Epioblasma obliquata - (Rafinesque, 1820)
Catspaw
Taxonomic Status: Accepted
Related ITIS Name(s): Dysnomia sulcata Lea (TSN 80224) ;Epioblasma obliquata (Rafinesque, 1820) (TSN 80323)
Unique Identifier: ELEMENT_GLOBAL.2.120618
Element Code: IMBIV16110
Informal Taxonomy: Animals, Invertebrates - Mollusks - Freshwater Mussels
 
Kingdom Phylum Class Order Family Genus
Animalia Mollusca Bivalvia Unionoida Unionidae Epioblasma
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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: Epioblasma obliquata
Taxonomic Comments: This species has a long and convoluted taxonomic history. It has been variously treated as a full species, a subspecies, or a variety. The current American Fisheries Society common and scientific names checklist (Turgeon et al., 1998) treats it as one species with two subspecies; the nominate form Epioblasma obliquata obliquata, called the catspaw, and Epioblasma obliquata perobliqua, the white catspaw. No justification has ever been published outlining the characters used to separate these two taxa. Nacre color is often cited, but it is an insufficient character for recognizing subspecies. It was placed in the subgenus Pilea by Johnson (1978) and was historically placed in the genera Dysnomia and Plagiola (Johnson, 1978).
Conservation Status
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NatureServe Status

Global Status: G1
Global Status Last Reviewed: 28Apr2009
Global Status Last Changed: 17Mar1998
Rounded Global Status: G1 - Critically Imperiled
Reasons: This species has declined to fewer than five disjunct occurrences from what was a formerly very wide range in the Ohio basin and continues to decline throughout its range. Distribution is greatly fragmented and only two or three populations are likely viable (area of occupancy 4-20 sq. km). Long-term viability of the species is questionable as it continues to face threats and is in decline.
Nation: United States
National Status: N1 (17Mar1998)

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 (SX), Illinois (SX), Indiana (SNR), Kentucky (S1), Michigan (SH), Ohio (SNR), Tennessee (SNA)

Other Statuses

Implied Status under the U.S. Endangered Species Act (USESA): PS
Comments on USESA: Subspecies perobliqua is designated endangered. Subspecies obliquata is designated endangered throughout its range, except where listed as an experimental nonessential population.
Convention on International Trade in Endangered Species Protection Status (CITES): Appendix I
American Fisheries Society Status: Endangered (01Jan1993)

NatureServe Global Conservation Status Factors

Range Extent: <100 square km (less than about 40 square miles)
Range Extent Comments: Historically the entire species was widespread in the Ohio River drainage. Now reproducing populations only exist in a few streams: Fish Creek, Indiana (but not seen in over 10 years- Grabarkiewicz and Crail, 2006) (Epioblasma obliquata perobliqua); and in Killubuck Creek, Ohio, Green River, Kentucky, and Cumberland River, Tennessee (latter possibly extirpated) (Epioblasma obliquata obliquata) (see Isom et al., 1979; Hoggarth et al., 1995; Parmalee and Bogan, 1998). A population (likely Epioblasma obliquata perobliqua) may also exist in the mainstem of the St. Joseph River in Allen Co., Indiana (Pryor, 2005). Also in Indiana, museum records are known for the Tippecanoe River (Cummings and Berlocher, 1990). Johnson (1978) did not differentiate between the two subspecies, and it is difficult to determine the range of these taxa based upon his work. E. obliquata obliquata as defined here once occurred in the Scioto River in Ohio; in the Lower Ohio River (Goodrich and van der Schalie, 1944) and its Kentucky tributaries of the Licking, Green, and Kentucky Rivers (Johnson, 1978); at Muscle Shoals, Alabama; in the Tennessee River and Caney Fork and Harpeth Rivers of the Cumberland River in Tennessee; and the Cumberland River proper in Kentucky (Johnson, 1978). It is apparently extirpated from Ohio, Alabama (Mirarchi et al., 2004), and Indiana and is now known only from Kentucky and Tennessee. Stansbery believed both subspecies were present in the Wabash River with E. obliquata perobliqua occurring more in the north. The Epioblasma obliquata sulcata of Call (1900) is E. obliquata perobliqua. E. obliquata perobliqua historically occurred in the Great Lakes drainages: Blanchard River, Auglaize River, and Fish Creek in Ohio; St. Mary's River, White River, and upper Wabash River in Indiana; the Maumee River in Ohio and Indiana; Otter Creek, River Basin, and Lake St. Clair in Michigan; Detroit River in Michigan and Ontario; Niagara River in New York [later to be determined a specimen of Obovaria olivaria (Strayer and Jirka, 1997)]; and from Lake Erie: Put-in-Bay, Ohio, La Plaisance Bay, and near Stony Creek, Michigan (Johnson, 1978). Occurrences in the Wabash River in Illinois have long been extirpated (Cummings and Mayer, 1997).

