3392 Federal Register / Vol. 76, No. 12 / Wednesday, January 19, 2011 / Proposed Rules 

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. 

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: http:// 

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 http:// 

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 

http://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 http://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 http://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). Yearone 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 peglike 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 suspensionfeed, 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 wildcollected 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 evenaged 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 largerstream 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 post1990 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

River Basin Stream Current Status 

Date of 

Last Live 

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 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 .......


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TABLE 1—SPECTACLECASE STATUS IN ALL STREAMS OF HISTORICAL OR CURRENT OCCURRENCE—Continued 

River Basin Stream Current Status 

Date of 

Last Live 

Observation 

Comments 

Little River ....................................... extirpated ........... ∼1911 .....

Little Tennessee River .................... extirpated ........... unknown relic shell 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 


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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 lengthfrequency 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 


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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 westcentral 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 severalyear 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 


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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... 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, and 4 relic spectaclecase 

were reported from three sites in this 

river reach based on Ohio State 

University Museum (OSUM) records. 

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.). 

Clinch River: The Clinch River is a 

major tributary of the upper Tennessee 

River in southwestern Virginia and 

northeastern Tennessee. Bo ̈pple 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 

(1991a, 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 & 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. 

Despite low numbers (0.02 per sq. ft (0.2 

per sq. m)) detected in quantitative 

sampling (428; 2.7 sq. ft (0.25 sq. m) 

quadrats) in 1994 (Ahlstedt & Tuberville 

1997, pp. 73, 81), the upper Clinch 

River in Tennessee may still yield two 

to three dozen specimens under 

individual slab boulders. Three 

individuals were collected at RM 223.6 

in Virginia in 2005, and 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 2008, pers. 

comm.). The specimens sampled likely 

recruited since the Norris Dam gates 

closed in 1936 (Fraley 2008, pers. 

comm.), despite the cold tailwaters that 

destroyed the majority of the mussel 

fauna in this once incredibly diverse 

river reach. 

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 (1991b, 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. 

Duck River: The Duck River is wholly 

in Tennessee and represents the farthest 

downstream significant tributary of the 


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Tennessee River, joining it in the 

headwaters of Kentucky Reservoir. A 

single spectaclecase, representing a new 

drainage record, was found live in lower 

Duck River, Hickman County, in 1999 

(Hubbs 1999, p. 1; Powell 2008, pers. 

comm.). Since then, at least two 

individuals from the lower part of the 

river in Humphreys County have been 

documented, 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). 

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 (19 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, Kansas, and 

Nebraska. 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 77 streams 

(including 1 canal) (Butler 2002b). Its 

distribution comprised portions of 14 

States (Alabama, Illinois, Indiana, Iowa, 

Kentucky, Minnesota, Mississippi, 

Missouri, Ohio, Pennsylvania, 

Tennessee, Virginia, West Virginia, and 

Wisconsin). Historical occurrence 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 (Hemlock Creek), 

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, Black, Yazoo (Big Sunflower 

River), Big Black Rivers). 

Sheepnose Current Range and 

Distribution 

Extant populations of the sheepnose 

are known from 24 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, 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 24 extant sheepnose populations 

occur in the following 14 States (with 

streams): 

• Alabama (Tennessee River), 

• Illinois (Mississippi, Kankakee, 

Ohio, Wabash 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 Rivers), 

• Pennsylvania (Allegheny River), 

• Tennessee (Tennessee, Holston, 

Clinch, Powell, Duck Rivers), 

• Virginia (Clinch, Powell Rivers), 

• West Virginia (Ohio, Kanawha 

Rivers), and 

• Wisconsin (Mississippi, St. Croix, 

Chippewa, Flambeau, Wisconsin 

Rivers). 

The sheepnose was last observed from 

over two dozen streams decades ago 

(e.g., 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 


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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 

Rivers; Saline River). 

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 (24 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 24 sheepnose 

populations that are considered extant, 

11 are thought to be stable and 8 are 

considered declining (Table 2). Five 

other populations (Walhonding, 

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 observation Comments 

Upper Mississippi River ................... Mississippi River ............................. Declining ............ 2008 .......

Minnesota River .............................. Extirpated ........... ~1944 ....

St. Croix River ................................ Extirpated ........... 1988 .......

Chippewa/Flambeau River ............. Stable ................. ~1994 ....

Wisconsin River .............................. Declining ............ 2002 .......

Rock River ...................................... Extirpated ........... 1926 .......

Iowa River ....................................... Extirpated ........... 1925 ....... Relic shell collected in 1999. 

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 1989. 

Quiver Creek ................................... Extirpated ........... 1881 .......

Illinois and Michigan (I & M) Canal Extirpated ........... ? .............

Meramec River ............................... Stable ................. 2002 .......

Bourbeuse River ............................. Declining ............ 1997 .......

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 ..................................... Unknown ............ 1999 ....... Represented by single specimen, 

presumably near extirpation. 

Ohio River ........................................ Ohio River ....................................... Stable ................. 2007 .......

Allegheny River ............................... Improving ........... 2008 .......

Hemlock Creek ............................... Extirpated ........... Unknown Relic shell collected in 1991. 

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 ............ 1998 .......

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 ................. 1995 .......

Vermillion River ............................... Extirpated ........... Unknown 

Embarras River ............................... Extirpated ........... 1953 .......

White River ..................................... Extirpated ........... 1913 .......

East White River ............................. Extirpated ........... 1969 .......


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TABLE 2—SHEEPNOSE STATUS AT HISTORICAL LOCATIONS—Continued 

River basin Stream Current status 

Date of 

last observation Comments 

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 ................. 2004 .......

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 .......

Black River ...................................... Extirpated ........... Unknown 

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. Schuster and Williams (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 eight 

Mississippi River tributaries 

(Minnesota, Rock, 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 is 

comprised of a few old individuals 

spread across a very large geographic 

range (MRP 3 through MRP 24 a 

distance of over 550 river miles (880 

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 jeopardized 

(Butler 2002b, p. 7). 

Pools with extant populations include 

MRP 3 (last seen live or fresh dead in 

2000–01), MRP 4 (2008), MRP 7 (2001), 

MRP 11 (2007), MRP 14 (2006–07), MRP 

15 (2005–06), MRP 16 (2003), MRP 17 

(2004), 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 comprised 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 


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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 2002b, p. 8). Balding 

and Balding (1996, p. 5) reported 50 live 

specimens sampled from 1989–1994, 

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 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. 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, 20 live specimens 

were found in a dense mussel bed near 

Port Andrew (Seitman 2008, 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 2010b, 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.). 

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 2002b, 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 2010, 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. 

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 2002b, p. 9). Two 

studies (Buchanan 1980, p. 4; Roberts & 

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 2002b, 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 2008, 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 2002b, 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 2010, 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 over 

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 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 (McGregor 2008, 

pers. comm.; Schuster and Williams 

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, 


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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 2002b, 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. A recruiting and 

improving population of sheepnose 

exists within the middle Allegheny 

River (Villella 2008, pers. comm.). 

Sampling efforts from 2006–2008 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 

2002b, p. 14). The Kanawha population 

appears to be limited to 5 river miles (8 

km) immediately below Kanawha Falls 

(Clayton 2008c, 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 2008c, 

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 westcentral Kentucky. Currently, a recruiting 

and improving population remains over 

an approximately 25 river mile (40 river 

km) reach in the upper Green River from 

the vicinity of Mammoth Cave National 

Park upstream into Hart County (Butler 

2002b, 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 2008, pers. comm.). 

Sampling over the past several years 

(2005–2007) 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 

2002b, 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 

2002b, 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 2008, pers. comm.; 

Fisher 2008, pers. comm.). 

Kentucky, Wabash, Eel, Muskingum, 

and Walhonding Rivers: In addition to 

the aforementioned populations, 

sheepnose in the Ohio River system are 

known from the Kentucky, Wabash, and 

Eel Rivers, which are each represented 

by two or fewer specimens collected in 

the past 25 years. Populations of the 

sheepnose in these three river systems 

are considered to be declining and may 

be nearing extirpation (Butler 2002b, p. 

15–16). 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). 

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, 

Harpeth, and Caney Fork Rivers). 

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). Sheepnose was 

last documented in the Tennessee 

portion of the river during the early 

1980s (Butler 2002b, p. 67). 

The only recent record for the 

Cumberland River is from 1987, at the 

extreme lower end of the river near its 

confluence with the Ohio River, below 

Barkley Dam (Butler 2002b, p. 18). This 

population may be influenced by the 

lower Ohio River sheepnose population 

(Butler 2002b, p. 18) and represents a 

population cluster. Surveys conducted 

in 2007–2009 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 & 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 


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adjacent to and downstream from 

Florence, Alabama (Butler 2002b, pp. 

20–21). 

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 

2010, 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 2008, 

pers. comm.). Survey work between 

1979 and 1994 (Ahlstedt & 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 0.021 and 0.006 

individuals per sq. m (0.226 and 0.064 

per sq. ft), respectively (Eckert 2008, 

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 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 0.01 

to 0.08 per sq. m (0.107 and 0.861 per 

sq. ft). Sampling efforts in 2004 reported 

densities from two sites in Lee County, 

Virginia (RM 120.3 and 117.3), of 0.012 

and 0.017 individuals per sq. m (0.129 

and 0.183 per sq. ft), respectively 

(Eckert 2008, 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 single 10+ year old 

animal in 2003. The sheepnose was 

likely always rare in the Duck River 

and, previous to 2003, the species was 

thought to be extirpated. The current 

status of the population is unknown. 

Holston River: In July 2002, sampling 

in 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 2008, pers. comm.). A 

total of 206 specimens were found with 

an overall relative abundance of 18.2 

percent among the 18 species reported 

live from this reach. The collection was 

comprised of 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 2002b, 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.). 

Lower Mississippi River System 

The sheepnose was apparently never 

widely distributed in the lower 

Mississippi River system. The only 

verified records are for 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 2002b, 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 over 

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. 

Previous Federal Actions 

We identified the spectaclecase and 

sheepnose as candidate species in a 

notice of review published in the 

Federal Register on May 4, 2004 (69 FR 

24875). The spectaclecase and 

sheepnose remained candidate species 

in subsequent notices, including: May 

11, 2005 (70 FR 24869), September 12, 

2006 (71 FR 53755), December 6, 2007 

(72 FR 69033), December 10, 2008 (73 

FR 75176), and November 9, 2009 (74 

FR 57804). A candidate species is a 

species for which we have on file 

sufficient information on biological 

vulnerability and threats to support 

issuing a proposed rule to list the 

species as endangered or threatened. 

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 


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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 & 

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, 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 & Flaute 2010, pp. 3– 

7; Williams & 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 lowhead 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. 

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. 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 & 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 & 

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 & 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 & 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 


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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 sediments are believed to 

impact riverine mollusks requiring 

clean, stable streams (Brim Box & Mosa 

1999, p. 99; Ellis 1936, pp. 39–40). 

Impacts resulting from sediments have 

been noted for many components of 

aquatic communities. For example, 

sediments have been shown to affect 

respiration, growth, reproductive 

success, and behavior of freshwater 

mussels, and to affect fish growth, 

survival, and reproduction (Waters 

1995, pp. 173–175). Potential sediment 

sources within a watershed include 

virtually all activities that disturb the 

land surface, and most localities 

currently occupied by the spectaclecase 

and sheepnose are affected to varying 

degrees by sedimentation. 

