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

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


County NameNumber of OccurrencesYear Last Observed
St. Clair1
Distribution map for Pisidium idahoense

Updated 5/15/2018. 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


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.


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).

Page Citation

Michigan Natural Features Inventory. 2007. Rare Species Explorer (Web Application). Available online at http://mnfi.anr.msu.edu/explorer [Accessed Aug 17, 2018]


Survey References

Technical References

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