An invasive species of mussel has found its way into Lake Piru, making the lake the first in Ventura County to play host to the fast-multiplying mollusk.

After inspecting a patrol boat returning from time on the lake, several adult mussels were found in a cluster. After identification, they were confirmed to be quagga (or zebra) mussels. Further testing found that the mussel had made its way to other areas of the lake.

That was last December; now, in Piru Creek, which receives water from the lake, the mussel has turned up as well.

“We have a consultant working for us who is determining the degree of the infestation,” said administrative service administrator for the United Water Conservation District Mary Kanatzer. “We hope to have results by this week to determine what we’re dealing with in the lake.”

The mussels live in fresh water and breed quickly, clogging vents and damaging boating and other equipment. The biggest ecological problem with the mussel is its ability to filter water. Mussels feed on a diet of plankton captured by processing the lake’s water through their valves and in turn leave the water clear, making it possible for more efficient sunlight penetration, creating the perfect environment for algae to bloom. The algae can disrupt the ecosystem and push out other species.

How the mussel arrived in the creek, however, remains a mystery. While the creek gets water from Lake Piru through the Santa Felicia Dam, it had previously been thought that the water traveled too fast through the piping for mussels to survive. For a short period of time in 2013, though, a bypass valve was used instead of the fast-moving release pipe.
It is also unlikely that the mussel arrived aboard recreational vehicles. Due to the drought, rafting hasn’t been allowed on Piru Creek since 2012.

The mussels reproduce by releasing larvae called veligers, which can float downstream and around lakes for several weeks before attaching to a boulder, wood or other water-dwelling object. Ridding lakes and streams of the mussels across the U.S. has proven near to impossible.

To further stress the matter, if the problem persists, farmers who rely on water from Piru Creek or the Santa Clara River could feel the squeeze if the United Water Conservation District decides to limit releases from the lake. Casitas Municipal Water District has asked the state to put a halt to releases from Lake Piru, hoping that the mussels can be removed sooner rather than later.

But Piru Creek receives water from Lake Piru through daily releases, as is required by the Endangered Species Act to protect the endangered steelhead trout, native to the waters.

“At this point we believe the only way we are allowed to stop our releases is if someone found that it wouldn’t be a detriment to the California steelhead,” said Kanatzer.

Jim Hines, conservation chair at the Los Padres chapter of the Sierra Club, said that he believes the damage has already been done and that the water district should stick to the requirements set by the Environmental Protection Act to protect the steelhead trout — meaning to continue to release the water into the creek.

“What bothers me and the Sierra Club is that United may try to use this to try to get out of the regulations of the federal endangered species act and not release the water,” said Hines. “The mussels don’t belong in the West — they’re here, among other places — but our concern is, No. 1 the protection of the steelhead trout and we can’t let this be used as an excuse to dry up the river.”

An ongoing investigation into how the mussel arrived in the lake may shed light on the situation, but United is not jumping to any conclusions, Kanatzer said.

“We really need to understand the situation,” said Kanatzer. “To take action and not fully understand what you’re doing, you sometimes take the wrong action.”