Endangered and Threatened Wildlife and Plants; Determination of Endangered Status for the Sheepnose and Spectaclecase Mussels Throughout Their Range
Federal RegisterMar 13, 2012
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DEPARTMENT OF THE INTERIOR
Fish and Wildlife Service
50 CFR Part 17
[Docket No. FWS-R3-ES-2010-0050; 4500030113]
RIN 1018-AV93
Endangered and Threatened Wildlife and Plants; Determination of Endangered Status for the Sheepnose and Spectaclecase Mussels Throughout Their Range
AGENCY:
Fish and Wildlife Service, Interior.
ACTION:
Final rule.
SUMMARY:
We, the U.S. Fish and Wildlife Service (Service), determine endangered status under the Endangered Species Act of 1973 (Act), as amended, for the spectaclecase
(Cumberlandia monodonta)
and sheepnose
(Plethobasus cyphyus),
two freshwater mussels. This final rule implements the Federal protections provided by the Act for these species throughout their ranges, including sheepnose in Alabama, Illinois, Indiana, Iowa, Kentucky, Minnesota, Mississippi, Missouri, Ohio, Pennsylvania, Tennessee, Virginia, West Virginia, and Wisconsin, and spectaclecase in Alabama, Arkansas, Illinois, Indiana, Iowa, Kansas, Kentucky, Minnesota, Missouri, Ohio, Tennessee, Virginia, West Virginia, and Wisconsin. We determined that critical habitat for the spectaclecase and sheepnose is prudent, but not determinable at this time.
DATES:
This rule becomes effective on April 12, 2012.
ADDRESSES:
This final rule is available on the Internet at
http://www.regulations.gov
at Docket No. FWS-R3-ES-2010-0050. Comments and materials received, as well as supporting documentation used in preparing this final rule will be available for public inspection, by appointment, during normal business hours, at the U.S. Fish and Wildlife Service, Rock Island, Illinois Ecological Services Field Office, 1511 47th Avenue, Moline, IL 61265; telephone 309-757-5800.
FOR FURTHER INFORMATION CONTACT:
Richard Nelson, Field Supervisor, at the U.S. Fish and Wildlife Service, Rock Island, Illinois Ecological Services Field Office, (see
ADDRESSES
section). If you use a telecommunications device for the deaf (TDD), call the Federal Information Relay Service (FIRS) at 800-877-8339.
SUPPLEMENTARY INFORMATION:
Background
Previous Federal Action
Federal actions for these species prior to January 19, 2011, are outlined in our proposed rule for these actions (76 FR 3392-3420). Publication of the proposed rule opened a 60-day comment period, which closed on March 21, 2011.
Species Descriptions
The spectaclecase
(Cumberlandia monodonta)
is a member of the mussel family Margaritiferidae and was originally described as
Unio monodonta
Say, 1829. The type locality is the Falls of the Ohio (on the Ohio River in the vicinity of Louisville, Kentucky, and adjacent Indiana), and the Wabash River (probably the lower portion in Illinois and Indiana) (Parmalee and Bogan 1998, p. 49). Parmalee and Bogan (1998, p. 49) summarized the synonymy of the spectaclecase. The species has been placed in the genera
Unio, Margaritana,
Alasmidonta, Margarita,
Margaron,
and
Margaritifera
at various times in history. Ortmann (1912, p. 13) placed it in the monotypic (a taxonomic group with only one biological type) genus
Cumberlandia
in the family Margaritiferidae. Currently recognized synonymy includes
Unio soleniformis
(Lea). Smith (2001, p. 43) reassigned the spectaclecase to the Holarctic genus
Margaritinopsis
based on shell and gill characters. The Service, however, will defer to the Committee on Scientific and Vernacular Names of Mollusks of the Council of Systematic Malacologists, American Malacological Union (Turgeon
et al.
1998), on whether the genus
Margaritinopsis
is accepted as valid for the spectaclecase. Until an official decision is made, the Service will use the commonly accepted
Cumberlandia
for the genus of this species. Spectaclecase is the accepted common name for
Cumberlandia monodonta
(Turgeon
et al.
1998, p. 32).
The spectaclecase is a large mussel that reaches at least 9.25 inches (23.5 centimeters (cm)) in length (Havlik 1994, p. 19). The shape of the shell is greatly elongated, sometimes arcuate (curved), and moderately inflated, with the valves being solid and moderately thick, especially in older individuals (Parmalee and Bogan 1998, p. 49). Both anterior and posterior ends of the shell are rounded with a shallow depression near the center of the shell (Baird 2000, p. 6; Parmalee and Bogan 1998, p. 49). The anterior end is higher than the posterior end (Baird 2000, p. 6). The posterior ridge is low and broadly rounded (Parmalee and Bogan 1998, p. 50). Year-one specimens have heavy ridges running parallel with the growth arrests, which are shell lines that indicate slower periods of growth, thought to be laid down annually (Baird 2000, p. 6). The periostracum (external shell surface) is somewhat smooth, rayless, and light yellow, greenish-tan, or brown in young specimens, becoming rough and dark brown to black in old shells (Parmalee and Bogan 1998, p. 50). The shell commonly will crack posteriorly when dried (Oesch 1984, p. 31).
Internally, the single pseudocardinal tooth (a triangular tooth-like structure along the hinge line of the internal portion of the shell) is simple and peg-like in the right valve, fitting into a depression in the left (Parmalee and Bogan 1998, p. 50). The lateral teeth are straight and single in the right valve, and double in the left valve, but become fused with age into an indistinct raised hinge line (Parmalee and Bogan 1998, p. 50). The soft anatomy was described by Williams
et al.
(2008, pp. 497-498). The color of the nacre (interior covering of the shell) is white, occasionally granular and pitted, mostly iridescent in young specimens, but becoming iridescent posteriorly in older shells (Parmalee and Bogan 1998, p. 50). There are no differences between the sexes in the shells of this species (Baird 2000, p. 19). Key characters for distinguishing the spectaclecase from other mussels are its large size, elongate shape, arcuate ventral margin, dark coloration, roughened periostracum, poorly developed teeth, and white nacre (Oesch 1984, pp. 31-32). No other North American mussel species has this suite of characters.
The sheepnose
(Plethobasus cyphyus)
is a member of the mussel family Unionidae and was originally described as
Obliquaria cyphya
Rafinesque, 1820. The type locality is the Falls of the Ohio (Parmalee and Bogan 1998, p. 175) on the Ohio River in the vicinity of Louisville, Kentucky, and adjacent Indiana. Parmalee and Bogan (1998, p. 175) summarized the synonymy of the species. Over the years, the name of this species has been variably spelled
cyphya, scyphius, cyphius, cyphia, cyphyum,
and ultimately
cyphyus.
Over the years the species has been placed in the genera
Obliquaria, Unio, Pleurobema, Margarita,
and
Margaron.
It was ultimately placed in the genus
Plethobasus
by Ortmann (1919, pp. 65-66), where it remains today (Turgeon
et al.
1998, p. 35). The Service recognizes
Unio aesopus
and
U. compertus
as synonyms of
Plethobasus cyphyus.
Sheepnose is the accepted common name for
Plethobasus cyphyus
as established by the Committee on Scientific and Vernacular Names of
Mollusks of the Council of Systematic Malacologists, American Malacological Union (Turgeon
et al.
1998, p. 35). The Service also recognizes “bullhead” and “clear profit” as older common names for the sheepnose.
Key characters useful for distinguishing the sheepnose from other mussels are its color, the occurrence of central tubercles, and its general shape. Oesch (1984, p. 120) and Parmalee and Bogan (1998, p. 176) describe the sheepnose as a medium-sized mussel that reaches nearly 5 inches (13 cm) in length. The shell is elongate ovate in shape, moderately inflated, and with thick, solid valves. The anterior end of the shell is rounded, but the posterior end is somewhat bluntly pointed to truncate. The dorsal margin of the shell is nearly straight, while the ventral margin is uniformly rounded or slightly convex. The posterior ridge is gently rounded, becoming flattened ventrally and somewhat biangular. There is a row of large, broad tubercular swellings on the center of the shell extending from the beak to the ventral margin. A broad, shallow sulcus (depression on the furrow on the outside surface of the shell) lies between the posterior ridge and central row. Beaks are elevated, high, and placed near the anterior margin. Juvenile beak sculpture consists of a few concentric ridges at the tip of the beaks. The periostracum is generally smooth, shiny, rayless, and light yellow to a dull yellowish brown. Concentric ridges resulting from growth arrests are usually darker.
Oesch (1984, p. 120) describes the internal anatomy of the sheepnose as the left valve having two heavy, erect, roughened, somewhat triangular, and divergent pseudocardinal teeth. The right valve has a large, triangular, roughened pseudocardinal tooth. The lateral teeth are heavy, long, slightly curved, and serrated. The beak cavity is shallow to moderately deep. The soft anatomy was described by Williams
et al.
(2008, p. 94). The color of the nacre is generally white, but may be pinkish to cream-colored and iridescent posteriorly. There are no differences between the sexes in the shells of this species. The shell of the sheepnose is extremely hard and was given the name “clear profit” by early commercial shellers, being too hard to cut into buttons (Wilson and Clark 1914, p. 57). The species also preserves well in archaeological material (Morrison 1942, p. 357).
Life History
The general biology of the spectaclecase and sheepnose are similar to other bivalve mollusks belonging to the families Margaritiferidae and Unionidae, order Unioniformes or Unionoida. Adult mussels suspension-feed, spending their entire lives partially or completely buried within the substrate (Murray and Leonard 1962, p. 27). Adults feed on algae, bacteria, detritus, microscopic animals, and dissolved organic material (Christian
et al.
2004, pp. 108-109; Nichols and Garling 2000, p. 873; Silverman
et al.
1997, p. 1859; Strayer
et al.
2004, pp. 430-431). Recent evidence suggests that adult mussels may also deposit feed on particles in the sediment (Raikow and Hamilton 2001, p. 520). For their first several months, juvenile mussels employ foot (pedal) feeding, consuming bacteria, algae, and detritus (Yeager
et al.
1994, p. 221).
As a group, mussel longevity varies tremendously with some species living only about 4 years (Haag and Rypel 2010, p. 5) but possibly up to 100 to 200 years in other species (Ziuganov
et al.
2000, p. 102). However, the vast majority of species live a few decades (Haag and Rypel 2010, pp. 4-6). Baird (2000, pp. 54, 59, 67) aged 278 specimens of the spectaclecase in Missouri by sectioning the hinge ligament, as most margaritiferids are aged. The maximum age determined was 56 years, but he surmised that some large individuals may have been older. A very large specimen (9.25 inches (23.5 cm)) from the St. Croix River, Minnesota and Wisconsin, was estimated (based on external growth ring counts) to be approximately 70 years old (Havlik 1994, p. 19). Sheepnose longevity has been reported as being nearly 30 years (Watters
et al.
2009, p. 221). Thick shelled mussels from large rivers, like sheepnose, are thought to live longer than other species (Stansbery 1961, p. 16).
Mussels tend to grow relatively rapidly for the first few years, and then slow appreciably at sexual maturity, when energy presumably is being diverted from growth to reproductive activities (Baird 2000, pp. 66-67). In spectaclecase, the biggest change in growth rate appears to occur at 10 to 15 years of age, which suggests that significant reproductive investment does not occur until they reach 10 years of age (Baird 2000, pp. 66-67).
Margaritiferids and unionids have an unusual mode of reproduction. With very few exceptions, their life cycle includes a brief, obligatory parasitic stage on a host organism, typically fish. Eggs develop into microscopic larvae (glochidia) within special gill chambers of the female. The female expels the mature glochidia, which must attach to an appropriate host species (generally a fish) to complete development. Host specificity varies among margaritiferids and unionids. Some species appear to use a single host, while others can transform on several host species. Following successful infestation, glochidia encyst (enclose in a cyst-like structure), remain attached to the host for several weeks, and then drop off as newly transformed juveniles. For further information on the life history of freshwater mussels, see Williams
et al.
2008.
Mussel biologists know relatively little about the specific life-history requirements of the spectaclecase and sheepnose. Most mussels, including the spectaclecase and sheepnose, have separate sexes. Age at sexual maturity of the spectaclecase was estimated to be 4 to 5 years for males and 5 to 7 years for females, with sex ratios approximating 50:50 (Baird 2000, p. 24). The spectaclecase life cycle includes a parasitic phase; however, despite extensive investigation, the host species is not yet known. The spectaclecase is thought to release glochidia from early April to late May in the Meramec and Gasconade Rivers, Missouri (Baird 2000, p. 26). Gordon and Smith (1990, p. 409) reported the species as producing two broods, one in spring or early summer and the other in the fall, also based on Meramec River specimens. In the Meramec and Gasconade Rivers, however, Baird (2000, pp. 26-27) found no evidence of two spawns in a given year.
Age at sexual maturity for the sheepnose is unknown, but given its estimated longevity, probably occurs after a few years. The sheepnose is thought to be a short-term brooder, with egg fertilization taking place in early summer (Parmalee and Bogan 1998, p. 177; Williams
et al.
1998, p. 498), and glochidial release presumably occurring later in the summer. Hermaphroditism occurs in many mussel species (van der Schalie 1966, p. 77), but is not known for the sheepnose. If hermaphroditism does occur in the sheepnose, it may explain the occurrence of small, but persistent populations over long periods of time.
Spectaclecase and sheepnose glochidia are released in conglutinates (gelatinous structures containing numerous glochidia and analogous to cold capsules). Spectaclecase glochidia lack hooks (teeth-like structures that presumably function to pierce through the host's skin tissue) and are the smallest glochidia known of any North American freshwater mussel; they measure approximately 0.0024 inch (0.06 mm) in both length and height (Baird 2000, p. 22). Tens to hundreds of
thousands of glochidia may occur in each conglutinate. Based on 8 Missouri spectaclecase specimens, the number of conglutinates released per female varied from 53 to 88, with a mean of 64.5 (Baird 2000, p. 23). Total fecundity (reproductive potential, including glochidia and ova) in Baird's (2000, p. 27) Missouri study varied from 1.93 million to 9.57 million per female. In mussels, fecundity is related positively to body size and inversely related to glochidia size (Bauer 1994, pp. 940-941). The reproductive potential of the spectaclecase is, therefore, phenomenal. However, the fact that extant populations are generally skewed towards larger adults strongly indicates that survival rates to the adult stage must be extraordinarily low.
Researchers in Wisconsin observed female spectaclecase under boulders in the St. Croix River simultaneously releasing their conglutinates (Heath 2008a, pers. comm.). The spectaclecase conglutinates are entrained along a transparent, sticky mucous strand up to several feet in length (Lee and Hove 1997, p. 9). Baird (2000, p. 29) observed the release of loose glochidia and small fragments of conglutinates. Based on his observations, he hypothesized that conglutinates sometimes contain mostly immature glochidia, and that conglutinates containing mostly immature glochidia may be aborted when disturbed.
Sheepnose conglutinates are narrow and lanceolate in outline, solid and red or pink in color, and discharged in unbroken form (Oesch 1984, pp. 118-119). Discharge of sheepnose conglutinates have been observed in late July (Ortmann 1911, p. 306) and August (Williams
et al.
2008, p. 498). Ortmann (1911, p. 306) described them as being pink and “lying behind the posterior end of the shell, which were greedily devoured by a number of minnows.” Sheepnose glochidia are semicircular in outline, with the ventral margin obliquely rounded, hinge line long, and medium in size. The length (0.009 inch (0.23 mm)) is slightly greater than the height (0.008 inch (0.20 mm)) (Oesch 1984, p. 119). Several hundred glochidia probably occur in each conglutinate. Judging from the size of the glochidia, total fecundity (including glochidia and ova) per female sheepnose is probably in the tens of thousands.
Like many freshwater mussels, the complex life histories of the spectaclecase and sheepnose have many vulnerable components that may prevent successful reproduction or recruitment of juveniles into existing populations. Glochidia must come into contact with a specific host species for their survival to be ensured. Without the proper host, the glochidia will perish. The host(s) for the spectaclecase is unknown, although more than 60 species of fish, amphibians, and crayfish have been tested in the lab during host suitability studies (Baird 2000, pp. 23-24; Henley and Neves 2006, p. 3; Hove
et al.
2009, pp. 22-23; Hove
et al.
1998, pp. 13-14; Hove
et al.
2008, p. 4; Knudsen and Hove 1997, p. 2; Lee and Hove 1997, pp. 9-10). Two of 690 wild-collected fish checked by Baird (2000, p. 24) had spectaclecase glochidia attached to their gills; these fish were the bigeye chub
(Hybopsis amblops)
and pealip redhorse
(Moxostoma pisolabrum).
However, these fish are not confirmed as hosts, because the encysted glochidia had not grown measurably and glochidial transformation was not observed (Baird 2000, p. 24). Spectaclecase populations are oftentimes highly aggregated (see
Habitat
) with many apparently even-aged individuals, suggesting that glochidia may excyst simultaneously from a host (Gordon and Layzer 1989, p. 19). Additional host work is underway to test the wild-collected fish species that were found with encysted spectaclecase glochidia (pealip redhorse and bigeye chub), as well as to test additional species of fish and other aquatic organisms for suitability. Host information is needed so that existing populations can be artificially cultured for potential population augmentation and reintroduction efforts.
