Medionidus penicillatus - (I. Lea, 1857)
Gulf Moccasinshell
Other English Common Names: gulf moccasinshell
Taxonomic Status: Accepted
Related ITIS Name(s): Medionidus penicillatus (I. Lea, 1857) (TSN 80266)
Unique Identifier: ELEMENT_GLOBAL.2.118702
Element Code: IMBIV28050
Informal Taxonomy: Animals, Invertebrates - Mollusks - Freshwater Mussels
 
Kingdom Phylum Class Order Family Genus
Animalia Mollusca Bivalvia Unionoida Unionidae Medionidus
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: Medionidus penicillatus
Taxonomic Comments: van der Schalie (1940) reported two species of Medionidus penicillatus from the Chipola River, M. penicillatus and Medionidus kingi . M. kingi was later synonomized under M. penicillatus by Clench and Turner (1956), who recognized only one species of Medionidus from the Suwannee, Ochlockonee, and Apalachicola River systems (Brim Box and Williams 2000). Their records of M. penicillatus from the Ochlockonee River are now recognized as Medionidus simpsonianus, and their Suwannee River records are now recognized as Medionidus walkeri; with Medionidus penicillatus restricted to the Apalachicola basin (Williams et al., 2008). Unlike previous authors (Johnson, 1977; Butler, 1989), Brim Box and Williams (2000) restricted the distribution of Medionidus penicillatus to the ACF and Econfina Creek drainages, based on zoogeographic considerations (with Medionidus from west of the ACF basin assigned to Medionidus acutissimus). Taxonomic questions exist as to the relationship between Mobile Basin M. acutissimus and what appears to be that species in the Choctawhatchee, Yellow, and Escambia drainages as slight conchological differences exist. M. acutissimus from the Escambia, Yellow, and Choctawhatchee River drainages are also similar morphologically to Medionidus penicillatus and some authors have included those populations in the range of M. penicillatus (Johnson, 1977; Butler, 1990; Williams and Butler, 1994), but those populations are included in the range of M. acutissimus by Williams et al. (2008) because faunal distribution patterns suggest that faunas in the Choctawhatchee, Yellow, and Escambia River drainages are more closely related to those of the Mobile Basin than those of the Apalachicola Basin.
Conservation Status
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NatureServe Status

Global Status: G2
Global Status Last Reviewed: 14Jan2014
Global Status Last Changed: 26Feb2007
Rounded Global Status: G2 - Imperiled
Reasons: This species has a limited range and is conclusively known from only two adjacent river systems, one of which is very small. Recent surveys have documented drastic declines in populations sizes (80% loss from historical levels) to the point where it is now known from less than 20 sites.
Nation: United States
National Status: N2 (26Feb2007)

U.S. & Canada State/Province Status
Due to latency between updates made in state, provincial or other NatureServe Network databases and when they appear on NatureServe Explorer, for state or provincial information you may wish to contact the data steward in your jurisdiction to obtain the most current data. Please refer to our Distribution Data Sources to find contact information for your jurisdiction.
United States Alabama (S1), Florida (S1), Georgia (S1)

Other Statuses

U.S. Endangered Species Act (USESA): LE: Listed endangered (16Mar1998)
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: 1000-5000 square km (about 400-2000 square miles)
Range Extent Comments: This species is restricted to the Apalachicola, Chattahoochee, and Flint (ACF) rivers in Florida, Alabama, and Georgia, and Econfina Creek, an independent drainage just west of the ACF Basin. Unlike previous authors (van der Schalie, 1940; Johnson, 1977; Butler, 1989), Brim Box and Williams (2000) restricted the distribution of M. penicillatus to the ACF and Econfina Creek (St. Andrews Bay drainage) drainages, based on zoogeographic considerations (with Medionidus from west of the ACF basin assigned to M. acutissimus). Historical sites listed by Johnson (1977) include Yellow River drainage, Alabama; Econfina Creek (= St. Andrews Bay) drainage, Florida; Chipola River drainage, Alabama; Chattahoochee River drainage, Georgia; Apalachicola River drainage, Florida (see Clench and Turner, 1956); and Flint River drainage, Georgia. It appears to be extirpated from historical localities in the Chattahoochee River mainstem and all of Alabama (barely hanging on still in one site in Chipola headwaters area); some Chattahoochee River system streams (Mulberry, Uchee, Little Uchee Creeks); some Flint River tributaries (Line, Patsiliga, Turkey, Sandy Mount, Gum, Cedar, Jones, Abrams, Mill, Ichawaynochaway, and Spring Creeks); the Apalachicola River mainstem; and some tributaries in the Chipola River system (Big, Marshall, Cowarts, Dry, Rocky, and both Spring Creeks; also both the Flint and Chipola River main stems). Proven extant in the last 10 years in Econfina Creek, the upper Chipola River system, tributaries of the Flint River, and two tributaries in the lower Chattahoochee River system. It was apparently extirpated from historical sites in Alabama (Chattahoochee River drainage) (USFWS, 2003; Butler, 1989; Williams et al., 2008).

