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Conservancy logoBowen Island Conservancy
    • About
    • Get Involved
  • Discovering Kwilákm
    • About
    • Get Involved
  • Changing Climate
    • Hotter Ocean Temperatures
    • Changing Ocean Chemistry
    • Rising Sea Levels and Intensifying Winter Storms
    • When Seashore Temperatures Spike – Killer Heat Dome 2021
  • Terminal Creek
    • Where does Terminal Creek’s Water Come From?
    • Signal Crayfish
    • Terminal Creek Fish Hatchery
  • The Lagoon
    • The Tidal Inlet that became the Lagoon
    • Aquatic Plants
    • Chum Salmon
    • The Beaver
    • Canada Geese
    • Three-Spined Stickleback
  • Shores
    • Nearshore Forests
    • Beaches
    • The Terminal Creek Sand Flats
    • The Curious Clay Beds of Kwilákm
    • Blue Mussels
    • Clams
    • Purple Stars
    • Oysters in Kwilákm
  • Shallows
    • Eelgrass
    • Young Chum Salmon
    • Winter Bay Birds
    • Year-Round Bay Birds
  • Deeper Waters
    • Plankton
    • Northern Anchovy
    • Harbour Seal
    • Octopus

Photo: Len Gilday

Shores

Does Kwilákm Have Two Species of Oyster

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Discover Kwilakm » Story » Shores » Does Kwilákm Have Two Species of Oyster?

Pacific Oyster

(Magallana gigas)

Oysters on the seabed at low tide.
Photo: Will Husby

The Pacific oyster is Kwilákm’s common oyster and a relative newcomer to our shores. Pacifics were introduced into aquaculture operation beginning in 1925 following the collapse of the Olympia oyster fishery.

Pacific oysters, originating from Asian waters and relatively tolerant of warmer waters, are expected to adapt to our warming climate. However, as seawater absorbs carbon from the atmosphere and oceans become more acidic, crabs, seastars, sea urchins and oysters are finding it difficult to build their calcium carbonate shells.

The Olympia oyster

(Ostrea lurida)

Olympia Oyster
Olympia Oysters rarely grow larger than 6 cm. in size. Photo: Puget Sound Restoration Fund

Olympias, known to its fans as “Olys”, are BC’s only native oyster. They are small, only four to six cm across, fitting neatly in the hand. They are rounder and more delicate looking overall than Pacific oysters. A typical Olympia oyster is not even a quarter the size of its bigger, non-native cousins.

Olympia oysters are not easy to discover. They generally live lower in the intertidal than Pacific Oysters, making them less visible to the casual observer.

By the 1930s, BC’s Olympic oysters were nearly wiped out through a combination of over-harvesting, shore side development (that disturbed soils, releasing fine sediments which smothered oyster beds) and poisons such as vessel anti-fouling paint and the tons of toxic chemicals dumped by paper mills directly into nearshore waters. In 2003, BC’s native Olympia oyster was added to the Canadian Species at Risk Act as a species of “Special Concern”.

Are any Olympias remaining in Kwilákm?

The Olympia Oyster Field Guide, a knowledgeable guide available from the Puget Sound Restoration Society (PSRS), offers this advice about searching for Olympia oysters: “Olys are wonderfully cryptic critters. They are not showy oysters; they do not jump out at us as we amble along the beach or even muck and poke about. In fact, they bear very little resemblance to the archetypal oyster that we have in our mind’s eye as our ‘oyster search image.’One has to be searching for Olympia oysters to find them.”

Researchers assume that small populations of Olympia oysters are currently stable at low levels in the Salish Sea. Do Olys still hang on in the Bay? Good question: much remains to learn about our oysters. Please be careful when wandering our beaches. Return rocks to where you found them to protect the homes of small creatures. Collecting or harvesting Kwilákm oysters is not allowed.

More About Shores

  • Shores
  • Nearshore Forests
  • Beaches
  • The Terminal Creek Sand Flats
  • The Curious Clay Beds of Kwilákm
  • Deep Bay Brickyards
  • Blue Mussels
  • Clams
  • Purple Stars
  • Oysters in Kwilákm
  • Does Kwilákm Have Two Species of Oyster?
  • Oyster are Pretty Awesome Creatures
  • Oysters and People
  • Oyster Harvesting: Health and Safety


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