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Pegias fabula 

Scope: Global
Language: English
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Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Mollusca Bivalvia Unionoida Unionidae

Scientific Name: Pegias fabula I. Lea, 1838
Common Name(s):
English Little Winged Pearly Mussel, Littlewing Pearlymussel
Taxonomic Notes: A list of synonyms for this species can be found on The MUSSEL project web site (Graf and Cummings 2011).

Assessment Information [top]

Red List Category & Criteria: Critically Endangered A2ace ver 3.1
Year Published: 2012
Date Assessed: 2012-06-07
Assessor(s): Cummings, K. & Cordeiro, J.
Reviewer(s): Bohm, M., Seddon, M. & Collen, B.
Contributor(s): Richman, N., Dyer, E., Soulsby, A.-M., Whitton, F., Kasthala, G., McGuinness, S., Milligan, HT, De Silva, R., Herdson, R., Thorley, J., McMillan, K., Collins, A., Duncan, C. & Offord, S.
Justification:
Pegias fabula has been assessed as Critically Endangered under criterion A2, as it is a declining regional endemic formerly known from 27 river systems with only very few widely disjunct populations remaining at fewer than a dozen sites. Habitat loss continues to threaten the species and some populations are no longer viable. This species has been extirpated from at least 80% of its range, experiencing severe fragmentation, inferring an 80% decline in the population over 25-50 years (J.Cordeiro pers.comm. 2011). Although the generation length is not known, the decline over 25-50 years is over 3 generation lengths using estimates from Haag and Rypel (2011). Furthermore, this species is currently considered to be declining and rare within known locations (A. Bogan pers. comm. 2010).
Previously published Red List assessments:

Geographic Range [top]

Range Description:Historically, this species was widespread but uncommon, known from 27 stream reaches in the Tennessee and Cumberland River systems in Alabama, North Carolina, Tennessee, Kentucky, and Virginia (USFWS 1989).

In Kentucky, the species was found in Rockcastle River, Laurel and Rockcastle Counties; Buck and Pitman Creeks, Pulaski County, and West Fork Red River, Todd County. Several sites are known from Virginia: South Fork Holston River, Washington County; Big Mocassin and Copper Creeks, Scott County.

Historically in Tennessee, it has been collected from the Collins River in Warren Co. (Athearn 1992); the Duck River; the Elk River at Estell Spring in Franklin Co.; Cane Creek in 1967, a tributary to the Caney Fork River (Athearn 1992); and Buck Creek and the Stones River in Rutherford Co.; all part of the Cumberland River drainage (Parmalee and Bogan 1998).

The species is probably extirpated from Alabama where it was historically found in Bluewater Creek, Lauderdale Co., and possibly other Tenenssee River tributaries (Mirarchi et al. 2004, USFWS 1989, Williams et al. 2008). Surveys in 1986 found this species in six short stream reaches of the Tennessee and Cumberland River basins. Over 55 potential or historic habitat areas were searched. The most recent record from Alabama was in the early 1900s.

It now believed to exist in only three sites in southeastern Kentucky in the Cumberland River drainage below Cumberland Falls (Cicerello and Schuster 2003), two sites in southeastern Virginia, and one site in central Tennessee (upper Caney Fork River drainage) (USFWS 1989, Parmalee and Bogan 1998).

Although the range of this species potentially still includes an area of over 40,000 km2, within this area it is confined to only a few locations (probably between 5 and 10 locations, as the species is known from around half a dozen populations; NatureServe 2009). Taking discontinuities in range into account, the extent of occurrence of this species is estimated as less than 1,000 km2, with an area of occupancy of less than 500 km2.
Countries occurrence:
Native:
United States (Alabama - Possibly Extinct, Kentucky, Tennessee, Virginia)
Additional data:
Estimated area of occupancy (AOO) - km2:100-500
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population:In North Carolina, Bogan (2002) cites the species from the Hiwassee and Little Tennessee River basins, but it is probably nearly extirpated there. LeGrand et al. (2006) also cite it from the Little Tennessee River in North Carolina and also formerly in Valley River in Cherokee Co. Its current range is limited to Horse Lick Creek, Jackson and Rockcastle County and Big and Little South Forks of the Cumberland River, McCreary and Wayne Counties, Kentucky. In Virginia, it is found in the Clinch River (Jones et al. 2001), Tazewell County, and North Fork Holston River, Smyth and Washington Counties. A recent survey of the North Fork Holston River in Virginia (Jones and Neves 2007) did not find this species, but other surveys did in previous years, although the last live specimen has not been collected in over 10 years. In Tennessee, it is found in Cane Creek, Van Buren County (Athearn 1992, USFWS 1989).

