Elliptio steinstansana - R.I. Johnson and Clarke, 1983
Tar River Spinymussel
Other English Common Names: Tar River spinymussel, Tar Spinymussel
Taxonomic Status: Accepted
Related ITIS Name(s): Elliptio steinstansana R. I. Johnson and Clarke, 1983 (TSN 79984)
Unique Identifier: ELEMENT_GLOBAL.2.107915
Element Code: IMBIV14270
Informal Taxonomy: Animals, Invertebrates - Mollusks - Freshwater Mussels
Image 12002

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Kingdom Phylum Class Order Family Genus
Animalia Mollusca Bivalvia Unionoida Unionidae Elliptio
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: Elliptio steinstansana
Conservation Status
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NatureServe Status

Global Status: G1
Global Status Last Reviewed: 15Sep2008
Global Status Last Changed: 25Oct1998
Rounded Global Status: G1 - Critically Imperiled
Reasons: This species now occupies less than 5% of its probable historical range. Extant metapopulations number fewer than five and have low densities and local populations have patchy distributions. Present and future land and water use impacts are expected to negatively impact extant populations. The species is not expected to survive on its own without significant recovery effort including reintroduction.
Nation: United States
National Status: N1 (25Oct1998)

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 North Carolina (S1)

Other Statuses

U.S. Endangered Species Act (USESA): LE: Listed endangered (27Jun1985)
U.S. Fish & Wildlife Service Lead Region: R4 - Southeast
IUCN Red List Category: CR - Critically endangered
American Fisheries Society Status: Endangered (01Jan1993)

NatureServe Global Conservation Status Factors

Range Extent: 100-250 square km (about 40-100 square miles)
Range Extent Comments: Historically, it was collected only from the mainstem of the Tar River from near Louisburg in Franklin Co. to the vicinity of Falkland in Pitt Co. (Clarke, 1983). This species probably once existed in rivers and larger creeks throughout most of the Tar and Neuse River basins in North Carolina prior to settlement of the area during the 1700s (USFWS, 1992). It is now limited to relatively small areas of these river basins with only one site remaining on a tributary of the lower Neuse River basin (Bogan, 2002).

Area of Occupancy: 26-500 4-km2 grid cells
Area of Occupancy Comments: Although historically known from five streams within the Tar River basin (Fishing Creek, Little Fishing Creek, Shocco Creek, Swift Creek, mainstem Tar Rvier) and one stream in the Neuse River basin (Little River), only one live individual had been found in the entire system (Tar River system) since 1990; however, in 152 man hours of surveys beginning July 2007, a total of 5 live specimens were found in Little Fishing Creek (all utilized in fish host studies); as well as 75 man hours of surveys in spring 2008 yielding 9 individuals in Fishing and Little Fishing Creeks (Eads et al., 2008).

Number of Occurrences: 1 - 5
Number of Occurrences Comments: Based upon historic and extant occurrences, it once occupied most river and large creek habitats within the Coastal Plain and Piedmont of the Tar and Neuse River basins in North Carolina. Within the Tar River Basin, extant populations now occur in two creeks within the Fishing Creek Subbasin, plus Swift Creek (a Tar River tributary from Vance to Edgecombe Co.), and the Tar River near Tarboro. During 1998, a small population was discovered in the lower Little River within the Neuse River Basin (North Carolina Wildlife Resources Commission, 1998). LeGrand et al. (2006) cites the following counties: Edgecombe, Franklin, Halifax, Johnston, Nash, Pitt (extirpated), and Warren. Although historically known from five streams within the Tar River basin (Fishing Creek, Little Fishing Creek, Shocco Creek, Swift Creek, mainstem Tar Rvier) and one stream in the Neuse River basin (Little River), only one live individual had been found in the entire system (Tar River system) since 1990; however, in 152 man hours of surveys beginning July 2007, a total of 5 live specimens were found in Little Fishing Creek (all utilized in fish host studies); as well as 75 man hours of surveys in spring 2008 yielding 9 individuals in Fishing and Little Fishing Creeks (Eads et al., 2008).