Little is known regarding host fish of the sheepnose. Until recently the only cited host for this species came from a 1914 report that found glochidia naturally attached to sauger
(Sander canadense)
in the wild. No confirmation of successful transformation was recorded in this early report (Surber 1913, p. 110; Wilson 1914, pp. 338-340). However, recent laboratory studies at the Genoa National Fish Hatchery, the University of Minnesota, and Ohio State University have successfully transformed sheepnose glochidia on fathead minnow
(Pimephales promelas),
creek chub
(Semotilus atrromaculatus),
central stoneroller
(Campostoma anomalum),
and brook stickleback
(Culaea inconstans)
(Watters
et al.
2005, pp. 11-12; Brady 2008, pers. comm.; Watters 2008, pers. comm.). Although these are identified as suitable hosts in laboratory studies, natural interactions between the aforementioned fishes and the sheepnose seem rare and infrequent due to habitat preferences. Fish that frequent medium to large rivers near mussel beds, like the sauger, may act as hosts in the natural environment.
Habitat
The spectaclecase generally inhabits large rivers, and is found in microhabitats sheltered from the main force of current. It occurs in substrates from mud and sand to gravel, cobble, and boulders in relatively shallow riffles and shoals with a slow to swift current (Baird 2000, pp. 5-6; Buchanan 1980, p. 13; Parmalee and Bogan 1998, p. 50). According to Stansbery (1967, pp. 29-30), this species is usually found in firm mud between large rocks in quiet water very near the interface with swift currents. Specimens have also been reported in tree stumps, in root masses, and in beds of rooted vegetation (Oesch 1984, p. 33). Similar to other margaritiferids, spectaclecase occurrences throughout much of its range tend to be aggregated (Gordon and Layzer 1989, p. 19), particularly under slab boulders or bedrock shelves (Baird 2000, p. 6; Buchanan 1980, p. 13; Parmalee and Bogan 1998, p. 50), where they are protected from the current. Up to 200 specimens have been reported from under a single large slab in the Tennessee River at Muscle Shoals, Alabama (Hinkley 1906, p. 54). Unlike most species that move about to some degree, the spectaclecase may seldom if ever move except to burrow deeper and may die from stranding during droughts (Oesch 1984, p. 17). At least one recent study, however, indicated that spectaclecase can be quite active; specifically, relocated individuals moved to more suitable habitat (Dunn
et al.
1999, pp.175, 177).
The sheepnose is a larger-stream species occurring primarily in shallow shoal habitats with moderate to swift currents over coarse sand and gravel (Oesch 1984, p. 121). Habitats with sheepnose may also have mud, cobble, and boulders. Sheepnose in larger rivers may occur at depths exceeding 6 m (Williams
et al.
2008, p. 498).
Genetics
A recent genetic study (Monroe
et al.
2007, pp. 7-13) indicates that much of the remaining genetic variability in the spectaclecase is represented in each of the remaining large populations, and that these populations do not appear to differ significantly from one another.
In contrast, genetics studies of the sheepnose (Roe 2011, pers. comm.) indicate that extant populations appear to be genetically isolated from each other. The conservation implications from this study are that each of its populations should be managed as independent entities for purposes of captive rearing and propagation until evidence indicates a particular
population may benefit from the introduction of novel genetic information (Roe 2011, pers. comm.).
Species Distribution
We use the term “population” here in a geographical and not genetic sense, defining it as all individuals of the spectaclecase or sheepnose living in one stream. Using the term in this way allows the status, trends, and threats to be discussed comparatively across streams where the species occur. In using this term we do not imply that their populations are currently reproducing and recruiting or that they are distinct genetic units. We considered populations of the spectaclecase and sheepnose as extant if live or fresh-dead specimens have been observed or collected since 1990. A “population cluster” refers to where two or more adjacent stream populations of a species occur without a barrier (for example, a dam and impoundment) between them.
Following are generalized sets of criteria that were used to categorize the relative status of populations of spectaclecase and sheepnose. The status of a population is considered “improving” if: (1) There is evidence that habitat degradation appears insignificant, (2) live or fresh dead mussel abundance has improved during post-1990 surveys, or (3) ample evidence of recent recruitment has been documented during post-1990 surveys. The status of a population is considered “stable” if: (1) There is little evidence of significant habitat loss or degradation, (2) live or fresh dead mussel abundance has been fairly consistent during post-1990 surveys, or (3) evidence of relatively recent recruitment has been documented during post-1990 surveys. The status of a population is considered “declining” if: (1) There is ample evidence of significant habitat loss or degradation, (2) live or fresh dead mussel numbers have declined during recent surveys, or (3) no evidence of relatively recent recruitment has been documented during recent surveys. The status of a population is considered “extirpated” if: (1) All known suitable habitat has been destroyed, or (2) no live or fresh dead mussels of any age have been located during recent surveys. The status of a population is considered “unknown” if the available information is inadequate to place the population in one of the above four categories. In a few cases, additional information not listed above may have been used to categorize a population.
Spectaclecase Historical Range and Distribution
The spectaclecase occurred historically in at least 44 streams in the Mississippi, Ohio, and Missouri River basins (Butler 2002b, p. 6, Heath 2008, pers. comm.). Its distribution comprised portions of 14 States (Alabama, Arkansas, Illinois, Indiana, Iowa, Kansas, Kentucky, Minnesota, Missouri, Ohio, Tennessee, Virginia, West Virginia, and Wisconsin). Historical occurrences by stream system (with tributaries) include the following:
• Upper Mississippi River system (Mississippi River (St. Croix), Chippewa, Rock, Salt, Illinois (Des Plaines, Kankakee Rivers), Meramec (Bourbeuse, Big Rivers), Kaskaskia Rivers; Joachim Creek);
• Lower Missouri River system (Missouri River (Platte, River Aux Vases, Osage (Sac, Marais des Cygnes Rivers), Gasconade (Osage Fork, Big Piney River) Rivers));
• Ohio River system (Ohio River (Muskingum, Kanawha, Green, Wabash Rivers));
• Cumberland River system (Cumberland River (Big South, Caney Fork; Stones, Red Rivers));
• Tennessee River system (Tennessee River (Holston, Nolichucky, Little, Little Tennessee, Clinch (Powell River), Sequatchie, Elk, Duck Rivers)); and
• Lower Mississippi River system (Mulberry, Ouachita Rivers).
Spectaclecase Current Range and Distribution
Extant populations of the spectaclecase are known from 20 streams in 11 States (Butler 2002b, p. 7). These include the following stream systems (with tributaries):
• Upper Mississippi River system (Mississippi River (St. Croix, Meramec (Bourbeuse, Big Rivers) Rivers));
• Lower Missouri River system (Osage, Sac, Gasconade (Osage Fork, Big Piney River) Rivers);
• Lower Ohio River system (lowermost Ohio River (Kanawha, Green Rivers));
• Cumberland River system (Cumberland River);
• Tennessee River system (Tennessee River (Nolichucky, Clinch, Duck Rivers)); and
• Lower Mississippi River system (Mulberry, Ouachita Rivers).
The 20 extant spectaclecase populations occur in the following 11 States (with streams):
• Alabama (Tennessee River),
• Arkansas (Mulberry, Ouachita Rivers),
• Illinois (Mississippi, Ohio Rivers),
• Iowa (Mississippi River),
• Kentucky (Ohio, Green, Cumberland Rivers),
• Minnesota (Mississippi, St. Croix Rivers),
• Missouri (Mississippi, Meramec, Bourbeuse, Big, Gasconade, Sac, Osage, Big Piney Rivers; Osage Fork),
• Tennessee (Tennessee, Clinch, Nolichucky, Duck Rivers),
• Virginia (Clinch River),
• West Virginia (Kanawha River), and
• Wisconsin (Mississippi, St. Croix Rivers).
Spectaclecase Population Estimates and Status
Based on historical and current data, the spectaclecase has declined significantly rangewide and is now known from only 20 of 44 streams (Table 1), representing a 55 percent decline. The species is presumed extirpated from thousands of river miles and from numerous reaches of habitat in which it occurred historically, including long reaches of upper Mississippi, Ohio, Cumberland, and Tennessee Rivers and many other streams and stream reaches. Of the 20 extant populations, 6 are represented by only one or two recent specimens each and are likely declining and some may be extirpated. Populations in Mississippi and Clinch Rivers have recently experienced significant population declines. Most surviving populations face significant threats and with few exceptions are highly fragmented and restricted to short stream reaches. The spectaclecase is considered extirpated from Indiana, Kansas, and Ohio. Reports of the spectaclecase from 1877 in the Blue and Elkhorn Rivers, Nebraska are not considered valid (Fritz 2010, pers. comm.). The only relatively strong populations remaining are in the Meramec and Gasconade Rivers in Missouri and in the St. Croix River in Minnesota and Wisconsin.
Table 1—Spectaclecase Status in All Streams of Historical or Current Occurrence
River basin
Stream
Current
status
Date of last live or fresh dead observation
Comments
Upper Mississippi River
Mississippi River
Declining
2009
St. Croix River
Stable
2008
Chippewa River
Extirpated
1989
Rock River
Extirpated
~1970
Salt River
Extirpated
1980
Illinois River
Extirpated
~1914
Des Plaines River
Extirpated
~1921
Kankakee River
Extirpated
1906
Meramec River
Stable
2003
Bourbeuse River
Stable
1997
Big River
Stable
2002
Kaskaskia River
Extirpated
~1970
Joachim Creek
Extirpated
~1965
Lower Missouri River
Missouri River
Extirpated
~1914
Platte River
Extirpated
~1917
River Aux Vases
Extirpated
~1974
Osage River
Unknown
2010
Sac River
Declining
2001
Marais des Cygnes River
Extirpated
Unknown
Relic shell observed in 1998.
Gasconade River
Stable
2007
Big Piney River
Unknown
2004
Osage Fork
Unknown
1999
Ohio River
Ohio River
Declining
1994
Single individual observed.
Muskingum River
Extirpated
Unknown
Relic shell observed in 1995.
Kanawha River
Unknown
2005
Two live individuals observed.
Green River
Unknown
2006
Wabash River
Extirpated
1970
Cumberland River
Cumberland River
Unknown
2008
Single individual observed.
Big South Fork
Extirpated
1911
Caney Fork
Extirpated
1988
Stones River
Extirpated
1968
Red River
Extirpated
1966
Tennessee River
Tennessee River
Unknown
2001
Holston River
Extirpated
1981
Nolichucky River
Unknown
1991
Little River
Extirpated
~1911
Little Tennessee River
Extirpated
Unknown
Relic shell observed in 1980, previous record archaeological.
Clinch River
Declining
2010
Powell River
Extirpated
~1978
Sequatchie River
Extirpated
~1925
Elk River
Extirpated
Unknown
Relic shell observed in 1998.
Duck River
Unknown
Early 2000s
Single individual observed.
Lower Mississippi River
Mulberry River
Unknown
~1995
Single individual observed.
Ouachita River
Declining
1990s
Two individuals observed.
Based on collections made more than 100 years ago, the spectaclecase was historically widespread and locally common in many streams rangewide. The spectaclecase is often absent from archaeological shell middens (Morrison 1942, p. 353) and is generally difficult to find due to its habit of occurring under rocks or ledges and burrowing deep into the substrate (Parmalee 1967, p. 25). Therefore, the chance of casually finding the species where population numbers are low is remote.
The spectaclecase was considered a rare species by mussel experts as early as 1970 (Stansbery 1970, p. 13), when the first attempt was made to compile a list of imperiled mussels. The spectaclecase is considered widely distributed but absent from many areas where it formerly occurred (Cummings and Mayer 1992, p. 22). The American Malacological Union and American Fisheries Society consider the spectaclecase to be threatened (Williams
et al.
1993, p. 10). Six of the 20 streams (or big river reaches) considered to harbor extant populations of the spectaclecase are represented by one or two recent specimens (for example, Ohio, Kanawha, Cumberland, Duck, Ouatchita, and Mulberry Rivers), exemplifying the species' imperiled status rangewide.
In some streams, the last reported records for the spectaclecase occurred decades ago (for example, Rock, Des Plaines, Kaskaskia, Platte, Wabash, Stones, Red, and Little Rivers; River Aux Vases; Big South Fork). Parmalee (1967, p. 25) considered the spectaclecase to be “rare and of local occurrence” in Illinois in the 1960s, but that it had “[a]pparently already been extirpated from the Illinois and Kankakee Rivers.” The only records known from some streams are relic specimens collected around 1975 (for example, Marais des Cygnes, Muskingum, and Elk Rivers).
Although quantitative historical abundance data for the spectaclecase is rare, generalized relative abundance (the percent abundance of a species, divided by the total abundance of all mussel species combined) was sometimes noted in the historical literature and can be
inferred from museum lots. The following is a summary of what is known about the relative abundance and trends of presumably extant spectaclecase populations by stream system.
Upper Mississippi River System
The spectaclecase was historically known from 13 streams in the upper Mississippi River system. Currently, in addition to the mainstem, only four streams in the system are thought to have extant spectaclecase populations.
Mississippi River mainstem:
In 1907, Bartsch found spectaclecase at approximately 9 of the 140 sampled sites from what are now Mississippi River Pools (MRP) 9 to 22 (Havlik 2001b, p. 10). Grier (1922, p. 11) did not find spectaclecase in sampled portions of MRP 4 to 6. The team of van der Schalie and van der Schalie (1950, p. 456), reporting on studies from the upper Mississippi River to the Missouri River mouth, stated that no live spectaclecase were found in their study of 254 sites during 1930-31. Havlik and Stansbery (1977, p. 12) thought the spectaclecase had disappeared from MRP 8 by the 1920s. Thiel (1981, p. 10) found only shell material in MRP 11 in a survey that spanned MRP 3 to 11 conducted during 1977 to 1980. Whitney
et al.
(1997, p. 12) recorded a single individual during 1994-95 in MRP 15, for a density of 0.004 per square foot (sq. ft) (0.04 per square meter (sq. m)). Helms (2008, p. 8) found eight live individuals and numerous shells during a search of MRP 19, representing the most recent and numerous collection of the species in the Mississippi River.
The spectaclecase is thought to be extant in at least four pools of the Mississippi River mainstem, albeit in very low numbers. Records include MRP 15 (Quad Cities area, Illinois and Iowa; in 1998), MRP 16 (Muscatine area, Iowa and Illinois in 1997), MRP 19 (Burlington area, Illinois and Iowa in 2009), and MRP 22 (Quincy, Illinois and Hannibal, Missouri, area in 1996). Populations may still persist in MRP 9 and 10 where specimens were found in the 1980s (Heath 2010a, pers. comm.). Only a relic spectaclecase shell was found in MRP 3 above the St. Croix River confluence in 2001, and none were found in subsequent surveys (Kelner 2008, pers. comm.). In general, spectaclecase population levels in the upper Mississippi River appear to have always been fairly small and difficult to locate, and are now of questionable long-term persistence.
St. Croix River:
The northernmost and one of the three most significant extant populations of the spectaclecase occurs in the St. Croix River, Minnesota and Wisconsin. The population is primarily found in the middle reaches of the river in Chisago and Washington Counties, Minnesota, and Polk and St. Croix Counties, Wisconsin (river miles (RM) 16 to 118). Seventeen live spectaclecase were collected from river mile 16 in the St. Croix River in 1994 (Dunn
et al.
1999, p. 174). Havlik (1994, p. 19) reported spectaclecase in the St. Croix Wild River State Park portion of the river (approximately RM 62 to 65) and the reproducing population below the St. Croix Falls Dam at St. Croix Falls, Wisconsin (dam located at approximately RM 52). Additional survey work in the lower river at Afton State Park (approximately RM 7 to 9) failed to find the spectaclecase (Havlik 1994, p. 19).
Hornbach (2001, p. 218) reported 68 live specimens from 4 of 16 river reaches. Relative abundance for the spectaclecase varied from 0.67 percent from RM 78 to 92 (20 live spectaclecase among 17 species collected), 0.008 percent from RM 63 to 78 (41 live, 24 species), 0.0006 percent from RM 42 to 52 (6 live, 33 species), and 0.003 percent from RM 40 to 42 (1 live, 21 species). Reaches where the spectaclecase is extant are fragmented by the pool formed from the power dam at St. Croix Falls.
Baird (2000, p. 70) presented a length-frequency histogram for the spectaclecase in the St. Croix River using data from an unpublished 1989 study. The 962 specimens were fairly evenly distributed over the length scale, indicating multiple age classes including healthy numbers of young spectaclecase recruiting into the population. Baird (2000, p. 70) used growth curves determined from his Missouri study of the species to estimate the ages of spectaclecase of known size in the St. Croix River. The percentage of newly recruited individuals (less than or equal to 10 years of age) in the St. Croix was 40 percent—considerably higher than that noted from the Gasconade (10.4 percent) and Meramec (2.8 percent) Rivers in Missouri, two other streams with abundant spectaclecase populations that he studied. The St. Croix spectaclecase population, while among the largest known, may also be the healthiest based on this metric. The spectaclecase is currently distributed from RM 17 to 118 and appears to be recruiting from RM 17 to 54 (downstream of the St. Croix Falls Dam) (Heath 2008, pers. comm.).