Area of Occupancy: 501-12,500 4-km2 grid cells
Area of Occupancy Comments: The Gulf moccasinshell once occurred in an estimated 1,142 river miles (rm) in Econfina Creek and the ACF river basin, and has lost 80 percent of its historic range. It is currently found in 21 subpopulations spread over 234 rm in 6 watersheds (USFWS, 2003). Linear occupancy is 200-1000 km.

Number of Occurrences: 6 - 80
Number of Occurrences Comments: Unlike previous authors (Johnson, 1977; Butler, 1989), Brim Box and Williams (2000) restricted the distribution of Medionidus penicillatus to the Apalachicola-Chattahoochee-Flint (ACF) and Econfina Creek (= St. Andrews Bay) drainages, based on zoogeographic considerations (with Medionidus from west of the ACF basin assigned to M. acutissimus). In the ACF basin of Alabama, Florida, and Georgia, this species was known historically from 93 collections from 52 sites (Brim Box and Williams, 2000), but now occurs at less than 20 known sites in the Flint, Chattahoochee, and Chipola rivers and their tributaries. In the Econfina Creek drainage, it is known from at least 2 localiti es. In a recent survey of >300 sites in the ACF Basin, 13 M. penicillatus were found from a total of nine sites, which is less than 3% of those surveyed (USFWS, 2003). In 1999 and 2001, this species was found in 2 sites (9 specimens) and 1 sites (17 specimens), respectively, in surveys of 5 sites (each year) in about a dozen tributary streams of the lower Flint River Basin, in southwestern Georgia; and is also known from the Chattahoochee River (Golladay et al., 2004). It is nearly extirpated in Alabama, extant only in Big Creek, Houston County (Chipola River headwaters) (Mirarchi et al., 2004; Williams et al., 2008).

Population Size: 1000 - 2500 individuals
Population Size Comments: Still abundant (e.g., more than 20 individuals) at one site each in Flint and Chipola river tributaries, and at one site in the main stem of Econfina Creek. Historically, several collections contained >50 individuals, and Johnson (1977) listed it as relatively abundant in the Apalachicola River system, especially the Flint River drainage, but scarce elsewhere. Based on recent surveys, it is usually uncommon at a site. In 1999, this species was found to comprise 0.07% (relative abundance) of the 14,873 mussels collected in surveys of 46 sites in 12 tributary streams of the lower Flint River basin, Georgia (Gagnon et al., 2006).

Number of Occurrences with Good Viability/Integrity: None to few (0-12)
Viability/Integrity Comments: 15 of 93 historic museum collections reported by Brim Box and Williams (2000) contained 12 or more specimens. The subpopulation in Waddells Mill Creek (Chipola River) is thought to be the largest remaining population (USFWS, 2003). In 1999 and 2001, this species was found in 2 sites (9 specimens) and 1 sites (17 specimens), respectively, in surveys of 5 sites (each year) in about a dozen tributary streams of the lower Flint River Basin, in southwestern Georgia (Golladay et al., 2004).

