YANKTON, S.D. (WNAX) – As zebra mussels continue to spread through the Missouri River system, various controls are showing mixed results.

Gavins Point Dam has experienced a heavy infestation, both inside and outside of the power house.

Operations Manager Tom Curran says they have been working to find some way to slow the spread.

Curran says they have had some luck in containing the shells.

Curran says they are still watching the UV light system for results.

The zebras have no natural predator and multiply rapidly, sticking thousands of shells to any underwater structure.