The long-term health of mussel populations in the St. Croix may be in jeopardy, however. Hornbach
et al.
(2001, pp. 12-13) determined that juvenile mussel density had suffered a statistically significant decline at three of four lower St. Croix sites sampled in the 1990s and in 2000. Zebra mussels also threaten the spectaclecase and other mussel populations in the lower St. Croix River. A 2000 survey at 20 sites on the lowermost 24 miles of the St. Croix River estimated that nearly one percent of the mussels were infested with zebra mussels (Kelner and Davis 2002, p. 36).
Meramec River:
The Meramec River flows into the Mississippi River downstream of St. Louis in east-central Missouri. Its spectaclecase population represents one of the best remaining rangewide. In the late 1970s, Buchanan (1980, p. 13) reported this species from 31 sites, 19 with live individuals. Live or fresh dead individuals occurred from RM 17.5 to 145.7. Buchanan (1980, p. 6) considered it to be common in the lower 108 miles (174 km) of the Meramec River, but locally abundant from RM 17.5 to 84. In 1997, Roberts and Bruenderman (2000, pp. 39, 44), using similar sampling methods as Buchanan (1980, pp. 4-5), resurveyed the Meramec River system and collected spectaclecase from 23 sites, 19 of which had live individuals. They found the largest populations between RM 56.7 and 118.8. Among 17 sites where spectaclecase were found during both surveys, the species was less abundant at 9 sites and more abundant at 5 sites in 1997. At three sites, only relic shells were found during both surveys.
In the 1970s, Buchanan (1980, p. 10) reported finding 456 live individuals among the 17 shared sites, whereas Roberts and Bruenderman (2000, p. 44) recorded only 198. A reduction in spectaclecase numbers (260 to 33) at RM 59.5 accounted for most of the overall decrease in abundance between the studies. Confounding the decrease in numbers among shared survey sites, Roberts and Bruenderman (2000, p. 44) surveyed three sites between RM 56.7 and 118.8 that were unsampled by Buchanan (1980, pp. 1-69) and found 500, 538, and 856 live spectaclecase. The most specimens found at a single site in the earlier study was 260 (RM 59.5). Currently, the population in the Meramec River stretches over much of the mainstem, a distance of more than 100 miles (161 km) from RM 18.5 to 120.4.
The spectaclecase represented 28 percent of all mussels sampled in the Meramec River in 1997 (Roberts and Bruenderman 2000, p. 39). Baird (2000, pp. 62, 68,77) extensively studied the demographics of the Meramec River spectaclecase population in the late
1990s. The mean estimated age of the population was 32 years. Individuals less than 10 years of age comprised only 2.8 percent of the Meramec population sampled (a total of 2,983 individuals). At the four sites he intentionally selected for their large spectaclecase populations, densities ranged from 0.01 to 0.12 per sq. ft (0.1 to 1.3 per sq. m) while estimated population numbers at these sites ranged from 933 to 22,697. Baird (2000, p. 71) thought that conditions for spectaclecase recruitment in the Meramec had declined in the past 20 to 30 years, but the causes were undetermined. The prevalence of larger adults in the Meramec population may be cause for concern, as it appears to indicate a low level of recruitment in the population.
Bourbeuse River:
The Bourbeuse River is a northern tributary of the Meramec River joining it at RM 68. Its spectaclecase population was sampled in 1997 at a single site (RM 10.3), and 7 live individuals were found (Roberts and Bruenderman 2000, p. 91). Sampling near the mouth (RM 0.4), Buchanan (1980, p. 16) found only relic shells. The Bourbeuse population is probably dependent on the much larger Meramec population for long-term sustainability.
Big River:
Another Meramec tributary with a population of the spectaclecase, the Big River flows northward into the Meramec River at RM 38. The spectaclecase is only known from the lower end (RM 1.3), where 14 live specimens were found in 1997 (Roberts and Bruenderman 2000, p. 96). At RM 0.4, Buchanan (1980, p. 13) found only relic shells. Similar to the Bourbeuse River population, the population in the Big River is probably dependent on the much larger Meramec population for sustainability. The Meramec River system, including the lower Bourbeuse, lower Big, and Meramec River mainstems, can be considered a single spectaclecase population cluster.
Lower Missouri River System
The spectaclecase was historically known from 10 streams in the Missouri River system. Currently, only five of these streams are thought to have extant populations.
Osage River:
The spectaclecase was considered extirpated from the Osage River in the 2002 status review of the species (Butler 2002b, pp. 57-58). However, fresh dead shells were collected at three sites during a 2001 survey (Ecological Specialists, Inc. 2003, chapter 3, p. 12) and 8 live individuals were found at a site in the lower Osage River in 2010 (Roberts 2011, pers. comm.). The status of the species in the Osage River is unknown.
Sac River:
The Sac River is a large tributary to the Osage River. The spectaclecase was considered extirpated in the 2002 status review of the species (Butler 2002b). However, three old, live individuals were collected at two sites during a survey of the Sac River in 2004 (Hutson and Barnhart 2004, p. 17). The same survey revealed “numerous” relic shells from six other sites, indicating that the spectaclecase may have been relatively abundant at one time. Prior to the 2004 survey, the spectaclecase had not been collected from this river since 1978 (Bruenderman 2001, pers. comm.). Given the age of the live individuals and the abundance of shell material, Hutson and Barnhart (2004, p. 17) predicted the species would “soon be extirpated” from the river.
Gasconade River:
The Gasconade River is a southern tributary of the Missouri River in south-central Missouri and flows into the mainstem east of Jefferson City. When Stansbery (1970, p. 13) included this species in the first compiled list of imperiled mussels, he noted that “the only population of substantial size presently known is found in the Gasconade River.” In 1994, Buchanan found more than 1,000 individuals between RM 7 and 84 (Buchanan 1994, pp. 5, 8-13). Today, one of the three best spectaclecase populations remaining rangewide occurs in the Gasconade. The spectaclecase population occurs over approximately 200 miles (322 km) of the mainstem from RM 4.9 upstream (Bruenderman
et al.
2001, p. 54). Baird (2000, pp. 61, 71) studied the demographics of the Gasconade River spectaclecase population in the late 1990s. Based on his limited number of sampling sites, this species comprised about 20 percent of the entire mussel fauna in this system. The mean estimated age of the population was 25 years. Individuals less than 10 years of age comprised 10.4 percent of the Gasconade population sampled (n = 2,111), indicating a significant level of recent recruitment.
Historically, Stansbery (1967, p. 29) noted that “[t]he size of some aggregation[s] * * * is impressive,” and that “the number of individuals may reach a density of well over a dozen per square foot.” Both statements are probably in reference to the Gasconade River, Missouri population, which he had described in the text of his note. Densities at the four sites Baird (2000, pp. 61, 71) intentionally selected for their large spectaclecase populations ranged from 0.03 to 0.06 per sq. ft (0.3 to 0.6 per sq. m); estimated population numbers at these selected sites ranged from 2,156 to 4,766. Baird (2000, p. 71) thought that conditions for spectaclecase recruitment in the Gasconade River had declined in the past 20 to 30 years, but the causes were undetermined.
Big Piney River:
The Big Piney River, a southern tributary of the Gasconade River, harbors a small population of the spectaclecase. Although overlooked during a 1999 survey (Bruenderman
et al.
2001, pp. 14, 28), 15 individuals were collected from the lower mainstem (RM 24) in 2004 (Barnhart
et al.
2004, p. 5). The status of the population is unknown, but it is probably dependent on the much larger source population in the Gasconade River for sustainability (McMurray 2008, pers. comm.).
Osage Fork:
The Osage Fork is a southwestern headwater tributary of the Gasconade River. The spectaclecase is known from the lower portion of this Gasconade River tributary, specifically from RM 13.9. Sampling in the Osage Fork in 1999 yielded 26 live individuals from this site (Bruenderman
et al.
2001, p. 9). Relative abundance of the spectaclecase in the Osage Fork was 3.9 percent, and catch-per-unit effort was 1.3 per person-hour. This population is thought to be stable, but it may also be dependent on the much larger source population in the Gasconade River for long-term sustainability. The Gasconade River system, including the lower Big Piney, lower Osage Fork, and Gasconade mainstems, can be considered a single population cluster.
Ohio River System
The spectaclecase's continued existence in the Ohio River is extremely uncertain. Once known from five rivers, it has been extirpated from two, and two of the remaining three are recently represented by only one or two individuals each.
Ohio River:
The Ohio River is the largest eastern tributary of the Mississippi River, with its confluence marking the divide between the upper and lower portions of the Mississippi River system. Historically, the spectaclecase was documented from the Ohio River from the vicinity of Cincinnati, Ohio, to its mouth. Although no specimens are known from the mainstem upstream of Cincinnati, populations are known from two upstream tributaries, the Muskingum and Kanawha Rivers. Nearly all spectaclecase records from the Ohio River were made around 1900 or before (Schuster 1988, p. 186). The only recent record is for a single live individual found in an abandoned gill net near the Illinois shore in 1994 (Cummings 2008a,
pers. comm.). If a population of the spectaclecase continues to occur in the Ohio River, its future persistence is extremely doubtful and continued existence seriously threatened by the exotic zebra mussel.
Kanawha River:
The Kanawha River is a major southern tributary of the Ohio River that drains much of West Virginia. The spectaclecase was not known from this stream until 2002, when a single, very old, live individual was discovered near Glasgow, Kanawha County (Zimmerman 2002, pers. comm.). Another live individual was found in the same vicinity in 2005, as well as two additional weathered shells in 2006 (Clayton 2008a, pers. comm.). This site is approximately 20 miles (32.2 km) downstream of Kanawha Falls, below which is the only significant mussel bed known from the Kanawha River. It is doubtful that a recruiting spectaclecase population occurs in the Kanawha River due to the small number of individuals found and their advanced age.
Green River:
The Green River is a lower Ohio River tributary in west-central Kentucky. The spectaclecase has been collected sparingly in the Green River. That it was not reported in early collections made in the system is indicative of the difficulty in finding specimens (Price 1900, pp. 75-79). Stansbery (1965, p. 13) was the first to find it in the mid-1960s at Munfordville, Hart County, where he reported 47 mussel species collected over a several-year period in the early 1960s. More recently, from 1987 to 1989, Cicerello and Hannan (1990, p. 20) reported single fresh dead specimens at six sites and relic specimens from an additional five sites in Mammoth Cave National Park (MCNP). A single specimen was recorded from MCNP, Edmonson County, in 1995. Sampling conducted from 1996 to 1998 located fresh dead specimens at two sites above MCNP, with a relic shell at a third site farther upstream (Cicerello 1999, pp. 17-18). At least one fresh dead specimen was reported from MCNP in 2001, as well as several live individuals in 2005 and 2006 (Layzer 2008a, pers. comm.).
A small spectaclecase population remains in the upper Green River from below Lock and Dam 5 upstream through MCNP, Edmonson County, into western Hart County. Most recent specimens have been reported from the upstream portion of this reach, where it is generally distributed from MCNP upstream to western Hart County. Its distribution is much more sporadic and localized in the lower portion of this reach due to the pooling effect of two locks and dams (5 and 6). In 2001, a concerted effort (approximately 15 person-hours) to locate rare mussels below Lock and Dam 5 and at other sites downstream failed to find spectaclecase (live or shell), although a fresh dead shell had been collected in this area in 1993 (Cicerello 2008, pers. comm.). The occurrence of variable-sized individuals in the 1990s indicates different year classes but not necessarily recent recruitment (Cicerello 2008, pers. comm.). The long-term sustainability of the Green River population, primarily limited to an approximately 15-mile (24-km) reach of the river, is therefore questionable, and its status is unknown.
Cumberland River System
With few exceptions, most records of the spectaclecase in the Cumberland River system were made before the 1920s. It was historically known from the mainstem and four tributaries but appears currently to be restricted to the lowermost Cumberland River a few miles above its confluence with the Ohio River.
Cumberland River mainstem:
The Cumberland River is a large southern tributary of the lower Ohio River. The spectaclecase was considered “not rare” in the Cumberland River by Hinkley and Marsh (1885, p. 6), whereas it was found at six sites by Wilson and Clark (1914, pp. 17, 19) during their survey primarily for commercial species in the Cumberland River system. In a 1947-49 survey of the Kentucky portion of the upper Cumberland River, Neel and Allen (1964, p. 453) reported live specimens only from one of six mainstem sites that they sampled below Cumberland Falls. Neel and Allen (1964, p. 432) considered it to be “uncommon” in the lower Cumberland River (where they did not sample), a statement possibly based on its sporadic occurrence as reported by Wilson and Clark (1914, pp. 17, 19). One of the last mainstem records is that of a single live specimen found in the cold tailwaters of Wolf Creek Dam, Kentucky, near the Tennessee border in 1982 (Miller
et al.
1984, p. 108). This was one of only two live mussels found during a survey of the dewatered river reach below the dam, the mussel community having been eliminated from decades of cold water releases. The most recent record is of a single live individual found at RM 10 in Kentucky below Barkley Lock and Dam in 2008 (Fortenbery 2008, p. 9). A thorough search of the area yielded no additional individuals.
Tennessee River System
The spectaclecase was originally known from the Tennessee River and nine of its stream systems. Ortmann (1924, p. 60) reported that the spectaclecase was “frequent * * * in the upper Tennessee,” while acknowledging in an earlier paper (Ortmann 1918, p. 527) that it was locally abundant in parts of the upper Tennessee River system, but noted that it was “generally regarded as a rare species” rangewide.
Hundreds of miles of large river habitat on the Tennessee mainstem have been converted under nine reservoirs, with additional dams constructed in tributaries historically harboring this species (for example, Clinch, Holston, and Elk Rivers). Watters (2000, p. 262) summarizes the tremendous loss of mussel species from various reaches of the Tennessee. The spectaclecase is now known only from the Tennessee mainstem and three of its tributaries. Despite this fact, the Tennessee River system continues to represent one of the last strongholds of the spectaclecase rangewide.
Tennessee River mainstem:
The Tennessee River is the largest tributary of the Ohio River, draining portions of seven states. The 53-mile (85-km) stretch of river in northwestern Alabama collectively referred to as the Muscle Shoals historically harbored 69 species of mussels, making it among the most diverse mussel faunas ever known (Garner and McGregor 2001, p. 155). The historical spectaclecase population in this reach was thought to be phenomenal given the amount of historical habitat that was available and literature accounts of the period. Hinkley (1906, p. 54), in 1904, considered the spectaclecase “plentiful,” noting 200 individuals under a single slab boulder. Twenty years later, Ortmann (1925, p. 327) stated that “this species must be, or have been, abundant” at Muscle Shoals based on the “considerable number of dead shells” he observed. In these quotes he predicted the demise of the spectaclecase. The construction of three dams (Wilson in 1925, Wheeler in 1930, Pickwick Landing in 1940) inundated most of the historical habitat, leaving only small habitat remnants (Garner and McGregor 2001, p. 155). The largest remnant habitat remaining is the Wilson Dam tailwaters, a reach adjacent to and downstream from Florence, Alabama.
With the exception of 1976-78 when it was “collected infrequently” from below Wilson Dam (Gooch
et al.
1979, p. 90), no collections of the spectaclecase were reported at Muscle Shoals from 1931 to 1995 despite surveys conducted in 1956-57, 1963-64, and 1991 (Garner and McGregor 2001, p. 156).
Elsewhere along the Tennessee mainstem, a specimen was recently
reported from the Guntersville Dam tailwaters in northern Alabama (Butler 2002b, p. 17). From 1997-99, Ohio State University Museum (OSUM) records reflect that 10 live, 1 fresh dead, and 4 relic spectaclecase were reported from three sites in this river reach. The species is found only occasionally in the lower Tennessee River below Pickwick Landing Dam in southeastern Tennessee, having been unreported in various surveys (for example, Scruggs 1960, p. 12; van der Schalie 1939, p. 456). Yokley (1972, p. 61) considered it rare, having only found fresh dead specimens in his 3-year study. Hubbs and Jones (2000, p. 28) reported two live specimens found in 1998 at RM 170, Hardin County. The current status of these small populations is unknown (Garner 2008, pers. comm.; Hubbs 2008, pers. comm.).
Nolichucky River:
The Nolichucky River is a tributary of the lower French Broad River, in the upper Tennessee River system in North Carolina and Tennessee. The spectaclecase population in this river was once sizable, judging from museum lots (for example, 23 fresh dead, OSUM 1971:0372). Sampling at 41 Nolichucky River sites in 1980, Ahlstedt (1991, pp. 136-137) reported 8 live spectaclecase from 6 sites between RM 11.4 to 31.9. A small population of the spectaclecase also persists in a relatively short reach of the lower river (Ahlstedt 2008, pers. comm.). The current status of the Nolichucky River population is unknown.
