Federal Register / Vol. 86, No. 170 / Tuesday, September 7, 2021 / Proposed Rules 49989 

United States contains, at most, less 

than 1 percent of the worldwide jaguar 

habitat, and has no resident population 

of jaguars (Rosemont 2020, p. 9). This 

information relates to the status of the 

species and does not address whether or 

not Unit 3 allows for the normal 

demographic function and possible 

range expansion of the Northwestern 

Recovery Unit. The petition also states 

that removal of the northern Santa Rita 

Mountains and Subunit 4b represents a 

very small percentage of the total 

critical habitat—about 6.5 percent—that 

would be removed by the petitioned 

action and will not prevent the 

remaining critical habitat from 

functioning as intended for the support 

of the Northwest Recovery Unit 

(Rosemont 2020, pp. 13–14). The 

recovery function and value of critical 

habitat for the jaguar within the United 

States is to contribute to the species’ 

persistence and, therefore, overall 

conservation by identifying areas that 

support some individuals during 

dispersal movements, that contain small 

patches of habitat (perhaps in some 

cases with a few resident jaguars), and 

that allow for cyclic expansion and 

contraction of the nearest core area and 

breeding population in the 

Northwestern Recovery Unit (79 FR 

12572, March 5, 2014, p. 79 FR 12574). 

Removal of the northern Santa Rita 

Mountains would withdraw areas that 

currently provide the physical and 

biological features of jaguar critical 

habitat and in which confirmed jaguar 

detections occurred between 2012 and 

2015 (U.S. Fish and Wildlife Service 

2016, p. 295). In addition, removal of 

Subunit 4b eliminates half of the 

available connections to Mexico for Unit 

4 (specifically to Subunit 4a), which is 

a unit in which the same jaguar that 

occupied the Santa Rita Mountains 

(Unit 3) was detected in 2011. The 

petition does not explain why these 

areas are no longer essential other than 

to assert that most critical habitat units 

would be unaffected, and that impacts 

to Unit 3 and Unit 4 would be minor 

and would not prevent the units from 

functioning as intended. This assertion 

does not demonstrate that changes have 

occurred to these areas such that the 

function they provide to jaguars, and the 

reason for which they were designated 

as critical habitat, is compromised. 

Therefore, the petition does not provide 

substantial scientific information that 

the northern Santa Rita Mountains in 

Unit 3 and all of Subunit 4b no longer 

function as critical habitat and are not 

essential in allowing for the normal 

demographic function and possible 

range expansion of the Northwestern 

Recovery Unit. 

The petition discusses the 2013 

biological opinion for the Rosemont 

Copper Mine, which was overturned by 

a court decision (Ctr. for Biological 

Diversity at 873), and our 2019 

amendments to the regulations at 50 

CFR 424.12 in its request to revise 

critical habitat for jaguars. We reviewed 

the petition’s argument and find that 

these documents are not relevant to the 

question of whether the petition 

contained substantial information to 

support the removal of areas from 

critical habitat. Neither line of 

discussion speaks to whether the areas 

petitioned for removal contain the 

physical or biological features essential 

to the conservation of the species or 

provides information that these features 

do not require special management 

considerations or protection (50 CFR 

424.14(e)(4). 

Based on our review of the petition 

and sources cited in the petition, we 

find that the petition does not present 

substantial scientific or commercial 

information indicating the petitioned 

action may be warranted for the jaguar. 

Because the petition does not present 

substantial information indicating that 

revision of critical habitat for jaguar may 

be warranted, we do not intend to 

proceed with any such revision. 

However, we ask that the public submit 

to us any new information that becomes 

available concerning this species’ 

habitat at any time by contacting the 

person listed under FOR FURTHER

INFORMATION CONTACT, above. 

References Cited 

A complete list of references cited in 

this document is available on the 

internet at http://www.regulations.gov 

and upon request from the Arizona 

Ecological Services Field Office (see FOR

FURTHER INFORMATION CONTACT). 

Authors 

The primary authors of this document 

are the staff members of the Arizona 

Ecological Services Field Office (see FOR

FURTHER INFORMATION CONTACT). 

Authority 

The authority for this action is the 

Endangered Species Act of 1973, as 

amended (16 U.S.C. 1531 et seq.). 

Martha Williams, 

Principal Deputy Director, Exercising the 

Delegated Authority of the Director, U.S. Fish 

and Wildlife Service. 

[FR Doc. 2021–19062 Filed 9–3–21; 8:45 am] 

BILLING CODE 4333–15–P 

DEPARTMENT OF THE INTERIOR 

Fish and Wildlife Service 

50 CFR Part 17 

[Docket No. FWS–R4–ES–2021–0092; 

FF09E21000 FXES11110900000 212] 

RIN 1018–BF43 

Endangered and Threatened Wildlife 

and Plants; Threatened Species Status 

With Section 4(d) Rule for Pyramid 

Pigtoe 

AGENCY: Fish and Wildlife Service, 

Interior. 

ACTION: Proposed rule. 

SUMMARY: We, the U.S. Fish and 

Wildlife Service (Service), announce our 

12-month finding on a petition to list 

the pyramid pigtoe (Pleurobema 

rubrum), a freshwater mussel species 

from Alabama, Arkansas, Kentucky, 

Louisiana, Mississippi, Ohio, 

Oklahoma, Tennessee, and Virginia, as 

an endangered or threatened species 

under the Endangered Species Act of 

1973, as amended (Act). After a review 

of the best available scientific and 

commercial information, we find that 

listing the species is warranted. 

Accordingly, we propose to list the 

pyramid pigtoe as a threatened species 

with a rule issued under section 4(d) of 

the Act (‘‘4(d) rule’’). If we finalize this 

rule as proposed, it would add this 

species to the List of Endangered and 

Threatened Wildlife and extend the 

Act’s protections to the species. 

DATES: We will accept comments 

received or postmarked on or before 

November 8, 2021. Comments submitted 

electronically using the Federal 

eRulemaking Portal (see ADDRESSES, 

below) must be received by 11:59 p.m. 

Eastern Time on the closing date. We 

must receive requests for a public 

hearing, in writing, at the address 

shown in FOR FURTHER INFORMATION

CONTACT by October 22, 2021. 

ADDRESSES: 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 box, 

enter the docket number or RIN for this 

rulemaking (presented above in the 

document headings). For best results, do 

not copy and paste either number; 

instead, type the docket number or RIN 

into the Search box using hyphens. 

Then, click on the Search button. On the 

resulting page, in the panel on the left 

side of the screen, under the Document 

Type heading, check the Proposed Rule 

box to locate this document. You may 


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submit a comment by clicking on 

‘‘Comment.’’ 

(2) By hard copy: Submit by U.S. mail 

to: Public Comments Processing, Attn: 

FWS–R4–ES–2021–0092, U.S. Fish and 

Wildlife Service, MS: PRB/3W, 5275 

Leesburg Pike, Falls Church, VA 22041– 

3803. 

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 

Information Requested, below, for more 

information). 

FOR FURTHER INFORMATION CONTACT: 

Janet Mizzi, Field Supervisor, U.S. Fish 

and Wildlife Service, Asheville 

Ecological Services Field Office, 160 

Zillicoa St, Asheville, NC 28801; 

telephone 828–258–3939. Persons who 

use a telecommunications device for the 

deaf (TDD) may call the Federal Relay 

Service at 800–877–8339. 

SUPPLEMENTARY INFORMATION: 

Executive Summary 

Why we need to publish a rule. Under 

the Endangered Species Act of 1973, as 

amended (Act; 16 U.S.C. 1531 et seq.), 

if we determine that a species is an 

endangered or threatened species 

throughout all or a significant portion of 

its range, we are required to promptly 

publish a proposal in the Federal 

Register and make a determination on 

our proposal within 1 year, unless, due 

to substantial disagreement regarding 

the sufficiency or accuracy of the 

available data, we extend the 1-year 

period for no more than 6 months to 

solicit additional data. To the maximum 

extent prudent and determinable, we 

must designate critical habitat for any 

species that we determine to be an 

endangered or threatened species under 

the Act. Listing a species as an 

endangered or threatened species can 

only be completed by issuing a rule. 

What this document does. We 

propose to list the pyramid pigtoe as a 

threatened species with a rule under 

section 4(d) of the Act. If made final, 

this action would add the species to the 

List of Endangered and Threatened 

Wildlife in title 50 of the Code of 

Federal Regulations (CFR) at 50 CFR 

17.11(h) and add specific provisions 

pertaining to the pyramid pigtoe to 50 

CFR 17.45. 

The basis for our action. Under the 

Act, we may determine that a species is 

an endangered or threatened species 

because of any of five factors: (A) The 

present or threatened destruction, 

modification, or curtailment of its 

habitat or range; (B) overutilization for 

commercial, recreational, scientific, or 

educational purposes; (C) disease or 

predation; (D) the inadequacy of 

existing regulatory mechanisms; or (E) 

other natural or manmade factors 

affecting its continued existence. We 

have determined that threats to the 

pyramid pigtoe include habitat 

degradation or loss from a variety of 

sources (e.g., dams and other barriers, 

resource extraction); degraded water 

quality from chemical contamination 

and erosion from development, 

agriculture, and mining operations; 

direct mortality from dredging; residual 

impacts (reduced population size) from 

historical harvest; and the proliferation 

of invasive, nonnative species. These 

threats also compound the negative 

effects associated with the species’ 

small population size. 

Section 4(a)(3) of the Act requires the 

Secretary of the Interior (Secretary) to 

designate critical habitat concurrent 

with listing to the maximum extent 

prudent and determinable. Section 

3(5)(A) of the Act defines critical habitat 

as (i) the specific areas within the 

geographical area occupied by the 

species, at the time it is listed, on which 

are found those physical or biological 

features (I) essential to the conservation 

of the species and (II) which may 

require special management 

considerations or protections; and (ii) 

specific areas outside the geographical 

area occupied by the species at the time 

it is listed, upon a determination by the 

Secretary that such areas are essential 

for the conservation of the species. 

Section 4(b)(2) of the Act states that the 

Secretary must make the designation on 

the basis of the best scientific data 

available and after taking into 

consideration the economic impact, the 

impact on national security, and any 

other relevant impacts of specifying any 

particular area as critical habitat. 

Critical habitat is not currently 

determinable. However, critical habitat 

is prudent, and we intend to propose 

critical habitat for the species within 1 

year of publishing this rule, after 

acquiring the information to determine 

the areas warranting critical habitat 

designation. 

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 governmental 

agencies, Native American Tribes, the 

scientific community, industry, or any 

other interested parties concerning this 

proposed rule. 

We particularly seek comments 

concerning: 

(1) The species’ biology, range, and 

population trends, including: 

(a) Biological or ecological 

requirements of the species, including 

habitat requirements for feeding, 

breeding, and sheltering; 

(b) Genetics and taxonomy; 

(c) Historical and current range, 

including distribution patterns; 

(d) Historical and current population 

levels, and current and projected trends; 

and 

(e) Past and ongoing conservation 

measures for the species, its habitat, or 

both. 

(2) Factors that may affect the 

continued existence of the species, 

which may include habitat modification 

or destruction, overutilization, disease, 

predation, the inadequacy of existing 

regulatory mechanisms, or other natural 

or manmade factors. 

(3) Biological, commercial trade, or 

other relevant data concerning any 

threats (or lack thereof) to this species 

and existing regulations that may be 

addressing those threats. 

(4) Additional information concerning 

the historical and current status, range, 

distribution, and population size of this 

species, including the locations of any 

additional populations of this species. 

(5) Information on regulations that are 

necessary and advisable to provide for 

the conservation of the pyramid pigtoe 

and that the Service can consider in 

developing a 4(d) rule for the species. In 

particular, information concerning the 

extent to which we should include any 

of the section 9 prohibitions in the 4(d) 

rule or whether we should consider any 

additional exceptions from the 

prohibitions in the 4(d) rule. 

(6) Which areas would be appropriate 

as critical habitat for the species and 

why areas should or should not be 

proposed for designation as critical 

habitat in the future. 

(7) Specific information on: 

(a) The amount and distribution of 

habitat for pyramid pigtoe that should 

be considered for proposed critical 

habitat; 

(b) What may constitute ‘‘physical or 

biological features essential to the 

conservation of the species within the 

geographical range currently occupied 

by the species’’; 

(c) Where these features are currently 

found; 

(d) Whether any of these features may 

require special management 

considerations or practices; 

(e) What areas that are currently 

occupied and contain features essential 

to the conservation of the species 

should be included in the designation 

and why; and 


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(f) What unoccupied areas are 

essential for the conservation of the 

species and why. 

Please include sufficient information 

with your submission (such as scientific 

journal articles or other publications) to 

allow us to verify any scientific or 

commercial information you include. 

Please note that submissions merely 

stating support for, or opposition to, the 

action under consideration without 

providing supporting information, 

although noted, will not be considered 

in making a determination, as section 

4(b)(1)(A) of the Act directs that 

determinations as to whether any 

species is an endangered or a threatened 

species must be made ‘‘solely on the 

basis of the best scientific and 

commercial data available.’’ 

You may submit your comments and 

materials concerning this proposed rule 

by one of the methods listed in 

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 website. 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. 

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. 

Because we will consider all 

comments and information we receive 

during the comment period, our final 

determinations may differ from this 

proposal. Based on the new information 

we receive (and any comments on that 

new information), we may conclude that 

the species is endangered instead of 

threatened, or we may conclude that the 

species does not warrant listing as either 

an endangered species or a threatened 

species. In addition, we may change the 

parameters of the prohibitions or the 

exceptions to those prohibitions in the 

4(d) rule if we conclude it is appropriate 

in light of comments and new 

information received. For example, we 

may expand the prohibitions to include 

prohibiting take associated with 

additional activities if we conclude that 

those additional activities are not 

compatible with conservation of the 

species. Conversely, we may establish 

additional exceptions to the 

prohibitions in the final rule if we 

conclude that the activities would 

facilitate or are compatible with the 

conservation and recovery of the 

species. 

Public Hearing 

Section 4(b)(5) of the Act provides for 

a public hearing on this proposal, if 

requested. Requests must be received by 

the date specified in DATES. Such 

requests must be sent to the address 

shown in FOR FURTHER INFORMATION

CONTACT. We will schedule a public 

hearing on this proposal, if requested, 

and announce the date, time, and place 

of the hearing, as well as how to obtain 

reasonable accommodations, in the 

Federal Register and local newspapers 

at least 15 days before the hearing. For 

the immediate future, we will provide 

these public hearings using webinars 

that will be announced on the Service’s 

website, in addition to the Federal 

Register. The use of these virtual public 

hearings is consistent with our 

regulations at 50 CFR 424.16(c)(3). 

Previous Federal Actions 

In our 1989 Animal Notice of Review 

(a notice identifying animal taxa that are 

native to the United States and being 

considered for addition to the List of 

Endangered and Threatened Wildlife), 

we categorized the pyramid pigtoe 

(which we referred to as ‘‘pink pigtoe’’) 

as a taxon not meeting the Act’s legal 

definition of a species, based on our 

taxonomic understanding of information 

in published scientific literature at that 

time (54 FR 554, January 6, 1989). While 

taxonomic uncertainty remains 

regarding some populations identified 

as pyramid pigtoe, the species is 

recognized as valid in current scientific 

literature (see Background, below). On 

April 20, 2010, we received a petition 

from the Center for Biological Diversity 

(CBD), Alabama Rivers Alliance, Clinch 

Coalition, Dogwood Alliance, Gulf 

Restoration Network, Tennessee Forests 

Council, and West Virginia Highlands 

Conservancy to list 404 aquatic, 

riparian, and wetland species, including 

the pyramid pigtoe (referred to as ‘‘pink 

pigtoe’’ in our National Domestic Listing 

Workplan) as endangered or threatened 

species under the Act. On September 

27, 2011, we published our 

determination that the petition 

contained substantial information 

indicating listing may be warranted (76 

FR 59836). On April 17, 2019, CBD filed 

a complaint challenging the Service’s 

failure to complete 12-month findings 

for these species within the statutory 

deadline. The Service and CBD reached 

a stipulated settlement agreement 

whereby the Service agreed to deliver a 

12-month finding for the pyramid pigtoe 

to the Office of the Federal Register by 

August 31, 2021. 

