Napa Closes Lake Hennessey Boat Launch To Guard Against Invasive Golden Mussel

Press release from the City of Napa:

NAPA, CA — Lake Hennessey boat launch is closed and no boats are allowed on the lake until further notice. An invasive species, the Golden Mussel or Limnoperna fortunei has been ound in the Deltaand for the first time in North America. There is a 30-day quarantine program in effect for all boats entering Lake Berryessa.

Lake Hennessey is an important water supply for the City of Napa, providing 40-60% of our drinking water in a typical year. We know from past observations and boating traffic patterns studied by Solano County Water Agency that boaters move from the delta to Lake Berryessa and to Lake Hennessey.

With the restrictions at Lake Berryessa in place, it’s highly probable there will be increased boating traffic to Lake Hennessey as a nearby alternative. The picture shows how these invasive mussels clog a water pipe. Golden mussels are highly invasive, prolific reproducers that threaten water supplies by fixing themselves to underwater surfaces and clogging intake pipes and conveyance facilities. They can throw off the ecological balance by displacing native species and sport fish. Once introduced, they are difficult to eradicate. The larval microscopic mussels can survive for extended periods of time in waters. They are easily transported in live wells, bilges, ballast tanks, engine system, plumbing or any other compartments onboard boats or watercraft.

Why are these Golden Mussels so concerning? The Golden Mussels are similar in appearance and biology to quagga and zebra mussels that have been of concern for years, but the Golden Mussel can survive in waters that have considerably lower calcium levels than are required by quagga and zebra mussels (minimum 12-15 mg/l). Lake Hennessey calcium levels were too low (7-8 mg/l) to support the survival of quagga and zebra mussels. The Golden Mussels are able to survive in waters with calcium levels as low as 2 mg/l.

These mussels are similar in shape and size to quagga and zebra mussels

• Small, typically under 1.5 inches in length
• Firmly attached to hard/semi-hard surfaces
• Upright, shell margins opposite of attached side
• Shell color is light golden to darker yellowish-brown to brown color
• Freshwater and brackish water

This press release was produced by the City of Napa. The views expressed here are the author’s own.