Villosa perpurpurea - (I. Lea, 1861)
Purple Bean
Taxonomic Status: Accepted
Related ITIS Name(s): Villosa perpurpurea (I. Lea, 1861) (TSN 80219)
Unique Identifier: ELEMENT_GLOBAL.2.108413
Element Code: IMBIV47110
Informal Taxonomy: Animals, Invertebrates - Mollusks - Freshwater Mussels
Image 11986

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Kingdom Phylum Class Order Family Genus
Animalia Mollusca Bivalvia Unionoida Unionidae Villosa
Genus Size: C - Small genus (6-20 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: Villosa perpurpurea
Taxonomic Comments: Taxonomy of the genus Villosa is uncertain. Villosa trabalis and Villosa perpurpurea are very similar. They are both treated as the same species by (Bogan and Parmalee, 1983). Both are regarded as good species by the American Fisheries Society list (Turgeon et al, 1998). Their relationship to each other and the genus Villosa remains unclear (Bogan and Parmalee, 1983). Simpson (1914) and Ortmann (1915) considered Villosa perpurpurea and Villosa trabalis to represent distinct species. However, Ortmann (1918) expressed doubts concerning their separation and later considered them to be varieties of the same species ("Micromya" trabalis in Ortmann, 1925). Recently, Hoggarth (1988) demonstrated that the glochidia of V. perpurpurea and V. trabalis are shaped differently, indicating that the two taxa are separate species. Revision of the genus Villosa may indicate that neither of these two species are actually members of that genus.
Conservation Status
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NatureServe Status

Global Status: G1
Global Status Last Reviewed: 24May2007
Global Status Last Changed: 28Oct2003
Rounded Global Status: G1 - Critically Imperiled
Reasons: The historical distribution was limited to the upper Tennessee River basin above the confluence of the Clinch River. Much of its former habitat has been inundated by resevoirs caused by dams or rendered uninhabitable by pollution from mining operations, and municipal, industrial, and agricultural sources. The species remains in only a select few sites with only one or two considered viable.
Nation: United States
National Status: N1 (15Dec1998)

U.S. & Canada State/Province Status
United States Tennessee (S1), Virginia (S1)

Other Statuses

U.S. Endangered Species Act (USESA): LE: Listed endangered (10Jan1997)
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: 250-1000 square km (about 100-400 square miles)
Range Extent Comments: Historically, this species was distributed throughout the upper Tennessee River system above the confluence with the Clinch River in 18 localities in southwestern Virginia and northeastern Tennessee (USFWS, 2003; 2004). Presently occurs in portions of the Clinch River, Indian Creek, Copper Creek, and Beech Creek in northeastern Tennessee and southwestern Virginia. It has been extirpated from the Powell, North Fork Holston, Emory Rivers and a portion of the upper Clinch River (USFWS, 1998; 2004).

Area of Occupancy: 126-2,500 4-km2 grid cells
Area of Occupancy Comments: Recently, critical habitat was designated for the Obed River (40 river km occupied, 0 river km unoccupied habitat) in Tennessee, Powell River (0 river km occupied, 154 river km unoccupied habitat) in Tennessee and Virginia, Clinch River (242 river km occupied, 0 river km unoccupied habitat) in Tennessee and Virginia, Copper Creek (21 river km occupied, 0 river km unoccupied habitat) in Virginia, Indian Creek (4 river km occupied, 0 river km unoccupied habitat) in Virginia, and Beech Creek (23 river km occupied, 0 river km unoccupied habitat) in Tennessee (USFWS, 2004).

Number of Occurrences: 1 - 5
Number of Occurrences Comments: Sporadic occurrences exist in five tributaries in Virginia and Tennessee in the Clinch River and Copper Creek (Tazewell, Russell, and Scott Counties, Virginia) (Fraley and Ahlstedt, 2000; Hanlon et al., 2004), Indian Creek (Tazewell County, Virginia), Obed River (Cumberland County, Tennessee), and Beech Creek (Hawkins County, Tennessee) (USFWS, 2003; 2004; Parmalee and Bogan, 1998; Jones et al., 2001). Most historical populations are extirpated and continued viability of extant occurrences are questionable with the exception of possibly the upper Clinch River in a short stretch.

