The California Department of Fish and Wildlife is asking retailers and consumers to help stop the spread of a dangerous invasive mussel found in aquarium moss balls sold in the state and nationwide.

Zebra mussels — highly invasive, freshwater mussels that are illegal to possess in California — were found at a national pet supply retailer on aquatic moss balls traced to a distributor in Southern California.

The state has ceased outgoing shipments and is investigating potential supply chains.

“If zebra mussels escape from aquaria and into the environment, they pose the risk of causing enormous environmental and economic impacts,” said Martha Volkoff, the department’s environmental program manager. “Once introduced to rivers, creeks, lakes and canals, mussels multiply quickly, encrust surfaces and disrupt ecosystems, water delivery systems and recreational opportunities. It is imperative that pet suppliers and aquarists take action to prevent these mussels that have entered the aquarium trade from reaching our waterways.”

For consumers, the department is urging them to empty and disinfect their aquariums if they have added moss balls within the past year. Details of how to do this are available on the CDFW website.

The public can also find details for an alternative approach, which involves a six-month quarantine for an aquarium.

For additional information and guidance, people can call CDFW’s Invasive Mussel Hotline at 866-440-9530 or visit online.