Area of Occupancy: 3-125 4-km2 grid cells
Area of Occupancy Comments:  

Number of Occurrences: 1 - 5
Number of Occurrences Comments: This species was historically widespread in the Ohio River drainage in Ohio, Indiana, Illinois, Kentucky, Tennessee, and Alabama (USFWS, 1990). It has been drastically reduced in range. Three extant populations of the Epioblasma obliquata obliquata are thought to exist; one in the Green River in Kentucky, Cumberland River in Tennessee, and Killbuck Creek in Ohio (Isom et al., 1979; Hoggarth et al., 1995; Parmalee and Bogan, 1998; Watters et al., 2009). The only known remaining population of Epioblasma obliquata perobliqua is thought to exist is in Fish Creek, Indiana (USFWS, 1990) into Williams Co., Ohio (Watters et al., 2009), but has not been seen in over 10 years (Grabarkiewicz and Crail, 2006). A population may also exist in the mainstem of the St. Joseph River in Allen Co., Indiana (Pryor, 2005). In Indiana, museum records are known for the Tippecanoe River (Cummings and Berlocher, 1990).

Population Size: 50 - 1000 individuals
Population Size Comments: Epioblasma obliquata perobliqua is thought to be very rare and may be the most imperiled mussel in North America (USFWS, 1990). Epioblasma obliquata obliquata is thought to be reproducing only in Killbuck Creek, Ohio. Only 15 live individuals were found in 1994.

Number of Occurrences with Good Viability/Integrity: None (zero)
Viability/Integrity Comments: Three extant populations of the Epioblasma obliquata obliquata are thought to exist; one in the Green River in Kentucky, Cumberland River in Tennessee, and Killbuck Creek in Ohio (Hoggarth et al., 1995). The only known remaining population of Epioblasma obliquata perobliqua is thought to exist is in Fish Creek, Indiana (USFWS, 1990), but has not been seen in over 10 years (Grabarkiewicz and Crail, 2006).