Overall Threat Impact: High
Overall Threat Impact Comments: 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. Principal causes of decline 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. Detailed information on these threats can be found in USFWS (2003) and include: (1) exploitation by native Americans and for pearls and pearl buttons plus overcollection for scientific purposes (very localized, low impact, historical only), (2) habitat alteration- impoundment causing loss of habitat, loss of shoal habitat, thermal alterations, daily discharge fluctuations, bank sloughing, seasonal oxygen deficiencies, coldwater releases, turbulence, high silt loads, and altered host fish distribution (widespread, high impact, ongoing); (3) impoundment- channelization for navigation and maintenance causing sedimentation and contamination (moderate scope, high impact, historical and ongoing); (4) habitat alteration- gravel mining causing riparian forest clearing, channel modification, disrupted flow, water quality modification, impacts on host fish populations, substrate disturbance/siltation, pollution (moderate scope, high impact, historical and ongoing); (5) contaminants- heavy metals, arsenic and ammonia from poultry and animal feedlots, industrial/municipal effluent, agricultural nutrient enrichment from poultry farms and livestock feedlots, herbicides/pesticides, nutrients from aquaculture ponds, urban stormwater runoff, municipal waste discharge (high-moderate scope, high impact, historical and ongoing); (6) sedimentation- from agricultural, silvicultural, and roadway activities, clearing of riparian vegetation, and flood control activities, gravel mining, livestock grazing (high-moderate scope, high impact, historical and ongoing); (7) urbanization- highways, infrastructure, recreational activities (low scope, moderate-low impact, historical and ongoing); (8) "deadhead logging"- disruption of habitat, increased sediment (localized in Florida only, moderate impact, potential future threat); (9) water withdrawel- mostly for irrigation (moderate impact, moderate scope, ongoing); (10) introduced species- Asiatic clam, zebra mussel, black carp (moderate-low scope, moderate impact, ongoing). 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. Following a recent drought from 1999-2001, this species experienced decline in abundance in the Flint River drainage in Georgia as evidenced by surveys in 2001 and 2002 (Chastain et al., 2005).

Short-term Trend: Decline of >70%
Short-term Trend Comments: Declining in range and individual population sizes. It was considered one of the rarest mussels encountered in a recent survey of the ACF basin, with extirpations in historical sites in Alabama (Chattahoochee River drainage) (Brim Box and Williams, 2000). Extirpated from the Yellow and Choctawhatchee river systems and Chattahoochee mainstem. Also considered extirpated from Alabama (Mulberry, Uchee, and Little Uchee Creeks in the Chattahoochee River system; Line, Patsiliga, Sandy Mount, Gum, Cedar, Jones, Abrams, Mill, Ichawaynochaway, and Spring Creeks, tributaries to the Flint River; and Big, Cowarts, Dry, Rocky, and both Spring Creeks in Chipola River system), but possibly might occur in Big creek, Houston Co. (Mirarchi et al., 2004); also eliminated from most of the Flint and Chipola mainstems (USFWS, 2003).

Long-term Trend: Decline of 70-90%
Long-term Trend Comments: The Gulf moccasinshell once occurred in an estimated 1,142 river miles (rm) in Econfina Creek and the ACF river basin but has lost 80 percent of its historic range. It is currently found in 21 subpopulations spread over 234 rm in 6 watersheds (USFWS, 2003). Historically, several collections contained >50 individuals, and Johnson (1977) listed it as relatively abundant in the Apalachicola River system, especially the Flint River drainage, but scarce elsewhere. In the ACF basin, historically this species was known from 93 collections from 52 sites (Brim Box and Williams, 2000), but is now known from <20 sites in the Flint and Chattahoochee River as well as previously in a Chipola River tributary, Chattahoochee River tributary, and two Flint River tributaries. In the Econfina Creek drainage, it is known from at least 2 sites. In a recent survey of >300 sites in the ACF Basin, 13 M. penicillatus were found at a total of nine localities, or less than 3% of the sites surveyed (USFWS, 2003).

Intrinsic Vulnerability: Highly to moderately vulnerable.
Intrinsic Vulnerability Comments: Freshwater mussels are inherently vulnerable to threats from siltation, pollution, eutrophication, channelization, impoundment, collection, drought and water withdrawal, competiton from invasive non-native mussels, and changes to larval host fish populations.

Environmental Specificity: Narrow. Specialist or community with key requirements common.
Environmental Specificity Comments: All southern forms in the genus are threatened, probably due to habitat degradation in riffle habitats.