Population Size: 50 - 1000 individuals
Population Size Comments: Currently all populations are small. In the Clinch River densities were calculated at 0.11 per square foot when sampled in both 1979 and 1988 (over 11-14 sites) but no specimens were taken in 1994 (Ahlstedt and Tuberville, 1997).

Number of Occurrences with Good Viability/Integrity: Very few (1-3)
Viability/Integrity Comments: Barr et al. (1994) determined (based on 1981 survey data) that viable populations exist in Copper Creek, Virginia. Populations with good viability include Beech Creek (Hawkins County, Tennessee), and the Clinch River/Indian Creek (Tazewell County, Virginia) prior to a 1998 chemical spil (USFWS, 2003; 2004).

Overall Threat Impact: Very high - high
Overall Threat Impact Comments: Much of the information below is derived from and expanded upon in USFWS (2004):
The greatest threat to this species in the Cumberlandian Region is habitat alteration. Principal causes include impoundments, channelization, pollution, and sedimentation that have altered or eliminated those habitats that are essential to the long-term viability of many riverine mussel populations. Impoundments result in the elimination of riffle and shoal habitats, disruption of a river's ecological processes, elimination of current and the covering of rocky and sand substrates by fine sediments, and alteration of downstream water quality and riverine habitat. Daily discharge fluctuations, bank sloughing, seasonal oxygen deficiencies, cold-water releases, turbulence, high silt loads, and altered host fish distribution have contributed to limited mussel recruitment and skewed demographics. Impoundments, as barriers to dispersal, contribute to the loss of local populations by blocking postextirpation recolonization. Population losses due to impoundments have probably contributed more to the decline of the Cumberlandian combshell, oyster mussel, and rough rabbitsfoot and most other Cumberlandian Region mussels than any other single factor (as the Cumberland elktoe and purple bean generally inhabit smaller rivers, impoundments have had less of an impact on them, although the impact is still significant).

The entire length of the Tennessee River and much of the Cumberland River is maintained as a navigation channel with a series of locks and dams--nine on the Tennessee River and four on the Cumberland River. Channel maintenance activities continue to cause substrate instability and alteration in these rivers and may serve to diminish what habitat remains for the recovery of riverine species.

Heavy metal-rich drainage from coal mining and associated sedimentation have adversely impacted many stream reaches, destroying mussel beds and preventing natural recolonization. Acid mine runoff may be having local impacts on the recruitment of, particularly, the Cumberland elktoe, since most of its range is within watersheds where coal mining is still occurring. Impacts associated with coal mining activities have particularly altered upper Cumberland River system streams with diverse historical mussel faunas and have been implicated in the decline of Epioblasma species, especially in the Big South Fork. Strip mining continues to threaten mussels in coal field drainages of the Cumberland Plateau with increased sedimentation loads and acid mine drainage, including Cumberland elktoe and Cumberlandian combshell populations. The Marsh Creek population of the Cumberland elktoe has also been adversely affected and is still threatened by potential spills from oil exploration activities. Coal mining activities also occur in portions of the upper Powell and Clinch River systems, primarily in Virginia. Polycyclic aromatic compounds (PAHs) are indicative of coal fines in the bottom sediments of streams. Known to be toxic to mussels and fishes, PAHs have been found at relatively high levels in the upper portions of the Clinch and Powell Rivers in Virginia.

