AIM

Unionidae

The freshwater mussels or naiades are poorly represented in headwater areas such as Montana. We have only 5 species for certain, of which 1 or 2 are recent additions. Montana is not yet well collected for mussels as many of its rivers are difficult to work in for much of the year. I get only a few good collections per year, often from already known localities. We surely have no populations of commercial value. There have been no studies here of life history or growth, which is probably very slow.

Conservation Issues

The collection of Mussels and their shells in Montana is restricted by the Montana Department of Fish, Wildlife and Parks. Unlike the national condition, none of our species appear threatened either within the state or in general, but Lasmigona complanata (Barns) has a very limited range in Montana as far as is known. The Zebra mussel may be a threat in Montana, but it will have to transported into favorable waters and will not likely get here on its own. Montana waters could probably support additional northern mussels. Attempting to relocated some critically endangered species in Montana does not seem very threatening, especially in and around reservoirs where the fish fauna, temperature and flow have already been much altered.

Simple key to the shells of the Montana species

  1. Hinge without teeth..Pyganodon grandis (Say)
  2. Hinge with teeth
    1. Inside of shell white
      1. Outside of shell dark brown to black, without rays, but with a dorsal wing..Lasmigona complanata (Barns)
      2. Outside of shell light brown to tan, often with greenish rays, but without a dorsal wing..Lampsilis siliquoidea (Barnes)
    2. Inside of shell purple to pink
      1. Ventral edge slightly concave, shell and teeth weak..Margaritifera falcata (Gould)
      2. Ventral edge convex, shell and teeth strong..Ligumia recta (Lamarck)
Updated on 30 DEC 1995 D.L. Gustafson
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dlg@rivers.oscs.montana.edu