Endangered and Threatened Wildlife and Plants; Endangered Species Status for the Fluted Kidneyshell and Slabside Pearlymussel and Designation of Critical Habitat

DEPARTMENT OF THE INTERIOR

Fish and Wildlife Service

50 CFR Part 17

[Docket No. FWS-R4-ES-2012-0004; 4500030113]

RIN 1018-AY06

Endangered and Threatened Wildlife and Plants; Endangered Species Status for the Fluted Kidneyshell and Slabside Pearlymussel and Designation of Critical Habitat

AGENCY:

Fish and Wildlife Service, Interior.

ACTION:

Proposed rule.

SUMMARY:

We, the U.S. Fish and Wildlife Service (Service), propose to list the fluted kidneyshell (

Ptychobranchus subtentum

) and slabside pearlymussel (

Pleuronaia dolabelloides

) as endangered species under the Endangered Species Act of 1973, as amended (Act), and we propose to designate critical habitat for both species. These two species are endemic to portions of the Cumberland and Tennessee River systems of Alabama, Kentucky, Mississippi, Tennessee, and Virginia. In total, approximately 2,218 river kilometers (1,380 river miles) are being proposed for designation as critical habitat. The proposed critical habitat for fluted kidneyshell is located in Limestone County, Alabama; Jackson, Laurel, McCreary, Pulaski, Rockcastle, and Wayne Counties, Kentucky; Bedford, Claiborne, Cocke, Fentress, Franklin, Giles, Grainger, Greene, Hamblen, Hancock, Hickman, Humphreys, Jefferson, Knox, Lincoln, Marshall, Maury, Moore, Morgan, Overton, Perry, Pickett, Polk, Scott, and Sevier Counties, Tennessee; and Bland, Lee, Russell, Scott, Smyth, Tazewell, Washington, and Wythe Counties, Virginia. The proposed critical habitat for slabside pearlymussel is located in Colbert, Jackson, Limestone, Madison, and Marshall Counties, Alabama; Tishomingo County, Mississippi; Bedford, Bledsoe, Claiborne, Cocke, Franklin, Giles, Greene, Hamblen, Hancock, Hickman, Humphreys, Lincoln, Marion, Marshall, Maury, Moore, Perry, Polk, and Sequatchie Counties, Tennessee; and Bland, Lee, Russell, Scott, Smyth, Tazewell, Washington, and Wythe Counties, Virginia.

DATES:

We will accept comments received or postmarked on or before December 3, 2012. We must receive requests for public hearings, in writing, at the address shown in the

FOR FURTHER INFORMATION CONTACT

section by November 19, 2012.

ADDRESSES:

Document availability:

This proposed rule is available on the Internet at

http://www.regulations.gov

and

http://www.fws.gov/cookeville/. Written comments:

You may submit comments by one of the following methods:

(1)

Electronically:

Go to the Federal eRulemaking Portal:

http://www.regulations.gov.

In the Search field, enter Docket No. FWS-R4-ES-2012-0004, which is the docket number for this rulemaking. Then, click the Search button. You may submit a comment by clicking on “Comment Now!”

(2)

By hard copy:

Submit by U.S. mail or hand-delivery to: Public Comments Processing, Attn: FWS-R4-ES-2012-0004; Division of Policy and Directives Management; U.S. Fish and Wildlife Service; 4401 N. Fairfax Drive, MS 2042-PDM; Arlington, VA 22203.

We request that you send comments only by the methods described above. We will post all comments on

http://www.regulations.gov.

This generally means that we will post any personal information you provide us (see the Information Requested section below for more information).

The coordinates or plot points or both from which the maps are generated are included in the administrative record for this critical habitat designation and are available at

http://www.fws.gov/cookeville, http://www.regulations.gov

at Docket No. [FWS-R4-ES-2012-0004], and at the Tennessee Ecological Services Field Office) (see

FOR FURTHER INFORMATION CONTACT

). Any additional tools or supporting information that we may develop for this critical habitat designation will also be available at the above locations.

FOR FURTHER INFORMATION CONTACT:

Mary Jennings, Field Supervisor, U.S. Fish and Wildlife Service, Tennessee Ecological Services Field Office, 446 Neal Street, Cookeville, TN 38501; telephone 931-528-6481; facsimile 931-528-7075. If you use a telecommunications device for the deaf (TDD), call the Federal Information Relay Service (FIRS) at 800-877-8339.

SUPPLEMENTARY INFORMATION:

This document consists of: (1) A proposed rule to list the fluted kidneyshell (

Ptychobranchus subtentum

) and slabside pearlymussel (

Pleuronaia dolabelloides

) as endangered species; and (2) proposed critical habitat designations for these two species.

Executive Summary

Why we need to publish a rule.

Under the Act, a species or subspecies may warrant protection through listing if it is an endangered or threatened species throughout all or a significant portion of its range. Both species have been eliminated from more than 50 percent of the streams from which they were historically known, and are now limited to a handful of viable populations, all of which are facing a variety of threats, including impoundments, mining, poor water quality, excessive sedimentation, and environmental contaminants.

The basis for our action.

Under the Act, a species may be determined to be endangered or threatened based on any of five factors: (A) Destruction, modification, or curtailment of its habitat or range; (B) overutilization; (C) disease or predation; (D) inadequate existing regulatory mechanisms; or (E) other natural or manmade factors. These two mussel species are facing threats due to three of these five factors (A, D, and E). The Act also requires that the Service designate critical habitat at the time of listing provided that it is prudent and determinable. We have determined that designating critical habitat is both prudent and determinable (see Critical Habitat for the Fluted Kidneyshell and Slabside Pearlymussel section below), and propose a total of approximately 2,218 river kilometers (rkm) (1,380 river miles (rmi)) of critical habitat in five States. Twenty-four units covering approximately 1,899 river kilometers (rkm) (1,181 river miles (rmi)) of critical habitat are being proposed for the fluted kidneyshell in Alabama, Kentucky, Tennessee, and Virginia. Thirteen units covering approximately 1,562 rkm (970 rmi) of critical habitat are being proposed for the slabside pearlymussel in Alabama, Mississippi, Tennessee, and Virginia.

We will seek peer review.

In addition to seeking public comments, we will solicit peer review of this proposal from at least three experts knowledgeable in mussel biology and basic conservation biology principles and concepts. Because we will consider all comments and information received during the comment period, our final determinations may differ from this proposal

Information Requested

We intend that any final action resulting from this proposed rule will be based on the best scientific and commercial data available and be as accurate and as effective as possible. Therefore, we request comments or

information from other concerned governmental agencies, the scientific community, industry, or any other interested parties concerning this proposed rule. We particularly seek comments concerning:

(1) Biological, commercial trade, or other relevant data concerning any threats (or lack thereof) to these species and regulations that may be addressing those threats.

(2) Additional information concerning the historical and current status, range, distribution, and population size of either of these species, including the locations of any additional populations.

(3) Any information on the biological or ecological requirements of these species, and ongoing conservation measures for the species and their habitat.

(4) Any information regarding water quality data that may be helpful in determining the water quality parameters necessary for the fluted kidneyshell and the slabside pearlymussel.

(5) Current or planned activities in the areas occupied by these species and possible impacts of these activities on these species.

(6) The factors that are the basis for making a listing determination for a species under section 4(a) of the Act (16 U.S.C. 1531

et seq.

), which are:

(a) The present or threatened destruction, modification, or curtailment of its habitat or range;

(b) Overutilization for commercial, recreational, scientific, or educational purposes;

(c) Disease or predation;

(d) The inadequacy of existing regulatory mechanisms; or

(e) Other natural or manmade factors affecting its continued existence.

(7) The reasons why we should or should not designate habitat as “critical habitat” under section 4 of the Act including whether there are threats to these species from human activity, the degree of which can be expected to increase due to the designation, and whether that increase in threat outweighs the benefit of designation such that the designation of critical habitat may not be prudent.

(8) Specific information on:

(a) The amount and distribution of habitat for the fluted kidneyshell and slabside pearlymussel;

(b) What areas, that were occupied at the time of the proposed listing and that contain features essential to the conservation of these species, should be included in the designation and why;

(c) Special management considerations or protection that may be needed in critical habitat areas we are proposing, including managing for the potential effects of climate change; and

(d) What areas not occupied at the time of the proposed listing are essential for the conservation of these species and why.

(9) Land use designations and current or planned activities in the subject areas and their possible impacts on proposed critical habitat.

(10) Information on the projected and reasonably likely impacts of climate change on these species and proposed critical habitat.

(11) Any probable economic, national security, or other relevant impacts of designating any area that may be included in the final designation; in particular, we seek information on any impacts on small entities or families, and the benefits of including or excluding areas that exhibit these impacts.

(12) Whether any specific areas we are proposing for critical habitat designation should be considered for exclusion under section 4(b)(2) of the Act, and whether the benefits of potentially excluding any specific area outweigh the benefits of including that area under section 4(b)(2) of the Act.

(13) Any impact that critical habitat designation would have, positive or negative, on conservation efforts associated with designated nonessential experimental populations for other listed species in the lower Holston and French Broad river systems in Tennessee, or the North Fork Holston River in Virginia.

(14) Information on habitat suitability for these two mussels in the proposed units that are not occupied at the time of the proposed listing, including the Rockcastle River, Kentucky, and the Sequatchie River, Tennessee.

(15) Whether we could improve or modify our approach to designating critical habitat in any way to provide for greater public participation and understanding, or to better accommodate public concerns and comments.

Please note that submissions merely stating support for or opposition to the action under consideration without providing supporting information, although noted, will not be considered in making a determination, as section 4(b)(1)(A) of the Act directs that determinations as to whether any species is a threatened or endangered species must be made “solely on the basis of the best scientific and commercial data available.”

You may submit your comments and materials concerning this proposed rule by one of the methods listed in

ADDRESSES

. We request that you send comments only by the methods described in

ADDRESSES

.

If you submit information via

http://www.regulations.gov,

your entire submission—including any personal identifying information—will be posted on the Web site. If your submission is made via a hardcopy that includes personal identifying information, you may request at the top of your document that we withhold this information from public review. However, we cannot guarantee that we will be able to do so. We will post all hardcopy submissions on

http://www.regulations.gov.

Please include sufficient information with your comments to allow us to verify any scientific or commercial information you include.

Comments and materials we receive, as well as supporting documentation we used in preparing this proposed rule, will be available for public inspection on

http://www.regulations.gov,

or by appointment, during normal business hours, at the U.S. Fish and Wildlife Service, Tennessee Ecological Services Field Office (see

FOR FURTHER INFORMATION CONTACT

).

Previous Federal Actions

The fluted kidneyshell was first identified as a candidate for protection under the Act in the October 25, 1999,

Federal Register

(64 FR 57534). Candidate species are those taxa for which the Service has sufficient information on their biological status and threats to list as an endangered or threatened species under the Act but for which the development of a listing regulation has been precluded to date by other higher priority listing activities. Candidates are assigned listing priority numbers (LPNs) based on immediacy and the magnitude of threat, as well as their taxonomic status. A lower LPN corresponds to a higher conservation priority, and we consider the LPN when prioritizing and funding conservation actions. In our 1999 (64 FR 57534), 2001 (66 FR 54808), 2002 (67 FR 40657), 2004 (69 FR 24876), 2005 (70 FR 24870), and 2006 (71 FR 53756)

Federal Register

Candidate Notices of Review, we identified the species as having an LPN of five, in accordance with our priority guidance published on September 21, 1983 (48 FR 43098). An LPN of five reflects threats that are nonimminent and high in magnitude, as well as the taxonomic classification of the fluted kidneyshell as a full species. We also determined that publication of a proposed rule to list the fluted kidneyshell was precluded by our work on higher priority listing actions. On May 11, 2004, we received a petition to list the fluted kidneyshell as an

endangered species. We published our petition finding in the 2005 Candidate Notice of Review (70 FR 24869), and have done so annually in subsequent years.

On December 6, 2007 (72 FR 69034), we changed the LPN for the fluted kidneyshell from five to two. A listing priority of two reflects threats that are both imminent and high in magnitude, as well as the taxonomic classification of the fluted kidneyshell as a full species. In our 2008 (73 FR 75176), 2009 (74 FR 57804), 2010 (75 FR 69222), and 2011 (76 FR 66370) Candidate Notices of Review, we retained a listing priority number of two for this species.

The slabside pearlymussel was first identified as a candidate for protection under the Act in the May 22, 1984,

Federal Register

(49 FR 21664). As a candidate, it was assigned a “Category 2” designation, which was given to those species with some evidence of vulnerability, but for which additional biological information was needed to support a proposed rule to list as endangered or threatened. In our 1989 (54 FR 554), 1991 (56 FR 58804), and 1994 (59 FR 58982)

Federal Register

Candidate Notices of Review, we retained a Category 2 designation for this species. Assigning categories to candidate species was discontinued in our Candidate Notice of Review dated February 28, 1996, and only species for which the Service had sufficient information on biological vulnerability and threats to support issuance of a proposed rule were retained as candidate species (61 FR 7596).

On October 25, 1999, we identified the slabside pearlymussel in the

Federal Register

as a candidate species with a listing priority number of five (64 FR 57534). In our 2001 (66 FR 54808), 2002 (67 FR 40657), 2004 (69 FR 24876), 2005 (70 FR 24870), 2006 (71 FR 53756), and 2007 (72 FR 69034) Candidate Notices of Review, we determined that publication of a proposed rule to list the species was precluded by our work on higher priority listing actions and retained a listing priority number of five for this species, in accordance with our priority guidance published on September 21, 1983 (48 FR 43098). We published a petition finding for slabside pearlymussel in the 2005 Candidate Notice of Review (70 FR 24870) in response to a petition received on May 11, 2004, and have published annual petition findings in subsequent Candidate Notices of Review.

On December 10, 2008 (73 FR 75176), we changed the listing priority number for the slabside pearlymussel from five to two. In our 2009 (74 FR 57804), 2010 (75 FR 69222), and 2011 (76 FR 66370) Candidate Notices of Review, we retained a listing priority number of two for this species.

Background

It is our intent to discuss only those topics directly relevant to the listing and critical habitat designations for the fluted kidneyshell and slabside pearlymussel in this proposed rule. A summary of topics relevant to this proposed rule is provided below. Additional information on both species may be found in the most recent Candidate Notice of Review, which was published October 26, 2011 (76 FR 66370).

Introduction

North American mussel fauna are more biologically diverse than anywhere else in the world, and historically numbered around 300 species (Williams

et al.

1993, p. 6). Mussels are in decline, however, and in the past century have become more imperiled than any other group of organisms (Williams

et al.

2008, p. 55). Approximately 72 percent of North America's mussel species are considered vulnerable to extinction or possibly extinct (Williams

et al.

1993, p. 6). Within North America, the southeastern United States is the hot spot for mussel diversity. Seventy-five percent of southeastern mussel species are in varying degrees of rarity or possibly extinct (Neves

et al.

1997, pp. 47-51). The central reason for the decline of mussels is the modification and destruction of their habitat, especially from dams, degraded water quality, and sedimentation (Neves

et al.

1997, p. 60; Bogan 1998, p. 376). These two mussels, like many other southeastern mussel species, have undergone considerable reductions in total range and population density.

Most studies of the distribution and population status of the fluted kidneyshell and slabside pearlymussel presented below were conducted after the early 1960s. Gordon and Layzer (1989, entire), Winston and Neves (1997, entire), and Parmalee and Bogan (1998, pp. 204-205) give most of the references for regional stream surveys. In addition to these publications, we have obtained more current, unpublished distribution and status information from State heritage programs, agency biologists, and other knowledgeable individuals.

These two species are bivalve mussels and are endemic to the Cumberland and Tennessee River drainages. The Cumberland River drainage originates in southeastern Kentucky and flows southwest across Tennessee before turning north and reentering Kentucky to empty into the lower Ohio River. The Cumberland River drainage spans the Appalachian Plateaus and Interior Low Plateaus Physiographic Provinces. The Tennessee River originates in southwest Virginia and western North Carolina, eastern Tennessee, and northern Georgia and flows southwesterly into western Tennessee and Alabama, then turns north and flows into Kentucky, before emptying into the Ohio River. The larger Tennessee River drainage spans five physiographic provinces, including the Blue Ridge, Valley and Ridge, Appalachian Plateaus, Interior Low Plateaus, and Coastal Plain.

Fluted Kidneyshell

Taxonomy and Species Description

The fluted kidneyshell,

Ptychobranchus subtentum

(Say, 1825), is in the family Unionidae (Turgeon

et al.

