Endangered and Threatened Wildlife and Plants; Proposed Rule To List the Scaleshell Mussel as Endangered

DEPARTMENT OF THE INTERIOR

Fish and Wildlife Service

50 CFR Part 17

RIN 1018-AF57

Endangered and Threatened Wildlife and Plants; Proposed Rule To

List the Scaleshell Mussel as Endangered

AGENCY: Fish and Wildlife Service, Interior.

ACTION: Proposed rule.

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SUMMARY: We, the U.S. Fish and Wildlife Service, propose endangered

status pursuant to the Endangered Species Act of 1973, as amended

(Act), for the scaleshell mussel (Leptodea leptodon). This species

historically occurred in 13 states in the eastern United States.

Currently, the species is known from a few scattered populations within

the Mississippi River Basin in Missouri, Oklahoma, and Arkansas.

Scaleshell inhabits medium-sized to large rivers with stable channels

and good water quality. The abundance and

distribution of scaleshell have decreased due to habitat loss and

adverse effects associated with water quality degradation, reservoir

construction, sedimentation, channelization, and dredging. These

habitat changes have resulted in significant extirpations, restricted

and fragmented distributions, and poor recruitment. This proposed rule,

if made final, would extend the Act's protection to the scaleshell

mussel.

DATES: Send your comments to reach us on or before October 12, 1999. We

will not consider comments received after the above date in making our

decision on the proposed rule. We must receive requests for public

hearings by September 27, 1999.

ADDRESSES: The complete administrative file for this rule is available

for inspection, by appointment, during normal business hours at the

U.S. Fish and Wildlife Service, Bishop Henry Whipple Federal Building,

1 Federal Drive, Fort Snelling, MN 55111-4056, (telephone 612-713-

5342).

FOR FURTHER INFORMATION CONTACT: Andy Roberts at the U.S. Fish and

Wildlife Service, Columbia Field Office, 608 East Cherry Street, Room

200, Columbia, Missouri 65201, (telephone 573-876-1911, ext. 110).

pointment, during normal business hours at the

U.S. Fish and Wildlife Service, Bishop Henry Whipple Federal Building,

1 Federal Drive, Fort Snelling, MN 55111-4056, (telephone 612-713-

5342).

FOR FURTHER INFORMATION CONTACT: Andy Roberts at the U.S. Fish and

Wildlife Service, Columbia Field Office, 608 East Cherry Street, Room

200, Columbia, Missouri 65201, (telephone 573-876-1911, ext. 110).

SUPPLEMENTARY INFORMATION:

Background

The scaleshell mussel (Leptodea leptodon) was described by

Rafinesque in 1820. Synonymy includes Unio velum (Say), Sympnynota

tenuissima (Lea), Lampsilis blatchleyi (Daniels), and Lampsilis

leptodon (Rafinesque).

Buchanan (1980), Cummings and Mayer (1992), Oesch (1995), and

Watters (1995) provide descriptions of the scaleshell mussel

(scaleshell). The shell grows to about three to ten centimeters (one to

four inches) in length. The shells are elongate, very thin, and

compressed. The anterior end is rounded. In males, the posterior 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 margin is straight and the ventral margin

is gently rounded. Beaks (the raised or domed part of the dorsal margin

of the shell) are small and low, 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 and one fine

tooth in the right. The beak cavity is very shallow. The nacre (the

interior layer of the shell) is pinkish white or light purple and

highly iridescent.

Life History

e 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 and one fine

tooth in the right. The beak cavity is very shallow. The nacre (the

interior layer of the shell) is pinkish white or light purple and

highly iridescent.

Life History

The general biology of scaleshell is similar to other bivalved

mollusks belonging to the family Unionidae. Adults are filter-feeders,

spending their entire lives partially or completely buried within the

substrate (Murray and Leonard 1962). Their food includes detritus,

plankton, and other microorganisms (Fuller, 1974). Unionids have an

unusual mode of reproduction. Their life cycle includes a brief,

obligatory parasitic stage on fish. Eggs develop into microscopic

larvae (glochidia) within special gill chambers (ectobranchous

marsupia) of the female. The female expels the mature glochidia and

they must attach to the gills or the fins of an appropriate fish host

to complete development. Host fish specificity varies among unionids.

Some species appear to use a single host, while others can transform on

several host species. Following proper infestation, glochidia transform

into juveniles and excyst (drop off). 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 scaleshell. Baker (1928) surmised that

scaleshell is a long-term brooder (spawns in fall months and females

brood the larvae in their gills until the following spring or summer).

Glochidia present in the ectobranchous marsupia 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)

onths and females

brood the larvae in their gills until the following spring or summer).

Glochidia present in the ectobranchous marsupia 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 (Roe and Lydeard 1997, Watters 1994).

Habitat Characteristics

The scaleshell occurs in a variety of river habitats. For example,

Buchanan (1980, 1994) and Gordon (1991) reported scaleshell from riffle

areas with substrate assemblages of gravel, cobble, boulder, and

occasionally mud or sand. Oesch (1995) considered scaleshell 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. The unifying characteristic appears

to be an intact system (stable channels) with good water quality. This

is consistent with the current distribution of scaleshell. Most extant

populations are restricted to river stretches with stable channels

(Buchanan 1980, Harris 1992) and that have maintained relatively good

water quality (Oesch 1995). Scaleshell is usually collected in

association with a high diversity of other freshwater mussels.

Distribution and Abundance

Scaleshell historically occurred across most of the eastern United

States. While the scaleshell had a broad distribution, locally it was a

rare species (Gordon 1991, Oesch 1995, Call 1900). Williams et al.

t have maintained relatively good

water quality (Oesch 1995). Scaleshell is usually collected in

association with a high diversity of other freshwater mussels.

Distribution and Abundance

Scaleshell historically occurred across most of the eastern United

States. While the scaleshell had a broad distribution, locally it was a

rare species (Gordon 1991, Oesch 1995, Call 1900). Williams et al.

(1993) reported the historical range as Alabama, Arkansas, Illinois,

Indiana, Iowa, Kentucky, Michigan, Mississippi, Missouri, Ohio,

Oklahoma, South Dakota, Tennessee, and Wisconsin. Clarke (1996) also

reported scaleshell occurrence from the Minnesota River, Minnesota.

Within the last 50 years, this species has become increasingly rare and

its range greatly restricted. Of the 53 historical populations, 13

remain scattered within the Mississippi River Basin, including the

Meramec, Bourbeuse, Big, and Gasconade Rivers in Missouri; the South

Spring, St. Francis, Little, Mountain Fork, Spring, and South LaFave

Rivers and Frog Bayou and Gates Creek in Arkansas; and the Kiamichi

River in Oklahoma.

