WORTHINGTON, Minn. — Seining efforts in Lake Okabena date back to 1926, and commercial fisherman returned earlier this month in hopes of removing common carp and harvesting buffalo fish in the Nobles County lake.
The most recent effort was led by Scott Deslauriers and came after 20,000 pounds of buffalo fish had been harvested from Lake Bella, south of Worthington.
Getting their nets through Lake Okabena was limited to one day, though, due to predicted higher winds and colder weather, as well as sonar data showing a lack of schooling fish.
During the seining effort, the fishermen captured an estimated 8,000 pounds of buffalo fish and 800 pounds of common carp. Although it sounds like a lot of fish, the fishermen and the Okabena-Ocheda Watershed District were disappointed with the haul.
The Okabena-Ocheda Watershed District wants to reduce common carp from Lake Okabena, and this was Deslauriers’ second attempt to sein rough fish this year. On Feb. 25, he removed roughly 4,000 pounds of buffalo fish and 600 pounds of carp from the Worthington lake.
Finding the carp
Okabena-Ocheda Watershed District Administrator Dan Livdahl has records that date back to 1926, when 529,754 pounds of roughfish were harvested from the local lake. Seining wasn’t done again until 1944, with four events that decade.
In the 1950s, seining in Lake Okabena was done every year, with the largest haul completed in 1957. That effort resulted in 74,593 pounds of buffalo fish and 44,202 pounds of carp being removed from the lake. Seining occurred twice in the 1980s and three times in the 1990s, but prior to February, the last seining effort on Lake Okabena was in 2006, when the Minnesota Department of Natural Resources harvested 7,430 pounds of carp.
The watershed district is focused on removing common carp from Lake Okabena as a way of improving water quality and clarity. Carp stir up sediment on the lake bottom and destroy vegetation. Studies in recent years by Wenck Associates have determined the lake is home to an abundance of the roughfish.
As a result, the watershed district has funded several efforts to track carp habits in the lake. Twice, Wenck biologists surgically implanted a dozen or more common carp with radio frequency devices that made it possible for Livdahl to monitor where the fish spawned in the springtime and where they tended to congregate. In addition, less invasive PIT tags were also implanted in nearly 200 Lake Okabena carp by Wenck biologists.
“The purpose of the tagging was two-fold,” Livdahl said.
Their first goal was to figure out where the carp went during the spawning season.
“I think we accomplished that — 70% to 80% of them were in Sunset Bay, so that seems to be where they’re spawning,” he said. “When the water was warm enough, we know they liked the shallowest areas of Sunset Bay, so I think we need to do something with Sunset Bay.”
The second goal was to find schools of carp by creating some Judas fish.
“Each radio-tagged fish represents a larger number of untagged fish in the school,” Livdahl said. “If we could scan the fish that were caught and compare those to the tagged carp, we’d have a good idea of the amount of carp in the lake.”
The difficulty came in actually trying to sein where large numbers of the tagged carp were known to be.
“Last winter when Scott seined, I thought there were a lot of tagged fish in that area, and somehow they got out,” Livdahl said.
“I think we’ve accomplished what we can with the radio-tagged fish,” Livdahl said, adding that the battery-operated radio frequency tags surgically implanted in carp in 2019 and 2020 are also at the end of their battery life.
The data gathered from the two tagging events will be useful going forward. The watershed district learned where the common carp prefer to spawn, and where they tend to be during the rest of the year.
What the district hasn’t learned is the quantity of carp they are dealing with in the lake.
While the February haul yielded no previously-tagged carp, the district decided not to have Wenck’s biologists return to Worthington to scan the roughfish captured by Deslauriers last week. Based on the small number of carp pulled in, it was cost-prohibitive.
“Last winter we had basically the same number of fish caught. We paid the consultant to come down and scan the fish … and it cost us $3,000 to do that,” Livdahl said. “We decided if we had a lot more fish, we would have definitely done it.”
With three different population density numbers for common carp in Lake Okabena — all of which seem high to the watershed district’s board of managers — Livdahl said the group planned to discuss the potential for another winter-time seining.
“I think we still need to try to do a removal through seining in order to know what the carp population is in the lake,” Livdahl said. “By seining, you have to remove half or more of the carp from the lake every year in order to make any progress on lowering the carp population in the lake. You have to know what the population is. Removing 1,000 pounds isn’t going to do any good if you need to remove 100,000 pounds.”