Pleurobema cordatum - (Rafinesque, 1820)
Ohio Pigtoe
Taxonomic Status: Accepted
Related ITIS Name(s): Pleurobema cordatum (Rafinesque, 1820) (TSN 80094)
Unique Identifier: ELEMENT_GLOBAL.2.117135
Element Code: IMBIV35090
Informal Taxonomy: Animals, Invertebrates - Mollusks - Freshwater Mussels
 
Kingdom Phylum Class Order Family Genus
Animalia Mollusca Bivalvia Unionoida Unionidae Pleurobema
Genus Size: D - Medium to large genus (21+ species)
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Concept Reference
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Concept Reference: Turgeon, D.D., J.F. Quinn, Jr., A.E. Bogan, E.V. Coan, F.G. Hochberg, W.G. Lyons, P.M. Mikkelsen, R.J. Neves, C.F.E. Roper, G. Rosenberg, B. Roth, A. Scheltema, F.G. Thompson, M. Vecchione, and J.D. Williams. 1998. Common and scientific names of aquatic invertebrates from the United States and Canada: Mollusks. 2nd Edition. American Fisheries Society Special Publication 26, Bethesda, Maryland: 526 pp.
Concept Reference Code: B98TUR01EHUS
Name Used in Concept Reference: Pleurobema cordatum
Taxonomic Comments: Is part of a complex of closely related species or ecophenotypes that includes P. cordatum, P. coccineum, P. plenum, and P. rubrum (Strayer and Jirka 1997). The identity of this species has been confused at times because of lumping by some authors of several closely related species either as synonyms under, or as subspecies of, Pleurobema cordatum (e.g., Ortmann, 1918; Burch, 1975). As a result, museum collections labeled as this species may contain only it, a jumble of several subspecies, or other species excluding P. cordatum. Published records also must be suspect.er species excluding P. cordatum. Published records also must be suspect.

The members of the genus Pleurobema are among the most difficult to identify in North America. Arguments arise even among taxonomists regarding the "species" represented in the genus Pleurobema. Stansbery (1983) summarized many of the problems and identified a few of the shell characters used to separate Pleurobema sintoxia from the morphologically similar and often co-occurring Pleurobema plenum, Pleurobema cordatum, and Pleurobema rubrum. A few "morphs" have been variously identified and named but no rigorous genetic, anatomic, or conchologic study has ever been published on this group to help elucidate species boundaries or relationships.
Conservation Status
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NatureServe Status

Global Status: G4
Global Status Last Reviewed: 12May2009
Global Status Last Changed: 21Feb2007
Rounded Global Status: G4 - Apparently Secure
Reasons: This species has become increasingly rare in occurrence and density. Of the remaining populations, some may be incapable of successful reproduction and long-term viability of many populations is questionable. However, despite sharp declines in numbers, it is still relatively wide-spread in its historic range across much of the United States with subnational extirpations in the far northeastern portion of its range.
Nation: United States
National Status: N4 (21Feb2007)

U.S. & Canada State/Province Status
Due to latency between updates made in state, provincial or other NatureServe Network databases and when they appear on NatureServe Explorer, for state or provincial information you may wish to contact the data steward in your jurisdiction to obtain the most current data. Please refer to our Distribution Data Sources to find contact information for your jurisdiction.
United States Alabama (S2), Arkansas (S1), Illinois (S1), Indiana (S2), Iowa (SX), Kentucky (S4), Michigan (SNR), New York (SX), Ohio (S1), Oklahoma (S2), Pennsylvania (SH), Tennessee (S3), Virginia (S1), West Virginia (S2)

Other Statuses

IUCN Red List Category: NT - Near threatened
American Fisheries Society Status: Special Concern (01Jan1993)

NatureServe Global Conservation Status Factors

Range Extent: 200,000-2,500,000 square km (about 80,000-1,000,000 square miles)
Range Extent Comments: This species was once known from the upper Mississippi River drainage and the St. Lawrence River drainage, from western New York west to Michigan, Wisconsin, Iowa, and Kansas, south to Arkansas and Alabama (Burch, 1975). Historically, it occurred throughout much of the Ohio River drainage. It is now quite sporadic with occurrences in the Ohio River and Muskingum River (Watters, 1995) and apparently extirpated from the Wabash and some other tributaries in Ohio. Localized occurrences exist in the Green, Tennessee and Cumberland river reservoirs and a few Tennessee River tributaries. Mathiak (1979) cites it as scattered over 30 (of 641) sites in Wisconsin but noted identification difficulties. It is somewhat widespread in Alabama but is considered a state watch list species due to recent declines (Mirarchi et al., 2004). In Kentucky, it is generally distributed to occasional nearly statewide (Cicerello and Schuster, 2003).