Of the 13 extant scaleshell populations, three are thought to be

stable (long term persistence is possible but unsure), two are

declining, four are presumed to be declining (long term persistence is

in doubt), and the status of four are unknown. Six additional

populations may also persist but their current status is uncertain due

to lack of recent collections or surveys (Szymanski 1998).

Upper Mississippi River Basin

Scaleshell 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 has not been found in more

ppi River Basin

Scaleshell 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 has not been found in more

than 50 years in the Upper Mississippi Basin and is believed extirpated

from that basin (Kevin Cummings, Illinois Natural History Survey, in

litt. 1994).

Middle Mississippi River Basin

Historically, scaleshell occurred in 25 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, and Big Piney Rivers in

Missouri; and the mainstem Missouri River in South Dakota. The

scaleshell has been extirpated from most of the middle Mississippi

River Basin. Currently, the scaleshell is extant in four, possibly

five, rivers within the Meramec River and Missouri River drainages in

Missouri as described below.

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. Seven of the

14 sites were in the lower 112 miles of the Meramec River, five in the

lower 54 miles of the Bourbeuse River, and two in the lower 10 miles of

the Big River. In addition to being restricted to only three rivers,

scaleshell is also locally rare

eyed for

mussels at 198 sites within the Meramec River Basin (Buchanan 1980). Of

these sites, 14 had evidence of live or dead scaleshell. Seven of the

14 sites were in the lower 112 miles of the Meramec River, five in the

lower 54 miles of the Bourbeuse River, and two in the lower 10 miles of

the Big River. In addition to being restricted to only three rivers,

scaleshell is also locally rare. Buchanan found that the species

comprised less than 0.1 percent of the 20,589 living naiades found in

the basin. He collected live specimens at four sites, three in the

Meramec and one in the Bourbeuse. Although the lower 108 miles of the

Meramec River had suitable habitat for many rare species, live

scaleshell were found only in the lower 40 miles (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 54 miles of the Bourbeuse River and lower 10 miles 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 (Sue

Bruenderman, Missouri Department of Conservation, in litt. 1998).

Similar to Buchanan's findings (1980), scaleshell represented only 0.4

percent of the living mussels, with specimens 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). The MDC documented live scaleshell at four of the five sites

where Buchanan previously collected live specimens on the Meramec River

(Sue Bruenderman, pers. comm. 1998). One site where they did not

reconfirm scaleshell had only two live mussels where Buchanan had

previously observed 93 living individuals. This site no longer supports

suitable mussel habitat. Although portions of the Meramec River

continue to provide suitable habitat, mussel species diversity and

abundance have declined noticeably above mile 64 since 1980

(Sue Bruenderman, pers. comm. 1998). One site where they did not

reconfirm scaleshell had only two live mussels where Buchanan had

previously observed 93 living individuals. This site no longer supports

suitable mussel habitat. Although portions of the Meramec River

continue to provide suitable habitat, mussel species diversity and

abundance have declined noticeably above mile 64 since 1980.

The number of scaleshell specimens 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 limited availability of mussel habitat and

the loss of mussel beds since 1980 from sedimentation, eutrophication,

and unstable substrates (Buchanan in litt. 1997; Sue Bruenderman pers.

comm. 1998) indicate that scaleshell populations within the Meramec

River Basin are threatened.

Missouri River drainage (South Dakota, Missouri)--Within the

Missouri River drainage, Buchanan (1980, 1994) and Oesch (1995)

reported scaleshell from Missouri, Gasconade, Big Piney and South Grand

Rivers and Auxvasse Creek. The last collection of Scaleshell from

Auxvasse Creek was in the late 1960s (Buchanan, in litt. 1997).

Similarly, the last known collection date for the South Grand is the

early 1970s, and this collection site, now inundated by Truman Lake, is

unsuitable for scaleshell (Buchanan, in litt. 1997). The only specimen

reported from the mainstem Missouri River is from South Dakota adjacent

to the Nebraska border (Hoke 1983). This occurrence represents the

westernmost record within the Upper Mississippi River Basin. A

subsequent survey failed to relocate live specimens or relict shells

(Clarke 1996). However, high water conditions limited Clarke's survey

and it is uncertain if scaleshell is still present below Gavin's Point

Dam (Nell McPhillips, U.S. Fish and Wildlife Service, in litt. 1998)

ka border (Hoke 1983). This occurrence represents the

westernmost record within the Upper Mississippi River Basin. A

subsequent survey failed to relocate live specimens or relict shells

(Clarke 1996). However, high water conditions limited Clarke's survey

and it is uncertain if scaleshell is still present below Gavin's Point

Dam (Nell McPhillips, U.S. Fish and Wildlife Service, in litt. 1998). A

single, fresh dead specimen was collected from Big Piney River in 1981

(Bruenderman, in litt. 1998). No other specimens of scaleshell have

been documented from this river.

Buchanan (1994) surveyed the Gasconade River, and he found it to

support 36 species of freshwater mussels. He collected scaleshell

specimens at eight sites between river miles 6 and 57.7. Buchanan found

only dead shells at two sites and eight live specimens at the remaining

six sites. Overall, scaleshell comprised less than 0.1% of the mussels

collected. If populations still exist in any of the rivers within the

Missouri River drainage, their long-term persistence is undoubtably

precarious.

Middle Mississippi River Basin summary--Of the 25 rivers and

tributaries in the middle Mississippi River Basin, four, and possibly

five, support scaleshell populations today. While populations in the

Meramec and Bourbeuse Rivers are likely stable, numbers in the Big and

Gasconade Rivers are presumed declining, and the status of populations

in the Big Piney River are unknown (Szymanski 1998).

Lower Mississippi River Basin

summary--Of the 25 rivers and

tributaries in the middle Mississippi River Basin, four, and possibly

five, support scaleshell populations today. While populations in the

Meramec and Bourbeuse Rivers are likely stable, numbers in the Big and

Gasconade Rivers are presumed declining, and the status of populations

in the Big Piney River are unknown (Szymanski 1998).

Lower Mississippi River Basin

Scaleshell historically occupied 20 rivers and tributaries in the

lower Mississippi River Basin. These include the St. Francis, White,

James, Spring, Little Missouri, Middle Fork Little Red, Saline,

Ouachita, Cossatot, South Fourche LaFave, 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.

St. Francis River (Arkansas and Missouri)--Bates and Dennis (1983),

Ahlstedt and Jenkinson (1987), Clarke (1985), and Rust (1993) conducted

mussel surveys on the St. Francis River in Arkansas and Missouri.

Records of dead mussels and relict shells indicate that at one time

mussels were distributed throughout the river (Bates and Dennis 1983).

Clarke (1985) documented scaleshell at two sites by single specimens.

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. Although scaleshell was not collected, they identified

48 miles of probable suitable mussel habitat: 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 river miles were unsuitable for mussels.

