[Federal Register Volume 66, Number 195 (Tuesday, October 9, 2001)]
[Rules and Regulations]
[Pages 51322-51339]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 01-24804]


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DEPARTMENT OF THE INTERIOR

Fish and Wildlife Service

50 CFR Part 17

RIN 1018-AF57


Endangered and Threatened Wildlife and Plants; Determination of 
Endangered Status for the Scaleshell Mussel

AGENCY: Fish and Wildlife Service, Interior.

ACTION: Final rule.

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SUMMARY: We, the U.S. Fish and Wildlife Service (Service), determine 
the scaleshell mussel (Leptodea leptodon) to be an endangered species 
under the Endangered Species Act of 1973, as amended (Act). The 
scaleshell mussel historically occurred in 55 rivers in 13 states in 
the eastern United States. Currently, the species is known to exist in 
14 rivers (and may occur in 6 others) within the Mississippi River 
Basin in Missouri, Oklahoma, and Arkansas. Its abundance and 
distribution have decreased markedly due to habitat loss and adverse 
effects associated with water quality degradation, sedimentation, 
channelization, sand and gravel mining, dredging, and reservoir 
construction.

DATES: This final rule is effective on November 8, 2001.

ADDRESSES: The complete file for this rule is available for inspection, 
by appointment, during normal business hours at the Columbia Field 
Office, U.S. Fish and Wildlife Service, 608 East Cherry Street, Room 
200, Columbia, Missouri 65201.

FOR FURTHER INFORMATION CONTACT: Andy Roberts (at the above address or 
telephone 573-876-1911, ext. 110; fax 573-876-1914). TTY users may 
contact us through the Federal Relay Service at 1-800-877-8339.

SUPPLEMENTARY INFORMATION:

Background

    Buchanan (1980), Cummings and Mayer (1992), Oesch (1995), and 
Watters (1995) provide descriptions of the scaleshell mussel. The shell 
grows to approximately three to ten centimeters (one to four inches) in 
length. The shells are elongate, very thin, and compressed. The 
anterior (front) end is rounded. In males, the posterior (rear) end is 
bluntly pointed. In females, the periostracum (the outside layer or 
covering of the shell) forms a wavy, fluted extension of the posterior 
end of the shell. The dorsal (top) margin is straight and the ventral 
(bottom) margin is gently rounded. Beaks (the raised or domed part of 
the dorsal margin of the shell) are small and low, and nearly even with 
the hinge line. The beak sculpture is inconspicuously compressed and 
consists of four or five double-looped ridges. The periostracum is 
smooth, yellowish green or brown, with numerous faint green rays. The 
pseudocardinal teeth (the triangular, often serrated, teeth located on 
the upper part of the shell) are reduced to a small thickened ridge. 
The lateral teeth (the elongated teeth along the hinge line of the 
shell) are moderately long with two indistinct teeth occurring in the 
left valve (shell) and one fine tooth in the right. The beak cavity (a 
cavity located inside the shell that extends into the beak) is very 
shallow. The nacre (the interior layer of the shell) is pinkish white 
or light purple and highly iridescent.

Life History

    The biology of the scaleshell mussel is similar to the biology of 
other bivalved mollusks belonging to the family Unionidae. Adult 
unionids are filter-feeders, spending their entire lives partially or 
completely buried in the stream bottom (Murray and Leonard 1962). The 
posterior margin of the shell is usually exposed and the siphons 
extended to facilitate feeding. During periods of activity, movement is 
accomplished by extending and contracting a single muscular foot 
between the valves. Extension of the foot also enables the mussel to 
wedge itself into the river bottom. Their food includes detritus 
(disintegrated organic material), plankton, and other microorganisms 
(Fuller 1974). Some freshwater mussel species are long-lived. 
Individuals of many species live more than 10 years and some have been 
reported to live over 100 years (Cummings and Mayer 1992).
    Unionids have an unusual and complex mode of reproduction, which 
includes a brief, obligatory parasitic

[[Page 51323]]

stage on fish. Males release sperm into the water column in the spring, 
summer, or early fall, and females using the incurrent water flow draw 
in the sperm. Fertilization takes place in the shell of the female. 
Fertilized eggs develop into microscopic larvae (glochidia) and are 
brooded within special gill chambers of the female. Once the glochidia 
are mature, they are expelled into the water where they must quickly 
attach to the gills or the fins of an appropriate fish host to complete 
development. Following proper host infestation, glochidia transform 
into juveniles and excyst (drop off). Juveniles must drop off into 
suitable habitat to survive. Host fish specificity varies among 
unionids. Some mussel species appear to require a single host species, 
while others can transform their glochidia into juvenile mussels on 
several fish species. For further information on the life history of 
freshwater mussels, see Gordon and Layzer (1989) and Watters (1995).
    Mussel biologists know relatively little about the specific life 
history requirements of the scaleshell mussel. Baker (1928) surmised 
that the scaleshell mussel is a long-term brooder (spawns in fall 
months and females brood the larvae in their gills until the following 
spring or summer). Glochidia found in the gill chambers in September, 
October, November, and March support that conclusion (Gordon 1991). The 
scaleshell mussel uses the freshwater drum (Aplodinotus grunniens) as 
the fish host for its larvae (Chris Barnhart, Southwest Missouri State 
University, pers. comm. 1998). Other species in the genus Leptodea and 
a closely related genus Potamilus are also known to use freshwater drum 
exclusively as a host (Watters 1994).
    Little is known about the life expectancy of the scaleshell mussel. 
However, recent collections from Missouri indicate that it is 
relatively short-lived compared to other species. A sample of 33 dead 
specimens and 2 living individuals collected in 2000 from a Gasconade 
River site did not contain any individuals exceeding seven years old 
(Chris Barnhart, pers. comm. 2000). Likewise, no individuals over six 
years old were observed out of 44 living individuals collected in 1997 
from the Meramec Basin (Roberts and Bruenderman 2000). Based on these 
collections, it appears that the life expectancy of the scaleshell 
mussel may be less than 10 years. In addition, the sex ratio of the 
above collections are significantly different from a 50/50 ratio (Chi-
Square Test, P 0.05). The Gasconade collection only contained eight 
females (including one living) out of 35 individuals, and the Meramec 
Basin collection only contained 15 females out of 44 living 
individuals. The reason females appear to be less common than males in 
the Gasconade River and Meramec Basin is unknown.

Habitat Characteristics

    The scaleshell mussel occurs in medium to large rivers with low to 
moderate gradients in a variety of stream habitats. Buchanan (1980, 
1994) and Gordon (1991) reported the scaleshell mussel from riffle 
areas with substrate consisting of gravel, cobble, boulder, and 
occasionally mud or sand. Oesch (1995) considered the scaleshell mussel 
a typical riffle species, occurring only in clear, unpolluted water 
with good current. Conversely, Call (1900), Goodrich and Van der 
Schalie (1944), and Cummings and Mayer (1992) reported collections from 
muddy bottoms of medium-sized and large rivers. Roberts and Bruenderman 
(2000) collected the scaleshell mussel primarily from mussel beds 
(areas with a high concentration of mussels that contain more than one 
species) with stable, gravel substrates. The characteristic common to 
these sites appears to be a stable stream bed and good water quality. 
These habitat observations are consistent with the current distribution 
of the scaleshell mussel. The scaleshell mussel is restricted to rivers 
that have maintained relatively good water quality (Oesch 1995) and to 
river stretches with stable channels (Buchanan 1980, Harris 1992). The 
scaleshell mussel is also usually collected in mussel beds in 
association with a high diversity of other mussel species.

Distribution and Abundance

    The scaleshell mussel historically occurred in 13 states in the 
eastern United States. While the scaleshell mussel had a broad 
distribution, it appears that it was a rare species locally (Gordon 
1991, Oesch 1995, Call 1900). Williams et al. (1993) reported the 
historical range as Alabama, Arkansas, Illinois, Indiana, Iowa, 
Kentucky, Missouri, Ohio, Oklahoma, South Dakota, Tennessee, and 
Wisconsin. Historical records also exist for the Minnesota River, 
Minnesota (Clarke 1996). Williams et al. (1993) also listed Michigan 
and Mississippi as part of the scaleshell mussel's range, but no valid 
records exist in these states. Therefore, its presence cannot be 
confirmed (Bob Jones, Mississippi Wildlife Fisheries and Parks, Museum 
of Natural Science, pers. comm. 2000; Szymanski 1998). Gordon (1991) 
included a portion of the St. Lawrence drainage in describing the 
distribution of the scaleshell mussel. However, the specimens that were 
the source of the St. Lawrence River record were later identified as 
wingless examples of Leptodea fragilis (fragile papershell), which are 
often seen in New York (David Strayer, Institute of Ecosystem Studies, 
New York, in litt. 1995). Given this and that no other authentic 
specimens have been found (David Stansbery, Ohio State Museum, in litt. 
1995), the historical occurrence of the species in St. Lawrence Basin 
is doubtful.
    Within the last 50 years the scaleshell mussel has become 
increasingly rare and its range greatly restricted. Historically, the 
scaleshell mussel occurred in 55 rivers. Today, the species is known 
from only 14 rivers including the Meramec, Bourbeuse, Big, Gasconade, 
and Osage Rivers in Missouri; Frog Bayou and the St. Francis, Spring, 
South Fork Spring, South Fourche LaFave, and White Rivers in Arkansas; 
and the Little, Mountain Fork, and Kiamichi Rivers in Oklahoma. An 
additional six rivers (Cossatot, Little Missouri, Saline, and 
Strawberry Rivers, and Myatt and Gates Creeks) in Arkansas and Oklahoma 
may support the scaleshell mussel, but the existence of the species in 
these rivers is uncertain. With the exception of the Meramec, 
Bourbeuse, and Gasconade Rivers, all rivers listed as supporting the 
scaleshell mussel are based on the collection of a few or a single 
individual specimen.

Assessment of the Presumed Health of Individual Populations

    For the purposes of this rule, the term ``population'' is used in a 
geographical sense and, unless otherwise indicated, is defined as all 
individuals living in one river or stream. By using this term we do not 
imply that a scaleshell mussel population is currently reproducing or 
that it is a distinct genetic unit. Using the term in this way allows 
the status, trends, and threats to be discussed separately for each 
river where the scaleshell mussel occurs, improving the clarity of the 
discussion.
    Due to the low densities of current scaleshell mussel populations, 
ascertaining status (an assessment of the current existence of a 
population) and trends (an assessment of change in a population's 
numbers and its probable future condition) is difficult. To facilitate 
population comparisons, a single classification system was devised to 
evaluate the probable current health of individual populations. The 
indicators of (or criteria for) the presumed health of scaleshell 
mussel populations are as follows. The

[[Page 51324]]

presumed health of a population is considered ``stable'' if (1) there 
is no evidence of significant habitat loss or degradation, and (2) 
there has been post-1980 collection of live or fresh dead mussels and, 
if surveys were thorough, evidence of recruitment was found. The 
presumed health of a population is considered ``declining'' if (1) 
habitat is limiting due to its small size, or a significant decrease in 
habitat quality or quantity has occurred, (2) there is no evidence of 
recruitment despite one or more thorough surveys, or (3) a significant 
decline in number of individual mussels has occurred. The presumed 
health of a population is considered ``extirpated'' if (1) despite one 
or more thorough post-1980 surveys, no scaleshell mussels, or only old 
dead shells, have been found, or (2) all known suitable habitat has 
been destroyed. The presumed health of a population is considered 
``unknown'' if the available information is inadequate to place the 
population in one of the above categories. In a few cases, additional 
biological information not listed above was used to categorize a 
population that otherwise would have been called ``unknown'' or which 
appeared to fit into multiple categories.
    Based on the above criteria, 14 scaleshell mussel populations are 
considered extant. Of these populations, the presumed health of 1 is 
thought to be stable and 13 are believed to be declining. Six other 
populations may also be extant, but their health is unknown due to lack 
of recent collections or surveys. The 14 extant populations and 6 
potentially extant populations are listed in Table 1 and included in 
the discussions below.

  Table 1.--Presumed Population Health of Extant and Potentially Extant
 Scaleshell Mussel Populations. S = stable, D = declining, UK = unknown
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                 Population                        Presumed health
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Big (MO)...................................  D
Bourbeuse (MO).............................  D
Cossatot (AR)..............................  UK
Frog Bayou (AR)............................  D
Gates Creek (OK)...........................  UK
Gasconade (MO).............................  D
Kiamichi (OK)..............................  D
Little Missouri (AR).......................  UK
Little (OK)................................  D
Meramec (MO)...............................  D
Mountain Fork (OK).........................  D
Myatt Creek (AR)...........................  UK
Osage River (MO)...........................  D
St. Francis (AR)...........................  D
Saline (AR)................................  UK
South Fork Spring (AR).....................  S
South Fourche LaFave (AR)..................  D
Spring River (AR)..........................  D
Strawberry (AR)............................  UK
White River (AR)...........................  D
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River Basin Specific Discussion of the Scaleshell Mussel Status

Upper Mississippi River Basin

    The scaleshell mussel formerly occurred in eight rivers and 
tributaries within the upper Mississippi River Basin, including the 
Mississippi River in Illinois, Iowa, and Wisconsin; the Minnesota River 
in Minnesota; Burdett's Slough in Iowa; the Iowa and Cedar Rivers in 
Iowa; and the Illinois, Sangamon, and Pecatonica Rivers in Illinois. 
However, the scaleshell mussel has not been found for more than 50 
years in the upper Mississippi River Basin and is believed extirpated 
from that basin (Kevin Cummings, Illinois Natural History Survey, in 
litt. 1994).