Population Size: 2500 - 10,000 individuals
Population Size Comments: Several thousand Tar River spinymussels may still exist. These animals exist within approximately a 1 mile reach of Shocco Creek, a 5 mile reach of Little Fishing Creek, a 30 mile reach of Swift Creek, a 1 mile reach of the Tar River, and a 1 mile reach of the Little River. In 152 man hours of surveys beginning July 2007, a total of 5 live specimens were found in Little Fishing Creek (all utilized in fish host studies); as well as 75 man hours of surveys in spring 2008 yielding 9 individuals in Fishing and Little Fishing Creeks; where previously only one live individual had been found in the entire system (Tar River system) since 1990 (Eads et al., 2008).

Number of Occurrences with Good Viability/Integrity: None (zero)
Viability/Integrity Comments: Presently, the best populations are found in or above the Fall Line, where relief is sufficient to maintain relatively silt-free substrates (North Carolina Wildlife Resources Commission, 1998). Several thousand Tar River spinymussels may still exist. These animals exist (as viable, reproducing populations) within approximately a 1 mile reach of Shocco Creek, a 5 mile reach of Little Fishing Creek, a 30 mile reach of Swift Creek, a 1 mile reach of the Tar River, and a 1 mile reach of the Little River. Although historically known from five streams within the Tar River basin (Fishing Creek, Little Fishing Creek, Shocco Creek, Swift Creek, mainstem Tar Rvier) and one stream in the Neuse River basin (Little River), only one live individual had been found in the entire system (Tar River system) since 1990; however, in 152 man hours of surveys beginning July 2007, a total of 5 live specimens were found in Little Fishing Creek (all utilized in fish host studies); as well as 75 man hours of surveys in spring 2008 yielding 9 individuals in Fishing and Little Fishing Creeks (Eads et al., 2008).

Overall Threat Impact: Very high - high
Overall Threat Impact Comments: Independent of pollution loading, the Shocco Creek and lower Tar River populations may be vulnerable to extirpation through stochastic events. Both populations appear to be extremely small. Additionally, the Tar River population near Tarboro is impacted by heavy sediment loading, point sources of pollution, and urban runoff from Rocky Mount. Sediment loading caused by poor land use practices is affecting habitats in Swift Creek and the Little River. A proposal is expected soon to create a reservoir in Wake County on the Little River above the Tar River spinymussel population. Downriver effects may significantly impact this population. Also, residential and other development are expanding in the Little River Subbasin above occupied habitat.

Historically, a massive mussel kill occurred in Swift Creek in 1990 wherein approximately 100 dead specimens of all ages were collected. The mussel kill was attributed to organophosphate or carbonate pesticides (USFWS, 1992). Fortunately, a healthy population of mussels continues to exist there.

The federal recovery plan (USFWS, 1992) lists the following threats:
(1) Pollution from private, municipal, industrial, silviculatural, and agricultural sources is believed to be one of the most significant factors contributing to the past and continuing decline of this species. Both point and nonpoint sources are believed to have had a severe effect. The upper and middle portions of the Tar River experience high pesticide and nutrient loading from agricultural and silvicultural activities and runoff or discharge of pesticides into Swift Creek has been implicated in mussel die-offs. Recent faunal changes in the Tar River near Tarboro and Rocky Mount probably resulted from sewage and other municipal pollution as well as effluent from sewage treatment facilities.
(2) Siltation, resulting from poorly implemented land use practices during construction, agricultural, and forestry activities is another serious threat. Soil erosion from land in the Tar and Neuse basins cause sediment loading. Gravel mining also causes excessive siltation as had logging activities in Swift Creek. Sedimentation has been cited as a cause of water quality problems in all tributaries of the Tar River within the range of this species.
(3) Impoundment is also a major threat. Construction of a dam near Rocky Mount has impounded the Tar River for several miles and suitable habitat has been lost. Hypolimnetic discharge from the impoundment has altered the conditions of the tailwater, possibly making the affected section of the river below the dam unsuitable for the mussel or its host(s). Smaller dams in the vicinity have blocked upstream expansion for over 50 years.
(4) Exotic species such as the Asiatic clam may also be a threat; it is well established in the Tar River and has expanded into Swift Creek.

