The members of the genus Fusconaia are among the most difficult to identify in North America. Arguments arise even among taxonomists regarding the "species" represented in the genus. Stansbery (1983) summarized many of the problems and identified a few of the shell characters used to separate Fusconaia subrotunda from the morphologically similar and often co-occurring Fusconaia flava and the "forms" Fusconaia trigona (Lea 1831), Fusconaia undata (Barnes 1823), and Fusconaia wagneri (Baker 1928). A few "morphs" have been variously identified and named but no rigorous genetic, anatomic, or conchological study has ever been published on this group to help elucidate species boundaries or relationships.

Synonyms include: Unio politus, Say 1834; Unio kirtlandianus, Lea 1834; Unio leseurianus, Lea 1840; Unio pilaris, Lea 1840; Unio globatus, Lea 1871; Unio bursa-pastoris, B.H. Wright 1896; Quadrula flexuosa, Simpson 1900; Quadrula andrewsii, Marsh 1902; and Quadrula beauchampii, Marsh 1902.

Campbell et al. (2005) found this species placed confidently within the genus Fusconaia.

A list of synonyms for this species can be found on The MUSSEL project web site (Graf and Cummings 2011).

Fusconaia subrotunda has been assessed as Vulnerable A2ce. Although this species still remains widespread, its distribution is greatly fragmented and many populations have questionable long-term viability, especially those in large rivers where Zebra Mussel populations are now established. Given the severely fragmented nature of existing location for this species, and current loss of habitat, this species has seen an inferred population reduction of at least between 28-45% since 1970 (assumed to represent three generations), though this is a conservative estimate (K. Cummings pers. comm. 2010). Further research regarding the taxonomy, population trends, ecology and life history (to verify assumptions made in the calculation of generation length), as well as threats impacting this species is required, and conservation measures including species and site protection would provide this species protection.

Historically, this species was distributed in the Ohio, Cumberland and Tennessee river drainages. Its current status is largely unknown throughout its range. It is thought to be extirpated from Illinois, having not been collected there since the 1940s (Cummings and Mayer 1997), and very rare in Indiana and North Carolina. It was once thought to be nearly extirpated from Kentucky (Schuster 1988), but is "sporadic in the lower Green River and eastward" (Cicerello and Schuster 2003). The species is endangered in Ohio where the only remaining population is thought to exist in the Muskingum River (Watters 1995, G.T. Watters pers. comm. 1998). Scattered occurrences are known for West Virginia (Elk and Little Kanawha) and Virginia and it might still be hanging on in Sugar Creek in Indiana; otherwise, Indiana and Illinois occurrences are extirpated (Cummings and Mayer 1997). Occurrences in Arkansas (Meek and Clark 1912) are questionable, but are probably attributed to another species of Fusconaia (ebena, flava, ozarkensis). This species is still extant in portions of the Allegheny River drainage (A. Bogan pers. comm. 2010).

Historically, this species was widely distributed in the Ohio River drainage. Current populations are thought to be restricted to the Muskingum River in Ohio and parts of the upper Tennessee and Cumberland river drainages. In Ohio, it is distributed in the Muskingum River system where it is rare (Watters 1995). In North Carolina, it is reported from the Hiwassee and French Broad Rivers (Bogan 2002) in Buncombe (extirpated), Cherokee, Clay, and Transylvania Cos. (LeGrand et al. 2006). In Tennessee, it occurs in the Clinch, Powell, Little Tennessee (probably now extirpated), Elk, lower Tennessee, and Cumberland Rivers with occasional specimens in the Holston River (Knox and Grainger Cos.), Tellico River (Monroe Co.), and the Hiwassee River (Polk Co.) (Parmalee and Bogan 1998). In Alabama, it occurred historically throughout much of the Tennessee, Cumberland, and Ohio River systems but is known to be extant only in the Tennessee River tailwaters of Guntersville and Wilson Dams (Mirarchi et al. 2004). In Kentucky, it is sporadic in the lower Green River and eastward (Cicerello and Schuster 2003). It has been collected in Kentucky in the Middle Green and Barren Rivers (Cochran and Layzer 1993). This species occurs in Muddy Creek (French Creek drainage) in the Erie NWR in Crawford Co., Pennsylvania (Mohler et al. 2006), and is also known from the Connoquenessing and Middle Allegheny- Tionesta in that state (PA NHP pers. comm. 2006). It was reported as relictual in Copper Creek (Upper Clinch drainage) in Virginia (Fraley and Ahlstedt 2000) as well as the upper Clinch River (Jones et al. 2001). It is rare in the Tippecanoe River, Indiana (Cummings and Berlocher 1990) and a single live specimen was collected from Sugar Creek in 1991, although Fisher (2006) lists it as extirpated from the entire Wabash basin.

