Invasive zebra mussels found in Pennington County

Dominik Dausch
Farm Forum
The first case of zebra mussel infestation in Pactola Reservoir, which is 15 miles west of Rapid City, was confirmed by the South Dakota Department of Game, Fish and Parks and the U.S. Bureau of Reclamation Thursday, July 14, 2022. This specimen discovered by a person spear fishing in the reservoir, who found the mollusk attached to a pair of sunglasses.

A new case of zebra mussel, an invasive mollusk, has been discovered in Pennington County.

That's according to the South Dakota Department of Game, Fish and Parks and U.S. Bureau of Reclamation, who announced Pactola Reservoir "is now considered infested with zebra mussels" in a press release Thursday.

According to Tanner Davis, GFP Aquatic Invasive Species Coordinator, the department was alerted to the presence of the species after it was sent a picture of a zebra mussel stuck to a pair of sunglasses.

BOR confirmed the infestation after taking water samples of the reservoir and finding zebra mussel larvae, also known as "veligers," contained within.

More: Here's how Enemy Swim Lake successfully kept zebra mussels at bay this summer

Zebra mussels are small, freshwater mollusks originally native to Russia and Ukraine. They have a walnut-brown/black shell and vary in size, some are as small as grains of sandpaper, while adults can grow up to 2 inches in length.

GFP said all motorized and non-motorized boats and other watercraft must stop by a Watercraft Inspection/Decontamination station before entering or leaving any of the larger reservoirs. The inspection stations are equipped with hot water sprayers that can kill residual mussel tissue and other aquatic invasive species.

GFP is reminding the public to "clean, drain, dry" to prevent the spread of zebra mussels:

  • Clean watercraft and trailers of all aquatic plants and mud.
  • Drain all water by removing all drains, plugs, bailers, or valves that retain water. Be sure to completely drain your lower unit of any water by lowering completely.
  • Dry all equipment that has made contact with the water before it's next use.

More: Resolution encourages state to research zebra mussels, other invasive species in SD lakes

Potential zebra mussel infestations can be reported to GFP by visiting

Dominik Dausch is the agriculture and environment reporter for the Argus Leader and editor of Farm Forum. Follow him on Twitter and Facebook @DomDNP and send news tips to