Short-term Trend: Decline of >70%
Short-term Trend Comments: During 1985 and 1986, extensive surveys of the Tar, Roanoke, Cashie, Neuse, and Trent Rivers located this species in only a 12-mile stretch of the Tar River in Edgecombe Co. Further surveys from 1986 to 1989 in the Tar River mainstem and tributaries in three counties found the species (mostly as relic shells with four live specimens) only in Edgecombe Co. plus a fresh dead shell in Nash Co. in 1990. The Swift Creek population was discovered in 1987 (USFWS, 1992). This species now appears to be extirpated from the Tar River above Rocky Mount, and an extremely small population remains extant in the Tar River near Tarboro. The Swift Creek population's extent and local abundances are declining. No negative trends have been documented for the Shocco Creek, Little Fishing Creek, or Little River populations; however, habitat quality is declining in the Little River. In the Little River Subbasin, extensive harvesting of timber is occurring, wooded buffers are not being maintained, stream banks are becoming unstable, and sediment loading is becoming a problem. This species now occupies less than 5% of its probable historical range.

Long-term Trend: Decline of >90%
Long-term Trend Comments: This species has always had a restricted distribution and is endemic to the Tar River drainage basin in eastern North Carolina. It now occupies less than 5% of its probable historical range.

Intrinsic Vulnerability: Highly vulnerable
Intrinsic Vulnerability Comments: Because local populations have relatively low densities, sampling impacts may significantly affect these populations. It is important that great care is exercised to limit impacts to substrates and individuals while surveying or monitoring an area. Due to slow growth and relative immobility, establishment of sustainable, viable populations requires decades of immigration and recruitment, even where suitable habitat exists (Neves, 1993). Mussel recruitment is typically low and sporadic, with population stability and viability maintained by numerous slow-growing cohorts and occasional good year classes (Neves and Widlak, 1987). Because of the recent population decline and its present small size, it is believed that the mussel will soon be extirpated without human intervention (Clarke, pers. comm; Biggins, pers. comm.). Recovery suggestions include artificial propagation and/or transplantation to other habitats.

Environmental Specificity: Narrow. Specialist or community with key requirements common.
Environmental Specificity Comments: Water quality and habitat degradation resulting from siltation and the runoff and discharge of agricultural, municipal, and industrial pollutants appear to be major factors in reducing the species' distribution and reproductive capacity.

Other NatureServe Conservation Status Information

Inventory Needs: Recent surveying and monitoring of habitats and populations need to continue.

Distribution
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Global Range: (100-250 square km (about 40-100 square miles)) Historically, it was collected only from the mainstem of the Tar River from near Louisburg in Franklin Co. to the vicinity of Falkland in Pitt Co. (Clarke, 1983). This species probably once existed in rivers and larger creeks throughout most of the Tar and Neuse River basins in North Carolina prior to settlement of the area during the 1700s (USFWS, 1992). It is now limited to relatively small areas of these river basins with only one site remaining on a tributary of the lower Neuse River basin (Bogan, 2002).

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 state or province

U.S. & Canada State/Province Distribution
United States NC

Range Map
No map available.


U.S. Distribution by County Help
State County Name (FIPS Code)
NC Edgecombe (37065), Franklin (37069), Halifax (37083), Johnston (37101), Nash (37127), Pitt (37147)*, Warren (37185), Wayne (37191)*
* Extirpated/possibly extirpated
U.S. Distribution by Watershed Help
Watershed Region Help Watershed Name (Watershed Code)
03 Lower Roanoke (03010107)*, Upper Tar (03020101)+, Fishing (03020102)+, Lower Tar (03020103)+, Upper Neuse (03020201)+, Middle Neuse (03020202)*, Lower Neuse (03020204)
+ Natural heritage record(s) exist for this watershed
* Extirpated/possibly extirpated
Ecology & Life History
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Basic Description: A freshwater mussel with up to 12 spines.
General Description: The Tar River spiny mussel is one of only three species of unionids that have spines on their shells. Mature individuals usually attain a shell length of about 60 mm. In outline, the shell is subrhomboidal, and valves are subinflated. The anterior end is regularly rounded while the posterior end is slightly broader, ending in a blunt point just below the medial line. A hinge ligament is prominent, but short. The posterior ridge of the shell is generally slightly angular, sometimes with a faint secondary ridge above it, and the posterior slope is smooth. Located in the anterior third of the shell, the umbos are slightly elevated above the hinge line, their sculpture consisting of about three short, strong bars. The shell has a smooth and shiny surface with fine concentric sculpture. Each valve is usually ornamented with from one to several short spines, although not every individual will possess them. Specimens less than 35 mm in length usually have two or three erect spines on each valve. They are about 2.6 mm in length and 1.5 mm wide at their bases. They project perpendicularly from the shell surface, the tips are slightly bent in a ventral direction, and are generally arranged in a radial row located slightly in front of the posterior ridge. The periostracum is orange-brown and covered with narrow and wide greenish rays when young, becoming darker or blackish brown with inconspicuous rays when mature (Johnson and Clarke, 1983).

