Fawnsfoot (Truncilla donaciformis)

One of the smaller freshwater mussels found in Ontario, the Fawnsfoot grows to an average size of only 35mm, with a maximum shell size of 52mm. The moderately thick shell of the mussel is very distinctive, as numerous dark green rays broken up into chevron-shaped markings cover the entire shell and are easily seen. These markings and its size make the Fawnsfoot very hard to misidentify, as the Deertoe is the only other mussel present in Ontario with the chevron markings, but grows much larger in size.

 Spawning for the Fawnsfoot is similar to that of most freshwater mussel species present in Ontario, and occurs during the spring. Unlike other mussel species that more directly attach glochidia to host fish, the female Fawnsfoot simply releases her young into the water column, after which they must find their own host fish. Potential host species include the Freshwater Drum and Sauger, of which the former has recently been recorded at sites along both the Middle and Lower East Sydenham. Although small, the Fawnsfoot can live for up to 20 years.

 The Fawnsfoot prefers medium to slow flowing waters, usually found in the lower section of larger rivers. It inhabits shallow water, ranging from 1 to 5 metres in depth, and is found on substrate comprised of mud, soft sand, and even gravel. While widespread throughout the United States (23 States), in Canada it is only found within Ontario, where its range is limited to only a few watercourses. In the Sydenham River there is only one identified site with the Fawnsfoot present. The main threats to this species are the invasive Zebra and Quagga mussels, the fragmented distribution of host fish, and impacted water quality due to nutrient loading and chemical contamination.


Photo courtesy of Bob Gress gpnc.org