Freshwater Mussels can be found all over the Pacific Northwest region. Once mature, they are quite sedentary and do not move very far during their adult lives. But these humble creatures can ascend waterfalls when they are newborns. The young attach to unwitting fish that carry them to new places in a watershed. This lets them traverse waterfalls, across lakes, and up and down rivers. They can live for more than 100 years.
These mussels are quite common on the coast. In the rest of North America, we are losing many species before we know much about them. Normally, freshwater mussels can outlive most animal species on Earth, one species on Vancouver Island can live longer than a century. But their longevity depends on stability in the environment where they live. Mussels are very sensitive to environmental changes and may indicate long-term problems in their ecosystems.
Nearly three-quarters of all 297 native freshwater mussel species in North America are imperiled with 35 of them going extinct in the last century. They are one of the most endangered groups of animals on Earth. Surprisingly little is known about their life history, habitat needs, or even how to distinguish different species, especially in the Pacific Northwest.
Mussels are mollusks that produce a bivalve shell. The two halves of the shell are connected by an elastic-like ligament along the dorsal hinge. The outside of the valves is covered with a material that gives the shell its colour, and the inside is lined with a smooth mother-of-pearl material called nacre.
The raised rounded area along the dorsal margin is called the beak, the shells grow outward from the beak in a concentric pattern. Mussels may possess teeth on the hinge that create a strong and sturdy connection between the valves.
The living mussel occupies the cavity between the two valves. The only body parts that are visible outside the shell are the foot which is used for locomotion and feeding, and the mantle edges are modified into inhalant and exhalant apertures.