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March 10, 2021 – The California Department of Fish and Wildlife (CDFW) is asking retailers and consumers to help stop the spread of a dangerous invasive mussel that has been found in aquarium moss balls sold in California and nationwide.

A zebra mussel on an aquarium moss ball. Photo courtesy of Oregon Dept. of Fish & Wildlife.

CDFW was notified last week that zebra mussels, highly invasive freshwater mussels which are illegal to possess in California, were found on aquatic moss balls at a national pet supply retailer. Investigators traced the origin of the mussel-contaminated moss balls to a distributor in Southern California. CDFW’s Law Enforcement Division worked with the distributor to immediately cease outgoing shipments and prevent the receipt of additional importations. State and federal law enforcement agencies continue to investigate the potential supply chains associated with this product, and have since identified several additional suppliers to California and nationwide.

“If zebra mussels escape from aquaria and into the environment, they pose the risk of causing enormous environmental and economic impacts,” said Martha Volkoff, CDFW 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.”

California law prohibits possession, importation, shipment and release of zebra mussels in any waters within the state. Possession of zebra mussels in California, live or dead, and whether intentional or not, is a violation of California Fish and Game Code section 2301.

CDFW is calling upon pet supply retailers and home aquarium enthusiasts to prevent the spread of mussels from aquariums.

Retailers:

  • Immediately pull moss balls from your shelves and store in a secure location until they can be destroyed. Also inspect all other moist and aquatic plant products. All moss balls, and any other products found to be contaminated with mussels should be placed in a bag, frozen overnight and disposed of in the municipal trash.
  • Immediately inspect all fish tanks and filtration systems for mussels. If mussels are found, cease sale of all products from those tanks. Remove all mussels and live plants, place in a bag, freeze overnight and dispose of in the municipal trash. Clean and disinfect all aquaria, filters and decorations.

Consumers:

If you have added moss balls to your aquarium or fish bowl in the past year, assume that you may have introduced zebra mussels and take one of the following actions:

Alternative 1. If you observe mussels in your aquaria, per U.S. Fish and Wildlife recommendations, empty and disinfect the aquarium and all of its contents: fws.gov/fisheries/ANS/zebra-mussel-disposal.html. Even if you do not observe mussels consider decontaminating your tank and all of its contents. (Considering the significant investment many aquarists make in establishing and maintaining their aquaria, disinfecting and reestablishing a system per these recommendations may not be a realistic expectation. If so, please adhere to Alternative 2.)

Alternative 2. Quarantine and monitor your aquarium for at least six months. Complete instructions for quarantining your tank, and an observation log to assist you with monitoring your tank, are available on CDFW’s website: wildlife.ca.gov/Conservation/Invasives/Aquarium-Moss-Balls. The quarantine would end six months after no mussels are observed.

For additional information and guidance, please call CDFW’s Invasive Mussel Hotline at (866) 440-9530 or visit wildlife.ca.gov/Conservation/Invasives/Quagga-Mussels.