TRENDS:
Due to problems obtaining a unbiased and complete sample, abundance in mussels is difficult to estimate, and no estimates of population size or abundance have been made for this species.

Populations of medium-sized and small river forms (there are many forms of this species) such as the upper Powell and Clinch Rivers, have remained stable and viable in Tennessee (Parmalee and Bogan 1998).

Overall, the species is declining throughout its range. It has been extirpated from Illinois and nearly so in Indiana, but was once found throughout the Wabash River (Cummings and Mayer 1997). Its Pennsylvania distribution has been reduced from a widespread western Pennsylvania range (Ortmann 1919) to basically French Creek, Connoquenessing, and Middle Allegheny- Tionesta (Mohler et al. 2006).

Hanlon et al. (2009) state that this species has been extirpated from Copper Creek, Virginia. Furthermore, it has been almost extirpated from the State of Ohio: it has been extirpated from the Scioto River, Maumee River, Mahoning River and there is a single record of this species from the Miami River and other rivers within Ohio (Watters et al. 2009).

In Alabama, it occurred historically throughout much of the Tennessee, Cumberland, and Ohio River systems but is known to be extant only in the Tennessee River tailwaters of Guntersville and Wilson Dams (Mirarchi et al. 2004).

Given the severly fragmented nature of existing location for this species, and current loss of habitat, this species has seen an inferred population reduction of between 30-50%, though this is likely to be a conservative estimate (K. Cummings pers. comm. 2010). The precise time period over which the decline has occurred is uncertain, but it is likely that the majority of the declines will have occurred in the last 50-70 years, and not exceeding 100 years. Assuming a constant decline over time, resulting in a 50% population decline from previous levels, we assume that declines over the past 42 years (since 1970) were somewhere between 28% (if decline occurred at a constant rate over a 100-year period) and 45% (if declines occurred at a constant rate over a time period of 50 years).

This species is found in small to large rivers in gravel with a strong current (Watters 1995). In headwater rivers it occurs in shoal habitats and in the Tennessee River today it can be found only in tailwaters of dams, where it is rare. There it may occur at depths of more than 6 m. The preferred substrate of this species is sand and gravel (Cicerello and Schuster 2003), or a mixture of gravel and sand, kept free of silt by current.

This species is a short-term brooder, gravid from early May through July (Ortmann 1909, 1913, 1919, 1921). Mature glochidia have been reported as early as mid-May (Ortmann 1921), but they may mature later in some populations (Ortmann 1913). Glochidial conglutinates are subcylindrical and red, pink or white (Ortmann 1912, 1918, 1921), and may be discharged intact or in pieces (Ortmann 1910, 1913). Glochidial hosts are unknown (Williams et al. 2010).

Direct life-history data are not available for this species. Freshwater mussels are highly variable in their longevity from species to species (e.g. Haag and Rypel 2010). Studies have shown longevity of species in the genus Fusconaia to range from 15 to 51 years (Haag and Rypel 2010). 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 Fusconaia cerina, F. cuneolus, and F. ebena; Haag and Rypel 2010), and derive an average longevity of around 33 years (using minimum and maximum ages observed, we derive upper and lower margins of 15 and 51 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 years in Quadrula asperata (Haag and Staton 2003). Assuming a first age of maturity of around five years, generation length (estimated as the average age of a parent in the population) is estimated as around 14 years, with three generations spanning approximately 42 years. As a result, we assess population decline estimates since around 1970 for the purpose of validation of criterion A. However, this may represent a vast underestimate of generation length, as it has been suggested that growth ring counts may underestimate age by a factor of between three and ten (Anthony et al. 2001).

This species is sensitive to pollution, siltation, habitat perturbation, inundation, and loss of its glochidial hosts. Smith (1971) ranked the causes of extirpation or declines in fish species in Illinois as follows (and it is likely that these causes affect most if not all aquatic species, including mussels, throughout North America): 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. 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 Ameiurus spp.) and Freshwater Drum (Aplodinotus grunniens) also consume large numbers of unionids.

This species is not utilized.

Although some populations occur in "protected" sanctuaries or natural areas, disturbances in the watershed impact populations regardless of site protection. No site is adequately protected. This species occurs in Muddy Creek (French Creek drainage) in the Erie NWR in Crawford Co., Pennsylvania (Mohler et al. 2006). Williams et al. (2010) list this species as according to the American Fisheries Society assessment. Further research regarding the taxonomy, population trends, ecology and threats impacting this species is required, and conservation measures including species and site protection would provide this species' protection.