Parks officials at lakes in San Luis Obispo and Monterey counties started an aggressive screening program two years ago to prevent invasive mussels from entering and damaging the ecosystem of local waters.
So far, their efforts have paid off.
Monthly inspections of Lopez, Santa Margarita, San Antonio and Nacimiento lakes have yielded no sign of quagga or zebra mussels — small, non-native shellfish that have the ability to clog boats and water pipes, affect fisheries and coat piers.
“The whole idea is not to get it, and once you have it there’s no way to eradicate it,” said Ernie Del Rio, San Luis Obispo County Parks Department superintendent.
Quagga and similar zebra mussels were first found in the 1980s in the Great Lakes waterways, possibly transported there in the ballast of ships.
In January 2007, quagga mussels were discovered at a marina in the Nevada portion of Lake Mead, and further investigation found they may have been in the lake as long as four years.
Mussels were then also identified in two other lakes on the Colorado River: Mohave Lake and Lake Havasu, and the river’s aqueduct system, which serves Southern California, according to the state Department of Fish and Game.
Boats that have been in infected waters — such as on Lake Mead and Lake Havasu — within the past 30 days will be rejected from entering Lopez and Santa Margarita. Boaters are free to come back to the lakes once that 30-day period is up, Del Rio said. From April 2009 through June, nearly 100 boaters were turned away from Lopez and Santa Margarita lakes after their boats were found to have water in their engine, bait tank, or other areas of their vessels, among other reasons.
That’s a small number, though, compared to the more than 21,000 boats that launched at those lakes.
Only 72 boats were rejected from launching at Lopez out of the more than 12,000 boats that visited the lake, according to a report of invasive mussel vessel inspections provided by Del Rio.
At Santa Margarita Lake, 9,380 boats visited during the same time period, and 20 were rejected.
Trained screeners at Nacimiento and San Antonio closely inspect all boats that have been on infected waters in the previous 30 days. They may be able to launch if they pass a thorough inspection, said Casey Nielsen, Monterey County managing parks ranger.
Since Memorial Day weekend, 20 to 30 boats at Nacimiento that have been labeled high-risk have been able to launch after a more thorough inspection process, he said.
About a dozen that have gone through that inspection process were rejected, and were unable to launch that day.
“The most important thing to put out to the public is when you come here, have your boat cleaned, drained and dry,” Nielsen said.
Nielsen said screeners have looked at thousands of boats, but exact numbers were not available.
Boaters launching at the two lakes have to fill out an inspection form stating their vessel is cleaned, drained and dry; has been inspected at a site prior to launch, if available; and has been properly decontaminated if used in the past 30 days on infected waters.
Boat owners have to keep the form on their boats and produce them if asked by any peace officer. Failure to do so can result in a citation.
Nacimiento Lake also offers launch ramps to its private communities. Parks officials don’t have access to the private areas on the lake, so they rely on education to alert boat owners of the need to launch clean, dry boats.
Parks officials in both counties say that boaters are happy to help keep their lakes quagga and zebra mussel-free.“Most are very conscientious,” Del Rio wrote in an e-mail. “They realize what would happen to boating fees, the restrictions that may be placed on recreation, and impacts these mussels could have on water delivery systems should they be transported into local lakes.”