If scaleshell is extant in the St. Francis River, it will be restricted

to the few patches of suitable habitat.

White River (Arkansas)--Clarke (1996) noted the collection, in

1902, of

, 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 river miles were unsuitable for mussels.

If scaleshell is extant in the St. Francis River, it will be restricted

to the few patches of suitable habitat.

White River (Arkansas)--Clarke (1996) noted the collection, in

1902, 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 individuals.

Navigation maintenance activities have relegated mussel populations to

a few refugial sites, none of which support scaleshell (Bates and

Dennis 1983). Specimens have not been collected from the James River, a

tributary of the White River, since before 1950 (Clarke 1996). It is

unlikely that either river currently supports scaleshell.

Spring River (Arkansas)--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

specimens (Cummings in litt. 1994, Clarke 1996, Arkansas State Highway

and Transportation Dept. 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 three miles of river were

completely depleted of mussels and contained no suitable habitat.

Harris did not document scaleshell in a 1993 survey of the Spring River

(John Harris, Arkansas State University, in litt. 1997).

Scaleshell was collected from the South Fork of the Spring River in

1983 and 1990. During the 1983 survey, Harris (in litt

ller and

Hartfield (1986), reported that the lower three miles of river were

completely depleted of mussels and contained no suitable habitat.

Harris did not document scaleshell in a 1993 survey of the Spring River

(John Harris, Arkansas State University, in litt. 1997).

Scaleshell was 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.

Strawberry River and Myatt Creek (Arkansas)--Records of scaleshell

from the Strawberry River and the Myatt Creek are based on single

specimen collections (Harris in litt. 1997). In 1996, Harris collected

a live specimen from the Strawberry River near the confluence with

Clayton Creek in Lawrence County. He also collected a single relict

specimen from Myatt Creek in Fulton County in 1996 (Harris in litt.

1997).

Little Red River (Arkansas)--The historical locality (near Shirley,

Van Buren County, Arkansas) where a single, specimen of scaleshell 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 six-mile stretch from the confluence of

Tick Creek upstream to the mouth of Meadow Creek.

Arkansas River Basin (Oklahoma and Arkansas)--Scaleshell has been

collected from the Arkansas River Basin in Oklahoma and Arkansas. The

species is reported from the Poteau River in Oklahoma (Gordon 1991),

Frog Bayou in Arkansas (Harris and Gordon 1987), and the South Fourche

La Fave and Mulberry Rivers in Arkansas (Gordon 1991 and Harris 1992)

Tick Creek upstream to the mouth of Meadow Creek.

Arkansas River Basin (Oklahoma and Arkansas)--Scaleshell has been

collected from the Arkansas River Basin in Oklahoma and Arkansas. The

species is reported from the Poteau River in Oklahoma (Gordon 1991),

Frog Bayou in Arkansas (Harris and Gordon 1987), and the South Fourche

La Fave and Mulberry Rivers in Arkansas (Gordon 1991 and Harris 1992).

Despite several freshwater mussel surveys of the Poteau River (Isely

1925, Branson 1984, Harris 1994), only a single, undated specimen has

been collected (Gordon 1980). The persistence of scaleshell in Poteau

River is doubtful.

Frog Bayou (Arkansas)--Gordon (1980) collected two scaleshell

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 scaleshell in Frog Bayou

is uncertain, any remaining individuals are in potential jeopardy due

to limited habitat and in-stream mining activities.

South Fork La Fave River (Arkansas)--The only scaleshell record

from the South Fork La Fave River is based on a single live specimen

found in 1991 (Harris 1992). The potential of discovering additional

populations in this river is unlikely due to the limited availability

of suitable substrate. Similarly, other major tributaries of the South

Fourche La Fave River provide little mussel habitat

South Fork La Fave River (Arkansas)--The only scaleshell record

from the South Fork La Fave River is based on a single live specimen

found in 1991 (Harris 1992). The potential of discovering additional

populations in this river is unlikely due to the limited availability

of suitable substrate. Similarly, other major tributaries of the South

Fourche La Fave River provide little mussel habitat. Like Frog Bayou,

the persistence of scaleshell in this river is in doubt.

Mulberry River (Arkansas)--Although Gordon (1991) reported

scaleshell from the Mulberry River, documentation is lacking (no

written acknowledgment). A recent survey did not find the species in

the Mulberry River (Craig Hilborne, U.S. Forest Service, pers. comm.

1995; Stoeckel et al. 1995). Persistence of scaleshell in the Mulberry

River is unlikely.

Red River Drainage (Oklahoma)--In the Red River drainage, Valentine

and Stansbery (1971) reported the collection of a single, undated

specimen from Gates Creek, a tributary of the Kiamichi River. Isley

(1925) first collected scaleshell from the Kiamichi River in 1925.

Based on his account, the Kiamichi River historically supported a

diverse and abundant mussel fauna. He collected 36 specimens of

scaleshell at one of 22 stations visited. 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 (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

Kiamichi River is in relatively good shape above the Hugo Reservoir,

(Clarke 1987) and may still support a remnant population of scaleshell

ogical 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

Kiamichi River is in relatively good shape above the Hugo Reservoir,

(Clarke 1987) and may still support a remnant population of scaleshell.

Little River, Red River Drainage (Oklahoma)--Although there is no

evidence of scaleshell persisting in the Little River, above the Pine

Creek Reservoir a healthy mussel population persists (Vaughn in litt.

1997). Below Pine Creek Lake, the mussel fauna is severely depleted but

recovers with increasing distance from the impoundment (Vaughn in litt.

1997). Valentine and Stansbery (1971) reported a single specimen from

Mountain Fork. Clarke (1987) hypothesized that, based on the presence

of mussel populations 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

populations have been severely depleted with most no longer containing

live mussels. Although extensive surveys throughout the length of the

Little River have not documented scaleshell, suitable habitat remains

and scaleshell individuals may persist (Vaughn in litt. 1997). However,

the discharge of reservoir water from Pine Creek and periodic discharge

of pollution from Rolling Fork Creek would seriously impact any

remaining viable populations and prohibit any future recolonization

(Clarke 1987).

If scaleshell still occurs in the Red River drainage in Oklahoma,

extant populations are probably small and are

eshell individuals may persist (Vaughn in litt. 1997). However,

the discharge of reservoir water from Pine Creek and periodic discharge

of pollution from Rolling Fork Creek would seriously impact any

remaining viable populations and prohibit any future recolonization

(Clarke 1987).

If scaleshell still occurs 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 in Oklahoma is

doubtful.

