Eastern Pondmussel

Ligumia nasuta (Say, 1817)

Fred Schueler

Bivalvia (Bivalves)
Unionidae (Unionid Mussels)
State Protection
Not Listed
Not listed or protected by New York State.
Federal Protection
Not Listed
State Conservation Status Rank
Imperiled in New York - Very vulnerable to disappearing from New York due to rarity or other factors; typically 6 to 20 populations or locations in New York, very few individuals, very restricted range, few remaining acres (or miles of stream), and/or steep declines.
Global Conservation Status Rank
Apparently Secure globally - Uncommon in the world but not rare; usually widespread, but may be rare in some parts of its range; possibly some cause for long-term concern due to declines or other factors.


Did you know?

Because of its relatively thin shell, this species has suffered greatly from the zebra mussel (Dreissena polymorpha) invasion (Strayer and Jirka 1997).

State Ranking Justification

This species has been heavily impacted by the zebra mussel invasion in the Hudson River estuary, St. Lawrence River basin, lower Great Lakes and elsewhere throughout the state (Strayer and Jirka 1997). There is some evidence from recent survey effort that it may be rebounding in the St. Lawrence and Great Lakes drainages.

Short-term Trends

Although not widespread in the state, L. nasuta can still be encountered regularly, and is sometimes abundant (Strayer and Jirka 1997). Average densities in the tidal Hudson River prior to the zebra mussel invasion were 0.08/sq. meter (Strayer et al. 1994), but densities were not reported post invasion. Only 3 individuals of this species were found in a late 1980's survey of 52 sites in many watersheds in the Lake Erie and Ontario basins (Strayer et al. 1991).

Long-term Trends

This species was once a major component of the lower Great lakes drainage basin, but is now virtually absent owing to the zebra mussel invasion. Ligumia nasuta comprised about 5% of the pre-1960 Unionid records in the lower Great Lakes in Ontario, but dropped to 2.5% of the records post-1960. Between 1930 to 1982 this species was the second most common Unionid in western Lake Erie (Nalepa et al. 1991), but by 1991 it had disappeared (Schloesser and Nalepa 1994). Live animals have been recently documented in 2018 from the St. Lawrence drainage basin in New York. Before that, all records were pre-1970.

Conservation and Management


The single most important cause of the decline of freshwater mussels during the last century is the destruction of their habitat by siltation, dredging, channelization, impoundments, and pollution. A healthy fish assemblage is critical to viable mussel populations and dams have resulted in heavy losses of mussels, mainly due to elimination of host fish species. Erosion due to deforestation, poor agricultural practices and the destruction of riparian zones, causes an increase in siltation and shifting substrates that can smother mussels. Domestic sewage, effluents from paper mills, tanneries, chemical industries and steel mills, acid mine runoff, heavy metals, and pesticides have all been implicated in the destruction of native mussel fauna. The zebra mussel invasion has dramatically lowered population numbers of this species, particularly in the lower Great Lakes basin (Metcalfe-Smith 1997). Owing to its thin shell, this species appears to be one of those most heavily affected by shell fouling by invasive zebra mussels. Unionids undergo tissue degrowth as a result of starvation, they become top-heavy, tip over and are unable to right themselves. Death is from starvation and complications arising from inproper orientation.

Conservation Strategies and Management Practices

It may be difficult to control the impacts of established zebra mussel populations, but managers can work to prevent the spread of this invasive species to river systems and smaller lakes not yet invaded. The effects of PCB's and other toxic chemicals, and general water pollution, should be investigated for their potential role in the decline of this species. Ligumia nasuta had the highest body burden of PCB's among 6 different mussel species studied by Muncaster et al. (1990), possibly due to its small size. When feasible, the removal of impoundments in order to restore rivers to their natural flow would be beneficial since these structures negatively effect required fish host species as well as the mussels themselves.

Research Needs

There is still much to learn about this species, especially determination of the host fish species. Details about habitat requirements (current speed, water depth, substrate grain size, substrate stability, water temperature, and water quality factors) also need work. However, Strayer et al. (1994) found that the distribution of Unionids was not related to these typical physical habitat qualities, but instead was related to long term stability of the substrate (i.e., flow refuges) and other large-scale habitat variables such as riparian zone vegetation (i.e., grassy vs. forested). Both large and smaller scale forces promoting the patchy occurrence of Unionid mussel beds is an active area of research (Strayer et al. 2004).



