OOWD Administrator Dan Livdahl said that during his survey work on the lake, there were areas with just two to six inches of water remaining under the ice and oxygen levels “really crashed.”
“Since then, the oxygen level’s been rising,” Livdahl shared with managers during a district meeting Tuesday.
Dissolved oxygen levels that had been near zero two weeks ago were back up to 20 parts per million, he said. The change is likely due to increased sunlight, warmer temperatures and melting ice.
By Thursday, Livdahl had returned to the lake and discovered dead fish in numerous spots along the west shore of the west basin. The most susceptible to low-oxygen, Livdahl said Freshwater Drum — also known as sheepshead — comprised nearly all of what could be seen floating in previously-drilled holes and open areas. Remains of buffalo fish were also visible, along with a couple of eagles who were feasting on the discovery.
The district began a drawdown on the lake late last summer with the hope of forcing a fish kill in the three basins, which are heavily infested with common carp. If the drawdown produces a major fish kill, the plan is to restock the lake with game fish to control carp populations in the future. Ridding the lake of its high levels of carp is anticipated to lead to the growth of aquatic vegetation and improved water quality.
On Tuesday, managers discussed the timeline for closing the gates on the Ocheda dam, which will allow water to begin rising in the lake and create a barrier for carp to get back into the west basin from downstream Peterson Slough and Lake Bella.
“There’s a good possibility carp left Lake Ocheda and swam down to Bella when water levels got low,” Livdahl said, noting that dissolved oxygen levels in Lake Bella were quite low this winter. “There may be a lot of fish down there trying to stay alive.”
With ice still on the dam as of Monday, Livdahl said the structure can’t be closed just yet but should be as soon as possible. The lake’s management plan calls for the gates to be closed in April.
Just as southwest Minnesota’s commercial fisherman, Scott Deslauriers, was seining carp from Worthington’s Lake Okabena last week, Livdahl and managers Rolf Mahlberg and Jay Milbrandt met with Wenck consultants to discuss options for additional carp control measures in Lake Okabena and Sunset Bay.
Two options came forward, including the installation of a fish barrier in the culverts between the lake and Sunset Bay, and blocking off the southern portion of the bay to trap carp in hopes of leading to a wintertime die-off.