1998, p. 36). The following description, biology, and life history of the fluted kidneyshell is taken from Parmalee and Bogan (1998, pp. 204-205) and Williams

et al.

(2008, pp. 627-629). The fluted kidneyshell is a relatively large mussel that reaches about 13 centimeters (cm) (5 inches (in)) in length. The shape of the shell is roughly oval elongate, and the solid, relatively heavy valves (shells) are moderately inflated. A series of flutings (parallel ridges or grooves) characterizes the posterior slope of each valve. Shell texture is smooth and somewhat shiny in young specimens, becoming duller with age. Shell color is greenish yellow, becoming brownish with age, with several broken, wide green rays. Internally, there are two types of teeth, which are raised, interlocking structures used to stabilize opposing shell halves. The pseudocardinal teeth are stumpy and triangular in shape. The lateral teeth are relatively heavy and nearly straight, with two in the left valve and one in the right valve. The color of the nacre (mother-of-pearl) is bluish-white to dull white with a wash of salmon in the older part of the shell (beak cavity).

Habitat and Life History

Mussels generally live embedded in the bottom of rivers and other bodies of water. They siphon water into their shells and across four gills that are specialized for respiration, food collection, and brooding larvae in females. Food items include detritus (disintegrated organic debris), algae, diatoms, and bacteria (Strayer

et al.

2004, pp. 430-431). Adult mussels can obtain their food by deposit feeding, pulling in food from the sediment and its interstitial (pore) water, and pedal-

feeding directly from the sediment (Yeager

et al.

1994, pp. 217-221; Vaughn and Hakenkamp 2001, 1432-1438). Adults are filter feeders and generally orient themselves on or near the substrate surface to take in food and oxygen from the water column. Juveniles typically burrow completely beneath the substrate surface and are deposit or pedal (foot) feeders, meaning that they bring food particles that adhere to the foot while it is extended outside the shell inside the shell for ingestion, until the structures for filter feeding are more fully developed (Yeager

et al.

1994, pp. 200-221; Gatenby

et al.

1996, p. 604). However, adults are also capable of deposit feeding and may do so depending on the availability of food resources (Nichols

et al.

2005, pp. 90-93).

Mussels tend to grow relatively rapidly for the first few years; then growth slows appreciably after sexual maturity, when energy is being diverted from growth to reproductive activities. Mussel longevity varies tremendously among species (from 4 to 5 years to well over 100 years), but most species live 10 to 50 years (Haag and Rypel 2011, pp. 230-236). Relatively large, heavy-shelled riverine species tend to be slower growing and have longer life spans. By thin-sectioning the valves, various authors have aged fluted kidneyshell from the Clinch River at 26 and 55 years (Henley

et al.

2002, p. 19; Davis and Layzer 2012, p. 92). Females can become sexually mature at age 5 (Davis and Layzer 2012, p. 79).

The gametogenic cycle (annual cycle in the development of reproductive cells or gametes) of fluted kidneyshell, like most mussels, is probably regulated by annual temperature regimes (Davis and Layzer, p. 90). Most mussels, including the fluted kidneyshell, have separate sexes. Males expel sperm into the water column, which are drawn in by females through their incurrent apertures or siphons. It has been hypothesized that pheromones might trigger synchronous sperm release among males, because all fertilization observed by females from the Clinch River occurred in fewer than 5 days (Davis and Layzer 2012, p. 90). Fertilization takes place internally, and the resulting zygotes develop into specialized larvae, termed glochidia, inside the water tubes of the females' gills. The fluted kidneyshell, along with other members of its genus, is unique in that the marsupial portion of the outer gills (portion of a brooding female's gill which holds embryos and glochidia) are folded in a curtain-like fashion. The fluted kidneyshell is thought to have a late summer or early fall fertilization period with the glochidia overwintering. Davis and Layzer (2012, p. 90) observed embryo development within the marsupium (brood pouch) at 4 weeks after fertilization. The following spring or early summer, glochidia are released as conglutinates, which are similar to cold capsules or gelatinous containers with scores of glochidia within. Davis and Layzer (2012, p. 86) report an average of 208 conglutinates and an average fecundity (total reproductive output) of 247,000 glochidia per female. Davis and Layzer (2012, p. 92) report a skewed adult sex ratio of 1.9 females per 1 male in the Clinch River, in Tennessee, although the cause of the skewed ratio is unknown. Using the observed sex ratio and percent of females that were gravid, Davis and Layzer (2012, p. 92) hypothesized that some females go through reproductive “pausing” periods to acquire the energy reserves needed to produce gametes in subsequent years.

Glochidia must come into contact with a specific host fish(es) quickly in order for their survival to be ensured. Without the proper species of host fish, the glochidia will perish. Conglutinate masses often mimic food items of glochidial fish hosts in order to attract and infest potential host fishes. Fluted kidneyshell conglutinates are shaped like black fly (Simuliidae) pupae and have an adhesive end that sticks to silt-free stones on the stream bottom, with an orientation that is also similar to that of blackfly pupae (Barnhart and Roberts 1997, p. 17; Barnhart

et al.

2008, p. 377; Williams

et al.

2008, p. 628). Insects are common food items of many stream fishes, including the fluted kidneyshell's host fishes, which include the barcheek darter (

Etheostoma obeyense

), fantail darter (

E. flabellare

), rainbow darter (

E. caeruleum

), redline darter (

E. rufilineatum

), bluebreast darter (

E. camurum

), dusky darter (

Percina sciera

), and banded sculpin (

Cottus carolinae

). These fishes are tricked into thinking that they have an easy insect meal when in fact they have infected themselves with parasitic mussel glochidia (Parmalee and Bogan 1998, p. 205; Davis and Layzer 2012, p. 88).

After a few weeks parasitizing the host fish's gill, newly metamorphosed juveniles drop off to begin a free-living existence on the stream bottom. Unless they drop off in suitable habitat, they will perish. Thus, the complex life history of the fluted kidneyshell and other mussels has many critical steps that may prevent successful reproduction or recruitment of juveniles into existing populations or both.

The fluted kidneyshell occurs in medium-sized creeks to large rivers, inhabiting sand and gravel substrates in relatively shallow riffles and shoals with moderate to swift current (Williams

et al.

2008, p. 628). In comparison to some co-occurring species, the fluted kidneyshell demonstrates strong habitat specificity by being associated with faster flows, greater shear stress (force of water pressure and velocity on the substrate), and low substrate embeddedness (Ostby 2005, pp. 51, 142-3).

Historical Range and Distribution

The fluted kidneyshell is a Cumberlandian Region mussel, meaning it is restricted to the Cumberland (in Kentucky and Tennessee) and Tennessee (in Alabama, Kentucky, Tennessee, and Virginia) River systems. Historically, this species occurred in the Cumberland River mainstem from below Cumberland Falls in southeastern Kentucky downstream through the Tennessee portion of the river to the vicinity of the Kentucky-Tennessee State line. In the Tennessee River mainstem it occurred from eastern to western Tennessee. Records are known from the following Cumberland River tributaries: Horse Lick Creek [KY], Middle Fork Rockcastle River [KY], Rockcastle River [KY], Buck Creek [KY], Rock Creek [KY], Kennedy Creek [KY], Little South Fork [KY], Big South Fork [KY, TN], Pitman Creek [KY], Otter Creek [KY], Wolf River [TN], Town Branch [TN], West Fork Obey River [TN], Obey River [TN], Caney Fork [TN], South Harpeth River [TN], and West Fork Red River [KY]. In addition, it is known from the following Tennessee River tributaries: South Fork Powell River [VA], Powell River [TN, VA], Indian Creek [VA], Little River [VA], Clinch River [TN, VA], Copper Creek [VA], North Fork Holston River [TN, VA], Big Moccasin Creek [VA], Middle Fork Holston River [VA], South Fork Holston River [TN, VA], Holston River [TN], Nolichucky River [TN], West Prong Little Pigeon River [TN], Tellico River [TN], French Broad River [TN], Little Tennessee River [TN], Hiwassee River [TN], Flint River [AL], Limestone Creek [AL], Elk River [AL, TN], Shoal Creek [AL], Buffalo River [TN], and Duck River [TN] (Gordon and Layzer 1989, entire; Winston and Neves 1997, entire; Parmalee and Bogan 1998, pp. 204-205; Layzer and Scott 2006, p. 481). The fluted kidneyshell's known historical and current occurrences, by water body and county, are shown in Table 1 below.

Table 1—Known Historical and Current Occurrences for the Fluted Kidneyshell

Water body

Drainage

County

State

Historical or current

Cumberland River

Cumberland

McCreary, Pulaski, Russell

KY

Historical.

Cumberland River

Cumberland

Stewart

TN

Historical.

Middle Fork Rockcastle River

Cumberland

Jackson

KY

Historical and Current.

Horse Lick Creek

Cumberland

Jackson, Rockcastle

KY

Historical and Current.

Rockcastle River

Cumberland

Laurel, Pulaski, Rockcastle

KY

Historical.

Buck Creek

Cumberland

Pulaski

KY

Historical and Current.

Big South Fork Cumberland River

Cumberland

McCreary, Pulaski

KY

Historical and Current.

Big South Fork Cumberland River

Cumberland

Fentress, Morgan, Scott

TN

Historical and Current.

Rock Creek

Cumberland

McCreary

KY

Historical and Current.

Little South Fork Cumberland River

Cumberland

McCreary, Wayne

KY

Historical and Current.

Kennedy Creek

Cumberland

Wayne

KY

Historical.

Pitman Creek

Cumberland

Pulaski

KY

Historical.

Otter Creek

Cumberland

Wayne

KY

Historical.

Wolf River

Cumberland

Fentress, Pickett

TN

Historical and Current.

Town Branch

Cumberland

Pickett

TN

Historical and Current.

Obey River

Cumberland

?

TN

Historical.

West Fork Obey River

Cumberland

Overton

TN

Historical and Current.

Caney Fork River

Cumberland

?

TN

Historical.

South Harpeth River

Cumberland

Davidson

TN

Historical.

West Fork Red River

Cumberland

Todd

KY

Historical.

South Fork Powell River

Tennessee

Wise

VA

Historical.

Powell River

Tennessee

Claiborne, Hancock

TN

Historical and Current.

Powell River

Tennessee

Campbell, Union

TN

Historical.

Powell River

Tennessee

Lee

VA

Historical and Current.

Indian Creek

Tennessee

Tazewell

VA

Historical and Current.

Clinch River

Tennessee

Hancock

TN

Historical and Current.

Clinch River

Tennessee

Anderson, Claiborne, Grainger, Roane, Union

TN

Historical.

Clinch River

Tennessee

Russell, Scott, Tazewell, Wise

VA

Historical and Current.

Little River

Tennessee

Russell, Tazewell

VA

Historical and Current.

Copper Creek

Tennessee

Scott

VA

Historical and Current.

North Fork Holston River

Tennessee

Hawkins, Sullivan

TN

Historical.

North Fork Holston River

Tennessee

Bland, Scott, Smyth, Washington

VA

Historical and Current.

Big Moccasin Creek

Tennessee

Scott

VA

Historical and Current.

Middle Fork Holston River

Tennessee

Smyth

VA

Historical and Current.

South Fork Holston River

Tennessee

Sullivan

TN

Historical.

South Fork Holston River

Tennessee

Washington

VA

Historical.

Holston River

Tennessee

Grainger, Hamblen, Jefferson, Knox

TN

Historical.

French Broad River

Tennessee

?

TN

Historical.

Tennessee River

Tennessee

Colbert, Jackson, Lauderdale

AL

Historical.

Tennessee River

Tennessee

Decatur, Knox, Meigs, Rhea

TN

Historical.

Nolichucky River

Tennessee

Greene

TN

Historical and Current.

West Prong Little Pigeon River

Tennessee

Sevier

TN

Historical.

Tellico River

Tennessee

Monroe

TN

Historical.

Little Tennessee River

Tennessee

Monroe

TN

Historical.

Hiwassee River

Tennessee

Polk

TN

Historical.

Flint River

Tennessee

Madison

AL

Historical.

Limestone Creek

Tennessee

Limestone

AL

Historical.

Elk River

Tennessee

Limestone

AL

Historical.

Elk River

Tennessee

Coffee, Franklin

TN

Historical.

Shoal Creek

Tennessee

Limestone

AL

Historical.

Duck River

Tennessee

Bedford, Marshall, Maury

TN

Historical and Current.

Buffalo River

Tennessee

Lewis

TN

Historical.

Note:

A ? represents a lack of specific locational information in the museum and literature record.

Prior to 1980, the fluted kidneyshell was fairly widespread and common in many Cumberlandian Region streams based on collections in museums and from the literature record. The extirpation of this species from numerous streams within its historical range indicates that substantial population losses and range reductions have occurred.

Current Range and Distribution

In this document, populations of the fluted kidneyshell are generally considered extant (current) if live individuals or fresh dead specimens have been collected since circa 1980. This criterion (circa 1980) was chosen because a large number of collections were conducted in the 1980s in the Cumberland and Tennessee River systems and due to the longevity of these species (40-55 years), they are still thought to occur in these areas.

Some of the historical occurences have not been surveyed since the 1980s. Based on this criterion, the species appears to be limited to Horse Lick Creek [KY], Middle Fork Rockcastle River [KY], Buck Creek [KY], Rock Creek [KY], Little South Fork Cumberland River [KY], Big South Fork Cumberland River [KY, TN], Wolf River [TN], Town Branch [TN], and West Fork Obey River [TN] in the Cumberland River system; and the Powell River [TN, VA], Indian Creek [VA], Little River

[VA], Clinch River [TN, VA], Copper Creek [VA], North Fork Holston River [VA], Big Moccasin Creek [VA], Middle Fork Holston River [VA], Nolichucky River [TN], and Duck River [TN] in the Tennessee River system (see Table 1). Where two or more stream populations occur contiguously with no barriers, such as impoundments or long reaches of unoccupied habitat, they are considered single population segments or clusters. Multi-stream population segments include the Wolf River and its tributary Town Branch in the Cumberland River system, and Clinch River and Copper Creek (but not the other two upper Clinch tributaries, Indian Creek and Little River) in the Tennessee River system. Thus, we consider 17 of 40 populations of fluted kidneyshell to be extant. The fluted kidneyshell has been eliminated from more than 50 percent of streams from which it was historically known.

Other populations considered extant at the time this species was elevated to candidate status in 1999 (e.g., Rockcastle River, Kennedy Creek) are now considered to be extirpated. In addition, the population in the upper North Fork Holston River, although still large, has declined substantially since circa 2000. The North Fork Holston River population is predominately composed of large individuals, unlike the Clinch River population, which is skewed towards smaller size classes (Ostby

et al.

2010, pp. 7, 22-24). These differences in population characteristics are a clear indication that recruitment in the Clinch River population is more observable than the population in the North Fork Holston River.

Resource managers have been making attempts to reintroduce the fluted kidneyshell into historical habitat over the past decade. In Tennessee, thousands of individuals of the species have been reintroduced into three sites in the upper Duck River, and into two sites in the Nolichucky River, by Tennessee Wildlife Resource Agency (TWRA) biologists translocating adult individuals from the Clinch River (Hubbs 2011, unpubl. data). In 2010, six individuals were collected during a quantitative survey at Lillard's Mill in the Duck River, confirming some level of survival and persistence of the reintroduced population (Hubbs 2011, unpubl. data). The individuals collected appeared in good condition and had grown noticeably since their release (as evidenced by external shell marks), but recruitment has yet to be documented (Hubbs 2011, unpubl. data). In 2008, the Kentucky Department of Fish and Wildlife Resources (KDFWR) translocated 144 individuals from the Clinch River into the Big South Fork of the Cumberland River, Kentucky (Hubbs 2011, unpubl. data). It is not known if the Nolichucky or Big South Fork reintroductions have been successful. Approximately 691 adult individuals of the species have been translocated from the Clinch River, Tennessee, into the Little Tennessee River bypass reach below Calderwood Dam, Tennessee (Moles 2012, pers. comm.). The Virginia Department of Game and Inland Fisheries (VDGIF) reintroduced 58 adults into Indian Creek, a tributary to the Clinch River, using Clinch River stock. They have also propagated and released 562 juveniles into the North Fork Holston River (Duncan 2012, pers. comm.).

