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Elliptoideus sloatianus

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Taxonomy [top]

Kingdom Phylum Class Order Family
ANIMALIA MOLLUSCA BIVALVIA UNIONOIDA UNIONIDAE

Scientific Name: Elliptoideus sloatianus
Species Authority: (I. Lea, 1840)
Common Name(s):
English Purple Bankclimber
Synonym(s):
Nephronaias sloatianus I. Lea, 1840
Taxonomic Notes: Frierson (1927) created the monotypic subgenus Elliptoideus under Elliptio for this species, although Clench and Turner (1956) considered Elliptiodeus sloatianus an Elliptio. Current authors, however, have given Elliptoideus generic status (e.g., Turgeon et al. 1998). E. sloatianus is monotypic. The use of all four gills for brooding is one diagnostic that separates it from the genus Elliptio. It has also tentatively been placed in the genus Plectomerus following genetic analysis (Serb et al. 2003).

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: Vulnerable A2ac ver 3.1
Year Published: 2012
Date Assessed: 2012-03-05
Assessor(s): Cummings, K. & Cordeiro, J.
Reviewer(s): Bohm, M., Collen, B. & Seddon, M.
Contributor(s): Richman, N., Dyer, E., Soulsby, A.-M., Whitton, F., Kasthala, G., McGuinness, S., De Silva, R., Milligan, HT, Herdson, R., Thorley, J., McMillan, K., Collins, A., Offord, S. & Duncan, C.
Justification:
Elliptoideus sloatianus has been assessed as Vulnerable under criterion A2ac. This species has a limited range in the Apalachicola, Chattahoochee and Flint (ACF) rivers, and is rarely found in the Ochlockonee River system with low numbers of occurrences (some with viability in question). The species faces multiple threats and has narrow habitat requirements. Moderate declines (39% loss) in range extent and perhaps more in occupied habitat have occurred in the ACF and Ochlockonee systems over the last 10-20 years, while three generations are likely to span at least 48 to 57 years. It is unlikely that populations were increasing previous to the 1990s, as this would be contrary to population trends observed in other mussel species from the area. Overall, we assume that the observed range decline over the past three generations equates to approximately 30% decline in population size.
History:
2000 Endangered
1996 Critically Endangered
1994 Indeterminate (Groombridge 1994)

Geographic Range [top]

Range Description: The Purple Bankclimber is known from 68 historical collections representing 25 occurrences in the Apalachicola, Chattahoochee and Flint (ACF) rivers in Alabama, Georgia and Florida, and from nine occurrences in the Ochlockonee River system in Florida and Georgia. Heard (1979) reported one shell of Elliptoideus from the Escambia River, near Century, Florida, but in Deyrup and Franz (1994), it was stated this record was based on the conchologically similar Plectomerus dombeyanus. It is known from fossil records from two additional Florida drainages (Bogan and Portell 1995, J. D. Williams pers. comm. 2010). It appears to be very rare or extirpated from the Chipola and Chattahoochee rivers. One specimen was recorded from the Chattahoochee in December of 2000, prior to that it had not been recorded since the 1800s. The last record from the Chipola River was in 1988 (Brim Box and Williams 2000). The range is likely to extend over an area of up to 45,000 km2, but because of the disjointed distribution of this species, taking discontinuities and only partially occupied basins into account makes the estimated range much smaller than this, and more in the region of no more than 5,000 km2 (NatureServe 2009).

The species once occurred in 737 river miles within the ACF and Ochlockonee river basins. It has lost 39% of its range (from 737 to 453 river miles) (USFWS 2003).
Countries:
Native:
United States (Alabama, Florida, Georgia)
Range Map: Click here to open the map viewer and explore range.

Population [top]

Population: In recent surveys throughout its historical range, the species was found at 30 of 324 sites surveyed in the ACF Basin in Alabama and Georgia (Apalachicola and Flint Rivers and one specimen from the Chattahoochee River system- first record since the 1800s) (Brim Box and Williams 2000) and 16 of 73 sites surveyed in the Ochlockonee River system [note that many of these sites can be lumped into fewer occurrences]. It is rarely collected in tributary streams or impoundments. There exists a recent discovery of a single live specimen on the Chattahoochee River. In Georgia, it has been found in the Flint, Chattahoochee and Ochlockonee rivers (USFWS 2003). In Alabama, it is restricted to the Chattahoochee River with a few historical records and extant records only in the tailwaters of Bartletts Ferry Dam in Lee Co. and Harris Co., Georgia (Williams et al. 2008).

Relatively high densities exist in the upper Apalachicola and Ochlockonee Rivers. Current population sizes in the Flint and Chipola Rivers are much smaller (USFWS 2003). Most occurrences in the Ochlockonee River are above Talquin Reservoir except for an anomalous small stream occurrence from an unnamed tributary of Mill Creek, Flint River system (one specimen in 1998) (USFWS 2003).

In 1987, 100 individuals/hr could be found at the best known site. Based on recent surveys, the species can be locally abundant in the main channels of the Flint and Apalachicola rivers (Brim Box and Williams 2000). Dozens of specimens were found in the mainstem of the Flint River in Decatur County, Georgia, and below the Jim Woodruff Lock and Dam in the main channel of the Apalachicola River. Hundreds were also observed in the main channel of the Ochlockonee River in Leon Co., Florida, during a 1993 survey (Brim Box pers. comm. 2010).