In-stream gravel mining has been implicated in the destruction of mussel populations. Negative impacts include riparian forest clearing (e.g., mine site establishment, access roads, lowered floodplain water table); stream channel modifications (e.g., geomorphic instability, altered habitat, disrupted flow patterns [including lowered elevation of stream flow], sediment transport); water quality modifications (e.g., increased turbidity, reduced light penetration, increased temperature); macroinvertebrate population changes (e.g., elimination, habitat disruption, increased sedimentation); and changes in fish populations (e.g., impacts to spawning and nursery habitat, food web disruptions). Gravel mining activities threaten the Cumberlandian combshell populations in the Powell River and in Buck Creek, the latter stream representing one of only two remaining populations of this species in the entire Cumberland River system. Mining activities on the Elk River may have played a role in the extirpation of the oyster mussel and Cumberlandian combshell from that river.

Contaminants contained in point and nonpoint discharges can degrade water and substrate quality and adversely impact, if not destroy, mussel populations. Although chemical spills and other point sources (e.g., ditch, swale, artificial channel, drainage pipe) of contaminants may directly result in mussel mortality, widespread decreases in density and diversity may result, in part, from the subtle, pervasive effects of chronic low-level contamination. Mussels appear to be among the most intolerant organisms to heavy metals, several of which are lethal, even at relatively low levels. Among other pollutants, ammonia has been shown to be lethal to mussels. Common contaminants associated with households and urban areas, particularly those from industrial and municipal effluents, may include heavy metals, ammonia, chlorine, phosphorus, and numerous organic compounds. Nonpoint-source runoff from urban areas tends to have the highest levels of many pollutants, such as phosphorus and ammonia, when compared to other catchments. Agricultural sources of chemical contaminants are considerable and include two broad categories--nutrients and pesticides. Nutrient enrichment generally occurs as a result of runoff from livestock farms and feedlots and from fertilizers used on row crops. Pesticide runoff that commonly ends up in streams may have effects (based on studies with laboratory-tested mussels) that are particularly profound.

Numerous Cumberlandian Region streams have experienced mussel kills from toxic chemical spills and other causes. The high number of jeopardized species in the upper Tennessee River system make accidental spills a particular concern to conservationists and resource managers.

Sedimentation, including siltation runoff, has been implicated as the number one factor in water quality impairment in the United States. Specific biological impacts on mussels from excessive sediment include reduced feeding and respiratory efficiency from clogged gills, disrupted metabolic processes, reduced growth rates, increased substrate instability, limited burrowing activity, and physical smothering. Host fish/mussel interactions may be indirectly impacted by changes in stream sediment regimes through three mechanisms: fish abundance, diversity, and reproduction reduced; impedes host fish attractant mechanisms; interfere with the ability of some species' adhesive conglutinates to adhere to rock particles. Waterborne sediment is produced by the erosion of stream banks, channels, plowed fields, unpaved roads, roadside ditches, upland gullies, and other soil disturbance sites. Agricultural activities produce the most significant amount of sediment that enters streams. Silvicultural sedimentation impacts are more the result of logging roads than the actual harvesting of timber.

Developmental activities associated with urbanization (e.g., highways, building construction, infrastructure creation, recreational facilities) may contribute significant amounts of sediment and other pollutants in quantities that may be detrimental to stream habitats. With development, watersheds become more impervious, resulting in increased storm-water runoff into streams and a doubling in annual flow rates in completely urbanized streams. Impervious surfaces may reduce sediment input into streams but result in channel instability by accelerating storm-water runoff, which increases bank erosion and bed scouring. Water withdrawals for agricultural irrigation and municipal and industrial water supplies are an increasing concern for all aquatic resources and are directly correlated with expanding human populations. This impact has the potential to be a particular problem for the Cumberland elktoe population in the Big South Fork system and the oyster mussel population in the Duck River.