The extant fluted kidneyshell populations (including the potentially reintroduced populations) in the Cumberlandian Region generally represent small, isolated occurrences. Only in the Clinch River is a population of the fluted kidneyshell known to be large, stable, and viable, but in a relatively short reach of river primarily in the vicinity of the Tennessee-Virginia State line. Jones (2012, unpub. data) estimates 500,000 to 1,000,000 individuals occur in the Clinch River from just a 32-river-kilometer (rkm) (20-river-mile (rmi)) reach (rkm 309 to 277 (rmi 172 to 192)). Live adults and juveniles have been observed over the past 10 years in shoal habitats in the upper Clinch River, Virginia, particularly at and above Cleveland Islands, and many more fresh dead shells have been collected in muskrat middens in this reach. Eckert and Pinder (2010, pp. 23-30) collected 18 individuals in quantitative samples and 11 individuals in semi-quantitative samples in the Clinch River at Cleveland Island in 2008, and 15 individuals in quantitative samples and 62 individuals in semi-quantitative samples in the Clinch River at Cleveland Island in 2002. Ostby and Angermeier (2011, entire) found two live individuals in the Little River (tributary to Clinch River). Henley

et al.

(1999, pp. 20, 22) collected live individuals at 6 of 25 sites surveyed in the Middle Fork Holston River in 1997 and 1998. The fluted kidneyshell was found in Copper Creek between creek rkm 2 and 31 (rmi 1 and 19) (Hanlon

et al.

2009, pp. 15-17). Petty

et al.

(2006, pp. 4, 36) found the species between Copper Creek rkm 24 and 31 (rmi 15 and 19) and reported evidence of reproduction and recruitment of the species at these locations. In 2008-09, 35 live individuals were found at 5 of 21 sites sampled in the Powell River, in both Tennessee and Virginia, and there was some indication of relatively recent recruitment (Johnson

et al.

in press, Table 4). Ostby

et al.

(2010, pp. 16-20) observed 772 individuals during qualitative surveys and 10 individuals in quantitative surveys in the North Fork Holston River, Virginia.

Live fluted kidneyshell have not been collected in the Middle Fork Rockcastle River since the mid-1980s (Layzer and Anderson 1992, p. 64). Haag and Warren (2004, p. 16) collected only fresh dead shell material in Horse Lick Creek, and reported that a small, extremely vulnerable population of the fluted kidneyshell may exist there, but at very low levels that they were not able to detect. Warren and Haag (2005, pp. 1384, 1388-1396) reported a vast reduction of the once sizable Little South Fork population since the late 1980s. Live fluted kidneyshell have not been collected in the Big South Fork since the mid-1980s (Ahlstedt

et al.

2003-2004, p. 65). In 2010, two individuals were found in Buck Creek and collected for future propagation efforts (McGregor 2010, unpub. data). Live fluted kidneyshell have not been collected in Rock Creek since 1988 (Layzer and Anderson 1992, p. 68). Layzer and Anderson (1992, p. 22) collected fluted kidneyshell at two sites in the West Fork Obey River. A small but recruiting population occurs in the Wolf River, Tennessee, based on 2005-06 sampling (Moles

et al.

2007, p. 79). This may be the best population remaining in the entire Cumberland River system, where most populations are very restricted in range and are highly imperiled. Given its longevity, small populations of this long-lived species may persist for decades despite total recruitment failure. Therefore, at least 5 of the extant populations may be functionally extirpated (e.g., Horse Lick Creek, Middle Fork Rockcastle River, Little South Fork Cumberland River, Rock Creek, West Fork Obey River).

Population Estimates and Status

Extirpated from both the Cumberland and Tennessee River mainstems, the fluted kidneyshell has been eliminated from approximately 50 percent of the total number of streams from which it was historically known. Population size data gathered during the past decade or two indicate that the fluted kidneyshell is rare in nearly all extant populations, the Clinch River being a notable exception. The fluted kidneyshell is particularly imperiled in Kentucky. Haag and Warren (2004, p. 16) reported that a small, extremely vulnerable population of the fluted kidneyshell may exist in Horse Lick Creek, but at

extremely low levels that they were not able to detect. They only collected fresh dead shell material in Horse Lick Creek. The vast reduction of the once sizable Little South Fork population since the late 1980s (Warren and Haag 2005, pp. 1384, 1388-1396) and the tenuous status of the other Cumberland River system populations put the species at risk of total extirpation from that Cumberland River system. In addition, the populations in the Powell River (post-1980) and the Middle Fork (post-1995) and upper North Fork (post-2000) Holston Rivers in Virginia have declined in recent years based on recent survey efforts (Henley

et al.

1999, p. 23; Ahlstedt

et al.

2005, p. 9; Jones and Neves 2007, p. 477; Johnson

et al.

in press). Populations of the fluted kidneyshell remain locally abundant in certain reaches of the North Fork Holston River but are reduced in overall range within the river (Ostby and Neves 2005, 2006a, and 2006b, entire; Dinkins 2010a, p. 3-1). Declines in mussel community abundance in the North Fork Holston River have been in the form of several die-offs. The cause for the observed die-offs is unknown (Jones and Neves 2007, p. 479), but may be related to agricultural runoff (Hanlon

et al.

2009, p. 11).

In summary, the fluted kidneyshell has been eliminated from approximately 50 percent of the total number of streams from which it was historically known. Populations in Buck Creek, Little South Fork, Horse Lick Creek, Powell River, and North Fork Holston River have clearly declined over the past two decades. Based on recent information, the overall population status of the fluted kidneyshell rangewide is declining. A few populations are considered to be viable (e.g., Wolf, Clinch, Little, North Fork Holston Rivers). However, all other populations are of questionable viability, with some on the verge of extirpation (e.g., Horse Lick and Rock Creeks). Newly reintroduced populations will hopefully begin to reverse the overall downward trend of this species.

The fluted kidneyshell was considered a species of special concern by Williams

et al.

(1993, p. 14), but two decades later is considered endangered in a reassessment of the North American mussel fauna by the Endangered Species Committee of the American Fisheries Society (Butler 2012, pers. comm.). The fluted kidneyshell is listed as a species of Greatest Conservation Need (GCN) in the Kentucky, Tennessee, and Virginia State Wildlife Action Plans (KDFWR 2005; TWRA 2005; VDGIF 2005).

Slabside Pearlymussel

Taxonomy and Species Description

The taxonomic status of the slabside pearlymussel (family Unionidae) as a distinct species is undisputed within the scientific community. The species is recognized as

Lexingtonia dolabelloides

(I. Lea, 1840) in the “Common and Scientific Names of Aquatic Invertebrates from the United States and Canada: Mollusks, Second Edition” (Turgeon

et al.

1998, p. 35). However, there are currently differing opinions on the appropriate genus to use for the species. Genetic analyses by Bogan

et al.

(unpublished data), as cited by Williams

et al.

(2008, p. 584), suggests that the type genus of

Lexingtonia, Unio subplana

Conrad, 1837, is synonymous with

Fusconaia masoni

(Conrad, 1834).

Lexingtonia

is therefore a junior synonym of

Fusconaia,

making

Lexingtonia

no longer available as a valid genus of mussel under the rules of the International Code of Zoological Nomenclature (Williams 2011, pers. comm.). Analyses by Campbell

et al.

(2005, pp. 141, 143, 147) and Campbell and Lydeard (2012a, pp. 3-6, 9; 2012b, pp. 25-27, 30, 34) suggest that “

Lexingtonia” dolabelloides,

“

Fusconaia” barnesiana,

and “

Pleurobema” gibberum

do not correspond to their currently assigned genera but form a closely related group. Williams

et al.

(2008, pp. 584-593) and Campbell and Lydeard (2012b, pp. 30, 34) picked the next available genus name for

dolabelloides,

which appears to be

Pleuronaia

(Frierson 1927). Based on this latest information, we currently consider

Pleuronaia

to be the most appropriate generic name for the slabside pearlymussel.

The following description, biology, and life history of the slabside pearlymussel is taken from data summarized in Parmalee and Bogan (1998, pp. 150-152). The slabside pearlymussel is a moderately sized mussel that reaches about 9 cm (3.5 in) in length. The shape of the shell is subtriangular, and the very solid, heavy valves are moderately inflated. Shell texture is smooth and somewhat shiny in young specimens, becoming duller with age. Shell color is greenish yellow, becoming brownish with age, with a few broken green rays or blotches, particularly in young individuals. Internally, the pseudocardinal teeth are triangular or blade-like in shape. The lateral teeth are slightly curved, with two in the left valve and one in the right valve. The color of the nacre is white, or rarely, straw-colored.

Habitat and Life History

General life history information for the slabside pearlymussel is similar to that given for the fluted kidneyshell above. Samples from approximately 150 shells of the slabside pearlymussel from the North Fork Holston River were thin-sectioned for age determination. The maximum age exceeded 40 years (Grobler

et al.

2005, p. 65).

The slabside pearlymussel utilizes all four gills as a marsupium for its glochidia. It is thought to have a spring or early summer fertilization period with the glochidia being released during the late summer in the form of conglutinates. Slabside pearlymussel conglutinates have not been described. The slabside pearlymussel's host fishes include 11 species of minnows (popeye shiner,

Notropis ariommus;

rosyface shiner,

N. rubellus;

saffron shiner,

N. rubricroceus;

silver shiner,

N. photogenis;

telescope shiner,

N. telescopus;

Tennessee shiner,

N. leuciodus;

whitetail shiner,

Cyprinella galactura;

striped shiner,

Luxilus chrysocephalus;

warpaint shiner,

L. coccogenis;

white shiner,

L. albeolus;

and eastern blacknose dace,

Rhinichthys atratulus

) (Kitchel 1985 and Neves 1991

in

Parmalee and Bogan 1998, pp. 150-152; Jones and Neves 2002, pp. 18-20).

The slabside pearlymussel is primarily a large creek to large river species, inhabiting sand, fine gravel, and cobble substrates in relatively shallow riffles and shoals with moderate current (Parmalee and Bogan 1998, p. 152; Williams

et al.

2008, p. 590). This species requires flowing, well-oxygenated waters to thrive.

Historical Range and Distribution

Historically, the slabside pearlymussel occurred in the lower Cumberland River mainstem from the vicinity of the Kentucky State line downstream to the the Caney Fork River, Tennessee, and in the Tennessee River mainstem from eastern Tennessee to western Tennessee. Records are known from two Cumberland River tributaries, the Caney Fork [TN] and Red Rivers [KY, TN]. In addition, it is known from 30 Tennessee River system tributaries, including the South Fork Powell River [VA], Powell River [TN, VA], Puckell Creek [VA], Clinch River [TN, VA], North Fork Holston River [TN, VA], Big Moccasin Creek [VA], Middle Fork Holston River [VA], South Fork Holston River [TN], Holston River [TN], Nolichucky River [TN], West Prong Little Pigeon River [TN], French Broad River [TN], Tellico River [TN], Little Tennessee River [TN], Hiwassee River [TN], Sequatchie River [TN],

Larkin Fork [AL], Estill Fork [AL], Hurricane Creek [AL], Paint Rock River [AL], Flint River [AL], Flint Creek [AL], Limestone Creek [AL], Elk River [AL, TN], Sugar Creek [AL], Bear Creek [AL, MS], North Fork Creek [TN], Big Rock Creek [TN], Buffalo River [TN], and Duck River [TN] (Gordon and Layzer 1989, entire; Winston and Neves 1997, entire; Parmalee and Bogan 1998, pp. 150-152). The slabside pearlymussel's known historical and current occurrences, by water body and county, are shown in Table 2 below.

Table 2—Known Historical and Current Occurrences for the Slabside Pearlymussel

Water body

Drainage

County

State

Historical or current

Cumberland River

Cumberland

Davidson, Smith

TN

Historical.

Caney Fork River

Cumberland

?

TN

Historical.

Red River

Cumberland

Logan

KY

Historical.

Red River

Cumberland

?

TN

Historical.

South Fork Powell River

Tennessee

Wise

VA

Historical.

Powell River

Tennessee

Claiborne

TN

Historical.

Powell River

Tennessee

Hancock

TN

Historical and Current.

Powell River

Tennessee

Lee

VA

Historical and Current.

Puckell Creek

Tennessee

Lee

VA

Historical.

Clinch River

Tennessee

Hancock

TN

Historical and Current.

Clinch River

Tennessee

Anderson, Campbell, Claiborne, Knox

TN

Historical.

Clinch River

Tennessee

Russell, Scott, Tazewell, Wise

VA

Historical and Current.

North Fork Holston River

Tennessee

Hawkins, Sullivan

TN

Historical.

North Fork Holston River

Tennessee

Bland, Scott, Smyth, Washington

VA

Historical and Current.

Big Moccasin Creek

Tennessee

Russell, Scott

VA

Historical and Current.

Middle Fork Holston River

Tennessee

Smyth, Washington, Wythe

VA

Historical and Current.

South Fork Holston River

Tennessee

Sullivan

TN

Historical.

Holston River

Tennessee

?

TN

Historical.

French Broad River

Tennessee

Sevier

TN

Historical.

Tennessee River

Tennessee

Colbert, Jackson, Lauderdale

AL

Historical.

Tennessee River

Tennessee

Hamilton, Hardin, Knox, Meigs, Rhea

TN

Historical.

Nolichucky River

Tennessee

Cocke, Greene, Hamblen

TN

Historical and Current.

West Prong Little Pigeon River

Tennessee

Sevier

TN

Historical.

Tellico River

Tennessee

Monroe

TN

Historical.

Little Tennessee River

Tennessee

Monroe

TN

Historical.

Hiwassee River

Tennessee

Polk

TN

Historical and Current.

Sequatchie River

Tennessee

Sequatchie

TN

Historical and Current.

Larkin Fork

Tennessee

Jackson

AL

Historical and Current.

Estill Fork

Tennessee

Jackson

AL

Historical and Current.

Hurricane Creek

Tennessee

Jackson

AL

Historical and Current.

Paint Rock River

Tennessee

Jackson, Madison, Marshall

AL

Historical and Current.

Flint River

Tennessee

Madison

AL

Historical.

Flint Creek

Tennessee

Morgan

AL

Historical.

Limestone Creek

Tennessee

Limestone

AL

Historical.

Elk River

Tennessee

Limestone

AL

Historical and Current.

Elk River

Tennessee

Lincoln

TN

Historical and Current.

Elk River

Tennessee

Coffee, Franklin, Moore

TN

Historical.

Sugar Creek

Tennessee

Limestone

AL

Historical.

Bear Creek

Tennessee

Franklin

AL

Historical and Current.

Bear Creek

Tennessee

Tishomingo

MS

Historical and Current.

Duck River

Tennessee

Bedford, Hickman, Marshall, Maury

TN

Historical and Current.

Duck River

Tennessee

Coffee

TN

Historical.

North Fork Creek

Tennessee

Bedford

TN

Historical.

Big Rock Creek

Tennessee

Marshall

TN

Historical.

Buffalo River

Tennessee

Humphreys, Perry

TN

Historical and Current.

Buffalo River

Tennessee

Lewis

TN

Historical.

Based on collections made in the early 1900s, the slabside pearlymussel was historically fairly widespread and common in many Cumberlandian Region streams. However, its decline in certain streams may have begun before European colonization. The slabside pearlymussel was considered rare by mussel experts as early as 1970 (Stansbery 1971, p.13), which represents the first attempt to compile such a list. The extirpation of this species from numerous streams within its historical range indicates that substantial population losses and range reductions have occurred.

Current Range and Distribution

In this document, populations of the slabside pearlymussel are generally considered extant (current) if live individuals or fresh dead specimens have been collected since circa 1980. This criterion (circa 1980) was chosen because a large number of collections were conducted in the 1980s in the Cumberland and Tennessee River systems and due to the longevity of these species (40-55 years), they are still thought to occur in these areas.

Some of the historical occurences have not been surveyed since the 1980s. Based on this criterion, extant populations remain in the Powell River [TN, VA], Clinch River [TN, VA], North Fork Holston River [VA], Nolichucky River [TN], Big Moccasin Creek [VA], Middle Fork Holston River [VA], Hiwassee River [TN], Sequatchie River [TN], Paint Rock River [AL], Larkin Fork [AL], Estill Fork [AL], Hurricane Creek [AL], Elk River [AL, TN], Buffalo River [TN], Duck River [TN], and Bear Creek

[AL, MS] (see Table 2). Where two or more stream populations occur contiguously with no absolute barriers (e.g., large impoundments) or long reaches of unoccupied habitat, they are considered to represent a single population segment. The Paint Rock River system (including Larkin Fork, Estill Fork, and Hurricane Creek) is considered a single population segment or cluster but it occurs only in the lower mile or so of the three tributary streams. Thus, we consider 13 of 30 populations of the slabside pearlymussel to be extant. The slabside pearlymussel has been eliminated from more than 50 percent of streams from which it was historically known.

