YANKTON, S.D. (WNAX) – The battle continues against the spread of zebra mussels in the Missouri River.

Tom Curran, Project Manager at Gavins Point Dam near Yankton says they have several cleaning and control systems in use.

Curran says it looks like they are making some progress.

Curran says the mussels continue to spread up the Missouri River.

The zebras multiply rapidly and their shells can clog any underwater structure or pipe. They have no natural predator and there is no effective control so far.