Middle Mississippi River Basin

    Historically, the scaleshell mussel occurred in 26 rivers and 
tributaries within the middle Mississippi River Basin including the 
Kaskaskia River in Illinois; the mainstem Ohio River in Kentucky and 
Ohio; the Wabash River in Illinois and Indiana; the White River and 
Sugar Creek in Indiana; the Green and Licking Rivers in Kentucky; the 
Scioto, St. Mary's, and East Fork Little Miami Rivers in Ohio; the 
Cumberland River in Kentucky and Tennessee; Beaver Creek in Kentucky; 
Caney Fork in Tennessee; the Tennessee River in Alabama and Tennessee; 
the Clinch, Holston, and Duck Rivers in Tennessee; Auxvasse Creek in 
Missouri; the Meramec, Bourbeuse, South Grand, Gasconade, Big, Osage, 
and Big Piney Rivers in Missouri; and the mainstem Missouri River in 
South Dakota and Missouri. The scaleshell mussel has been extirpated 
from most of the middle Mississippi River Basin. Currently, the 
scaleshell mussel is extant in five rivers within the Meramec River 
basin and tributaries of the Missouri River drainages in Missouri.
    Ohio River Drainage--The scaleshell mussel has been extirpated from 
the entire Ohio River system. The most recent collection date from the 
Ohio River Basin is 1964 from the Greene River (Wayne Davis, Kentucky 
Department of Fish and Wildlife, in litt. 1994). All other records are 
pre-1950 (Kevin Cummings, in litt. 1994; Catherine Gremillion-Smith, 
Indiana Department of Natural Resources, in litt. 1994; Ron Cicerello, 
Kentucky Department of Fish and Wildlife, in litt., 1994; Paul 
Parmelee, University of Tennessee, pers. comm. 1995).
    Meramec River Basin (Missouri)--In 1979, Buchanan surveyed for 
mussels at 198 sites within the Meramec River Basin (Buchanan 1980). Of 
these sites, 14 had evidence of live or dead scaleshell mussels. Seven 
of the 14 sites were in the lower 180 kilometers (km) (112 miles (mi)) 
of the Meramec River, five in the lower 87 km (54 mi) of the Bourbeuse 
River, and two in the lower 16 km (10 mi) of the Big River. Buchanan 
found that the species comprised less than 0.1 percent of the 20,589 
living mussels he examined in the basin. He collected live scaleshell 
mussels at only four sites, three in the Meramec and one in the 
Bourbeuse. Although the lower 174 km (108 mi) of the Meramec River had 
suitable habitat for many rare species, live scaleshell mussels were 
found only in the lower 64 km (40 mi) (Buchanan 1980). Both the 
Bourbeuse and Big Rivers had lower species diversity and less suitable 
habitat than the Meramec River. Suitable habitat occurs only in the 
lower 87 km (54 mi) of the Bourbeuse River and lower 16 km (10 mi) of 
the Big River (Buchanan 1980).
    The Missouri Department of Conservation (MDC) sampled 78 sites in 
an intensive resurvey of the Meramec River basin in 1997 (Roberts and 
Bruenderman 2000). Similar to Buchanan's findings (1980), scaleshell 
mussels represented only 0.4 percent of the living mussels. Live 
specimens were collected from the mainstem Meramec River (34 specimens 
from 9 sites), the Bourbeuse River (10 specimens from 5 sites), and the 
Big River (2 specimens from 1 site). In addition to the nine sites 
surveyed by Buchanan (1979), new sites were included in the 1997 
survey. Living or dead scaleshell mussels were found at four of the 
five sites in the Meramec River and two of the four sites in the 
Bourbeuse River. The three sites where the presence of scaleshell 
mussels was not reconfirmed no longer support suitable mussel habitat 
due to stream bed degradation. Other species that were found in mussel 
beds at those sites in the earlier surveys were no longer present in 
1997. Although portions of the Meramec River basin continue to provide 
suitable habitat, mussel species diversity and abundance have declined 
noticeably since 1980 and

[[Page 51325]]

significant losses of mussel habitat have occurred (Roberts and 
Bruenderman 2000).
    The number of scaleshell mussel specimens the MDC collected in 1997 
is greater than that reported by Buchanan's study (Buchanan 1980); 
however, the small number of specimens collected, especially from the 
Bourbeuse and Big Rivers, indicates that the long-term viability of 
these populations is tenuous. Moreover, the long-term persistence of 
populations in the Meramec Basin is in question because of the limited 
availability of mussel habitat and the loss of mussel beds since 1980 
from bank and channel degradation, sedimentation, and eutrophication 
(excessive fertilization caused by pollution of plant nutrients) 
(Roberts and Bruenderman 2000; Alan Buchanan, MDC, in litt. 1997; Sue 
Bruenderman, MDC, pers. comm. 1998).
    Missouri River drainage (South Dakota and Missouri)--Within the 
Missouri River drainage, Buchanan (1980, 1994) and Oesch (1995) 
reported scaleshell mussels from the Missouri, Gasconade, Big Piney, 
South Grand, Osage Rivers, and Auxvasse Creek. The last collection of 
scaleshell mussels from Auxvasse Creek was in the late 1960s (Alan 
Buchanan, in litt. 1997). Similarly, the last known collection date for 
the South Grand is the early 1970s. This collection site is now 
inundated by Truman Lake and is unsuitable for the scaleshell mussel 
(Alan Buchanan, in litt. 1997). A single, fresh dead specimen was 
collected from Big Piney River in 1981 (Sue Bruenderman, in litt. 
1998). However, the scaleshell mussel has not been found in recent 
surveys of this river. Between 1994 and 1996, 70 sites were sampled in 
the Big Piney River from the mouth to the headwaters. While 3,331 
mussels of 26 species were collected, no evidence of scaleshell mussels 
were found (Janet Sternberg, MDC, pers. comm. 2000). Another survey was 
conducted in 1998, in which 10 sites were sampled between river miles 
53.6 and 96.0. Over 1,000 living mussels were collected representing 15 
species, but no living or dead scaleshell mussels were found (Sue 
Bruenderman, pers. comm. 2000).
    Only two records (both single dead shells) of scaleshell mussels 
exist for the mainstem of the Missouri River. In 1981 and 1982, the 
Missouri River was surveyed from Santee to Omaha, Nebraska (Hoke 1983). 
A single fresh dead shell was found during this study just below 
Gavin's Point Dam, South Dakota. This occurrence represents the 
westernmost record of the scaleshell mussel in North America. However, 
this species has not been found in subsequent surveys on the Missouri 
River just below Gavin's Point dam. In 1995, Clarke (1996) found no 
evidence of scaleshell mussels in a survey conducted from Gavin's Point 
Dam to 48 river km (30 mi) downstream. However, high water conditions 
limited Clark's search efforts, and only 10 individual mussels were 
found. In 1999, the Omaha District of the U.S. Army Corps of Engineers 
(Corps) funded a mussel survey between Gavin's Point Dam and Ponca, 
Nebraska, a distance of 96 river km (60 mi). In all, 355 live and 1,709 
dead individual mussels were collected representing 16 species, but no 
living or dead scaleshell mussels were found (Candace M. Gordon, Corps, 
Omaha District, in litt. 2000). The second scaleshell mussel record 
from the mainstem of the Missouri River is a single fresh dead 
individual that was collected in 1990 from Gasconade County, Missouri. 
This specimen was found during an extensive survey conducted from 
Gavin's Point Dam to St. Louis (Hoke 2000). However, the site of this 
collection was subsequently destroyed.
    Since no living scaleshell mussel has been found in the Missouri 
River, its habitat cannot be determined. However, both dead shells were 
collected from areas shielded from the main flow of the river in 
relatively stable, sandy bottoms with moderate current (Hoke 2000). 
Hoke (2000) described scaleshell mussel as ``extremely rare'' and its 
habitat ``very uncommon * * * and existing in only widely separated 
locals'' in the Missouri River. Based on the criteria used to assign 
presumed health to scaleshell mussel populations (Table 1), we consider 
this potential population to be extirpated at this time. Of the two 
known Missouri River records for scaleshell mussel, one locality has 
been destroyed and recent surveys have not found any evidence of this 
species at or in the vicinity of the other site. Further, no other 
scaleshell mussel specimens were found during Hoke's survey from 
Gavin's Point Dam to St. Louis. More information is needed on the 
existence of the scaleshell mussel and its habitat in the Missouri 
River. Furthermore, more information is needed on the location of 
sampling sites, distribution and habitat use of mussels, etc. from 
Hoke's survey work on the Missouri River, which is unavailable at this 
time.
    Buchanan (1994) surveyed the lower 137 km (85 mi) of the Gasconade 
River, and documented 36 species of freshwater mussels. He collected 
scaleshell mussel specimens at eight sites between river miles 6.0 and 
57.7. Buchanan found only dead shells at two sites and eight live 
specimens from the remaining six sites. Overall, scaleshell mussels 
comprised less than 0.1 percent of the mussels collected. In 1998-99, 
the Gasconade River was surveyed at 46 sites from mile 92.0 to 256.0. 
At sites where scaleshell mussels were collected, living individuals 
represented less than 0.5 percent of the total number of mussels found. 
A total of 12 living scaleshell mussels were found at 9 sites, and dead 
shells were found at an additional 10 sites between river miles 92.0 
and 230.3 (Sue Bruenderman, pers. comm. 2000).
    A scaleshell mussel has recently been discovered in the lower Osage 
River in Osage County, Missouri. On July 16, 2001, one live male 
specimen was found at river mile 20 (Heidi Dunn, pers. comm.). This 
individual was found during a mussel survey that is currently underway 
in the lower 80 miles of the Osage River and its tributaries. To date, 
33 sites have been surveyed including 24 in the mainstem. A total of 
3,904 living mussels have been found representing 29 living species. No 
other evidence of scaleshell mussels were found during the survey, but 
more intensive sampling is planned for these same sites in the near 
future.
    Until this recent discovery, the scaleshell mussel had never been 
reported from the Osage system in past surveys. Utterback (1917) found 
34 species in the basin. No other information is available because his 
notes and collections have since been lost. Oesch (1995) collected 
mussels in the 1970s at a number of sites in the basin and reported 39 
species. In 1980, a detailed study of mussel distribution was conducted 
by Grace and Buchanan (1981) of the Lower 80 miles of the Osage River 
and two tributaries below Bagnell Dam. A total of 43 sites were 
surveyed and 21,593 living mussels were found representing 36 species. 
No evidence of scaleshell mussels was found in any of these surveys.
    This new record of the scaleshell mussel does not significantly 
increase its range or lessen its risk of extinction. Similar to other 
records for the species, the one individual found indicates that a 
small population is present. No other evidence of the species was found 
during the 2001 survey. If a significant population of scaleshell 
mussels existed in the Osage River, dead shells would have been found. 
This is because dead shells accumulate over time, which makes them 
easier to detect than live specimens. Additionally, there are 
significant threats to scaleshell mussel in the Osage River from the 
operation of Bagnell Dam and instream gravel mining. Due to these 
habitat conditions, we categorized the Osage River

[[Page 51326]]

scaleshell mussel population's presumed health as declining.
    Middle Mississippi River Basin summary--Of the 26 rivers and 
tributaries in the middle Mississippi River Basin that historically 
supported scaleshell mussels, the species is still present in 5 
including the Meramec, Bourbeuse, Big, Osage, and Gasconade Rivers. The 
presumed health of all of these populations is thought to be declining.