The extant occurrences in the Tennessee River system represent 11 isolated populations. Population size data gathered during the past two decades indicate that the slabside pearlymussel is rare (experienced surveyors may find four or fewer specimens per site of occurrence) in about half of its extant populations. Only a few individuals have been found in the Powell River since 1988; therefore, this population is considered extremely rare (Ahlstedt

et al.

2005, p. 9). In 2009, 4 individuals were collected in the Powell River (Johnson 2010, p. 39). A single live individual was found in 2006 in Big Moccasin Creek, Virginia (Ostby

et al.

2006, p. 3). The slabside pearlymussel is uncommon to rare in the Clinch River, with only a few individuals found per effort (Ahlstedt

et al.

2005, p. 8). Eckert and Pinder (2010, pp. 23-30) collected 1 individual in quantitative samples and 5 individuals in semi-quantitative samples in the Clinch River at Cleveland Island in 2008, and 2 individuals in quantitative samples and 13 individuals in semi-quantitative samples in the Clinch River at Cleveland Island in 2002. In 2005, approximately 20 individuals were found near Harms Mill (one of five sites surveyed) in the Elk River, Tennessee, and 13 individuals (at two of five survey sites, spanning approximately 48 rkm (30 rmi)) were found in 2008 (Howard 2009, pers. comm.; Tennessee Valley Authority (TVA) 2009, p. 59). In 2002, one live individual was found in the Hiwassee River (Ahlstedt 2003, p. 3). The slabside pearlymussel was last found in the Sequatchie River 2 miles north of Dunlap, Tennessee, in 1980 (Hatcher and Ahlstedt 1982, p. 9). A small population is limited to Bear Creek in Mississippi, its only occurrence in that State (Jones 2012, pers. comm.). In 2009, TVA collected 9 individuals at one site in Bear Creek (TVA 2010, p. 69). This population is recruiting as evidenced by collection of fresh dead juvenile shells in 2011 (Johnson 2011, pers. comm.). Given its longevity, small populations of this long-lived species may persist for decades despite total recruitment failure. The species has undergone decline in the North and Middle Forks of the Holston River (Jones and Neves 2005, pp. 8-9). This is especially true for the North Fork, where the species has been nearly eliminated (Hanlon 2006, unpub. data). The cause for the observed die-offs is unknown (Jones and Neves 2007, p. 479). Ostby

et al.

(2010, pp. 16-20) observed 8 individuals in qualitative surveys at one site, but did not observe the species in quantitative surveys in the Upper North Fork Holston River. Slabside pearlymussels have declined at 3 of 4 survey sites on the Middle Fork Holston River (Henley 2011, pers. comm.). A single valve of a fresh dead specimen was found in the Nolichucky River in 2011 (Dinkins 2010b, p. 2-1). In 2011, TVA collected one live individual in the Buffalo River (Wales 2012, pers. comm.).

The Duck and Paint Rock Rivers appear to have the best populations remaining rangewide based on population size and the evidence of recent recruitment. The slabside pearlymussel is found at numerous sites in the Duck River within a 64-rkm (40-rmi) reach, and is found at numerous sites within a 72-rkm (45-rmi) reach of the Paint Rock River (Ahlstedt

et al.

2004, p. 84; Fobian

et al.

2008, pp. 15-16). A 2010 quantitative survey of the Duck River found the slabside pearlymussel present but rare at 4 of 6 sites sampled (Hubbs

et al.

2011, pp. 19-25).

Population Estimates and Status

A recent study of major population centers concluded that all populations of the species were fairly similar in genetic structure (Grobler

et al.

2005, p. 1). However, the population in the Duck River was deemed relatively distinct enough from those in the middle (i.e., Paint Rock River) and upper (i.e., Clinch, North and Middle Forks Holston Rivers) Tennessee River system to warrant recognition as a distinct management unit.

Current status information for most of the 13 extant populations is available from recent periodic sampling efforts (sometimes annually) and other field studies. Comprehensive surveys have taken place in the Middle and North Forks Holston River, Paint Rock River, and Duck River in the past several years. Based on this information, the overall population of the slabside pearlymussel appears to be declining rangewide, and the species remains in relatively good numbers and appears viable in just two streams (Duck and Paint Rock Rivers). Two of the four largest populations in the mid-1990s have undergone drastic recent declines (i.e., North and Middle Forks Holston Rivers), especially in the North Fork. Most of the other populations are of questionable viability and may be on the verge of extirpation (e.g., Powell and Hiwassee Rivers; Big Moccasin Creek).

The slabside pearlymussel was considered threatened by Williams

et al.

(1993, p. 13), but two decades later is considered endangered in a reassessment of the North American mussel fauna by the Endangered Species Committee of the American Fisheries Society (Butler 2012, pers. comm.). The slabside pearlymussel is listed as a species of Greatest Conservation Need (GCN) in the Alabama, Mississippi, Tennessee, and Virginia State Wildlife Action Plans (Alabama Department of Conservation and Natural Resources, Division of Wildlife and Freshwater Fisheries, 2005; KDFWR 2005; Mississippi Department of Wildlife, Fisheries and Parks, 2005; TWRA 2005; VDGIF 2005).

Summary of Factors Affecting the Species

Section 4 of the Act, and its implementing regulations at 50 CFR part 424, set forth the procedures for adding species to the Federal Lists of Endangered and Threatened Wildlife and Plants. Under section 4(a)(1) of the Act, we may list a species based on any of the following five factors: (A) The present or threatened destruction, modification, or curtailment of its habitat or range; (B) overutilization for commercial, recreational, scientific, or educational purposes; (C) disease or predation; (D) the inadequacy of existing regulatory mechanisms; and (E) other natural or manmade factors affecting its continued existence. Listing actions may be warranted based on any of the above factors, singly or in combination. Each of these factors is discussed below.

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

The decline of the fluted kidneyshell and slabside pearlymussel in the Cumberlandian Region and other mussel species in the eastern United States is primarily the result of habitat loss and degradation. Chief among the causes of decline are impoundments, gravel and coal mining, sedimentation, water pollution, and stream channel alterations (Neves 1993, pp. 4-5;

Williams

et al.

1993, p. 7; Neves

et al.

1997, pp. 60-78).

Impoundments

Impoundments result in the dramatic modification of riffle and shoal habitats and the resulting loss of mussel resources, especially in larger rivers. Impoundment impacts are most profound in riffle and shoal areas, which harbor the largest assemblages of mussel species, including the fluted kidneyshell and slabside pearlymussel. Mussels are relatively immobile and, therefore, require a stable substrate to survive and reproduce, and are particularly susceptible to channel instability (Neves

et al.

1997, p. 23) and alteration in the dynamic processes involved in maintaining stream stability. Dams interrupt most of a river's ecological processes by modifying flood pulses; controlling impounded water elevations; altering water flow, sediments, nutrients, energy inputs, and outputs; increasing depth; decreasing habitat heterogeneity; and decreasing bottom stability due to subsequent sedimentation. In addition, dams can also seriously alter downstream water quality and riverine habitat and negatively impact tailwater mussel populations. These changes include thermal alterations immediately below dams; changes in channel characteristics, habitat availability, and flow regime; daily discharge fluctuations; increased silt loads; and altered host fish communities. For these above-mentioned reasons, the reproductive process of riverine mussels is generally disrupted by impoundments, making them unable to successfully reproduce and recruit under reservoir conditions. Coldwater releases from large non-navigational dams and scouring of the river bed from highly fluctuating, turbulent tailwater flows have also been implicated in the demise of mussel faunas (see critical habitat descriptions for Units FK19 and FK20, below).

The damming of rivers has been a major factor contributing to the demise of mussels (Bogan 1993, p. 604). Dams eliminate or reduce river flow within impounded areas, trap silts and cause sediment deposition, alter water temperature and dissolved oxygen levels, change downstream water flow and quality, affect normal flood patterns, and block upstream and downstream movement of mussels and their host fishes (Bogan 1993, p. 604; Vaughn and Taylor 1999, pp. 915

-

917; Watters 1999, pp. 261-264; McAllister

et al.

2000, p. iii; Marcinek

et al.

2005, pp. 20-21). Below dams, mollusk declines are associated with changes and fluctuation in flow regime, scouring and erosion, reduced dissolved oxygen levels, reduced food availability, water temperature alteration, and changes in resident fish assemblages (Williams

et al.

1993, p. 7; Neves

et al.

1997, pp. 63-64; Watters 1999, pp. 261-264; Marcinek

et al.

2005, pp. 20-21; Moles and Layzer 2008, p. 220). Because rivers are linear systems, these alterations can cause mussel declines for many miles below the dam (Moles and Layzer 2008, p. 220; Vaughn and Taylor 1999, p. 916).

Population losses due to impoundments have probably contributed more to the decline of the fluted kidneyshell, slabside pearlymussel, and other Cumberlandian Region mussels than has any other single factor. The majority of the Cumberland and Tennessee River mainstems and many of their largest tributaries are now impounded, and therefore, are unsuitable for Cumberlandian Region mussels. For example, approximately 90 percent of the 904-rkm (562-rmi) length of the Cumberland River downstream of Cumberland Falls is either impounded (three locks and dams and Wolf Creek Dam) or otherwise adversely impacted by coldwater discharges from Wolf Creek Dam. Other major U.S. Army Corps of Engineers (Corps) impoundments on Cumberland River tributaries (e.g., Obey River, Caney Fork) have inundated over 161 rkm (100 rmi) of riverine habitat for the fluted kidneyshell and the slabside pearlymussel. Layzer

et al.

(1993, p. 68) reported that 37 of the 60 mussel species present in the Caney Fork River pre-impoundment have been extirpated. By 1971, approximately 3,700 rkm (2,300 rmi) (about 20 percent) of the Tennessee River and its tributaries with drainage areas of 65 square rkm (25 square rmi) or greater were impounded by the TVA (TVA 1971, p. 5). The subsequent completion of additional major impoundments on tributary streams (e.g., Duck River in 1976, Little Tennessee River in 1979) significantly increased the total river kilometers (miles) impounded behind the 36 major dams in the Tennessee River system.

Given projected population increases and the need for municipal water supply, other proposals for small impoundment construction are likely in the future within the Cumberland and Tennessee River systems.

Mining and Commercial Navigation

Instream gravel mining has been implicated in the destruction of mussel populations. Negative impacts associated with gravel mining include stream channel modifications (e.g., altered habitat, disrupted flow patterns, sediment transport), water quality modifications (e.g., increased turbidity, reduced light penetration, increased temperature), macroinvertebrate population changes (e.g., elimination, habitat disruption, increased sedimentation), and changes in fish populations (e.g., impacts to spawning and nursery habitat, food web disruptions) (Kanehl and Lyons 1992, pp. 26-27).

Gravel mining activities negatively impact the habitat of the fluted kidneyshell in Buck Creek, one of the few remaining populations of this species in the entire Cumberland River system. Gravel mining activities also negatively impact the habitat of the slabside pearlymussel in the Powell and Elk Rivers in the Tennessee River system.

Channel modification for commercial navigation has been shown to increase flood heights (Belt 1975, p. 684), partly as a result of an increase in stream bed slope (Hubbard

et al.

1993, p. 137). Flood events are exacerbated, conveying large quantities of sediment, potentially with adsorbed contaminants, into streams. Channel maintenance often results in increased turbidity and sedimentation that often smothers mussels (Stansbery 1970, p. 10).

Heavy metal-rich drainage from coal mining and associated sedimentation has adversely impacted upper Cumberland and Tennessee River system streams with historically diverse mussel faunas. Strip mining continues to threaten mussel habitats in coal field drainages of the Cumberland Plateau, including streams harboring small fluted kidneyshell populations (e.g., Horse Lick Creek, Little South Fork, Powell River, Indian Creek). Portions of the upper Tennessee River system are also influenced by coal mining activities. Powell River mussel populations were inversely correlated with coal fines in the substrate; when coal fines were present, decreased filtration times and increased movements were noted in laboratory-held mussels (Kitchel

et al.

1981, p. 25). In a quantitative study in the Powell River, a decline of federally listed mussels and the long-term decrease in overall species composition since about 1980 was attributed to general stream degradation due primarily to coal mining activities in the headwaters (Ahlstedt and Tuberville 1997, pp. 74-76). Numerous gray-water and black-water spill events have been documented in the Powell and Clinch River drainages over the past several years. The habitats of Fluted

kidneyshell, slabside pearlymussel, and other mussels in the Clinch and Powell rivers are increasingly being threatened by coal mining activities.

Oil and Natural Gas Development

Oil and natural gas resources are present in some of the watersheds that are known or historically were known to support the fluted kidneyshell and slabside pearlymussel, including the Clinch, Powell, and Big South Fork Rivers. Exploration and extraction of these energy resources has the potential to result in increased siltation, a changed hydrograph (flow regime), and altered water quantity and quality even at a distance from the mine or well field. Although oil and natural gas extraction generally occurs away from the river, extensive road and pipeline networks are required to construct and maintain wells and transport the extracted resources. These road and pipeline networks frequently cross or occur near tributaries, contributing sediment to the receiving waterway. In addition, the construction and operation of wells may result in the illegal discharge of chemical contaminants and subsurface minerals.

Sedimentation

Sedimentation is one of the most significant pollution problems for aquatic organisms (Waters 1995, pp. 2-3), and has been determined to be a major factor in mussel declines (Ellis 1936, pp. 39-40). Sources of silt and sediment include poorly designed and executed timber harvesting operations and associated activities; complete clearing of riparian vegetation for agricultural, silvicultural, or other purposes; and those construction, mining, and other practices that allow exposed earth to enter streams. Agricultural activities, specifically an increase in cattle grazing and the resultant nutrient enrichment and loss of riparian vegetation along the stream, are responsible for much of the sediment (Fraley and Ahlstedt 2000, p. 193; Hanlon

et al.

2009, pp. 11-12).

Heavy sediment loads can destroy mussel habitat, resulting in a corresponding shift in mussel fauna (Brim Box and Mossa 1999, p. 100). Excessive sedimentation can lead to rapid changes in stream channel position, channel shape, and bed elevation (Brim Box and Mossa 1999, p. 102). Sedimentation has also been shown to impair the filter feeding ability of mussels, and high amounts of suspended sediments can dilute their food source (Dennis 1984, p. 212). We will describe the detrimental actions of sedimentation in Factor E, below.

Chemical Contaminants

Chemical contaminants are ubiquitous throughout the environment and are considered a major threat in the decline of mussel species (Richter

et al.

1997, p. 1081; Strayer

et al.

2004, p. 436; Wang

et al.

2007a, p. 2029; Cope

et al.

2008, p. 451). Chemicals enter the environment through both point and nonpoint discharges including spills, industrial sources, municipal effluents, and agricultural runoff. These sources contribute organic compounds, heavy metals, pesticides, and a wide variety of newly emerging contaminants to the aquatic environment. As a result, water and sediment quality can be degraded to the extent that mussel habitats and populations are adversely impacted. We will describe the detrimental actions of chemicals in Factor E, below.

Other Stream Channel Alterations

Other stream channel alterations that can impact mussel habitats include bridges, other road crossing structures, and activities that lower water tables (withdrawals). Culverts can act as barriers to fish passage (Wheeler

et al.

2005, p. 149), particularly by increasing flow velocity (Warren and Pardew 1998, p. 637). Stream channels become destabilized when improperly designed culverts or bridges change the morphology and interrupt the transport of woody debris, substrate, and water (Wheeler

et al.

2005, p. 152). Water withdrawals for irrigation, municipal, and industrial water supplies are an increasing concern. U.S. water consumption doubled from 1960 to 2000, and is likely to increase further (Naiman and Turner 2000, p. 960). Therefore, we anticipate road crossings, water withdrawals, and potential stream dewatering to be threats to the habitat of the fluted kidneyshell and slabside pearlymussel.

