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Don't Move a Mussel

Don't Move a Mussel!

Lake Nacimiento and San Antonio face a serious threat - dreissenid mussles. Here are basic guidelines on what is at risk, and what you can do to keep area lakes dreissenid mussel free.

What would happen if Lake Nacimiento or San Antonio was infested?


The lake ecosystem would never be the same.


There is no known means of eradication without killing everything else in the lake(s). In other words, once mussels get a foothold, there is no known way to get them out of our lakes. The balance of fish and other species in the lake would be noticeably impacted. Clumps and clusters of mussels would develop and their carcasses would accumulate on the shore.

We would have to declare ourselves an infected water body, a deterrent to boating and a negative impact on the local economy. Boats based at an infected lake would no longer be welcome on other lakes seeking to remain mussel-free.

Don't Let Our Lake Nacimiento Become Infested!!!

  • Make sure your vessel is Clean, Drained, and Dry.

  • Make sure you have a current Vessel Screening Permit, or a Resident Vessel Sticker and Resident Vessel Certificate.

  • If you are on the lake without a Vessel Screening Permit or a Resident Vessel Sticker and Certificate you are subject to a $2000 fine.

  • Repeated violation of the above may result in your launch ramp being closed.

Current Mussel-Infested California Lakes


Been on ANY of these lakes in the last 10 Days ?

   >>--->   DON'T Launch!

Last 30 Days?

  >>--->   MUST pass inspection before you launch!

More About The Mussels


Zebra and Quagga Mussels

Dreissena Polymorpha and Dreissena Bugensis


What are Zebra and Quagga Mussels?

  • A fresh water mussel

  • Average life span 3 to 5 years

  • One million eggs per year!!

  • Filter Feeder (eats microscopic organisms)

  • Attach to surfaces with byssal threads

  • Roughly about the size of an adult human’s thumbnail


Mussel Infestation Impact

Mussel Infestation Impacts the Lake Environment

Fills the air with the stench of decay (pseudofeces)

Disrupts ecosystem;"bad" algae and bacteria growth


Ecological damage to native habitat


Competes with native species for food


Creates a layer of broken shells over sandy beaches

Mussel Infestation Impacts Recreation

Encrust boar Cooling Systems


Reservoir Closures (Ex. San Justo Res.)

Clogs boat engines and components

Beach users impacted by sharp shell fragments

Mussel Infestation Impacts Local Economy

Reduced lake area property values.

Huge loss of tourist dollars for local economy

Destroys water conveyance systems

Increased operation & maintenance costs

Rapidly clogs water pipes decreasing flow

Mussel Prevention

Lake Nacimiento Mussel Prevention Program

Program adapts to best management practices

Over 380 volunteers

Annual Minimum Standards adopted by local agencies

Resident/Private ramp partnership with local agencies create policy improvements

Mussel Prevention Hotline

(805) 788-6006

Mussel Prevention Program Standards

All vessels must be CLEAN, DRAINED and DRY prior to inspection and launch.

Vessels exiting the Monterey County ramps may choose to be banded on exit. Banded vessels will complete a screening form to carry while on the lake and may not be required to undergo a screening or inspection.

All vessel operations must complete a Vessel Screening Permit or be enrolled and complying with the provisions of the Resident Vessel Program.

Vessels that have been on an infested lake within the past 30 days and/or fail to arrive in a CLEAN, DRAINED and DRY condition will be required to undergo a full inspection.

All vessels must pass a screening inspection, Vessel Screening Permit must be stamped by a certified screener, and stamped permit or valid Resident Vessel Certificate and Affidavit must be carried on the vessel.

No vessel will be allowed to launch that have been on an infested lake within the past 10 days or that fail inspection.

Permits are required on all vessels that have or should have Vessel Certificates of Numbers (CF#) and canoes, kayaks and pedal boats that have assigned serial numbers.  Permits can be issued for any vessel that does not meet the above guidelines if requested by the operator.

Monterey County Water Resource Agency

San Luis Obispo County Water

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