Endangered and Threatened Wildlife and Plants; Endangered Status for the Sheepnose and Spectaclecase Mussels, 3392-3420 [2011-469]

Agencies

• Fish and Wildlife Service
• DEPARTMENT OF THE INTERIOR

[Federal Register Volume 76, Number 12 (Wednesday, January 19, 2011)]
[Proposed Rules]
[Pages 3392-3420]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 2011-469]



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Part IV





Department of the Interior





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Fish and Wildlife Service



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50 CFR Part 17



Endangered and Threatened Wildlife and Plants; Endangered Status for 
the Sheepnose and Spectaclecase Mussels; Proposed Rule

Federal Register / Vol. 76 , No. 12 / Wednesday, January 19, 2011 / 
Proposed Rules

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DEPARTMENT OF THE INTERIOR

Fish and Wildlife Service

50 CFR Part 17

[Docket No. FWS-R3-ES-2010-0050; MO 92210-0-0008-B2]
RIN 1018-AV93


Endangered and Threatened Wildlife and Plants; Endangered Status 
for the Sheepnose and Spectaclecase Mussels

AGENCY: Fish and Wildlife Service, Interior.

ACTION: Proposed rule.

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SUMMARY: We, the U.S. Fish and Wildlife Service (Service), propose to 
list two freshwater mussels, the spectaclecase mussel (Cumberlandia 
monodonta) and sheepnose (Plethobasus cyphyus) as endangered under the 
Endangered Species Act of 1973, as amended (Act). If we finalize this 
rule as proposed, it would extend the Act's protections to 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, 
Kentucky, Kansas, Minnesota, Missouri, Nebraska, Ohio, Tennessee, 
Virginia, West Virginia, and Wisconsin. We determined that critical 
habitat for these species is prudent, but not determinable at this 
time. The Service seeks data and comments from the public on this 
proposed listing rule.

DATES: We will consider comments and information we receive from all 
interested parties by March 21, 2011. We must receive requests for 
public hearings, in writing, at the address shown in the FOR FURTHER 
INFORMATION CONTACT section by March 7, 2011.

ADDRESSES: You may submit comments by one of the following methods:
     Federal eRulemaking Portal: https://www.regulations.gov. 
Follow the instructions for submitting comments on docket number FWS-
R3-ES-2010-0050.
     U.S. mail or hand-delivery: Public Comments Processing, 
Attn: FWS-R3-2010-0050; Division of Policy and Directives Management; 
U.S. Fish and Wildlife Service; 4401 North Fairfax Drive, Suite 222; 
Arlington, VA 22203.
    We will post all comments on https://www.regulations.gov. This 
generally means that we will post any personal information you provide 
us (see Public Comments section below for more information).

FOR FURTHER INFORMATION CONTACT: Richard Nelson, Field Supervisor, 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).

SUPPLEMENTARY INFORMATION:

Public Comments

    Our intent is to use the best available commercial and scientific 
data as the foundation for all endangered and threatened species 
classification decisions. We request comments or suggestions from other 
concerned governmental agencies, the scientific community, industry, or 
any other interested party concerning this proposed rule to list the 
spectaclecase and sheepnose mussels as endangered. We particularly seek 
comments concerning:
    (1) Biological, commercial trade, or other relevant data concerning 
any threats (or lack thereof) to the species and regulations that may 
be addressing those threats.
    (2) Additional information concerning the ranges, distributions, 
and population sizes of the species, including the locations of any 
additional populations of these species.
    (3) Any additional information on the biological or ecological 
requirements of these species.
    (4) Current or planned activities in the areas occupied by these 
species and possible impacts of these activities on the species and 
their habitats.
    (5) Potential effects of climate change on these species and their 
habitats.
    (6) The reasons why areas should or should not be designated as 
critical habitat as provided by section 4 of the Act (16 U.S.C. 1531 et 
seq.), including whether the benefits of designation would outweigh 
threats to the species that designation could cause (e.g., exacerbation 
of existing threats, such as overcollection), such that the designation 
of critical habitat is prudent.
    (7) Specific information on:
     What areas contain physical and biological features 
essential for the conservation of these species;
     What areas are essential to the conservation of these 
species and
     Special management considerations or protection that 
proposed critical habitat may require.
    Please note that submissions merely stating support for or 
opposition to the action under consideration without providing 
supporting information, although noted, will not be considered in 
making a determination, as section 4(b)(1)(A) of the Act directs that 
determinations as to whether any species is an endangered or threatened 
species must be made ``solely on the basis of the best scientific and 
commercial data available.''
    You may submit your comments and materials concerning this proposed 
rule by one of the methods listed in the ADDRESSES section. We will not 
accept comments sent by e-mail or fax or to an address not listed in 
the ADDRESSES section. Comments must be submitted to https://www.regulations.gov before 11:59 (Eastern Time) on the date specified 
in the DATES section. We will not consider hand-delivered comments that 
we do not receive, or mailed comments that are not postmarked, by the 
date specified in the DATES section.
    We will post your entire comment--including your personal 
identifying information--on https://www.regulations.gov. If you provide 
personal identifying information in your comment, you may request at 
the top of your document that we withhold this information from public 
review. However, we cannot guarantee that we will be able to do so.
    Comments and materials we receive, as well as supporting 
documentation we used in preparing this proposed rule, will be 
available for public inspection on https://www.regulations.gov, or by 
appointment, during normal business hours at the Rock Island, Illinois 
Ecological Services Field Office (see the FOR FURTHER INFORMATION 
CONTACT section).