Supporting Documents 

A species status assessment (SSA) 

team prepared an SSA report for the 

pyramid pigtoe. The SSA team was 

composed of Service biologists, in 

consultation with other species experts. 

The SSA report represents a 

compilation of the best scientific and 

commercial data available concerning 

the status of the species, including the 

impacts of past, present, and future 

factors (both negative and beneficial) 

affecting the species. In accordance with 

our joint policy on peer review 

published in the Federal Register on 

July 1, 1994 (59 FR 34270), and our 

August 22, 2016, memorandum 

updating and clarifying the role of peer 

review of listing actions under the Act, 

we sought the expert opinions of three 

appropriate specialists regarding the 

SSA. We received two responses. We 

also received SSA report reviews from 

one Federal agency and five State 

agency partners, including scientists 

with expertise in aquatic ecology, 

freshwater mussel biology, taxonomy, 

and conservation. In addition, more 

than 50 individuals at Federal or State 

agencies, colleges or universities, or 

consultants provided data used in the 

SSA report. 

I. Proposed Listing Determination 

Background 

A thorough review of the taxonomy, 

life history, and ecology of the pyramid 

pigtoe (Pleurobema rubrum) is 

presented in the SSA report (version 

1.0; Service 2021, pp. 19–36). 

The pyramid pigtoe is a freshwater 

mussel, reddish to chestnut brown in 

color, with a smooth periostracum 

(outer shell surface) that darkens with 

age (Watters et al. 2009, p. 233). 

Juveniles may have green rays that 

typically disappear with age. The shell 

is thick, triangular, and medium-sized 

(up to 3.6 inches (in) (91 millimeters 

(mm)) (Williams et al. 2008, p. 564). It 

has a shallow sulcus (depressed 

channel) and high anteriorly directed 

beak that is elevated above the hinge 

line (Stansbery 1967, p. 3). 

The pyramid pigtoe is found in 

medium to large rivers, in a mixture of 

sand, gravel, and cobble substrates. It 

currently occurs in Kentucky, 

Tennessee, Virginia, Ohio, Alabama, 

Oklahoma, Arkansas, Mississippi, and 

Louisiana. It is considered extirpated 

from Pennsylvania, West Virginia, 

Indiana, Illinois, Wisconsin, Minnesota, 

Iowa, Kansas, and Missouri. Extant 

populations of pyramid pigtoe occur in 


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49992 Federal Register / Vol. 86, No. 170 / Tuesday, September 7, 2021 / Proposed Rules 

the Arkansas-White-Red, Lower 

Mississippi, Missouri, and Ohio River 

regions (Hydrologic Unit Code 2 scale, 

Seaber et al. 1987, pp. 3–4), and it is 

extirpated from the Missouri and Upper 

Mississippi River regions (Figure 1). 

Relying on fish hosts for successful 

reproduction, the pyramid pigtoe has a 

complex life cycle similar to other 

mussels. In general, mussels are either 

male or female, but differences between 

sexes in shell shape are subtle (Haag 

2012, p. 54). Males release sperm into 

the water column, which is taken in by 

the female through the incurrent 

aperture, where water enters the mantle 

cavity. The sperm fertilize eggs in the 

suprabranchial chamber (located above 

the gills) as ova are passed from the 

gonad to the marsupia (Yokley 1972, p. 

357). Developing larvae remain in the 

gill chamber until they mature (called 

glochidia) and are ready for release. 

Once released, the glochidia draw 

nutrients from fish hosts and develop 

into juvenile mussels, dropping from 

the hosts weeks to months after initial 

attachment. Only a few glochidia reach 

the free-living juvenile stage, and 

mortality rates for the glochidial stage 

have been estimated at 99 percent, 

making this a critical phase in the life 

history of freshwater mussels (Jansen et 

al. 2001, p. 211). 

The pyramid pigtoe is a short-term 

brooder and has been recorded as gravid 

in the Cumberland River in May, June, 

and July (Gordon and Layzer 1989, p. 

50). Host fish species are minnows of 

the family Cyprinidae and genera 

Cyprinella, Erimystax, Lythrurus, and 

Notropis (Culp et al. 2009, p. 19). 

Similar to other species in its tribe, 

Pleurobemini (taxonomic rank above 

genus and below family), the pyramid 

pigtoe targets drift-feeding minnow 

species by releasing glochidia contained 

in packets called conglutinates (Haag 

2012, p. 163). Following release from 

the female mussel, the semi-buoyant 

conglutinates drift in the water column 

where they are targeted by sight-feeding 

minnows (Culp et al, 2009, p. 21). 

A relatively long-lived species, the 

pyramid pigtoe has a lifespan that likely 

averages 20 to 30 years, based on 

observations of the closely related Ohio 

pigtoe and round pigtoe (Slater 2018, p. 

35; Watters et al. 2009, p. 299). Given 

the longevity of closely related species, 

it possibly lives up to 40–45 years in 

some locations (Ostby and Beaty 2016, 

p. 117). 

The pyramid pigtoe exhibits a 

preference for sand and gravel in rivers 

but also may be found in coarse sand in 

larger rivers (Gordon and Layzer 1989, 

p. 31). They can be found at depths less 

than 3 ft (1 m) but in large rivers can 

be found commonly at depths of 13 to 


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Extant Basins 

E:23. Arkansas-White-Red 

~ Lower Mississippi 

~Ohio 

F:: 1 Tennessee 

Rangewide Distribution of Pyramid Pigtoe 

Extirpated Basins 

-Mlssot1ri 

- Upper Mississippi 

1 inch = 864 Kilometers 

1 inch = 537 miles 

Figure 1. Rangewide distribution of pyramid pigtoe. 

A 
Federal Register / Vol. 86, No. 170 / Tuesday, September 7, 2021 / Proposed Rules 49993 

20 ft (4 to 6 m) or greater (Parmalee and 

Bogan 1998, p. 193; Williams et al. 

2008, p. 566). Adult freshwater mussels 

within the genus Pleurobema are 

suspension-feeders that filter water and 

nutrients to eat. Mussels may shift to 

deposit feeding, though reasons for this 

are poorly known and may depend on 

flow conditions or temperature. Their 

diet consists of a mixture of algae, 

bacteria, detritus, and microscopic 

animals (Gatenby et al. 1996, p. 606; 

Strayer et al. 2004, p. 430). It has also 

been surmised that dissolved organic 

matter may be a significant source of 

nutrition (Strayer et al. 2004, p. 431). 

The pyramid pigtoe (Pleurobema 

rubrum) belongs to a complex of four 

morphologically similar species, which 

includes the Ohio pigtoe (P. cordatum), 

rough pigtoe (P. plenum) and round 

pigtoe (P. sintoxia). Since its original 

description as a species (Rafinesque 

1820, p. 314), Pleurobema rubrum has 

undergone several scientific name 

changes, due to its widespread 

distribution, variability in shell shape 

and size throughout its range, and 

similarity in morphological characters 

to other closely related species. 

Additionally, based on shell characters 

alone, the pyramid pigtoe has been 

periodically considered a subspecies of 

the Ohio pigtoe (Ortmann 1911, p. 331). 

Since its initial description in 1820, the 

pyramid pigtoe has sometimes been 

referred to as pink pigtoe by commercial 

shell harvesters and biologists. 

However, the common name applied to 

the species in the scientific literature 

and in the Integrated Taxonomic 

Information System is pyramid pigtoe. 

Genetic studies to clarify the 

taxonomic relationships among 

Pleurobema indicate potential 

differences between pyramid pigtoe 

populations occupying separate river 

drainages. Mitochondrial DNA samples 

from two specimens of pyramid pigtoe 

indicated the Duck River, Tennessee, 

specimen was genetically distinct from 

the St. Francis River, Arkansas, 

specimen (Campbell et al. 2005, p. 143). 

These same data were included in 

subsequent phylogenetic studies 

focused on Fusconaia (Burdick and 

White 2007, p. 372) and Pleurobema 

(Campbell et al. 2008, p. 714; Campbell 

and Lydeard 2012b, p. 27) with similar 

results. Phylogeographic structuring has 

been observed between pyramid pigtoe 

from the Ouachita and St. Francis 

drainages in Arkansas that may 

represent species-level variation 

(Christian et al. 2008, p. 9; Harris et al. 

2009, p. 74). Additionally, an analysis 

that included all previously published 

and new data representing a broad 

sampling across Pleurobemini revealed 

that pyramid pigtoe and round pigtoe 

may represent a single species, with two 

out of three species delineation models 

indicating one lineage present in 

specimens identified as round pigtoe 

and pyramid pigtoe (Inoue et al. 2018, 

p. 694). However, one of the three 

models indicated separate lineages of 

the two species. While there is some 

uncertainty in the taxonomic identity of 

populations referred to as pyramid 

pigtoe, especially those outside the 

Ohio, Cumberland, and Tennessee 

basins, our SSA report analyzed the 

status of the single species currently 

recognized by the scientific community 

(Williams et al. 2017, p. 42; Graf and 

Cummings 2021, p. 19). 

Regulatory and Analytical Framework 

Regulatory Framework 

Section 4 of the Act (16 U.S.C. 1533) 

and its implementing regulations (50 

CFR part 424) set forth the procedures 

for determining whether a species is an 

endangered species or a threatened 

species. The Act defines an endangered 

species as a species that is ‘‘in danger 

of extinction throughout all or a 

significant portion of its range’’ and a 

threatened species as a species that is 

‘‘likely to become an endangered 

species within the foreseeable future 

throughout all or a significant portion of 

its range.’’ The Act requires that we 

determine whether any species is an 

endangered species or a threatened 

species because of any of the following 

factors: 

(A) The present or threatened 

destruction, modification, or 

curtailment of its habitat or range; 

(B) Overutilization for commercial, 

recreational, scientific, or educational 

purposes; 

(C) Disease or predation; 

(D) The inadequacy of existing 

regulatory mechanisms; or 

(E) Other natural or manmade factors 

affecting its continued existence. 

These factors represent broad 

categories of natural or human-caused 

actions or conditions that could have an 

effect on a species’ continued existence. 

In evaluating these actions and 

conditions, we look for those that may 

have a negative effect on individuals of 

the species, as well as other actions or 

conditions that may ameliorate any 

negative effects or may have positive 

effects. 

We use the term ‘‘threat’’ to refer in 

general to actions or conditions that are 

known to or are reasonably likely to 

negatively affect individuals of a 

species. The term ‘‘threat’’ includes 

actions or conditions that have a direct 

impact on individuals (direct impacts), 

as well as those that affect individuals 

through alteration of their habitat or 

required resources (stressors). The term 

‘‘threat’’ may encompass—either 

together or separately—the source of the 

action or condition or the action or 

condition itself. 

However, the mere identification of 

any threat(s) does not necessarily mean 

that the species meets the statutory 

definition of an ‘‘endangered species’’ or 

a ‘‘threatened species.’’ In determining 

whether a species meets either 

definition, we must evaluate all 

identified threats by considering the 

expected response by the species, and 

the effects of the threats—in light of 

those actions and conditions that will 

ameliorate the threats—on an 

individual, population, and species 

level. We evaluate each threat and its 

expected effects on the species, then 

analyze the cumulative effect of all of 

the threats on the species as a whole. 

We also consider the cumulative effect 

of the threats in light of those actions 

and conditions that will have positive 

effects on the species, such as any 

existing regulatory mechanisms or 

conservation efforts. The Secretary 

determines whether the species meets 

the definition of an ‘‘endangered 

species’’ or a ‘‘threatened species’’ only 

after conducting this cumulative 

analysis and describing the expected 

effect on the species now and in the 

foreseeable future. 

The Act does not define the term 

‘‘foreseeable future,’’ which appears in 

the statutory definition of ‘‘threatened 

species.’’ Our implementing regulations 

at 50 CFR 424.11(d) set forth a 

framework for evaluating the foreseeable 

future on a case-by-case basis. The term 

‘‘foreseeable future’’ extends only so far 

into the future as the Service can 

reasonably determine that both the 

future threats and the species’ responses 

to those threats are likely. In other 

words, the foreseeable future is the 

period of time in which we can make 

reliable predictions. ‘‘Reliable’’ does not 

mean ‘‘certain’’; it means sufficient to 

provide a reasonable degree of 

confidence in the prediction. Thus, a 

prediction is reliable if it is reasonable 

to depend on it when making decisions. 

It is not always possible or necessary 

to define foreseeable future as a 

particular number of years. Analysis of 

the foreseeable future uses the best 

scientific and commercial data available 

and should consider the timeframes 

applicable to the relevant threats and to 

the species’ likely responses to those 

threats in view of its life-history 

characteristics. Data that are typically 

relevant to assessing the species’ 

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specific factors such as lifespan, 

reproductive rates or productivity, 

certain behaviors, and other 

demographic factors. 

Analytical Framework 

The SSA report documents the results 

of our comprehensive biological review 

of the best scientific and commercial 

data regarding the status of the species, 

including an assessment of the potential 

threats to the species. The SSA report 

does not represent a decision by the 

Service on whether the species should 

be proposed for listing as an endangered 

or threatened species under the Act. 

However, it does provide the scientific 

basis that informs our regulatory 

decisions, which involve the further 

application of standards within the Act 

and its implementing regulations and 

policies. The following is a summary of 

the key results and conclusions from the 

SSA report; the full SSA report can be 

found at Docket FWS–R4–ES–2021– 

0092 on http://www.regulations.gov and 

at https://www.fws.gov/Asheville/. 

To assess pyramid pigtoe viability, we 

used the three conservation biology 

principles of resiliency, redundancy, 

and representation (Shaffer and Stein 

2000, pp. 306–310). Briefly, resiliency 

supports the ability of the species to 

withstand environmental and 

demographic stochasticity (for example, 

wet or dry, warm or cold years), 

redundancy supports the ability of the 

species to withstand catastrophic events 

(for example, droughts, large pollution 

events), and representation supports the 

ability of the species to adapt over time 

to long-term changes in the environment 

(for example, climate changes). In 

general, the more resilient and 

redundant a species is and the more 

representation it has, the more likely it 

is to sustain populations over time, even 

under changing environmental 

conditions. Using these principles, we 

identified the species’ ecological 

requirements for survival and 

reproduction at the individual, 

population, and species levels, and 

described the beneficial and risk factors 

influencing the species’ viability. 

The SSA process can be categorized 

into three sequential stages. During the 

first stage, we evaluated the individual 

species’ life-history needs. The next 

stage involved an assessment of the 

historical and current condition of the 

species’ demographics and habitat 

characteristics, including an 

explanation of how the species arrived 

at its current condition. The final stage 

of the SSA involved making predictions 

about the species’ responses to positive 

and negative environmental and 

anthropogenic influences. Throughout 

all of these stages, we used the best 

available information to characterize 

viability as the ability of a species to 

sustain populations in the wild over 

time. We use this information to inform 

our regulatory decision. 

Summary of Biological Status and 

Threats 

In this discussion, we review the 

biological condition of the species and 

its resources, and the threats that 

influence the species’ current and future 

condition, in order to assess the species’ 

overall viability and the risks to that 

viability. 