Area of Occupancy: >12,500 4-km2 grid cells
Area of Occupancy Comments:  

Number of Occurrences: 81 - 300
Number of Occurrences Comments: Number of occurrences is difficult to assess with present data. Increasingly, this species is found to be rare in non-impounded areas and occurrences in some reservoirs are poorly documented. Significant declines have been noted in reservoirs with commercial harvest. In Tennessee, where it formerly was widespread in the Cumberland, Tennessee, Little Tennessee, Holston, Nolichucky, Elk, Duck, Clinch, French Broad and Hatchie Rivers, it is now restricted to a limited number of sites within these systems and has been extirpated from the Little Tennessee and French Broad Rivers (Parmalee and Bogan, 1998). In Alabama, it is found throughout the Tennessee River in northern Alabama and was historically the most abundant species there, but today is found only in small numbers in tailwaters of Guntersville and Wilson dams (Mirarchi, 2004; Williams et al., 2008) and Paint Rock River (Ahlstedt, 1996). In Arkansas, it occurs in the Mississippi Alluvian Plain (St. Francis and White River drainages- see Gordon, 1982) Ozark Highlands (White River drainage), and South Central Plains (Ouachita River drainage), although some records may represent Pleurobema rubrum (Anderson, 2006). It has been collected in Kentucky in the Red (Clark, 1988), Middle Green and Barren Rivers (Cochran and Layzer, 1993), but is generally distributed to occasional nearly statewide (Cicerello and Schuster, 2003). Oklahoma distribution for Pleurobema cordatum includes: Chikaskia (as P. coccineum), Little, Kiamichi, Verdigris, Neosho, Poteau, Mountain Fork, and Spring Rivers (Branson, 1983), however the northern to northeast occurrences are likely Pleurobema sintoxia. In Illinois, it is now restricted to the Ohio River where it is generally distributed (Cummings and Mayer, 1997). In Ohio, it is limited to the lower Muskingum River, Big Darby Creek, and a few sites in the Ohio River (Watters, 1995; Watters et al., 2009). This species was recently reported from the first time in Ohio Brush Creek, Ohio (Matter et al., 2006). In West Virginia, it occurs in the Upper Ohio/Kanawha (Zeto et al., 1987). In Kentucky, Cicerello and Schuster (2003) list distribution as generally distributed to occasional nearly statewide while Clark (1987) list it in their study of the Red River drainage. In Wisconsin, Mathiak (1979) cites it from 30 localities across the state including the Mississippi and lower Wisconsin Rivers, and sites in northwestern and southeastern Wisconsin.

Population Size: Unknown
Population Size Comments: Population size is difficult to assess due to the area involved and lack of quantitative estimates. Sharp declines have been noted in both general occurrence and in commercial harvests. Some populations may not be reproducing successfully. Scruggs (1960) estimated it comprised almost 53% of the mussel fauna in Guntersville Dam tailwaters in the Tennessee River (20,566,000 individuals in an 8 mile stretch below the dam in 1956-1957); while in 1997 it comprised only 6% of the fauna (J. Garner in Williams et al., 2008) (no individuals in 1991- Ahlstedt and McDonough, 1993).

Number of Occurrences with Good Viability/Integrity: Few to many (4-125)
Viability/Integrity Comments: Watters (1995) cites it as abundant in the lower Muskingum River in Ohio.

Overall Threat Impact Comments: Chemical and organic pollution, alteration and inundation of river channels (including loss of glochidial hosts), siltation from various sources, toxic run-off from mines, die-offs of various unidentified causes (Yokley, 1972; Neves, 1987) and commercial harvest of shells have and continue to severely impact this species. It is also considered a prime commercial shell. Impoundment has caused the decline of this species in many areas (Parmalee and Bogan, 1998).

