WORTHINGTON — For the second time in less than five months, an electrofishing boat made the rounds on Lake Okabena and Sunset Bay this week on a quest to find carp.
Wenck Associates Project Biologist Aaron Claus and Environmental Scientist Nick Omodt arrived in Worthington Thursday morning for a two-day search for the rough fish. This time their goal was to capture approximately 200 carp, insert Passive Integrated Transponder (PIT) tags into their body cavities and release them back to the water.
This second round of tagging is hoped to enhance the carp management effort in the Worthington lake. The work is the result of assessments Wenck conducted in 2017 and 2018 that revealed the lake’s carp population was 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.
In May, Wenck staff surgically implanted radio transmitting devices into 15 carp in Lake Okabena. Since then, Okabena-Ocheda Watershed District Administrator Dan Livdahl has tracked the carp and collected data on where they congregate.
Thursday morning, with the aid of radio frequency equipment, Livdahl found six of the carp in Sunset Bay and another two near the grade in Lake Okabena by checking only half of the spots he normally visits.
“That’s consistent with where the carp have been since soon after they were tagged,” Livdahl said of the area near the grade. “We had 11 of them in the bay three weeks after they were tagged.”
The Okabena-Ocheda Watershed District budgeted $21,000 for the carp tagging effort in May. When only about half of that was spent, Claus suggested this less commonly used, less invasive method of tagging on a higher population of carp.
“This was a way to intelligently use the extra budget that was allotted to add more certainty and information to the abundance of density estimates,” Claus said.
“The two tags do give us different information,” added Omodt.
The PIT tags were inserted through the bottom, lateral side of the carp and into the body cavity using a small tagging device with a hypodermic needle. The tags are the same as those used for microchip identification in pets.
By inserting PIT tags into the carp, Claus said they will be able to get a more accurate count of carp in the lake during the seining process anticipated to be done in early 2020.
“We just want to be able to, with the best methods available, track where we’re at,” Claus said, adding that this week’s effort was to get a random sample of various sized carp.
Of the 15 carp tagged with radio tracking devices in May, Livdahl said he’s been able to find 13 of them each time he’s been out with his equipment. It’s unknown if the two that are missing died at some point, or if they’ve stayed in deeper water where they can’t be detected on the radar.