Overall Threat Impact: Very high - high
Overall Threat Impact Comments: Smith (1971) ranked the causes of extirpation or declines in fish species as follows: siltation, drainage of bottomland lakes, swamps, and prairie marshes, desiccation during drought, species introductions, pollution, impoundments, and increased water temperatures. All of these factors render habitats unsuitable, cause extirpations, and lead to the isolation of populations thereby increasing their vulnerability to extirpation for many aquatic species (including mussels) throughout North America. Zebra mussels, Dreissena polymorpha, have destroyed mussel populations in the Great Lakes and significantly reduced mussels in many of the large rivers of eastern North America. Zebra mussels have the potential to severely threaten other populations especially if they make their way into smaller streams. Pollution through point (industrial and residential discharge) and non-point (siltation, herbicide and fertilizer run-off) sources is perhaps the greatest on-going threat to this species and most freshwater mussels. Lowered dissolved oxygen content and elevated ammonia levels (frequently associated with agricultural runoff and sewage discharge) have been shown to be lethal to some species of freshwater naiads (Horne and McIntosh, 1979). Residential, mineral and industrial development also pose a significant threat. Rotenone, a toxin used to kill fish in bodies of water for increased sport fishery quality, has been shown to be lethal to mussels as well (Heard, 1970). Destruction of habitat through stream channelization and maintenance and the construction of dams is still a threat in some areas. Impoundments reduce currents that are necessary for basic physiological activities such as feeding, waste removal and reproduction. In addition, reduced water flow typically results in a reduction in water oxygen levels and a settling out of suspended solids (silt, etc.), both of which are detrimental. Dredging of streams has an immediate effect on existing populations by physically removing and destroying individuals. Dredging also affects the long-term recolonization abilities by destroying much of the potential habitat, making the substrates and flow rates uniform throughout the system. Natural predators include raccoons, otter, mink, muskrats, turtles and some birds (Simpson, 1899; Boepple and Coker, 1912; Evermann and Clark, 1918; Coker et al., 1921; Parmalee, 1967; Snyder and Snyder, 1969). Domestic animals such as hogs can root mussel beds to pieces (Meek and Clark, 1912). Fishes, particularly catfish, Ictalurus spp. and Ameirus spp.., and freshwater drum, Aplodinotus grunniens, also consume large numbers of unionids.
USFWS (1990; 1992) summarizes the major threats to the subspecies. Many historic populations were eliminated when river sections they inhabited were impounded (similarly affected host fish). The Green River in Kentucky has experienced water quality problems related to impacts from oil and gas production in the watershed, and commercial mussel fishing has occurred in the watershed in recent years past. Individuals still surviving in the Cumberland River watershed are potentially threatened by gravel dredging, channel maintenance, and commercial mussel fishing (recent past only- incidental take).

Short-term Trend: Decline of >50%
Short-term Trend Comments: The few remaining populations are small and isolated. A recent fuel spill into Fish Creek may have eliminated the last remaining population of Epioblasma obliquata perobliquata as it has not been seen in over 10 years (Grabarkiewicz and Crail, 2006).

Long-term Trend: Decline of >90%
Long-term Trend Comments: This species has declined to fewer than five (some possibly not viable) remaining occurrences from a formerly wide range in the Ohio basin. All historical records in Alabama are from the Tennessee River in the vicinity of Muscle Shoals (most recent 1924), but an archaeological specimen from the Tennessee River in eastern Tennessee suggests it occurred across the state, at least prehistorically (Williams et al., 2008). In Ohio, subspecies perpliquata is extirpated from all sites (Maumee and Auglaize Rivers) except possibly Fish Creek in Williams Co.; while subspecies obliquata is extirpated from all sites (Ohio River at Cincinnati, Portsmouth, and Marietta, Scioto River at Circleville, Walhonding River) except lower Killbuck Creek (Watters et al., 2009).

Intrinsic Vulnerability: Moderately vulnerable

Environmental Specificity: Narrow. Specialist or community with key requirements common.
Environmental Specificity Comments: The decline in the overall range suggests that this mussel is not tolerant of poor water quality. It is sensitive to pollution, siltation, habitat perturbation, inundation, and loss of glochidial hosts. This species was not found in the heavily modified portion of Killbuck Creek that lacked wooded riparian corridors or had significant erosion problems.

Other NatureServe Conservation Status Information

Inventory Needs: Historical distribution is reasonably well known. Given the discovery of the Killbuck Creek population in 1994 (Hoggarth et al., 1995) additional survey work in areas likely to support this species is warranted. Periodic status surveys are needed to monitor changes in the remaining populations of this mussel.