Lower Mississippi River Basin

    The scaleshell mussel historically occupied 21 rivers and 
tributaries in the lower Mississippi River Basin. These include the St. 
Francis, White, James, Spring, Little Missouri, Middle Fork Little Red, 
Saline (of the Ouachita River), Ouachita, Cossatot, Saline (of the 
Little River), South Fourche LaFave, Mulberry, and Strawberry Rivers in 
Arkansas; South Fork Spring, Frog Bayou, and Myatt Creek in Arkansas; 
Poteau, Little, and Kiamichi Rivers in Oklahoma; and Gates Creek and 
Mountain Fork in Oklahoma. These rivers are organized and discussed 
below according to drainage (St. Francis, White, Arkansas, and Red 
River drainages).
    St. Francis River drainage (Arkansas)--Bates and Dennis (1983), 
Clarke (1985), and Ahlstedt and Jenkinson (1987) conducted mussel 
surveys on the St. Francis River in Arkansas and Missouri. Of these 
surveys, scaleshell mussels were only documented from two sites, both 
of which are single-specimen records (Clarke 1985). Records of dead 
shells of various species indicate that at one time freshwater mussels 
occurred throughout the river (Bates and Dennis 1983). Bates and Dennis 
(1983) determined that of the 54 sites sampled, 15 were productive, 10 
marginal, and 29 had either no shells or dead specimens only; 
scaleshell mussels were not documented at any of the 54 sites. They 
identified 77 km (48 mi.) of habitat generally suitable for mussels: 
Wappapello Dam to Mingo Ditch, Missouri; Parkin to Madison, Arkansas; 
and Marianna to the confluence with the Mississippi River at Helena, 
Arkansas. They indicated that the remaining portions of the river were 
no longer suitable for mussels. If the scaleshell mussel is extant in 
the St. Francis River, it is restricted to the few patches of suitable 
habitat.
    White River drainage (Arkansas)--Clarke (1996) noted a 1902 
collection of a single specimen from the White River near Garfield, 
Arkansas. A late 1970s survey of the White River between Beaver 
Reservoir and its headwaters failed to relocate live or dead scaleshell 
mussel individuals. However, in 1999, a single live specimen was 
collected from the White River near Newport by John Harris (John 
Harris, Arkansas Department of Transportation, pers. comm. 2000). 
Navigation maintenance activities have relegated the mussel fauna to a 
few refugial sites (Bates and Dennis 1983). Specimens have not been 
collected from the James River, a tributary of the White River, since 
before 1950 (Clarke 1996).
    An eight-mile section of the Spring River in Arkansas supports a 
diverse assemblage of freshwater mussels (Gordon et al. 1984, Arkansas 
Highway and Transportation Dept 1984, Miller and Hartfield 1986). The 
collections from this river total eight scaleshell mussel specimens 
(Kevin Cummings, in litt. 1994; Clarke 1996, Arkansas State Highway and 
Transportation Department, 1984). Gordon et al. (1984) surveyed the 
river and reported suitable mussel habitat between river miles 3.2 and 
11.0, although species richness below river mile 9 had declined 
markedly compared to past surveys. Gordon et al. (1984), as well as 
Miller and Hartfield (1986), reported that the lower 5.0 km (3.0 mi) of 
river were completely depleted of mussels and contained no suitable 
habitat. Harris did not find scaleshell mussels in a 1993 survey of the 
Spring River (John Harris, in litt. 1997).
    Scaleshell mussels were collected from the South Fork of the Spring 
River in 1983 and 1990. During the 1983 survey, Harris (in litt. 1997) 
collected four specimens near Saddle, Arkansas, and one specimen and 
one valve north of Hunt, Arkansas. During a subsequent visit in 1990, 
Harris collected young adults (Harris, pers. comm. 1995). Although 
juveniles were not found, the presence of young adults suggests that 
reproduction recently occurred.
    Records of scaleshell mussels from the Strawberry River and the 
Myatt Creek are based on single specimen collections, both made in 1996 
(John Harris, in litt. 1997). Harris collected a live specimen from the 
Strawberry River near the confluence with Clayton Creek in Lawrence 
County. He also collected a single relict (a weathered shell that has 
been dead a long period of time) specimen from Myatt Creek in Fulton 
County (John Harris, in litt. 1997). Comprehensive surveys have not 
been conducted in these rivers since 1996.
    The historical locality (near Shirley, Van Buren County, Arkansas) 
where a single scaleshell mussel specimen was collected from the Middle 
Fork of the Little Red River no longer provides mussel habitat. Clarke 
(1987) stated that suitable mussel habitat was restricted to a 9.6 km 
(6.0 mi) stretch from the confluence of Tick Creek upstream to the 
mouth of Meadow Creek.
    Arkansas River drainage (Oklahoma and Arkansas)--The scaleshell 
mussel has been collected from the following streams from the Arkansas 
River drainage: Poteau River in Oklahoma (Gordon 1991), Frog Bayou in 
Arkansas (Harris and Gordon 1987), and the South Fourche LaFave and 
Mulberry Rivers in Arkansas (Gordon 1991; Harris 1992). A single 
scaleshell mussel specimen was collected in the Poteau River (Gordon 
1980). However, it has not been documented in subsequent surveys of 
this river (Branson 1984; Harris 1994). The existence of scaleshell 
mussels in Poteau River is doubtful.
    Gordon (1980) collected two scaleshell mussel specimens from Frog 
Bayou. Beaver Reservoir now inundates one of the Frog Bayou collection 
sites. The most recent collection was a fresh dead individual during a 
1979 survey (Gordon 1980). Gordon noted that stream bank bulldozing 
upstream recently disturbed this site and other nearby sites. He also 
reported in-stream gravel mining activities at several sites. Within 
Frog Bayou, potential habitat is restricted to the area between Rudy 
and the confluence of the Arkansas River. Above Rudy, two reservoirs 
impact the river; one near Maddux Spring and the other at Mountainburg. 
Live mussels have not been found at the confluence of the Arkansas 
River, likely due to dredging activities (Gordon 1980). Although the 
current status of the scaleshell mussel in Frog Bayou is uncertain, any 
remaining individuals are in potential jeopardy due to limited habitat 
and in-stream mining activities.
    The only scaleshell mussel record from the South Fourche LaFave 
River is based on a single live specimen found in 1991 (Harris 1992). 
An 86-acre reservoir is approved for construction on Bear Creek 
approximately six miles upstream from this site. However, the effect of 
this impoundment on scaleshell mussels is uncertain. The potential for 
discovering additional scaleshell mussel sites in this river is 
unlikely due to the limited availability of suitable substrate. 
Similarly, other major tributaries of the South Fourche LaFave River 
provide little mussel habitat. Like Frog Bayou, the persistence of 
scaleshell mussels in this river is in doubt.
    Although Gordon (1991) reported scaleshell mussels from the 
Mulberry River, documentation is lacking. Recent surveys did not find 
the species in the Mulberry River (Craig Hilborne, U.S. Forest Service, 
pers. comm. 1995;

[[Page 51327]]

Stoeckel et al. 1995). The existence of scaleshell mussels in the 
Mulberry River is unlikely.
    Red River drainage (Oklahoma and Arkansas)--The scaleshell mussel 
has been documented from the following streams in the Red River 
drainage: the Kiamichi River, Gates Creek, Little River, Mountain Fork; 
and the Cossatot, Ouachita, Little Missouri, and Saline Rivers. Isley 
(1925) first collected scaleshell mussels from the Kiamichi River in 
1925. Based on his account, the Kiamichi River historically supported a 
diverse and abundant mussel fauna. He collected 36 scaleshell mussel 
specimens at one of 22 stations visited. A single specimen was also 
collected from Gates Creek, a tributary of the Kiamichi River, by 
Valentine and Stansbery (1971). As recently as 1987, Clarke described 
the Kiamichi River as ``in remarkably good condition'' and a ``faunal 
treasure'' (Clarke 1987). However, despite extensive searches of the 
Kiamichi River over the last 11 years, only a single fresh dead shell 
of scaleshell mussel (in 1987) has been collected (Caryn Vaughn, 
Oklahoma Biological Survey, pers. comm. 1997; Charles Mather, 
University of Science and Arts of Oklahoma, in litt. 1984 and 1995). 
Vaughn (pers. comm. 1997) failed to find even a dead shell during three 
years (1993-1996) of surveys in the Red River Basin. However, the 
mussel habitat in the Kiamichi River is in relatively good condition 
above the Hugo Reservoir (Clarke 1987) and may still support a remnant 
population of scaleshell mussels.
    Although there is no evidence of scaleshell mussels persisting in 
the Little River, healthy mussel beds exist above the Pine Creek 
Reservoir (Caryn Vaughn, in litt. 1997). Below Pine Creek Reservoir, 
the mussel fauna is severely depleted but recovers with increasing 
distance from the impoundment (Caryn Vaughn, in litt. 1997). Although 
scaleshell mussels have not been documented during extensive surveys 
throughout the length of the Little River, suitable habitat remains and 
the species may persist (Caryn Vaughn, in litt. 1997). However, the 
discharge of reservoir water from Pine Creek and periodic discharge of 
pollution from Rolling Fork Creek may seriously impact any remaining 
viable scaleshell mussel populations and prohibit any future 
recolonization (Clarke 1987). Valentine and Stansbery (1971) reported a 
single specimen from Mountain Fork. Clarke (1987) hypothesized that, 
based on the presence of mussels at the confluence of Mountain Fork and 
beyond the Arkansas border, damage to Mountain Fork from the Broken Bow 
Reservoir has not occurred. However, Vaughn (in litt. 1997) indicated 
that these areas have been severely depleted with most no longer 
containing live mussels.
    If scaleshell mussels still occur in the Red River drainage in 
Oklahoma, extant populations are probably small and are likely 
restricted to isolated areas of suitable habitat in the Kiamichi and 
Mountain Fork Rivers. Given the extensive survey effort over the last 
decade, long-term survival of the scaleshell mussel in Oklahoma is 
doubtful.
    Harris collected single scaleshell mussel specimens from the 
Cossatot and Saline Rivers in Arkansas in 1983 (John Harris, in litt. 
1997) and 1987 (John Harris, pers. comm. 1995), respectively. No other 
information is available for either river.
    The existence of scaleshell mussels in the Ouachita River and its 
two tributaries, the Saline River and Little Missouri River, is 
questionable as well. Both the Little Missouri and Saline Rivers 
records are based on single specimens. The Saline River specimen was 
collected in 1964 (Clarke 1996), and the Little Missouri River 
collection record is from 1995 (John Harris, in litt. 1997). Four 
undated museum specimens of scaleshell mussels from the Ouachita River 
in Arkadelphia, Clark County, Arkansas are listed in Clarke (1996), but 
details are unavailable. Based on the few collections and the limited 
habitat available, the long-term persistence of scaleshell mussel in 
Cossatot, Saline, Little Missouri, and Ouachita Rivers appears 
precarious.
    Lower Mississippi River Basin summary--Of these 21 rivers and 
tributaries in the lower Mississippi River Basin that historically 
supported scaleshell mussels, nine, and possibly an additional six, 
support the species today. Of these populations, the South Fork Spring 
River could possibly be stable; the St. Francis River, Kiamichi River, 
Little River, Mountain Fork, Spring River, Frog Bayou, South Fourche 
LaFave River, and White River are presumed to be declining; and the 
status of the Myatt and Gates Creeks and the Strawberry, Cossatot, 
Saline, and Little Missouri Rivers populations are unknown.

Previous Federal Action

    We had identified the scaleshell mussel as a Category 2 candidate 
species in a notice of review published in the Federal Register on May 
22, 1984 (49 FR 21664). The scaleshell mussel remained a Category 2 
candidate species in subsequent notices including January 6, 1989 (54 
FR 554), November 21, 1991 (56 FR 58804), and November 15, 1994 (59 FR 
58982). Prior to 1996, a Category 2 candidate species was one that we 
were considering for possible addition to the Federal List of 
Endangered and Threatened Wildlife, but for which conclusive data on 
biological vulnerability and threats were not available to support a 
proposed rule. We discontinued designating Category 2 species in the 
February 28, 1996, Notice of Review (61 FR 7596). We now define a 
candidate species as a species for which we have on file sufficient 
information on biological vulnerability and threats to support issuance 
of a proposed rule. We designated the scaleshell mussel as a candidate 
species on October 16, 1998.
    On August 13, 1999 (64 FR 44171), we published a proposal to list 
the scaleshell mussel as an endangered species and opened a 60-day 
comment period on the proposal. On November 29, 1999 (64 FR 66600), we 
reopened the comment period for 39 days in order to hold a public 
hearing. The hearing was held in Jefferson City, Missouri, on December 
8, 1999.

Summary of Comments and Recommendations

    In the August 13, 1999, proposed rule, and through associated 
notifications, we requested all interested parties to submit factual 
reports or information that might contribute to the development of a 
final rule. We contacted appropriate Federal and State agencies, County 
governments, scientific organizations, and interested parties and 
requested their comments. We published notices inviting public comment 
in the following newspapers in 1999: The Chicago Sun Times, The Chicago 
Tribune, The Peoria Journal Star, State Journal-Register, The Journal 
Gazette Co., The Indianapolis Star, The Columbia Daily Tribune, The 
Kansas City Star, The St. Louis Post-Dispatch, The South Bend Tribune, 
The Cedar Rapids Gazette, Quad City Times, The Des Moines Register, The 
Cincinnati Post, The Cleveland Plain Dealer,
The Columbus Dispatch, Cuba Free Press, Steelville Star-Crawford 
Mirror, Jefferson County Journal, Jefferson County Leader, Jefferson 
County News Democrat Journal, Meramec Journal, Jefferson County 
Watchman, TriCounty Journal, County Star Journal West, Chesterfield 
Journal, Clayton-St. Louis County Watchman, North County Journal-West, 
Florissant Valley Reporter, North County Journal-East, North Side 
Journal, County Star Journal-East, Concord Call, Mid-County Journal, 
Oakville Call, Oakville/Mehlville Journal, St. Louis Countian, South

[[Page 51328]]

