Plants and Animals

Pisidium amnicum Greater European pea clam

Key Characteristics

With a maximum length of about .4 inches, the greater European pea clam is the largest Pisidium, characterized by its general oval shape and thick, heavily striated shell of a yellow to brown color, compressed near the front end and elsewhere inflated. The beak is low, broad and posteriorly placed.

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: SNA - Not applicable (element is not a suitable target for conservation)


CountyNumber of OccurrencesYear Last Observed
Bay 2 Historical
Wayne 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.


The greater European pea clam most commonly occurs in slow moving rivers and lakes with soft substrates of sand or mud (Kipp and Benson 2011)

Natural Community Types

  • Great lake, littoral, benthic
  • Great lake, pelagic, benthic
  • Inland lake, littoral, benthic
  • Inland lake, pelagic, 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

Rising populations of zebra mussels, which outcompete pea clams for important food items, have been related to drastic declines of this group in the great lakes region (Lozano et al. 2000, Nalepa et al. 1998). Limiting the spread of zebra mussels by cleaning boat hulls, trailers, and scuba/fishing gear before moving between water bodies, will benefit the greater European pea clam. As members of the pea clam family may be especially vulnerable to chemical pollutants (Zischke and Arthur 1987), heavy metals, and low dissolved oxygen conditions (Kullman et al. 2007), maintaining high water quality is important. Monitoring and mitigation for resident aquatic organisms should be put in place before major alterations to habitat such as river impoundment, dredging, or construction are undertaken. Sudden population declines of the greater European pea clam have been documented following periods of high water temperature, indicating that global climate change may negatively affect this species (Mouthon and Daufresne 2008).

Survey Methods

Peaclams are best surveyed for by collecting with a grab sampler, such as an Ekman or Peterson grab, or dip net. Collected samples are washed through sieves with a fine mesh (.40 mm openings) in order to retain the smallest individuals. Light-duty forceps can be used to hand-pick peaclams from debris (Mackie 2007).

D-frame net, dip net

Survey Period: From first week of April to first week of October

Time of Day: Daytime


Survey References

  • Mackie, G.L. 2007. Biology of Freshwater Corbiculid and Sphaeriid Clams of North America. Ohio Biological Survey Bulletin New Series. Volume XV, Number 3. ix + 436 pp.

Technical References

  • Dillon, R.T. Jr. 2000. The Ecology of Freshwater Molluscs. Cambridge University Press, Cambridge, UK. 509pp.
  • Herrington, H.B. 1962. A revision of the Sphaeriidae (Mollusca: Pelecypoda) of the North American Great Lakes. American Midland Naturalist 67(1):194-198.
  • Kipp, R.M. and A. Benson. 2011. Pisidium amnicum. USGS Nonindigenous Aquatic Species Database, Gainesville, FL.
  • Kullman, M.A., C.L. Podemski, and K.A. Kidd. 2007. A sediment bioassay to assess the effects of aquaculture waste on growth, reproduction, and survival of Sphaerium simile (Say) (Bivalvia: Sphaeriidae). Auquaculture 266:144-152.
  • Lozano, S.J., J.V. Scharold, and T.F. Nalepa. 2001. Recent declines in benthic macroinvertebrate densities in Lake Ontario. Canadian Journal of Fisheries and Aquatic Sciences 58(3):518-29.
  • Mackie, G.L. 2007. Biology of Freshwater Corbiculid and Sphaeriid Clams of North America. Ohio Biological Survey Bulletin New Series. Volume XV, Number 3. ix + 436 pp.
  • Mackie, G.L., D.S. White, and T.W. Zbeda. 1980. A Guide to Freshwater Mollusks of the Laurentian Great Lakes with Special Emphasis on the Genus Pisidium. EPA Report 600/3-80-068. Environmental Research Laboratory, Office of Research and Development, U.S. Environmental Protection Agency, Duluth. 144 pp.
  • Mouthon, J., and M. Daufresne. 2008. Population dynamics and life cycle of Pisidium amnicum (Muller) (Bivalvia: Sphaeriidae) and Valvata piscinalis (Muller) (Gastropoda: Prosobranchia) in the Saone river, a nine-year study. International Journal of Limnology 44(4):241-251.
  • Nalepa, T.F., D.J. Hartson, D.L. Fanslow, G.A. Lang, S.J. Lozano. 1998. Declines in benthic macroinvertebrate populations in southern Lake Michigan, 1980-1993. Canadian Journal of Fisheries and Aquatic Sciences 55:2402-13.
  • Zischke, J.A., and J.W. Arthur. 1987. Effects of elevated ammonia levels on the fingernail clam, Musculium transversum, in outdoor experimental streams. Archives of Environmental Contamination and Toxicology 16:225-31.