Sedimentation has been implicated in 

the decline of mussel populations 

nationwide, and is a threat to 

spectaclecase and sheepnose (Brim Box 

& Mosa 1999, p. 99; Dennis 1984, p. 212; 

Ellis 1936, pp. 39–40; Fraley & Ahlstedt 

2000, pp. 193–194; Poole & Downing 

2004, pp. 119–122; Vannote & Minshall 

1982, pp. 4105–4106). Specific 

biological impacts include reduced 

feeding and respiratory efficiency from 

clogged gills, disrupted metabolic 

processes, reduced growth rates, limited 

burrowing activity, physical smothering, 

and disrupted host fish attractant 

mechanisms (Ellis 1936, pp. 39–40; 

Hartfield & Hartfield 1996, p. 373; 

Marking & Bills 1979, p. 210; Vannote 

& Minshall 1982, pp. 4105–4106; Waters 

1995, pp. 173–175). In addition, mussels 

may be indirectly affected if high 

turbidity levels significantly reduce the 

amount of light available for 

photosynthesis and thus the production 

of certain food items (Kanehl & Lyons 

1992, p. 7). 

Studies indicate that the primary 

impacts of excess sediment on mussels 

are sublethal, with detrimental effects 

not immediately apparent (Brim Box & 

Mosa 1999, p. 101). The physical effects 

of sediment on mussels are multifold, 

and include changes in suspended and 

bed material load; changes in bed 

sediment composition associated with 

increased sediment production and runoff in the watershed; changes in the 

form, position, and stability of channels; 

changes in depth or the width-to-depth 

ratio, which affects light penetration 

and flow regime; actively aggrading 

(filling) or degrading (scouring) 

channels; and changes in channel 

position that may leave mussels 

stranded (Brim Box & Mosa 1999, pp. 

109–112; Kanehl & Lyons 1992, pp. 4– 

5; Vannote & Minshall 1982, p. 4106). 

The Chippewa River in Wisconsin, for 

example, has a tremendous bedload 

composed primarily of sand that 

requires dredging to maintain barge 

traffic on the mainstem Mississippi 

below its confluence (Thiel 1981, p. 20). 

The mussel diversity in the Mississippi 

River below the confluence with the 

Chippewa River has predictably 

declined from historical times. Lake 

Pepin, a once natural lake formed in the 

upper Mississippi River upstream from 

the mouth of the Chippewa River, has 

become increasingly silted in over the 

past century, reducing habitat for the 

spectaclecase and sheepnose (Thiel 

1981, p. 20). 

Increased sedimentation and siltation 

may explain in part why spectaclecase 

and sheepnose mussels appear to be 

experiencing recruitment failure in 

some streams. Interstitial spaces in the 

substrate provide crucial habitat for 

juvenile mussels. When clogged, 

interstitial flow rates and spaces are 

reduced (Brim Box & Mosa 1999, p. 

100), thus reducing juvenile habitat. 

Furthermore, sediment may act as a 

vector for delivering contaminants such 

as nutrients and pesticides to streams 

and juveniles may ingest contaminants 

adsorbed to silt particles during normal 

feeding activities. Female spectaclecase 

and sheepnose produce conglutinates 

that attract hosts. Such a reproductive 

strategy depends on clear water during 

the critical time of the year when 

mussels are releasing their glochidia. 

Agricultural activities are responsible 

for much of the sediment (Waters 1995, 

p. 170) and chemical discharge into 

streams, affecting 60 percent of the 

impaired river miles in the country 

(EPA 2007, p. 10). Unrestricted livestock 

access occurs on many streams and 

potentially threatens their mussel 

populations (Fraley & Ahlstedt 2000, 

pp. 193–194). Grazing may reduce 

infiltration rates and increase runoff; 

trampling and vegetation removal 

increases the probability of erosion 

(Armour et al. 1991, pp. 8–10; Brim Box 

& Mosa 1999, p. 103). The majority of 

the remaining spectaclecase and 

sheepnose populations are threatened 

by some form of agricultural runoff 

(nutrients, pesticides, sediment). Copper 

Creek, a tributary to the Clinch River, 

for example, has a drainage area that 

contains approximately 41 percent 

agricultural land (Hanlon et al. 2009, p. 

3). Fraley and Ahlstedt (2000, p. 193) 

and Hanlon et al. (2009, pp. 11–12) 

attributed the decline of the Copper 

Creek mussel fauna to an increase in 

cattle grazing and resultant nutrient 

enrichment and loss of riparian 

vegetation along the stream, among 

other factors. This scenario is similar in 

other parts of the extant range of the 

spectaclecase and sheepnose. 

Sedimentation and urban runoff may 

also be threats to the sheepnose in the 

Kankakee River system as the Chicago 

Metro area continues to expand. 

Declines in mussel diversity observed in 

the Ohio River are in part due to 

pollution from urban centers; in many 

of these areas the loss of diversity has 

not recovered from water quality 

problems that began prior to dam 

construction (Watters & Flaute 2010, pp. 

3–7). 

As the spectaclecase primarily 

inhabits deep water along the outside of 

bends, it may be particularly vulnerable 

to siltation. The current often slackens 

in this habitat, more so than in riffles 

and runs where other mussel species are 

typically found, and suspended 

sediment settles out. Spectaclecase beds 

covered with a thick layer of silt have 

been observed in Missouri, often 

downstream from reaches with eroding 

banks (Roberts 2008, pers. comm.). 

Channelization 

Dredging and channelization 

activities have profoundly altered 

riverine habitats nationwide. Hartfield 

(1993, pp. 131–139), Neves et al. (1997, 

pp. 71–72), and Watters (2000, pp. 268– 

269) reviewed the specific effects of 

channelization on freshwater mussels. 

Channelization impacts stream 

physically (for example accelerated 

erosion, reduced depth, decreased 

habitat diversity, geomorphic 

instability, and loss of riparian 

vegetation) and biologically (for 

example decreased fish and mussel 

diversity, altered species composition 

and abundance, decreased biomass, and 

reduced growth rates) (Hartfield 1993, 

pp. 131–139). Channel construction for 

navigation increases flood heights (Belt 

1975, p. 684), partly as a result of a 

decrease in stream length and an 

increase in gradient (Hubbard et al. 

1993, p. 137 (in Hartfield 1993, p. 131)). 

Flood events may thus be exacerbated, 

conveying into streams large quantities 

of sediment, potentially with adsorbed 

contaminants. Channel maintenance 

may result in profound impacts 

downstream (Stansbery 1970, p. 10), 

such as increases in turbidity and 

sedimentation, which may smother 

bottom-dwelling organisms. 

Channel maintenance operations for 

commercial navigation have impacted 

habitat for the sheepnose and 

spectaclecase in many large rivers 


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rangewide. Periodic channel 

maintenance may continue to adversely 

affect this species in the upper 

Mississippi, Ohio, Muskingum, and 

Tennessee rivers. Further modifications 

to the Mississippi River channel are 

anticipated with the recently authorized 

Navigation and Environmental 

Sustainability Program (NESP) (Water 

Resources Development Act of 2007 

(Pub. L. 110–114)), which will consist of 

construction of larger locks and other 

navigation improvements downstream 

of MRP 14. Continual maintenance of 

the Mississippi River navigation 

channel requires dredging, wing and 

closing dam reconstruction and 

maintenance, and bank armoring. 

Dredging, maintenance, and 

construction activities destabilize 

instream fine sediments are likely to 

adversely affect the spectaclecase and 

the sheepnose. Spectaclecase tend to 

inhabit relatively deep water where they 

are particularly vulnerable to siltation. 

The current is slower in this habitat 

than in riffles and runs, and suspended 

sediment settles out in greater volume. 

Dredging to maintain barge traffic on the 

Mississippi River below the mouth of 

the Chippewa River in Wisconsin has 

reduced mussel diversity due to the 

increase in unstable sand substrates 

(Thiel 1981, p. 20; U.S. Army Corps of 

Engineers 1996, p. 1, Tab 14). 

Channel maintenance dredging is also 

a major concern for mussel populations. 

A large amount of spoil (dredged earth 

and rock) was dumped directly on a 

mussel bed in the Muskingum River that 

included the sheepnose in the late 

1990s (Watters 2008, pers. comm.). 

Thousands of mussels were killed as the 

result of this single event. Watters and 

Dunn (1995 p. 231) also noted that the 

lower ends of two mussel beds 

coincided with the mouths of Wolf and 

Bear Creeks. This led them to surmise 

that pollutants, such as sediment loads 

or agricultural runoff, in their 

watersheds may adversely impact 

mussels in the mainstem Muskingum 

River below the confluences of Wolf 

Creek and Bear Creek. 

Mussels require a stable substrate to 

survive and reproduce and are 

particularly susceptible to channel 

instability (Neves et al. 1997, p. 23; 

Parmalee & Bogan 1998). Channel and 

bank degradation have led to the loss of 

stable substrates in the Meramec River 

Basin. Roberts and Bruenderman (2000, 

pp. 7–8, 21–23) pointed to the loss of 

suitable stable habitat as a major cause 

of decline in mussel abundance at sites 

previously surveyed in 1979. 

The Tennessee River was once a 

stronghold for the spectaclecase 

(Ortmann 1924, p. 60; 1925, p. 327), and 

the sheepnose was originally known to 

occur in the Tennessee River and 10 of 

its tributaries (Ortmann 1925, p. 328). 

The mainstem of the Tennessee River is 

maintained as a navigational channel, 

and a plan to deepen it has been 

proposed (Hubbs 2008, pers. comm.). 

Severe bank erosion is ongoing along 

some reaches of the river below 

Pickwick Landing Dam, with some sites 

losing several feet of stream bank per 

year (Hubbs 2008, pers. comm.). 

The sheepnose population within the 

Big Sunflower River is threatened by a 

Corps flood control project (Jones 2008, 

pers. comm.). Dredging for this project 

is planned to take place downstream of 

Indianaola, but head-cutting may 

ultimately destabilize the substrate in 

which sheepnose now exists. This 

activity, coupled with other threats 

potentially affecting sheepnose (see 

below), may lead to extirpation of the 

population within 10 years (Jones 2008, 

pers. comm.). 

The upper Kankakee River in Indiana 

was channelized several decades ago. 

The sheepnose is now considered 

extirpated from the upper Kankakee, 

and is restricted to the unchannelized 

portion of the river in Illinois 

(Cummings 2008, pers. comm.). 

Mining 

Instream gravel mining has been 

implicated in the destruction of mussel 

populations (Hartfield 1993, pp. 136– 

138). Negative impacts associated with 

gravel mining include stream channel 

modifications (altered habitat, disrupted 

flow patterns, and sediment transport), 

water quality modifications (increased 

turbidity, reduced light penetration, and 

increased temperature), 

macroinvertebrate population changes 

(elimination, habitat disruption, and 

increased sedimentation), and changes 

in fish populations (impacts to 

spawning and nursery habitat and food 

web disruptions) (Kanehl & Lyons 1992, 

pp. 4–10). 

Heavy metal-rich drainage from coal 

mining and associated sedimentation 

has adversely impacted portions of the 

Tennessee River system in Virginia. 

Low pH commonly associated with 

mine runoff can reduce glochidial 

encystment (attachment) rates (Huebner 

& Pynnonen 1992, pp. 2350–2353). Acid 

mine runoff may thus have local 

impacts on recruitment of the mussel 

populations close to mines. 

Coal-related toxins in the Clinch River 

may explain the decline and lack of 

mussel recruitment at some sites in the 

Virginia portion of that stream (Ahlstedt 

2008, pers. comm.). Patterns of mussel 

distribution and abundances have been 

found to be negatively correlated with 

proximity to coal-mining activities 

(Ahlstedt & Tuberville 1997, pp. 74–75). 