Short-term Trend: Decline of 10-30%
Short-term Trend Comments: This species has been extirpated from or occurs in greatly reduced numbers through considerable portions of its historical range (e.g., Cummings et al., 1987, 1988; Pardue, 1981; Jenkinson, 1988; Jenkinson and Ahlstedt, 1988; Mirarchi et al., 2004). For example, Pleurobema cordatum in the Kentucky Resevoir section of the Tennessee River has declined from the dominant mussel species (Scruggs, 1960) to a rather rare component of the fauna (Layzer and Gordon, 1990). Williams and Schuster (1989) have documented temporal changes in relative abundance in the Ohio River bordering Kentucky, and it appears to have been extirpated completely from the Wabash River basin. Parmalee and Bogan (1998) claim it has been extirpated from the Little Tennessee and French Broad Rivers and is now a relict population in the Tennessee River upstream from Chattanooga. It is now quite sporadic with occurrences in the Ohio River and Muskingum River (Watters, 1995) and apparently extirpated from the Wabash and some other tributaries in Ohio. Scruggs (1960) estimated it comprised almost 53% of the mussel fauna in Guntersville Dam tailwaters in the Tennessee River (20,566,000 individuals in an 8 mile stretch below the dam in 1956-1957); while in 1997 it comprised only 6% of the fauna (J. Garner in Williams et al., 2008) (no individuals in 1991- Ahlstedt and McDonough, 1993).

Long-term Trend: Decline of 30-50%
Long-term Trend Comments: This species is extirpated in Pennsylvania (Bogan, 1993; Spoo, 2008) where it formerly occurred in the Upper Ohio, Middle Allegheny-Redbank, and Lower Monongahela drainages (Ortmann, 1919) as well as New York where it formerly occurred in the far western portion of the state (Strayer and Jirka, 1997). In Alabama, it is found throughout the Tennessee River in northern Alabama and was historically the most abundant species there, but today is found only in small numbers in tailwaters of Guntersville and Wilson dams (Mirarchi, 2004).

Intrinsic Vulnerability Comments: Sensitive to pollution, siltation, habitat perturbation, inundation, excessive harvests, and loss of glochidial hosts.

Other NatureServe Conservation Status Information

Inventory Needs: Determine extent of existing populations, continue surveys for additional EOs, and assess potential sites for reintroduction.

Protection Needs: All populations should receive protection through acquisition, easement, registry, and working with local, state, and federal government agencies on issues relating to development, water quality, river designation, etc. Besides preservation and restoration of habitat, commercial harvesting should be strictly controlled or curtailed.

Distribution
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Global Range: (200,000-2,500,000 square km (about 80,000-1,000,000 square miles)) This species was once known from the upper Mississippi River drainage and the St. Lawrence River drainage, from western New York west to Michigan, Wisconsin, Iowa, and Kansas, south to Arkansas and Alabama (Burch, 1975). Historically, it occurred throughout much of the Ohio River drainage. It is now quite sporadic with occurrences in the Ohio River and Muskingum River (Watters, 1995) and apparently extirpated from the Wabash and some other tributaries in Ohio. Localized occurrences exist in the Green, Tennessee and Cumberland river reservoirs and a few Tennessee River tributaries. Mathiak (1979) cites it as scattered over 30 (of 641) sites in Wisconsin but noted identification difficulties. It is somewhat widespread in Alabama but is considered a state watch list species due to recent declines (Mirarchi et al., 2004). In Kentucky, it is generally distributed to occasional nearly statewide (Cicerello and Schuster, 2003).

U.S. States and Canadian Provinces

Due to latency between updates made in state, provincial or other NatureServe Network databases and when they appear on NatureServe Explorer, for state or provincial information you may wish to contact the data steward in your jurisdiction to obtain the most current data. Please refer to our Distribution Data Sources to find contact information for your jurisdiction.
Color legend for Distribution Map
Endemism: endemic to a single nation

U.S. & Canada State/Province Distribution
United States AL, AR, IAextirpated, IL, IN, KY, MI, NYextirpated, OH, OK, PA, TN, VA, WV

Range Map
No map available.


