Lake Almanor and Golden Mussels

Golden Mussels

     Let’s begin with some background; A Golden Mussel or Limnoperna fortunei is a medium sized bivalve mollusk that lives in fresh and brackish water. Originally native to China, it has been introduced to other countries around the world including several in Asia and South America where it has proven to be an invasive species. Golden Mussels are small, usually less than an inch and a half in length, with shells that range from a light golden to yellowish-brown to brown in color. The mussels are generally found firmly attached to hard or semi-hard surface found in the water such as pilings and concrete infrastructure. Golden Mussels are filter feeders that consume very small organisms and organic matter. Each mature mussel is capable of filtering one liter of water in a 24-hour period, with their colonies able to reach densities of 80,000 to 200,000 individuals per square meter, they can have significant impacts to ecosystems.

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Golden Mussels found October 2024 in the Sacramento San Joaquin Delta.

     First discovered in California, near Stockton, in the Sacramento / San Joaquin Delta in October 2024, this is the first known occurrence in North America. The Golden Mussels were likely introduced to the delta by a ship arriving from an international port. California is not new to invasive mussels, Quagga and Zebra Mussels have been found in the state and been a topic of conversation for years. The Golden Mussel is thought to be an even more menacing threat as they can adapt and live in a wider range of water conditions.

     California’s response has been largely one of education, with press releases and an emergency listing by the State Fish and Game Commission as a restricted species. Other agencies, responsible for California reservoirs, have taken a stronger approach, some closing or restricting access to boat launching, while others use boat decontamination stations all in hopes of preventing spread. Lake Berryessa, Lake Comanche, New Melones, Pardee and Lake Don Pedro are just a few that are popular with recreational fishermen and all have some type of restrictions in place.

The Wakasagi or Japanese Pond Smelt is a key part of the forage base in Lake Almanor.

     What does this all mean for Lake Almanor? The introduction and subsequent spread of Golden Mussels in Lake Almanor would be disastrous for the lake’s world-class sport fish population, which relies on Almanor’s rich forage base to support itself. As mentioned above, the mussels survive by filtering small organisms such as aquatic bug larvae, and plankton, both of which are key food sources for the Wakasagi or Japanese Pond Smelt, which in turn are a prime food source throughout the year for the sport fish.

     As of this writing, there are no signs of Golden Mussels in Lake Almanor or other surrounding lakes, which is good news. There are no current restrictions to launching watercraft into the lake, however it is always a good idea to check for the most up to date information prior to traveling to the area. This means, as of now, it is up to the individual watercraft owner to be responsible and take precautions. California has used “Don’t Move A Mussel” and “Clean Drain And Dry” as catch phrases to promote awareness of potential pathways of spread. When bringing your watercraft of any type and size to Lake Almanor, please be sure there are no pockets of water that may hold the larvae of these invasive species, this includes the motor(s), bilge, pumps, waterlines, fish boxes, live-wells and ballast tanks. Certainly, inspect and clean the hull and trailer.  If you have boated in the delta or other waters with known populations, please consider having your boat decontaminated with hot water including the systems mentioned above. I realize this is an extra time and expense but we all come to Almanor because we love the lake and the area it would be a shame to lose it.