The alien Asian clam (Corbicula flumminea) was first reported from the Cumberlandian Region around 1959. This species has been implicated as a competitor with native mussels for resources such as food, nutrients, and space, particularly as juveniles. Densities of Asian clams are sometimes heavy in Cumberlandian Region streams, making competition with populations of some of these five species likely. Paradoxically, large, seemingly healthy, populations of unionids may coexist with Asian clams. The invasion of the nonnative zebra mussel (Dreissena polymorpha) poses a threat to the mussel fauna of the Cumberlandian Region. Although zebra mussels are now in the Tennessee and Cumberland River systems, the extent to which they will impact native mussels is unknown. However, as zebra mussels are likely to reach higher densities in the main stems, large tributaries, and below infested reservoirs, native mussels in these areas will likely be more heavily impacted than mussels in smaller streams without upstream reservoirs. Mussel extinctions are expected as a result of the continued spread of zebra mussels in the Eastern United States. Other potential threats from alien species on native mussels include the black carp (Mylopharyngodon piceus), a native of China. If these species invade Cumberlandian Region streams, they could wreak havoc on already stressed native mussel populations. The round goby (Neogobius melanostomus) is another alien invader fish species released in the 1980s into the Great Lakes in ballast waters originating in southeastern Europe. The arrival of round gobies may therefore have important indirect effects on unionid communities through negative impacts to their host fishes.

The overall threat to this species, posed by piscine and invertebrate predators, in most instances is not thought to be significant. Although parasitism is not thought to be a significant problem in mussels, excessive trematode infestations in their gonads have been implicated in inducing mussel senescence. The harvest of Cumberlandian Region mussel species for commercial purposes is well documented (Anthony and Downing, 2001). It is doubtful, however, that this species has ever been overly exploited for pearling, pearl buttons, cultured pearls, or any other exploitative activity (USFWS, 2004).

Short-term Trend: Decline of >70%
Short-term Trend Comments: Number of occurrence and abundance have declined dramatically. This trend has continued over the past ten years. The species is extirpated from Powell River, Emory River, North Fork Beech Creek, and North Fork Holston Rivers (USFWS, 2003; 2004; Parmalee and Bogan, 1998).

Long-term Trend: Decline of 70-90%

Intrinsic Vulnerability: Highly to moderately vulnerable.
Intrinsic Vulnerability Comments: Without the level of genetic interchange these species experienced historically, many small and isolated populations that are now comprised predominantly of adult specimens may be slowly dying out due to various factors. This may, in part, account for the relatively recent demise of numerous tributary populations. Even given the improbable absence of the impacts from current and existing threats, smaller isolated populations of this species may be lost to the devastating consequences of below-threshold effective population size (EPS). Once-sizable populations of many Cumberlandian mussel species occurred throughout significant portions of the main stems of the large rivers and tributary systems comprising the Cumberlandian Region. This was particularly true for the Cumberlandian combshell and oyster mussel. Historically, there were no natural absolute barriers to genetic interchange among their tributary subpopulations and those of their host fishes (with the notable exception of Cumberland Falls. Without the level of genetic interchange these species experienced historically (because of anthropogenic threats), many small and isolated populations that are now comprised predominantly of adult specimens may be slowly dying out due to various factors (USFWS, 2004).

Environmental Specificity: Narrow. Specialist or community with key requirements common.
Environmental Specificity Comments: The habitat is creeks to medium-sized rivers and occasionally headwaters. The mussel is generally associated with riffles, but may be out of direct current, in pools, or flats in streams with season flows in riffles. It is not found in backwaters. Substrates range from silty-sand to boulder-sized rocks. Currents vary from fast to slight and water depths are typically shallow (< 0.5 m). Inhabits small headwater streams to medium-sized rivers in moderate to fast-flowing riffles with sand, gravel, or cobble substrates and rarely occurs in pools or slack water. Sometimes found out of the main current adjacent to water-willow beds under flat rocks (FWS, 2003; USFWS, 2003).

Other NatureServe Conservation Status Information

Inventory Needs: Condition of populations at known occurrences should be assessed and periodically monitored. Surveys for additional occurrences should continue.

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. Watershed management with particular emphasis on control of acid coal mine run-off and agricultural induced siltation is critical. Critical habitat proposed (USFWS, 2003; 2004).