U.S. Distribution by County Help
State County Name (FIPS Code)
AL Colbert (01033), Jackson (01071), Lauderdale (01077), Lawrence (01079)*, Limestone (01083)*, Madison (01089), Marshall (01095), Morgan (01103)
AR Ashley (05003), Bradley (05011), Crittenden (05035), Grant (05053), Jackson (05067), Lawrence (05075), Randolph (05121), Saline (05125), Sevier (05133), Sharp (05135), St. Francis (05123), White (05145), Woodruff (05147)
IL Hancock (17067), Massac (17127), Pulaski (17153)
IN Carroll (18015), Cass (18017), Crawford (18025), Daviess (18027), Delaware (18035), Dubois (18037), Floyd (18043), Fountain (18045), Gibson (18051), Greene (18055), Harrison (18061), Jackson (18071), Jefferson (18077), Knox (18083), Lawrence (18093), Martin (18101), Owen (18119), Parke (18121), Perry (18123), Pike (18125), Posey (18129), Pulaski (18131), Spencer (18147), Sullivan (18153), Switzerland (18155), Tippecanoe (18157), Vanderburgh (18163), Vermillion (18165), Vigo (18167), Wabash (18169), Warren (18171), Warrick (18173), White (18181)
OH Adams (39001), Brown (39015)*, Clermont (39025), Coshocton (39031), Gallia (39053), Hamilton (39061)*, Lawrence (39087), Marion (39101)*, Morgan (39115), Pickaway (39129), Scioto (39145), Washington (39167)
OK Cherokee (40021), McCurtain (40089), Pushmataha (40127)
PA Allegheny (42003)*, Armstrong (42005)*, Beaver (42007)*, Lawrence (42073)*, Mercer (42085)*, Washington (42125)*, Westmoreland (42129)*
TN Hardin (47071)
VA Scott (51169)*
WV Cabell (54011), Jackson (54035), Mason (54053), Wood (54107)
* Extirpated/possibly extirpated
U.S. Distribution by Watershed Help
Watershed Region Help Watershed Name (Watershed Code)
05 Middle Allegheny-Redbank (05010006)+*, Lower Monongahela (05020005)+*, Upper Ohio (05030101)+*, Shenango (05030102)+*, Little Muskingum-Middle Island (05030201)+, Upper Ohio-Shade (05030202)+, Walhonding (05040003)+, Muskingum (05040004)+, Upper Scioto (05060001)+, Raccoon-Symmes (05090101)+, Little Scioto-Tygarts (05090103)+, Ohio Brush-Whiteoak (05090201)+, Middle Ohio-Laughery (05090203)+, Upper Wabash (05120101)+, Middle Wabash-Deer (05120105)+, Tippecanoe (05120106)+, Middle Wabash-Little Vermilion (05120108)+, Middle Wabash-Busseron (05120111)+, Lower Wabash (05120113)+, Upper White (05120201)+, Lower White (05120202)+, Eel (05120203)+, Upper East Fork White (05120206)+, Lower East Fork White (05120208)+, Silver-Little Kentucky (05140101)+, Blue-Sinking (05140104)+, Lower Ohio-Little Pigeon (05140201)+, Highland-Pigeon (05140202)+, Lower Ohio (05140206)+
06 Upper Clinch (06010205)+*, Guntersville Lake (06030001)+, Wheeler Lake (06030002)+, Pickwick Lake (06030005)+, Lower Tennessee-Beech (06040001)+
07 Flint-Henderson (07080104)+
08 Lower St. Francis (08020203)+, Upper Saline (08040203)+, Lower Saline (08040204)+
11 Spring (11010010)+, Upper White-Village (11010013)+, Illinois (11110103)+, Kiamichi (11140105)+, Upper Little (11140107)+, Lower Little (11140109)+
+ Natural heritage record(s) exist for this watershed
* Extirpated/possibly extirpated
U.S. Distribution by Watershed (based on multiple information sources) Help
Ecology & Life History
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Basic Description: A freshwater mussel, with a subtriangular, heavy and inflated shell.
General Description: Shell subtriangular, heavy, inflated; anterior margin rounded, ventral margin straight to slightly sinuate posteriorly; posterior margin flatly convex, posterio-ventral junction biangulate to bluntly pointed, posterio-dorsal junction barely perceiveable; dorsal margin strongly arched, posterior portion rather straight, anterior portion slightly concave before beaks (i.e. lunule region), anterio-dorsal junction angular; beaks considerably elevated, inclined anteriorly, decurved over lunule; beak sculpture consists of a few coarse, irregular ridges, arched and nodulous on posterior ridge (Simpson, 1914); maximum inflation forms central radial ridge; posterior ridge convex, subangular, double, distinct sulcus anteriorly, both of these structures become flattened ventrally, a few radial carina on posterior slope; periostracum dull or textured, yellowish-brown to reddish-brown or black, mat be obscurly rayed with dark green, growth increments strongly marked. Pseudocardinal teeth heavy, elevated, serrated, double and dorsally confluent in left valve, single and surrounded by sulci in the right, pyramidal, accessary denticles anteriorly and posteriorly to sulci; interdentum wide, moderately long; lateral teeth moderately long; double in left valve, single in right but may develop vestigial tooth dorsally; anterior muscle scars confluent, very deep, rough; pallial line impressed anteriorly, faint posteriorly; posterior muscle scars distinct, impressed; beak cavities relatively deep; nacre white, somewhat iridescent posteriorly.