Public Hearing

    The Act provides for one or more public hearings on this proposal, 
if requested. Requests must be received by March 7, 2011. Such requests 
must be made in writing and be addressed to the Field Supervisor at the 
address provided in the FOR FURTHER INFORMATION CONTACT section. We 
will schedule public hearings on this proposal, if any are requested, 
and announce the dates, times, and places of those hearings, as well as 
how to obtain reasonable accommodations, in the Federal Register and 
local newspapers at least 15 days before the hearing.
    Persons needing reasonable accommodations to attend and participate 
in a public hearing should contact the Rock Island, Illinois Ecological 
Services Field Office by telephone at 309-757-5800, as soon as 
possible. To allow sufficient time to process requests, please call no 
later than one week before the hearing date. Information regarding this 
proposed rule is available in alternative formats upon request.

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Background

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. 
However, the Service 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 & Bogan 1998, p. 49). 
Both anterior and posterior ends of the shell are rounded with a 
shallow depression near the center of shell (Baird 2000, p. 6; Parmalee 
& 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 & 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 & 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 & 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 & 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 & 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 
& 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 furrow on the outside 
surface of 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 & 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

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al. 2004, pp. 108-109; Nichols & 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 & 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 & 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 & 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 to15 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 & 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.
    Glochidia of spectaclecase and sheepnose 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 skin tissue 
of the host) and are the smallest glochidia known of any North American 
freshwater mussel; they measure approximately 0.0024 inches (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 eight 
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 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 2008, pers. comm.). The spectaclecase 
conglutinates are entrained along a transparent, sticky mucous strand 
up to several feet in length (Lee & 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 inches (0.23 mm)) is slightly 
greater than the height (0.008 inches (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 over 60 species of fish, amphibians, and crayfish 
have been tested in the lab during host suitability studies (Baird 
2000, pp. 23-24; Henley & Neves 2006, p. 3; Hove et al. 2009b, pp. 22-
23; Hove et al. 1998,

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pp. 13-14; Hove et al. 2008, p. 4; Knudsen & Hove 1997, p. 2; Lee & 
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 & 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 1912, 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 & 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 
& Layzer 1989, p. 19), particularly under slab boulders or bedrock 
shelves (Baird 2000, p. 6; Buchanan 1980, p. 13; Parmalee & 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).
    The sheepnose is primarily 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. 
Genetics studies of sheepnose are currently under investigation; 
however, no conclusions were available at the time of publication (Roe 
2010, 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 2002a, p. 6, 
Heath 2008, pers. comm.). Its distribution comprised portions of 15 
States (Alabama, Arkansas, Illinois, Indiana, Iowa, Kansas, Kentucky, 
Minnesota, Missouri, Nebraska, Ohio, Tennessee, Virginia, West 
Virginia, and Wisconsin). Historical occurrence by stream system (with 
tributaries) include the: 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

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(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)); lower Mississippi River system (Mulberry, Ouachita Rivers).

Spectaclecase Current Range and Distribution

    Extant populations of the spectaclecase are known from 19 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 (Sac and 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 19 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 Rivers),
     Minnesota (Mississippi, St. Croix Rivers),
     Missouri (Mississippi, Meramec, Bourbeuse, Big, Gasconade, 
Sac, Big Piney Rivers; Osage Fork),
     Tennessee (Tennessee, Clinch, Nolichucky, Duck Rivers; 
Caney Fork),
     Virginia (Cumberland, Clinch Rivers),
     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 19 of 44 
streams (Table 1), representing a 57 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 19 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, Nebraska, and Ohio. 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
----------------------------------------------------------------------------------------------------------------
                                                                           Date of Last Live
           River Basin                  Stream          Current Status        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.......  extirpated........  1980..............  ..................
                                  Sac River.........  declining.........  2001..............  ..................
                                  Marais des Cygnes   extirpated........  unknown...........  relic shell
                                   River.                                                      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..............  ..................

[[Page 3397]]

 
                                  Little River......  extirpated........  ~1911.............  ..................
                                  Little Tennessee    extirpated........  unknown...........  relic shell
                                   River.                                                      observed in 1980,
                                                                                               previous record
                                                                                               archaeological.
                                  Clinch River......  declining.........  2005..............  ..................
                                  Powell River......  extirpated........  ~1978.............  ..................
                                  Sequatchie River..  extirpated........  ~1925.............  ..................
                                  Elk River.........  extirpated........  unknown...........  relic shell
                                                                                               observed in 1998.
                                  Duck River........  declining.........  1999..............  single individual
                                                                                               observed.
Lower Mississippi River.........  Mulberry River....  unknown...........  ~1995.............  single individual
                                                                                               observed.
                                  Ouachita River....  declining.........  2000..............  two individuals
                                                                                               observed.
----------------------------------------------------------------------------------------------------------------

    Based on collections made over 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 & 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 
19 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, only four streams in the 
system are thought to have extant spectaclecase populations.
    Mississippi River mainstem: In 1907, Bartsch found spectaclecase at 
approximately nine 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. 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 1994-1995 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 recent 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) 
17 to 118). 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

[[Page 3398]]

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 & 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 nine sites and more abundant at five 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 over 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 & 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 & 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 & 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 four of these streams are 
thought to have extant populations.
    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 2002a). However, three old, live individuals 
were collected at two sites during a survey of the Sac River in 2004 
(Hutson & 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 & 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 over 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

[[Page 3399]]

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 2008, 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 2008, 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 1947-1949 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

[[Page 3400]]

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 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[hellip] 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 & 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 & 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 1976-1978 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 1956-1957, 1963-1964, and 
1991 (Garner & McGregor 2001, p. 156).
    Elsewhere along the Tennessee mainstem, a specimen was recently 
reported from the Guntersville Dam tailwaters in northern Alabama 
(Butler 2002a, p. 17). From 1997-1999, 10 live, 1 fresh dead, a