Distribution
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Global Range: (<100 square km (less than about 40 square miles)) Historically the entire species was widespread in the Ohio River drainage. Now reproducing populations only exist in a few streams: Fish Creek, Indiana (but not seen in over 10 years- Grabarkiewicz and Crail, 2006) (Epioblasma obliquata perobliqua); and in Killubuck Creek, Ohio, Green River, Kentucky, and Cumberland River, Tennessee (latter possibly extirpated) (Epioblasma obliquata obliquata) (see Isom et al., 1979; Hoggarth et al., 1995; Parmalee and Bogan, 1998). A population (likely Epioblasma obliquata perobliqua) may also exist in the mainstem of the St. Joseph River in Allen Co., Indiana (Pryor, 2005). Also in Indiana, museum records are known for the Tippecanoe River (Cummings and Berlocher, 1990). Johnson (1978) did not differentiate between the two subspecies, and it is difficult to determine the range of these taxa based upon his work. E. obliquata obliquata as defined here once occurred in the Scioto River in Ohio; in the Lower Ohio River (Goodrich and van der Schalie, 1944) and its Kentucky tributaries of the Licking, Green, and Kentucky Rivers (Johnson, 1978); at Muscle Shoals, Alabama; in the Tennessee River and Caney Fork and Harpeth Rivers of the Cumberland River in Tennessee; and the Cumberland River proper in Kentucky (Johnson, 1978). It is apparently extirpated from Ohio, Alabama (Mirarchi et al., 2004), and Indiana and is now known only from Kentucky and Tennessee. Stansbery believed both subspecies were present in the Wabash River with E. obliquata perobliqua occurring more in the north. The Epioblasma obliquata sulcata of Call (1900) is E. obliquata perobliqua. E. obliquata perobliqua historically occurred in the Great Lakes drainages: Blanchard River, Auglaize River, and Fish Creek in Ohio; St. Mary's River, White River, and upper Wabash River in Indiana; the Maumee River in Ohio and Indiana; Otter Creek, River Basin, and Lake St. Clair in Michigan; Detroit River in Michigan and Ontario; Niagara River in New York [later to be determined a specimen of Obovaria olivaria (Strayer and Jirka, 1997)]; and from Lake Erie: Put-in-Bay, Ohio, La Plaisance Bay, and near Stony Creek, Michigan (Johnson, 1978). Occurrences in the Wabash River in Illinois have long been extirpated (Cummings and Mayer, 1997).

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 ALextirpated, ILextirpated, IN, KY, MI, OH, TN

Range Map
No map available.


U.S. Distribution by County Help
State County Name (FIPS Code)
AL Colbert (01033)*, Lauderdale (01077)*
IN Allen (18003)*, De Kalb (18033)*, Fountain (18045)*, Kosciusko (18085)*, Marion (18097)*, Owen (18119)*, Parke (18121)*, Vermillion (18165)*, Warren (18171)*
KY Boone (21015)*, Butler (21031), Campbell (21037)*, Cumberland (21057)*, Edmonson (21061)*, Greenup (21089)*, Hart (21099)*, Henderson (21101)*, Kenton (21117)*, Lewis (21135)*, Muhlenberg (21177)*, Ohio (21183)*, Pendleton (21191)*, Pulaski (21199)*, Warren (21227)
MI Monroe (26115)*, Wayne (26163)*
OH Coshocton (39031), Putnam (39137), Williams (39171)
TN DeKalb (47041)*, Putnam (47141)*, Smith (47159), Trousdale (47169), Wilson (47189)
* Extirpated/possibly extirpated
U.S. Distribution by Watershed Help
Watershed Region Help Watershed Name (Watershed Code)
04 Lake St. Clair (04090002)+, Detroit (04090004)*, Ottawa-Stony (04100001)+*, St. Joseph (04100003)+, St. Marys (04100004)+*, Upper Maumee (04100005)+*, Auglaize (04100007)+
05 Walhonding (05040003)+, Muskingum (05040004)*, Lower Scioto (05060002)*, Little Scioto-Tygarts (05090103)+*, Ohio Brush-Whiteoak (05090201)+*, Middle Ohio-Laughery (05090203)+*, Licking (05100101)+*, Upper Green (05110001)+, Middle Green (05110003)+*, Lower Green (05110005)+*, Upper Wabash (05120101)*, Tippecanoe (05120106)+*, Middle Wabash-Little Vermilion (05120108)+*, Middle Wabash-Busseron (05120111)*, Lower Wabash (05120113)*, Upper White (05120201)+*, Lower White (05120202)+*, Upper East Fork White (05120206), Upper Cumberland-Lake Cumberland (05130103)+*, South Fork Cumberland (05130104)+*, Upper Cumberland-Cordell Hull (05130106)*, Caney (05130108)+*, Lower Cumberland-Old Hickory Lake (05130201)+, Harpeth (05130204)*, Lower Cumberland (05130205)*, Lower Ohio-Little Pigeon (05140201)+*, Highland-Pigeon (05140202)*, Lower Ohio-Bay (05140203)*
06 Pickwick Lake (06030005)+*, Lower Tennessee-Beech (06040001)*
+ 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: Males and females both yellowish brown or brown but much different in shape; males oblong and solid, with a shallow sulcus running along the posterior ridge from the umbo to the ventral margin; females rectangular, truncated, and inflated posteriorly with a finely grooved surface and serrated growth lines.
General Description: SHELL: (from Bogan and Parmalee, 1983, p 33-4) "The shell is medium sized, subquadrate, subtrapezoid or quadrate in outline. Valves are very inequilateral, inflated and solid. The anterior end of the male is squarely subtruncate, regularly rounded in females. The posterior end of the male is somewhat bluntly pointed above, sloping and truncated below; in the female it is truncated posteriorly. The ventral margin of males is broadly curved, but is almost straight in females. The posterior ridge of the male is doubled, rather low and faint. The posterior ridge in female specimens is somewhat obscured by a sharp sulcus before the brood pouch swelling. Beaks are elevated, prominent, located at the extreme anterior end. Beak sculpture consists of a few faint corrugations, sometimes broken or occasionally double-looped. The surface is interrupted with numerous strong growth rest lines. The epidermis is smooth and shiny, yellowish-green, yellow or brownish, usually with numerous fine, faint, wavy green rays. The shell often has a satin-like epidermis when young, but with age it becomes brownish and the rays become obscured. The left valve has two subtriangular, ragged, elevated pseudocardinal teeth, a narrow interdentum and two short, straight lateral teeth. The right valve has one, sometimes three pseudocardinal teeth, one larger triangular tooth with a smaller tooth before and behind it. There is one short lateral tooth, often with a vestigial tooth below it. Beak cavities are rather shallow. The muscle scars and pallial line are impressed." The nacre in E. OBLIQUATA OBLIQUATA is predominantly deep purple or bluish, while in E. OBLIQUATA PEROBLIQUA it is white. The shell of PEROBLIQUA is more greenish, more laterally compressed, higher, and with lower umbos than OBLIQUATA.