County Journal, South County Times, Southwest County Journal, Webster-
Kirkwood Times, West County Journal, Citizen Journal, Webster/Kirkwood 
Journal, South County News-Times, Press Journal, New Haven Leader, St. 
Clair Missourian, Sullivan Independent-News, Franklin County Watchman, 
Union Missourian, Washington Missourian, Bland Courier, Advertiser-
Courier, Gasconade County Republican, Unterrified Democrat, Dixon 
Pilot, The Richland Mirror, Fort Leonard Wood Essayons, and The Daily 
Guide.
    The Service hosted a public hearing (December 8, 1999, in Jefferson 
City, Missouri) at the request of Two Rivers Levee and Drainage 
Association, Law Offices of John C. Franken, Howard/Cooper County 
Regional Port Authority, and 180 private citizens. To accommodate this 
request, we reopened the comment period from November 29, 1999, to 
January 7, 2000, to allow for consideration of, and to provide an 
opportunity for, further comments. A notice of the hearing and 
reopening of the comment period was published in the Federal Register 
on November 29, 1999 (64 FR 66600), and in legal notices in the 
newspapers listed above.
    We received 26 letters providing comments and information during 
the comment periods. Additionally, six individuals provided oral 
statements at the public hearing. We have updated this rule to reflect 
any changes in information concerning distribution, status, and threats 
since the publication of the proposed rule. All pertinent comments have 
been considered in the formulation of this final rule. Written comments 
received during the comment periods and written comments and oral 
statements presented at the public hearings are addressed in the 
following summary. Comments of a similar nature or point are grouped 
together (referred to as ``Issues'' for the purpose of this summary) 
below, along with the Service's response to each.
    Issue 1: One respondent was unsure of what this listing would 
accomplish beyond the recovery efforts of other mussel species already 
federally listed in Missouri.
    Response: This action will extend the Act's protection to this 
species. Federal listing results in an increased awareness of this 
species' status and its need for conservation attention. It also 
provides for opportunities for funding research, management activities, 
and conservation actions specifically targeted for this species. In 
addition to better funding opportunities, Federal endangered status 
encourages scientists and natural resource managers to focus research 
and conservation actions specifically for the scaleshell mussel.
    There are currently four federally listed mussel species in 
Missouri (Missouri Natural Heritage Database 1999). These are the pink 
mucket (Lampsilis abrupta), Curtis pearlymussel (Epioblasma florentina 
curtisi), Higgins' eye (Lampsilis higginsii), and fat pocketbook 
(Potamilus capax). We agree that where overlap of listed mussels 
occurs, the prohibitions of the Act will provide little additional 
protection of habitat. However, the current range of scaleshell mussel 
extends to areas where there are no federally listed species. The Act 
will provide protection from further habitat loss and degradation in 
these areas.
    Issue 2: One respondent was concerned that the public will not know 
what impacts this listing will have on activities on private property 
until after the recovery plan is completed. The respondent was 
referring to potential impacts of recovery actions on private land in 
particular.
    Response: While recovery plans are not developed until after a 
species is listed, there is opportunity for public input in the 
recovery planning stage. The purpose of the recovery plan is to set 
recovery objectives (goals) and identify the tasks needed to meet those 
objectives before a species can be downlisted or delisted. As the draft 
recovery plan is announced in the Federal Register, we will solicit 
comment from species experts, natural resource managers, and other 
interested parties. To ensure broad participation in the review of the 
recovery plan, we will notify all interested parties that were 
identified during the listing process (for example, those that provided 
comments or requested to be on our mailing list).
    Although actions that could be affected by the listing were 
identified in the proposed rule, we acknowledge that impact upon 
private actions cannot be fully assessed until a recovery plan is 
developed. However, in ascertaining whether a species warrants Federal 
protection under the Act, we may consider only biological factors. In 
accordance with 16 U.S.C. sec. 1533(b)(1)(A) and 50 CFR 424.11, listing 
decisions are made solely on the basis of the best scientific and 
commercial data available. The legislative history of the 1982 Act 
amendments states: ``The addition of the word ``solely'' is intended to 
remove from the process of the listing or delisting of species any 
factor not related to the biological status of the species. The 
Committee strongly believes that economic considerations have no 
relevance to determinations regarding the status of the species. * * 
*'' H.R. Rep. No. 567, Part I, 97th Congress, 2nd Session 20 (1982). 
Thus, the impact of listing on private activities, although of great 
interest and importance to the public, is not a factor we may consider 
in our listing determination.
    Issue 3: One respondent questioned whether the range of the 
scaleshell mussel, particularly in the Missouri River, is based on 
records that were identified correctly. Scaleshell mussels can be 
easily confused with the fragile papershell (Leptodea fragilis) or the 
pink papershell (Potamilus ohioensis), which are more common and 
widespread.
    Response: We acknowledge that scaleshell mussels may be confused 
with other species by the casual observer. Freshwater mussels are often 
difficult to identify by shell shape alone. However, to malacologists 
(a person who studies mollusks) and other properly trained biologists, 
there are no ambiguities in distinguishing scaleshell mussels from 
other species. Female scaleshell mussels are unique and unlikely to be 
mistaken with any other species. Females are small, very elongated, and 
the posterior edge is ruffled. Male scaleshell mussels can possibly be 
confused with other species, particularly the fragile papershell. 
However, several external characteristics distinguish male scaleshell 
mussels from the fragile papershell, the pink papershell, and other 
species. These characteristics include the presence of green rays, 
light brown periostracum, pointed posterior end, absence of dorsal 
wings, elongated shell, straight dorsal margin, and rounded ventral 
margin (Parmalee and Bogan 1998, Oesch 1995, Watters 1995).
    While it is possible that a small number of scaleshell mussel 
specimens have been misidentified, we are confident that the range of 
this species is based on valid specimens because many records are 
represented by voucher specimens that are housed in museums. The 
identification of these specimens has been verified by expert 
malacologists. In particular, the records of scaleshell mussel from the 
Missouri River were identified by Dr. David H. Stansbery, who is a 
leading authority in North America on freshwater mussel identification 
at the Ohio State Museum located at Ohio State University in Columbus, 
Ohio.
    Issue 4: The proposed rule states that gravel mining has recently 
become a more serious threat for scaleshell mussel range-wide because 
the Corps' authority to regulate instream gravel mining has been 
reduced. One respondent stated that this issue will probably not be

[[Page 51329]]

overlooked by the State agencies. In other words, gravel mining will 
probably be regulated by State agencies now that the Corps has less 
authority to regulate this activity.
    Response: Section 404 of the Clean Water Act of 1972 (CWA) provides 
regulations for discharge of dredged and fill materials in surface 
waters, including a permit program to ensure that such discharges 
comply with other State and Federal environmental regulations. The 
Corps is the Federal agency responsible for implementing this section 
of the CWA. Until 1997, instream mining was more strictly regulated, 
because incidental fallback of material during a dredging action was 
considered fill in surface waters, and thus triggered section 404 
compliance. Due to a 1997 Federal court decision, however, incidental 
fallback of material is no longer considered fill. Consequently, only 
activities that result in discharge of fill material greater than 
incidental fallback are regulated under section 404 (see factors A and 
D under the ``Summary of Factors Affecting the Species'' section for 
further information on this issue).
    As discussed in Issue 1, federally listed species frequently 
coexist with scaleshell mussels. Section 7 of the Act requires all 
Federal agencies, including the Corps, to consult with the Service 
regarding any action that may adversely affect listed species. Through 
this consultation process, the Service identifies conservation 
measures, which minimize adverse impacts to listed species. With 
incidental fallback no longer requiring a Corps section 404 permit, the 
section 7 consultation process is no longer applicable for many 
instream gravel mining activities.
    Some State agencies have authority to regulate gravel mining within 
their state. In Arkansas, instream gravel mining is regulated by the 
Arkansas Open-Cut Mining and Land Reclamation Code, which contains 
guidelines to reduce impacts (Roell 1999). The Missouri Department of 
Natural Resources (MDNR) also has the authority to regulate gravel 
mining in Missouri under the Land Reclamation Act. However, their 
regulatory authority is limited. First, only commercial operators are 
required to obtain a permit to remove gravel from streams and rivers. 
City, county, and state operators using their own equipment and private 
operations are not required to obtain a permit from MDNR. Also, these 
operators are not obligated to comply with permit conditions that are 
crucial in avoiding adverse impacts to the stream environment. Second, 
MDNR's conditions for gravel mining permits are less stringent than 
those required previously by the Corps (Mike Larson, Missouri 
Department of Natural Resources, pers. comm. 2000). For example, the 
MDNR permit does not prohibit the modification of water conveyance, 
limit excavation to unconsolidated areas, require bank and water buffer 
strips, or minimize the removal of aquatic and terrestrial vegetation. 
All of these factors could adversely affect the scaleshell mussel and 
its habitat.
    Issue 5: Several respondents are concerned that this listing will 
impact activities on private property. One respondent was concerned 
that impoundments will be more difficult to construct after the 
listing.
    Response: This listing will protect scaleshell mussels from take 
under section 9 (Prohibited Acts) of the Act. Take is defined by the 
Act as ``harass, harm, pursue, hunt, shoot, wound, capture, collect, or 
attempt to engage in any such conduct.'' Take is further defined by 
regulation to include ``significant habitat modification or degradation 
that actually kills or injures wildlife,'' (50 CFR 17.3 ``Harm''). Non-
Federal property owners, such as private landowners, corporations, or 
State or local governments, wishing to conduct activities on their land 
that might result in the incidental take of scaleshell mussels can 
obtain an incidental take permit from the U.S. Fish and Wildlife 
Service. Section 10 of the Act provides for the issuance of permits to 
conduct otherwise prohibited activities. Through section 10, there is 
an opportunity to provide species protection and habitat conservation 
for non-Federal development and land use activities that may result in 
incidental take of a listed species. For landowners and local 
governments, these incidental take permits, and their associated 
habitat conservation plans (HCP), provide long-term assurances that 
their activities will be in compliance with the requirements of the 
Act. Biologically, they provide the Service with a tool to offset the 
incidental take of listed species by reconciling species conservation 
with economic development. The HCP process allows private development 
to proceed while promoting listed species conservation.
    The No Surprises policy provides assurances to non-Federal 
landowners participating in HCP efforts through the section 10(a)(1)(B) 
process. Essentially, landowners are assured that if ``unforeseen 
circumstances'' arise, the Services will not require, without the 
consent of the permittee, the commitment of additional land, water or 
financial compensation or additional restrictions on the use of land, 
water, or other natural resources beyond the level otherwise agreed to 
in the HCP. The government will honor these assurances as long as a 
permittee is implementing the terms and conditions of the HCP, permit, 
and other associated documents in good faith. In effect, this 
regulation states that the government will honor its commitment as long 
as HCP permittees honor theirs.
    An activity on private land could also possibly be affected by this 
listing if that project (1) would need to be authorized, permitted, or 
funded by the Federal government, (2) would be located in habitat 
occupied by the scaleshell mussel or in designated critical habitat for 
the species, and (3) would have a direct or indirect effect on the 
species or its designated critical habitat. Federal programs and 
activities of this nature would usually require consultation with the 
Service under section 7 of the Act to evaluate the nature and extent of 
the adverse impacts and determine if project modification is necessary 
to reduce those impacts. Proposed impoundments within currently 
occupied streams and rivers are one type of activity that will require 
consultation. See the ``Available Conservation Measures'' section for 
additional examples of activities that will and will not require 
consultation.
    While certain activities may require consultation, projects are 
rarely terminated due to the presence of a federally listed species, 
and private landowners are usually not affected. The consultation 
process is the responsibility of the Federal agencies involved. The 
majority of section 7 consultations are resolved informally. For 
example, consultation is ended at an early stage if the potential 
impacts of a proposed project are expected to be discountable, 
insignificant, or beneficial to the species. Even if a significant 
adverse effect is expected, the consultation can usually be concluded 
by developing minor modifications to project plans or designs that 
avoid those impacts. If potential impacts are of such nature that a 
federally listed species is likely to be adversely affected and such 
effects cannot be removed, formal consultation would be required. 
However, section 7(b)(4) of the Act allows incidental take of the 
listed species resulting from Federal actions if such take is not 
likely to jeopardize the continued existence of the species and if 
reasonable and prudent measures are implemented to minimize the adverse 
impacts of such take. A General Accounting Office audit (1992), which 
found that 99.9 percent of all projects reviewed between 1988 and 1992 
went

[[Page 51330]]

