New threat to our beaches

Photo: OBWB-OkWaterWise

The discovery of endangered mussels in much of the Okanagan could have a severe impact on future beach quality throughout the region.

Rocky Mountain ridged mussels were found in the Vernon arm of Okanagan Lake, and subsequent surveys have found the native species all the way south to Osoyoos.

The mussels are not the same as invasive zebra and quagga mussels, which have caused concern across North America with their fouling of waterways and infrastructure.

But they could have a severe impact all the same, rendering some beaches virtually unswimmable. Not because they spread invasively, but because the Okanagan Basin Water Board may have to curtail its milfoil control program so as not to harm the mussels.

Winter harvesting of milfoil lake weeds has been halted in several areas while the water board awaits a permit from the province and new regulations to protect the mussels.

Water board spokesperson Corinne Jackson says the organization is working with the province to obtain a permit to continue rototilling the lake weeds.

"We're working with them to find a way forward while not harming the (native) mussels, but keeping beaches clean for swimmers," Jackson says.

Jackson explains the milfoil is "de-rooted" in winter months using the familiar lake rototillers. In the summer, however, the weeds are mowed down rather than pulled out.

Water board operations manager James Littley says the mussels have been found all across Kin Beach in Vernon and extending south along both shores, as well as in the northwest corner of the lake's north arm.

Further south, they have been found in the Casa Loma area of West Kelowna, along most of the Summerland foreshore, in Naramata, and also in Skaha Lake south of Penticton, Vaseaux Lake and in the north end of Osoyoos Lake, by Haynes Point Provincial Park.

What this means for tourism is unclear.

But Littley says anywhere the mussels have been found has been flagged as a red zone, and will not receive milfoil treatment until the province provides regulation.

"We could expect as early as this summer, more weeds, but over a few years, as they re-establish and densify, the milfoil can form thick mats on the surface of the water."

This would make beaches virtually unusable for both swimmers and boaters.

"We're waiting to see what regulation will mean for our program," said Littley.

One option is mowing the weeds in a "depth zone" style where they are trimmed to two metres beneath the surface, but left to grow below that.

Littley says more data is needed on whether the mussels could even survive in a thick carpet of weeds, and it just might be possible that continuing to harvest the milfoil is the best option.

He said recent data shows the mussels, while listed as endangered, are not at risk of extirpation in the Okanagan, so weed harvesting in the most popular beach areas may leave the mussels to flourish in the rest of the lake.