Other NatureServe Conservation Status Information

Inventory Needs: Conduct additional surveys of the Econfina Creek system. Determine the viability (i.e., recruitment) of existing populations. Inventory potential habitats for future reintroduction of cultured stock/tranplants, if future culture is deemed appropriate.

Protection Needs: Maintain high water and benthic habitat (substrate) qualities, as well as adequate flow regimes, throughout all occupied river systems. This may be partially accomplished via establishment of buffers and streamside management zones for all agricultural, silvicultural, mining, and developmental activities; protection of floodplain forests and adjoining upland habitat is paramount. Best management practices to follow include employing forestry practices that cause minimal soil erosion; preventing access of livestock to natural surface waters and drains; situating roads at least 0.25 mi. (0.4 km) from heads of all tributaries, even more on steep slopes; using silt fencing and vegetation to control runoff and siltation at all stream crossings, especially during construction and maintenance; using and maintaining sewer systems rather than septic tanks and stream-dumping for management of wastewater; and avoiding use of agricultural pesticides on porous soils near streams. Prevent damming, dredging, and pollution throughout drainages, but especially near recorded sites. Remove existing dams, but with great care to limit downstream sedimentation. Limit withdrawal of surface and subterranean waters as necessary to maintain normal stream flows, especially during drought. Prevent or limit establishment of invasive species (including zebra mussel, Dreissena polymorpha) to the extent possible. Where appropriate, protect populations through acquisitions and easements over streamside lands by working with government agencies and conservation organizations.
For more details, see federal recovery plan (USFWS, 2003).

Distribution
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Global Range: (1000-5000 square km (about 400-2000 square miles)) This species is restricted to the Apalachicola, Chattahoochee, and Flint (ACF) rivers in Florida, Alabama, and Georgia, and Econfina Creek, an independent drainage just west of the ACF Basin. Unlike previous authors (van der Schalie, 1940; Johnson, 1977; Butler, 1989), Brim Box and Williams (2000) restricted the distribution of M. penicillatus to the ACF and Econfina Creek (St. Andrews Bay drainage) drainages, based on zoogeographic considerations (with Medionidus from west of the ACF basin assigned to M. acutissimus). Historical sites listed by Johnson (1977) include Yellow River drainage, Alabama; Econfina Creek (= St. Andrews Bay) drainage, Florida; Chipola River drainage, Alabama; Chattahoochee River drainage, Georgia; Apalachicola River drainage, Florida (see Clench and Turner, 1956); and Flint River drainage, Georgia. It appears to be extirpated from historical localities in the Chattahoochee River mainstem and all of Alabama (barely hanging on still in one site in Chipola headwaters area); some Chattahoochee River system streams (Mulberry, Uchee, Little Uchee Creeks); some Flint River tributaries (Line, Patsiliga, Turkey, Sandy Mount, Gum, Cedar, Jones, Abrams, Mill, Ichawaynochaway, and Spring Creeks); the Apalachicola River mainstem; and some tributaries in the Chipola River system (Big, Marshall, Cowarts, Dry, Rocky, and both Spring Creeks; also both the Flint and Chipola River main stems). Proven extant in the last 10 years in Econfina Creek, the upper Chipola River system, tributaries of the Flint River, and two tributaries in the lower Chattahoochee River system. It was apparently extirpated from historical sites in Alabama (Chattahoochee River drainage) (USFWS, 2003; Butler, 1989; Williams et al., 2008).

U.S. States and Canadian Provinces

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

U.S. & Canada State/Province Distribution
United States AL, FL, GA

Range Map
No map available.