ANIMAL: No specific information is available. The following is the description of Ortmann (1912, p 354) for the genus in general (as TRUNCILLA): "Inner laminae of inner gills entirely connected with abdominal sac. In the female, the inner edge of the mantle in front of the branchial is not parallel to the outer edge, but is more or less remote from it, often quite distant, and it has finer or coarser papillae. Toward the middle of the lower margin, the two edges again approach each other, and are normal farther forward. The mantle between the two edges is peculiarly spongy. Thus an inner compartment is formed in front of the branchial opening. In the male, the two edges of the mantle do not have this structure, or it is merely indicated. Brood pouch swollen, kidney-shaped, formed by many ovisacs, occupying the posterior section of the outer gill. Edge of brood pouch blunt, beaded, but not pigmented."

EPIOBLASMA O. OBLIQUATA has been illustrated by Parmalee (1967), Johnson (1978), Bogan and Parmalee (1983), Stansbery (1971), and Burch (1975).

Reproduction Comments: Nothing is known specifically for either subspecies. Surber (1912: 7) reported Epioblasma obliquata sulcata (syn. of Epioblasma obliquata perobliqua) to be gravid in September and October.

The host fish is not known. Hill (1986) reported that several species of darters, the Log perch, and the Banded sculpin may be hosts for other species of Epioblasma.

Based upon counts of annular growth lines, both subspecies may reach 15+ years of age. It is not known at what ages reproductive maturity begins and ends. Because of the rarity of live material, it not known if existing populations are reproductively active. And because of their small size, it is not known if juveniles are present in any of the populations. It must be emphasized that if the host fish is not present within the range, then existing large, healthy, reproductively active populations may still be in imminent danger of extinction.

Host fish for Epioblasma obliquata obliquata have been determined to be rock bass (Ambloplites rupestris), mottled sculpin (Cottus bairdi), greenside darter (Etheostoma blennioides), stonecat (Noturus flavus), logperch (Percina caprodes), and blackside darter (Percina maculata) (Watters et al., 1999).