Diagnostic Characteristics: The shell is similar to several PLEUROBEMA spp. and FUSCONAIA EBENA (Lea, 1831). The latter species and P.COCCINEUM have more rounded outlines, low broadly rounded posterior ridges, and little, if any, development of the radial sulci anterior to the posterior ridge. PLEUROBEMA PLENUM has a more angular appearance, broader and more flattened beaks, and a disinctively angular posterior ridge with a narrow and poorly developed radial sulcus (the sulcus is often more strongly developed ventrally). PLEUROBEMA PYRAMIDATUM resembles an elongate scaline triangle, almost elliptical in appearance. Its posterior ridge is rounded but distinct with a shallow sulcus anteriorly. These features are most pronounced in the region of the beaks, becoming flattened and obscurred ventrally. Height: 95mm
Reproduction Comments: Pleurobema cordatum is a short-termed brooder with embryonic or larval forms reported from echtobranchous marsupia between April and August. Previously, Notropis ardens (rosefin shiner)was the only fish on which successful metemorphosis of glochidia has been reported (Yokley, 1972; Fuller, 1974). Previously, Lepomis macrochirus (bluegill) had been also considered to serve as a host (Fuller, 1974; Gordon and Lazer, 1989), but this was from a report in Surber (1913) for "Quadrula solida" (= Pleurobema catillua) which is a junior synonym of Pleurobema coccineum. The distribution of P. cordatum is considerably larger and occupies a greater range of habitats than Notropis ardens, indicating that other hosts exist for this mussel. Recently, other host fish were found to be creek chub (Semotilus atromaculatus), guppy (Lebistes reticulatus), brook stickleback (Culaea inconstans); also no support for previously reported bluegill (Lepomis macrochirus) (Watters and Kuehn, 2004). New host fish confirmation from Watters et al. (2005) include: brook stickleback (Culaea inconstans), creek chub (Semotilus atromaculatus), and guppy (Lebistes reticulatus).
Ecology Comments: No ecological studies have specifically considered this species. Representative densities of disturbed populations have been estimated in Jenkinson (1988) and Jenkinson and Ahlstedt (1988), and data relative to several environmental parameters were presented in Yokley (1972) but were not correlated to the specific occurrence of mussels. Williams and Schuster (1989) considered demographics of Ohio River populations.
Habitat Type: Freshwater
Non-Migrant: N
Locally Migrant: N
Long Distance Migrant: N
Mobility and Migration Comments: This species is probably rather sessile with only limited movement through the substrate. Passive downstream movement may occur when mussels are displaced from the substrate during flooods. Major dispersal occurs while glochidia are encysted on their hosts.
Riverine Habitat(s): BIG RIVER, Low gradient, MEDIUM RIVER, Moderate gradient, Riffle
Lacustrine Habitat(s): Shallow water
Special Habitat Factors: Benthic
Habitat Comments: This species primarily inhabits large rivers but may be found in medium-sized rivers. It is also tolerant of some reservoir environments. In lotic situations it is found in or immediately above riffles in heterogenous assemblages of gravel, cobble, and boulder. It also occurs in some habitats with greater depth and substrates of mud/sand/gravel but seems to require flowing water. In reservoirs, it tends to occur in the sublotic areas of dam tailwaters and may be in some overbank beds (Gordon and Layzer, 1989).
Adult Food Habits: Detritivore
Immature Food Habits: Parasitic
Food Comments: Larvae (glochidia) of freshwater mussels generally are parasitic on fish and display varying degrees of host specificity. No specific trophic studies have been conducted on this species. General literature claims that mussels are filter-feeders that remove phytoplankton from the water column. These assumptions are based on casual observations on mussels in situ and a few examinations of rectal contents. Baker (1928) speculated that detritus was the primary energy source. This has been substantiated by James (1987) and correlates well with observed microhabitat utilization. This suggests that musssels may occupy a variety of guilds such as postulated for the Sphaeriidae (see Lopez and Holopaien, 1987; Gordon and Layzer, 1989).
Phenology Comments: Little is known concerning the phenology of mussels other than when eggs/glochidia are held in the branchial marsupia. Being poikilothermic, activity levels would expectedly be reduced greatly during cold temperature months.
Length: 11.5 centimeters
Economic Attributes Not yet assessed
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Management Summary
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Biological Research Needs: Determine habitat preferences and environmental tolerances, particularily to pollutants and siltation. Re-examine and continue research on reproductive biology and potential glochidial hosts.
Population/Occurrence Delineation
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Group Name: Freshwater Mussels

