boats will span out across its surface, treating the water for carp. Unfortunately, common carp have invaded many sandhills lakes, making them inhabitable to game fish and unsuitable habitats for waterfowl. To restore these beautiful habitats, the Sandhills Task Force (STF), US Fish and Wildlife Service (USFWS) Partners Program, and the Nebraska Game and Parks Commission (NGPC) formed a partnership to renovate privately owned sandhills lakes.

The sun rises over Vrenders Marsh in the heart of the Sandhills of Cherry County, Nebraska. (Photo: Ashley Garrelts; STF)

Lake renovation projects are unique. They often involve more than one landowner and occur over a large area, typically encompassing an entire watershed. The goal is to impede invasive carp's upstream movement by installing solar-powered rotating fish barrier screens. The lake is then treated with rotenone (a fish pesticide), and desirable fish species are restocked. When renovating, it is best to start at the beginning of the watershed and work downstream, installing screens on the lake’s downstream side and treating the lake and the associated upstream watershed, i.e., marshes, wetlands, small tributaries, etc. There are five lakes in the Rat and Beaver Lake watershed- upstream Beaver and Rat, mid-stream Vrenders Marsh, Big Lake (too alkaline to support fish), and downstream Eby.

In 2013, the NGPC began working with the Galen Sherman, the Rat Lake Fishing Club, and the late Keith Colburn to renovate Rat and Beaver lakes. At the same time, the STF and USFWS identified that Vrenders Marsh and Eby Lake were also carp infested.

Solar-powered rotating fish screen impede the movement of carp in a watershed. (Photo: Ashley Garrelts; STF)

Keith, who owned most of the land around Vrenders Marsh, known to the locals as Vrenders Swamp, expressed interest in renovation but was concerned with public access. It wasn’t until 2015 after Rat and Beaver had been renovated, that an agreement was reached. This agreement was mainly due to the Sandhills Task Force’s partnership between landowners and state and federal conservation agencies. There isn’t a return on the investment in renovating a lake, at least to the bottom line of a cattle ranch. Instead, benefits are more aesthetic. When landowners decide to renovate, it is either because they are avid fishermen, or waterfowl hunters, want to provide fishing opportunities for kids or grandkids, or are passionate about conserving sandhills’ wildlife habitats. Keith was an avid fisherman and a great steward of the land. “Vrenders was a great perch lake when Dad was my age,” reports Mark Colburn, Keith’s son, when asked about the completed renovation. Mark has only known the lake as a “carp lake,” and he isn’t a fisherman like his dad. He enjoys watching the waterfowl and other wildlife that use the lake and its associated wetlands. When asked what he looks most forward to after the completed renovation, he replies, “Clean, clear water.”

Common carp disturb particulates and pull up vegetation as they feed along the bottom of a body of water—this “muddying” of the water results in an unhealthy habitat for native fish and waterfowl. Chad Christiansen, a native Nebraskan and wildlife biologist with the USFWS Partners Program, explains, “Common carp feeding patterns stir up the floor of the lake, reducing the ability of aquatic plants to receive sunlight. The plants slowly die off and reduce macroinvertebrate growth, which serves as a food source for waterfowl.” As the lake gets muddier, there is less food for waterfowl and small fish species. Lake renovation removes the carp and restores water clarity allowing water quality parameters to return to pre-carp conditions. After a renovation, clean water is the first visible result. “Vrenders was just a mudhole,” recalls Galen Sherman. “Now, even a few months later [after renovation], it is cleaner and clearer.” Sherman was born and raised on the edge of Eby Lake. Today his family still raises cattle along its shores, but he can remember when the lake was much smaller. “We used to harvest grass hay off a meadow where Eby lake is now. I don’t think that will happen again. Water levels are just too high,” He explains.

Vrenders Swamp, a typical shallow sandhills lake provides habitat to many waterfowl and fish species. (Photo: Ashley Garrelts; STF)

Carp are also known to move through the shallowest of waters, so the placement of the screens is critical to the ultimate success of a lake renovation project. The planned location of the Vrenders Swamp fish barrier structure was moved several times during the planning process. A final location was settled on in 2017, and a solar-powered rotating fish screen structure was installed. However, due to the high lake levels, rotenone treatment did not occur then, nor in 2018. “Rotenone, to be effective, needs to be applied when lake levels are at their lowest,” explains Zac Brashears, an NGPC Fish Biologist involved in the project. Brashears has worked for the NGPC Fisheries Division since 2004 and has been involved in 14 lake renovations. “Low lake levels allow us to successfully treat the shallow wetland areas around cattails and other marshy vegetation, where small carp inhabit.” The high water of 2017 and 2018 was enough to warrant the delayed treatment to ensure a successful project.

Another setback occurred in early 2019 with that year’s historic flooding. An unknown ditch leading from the meadow below Vrenders Marsh into Eby lake was found, which could have let carp from infested Eby flow into Vrenders. The high-water delay was a blessing in the project’s ultimate success.

Common carp, native to Europe and Asia, was introduced in the US and has invaded many Sandhills lakes. (Photo: Zac Brashears; NGPC)

In 2015, during the initial planning phase, The Eby Lake Fishing Club and area landowners were unsure about the renovation process. “At the time they [STF, NGPC, and USFWS] were to renovate Vrenders, we were still catching decent perch,” says Rob Lee, an Eby Lake landowner, and fisherman. Rob and his family spend many hours catching fish on Eby Lake. “The carp were not that bad yet,” he adds. But in 2019, the club and area landowners had seen the successful renovation of Rat and Beaver, and they and the lake were both ready for a renovation.

Partners and landowners agreed to move the fish structure to the outlet of Eby Lake and renovate both lakes. The structure was redesigned with help from the Natural Resources Conservation Service engineers, and permission was obtained from the Cherry County Commissioners to place the structure under the county road. The structure was built in September 2021, and rotenone treatment of the lakes occurred just weeks later. The NGPC restocked the lakes about a month after treatment. Species included bluegill, yellow perch, and largemouth bass.

Nebraska Game and Parks' employees prepare to apply roteonone to Vrenders Marsh. (Photo: Ashley Garrelts; STF)

Now in 2022, the lakes are cleaner and used by swans, ducks, geese, and many species of migratory waterfowl. While most STF-funded projects do not take this long to complete, lake renovation projects involve many moving parts and are more complicated. However, they are very rewarding for landowners and wildlife enthusiasts.

Mark comments that he likes watching the swans that now inhabit Rat and Beaver and is looking forward to them hopefully raising some cygnets on Vrenders Swamp maybe as early as this summer. Eight years after the project to renovate the Rat and Beaver Lake watershed was initiated, the lakes are well on their way to being restored to pre-carp conditions. “I think my dad [Keith] would be very pleased,” Mark comments about his dad passing before the watershed project was completed. “He did catch some largemouth bass on Rat and Beaver, though, and I am very happy about that.”

Eby Lake hours after rotenone was applied (Photo: Ashley Garrelts; STF)

This project was made possible by the Sandhills Task Force, Nebraska Game and Parks Commission, US Fish and Wildlife Service Partners Program, Ducks Unlimited, Natural Resources Conservation Service, and Nebraska Environmental Trust. Landowners were also integral partners in this project.


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