Known mussel toxicants, such as 

polycyclic aromatic hydrocarbons, 

heavy metals (for example, copper, 

manganese, and zinc), and other 

chemicals from coal mining and other 

activities contaminate sediments in the 

Clinch River (Ahlstedt & Tuberville 

1997, p. 75). These chemicals are toxic 

to juvenile mussels (Ahlstedt & 

Tuberville 1997, p. 75). Pollutant inputs 

to the Clinch River from a coal-burning 

power plant in Carbo, Virginia, were 

shown to increase mortality and reduce 

cellulolytic activity (breaking down 

cellulose) in transplanted mussels 

(Farris et al. 1988, pp. 705–706). Sitespecific copper toxicity studies of 

unionid glochidia in the Clinch River 

showed that freshwater mussels as a 

group were generally sensitive to 

copper, the toxic constituent of the 

power plant effluent (Cherry et al. 2002, 

p. 596). All of these studies indicate that 

acid mine runoff may have local 

impacts on spectaclecase recruitment 

and survival in this river. 

Gravel-mining activities may also be a 

localized threat in some streams with 

extant sheepnose and spectaclecase 

populations. Gravel mining causes 

stream instability, increasing erosion, 

turbidity, and subsequent sediment 

deposition (Meador & Layher 1998, pp. 

8–9). Gravel mining is common in the 

Meramec River system. Between 1997 

and 2008, the Missouri Department of 

Natural Resources issued permits for 

102 sand- and gravel-mining sites in the 

Meramec River (Zeaman 2008, pers. 

comm.). Although rigid guidelines 

prohibited instream mining and 

required streamside buffers, a court 

ruling deauthorized the Corps from 

regulating these habitat protective 

measures. The Corps still retains 

oversight for gravel mining, but many 

mining operations do not fall under 

Corps jurisdiction (Roberts & 

Bruenderman 2000, p. 23). In the lower 

Tennessee River, mining is permitted in 

18 reaches for a total of 47.9 river miles 

(77.1 km) between the Duck River 

confluence and Pickwick Landing Dam, 

a distance of over 95 miles (153 km) 

(Hubbs 2008, pers. comm.). This is the 

reach where mussel recruitment has 

been noted for many rare species in 

recent years. These activities have the 

potential to impact the river’s small 

sheepnose population. The Gasconade 

River and its tributaries have been 

subject to gravel mining and other 

channel modifying practices that 

accelerate channel destabilization. 

These physical habitat threats combined 

with poor water quality and agricultural 


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nonpoint source pollution are serious 

threats to all existing mussel fauna in 

the system. 

Oil and Gas Development 

Coal, oil, and natural gas resources are 

present in some of the watersheds that 

are known to support sheepnose, 

including the Allegheny River. 

Exploration and extraction of these 

energy resources can result in increased 

siltation, a changed hydrograph, and 

altered water quality even at a distance 

from the mine or well field. Sheepnose 

habitat in larger streams can be 

threatened by the cumulative effects of 

multiple mines and well fields (adapted 

from Service 2008, p. 11). 

Coal, oil, and gas resources are 

present in a number of the basins where 

sheepnose occur, and extraction of these 

resources has increased dramatically in 

recent years, particularly in 

Pennsylvania and West Virginia. 

Although oil and gas extraction 

generally occurs away from the river, 

extensive road networks are required to 

construct and maintain wells. These 

road networks frequently cross or occur 

near tributaries, contributing sediment 

to the receiving waterway. In addition, 

the construction and operation of wells 

may result in the discharge of brine. 

Point source discharges are typically 

regulated; however, nonpoint inputs 

such as silt and other contaminants may 

not be sufficiently regulated, 

particularly those originating some 

distance from a waterway. In 2006, more 

than 3,700 permits were issued for oil 

and gas wells by the Pennsylvania 

Department of Environmental 

Protection, which also issued 98 

citations for permit violations at 54 

wells (Hopey 2007; adapted from 

Service 2008, p. 12). 

Chemical Contaminants 

Chemical contaminants are 

ubiquitous throughout the environment 

and are considered a major threat in the 

decline of freshwater mussel species 

(Cope et al. 2008, p. 451; Richter et al. 

1997, p. 1081; Strayer et al. 2004, p. 436; 

Wang et al. 2007a, p. 2029). Chemicals 

enter the environment through both 

point and nonpoint discharges 

including spills, industrial sources, 

municipal effluents, and agricultural 

runoff. These sources contribute organic 

compounds, heavy metals, pesticides, 

and a wide variety of newly emerging 

contaminants to the aquatic 

environment. As a result, water and 

sediment quality can be degraded to the 

extent that mussel populations are 

adversely impacted. 

Chemical spills can be especially 

devastating to mussels because they 

may result in exposure of a relatively 

immobile species to extremely elevated 

concentrations that far exceed toxic 

levels and any water quality standards 

that might be in effect. Some notable 

spills that released large quantities of 

highly concentrated chemicals resulting 

in mortality to mussels include: 

• Massive mussel kills on the Clinch 

River at Carbo, Virginia occurred from a 

power plant alkaline fly ash pond spill 

in 1967, and a sulfuric acid spill in 1970 

(Crossman et al. 1973, p. 6); 

• Approximately 18,000 mussels of 

several species, including 750 

individuals from three endangered 

mussel species, were eliminated from 

the upper Clinch River near Cedar Bluff, 

Virginia in 1998, when an overturned 

tanker truck released 1,600 gallons 

(6,056 liters) of a chemical used in 

rubber manufacturing (Jones et al. 2001, 

p. 20; Schmerfeld 2006, p. 12); and 

• An on-going release of sodium 

dimethyl dithiocarbamate, a chemical 

used to reduce and precipitate 

hexachrome, starting in 1999 impacted 

approximately 10 river miles (16 km) of 

the Ohio River and resulted in an 

estimated loss of one million mussels, 

including individuals from two 

federally listed species (DeVault 2009, 

pers. comm.; Clayton 2008b, pers. 

comm.). 

These are not the only instances 

where chemical spills have resulted in 

the loss of high numbers of mussels 

(Brown et al. 2005, p. 1457; Jones et al. 

2001, p. 20; Neves 1991, p. 252; 

Schmerfeld 2006, pp. 12–13), but are 

provided as examples of the serious 

threat chemical spills pose to mussel 

species. The sheepnose and 

spectaclecase are especially threatened 

by chemical spills because these spills 

can occur anywhere that highways with 

tanker trucks, industries, or mines 

overlap with sheepnose and 

spectaclecase distribution. 

Exposure of mussels to lower 

concentrations of contaminants more 

likely to be found in aquatic 

environments can also adversely affect 

mussels and result in the decline of 

freshwater mussel species. Such 

concentrations may not be immediately 

lethal, but over time, can result in 

mortality, reduced filtration efficiency, 

reduced growth, decreased 

reproduction, changes in enzyme 

activity, and behavioral changes to all 

mussel life stages. Frequently, 

procedures which evaluate the ‘‘safe’’ 

concentration of an environmental 

contaminant (for example, national 

water quality criteria) do not have data 

for freshwater mussel species or exclude 

data that are available for freshwater 

mussels (March et al. 2007, pp. 2066– 

2067, 2073). 

Current research is now starting to 

focus on the contaminant sensitivity of 

freshwater mussel glochidia and newlyreleased juvenile mussels (Goudreau et 

al. 1993, pp. 219–222; Jacobson et al. 

1997, p. 2390; March et al. 2007, pp. 

2068–2073; Valenti et al. 2006, pp. 

2514–2517; Valenti et al. 2005, pp. 

1244–1245; Wang et al. 2007c, pp. 

2041–2046) and juveniles (Augspurger 

et al. 2003, p. 2569; Bartsch et al. 2003, 

p. 2561; March et al. 2007, pp. 2068– 

2073; Mummert et al. 2003, p. 2549; 

Valenti et al. 2006, pp. 2514–2517; 

Valenti et al. 2005, pp. 1244–1245; 

Wang et al. 2007b, pp. 2053–2055; 

Wang et al. 2007c, pp. 2041–2046) to 

such contaminants as ammonia, metals, 

chlorine, and pesticides. The toxicity 

information presented in this section 

focuses on recent water-only laboratory 

acute (sudden and severe exposure) and 

chronic (prolonged or repeated 

exposure) toxicity tests with early life 

stages of freshwater mussels using the 

standard testing methodology published 

by the American Society for Testing and 

Materials (ASTM) (American Society for 

Testing and Materials. 2008. Standard 

guide for conducting laboratory toxicity 

tests with freshwater mussels E2455–06. 

In Annual Book of ASTM Standards, 

Vol 11.06. Philadelphia, PA, pp. 1442– 

1493.) Use of this standard testing 

method generates consistent, reliable 

toxicity data with acceptable precision 

and accuracy (Wang et al. 2007a, p. 

2035) and was used for toxicity tests on 

ammonia, copper, chlorine and select 

pesticides (Augspurger et al. 2007, p. 

2025; Bringolf et al. 2007b, p. 2101; 

Bringolf et al. 2007c, p. 2087; Wang et 

al. 2007a, p. 2029; Wang et al. 2007b, p. 

2048; Wang et al. 2007c, p. 2036). Use 

of these tests has documented that, 

while mussels are sensitive to some 

contaminants, they are not universally 

sensitive to all contaminants 

(Augspurger et al. 2007, pp. 2025–2026). 

One chemical that is particularly toxic 

to early life stages of mussels is 

ammonia. Sources of ammonia include 

agricultural wastes (animal feedlots and 

nitrogenous fertilizers), municipal 

wastewater treatment plants, and 

industrial waste (Augspurger et al. 2007, 

p. 2026) as well as precipitation and 

natural processes (decomposition of 

organic nitrogen) (Augspurger et al. 

2003, p. 2569; Goudreau et al. 1993, p. 

212; Hickey & Martin 1999, p. 44; 

Newton 2003, p. 1243). Therefore, 

ammonia is considered a limiting factor 

for survival and recovery of some 

mussel species due to its ubiquity in 

aquatic environments and high level of 

toxicity, and because the highest 


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concentrations typically occur in mussel 

microhabitats (Augspurger et al. 2003, 

p. 2574). In addition, studies have 

shown that ammonia concentrations 

increase with increasing temperature 

and low flow conditions (Cherry et al. 

2005, p. 378; Cooper et al. 2005, p. 381), 

which may be exacerbated by the effects 

of climate change, and may cause 

ammonia to become more problematic 

for juvenile mussels. The EPAestablished ammonia water quality 

criteria (EPA 1985, pp. 94–99) may not 

be protective of mussels (Augspurger et 

al. 2003, p. 2572; Sharpe 2005, p. 28) 

under current and future climate 

conditions. 

Mussels are also affected by metals 

(Keller & Zam 1991, p. 543), such as 

cadmium, chromium, copper, mercury, 

and zinc, which can negatively affect 

biological processes such as growth, 

filtration efficiency, enzyme activity, 

valve closure, and behavior (Jacobson et 

al. 1997, p. 2390; Keller & Zam 1991, p. 

543; Naimo 1995, pp. 351–355; Valenti 

et al. 2005, p. 1244). Metals occur in 

industrial and wastewater effluents and 

are often a result of atmospheric 

deposition from industrial processes 

and incinerators. Glochidia and juvenile 

freshwater mussels have recently been 

studied to determine the acute and 

chronic toxicity of copper to these life 

stages (Wang et al. 2007b, pp. 2048– 

2056; Wang et al. 2007c, pp. 2036– 

2047). The chronic values determined 

for copper ranged from 8.5 to 9.8 

micrograms per liter (ug/L) for survival 

and from 4.6 to 8.5 ug/L for growth of 

juveniles. These chronic values are 

below the EPA 1996 chronic water 

quality criterion of 15 ug/L (hardness 

170 mg/L) for copper (Wang et al. 

