Zebra mussel shells found in November in Roosevelt Lake should not pose a threat in Lake Havasu local officials said Wednesday.

The zebra mussel shells were found in the filter of an air conditioning unit of a 35-foot cabin cruiser boat that had been moored at Roosevelt Lake since 2005, according to a press release. State authorities found no live mussels or any other compelling evidence that invasive mussels found their way into the lake in central Arizona.

“I don’t think the zebra (mussel) is going to be an issue for us,” Lake Havasu City Water Resources Coordinator Doyle Wilson said. “The zebra may not get a chance to get a foothold here because it’s competing with the quagga. Really it’s about a competition on filter feeding and the quagga has a huge step up on it.”

Tom McMahon, invasive species coordinator for the Arizona Game and Fish Department, said the shells found on the boat in Roosevelt have so far not indicated any issues in Arizona.

“We are very confident that these shells did not originate in Arizona, but were most likely transported to Roosevelt Lake within the interior of the boat in 2005 and probably not viable,” he McMahon said in a release. “The Arizona Game and Fish Department, along with the Salt River Project, will continue to survey Roosevelt and other waters in the state for quagga and zebra mussels.”

The quagga mussel, first discovered in January 2007, has disrupted the ecosystem in Lake Havasu, Wilson said. Both the zebra and quagga mussels are “freshwater, bivalve mollusks that typically have a dark and white (zebra-like) pattern on their shells,” according to a release. “Although quagga mussels have been found in the lower Colorado River and in lakes Mead, Mohave, Havasu and Pleasant, no zebra mussels have been discovered in Arizona.”

Wilson said he attends regular meetings concerning the quagga mussel and said several different strategies are being developed to handle the issue but none is immediate. He added an ongoing study in Lake Havasu might produce results in the next six months, which will give clear direction on strategies.

“In our area what’s happened, with some of the research in Lake Mead, there has been a leveling off of the quagga population,” Doyle said, cautioning the news is not as positive as it seems. “With any invasive species, there will come a point when there is overfeeding and the population levels off because of food source. I think that’s what we’re seeing here. The problem is never truly going to go away unless we develop some sort of treatment.”

The dangers of the quagga mussel persist in Lake Havasu, Wilson said.

“Basically the quagga is an extremely efficient bottom filter feeder,” he said. The mussels consume small algae and possible toxins, consuming the nutrients and expelling the toxins. “All those pollutants they expel turn into small pellets and they get eaten by small fish. And it works its way up the food chain into everything else in the lake.”

While the redear sunfish consumes mussels in Lake Havasu, Wilson said it has no affect on stunting the population growth.

“In some areas, you can see as much as 40,000 (quagga mussels) per square meter,” he said. “On top of that, they produce 6 million eggs per cycle and have about six cycles per year. The sunfish aren’t even making a tiny dent. The population is just too large.”

One positive for Lake Havasu City is that there is little fear of quagga mussels clogging water supply systems, Wilson said.

“We’re in a good situation because we have one intake valve to maintain,” he said. “In some cities, there are several and it costs millions to keep them out of there. The fact that we get most of our drinking supplies from a well is actually protecting us from quagga problems.”

Wilson said he does see continued positive change in the future, which could be augmented if House Resolution 3481 passes. The bill not only would bring continued funding to river cities, it includes provisions to address quagga mussel issues, Wilson said.

“I think that’s going to be the best thing for the problem if it happens,” he said. “It’s a stepping stone that might finally allow us to manage and mitigate the quagga mussel situation.”

You can contact the reporter at nbruttell@havasunews.com.