forward unchanged or with only minor modifications as a result of the 
section 7 consultation, attests to the regulatory flexibility afforded 
by the Act.
    Issue 6: One commenter stated that the same threats (i.e., water 
pollution, sedimentation, channelization, and impoundments) listed as 
impacting scaleshell mussel in the past (prior to 1950) are stated for 
present and future populations. The commenter stated that these 
conditions have improved. In Missouri, most of the channelization was 
established before the 1930s. Since 1950 land management practices have 
also evolved to more effectively control erosion and runoff, and the 
impacts of water pollution and sedimentation have been reduced.
    Response: The Service recognizes that some of these factors have 
improved, particularly land management practices to reduce erosion and 
runoff. In fact, the reason scaleshell mussels continue to persist 
could possibly be due to these improvements. However, the same threats 
that contributed to scaleshell mussels' decline before 1950, are still 
being observed and continue to impact scaleshell mussels. 
Channelization and new impoundments are currently proposed within the 
range of the scaleshell mussel, and water quality degradation and 
siltation has recently been documented as a serious threat in areas 
still occupied by scaleshell mussels. These threats are ongoing and 
qualify the scaleshell mussel for listing (See factor A in the 
``Summary of Factors Affecting the Species'' section). The small number 
and low density of the remaining populations exacerbate threats and 
adverse effects of chance events on the species.
    Issue 7: The data cited in the notice of proposed listing provide 
inadequate support for listing the scaleshell mussel as an endangered 
species. The decline of the scaleshell mussel is not serious enough to 
warrant listing. The six potential additional populations (status 
unknown), which would increase the current number of populations by 
almost 50 percent, merit further investigation before the listing 
decision is made.
    Response: Under section 4(b)(1)(A) of the Act, a listing 
determination must be based solely on the best scientific and 
commercial data available regarding the species' biological status and 
threats to its existence. Endangered status is assigned to species 
which are in danger of extinction throughout all or significant portion 
of their range. A species may be determined to be an endangered or 
threatened species due to one or more of the five factors described in 
section 4(a)(1) of the Act. These factors include (1) the present or 
threatened destruction, modification, or curtailment of its habitat or 
range; (2) overutilization for commercial, recreational, scientific, or 
educational purposes; (3) disease or predation; (4) the inadequacy of 
existing regulatory mechanisms; and (5) other natural or manmade 
factors affecting its continued existence.
    The scaleshell mussel has undergone one of the most extensive range 
reductions of all the federally listed freshwater mussel species. It is 
considered extirpated from ten states and from 39 of the 55 rivers 
within its historical range. Although 14 populations, and possibly six 
others, persist, the long-term viability of these populations is 
threatened by a variety of ongoing threats (see ``Summary of Factors 
Affecting the Species'' discussion). Given the extent of range 
reduction that has occurred and the persistence of threats to the 
remaining populations, we believe the scaleshell mussel is in danger of 
extinction throughout a significant portion of its range.
    Issue 8: Detecting population changes by using available data for a 
rare species is speculative. Specifically, the proposed rule states 
that the long-term viability of scaleshell mussel populations in the 
Meramec basin is tenuous. In a recent survey on the Meramec River, more 
scaleshell mussels were found than in a past survey. The respondent did 
not understand how those data could support a conclusion that the 
species is declining.
    Response: The Service acknowledges that rare species are difficult 
to census, and thus, deriving population trends based on counts of 
individuals is difficult and sometimes impossible. It is a common 
problem in rare species conservation that, as numbers of a rare species 
continue to decline, it becomes increasingly difficult to find and 
count the individuals in order to ``prove'' the decline is continuing. 
However, reliable inferences on the status and long-term viability of 
individual populations, as well as for a species as a whole, can be 
made based on ecological principles, small population biology theory, 
and observations of threats and habitat loss from field investigations. 
For example, population stability implies that recruitment exceeds 
mortality. For freshwater mussels, the presence of juveniles serves as 
the best evidence for recruitment. Thus, failure to collect juvenile 
specimens suggests that the population is declining. Similarly, small 
populations are more susceptible to extinction due to chance events, 
such as disease, drought, accidental spills of contaminants, or other 
fluctuations in local environmental conditions. Thus, even without 
multiple years of survey data, we know that low density mussel 
populations are vulnerable. Small populations must also rely on 
movement of individuals among populations to remain genetically viable. 
Thus, mussel populations that are isolated are threatened. In addition 
to these biological factors, the presence of threats, regardless of 
population size, can substantially influence the conservation status of 
a population. Using these factors, the health of individual populations 
and the species can be determined.
    To ensure consistency and objectivity, Szymanski (1998) developed 
criteria based on the aforementioned factors to assign status and trend 
categories to each scaleshell mussel population. These criteria were 
utilized in the proposed rule. However, a discussion of status and 
trends using the same set of limited data was confusing and redundant 
to readers. Therefore, in this final rule, we devised a single 
classification system (i.e., combined status and trend categories) to 
assess population health (Table 1). The revised classification system 
differs only in the presentation of the data and the results of its 
application are similar to those derived from the Szymanski (1998) 
methodology. As a result of additional information that was obtained 
during the public comment period, the status or trends reported in the 
proposed rule for a few populations differs from those reported herein. 
For example, the status of the White River population changed from 
extirpated to presumed declining as new information documented a 1999 
live scaleshell mussel collection from this river. A discussion of the 
criteria used for this classification system is provided in the 
``Distribution and Abundance'' section.
    With respect to the recent survey work in the Meramec River, the 
greater number of scaleshell mussels found in the 1997 survey was 
likely due to two aspects of the survey, and not a result of a 
population increase (Roberts and Brunderman 2000). First, a special 
effort was made to collect this species (i.e., raking the top layer of 
the substrate by hand) because it often lies buried in the substrate. 
This method likely increased the probability of finding the species 
compared to past surveys. Second, lower water levels from drought 
conditions exposed a mussel bed at one site, causing scaleshell mussels 
to actively crawl on top of the substrate. The collection of only 19 
scaleshell mussels, when viewed in light of the modified survey 
techniques and the

[[Page 51331]]

high visibility of individual mussels at one mussel bed, is strong 
evidence of the extreme rarity of this species.
    When attempting to monitor rare species, for which surveys usually 
locate only one or several surviving individuals, it is not uncommon 
for variations in survey methodology, weather conditions, and even time 
of day to affect the results of the survey. For species of extreme 
rarity, the effects of these factors can easily obscure the true 
population trend for the species. For this reason, we usually use 
criteria, in addition to population or density estimates, to evaluate 
the health of individual populations and the species as a whole.
    Based on the criteria described earlier, the three scaleshell 
mussel populations in the Meramec Basin (the Meramec, Bourbeuse, and 
Big Rivers) are believed to be declining at the present time. The long-
term persistence of these populations is considered questionable 
because of marked habitat loss and other existing threats. Furthermore, 
the small number of individuals and low density of these populations 
exacerbate the magnitude and adverse impacts of threats (see ``Summary 
of Factors Affecting the Species''). Thus, despite the fact that more 
scaleshell mussels were collected from the Meramec River in a recent 
survey than in the past, other factors indicate that these populations 
are threatened and are declining.
    Issue 9: One respondent requested clarification of references to 
historical and existing distribution and abundance of scaleshell 
mussels. The respondent asked if the terms ``populations'' and 
``occurrences'' are equivalent and if populations are equal in size and 
other qualities.
    Response: A ``historical record'' is any site where the scaleshell 
mussel has been documented regardless of when it was collected. The 
Service believes that recently discovered sites do not represent areas 
that have been colonized recently, but rather, they are sites that have 
existed historically (i.e., in historical times) and have not been 
previously known or sampled by collectors. A description of the 
historical range of the scaleshell mussel includes all known records. 
In contrast, a description of the existing distribution of the 
scaleshell mussel would include only its extant (that is, currently 
existing) range.
    An ``occurrence'' refers to a site where a scaleshell mussel 
specimen has been collected. An occurrence, which may be represented by 
one or more specimens, usually indicates the species is present or once 
existed in that area, depending on whether the specimen(s) is living or 
dead.
    In the context of this rule, the term ``population'' refers to all 
the current and historical occurrences of scaleshell mussels within a 
single river.
    It is impossible to determine if past and present scaleshell mussel 
populations are equal in size (in terms of number of individuals or 
length of stream inhabited), because many surveys conducted near the 
turn of the century were not thorough. However, it is believed that 
scaleshell mussels historically have always been rare relative to many 
other mussel species. Inferences regarding population trend can be made 
from existing data (e.g., age-structure, historical vs. current 
collections, habitat availability and condition, and threats). For 
example, scaleshell mussels were locally abundant in the Kiamichi River 
in the past (with 36 specimens collected from one sampling station). 
Today, however, no living scaleshell mussel specimens and only 1 fresh 
dead specimen were found during exhaustive survey efforts. It is 
apparent that scaleshell mussels, although always rare, occur today at 
lower densities than in the past in the Kiamichi River (see Issue 8 for 
further discussion regarding assessing conservation status). Within 
this final rule, populations that were assigned to the same 
conservation status do not necessarily have similar population size 
(although all populations persist at very low densities) or habitat 
quality.
    Issue 10: The proposed rule states that scaleshell mussels have not 
been found in the Upper Mississippi River basin in over 50 years. One 
respondent asked how often sampling has been conducted in the Upper 
Mississippi River basin, and what is the likelihood of detecting a 
locally rare species.
    Response: The historical range of the scaleshell mussel in the 
Upper Mississippi River basin includes the states of Illinois, Iowa, 
Minnesota, and Wisconsin. Natural resource agencies in these states are 
confident enough to consider the scaleshell mussel extirpated since it 
has not been collected in over 50 years despite a considerable number 
of surveys. Rivers with documented scaleshell mussel occurrences in the 
Upper Mississippi River basin include the Mississippi, Minnesota, Iowa, 
Cedar, Illinois, Sangamon, and Pecatonica Rivers, and Burdett's Slough 
of the Mississippi River (see ``Distribution and Abundance''). All of 
these rivers have been surveyed in the last 10-15 years. Surveys 
considered here are formal mussel surveys published in technical 
reports and scientific journals. Numerous other surveys, which are not 
discussed here, also have been conducted in these streams at selected 
sites for various Federal projects (e.g., proposed bridges, pipelines, 
channelization, etc.). Surveys have been conducted on the Minnesota 
River in 1977 and 1999 (Marian Havlik, Malacological Consultants, in 
litt. 2000; Tim Yager, Corps, St. Paul District, in litt. 2000). The 
Mississippi River mainstem, in particular, has been surveyed 
extensively since 1950. The Illinois, Sanagamon, and Pecatonica Rivers 
have also been surveyed extensively in the last 15 years (Kevin 
Cummings, pers. comm. 2000).
    The likelihood of detecting a locally rare species depends on the 
amount of time spent searching and the search methods employed. The 
most common method used for surveys is timed searches, which produce a 
measurement of the number of mussels collected per unit of time spent 
searching. Timed searches produce the most complete list of species 
(including rare species) at a given site (Strayer et al. 1997, Vaughn 
et al. 1997).
    Furthermore, the deficiency of suitable mussel habitat, both in 
quality and quantity, remaining in this drainage also suggest that 
scaleshell mussel persistence is highly unlikely. This is not to say 
individuals may not persist in the Upper Mississippi River drainage, 
but that the best available scientific information indicates that 
population viability is doubtful.
    Issue 11: One respondent believes that water turbulence produced by 
jet boat motors may be adversely affecting scaleshell mussels and other 
freshwater mussels in the Meramec River in Missouri.
    Response: The Service recognizes that jet boats, which can produce 
powerful water turbulence, could potentially have adverse affects on 
freshwater mussels including scaleshell mussels. Jet wash from motors 
may contribute to substrate destabilization and/or could dislodge adult 
and juvenile mussels from suitable habitat, particularly from shallow 
riffles where mussels typically occur. The magnitude and extent to 
which this factor may threaten populations, however, is unknown.

Peer Review

    In accordance with our July 1, 1994, Interagency Policy on Peer 
Review (59 FR 34270) we requested the expert opinions of independent 
specialists regarding pertinent scientific or commercial data and 
assumptions relating to the supportive biological and ecological 
information in the proposed rule. The purpose of such review is to

[[Page 51332]]

ensure that the listing decision is based on scientifically sound data, 
assumptions, and analyses, including input of appropriate experts and 
specialists.
    We requested a formal scientific peer review from four 
malacologists who possess expertise on the scaleshell mussel. We 
received a written response and comments from two of these experts 
within the open comment periods. These experts strongly supported the 
listing proposal and agreed with the Service that this species is in 
need of Federal protection as an endangered species. One reviewer 
stated that the Service was thorough in reviewing this species and that 
the status and threats are accurately described. This reviewer felt 
that the threats posed by the zebra mussel to the scaleshell mussel, as 
discussed in the proposed rule, should not be underestimated. 
Additionally, more information was provided in one response regarding 
the extant distribution of the scaleshell mussel and threats to its 
existence. That information is incorporated into this final rule.

Summary of Factors Affecting the Species

    After a thorough review and consideration of all information 
available, we determine that the scaleshell mussel should be classified 
as an endangered species. We followed the procedures found at section 
4(a)(1) of the Act (16 U.S.C. 1531 et seq.) and regulations (50 CFR 
part 424) implementing the listing provisions of the Act. We may 
determine a species to be endangered or threatened due to one or more 
of the five factors described in section 4(a)(1). These factors and 
their application to the scaleshell mussel (Leptodea leptodon) are as 
follows:

A. The Present or Threatened Destruction, Modification, or Curtailment 
of its Habitat or Range.

    Arguably, the scaleshell mussel has suffered a greater range 
reduction than any other unionid. The range of this species was once 
expansive, spanning the Mississippi River Basin in at least 55 rivers 
in 13 states (Szymanski 1998). Today, the range is significantly 
reduced with known extant populations persisting in only 14, 
potentially 20, rivers in three states. The scaleshell mussel has been 
eliminated from the entire upper and most of the middle Mississippi 
River drainages. Although much of the decline occurred before 1950, 
population declines continue in most portions of the species' range, 
and numerous threats are impacting the few remaining extant 
populations. Water pollution, sedimentation, channelization, sand and 
gravel mining, dredging, and impoundments contribute to the decline of 
the scaleshell mussel throughout its range and continue to affect 
existing populations. A general description of how these factors affect 
mussels is given below, followed by specific examples of how these 
threats are affecting scaleshell mussels in its extant range. Refer to 
Szymanski (1998) for a more detailed discussion of threats to 
freshwater mussels.
    Mussel biologists generally agree that contaminants are partially 
responsible for the decline of mussels (Havlik and Marking 1987, 
Williams et al. 1993, Biggins et al. 1996). Mussels are sedentary 
filter feeders and are vulnerable to contaminants that are dissolved in 
water, associated with suspended particles, or deposited in bottom 
sediments (Naimo et al. 1992).
    Contaminants enter streams from point and nonpoint sources. Point 
source pollution is the entry of material from a discrete, identifiable 
source such as industrial effluents, sewage treatment plants, and solid 
waste disposal sites. Freshwater mussel mortality from toxic spills and 
polluted water is well documented (Ortmann 1909, Baker 1928, Cairns et 
al. 1971, Goudreau et al. 1988). Decline and elimination of populations 
may be due to acute and chronic toxic effects that result in direct 
mortality, reduced reproductive success, or compromised health of the 
animal or host fish.
    Nonpoint source pollution is the entry of material into the 
environment from a diffuse source such as runoff from cultivated 
fields, pastures, private wastewater effluents, agricultural feed-lots 
and poultry houses, active and abandoned mines, construction, and 
highway and road drainage. Stream discharge from these sources may 
accelerate eutrophication (i.e., organic enrichment), decrease oxygen 
concentration, increase acidity and conductivity, and cause other 
changes in water chemistry that are detrimental to the survival of most 
mussel species and may impact host fishes (Goudreau et al. 1988, Dance 
1981, Fuller 1974).
    Sediment is material that is suspended in the water, and is being 
transported, or has been moved, as the result of erosion (USSCS 1988). 
Although sedimentation is a natural process, agricultural encroachment, 
channelization, impoundments, timber harvesting within riparian zones, 
heavy recreational use, urbanization, and other land use activities can 
accelerate erosion (Waters 1995, Myers et al. 1985, Chesters and 
Schierow 1985). The water quality impacts caused by sedimentation are 
numerous. Generally, it affects aquatic biota by altering the 
substratum and by altering the chemical and physical composition of the 
water (Ellis 1936, Myers et al. 1985, USSCS 1988). Sedimentation 
directly affects freshwater mussel survival by interfering with 
respiration and feeding. Due to their difficulty in escaping smothering 
conditions (Imlay 1972, Aldridge et al. 1987), a sudden or slow 
blanketing of stream bottom with sediment can suffocate freshwater 
mussels (Ellis 1936). Sediment particles may carry contaminants toxic 
to mussels (Naimo et al. 1992). Increased sediment levels may also 
reduce feeding efficiency (Ellis 1936), which can lead to decreased 
growth and survival (Bayne et al. 1981).
    Channelization, sand and gravel mining, and dredging operations 
physically remove mussels from the water and may also bury or crush 
mussels (Watters 1995). Other effects of these activities extend 
upstream and downstream of the excavated area. Headcutting, the 
upstream progression of stream bed destabilization and accelerated bank 
erosion, can affect an area much larger than the dredging site 
(Hartfield 1993). In severe cases, this erosional process can extend 
for several miles upstream. As relatively immobile bottom-dwelling 
invertebrates, mussels are particularly vulnerable to channel 
degradation (Hartfield 1993). Accelerated erosion also releases 
sediment and pollutants, and in some instances, diminishes mussel 
diversity and habitat as documented in the Yellow and Kankakee Rivers 
in Indiana, the Big Vermillion River in Illinois, and the Ohio River 
(Fuller 1974).
    Gravel mining has recently become a more serious threat for 
scaleshell mussels range-wide. In 1997, a court ruling changed the 
interpretation of the CWA as it applies to the regulation of gravel 
mining (Roell 1999). Previously, gravel mining was more strictly 
regulated because ``incidental fallback'' (the incidental soil movement 
from excavation, such as the soil that is disturbed when dirt is 
shoveled, or back-spill that comes off a bucket and falls into the same 
place from which it was removed) was considered fill in surface waters, 
thus triggering section 404 of the CWA and the permitting process of 
the Corps. Prior to the 1997 ruling, gravel mining operators were 
required to obtain a Corps section 404 permit and follow several 
conditions outlined on the permit. Except in very small tributaries, 
the Corps required all operators to establish a streamside and riparian 
buffer and prohibited removing gravel from flowing water (i.e., no in-
stream mining) or from below the water