Few sites have much viability; exceptions include Horse Lick Creek and Big South Fork Cumberland River. All populations inhabit only short stream reaches within 1 to 5 miles of bridges and fords (USFWS 1989). Only 17 live mussels were found during extensive surveys in 1986. It is likely that each of the remaining half dozen or so populations, with the exception of Horse Lick Creek and Big South Fork Cumberland River, contain less than 500 individuals (USFWS 1989).

TRENDS:
This species has been extirpated from at least 80% of its range over the last 25 to 50 years, experiencing severe fragmentation. Furthermore, this species is currently considered to be declining and rare within known locations (A. Bogan pers. comm. 2010).
Current Population Trend:Decreasing
Additional data:
Population severely fragmented:No

Habitat and Ecology [top]

Habitat and Ecology:This is a species of creeks and small to medium rivers. Parmalee and Bogan (1998) give “clear, cool, high-gradient streams” as its habitat. However, Bluewater Creek, Lauderdale County, Alabama, from which most of the Alabama records came, has only a moderate gradient. This species is most common at the head of riffles, but also found in and below riffles on sand and gravel substrates with scattered cobbles. It also inhabits sand pockets between rocks, cobbles and boulders, and can be found underneath large rocks (Gordon and Layzer 1989). It is restricted to small, cool streams. It is usually found lying on top or partially buried in sand and fine gravel between cobble in only 6 to 10 inches of water (Bogan and Parmalee 1983, Stansbery 1976). It remains well-buried in the substrate or under large rocks for most of the year (Ahlstedt and Saylor 1996).

It is a long-term brooder, becoming gravid in September and presumably remaining gravid until the following spring or summer (Ortmann 1914, 1921). It has been observed lying exposed on the substrate surface in late September and early October in Cumberland and Tennessee River tributaries (Blankenship 1971, Starnes and Starnes 1980, Ahlstedt and Saylor 1996). This behavior is thought to be related to reproductive activities. Those reported by Ahlstedt and Saylor (1996) were gravid females, but Ahlstedt et al. (2005) reported nongravid individuals lying in a similar posture during March. Fishes reported to serve as glochidial hosts of the species include Cottus baileyi (Black Sculpin) (Cottidae); and Etheostoma baileyi (Emerald Darter) and Etheostoma blennioides (Greenside Darter) (Percidae) (Layzer and Anderson 1992, Williams et al. 2008).
Little is known about the life history of this species, specifically with regard to age of maturity and longevity. However, taking into account of what is known for other mussel species (e.g., see Haag and Rypel 2011), it is more than likely that the declines observed over the past 25-50 years fall within three generation lengths for this species. Therefore, although we do not have definitive data on generation length, we believe that the dramatic declines experienced by this species in the past warrant a highly precautionary attitude to its assessment.
Systems:Freshwater
Congregatory:Congregatory (and dispersive)

Use and Trade [top]

Use and Trade: This species is not utilized.

Threats [top]

Major Threat(s): Deterioration of water quality, especially from acid mine drainage is the primary threat to the species. Development of coal, oil, and/or natural gas reserves in the watersheds of the Horse Lick Creek, Big South Fork Cumberland River, Little South Fork Cumberland River, Clinch River, and Cane Creek are potential threats. All populations could potentially be impacted by road construction, stream channel modifications, logging activities, agricultural activities, impoundments, land use changes, and pesticide use (Parmalee and Bogan 1998). Because all populations inhabit only short stream reaches within 1 to 5 miles of bridges and fords, they are also vulnerable to toxic spills (USFWS 1989). It is also affected by domestic pollution and impoundments (Bogan and Parmalee 1983).

All populations are small and isolated, restricting genetic interchange and impeding natural dispersal capability (USFWS 1989).

Conservation Actions [top]

Conservation Actions: This species was listed as federally endangered in the U.S. in 1988 (USFWS 1988) and a recovery plan was created (USFWS 1989). Williams et al. (2010) lists this species as endangered according to the American Fisheries Society (AFS) assessment.

The recovery plan outlines the following: (1) preserve present populations and occupied habitat, (2) determine threats to the species, conduct research necessary for management and recovery, and implement management where needed, (3) search for additional populations and/or habitat suitable for reintroduction efforts, (4) determine feasibility of reestablishing the species in historic habitat and reintroduce where feasible, (5) develop and implement a program to monitor population levels and habitat conditions of presently established populations as well as newly discovered, introduced, or expanding populations, (6) annually assess overall success of the recovery program and recommend action.

Several streams which support populations flow through the Daniel Boone National Forest in Kentucky (USFWS 1989).

Citation: Cummings, K. & Cordeiro, J. 2012. Pegias fabula. The IUCN Red List of Threatened Species 2012: e.T16479A1074877. . Downloaded on 24 September 2017.
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