Glochidial hosts have not been determined for Epioblasma obliquata perobliqua.

Ecology Comments: Refer to the General Freshwater Mussel ESA.
Habitat Type: Freshwater
Non-Migrant: N
Locally Migrant: N
Long Distance Migrant: N
Riverine Habitat(s): BIG RIVER, High gradient, MEDIUM RIVER, Riffle
Special Habitat Factors: Benthic
Habitat Comments: Although this species has been collected from water to about 30 feet, there is little doubt that is primarily a riffle species of sand/gravel (Ortmann, 1919; Johnson, 1978; Bogan and Parmalee, 1983). Like most members of the genus, it appears to require swiftly moving water, perhaps linked to high oxygen concentrations, in order to survive. Epioblasma obliquata obliquata, in particular, is a species found in riffle areas of larger streams and rivers which have been all but eliminated by impoundment and dredging for barge canals (Stansbery, 1970; 1971). Of the eleven or so species of naiads thought to be extinct in 1971 by Stansbery, most were from this type of habitat and all were species of Epioblasma.
Economic Attributes Not yet assessed
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Management Summary
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Stewardship Overview: Recovery plans have been drafted for Epioblasma obliquata obliquata (USFWS, 1990a) and Epioblasma obliquata perobliqua (USFWS, 1990b) and each was listed as federally endangered in the U.S. (1990 and 1976, respectively). Nonessessential Experimental Populations (NEPs) of Epioblasma obliquata obliquata have been established in the Tennessee River below Wilson Dam, Colbert and Lauderdale Cos., Alabama, extending 13.4 km and including the lower 8 km of all tributaries that enter the Wilson Dam tailwaters (USFWS, 2001).
Restoration Potential: Most of the large stream riffle areas have been eliminated by impoundment and dredging and realistically cannot be recovered. Bogan and Parmalee (1983) have suggested transplanting a population to an alternate site. However, until the host fish has been identified, it is unlikely a successful program to conserve this species can be realistically undertaken. Efforts should be made to save remaining populations in the interim.
Preserve Selection & Design Considerations: In view of the fact that commercial fishing may be one of the most serious threats to E. OBLIQUATA OBLIQUATA, some effort should be made to curtail its collection. That subspecies is Endangered in Kentucky and applicable enforcement could be used there. However, it is not Endangered or Threatened in Tennessee, and alternative methods such as making the shellers aware of the problem should be tried.

Refer to the General Freshwater Mussel ESA.

Management Requirements: Refer to the General Freshwater Mussel ESA.
Monitoring Requirements: At present these naiads are in danger of imminent extinction. Populations must be promptly located and, if necessary, relocated.

Refer to the General Freshwater Mussel ESA.

Management Research Needs: Refer to the General Freshwater Mussel ESA.
Biological Research Needs: In order to effectively manage mussel species it is necessary to work out certain life history characteristics first. Because of their unusual life-cycle and dependence on fish for completion of that cycle, it is imperative that the host species for the catspaw be ascertained. Life history studies need to be done to identify age and size at sexual maturity, recruitment success, age class structure, and other important life history parameters.

Research is needed to assess the success of watershed protection on mussel populations. Abundance and distribution of selected species need to be monitored in order to ascertain how species abundances change over time. From that we can assess what land-use changes, conservation practices, and physical/chemical parameters are correlated with, and possibly responsible for, the biological changes.

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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Authors/Contributors
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NatureServe Conservation Status Factors Edition Date: 28Apr2009
NatureServe Conservation Status Factors Author: Cordeiro, J. (2009); Cummings, K. S. (2000)
Management Information Edition Date: 29Nov2007
Management Information Edition Author: Cordeiro, J. (2007); Watters, G. Thomas (1986)
Element Ecology & Life History Edition Date: 06Dec2006
Element Ecology & Life History Author(s): Cordeiro, J. (2006): WATTERS, T. G (1986)

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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  • Boepple, J.F. and R.E. Coker. 1912. Mussel resources of the Holston and Clinch rivers of eastern Tennessee. Bureau of Fisheries Document 765. 13 pp.