[[Page 51333]]

table (Danny McKlendon, Corps, St. Louis District, pers. comm. 1998). 
These requirements avoided most adverse effects to mussels including 
headcutting, channel modification, and the physical crushing or removal 
of mussels. Furthermore, the Corps' permit process included 
consultation with the Service concerning the presence of federally 
listed species at each proposed mining site. However, the 1997 ruling 
eliminated the Corps authority to regulate most instream gravel mining 
activities, thereby eliminating the section 404 permit and the 
conditions that protected mussel beds. Therefore, the scaleshell mussel 
has lost much of its protection from gravel mining. Only activities 
resulting in discharge of fill material greater than incidental 
fallback (such as instream gravel stockpiling, stream crossings, and 
select removal methods) are regulated. However, many gravel mining 
operations may not fall under this category.
    Impoundments negatively affect mussels both upstream and downstream 
by inducing scouring, changing water temperature regimes, and altering 
habitat, food, and fish host availability (Caryn Vaughn, in litt. 
1997). Impoundments permanently flood stream channels and eliminate 
flowing water that is essential habitat for most unionids, including 
scaleshell mussels (Fuller 1974, Oesch 1995). Scouring is a major cause 
of mussel mortality below dams (Layzer et al. 1993). Most detrimental, 
however, is the disruption of reproductive processes. Impoundments 
interfere with movement of host fishes, alter fish host assemblages, 
and isolate mussel beds from each other and from host fishes (Stansbery 
1973, Fuller 1974, Vaughn 1993, Williams et al. 1993). The result is 
diminished recruitment (Layzer et al. 1993). Dams are effective 
barriers to fish host movement and migration that unionids depend on 
for dispersal. Mussels living upstream from the dam can become 
reproductively isolated from those living downstream causing a decrease 
in genetic diversity. Even small, lowhead dams can hinder fish movement 
and isolate mussel beds from fish hosts and from each other. For 
example, Watters (1996) determined that the upstream distribution of 
two mussel species, the fragile papershell (Leptodea fragilis) and pink 
heelsplitter (Potamilus alatus) stopped at lowhead dams. These species, 
like the scaleshell mussel, are believed to use the freshwater drum as 
a sole host.
    The same threats that caused the extirpation of historical 
populations of scaleshell mussel still exist and continue to threaten 
extant populations. This species appears to be especially susceptible 
to contamination and sedimentation. Historically, the species was 
widespread and occurred in diverse habitats. Today, scaleshell mussels 
no longer occur at disturbed sites that still support other endangered 
unionids (Szymanski 1998). This suggests that scaleshell mussels are 
especially sensitive to degraded water quality. Given the pervasiveness 
of the sources of pollution and sedimentation, it is apparent that 
these threats continue to be problematic for the remaining scaleshell 
mussel populations.

Upper Mississippi River Basin

    The scaleshell mussel formerly occurred in eight rivers and 
tributaries within the Upper Mississippi Basin. However, this species 
has not been found in more than 50 years and is believed extirpated 
from this region (Kevin Cummings, in litt. 1994). We believe the same 
factors that have caused declines and extirpations of other mussel 
species including impoundments, pollution, sedimentation, and 
channelization and dredging activities, have caused the disappearance 
of scaleshell mussels from the Upper Mississippi River Basin.

Middle Mississippi River Basin

    Similar to the Upper Mississippi River Basin, impoundments, 
pollution, sedimentation, and channelization and dredging activities 
are believed to have led to the extirpation of the scaleshell mussel 
from the entire Ohio River Basin. These same threats continue to 
adversely affect extant populations in the middle Mississippi River 
Basin. Scaleshell mussel habitat in the Meramec River Basin has been 
reduced in recent years. In 1979, Buchanan found living or dead 
scaleshell mussels in the lower 180 km (112 mi) of the Meramec River 
(Buchanan 1980). In 1997, living or dead scaleshell mussels were 
collected only in the lower 96 km (60 mi) of the river (Roberts and 
Bruenderman 2000). While portions of the lower reach continue to 
provide suitable habitat, mussel species diversity and abundance above 
mile 60 have declined noticeably in the last 20 years and 9 mussel beds 
are no longer present between river mile 21.5 and 145.7. Roberts and 
Bruenderman (2000) attributed this decline primarily to the loss of 
channel stability. Within the Meramec Basin, the Bourbeuse River has 
undergone the greatest change with respect to mussel populations. In 
particular, mussel populations have declined in the lower river. 
Whereas Buchanan (1980) found this section of the Bourbeuse River to 
have the greatest mussel diversity, this stretch was nearly devoid of 
mussels when resurveyed in 1997. Additionally, five mussel beds are no 
longer present between miles 0.4 and 137. Buchanan (in litt. 1997) and 
Roberts and Bruenderman (2000) attributed this decline to habitat loss 
from sedimentation, eutrophication, and substrate destabilization.
    The Big River has the lowest species diversity and abundance in the 
Meramec River Basin. Buchanan (1980) attributed this to the effects of 
lead and barite mining. While most mining operations have ceased, 45 
dams retaining mine waste and numerous waste piles remain in the Big 
River Basin. Most of those dams were improperly constructed or 
maintained. The Corps found that only one of the 45 dams was safe and 
27 received the worst possible rating and could fail during a flood. 
The poor condition of the dams has led to large influxes of mine waste 
into the Big River from dam collapse (MDC 1997). For example, since 
1978, a ruptured tailings dam has discharged 63,000 cubic meters 
(81,000 cubic yards) of mine tailings into the Big River covering 40 km 
(25 mi) of stream bottom and negatively impacting the lower 129 km (80 
mi) of the river (Alan Buchanan, in litt. 1995), making it less 
suitable for mussels.
    While no major impoundments exist in the Meramec River Basin, 
several old mill dams (low-head dams) affect the mainstem of the Big 
and Bourbeuse Rivers. Five dams are still in place along the lower 48 
km (30 mi) of the Big River, and one dam exists in the lower Bourbeuse 
River. These structures are barriers to host fish movement during 
normal flows (MDC 1997) and thus, continue to depress reproductive 
rates of scaleshell and other mussels.
    Gravel mining poses an imminent threat to scaleshell mussel 
populations in the Meramec River Basin due to the high, and increasing, 
level of interest in gravel mining in the basin (Roberts and Brunderman 
2000). For example, between 1994 and 1998, the Corps issued permits for 
230 sites. Additional sites were mined without a permit, but the number 
of these unauthorized operations is unknown. (Danny McKlendon, Corps, 
St. Louis District, in litt. 1998).
    In 1994, several areas of the Gasconade River channel were highly 
unstable, possibly a result of riparian vegetation removal in 
conjunction with the 1993 flood. These areas had high cut mud banks 
with trees fallen into the river, unstable substrate, and contained 
very few mussels. Buchanan (1994) predicted that habitat degradation on 
this river would continue and

[[Page 51334]]

postulated that the mussel fauna would be further impacted with some 
species possibly disappearing. He noted that below river mile 6, only 
one stable gravel bar contained a diverse mussel fauna. High silt 
deposition from the Missouri River prohibits the formation of mussel 
habitat below this area.
    The majority of the Osage River system has been impounded and is no 
longer suitable for freshwater mussels. The majority of remaining 
mussel habitat occurs below Bagnell dam in the lower 80 miles of the 
Osage River proper. This river reach is affected by the operation of 
Bagnell dam, which alters flow and temperature regimes, lowers 
dissolved oxygen levels, and causes channel scouring and accelerated 
bank erosion. Several instream gravel mining operations currently exist 
in the Osage River that physically remove mussels from the water and 
cause headcutting and siltation.

Lower Mississippi River Basin

    Channelization, levee construction, diversion ditches, control 
structures, and floodways have drastically altered much of the St. 
Francis River from the mouth above Helena, Arkansas, to Wappapello Dam, 
Missouri (Ahlstedt and Jenkinson 1987, Bates and Dennis 1983). Bates 
and Dennis (1983) determined that of the 54 sites sampled, 15 were 
productive, 10 were marginal, and 29 had either no shells or dead 
specimens only. They identified 77 km (48 mi) that may still provide 
suitable mussel habitat, but did not collect scaleshell mussels. All 
the remaining river miles are unsuitable for mussels.
    The White River between Beaver Reservoir and its headwaters, due to 
municipal pollution, gravel dredging, and dam construction, is no 
longer suitable for mussels (Gordon 1980). Navigational maintenance 
activities continue to destroy habitat from Newport to the confluence 
of the Mississippi River (Bates and Dennis 1983). This habitat 
destruction has relegated mussel species to a few refugial sites.
    Species richness in the Spring River below river mile nine has 
declined markedly from past surveys, with the lower 5.0 km (3.0 mi) of 
river completely depleted of mussels and no longer supporting suitable 
habitat (Miller and Hartfield 1986, Gordon et al. 1984). Sand and 
gravel dredging; the destruction of stream banks, disturbance of mussel 
beds, and the deposition of wastes from livestock movements; siltation; 
and surface run-off of pesticide and fertilizer appear to be 
contributing factors in the degradation of this river reach (Gordon et 
al. 1984).
    Within Frog Bayou, potential habitat is restricted to the area 
between Rudy and the confluence of the Arkansas River. Within this 
area, streambank modifications and in-stream gravel mining are 
degrading scaleshell mussel habitat. Two reservoirs, one near Maddux 
Spring and the other at Mountainburg, impact the river above Rudy. 
Below the confluence of the Arkansas River, Gordon (1980) did not find 
live mussels, likely due to dredging activities (Gordon 1980).
    The proposed Tuskahoma Reservoir (located above Hugo Reservoir) is 
a potential threat to mussels in the Kiamichi River. Although the Corps 
has authorized construction, the lack of a local sponsor has rendered 
the project ``inactive'' (David Martinez, Service, Tulsa, pers. comm. 
1997). If constructed, the adverse effects associated with reservoirs 
(including permanent flooding of the channel and disruption of 
reproduction) are likely to destroy the mussel fauna both above and 
below the proposed dam site.
    Sewage pollution, gravel dredging, and reservoirs continue to 
impact the Little River. Pine Creek Reservoir impounds the mainstem of 
the river. Further downstream, Broken Bow Reservoir impounds a major 
tributary to the Little River, the Mountain Fork River. Below Pine 
Creek Lake, the mussel fauna is severely depleted but recovers with 
increasing distance from the impoundment (Caryn Vaughn, in litt. 1997). 
However, the discharge of reservoir water from Pine Creek and periodic 
discharge of pollution from Rolling Fork Creek seriously impact any 
remaining scaleshell mussels and prohibit any future recolonization 
(Clarke 1987).
    Hydroelectric dams and artificial lakes have impacted the Ouachita 
River. The ``Old River'' (an oxbow system off the mainstem), is now 
essentially a series of muddy, stagnant pools, with water quality 
problems resulting from surrounding dumps (Clarke 1987).
    In summary, many of the same threats that caused the extirpation of 
historical populations of scaleshell mussels still exist and continue 
to threaten extant populations. Nonpoint and point source pollution is 
currently affecting the Spring River in Arkansas (Gordon et al. 1984, 
Miller and Hartfield 1986) and the Little River in Oklahoma (Clarke 
1987, Vaughn 1994). Loss of stable substrates and sedimentation is 
causing deleterious effects in the Meramec and Bourbeuse Rivers, 
Missouri (Sue Bruenderman, pers. comm. 1998); Gasconade River, Missouri 
(Buchanan 1994); Frog Bayou, Arkansas (Gordon 1980); and Spring River, 
Arkansas (Gordon et al. 1984). Unregulated sand and gravel mining are 
eliminating important pool habitat (for both scaleshell mussels and 
potential fish hosts) in the Meramec, Bourbeuse, Big, and Gasconade 
Rivers in Missouri (Bruenderman, MDC, pers. comm. 1998). Impoundments, 
channelization, and other dredging activities (e.g., sand and gravel 
mining) are destroying mussel beds and impairing water quality in Frog 
Bayou, Arkansas (Gordon 1980); St. Francis River, Arkansas (Ahlstedt 
and Jenkinson 1987); White River, Arkansas (Bates and Dennis 1983); 
Spring River, Arkansas (Gordon et al. 1984); and Ouachita River, 
Arkansas (Clarke 1987). The proposed Kiamichi River Reservoir, if 
constructed, will have adverse impacts on any remaining populations in 
Oklahoma. Nearly all scaleshell mussel populations are now restricted 
to small stretches of rivers with little, if any, potential for 
expansion or recolonization to other areas. For example, sewage 
pollution, gravel dredging, and reservoir construction have degraded 
the Little River in Oklahoma to the extent that only a few small 
stretches are able to support mussels.