Distribution
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Global Range: (250-1000 square km (about 100-400 square miles)) Historically, this species was distributed throughout the upper Tennessee River system above the confluence with the Clinch River in 18 localities in southwestern Virginia and northeastern Tennessee (USFWS, 2003; 2004). Presently occurs in portions of the Clinch River, Indian Creek, Copper Creek, and Beech Creek in northeastern Tennessee and southwestern Virginia. It has been extirpated from the Powell, North Fork Holston, Emory Rivers and a portion of the upper Clinch River (USFWS, 1998; 2004).

U.S. States and Canadian Provinces
Color legend for Distribution Map
Endemism: endemic to a single nation

U.S. & Canada State/Province Distribution
United States TN, VA

Range Map
No map available.


U.S. Distribution by County Help
State County Name (FIPS Code)
TN Cumberland (47035), Hancock (47067), Hawkins (47073), Morgan (47129), Roane (47145)*, Sullivan (47163)*
VA Lee (51105)*, Russell (51167)*, Scott (51169), Tazewell (51185), Washington (51191)*
* Extirpated/possibly extirpated
U.S. Distribution by Watershed Help
Watershed Region Help Watershed Name (Watershed Code)
06 North Fork Holston (06010101)+*, Holston (06010104)+, Upper Clinch (06010205)+, Powell (06010206)+*, Emory (06010208)+
+ Natural heritage record(s) exist for this watershed
* Extirpated/possibly extirpated
Ecology & Life History
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Basic Description: A freshwater mussel with a dark brown to black shell with numerous closely spaced fine green rays.
General Description: Shell small to medium-sized, subrhombodial to suboval, compressed to barely inflated, relatively thin to solid but thinner posteriorly; anterior end rounded; ventral margin slightly convex to flat or slightly concave posteriorly; posterio-ventral junction bluntly pointed to biangulate; posteriormargin oblique, subtruncated, relatively flat; dorsal margin straight to slightly curved; anterio-dorsal junction rounded to slightly angular, beaks small, low, barely projecting above dorsal margin, sculpted above a few double-looped ridges, positioned in the anterior 30% of shell length; posterior ridge low, faintly double, narrow radial furrow immediately dorsal to ridge, posterior slope concave; periostracum tawny with numerous closely spaced fine green wavy rays most prominent posteriorly, more often periostracum is dark brown to black, annual growth increments well marked. Pseudocardinal teeth triangular, heavy, somewhat roughened, double in left valve, single in right with small lamellae developed adjacent to contiguous sulci; interdentum short, moderately developed; lateral teeth relatively short and straight, double in left valve, single in right; beak cavity developed but rather shallow; anterior muscle scars impressed, small, distinct; pallial line impressed, lighter posteriorly; posterior muscle scars impressed, confluent; nacre purple, iridescent posteriorly, but may fade rapidly to white in dead specimens.
Diagnostic Characteristics: Villosa perpurpurea most closely resembles Villosa trabalis. The most obvious difference is the purple nacre of the former in comparison to the white nacre of the latter. However, this character is somewhat variable as noted by Ortmann (1925) and the purple color may fade to white fairly rapidly in dead specimens. With regards to other shell characters, V. perpurpureatends to be more compressed, thinner, slightly broader, the beak is less developed, and the emargination of the ventral margin in female shells is not as pronounced. The base color of the periostracum in V. trabalis is greenish. Simpson (1914) noted that V. perpurpurea was "less exaggerated in its particular characters than V. trabalis". The glochidia of the two species are also shaped differently (Hoggarth, 1988). Viollosa vanuxemii (Lea, 1838) may be sympatric with V. perpurpurea, but it tends to be a bit larger. Its nacre is shiny purple but tends to be reddish or brownish in the area of the beak cavity and be lighter around the periphery of the shell, the base color of the periostracum is brown, and raying is rather obscure. Female shells are strongly truncated, often with a distinct notch just ventral to the terminus of the posterior ridge which runs approximately parallel to the dorsal margin. Height: 27mm.
Reproduction Comments: Gravid females have been observed in January and February, indicating that this species is a long-term brooder. Watson and Neves (1996; 1997) report the following fish as suitable glochidial hosts: Cottus carolinae (sculpin), Etheostoma blennioides (greenside darter), Etheostoma rufilineatum (redline darter), and Etheostoma flabellare (fantail darter). Transformation took from 11 to 25 days at 70.7 degrees F (FWS, 2003; USFWS, 2003). Schultz and Marbain (1998) also confirmed Etheostoma flabellare (fantail darter), Etheostoma kennicotti (stripetail darter), Etheostoma obeyense (barcheek darter), Etheostoma virgatum (striped darter), and Cottus carolinae and/or Cottus bairdi (sculpin) as glochidial hosts.
Ecology Comments: No studies have considered this species specifically. Ahlstedt (1986) and Jenkinson and Ahlstedt (1988) have presented density estimates of represent populations which reflect the decline in population structure.
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): CREEK, High gradient, Low gradient, MEDIUM RIVER, Riffle
Special Habitat Factors: Benthic
Habitat Comments: The habitat is creeks to medium-sized rivers and occasionally headwaters. The mussel is generally associated with riffles, but may be out of direct current, in pools, or flats in streams with season flows in riffles. It is not found in backwaters. Substrates range from silty-sand to boulder-sized rocks. Currents vary from fast to slight and water depths are typically shallow (< 0.5 m). Inhabits small headwater streams to medium-sized rivers in moderate to fast-flowing riffles with sand, gravel, or cobble substrates and rarely occurs in pools or slack water. Sometimes found out of the main current adjacent to water-willow beds under flat rocks (FWS, 2003; USFWS, 2003).
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: 7.5 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 1997 and a recovery plan published (USFWS, 2004) with recovery objective: delisting.

