Invasive mussel shells on top of the mussel masher used to remove them from the bottom of Lake Michigan at the School of Freshwater Sciences on East Greenfield Avenue in Milwaukee on May 7, 2025. The University of Wisconsin Milwaukee, along with federal agencies around Lake Michigan, are studying ways to remove invasive zebra and quagga mussels from Lake Michigan.
Lake Oroville, California – California is in the midst of a slow-moving ecological emergency that could soon spiral into a full-blown crisis. A destructive, invasive species known as the golden mussel—native to Southeast Asia—has taken hold in the state’s water system, with more than 50 confirmed infestations across the state, including in the Sacramento-San Joaquin River Delta, the heart of California’s water infrastructure. It’s the first known golden mussel invasion in North America, and experts warn the damage may already be irreversible.
First discovered last October encrusting a float near the Port of Stockton, authorities have detected golden mussels throughout the Delta’s vast network of pumps, canals, and reservoirs that supply drinking water to 30 million Californians and irrigate millions of acres of farmland. Their larvae—microscopic and nearly impossible to detect—are now spreading silently through the system.
Water agencies have shifted from eradication to mitigation. Once the mussels are established, there is no known way to remove them. Instead, state agencies are scrambling to protect key pumping stations and water treatment infrastructure. But the scale of the effort is massive, and the resources are already stretched thin.
California has no funding in its state budget dedicated explicitly to fighting golden mussels. The California Department of Fish and Wildlife is operating with roughly one-third of the staff needed to meet its own law enforcement and conservation responsibilities. Governor Gavin Newsom’s recent budget proposal included cuts to already-vacant warden positions—though lawmakers have so far blocked those reductions.
At Lake Oroville, the state’s second-largest reservoir, prevention efforts are in full force. Boats entering the lake undergo inspection and, if necessary, high-temperature decontamination. Specially trained detection dogs like Allee, one of only 14 in the state, help search for mussels before boats launch. But there are thousands of lakes across California, and many of them—especially those not connected to the Delta—remain vulnerable. A patchwork of inspections and quarantines is in place, but some of the state’s most popular boating destinations, including Shasta and Whiskeytown lakes, have no mandatory programs.
Public frustration is growing. Quarantine periods of 30 to 60 days have driven some boaters to seek out less-regulated lakes, creating potential new pathways for the mussels to spread. And even with rigorous programs in places like Lake Tahoe, enforcement can’t keep pace with the volume of watercraft moving through the state.
California has managed invasive species before, but golden mussels pose a distinct challenge—adaptable, fast-spreading, and uniquely suited to the state’s freshwater systems. While containment remains technically possible, each passing day without a coordinated, statewide response narrows that window. The mussels are already here. The question now is whether California can act quickly enough to stop them from becoming permanent residents in every lake, river, and reservoir it has left.