2007b, pp. 2052–2055). March (2007, 

pp. 2066, 2073) identifies that copper 

water quality criteria and modified State 

water quality standards may not be 

protective of mussels. 

Mercury is another heavy metal that 

has the potential to negatively affect 

mussel populations, and it is receiving 

attention due to its widespread 

distribution and potential to adversely 

impact the environment. Mercury has 

been detected throughout aquatic 

environments as a product of municipal 

and industrial waste and atmospheric 

deposition from coal-burning plants. 

One recent study evaluated the 

sensitivity of early life stages of mussels 

to mercury (Valenti et al. 2005, p. 1242). 

This study determined that for the 

mussel species used (rainbow mussel, 

Villosa iris) glochidia were more 

sensitive to mercury than were juvenile 

mussels, with the median lethal 

concentration value of 14 ug/L 

compared to 114 ug/L for the juvenile 

life stage. The chronic toxicity tests 

conducted determined that juveniles 

exposed to mercury greater than or 

equal to 8 ug/L exhibited reduced 

growth. These observed toxicity values 

are below EPA’s Criteria Continuous 

Concentration and Criteria Maximum 

Concentration, which are 0.77 ug/L and 

1.4 ug/L, respectively. Based on these 

data, we believe that EPA’s water 

quality standards for mercury should be 

protective of juvenile mussels and 

glochidia, except in cases of illegal 

dumping, permit violations, or spills. 

However, impacts to mussels from 

mercury toxicity may be occurring in 

some streams. According to the National 

Summary Data reported by States to the 

EPA, 3,770 monitored waters do not 

meet EPA standards for mercury in the 

United States. (http://iaspub.epa.gov/

waters10/attains_nation_cy.control?p_

report_type=T, accessed 6/28/2010). 

Acute mercury toxicity was determined 

to be the cause of extirpation of a 

diverse mussel fauna for a 70-mile (112- 

km) portion of the North Fork Holston 

River (Brown et al. 2005, pp. 1455– 

1457). 

In addition to ammonia, agricultural 

sources of chemical contaminants 

include two broad categories that have 

the potential to adversely impact mussel 

species: Nutrients and pesticides. 

Nutrients (such as nitrogen and 

phosphorus) can impact streams when 

their concentrations reach levels that 

cannot be assimilated, a condition 

known as over-enrichment. Nutrient 

over-enrichment is primarily a result of 

runoff from livestock farms, feedlots, 

and heavily fertilized row crops 

(Peterjohn & Correll 1984, p. 1471). 

Over-enriched conditions are 

exacerbated by low-flow conditions, 

such as those experienced during 

typical summer-season flows and that 

might occur with greater frequency and 

magnitude as a result of climate change. 

Bauer (1988, p. 244) found that 

excessive nitrogen concentrations can 

be detrimental to the adult freshwater 

pearl mussel (Margaritifera 

margaritifera), as was evident by the 

positive linear relationship between 

mortality and nitrate concentration. 

Also, a study of mussel life span and 

size (Bauer 1992, p. 425) showed a 

negative correlation between growth 

rate and eutrophication, and longevity 

was reduced as the concentration of 

nitrates increased. Nutrient overenrichment can result in an increase in 

primary productivity, and the 

subsequent respiration depletes 

dissolved oxygen levels. This may be 

particularly detrimental to juvenile 

mussels that inhabit the interstitial 

spaces in the substrate where lower 

dissolved oxygen concentrations are 

more likely than on the sediment 

surface where adults tend to live 

(Sparks & Strayer 1998, pp. 132–133). 

Elevated concentrations of pesticide 

frequently occur in streams due to 

pesticide runoff, overspray application 

to row crops, and lack of adequate 

riparian buffers. Agricultural pesticide 

applications often coincide with the 

reproductive and early life stages of 

mussel, and thus impacts to mussels 

due to pesticides may be increased 

(Bringolf et al. 2007a, p. 2094). Little is 

known regarding the impact of currently 

used pesticides to freshwater mussels 

even though some pesticides, such as 

glyphosate (Roundup), are used 

globally. Recent studies tested the 

toxicity of glyphosate, its formulations, 

and a surfactant (MON 0818) used in 

several glyphosate formulations, to early 

life stages of the fatmucket (Lampsilis 

siliquoidea), a native freshwater mussel 

(Bringolf et al. 2007a, p. 2094). Studies 

conducted with juvenile mussels and 

glochidia determined that the surfactant 

(MON 0818) was the most toxic of the 

compounds tested and that L. 

siliquoidea glochidia were the most 

sensitive organism tested to date 

(Bringolf et al. 2007a, p. 2094). 

Roundup, technical grade glyphosate 

isopropylamine salt, and 

isopropylamine were also acutely toxic 

to juveniles and glochidia (Bringolf et 

al. 2007a, p. 2097). The impacts of other 

pesticides including atrazine, 

chlorpyrifos, and permethrin on 

glochidia and juvenile life stages have 

also recently been studied (Bringolf et 

al. 2007b, p. 2101). This study 

determined that chlorpyrifos was toxic 

to both L. siliquoidea glochidia and 

juveniles (Bringolf et al. 2007b, p. 2104). 

The above results indicate the potential 

toxicity of commonly applied pesticides 

and the threat to mussel species as a 

result of the widespread use of these 

pesticides. All of these pesticides are 

commonly used throughout the range of 

the sheepnose and spectaclecase. 

A potential, but undocumented, threat 

to freshwater mussel species, including 

sheepnose and spectaclecase, are 

contaminants referred to as ‘‘emerging 

contaminants’’ that are being detected in 

aquatic ecosystems at an increasing rate. 

Pharmaceuticals, hormones, and other 

organic contaminants have been 

detected downstream from urban areas 

and livestock production (Kolpin et al. 

2002, p. 1202). A large potential source 

of these emerging contaminants is 

wastewater being discharged through 

both permitted (National Pollutant 

Discharge Elimination System, or 

NPDES) and non-permitted sites 


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throughout the country. Permitted 

discharge sites are ubiquitous in 

watersheds with sheepnose and 

spectaclecase populations, providing 

ample opportunities for contaminants to 

impact the species (for example, there 

are more than 250 NPDES sites in the 

Meramec River, Missouri system, which 

harbors large, but declining, populations 

of sheepnose and spectaclecase; Roberts 

and Bruenderman 2000, p. 78). 

The information presented in this 

section represents some of the threats 

from chemical contaminants that have 

been documented both in the laboratory 

and field and demonstrates that 

chemical contaminants pose a 

substantial threat to sheepnose and 

spectaclecase. This information 

indicates the potential for contaminants 

from spills that are immediately lethal 

to species, to chronic contaminant 

exposure, which results in death, 

reduced growth, or reduced 

reproduction of sheepnose and 

spectaclecase to contribute to declining 

sheepnose and spectaclecase 

populations. 

Summary of Factor A 

The decline of the freshwater mussels 

in the eastern United States is primarily 

the result of the long-lasting effects of 

habitat alterations such as 

impoundments, channelization, 

chemical contaminants, mining, oil and 

gas development, and sedimentation. 

Although efforts have been made to 

restore habitat in some areas, the longterm effects of large-scale and wideranging habitat modification, 

destruction, and curtailment will 

continue into the foreseeable future. 

B. Overutilization for Commercial, 

Recreational, Scientific, or Educational 

Purposes 

The spectaclecase and sheepnose are 

not commercially valuable species but 

may be increasingly sought by collectors 

as they become rarer. Although 

scientific collecting is not thought to 

represent a significant threat, 

unregulated collecting could adversely 

affect localized spectaclecase and 

sheepnose populations. 

Mussel harvest is illegal in some 

States (for example, Indiana and Ohio), 

but regulated in others (for example, 

Alabama, Kentucky, Tennessee, and 

Wisconsin). These species may be 

inadvertently harvested by 

inexperienced commercial harvesters 

unfamiliar with species identification. 

Although illegal harvest of protected 

mussel beds occurs (Watters and Dunn 

1995, p. 225, 247–250), commercial 

harvest is not known to have a 

significant impact on the spectaclecase 

and sheepnose. 

On the basis of this analysis, we find 

that overutilization for commercial, 

recreational, scientific, or educational 

purposes is not now a threat to the 

spectaclecase or sheepnose in any 

portion of its range or likely to become 

a significant threat in the foreseeable 

future. 

C. Disease or Predation 

Little is known about diseases in 

freshwater mussels (Grizzle & Brunner 

2007, p. 6). However, mussel die-offs 

have been documented in spectaclecase 

and sheepnose streams (Neves 1986, p. 

9), and some researchers believe that 

disease may be a factor contributing to 

the die-offs (Buchanan 1986, p. 53; 

Neves 1986, p. 11). Mussel parasites 

include water mites, trematodes, 

oligochaetes, leeches, copepods, 

bacteria, and protozoa (Grizzle & 

Brunner 2007, p. 4). Generally, parasites 

are not suspected of being a major 

limiting factor (Oesch 1984, p. 6), but a 

recent study provides contrary 

evidence. Reproductive output and 

physiological condition were negatively 

correlated with mite and trematode 

abundance, respectively (Gangloff et al. 

2008, pp. 28–30). Stressors that reduce 

fitness may make mussels more 

susceptible to parasites (Butler 2007, p. 

90). Furthermore, nonnative mussels 

may carry diseases and parasites that are 

potentially devastating to the native 

mussel fauna, including spectaclecase 

and sheepnose (Strayer 1999, p. 88). 

The muskrat (Ondatra zibethicus) is 

cited as the most prevalent mussel 

predator (Convey et al. 1989, p. 654– 

655; Hanson et al. 1989, pp. 15–16; 

Kunz 1898, p. 328). Muskrat predation 

may limit the recovery potential of 

endangered mussels or contribute to 

local extirpations of previously stressed 

populations, according to Neves and 

Odom (1989, p. 940), but they consider 

it primarily a seasonal or localized 

threat. Bo ̈pple and Coker (1912, p. 9) 

noted the occurrence of ‘‘large piles of 

shells made by the muskrats’’ on an 

island in the Clinch River, Tennessee, 

composed of ‘‘about one-third’’ 

spectaclecase shells. Predation by 

muskrats may be a seasonal and 

localized threat to spectaclecase and 

sheepnose populations but is probably 

not a significant threat rangewide. 

Some species of fish feed on mussels 

(for example, common carp (Cyprinus 

carpio), freshwater drum (Aplodinotus 

grunniens), redear sunfish (Lepomis 

microlophus)) and potentially on this 

species when young. Various 

invertebrates, such as flatworms, hydra, 

non-biting midge larvae, dragonfly 

larvae, and crayfish, may feed on 

juvenile mussels (Neves 2008, pers. 

comm.). Although predation by 

naturally occurring predators is a 

normal aspect of the population 

dynamics of a healthy mussel 

population, predation may amplify 

declines in small populations of this 

species. In addition, the potential now 

exists for the black carp 

(Mylopharyngodon piceus), a molluskeating Asian fish recently introduced 

into the waters of the United States 

(Strayer 1999, p. 89), to eventually 

disperse throughout the range of the 

spectaclecase and sheepnose. 

The life cycle of freshwater mussels is 

intimately related to that of the 

freshwater fish they use as hosts for 

their parasitic glochidia. For this reason, 

diseases that impact populations of 

freshwater fishes also pose a significant 

threat to mussels. Viral hemorrhagic 

septicemia (VHS) disease has been 

confirmed from much of the Great Lakes 

and St. Lawrence River system. In June 

2008, muskellunge (Esox masquinongy) 

from Clearfork Reservoir, near 

Mansfield, Ohio, tested positive for 

carrying VHS virus. This is the first 

known occurrence of VHS virus in the 

Mississippi River basin. 

