The Quagga Mussel is a small, non-native freshwater mollusk that the Department of Water  Resources (DWR) had successfully prevented from infesting the State Water Project (SWP) since the species  was first discovered in California in 2007.

However, on December 8, six adult quagga mussels were found in the Angeles Tunnel, which serves as a connector between Pyramid Lake and Elderberry Forebay, two SWP components north of Los Angeles.

The California Department of Fish and Wildlife (CDFW) has concluded that Pyramid Lake must be considered infested with the invasive species, and Elderberry Forebay and Castaic Lake, both downstream from Pyramid Lake, are presumed infested with the mussels.

DWR discovered the mussels during a scheduled inspection of Angeles Tunnel. Six adult quagga mussels were found in the tunnel. DWR said there is no evidence of mussel reproduction, and no larval or “veliger” stage mussels have been found in Pyramid Lake during DWR’s routine monthly veliger detection monitoring.

No young sub-adult mussels were found in the tunnel, and no mussels have been found in Castaic Lake. Both lakes are actively monitored each month.

The “infested” determination for Pyramid Lake means boats must be inspected and thoroughly washed upon leaving the lake. It also means those boats will not be granted a “clean boat” tag that normally is given to boats when they leave water bodies that do not contain quagga mussels.

The tag is a visual sign that the boat does not require inspection prior to entering other bodies of water. DWR currently is implementing the steps outlined in its rapid response plan. Notifications have been sent to CDFW, the Los Angeles Department of Water and Power, the Los Angeles County Parks Department, the Metropolitan Water District of Southern California and SWP contractors affected by this discovery.

DWR’s response team is preparing to mobilize and delineate the extent of the mussel population. These efforts are being coordinated with CDFW, the State’s lead agency in invasive mussel management.

Quagga mussels can clog water systems, alter food webs in ecosystems and damage boat engines.