Summary of Factor A

Habitat loss and degradation negatively impact the fluted kidneyshell and slabside pearlymussel. Severe degradation from impoundments, gravel and coal mining, oil and natural gas development, sedimentation, chemical contaminants, and stream channel alterations threaten the stream habitat and water quality on which these species depend. Contaminants associated with coal mining (metals, other dissolved solids), municipal effluents (bacteria, nutrients, pharmaceuticals), and agriculture (fertilizers, pesticides, herbicides, and animal waste) cause degradation of water quality and habitats through increased acidity and conductivity, instream oxygen deficiencies, excess nutrification, and excessive algal growths. Furthermore, these threats faced by the fluted kidneyshell and slabside pearlymussel are imminent; the result of ongoing projects that are expected to continue indefinitely, therefore perpetuating these impacts. As a result of the imminence of these threats, combined with the vulnerability of the remaining small, isolated populations to extirpation from natural and manmade threats, we have determined that the present or threatened destruction, modification, or curtailment of the habitat and range of these species represents a threat to both the fluted kidneyshell and slabside pearlymussel.

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

The fluted kidneyshell and slabside pearlymussel are not commercially valuable species, but may be increasingly sought by collectors, due to their increasing rarity. Although scientific collecting is not thought to represent a significant threat, localized populations could become impacted, and possibly extirpated, by overcollecting, particularly if regulations governing collection activity (currently scientific collection is controlled by the States through the issuance of collection permits; see Factor D below) are not enforced.

In summary, the fluted kidneyshell and slabside pearlymussel are not commercially utilized but might be increasingly sought for scientific or educational purposes as their rarity becomes known. We do not consider overutilization for commercial, recreational, scientific, or educational purposes to be a threat to either species now or likely to become a threat in the future.

C. Disease or Predation

Little is known about diseases in mussels (Grizzle and Brunner 2007, p. 6). Several mussel dieoffs have been documented during the past 20 years (Neves 1987, pp. 8-11). Although the ultimate cause is unknown, some researchers believe that disease may be a factor. Warren and Haag (2005, p. 1394) hypothesized that declines in the Little South Fork Cumberland River, Kentucky, mussel fauna, including the once abundant fluted kidneyshell population, may have been at least partially attributed to disease, but no definitive cause has been determined. We have no specific documentation indicating that disease poses a threat to slabside pearlymussel populations.

Juvenile and adult mussels are prey items for some invertebrate predators and parasites (for example, nematodes and mites), and are prey for a few vertebrate species (for example, raccoons, muskrats, otters, and turtles) (Hart and Fuller 1974, pp. 225-240). Mussel parasites include water mites, trematodes, oligochaetes, leeches, copepods, bacteria, and protozoa (Grizzle and Brunner 2007, p. 6). Generally, parasites are not suspected of being a major limiting factor (Oesch 1984, p. 16); however, Gangloff

et al.

(2008, pp. 28-30) found that reproductive output and physiological condition were negatively correlated with mite and trematodes abundance, respectively. Stressors that reduce fitness may make mussels more susceptible to parasites (Butler 2007, p. 90).

Muskrat predation on the fluted kidneyshell represents a localized threat, as determined by Neves and Odum (1989, entire) in the upper North Fork Holston River in Virginia. They concluded that muskrat predation could limit the recovery potential of endangered mussel species or contribute to the local extirpation of already depleted mussel populations. Although other mammals (e.g., raccoon, mink) occasionally feed on mussels, the threat from these predators is not considered to be significant. Predation does occur, but it is considered to be a normal aspect of the species' population dynamics.

In summary, there is little information on disease in mussels, and disease is not currently considered to be a threat to the fluted kidneyshell or slabside pearlymussel and it is not likely to become so in the future. Although predation does occur and impacts local populations, we conclude that predation is not a threat to these species as a whole or likely to become so in the future.

D. The Inadequacy of Existing Regulatory Mechanisms

The objective of the Federal Water Pollution Control Act, commonly referred to as the Clean Water Act (CWA) (33 U.S.C. 1251

et seq.

), is to restore and maintain the chemical, physical, and biological integrity of the nation's waters by preventing point and nonpoint pollution sources. The CWA has a stated goal that “* * * wherever attainable, an interim goal of water quality which provides for the protection and propagation of fish, shellfish, and wildlife and provides for recreation in and on the water be achieved by July 1, 1983.” States are responsible for setting and implementing water quality standards that align with the requirements of the CWA. Overall, implementation of the CWA could benefit both mussel species through the point and nonpoint programs.

Nonpoint source (NPS) pollution comes from many diffuse sources, unlike pollution from industrial and sewage treatment plants. NPS pollution is caused by rainfall or snowmelt moving over and through the ground. As the runoff moves, it transports natural and human-made pollutants to lakes, rivers, wetlands, coastal waters and ground waters. States report that nonpoint source pollution is the leading remaining cause of water quality problems. The effects of nonpoint source pollutants on specific waters vary and may not always be fully assessed. However, these pollutants have harmful effects on fisheries and wildlife (

http://www.epa.gov/owow_keep/NPS/whatis.html

).

Sources of NPS pollution within the watersheds occupied by both mussels include agriculture, clearing of riparian vegetation, urbanization, road construction, and other practices that allow bare earth to enter streams. The Service has no information concerning the implementation of the CWA regarding NPS pollution specific to protection of both mussels. However, insufficient implementation could become a threat to both mussel species if they continue to decline in numbers.

The fluted kidneyshell and slabside pearlymussel continue to decline due to the effects of habitat destruction, poor water quality, contaminants, and other factors. However, there is no specific information known about the sensitivity of these mussels to common point source pollutants like industrial and municipal pollutants and very little information on other freshwater mussels. Because there is very little information known about water quality parameters necessary to fully protect freshwater mussels, such as the fluted kidneyshell and slabside pearlymussel, it is difficult to determine whether the CWA is adequately addressing the habitat and water quality threats to these species. However, given that a goal of the CWA is to establish water quality standards that protect shellfish and given that documented declines of these mussel species still continue due to poor water quality and other factors, we take a conservative approach in favor of the species and conclude that the CWA has been insufficient to significantly reduce or remove the threats to the fluted kidneyshell and slabside pearlymussel. We invite public comment on this matter, and solicit information especially regarding water quality data that may be helpful in determining the water quality parameters necessary for these species' survival (see Information Requested, item #4).

Summary of Factor D

In summary, the CWA has a stated goal to establish water quality standards that protect aquatic species, including the fluted kidneyshell and slabside pearlymussel. However, the CWA has generally been insufficient at protecting mussels, and adequate water quality criteria that are protective of all life stages, particularly glochidia and juveniles, may not be established. Little information is known about specific sensitivities of mussels to various pollutants, but both species continue to decline due to the effects of habitat destruction, poor water quality, contaminants, and other factors. Based on our analysis of the best available scientific and commercial data, we conclude that the current implementation of the provisions under the CWA to protect water quality for aquatic species is inadequate to reduce or remove threats to the fluted kidneyshell and slabside pearlymussel throughout all of their range.

E. Other Natural or Manmade Factors Affecting Its Continued Existence

Altered Temperature Regimes

Natural temperature regimes can be altered by impoundments, water releases from dams, industrial and municipal effluents, and changes in riparian habitat. Critical thermal limits for survival and normal functioning of many mussel species are unknown. High temperatures can reduce dissolved oxygen concentrations in the water, which slows growth, reduces glycogen stores, impairs respiration, and may inhibit reproduction (Hart and Fuller 1974, pp. 240-241). Low temperatures can significantly delay or prevent metamorphosis (Watters and O'Dee 1999, pp. 454-455). Water temperature increases have been documented to shorten the period of glochidial encystment, reduce the speed in which they turn upright, increase oxygen consumption, and slow burrowing and movement responses (Hart and Fuller 1974, pp. 240-241; Bartsch

et al.

2000, p. 237; Watters

et al.

2001, p. 546; Schwalb and Pusch 2007, pp. 264-265). Several studies have documented the influence of temperature on the timing of aspects of mussel reproduction (for example, Gray

et al.

2002, p. 156; Allen

et al.

2007, p. 85; Steingraeber

et al.

2007, pp. 303-309). Peak glochidial

releases are associated with water temperature thresholds that can be thermal minimums or thermal maximums, depending on the species (Watters and O'Dee 2000, p. 136). Abnormal temperature changes may cause particular problems to mussels whose reproductive cycles may be linked to fish reproductive cycles Young and Williams 1984, entire).

Chemical Contaminants

Chemical spills can be especially devastating to mussels because they may result in exposure of a relatively immobile species to extremely elevated contaminant concentrations that far exceed toxic levels and any water quality standards that might be in effect. Some notable spills that released large quantities of highly concentrated chemicals resulting in mortality to mussels and host fish include a kill on the Clinch River at Carbo, Virginia, from a power plant alkaline fly ash pond spill in 1967, and a sulfuric acid spill in 1970 (Crossman

et al.

1973, p. 6). Approximately 18,000 mussels of several species, including the fluted kidneyshell and 750 individuals from three endangered mussel species (tan riffleshell,

Epioblasma florentina walkeri;

purple bean,

Villosa perpurpurea;

and rough rabbitsfoot,

Quadrula cylindrica strigillata

), were eliminated from the upper Clinch River near Cedar Bluff, Virginia, in 1998, when an overturned tanker truck released approximately 6,100 liters (1,600 gallons) of a chemical used in rubber manufacturing (Jones

et al.

2001, p. 20; Schmerfeld 2006, p. 12). These are not the only instances where chemical spills have resulted in the loss of high numbers of mussels (Neves 1991, p. 252; Jones

et al.

2001, p. 20; Brown

et al.

2005, p. 1457; Schmerfeld 2006, pp. 12-13), but are provided as examples of the serious threat chemical spills pose to mussel species, such as the fluted kidneyshell and slabside pearlymussel.

Cope

et al.

(2008, p. 451) evaluated the pathways of exposure to environmental pollutants for all four mollusk life stages (free glochidia, encysted glochidia, juveniles, and adults) and found that each life stage has both common and unique characteristics that contribute to observed differences in contaminant exposure and sensitivity. Very little is known of the potential mechanisms and consequences of waterborne toxicants on sperm viability. However, Watters (2011) demonstrated that the spermatozeugmata (sperm ball) produced and released by male mussels are sensitive to varying levels of salinity. When exposed to high enough salinity levels, the spermatozeugmata disassociate and can be rendered nonviable if they disassociate prior to entering a female mussel. This may pose yet another significant challenge for mussels to successfully fertilize eggs and promote recruitment if exposed to elevated salinity or conductivity levels in the ambient water column.

In the female mollusk, the marsupial region of the gill currently is thought to be physiologically isolated from respiratory functions, and this isolation may provide some level of protection from contaminant interference with a female's ability to achieve fertilization or brood glochidia (Cope

et al.

2008, p. 454). A major exception to this assertion is with chemicals that act directly on the neuroendocrine pathways controlling reproduction (see discussion below). Nutritional and ionic exchange is possible between a brooding female and her glochidia, providing a route for chemicals (accumulated or waterborne) to disrupt biochemical and physiological pathways (such as maternal calcium transport for construction of the glochidial shell).

Juvenile mussels typically remain burrowed beneath the sediment surface for 2 to 4 years. Residence beneath the sediment surface necessitates deposit (pedal) feeding and a reliance on interstitial (pore) water for dissolved oxygen (Watters 2007, p. 56). The relative importance of juvenile fluted kidneyshell and slabside pearlymussel exposure to contaminants in overlying surface water, interstitial (pore) water, whole sediment, or food has not been adequately assessed. Exposure to contaminants from each of these routes varies with certain periods and environmental conditions (Cope

et al.

2008, pp. 453, 457).

The primary routes of exposure to contaminants for adult fluted kidneyshell and slabside pearlymussel are surface water, sediment, interstitial (pore) water, and diet; adults can be exposed when either partially or completely burrowed in the substrate (Cope

et al.

2008, p. 453). Adult mussels have some ability to detect certain toxicants in the water and close their valves to avoid exposure (Van Hassel and Farris 2007, p. 6). Adult mussel toxicity and relative sensitivity (exposure and uptake of toxicants) may be reduced at high rather than at low toxicant concentrations because uptake is affected by the prolonged or periodic toxicant avoidance responses (when the avoidance behavior can no longer be sustained for physiological reasons) (Cope

et al.

2008, p. 454). Toxicity results based on low-level exposure of adults are similar to estimates for glochidia and juveniles for some toxicants (for example, copper). The duration of any toxicant avoidance response by an adult mussel is likely to be affected by several variables, such as species, age, shell thickness and gape, properties of the toxicant, and water temperature. There is a lack of information on toxicant response(s) specific to adult mussels (including the fluted kidneyshell and slabside pearlymussel), but results of tests using glochidia and juveniles may be valuable for protecting adults (Cope

et al.

2008, p. 454).

Exposure to lower concentrations of contaminants, more likely to be found in aquatic environments, can also adversely affect mussels and result in the decline of mussel species. Such concentrations may not be immediately lethal, but over time, can result in mortality, reduced filtration efficiency, reduced growth, decreased reproduction, changes in enzyme activity, and behavioral changes to all mussel life stages. Frequently, procedures that evaluate the `safe' concentration of an environmental contaminant (e.g., national water quality criteria) do not have data for mussel species or exclude data that is available for mussels (March

et al.

2007, pp. 2066-2067, 2073).

Current research is now focusing on the contaminant sensitivity of mussel glochidia and newly-released juvenile mussels (Goudreau

et al.

1993, pp. 219-222; Jacobson

et al.

1997, p. 2390; Valenti

et al.

2005, pp. 1244-1245; Valenti

et al.

2006, pp. 2514-2517; March

et al.

2007, pp. 2068-2073; Wang

et al.

2007b, pp. 2041-2046) and juveniles (Augspurger

et al.

2003, p. 2569; Bartsch

et al.

2003, p. 2561; Mummert

et al.

2003, p. 2549; Valenti

et al.

2005, pp. 1244-1245; Valenti

et al.

2006, pp. 2514-2517; March

et al.

2007, pp. 2068-2073; Wang

et al.

2007b, pp. 2041-2046; Wang

et al.

2007c, pp. 2053-2055) to such contaminants as ammonia, metals, chlorine, and pesticides.

One chemical that is particularly toxic to early life stages of mussels is ammonia. Sources of ammonia include agriculture (animal feedlots and nitrogenous fertilizers), municipal wastewater treatment plants, and industrial waste (Augspurger

et al.

2007, p. 2026) as well as precipitation and natural processes (i.e., decomposition of organic nitrogen) (Goudreau

et al.

1993, p. 212; Hickey and Martin 1999, p. 44; Augspurger

et al.

2003, p. 2569; Newton 2003, p. 1243). Therefore, ammonia is considered a limiting factor for survival and recovery of some mussel species

due to its ubiquity in aquatic environments and high level of toxicity, and because the highest concentrations typically occur within microhabitats inhabited by mussels (Augspurger

et al.

2003, p. 2574). In addition, studies have shown that ammonia concentrations increase with increasing temperature and low flow conditions (Cherry

et al.

2005, p. 378; Cooper

et al.

2005, p. 381), which may be exacerbated by the effects of climate change, and may cause ammonia to become more problematic for juvenile mussels.

Mussels are also affected by heavy metals (Keller and Zam 1991, p. 543) such as cadmium, chromium, copper, mercury, and zinc, which can negatively affect biological processes such as growth, filtration efficiency, enzyme activity, valve closure, and behavior (Keller and Zam 1991, p. 543; Naimo 1995, pp. 351-355; Jacobson

et al.

1997, p. 2390; Valenti

et al.

2005, p. 1244). Heavy metals occur in industrial and wastewater effluents and are often a result of atmospheric deposition from industrial processes and incinerators. Glochidia and juvenile mussels have recently been studied to determine the acute and chronic toxicity of copper to these life stages (Wang

et al.

2007b, pp. 2036-2047; Wang

et al.

2007c, pp. 2048-2056). The chronic values determined for copper for survival and growth of juveniles are below the Environmental Protection Agency (EPA) 1996 chronic water quality criterion for copper (Wang

et al.

2007c, pp. 2052-2055). March (2007, pp. 2066 and 2073) identified that copper water quality criteria and modified State water quality standards may not be protective of mussels.

Mercury is another heavy metal that has the potential to negatively affect mussel populations, and it is receiving attention due to its widespread distribution and potential to adversely impact the environment. Mercury has been detected throughout aquatic environments as a product of municipal and industrial waste and atmospheric deposition from coal burning plants. Valenti

et al.

