Native oysters a sentinel of Gorge Waterway health

Abundant population under Craigflower Bridge brings implications for construction timeline

Nicole Barrette shows off the difference in size between the native Olympia oyster and the larger

Few people likely know the Gorge is home to a native species of oyster, but this little creature has played a part in delaying the construction of the new Craigflower Bridge.

“The oysters are probably the key issue,” said Jim Hemstock, Saanich’s special-projects manager in the engineering department.

The law requires that the bridge-replacement project results in no net loss of habitat, he explained. “If we’re disrupting the oysters, then we need to compensate.”

While Olympia oysters are listed as a species of special concern, they are more abundant in the Gorge than anywhere else on Vancouver Island.

The World Fisheries Trust has been monitoring their population every July since 2009.

The counts show the numbers increase as you travel up the Gorge, said Nicole Barrette, summer student in charge of this’ year’s count. Last week, she and other researchers collected the oysters at three index sites and transported them to headquarters in Vic West. The oysters lived in tanks while she counted and measured them before returning them to their beds.

For this first time, the 79-year-old Craigflower Bridge was included in the survey. Investigation revealed that the Olympia oyster population is significantly more dense between the wooden pilings than any other oyster bed along the waterway.

Under the bridge, there are 400 oysters per square metre, compared to 250 oysters per square metre elsewhere.

The findings have big implications for Saanich and View Royal, which are jointly replacing the bridge.

While the environmental mitigation plan has yet to be approved by the federal government, it likely involves transplanting each oyster, Hemstock said. “It’s going to be very expensive.”

World Fisheries Trust has been hired to help design the compensation plan.

“The new pilings will be concrete, which oysters like,” said Trust executive director Joachim Carolsfeld.

To help oyster larvae settle on the pilings, he recommends texturing the concrete with horizontal ridges.

To help predict other factors in the oysters’ survival, he is overseeing related studies in the Gorge. One is looking into the presence of invasive species and their interaction with Olympia oysters. Pending the receipt of a grant, he also plans to look at the movement of oyster larvae.

Keeping watch of the oyster population is important because they provide a good sentinel of water quality and health of the ecosystem, Carolsfeld said. They’re also important in their own right, he said, as they filter water and provide habitat for other sea life.

rholmen@vicnews.com

Get local stories you won't find anywhere else right to your inbox.
Sign up here

Just Posted

Cold water swimming a morning ritual for Willows Beach crew

Group turned heads when they slow-walked into the Polar Plunge

South Vancouver Island B.C. Hydro Customers without power

Due to high winds nearly 3,900 B.C. Hydro customer will be out of power

Sidney signs off on 2020 budget with 1.79 per cent tax increase

Budget also includes additional funding for Shaw Centre for the Salish Sea

Search begins for two missing scouts near Sooke

Crews headed to Jordan River area after receiving call just after 2 p.m.

Scaffolding falls due to strong winds at Millstream Village Sunday afternoon

No injuries or vehicles damaged, according to West Shore RCMP

VIDEO: 2020 BC Winter Games wrap up in Fort St. John as torch passes to Maple Ridge

More than 1,000 athletes competed in the 2020 BC Winter Games

Massive early-morning blaze destroys Vancouver Island home

Firefighters from three departments called in to battle fire at unoccupied residence

Still six cases of COVID-19 in B.C. despite reports of Air Canada passenger: ministry

Health ministry wouldn’t comment on specific flight routes

Violent ends to past Indigenous protests haunt Trudeau government

Trudeau adopted a more assertive tone Friday, insisting the barricade must come down

VIDEO: Wounded Warrior Run leaves Port Hardy on eight-day trek down Vancouver island

The team’s fundraising goal this year is $250,000, which is double last year’s goal.

HIGHLIGHTS: Day one and two at the 2020 BC Winter Games

Athletes had sunny – but cold – weather to work with in Fort St. John

Most Read