Species Needs 

We assessed the best available 

information to identify the physical and 

biological needs to support individual 

fitness at all life stages for the pyramid 

pigtoe. Full descriptions of all needs are 

available in chapter 4 of the SSA report 

(Service 2021, pp. 29–36), which can be 

found in docket number FWS–R4–ES– 

2021–0092 on http://

www.regulations.gov, and on our 

internet site https://www.fws.gov/ 

Asheville/. To maintain viability, 

individual pyramid pigtoes need clean 

flowing water, appropriate water quality 

and temperatures (parameters listed in 

Service 2021, p. 29), low levels of 

sedimentation, and food and nutrients. 

Pyramid pigtoe habitat is in rivers with 

natural flow regimes. Perturbations that 

disrupt natural flow patterns (e.g., 

dams) have a negative influence on 

pyramid pigtoe and host fish resilience. 

Pyramid pigtoe habitat must have 

adequate flow to deliver oxygen, enable 

passive reproduction, and deliver food. 

At the population and species 

(rangewide) level, the pyramid pigtoe 

needs habitat connectivity and positive 

demographic attributes (population 

density and growth rate, age class 

structure, recruitment) to maintain 

viability (Service 2021, pp. 32–33). 

Dendritic, or branched, orientation of 

stream systems can enhance 

metapopulation persistence compared 

to linear or two-dimensional systems 

(Fagan 2002, p. 3,243). Tributary 

connection to river mainstems allows 

movement of host fishes and helps 

facilitate dispersal and colonization of 

appropriate habitat patches by mussels. 

A high degree of connection between 

habitat patches and occupied reaches is 

necessary, because mussels are heavily 

dependent on gene exchange and host 

fish movement and dispersal within 

river corridors to maintain viable 

populations (Newton et al. 2008, p. 

425). 

Fragmentation of stream habitat 

results in barriers to host fish 

movement, which in turn, influences 

mussel distributions, increasing the 

likelihood and compounding the 

significance of local extirpation events 

(Fagan 2002, p. 3,248). The pyramid 

pigtoe and other mussel species that use 

small host fishes, such as minnows and 

shiners (family Cyprinidae), are more 

susceptible to impacts from habitat 

fragmentation. This is due to increasing 

distance between suitable habitat 

patches and low likelihood of small host 

fish swimming over that distance as 

compared to large host fishes (Vaughn 

2012, p. 7). Barriers to movement can 

cause isolated or patchy distributions of 

mussels, which may limit both genetic 

exchange and recolonization (Jones et 

al. 2006, p. 528). 

Mussel abundance in a given river 

reach is a product of the number of 

mussel beds (aggregations of freshwater 

mussels) and the density of mussels 

within those beds. Healthy pyramid 

pigtoe populations have numerous 

individuals, with multiple age classes, 

and exhibit regular recruitment of new 

age classes. For pyramid pigtoe 

populations to be resilient, there must 

be multiple mussel beds of sufficient 

density such that local stochastic events 

do not eliminate the bed(s), allowing the 

mussel bed and the overall local 

population within a river reach to 

recover from any one event. A dendritic 

distribution (branching, such that there 

is not a line connecting a single 

upstream and downstream aggregation) 

over a large area also helps buffer 

against stochastic events that may 

impact populations. Mussels do not 

actively seek mates; rather, males 

release sperm into the water column, 

where it drifts until a female takes it in 

(Moles and Layzer 2008, p. 212). 

Therefore, successful individual 

reproduction and population viability 

require sufficient numbers of female 

mussels downstream of sufficient 

numbers of male mussels; higher 

density (number of mussels per unit 

area) increases the likelihood of 

fertilization. 

Threats 

We have determined that past and 

current threats to the pyramid pigtoe 

include habitat degradation or loss from 

a variety of sources (e.g., dams and other 

barriers, resource extraction); degraded 

water quality from chemical 

contamination and erosion from 

development, agriculture, and mining 

operations; direct mortality from 

dredging; residual impacts (reduced 

population size) from historical harvest; 

and the proliferation of invasive, 

nonnative species. Cumulatively, these 

threats also contribute to the negative 


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effects associated with the species’ 

small population size in certain areas. 

The following discussions include 

evaluations of three current threats and 

associated sources that are affecting the 

pyramid pigtoe and its habitat: (1) 

Habitat (including water quality) 

degradation or loss, (2) invasive and 

nonnative species, and (3) negative 

effects associated with small population 

size (Service 2021, pp. 51–83). We also 

considered impacts from climate 

change, but found no evidence linking 

climate change impacts to the current 

status of the pyramid pigtoe. We note 

that overutilization (commercial mussel 

harvest) was a threat historically and 

likely reduced the size of many 

populations such that they have not 

recovered to historical abundance 

levels, but it is not currently a threat. In 

addition, potential impacts from 

disease, parasites, and predation, as 

well as potential impacts to host 

species, were evaluated but were found 

to have minimal effects on viability of 

the pyramid pigtoe based on current 

knowledge (Service 2021, pp. 78–79). 

Although not a widespread threat, 

disease is likely affecting at least one 

population of pyramid pigtoe: The 

Clinch River mussel assemblage, which 

includes a pyramid pigtoe population, 

has recently undergone a die-off that is 

associated with a novel densovirus 

(Richard et al. 2020, entire). Finally, we 

also considered effects associated with 

enigmatic population declines 

(unexplained die-offs of large numbers 

of mussels over a short period of time), 

which have been documented in fresh 

water river mussel populations since the 

1960s; despite speculation and repeated 

aquatic organism surveys and water 

quality monitoring, the causes of these 

events are largely unknown (Haag 2019, 

p. 43). 

Predominant threats affecting each 

pyramid pigtoe population are listed in 

Table 1. Based on threat information in 

the literature or State Wildlife Action 

Plans, we categorized the threat level as 

low, moderate, or high depending on 

their magnitude and immediacy: 

• Low—Threats to aquatic fauna far 

enough removed in time or space that 

they are currently exerting minimal 

influence on mussel populations. 

• Moderate—Multiple threats linked 

to negative effects on mussels are 

present. Some threats currently acting 

on mussel habitat, reducing resource 

needs, and limiting recruitment and 

population growth. 

• High—Multiple threats linked to 

negative effects on mussels are present 

and have been acting cumulatively on 

mussel habitat, prohibiting sustained 

recruitment and population growth. 

TABLE 1—CURRENT THREATS AND LEVEL OF THREAT TO THE PYRAMID PIGTOE BY RIVER BASIN AND POPULATION

[Adapted and modified from SSA report, Service 2021, pp. 157–164] 

Population Threat level 

category Threats 

OHIO RIVER BASIN 

Muskingum River ...................... High ................ Hydropower development; impoundment; dredging; population isolation; past commercial 

harvest. 

Upper Green River .................... Low ................. Impoundment; habitat loss and water quality degradation; resource extraction; past commercial harvest. 

Barren River .............................. Moderate ........ Impoundment; habitat loss and water quality degradation; resource extraction; past commercial harvest. 

Middle Green River ................... Moderate ........ Impoundment; habitat loss and water quality degradation; resource extraction; past commercial harvest. 

Lower Green River .................... Moderate ........ Impoundment; habitat loss and water quality degradation; resource extraction; past commercial harvest. 

Cumberland River ..................... High ................ Habitat fragmentation, hypolimnetic discharges. 

TENNESSEE RIVER BASIN 

Holston River ............................ High ................ Habitat fragmentation, hypolimnetic discharges. 

Clinch River ............................... Moderate ........ Development; agricultural activities; dams; overharvest historically; contaminants; resource 

extraction; degraded water quality; enigmatic die-offs. 

Paint Rock River ....................... Low ................. Habitat loss through channel maintenance (snag removal); habitat fragmentation and population isolation due to impoundment; agriculture. 

Tennessee River (Wheeler Reservoir).High ................ Impoundment; habitat degradation from flow releases; past commercial harvest. 

Tennessee River (Pickwick 

Reservoir).

High ................ Impoundment; dredging; navigation impacts; past commercial harvest. 

Tennessee River (Kentucky 

Reservoir).

High ................ Impoundment; dredging and navigation impacts; agriculture. 

Upper Duck River ..................... Moderate ........ Development; agricultural activities; water quality degradation; impoundments; fragmented 

populations. 

Lower Duck River ..................... Moderate ........ Development and water quality degradation. 

ARKANSAS-WHITE-RED BASIN 

Petit Jean River ........................ Moderate ........ Agriculture; habitat loss and water quality degradation. 

Eleven Point River .................... Low ................. Habitat loss and water quality degradation; agricultural effects. 

Little River ................................. Moderate ........ Impoundment, habitat loss, and water quality degradation. 

LOWER MISSISSIPPI BASIN 

Lower Black River ..................... Moderate ........ Agriculture, habitat loss, and water quality degradation. 

Lower St. Francis River ............ High ................ Agriculture, habitat loss, and water quality degradation. 

Tyronza River ............................ High ................ Agriculture, habitat loss, and water quality degradation. 

White River ............................... Moderate ........ Impoundment, resource extraction, habitat loss, and water quality degradation. 


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TABLE 1—CURRENT THREATS AND LEVEL OF THREAT TO THE PYRAMID PIGTOE BY RIVER BASIN AND POPULATION— 

Continued 

[Adapted and modified from SSA report, Service 2021, pp. 157–164] 

Population Threat level 

category Threats 

Upper Ouachita River ............... Moderate ........ Impoundment, navigation, habitat loss, and water quality degradation. 

Little Missouri River .................. Moderate ........ Agriculture, habitat loss, and water quality degradation. 

Ouachita River .......................... Moderate ........ Impoundment, navigation, habitat loss, and water quality degradation. 

Upper Saline River .................... Moderate ........ Impoundment, navigation; agriculture; resource extraction; habitat loss and water quality 

degradation. 

Lower Saline River .................... Moderate ........ Impoundment, navigation, agriculture, resource extraction, habitat loss, and water quality 

degradation. 

Bayou Bartholomew .................. High ................ Agriculture, habitat loss and water quality degradation. 

Lower Ouachita River ............... High ................ Impoundment; navigation; habitat loss and water quality degradation. 

Big Sunflower River .................. High ................ Agriculture; habitat loss and water quality degradation. 

Hushpuckna River ..................... High ................ Impoundment; agriculture; navigation; habitat loss and water quality degradation. 

Bogue Phalia ............................. High ................ Impoundment; agriculture; navigation; habitat loss and water quality degradation. 

Little Sunflower River ................ High ................ Impoundment; agriculture; navigation; habitat loss and water quality degradation. 

Sunflower River ......................... High ................ Impoundment; agriculture; navigation; habitat loss and water quality degradation. 

Sandy Bayou ............................. High ................ Impoundment; agriculture; navigation; habitat loss and water quality degradation. 

Big Black River ......................... High ................ Impoundment; agriculture, habitat loss and water quality degradation. 

Habitat Degradation or Loss 

Development and Urbanization 

Development and urbanization 

activities that may contribute to 

pyramid pigtoe habitat degradation or 

loss, including reduced water quality, 

occur throughout the species’ range. The 

term ‘‘development’’ refers to 

urbanization of the landscape, including 

(but not limited to) land conversion for 

residential, commercial, and industrial 

uses and the accompanying 

infrastructure. The effects of 

urbanization may include alterations to 

water quality, water quantity, and 

habitat (both in-stream and streamside) 

(Ren et al. 2003, p. 649; Wilson 2015, p. 

424). Urban development can lead to 

increased variability in streamflow, 

typically increasing the extent and 

volume of water entering a stream after 

a storm and decreasing the time it takes 

for the water to travel over the land 

before entering the stream (Giddings et 

al. 2009, p. 1). Deleterious effects on 

streams (i.e., water collection on 

impervious surfaces that rapidly flows 

into storm drains and local streams), 

including those that may be occupied by 

the pyramid pigtoe, include: 

• Water Quantity: Storm drains 

deliver large volumes of water to 

streams much faster than would 

naturally occur, often resulting in 

flooding and bank erosion that reshapes 

the channel and causes substrate 

instability, resulting in destabilization 

of bottom sediments. Increased, highvelocity discharges can cause pyramid 

pigtoe to become stressed, displaced, or 

killed by fast-moving water and the 

debris and sediment carried in it. 

• Water Quality: Pollutants (e.g., 

gasoline, oil drips, fertilizers) that 

accumulate on impervious surfaces may 

be washed directly into streams during 

storm events thereby directing killing 

pyramid pigtoe individuals. 

• Water Temperature: During warm 

weather, rain that falls on impervious 

surfaces becomes superheated and can 

stress or kill pyramid pigtoe individuals 

when it enters streams. 

Water infrastructure to support 

development, including water supply, 

reclamation, and wastewater treatment, 

results in pollution or contaminant 

discharges to streams. Right of way 

(ROW) crossings for waterlines and 

other utility lines also affect stream 

habitats. Direct impacts from utility 

crossings include direct exposure or 

crushing of individuals, sedimentation, 

and flow disturbance. The most 

significant cumulative impact involves 

cleared ROWs that result in direct 

runoff and increased stream temperature 

at the crossing locations. Maintenance 

or clearing of ROWs may entail 

herbicide applications that subsequently 

enter streams via stream runoff. 

Most populations of pyramid pigtoe 

in urban areas with large human 

populations have been diminished or 

lost. Secondary impacts resulting from 

development, such as the increased 

contaminant introduction, stream 

disturbance caused by impervious 

surfaces, barrier construction, and forest 

conversion to other land use types such 

as agriculture or urban uses are likely 

acting cumulatively on the species. 

Increased human population growth 

projections indicate urban sprawl (a 

current process) will affect pyramid 

pigtoe populations in the Tennessee and 

Ohio basins (Terando et al. 2014, p. 7; 

Tayyebi et al. 2015, p. 110). In the 

Upper and Lower Duck River MUs, the 

species is currently impacted by rapid 

development encroaching from the city 

of Nashville and nearby smaller urban 

areas such as Columbia, TN (TWRA 

2016, p. 15). The pyramid pigtoe 

population in the Muskingum River is 

downstream of the Tuscarawas River, 

which has been severely degraded by 

industrial development that continues 

to affect water quality (Hoggarth 1994, 

p. 3; Haefner and Simonson 2018, p. 1). 

Threats to the pyramid pigtoe from 

development are partly mitigated by 

Federal lands. Several locations where 

the pyramid pigtoe occurs in water 

bodies located on or immediately 

adjacent to Federal lands receive some 

indirect benefits to viability such as lack 

of urbanization and land development 

pressure. These include the Pond Creek 

Refuge in Arkansas (Arkansas-WhiteRed basin) as well as Upper Ouachita, 

Felsenthal, and White River Refuges 

(Lower Mississippi basin), and Wheeler 

Refuge (Tennessee Basin) that are 

adjacent to large rivers where the 

pyramid pigtoe occurs. Mammoth Cave 

National Park also provides a level of 

localized protection against 

development pressures for the pyramid 

pigtoe population in the upper Green 

River, Kentucky (Ohio Basin). 

On private lands, the Saline-CaddoOuachita Programmatic Safe Harbor 

Agreement and Candidate Conservation 

Agreement with Assurances programs 

are voluntary conservation programs 

that support ongoing stewardship for 

imperiled species, including the 

pyramid pigtoe. Large tracts of private 

land in the upper Saline and Ouachita 

River systems adjacent to streams and 

upland areas are covered under these 

programs. These lands are mostly 

upstream of pyramid pigtoe sites 


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(Service 2015, p. 6) but could have a 

positive indirect long-term benefit to the 

species by reducing sediment and 

pollutant runoff and improving water 

quality downstream. Some private lands 

in pyramid pigtoe MUs also are 

managed for conservation through The 

Nature Conservancy (TNC) programs in 

the upper Green River in Kentucky, the 

upper Clinch/Powell River, Tennessee 

and Virginia, the Saline River in 

Arkansas, and the Paint Rock River in 

Alabama. In these watersheds, TNC has 

a few riparian inholdings that are 

protected from developments. In 

addition, within these watersheds, TNC 

implements community-based and 

partner-oriented projects to address 

aquatic species and instream habitat 

conservation by restoring and protecting 

streambanks and riparian zones. 

