A Cause for Shell-ebration

Native oysters rebounding in Boundary Bay

Written by Amelia Hesketh, former Restoration Biologist

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The bustling tube feet of sea stars, the biting chelipeds of crabs, the sporadic squirts of burrowing clams — beside the other creatures of British Columbia’s coastlines, the small and sedentary Olympia oyster can seem rather unexciting. However, these native shellfish are a vital food source for both marine and terrestrial predators, including humans, and — because they filter seawater to extract phytoplankton food — can dramatically improve water quality where they occur.

The Olympia oyster was extremely abundant in Boundary Bay in the early 1900s, when it was farmed on the shores of Crescent Beach and Mud Bay by colonists. However, when farms shifted to producing faster- and larger-growing non-native oysters and naturally occurring oyster beds were overharvested, the abundance of Olympia oysters in the region plummeted. As part of a province-wide survey in 2009, only six Olympia oysters were found in Boundary Bay after nearly four hours of careful searching. Within BC as a whole, Olympia oysters are now officially classified as a species-at-risk.

This summer, A Rocha Canada led efforts to re-survey Boundary Bay’s Olympia oyster populations. Mirroring efforts from 2009, volunteers and staff scoured the shoreline, enduring barnacle battles and overturning boulders for an hour at five different sites. In contrast to 15 years ago, we were delighted to find not six, but 103 Olympia oysters.

We suspect that the increased distribution and abundance of Olympia oysters in the region may be due to ongoing restoration efforts in Drayton Harbour and other parts of Washington State. You may ask, how have these sedentary animals traveled so far? For the first month or so of their life, oysters are planktonic, and remain suspended in seawater, eating and growing large enough to cement their heads to a suitable rock or shell on the seashore. Thus, Olympia oyster larvae produced by adult oysters many kilometres away may be reaching Boundary Bay, repopulating our shores.

In the coming year, we plan to carefully map Olympia oyster in Boundary Bay and estimate their total population size. Eventually, we hope to catalyze Olympia oyster restoration efforts in Canadian waters, both to help improve local water quality, and to allow for traditional shellfish harvest.