Cossatot and Saline Rivers (Arkansas)--Harris collected single

specimens of scaleshell from the Cossatot and Saline Rivers in Arkansas

in 1983 (Harris in litt. 1997) and 1987 (Harris pers. comm. 1995),

respectively. No other information is available for either river. The

existence of scaleshell in the Ouachita River and its two tributaries,

the Saline River and Little Missouri River, is sporadic as well. Both

the Little Missouri and Saline rivers records are based on single

specimens. The Saline River specimen was collected in 1946 (Clarke

1996), and the Little Missouri River collection record is from 1995

(Harris in litt. 1997). Four undated museum specimens taken from

Arkadelphia, Clark County, Arkansas document the occurrence of

scaleshell in the Ouachita River (Clarke 1996). Based on the few

collections and the limited habitat available, the long-term

persistence of scaleshell in Cossatot, Saline, Little Missouri, and

Ouachita Rivers is precarious.

Lower Mississippi River Basin summary--Of these 20 rivers and

tributaries in the lower Mississippi River Basin, nine, and possibly an

additional five, support scaleshell populations today. Of these

populations, the South Spring River is likely stable; the St

ted habitat available, the long-term

persistence of scaleshell in Cossatot, Saline, Little Missouri, and

Ouachita Rivers is precarious.

Lower Mississippi River Basin summary--Of these 20 rivers and

tributaries in the lower Mississippi River Basin, nine, and possibly an

additional five, support scaleshell populations today. Of these

populations, the South Spring River is likely stable; the St. Francis

River, Kiamichi River, Little River, and Mountain Fork are declining;

the Spring River, Frog Bayou, South Fourche LaFave River, and Gates

Creek are presumed declining; and the status of populations in Mayatt

Creek, Strawberry River, Cossatot River, Saline River and Little

Missouri River are unknown (Szymanski 1998).

Previous Federal Action

We had identified the scaleshell as a Category 2 species in notices

of review published in the Federal Register on May 22, 1984 (49 FR

21664). Scaleshell remained a Category 2 in subsequent notices

including January 6, 1989 (54 FR 554), November 21, 1991 (56 FR 58804),

November 15, 1994 (59 FR 58982). Prior to 1996, a Category 2 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 threat were not available to

support a proposed rule. We stopped 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 to propose it for protection under the Act. We designated

scaleshell as a candidate species on October 16, 1998.

On May 8, 1998, we published Listing Priority Guidance for Fiscal

Years 1998 and 1999 (63 FR 25502)

signating 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 to propose it for protection under the Act. We designated

scaleshell as a candidate species on October 16, 1998.

On May 8, 1998, we published Listing Priority Guidance for Fiscal

Years 1998 and 1999 (63 FR 25502). The guidance clarifies the order in

which we will process rulemakings, giving highest priority (Tier 1) to

processing emergency rules to add species to the Lists of Endangered

and Threatened Wildlife and Plants (Lists); second priority (Tier 2) to

processing final determinations on proposals to add species to the

Lists, processing new proposals to add species to the Lists, processing

administrative findings on petitions (to add species to the Lists,

delist species, or reclassify listed species), and processing a limited

number of proposed or final rules to delist or reclassify species; and

third priority (Tier 3) to processing proposed or final rules

designating critical habitat. The processing of this proposed rule

falls under Tier 2.

Summary of Factors Affecting the Species

Section 4 of the Act and regulations (50 CFR Part 424) promulgated

to implement the listing provisions of the Act set forth the procedures

for adding species to the Federal lists. 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

scaleshell (Leptodea leptodon) are as follows:

A. The Present or Threatened Destruction, Modification, or

Curtailment of its Habitat or Range. The loss of mussel diversity in

the United States has been well documented and is a major concern for

conservation biologists. In a review of the conservation status of

native freshwater fauna, the American Fisheries Society found that of

the 297 native freshwater mussels, 71 percent are imperiled (Williams

et al. 1993)

tened Destruction, Modification, or

Curtailment of its Habitat or Range. The loss of mussel diversity in

the United States has been well documented and is a major concern for

conservation biologists. In a review of the conservation status of

native freshwater fauna, the American Fisheries Society found that of

the 297 native freshwater mussels, 71 percent are imperiled (Williams

et al. 1993). Similarly, The Nature Conservancy recognizes 55 percent

of North America's mussel fauna as extinct or imperiled (Master 1990 in

LaRoe et al. 1995). Habitat loss and degradation are the primary causes

of the precipitous decline of unionids (Neves 1993).

Arguably, the scaleshell has suffered a greater range restriction

than any other unionid. The range of this species was once expansive,

spanning the Mississippi River Basin in at least 53 rivers and 13

States. Today, the range is significantly reduced with known extant

populations persisting in only 13 rivers in three states. Scaleshell

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 some portions of the

species' range and numerous threats are likely to impact the few

remaining viable extant populations. Water pollution, sedimentation,

channelization, and impoundments contributed to the decline of

scaleshell throughout its range. A general description of how these

factors affect mussels is given below. Refer to Szymanski (1998) for a

more detailed discussion.

Mussel biologists generally accept that contaminants are partially

responsible for the decline of mussels (Havlik and Marking 1987,

Williams et al. 1993, Biggins et al. 1996). Because mussels are

sedentary, they are extremely vulnerable to toxic effluents and changes

in water chemistry from point and nonpoint source pollution

n below. Refer to Szymanski (1998) for a

more detailed discussion.

Mussel biologists generally accept that contaminants are partially

responsible for the decline of mussels (Havlik and Marking 1987,

Williams et al. 1993, Biggins et al. 1996). Because mussels are

sedentary, they are extremely vulnerable to toxic effluents and changes

in water chemistry from point and nonpoint source pollution. 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 are 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 in suspension, 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,

74).

Sediment is material that is in suspension, 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 (Ellis 1936, USSCS 1988, Myers et al. 1985) 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). 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 other dredging

operations physically remove mussels along with the dredged material

and may also bury or crush mussels (Watters 1995). Other effects of

dredging extend beyond the excavated area. Headcutting, the upstream

progression of substrate 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 throughout an entire

system (Smith and Patrick 1991). As relatively immobile benthic

invertebrates, mussels are particularly vulnerable to channel

degradation (Hartfield 1993)

eadcutting, the upstream

progression of substrate 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 throughout an entire

system (Smith and Patrick 1991). As relatively immobile benthic

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).

Impoundments affect both upstream and downstream mussel populations

by inducing scouring, changing temperature regimes, and altering

habitat, food, and fish host availability (Vaughn, in litt. 1997).

Impoundments permanently flood stream channels and eliminate flowing

water that are essential habitat for most unionids including scaleshell

(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 populations from each other and from host fishes (Stansbery

1973, Fuller 1974, Vaughn 1993, Williams et al. 1993). The result of

these factors is diminished recruitment success (Layzer et al. 1993).

Dams are effective barriers to fish host movement and migration that

unionids depend on for dispersal. Upstream populations can become

reproductively isolated causing a decrease in genetic diversity. Even

small, lowhead dams can hinder fish movement and isolate mussel

populations from fish hosts

et al. 1993). The result of

these factors is diminished recruitment success (Layzer et al. 1993).

