California Aquaculture Association

Background

Quagga (Dreissena bugensis) and zebra (D. polymorpha) mussels arrived in the Great Lakes from European waters via ballast water in the 1980’s. Since that time, they have spread to many eastern rivers, canals and water bodies causing billions of dollars of damage to the environment and water delivery facilities. These mussels have moved westward. Quagga mussels were found in Lake Mead Arizona in early 2007 and have since spread throughout the Colorado River system; in the summer of 2007 they were found in the Colorado River Aqueduct and are now in several water bodies in California. In January 2008, zebra mussels were found in San Benito County, California. The most likely mechanism for transfer between non-contiguous water bodies in the US is through contaminated boats.  Introduction can occur when adult mussels are brought on boat hulls or through veliger-infested water contained in bilges, motors or trailers.   

To date no quagga/zebra mussels have been found in any California aquaculture facility, nor has aquaculture in other parts of the USA been implicated in the spread of quagga or zebra mussels.  However, the potential for aquaculture operations to become infested and/or spread invasive mussels exists.

As part of a state and federal response to the invasion of quagga and zebra mussels in California, aquaculture staff, the Fisheries Branch and the Invasive Species Program of the California Department of Fish and Game convened a workshop June 11-12, 2008, at the University of California Riverside, Palm Desert California to:

• increase general awareness of the risks that the quagga and zebra mussels pose to California aquaculture;
• examine practical means to reduce the risk of spreading the mussels to and from aquaculture facilities; and
• develop practical and effective aquaculture guidelines.

The guidelines are considered draft guidelines at present and are based on currently available information presented at a workshop convened by the California Department of Fish and Game. The participants of the workshop helped develop the guidelines and approved the contents. It is recognized that as information on treatment, impacts, and distribution of the mussels improves, the guidelines will evolve to reflect the best available information.

The draft guidelines will soon be available on CAA and DFG websites.  These guidelines are at present voluntary and rely on individual farms to:

• assess their risk of acquiring and spreading the mussels,
• monitor and report presence and absence of the mussels,
• take precautionary measures in high risk areas,
• take appropriate action if an infestations is found, and
• spread information on good farming practices throughout the industry.

The draft guidelines provide a risk-based approach to managing quagga/zebra mussels that includes development of a Hazard Analysis and Critical Control Point (HAACP) plan. The basic elements of the guidelines are listed below, with more detail in the following section.

For facilities in infested counties:

• Facilities within infested counties but that have not found mussels at their facility or in their water supply should, at a minimum, conduct regular monitoring and reporting.
• If mussels are found in the immediate water supply of a farm, at a minimum a water management plan should be developed, transport water must be treated and regular monitoring and reporting should be conducted.
• If mussels are found in a facility, then disinfection, quarantine and other measures as appropriate must be taken.

For facilities in un-infested counties:

• Facilities should develop HAACP.
• Facilities should conduct regular monitoring and reporting.
• Treat as appropriate.

Actions a farm must take will depend on the level of risk and the distribution of the invasive mussels. Actions will change as the distribution of the mussel changes.

For more information see California Department of Fish and Game Invasive Species program: Quagga and Zebra mussels: http://www.dfg.ca.gov/invasives/quaggamussel/ or contact  Devin M. Bartley, Aquaculture Coordinator, 1416 9th Street, Sacramento CA 95814. dbartley@dfg.ca.gov, tel 916 651-7824.