The VHS virus has been implicated as 

a mortality factor in fish kills 

throughout the Great Lakes region. It has 

been confirmed in 28 fish species, but 

no identified hosts for sheepnose are on 

the U.S. Department of Agriculture’s 

Animal and Plant Health Inspection 

Service (APHIS) list of fish species 

susceptible to VHS (APHIS 2008, pp. 1– 

2). Since the host for spectaclecase is 

unknown, we do not know how VHS 

could affect reproduction for 

spectaclecase. If the VHS virus 

successfully migrates out of the 

Clearfork Reservoir and into the Ohio 

River, it could spread rapidly and cause 

fish kills throughout the Mississippi 

River basin. Few spectaclecase and 

sheepnose populations are currently 

recruiting at sustainable levels, and fish 

kills could further reduce encounters 

with hosts and potentially reduce 

recruitment. 

In summary, disease in freshwater 

mollusks is poorly known and not 

currently considered a threat. Although 

there is no direct evidence at this time 

that predation is detrimentally affecting 

the spectaclecase or sheepnose, their 

small populations and limited ranges 

leaves them vulnerable to threats of 

predation from natural or introduced 

predators. Therefore, we conclude that 

predation currently represents a threat 

of low magnitude, but it could 

potentially become a significant future 

threat to the spectaclecase and 


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sheepnose due to their small population 

sizes. 

D. The Inadequacy of Existing 

Regulatory Mechanisms 

States with extant spectaclecase and 

sheepnose populations prohibit the 

taking of mussels for scientific purposes 

without a State collecting permit. 

However, enforcement of this permit 

requirement is difficult. 

The level of protection that 

spectaclecase and sheepnose receive 

from State listing varies from State to 

State. The sheepnose is State-listed in 

every State that keeps such a list. 

Collection of sheepnose in Pennsylvania 

for use as fish bait is limited to 50 

individuals per day. The spectaclecase 

is State-listed in 8 of the 10 States that 

harbor extant populations. Only in 

Missouri and Tennessee is the 

spectaclecase not assigned conservation 

status and West Virginia does not have 

any State-specific legislation similar to 

the Act. 

Nonpoint source pollution is 

considered a primary threat to 

sheepnose and spectaclecase habitat; 

however, current laws do not 

adequately protect spectaclecase and 

sheepnose habitat from nonpoint source 

pollution, as the laws to prevent 

sediment entering water ways are poorly 

enforced. Best management practices for 

sediment and erosion control are often 

recommended or required by local 

ordinances for construction projects; 

however, compliance, monitoring, and 

enforcement of these recommendations 

are often poorly implemented. 

Furthermore, there are currently no 

requirements within the scope of 

Federal environmental laws to 

specifically consider the spectaclecase 

and sheepnose during Federal activities. 

Point source discharges within the 

range of the spectaclecase and 

sheepnose have been reduced since the 

inception of the Clean Water Act (33 

U.S.C. 1251 et seq.), but this may not 

provide adequate protection for filter 

feeding organisms that can be impacted 

by extremely low levels of contaminants 

(see ‘‘Chemical Contaminants’’ 

discussion under Factor A). There is no 

specific information on the sensitivity of 

the spectaclecase and sheepnose to 

common industrial and municipal 

pollutants, and very little information 

on other freshwater mussels. Therefore, 

it appears that a lack of adequate 

research and data prevents existing 

regulations, such as the Clean Water Act 

(administered by the EPA and the 

Corps), from being fully used or 

effective. 

The U.S. Army Corps of Engineers 

retains oversight authority and requires 

a permit for gravel-mining activities that 

deposit fill into streams under section 

404 of the Clean Water Act. 

Additionally, a Corps permit is required 

under section 10 of the Rivers and 

Harbors Act (33 U.S.C. 401 et seq.) for 

navigable waterways including the 

lower 50 miles (80 km) of the Meramec 

River. However, many gravel-mining 

operations do not fall under these two 

categories. 

Despite these existing regulatory 

mechanisms, the spectaclecase and 

sheepnose continue to decline due to 

the effects of habitat destruction, poor 

water quality, contaminants, and other 

factors. We find that these regulatory 

measures have been insufficient to 

significantly reduce or remove the 

threats to the spectaclecase and 

sheepnose, and therefore that the 

inadequacy of existing regulatory 

mechanisms is a threat to these species 

throughout all of their ranges. 

Based on our analysis of the best 

available information, we have no 

reason to believe that the 

aforementioned regulations will offer 

adequate protection to the spectaclecase 

and sheepnose in the foreseeable future. 

E. Other Natural or Manmade Factors 

Affecting Its Continued Existence 

Temperature 

Natural temperature regimes can be 

altered by impoundments, water 

releases from dams, industrial and 

municipal effluents, and changes in 

riparian habitat. Critical thermal limits 

for survival and normal functioning of 

many freshwater mussel species are 

unknown. High temperatures can 

reduce dissolved oxygen concentrations 

in the water, which slows growth, 

reduces glycogen stores, impairs 

respiration, and may inhibit 

reproduction (Fuller 1974, pp. 240– 

241). Low temperatures can 

significantly delay or prevent 

metamorphosis (Watters & O’Dee 1999, 

pp. 454–455). Water temperature 

increases have been documented to 

shorten the period of glochidial 

encystment, reduce righting speed, 

increase oxygen consumption, and slow 

burrowing and movement responses 

(Bartsch et al. 2000, p. 237; Fuller 1974, 

pp. 240–241; Schwalb & Pusch 2007, 

pp. 264–265; Watters et al. 2001, p. 

546). Several studies have documented 

the influence of temperature on the 

timing of aspects of mussel 

reproduction (for example, Allen et al. 

2007, p. 85; Gray et al. 2002, p. 156; 

Steingraeber et al. 2007, pp. 303–309). 

Peak glochidial releases are associated 

with water temperature thresholds that 

can be thermal minimums or thermal 

maximums, depending on the species 

(Watters & O’Dee 2000, p. 136). 

Abnormal temperature changes may 

cause particular problems to mussels 

whose reproductive cycles may be 

linked to fish reproductive cycles (for 

example,Young & Williams 1984). 

Climate Change 

It is a widely accepted fact that 

changes in climate are occurring 

worldwide (IPCC 2007, p. 30). 

Understanding the effects of climate 

change on freshwater mussels is of 

crucial importance, because the extreme 

fragmentation of freshwater drainage 

systems, coupled with the limited 

ability of mussels to migrate, will make 

it particularly difficult for mussels to 

adjust their range in response to changes 

in climate (Strayer 2008, p. 30). For 

example, changes in temperature and 

precipitation can increase the likelihood 

of flooding or increase drought duration 

and intensity, resulting in direct 

impacts to freshwater mussels (Golladay 

et al. 2004, p. 503; Hastie et al. 2003, pp. 

40–43). Indirect effects of climate 

change may include declines in host 

fish stocks, sea level rise, habitat 

reduction, and changes in human 

activity in response to climate change 

(Hastie et al. 2003, pp. 43–44). 

Population Fragmentation and Isolation 

Most of the remaining spectaclecase 

and sheepnose populations are small 

and isolated and thus are susceptible to 

genetic drift, inbreeding depression, and 

random or chance changes to the 

environment, such as toxic chemical 

spills (Avise and Hamrick 1996, pp. 

463–466; Smith 1990, pp. 311–321; 

Watters and Dunn 1995, pp. 257–258 

Inbreeding depression can result in 

death, decreased fertility, smaller body 

size, loss of vigor, reduced fitness, and 

various chromosome abnormalities 

(Smith 1990, pp. 311–321). Despite any 

evolutionary adaptations for rarity, 

habitat loss and degradation increase a 

species’ vulnerability to extinction 

(Noss and Cooperrider 1994, pp. 58–62). 

Numerous authors (including Noss and 

Cooperrider 1994, pp. 58–62; Thomas 

1994, p. 373) have indicated that the 

probability of extinction increases with 

decreasing habitat availability. Although 

changes in the environment may cause 

populations to fluctuate naturally, small 

and low-density populations are more 

likely to fluctuate below a minimum 

viable population (the minimum or 

threshold number of individuals needed 

in a population to persist in a viable 

state for a given interval) (Gilpin and 

Soule 1986, pp. 25–33; Shaffer 1981, p. 

131; Shaffer and Samson 1985, pp. 148– 

150). 


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These species were widespread 

throughout much of the upper twothirds of the Mississippi River system, 

for example, when few natural barriers 

existed to prevent migration (via host 

species) among suitable habitats. 

Construction of dams, however, 

destroyed many spectaclecase and 

sheepnose populations and isolated 

others. Recruitment reduction or failure 

is a potential problem for many small 

sheepnose populations rangewide, a 

potential condition exacerbated by its 

reduced range and increasingly isolated 

populations. If these trends continue, 

further significant declines in total 

sheepnose population size and 

consequent reduction in long-term 

survivability may soon become 

apparent. 

Spectaclecase are long-lived (up to 70 

years; Havlik 1994, p. 19) while 

sheepnose are relatively long-lived 

(approximately 30 years; Watters et al. 

2009, p. 221) Therefore, it may take 

decades for non-reproducing 

populations of both species to become 

extinct following their isolation by, for 

example, the construction of a dam. The 

occasional discovery of relatively young 

spectaclecase in river reaches between 

impoundments indicates that some 

post-impoundment recruitment has 

occurred. The level of recruitment in 

these cases, however, appears to be 

insufficient to ensure the long-term 

sustainability of the spectaclecase. 

Small isolated populations of 

spectaclecase and sheepnose that may 

now be comprised predominantly of 

adult specimens could be dying out 

slowly in the absence of recruitment, 

even without other threats described 

above. Isolated populations usually face 

other threats that result in continually 

decreasing patches of suitable habitat. 

Genetic considerations for managing 

imperiled mussels and for captive 

propagation were reviewed by Neves 

(1997a, p. 1422) and Jones et al. (2006, 

pp. 527–535), respectively. The 

likelihood is high that some populations 

of the spectaclecase and sheepnose are 

below the effective population size 

(EPS) (Soule 1980, pp. 162–164) 

necessary to adapt to environmental 

change and persist in the long term. 

Isolated populations eventually die out 

when population size drops below the 

EPS or threshold level of sustainability. 

Evidence of recruitment in many 

populations of these two species is 

scant, making recruitment reduction or 

outright failure suspect. These 

populations may be experiencing the 

bottleneck effect of not attaining the 

effective population size. Small, 

isolated, below effective population 

size-threshold populations of shortlived species (most host fishes) 

theoretically die out within a decade or 

so, while below-threshold populations 

of long-lived species, such as the 

spectaclecase and sheepnose, might take 

decades to die out even given years of 

total recruitment failure. Without 

historical barriers to genetic 

interchange, small, isolated populations 

could be slowly expiring, a 

phenomenon termed the extinction debt 

(Tilman et al. 1994, pp. 65–66). Even 

given the totally improbable absence of 

anthropogenic threats, we may lose 

disjunct populations to below-threshold 

effective population size. However, 

evidence indicates that general 

degradation continues to decrease 

habitat patch size and to act insidiously 

in the decline of spectaclecase and 

sheepnose populations. 

Spectaclecase and sheepnose mussels’ 

scarcity and decreased population size 

makes maintaining adequate 

heterogeneity problematic for resource 

managers. Neves (1997b, p. 6) warned 

that ‘‘[i]f we let conservation genetics 

become the goal rather than the 

guidelines for restoring and recovering 

mussel populations, then we will be 

doomed to failure with rare species.’’ 