Dams are effective barriers to fish host movement and migration that

unionids depend on for dispersal. Upstream populations can become

reproductively isolated causing a decrease in genetic diversity. Even

small, lowhead dams can hinder fish movement and isolate mussel

populations from fish hosts. For example, Watters (1996) determined

that the upstream distribution of two mussel species, the fragile

papershell (Leptodea fragilis) and pink heelsplitter (Potamilus

alatus), which like scaleshell are also believed to use the freshwater

drum as a sole host, stopped at lowhead dams.

Many of the same threats that caused the extirpation of historical

populations of scaleshell 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 habitat. Today, scaleshell no longer

occurs at disturbed sites that still support other endangered unionids

(Szymanski 1998). This suggests that scaleshell is especially sensitive

to degraded water quality. Given the pervasiveness of the sources of

pollution and sedimentation, it is apparent that these threats will

continue to be problematic for the remaining scaleshell populations.

Upper Mississippi River Basin

Scaleshell 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, Illinois Natural History Survey, 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 from the Upper Mississippi River Basin.

Middle Mississippi River Basin

irpated from this region

(Kevin Cummings, Illinois Natural History Survey, 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 from the Upper Mississippi River Basin.

Middle Mississippi River Basin

Similar to the Upper Mississippi River Basin, threats have lead to

the extirpation of scaleshell from the entire Ohio River Basin. Many of

these threats continue to adversely affect extant populations in the

middle Mississippi River Basin. Scaleshell habitat in the Meramec River

Basin has been reduced in recent years. Buchanan (1980) found

scaleshell in the lower 112 miles of the Meramec River. In 1997,

scaleshell was collected only in the lower 60 miles of the river. 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. Bruenderman (pers. comm. 1998)

attributed this decline primarily to the loss of channel stability. 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 void of mussels when resurveyed in 1997. Buchanan (in litt.

1997) and Bruenderman (pers. comm. 1998) attributed this decline to

several factors, including sedimentation, eutrophication, and unstable

substrates.

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 U.S

ication, and unstable

substrates.

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 U.S. Army Corps of Engineers 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 (Missouri

Department of Conservation 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 25 miles of stream and

negatively impacting the lower 80 miles of the river (Alan Buchanan,

Missouri Department of Conservation, in litt. 1995).

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 30

miles of the Big River, and one dam exists in the lower Bourbeuse

River. These structures are barriers to fish movement during normal

flows (Missouri Department of Conservation 1997).

Gravel mining poses an imminent threat to scaleshell populations in

the Meramec River Basin. In 1998, a court ruling deauthorized the Army

Corps of Engineers (Corps) from regulating gravel mining in the basin.

Prior to that ruling, the Corps required operators to obtain a permit

and follow several guidelines, which avoided adverse effects to

mussels. 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 table. There are many gravel mining

Prior to that ruling, the Corps required operators to obtain a permit

and follow several guidelines, which avoided adverse effects to

mussels. 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 table. There are many gravel mining

operations in the Meramec River Basin. Between 1994 and 1998, the Corps

issued permits for 230 sites (excluding undocumented events). Existing

and future mining operations will not need to obtain a permit or follow

guidelines and may legally mine gravel directly from the Meramec River

and all tributaries (Danny McKlendon, U.S. Army Corps of Engineers, St.

Louis District, pers. comm. 1998).

In 1994, several areas of the Gasconade River were highly unstable,

possibly a result of row-crop farming near the bank 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 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. If populations still exist in any of

the rivers within the Missouri River drainage, their long-term

persistence is undoubtably precarious.

Lower Mississippi River Basin

ies 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. If populations still exist in any of

the rivers within the Missouri River drainage, their long-term

persistence is undoubtably precarious.

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 marginal, and 29 had either no shells or dead specimens

only. They identified 48 miles that may still provide suitable mussel

habitat, but did not collect scaleshell. All the remaining river miles

are unsuitable for mussels. If the scaleshell is extant in the St.

Francis River, it occurs in very small numbers and is restricted to the

remaining few patches of suitable habitat.

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 populations to a few refugial sites,

none of which support scaleshell.

Species richness in the Spring River below river mile 9 has

declined markedly from past surveys, with the lower three miles of

river completely depleted of mussels and no longer supporting suitable

habitat (Miller and Hartfield 1986, Gordon et al. 1984)

Bates and Dennis 1983). This habitat

destruction has relegated mussel populations to a few refugial sites,

none of which support scaleshell.

Species richness in the Spring River below river mile 9 has

declined markedly from past surveys, with the lower three miles of

river completely depleted of mussels and no longer supporting suitable

habitat (Miller and Hartfield 1986, Gordon et al. 1984). Sand and

gravel dredging, livestock movements (i.e., destruction of stream

banks, disturbance of mussel beds, deposition of wastes, etc.),

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 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). Although the

current status of scaleshell in Frog Bayou is uncertain, any remaining

individuals are probably in jeopardy due to limited habitat and in-

stream mining activities.

The proposed Tuskahoma Reservoir (located above Hugo Reservoir) is

a potential threat to mussels in the Kiamichi River. Although the U.S.

Army Corps of Engineers has authorized construction, the lack of a

local sponsor has rendered the project ``inactive'' (David Martinez,

U.S. Fish and Wildlife Service, 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.

Sewage pollution, gravel dredging, and reservoirs continue to

impact the Little River. Pine Creek Reservoir impounds the mainstem of

the river

'' (David Martinez,

U.S. Fish and Wildlife Service, 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.

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 (Vaughn in litt. 1997). The

discharge of reservoir water from Pine Creek and periodic discharge of

pollution from Rolling Fork Creek, however, would seriously impact any

remaining viable populations 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 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). Sedimentation is causing deleterious effects in the

Meramec and Bourbeuse Rivers, MO (Sue Bruenderman, pers. comm. 1998);

Gasconade River, MO (Buchanan 1994); Frog Bayou, AR (Gordon 1980); and

Spring River, AR (Gordon et al. 1984). Unregulated sand and gravel

mining are eliminating important pool habitat (for both scaleshell and

potential fish hosts) in the Meramec, Bourbeuse, Big, and Gasconade

rivers in Missouri (Bruenderman pers. comm. 1998)

eramec and Bourbeuse Rivers, MO (Sue Bruenderman, pers. comm. 1998);

Gasconade River, MO (Buchanan 1994); Frog Bayou, AR (Gordon 1980); and

Spring River, AR (Gordon et al. 1984). Unregulated sand and gravel

mining are eliminating important pool habitat (for both scaleshell and

potential fish hosts) in the Meramec, Bourbeuse, Big, and Gasconade

rivers in Missouri (Bruenderman pers. comm. 1998). Impoundments,

channelization, and other dredging activities (e.g., sand and gravel

mining) are destroying mussel populations and impairing water quality

in Frog Bayou, AR (Gordon 1980); St. Francis River, AR (Ahlstedt and

Jenkinson 1987); White River, AR (Bates and Dennis 1983); Spring River,

AR (Gordon et al. 1984); and Ouachita River, AR (Clarke 1987). The

proposed Kiamichi River Reservoir, if constructed, will have adverse

impacts on any remaining populations in Oklahoma. Nearly all scaleshell

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 so degraded the Little River in Oklahoma that only a

few small stretches are able to support mussel populations.