Use Class: Not applicable
Minimum Criteria for an Occurrence: Occurrences are based on some evidence of historical or current presence of single or multiple specimens, including live specimens or recently dead shells (i.e., soft tissue still attached and/or nacre still glossy and iridescent without signs of external weathering or staining), at a given location with potentially recurring existence. Weathered shells constitute a historic occurrence. Evidence is derived from reliable published observation or collection data; unpublished, though documented (i.e. government or agency reports, web sites, etc.) observation or collection data; or museum specimen information.
Mapping Guidance: Based on the separation distances outlined herein, for freshwater mussels in STANDING WATER (or backwater areas of flowing water such as oxbows and sloughs), all standing water bodies with either (1) greater than 2 km linear distance of unsuitable habitat between (i.e. lotic connections), or (2) more than 10 km of apparently unoccupied though suitable habitat (including lentic shoreline, linear distance across water bodies, and lentic water bodies with proper lotic connections), are considered separate element occurrences. Only the largest standing water bodies (with 20 km linear shoreline or greater) may have greater than one element occurrence within each. Multiple collection or observation locations in one lake, for example, would only constitute multiple occurrences in the largest lakes, and only then if there was some likelihood that unsurveyed areas between collections did not contain the element.

For freshwater mussels in FLOWING WATER conditions, occurrences are separated by a distance of more than 2 stream km of unsuitable habitat, or a distance of more than 10 stream km of apparently unoccupied though suitable habitat. Standing water between occurrences is considered suitable habitat when calculating separation distance for flowing water mussel species unless dispersal barriers (see Separation Barriers) are in place.

Several mussel species in North America occur in both standing and flowing water (see Specs Notes). Calculation of separation distance and determination of separation barriers for these taxa should take into account the environment in which the element was collected. Juvenile mussels do not follow this pattern and juveniles are typically missed by most standard sampling methods (Hastie and Cosgrove, 2002; Neves and Widlak, 1987), therefore juvenile movement is not considered when calculating separation distance.

Separation Barriers: Separation barriers within standing water bodies are based solely on separation distance (see Separation Distance-suitable, below). Separation barriers between standing water bodies and within flowing water systems include lack of lotic connections, natural barriers such as upland habitat, absence of appropriate species specific fish hosts, water depth greater than 10 meters (Cvancara, 1972; Moyle and Bacon, 1969) or anthropogenic barriers to water flow such as dams or other impoundments and high waterfalls.
Separation Distance for Unsuitable Habitat: 2 km
Separation Distance for Suitable Habitat: 10 km
Alternate Separation Procedure: None
Separation Justification: Adult freshwater mussels are largely sedentary spending their entire lives very near to the place where they first successfully settled (Coker et al., 1921; Watters, 1992). Strayer (1999) demonstrated in field trials that mussels in streams occur chiefly in flow refuges, or relatively stable areas that displayed little movement of particles during flood events. Flow refuges conceivably allow relatively immobile mussels to remain in the same general location throughout their entire lives. Movement occurs with the impetus of some stimulus (nearby water disturbance, physical removal from the water such as during collection, exposure conditions during low water, seasonal temperature change or associated diurnal cycles) and during spawning. Movement is confined to either vertical movement burrowing deeper into sediments though rarely completely beneath the surface, or horizontal movement in a distinct path often away from the area of stimulus. Vertical movement is generally seasonal with rapid descent into the sediment in autumn and gradual reappearance at the surface during spring (Amyot and Downing, 1991; 1997). Horizontal movement is generally on the order of a few meters at most and is associated with day length and during times of spawning (Amyot and Downing, 1997). Such locomotion plays little, if any, part in the distribution of freshwater mussels as these limited movements are not dispersal mechanisms. Dispersal patterns are largely speculative but have been attributed to stream size and surface geology (Strayer, 1983; Strayer and Ralley, 1993; van der Schalie, 1938), utilization of flow refuges during flood stages (Strayer, 1999), and patterns of host fish distribution during spawning periods (Haag and Warren, 1998; Watters, 1992). Lee and DeAngelis (1997) modeled the dispersal of freshwater into unoccupied habitats as a traveling wave front with a velocity ranging from 0.87 to 2.47 km/year (depending on mussel life span) with increase in glochidial attachment rate to fish having no effect on wave velocity.