Habitat alteration, not lack of genetic 

variability, is the driving force of 

population extirpation (Caro and 

Laurenson 1994, pp. 485–486; Neves et 

al. 1997, p. 60). Nevertheless, genetics 

issues should be considered in 

maintaining high levels of 

heterozygosity during spectaclecase 

recovery efforts. Treating disjunct 

occurrences of this wide-ranging species 

as a metapopulation would facilitate 

conservation management while 

increasing recovery options (for 

example, translocating adults or 

introducing infested hosts and 

propagated juveniles) to establish and 

maintain viable populations (Neves 

1997b, p. 6). Due to small population 

size and probable reduction of genetic 

diversity within populations, efforts 

should be made to maximize genetic 

heterogeneity to avoid both inbreeding 

(Templeton & Read 1984, p. 189) and 

outbreeding depression (Avise & 

Hamrick 1996, pp. 463–466) whenever 

feasible in propagation and 

translocation efforts (Jones et al. 2006, 

p. 529). 

We find that fragmentation and 

isolation of small remaining populations 

of the spectaclecase and sheepnose are 

current and ongoing threats to both 

species throughout all of their ranges 

that will continue into the foreseeable 

future. Further, stochastic events may 

play a magnified role in population 

extirpation when small, isolated 

populations are involved. 

Exotic Species 

Various exotic or nonnative species of 

aquatic organisms are firmly established 

in the range of the spectaclecase and 

sheepnose. The exotic species that poses 

the most significant threat to the 

spectaclecase and sheepnose is the 

zebra mussel (Dreissena polymorpha). 

Its invasion of freshwater habitats in the 

United States poses a threat to mussel 

faunas in many regions, and species’ 

extinctions are expected as a result of its 

continued spread in the eastern United 

States (Ricciardi et al. 1998, p. 615). 

Strayer (1999, pp. 75–80) reviewed in 

detail the mechanisms in which zebra 

mussels impact native mussels. The 

primary means of impact is direct 

fouling of the shells of live native 

mussels. Zebra mussels attach in large 

numbers to the shells of live native 

mussels and are implicated in the loss 

of entire native mussel beds. Fouling 

impacts include impeding locomotion 

(both laterally and vertically), 

interfering with normal valve 

movements, deforming valve margins, 

and locally depleting food resources and 

increasing waste products. Heavy 

infestations of zebra mussels on native 

mussels may overly stress the animals 

by reducing their energy stores. They 

may also reduce food concentrations to 

levels too low to support reproduction, 

or even survival in extreme cases. 

Other ways zebra mussels may impact 

spectaclecase and sheepnose is through 

filtering their sperm and possibly 

glochidia from the water column, thus 

reducing reproductive potential. Habitat 

for native mussels may also be degraded 

by large deposits of zebra mussel 

pseudofeces (undigested waste material 

passed out of the incurrent siphon) 

(Vaughan 1997, p. 11). Because 

spectaclecase are found in pools and 

zebra mussel veligers (larvae) attach to 

hard substrates at the point at which 

they settle out from the water column, 

spectaclecase are particularly vulnerable 

to zebra mussel invasion. The 

spectaclecase’s colonial tendency could 

allow for very large numbers to be 

affected by a single favorable year for 

zebra mussels. 

Zebra mussels are established 

throughout the upper Mississippi, lower 

St. Croix, Ohio, and Tennessee Rivers, 

overlapping much of the current range 

of the spectaclecase and sheepnose. The 

greatest potential for present zebra 

mussel impacts to the spectaclecase and 

sheepnose appears to be in the upper 

Mississippi River. Kelner and Davis 

(2002, p. ii) stated that zebra mussels in 

the Mississippi River from Mississippi 

River Pool 4 downstream are ‘‘extremely 

abundant and are decimating the native 


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mussel communities.’’ Huge numbers of 

dead and live zebra mussels cover the 

bottom of the river in some localities up 

to 1 to 2 inches (2.5 to 5.1 centimeters 

(cm)) deep (Havlik 2001a, p. 16), where 

they have reduced significantly the 

quality of the habitat with their 

pseudofeces (Fraley 2008, pers. comm.). 

Zebra mussels likely have reduced 

spectaclecase and sheepnose 

populations in these heavily infested 

waters. 

As zebra mussels may maintain high 

densities in big rivers, large tributaries, 

and below infested reservoirs, 

spectaclecase and sheepnose 

populations in affected areas may be 

significantly impacted. For example, 

zebra mussel densities in the Tennessee 

River remained low until 2002, but are 

now abundant enough below Wilson 

Dam to be measured quantitatively 

(Garner 2008, pers. comm.). In addition, 

there is long-term potential for zebra 

mussel invasions into other systems that 

currently harbor spectaclecase and 

sheepnose populations. Zebra mussels 

occur in the lower St. Croix River, one 

of the strongholds for spectaclecase, 

although it is unclear whether they are 

likely to spread much further upstream 

due to the transition from lake-like 

conditions to almost exclusively 

riverine conditions above RM 25. 

The Asian clam (Corbicula fluminea) 

has spread throughout the range of the 

spectaclecase and sheepnose since its 

introduction in the mid-1900s. Asian 

clams compete with native mussels, 

especially juveniles, for food, nutrients, 

and space (Leff et al. 1990, p. 415; Neves 

& Widlak 1987, p. 6) and may ingest 

unionid sperm, glochidia, and newly 

metamorphosed juveniles of native 

mussels (Strayer 1999, p. 82; Yeager et 

al. 2000, p. 255). Dense Asian clam 

populations actively disturb sediments 

that may reduce habitat for juveniles of 

native mussels (Strayer 1999, p. 82). 

Asian clam densities vary widely in 

the absence of native mussels or in 

patches with sparse mussel 

concentrations, but Asian clam density 

is never high in dense mussel beds, 

indicating that the clam is unable to 

successfully invade small-scale habitat 

patches with high unionid biomass 

(Vaughn & Spooner 2006, pp. 334–335). 

The invading clam therefore appears to 

preferentially invade sites where 

mussels are already in decline (Strayer 

1999, pp. 82–83; Vaughn & Spooner 

2006, pp. 332–336) and does not appear 

be a causative factor in the decline of 

mussels in dense beds. However, an 

Asian clam population that thrives in 

previously stressed, sparse mussel 

populations might exacerbate unionid 

imperilment through competition and 

impeding mussel population expansion 

(Vaughn & Spooner 2006, pp. 335–336). 

A molluscivore (mollusk eater), the 

black carp (Mylopharyngodon piceus) is 

a potential threat to native mussels 

(Strayer 1999, p. 89); it has been 

introduced into North America since the 

1970s. The species has been proposed 

for widespread use by aquaculturists to 

control snails, the intermediate host of 

a trematode (flatworm) parasite that 

affects catfish in commercial culture 

ponds in the southeast and lower 

Midwest. Black carp are known to eat 

clams (Corbicula spp.) and unionid 

mussels in China, in addition to snails. 

They are the largest of the Asian carp 

species, reaching more than 4 ft. in 

length and achieving a weight in excess 

of 150 pounds (Nico & Williams 1996, 

p. 6). Foraging rates for a 4-year-old fish 

average 3 or 4 pounds (1.4–1.8 kg) a day, 

indicating that a single individual could 

consume 10 tons (9,072 kg) of native 

mollusks over its lifetime (MICRA 2005, 

p. 1). In 1994, 30 black carp escaped 

from an aquaculture facility in Missouri 

during a flood. Other escapes into the 

wild by non-sterile black carp are likely 

to occur. 

The round goby (Neogobius 

melanostomus) is another exotic fish 

species released into the Great Lakes 

that is well established and likely to 

spread through the Mississippi River 

system (Strayer 1999, pp. 87–88). This 

species is an aggressive competitor of 

similar sized benthic fishes (sculpins, 

darters), as well as a voracious 

carnivore, despite its size (less than 10 

in. (25.4 cm) in length), preying on a 

variety of foods, including small 

mussels and fishes that could serve as 

glochidial hosts (Janssen and Jude 2001, 

p. 325; Strayer 1999, p. 88). Round 

gobies may therefore have important 

indirect effects on the spectaclecase and 

sheepnose through negative effects to 

their hosts. 

Additional exotic species will 

invariably become established in the 

foreseeable future (Strayer 1999, pp. 88– 

89). Added to potential direct threats, 

exotic species could carry diseases and 

parasites that may be devastating to the 

native biota. Because of our ignorance of 

mollusk diseases and parasites, ‘‘it is 

imprudent to conclude that alien 

diseases and parasites are unimportant’’ 

(Strayer 1999, p. 88). 

Exotic species, such as those 

described above, are an ongoing threat 

to the spectaclecase and sheepnose—a 

threat that is likely to increase as these 

exotic species expand their occupancy 

within the ranges of the spectaclecase 

and sheepnose. 

Summary of Threats 

The decline of the spectaclecase and 

sheepnose in the eastern United States 

(described by Butler 2002a, entire; 

Butler 2002b, entire) is primarily the 

result of habitat loss and degradation 

(Neves 1991, p. 252). These losses have 

been well documented since the mid19th century (Higgins 1858, p. 550). 

Chief among the causes of decline are 

impoundments, channelization, 

chemical contaminants, mining, and 

sedimentation (Neves 1991, p. 252; 

Neves 1993, pp. 4–6; Neves et al. 1997, 

pp. 60, 63–75; Watters 2000, pp. 262– 

267; Williams et al. 1993, pp. 7–9). 

These stressors have had profound 

impacts on sheepnose and spectaclecase 

populations and their habitat. 

The majority of the remaining 

populations of the spectaclecase and 

sheepnose are generally small and 

geographically isolated (Butler 2002a, p. 

27; 2002b, p. 27). The patchy 

distributional pattern of populations in 

short river reaches makes them much 

more susceptible to extirpation from 

single catastrophic events, such as toxic 

chemical spills (Watters and Dunn 1995, 

p. 257). Furthermore, this level of 

isolation makes natural repopulation of 

any extirpated population virtually 

impossible without human intervention. 

In addition, the fish host of 

spectaclecase is unknown; thus, 

propagation to reestablish the species in 

restored habitats and to maintain nonreproducing populations and focused 

conservation of its fish host are 

currently not possible. Although there 

are ongoing attempts to alleviate some 

of these threats at some locations, there 

appear to be no populations without 

significant threats, and many threats are 

without obvious or readily available 

solutions. 

Recruitment reduction or failure is a 

threat for many small spectaclecase and 

sheepnose populations rangewide, a 

condition exacerbated by reduced range 

and increasingly isolated populations 

(Butler 2002a, p. 28; 2002b, p. 28). If 

these trends continue, further 

significant declines in total 

spectaclecase and sheepnose population 

size and consequent reduction in longterm viability may soon become 

apparent. 

Various exotic species of aquatic 

organisms are firmly established in the 

range of the spectaclecase and 

sheepnose. The exotic species that poses 

the most significant threat to the 

spectaclecase and sheepnose is the 

zebra mussel. The invasion of the zebra 

mussel poses a serious threat to mussel 

faunas in many regions, and species 

extinctions are expected as a result of its 


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continued spread in the eastern United 

States (Ricciardi et al. 1998, p. 618). 

Proposed Determination 

The Act defines an endangered 

species as any species that is ‘‘in danger 

of extinction throughout all or a 

significant portion of its range’’ and a 

threatened species as any species ‘‘that 

is likely to become endangered 

throughout all or a significant portion of 

its range within the foreseeable future.’’ 