U.S. Distribution by County Help
State County Name (FIPS Code)
FL Bay (12005), Calhoun (12013), Gadsden (12039)*, Jackson (12063)
GA Baker (13007), Calhoun (13037), Cobb (13067)*, Coweta (13077)*, Crisp (13081), Decatur (13087)*, Dooly (13093), Dougherty (13095), Early (13099), Fayette (13113), Fulton (13121)*, Harris (13145)*, Lee (13177), Meriwether (13199)*, Miller (13201)*, Mitchell (13205)*, Muscogee (13215)*, Pike (13231)*, Spalding (13255)*, Sumter (13261), Taylor (13269)*, Terrell (13273), Webster (13307), Worth (13321)
* Extirpated/possibly extirpated
U.S. Distribution by Watershed Help
Watershed Region Help Watershed Name (Watershed Code)
03 Upper Chattahoochee (03130001)*, Middle Chattahoochee-Lake Harding (03130002)+*, Middle Chattahoochee-Walter F. George Reservoir (03130003)+*, Lower Chattahoochee (03130004)+, Upper Flint (03130005)+, Middle Flint (03130006)+, Kinchafoonee-Muckalee (03130007)+, Lower Flint (03130008)+, Ichawaynochaway (03130009)+, Spring (03130010)+, Apalachicola (03130011)+, Chipola (03130012)+, St. Andrew-St. Joseph Bays (03140101)+
+ Natural heritage record(s) exist for this watershed
* Extirpated/possibly extirpated
U.S. Distribution by Watershed (based on multiple information sources) Help
Ecology & Life History
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Basic Description: A small, sculptured, rayed freshwater mussel.
General Description: See Johnson (1977) and Deyrup and Franz (1994). The shell is elongate-elliptical or rhomboidal and fairly inflated, and has relatively thin valves. Ventral margin is nearly straight or slightly rounded. Posterior ridge is rounded to slightly angled and intersects the end of the shell at the base line. Females tend to have the posterior point above the ventral margin and are somewhat more inflated. Sculpturing consists of a series of thin, radially oriented plication along the length of the posterior slope. The remainder of the surface is smooth and yellowish to greenish brown with fine, typically interrupted green rays. the left valve has two stubby pseudocardinal and two arcuate lateral teeth. The right valve has one pseudocardinal and lateral tooth. Nacre color is smokey purple or greenish and slightly iridescent at the posterior end (Butler and Alam, 1999).
Diagnostic Characteristics: Fairly elongate, low posterior ridge with a distinctly but finely sculptured brownish to greenish periostracum, nearly straight ventral margin.
Reproduction Comments: Gulf moccasinshell glochidia are released in early to late spring, while gravid females were found in March, April, September, and November (O'Brien and Williams, 2002). The presence of gravid specimens of this lampsiline species in late summer and fall months suggests that the Gulf moccasinshell is a parent overwintering, summer releasing species. Glochidial morphology was described and figured by O'Brien and Williams (2002). Primary host fish include Etheostoma edwini (brown darter), Percina nigrofasciata (blackbanded darter), Gambusia holbrooki (eastern mosquitofish), Poecilia reticulata (guppy) (Butler and Alam, 1999; USFWS, 2003; O'Brien, 1998; O'Brien and Williams, 2002). Laboratory tests reveal that 100 percent of the fish of these two species transformed the glochidia that were exposed to them. Glochidia metamorphosed in 29 to 33 days for the blackbanded darter and 30 to 37 days for the brown darter. Two other fishes, the eastern mosquitofish and guppy, also transformed glochidia but at lower percentage rates. All tests were conducted at 70.7 2.7F (O'Brien and Williams, 2002).

Habitat Type: Freshwater
Non-Migrant: N
Locally Migrant: N
Long Distance Migrant: N
Mobility and Migration Comments: Greatest potential during glochidial stage on fish. Adults of this species are essentially sessile however some passive movement downstream may occur during high flows.
Riverine Habitat(s): BIG RIVER, CREEK, Low gradient, MEDIUM RIVER, Moderate gradient, Riffle
Special Habitat Factors: Benthic
Habitat Comments: It occurs in a wide range of habitats, including sandy areas with a slight current (Jenkinson, 1973), streams and rivers where there is a moderate current and sand and gravel substrates (Clench and Turner, 1956), and in muddy sand substrates around tree roots in medium-sized stream with moderate current (Heard, 1975). In Florida, this species is also known from sand and fine gravel substrates in slight to moderate current (Heard, 1979). In the ACF Basin this species was found at sites that contained a combination of sand and limestone rock substrates (Brim Box and Williams, 2000). According to USFWS (2003), this species inhabits channels of medium sized creeks to large rivers with sand and gravel or silty sand substrates in slow to moderate currents.
Adult Food Habits: Detritivore
Immature Food Habits: Parasitic
Food Comments: Presumably fine particulate organic matter, primarily detritus, and/or zooplankton, and/or phytoplankton (Fuller, 1974). Larvae (glochidia) of freshwater mussels are parasitic on fish and there may be a specificity among some species.
Length: 5.2 centimeters
Economic Attributes Not yet assessed
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Management Summary
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Stewardship Overview: This species was added to the U.S. federal endangered species list in 1998 (USFWS, 1998). A recovery plan was created for this species (USFWS, 2003).

