Plants and Animals

Sphaerium fabale River fingernail clam

Key Characteristics

The river fingernail clam has a dull yellow to brown, laterally compressed and rounded shell reaching a length of about .5 inches. The shell is finely striated near the low and somewhat pointed beak, becoming coarsely and unevenly striated toward the ventral margin.

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
Alpena 2 Historical
Clare 1 Historical
Crawford 1 1916
Ingham 2 Historical
Jackson 3 1954
Kalamazoo 2 Historical
Kent 1 Historical
Lake 1 Historical
Lenawee 1 1959
Livingston 3 1959
Marquette 1 Historical
Mason 1 Historical
Menominee 1 1927
Montcalm 1 1927
Newaygo 1 Historical
Oakland 1 Historical
Schoolcraft 1 Historical
Tuscola 1 Historical
Washtenaw 3 1959

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.


This species prefers coarse sand or gravel in both creeks and rivers (Herrington 1962). It has also been found in the Great Lakes (Mackie 2007).

Natural Community Types

  • Great lake, littoral, benthic
  • Great lake, pelagic, benthic
  • Headwater stream (1st-2nd order), riffle
  • Headwater stream (1st-2nd order), pool
  • Headwater stream (1st-2nd order), run
  • 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

Invading zebra mussels can outcompete pea clams for food, and have been linked to drastic declines of this group in the Great Lakes (Lozano et al. 2000, Nalepa et al. 1998). Controlling the spread of zebra mussels by cleaning boat hulls, trailers, and scuba/fishing gear before moving between waterbodies will benefit the river fingernail clam. The pea clam family is especially sensitive to chemical pollutants (Zischke and Arthur 1987), heavy metals and low dissolved oxygen conditions (Kullman et al. 2007). Taking steps to improve water quality should be part of any effort to manage for benthic macroinvertebrates. 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.

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.
  • 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.
  • 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.
  • 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.