Native Olympia Oysters
We have been looking after the Olympia oyster population in the Gorge Waterway of Victoria, BC since 2009 and are one of the only BC NGOs looking into this species. The Gorge population is quite large compared to most on our coast, this is likely due to a combination of factors including large fluctuations in temperature and salinity with the tides and a lack of predation from sea stars and crabs. Due to these tidal fluctuations however, the Gorge oysters don’t grow as large or live as long as Olympias in other areas, but they sure make up for it in numbers!
What are we doing?
You can often find us in the Gorge switching out settling stakes to monitor recruitment patterns, doing surveys, checking on our artificial reefs and more! This information is vital to better predict population fluctuations and what is needed for successful restoration.
We have been testing enhanced settling substrates since 2017, including artificial pacific oyster shell reefs, reef balls, and ECOncrete oyster disks. Our hope is that we will one day help to increase the number of breeding populations in BC by transfering settled substrates to other areas!
In 2019 we started our first reintroduction project by salvaging over 400 Olympia oysters from a construction site and moving them to an oyster cage at Fisherman’s wharf. We have continued to monitor these oysters and will be assessing the surrounding area for new ones.
We are part of a coast-wide collaborative of organizations and agencies working on Olympia oysters.
We have developed both an in-class and a field program on the Olympia oyster and its ecosystem with our sister division, Seaquaria Ocean Education.
This species of oyster is quite small, growing at most to 9cm in length over the course of their 3-10 year lifespan. They can be found from British Columbia to Baja California in the very low intertidal and high subtidal zones of estuaries, lagoons, bays and channels. They are often found attached to other shells, rocks, docks or pilings.
Their breeding season in BC starts as early as May and goes as late as September. Male Olympia oysters release sperm into the current and the female oysters filter the sperm from the water to fertilize their eggs. The fertilized eggs develop into larvae, which are brooded by the female for approximately 10-12 days before being released – which likely reduces their sensitivity to ocean acidification. Roughly two weeks later the free-swimming larvae attach themselves to hard substrates and within 5 months are able to reproduce.
Gorge Waterway Olympia oysters.
Pollution associated with urbanization, pressures from global warming, introduced oysters that compete for space, introduced predators and invasive fouling organisms are some of the major threats to Olympia oysters. One of the largest issues in the Gorge is sediments that wash down from streams, roads, and subdivisions to settle out in the Gorge. This smothers oysters already struggling to stay above the mud and buries the hard surfaces new oysters require to settle on.
Why do we care?
The Olympia oyster is the only native oyster species on British Columbia’s coast. These small oysters were once an important food source for local First Nations people but over harvesting during the Gold Rush and the introduction of invasive species resulted in population crashes up and down the coast, many of which have never recovered. In 2003 the Olympia oyster was added to the Canadian Species at Risk Act as a species of “Special Concern.”
Oysters are important “ecological engineers.” They filter large volumes of water and provide habitat and food for many other animals. As they filter water for food they help clean the water and incorporate carbon dioxide in their shells, contributing to the fight against climate change.
Surveying Craigflower Bridge for adult Olympias.
Checking on our relocated Olympia oysters.
Doing a snorkel survey of our oyster reefs.
Assessing ECOncrete oyster disks for Olympias.