WORTHINGTON — During their Tuesday afternoon meeting via Zoom, Okabena-Ocheda Watershed District managers authorized up to $15,000 for additional radio tagging of carp in Lake Okabena.
Wenck Associates, an environmental consulting and engineering firm with offices in Minnesota, has worked with the watershed district in recent years on a project to tag and track carp movement in the Worthington lake. The data is being collected to learn where the carp congregate in hopes of doing a wintertime seining and removal of the rough fish.
In early May 2019, biologists with Wenck surgically implanted radio tags in 15 Lake Okabena carp. The carp have been tracked via radio frequency since then, with the goal of doing an early 2020 seining event.
When tracking data showed the carp didn’t congregate as anticipated last winter, the seining wasn’t done. Now, there’s concern the battery life of the radio tags won’t last into the next winter.
“The batteries may run out before we have a chance to do seining,” OOWD Administrator Dan Livdahl told board members Tuesday. “They (Wenck) suggest installing 15 more radio tags for an amount not to exceed $11,980.”
The radio tags need to be ordered soon to be ready when the weather is again cold enough and the carp would be less stressed for the surgical implants. At this time, the plan is to have Wenck staff do the implanting in October.
Of the 15 carp originally implanted with radio tags, Livdahl can still locate eight of them moving about the lake and the bay through their individualized tracking signal. Signals from another five carp still register, but he said those five carp haven’t moved since last fall and he believes they are dead.
Another 200 carp in the lake were captured by Wenck staff in early October 2019, with Passive Integrated Transponder (PIT) tags inserted into their body cavities in a less invasive procedure. The PIT tags were to help get a better estimate of the number of carp in the lake once a seining event was done.
Wenck conducted an assessment of the lake’s carp population in 2017 and 2018. During that project, it found the lake’s carp population to be approximately 312 pounds per acre, while Sunset Bay has about 330 pounds of carp per acre. Any amount over 89 pounds of carp per acre can have a significant impact on water quality.
Manager Jay Milbrandt said the carp tracking project is enlightening, and he sees a benefit to doing another round of radio-tagging carp. However, it can’t be done forever.
“I think the community would like us to continue to carry on this project and see what benefit we could get,” added Manager Rolf Mahlberg.
Lake Ocheda drawdown to begin Aug. 17
The committee that oversees the Lake Ocheda Management Plan has decided to proceed with a second temporary drawdown of the 1,800-acre Lake Ocheda after efforts last winter were unsuccessful in trying to freeze out the fish population. Lake Ocheda is heavily infested with carp, which stir up sediment and destroy vegetation, resulting in poor water quality.
Through a natural drawdown, water levels can be reduced by 2 feet, which still leaves 2 to 2.5 feet of water in the lake. The hope is that a hard winter freeze would then lead to a fish kill. Last winter did not bring the hard freeze that was needed, as tile lines were still pushing water and oxygen into the lake.
The temporary drawdown will begin when the first stoplogs are removed from the Lake Ocheda Dam on Aug. 17. The stoplogs will be put back into place in mid-April 2021 to restore the lake level to normal.
In other action, the board:
Approved $6,295.50 in cost-share to Dennis Bonsma for a waterway reconstruction project on land he owns in Section 35 of Bigelow Township, east of Lake Bella. The total cost of the reconstruction is nearly $22,500.
Approved a $500 cost-share payment to Paul Langseth for replacement of a septic system.
Learned the watershed district will receive $150,700 from the Federal Emergency Management Agency and state disaster assistance as reimbursement for repairs to the Prairie View spillway after it was damaged by flooding.
Approved a permit for Bruce and Beverly Kness, Worthington, to repair a retaining wall on their property on the Lake Okabena shoreline; and an erosion control permit for Minnesota Energy Resources Corp. to expand a parking lot at 650 Sherwood St., Worthington.
Discussed a request to improve the rustic trails at Lake Bella to create a smoother ride for people who use it for mountain biking. Without a lot of use by bikers (more walkers are frequenting the trails), the mowed path is a rough ride for certain types of bikes.
“I don’t know that there’s a really good way to make it something like that without a lot of traffic,” said Milbrandt. “I don’t know if there’s enough people going out there with their bikes to even warrant it.”
Milbrandt said if the city of Worthington proceeds with trail development at Prairie View, that’s where people will eventually go with their bikes for trail riding.
“I would wait to see what happens there before we do anything more with Bella,” Milbrandt said. “I do know people are using (the Bella trails). It will continue to grow, I think.”
Approved the 2019 financial audit report and briefly discussed the 2021 budget.