Clinch River:
The Clinch River is a major tributary of the upper Tennessee River in southwestern Virginia and northeastern Tennessee. Böpple and Coker (1912, p. 9) noted numerous spectaclecase shells in muskrat middens in a portion of the Clinch that is now inundated by Norris Reservoir. Ortmann (1918, p. 527) reported the spectaclecase as being locally abundant in the lower Clinch River, again in an area mostly flooded by Norris Reservoir. Oddly, he failed to find this species upstream of Claiborne County, yet, in later years, one of the spectaclecase's largest known populations was identified in this reach. The species was locally common at sites in the upper Clinch River, according to OSUM records from the 1960s. Ahlstedt (1991, p. 98) considered this species to be relatively rare in the Clinch River based on survey work conducted during 1978 to 1983. He recorded 78 live specimens from 22 sites between RM 151 and 223, for an average of 3.5 per site. The spectaclecase population reported by Ahlstedt (1991a, pp. 89-90) from the lower Clinch River between Melton Hill and Norris Dam (11 specimens from 4 sites between RM 45 and 73) was considered to be small but stable. Once considered abundant in the Clinch River at Speers Ferry, Scott County, Virginia (Bates and Dennis 1978, pp. 18-19), the species is now extremely rare at this site (Neves 1991, p. 264).
Currently, the species is locally common in the Tennessee River system only in the upper Clinch River, and populations are primarily restricted to the Tennessee portion of that stream. Low numbers (0.02 per sq. ft (0.2 per sq. m)) were detected in quantitative sampling (428; 2.7 sq. ft (0.25 sq. m) quadrats) in 1994 (Ahlstedt and Tuberville 1997, pp. 73, 81). Three individuals were collected at RM 223.6 in Virginia in 2005 and a few more live spectaclecase were found in 2010 (Watson 2011, pers. comm.). One old individual was collected in 2007 at RM 270.8, representing the farthest upstream record for the species (Eckert 2008, pers. comm.). The upper Clinch River population is considered to be reproducing, with fairly young individuals occasionally found, but overall the population appears to be declining (Ahlstedt 2008, pers. comm.). The recent occurrence of a disjunct population in the lower Clinch River (separated from the upper Clinch River population by Norris Reservoir) was recently verified (Fraley 2008a, pers. comm.). The specimens sampled likely recruited since the Norris Dam gates closed in 1936 (Fraley 2008a, pers. comm.), despite the cold tailwaters that destroyed the majority of the mussel fauna in this once incredibly diverse river reach.
Duck River:
The Duck River is wholly in Tennessee and represents the farthest downstream significant tributary of the Tennessee River, joining it in the headwaters of Kentucky Reservoir. A single spectaclecase, representing a new drainage record, was found live in the lower Duck River, Hickman County, in 1999 (Hubbs 1999, p. 1; Powell 2008, pers. comm.). Since then, at least one live and one fresh dead individual from the lower part of the river in Humphreys County have been documented (Ahlstedt
et al.
2004, pp. 14-15; Schilling and Williams 2002, p. 410), and several relic specimens have been reported farther upstream (Hubbs 2008, pers. comm.; Powell 2008, pers. comm.). These records cover an approximately 20-mile (32-km) reach of river, with the live individual reported from the lower end of this reach. The spectaclecase is considered extremely rare in the Duck River, and its status is unknown.
Lower Mississippi River System
The spectaclecase was apparently never widely distributed in the lower Mississippi River system. Records from only two streams are known, both from Arkansas.
Mulberry River:
The Mulberry River is a tributary of the Arkansas River in northwestern Arkansas. Other than the Ouachita River records, the only other record of the spectaclecase in the lower Mississippi River system is a single specimen found in the mid-1990s in the Mulberry River. There is some uncertainty regarding the validity of this record, as the collectors were not experienced malacologists, and no specimen or photograph is available to substantiate the record. This record is, however, accepted as valid (Harris
et al.
2009, p. 67; Harris 2010, pers. comm.). The status of the spectaclecase in the Mulberry River is unknown.
Ouachita River:
The Ouachita River flows into lower Red River, a major western tributary of the lower Mississippi River, draining portions of Arkansas and Louisiana. This species was first reported in this portion of its range from the Ouachita River, southwestern Arkansas, in the early 1900s (Wheeler 1918, p. 121). Spectaclecase records in the Ouachita span a three-county reach of river. Only two live specimens were found in the mid-1990s, both in the lower portion of Ouachita County. A single relic shell (paired valves) was found in Montgomery County, at the upper end of its Ouachita River range in 2000. The population is considered very small and declining (Harris
et al.
2009, p. 67; Harris 2010, pers. comm.).
Summary of Extant Spectaclecase Populations
The spectaclecase appears to be declining rangewide, with the exception of a few significant populations. Its occurrence in the St. Croix, Meramec, Gasconade, and Clinch Rivers represent the only sizable, sustainable, and reproducing populations remaining, although the Clinch River population appears to be in decline. The spectaclecase has been eliminated from three-fifths of the total number of streams from which it was historically known (20 streams currently compared to 44 streams historically). This species has also been eliminated from long reaches of former habitat in thousands of miles of the Illinois, Ohio, Cumberland, and other rivers, and from long reaches of the Mississippi and Tennessee Rivers. In addition, the species is no longer known from the States of Ohio, Indiana, and Kansas. The
extirpation of this species from numerous streams and stream reaches within its historical range signifies that substantial population losses have occurred.
Sheepnose Historical Range and Distribution
Historically, the sheepnose occurred in the Mississippi, Ohio, Cumberland, and Tennessee River systems and their tributaries, totaling at least 76 streams (including 1 canal) (Butler 2002a, pp. 6-7). Its distribution comprised portions of 14 States (Alabama, Illinois, Indiana, Iowa, Kentucky, Minnesota, Mississippi, Missouri, Ohio, Pennsylvania, Tennessee, Virginia, West Virginia, and Wisconsin). Historical occurrences by stream system (with tributaries) include the following:
• Upper Mississippi River system (Mississippi River (Minnesota, St. Croix, Chippewa (Flambeau River), Wisconsin, Rock, Iowa, Des Moines, Illinois (Des Plaines, Kankakee, Fox, Mackinaw, Spoon, Sangamon (Salt Creek) Rivers; Quiver Creek; Illinois and Michigan Canal), Meramec (Bourbeuse, Big Rivers), Kaskaskia, Saline, Castor, Whitewater Rivers));
• Lower Missouri River system (Little Sioux, Little Blue, Gasconade (Osage Fork) Rivers);
• Ohio River system (Ohio River (Allegheny), Monongahela, Beaver, Duck Creek, Muskingum (Tuscarawas, Walhonding (Mohican River), Otter Fork Licking Rivers), Kanawha, Scioto, Little Miami, Licking, Kentucky, Salt, Green (Barren River), Wabash (Mississinewa, Eel, Tippecanoe, Vermillion, Embarras, White (East, West Forks White River) Rivers) Rivers);
• Cumberland River system (Cumberland River (Obey, Harpeth Rivers; Caney Fork));
• Tennessee River system (Tennessee River (Holston (North Fork Holston River), French Broad (Little Pigeon River), Little Tennessee, Clinch (North Fork Clinch, Powell Rivers), Hiwassee, Duck Rivers)); and
• Lower Mississippi River system (Hatchie, Yazoo (Big Sunflower River), Big Black Rivers).
Sheepnose Current Range and Distribution
Extant populations of the sheepnose are known from 25 rivers in all 14 States of historical occurrence. Current populations occur in the following systems (with tributaries):
• Upper Mississippi River system (Mississippi River (Chippewa (Flambeau River), Wisconsin, Rock, Kankakee, Meramec (Bourbeuse River) Rivers));
• Lower Missouri River system (Osage Fork Gasconade River);
• Ohio River system (Ohio River (Allegheny, Muskingum (Walhonding River), Kanawha, Licking, Kentucky, Tippecanoe, Eel, Green Rivers));
• Tennessee River system (Tennessee River (Holston, Clinch, Duck (Powell River) Rivers)); and
• Lower Mississippi River system (Big Sunflower River).
The 25 extant sheepnose populations occur in the following 14 States (with streams):
• Alabama (Tennessee River),
• Illinois (Mississippi, Kankakee, Ohio, Rock Rivers),
• Indiana (Ohio, Tippecanoe, Eel Rivers),
• Iowa (Mississippi River),
• Kentucky (Ohio, Licking, Kentucky, Green Rivers),
• Minnesota (Mississippi River),
• Mississippi (Big Sunflower River),
• Missouri (Mississippi, Meramec, Bourbeuse, Osage Fork Gasconade Rivers),
• Ohio (Ohio, Muskingum, Walhonding Rivers),
• Pennsylvania (Allegheny River),
• Tennessee (Tennessee, Holston, Clinch, Powell, Duck Rivers),
• Virginia (Clinch, Powell Rivers),
• West Virginia (Ohio, Kanawha Rivers), and
• Wisconsin (Mississippi, Chippewa, Flambeau, Wisconsin Rivers).
The sheepnose was last observed from over two dozen streams decades ago (for example, Minnesota, Rock, Iowa, Illinois, Des Plaines, Fox, Mackinaw, Spoon, Castor, Little Sioux, Little Blue, Monongahela, Beaver, Scioto, Little Miami, Salt, Mississenewa, Vermilion, Embarras, White, Obey, Harpeth, North Fork Holston, French Broad, North Fork Clinch Rivers; Caney Fork). According to Parmalee and Bogan (1998, p. 177) and Neves (1991, pp. 280-281), the sheepnose has been extirpated throughout much of its former range or reduced to isolated populations. The only records known from some streams are archeological specimens (for example, Little Pigeon, Big Black, Yazoo, Saline Rivers).
Sheepnose Population Estimates and Status
The sheepnose has been eliminated from two-thirds of the total number of streams from which it was historically known (25 streams currently occupied compared to 77 streams historically) (Table 2). This species has also been eliminated from long reaches of former habitat including thousands of miles of the Mississippi, Wisconsin, Illinois, Ohio, Cumberland, and Tennessee Rivers and dozens of other streams and stream reaches.
Based on the population designation criteria (see
Species Distribution
section, above), of the 25 sheepnose populations that are considered extant, 9 are thought to be stable and 8 are considered declining (Table 2). Six other populations (Walhonding, Rock, Gasconade, Muskingum, Osage Fork, and Duck Rivers) are considered extant, but the status of these populations is unknown.
Table 2—Sheepnose Status at Historical Locations
River Basin
Stream
Current
status
Date of last live or fresh dead observation
Comments
Upper Mississippi River
Mississippi River
Declining
2010.
Minnesota River
Extirpated
~1944.
St. Croix River
Extirpated
1988.
Chippewa/Flambeau River
Stable
2008.
Wisconsin River
Declining
2007.
Rock River
Unknown
2007
Represented by single specimen presumably near extirpation.
Iowa River
Extirpated
1985
Relic shell collected in 2011.
Des Moines River
Extirpated
~1915.
Illinois River
Extirpated
1940
Relic shell collected in 1999.
Des Plaines River
Extirpated
~1970.
Kankakee River
Stable
2007.
Fox River
Extirpated
~1913.
Mackinaw River
Extirpated
~1970.
Spoon River
Extirpated
1929.
Sangamon River
Extirpated
~1919
Relic shell collected in 1989.
Salt Creek
Extirpated
Unknown
Relic shell collected in 2007.
Quiver Creek
Extirpated
1881.
Illinois and Michigan (I and M) Canal
Extirpated
?
Meramec River
Stable
2011.
Bourbeuse River
Declining
2006.
Big River
Extirpated
1978.
Kaskaskia River
Extirpated
1970.
Saline River
Extirpated
?
Castor River
Extirpated
~1965.
Whitewater River
Extirpated
1970s.
Lower Missouri River
Little Sioux River
Extirpated
1916.
Little Blue River
Extirpated
~1915.
Gasconade River
Unknown
~1965.
Osage Fork Gasconade River
Unknown
1999
Represented by single specimen, presumably near extirpation.
Ohio River
Ohio River
Stable
2007.
Allegheny River
Improving
2008.
Monongahela River
Extirpated
~1897.
Beaver River
Extirpated
~1910.
Duck Creek
Extirpated
1930.
Muskingum River
Unknown
1993.
Tuscarawas River
Extirpated
Unknown
Relic shell collected in 1998.
Walhonding River
Unknown
1993.
Mohican River
Extirpated
1977.
Otter Fork Licking River
Extirpated
1973.
Kanawha River
Stable
2005.
Scioto River
Extirpated
1963.
Little Miami River
Extirpated
~1953.
Licking River
Declining
2007.
Kentucky River
Declining
1996.
Salt River
Extirpated
~1900.
Green River
Improving
2007.
Barren River
Extirpated
Unknown
Relic shell collected in 1993.
Wabash River
Extirpated
1988.
Mississinewa River
Extirpated
1899.
Eel River
Declining
1997.
Tippecanoe River
Stable
2009.
Vermillion River
Extirpated
Unknown.
Embarras River
Extirpated
1953.
White River
Extirpated
1913.
East White River
Extirpated
1969.
West Fork White River
Extirpated
1908
Relic shell collected in 2000.
Cumberland River
Cumberland River
Extirpated
1987.
Obey River
Extirpated
1939.
Harpeth River
Extirpated
?
Caney Fork River
Extirpated
Unknown
Relic shell collected in 1990.
Tennessee River
Tennessee River
Stable
2008.
Holston River
Declining
2007.
North Fork Holston River
Extirpated
1913.
French Broad River
Extirpated
1914.
Little Pigeon River
Extirpated
Unknown.
Little Tennessee River
Extirpated
Unknown
Relic shell collected in 1971.
Clinch River
Stable
2006.
North Fork Clinch River
Extirpated
~1921.
Powell River
Stable
2004.
Hiwassee
Extirpated
Unknown
Relic shell collected in 1975.
Duck River
Unknown
2003
Record represented by single specimen.
Lower Mississippi River
Hatchie River
Extirpated
1983.
Yazoo River
Extirpated
Unknown.
Big Sunflower River
Declining
2000.
Big Black River
Extirpated
Unknown.
Historically, the sheepnose was fairly widespread in many Mississippi River system streams, although rarely common. Archaeological evidence on relative abundance indicates that it has been an uncommon or even rare species in many streams for centuries (Morrison 1942, p. 357; Patch 1976, pp. 44-52; Parmalee
et al.
1980, p. 101; Parmalee
et al.
1982, p. 82; Parmalee and Bogan 1986, pp. 28, 30; Parmalee and Hughes 1994, pp. 25-26), and relatively common in only a few (Bogan 1990, p. 135).
Museum collections of this species are almost always few in number (Cummings 2010, pers. comm.), with the exception of the 1960s collections from the Clinch and Powell Rivers, Tennessee and Virginia. Moderate numbers of individuals were also commonly recorded historically from the upper Muskingum River system in Ohio and the lower Wabash River in Indiana and Ohio, based on museum lots. Williams and Schuster (1989, p. 21) reported the species as being not common in the Ohio River, while Cummings and Mayer (1992, p. 50) considered it rare throughout its range. The American Malacological Union considers the sheepnose to be threatened (Williams
et al.
1993, p. 13).
Some known populations of the sheepnose are represented by the collection of a single specimen. Other populations have seen a dramatic range decline (for example, reduced from several hundred river miles to a single bed of a river system) or we have limited recent information on population status. The following summaries focus primarily on those populations for which we have sufficient information to make status and trend determinations, and less on those populations that are nearly extirpated, have no recruitment, or are of unknown status.
Upper Mississippi River System
Judging from the archeological record, the sheepnose may have been common at some sites on the Mississippi River (Bogan 1990, p. 135) but over the past century it has become a rare species throughout the mainstem (Grier 1922, pp. 13-31; van der Schalie and van der Schalie 1950, pp. 454-457). Robust populations may have been found in some tributary rivers. The sheepnose has been extirpated from seven Mississippi River tributaries (Minnesota, Iowa, Des Moines, Kaskaskia, Saline, Castor, and Whitewater Rivers) and all but one Illinois River tributary (the Kankakee River). Today, the sheepnose is extant (though in low numbers) in ten mainstem pools, and six tributary rivers of the Upper Mississippi River System.
Mississippi River mainstem:
Sheepnose populations in the mainstem of the Upper Mississippi River are declining. Despite the discovery of a juvenile in Mississippi River Pool (MRP) 7 in 2001, recruitment is limited at best. The mainstem population comprises a few old individuals spread across a very large geographic range (MRP 4 through MRP 24, a distance of more than 530 river miles (850 river km)) (Thiel 1981, p. 10; Havlik and Marking 1981, p. 32; Whitney
et al.
1996, p. 17; Helms and Associates, Ecological Specialists, Inc. 2008, p. 16). The status of this species in the Mississippi River is highly vulnerable (Butler 2002a, p. 7).