Various small, isolated parcels of 

State land (e.g., State parks, State 

forests, wildlife management areas) 

along MUs where the pyramid pigtoe 

occurs also provide a conservation 

benefit as a buffer to development. 

However, vast tracks of riparian lands in 

the range of the pyramid pigtoe are 

privately owned, without conservation 

programs, and the prevalence of 

privately owned lands along rivers is 

comparatively much larger than the 

species’ occurrence on public lands. 

Limited overlap of the species’ range 

with public lands and private lands 

with conservation programs diminishes 

their ability to protect the species, 

because the habitat protection benefits 

these lands provide are at significant 

risk of being negated by detrimental 

activities upstream or immediately 

downstream. 

Transportation 

Transportation-related impacts 

include both road development and 

river navigation. Road development 

increases impervious surfaces as well as 

land clearing and habitat fragmentation. 

Roads are generally associated with 

negative effects on the biotic integrity of 

aquatic ecosystems, including changes 

in surface water temperatures and 

patterns of runoff, sedimentation, 

adding heavy metals (especially lead), 

salts, organics, and nutrients to stream 

systems (Trombulak and Frissell 2000, 

p. 18). 

With regard to river navigation, 

dredging and channelization activities 

(as a means of maintaining waterways) 

have altered riverine habitats 

nationwide (Ebert 1993, p. 157). 

Channelization affects many physical 

characteristics of streams through 

accelerated erosion, increased bedload, 

reduced depth, decreased habitat 

diversity, geomorphic instability, and 

riparian canopy loss (Hartfield 1993, p. 

139). All of these impacts contribute to 

loss of habitat for the pyramid pigtoe 

and host fishes. Increases in turbulence, 

suspended and deposited sediments, 

and turbidity resulting from river 

transportation and associated activities 

may affect mussel feeding and 

respiration (Aldridge et al. 1987, p. 25). 

In addition to dredging and channel 

maintenance, impacts associated with 

barge traffic, which includes 

construction of fleeting areas, mooring 

cells, docking facilities, and propeller 

wash, also destroy and disrupt mussel 

habitat (see Miller et al. (1989, pp. 48– 

49) as an example for disturbance from 

barges). 

Transportation-related impacts across 

the range of the pyramid pigtoe include 

(but are not limited to) the following 

examples: 

• Extensive stream channelization 

and snag removal has severely affected 

the freshwater mussel fauna and habitat 

in the Paint Rock River system, 

including the lower reaches of Estill 

Fork and Hurricane Creek (Ahlstedt 

1995–96, p. 65). Even if active 

channelization activities are not 

currently occurring in rivers and 

streams occupied by the pyramid pigtoe, 

impacts of past actions can have 

permanent effects (Haag and Cicerello 

2016, p. 60; Hubbard et al. 1993, p. 142; 

Watters 2000, p. 274). 

• Commercial navigation previously 

took place in the lower Green and 

Barren Rivers, where navigation dams 

remain but are not in operation. Past 

dredging and navigation affected mussel 

beds in the mainstem Cumberland 

River, which has the last remaining 

population of pyramid pigtoe in the 

Cumberland River system (Hubbs 2012, 

p. 9). 

• Currently, all three of the Tennessee 

River mainstem pyramid pigtoe MUs are 

likely affected to some extent by 

channel maintenance and navigation 

operations, due to their clustered 

distribution and proximity to navigation 

dams. 

• Two navigation dams are operated 

on the Ouachita River, which is 

maintained by the Corps as a waterway, 

and affect three MUs. 

Contaminants 

Contaminants contained in point and 

non-point discharges can degrade water 

and substrate quality and adversely 

impact mussel populations. The effects 

of contaminants such as metals, 

chlorine, and ammonia are profound on 

juvenile mussels (Bartsch et al. 2003, p. 

2,566; Augspurger et al. 2003, p. 2,571). 

Juvenile mussels may readily ingest 

contaminants bound to sediment 

particles (Newton and Cope 2007, p. 

276). These contaminants also affect 

mussel glochidia, which are very 

sensitive to some toxicants (Goudreau et 

al. 1993, p. 221; Jacobson et al. 1997, p. 

2,386; Valenti et al. 2005, p. 1,243). 

High levels of suspended solids alone 

(without bound contaminants) can 

result in mussel reproductive failure or 

low fertilization rates of long-term 

brooders, such as species of the genus 

Pleurobema (Gascho-Landis and 

Stoeckel 2015, p. 229). 

Current State regulations regarding 

pollutants are designed to be protective 

of aquatic organisms; however, 

freshwater mussels may be more 

susceptible to some pollutants than the 

test organisms commonly used in 

bioassays. Additionally, water quality 

criteria may not incorporate data 

available for freshwater mussels (March 

et al. 2007, pp. 2,066–2,067). A 

multitude of bioassays conducted on 16 

mussel species (summarized by 

Augspurger et al. 2007, pp. 2,025–2,028) 

show that freshwater mollusks are more 

sensitive than previously believed to 

some chemical pollutants, including 

chlorine, ammonia, copper, fungicides, 

and herbicide surfactants. Nickel and 

chloride were toxic to federally 

threatened mussel species at levels 

below the current criteria and are 

sensitive to sodium dodecyl sulfate 

(SDS), a surfactant commonly used in 

household detergents, for which water 

quality criteria do not currently exist 

(Gibson 2015, p. 80, p. 90; Gibson et al. 

2018, pp. 247–250). None of the States 

in the range of the pyramid pigtoe have 

fully adopted the Environmental 

Protection Agency’s 2013 recommended 

ammonia criteria for freshwater 

mollusks (78 FR 52192, August 22, 

2013). 

Contaminant inputs (including 

sediments) to pyramid pigtoe habitat 

stem from multiple threats, including 

urbanization, resource extraction, 

agriculture, and channel maintenance 

for navigation, diminishing water 

quality in many areas of the four basins 

where the species occurs. Examples of 

contaminant-related impacts in the 

range of the pyramid pigtoe include (but 

are not limited to) the following: 

• Long-term declines and extirpation 

of mussels from reaches of the Upper 

Clinch MU in Virginia attributed, in 

part, to copper and zinc contamination 

originating from wastewater discharges 

at coal-fired power plants (Price et al. 

2014, p. 12; Zipper et al. 2014, p. 9). 

Coal plants also are located on the 

Lower Green and Cumberland-Old 

Hickory MUs. 

• Heavy metals toxicity to mussels 

has been documented in the 


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Muskingum, Upper Clinch, and all 

Tennessee River MUs (Havlik and 

Marking 1987, pp. 4–9). 

• A chemical spill from a tanker truck 

accident flowed into the Upper Clinch 

MU in Virginia and eliminated 

approximately 18,000 individuals of 

several mussel species (Jones et al. 2001, 

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

including approximately 750 

individuals of three federally listed 

species (Schmerfeld 2006, p. 12). A 

catastrophic chemical spill in 1999 

affected approximately 10 miles of the 

Ohio River and resulted in the loss of an 

estimated 1 million mussels, including 

two federally listed species (Butler 

2005, p. 24). 

State and Federal water quality 

programs provide a level of protection 

to the pyramid pigtoe from 

development, agriculture, and river 

navigation activities by regulating storm 

water and point source (end of pipe) 

discharges to streams. Section 401 of the 

Federal Clean Water Act (CWA; 33 

U.S.C. 1251 et seq.) requires that an 

applicant for a Federal license or permit 

provide a certification that any 

discharges from the facility will not 

degrade water quality or violate waterquality standards, including those 

established by States. Section 404 of the 

CWA establishes a program to regulate 

the discharge of dredged and fill 

material into waters of the United 

States. Under the CWA, permits to fill 

wetlands and culvert, bridge, or realign 

streams or water features are issued by 

the U.S. Army Corps of Engineers. 

Current State regulations regarding 

pollutants are designed to be protective 

of aquatic organisms; however, as 

discussed above, freshwater mussels 

may be more susceptible to some 

pollutants than the aquatic biota for 

which water quality criteria are 

currently established. 

Despite existing authorities such as 

the CWA, pollutants continue to impair 

the water quality in areas of the pyramid 

pigtoe’s range. State and Federal 

regulatory mechanisms have helped 

reduce the negative effects of point 

source discharges since the 1970s, yet 

these regulations are difficult to 

implement and enforce. Although new 

water quality criteria are under 

development that will take into account 

more sensitive aquatic species, most 

current criteria do not. It is expected 

that several years will be needed to 

implement new water quality criteria 

throughout the species’ range. 

Agriculture 

Agricultural activities occur across 

the range of the pyramid pigtoe and are 

a factor in its historical decline and 

localized extirpations. The advent of 

intensive row crop agricultural practices 

corresponds with freshwater mussel 

declines, and species extirpations, in 

the eastern United States (Peacock et al. 

2005, p. 550). Nutrient enrichment and 

water withdrawals, threats commonly 

associated with agricultural activities, 

may be localized and limited in scope, 

and have the potential to affect 

individual pyramid pigtoe mussels. 

However, chemical control using 

pesticides may have broader impacts. 

Pesticides, including herbicides, 

fungicides, and insecticides as well as 

their surfactants and adjuvants, are 

highly toxic to juvenile and adult 

freshwater mussels (Bringolf et al. 2007, 

p. 2,092) and deleterious if not properly 

applied to agricultural operations. 

Waste from confined animal feeding and 

commercial livestock operations is 

another potential source of 

contaminants that come from 

agricultural runoff. The concentrations 

of these contaminants from fields or 

pastures may be at levels that can affect 

an entire population, especially given 

the highly fragmented distribution of 

the pyramid pigtoe. 

Agencies such as the Natural 

Resources Conservation Service (NRCS) 

and the Soil and Water Conservation 

Districts provide technical and financial 

assistance to farmers and private 

landowners. Additionally, county 

resource development councils and 

university agricultural extension 

services disseminate information on the 

importance of minimizing land use 

impacts, specifically agriculture, on 

aquatic resources. These programs help 

identify opportunities for conservation 

through projects such as exclusion 

fencing and alternate water supply 

sources, which help decrease nutrient 

inputs and water withdrawals and help 

keep livestock off stream banks and 

shorelines, reducing erosion. However, 

the overall effectiveness of these 

programs over a large scale is unknown 

given the pyramid pigtoe’s wide 

distribution and varying agricultural 

intensities in its range. 

Dams and Barriers 

Whether for flood control, 

hydropower, river navigation, or as 

abandoned mill structures, dams and 

their impoundments are one of the most 

pervasive threats to pyramid pigtoe 

rangewide: 26 of 35 populations and all 

4 major basins in the species’ range are 

affected (Table 1). Dams have many 

impacts on stream ecosystems, and the 

effects of impoundments and barriers on 

aquatic habitats and freshwater mussels 

are relatively well-documented (Watters 

2000, p. 261). Extinction and extirpation 

of many North American freshwater 

mussels can be traced to impoundment 

and inundation of riffle habitats in all 

major river basins of the central and 

eastern United States (Haag 2009, p. 

107). Reductions in the diversity and 

abundance of mussels are primarily 

attributed to habitat shifts, alteration 

and disruption of connectivity, and 

diminished water quality as a result of 

reservoir construction (Neves et al. 

1997, p. 63). The survival and 

reproductive success of mussels are 

influenced upstream of dams as flowing 

waters change to impounded waters, 

with increased depths and buildup of 

sediments, decreased dissolved oxygen, 

and drastic alteration of resident fish 

assemblages. Downstream of dams, 

biotic and physical habitat conditions 

provided by natural flow regimes are 

altered by minimal releases or scouring 

flows, seasonal dissolved oxygen 

depletion, and reduced or increased 

water temperatures. The number of fish 

species is greatly reduced where 

coldwater flow (hypolimnetic discharge) 

is released. Additionally, dams fragment 

habitat, limiting dispersal of mussels on 

their fish hosts, which leads to genetic 

isolation of mussel populations. 

Resource Extraction 

Predominant resource extraction 

threats in the range of the pyramid 

pigtoe stem from mining (primarily coal 

but including other mineral resources) 

and oil and gas exploration. Activities 

associated with coal mining and oil and 

gas drilling can contribute chemical 

pollutants to streams. Acid mine 

drainage is created from the oxidation of 

iron-sulfide minerals such as pyrite, 

forming sulfuric acid (Sams and Beer 

2000, p. 3). This acid mine drainage 

may be associated with high 

concentrations of aluminum, 

manganese, zinc, and other constituents 

(Tennessee Department of Environment 

and Conservation (TDEC) 2014, p. 72). 

The metals, and the high acidity 

typically associated with acid mine 

drainage, can be acutely and chronically 

toxic to aquatic life (Jones 1964, p. 96). 

Implementation of the Surface Mining 

Control and Reclamation Act of 1977 

(SMCRA; 30 U.S.C. 1201 et seq.) has 

significantly reduced acid mine 

drainage from new coal mines; however, 

un-reclaimed areas mined prior to the 

SMCRA continue to generate acid mine 

drainage in portions of the pyramid 

pigtoe’s range. Direct impacts to the 

pyramid pigtoe from acid mine drainage 

in most occupied river reaches are 

unlikely because coal mining sites tend 

to be adjacent to smaller headwater 

streams, but mining pollutants can be 


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transferred downstream to pyramid 

pigtoe habitats. 

Surface mining has been identified as 

a source of impairment for 

approximately 775 mi (1,247 km) of 

streams in Kentucky (Kentucky 

Department for Environmental 

Protection 2014, p. 66). Weathering of 

soils and rock broken apart to access 

coal seams typically increases 

alkalinity, total dissolved solids, 

salinity, and sedimentation and alters 

hydrology and physical habitat of 

streams receiving surface mine drainage, 

impacting fish and aquatic invertebrate 

communities (e.g., Bernhardt and 

Palmer 2011, pp. 42–49; Linberg et al. 

2011, entire; Hopkins and Roush 2013, 

pp. 585–586; Hitt and Chambers 2014, 

p. 923; Hitt et al. 2016, pp. 47–53). 

Mining continues to impair water 

quality in streams in the Cumberland 

Plateau and Central Appalachian 

regions of Tennessee and Kentucky 

(TDEC 2014, p. 62), which contain 

portions of the Tennessee and 

Cumberland River basins, and is the 

primary source of low pH impairment of 

376 mi (605 km) of rivers in Tennessee 

(TDEC 2014, p. 53). Coal mining has 

resulted in discharges of industrial and 

mine wastes from coal mines and coal 

processing facilities in the Clinch and 

Powell Rivers (Ahlstedt et al. 2016, p. 

8). Direct impacts to the pyramid pigtoe 

from acid mine drainage or total 

dissolved solids in most occupied river 

reaches are unlikely because coal 

mining sites tend to be adjacent to 

smaller headwater streams, but 

associated mining pollutants (fine 

sediments, metals, and salts) can be 

transferred downstream to medium and 

large river pyramid pigtoe habitats 

(Bernhardt and Palmer, 2011 p. 46). 

Natural gas extraction in the 

Appalachians, including the 

Cumberland River basin, has negatively 

affected water quality through 

accidental spills and discharges, as well 

as increased sedimentation due to 

development of road construction, 

pipeline, drill pad construction, as well 

as tree removal required to clear the 

construction areas (Vidic et al. 2013, p. 

6). Disposal of insufficiently treated 

brine wastewater, more saline than 

seawater, has specifically been found to 

adversely affect freshwater mussels 

(Patnode et al. 2015, p. 62). Potential 

threats from natural gas and oil 

exploration are also a concern in the 

White River basin. 