Recently, critical habitat was designated for the Obed River (40 river km occupied, 0 river km unoccupied habitat) in Tennessee, Powell River (0 river km occupied, 154 river km unoccupied habitat) in Tennessee and Virginia, Clinch River (242 river km occupied, 0 river km unoccupied habitat) in Tennessee and Virginia, Copper Creek (21 river km occupied, 0 river km unoccupied habitat) in Virginia, Indian Creek (4 river km occupied, 0 river km unoccupied habitat) in Virginia, and Beech Creek (23 river km occupied, 0 river km unoccupied habitat) in Tennessee (USFWS, 2004).

Recovery Strategy: The preservation of extant populations and the occupied habitats of these five species is the most immediate and important recovery priority for these mussels. Preservation and protection of these populations will be achieved by continuing to use existing regulatory mechanisms, establishing partnerships with various stakeholders, using best management practices, and minimizing or eliminating threats to the species. Each extant population must also be viable to achieve recovery. Unless a previously unknown population is found, other viable populations within the historic range of each of the five species must be reestablished and protected to effect recovery. Reestablishing new viable populations will require close coordination with and concurrence of the State(s) involved and with other partners that have interests at any potential reintroduction sites. Additional research into the life history and ecological requirements of these mussels as defined in this plan will help formulate the biological information necessary for the preservation of existing or reestablishment and maintenance of other viable populations. Knowledge of the effective population size is particularly critical for determining the size and demographic makeup of a viable population for these species. Due to the rarity of extant populations, propagation of laboratory or hatchery-reared progeny is the most logical means of providing individuals for the establishment of new populations. Facilities that attempt to propagate these mussels should follow the Service's established controlled propagation policy. Priorities for recovery efforts for the five species via propagation should be to develop propagation technology, augment and expand the ranges of extant populations to ensure their viability, and reestablish viable populations in other streams within their historical range that have suitable habitat and water quality. Pursuing and implementing these efforts will enable the recovery of the five species.
Recovery Criteria: Downlisting from endangered to threatened status will occur when the following criteria are met for the protection of extant stream populations, discovery of currently unknown stream populations, and/or reestablishment of historical stream populations: (1) five streams with distinct viable populations of the Cumberland elktoe, six streams with distinct viable populations of the oyster mussel and Cumberlandian combshell, four streams with distinct viable populations of the purple bean, and three streams with distinct viable populations of the rough rabbitsfoot have been established; (2) one distinct naturally reproduced year class exists within each of the viable populations; (3) research studies of the mussels' biological and ecological requirements have been completed and any required recovery measures developed and implemented from these studies are beginning to be successful, as evidenced by an increase in population density of approximately 20 percent and/or an increase in the length of the river reach of approximately 10 percent inhabited by the species as determined through biennial monitoring; (4) no foreseeable threats exist that would likely impact the survival of the species over a significant portion of their ranges; (5) within larger streams the species are distributed over a long enough reach that a single catastrophic event is not likely to eliminate or significantly reduce the entire population in that stream to a status of nonviable; and (6) biennial monitoring of the five species yields the results outlined in criterion (1) above over a 10-year period.
Actions Needed:
1. Utilize existing legislation/regulations to protect current and newly discovered populations.
2. Determine the species' life history requirements and threats and reduce or alleviate those threats which threaten the species.
3. Develop and use an information/education program to solicit the assistance of local landowners, communities, and others to recover the species.
4. Search for additional populations, and through propagation activities, pursue augmentations or reintroductions in order to establish viable populations.
5. Conduct anatomical and molecular genetic analysis of the species to determine the potential occurrence of species complexes or hidden biodiversity.
6. Develop and implement a monitoring program, and annually assess the recovery program where needed.

