Lilliput Range Expansion Through iNat

Whereas some of our river mussels are charismatic (to a mussel enthusiast) with large sizes, dramatic colours and patterns, and interesting textures, the Lilliput (Toxolasma parvum) may be about as drab and inconspicuous as they come.

It's a small mussel often not much larger than a thumb with a plain brown, cloth-like exterior. While most mussels prefer running water and a mix of sand, cobble, and gravel substrate, the Lilliput is perfectly content in warm muddy backwaters - and even excels there! Because of their unassuming appearance and preference for mucky habitats, they're often missed in conventional mussel surveys.

The difficulty in detecting this species has led to uncertainty about its population status, prompting its assessment as Endangered federally, and Threatened in Ontario. Currently, populations are known in Ontario in the following locations.
In Lake St. Clair Watersheds:
-Canard River
-Ruscom River
-Belle River
-Sydenham River
In Lake Erie Watersheds:
-Grand River
-Thames River (with new occurrences detected in 2022),
-Pelee Island
-Welland River
-Lake Erie proper
In Lake Ontario Watersheds:
-Hamilton Harbour
-Jordan Harbour

That said, in December of last year I was fortunate to find a tiny weathered valve of a Lilliput in Port Franks of the Ausable River. This would represent a significant range expansion into the Canadian side of Lake Huron! Though with only a single weathered valve there are always doubts.. could this be a one-off? is the identification correct? But then in April 2024, @burgbirder discovered two more Lilliput valves from the same location! This provided additional confidence in the first valve and seems to suggest there is indeed a population currently within the Ausable River. Although it's unknown if this population has been introduced (Lilliput are fantastic colonizers) or always present and just undetected, it certainly warrants future investigations into Lake Huron-draining watersheds.

Without iNat, this expansion certainly wouldn't have been possible. So big thanks to @burbirder and of course many thanks to everyone who has contributed to the Canaiad project thus far. Some may remember me reaching out in 2022 for information regarding Lilliput observations; the Canaiad project was happy to provide Fisheries and Oceans Canada (DFO) with Lilliput coordinates for the reassessment of the species currently underway. I look forward to seeing what other discoveries can be made.

In the future, I hope to write more journal posts highlighting interesting finds, and maybe bring some attention to previous ones as well.

Happy musseling,

Posted on May 23, 2024 02:53 AM by sam10turner sam10turner


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