Instream sand and alluvial gravel 

mining has been implicated in the 

destruction of mussel populations 

(Hartfield 1993, p. 138). Negative 

impacts associated with gravel mining 

include stream channel modifications 

such as altered habitat, disrupted flow 

patterns, and sediment transport (Hubbs 

et al. 2006, p. 170). Additionally, water 

quality modifications including 

increased turbidity, reduced light 

penetration, increased temperature, and 

increased sedimentation result from 

gravel mining. Commercial sand and 

gravel mining and dredging directly 

affects the pyramid pigtoe in the 

Tennessee River, specifically within the 

Lower Tennessee–Beech MU (Hubbs et 

al. 2006, p. 170). The Lower 

Cumberland Old Hickory MU has also 

been affected by gravel mining and 

dredging in the past (Sickel 1982, p. 4) 

that has resulted in permanent 

alteration of substrates and hydraulic 

patterns, contributing to habitat loss for 

freshwater mussels. 

Invasive and Nonnative Species 

Invasive and nonnative species in the 

range of the pyramid pigtoe include the 

Asian clam, zebra mussel, black carp, 

and the plant species, hydrilla. These 

nonnative species impact the pyramid 

pigtoe through competitive interactions, 

water quality degradation, predation, 

and habitat alteration. 

The Asian clam, found throughout the 

range of the pyramid pigtoe, alters 

benthic substrates, may filter native 

mussel sperm or glochidia, competes 

with native species for limited 

resources, and causes ammonia spikes 

in surrounding water when dying off en 

masse (Scheller 1997, p. 2). A typical 

settlement of the Asian clam occurs 

with a population density ranging from 

100 to 200 clams per square meter, 

which may not be detrimental to native 

unionids; however, populations can 

grow as large as 3,000 clams per square 

meter, which would influence both food 

resources and competition for space for 

the pyramid pigtoe. 

Within the range of the pyramid 

pigtoe, the zebra mussel occurs in the 

Ohio, Tennessee, and Arkansas-WhiteRed River basins. Native mussels, such 

as the pyramid pigtoe, are negatively 

affected by zebra mussels through direct 

colonization, reduction of available 

habitat, changes in the biotic 

environment, or a reduction in food 

sources (MacIsaac 1996, p. 292). One of 

the direct consequences of the invasion 

of zebra mussels is the local extirpation 

of native freshwater mussel populations 

from (1) attachment to the shells of 

native mussels, which can kill them 

(zebra mussels are sessile, and cling to 

hard surfaces); (2) affecting vertical and 

lateral movements of native mussels, 

due to heavy infestations, which can 

prevent valve closure; and (3) 

outcompeting native mussels and other 

filter-feeding invertebrates for food. This 

problem has been particularly acute in 

the Ohio and Tennessee River systems. 

Densities of zebra mussels attained 

17,000 per square meter in the 

Tennessee River below Wilson Dam in 

2017, although recent survey efforts 

indicate a decline from that population 

explosion (Garner 2018, pers. comm.). 

The black carp, which feeds on 

mollusks, is listed as ‘‘injurious’’ under 

the Lacey Act and occurs in the Ohio, 

Tennessee, Lower Mississippi and 

Arkansas-White-Red basins where it 

overlaps populations of the pyramid 

pigtoe. It is highly likely that this 

nonnative fish will negatively impact 

native aquatic communities by direct 

predation, thus reducing populations of 

native mussels (Nico et al. 2005, p. 193). 

Because black carp attain a large size 

and have a lifespan reportedly over 15 

years, they have the potential to cause 

significant harm to native mollusks by 

predation on multiple age classes (Nico 

et al. 2005, p. 77). 

In addition to negative impacts of 

nonnative animals, the invasive 

nonnative plant hydrilla can affect 

native mussels by covering spawning 

areas for native fish, which may be hosts 

for glochidia, and can cause significant 

reductions in stream oxygen levels 

(Colle et al. 1987, p. 410). Hydrilla is 

widespread in the Ohio, Cumberland, 

and Tennessee River systems. In 

general, invasive aquatic plants grow 

uncontrolled and can cause habitat to 

fill in, affect flow dynamics, and 

increase water temperature, 

exacerbating drought impacts in stream 

habitats (Colle et al. 1987, p. 416). 

The Aquatic Nuisance Species (ANS) 

Task Force, co-chaired by the Service 

and the National Oceanic and 

Atmospheric Administration (NOAA), 

encourages State and interstate planning 

entities to develop management plans 

describing detection and monitoring 

efforts of aquatic nuisance and 

nonnative species, prevention efforts to 

stop their introduction and spread, and 

control efforts to reduce their impacts. 

Management plan approval by the ANS 

Task Force is required to obtain funding 

under Section 1204 of the ANS 

Prevention and Control Act. Each state 

within the range of the pyramid pigtoe 

has either a plan approved by or 

submitted to the ANS Task Force, or a 

plan under development. These plans 

have been effective in terms of raising 

awareness at the state level of the 

severity of ecological damage that nonnative and nuisance species are capable 

of, but many are in early stages of 

implementation. Although laws and 

efforts are in place which may be 

effective in controlling or diminishing 

non-native and invasive species, these 


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organisms are a current and future 

threat to the pyramid pigtoe throughout 

its range. 

Small Population Size 

Historically, an extensive, largely 

contiguous pyramid pigtoe population 

occurred through much of the eastern 

half of the United States, and there were 

limited barriers preventing genetic 

interchange among river systems. With 

the completion of hundreds of dams in 

the 1900s, many large-river pyramid 

pigtoe populations were lost, resulting 

in isolation of tributary populations. 

The population size of a long-lived 

species, such as the pyramid pigtoe, 

may take decades to decline to 

extirpation post-impoundment. At best, 

limited post-impoundment recruitment 

may be occurring in the isolated 

pyramid pigtoe populations, indicating 

that these small populations are not 

likely viable long term. 

Currently, the pyramid pigtoe exhibits 

several traits that reduce population 

viability, including small population 

size and low fecundity at many 

locations compared to other mussels. 

Smaller population size puts the species 

at greater risk of extirpation from 

stochastic events (e.g., drought) or 

anthropomorphic changes and 

management activities that affect 

habitat. In addition, smaller populations 

may have reduced genetic diversity, be 

less genetically fit, and more susceptible 

to disease during extreme 

environmental conditions (Frankham 

1996, p. 1,505). Moreover, small and 

isolated populations are at higher risk of 

further loss of genetic variation due to 

genetic drift, thereby lessening the 

affected species’ ability to adapt to a 

continuously changing environment. 

Lastly, the relatively low fecundity, 

coupled with low juvenile survivorship, 

limit the pyramid pigtoe’s ability to 

withstand and recover from population 

losses. While several populations of 

pyramid pigtoe are at risk of extirpation 

due to their small size, other 

populations are large enough and 

sufficiently connected within their MU 

that they are regularly recruiting new 

cohorts. Therefore, small population 

size is a population-level threat but not 

currently a species-level or rangewide 

threat. 

Changing Climate Conditions 

Climate change threats for freshwater 

mussels include alteration of natural 

stream flow and water temperature 

regimes as drought, precipitation, and 

temperature patterns shift. Population 

discontinuity and isolation is possible 

due to the dynamics in range shifts of 

mussels and their host fishes as a result 

of warming climates, based on lifehistory traits (Archambault et al. 2018, 

p. 880). However, the mechanisms 

behind these shifts and how they alter 

population connectivity and gene flow 

are uncertain, and there is no evidence 

linking climate change impacts 

specifically to the current status of the 

pyramid pigtoe. 

Cumulative/Synergistic Effects 

Collectively, threats to the pyramid 

pigtoe have acted on the species to 

reduce the number of historical 

populations and fragment and reduce 

the size of extant populations. 

Currently, 15 of the 35 extant 

populations are small in size, 

represented by fewer than 10 

individuals observed over the past 20 

years. Factors such as low effective 

population size, genetic isolation, 

relatively low levels of fecundity and 

recruitment, and limited juvenile 

survival could affect the ability of these 

species to maintain current population 

levels and to rebound if a reduction in 

population occurs (e.g., through 

predation, toxic releases or spills, or 

poor environmental conditions that 

inhibit successful reproduction). 

Additionally, fragmentation (i.e., the 

breaking apart of habitat segments, 

independent of habitat loss (Fahrig 

2003; p. 299)) and isolation contribute 

to the extinction risk that mussel 

populations face from stochastic events 

(see Haag 2012, pp. 336–338). 

Throughout the range of the pyramid 

pigtoe, impoundments fragment and 

isolate populations from one another, 

prevent dispersal, which reduces gene 

flow (Vaughn 2012, p. 6; Service 2018, 

pp. 59–60; Service 2019, p. 74), and 

compound other threats, such as the 

introduction of contaminants and 

pollution resulting from mining, oil and 

gas exploration, agricultural runoff, and 

untreated or poorly treated wastewater 

discharges. 

Current Conditions 

Current (and future) conditions are 

described using the following categories 

that characterize the overall condition 

(resiliency) of the pyramid pigtoe 

populations: 

• High—Population with more than 

50 individuals reported since 2000, 

distributed over a more or less 

contiguous river or stream of at least 31 

miles (mi) (50 kilometers (km)) in 

length, with evidence of recent 

recruitment. Water quality and habitat 

conditions remain optimal for 

recruitment, and multiple age classes 

are represented. Populations are not 

linearly distributed and occur in more 

than one stream within the river system. 

• Medium—small restricted 

populations (10 to 50 individuals 

reported since 2000) generally 

distributed over a more or less 

contiguous length of river or stream of 

at least 6.2 mi (10 km) but less than 31 

mi (50 km)), with some level of age class 

structure, but vulnerable to existing 

threats. Appropriate substrates are 

generally maintained with instream 

flows that mimic natural conditions. 

Water quality and habitat degradation 

may occur but not at a level that 

negatively affects both the density and 

extent of a population. 

• Low—very small and highly 

restricted populations (fewer than 10 

individuals reported since 2000), 

distributed over less than 6.2 mi (10 km) 

of river or stream, with little to no 

evidence of age class structure (only 

older individuals observable). Loss of 

mussel habitat or water quality 

degradation within the formerly 

occupied river or stream reach has been 

measured or observed, and imminent 

threats are documented. Population is 

linearly distributed and geographically 

restricted and is not likely to withstand 

stochastic events. 

We assessed resiliency and 

redundancy based on management units 

(MUs) defined at the hydrologic unit 

code (HUC) scale (Seaber et al. 1987, 

entire; U.S. Geological Survey 2018, 

entire). Management units consisted of 

HUC–8 regions, which are analogous to 

medium-sized river basins across the 

United States. An MU consisting of a 

linear reach of stream could harbor one 

population or, if it contained a large gap 

in the species’ distribution as a result of 

an impoundment or physiographic 

boundary, more than one population. If 

multiple tributaries were occupied 

(dendritic distribution) each tributary 

within the MU was considered to 

represent a population. A majority of 

MUs contained one population, given 

that the pyramid pigtoe occurs only in 

large or medium-sized rivers and not 

smaller tributaries. 

Representation was assessed at the 

larger HUC–2 region (major basin) scale, 

and representation units were 

delineated to capture the variation in 

adaptive traits and genetic diversity. See 

chapter 2 in the SSA report for further 

explanation of the analysis methodology 

(Service 2021, pp. 20–22). Each major 

basin contains unique physiographic 

provinces and ecoregions. Therefore, the 

populations within each major basin 

may harbor basin-specific adaptive traits 

and as such species representation has 

been reduced from six basins to four 

basins. Historical connectivity between 

the major basins has been lost due 

habitat degradation and construction of 


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impoundments and there is no 

opportunity for exchange of beneficial, 

or adaptive, genes between the basins. 

The pyramid pigtoe’s current range 

extends over nine States, including 

Alabama, Arkansas, Kentucky, 

Louisiana, Mississippi, Ohio, 

Oklahoma, Tennessee, and Virginia. The 

species is considered extirpated in 

Indiana, Illinois, Iowa, Kansas, 

Minnesota, Missouri, Pennsylvania, 

West Virginia, and Wisconsin. Its 

current range is within four major HUC– 

2 regions (the Arkansas-White-Red, 

Lower Mississippi, Ohio, and Tennessee 

River regions, Figure 1). It is extirpated 

in the Missouri and Upper Mississippi 

River HUC–2 regions. Overall, the 

pyramid pigtoe formerly occupied at 

least 135 MUs but currently occurs in 28 

MUs (Figure 2). Known populations 

have declined in number, from 151 

historically to 35 today. Currently, 15 

MUs have low resiliency, 9 MUs have 

medium resiliency, and 4 MUs have 

high resiliency (Table 2, in Future 

Conditions). 

BILLING CODE 4333–15–P 


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BILLING CODE 4333–15–C 

Future Conditions 

In the SSA report, we forecast the 

pyramid pigtoe’s response to plausible 

future scenarios of environmental 

conditions. The future scenarios project 

the range in magnitude and scope of 

threats into the future. Uncertainty is 

inherent in any risk assessment, so we 

must consider plausible conditions to 

make our determinations. When 

assessing the future, viability is not a 

specific state, but rather a continuous 

measure of the likelihood that the 

species will sustain populations over 

time. 

The scenarios described in the SSA 

report represent two possible future 

conditions. Under scenario 1, the threat 


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Rangewide Distribution of Pyramid Pigtoe 

~ Extant Management Units 

1111 Extirpated Management Units 

1 inch = 353 Kilometers 

1 inch= 219 miles 

Figure 2. Extant and extirpated MUs (HUC-8) of pyramid pigtoe across its entire 

historical and current range. 
Federal Register / Vol. 86, No. 170 / Tuesday, September 7, 2021 / Proposed Rules 50003 

levels remain unchanged (threats 

continue to act on the species at the 

current rate), whereas under scenario 2 

the threat levels increase. Both scenarios 

project existing regulatory mechanisms 

and voluntary conservation measures 

benefiting the species remaining in 

place. We did not analyze a scenario 

whereby threat levels lessen because the 

primary threats that have fragmented 

and isolated populations will persist. 

Developed areas, large dams, and most 

of the small and retired dams affecting 

the species will remain in place. 

We included climate change in our 

future scenarios as a factor that would 

add to the negative impacts of the 

primary threats on the species’ habitat. 

Climate change is expected to alter the 

natural flow regime through increased 

drought and flooding worsening 

desiccation, scour, and sedimentation in 

each MU. However, in our analysis the 

influence of climate change, as a 

secondary threat, does not alter the 

projected future viability of any 

population or management unit. Those 

future outcomes are driven by the 

primary threats of habitat alteration or 

loss, nonnative invasive species, and the 

effects of small population size. 

Using the scenarios, we project the 

pyramid pigtoe’s viability over 20 to 30 

years. We selected this duration because 

the species is slow growing and longlived and has relatively low fecundity; 

long-term trend information on pyramid 

pigtoe abundance and threats is not 

available across the species’ range to 

contribute to meaningful alternative 

timeframes. 

Future resiliency of pyramid pigtoe 

populations depends on the extent to 

which the species’ needs are met for 

water quality, flow, substrate suitability, 

abundance and distribution of host fish 

species, and habitat connectivity. We 

projected the expected future resiliency 

of each population based on how events 

likely to occur under each scenario 

would affect the species’ resource 

needs. Future resiliency of each 

population is classified as high, 

medium, low, or very low. Where 

multiple populations occur within an 

MU, the MU condition is the average of 

the population condition classifications; 

however, there are no management units 

where the population classifications 

vary (i.e., all populations within the MU 

have the same classification). These 

projections are informed by 

development planning documents, peerreviewed literature, vetting of initial 

condition ranking by mussel experts, 

and our best professional judgment. 

Very low condition populations will 

become extirpated; low condition 

populations will become functionally 

extirpated (no recruitment); medium 

condition populations will exhibit 

limited recruitment and be linearly 

distributed and thus will have impaired 

ability to recover from disturbances and 

will be vulnerable to catastrophic 

events; and high condition populations 

will consistently recruit and be 

distributed over long distances and in 

connected mainstem and tributary river 

reaches (see SSA report for detailed 

future condition category definitions, 

Service 2021, pp. 84–85). 

