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

Just Posted

Join Groove Kitchen for a funky free concert at Brydon Park in Saanich

The July 23 concert is one of eight hosted by Saanich Parks and Recreation this summer

City of Victoria to hold formal safety review after man was left hanging from raised bridge

More and more people seen ignoring safety measurements in place, city staff say

Saanich council will consider tax reduction scenarios for 2020 budget

Coun. Rebecca Mersereau however warns of cutting additional funding for capital expenditures

Oak Bay instructors teach free outdoor yoga classes at Willow Beach Park

Practise yoga for free Tuesdays at 6 p.m. all summer

Jurors talk about trial of U.S. man convicted in 1987 murders of Saanich couple

Three jurors offer a window into deliberations during the trial

VIDEO: Missing teens named as suspects in three northern B.C. killings

Kam McLeod and Bryer Schmegelsky are wanted in the deaths of Lucas Fowler, Chynna Deese, unknown man

POLL: Do you use a food delivery app?

With modern life becoming more hectic with each passing day and so… Continue reading

Vancouver Island teacher suspended for professional misconduct

Grade 8 shop teacher admits to use of vulgar language and profanities toward students, parents

Northern B.C. double homicide, suspicious death: A timeline of what we know

Two teens from Port Alberni are now wanted Canada-wide in connection to the three deaths

B.C. wine industry legend Harry McWatters dies

Among his accomplishments, McWatters founded the province’s first estate winery, Sumac Ridge Estate

Provincial health body refuses to release full findings of cancer triage system audit

Information and Privacy Commissioner asked to review redactions

Southern resident killer whale died of blunt trauma, likely from ship

J34 was found more than two years ago near Sechelt, but the necropsy findings have now been released

B.C. rail crossing death highlights risks for people in wheelchairs: watchdog

Transportation Safety Board points to ‘persistent risks faced by persons using assistive devices’

B.C. teens wanted in double homicide, suspicious death spotted in Manitoba

Kam McLeod and Bryer Schmegelsky were thought to have been seen in the Gillam area

Most Read