Imagine snorkeling in a crystal-clear, mid-size river running through a deep and narrow valley whose slopes are covered by a lush, mature forest that has never been logged! This old-growth forest has been in climax for centuries, with massive cedar, maple and birch trees creating a precious shady riparian zone for all cold-water aquatic animals. As an aquatic biologist and a malacologist (a specialist in mussel biology), I have had the privilege of exploring such an extraordinary area: the Kinonge River, also named the Salmon River historically. This river is located on the Kenauk Institute property, a vast, private wilderness area owned in partnership with the Nature Conservancy of Canada and located on the north shore of the Ottawa River, less than 100 km east of Gatineau, Quebec.  

A river with thick forest on both banks.
The Kinonge River, September 2018. Note the old-growth forest bordering the river. Many white cedars seen in this picture are over 50 cm in diameter. Image: A.L. Martel © Canadian Museum of Nature

I arrived at Kenauk on a sunny morning in early September 2018 to search for mussels that might live in the Kinonge River, for which there was no record of freshwater mussels. I had previously explored numerous tributaries of the Ottawa River but not the Kinonge. A fellow malacology team member explored the river’s edge in his chest waders, observing through an aquascope, while I went snorkeling with full wetsuit, mask, snorkel and fins. To my utter surprise, in less than 10 minutes, I found Eastern pearlshell mussels (Margaritifera margaritifera) partly buried among the sandy-gravely substrate on the bottom of the river, filter-feeding. A population of this species so far inland within the Ottawa River valley was quite unbelievable. 

A freshwater clam on the river bottom.
Macrophotograph of a cluster of Eastern pearlshell mussels filter-feeding the water of the Kinonge River. Note the wide incurrent aperture where water is drawn-in during filter-feeding. The elongated narrower excurrent aperture can also be seen. Image: A.L. Martel © Canadian Museum of Nature 
A person snorkeling in a clear river with numerous black objects on the bottom.
André conducting a survey of the Eastern pearlshell mussel in the Kinonge River. Notice the clarity of the water. Image: Noel Alfonso © Canadian Museum of Nature 

That morning I had just discovered Canada’s western-most population of this unique species. Although they occur in some tributaries of the fluvial portion of the St. Lawrence River, they are typically found in rivers draining into the St. Lawrence estuary and coastal rivers of the Atlantic provinces of Canada (also coastal rivers of New England in the northeast USA). This species is typically associated with the presence of its primary host fish, the Atlantic Salmon. During reproduction, the female pearlshell mussel releases tiny larvae (called glochidia) which must attach themselves to the gills of a young salmonid fish to complete their larval development. After many months, they drop off and start their bottom life as tiny juvenile mussels. But in the Kinonge River, there are no Atlantic Salmon (at least not anymore) and the only salmonid fish present is the Brook Trout, a fish that is also known to be a host of this mussel in the absence of Atlantic Salmon. 

Two pictures of a river. On the right, a man stands on a log crossing the waters.
The West Kinonge River, the main tributary of the Kinonge River. It is here where a healthy population of Eastern pearlshell mussels is found, along with a population of wild Brook Trout. Note the narrow river channel, as well as a shaded, healthy riparian zone. Image: A.L. Martel © Canadian Museum of Nature 

At Kenauk, the pearlshell mussels are most abundant in the West Kinonge River, the main tributary of the Kinonge where a population of wild Brook Trout occurs. Here, water temperatures during the summer are significantly cooler than that of the main Kinonge, being narrower and even more shaded. This helps make the area an ideal refugium for the cold-water Brook Trout, who are vulnerable to climate warming in the southern portion of its North American range. With no dams or other obstructions connecting the Kinonge to the Ottawa River, the fish community is rich and easily observed while snorkeling: fallfish, minnows, darters, perch, bass, sunfish, to name just a few. This abundance of fish was recorded by sampling, as well as by video taken just below a waterfall upstream along the Kinonge River.  

Eastern pearlshell mussels filter-feeding in fast current. A.L. Martel © Canadian Museum of Nature
Fallfish (Semotilus corporalis) and Creek Chub (Semotilus atromaculatus) swimming below a waterfall. A.L. Martel © Canadian Museum of Nature

The discovery of an Eastern pearlshell mussel population at Kenauk led to an interesting multi-disciplinary research project involving the Canadian Museum of Nature, Carleton University, Technical University of Munich, Ministère des Forêts, de la Faune et des Parcs du Québec, as well as biologists at the Kenauk Institute. Our teams have been studying the ecology, genetics and recruitment of the pearlshell mussels in the Kinonge River system. It turns out that these mussels have a unique genome compared with populations found along the Atlantic coast, suggesting a higher genetic differentiation. This jewel of a preserve holds a rich forest ecosystem, a pristine river and a highly distinctive population of pearlshell mussels that will continue to be protected and conserved.