Utterbackia imbecillis
Paper pondshell

Key Characteristics

Paper pondshell is a medium-sized (to about 4.5 inches), elongate, inflated, and very thin-shelled mussel. Other key features include its general oval shape, wide and flattened beak, and two posterior ridges often descending into a low dorsal wing. The shell varies in color from yellow or tan to light green, with dim green rays sometimes visible. Nacre is iridescent silvery-white.

Status and Rank

  • State Status: SC
  • State Rank: S2S3
  • Global Rank: G5


County NameNumber of OccurrencesYear Last Observed
Grand Traverse11949
Distribution map for Utterbackia imbecillis

Updated 1/31/2017. Information is summarized from MNFI's database of rare species and community occurrences. Data may not reflect true distribution since much of the state has not been thoroughly surveyed.


Paper pondshell is most often observed in lakes, ponds and impoundments with soft mud or sand substrates (Watters et al.)

Natural Community Types


For each species, lists of natural communities were derived from review of the nearly 6,500 element occurrences in the MNFI database, in addition to herbarium label data for some taxa. In most cases, at least one specimen record exists for each listed natural community. For certain taxa, especially poorly collected or extirpated species of prairie and savanna habitats, natural community lists were derived from inferences from collection sites and habitat preferences in immediately adjacent states (particularly Indiana and Illinois). Natural communities are not listed for those species documented only from altered or ruderal habitats in Michigan, especially for taxa that occur in a variety of habitats outside of the state.

Natural communities are not listed in order of frequency of occurrence, but are rather derived from the full set of natural communities, organized by Ecological Group. In many cases, the general habitat descriptions should provide greater clarity and direction to the surveyor. In future versions of the Rare Species Explorer, we hope to incorporate natural community fidelity ranks for each taxon.

Feel free to send questions and comments to Brad Slaughter at slaugh14@msu.edu.


Approximately 70% of North American unionids are imperiled. Threats include alteration of physical habitat, host fish population declines, invasive species introduction and compromised water quality (Bringolf et al. 2007). As with all species of this group, paper pondshell has been found to be highly vulnerable to chemical pollutants (Conners and Black 2004) and heavy metals (Pip 1995) found in many herbicides and pesticides, and in other forms of point and non-point source pollution. Sedimentation of waterways causes harm to a wide variety of freshwater organisms. Management of all native mussels must include maintaining healthy habitat structure and high water quality standards. Zebra mussels must be prevented from spreading to new waterways through the careful cleaning of fishing gear, boats and trailers, and scuba equipment in order to protect paper pondshell populations from infestation.

Active Period

Gravid from first week of July to fourth week of June

Survey Methods

Visual and tactile search using scuba or glass-bottom buckets. Tactile search (by hand) is especially important where water turbidity and pebbles/rocks make visual detection difficult. After identification, live mussels should be planted back into the substrate anterior end down. Surveys should not take place after heavy rains or during periods of high water as these conditions can make detection much more difficult.  Methods of documenting survey effort include: searching a large measured area, e.g. 128m2; taking multiple quadrat samples; and recording search time (person hours).  For all methods, at least some excavation of substrate (by hand, 5-10cm down) should be done to detect buried mussels.  Searching a large measured area or timed searches are generally better for detecting rare species and generating a species list than quadrat sampling.  These two methods allow more types of microhabitats and a larger area to be covered.  Quadrat sampling is better suited for documenting changes in density and other statistical analyses at the site level (Strayer and Smith 2003).

Page Citation

Michigan Natural Features Inventory. 2007. Rare Species Explorer (Web Application). Available online at http://mnfi.anr.msu.edu/explorer [Accessed Mar 30, 2017]


Technical References