Biological Research Needs: Determine the habitat preferences and environmental tolerances, sensitivity to various pollutants, siltation, and glochidial hosts/reproductive biology should be determined. Identify potential reintroduction sites.
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: 24May2007
NatureServe Conservation Status Factors Author: Cordeiro, J.
Management Information Edition Date: 24May2007
Management Information Edition Author: Cordeiro, J.
Element Ecology & Life History Edition Date: 24May2007
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. 1982. The molluscan fauna of Copper Creek (Clinch River system) in Southwestern Virginia. Bulletin of the American Malcological Union, 1981: 4-6.

  • 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. and J.M. Tuberville. 1997. Quantitative reassessment of the freshwater mussel fauna in the Clinch and Powell rivers, Tennessee and Virginia. Pages 72-97 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, 16-18 October 1995, St. Louis, Missouri. Upper Mississippi River Conservation Committee, Rock Island, Illinois.

  • Ahlstedt, Steven A. 1986. Activity 1: Mussel Distribution Surveys. Cumberlandian Mollusk Conservation Program. TVA.

  • Anthony, J.L. and J.A. Downing. 2001. Exploitation trajectory of a declining fauna: a century of freshwater mussel fisheries in North America. Canadian Journal of Fisheries and Aquatic Sciences, 58: 2071-2090.

  • 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.

  • Fraley, S.J. and S.A. Ahlstedt. 2000. The recent decline of the native mussels (Unionidae) of Copper Creek, Russell and Scott Counties, Virginia. Pages 189-195 in R.A. Tankersley, D.I. Warmolts, G.T. Watters, B.J. Armitage, P.D. Johnson, and R.S. Butler (eds.). Freshwater Mollusk Symposia Proceedings. Ohio Biological Survey, Columbus, Ohio. 274 pp.

  • Gordon, M.E. and J.B. Layzer. 1989. Mussels (Bivalvia: Unionoidea) of the Cumberland River review of life histories and ecological relationships. U.S. Fish and Wildlife Service Biological Report, 89(15): 1-99.

  • Hoggarth, M.A. 1988. The use of glochidia in the systematics of the Unionidae (Mollusca:Bivalvia). Ph.D. dissertation, Ohio State University, Columbus, OH. 340pp.

  • 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.

  • Jenkinson, J.J. and S.A. Ahlsedt. 1988a. Quantitative reassessment of the freshwater mussel fauna in the Clinch River, Tennessee and Virginia. Tennessee Valley Authority, Knoxville, Tennessee. 28 pp.

  • Jones, J.W., R.J. Neves, M.A. Patterson, C.R. Good, and A. DiVittorio. 2001. A status survey of freshwater mussel populations in the upper Clinch River, Tazewell County, Virginia. Banisteria, 17: 20-30.