Nearly all mussels require a host or hosts during the parasitic larval portion of their life cycle. Hosts are usually fish, but a few exceptional species utilize amphibians as hosts (Van Snik Gray et al., 2002; Howard, 1915) or may metamorphose without a host (Allen, 1924; Barfield et al., 1998; Lefevre and Curtis, 1911; 1912). Haag and Warren (1998) found that densities of host generalist mussels (using a variety of hosts from many different families) and displaying host specialists (using a small number of hosts usually in the same family but mussel females have behavioral modifications to attract hosts to the gravid female) were independent of the densities of their hosts. Densities of non-displaying host specialist mussels (using a small number of hosts usually in the same family but without host-attracting behavior) were correlated positively with densities of their hosts. Upstream dispersal of host fish for non-displaying host specialist mussels could, theoretically, transport mussel larvae (glochidia) over long distances through unsuitable habitat, but it is unlikely that this occurs very often. D. Strayer (personal communication) suggested a distance of at least 10 km, but a greater distance between occurrences may be necessary to constitute genetic separation of populations. As such, separation distance is based on a set, though arbitrary, distance between two known points of occurrence.

Date: 18Oct2004
Author: Cordeiro, J.
Notes: Contact Jay Cordeiro (jay_cordeiro@natureserve.org) for a complete list of freshwater mussel taxa sorted by flow regime.
Population/Occurrence Viability
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U.S. Invasive Species Impact Rank (I-Rank) Not yet assessed
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Authors/Contributors
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NatureServe Conservation Status Factors Edition Date: 12May2009
NatureServe Conservation Status Factors Author: Cordeiro, J. (2009); Gordon, M.E. (1992); Whittaker, J.C. (1994)
Element Ecology & Life History Edition Date: 21Feb2007
Element Ecology & Life History Author(s): Cordeiro, J.

Zoological data developed by NatureServe and its network of natural heritage programs (see Local Programs) and other contributors and cooperators (see Sources).

References
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  • Ahlstedt, S.A. 1984. Twentieth century changes in the freshwater mussel fauna of the Clinch River (Tennessee and Virginia). M.S. Thesis, The University of Tennessee, Knoxville, Tennessee. 102 pp.

  • Ahlstedt, S.A. 1986. Cumberlandian mollusk conservation program, activity 1: mussel distribution surveys. Office of Natural Resources and Economic Development, Tennessee Valley Authority, Knoxville, Tennessee. 125 pp.

  • Ahlstedt, S.A. 1989. Update of the Watts Bar nuclear plant preoperational monitoring of the mussel fauna in upper Chickamunga. Tennessee Valley Authority Tech Report Series TVA/WR/AB-998/9: 1-26.

  • Ahlstedt, S.A. and T.A. McDonough. 1993. Quantitative evaluation of commercial mussel populations in the Tennessee River portion of Wheeler Reservoir, Alabama. Pages 38-49 in K.S. Cummings, A.C. Buchanan, and L.M. Koch (eds.) Conservation and Management of Freshwater Mussels. Proceedings of a UMRCC Symposium, 12-14 October 1992, St. Louis, Missouri.l Upper Mississippi River Conservation Committee, Rock Island, Illinois.

  • Ahlstedt, Steven Albin. 1984. Twentieth century changes in the freshwater mussel fauna of the Clinch River (Tennessee a nd Virginia). The University of Tennessee. 102pp.

  • Anderson, J.E. (ed.) 2006. Arkansas Wildlife Action Plan. Arkansas Game and Fish Commission, Little Rock, Arkansas. 2028 pp.