Pools with extant populations include MRP 4 (2008), MRP 5 (2008), MRP 7 (2001), MRP 11 (2007), MRP 14 (2006-07), MRP 15 (2005-06), MRP 16 (2003), MRP 17 (2010), MRP 20 (1992), and MRP 24 (1999). The 2001 MRP 7 record was for a live juvenile 1.3 inches (3.3 cm) long and estimated to be 3 years old (Davis 2008, pers. comm.).
St. Croix River:
The St. Croix River population is isolated and composed of old individuals with little to no recruitment (Heath 2010b, pers. comm.). Currently, the population is thought to be restricted to the lowermost mainstem below RM 1 in Washington County, Minnesota, and Pierce County, Wisconsin (Heath 2010b, pers. comm.). Three live individuals were collected in 1988, during a mussel relocation project for the U.S. Highway 10 bridge immediately upstream of the confluence with the Mississippi River (Heath 1989, p. 16). Hornbach (2001, p. 218) analyzed mussel collections throughout the St. Croix River and found that the sheepnose was absent in 15 of the 16 river reaches he sampled, only noting the 1988 occurrence. One historical occurrence is known from the vicinity of RM 53 in 1930; however, this is the only known record upstream of RM 1 (Heath 2010b, pers. comm.). Because there have been no recent collections in the St. Croix River since 1988, this population is most likely extirpated.
Chippewa/Flambeau River:
The sheepnose population in the Chippewa River is extant in much of the river system including the lower end of its tributary, the Flambeau River. This population is stable with documented recruitment (Butler 2002a, p. 8). Balding and Balding (1996, p. 5) reported 50 live specimens sampled from 1989 through 1994, but more recent collections have expanded sites of occurrence to 20 of 67 sites in the middle and upper portions of the Chippewa River, with a relative abundance of 0.8 percent (Balding 2001, pers. comm.). Balding (1992, p. 166) found 12 live specimens and 31 dead shells from 5 of 37 sites in the lower river. Additional survey work extended the number of sites where it was found live to 10 of 45 (Balding 2001, pers. comm.). The Chippewa River sheepnose population is considered one of the best known extant populations. The Flambeau River supports a small sheepnose population below its lowest dam and near its confluence with the Chippewa River (lower 8 miles (13 km) of river), and is most likely dependent on the source population in the Chippewa River.
Wisconsin River:
The sheepnose is declining in the Wisconsin River. Historical records for the sheepnose are available throughout the lower 335 miles (539 km) of the 420-mile (676-km) Wisconsin River (Heath 2010c, pers. comm.). In July 2002, researchers found 20 live specimens in a dense mussel bed near Port Andrew (Seitman 2011, pers. comm.). Currently, the sheepnose is primarily confined to RM 133.7 downstream (a reduction of over 201 river miles (232 km)). The sheepnose population is probably recruiting in the river, primarily in the lower section (below RM 82) (Heath 2010c, pers. comm.). It is unknown if the middle river population, from RM 93 to 133.7, is recruiting because only three living individuals have been found in recent years (Heath 2010c, pers. comm.).
Rock River:
The Rock River population is represented by a single sheepnose specimen and is near extirpation. This individual was located in 2007 south of Como, Illinois (Tiemann 2011, pers. comm.; Cummings 2010a, pers. comm.). Although there have been several relict shells found in the Rock River since 1990, the 2007 collection is the only known live collection in the past 50 years.
Kankakee River:
The sheepnose once occurred along the lower two-thirds of the Kankakee River, an Upper Illinois River tributary, in Indiana and Illinois (Wilson and Clark 1912, p. 47; Lewis and Brice 1980, p. 4). The sheepnose has been extirpated from the channelized portion of the Kankakee in Indiana but persists in the Illinois portion of the river where it appears stable, with evidence of recent recruitment (Butler 2002a, p. 9). Records since 1986 identify the sheepnose in the Kankakee River from the Iroquois River confluence downstream approximately 30 river miles (48 km) (Cummings 2010b, pers. comm.; Helms and Associates 2005, p. 3). A mussel relocation effort for a pipeline crossing in the Kankakee River in July 2002
found 11 sheepnose individuals, representing 0.32 percent of the total mussels relocated (Helms 2004, p. D-1). Subsequent monitoring of the site in 2004 and 2007 located four new individuals. One individual collected in 2004 measured 1.6 inches (40 mm) and was estimated to be a juvenile of 3 years of age. No sheepnose were found in a 2011 search of this area (Roe 2011, pers. comm.).
Meramec River:
The Meramec River flows into the Mississippi River downstream of St. Louis and drains east-central Missouri. The Meramec sheepnose population is stable and recruiting, and represents one of the best rangewide (Butler 2002a, p. 9). Two studies (Buchanan 1980, p. 4; Roberts and Bruenderman 2000, p. 20) extensively surveyed the mussel fauna of the Meramec River. The most notable difference in the results of these studies was the reduced range in which sheepnose were found. Buchanan (1980, p. 34) found live or fresh dead individuals from RM 4.5 to 145.7 (141.2 river miles (227.2 km)), whereas Roberts and Bruenderman (2000, p. 20) found live or fresh dead individuals from RM 25.6 to 91.3 (65.7 river miles (105.7 km)). The trend data from the late 1970s to 1997 indicate that the sheepnose declined 75.5 river miles (121.5 km) in total range within the Meramec River. The extent of the population in the lower end appears to be shrinking upriver (Butler 2002a, p. 10).
In 2002, a site associated with a railroad crossing in St. Louis County at RM 28 yielded 43 live specimens over 3 days of sampling, including at least one gravid female (Roberts 2008a, pers. comm.). Collectively, these data reinforce the level of importance of the Meramec population for the sheepnose rangewide. Although the existing population has been described as stable and recruitment has been documented in the system (Butler 2002a, pp. 11-12), the population has shrunk by half of its former geographic range over the past 30 years.
Bourbeuse River:
The Bourbeuse River sheepnose population is distributed in the downstream 90 river miles (145 km) of the river (Buchanan 1980, p. 34), but is considered rare. Although recruitment has been documented in the Bourbeuse River, the sheepnose population is considered declining (Roberts and Bruenderman 2000, p. 130; Roberts 2008b, pers. comm.). In the late 1970s, Buchanan (1980, p. 10) found the sheepnose to represent 0.1 percent of the Bourbeuse River mussel fauna, with 10 live specimens sampled from 7 sites. Based on data collected by Buchanan (1980, p. 34) and additional survey work in 1980, live or fresh-dead individuals were found in the Bourbeuse from RM 6.5 to 90.0. Data from a resurvey of the Bourbeuse River collected in 1997 yielded nine live sheepnose from four sites (Roberts and Bruenderman 2000, p. 39), and fresh dead shells were located at an additional site. Sheepnose relative abundance was 0.4 percent. Live or fresh dead sheepnose were found between RM 1.4 to 66.3. This comparison indicates a decrease in the number of extant sites (7 to 4) and a range contraction of 18 river miles (29 km). The sheepnose in the Meramec and Bourbeuse Rivers represents a population cluster.
Lower Missouri River System
Osage Fork Gasconade River:
The Lower Missouri River system population is represented by a single sheepnose specimen and is near extirpation. This individual was located in 1999 at RM 21.2 in the Osage Fork, a tributary to the Gasconade River (Bruenderman
et al.
2001, p. 14). It is the only known record for sheepnose in the Gasconade River drainage for more than 25 years.
Ohio River System
Historically, the sheepnose was documented from the entire length of the Ohio River (its type locality), and was first collected there in the early 1800s. Ohio River sampling of 664 river miles (1,068 km) along the northern border of Kentucky yielded 41 sheepnose (Williams 1969, p. 58). Most of these (29) were found in the upper portions of the river (from RM 317 to 538), but the population extended downstream to RM 871. Relative abundance was 0.7 percent for the entire reach sampled. Currently, the mainstem Ohio River and 10 tributary streams have extant sheepnose populations.
Ohio River mainstem:
The sheepnose is generally distributed, but rare, in most mainstem pools of the Ohio River. The population appears to be more abundant in the lower section of the river with a smaller population in the upper Ohio River pools (Williams and Schuster 1989, p. 24; Zeto
et al.
1987, p. 184). Long-term monitoring data from 1993 to 2007 at RM 176 shows the sheepnose is usually collected each survey, recruitment is occurring, and the species comprises 1.0 percent of the mussels at the site (relative abundance) (Morrison 2008, pers. comm.). Live sheepnose have also been collected in recent years at RM 725 and RM 300 (Morrison 2008, pers. comm.). The population in the lower Ohio River mainstem is viable with documented recruitment, but the population overall continues to show signs of decline (Butler 2002a, p. 12).
Allegheny River:
The Allegheny River drains northwestern Pennsylvania and western New York and joins the Monongahela River at Pittsburgh to form the Ohio River. Historical populations of sheepnose were located in the Allegheny in the sections of the river that are now Pools 5-8 (Urban pers. comm. 2011). In their surveys conducted from 2005-07, Smith and Meyer (2010, p 558), found no sheepnose in Pools 4-7. All of these populations have been extirpated leaving only the population in the middle Allegheny located above Pool 9 and below the Kinzua Dam (Urban 2011, pers. comm.). This remaining population has shown recent recruitment and is considered improving (Villella 2008, pers. comm.). Sampling efforts from 2006-08 at 63 sites over 78 miles (125 km) of river produced sheepnose at 18 sites. A total of 244 individuals of 7 different age classes were collected (Villella 2008, pers. comm.) providing ample evidence of recent recruitment.
Kanawha River:
The Kanawha River is a major southern tributary of the Ohio River draining much of West Virginia and with headwaters in Virginia and North Carolina. The Kanawha River harbors a small, but recruiting and stable, population of sheepnose in Fayette County, West Virginia (Butler 2002a, p. 14). The Kanawha population appears to be limited to 5 river miles (8 km) immediately below Kanawha Falls (Clayton 2008b, pers. comm.). Sheepnose collections from this reach in 1987 resulted in a density of 0.013 per sq. m (0.140 per sq. ft), and collections from 2005 found a density of 0.016 per sq. m (0.172 per sq. ft) (Clayton 2008b, pers. comm.).
Licking River:
The sheepnose is known from the lower half of the Licking River, a southern tributary of the Ohio River in northeastern Kentucky. Currently, the species is known from roughly five sites in the middle Licking River (McGregor 2008, pers. comm.). There is no documented evidence of recent recruitment, and, therefore, the sustainability of the population is unknown. It is possible this population represents a population cluster with the Ohio River.
Green River:
The Green River is a lower Ohio River tributary in west-central Kentucky. Currently, a recruiting and improving population remains over an approximately 25 river mile (40 km) reach in the upper Green River from the vicinity of Mammoth Cave National Park upstream into Hart County (Butler 2002a, p. 15). An investigation of
muskrat middens from 2002 and 2003 revealed 42 sheepnose shells, with 39 of the 42 between 1.2 and 2.2 inches (3.0 and 5.6 cm) in length and described as juveniles (Layzer 2008b, pers. comm.). Sampling over the past several years (2005-07) has documented a number of beds experiencing recruitment (McGregor 2008, pers. comm.).
Tippecanoe River:
The Tippecanoe River drains the central portion of northern Indiana in the upper Wabash River system. This population of sheepnose is considered stable with relatively recent recruitment (Butler 2002a, p. 17). Survey work between 1987 and 1995 documented sheepnose at 14 sites throughout the river and extended the known range of the species upstream into Marshall County (Butler 2002a, p. 17). The sheepnose is now known from 45 miles (72 km) of the Tippecanoe River (Ecological Specialists, Inc. 1993, pp. 80-81; Cummings and Berlocher 1990, pp. 84, 98; Cummings 2008b, pers. comm.; Fisher 2008, pers. comm.).
Kentucky, Eel, Muskingum, and Walhonding Rivers:
In addition to the aforementioned populations, sheepnose in the Ohio River system are known from the Kentucky and Eel Rivers, which are each represented by two or fewer specimens collected in the past 25 years. A population cluster in two additional rivers, the Muskingum River and its tributary, the Walhonding River, have unknown populations. Although Watters and Dunn (1995, p. 240) documented recruitment in the lower Muskingum River in the mid-1980s, the sheepnose population in the river is extremely small, and distribution has been reduced to only the lower portion of the river where six individuals were collected in 1992 (Watters and Dunn 1995, pp. 253-254). Populations of the sheepnose in these three river systems are considered to be declining and may be nearing extirpation (Butler 2002a, pp. 15-16).
Cumberland River System
Historical sheepnose records in the system are known from throughout the mainstem downstream of Cumberland Falls and three of its tributaries (Obey and Harpeth Rivers and Caney Fork). Wilson and Clark (1914, pp. 15-19, 57) reported the species to be generally uncommon from 14 mainstem sites from what is now Cumberland Reservoir, Kentucky, downstream to Stewart County, Tennessee, a distance of nearly 500 miles (805 km). The sheepnose was last documented in the Tennessee portion of the river during the early 1980s (Butler 2002a, p. 67).
The only recent sheepnose record for the Cumberland River is from 1987, at the extreme lower end of the river in Kentucky near its confluence with the Ohio River, below Barkley Dam (Butler 2002a, p. 18). This population may be influenced by the lower Ohio River sheepnose population (Butler 2002a, p. 18) and represents a population cluster. Surveys conducted in 2007-09 in the Tennessee reach of the river found no sheepnose (Hubbs, 2010, pers. comm.), and so this population may be extirpated.
Tennessee River System
The sheepnose was originally known from the Tennessee River and 10 of its tributary streams. Historically, Ortmann (1925, p. 328) considered the sheepnose to occur “sparingly” in the lower Tennessee River, and to be “rare” in the upper part of the system (Ortmann 1918, p. 545). Hundreds of miles of large river habitat on the Tennessee River mainstem have been converted under nine reservoirs, with additional dams constructed in tributaries historically harboring the sheepnose (for example, Clinch, Holston, Little Tennessee, Hiwassee Rivers) (Tennessee Valley Authority 1971, p. 5). Sheepnose populations currently persist in limited reaches of the Tennessee River mainstem and four tributaries.
Tennessee River mainstem:
The 53-mile (85-km) stretch of river in northwestern Alabama referred to as the Muscle Shoals historically harbored 69 species of mussels, making it the most diverse mussel fauna ever known (Garner and McGregor 2001, pp. 155-157). However, with the construction of three dams (Wilson in 1925, Wheeler in 1930, and Pickwick Landing in 1940) most of the historical habitat was inundated, leaving only small, flowing habitat remnants (Garner and McGregor 2001, p. 158).
The species is found only occasionally in the lower Tennessee River below Pickwick Landing Dam in southwestern Tennessee. Scruggs (1960, p. 11) recorded a relative abundance of 0.2 percent, while Yokley (1972, p. 64) considered it to be “very rare” in this reach (relative abundance of 0.1 percent). Yokley reported only two specimens that were each estimated to be 20 or more years old.
The sheepnose persists in the tailwaters of Guntersville, Wilson, Pickwick Landing, and Kentucky Dams on the mainstem Tennessee River, where it is considered uncommon (Garner and McGregor 2001, p. 165; Gooch
et al.
1979, p. 9). These populations are considered stable overall but with very limited recruitment (Garner and McGregor 2001, p. 165; McGregor 2008, pers. comm.). The species has been found in low numbers over the past 80 years from relic habitat in the Wilson Dam tailwaters, a several-mile reach adjacent to and downstream from Florence, Alabama (Butler 2002a, pp. 20-21).
Holston River:
In July 2002, sampling in the Holston River produced live sheepnose at 16 of 20 sites sampled below the Cherokee Dam. This reach extended from Nance Ferry to Monday Island (RM 14.6), Jefferson and Knox Counties (Fraley 2008b, pers. comm.). A total of 206 specimens was found with an overall relative abundance of 18.2 percent among the 18 species reported live from this reach. The collection comprised extremely old individuals with no recently recruited individuals being found. Although the population appeared significant in numbers, the lack of recruitment in this population is indicative of a remnant population on its way to extirpation (Butler 2002a, p. 19). In 2007, Tennessee Valley Authority biologists located sheepnose in the Holston River while conducting fish surveys; however, no additional mussel survey work has been completed in the area since 2002 (Baxter 2010, pers. comm.).
Clinch River:
The Clinch River in southwestern Virginia and northeastern Tennessee is one of the largest and most significant tributaries of the upper Tennessee River system. Based on archeological evidence, the sheepnose was “extremely rare” in the lower Clinch River (Parmalee and Bogan 1986, p. 28). As of 2002, the largest lots of museum material available for the sheepnose had been from the Clinch River and its tributary, the Powell River (Watters 2010a, pers. comm.). Individual Clinch River museum lots collected during 1963 to 1969 include 36, 39, 70, and 82 fresh dead specimens. The sheepnose population in the Clinch River currently occurs over approximately 60 river miles (96 km) from northern Scott County, Virginia, downstream into Hancock County, Tennessee, and is considered stable with recently documented recruitment (Eckert 2008b, pers. comm.). Survey work between 1979 and 1994 (Ahlstedt and Tuberville 1997, p. 73) reported low densities of 0.009 to 0.018 individuals per sq. ft. (0.1 to 0.2 per sq. m). Sampling efforts in 2005 and 2006 reported densities from two sites (RM 223.6 and 213.2) in Scott County, Virginia, of 0.226 and 0.064 individuals per sq. ft (0.021 and 0.006 per sq. m), respectively (Eckert 2008b, pers. comm.). Relative abundance for
sheepnose at these locations was 1.5 percent and 1.0 percent, respectively.