  • 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.

  • Lopez, G.R. and I.J. Holopainen. 1987. Interstitial suspension-feeding by Pisidium spp. (Pisidiiae: Bivalvia): a new guild in lentic benthos? American Malacological Bulletin, 5: 21-29.

  • 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.

  • Ortmann, A.E. 1915. Studies in naiades. The Nautilus, 29: 63-67.

  • Ortmann, A.E. 1918a. The nayades (freshwater mussels) of the Upper Tennessee Drainage. Proceedings of the American Philosophical Society 57: 577-580.

  • Ortmann, A.E. 1925. The naiad fauna of the Tennessee River system below Walden Gorge. The American Midland Naturalist, 9(7): 321-371.

  • Parmalee, P.W. and A.E. Bogan. 1998. The Freshwater Mussels of Tennessee. University of Tennessee Press: Knoxville, Tennessee. 328 pp.

  • Schulz, C. and K. Marbain. 1998. Hosts species for rare freshwater mussels in Virginia. Triannual Unionid Report, 15: 32-38.

  • Simpson, C.T. 1914. A Descriptive Catalogue of the Naiades or Pearly Fresh-water Mussels. Bryant Walker: Detroit, Michigan. 1540 pp.

  • 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). 1997. Determination of Endangered Status for the Cumberland Elktoe, Oyster Mussel, Cumberlandian Combshell, Purple Bean, and Rough Rabbitsfoot. Final rule. Federal Register, 62(7): 1647-1658.

  • U.S. Fish and Wildlife Service (USFWS). 1998. Cumberland elktoe (Alasmidontaq atropurpurea), oyster mussel (Epioblasma capsaeformis), Cumberlandian combshell (Epioblasma brevidens), purple bean (Villosa perpurpurea), and rough rabbitsfoot (Quadrula cylindrica strigillata): Technical Draft Recovery Plan. U.S. Fish and Wildlife Service: Asheville, North Carolina. 119 pp.

  • U.S. Fish and Wildlife Service (USFWS). 2003. Agency draft recovery plan for Cumberland elktoe, oyster mussel, Cumberlandian combshell, purple bean, and rough rabbitsfoot. R.S. Butler and R.C. Biggins, eds. U.S. Fish and Wildlife Service, Atlanta, Georgia. 176 pp.

  • U.S. Fish and Wildlife Service (USFWS). 2003. Endangered and Threatened Widlife and plants; proposed designation of critical habitat for five threatened mussels in the Tennessee and Cumberland River basins; proposed rule. Federal Register, 68(106): 33234-33282

  • U.S. Fish and Wildlife Service (USFWS). 2004. Endangered and Threatened Widlife and plants; designation of critical habitat for five endangered mussels in the Tennessee and Cumberland River basins; final rule. Federal Register, 69(168): 53135-53180.

  • U.S. Fish and Wildlife Service (USFWS). 2004. Recovery plan for Cumberland elktoe, oyster mussel, Cumberlandian combshell, purple bean, and rough rabbitsfoot. U.S. Fish and Widlife Service, Atlanta, Georgia. 168 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.

  • Watson, B.T. and R.J. Neves. 1996. Host fishes for two federally endangered species of mussels. Triannual Unionid Report, 10: 13.

  • Watson, B.T. and R.J. Neves. 1997. Life history characteristics of two federally endangered freshwater mussels (family Unionidae). Association of Southeastern Biologists Bulletin, 44(2): 110.

  • 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
  • Barr, W.C., S.A. Ahlstedt, G.D. Hickman, and D.M. Hill. 1993-1994. Cumberlandian mollusk conservation program. Activity 8: Analysis of macrofauna factors. Walkerana 7(17/18):159-224.

  • Hanlon, S.D., M.A. Petty, and R.J. Neves. 2009. Status of native freshwater mussels in Copper Creek, Virginia. Southeastern Naturalist 8(1):1-18.

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