B. Overutilization for Commercial, Recreational, Scientific, or

Educational Purposes. It is unlikely that commercial mussel collectors

ever purposefully collected scaleshell because of its small size and

thin shell. It is probable, however, that over-harvesting activities

that removed entire mussel beds impacted scaleshell 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, habitat destruction, removal of individuals from the

stream and improper replacement may have indirectly impacted scaleshell

populations. Today, incidental collecting could adversely affect

g 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, habitat destruction, removal of individuals from the

stream and improper replacement may have indirectly impacted scaleshell

populations. Today, incidental collecting could adversely affect

existing populations. In addition to disturbance of the stream bed,

collection or improper replacement of only a few individuals, given

that scaleshell now occurs in very small, isolated populations, could

decimate an entire population. Even for mussels returned to the stream,

mortality can still occur (Williams et al. 1993).

As scaleshell becomes more uncommon, the interest of scientific and

shell collectors will increase. Populations considered in this rule are

generally localized, easily accessible, exposed during low flow

periods, and are 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 bait (Sue

Bruenderman, pers. comm. 1998).

C. Disease or Predation. Although natural predation is not a factor

for stable, healthy mussel populations, small mammal predation could

potentially pose a problem for scaleshell populations (Gordon 1991).

While the large size and/or thick shells of some species afford

protection from small mammal predators, the small size and fragile

shell of scaleshell makes it an easy and desirable prey species. A

freshwater mussel survey of the Meramec and Bourbeuse Rivers found

fresh scaleshell shells at several active racoon feeding areas (Sue

Bruenderman pers. comm. 1998). Extant scaleshell populations in

Arkansas and Oklahoma are small, isolated and have very limited

recolonization potential. Consequently, predation could exacerbate

ongoing population declines

n easy and desirable prey species. A

freshwater mussel survey of the Meramec and Bourbeuse Rivers found

fresh scaleshell shells at several active racoon feeding areas (Sue

Bruenderman pers. comm. 1998). Extant scaleshell populations in

Arkansas and Oklahoma are small, isolated and have very limited

recolonization potential. Consequently, predation could exacerbate

ongoing population declines.

Bacteria and protozoans persist at unnaturally high concentrations

in streams with high sediment load or in waterbodies affected by point

source pollution, such as sewage treatment plants (Goudreau et al.

1988). At these densities, ova and glochidia are subject to infection

(Ellis 1929) and mussel growth can be slowed (Imlay and Paige 1972).

Disease and parasites may have caused major die-offs of freshwater

mussels in the late 1970's 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 Clean Water Act of 1972 (CWA) set the stage for the regulations and

the water standards that exist today. Goals of the CWA include

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.

Although the passage of these Acts has resulted in positive

consequences (including a decrease in lead and fecal coliform

bacteria), degraded water quality still presents problems for sensitive

aquatic organisms such as freshwater mussels. Specifically, nationwide

sampling has indicated increases in nitrate, chloride, arsenic, and

cadmium concentrations (Neves 1993)

lutants into U.S. waters.

Although the passage of these Acts has resulted in positive

consequences (including a decrease in lead and fecal coliform

bacteria), degraded water quality still presents problems for sensitive

aquatic organisms such as freshwater mussels. Specifically, nationwide

sampling has indicated 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., Clean Water Act) 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 scaleshell. Nonetheless, scaleshell is highly restricted

in numbers and distribution and shows little evidence of recovering

from historic habitat losses.

Although recognized by species experts as threatened in Arkansas,

the scaleshell is not afforded State protection. Missouri and Oklahoma

list the scaleshell as a species of conservation concern (Bruenderman,

in litt. 1998; Caryn Vaughn pers. comm. 1995). However, these

designations are used primarily for planning and communication purposes

and do not afford State protective status from direct take and habitat

destruction (David Martinez; Paul McKenzie; U.S. Fish and Wildlife

Service, pers. comm. 1997). Without habitat protection, populations of

scaleshell will continue to decline.

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 a specific host fish (Neves

1993). The scaleshell is believed to use freshwater drum as a sole

host

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 a specific host fish (Neves

1993). The scaleshell is believed to use freshwater drum as a sole

host. Despite the tremendous fecundity of female mussels, 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. Obviously, reduction or loss of

host fish populations will adversely impact scaleshell 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 transformation and

excystment 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, 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

populations exacerbate the threats to its survival posed by the above

factors. Although the scaleshell was always locally rare if 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)

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, 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, 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. 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

and survivorship. Lastly, chance variation in age and sex ratios can

affect birth and deaths rates. Skewing of the demographics 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

which reduces fertility

and survivorship. Lastly, chance variation in age and sex ratios can

affect birth and deaths rates. Skewing of the demographics 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 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, the current decline to

extinction will be accelerated.

Furthermore, species that occur in low numbers must rely on

dispersal and recolonization for long-term persistence. In order to

retain genetic viability and guard against chance extinction, movement

between local populations must occur. Although the scaleshell naturally

occurs in patches and necessarily possesses mechanisms to adapt to such

a population structure, anthropogenic influences have fragmented and

further lengthened the distance between populations. Empirical studies

have shown that with increasing isolation, colonization rates decrease.

Also, as previously explained, natural recolonization of mussels occurs

at a very low rate (Vaughn 1993). Therefore, preservation of a

metapopulation (interconnected subpopulations) structure is imperative

for long-term freshwater mussel survival. Unfortunately, many of the

extant scaleshell populations now occur as single, isolated sites.

These insular populations are very susceptible to chance events and

extinction 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)

for long-term freshwater mussel survival. Unfortunately, many of the

extant scaleshell populations now occur as single, isolated sites.

These insular populations are very susceptible to chance events and

extinction 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). The spread of this species has caused severe

declines in native freshwater mussel species. Currently, the zebra

mussel invasion of the Mississippi and Ohio rivers threaten native

freshwater mussel fauna (Clarke 1995). Zebra mussels starve and

suffocate native mussels by attaching to their shells in large numbers.