The left valve has two triangular pseudocardinal teeth, with the larger in front of the smaller. The hinge line is short and narrow, with two straight, elevated, compressed, obliquely descending lateral teeth. Two parallel pseudocardinals are found on the right valve: the posterior one is triangular and serrate, while the more anterior one is low and quite vestigial. There is one lateral tooth on the right valve and a thick, low, interdental projection, which articulates with a shallow cavity in the left valve. Beak cavities are rather shallow, and although the anterior adductor muscle scars are well inpressed, the posterior ones are faint. The pallial line is impressed anteriorly, and faint posteriorly. The nacre is yellowish or pinkish anteriorly, bluish white and iridescent posteriorly (Johnson and Clarke, 1983).

Diagnostic Characteristics: Short spines (up to 5 mm long) found on most specimens (Adams et al., 1990).
Reproduction Comments: This species is probably a tachytictic reproducer with gravid famales present at some time from April through August (see Adams et al., 1990). It has been suggested that Elliptio steinstansana and Pleurobema collina may be closely related. If such is the case, it is probable that E. steinstansana and P. collina have similar reproductive biology and utilize similar fish hosts (Clarke and Neves, 1984). Recently Eads et al. (2008) determined that the following fish species facilitated transformation into teh juvenile stage and were determined to be hosts: Nocomis leptocephalus (Bluehead chub), Lythrurus matutinus (pinewood shiner), Cyprinella analostana (satinfin shiner), and Luxilus albeolus (white shiner).
Ecology Comments: There is no information presently available on the life history of the species. It is sometimes found in association with other unionid species, including Leptodea ochracea and Elliptio complanata (Clarke, 1983). Refer to the General Freshwater Mussel ESA for general biology-ecology of mussels.
Habitat Type: Freshwater
Non-Migrant: Y
Locally Migrant: N
Long Distance Migrant: N
Riverine Habitat(s): MEDIUM RIVER, Moderate gradient, Riffle
Special Habitat Factors: Benthic
Habitat Comments: This species is found in rivers and large creeks. It occurs in relatively fast-flowing, well-oxygenated water. The preferred habitat is unconsolidated beds of coarse sand and pea gravel below consolidated beds of similar substrates (often mixed with cobble and boulder). Less often, this species can be found in the consolidated beds or in finer substrates. Best populations are closely associated with landscapes dominated by woodland, stable streambanks maintained by extensive root systems, limited point and nonpoint sources of pollution, very high overall aquatic biodiversity, and high abundances of various aquatic taxa, including insects, snails, other mussel species, and fish (USFWS, 1992). Presently, the best populations are found in or above the Fall Line, where relief is sufficient to maintain relatively silt-free substrates (North Carolina Wildlife Resources Commission, 1998).
Length: 6 centimeters
Economic Attributes Not yet assessed
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Management Summary
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Stewardship Overview: This species was listed as federally endangered in the U.S. in 1985 and a recovery plan drafted (USFWS, 1992). Management for this mussel should include 1. Improving water quality in the Tar River, including a moratorium on further impoundments. 2. Monitor and regulate land use upstream to minimize erosion of silt to rivers. 3. Research is necessary to determine the species life history and identify its fish host. 4. Enhancement of the current population in the Tar River by artificial propagation. A suitable site(s) for transplant of some of the newly propagated individuals, which includes host fish, should be located.
Restoration Potential: Because of the recent population decline and its present small size, it is believed that the mussel will soon be extirpated without human intervention (Clarke, pers. comm; Biggins, pers. comm.). Recovery suggestions include artificial propagation and/or transplantation to other habitats.
Preserve Selection & Design Considerations: The size of river habitat necessary to maintain the species is uncertain, particularly because the fish host (and therefore its habitat requirements) are unknown. Probably the entire length of river containing the last known individuals (Clarke, 1983) should be protected.
Management Requirements: Needs include maintenance of good water quality in the Tar River, with no further impoundments in areas of the river where the mussels have been located. Clarke (1983) feels that it is necessary to transplant mussels to a habitat where CORBICULA is not found, although a competitive mechanism has not been identified. Because of its rarity and uniqueness, the Tar River spiny mussel may be particularly attractive to shell collectors. For this reason, the U.S. Fish and Wildlife Service has not made a Critical Habitat designation, although they will be evaluating environmental impacts of any proposed construction or dredging operation (Endangered Species Technical Bulletin, 1985). There are currently no state standards to limit residual chlorine levels of waste water effluents, except when the receiving waters are known trout streams. The North Carolina Wildlife Resources Commission would be willing to suggest setting/changing water quality standards in the Tar River, if they could get some assistance in compiling information to make a case (Contact: Debbie Paul, North Carolina Wildlife Resources Commission.). The Endangered and Non-game Wildlife program is presently spending their funding on other projects, and although the spiny mussel is on their list of priorities, money will probably not be available in the near future (Paul, pers. comm.).