Although large populations persist at multiple localities, this species is now rare or extirpated from two of the five rivers where it was historically found. Based on recent surveys, little evidence of recent recruitment was found throughout its historical range. It is extirpated from Chattahoochee River (only former locality in Alabama) except for a single specimen collected recently (Brim Box and Williams 2000); Line Creek, upper Flint River system; Little River, Ochlockonee River system (Butler and Alam 1999).

The threatened Purple Bankclimber once occurred in 737 river miles within the ACF and Ochlockonee river basins. It has lost 39% of its range over the last 10-20 years (from 737 to 453 river miles) (USFWS 2003).
Population Trend: Decreasing

Habitat and Ecology [top]

Habitat and Ecology: This species is found in sand, fine gravel or muddy sand substrates in moderate current (Heard 1975) in large rivers or streams (Clench and Turner 1956). In the ACF Basin it was found primarily at main channel sites (small to large river channels) in slow to moderate current with sand/limestone substrates, and frequently in waters over 3 m in depth (Brim Box and Williams 2000, USFWS 2003, 2006). In the Ochlockonee River system, it was found in the main channel in sandy substrates in moderate to swift currents.

Direct life-history data is not available for this species. Freshwater mussels are highly variable in their longevity from species to species (e.g. Haag and Rypel 2011). Studies have shown longevity of species in the tribe Pleurobemini, to which this species belongs, to range from 14 to 57 years (Haag and Rypel 2011). In order to put population declines in perspective, we develop an estimate of longevity based on the average of observed maximum ages (from populations of Elliptio arca, E. complanata, E. crassidens, Fusconaia cerina, F. cuneolus, F. ebena, Pleurobema coccineum, P. collina and P. decisum; Haag and Rypel 2011), and derive an average longevity of 31-32 years (using minimum and maximum ages observed, we derive upper and lower margins of 19 and 57 years respectively). In a study of fecundity and maturity in a number of freshwater mussels, age at maturity ranged from less than one year in Lampsilis ornata to up to nine year in Quadrula asperata; the sole representative of the tribe Pleurobemini, Elliptio arca, matured early at an age of two years (Haag and Staton 2003). Assuming a first age of maturity of around 2-5 years, generation length (estimated as the average age of a parent in the population) is estimated as around 16 to 19 years, with three generations spanning approximately 48 to 57 years. As a result, we assess population decline estimates since around 1955 to 1965 for the purpose of validation of criterion A.
Systems: Freshwater

Use and Trade [top]

Use and Trade: This species is not utilised.

Threats [top]

Major Threat(s): This species is highly restricted in distribution, occurs in generally small subpopulations, and shows little evidence of recovering from historical habitat losses without significant positive human intervention. This species does not tolerate impounded conditions. Principle causes of decline include impoundments, channelisation, pollution, and sedimentation that have altered or eliminated those habitats that are essential to the long-term viability of many riverine mussel populations. Detailed information on these threats can be found in USFWS (2003). Many of the impacts discussed in USFWS (2003) occurred in the past as unintended consequences of human development in the Apalachicolan Region. However, the species and its habitats continue to be impacted by excessive sediment bed loads of smaller sediment particles, changes in turbidity, increased suspended solids (primarily resulting from nonpoint-source loading from poor land-use practices, lack of BMPs, and maintenance of existing BMPs), and pesticides. Other primarily localised impacts include gravel mining, reduced water quality below dams, developmental activities, water withdrawal, impoundments, and alien species. Toxic spills are also a possibility in all extant populations (USFWS 2003). Barge maintenance dredging in Apalachicola and Chattahoochee rivers probably eradicated EOs. Since this species is restricted to the main channel of large rivers, excess sedimentation as a result of bank destabilisation and poor land management practices could alter suitable habitats. It is also  threatened by agricultural runoff and pollution.

Conservation Actions [top]

Conservation Actions: This species has been assigned a NatureServe Global Heritage Status Rank of G2 - Imperilled, and a State/Province Status Rank of S2 - Imperilled for Georgia, S1 - Critically Imperilled in Alabama, and S1S2 - Critically Imperilled to Imperilled in Florida (NatureServe 2009). Williams et al. (2010) lists this species as endangered according to the American Fisheries Society (AFS) assessment.  This species was added to the U.S. Federal Endangered Species list in 1998, and a recovery plan was created for this species (USFWS 2003). Critical habitat has been designated for 380.4 km of the Upper Flint River, Georgia; 302.3 km of the Middle Flint River, Georgia; 396.7 km of the Lower Flint River, Georgia; 155.4 km of the Apalachicola River in Florida; 177.3 km of the Upper Ochlockonee River, Florida and Georgia; and 75.4 km of the Lower Ochlockonee River in Florida (USFWS 2006). Occurrences in the lower Ochlockonee and Apalachicola rivers border the Apalachicola National Forest.

Further research is required regarding the taxonomy, population status, ecology and threats impacting this species. Conservation and legislative protection is also required.

Citation: Cummings, K. & Cordeiro, J. 2012. Elliptoideus sloatianus. The IUCN Red List of Threatened Species. Version 2014.2. <www.iucnredlist.org>. Downloaded on 22 September 2014.
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