Carp removal project considered on Worthington’s Lake Okabena
WORTHINGTON — The number of carp in Worthington’s Lake Okabena and Sunset Bay has Okabena-Ocheda Watershed District managers discussing options to tag, track and remove the roughfish from the basins.
During its Tuesday meeting, the board heard a presentation from Tom Langer, an aquatic biologist with Wenck Associates, who traversed the shorelines of the two basins in July with an electrofishing boat.
As the carp were temporarily shocked and rose to the surface, they were counted, weighed and measured. Using a formula developed by the University of Minnesota to determine carp density, Langer said the lake and bay are infested with three times more carp than what is deemed critically impaired.
Carp, bottom-feeders that stir up sediment and nutrients, cause decreased water clarity, decreased vegetation and diminished habitat in lakes.
“Lake Okabena has 791 pounds per year of internal load reduction requirements,” Langer said. “There’s need for improvement internally, and carp management is one of those tools.”
He proposed the district consider tracking carp, age-testing them and doing large-scale carp removals, followed by population assessments, water quality monitoring and annual vegetation monitoring.
“Tracking and aging would improve our understanding and assist management efforts toward carp within Lake Okabena,” Langer said.
Tagging would include surgically implanting radio tags in 15 carp — a process done in the fall of the year when the water is cooler — and then tracking fish movement. The radio tags last about three years each and provide information on where the carp spawn, migrate and overwinter.
Langer also suggested doing an optional age assessment, which involves removing the otolith from 50 carp in the lake. The otolith is a hardened bone in the internal ear of the carp. The bone contains rings much like a tree, which are used to determine approximate age.
The estimated cost for radio tagging and tracking, as well as age assessment, is $29,000. In year two, which would include additional carp tracking and carp seining, the cost could range from $15,000 to $50,000.
“Commercial fishermen sometimes come out for free,” Langer said. “Sometimes they ask for a bounty.”
The last commercial carp removal was done on Lake Okabena in 2006.
Worthington City Council member Alan Oberloh, who attended the presentation, asked about financing the project.
“Don’t shy away from making a presentation to the city council,” he said. “The residents of this community benefit more than anyone else.”
OOWD Administrator Dan Livdahl said the watershed district could ask the E.O. Olson Trust for financial assistance with the project. He also noted that Nobles County has Aquatic Invasive Species funding available.
OOWD Manager Jay Milbrandt found the proposed project interesting, particularly with the plans to draw down Lake Ocheda next year to force a fish kill in that carp-infested three-basin lake. He said the Lake Okabena Improvement Association may also be interested in contributing funds toward the project.
“We’re here to clean up the water in our watershed,” said OOWD Manager Jeff Rogers. “We did the electrofishing just to see if the population was there and impacting our water quality. Tracking just makes the seining so much more successful.”
The board directed Livdahl to discuss funding for the project with the E.O. Olson Trust and the city of Worthington, as well as to contact southwest Minnesota’s commercial fisherman, Scott Deslauriers.
In other business, the board:
- Reviewed the proposed 2019 budget and set the levy. The watershed district anticipates $262,300 in revenues in the coming year, with $545,100 in expenditures. Much of the expenditures will be for the Lake Ocheda dam modification project planned in 2019. The district has been setting money aside in savings for the project.
- Received an update on Prairie View project repairs. Duininck Inc. submitted an estimate of $114,500, which includes site restoration of the spillway and filter areas, reinstallation of the Flexamat, removal of the existing sand used for filtering and replacement with new sand, among other materials. Wenck, which designed the system, will be responsible for the largest share of the cost at $92,580, with the watershed district’s share estimated at nearly $22,000.
Livdahl said Wenck’s insurer wants an agreement with Duininck that the costs will not exceed its share of $92,580, which has kept the repair project in limbo. The board approved the contract and set up an ad hoc committee to meet if necessary to review the release agreement.
- Approved a stormwater pollution prevention plan for Road to Rail as it constructs its transloading facility near Org; and an erosion control permit for Bedford Industries during construction of a 34- by 176-foot addition (truck bays).
- Discussed maintenance issues at Bella Park. Manager Les Johnson had done a lot of work in the park over the years, and with his term on the board coming to an end, there was discussion about long-term plans for controlled burns on the watershed property.
In addition, high waters this summer resulted in some of the rock around the pond at the Bella dam being pushed off and exposing the riprap. Johnson said he would be willing to serve on the watershed’s advisory board and do some burns and work in the future for reimbursed expenses.