B. Overutilization for Commercial, Recreational, Scientific, or 
Educational Purposes

    It is unlikely that commercial mussel collectors ever purposefully 
collected scaleshell mussels because of their small size and thin 
shell. It is probable, however, that over-harvesting activities that 
removed entire mussel beds impacted scaleshell mussel populations. For 
example, according to local fishermen, during a period of extended 
drought, mussel harvesters severely over-collected mussel beds in the 
Spring and Black Rivers and completely destroyed most beds (Gordon et 
al. 1984). Thus, scaleshell mussel populations may have been impacted 
by habitat destruction (i.e., disturbance of stream bottom), trampling, 
and removal of individuals from the stream. Individuals dislodged from 
the stream bottom could be washed away into unsuitable habitat. Even 
for mussels returned to the stream, mortality can still occur (Williams 
et al. 1993). Today, intensive mussel collecting activity will have 
severe adverse affects on existing populations, because scaleshell 
mussels now occur in very small, isolated areas. The destruction of 
only a few individuals could be a contributing factor in the 
extirpation of some populations.
    As scaleshell mussels become more uncommon, the interest of 
scientific and

[[Page 51335]]

shell collectors will increase. Scaleshell mussel occurrences are 
generally localized, easily accessible, and exposed during low flow 
periods, and, therefore, are also vulnerable to take for fish bait, 
curiosity, or vandalism. Up to five freshwater mussels per day, 
including scaleshell, may be legally collected in Missouri and used for 
fishing bait (Sue Bruenderman, pers. comm. 1998). However, the low 
density of scaleshell mussels minimizes the likelihood of a scaleshell 
being collected.

C. Disease or Predation

    Although natural predation is usually not a factor for stable, 
healthy mussel populations, small mammal predation could pose a problem 
for scaleshell mussel populations (Gordon 1991). While the large size 
or thick shells of some species afford protection from small mammal 
predators, the small size and fragile shell of the scaleshell mussel 
makes it an easy and desirable prey species. Small mammals, such as 
muskrats and racoons, may be common predators of scaleshell mussels 
throughout their range, particularly during periods of low water. For 
example, fresh scaleshell mussel shells were found among other species 
at several active raccoon middens (feeding areas) during a freshwater 
mussel survey of the Meramec and Bourbeuse Rivers (Roberts and 
Bruenderman 2000). These mammals are so effective at finding and eating 
freshwater mussels that malacologists consider collecting dead shells 
from middens a good way to determine the presence of rare species. 
Extant scaleshell mussel populations in Arkansas and Oklahoma are 
small, isolated, and have very limited recolonization potential. Thus, 
the removal of even a small number of individuals could significantly 
affect these populations. Small populations are less resilient to these 
natural predators, and therefore, are much more threatened by them. 
Consequently, predation could exacerbate ongoing population declines of 
scaleshell mussels.
    Bacteria and protozoans persist at unnaturally high concentrations 
in streams with high sediment load or in water bodies affected by point 
source pollution, such as sewage treatment plants (Goudreau et al. 
1988). At such concentrations, mussel ova and glochidia are more 
subject to infection (Ellis 1929). Disease and parasites may have 
caused major die-offs of freshwater mussels in the late 1970s 
throughout the eastern United States (Neves 1986). For example, 
significant die-offs of freshwater mussels occurred in 1977 and 1978 in 
the Meramec and Bourbeuse Rivers. Large numbers of mussels of all 
species, including scaleshell, were lost. Buchanan (1986) presumed an 
epizootic or other disease caused the die-off since no environmental 
impact was reported or could be found.

D. The Inadequacy of Existing Regulatory Mechanisms

    The passage of the CWA resulted in many positive consequences for 
freshwater ecosystems (including a decrease in lead and fecal coliform 
bacteria), and set the stage for the regulations and the water 
standards that exist today. Goals of the CWA include the protection and 
enhancement of fish, shellfish, and wildlife; providing conditions 
suitable for recreation in surface waters; and eliminating the 
discharge of pollutants into U.S. waters. However, despite the 
implementation of the CWA, degraded water quality still presents 
problems for sensitive aquatic organisms such as freshwater mussels. 
Specifically, nationwide stream and lake sampling has indicated 
continuing increases in nitrate, chloride, arsenic, and cadmium 
concentrations (Neves 1993). Nonpoint pollution sources appear to be 
the cause of increases in nitrogen. Many of the impacts discussed above 
occurred in the past as unintended consequences of human development. 
Improved understanding of these consequences has led to regulatory 
(e.g., CWA) and voluntary measures (e.g., best management practices for 
agriculture and silviculture) and improved land use practices that are 
generally compatible with the continued existence of the scaleshell 
mussel. Nonetheless, the scaleshell mussel is highly restricted in 
numbers and distribution and shows little evidence of recovering from 
historical habitat degradation and losses.
    As discussed previously (see Factor A under ``Summary of Factors 
Affecting the Species'' and Issue 4), a 1997 court ruling reduced the 
Corps' authority to regulate instream gravel mining. The MDNR is 
currently responsible for regulating gravel mining in Missouri, but has 
limited regulatory authority, and several conditions that were 
previously required by the Corps are no longer in place. These 
guidelines avoided many adverse effects to mussels including 
headcutting, channel modification, and the physical removal of mussels. 
Further, city, county, and State operators using their own equipment 
and private operations are not required to obtain a MDNR permit for 
instream gravel mining. In Arkansas, instream gravel mining will still 
be controlled by the Arkansas Open-Cut Mining and Land Reclamation 
Code, which contains required conditions to reduce impacts (Roell 
1999).
    Additionally, since MDNR is not a Federal agency, section 7 of the 
Act, which required the Corps to consult with the Service regarding the 
presence of federally listed species at proposed gravel mining sites, 
is no longer applicable. Without the section 7 consultation process, 
mussel beds containing federally listed species could be adversely 
affected by gravel mining operations.
    The Corps will still retain oversight authority and require a 
permit for gravel mining activities that deposit fill into streams 
under section 404 of the CWA. Additionally, a Corps permit would be 
required under section 10 of the Rivers and Harbors Act for navigable 
waterways including the lower 80 km (50 mi) of the Meramec River. 
However, many gravel mining operations do not fall under these two 
categories.
    Although recognized by species experts as threatened in Arkansas, 
the scaleshell mussel is not afforded state protection. Missouri and 
Oklahoma list the scaleshell mussel as a species of conservation 
concern (Sue Bruenderman, in litt. 1998; Caryn Vaughn, pers. comm. 
1995). However, these designations are primarily used for planning and 
communication purposes and do not afford any significant State 
protection from direct take and habitat destruction (David Martinez, 
pers. comm. 1997; Paul McKenzie, Service, Columbia, MO, pers. comm. 
1997). Therefore, scaleshell mussels may be collected, harmed, or 
killed in Missouri and Oklahoma without a permit. Without additional 
regulations providing habitat protection, as well as protection from 
direct and indirect take, populations of scaleshell mussels will 
continue to decline and disappear.

E. Other Natural or Manmade Factors Affecting Its Continued Existence

    As a consequence of the above factors, the inherent biological 
traits of freshwater mussels increase their vulnerability to extinction 
(Neves 1993). For example, the larval stage (glochidium) of most 
mussels is dependent on a few or one specific host fish (Neves 1993). 
The scaleshell mussel is believed to use the freshwater drum as its 
sole host fish species. This trait greatly reduces the likelihood of 
contact between glochidia and suitable hosts. Watters (1995) postulated 
that the glochidia must acquire suitable hosts within 24 hours to 
survive. Therefore, a reduction or loss of host fish

[[Page 51336]]

populations will lead to reduced glochidial survival and a decline in 
reproductive success, which will inevitably adversely impact scaleshell 
mussel populations.
    Once a larva successfully transforms on a host, it is further 
challenged with dropping off onto suitable habitat. Watters (1995) 
reported that estimated chances of successful glochidial transformation 
and excystment (detachment) range between 0.0001 percent (Jansen and 
Hanson 1991) and 0.000001 percent (Young and Williams 1984). As a 
result of fish host-specificity and the difficulty of locating suitable 
habitat, even under optimal conditions, freshwater mussel population 
growth occurs very slowly. Furthermore, the sedentary nature of mussels 
limits their dispersal capability. This trait, coupled with low 
recruitment success, translates into the need for decades of 
immigration and recruitment for re-establishment of self-sustaining 
populations.
    The small number and low density of the remaining scaleshell mussel 
populations exacerbate the threats to its survival posed by the above 
factors. Although the scaleshell mussel was always locally rare though 
broadly distributed, the widespread loss of populations and the limited 
number of collections in recent years indicates that the current 
population densities are much lower (due to the previously identified 
threats) than historical levels. Despite any evolutionary adaptations 
for rarity, habitat loss and degradation increase a species' 
vulnerability to extinction (Noss and Cooperrider 1994). Numerous 
studies have shown that with decreasing habitat availability, the 
probability of extinction increases. Similarly, as the number of 
occupied sites decreases, and the distances between them increases, the 
likelihood of extinction increases (Vaughn 1993). This increased 
vulnerability is the result of chance events. Environmental variation, 
random or predictable, naturally causes fluctuations in populations. 
However, small and low density populations are more likely to fluctuate 
below the minimum viable population (i.e., the minimum number of 
individuals needed in a population to persist). If population levels 
stay below this minimum size, an inevitable, and often irreversible, 
slide toward extinction will occur. Further, the shorter life span of 
the scaleshell mussel may render it less able to tolerate periods of 
poor recruitment or increased mortality than are longer-lived mussel 
species (Chris Barnhart, in litt. 1999).
    Small populations are also more susceptible to inbreeding 
depression and genetic drift. Populations subjected to either of these 
problems usually have low genetic diversity, which reduces fertility, 
survivorship, and the ability to adapt to environmental changes. Also, 
chance variation in age and sex ratios can affect birth and deaths 
rates. Skewing of these ratios may lead to death rates exceeding the 
birth rates, and when this occurs in small populations there is a 
higher risk of extinction.
    Similarly, the fertilization success of mussels may be related to 
population density, with a threshold density required for any 
reproductive success to occur (Downing et al. 1993). Small mussel 
populations may have individuals too scattered to reproduce 
effectively. Many of the remaining scaleshell mussel populations may be 
at or below this threshold density. These populations will be, if the 
aforementioned threats go unabated, forced below or forced to remain 
below the minimum threshold. As a result, reproduction is diminished or 
ceases, and the current decline to extinction will be accelerated.
    Furthermore, species that occur in low numbers must rely on 
dispersal and immigration for long-term persistence. In order to retain 
genetic viability and guard against chance extinction, movement between 
populations must occur. Although the scaleshell mussel naturally occurs 
in patches within a river and necessarily possesses mechanisms to adapt 
to such a discontinuous distribution, anthropogenic (man-made) 
influences have fragmented and further lengthened the distance between 
patches. Empirical studies have shown that with increasing isolation, 
immigration and colonization rates decrease. Also, as previously 
explained, natural recolonization of mussels occurs at a very low rate 
(Vaughn 1993). Therefore, preservation of a population (including all 
partially isolated patches in a river) structure is imperative for 
long-term freshwater mussel survival. Unfortunately, many of the extant 
scaleshell mussel populations now occur as single, isolated sites. 
These highly isolated populations are very susceptible to chance events 
and local extirpation with no chance of recolonization.
    Lastly, the recent invasion of the exotic zebra mussel (Dreissena 
polymorpha) poses a substantial threat to native unionids (Herbert et 
al. 1989). The introduction of Dreissena into North America probably 
resulted from an ocean-crossing vessel that discharged freshwater 
ballast from Europe containing free-swimming larvae of the zebra mussel 
(Griffiths et al. 1991). Since its introduction in 1985, this prolific 
species has spread throughout the Mississippi River and many of its 
tributaries including the Illinois and Ohio basins and the Arkansas and 
Tennessee rivers. Zebra mussels starve and suffocate native mussels by 
attaching to their shells in large numbers. The spread of this prolific 
species has caused severe declines of native freshwater mussel species 
in many areas (Tucker et al. 1993; Kent Kroonemeyer, Service in litt. 
1994; Illinois Natural History Survey, in litt. 1995; Corps, in litt. 
2000).
    Given that recreational and commercial vessels greatly facilitate 
the spread of zebra mussels, and because of the proliferation and 
spread that has already occurred, invasion of the zebra mussel into 
portions of the middle and lower Mississippi Basin is likely (Alan 
Buchanan, pers. comm. 1995). If zebra mussels successfully colonize 
rivers occupied by scaleshell mussels, its continued survival will be 
further jeopardized. The zebra mussel has been found recently within 
the scaleshell mussels' extant range in the middle Mississippi Basin. 
In the summer of 1999, a live zebra mussel was collected in the Lower 
Meramec River at river mile 6.9 (Chris Barnhart, in litt. 1999). The 
Meramec Basin appears to support the largest remaining populations of 
scaleshell mussels. Zebra mussels are likely to successfully colonize 
the Meramec River, because it appears to be similar in most ways to 
other tributaries of the Mississippi River that already have 
established populations of zebra mussels. Another live zebra mussel was 
collected in 1999 from the Missouri River near Sioux City, Iowa (John 
LaRandeau, in litt. 1999). If zebra mussels have successfully colonized 
the Missouri River, it is likely that they will spread into the 
Gasconade River, which has perhaps the largest population of scaleshell 
mussels next to those in the Meramec Basin.

