WORTHINGTON — With a metal antenna held at arm’s length, Dan Livdahl makes a sweeping motion toward the water in hopes of hearing a ping as he dials through the radio frequencies programmed into the monitor dangling from his neck.
It’s been two months since 15 Lake Okabena carp were implanted with radio tracking devices — two months since Livdahl began collecting data on where the carp are and whether they are on the move.
“Ogre is the one that has done the most travelling around,” said Livdahl, Okabena-Ocheda Watershed District administrator.
Ogre — aptly named as one of the largest carp to be implanted with a tracking device — was in Sunset Bay earlier in the spawning season, traveled into Lake Okabena and then up Whiskey Ditch to the stormwater pond at Bedford Industries. A week later, Ogre’s ping registered from the E.O. Olson Stormwater Pond on the Minnesota West Community & Technical College campus. On Thursday morning, Ogre was in the West Lake neighborhood, midway between Whiskey Ditch and the point.
Ogre is No. 092 on the radio frequency dial. Each of the 15 carp has its own frequency, and a name that begins with the letter “O” for Okabena. Among the others are Olivia, Orville, Oma, Ole, Olga, Oops and, oh — you get the idea.
During the height of carp spawning season in May and June, Livdahl gathered up his gear and a notebook and spent up to six hours per week tracking the 15 radio-tagged carp. Now shifting to a once-a-month tracking, he was on a quest Thursday morning to collect his carp data for July.
He found 12 of the 15, and said the frequencies haven’t registered on the three missing carp — Oke, Otto and Oscar — for the past several weeks. It’s possible the carp went upstream or downstream, though Livdahl has done his best to check the streams north to Prairie View and south to Lake Ocheda. It’s also possible the carp are simply enjoying the cooler waters in the deeper depths of Lake Okabena. If a fish is in waters deeper than five feet, it’s likely the tracking device won’t register a blip on Livdahl’s radar equipment.
Just two months into data collection, the tracking maps Livdahl has shared with Okabena-Ocheda Watershed District managers show the carp spent considerable time in May and early June in Sunset Bay, and have since spread out to points all around Lake Okabena.
The tracking will continue monthly through the rest of the summer, fall and winter. Livdahl then intends to start weekly tracking again next May, when spawning season ramps up for the roughfish.
It’s still too early to say just how the district will address the overly abundant carp population in Lake Okabena and Sunset Bay.
“When we went into it this spring, the plan was to do carp removal this winter,” Livdahl said.
Now, he’s not as confident it will happen that soon.
“Carp are really smart,” he said.
A winter-time seining means cutting through the ice to get nets in. The sound alone could send a school of carp scattering.
“We want to be confident we can pull a large volume of carp from the lake,” Livdahl shared. “Unless we find a bunch of them schooled together this winter, we may not do the seining this year.”
While seining will be necessary to remove the adult carp from Lake Okabena and Sunset Bay, it isn’t the only option in the watershed district’s tackle box.
“The whole goal of this is to find out where the fish are spawning in the springtime,” Livdahl said. “If they’re spawning in a place where no predator fish exist, we want to figure out a way to either introduce predator fish (to those areas) … or exclude (the carp) somehow from that area.”
Lake Okabena and Sunset Bay already have a healthy population of predator fish — sunfish and bluegill are excellent feasters on carp eggs during spawning. Add in perch, walleye and northern pike that feed on young carp, and the population of rough fish has the potential to be kept under control.
“If a carp is going to make it from egg to breeding adult, it will happen in areas where there aren’t enough predator fish,” Livdahl said.
Developing a plan for carp control in Lake Okabena isn’t just a one-year deal; it will be a multi-year program. Funding for the radio tracking equipment came from the city of Worthington, with the watershed district financing Livdahl’s time spent collecting the data. The E.O. Olson Trust has already set money aside to finance the tracking program in 2020.
“We’re trying to reduce the number of carp in the lake below the level that they adversely affect water quality — below 89 pounds per acre,” Livdahl said.