Powell River:
The largest sheepnose collection (OSUM) known rangewide was collected in the Powell River, the Clinch River's largest tributary, and included 6 live and 141 fresh dead specimens. Today, the sheepnose population in the Powell River is considered stable, and recruitment has been documented. In 1979, Ahlstedt (1991b, pp. 129-130) reported 45 live specimens from 17 of 78 sites (an average of 2.6 individuals per site). Ahlstedt and Tuberville (1997, p. 96) conducted quantitative sampling in the Powell between 1979 and 1994, and found the sheepnose at densities of 0.107 and 0.861 per sq. ft (0.01 to 0.08 per sq. m). Sampling efforts in 2004 reported densities from two sites in Lee County, Virginia (RM 120.3 and 117.3), of 0.129 and 0.183 individuals per sq. ft (0.012 and 0.017 per sq. m), respectively (Eckert 2008b, pers. comm.). Relative abundance for sheepnose was 0.82 percent and 0.99 percent, respectively.
Duck River:
The Duck River population is recently represented by the collection of a single, live, 10+-year-old animal in 2003 (Saylors 2008, pers. comm.; Ahlstedt et al 2004, p. 24). The sheepnose was likely always rare in the Duck River (Ahlstedt et al 2004, p. 24) and, previous to 2003, the species was thought to be extirpated as the species had not been collected in the River for 100 years. The current status of the population is unknown.
Lower Mississippi River System
The sheepnose was apparently never widely distributed in the lower Mississippi River system. The only verified records are for the Hatchie River in Tennessee and the Delta region in Mississippi. The only records for the Yazoo and Big Black Rivers are from archeological sites (Butler 2002a, p. 21). The sheepnose population in the Big Sunflower River, Mississippi, is the only one remaining in the lower Mississippi River system. Once abundant, judging from museum and archeological records, there is now only a small declining population in the Big Sunflower River (Jones 2008, pers. comm.). The population is believed to be limited to a 12- to 15-mile (19- to 24-km) reach upstream of Indianola in Sunflower County, Mississippi. Although no juvenile mussels have been found in recent sampling efforts, variably sized individuals indicate some, possibly very low, level of recruitment in the population (Jones 2008, pers. comm.).
Summary of Extant Sheepnose Populations
The sheepnose has experienced a significant reduction in range, and many of the extant populations are disjunct, isolated, and appear to be declining. The extirpation of this species from more than 50 streams (more than 65 percent) within its historical range indicates that substantial population losses have occurred. In the majority of streams with extant populations, the sheepnose appears to be uncommon at best. Only in the Allegheny and Green Rivers is the species considered to be improving in population status. Several other extant populations are thought to exhibit some level of stability and have experienced relatively recent recruitment (Chippewa/Flambeau, Meramec, Ohio, Tippecanoe, Clinch, and Powell Rivers). Given the compilation of current distribution, abundance, and status trend information, the sheepnose appears to exhibit a high level of imperilment.
Summary of Comments and Recommendations
In the proposed rule published on January 19, 2011 (76 FR 3392-3420), we requested that all interested parties submit written comments on the proposal by March 21, 2011. We contacted appropriate State and Federal agencies, county governments, elected officials, scientific organizations, and other interested parties and invited them to comment. We also published notices inviting general public comment in 12 newspapers throughout the range of the species. We did not receive any requests for a public hearing.
During the comment period for the proposed rule, we received a total of 16 comment letters directly addressing the proposed listing of the sheepnose and spectaclecase with endangered status. Six State agencies, three Federal agencies, six groups, and four individuals submitted comments. Of those, 15 were comments in support of the listing, 2 were not in support of the listing, and 2 did not express a clear position. The State of Virginia provided additional records of both species, and Pennsylvania provided information about additional threats to the sheepnose. The State of Missouri provided additional information about both species and their threats. The States of Iowa, Pennsylvania, Missouri, Virginia, and Wisconsin expressed their support of the listings. The remainder of the States did not express a position on the actions. All substantive information provided during the comment period has either been incorporated directly into this final determination or addressed below. For readers' convenience, we have combined similar comments into single comments and responses.
Peer Review
In accordance with our peer review policy published in the
Federal Register
on July 1, 1994 (59 FR 34270), we solicited expert opinion from eight knowledgeable individuals with scientific expertise on freshwater mollusks, applicable river basins, and conservation biology principles. The purpose of such review is to ensure that the designation is based on scientifically sound data, assumptions, and analyses, including input of appropriate experts and specialists.
We received written responses from three peer reviewers. All peer reviewers stated that the proposal included a thorough and accurate review of the available scientific and commercial data on these mollusks and their habitats. One peer reviewer provided information on observed behavior of the spectaclecase. Two reviewers provided additional location information for the spectaclecase and the sheepnose. One reviewer provided information on additional or emerging threats to one or both species. Peer reviewer comments are addressed in the following summary and incorporated into the final rule as appropriate.
Peer Reviewer Comments
(1)
Comment:
Peer reviewers provided updated information on spectaclecase and sheepnose populations throughout the ranges of these species.
Our Response:
The updates have been incorporated into this final rule. These changes made to the known populations have not changed our final determinations.
(2)
Comment:
Peer reviewers agreed with the Service and commented that both species were valid species, the data provided was valid and adequate, and the threats presented were real to both species.
Our Response:
These comments support the Service's proposal.
(3)
Comment:
One peer reviewer commented that the spectaclecase may be more active than stated in the proposal and cited a relocation study in the St. Croix River where spectaclecase were observed as the most active species among those relocated.
Our Response:
We have incorporated information into the Background section of this final rule. Movement of this species may deserve further investigation during recovery planning and implementation.
(4)
Comment:
Peer reviewers commented that the Service provided sufficient evidence to show that both species are threatened by habitat destruction and curtailment. They further stated that both species depend on stable substrate within medium to large rivers and that rivers within their ranges have been modified by impoundment, channelization, and contamination. One reviewer stated that these threats may increase in the future with completion of restorations to the lock and dam system on the Ohio River and the planned navigation improvements on the Mississippi River associated with the authorized Navigation and Ecosystem Sustainability Program (NESP). The stability of habitat is further threatened by changes in local hydraulics due to instream construction and modification, and by the increased frequency of large-scale flooding (a result of climate change, destruction of riparian corridors, and decreased permeability within watersheds).
Our Response:
These comments support the Service's proposal. Further discussion regarding this topic is under
Factor A: The Present or Threatened Destruction, Modification, or Curtailment of Their Habitat or Range
and
Factor E: Other Natural or Manmade Factors Affecting Its Continued Existence
of this final rule.
(5)
Comment:
Peer reviewers agreed with the Service and commented that both species are not overutilized for commercial, recreational, scientific, or educational purposes.
Our Response:
These comments support the Service's proposal. Further discussion regarding this topic is under
Factor B: Overutilization for Commercial, Recreational, Scientific, or Educational Purposes
of this final rule.
(6)
Comment:
Peer reviewers commented that little is known about the effects of disease or predation on these species and that, while these factors do not seem to currently be an imminent threat, small and disjunct populations are more vulnerable to these factors.
Our Response:
These comments support the Service's proposal. Further discussion regarding disease and predation is under
Factor C: Disease or Predation
of this final rule. Disease and predation may be further investigated during recovery planning and implementation for both species.
(7)
Comment:
One peer reviewer commented that chemical contamination from both point and nonpoint discharges will continue as significant threats to freshwater mussels due to their sedentary life form, which limits their ability to avoid exposure.
Our Response:
These comments support the Service's proposal. The potential effects of contaminants on freshwater mussels are further discussed under
Factor A: The Present or Threatened Destruction, Modification, or Curtailment of Their Habitat or Range.
(8)
Comment:
One peer reviewer commented that the distribution of mussels in river systems appears to be greatly dependent on complex hydraulic characteristics and that the increased frequency of extreme events in the wake of global climate change could be major contributors to future habitat availability for these mussel species.
Our Response:
These comments support the Service's proposal. The potential effects of climate change on freshwater mussels are further discussed under
Factor E: Other Natural or Manmade Factors Affecting Its Continued Existence
of this final rule. The effects of climate change may be further investigated during recovery planning and implementation for both species.
(9)
Comment:
Peer reviewers commented that existing regulatory mechanisms do not prevent the destruction or modification of habitat for these species and that these species continue to decline despite existing regulations. The peer reviewer stated that endangered status would provide additional protection for remaining populations.
Our Response:
These comments support the Service's proposal. Existing regulations are discussed under
Factor D: The Inadequacy of Existing Regulatory Mechanisms
of this final rule.
(10)
Comment:
Peer reviewers commented that the effects of zebra mussels are well documented in the rule and the effects of other invasive species will add to the stresses these species face; the effects of invasive species on both the spectaclecase and sheepnose need further study.
Our Response:
These comments support the Service's proposal. The potential effects of invasive species on freshwater mussels are further discussed under
Factor E: Other Natural or Manmade Factors Affecting Its Continued Existence
of this final rule. The effects of invasive species may be further investigated during recovery planning and implementation for both species.
(11)
Comment:
One peer reviewer commented that, in order to effectively protect these mussels, further study is needed to determine how temperature affects both species.
Our Response:
These comments support the Service's proposal. The potential effects of temperature on freshwater mussels are further discussed under
Factor E: Other Natural or Manmade Factors Affecting Its Continued Existence
of this final rule. The effects of temperature on both species may be further investigated during recovery planning and implementation.
(12)
Comment:
One peer reviewer commented that, in order to effectively protect these mussels, further study is needed on the genetics of both species.
Our Response:
These comments support the Service's proposal. The genetics of both species are discussed under
Factor E: Other Natural or Manmade Factors Affecting Its Continued Existence
of this final rule. The effects of invasive species may be further investigated during recovery planning and implementation for both species.
(13)
Comment:
One peer reviewer commented that a recent genetic study of the sheepnose indicates that extant populations appear to be genetically isolated from each other and that populations should be managed as independent entities for purposes of captive rearing and propagation unless there is additional evidence to do otherwise. This reviewer provided updated information of collections of the sheepnose mussel from several locations.
Our Response:
We appreciate the submission of this updated information. These comments have been added to the Background section of this final rule.
(14)
Comment:
One peer reviewer recommended that large rock and rock structures be considered for inclusion as possible critical habitat for the spectaclecase mussel.
Our Response:
We appreciate the comments. This rule only covers the listing of the two mussel species. We determined that, although the designation of critical habitat is prudent, it is not determinable at this time. Therefore, we did not propose critical habitat in the proposed listing rule and no critical habitat is designated with this final listing rule. We will use information provided to us in developing a future critical habitat proposal. Once a proposal is published, we will seek additional public comment on our proposed critical habitat designation.
State Comments
(15)
Comment:
The Pennsylvania Fish and Boat Commission, Wisconsin
Department of Natural Resources Bureau of Fisheries and Habitat and Endangered Resources, Missouri Department of Conservation, Iowa Department of Natural Resources, and Virginia Department of Game and Inland Fisheries provided comments stating that they support the proposal to list both species.
Our Response:
We are grateful for support of the States and recognize that State partnerships are essential for the conservation of these species.
(16)
Comment:
The Pennsylvania Fish and Boat Commission, Wisconsin Department of Natural Resources Bureau of Fisheries and Habitat and Endangered Resources, Missouri Department of Conservation, and Virginia Department of Game and Inland Fisheries provided updated historical and current information on populations of one or both species in their States.
Our Response:
We appreciate the submission of the updated information. The updates have been incorporated into this final rule.
(17)
Comment:
The Pennsylvania Fish and Boat Commission stated that the record of occurrence for the sheepnose in Hemlock Creek is not accurate. The occurrence record is from the Allegheny River in Venango County, Pennsylvania, near the mouth of Hemlock Creek. Further, the reference to Duck Creek in the Beaver River drainage should be clarified. Duck Creek is a tributary to the Mahoning River, which flows through eastern Ohio and into Pennsylvania. The Mahoning River joins the Shenango River at New Castle, Pennsylvania, to form the Beaver River. The Beaver River mainstem, which flows to the Ohio River, is contained entirely within the borders of Pennsylvania.
Our Response:
We appreciate the submission of the updated information. The updates have been incorporated into this final rule.
(18)
Comment:
The Virginia Department of Game and Inland Fisheries was not aware of historical records of the spectaclecase in the Powell River in Virginia.
Our Response:
We are aware of two spectaclecase records in the Powell River in Tennessee from 1978 and 1999 (Ahlstedt 2001, pers. comm.) but agree that no records are known from the Virginia portion of the river; therefore, we have kept the Powell River as a historical location for spectaclecase in this final rule.
(19)
Comment:
The Pennsylvania Fish and Boat Commission and the Missouri Department of Natural Resources provided updated information on State protection of these species in their respective States. The spectaclecase is considered to be a Species of Conservation Concern in Missouri, and is therefore afforded certain protections under Missouri's Wildlife Code (3 CSR 10-9, 110(1) (B)); the spectaclecase is not currently listed as endangered in the State of Missouri (3 CSR 10-4, `111). The sheepnose was State-listed as threatened in Pennsylvania on July 11, 2009.
Our Response:
The Service appreciates the clarifications. We have corrected information under
Factor D; The Inadequacy of Existing Regulatory Mechanisms
in this final rule.
(20)
Comment:
The Pennsylvania Fish and Boat Commission provided information on threats to the sheepnose from a flood control project that could subject the species to changes in the thermal or flow regimes. Current flow management from the Allegheny Reservoir should be maintained or improved, where possible, in order to sustain downstream mussel populations. Flow management from the Kinzua Dam could be used to maintain mussel populations if faced with future impacts from climate change.
Our Response:
We appreciate the submission of information on the potential threats of flood control and water management as it supports our assumption that these activities could threaten multiple populations of the sheepnose. The information has been incorporated into this final rule under
Factor A: The Present or Threatened Destruction, Modification, or Curtailment of Their Habitat or Range.
(21)
Comment:
The Pennsylvania Fish and Boat Commission commented on the importance of restoring host fish passage between navigation pools in the Allegheny and Ohio Rivers in order to promote the recolonization of the sheepnose via its host fish. They noted that current plans to restore fish passage around upper Ohio River locks and dams are at risk and a recent study described the implementation of fish passage as infeasible.
Our Response:
We appreciate the comments. The issue of the fish passage will be investigated further under recovery planning and implementation for both species.
(22)
Comment:
The Missouri Department of Conservation provided information on threats to both species from heavy metal sedimentation in the Big River, Missouri.
Our Response:
We appreciate the submission of information on the potential threats of heavy metal sedimentation as it supports our assumption that this activity could threaten multiple populations of the sheepnose and spectaclecase. The information has been incorporated into this final rule under
Factor A: The Present or Threatened Destruction, Modification, or Curtailment of Their Habitat or Range.
(23)
Comment:
The Missouri Department of Conservation provided information on threats to the spectaclecase from operation of hydropower facilities in the Salt River, Missouri.
Our Response:
Although there are historical records of spectaclecase in the Salt River, we are unaware of any recent extant records of spectaclecase in the Salt River. The potential effects of the hydropower dam would be considered in recovery planning and implementation if any populations are discovered in the future. The information has been incorporated into this final rule under
Factor A: The Present or Threatened Destruction, Modification, or Curtailment of Their Habitat or Range.
(24)
Comment:
The Pennsylvania Fish and Boat Commission provided information on threats to the sheepnose from natural gas extraction from the Marcellus Shale formation. Current increases in natural gas extraction related to Marcellus Shale present a number of potential threats to the sheepnose, including the removal of large volumes of surface and groundwater for hydrofracking, spills of untreated fracking flowback water, and development of infrastructure associated with natural gas extraction.
Our Response:
We appreciate the submission of information on the potential threats of natural gas extraction as it supports our assumption that this activity could threaten multiple populations of the sheepnose and spectaclecase. The information has been incorporated into this final rule under
Factor A: The Present or Threatened Destruction, Modification, or Curtailment of Their Habitat or Range
and
Factor E: Other Natural or Manmade Factors Affecting Their Continued Existence.
(25)
Comment:
The Pennsylvania Fish and Boat Commission and the Pennsylvania Biological Survey provided information on golden algae (
Prymnesium parvum
) as a threat to sheepnose populations in areas where water is withdrawn for shale gas drilling. Shale gas drilling has the potential to impact at least one of the best remaining sheepnose populations.
Our Response:
We appreciate the submission of information on the potential threats of golden algae as it supports our assumption that this activity could threaten multiple
populations of the sheepnose and spectaclecase. The information has been incorporated into this final rule under
Factor E: Other Natural or Manmade Factors Affecting Their Continued Existence.