Our analysis shows that whether 

threats remain constant or increase into 

the future, all 35 populations are 

expected to experience negative changes 

to their important habitat requisites or 

resource needs, and the condition of 

many of the populations would decrease 

(Table 2). Under scenario 1, we expect 

23 populations will be in low or very 

low condition and 9 in medium 

condition, with no to little resiliency, 

respectively. The remaining 3 

populations occurring within the Saline 

or Upper Ouachita Rivers, where the 

impact of impoundments is not as 

severe as elsewhere in the species’ 

range, are expected to maintain a high 

condition. Under scenario 2, we expect 

31 populations to be either functionally 

extirpated (low condition) or extirpated 

(very low condition) and 4 to be in 

medium condition. With increasing 

threat levels, the population condition 

of the Saline and Upper Ouachita Rivers 

decline, and, thus, within 20 to 30 years 

no high condition populations remain. 

TABLE 2—SUMMARY OF PYRAMID PIGTOE CURRENT MUSSEL POPULATION SIZE, EXTENT, THREAT LEVEL, AND

PROJECTED FUTURE CONDITIONS. ONLY OVERALL CONDITION IS LISTED FOR FUTURE SCENARIOS

Management unit Contiguous population 

(occupied river) 

Population 

size 

Population 

extent Threat level Current condition 

Future condition 

Scenario 

1 

Scenario 

2 

OHIO BASIN 

Muskingum ............................... Muskingum River ..................... Small ............. Small ............. High .............. Low ............... Very Low ...... Very Low. 

Upper Green ............................ Upper Green River .................. Large ............ Large ............ Low ............... High .............. Medium ......... Medium. 

Barren ...................................... Barren River ............................. Small ............. Small ............. Mod ............... Med ............... Medium ......... Low. 

Middle Green ........................... Middle Green River .................. Medium ......... Medium ......... Mod ............... Med ............... Medium ......... Low. 

Lower Green ............................ Lower Green River .................. Small ............. Small ............. Mod ............... Low ............... Low ............... Very Low. 

Lower Cumberland-Old Hickory 

Lake.

Cumberland River (Old Hickory 

Reservoir) Cordell Hull 

Tailwater.

Medium ......... Small ............. High .............. Low ............... Very Low ...... Very Low. 

TENNESSEE BASIN 

Holston ..................................... Holston River ........................... Small ............. Small ............. High .............. Low ............... Very Low ...... Very Low. 

Upper Clinch ............................ Clinch River ............................. Medium ......... Medium ......... Mod ............... Med ............... Low ............... Low. 

Wheeler Lake ........................... Paint Rock River ...................... Small ............. Small ............. Mod ............... Low ............... Low ............... Very Low. 

Tennessee River (Wheeler 

Reservoir) Guntersville 

Tailwater.

Medium ......... Small ............. High .............. Low ............... Low ............... Very Low. 

Pickwick Lake .......................... Tennessee River (Pickwick 

Reservoir) Wilson Tailwater.

Medium ......... Medium ......... High .............. Low ............... Low ............... Low. 

Lower Tennessee-Beech ......... Tennessee River (Kentucky 

Reservoir) Pickwick 

Tailwater.

Small ............. Small ............. High .............. Low ............... Low ............... Low. 

Upper Duck .............................. Upper Duck River .................... Large ............ Medium ......... Mod ............... Med ............... Medium ......... Low. 

Lower Duck .............................. Lower Duck River .................... Large ............ Small ............. Mod ............... Med ............... Low ............... Very Low. 

ARKANSAS–WHITE–RED BASIN 

Petit Jean ................................. Petit Jean River ....................... Small ............. Small ............. Mod ............... Low ............... Low ............... Very Low. 

Eleven Point ............................. Eleven Point River ................... Small ............. Small ............. Low ............... Low ............... Low ............... Very Low. 


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TABLE 2—SUMMARY OF PYRAMID PIGTOE CURRENT MUSSEL POPULATION SIZE, EXTENT, THREAT LEVEL, AND

PROJECTED FUTURE CONDITIONS. ONLY OVERALL CONDITION IS LISTED FOR FUTURE SCENARIOS—Continued 

Management unit Contiguous population 

(occupied river) 

Population 

size 

Population 

extent Threat level Current condition 

Future condition 

Scenario 

1 

Scenario 

2 

Lower Little ............................... Little River ................................ Medium ......... Small ............. Mod ............... Low ............... Low ............... Very Low. 

LOWER MISSISSIPPI BASIN 

Lower Black ............................. Lower Black River .................... Small ............. Small ............. Mod ............... Low ............... Low ............... Very Low. 

Lower St. Francis ..................... St. Francis River ...................... Medium ......... Small ............. High .............. Med ............... Medium ......... Low. 

Tyronza River .......................... Medium ......... Large ............ High .............. Med ............... Medium ......... Low. 

Middle White ............................ Middle White River .................. Small ............. Small ............. Mod ............... Low ............... Low ............... Very Low. 

Upper Ouachita ........................ Upper Ouachita River .............. Large ............ Large ............ Mod ............... High .............. High .............. Medium. 

Little Missouri ........................... Little Missouri River ................. Large ............ Medium ......... Mod ............... Med ............... Medium ......... Low. 

Lower Ouachita-Smackover ..... Lower Ouachita River 

(Smackover).

Medium ......... Medium ......... Mod ............... Med ............... Medium ......... Low. 

Upper Saline ............................ Upper Saline River .................. Large ............ Large ............ Mod ............... High .............. High .............. Medium. 

Lower Saline ............................ Lower Saline River .................. Large ............ Large ............ High .............. High .............. High .............. Medium. 

Bayou Bartholomew ................. Bayou Bartholomew ................. Large ............ Large ............ High .............. Med ............... Medium ......... Low. 

Lower Ouachita-Bayou De 

Loutre.

Lower Ouachita River (Bayou 

De Loutre).

Medium ......... Medium ......... High .............. Low ............... Low ............... Low. 

Big Sunflower ........................... Hushpuckna River ................... Small ............. Small ............. High .............. Med ............... Low ............... Very Low. 

Bogue Phalia ........................... Small ............. Small ............. High .............. Med ............... Low ............... Very Low. 

Little Sunflower River ............... Small ............. Small ............. High .............. Med ............... Low ............... Very Low. 

Sunflower River ....................... Medium ......... Large ............ High .............. Med ............... Low ............... Very Low. 

Sandy Bayou ........................... Small ............. Small ............. High .............. Med ............... Low ............... Very Low. 

Big Sunflower River ................. Medium ......... Large ............ High .............. Med ............... Low ............... Very Low. 

Lower Big Black ....................... Big Black River ........................ Small ............. Small ............. High .............. Low ............... Very Low ...... Very Low. 

The viability implications associated 

with the expected change in population 

conditions can be discerned at the MU 

and HUC–2 scales. Under scenario 1, we 

expect 3 MUs (11 percent) remain in 

high condition; 9 MUs (32 percent), in 

medium condition; 12 MUs (43 

percent), in low condition; and 4 (14 

percent), in very low condition. 

Therefore, the species’ ability to 

withstand natural environmental 

variation and threats will be greatly 

limited. Loss of the three MUs reduces 

the species’ distribution, increasing its 

risk to catastrophic events. The pyramid 

pigtoe will continue to be represented in 

the Ohio, Tennessee, and Lower 

Mississippi basins, but reduced to six 

States (as compared to the current nine 

States) occupied by the species. 

Representation will be lost from the 

Arkansas-White-Red basin, as all of its 

MUs are expected to be in low 

condition. It will take many years 

(potentially beyond the 20- to 30-year 

timeframe analyzed), for full evaluation 

of the species’ response to any current 

beneficial actions, such as removal of 

Lock and Dam 6 on the Green River, or 

the safe harbor agreements and 

candidate conservation agreements with 

assurances in the Upper Ouachita and 

Upper Saline Rivers. 

Under scenario 2, none of the MUs are 

expected to be in high condition, 4 (14 

percent) are in medium condition, 11 

(39 percent) are in low condition, and 

13 (46 percent) are in very low 

condition. Given no MUs will be in high 

condition, the species’ ability to 

withstand natural environmental 

variation and threats will be 

substantially limited. Redundancy will 

also be substantially reduced with no 

high condition MUs remaining and the 

expected loss of 13 (46 percent) MUs. 

Loss of the species from the ArkansasWhite-Red basin, with no high 

condition MUs in any basin, and 

potential extirpation of the species from 

the States of Virginia, Ohio, Oklahoma, 

and Mississippi will substantially 

reduce the species’ genetic diversity, 

thereby decreasing its ability to adapt to 

changing environmental conditions. 

We note that, by using the SSA 

framework to guide our analysis of the 

scientific information documented in 

the SSA report, we have not only 

analyzed individual effects on the 

species, but we have also analyzed their 

potential cumulative effects. We 

incorporate the cumulative effects into 

our SSA analysis when we characterize 

the current and future condition of the 

species. To assess the current and future 

condition of the species, we undertake 

an iterative analysis that encompasses 

and incorporates the threats 

individually and then accumulates and 

evaluates the effects of all the factors 

that may be influencing the species, 

including threats and conservation 

efforts. Because the SSA framework 

considers not just the presence of the 

factors, but to what degree they 

collectively influence risk to the entire 

species, our assessment integrates the 

cumulative effects of the factors and 

replaces a standalone cumulative effects 

analysis. 

Conservation Efforts and Regulatory 

Mechanisms 

As discussed under Threats, Federal 

and State lands and water quality 

regulations afford the pyramid pigtoe 

and its habitats some protection from 

land development, industrial, and 

transportation activities. Additionally, 

laws intended to reduce the threat of 

nonnative species are in place. Many 

populations of the pyramid pigtoe were 

extirpated or reduced prior to 

development of modern conservation 

programs and regulatory mechanisms. 

As such, historical threats no longer 

present on the landscape impart a 

legacy effect (small population size or 

degraded habitat) on some current 

populations. Further, some water 

quality regulations have not been fully 

adopted or consistently applied across 

the species’ range. Therefore, despite 

the existing regulatory mechanisms in 

place, the combined threats and impacts 

of actions that occurred prior to the 

implementation of these regulatory 

mechanisms continue to negatively 

affect the pyramid pigtoe. 

Determination of Pyramid Pigtoe Status 

Section 4 of the Act (16 U.S.C. 1533) 

and its implementing regulations (50 

CFR part 424) set forth the procedures 

for determining whether a species meets 

the definition of an endangered species 

or a threatened species. The Act defines 

an endangered species as a species ‘‘in 


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danger of extinction throughout all or a 

significant portion of its range’’ and a 

threatened species as a species ‘‘likely 

to become an endangered species within 

the foreseeable future throughout all or 

a significant portion of its range.’’ The 

Act requires that we determine whether 

a species meets the definition of an 

endangered species or a threatened 

species because of any of the following 

factors: (A) The present or threatened 

destruction, modification, or 

curtailment of its habitat or range; (B) 

overutilization for commercial, 

recreational, scientific, or educational 

purposes; (C) disease or predation; (D) 

the inadequacy of existing regulatory 

mechanisms; or (E) other natural or 

manmade factors affecting its continued 

existence. 

Status Throughout All of Its Range 

Historically, the pyramid pigtoe 

occurred within 151 populations and 

136 MUs, in 6 basins across 18 States 

(Figure 2). Currently, the species occurs 

within 35 populations and 28 MUs, in 

4 basins across 9 States, which 

represents a 77 percent reduction of its 

historically occupied populations. Of 

the extant MUs, 4 are highly resilient, 

while 9 and 15 have medium and low 

resiliency, respectively. The threats 

leading to its current condition include 

past and ongoing habitat degradation or 

loss (Factor A), residual impacts from 

past harvest and overutilization (Factor 

B), and ongoing competition, predation, 

and habitat alteration from invasive, 

nonnative species (Factor E). 

Collectively, these threats reduce 

population abundance, thereby 

precipitating negative genetic and 

demographic effects associated with 

small population size (Factor E) within 

some of the smaller populations. 

Although downtrends from historical 

numbers are evident and declines are 

likely to continue, four high resilient 

MUs are distributed across two of the 

four occupied major river basins. These 

four MUs provide for current 

representation and redundancy of the 

species. Thus, after assessing the best 

available information, we conclude that 

the pyramid pigtoe is not in danger of 

extinction throughout all of its range. 

We, therefore, proceed with determining 

whether the pyramid pigtoe is likely to 

become endangered within the 

foreseeable future throughout all of its 

range. 

The best available information 

suggests that the threats currently acting 

upon the pyramid pigtoe will continue 

into the foreseeable future. In areas 

experiencing human population and 

land development growth, these threats 

(e.g., water quality and habitat 

degradation) are reasonably expected to 

increase over time, further reducing the 

species’ resiliency, redundancy, and 

representation. Our foreseeable future 

(20 to 30 years) reflects the period of 

time over which we can reliably predict 

both the threats to the pyramid pigtoe 

and the pyramid pigtoe’s response to 

those threats based on the best available 

information. Within the foreseeable 

future, even if threats were to remain at 

current levels and not increase, 23 of the 

35 populations are projected to become 

extirpated or functionally extirpated 

(Table 2). Additionally, with no change 

in threat levels, the condition of one of 

the four high resilient populations will 

decline to medium resiliency and the 

remaining three high resilient 

populations would be confined to a 

single basin. At the MU scale, only 3 of 

the 28 extant MUs remain in high 

condition, with 17 MUs projected to 

become extirpated or functionally 

extirpated within 20 to 30 years. If 

threats increase, 19 populations will 

likely be extirpated within 20 to 30 

years, leading to only 4 MUs persisting. 

These MUs will have limited 

recruitment potential and restricted 

distribution, thus impairing the species’ 

ability to recover from disturbances and 

increasing its vulnerability to 

catastrophic events. In summary, threats 

currently acting on the species are likely 

to persist or increase in the foreseeable 

future, resulting in zero to three high 

resilient populations in one of its six 

historical major basins and resulting in 

a high risk of impacts from a single 

catastrophe or stochastic events. Thus, 

after assessing the best available 

information, we conclude that the 

pyramid pigtoe is likely to become in 

danger of extinction within the 

foreseeable future throughout all of its 

range. 

Status Throughout a Significant Portion 

of Its Range 

Under the Act and our implementing 

regulations, a species may warrant 

listing if it is in danger of extinction or 

likely to become so in the foreseeable 

future throughout all or a significant 

portion of its range. The court in Center 

for Biological Diversity v. Everson, 2020 

WL 437289 (D.D.C. Jan. 28, 2020) 

(Center for Biological Diversity), vacated 

the aspect of the Final Policy on 

Interpretation of the Phrase ‘‘Significant 

Portion of Its Range’’ in the Endangered 

Species Act’s Definitions of 

‘‘Endangered Species’’ and ‘‘Threatened 

Species’’ (79 FR 37578; July 1, 2014) 

that provided that the Service does not 

undertake an analysis of significant 

portions of a species’ range if the 

species warrants listing as threatened 

throughout all of its range. Therefore, 

we proceed to evaluating whether the 

species is endangered in a significant 

portion of its range—that is, whether 

there is any portion of the species’ range 

for which both (1) the portion is 

significant and (2) the species is in 

danger of extinction in that portion. 

Depending on the case, it might be more 

efficient for us to address the 

‘‘significance’’ question or the ‘‘status’’ 

question first. We can choose to address 

either question first. Regardless of 

which question we address first, if we 

reach a negative answer with respect to 

the first question that we address, we do 

not need to evaluate the other question 

for that portion of the species’ range. 

