The no-swimming rule keeps people out of Lake Cachuma, but it also applies to certain freshwater pests.

Since 2017, staff at Lake Cachuma have worked to prevent the spread of a foreign species of mussels that could harm Santa Barbara County’s water supply and damage the fragile ecosystem of the lake.

The fear over the mussels entering the lake goes back to 2013, when it was discovered that the invasive species had been introduced to Lake Piru in Ventura Count.

The local prevention program is funded by the California State Parks Division of Boating and Waterways, with another two years of grant funding approved in August.

According to Parker Medel, a park naturalist at Lake Cachuma, quagga mussels and zebra mussels — species native to Eastern Europe — pose multiple risks to the ecosystem.

One of these reasons is the mussel’s ability to attach itself to almost any kind of surface using a special body part, known as a byssal thread. The mussels use these threads to attach themselves to hard surfaces and can be incredibly hard to remove.

“Think of it as really intense super glue,” Medel said. “And so, this connection to whatever substrate they attach to makes them really, really difficult to move. So, once they settle somewhere, they’re virtually impossible to remove.”

This ability sets quagga and zebra mussels apart from other freshwater mussels, which do not have this ability. This means that the invasive species can attach themselves to areas where other mussels cannot go.

The quagga and zebra mussels can also affect the ecosystem through their feeding habits. They are what is known as extreme filter feeders and suck the plankton out of the water.

“They filter phytoplankton and zooplankton from the water, which is an essential food source for other native fish species or mussel species,” Medel said. “And that creates kind of a crash in the food web.”

Medel added that a side effect of the invasive mussels is clear water due to the lack of plankton, but it can also lead to unwanted vegetation growth.

The last concern is how fast the shellfish can breed and spread. Medel said the zebra and quagga mussels can spawn multiple times a year and can produce millions of offspring in that time.

Their ability to spread so fast allows them to outcompete local species of mussels. Along with their ability to eat so much of the local food supply, the invasive species can quickly overwhelm the local ecosystem.

The Santa Barbara County Board of Supervisors recently approved the state grant of $368,788, which will fund two years of the prevention program including two staff positions, training, decontamination equipment, and public outreach.

One of the ways staff keep the mussels out of Lake Cachuma is through a strict inspection process for boats.

Before boats can be used at the lake, they must undergo an inspection and may have to undergo a waiting period depending on the size of the boat. The waiting period is meant to prevent the spread of the invasive species from other bodies of water.

“I really want people to know that, because these species are microscopic in their first stage of life … there could be hundreds in a single drop of water that we visually can’t see,” Medel said. “So, that 30-day quarantine gives us a barrier in the ability to make sure that these mussels will dry out or die off.”

Protecting the Water Supply

One of the concerns for local water districts is what happens if the mussels enter the pipe system that supplies water to residents, farmers and businesses across the region.

According to Dave Matson, the general manager for the Goleta Water District, if the mussels were to enter the water system, it would affect more than 250,000 people who live on the South Coast.

“Invasive mussels are extremely destructive from a water treatment perspective,” Matson said. “And (they) can clog the intake gates used to deliver water to treatment plants, as well as the pipes, screens, filters and vast pumping equipment used to move water, resulting in expensive repairs and more advanced treatment regimens.”

He added that the cost to remove the pipes could be in the millions, and the cost would likely be felt by the public.

“That’s why proactive monitoring programs to keep them out of the lake remain critical,” he said.

Cachuma Boat Inspection Program

Staff inspect boats for signs of mussels and standing water. Smaller boats, also known as simple boats, can launch on the same day as an inspection. Larger boats must wait a minimum of 30 days before they can launch from the lake.

The two species can look very similar, but quagga mussels can grow up to 2 inches and are lighter than zebra mussels. Their size can range from microscopic to 2 inches at their adult size, but most tend to be the size of a fingernail.

Zebra mussels tend to be smaller and more triangular compared to the rounded quagga mussels. They also have a distinct stripe pattern on their shells. 

Simple boats must arrive at the lake clean, drained and dry. These boats also must be inspected, undergo a heated power wash, and vessels with motors must conduct a heated engine flush.

The larger boats, or pleasure boats, go through a more intensive inspection since many have compartments and are more likely to have standing water containing mussels.

After the pleasure boats are tagged by lake staff, they must remain dry for at least 30 days. After the boat is used at Lake Cachuma, it gets a new tag that says it can return to the lake without an inspection.

However, if the owner decides to use the boat at a different body of water, the process must start over again.  

Overall, Medel says prevention is the best way to protect the lake, and it is hard to respond to the mussels if they do enter the water system. She encouraged the public to be aware of the regulations for Cachuma and other lakes before going out on any boats.

“Education is super important. So, if you’re going on that weekend trip to a lake, (know) the rules and regulations of the bodies of water you’re going into,” she said.