(26)
Comment:
The Pennsylvania Fish and Boat Commission provided a comment regarding black carp
(Mylopharyngodon piceus),
a molluscivore (mussel-eater), as a potential threat to these species. Although the black carp is currently known from the Mississippi River and Illinois River drainages, there has been inadequate sampling in the Ohio River drainage and the potential for the species to move to the Allegheny River via the Ohio River is a real threat.
Our Response:
We appreciate the submission of information on the potential threats of black carp as it supports our assumption that this activity could threaten multiple populations of the sheepnose and spectaclecase. Information on the black carp as a threat to these species has been incorporated into this final rule under
Factor E: Other Natural or Manmade Factors Affecting Their Continued Existence.
(27)
Comment:
The Wisconsin Department of Natural Resources Bureau of Fisheries and Habitat and Endangered Resources provided a comment indicating the importance of determining the host fish of the spectaclecase and that, if the host fish is negatively impacted, the species is also negatively impacted.
Our Response:
Discussion on the role of the host fish was included in the proposed rule in the Life History section and under
Factor A: The Present or Threatened Destruction, Modification, or Curtailment of Their Habitat or Range
and
Factor E: Other Natural or Manmade Factors Affecting Their Continued Existence.
The issue of the host fish determination and conservation will be investigated further under recovery planning and implementation for the species.
(28)
Comment:
The Virginia Department of Mines, Minerals and Energy comments did not support the proposed rule to list either species. They stated that, for the past 30 years, the Virginia Department of Mines, Minerals, and Energy has worked with the mining industry to regulate the mining industry in southwestern Virginia. The Surface Mining Control and Reclamation Act of 1977 has helped reduce impacts to land and water resources throughout the Clinch River and Powell River watersheds that harbor many species of freshwater mussels. Sheepnose populations are considered stable in the Clinch River; however, the statement regarding coal mining and “coal-related toxins” in the proposed rule attempts to relate declining populations with mining in Virginia. The proposal failed to include a 2007 Service study of the toxicity of Powell River mining effluent screenings and slurry on juvenile mussels. This study showed no effect on survival or growth of the tested mussels.
Our Response:
The 2007 study cited by the commenter was part of a 3-year (2007-10) study that the Service conducted in conjunction with the U.S. Geological Survey (for example, Wang
et al.
2007c). In 2007, Wang
et al.
(2007d, p. 1) reported that 100 percent of the coal slurry tested for a 48-hour exposure time resulted in a statistically significant reduced survival of juvenile rainbow mussels
(Villosa iris).
Slurry particles mixed with well-water were not acutely or chronically toxic to the juvenile mussels, indicating that the toxicity in this instance is related to contaminants in the slurry water (Wang
et al.
2007d, p. 1). Further investigations by Kunz
et al.
(2010, p. 1) assessed the potential effects of coal-associated contaminants in sediment on wavy-rayed lamp-mussels
(Lampsilis fasciola),
rainbow mussels, and commonly tested amphipods and midges.
Kunz
et al.
(2010, p. 1) studied sediment samples collected from 13 sites with historically impacted mussel communities and coal mining or gas well activities and 5 reference sites with healthy mussel communities and no or limited coal mining activities in the Clinch and Powell River basins in Tennessee and Virginia. Mean survival or growth of one or more test organisms was reduced in 9 of 13 sediments from sites with active coal mining or gas well activities relative to the response of test organisms in 5 reference sites. A higher proportion of samples were designated as toxic to the mussels (71 percent) compared to amphipods (29 percent) or midge (29 percent) in sediment samples tested with all three species. Mussel growth or biomass decreased with increasing mean metal probable effect concentration (PEC)-quotient or with increasing concentrations of total polycyclic aromatic hydrocarbon compounds (PAHs), indicating juvenile mussels may be more sensitive to metals and PAHs than other test organisms, and the PEC threshold may need to be lowered to be protective of mussels (Kunz
et al.
2010, p. 1). Polycyclic aromatic hydrocarbon compounds have been found at relatively high levels in the upper portions of the Clinch and Powell Rivers in Virginia (Hampson
et al.
2000, p. 20). Mussel growth also tended to decrease with increasing concentrations of major anions (sulfate and chloride), major cations (sodium and potassium), or conductivity in pore-water of sediments (Kunz et al. 2010), which was consistent with previous findings of reduced mussel survival in reconstituted waters with elevated concentrations of major anions and major cations (Wang
et al.
2010, pp. 14-25).
Despite considerable information on the effects of contaminants on fish and other aquatic species, there are few studies that allow us to confidently predict the effects of individual contaminants on the survival, reproduction, and behavior of freshwater mussels in general, and spectaclecase and sheepnose mussels and their hosts fish in particular, under the variety of contaminant concentrations and conditions that may be encountered. Information on the effects of cadmium, ammonia, potassium, and copper is sufficient to predict effects with knowledge of concentrations, but other contaminants, such as EDCs, boron, manganese, and others, have largely unstudied effects on mussels. In the absence of species-specific data, we assume that the spectaclecase and sheepnose may be more sensitive to contaminants than standard test organisms for toxicity testing, based in part on studies that have demonstrated greater sensitivity (for example, Keller and Zam 1991; Jacobson
et al.
1997; Cherry
et al.
2002; Augspurger
et al.
2003; Wang
et al.
2007a, b; Bringolf
et al.
2007a, b, c).
We also demonstrated that established criteria or benchmarks currently in place to protect aquatic life may not be adequate to protect the spectaclecase and sheepnose mussels. Since the Virginia Department of Mines, Minerals, and Energy did not provide definitive information as to the relative safety of mined materials and chemicals on the spectaclecase and sheepnose, we will rely on the data we have compiled in this final rule to support our determination.
(29)
Comment:
The Virginia Department of Mines, Minerals, and Energy commented that regulations and best management practices that are currently in place in Virginia emphasize improving water quality in areas impacted by mining and other activities. Areas in the Clinch River have improved such that there is emerging interest in reintroducing propagated mussels there. River ecosystems have shown signs of improved water quality and habitat since the sheepnose and spectaclecase mussels were identified as candidate species in 2004. They further
stated that a 5-year timeframe of investigation does not seem adequate when attempting to gauge the response of an organism to water quality improvements.
Our Response:
The Code of Virginia states that discharges of water from areas disturbed by surface mining activities shall be made in compliance with all applicable State and Federal water quality laws, standards, and regulations and with the effluent limitations for coal mining promulgated by the U.S. Environmental Protection Agency set forth in 40 CFR 434 (45.1-161.3 and 45.1-230 of the Code of Virginia available online at
http://leg1.state.va.us/000/reg/TOC04025.HTM
). However, as we have indicated in the Summary of Factors Affecting the Species section of this final rule, Federal and State water quality regulations are not adequate to protect the spectaclecase and sheepnose mussels. Best management practices for sediment and erosion control may be required by local ordinances for mining projects; however, compliance, monitoring, and enforcement of these recommendations are often poorly implemented. A myriad of pollutants, such as heavy metals, heavy sediment loads, and polycyclic aromatic hydrocarbon compounds, in mining wastewater discharge can be problematic to waterways when present in elevated levels.
While recent improvements to water quality may have occurred in some areas, current population data for the spectaclecase continues to show little evidence of recent recruitment (Butler 2012, pers. comm.). The upper Clinch River has reproducing populations of spectaclecase; however, the overall population of spectaclecase in the Clinch River is declining. The Clinch River is one of the few locations where sheepnose populations are considered stable with evidence of recent recruitment (Butler 2012, pers. comm.), though the population densities are relatively low. Although the species' response to water quality improvements may not be completely evident over the last 5 years, throughout the recovery process for these species, we will monitor whether those recent water quality improvements will lead to improving sheepnose and spectaclecase populations.
Federal Agencies Comments
(30)
Comment:
The Natural Resources Conservation Service of West Virginia provided comments stating that it would be unfortunate if both species were listed. They stated that several Federal programs, such as the Wildlife Habitat Incentives Program and the Environmental Quality Incentives Program, emphasize stream habitat restoration. Water quality and habitat improvement projects brought to fruition through these conservation practices may prevent the need to list these species.
Our Response:
Restoration programs such as those listed above are important conservation tools and may aid species recovery. Despite these programs, the Service has documented significant declines in the range and population size of spectaclecase and sheepnose and significant threats to these species (see Background and the Summary of Factors Affecting the Species section of this final rule). Based on our analysis of the best data available, we have no reason to believe that population trends for either species addressed in this final rule will improve, nor will the effects of current threats acting on the species be ameliorated in the foreseeable future. We recognize that partnerships are essential for the conservation of these species.
(31)
Comment:
The Natural Resources Conservation Service of West Virginia provided comments encouraging agency partnerships with the Service to conserve both species.
Our Response:
The Service seeks partnerships with all interested parties to conserve these species. We encourage the Natural Resources Conservation Service to be an active participant in the recovery planning and implementation process for these species in West Virginia and in other States as well.
(32)
Comment:
Under section 7 of the Act, Federal permitting agencies must determine if their projects may affect listed species. Will mussel survey standards be established to determine if mussels are in an area of a project? Also, are standards proposed in order for individuals to be qualified to survey for these species? Is there a level of impact that the Service would programmatically concur is not likely to adversely affect listed species?
Our Response:
Under section 7 of the Act, Federal action agencies will need to consult with us should their activities adversely affect the species. If a Federal agency wants to consult on a program that may affect these listed mussels, we will conduct a programmatic section 7 consultation with that agency on that program. A determination of not likely to adversely affect needs to be made by the Federal agency and be supported by the appropriate documentation before we can provide concurrence. We will work with agencies to ensure that the best available data is used during consultation. Issues of standardizing survey protocols and surveyor qualifications may be further discussed during the recovery planning and implementation process for both species.
Public Comments
(33)
Comment:
The Service received comments from three groups supporting the proposal to list both species. Additionally, the Pennsylvania Biological Survey and the Western Pennsylvania Conservancy supported the listing of the sheepnose but did not comment on the spectaclecase, since that species is not historically known from Pennsylvania.
Our Response:
These comments support the Service's proposal. We are grateful for the support of these nongovernmental organizations and recognize that partnerships are essential for the conservation of these species.
(34)
Comment:
Western Pennsylvania Conservancy and Pennsylvania Biological Survey provided clarifications on historical and current information on populations of the sheepnose in Pennsylvania.
Our Response:
We appreciate the submission of the updated information. The updates have been incorporated into this final rule.
(35)
Comment:
The Nature Conservancy in West Virginia, Virginia, Kentucky, and Ohio commented that several of the rivers with extant populations of both species are within the Conservancy's freshwater portfolio as places important for the conservation of freshwater diversity, and they stressed the importance of continued conservation of those areas.
Our Response:
These comments support the Service's proposal. We are grateful for support of these nongovernmental organizations and recognize that partnerships are essential for the conservation of these species in priority rivers established by The Nature Conservancy in these states and elsewhere.
(36)
Comment:
The Nature Conservancy in West Virginia, Virginia, Kentucky, and Ohio, and the Pennsylvania Biological Survey commented on additional threats to both species from recent and legacy energy development and activities (for example, coal mining, gas drilling, energy transmission, and development infrastructure) and their potential impacts to mussel habitat and water quality.
Our Response:
These comments support the Service's proposal. Discussion on these threats was included under
Factor A: The Present or Threatened Destruction, Modification,
or Curtailment of Their Habitat or Range
and
Factor E: Other Natural or Manmade Factors Affecting Their Continued Existence.
(37)
Comment:
The Nature Conservancy in West Virginia, Virginia, Kentucky, and Ohio expressed their support of continued propagation and restoration efforts and noted some of the complexities that may surround those efforts.
Our Response:
These comments support the Service's proposal. We are grateful for support of these nongovernmental organizations and recognize that partnerships are essential for the conservation of these species. Propagation and restoration efforts will be investigated further under recovery planning and implementation for both species.
(38)
Comment:
The Nature Conservancy in West Virginia, Virginia, Kentucky, and Ohio, commented on the importance of restoring host fish passage in the Ohio River in order to promote the recolonization of both species via their host fish. The Ohio River Basin Fish Habitat Partnership was recently formed to protect, restore, and enhance priority habitat for fish and mussels in the Ohio River Basin. The Partnership aims to improve and reconnect stream habitats. The Nature Conservancy is working with the Partnership and others to explore improving fish passage on the Ohio River.
Our Response:
These comments support the Service's proposal. We are grateful for support of these nongovernmental organizations and recognize that partnerships are essential for the conservation of these species. Restoration issues will be investigated further under recovery planning and implementation for both species.
(39)
Comment:
The Nature Conservancy, Pennsylvania Biological Survey, and Western Pennsylvania Conservancy provided information on threats to the sheepnose from natural gas extraction from the Marcellus Shale formation.
Our Response:
We appreciate the submission of information on the potential threats of natural gas extraction as it supports our assumption that this activity could threaten multiple populations of the sheepnose. The information has been incorporated into this final rule under
Factor A: The Present or Threatened Destruction, Modification, or Curtailment of Their Habitat or Range.
(40)
Comment:
The Western Pennsylvania Conservancy provided information on the potential future threats to the sheepnose from natural gas extraction from the Utica Shale formation within the Ohio River drainage.
Our Response:
We appreciate the submission of information on the potential threats of natural gas extraction as it supports our assumption that this activity could threaten multiple populations of the sheepnose. The information has been incorporated into this final rule under
Factor A: The Present or Threatened Destruction, Modification, or Curtailment of Their Habitat or Range.
(41)
Comment:
The Pennsylvania Biological Survey and the Western Pennsylvania Conservancy commented on the large proportion of sheepnose habitat that has been eliminated in the Allegheny and Ohio Rivers since the construction of dams and the navigational pools, which may be the biggest cause of decline for the sheepnose in Pennsylvania.
Our Response:
We appreciate the submission of this information. These comments support the Service's proposal. The information has been incorporated into this final rule under
Factor A: The Present or Threatened Destruction, Modification, or Curtailment of Their Habitat or Range.
(42)
Comment:
American Rivers commented that both species are threatened by habitat destruction and curtailment, particularly, habitat loss due to isolation by barriers, impoundments, and channelization, along with reduced water quality caused by wastewater discharges, nonpoint-source pollution, agricultural runoff, and invasive species. American Rivers has a record of advocacy and action regarding dam removal, river restoration, and water quality improvement.
Our Response:
These comments support the Service's proposal. We are grateful for support of these nongovernmental organizations and recognize that partnerships are essential for the conservation of these species. Further discussion regarding these topics are included under
Factor A: The Present or Threatened Destruction, Modification, or Curtailment of Their Habitat or Range
and
Factor E. Other Natural or Manmade Factors Affecting Its Continued Existence
of this final rule.
(43)
Comment:
The Pennsylvania Biological Survey, the Western Pennsylvania Conservancy and American Rivers provided comments regarding black carp
(Mylopharyngodon piceus),
a notorious molluscivore (mussel-eater), as a potential threat.
Our Response:
We appreciate the submission of the information. These comments support the Service's proposal. Information on the black carp as a threat to these species has been incorporated into the rule under
Factor E: Other Natural or Manmade Factors Affecting Their Continued Existence.
(44)
Comment:
The Pennsylvania Biological Survey and the Western Pennsylvania Conservancy provided comments regarding didymo
(Didymosphenia geminata),
a diatomaceous alga, as a potential threat to the sheepnose since it has recently been reported in the Delaware River watershed.
Our Response:
We appreciate the submission of the information. These comments support the Service's proposal. Information on didymo as a threat to these species has been incorporated into this final rule under
Factor E: Other Natural or Manmade Factors Affecting Their Continued Existence.
(45)
Comment:
The Pennsylvania Biological Survey provided their concerns about sand and gravel mining in the Allegheny River and the potential for further degradation of habitat and water quality due to those activities.
Our Response:
We appreciate the submission of information on the potential threats of instream sand and gravel mining as it supports our assumption that this activity could threaten multiple sheepnose populations. Additional information has been incorporated into this final rule under
Factor A: The Present or Threatened Destruction, Modification, or Curtailment of Their Habitat or Range.
(46)
Comment:
The Western Pennsylvania Conservancy provided information on threats to the sheepnose from the flow management from the Kinzua Dam on the Allegheny River, which could subject the species to changes in the thermal or flow regimes. Current flow along the Allegheny River should be maintained or improved, where possible, in order to sustain downstream mussel populations. Flow management from the Kinzua Dam could be used to maintain mussel populations if faced with future climate change.
Our Response:
We appreciate the submission of information on the potential threats of water management as it supports our assumption that these activities could threaten multiple populations of the sheepnose. The information has been incorporated into this final rule under
Factor A: The Present or Threatened Destruction, Modification, or Curtailment of Their Habitat or Range.
(47)
Comment:
The Western Pennsylvania Conservancy commented that global climate change could be a major threat limiting future habitat availability for the sheepnose.
Our Response:
These comments support the Service's proposal. The potential effects of climate change on freshwater mussels are discussed under
Factor E: Other Natural or Manmade Factors Affecting Its Continued Existence
of this final rule. The effects of climate change may be further investigated during recovery planning and implementation for both species.