(2005, p. 1242) determined that for rainbow mussel,

Villosa iris,

glochidia were more sensitive to mercury than juvenile mussels, and that reduced growth in juveniles is seen when observed concentrations are higher than EPA's criteria for mercury. Based on these data, we believe that EPA's water quality standards for mercury should be protective of juvenile mussels and glochidia, except in cases of illegal dumping, permit violations, or spills. However, impacts to mussels from mercury toxicity may be occurring in some streams. According to the National Summary Data reported by States to the EPA, 4,716 monitored waters do not meet EPA standards for mercury in the United States (

http://iaspub.epa.gov/waters10/attains_nation_cy.control?p_report_type=T,

accessed 6/28/2012). Acute mercury toxicity was determined to be the cause of extirpation of a diverse mussel fauna for a 112-rkm (70-rmi) portion of the North Fork Holston River (Brown

et al.

2005, pp. 1455-1457).

In addition to ammonia, agricultural sources of chemical contaminants include two broad categories that have the potential to adversely impact mussel species: nutrients and pesticides. Nutrients (such as nitrogen and phosphorus) can impact streams when their concentrations reach levels that cannot be assimilated, a condition known as over-enrichment. Nutrient over-enrichment is primarily a result of runoff from livestock farms, feedlots, and heavily fertilized row crops (Peterjohn and Correll 1984, p. 1471). Over-enriched conditions are exacerbated by low-flow conditions, such as those experienced during typical summer-season flows and that might occur with greater frequency and magnitude as a result of climate change. Bauer (1988, p. 244) found that excessive nitrogen concentrations can be detrimental to the adult pearl mussel (

Margaritifera margaritifera

), as was evident by the positive linear relationship between mortality and nitrate concentration. Also, a study of mussel life span and size (Bauer 1992, p. 425) showed a negative correlation between growth rate and eutrophication, and longevity was reduced as the concentration of nitrates increased. Nutrient over-enrichment can result in an increase in primary productivity, and the subsequent respiration depletes dissolved oxygen levels. This may be particularly detrimental to juvenile mussels, which inhabit the interstitial spaces in the substrate, where lower dissolved oxygen concentrations are more likely than on the sediment surface where adults tend to live (Sparks and Strayer 1998, pp. 132-133).

Elevated concentrations of pesticide frequently occur in streams due to runoff, overspray application to row crops, and lack of adequate riparian buffers. Agricultural pesticide applications and the reproductive and early life stages of mussels often coincide in the spring and summer, and thus impacts to mussels due to pesticides may be increased (Bringolf

et al.

2007c, p. 2094). Little is known regarding the impact of currently used pesticides to mussels even though some pesticides, such as glyphosate (e.g., Roundup

TM

), are used globally. Recent studies tested the toxicity of glyphosate, its formulations, and a surfactant (MON 0818) used in several glyphosate formulations, to early life stages of the fatmucket (

Lampsilis siliquoidea

) (Bringolf

et al.

2007c, p. 2094). Studies conducted with juvenile mussels and glochidia determined that the surfactant (MON 0818) was the most toxic of the compounds tested and that fatmucket glochidia were the most sensitive of organisms tested to date (Bringolf

et al.

2007c, p. 2094). Roundup

TM

), technical grade glyphosate isopropylamine salt, and isopropylamine were also acutely toxic to juveniles and glochidia (Bringolf

et al.

2007c, p. 2097). The impacts of other pesticides including atrazine, chlorpyrifos, and permethrin on glochidia and juvenile life stages have also recently been studied (Bringolf

et al.

2007a, p. 2101). This study determined that chlorpyrifos was toxic to both fatmucket glochidia and juveniles (Bringolf

et al.

2007a, p. 2104). The above results indicate the potential toxicity of commonly applied pesticides and the threat to mussel species as a result of the widespread use of these pesticides. All of these pesticides are commonly used throughout the range of the fluted kidneyshell and slabside pearlymussel.

Pharmaceutical chemicals used in commonly consumed drugs are increasingly found in surface waters downstream from municipal effluents. A recent nationwide study sampling 139 stream sites in 30 States detected the presence of numerous pharmaceuticals, hormones, and other organic wastewater contaminants downstream from urban development and livestock production areas (Kolpin

et al.

2002, pp. 1208-1210). Exposure to waterborne and, potentially to sediment, toxicant chemicals that act directly on the neuroendocrine pathways controlling reproduction can cause premature release of viable or nonviable glochidia. For example, the active ingredient in many human prescription anti-depressant drugs belonging to the class of selective serotonin reuptake inhibitors may exert negative reproductive effects on mussels because of their action on serotonin and other neuroendocrine pathways (Cope

et al.

2008, pp. 455). These waterborne chemicals alter mussel behavior and influence successful attachment of glochidia on fish hosts and, therefore, may have population level implications for the fluted kidneyshell and slabside pearlymussel.

This information indicates it is likely that chemical contaminants have contributed to declining fluted

kidneyshell and slabside pearlymussel populations, and will likely continue to be a threat to these species in the future. These threats result from spills that are immediately lethal to species, as well as chronic contaminant exposure, which results in death, reduced growth, or reduced reproduction of fluted kidneyshell and slabside pearlymussel.

Sedimentation

Impacts resulting from sediments have been noted for many components of aquatic communities. For example, sediments have been shown to abrade or suffocate periphyton (organisms attached to underwater surfaces); affect respiration, growth, reproductive success, and behavior of aquatic insects and mussels; and affect fish growth, survival, and reproduction (Waters 1995, pp. 173-175). When in high silt environments, mussels may keep their valves closed more often, resulting in reduced feeding activity (Ellis 1936, p. 30).

Increased turbidity from suspended sediment can reduce or eliminate juvenile mussel recruitment (Negus 1966, p. 525; Box and Mossa 1999, pp. 101-102). Many mussel species use visual cues to attract host fishes; such a reproductive strategy depends on clear water for success. For example, increased turbidity may impact the southern sandshell,

Hamiota australis,

life

cycle by reducing the chance that a sight

-

feeding host fish will encounter the visual display of its superconglutinate lure (Haag

et al.

1995, p. 475; Blalock

-

Herod

et al.

2002, p. 1885). If the superconglutinate is not encountered by a host within a short time period, the glochidia will become nonviable (O'Brien and Brim Box 1999, p. 133). Also, evidence suggests that conglutinates of the southern kidneyshell (another species of

Ptychobranchus, P. jonesi

), once released from the female mussel in an attempt to lure potential host fish, must adhere to hard surfaces in order to be seen by its fish host. If the surface becomes covered in fine sediments, the conglutinate cannot attach and is swept away (Hartfield and Hartfield 1996, p. 373).

Population Fragmentation and Isolation

Population isolation prohibits the natural interchange of genetic material between populations, and small population size reduces the reservoir of genetic diversity within populations, which can lead to inbreeding depression (Allendorf and Luikart 2007, pp. 117-146). Small, isolated populations, therefore, are more susceptible to environmental pressures, including habitat degradation and stochastic events, and thus are the most susceptible to extinction (Primack 2008, pp. 151-153). It is likely that some populations of the fluted kidneyshell and slabside pearlymussel are below the effective population size (Soulé 1980, pp. 162-264; Allendorf and Luikart 2007, pp. 147-170) required to maintain long-term genetic and population viability.

The present distribution and status of the fluted kidneyshell in the upper Cumberland River system in Kentucky may provide an excellent example of the detrimental bottleneck effect resulting when a minimum viable population size is not maintained. A once large population of this species occurred throughout the upper Cumberland River mainstem below Cumberland Falls and in several larger tributary systems. In this region, there were no absolute barriers to genetic interchange among its subpopulations (and those of its host fishes) that occurred in various streams. With the completion of Wolf Creek Dam in the late 1960s, the mainstem population was soon extirpated, and the remaining populations isolated by the filling of Cumberland Reservoir. Whereas small, isolated, tributary populations of imperiled short-lived species (e.g., most fishes) would have died out within a decade or so after impoundment, the long-lived fluted kidneyshell would potentially take decades to expire post-impoundment. Without the level of genetic interchange the species experienced historically (i.e., without the reservoir barrier), isolated populations may be slowly dying out. The fluted kidneyshell and slabside pearlymussel were similarly isolated by the completion of multiple reservoirs in the Tennessee River system. Even given the improbable absence of anthropogenic impacts, we may lose smaller isolated populations of the fluted kidneyshell and slabside pearlymussel to the devastating consequences of below-threshold effective population size (the minimum population size that is needed for the population to reproduce and continue to be viable). In reality, degradation of these isolated stream reaches and the resulting decline in suitable habitat is contributing to the decline of both species.

Random Catastrophic Events

The remaining populations of the fluted kidneyshell and slabside pearlymussel are generally small and geographically isolated. The patchy distribution pattern of populations in short river reaches makes them much more susceptible to extirpation from single catastrophic events, such as toxic chemical spills. Such a spill occurred in the upper Clinch River in 1998, killing many fluted kidneyshell and thousands of specimens of other mussel species, including three federally listed species (Henley

et al.

2002, entire). High levels of isolation makes natural recolonization of any extirpated population impossible.

Climate Change

Our analyses under the Act include consideration of ongoing and projected changes in climate. The terms “climate” and “climate change” are defined by the Intergovernmental Panel on Climate Change (IPCC). “Climate” refers to the mean (average) and variability of different types of weather conditions over time, with 30 years being a typical period for such measurements, although shorter or longer periods also may be used (IPCC 2007, p. 78). The term “climate change” thus refers to a change in the mean or variability of one or more measures of climate (e.g., temperature or precipitation) that persists for an extended period, typically decades or longer, whether the change is due to natural variability, human activity, or both (IPCC 2007, p. 78). Various types of changes in climate can have direct or indirect effects on species. These effects may be positive, neutral, or negative and they may change over time, depending on the species and other relevant considerations, such as the effects of interactions of climate with other variables (e.g., habitat fragmentation) (IPCC 2007, pp. 8-14, 18-19). In our analyses, we use our expert judgment to weigh relevant information, including uncertainty, in our consideration of various aspects of climate change.

There is a growing concern that climate change may lead to increased frequency of severe storms and droughts (McLaughlin

et al.

2002, p. 6074; Cook

et al.

2004, p. 1015; Golladay

et al.

2004, p. 504). Specific effects of climate change to mussels, their habitat, and their fish hosts could include changes in stream temperature regimes, the timing and levels of precipitation causing more frequent and severe floods and droughts, and nonindigenous species introductions. Increases in temperature and reductions in flow may also lower dissolved oxygen levels in interstitial habitats which can be lethal to juveniles (Sparks and Strayer 1998, pp. 131-133). Effects to mussel populations from these environmental changes could include reduced abundance and biomass, altered species composition, and reduced host fish availability (Galbraith

et al.

2010, pp. 1180-1182). The present conservation status, complex life

histories, and specific habitat requirements of mussels suggest that they may be quite sensitive to the effects of climate change (Hastie

et al.

2003, p. 45).

During high flows, flood scour can dislodge mussels where they may be injured, buried, swept into unsuitable habitats, or stranded and perish when flood waters recede (Vannote and Minshall 1982, p. 4105; Tucker 1996, p. 435; Hastie

et al.

2001, pp. 107-115; Peterson

et al.

2011, unpaginated). During drought, stream channels may become disconnected pools where mussels are exposed to higher water temperatures, lower dissolved oxygen levels, and easier collection by predators, or channels may become dewatered entirely. Increased human demand and competition for surface and ground water resources for irrigation and consumption during drought can cause drastic reductions in stream flows and alterations to hydrology (Golladay

et al.

2004, p. 504; Golladay

et al.

2007, unpaginated). Extended droughts occurred in the Southeast during 1998 to 2002, and again in 2006 to 2008. The effects of these recent droughts on these mussels are unknown; however, substantial declines in mussel diversity and abundance as a direct result of drought have been documented in southeastern streams (Golladay

et al.

2004, pp. 494-503; Haag and Warren 2008, p. 1165).

Nonindigenous Species

The Asian clam (

Corbicula fluminea

) has been introduced to the Cumberland and Tennessee River drainages and may be adversely affecting the fluted kidneyshell and slabside pearlymussel through direct competition for space and resources. The Asian clam may pose a direct threat to native mussels, particularly as juveniles, as a competitor for resources such as food, nutrients, and space (Neves and Widlak 1987, p. 6). Dense populations of Asian clams may ingest large numbers of unionid sperm, glochidia, and newly metamorphosed juveniles, and may actively disturb sediments, reducing habitable space for juvenile native mussels or displacing them downstream (Strayer 1999, p. 82; Yeager

et al.

2000, pp. 255

-

256).

Asian clam densities vary widely in the absence of native mussels or in patches with sparse mussel concentrations, but Asian clam density is rarely observed to be high in dense mussel beds, indicating that the clam is unable to successfully invade small-scale habitat patches with high unionid biomass (Vaughn and Spooner 2006, pp. 334-335). The invading clam, therefore, appears to preferentially invade sites where mussels are already in decline (Strayer 1999, pp. 82-83; Vaughn and Spooner 2006, pp. 332-336) and does not appear to be a causative factor in the decline of mussels in dense beds. However, an Asian clam population that thrives in previously stressed, sparse mussel populations might exacerbate unionid imperilment through competition and impeding mussel population expansion (Vaughn and Spooner 2006, pp. 335-336).

Summary for Factor E

We have determined that other natural and manmade factors, such as alteration of natural temperature regimes; chemical contaminants; sedimentation; small, isolated populations; and low genetic diversity, combined with localized extinctions from point source pollution or accidental toxic chemical spills, habitat modification and progressive degradation by nonpoint source pollutants, natural catastrophic changes to habitat through flood scour or drought, and nonindigenous species are threats to remaining populations of the fluted kidneyshell and slabside pearlymussel across their respective ranges.

Proposed Determination

We have carefully assessed the best scientific and commercial information available regarding the past, present, and future threats to the fluted kidneyshell and slabside pearlymussel. Section 3(6) of the Act defines an endangered species as “any species which is in danger of extinction throughout all or a significant portion of its range,” and section 3(20) of the Act defines a threatened species as “any species which is likely to become an endangered species within the foreseeable future throughout all or a significant portion of its range.” As described in detail above, these two species occupy only portions of their historical ranges, are limited to a handful of viable populations, and are currently at risk throughout all of their respective ranges due to ongoing threats of habitat destruction and modification (Factor A), inadequacy of existing regulatory mechanisms (Factor D), and other natural or manmade factors affecting their continued existence (Factor E). Specifically, these threats include impoundments, mining, oil and gas exploration, sedimentation, chemical contaminants, temperature regime alterations, recurring drought and flooding, population fragmentation and isolation, loss of fish hosts, and the introduced Asian clam. We believe these threats are currently impacting these species and are projected to continue and potentially worsen in the future.

Species with small ranges, few populations, and small or declining population sizes are the most vulnerable to extinction (Primack 2008, p. 137). The effects of certain factors, particularly habitat degradation and loss, catastrophic events, and introduced species, increase in magnitude when population size is small (Soulé 1987, pp. 33, 71; Primack 2008, pp. 133-135, 152). We believe that, when combining the effects of historical, current, and future habitat loss and degradation; historical and ongoing drought; and the exacerbating effects of small and declining population sizes and curtailed ranges, the fluted kidneyshell and slabside pearlymussel are in danger of extinction throughout all of their ranges. In addition, any factor (i.e., habitat loss or natural and manmade factors) that results in a further decline in habitat or individuals may be problematic for the long-term recovery of these species.

Therefore, based on the best available scientific and commercial information, we propose to list the fluted kidneyshell and slabside pearlymussel as endangered species throughout all of their ranges. We believe that, when combining the effects of historical, current, and future habitat loss and degradation; historical and ongoing drought; and the exacerbating effects of small and declining population sizes and curtailed ranges, the fluted kidneyshell and slabside pearlymussel are in danger of extinction throughout all of their ranges. Furthermore, we examined both species to analyze if any significant portions of their ranges may warrant a different status. However, because of their limited and curtailed ranges, and uniformity of the threats throughout their entire respective ranges, we find there are no significant portions of any of the species' ranges that may warrant a different determination of status.

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 results in public awareness and conservation by Federal, State, and local agencies; private organizations; and individuals. The Act encourages cooperation with the States and requires that recovery actions be carried out for all listed

species. The protection measures required of Federal agencies and the prohibitions against certain activities involving listed wildlife are discussed in Effects of Critical Habitat Designation and are further discussed, in part, below.

The primary purpose of the Act is the conservation of endangered and threatened species and the ecosystems upon which they depend. The ultimate goal of such conservation efforts is the recovery of these listed species, so that they no longer need the protective measures of the Act. Subsection 4(f) of the Act requires the Service to develop and implement recovery plans for the conservation of endangered and threatened species. The recovery planning process involves the identification of actions that are necessary to halt or reverse the species' decline by addressing the threats to its survival and recovery. The goal of this process is to restore listed species to a point where they are secure, self-sustaining, and functioning components of their ecosystems.