The natural history of zebra mussels is not completely understood;

therefore, effective control measures are not yet known. Given that

recreational and commercial vessels greatly facilitate zebra mussel

movement, and because of the proliferation and spread that has

occurred, invasion of the zebra mussel into portions of the middle and

lower Mississippi Basin is likely (Buchanan pers. comm. 1995). Massive

unionid mortality and extinctions are expected in some areas colonized

by zebra mussels (Biggins 1992). If zebra mussel invasion does occur,

the continued survival of scaleshell will be further jeopardized.

Conclusion

proliferation and spread that has

occurred, invasion of the zebra mussel into portions of the middle and

lower Mississippi Basin is likely (Buchanan pers. comm. 1995). Massive

unionid mortality and extinctions are expected in some areas colonized

by zebra mussels (Biggins 1992). If zebra mussel invasion does occur,

the continued survival of scaleshell will be further jeopardized.

Conclusion

Significant habitat loss, range restriction, and population

fragmentation and size reduction have rendered the scaleshell mussel

vulnerable to extinction. The scaleshell has disappeared from the

entire upper and most of the middle Mississippi River drainages. Of the

53 known historical populations, 13 remain. Although much of the

decline occurred before 1950, population declines continue in some

portions of the species' range and numerous threats are likely to

impact the few remaining viable extant populations. The small number

and low density of the remaining scaleshell populations exacerbate the

threats and effects of chance events to scaleshell. The survival of all

scaleshell populations is threatened by water quality degradation,

impoundments, sedimentation, channelization, or dredging. The recent

deregulation of gravel mining is a significant threat to scaleshell

populations in three rivers within the Meramec River Basin, Missouri.

We have carefully assessed the best scientific and commercial

information available regarding the past, present, and future threats

faced by the scaleshell in determining to make this proposed rule. The

present distribution and abundance of the scaleshell is at risk given

the potential for these impacts to continue. Federal listing under

authority of the Endangered Species Act is the only mechanism we can

presently identify that ensures protection to scaleshell. Therefore,

based on this evaluation, the preferred action is to list the

scaleshell mussel as an endangered species

osed rule. The

present distribution and abundance of the scaleshell is at risk given

the potential for these impacts to continue. Federal listing under

authority of the Endangered Species Act is the only mechanism we can

presently identify that ensures protection to scaleshell. Therefore,

based on this evaluation, the preferred action is to list the

scaleshell mussel 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 due to habitat loss, range

restriction, and population fragmentation.

Critical Habitat

Section 3 of the Act defines critical habitat 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 geographic 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, we designate critical habitat at the time the species

is determined to be endangered or threatened

vation'' 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, we designate critical habitat at the time the species

is determined to be endangered or threatened. Our regulations (50 CFR

424.12(a)(1)) state that the designation of critical habitat is not

prudent when one or both of the following situations exist--(1) the

species is threatened by taking or other human activity, and

identification of critical habitat can be expected to increase the

degree of threat to the species, or (2) such designation of critical

habitat would not be beneficial to the species. We find that

designation of critical habitat is not prudent for scaleshell for both

reasons stated above.

Potential benefits of critical habitat designation derive from

section 7(a)(2) of the Act, which requires Federal agencies, in

consultation with us, to ensure that their actions are not likely to

jeopardize the continued existence of listed species or to result in

the destruction or adverse modification of critical habitat of such

species. Critical habitat designation, by definition, directly affects

only Federal agency actions. Since the scaleshell is aquatic, Federal

actions that might affect this species and its habitat include those

with impacts on stream channel geometry, bottom substrate composition,

water quantity and quality, and stormwater runoff. Such activities that

impact scaleshell habitat would be subject to review under section

7(a)(2) of the Act, whether or not critical habitat was designated. The

scaleshell has become so restricted in distribution that any

significant adverse modification or destruction of occupied habitats

would likely jeopardize the continued existence of this species

ntity and quality, and stormwater runoff. Such activities that

impact scaleshell habitat would be subject to review under section

7(a)(2) of the Act, whether or not critical habitat was designated. The

scaleshell has become so restricted in distribution that any

significant adverse modification or destruction of occupied habitats

would likely jeopardize the continued existence of this species.

Additionally, our regulations (50 CFR part 402) specify that the

jeopardy analysis, like the adverse modification or destruction of

critical habitat analysis, consider the detrimental effect to both

survival and recovery. Therefore, even as the species recovers

and its numbers increase, the jeopardy analysis would continue to

protect scaleshell habitat. As part of the outreach from this proposed

rule, we will notify the State and Federal agencies of this species'

general distribution, and request that they provide data on proposed

Federal actions that might adversely affect the species. Should any

future projects be proposed in areas inhabited by this mussel, the

involved Federal agency will have the distributional data needed to

determine if their action may impact the species, and if needed, we

will provide more specific distributional information. Therefore,

habitat protection for the scaleshell can be accomplished through the

implementation of section 7 jeopardy standard and there is no benefit

in designating currently occupied habitat of this species as critical

habitat.

Recovery of this species may require the identification of

unoccupied stream and river reaches appropriate for reintroduction.

Critical habitat designation of unoccupied stream and river reaches

might benefit this species by alerting permitting agencies to potential

sites for reintroduction and allowing them the opportunity to evaluate

projects that may affect these areas

critical

habitat.

Recovery of this species may require the identification of

unoccupied stream and river reaches appropriate for reintroduction.

Critical habitat designation of unoccupied stream and river reaches

might benefit this species by alerting permitting agencies to potential

sites for reintroduction and allowing them the opportunity to evaluate

projects that may affect these areas. We are currently working with

state and other Federal agencies to periodically survey and assess

habitat potential of stream and river reaches for listed and candidate

aquatic species. This process provides up to date information on

instream habitat conditions in response to land use changes within

watersheds. We distribute the information generated from river surveys

and assessments through our coordination with other agencies. We will

continue to work with State and Federal agencies, as well as private

property owners and other affected parties, through the recovery

process to identify stream reaches and potential sites for

reintroduction of this species. Thus, any benefit that might be

provided by designation of unoccupied habitat as critical will be

accomplished more effectively with the current coordination process,

and is preferable for aquatic habitats which change rapidly in response

to watershed land use practices. In addition, we believe that any

potential benefits to critical habitat designation on occupied and

unoccupied habitats are outweighed by additional threats to the species

that would result from such designation, as discussed below.

All known populations of scaleshell occur in streams flowing

through private lands, and if unoccupied habitat is needed for

recovery, private lands may also be involved. One threat to all

surviving populations appears to be pollutants in stormwater runoff

that originate from private land activities. Therefore, the survival

and recovery of this species will be highly dependent on landowner

cooperation in reducing land use impacts

uld be undetectable and

uncontrolled.

We believe that the potential for taking represents a significant

threat to scaleshell populations. The rarity of this species increases

the likelihood that it will be sought by shell collectors and for

scientific purposes. The publication of critical habitat, maps, and

other publicity accompanying critical habitat designation could

increase that threat. The locations of populations of this species have

consequently been described only in general terms for purposes of this

rulemaking action.