Following the court’s holding in 

Center for Biological Diversity, we now 

consider whether there are any 

significant portions of the species’ range 

where the species is in danger of 

extinction now (i.e., endangered). In 

undertaking this analysis for the 

pyramid pigtoe, we choose to address 

the status question first—we consider 

information pertaining to the geographic 

distribution of both the species and the 

threats that the species faces to identify 

any portions of the range where the 

species is endangered. 

For the pyramid pigtoe, we 

considered whether the threats are 

geographically concentrated in any 

portion of the species’ range at a 

biologically meaningful scale. We 

examined the following threats: Habitat 

degradation or loss, invasive and 

nonnative species, and negative effects 

associated with small population size, 

including cumulative effects. Habitat 

degradation or loss, including 

diminished water quality, is a threat in 

all four basins occupied by the pyramid 

pigtoe, although the contribution by 

source (e.g., agriculture, urbanization, 

mining, dredging) varies. Invasive or 

nonnative species also is a threat in 

each occupied basin. Lastly, large 

populations (number of individuals) 

occur in three of the four basins, and 

medium populations occur in all four 

basins. 

We examined the Arkansas-WhiteRed basin (the only basin not containing 

any large populations) to determine if 

there is a concentration of threats 

because, of the three populations in the 

basin, two have a moderate threat level 

and one has a low threat level. All three 

of these populations are in a low current 

condition, and two of the three 

populations have small numbers of 

individuals. Thus, the cumulative 

effects of small population size with the 

other identified threats may be 

concentrated in this basin. 


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We then evaluated whether the 

Arkansas-White-Red basin may be 

biologically important to the overall 

species’ viability, i.e., significant. This 

basin contains 3 of the 35 (8.6 percent) 

pyramid pigtoe populations. By length 

of river, the populations combined 

occupy about 5 percent of the species’ 

range. Therefore, the populations in the 

Arkansas-White-Red basin minimally 

contribute to the overall viability of the 

species. 

The pyramid pigtoe occurs in similar 

habitats across the four basins it 

occupies and does not use unique 

observable environmental 

characteristics attributable to any of the 

basins. The Arkansas-White-Red basin 

populations occur in stream habitat 

with substrate types and water quality 

similar to the other basins where the 

pyramid pigtoe performs the important 

life-history functions of breeding, 

feeding, and sheltering. The basin does 

not act as a refugium for the species or 

as an important spawning ground. In 

addition, the water quality is similar 

throughout the species’ range, with 

impaired water quality occurring in all 

four basins. Because the pyramid pigtoe 

occurs in similar aquatic habitats, the 

Arkansas-White-Red basin population 

exhibits similar habitat use as 

populations in the remainder of the 

range. 

Overall, we found no substantial 

information that would indicate the 

Arkansas-White-Red basin is a portion 

of the range that may be significant in 

terms of its overall contribution to the 

species’ resiliency, redundancy, and 

representation, or that it is significant in 

terms of high-quality habitat or habitat 

that is otherwise important for the 

species’ life history. Additionally, 

within each of the other three basins (or 

portions of the range) there was no 

concentration of threats that would 

indicate the species is facing elevated 

threats in those portions. As a result, we 

determined there is no portion of the 

pyramid pigtoe’s range that constitutes 

a significant portion of the range where 

the species is currently endangered. 

Accordingly, we determine that the 

species is likely to become in danger of 

extinction within the foreseeable future 

throughout all of its range. This is 

consistent with the courts’ holdings in 

Desert Survivors v. Department of the 

Interior, No. 16–cv–01165–JCS, 2018 

WL 4053447 (N.D. Cal. Aug. 24, 2018), 

and Center for Biological Diversity v. 

Jewell, 248 F. Supp. 3d, 946, 959 (D. 

Ariz. 2017). 

Determination of Status 

Our review of the best available 

scientific and commercial information 

indicates that the pyramid pigtoe meets 

the definition of a threatened species. 

Therefore, we propose to list the 

pyramid pigtoe as a threatened species 

in accordance with sections 3(20) and 

4(a)(1) of the Act. 

Available Conservation Measures 

Conservation measures provided to 

species listed as endangered or 

threatened species 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, Tribal, and local 

agencies, private organizations, and 

individuals. The Act encourages 

cooperation with the States and other 

countries and calls for recovery actions 

to be carried out for listed species. The 

protection required by Federal agencies 

and the prohibitions against certain 

activities are discussed, in part, below. 

The primary purpose of the Act is the 

conservation of endangered and 

threatened species and the ecosystems 

upon which they depend. The ultimate 

goal of such conservation efforts is the 

recovery of these listed species, so that 

they no longer need the protective 

measures of the Act. Section 4(f) of the 

Act calls for 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, selfsustaining, and functioning components 

of their ecosystems. 

Recovery planning consists of 

preparing draft and final recovery plans, 

beginning with the development of a 

recovery outline and making it available 

to the public following a final listing 

determination. The recovery outline 

guides the immediate implementation of 

urgent recovery actions and describes 

the process to be used to develop a 

recovery plan. Revisions of the plan 

may be done to address continuing or 

new threats to the species, as new 

substantive information becomes 

available. The recovery plan also 

identifies recovery criteria for review of 

when a species may be ready for 

reclassification from endangered to 

threatened (‘‘downlisting’’) or removal 

from protected status (‘‘delisting’’), 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 

(composed of species experts, Federal 

and State agencies, nongovernmental 

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 website (http://www.fws.gov/ 

endangered), or from our Asheville 

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, Tribes, 

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, pursuant to section 6 of the 

Act, the States of Alabama, Arkansas, 

Kentucky, Louisiana, Mississippi, Ohio, 

Oklahoma, Tennessee, and Virginia 

would be eligible for Federal funds to 

implement management actions that 

promote the protection or recovery of 

the pyramid pigtoe. Information on our 

grant programs that are available to aid 

species recovery can be found at: http:// 

www.fws.gov/grants. 

Although the pyramid pigtoe is 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 an endangered 

or threatened species 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 


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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 consultation 

with the Service. 

Federal agency actions within the 

species’ habitat that may require 

conference, consultation, or both as 

described in the preceding paragraph 

include management and any other 

landscape-altering activities on Federal 

lands administered by the following: 

(1) U.S. Army Corps of Engineers 

(channel dredging and maintenance; 

dam projects including flood control, 

navigation, hydropower, bridge projects, 

stream restoration, and Clean Water Act 

permitting). 

(2) U.S. Department of Agriculture, 

including the Natural Resources 

Conservation Service and Farm Service 

Agency (technical and financial 

assistance for projects) and the Forest 

Service (aquatic habitat restoration, fire 

management plans, fire suppression, 

fuel reduction treatments, forest plans, 

mining permits). 

(3) U.S. Department of Energy 

(renewable and alternative energy 

projects). 

(4) Federal Energy Regulatory 

Commission (interstate pipeline 

construction and maintenance, dam 

relicensing, and hydrokinetics). 

(5) U.S. Department of Transportation 

(highway and bridge construction and 

maintenance). 

(6) U.S. Fish and Wildlife Service 

(issuance of section 10 permits for 

enhancement of survival, habitat 

conservation plans, and safe harbor 

agreements; National Wildlife Refuge 

planning and refuge activities; Partners 

for Fish and Wildlife program projects 

benefiting these species or other listed 

species; Wildlife and Sportfish 

Restoration program sportfish stocking). 

(7) Environmental Protection Agency 

(water quality criteria, permitting). 

(8) Tennessee Valley Authority (flood 

control, navigation, hydropower, and 

land management for the Tennessee 

River system). 

(9) Office of Surface Mining 

Reclamation and Enforcement (land 

resource management plans, mining 

permits, oil and natural gas permits, 

abandoned mine land projects, and 

renewable energy development). 

(10) National Park Service (aquatic 

habitat restoration, fire management 

plans, fire suppression, fuel reduction 

treatments, land management plans, 

mining permits). 

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 the species proposed for 

listing. The discussion below regarding 

protective regulations under section 4(d) 

of the Act complies with our policy. 

II. Proposed Rule Issued Under Section 

4(d) of the Act 

Background 

Section 4(d) of the Act contains two 

sentences. The first sentence states that 

the Secretary shall issue such 

regulations as he deems necessary and 

advisable to provide for the 

conservation of species listed as 

threatened. The U.S. Supreme Court has 

noted that statutory language like 

‘‘necessary and advisable’’ demonstrates 

a large degree of deference to the agency 

(see Webster v. Doe, 486 U.S. 592 

(1988)). Conservation is defined in the 

Act to mean the use of all methods and 

procedures which are necessary to bring 

any endangered species or threatened 

species to the point at which the 

measures provided pursuant to the Act 

are no longer necessary. Additionally, 

the second sentence of section 4(d) of 

the Act states that the Secretary may by 

regulation prohibit with respect to any 

threatened species any act prohibited 

under section 9(a)(1), in the case of fish 

or wildlife, or section 9(a)(2), in the case 

of plants. Thus, the combination of the 

two sentences of section 4(d) provides 

the Secretary with wide latitude of 

discretion to select and promulgate 

appropriate regulations tailored to the 

specific conservation needs of the 

threatened species. The second sentence 

grants particularly broad discretion to 

the Service when adopting the 

prohibitions under section 9. 

The courts have recognized the extent 

of the Secretary’s discretion under this 

standard to develop rules that are 

appropriate for the conservation of a 

species. For example, courts have 

upheld rules developed under section 

4(d) as a valid exercise of agency 

authority where they prohibited take of 

threatened wildlife, or include a limited 

taking prohibition (see Alsea Valley 

Alliance v. Lautenbacher, 2007 U.S. 

Dist. Lexis 60203 (D. Or. 2007); 

Washington Environmental Council v. 

National Marine Fisheries Service, 2002 

U.S. Dist. Lexis 5432 (W.D. Wash. 

2002)). Courts have also upheld 4(d) 

rules that do not address all of the 

threats a species faces (see State of 

Louisiana v. Verity, 853 F.2d 322 (5th 

Cir. 1988)). As noted in the legislative 

history when the Act was initially 

enacted, ‘‘once an animal is on the 

threatened list, the Secretary has an 

almost infinite number of options 

available to him with regard to the 

permitted activities for those species. He 

may, for example, permit taking, but not 

importation of such species, or he may 

choose to forbid both taking and 

importation but allow the transportation 

of such species’’ (H.R. Rep. No. 412, 

93rd Cong., 1st Sess. 1973). 

Exercising this authority under 

section 4(d), we have developed a 

proposed rule that is designed to 

address the pyramid pigtoe’s 

conservation needs. Although the 

statute does not require us to make a 

‘‘necessary and advisable’’ finding with 

respect to the adoption of specific 

prohibitions under section 9, we find 

that this rule as a whole satisfies the 

requirement in section 4(d) of the Act to 

issue regulations deemed necessary and 

advisable to provide for the 

conservation of the pyramid pigtoe. 

As discussed above under Summary 

of Biological Status and Threats, we 

have concluded that the pyramid pigtoe 

is likely to become in danger of 

extinction within the foreseeable future 

primarily due to declines in water 

quality, alteration and deterioration of 

instream habitats, fragmentation and 

isolation of populations, and nonnative 

species. These threats, which are 

expected to be exacerbated by continued 

urbanization and land development, 

were central to our assessment of the 

future viability of the pyramid pigtoe. 

The provisions of this proposed 4(d) 

rule would promote conservation of the 

pyramid pigtoe by encouraging 

management of the landscape in ways 

that meet the conservation needs of the 

pyramid pigtoe and are consistent with 

land management considerations. The 

provisions of this proposed rule are one 

of many tools that we would use to 

promote the conservation of the 

pyramid pigtoe. This proposed 4(d) rule 

would apply only if and when we make 

final the listing of the pyramid pigtoe as 

a threatened species. 

Section 7(a)(2) of the Act requires 

Federal agencies, including the Service, 

to ensure that any action they fund, 


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authorize, or carry out is not likely to 

jeopardize the continued existence of 

any endangered species or threatened 

species or result in the destruction or 

adverse modification of designated 

critical habitat of such species. In 

addition, section 7(a)(4) of the Act 

requires Federal agencies to confer with 

the Service on any agency action which 

is likely to jeopardize the continued 

existence of any species proposed to be 

listed under the Act or result in the 

destruction or adverse modification of 

proposed critical habitat. 

If a Federal action may affect a listed 

species or its critical habitat, the 

responsible Federal agency (action 

agency) must enter into consultation 

with us. Examples of actions that are 

subject to the section 7 consultation 

process are actions on State, Tribal, 

local, or private lands that require a 

Federal permit or that involve some 

other Federal action such as funding, 

like those listed above under Available 

Conservation Measures. Federal actions 

not affecting listed species or critical 

habitat—and actions on State, Tribal, 

local, or private lands that are not 

federally funded, authorized, or carried 

out by a Federal agency—do not require 

section 7 consultation. 

This obligation does not change in 

any way for a threatened species with a 

species-specific 4(d) rule. Actions that a 

Federal agency determines ‘‘may affect’’ 

listed species or critical habitat continue 

to require consultation and actions that 

are ‘‘likely to adversely affect’’ a species 

require formal consultation and the 

formulation of a biological opinion. 

Provisions of the Proposed 4(d) Rule 

This proposed 4(d) rule would 

provide for the conservation of the 

pyramid pigtoe by prohibiting the 

following activities, except as otherwise 

authorized or permitted: Importing or 

exporting; take; possession and other 

acts with unlawfully taken specimens; 

delivering, receiving, transporting, or 

shipping in interstate or foreign 

commerce in the course of commercial 

activity; or selling or offering for sale in 

interstate or foreign commerce. 

As discussed above under Summary 

of Biological Status and Threats, 

multiple factors are affecting the status 

of the pyramid pigtoe. A range of 

activities have the potential to affect the 

pyramid pigtoe, including declines in 

water quality, alteration and 

deterioration of instream habitats, 

fragmentation and isolation of 

populations, and nonnative species. 

These threats, which are expected to 

continue due to land development for 

urbanization, agriculture, and resource 

extraction, channel navigation, and dam 

operations were central to our 

assessment of the future viability of the 

pyramid pigtoe. Therefore, we prohibit 

actions resulting in the incidental take 

of the pyramid pigtoe by altering or 

degrading its habitat. 

Under the Act, ‘‘take’’ means to 

harass, harm, pursue, hunt, shoot, 

wound, kill, trap, capture, or collect, or 

to attempt to engage in any such 

conduct. Some of these provisions have 

been further defined in regulations at 50 

CFR 17.3. Take can result knowingly or 

otherwise, by direct and indirect 

impacts, intentionally or incidentally. 

Regulating incidental and/or intentional 

take would help preserve the species’ 

remaining populations, slow their rate 

of decline, and decrease synergistic, 

negative effects from other stressors. 

We may issue permits to carry out 

otherwise prohibited activities, 

including those described above, 

involving threatened wildlife under 

certain circumstances. Regulations 

governing permits are codified at 50 

CFR 17.32. With regard to threatened 

wildlife, a permit may be issued for the 

following purposes: For scientific 

purposes, to enhance propagation or 

survival, for economic hardship, for 

zoological exhibition, for educational 

purposes, for incidental taking, or for 

special purposes consistent with the 

purposes of the Act. The statute also 

contains certain exemptions from the 

prohibitions, which are found in 

sections 9 and 10 of the Act. 

The proposed 4(d) rule would also 

provide for the conservation of the 

species by allowing exceptions for take 

associated with actions and activities 

that, while they may have some 

minimal level of disturbance to pyramid 

pigtoe, are not expected to negatively 

impact conservation and recovery 

efforts for the species. The proposed 

exceptions to these prohibitions include 

incidental take associated with (1) 

conservation efforts by the Service or 

State wildlife agencies, (2) channel 

restoration projects, (3) bank restoration 

projects, and (4) take necessary to aid a 

sick or injured specimen, or to salvage 

a dead specimen. 

