Plants and Animals

Elliptio complanata Eastern elliptio

species photo
Peter Badra
species photo
Peter Badra
species photo
Kurt Stepnitz

Key Characteristics

The Eastern elliptio has a posterior ridge running from the beak to the posterior-ventral corner of the shell. This ridge is sometimes pronounced but can be more rounded and subtle in some individuals. The shell has no remarkable texture or bumps. Maximum length is 13.0 cm with a life span around 20 years. Eastern elliptio has a wedged shaped outline at the posterior end with the posterior point of the shell far to the ventral side, and an elliptical outline at the anterior end. This mussel is relatively compressed. Beak sculpture is two to six concentric ‘U’ shaped or angled ridges. The beak is not inflated, and the beak cavity is shallow. Color ranges from dark brown to yellow green. Rays are not usually present. The cardinal teeth are triangular, and the lateral teeth are long and thin. Nacre color can be purple, rose, or salmon.

Status and Rank

US Status: No Status/Not Listed
State Status: SC - Special Concern (rare or uncertain; not legally protected)
Global Rank: G5 - Secure
State Rank: S2 - Imperiled

Occurrences

CountyNumber of OccurrencesYear Last Observed
Alger 2 1979
Benzie 1 Historical
Chippewa 5 2007
Delta 1 Historical
Keweenaw 3 2010
Luce 1 Historical
Mackinac 1 1941
Manistee 1 Historical
Marquette 3 2010
Menominee 1 1969
Presque Isle 2 2018
Saginaw 1 2008
Schoolcraft 1 Historical

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.

Habitat

The Eastern elliptio is found in small- to large-sized rivers, lakes, and ponds, in a wide range of substrates (mud, sand, pebble, gravel, and cobble).

Natural Community Types

  • Inland lake, littoral, benthic
  • Mainstem stream (3rd-4th order), pool
  • Mainstem stream (3rd-4th order), run
  • Mainstem stream (3rd-4th order), riffle
  • River (5th-6th order), pool
  • River (5th-6th order), run
  • River (5th-6th order), riffle

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.

Management Recommendations

The Eastern elliptio is at risk from point source pollution, non-point source pollution, alteration of natural stream flow patterns, barriers to host fish passage, direct alteration of habitat, and invasive zebra mussels.

Limit or eliminate point source discharges of ammonia, chloride, sulfate, heavy metals, and other substances toxic to native mussels. Avoid use of aquatic herbicides containing copper whenever possible. Maintain riparian buffers along streams and promote land conservation programs to help reduce excessive erosion, sedimentation, and nutrient input from non-point sources. Maintain integrity of headwater streams and wetlands, which support the ecological function of downstream river habitats. Improve passage for fish by removing unnecessary dams and upgrading poor stream/road crossings such as culverts that are too small or are perched. Eastern elliptio and other native mussels require fish hosts to complete their life cycle and rely on fish passage to travel to new habitats and facilitate gene flow among mussel populations. Avoid dredging, channelization, and other in-stream impacts whenever possible.

The spread of zebra mussels into Michigan’s streams and lakes remains a serious threat. Since the range of Eastern elliptio is restricted to the northern part of the state were zebra mussels are not yet well established, there is an opportunity to minimize the spread of zebra mussels into the Eastern elliptio’s range. Avoid the transport of water or aquatic plants – which can contain zebra mussel larvae – from one body of water to another while boating, fishing, and hunting. Wash boats, trailers, and gear, and let them dry over night to reduce the potential for spreading zebra mussels.

Active Period

Spawning from third week of April to second week of June

Survey Methods

In water shallower than waist deep, wading with a glass bottom bucket or, if water quality is good, swimming with a snorkel and mask is an effective way to search for Eastern elliptio. SCUBA or other dive gear is required for greater water depths. River and lake substrate should be searched both visually and tactilely, by sweeping the fingers through the substrate. Though Eastern elliptio are typically found at least partly exposed to the water column, they can be completely buried at times and difficult to detect visually. Empty shells may be found along riverbanks and occasionally in shell middens created by predators such as muskrats. A scientific collector’s permit is required to possess live native mussels shell or live individuals. Mussel surveys related to permitted projects in rivers and lakes should follow the Michigan Freshwater Mussel Survey Protocols and Relocation Procedures. Federal and/or state threatened and endangered species permits must be obtained prior to surveying for native mussels within waterbodies likely to support these species. Refer to the Mussel Map Viewer available on MNFI’s website.

Glass-bottom bucket less than waist deep water

Survey Period: From first week of June to second week of October

SCUBA greater than waist deep water

Survey Period: From first week of June to second week of October

Survey Method Comment: Surface supplied diving may be appropriate in some cases.

Snorkeling searches

Survey Period: From first week of June to second week of October

Survey Method Comment: Use this method only when water quality and conditions are safe for swimming.

References

Survey References

  • Hanshue, S., J. Rathbun, P. Badra, J. Bettaso, B. Hosler, J. Pruden, and J. Grabarkiewicz. 2019. Michigan Freshwater Mussel Survey Protocols and Relocation Procedures [for rivers], Version 2. Michigan Department of Natural Resources.
  • Metcalfe-Smith, J., A. MacKenzie, I. Carmichael, and D. McGoldrick. 2005. Photo Field Guide to the Freshwater Mussels of Ontario. St. Thomas Field Naturalist Club Inc, 60 pp.
  • Mulcrone, R.S., and J.E. Rathbun. 2018. Field Guide to the Freshwater Mussels of Michigan.  Michigan Department of Natural Resources, 59 pp.
  • Watters, G.T., M.A. Hoggarth, and D.H. Stansbery. 2009. The Freshwater Mussels of Ohio. The Ohio State University Press, Columbus, 421 pp.

Technical References

  • Blevins, E., L. McMullen, S. Jepsen, M. Blackburn., A. Code, and S.H. Black. 2017. Conserving the Gems of Our Waters: Best Management Practices for Protecting Native Western Freshwater Mussels During Aquatic and Riparian Restoration, Construction, and Land Management Projects and Activities. 108 pp. Portland, OR: The Xerces Society for Invertebrate Conservation.
  • Brim-Box, J., and J. Mossa. 1999. Sediment, land use, and freshwater mussels: Prospects and problems. Journal of the North American Benthological Society 18: 99-117.
  • Colvin, S.A.R., S.M.P. Sullivan, P.D. Shirey, R.W. Colvin, K.O. Winemiller, R.M. Hughes, K.D. Fausch, D.M. Infante, J.D. Olden, K.R. Bestgen, R.J. Danehy, and L. Eby. 2019. Headwater streams and wetlands are critical for sustaining fish, fisheries, and ecosystem services. American Fisheries Society Special Report. Fisheries 44: 73-91.
  • Freshwater Mollusk Conservation Society. 2016. A national strategy for the conservation of native freshwater mollusks. Freshwater Mollusk Biology and Conservation 19: 1-21.
  • Haag, W.R. 2012. North American Freshwater Mussels: Natural History, Ecology, and Conservation. Cambridge University Press, New York, 505 pp.
  • Strayer, D.L. and D.R. Smith. 2003. A Guide to Sampling Freshwater Mussel Populations. American Fisheries Society Monograph 8, Bethesda. 103pp.
  • Watters, G.T. 1996. Small dams as barriers to freshwater mussels (Bivalvia, Unionoida) and their hosts. Biological Conservation 75: 79-85.