In 2023, someone photographed a discarded shell near a boat-towing business in Port Coquitlam and uploaded it to iNaturalist, the online citizen-science forum. That single post set off a three-year scientific search and ended up rewriting the known range of one of Canada’s most endangered freshwater species.
The shell belonged to the Rocky Mountain Ridged Mussel (Gonidea angulata), a large, distinct bivalve known for its thick-walled, trapezoidal shell and a sharp ridge running from its dorsal margin to its posterior edge.
In Canada, it’s assessed as endangered by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC). It’s also recommended for federal listing under the Species at Risk Act. Until now, its known Canadian range was thought to be confined to the south-central Okanagan watershed, with only vague historical records elsewhere in the Kootenays, Vancouver Island, and Cache Creek.
That’s what made the Port Coquitlam shell so strange. The Fraser River watershed, where it turned up, has no present-day aquatic connection to the Okanagan system. So how did it get there?
A photo that sparked two years of research
Because the shell surfaced near a boat-towing business, researchers from the BC Ministry of Water, Land and Resource Stewardship and the BC Conservation Foundation couldn’t rule out a simpler explanation: that it had hitched a ride from the Okanagan on a recreational boat trailer.
But, to prove that the mussel actually belonged in the Fraser watershed the researchers had to find live, animals in their natural habitat.
So began a major field effort. Between 2023 and 2025, the team surveyed 62 sites and logged more than 158 cumulative hours searching the watershed, contending with busy marine traffic, fast-moving and deep water, rising tides, and the seasonal freshet.
They worked the shifting, tidal shoreline using beach walking, wading, and snorkeling surveys. And because the water was frequently clouded by disturbed silt and mud, the researchers had to get creative, constructing a DIY dipping tool by duct-taping a metal mesh deep-fryer basket to a broom handle. This device allowed them to scoop up submerged objects and let the silt wash away, making it easy to confirm the identity of any mussels they retrieved.
The find
The persistence paid off. About 5.4 kilometers upstream from where the original shell was found, the team confirmed a live, subpopulation – 81 specimens in total across the three-year search.
Most were tucked into deep pools that become isolated from the main river channel at low tide, along a stretch of flat mud beach on the west side of the lower Pitt River, near a public trail between Prairie Avenue and Dominion Avenue.
The discovery, now published in the open-access, peer-reviewed Biodiversity Data Journal, marks a significant range extension for the species into the Fraser River watershed – the first confirmed live population outside the Okanagan.
However, the find doesn’t ease the species’ conservation status. Because this subpopulation is hydrologically isolated from both the Okanagan watershed and the nearest known populations in Washington State’s Chehalis River, the overall conservation concern for the species remains extremely high.
Whether the newly found subpopulation is genetically distinct from other populations – a question with real implications for how it’s managed and protected – is still unanswered; that’s the next piece of research the team is pursuing.
Nonetheless, this breakthrough stands as a testament to the value of citizen science. The upload of a single photograph to iNaturalist sparked a big field survey, proving that community-based monitoring and public stewardship can directly help protect B.C.’s most vulnerable freshwater species.
Original source:
Heron J, Jessome R, Yoon-Henderson K, Achal S (2026) Range extension and natural history notes on Rocky Mountain Ridged Mussel Gonidea angulata (Lea, 1838) (Mollusca, Unionidae) in Canada. Biodiversity Data Journal 14: e191607. https://doi.org/10.3897/BDJ.14.e191607