The first exception is for conservation 

and restoration efforts for pyramid 

pigtoe by the Service or State wildlife 

agencies, and including, but not limited 

to, collection of broodstock, tissue 

collection for genetic analysis, captive 

propagation, and subsequent stocking 

into unoccupied areas within the 

historical range of the species. We 

recognize the special and unique 

relationship with our State natural 

resource agency partners in contributing 

to conservation of listed species. State 

agencies often possess scientific data 

and valuable expertise on the status and 

distribution of endangered, threatened, 

and candidate species of wildlife and 

plants. State agencies, because of their 

authorities and their close working 

relationships with local governments 

and landowners, are in a unique 

position to assist the Service in 

implementing all aspects of the Act. In 

this regard, section 6 of the Act provides 

that the Service shall cooperate to the 

maximum extent practicable with the 

States in carrying out programs 

authorized by the Act. Therefore, any 

qualified employee or agent of a State 

conservation agency that is a party to a 

cooperative agreement with the Service 

in accordance with section 6(c) of the 

Act, who is designated by his or her 

agency for such purposes, would be able 

to conduct activities designed to 

conserve the pyramid pigtoe that may 

result in otherwise prohibited take 

without additional authorization. 

The second and third exceptions are 

for channel and bank restoration 

projects for creation of natural, 

physically stable, ecologically 

functioning streams, taking into 

consideration connectivity with 

floodplain and groundwater aquifers. 

These exceptions include a requirement 

that bank restoration projects require 

planting appropriate native vegetation, 

including woody species appropriate for 

the region and habitat. We also propose 

language that would require surveys and 

relocation prior to commencement of 

restoration actions for pyramid pigtoe 

that would otherwise be negatively 

affected by the actions. We reiterate that 

these actions and activities may have 

some minimal level of take of pyramid 

pigtoe, but any such take is expected to 

be rare and insignificant and is not 

expected to negatively impact 

conservation and recovery efforts. 

Rather, we expect they would have a net 

beneficial effect on the species. Across 

the species’ range, instream habitats 

have been degraded physically by 

sedimentation and by direct and 

indirect channel disturbance. The 

habitat restoration activities in the 

proposed 4(d) rule are intended to 

improve habitat conditions for the 

species in the long term. 

Finally, the proposed 4(d) rule would 

allow take of pyramid pigtoe without a 

permit by any employee or agent of the 

Service or a State conservation agency 

designated by the agency for such 

purposes and when acting in the course 

of their official duties if such action is 

necessary to aid a sick or injured 

specimen, or to salvage a dead specimen 

which may be useful for scientific 

study. In addition, Federal and State 

wildlife law enforcement officers, 


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working in coordination with Service 

field office personnel, may possess, 

deliver, carry, transport, or ship 

pyramid pigtoe taken in violation of the 

Act as necessary. 

Nothing in this proposed 4(d) rule 

would change in any way the recovery 

planning provisions of section 4(f) of the 

Act, the consultation requirements 

under section 7 of the Act, or the ability 

of the Service to enter into partnerships 

for the management and protection of 

the pyramid pigtoe. However, 

interagency cooperation may be further 

streamlined through planned 

programmatic consultations for the 

species between Federal agencies and 

the Service, where appropriate. We ask 

the public, particularly State agencies 

and other interested stakeholders that 

may be affected by the proposed 4(d) 

rule, to provide comments and 

suggestions regarding additional 

guidance and methods that the Service 

could provide or use, respectively, to 

streamline the implementation of this 

proposed 4(d) rule (see Information 

Requested, above). 

III. Critical Habitat 

Prudency Determination 

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

amended, and implementing regulations 

(50 CFR 424.12) require that, to the 

maximum extent prudent and 

determinable, the Secretary shall 

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 Secretary may, but is not 

required to, determine that a 

designation would not be prudent in the 

following circumstances: 

(i) The species is threatened by taking 

or other human activity and 

identification of critical habitat can be 

expected to increase the degree of such 

threat to the species; 

(ii) The present or threatened 

destruction, modification, or 

curtailment of a species’ habitat or range 

is not a threat to the species, or threats 

to the species’ habitat stem solely from 

causes that cannot be addressed through 

management actions resulting from 

consultations under section 7(a)(2) of 

the Act; 

(iii) Areas within the jurisdiction of 

the United States provide no more than 

negligible conservation value, if any, for 

a species occurring primarily outside 

the jurisdiction of the United States; 

(iv) No areas meet the definition of 

critical habitat; or 

(v) The Secretary otherwise 

determines that designation of critical 

habitat would not be prudent based on 

the best scientific data available. 

As discussed earlier in this document, 

there is currently no imminent threat of 

collection or vandalism identified under 

Factor B for this species, and 

identification and mapping of critical 

habitat is not expected to initiate any 

such threat. In our SSA and proposed 

listing determination for the pyramid 

pigtoe, we determined that the present 

or threatened destruction, modification, 

or curtailment of habitat or range is a 

threat to the pyramid pigtoe and that 

those threats in some way can be 

addressed by section 7(a)(2) 

consultation measures. The species 

occurs wholly in the jurisdiction of the 

United States, and we are able to 

identify areas that meet the definition of 

critical habitat. Therefore, because none 

of the circumstances enumerated in our 

regulations at 50 CFR 424.12(a)(1) have 

been met and because there are no other 

circumstances the Secretary has 

identified for which this designation of 

critical habitat would be not prudent, 

we have determined that the 

designation of critical habitat is prudent 

for the pyramid pigtoe. 

Critical Habitat Determinability 

Having determined that designation is 

prudent, under section 4(a)(3) of the Act 

we consider whether critical habitat for 

the pyramid pigtoe 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) Data sufficient to perform required 

analyses are lacking, or 

(ii) The biological needs of the species 

are not sufficiently well known to 

identify any area that meets the 

definition of ‘‘critical habitat.’’ 

For the pyramid pigtoe, the species’ 

needs are sufficiently well known. 

However, there is some uncertainty 

regarding the taxonomic identity of 

populations outside the Ohio, 

Cumberland, and Tennessee River 

basins (see Background), which is 

currently under investigation using 

different genetic markers than assessed 

thus far. Results of this taxonomic 

investigation, which may more 

accurately delineate the species’ 

occupied range, are likely to be 

completed and submitted to a peerreviewed journal within 1 year. In 

addition to this taxonomic investigation 

that may better determine critical 

habitat areas, a careful assessment of the 

economic impacts that may occur due to 

a critical habitat designation is ongoing, 

and we are in the process of acquiring 

the necessary information to perform 

that assessment. Because the 

information sufficient to perform a 

required analysis of the impacts of the 

designation is lacking, we find 

designation of critical habitat for the 

pyramid pigtoe to be not determinable 

at this time. The Act allows the Service 

an additional year to publish a critical 

habitat designation that is not 

determinable at the time of listing (16 

U.S.C. 1533(b)(6)(C)(ii)). 

Required Determinations 

Clarity of the Rule 

We are required by Executive Orders 

12866 and 12988 and by the 

Presidential Memorandum of June 1, 

1998, to write all rules in plain 

language. This means that each rule we 

publish must: 

(1) Be logically organized; 

(2) Use the active voice to address 

readers directly; 

(3) Use clear language rather than 

jargon; 

(4) Be divided into short sections and 

sentences; and 

(5) Use lists and tables wherever 

possible. 

If you feel that we have not met these 

requirements, send us comments by one 

of the methods listed in ADDRESSES. To 

better help us revise the rule, your 

comments should be as specific as 

possible. For example, you should tell 

us the numbers of the sections or 

paragraphs that are unclearly written, 

which sections or sentences are too 

long, the sections where you feel lists or 

tables would be useful, etc. 

National Environmental Policy Act (42 

U.S.C. 4321 et seq.) 

It is our position that, outside the 

jurisdiction of the U.S. Court of Appeals 

for the Tenth Circuit, we do not need to 

prepare environmental analyses 

pursuant to the National Environmental 

Policy Act (NEPA; 42 U.S.C. 4321 et 

seq.) in connection with regulations 

adopted pursuant to section 4(a) of the 

Act. We published a notice outlining 

our reasons for this determination in the 

Federal Register on October 25, 1983 

(48 FR 49244). This position was upheld 

by the U.S. Court of Appeals for the 

Ninth Circuit (Douglas County v. 

Babbitt, 48 F.3d 1495 (9th Cir. 1995), 

cert. denied 516 U.S. 1042 (1996)). 

Government-to-Government 

Relationship With Tribes 

In accordance with the President’s 

memorandum of April 29, 1994 

(Government-to-Government Relations 

with Native American Tribal 

Governments; 59 FR 22951), Executive 

Order 13175 (Consultation and 

Coordination with Indian Tribal 


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Governments), and the Department of 

the Interior’s manual at 512 DM 2, we 

readily acknowledge our responsibility 

to communicate meaningfully with 

recognized Federal Tribes on a 

government-to-government basis. In 

accordance with Secretarial Order 3206 

of June 5, 1997 (American Indian Tribal 

Rights, Federal-Tribal Trust 

Responsibilities, and the Endangered 

Species Act), we readily acknowledge 

our responsibilities to work directly 

with Tribes in developing programs for 

healthy ecosystems, to acknowledge that 

Tribal lands are not subject to the same 

controls as Federal public lands, to 

remain sensitive to Indian culture, and 

to make information available to Tribes. 

There are no Tribal lands within or 

adjacent to known pyramid pigtoe 

occupied habitat. We will coordinate 

with Tribes whose lands are close to 

pyramid pigtoe populations. 

References Cited 

A complete list of references cited in 

this rulemaking is available on the 

internet at http://www.regulations.gov 

and upon request from the Asheville 

Ecological Services Field Office (see FOR

FURTHER INFORMATION CONTACT). 

Authors 

The primary authors of this proposed 

rule are the staff members of the Fish 

and Wildlife Service’s Species 

Assessment Team and the Asheville 

Ecological Services Field Office. 

List of Subjects in 50 CFR Part 17 

Endangered and threatened species, 

Exports, Imports, Reporting and 

recordkeeping requirements, 

Transportation. 

Accordingly, we propose to amend 

part 17, subchapter B of chapter I, title 

50 of the Code of Federal Regulations, 

as set forth below: 

PART 17—ENDANGERED AND 

THREATENED WILDLIFE AND PLANTS 

■ 1. The authority citation for part 17 

continues to read as follows: 

Authority: 16 U.S.C. 1361–1407; 1531– 

1544; and 4201–4245, unless otherwise 

noted. 

■ 2. Amend § 17.11(h) by adding an 

entry for ‘‘Pigtoe, pyramid’’ to the List 

of Endangered and Threatened Wildlife 

in alphabetical order under Clams to 

read as set forth below: 

§ 17.11 Endangered and threatened 

wildlife. 

* * * * * 

(h) * * * 

Common name Scientific name Where listed Status Listing citations and applicable rules 

*******

CLAMS

* * * * * * * 

Pigtoe, pyramid .. Pleurobema 

rubrum.

Wherever found .. T ........... [Federal Register citation when published as a final rule]; 50 CFR 

17.45(e); 4d. 

* * * * * * * 

■ 3. As proposed to be added at 83 FR 

51570 (Oct. 11, 2018), and amended at 

85 FR 44821 (July 24, 2020), 85 FR 

59487 (Sept. 22, 2020), 85 FR 61384 

(Sept. 29, 2020), and 86 FR 47916 

(August 26, 2021), § 17.45 is further 

amended by adding paragraph (e) to 

read as follows: 

§ 17.45 Special rules—snails and clams. 

* * * * * 

(e) Pyramid pigtoe (Pleurobema 

rubrum). 

(1) Prohibitions. The following 

prohibitions that apply to endangered 

wildlife also apply to the pyramid 

pigtoe. Except as provided under 

paragraph (e)(2) of this section and 

§§ 17.4 and 17.5, it is unlawful for any 

person subject to the jurisdiction of the 

United States to commit, to attempt to 

commit, to solicit another to commit, or 

cause to be committed, any of the 

following acts in regard to this species: 

(i) Import or export, as set forth at 

§ 17.21(b) for endangered wildlife. 

(ii) Take, as set forth at § 17.21(c)(1) 

for endangered wildlife. 

(iii) Possession and other acts with 

unlawfully taken specimens, as set forth 

at § 17.21(d)(1) for endangered wildlife. 

(iv) Interstate or foreign commerce in 

the course of commercial activity, as set 

forth at § 17.21(e) for endangered 

wildlife. 

(v) Sale or offer for sale, as set forth 

at § 17.21(f) for endangered wildlife. 

(2) Exceptions from prohibitions. In 

regard to this species, you may: 

(i) Conduct activities as authorized by 

a permit under § 17.32. 

(ii) Take, as set forth at § 17.21(c)(3) 

and (4) for endangered wildlife. 

(iii) Take as set forth at § 17.31(b). 

(iv) Take incidental to an otherwise 

lawful activity caused by: 

(A) Channel restoration projects that 

create natural, physically stable, 

ecologically functioning streams (or 

stream and wetland systems). These 

projects can be accomplished using a 

variety of methods, but the desired 

outcome is a natural channel with low 

shear stress (force of water moving 

against the channel); bank heights that 

enable reconnection to the floodplain; 

connection of surface and groundwater 

systems, resulting in perennial flows in 

the channel; riffles and pools composed 

of existing soil, rock, and wood instead 

of large imported materials; low 

compaction of soils within adjacent 

riparian areas; and inclusion of riparian 

wetlands. Streams reconstructed in this 

way would offer suitable habitats for the 

pyramid pigtoe and contain stable 

channel features, such as pools, glides, 

runs, and riffles, which could be used 

by the species and its host fish for 

spawning, rearing, growth, feeding, 

migration, and other normal behaviors. 

Prior to commencement of restoration 

actions, surveys to determine presence 

of the pyramid pigtoe must be 

performed, and, if any pyramid pigtoe 

are located, in coordination with the 

local Service field office, they must be 

relocated prior to project 

implementation and monitored postimplementation. To qualify under this 

exemption, a channel restoration project 

must satisfy all Federal, State, and local 

permitting requirements. 

(B) Bank restoration projects that use 

bioengineering methods to replace 

preexisting, bare, eroding stream banks 

with vegetated, stable stream banks, 

thereby reducing bank erosion and 

instream sedimentation and improving 

habitat conditions for the species. 

Following these bioengineering 

methods, stream banks may be 

stabilized using native species live 

stakes (live, vegetative cuttings inserted 


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or tamped into the ground in a manner 

that allows the stake to take root and 

grow), native species live fascines (live 

branch cuttings, usually willows, bound 

together into long, cigar-shaped 

bundles), or native species brush 

layering (cuttings or branches of easily 

rooted tree species layered between 

successive lifts of soil fill). Bank 

restoration projects would require 

planting appropriate native vegetation, 

including woody species appropriate for 

the region and habitat. These methods 

will not include the sole use of quarried 

rock (rip-rap) or the use of rock baskets 

or gabion structures. Prior to 

commencement of bank stabilization 

actions, surveys to determine presence 

of pyramid pigtoe must be performed, 

and, if any pyramid pigtoe are located, 

in coordination with the local Service 

field office, they must be relocated prior 

to project implementation and 

monitored post-implementation. To 

qualify under this exemption, a bank 

restoration project must satisfy all 

Federal, State, and local permitting 

requirements. 

(v) Possess and engage in other acts 

with unlawfully taken wildlife, as set 

forth at § 17.21(d)(2) for endangered 

wildlife. 

Martha Williams, 

Principal Deputy Director, Exercising the 

Delegated Authority of the Director, U.S. Fish 

and Wildlife Service. 

[FR Doc. 2021–19091 Filed 9–3–21; 8:45 am] 

BILLING CODE 4333–15–P 


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