GFP Continues Fall Inspections on South Dakota's Lakes and Rivers

September 28, 2023

South Dakota Game, Fish and Parks (GFP) employees have been continuing to survey and sample lakes and rivers across the state to monitor fish and other wildlife populations, which includes inspecting for the presence of zebra mussels.

"Fall is a busy time of year in South Dakota, as staff conduct surveys and many boats, docks, and lifts are removed for the year as well," said Aquatic Invasive Species Coordinator, Tanner Davis. "In the fall, zebra mussels have attached to hard substance and can be easily detected, which is why we have included inspecting for zebra mussels in our fall sampling."

As summer transitions to fall, veligers, or microscopic zebra mussel larvae, will attach to hard surfaces where they form their shells and begin to colonize.

"While conducting river otter surveys on the Big Sioux River, GFP staff found zebra mussels at two locations," said Davis. "The zebra mussels were detected roughly five miles south of Watertown, and downstream of the connected zebra mussel positive waterbody of Lake Kampeska.."

Following this detection, the Big Sioux River from Lake Kampeska to the confluence of the Big Sioux and Missouri River is now considered infested. The Zebra Mussel Rapid Response Team will place high-profile signs on access areas, actively engage boaters using the infested water, reiterate information on decontamination requirements, and identify groups of people and entities that will be potentially affected by the infestation.

"We are currently working to have signage placed at all access areas on the Big Sioux River," Davis continued. 

"Fall is an important time of year for detecting zebra mussels," said GFP Communications Manager, Nick Harrington. "Individuals who believe they may have found a mussel on their boats, docks, or lifts are reminded to contact their local GFP office and provide a photo and location of the suspect mussels. Zebra mussels that are found on boating infrastructure are most likely juvenile zebra mussels will be 1/3 inch in length or smaller, so look very close when inspecting your equipment this fall. 

GFP has significantly enhanced efforts to slow the spread of aquatic invasive species (AIS) in recent years, both educating anglers and boaters to clean, drain, dry every time they are on the water as well as physically inspecting boats prior to and/or after loading.

"Whether individuals are out enjoying the great fall fishing, duck hunting, or simply out for one last float of the year, boaters are reminded to clean, drain, and dry every time,” concluded Harrington.

You can learn more about AIS by visiting


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