We find that the spectaclecase and 

sheepnose are presently in danger of 

extinction throughout their entire range, 

based on the immediacy, severity, and 

scope of the threats described under 

Factors A, D, and E, above. Although 

there are ongoing attempts to alleviate 

some threats, there appear to be no 

populations without current significant 

threats, and many threats are without 

obvious or readily available solutions. 

These isolated species have a limited 

ability to recolonize historically 

occupied stream and river reaches and 

are vulnerable to natural or humancaused changes in their stream and river 

habitats. Their range curtailment, small 

population size, and isolation make the 

spectaclecase and sheepnose more 

vulnerable to threats such as 

sedimentation, disturbance of riparian 

corridors, changes in channel 

morphology, point and nonpoint source 

pollutants, urbanization, and introduced 

species and to stochastic events (for 

example, chemical spills). Therefore, on 

the basis of the best available scientific 

and commercial information, we 

propose listing the spectaclecase and 

sheepnose as endangered in accordance 

with sections 3(6) and 4(a)(1) of the Act. 

Under the Act and our implementing 

regulations, a species may warrant 

listing if it is endangered or threatened 

throughout all or a significant portion of 

its range. Threats to the spectaclecase 

and sheepnose occur throughout their 

ranges; therefore, we assessed the status 

of the species throughout their entire 

ranges. The threats to the survival of the 

species occur throughout the species’ 

ranges and are not restricted to any 

particular significant portion of those 

ranges. Accordingly, our assessment and 

proposed determination applies to both 

species throughout their entire ranges. 

Available Conservation Measures 

Conservation measures provided to 

species listed as endangered or 

threatened under the Act include 

recognition, recovery actions, 

requirements for Federal protection, and 

prohibitions against certain practices. 

Recognition through listing encourages 

and results in public awareness and 

conservation by Federal, State, and local 

agencies, private organizations, and 

individuals. The Act encourages 

cooperation with the States and requires 

that recovery actions be carried out for 

all listed species. The protection 

required of Federal agencies and the 

prohibitions against take and harm are 

discussed, in part, below. 

The primary purpose of the Act is the 

conservation of endangered and 

threatened species and the ecosystems 

upon which they depend. The ultimate 

goal of such conservation efforts is the 

recovery of these listed species, so that 

they no longer need the protective 

measures of the Act. Subsection 4(f) of 

the Act requires the Service to develop 

and implement recovery plans for the 

conservation of endangered and 

threatened species, unless such a plan 

will not promote the conservation of the 

species. The recovery planning process 

involves the identification of actions 

that are necessary to halt or reverse the 

species’ decline by addressing the 

threats to its survival and recovery. The 

goal of this process is to restore listed 

species to a point where they are secure, 

self-sustaining, and functioning 

components of their ecosystems. 

Recovery planning includes the 

development of a recovery outline 

shortly after a species is listed, 

preparation of a draft and final recovery 

plan, and revisions to the plan as 

significant new information becomes 

available. The recovery outline guides 

the immediate implementation of urgent 

recovery actions and describes the 

process to be used to develop a recovery 

plan. The recovery plan identifies sitespecific management actions that will 

achieve recovery of the species, 

measurable criteria that determine when 

a species may be downlisted or delisted, 

and methods for monitoring recovery 

progress. Recovery plans also establish 

a framework for agencies to coordinate 

their recovery efforts and provide 

estimates of the cost of implementing 

recovery tasks. Recovery teams 

(comprised of species experts, Federal 

and State agencies, non-government 

organizations, and stakeholders) are 

often established to develop recovery 

plans. When completed, the recovery 

outline, draft recovery plan, and the 

final recovery plan will be available on 

our Web site (http://www.fws.gov/ 

endangered), or from our Rock Island, 

Illinois, Ecological Services Field Office 

(see FOR FURTHER INFORMATION CONTACT

section). 

Implementation of recovery actions 

generally requires the participation of a 

broad range of partners, including other 

Federal agencies, States, Tribal, 

nongovernmental organizations, 

businesses, and private landowners. 

Examples of recovery actions include 

habitat restoration (e.g., restoration of 

native vegetation), research, captive 

propagation and reintroduction, and 

outreach and education. The recovery of 

many listed species cannot be 

accomplished solely on Federal lands 

because their range may occur primarily 

or solely on non-Federal lands. To 

achieve recovery of these species 

requires cooperative conservation efforts 

on private, State, and Tribal lands. 

Listing will also require the Service to 

review any actions on Federal lands and 

activities under Federal jurisdiction that 

may adversely affect the two species; 

allow State plans to be developed under 

section 6 of the Act; encourage scientific 

investigations of efforts to enhance the 

propagation or survival of the animals 

under section 10(a)(1)(A) of the Act; and 

promote habitat conservation plans on 

non-Federal lands and activities under 

section 10(a)(1)(B) of the Act. 

Section 7(a) of the Act, as amended, 

requires Federal agencies to evaluate 

their actions with respect to any species 

that is proposed or listed as endangered 

or threatened and with respect to its 

critical habitat, if any is designated. 

Regulations implementing this 

interagency cooperation provision of the 

Act are codified at 50 CFR part 402. 

Federal agencies are required to confer 

with us informally on any action that is 

likely to jeopardize the continued 

existence of a proposed species. Section 

7(a)(4) requires Federal agencies to 

confer with the Service on any action 

that is likely to jeopardize the continued 

existence of a species proposed for 

listing or result in destruction or 

adverse modification of proposed 

critical habitat. If a species is listed 

subsequently, section 7(a)(2) requires 

Federal agencies to ensure that activities 

they authorize, fund, or carry out are not 

likely to jeopardize the continued 

existence of the species or destroy or 

adversely modify its critical habitat. If a 

Federal action may adversely affect a 

listed species or its critical habitat, the 

responsible Federal agency must enter 

into formal consultation with the 

Service. 

Federal activities that may affect the 

sheepnose and spectaclecase include, 

but are not limited to, the funding of, 

carrying out of, or the issuance of 

permits for reservoir construction, 

natural gas extraction, stream 

alterations, discharges, wastewater 

facility development, water withdrawal 

projects, pesticide registration, mining, 

and road and bridge construction. 

Jeopardy Standard 

Prior to and following listing and 

designation of critical habitat, if prudent 


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and determinable, the Service applies 

an analytical framework for jeopardy 

analyses that relies heavily on the 

importance of core area populations to 

the survival and recovery of the species. 

The section 7(a)(2) analysis is focused 

not only on these populations but also 

on the habitat conditions necessary to 

support them. 

The jeopardy analysis usually 

expresses the survival and recovery 

needs of the species in a qualitative 

fashion without making distinctions 

between what is necessary for survival 

and what is necessary for recovery. 

Generally, if a proposed Federal action 

is incompatible with the viability of the 

affected core area population(s), 

inclusive of associated habitat 

conditions, a jeopardy finding is 

considered to be warranted, because of 

the relationship of each core area 

population to the survival and recovery 

of the species as a whole. 

Section 9 Take 

Section 9(a)(2) of the Act, and its 

implementing regulations found at 50 

CFR 17.21, set forth a series of general 

prohibitions and exceptions that apply 

to all endangered wildlife. These 

prohibitions, in part, make it illegal for 

any person subject to the jurisdiction of 

the United States to take (includes 

harass, harm, pursue, hunt, shoot, 

wound, kill, trap, or collect, or to 

attempt any of these), import or export, 

ship in interstate commerce in the 

course of commercial activity, or sell or 

offer for sale in interstate or foreign 

commerce any listed species. It also is 

illegal to knowingly possess, sell, 

deliver, carry, transport, or ship any 

wildlife that has been taken illegally. 

Certain exceptions apply to agents of the 

Service and State conservation agencies. 

We may issue permits to carry out 

otherwise prohibited activities 

involving endangered wildlife species 

under certain circumstances. 

Regulations governing permits are at 50 

CFR 17.22 for endangered species. Such 

permits are available for scientific 

purposes, to enhance the propagation or 

survival of the species, or for incidental 

take in connection with otherwise 

lawful activities. 

Our policy, as published in the 

Federal Register on July 1, 1994 (59 FR 

34272), is to identify, to the maximum 

extent practicable, those activities that 

would or would not likely constitute a 

violation of section 9 of the Act. The 

intent of this policy is to increase public 

awareness as to the potential effects of 

this final listing on future and ongoing 

activities within a species’ range. We 

believe that the following activities are 

unlikely to result in a violation of 

section 9: 

(1) Existing discharges into waters 

supporting these species, provided these 

activities are carried out in accordance 

with existing regulations and permit 

requirements (for example, activities 

subject to sections 402, 404, and 405 of 

the Clean Water Act and discharges 

regulated under the National Pollutant 

Discharge Elimination System). 

(2) Actions that may affect the 

spectaclecase or sheepnose and are 

authorized, funded, or carried out by a 

Federal agency when the action is 

conducted in accordance with any 

reasonable and prudent measures we 

have specified in accordance with 

section 7 of the Act. 

(3) Development and construction 

activities designed and implemented 

under Federal, State, and local water 

quality regulations and implemented 

using approved best management 

practices. 

(4) Existing recreational activities, 

such as swimming, wading, canoeing, 

and fishing, that are in accordance with 

State and local regulations, provided 

that if a spectaclecase or sheepnose is 

collected, it is immediately released, 

unharmed. 

Activities that we believe could 

potentially result in take of 

spectaclecase or sheepnose include but 

are not limited to: 

(1) Illegal collection or capture of the 

species; 

(2) Unlawful destruction or alteration 

of the species’ occupied habitat (for 

example, unpermitted instream 

dredging, channelization, or discharge 

of fill material); 

(3) Violation of any discharge or water 

withdrawal permit within the species’ 

occupied range; and 

(4) Illegal discharge or dumping of 

toxic chemicals or other pollutants into 

waters supporting spectaclecase or 

sheepnose. 

We will review other activities not 

identified above on a case-by-case basis 

to determine whether they are likely to 

result in a violation of section 9 of the 

Act. We do not consider these lists to be 

exhaustive and provide them as 

information to the public. 

You should direct questions regarding 

whether specific activities may 

constitute a future violation of section 9 

to the Field Supervisor of the Service’s 

Rock Island, Illinois Ecological Services 

Field Office (see FOR FURTHER

INFORMATION CONTACT section). You may 

request copies of the regulations 

regarding listed wildlife from and 

address questions about prohibitions 

and permits to the U.S. Fish and 

Wildlife Service, Ecological Services 

Division, Henry Whipple Federal 

Building, 1 Federal Drive, Fort Snelling, 

MN 55111 (Phone (612) 713–5350; Fax 

(612) 713–5292). 

Critical Habitat 

Background 

Critical habitat is defined in section 3 

of the Act as: 

(i) The specific areas within the 

geographical area occupied by a species, 

at the time it is listed in accordance 

with the Act, on which are found those 

physical or biological features 

(I) Essential to the conservation of the 

species, and 

(II) That may require special 

management considerations or 

protection; and 

(ii) Specific areas outside the 

geographical area occupied by a species 

at the time it is listed, upon a 

determination that such areas are 

essential for the conservation of the 

species. 

Conservation is defined in section 3 of 

the Act as the use of all methods and 

procedures needed to bring the species 

to the point at which listing under the 

Act is no longer necessary. 