The recovery plan (USFWS. 2003) outlines the following objectives for recovery: (1) preserve extant subpopulations and currently occupied habitats and ensure subpopulation viability, (2) search for additional subpopulations of the species and suitable habitat, (3) determine through research and propagation technology the feasibility of augmenting extant subpopulations and reintroducing the species into historical habitat, (4) evaluate efforts and monitor subpopulation levels and habitat conditions of existing subpopulations, as well as newly discovered, introduced, or expanding subpopulations, (5) develop and implement cryogenic techniques to preserve genetic material until such time as conditions are suitable for reintroduction, (6) develop and utilize a public outreach and environmental education program, (7) assess the overall success of the recovery program and recommend actions (e.g., changes in recovery objectives, delist, implement new measures, conduct additional studies).


Critical habitat has been designated for 31.4 km of Econfina Creek in Florida; 190.0 km of the Chipola River, Alabama and Florida; 37.8 km of Sawhatchee Creek and Kirkland Creek, Georgia; 380.4 km of the Upper Flint River, Georgia; 302.3 km of the Middle Flint River, Georgia; and 396.7 km of the Lower Flint River, Georgia (USFWS, 2006).

Biological Research Needs: Determine life history, microhabitat requirements, and sensitivity to excess sedimentation and pollutants. Develop propagation techniques.
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: 14Jan2014
NatureServe Conservation Status Factors Author: Jackson, D. R. (2014); Cordeiro, J. (2009); Butler, R.S. (1992); Brim Box, J., and C.
Element Ecology & Life History Edition Date: 13Feb2007
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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  • Athearn, H.D. 1970. H.D. Discussion of Dr. Heard's paper on eastern freshwater mollusks, the south Atlantic, and Gulf drainages. Pages 28-31 in A.H. Clarke, ed. Papers on the rare and endangered mollusks of North America. Malacologia, 10(1): 28-31.

  • BRIM-BOX, J., AND J.D. WILLIAMS. 1997. UNIONID MOLLUSKS OF THE APALACHICOLA BASIN IN ALABAMA, FLORIDA, AND GEORGIA. DRAFT REPORT. USGS, BIOLOGICAL RESOURCES DIVISION, GAINESVILLE. 314PP.

  • BUTLER, ROBERT S. 1993. RESULTS OF A STATUS SURVEY FOR EIGHT FRESHWATER MUSSELS ENDEMIC TO EASTERN GULF SLOPE DRAINAGES OF THE APALACHICOLAN REGION OF SOUTHEAST ALABAMA, SOUTHWEST GEORGIA, AND NORTH FLORIDA. USFWS RPT. 30PP + MAPS, FIGS.

  • Brim Box, J., and J. D. Williams. 2000. Unionid mollusks of the Apalachicola Basin in Alabama, Florida, and Georgia. Bull. Alabama Mus. Nat. Hist. 21:1-143.

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

  • Chastain, C.A., S.W. Golladay, and T.K. Muenz. 2005. Distribution of unionid mussels in tributaries of the lower Flint River, southwestern Georgia: an examination of current and historical trends. Presented at the Proceedings of the 2005 Georgia Water Resources Conference, 25-27 April 2005, University of Georgia.

  • Clench, W.J. and R.D. Turner. 1956. Freshwater mollusks of Alabama, Georgia, and Florida from the Escambia to the Suwanee River. Bulletin of the Florida State Museum Biological Sciences, 1(3): 97-239.

  • Clench, William J., and Ruth D. Turner. 1956. Freshwater mollusks of Alabama, Georgia, and Florida from the Escambia to the Suwanee River. Bulletin of the Florida State Museum Biological Sciences. I(3):180-181.

  • Deyrup, M. and R. Franz. 1994. Rare and Endangered Biota of Florida, Volume IV. Invertebrates. University Press of Florida: Gainesville, Florida. 798 pp.

