Game, Fish and Parks officials say they’ve detected zebra mussels in Sheridan Reservoir in the Black Hills.

This is the second confirmation of the invasive species in western South Dakota. The first was at Pactola Reservoir in 2022.

"GFP has been working closely with the U.S. Fish and Wildlife Service, US Forest Service, and Bureau of Reclamation to conduct both watercraft inspections and monitor for zebra mussels," said Tanner Davis, Aquatic Invasive Species Coordinator.

Specifically in 2025, there were 1,614 inspections at Sheridan Lake alone, Davis said. Combined, 14,595 inspections were conducted on all five major reservoirs.

Zebra mussels are more prevalent in eastern South Dakota. They’ve been found in roughly two dozen lakes since the first confirmation in 2015

Officials say zebra mussels disrupt food chains and can harm native aquatic life.

"This is an important time of year for monitoring the spread of zebra mussels," said Davis. "Age-0 mussels, or those in their first year of growth, will be able to be detected on structures that have been placed in the water throughout the summer months."

Game, Fish and Parks officials are asking boat and dock owners to keep an eye out as they winterize their equipment. If you spot them, contact your local GFP office or report it on the state's citizen monitoring page.