  • Baker, F.C. 1928b. The freshwater Mollusca of Wisconsin: Part II. Pelecypoda. Bulletin of the Wisconsin Geological and Natural History Survey, University of Wisconsin, 70(2): 1-495.

  • Burch, J.B. 1975c. Freshwater Unionacean Clams (Mollusca: Pelecypoda) of North America: Biota of Freshwater Ecosystems, Identification Manual No 11. Environmental Protection Agency, Washington, D.C. 176 pp.

  • Cicerello, R.R. and R.R. Hannan. 1990. Survey of the freshwater unionids (mussels) (Bivalvia: Margaritiferidae and Unionidae) in the Green river in the Mammoth Cave National Park, KY. Kentucky State Nature Preserve Commision, Frankfort, Kentucky. 44 pp.

  • Clark, C.F. 1988. Some fresh-water mussels from the Red River drainage, Kentucky. Malacology Data Net, 2(3/4): 100-104.

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  • Cummings, K.S. and C.A. Mayer. 1992. Field guide to freshwater mussels of the Midwest. Ill. Nat. Hist. Surv. Manual 5. 194pp.

  • Cummings, K.S. and C.A. Mayer. 1997. Distributional checklist and status of Illinois freshwater mussels (Mollusca: Unionacea). Pages 129-145 in: K.S. Cummings, A.C. Buchanan, C.A. Mayer, and T.J. Naimo (eds.) Conservation and management of freshwater mussels II: initiatives for the future. Proceedings of a UMRCC Symposium, October 1995, St. Louis, Missouri. Upper Mississippi River Conservation Committee, Rock Island, Illinois.

  • Cummings, K.S., C.A. Mayer, L.M. Page and J.M.K. Berlocher. 1987. Survey of freshwater mussels (Mollusca:Unionidae) of the Wabash River, phase I: Lower Wabash and Tippecanoe Rivers. Illinois Natural History Survey, Section of Faunistic Surveys and Insect Identification Technical Report, 1987(5):1-168.

  • Cummings, K.S., C.A. Mayer, and L.M. Page. 1988a. Survey of freshwater mussels (Bivalvia:Unionidae) in the Little Wabash River drainage, Illinois. Il. Nat. History Survey, Section of Faunistic Survey and Insect Id. Tech. Report 1988(1):1-71

  • Cummings, K.S., C.A. Mayer, and L.M. Page. 1988c. Survey of the freshwater mussels (Mollusca: Unionidae) of the Wabash River drainage, phase II: upper and middle Wabash River. Illinois Natural History Survey, Section of Faunistic Survey and Insect Identification, Technical Report 1988(8):1-79.

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  • Cummings, Kevin S. et al. 1992. Survey of the Freshwater Mussels (Mollusca: Unionidae) of the Wabash River Drainage. Final Report. INHS Center for Biodiversity Tech. Rep. 1992 (1):210 pp.

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  • Howard, A.D. 1915. Some exceptional cases of breeding among the Unionidae. The Nautilus 29:4-11.

  • James, M.R. 1987. Ecology of the freshwater mussel Hyridella menziesi in a small oliogotrophic lake. Archives of Hydrobiology 108:337-348.

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  • Lazer, J.B, and M.E. Gordon. 1990. Development and testing of sampling designs for assessing mussel populations in medium and large size rivers: final report. Tennessee Wildlife Resources Agency, Nashville. 25pp.

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  • Neves, R.J., ed. 1987. Proceedings of the workshop on die-offs of freshwater mussels in the U.S. U.S. Fish and Wildlife Service, Upper Mississippi River Conservation Committee, Rock Island, Illinois. 166 pp.

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  • Pardue, W.J. 1978. A survey of the mussels (Unionidae ) of the Upper Tennessee River- 1978. Sterkiana, 71: 41-51.

  • Parmalee, P.W. 1967. The fresh-water mussels of Illinois. Ill. State Mus., Popular Sci. Series Vol. VIII. 108pp.

  • Parmalee, P.W. and A.E. Bogan. 1998. The freshwater mussels of Tennessee. University of Tennessee Press, Knoxville, Tennesee. 328 pp.

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References for Watershed Distribution Map
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  • Williams, J.D., A.E. Bogan, and J.T. Garner. 2008. Freshwater Mussels of Alabama & the Mobile Basin in Georgia, Mississippi & Tennessee. University of Alabama Press: Tuscaloosa, Alabama. 908 pp.

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