  • Deyrup, M., and R. Franz. 1994. Rare and Endangered Biota of Florida, Volume IV: Invertebrates. University Press of Florida, Gainesville. 798 pp.

  • Frierson, L.S. 1927. A Classified and Annotated Checklist of the North American Naiades. Baylor University Press: Waco, Texas. 111 pp.

  • Fuller, S.L.H. 1974. Chapter 8: Clams and mussels (Mollusca: Bivalvia). Pages 215-273 in: C.W. Hart, Jr. and S.L.H. Fuller (eds.) Pollution Ecology of Freshwater Invertebrates. Academic Press: New York. 389 pp.

  • Gagnon, P., W. Michener, M. Freeman, and J. Brim Box. 2006. Unionid habitat and assemblage composition in coastal plain tributaries of Flint River (Georgia). Southeastern Naturalist, 5(1): 31-52.

  • Golladay, S.W., P. Gagnon, M. Kearns, J.M. Battle, and D.W. Hicks. 2004. Response of freshwater mussel assemblages (Bivalvia: Unionidae) to a record drought in the Gulf Coastal Plain of southwestern Georgia. Journal of the North American Benthological Society, 23(3): 494-506.

  • Heard, W.H. 1975. Determination of the endangered status of freshwater clams of the Gulf and Southeastern states. Report for the Office of Endangered Species, Bureau of Fisheries and Wildlife, U.S. Department of the Interior. Washington, D.C. 31 pp.

  • Heard, W.H. 1979. Identification manual of the fresh water clams of Florida. State of Florida, Department of Environmental Regulation, Technical Series, 4(2): 1-82.

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

  • JOHNSON, R.I. 1970. THE SYSTEMATICS AND ZOOGEOGRAPHY OF THE UNIONIDAE OF THE SOUTHERN ATLANTIC SLOPE REGION. BULL. MUS. COMP. ZOOL., HARVARD UNIV., CAMBRIDGE, MA. 140(6):263-450.

  • Johnson, R.I. 1970a. The systematics and zoogeography of the Unionidae (Mollusca: Bivalvia) of the southern Atlantic slope region. Bulletin of the Museum of Comparative Zoology, Harvard University 140(6): 263-449.

  • 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.

  • Mirarchi, R.E., J.T. Garner, M.F. Mettee, and P.E. O'Neil. 2004b. Alabama wildlife. Volume 2. Imperiled aquatic mollusks and fishes. University of Alabama Press, Tuscaloosa, Alabama. xii + 255 pp.

  • 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.

  • O'Brien, C.A. 1998. Reproductive biology for four mussel species of the Gulf Coastal Plain. Pages 29-30 in Conservation, Captive Care, and Propagation. Freshwater Mussels Symposium Program and Abstracts, 6-8 March 1998, Columbus, Ohio. 43 pp.

  • O'Brien, C.A. and J.D. Williams. 2002. Reproductive biology of four freshwater mussels (Bivalvia: Unionidae) endemic to eastern gulf coastal plain drainages of Alabama, Florida, and Georgia. American Malacological Bulletin, 17(1/2): 147-158.

  • Stansbery, D. H. 1971. Rare and endangered freshwater mollusks in eastern United States. Pages 5-18 in S.E. Jorgensen, and R.W. Sharp. Proceedings of a symposium of rare and endangered mollusks (naiads) of the United States. U.S. Department of the Interior: Twin Cities, Minnesota. 79 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., A.E. Bogan, E.V. Coan, W.K. Emerson, W.G. Lyons, W.L. Pratt, C.F.E. Roper, A. Scheltema, F.G. Thompson, and J.D. Williams. 1988. Common and scientific names of aquatic invertebrates from the United States and Canada: mollusks. American Fisheries Society Special Publication 16: viii + 277 pp., 12 pls.

  • 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) (Butler, R.S., J. Ziewitz, S.K. Alam, and H.N. Blalock-Herod). 2003. Agency draft recovery plan for endangered fat threeridge (Amblema neislerii), shinyrayed pocketbook (Lampsilis subangulata), gulf moccasinshell (Medionidus penicillatus), ochlockonee moccasinshell (Medionidus simpsonianus), oval pigtoe (Pleurobema pyriforme) and threatened chipola slabshell (Elliptio chipolaensis), and purple bankclimber (Elliptoideus sloatianus). United States Fish and Widllife Service, Atlanta, Georgia. 144 pp.