Recovery planning includes the development of a recovery outline shortly after a species is listed, preparation of a draft and final recovery plan, and revisions to the plan as significant new information becomes available. The recovery outline guides the immediate implementation of urgent recovery actions and describes the process to be used to develop a recovery plan. The recovery plan identifies site-specific management actions that will achieve recovery of the species, measurable criteria that determine when a species may be downlisted or delisted, and methods for monitoring recovery progress. Recovery plans also establish a framework for agencies to coordinate their recovery efforts and provide estimates of the cost of implementing recovery tasks. Recovery teams (comprised of species experts, Federal and State agencies, nongovernment organizations, and stakeholders) are often established to develop recovery plans. When completed, the recovery outline, draft recovery plan, and the final recovery plan will be available on our Web site (

http://www.fws.gov/endangered

), or from our Tennessee Ecological Services Field Office (see

FOR FURTHER INFORMATION CONTACT

).

Implementation of recovery actions generally requires the participation of a broad range of partners, including other Federal agencies, States, Tribal, nongovernmental organizations, businesses, and private landowners. Examples of recovery actions include habitat restoration (e.g., restoration of native vegetation), research, captive propagation and reintroduction, and outreach and education. The recovery of many listed species cannot be accomplished solely on Federal lands because their range may occur primarily or solely on non-Federal lands. To achieve recovery of these species requires cooperative conservation efforts on private, State, and Tribal lands.

If this species is listed, funding for recovery actions will be available from a variety of sources, including Federal budgets, State programs, and cost share grants for non-Federal landowners, the academic community, and nongovernmental organizations. In addition, under section 6 of the Act, States would be eligible for Federal funds to implement management actions that promote the protection and recovery of these two species. Information on our grant programs that are available to aid species recovery can be found at:

http://www.fws.gov/grants.

Although the fluted kidneyshell and slabside pearlymussel are only proposed for listing under the Act at this time, please let us know if you are interested in participating in recovery efforts for this species. Additionally, we invite you to submit any new information on this species whenever it becomes available and any information you may have for recovery planning purposes (see

FOR FURTHER INFORMATION CONTACT

).

Section 7(a) of the Act requires Federal agencies to evaluate their actions with respect to any species that is proposed or listed as endangered or threatened and with respect to its critical habitat, if any is designated. Regulations implementing this interagency cooperation provision of the Act are codified at 50 CFR part 402. Section 7(a)(4) of the Act requires Federal agencies to confer with the Service on any action that is likely to jeopardize the continued existence of a species proposed for listing or result in destruction or adverse modification of proposed critical habitat. If a species is listed subsequently, section 7(a)(2) 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 the species or 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 the Service.

Federal agency actions within the species habitat that may require conference or consultation or both as described in the preceding paragraph include management of and any other landscape altering activities on Federal lands administered by the U.S. Forest Service; issuance of section 404 CWA permits by the U.S. Army Corps of Engineers; licensing of hydroelectric dams, and construction and management of gas pipeline and power line rights-of-way approved by the Federal Energy Regulatory Commission; issuance of 26a permits by the Tennessee Valley Authority; construction and maintenance of roads or highways funded by the Federal Highway Administration; and land management practices administered by the U.S. Department of Agriculture. It has been the experience of the Service from consultations on other species, however, that nearly all section 7 consultations have been resolved so that the species have been protected and the project objectives have been met.

The Act and its 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 for endangered wildlife, 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, 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. Under the Lacey Act (18 U.S.C. 42-43; 16 U.S.C. 3371-3378), it is also illegal to possess, sell, deliver, carry, transport, or ship any such wildlife that has been taken illegally. Certain exceptions apply to agents of the Service and State conservation agencies.

We may issue permits to carry out otherwise prohibited activities involving endangered and threatened wildlife species under certain circumstances. Regulations governing permits are codified at 50 CFR 17.22 for endangered species, and at 17.32 for threatened species. With regard to endangered wildlife, a permit must be issued for the following purposes: for scientific purposes, to enhance the propagation or survival of the species, and for incidental take in connection with otherwise lawful activities.

It is our policy, as published in the

Federal Register

on July 1, 1994 (59 FR 34272), to identify, to the maximum extent practicable at the time a species is listed, those activities that would or would not constitute a violation of section 9 of the Act. The intent of this policy is to increase public awareness of the effect of a proposed listing on proposed and ongoing activities within the range of species proposed for listing. The following activities could potentially result in a violation of

section 9 of the Act; this list is not comprehensive:

(1) Unauthorized collecting, handling, possessing, selling, delivering, carrying, or transporting of the species, including import or export across State lines and international boundaries, except for properly documented antique specimens of these taxa at least 100 years old, as defined by section 10(h)(1) of the Act.

(2) Introduction of nonnative species that compete with or prey upon these mussel species, such as the zebra mussel (

Dreissena polymorpha

) and Asian clam (

Corbicula fluminea

).

(3) Unauthorized modification of the channel, substrate, temperature, or water flow of any stream or water body in which these species are known to occur.

(4) Unauthorized discharge of chemicals or fill material into any waters in which the fluted kidneyshell and slabside pearlymussel are known to occur.

Questions regarding whether specific activities would constitute a violation of section 9 of the Act should be directed to the Tennessee Ecological Services Field Office (see

FOR FURTHER INFORMATION CONTACT

). Requests for copies of the regulations concerning listed animals and general inquiries regarding prohibitions and permits may be addressed to the U.S. Fish and Wildlife Service, Endangered Species Permits, 1875 Century Boulevard, Suite 200, Atlanta, GA 30345; telephone: 404-679-7140; facsimile: 404-679-7081.

Critical Habitat for the Fluted Kidneyshell and Slabside Pearlymussel

Background

It is our intent to discuss below only those topics directly relevant to the designation of critical habitat for the fluted kidneyshell and slabside pearlymussel in this section of the proposed rule.

Critical habitat is defined in section 3 of the Act as:

(1) The specific areas within the geographical area occupied by the species, at the time it is listed in accordance with the Act, on which are found those physical or biological features

(a) Essential to the conservation of the species and

(b) Which may require special management considerations or protection; and

(2) Specific areas outside the geographical area occupied by the species at the time it is listed, upon a determination that such areas are essential for the conservation of the species.

Conservation, as defined under section 3 of the Act, means to use and the use of all methods and procedures that are necessary to bring an endangered or threatened species to the point at which the measures provided pursuant to the Act are no longer necessary. Such methods and procedures include, but are not limited to, all activities associated with scientific resources management such as research, census, law enforcement, habitat acquisition and maintenance, propagation, live trapping, and transplantation, and, in the extraordinary case where population pressures within a given ecosystem cannot be otherwise relieved, may include regulated taking.

Critical habitat receives protection under section 7 of the Act through the requirement that Federal agencies ensure, in consultation with the Service, that any action they authorize, fund, or carry out is not likely to result in the destruction or adverse modification of critical habitat. The designation of critical habitat does not affect land ownership or establish a refuge, wilderness, reserve, preserve, or other conservation area. Such designation does not allow the government or public to access private lands. Such designation does not require implementation of restoration, recovery, or enhancement measures by non-Federal landowners. Where a landowner seeks or requests Federal agency funding or authorization for an action that may affect a listed species or critical habitat, the consultation requirements of section 7(a)(2) would apply, but even in the event of a destruction or adverse modification finding, the obligation of the Federal action agency and the landowner is not to restore or recover the species, but to implement reasonable and prudent alternatives to avoid destruction or adverse modification of critical habitat.

Under the first prong of the Act's definition of critical habitat, areas within the geographical area occupied by the species at the time it is listed must contain physical or biological features (PBFs) which are (1) essential to the conservation of the species and (2) which may require special management considerations or protection. For these areas, critical habitat designations identify, to the extent known using the best scientific and commercial data available, those PBFs that are essential to the conservation of the species (such as space, food, cover, and protected habitat). In identifying those physical and biological features within an area, we focus on the principal biological or physical constituent elements (primary constituent elements such as roost sites, nesting grounds, seasonal wetlands, water quality, tide, soil type) that are essential to the conservation of the species. Primary constituent elements are the specific elements of PBFs that provide for a species' life-history processes.

Under the second prong of the Act's definition of critical habitat, we can designate critical habitat in areas outside the geographical area occupied by the species at the time it is listed, upon a determination that such areas are essential for the conservation of the species. We designate critical habitat in areas outside the geographical area occupied by a species only when a designation limited to its range would be inadequate to ensure the conservation of the species.

Section 4 of the Act requires that we designate critical habitat on the basis of the best scientific and commercial data available. Further, our Policy on Information Standards under the Endangered Species Act (published in the

Federal Register

on July 1, 1994 (59 FR 34271)), the Information Quality Act (section 515 of the Treasury and General Government Appropriations Act for Fiscal Year 2001 (Pub. L. 106-554; H.R. 5658)), and our associated Information Quality Guidelines, provide criteria, establish procedures, and provide guidance to ensure that our decisions are based on the best scientific data available. They require our biologists, to the extent consistent with the Act and with the use of the best scientific data available, to use primary and original sources of information as the basis for recommendations to designate critical habitat.

When we are determining which areas should be designated as critical habitat, our primary source of information is generally the information developed during the listing process for the species. Additional information sources may include articles in peer-reviewed journals, conservation plans developed by States and counties, scientific status surveys and studies, biological assessments, or other unpublished materials and expert opinion or personal knowledge.

Habitat is dynamic, and species may move from one area to another over time. Climate change will be a particular challenge for biodiversity because the interaction of additional stressors associated with climate change and current stressors may push species beyond their ability to survive (Lovejoy 2005, pp. 325-326).

We recognize that critical habitat designated at a particular point in time may not include all of the habitat areas

that we may later determine are necessary for the recovery of the species. For these reasons, a critical habitat designation does not signal that habitat outside the designated area is unimportant or may not be needed for recovery of the species. Areas that are important to the conservation of the species, both inside and outside the critical habitat designation, will continue to be subject to: (1) Conservation actions implemented under section 7(a)(1) of the Act, (2) regulatory protections afforded by the requirement in section 7(a)(2) of the Act for Federal agencies to insure their actions are not likely to jeopardize the continued existence of any endangered or threatened species, and (3) the prohibitions of section 9 of the Act if actions occurring in these areas may affect the species. Federally funded or permitted projects affecting listed species outside their designated critical habitat areas may still result in jeopardy findings in some cases. These protections and conservation tools would continue to contribute to recovery of these species. Similarly, critical habitat designations made on the basis of the best available information at the time of designation would not control the direction and substance of future recovery plans, habitat conservation plans (HCPs), or other species conservation planning efforts if new information available at the time of these planning efforts calls for a different outcome.

Prudency Determination

Section 4(a)(3) of the Act, as amended, and implementing regulations (50 CFR 424.12), require that, to the maximum extent prudent and determinable, the Secretary designate critical habitat at the time the species is determined to be an endangered or threatened species. 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.

As discussed above under Factor B, there is currently no imminent threat of take attributed to collection or vandalism for these species, and identification and mapping of critical habitat is not expected to initiate any such threat. In the absence of finding that the designation of critical habitat would increase threats to a species, if there are any benefits to a critical habitat designation, then a prudent finding is warranted. The potential benefits of designation include: (1) Triggering consultation under section 7 of the Act, in new areas for actions in which there may be a Federal nexus where it would not otherwise occur because, for example, it is or has become unoccupied or the occupancy is in question; (2) focusing conservation activities on the most essential features and areas; (3) providing educational benefits to State or county governments or private entities; and (4) preventing people from causing inadvertent harm to the species. Therefore, because we have determined that the designation of critical habitat will not likely increase the degree of threat to the species and may provide some measure of benefit, we find that designation of critical habitat is prudent for the fluted kidneyshell and slabside pearlymussel.

Critical Habitat Determinability

Having determined that designation is prudent, under section 4(a)(3) of the Act we must find whether critical habitat for the two species is determinable. Our regulations at 50 CFR 424.12(a)(2) state that critical habitat is not determinable when one or both of the following situations exist:

(i) Information sufficient to perform required analyses of the impacts of the designation is lacking, or

(ii) The biological needs of the species are not sufficiently well known to permit identification of an area as critical habitat.

When critical habitat is not determinable, the Act allows the Service an additional year to publish a critical habitat designation (16 U.S.C. 1533(b)(6)(C)(ii)).

We reviewed the available information pertaining to the biological needs of the species and habitat characteristics where these species are located. This and other information represent the best scientific data available and led us to conclude that critical habitat is determinable for these two species.

Physical and Biological Features

In accordance with sections 3(5)(A)(i) and 4(b)(1)(A) of the Act and the regulations at 50 CFR 424.12, in determining which areas within the geographical area occupied at the time of listing to propose as critical habitat, we consider the PBFs essential to the conservation of the species which may require special management considerations or protection. These include, but are not limited to:

(1) Space for individual and population growth and for normal behavior;

(2) Food, water, air, light, minerals, or other nutritional or physiological requirements;

(3) Cover or shelter;

(4) Sites for breeding, reproduction, or rearing (or development) of offspring; and

(5) Habitats that are protected from disturbance or are representative of the historic, geographical, and ecological distributions of a species.

We derive the specific PBFs required for the fluted kidneyshell and slabside pearlymussel based on their biological needs. Little is known of the specific habitat requirements of these two mussel species other than they require flowing water, stable stream channels, adequate water quality, and fish hosts for development of larva to metamorphose into juvenile mussels. To identify the physical and biological needs of the species, we have relied on current conditions at locations where the species survive, the limited information available on these two mussels and their close relatives, and factors associated with the decline and extirpation of these and other mussels from portions of the Cumberland and Tennessee River systems. Additional information can be found in the Background section of this proposed rule. We have determined that the following PBFs are essential for the fluted kidneyshell and slabside pearlymussel.

Space for Individual and Population Growth and for Normal Behavior

The fluted kidneyshell and slabside pearlymussel are historically associated with the Cumberland and Tennessee River drainages in Alabama, Kentucky, Mississippi, Tennessee, and Virginia. Mussels generally live embedded in the bottom of stable streams and other bodies of water, and within riffle areas of sufficient current velocities to remove finer sediments and provide well-oxygenated waters. The fluted kidneyshell is primarily a medium-sized creek to large river species, inhabiting sand and gravel substrates in relatively shallow riffles and shoals with moderate to swift current (Parmalee and Bogan 1998, p. 205). In comparison to co-occurring species, the fluted kidneyshell demonstrates strong habitat specificity. It is associated with faster flows, greater baseflow shear stress, and low substrate embeddedness (Ostby 2005, pp. 51, 142-143). The slabside pearlymussel is primarily a large creek to large river species, inhabiting sand, fine gravel, and cobble substrates in relatively

shallow riffles and shoals with moderate current (Parmalee and Bogan 1998, p. 152).

Fluted kidneyshell and slabside pearlymussel, similar to other mussels, are dependent on areas with flow refuges where shear stress is relatively low, although the fluted kidneyshell is more tolerant of shear stress than other species, and sediments remain stable during flood events (Layzer and Madison 1995, p. 341; Strayer 1999, pp. 468 and 472; Hastie

et al.

2001, pp. 111-114). Flow refuges conceivably allow relatively immobile mussels such as the fluted kidneyshell and slabside pearlymussel to remain in the same general location throughout their entire lives.

Natural river or creek channel stability are achieved by allowing the river or creek to develop a stable dimension, pattern, and profile such that, over time, channel features are maintained and the river or creek system neither aggrades nor degrades. Channel instability occurs when the scouring process leads to degradation, or excessive sediment deposition results in aggradation. Stable rivers and creeks consistently transport their sediment load, both in size and type, associated with local deposition and scour (Rosgen 1996, p. 1-3). Sedimentation has been determined to be a major factor in habitat destruction, resulting in corresponding shift in mussel fauna (Brim Box and Mossa 1999, p. 102). Stable stream bottom substrates not only provide space for populations of these mussel species, but also provide cover and shelter and sites for breeding, reproduction, and growth of offspring.

Habitat conditions described in the previous paragraphs provide space, cover, shelter, and sites for breeding, reproduction, and growth of offspring for the fluted kidneyshell and slabside pearlymussel. These habitats are dynamic and are formed and maintained by water quantity, channel features (dimension, pattern, and profile), and sediment input to the system through periodic flooding, which maintains connectivity and interaction with the flood plain. Changes in one or more of these parameters can result in channel degradation or aggradation, with serious effects to mussels.

