Plants and Animals

Pisidium idahoense Giant northern pea clam

Key Characteristics

The giant northern pea clam is characterized by a rounded, thick, and inflated shell nearly as high as it is long (maximum .4 inches), glossy and finely striated. Young individuals are yellowish in color, becoming more brown with age.

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: SNR - Not ranked


CountyNumber of OccurrencesYear Last Observed
Charlevoix 3 Historical
Cheboygan 3 1959
Clare 1 1927
Emmet 1 Historical
Isabella 1 1927
Keweenaw 4 Historical
St. Clair 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.


Primarily a lake species, the giant northern pea clam occurs in mud or sand substrates in water up 130 feet deep (Mackie et al. 1980).

Natural Community Types

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

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

Improved water quality has a direct relationship with increased occurence and diversity of pea clams, as well as many other aquatic species (Diggins and Snyder 2003). Management of the giant northern pea clam should include efforts to reduce point and non-point source pollution, as this group exhibits high rates of chemical (Zischke and Arthur 1987) and heavy metal absorption (Duncan et al. 1987) . Lake areas where the giant northern pea clam occurs should not be treated with herbicides or pesticides containing copper or other heavy metals. Zebra mussels impact pea clam populations through food competition, and have contributed to dramatic declines of this group in the Great Lakes (Lozano et al. 2000, Nalepa et al. 1998). People can avoid transporting zebra mussel adults and larvae to new waterbodies by cleaning boat hulls, trailers and scuba/fishing gear.

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

  • Diggins,T.P., and R.J. Snyder. 2003. Three decades of change in the benthic macroinvertebrate community and water quality in the buffalo river area of concern, 1964-1993. Journal of Great Lakes Research 29(4):652-653.
  • Duncan, W.F.A., M.J.S. Tevesz, and R.L.R. Towns. 1987. Use of fingernail clams (Pisidiidae) and x-ray fluorescence spectrometry for monitoring metal pollution in Contwoyto Lake, N.W.T. Water Pollution Research Journal Canada 22(2):270-79.
  • Herrington, H.B. 1962. A revision of the Sphaeriidae (Mollusca: Pelecypoda) of the North American Great Lakes. American Midland Naturalist 67(1):194-198.
  • 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.
  • Montana Natural Heritage Program. 2011. Giant Northern Peaclam, Pisidium idahoense. Montana Field Guide. Retrieved on May 10, 2011, from
  • 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.