  • Bogan, A.E. and P.W. Parmalee. 1983. Tennessee's Rare Wildlife: Volume II: The Mollusks. Report to the Tennessee Natural Heritage Program and Tennessee Wildlife Resources Agency: Nashville, Tennessee. 123 pp.

  • Burch, J.B. 1975a. Freshwater unionacean clams (Mollusca: Pelecypoda) of North America. Malacological Publications: Hamburg, Michigan. 204 pp.

  • Call, R.E. 1900. A descriptive illustrated catalogue of the mollusca of Indiana. Annual Report of the Indiana Department of Geology and Natural Resources, 24: 335-535.

  • Coker, R.E., A.F. Shira, H.W. Clark, and A.D. Howard. 1921. Natural history and propagation of fresh-water mussels. Bulletin of the Bureau of Fisheries [Issued separately as U.S. Bureau of Fisheries Document 839] 37(1919-20):77-181 + 17 pls.

  • Cummings, K.S. and C.A. Mayer. 1992. Field Guide to Freshwater Mussels of the Midwest. Illinois Natural History Survey Manual 5, Illinois. 194 pp.

  • Cummings, K.S. and C.A. Mayer. 1997. Distributional checklist and status of Illinois freshwater mussels (Mollusca: Unionacea). Pages 129-145 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, October 1995, St. Louis, Missouri. Upper Mississippi River Conservation Committee, Rock Island, Illinois.

  • Cummings, K.S. and J.M. Berlocher. 1990. The naiades or freshwater mussels (Bivalvia: Unionidae) of the Tippecanoe River, Indiana. Malacological Review 23:83-98.

  • Evermann, B.W. and H.W. Clark. 1918. The Unionidae of Lake Maxinkukee. Proceedings of the Indiana Academy of Science 1917:251-285.

  • Goodrich, C. and H. van der Schalie. 1944. A revision of the Mollusca of Indiana. The American Midland Naturalist, 32: 257-326.

  • Grabarkiewicz, J. and T. Crail. 2006. Freshwater Mussels of the Maumee Drainage. A Compendium and Guide to the Unionids of the Maumee River and Tributaries. Lucas Soil and Water Conservation District, Maumee, Ohio. 61 pp.

  • Heard, W.H. 1970. Eastern freshwater mollusks. 1. The south Atlantic and Gulf drainages. In: A.H. Clarke (ed.) Rare and endangered molluscs of North America. Malacologia 10:1-56.

  • Hill, D.M. 1986. Cumberlandian mollusk conservation program, activity 3: identification of fish hosts. Office of Natural Resources and Economic Development, Tennessee Valley Authority, Knoxville, Tennessee. 55 pp.

  • Hoggarth, M.A., D.L. Rice, and D.M. Lee. 1995. Discovery of the federally endangered freshwater mussel, Epioblasma obliquata obliquata (Rafinesque, 1820) (Unionidae), in Ohio. Ohio Journal of Science 95(4):298-299.

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

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

  • Isom, B.G., C. Gooch, and S.D. Dennis. 1979. Rediscovery of a presumed extinct river mussel, Dysnomia sulcata (Unionidae). The Nautilus, 93(2-3): 84.

  • 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.

  • Meek, S. E., and H.W. Clark. 1912. The mussels of the Big Buffalo Fork of White River, Arkansas. Report and Special Papers of the U.S. Fish Commission [Issued separately as U.S. Bureau of Fisheries Document 759] 1911:1-20.

  • 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.

  • Ortmann, A.E. 1912. Notes upon the families and genera of the najades. Annals of the Carnegie Museum 8(2):222-365.

  • Ortmann, A.E. 1919. Monograph of the naiades of Pennsylvania. Part III. Systematic account of the genera and species. Memoirs of the Carnegie Museum 8(1):1-385.

  • Parmalee, P.W. 1967. The freshwater mussels of Illinois. Illinois State Museum, Popular Science Series 8:1-108.