Critical habitat receives protection 

under section 7 of the Act through the 

prohibition against Federal agencies 

carrying out, funding, or authorizing the 

destruction or adverse modification of 

critical habitat. Section 7(a)(2) requires 

consultation on Federal actions that 

may affect critical habitat. The 

designation of critical habitat does not 

affect land ownership or establish a 

refuge, wilderness, reserve, preserve, or 

other conservation area. Such 

designation does not allow the 

government or public to access private 

lands. Such designation does not 

require implementation of restoration, 

recovery, or enhancement measures by 

non-Federal landowners. Where a 

landowner seeks or requests Federal 

agency funding or authorization for an 

action that may affect a listed species or 

critical habitat, the consultation 

requirements of section 7(a)(2) of the 

Act would apply, but even in the event 

of a destruction or adverse modification 

finding, the obligation of the Federal 

action agency and the applicant is not 

to restore or recover the species, but to 

implement reasonable and prudent 

alternatives to avoid destruction or 

adverse modification of critical habitat. 

Prudency Determination 

Section 4(a)(3) of the Act, as 

amended, and implementing regulations 

(50 CFR 424.12), require that, to the 

maximum extent prudent and 

determinable, we designate critical 


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habitat at the time the species is 

determined to be endangered or 

threatened. Our regulations (50 CFR 

424.12(a)(1)) state that the designation 

of critical habitat is not prudent when 

one or both of the following situations 

exist: (1) The species is threatened by 

taking or other human activity, and 

identification of critical habitat can be 

expected to increase the degree of threat 

to the species, or (2) such designation of 

critical habitat would not be beneficial 

to the species. 

There is currently no imminent threat 

of take attributed to collection or 

vandalism under Factor B 

(overutilization for commercial, 

recreational, scientific, or educational 

purposes) for sheepnose and 

spectaclecase and identification of 

critical habitat is not expected to initiate 

such a threat. In the absence of finding 

that the designation of critical habitat 

would increase threats to a species, if 

there are any benefits to a critical 

habitat designation, then a prudent 

finding is warranted. The potential 

benefits include: (1) Triggering 

consultation under section 7(a)(2) of the 

Act, in new areas for actions in which 

there may be a Federal nexus where it 

would not otherwise occur because the 

species may not be present; (2) focusing 

conservation activities on the most 

essential habitat features and areas; (3) 

increasing awareness of important 

habitat areas among State or county 

governments or private entities; and (4) 

preventing inadvertent harm to the 

species. 

Critical habitat designation includes 

the identification of the physical and 

biological features of the habitat 

essential to the conservation of each 

species that may require special 

management and protection. As such, 

these designations will provide useful 

information to individuals, local and 

State governments, and other entities 

engaged in activities or long-range 

planning that may affect areas essential 

to the conservation of the species. 

Conservation of the spectaclecase and 

sheepnose and essential features of their 

habitats will require habitat 

management, protection, and 

restoration, which will be facilitated by 

disseminating information on the 

locations and the key physical and 

biological features of those habitats. In 

the case of spectaclecase and sheepnose, 

these aspects of critical habitat 

designation would potentially benefit 

the conservation of the species. 

Therefore, since we have determined 

that the designation of critical habitat 

will not likely increase the degree of 

threat to these species and may provide 

some measure of benefit, we find that 

designation of critical habitat is prudent 

for the spectaclecase and sheepnose. 

Primary Constituent Elements 

In accordance with sections 3(5)(A)(i) 

and 4(b)(1)(A) of the Act and regulations 

at 50 CFR 424.12, in determining which 

areas to propose as critical habitat, we 

must consider those physical and 

biological features—primary constituent 

elements in the necessary and 

appropriate quantity and spatial 

arrangement—essential to the 

conservation of the species. We must 

also consider those areas essential to the 

conservation of the species that are 

outside the geographical area occupied 

by the species. Primary constituent 

elements include, but are not limited to: 

(1) Space for individual and 

population growth and for normal 

behavior; 

(2) Food, water, air, light, minerals, or 

other nutritional or physiological 

requirements; 

(3) Cover or shelter; 

(4) Sites for breeding, reproduction, 

and rearing (or development) of 

offspring; and 

(5) Habitats that are protected from 

disturbance or are representative of the 

historical, geographical, and ecological 

distribution of a species. 

We are currently unable to identify 

the primary constituent elements for 

spectaclecase and sheepnose because 

information on the physical and 

biological features that are considered 

essential to the conservation of these 

species is not known at this time. The 

apparent poor viability of the species’ 

occurrences observed in recent years 

indicates that current conditions are not 

sufficient to meet the basic biological 

requirements of these species in many 

rivers. Since spectaclecase and 

sheepnose have not been observed for 

decades in many of their historical 

locations, and much of the habitat in 

which they still persists has been 

drastically altered, the optimal 

conditions that would provide the 

biological or ecological requisites of 

these species are not known. Although 

we can surmise that habitat degradation 

from a variety of factors has contributed 

to the decline of these species, we do 

not know specifically what essential 

physical or biological features of that 

habitat are currently lacking for 

spectaclecase and sheepnose. 

Key features of the basic life history, 

ecology, reproductive biology, and 

habitat requirements of most mussels, 

including spectaclecase and sheepnose, 

are unknown. Species-specific 

ecological requirements have not been 

determined (for example, minimum 

water flow and effects of particular 

pollutants). Population dynamics, such 

as species’ interactions and community 

structure, population trends, and 

population size and age class structure 

necessary to maintain a long-term 

viability, have not been determined for 

these species. Basics of reproductive 

biology for these species are unknown, 

such as age and size at earliest maturity, 

reproductive longevity, and the level of 

recruitment needed for species survival 

and long-term viability. Of particular 

concern to the spectaclecase is the lack 

of known host(s) species essential for 

glochidia survival and reproductive 

success. Similarly, although recent 

laboratory studies have produced 

successful transformation of sheepnose 

glochidia on a few fish species, many 

questions remain concerning the natural 

interactions between the sheepnose and 

its known hosts. Because the host(s) for 

spectaclecase is unknown and little is 

known about the sheepnose hosts, there 

is a degree of uncertainty at this time as 

to which specific areas might be 

essential to the conservation of these 

species (for example, the host(s)’s 

biological needs and population sizes 

necessary to support mussel 

reproduction and population viability) 

and thus meet a key aspect of the 

definition of critical habitat. As we are 

unable to identify many physical and 

biological features essential to the 

conservation of spectaclecase and 

sheepnose, we are unable to identify 

areas that contain these features. 

Therefore, although we have determined 

that the designation of critical habitat is 

prudent for spectaclecase and 

sheepnose, because the biological and 

physical requirements of these species 

are not sufficiently known, we find that 

critical habitat for spectaclecase and 

sheepnose is not determinable at this 

time. 

Peer Review 

In accordance with our policy, 

‘‘Notice of Interagency Cooperative 

Policy for Peer Review in Endangered 

Species Act Activities,’’ that was 

published on July 1, 1994 (59 FR 

34270), we will seek the expert opinion 

of at least three appropriate 

independent specialists regarding this 

proposed rule. The purpose of such 

review is to ensure listing decisions are 

based on scientifically sound data, 

assumptions, and analysis. We will send 

copies of this proposed rule to the peer 

reviewers immediately following 

publication in the Federal Register. We 

will invite these peer reviewers to 

comment, during the public comment 

period, on the specific assumptions and 

the data that are the basis for our 

conclusions regarding the proposal to 


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list spectaclecase and sheepnose as 

endangered and our proposal regarding 

critical habitat for this species. 

Required Determinations 

Clarity of the Rule 

We are required by Executive Orders 

12866 and 12988 and by the 

Presidential Memorandum of June 1, 

1998, to write all rules in plain 

language. This means that each rule we 

publish must: 

(a) Be logically organized; 

(b) Use the active voice to address 

readers directly; 

(c) Use clear language rather than 

jargon; 

(d) Be divided into short sections and 

sentences; and 

(e) Use lists and tables wherever 

possible. 

If you feel that we have not met these 

requirements, send us comments by one 

of the methods listed in the ADDRESSES

section. To better help us revise the 

rule, your comments should be as 

specific as possible. For example, you 

should tell us the names of the sections 

or paragraphs that are unclearly written, 

which sections or sentences are too 

long, the sections where you feel lists or 

tables would be useful, etc. 

Executive Order 13211 

On May 18, 2001, the President issued 

Executive Order 13211 on regulations 

that significantly affect energy supply, 

distribution, and use. Executive Order 

13211 requires agencies to prepare 

Statements of Energy Effects when 

undertaking certain actions. This rule is 

not expected to significantly affect 

energy supplies, distribution, or use. 

Therefore, this action is not a significant 

energy action, and no Statement of 

Energy Effects is required. 

Paperwork Reduction Act of 1995 (44 

U.S.C. 3501 et seq.) 

This proposed rule does not contain 

any new collections of information that 

require approval by the Office of 

Management and Budget (OMB) under 

the Paperwork Reduction Act. The rule 

would not impose new recordkeeping or 

reporting requirements on State or local 

governments, individuals, businesses, or 

organizations. We may not conduct or 

sponsor, and you are not required to 

respond to, a collection of information 

unless it displays a currently valid OMB 

control number. 

National Environmental Policy Act 

We determined that we do not need 

to prepare an environmental 

assessment, as defined under the 

authority of the National Environmental 

Policy Act of 1969 (42 U.S.C. 4321 et 

seq.), in connection with regulations 

adopted under section 4(a) of the Act. 

We published a notice outlining our 

reasons for this determination in the 

Federal Register on October 25, 1983 

(48 FR 49244). 

References Cited 

A complete list of all references cited 

in this rule is available on the Internet 

at http://www.regulations.gov or upon 

request from the Field Supervisor, Rock 

Island, Illinois Ecological Services Field 

Office (see FOR FURTHER INFORMATION

CONTACT section). 

Authors 

The primary authors of this proposed 

rule are the staff members of the 

Service’s Rock Island and Twin Cities 

Field Offices (see FOR FURTHER

INFORMATION CONTACT section). 

List of Subjects in 50 CFR Part 17 

Endangered and threatened species, 

Exports, Imports, Reporting and 

recordkeeping requirements, 

Transportation. 

Proposed Regulation Promulgation 

Accordingly, we propose to amend 

part 17, subchapter B of chapter I, title 

50 of the Code of Feral Regulations, as 

follows: 

PART 17—[AMENDED] 

1. The authority citation for part 17 

continues to read as follows: 

Authority: 16 U.S.C. 1361–1407; 16 U.S.C. 

1531–1544; 16 U.S.C. 4201–4245; Pub. L. 99– 

625, 100 Stat. 3500; unless otherwise noted. 

2. In § 17.11(h) add the entries for 

‘‘Sheepnose’’ and ‘‘Spectaclecase’’ in 

alphabetical order under CLAMS to the 

List of Endangered and Threatened 

Wildlife, as follows: 

§ 17.11 Endangered and threatened 

wildlife. 

* * * * * 

(h) * * * 

Species 

Historical range 

Vertebrate population 

where 

endangered or 

threatened 

Status When 

listed 

Critical 

habitat 

Special 

rules Common name Scientific name 

*******

CLAMS 

*******

Sheepnose ................. Plethobasus cyphyus U.S.A. (AL, IL, IN, IA, 

KY, MN, MS, MO, 

OH, PA, TN, VA, 

WV, WI).

NA ............................. E NA NA 

*******

Spectaclecase Cumberlandia 

monodonta.

U.S.A. (AL, AR, IL, 

IN, IA, KS, KY, MN, 

MO, NE, OH, TN, 

VA, WV, WI).

NA ............................. E NA NA 

*******


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* * * * * Dated: December 16, 2010. 

Rowan W. Gould, 

Acting Director, U.S. Fish and Wildlife 

Service. 

[FR Doc. 2011–469 Filed 1–18–11; 8:45 am] 

BILLING CODE 4310–55–P 


EMCDONALD on DSK2BSOYB1PROD with MISCELLANEOUS