Water quality standards for any effluents discharged in the area should be maintained through close monitoring. Residual chlorine levels of the effluent from the Rocky Mount waste water treatment plant should be sharply reduced, and closely monitored. Construction and agricultural practices in the watershed should be studied in an effort to reduce siltation to the river.

Monitoring Requirements: Until recovery plans are underway, the population must be monitored.

Past searches have been made by wading in the river during periods of low flow, making visual searches in locations where the mussel has been observed in the past. Clarke's (1983) report represents his best estimate of population size based on the sites in which he collected, although he did not survey areas of deeper water or sites which were otherwise inaccessible.

Refer to the General Freshwater Mussel ESA.

Management Research Needs: 1. Determine life history, including the identification of the host fish. This would require collection of gravid female mussels, which would then be taken into the laboratory to recover glochidia. Potential fish host species would also be collected and placed in aquaria containing glochidia. Successful encystment by glochidia on a fish would indicate that it was an appropriate host. 2. Determine the specific ecological requirements. 3. Determine whether the Asiatic clam is having a negative impact on the Tar River spiny mussel. Because of the small remaining population of the spiny mussel, it may not be appropriate to conduct a competition experiment with this species, although a surrogate could be used.
Biological Research Needs: The long-term impacts to aquatic ecosystems from implemented silvicultural and agricultural best management practices need to be determined.
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: 15Sep2008
NatureServe Conservation Status Factors Author: Cordeiro, J. (2008); Alderman, J. (1998)
Management Information Edition Date: 01Aug1986
Management Information Edition Author: Lauritsen, Diane.
Element Ecology & Life History Edition Date: 15Sep2008
Element Ecology & Life History Author(s): Cordeiro, J. (2008); LAURITSEN, D. (1991)

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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  • Adams, W.F., J.M. Alderman, R.G. Biggins, A.G. Gerberich, E.P. Keferl, H.J. Porter, and A.S. van Davender (eds.) 1990. A report on the conservation status of North Carolina's freshwater and terrestrial molluscan fauna. Report to NCWRC by Scientific Council on Freshwater and Terrestrial Mollusks. 246 pp.

  • Clarke, A.H. 1983. Status survey of the Tar River Spiny Mussel. Report to the U.S. Fish and Wildlife Service, Asheville, North Carolina. Contract No. 14-16-0004-82-014.

  • Clarke, A.H. 1984. Status survey of the James River spiny mussel, Canthyria collina (Conrad), in the James River drainage system. (Contract #4107). Final report to VPI & SU, Office of Sponsored Programs, Blacksburg, Virginia.

  • Eads, C.B., R. Nichols, C.J. Woods, and J.F. Levine. 2008. Captive spawning and host determination of the federally endangered Tar River spinymussel (Elliptio steinstansana). Ellipsaria, 10(2): 7-8.