Conclusion

    Significant habitat loss, range restriction, and population 
fragmentation and size reduction have rendered the scaleshell mussel 
vulnerable to extinction. The scaleshell mussel has disappeared from 
the entire upper and most of the middle Mississippi River drainages. Of 
the 55 known historical populations, 14 and possibly 20, remain. 
Although much of the decline occurred before 1950, population declines 
continue in most of the species' range, and numerous threats, including 
water quality degradation, loss of stable substrates, sedimentation, 
channelization, gravel mining, dredging, and impoundments,

[[Page 51337]]

are impacting the few remaining viable extant populations. The small 
number and low density of the remaining scaleshell mussel populations 
exacerbate the threats and adverse effects of chance events to 
scaleshell mussels. Only one of the remaining populations is believed 
to be stable.
    We have carefully assessed the best scientific and commercial 
information available regarding the past, present, and future threats 
faced by the scaleshell mussel in determining this rule final. The 
present distribution and abundance of the scaleshell mussel are at risk 
given the potential for these impacts to continue. Therefore, based on 
this evaluation, it is appropriate that the scaleshell mussel be listed 
as an endangered species. The Act defines an endangered species as one 
that is in danger of extinction throughout all or a significant portion 
of its range. A threatened species is one that is likely to become an 
endangered species in the foreseeable future throughout all or a 
significant portion of its range. Endangered status is appropriate for 
the scaleshell mussel given the extent and magnitude of habitat loss, 
range restriction, and population fragmentation that has occurred, and 
the continued vulnerability of this species to such threats. These 
threats are ongoing, and there is clear evidence that some of them, 
such as sand and gravel mining in the core of the species' current 
range, have actually increased their adverse impacts on mussel habitat 
in the last several years.

Critical Habitat

    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 means 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.
    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, the Secretary designate critical habitat at the time 
the species is determined to be endangered or threatened. Section 
4(b)(2) of the Act requires us to consider economic and other relevant 
impacts of designating a particular area as critical habitat on the 
basis of the best scientific data available. The Secretary may exclude 
any area from critical habitat if she/he determines that the benefits 
of such exclusion outweigh the benefits of its inclusion, unless to do 
so would result in the extinction of the species. Our regulations (50 
CFR 424.12(a)) state that designation of critical habitat is not 
prudent when one or both of the following situations exist--(i) the 
species is threatened by taking or other activity and the 
identification of critical habitat can be expected to increase the 
degree of threat to the species or (ii) such designation of critical 
habitat would not be beneficial to the species.
    In the proposed rule, we indicated that designation of critical 
habitat was not prudent because of a concern that publication of 
precise maps and descriptions of critical habitat in the Federal 
Register could increase the vulnerability of this species to incidents 
of collection and vandalism. We also indicated that designation of 
critical habitat was not prudent because we believed it would not 
provide any additional benefit beyond that provided by the listing as 
endangered.
    In the last few years, a series of court decisions have overturned 
Service determinations regarding a variety of species that designation 
of critical habitat would not be prudent (e.g., Natural Resources 
Defense Council v. U.S. Department of the Interior 113 F. 3d 1121 (9th 
Cir. 1997); Conservation Council for Hawaii v. Babbitt, 2 F. Supp. 2d 
1280 (D. Hawaii 1998)). Based on the standards applied in those 
judicial opinions, we have reexamined the question of whether critical 
habitat for the scaleshell mussel would be prudent.
    Due to small population size, the scaleshell mussel is vulnerable 
to unrestricted collection, vandalism, or other disturbance. We remain 
concerned that these threats might be exacerbated by the publication of 
critical habitat maps and further dissemination of locational 
information. However, we have examined the evidence available for the 
scaleshell mussel and have not found specific evidence of taking, 
vandalism, collection, or trade of these species or any similarly 
situated species. Consequently, consistent with applicable regulations 
(50 CFR 424.12(a)(1)(i)) and recent case law, at this time we do not 
expect that the identification of critical habitat will increase the 
degree of threat to this species of taking or other human activity.
    In the absence of a finding that critical habitat would increase 
threats to a species, if any benefits would result from a critical 
habitat designation, then a prudent finding is warranted. In the case 
of scaleshell mussel, designation of critical habitat may provide some 
benefits.
    In general, critical habitat identifies areas that may require 
special management considerations or protection, and its designation 
may provide protection to areas where significant threats to a species 
have been identified. Critical habitat receives protection from 
destruction or adverse modification through required consultation under 
section 7 of the Act with regard to actions carried out, funded, or 
authorized by a Federal agency. Section 7 also requires conferences on 
Federal actions that are likely to result in the adverse modification 
or destruction of proposed critical habitat. Aside from the protection 
that may be provided under section 7, the Act does not provide any 
other forms of protection to lands designated as critical habitat.
    Section 7(a)(2) of the Act requires Federal agencies to consult 
with the Service to ensure that any action they carry out, authorize, 
or fund does not jeopardize the continued existence of a federally 
listed species or destroy or adversely modify designated critical 
habitat. A critical habitat designation for habitat currently occupied 
by a species would usually result in the same outcome under section 7 
consultation as would occur if the critical habitat had not been 
designated, because an action that destroys or adversely modifies such 
critical habitat would also be likely to result in jeopardy for the 
species. However, there may be instances where section 7 consultation, 
and subsequent protection, would be triggered only if critical habitat 
is designated, such as areas where a species is not believed to 
currently exist, but where reestablishment is needed to conserve the 
species. In the case of the scaleshell mussel, the species' low numbers 
and highly fragmented distribution will likely require the 
establishment of additional populations beyond the 14 known extant 
populations. Critical habitat designation of areas most suitable for 
future establishment of scaleshell mussel populations would provide 
habitat protection by triggering section 7 consultations for Federal 
agency actions.
    Designation of critical habitat can help focus conservation 
activities for a listed species by identifying areas that contain the 
physical and biological features essential for the conservation of

[[Page 51338]]

that species, regardless of whether the areas are currently used by the 
species. Designation of critical habitat alerts the public as well as 
land-managing agencies to the importance of these areas.
    We find that critical habitat designation is prudent for the 
scaleshell mussel due to the probable benefits to the species described 
above. We find that these benefits are not outweighed by potential 
increased threats from designating critical habitat.
    However, our budget for listing activities is currently 
insufficient to allow us to immediately complete all of the listing 
actions required by the Act. Listing the scaleshell mussel without 
designation of critical habitat will allow us to concentrate our 
limited resources on other listing actions that must be addressed, 
while allowing us to invoke protections needed for the conservation of 
this species without further delay. This is consistent with section 
4(b)(6)(C)(i) of the Act, which states that final listing decisions may 
be issued without critical habitat designations when it is essential 
that such determinations be promptly published. The legislative history 
of the 1982 Act amendments also emphasized this point: ``The Committee 
feels strongly, however, that, where biology relating to the status of 
the species is clear, it should not be denied the protection of the Act 
because of the inability of the Secretary to complete the work 
necessary to designate critical habitat. * * * The committee expects 
the agencies to make the strongest attempt possible to determine 
critical habitat within the time period designated for listing, but 
stresses that the listing of species is not to be delayed in any 
instance past the time period allocated for such listing if the 
biological data is clear but the habitat designation process is not 
complete'' (H.R. Rep. No. 97-567 at 20 (1982)). We will prepare a 
critical habitat designation in the future as soon as there are 
resources available and other listing duties under the Act will allow.

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 
conservation actions by Federal, State, and local agencies, private 
organizations, and individuals. The Act provides for possible land 
acquisition and 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 taking and harm are 
discussed, in part, below.
    Section 7(a) of the Act, as amended, requires Federal agencies to 
evaluate their actions with respect to any species that is listed as 
endangered or threatened and with respect to its critical habitat, if 
any is being designated. Regulations implementing this interagency 
cooperation provision of the Act are codified at 50 CFR Part 402. 
Section 7(a)(2) of the Act requires Federal agencies to ensure that 
activities they authorize, fund, or carry out are not likely to 
jeopardize the continued existence of such a species or to destroy or 
adversely modify its critical habitat. If a Federal action may affect a 
listed species or its critical habitat, the responsible Federal agency 
must enter into consultation with us.
    Federal activities that could occur and impact the scaleshell 
mussel, include, but are not limited to, issuance of permits for 
reservoir construction, stream alterations, waste-water facility 
development, water withdrawal projects, pesticide registration, 
agricultural assistance programs, mining, road and bridge construction, 
Federal loan programs, water allocation, and hydropower licensing or 
relicensing. In our experience, nearly all section 7 consultations 
result in protecting the species while still meeting the project's 
objectives.
    The Act and implementing regulations found at 50 CFR 17.21 set 
forth a series of general prohibitions and exceptions that apply to all 
endangered wildlife. The 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, 
capture, 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 endangered 
species. It also is illegal to possess, sell, deliver, carry, 
transport, or ship any such wildlife that has been taken illegally. 
Certain exceptions apply to our agents and agents of State conservation 
agencies.
    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 (e.g., activities subject to 
sections 402, 404, and 405 of the CWA and discharges regulated under 
the National Pollutant Discharge Elimination System).
    (2) Actions that may affect the scaleshell mussel 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 pursuant to 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 if a scaleshell mussel is collected it is 
immediately released, unharmed.
    Activities that we believe could potentially result in take of 
scaleshell mussels include but are not limited to:
    (1) Illegal collection or capture of the species;
    (2) Unlawful destruction or alteration of the species' occupied 
habitat (e.g., 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 scaleshell mussels.
    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 Columbia, Missouri Field office (see ADDRESSES). 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, Whipple Federal 
Building, 1 Federal Drive, Fort Snelling, MN 55111 (Phone 612/713-5350; 
Fax 612/713-5292).

[[Page 51339]]

National Environmental Policy Act

    We have determined that we do not need to prepare an Environmental 
Assessment, as defined under the authority of the National 
Environmental Policy Act of 1969, in connection with regulations 
adopted pursuant to section 4(a) of the Endangered Species Act, as 
amended. We published a notice outlining our reasons for this 
determination in the Federal Register on October 25, 1983 (48 FR 
49244).

Paperwork Reduction Act

    This rule does not contain any new collections of information other 
than those already approved under the Paperwork Reduction Act, 44 
U.S.C. 3501 et seq., and assigned Office of Management and Budget 
control number 1018-0094. An agency may not conduct or sponsor, and a 
person is not required to respond to a collection of information, 
unless it displays a currently valid control number. For additional 
information concerning permit and associated requirements for 
endangered species, see 50 CFR 17.22.

References Cited

    A complete list of all references cited herein, as well as others, 
is available upon request from the Field Supervisor (see ADDRESSES).

Authors

    The primary authors of this final rule are Mr. Andy Roberts (see 
FOR FURTHER INFORMATION CONTACT) and Ms. Jennifer Szymanski (U.S. Fish 
and Wildlife Service, Whipple Federal Building, 1 Federal Drive, Fort 
Snelling, MN 55111-4056).

List of Subjects in 50 CFR Part 17

    Endangered and threatened species, Exports, Imports, Reporting and 
record keeping requirements, Transportation.

Regulation Promulgation

    Accordingly, we hereby amend part 17, subchapter B of chapter I, 
title 50 of the Code of Federal Regulations, as set forth below:

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. Section 17.11(h) is amended by adding the following, in 
alphabetical order, under Clams to the List of Endangered and 
Threatened Wildlife to read as follows:


Sec. 17.11  Endangered and threatened wildlife.

* * * * *
    (h) * * *

--------------------------------------------------------------------------------------------------------------------------------------------------------
                        Species                                                    Vertebrate
--------------------------------------------------------                        population where                                  Critical     Special
                                                            Historic range       endangered or         Status      When listed    habitat       rules
           Common name                Scientific name                              threatened
--------------------------------------------------------------------------------------------------------------------------------------------------------
 
                   *                  *                  *                  *                  *                  *                  *
              Clams
 
                   *                  *                  *                  *                  *                  *                  *
Mussel, scaleshell...............  Leptodea leptodon...  U.S.A. (AL, AR, IA,  NA.................  E                       714           NA           NA
                                                          IL, IN, KY, MN,
                                                          MO, OH, OK, SD,
                                                          TN, WI).
 
                   *                  *                  *                  *                  *                  *                  *
--------------------------------------------------------------------------------------------------------------------------------------------------------


    Dated: September 28, 2001.
Marshall P. Jones, Jr.
Acting Director, Fish and Wildlife Service.
[FR Doc. 01-24804 Filed 10-5-01; 8:45 am]
BILLING CODE 4310-55-P