Unionid mussels of Eastern Ontario

this will provide both a list of species known from eastern Ontario (a vaguely defined region, more-or-less bounded by the Petawawa and Moira river drainages), and thoughts on their systematic status, ecology, and conservation status. Right now it's under construction – you'll know a species has been done when its name is a link rather than just text.



Actinonaias ligamentina

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Alasmidonta marginata

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Alasmidonta undulata

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Anodonta implicata

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Anodontoides ferussacianus

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Elliptio

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Elliptio complanata

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Elliptio dilatata

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Elliptio cf crassidens

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Lampsilis

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Lampsilis cariosa

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Lampsilis cf fasciola

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Lampsilis radiata

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Lampsilis radiata cf radiata

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Lampsilis radiata cf siliquoidea

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Lampsilis ventricosa/ovata/cardium

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Lasmigona compressa

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Lasmigona costata

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Leptodea fragilis

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Leptodea ochracea

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Ligumia nasuta

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Ligumia recta

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Obovaria olivaria

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Potamilus alatus

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Pyganodon spp.

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Pyganodon grandis

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Strophitus undulatus

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Utterbackia imbecillis

Study Unionoid mussels!

our subtly beautiful largest invertebrate animals


Ligumia nasuta from Lyn Creek, Lyn, Ontario




Before European settlement, our long-lived native Unionoid Mussels were the dominant filter-feeding organisms in North American rivers and lakes, often covering the bottoms at densities of hundreds per square metre, and with astonishing numbers of species in a single bed. Their filtering kept the water clear, and the digging action of their feet kept the sediments oxygenated. They have long been declining, due to harvesting for shells and pearls, sedimentation, and pollution. Introduced European Zebra Mussels are eliminating entire species and faunas by smothering, displacement, and starvation. It behooves naturalists to get to work before these subtly lovely bivalves, our largest invertebrate animals, are gone from many places where we wouldn't have even known that they occurred. Unionids depend on fish to disperse their larvae, and live for many decades, so adults may persist long after reproduction has ceased. Shells may be found long after the last animals at a site have died.

Because of their constant filtering, Unionids are the heavy-duty in-stream providers of "water quality," and unlike fish, they can't get out of the way and then quickly swim back to recolonize a site. Stream projects should avoid disturbing the sreambed where they're abundant, since the mussels take 10 years or so to mature, and mature individuals can keep providing improved water quality for decades.

There's no better way to spend a summer than wading or canoeing creeks, rivers, and lakes to document hidden nodes of unionoid abundance. It's different from looking for frogs or birds, because there's nothing like a random transect through an area. You have to go to very specific sites, and each stretch of stream or lakeshore may have a different mix of species, depending on substrate, water flow and hardness, phytoplankton, movements of host fish, and bottom disturbance or interruptions of flow over the past few decades.

To become the local unioniod expert, search shores and bottoms of streams, and shores and shallows of lakes, concentrating on clear-water habitats and on riffles, and especially on streams right below dams and lake outlets, where phytoplanktonic food that grows in still water flows by filter-feeders like a perpetual buffet. Some species are wedged into the mucky banks of streams. Muskrats accumulate shell piles beside stumps and rocks on the bank, which you'll find easily once you begin to think like a Muskrat. Otters scatter shells, and Beavers cover big areas of the bottom with shells. Flood waters concentrate shells at the foot of bars, or in eddies. It's important to examine lots of animals and collect lots of shells, because many species are superficially hard to tell apart. But they're no harder than fall Warblers or Damselflies. And since you can collect dead shells without harming the populations, it's possible to gather material documentation of the occurrence of species, and their variation.

We've prepared a datasheet that observers can use to describe the circumstance in which they find shells. Print this datasheet on good (bond) paper in waterproof ink, gather a common plastic grocery bagfull of shells from each site where you notice them, fill out the sheet, and send them to us. We'll identify the shells, catalogue them into the BMNHC collection, and send an account of the sample to you, along with identified shells that will help you learn the species in your river or watershed. you can download the datasheet here













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