Based on the above analysis, we have concluded that critical

habitat designation would provide little additional benefit for this

species beyond those that would accrue from listing under the Act. We

also conclude that any potential benefit from such a designation would

be offset by an increased level of vulnerability to vandalism or

collecting and by a possible reduction in landowner cooperation to

manage and recover this species. We have concluded therefore that the

designation of critical habitat for scaleshell is not prudent.

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 proposed or

listed as endangered or threatened and with respect to its critical

habitat, if any is being designated

rried 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 proposed or

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)(4) requires Federal agencies to confer

informally with us on any action that is likely to jeopardize the

continued existence of a proposed species or result in destruction or

adverse modification of proposed critical habitat. If a species is

listed subsequently, 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 formal consultation with us.

Federal agency actions that may require conference and/or

consultation as described in the preceding paragraph include the

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

relicensing. In our experience, nearly all section 7 consultations

result in protecting the species and meeting the project's objectives.

The Act and implementing regulations set forth a series of general

prohibitions and exceptions that apply to all endangered wildlife. The

prohibitions, codified at 50 CFR 17.21, in part, make it illegal for

any person subject to the jurisdiction of the United

licensing. In our experience, nearly all section 7 consultations

result in protecting the species and meeting the project's objectives.

The Act and implementing regulations set forth a series of general

prohibitions and exceptions that apply to all endangered wildlife. The

prohibitions, codified at 50 CFR 17.21, 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 listed 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.

We may issue permits to carry out otherwise prohibited activities

involving endangered wildlife under certain circumstances. We codified

the regulations governing permits for endangered species at 50 CFR

17.22. Such permits are available for scientific purposes, to enhance

the propagation or survival of the species, and/or for incidental take

in the course of otherwise lawful activities.

It is our policy, published in the Federal Register on July 1, 1994

(59 FR 34272), to identify, to the maximum extent practicable, those

activities that are or are not likely to 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 proposed 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:

y, to the maximum extent practicable, those

activities that are or are not likely to 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 proposed 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 Clean Water Act and discharges

regulated under the National Pollutant Discharge Elimination System).

(2) Actions that may affect the scaleshell 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.

(4) Existing recreational activities such as swimming, wading,

canoeing, and fishing.

We believe the following activities would be likely to result in a

violation of section 9; however, possible violations are not limited to

these actions alone:

(1) Unauthorized collection or capture of the species;

(2) Unauthorized destruction or alteration of the species habitat

(e.g., in-stream dredging, channelization, discharge of fill material);

(3) violation of any discharge or water withdrawal permit within

the species' occupied range; and

sult in a

violation of section 9; however, possible violations are not limited to

these actions alone:

(1) Unauthorized collection or capture of the species;

(2) Unauthorized destruction or alteration of the species habitat

(e.g., in-stream dredging, channelization, 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 the species.

We will review other activities not identified above on a case-by-

case basis to determine whether they may be 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 Field office (see ADDRESSES section). You may

request copies of the regulations regarding listed wildlife from and

address questions about prohibitions and permits to the U.S. Fish and

Wildlife Service, Ecological Services Division, Henry Whipple Federal

Building, 1 Federal Drive, Fort Snelling, MN 55111 (Phone 612/713-5350;

Fax 612/713-5292).

We intend that any final action resulting from this proposal will

be as accurate and as effective as possible. Therefore, we request

comments or suggestions from the public, other concerned governmental

agencies, the scientific community, industry, or any other interested

party concerning this proposed rule. Comments particularly are sought

concerning:

(1) Biological, commercial trade, or other relevant data concerning

any threat (or lack thereof) to this species;

(2) The location of any additional populations of this species and

the reasons why any habitat should or should not be determined to be

critical habitat as provided by Section 4 of the Act;

erested

party concerning this proposed rule. Comments particularly are sought

concerning:

(1) Biological, commercial trade, or other relevant data concerning

any threat (or lack thereof) to this species;

(2) The location of any additional populations of this species and

the reasons why any habitat should or should not be determined to be

critical habitat as provided by Section 4 of the Act;

(3) Additional information concerning the range, distribution, and

population size of this species;

(4) Current or planned activities in the subject area and their

possible impacts on this species.

We will take into consideration your comments and any additional

information received on this species when making a final determination

regarding this proposal. We will also submit the available scientific

data and information to appropriate, independent specialists for

review. We will summarize the opinions of these reviewers in the final

decision document. The final determination may differ from this

proposal based upon the information we receive.

The Act provides for a public hearing on this proposal, if

requested. We must receive requests within 45 days of the date of

publication of the proposal in the Federal Register. Such requests must

be made in writing and addressed to Field Supervisor, U.S. Fish and

Wildlife Service, Ecological Services Field Office, 608 East Cherry

Street Room 200, Columbia, Missouri 65201.

Executive Order 12866

Act provides for a public hearing on this proposal, if

requested. We must receive requests within 45 days of the date of

publication of the proposal in the Federal Register. Such requests must

be made in writing and addressed to Field Supervisor, U.S. Fish and

Wildlife Service, Ecological Services Field Office, 608 East Cherry

Street Room 200, Columbia, Missouri 65201.

Executive Order 12866

Executive Order 12866 requires each agency to write regulations

that are easy to understand. We invite your comments on how to make

this rule easier to understand including answers to the following: (1)

Are the requirements of the rule clear? (2) Is the discussion of the

rule in the Supplementary Information section of the preamble helpful

in understanding the rule? (3) What else could we do to make the rule

easier to understand?

Send a copy of any comments that concern how we could make this

rule easier to understand to the office identified in the ADDRESSES

section at the beginning of this document.

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 Act. 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

clearance 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

threatened species, see 50 CFR 17.22.

References Cited

, 44

U.S.C. 3501 et seq., and assigned Office of Management and Budget

clearance 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

threatened 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

section).

Authors: The primary authors of this proposed rule are Mr. Andy

Roberts (see FOR FURTHER INFORMATION CONTACT section) and Ms. Jennifer

Szymanski (see ADDRESSES section).

List of Subjects in 50 CFR Part 17

Endangered and threatened species, Exports, Imports, Reporting and

record keeping requirements, Transportation.

Regulation Promulgation

Accordingly, the Service amends 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:

Sec. 17.11 Endangered and threatened wildlife.

* * * * *

e 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:

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, IL, NA................. E NA NA

IN, IA, KY, MN,

MO, OH, OK, SD,

TN, WI).

* * * * * * *

--------------------------------------------------------------------------------------------------------------------------------------------------------

Dated: July 29, 1999.

John G. Rogers,

Acting Director, Fish and Wildlife Service.

[FR Doc. 99-20965 Filed 8-12-99; 8:45 am]

BILLING CODE 4310-55-P