  • U.S. Fish and Wildlife Service (USFWS). 1998. Determination of Endangered Status for five freshwater mussels and Threatened status for two freshwater mussels from the eastern Gulf Slope drainages of Alabama, Florida, and Georgia. Final Rule. Federal Register, 63(50): 12664-12687.

  • U.S. Fish and Wildlife Service (USFWS). 1999. Technical/agency draft recovery plan for endangered fat threeridge (Amblema neislerii), shinyrayed pocketbook (Lampsilis subangulata), gulf moccasinshell (Medionidus penicillatus), ochlockonee moccasinshell (Medionidus penicillatus), oval pigtoe (Pleurobema pyriforme), and purple bankclimber (Elliptoideus sloatianus) and threatened chipola slabshell (Elliptio chipolaensis), and purple bankclimber (Elliptoideus sloatianus). U.S. Fish and Wildlife Service: Atlanta, Georgia. 106 pp.

  • U.S. Fish and Wildlife Service (USFWS). 2006. Endangered and Threatned Wildlife and Plants; Critical Habitat for five endangered and two threatened mussels in four northeast Gulf of Mexico drainages; proposed rule. Federal Register, 71(108): 32746-32795.

  • 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., A. E. Bogan, and J. T Garner. 2008. Freshwater mussels of Alabama & the Mobile Basin in Georgia, Mississippi, & Tennessee. University of Alabama Press, Tuscaloosa, Alabama. 908 pages.

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

  • Williams, J. D., R. S. Butler, G. L. Warren, and N. A. Johnson. 2014. Freshwater Mussels of Florida. University of Alabama Press, Tuscaloosa. 498 pp.

  • Williams, J. D., R. S. Butler, G. L. Warren, and N. A. Johnson. 2014a. Freshwater Mussels of Florida. University of Alabama Press, Tuscaloosa, Alabama. 498 pp.

  • Williams, J.D. and R.S. Butler. 1994. Freshwater mussels. Vol. 6, Invertebrates. R Frantz, ed. Rare and endangered biota of Florida. FL Committee on Rare and Endangered Plants and Animals, Univ. Presses of FL.

  • 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.

  • van der Schalie, H. 1940. The naiad fauna of the Chipola River in northwestern Florida. Lloydia 3(3):191-208.

References for Watershed Distribution Map
  • Biological Resources Division, USGS. 1997. Database of museum records of aquatic species. Compiled by J. Williams (USGS-BRD, Gainesville, FL).

  • Brim Box, J. and J.D. Williams. 2000. Unionid mollusks of the Apalachicola Basin in Alabama, Florida, and Georgia. Alabama Museum of Natural History Bulletin, 21: 1-143.

  • Butler, R.S. 1989. Distributional records for freshwater mussels (Bivalvia: Unionidae) in Florida and south Alabama, with zoogeographic and taxonomic notes. Walkerana, 3(10): 239-261.

  • Johnson, R.I. 1977. Monograph of the genus Medionidus (Bivalvia: Unionidae) mostly from the Apalachicolan region, southeastern United States. Occasional Papers on Mollusks, 4(56): 161-187.

  • U.S. Fish and Wildlife Service (USFWS). 2003. Recovery plan for endangered fat threeridge (Amblema neislerii), shinyrayed pocketbook (Lampsilis subangulata), gulf moccasinshell (Medionidus penicillatus), Ochlockonee moccasinshell (Medionidus simpsonianus), and oval pigtoe (Pleurobema pyriforme); and threatened chipola slapshell (Elliptio chipolaensis), and purple bankclimber (Elliptoideus sloatianus). U.S. Fish and Wildlife Service, Atlanta, Georgia. 142 pp.

  • U.S. Fish and Wildlife Service (USFWS. 2003. Endangered and threatened wildlife and plants; final rule to list the Columbia Basin Distinct Population Segment of the Pygmy Rabbit (Brachylagus idahoensis) as endangered. Federal Register 68:10388-10409.

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

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