  • Endangered Species Technical Bulletin. 1985. Vol. 2. No. 11. Wildland Management Center, School of Natural Resources, University of Michigan, Ann Arbor, Michigan.

  • Fuller, S.L.H. 1977. Freshwater and terrestrial mollusks. Pages 143-194 in J. E. Cooper, S. S. Robinson, and J. B. Funderburg (eds.). Endangered and Threatened Plants and Animals of North Carolina. North Carolina State Museaum of Natural History, Raleigh, North Carolina.

  • Horne, F.R. and S. McIntosh. 1979. Factors influencing distribution of mussels in the Blanco River of central Texas. The Nautilus 94(4):119-133.

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

  • Johnson, R.I. and A.H. Clarke. 1983. A new spiny mussel, Elliptio (Canthyria) steinstansana (Bivalvia: Unionidae), from the Tar River, North Carolina. Occasional Papers on Mollusks, Museum of Comparative Zoology, Harvard University, 4(61): 289-298.

  • Lauritsen, D.D. 1982. Biological interactions between mussels and the Asiatic clam Corbicula fluminea in Lake Waccamaw, NC (abstract). North American Benthological Society Annual Meeting, Ann Arbor, Michigan.

  • Lefevre, G. and W.T. Curtis. 1912. Studies on the reproduction and artificial propogation of fresh-water mussels. Bulletin of the Bureau of Fisheries 30:102-201.

  • Moyle, P. and J. Bacon. 1969. Distribution and abundance of molluscs in a fresh water environment. Journal of the Minnesota Academy of Science 35(2/3):82-85.

  • Neves, R.J. 1993. A state-of-the unionid address. Pages 1-10 in K.S. Cummings, A.C. Buchanan, and L.M. Koch (eds.) Conservation and management of freshwater mussels. Proceedings of a UMRCC symposium, October 1992, St. Louis, Missouri. Upper Mississippi River Conservation Committee, Rock Island, Illinois.

  • Neves, R.J. and J.C. Widlak. 1987. Habitat ecology of juvenile freshwater mussels (Bivalvia: Unionidae) in a headwater stream in Virginia. American Malacological Bulletin, 5: 1-7.

  • North Carolina Division of Environmental Management (NCDEM). 1986. STORET data on the Tar River, North Carolina.

  • North Carolina Wildlife Resources Commission. Database containing location information and habitat characteristics of freshwater mussels.

  • Strayer, D. 1983. The effects of surface geology and stream size on freshwater mussel (Bivalvia, Unionidae) distribution in southeastern Michigan, U.S.A. Freshwater Biology 13:253-264.

  • Strayer, D.L. 1999a. Use of flow refuges by unionid mussels in rivers. Journal of the North American Benthological Society 18(4):468-476.

  • Strayer, D.L. and J. Ralley. 1993. Microhabitat use by an assemblage of stream-dwelling unionaceans (Bivalvia) including two rare species of Alasmidonta. Journal of the North American Benthological Society 12(3):247-258.

  • 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.

  • U.S. Fish and Wildlife Service (USFWS). 1992. Revised Tar River spinymussel recovery plan. U.S. Fish and Widlife Service, Atlanta, Georgia. 34 pp.

  • Van der Schalie, H. 1938a. The naiad fauna of the Huron River in southeastern Michigan. Miscellaneous Publication of the Museum of Zoology, University of Michigan 40:7-78.

  • Watters, G.T. 1992a. Unionids, fishes, and the species-area curve. Journal of Biogeography 19:481-490.

  • Williams, J.D., M.L. Warren, Jr., K.S. Cummings, J.L. Harris, and R.J. Neves. 1993b. Conservation status of freshwater mussels of the United States and Canada. Fisheries 18(9): 6-22.

References for Watershed Distribution Map
  • Bogan, A.E. 2002. Workbook and key to the freshwater bivalves of North Carolina. North Carolina Museum of Natural Sciences: Raleigh, North Carolina. 101 pp.

  • LeGrand, H.E., Jr., S.P. Hall, S.E. McRae, and J.T. Finnegan. 2006. Natural Heritage Program List of the Rare Animal Species of North Carolina. North Carolina Natural Heritage Program, Raleigh, North Carolina. 104 pp.

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