Mussell inspection program aims to keep aquatic invasive species out of Lake Berryessa

A boat receives a free decontamination service where Watercraft Inspectors target areas with hot water to effectively kill any mussels or veligers. Courtesy photo

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By Sabrina Colias and Zach Hyer
Special to the Express

As many long time Lake Berryessa visitors can attest to, mussel inspections never existed. Some may be wondering why now and why aren’t these people clad in orange shirts present to ask me the same question all the time?

This process is known as the Lake Berryessa Mussel Prevention Program and it is spearheaded by the Solano County Water Agency in coordination with the Bureau of Reclamation, Concessionaires, and California Department of Fish and Wildlife. The Mussel Program is dedicated to keeping Lake Berryessa free of aquatic invasive species, primarily Zebra and Quagga mussels.

Native to Ukraine, they were accidentally introduced into the Great Lakes by Trans- Atlantic freighters. Over the past 20 years, infestations swept across the nation from east to west. Hitting close to home, these mussels shut down San Justo Reservoir in 2008 and have completely taken over. Zebra and Quagga mussels have yet to fail at demonstrating their adverse impacts on the environment, recreation, and infrastructure.

The real threat to Lake Berryessa is not matured mussels stuck to the hull of a boat, but their eggs. The eggs (veligers) are naked to the human eye and are unknowingly transported in water taken on by watercraft bilges, intakes, ballast tanks/bags, live wells, bait tanks, and even recreational equipment such as flotation devices. With no natural predator in the United States, there is no stopping them once introduced.

One mussel can produce a million eggs in one year and when they hatch into mussels, the detrimental damage will begin to show itself. They will adhere to hard surfaces with what are known as byssal threads. These hard surfaces include watercraft, docks, lines, and native clams and crustaceans including themselves, enabling a clogging effect in intakes and pipes of watercraft and water delivery systems. A single mussel can filter feed a liter a day, consuming the same fresh water plankton that fish populations rely on. The mussels leave something in return called pseudofeces, which is a silty filth blanketing the lake bed preventing new vegetation growth along with their shells littering the shorelines.

The Mussel Program mitigates the risks of infestation through educational screenings, inspections, and free decontaminations. The screening process is currently the most efficient way to determine if a boater is unknowingly transporting mussel eggs. The inspectors ask the boater where they have last launched to determine if they are coming from a geographical area with known infestations. If so, the inspector then needs to determine if there is any water onboard that could be holding veligers – thus triggering a physical inspection. If water is found onboard or the boater cannot verify where the boat last launched, they will be directed to the free decontamination service. This service flushes the watercraft in targeted areas with hot water, safe enough to run through a watercraft and effective enough to kill any mussels or veligers.

Most of the time, a screening does not lead to a decontamination because so many of us only boat locally in Northern California Lakes. The reason for screening every boat is because it only takes one watercraft to ruin it all.

What happens when boats are not being inspected? Because Lake Berryessa receives hundreds of thousands of visitors each year, inspectors can’t do it all alone. This is why education is so important, so boaters can be responsible and take the easy proper precautions before launching.

Boaters of Lake Berryessa are asked to help keep Lake Berryessa mussel free by remembering to clean, drain and dry every time and by taking these steps before and after leaving any recreation area:

~Remove plants, animals and mud from gear, boat, trailer, and vehicle.
~Clean your gear.
~Drain bilge, ballast, wells, and buckets.
~Dry equipment including waders, line, toys, PFDs, and the hull of your boat.
~Dispose of unwanted bait in the trash.
~Wait before launching into different fresh waters. The recommended drying period is 30 days.

Solano County Water Agency staff offer free inspections and decontaminations to all boaters.

If you believe your watercraft is at risk for harboring zebra or quagga mussels, or for more information, visit

This is our Lake, and we need to work together as a community to protect it.

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