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

  • Pryor, W.W. 2005. Distribution of the native freshwater mussels in the rivers of Allen County, Indiana. Report to the St. Joseph River Watershed Initiative, Fort Wayne, Indiana. 71 pp.

  • Simpson, C.T. 1899. The pearly fresh-water mussels of the United States; their habits, enemies, and diseases, with suggestions for their protection. Bulletin of the U.S. Fish Commission [Issued separately as U.S. Bureau of Fisheries Document 413] 18(1898):279-288.

  • Smith, P.W. 1971. Illinois streams: A classification based on their fishes and an analysis of factors responsible for disappearance of native species. Illinois Natural History Survey Biological Notes 76:1-14.

  • Snyder, N. and H. Snyder. 1969. A comparative study of mollusk predation by Limpkins, Everglade Kites, and Boat-tailed Grackles. Eighth Annual Report of the Cornell Laboratory of Ornithology 8:177-223.

  • 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.

  • Stansbery, D.H. 1970. Eastern freshwater mollusks (I): The Mississippi and St. Lawrence River systems. Malacologia, 10(1): 9-22.

  • 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.

  • Strayer, D.L. and K.J. Jirka. 1997. The Pearly Mussels of New York State. New York State Museum Memoir 26. The University of the State of New York. 113 pp. + figures.

  • Surber, T. 1912. Identification of the glochidia of freshwater mussels. Report submitted to U.S. Bureau of Fisheries, document 777: 1-10.

  • 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). 1990d. Purple cat's paw pearly mussel recovery plan. U.S. Fish and Wildlife Service: Atlanta, Georgia. 26 pp.

  • U.S. Fish and Wildlife Service (USFWS). 1992. Recovery plan for purple cat's paw pearlymussel (Epioblasma (=Dysnomia) obliquata obliquata (=Epioblasma sulcata sulcata)). Prepared by R.G. Biggins, U.S. Fish and Wildlife Service: Atlanta, Georgia. 26 pp.

  • U.S. Fish and Wildlife Service (USFWS). 2001. Endangered and Threatened Wildlife and Plants; establishment of nonessential experimental population status for 16 freshwater mussels and 1 freshwater snail (Anthony's Riversnail) in the free-flowing reach of the Tennessee River below the Wilson Dam, Colbert and Lauderdale Counties, Alabama. Federal Register, 66(115): 32250-32264.

  • 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.

  • Watters, G.T., S.W. Chordas, S.H. O'Dee, and J. Reiger. 1999. Host identification studies for six species of Unionidae. Pages 75-76 in Program Guide & Abstract of the First Symposium of the Freshwater Conservation Society, 17-19 March 1999, Chattanooga, Tennessee. 92 pp.

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

  • Cicerello, R.R. and G.A. Schuster. 2003. A guide to the freshwater mussels of Kentucky. Kentucky State Nature Preserves Commission Scientific and Technical Series 7:1-62.

  • Graf, D.L. 2002. Historical biogeography and late glacial origin of the freshwater pearly mussel (Bivalvia: Unionidae) faunas of Lake Erie, North America. Occasional Papers on Mollusks 6(82):175-211.

  • Johnson, R.I. 1978. Systematics and zoogeography of Plagiola (= Dysnomia = Epioblasma), an almost extinct genus of freshwater mussels (Bivalvia: Unionidae) from middle North America. Bulletin of the Museum of Comparative Zoology, 148(6): 239-320.

  • NatureServe. No Date. Full species reconciliation of subspecies-by-watershed source data for freshwater fish, mussel and crayfish for use in the watershed distribution databases.

  • U.S. Fish and Wildlife Service (USFWS). 1990e. White cat's paw pearly mussel recovery plan. U.S. Fish and Wildlife Service: Twin Cities, Minnesota. 42 pp.

  • Watters, G.T. 1995a. A field guide to the freshwater mussels of Ohio. revised 3rd edition. Ohio Department of Natural Resources, Division of Wildlife, Columbus, Ohio. 122 pp.

  • Watters, G.T., M.A. Hoggarth, and D.H. Stansbery. 2009b. The Freshwater Mussels of Ohio. Ohio State University Press: Columbus, Ohio. 421 pp.

  • 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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