(48)
Comment:
The Western Pennsylvania Conservancy commented that the status of the Allegheny River sheepnose population should not be “Improving.” The sheepnose is likely extirpated from approximately 70 miles of the Allegheny River. There is an apparently stable population in the middle of the river; however, this section of the river faces several threats that may affect the health of the river.
Our Response:
We appreciate the submission of the information on the status of the population of sheepnose in the Allegheny River. Additional information has been incorporated into this final rule describing historical populations of sheepnose in the Allegheny River that are now extirpated and that supports our assertion that the status of the Allegheny River population is improving.
(49)
Comment:
The Western Pennsylvania Conservancy commented about the risk of toxic spills to sheepnose due to the proximity of commercial railroads to the Allegheny River and given the documented occasional railroad derailment and resulting spill of toxic materials.
Our Response:
We appreciate the submission of the information. Information on toxic spills as a threat to these species has been incorporated into this final rule under
Factor A: The Present or Threatened Destruction, Modification, or Curtailment of Their Habitat or Range.
(50)
Comment:
American Rivers commented that it supports the designation of critical habitat for both species.
Our Response:
We determined that, although the designation of critical habitat is prudent, it is not determinable at this time. Therefore, we did not propose critical habitat in the proposed listing rule and no critical habitat is designated with this final listing rule. We will use information provided to us in developing a future critical habitat proposal. Once a proposal is published, we will seek additional public comment on our proposed critical habitat designation.
(51)
Comment:
The Western Pennsylvania Conservancy commented that the implications of designating critical habitat to the repatriation of the sheepnose to presently unoccupied portions of its past range should be taken into consideration should it be restored to those presently extirpated areas.
Our Response:
We determined that, although the designation of critical habitat is prudent, it is not determinable at this time. Therefore, we did not propose critical habitat in the proposed listing rule and no critical habitat is designated with this final listing rule. We will use information provided to us and consider whether designating unoccupied habitat is appropriate in developing a future critical habitat proposal. Once a proposal is published, we will seek additional public comment on our proposed critical habitat designation.
(52)
Comment:
American Rivers commented that both species benefit from the protections such as the Wild and Scenic and National Scenic Riverway in the St. Croix River basin of Wisconsin and Minnesota and receive indirect benefits from their work to restore more natural riverine conditions throughout Mississippi River tributaries.
Our Response:
We are grateful for support of these nongovernmental organizations and recognize that partnerships are essential for the conservation of these species.
(53)
Comment:
The Columbia Power and Water Systems, Tennessee, did not support the proposed rule to list either species believing that the data we presented were inadequate to make such a decision. They also thought that strict permit conditions for water withdrawals and wastewater discharges will damage local economies. Finally, they stated that conservation measures to maintain or create critical habitat is an abuse of Federal power.
Our Response:
In weighing the data on the current population status of these species and threats to their continued existence, we have determined that they both warrant endangered status. Under the Act, a decision to list a species is made solely on the basis of the best scientific and commercial data available, and does not consider potential economic impacts. We used the best scientific and commercial data available in developing this final listing rule. We determined that, although the designation of critical habitat is prudent, it is not determinable at this time. Therefore, we did not propose critical habitat in the proposed listing rule and no critical habitat is designated with this final listing rule. We will use information provided to us in developing a future critical habitat proposal. Once a proposal is published, we will seek additional public comment on our proposed critical habitat designation. When critical habitat is designated, the Service must take into consideration the potential economic impact, as well as any other benefits or impacts, of specifying any particular area as critical habitat. Any area may be excluded from critical habitat if it is determined that the benefits of excluding it outweigh the benefits of specifying the area as part of critical habitat, unless the Service determines that the failure to designate the area as critical habitat will result in the extinction of the species.
(54)
Comment:
The Columbia Power and Water Systems commented that the entire Duck River watershed should not be included in critical habitat designation.
Our Response:
We determined that, although the designation of critical habitat is prudent, it is not determinable at this time. Therefore, we did not propose critical habitat in the proposed listing rule and no critical habitat is designated with this final listing rule. We will use information provided to us in developing a future critical habitat proposal. Once a proposal is published, we will seek additional public comment on our proposed critical habitat designation.
(55)
Comment:
The Columbia Power and Water Systems commented that the entire Duck River should not be included in either species' range. Only four collections of both species is not justification for including the entire watershed.
Our Response:
The commenter did not provide additional information to support their position. The spectaclecase and sheepnose are both considered to be extant in the Duck River (Tennessee River drainage), although both species were likely always rare in the Duck River (Hubbs 2008, pers. comm.; Ahlstedt
et al.
2004, pp. 14-15, 24). A single spectaclecase was recently found live in lower Duck River, Hickman County (Hubbs 1999, p. 1; Powell 2008, pers. comm.; Ahlstedt
et al.
2004, pp. 14-15), at least two individuals have been documented from the lower part of the river in Humphreys County, and several relic specimens have been reported farther upstream (Hubbs 2008, pers. comm.; Powell 2008, pers. comm.). These records of spectaclecase cover an approximately 20-mile (32-km) reach of river. One live individual sheepnose was collected in
the Duck River in 2003 (Saylors 2008, pers. comm.; Ahlstedt
et al.
2004, p. 24). Further discussion regarding this topic is under the Background section of this final rule.
(56)
Comment:
The Columbia Power and Water Systems suggested the economic impacts of critical habitat should be determined prior to any decision being made. Local watershed economic development agencies should be given the opportunity to provide input regarding economic harm caused by this rule.
Our Response:
We determined that, although the designation of critical habitat is prudent, it is not determinable at this time. When critical habitat is proposed for the species, we will seek additional public comment on our proposed designation. When critical habitat is designated, the Service must take into consideration the potential economic impact, as well as any other benefits or impacts, of specifying any particular area as critical habitat. Local watershed economic development agencies will be given the opportunity to provide input on this economic analysis. Any area may be excluded from critical habitat if it is determined that the benefits of excluding it outweigh the benefits of specifying the area as part of critical habitat, unless the Service determines that the failure to designate the area as critical habitat will result in the extinction of the species.
(57)
Comment:
The Service received two comments from individuals supporting the proposal to list both species. We received two additional comments from individuals that provided anecdotal information without expressing clear support or disapproval of the rule.
Our Response:
We are grateful for support of private citizens and recognize that partnerships are essential for the conservation of these species. These comments support the Service's proposal.
(58)
Comment:
The Service received information from one individual who expressed concern over the proposal's lack of specificity on how the Service plans to halt and reverse the declining populations of both species. The commenter is concerned how the Service plans to address threats such as the zebra mussel, and wanted more information on the host identification studies. The commenter was interested to know if the Service plans to engage in a public policy campaign to encourage practices among lay people that would benefit the mussels, and if so, details of these actions.
Our Response:
We are grateful for the support of private citizens and recognize that partnerships are essential for the conservation of these species. This final rule cites several documents that give further detail of both species' life history, threats, and host identification. Further discussion on the threats of invasive species, host identification, and outreach will be discussed during recovery planning and implementation for both species.
Summary of Changes From the Proposed Rule
We have considered all comments and information received during the open comment period for the proposed rule to list the spectaclecase and sheepnose as endangered. In this final rule, we modified the historical range of the spectaclecase to exclude the state of Nebraska, which was erroneously included in the proposed rule. In addition, based on the recent discovery of live spectaclecase in the Osage River, the number of rivers with extant populations of spectaclecase increased from 19 to 20 rivers. We have also increased the number of extant populations of sheepnose from 24 to 25 based on a collection in the Rock River in 2007, and removed one extant sheepnose record from Pool 3 of the Mississippi River from 2001 as it was not a fresh dead shell but a relict shell found during the 2001 survey (Minnesota Department of Natural Resources 2011). We also removed an historical occurrence of sheepnose from Hemlock Creek in Pennsylvania as the record was actually from the Allegheny River at the mouth of Hemlock Creek. We have included Marcellus shale extraction under
Factor A: The Present or Threatened Destruction, Modification, or Curtailment of Its Habitat or Range
and added other invasive species (didymo and golden algae) under
Factor E: Other Natural or Manmade Factors Affecting Its Continued Existence
in this final rule.
Summary of Factors Affecting the Species
Section 4 of the Act (16 U.S.C. 1533), and its implementing regulations at 50 CFR part 424, set forth the procedures for adding species to the Federal Lists of Endangered and Threatened Wildlife and Plants. Under section 4(a)(1) of the Act, we may determine a species to be endangered or threatened due to one or more of the following five factors: (A) The present or threatened destruction, modification, or curtailment of its habitat or range; (B) overutilization for commercial, recreational, scientific, or educational purposes; (C) disease or predation; (D) the inadequacy of existing regulatory mechanisms; or (E) other natural or manmade factors affecting its continued existence. Listing actions may be warranted based on any of the above threat factors, singly or in combination. Each of these factors is discussed below.
A. The Present or Threatened Destruction, Modification, or Curtailment of Its Habitat or Range
The decline of mussels such as the spectaclecase and sheepnose is primarily the result of habitat loss and degradation (Neves 1991, pp. 252, 265). Chief among the causes of decline are impoundments, channelization, chemical contaminants, mining, oil and gas development, and sedimentation (Neves 1991, pp. 252, 260-261; Neves 1993, pp. 1-7; Neves
et al.
1997, pp. 63-72; Strayer
et al.
2004, pp. 435-437; Watters 2000, pp. 261-268; Williams
et al.
1993, p. 7). These threats to mussels in general (and spectaclecase and sheepnose where specifically known) are individually discussed below.
Dams and Impoundments
Dams eliminate or reduce river flow within impounded areas, trap silts and cause sediment deposition, alter water temperature and dissolved oxygen levels, change downstream water flow and quality, decrease habitat heterogeneity, affect normal flood patterns, and block upstream and downstream movement of species (Layzer
et al.
1993, pp. 68-69; Neves
et al.
1997, pp. 63-64; Watters 2000, pp. 261-264). Within impounded waters, decline of freshwater mollusks has been attributed to sedimentation, decreased dissolved oxygen, and alteration in resident fish populations (Neves
et al.
1997, pp. 63-64; Pringle
et al.
2009, pp. 810-815; Watters 2000, pp. 261-264). Dams significantly alter downstream water quality and habitats (Allen and Flecker 1993, p. 36), and negatively affect tailwater mussel populations (Layzer
et al.
1993, p. 69; Neves
et al.
1997, p. 63; Watters 2000, pp. 265-266). Below dams, including those operated to generate hydroelectric power, mussel declines are associated with changes and fluctuation in flow regime, scouring and erosion, reduced dissolved oxygen levels and water temperatures, and changes in resident fish assemblages (Layzer
et al.
1993, p. 69; Neves
et al.
1997, pp. 63-64; Pringle
et al.
2009, pp. 810-815; Watters 2000, pp. 265-266; Williams
et al.
1992, p. 7). The decline and imperilment of freshwater mussels in several tributaries within the Tennessee, Cumberland, Mississippi, Missouri, and Ohio River basins have been directly attributed to construction of numerous impoundments in those
river systems (Hanlon
et al.
2009, pp. 11-12; Layzer
et al.
1993, pp. 68-69; Miller
et al.
1984, p. 109; Neves
et al.
1997, pp. 63-64; Sickel
et al.
2007, pp. 71-78; Suloway 1981, pp. 237-238; Watters 2000, pp. 262-263; Watters and Flaute 2010, pp. 3-7; Williams and Schuster 1989, pp. 7-10).
Population losses due to impoundments have likely contributed more to the decline and imperilment of the spectaclecase and the sheepnose than any other factor. Large river habitat throughout nearly all of the range of both species has been impounded, leaving generally short, isolated patches of vestigial habitat in the area below dams. Navigational locks and dams, (for example, on the upper Mississippi, Ohio, Allegheny, Muskingum, Kentucky, Green, and Barren Rivers), some high-wall dams (for example, on the Wisconsin, Kaskaskia, Walhonding, and Tippecanoe Rivers), and many low-head dams (for example, on the St. Croix, Chippewa, Flambeau, Wisconsin, Kankakee, and Bourbeuse Rivers) have contributed significantly to the loss of sheepnose and spectaclecase habitat (Butler 2002a, pp. 11-20 2002b, pp. 9-25).
The majority of the Tennessee and Cumberland River main stems and many of their largest tributaries are now impounded. There are 36 major dams located in the Tennessee River system, and about 90 percent of the Cumberland River downstream of Cumberland Falls (RM 550 (RKM 886)) is either directly impounded by U.S. Army Corps of Engineers (Corps) structures or otherwise impacted by cold tail water released from several dams. Major Corps impoundments on Cumberland River tributaries (for example, Stones River and Caney Fork) have inundated an additional 100 miles (161 km) or more of spectaclecase and sheepnose habitat. Coldwater releases from Wolf Creek, Dale Hollow (Obey River), and Center Hill (Caney Fork) Dams continue to degrade spectaclecase and sheepnose habitat in the Cumberland River system. For example, the scouring effects caused by 40 years of operation of the Center Hill Dam for hydroelectric power generation has dramatically altered the river morphology for 7 miles (12 km) downstream of the dam (Layzer
et al.
1993, p. 69). Layzer
et al.
(1993, p. 68) reported that 37 of the 60 pre-impoundment mussel species of the Caney Fork River have been extirpated. Watters (2000, pp. 262-263) summarizes the tremendous loss of mussel species from various portions of the Tennessee and Cumberland River systems. Approximately one-third of the historical sheepnose and spectaclecase streams are in the Tennessee and Cumberland River systems.
Navigational improvements on the Ohio River began in 1830, and now include 21 lock and dam structures stretching from Pittsburgh, Pennsylvania, to Olmsted, Illinois, near its confluence with the Mississippi River. Historically, habitat now under navigational pools once supported up to 50 species of mussels, including the spectaclecase and sheepnose. Tributaries to the Ohio River, such as the Green and Allegheny Rivers, were also altered by impoundments. The Allegheny River once supported sheepnose populations in what are now Pools 5-8; however, all of the sheepnose in the navigation pools have been extirpated, and the only remaining population exists above Pool 9 and below the Kinzua Dam (Urban pers. comm. 201, Smith and Meyer 2010, p. 558). The fluctuating water levels released from the Kinzua Dam and Reservoir on the Allegheny River may have an impact on this last remaining sheepnose population, which is located approximately 25 miles (40 km) downstream. A series of six locks and dams was constructed on the lower half of the Green River decades ago and extend upstream to the western boundary of Mammoth Cave National Park (MCNP). The upper two locks and dams destroyed spectaclecase habitat, particularly Lock and Dam 6, which flooded the central and western portions of MCNP. Approximately 30 river miles (48 km) of mainstem habitat were also eliminated with the construction of the Green River Dam in 1969. Locks and dams were also constructed on the lower reaches of the Allegheny, Kanawha, Muskingum, and Kentucky Rivers, which disrupted historical riverine habitat for the sheepnose.
Similarly, dams impound most of the upper Mississippi River and many of its tributaries. A series of 29 locks and dams constructed since the 1930s in the mainstem resulted in profound changes to the nature of the river, primarily replacing a free-flowing alluvial (flood plain) system with a stepped gradient (higher pool area to riffle area ratio) river. Modifications fragmented the mussel beds where spectaclecase and sheepnose were found in the Mississippi River, reduced stable riverine habitat, and disrupted fish host migration and habitat use.
Dams and impoundments have fragmented and altered stream habitats throughout the Sac River Basin in the lower Missouri River system. Stockton Dam impounds 39 miles (63 km) of the upper Sac River, and the Truman Dam inundates about 8 miles (13 km) of the lower Sac River and its tributaries (Hutson and Barnhart 2004, p. 7). The rarity of live spectaclecase in the Sac River, coupled with the large number of dead shells observed in a recent study, suggests that this species has decreased since the river was impounded, and that spectaclecase may soon be extirpated from the Sac River system (Hutson and Barnhart 2004, p. 17).
Dam construction has a secondary effect of fragmenting the ranges of aquatic mollusk species, leaving relict habitats and populations isolated by the structures as well as by extensive areas of deep uninhabitable, impounded waters. These isolated populations are unable to naturally recolonize suitable habitat that is impacted by temporary, but devastating events, such as severe drought, chemical spills, or unauthorized discharges (Cope
et al.
1997, pp. 235-237; Layzer
et al.
1993, pp. 68-69; Miller and Payne 2001, pp. 14-15; Neves
et al.
1997, pp. 63-75; Pringle
et al.
2009, pp. 810-815; Watters 2000, pp. 264-265, 268; Watters and Flaute 2010, pp. 3-7).
Sedimentation
Nonpoint source pollution from land surface runoff originates from virtually all land use activities and includes sediments; fertilizer, herbicide, and pesticide residues; animal or human wastes; septic tank leakage and gray water discharge; and oils and greases. Nonpoint-source pollution can cause excess sedimentation, nutrification, decreased dissolved oxygen concentration, increased acidity and conductivity, and other changes in water chemistry that can negatively impact freshwater mussels. Land use types around the sheepnose and spectaclecase populations include pastures, row crops, timber, and urban and rural communities.
Excessive sedi
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