The eastern pondmussel appears to be somewhat of a habitat generalist, but it is most often found in quiet waters in estuaries, lakes, canals, or slow streams, and has also been found in the slackwater areas of larger rivers such as the Niagara, as well as in protected areas of small lakes (Clarke 1981, Strayer and Jirka 1997).

Associated Ecological Communities

  • Canal
    The aquatic community of an artificial waterway or modified stream channel constructed for inland navigation or irrigation.
  • Confined river (guide)
    The aquatic community of relatively large, fast flowing sections of streams with a moderate to gentle gradient.
  • Deepwater river
    The aquatic community of very large, very deep, quiet, base level sections of streams with a very low gradient. In places the water is deep enough so that light cannot reach the river bottom.
  • Freshwater tidal creek (guide)
    The aquatic community of a shallow, tidally flooded freshwater creek with submerged areas averaging less than 2 m (6 ft) deep at low tide.
  • Riverside sand/gravel bar (guide)
    A meadow community that occurs on sand and gravel bars deposited within, or adjacent to, a river channel. The community may be very sparsely vegetated, depending on the rates of deposition and erosion of the sand or gravel.

Associated Species

  • Triangle Floater (Alasmidonta undulata)
  • Brook Floater (Alasmidonta varicosa) (guide)
  • Threeridge (Amblema plicata)
  • Eastern Elliptio (Elliptio complanata)
  • Eastern Lampmussel (Lampsilis radiata)
  • Fatmucket (Lampsilis siliquoidea)
  • Eastern Floater (Pyganodon cataracta)
  • Giant Floater (Pyganodon grandis)
  • Creeper (Strophitus undulatus)
  • Alewife Floater (Utterbackiana implicata) (guide)


New York State Distribution

Although L. nasuta originated on the Atlantic slope, it has dispersed across much of the state, probably through the Erie Canal. It can be found only sporadically in the Hudson, Delaware, and Housatonic basins and is scattered in the Erie-Niagara drainage, and in central New York. It appears that the species has been lost from the St. Lawrence watershed, since all of the records of live animals are pre-1970 sightings. However, since 1980 the species has been found at three new locations in the Allegheny basin: Chautaqua Lake (most likely introduced through fish stocking), Cassdadaga Creek, and the Chadokin River (Strayer and Jirka 1997).

Global Distribution

This is primarily an Atlantic slope species, but is also known from the lower Great Lakes. Overall it ranges from Lake Ontario and Lake Erie in Canada, south and east to the Altantic drainages in South Carolina (Connecticut, Delaware, Massachusettes, Maryland, Michigan, North Carolina, New Hampshire, New Jersey, New York, Ohio, Ontario, Pennsylvania, Rhode Island, South Carolina, Virginia, Vermont, Washington DC).

Best Places to See

  • Lake Taghkanic

Identification Comments

General Description

The shell of the eastern pondmussel is elongate, subelliptical, with a distinct posterior ridge, medium thick, most often < 75 mm long. The posterior end of the shell is drawn out into a well defined blunt point near the midline of the shell. Its beak sculpture is double-looped, the periostracum dark, green to brown, sometimes with fine rays over the posterior part of the shell. Its hinge teeth are well-developed, sharp and delicate; the nacre is a bluish to creamy white (Strayer and Jirka 1997) .

Identifying Characteristics

The long shell, with its distinctive posterior end, makes this species easy to recognize (Strayer and Jirka 1997).

Best Life Stage for Proper Identification



Adults of this species are sessile with only limited movement in the substrate. Passive downstream movement may occur when they are displaced from the substrate during floods. More major dispersal occurs while glochidia are encysted on their as yet, unknown host(s). Being ectothermic, activity levels of mussels are presumably reduced greatly during colder months of the year. Gravid females of Ligumia display marginal papillae to attract fish hosts for their parasitic larvae. The moving displays attract fish (bass, sunfish, darters), which readily attack displaying females, causing them to release glochidia onto the gills of the fish. These displays slow in low light and stop in the dark, so highly turbid waters may affect the reproductive biology of this species (Corey et al. 2006).


Adult mussels are filter feeders. Algae, detritus and bacteria are all important food sources. Mussels in turn are eaten by muskrats, raccoons, fish, and birds. The glochidial (larval) host fish species has not been determined, but several Centrachid (sunfish) species as well as bass seem to be suitable (Strayer and Jirka 1997, Corey et al. 2006).