Therefore, based on the information above, we identify riffles of large creeks and rivers with sand, gravel, and cobble substrates; areas of moderate to high amount of flow, but with refugia of low shear stress; stream channel stability; and floodplain connectivity to be PBFs for both of these species.

Food, Water, Air, Light, Minerals, or Other Nutritional or Physiological Requirements

Mussels, such as these two species, siphon water into their shells and across four gills that are specialized for respiration, food collection, and brooding larvae in females. Food items include detritus (disintegrated organic debris), algae, diatoms, and bacteria (Strayer

et al.

2004, pp. 430-431). Encysted glochidia are nourished by their fish hosts and feed for a period of one week to several months. Nutrient uptake by glochidia is not well understood, but probably occurs through the microvillae of the mantle (Watters 2007, p. 55). For the first several months, juvenile mussels partially employ pedal (foot) feeding, extracting bacteria, algae, and detritus from the sediment, although they also may filter interstitial (pore) water (Yeager

et al.

1994, pp. 217-221). However, their gills are rudimentary and generally incapable of filtering particles (Watters 2007, p. 56). Adult mussels also can obtain their food by deposit feeding, pulling in food from the sediment and its interstitial (pore) water and pedal feeding directly from the sediment (Yeager

et al.

1994, pp. 217-221; Vaughn and Hakenkamp 2001, pp. 1432-1438). Food availability and quality for the fluted kidneyshell and slabside pearlymussel in their habitats are affected by habitat stability, floodplain connectivity, flow, and water and sediment quality. Excessive sedimentation has been shown to impair the filter feeding ability of mussels. When in high silt environments, mussels may keep their valves closed more often, resulting in reduced feeding activity (Ellis 1936, p. 30), and high amounts of suspended sediments can dilute their food source (Dennis 1984, p. 212). Adequate food availability and quality is essential for normal behavior, growth, and viability during all life stages of these two species. Excessive sedimentation often results in fine silt particles culminating within interstitial spaces, embedding and even concretizing the substrate and virtually altering habitat to such a degree that it becomes uninhabitable for mussels, particularly juveniles.

The fluted kidneyshell and slabside pearlymussel are riverine species that depend upon adequate water flow. Continuously flowing water is a habitat feature associated with both of these species. Flowing water maintains the stream bottom habitats where these species are found, transports food items to the sedentary juvenile and adult life stages, removes wastes, and provides oxygen for respiration. A natural flow regime that includes periodic flooding and maintains connectivity and interaction with the floodplain is critical for the exchange of nutrients, movement of and spawning activities for potential fish hosts, and maintenance of flow refuges in riffle and run habitats. Further, riffle areas are often defined by an abundance and diversity of organisms that likely have dependent and competitive interactions yet unknown, but that are important for riffle-dwelling mussel species such as the fluted kidneyshell and slabside pearlymussel.

The ranges of standard physical and chemical water quality parameters (such as temperature, dissolved oxygen, pH, and conductivity) that define suitable habitat conditions for the two species have not been investigated or are poorly understood. However, as relatively sedentary animals, mussels must tolerate the full range of such parameters that occur naturally within the streams where they persist. The pathways of exposure to a variety of environmental pollutants for all four mussel life stages (free and encysted glochidia, juveniles, and adults) and differences in exposure and sensitivity were previously discussed (see Factor A). Environmental contamination is a causal (contributing) factor in the decline of mussel populations.

We currently believe that most numeric standards for pollutants and water quality parameters (for example, dissolved oxygen, pH, and heavy metals) that have been adopted by the States under the CWA represent levels that are essential to the conservation of both mussels. The Service is currently in consultation with the EPA to evaluate the protectiveness of criteria approved in EPA's water quality standards for endangered and threatened species and their critical habitats as described in the Memorandum of Agreement that our agencies signed in 2001 (66 FR 11201, February 22, 2001). Other factors that can potentially alter water quality are droughts and periods of low flow, nonpoint source runoff from adjacent land surfaces (for example, excessive amounts of sediments, nutrients, and pesticides), point source discharges from municipal and industrial wastewater treatment facilities (for example, excessive amounts of ammonia, chlorine, and metals), thermal and flow modifications resulting from hydropower generation, and random spills or unregulated discharge events. This could be particularly harmful during drought conditions, when flows are depressed and pollutants are more concentrated.

Both the amount (flow) and the physical and chemical conditions (water quality) where both species currently exist vary widely according to season, precipitation events, and seasonal human activities within the watershed. Conditions across their historical ranges vary even more due to watershed size, geology, geography, and differences in human population densities and land uses. In general, both of the species survive in areas where the magnitude, frequency, duration, and seasonality of water flow are adequate to maintain stable habitats (for example, sufficient flow to remove fine particles and sediments without causing degradation), and where water quality is adequate for year-round survival (for example, moderate to high levels of dissolved oxygen, low to moderate input of nutrients, and relatively unpolluted water and sediments). Therefore, based on the information above, we identify adequate food items for all life stages, sufficient water flow, and adequate water quality to be PBFs for both of these species.

Sites for Breeding, Reproduction, or Rearing

Mussels require a host fish for transformation of larval mussels (glochidia) to juvenile mussels (Williams

et al.

2008, p. 68). Thus, the presence of the appropriate host fishes to complete the reproductive life cycle is essential to the conservation of these two mussels. The known host fishes of the fluted kidneyshell include: barcheek darter (

Etheostoma obeyense

), fantail darter (

E. flabellare

), rainbow darter (

E. caeruleum

), redline darter (

E. rufilineatum

), bluebreast darter (

E. camurum

), dusky darter (

Percina sciera

), and banded sculpin (

Cottus carolinae

). The known host fishes of the slabside pearlymussel include: popeye shiner (

Notropis ariommus

), rosyface shiner (

N. rubellus

), saffron shiner (

N. rubricroceus

), silver shiner (

N. photogenis

), telescope shiner (

N. telescopus

), Tennessee shiner (

N. leuciodus

), whitetail shiner (

Cyprinella galactura

), striped shiner (

Luxilus chrysocephalus

), warpaint shiner (

L. coccogenis

), white shiner (

L. albeolus

), and eastern blacknose dace (

Rhinichthys atratulus

). There are likely other suitable host fishes that have not yet been studied or confirmed.

Juvenile mussels require stable bottom habitats for growth and survival. Fluted kidneyshell and slabside pearlymussel juveniles require stable habitats with adequate water quantity and quality as previously described for growth and survival. Excessive sediments or dense growth of filamentous algae can expose juvenile mussels to entrainment or predation and be detrimental to the survival of juvenile mussels (Hartfield and Hartfield 1996, pp. 372-374). Geomorphic instability can result in the loss of interstitial habitats and juvenile mussels due to scouring or deposition (Hartfield 1993, pp. 372-373). Water quality, sediment quality, stable habitat, health of fish hosts, and diet (of all life stages) all influence survival of each life stage and subsequent reproduction and recruitment (Cope

et al.

2008, p. 452).

Periodic floodplain connectivity that occurs during wet years provides habitats for spawning and foraging activities for fish hosts that require floodplain habitats for successful reproduction and recruitment to adulthood. Barko

et al.

(2006, pp. 252-256) found that several fish host or potential host species (none of which are documented hosts for the fluted kidneyshell or slabside pearlymussel) benefited from resource exploitation of floodplain habitats that were not typically available for use during years of normal flows. Furthermore, Kwak (1988, pp. 243-247) and Slipke and Maceina (2005, p. 289) indicated that periodic inundation of floodplain habitats increased successful fish reproduction, which leads to increased availability of native host fishes for mussel reproduction. However, Rypel

et al.

(2009, p. 502) indicated that mussels tended to exhibit minimal growth during high flow years. Therefore, optimal flooding of these habitats would not be too frequent and may need to occur at similar frequencies to that of the natural hydrologic regime of the rivers and creeks inhabited by the fluted kidneyshell and slabside pearlymussel.

Natural temperature regimes can be altered by impoundments, water releases from dams, industrial and municipal effluents, and changes in riparian habitat. Critical thermal limits for survival and normal functioning of many mussel species are unknown. High temperatures can reduce dissolved oxygen concentrations in the water, which slows growth, reduces glycogen stores, impairs respiration, and may inhibit reproduction (Hart and Fuller 1974, pp. 240-241). Low temperatures can significantly delay or prevent metamorphosis (Watters and O'Dee 1999, pp. 454-455). Water temperature increases have been documented to shorten the period of glochidial encystment, reduce the speed in which they turn upright, increase oxygen consumption, and slow burrowing and movement responses (Hart and Fuller 1974, pp. 240-241; Bartsch

et al.

2000, p. 237; Watters

et al.

2001, p. 546; Schwalb and Pusch 2007, pp. 264-265). Several studies have documented the influence of temperature on the timing of aspects of mussel reproduction (for example, Gray

et al.

2002, p. 156; Allen

et al.

2007, p. 85; Steingraeber

et al.

2007, pp. 303-309). Peak glochidial releases are associated with water temperature thresholds that can be thermal minimums or maximums, depending on the species (Watters and O'Dee 2000, p. 136). Abnormal temperature changes may cause particular problems to mussels whose reproductive cycles may be linked to fish reproductive cycles (for example, Young and Williams 1984, entire). Therefore, based on the information above, we identify health of fish hosts, water quality, sediment quality, stable habitat, food for all life stages, periodic flooding of floodplain habitat, and a natural temperature regime to be PBFs for both of these species.

Primary Constituent Elements for the Fluted Kidneyshell and Slabside Pearlymussel

Under the Act and its implementing regulations, we are required to identify the PBFs essential to the conservation of these mussel species in areas occupied at the time of listing, focusing on the features' primary constituent elements (PCEs). We consider PCEs to be the elements of PBFs that provide for a species' life-history processes and are essential to the conservation of the species.

Based on the above needs and our current knowledge of the life history, biology, and ecology of the species and the habitat requirements for sustaining the essential life-history functions of the species, we have determined that the PCEs for the fluted kidneyshell and slabside pearlymussel are:

(1) Riffle habitats within large, geomorphically stable stream channels (channels that maintain lateral dimensions, longitudinal profiles, and sinuosity patterns over time without an aggrading or degrading bed elevation).

(2) Stable substrates of sand, gravel, and cobble with low to moderate amounts of fine sediment and containing flow refugia with low shear stress.

(3) A natural hydrologic flow regime (the magnitude, frequency, duration, and seasonality of discharge over time) necessary to maintain benthic habitats where the species are found, and connectivity of rivers with the floodplain, allowing the exchange of nutrients and sediment for habitat maintenance, food availability for all life stages, and spawning habitat for native fishes.

(4) Water quality with low levels of pollutants and including a natural temperature regime, pH (between 6.0 to 8.5), oxygen content (not less than 5.0 milligrams per liter (mg/L)), hardness, and turbidity necessary for normal behavior, growth, and viability of all life stages.

(5) The presence of abundant fish hosts necessary for recruitment of the fluted kidneyshell and slabside pearlymussel.

Special Management Considerations or Protection

When designating critical habitat, we assess whether the specific areas within the geographical area occupied by the species at the time of listing contain features which are essential to the conservation of the species and which may require special management considerations or protection. The 29 occupied units we are proposing for designation as critical habitat for the fluted kidneyshell (16) and slabside pearlymussel (13) will require some level of management to address the current and future threats to the PBFs of the species. Of the 29 total occupied units, a portion of 5 units are located on the Daniel Boone National Forest (DBNF), 14 are almost entirely on private land, 1 is located on the Big South Fork National River and Recreational Area (BSFNRRA), 1 is located on the Cherokee National Forest (CNF), and 8 units have mixed ownership with private, State park, and national wildlife refuge lands.

Due to their location on the DBNF, at least a portion of 5 of the 29 occupied proposed critical habitat units are being managed and protected under DBNF's Land and Resource Management Plan (LRMP), and the Hiwassee River unit is protected under CNF's LRMP (United States Forest Service (USFS) 2004a, pp. 1-14; 2004b, entire). The LRMPs are implemented through a series of project-level decisions based on appropriate site-specific analysis and disclosure. The LRMPs do not contain a commitment to select any specific project; rather, they set up a framework of desired future conditions with goals, objectives, and standards to guide project proposals. Projects are proposed to solve resource management problems, move the forest environment toward desired future conditions, and supply goods and services to the public (USFS 2004a, pp. 1-14). The LRMPs contain a number of protective standards that in general are designed to avoid and minimize potential adverse effects to the fluted kidneyshell, slabside pearlymussel, and federally listed species; however, the DBNF and CNF would continue to conduct project-specific section 7 consultations under the Act when their activities may adversely affect the fluted kidneyshell, slabside pearlymussel, and other federally listed species or adversely modify their designated critical habitats.

Fourteen of the 29 occupied proposed critical habitat units are located almost entirely on private property and are not presently under the special management or protection provided by a legally operative plan or agreement for the conservation of the species.

One of the 29 occupied proposed critical habitat units (Big South Fork Cumberland River) is located almost entirely on Federal lands within the BSFNRRA. Land and resource management decisions and activities within the BSFNRRA are guided by the National Park Service General Management Plan, Field Management Plan, and Draft Non-Federal Oil and Gas Management Plan (NPS 2005, entire; NPS 2006, pp. 1-12; NPS 2011, entire).

Eight of the 29 occupied proposed critical habitat units (Clinch and Duck Rivers) have mixed ownership with private, State park, and national wildlife refuge lands. These lands are operated under various plans that may or may not provide the special management or protection provided by a legally operative plan or agreement for the conservation of these species.

Various activities in or adjacent to each of the occupied critical habitat units described in this proposed rule may affect one or more of the PCEs. Some of these activities include, but are not limited to, those discussed in the Summary of Factors Affecting the Species, above (e.g., impoundments, gravel and coal mining, water pollution, invasive species; see Factors A, D, and E, above). Other activities that may affect PBFs in the proposed critical habitat units include those listed in Available Conservation Measures above.

Management activities that could ameliorate threats on both Federal and non-Federal lands include, but are not limited to: Use of BMPs designed to reduce sedimentation, erosion, and stream bank alteration; moderation of surface and ground water withdrawals to maintain natural flow regimes; increase of stormwater management and reduction of stormwater flows into the systems; preservation of headwater streams; regulation of off-road vehicle use; and reduction of other watershed and floodplain disturbances that release sediments, pollutants, or nutrients into the water.

In summary, we find that the areas we are proposing as occupied critical habitat for the fluted kidneyshell and slabside pearlymussel contain the PBFs necessary for the species, and that these features may require special management considerations or protection. Special management consideration or protection may be required to eliminate, or to reduce to negligible levels, the threats affecting the PBFs of each unit. Additional discussion of threats facing individual units is provided in the individual unit descriptions below.

Criteria Used To Identify Critical Habitat

As required by section 4(b) of the Act, we use the best scientific and commercial data to designate critical habitat. We review available information pertaining to the habitat requirements of the species. In accordance with the Act and its implementing regulation at 50 CFR 424.12(e), we consider whether designating additional areas—outside those currently occupied as well as those occupied at the time of listing (if listing occurs before designation of a species' critical habitat)—are necessary to ensure the conservation of the species. We are proposing to designate critical habitat in areas within the geographic area currently occupied by the species. We also are proposing to designate specific areas outside the geographic area currently occupied by the species, which were historically occupied but are presently unoccupied, because such areas are essential for the conservation of the species.

We began our analysis by considering historical and current ranges of both species. We used various sources including published literature and museum collection databases, as well as surveys, reports, and field notes prepared by biologists (see Background section). We then identified the specific areas that are occupied by both mussels and that contain one or more of the PBFs. We defined occupied habitat as those stream reaches known to be currently occupied by either of the two species. To identify the currently occupied stream reaches, we used post-1980 survey data. To identify the unoccupied stream reaches, we used survey data between the late 1800s and 1979. Therefore, if a species was known to occur in an area prior to 1980, but was not collected since then, the stream reach is considered unoccupied. This criterion was chosen because a large number of collections were conducted in the 1980s in the Cumberland and Tennessee River systems. Some of the historical occurrences have not been surveyed since the 1980s. However, because of the longevity of these species

(40-55 years), they are still thought to occur in these areas.

We then evaluated occupied stream reaches to delineate the probable upstream and downstream extent of each species' distribution. Known occurrences for some mussel species are extremely localized, and rare mussels can be difficult to locate. In addition, stream habitats are highly dependent upon upstream and downstream channe

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