Wildlife officials say quagga mussels are now present in three popular lakes in the Tonto National Forest.
The Arizona Game and Fish Department said Monday there is conclusive evidence of the mussels in Canyon, Saguaro and Apache lakes.
Officials say there is no infestation but the lakes are now listed as being waters affected by aquatic-invasive species.
Quagga mussels can ruin boat motors and clog water intakes such as pipes and screens.
Under state law, boaters and anyone doing water recreation activities in affected waters must properly clean, drain and dry watercraft and other equipment.