Best Time to See

Little is known about the activity periods of Unionid mussels but they are presumed to be greatly reduced during cold times of the year. Freshwater mussels are most often easiest to locate during late summer when water levels are lowest. This species breeds from August until the following June (Clarke 1981).

  • Active
  • Reproducing

The time of year you would expect to find Eastern Pondmussel active and reproducing in New York.

Similar Species

  • Eastern Elliptio (Elliptio complanata)
    Elliptio species usually have shorter shells and much heavier hinge teeth.
  • Black Sandshell (Ligumia recta) (guide)
    Ligumia recta has a smoother periostracum, heavier hinge teeth, and a more rounded posterior end.

Eastern Pondmussel Images


Eastern Pondmussel
Ligumia nasuta (Say, 1817)

  • Kingdom Animalia
    • Phylum Mollusca (Mollusks)
      • Class Bivalvia (Bivalves)
        • Order Unionoida (Freshwater Mussels)
          • Family Unionidae (Unionid Mussels)

Additional Resources


Burch, J.B. 1975. Freshwater unionacean clams (mollusca: pelecypoda) of North America. Malcological Publications. Hamburg, Michigan. 204 pp.

Clarke, A.H. 1981a. The Freshwater Molluscs of Canada. National Museum of Natural Sciences, National Museums of Canada, D.W. Friesen and Sons, Ltd.: Ottawa, Canada. 446 pp.

Clarke, A.H. and C.O. Berg. 1959. The freshwater mussels of central New York. Cornell University Agricultural Experiment Station Memoir 367.

Corey, C.A., R. Dowling, and D.L. Strayer. 2006. Display behavior of Ligumia (Bivalvia: Unionidae). Northeastern Naturalist 13:319-332.

Letson, E. J. 1905. Checklist of the Mollusca of New York. Bulletin. No. 88. New York State Museum, Albany, NY.

Metcalfe-Smith, J.L., S.K. Staton, G.L. Mackie, and N.M. Lane. 1997. Biodiversity of freshwater mussels in the lower Great Lakes drainage basin. Plenary presentation at the Third National Eman Meeting, Saskatoon, SK.

Muncaster, B.W., P.D.N. Hebert, and R Lazar. 1990. Biological and Physical factors affecting the body burden of organic contaminants in freshwater mussels. Archives of Environmental Contamination and Toxicology 19:25-34.

Nalepa, T.F., B.A. Manny, J.C. Roth, S.C. Mozley, and D.W. Schloesser. 1991. Long-term decline in freshwater mussels of the western basin of Lake Erie. Journal of Great Lakes Research 17:214-219.

New York Natural Heritage Program. 2024. New York Natural Heritage Program Databases. Albany, NY.

New York State Department of Environmental Conservation. 2020. ArcGIS layer package on mussel records in New York State.

Robertson, I. and C. Blakeslee. 1948. The mollusca of the Niagara Frontier region. Bulletin Buffalo Society Natural Science 19: 1-191.

Schloesser, D.W., and T.F. Nalepa. 1994. Dramatic decline of Unionid bivalves in offshore waters of western Lake Erie after infestation by the zebra mussel, Dreissena polymorpha. Canadian Journal of Fisheries and Aquatic Science 51:2234-2242.

Strayer, David L. 1987. Ecology and zoogeography of the freshwater mollusks of the Hudson River basin. Malacological Review 20:1-68.

Strayer, David L. and K.J. Jirka. 1997. The Pearly Mussels (Bivalva: Unionoidea) of New York State. New York State Museum Memoir 26. The New York State Education Department.

Strayer, David L., D.C. Hunter, L.C. Smith, and C.K. Borg. 1994. Distribution, abundance, and roles of freshwater clams (Bivalva, Unionidae) in the freshwater tidal Hudson River. Freshwater Biology 31:239-248.

Strayer, David L., J.A. Dowling, W.R. Haag, T.L. King, J.B. Layzer, T.J. Newton and S.J. Nichols. 2004. Changing perspectives on Pearly Mussels, North America's most Imperiled Animals. BioScience 54:429-439.

Strayer, David L., Kurt J. Jirka, and Kathryn J. Schneider. 1991. Recent collections of freshwater mussels (Bivalvia: Unionidae) from western New York. Walkerana 5(12): 63-72.


About This Guide

Information for this guide was last updated on: June 22, 2007

Please cite this page as:
New York Natural Heritage Program. 2024. Online Conservation Guide for Ligumia nasuta. Available from: https://guides.nynhp.org/eastern-pondmussel/. Accessed May 26, 2024.